1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2018, Joyent, Inc. 24 * Copyright (c) 2011, 2018 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29/* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74/* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal ARC algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * ARC list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each ARC state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an ARC list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * It as also possible to register a callback which is run when the 103 * arc_meta_limit is reached and no buffers can be safely evicted. In 104 * this case the arc user should drop a reference on some arc buffers so 105 * they can be reclaimed and the arc_meta_limit honored. For example, 106 * when using the ZPL each dentry holds a references on a znode. These 107 * dentries must be pruned before the arc buffer holding the znode can 108 * be safely evicted. 109 * 110 * Note that the majority of the performance stats are manipulated 111 * with atomic operations. 112 * 113 * The L2ARC uses the l2ad_mtx on each vdev for the following: 114 * 115 * - L2ARC buflist creation 116 * - L2ARC buflist eviction 117 * - L2ARC write completion, which walks L2ARC buflists 118 * - ARC header destruction, as it removes from L2ARC buflists 119 * - ARC header release, as it removes from L2ARC buflists 120 */ 121 122/* 123 * ARC operation: 124 * 125 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure. 126 * This structure can point either to a block that is still in the cache or to 127 * one that is only accessible in an L2 ARC device, or it can provide 128 * information about a block that was recently evicted. If a block is 129 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough 130 * information to retrieve it from the L2ARC device. This information is 131 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block 132 * that is in this state cannot access the data directly. 133 * 134 * Blocks that are actively being referenced or have not been evicted 135 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within 136 * the arc_buf_hdr_t that will point to the data block in memory. A block can 137 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC 138 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and 139 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd). 140 * 141 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the 142 * ability to store the physical data (b_pabd) associated with the DVA of the 143 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block, 144 * it will match its on-disk compression characteristics. This behavior can be 145 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the 146 * compressed ARC functionality is disabled, the b_pabd will point to an 147 * uncompressed version of the on-disk data. 148 * 149 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each 150 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it. 151 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC 152 * consumer. The ARC will provide references to this data and will keep it 153 * cached until it is no longer in use. The ARC caches only the L1ARC's physical 154 * data block and will evict any arc_buf_t that is no longer referenced. The 155 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the 156 * "overhead_size" kstat. 157 * 158 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or 159 * compressed form. The typical case is that consumers will want uncompressed 160 * data, and when that happens a new data buffer is allocated where the data is 161 * decompressed for them to use. Currently the only consumer who wants 162 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it 163 * exists on disk. When this happens, the arc_buf_t's data buffer is shared 164 * with the arc_buf_hdr_t. 165 * 166 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The 167 * first one is owned by a compressed send consumer (and therefore references 168 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be 169 * used by any other consumer (and has its own uncompressed copy of the data 170 * buffer). 171 * 172 * arc_buf_hdr_t 173 * +-----------+ 174 * | fields | 175 * | common to | 176 * | L1- and | 177 * | L2ARC | 178 * +-----------+ 179 * | l2arc_buf_hdr_t 180 * | | 181 * +-----------+ 182 * | l1arc_buf_hdr_t 183 * | | arc_buf_t 184 * | b_buf +------------>+-----------+ arc_buf_t 185 * | b_pabd +-+ |b_next +---->+-----------+ 186 * +-----------+ | |-----------| |b_next +-->NULL 187 * | |b_comp = T | +-----------+ 188 * | |b_data +-+ |b_comp = F | 189 * | +-----------+ | |b_data +-+ 190 * +->+------+ | +-----------+ | 191 * compressed | | | | 192 * data | |<--------------+ | uncompressed 193 * +------+ compressed, | data 194 * shared +-->+------+ 195 * data | | 196 * | | 197 * +------+ 198 * 199 * When a consumer reads a block, the ARC must first look to see if the 200 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new 201 * arc_buf_t and either copies uncompressed data into a new data buffer from an 202 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a 203 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the 204 * hdr is compressed and the desired compression characteristics of the 205 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the 206 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be 207 * the last buffer in the hdr's b_buf list, however a shared compressed buf can 208 * be anywhere in the hdr's list. 209 * 210 * The diagram below shows an example of an uncompressed ARC hdr that is 211 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is 212 * the last element in the buf list): 213 * 214 * arc_buf_hdr_t 215 * +-----------+ 216 * | | 217 * | | 218 * | | 219 * +-----------+ 220 * l2arc_buf_hdr_t| | 221 * | | 222 * +-----------+ 223 * l1arc_buf_hdr_t| | 224 * | | arc_buf_t (shared) 225 * | b_buf +------------>+---------+ arc_buf_t 226 * | | |b_next +---->+---------+ 227 * | b_pabd +-+ |---------| |b_next +-->NULL 228 * +-----------+ | | | +---------+ 229 * | |b_data +-+ | | 230 * | +---------+ | |b_data +-+ 231 * +->+------+ | +---------+ | 232 * | | | | 233 * uncompressed | | | | 234 * data +------+ | | 235 * ^ +->+------+ | 236 * | uncompressed | | | 237 * | data | | | 238 * | +------+ | 239 * +---------------------------------+ 240 * 241 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd 242 * since the physical block is about to be rewritten. The new data contents 243 * will be contained in the arc_buf_t. As the I/O pipeline performs the write, 244 * it may compress the data before writing it to disk. The ARC will be called 245 * with the transformed data and will bcopy the transformed on-disk block into 246 * a newly allocated b_pabd. Writes are always done into buffers which have 247 * either been loaned (and hence are new and don't have other readers) or 248 * buffers which have been released (and hence have their own hdr, if there 249 * were originally other readers of the buf's original hdr). This ensures that 250 * the ARC only needs to update a single buf and its hdr after a write occurs. 251 * 252 * When the L2ARC is in use, it will also take advantage of the b_pabd. The 253 * L2ARC will always write the contents of b_pabd to the L2ARC. This means 254 * that when compressed ARC is enabled that the L2ARC blocks are identical 255 * to the on-disk block in the main data pool. This provides a significant 256 * advantage since the ARC can leverage the bp's checksum when reading from the 257 * L2ARC to determine if the contents are valid. However, if the compressed 258 * ARC is disabled, then the L2ARC's block must be transformed to look 259 * like the physical block in the main data pool before comparing the 260 * checksum and determining its validity. 261 */ 262 263#include <sys/spa.h> 264#include <sys/zio.h> 265#include <sys/spa_impl.h> 266#include <sys/zio_compress.h> 267#include <sys/zio_checksum.h> 268#include <sys/zfs_context.h> 269#include <sys/arc.h> 270#include <sys/refcount.h> 271#include <sys/vdev.h> 272#include <sys/vdev_impl.h> 273#include <sys/dsl_pool.h> 274#include <sys/zio_checksum.h> 275#include <sys/multilist.h> 276#include <sys/abd.h> 277#ifdef _KERNEL 278#include <sys/dnlc.h> 279#include <sys/racct.h> 280#endif 281#include <sys/callb.h> 282#include <sys/kstat.h> 283#include <sys/trim_map.h> 284#include <sys/zthr.h> 285#include <zfs_fletcher.h> 286#include <sys/sdt.h> 287#include <sys/aggsum.h> 288#include <sys/cityhash.h> 289 290#include <machine/vmparam.h> 291 292#ifdef illumos 293#ifndef _KERNEL 294/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 295boolean_t arc_watch = B_FALSE; 296int arc_procfd; 297#endif 298#endif /* illumos */ 299 300/* 301 * This thread's job is to keep enough free memory in the system, by 302 * calling arc_kmem_reap_now() plus arc_shrink(), which improves 303 * arc_available_memory(). 304 */ 305static zthr_t *arc_reap_zthr; 306 307/* 308 * This thread's job is to keep arc_size under arc_c, by calling 309 * arc_adjust(), which improves arc_is_overflowing(). 310 */ 311static zthr_t *arc_adjust_zthr; 312 313static kmutex_t arc_adjust_lock; 314static kcondvar_t arc_adjust_waiters_cv; 315static boolean_t arc_adjust_needed = B_FALSE; 316 317static kmutex_t arc_dnlc_evicts_lock; 318static kcondvar_t arc_dnlc_evicts_cv; 319static boolean_t arc_dnlc_evicts_thread_exit; 320 321uint_t arc_reduce_dnlc_percent = 3; 322 323/* 324 * The number of headers to evict in arc_evict_state_impl() before 325 * dropping the sublist lock and evicting from another sublist. A lower 326 * value means we're more likely to evict the "correct" header (i.e. the 327 * oldest header in the arc state), but comes with higher overhead 328 * (i.e. more invocations of arc_evict_state_impl()). 329 */ 330int zfs_arc_evict_batch_limit = 10; 331 332/* number of seconds before growing cache again */ 333int arc_grow_retry = 60; 334 335/* 336 * Minimum time between calls to arc_kmem_reap_soon(). Note that this will 337 * be converted to ticks, so with the default hz=100, a setting of 15 ms 338 * will actually wait 2 ticks, or 20ms. 339 */ 340int arc_kmem_cache_reap_retry_ms = 1000; 341 342/* shift of arc_c for calculating overflow limit in arc_get_data_impl */ 343int zfs_arc_overflow_shift = 8; 344 345/* shift of arc_c for calculating both min and max arc_p */ 346int arc_p_min_shift = 4; 347 348/* log2(fraction of arc to reclaim) */ 349int arc_shrink_shift = 7; 350 351/* 352 * log2(fraction of ARC which must be free to allow growing). 353 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 354 * when reading a new block into the ARC, we will evict an equal-sized block 355 * from the ARC. 356 * 357 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 358 * we will still not allow it to grow. 359 */ 360int arc_no_grow_shift = 5; 361 362 363/* 364 * minimum lifespan of a prefetch block in clock ticks 365 * (initialized in arc_init()) 366 */ 367static int zfs_arc_min_prefetch_ms = 1; 368static int zfs_arc_min_prescient_prefetch_ms = 6; 369 370/* 371 * If this percent of memory is free, don't throttle. 372 */ 373int arc_lotsfree_percent = 10; 374 375static boolean_t arc_initialized; 376extern boolean_t zfs_prefetch_disable; 377 378/* 379 * The arc has filled available memory and has now warmed up. 380 */ 381static boolean_t arc_warm; 382 383/* 384 * log2 fraction of the zio arena to keep free. 385 */ 386int arc_zio_arena_free_shift = 2; 387 388/* 389 * These tunables are for performance analysis. 390 */ 391uint64_t zfs_arc_max; 392uint64_t zfs_arc_min; 393uint64_t zfs_arc_meta_limit = 0; 394uint64_t zfs_arc_meta_min = 0; 395uint64_t zfs_arc_dnode_limit = 0; 396uint64_t zfs_arc_dnode_reduce_percent = 10; 397int zfs_arc_grow_retry = 0; 398int zfs_arc_shrink_shift = 0; 399int zfs_arc_no_grow_shift = 0; 400int zfs_arc_p_min_shift = 0; 401uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 402u_int zfs_arc_free_target = 0; 403 404/* Absolute min for arc min / max is 16MB. */ 405static uint64_t arc_abs_min = 16 << 20; 406 407/* 408 * ARC dirty data constraints for arc_tempreserve_space() throttle 409 */ 410uint_t zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */ 411uint_t zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */ 412uint_t zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */ 413 414boolean_t zfs_compressed_arc_enabled = B_TRUE; 415 416static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 417static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 418static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 419static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 420static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS); 421 422#if defined(__FreeBSD__) && defined(_KERNEL) 423static void 424arc_free_target_init(void *unused __unused) 425{ 426 427 zfs_arc_free_target = vm_cnt.v_free_target; 428} 429SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 430 arc_free_target_init, NULL); 431 432TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 433TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 434TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 435TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry); 436TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift); 437SYSCTL_DECL(_vfs_zfs); 438SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 439 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 440SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 441 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 442SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN, 443 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U", 444 "log2(fraction of ARC which must be free to allow growing)"); 445SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 446 &zfs_arc_average_blocksize, 0, 447 "ARC average blocksize"); 448SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 449 &arc_shrink_shift, 0, 450 "log2(fraction of arc to reclaim)"); 451SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW, 452 &arc_grow_retry, 0, 453 "Wait in seconds before considering growing ARC"); 454SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 455 &zfs_compressed_arc_enabled, 0, 456 "Enable compressed ARC"); 457SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_kmem_cache_reap_retry_ms, CTLFLAG_RWTUN, 458 &arc_kmem_cache_reap_retry_ms, 0, 459 "Interval between ARC kmem_cache reapings"); 460 461/* 462 * We don't have a tunable for arc_free_target due to the dependency on 463 * pagedaemon initialisation. 464 */ 465SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 466 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 467 sysctl_vfs_zfs_arc_free_target, "IU", 468 "Desired number of free pages below which ARC triggers reclaim"); 469 470static int 471sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 472{ 473 u_int val; 474 int err; 475 476 val = zfs_arc_free_target; 477 err = sysctl_handle_int(oidp, &val, 0, req); 478 if (err != 0 || req->newptr == NULL) 479 return (err); 480 481 if (val < minfree) 482 return (EINVAL); 483 if (val > vm_cnt.v_page_count) 484 return (EINVAL); 485 486 zfs_arc_free_target = val; 487 488 return (0); 489} 490 491/* 492 * Must be declared here, before the definition of corresponding kstat 493 * macro which uses the same names will confuse the compiler. 494 */ 495SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 496 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 497 sysctl_vfs_zfs_arc_meta_limit, "QU", 498 "ARC metadata limit"); 499#endif 500 501/* 502 * Note that buffers can be in one of 6 states: 503 * ARC_anon - anonymous (discussed below) 504 * ARC_mru - recently used, currently cached 505 * ARC_mru_ghost - recentely used, no longer in cache 506 * ARC_mfu - frequently used, currently cached 507 * ARC_mfu_ghost - frequently used, no longer in cache 508 * ARC_l2c_only - exists in L2ARC but not other states 509 * When there are no active references to the buffer, they are 510 * are linked onto a list in one of these arc states. These are 511 * the only buffers that can be evicted or deleted. Within each 512 * state there are multiple lists, one for meta-data and one for 513 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 514 * etc.) is tracked separately so that it can be managed more 515 * explicitly: favored over data, limited explicitly. 516 * 517 * Anonymous buffers are buffers that are not associated with 518 * a DVA. These are buffers that hold dirty block copies 519 * before they are written to stable storage. By definition, 520 * they are "ref'd" and are considered part of arc_mru 521 * that cannot be freed. Generally, they will aquire a DVA 522 * as they are written and migrate onto the arc_mru list. 523 * 524 * The ARC_l2c_only state is for buffers that are in the second 525 * level ARC but no longer in any of the ARC_m* lists. The second 526 * level ARC itself may also contain buffers that are in any of 527 * the ARC_m* states - meaning that a buffer can exist in two 528 * places. The reason for the ARC_l2c_only state is to keep the 529 * buffer header in the hash table, so that reads that hit the 530 * second level ARC benefit from these fast lookups. 531 */ 532 533typedef struct arc_state { 534 /* 535 * list of evictable buffers 536 */ 537 multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; 538 /* 539 * total amount of evictable data in this state 540 */ 541 zfs_refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 542 /* 543 * total amount of data in this state; this includes: evictable, 544 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 545 */ 546 zfs_refcount_t arcs_size; 547 /* 548 * supports the "dbufs" kstat 549 */ 550 arc_state_type_t arcs_state; 551} arc_state_t; 552 553/* 554 * Percentage that can be consumed by dnodes of ARC meta buffers. 555 */ 556int zfs_arc_meta_prune = 10000; 557unsigned long zfs_arc_dnode_limit_percent = 10; 558int zfs_arc_meta_strategy = ARC_STRATEGY_META_ONLY; 559int zfs_arc_meta_adjust_restarts = 4096; 560 561SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_meta_strategy, CTLFLAG_RWTUN, 562 &zfs_arc_meta_strategy, 0, 563 "ARC metadata reclamation strategy " 564 "(0 = metadata only, 1 = balance data and metadata)"); 565 566/* The 6 states: */ 567static arc_state_t ARC_anon; 568static arc_state_t ARC_mru; 569static arc_state_t ARC_mru_ghost; 570static arc_state_t ARC_mfu; 571static arc_state_t ARC_mfu_ghost; 572static arc_state_t ARC_l2c_only; 573 574typedef struct arc_stats { 575 kstat_named_t arcstat_hits; 576 kstat_named_t arcstat_misses; 577 kstat_named_t arcstat_demand_data_hits; 578 kstat_named_t arcstat_demand_data_misses; 579 kstat_named_t arcstat_demand_metadata_hits; 580 kstat_named_t arcstat_demand_metadata_misses; 581 kstat_named_t arcstat_prefetch_data_hits; 582 kstat_named_t arcstat_prefetch_data_misses; 583 kstat_named_t arcstat_prefetch_metadata_hits; 584 kstat_named_t arcstat_prefetch_metadata_misses; 585 kstat_named_t arcstat_mru_hits; 586 kstat_named_t arcstat_mru_ghost_hits; 587 kstat_named_t arcstat_mfu_hits; 588 kstat_named_t arcstat_mfu_ghost_hits; 589 kstat_named_t arcstat_allocated; 590 kstat_named_t arcstat_deleted; 591 /* 592 * Number of buffers that could not be evicted because the hash lock 593 * was held by another thread. The lock may not necessarily be held 594 * by something using the same buffer, since hash locks are shared 595 * by multiple buffers. 596 */ 597 kstat_named_t arcstat_mutex_miss; 598 /* 599 * Number of buffers skipped when updating the access state due to the 600 * header having already been released after acquiring the hash lock. 601 */ 602 kstat_named_t arcstat_access_skip; 603 /* 604 * Number of buffers skipped because they have I/O in progress, are 605 * indirect prefetch buffers that have not lived long enough, or are 606 * not from the spa we're trying to evict from. 607 */ 608 kstat_named_t arcstat_evict_skip; 609 /* 610 * Number of times arc_evict_state() was unable to evict enough 611 * buffers to reach it's target amount. 612 */ 613 kstat_named_t arcstat_evict_not_enough; 614 kstat_named_t arcstat_evict_l2_cached; 615 kstat_named_t arcstat_evict_l2_eligible; 616 kstat_named_t arcstat_evict_l2_ineligible; 617 kstat_named_t arcstat_evict_l2_skip; 618 kstat_named_t arcstat_hash_elements; 619 kstat_named_t arcstat_hash_elements_max; 620 kstat_named_t arcstat_hash_collisions; 621 kstat_named_t arcstat_hash_chains; 622 kstat_named_t arcstat_hash_chain_max; 623 kstat_named_t arcstat_p; 624 kstat_named_t arcstat_c; 625 kstat_named_t arcstat_c_min; 626 kstat_named_t arcstat_c_max; 627 /* Not updated directly; only synced in arc_kstat_update. */ 628 kstat_named_t arcstat_size; 629 /* 630 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. 631 * Note that the compressed bytes may match the uncompressed bytes 632 * if the block is either not compressed or compressed arc is disabled. 633 */ 634 kstat_named_t arcstat_compressed_size; 635 /* 636 * Uncompressed size of the data stored in b_pabd. If compressed 637 * arc is disabled then this value will be identical to the stat 638 * above. 639 */ 640 kstat_named_t arcstat_uncompressed_size; 641 /* 642 * Number of bytes stored in all the arc_buf_t's. This is classified 643 * as "overhead" since this data is typically short-lived and will 644 * be evicted from the arc when it becomes unreferenced unless the 645 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 646 * values have been set (see comment in dbuf.c for more information). 647 */ 648 kstat_named_t arcstat_overhead_size; 649 /* 650 * Number of bytes consumed by internal ARC structures necessary 651 * for tracking purposes; these structures are not actually 652 * backed by ARC buffers. This includes arc_buf_hdr_t structures 653 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 654 * caches), and arc_buf_t structures (allocated via arc_buf_t 655 * cache). 656 * Not updated directly; only synced in arc_kstat_update. 657 */ 658 kstat_named_t arcstat_hdr_size; 659 /* 660 * Number of bytes consumed by ARC buffers of type equal to 661 * ARC_BUFC_DATA. This is generally consumed by buffers backing 662 * on disk user data (e.g. plain file contents). 663 * Not updated directly; only synced in arc_kstat_update. 664 */ 665 kstat_named_t arcstat_data_size; 666 /* 667 * Number of bytes consumed by ARC buffers of type equal to 668 * ARC_BUFC_METADATA. This is generally consumed by buffers 669 * backing on disk data that is used for internal ZFS 670 * structures (e.g. ZAP, dnode, indirect blocks, etc). 671 * Not updated directly; only synced in arc_kstat_update. 672 */ 673 kstat_named_t arcstat_metadata_size; 674 /* 675 * Number of bytes consumed by dmu_buf_impl_t objects. 676 */ 677 kstat_named_t arcstat_dbuf_size; 678 /* 679 * Number of bytes consumed by dnode_t objects. 680 */ 681 kstat_named_t arcstat_dnode_size; 682 /* 683 * Number of bytes consumed by bonus buffers. 684 */ 685 kstat_named_t arcstat_bonus_size; 686#if defined(__FreeBSD__) && defined(COMPAT_FREEBSD11) 687 /* 688 * Sum of the previous three counters, provided for compatibility. 689 */ 690 kstat_named_t arcstat_other_size; 691#endif 692 /* 693 * Total number of bytes consumed by ARC buffers residing in the 694 * arc_anon state. This includes *all* buffers in the arc_anon 695 * state; e.g. data, metadata, evictable, and unevictable buffers 696 * are all included in this value. 697 * Not updated directly; only synced in arc_kstat_update. 698 */ 699 kstat_named_t arcstat_anon_size; 700 /* 701 * Number of bytes consumed by ARC buffers that meet the 702 * following criteria: backing buffers of type ARC_BUFC_DATA, 703 * residing in the arc_anon state, and are eligible for eviction 704 * (e.g. have no outstanding holds on the buffer). 705 * Not updated directly; only synced in arc_kstat_update. 706 */ 707 kstat_named_t arcstat_anon_evictable_data; 708 /* 709 * Number of bytes consumed by ARC buffers that meet the 710 * following criteria: backing buffers of type ARC_BUFC_METADATA, 711 * residing in the arc_anon state, and are eligible for eviction 712 * (e.g. have no outstanding holds on the buffer). 713 * Not updated directly; only synced in arc_kstat_update. 714 */ 715 kstat_named_t arcstat_anon_evictable_metadata; 716 /* 717 * Total number of bytes consumed by ARC buffers residing in the 718 * arc_mru state. This includes *all* buffers in the arc_mru 719 * state; e.g. data, metadata, evictable, and unevictable buffers 720 * are all included in this value. 721 * Not updated directly; only synced in arc_kstat_update. 722 */ 723 kstat_named_t arcstat_mru_size; 724 /* 725 * Number of bytes consumed by ARC buffers that meet the 726 * following criteria: backing buffers of type ARC_BUFC_DATA, 727 * residing in the arc_mru state, and are eligible for eviction 728 * (e.g. have no outstanding holds on the buffer). 729 * Not updated directly; only synced in arc_kstat_update. 730 */ 731 kstat_named_t arcstat_mru_evictable_data; 732 /* 733 * Number of bytes consumed by ARC buffers that meet the 734 * following criteria: backing buffers of type ARC_BUFC_METADATA, 735 * residing in the arc_mru state, and are eligible for eviction 736 * (e.g. have no outstanding holds on the buffer). 737 * Not updated directly; only synced in arc_kstat_update. 738 */ 739 kstat_named_t arcstat_mru_evictable_metadata; 740 /* 741 * Total number of bytes that *would have been* consumed by ARC 742 * buffers in the arc_mru_ghost state. The key thing to note 743 * here, is the fact that this size doesn't actually indicate 744 * RAM consumption. The ghost lists only consist of headers and 745 * don't actually have ARC buffers linked off of these headers. 746 * Thus, *if* the headers had associated ARC buffers, these 747 * buffers *would have* consumed this number of bytes. 748 * Not updated directly; only synced in arc_kstat_update. 749 */ 750 kstat_named_t arcstat_mru_ghost_size; 751 /* 752 * Number of bytes that *would have been* consumed by ARC 753 * buffers that are eligible for eviction, of type 754 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 755 * Not updated directly; only synced in arc_kstat_update. 756 */ 757 kstat_named_t arcstat_mru_ghost_evictable_data; 758 /* 759 * Number of bytes that *would have been* consumed by ARC 760 * buffers that are eligible for eviction, of type 761 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 762 * Not updated directly; only synced in arc_kstat_update. 763 */ 764 kstat_named_t arcstat_mru_ghost_evictable_metadata; 765 /* 766 * Total number of bytes consumed by ARC buffers residing in the 767 * arc_mfu state. This includes *all* buffers in the arc_mfu 768 * state; e.g. data, metadata, evictable, and unevictable buffers 769 * are all included in this value. 770 * Not updated directly; only synced in arc_kstat_update. 771 */ 772 kstat_named_t arcstat_mfu_size; 773 /* 774 * Number of bytes consumed by ARC buffers that are eligible for 775 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 776 * state. 777 * Not updated directly; only synced in arc_kstat_update. 778 */ 779 kstat_named_t arcstat_mfu_evictable_data; 780 /* 781 * Number of bytes consumed by ARC buffers that are eligible for 782 * eviction, of type ARC_BUFC_METADATA, and reside in the 783 * arc_mfu state. 784 * Not updated directly; only synced in arc_kstat_update. 785 */ 786 kstat_named_t arcstat_mfu_evictable_metadata; 787 /* 788 * Total number of bytes that *would have been* consumed by ARC 789 * buffers in the arc_mfu_ghost state. See the comment above 790 * arcstat_mru_ghost_size for more details. 791 * Not updated directly; only synced in arc_kstat_update. 792 */ 793 kstat_named_t arcstat_mfu_ghost_size; 794 /* 795 * Number of bytes that *would have been* consumed by ARC 796 * buffers that are eligible for eviction, of type 797 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 798 * Not updated directly; only synced in arc_kstat_update. 799 */ 800 kstat_named_t arcstat_mfu_ghost_evictable_data; 801 /* 802 * Number of bytes that *would have been* consumed by ARC 803 * buffers that are eligible for eviction, of type 804 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 805 * Not updated directly; only synced in arc_kstat_update. 806 */ 807 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 808 kstat_named_t arcstat_l2_hits; 809 kstat_named_t arcstat_l2_misses; 810 kstat_named_t arcstat_l2_feeds; 811 kstat_named_t arcstat_l2_rw_clash; 812 kstat_named_t arcstat_l2_read_bytes; 813 kstat_named_t arcstat_l2_write_bytes; 814 kstat_named_t arcstat_l2_writes_sent; 815 kstat_named_t arcstat_l2_writes_done; 816 kstat_named_t arcstat_l2_writes_error; 817 kstat_named_t arcstat_l2_writes_lock_retry; 818 kstat_named_t arcstat_l2_evict_lock_retry; 819 kstat_named_t arcstat_l2_evict_reading; 820 kstat_named_t arcstat_l2_evict_l1cached; 821 kstat_named_t arcstat_l2_free_on_write; 822 kstat_named_t arcstat_l2_abort_lowmem; 823 kstat_named_t arcstat_l2_cksum_bad; 824 kstat_named_t arcstat_l2_io_error; 825 kstat_named_t arcstat_l2_lsize; 826 kstat_named_t arcstat_l2_psize; 827 /* Not updated directly; only synced in arc_kstat_update. */ 828 kstat_named_t arcstat_l2_hdr_size; 829 kstat_named_t arcstat_l2_write_trylock_fail; 830 kstat_named_t arcstat_l2_write_passed_headroom; 831 kstat_named_t arcstat_l2_write_spa_mismatch; 832 kstat_named_t arcstat_l2_write_in_l2; 833 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 834 kstat_named_t arcstat_l2_write_not_cacheable; 835 kstat_named_t arcstat_l2_write_full; 836 kstat_named_t arcstat_l2_write_buffer_iter; 837 kstat_named_t arcstat_l2_write_pios; 838 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 839 kstat_named_t arcstat_l2_write_buffer_list_iter; 840 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 841 kstat_named_t arcstat_memory_throttle_count; 842 kstat_named_t arcstat_memory_direct_count; 843 kstat_named_t arcstat_memory_indirect_count; 844 kstat_named_t arcstat_memory_all_bytes; 845 kstat_named_t arcstat_memory_free_bytes; 846 kstat_named_t arcstat_memory_available_bytes; 847 kstat_named_t arcstat_no_grow; 848 kstat_named_t arcstat_tempreserve; 849 kstat_named_t arcstat_loaned_bytes; 850 kstat_named_t arcstat_prune; 851 /* Not updated directly; only synced in arc_kstat_update. */ 852 kstat_named_t arcstat_meta_used; 853 kstat_named_t arcstat_meta_limit; 854 kstat_named_t arcstat_dnode_limit; 855 kstat_named_t arcstat_meta_max; 856 kstat_named_t arcstat_meta_min; 857 kstat_named_t arcstat_async_upgrade_sync; 858 kstat_named_t arcstat_demand_hit_predictive_prefetch; 859 kstat_named_t arcstat_demand_hit_prescient_prefetch; 860} arc_stats_t; 861 862static arc_stats_t arc_stats = { 863 { "hits", KSTAT_DATA_UINT64 }, 864 { "misses", KSTAT_DATA_UINT64 }, 865 { "demand_data_hits", KSTAT_DATA_UINT64 }, 866 { "demand_data_misses", KSTAT_DATA_UINT64 }, 867 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 868 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 869 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 870 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 871 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 872 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 873 { "mru_hits", KSTAT_DATA_UINT64 }, 874 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 875 { "mfu_hits", KSTAT_DATA_UINT64 }, 876 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 877 { "allocated", KSTAT_DATA_UINT64 }, 878 { "deleted", KSTAT_DATA_UINT64 }, 879 { "mutex_miss", KSTAT_DATA_UINT64 }, 880 { "access_skip", KSTAT_DATA_UINT64 }, 881 { "evict_skip", KSTAT_DATA_UINT64 }, 882 { "evict_not_enough", KSTAT_DATA_UINT64 }, 883 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 884 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 885 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 886 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 887 { "hash_elements", KSTAT_DATA_UINT64 }, 888 { "hash_elements_max", KSTAT_DATA_UINT64 }, 889 { "hash_collisions", KSTAT_DATA_UINT64 }, 890 { "hash_chains", KSTAT_DATA_UINT64 }, 891 { "hash_chain_max", KSTAT_DATA_UINT64 }, 892 { "p", KSTAT_DATA_UINT64 }, 893 { "c", KSTAT_DATA_UINT64 }, 894 { "c_min", KSTAT_DATA_UINT64 }, 895 { "c_max", KSTAT_DATA_UINT64 }, 896 { "size", KSTAT_DATA_UINT64 }, 897 { "compressed_size", KSTAT_DATA_UINT64 }, 898 { "uncompressed_size", KSTAT_DATA_UINT64 }, 899 { "overhead_size", KSTAT_DATA_UINT64 }, 900 { "hdr_size", KSTAT_DATA_UINT64 }, 901 { "data_size", KSTAT_DATA_UINT64 }, 902 { "metadata_size", KSTAT_DATA_UINT64 }, 903 { "dbuf_size", KSTAT_DATA_UINT64 }, 904 { "dnode_size", KSTAT_DATA_UINT64 }, 905 { "bonus_size", KSTAT_DATA_UINT64 }, 906#if defined(__FreeBSD__) && defined(COMPAT_FREEBSD11) 907 { "other_size", KSTAT_DATA_UINT64 }, 908#endif 909 { "anon_size", KSTAT_DATA_UINT64 }, 910 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 911 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 912 { "mru_size", KSTAT_DATA_UINT64 }, 913 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 914 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 915 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 916 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 917 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 918 { "mfu_size", KSTAT_DATA_UINT64 }, 919 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 920 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 921 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 922 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 923 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 924 { "l2_hits", KSTAT_DATA_UINT64 }, 925 { "l2_misses", KSTAT_DATA_UINT64 }, 926 { "l2_feeds", KSTAT_DATA_UINT64 }, 927 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 928 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 929 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 930 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 931 { "l2_writes_done", KSTAT_DATA_UINT64 }, 932 { "l2_writes_error", KSTAT_DATA_UINT64 }, 933 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 934 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 935 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 936 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 937 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 938 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 939 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 940 { "l2_io_error", KSTAT_DATA_UINT64 }, 941 { "l2_size", KSTAT_DATA_UINT64 }, 942 { "l2_asize", KSTAT_DATA_UINT64 }, 943 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 944 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 945 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 946 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 947 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 948 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 949 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 950 { "l2_write_full", KSTAT_DATA_UINT64 }, 951 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 952 { "l2_write_pios", KSTAT_DATA_UINT64 }, 953 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 954 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 955 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 956 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 957 { "memory_direct_count", KSTAT_DATA_UINT64 }, 958 { "memory_indirect_count", KSTAT_DATA_UINT64 }, 959 { "memory_all_bytes", KSTAT_DATA_UINT64 }, 960 { "memory_free_bytes", KSTAT_DATA_UINT64 }, 961 { "memory_available_bytes", KSTAT_DATA_UINT64 }, 962 { "arc_no_grow", KSTAT_DATA_UINT64 }, 963 { "arc_tempreserve", KSTAT_DATA_UINT64 }, 964 { "arc_loaned_bytes", KSTAT_DATA_UINT64 }, 965 { "arc_prune", KSTAT_DATA_UINT64 }, 966 { "arc_meta_used", KSTAT_DATA_UINT64 }, 967 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 968 { "arc_dnode_limit", KSTAT_DATA_UINT64 }, 969 { "arc_meta_max", KSTAT_DATA_UINT64 }, 970 { "arc_meta_min", KSTAT_DATA_UINT64 }, 971 { "async_upgrade_sync", KSTAT_DATA_UINT64 }, 972 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 973 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 }, 974}; 975 976#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 977 978#define ARCSTAT_INCR(stat, val) \ 979 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 980 981#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 982#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 983 984#define ARCSTAT_MAX(stat, val) { \ 985 uint64_t m; \ 986 while ((val) > (m = arc_stats.stat.value.ui64) && \ 987 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 988 continue; \ 989} 990 991#define ARCSTAT_MAXSTAT(stat) \ 992 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 993 994/* 995 * We define a macro to allow ARC hits/misses to be easily broken down by 996 * two separate conditions, giving a total of four different subtypes for 997 * each of hits and misses (so eight statistics total). 998 */ 999#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 1000 if (cond1) { \ 1001 if (cond2) { \ 1002 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 1003 } else { \ 1004 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 1005 } \ 1006 } else { \ 1007 if (cond2) { \ 1008 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 1009 } else { \ 1010 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 1011 } \ 1012 } 1013 1014kstat_t *arc_ksp; 1015static arc_state_t *arc_anon; 1016static arc_state_t *arc_mru; 1017static arc_state_t *arc_mru_ghost; 1018static arc_state_t *arc_mfu; 1019static arc_state_t *arc_mfu_ghost; 1020static arc_state_t *arc_l2c_only; 1021 1022/* 1023 * There are several ARC variables that are critical to export as kstats -- 1024 * but we don't want to have to grovel around in the kstat whenever we wish to 1025 * manipulate them. For these variables, we therefore define them to be in 1026 * terms of the statistic variable. This assures that we are not introducing 1027 * the possibility of inconsistency by having shadow copies of the variables, 1028 * while still allowing the code to be readable. 1029 */ 1030#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 1031#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 1032#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 1033#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 1034#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 1035#define arc_dnode_limit ARCSTAT(arcstat_dnode_limit) /* max size for dnodes */ 1036#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 1037#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 1038#define arc_dbuf_size ARCSTAT(arcstat_dbuf_size) /* dbuf metadata */ 1039#define arc_dnode_size ARCSTAT(arcstat_dnode_size) /* dnode metadata */ 1040#define arc_bonus_size ARCSTAT(arcstat_bonus_size) /* bonus buffer metadata */ 1041 1042/* compressed size of entire arc */ 1043#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 1044/* uncompressed size of entire arc */ 1045#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 1046/* number of bytes in the arc from arc_buf_t's */ 1047#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 1048 1049/* 1050 * There are also some ARC variables that we want to export, but that are 1051 * updated so often that having the canonical representation be the statistic 1052 * variable causes a performance bottleneck. We want to use aggsum_t's for these 1053 * instead, but still be able to export the kstat in the same way as before. 1054 * The solution is to always use the aggsum version, except in the kstat update 1055 * callback. 1056 */ 1057aggsum_t arc_size; 1058aggsum_t arc_meta_used; 1059aggsum_t astat_data_size; 1060aggsum_t astat_metadata_size; 1061aggsum_t astat_hdr_size; 1062aggsum_t astat_bonus_size; 1063aggsum_t astat_dnode_size; 1064aggsum_t astat_dbuf_size; 1065aggsum_t astat_l2_hdr_size; 1066 1067static list_t arc_prune_list; 1068static kmutex_t arc_prune_mtx; 1069static taskq_t *arc_prune_taskq; 1070 1071static int arc_no_grow; /* Don't try to grow cache size */ 1072static hrtime_t arc_growtime; 1073static uint64_t arc_tempreserve; 1074static uint64_t arc_loaned_bytes; 1075 1076typedef struct arc_callback arc_callback_t; 1077 1078struct arc_callback { 1079 void *acb_private; 1080 arc_read_done_func_t *acb_done; 1081 arc_buf_t *acb_buf; 1082 boolean_t acb_compressed; 1083 zio_t *acb_zio_dummy; 1084 zio_t *acb_zio_head; 1085 arc_callback_t *acb_next; 1086}; 1087 1088typedef struct arc_write_callback arc_write_callback_t; 1089 1090struct arc_write_callback { 1091 void *awcb_private; 1092 arc_write_done_func_t *awcb_ready; 1093 arc_write_done_func_t *awcb_children_ready; 1094 arc_write_done_func_t *awcb_physdone; 1095 arc_write_done_func_t *awcb_done; 1096 arc_buf_t *awcb_buf; 1097}; 1098 1099/* 1100 * ARC buffers are separated into multiple structs as a memory saving measure: 1101 * - Common fields struct, always defined, and embedded within it: 1102 * - L2-only fields, always allocated but undefined when not in L2ARC 1103 * - L1-only fields, only allocated when in L1ARC 1104 * 1105 * Buffer in L1 Buffer only in L2 1106 * +------------------------+ +------------------------+ 1107 * | arc_buf_hdr_t | | arc_buf_hdr_t | 1108 * | | | | 1109 * | | | | 1110 * | | | | 1111 * +------------------------+ +------------------------+ 1112 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 1113 * | (undefined if L1-only) | | | 1114 * +------------------------+ +------------------------+ 1115 * | l1arc_buf_hdr_t | 1116 * | | 1117 * | | 1118 * | | 1119 * | | 1120 * +------------------------+ 1121 * 1122 * Because it's possible for the L2ARC to become extremely large, we can wind 1123 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 1124 * is minimized by only allocating the fields necessary for an L1-cached buffer 1125 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 1126 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 1127 * words in pointers. arc_hdr_realloc() is used to switch a header between 1128 * these two allocation states. 1129 */ 1130typedef struct l1arc_buf_hdr { 1131 kmutex_t b_freeze_lock; 1132 zio_cksum_t *b_freeze_cksum; 1133#ifdef ZFS_DEBUG 1134 /* 1135 * Used for debugging with kmem_flags - by allocating and freeing 1136 * b_thawed when the buffer is thawed, we get a record of the stack 1137 * trace that thawed it. 1138 */ 1139 void *b_thawed; 1140#endif 1141 1142 arc_buf_t *b_buf; 1143 uint32_t b_bufcnt; 1144 /* for waiting on writes to complete */ 1145 kcondvar_t b_cv; 1146 uint8_t b_byteswap; 1147 1148 /* protected by arc state mutex */ 1149 arc_state_t *b_state; 1150 multilist_node_t b_arc_node; 1151 1152 /* updated atomically */ 1153 clock_t b_arc_access; 1154 uint32_t b_mru_hits; 1155 uint32_t b_mru_ghost_hits; 1156 uint32_t b_mfu_hits; 1157 uint32_t b_mfu_ghost_hits; 1158 uint32_t b_l2_hits; 1159 1160 /* self protecting */ 1161 zfs_refcount_t b_refcnt; 1162 1163 arc_callback_t *b_acb; 1164 abd_t *b_pabd; 1165} l1arc_buf_hdr_t; 1166 1167typedef struct l2arc_dev l2arc_dev_t; 1168 1169typedef struct l2arc_buf_hdr { 1170 /* protected by arc_buf_hdr mutex */ 1171 l2arc_dev_t *b_dev; /* L2ARC device */ 1172 uint64_t b_daddr; /* disk address, offset byte */ 1173 uint32_t b_hits; 1174 1175 list_node_t b_l2node; 1176} l2arc_buf_hdr_t; 1177 1178struct arc_buf_hdr { 1179 /* protected by hash lock */ 1180 dva_t b_dva; 1181 uint64_t b_birth; 1182 1183 arc_buf_contents_t b_type; 1184 arc_buf_hdr_t *b_hash_next; 1185 arc_flags_t b_flags; 1186 1187 /* 1188 * This field stores the size of the data buffer after 1189 * compression, and is set in the arc's zio completion handlers. 1190 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1191 * 1192 * While the block pointers can store up to 32MB in their psize 1193 * field, we can only store up to 32MB minus 512B. This is due 1194 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1195 * a field of zeros represents 512B in the bp). We can't use a 1196 * bias of 1 since we need to reserve a psize of zero, here, to 1197 * represent holes and embedded blocks. 1198 * 1199 * This isn't a problem in practice, since the maximum size of a 1200 * buffer is limited to 16MB, so we never need to store 32MB in 1201 * this field. Even in the upstream illumos code base, the 1202 * maximum size of a buffer is limited to 16MB. 1203 */ 1204 uint16_t b_psize; 1205 1206 /* 1207 * This field stores the size of the data buffer before 1208 * compression, and cannot change once set. It is in units 1209 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1210 */ 1211 uint16_t b_lsize; /* immutable */ 1212 uint64_t b_spa; /* immutable */ 1213 1214 /* L2ARC fields. Undefined when not in L2ARC. */ 1215 l2arc_buf_hdr_t b_l2hdr; 1216 /* L1ARC fields. Undefined when in l2arc_only state */ 1217 l1arc_buf_hdr_t b_l1hdr; 1218}; 1219 1220#if defined(__FreeBSD__) && defined(_KERNEL) 1221static int 1222sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1223{ 1224 uint64_t val; 1225 int err; 1226 1227 val = arc_meta_limit; 1228 err = sysctl_handle_64(oidp, &val, 0, req); 1229 if (err != 0 || req->newptr == NULL) 1230 return (err); 1231 1232 if (val <= 0 || val > arc_c_max) 1233 return (EINVAL); 1234 1235 arc_meta_limit = val; 1236 1237 mutex_enter(&arc_adjust_lock); 1238 arc_adjust_needed = B_TRUE; 1239 mutex_exit(&arc_adjust_lock); 1240 zthr_wakeup(arc_adjust_zthr); 1241 1242 return (0); 1243} 1244 1245static int 1246sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS) 1247{ 1248 uint32_t val; 1249 int err; 1250 1251 val = arc_no_grow_shift; 1252 err = sysctl_handle_32(oidp, &val, 0, req); 1253 if (err != 0 || req->newptr == NULL) 1254 return (err); 1255 1256 if (val >= arc_shrink_shift) 1257 return (EINVAL); 1258 1259 arc_no_grow_shift = val; 1260 return (0); 1261} 1262 1263static int 1264sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1265{ 1266 uint64_t val; 1267 int err; 1268 1269 val = zfs_arc_max; 1270 err = sysctl_handle_64(oidp, &val, 0, req); 1271 if (err != 0 || req->newptr == NULL) 1272 return (err); 1273 1274 if (zfs_arc_max == 0) { 1275 /* Loader tunable so blindly set */ 1276 zfs_arc_max = val; 1277 return (0); 1278 } 1279 1280 if (val < arc_abs_min || val > kmem_size()) 1281 return (EINVAL); 1282 if (val < arc_c_min) 1283 return (EINVAL); 1284 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1285 return (EINVAL); 1286 1287 arc_c_max = val; 1288 1289 arc_c = arc_c_max; 1290 arc_p = (arc_c >> 1); 1291 1292 if (zfs_arc_meta_limit == 0) { 1293 /* limit meta-data to 1/4 of the arc capacity */ 1294 arc_meta_limit = arc_c_max / 4; 1295 } 1296 1297 /* if kmem_flags are set, lets try to use less memory */ 1298 if (kmem_debugging()) 1299 arc_c = arc_c / 2; 1300 1301 zfs_arc_max = arc_c; 1302 1303 mutex_enter(&arc_adjust_lock); 1304 arc_adjust_needed = B_TRUE; 1305 mutex_exit(&arc_adjust_lock); 1306 zthr_wakeup(arc_adjust_zthr); 1307 1308 return (0); 1309} 1310 1311static int 1312sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1313{ 1314 uint64_t val; 1315 int err; 1316 1317 val = zfs_arc_min; 1318 err = sysctl_handle_64(oidp, &val, 0, req); 1319 if (err != 0 || req->newptr == NULL) 1320 return (err); 1321 1322 if (zfs_arc_min == 0) { 1323 /* Loader tunable so blindly set */ 1324 zfs_arc_min = val; 1325 return (0); 1326 } 1327 1328 if (val < arc_abs_min || val > arc_c_max) 1329 return (EINVAL); 1330 1331 arc_c_min = val; 1332 1333 if (zfs_arc_meta_min == 0) 1334 arc_meta_min = arc_c_min / 2; 1335 1336 if (arc_c < arc_c_min) 1337 arc_c = arc_c_min; 1338 1339 zfs_arc_min = arc_c_min; 1340 1341 return (0); 1342} 1343#endif 1344 1345#define GHOST_STATE(state) \ 1346 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1347 (state) == arc_l2c_only) 1348 1349#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1350#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1351#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1352#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1353#define HDR_PRESCIENT_PREFETCH(hdr) \ 1354 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) 1355#define HDR_COMPRESSION_ENABLED(hdr) \ 1356 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1357 1358#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1359#define HDR_L2_READING(hdr) \ 1360 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1361 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1362#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1363#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1364#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1365#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1366 1367#define HDR_ISTYPE_METADATA(hdr) \ 1368 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1369#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1370 1371#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1372#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1373 1374/* For storing compression mode in b_flags */ 1375#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1376 1377#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1378 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1379#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1380 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1381 1382#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1383#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) 1384#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) 1385 1386/* 1387 * Other sizes 1388 */ 1389 1390#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1391#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1392 1393/* 1394 * Hash table routines 1395 */ 1396 1397#define HT_LOCK_PAD CACHE_LINE_SIZE 1398 1399struct ht_lock { 1400 kmutex_t ht_lock; 1401#ifdef _KERNEL 1402 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1403#endif 1404}; 1405 1406#define BUF_LOCKS 256 1407typedef struct buf_hash_table { 1408 uint64_t ht_mask; 1409 arc_buf_hdr_t **ht_table; 1410 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1411} buf_hash_table_t; 1412 1413static buf_hash_table_t buf_hash_table; 1414 1415#define BUF_HASH_INDEX(spa, dva, birth) \ 1416 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1417#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1418#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1419#define HDR_LOCK(hdr) \ 1420 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1421 1422uint64_t zfs_crc64_table[256]; 1423 1424/* 1425 * Level 2 ARC 1426 */ 1427 1428#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1429#define L2ARC_HEADROOM 2 /* num of writes */ 1430/* 1431 * If we discover during ARC scan any buffers to be compressed, we boost 1432 * our headroom for the next scanning cycle by this percentage multiple. 1433 */ 1434#define L2ARC_HEADROOM_BOOST 200 1435#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1436#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1437 1438#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1439#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1440 1441/* L2ARC Performance Tunables */ 1442uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1443uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1444uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1445uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1446uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1447uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1448boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1449boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1450boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1451 1452SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RWTUN, 1453 &l2arc_write_max, 0, "max write size"); 1454SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RWTUN, 1455 &l2arc_write_boost, 0, "extra write during warmup"); 1456SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RWTUN, 1457 &l2arc_headroom, 0, "number of dev writes"); 1458SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RWTUN, 1459 &l2arc_feed_secs, 0, "interval seconds"); 1460SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RWTUN, 1461 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1462 1463SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RWTUN, 1464 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1465SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RWTUN, 1466 &l2arc_feed_again, 0, "turbo warmup"); 1467SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RWTUN, 1468 &l2arc_norw, 0, "no reads during writes"); 1469 1470SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1471 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1472SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1473 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1474 "size of anonymous state"); 1475SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1476 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1477 "size of anonymous state"); 1478 1479SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1480 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1481SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1482 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1483 "size of metadata in mru state"); 1484SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1485 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1486 "size of data in mru state"); 1487 1488SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1489 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1490SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1491 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1492 "size of metadata in mru ghost state"); 1493SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1494 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1495 "size of data in mru ghost state"); 1496 1497SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1498 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1499SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1500 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1501 "size of metadata in mfu state"); 1502SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1503 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1504 "size of data in mfu state"); 1505 1506SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1507 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1508SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1509 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1510 "size of metadata in mfu ghost state"); 1511SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1512 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1513 "size of data in mfu ghost state"); 1514 1515SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1516 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1517 1518SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prefetch_ms, CTLFLAG_RW, 1519 &zfs_arc_min_prefetch_ms, 0, "Min life of prefetch block in ms"); 1520SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prescient_prefetch_ms, CTLFLAG_RW, 1521 &zfs_arc_min_prescient_prefetch_ms, 0, "Min life of prescient prefetched block in ms"); 1522 1523/* 1524 * L2ARC Internals 1525 */ 1526struct l2arc_dev { 1527 vdev_t *l2ad_vdev; /* vdev */ 1528 spa_t *l2ad_spa; /* spa */ 1529 uint64_t l2ad_hand; /* next write location */ 1530 uint64_t l2ad_start; /* first addr on device */ 1531 uint64_t l2ad_end; /* last addr on device */ 1532 boolean_t l2ad_first; /* first sweep through */ 1533 boolean_t l2ad_writing; /* currently writing */ 1534 kmutex_t l2ad_mtx; /* lock for buffer list */ 1535 list_t l2ad_buflist; /* buffer list */ 1536 list_node_t l2ad_node; /* device list node */ 1537 zfs_refcount_t l2ad_alloc; /* allocated bytes */ 1538}; 1539 1540static list_t L2ARC_dev_list; /* device list */ 1541static list_t *l2arc_dev_list; /* device list pointer */ 1542static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1543static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1544static list_t L2ARC_free_on_write; /* free after write buf list */ 1545static list_t *l2arc_free_on_write; /* free after write list ptr */ 1546static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1547static uint64_t l2arc_ndev; /* number of devices */ 1548 1549typedef struct l2arc_read_callback { 1550 arc_buf_hdr_t *l2rcb_hdr; /* read header */ 1551 blkptr_t l2rcb_bp; /* original blkptr */ 1552 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1553 int l2rcb_flags; /* original flags */ 1554 abd_t *l2rcb_abd; /* temporary buffer */ 1555} l2arc_read_callback_t; 1556 1557typedef struct l2arc_write_callback { 1558 l2arc_dev_t *l2wcb_dev; /* device info */ 1559 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1560} l2arc_write_callback_t; 1561 1562typedef struct l2arc_data_free { 1563 /* protected by l2arc_free_on_write_mtx */ 1564 abd_t *l2df_abd; 1565 size_t l2df_size; 1566 arc_buf_contents_t l2df_type; 1567 list_node_t l2df_list_node; 1568} l2arc_data_free_t; 1569 1570static kmutex_t l2arc_feed_thr_lock; 1571static kcondvar_t l2arc_feed_thr_cv; 1572static uint8_t l2arc_thread_exit; 1573 1574static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *, boolean_t); 1575static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1576static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *, boolean_t); 1577static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); 1578static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1579static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); 1580static void arc_hdr_free_pabd(arc_buf_hdr_t *); 1581static void arc_hdr_alloc_pabd(arc_buf_hdr_t *, boolean_t); 1582static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1583static boolean_t arc_is_overflowing(); 1584static void arc_buf_watch(arc_buf_t *); 1585static void arc_prune_async(int64_t); 1586 1587static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1588static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1589static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1590static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1591 1592static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1593static void l2arc_read_done(zio_t *); 1594 1595static void 1596l2arc_trim(const arc_buf_hdr_t *hdr) 1597{ 1598 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1599 1600 ASSERT(HDR_HAS_L2HDR(hdr)); 1601 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1602 1603 if (HDR_GET_PSIZE(hdr) != 0) { 1604 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1605 HDR_GET_PSIZE(hdr), 0); 1606 } 1607} 1608 1609/* 1610 * We use Cityhash for this. It's fast, and has good hash properties without 1611 * requiring any large static buffers. 1612 */ 1613static uint64_t 1614buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1615{ 1616 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth)); 1617} 1618 1619#define HDR_EMPTY(hdr) \ 1620 ((hdr)->b_dva.dva_word[0] == 0 && \ 1621 (hdr)->b_dva.dva_word[1] == 0) 1622 1623#define HDR_EQUAL(spa, dva, birth, hdr) \ 1624 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1625 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1626 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1627 1628static void 1629buf_discard_identity(arc_buf_hdr_t *hdr) 1630{ 1631 hdr->b_dva.dva_word[0] = 0; 1632 hdr->b_dva.dva_word[1] = 0; 1633 hdr->b_birth = 0; 1634} 1635 1636static arc_buf_hdr_t * 1637buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1638{ 1639 const dva_t *dva = BP_IDENTITY(bp); 1640 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1641 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1642 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1643 arc_buf_hdr_t *hdr; 1644 1645 mutex_enter(hash_lock); 1646 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1647 hdr = hdr->b_hash_next) { 1648 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1649 *lockp = hash_lock; 1650 return (hdr); 1651 } 1652 } 1653 mutex_exit(hash_lock); 1654 *lockp = NULL; 1655 return (NULL); 1656} 1657 1658/* 1659 * Insert an entry into the hash table. If there is already an element 1660 * equal to elem in the hash table, then the already existing element 1661 * will be returned and the new element will not be inserted. 1662 * Otherwise returns NULL. 1663 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1664 */ 1665static arc_buf_hdr_t * 1666buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1667{ 1668 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1669 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1670 arc_buf_hdr_t *fhdr; 1671 uint32_t i; 1672 1673 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1674 ASSERT(hdr->b_birth != 0); 1675 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1676 1677 if (lockp != NULL) { 1678 *lockp = hash_lock; 1679 mutex_enter(hash_lock); 1680 } else { 1681 ASSERT(MUTEX_HELD(hash_lock)); 1682 } 1683 1684 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1685 fhdr = fhdr->b_hash_next, i++) { 1686 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1687 return (fhdr); 1688 } 1689 1690 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1691 buf_hash_table.ht_table[idx] = hdr; 1692 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1693 1694 /* collect some hash table performance data */ 1695 if (i > 0) { 1696 ARCSTAT_BUMP(arcstat_hash_collisions); 1697 if (i == 1) 1698 ARCSTAT_BUMP(arcstat_hash_chains); 1699 1700 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1701 } 1702 1703 ARCSTAT_BUMP(arcstat_hash_elements); 1704 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1705 1706 return (NULL); 1707} 1708 1709static void 1710buf_hash_remove(arc_buf_hdr_t *hdr) 1711{ 1712 arc_buf_hdr_t *fhdr, **hdrp; 1713 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1714 1715 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1716 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1717 1718 hdrp = &buf_hash_table.ht_table[idx]; 1719 while ((fhdr = *hdrp) != hdr) { 1720 ASSERT3P(fhdr, !=, NULL); 1721 hdrp = &fhdr->b_hash_next; 1722 } 1723 *hdrp = hdr->b_hash_next; 1724 hdr->b_hash_next = NULL; 1725 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1726 1727 /* collect some hash table performance data */ 1728 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1729 1730 if (buf_hash_table.ht_table[idx] && 1731 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1732 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1733} 1734 1735/* 1736 * Global data structures and functions for the buf kmem cache. 1737 */ 1738static kmem_cache_t *hdr_full_cache; 1739static kmem_cache_t *hdr_l2only_cache; 1740static kmem_cache_t *buf_cache; 1741 1742static void 1743buf_fini(void) 1744{ 1745 int i; 1746 1747 kmem_free(buf_hash_table.ht_table, 1748 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1749 for (i = 0; i < BUF_LOCKS; i++) 1750 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1751 kmem_cache_destroy(hdr_full_cache); 1752 kmem_cache_destroy(hdr_l2only_cache); 1753 kmem_cache_destroy(buf_cache); 1754} 1755 1756/* 1757 * Constructor callback - called when the cache is empty 1758 * and a new buf is requested. 1759 */ 1760/* ARGSUSED */ 1761static int 1762hdr_full_cons(void *vbuf, void *unused, int kmflag) 1763{ 1764 arc_buf_hdr_t *hdr = vbuf; 1765 1766 bzero(hdr, HDR_FULL_SIZE); 1767 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1768 zfs_refcount_create(&hdr->b_l1hdr.b_refcnt); 1769 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1770 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1771 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1772 1773 return (0); 1774} 1775 1776/* ARGSUSED */ 1777static int 1778hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1779{ 1780 arc_buf_hdr_t *hdr = vbuf; 1781 1782 bzero(hdr, HDR_L2ONLY_SIZE); 1783 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1784 1785 return (0); 1786} 1787 1788/* ARGSUSED */ 1789static int 1790buf_cons(void *vbuf, void *unused, int kmflag) 1791{ 1792 arc_buf_t *buf = vbuf; 1793 1794 bzero(buf, sizeof (arc_buf_t)); 1795 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1796 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1797 1798 return (0); 1799} 1800 1801/* 1802 * Destructor callback - called when a cached buf is 1803 * no longer required. 1804 */ 1805/* ARGSUSED */ 1806static void 1807hdr_full_dest(void *vbuf, void *unused) 1808{ 1809 arc_buf_hdr_t *hdr = vbuf; 1810 1811 ASSERT(HDR_EMPTY(hdr)); 1812 cv_destroy(&hdr->b_l1hdr.b_cv); 1813 zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1814 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1815 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1816 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1817} 1818 1819/* ARGSUSED */ 1820static void 1821hdr_l2only_dest(void *vbuf, void *unused) 1822{ 1823 arc_buf_hdr_t *hdr = vbuf; 1824 1825 ASSERT(HDR_EMPTY(hdr)); 1826 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1827} 1828 1829/* ARGSUSED */ 1830static void 1831buf_dest(void *vbuf, void *unused) 1832{ 1833 arc_buf_t *buf = vbuf; 1834 1835 mutex_destroy(&buf->b_evict_lock); 1836 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1837} 1838 1839/* 1840 * Reclaim callback -- invoked when memory is low. 1841 */ 1842/* ARGSUSED */ 1843static void 1844hdr_recl(void *unused) 1845{ 1846 dprintf("hdr_recl called\n"); 1847 /* 1848 * umem calls the reclaim func when we destroy the buf cache, 1849 * which is after we do arc_fini(). 1850 */ 1851 if (arc_initialized) 1852 zthr_wakeup(arc_reap_zthr); 1853} 1854 1855static void 1856buf_init(void) 1857{ 1858 uint64_t *ct; 1859 uint64_t hsize = 1ULL << 12; 1860 int i, j; 1861 1862 /* 1863 * The hash table is big enough to fill all of physical memory 1864 * with an average block size of zfs_arc_average_blocksize (default 8K). 1865 * By default, the table will take up 1866 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1867 */ 1868 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1869 hsize <<= 1; 1870retry: 1871 buf_hash_table.ht_mask = hsize - 1; 1872 buf_hash_table.ht_table = 1873 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1874 if (buf_hash_table.ht_table == NULL) { 1875 ASSERT(hsize > (1ULL << 8)); 1876 hsize >>= 1; 1877 goto retry; 1878 } 1879 1880 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1881 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1882 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1883 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1884 NULL, NULL, 0); 1885 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1886 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1887 1888 for (i = 0; i < 256; i++) 1889 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1890 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1891 1892 for (i = 0; i < BUF_LOCKS; i++) { 1893 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1894 NULL, MUTEX_DEFAULT, NULL); 1895 } 1896} 1897 1898/* 1899 * This is the size that the buf occupies in memory. If the buf is compressed, 1900 * it will correspond to the compressed size. You should use this method of 1901 * getting the buf size unless you explicitly need the logical size. 1902 */ 1903int32_t 1904arc_buf_size(arc_buf_t *buf) 1905{ 1906 return (ARC_BUF_COMPRESSED(buf) ? 1907 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); 1908} 1909 1910int32_t 1911arc_buf_lsize(arc_buf_t *buf) 1912{ 1913 return (HDR_GET_LSIZE(buf->b_hdr)); 1914} 1915 1916enum zio_compress 1917arc_get_compression(arc_buf_t *buf) 1918{ 1919 return (ARC_BUF_COMPRESSED(buf) ? 1920 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); 1921} 1922 1923#define ARC_MINTIME (hz>>4) /* 62 ms */ 1924 1925static inline boolean_t 1926arc_buf_is_shared(arc_buf_t *buf) 1927{ 1928 boolean_t shared = (buf->b_data != NULL && 1929 buf->b_hdr->b_l1hdr.b_pabd != NULL && 1930 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && 1931 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); 1932 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1933 IMPLY(shared, ARC_BUF_SHARED(buf)); 1934 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); 1935 1936 /* 1937 * It would be nice to assert arc_can_share() too, but the "hdr isn't 1938 * already being shared" requirement prevents us from doing that. 1939 */ 1940 1941 return (shared); 1942} 1943 1944/* 1945 * Free the checksum associated with this header. If there is no checksum, this 1946 * is a no-op. 1947 */ 1948static inline void 1949arc_cksum_free(arc_buf_hdr_t *hdr) 1950{ 1951 ASSERT(HDR_HAS_L1HDR(hdr)); 1952 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1953 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1954 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1955 hdr->b_l1hdr.b_freeze_cksum = NULL; 1956 } 1957 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1958} 1959 1960/* 1961 * Return true iff at least one of the bufs on hdr is not compressed. 1962 */ 1963static boolean_t 1964arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) 1965{ 1966 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { 1967 if (!ARC_BUF_COMPRESSED(b)) { 1968 return (B_TRUE); 1969 } 1970 } 1971 return (B_FALSE); 1972} 1973 1974/* 1975 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data 1976 * matches the checksum that is stored in the hdr. If there is no checksum, 1977 * or if the buf is compressed, this is a no-op. 1978 */ 1979static void 1980arc_cksum_verify(arc_buf_t *buf) 1981{ 1982 arc_buf_hdr_t *hdr = buf->b_hdr; 1983 zio_cksum_t zc; 1984 1985 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1986 return; 1987 1988 if (ARC_BUF_COMPRESSED(buf)) { 1989 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 1990 arc_hdr_has_uncompressed_buf(hdr)); 1991 return; 1992 } 1993 1994 ASSERT(HDR_HAS_L1HDR(hdr)); 1995 1996 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1997 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1998 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1999 return; 2000 } 2001 2002 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); 2003 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 2004 panic("buffer modified while frozen!"); 2005 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2006} 2007 2008static boolean_t 2009arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 2010{ 2011 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 2012 boolean_t valid_cksum; 2013 2014 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 2015 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 2016 2017 /* 2018 * We rely on the blkptr's checksum to determine if the block 2019 * is valid or not. When compressed arc is enabled, the l2arc 2020 * writes the block to the l2arc just as it appears in the pool. 2021 * This allows us to use the blkptr's checksum to validate the 2022 * data that we just read off of the l2arc without having to store 2023 * a separate checksum in the arc_buf_hdr_t. However, if compressed 2024 * arc is disabled, then the data written to the l2arc is always 2025 * uncompressed and won't match the block as it exists in the main 2026 * pool. When this is the case, we must first compress it if it is 2027 * compressed on the main pool before we can validate the checksum. 2028 */ 2029 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 2030 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2031 uint64_t lsize = HDR_GET_LSIZE(hdr); 2032 uint64_t csize; 2033 2034 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE); 2035 csize = zio_compress_data(compress, zio->io_abd, 2036 abd_to_buf(cdata), lsize); 2037 2038 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 2039 if (csize < HDR_GET_PSIZE(hdr)) { 2040 /* 2041 * Compressed blocks are always a multiple of the 2042 * smallest ashift in the pool. Ideally, we would 2043 * like to round up the csize to the next 2044 * spa_min_ashift but that value may have changed 2045 * since the block was last written. Instead, 2046 * we rely on the fact that the hdr's psize 2047 * was set to the psize of the block when it was 2048 * last written. We set the csize to that value 2049 * and zero out any part that should not contain 2050 * data. 2051 */ 2052 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize); 2053 csize = HDR_GET_PSIZE(hdr); 2054 } 2055 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL); 2056 } 2057 2058 /* 2059 * Block pointers always store the checksum for the logical data. 2060 * If the block pointer has the gang bit set, then the checksum 2061 * it represents is for the reconstituted data and not for an 2062 * individual gang member. The zio pipeline, however, must be able to 2063 * determine the checksum of each of the gang constituents so it 2064 * treats the checksum comparison differently than what we need 2065 * for l2arc blocks. This prevents us from using the 2066 * zio_checksum_error() interface directly. Instead we must call the 2067 * zio_checksum_error_impl() so that we can ensure the checksum is 2068 * generated using the correct checksum algorithm and accounts for the 2069 * logical I/O size and not just a gang fragment. 2070 */ 2071 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 2072 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, 2073 zio->io_offset, NULL) == 0); 2074 zio_pop_transforms(zio); 2075 return (valid_cksum); 2076} 2077 2078/* 2079 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a 2080 * checksum and attaches it to the buf's hdr so that we can ensure that the buf 2081 * isn't modified later on. If buf is compressed or there is already a checksum 2082 * on the hdr, this is a no-op (we only checksum uncompressed bufs). 2083 */ 2084static void 2085arc_cksum_compute(arc_buf_t *buf) 2086{ 2087 arc_buf_hdr_t *hdr = buf->b_hdr; 2088 2089 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2090 return; 2091 2092 ASSERT(HDR_HAS_L1HDR(hdr)); 2093 2094 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 2095 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 2096 ASSERT(arc_hdr_has_uncompressed_buf(hdr)); 2097 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2098 return; 2099 } else if (ARC_BUF_COMPRESSED(buf)) { 2100 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2101 return; 2102 } 2103 2104 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2105 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 2106 KM_SLEEP); 2107 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, 2108 hdr->b_l1hdr.b_freeze_cksum); 2109 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2110#ifdef illumos 2111 arc_buf_watch(buf); 2112#endif 2113} 2114 2115#ifdef illumos 2116#ifndef _KERNEL 2117typedef struct procctl { 2118 long cmd; 2119 prwatch_t prwatch; 2120} procctl_t; 2121#endif 2122 2123/* ARGSUSED */ 2124static void 2125arc_buf_unwatch(arc_buf_t *buf) 2126{ 2127#ifndef _KERNEL 2128 if (arc_watch) { 2129 int result; 2130 procctl_t ctl; 2131 ctl.cmd = PCWATCH; 2132 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 2133 ctl.prwatch.pr_size = 0; 2134 ctl.prwatch.pr_wflags = 0; 2135 result = write(arc_procfd, &ctl, sizeof (ctl)); 2136 ASSERT3U(result, ==, sizeof (ctl)); 2137 } 2138#endif 2139} 2140 2141/* ARGSUSED */ 2142static void 2143arc_buf_watch(arc_buf_t *buf) 2144{ 2145#ifndef _KERNEL 2146 if (arc_watch) { 2147 int result; 2148 procctl_t ctl; 2149 ctl.cmd = PCWATCH; 2150 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 2151 ctl.prwatch.pr_size = arc_buf_size(buf); 2152 ctl.prwatch.pr_wflags = WA_WRITE; 2153 result = write(arc_procfd, &ctl, sizeof (ctl)); 2154 ASSERT3U(result, ==, sizeof (ctl)); 2155 } 2156#endif 2157} 2158#endif /* illumos */ 2159 2160static arc_buf_contents_t 2161arc_buf_type(arc_buf_hdr_t *hdr) 2162{ 2163 arc_buf_contents_t type; 2164 if (HDR_ISTYPE_METADATA(hdr)) { 2165 type = ARC_BUFC_METADATA; 2166 } else { 2167 type = ARC_BUFC_DATA; 2168 } 2169 VERIFY3U(hdr->b_type, ==, type); 2170 return (type); 2171} 2172 2173boolean_t 2174arc_is_metadata(arc_buf_t *buf) 2175{ 2176 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); 2177} 2178 2179static uint32_t 2180arc_bufc_to_flags(arc_buf_contents_t type) 2181{ 2182 switch (type) { 2183 case ARC_BUFC_DATA: 2184 /* metadata field is 0 if buffer contains normal data */ 2185 return (0); 2186 case ARC_BUFC_METADATA: 2187 return (ARC_FLAG_BUFC_METADATA); 2188 default: 2189 break; 2190 } 2191 panic("undefined ARC buffer type!"); 2192 return ((uint32_t)-1); 2193} 2194 2195void 2196arc_buf_thaw(arc_buf_t *buf) 2197{ 2198 arc_buf_hdr_t *hdr = buf->b_hdr; 2199 2200 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2201 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2202 2203 arc_cksum_verify(buf); 2204 2205 /* 2206 * Compressed buffers do not manipulate the b_freeze_cksum or 2207 * allocate b_thawed. 2208 */ 2209 if (ARC_BUF_COMPRESSED(buf)) { 2210 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2211 arc_hdr_has_uncompressed_buf(hdr)); 2212 return; 2213 } 2214 2215 ASSERT(HDR_HAS_L1HDR(hdr)); 2216 arc_cksum_free(hdr); 2217 2218 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 2219#ifdef ZFS_DEBUG 2220 if (zfs_flags & ZFS_DEBUG_MODIFY) { 2221 if (hdr->b_l1hdr.b_thawed != NULL) 2222 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2223 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 2224 } 2225#endif 2226 2227 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2228 2229#ifdef illumos 2230 arc_buf_unwatch(buf); 2231#endif 2232} 2233 2234void 2235arc_buf_freeze(arc_buf_t *buf) 2236{ 2237 arc_buf_hdr_t *hdr = buf->b_hdr; 2238 kmutex_t *hash_lock; 2239 2240 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2241 return; 2242 2243 if (ARC_BUF_COMPRESSED(buf)) { 2244 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2245 arc_hdr_has_uncompressed_buf(hdr)); 2246 return; 2247 } 2248 2249 hash_lock = HDR_LOCK(hdr); 2250 mutex_enter(hash_lock); 2251 2252 ASSERT(HDR_HAS_L1HDR(hdr)); 2253 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 2254 hdr->b_l1hdr.b_state == arc_anon); 2255 arc_cksum_compute(buf); 2256 mutex_exit(hash_lock); 2257} 2258 2259/* 2260 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 2261 * the following functions should be used to ensure that the flags are 2262 * updated in a thread-safe way. When manipulating the flags either 2263 * the hash_lock must be held or the hdr must be undiscoverable. This 2264 * ensures that we're not racing with any other threads when updating 2265 * the flags. 2266 */ 2267static inline void 2268arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2269{ 2270 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2271 hdr->b_flags |= flags; 2272} 2273 2274static inline void 2275arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2276{ 2277 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2278 hdr->b_flags &= ~flags; 2279} 2280 2281/* 2282 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 2283 * done in a special way since we have to clear and set bits 2284 * at the same time. Consumers that wish to set the compression bits 2285 * must use this function to ensure that the flags are updated in 2286 * thread-safe manner. 2287 */ 2288static void 2289arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 2290{ 2291 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2292 2293 /* 2294 * Holes and embedded blocks will always have a psize = 0 so 2295 * we ignore the compression of the blkptr and set the 2296 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 2297 * Holes and embedded blocks remain anonymous so we don't 2298 * want to uncompress them. Mark them as uncompressed. 2299 */ 2300 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 2301 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2302 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 2303 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 2304 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2305 } else { 2306 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2307 HDR_SET_COMPRESS(hdr, cmp); 2308 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2309 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2310 } 2311} 2312 2313/* 2314 * Looks for another buf on the same hdr which has the data decompressed, copies 2315 * from it, and returns true. If no such buf exists, returns false. 2316 */ 2317static boolean_t 2318arc_buf_try_copy_decompressed_data(arc_buf_t *buf) 2319{ 2320 arc_buf_hdr_t *hdr = buf->b_hdr; 2321 boolean_t copied = B_FALSE; 2322 2323 ASSERT(HDR_HAS_L1HDR(hdr)); 2324 ASSERT3P(buf->b_data, !=, NULL); 2325 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2326 2327 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; 2328 from = from->b_next) { 2329 /* can't use our own data buffer */ 2330 if (from == buf) { 2331 continue; 2332 } 2333 2334 if (!ARC_BUF_COMPRESSED(from)) { 2335 bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); 2336 copied = B_TRUE; 2337 break; 2338 } 2339 } 2340 2341 /* 2342 * There were no decompressed bufs, so there should not be a 2343 * checksum on the hdr either. 2344 */ 2345 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); 2346 2347 return (copied); 2348} 2349 2350/* 2351 * Given a buf that has a data buffer attached to it, this function will 2352 * efficiently fill the buf with data of the specified compression setting from 2353 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr 2354 * are already sharing a data buf, no copy is performed. 2355 * 2356 * If the buf is marked as compressed but uncompressed data was requested, this 2357 * will allocate a new data buffer for the buf, remove that flag, and fill the 2358 * buf with uncompressed data. You can't request a compressed buf on a hdr with 2359 * uncompressed data, and (since we haven't added support for it yet) if you 2360 * want compressed data your buf must already be marked as compressed and have 2361 * the correct-sized data buffer. 2362 */ 2363static int 2364arc_buf_fill(arc_buf_t *buf, boolean_t compressed) 2365{ 2366 arc_buf_hdr_t *hdr = buf->b_hdr; 2367 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 2368 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2369 2370 ASSERT3P(buf->b_data, !=, NULL); 2371 IMPLY(compressed, hdr_compressed); 2372 IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); 2373 2374 if (hdr_compressed == compressed) { 2375 if (!arc_buf_is_shared(buf)) { 2376 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, 2377 arc_buf_size(buf)); 2378 } 2379 } else { 2380 ASSERT(hdr_compressed); 2381 ASSERT(!compressed); 2382 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2383 2384 /* 2385 * If the buf is sharing its data with the hdr, unlink it and 2386 * allocate a new data buffer for the buf. 2387 */ 2388 if (arc_buf_is_shared(buf)) { 2389 ASSERT(ARC_BUF_COMPRESSED(buf)); 2390 2391 /* We need to give the buf it's own b_data */ 2392 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2393 buf->b_data = 2394 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2395 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2396 2397 /* Previously overhead was 0; just add new overhead */ 2398 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2399 } else if (ARC_BUF_COMPRESSED(buf)) { 2400 /* We need to reallocate the buf's b_data */ 2401 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), 2402 buf); 2403 buf->b_data = 2404 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2405 2406 /* We increased the size of b_data; update overhead */ 2407 ARCSTAT_INCR(arcstat_overhead_size, 2408 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); 2409 } 2410 2411 /* 2412 * Regardless of the buf's previous compression settings, it 2413 * should not be compressed at the end of this function. 2414 */ 2415 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; 2416 2417 /* 2418 * Try copying the data from another buf which already has a 2419 * decompressed version. If that's not possible, it's time to 2420 * bite the bullet and decompress the data from the hdr. 2421 */ 2422 if (arc_buf_try_copy_decompressed_data(buf)) { 2423 /* Skip byteswapping and checksumming (already done) */ 2424 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); 2425 return (0); 2426 } else { 2427 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2428 hdr->b_l1hdr.b_pabd, buf->b_data, 2429 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2430 2431 /* 2432 * Absent hardware errors or software bugs, this should 2433 * be impossible, but log it anyway so we can debug it. 2434 */ 2435 if (error != 0) { 2436 zfs_dbgmsg( 2437 "hdr %p, compress %d, psize %d, lsize %d", 2438 hdr, HDR_GET_COMPRESS(hdr), 2439 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2440 return (SET_ERROR(EIO)); 2441 } 2442 } 2443 } 2444 2445 /* Byteswap the buf's data if necessary */ 2446 if (bswap != DMU_BSWAP_NUMFUNCS) { 2447 ASSERT(!HDR_SHARED_DATA(hdr)); 2448 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2449 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2450 } 2451 2452 /* Compute the hdr's checksum if necessary */ 2453 arc_cksum_compute(buf); 2454 2455 return (0); 2456} 2457 2458int 2459arc_decompress(arc_buf_t *buf) 2460{ 2461 return (arc_buf_fill(buf, B_FALSE)); 2462} 2463 2464/* 2465 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. 2466 */ 2467static uint64_t 2468arc_hdr_size(arc_buf_hdr_t *hdr) 2469{ 2470 uint64_t size; 2471 2472 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2473 HDR_GET_PSIZE(hdr) > 0) { 2474 size = HDR_GET_PSIZE(hdr); 2475 } else { 2476 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2477 size = HDR_GET_LSIZE(hdr); 2478 } 2479 return (size); 2480} 2481 2482/* 2483 * Increment the amount of evictable space in the arc_state_t's refcount. 2484 * We account for the space used by the hdr and the arc buf individually 2485 * so that we can add and remove them from the refcount individually. 2486 */ 2487static void 2488arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2489{ 2490 arc_buf_contents_t type = arc_buf_type(hdr); 2491 2492 ASSERT(HDR_HAS_L1HDR(hdr)); 2493 2494 if (GHOST_STATE(state)) { 2495 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2496 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2497 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2498 (void) zfs_refcount_add_many(&state->arcs_esize[type], 2499 HDR_GET_LSIZE(hdr), hdr); 2500 return; 2501 } 2502 2503 ASSERT(!GHOST_STATE(state)); 2504 if (hdr->b_l1hdr.b_pabd != NULL) { 2505 (void) zfs_refcount_add_many(&state->arcs_esize[type], 2506 arc_hdr_size(hdr), hdr); 2507 } 2508 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2509 buf = buf->b_next) { 2510 if (arc_buf_is_shared(buf)) 2511 continue; 2512 (void) zfs_refcount_add_many(&state->arcs_esize[type], 2513 arc_buf_size(buf), buf); 2514 } 2515} 2516 2517/* 2518 * Decrement the amount of evictable space in the arc_state_t's refcount. 2519 * We account for the space used by the hdr and the arc buf individually 2520 * so that we can add and remove them from the refcount individually. 2521 */ 2522static void 2523arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2524{ 2525 arc_buf_contents_t type = arc_buf_type(hdr); 2526 2527 ASSERT(HDR_HAS_L1HDR(hdr)); 2528 2529 if (GHOST_STATE(state)) { 2530 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2531 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2532 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2533 (void) zfs_refcount_remove_many(&state->arcs_esize[type], 2534 HDR_GET_LSIZE(hdr), hdr); 2535 return; 2536 } 2537 2538 ASSERT(!GHOST_STATE(state)); 2539 if (hdr->b_l1hdr.b_pabd != NULL) { 2540 (void) zfs_refcount_remove_many(&state->arcs_esize[type], 2541 arc_hdr_size(hdr), hdr); 2542 } 2543 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2544 buf = buf->b_next) { 2545 if (arc_buf_is_shared(buf)) 2546 continue; 2547 (void) zfs_refcount_remove_many(&state->arcs_esize[type], 2548 arc_buf_size(buf), buf); 2549 } 2550} 2551 2552/* 2553 * Add a reference to this hdr indicating that someone is actively 2554 * referencing that memory. When the refcount transitions from 0 to 1, 2555 * we remove it from the respective arc_state_t list to indicate that 2556 * it is not evictable. 2557 */ 2558static void 2559add_reference(arc_buf_hdr_t *hdr, void *tag) 2560{ 2561 ASSERT(HDR_HAS_L1HDR(hdr)); 2562 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2563 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2564 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2565 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2566 } 2567 2568 arc_state_t *state = hdr->b_l1hdr.b_state; 2569 2570 if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2571 (state != arc_anon)) { 2572 /* We don't use the L2-only state list. */ 2573 if (state != arc_l2c_only) { 2574 multilist_remove(state->arcs_list[arc_buf_type(hdr)], 2575 hdr); 2576 arc_evictable_space_decrement(hdr, state); 2577 } 2578 /* remove the prefetch flag if we get a reference */ 2579 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2580 } 2581} 2582 2583/* 2584 * Remove a reference from this hdr. When the reference transitions from 2585 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2586 * list making it eligible for eviction. 2587 */ 2588static int 2589remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2590{ 2591 int cnt; 2592 arc_state_t *state = hdr->b_l1hdr.b_state; 2593 2594 ASSERT(HDR_HAS_L1HDR(hdr)); 2595 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2596 ASSERT(!GHOST_STATE(state)); 2597 2598 /* 2599 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2600 * check to prevent usage of the arc_l2c_only list. 2601 */ 2602 if (((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2603 (state != arc_anon)) { 2604 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); 2605 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2606 arc_evictable_space_increment(hdr, state); 2607 } 2608 return (cnt); 2609} 2610 2611/* 2612 * Returns detailed information about a specific arc buffer. When the 2613 * state_index argument is set the function will calculate the arc header 2614 * list position for its arc state. Since this requires a linear traversal 2615 * callers are strongly encourage not to do this. However, it can be helpful 2616 * for targeted analysis so the functionality is provided. 2617 */ 2618void 2619arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index) 2620{ 2621 arc_buf_hdr_t *hdr = ab->b_hdr; 2622 l1arc_buf_hdr_t *l1hdr = NULL; 2623 l2arc_buf_hdr_t *l2hdr = NULL; 2624 arc_state_t *state = NULL; 2625 2626 memset(abi, 0, sizeof (arc_buf_info_t)); 2627 2628 if (hdr == NULL) 2629 return; 2630 2631 abi->abi_flags = hdr->b_flags; 2632 2633 if (HDR_HAS_L1HDR(hdr)) { 2634 l1hdr = &hdr->b_l1hdr; 2635 state = l1hdr->b_state; 2636 } 2637 if (HDR_HAS_L2HDR(hdr)) 2638 l2hdr = &hdr->b_l2hdr; 2639 2640 if (l1hdr) { 2641 abi->abi_bufcnt = l1hdr->b_bufcnt; 2642 abi->abi_access = l1hdr->b_arc_access; 2643 abi->abi_mru_hits = l1hdr->b_mru_hits; 2644 abi->abi_mru_ghost_hits = l1hdr->b_mru_ghost_hits; 2645 abi->abi_mfu_hits = l1hdr->b_mfu_hits; 2646 abi->abi_mfu_ghost_hits = l1hdr->b_mfu_ghost_hits; 2647 abi->abi_holds = zfs_refcount_count(&l1hdr->b_refcnt); 2648 } 2649 2650 if (l2hdr) { 2651 abi->abi_l2arc_dattr = l2hdr->b_daddr; 2652 abi->abi_l2arc_hits = l2hdr->b_hits; 2653 } 2654 2655 abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON; 2656 abi->abi_state_contents = arc_buf_type(hdr); 2657 abi->abi_size = arc_hdr_size(hdr); 2658} 2659 2660/* 2661 * Move the supplied buffer to the indicated state. The hash lock 2662 * for the buffer must be held by the caller. 2663 */ 2664static void 2665arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2666 kmutex_t *hash_lock) 2667{ 2668 arc_state_t *old_state; 2669 int64_t refcnt; 2670 uint32_t bufcnt; 2671 boolean_t update_old, update_new; 2672 arc_buf_contents_t buftype = arc_buf_type(hdr); 2673 2674 /* 2675 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2676 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2677 * L1 hdr doesn't always exist when we change state to arc_anon before 2678 * destroying a header, in which case reallocating to add the L1 hdr is 2679 * pointless. 2680 */ 2681 if (HDR_HAS_L1HDR(hdr)) { 2682 old_state = hdr->b_l1hdr.b_state; 2683 refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt); 2684 bufcnt = hdr->b_l1hdr.b_bufcnt; 2685 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); 2686 } else { 2687 old_state = arc_l2c_only; 2688 refcnt = 0; 2689 bufcnt = 0; 2690 update_old = B_FALSE; 2691 } 2692 update_new = update_old; 2693 2694 ASSERT(MUTEX_HELD(hash_lock)); 2695 ASSERT3P(new_state, !=, old_state); 2696 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2697 ASSERT(old_state != arc_anon || bufcnt <= 1); 2698 2699 /* 2700 * If this buffer is evictable, transfer it from the 2701 * old state list to the new state list. 2702 */ 2703 if (refcnt == 0) { 2704 if (old_state != arc_anon && old_state != arc_l2c_only) { 2705 ASSERT(HDR_HAS_L1HDR(hdr)); 2706 multilist_remove(old_state->arcs_list[buftype], hdr); 2707 2708 if (GHOST_STATE(old_state)) { 2709 ASSERT0(bufcnt); 2710 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2711 update_old = B_TRUE; 2712 } 2713 arc_evictable_space_decrement(hdr, old_state); 2714 } 2715 if (new_state != arc_anon && new_state != arc_l2c_only) { 2716 2717 /* 2718 * An L1 header always exists here, since if we're 2719 * moving to some L1-cached state (i.e. not l2c_only or 2720 * anonymous), we realloc the header to add an L1hdr 2721 * beforehand. 2722 */ 2723 ASSERT(HDR_HAS_L1HDR(hdr)); 2724 multilist_insert(new_state->arcs_list[buftype], hdr); 2725 2726 if (GHOST_STATE(new_state)) { 2727 ASSERT0(bufcnt); 2728 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2729 update_new = B_TRUE; 2730 } 2731 arc_evictable_space_increment(hdr, new_state); 2732 } 2733 } 2734 2735 ASSERT(!HDR_EMPTY(hdr)); 2736 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2737 buf_hash_remove(hdr); 2738 2739 /* adjust state sizes (ignore arc_l2c_only) */ 2740 2741 if (update_new && new_state != arc_l2c_only) { 2742 ASSERT(HDR_HAS_L1HDR(hdr)); 2743 if (GHOST_STATE(new_state)) { 2744 ASSERT0(bufcnt); 2745 2746 /* 2747 * When moving a header to a ghost state, we first 2748 * remove all arc buffers. Thus, we'll have a 2749 * bufcnt of zero, and no arc buffer to use for 2750 * the reference. As a result, we use the arc 2751 * header pointer for the reference. 2752 */ 2753 (void) zfs_refcount_add_many(&new_state->arcs_size, 2754 HDR_GET_LSIZE(hdr), hdr); 2755 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2756 } else { 2757 uint32_t buffers = 0; 2758 2759 /* 2760 * Each individual buffer holds a unique reference, 2761 * thus we must remove each of these references one 2762 * at a time. 2763 */ 2764 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2765 buf = buf->b_next) { 2766 ASSERT3U(bufcnt, !=, 0); 2767 buffers++; 2768 2769 /* 2770 * When the arc_buf_t is sharing the data 2771 * block with the hdr, the owner of the 2772 * reference belongs to the hdr. Only 2773 * add to the refcount if the arc_buf_t is 2774 * not shared. 2775 */ 2776 if (arc_buf_is_shared(buf)) 2777 continue; 2778 2779 (void) zfs_refcount_add_many( 2780 &new_state->arcs_size, 2781 arc_buf_size(buf), buf); 2782 } 2783 ASSERT3U(bufcnt, ==, buffers); 2784 2785 if (hdr->b_l1hdr.b_pabd != NULL) { 2786 (void) zfs_refcount_add_many( 2787 &new_state->arcs_size, 2788 arc_hdr_size(hdr), hdr); 2789 } else { 2790 ASSERT(GHOST_STATE(old_state)); 2791 } 2792 } 2793 } 2794 2795 if (update_old && old_state != arc_l2c_only) { 2796 ASSERT(HDR_HAS_L1HDR(hdr)); 2797 if (GHOST_STATE(old_state)) { 2798 ASSERT0(bufcnt); 2799 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2800 2801 /* 2802 * When moving a header off of a ghost state, 2803 * the header will not contain any arc buffers. 2804 * We use the arc header pointer for the reference 2805 * which is exactly what we did when we put the 2806 * header on the ghost state. 2807 */ 2808 2809 (void) zfs_refcount_remove_many(&old_state->arcs_size, 2810 HDR_GET_LSIZE(hdr), hdr); 2811 } else { 2812 uint32_t buffers = 0; 2813 2814 /* 2815 * Each individual buffer holds a unique reference, 2816 * thus we must remove each of these references one 2817 * at a time. 2818 */ 2819 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2820 buf = buf->b_next) { 2821 ASSERT3U(bufcnt, !=, 0); 2822 buffers++; 2823 2824 /* 2825 * When the arc_buf_t is sharing the data 2826 * block with the hdr, the owner of the 2827 * reference belongs to the hdr. Only 2828 * add to the refcount if the arc_buf_t is 2829 * not shared. 2830 */ 2831 if (arc_buf_is_shared(buf)) 2832 continue; 2833 2834 (void) zfs_refcount_remove_many( 2835 &old_state->arcs_size, arc_buf_size(buf), 2836 buf); 2837 } 2838 ASSERT3U(bufcnt, ==, buffers); 2839 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2840 (void) zfs_refcount_remove_many( 2841 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2842 } 2843 } 2844 2845 if (HDR_HAS_L1HDR(hdr)) 2846 hdr->b_l1hdr.b_state = new_state; 2847 2848 /* 2849 * L2 headers should never be on the L2 state list since they don't 2850 * have L1 headers allocated. 2851 */ 2852 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2853 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2854} 2855 2856void 2857arc_space_consume(uint64_t space, arc_space_type_t type) 2858{ 2859 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2860 2861 switch (type) { 2862 case ARC_SPACE_DATA: 2863 aggsum_add(&astat_data_size, space); 2864 break; 2865 case ARC_SPACE_META: 2866 aggsum_add(&astat_metadata_size, space); 2867 break; 2868 case ARC_SPACE_BONUS: 2869 aggsum_add(&astat_bonus_size, space); 2870 break; 2871 case ARC_SPACE_DNODE: 2872 aggsum_add(&astat_dnode_size, space); 2873 break; 2874 case ARC_SPACE_DBUF: 2875 aggsum_add(&astat_dbuf_size, space); 2876 break; 2877 case ARC_SPACE_HDRS: 2878 aggsum_add(&astat_hdr_size, space); 2879 break; 2880 case ARC_SPACE_L2HDRS: 2881 aggsum_add(&astat_l2_hdr_size, space); 2882 break; 2883 } 2884 2885 if (type != ARC_SPACE_DATA) 2886 aggsum_add(&arc_meta_used, space); 2887 2888 aggsum_add(&arc_size, space); 2889} 2890 2891void 2892arc_space_return(uint64_t space, arc_space_type_t type) 2893{ 2894 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2895 2896 switch (type) { 2897 case ARC_SPACE_DATA: 2898 aggsum_add(&astat_data_size, -space); 2899 break; 2900 case ARC_SPACE_META: 2901 aggsum_add(&astat_metadata_size, -space); 2902 break; 2903 case ARC_SPACE_BONUS: 2904 aggsum_add(&astat_bonus_size, -space); 2905 break; 2906 case ARC_SPACE_DNODE: 2907 aggsum_add(&astat_dnode_size, -space); 2908 break; 2909 case ARC_SPACE_DBUF: 2910 aggsum_add(&astat_dbuf_size, -space); 2911 break; 2912 case ARC_SPACE_HDRS: 2913 aggsum_add(&astat_hdr_size, -space); 2914 break; 2915 case ARC_SPACE_L2HDRS: 2916 aggsum_add(&astat_l2_hdr_size, -space); 2917 break; 2918 } 2919 2920 if (type != ARC_SPACE_DATA) { 2921 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0); 2922 /* 2923 * We use the upper bound here rather than the precise value 2924 * because the arc_meta_max value doesn't need to be 2925 * precise. It's only consumed by humans via arcstats. 2926 */ 2927 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used)) 2928 arc_meta_max = aggsum_upper_bound(&arc_meta_used); 2929 aggsum_add(&arc_meta_used, -space); 2930 } 2931 2932 ASSERT(aggsum_compare(&arc_size, space) >= 0); 2933 aggsum_add(&arc_size, -space); 2934} 2935 2936/* 2937 * Given a hdr and a buf, returns whether that buf can share its b_data buffer 2938 * with the hdr's b_pabd. 2939 */ 2940static boolean_t 2941arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2942{ 2943 /* 2944 * The criteria for sharing a hdr's data are: 2945 * 1. the hdr's compression matches the buf's compression 2946 * 2. the hdr doesn't need to be byteswapped 2947 * 3. the hdr isn't already being shared 2948 * 4. the buf is either compressed or it is the last buf in the hdr list 2949 * 2950 * Criterion #4 maintains the invariant that shared uncompressed 2951 * bufs must be the final buf in the hdr's b_buf list. Reading this, you 2952 * might ask, "if a compressed buf is allocated first, won't that be the 2953 * last thing in the list?", but in that case it's impossible to create 2954 * a shared uncompressed buf anyway (because the hdr must be compressed 2955 * to have the compressed buf). You might also think that #3 is 2956 * sufficient to make this guarantee, however it's possible 2957 * (specifically in the rare L2ARC write race mentioned in 2958 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that 2959 * is sharable, but wasn't at the time of its allocation. Rather than 2960 * allow a new shared uncompressed buf to be created and then shuffle 2961 * the list around to make it the last element, this simply disallows 2962 * sharing if the new buf isn't the first to be added. 2963 */ 2964 ASSERT3P(buf->b_hdr, ==, hdr); 2965 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; 2966 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; 2967 return (buf_compressed == hdr_compressed && 2968 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2969 !HDR_SHARED_DATA(hdr) && 2970 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); 2971} 2972 2973/* 2974 * Allocate a buf for this hdr. If you care about the data that's in the hdr, 2975 * or if you want a compressed buffer, pass those flags in. Returns 0 if the 2976 * copy was made successfully, or an error code otherwise. 2977 */ 2978static int 2979arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed, 2980 boolean_t fill, arc_buf_t **ret) 2981{ 2982 arc_buf_t *buf; 2983 2984 ASSERT(HDR_HAS_L1HDR(hdr)); 2985 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2986 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2987 hdr->b_type == ARC_BUFC_METADATA); 2988 ASSERT3P(ret, !=, NULL); 2989 ASSERT3P(*ret, ==, NULL); 2990 2991 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2992 buf->b_hdr = hdr; 2993 buf->b_data = NULL; 2994 buf->b_next = hdr->b_l1hdr.b_buf; 2995 buf->b_flags = 0; 2996 2997 add_reference(hdr, tag); 2998 2999 /* 3000 * We're about to change the hdr's b_flags. We must either 3001 * hold the hash_lock or be undiscoverable. 3002 */ 3003 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3004 3005 /* 3006 * Only honor requests for compressed bufs if the hdr is actually 3007 * compressed. 3008 */ 3009 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 3010 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; 3011 3012 /* 3013 * If the hdr's data can be shared then we share the data buffer and 3014 * set the appropriate bit in the hdr's b_flags to indicate the hdr is 3015 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new 3016 * buffer to store the buf's data. 3017 * 3018 * There are two additional restrictions here because we're sharing 3019 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be 3020 * actively involved in an L2ARC write, because if this buf is used by 3021 * an arc_write() then the hdr's data buffer will be released when the 3022 * write completes, even though the L2ARC write might still be using it. 3023 * Second, the hdr's ABD must be linear so that the buf's user doesn't 3024 * need to be ABD-aware. 3025 */ 3026 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && 3027 abd_is_linear(hdr->b_l1hdr.b_pabd); 3028 3029 /* Set up b_data and sharing */ 3030 if (can_share) { 3031 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); 3032 buf->b_flags |= ARC_BUF_FLAG_SHARED; 3033 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 3034 } else { 3035 buf->b_data = 3036 arc_get_data_buf(hdr, arc_buf_size(buf), buf); 3037 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 3038 } 3039 VERIFY3P(buf->b_data, !=, NULL); 3040 3041 hdr->b_l1hdr.b_buf = buf; 3042 hdr->b_l1hdr.b_bufcnt += 1; 3043 3044 /* 3045 * If the user wants the data from the hdr, we need to either copy or 3046 * decompress the data. 3047 */ 3048 if (fill) { 3049 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); 3050 } 3051 3052 return (0); 3053} 3054 3055static char *arc_onloan_tag = "onloan"; 3056 3057static inline void 3058arc_loaned_bytes_update(int64_t delta) 3059{ 3060 atomic_add_64(&arc_loaned_bytes, delta); 3061 3062 /* assert that it did not wrap around */ 3063 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 3064} 3065 3066/* 3067 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 3068 * flight data by arc_tempreserve_space() until they are "returned". Loaned 3069 * buffers must be returned to the arc before they can be used by the DMU or 3070 * freed. 3071 */ 3072arc_buf_t * 3073arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) 3074{ 3075 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, 3076 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); 3077 3078 arc_loaned_bytes_update(arc_buf_size(buf)); 3079 3080 return (buf); 3081} 3082 3083arc_buf_t * 3084arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, 3085 enum zio_compress compression_type) 3086{ 3087 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, 3088 psize, lsize, compression_type); 3089 3090 arc_loaned_bytes_update(arc_buf_size(buf)); 3091 3092 return (buf); 3093} 3094 3095 3096/* 3097 * Return a loaned arc buffer to the arc. 3098 */ 3099void 3100arc_return_buf(arc_buf_t *buf, void *tag) 3101{ 3102 arc_buf_hdr_t *hdr = buf->b_hdr; 3103 3104 ASSERT3P(buf->b_data, !=, NULL); 3105 ASSERT(HDR_HAS_L1HDR(hdr)); 3106 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 3107 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 3108 3109 arc_loaned_bytes_update(-arc_buf_size(buf)); 3110} 3111 3112/* Detach an arc_buf from a dbuf (tag) */ 3113void 3114arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 3115{ 3116 arc_buf_hdr_t *hdr = buf->b_hdr; 3117 3118 ASSERT3P(buf->b_data, !=, NULL); 3119 ASSERT(HDR_HAS_L1HDR(hdr)); 3120 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 3121 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 3122 3123 arc_loaned_bytes_update(arc_buf_size(buf)); 3124} 3125 3126static void 3127l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) 3128{ 3129 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 3130 3131 df->l2df_abd = abd; 3132 df->l2df_size = size; 3133 df->l2df_type = type; 3134 mutex_enter(&l2arc_free_on_write_mtx); 3135 list_insert_head(l2arc_free_on_write, df); 3136 mutex_exit(&l2arc_free_on_write_mtx); 3137} 3138 3139static void 3140arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 3141{ 3142 arc_state_t *state = hdr->b_l1hdr.b_state; 3143 arc_buf_contents_t type = arc_buf_type(hdr); 3144 uint64_t size = arc_hdr_size(hdr); 3145 3146 /* protected by hash lock, if in the hash table */ 3147 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3148 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3149 ASSERT(state != arc_anon && state != arc_l2c_only); 3150 3151 (void) zfs_refcount_remove_many(&state->arcs_esize[type], 3152 size, hdr); 3153 } 3154 (void) zfs_refcount_remove_many(&state->arcs_size, size, hdr); 3155 if (type == ARC_BUFC_METADATA) { 3156 arc_space_return(size, ARC_SPACE_META); 3157 } else { 3158 ASSERT(type == ARC_BUFC_DATA); 3159 arc_space_return(size, ARC_SPACE_DATA); 3160 } 3161 3162 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); 3163} 3164 3165/* 3166 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 3167 * data buffer, we transfer the refcount ownership to the hdr and update 3168 * the appropriate kstats. 3169 */ 3170static void 3171arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3172{ 3173 arc_state_t *state = hdr->b_l1hdr.b_state; 3174 3175 ASSERT(arc_can_share(hdr, buf)); 3176 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3177 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3178 3179 /* 3180 * Start sharing the data buffer. We transfer the 3181 * refcount ownership to the hdr since it always owns 3182 * the refcount whenever an arc_buf_t is shared. 3183 */ 3184 zfs_refcount_transfer_ownership(&state->arcs_size, buf, hdr); 3185 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); 3186 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, 3187 HDR_ISTYPE_METADATA(hdr)); 3188 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 3189 buf->b_flags |= ARC_BUF_FLAG_SHARED; 3190 3191 /* 3192 * Since we've transferred ownership to the hdr we need 3193 * to increment its compressed and uncompressed kstats and 3194 * decrement the overhead size. 3195 */ 3196 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3197 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3198 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf)); 3199} 3200 3201static void 3202arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3203{ 3204 arc_state_t *state = hdr->b_l1hdr.b_state; 3205 3206 ASSERT(arc_buf_is_shared(buf)); 3207 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3208 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3209 3210 /* 3211 * We are no longer sharing this buffer so we need 3212 * to transfer its ownership to the rightful owner. 3213 */ 3214 zfs_refcount_transfer_ownership(&state->arcs_size, hdr, buf); 3215 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3216 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); 3217 abd_put(hdr->b_l1hdr.b_pabd); 3218 hdr->b_l1hdr.b_pabd = NULL; 3219 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 3220 3221 /* 3222 * Since the buffer is no longer shared between 3223 * the arc buf and the hdr, count it as overhead. 3224 */ 3225 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3226 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3227 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 3228} 3229 3230/* 3231 * Remove an arc_buf_t from the hdr's buf list and return the last 3232 * arc_buf_t on the list. If no buffers remain on the list then return 3233 * NULL. 3234 */ 3235static arc_buf_t * 3236arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3237{ 3238 ASSERT(HDR_HAS_L1HDR(hdr)); 3239 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3240 3241 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; 3242 arc_buf_t *lastbuf = NULL; 3243 3244 /* 3245 * Remove the buf from the hdr list and locate the last 3246 * remaining buffer on the list. 3247 */ 3248 while (*bufp != NULL) { 3249 if (*bufp == buf) 3250 *bufp = buf->b_next; 3251 3252 /* 3253 * If we've removed a buffer in the middle of 3254 * the list then update the lastbuf and update 3255 * bufp. 3256 */ 3257 if (*bufp != NULL) { 3258 lastbuf = *bufp; 3259 bufp = &(*bufp)->b_next; 3260 } 3261 } 3262 buf->b_next = NULL; 3263 ASSERT3P(lastbuf, !=, buf); 3264 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); 3265 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); 3266 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); 3267 3268 return (lastbuf); 3269} 3270 3271/* 3272 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's 3273 * list and free it. 3274 */ 3275static void 3276arc_buf_destroy_impl(arc_buf_t *buf) 3277{ 3278 arc_buf_hdr_t *hdr = buf->b_hdr; 3279 3280 /* 3281 * Free up the data associated with the buf but only if we're not 3282 * sharing this with the hdr. If we are sharing it with the hdr, the 3283 * hdr is responsible for doing the free. 3284 */ 3285 if (buf->b_data != NULL) { 3286 /* 3287 * We're about to change the hdr's b_flags. We must either 3288 * hold the hash_lock or be undiscoverable. 3289 */ 3290 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3291 3292 arc_cksum_verify(buf); 3293#ifdef illumos 3294 arc_buf_unwatch(buf); 3295#endif 3296 3297 if (arc_buf_is_shared(buf)) { 3298 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3299 } else { 3300 uint64_t size = arc_buf_size(buf); 3301 arc_free_data_buf(hdr, buf->b_data, size, buf); 3302 ARCSTAT_INCR(arcstat_overhead_size, -size); 3303 } 3304 buf->b_data = NULL; 3305 3306 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3307 hdr->b_l1hdr.b_bufcnt -= 1; 3308 } 3309 3310 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 3311 3312 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { 3313 /* 3314 * If the current arc_buf_t is sharing its data buffer with the 3315 * hdr, then reassign the hdr's b_pabd to share it with the new 3316 * buffer at the end of the list. The shared buffer is always 3317 * the last one on the hdr's buffer list. 3318 * 3319 * There is an equivalent case for compressed bufs, but since 3320 * they aren't guaranteed to be the last buf in the list and 3321 * that is an exceedingly rare case, we just allow that space be 3322 * wasted temporarily. 3323 */ 3324 if (lastbuf != NULL) { 3325 /* Only one buf can be shared at once */ 3326 VERIFY(!arc_buf_is_shared(lastbuf)); 3327 /* hdr is uncompressed so can't have compressed buf */ 3328 VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); 3329 3330 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3331 arc_hdr_free_pabd(hdr); 3332 3333 /* 3334 * We must setup a new shared block between the 3335 * last buffer and the hdr. The data would have 3336 * been allocated by the arc buf so we need to transfer 3337 * ownership to the hdr since it's now being shared. 3338 */ 3339 arc_share_buf(hdr, lastbuf); 3340 } 3341 } else if (HDR_SHARED_DATA(hdr)) { 3342 /* 3343 * Uncompressed shared buffers are always at the end 3344 * of the list. Compressed buffers don't have the 3345 * same requirements. This makes it hard to 3346 * simply assert that the lastbuf is shared so 3347 * we rely on the hdr's compression flags to determine 3348 * if we have a compressed, shared buffer. 3349 */ 3350 ASSERT3P(lastbuf, !=, NULL); 3351 ASSERT(arc_buf_is_shared(lastbuf) || 3352 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 3353 } 3354 3355 /* 3356 * Free the checksum if we're removing the last uncompressed buf from 3357 * this hdr. 3358 */ 3359 if (!arc_hdr_has_uncompressed_buf(hdr)) { 3360 arc_cksum_free(hdr); 3361 } 3362 3363 /* clean up the buf */ 3364 buf->b_hdr = NULL; 3365 kmem_cache_free(buf_cache, buf); 3366} 3367 3368static void 3369arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr, boolean_t do_adapt) 3370{ 3371 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 3372 ASSERT(HDR_HAS_L1HDR(hdr)); 3373 ASSERT(!HDR_SHARED_DATA(hdr)); 3374 3375 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3376 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, do_adapt); 3377 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3378 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3379 3380 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3381 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3382} 3383 3384static void 3385arc_hdr_free_pabd(arc_buf_hdr_t *hdr) 3386{ 3387 ASSERT(HDR_HAS_L1HDR(hdr)); 3388 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3389 3390 /* 3391 * If the hdr is currently being written to the l2arc then 3392 * we defer freeing the data by adding it to the l2arc_free_on_write 3393 * list. The l2arc will free the data once it's finished 3394 * writing it to the l2arc device. 3395 */ 3396 if (HDR_L2_WRITING(hdr)) { 3397 arc_hdr_free_on_write(hdr); 3398 ARCSTAT_BUMP(arcstat_l2_free_on_write); 3399 } else { 3400 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, 3401 arc_hdr_size(hdr), hdr); 3402 } 3403 hdr->b_l1hdr.b_pabd = NULL; 3404 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3405 3406 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3407 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3408} 3409 3410static arc_buf_hdr_t * 3411arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 3412 enum zio_compress compression_type, arc_buf_contents_t type) 3413{ 3414 arc_buf_hdr_t *hdr; 3415 3416 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 3417 3418 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3419 ASSERT(HDR_EMPTY(hdr)); 3420 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3421 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 3422 HDR_SET_PSIZE(hdr, psize); 3423 HDR_SET_LSIZE(hdr, lsize); 3424 hdr->b_spa = spa; 3425 hdr->b_type = type; 3426 hdr->b_flags = 0; 3427 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 3428 arc_hdr_set_compress(hdr, compression_type); 3429 3430 hdr->b_l1hdr.b_state = arc_anon; 3431 hdr->b_l1hdr.b_arc_access = 0; 3432 hdr->b_l1hdr.b_bufcnt = 0; 3433 hdr->b_l1hdr.b_buf = NULL; 3434 3435 /* 3436 * Allocate the hdr's buffer. This will contain either 3437 * the compressed or uncompressed data depending on the block 3438 * it references and compressed arc enablement. 3439 */ 3440 arc_hdr_alloc_pabd(hdr, B_TRUE); 3441 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3442 3443 return (hdr); 3444} 3445 3446/* 3447 * Transition between the two allocation states for the arc_buf_hdr struct. 3448 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 3449 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 3450 * version is used when a cache buffer is only in the L2ARC in order to reduce 3451 * memory usage. 3452 */ 3453static arc_buf_hdr_t * 3454arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 3455{ 3456 ASSERT(HDR_HAS_L2HDR(hdr)); 3457 3458 arc_buf_hdr_t *nhdr; 3459 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3460 3461 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 3462 (old == hdr_l2only_cache && new == hdr_full_cache)); 3463 3464 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 3465 3466 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 3467 buf_hash_remove(hdr); 3468 3469 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 3470 3471 if (new == hdr_full_cache) { 3472 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3473 /* 3474 * arc_access and arc_change_state need to be aware that a 3475 * header has just come out of L2ARC, so we set its state to 3476 * l2c_only even though it's about to change. 3477 */ 3478 nhdr->b_l1hdr.b_state = arc_l2c_only; 3479 3480 /* Verify previous threads set to NULL before freeing */ 3481 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); 3482 } else { 3483 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3484 ASSERT0(hdr->b_l1hdr.b_bufcnt); 3485 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3486 3487 /* 3488 * If we've reached here, We must have been called from 3489 * arc_evict_hdr(), as such we should have already been 3490 * removed from any ghost list we were previously on 3491 * (which protects us from racing with arc_evict_state), 3492 * thus no locking is needed during this check. 3493 */ 3494 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3495 3496 /* 3497 * A buffer must not be moved into the arc_l2c_only 3498 * state if it's not finished being written out to the 3499 * l2arc device. Otherwise, the b_l1hdr.b_pabd field 3500 * might try to be accessed, even though it was removed. 3501 */ 3502 VERIFY(!HDR_L2_WRITING(hdr)); 3503 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3504 3505#ifdef ZFS_DEBUG 3506 if (hdr->b_l1hdr.b_thawed != NULL) { 3507 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3508 hdr->b_l1hdr.b_thawed = NULL; 3509 } 3510#endif 3511 3512 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3513 } 3514 /* 3515 * The header has been reallocated so we need to re-insert it into any 3516 * lists it was on. 3517 */ 3518 (void) buf_hash_insert(nhdr, NULL); 3519 3520 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 3521 3522 mutex_enter(&dev->l2ad_mtx); 3523 3524 /* 3525 * We must place the realloc'ed header back into the list at 3526 * the same spot. Otherwise, if it's placed earlier in the list, 3527 * l2arc_write_buffers() could find it during the function's 3528 * write phase, and try to write it out to the l2arc. 3529 */ 3530 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 3531 list_remove(&dev->l2ad_buflist, hdr); 3532 3533 mutex_exit(&dev->l2ad_mtx); 3534 3535 /* 3536 * Since we're using the pointer address as the tag when 3537 * incrementing and decrementing the l2ad_alloc refcount, we 3538 * must remove the old pointer (that we're about to destroy) and 3539 * add the new pointer to the refcount. Otherwise we'd remove 3540 * the wrong pointer address when calling arc_hdr_destroy() later. 3541 */ 3542 3543 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), 3544 hdr); 3545 (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), 3546 nhdr); 3547 3548 buf_discard_identity(hdr); 3549 kmem_cache_free(old, hdr); 3550 3551 return (nhdr); 3552} 3553 3554/* 3555 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 3556 * The buf is returned thawed since we expect the consumer to modify it. 3557 */ 3558arc_buf_t * 3559arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) 3560{ 3561 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 3562 ZIO_COMPRESS_OFF, type); 3563 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3564 3565 arc_buf_t *buf = NULL; 3566 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf)); 3567 arc_buf_thaw(buf); 3568 3569 return (buf); 3570} 3571 3572/* 3573 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this 3574 * for bufs containing metadata. 3575 */ 3576arc_buf_t * 3577arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, 3578 enum zio_compress compression_type) 3579{ 3580 ASSERT3U(lsize, >, 0); 3581 ASSERT3U(lsize, >=, psize); 3582 ASSERT(compression_type > ZIO_COMPRESS_OFF); 3583 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); 3584 3585 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 3586 compression_type, ARC_BUFC_DATA); 3587 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3588 3589 arc_buf_t *buf = NULL; 3590 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf)); 3591 arc_buf_thaw(buf); 3592 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3593 3594 if (!arc_buf_is_shared(buf)) { 3595 /* 3596 * To ensure that the hdr has the correct data in it if we call 3597 * arc_decompress() on this buf before it's been written to 3598 * disk, it's easiest if we just set up sharing between the 3599 * buf and the hdr. 3600 */ 3601 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); 3602 arc_hdr_free_pabd(hdr); 3603 arc_share_buf(hdr, buf); 3604 } 3605 3606 return (buf); 3607} 3608 3609static void 3610arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 3611{ 3612 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 3613 l2arc_dev_t *dev = l2hdr->b_dev; 3614 uint64_t psize = arc_hdr_size(hdr); 3615 3616 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 3617 ASSERT(HDR_HAS_L2HDR(hdr)); 3618 3619 list_remove(&dev->l2ad_buflist, hdr); 3620 3621 ARCSTAT_INCR(arcstat_l2_psize, -psize); 3622 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 3623 3624 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0); 3625 3626 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, psize, hdr); 3627 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3628} 3629 3630static void 3631arc_hdr_destroy(arc_buf_hdr_t *hdr) 3632{ 3633 if (HDR_HAS_L1HDR(hdr)) { 3634 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3635 hdr->b_l1hdr.b_bufcnt > 0); 3636 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3637 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3638 } 3639 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3640 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3641 3642 if (!HDR_EMPTY(hdr)) 3643 buf_discard_identity(hdr); 3644 3645 if (HDR_HAS_L2HDR(hdr)) { 3646 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3647 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3648 3649 if (!buflist_held) 3650 mutex_enter(&dev->l2ad_mtx); 3651 3652 /* 3653 * Even though we checked this conditional above, we 3654 * need to check this again now that we have the 3655 * l2ad_mtx. This is because we could be racing with 3656 * another thread calling l2arc_evict() which might have 3657 * destroyed this header's L2 portion as we were waiting 3658 * to acquire the l2ad_mtx. If that happens, we don't 3659 * want to re-destroy the header's L2 portion. 3660 */ 3661 if (HDR_HAS_L2HDR(hdr)) { 3662 l2arc_trim(hdr); 3663 arc_hdr_l2hdr_destroy(hdr); 3664 } 3665 3666 if (!buflist_held) 3667 mutex_exit(&dev->l2ad_mtx); 3668 } 3669 3670 if (HDR_HAS_L1HDR(hdr)) { 3671 arc_cksum_free(hdr); 3672 3673 while (hdr->b_l1hdr.b_buf != NULL) 3674 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); 3675 3676#ifdef ZFS_DEBUG 3677 if (hdr->b_l1hdr.b_thawed != NULL) { 3678 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3679 hdr->b_l1hdr.b_thawed = NULL; 3680 } 3681#endif 3682 3683 if (hdr->b_l1hdr.b_pabd != NULL) { 3684 arc_hdr_free_pabd(hdr); 3685 } 3686 } 3687 3688 ASSERT3P(hdr->b_hash_next, ==, NULL); 3689 if (HDR_HAS_L1HDR(hdr)) { 3690 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3691 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3692 kmem_cache_free(hdr_full_cache, hdr); 3693 } else { 3694 kmem_cache_free(hdr_l2only_cache, hdr); 3695 } 3696} 3697 3698void 3699arc_buf_destroy(arc_buf_t *buf, void* tag) 3700{ 3701 arc_buf_hdr_t *hdr = buf->b_hdr; 3702 kmutex_t *hash_lock = HDR_LOCK(hdr); 3703 3704 if (hdr->b_l1hdr.b_state == arc_anon) { 3705 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3706 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3707 VERIFY0(remove_reference(hdr, NULL, tag)); 3708 arc_hdr_destroy(hdr); 3709 return; 3710 } 3711 3712 mutex_enter(hash_lock); 3713 ASSERT3P(hdr, ==, buf->b_hdr); 3714 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3715 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3716 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3717 ASSERT3P(buf->b_data, !=, NULL); 3718 3719 (void) remove_reference(hdr, hash_lock, tag); 3720 arc_buf_destroy_impl(buf); 3721 mutex_exit(hash_lock); 3722} 3723 3724/* 3725 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3726 * state of the header is dependent on its state prior to entering this 3727 * function. The following transitions are possible: 3728 * 3729 * - arc_mru -> arc_mru_ghost 3730 * - arc_mfu -> arc_mfu_ghost 3731 * - arc_mru_ghost -> arc_l2c_only 3732 * - arc_mru_ghost -> deleted 3733 * - arc_mfu_ghost -> arc_l2c_only 3734 * - arc_mfu_ghost -> deleted 3735 */ 3736static int64_t 3737arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3738{ 3739 arc_state_t *evicted_state, *state; 3740 int64_t bytes_evicted = 0; 3741 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ? 3742 zfs_arc_min_prescient_prefetch_ms : zfs_arc_min_prefetch_ms; 3743 3744 ASSERT(MUTEX_HELD(hash_lock)); 3745 ASSERT(HDR_HAS_L1HDR(hdr)); 3746 3747 state = hdr->b_l1hdr.b_state; 3748 if (GHOST_STATE(state)) { 3749 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3750 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3751 3752 /* 3753 * l2arc_write_buffers() relies on a header's L1 portion 3754 * (i.e. its b_pabd field) during it's write phase. 3755 * Thus, we cannot push a header onto the arc_l2c_only 3756 * state (removing it's L1 piece) until the header is 3757 * done being written to the l2arc. 3758 */ 3759 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3760 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3761 return (bytes_evicted); 3762 } 3763 3764 ARCSTAT_BUMP(arcstat_deleted); 3765 bytes_evicted += HDR_GET_LSIZE(hdr); 3766 3767 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3768 3769 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3770 if (HDR_HAS_L2HDR(hdr)) { 3771 /* 3772 * This buffer is cached on the 2nd Level ARC; 3773 * don't destroy the header. 3774 */ 3775 arc_change_state(arc_l2c_only, hdr, hash_lock); 3776 /* 3777 * dropping from L1+L2 cached to L2-only, 3778 * realloc to remove the L1 header. 3779 */ 3780 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3781 hdr_l2only_cache); 3782 } else { 3783 arc_change_state(arc_anon, hdr, hash_lock); 3784 arc_hdr_destroy(hdr); 3785 } 3786 return (bytes_evicted); 3787 } 3788 3789 ASSERT(state == arc_mru || state == arc_mfu); 3790 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3791 3792 /* prefetch buffers have a minimum lifespan */ 3793 if (HDR_IO_IN_PROGRESS(hdr) || 3794 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3795 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < min_lifetime * hz)) { 3796 ARCSTAT_BUMP(arcstat_evict_skip); 3797 return (bytes_evicted); 3798 } 3799 3800 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt)); 3801 while (hdr->b_l1hdr.b_buf) { 3802 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3803 if (!mutex_tryenter(&buf->b_evict_lock)) { 3804 ARCSTAT_BUMP(arcstat_mutex_miss); 3805 break; 3806 } 3807 if (buf->b_data != NULL) 3808 bytes_evicted += HDR_GET_LSIZE(hdr); 3809 mutex_exit(&buf->b_evict_lock); 3810 arc_buf_destroy_impl(buf); 3811 } 3812 3813 if (HDR_HAS_L2HDR(hdr)) { 3814 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3815 } else { 3816 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3817 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3818 HDR_GET_LSIZE(hdr)); 3819 } else { 3820 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3821 HDR_GET_LSIZE(hdr)); 3822 } 3823 } 3824 3825 if (hdr->b_l1hdr.b_bufcnt == 0) { 3826 arc_cksum_free(hdr); 3827 3828 bytes_evicted += arc_hdr_size(hdr); 3829 3830 /* 3831 * If this hdr is being evicted and has a compressed 3832 * buffer then we discard it here before we change states. 3833 * This ensures that the accounting is updated correctly 3834 * in arc_free_data_impl(). 3835 */ 3836 arc_hdr_free_pabd(hdr); 3837 3838 arc_change_state(evicted_state, hdr, hash_lock); 3839 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3840 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3841 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3842 } 3843 3844 return (bytes_evicted); 3845} 3846 3847static uint64_t 3848arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3849 uint64_t spa, int64_t bytes) 3850{ 3851 multilist_sublist_t *mls; 3852 uint64_t bytes_evicted = 0; 3853 arc_buf_hdr_t *hdr; 3854 kmutex_t *hash_lock; 3855 int evict_count = 0; 3856 3857 ASSERT3P(marker, !=, NULL); 3858 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3859 3860 mls = multilist_sublist_lock(ml, idx); 3861 3862 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3863 hdr = multilist_sublist_prev(mls, marker)) { 3864 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3865 (evict_count >= zfs_arc_evict_batch_limit)) 3866 break; 3867 3868 /* 3869 * To keep our iteration location, move the marker 3870 * forward. Since we're not holding hdr's hash lock, we 3871 * must be very careful and not remove 'hdr' from the 3872 * sublist. Otherwise, other consumers might mistake the 3873 * 'hdr' as not being on a sublist when they call the 3874 * multilist_link_active() function (they all rely on 3875 * the hash lock protecting concurrent insertions and 3876 * removals). multilist_sublist_move_forward() was 3877 * specifically implemented to ensure this is the case 3878 * (only 'marker' will be removed and re-inserted). 3879 */ 3880 multilist_sublist_move_forward(mls, marker); 3881 3882 /* 3883 * The only case where the b_spa field should ever be 3884 * zero, is the marker headers inserted by 3885 * arc_evict_state(). It's possible for multiple threads 3886 * to be calling arc_evict_state() concurrently (e.g. 3887 * dsl_pool_close() and zio_inject_fault()), so we must 3888 * skip any markers we see from these other threads. 3889 */ 3890 if (hdr->b_spa == 0) 3891 continue; 3892 3893 /* we're only interested in evicting buffers of a certain spa */ 3894 if (spa != 0 && hdr->b_spa != spa) { 3895 ARCSTAT_BUMP(arcstat_evict_skip); 3896 continue; 3897 } 3898 3899 hash_lock = HDR_LOCK(hdr); 3900 3901 /* 3902 * We aren't calling this function from any code path 3903 * that would already be holding a hash lock, so we're 3904 * asserting on this assumption to be defensive in case 3905 * this ever changes. Without this check, it would be 3906 * possible to incorrectly increment arcstat_mutex_miss 3907 * below (e.g. if the code changed such that we called 3908 * this function with a hash lock held). 3909 */ 3910 ASSERT(!MUTEX_HELD(hash_lock)); 3911 3912 if (mutex_tryenter(hash_lock)) { 3913 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3914 mutex_exit(hash_lock); 3915 3916 bytes_evicted += evicted; 3917 3918 /* 3919 * If evicted is zero, arc_evict_hdr() must have 3920 * decided to skip this header, don't increment 3921 * evict_count in this case. 3922 */ 3923 if (evicted != 0) 3924 evict_count++; 3925 3926 /* 3927 * If arc_size isn't overflowing, signal any 3928 * threads that might happen to be waiting. 3929 * 3930 * For each header evicted, we wake up a single 3931 * thread. If we used cv_broadcast, we could 3932 * wake up "too many" threads causing arc_size 3933 * to significantly overflow arc_c; since 3934 * arc_get_data_impl() doesn't check for overflow 3935 * when it's woken up (it doesn't because it's 3936 * possible for the ARC to be overflowing while 3937 * full of un-evictable buffers, and the 3938 * function should proceed in this case). 3939 * 3940 * If threads are left sleeping, due to not 3941 * using cv_broadcast here, they will be woken 3942 * up via cv_broadcast in arc_adjust_cb() just 3943 * before arc_adjust_zthr sleeps. 3944 */ 3945 mutex_enter(&arc_adjust_lock); 3946 if (!arc_is_overflowing()) 3947 cv_signal(&arc_adjust_waiters_cv); 3948 mutex_exit(&arc_adjust_lock); 3949 } else { 3950 ARCSTAT_BUMP(arcstat_mutex_miss); 3951 } 3952 } 3953 3954 multilist_sublist_unlock(mls); 3955 3956 return (bytes_evicted); 3957} 3958 3959/* 3960 * Evict buffers from the given arc state, until we've removed the 3961 * specified number of bytes. Move the removed buffers to the 3962 * appropriate evict state. 3963 * 3964 * This function makes a "best effort". It skips over any buffers 3965 * it can't get a hash_lock on, and so, may not catch all candidates. 3966 * It may also return without evicting as much space as requested. 3967 * 3968 * If bytes is specified using the special value ARC_EVICT_ALL, this 3969 * will evict all available (i.e. unlocked and evictable) buffers from 3970 * the given arc state; which is used by arc_flush(). 3971 */ 3972static uint64_t 3973arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3974 arc_buf_contents_t type) 3975{ 3976 uint64_t total_evicted = 0; 3977 multilist_t *ml = state->arcs_list[type]; 3978 int num_sublists; 3979 arc_buf_hdr_t **markers; 3980 3981 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3982 3983 num_sublists = multilist_get_num_sublists(ml); 3984 3985 /* 3986 * If we've tried to evict from each sublist, made some 3987 * progress, but still have not hit the target number of bytes 3988 * to evict, we want to keep trying. The markers allow us to 3989 * pick up where we left off for each individual sublist, rather 3990 * than starting from the tail each time. 3991 */ 3992 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3993 for (int i = 0; i < num_sublists; i++) { 3994 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3995 3996 /* 3997 * A b_spa of 0 is used to indicate that this header is 3998 * a marker. This fact is used in arc_adjust_type() and 3999 * arc_evict_state_impl(). 4000 */ 4001 markers[i]->b_spa = 0; 4002 4003 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 4004 multilist_sublist_insert_tail(mls, markers[i]); 4005 multilist_sublist_unlock(mls); 4006 } 4007 4008 /* 4009 * While we haven't hit our target number of bytes to evict, or 4010 * we're evicting all available buffers. 4011 */ 4012 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 4013 int sublist_idx = multilist_get_random_index(ml); 4014 uint64_t scan_evicted = 0; 4015 4016 /* 4017 * Try to reduce pinned dnodes with a floor of arc_dnode_limit. 4018 * Request that 10% of the LRUs be scanned by the superblock 4019 * shrinker. 4020 */ 4021 if (type == ARC_BUFC_DATA && aggsum_compare(&astat_dnode_size, 4022 arc_dnode_limit) > 0) { 4023 arc_prune_async((aggsum_upper_bound(&astat_dnode_size) - 4024 arc_dnode_limit) / sizeof (dnode_t) / 4025 zfs_arc_dnode_reduce_percent); 4026 } 4027 4028 /* 4029 * Start eviction using a randomly selected sublist, 4030 * this is to try and evenly balance eviction across all 4031 * sublists. Always starting at the same sublist 4032 * (e.g. index 0) would cause evictions to favor certain 4033 * sublists over others. 4034 */ 4035 for (int i = 0; i < num_sublists; i++) { 4036 uint64_t bytes_remaining; 4037 uint64_t bytes_evicted; 4038 4039 if (bytes == ARC_EVICT_ALL) 4040 bytes_remaining = ARC_EVICT_ALL; 4041 else if (total_evicted < bytes) 4042 bytes_remaining = bytes - total_evicted; 4043 else 4044 break; 4045 4046 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 4047 markers[sublist_idx], spa, bytes_remaining); 4048 4049 scan_evicted += bytes_evicted; 4050 total_evicted += bytes_evicted; 4051 4052 /* we've reached the end, wrap to the beginning */ 4053 if (++sublist_idx >= num_sublists) 4054 sublist_idx = 0; 4055 } 4056 4057 /* 4058 * If we didn't evict anything during this scan, we have 4059 * no reason to believe we'll evict more during another 4060 * scan, so break the loop. 4061 */ 4062 if (scan_evicted == 0) { 4063 /* This isn't possible, let's make that obvious */ 4064 ASSERT3S(bytes, !=, 0); 4065 4066 /* 4067 * When bytes is ARC_EVICT_ALL, the only way to 4068 * break the loop is when scan_evicted is zero. 4069 * In that case, we actually have evicted enough, 4070 * so we don't want to increment the kstat. 4071 */ 4072 if (bytes != ARC_EVICT_ALL) { 4073 ASSERT3S(total_evicted, <, bytes); 4074 ARCSTAT_BUMP(arcstat_evict_not_enough); 4075 } 4076 4077 break; 4078 } 4079 } 4080 4081 for (int i = 0; i < num_sublists; i++) { 4082 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 4083 multilist_sublist_remove(mls, markers[i]); 4084 multilist_sublist_unlock(mls); 4085 4086 kmem_cache_free(hdr_full_cache, markers[i]); 4087 } 4088 kmem_free(markers, sizeof (*markers) * num_sublists); 4089 4090 return (total_evicted); 4091} 4092 4093/* 4094 * Flush all "evictable" data of the given type from the arc state 4095 * specified. This will not evict any "active" buffers (i.e. referenced). 4096 * 4097 * When 'retry' is set to B_FALSE, the function will make a single pass 4098 * over the state and evict any buffers that it can. Since it doesn't 4099 * continually retry the eviction, it might end up leaving some buffers 4100 * in the ARC due to lock misses. 4101 * 4102 * When 'retry' is set to B_TRUE, the function will continually retry the 4103 * eviction until *all* evictable buffers have been removed from the 4104 * state. As a result, if concurrent insertions into the state are 4105 * allowed (e.g. if the ARC isn't shutting down), this function might 4106 * wind up in an infinite loop, continually trying to evict buffers. 4107 */ 4108static uint64_t 4109arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 4110 boolean_t retry) 4111{ 4112 uint64_t evicted = 0; 4113 4114 while (zfs_refcount_count(&state->arcs_esize[type]) != 0) { 4115 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 4116 4117 if (!retry) 4118 break; 4119 } 4120 4121 return (evicted); 4122} 4123 4124/* 4125 * Helper function for arc_prune_async() it is responsible for safely 4126 * handling the execution of a registered arc_prune_func_t. 4127 */ 4128static void 4129arc_prune_task(void *ptr) 4130{ 4131 arc_prune_t *ap = (arc_prune_t *)ptr; 4132 arc_prune_func_t *func = ap->p_pfunc; 4133 4134 if (func != NULL) 4135 func(ap->p_adjust, ap->p_private); 4136 4137 zfs_refcount_remove(&ap->p_refcnt, func); 4138} 4139 4140/* 4141 * Notify registered consumers they must drop holds on a portion of the ARC 4142 * buffered they reference. This provides a mechanism to ensure the ARC can 4143 * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers. This 4144 * is analogous to dnlc_reduce_cache() but more generic. 4145 * 4146 * This operation is performed asynchronously so it may be safely called 4147 * in the context of the arc_reclaim_thread(). A reference is taken here 4148 * for each registered arc_prune_t and the arc_prune_task() is responsible 4149 * for releasing it once the registered arc_prune_func_t has completed. 4150 */ 4151static void 4152arc_prune_async(int64_t adjust) 4153{ 4154 arc_prune_t *ap; 4155 4156 mutex_enter(&arc_prune_mtx); 4157 for (ap = list_head(&arc_prune_list); ap != NULL; 4158 ap = list_next(&arc_prune_list, ap)) { 4159 4160 if (zfs_refcount_count(&ap->p_refcnt) >= 2) 4161 continue; 4162 4163 zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc); 4164 ap->p_adjust = adjust; 4165 if (taskq_dispatch(arc_prune_taskq, arc_prune_task, 4166 ap, TQ_SLEEP) == TASKQID_INVALID) { 4167 zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc); 4168 continue; 4169 } 4170 ARCSTAT_BUMP(arcstat_prune); 4171 } 4172 mutex_exit(&arc_prune_mtx); 4173} 4174 4175/* 4176 * Evict the specified number of bytes from the state specified, 4177 * restricting eviction to the spa and type given. This function 4178 * prevents us from trying to evict more from a state's list than 4179 * is "evictable", and to skip evicting altogether when passed a 4180 * negative value for "bytes". In contrast, arc_evict_state() will 4181 * evict everything it can, when passed a negative value for "bytes". 4182 */ 4183static uint64_t 4184arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 4185 arc_buf_contents_t type) 4186{ 4187 int64_t delta; 4188 4189 if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) { 4190 delta = MIN(zfs_refcount_count(&state->arcs_esize[type]), 4191 bytes); 4192 return (arc_evict_state(state, spa, delta, type)); 4193 } 4194 4195 return (0); 4196} 4197 4198/* 4199 * The goal of this function is to evict enough meta data buffers from the 4200 * ARC in order to enforce the arc_meta_limit. Achieving this is slightly 4201 * more complicated than it appears because it is common for data buffers 4202 * to have holds on meta data buffers. In addition, dnode meta data buffers 4203 * will be held by the dnodes in the block preventing them from being freed. 4204 * This means we can't simply traverse the ARC and expect to always find 4205 * enough unheld meta data buffer to release. 4206 * 4207 * Therefore, this function has been updated to make alternating passes 4208 * over the ARC releasing data buffers and then newly unheld meta data 4209 * buffers. This ensures forward progress is maintained and meta_used 4210 * will decrease. Normally this is sufficient, but if required the ARC 4211 * will call the registered prune callbacks causing dentry and inodes to 4212 * be dropped from the VFS cache. This will make dnode meta data buffers 4213 * available for reclaim. 4214 */ 4215static uint64_t 4216arc_adjust_meta_balanced(uint64_t meta_used) 4217{ 4218 int64_t delta, prune = 0, adjustmnt; 4219 uint64_t total_evicted = 0; 4220 arc_buf_contents_t type = ARC_BUFC_DATA; 4221 int restarts = MAX(zfs_arc_meta_adjust_restarts, 0); 4222 4223restart: 4224 /* 4225 * This slightly differs than the way we evict from the mru in 4226 * arc_adjust because we don't have a "target" value (i.e. no 4227 * "meta" arc_p). As a result, I think we can completely 4228 * cannibalize the metadata in the MRU before we evict the 4229 * metadata from the MFU. I think we probably need to implement a 4230 * "metadata arc_p" value to do this properly. 4231 */ 4232 adjustmnt = meta_used - arc_meta_limit; 4233 4234 if (adjustmnt > 0 && 4235 zfs_refcount_count(&arc_mru->arcs_esize[type]) > 0) { 4236 delta = MIN(zfs_refcount_count(&arc_mru->arcs_esize[type]), 4237 adjustmnt); 4238 total_evicted += arc_adjust_impl(arc_mru, 0, delta, type); 4239 adjustmnt -= delta; 4240 } 4241 4242 /* 4243 * We can't afford to recalculate adjustmnt here. If we do, 4244 * new metadata buffers can sneak into the MRU or ANON lists, 4245 * thus penalize the MFU metadata. Although the fudge factor is 4246 * small, it has been empirically shown to be significant for 4247 * certain workloads (e.g. creating many empty directories). As 4248 * such, we use the original calculation for adjustmnt, and 4249 * simply decrement the amount of data evicted from the MRU. 4250 */ 4251 4252 if (adjustmnt > 0 && 4253 zfs_refcount_count(&arc_mfu->arcs_esize[type]) > 0) { 4254 delta = MIN(zfs_refcount_count(&arc_mfu->arcs_esize[type]), 4255 adjustmnt); 4256 total_evicted += arc_adjust_impl(arc_mfu, 0, delta, type); 4257 } 4258 4259 adjustmnt = meta_used - arc_meta_limit; 4260 4261 if (adjustmnt > 0 && 4262 zfs_refcount_count(&arc_mru_ghost->arcs_esize[type]) > 0) { 4263 delta = MIN(adjustmnt, 4264 zfs_refcount_count(&arc_mru_ghost->arcs_esize[type])); 4265 total_evicted += arc_adjust_impl(arc_mru_ghost, 0, delta, type); 4266 adjustmnt -= delta; 4267 } 4268 4269 if (adjustmnt > 0 && 4270 zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type]) > 0) { 4271 delta = MIN(adjustmnt, 4272 zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type])); 4273 total_evicted += arc_adjust_impl(arc_mfu_ghost, 0, delta, type); 4274 } 4275 4276 /* 4277 * If after attempting to make the requested adjustment to the ARC 4278 * the meta limit is still being exceeded then request that the 4279 * higher layers drop some cached objects which have holds on ARC 4280 * meta buffers. Requests to the upper layers will be made with 4281 * increasingly large scan sizes until the ARC is below the limit. 4282 */ 4283 if (meta_used > arc_meta_limit) { 4284 if (type == ARC_BUFC_DATA) { 4285 type = ARC_BUFC_METADATA; 4286 } else { 4287 type = ARC_BUFC_DATA; 4288 4289 if (zfs_arc_meta_prune) { 4290 prune += zfs_arc_meta_prune; 4291 arc_prune_async(prune); 4292 } 4293 } 4294 4295 if (restarts > 0) { 4296 restarts--; 4297 goto restart; 4298 } 4299 } 4300 return (total_evicted); 4301} 4302 4303/* 4304 * Evict metadata buffers from the cache, such that arc_meta_used is 4305 * capped by the arc_meta_limit tunable. 4306 */ 4307static uint64_t 4308arc_adjust_meta_only(uint64_t meta_used) 4309{ 4310 uint64_t total_evicted = 0; 4311 int64_t target; 4312 4313 /* 4314 * If we're over the meta limit, we want to evict enough 4315 * metadata to get back under the meta limit. We don't want to 4316 * evict so much that we drop the MRU below arc_p, though. If 4317 * we're over the meta limit more than we're over arc_p, we 4318 * evict some from the MRU here, and some from the MFU below. 4319 */ 4320 target = MIN((int64_t)(meta_used - arc_meta_limit), 4321 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) + 4322 zfs_refcount_count(&arc_mru->arcs_size) - arc_p)); 4323 4324 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4325 4326 /* 4327 * Similar to the above, we want to evict enough bytes to get us 4328 * below the meta limit, but not so much as to drop us below the 4329 * space allotted to the MFU (which is defined as arc_c - arc_p). 4330 */ 4331 target = MIN((int64_t)(meta_used - arc_meta_limit), 4332 (int64_t)(zfs_refcount_count(&arc_mfu->arcs_size) - 4333 (arc_c - arc_p))); 4334 4335 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4336 4337 return (total_evicted); 4338} 4339 4340static uint64_t 4341arc_adjust_meta(uint64_t meta_used) 4342{ 4343 if (zfs_arc_meta_strategy == ARC_STRATEGY_META_ONLY) 4344 return (arc_adjust_meta_only(meta_used)); 4345 else 4346 return (arc_adjust_meta_balanced(meta_used)); 4347} 4348 4349/* 4350 * Return the type of the oldest buffer in the given arc state 4351 * 4352 * This function will select a random sublist of type ARC_BUFC_DATA and 4353 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 4354 * is compared, and the type which contains the "older" buffer will be 4355 * returned. 4356 */ 4357static arc_buf_contents_t 4358arc_adjust_type(arc_state_t *state) 4359{ 4360 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; 4361 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; 4362 int data_idx = multilist_get_random_index(data_ml); 4363 int meta_idx = multilist_get_random_index(meta_ml); 4364 multilist_sublist_t *data_mls; 4365 multilist_sublist_t *meta_mls; 4366 arc_buf_contents_t type; 4367 arc_buf_hdr_t *data_hdr; 4368 arc_buf_hdr_t *meta_hdr; 4369 4370 /* 4371 * We keep the sublist lock until we're finished, to prevent 4372 * the headers from being destroyed via arc_evict_state(). 4373 */ 4374 data_mls = multilist_sublist_lock(data_ml, data_idx); 4375 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 4376 4377 /* 4378 * These two loops are to ensure we skip any markers that 4379 * might be at the tail of the lists due to arc_evict_state(). 4380 */ 4381 4382 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 4383 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 4384 if (data_hdr->b_spa != 0) 4385 break; 4386 } 4387 4388 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 4389 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 4390 if (meta_hdr->b_spa != 0) 4391 break; 4392 } 4393 4394 if (data_hdr == NULL && meta_hdr == NULL) { 4395 type = ARC_BUFC_DATA; 4396 } else if (data_hdr == NULL) { 4397 ASSERT3P(meta_hdr, !=, NULL); 4398 type = ARC_BUFC_METADATA; 4399 } else if (meta_hdr == NULL) { 4400 ASSERT3P(data_hdr, !=, NULL); 4401 type = ARC_BUFC_DATA; 4402 } else { 4403 ASSERT3P(data_hdr, !=, NULL); 4404 ASSERT3P(meta_hdr, !=, NULL); 4405 4406 /* The headers can't be on the sublist without an L1 header */ 4407 ASSERT(HDR_HAS_L1HDR(data_hdr)); 4408 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 4409 4410 if (data_hdr->b_l1hdr.b_arc_access < 4411 meta_hdr->b_l1hdr.b_arc_access) { 4412 type = ARC_BUFC_DATA; 4413 } else { 4414 type = ARC_BUFC_METADATA; 4415 } 4416 } 4417 4418 multilist_sublist_unlock(meta_mls); 4419 multilist_sublist_unlock(data_mls); 4420 4421 return (type); 4422} 4423 4424/* 4425 * Evict buffers from the cache, such that arc_size is capped by arc_c. 4426 */ 4427static uint64_t 4428arc_adjust(void) 4429{ 4430 uint64_t total_evicted = 0; 4431 uint64_t bytes; 4432 int64_t target; 4433 uint64_t asize = aggsum_value(&arc_size); 4434 uint64_t ameta = aggsum_value(&arc_meta_used); 4435 4436 /* 4437 * If we're over arc_meta_limit, we want to correct that before 4438 * potentially evicting data buffers below. 4439 */ 4440 total_evicted += arc_adjust_meta(ameta); 4441 4442 /* 4443 * Adjust MRU size 4444 * 4445 * If we're over the target cache size, we want to evict enough 4446 * from the list to get back to our target size. We don't want 4447 * to evict too much from the MRU, such that it drops below 4448 * arc_p. So, if we're over our target cache size more than 4449 * the MRU is over arc_p, we'll evict enough to get back to 4450 * arc_p here, and then evict more from the MFU below. 4451 */ 4452 target = MIN((int64_t)(asize - arc_c), 4453 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) + 4454 zfs_refcount_count(&arc_mru->arcs_size) + ameta - arc_p)); 4455 4456 /* 4457 * If we're below arc_meta_min, always prefer to evict data. 4458 * Otherwise, try to satisfy the requested number of bytes to 4459 * evict from the type which contains older buffers; in an 4460 * effort to keep newer buffers in the cache regardless of their 4461 * type. If we cannot satisfy the number of bytes from this 4462 * type, spill over into the next type. 4463 */ 4464 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 4465 ameta > arc_meta_min) { 4466 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4467 total_evicted += bytes; 4468 4469 /* 4470 * If we couldn't evict our target number of bytes from 4471 * metadata, we try to get the rest from data. 4472 */ 4473 target -= bytes; 4474 4475 total_evicted += 4476 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4477 } else { 4478 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4479 total_evicted += bytes; 4480 4481 /* 4482 * If we couldn't evict our target number of bytes from 4483 * data, we try to get the rest from metadata. 4484 */ 4485 target -= bytes; 4486 4487 total_evicted += 4488 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4489 } 4490 4491 /* 4492 * Re-sum ARC stats after the first round of evictions. 4493 */ 4494 asize = aggsum_value(&arc_size); 4495 ameta = aggsum_value(&arc_meta_used); 4496 4497 /* 4498 * Adjust MFU size 4499 * 4500 * Now that we've tried to evict enough from the MRU to get its 4501 * size back to arc_p, if we're still above the target cache 4502 * size, we evict the rest from the MFU. 4503 */ 4504 target = asize - arc_c; 4505 4506 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 4507 ameta > arc_meta_min) { 4508 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4509 total_evicted += bytes; 4510 4511 /* 4512 * If we couldn't evict our target number of bytes from 4513 * metadata, we try to get the rest from data. 4514 */ 4515 target -= bytes; 4516 4517 total_evicted += 4518 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4519 } else { 4520 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4521 total_evicted += bytes; 4522 4523 /* 4524 * If we couldn't evict our target number of bytes from 4525 * data, we try to get the rest from data. 4526 */ 4527 target -= bytes; 4528 4529 total_evicted += 4530 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4531 } 4532 4533 /* 4534 * Adjust ghost lists 4535 * 4536 * In addition to the above, the ARC also defines target values 4537 * for the ghost lists. The sum of the mru list and mru ghost 4538 * list should never exceed the target size of the cache, and 4539 * the sum of the mru list, mfu list, mru ghost list, and mfu 4540 * ghost list should never exceed twice the target size of the 4541 * cache. The following logic enforces these limits on the ghost 4542 * caches, and evicts from them as needed. 4543 */ 4544 target = zfs_refcount_count(&arc_mru->arcs_size) + 4545 zfs_refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 4546 4547 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 4548 total_evicted += bytes; 4549 4550 target -= bytes; 4551 4552 total_evicted += 4553 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 4554 4555 /* 4556 * We assume the sum of the mru list and mfu list is less than 4557 * or equal to arc_c (we enforced this above), which means we 4558 * can use the simpler of the two equations below: 4559 * 4560 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 4561 * mru ghost + mfu ghost <= arc_c 4562 */ 4563 target = zfs_refcount_count(&arc_mru_ghost->arcs_size) + 4564 zfs_refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 4565 4566 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 4567 total_evicted += bytes; 4568 4569 target -= bytes; 4570 4571 total_evicted += 4572 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 4573 4574 return (total_evicted); 4575} 4576 4577void 4578arc_flush(spa_t *spa, boolean_t retry) 4579{ 4580 uint64_t guid = 0; 4581 4582 /* 4583 * If retry is B_TRUE, a spa must not be specified since we have 4584 * no good way to determine if all of a spa's buffers have been 4585 * evicted from an arc state. 4586 */ 4587 ASSERT(!retry || spa == 0); 4588 4589 if (spa != NULL) 4590 guid = spa_load_guid(spa); 4591 4592 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 4593 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 4594 4595 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 4596 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 4597 4598 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 4599 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 4600 4601 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 4602 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 4603} 4604 4605static void 4606arc_reduce_target_size(int64_t to_free) 4607{ 4608 uint64_t asize = aggsum_value(&arc_size); 4609 if (arc_c > arc_c_min) { 4610 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 4611 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 4612 if (arc_c > arc_c_min + to_free) 4613 atomic_add_64(&arc_c, -to_free); 4614 else 4615 arc_c = arc_c_min; 4616 4617 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 4618 if (asize < arc_c) 4619 arc_c = MAX(asize, arc_c_min); 4620 if (arc_p > arc_c) 4621 arc_p = (arc_c >> 1); 4622 4623 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 4624 arc_p); 4625 4626 ASSERT(arc_c >= arc_c_min); 4627 ASSERT((int64_t)arc_p >= 0); 4628 } 4629 4630 if (asize > arc_c) { 4631 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize, 4632 uint64_t, arc_c); 4633 /* See comment in arc_adjust_cb_check() on why lock+flag */ 4634 mutex_enter(&arc_adjust_lock); 4635 arc_adjust_needed = B_TRUE; 4636 mutex_exit(&arc_adjust_lock); 4637 zthr_wakeup(arc_adjust_zthr); 4638 } 4639} 4640 4641typedef enum free_memory_reason_t { 4642 FMR_UNKNOWN, 4643 FMR_NEEDFREE, 4644 FMR_LOTSFREE, 4645 FMR_SWAPFS_MINFREE, 4646 FMR_PAGES_PP_MAXIMUM, 4647 FMR_HEAP_ARENA, 4648 FMR_ZIO_ARENA, 4649} free_memory_reason_t; 4650 4651int64_t last_free_memory; 4652free_memory_reason_t last_free_reason; 4653 4654/* 4655 * Additional reserve of pages for pp_reserve. 4656 */ 4657int64_t arc_pages_pp_reserve = 64; 4658 4659/* 4660 * Additional reserve of pages for swapfs. 4661 */ 4662int64_t arc_swapfs_reserve = 64; 4663 4664/* 4665 * Return the amount of memory that can be consumed before reclaim will be 4666 * needed. Positive if there is sufficient free memory, negative indicates 4667 * the amount of memory that needs to be freed up. 4668 */ 4669static int64_t 4670arc_available_memory(void) 4671{ 4672 int64_t lowest = INT64_MAX; 4673 int64_t n; 4674 free_memory_reason_t r = FMR_UNKNOWN; 4675 4676#ifdef _KERNEL 4677#ifdef __FreeBSD__ 4678 /* 4679 * Cooperate with pagedaemon when it's time for it to scan 4680 * and reclaim some pages. 4681 */ 4682 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 4683 if (n < lowest) { 4684 lowest = n; 4685 r = FMR_LOTSFREE; 4686 } 4687 4688#else 4689 if (needfree > 0) { 4690 n = PAGESIZE * (-needfree); 4691 if (n < lowest) { 4692 lowest = n; 4693 r = FMR_NEEDFREE; 4694 } 4695 } 4696 4697 /* 4698 * check that we're out of range of the pageout scanner. It starts to 4699 * schedule paging if freemem is less than lotsfree and needfree. 4700 * lotsfree is the high-water mark for pageout, and needfree is the 4701 * number of needed free pages. We add extra pages here to make sure 4702 * the scanner doesn't start up while we're freeing memory. 4703 */ 4704 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 4705 if (n < lowest) { 4706 lowest = n; 4707 r = FMR_LOTSFREE; 4708 } 4709 4710 /* 4711 * check to make sure that swapfs has enough space so that anon 4712 * reservations can still succeed. anon_resvmem() checks that the 4713 * availrmem is greater than swapfs_minfree, and the number of reserved 4714 * swap pages. We also add a bit of extra here just to prevent 4715 * circumstances from getting really dire. 4716 */ 4717 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 4718 desfree - arc_swapfs_reserve); 4719 if (n < lowest) { 4720 lowest = n; 4721 r = FMR_SWAPFS_MINFREE; 4722 } 4723 4724 4725 /* 4726 * Check that we have enough availrmem that memory locking (e.g., via 4727 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 4728 * stores the number of pages that cannot be locked; when availrmem 4729 * drops below pages_pp_maximum, page locking mechanisms such as 4730 * page_pp_lock() will fail.) 4731 */ 4732 n = PAGESIZE * (availrmem - pages_pp_maximum - 4733 arc_pages_pp_reserve); 4734 if (n < lowest) { 4735 lowest = n; 4736 r = FMR_PAGES_PP_MAXIMUM; 4737 } 4738 4739#endif /* __FreeBSD__ */ 4740#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4741 /* 4742 * If we're on an i386 platform, it's possible that we'll exhaust the 4743 * kernel heap space before we ever run out of available physical 4744 * memory. Most checks of the size of the heap_area compare against 4745 * tune.t_minarmem, which is the minimum available real memory that we 4746 * can have in the system. However, this is generally fixed at 25 pages 4747 * which is so low that it's useless. In this comparison, we seek to 4748 * calculate the total heap-size, and reclaim if more than 3/4ths of the 4749 * heap is allocated. (Or, in the calculation, if less than 1/4th is 4750 * free) 4751 */ 4752 n = uma_avail() - (long)(uma_limit() / 4); 4753 if (n < lowest) { 4754 lowest = n; 4755 r = FMR_HEAP_ARENA; 4756 } 4757#endif 4758 4759 /* 4760 * If zio data pages are being allocated out of a separate heap segment, 4761 * then enforce that the size of available vmem for this arena remains 4762 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free. 4763 * 4764 * Note that reducing the arc_zio_arena_free_shift keeps more virtual 4765 * memory (in the zio_arena) free, which can avoid memory 4766 * fragmentation issues. 4767 */ 4768 if (zio_arena != NULL) { 4769 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 4770 (vmem_size(zio_arena, VMEM_ALLOC) >> 4771 arc_zio_arena_free_shift); 4772 if (n < lowest) { 4773 lowest = n; 4774 r = FMR_ZIO_ARENA; 4775 } 4776 } 4777 4778#else /* _KERNEL */ 4779 /* Every 100 calls, free a small amount */ 4780 if (spa_get_random(100) == 0) 4781 lowest = -1024; 4782#endif /* _KERNEL */ 4783 4784 last_free_memory = lowest; 4785 last_free_reason = r; 4786 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 4787 return (lowest); 4788} 4789 4790 4791/* 4792 * Determine if the system is under memory pressure and is asking 4793 * to reclaim memory. A return value of B_TRUE indicates that the system 4794 * is under memory pressure and that the arc should adjust accordingly. 4795 */ 4796static boolean_t 4797arc_reclaim_needed(void) 4798{ 4799 return (arc_available_memory() < 0); 4800} 4801 4802extern kmem_cache_t *zio_buf_cache[]; 4803extern kmem_cache_t *zio_data_buf_cache[]; 4804extern kmem_cache_t *range_seg_cache; 4805extern kmem_cache_t *abd_chunk_cache; 4806 4807static __noinline void 4808arc_kmem_reap_soon(void) 4809{ 4810 size_t i; 4811 kmem_cache_t *prev_cache = NULL; 4812 kmem_cache_t *prev_data_cache = NULL; 4813 4814 DTRACE_PROBE(arc__kmem_reap_start); 4815#ifdef _KERNEL 4816 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) { 4817 /* 4818 * We are exceeding our meta-data cache limit. 4819 * Purge some DNLC entries to release holds on meta-data. 4820 */ 4821 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4822 } 4823#if defined(__i386) 4824 /* 4825 * Reclaim unused memory from all kmem caches. 4826 */ 4827 kmem_reap(); 4828#endif 4829#endif 4830 4831 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4832 if (zio_buf_cache[i] != prev_cache) { 4833 prev_cache = zio_buf_cache[i]; 4834 kmem_cache_reap_soon(zio_buf_cache[i]); 4835 } 4836 if (zio_data_buf_cache[i] != prev_data_cache) { 4837 prev_data_cache = zio_data_buf_cache[i]; 4838 kmem_cache_reap_soon(zio_data_buf_cache[i]); 4839 } 4840 } 4841 kmem_cache_reap_soon(abd_chunk_cache); 4842 kmem_cache_reap_soon(buf_cache); 4843 kmem_cache_reap_soon(hdr_full_cache); 4844 kmem_cache_reap_soon(hdr_l2only_cache); 4845 kmem_cache_reap_soon(range_seg_cache); 4846 4847#ifdef illumos 4848 if (zio_arena != NULL) { 4849 /* 4850 * Ask the vmem arena to reclaim unused memory from its 4851 * quantum caches. 4852 */ 4853 vmem_qcache_reap(zio_arena); 4854 } 4855#endif 4856 DTRACE_PROBE(arc__kmem_reap_end); 4857} 4858 4859/* ARGSUSED */ 4860static boolean_t 4861arc_adjust_cb_check(void *arg, zthr_t *zthr) 4862{ 4863 /* 4864 * This is necessary in order for the mdb ::arc dcmd to 4865 * show up to date information. Since the ::arc command 4866 * does not call the kstat's update function, without 4867 * this call, the command may show stale stats for the 4868 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4869 * with this change, the data might be up to 1 second 4870 * out of date(the arc_adjust_zthr has a maximum sleep 4871 * time of 1 second); but that should suffice. The 4872 * arc_state_t structures can be queried directly if more 4873 * accurate information is needed. 4874 */ 4875 if (arc_ksp != NULL) 4876 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4877 4878 /* 4879 * We have to rely on arc_get_data_impl() to tell us when to adjust, 4880 * rather than checking if we are overflowing here, so that we are 4881 * sure to not leave arc_get_data_impl() waiting on 4882 * arc_adjust_waiters_cv. If we have become "not overflowing" since 4883 * arc_get_data_impl() checked, we need to wake it up. We could 4884 * broadcast the CV here, but arc_get_data_impl() may have not yet 4885 * gone to sleep. We would need to use a mutex to ensure that this 4886 * function doesn't broadcast until arc_get_data_impl() has gone to 4887 * sleep (e.g. the arc_adjust_lock). However, the lock ordering of 4888 * such a lock would necessarily be incorrect with respect to the 4889 * zthr_lock, which is held before this function is called, and is 4890 * held by arc_get_data_impl() when it calls zthr_wakeup(). 4891 */ 4892 return (arc_adjust_needed); 4893} 4894 4895/* 4896 * Keep arc_size under arc_c by running arc_adjust which evicts data 4897 * from the ARC. */ 4898/* ARGSUSED */ 4899static void 4900arc_adjust_cb(void *arg, zthr_t *zthr) 4901{ 4902 uint64_t evicted = 0; 4903 4904 /* Evict from cache */ 4905 evicted = arc_adjust(); 4906 4907 /* 4908 * If evicted is zero, we couldn't evict anything 4909 * via arc_adjust(). This could be due to hash lock 4910 * collisions, but more likely due to the majority of 4911 * arc buffers being unevictable. Therefore, even if 4912 * arc_size is above arc_c, another pass is unlikely to 4913 * be helpful and could potentially cause us to enter an 4914 * infinite loop. Additionally, zthr_iscancelled() is 4915 * checked here so that if the arc is shutting down, the 4916 * broadcast will wake any remaining arc adjust waiters. 4917 */ 4918 mutex_enter(&arc_adjust_lock); 4919 arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) && 4920 evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0; 4921 if (!arc_adjust_needed) { 4922 /* 4923 * We're either no longer overflowing, or we 4924 * can't evict anything more, so we should wake 4925 * up any waiters. 4926 */ 4927 cv_broadcast(&arc_adjust_waiters_cv); 4928 } 4929 mutex_exit(&arc_adjust_lock); 4930} 4931 4932/* ARGSUSED */ 4933static boolean_t 4934arc_reap_cb_check(void *arg, zthr_t *zthr) 4935{ 4936 int64_t free_memory = arc_available_memory(); 4937 4938 /* 4939 * If a kmem reap is already active, don't schedule more. We must 4940 * check for this because kmem_cache_reap_soon() won't actually 4941 * block on the cache being reaped (this is to prevent callers from 4942 * becoming implicitly blocked by a system-wide kmem reap -- which, 4943 * on a system with many, many full magazines, can take minutes). 4944 */ 4945 if (!kmem_cache_reap_active() && 4946 free_memory < 0) { 4947 arc_no_grow = B_TRUE; 4948 arc_warm = B_TRUE; 4949 /* 4950 * Wait at least zfs_grow_retry (default 60) seconds 4951 * before considering growing. 4952 */ 4953 arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 4954 return (B_TRUE); 4955 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4956 arc_no_grow = B_TRUE; 4957 } else if (gethrtime() >= arc_growtime) { 4958 arc_no_grow = B_FALSE; 4959 } 4960 4961 return (B_FALSE); 4962} 4963 4964/* 4965 * Keep enough free memory in the system by reaping the ARC's kmem 4966 * caches. To cause more slabs to be reapable, we may reduce the 4967 * target size of the cache (arc_c), causing the arc_adjust_cb() 4968 * to free more buffers. 4969 */ 4970/* ARGSUSED */ 4971static void 4972arc_reap_cb(void *arg, zthr_t *zthr) 4973{ 4974 int64_t free_memory; 4975 4976 /* 4977 * Kick off asynchronous kmem_reap()'s of all our caches. 4978 */ 4979 arc_kmem_reap_soon(); 4980 4981 /* 4982 * Wait at least arc_kmem_cache_reap_retry_ms between 4983 * arc_kmem_reap_soon() calls. Without this check it is possible to 4984 * end up in a situation where we spend lots of time reaping 4985 * caches, while we're near arc_c_min. Waiting here also gives the 4986 * subsequent free memory check a chance of finding that the 4987 * asynchronous reap has already freed enough memory, and we don't 4988 * need to call arc_reduce_target_size(). 4989 */ 4990 delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000); 4991 4992 /* 4993 * Reduce the target size as needed to maintain the amount of free 4994 * memory in the system at a fraction of the arc_size (1/128th by 4995 * default). If oversubscribed (free_memory < 0) then reduce the 4996 * target arc_size by the deficit amount plus the fractional 4997 * amount. If free memory is positive but less then the fractional 4998 * amount, reduce by what is needed to hit the fractional amount. 4999 */ 5000 free_memory = arc_available_memory(); 5001 5002 int64_t to_free = 5003 (arc_c >> arc_shrink_shift) - free_memory; 5004 if (to_free > 0) { 5005#ifdef _KERNEL 5006#ifdef illumos 5007 to_free = MAX(to_free, ptob(needfree)); 5008#endif 5009#endif 5010 arc_reduce_target_size(to_free); 5011 } 5012} 5013 5014static u_int arc_dnlc_evicts_arg; 5015extern struct vfsops zfs_vfsops; 5016 5017static void 5018arc_dnlc_evicts_thread(void *dummy __unused) 5019{ 5020 callb_cpr_t cpr; 5021 u_int percent; 5022 5023 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 5024 5025 mutex_enter(&arc_dnlc_evicts_lock); 5026 while (!arc_dnlc_evicts_thread_exit) { 5027 CALLB_CPR_SAFE_BEGIN(&cpr); 5028 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 5029 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 5030 if (arc_dnlc_evicts_arg != 0) { 5031 percent = arc_dnlc_evicts_arg; 5032 mutex_exit(&arc_dnlc_evicts_lock); 5033#ifdef _KERNEL 5034 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 5035#endif 5036 mutex_enter(&arc_dnlc_evicts_lock); 5037 /* 5038 * Clear our token only after vnlru_free() 5039 * pass is done, to avoid false queueing of 5040 * the requests. 5041 */ 5042 arc_dnlc_evicts_arg = 0; 5043 } 5044 } 5045 arc_dnlc_evicts_thread_exit = FALSE; 5046 cv_broadcast(&arc_dnlc_evicts_cv); 5047 CALLB_CPR_EXIT(&cpr); 5048 thread_exit(); 5049} 5050 5051void 5052dnlc_reduce_cache(void *arg) 5053{ 5054 u_int percent; 5055 5056 percent = (u_int)(uintptr_t)arg; 5057 mutex_enter(&arc_dnlc_evicts_lock); 5058 if (arc_dnlc_evicts_arg == 0) { 5059 arc_dnlc_evicts_arg = percent; 5060 cv_broadcast(&arc_dnlc_evicts_cv); 5061 } 5062 mutex_exit(&arc_dnlc_evicts_lock); 5063} 5064 5065/* 5066 * Adapt arc info given the number of bytes we are trying to add and 5067 * the state that we are comming from. This function is only called 5068 * when we are adding new content to the cache. 5069 */ 5070static void 5071arc_adapt(int bytes, arc_state_t *state) 5072{ 5073 int mult; 5074 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 5075 int64_t mrug_size = zfs_refcount_count(&arc_mru_ghost->arcs_size); 5076 int64_t mfug_size = zfs_refcount_count(&arc_mfu_ghost->arcs_size); 5077 5078 if (state == arc_l2c_only) 5079 return; 5080 5081 ASSERT(bytes > 0); 5082 /* 5083 * Adapt the target size of the MRU list: 5084 * - if we just hit in the MRU ghost list, then increase 5085 * the target size of the MRU list. 5086 * - if we just hit in the MFU ghost list, then increase 5087 * the target size of the MFU list by decreasing the 5088 * target size of the MRU list. 5089 */ 5090 if (state == arc_mru_ghost) { 5091 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 5092 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 5093 5094 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 5095 } else if (state == arc_mfu_ghost) { 5096 uint64_t delta; 5097 5098 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 5099 mult = MIN(mult, 10); 5100 5101 delta = MIN(bytes * mult, arc_p); 5102 arc_p = MAX(arc_p_min, arc_p - delta); 5103 } 5104 ASSERT((int64_t)arc_p >= 0); 5105 5106 /* 5107 * Wake reap thread if we do not have any available memory 5108 */ 5109 if (arc_reclaim_needed()) { 5110 zthr_wakeup(arc_reap_zthr); 5111 return; 5112 } 5113 5114 if (arc_no_grow) 5115 return; 5116 5117 if (arc_c >= arc_c_max) 5118 return; 5119 5120 /* 5121 * If we're within (2 * maxblocksize) bytes of the target 5122 * cache size, increment the target cache size 5123 */ 5124 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) > 5125 0) { 5126 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 5127 atomic_add_64(&arc_c, (int64_t)bytes); 5128 if (arc_c > arc_c_max) 5129 arc_c = arc_c_max; 5130 else if (state == arc_anon) 5131 atomic_add_64(&arc_p, (int64_t)bytes); 5132 if (arc_p > arc_c) 5133 arc_p = arc_c; 5134 } 5135 ASSERT((int64_t)arc_p >= 0); 5136} 5137 5138/* 5139 * Check if arc_size has grown past our upper threshold, determined by 5140 * zfs_arc_overflow_shift. 5141 */ 5142static boolean_t 5143arc_is_overflowing(void) 5144{ 5145 /* Always allow at least one block of overflow */ 5146 int64_t overflow = MAX(SPA_MAXBLOCKSIZE, 5147 arc_c >> zfs_arc_overflow_shift); 5148 5149 /* 5150 * We just compare the lower bound here for performance reasons. Our 5151 * primary goals are to make sure that the arc never grows without 5152 * bound, and that it can reach its maximum size. This check 5153 * accomplishes both goals. The maximum amount we could run over by is 5154 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block 5155 * in the ARC. In practice, that's in the tens of MB, which is low 5156 * enough to be safe. 5157 */ 5158 return (aggsum_lower_bound(&arc_size) >= (int64_t)arc_c + overflow); 5159} 5160 5161static abd_t * 5162arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag, boolean_t do_adapt) 5163{ 5164 arc_buf_contents_t type = arc_buf_type(hdr); 5165 5166 arc_get_data_impl(hdr, size, tag, do_adapt); 5167 if (type == ARC_BUFC_METADATA) { 5168 return (abd_alloc(size, B_TRUE)); 5169 } else { 5170 ASSERT(type == ARC_BUFC_DATA); 5171 return (abd_alloc(size, B_FALSE)); 5172 } 5173} 5174 5175static void * 5176arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 5177{ 5178 arc_buf_contents_t type = arc_buf_type(hdr); 5179 5180 arc_get_data_impl(hdr, size, tag, B_TRUE); 5181 if (type == ARC_BUFC_METADATA) { 5182 return (zio_buf_alloc(size)); 5183 } else { 5184 ASSERT(type == ARC_BUFC_DATA); 5185 return (zio_data_buf_alloc(size)); 5186 } 5187} 5188 5189/* 5190 * Allocate a block and return it to the caller. If we are hitting the 5191 * hard limit for the cache size, we must sleep, waiting for the eviction 5192 * thread to catch up. If we're past the target size but below the hard 5193 * limit, we'll only signal the reclaim thread and continue on. 5194 */ 5195static void 5196arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag, boolean_t do_adapt) 5197{ 5198 arc_state_t *state = hdr->b_l1hdr.b_state; 5199 arc_buf_contents_t type = arc_buf_type(hdr); 5200 5201 if (do_adapt) 5202 arc_adapt(size, state); 5203 5204 /* 5205 * If arc_size is currently overflowing, and has grown past our 5206 * upper limit, we must be adding data faster than the evict 5207 * thread can evict. Thus, to ensure we don't compound the 5208 * problem by adding more data and forcing arc_size to grow even 5209 * further past it's target size, we halt and wait for the 5210 * eviction thread to catch up. 5211 * 5212 * It's also possible that the reclaim thread is unable to evict 5213 * enough buffers to get arc_size below the overflow limit (e.g. 5214 * due to buffers being un-evictable, or hash lock collisions). 5215 * In this case, we want to proceed regardless if we're 5216 * overflowing; thus we don't use a while loop here. 5217 */ 5218 if (arc_is_overflowing()) { 5219 mutex_enter(&arc_adjust_lock); 5220 5221 /* 5222 * Now that we've acquired the lock, we may no longer be 5223 * over the overflow limit, lets check. 5224 * 5225 * We're ignoring the case of spurious wake ups. If that 5226 * were to happen, it'd let this thread consume an ARC 5227 * buffer before it should have (i.e. before we're under 5228 * the overflow limit and were signalled by the reclaim 5229 * thread). As long as that is a rare occurrence, it 5230 * shouldn't cause any harm. 5231 */ 5232 if (arc_is_overflowing()) { 5233 arc_adjust_needed = B_TRUE; 5234 zthr_wakeup(arc_adjust_zthr); 5235 (void) cv_wait(&arc_adjust_waiters_cv, 5236 &arc_adjust_lock); 5237 } 5238 mutex_exit(&arc_adjust_lock); 5239 } 5240 5241 VERIFY3U(hdr->b_type, ==, type); 5242 if (type == ARC_BUFC_METADATA) { 5243 arc_space_consume(size, ARC_SPACE_META); 5244 } else { 5245 arc_space_consume(size, ARC_SPACE_DATA); 5246 } 5247 5248 /* 5249 * Update the state size. Note that ghost states have a 5250 * "ghost size" and so don't need to be updated. 5251 */ 5252 if (!GHOST_STATE(state)) { 5253 5254 (void) zfs_refcount_add_many(&state->arcs_size, size, tag); 5255 5256 /* 5257 * If this is reached via arc_read, the link is 5258 * protected by the hash lock. If reached via 5259 * arc_buf_alloc, the header should not be accessed by 5260 * any other thread. And, if reached via arc_read_done, 5261 * the hash lock will protect it if it's found in the 5262 * hash table; otherwise no other thread should be 5263 * trying to [add|remove]_reference it. 5264 */ 5265 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 5266 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5267 (void) zfs_refcount_add_many(&state->arcs_esize[type], 5268 size, tag); 5269 } 5270 5271 /* 5272 * If we are growing the cache, and we are adding anonymous 5273 * data, and we have outgrown arc_p, update arc_p 5274 */ 5275 if (aggsum_upper_bound(&arc_size) < arc_c && 5276 hdr->b_l1hdr.b_state == arc_anon && 5277 (zfs_refcount_count(&arc_anon->arcs_size) + 5278 zfs_refcount_count(&arc_mru->arcs_size) > arc_p)) 5279 arc_p = MIN(arc_c, arc_p + size); 5280 } 5281 ARCSTAT_BUMP(arcstat_allocated); 5282} 5283 5284static void 5285arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) 5286{ 5287 arc_free_data_impl(hdr, size, tag); 5288 abd_free(abd); 5289} 5290 5291static void 5292arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) 5293{ 5294 arc_buf_contents_t type = arc_buf_type(hdr); 5295 5296 arc_free_data_impl(hdr, size, tag); 5297 if (type == ARC_BUFC_METADATA) { 5298 zio_buf_free(buf, size); 5299 } else { 5300 ASSERT(type == ARC_BUFC_DATA); 5301 zio_data_buf_free(buf, size); 5302 } 5303} 5304 5305/* 5306 * Free the arc data buffer. 5307 */ 5308static void 5309arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 5310{ 5311 arc_state_t *state = hdr->b_l1hdr.b_state; 5312 arc_buf_contents_t type = arc_buf_type(hdr); 5313 5314 /* protected by hash lock, if in the hash table */ 5315 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 5316 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5317 ASSERT(state != arc_anon && state != arc_l2c_only); 5318 5319 (void) zfs_refcount_remove_many(&state->arcs_esize[type], 5320 size, tag); 5321 } 5322 (void) zfs_refcount_remove_many(&state->arcs_size, size, tag); 5323 5324 VERIFY3U(hdr->b_type, ==, type); 5325 if (type == ARC_BUFC_METADATA) { 5326 arc_space_return(size, ARC_SPACE_META); 5327 } else { 5328 ASSERT(type == ARC_BUFC_DATA); 5329 arc_space_return(size, ARC_SPACE_DATA); 5330 } 5331} 5332 5333/* 5334 * This routine is called whenever a buffer is accessed. 5335 * NOTE: the hash lock is dropped in this function. 5336 */ 5337static void 5338arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 5339{ 5340 clock_t now; 5341 5342 ASSERT(MUTEX_HELD(hash_lock)); 5343 ASSERT(HDR_HAS_L1HDR(hdr)); 5344 5345 if (hdr->b_l1hdr.b_state == arc_anon) { 5346 /* 5347 * This buffer is not in the cache, and does not 5348 * appear in our "ghost" list. Add the new buffer 5349 * to the MRU state. 5350 */ 5351 5352 ASSERT0(hdr->b_l1hdr.b_arc_access); 5353 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5354 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 5355 arc_change_state(arc_mru, hdr, hash_lock); 5356 5357 } else if (hdr->b_l1hdr.b_state == arc_mru) { 5358 now = ddi_get_lbolt(); 5359 5360 /* 5361 * If this buffer is here because of a prefetch, then either: 5362 * - clear the flag if this is a "referencing" read 5363 * (any subsequent access will bump this into the MFU state). 5364 * or 5365 * - move the buffer to the head of the list if this is 5366 * another prefetch (to make it less likely to be evicted). 5367 */ 5368 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5369 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5370 /* link protected by hash lock */ 5371 ASSERT(multilist_link_active( 5372 &hdr->b_l1hdr.b_arc_node)); 5373 } else { 5374 arc_hdr_clear_flags(hdr, 5375 ARC_FLAG_PREFETCH | 5376 ARC_FLAG_PRESCIENT_PREFETCH); 5377 ARCSTAT_BUMP(arcstat_mru_hits); 5378 } 5379 hdr->b_l1hdr.b_arc_access = now; 5380 return; 5381 } 5382 5383 /* 5384 * This buffer has been "accessed" only once so far, 5385 * but it is still in the cache. Move it to the MFU 5386 * state. 5387 */ 5388 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 5389 /* 5390 * More than 125ms have passed since we 5391 * instantiated this buffer. Move it to the 5392 * most frequently used state. 5393 */ 5394 hdr->b_l1hdr.b_arc_access = now; 5395 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5396 arc_change_state(arc_mfu, hdr, hash_lock); 5397 } 5398 atomic_inc_32(&hdr->b_l1hdr.b_mru_hits); 5399 ARCSTAT_BUMP(arcstat_mru_hits); 5400 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 5401 arc_state_t *new_state; 5402 /* 5403 * This buffer has been "accessed" recently, but 5404 * was evicted from the cache. Move it to the 5405 * MFU state. 5406 */ 5407 5408 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5409 new_state = arc_mru; 5410 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) { 5411 arc_hdr_clear_flags(hdr, 5412 ARC_FLAG_PREFETCH | 5413 ARC_FLAG_PRESCIENT_PREFETCH); 5414 } 5415 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 5416 } else { 5417 new_state = arc_mfu; 5418 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5419 } 5420 5421 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5422 arc_change_state(new_state, hdr, hash_lock); 5423 5424 atomic_inc_32(&hdr->b_l1hdr.b_mru_ghost_hits); 5425 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 5426 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 5427 /* 5428 * This buffer has been accessed more than once and is 5429 * still in the cache. Keep it in the MFU state. 5430 * 5431 * NOTE: an add_reference() that occurred when we did 5432 * the arc_read() will have kicked this off the list. 5433 * If it was a prefetch, we will explicitly move it to 5434 * the head of the list now. 5435 */ 5436 5437 atomic_inc_32(&hdr->b_l1hdr.b_mfu_hits); 5438 ARCSTAT_BUMP(arcstat_mfu_hits); 5439 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5440 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 5441 arc_state_t *new_state = arc_mfu; 5442 /* 5443 * This buffer has been accessed more than once but has 5444 * been evicted from the cache. Move it back to the 5445 * MFU state. 5446 */ 5447 5448 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5449 /* 5450 * This is a prefetch access... 5451 * move this block back to the MRU state. 5452 */ 5453 new_state = arc_mru; 5454 } 5455 5456 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5457 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5458 arc_change_state(new_state, hdr, hash_lock); 5459 5460 atomic_inc_32(&hdr->b_l1hdr.b_mfu_ghost_hits); 5461 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 5462 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 5463 /* 5464 * This buffer is on the 2nd Level ARC. 5465 */ 5466 5467 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5468 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5469 arc_change_state(arc_mfu, hdr, hash_lock); 5470 } else { 5471 ASSERT(!"invalid arc state"); 5472 } 5473} 5474 5475/* 5476 * This routine is called by dbuf_hold() to update the arc_access() state 5477 * which otherwise would be skipped for entries in the dbuf cache. 5478 */ 5479void 5480arc_buf_access(arc_buf_t *buf) 5481{ 5482 mutex_enter(&buf->b_evict_lock); 5483 arc_buf_hdr_t *hdr = buf->b_hdr; 5484 5485 /* 5486 * Avoid taking the hash_lock when possible as an optimization. 5487 * The header must be checked again under the hash_lock in order 5488 * to handle the case where it is concurrently being released. 5489 */ 5490 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { 5491 mutex_exit(&buf->b_evict_lock); 5492 ARCSTAT_BUMP(arcstat_access_skip); 5493 return; 5494 } 5495 5496 kmutex_t *hash_lock = HDR_LOCK(hdr); 5497 mutex_enter(hash_lock); 5498 5499 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { 5500 mutex_exit(hash_lock); 5501 mutex_exit(&buf->b_evict_lock); 5502 ARCSTAT_BUMP(arcstat_access_skip); 5503 return; 5504 } 5505 5506 mutex_exit(&buf->b_evict_lock); 5507 5508 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5509 hdr->b_l1hdr.b_state == arc_mfu); 5510 5511 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5512 arc_access(hdr, hash_lock); 5513 mutex_exit(hash_lock); 5514 5515 ARCSTAT_BUMP(arcstat_hits); 5516 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5517 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits); 5518} 5519 5520/* a generic arc_read_done_func_t which you can use */ 5521/* ARGSUSED */ 5522void 5523arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, 5524 arc_buf_t *buf, void *arg) 5525{ 5526 if (buf == NULL) 5527 return; 5528 5529 bcopy(buf->b_data, arg, arc_buf_size(buf)); 5530 arc_buf_destroy(buf, arg); 5531} 5532 5533/* a generic arc_read_done_func_t */ 5534/* ARGSUSED */ 5535void 5536arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, 5537 arc_buf_t *buf, void *arg) 5538{ 5539 arc_buf_t **bufp = arg; 5540 if (buf == NULL) { 5541 ASSERT(zio == NULL || zio->io_error != 0); 5542 *bufp = NULL; 5543 } else { 5544 ASSERT(zio == NULL || zio->io_error == 0); 5545 *bufp = buf; 5546 ASSERT(buf->b_data != NULL); 5547 } 5548} 5549 5550static void 5551arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 5552{ 5553 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 5554 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 5555 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 5556 } else { 5557 if (HDR_COMPRESSION_ENABLED(hdr)) { 5558 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 5559 BP_GET_COMPRESS(bp)); 5560 } 5561 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 5562 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 5563 } 5564} 5565 5566static void 5567arc_read_done(zio_t *zio) 5568{ 5569 arc_buf_hdr_t *hdr = zio->io_private; 5570 kmutex_t *hash_lock = NULL; 5571 arc_callback_t *callback_list; 5572 arc_callback_t *acb; 5573 boolean_t freeable = B_FALSE; 5574 boolean_t no_zio_error = (zio->io_error == 0); 5575 5576 /* 5577 * The hdr was inserted into hash-table and removed from lists 5578 * prior to starting I/O. We should find this header, since 5579 * it's in the hash table, and it should be legit since it's 5580 * not possible to evict it during the I/O. The only possible 5581 * reason for it not to be found is if we were freed during the 5582 * read. 5583 */ 5584 if (HDR_IN_HASH_TABLE(hdr)) { 5585 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 5586 ASSERT3U(hdr->b_dva.dva_word[0], ==, 5587 BP_IDENTITY(zio->io_bp)->dva_word[0]); 5588 ASSERT3U(hdr->b_dva.dva_word[1], ==, 5589 BP_IDENTITY(zio->io_bp)->dva_word[1]); 5590 5591 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 5592 &hash_lock); 5593 5594 ASSERT((found == hdr && 5595 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 5596 (found == hdr && HDR_L2_READING(hdr))); 5597 ASSERT3P(hash_lock, !=, NULL); 5598 } 5599 5600 if (no_zio_error) { 5601 /* byteswap if necessary */ 5602 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 5603 if (BP_GET_LEVEL(zio->io_bp) > 0) { 5604 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 5605 } else { 5606 hdr->b_l1hdr.b_byteswap = 5607 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 5608 } 5609 } else { 5610 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 5611 } 5612 } 5613 5614 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 5615 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 5616 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 5617 5618 callback_list = hdr->b_l1hdr.b_acb; 5619 ASSERT3P(callback_list, !=, NULL); 5620 5621 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) { 5622 /* 5623 * Only call arc_access on anonymous buffers. This is because 5624 * if we've issued an I/O for an evicted buffer, we've already 5625 * called arc_access (to prevent any simultaneous readers from 5626 * getting confused). 5627 */ 5628 arc_access(hdr, hash_lock); 5629 } 5630 5631 /* 5632 * If a read request has a callback (i.e. acb_done is not NULL), then we 5633 * make a buf containing the data according to the parameters which were 5634 * passed in. The implementation of arc_buf_alloc_impl() ensures that we 5635 * aren't needlessly decompressing the data multiple times. 5636 */ 5637 int callback_cnt = 0; 5638 for (acb = callback_list; acb != NULL; acb = acb->acb_next) { 5639 if (!acb->acb_done) 5640 continue; 5641 5642 callback_cnt++; 5643 5644 if (no_zio_error) { 5645 int error = arc_buf_alloc_impl(hdr, acb->acb_private, 5646 acb->acb_compressed, zio->io_error == 0, 5647 &acb->acb_buf); 5648 if (error != 0) { 5649 /* 5650 * Decompression failed. Set io_error 5651 * so that when we call acb_done (below), 5652 * we will indicate that the read failed. 5653 * Note that in the unusual case where one 5654 * callback is compressed and another 5655 * uncompressed, we will mark all of them 5656 * as failed, even though the uncompressed 5657 * one can't actually fail. In this case, 5658 * the hdr will not be anonymous, because 5659 * if there are multiple callbacks, it's 5660 * because multiple threads found the same 5661 * arc buf in the hash table. 5662 */ 5663 zio->io_error = error; 5664 } 5665 } 5666 } 5667 /* 5668 * If there are multiple callbacks, we must have the hash lock, 5669 * because the only way for multiple threads to find this hdr is 5670 * in the hash table. This ensures that if there are multiple 5671 * callbacks, the hdr is not anonymous. If it were anonymous, 5672 * we couldn't use arc_buf_destroy() in the error case below. 5673 */ 5674 ASSERT(callback_cnt < 2 || hash_lock != NULL); 5675 5676 hdr->b_l1hdr.b_acb = NULL; 5677 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5678 if (callback_cnt == 0) { 5679 ASSERT(HDR_PREFETCH(hdr)); 5680 ASSERT0(hdr->b_l1hdr.b_bufcnt); 5681 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5682 } 5683 5684 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 5685 callback_list != NULL); 5686 5687 if (no_zio_error) { 5688 arc_hdr_verify(hdr, zio->io_bp); 5689 } else { 5690 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 5691 if (hdr->b_l1hdr.b_state != arc_anon) 5692 arc_change_state(arc_anon, hdr, hash_lock); 5693 if (HDR_IN_HASH_TABLE(hdr)) 5694 buf_hash_remove(hdr); 5695 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5696 } 5697 5698 /* 5699 * Broadcast before we drop the hash_lock to avoid the possibility 5700 * that the hdr (and hence the cv) might be freed before we get to 5701 * the cv_broadcast(). 5702 */ 5703 cv_broadcast(&hdr->b_l1hdr.b_cv); 5704 5705 if (hash_lock != NULL) { 5706 mutex_exit(hash_lock); 5707 } else { 5708 /* 5709 * This block was freed while we waited for the read to 5710 * complete. It has been removed from the hash table and 5711 * moved to the anonymous state (so that it won't show up 5712 * in the cache). 5713 */ 5714 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 5715 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5716 } 5717 5718 /* execute each callback and free its structure */ 5719 while ((acb = callback_list) != NULL) { 5720 if (acb->acb_done != NULL) { 5721 if (zio->io_error != 0 && acb->acb_buf != NULL) { 5722 /* 5723 * If arc_buf_alloc_impl() fails during 5724 * decompression, the buf will still be 5725 * allocated, and needs to be freed here. 5726 */ 5727 arc_buf_destroy(acb->acb_buf, acb->acb_private); 5728 acb->acb_buf = NULL; 5729 } 5730 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp, 5731 acb->acb_buf, acb->acb_private); 5732 } 5733 5734 if (acb->acb_zio_dummy != NULL) { 5735 acb->acb_zio_dummy->io_error = zio->io_error; 5736 zio_nowait(acb->acb_zio_dummy); 5737 } 5738 5739 callback_list = acb->acb_next; 5740 kmem_free(acb, sizeof (arc_callback_t)); 5741 } 5742 5743 if (freeable) 5744 arc_hdr_destroy(hdr); 5745} 5746 5747/* 5748 * "Read" the block at the specified DVA (in bp) via the 5749 * cache. If the block is found in the cache, invoke the provided 5750 * callback immediately and return. Note that the `zio' parameter 5751 * in the callback will be NULL in this case, since no IO was 5752 * required. If the block is not in the cache pass the read request 5753 * on to the spa with a substitute callback function, so that the 5754 * requested block will be added to the cache. 5755 * 5756 * If a read request arrives for a block that has a read in-progress, 5757 * either wait for the in-progress read to complete (and return the 5758 * results); or, if this is a read with a "done" func, add a record 5759 * to the read to invoke the "done" func when the read completes, 5760 * and return; or just return. 5761 * 5762 * arc_read_done() will invoke all the requested "done" functions 5763 * for readers of this block. 5764 */ 5765int 5766arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_read_done_func_t *done, 5767 void *private, zio_priority_t priority, int zio_flags, 5768 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 5769{ 5770 arc_buf_hdr_t *hdr = NULL; 5771 kmutex_t *hash_lock = NULL; 5772 zio_t *rzio; 5773 uint64_t guid = spa_load_guid(spa); 5774 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0; 5775 int rc = 0; 5776 5777 ASSERT(!BP_IS_EMBEDDED(bp) || 5778 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 5779 5780top: 5781 if (!BP_IS_EMBEDDED(bp)) { 5782 /* 5783 * Embedded BP's have no DVA and require no I/O to "read". 5784 * Create an anonymous arc buf to back it. 5785 */ 5786 hdr = buf_hash_find(guid, bp, &hash_lock); 5787 } 5788 5789 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { 5790 arc_buf_t *buf = NULL; 5791 *arc_flags |= ARC_FLAG_CACHED; 5792 5793 if (HDR_IO_IN_PROGRESS(hdr)) { 5794 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head; 5795 5796 ASSERT3P(head_zio, !=, NULL); 5797 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 5798 priority == ZIO_PRIORITY_SYNC_READ) { 5799 /* 5800 * This is a sync read that needs to wait for 5801 * an in-flight async read. Request that the 5802 * zio have its priority upgraded. 5803 */ 5804 zio_change_priority(head_zio, priority); 5805 DTRACE_PROBE1(arc__async__upgrade__sync, 5806 arc_buf_hdr_t *, hdr); 5807 ARCSTAT_BUMP(arcstat_async_upgrade_sync); 5808 } 5809 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5810 arc_hdr_clear_flags(hdr, 5811 ARC_FLAG_PREDICTIVE_PREFETCH); 5812 } 5813 5814 if (*arc_flags & ARC_FLAG_WAIT) { 5815 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 5816 mutex_exit(hash_lock); 5817 goto top; 5818 } 5819 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5820 5821 if (done) { 5822 arc_callback_t *acb = NULL; 5823 5824 acb = kmem_zalloc(sizeof (arc_callback_t), 5825 KM_SLEEP); 5826 acb->acb_done = done; 5827 acb->acb_private = private; 5828 acb->acb_compressed = compressed_read; 5829 if (pio != NULL) 5830 acb->acb_zio_dummy = zio_null(pio, 5831 spa, NULL, NULL, NULL, zio_flags); 5832 5833 ASSERT3P(acb->acb_done, !=, NULL); 5834 acb->acb_zio_head = head_zio; 5835 acb->acb_next = hdr->b_l1hdr.b_acb; 5836 hdr->b_l1hdr.b_acb = acb; 5837 mutex_exit(hash_lock); 5838 return (0); 5839 } 5840 mutex_exit(hash_lock); 5841 return (0); 5842 } 5843 5844 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5845 hdr->b_l1hdr.b_state == arc_mfu); 5846 5847 if (done) { 5848 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5849 /* 5850 * This is a demand read which does not have to 5851 * wait for i/o because we did a predictive 5852 * prefetch i/o for it, which has completed. 5853 */ 5854 DTRACE_PROBE1( 5855 arc__demand__hit__predictive__prefetch, 5856 arc_buf_hdr_t *, hdr); 5857 ARCSTAT_BUMP( 5858 arcstat_demand_hit_predictive_prefetch); 5859 arc_hdr_clear_flags(hdr, 5860 ARC_FLAG_PREDICTIVE_PREFETCH); 5861 } 5862 5863 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) { 5864 ARCSTAT_BUMP( 5865 arcstat_demand_hit_prescient_prefetch); 5866 arc_hdr_clear_flags(hdr, 5867 ARC_FLAG_PRESCIENT_PREFETCH); 5868 } 5869 5870 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 5871 /* Get a buf with the desired data in it. */ 5872 rc = arc_buf_alloc_impl(hdr, private, 5873 compressed_read, B_TRUE, &buf); 5874 if (rc != 0) { 5875 arc_buf_destroy(buf, private); 5876 buf = NULL; 5877 } 5878 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) || 5879 rc == 0 || rc != ENOENT); 5880 } else if (*arc_flags & ARC_FLAG_PREFETCH && 5881 zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5882 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5883 } 5884 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5885 arc_access(hdr, hash_lock); 5886 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) 5887 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); 5888 if (*arc_flags & ARC_FLAG_L2CACHE) 5889 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5890 mutex_exit(hash_lock); 5891 ARCSTAT_BUMP(arcstat_hits); 5892 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5893 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5894 data, metadata, hits); 5895 5896 if (done) 5897 done(NULL, zb, bp, buf, private); 5898 } else { 5899 uint64_t lsize = BP_GET_LSIZE(bp); 5900 uint64_t psize = BP_GET_PSIZE(bp); 5901 arc_callback_t *acb; 5902 vdev_t *vd = NULL; 5903 uint64_t addr = 0; 5904 boolean_t devw = B_FALSE; 5905 uint64_t size; 5906 5907 if (hdr == NULL) { 5908 /* this block is not in the cache */ 5909 arc_buf_hdr_t *exists = NULL; 5910 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 5911 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 5912 BP_GET_COMPRESS(bp), type); 5913 5914 if (!BP_IS_EMBEDDED(bp)) { 5915 hdr->b_dva = *BP_IDENTITY(bp); 5916 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 5917 exists = buf_hash_insert(hdr, &hash_lock); 5918 } 5919 if (exists != NULL) { 5920 /* somebody beat us to the hash insert */ 5921 mutex_exit(hash_lock); 5922 buf_discard_identity(hdr); 5923 arc_hdr_destroy(hdr); 5924 goto top; /* restart the IO request */ 5925 } 5926 } else { 5927 /* 5928 * This block is in the ghost cache. If it was L2-only 5929 * (and thus didn't have an L1 hdr), we realloc the 5930 * header to add an L1 hdr. 5931 */ 5932 if (!HDR_HAS_L1HDR(hdr)) { 5933 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 5934 hdr_full_cache); 5935 } 5936 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5937 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 5938 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5939 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5940 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 5941 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 5942 5943 /* 5944 * This is a delicate dance that we play here. 5945 * This hdr is in the ghost list so we access it 5946 * to move it out of the ghost list before we 5947 * initiate the read. If it's a prefetch then 5948 * it won't have a callback so we'll remove the 5949 * reference that arc_buf_alloc_impl() created. We 5950 * do this after we've called arc_access() to 5951 * avoid hitting an assert in remove_reference(). 5952 */ 5953 arc_adapt(arc_hdr_size(hdr), hdr->b_l1hdr.b_state); 5954 arc_access(hdr, hash_lock); 5955 arc_hdr_alloc_pabd(hdr, B_FALSE); 5956 } 5957 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5958 size = arc_hdr_size(hdr); 5959 5960 /* 5961 * If compression is enabled on the hdr, then will do 5962 * RAW I/O and will store the compressed data in the hdr's 5963 * data block. Otherwise, the hdr's data block will contain 5964 * the uncompressed data. 5965 */ 5966 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5967 zio_flags |= ZIO_FLAG_RAW; 5968 } 5969 5970 if (*arc_flags & ARC_FLAG_PREFETCH) 5971 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5972 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) 5973 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); 5974 5975 if (*arc_flags & ARC_FLAG_L2CACHE) 5976 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5977 if (BP_GET_LEVEL(bp) > 0) 5978 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5979 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5980 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5981 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5982 5983 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5984 acb->acb_done = done; 5985 acb->acb_private = private; 5986 acb->acb_compressed = compressed_read; 5987 5988 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5989 hdr->b_l1hdr.b_acb = acb; 5990 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5991 5992 if (HDR_HAS_L2HDR(hdr) && 5993 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5994 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5995 addr = hdr->b_l2hdr.b_daddr; 5996 /* 5997 * Lock out L2ARC device removal. 5998 */ 5999 if (vdev_is_dead(vd) || 6000 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 6001 vd = NULL; 6002 } 6003 6004 /* 6005 * We count both async reads and scrub IOs as asynchronous so 6006 * that both can be upgraded in the event of a cache hit while 6007 * the read IO is still in-flight. 6008 */ 6009 if (priority == ZIO_PRIORITY_ASYNC_READ || 6010 priority == ZIO_PRIORITY_SCRUB) 6011 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 6012 else 6013 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 6014 6015 /* 6016 * At this point, we have a level 1 cache miss. Try again in 6017 * L2ARC if possible. 6018 */ 6019 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 6020 6021 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 6022 uint64_t, lsize, zbookmark_phys_t *, zb); 6023 ARCSTAT_BUMP(arcstat_misses); 6024 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 6025 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 6026 data, metadata, misses); 6027#ifdef _KERNEL 6028#ifdef RACCT 6029 if (racct_enable) { 6030 PROC_LOCK(curproc); 6031 racct_add_force(curproc, RACCT_READBPS, size); 6032 racct_add_force(curproc, RACCT_READIOPS, 1); 6033 PROC_UNLOCK(curproc); 6034 } 6035#endif /* RACCT */ 6036 curthread->td_ru.ru_inblock++; 6037#endif 6038 6039 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 6040 /* 6041 * Read from the L2ARC if the following are true: 6042 * 1. The L2ARC vdev was previously cached. 6043 * 2. This buffer still has L2ARC metadata. 6044 * 3. This buffer isn't currently writing to the L2ARC. 6045 * 4. The L2ARC entry wasn't evicted, which may 6046 * also have invalidated the vdev. 6047 * 5. This isn't prefetch and l2arc_noprefetch is set. 6048 */ 6049 if (HDR_HAS_L2HDR(hdr) && 6050 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 6051 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 6052 l2arc_read_callback_t *cb; 6053 abd_t *abd; 6054 uint64_t asize; 6055 6056 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 6057 ARCSTAT_BUMP(arcstat_l2_hits); 6058 atomic_inc_32(&hdr->b_l2hdr.b_hits); 6059 6060 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 6061 KM_SLEEP); 6062 cb->l2rcb_hdr = hdr; 6063 cb->l2rcb_bp = *bp; 6064 cb->l2rcb_zb = *zb; 6065 cb->l2rcb_flags = zio_flags; 6066 6067 asize = vdev_psize_to_asize(vd, size); 6068 if (asize != size) { 6069 abd = abd_alloc_for_io(asize, 6070 HDR_ISTYPE_METADATA(hdr)); 6071 cb->l2rcb_abd = abd; 6072 } else { 6073 abd = hdr->b_l1hdr.b_pabd; 6074 } 6075 6076 ASSERT(addr >= VDEV_LABEL_START_SIZE && 6077 addr + asize <= vd->vdev_psize - 6078 VDEV_LABEL_END_SIZE); 6079 6080 /* 6081 * l2arc read. The SCL_L2ARC lock will be 6082 * released by l2arc_read_done(). 6083 * Issue a null zio if the underlying buffer 6084 * was squashed to zero size by compression. 6085 */ 6086 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 6087 ZIO_COMPRESS_EMPTY); 6088 rzio = zio_read_phys(pio, vd, addr, 6089 asize, abd, 6090 ZIO_CHECKSUM_OFF, 6091 l2arc_read_done, cb, priority, 6092 zio_flags | ZIO_FLAG_DONT_CACHE | 6093 ZIO_FLAG_CANFAIL | 6094 ZIO_FLAG_DONT_PROPAGATE | 6095 ZIO_FLAG_DONT_RETRY, B_FALSE); 6096 acb->acb_zio_head = rzio; 6097 6098 if (hash_lock != NULL) 6099 mutex_exit(hash_lock); 6100 6101 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 6102 zio_t *, rzio); 6103 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 6104 6105 if (*arc_flags & ARC_FLAG_NOWAIT) { 6106 zio_nowait(rzio); 6107 return (0); 6108 } 6109 6110 ASSERT(*arc_flags & ARC_FLAG_WAIT); 6111 if (zio_wait(rzio) == 0) 6112 return (0); 6113 6114 /* l2arc read error; goto zio_read() */ 6115 if (hash_lock != NULL) 6116 mutex_enter(hash_lock); 6117 } else { 6118 DTRACE_PROBE1(l2arc__miss, 6119 arc_buf_hdr_t *, hdr); 6120 ARCSTAT_BUMP(arcstat_l2_misses); 6121 if (HDR_L2_WRITING(hdr)) 6122 ARCSTAT_BUMP(arcstat_l2_rw_clash); 6123 spa_config_exit(spa, SCL_L2ARC, vd); 6124 } 6125 } else { 6126 if (vd != NULL) 6127 spa_config_exit(spa, SCL_L2ARC, vd); 6128 if (l2arc_ndev != 0) { 6129 DTRACE_PROBE1(l2arc__miss, 6130 arc_buf_hdr_t *, hdr); 6131 ARCSTAT_BUMP(arcstat_l2_misses); 6132 } 6133 } 6134 6135 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size, 6136 arc_read_done, hdr, priority, zio_flags, zb); 6137 acb->acb_zio_head = rzio; 6138 6139 if (hash_lock != NULL) 6140 mutex_exit(hash_lock); 6141 6142 if (*arc_flags & ARC_FLAG_WAIT) 6143 return (zio_wait(rzio)); 6144 6145 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 6146 zio_nowait(rzio); 6147 } 6148 return (0); 6149} 6150 6151arc_prune_t * 6152arc_add_prune_callback(arc_prune_func_t *func, void *private) 6153{ 6154 arc_prune_t *p; 6155 6156 p = kmem_alloc(sizeof (*p), KM_SLEEP); 6157 p->p_pfunc = func; 6158 p->p_private = private; 6159 list_link_init(&p->p_node); 6160 zfs_refcount_create(&p->p_refcnt); 6161 6162 mutex_enter(&arc_prune_mtx); 6163 zfs_refcount_add(&p->p_refcnt, &arc_prune_list); 6164 list_insert_head(&arc_prune_list, p); 6165 mutex_exit(&arc_prune_mtx); 6166 6167 return (p); 6168} 6169 6170void 6171arc_remove_prune_callback(arc_prune_t *p) 6172{ 6173 boolean_t wait = B_FALSE; 6174 mutex_enter(&arc_prune_mtx); 6175 list_remove(&arc_prune_list, p); 6176 if (zfs_refcount_remove(&p->p_refcnt, &arc_prune_list) > 0) 6177 wait = B_TRUE; 6178 mutex_exit(&arc_prune_mtx); 6179 6180 /* wait for arc_prune_task to finish */ 6181 if (wait) 6182 taskq_wait(arc_prune_taskq); 6183 ASSERT0(zfs_refcount_count(&p->p_refcnt)); 6184 zfs_refcount_destroy(&p->p_refcnt); 6185 kmem_free(p, sizeof (*p)); 6186} 6187 6188/* 6189 * Notify the arc that a block was freed, and thus will never be used again. 6190 */ 6191void 6192arc_freed(spa_t *spa, const blkptr_t *bp) 6193{ 6194 arc_buf_hdr_t *hdr; 6195 kmutex_t *hash_lock; 6196 uint64_t guid = spa_load_guid(spa); 6197 6198 ASSERT(!BP_IS_EMBEDDED(bp)); 6199 6200 hdr = buf_hash_find(guid, bp, &hash_lock); 6201 if (hdr == NULL) 6202 return; 6203 6204 /* 6205 * We might be trying to free a block that is still doing I/O 6206 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 6207 * dmu_sync-ed block). If this block is being prefetched, then it 6208 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 6209 * until the I/O completes. A block may also have a reference if it is 6210 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 6211 * have written the new block to its final resting place on disk but 6212 * without the dedup flag set. This would have left the hdr in the MRU 6213 * state and discoverable. When the txg finally syncs it detects that 6214 * the block was overridden in open context and issues an override I/O. 6215 * Since this is a dedup block, the override I/O will determine if the 6216 * block is already in the DDT. If so, then it will replace the io_bp 6217 * with the bp from the DDT and allow the I/O to finish. When the I/O 6218 * reaches the done callback, dbuf_write_override_done, it will 6219 * check to see if the io_bp and io_bp_override are identical. 6220 * If they are not, then it indicates that the bp was replaced with 6221 * the bp in the DDT and the override bp is freed. This allows 6222 * us to arrive here with a reference on a block that is being 6223 * freed. So if we have an I/O in progress, or a reference to 6224 * this hdr, then we don't destroy the hdr. 6225 */ 6226 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 6227 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 6228 arc_change_state(arc_anon, hdr, hash_lock); 6229 arc_hdr_destroy(hdr); 6230 mutex_exit(hash_lock); 6231 } else { 6232 mutex_exit(hash_lock); 6233 } 6234 6235} 6236 6237/* 6238 * Release this buffer from the cache, making it an anonymous buffer. This 6239 * must be done after a read and prior to modifying the buffer contents. 6240 * If the buffer has more than one reference, we must make 6241 * a new hdr for the buffer. 6242 */ 6243void 6244arc_release(arc_buf_t *buf, void *tag) 6245{ 6246 arc_buf_hdr_t *hdr = buf->b_hdr; 6247 6248 /* 6249 * It would be nice to assert that if it's DMU metadata (level > 6250 * 0 || it's the dnode file), then it must be syncing context. 6251 * But we don't know that information at this level. 6252 */ 6253 6254 mutex_enter(&buf->b_evict_lock); 6255 6256 ASSERT(HDR_HAS_L1HDR(hdr)); 6257 6258 /* 6259 * We don't grab the hash lock prior to this check, because if 6260 * the buffer's header is in the arc_anon state, it won't be 6261 * linked into the hash table. 6262 */ 6263 if (hdr->b_l1hdr.b_state == arc_anon) { 6264 mutex_exit(&buf->b_evict_lock); 6265 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6266 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 6267 ASSERT(!HDR_HAS_L2HDR(hdr)); 6268 ASSERT(HDR_EMPTY(hdr)); 6269 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 6270 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 6271 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 6272 6273 hdr->b_l1hdr.b_arc_access = 0; 6274 6275 /* 6276 * If the buf is being overridden then it may already 6277 * have a hdr that is not empty. 6278 */ 6279 buf_discard_identity(hdr); 6280 arc_buf_thaw(buf); 6281 6282 return; 6283 } 6284 6285 kmutex_t *hash_lock = HDR_LOCK(hdr); 6286 mutex_enter(hash_lock); 6287 6288 /* 6289 * This assignment is only valid as long as the hash_lock is 6290 * held, we must be careful not to reference state or the 6291 * b_state field after dropping the lock. 6292 */ 6293 arc_state_t *state = hdr->b_l1hdr.b_state; 6294 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6295 ASSERT3P(state, !=, arc_anon); 6296 6297 /* this buffer is not on any list */ 6298 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); 6299 6300 if (HDR_HAS_L2HDR(hdr)) { 6301 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 6302 6303 /* 6304 * We have to recheck this conditional again now that 6305 * we're holding the l2ad_mtx to prevent a race with 6306 * another thread which might be concurrently calling 6307 * l2arc_evict(). In that case, l2arc_evict() might have 6308 * destroyed the header's L2 portion as we were waiting 6309 * to acquire the l2ad_mtx. 6310 */ 6311 if (HDR_HAS_L2HDR(hdr)) { 6312 l2arc_trim(hdr); 6313 arc_hdr_l2hdr_destroy(hdr); 6314 } 6315 6316 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 6317 } 6318 6319 /* 6320 * Do we have more than one buf? 6321 */ 6322 if (hdr->b_l1hdr.b_bufcnt > 1) { 6323 arc_buf_hdr_t *nhdr; 6324 uint64_t spa = hdr->b_spa; 6325 uint64_t psize = HDR_GET_PSIZE(hdr); 6326 uint64_t lsize = HDR_GET_LSIZE(hdr); 6327 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 6328 arc_buf_contents_t type = arc_buf_type(hdr); 6329 VERIFY3U(hdr->b_type, ==, type); 6330 6331 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 6332 (void) remove_reference(hdr, hash_lock, tag); 6333 6334 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { 6335 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 6336 ASSERT(ARC_BUF_LAST(buf)); 6337 } 6338 6339 /* 6340 * Pull the data off of this hdr and attach it to 6341 * a new anonymous hdr. Also find the last buffer 6342 * in the hdr's buffer list. 6343 */ 6344 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 6345 ASSERT3P(lastbuf, !=, NULL); 6346 6347 /* 6348 * If the current arc_buf_t and the hdr are sharing their data 6349 * buffer, then we must stop sharing that block. 6350 */ 6351 if (arc_buf_is_shared(buf)) { 6352 VERIFY(!arc_buf_is_shared(lastbuf)); 6353 6354 /* 6355 * First, sever the block sharing relationship between 6356 * buf and the arc_buf_hdr_t. 6357 */ 6358 arc_unshare_buf(hdr, buf); 6359 6360 /* 6361 * Now we need to recreate the hdr's b_pabd. Since we 6362 * have lastbuf handy, we try to share with it, but if 6363 * we can't then we allocate a new b_pabd and copy the 6364 * data from buf into it. 6365 */ 6366 if (arc_can_share(hdr, lastbuf)) { 6367 arc_share_buf(hdr, lastbuf); 6368 } else { 6369 arc_hdr_alloc_pabd(hdr, B_TRUE); 6370 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, 6371 buf->b_data, psize); 6372 } 6373 VERIFY3P(lastbuf->b_data, !=, NULL); 6374 } else if (HDR_SHARED_DATA(hdr)) { 6375 /* 6376 * Uncompressed shared buffers are always at the end 6377 * of the list. Compressed buffers don't have the 6378 * same requirements. This makes it hard to 6379 * simply assert that the lastbuf is shared so 6380 * we rely on the hdr's compression flags to determine 6381 * if we have a compressed, shared buffer. 6382 */ 6383 ASSERT(arc_buf_is_shared(lastbuf) || 6384 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 6385 ASSERT(!ARC_BUF_SHARED(buf)); 6386 } 6387 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 6388 ASSERT3P(state, !=, arc_l2c_only); 6389 6390 (void) zfs_refcount_remove_many(&state->arcs_size, 6391 arc_buf_size(buf), buf); 6392 6393 if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 6394 ASSERT3P(state, !=, arc_l2c_only); 6395 (void) zfs_refcount_remove_many( 6396 &state->arcs_esize[type], 6397 arc_buf_size(buf), buf); 6398 } 6399 6400 hdr->b_l1hdr.b_bufcnt -= 1; 6401 arc_cksum_verify(buf); 6402#ifdef illumos 6403 arc_buf_unwatch(buf); 6404#endif 6405 6406 mutex_exit(hash_lock); 6407 6408 /* 6409 * Allocate a new hdr. The new hdr will contain a b_pabd 6410 * buffer which will be freed in arc_write(). 6411 */ 6412 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 6413 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 6414 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 6415 ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt)); 6416 VERIFY3U(nhdr->b_type, ==, type); 6417 ASSERT(!HDR_SHARED_DATA(nhdr)); 6418 6419 nhdr->b_l1hdr.b_buf = buf; 6420 nhdr->b_l1hdr.b_bufcnt = 1; 6421 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 6422 buf->b_hdr = nhdr; 6423 6424 mutex_exit(&buf->b_evict_lock); 6425 (void) zfs_refcount_add_many(&arc_anon->arcs_size, 6426 arc_buf_size(buf), buf); 6427 } else { 6428 mutex_exit(&buf->b_evict_lock); 6429 ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 6430 /* protected by hash lock, or hdr is on arc_anon */ 6431 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 6432 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6433 arc_change_state(arc_anon, hdr, hash_lock); 6434 hdr->b_l1hdr.b_arc_access = 0; 6435 mutex_exit(hash_lock); 6436 6437 buf_discard_identity(hdr); 6438 arc_buf_thaw(buf); 6439 } 6440} 6441 6442int 6443arc_released(arc_buf_t *buf) 6444{ 6445 int released; 6446 6447 mutex_enter(&buf->b_evict_lock); 6448 released = (buf->b_data != NULL && 6449 buf->b_hdr->b_l1hdr.b_state == arc_anon); 6450 mutex_exit(&buf->b_evict_lock); 6451 return (released); 6452} 6453 6454#ifdef ZFS_DEBUG 6455int 6456arc_referenced(arc_buf_t *buf) 6457{ 6458 int referenced; 6459 6460 mutex_enter(&buf->b_evict_lock); 6461 referenced = (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 6462 mutex_exit(&buf->b_evict_lock); 6463 return (referenced); 6464} 6465#endif 6466 6467static void 6468arc_write_ready(zio_t *zio) 6469{ 6470 arc_write_callback_t *callback = zio->io_private; 6471 arc_buf_t *buf = callback->awcb_buf; 6472 arc_buf_hdr_t *hdr = buf->b_hdr; 6473 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 6474 6475 ASSERT(HDR_HAS_L1HDR(hdr)); 6476 ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 6477 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 6478 6479 /* 6480 * If we're reexecuting this zio because the pool suspended, then 6481 * cleanup any state that was previously set the first time the 6482 * callback was invoked. 6483 */ 6484 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 6485 arc_cksum_free(hdr); 6486#ifdef illumos 6487 arc_buf_unwatch(buf); 6488#endif 6489 if (hdr->b_l1hdr.b_pabd != NULL) { 6490 if (arc_buf_is_shared(buf)) { 6491 arc_unshare_buf(hdr, buf); 6492 } else { 6493 arc_hdr_free_pabd(hdr); 6494 } 6495 } 6496 } 6497 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6498 ASSERT(!HDR_SHARED_DATA(hdr)); 6499 ASSERT(!arc_buf_is_shared(buf)); 6500 6501 callback->awcb_ready(zio, buf, callback->awcb_private); 6502 6503 if (HDR_IO_IN_PROGRESS(hdr)) 6504 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 6505 6506 arc_cksum_compute(buf); 6507 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6508 6509 enum zio_compress compress; 6510 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 6511 compress = ZIO_COMPRESS_OFF; 6512 } else { 6513 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 6514 compress = BP_GET_COMPRESS(zio->io_bp); 6515 } 6516 HDR_SET_PSIZE(hdr, psize); 6517 arc_hdr_set_compress(hdr, compress); 6518 6519 6520 /* 6521 * Fill the hdr with data. If the hdr is compressed, the data we want 6522 * is available from the zio, otherwise we can take it from the buf. 6523 * 6524 * We might be able to share the buf's data with the hdr here. However, 6525 * doing so would cause the ARC to be full of linear ABDs if we write a 6526 * lot of shareable data. As a compromise, we check whether scattered 6527 * ABDs are allowed, and assume that if they are then the user wants 6528 * the ARC to be primarily filled with them regardless of the data being 6529 * written. Therefore, if they're allowed then we allocate one and copy 6530 * the data into it; otherwise, we share the data directly if we can. 6531 */ 6532 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { 6533 arc_hdr_alloc_pabd(hdr, B_TRUE); 6534 6535 /* 6536 * Ideally, we would always copy the io_abd into b_pabd, but the 6537 * user may have disabled compressed ARC, thus we must check the 6538 * hdr's compression setting rather than the io_bp's. 6539 */ 6540 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 6541 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, 6542 ZIO_COMPRESS_OFF); 6543 ASSERT3U(psize, >, 0); 6544 6545 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); 6546 } else { 6547 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); 6548 6549 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, 6550 arc_buf_size(buf)); 6551 } 6552 } else { 6553 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); 6554 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); 6555 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 6556 6557 arc_share_buf(hdr, buf); 6558 } 6559 6560 arc_hdr_verify(hdr, zio->io_bp); 6561} 6562 6563static void 6564arc_write_children_ready(zio_t *zio) 6565{ 6566 arc_write_callback_t *callback = zio->io_private; 6567 arc_buf_t *buf = callback->awcb_buf; 6568 6569 callback->awcb_children_ready(zio, buf, callback->awcb_private); 6570} 6571 6572/* 6573 * The SPA calls this callback for each physical write that happens on behalf 6574 * of a logical write. See the comment in dbuf_write_physdone() for details. 6575 */ 6576static void 6577arc_write_physdone(zio_t *zio) 6578{ 6579 arc_write_callback_t *cb = zio->io_private; 6580 if (cb->awcb_physdone != NULL) 6581 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 6582} 6583 6584static void 6585arc_write_done(zio_t *zio) 6586{ 6587 arc_write_callback_t *callback = zio->io_private; 6588 arc_buf_t *buf = callback->awcb_buf; 6589 arc_buf_hdr_t *hdr = buf->b_hdr; 6590 6591 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6592 6593 if (zio->io_error == 0) { 6594 arc_hdr_verify(hdr, zio->io_bp); 6595 6596 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 6597 buf_discard_identity(hdr); 6598 } else { 6599 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 6600 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 6601 } 6602 } else { 6603 ASSERT(HDR_EMPTY(hdr)); 6604 } 6605 6606 /* 6607 * If the block to be written was all-zero or compressed enough to be 6608 * embedded in the BP, no write was performed so there will be no 6609 * dva/birth/checksum. The buffer must therefore remain anonymous 6610 * (and uncached). 6611 */ 6612 if (!HDR_EMPTY(hdr)) { 6613 arc_buf_hdr_t *exists; 6614 kmutex_t *hash_lock; 6615 6616 ASSERT3U(zio->io_error, ==, 0); 6617 6618 arc_cksum_verify(buf); 6619 6620 exists = buf_hash_insert(hdr, &hash_lock); 6621 if (exists != NULL) { 6622 /* 6623 * This can only happen if we overwrite for 6624 * sync-to-convergence, because we remove 6625 * buffers from the hash table when we arc_free(). 6626 */ 6627 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 6628 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6629 panic("bad overwrite, hdr=%p exists=%p", 6630 (void *)hdr, (void *)exists); 6631 ASSERT(zfs_refcount_is_zero( 6632 &exists->b_l1hdr.b_refcnt)); 6633 arc_change_state(arc_anon, exists, hash_lock); 6634 mutex_exit(hash_lock); 6635 arc_hdr_destroy(exists); 6636 exists = buf_hash_insert(hdr, &hash_lock); 6637 ASSERT3P(exists, ==, NULL); 6638 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 6639 /* nopwrite */ 6640 ASSERT(zio->io_prop.zp_nopwrite); 6641 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6642 panic("bad nopwrite, hdr=%p exists=%p", 6643 (void *)hdr, (void *)exists); 6644 } else { 6645 /* Dedup */ 6646 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 6647 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 6648 ASSERT(BP_GET_DEDUP(zio->io_bp)); 6649 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 6650 } 6651 } 6652 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6653 /* if it's not anon, we are doing a scrub */ 6654 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 6655 arc_access(hdr, hash_lock); 6656 mutex_exit(hash_lock); 6657 } else { 6658 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6659 } 6660 6661 ASSERT(!zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 6662 callback->awcb_done(zio, buf, callback->awcb_private); 6663 6664 abd_put(zio->io_abd); 6665 kmem_free(callback, sizeof (arc_write_callback_t)); 6666} 6667 6668zio_t * 6669arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 6670 boolean_t l2arc, const zio_prop_t *zp, arc_write_done_func_t *ready, 6671 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone, 6672 arc_write_done_func_t *done, void *private, zio_priority_t priority, 6673 int zio_flags, const zbookmark_phys_t *zb) 6674{ 6675 arc_buf_hdr_t *hdr = buf->b_hdr; 6676 arc_write_callback_t *callback; 6677 zio_t *zio; 6678 zio_prop_t localprop = *zp; 6679 6680 ASSERT3P(ready, !=, NULL); 6681 ASSERT3P(done, !=, NULL); 6682 ASSERT(!HDR_IO_ERROR(hdr)); 6683 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6684 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6685 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 6686 if (l2arc) 6687 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 6688 if (ARC_BUF_COMPRESSED(buf)) { 6689 /* 6690 * We're writing a pre-compressed buffer. Make the 6691 * compression algorithm requested by the zio_prop_t match 6692 * the pre-compressed buffer's compression algorithm. 6693 */ 6694 localprop.zp_compress = HDR_GET_COMPRESS(hdr); 6695 6696 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); 6697 zio_flags |= ZIO_FLAG_RAW; 6698 } 6699 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 6700 callback->awcb_ready = ready; 6701 callback->awcb_children_ready = children_ready; 6702 callback->awcb_physdone = physdone; 6703 callback->awcb_done = done; 6704 callback->awcb_private = private; 6705 callback->awcb_buf = buf; 6706 6707 /* 6708 * The hdr's b_pabd is now stale, free it now. A new data block 6709 * will be allocated when the zio pipeline calls arc_write_ready(). 6710 */ 6711 if (hdr->b_l1hdr.b_pabd != NULL) { 6712 /* 6713 * If the buf is currently sharing the data block with 6714 * the hdr then we need to break that relationship here. 6715 * The hdr will remain with a NULL data pointer and the 6716 * buf will take sole ownership of the block. 6717 */ 6718 if (arc_buf_is_shared(buf)) { 6719 arc_unshare_buf(hdr, buf); 6720 } else { 6721 arc_hdr_free_pabd(hdr); 6722 } 6723 VERIFY3P(buf->b_data, !=, NULL); 6724 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 6725 } 6726 ASSERT(!arc_buf_is_shared(buf)); 6727 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6728 6729 zio = zio_write(pio, spa, txg, bp, 6730 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), 6731 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, 6732 (children_ready != NULL) ? arc_write_children_ready : NULL, 6733 arc_write_physdone, arc_write_done, callback, 6734 priority, zio_flags, zb); 6735 6736 return (zio); 6737} 6738 6739static int 6740arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg) 6741{ 6742#ifdef _KERNEL 6743 uint64_t available_memory = ptob(freemem); 6744 6745#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 6746 available_memory = MIN(available_memory, uma_avail()); 6747#endif 6748 6749 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 6750 return (0); 6751 6752 if (txg > spa->spa_lowmem_last_txg) { 6753 spa->spa_lowmem_last_txg = txg; 6754 spa->spa_lowmem_page_load = 0; 6755 } 6756 /* 6757 * If we are in pageout, we know that memory is already tight, 6758 * the arc is already going to be evicting, so we just want to 6759 * continue to let page writes occur as quickly as possible. 6760 */ 6761 if (curproc == pageproc) { 6762 if (spa->spa_lowmem_page_load > 6763 MAX(ptob(minfree), available_memory) / 4) 6764 return (SET_ERROR(ERESTART)); 6765 /* Note: reserve is inflated, so we deflate */ 6766 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8); 6767 return (0); 6768 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) { 6769 /* memory is low, delay before restarting */ 6770 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 6771 return (SET_ERROR(EAGAIN)); 6772 } 6773 spa->spa_lowmem_page_load = 0; 6774#endif /* _KERNEL */ 6775 return (0); 6776} 6777 6778void 6779arc_tempreserve_clear(uint64_t reserve) 6780{ 6781 atomic_add_64(&arc_tempreserve, -reserve); 6782 ASSERT((int64_t)arc_tempreserve >= 0); 6783} 6784 6785int 6786arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg) 6787{ 6788 int error; 6789 uint64_t anon_size; 6790 6791 if (reserve > arc_c/4 && !arc_no_grow) { 6792 arc_c = MIN(arc_c_max, reserve * 4); 6793 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 6794 } 6795 if (reserve > arc_c) 6796 return (SET_ERROR(ENOMEM)); 6797 6798 /* 6799 * Don't count loaned bufs as in flight dirty data to prevent long 6800 * network delays from blocking transactions that are ready to be 6801 * assigned to a txg. 6802 */ 6803 6804 /* assert that it has not wrapped around */ 6805 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 6806 6807 anon_size = MAX((int64_t)(zfs_refcount_count(&arc_anon->arcs_size) - 6808 arc_loaned_bytes), 0); 6809 6810 /* 6811 * Writes will, almost always, require additional memory allocations 6812 * in order to compress/encrypt/etc the data. We therefore need to 6813 * make sure that there is sufficient available memory for this. 6814 */ 6815 error = arc_memory_throttle(spa, reserve, txg); 6816 if (error != 0) 6817 return (error); 6818 6819 /* 6820 * Throttle writes when the amount of dirty data in the cache 6821 * gets too large. We try to keep the cache less than half full 6822 * of dirty blocks so that our sync times don't grow too large. 6823 * 6824 * In the case of one pool being built on another pool, we want 6825 * to make sure we don't end up throttling the lower (backing) 6826 * pool when the upper pool is the majority contributor to dirty 6827 * data. To insure we make forward progress during throttling, we 6828 * also check the current pool's net dirty data and only throttle 6829 * if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty 6830 * data in the cache. 6831 * 6832 * Note: if two requests come in concurrently, we might let them 6833 * both succeed, when one of them should fail. Not a huge deal. 6834 */ 6835 uint64_t total_dirty = reserve + arc_tempreserve + anon_size; 6836 uint64_t spa_dirty_anon = spa_dirty_data(spa); 6837 6838 if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 && 6839 anon_size > arc_c * zfs_arc_anon_limit_percent / 100 && 6840 spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) { 6841 uint64_t meta_esize = 6842 zfs_refcount_count( 6843 &arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6844 uint64_t data_esize = 6845 zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6846 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 6847 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 6848 arc_tempreserve >> 10, meta_esize >> 10, 6849 data_esize >> 10, reserve >> 10, arc_c >> 10); 6850 return (SET_ERROR(ERESTART)); 6851 } 6852 atomic_add_64(&arc_tempreserve, reserve); 6853 return (0); 6854} 6855 6856static void 6857arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 6858 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 6859{ 6860 size->value.ui64 = zfs_refcount_count(&state->arcs_size); 6861 evict_data->value.ui64 = 6862 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 6863 evict_metadata->value.ui64 = 6864 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 6865} 6866 6867static int 6868arc_kstat_update(kstat_t *ksp, int rw) 6869{ 6870 arc_stats_t *as = ksp->ks_data; 6871 6872 if (rw == KSTAT_WRITE) { 6873 return (EACCES); 6874 } else { 6875 arc_kstat_update_state(arc_anon, 6876 &as->arcstat_anon_size, 6877 &as->arcstat_anon_evictable_data, 6878 &as->arcstat_anon_evictable_metadata); 6879 arc_kstat_update_state(arc_mru, 6880 &as->arcstat_mru_size, 6881 &as->arcstat_mru_evictable_data, 6882 &as->arcstat_mru_evictable_metadata); 6883 arc_kstat_update_state(arc_mru_ghost, 6884 &as->arcstat_mru_ghost_size, 6885 &as->arcstat_mru_ghost_evictable_data, 6886 &as->arcstat_mru_ghost_evictable_metadata); 6887 arc_kstat_update_state(arc_mfu, 6888 &as->arcstat_mfu_size, 6889 &as->arcstat_mfu_evictable_data, 6890 &as->arcstat_mfu_evictable_metadata); 6891 arc_kstat_update_state(arc_mfu_ghost, 6892 &as->arcstat_mfu_ghost_size, 6893 &as->arcstat_mfu_ghost_evictable_data, 6894 &as->arcstat_mfu_ghost_evictable_metadata); 6895 6896 ARCSTAT(arcstat_size) = aggsum_value(&arc_size); 6897 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used); 6898 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size); 6899 ARCSTAT(arcstat_metadata_size) = 6900 aggsum_value(&astat_metadata_size); 6901 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size); 6902 ARCSTAT(arcstat_bonus_size) = aggsum_value(&astat_bonus_size); 6903 ARCSTAT(arcstat_dnode_size) = aggsum_value(&astat_dnode_size); 6904 ARCSTAT(arcstat_dbuf_size) = aggsum_value(&astat_dbuf_size); 6905#if defined(__FreeBSD__) && defined(COMPAT_FREEBSD11) 6906 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_bonus_size) + 6907 aggsum_value(&astat_dnode_size) + 6908 aggsum_value(&astat_dbuf_size); 6909#endif 6910 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size); 6911 } 6912 6913 return (0); 6914} 6915 6916/* 6917 * This function *must* return indices evenly distributed between all 6918 * sublists of the multilist. This is needed due to how the ARC eviction 6919 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 6920 * distributed between all sublists and uses this assumption when 6921 * deciding which sublist to evict from and how much to evict from it. 6922 */ 6923unsigned int 6924arc_state_multilist_index_func(multilist_t *ml, void *obj) 6925{ 6926 arc_buf_hdr_t *hdr = obj; 6927 6928 /* 6929 * We rely on b_dva to generate evenly distributed index 6930 * numbers using buf_hash below. So, as an added precaution, 6931 * let's make sure we never add empty buffers to the arc lists. 6932 */ 6933 ASSERT(!HDR_EMPTY(hdr)); 6934 6935 /* 6936 * The assumption here, is the hash value for a given 6937 * arc_buf_hdr_t will remain constant throughout it's lifetime 6938 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 6939 * Thus, we don't need to store the header's sublist index 6940 * on insertion, as this index can be recalculated on removal. 6941 * 6942 * Also, the low order bits of the hash value are thought to be 6943 * distributed evenly. Otherwise, in the case that the multilist 6944 * has a power of two number of sublists, each sublists' usage 6945 * would not be evenly distributed. 6946 */ 6947 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 6948 multilist_get_num_sublists(ml)); 6949} 6950 6951#ifdef _KERNEL 6952static eventhandler_tag arc_event_lowmem = NULL; 6953 6954static void 6955arc_lowmem(void *arg __unused, int howto __unused) 6956{ 6957 int64_t free_memory, to_free; 6958 6959 arc_no_grow = B_TRUE; 6960 arc_warm = B_TRUE; 6961 arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 6962 free_memory = arc_available_memory(); 6963 to_free = (arc_c >> arc_shrink_shift) - MIN(free_memory, 0); 6964 DTRACE_PROBE2(arc__needfree, int64_t, free_memory, int64_t, to_free); 6965 arc_reduce_target_size(to_free); 6966 6967 mutex_enter(&arc_adjust_lock); 6968 arc_adjust_needed = B_TRUE; 6969 zthr_wakeup(arc_adjust_zthr); 6970 6971 /* 6972 * It is unsafe to block here in arbitrary threads, because we can come 6973 * here from ARC itself and may hold ARC locks and thus risk a deadlock 6974 * with ARC reclaim thread. 6975 */ 6976 if (curproc == pageproc) 6977 (void) cv_wait(&arc_adjust_waiters_cv, &arc_adjust_lock); 6978 mutex_exit(&arc_adjust_lock); 6979} 6980#endif 6981 6982static void 6983arc_state_init(void) 6984{ 6985 arc_anon = &ARC_anon; 6986 arc_mru = &ARC_mru; 6987 arc_mru_ghost = &ARC_mru_ghost; 6988 arc_mfu = &ARC_mfu; 6989 arc_mfu_ghost = &ARC_mfu_ghost; 6990 arc_l2c_only = &ARC_l2c_only; 6991 6992 arc_mru->arcs_list[ARC_BUFC_METADATA] = 6993 multilist_create(sizeof (arc_buf_hdr_t), 6994 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6995 arc_state_multilist_index_func); 6996 arc_mru->arcs_list[ARC_BUFC_DATA] = 6997 multilist_create(sizeof (arc_buf_hdr_t), 6998 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6999 arc_state_multilist_index_func); 7000 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = 7001 multilist_create(sizeof (arc_buf_hdr_t), 7002 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7003 arc_state_multilist_index_func); 7004 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = 7005 multilist_create(sizeof (arc_buf_hdr_t), 7006 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7007 arc_state_multilist_index_func); 7008 arc_mfu->arcs_list[ARC_BUFC_METADATA] = 7009 multilist_create(sizeof (arc_buf_hdr_t), 7010 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7011 arc_state_multilist_index_func); 7012 arc_mfu->arcs_list[ARC_BUFC_DATA] = 7013 multilist_create(sizeof (arc_buf_hdr_t), 7014 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7015 arc_state_multilist_index_func); 7016 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = 7017 multilist_create(sizeof (arc_buf_hdr_t), 7018 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7019 arc_state_multilist_index_func); 7020 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = 7021 multilist_create(sizeof (arc_buf_hdr_t), 7022 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7023 arc_state_multilist_index_func); 7024 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = 7025 multilist_create(sizeof (arc_buf_hdr_t), 7026 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7027 arc_state_multilist_index_func); 7028 arc_l2c_only->arcs_list[ARC_BUFC_DATA] = 7029 multilist_create(sizeof (arc_buf_hdr_t), 7030 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 7031 arc_state_multilist_index_func); 7032 7033 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 7034 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 7035 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 7036 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 7037 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 7038 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 7039 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 7040 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 7041 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 7042 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 7043 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 7044 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 7045 7046 zfs_refcount_create(&arc_anon->arcs_size); 7047 zfs_refcount_create(&arc_mru->arcs_size); 7048 zfs_refcount_create(&arc_mru_ghost->arcs_size); 7049 zfs_refcount_create(&arc_mfu->arcs_size); 7050 zfs_refcount_create(&arc_mfu_ghost->arcs_size); 7051 zfs_refcount_create(&arc_l2c_only->arcs_size); 7052 7053 aggsum_init(&arc_meta_used, 0); 7054 aggsum_init(&arc_size, 0); 7055 aggsum_init(&astat_data_size, 0); 7056 aggsum_init(&astat_metadata_size, 0); 7057 aggsum_init(&astat_hdr_size, 0); 7058 aggsum_init(&astat_bonus_size, 0); 7059 aggsum_init(&astat_dnode_size, 0); 7060 aggsum_init(&astat_dbuf_size, 0); 7061 aggsum_init(&astat_l2_hdr_size, 0); 7062} 7063 7064static void 7065arc_state_fini(void) 7066{ 7067 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 7068 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 7069 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 7070 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 7071 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 7072 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 7073 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 7074 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 7075 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 7076 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 7077 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 7078 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 7079 7080 zfs_refcount_destroy(&arc_anon->arcs_size); 7081 zfs_refcount_destroy(&arc_mru->arcs_size); 7082 zfs_refcount_destroy(&arc_mru_ghost->arcs_size); 7083 zfs_refcount_destroy(&arc_mfu->arcs_size); 7084 zfs_refcount_destroy(&arc_mfu_ghost->arcs_size); 7085 zfs_refcount_destroy(&arc_l2c_only->arcs_size); 7086 7087 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); 7088 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 7089 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); 7090 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 7091 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); 7092 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 7093 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); 7094 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 7095 7096 aggsum_fini(&arc_meta_used); 7097 aggsum_fini(&arc_size); 7098 aggsum_fini(&astat_data_size); 7099 aggsum_fini(&astat_metadata_size); 7100 aggsum_fini(&astat_hdr_size); 7101 aggsum_fini(&astat_bonus_size); 7102 aggsum_fini(&astat_dnode_size); 7103 aggsum_fini(&astat_dbuf_size); 7104 aggsum_fini(&astat_l2_hdr_size); 7105} 7106 7107uint64_t 7108arc_max_bytes(void) 7109{ 7110 return (arc_c_max); 7111} 7112 7113void 7114arc_init(void) 7115{ 7116 int i, prefetch_tunable_set = 0; 7117 7118 /* 7119 * allmem is "all memory that we could possibly use". 7120 */ 7121#ifdef illumos 7122#ifdef _KERNEL 7123 uint64_t allmem = ptob(physmem - swapfs_minfree); 7124#else 7125 uint64_t allmem = (physmem * PAGESIZE) / 2; 7126#endif 7127#else 7128 uint64_t allmem = kmem_size(); 7129#endif 7130 mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL); 7131 cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL); 7132 7133 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 7134 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 7135 7136 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 7137 arc_c_min = MAX(allmem / 32, arc_abs_min); 7138 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ 7139 if (allmem >= 1 << 30) 7140 arc_c_max = allmem - (1 << 30); 7141 else 7142 arc_c_max = arc_c_min; 7143 arc_c_max = MAX(allmem * 5 / 8, arc_c_max); 7144 7145 /* 7146 * In userland, there's only the memory pressure that we artificially 7147 * create (see arc_available_memory()). Don't let arc_c get too 7148 * small, because it can cause transactions to be larger than 7149 * arc_c, causing arc_tempreserve_space() to fail. 7150 */ 7151#ifndef _KERNEL 7152 arc_c_min = arc_c_max / 2; 7153#endif 7154 7155#ifdef _KERNEL 7156 /* 7157 * Allow the tunables to override our calculations if they are 7158 * reasonable. 7159 */ 7160 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { 7161 arc_c_max = zfs_arc_max; 7162 arc_c_min = MIN(arc_c_min, arc_c_max); 7163 } 7164 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 7165 arc_c_min = zfs_arc_min; 7166#endif 7167 7168 arc_c = arc_c_max; 7169 arc_p = (arc_c >> 1); 7170 7171 /* limit meta-data to 1/4 of the arc capacity */ 7172 arc_meta_limit = arc_c_max / 4; 7173 7174#ifdef _KERNEL 7175 /* 7176 * Metadata is stored in the kernel's heap. Don't let us 7177 * use more than half the heap for the ARC. 7178 */ 7179#ifdef __FreeBSD__ 7180 arc_meta_limit = MIN(arc_meta_limit, uma_limit() / 2); 7181 arc_dnode_limit = arc_meta_limit / 10; 7182#else 7183 arc_meta_limit = MIN(arc_meta_limit, 7184 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 7185#endif 7186#endif 7187 7188 /* Allow the tunable to override if it is reasonable */ 7189 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 7190 arc_meta_limit = zfs_arc_meta_limit; 7191 7192 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 7193 arc_c_min = arc_meta_limit / 2; 7194 7195 if (zfs_arc_meta_min > 0) { 7196 arc_meta_min = zfs_arc_meta_min; 7197 } else { 7198 arc_meta_min = arc_c_min / 2; 7199 } 7200 7201 /* Valid range: <arc_meta_min> - <arc_c_max> */ 7202 if ((zfs_arc_dnode_limit) && (zfs_arc_dnode_limit != arc_dnode_limit) && 7203 (zfs_arc_dnode_limit >= zfs_arc_meta_min) && 7204 (zfs_arc_dnode_limit <= arc_c_max)) 7205 arc_dnode_limit = zfs_arc_dnode_limit; 7206 7207 if (zfs_arc_grow_retry > 0) 7208 arc_grow_retry = zfs_arc_grow_retry; 7209 7210 if (zfs_arc_shrink_shift > 0) 7211 arc_shrink_shift = zfs_arc_shrink_shift; 7212 7213 if (zfs_arc_no_grow_shift > 0) 7214 arc_no_grow_shift = zfs_arc_no_grow_shift; 7215 /* 7216 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 7217 */ 7218 if (arc_no_grow_shift >= arc_shrink_shift) 7219 arc_no_grow_shift = arc_shrink_shift - 1; 7220 7221 if (zfs_arc_p_min_shift > 0) 7222 arc_p_min_shift = zfs_arc_p_min_shift; 7223 7224 /* if kmem_flags are set, lets try to use less memory */ 7225 if (kmem_debugging()) 7226 arc_c = arc_c / 2; 7227 if (arc_c < arc_c_min) 7228 arc_c = arc_c_min; 7229 7230 zfs_arc_min = arc_c_min; 7231 zfs_arc_max = arc_c_max; 7232 7233 arc_state_init(); 7234 7235 /* 7236 * The arc must be "uninitialized", so that hdr_recl() (which is 7237 * registered by buf_init()) will not access arc_reap_zthr before 7238 * it is created. 7239 */ 7240 ASSERT(!arc_initialized); 7241 buf_init(); 7242 7243 list_create(&arc_prune_list, sizeof (arc_prune_t), 7244 offsetof(arc_prune_t, p_node)); 7245 mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL); 7246 7247 arc_prune_taskq = taskq_create("arc_prune", max_ncpus, minclsyspri, 7248 max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC); 7249 7250 arc_dnlc_evicts_thread_exit = FALSE; 7251 7252 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 7253 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 7254 7255 if (arc_ksp != NULL) { 7256 arc_ksp->ks_data = &arc_stats; 7257 arc_ksp->ks_update = arc_kstat_update; 7258 kstat_install(arc_ksp); 7259 } 7260 7261 arc_adjust_zthr = zthr_create_timer(arc_adjust_cb_check, 7262 arc_adjust_cb, NULL, SEC2NSEC(1)); 7263 arc_reap_zthr = zthr_create_timer(arc_reap_cb_check, 7264 arc_reap_cb, NULL, SEC2NSEC(1)); 7265 7266#ifdef _KERNEL 7267 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 7268 EVENTHANDLER_PRI_FIRST); 7269#endif 7270 7271 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 7272 TS_RUN, minclsyspri); 7273 7274 arc_initialized = B_TRUE; 7275 arc_warm = B_FALSE; 7276 7277 /* 7278 * Calculate maximum amount of dirty data per pool. 7279 * 7280 * If it has been set by /etc/system, take that. 7281 * Otherwise, use a percentage of physical memory defined by 7282 * zfs_dirty_data_max_percent (default 10%) with a cap at 7283 * zfs_dirty_data_max_max (default 4GB). 7284 */ 7285 if (zfs_dirty_data_max == 0) { 7286 zfs_dirty_data_max = ptob(physmem) * 7287 zfs_dirty_data_max_percent / 100; 7288 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 7289 zfs_dirty_data_max_max); 7290 } 7291 7292#ifdef _KERNEL 7293 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 7294 prefetch_tunable_set = 1; 7295 7296#ifdef __i386__ 7297 if (prefetch_tunable_set == 0) { 7298 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 7299 "-- to enable,\n"); 7300 printf(" add \"vfs.zfs.prefetch_disable=0\" " 7301 "to /boot/loader.conf.\n"); 7302 zfs_prefetch_disable = 1; 7303 } 7304#else 7305 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 7306 prefetch_tunable_set == 0) { 7307 printf("ZFS NOTICE: Prefetch is disabled by default if less " 7308 "than 4GB of RAM is present;\n" 7309 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 7310 "to /boot/loader.conf.\n"); 7311 zfs_prefetch_disable = 1; 7312 } 7313#endif 7314 /* Warn about ZFS memory and address space requirements. */ 7315 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 7316 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 7317 "expect unstable behavior.\n"); 7318 } 7319 if (allmem < 512 * (1 << 20)) { 7320 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 7321 "expect unstable behavior.\n"); 7322 printf(" Consider tuning vm.kmem_size and " 7323 "vm.kmem_size_max\n"); 7324 printf(" in /boot/loader.conf.\n"); 7325 } 7326#endif 7327} 7328 7329void 7330arc_fini(void) 7331{ 7332 arc_prune_t *p; 7333 7334#ifdef _KERNEL 7335 if (arc_event_lowmem != NULL) 7336 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 7337#endif 7338 7339 /* Use B_TRUE to ensure *all* buffers are evicted */ 7340 arc_flush(NULL, B_TRUE); 7341 7342 mutex_enter(&arc_dnlc_evicts_lock); 7343 arc_dnlc_evicts_thread_exit = TRUE; 7344 /* 7345 * The user evicts thread will set arc_user_evicts_thread_exit 7346 * to FALSE when it is finished exiting; we're waiting for that. 7347 */ 7348 while (arc_dnlc_evicts_thread_exit) { 7349 cv_signal(&arc_dnlc_evicts_cv); 7350 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 7351 } 7352 mutex_exit(&arc_dnlc_evicts_lock); 7353 7354 arc_initialized = B_FALSE; 7355 7356 if (arc_ksp != NULL) { 7357 kstat_delete(arc_ksp); 7358 arc_ksp = NULL; 7359 } 7360 7361 taskq_wait(arc_prune_taskq); 7362 taskq_destroy(arc_prune_taskq); 7363 7364 mutex_enter(&arc_prune_mtx); 7365 while ((p = list_head(&arc_prune_list)) != NULL) { 7366 list_remove(&arc_prune_list, p); 7367 zfs_refcount_remove(&p->p_refcnt, &arc_prune_list); 7368 zfs_refcount_destroy(&p->p_refcnt); 7369 kmem_free(p, sizeof (*p)); 7370 } 7371 mutex_exit(&arc_prune_mtx); 7372 7373 list_destroy(&arc_prune_list); 7374 mutex_destroy(&arc_prune_mtx); 7375 7376 (void) zthr_cancel(arc_adjust_zthr); 7377 zthr_destroy(arc_adjust_zthr); 7378 7379 mutex_destroy(&arc_dnlc_evicts_lock); 7380 cv_destroy(&arc_dnlc_evicts_cv); 7381 7382 (void) zthr_cancel(arc_reap_zthr); 7383 zthr_destroy(arc_reap_zthr); 7384 7385 mutex_destroy(&arc_adjust_lock); 7386 cv_destroy(&arc_adjust_waiters_cv); 7387 7388 /* 7389 * buf_fini() must proceed arc_state_fini() because buf_fin() may 7390 * trigger the release of kmem magazines, which can callback to 7391 * arc_space_return() which accesses aggsums freed in act_state_fini(). 7392 */ 7393 buf_fini(); 7394 arc_state_fini(); 7395 7396 ASSERT0(arc_loaned_bytes); 7397} 7398 7399/* 7400 * Level 2 ARC 7401 * 7402 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 7403 * It uses dedicated storage devices to hold cached data, which are populated 7404 * using large infrequent writes. The main role of this cache is to boost 7405 * the performance of random read workloads. The intended L2ARC devices 7406 * include short-stroked disks, solid state disks, and other media with 7407 * substantially faster read latency than disk. 7408 * 7409 * +-----------------------+ 7410 * | ARC | 7411 * +-----------------------+ 7412 * | ^ ^ 7413 * | | | 7414 * l2arc_feed_thread() arc_read() 7415 * | | | 7416 * | l2arc read | 7417 * V | | 7418 * +---------------+ | 7419 * | L2ARC | | 7420 * +---------------+ | 7421 * | ^ | 7422 * l2arc_write() | | 7423 * | | | 7424 * V | | 7425 * +-------+ +-------+ 7426 * | vdev | | vdev | 7427 * | cache | | cache | 7428 * +-------+ +-------+ 7429 * +=========+ .-----. 7430 * : L2ARC : |-_____-| 7431 * : devices : | Disks | 7432 * +=========+ `-_____-' 7433 * 7434 * Read requests are satisfied from the following sources, in order: 7435 * 7436 * 1) ARC 7437 * 2) vdev cache of L2ARC devices 7438 * 3) L2ARC devices 7439 * 4) vdev cache of disks 7440 * 5) disks 7441 * 7442 * Some L2ARC device types exhibit extremely slow write performance. 7443 * To accommodate for this there are some significant differences between 7444 * the L2ARC and traditional cache design: 7445 * 7446 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 7447 * the ARC behave as usual, freeing buffers and placing headers on ghost 7448 * lists. The ARC does not send buffers to the L2ARC during eviction as 7449 * this would add inflated write latencies for all ARC memory pressure. 7450 * 7451 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 7452 * It does this by periodically scanning buffers from the eviction-end of 7453 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 7454 * not already there. It scans until a headroom of buffers is satisfied, 7455 * which itself is a buffer for ARC eviction. If a compressible buffer is 7456 * found during scanning and selected for writing to an L2ARC device, we 7457 * temporarily boost scanning headroom during the next scan cycle to make 7458 * sure we adapt to compression effects (which might significantly reduce 7459 * the data volume we write to L2ARC). The thread that does this is 7460 * l2arc_feed_thread(), illustrated below; example sizes are included to 7461 * provide a better sense of ratio than this diagram: 7462 * 7463 * head --> tail 7464 * +---------------------+----------+ 7465 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 7466 * +---------------------+----------+ | o L2ARC eligible 7467 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 7468 * +---------------------+----------+ | 7469 * 15.9 Gbytes ^ 32 Mbytes | 7470 * headroom | 7471 * l2arc_feed_thread() 7472 * | 7473 * l2arc write hand <--[oooo]--' 7474 * | 8 Mbyte 7475 * | write max 7476 * V 7477 * +==============================+ 7478 * L2ARC dev |####|#|###|###| |####| ... | 7479 * +==============================+ 7480 * 32 Gbytes 7481 * 7482 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 7483 * evicted, then the L2ARC has cached a buffer much sooner than it probably 7484 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 7485 * safe to say that this is an uncommon case, since buffers at the end of 7486 * the ARC lists have moved there due to inactivity. 7487 * 7488 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 7489 * then the L2ARC simply misses copying some buffers. This serves as a 7490 * pressure valve to prevent heavy read workloads from both stalling the ARC 7491 * with waits and clogging the L2ARC with writes. This also helps prevent 7492 * the potential for the L2ARC to churn if it attempts to cache content too 7493 * quickly, such as during backups of the entire pool. 7494 * 7495 * 5. After system boot and before the ARC has filled main memory, there are 7496 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 7497 * lists can remain mostly static. Instead of searching from tail of these 7498 * lists as pictured, the l2arc_feed_thread() will search from the list heads 7499 * for eligible buffers, greatly increasing its chance of finding them. 7500 * 7501 * The L2ARC device write speed is also boosted during this time so that 7502 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 7503 * there are no L2ARC reads, and no fear of degrading read performance 7504 * through increased writes. 7505 * 7506 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 7507 * the vdev queue can aggregate them into larger and fewer writes. Each 7508 * device is written to in a rotor fashion, sweeping writes through 7509 * available space then repeating. 7510 * 7511 * 7. The L2ARC does not store dirty content. It never needs to flush 7512 * write buffers back to disk based storage. 7513 * 7514 * 8. If an ARC buffer is written (and dirtied) which also exists in the 7515 * L2ARC, the now stale L2ARC buffer is immediately dropped. 7516 * 7517 * The performance of the L2ARC can be tweaked by a number of tunables, which 7518 * may be necessary for different workloads: 7519 * 7520 * l2arc_write_max max write bytes per interval 7521 * l2arc_write_boost extra write bytes during device warmup 7522 * l2arc_noprefetch skip caching prefetched buffers 7523 * l2arc_headroom number of max device writes to precache 7524 * l2arc_headroom_boost when we find compressed buffers during ARC 7525 * scanning, we multiply headroom by this 7526 * percentage factor for the next scan cycle, 7527 * since more compressed buffers are likely to 7528 * be present 7529 * l2arc_feed_secs seconds between L2ARC writing 7530 * 7531 * Tunables may be removed or added as future performance improvements are 7532 * integrated, and also may become zpool properties. 7533 * 7534 * There are three key functions that control how the L2ARC warms up: 7535 * 7536 * l2arc_write_eligible() check if a buffer is eligible to cache 7537 * l2arc_write_size() calculate how much to write 7538 * l2arc_write_interval() calculate sleep delay between writes 7539 * 7540 * These three functions determine what to write, how much, and how quickly 7541 * to send writes. 7542 */ 7543 7544static boolean_t 7545l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 7546{ 7547 /* 7548 * A buffer is *not* eligible for the L2ARC if it: 7549 * 1. belongs to a different spa. 7550 * 2. is already cached on the L2ARC. 7551 * 3. has an I/O in progress (it may be an incomplete read). 7552 * 4. is flagged not eligible (zfs property). 7553 */ 7554 if (hdr->b_spa != spa_guid) { 7555 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 7556 return (B_FALSE); 7557 } 7558 if (HDR_HAS_L2HDR(hdr)) { 7559 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 7560 return (B_FALSE); 7561 } 7562 if (HDR_IO_IN_PROGRESS(hdr)) { 7563 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 7564 return (B_FALSE); 7565 } 7566 if (!HDR_L2CACHE(hdr)) { 7567 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 7568 return (B_FALSE); 7569 } 7570 7571 return (B_TRUE); 7572} 7573 7574static uint64_t 7575l2arc_write_size(void) 7576{ 7577 uint64_t size; 7578 7579 /* 7580 * Make sure our globals have meaningful values in case the user 7581 * altered them. 7582 */ 7583 size = l2arc_write_max; 7584 if (size == 0) { 7585 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 7586 "be greater than zero, resetting it to the default (%d)", 7587 L2ARC_WRITE_SIZE); 7588 size = l2arc_write_max = L2ARC_WRITE_SIZE; 7589 } 7590 7591 if (arc_warm == B_FALSE) 7592 size += l2arc_write_boost; 7593 7594 return (size); 7595 7596} 7597 7598static clock_t 7599l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 7600{ 7601 clock_t interval, next, now; 7602 7603 /* 7604 * If the ARC lists are busy, increase our write rate; if the 7605 * lists are stale, idle back. This is achieved by checking 7606 * how much we previously wrote - if it was more than half of 7607 * what we wanted, schedule the next write much sooner. 7608 */ 7609 if (l2arc_feed_again && wrote > (wanted / 2)) 7610 interval = (hz * l2arc_feed_min_ms) / 1000; 7611 else 7612 interval = hz * l2arc_feed_secs; 7613 7614 now = ddi_get_lbolt(); 7615 next = MAX(now, MIN(now + interval, began + interval)); 7616 7617 return (next); 7618} 7619 7620/* 7621 * Cycle through L2ARC devices. This is how L2ARC load balances. 7622 * If a device is returned, this also returns holding the spa config lock. 7623 */ 7624static l2arc_dev_t * 7625l2arc_dev_get_next(void) 7626{ 7627 l2arc_dev_t *first, *next = NULL; 7628 7629 /* 7630 * Lock out the removal of spas (spa_namespace_lock), then removal 7631 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 7632 * both locks will be dropped and a spa config lock held instead. 7633 */ 7634 mutex_enter(&spa_namespace_lock); 7635 mutex_enter(&l2arc_dev_mtx); 7636 7637 /* if there are no vdevs, there is nothing to do */ 7638 if (l2arc_ndev == 0) 7639 goto out; 7640 7641 first = NULL; 7642 next = l2arc_dev_last; 7643 do { 7644 /* loop around the list looking for a non-faulted vdev */ 7645 if (next == NULL) { 7646 next = list_head(l2arc_dev_list); 7647 } else { 7648 next = list_next(l2arc_dev_list, next); 7649 if (next == NULL) 7650 next = list_head(l2arc_dev_list); 7651 } 7652 7653 /* if we have come back to the start, bail out */ 7654 if (first == NULL) 7655 first = next; 7656 else if (next == first) 7657 break; 7658 7659 } while (vdev_is_dead(next->l2ad_vdev)); 7660 7661 /* if we were unable to find any usable vdevs, return NULL */ 7662 if (vdev_is_dead(next->l2ad_vdev)) 7663 next = NULL; 7664 7665 l2arc_dev_last = next; 7666 7667out: 7668 mutex_exit(&l2arc_dev_mtx); 7669 7670 /* 7671 * Grab the config lock to prevent the 'next' device from being 7672 * removed while we are writing to it. 7673 */ 7674 if (next != NULL) 7675 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 7676 mutex_exit(&spa_namespace_lock); 7677 7678 return (next); 7679} 7680 7681/* 7682 * Free buffers that were tagged for destruction. 7683 */ 7684static void 7685l2arc_do_free_on_write() 7686{ 7687 list_t *buflist; 7688 l2arc_data_free_t *df, *df_prev; 7689 7690 mutex_enter(&l2arc_free_on_write_mtx); 7691 buflist = l2arc_free_on_write; 7692 7693 for (df = list_tail(buflist); df; df = df_prev) { 7694 df_prev = list_prev(buflist, df); 7695 ASSERT3P(df->l2df_abd, !=, NULL); 7696 abd_free(df->l2df_abd); 7697 list_remove(buflist, df); 7698 kmem_free(df, sizeof (l2arc_data_free_t)); 7699 } 7700 7701 mutex_exit(&l2arc_free_on_write_mtx); 7702} 7703 7704/* 7705 * A write to a cache device has completed. Update all headers to allow 7706 * reads from these buffers to begin. 7707 */ 7708static void 7709l2arc_write_done(zio_t *zio) 7710{ 7711 l2arc_write_callback_t *cb; 7712 l2arc_dev_t *dev; 7713 list_t *buflist; 7714 arc_buf_hdr_t *head, *hdr, *hdr_prev; 7715 kmutex_t *hash_lock; 7716 int64_t bytes_dropped = 0; 7717 7718 cb = zio->io_private; 7719 ASSERT3P(cb, !=, NULL); 7720 dev = cb->l2wcb_dev; 7721 ASSERT3P(dev, !=, NULL); 7722 head = cb->l2wcb_head; 7723 ASSERT3P(head, !=, NULL); 7724 buflist = &dev->l2ad_buflist; 7725 ASSERT3P(buflist, !=, NULL); 7726 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 7727 l2arc_write_callback_t *, cb); 7728 7729 if (zio->io_error != 0) 7730 ARCSTAT_BUMP(arcstat_l2_writes_error); 7731 7732 /* 7733 * All writes completed, or an error was hit. 7734 */ 7735top: 7736 mutex_enter(&dev->l2ad_mtx); 7737 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 7738 hdr_prev = list_prev(buflist, hdr); 7739 7740 hash_lock = HDR_LOCK(hdr); 7741 7742 /* 7743 * We cannot use mutex_enter or else we can deadlock 7744 * with l2arc_write_buffers (due to swapping the order 7745 * the hash lock and l2ad_mtx are taken). 7746 */ 7747 if (!mutex_tryenter(hash_lock)) { 7748 /* 7749 * Missed the hash lock. We must retry so we 7750 * don't leave the ARC_FLAG_L2_WRITING bit set. 7751 */ 7752 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 7753 7754 /* 7755 * We don't want to rescan the headers we've 7756 * already marked as having been written out, so 7757 * we reinsert the head node so we can pick up 7758 * where we left off. 7759 */ 7760 list_remove(buflist, head); 7761 list_insert_after(buflist, hdr, head); 7762 7763 mutex_exit(&dev->l2ad_mtx); 7764 7765 /* 7766 * We wait for the hash lock to become available 7767 * to try and prevent busy waiting, and increase 7768 * the chance we'll be able to acquire the lock 7769 * the next time around. 7770 */ 7771 mutex_enter(hash_lock); 7772 mutex_exit(hash_lock); 7773 goto top; 7774 } 7775 7776 /* 7777 * We could not have been moved into the arc_l2c_only 7778 * state while in-flight due to our ARC_FLAG_L2_WRITING 7779 * bit being set. Let's just ensure that's being enforced. 7780 */ 7781 ASSERT(HDR_HAS_L1HDR(hdr)); 7782 7783 if (zio->io_error != 0) { 7784 /* 7785 * Error - drop L2ARC entry. 7786 */ 7787 list_remove(buflist, hdr); 7788 l2arc_trim(hdr); 7789 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 7790 7791 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr)); 7792 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 7793 7794 bytes_dropped += arc_hdr_size(hdr); 7795 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, 7796 arc_hdr_size(hdr), hdr); 7797 } 7798 7799 /* 7800 * Allow ARC to begin reads and ghost list evictions to 7801 * this L2ARC entry. 7802 */ 7803 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 7804 7805 mutex_exit(hash_lock); 7806 } 7807 7808 atomic_inc_64(&l2arc_writes_done); 7809 list_remove(buflist, head); 7810 ASSERT(!HDR_HAS_L1HDR(head)); 7811 kmem_cache_free(hdr_l2only_cache, head); 7812 mutex_exit(&dev->l2ad_mtx); 7813 7814 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 7815 7816 l2arc_do_free_on_write(); 7817 7818 kmem_free(cb, sizeof (l2arc_write_callback_t)); 7819} 7820 7821/* 7822 * A read to a cache device completed. Validate buffer contents before 7823 * handing over to the regular ARC routines. 7824 */ 7825static void 7826l2arc_read_done(zio_t *zio) 7827{ 7828 l2arc_read_callback_t *cb; 7829 arc_buf_hdr_t *hdr; 7830 kmutex_t *hash_lock; 7831 boolean_t valid_cksum; 7832 7833 ASSERT3P(zio->io_vd, !=, NULL); 7834 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 7835 7836 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 7837 7838 cb = zio->io_private; 7839 ASSERT3P(cb, !=, NULL); 7840 hdr = cb->l2rcb_hdr; 7841 ASSERT3P(hdr, !=, NULL); 7842 7843 hash_lock = HDR_LOCK(hdr); 7844 mutex_enter(hash_lock); 7845 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 7846 7847 /* 7848 * If the data was read into a temporary buffer, 7849 * move it and free the buffer. 7850 */ 7851 if (cb->l2rcb_abd != NULL) { 7852 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 7853 if (zio->io_error == 0) { 7854 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd, 7855 arc_hdr_size(hdr)); 7856 } 7857 7858 /* 7859 * The following must be done regardless of whether 7860 * there was an error: 7861 * - free the temporary buffer 7862 * - point zio to the real ARC buffer 7863 * - set zio size accordingly 7864 * These are required because zio is either re-used for 7865 * an I/O of the block in the case of the error 7866 * or the zio is passed to arc_read_done() and it 7867 * needs real data. 7868 */ 7869 abd_free(cb->l2rcb_abd); 7870 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 7871 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; 7872 } 7873 7874 ASSERT3P(zio->io_abd, !=, NULL); 7875 7876 /* 7877 * Check this survived the L2ARC journey. 7878 */ 7879 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); 7880 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 7881 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 7882 7883 valid_cksum = arc_cksum_is_equal(hdr, zio); 7884 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 7885 mutex_exit(hash_lock); 7886 zio->io_private = hdr; 7887 arc_read_done(zio); 7888 } else { 7889 /* 7890 * Buffer didn't survive caching. Increment stats and 7891 * reissue to the original storage device. 7892 */ 7893 if (zio->io_error != 0) { 7894 ARCSTAT_BUMP(arcstat_l2_io_error); 7895 } else { 7896 zio->io_error = SET_ERROR(EIO); 7897 } 7898 if (!valid_cksum) 7899 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 7900 7901 /* 7902 * If there's no waiter, issue an async i/o to the primary 7903 * storage now. If there *is* a waiter, the caller must 7904 * issue the i/o in a context where it's OK to block. 7905 */ 7906 if (zio->io_waiter == NULL) { 7907 zio_t *pio = zio_unique_parent(zio); 7908 7909 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 7910 7911 zio = zio_read(pio, zio->io_spa, zio->io_bp, 7912 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, 7913 hdr, zio->io_priority, cb->l2rcb_flags, 7914 &cb->l2rcb_zb); 7915 for (struct arc_callback *acb = hdr->b_l1hdr.b_acb; 7916 acb != NULL; acb = acb->acb_next) 7917 acb->acb_zio_head = zio; 7918 mutex_exit(hash_lock); 7919 zio_nowait(zio); 7920 } else 7921 mutex_exit(hash_lock); 7922 } 7923 7924 kmem_free(cb, sizeof (l2arc_read_callback_t)); 7925} 7926 7927/* 7928 * This is the list priority from which the L2ARC will search for pages to 7929 * cache. This is used within loops (0..3) to cycle through lists in the 7930 * desired order. This order can have a significant effect on cache 7931 * performance. 7932 * 7933 * Currently the metadata lists are hit first, MFU then MRU, followed by 7934 * the data lists. This function returns a locked list, and also returns 7935 * the lock pointer. 7936 */ 7937static multilist_sublist_t * 7938l2arc_sublist_lock(int list_num) 7939{ 7940 multilist_t *ml = NULL; 7941 unsigned int idx; 7942 7943 ASSERT(list_num >= 0 && list_num <= 3); 7944 7945 switch (list_num) { 7946 case 0: 7947 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; 7948 break; 7949 case 1: 7950 ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; 7951 break; 7952 case 2: 7953 ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; 7954 break; 7955 case 3: 7956 ml = arc_mru->arcs_list[ARC_BUFC_DATA]; 7957 break; 7958 } 7959 7960 /* 7961 * Return a randomly-selected sublist. This is acceptable 7962 * because the caller feeds only a little bit of data for each 7963 * call (8MB). Subsequent calls will result in different 7964 * sublists being selected. 7965 */ 7966 idx = multilist_get_random_index(ml); 7967 return (multilist_sublist_lock(ml, idx)); 7968} 7969 7970/* 7971 * Evict buffers from the device write hand to the distance specified in 7972 * bytes. This distance may span populated buffers, it may span nothing. 7973 * This is clearing a region on the L2ARC device ready for writing. 7974 * If the 'all' boolean is set, every buffer is evicted. 7975 */ 7976static void 7977l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 7978{ 7979 list_t *buflist; 7980 arc_buf_hdr_t *hdr, *hdr_prev; 7981 kmutex_t *hash_lock; 7982 uint64_t taddr; 7983 7984 buflist = &dev->l2ad_buflist; 7985 7986 if (!all && dev->l2ad_first) { 7987 /* 7988 * This is the first sweep through the device. There is 7989 * nothing to evict. 7990 */ 7991 return; 7992 } 7993 7994 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 7995 /* 7996 * When nearing the end of the device, evict to the end 7997 * before the device write hand jumps to the start. 7998 */ 7999 taddr = dev->l2ad_end; 8000 } else { 8001 taddr = dev->l2ad_hand + distance; 8002 } 8003 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 8004 uint64_t, taddr, boolean_t, all); 8005 8006top: 8007 mutex_enter(&dev->l2ad_mtx); 8008 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 8009 hdr_prev = list_prev(buflist, hdr); 8010 8011 hash_lock = HDR_LOCK(hdr); 8012 8013 /* 8014 * We cannot use mutex_enter or else we can deadlock 8015 * with l2arc_write_buffers (due to swapping the order 8016 * the hash lock and l2ad_mtx are taken). 8017 */ 8018 if (!mutex_tryenter(hash_lock)) { 8019 /* 8020 * Missed the hash lock. Retry. 8021 */ 8022 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 8023 mutex_exit(&dev->l2ad_mtx); 8024 mutex_enter(hash_lock); 8025 mutex_exit(hash_lock); 8026 goto top; 8027 } 8028 8029 /* 8030 * A header can't be on this list if it doesn't have L2 header. 8031 */ 8032 ASSERT(HDR_HAS_L2HDR(hdr)); 8033 8034 /* Ensure this header has finished being written. */ 8035 ASSERT(!HDR_L2_WRITING(hdr)); 8036 ASSERT(!HDR_L2_WRITE_HEAD(hdr)); 8037 8038 if (!all && (hdr->b_l2hdr.b_daddr >= taddr || 8039 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 8040 /* 8041 * We've evicted to the target address, 8042 * or the end of the device. 8043 */ 8044 mutex_exit(hash_lock); 8045 break; 8046 } 8047 8048 if (!HDR_HAS_L1HDR(hdr)) { 8049 ASSERT(!HDR_L2_READING(hdr)); 8050 /* 8051 * This doesn't exist in the ARC. Destroy. 8052 * arc_hdr_destroy() will call list_remove() 8053 * and decrement arcstat_l2_lsize. 8054 */ 8055 arc_change_state(arc_anon, hdr, hash_lock); 8056 arc_hdr_destroy(hdr); 8057 } else { 8058 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 8059 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 8060 /* 8061 * Invalidate issued or about to be issued 8062 * reads, since we may be about to write 8063 * over this location. 8064 */ 8065 if (HDR_L2_READING(hdr)) { 8066 ARCSTAT_BUMP(arcstat_l2_evict_reading); 8067 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 8068 } 8069 8070 arc_hdr_l2hdr_destroy(hdr); 8071 } 8072 mutex_exit(hash_lock); 8073 } 8074 mutex_exit(&dev->l2ad_mtx); 8075} 8076 8077/* 8078 * Find and write ARC buffers to the L2ARC device. 8079 * 8080 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 8081 * for reading until they have completed writing. 8082 * The headroom_boost is an in-out parameter used to maintain headroom boost 8083 * state between calls to this function. 8084 * 8085 * Returns the number of bytes actually written (which may be smaller than 8086 * the delta by which the device hand has changed due to alignment). 8087 */ 8088static uint64_t 8089l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 8090{ 8091 arc_buf_hdr_t *hdr, *hdr_prev, *head; 8092 uint64_t write_asize, write_psize, write_lsize, headroom; 8093 boolean_t full; 8094 l2arc_write_callback_t *cb; 8095 zio_t *pio, *wzio; 8096 uint64_t guid = spa_load_guid(spa); 8097 int try; 8098 8099 ASSERT3P(dev->l2ad_vdev, !=, NULL); 8100 8101 pio = NULL; 8102 write_lsize = write_asize = write_psize = 0; 8103 full = B_FALSE; 8104 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 8105 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 8106 8107 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 8108 /* 8109 * Copy buffers for L2ARC writing. 8110 */ 8111 for (try = 0; try <= 3; try++) { 8112 multilist_sublist_t *mls = l2arc_sublist_lock(try); 8113 uint64_t passed_sz = 0; 8114 8115 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 8116 8117 /* 8118 * L2ARC fast warmup. 8119 * 8120 * Until the ARC is warm and starts to evict, read from the 8121 * head of the ARC lists rather than the tail. 8122 */ 8123 if (arc_warm == B_FALSE) 8124 hdr = multilist_sublist_head(mls); 8125 else 8126 hdr = multilist_sublist_tail(mls); 8127 if (hdr == NULL) 8128 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 8129 8130 headroom = target_sz * l2arc_headroom; 8131 if (zfs_compressed_arc_enabled) 8132 headroom = (headroom * l2arc_headroom_boost) / 100; 8133 8134 for (; hdr; hdr = hdr_prev) { 8135 kmutex_t *hash_lock; 8136 8137 if (arc_warm == B_FALSE) 8138 hdr_prev = multilist_sublist_next(mls, hdr); 8139 else 8140 hdr_prev = multilist_sublist_prev(mls, hdr); 8141 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 8142 HDR_GET_LSIZE(hdr)); 8143 8144 hash_lock = HDR_LOCK(hdr); 8145 if (!mutex_tryenter(hash_lock)) { 8146 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 8147 /* 8148 * Skip this buffer rather than waiting. 8149 */ 8150 continue; 8151 } 8152 8153 passed_sz += HDR_GET_LSIZE(hdr); 8154 if (passed_sz > headroom) { 8155 /* 8156 * Searched too far. 8157 */ 8158 mutex_exit(hash_lock); 8159 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 8160 break; 8161 } 8162 8163 if (!l2arc_write_eligible(guid, hdr)) { 8164 mutex_exit(hash_lock); 8165 continue; 8166 } 8167 8168 /* 8169 * We rely on the L1 portion of the header below, so 8170 * it's invalid for this header to have been evicted out 8171 * of the ghost cache, prior to being written out. The 8172 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 8173 */ 8174 ASSERT(HDR_HAS_L1HDR(hdr)); 8175 8176 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 8177 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 8178 ASSERT3U(arc_hdr_size(hdr), >, 0); 8179 uint64_t psize = arc_hdr_size(hdr); 8180 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 8181 psize); 8182 8183 if ((write_asize + asize) > target_sz) { 8184 full = B_TRUE; 8185 mutex_exit(hash_lock); 8186 ARCSTAT_BUMP(arcstat_l2_write_full); 8187 break; 8188 } 8189 8190 if (pio == NULL) { 8191 /* 8192 * Insert a dummy header on the buflist so 8193 * l2arc_write_done() can find where the 8194 * write buffers begin without searching. 8195 */ 8196 mutex_enter(&dev->l2ad_mtx); 8197 list_insert_head(&dev->l2ad_buflist, head); 8198 mutex_exit(&dev->l2ad_mtx); 8199 8200 cb = kmem_alloc( 8201 sizeof (l2arc_write_callback_t), KM_SLEEP); 8202 cb->l2wcb_dev = dev; 8203 cb->l2wcb_head = head; 8204 pio = zio_root(spa, l2arc_write_done, cb, 8205 ZIO_FLAG_CANFAIL); 8206 ARCSTAT_BUMP(arcstat_l2_write_pios); 8207 } 8208 8209 hdr->b_l2hdr.b_dev = dev; 8210 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 8211 arc_hdr_set_flags(hdr, 8212 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 8213 8214 mutex_enter(&dev->l2ad_mtx); 8215 list_insert_head(&dev->l2ad_buflist, hdr); 8216 mutex_exit(&dev->l2ad_mtx); 8217 8218 (void) zfs_refcount_add_many(&dev->l2ad_alloc, psize, 8219 hdr); 8220 8221 /* 8222 * Normally the L2ARC can use the hdr's data, but if 8223 * we're sharing data between the hdr and one of its 8224 * bufs, L2ARC needs its own copy of the data so that 8225 * the ZIO below can't race with the buf consumer. 8226 * Another case where we need to create a copy of the 8227 * data is when the buffer size is not device-aligned 8228 * and we need to pad the block to make it such. 8229 * That also keeps the clock hand suitably aligned. 8230 * 8231 * To ensure that the copy will be available for the 8232 * lifetime of the ZIO and be cleaned up afterwards, we 8233 * add it to the l2arc_free_on_write queue. 8234 */ 8235 abd_t *to_write; 8236 if (!HDR_SHARED_DATA(hdr) && psize == asize) { 8237 to_write = hdr->b_l1hdr.b_pabd; 8238 } else { 8239 to_write = abd_alloc_for_io(asize, 8240 HDR_ISTYPE_METADATA(hdr)); 8241 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize); 8242 if (asize != psize) { 8243 abd_zero_off(to_write, psize, 8244 asize - psize); 8245 } 8246 l2arc_free_abd_on_write(to_write, asize, 8247 arc_buf_type(hdr)); 8248 } 8249 wzio = zio_write_phys(pio, dev->l2ad_vdev, 8250 hdr->b_l2hdr.b_daddr, asize, to_write, 8251 ZIO_CHECKSUM_OFF, NULL, hdr, 8252 ZIO_PRIORITY_ASYNC_WRITE, 8253 ZIO_FLAG_CANFAIL, B_FALSE); 8254 8255 write_lsize += HDR_GET_LSIZE(hdr); 8256 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 8257 zio_t *, wzio); 8258 8259 write_psize += psize; 8260 write_asize += asize; 8261 dev->l2ad_hand += asize; 8262 8263 mutex_exit(hash_lock); 8264 8265 (void) zio_nowait(wzio); 8266 } 8267 8268 multilist_sublist_unlock(mls); 8269 8270 if (full == B_TRUE) 8271 break; 8272 } 8273 8274 /* No buffers selected for writing? */ 8275 if (pio == NULL) { 8276 ASSERT0(write_lsize); 8277 ASSERT(!HDR_HAS_L1HDR(head)); 8278 kmem_cache_free(hdr_l2only_cache, head); 8279 return (0); 8280 } 8281 8282 ASSERT3U(write_psize, <=, target_sz); 8283 ARCSTAT_BUMP(arcstat_l2_writes_sent); 8284 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize); 8285 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize); 8286 ARCSTAT_INCR(arcstat_l2_psize, write_psize); 8287 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); 8288 8289 /* 8290 * Bump device hand to the device start if it is approaching the end. 8291 * l2arc_evict() will already have evicted ahead for this case. 8292 */ 8293 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 8294 dev->l2ad_hand = dev->l2ad_start; 8295 dev->l2ad_first = B_FALSE; 8296 } 8297 8298 dev->l2ad_writing = B_TRUE; 8299 (void) zio_wait(pio); 8300 dev->l2ad_writing = B_FALSE; 8301 8302 return (write_asize); 8303} 8304 8305/* 8306 * This thread feeds the L2ARC at regular intervals. This is the beating 8307 * heart of the L2ARC. 8308 */ 8309/* ARGSUSED */ 8310static void 8311l2arc_feed_thread(void *unused __unused) 8312{ 8313 callb_cpr_t cpr; 8314 l2arc_dev_t *dev; 8315 spa_t *spa; 8316 uint64_t size, wrote; 8317 clock_t begin, next = ddi_get_lbolt(); 8318 8319 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 8320 8321 mutex_enter(&l2arc_feed_thr_lock); 8322 8323 while (l2arc_thread_exit == 0) { 8324 CALLB_CPR_SAFE_BEGIN(&cpr); 8325 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 8326 next - ddi_get_lbolt()); 8327 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 8328 next = ddi_get_lbolt() + hz; 8329 8330 /* 8331 * Quick check for L2ARC devices. 8332 */ 8333 mutex_enter(&l2arc_dev_mtx); 8334 if (l2arc_ndev == 0) { 8335 mutex_exit(&l2arc_dev_mtx); 8336 continue; 8337 } 8338 mutex_exit(&l2arc_dev_mtx); 8339 begin = ddi_get_lbolt(); 8340 8341 /* 8342 * This selects the next l2arc device to write to, and in 8343 * doing so the next spa to feed from: dev->l2ad_spa. This 8344 * will return NULL if there are now no l2arc devices or if 8345 * they are all faulted. 8346 * 8347 * If a device is returned, its spa's config lock is also 8348 * held to prevent device removal. l2arc_dev_get_next() 8349 * will grab and release l2arc_dev_mtx. 8350 */ 8351 if ((dev = l2arc_dev_get_next()) == NULL) 8352 continue; 8353 8354 spa = dev->l2ad_spa; 8355 ASSERT3P(spa, !=, NULL); 8356 8357 /* 8358 * If the pool is read-only then force the feed thread to 8359 * sleep a little longer. 8360 */ 8361 if (!spa_writeable(spa)) { 8362 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 8363 spa_config_exit(spa, SCL_L2ARC, dev); 8364 continue; 8365 } 8366 8367 /* 8368 * Avoid contributing to memory pressure. 8369 */ 8370 if (arc_reclaim_needed()) { 8371 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 8372 spa_config_exit(spa, SCL_L2ARC, dev); 8373 continue; 8374 } 8375 8376 ARCSTAT_BUMP(arcstat_l2_feeds); 8377 8378 size = l2arc_write_size(); 8379 8380 /* 8381 * Evict L2ARC buffers that will be overwritten. 8382 */ 8383 l2arc_evict(dev, size, B_FALSE); 8384 8385 /* 8386 * Write ARC buffers. 8387 */ 8388 wrote = l2arc_write_buffers(spa, dev, size); 8389 8390 /* 8391 * Calculate interval between writes. 8392 */ 8393 next = l2arc_write_interval(begin, size, wrote); 8394 spa_config_exit(spa, SCL_L2ARC, dev); 8395 } 8396 8397 l2arc_thread_exit = 0; 8398 cv_broadcast(&l2arc_feed_thr_cv); 8399 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 8400 thread_exit(); 8401} 8402 8403boolean_t 8404l2arc_vdev_present(vdev_t *vd) 8405{ 8406 l2arc_dev_t *dev; 8407 8408 mutex_enter(&l2arc_dev_mtx); 8409 for (dev = list_head(l2arc_dev_list); dev != NULL; 8410 dev = list_next(l2arc_dev_list, dev)) { 8411 if (dev->l2ad_vdev == vd) 8412 break; 8413 } 8414 mutex_exit(&l2arc_dev_mtx); 8415 8416 return (dev != NULL); 8417} 8418 8419/* 8420 * Add a vdev for use by the L2ARC. By this point the spa has already 8421 * validated the vdev and opened it. 8422 */ 8423void 8424l2arc_add_vdev(spa_t *spa, vdev_t *vd) 8425{ 8426 l2arc_dev_t *adddev; 8427 8428 ASSERT(!l2arc_vdev_present(vd)); 8429 8430 vdev_ashift_optimize(vd); 8431 8432 /* 8433 * Create a new l2arc device entry. 8434 */ 8435 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 8436 adddev->l2ad_spa = spa; 8437 adddev->l2ad_vdev = vd; 8438 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 8439 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 8440 adddev->l2ad_hand = adddev->l2ad_start; 8441 adddev->l2ad_first = B_TRUE; 8442 adddev->l2ad_writing = B_FALSE; 8443 8444 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 8445 /* 8446 * This is a list of all ARC buffers that are still valid on the 8447 * device. 8448 */ 8449 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 8450 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 8451 8452 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 8453 zfs_refcount_create(&adddev->l2ad_alloc); 8454 8455 /* 8456 * Add device to global list 8457 */ 8458 mutex_enter(&l2arc_dev_mtx); 8459 list_insert_head(l2arc_dev_list, adddev); 8460 atomic_inc_64(&l2arc_ndev); 8461 mutex_exit(&l2arc_dev_mtx); 8462} 8463 8464/* 8465 * Remove a vdev from the L2ARC. 8466 */ 8467void 8468l2arc_remove_vdev(vdev_t *vd) 8469{ 8470 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 8471 8472 /* 8473 * Find the device by vdev 8474 */ 8475 mutex_enter(&l2arc_dev_mtx); 8476 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 8477 nextdev = list_next(l2arc_dev_list, dev); 8478 if (vd == dev->l2ad_vdev) { 8479 remdev = dev; 8480 break; 8481 } 8482 } 8483 ASSERT3P(remdev, !=, NULL); 8484 8485 /* 8486 * Remove device from global list 8487 */ 8488 list_remove(l2arc_dev_list, remdev); 8489 l2arc_dev_last = NULL; /* may have been invalidated */ 8490 atomic_dec_64(&l2arc_ndev); 8491 mutex_exit(&l2arc_dev_mtx); 8492 8493 /* 8494 * Clear all buflists and ARC references. L2ARC device flush. 8495 */ 8496 l2arc_evict(remdev, 0, B_TRUE); 8497 list_destroy(&remdev->l2ad_buflist); 8498 mutex_destroy(&remdev->l2ad_mtx); 8499 zfs_refcount_destroy(&remdev->l2ad_alloc); 8500 kmem_free(remdev, sizeof (l2arc_dev_t)); 8501} 8502 8503void 8504l2arc_init(void) 8505{ 8506 l2arc_thread_exit = 0; 8507 l2arc_ndev = 0; 8508 l2arc_writes_sent = 0; 8509 l2arc_writes_done = 0; 8510 8511 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 8512 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 8513 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 8514 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 8515 8516 l2arc_dev_list = &L2ARC_dev_list; 8517 l2arc_free_on_write = &L2ARC_free_on_write; 8518 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 8519 offsetof(l2arc_dev_t, l2ad_node)); 8520 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 8521 offsetof(l2arc_data_free_t, l2df_list_node)); 8522} 8523 8524void 8525l2arc_fini(void) 8526{ 8527 /* 8528 * This is called from dmu_fini(), which is called from spa_fini(); 8529 * Because of this, we can assume that all l2arc devices have 8530 * already been removed when the pools themselves were removed. 8531 */ 8532 8533 l2arc_do_free_on_write(); 8534 8535 mutex_destroy(&l2arc_feed_thr_lock); 8536 cv_destroy(&l2arc_feed_thr_cv); 8537 mutex_destroy(&l2arc_dev_mtx); 8538 mutex_destroy(&l2arc_free_on_write_mtx); 8539 8540 list_destroy(l2arc_dev_list); 8541 list_destroy(l2arc_free_on_write); 8542} 8543 8544void 8545l2arc_start(void) 8546{ 8547 if (!(spa_mode_global & FWRITE)) 8548 return; 8549 8550 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 8551 TS_RUN, minclsyspri); 8552} 8553 8554void 8555l2arc_stop(void) 8556{ 8557 if (!(spa_mode_global & FWRITE)) 8558 return; 8559 8560 mutex_enter(&l2arc_feed_thr_lock); 8561 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 8562 l2arc_thread_exit = 1; 8563 while (l2arc_thread_exit != 0) 8564 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 8565 mutex_exit(&l2arc_feed_thr_lock); 8566} 8567