arc.c revision 339114
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 * Note that the majority of the performance stats are manipulated 103 * with atomic operations. 104 * 105 * The L2ARC uses the l2ad_mtx on each vdev for the following: 106 * 107 * - L2ARC buflist creation 108 * - L2ARC buflist eviction 109 * - L2ARC write completion, which walks L2ARC buflists 110 * - ARC header destruction, as it removes from L2ARC buflists 111 * - ARC header release, as it removes from L2ARC buflists 112 */ 113 114/* 115 * ARC operation: 116 * 117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure. 118 * This structure can point either to a block that is still in the cache or to 119 * one that is only accessible in an L2 ARC device, or it can provide 120 * information about a block that was recently evicted. If a block is 121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough 122 * information to retrieve it from the L2ARC device. This information is 123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block 124 * that is in this state cannot access the data directly. 125 * 126 * Blocks that are actively being referenced or have not been evicted 127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within 128 * the arc_buf_hdr_t that will point to the data block in memory. A block can 129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC 130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and 131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd). 132 * 133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the 134 * ability to store the physical data (b_pabd) associated with the DVA of the 135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block, 136 * it will match its on-disk compression characteristics. This behavior can be 137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the 138 * compressed ARC functionality is disabled, the b_pabd will point to an 139 * uncompressed version of the on-disk data. 140 * 141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each 142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it. 143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC 144 * consumer. The ARC will provide references to this data and will keep it 145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical 146 * data block and will evict any arc_buf_t that is no longer referenced. The 147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the 148 * "overhead_size" kstat. 149 * 150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or 151 * compressed form. The typical case is that consumers will want uncompressed 152 * data, and when that happens a new data buffer is allocated where the data is 153 * decompressed for them to use. Currently the only consumer who wants 154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it 155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared 156 * with the arc_buf_hdr_t. 157 * 158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The 159 * first one is owned by a compressed send consumer (and therefore references 160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be 161 * used by any other consumer (and has its own uncompressed copy of the data 162 * buffer). 163 * 164 * arc_buf_hdr_t 165 * +-----------+ 166 * | fields | 167 * | common to | 168 * | L1- and | 169 * | L2ARC | 170 * +-----------+ 171 * | l2arc_buf_hdr_t 172 * | | 173 * +-----------+ 174 * | l1arc_buf_hdr_t 175 * | | arc_buf_t 176 * | b_buf +------------>+-----------+ arc_buf_t 177 * | b_pabd +-+ |b_next +---->+-----------+ 178 * +-----------+ | |-----------| |b_next +-->NULL 179 * | |b_comp = T | +-----------+ 180 * | |b_data +-+ |b_comp = F | 181 * | +-----------+ | |b_data +-+ 182 * +->+------+ | +-----------+ | 183 * compressed | | | | 184 * data | |<--------------+ | uncompressed 185 * +------+ compressed, | data 186 * shared +-->+------+ 187 * data | | 188 * | | 189 * +------+ 190 * 191 * When a consumer reads a block, the ARC must first look to see if the 192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new 193 * arc_buf_t and either copies uncompressed data into a new data buffer from an 194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a 195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the 196 * hdr is compressed and the desired compression characteristics of the 197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the 198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be 199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can 200 * be anywhere in the hdr's list. 201 * 202 * The diagram below shows an example of an uncompressed ARC hdr that is 203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is 204 * the last element in the buf list): 205 * 206 * arc_buf_hdr_t 207 * +-----------+ 208 * | | 209 * | | 210 * | | 211 * +-----------+ 212 * l2arc_buf_hdr_t| | 213 * | | 214 * +-----------+ 215 * l1arc_buf_hdr_t| | 216 * | | arc_buf_t (shared) 217 * | b_buf +------------>+---------+ arc_buf_t 218 * | | |b_next +---->+---------+ 219 * | b_pabd +-+ |---------| |b_next +-->NULL 220 * +-----------+ | | | +---------+ 221 * | |b_data +-+ | | 222 * | +---------+ | |b_data +-+ 223 * +->+------+ | +---------+ | 224 * | | | | 225 * uncompressed | | | | 226 * data +------+ | | 227 * ^ +->+------+ | 228 * | uncompressed | | | 229 * | data | | | 230 * | +------+ | 231 * +---------------------------------+ 232 * 233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd 234 * since the physical block is about to be rewritten. The new data contents 235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write, 236 * it may compress the data before writing it to disk. The ARC will be called 237 * with the transformed data and will bcopy the transformed on-disk block into 238 * a newly allocated b_pabd. Writes are always done into buffers which have 239 * either been loaned (and hence are new and don't have other readers) or 240 * buffers which have been released (and hence have their own hdr, if there 241 * were originally other readers of the buf's original hdr). This ensures that 242 * the ARC only needs to update a single buf and its hdr after a write occurs. 243 * 244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The 245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means 246 * that when compressed ARC is enabled that the L2ARC blocks are identical 247 * to the on-disk block in the main data pool. This provides a significant 248 * advantage since the ARC can leverage the bp's checksum when reading from the 249 * L2ARC to determine if the contents are valid. However, if the compressed 250 * ARC is disabled, then the L2ARC's block must be transformed to look 251 * like the physical block in the main data pool before comparing the 252 * checksum and determining its validity. 253 */ 254 255#include <sys/spa.h> 256#include <sys/zio.h> 257#include <sys/spa_impl.h> 258#include <sys/zio_compress.h> 259#include <sys/zio_checksum.h> 260#include <sys/zfs_context.h> 261#include <sys/arc.h> 262#include <sys/refcount.h> 263#include <sys/vdev.h> 264#include <sys/vdev_impl.h> 265#include <sys/dsl_pool.h> 266#include <sys/zio_checksum.h> 267#include <sys/multilist.h> 268#include <sys/abd.h> 269#ifdef _KERNEL 270#include <sys/dnlc.h> 271#include <sys/racct.h> 272#endif 273#include <sys/callb.h> 274#include <sys/kstat.h> 275#include <sys/trim_map.h> 276#include <zfs_fletcher.h> 277#include <sys/sdt.h> 278#include <sys/aggsum.h> 279#include <sys/cityhash.h> 280 281#include <machine/vmparam.h> 282 283#ifdef illumos 284#ifndef _KERNEL 285/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 286boolean_t arc_watch = B_FALSE; 287int arc_procfd; 288#endif 289#endif /* illumos */ 290 291static kmutex_t arc_reclaim_lock; 292static kcondvar_t arc_reclaim_thread_cv; 293static boolean_t arc_reclaim_thread_exit; 294static kcondvar_t arc_reclaim_waiters_cv; 295 296static kmutex_t arc_dnlc_evicts_lock; 297static kcondvar_t arc_dnlc_evicts_cv; 298static boolean_t arc_dnlc_evicts_thread_exit; 299 300uint_t arc_reduce_dnlc_percent = 3; 301 302/* 303 * The number of headers to evict in arc_evict_state_impl() before 304 * dropping the sublist lock and evicting from another sublist. A lower 305 * value means we're more likely to evict the "correct" header (i.e. the 306 * oldest header in the arc state), but comes with higher overhead 307 * (i.e. more invocations of arc_evict_state_impl()). 308 */ 309int zfs_arc_evict_batch_limit = 10; 310 311/* number of seconds before growing cache again */ 312static int arc_grow_retry = 60; 313 314/* number of milliseconds before attempting a kmem-cache-reap */ 315static int arc_kmem_cache_reap_retry_ms = 0; 316 317/* shift of arc_c for calculating overflow limit in arc_get_data_impl */ 318int zfs_arc_overflow_shift = 8; 319 320/* shift of arc_c for calculating both min and max arc_p */ 321static int arc_p_min_shift = 4; 322 323/* log2(fraction of arc to reclaim) */ 324static int arc_shrink_shift = 7; 325 326/* 327 * log2(fraction of ARC which must be free to allow growing). 328 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 329 * when reading a new block into the ARC, we will evict an equal-sized block 330 * from the ARC. 331 * 332 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 333 * we will still not allow it to grow. 334 */ 335int arc_no_grow_shift = 5; 336 337 338/* 339 * minimum lifespan of a prefetch block in clock ticks 340 * (initialized in arc_init()) 341 */ 342static int zfs_arc_min_prefetch_ms = 1; 343static int zfs_arc_min_prescient_prefetch_ms = 6; 344 345/* 346 * If this percent of memory is free, don't throttle. 347 */ 348int arc_lotsfree_percent = 10; 349 350static int arc_dead; 351extern boolean_t zfs_prefetch_disable; 352 353/* 354 * The arc has filled available memory and has now warmed up. 355 */ 356static boolean_t arc_warm; 357 358/* 359 * log2 fraction of the zio arena to keep free. 360 */ 361int arc_zio_arena_free_shift = 2; 362 363/* 364 * These tunables are for performance analysis. 365 */ 366uint64_t zfs_arc_max; 367uint64_t zfs_arc_min; 368uint64_t zfs_arc_meta_limit = 0; 369uint64_t zfs_arc_meta_min = 0; 370int zfs_arc_grow_retry = 0; 371int zfs_arc_shrink_shift = 0; 372int zfs_arc_no_grow_shift = 0; 373int zfs_arc_p_min_shift = 0; 374uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 375u_int zfs_arc_free_target = 0; 376 377/* Absolute min for arc min / max is 16MB. */ 378static uint64_t arc_abs_min = 16 << 20; 379 380boolean_t zfs_compressed_arc_enabled = B_TRUE; 381 382static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 383static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 384static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 385static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 386static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS); 387 388#if defined(__FreeBSD__) && defined(_KERNEL) 389static void 390arc_free_target_init(void *unused __unused) 391{ 392 393 zfs_arc_free_target = vm_pageout_wakeup_thresh; 394} 395SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 396 arc_free_target_init, NULL); 397 398TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 399TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 400TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 401TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry); 402TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift); 403SYSCTL_DECL(_vfs_zfs); 404SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 405 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 406SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 407 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 408SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN, 409 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U", 410 "log2(fraction of ARC which must be free to allow growing)"); 411SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 412 &zfs_arc_average_blocksize, 0, 413 "ARC average blocksize"); 414SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 415 &arc_shrink_shift, 0, 416 "log2(fraction of arc to reclaim)"); 417SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW, 418 &arc_grow_retry, 0, 419 "Wait in seconds before considering growing ARC"); 420SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 421 &zfs_compressed_arc_enabled, 0, 422 "Enable compressed ARC"); 423SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_kmem_cache_reap_retry_ms, CTLFLAG_RWTUN, 424 &arc_kmem_cache_reap_retry_ms, 0, 425 "Interval between ARC kmem_cache reapings"); 426 427/* 428 * We don't have a tunable for arc_free_target due to the dependency on 429 * pagedaemon initialisation. 430 */ 431SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 432 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 433 sysctl_vfs_zfs_arc_free_target, "IU", 434 "Desired number of free pages below which ARC triggers reclaim"); 435 436static int 437sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 438{ 439 u_int val; 440 int err; 441 442 val = zfs_arc_free_target; 443 err = sysctl_handle_int(oidp, &val, 0, req); 444 if (err != 0 || req->newptr == NULL) 445 return (err); 446 447 if (val < minfree) 448 return (EINVAL); 449 if (val > vm_cnt.v_page_count) 450 return (EINVAL); 451 452 zfs_arc_free_target = val; 453 454 return (0); 455} 456 457/* 458 * Must be declared here, before the definition of corresponding kstat 459 * macro which uses the same names will confuse the compiler. 460 */ 461SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 462 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 463 sysctl_vfs_zfs_arc_meta_limit, "QU", 464 "ARC metadata limit"); 465#endif 466 467/* 468 * Note that buffers can be in one of 6 states: 469 * ARC_anon - anonymous (discussed below) 470 * ARC_mru - recently used, currently cached 471 * ARC_mru_ghost - recentely used, no longer in cache 472 * ARC_mfu - frequently used, currently cached 473 * ARC_mfu_ghost - frequently used, no longer in cache 474 * ARC_l2c_only - exists in L2ARC but not other states 475 * When there are no active references to the buffer, they are 476 * are linked onto a list in one of these arc states. These are 477 * the only buffers that can be evicted or deleted. Within each 478 * state there are multiple lists, one for meta-data and one for 479 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 480 * etc.) is tracked separately so that it can be managed more 481 * explicitly: favored over data, limited explicitly. 482 * 483 * Anonymous buffers are buffers that are not associated with 484 * a DVA. These are buffers that hold dirty block copies 485 * before they are written to stable storage. By definition, 486 * they are "ref'd" and are considered part of arc_mru 487 * that cannot be freed. Generally, they will aquire a DVA 488 * as they are written and migrate onto the arc_mru list. 489 * 490 * The ARC_l2c_only state is for buffers that are in the second 491 * level ARC but no longer in any of the ARC_m* lists. The second 492 * level ARC itself may also contain buffers that are in any of 493 * the ARC_m* states - meaning that a buffer can exist in two 494 * places. The reason for the ARC_l2c_only state is to keep the 495 * buffer header in the hash table, so that reads that hit the 496 * second level ARC benefit from these fast lookups. 497 */ 498 499typedef struct arc_state { 500 /* 501 * list of evictable buffers 502 */ 503 multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; 504 /* 505 * total amount of evictable data in this state 506 */ 507 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 508 /* 509 * total amount of data in this state; this includes: evictable, 510 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 511 */ 512 refcount_t arcs_size; 513} arc_state_t; 514 515/* The 6 states: */ 516static arc_state_t ARC_anon; 517static arc_state_t ARC_mru; 518static arc_state_t ARC_mru_ghost; 519static arc_state_t ARC_mfu; 520static arc_state_t ARC_mfu_ghost; 521static arc_state_t ARC_l2c_only; 522 523typedef struct arc_stats { 524 kstat_named_t arcstat_hits; 525 kstat_named_t arcstat_misses; 526 kstat_named_t arcstat_demand_data_hits; 527 kstat_named_t arcstat_demand_data_misses; 528 kstat_named_t arcstat_demand_metadata_hits; 529 kstat_named_t arcstat_demand_metadata_misses; 530 kstat_named_t arcstat_prefetch_data_hits; 531 kstat_named_t arcstat_prefetch_data_misses; 532 kstat_named_t arcstat_prefetch_metadata_hits; 533 kstat_named_t arcstat_prefetch_metadata_misses; 534 kstat_named_t arcstat_mru_hits; 535 kstat_named_t arcstat_mru_ghost_hits; 536 kstat_named_t arcstat_mfu_hits; 537 kstat_named_t arcstat_mfu_ghost_hits; 538 kstat_named_t arcstat_allocated; 539 kstat_named_t arcstat_deleted; 540 /* 541 * Number of buffers that could not be evicted because the hash lock 542 * was held by another thread. The lock may not necessarily be held 543 * by something using the same buffer, since hash locks are shared 544 * by multiple buffers. 545 */ 546 kstat_named_t arcstat_mutex_miss; 547 /* 548 * Number of buffers skipped when updating the access state due to the 549 * header having already been released after acquiring the hash lock. 550 */ 551 kstat_named_t arcstat_access_skip; 552 /* 553 * Number of buffers skipped because they have I/O in progress, are 554 * indirect prefetch buffers that have not lived long enough, or are 555 * not from the spa we're trying to evict from. 556 */ 557 kstat_named_t arcstat_evict_skip; 558 /* 559 * Number of times arc_evict_state() was unable to evict enough 560 * buffers to reach it's target amount. 561 */ 562 kstat_named_t arcstat_evict_not_enough; 563 kstat_named_t arcstat_evict_l2_cached; 564 kstat_named_t arcstat_evict_l2_eligible; 565 kstat_named_t arcstat_evict_l2_ineligible; 566 kstat_named_t arcstat_evict_l2_skip; 567 kstat_named_t arcstat_hash_elements; 568 kstat_named_t arcstat_hash_elements_max; 569 kstat_named_t arcstat_hash_collisions; 570 kstat_named_t arcstat_hash_chains; 571 kstat_named_t arcstat_hash_chain_max; 572 kstat_named_t arcstat_p; 573 kstat_named_t arcstat_c; 574 kstat_named_t arcstat_c_min; 575 kstat_named_t arcstat_c_max; 576 /* Not updated directly; only synced in arc_kstat_update. */ 577 kstat_named_t arcstat_size; 578 /* 579 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. 580 * Note that the compressed bytes may match the uncompressed bytes 581 * if the block is either not compressed or compressed arc is disabled. 582 */ 583 kstat_named_t arcstat_compressed_size; 584 /* 585 * Uncompressed size of the data stored in b_pabd. If compressed 586 * arc is disabled then this value will be identical to the stat 587 * above. 588 */ 589 kstat_named_t arcstat_uncompressed_size; 590 /* 591 * Number of bytes stored in all the arc_buf_t's. This is classified 592 * as "overhead" since this data is typically short-lived and will 593 * be evicted from the arc when it becomes unreferenced unless the 594 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 595 * values have been set (see comment in dbuf.c for more information). 596 */ 597 kstat_named_t arcstat_overhead_size; 598 /* 599 * Number of bytes consumed by internal ARC structures necessary 600 * for tracking purposes; these structures are not actually 601 * backed by ARC buffers. This includes arc_buf_hdr_t structures 602 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 603 * caches), and arc_buf_t structures (allocated via arc_buf_t 604 * cache). 605 * Not updated directly; only synced in arc_kstat_update. 606 */ 607 kstat_named_t arcstat_hdr_size; 608 /* 609 * Number of bytes consumed by ARC buffers of type equal to 610 * ARC_BUFC_DATA. This is generally consumed by buffers backing 611 * on disk user data (e.g. plain file contents). 612 * Not updated directly; only synced in arc_kstat_update. 613 */ 614 kstat_named_t arcstat_data_size; 615 /* 616 * Number of bytes consumed by ARC buffers of type equal to 617 * ARC_BUFC_METADATA. This is generally consumed by buffers 618 * backing on disk data that is used for internal ZFS 619 * structures (e.g. ZAP, dnode, indirect blocks, etc). 620 * Not updated directly; only synced in arc_kstat_update. 621 */ 622 kstat_named_t arcstat_metadata_size; 623 /* 624 * Number of bytes consumed by various buffers and structures 625 * not actually backed with ARC buffers. This includes bonus 626 * buffers (allocated directly via zio_buf_* functions), 627 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 628 * cache), and dnode_t structures (allocated via dnode_t cache). 629 * Not updated directly; only synced in arc_kstat_update. 630 */ 631 kstat_named_t arcstat_other_size; 632 /* 633 * Total number of bytes consumed by ARC buffers residing in the 634 * arc_anon state. This includes *all* buffers in the arc_anon 635 * state; e.g. data, metadata, evictable, and unevictable buffers 636 * are all included in this value. 637 * Not updated directly; only synced in arc_kstat_update. 638 */ 639 kstat_named_t arcstat_anon_size; 640 /* 641 * Number of bytes consumed by ARC buffers that meet the 642 * following criteria: backing buffers of type ARC_BUFC_DATA, 643 * residing in the arc_anon state, and are eligible for eviction 644 * (e.g. have no outstanding holds on the buffer). 645 * Not updated directly; only synced in arc_kstat_update. 646 */ 647 kstat_named_t arcstat_anon_evictable_data; 648 /* 649 * Number of bytes consumed by ARC buffers that meet the 650 * following criteria: backing buffers of type ARC_BUFC_METADATA, 651 * residing in the arc_anon state, and are eligible for eviction 652 * (e.g. have no outstanding holds on the buffer). 653 * Not updated directly; only synced in arc_kstat_update. 654 */ 655 kstat_named_t arcstat_anon_evictable_metadata; 656 /* 657 * Total number of bytes consumed by ARC buffers residing in the 658 * arc_mru state. This includes *all* buffers in the arc_mru 659 * state; e.g. data, metadata, evictable, and unevictable buffers 660 * are all included in this value. 661 * Not updated directly; only synced in arc_kstat_update. 662 */ 663 kstat_named_t arcstat_mru_size; 664 /* 665 * Number of bytes consumed by ARC buffers that meet the 666 * following criteria: backing buffers of type ARC_BUFC_DATA, 667 * residing in the arc_mru state, and are eligible for eviction 668 * (e.g. have no outstanding holds on the buffer). 669 * Not updated directly; only synced in arc_kstat_update. 670 */ 671 kstat_named_t arcstat_mru_evictable_data; 672 /* 673 * Number of bytes consumed by ARC buffers that meet the 674 * following criteria: backing buffers of type ARC_BUFC_METADATA, 675 * residing in the arc_mru state, and are eligible for eviction 676 * (e.g. have no outstanding holds on the buffer). 677 * Not updated directly; only synced in arc_kstat_update. 678 */ 679 kstat_named_t arcstat_mru_evictable_metadata; 680 /* 681 * Total number of bytes that *would have been* consumed by ARC 682 * buffers in the arc_mru_ghost state. The key thing to note 683 * here, is the fact that this size doesn't actually indicate 684 * RAM consumption. The ghost lists only consist of headers and 685 * don't actually have ARC buffers linked off of these headers. 686 * Thus, *if* the headers had associated ARC buffers, these 687 * buffers *would have* consumed this number of bytes. 688 * Not updated directly; only synced in arc_kstat_update. 689 */ 690 kstat_named_t arcstat_mru_ghost_size; 691 /* 692 * Number of bytes that *would have been* consumed by ARC 693 * buffers that are eligible for eviction, of type 694 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 695 * Not updated directly; only synced in arc_kstat_update. 696 */ 697 kstat_named_t arcstat_mru_ghost_evictable_data; 698 /* 699 * Number of bytes that *would have been* consumed by ARC 700 * buffers that are eligible for eviction, of type 701 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 702 * Not updated directly; only synced in arc_kstat_update. 703 */ 704 kstat_named_t arcstat_mru_ghost_evictable_metadata; 705 /* 706 * Total number of bytes consumed by ARC buffers residing in the 707 * arc_mfu state. This includes *all* buffers in the arc_mfu 708 * state; e.g. data, metadata, evictable, and unevictable buffers 709 * are all included in this value. 710 * Not updated directly; only synced in arc_kstat_update. 711 */ 712 kstat_named_t arcstat_mfu_size; 713 /* 714 * Number of bytes consumed by ARC buffers that are eligible for 715 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 716 * state. 717 * Not updated directly; only synced in arc_kstat_update. 718 */ 719 kstat_named_t arcstat_mfu_evictable_data; 720 /* 721 * Number of bytes consumed by ARC buffers that are eligible for 722 * eviction, of type ARC_BUFC_METADATA, and reside in the 723 * arc_mfu state. 724 * Not updated directly; only synced in arc_kstat_update. 725 */ 726 kstat_named_t arcstat_mfu_evictable_metadata; 727 /* 728 * Total number of bytes that *would have been* consumed by ARC 729 * buffers in the arc_mfu_ghost state. See the comment above 730 * arcstat_mru_ghost_size for more details. 731 * Not updated directly; only synced in arc_kstat_update. 732 */ 733 kstat_named_t arcstat_mfu_ghost_size; 734 /* 735 * Number of bytes that *would have been* consumed by ARC 736 * buffers that are eligible for eviction, of type 737 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 738 * Not updated directly; only synced in arc_kstat_update. 739 */ 740 kstat_named_t arcstat_mfu_ghost_evictable_data; 741 /* 742 * Number of bytes that *would have been* consumed by ARC 743 * buffers that are eligible for eviction, of type 744 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 745 * Not updated directly; only synced in arc_kstat_update. 746 */ 747 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 748 kstat_named_t arcstat_l2_hits; 749 kstat_named_t arcstat_l2_misses; 750 kstat_named_t arcstat_l2_feeds; 751 kstat_named_t arcstat_l2_rw_clash; 752 kstat_named_t arcstat_l2_read_bytes; 753 kstat_named_t arcstat_l2_write_bytes; 754 kstat_named_t arcstat_l2_writes_sent; 755 kstat_named_t arcstat_l2_writes_done; 756 kstat_named_t arcstat_l2_writes_error; 757 kstat_named_t arcstat_l2_writes_lock_retry; 758 kstat_named_t arcstat_l2_evict_lock_retry; 759 kstat_named_t arcstat_l2_evict_reading; 760 kstat_named_t arcstat_l2_evict_l1cached; 761 kstat_named_t arcstat_l2_free_on_write; 762 kstat_named_t arcstat_l2_abort_lowmem; 763 kstat_named_t arcstat_l2_cksum_bad; 764 kstat_named_t arcstat_l2_io_error; 765 kstat_named_t arcstat_l2_lsize; 766 kstat_named_t arcstat_l2_psize; 767 /* Not updated directly; only synced in arc_kstat_update. */ 768 kstat_named_t arcstat_l2_hdr_size; 769 kstat_named_t arcstat_l2_write_trylock_fail; 770 kstat_named_t arcstat_l2_write_passed_headroom; 771 kstat_named_t arcstat_l2_write_spa_mismatch; 772 kstat_named_t arcstat_l2_write_in_l2; 773 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 774 kstat_named_t arcstat_l2_write_not_cacheable; 775 kstat_named_t arcstat_l2_write_full; 776 kstat_named_t arcstat_l2_write_buffer_iter; 777 kstat_named_t arcstat_l2_write_pios; 778 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 779 kstat_named_t arcstat_l2_write_buffer_list_iter; 780 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 781 kstat_named_t arcstat_memory_throttle_count; 782 /* Not updated directly; only synced in arc_kstat_update. */ 783 kstat_named_t arcstat_meta_used; 784 kstat_named_t arcstat_meta_limit; 785 kstat_named_t arcstat_meta_max; 786 kstat_named_t arcstat_meta_min; 787 kstat_named_t arcstat_async_upgrade_sync; 788 kstat_named_t arcstat_demand_hit_predictive_prefetch; 789 kstat_named_t arcstat_demand_hit_prescient_prefetch; 790} arc_stats_t; 791 792static arc_stats_t arc_stats = { 793 { "hits", KSTAT_DATA_UINT64 }, 794 { "misses", KSTAT_DATA_UINT64 }, 795 { "demand_data_hits", KSTAT_DATA_UINT64 }, 796 { "demand_data_misses", KSTAT_DATA_UINT64 }, 797 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 798 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 799 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 800 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 801 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 802 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 803 { "mru_hits", KSTAT_DATA_UINT64 }, 804 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 805 { "mfu_hits", KSTAT_DATA_UINT64 }, 806 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 807 { "allocated", KSTAT_DATA_UINT64 }, 808 { "deleted", KSTAT_DATA_UINT64 }, 809 { "mutex_miss", KSTAT_DATA_UINT64 }, 810 { "access_skip", KSTAT_DATA_UINT64 }, 811 { "evict_skip", KSTAT_DATA_UINT64 }, 812 { "evict_not_enough", KSTAT_DATA_UINT64 }, 813 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 814 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 815 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 816 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 817 { "hash_elements", KSTAT_DATA_UINT64 }, 818 { "hash_elements_max", KSTAT_DATA_UINT64 }, 819 { "hash_collisions", KSTAT_DATA_UINT64 }, 820 { "hash_chains", KSTAT_DATA_UINT64 }, 821 { "hash_chain_max", KSTAT_DATA_UINT64 }, 822 { "p", KSTAT_DATA_UINT64 }, 823 { "c", KSTAT_DATA_UINT64 }, 824 { "c_min", KSTAT_DATA_UINT64 }, 825 { "c_max", KSTAT_DATA_UINT64 }, 826 { "size", KSTAT_DATA_UINT64 }, 827 { "compressed_size", KSTAT_DATA_UINT64 }, 828 { "uncompressed_size", KSTAT_DATA_UINT64 }, 829 { "overhead_size", KSTAT_DATA_UINT64 }, 830 { "hdr_size", KSTAT_DATA_UINT64 }, 831 { "data_size", KSTAT_DATA_UINT64 }, 832 { "metadata_size", KSTAT_DATA_UINT64 }, 833 { "other_size", KSTAT_DATA_UINT64 }, 834 { "anon_size", KSTAT_DATA_UINT64 }, 835 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 836 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 837 { "mru_size", KSTAT_DATA_UINT64 }, 838 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 839 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 840 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 841 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 842 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 843 { "mfu_size", KSTAT_DATA_UINT64 }, 844 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 845 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 846 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 847 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 848 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 849 { "l2_hits", KSTAT_DATA_UINT64 }, 850 { "l2_misses", KSTAT_DATA_UINT64 }, 851 { "l2_feeds", KSTAT_DATA_UINT64 }, 852 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 853 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 854 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 855 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 856 { "l2_writes_done", KSTAT_DATA_UINT64 }, 857 { "l2_writes_error", KSTAT_DATA_UINT64 }, 858 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 859 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 860 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 861 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 862 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 863 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 864 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 865 { "l2_io_error", KSTAT_DATA_UINT64 }, 866 { "l2_size", KSTAT_DATA_UINT64 }, 867 { "l2_asize", KSTAT_DATA_UINT64 }, 868 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 869 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 870 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 871 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 872 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 873 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 874 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 875 { "l2_write_full", KSTAT_DATA_UINT64 }, 876 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 877 { "l2_write_pios", KSTAT_DATA_UINT64 }, 878 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 879 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 880 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 881 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 882 { "arc_meta_used", KSTAT_DATA_UINT64 }, 883 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 884 { "arc_meta_max", KSTAT_DATA_UINT64 }, 885 { "arc_meta_min", KSTAT_DATA_UINT64 }, 886 { "async_upgrade_sync", KSTAT_DATA_UINT64 }, 887 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 888 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 }, 889}; 890 891#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 892 893#define ARCSTAT_INCR(stat, val) \ 894 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 895 896#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 897#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 898 899#define ARCSTAT_MAX(stat, val) { \ 900 uint64_t m; \ 901 while ((val) > (m = arc_stats.stat.value.ui64) && \ 902 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 903 continue; \ 904} 905 906#define ARCSTAT_MAXSTAT(stat) \ 907 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 908 909/* 910 * We define a macro to allow ARC hits/misses to be easily broken down by 911 * two separate conditions, giving a total of four different subtypes for 912 * each of hits and misses (so eight statistics total). 913 */ 914#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 915 if (cond1) { \ 916 if (cond2) { \ 917 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 918 } else { \ 919 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 920 } \ 921 } else { \ 922 if (cond2) { \ 923 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 924 } else { \ 925 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 926 } \ 927 } 928 929kstat_t *arc_ksp; 930static arc_state_t *arc_anon; 931static arc_state_t *arc_mru; 932static arc_state_t *arc_mru_ghost; 933static arc_state_t *arc_mfu; 934static arc_state_t *arc_mfu_ghost; 935static arc_state_t *arc_l2c_only; 936 937/* 938 * There are several ARC variables that are critical to export as kstats -- 939 * but we don't want to have to grovel around in the kstat whenever we wish to 940 * manipulate them. For these variables, we therefore define them to be in 941 * terms of the statistic variable. This assures that we are not introducing 942 * the possibility of inconsistency by having shadow copies of the variables, 943 * while still allowing the code to be readable. 944 */ 945#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 946#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 947#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 948#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 949#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 950#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 951#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 952 953/* compressed size of entire arc */ 954#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 955/* uncompressed size of entire arc */ 956#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 957/* number of bytes in the arc from arc_buf_t's */ 958#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 959 960/* 961 * There are also some ARC variables that we want to export, but that are 962 * updated so often that having the canonical representation be the statistic 963 * variable causes a performance bottleneck. We want to use aggsum_t's for these 964 * instead, but still be able to export the kstat in the same way as before. 965 * The solution is to always use the aggsum version, except in the kstat update 966 * callback. 967 */ 968aggsum_t arc_size; 969aggsum_t arc_meta_used; 970aggsum_t astat_data_size; 971aggsum_t astat_metadata_size; 972aggsum_t astat_hdr_size; 973aggsum_t astat_other_size; 974aggsum_t astat_l2_hdr_size; 975 976static int arc_no_grow; /* Don't try to grow cache size */ 977static uint64_t arc_tempreserve; 978static uint64_t arc_loaned_bytes; 979 980typedef struct arc_callback arc_callback_t; 981 982struct arc_callback { 983 void *acb_private; 984 arc_read_done_func_t *acb_done; 985 arc_buf_t *acb_buf; 986 boolean_t acb_compressed; 987 zio_t *acb_zio_dummy; 988 zio_t *acb_zio_head; 989 arc_callback_t *acb_next; 990}; 991 992typedef struct arc_write_callback arc_write_callback_t; 993 994struct arc_write_callback { 995 void *awcb_private; 996 arc_write_done_func_t *awcb_ready; 997 arc_write_done_func_t *awcb_children_ready; 998 arc_write_done_func_t *awcb_physdone; 999 arc_write_done_func_t *awcb_done; 1000 arc_buf_t *awcb_buf; 1001}; 1002 1003/* 1004 * ARC buffers are separated into multiple structs as a memory saving measure: 1005 * - Common fields struct, always defined, and embedded within it: 1006 * - L2-only fields, always allocated but undefined when not in L2ARC 1007 * - L1-only fields, only allocated when in L1ARC 1008 * 1009 * Buffer in L1 Buffer only in L2 1010 * +------------------------+ +------------------------+ 1011 * | arc_buf_hdr_t | | arc_buf_hdr_t | 1012 * | | | | 1013 * | | | | 1014 * | | | | 1015 * +------------------------+ +------------------------+ 1016 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 1017 * | (undefined if L1-only) | | | 1018 * +------------------------+ +------------------------+ 1019 * | l1arc_buf_hdr_t | 1020 * | | 1021 * | | 1022 * | | 1023 * | | 1024 * +------------------------+ 1025 * 1026 * Because it's possible for the L2ARC to become extremely large, we can wind 1027 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 1028 * is minimized by only allocating the fields necessary for an L1-cached buffer 1029 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 1030 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 1031 * words in pointers. arc_hdr_realloc() is used to switch a header between 1032 * these two allocation states. 1033 */ 1034typedef struct l1arc_buf_hdr { 1035 kmutex_t b_freeze_lock; 1036 zio_cksum_t *b_freeze_cksum; 1037#ifdef ZFS_DEBUG 1038 /* 1039 * Used for debugging with kmem_flags - by allocating and freeing 1040 * b_thawed when the buffer is thawed, we get a record of the stack 1041 * trace that thawed it. 1042 */ 1043 void *b_thawed; 1044#endif 1045 1046 arc_buf_t *b_buf; 1047 uint32_t b_bufcnt; 1048 /* for waiting on writes to complete */ 1049 kcondvar_t b_cv; 1050 uint8_t b_byteswap; 1051 1052 /* protected by arc state mutex */ 1053 arc_state_t *b_state; 1054 multilist_node_t b_arc_node; 1055 1056 /* updated atomically */ 1057 clock_t b_arc_access; 1058 1059 /* self protecting */ 1060 refcount_t b_refcnt; 1061 1062 arc_callback_t *b_acb; 1063 abd_t *b_pabd; 1064} l1arc_buf_hdr_t; 1065 1066typedef struct l2arc_dev l2arc_dev_t; 1067 1068typedef struct l2arc_buf_hdr { 1069 /* protected by arc_buf_hdr mutex */ 1070 l2arc_dev_t *b_dev; /* L2ARC device */ 1071 uint64_t b_daddr; /* disk address, offset byte */ 1072 1073 list_node_t b_l2node; 1074} l2arc_buf_hdr_t; 1075 1076struct arc_buf_hdr { 1077 /* protected by hash lock */ 1078 dva_t b_dva; 1079 uint64_t b_birth; 1080 1081 arc_buf_contents_t b_type; 1082 arc_buf_hdr_t *b_hash_next; 1083 arc_flags_t b_flags; 1084 1085 /* 1086 * This field stores the size of the data buffer after 1087 * compression, and is set in the arc's zio completion handlers. 1088 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1089 * 1090 * While the block pointers can store up to 32MB in their psize 1091 * field, we can only store up to 32MB minus 512B. This is due 1092 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1093 * a field of zeros represents 512B in the bp). We can't use a 1094 * bias of 1 since we need to reserve a psize of zero, here, to 1095 * represent holes and embedded blocks. 1096 * 1097 * This isn't a problem in practice, since the maximum size of a 1098 * buffer is limited to 16MB, so we never need to store 32MB in 1099 * this field. Even in the upstream illumos code base, the 1100 * maximum size of a buffer is limited to 16MB. 1101 */ 1102 uint16_t b_psize; 1103 1104 /* 1105 * This field stores the size of the data buffer before 1106 * compression, and cannot change once set. It is in units 1107 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1108 */ 1109 uint16_t b_lsize; /* immutable */ 1110 uint64_t b_spa; /* immutable */ 1111 1112 /* L2ARC fields. Undefined when not in L2ARC. */ 1113 l2arc_buf_hdr_t b_l2hdr; 1114 /* L1ARC fields. Undefined when in l2arc_only state */ 1115 l1arc_buf_hdr_t b_l1hdr; 1116}; 1117 1118#if defined(__FreeBSD__) && defined(_KERNEL) 1119static int 1120sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1121{ 1122 uint64_t val; 1123 int err; 1124 1125 val = arc_meta_limit; 1126 err = sysctl_handle_64(oidp, &val, 0, req); 1127 if (err != 0 || req->newptr == NULL) 1128 return (err); 1129 1130 if (val <= 0 || val > arc_c_max) 1131 return (EINVAL); 1132 1133 arc_meta_limit = val; 1134 return (0); 1135} 1136 1137static int 1138sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS) 1139{ 1140 uint32_t val; 1141 int err; 1142 1143 val = arc_no_grow_shift; 1144 err = sysctl_handle_32(oidp, &val, 0, req); 1145 if (err != 0 || req->newptr == NULL) 1146 return (err); 1147 1148 if (val >= arc_shrink_shift) 1149 return (EINVAL); 1150 1151 arc_no_grow_shift = val; 1152 return (0); 1153} 1154 1155static int 1156sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1157{ 1158 uint64_t val; 1159 int err; 1160 1161 val = zfs_arc_max; 1162 err = sysctl_handle_64(oidp, &val, 0, req); 1163 if (err != 0 || req->newptr == NULL) 1164 return (err); 1165 1166 if (zfs_arc_max == 0) { 1167 /* Loader tunable so blindly set */ 1168 zfs_arc_max = val; 1169 return (0); 1170 } 1171 1172 if (val < arc_abs_min || val > kmem_size()) 1173 return (EINVAL); 1174 if (val < arc_c_min) 1175 return (EINVAL); 1176 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1177 return (EINVAL); 1178 1179 arc_c_max = val; 1180 1181 arc_c = arc_c_max; 1182 arc_p = (arc_c >> 1); 1183 1184 if (zfs_arc_meta_limit == 0) { 1185 /* limit meta-data to 1/4 of the arc capacity */ 1186 arc_meta_limit = arc_c_max / 4; 1187 } 1188 1189 /* if kmem_flags are set, lets try to use less memory */ 1190 if (kmem_debugging()) 1191 arc_c = arc_c / 2; 1192 1193 zfs_arc_max = arc_c; 1194 1195 return (0); 1196} 1197 1198static int 1199sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1200{ 1201 uint64_t val; 1202 int err; 1203 1204 val = zfs_arc_min; 1205 err = sysctl_handle_64(oidp, &val, 0, req); 1206 if (err != 0 || req->newptr == NULL) 1207 return (err); 1208 1209 if (zfs_arc_min == 0) { 1210 /* Loader tunable so blindly set */ 1211 zfs_arc_min = val; 1212 return (0); 1213 } 1214 1215 if (val < arc_abs_min || val > arc_c_max) 1216 return (EINVAL); 1217 1218 arc_c_min = val; 1219 1220 if (zfs_arc_meta_min == 0) 1221 arc_meta_min = arc_c_min / 2; 1222 1223 if (arc_c < arc_c_min) 1224 arc_c = arc_c_min; 1225 1226 zfs_arc_min = arc_c_min; 1227 1228 return (0); 1229} 1230#endif 1231 1232#define GHOST_STATE(state) \ 1233 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1234 (state) == arc_l2c_only) 1235 1236#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1237#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1238#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1239#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1240#define HDR_PRESCIENT_PREFETCH(hdr) \ 1241 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) 1242#define HDR_COMPRESSION_ENABLED(hdr) \ 1243 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1244 1245#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1246#define HDR_L2_READING(hdr) \ 1247 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1248 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1249#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1250#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1251#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1252#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1253 1254#define HDR_ISTYPE_METADATA(hdr) \ 1255 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1256#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1257 1258#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1259#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1260 1261/* For storing compression mode in b_flags */ 1262#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1263 1264#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1265 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1266#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1267 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1268 1269#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1270#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) 1271#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) 1272 1273/* 1274 * Other sizes 1275 */ 1276 1277#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1278#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1279 1280/* 1281 * Hash table routines 1282 */ 1283 1284#define HT_LOCK_PAD CACHE_LINE_SIZE 1285 1286struct ht_lock { 1287 kmutex_t ht_lock; 1288#ifdef _KERNEL 1289 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1290#endif 1291}; 1292 1293#define BUF_LOCKS 256 1294typedef struct buf_hash_table { 1295 uint64_t ht_mask; 1296 arc_buf_hdr_t **ht_table; 1297 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1298} buf_hash_table_t; 1299 1300static buf_hash_table_t buf_hash_table; 1301 1302#define BUF_HASH_INDEX(spa, dva, birth) \ 1303 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1304#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1305#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1306#define HDR_LOCK(hdr) \ 1307 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1308 1309uint64_t zfs_crc64_table[256]; 1310 1311/* 1312 * Level 2 ARC 1313 */ 1314 1315#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1316#define L2ARC_HEADROOM 2 /* num of writes */ 1317/* 1318 * If we discover during ARC scan any buffers to be compressed, we boost 1319 * our headroom for the next scanning cycle by this percentage multiple. 1320 */ 1321#define L2ARC_HEADROOM_BOOST 200 1322#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1323#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1324 1325#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1326#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1327 1328/* L2ARC Performance Tunables */ 1329uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1330uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1331uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1332uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1333uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1334uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1335boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1336boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1337boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1338 1339SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1340 &l2arc_write_max, 0, "max write size"); 1341SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1342 &l2arc_write_boost, 0, "extra write during warmup"); 1343SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1344 &l2arc_headroom, 0, "number of dev writes"); 1345SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1346 &l2arc_feed_secs, 0, "interval seconds"); 1347SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1348 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1349 1350SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1351 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1352SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1353 &l2arc_feed_again, 0, "turbo warmup"); 1354SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1355 &l2arc_norw, 0, "no reads during writes"); 1356 1357SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1358 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1359SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1360 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1361 "size of anonymous state"); 1362SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1363 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1364 "size of anonymous state"); 1365 1366SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1367 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1368SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1369 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1370 "size of metadata in mru state"); 1371SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1372 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1373 "size of data in mru state"); 1374 1375SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1376 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1377SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1378 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1379 "size of metadata in mru ghost state"); 1380SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1381 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1382 "size of data in mru ghost state"); 1383 1384SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1385 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1386SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1387 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1388 "size of metadata in mfu state"); 1389SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1390 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1391 "size of data in mfu state"); 1392 1393SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1394 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1395SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1396 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1397 "size of metadata in mfu ghost state"); 1398SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1399 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1400 "size of data in mfu ghost state"); 1401 1402SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1403 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1404 1405SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prefetch_ms, CTLFLAG_RW, 1406 &zfs_arc_min_prefetch_ms, 0, "Min life of prefetch block in ms"); 1407SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prescient_prefetch_ms, CTLFLAG_RW, 1408 &zfs_arc_min_prescient_prefetch_ms, 0, "Min life of prescient prefetched block in ms"); 1409 1410/* 1411 * L2ARC Internals 1412 */ 1413struct l2arc_dev { 1414 vdev_t *l2ad_vdev; /* vdev */ 1415 spa_t *l2ad_spa; /* spa */ 1416 uint64_t l2ad_hand; /* next write location */ 1417 uint64_t l2ad_start; /* first addr on device */ 1418 uint64_t l2ad_end; /* last addr on device */ 1419 boolean_t l2ad_first; /* first sweep through */ 1420 boolean_t l2ad_writing; /* currently writing */ 1421 kmutex_t l2ad_mtx; /* lock for buffer list */ 1422 list_t l2ad_buflist; /* buffer list */ 1423 list_node_t l2ad_node; /* device list node */ 1424 refcount_t l2ad_alloc; /* allocated bytes */ 1425}; 1426 1427static list_t L2ARC_dev_list; /* device list */ 1428static list_t *l2arc_dev_list; /* device list pointer */ 1429static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1430static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1431static list_t L2ARC_free_on_write; /* free after write buf list */ 1432static list_t *l2arc_free_on_write; /* free after write list ptr */ 1433static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1434static uint64_t l2arc_ndev; /* number of devices */ 1435 1436typedef struct l2arc_read_callback { 1437 arc_buf_hdr_t *l2rcb_hdr; /* read header */ 1438 blkptr_t l2rcb_bp; /* original blkptr */ 1439 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1440 int l2rcb_flags; /* original flags */ 1441 abd_t *l2rcb_abd; /* temporary buffer */ 1442} l2arc_read_callback_t; 1443 1444typedef struct l2arc_write_callback { 1445 l2arc_dev_t *l2wcb_dev; /* device info */ 1446 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1447} l2arc_write_callback_t; 1448 1449typedef struct l2arc_data_free { 1450 /* protected by l2arc_free_on_write_mtx */ 1451 abd_t *l2df_abd; 1452 size_t l2df_size; 1453 arc_buf_contents_t l2df_type; 1454 list_node_t l2df_list_node; 1455} l2arc_data_free_t; 1456 1457static kmutex_t l2arc_feed_thr_lock; 1458static kcondvar_t l2arc_feed_thr_cv; 1459static uint8_t l2arc_thread_exit; 1460 1461static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *); 1462static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1463static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *); 1464static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); 1465static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1466static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); 1467static void arc_hdr_free_pabd(arc_buf_hdr_t *); 1468static void arc_hdr_alloc_pabd(arc_buf_hdr_t *); 1469static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1470static boolean_t arc_is_overflowing(); 1471static void arc_buf_watch(arc_buf_t *); 1472 1473static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1474static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1475static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1476static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1477 1478static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1479static void l2arc_read_done(zio_t *); 1480 1481static void 1482l2arc_trim(const arc_buf_hdr_t *hdr) 1483{ 1484 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1485 1486 ASSERT(HDR_HAS_L2HDR(hdr)); 1487 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1488 1489 if (HDR_GET_PSIZE(hdr) != 0) { 1490 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1491 HDR_GET_PSIZE(hdr), 0); 1492 } 1493} 1494 1495/* 1496 * We use Cityhash for this. It's fast, and has good hash properties without 1497 * requiring any large static buffers. 1498 */ 1499static uint64_t 1500buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1501{ 1502 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth)); 1503} 1504 1505#define HDR_EMPTY(hdr) \ 1506 ((hdr)->b_dva.dva_word[0] == 0 && \ 1507 (hdr)->b_dva.dva_word[1] == 0) 1508 1509#define HDR_EQUAL(spa, dva, birth, hdr) \ 1510 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1511 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1512 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1513 1514static void 1515buf_discard_identity(arc_buf_hdr_t *hdr) 1516{ 1517 hdr->b_dva.dva_word[0] = 0; 1518 hdr->b_dva.dva_word[1] = 0; 1519 hdr->b_birth = 0; 1520} 1521 1522static arc_buf_hdr_t * 1523buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1524{ 1525 const dva_t *dva = BP_IDENTITY(bp); 1526 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1527 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1528 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1529 arc_buf_hdr_t *hdr; 1530 1531 mutex_enter(hash_lock); 1532 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1533 hdr = hdr->b_hash_next) { 1534 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1535 *lockp = hash_lock; 1536 return (hdr); 1537 } 1538 } 1539 mutex_exit(hash_lock); 1540 *lockp = NULL; 1541 return (NULL); 1542} 1543 1544/* 1545 * Insert an entry into the hash table. If there is already an element 1546 * equal to elem in the hash table, then the already existing element 1547 * will be returned and the new element will not be inserted. 1548 * Otherwise returns NULL. 1549 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1550 */ 1551static arc_buf_hdr_t * 1552buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1553{ 1554 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1555 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1556 arc_buf_hdr_t *fhdr; 1557 uint32_t i; 1558 1559 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1560 ASSERT(hdr->b_birth != 0); 1561 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1562 1563 if (lockp != NULL) { 1564 *lockp = hash_lock; 1565 mutex_enter(hash_lock); 1566 } else { 1567 ASSERT(MUTEX_HELD(hash_lock)); 1568 } 1569 1570 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1571 fhdr = fhdr->b_hash_next, i++) { 1572 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1573 return (fhdr); 1574 } 1575 1576 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1577 buf_hash_table.ht_table[idx] = hdr; 1578 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1579 1580 /* collect some hash table performance data */ 1581 if (i > 0) { 1582 ARCSTAT_BUMP(arcstat_hash_collisions); 1583 if (i == 1) 1584 ARCSTAT_BUMP(arcstat_hash_chains); 1585 1586 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1587 } 1588 1589 ARCSTAT_BUMP(arcstat_hash_elements); 1590 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1591 1592 return (NULL); 1593} 1594 1595static void 1596buf_hash_remove(arc_buf_hdr_t *hdr) 1597{ 1598 arc_buf_hdr_t *fhdr, **hdrp; 1599 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1600 1601 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1602 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1603 1604 hdrp = &buf_hash_table.ht_table[idx]; 1605 while ((fhdr = *hdrp) != hdr) { 1606 ASSERT3P(fhdr, !=, NULL); 1607 hdrp = &fhdr->b_hash_next; 1608 } 1609 *hdrp = hdr->b_hash_next; 1610 hdr->b_hash_next = NULL; 1611 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1612 1613 /* collect some hash table performance data */ 1614 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1615 1616 if (buf_hash_table.ht_table[idx] && 1617 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1618 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1619} 1620 1621/* 1622 * Global data structures and functions for the buf kmem cache. 1623 */ 1624static kmem_cache_t *hdr_full_cache; 1625static kmem_cache_t *hdr_l2only_cache; 1626static kmem_cache_t *buf_cache; 1627 1628static void 1629buf_fini(void) 1630{ 1631 int i; 1632 1633 kmem_free(buf_hash_table.ht_table, 1634 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1635 for (i = 0; i < BUF_LOCKS; i++) 1636 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1637 kmem_cache_destroy(hdr_full_cache); 1638 kmem_cache_destroy(hdr_l2only_cache); 1639 kmem_cache_destroy(buf_cache); 1640} 1641 1642/* 1643 * Constructor callback - called when the cache is empty 1644 * and a new buf is requested. 1645 */ 1646/* ARGSUSED */ 1647static int 1648hdr_full_cons(void *vbuf, void *unused, int kmflag) 1649{ 1650 arc_buf_hdr_t *hdr = vbuf; 1651 1652 bzero(hdr, HDR_FULL_SIZE); 1653 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1654 refcount_create(&hdr->b_l1hdr.b_refcnt); 1655 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1656 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1657 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1658 1659 return (0); 1660} 1661 1662/* ARGSUSED */ 1663static int 1664hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1665{ 1666 arc_buf_hdr_t *hdr = vbuf; 1667 1668 bzero(hdr, HDR_L2ONLY_SIZE); 1669 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1670 1671 return (0); 1672} 1673 1674/* ARGSUSED */ 1675static int 1676buf_cons(void *vbuf, void *unused, int kmflag) 1677{ 1678 arc_buf_t *buf = vbuf; 1679 1680 bzero(buf, sizeof (arc_buf_t)); 1681 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1682 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1683 1684 return (0); 1685} 1686 1687/* 1688 * Destructor callback - called when a cached buf is 1689 * no longer required. 1690 */ 1691/* ARGSUSED */ 1692static void 1693hdr_full_dest(void *vbuf, void *unused) 1694{ 1695 arc_buf_hdr_t *hdr = vbuf; 1696 1697 ASSERT(HDR_EMPTY(hdr)); 1698 cv_destroy(&hdr->b_l1hdr.b_cv); 1699 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1700 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1701 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1702 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1703} 1704 1705/* ARGSUSED */ 1706static void 1707hdr_l2only_dest(void *vbuf, void *unused) 1708{ 1709 arc_buf_hdr_t *hdr = vbuf; 1710 1711 ASSERT(HDR_EMPTY(hdr)); 1712 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1713} 1714 1715/* ARGSUSED */ 1716static void 1717buf_dest(void *vbuf, void *unused) 1718{ 1719 arc_buf_t *buf = vbuf; 1720 1721 mutex_destroy(&buf->b_evict_lock); 1722 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1723} 1724 1725/* 1726 * Reclaim callback -- invoked when memory is low. 1727 */ 1728/* ARGSUSED */ 1729static void 1730hdr_recl(void *unused) 1731{ 1732 dprintf("hdr_recl called\n"); 1733 /* 1734 * umem calls the reclaim func when we destroy the buf cache, 1735 * which is after we do arc_fini(). 1736 */ 1737 if (!arc_dead) 1738 cv_signal(&arc_reclaim_thread_cv); 1739} 1740 1741static void 1742buf_init(void) 1743{ 1744 uint64_t *ct; 1745 uint64_t hsize = 1ULL << 12; 1746 int i, j; 1747 1748 /* 1749 * The hash table is big enough to fill all of physical memory 1750 * with an average block size of zfs_arc_average_blocksize (default 8K). 1751 * By default, the table will take up 1752 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1753 */ 1754 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1755 hsize <<= 1; 1756retry: 1757 buf_hash_table.ht_mask = hsize - 1; 1758 buf_hash_table.ht_table = 1759 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1760 if (buf_hash_table.ht_table == NULL) { 1761 ASSERT(hsize > (1ULL << 8)); 1762 hsize >>= 1; 1763 goto retry; 1764 } 1765 1766 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1767 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1768 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1769 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1770 NULL, NULL, 0); 1771 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1772 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1773 1774 for (i = 0; i < 256; i++) 1775 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1776 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1777 1778 for (i = 0; i < BUF_LOCKS; i++) { 1779 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1780 NULL, MUTEX_DEFAULT, NULL); 1781 } 1782} 1783 1784/* 1785 * This is the size that the buf occupies in memory. If the buf is compressed, 1786 * it will correspond to the compressed size. You should use this method of 1787 * getting the buf size unless you explicitly need the logical size. 1788 */ 1789int32_t 1790arc_buf_size(arc_buf_t *buf) 1791{ 1792 return (ARC_BUF_COMPRESSED(buf) ? 1793 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); 1794} 1795 1796int32_t 1797arc_buf_lsize(arc_buf_t *buf) 1798{ 1799 return (HDR_GET_LSIZE(buf->b_hdr)); 1800} 1801 1802enum zio_compress 1803arc_get_compression(arc_buf_t *buf) 1804{ 1805 return (ARC_BUF_COMPRESSED(buf) ? 1806 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); 1807} 1808 1809#define ARC_MINTIME (hz>>4) /* 62 ms */ 1810 1811static inline boolean_t 1812arc_buf_is_shared(arc_buf_t *buf) 1813{ 1814 boolean_t shared = (buf->b_data != NULL && 1815 buf->b_hdr->b_l1hdr.b_pabd != NULL && 1816 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && 1817 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); 1818 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1819 IMPLY(shared, ARC_BUF_SHARED(buf)); 1820 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); 1821 1822 /* 1823 * It would be nice to assert arc_can_share() too, but the "hdr isn't 1824 * already being shared" requirement prevents us from doing that. 1825 */ 1826 1827 return (shared); 1828} 1829 1830/* 1831 * Free the checksum associated with this header. If there is no checksum, this 1832 * is a no-op. 1833 */ 1834static inline void 1835arc_cksum_free(arc_buf_hdr_t *hdr) 1836{ 1837 ASSERT(HDR_HAS_L1HDR(hdr)); 1838 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1839 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1840 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1841 hdr->b_l1hdr.b_freeze_cksum = NULL; 1842 } 1843 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1844} 1845 1846/* 1847 * Return true iff at least one of the bufs on hdr is not compressed. 1848 */ 1849static boolean_t 1850arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) 1851{ 1852 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { 1853 if (!ARC_BUF_COMPRESSED(b)) { 1854 return (B_TRUE); 1855 } 1856 } 1857 return (B_FALSE); 1858} 1859 1860/* 1861 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data 1862 * matches the checksum that is stored in the hdr. If there is no checksum, 1863 * or if the buf is compressed, this is a no-op. 1864 */ 1865static void 1866arc_cksum_verify(arc_buf_t *buf) 1867{ 1868 arc_buf_hdr_t *hdr = buf->b_hdr; 1869 zio_cksum_t zc; 1870 1871 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1872 return; 1873 1874 if (ARC_BUF_COMPRESSED(buf)) { 1875 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 1876 arc_hdr_has_uncompressed_buf(hdr)); 1877 return; 1878 } 1879 1880 ASSERT(HDR_HAS_L1HDR(hdr)); 1881 1882 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1883 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1884 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1885 return; 1886 } 1887 1888 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); 1889 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1890 panic("buffer modified while frozen!"); 1891 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1892} 1893 1894static boolean_t 1895arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1896{ 1897 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1898 boolean_t valid_cksum; 1899 1900 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1901 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1902 1903 /* 1904 * We rely on the blkptr's checksum to determine if the block 1905 * is valid or not. When compressed arc is enabled, the l2arc 1906 * writes the block to the l2arc just as it appears in the pool. 1907 * This allows us to use the blkptr's checksum to validate the 1908 * data that we just read off of the l2arc without having to store 1909 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1910 * arc is disabled, then the data written to the l2arc is always 1911 * uncompressed and won't match the block as it exists in the main 1912 * pool. When this is the case, we must first compress it if it is 1913 * compressed on the main pool before we can validate the checksum. 1914 */ 1915 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1916 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1917 uint64_t lsize = HDR_GET_LSIZE(hdr); 1918 uint64_t csize; 1919 1920 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE); 1921 csize = zio_compress_data(compress, zio->io_abd, 1922 abd_to_buf(cdata), lsize); 1923 1924 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1925 if (csize < HDR_GET_PSIZE(hdr)) { 1926 /* 1927 * Compressed blocks are always a multiple of the 1928 * smallest ashift in the pool. Ideally, we would 1929 * like to round up the csize to the next 1930 * spa_min_ashift but that value may have changed 1931 * since the block was last written. Instead, 1932 * we rely on the fact that the hdr's psize 1933 * was set to the psize of the block when it was 1934 * last written. We set the csize to that value 1935 * and zero out any part that should not contain 1936 * data. 1937 */ 1938 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize); 1939 csize = HDR_GET_PSIZE(hdr); 1940 } 1941 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL); 1942 } 1943 1944 /* 1945 * Block pointers always store the checksum for the logical data. 1946 * If the block pointer has the gang bit set, then the checksum 1947 * it represents is for the reconstituted data and not for an 1948 * individual gang member. The zio pipeline, however, must be able to 1949 * determine the checksum of each of the gang constituents so it 1950 * treats the checksum comparison differently than what we need 1951 * for l2arc blocks. This prevents us from using the 1952 * zio_checksum_error() interface directly. Instead we must call the 1953 * zio_checksum_error_impl() so that we can ensure the checksum is 1954 * generated using the correct checksum algorithm and accounts for the 1955 * logical I/O size and not just a gang fragment. 1956 */ 1957 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1958 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, 1959 zio->io_offset, NULL) == 0); 1960 zio_pop_transforms(zio); 1961 return (valid_cksum); 1962} 1963 1964/* 1965 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a 1966 * checksum and attaches it to the buf's hdr so that we can ensure that the buf 1967 * isn't modified later on. If buf is compressed or there is already a checksum 1968 * on the hdr, this is a no-op (we only checksum uncompressed bufs). 1969 */ 1970static void 1971arc_cksum_compute(arc_buf_t *buf) 1972{ 1973 arc_buf_hdr_t *hdr = buf->b_hdr; 1974 1975 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1976 return; 1977 1978 ASSERT(HDR_HAS_L1HDR(hdr)); 1979 1980 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1981 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1982 ASSERT(arc_hdr_has_uncompressed_buf(hdr)); 1983 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1984 return; 1985 } else if (ARC_BUF_COMPRESSED(buf)) { 1986 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1987 return; 1988 } 1989 1990 ASSERT(!ARC_BUF_COMPRESSED(buf)); 1991 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1992 KM_SLEEP); 1993 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, 1994 hdr->b_l1hdr.b_freeze_cksum); 1995 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1996#ifdef illumos 1997 arc_buf_watch(buf); 1998#endif 1999} 2000 2001#ifdef illumos 2002#ifndef _KERNEL 2003typedef struct procctl { 2004 long cmd; 2005 prwatch_t prwatch; 2006} procctl_t; 2007#endif 2008 2009/* ARGSUSED */ 2010static void 2011arc_buf_unwatch(arc_buf_t *buf) 2012{ 2013#ifndef _KERNEL 2014 if (arc_watch) { 2015 int result; 2016 procctl_t ctl; 2017 ctl.cmd = PCWATCH; 2018 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 2019 ctl.prwatch.pr_size = 0; 2020 ctl.prwatch.pr_wflags = 0; 2021 result = write(arc_procfd, &ctl, sizeof (ctl)); 2022 ASSERT3U(result, ==, sizeof (ctl)); 2023 } 2024#endif 2025} 2026 2027/* ARGSUSED */ 2028static void 2029arc_buf_watch(arc_buf_t *buf) 2030{ 2031#ifndef _KERNEL 2032 if (arc_watch) { 2033 int result; 2034 procctl_t ctl; 2035 ctl.cmd = PCWATCH; 2036 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 2037 ctl.prwatch.pr_size = arc_buf_size(buf); 2038 ctl.prwatch.pr_wflags = WA_WRITE; 2039 result = write(arc_procfd, &ctl, sizeof (ctl)); 2040 ASSERT3U(result, ==, sizeof (ctl)); 2041 } 2042#endif 2043} 2044#endif /* illumos */ 2045 2046static arc_buf_contents_t 2047arc_buf_type(arc_buf_hdr_t *hdr) 2048{ 2049 arc_buf_contents_t type; 2050 if (HDR_ISTYPE_METADATA(hdr)) { 2051 type = ARC_BUFC_METADATA; 2052 } else { 2053 type = ARC_BUFC_DATA; 2054 } 2055 VERIFY3U(hdr->b_type, ==, type); 2056 return (type); 2057} 2058 2059boolean_t 2060arc_is_metadata(arc_buf_t *buf) 2061{ 2062 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); 2063} 2064 2065static uint32_t 2066arc_bufc_to_flags(arc_buf_contents_t type) 2067{ 2068 switch (type) { 2069 case ARC_BUFC_DATA: 2070 /* metadata field is 0 if buffer contains normal data */ 2071 return (0); 2072 case ARC_BUFC_METADATA: 2073 return (ARC_FLAG_BUFC_METADATA); 2074 default: 2075 break; 2076 } 2077 panic("undefined ARC buffer type!"); 2078 return ((uint32_t)-1); 2079} 2080 2081void 2082arc_buf_thaw(arc_buf_t *buf) 2083{ 2084 arc_buf_hdr_t *hdr = buf->b_hdr; 2085 2086 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2087 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2088 2089 arc_cksum_verify(buf); 2090 2091 /* 2092 * Compressed buffers do not manipulate the b_freeze_cksum or 2093 * allocate b_thawed. 2094 */ 2095 if (ARC_BUF_COMPRESSED(buf)) { 2096 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2097 arc_hdr_has_uncompressed_buf(hdr)); 2098 return; 2099 } 2100 2101 ASSERT(HDR_HAS_L1HDR(hdr)); 2102 arc_cksum_free(hdr); 2103 2104 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 2105#ifdef ZFS_DEBUG 2106 if (zfs_flags & ZFS_DEBUG_MODIFY) { 2107 if (hdr->b_l1hdr.b_thawed != NULL) 2108 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2109 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 2110 } 2111#endif 2112 2113 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2114 2115#ifdef illumos 2116 arc_buf_unwatch(buf); 2117#endif 2118} 2119 2120void 2121arc_buf_freeze(arc_buf_t *buf) 2122{ 2123 arc_buf_hdr_t *hdr = buf->b_hdr; 2124 kmutex_t *hash_lock; 2125 2126 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2127 return; 2128 2129 if (ARC_BUF_COMPRESSED(buf)) { 2130 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2131 arc_hdr_has_uncompressed_buf(hdr)); 2132 return; 2133 } 2134 2135 hash_lock = HDR_LOCK(hdr); 2136 mutex_enter(hash_lock); 2137 2138 ASSERT(HDR_HAS_L1HDR(hdr)); 2139 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 2140 hdr->b_l1hdr.b_state == arc_anon); 2141 arc_cksum_compute(buf); 2142 mutex_exit(hash_lock); 2143} 2144 2145/* 2146 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 2147 * the following functions should be used to ensure that the flags are 2148 * updated in a thread-safe way. When manipulating the flags either 2149 * the hash_lock must be held or the hdr must be undiscoverable. This 2150 * ensures that we're not racing with any other threads when updating 2151 * the flags. 2152 */ 2153static inline void 2154arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2155{ 2156 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2157 hdr->b_flags |= flags; 2158} 2159 2160static inline void 2161arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2162{ 2163 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2164 hdr->b_flags &= ~flags; 2165} 2166 2167/* 2168 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 2169 * done in a special way since we have to clear and set bits 2170 * at the same time. Consumers that wish to set the compression bits 2171 * must use this function to ensure that the flags are updated in 2172 * thread-safe manner. 2173 */ 2174static void 2175arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 2176{ 2177 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2178 2179 /* 2180 * Holes and embedded blocks will always have a psize = 0 so 2181 * we ignore the compression of the blkptr and set the 2182 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 2183 * Holes and embedded blocks remain anonymous so we don't 2184 * want to uncompress them. Mark them as uncompressed. 2185 */ 2186 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 2187 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2188 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 2189 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 2190 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2191 } else { 2192 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2193 HDR_SET_COMPRESS(hdr, cmp); 2194 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2195 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2196 } 2197} 2198 2199/* 2200 * Looks for another buf on the same hdr which has the data decompressed, copies 2201 * from it, and returns true. If no such buf exists, returns false. 2202 */ 2203static boolean_t 2204arc_buf_try_copy_decompressed_data(arc_buf_t *buf) 2205{ 2206 arc_buf_hdr_t *hdr = buf->b_hdr; 2207 boolean_t copied = B_FALSE; 2208 2209 ASSERT(HDR_HAS_L1HDR(hdr)); 2210 ASSERT3P(buf->b_data, !=, NULL); 2211 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2212 2213 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; 2214 from = from->b_next) { 2215 /* can't use our own data buffer */ 2216 if (from == buf) { 2217 continue; 2218 } 2219 2220 if (!ARC_BUF_COMPRESSED(from)) { 2221 bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); 2222 copied = B_TRUE; 2223 break; 2224 } 2225 } 2226 2227 /* 2228 * There were no decompressed bufs, so there should not be a 2229 * checksum on the hdr either. 2230 */ 2231 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); 2232 2233 return (copied); 2234} 2235 2236/* 2237 * Given a buf that has a data buffer attached to it, this function will 2238 * efficiently fill the buf with data of the specified compression setting from 2239 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr 2240 * are already sharing a data buf, no copy is performed. 2241 * 2242 * If the buf is marked as compressed but uncompressed data was requested, this 2243 * will allocate a new data buffer for the buf, remove that flag, and fill the 2244 * buf with uncompressed data. You can't request a compressed buf on a hdr with 2245 * uncompressed data, and (since we haven't added support for it yet) if you 2246 * want compressed data your buf must already be marked as compressed and have 2247 * the correct-sized data buffer. 2248 */ 2249static int 2250arc_buf_fill(arc_buf_t *buf, boolean_t compressed) 2251{ 2252 arc_buf_hdr_t *hdr = buf->b_hdr; 2253 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 2254 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2255 2256 ASSERT3P(buf->b_data, !=, NULL); 2257 IMPLY(compressed, hdr_compressed); 2258 IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); 2259 2260 if (hdr_compressed == compressed) { 2261 if (!arc_buf_is_shared(buf)) { 2262 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, 2263 arc_buf_size(buf)); 2264 } 2265 } else { 2266 ASSERT(hdr_compressed); 2267 ASSERT(!compressed); 2268 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2269 2270 /* 2271 * If the buf is sharing its data with the hdr, unlink it and 2272 * allocate a new data buffer for the buf. 2273 */ 2274 if (arc_buf_is_shared(buf)) { 2275 ASSERT(ARC_BUF_COMPRESSED(buf)); 2276 2277 /* We need to give the buf it's own b_data */ 2278 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2279 buf->b_data = 2280 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2281 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2282 2283 /* Previously overhead was 0; just add new overhead */ 2284 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2285 } else if (ARC_BUF_COMPRESSED(buf)) { 2286 /* We need to reallocate the buf's b_data */ 2287 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), 2288 buf); 2289 buf->b_data = 2290 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2291 2292 /* We increased the size of b_data; update overhead */ 2293 ARCSTAT_INCR(arcstat_overhead_size, 2294 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); 2295 } 2296 2297 /* 2298 * Regardless of the buf's previous compression settings, it 2299 * should not be compressed at the end of this function. 2300 */ 2301 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; 2302 2303 /* 2304 * Try copying the data from another buf which already has a 2305 * decompressed version. If that's not possible, it's time to 2306 * bite the bullet and decompress the data from the hdr. 2307 */ 2308 if (arc_buf_try_copy_decompressed_data(buf)) { 2309 /* Skip byteswapping and checksumming (already done) */ 2310 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); 2311 return (0); 2312 } else { 2313 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2314 hdr->b_l1hdr.b_pabd, buf->b_data, 2315 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2316 2317 /* 2318 * Absent hardware errors or software bugs, this should 2319 * be impossible, but log it anyway so we can debug it. 2320 */ 2321 if (error != 0) { 2322 zfs_dbgmsg( 2323 "hdr %p, compress %d, psize %d, lsize %d", 2324 hdr, HDR_GET_COMPRESS(hdr), 2325 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2326 return (SET_ERROR(EIO)); 2327 } 2328 } 2329 } 2330 2331 /* Byteswap the buf's data if necessary */ 2332 if (bswap != DMU_BSWAP_NUMFUNCS) { 2333 ASSERT(!HDR_SHARED_DATA(hdr)); 2334 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2335 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2336 } 2337 2338 /* Compute the hdr's checksum if necessary */ 2339 arc_cksum_compute(buf); 2340 2341 return (0); 2342} 2343 2344int 2345arc_decompress(arc_buf_t *buf) 2346{ 2347 return (arc_buf_fill(buf, B_FALSE)); 2348} 2349 2350/* 2351 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. 2352 */ 2353static uint64_t 2354arc_hdr_size(arc_buf_hdr_t *hdr) 2355{ 2356 uint64_t size; 2357 2358 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2359 HDR_GET_PSIZE(hdr) > 0) { 2360 size = HDR_GET_PSIZE(hdr); 2361 } else { 2362 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2363 size = HDR_GET_LSIZE(hdr); 2364 } 2365 return (size); 2366} 2367 2368/* 2369 * Increment the amount of evictable space in the arc_state_t's refcount. 2370 * We account for the space used by the hdr and the arc buf individually 2371 * so that we can add and remove them from the refcount individually. 2372 */ 2373static void 2374arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2375{ 2376 arc_buf_contents_t type = arc_buf_type(hdr); 2377 2378 ASSERT(HDR_HAS_L1HDR(hdr)); 2379 2380 if (GHOST_STATE(state)) { 2381 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2382 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2383 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2384 (void) refcount_add_many(&state->arcs_esize[type], 2385 HDR_GET_LSIZE(hdr), hdr); 2386 return; 2387 } 2388 2389 ASSERT(!GHOST_STATE(state)); 2390 if (hdr->b_l1hdr.b_pabd != NULL) { 2391 (void) refcount_add_many(&state->arcs_esize[type], 2392 arc_hdr_size(hdr), hdr); 2393 } 2394 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2395 buf = buf->b_next) { 2396 if (arc_buf_is_shared(buf)) 2397 continue; 2398 (void) refcount_add_many(&state->arcs_esize[type], 2399 arc_buf_size(buf), buf); 2400 } 2401} 2402 2403/* 2404 * Decrement the amount of evictable space in the arc_state_t's refcount. 2405 * We account for the space used by the hdr and the arc buf individually 2406 * so that we can add and remove them from the refcount individually. 2407 */ 2408static void 2409arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2410{ 2411 arc_buf_contents_t type = arc_buf_type(hdr); 2412 2413 ASSERT(HDR_HAS_L1HDR(hdr)); 2414 2415 if (GHOST_STATE(state)) { 2416 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2417 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2418 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2419 (void) refcount_remove_many(&state->arcs_esize[type], 2420 HDR_GET_LSIZE(hdr), hdr); 2421 return; 2422 } 2423 2424 ASSERT(!GHOST_STATE(state)); 2425 if (hdr->b_l1hdr.b_pabd != NULL) { 2426 (void) refcount_remove_many(&state->arcs_esize[type], 2427 arc_hdr_size(hdr), hdr); 2428 } 2429 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2430 buf = buf->b_next) { 2431 if (arc_buf_is_shared(buf)) 2432 continue; 2433 (void) refcount_remove_many(&state->arcs_esize[type], 2434 arc_buf_size(buf), buf); 2435 } 2436} 2437 2438/* 2439 * Add a reference to this hdr indicating that someone is actively 2440 * referencing that memory. When the refcount transitions from 0 to 1, 2441 * we remove it from the respective arc_state_t list to indicate that 2442 * it is not evictable. 2443 */ 2444static void 2445add_reference(arc_buf_hdr_t *hdr, void *tag) 2446{ 2447 ASSERT(HDR_HAS_L1HDR(hdr)); 2448 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2449 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2450 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2451 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2452 } 2453 2454 arc_state_t *state = hdr->b_l1hdr.b_state; 2455 2456 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2457 (state != arc_anon)) { 2458 /* We don't use the L2-only state list. */ 2459 if (state != arc_l2c_only) { 2460 multilist_remove(state->arcs_list[arc_buf_type(hdr)], 2461 hdr); 2462 arc_evictable_space_decrement(hdr, state); 2463 } 2464 /* remove the prefetch flag if we get a reference */ 2465 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2466 } 2467} 2468 2469/* 2470 * Remove a reference from this hdr. When the reference transitions from 2471 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2472 * list making it eligible for eviction. 2473 */ 2474static int 2475remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2476{ 2477 int cnt; 2478 arc_state_t *state = hdr->b_l1hdr.b_state; 2479 2480 ASSERT(HDR_HAS_L1HDR(hdr)); 2481 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2482 ASSERT(!GHOST_STATE(state)); 2483 2484 /* 2485 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2486 * check to prevent usage of the arc_l2c_only list. 2487 */ 2488 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2489 (state != arc_anon)) { 2490 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); 2491 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2492 arc_evictable_space_increment(hdr, state); 2493 } 2494 return (cnt); 2495} 2496 2497/* 2498 * Move the supplied buffer to the indicated state. The hash lock 2499 * for the buffer must be held by the caller. 2500 */ 2501static void 2502arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2503 kmutex_t *hash_lock) 2504{ 2505 arc_state_t *old_state; 2506 int64_t refcnt; 2507 uint32_t bufcnt; 2508 boolean_t update_old, update_new; 2509 arc_buf_contents_t buftype = arc_buf_type(hdr); 2510 2511 /* 2512 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2513 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2514 * L1 hdr doesn't always exist when we change state to arc_anon before 2515 * destroying a header, in which case reallocating to add the L1 hdr is 2516 * pointless. 2517 */ 2518 if (HDR_HAS_L1HDR(hdr)) { 2519 old_state = hdr->b_l1hdr.b_state; 2520 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2521 bufcnt = hdr->b_l1hdr.b_bufcnt; 2522 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); 2523 } else { 2524 old_state = arc_l2c_only; 2525 refcnt = 0; 2526 bufcnt = 0; 2527 update_old = B_FALSE; 2528 } 2529 update_new = update_old; 2530 2531 ASSERT(MUTEX_HELD(hash_lock)); 2532 ASSERT3P(new_state, !=, old_state); 2533 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2534 ASSERT(old_state != arc_anon || bufcnt <= 1); 2535 2536 /* 2537 * If this buffer is evictable, transfer it from the 2538 * old state list to the new state list. 2539 */ 2540 if (refcnt == 0) { 2541 if (old_state != arc_anon && old_state != arc_l2c_only) { 2542 ASSERT(HDR_HAS_L1HDR(hdr)); 2543 multilist_remove(old_state->arcs_list[buftype], hdr); 2544 2545 if (GHOST_STATE(old_state)) { 2546 ASSERT0(bufcnt); 2547 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2548 update_old = B_TRUE; 2549 } 2550 arc_evictable_space_decrement(hdr, old_state); 2551 } 2552 if (new_state != arc_anon && new_state != arc_l2c_only) { 2553 2554 /* 2555 * An L1 header always exists here, since if we're 2556 * moving to some L1-cached state (i.e. not l2c_only or 2557 * anonymous), we realloc the header to add an L1hdr 2558 * beforehand. 2559 */ 2560 ASSERT(HDR_HAS_L1HDR(hdr)); 2561 multilist_insert(new_state->arcs_list[buftype], hdr); 2562 2563 if (GHOST_STATE(new_state)) { 2564 ASSERT0(bufcnt); 2565 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2566 update_new = B_TRUE; 2567 } 2568 arc_evictable_space_increment(hdr, new_state); 2569 } 2570 } 2571 2572 ASSERT(!HDR_EMPTY(hdr)); 2573 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2574 buf_hash_remove(hdr); 2575 2576 /* adjust state sizes (ignore arc_l2c_only) */ 2577 2578 if (update_new && new_state != arc_l2c_only) { 2579 ASSERT(HDR_HAS_L1HDR(hdr)); 2580 if (GHOST_STATE(new_state)) { 2581 ASSERT0(bufcnt); 2582 2583 /* 2584 * When moving a header to a ghost state, we first 2585 * remove all arc buffers. Thus, we'll have a 2586 * bufcnt of zero, and no arc buffer to use for 2587 * the reference. As a result, we use the arc 2588 * header pointer for the reference. 2589 */ 2590 (void) refcount_add_many(&new_state->arcs_size, 2591 HDR_GET_LSIZE(hdr), hdr); 2592 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2593 } else { 2594 uint32_t buffers = 0; 2595 2596 /* 2597 * Each individual buffer holds a unique reference, 2598 * thus we must remove each of these references one 2599 * at a time. 2600 */ 2601 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2602 buf = buf->b_next) { 2603 ASSERT3U(bufcnt, !=, 0); 2604 buffers++; 2605 2606 /* 2607 * When the arc_buf_t is sharing the data 2608 * block with the hdr, the owner of the 2609 * reference belongs to the hdr. Only 2610 * add to the refcount if the arc_buf_t is 2611 * not shared. 2612 */ 2613 if (arc_buf_is_shared(buf)) 2614 continue; 2615 2616 (void) refcount_add_many(&new_state->arcs_size, 2617 arc_buf_size(buf), buf); 2618 } 2619 ASSERT3U(bufcnt, ==, buffers); 2620 2621 if (hdr->b_l1hdr.b_pabd != NULL) { 2622 (void) refcount_add_many(&new_state->arcs_size, 2623 arc_hdr_size(hdr), hdr); 2624 } else { 2625 ASSERT(GHOST_STATE(old_state)); 2626 } 2627 } 2628 } 2629 2630 if (update_old && old_state != arc_l2c_only) { 2631 ASSERT(HDR_HAS_L1HDR(hdr)); 2632 if (GHOST_STATE(old_state)) { 2633 ASSERT0(bufcnt); 2634 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2635 2636 /* 2637 * When moving a header off of a ghost state, 2638 * the header will not contain any arc buffers. 2639 * We use the arc header pointer for the reference 2640 * which is exactly what we did when we put the 2641 * header on the ghost state. 2642 */ 2643 2644 (void) refcount_remove_many(&old_state->arcs_size, 2645 HDR_GET_LSIZE(hdr), hdr); 2646 } else { 2647 uint32_t buffers = 0; 2648 2649 /* 2650 * Each individual buffer holds a unique reference, 2651 * thus we must remove each of these references one 2652 * at a time. 2653 */ 2654 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2655 buf = buf->b_next) { 2656 ASSERT3U(bufcnt, !=, 0); 2657 buffers++; 2658 2659 /* 2660 * When the arc_buf_t is sharing the data 2661 * block with the hdr, the owner of the 2662 * reference belongs to the hdr. Only 2663 * add to the refcount if the arc_buf_t is 2664 * not shared. 2665 */ 2666 if (arc_buf_is_shared(buf)) 2667 continue; 2668 2669 (void) refcount_remove_many( 2670 &old_state->arcs_size, arc_buf_size(buf), 2671 buf); 2672 } 2673 ASSERT3U(bufcnt, ==, buffers); 2674 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2675 (void) refcount_remove_many( 2676 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2677 } 2678 } 2679 2680 if (HDR_HAS_L1HDR(hdr)) 2681 hdr->b_l1hdr.b_state = new_state; 2682 2683 /* 2684 * L2 headers should never be on the L2 state list since they don't 2685 * have L1 headers allocated. 2686 */ 2687 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2688 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2689} 2690 2691void 2692arc_space_consume(uint64_t space, arc_space_type_t type) 2693{ 2694 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2695 2696 switch (type) { 2697 case ARC_SPACE_DATA: 2698 aggsum_add(&astat_data_size, space); 2699 break; 2700 case ARC_SPACE_META: 2701 aggsum_add(&astat_metadata_size, space); 2702 break; 2703 case ARC_SPACE_OTHER: 2704 aggsum_add(&astat_other_size, space); 2705 break; 2706 case ARC_SPACE_HDRS: 2707 aggsum_add(&astat_hdr_size, space); 2708 break; 2709 case ARC_SPACE_L2HDRS: 2710 aggsum_add(&astat_l2_hdr_size, space); 2711 break; 2712 } 2713 2714 if (type != ARC_SPACE_DATA) 2715 aggsum_add(&arc_meta_used, space); 2716 2717 aggsum_add(&arc_size, space); 2718} 2719 2720void 2721arc_space_return(uint64_t space, arc_space_type_t type) 2722{ 2723 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2724 2725 switch (type) { 2726 case ARC_SPACE_DATA: 2727 aggsum_add(&astat_data_size, -space); 2728 break; 2729 case ARC_SPACE_META: 2730 aggsum_add(&astat_metadata_size, -space); 2731 break; 2732 case ARC_SPACE_OTHER: 2733 aggsum_add(&astat_other_size, -space); 2734 break; 2735 case ARC_SPACE_HDRS: 2736 aggsum_add(&astat_hdr_size, -space); 2737 break; 2738 case ARC_SPACE_L2HDRS: 2739 aggsum_add(&astat_l2_hdr_size, -space); 2740 break; 2741 } 2742 2743 if (type != ARC_SPACE_DATA) { 2744 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0); 2745 /* 2746 * We use the upper bound here rather than the precise value 2747 * because the arc_meta_max value doesn't need to be 2748 * precise. It's only consumed by humans via arcstats. 2749 */ 2750 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used)) 2751 arc_meta_max = aggsum_upper_bound(&arc_meta_used); 2752 aggsum_add(&arc_meta_used, -space); 2753 } 2754 2755 ASSERT(aggsum_compare(&arc_size, space) >= 0); 2756 aggsum_add(&arc_size, -space); 2757} 2758 2759/* 2760 * Given a hdr and a buf, returns whether that buf can share its b_data buffer 2761 * with the hdr's b_pabd. 2762 */ 2763static boolean_t 2764arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2765{ 2766 /* 2767 * The criteria for sharing a hdr's data are: 2768 * 1. the hdr's compression matches the buf's compression 2769 * 2. the hdr doesn't need to be byteswapped 2770 * 3. the hdr isn't already being shared 2771 * 4. the buf is either compressed or it is the last buf in the hdr list 2772 * 2773 * Criterion #4 maintains the invariant that shared uncompressed 2774 * bufs must be the final buf in the hdr's b_buf list. Reading this, you 2775 * might ask, "if a compressed buf is allocated first, won't that be the 2776 * last thing in the list?", but in that case it's impossible to create 2777 * a shared uncompressed buf anyway (because the hdr must be compressed 2778 * to have the compressed buf). You might also think that #3 is 2779 * sufficient to make this guarantee, however it's possible 2780 * (specifically in the rare L2ARC write race mentioned in 2781 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that 2782 * is sharable, but wasn't at the time of its allocation. Rather than 2783 * allow a new shared uncompressed buf to be created and then shuffle 2784 * the list around to make it the last element, this simply disallows 2785 * sharing if the new buf isn't the first to be added. 2786 */ 2787 ASSERT3P(buf->b_hdr, ==, hdr); 2788 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; 2789 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; 2790 return (buf_compressed == hdr_compressed && 2791 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2792 !HDR_SHARED_DATA(hdr) && 2793 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); 2794} 2795 2796/* 2797 * Allocate a buf for this hdr. If you care about the data that's in the hdr, 2798 * or if you want a compressed buffer, pass those flags in. Returns 0 if the 2799 * copy was made successfully, or an error code otherwise. 2800 */ 2801static int 2802arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed, 2803 boolean_t fill, arc_buf_t **ret) 2804{ 2805 arc_buf_t *buf; 2806 2807 ASSERT(HDR_HAS_L1HDR(hdr)); 2808 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2809 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2810 hdr->b_type == ARC_BUFC_METADATA); 2811 ASSERT3P(ret, !=, NULL); 2812 ASSERT3P(*ret, ==, NULL); 2813 2814 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2815 buf->b_hdr = hdr; 2816 buf->b_data = NULL; 2817 buf->b_next = hdr->b_l1hdr.b_buf; 2818 buf->b_flags = 0; 2819 2820 add_reference(hdr, tag); 2821 2822 /* 2823 * We're about to change the hdr's b_flags. We must either 2824 * hold the hash_lock or be undiscoverable. 2825 */ 2826 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2827 2828 /* 2829 * Only honor requests for compressed bufs if the hdr is actually 2830 * compressed. 2831 */ 2832 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 2833 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; 2834 2835 /* 2836 * If the hdr's data can be shared then we share the data buffer and 2837 * set the appropriate bit in the hdr's b_flags to indicate the hdr is 2838 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new 2839 * buffer to store the buf's data. 2840 * 2841 * There are two additional restrictions here because we're sharing 2842 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be 2843 * actively involved in an L2ARC write, because if this buf is used by 2844 * an arc_write() then the hdr's data buffer will be released when the 2845 * write completes, even though the L2ARC write might still be using it. 2846 * Second, the hdr's ABD must be linear so that the buf's user doesn't 2847 * need to be ABD-aware. 2848 */ 2849 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && 2850 abd_is_linear(hdr->b_l1hdr.b_pabd); 2851 2852 /* Set up b_data and sharing */ 2853 if (can_share) { 2854 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); 2855 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2856 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2857 } else { 2858 buf->b_data = 2859 arc_get_data_buf(hdr, arc_buf_size(buf), buf); 2860 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2861 } 2862 VERIFY3P(buf->b_data, !=, NULL); 2863 2864 hdr->b_l1hdr.b_buf = buf; 2865 hdr->b_l1hdr.b_bufcnt += 1; 2866 2867 /* 2868 * If the user wants the data from the hdr, we need to either copy or 2869 * decompress the data. 2870 */ 2871 if (fill) { 2872 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); 2873 } 2874 2875 return (0); 2876} 2877 2878static char *arc_onloan_tag = "onloan"; 2879 2880static inline void 2881arc_loaned_bytes_update(int64_t delta) 2882{ 2883 atomic_add_64(&arc_loaned_bytes, delta); 2884 2885 /* assert that it did not wrap around */ 2886 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 2887} 2888 2889/* 2890 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2891 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2892 * buffers must be returned to the arc before they can be used by the DMU or 2893 * freed. 2894 */ 2895arc_buf_t * 2896arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) 2897{ 2898 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, 2899 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); 2900 2901 arc_loaned_bytes_update(arc_buf_size(buf)); 2902 2903 return (buf); 2904} 2905 2906arc_buf_t * 2907arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, 2908 enum zio_compress compression_type) 2909{ 2910 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, 2911 psize, lsize, compression_type); 2912 2913 arc_loaned_bytes_update(arc_buf_size(buf)); 2914 2915 return (buf); 2916} 2917 2918 2919/* 2920 * Return a loaned arc buffer to the arc. 2921 */ 2922void 2923arc_return_buf(arc_buf_t *buf, void *tag) 2924{ 2925 arc_buf_hdr_t *hdr = buf->b_hdr; 2926 2927 ASSERT3P(buf->b_data, !=, NULL); 2928 ASSERT(HDR_HAS_L1HDR(hdr)); 2929 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2930 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2931 2932 arc_loaned_bytes_update(-arc_buf_size(buf)); 2933} 2934 2935/* Detach an arc_buf from a dbuf (tag) */ 2936void 2937arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2938{ 2939 arc_buf_hdr_t *hdr = buf->b_hdr; 2940 2941 ASSERT3P(buf->b_data, !=, NULL); 2942 ASSERT(HDR_HAS_L1HDR(hdr)); 2943 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2944 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2945 2946 arc_loaned_bytes_update(arc_buf_size(buf)); 2947} 2948 2949static void 2950l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) 2951{ 2952 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2953 2954 df->l2df_abd = abd; 2955 df->l2df_size = size; 2956 df->l2df_type = type; 2957 mutex_enter(&l2arc_free_on_write_mtx); 2958 list_insert_head(l2arc_free_on_write, df); 2959 mutex_exit(&l2arc_free_on_write_mtx); 2960} 2961 2962static void 2963arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2964{ 2965 arc_state_t *state = hdr->b_l1hdr.b_state; 2966 arc_buf_contents_t type = arc_buf_type(hdr); 2967 uint64_t size = arc_hdr_size(hdr); 2968 2969 /* protected by hash lock, if in the hash table */ 2970 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2971 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2972 ASSERT(state != arc_anon && state != arc_l2c_only); 2973 2974 (void) refcount_remove_many(&state->arcs_esize[type], 2975 size, hdr); 2976 } 2977 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2978 if (type == ARC_BUFC_METADATA) { 2979 arc_space_return(size, ARC_SPACE_META); 2980 } else { 2981 ASSERT(type == ARC_BUFC_DATA); 2982 arc_space_return(size, ARC_SPACE_DATA); 2983 } 2984 2985 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); 2986} 2987 2988/* 2989 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2990 * data buffer, we transfer the refcount ownership to the hdr and update 2991 * the appropriate kstats. 2992 */ 2993static void 2994arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2995{ 2996 arc_state_t *state = hdr->b_l1hdr.b_state; 2997 2998 ASSERT(arc_can_share(hdr, buf)); 2999 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3000 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3001 3002 /* 3003 * Start sharing the data buffer. We transfer the 3004 * refcount ownership to the hdr since it always owns 3005 * the refcount whenever an arc_buf_t is shared. 3006 */ 3007 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 3008 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); 3009 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, 3010 HDR_ISTYPE_METADATA(hdr)); 3011 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 3012 buf->b_flags |= ARC_BUF_FLAG_SHARED; 3013 3014 /* 3015 * Since we've transferred ownership to the hdr we need 3016 * to increment its compressed and uncompressed kstats and 3017 * decrement the overhead size. 3018 */ 3019 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3020 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3021 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf)); 3022} 3023 3024static void 3025arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3026{ 3027 arc_state_t *state = hdr->b_l1hdr.b_state; 3028 3029 ASSERT(arc_buf_is_shared(buf)); 3030 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3031 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3032 3033 /* 3034 * We are no longer sharing this buffer so we need 3035 * to transfer its ownership to the rightful owner. 3036 */ 3037 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 3038 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3039 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); 3040 abd_put(hdr->b_l1hdr.b_pabd); 3041 hdr->b_l1hdr.b_pabd = NULL; 3042 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 3043 3044 /* 3045 * Since the buffer is no longer shared between 3046 * the arc buf and the hdr, count it as overhead. 3047 */ 3048 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3049 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3050 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 3051} 3052 3053/* 3054 * Remove an arc_buf_t from the hdr's buf list and return the last 3055 * arc_buf_t on the list. If no buffers remain on the list then return 3056 * NULL. 3057 */ 3058static arc_buf_t * 3059arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3060{ 3061 ASSERT(HDR_HAS_L1HDR(hdr)); 3062 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3063 3064 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; 3065 arc_buf_t *lastbuf = NULL; 3066 3067 /* 3068 * Remove the buf from the hdr list and locate the last 3069 * remaining buffer on the list. 3070 */ 3071 while (*bufp != NULL) { 3072 if (*bufp == buf) 3073 *bufp = buf->b_next; 3074 3075 /* 3076 * If we've removed a buffer in the middle of 3077 * the list then update the lastbuf and update 3078 * bufp. 3079 */ 3080 if (*bufp != NULL) { 3081 lastbuf = *bufp; 3082 bufp = &(*bufp)->b_next; 3083 } 3084 } 3085 buf->b_next = NULL; 3086 ASSERT3P(lastbuf, !=, buf); 3087 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); 3088 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); 3089 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); 3090 3091 return (lastbuf); 3092} 3093 3094/* 3095 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's 3096 * list and free it. 3097 */ 3098static void 3099arc_buf_destroy_impl(arc_buf_t *buf) 3100{ 3101 arc_buf_hdr_t *hdr = buf->b_hdr; 3102 3103 /* 3104 * Free up the data associated with the buf but only if we're not 3105 * sharing this with the hdr. If we are sharing it with the hdr, the 3106 * hdr is responsible for doing the free. 3107 */ 3108 if (buf->b_data != NULL) { 3109 /* 3110 * We're about to change the hdr's b_flags. We must either 3111 * hold the hash_lock or be undiscoverable. 3112 */ 3113 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3114 3115 arc_cksum_verify(buf); 3116#ifdef illumos 3117 arc_buf_unwatch(buf); 3118#endif 3119 3120 if (arc_buf_is_shared(buf)) { 3121 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3122 } else { 3123 uint64_t size = arc_buf_size(buf); 3124 arc_free_data_buf(hdr, buf->b_data, size, buf); 3125 ARCSTAT_INCR(arcstat_overhead_size, -size); 3126 } 3127 buf->b_data = NULL; 3128 3129 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3130 hdr->b_l1hdr.b_bufcnt -= 1; 3131 } 3132 3133 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 3134 3135 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { 3136 /* 3137 * If the current arc_buf_t is sharing its data buffer with the 3138 * hdr, then reassign the hdr's b_pabd to share it with the new 3139 * buffer at the end of the list. The shared buffer is always 3140 * the last one on the hdr's buffer list. 3141 * 3142 * There is an equivalent case for compressed bufs, but since 3143 * they aren't guaranteed to be the last buf in the list and 3144 * that is an exceedingly rare case, we just allow that space be 3145 * wasted temporarily. 3146 */ 3147 if (lastbuf != NULL) { 3148 /* Only one buf can be shared at once */ 3149 VERIFY(!arc_buf_is_shared(lastbuf)); 3150 /* hdr is uncompressed so can't have compressed buf */ 3151 VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); 3152 3153 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3154 arc_hdr_free_pabd(hdr); 3155 3156 /* 3157 * We must setup a new shared block between the 3158 * last buffer and the hdr. The data would have 3159 * been allocated by the arc buf so we need to transfer 3160 * ownership to the hdr since it's now being shared. 3161 */ 3162 arc_share_buf(hdr, lastbuf); 3163 } 3164 } else if (HDR_SHARED_DATA(hdr)) { 3165 /* 3166 * Uncompressed shared buffers are always at the end 3167 * of the list. Compressed buffers don't have the 3168 * same requirements. This makes it hard to 3169 * simply assert that the lastbuf is shared so 3170 * we rely on the hdr's compression flags to determine 3171 * if we have a compressed, shared buffer. 3172 */ 3173 ASSERT3P(lastbuf, !=, NULL); 3174 ASSERT(arc_buf_is_shared(lastbuf) || 3175 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 3176 } 3177 3178 /* 3179 * Free the checksum if we're removing the last uncompressed buf from 3180 * this hdr. 3181 */ 3182 if (!arc_hdr_has_uncompressed_buf(hdr)) { 3183 arc_cksum_free(hdr); 3184 } 3185 3186 /* clean up the buf */ 3187 buf->b_hdr = NULL; 3188 kmem_cache_free(buf_cache, buf); 3189} 3190 3191static void 3192arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr) 3193{ 3194 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 3195 ASSERT(HDR_HAS_L1HDR(hdr)); 3196 ASSERT(!HDR_SHARED_DATA(hdr)); 3197 3198 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3199 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr); 3200 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3201 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3202 3203 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3204 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3205} 3206 3207static void 3208arc_hdr_free_pabd(arc_buf_hdr_t *hdr) 3209{ 3210 ASSERT(HDR_HAS_L1HDR(hdr)); 3211 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3212 3213 /* 3214 * If the hdr is currently being written to the l2arc then 3215 * we defer freeing the data by adding it to the l2arc_free_on_write 3216 * list. The l2arc will free the data once it's finished 3217 * writing it to the l2arc device. 3218 */ 3219 if (HDR_L2_WRITING(hdr)) { 3220 arc_hdr_free_on_write(hdr); 3221 ARCSTAT_BUMP(arcstat_l2_free_on_write); 3222 } else { 3223 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, 3224 arc_hdr_size(hdr), hdr); 3225 } 3226 hdr->b_l1hdr.b_pabd = NULL; 3227 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3228 3229 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3230 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3231} 3232 3233static arc_buf_hdr_t * 3234arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 3235 enum zio_compress compression_type, arc_buf_contents_t type) 3236{ 3237 arc_buf_hdr_t *hdr; 3238 3239 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 3240 3241 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3242 ASSERT(HDR_EMPTY(hdr)); 3243 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3244 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 3245 HDR_SET_PSIZE(hdr, psize); 3246 HDR_SET_LSIZE(hdr, lsize); 3247 hdr->b_spa = spa; 3248 hdr->b_type = type; 3249 hdr->b_flags = 0; 3250 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 3251 arc_hdr_set_compress(hdr, compression_type); 3252 3253 hdr->b_l1hdr.b_state = arc_anon; 3254 hdr->b_l1hdr.b_arc_access = 0; 3255 hdr->b_l1hdr.b_bufcnt = 0; 3256 hdr->b_l1hdr.b_buf = NULL; 3257 3258 /* 3259 * Allocate the hdr's buffer. This will contain either 3260 * the compressed or uncompressed data depending on the block 3261 * it references and compressed arc enablement. 3262 */ 3263 arc_hdr_alloc_pabd(hdr); 3264 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3265 3266 return (hdr); 3267} 3268 3269/* 3270 * Transition between the two allocation states for the arc_buf_hdr struct. 3271 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 3272 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 3273 * version is used when a cache buffer is only in the L2ARC in order to reduce 3274 * memory usage. 3275 */ 3276static arc_buf_hdr_t * 3277arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 3278{ 3279 ASSERT(HDR_HAS_L2HDR(hdr)); 3280 3281 arc_buf_hdr_t *nhdr; 3282 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3283 3284 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 3285 (old == hdr_l2only_cache && new == hdr_full_cache)); 3286 3287 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 3288 3289 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 3290 buf_hash_remove(hdr); 3291 3292 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 3293 3294 if (new == hdr_full_cache) { 3295 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3296 /* 3297 * arc_access and arc_change_state need to be aware that a 3298 * header has just come out of L2ARC, so we set its state to 3299 * l2c_only even though it's about to change. 3300 */ 3301 nhdr->b_l1hdr.b_state = arc_l2c_only; 3302 3303 /* Verify previous threads set to NULL before freeing */ 3304 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); 3305 } else { 3306 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3307 ASSERT0(hdr->b_l1hdr.b_bufcnt); 3308 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3309 3310 /* 3311 * If we've reached here, We must have been called from 3312 * arc_evict_hdr(), as such we should have already been 3313 * removed from any ghost list we were previously on 3314 * (which protects us from racing with arc_evict_state), 3315 * thus no locking is needed during this check. 3316 */ 3317 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3318 3319 /* 3320 * A buffer must not be moved into the arc_l2c_only 3321 * state if it's not finished being written out to the 3322 * l2arc device. Otherwise, the b_l1hdr.b_pabd field 3323 * might try to be accessed, even though it was removed. 3324 */ 3325 VERIFY(!HDR_L2_WRITING(hdr)); 3326 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3327 3328#ifdef ZFS_DEBUG 3329 if (hdr->b_l1hdr.b_thawed != NULL) { 3330 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3331 hdr->b_l1hdr.b_thawed = NULL; 3332 } 3333#endif 3334 3335 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3336 } 3337 /* 3338 * The header has been reallocated so we need to re-insert it into any 3339 * lists it was on. 3340 */ 3341 (void) buf_hash_insert(nhdr, NULL); 3342 3343 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 3344 3345 mutex_enter(&dev->l2ad_mtx); 3346 3347 /* 3348 * We must place the realloc'ed header back into the list at 3349 * the same spot. Otherwise, if it's placed earlier in the list, 3350 * l2arc_write_buffers() could find it during the function's 3351 * write phase, and try to write it out to the l2arc. 3352 */ 3353 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 3354 list_remove(&dev->l2ad_buflist, hdr); 3355 3356 mutex_exit(&dev->l2ad_mtx); 3357 3358 /* 3359 * Since we're using the pointer address as the tag when 3360 * incrementing and decrementing the l2ad_alloc refcount, we 3361 * must remove the old pointer (that we're about to destroy) and 3362 * add the new pointer to the refcount. Otherwise we'd remove 3363 * the wrong pointer address when calling arc_hdr_destroy() later. 3364 */ 3365 3366 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 3367 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 3368 3369 buf_discard_identity(hdr); 3370 kmem_cache_free(old, hdr); 3371 3372 return (nhdr); 3373} 3374 3375/* 3376 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 3377 * The buf is returned thawed since we expect the consumer to modify it. 3378 */ 3379arc_buf_t * 3380arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) 3381{ 3382 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 3383 ZIO_COMPRESS_OFF, type); 3384 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3385 3386 arc_buf_t *buf = NULL; 3387 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf)); 3388 arc_buf_thaw(buf); 3389 3390 return (buf); 3391} 3392 3393/* 3394 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this 3395 * for bufs containing metadata. 3396 */ 3397arc_buf_t * 3398arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, 3399 enum zio_compress compression_type) 3400{ 3401 ASSERT3U(lsize, >, 0); 3402 ASSERT3U(lsize, >=, psize); 3403 ASSERT(compression_type > ZIO_COMPRESS_OFF); 3404 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); 3405 3406 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 3407 compression_type, ARC_BUFC_DATA); 3408 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3409 3410 arc_buf_t *buf = NULL; 3411 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf)); 3412 arc_buf_thaw(buf); 3413 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3414 3415 if (!arc_buf_is_shared(buf)) { 3416 /* 3417 * To ensure that the hdr has the correct data in it if we call 3418 * arc_decompress() on this buf before it's been written to 3419 * disk, it's easiest if we just set up sharing between the 3420 * buf and the hdr. 3421 */ 3422 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); 3423 arc_hdr_free_pabd(hdr); 3424 arc_share_buf(hdr, buf); 3425 } 3426 3427 return (buf); 3428} 3429 3430static void 3431arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 3432{ 3433 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 3434 l2arc_dev_t *dev = l2hdr->b_dev; 3435 uint64_t psize = arc_hdr_size(hdr); 3436 3437 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 3438 ASSERT(HDR_HAS_L2HDR(hdr)); 3439 3440 list_remove(&dev->l2ad_buflist, hdr); 3441 3442 ARCSTAT_INCR(arcstat_l2_psize, -psize); 3443 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 3444 3445 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0); 3446 3447 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr); 3448 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3449} 3450 3451static void 3452arc_hdr_destroy(arc_buf_hdr_t *hdr) 3453{ 3454 if (HDR_HAS_L1HDR(hdr)) { 3455 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3456 hdr->b_l1hdr.b_bufcnt > 0); 3457 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3458 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3459 } 3460 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3461 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3462 3463 if (!HDR_EMPTY(hdr)) 3464 buf_discard_identity(hdr); 3465 3466 if (HDR_HAS_L2HDR(hdr)) { 3467 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3468 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3469 3470 if (!buflist_held) 3471 mutex_enter(&dev->l2ad_mtx); 3472 3473 /* 3474 * Even though we checked this conditional above, we 3475 * need to check this again now that we have the 3476 * l2ad_mtx. This is because we could be racing with 3477 * another thread calling l2arc_evict() which might have 3478 * destroyed this header's L2 portion as we were waiting 3479 * to acquire the l2ad_mtx. If that happens, we don't 3480 * want to re-destroy the header's L2 portion. 3481 */ 3482 if (HDR_HAS_L2HDR(hdr)) { 3483 l2arc_trim(hdr); 3484 arc_hdr_l2hdr_destroy(hdr); 3485 } 3486 3487 if (!buflist_held) 3488 mutex_exit(&dev->l2ad_mtx); 3489 } 3490 3491 if (HDR_HAS_L1HDR(hdr)) { 3492 arc_cksum_free(hdr); 3493 3494 while (hdr->b_l1hdr.b_buf != NULL) 3495 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); 3496 3497#ifdef ZFS_DEBUG 3498 if (hdr->b_l1hdr.b_thawed != NULL) { 3499 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3500 hdr->b_l1hdr.b_thawed = NULL; 3501 } 3502#endif 3503 3504 if (hdr->b_l1hdr.b_pabd != NULL) { 3505 arc_hdr_free_pabd(hdr); 3506 } 3507 } 3508 3509 ASSERT3P(hdr->b_hash_next, ==, NULL); 3510 if (HDR_HAS_L1HDR(hdr)) { 3511 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3512 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3513 kmem_cache_free(hdr_full_cache, hdr); 3514 } else { 3515 kmem_cache_free(hdr_l2only_cache, hdr); 3516 } 3517} 3518 3519void 3520arc_buf_destroy(arc_buf_t *buf, void* tag) 3521{ 3522 arc_buf_hdr_t *hdr = buf->b_hdr; 3523 kmutex_t *hash_lock = HDR_LOCK(hdr); 3524 3525 if (hdr->b_l1hdr.b_state == arc_anon) { 3526 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3527 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3528 VERIFY0(remove_reference(hdr, NULL, tag)); 3529 arc_hdr_destroy(hdr); 3530 return; 3531 } 3532 3533 mutex_enter(hash_lock); 3534 ASSERT3P(hdr, ==, buf->b_hdr); 3535 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3536 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3537 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3538 ASSERT3P(buf->b_data, !=, NULL); 3539 3540 (void) remove_reference(hdr, hash_lock, tag); 3541 arc_buf_destroy_impl(buf); 3542 mutex_exit(hash_lock); 3543} 3544 3545/* 3546 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3547 * state of the header is dependent on it's state prior to entering this 3548 * function. The following transitions are possible: 3549 * 3550 * - arc_mru -> arc_mru_ghost 3551 * - arc_mfu -> arc_mfu_ghost 3552 * - arc_mru_ghost -> arc_l2c_only 3553 * - arc_mru_ghost -> deleted 3554 * - arc_mfu_ghost -> arc_l2c_only 3555 * - arc_mfu_ghost -> deleted 3556 */ 3557static int64_t 3558arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3559{ 3560 arc_state_t *evicted_state, *state; 3561 int64_t bytes_evicted = 0; 3562 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ? 3563 zfs_arc_min_prescient_prefetch_ms : zfs_arc_min_prefetch_ms; 3564 3565 ASSERT(MUTEX_HELD(hash_lock)); 3566 ASSERT(HDR_HAS_L1HDR(hdr)); 3567 3568 state = hdr->b_l1hdr.b_state; 3569 if (GHOST_STATE(state)) { 3570 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3571 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3572 3573 /* 3574 * l2arc_write_buffers() relies on a header's L1 portion 3575 * (i.e. its b_pabd field) during it's write phase. 3576 * Thus, we cannot push a header onto the arc_l2c_only 3577 * state (removing it's L1 piece) until the header is 3578 * done being written to the l2arc. 3579 */ 3580 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3581 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3582 return (bytes_evicted); 3583 } 3584 3585 ARCSTAT_BUMP(arcstat_deleted); 3586 bytes_evicted += HDR_GET_LSIZE(hdr); 3587 3588 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3589 3590 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3591 if (HDR_HAS_L2HDR(hdr)) { 3592 /* 3593 * This buffer is cached on the 2nd Level ARC; 3594 * don't destroy the header. 3595 */ 3596 arc_change_state(arc_l2c_only, hdr, hash_lock); 3597 /* 3598 * dropping from L1+L2 cached to L2-only, 3599 * realloc to remove the L1 header. 3600 */ 3601 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3602 hdr_l2only_cache); 3603 } else { 3604 arc_change_state(arc_anon, hdr, hash_lock); 3605 arc_hdr_destroy(hdr); 3606 } 3607 return (bytes_evicted); 3608 } 3609 3610 ASSERT(state == arc_mru || state == arc_mfu); 3611 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3612 3613 /* prefetch buffers have a minimum lifespan */ 3614 if (HDR_IO_IN_PROGRESS(hdr) || 3615 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3616 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < min_lifetime * hz)) { 3617 ARCSTAT_BUMP(arcstat_evict_skip); 3618 return (bytes_evicted); 3619 } 3620 3621 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3622 while (hdr->b_l1hdr.b_buf) { 3623 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3624 if (!mutex_tryenter(&buf->b_evict_lock)) { 3625 ARCSTAT_BUMP(arcstat_mutex_miss); 3626 break; 3627 } 3628 if (buf->b_data != NULL) 3629 bytes_evicted += HDR_GET_LSIZE(hdr); 3630 mutex_exit(&buf->b_evict_lock); 3631 arc_buf_destroy_impl(buf); 3632 } 3633 3634 if (HDR_HAS_L2HDR(hdr)) { 3635 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3636 } else { 3637 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3638 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3639 HDR_GET_LSIZE(hdr)); 3640 } else { 3641 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3642 HDR_GET_LSIZE(hdr)); 3643 } 3644 } 3645 3646 if (hdr->b_l1hdr.b_bufcnt == 0) { 3647 arc_cksum_free(hdr); 3648 3649 bytes_evicted += arc_hdr_size(hdr); 3650 3651 /* 3652 * If this hdr is being evicted and has a compressed 3653 * buffer then we discard it here before we change states. 3654 * This ensures that the accounting is updated correctly 3655 * in arc_free_data_impl(). 3656 */ 3657 arc_hdr_free_pabd(hdr); 3658 3659 arc_change_state(evicted_state, hdr, hash_lock); 3660 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3661 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3662 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3663 } 3664 3665 return (bytes_evicted); 3666} 3667 3668static uint64_t 3669arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3670 uint64_t spa, int64_t bytes) 3671{ 3672 multilist_sublist_t *mls; 3673 uint64_t bytes_evicted = 0; 3674 arc_buf_hdr_t *hdr; 3675 kmutex_t *hash_lock; 3676 int evict_count = 0; 3677 3678 ASSERT3P(marker, !=, NULL); 3679 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3680 3681 mls = multilist_sublist_lock(ml, idx); 3682 3683 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3684 hdr = multilist_sublist_prev(mls, marker)) { 3685 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3686 (evict_count >= zfs_arc_evict_batch_limit)) 3687 break; 3688 3689 /* 3690 * To keep our iteration location, move the marker 3691 * forward. Since we're not holding hdr's hash lock, we 3692 * must be very careful and not remove 'hdr' from the 3693 * sublist. Otherwise, other consumers might mistake the 3694 * 'hdr' as not being on a sublist when they call the 3695 * multilist_link_active() function (they all rely on 3696 * the hash lock protecting concurrent insertions and 3697 * removals). multilist_sublist_move_forward() was 3698 * specifically implemented to ensure this is the case 3699 * (only 'marker' will be removed and re-inserted). 3700 */ 3701 multilist_sublist_move_forward(mls, marker); 3702 3703 /* 3704 * The only case where the b_spa field should ever be 3705 * zero, is the marker headers inserted by 3706 * arc_evict_state(). It's possible for multiple threads 3707 * to be calling arc_evict_state() concurrently (e.g. 3708 * dsl_pool_close() and zio_inject_fault()), so we must 3709 * skip any markers we see from these other threads. 3710 */ 3711 if (hdr->b_spa == 0) 3712 continue; 3713 3714 /* we're only interested in evicting buffers of a certain spa */ 3715 if (spa != 0 && hdr->b_spa != spa) { 3716 ARCSTAT_BUMP(arcstat_evict_skip); 3717 continue; 3718 } 3719 3720 hash_lock = HDR_LOCK(hdr); 3721 3722 /* 3723 * We aren't calling this function from any code path 3724 * that would already be holding a hash lock, so we're 3725 * asserting on this assumption to be defensive in case 3726 * this ever changes. Without this check, it would be 3727 * possible to incorrectly increment arcstat_mutex_miss 3728 * below (e.g. if the code changed such that we called 3729 * this function with a hash lock held). 3730 */ 3731 ASSERT(!MUTEX_HELD(hash_lock)); 3732 3733 if (mutex_tryenter(hash_lock)) { 3734 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3735 mutex_exit(hash_lock); 3736 3737 bytes_evicted += evicted; 3738 3739 /* 3740 * If evicted is zero, arc_evict_hdr() must have 3741 * decided to skip this header, don't increment 3742 * evict_count in this case. 3743 */ 3744 if (evicted != 0) 3745 evict_count++; 3746 3747 /* 3748 * If arc_size isn't overflowing, signal any 3749 * threads that might happen to be waiting. 3750 * 3751 * For each header evicted, we wake up a single 3752 * thread. If we used cv_broadcast, we could 3753 * wake up "too many" threads causing arc_size 3754 * to significantly overflow arc_c; since 3755 * arc_get_data_impl() doesn't check for overflow 3756 * when it's woken up (it doesn't because it's 3757 * possible for the ARC to be overflowing while 3758 * full of un-evictable buffers, and the 3759 * function should proceed in this case). 3760 * 3761 * If threads are left sleeping, due to not 3762 * using cv_broadcast, they will be woken up 3763 * just before arc_reclaim_thread() sleeps. 3764 */ 3765 mutex_enter(&arc_reclaim_lock); 3766 if (!arc_is_overflowing()) 3767 cv_signal(&arc_reclaim_waiters_cv); 3768 mutex_exit(&arc_reclaim_lock); 3769 } else { 3770 ARCSTAT_BUMP(arcstat_mutex_miss); 3771 } 3772 } 3773 3774 multilist_sublist_unlock(mls); 3775 3776 return (bytes_evicted); 3777} 3778 3779/* 3780 * Evict buffers from the given arc state, until we've removed the 3781 * specified number of bytes. Move the removed buffers to the 3782 * appropriate evict state. 3783 * 3784 * This function makes a "best effort". It skips over any buffers 3785 * it can't get a hash_lock on, and so, may not catch all candidates. 3786 * It may also return without evicting as much space as requested. 3787 * 3788 * If bytes is specified using the special value ARC_EVICT_ALL, this 3789 * will evict all available (i.e. unlocked and evictable) buffers from 3790 * the given arc state; which is used by arc_flush(). 3791 */ 3792static uint64_t 3793arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3794 arc_buf_contents_t type) 3795{ 3796 uint64_t total_evicted = 0; 3797 multilist_t *ml = state->arcs_list[type]; 3798 int num_sublists; 3799 arc_buf_hdr_t **markers; 3800 3801 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3802 3803 num_sublists = multilist_get_num_sublists(ml); 3804 3805 /* 3806 * If we've tried to evict from each sublist, made some 3807 * progress, but still have not hit the target number of bytes 3808 * to evict, we want to keep trying. The markers allow us to 3809 * pick up where we left off for each individual sublist, rather 3810 * than starting from the tail each time. 3811 */ 3812 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3813 for (int i = 0; i < num_sublists; i++) { 3814 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3815 3816 /* 3817 * A b_spa of 0 is used to indicate that this header is 3818 * a marker. This fact is used in arc_adjust_type() and 3819 * arc_evict_state_impl(). 3820 */ 3821 markers[i]->b_spa = 0; 3822 3823 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3824 multilist_sublist_insert_tail(mls, markers[i]); 3825 multilist_sublist_unlock(mls); 3826 } 3827 3828 /* 3829 * While we haven't hit our target number of bytes to evict, or 3830 * we're evicting all available buffers. 3831 */ 3832 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3833 /* 3834 * Start eviction using a randomly selected sublist, 3835 * this is to try and evenly balance eviction across all 3836 * sublists. Always starting at the same sublist 3837 * (e.g. index 0) would cause evictions to favor certain 3838 * sublists over others. 3839 */ 3840 int sublist_idx = multilist_get_random_index(ml); 3841 uint64_t scan_evicted = 0; 3842 3843 for (int i = 0; i < num_sublists; i++) { 3844 uint64_t bytes_remaining; 3845 uint64_t bytes_evicted; 3846 3847 if (bytes == ARC_EVICT_ALL) 3848 bytes_remaining = ARC_EVICT_ALL; 3849 else if (total_evicted < bytes) 3850 bytes_remaining = bytes - total_evicted; 3851 else 3852 break; 3853 3854 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3855 markers[sublist_idx], spa, bytes_remaining); 3856 3857 scan_evicted += bytes_evicted; 3858 total_evicted += bytes_evicted; 3859 3860 /* we've reached the end, wrap to the beginning */ 3861 if (++sublist_idx >= num_sublists) 3862 sublist_idx = 0; 3863 } 3864 3865 /* 3866 * If we didn't evict anything during this scan, we have 3867 * no reason to believe we'll evict more during another 3868 * scan, so break the loop. 3869 */ 3870 if (scan_evicted == 0) { 3871 /* This isn't possible, let's make that obvious */ 3872 ASSERT3S(bytes, !=, 0); 3873 3874 /* 3875 * When bytes is ARC_EVICT_ALL, the only way to 3876 * break the loop is when scan_evicted is zero. 3877 * In that case, we actually have evicted enough, 3878 * so we don't want to increment the kstat. 3879 */ 3880 if (bytes != ARC_EVICT_ALL) { 3881 ASSERT3S(total_evicted, <, bytes); 3882 ARCSTAT_BUMP(arcstat_evict_not_enough); 3883 } 3884 3885 break; 3886 } 3887 } 3888 3889 for (int i = 0; i < num_sublists; i++) { 3890 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3891 multilist_sublist_remove(mls, markers[i]); 3892 multilist_sublist_unlock(mls); 3893 3894 kmem_cache_free(hdr_full_cache, markers[i]); 3895 } 3896 kmem_free(markers, sizeof (*markers) * num_sublists); 3897 3898 return (total_evicted); 3899} 3900 3901/* 3902 * Flush all "evictable" data of the given type from the arc state 3903 * specified. This will not evict any "active" buffers (i.e. referenced). 3904 * 3905 * When 'retry' is set to B_FALSE, the function will make a single pass 3906 * over the state and evict any buffers that it can. Since it doesn't 3907 * continually retry the eviction, it might end up leaving some buffers 3908 * in the ARC due to lock misses. 3909 * 3910 * When 'retry' is set to B_TRUE, the function will continually retry the 3911 * eviction until *all* evictable buffers have been removed from the 3912 * state. As a result, if concurrent insertions into the state are 3913 * allowed (e.g. if the ARC isn't shutting down), this function might 3914 * wind up in an infinite loop, continually trying to evict buffers. 3915 */ 3916static uint64_t 3917arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3918 boolean_t retry) 3919{ 3920 uint64_t evicted = 0; 3921 3922 while (refcount_count(&state->arcs_esize[type]) != 0) { 3923 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3924 3925 if (!retry) 3926 break; 3927 } 3928 3929 return (evicted); 3930} 3931 3932/* 3933 * Evict the specified number of bytes from the state specified, 3934 * restricting eviction to the spa and type given. This function 3935 * prevents us from trying to evict more from a state's list than 3936 * is "evictable", and to skip evicting altogether when passed a 3937 * negative value for "bytes". In contrast, arc_evict_state() will 3938 * evict everything it can, when passed a negative value for "bytes". 3939 */ 3940static uint64_t 3941arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3942 arc_buf_contents_t type) 3943{ 3944 int64_t delta; 3945 3946 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3947 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3948 return (arc_evict_state(state, spa, delta, type)); 3949 } 3950 3951 return (0); 3952} 3953 3954/* 3955 * Evict metadata buffers from the cache, such that arc_meta_used is 3956 * capped by the arc_meta_limit tunable. 3957 */ 3958static uint64_t 3959arc_adjust_meta(uint64_t meta_used) 3960{ 3961 uint64_t total_evicted = 0; 3962 int64_t target; 3963 3964 /* 3965 * If we're over the meta limit, we want to evict enough 3966 * metadata to get back under the meta limit. We don't want to 3967 * evict so much that we drop the MRU below arc_p, though. If 3968 * we're over the meta limit more than we're over arc_p, we 3969 * evict some from the MRU here, and some from the MFU below. 3970 */ 3971 target = MIN((int64_t)(meta_used - arc_meta_limit), 3972 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3973 refcount_count(&arc_mru->arcs_size) - arc_p)); 3974 3975 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3976 3977 /* 3978 * Similar to the above, we want to evict enough bytes to get us 3979 * below the meta limit, but not so much as to drop us below the 3980 * space allotted to the MFU (which is defined as arc_c - arc_p). 3981 */ 3982 target = MIN((int64_t)(meta_used - arc_meta_limit), 3983 (int64_t)(refcount_count(&arc_mfu->arcs_size) - 3984 (arc_c - arc_p))); 3985 3986 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3987 3988 return (total_evicted); 3989} 3990 3991/* 3992 * Return the type of the oldest buffer in the given arc state 3993 * 3994 * This function will select a random sublist of type ARC_BUFC_DATA and 3995 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3996 * is compared, and the type which contains the "older" buffer will be 3997 * returned. 3998 */ 3999static arc_buf_contents_t 4000arc_adjust_type(arc_state_t *state) 4001{ 4002 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; 4003 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; 4004 int data_idx = multilist_get_random_index(data_ml); 4005 int meta_idx = multilist_get_random_index(meta_ml); 4006 multilist_sublist_t *data_mls; 4007 multilist_sublist_t *meta_mls; 4008 arc_buf_contents_t type; 4009 arc_buf_hdr_t *data_hdr; 4010 arc_buf_hdr_t *meta_hdr; 4011 4012 /* 4013 * We keep the sublist lock until we're finished, to prevent 4014 * the headers from being destroyed via arc_evict_state(). 4015 */ 4016 data_mls = multilist_sublist_lock(data_ml, data_idx); 4017 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 4018 4019 /* 4020 * These two loops are to ensure we skip any markers that 4021 * might be at the tail of the lists due to arc_evict_state(). 4022 */ 4023 4024 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 4025 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 4026 if (data_hdr->b_spa != 0) 4027 break; 4028 } 4029 4030 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 4031 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 4032 if (meta_hdr->b_spa != 0) 4033 break; 4034 } 4035 4036 if (data_hdr == NULL && meta_hdr == NULL) { 4037 type = ARC_BUFC_DATA; 4038 } else if (data_hdr == NULL) { 4039 ASSERT3P(meta_hdr, !=, NULL); 4040 type = ARC_BUFC_METADATA; 4041 } else if (meta_hdr == NULL) { 4042 ASSERT3P(data_hdr, !=, NULL); 4043 type = ARC_BUFC_DATA; 4044 } else { 4045 ASSERT3P(data_hdr, !=, NULL); 4046 ASSERT3P(meta_hdr, !=, NULL); 4047 4048 /* The headers can't be on the sublist without an L1 header */ 4049 ASSERT(HDR_HAS_L1HDR(data_hdr)); 4050 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 4051 4052 if (data_hdr->b_l1hdr.b_arc_access < 4053 meta_hdr->b_l1hdr.b_arc_access) { 4054 type = ARC_BUFC_DATA; 4055 } else { 4056 type = ARC_BUFC_METADATA; 4057 } 4058 } 4059 4060 multilist_sublist_unlock(meta_mls); 4061 multilist_sublist_unlock(data_mls); 4062 4063 return (type); 4064} 4065 4066/* 4067 * Evict buffers from the cache, such that arc_size is capped by arc_c. 4068 */ 4069static uint64_t 4070arc_adjust(void) 4071{ 4072 uint64_t total_evicted = 0; 4073 uint64_t bytes; 4074 int64_t target; 4075 uint64_t asize = aggsum_value(&arc_size); 4076 uint64_t ameta = aggsum_value(&arc_meta_used); 4077 4078 /* 4079 * If we're over arc_meta_limit, we want to correct that before 4080 * potentially evicting data buffers below. 4081 */ 4082 total_evicted += arc_adjust_meta(ameta); 4083 4084 /* 4085 * Adjust MRU size 4086 * 4087 * If we're over the target cache size, we want to evict enough 4088 * from the list to get back to our target size. We don't want 4089 * to evict too much from the MRU, such that it drops below 4090 * arc_p. So, if we're over our target cache size more than 4091 * the MRU is over arc_p, we'll evict enough to get back to 4092 * arc_p here, and then evict more from the MFU below. 4093 */ 4094 target = MIN((int64_t)(asize - arc_c), 4095 (int64_t)(refcount_count(&arc_anon->arcs_size) + 4096 refcount_count(&arc_mru->arcs_size) + ameta - arc_p)); 4097 4098 /* 4099 * If we're below arc_meta_min, always prefer to evict data. 4100 * Otherwise, try to satisfy the requested number of bytes to 4101 * evict from the type which contains older buffers; in an 4102 * effort to keep newer buffers in the cache regardless of their 4103 * type. If we cannot satisfy the number of bytes from this 4104 * type, spill over into the next type. 4105 */ 4106 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 4107 ameta > arc_meta_min) { 4108 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4109 total_evicted += bytes; 4110 4111 /* 4112 * If we couldn't evict our target number of bytes from 4113 * metadata, we try to get the rest from data. 4114 */ 4115 target -= bytes; 4116 4117 total_evicted += 4118 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4119 } else { 4120 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4121 total_evicted += bytes; 4122 4123 /* 4124 * If we couldn't evict our target number of bytes from 4125 * data, we try to get the rest from metadata. 4126 */ 4127 target -= bytes; 4128 4129 total_evicted += 4130 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4131 } 4132 4133 /* 4134 * Re-sum ARC stats after the first round of evictions. 4135 */ 4136 asize = aggsum_value(&arc_size); 4137 ameta = aggsum_value(&arc_meta_used); 4138 4139 /* 4140 * Adjust MFU size 4141 * 4142 * Now that we've tried to evict enough from the MRU to get its 4143 * size back to arc_p, if we're still above the target cache 4144 * size, we evict the rest from the MFU. 4145 */ 4146 target = asize - arc_c; 4147 4148 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 4149 ameta > arc_meta_min) { 4150 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4151 total_evicted += bytes; 4152 4153 /* 4154 * If we couldn't evict our target number of bytes from 4155 * metadata, we try to get the rest from data. 4156 */ 4157 target -= bytes; 4158 4159 total_evicted += 4160 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4161 } else { 4162 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4163 total_evicted += bytes; 4164 4165 /* 4166 * If we couldn't evict our target number of bytes from 4167 * data, we try to get the rest from data. 4168 */ 4169 target -= bytes; 4170 4171 total_evicted += 4172 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4173 } 4174 4175 /* 4176 * Adjust ghost lists 4177 * 4178 * In addition to the above, the ARC also defines target values 4179 * for the ghost lists. The sum of the mru list and mru ghost 4180 * list should never exceed the target size of the cache, and 4181 * the sum of the mru list, mfu list, mru ghost list, and mfu 4182 * ghost list should never exceed twice the target size of the 4183 * cache. The following logic enforces these limits on the ghost 4184 * caches, and evicts from them as needed. 4185 */ 4186 target = refcount_count(&arc_mru->arcs_size) + 4187 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 4188 4189 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 4190 total_evicted += bytes; 4191 4192 target -= bytes; 4193 4194 total_evicted += 4195 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 4196 4197 /* 4198 * We assume the sum of the mru list and mfu list is less than 4199 * or equal to arc_c (we enforced this above), which means we 4200 * can use the simpler of the two equations below: 4201 * 4202 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 4203 * mru ghost + mfu ghost <= arc_c 4204 */ 4205 target = refcount_count(&arc_mru_ghost->arcs_size) + 4206 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 4207 4208 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 4209 total_evicted += bytes; 4210 4211 target -= bytes; 4212 4213 total_evicted += 4214 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 4215 4216 return (total_evicted); 4217} 4218 4219void 4220arc_flush(spa_t *spa, boolean_t retry) 4221{ 4222 uint64_t guid = 0; 4223 4224 /* 4225 * If retry is B_TRUE, a spa must not be specified since we have 4226 * no good way to determine if all of a spa's buffers have been 4227 * evicted from an arc state. 4228 */ 4229 ASSERT(!retry || spa == 0); 4230 4231 if (spa != NULL) 4232 guid = spa_load_guid(spa); 4233 4234 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 4235 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 4236 4237 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 4238 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 4239 4240 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 4241 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 4242 4243 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 4244 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 4245} 4246 4247void 4248arc_shrink(int64_t to_free) 4249{ 4250 uint64_t asize = aggsum_value(&arc_size); 4251 if (arc_c > arc_c_min) { 4252 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 4253 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 4254 if (arc_c > arc_c_min + to_free) 4255 atomic_add_64(&arc_c, -to_free); 4256 else 4257 arc_c = arc_c_min; 4258 4259 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 4260 if (asize < arc_c) 4261 arc_c = MAX(asize, arc_c_min); 4262 if (arc_p > arc_c) 4263 arc_p = (arc_c >> 1); 4264 4265 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 4266 arc_p); 4267 4268 ASSERT(arc_c >= arc_c_min); 4269 ASSERT((int64_t)arc_p >= 0); 4270 } 4271 4272 if (asize > arc_c) { 4273 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize, 4274 uint64_t, arc_c); 4275 (void) arc_adjust(); 4276 } 4277} 4278 4279typedef enum free_memory_reason_t { 4280 FMR_UNKNOWN, 4281 FMR_NEEDFREE, 4282 FMR_LOTSFREE, 4283 FMR_SWAPFS_MINFREE, 4284 FMR_PAGES_PP_MAXIMUM, 4285 FMR_HEAP_ARENA, 4286 FMR_ZIO_ARENA, 4287 FMR_ZIO_FRAG, 4288} free_memory_reason_t; 4289 4290int64_t last_free_memory; 4291free_memory_reason_t last_free_reason; 4292 4293/* 4294 * Additional reserve of pages for pp_reserve. 4295 */ 4296int64_t arc_pages_pp_reserve = 64; 4297 4298/* 4299 * Additional reserve of pages for swapfs. 4300 */ 4301int64_t arc_swapfs_reserve = 64; 4302 4303/* 4304 * Return the amount of memory that can be consumed before reclaim will be 4305 * needed. Positive if there is sufficient free memory, negative indicates 4306 * the amount of memory that needs to be freed up. 4307 */ 4308static int64_t 4309arc_available_memory(void) 4310{ 4311 int64_t lowest = INT64_MAX; 4312 int64_t n; 4313 free_memory_reason_t r = FMR_UNKNOWN; 4314 4315#ifdef _KERNEL 4316#ifdef __FreeBSD__ 4317 /* 4318 * Cooperate with pagedaemon when it's time for it to scan 4319 * and reclaim some pages. 4320 */ 4321 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 4322 if (n < lowest) { 4323 lowest = n; 4324 r = FMR_LOTSFREE; 4325 } 4326 4327#else 4328 if (needfree > 0) { 4329 n = PAGESIZE * (-needfree); 4330 if (n < lowest) { 4331 lowest = n; 4332 r = FMR_NEEDFREE; 4333 } 4334 } 4335 4336 /* 4337 * check that we're out of range of the pageout scanner. It starts to 4338 * schedule paging if freemem is less than lotsfree and needfree. 4339 * lotsfree is the high-water mark for pageout, and needfree is the 4340 * number of needed free pages. We add extra pages here to make sure 4341 * the scanner doesn't start up while we're freeing memory. 4342 */ 4343 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 4344 if (n < lowest) { 4345 lowest = n; 4346 r = FMR_LOTSFREE; 4347 } 4348 4349 /* 4350 * check to make sure that swapfs has enough space so that anon 4351 * reservations can still succeed. anon_resvmem() checks that the 4352 * availrmem is greater than swapfs_minfree, and the number of reserved 4353 * swap pages. We also add a bit of extra here just to prevent 4354 * circumstances from getting really dire. 4355 */ 4356 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 4357 desfree - arc_swapfs_reserve); 4358 if (n < lowest) { 4359 lowest = n; 4360 r = FMR_SWAPFS_MINFREE; 4361 } 4362 4363 4364 /* 4365 * Check that we have enough availrmem that memory locking (e.g., via 4366 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 4367 * stores the number of pages that cannot be locked; when availrmem 4368 * drops below pages_pp_maximum, page locking mechanisms such as 4369 * page_pp_lock() will fail.) 4370 */ 4371 n = PAGESIZE * (availrmem - pages_pp_maximum - 4372 arc_pages_pp_reserve); 4373 if (n < lowest) { 4374 lowest = n; 4375 r = FMR_PAGES_PP_MAXIMUM; 4376 } 4377 4378#endif /* __FreeBSD__ */ 4379#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4380 /* 4381 * If we're on an i386 platform, it's possible that we'll exhaust the 4382 * kernel heap space before we ever run out of available physical 4383 * memory. Most checks of the size of the heap_area compare against 4384 * tune.t_minarmem, which is the minimum available real memory that we 4385 * can have in the system. However, this is generally fixed at 25 pages 4386 * which is so low that it's useless. In this comparison, we seek to 4387 * calculate the total heap-size, and reclaim if more than 3/4ths of the 4388 * heap is allocated. (Or, in the calculation, if less than 1/4th is 4389 * free) 4390 */ 4391 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 4392 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 4393 if (n < lowest) { 4394 lowest = n; 4395 r = FMR_HEAP_ARENA; 4396 } 4397#define zio_arena NULL 4398#else 4399#define zio_arena heap_arena 4400#endif 4401 4402 /* 4403 * If zio data pages are being allocated out of a separate heap segment, 4404 * then enforce that the size of available vmem for this arena remains 4405 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free. 4406 * 4407 * Note that reducing the arc_zio_arena_free_shift keeps more virtual 4408 * memory (in the zio_arena) free, which can avoid memory 4409 * fragmentation issues. 4410 */ 4411 if (zio_arena != NULL) { 4412 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 4413 (vmem_size(zio_arena, VMEM_ALLOC) >> 4414 arc_zio_arena_free_shift); 4415 if (n < lowest) { 4416 lowest = n; 4417 r = FMR_ZIO_ARENA; 4418 } 4419 } 4420 4421 /* 4422 * Above limits know nothing about real level of KVA fragmentation. 4423 * Start aggressive reclamation if too little sequential KVA left. 4424 */ 4425 if (lowest > 0) { 4426 n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ? 4427 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 4428 INT64_MAX; 4429 if (n < lowest) { 4430 lowest = n; 4431 r = FMR_ZIO_FRAG; 4432 } 4433 } 4434 4435#else /* _KERNEL */ 4436 /* Every 100 calls, free a small amount */ 4437 if (spa_get_random(100) == 0) 4438 lowest = -1024; 4439#endif /* _KERNEL */ 4440 4441 last_free_memory = lowest; 4442 last_free_reason = r; 4443 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 4444 return (lowest); 4445} 4446 4447 4448/* 4449 * Determine if the system is under memory pressure and is asking 4450 * to reclaim memory. A return value of B_TRUE indicates that the system 4451 * is under memory pressure and that the arc should adjust accordingly. 4452 */ 4453static boolean_t 4454arc_reclaim_needed(void) 4455{ 4456 return (arc_available_memory() < 0); 4457} 4458 4459extern kmem_cache_t *zio_buf_cache[]; 4460extern kmem_cache_t *zio_data_buf_cache[]; 4461extern kmem_cache_t *range_seg_cache; 4462extern kmem_cache_t *abd_chunk_cache; 4463 4464static __noinline void 4465arc_kmem_reap_now(void) 4466{ 4467 size_t i; 4468 kmem_cache_t *prev_cache = NULL; 4469 kmem_cache_t *prev_data_cache = NULL; 4470 4471 DTRACE_PROBE(arc__kmem_reap_start); 4472#ifdef _KERNEL 4473 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) { 4474 /* 4475 * We are exceeding our meta-data cache limit. 4476 * Purge some DNLC entries to release holds on meta-data. 4477 */ 4478 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4479 } 4480#if defined(__i386) 4481 /* 4482 * Reclaim unused memory from all kmem caches. 4483 */ 4484 kmem_reap(); 4485#endif 4486#endif 4487 4488 /* 4489 * If a kmem reap is already active, don't schedule more. We must 4490 * check for this because kmem_cache_reap_soon() won't actually 4491 * block on the cache being reaped (this is to prevent callers from 4492 * becoming implicitly blocked by a system-wide kmem reap -- which, 4493 * on a system with many, many full magazines, can take minutes). 4494 */ 4495 if (kmem_cache_reap_active()) 4496 return; 4497 4498 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4499 if (zio_buf_cache[i] != prev_cache) { 4500 prev_cache = zio_buf_cache[i]; 4501 kmem_cache_reap_soon(zio_buf_cache[i]); 4502 } 4503 if (zio_data_buf_cache[i] != prev_data_cache) { 4504 prev_data_cache = zio_data_buf_cache[i]; 4505 kmem_cache_reap_soon(zio_data_buf_cache[i]); 4506 } 4507 } 4508 kmem_cache_reap_soon(abd_chunk_cache); 4509 kmem_cache_reap_soon(buf_cache); 4510 kmem_cache_reap_soon(hdr_full_cache); 4511 kmem_cache_reap_soon(hdr_l2only_cache); 4512 kmem_cache_reap_soon(range_seg_cache); 4513 4514#ifdef illumos 4515 if (zio_arena != NULL) { 4516 /* 4517 * Ask the vmem arena to reclaim unused memory from its 4518 * quantum caches. 4519 */ 4520 vmem_qcache_reap(zio_arena); 4521 } 4522#endif 4523 DTRACE_PROBE(arc__kmem_reap_end); 4524} 4525 4526/* 4527 * Threads can block in arc_get_data_impl() waiting for this thread to evict 4528 * enough data and signal them to proceed. When this happens, the threads in 4529 * arc_get_data_impl() are sleeping while holding the hash lock for their 4530 * particular arc header. Thus, we must be careful to never sleep on a 4531 * hash lock in this thread. This is to prevent the following deadlock: 4532 * 4533 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L", 4534 * waiting for the reclaim thread to signal it. 4535 * 4536 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4537 * fails, and goes to sleep forever. 4538 * 4539 * This possible deadlock is avoided by always acquiring a hash lock 4540 * using mutex_tryenter() from arc_reclaim_thread(). 4541 */ 4542/* ARGSUSED */ 4543static void 4544arc_reclaim_thread(void *unused __unused) 4545{ 4546 hrtime_t growtime = 0; 4547 hrtime_t kmem_reap_time = 0; 4548 callb_cpr_t cpr; 4549 4550 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4551 4552 mutex_enter(&arc_reclaim_lock); 4553 while (!arc_reclaim_thread_exit) { 4554 uint64_t evicted = 0; 4555 4556 /* 4557 * This is necessary in order for the mdb ::arc dcmd to 4558 * show up to date information. Since the ::arc command 4559 * does not call the kstat's update function, without 4560 * this call, the command may show stale stats for the 4561 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4562 * with this change, the data might be up to 1 second 4563 * out of date; but that should suffice. The arc_state_t 4564 * structures can be queried directly if more accurate 4565 * information is needed. 4566 */ 4567 if (arc_ksp != NULL) 4568 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4569 4570 mutex_exit(&arc_reclaim_lock); 4571 4572 /* 4573 * We call arc_adjust() before (possibly) calling 4574 * arc_kmem_reap_now(), so that we can wake up 4575 * arc_get_data_impl() sooner. 4576 */ 4577 evicted = arc_adjust(); 4578 4579 int64_t free_memory = arc_available_memory(); 4580 if (free_memory < 0) { 4581 hrtime_t curtime = gethrtime(); 4582 arc_no_grow = B_TRUE; 4583 arc_warm = B_TRUE; 4584 4585 /* 4586 * Wait at least zfs_grow_retry (default 60) seconds 4587 * before considering growing. 4588 */ 4589 growtime = curtime + SEC2NSEC(arc_grow_retry); 4590 4591 /* 4592 * Wait at least arc_kmem_cache_reap_retry_ms 4593 * between arc_kmem_reap_now() calls. Without 4594 * this check it is possible to end up in a 4595 * situation where we spend lots of time 4596 * reaping caches, while we're near arc_c_min. 4597 */ 4598 if (curtime >= kmem_reap_time) { 4599 arc_kmem_reap_now(); 4600 kmem_reap_time = gethrtime() + 4601 MSEC2NSEC(arc_kmem_cache_reap_retry_ms); 4602 } 4603 4604 /* 4605 * If we are still low on memory, shrink the ARC 4606 * so that we have arc_shrink_min free space. 4607 */ 4608 free_memory = arc_available_memory(); 4609 4610 int64_t to_free = 4611 (arc_c >> arc_shrink_shift) - free_memory; 4612 if (to_free > 0) { 4613#ifdef _KERNEL 4614#ifdef illumos 4615 to_free = MAX(to_free, ptob(needfree)); 4616#endif 4617#endif 4618 arc_shrink(to_free); 4619 } 4620 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4621 arc_no_grow = B_TRUE; 4622 } else if (gethrtime() >= growtime) { 4623 arc_no_grow = B_FALSE; 4624 } 4625 4626 mutex_enter(&arc_reclaim_lock); 4627 4628 /* 4629 * If evicted is zero, we couldn't evict anything via 4630 * arc_adjust(). This could be due to hash lock 4631 * collisions, but more likely due to the majority of 4632 * arc buffers being unevictable. Therefore, even if 4633 * arc_size is above arc_c, another pass is unlikely to 4634 * be helpful and could potentially cause us to enter an 4635 * infinite loop. 4636 */ 4637 if (aggsum_compare(&arc_size, arc_c) <= 0|| evicted == 0) { 4638 /* 4639 * We're either no longer overflowing, or we 4640 * can't evict anything more, so we should wake 4641 * up any threads before we go to sleep. 4642 */ 4643 cv_broadcast(&arc_reclaim_waiters_cv); 4644 4645 /* 4646 * Block until signaled, or after one second (we 4647 * might need to perform arc_kmem_reap_now() 4648 * even if we aren't being signalled) 4649 */ 4650 CALLB_CPR_SAFE_BEGIN(&cpr); 4651 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4652 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4653 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4654 } 4655 } 4656 4657 arc_reclaim_thread_exit = B_FALSE; 4658 cv_broadcast(&arc_reclaim_thread_cv); 4659 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4660 thread_exit(); 4661} 4662 4663static u_int arc_dnlc_evicts_arg; 4664extern struct vfsops zfs_vfsops; 4665 4666static void 4667arc_dnlc_evicts_thread(void *dummy __unused) 4668{ 4669 callb_cpr_t cpr; 4670 u_int percent; 4671 4672 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 4673 4674 mutex_enter(&arc_dnlc_evicts_lock); 4675 while (!arc_dnlc_evicts_thread_exit) { 4676 CALLB_CPR_SAFE_BEGIN(&cpr); 4677 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 4678 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 4679 if (arc_dnlc_evicts_arg != 0) { 4680 percent = arc_dnlc_evicts_arg; 4681 mutex_exit(&arc_dnlc_evicts_lock); 4682#ifdef _KERNEL 4683 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 4684#endif 4685 mutex_enter(&arc_dnlc_evicts_lock); 4686 /* 4687 * Clear our token only after vnlru_free() 4688 * pass is done, to avoid false queueing of 4689 * the requests. 4690 */ 4691 arc_dnlc_evicts_arg = 0; 4692 } 4693 } 4694 arc_dnlc_evicts_thread_exit = FALSE; 4695 cv_broadcast(&arc_dnlc_evicts_cv); 4696 CALLB_CPR_EXIT(&cpr); 4697 thread_exit(); 4698} 4699 4700void 4701dnlc_reduce_cache(void *arg) 4702{ 4703 u_int percent; 4704 4705 percent = (u_int)(uintptr_t)arg; 4706 mutex_enter(&arc_dnlc_evicts_lock); 4707 if (arc_dnlc_evicts_arg == 0) { 4708 arc_dnlc_evicts_arg = percent; 4709 cv_broadcast(&arc_dnlc_evicts_cv); 4710 } 4711 mutex_exit(&arc_dnlc_evicts_lock); 4712} 4713 4714/* 4715 * Adapt arc info given the number of bytes we are trying to add and 4716 * the state that we are comming from. This function is only called 4717 * when we are adding new content to the cache. 4718 */ 4719static void 4720arc_adapt(int bytes, arc_state_t *state) 4721{ 4722 int mult; 4723 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4724 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4725 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4726 4727 if (state == arc_l2c_only) 4728 return; 4729 4730 ASSERT(bytes > 0); 4731 /* 4732 * Adapt the target size of the MRU list: 4733 * - if we just hit in the MRU ghost list, then increase 4734 * the target size of the MRU list. 4735 * - if we just hit in the MFU ghost list, then increase 4736 * the target size of the MFU list by decreasing the 4737 * target size of the MRU list. 4738 */ 4739 if (state == arc_mru_ghost) { 4740 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4741 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4742 4743 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4744 } else if (state == arc_mfu_ghost) { 4745 uint64_t delta; 4746 4747 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4748 mult = MIN(mult, 10); 4749 4750 delta = MIN(bytes * mult, arc_p); 4751 arc_p = MAX(arc_p_min, arc_p - delta); 4752 } 4753 ASSERT((int64_t)arc_p >= 0); 4754 4755 if (arc_reclaim_needed()) { 4756 cv_signal(&arc_reclaim_thread_cv); 4757 return; 4758 } 4759 4760 if (arc_no_grow) 4761 return; 4762 4763 if (arc_c >= arc_c_max) 4764 return; 4765 4766 /* 4767 * If we're within (2 * maxblocksize) bytes of the target 4768 * cache size, increment the target cache size 4769 */ 4770 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) > 4771 0) { 4772 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4773 atomic_add_64(&arc_c, (int64_t)bytes); 4774 if (arc_c > arc_c_max) 4775 arc_c = arc_c_max; 4776 else if (state == arc_anon) 4777 atomic_add_64(&arc_p, (int64_t)bytes); 4778 if (arc_p > arc_c) 4779 arc_p = arc_c; 4780 } 4781 ASSERT((int64_t)arc_p >= 0); 4782} 4783 4784/* 4785 * Check if arc_size has grown past our upper threshold, determined by 4786 * zfs_arc_overflow_shift. 4787 */ 4788static boolean_t 4789arc_is_overflowing(void) 4790{ 4791 /* Always allow at least one block of overflow */ 4792 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4793 arc_c >> zfs_arc_overflow_shift); 4794 4795 /* 4796 * We just compare the lower bound here for performance reasons. Our 4797 * primary goals are to make sure that the arc never grows without 4798 * bound, and that it can reach its maximum size. This check 4799 * accomplishes both goals. The maximum amount we could run over by is 4800 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block 4801 * in the ARC. In practice, that's in the tens of MB, which is low 4802 * enough to be safe. 4803 */ 4804 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow); 4805} 4806 4807static abd_t * 4808arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4809{ 4810 arc_buf_contents_t type = arc_buf_type(hdr); 4811 4812 arc_get_data_impl(hdr, size, tag); 4813 if (type == ARC_BUFC_METADATA) { 4814 return (abd_alloc(size, B_TRUE)); 4815 } else { 4816 ASSERT(type == ARC_BUFC_DATA); 4817 return (abd_alloc(size, B_FALSE)); 4818 } 4819} 4820 4821static void * 4822arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4823{ 4824 arc_buf_contents_t type = arc_buf_type(hdr); 4825 4826 arc_get_data_impl(hdr, size, tag); 4827 if (type == ARC_BUFC_METADATA) { 4828 return (zio_buf_alloc(size)); 4829 } else { 4830 ASSERT(type == ARC_BUFC_DATA); 4831 return (zio_data_buf_alloc(size)); 4832 } 4833} 4834 4835/* 4836 * Allocate a block and return it to the caller. If we are hitting the 4837 * hard limit for the cache size, we must sleep, waiting for the eviction 4838 * thread to catch up. If we're past the target size but below the hard 4839 * limit, we'll only signal the reclaim thread and continue on. 4840 */ 4841static void 4842arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4843{ 4844 arc_state_t *state = hdr->b_l1hdr.b_state; 4845 arc_buf_contents_t type = arc_buf_type(hdr); 4846 4847 arc_adapt(size, state); 4848 4849 /* 4850 * If arc_size is currently overflowing, and has grown past our 4851 * upper limit, we must be adding data faster than the evict 4852 * thread can evict. Thus, to ensure we don't compound the 4853 * problem by adding more data and forcing arc_size to grow even 4854 * further past it's target size, we halt and wait for the 4855 * eviction thread to catch up. 4856 * 4857 * It's also possible that the reclaim thread is unable to evict 4858 * enough buffers to get arc_size below the overflow limit (e.g. 4859 * due to buffers being un-evictable, or hash lock collisions). 4860 * In this case, we want to proceed regardless if we're 4861 * overflowing; thus we don't use a while loop here. 4862 */ 4863 if (arc_is_overflowing()) { 4864 mutex_enter(&arc_reclaim_lock); 4865 4866 /* 4867 * Now that we've acquired the lock, we may no longer be 4868 * over the overflow limit, lets check. 4869 * 4870 * We're ignoring the case of spurious wake ups. If that 4871 * were to happen, it'd let this thread consume an ARC 4872 * buffer before it should have (i.e. before we're under 4873 * the overflow limit and were signalled by the reclaim 4874 * thread). As long as that is a rare occurrence, it 4875 * shouldn't cause any harm. 4876 */ 4877 if (arc_is_overflowing()) { 4878 cv_signal(&arc_reclaim_thread_cv); 4879 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4880 } 4881 4882 mutex_exit(&arc_reclaim_lock); 4883 } 4884 4885 VERIFY3U(hdr->b_type, ==, type); 4886 if (type == ARC_BUFC_METADATA) { 4887 arc_space_consume(size, ARC_SPACE_META); 4888 } else { 4889 arc_space_consume(size, ARC_SPACE_DATA); 4890 } 4891 4892 /* 4893 * Update the state size. Note that ghost states have a 4894 * "ghost size" and so don't need to be updated. 4895 */ 4896 if (!GHOST_STATE(state)) { 4897 4898 (void) refcount_add_many(&state->arcs_size, size, tag); 4899 4900 /* 4901 * If this is reached via arc_read, the link is 4902 * protected by the hash lock. If reached via 4903 * arc_buf_alloc, the header should not be accessed by 4904 * any other thread. And, if reached via arc_read_done, 4905 * the hash lock will protect it if it's found in the 4906 * hash table; otherwise no other thread should be 4907 * trying to [add|remove]_reference it. 4908 */ 4909 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4910 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4911 (void) refcount_add_many(&state->arcs_esize[type], 4912 size, tag); 4913 } 4914 4915 /* 4916 * If we are growing the cache, and we are adding anonymous 4917 * data, and we have outgrown arc_p, update arc_p 4918 */ 4919 if (aggsum_compare(&arc_size, arc_c) < 0 && 4920 hdr->b_l1hdr.b_state == arc_anon && 4921 (refcount_count(&arc_anon->arcs_size) + 4922 refcount_count(&arc_mru->arcs_size) > arc_p)) 4923 arc_p = MIN(arc_c, arc_p + size); 4924 } 4925 ARCSTAT_BUMP(arcstat_allocated); 4926} 4927 4928static void 4929arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) 4930{ 4931 arc_free_data_impl(hdr, size, tag); 4932 abd_free(abd); 4933} 4934 4935static void 4936arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) 4937{ 4938 arc_buf_contents_t type = arc_buf_type(hdr); 4939 4940 arc_free_data_impl(hdr, size, tag); 4941 if (type == ARC_BUFC_METADATA) { 4942 zio_buf_free(buf, size); 4943 } else { 4944 ASSERT(type == ARC_BUFC_DATA); 4945 zio_data_buf_free(buf, size); 4946 } 4947} 4948 4949/* 4950 * Free the arc data buffer. 4951 */ 4952static void 4953arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4954{ 4955 arc_state_t *state = hdr->b_l1hdr.b_state; 4956 arc_buf_contents_t type = arc_buf_type(hdr); 4957 4958 /* protected by hash lock, if in the hash table */ 4959 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4960 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4961 ASSERT(state != arc_anon && state != arc_l2c_only); 4962 4963 (void) refcount_remove_many(&state->arcs_esize[type], 4964 size, tag); 4965 } 4966 (void) refcount_remove_many(&state->arcs_size, size, tag); 4967 4968 VERIFY3U(hdr->b_type, ==, type); 4969 if (type == ARC_BUFC_METADATA) { 4970 arc_space_return(size, ARC_SPACE_META); 4971 } else { 4972 ASSERT(type == ARC_BUFC_DATA); 4973 arc_space_return(size, ARC_SPACE_DATA); 4974 } 4975} 4976 4977/* 4978 * This routine is called whenever a buffer is accessed. 4979 * NOTE: the hash lock is dropped in this function. 4980 */ 4981static void 4982arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4983{ 4984 clock_t now; 4985 4986 ASSERT(MUTEX_HELD(hash_lock)); 4987 ASSERT(HDR_HAS_L1HDR(hdr)); 4988 4989 if (hdr->b_l1hdr.b_state == arc_anon) { 4990 /* 4991 * This buffer is not in the cache, and does not 4992 * appear in our "ghost" list. Add the new buffer 4993 * to the MRU state. 4994 */ 4995 4996 ASSERT0(hdr->b_l1hdr.b_arc_access); 4997 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4998 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4999 arc_change_state(arc_mru, hdr, hash_lock); 5000 5001 } else if (hdr->b_l1hdr.b_state == arc_mru) { 5002 now = ddi_get_lbolt(); 5003 5004 /* 5005 * If this buffer is here because of a prefetch, then either: 5006 * - clear the flag if this is a "referencing" read 5007 * (any subsequent access will bump this into the MFU state). 5008 * or 5009 * - move the buffer to the head of the list if this is 5010 * another prefetch (to make it less likely to be evicted). 5011 */ 5012 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5013 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5014 /* link protected by hash lock */ 5015 ASSERT(multilist_link_active( 5016 &hdr->b_l1hdr.b_arc_node)); 5017 } else { 5018 arc_hdr_clear_flags(hdr, 5019 ARC_FLAG_PREFETCH | 5020 ARC_FLAG_PRESCIENT_PREFETCH); 5021 ARCSTAT_BUMP(arcstat_mru_hits); 5022 } 5023 hdr->b_l1hdr.b_arc_access = now; 5024 return; 5025 } 5026 5027 /* 5028 * This buffer has been "accessed" only once so far, 5029 * but it is still in the cache. Move it to the MFU 5030 * state. 5031 */ 5032 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 5033 /* 5034 * More than 125ms have passed since we 5035 * instantiated this buffer. Move it to the 5036 * most frequently used state. 5037 */ 5038 hdr->b_l1hdr.b_arc_access = now; 5039 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5040 arc_change_state(arc_mfu, hdr, hash_lock); 5041 } 5042 ARCSTAT_BUMP(arcstat_mru_hits); 5043 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 5044 arc_state_t *new_state; 5045 /* 5046 * This buffer has been "accessed" recently, but 5047 * was evicted from the cache. Move it to the 5048 * MFU state. 5049 */ 5050 5051 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5052 new_state = arc_mru; 5053 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) { 5054 arc_hdr_clear_flags(hdr, 5055 ARC_FLAG_PREFETCH | 5056 ARC_FLAG_PRESCIENT_PREFETCH); 5057 } 5058 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 5059 } else { 5060 new_state = arc_mfu; 5061 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5062 } 5063 5064 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5065 arc_change_state(new_state, hdr, hash_lock); 5066 5067 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 5068 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 5069 /* 5070 * This buffer has been accessed more than once and is 5071 * still in the cache. Keep it in the MFU state. 5072 * 5073 * NOTE: an add_reference() that occurred when we did 5074 * the arc_read() will have kicked this off the list. 5075 * If it was a prefetch, we will explicitly move it to 5076 * the head of the list now. 5077 */ 5078 5079 ARCSTAT_BUMP(arcstat_mfu_hits); 5080 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5081 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 5082 arc_state_t *new_state = arc_mfu; 5083 /* 5084 * This buffer has been accessed more than once but has 5085 * been evicted from the cache. Move it back to the 5086 * MFU state. 5087 */ 5088 5089 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) { 5090 /* 5091 * This is a prefetch access... 5092 * move this block back to the MRU state. 5093 */ 5094 new_state = arc_mru; 5095 } 5096 5097 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5098 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5099 arc_change_state(new_state, hdr, hash_lock); 5100 5101 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 5102 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 5103 /* 5104 * This buffer is on the 2nd Level ARC. 5105 */ 5106 5107 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5108 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5109 arc_change_state(arc_mfu, hdr, hash_lock); 5110 } else { 5111 ASSERT(!"invalid arc state"); 5112 } 5113} 5114 5115/* 5116 * This routine is called by dbuf_hold() to update the arc_access() state 5117 * which otherwise would be skipped for entries in the dbuf cache. 5118 */ 5119void 5120arc_buf_access(arc_buf_t *buf) 5121{ 5122 mutex_enter(&buf->b_evict_lock); 5123 arc_buf_hdr_t *hdr = buf->b_hdr; 5124 5125 /* 5126 * Avoid taking the hash_lock when possible as an optimization. 5127 * The header must be checked again under the hash_lock in order 5128 * to handle the case where it is concurrently being released. 5129 */ 5130 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { 5131 mutex_exit(&buf->b_evict_lock); 5132 ARCSTAT_BUMP(arcstat_access_skip); 5133 return; 5134 } 5135 5136 kmutex_t *hash_lock = HDR_LOCK(hdr); 5137 mutex_enter(hash_lock); 5138 5139 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { 5140 mutex_exit(hash_lock); 5141 mutex_exit(&buf->b_evict_lock); 5142 ARCSTAT_BUMP(arcstat_access_skip); 5143 return; 5144 } 5145 5146 mutex_exit(&buf->b_evict_lock); 5147 5148 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5149 hdr->b_l1hdr.b_state == arc_mfu); 5150 5151 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5152 arc_access(hdr, hash_lock); 5153 mutex_exit(hash_lock); 5154 5155 ARCSTAT_BUMP(arcstat_hits); 5156 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5157 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits); 5158} 5159 5160/* a generic arc_read_done_func_t which you can use */ 5161/* ARGSUSED */ 5162void 5163arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, 5164 arc_buf_t *buf, void *arg) 5165{ 5166 if (buf == NULL) 5167 return; 5168 5169 bcopy(buf->b_data, arg, arc_buf_size(buf)); 5170 arc_buf_destroy(buf, arg); 5171} 5172 5173/* a generic arc_read_done_func_t */ 5174/* ARGSUSED */ 5175void 5176arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp, 5177 arc_buf_t *buf, void *arg) 5178{ 5179 arc_buf_t **bufp = arg; 5180 if (buf == NULL) { 5181 ASSERT(zio == NULL || zio->io_error != 0); 5182 *bufp = NULL; 5183 } else { 5184 ASSERT(zio == NULL || zio->io_error == 0); 5185 *bufp = buf; 5186 ASSERT(buf->b_data != NULL); 5187 } 5188} 5189 5190static void 5191arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 5192{ 5193 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 5194 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 5195 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 5196 } else { 5197 if (HDR_COMPRESSION_ENABLED(hdr)) { 5198 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 5199 BP_GET_COMPRESS(bp)); 5200 } 5201 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 5202 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 5203 } 5204} 5205 5206static void 5207arc_read_done(zio_t *zio) 5208{ 5209 arc_buf_hdr_t *hdr = zio->io_private; 5210 kmutex_t *hash_lock = NULL; 5211 arc_callback_t *callback_list; 5212 arc_callback_t *acb; 5213 boolean_t freeable = B_FALSE; 5214 boolean_t no_zio_error = (zio->io_error == 0); 5215 5216 /* 5217 * The hdr was inserted into hash-table and removed from lists 5218 * prior to starting I/O. We should find this header, since 5219 * it's in the hash table, and it should be legit since it's 5220 * not possible to evict it during the I/O. The only possible 5221 * reason for it not to be found is if we were freed during the 5222 * read. 5223 */ 5224 if (HDR_IN_HASH_TABLE(hdr)) { 5225 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 5226 ASSERT3U(hdr->b_dva.dva_word[0], ==, 5227 BP_IDENTITY(zio->io_bp)->dva_word[0]); 5228 ASSERT3U(hdr->b_dva.dva_word[1], ==, 5229 BP_IDENTITY(zio->io_bp)->dva_word[1]); 5230 5231 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 5232 &hash_lock); 5233 5234 ASSERT((found == hdr && 5235 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 5236 (found == hdr && HDR_L2_READING(hdr))); 5237 ASSERT3P(hash_lock, !=, NULL); 5238 } 5239 5240 if (no_zio_error) { 5241 /* byteswap if necessary */ 5242 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 5243 if (BP_GET_LEVEL(zio->io_bp) > 0) { 5244 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 5245 } else { 5246 hdr->b_l1hdr.b_byteswap = 5247 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 5248 } 5249 } else { 5250 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 5251 } 5252 } 5253 5254 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 5255 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 5256 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 5257 5258 callback_list = hdr->b_l1hdr.b_acb; 5259 ASSERT3P(callback_list, !=, NULL); 5260 5261 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) { 5262 /* 5263 * Only call arc_access on anonymous buffers. This is because 5264 * if we've issued an I/O for an evicted buffer, we've already 5265 * called arc_access (to prevent any simultaneous readers from 5266 * getting confused). 5267 */ 5268 arc_access(hdr, hash_lock); 5269 } 5270 5271 /* 5272 * If a read request has a callback (i.e. acb_done is not NULL), then we 5273 * make a buf containing the data according to the parameters which were 5274 * passed in. The implementation of arc_buf_alloc_impl() ensures that we 5275 * aren't needlessly decompressing the data multiple times. 5276 */ 5277 int callback_cnt = 0; 5278 for (acb = callback_list; acb != NULL; acb = acb->acb_next) { 5279 if (!acb->acb_done) 5280 continue; 5281 5282 callback_cnt++; 5283 5284 if (no_zio_error) { 5285 int error = arc_buf_alloc_impl(hdr, acb->acb_private, 5286 acb->acb_compressed, zio->io_error == 0, 5287 &acb->acb_buf); 5288 if (error != 0) { 5289 /* 5290 * Decompression failed. Set io_error 5291 * so that when we call acb_done (below), 5292 * we will indicate that the read failed. 5293 * Note that in the unusual case where one 5294 * callback is compressed and another 5295 * uncompressed, we will mark all of them 5296 * as failed, even though the uncompressed 5297 * one can't actually fail. In this case, 5298 * the hdr will not be anonymous, because 5299 * if there are multiple callbacks, it's 5300 * because multiple threads found the same 5301 * arc buf in the hash table. 5302 */ 5303 zio->io_error = error; 5304 } 5305 } 5306 } 5307 /* 5308 * If there are multiple callbacks, we must have the hash lock, 5309 * because the only way for multiple threads to find this hdr is 5310 * in the hash table. This ensures that if there are multiple 5311 * callbacks, the hdr is not anonymous. If it were anonymous, 5312 * we couldn't use arc_buf_destroy() in the error case below. 5313 */ 5314 ASSERT(callback_cnt < 2 || hash_lock != NULL); 5315 5316 hdr->b_l1hdr.b_acb = NULL; 5317 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5318 if (callback_cnt == 0) { 5319 ASSERT(HDR_PREFETCH(hdr)); 5320 ASSERT0(hdr->b_l1hdr.b_bufcnt); 5321 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5322 } 5323 5324 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 5325 callback_list != NULL); 5326 5327 if (no_zio_error) { 5328 arc_hdr_verify(hdr, zio->io_bp); 5329 } else { 5330 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 5331 if (hdr->b_l1hdr.b_state != arc_anon) 5332 arc_change_state(arc_anon, hdr, hash_lock); 5333 if (HDR_IN_HASH_TABLE(hdr)) 5334 buf_hash_remove(hdr); 5335 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5336 } 5337 5338 /* 5339 * Broadcast before we drop the hash_lock to avoid the possibility 5340 * that the hdr (and hence the cv) might be freed before we get to 5341 * the cv_broadcast(). 5342 */ 5343 cv_broadcast(&hdr->b_l1hdr.b_cv); 5344 5345 if (hash_lock != NULL) { 5346 mutex_exit(hash_lock); 5347 } else { 5348 /* 5349 * This block was freed while we waited for the read to 5350 * complete. It has been removed from the hash table and 5351 * moved to the anonymous state (so that it won't show up 5352 * in the cache). 5353 */ 5354 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 5355 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5356 } 5357 5358 /* execute each callback and free its structure */ 5359 while ((acb = callback_list) != NULL) { 5360 if (acb->acb_done != NULL) { 5361 if (zio->io_error != 0 && acb->acb_buf != NULL) { 5362 /* 5363 * If arc_buf_alloc_impl() fails during 5364 * decompression, the buf will still be 5365 * allocated, and needs to be freed here. 5366 */ 5367 arc_buf_destroy(acb->acb_buf, acb->acb_private); 5368 acb->acb_buf = NULL; 5369 } 5370 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp, 5371 acb->acb_buf, acb->acb_private); 5372 } 5373 5374 if (acb->acb_zio_dummy != NULL) { 5375 acb->acb_zio_dummy->io_error = zio->io_error; 5376 zio_nowait(acb->acb_zio_dummy); 5377 } 5378 5379 callback_list = acb->acb_next; 5380 kmem_free(acb, sizeof (arc_callback_t)); 5381 } 5382 5383 if (freeable) 5384 arc_hdr_destroy(hdr); 5385} 5386 5387/* 5388 * "Read" the block at the specified DVA (in bp) via the 5389 * cache. If the block is found in the cache, invoke the provided 5390 * callback immediately and return. Note that the `zio' parameter 5391 * in the callback will be NULL in this case, since no IO was 5392 * required. If the block is not in the cache pass the read request 5393 * on to the spa with a substitute callback function, so that the 5394 * requested block will be added to the cache. 5395 * 5396 * If a read request arrives for a block that has a read in-progress, 5397 * either wait for the in-progress read to complete (and return the 5398 * results); or, if this is a read with a "done" func, add a record 5399 * to the read to invoke the "done" func when the read completes, 5400 * and return; or just return. 5401 * 5402 * arc_read_done() will invoke all the requested "done" functions 5403 * for readers of this block. 5404 */ 5405int 5406arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_read_done_func_t *done, 5407 void *private, zio_priority_t priority, int zio_flags, 5408 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 5409{ 5410 arc_buf_hdr_t *hdr = NULL; 5411 kmutex_t *hash_lock = NULL; 5412 zio_t *rzio; 5413 uint64_t guid = spa_load_guid(spa); 5414 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0; 5415 int rc = 0; 5416 5417 ASSERT(!BP_IS_EMBEDDED(bp) || 5418 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 5419 5420top: 5421 if (!BP_IS_EMBEDDED(bp)) { 5422 /* 5423 * Embedded BP's have no DVA and require no I/O to "read". 5424 * Create an anonymous arc buf to back it. 5425 */ 5426 hdr = buf_hash_find(guid, bp, &hash_lock); 5427 } 5428 5429 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { 5430 arc_buf_t *buf = NULL; 5431 *arc_flags |= ARC_FLAG_CACHED; 5432 5433 if (HDR_IO_IN_PROGRESS(hdr)) { 5434 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head; 5435 5436 ASSERT3P(head_zio, !=, NULL); 5437 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 5438 priority == ZIO_PRIORITY_SYNC_READ) { 5439 /* 5440 * This is a sync read that needs to wait for 5441 * an in-flight async read. Request that the 5442 * zio have its priority upgraded. 5443 */ 5444 zio_change_priority(head_zio, priority); 5445 DTRACE_PROBE1(arc__async__upgrade__sync, 5446 arc_buf_hdr_t *, hdr); 5447 ARCSTAT_BUMP(arcstat_async_upgrade_sync); 5448 } 5449 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5450 arc_hdr_clear_flags(hdr, 5451 ARC_FLAG_PREDICTIVE_PREFETCH); 5452 } 5453 5454 if (*arc_flags & ARC_FLAG_WAIT) { 5455 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 5456 mutex_exit(hash_lock); 5457 goto top; 5458 } 5459 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5460 5461 if (done) { 5462 arc_callback_t *acb = NULL; 5463 5464 acb = kmem_zalloc(sizeof (arc_callback_t), 5465 KM_SLEEP); 5466 acb->acb_done = done; 5467 acb->acb_private = private; 5468 acb->acb_compressed = compressed_read; 5469 if (pio != NULL) 5470 acb->acb_zio_dummy = zio_null(pio, 5471 spa, NULL, NULL, NULL, zio_flags); 5472 5473 ASSERT3P(acb->acb_done, !=, NULL); 5474 acb->acb_zio_head = head_zio; 5475 acb->acb_next = hdr->b_l1hdr.b_acb; 5476 hdr->b_l1hdr.b_acb = acb; 5477 mutex_exit(hash_lock); 5478 return (0); 5479 } 5480 mutex_exit(hash_lock); 5481 return (0); 5482 } 5483 5484 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5485 hdr->b_l1hdr.b_state == arc_mfu); 5486 5487 if (done) { 5488 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5489 /* 5490 * This is a demand read which does not have to 5491 * wait for i/o because we did a predictive 5492 * prefetch i/o for it, which has completed. 5493 */ 5494 DTRACE_PROBE1( 5495 arc__demand__hit__predictive__prefetch, 5496 arc_buf_hdr_t *, hdr); 5497 ARCSTAT_BUMP( 5498 arcstat_demand_hit_predictive_prefetch); 5499 arc_hdr_clear_flags(hdr, 5500 ARC_FLAG_PREDICTIVE_PREFETCH); 5501 } 5502 5503 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) { 5504 ARCSTAT_BUMP( 5505 arcstat_demand_hit_prescient_prefetch); 5506 arc_hdr_clear_flags(hdr, 5507 ARC_FLAG_PRESCIENT_PREFETCH); 5508 } 5509 5510 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 5511 /* Get a buf with the desired data in it. */ 5512 rc = arc_buf_alloc_impl(hdr, private, 5513 compressed_read, B_TRUE, &buf); 5514 if (rc != 0) { 5515 arc_buf_destroy(buf, private); 5516 buf = NULL; 5517 } 5518 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) || 5519 rc == 0 || rc != ENOENT); 5520 } else if (*arc_flags & ARC_FLAG_PREFETCH && 5521 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5522 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5523 } 5524 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5525 arc_access(hdr, hash_lock); 5526 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) 5527 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); 5528 if (*arc_flags & ARC_FLAG_L2CACHE) 5529 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5530 mutex_exit(hash_lock); 5531 ARCSTAT_BUMP(arcstat_hits); 5532 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5533 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5534 data, metadata, hits); 5535 5536 if (done) 5537 done(NULL, zb, bp, buf, private); 5538 } else { 5539 uint64_t lsize = BP_GET_LSIZE(bp); 5540 uint64_t psize = BP_GET_PSIZE(bp); 5541 arc_callback_t *acb; 5542 vdev_t *vd = NULL; 5543 uint64_t addr = 0; 5544 boolean_t devw = B_FALSE; 5545 uint64_t size; 5546 5547 if (hdr == NULL) { 5548 /* this block is not in the cache */ 5549 arc_buf_hdr_t *exists = NULL; 5550 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 5551 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 5552 BP_GET_COMPRESS(bp), type); 5553 5554 if (!BP_IS_EMBEDDED(bp)) { 5555 hdr->b_dva = *BP_IDENTITY(bp); 5556 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 5557 exists = buf_hash_insert(hdr, &hash_lock); 5558 } 5559 if (exists != NULL) { 5560 /* somebody beat us to the hash insert */ 5561 mutex_exit(hash_lock); 5562 buf_discard_identity(hdr); 5563 arc_hdr_destroy(hdr); 5564 goto top; /* restart the IO request */ 5565 } 5566 } else { 5567 /* 5568 * This block is in the ghost cache. If it was L2-only 5569 * (and thus didn't have an L1 hdr), we realloc the 5570 * header to add an L1 hdr. 5571 */ 5572 if (!HDR_HAS_L1HDR(hdr)) { 5573 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 5574 hdr_full_cache); 5575 } 5576 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5577 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 5578 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5579 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5580 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 5581 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 5582 5583 /* 5584 * This is a delicate dance that we play here. 5585 * This hdr is in the ghost list so we access it 5586 * to move it out of the ghost list before we 5587 * initiate the read. If it's a prefetch then 5588 * it won't have a callback so we'll remove the 5589 * reference that arc_buf_alloc_impl() created. We 5590 * do this after we've called arc_access() to 5591 * avoid hitting an assert in remove_reference(). 5592 */ 5593 arc_access(hdr, hash_lock); 5594 arc_hdr_alloc_pabd(hdr); 5595 } 5596 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5597 size = arc_hdr_size(hdr); 5598 5599 /* 5600 * If compression is enabled on the hdr, then will do 5601 * RAW I/O and will store the compressed data in the hdr's 5602 * data block. Otherwise, the hdr's data block will contain 5603 * the uncompressed data. 5604 */ 5605 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5606 zio_flags |= ZIO_FLAG_RAW; 5607 } 5608 5609 if (*arc_flags & ARC_FLAG_PREFETCH) 5610 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5611 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH) 5612 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH); 5613 5614 if (*arc_flags & ARC_FLAG_L2CACHE) 5615 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5616 if (BP_GET_LEVEL(bp) > 0) 5617 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5618 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5619 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5620 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5621 5622 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5623 acb->acb_done = done; 5624 acb->acb_private = private; 5625 acb->acb_compressed = compressed_read; 5626 5627 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5628 hdr->b_l1hdr.b_acb = acb; 5629 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5630 5631 if (HDR_HAS_L2HDR(hdr) && 5632 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5633 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5634 addr = hdr->b_l2hdr.b_daddr; 5635 /* 5636 * Lock out L2ARC device removal. 5637 */ 5638 if (vdev_is_dead(vd) || 5639 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 5640 vd = NULL; 5641 } 5642 5643 /* 5644 * We count both async reads and scrub IOs as asynchronous so 5645 * that both can be upgraded in the event of a cache hit while 5646 * the read IO is still in-flight. 5647 */ 5648 if (priority == ZIO_PRIORITY_ASYNC_READ || 5649 priority == ZIO_PRIORITY_SCRUB) 5650 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5651 else 5652 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5653 5654 /* 5655 * At this point, we have a level 1 cache miss. Try again in 5656 * L2ARC if possible. 5657 */ 5658 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 5659 5660 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 5661 uint64_t, lsize, zbookmark_phys_t *, zb); 5662 ARCSTAT_BUMP(arcstat_misses); 5663 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5664 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5665 data, metadata, misses); 5666#ifdef _KERNEL 5667#ifdef RACCT 5668 if (racct_enable) { 5669 PROC_LOCK(curproc); 5670 racct_add_force(curproc, RACCT_READBPS, size); 5671 racct_add_force(curproc, RACCT_READIOPS, 1); 5672 PROC_UNLOCK(curproc); 5673 } 5674#endif /* RACCT */ 5675 curthread->td_ru.ru_inblock++; 5676#endif 5677 5678 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5679 /* 5680 * Read from the L2ARC if the following are true: 5681 * 1. The L2ARC vdev was previously cached. 5682 * 2. This buffer still has L2ARC metadata. 5683 * 3. This buffer isn't currently writing to the L2ARC. 5684 * 4. The L2ARC entry wasn't evicted, which may 5685 * also have invalidated the vdev. 5686 * 5. This isn't prefetch and l2arc_noprefetch is set. 5687 */ 5688 if (HDR_HAS_L2HDR(hdr) && 5689 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5690 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5691 l2arc_read_callback_t *cb; 5692 abd_t *abd; 5693 uint64_t asize; 5694 5695 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5696 ARCSTAT_BUMP(arcstat_l2_hits); 5697 5698 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5699 KM_SLEEP); 5700 cb->l2rcb_hdr = hdr; 5701 cb->l2rcb_bp = *bp; 5702 cb->l2rcb_zb = *zb; 5703 cb->l2rcb_flags = zio_flags; 5704 5705 asize = vdev_psize_to_asize(vd, size); 5706 if (asize != size) { 5707 abd = abd_alloc_for_io(asize, 5708 HDR_ISTYPE_METADATA(hdr)); 5709 cb->l2rcb_abd = abd; 5710 } else { 5711 abd = hdr->b_l1hdr.b_pabd; 5712 } 5713 5714 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5715 addr + asize <= vd->vdev_psize - 5716 VDEV_LABEL_END_SIZE); 5717 5718 /* 5719 * l2arc read. The SCL_L2ARC lock will be 5720 * released by l2arc_read_done(). 5721 * Issue a null zio if the underlying buffer 5722 * was squashed to zero size by compression. 5723 */ 5724 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5725 ZIO_COMPRESS_EMPTY); 5726 rzio = zio_read_phys(pio, vd, addr, 5727 asize, abd, 5728 ZIO_CHECKSUM_OFF, 5729 l2arc_read_done, cb, priority, 5730 zio_flags | ZIO_FLAG_DONT_CACHE | 5731 ZIO_FLAG_CANFAIL | 5732 ZIO_FLAG_DONT_PROPAGATE | 5733 ZIO_FLAG_DONT_RETRY, B_FALSE); 5734 acb->acb_zio_head = rzio; 5735 5736 if (hash_lock != NULL) 5737 mutex_exit(hash_lock); 5738 5739 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5740 zio_t *, rzio); 5741 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5742 5743 if (*arc_flags & ARC_FLAG_NOWAIT) { 5744 zio_nowait(rzio); 5745 return (0); 5746 } 5747 5748 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5749 if (zio_wait(rzio) == 0) 5750 return (0); 5751 5752 /* l2arc read error; goto zio_read() */ 5753 if (hash_lock != NULL) 5754 mutex_enter(hash_lock); 5755 } else { 5756 DTRACE_PROBE1(l2arc__miss, 5757 arc_buf_hdr_t *, hdr); 5758 ARCSTAT_BUMP(arcstat_l2_misses); 5759 if (HDR_L2_WRITING(hdr)) 5760 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5761 spa_config_exit(spa, SCL_L2ARC, vd); 5762 } 5763 } else { 5764 if (vd != NULL) 5765 spa_config_exit(spa, SCL_L2ARC, vd); 5766 if (l2arc_ndev != 0) { 5767 DTRACE_PROBE1(l2arc__miss, 5768 arc_buf_hdr_t *, hdr); 5769 ARCSTAT_BUMP(arcstat_l2_misses); 5770 } 5771 } 5772 5773 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size, 5774 arc_read_done, hdr, priority, zio_flags, zb); 5775 acb->acb_zio_head = rzio; 5776 5777 if (hash_lock != NULL) 5778 mutex_exit(hash_lock); 5779 5780 if (*arc_flags & ARC_FLAG_WAIT) 5781 return (zio_wait(rzio)); 5782 5783 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5784 zio_nowait(rzio); 5785 } 5786 return (0); 5787} 5788 5789/* 5790 * Notify the arc that a block was freed, and thus will never be used again. 5791 */ 5792void 5793arc_freed(spa_t *spa, const blkptr_t *bp) 5794{ 5795 arc_buf_hdr_t *hdr; 5796 kmutex_t *hash_lock; 5797 uint64_t guid = spa_load_guid(spa); 5798 5799 ASSERT(!BP_IS_EMBEDDED(bp)); 5800 5801 hdr = buf_hash_find(guid, bp, &hash_lock); 5802 if (hdr == NULL) 5803 return; 5804 5805 /* 5806 * We might be trying to free a block that is still doing I/O 5807 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5808 * dmu_sync-ed block). If this block is being prefetched, then it 5809 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5810 * until the I/O completes. A block may also have a reference if it is 5811 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5812 * have written the new block to its final resting place on disk but 5813 * without the dedup flag set. This would have left the hdr in the MRU 5814 * state and discoverable. When the txg finally syncs it detects that 5815 * the block was overridden in open context and issues an override I/O. 5816 * Since this is a dedup block, the override I/O will determine if the 5817 * block is already in the DDT. If so, then it will replace the io_bp 5818 * with the bp from the DDT and allow the I/O to finish. When the I/O 5819 * reaches the done callback, dbuf_write_override_done, it will 5820 * check to see if the io_bp and io_bp_override are identical. 5821 * If they are not, then it indicates that the bp was replaced with 5822 * the bp in the DDT and the override bp is freed. This allows 5823 * us to arrive here with a reference on a block that is being 5824 * freed. So if we have an I/O in progress, or a reference to 5825 * this hdr, then we don't destroy the hdr. 5826 */ 5827 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5828 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5829 arc_change_state(arc_anon, hdr, hash_lock); 5830 arc_hdr_destroy(hdr); 5831 mutex_exit(hash_lock); 5832 } else { 5833 mutex_exit(hash_lock); 5834 } 5835 5836} 5837 5838/* 5839 * Release this buffer from the cache, making it an anonymous buffer. This 5840 * must be done after a read and prior to modifying the buffer contents. 5841 * If the buffer has more than one reference, we must make 5842 * a new hdr for the buffer. 5843 */ 5844void 5845arc_release(arc_buf_t *buf, void *tag) 5846{ 5847 arc_buf_hdr_t *hdr = buf->b_hdr; 5848 5849 /* 5850 * It would be nice to assert that if it's DMU metadata (level > 5851 * 0 || it's the dnode file), then it must be syncing context. 5852 * But we don't know that information at this level. 5853 */ 5854 5855 mutex_enter(&buf->b_evict_lock); 5856 5857 ASSERT(HDR_HAS_L1HDR(hdr)); 5858 5859 /* 5860 * We don't grab the hash lock prior to this check, because if 5861 * the buffer's header is in the arc_anon state, it won't be 5862 * linked into the hash table. 5863 */ 5864 if (hdr->b_l1hdr.b_state == arc_anon) { 5865 mutex_exit(&buf->b_evict_lock); 5866 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5867 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5868 ASSERT(!HDR_HAS_L2HDR(hdr)); 5869 ASSERT(HDR_EMPTY(hdr)); 5870 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5871 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5872 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5873 5874 hdr->b_l1hdr.b_arc_access = 0; 5875 5876 /* 5877 * If the buf is being overridden then it may already 5878 * have a hdr that is not empty. 5879 */ 5880 buf_discard_identity(hdr); 5881 arc_buf_thaw(buf); 5882 5883 return; 5884 } 5885 5886 kmutex_t *hash_lock = HDR_LOCK(hdr); 5887 mutex_enter(hash_lock); 5888 5889 /* 5890 * This assignment is only valid as long as the hash_lock is 5891 * held, we must be careful not to reference state or the 5892 * b_state field after dropping the lock. 5893 */ 5894 arc_state_t *state = hdr->b_l1hdr.b_state; 5895 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5896 ASSERT3P(state, !=, arc_anon); 5897 5898 /* this buffer is not on any list */ 5899 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); 5900 5901 if (HDR_HAS_L2HDR(hdr)) { 5902 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5903 5904 /* 5905 * We have to recheck this conditional again now that 5906 * we're holding the l2ad_mtx to prevent a race with 5907 * another thread which might be concurrently calling 5908 * l2arc_evict(). In that case, l2arc_evict() might have 5909 * destroyed the header's L2 portion as we were waiting 5910 * to acquire the l2ad_mtx. 5911 */ 5912 if (HDR_HAS_L2HDR(hdr)) { 5913 l2arc_trim(hdr); 5914 arc_hdr_l2hdr_destroy(hdr); 5915 } 5916 5917 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5918 } 5919 5920 /* 5921 * Do we have more than one buf? 5922 */ 5923 if (hdr->b_l1hdr.b_bufcnt > 1) { 5924 arc_buf_hdr_t *nhdr; 5925 uint64_t spa = hdr->b_spa; 5926 uint64_t psize = HDR_GET_PSIZE(hdr); 5927 uint64_t lsize = HDR_GET_LSIZE(hdr); 5928 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5929 arc_buf_contents_t type = arc_buf_type(hdr); 5930 VERIFY3U(hdr->b_type, ==, type); 5931 5932 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5933 (void) remove_reference(hdr, hash_lock, tag); 5934 5935 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { 5936 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5937 ASSERT(ARC_BUF_LAST(buf)); 5938 } 5939 5940 /* 5941 * Pull the data off of this hdr and attach it to 5942 * a new anonymous hdr. Also find the last buffer 5943 * in the hdr's buffer list. 5944 */ 5945 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 5946 ASSERT3P(lastbuf, !=, NULL); 5947 5948 /* 5949 * If the current arc_buf_t and the hdr are sharing their data 5950 * buffer, then we must stop sharing that block. 5951 */ 5952 if (arc_buf_is_shared(buf)) { 5953 VERIFY(!arc_buf_is_shared(lastbuf)); 5954 5955 /* 5956 * First, sever the block sharing relationship between 5957 * buf and the arc_buf_hdr_t. 5958 */ 5959 arc_unshare_buf(hdr, buf); 5960 5961 /* 5962 * Now we need to recreate the hdr's b_pabd. Since we 5963 * have lastbuf handy, we try to share with it, but if 5964 * we can't then we allocate a new b_pabd and copy the 5965 * data from buf into it. 5966 */ 5967 if (arc_can_share(hdr, lastbuf)) { 5968 arc_share_buf(hdr, lastbuf); 5969 } else { 5970 arc_hdr_alloc_pabd(hdr); 5971 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, 5972 buf->b_data, psize); 5973 } 5974 VERIFY3P(lastbuf->b_data, !=, NULL); 5975 } else if (HDR_SHARED_DATA(hdr)) { 5976 /* 5977 * Uncompressed shared buffers are always at the end 5978 * of the list. Compressed buffers don't have the 5979 * same requirements. This makes it hard to 5980 * simply assert that the lastbuf is shared so 5981 * we rely on the hdr's compression flags to determine 5982 * if we have a compressed, shared buffer. 5983 */ 5984 ASSERT(arc_buf_is_shared(lastbuf) || 5985 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 5986 ASSERT(!ARC_BUF_SHARED(buf)); 5987 } 5988 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5989 ASSERT3P(state, !=, arc_l2c_only); 5990 5991 (void) refcount_remove_many(&state->arcs_size, 5992 arc_buf_size(buf), buf); 5993 5994 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5995 ASSERT3P(state, !=, arc_l2c_only); 5996 (void) refcount_remove_many(&state->arcs_esize[type], 5997 arc_buf_size(buf), buf); 5998 } 5999 6000 hdr->b_l1hdr.b_bufcnt -= 1; 6001 arc_cksum_verify(buf); 6002#ifdef illumos 6003 arc_buf_unwatch(buf); 6004#endif 6005 6006 mutex_exit(hash_lock); 6007 6008 /* 6009 * Allocate a new hdr. The new hdr will contain a b_pabd 6010 * buffer which will be freed in arc_write(). 6011 */ 6012 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 6013 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 6014 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 6015 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 6016 VERIFY3U(nhdr->b_type, ==, type); 6017 ASSERT(!HDR_SHARED_DATA(nhdr)); 6018 6019 nhdr->b_l1hdr.b_buf = buf; 6020 nhdr->b_l1hdr.b_bufcnt = 1; 6021 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 6022 buf->b_hdr = nhdr; 6023 6024 mutex_exit(&buf->b_evict_lock); 6025 (void) refcount_add_many(&arc_anon->arcs_size, 6026 arc_buf_size(buf), buf); 6027 } else { 6028 mutex_exit(&buf->b_evict_lock); 6029 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 6030 /* protected by hash lock, or hdr is on arc_anon */ 6031 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 6032 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6033 arc_change_state(arc_anon, hdr, hash_lock); 6034 hdr->b_l1hdr.b_arc_access = 0; 6035 mutex_exit(hash_lock); 6036 6037 buf_discard_identity(hdr); 6038 arc_buf_thaw(buf); 6039 } 6040} 6041 6042int 6043arc_released(arc_buf_t *buf) 6044{ 6045 int released; 6046 6047 mutex_enter(&buf->b_evict_lock); 6048 released = (buf->b_data != NULL && 6049 buf->b_hdr->b_l1hdr.b_state == arc_anon); 6050 mutex_exit(&buf->b_evict_lock); 6051 return (released); 6052} 6053 6054#ifdef ZFS_DEBUG 6055int 6056arc_referenced(arc_buf_t *buf) 6057{ 6058 int referenced; 6059 6060 mutex_enter(&buf->b_evict_lock); 6061 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 6062 mutex_exit(&buf->b_evict_lock); 6063 return (referenced); 6064} 6065#endif 6066 6067static void 6068arc_write_ready(zio_t *zio) 6069{ 6070 arc_write_callback_t *callback = zio->io_private; 6071 arc_buf_t *buf = callback->awcb_buf; 6072 arc_buf_hdr_t *hdr = buf->b_hdr; 6073 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 6074 6075 ASSERT(HDR_HAS_L1HDR(hdr)); 6076 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 6077 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 6078 6079 /* 6080 * If we're reexecuting this zio because the pool suspended, then 6081 * cleanup any state that was previously set the first time the 6082 * callback was invoked. 6083 */ 6084 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 6085 arc_cksum_free(hdr); 6086#ifdef illumos 6087 arc_buf_unwatch(buf); 6088#endif 6089 if (hdr->b_l1hdr.b_pabd != NULL) { 6090 if (arc_buf_is_shared(buf)) { 6091 arc_unshare_buf(hdr, buf); 6092 } else { 6093 arc_hdr_free_pabd(hdr); 6094 } 6095 } 6096 } 6097 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6098 ASSERT(!HDR_SHARED_DATA(hdr)); 6099 ASSERT(!arc_buf_is_shared(buf)); 6100 6101 callback->awcb_ready(zio, buf, callback->awcb_private); 6102 6103 if (HDR_IO_IN_PROGRESS(hdr)) 6104 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 6105 6106 arc_cksum_compute(buf); 6107 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6108 6109 enum zio_compress compress; 6110 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 6111 compress = ZIO_COMPRESS_OFF; 6112 } else { 6113 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 6114 compress = BP_GET_COMPRESS(zio->io_bp); 6115 } 6116 HDR_SET_PSIZE(hdr, psize); 6117 arc_hdr_set_compress(hdr, compress); 6118 6119 6120 /* 6121 * Fill the hdr with data. If the hdr is compressed, the data we want 6122 * is available from the zio, otherwise we can take it from the buf. 6123 * 6124 * We might be able to share the buf's data with the hdr here. However, 6125 * doing so would cause the ARC to be full of linear ABDs if we write a 6126 * lot of shareable data. As a compromise, we check whether scattered 6127 * ABDs are allowed, and assume that if they are then the user wants 6128 * the ARC to be primarily filled with them regardless of the data being 6129 * written. Therefore, if they're allowed then we allocate one and copy 6130 * the data into it; otherwise, we share the data directly if we can. 6131 */ 6132 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { 6133 arc_hdr_alloc_pabd(hdr); 6134 6135 /* 6136 * Ideally, we would always copy the io_abd into b_pabd, but the 6137 * user may have disabled compressed ARC, thus we must check the 6138 * hdr's compression setting rather than the io_bp's. 6139 */ 6140 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 6141 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, 6142 ZIO_COMPRESS_OFF); 6143 ASSERT3U(psize, >, 0); 6144 6145 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); 6146 } else { 6147 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); 6148 6149 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, 6150 arc_buf_size(buf)); 6151 } 6152 } else { 6153 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); 6154 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); 6155 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 6156 6157 arc_share_buf(hdr, buf); 6158 } 6159 6160 arc_hdr_verify(hdr, zio->io_bp); 6161} 6162 6163static void 6164arc_write_children_ready(zio_t *zio) 6165{ 6166 arc_write_callback_t *callback = zio->io_private; 6167 arc_buf_t *buf = callback->awcb_buf; 6168 6169 callback->awcb_children_ready(zio, buf, callback->awcb_private); 6170} 6171 6172/* 6173 * The SPA calls this callback for each physical write that happens on behalf 6174 * of a logical write. See the comment in dbuf_write_physdone() for details. 6175 */ 6176static void 6177arc_write_physdone(zio_t *zio) 6178{ 6179 arc_write_callback_t *cb = zio->io_private; 6180 if (cb->awcb_physdone != NULL) 6181 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 6182} 6183 6184static void 6185arc_write_done(zio_t *zio) 6186{ 6187 arc_write_callback_t *callback = zio->io_private; 6188 arc_buf_t *buf = callback->awcb_buf; 6189 arc_buf_hdr_t *hdr = buf->b_hdr; 6190 6191 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6192 6193 if (zio->io_error == 0) { 6194 arc_hdr_verify(hdr, zio->io_bp); 6195 6196 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 6197 buf_discard_identity(hdr); 6198 } else { 6199 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 6200 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 6201 } 6202 } else { 6203 ASSERT(HDR_EMPTY(hdr)); 6204 } 6205 6206 /* 6207 * If the block to be written was all-zero or compressed enough to be 6208 * embedded in the BP, no write was performed so there will be no 6209 * dva/birth/checksum. The buffer must therefore remain anonymous 6210 * (and uncached). 6211 */ 6212 if (!HDR_EMPTY(hdr)) { 6213 arc_buf_hdr_t *exists; 6214 kmutex_t *hash_lock; 6215 6216 ASSERT3U(zio->io_error, ==, 0); 6217 6218 arc_cksum_verify(buf); 6219 6220 exists = buf_hash_insert(hdr, &hash_lock); 6221 if (exists != NULL) { 6222 /* 6223 * This can only happen if we overwrite for 6224 * sync-to-convergence, because we remove 6225 * buffers from the hash table when we arc_free(). 6226 */ 6227 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 6228 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6229 panic("bad overwrite, hdr=%p exists=%p", 6230 (void *)hdr, (void *)exists); 6231 ASSERT(refcount_is_zero( 6232 &exists->b_l1hdr.b_refcnt)); 6233 arc_change_state(arc_anon, exists, hash_lock); 6234 mutex_exit(hash_lock); 6235 arc_hdr_destroy(exists); 6236 exists = buf_hash_insert(hdr, &hash_lock); 6237 ASSERT3P(exists, ==, NULL); 6238 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 6239 /* nopwrite */ 6240 ASSERT(zio->io_prop.zp_nopwrite); 6241 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6242 panic("bad nopwrite, hdr=%p exists=%p", 6243 (void *)hdr, (void *)exists); 6244 } else { 6245 /* Dedup */ 6246 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 6247 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 6248 ASSERT(BP_GET_DEDUP(zio->io_bp)); 6249 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 6250 } 6251 } 6252 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6253 /* if it's not anon, we are doing a scrub */ 6254 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 6255 arc_access(hdr, hash_lock); 6256 mutex_exit(hash_lock); 6257 } else { 6258 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6259 } 6260 6261 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 6262 callback->awcb_done(zio, buf, callback->awcb_private); 6263 6264 abd_put(zio->io_abd); 6265 kmem_free(callback, sizeof (arc_write_callback_t)); 6266} 6267 6268zio_t * 6269arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 6270 boolean_t l2arc, const zio_prop_t *zp, arc_write_done_func_t *ready, 6271 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone, 6272 arc_write_done_func_t *done, void *private, zio_priority_t priority, 6273 int zio_flags, const zbookmark_phys_t *zb) 6274{ 6275 arc_buf_hdr_t *hdr = buf->b_hdr; 6276 arc_write_callback_t *callback; 6277 zio_t *zio; 6278 zio_prop_t localprop = *zp; 6279 6280 ASSERT3P(ready, !=, NULL); 6281 ASSERT3P(done, !=, NULL); 6282 ASSERT(!HDR_IO_ERROR(hdr)); 6283 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6284 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6285 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 6286 if (l2arc) 6287 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 6288 if (ARC_BUF_COMPRESSED(buf)) { 6289 /* 6290 * We're writing a pre-compressed buffer. Make the 6291 * compression algorithm requested by the zio_prop_t match 6292 * the pre-compressed buffer's compression algorithm. 6293 */ 6294 localprop.zp_compress = HDR_GET_COMPRESS(hdr); 6295 6296 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); 6297 zio_flags |= ZIO_FLAG_RAW; 6298 } 6299 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 6300 callback->awcb_ready = ready; 6301 callback->awcb_children_ready = children_ready; 6302 callback->awcb_physdone = physdone; 6303 callback->awcb_done = done; 6304 callback->awcb_private = private; 6305 callback->awcb_buf = buf; 6306 6307 /* 6308 * The hdr's b_pabd is now stale, free it now. A new data block 6309 * will be allocated when the zio pipeline calls arc_write_ready(). 6310 */ 6311 if (hdr->b_l1hdr.b_pabd != NULL) { 6312 /* 6313 * If the buf is currently sharing the data block with 6314 * the hdr then we need to break that relationship here. 6315 * The hdr will remain with a NULL data pointer and the 6316 * buf will take sole ownership of the block. 6317 */ 6318 if (arc_buf_is_shared(buf)) { 6319 arc_unshare_buf(hdr, buf); 6320 } else { 6321 arc_hdr_free_pabd(hdr); 6322 } 6323 VERIFY3P(buf->b_data, !=, NULL); 6324 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 6325 } 6326 ASSERT(!arc_buf_is_shared(buf)); 6327 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6328 6329 zio = zio_write(pio, spa, txg, bp, 6330 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), 6331 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, 6332 (children_ready != NULL) ? arc_write_children_ready : NULL, 6333 arc_write_physdone, arc_write_done, callback, 6334 priority, zio_flags, zb); 6335 6336 return (zio); 6337} 6338 6339static int 6340arc_memory_throttle(uint64_t reserve, uint64_t txg) 6341{ 6342#ifdef _KERNEL 6343 uint64_t available_memory = ptob(freemem); 6344 static uint64_t page_load = 0; 6345 static uint64_t last_txg = 0; 6346 6347#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 6348 available_memory = 6349 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 6350#endif 6351 6352 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 6353 return (0); 6354 6355 if (txg > last_txg) { 6356 last_txg = txg; 6357 page_load = 0; 6358 } 6359 /* 6360 * If we are in pageout, we know that memory is already tight, 6361 * the arc is already going to be evicting, so we just want to 6362 * continue to let page writes occur as quickly as possible. 6363 */ 6364 if (curproc == pageproc) { 6365 if (page_load > MAX(ptob(minfree), available_memory) / 4) 6366 return (SET_ERROR(ERESTART)); 6367 /* Note: reserve is inflated, so we deflate */ 6368 page_load += reserve / 8; 6369 return (0); 6370 } else if (page_load > 0 && arc_reclaim_needed()) { 6371 /* memory is low, delay before restarting */ 6372 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 6373 return (SET_ERROR(EAGAIN)); 6374 } 6375 page_load = 0; 6376#endif 6377 return (0); 6378} 6379 6380void 6381arc_tempreserve_clear(uint64_t reserve) 6382{ 6383 atomic_add_64(&arc_tempreserve, -reserve); 6384 ASSERT((int64_t)arc_tempreserve >= 0); 6385} 6386 6387int 6388arc_tempreserve_space(uint64_t reserve, uint64_t txg) 6389{ 6390 int error; 6391 uint64_t anon_size; 6392 6393 if (reserve > arc_c/4 && !arc_no_grow) { 6394 arc_c = MIN(arc_c_max, reserve * 4); 6395 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 6396 } 6397 if (reserve > arc_c) 6398 return (SET_ERROR(ENOMEM)); 6399 6400 /* 6401 * Don't count loaned bufs as in flight dirty data to prevent long 6402 * network delays from blocking transactions that are ready to be 6403 * assigned to a txg. 6404 */ 6405 6406 /* assert that it has not wrapped around */ 6407 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 6408 6409 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 6410 arc_loaned_bytes), 0); 6411 6412 /* 6413 * Writes will, almost always, require additional memory allocations 6414 * in order to compress/encrypt/etc the data. We therefore need to 6415 * make sure that there is sufficient available memory for this. 6416 */ 6417 error = arc_memory_throttle(reserve, txg); 6418 if (error != 0) 6419 return (error); 6420 6421 /* 6422 * Throttle writes when the amount of dirty data in the cache 6423 * gets too large. We try to keep the cache less than half full 6424 * of dirty blocks so that our sync times don't grow too large. 6425 * Note: if two requests come in concurrently, we might let them 6426 * both succeed, when one of them should fail. Not a huge deal. 6427 */ 6428 6429 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 6430 anon_size > arc_c / 4) { 6431 uint64_t meta_esize = 6432 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6433 uint64_t data_esize = 6434 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6435 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 6436 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 6437 arc_tempreserve >> 10, meta_esize >> 10, 6438 data_esize >> 10, reserve >> 10, arc_c >> 10); 6439 return (SET_ERROR(ERESTART)); 6440 } 6441 atomic_add_64(&arc_tempreserve, reserve); 6442 return (0); 6443} 6444 6445static void 6446arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 6447 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 6448{ 6449 size->value.ui64 = refcount_count(&state->arcs_size); 6450 evict_data->value.ui64 = 6451 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 6452 evict_metadata->value.ui64 = 6453 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 6454} 6455 6456static int 6457arc_kstat_update(kstat_t *ksp, int rw) 6458{ 6459 arc_stats_t *as = ksp->ks_data; 6460 6461 if (rw == KSTAT_WRITE) { 6462 return (EACCES); 6463 } else { 6464 arc_kstat_update_state(arc_anon, 6465 &as->arcstat_anon_size, 6466 &as->arcstat_anon_evictable_data, 6467 &as->arcstat_anon_evictable_metadata); 6468 arc_kstat_update_state(arc_mru, 6469 &as->arcstat_mru_size, 6470 &as->arcstat_mru_evictable_data, 6471 &as->arcstat_mru_evictable_metadata); 6472 arc_kstat_update_state(arc_mru_ghost, 6473 &as->arcstat_mru_ghost_size, 6474 &as->arcstat_mru_ghost_evictable_data, 6475 &as->arcstat_mru_ghost_evictable_metadata); 6476 arc_kstat_update_state(arc_mfu, 6477 &as->arcstat_mfu_size, 6478 &as->arcstat_mfu_evictable_data, 6479 &as->arcstat_mfu_evictable_metadata); 6480 arc_kstat_update_state(arc_mfu_ghost, 6481 &as->arcstat_mfu_ghost_size, 6482 &as->arcstat_mfu_ghost_evictable_data, 6483 &as->arcstat_mfu_ghost_evictable_metadata); 6484 6485 ARCSTAT(arcstat_size) = aggsum_value(&arc_size); 6486 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used); 6487 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size); 6488 ARCSTAT(arcstat_metadata_size) = 6489 aggsum_value(&astat_metadata_size); 6490 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size); 6491 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_other_size); 6492 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size); 6493 } 6494 6495 return (0); 6496} 6497 6498/* 6499 * This function *must* return indices evenly distributed between all 6500 * sublists of the multilist. This is needed due to how the ARC eviction 6501 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 6502 * distributed between all sublists and uses this assumption when 6503 * deciding which sublist to evict from and how much to evict from it. 6504 */ 6505unsigned int 6506arc_state_multilist_index_func(multilist_t *ml, void *obj) 6507{ 6508 arc_buf_hdr_t *hdr = obj; 6509 6510 /* 6511 * We rely on b_dva to generate evenly distributed index 6512 * numbers using buf_hash below. So, as an added precaution, 6513 * let's make sure we never add empty buffers to the arc lists. 6514 */ 6515 ASSERT(!HDR_EMPTY(hdr)); 6516 6517 /* 6518 * The assumption here, is the hash value for a given 6519 * arc_buf_hdr_t will remain constant throughout it's lifetime 6520 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 6521 * Thus, we don't need to store the header's sublist index 6522 * on insertion, as this index can be recalculated on removal. 6523 * 6524 * Also, the low order bits of the hash value are thought to be 6525 * distributed evenly. Otherwise, in the case that the multilist 6526 * has a power of two number of sublists, each sublists' usage 6527 * would not be evenly distributed. 6528 */ 6529 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 6530 multilist_get_num_sublists(ml)); 6531} 6532 6533#ifdef _KERNEL 6534static eventhandler_tag arc_event_lowmem = NULL; 6535 6536static void 6537arc_lowmem(void *arg __unused, int howto __unused) 6538{ 6539 6540 mutex_enter(&arc_reclaim_lock); 6541 DTRACE_PROBE1(arc__needfree, int64_t, ((int64_t)freemem - zfs_arc_free_target) * PAGESIZE); 6542 cv_signal(&arc_reclaim_thread_cv); 6543 6544 /* 6545 * It is unsafe to block here in arbitrary threads, because we can come 6546 * here from ARC itself and may hold ARC locks and thus risk a deadlock 6547 * with ARC reclaim thread. 6548 */ 6549 if (curproc == pageproc) 6550 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 6551 mutex_exit(&arc_reclaim_lock); 6552} 6553#endif 6554 6555static void 6556arc_state_init(void) 6557{ 6558 arc_anon = &ARC_anon; 6559 arc_mru = &ARC_mru; 6560 arc_mru_ghost = &ARC_mru_ghost; 6561 arc_mfu = &ARC_mfu; 6562 arc_mfu_ghost = &ARC_mfu_ghost; 6563 arc_l2c_only = &ARC_l2c_only; 6564 6565 arc_mru->arcs_list[ARC_BUFC_METADATA] = 6566 multilist_create(sizeof (arc_buf_hdr_t), 6567 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6568 arc_state_multilist_index_func); 6569 arc_mru->arcs_list[ARC_BUFC_DATA] = 6570 multilist_create(sizeof (arc_buf_hdr_t), 6571 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6572 arc_state_multilist_index_func); 6573 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = 6574 multilist_create(sizeof (arc_buf_hdr_t), 6575 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6576 arc_state_multilist_index_func); 6577 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = 6578 multilist_create(sizeof (arc_buf_hdr_t), 6579 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6580 arc_state_multilist_index_func); 6581 arc_mfu->arcs_list[ARC_BUFC_METADATA] = 6582 multilist_create(sizeof (arc_buf_hdr_t), 6583 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6584 arc_state_multilist_index_func); 6585 arc_mfu->arcs_list[ARC_BUFC_DATA] = 6586 multilist_create(sizeof (arc_buf_hdr_t), 6587 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6588 arc_state_multilist_index_func); 6589 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = 6590 multilist_create(sizeof (arc_buf_hdr_t), 6591 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6592 arc_state_multilist_index_func); 6593 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = 6594 multilist_create(sizeof (arc_buf_hdr_t), 6595 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6596 arc_state_multilist_index_func); 6597 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = 6598 multilist_create(sizeof (arc_buf_hdr_t), 6599 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6600 arc_state_multilist_index_func); 6601 arc_l2c_only->arcs_list[ARC_BUFC_DATA] = 6602 multilist_create(sizeof (arc_buf_hdr_t), 6603 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6604 arc_state_multilist_index_func); 6605 6606 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6607 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6608 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6609 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6610 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6611 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6612 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6613 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6614 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6615 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6616 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6617 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6618 6619 refcount_create(&arc_anon->arcs_size); 6620 refcount_create(&arc_mru->arcs_size); 6621 refcount_create(&arc_mru_ghost->arcs_size); 6622 refcount_create(&arc_mfu->arcs_size); 6623 refcount_create(&arc_mfu_ghost->arcs_size); 6624 refcount_create(&arc_l2c_only->arcs_size); 6625 6626 aggsum_init(&arc_meta_used, 0); 6627 aggsum_init(&arc_size, 0); 6628 aggsum_init(&astat_data_size, 0); 6629 aggsum_init(&astat_metadata_size, 0); 6630 aggsum_init(&astat_hdr_size, 0); 6631 aggsum_init(&astat_other_size, 0); 6632 aggsum_init(&astat_l2_hdr_size, 0); 6633} 6634 6635static void 6636arc_state_fini(void) 6637{ 6638 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6639 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6640 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6641 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6642 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6643 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6644 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6645 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6646 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6647 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6648 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6649 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6650 6651 refcount_destroy(&arc_anon->arcs_size); 6652 refcount_destroy(&arc_mru->arcs_size); 6653 refcount_destroy(&arc_mru_ghost->arcs_size); 6654 refcount_destroy(&arc_mfu->arcs_size); 6655 refcount_destroy(&arc_mfu_ghost->arcs_size); 6656 refcount_destroy(&arc_l2c_only->arcs_size); 6657 6658 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); 6659 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 6660 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); 6661 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 6662 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); 6663 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 6664 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); 6665 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 6666} 6667 6668uint64_t 6669arc_max_bytes(void) 6670{ 6671 return (arc_c_max); 6672} 6673 6674void 6675arc_init(void) 6676{ 6677 int i, prefetch_tunable_set = 0; 6678 6679 /* 6680 * allmem is "all memory that we could possibly use". 6681 */ 6682#ifdef illumos 6683#ifdef _KERNEL 6684 uint64_t allmem = ptob(physmem - swapfs_minfree); 6685#else 6686 uint64_t allmem = (physmem * PAGESIZE) / 2; 6687#endif 6688#else 6689 uint64_t allmem = kmem_size(); 6690#endif 6691 6692 6693 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 6694 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 6695 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 6696 6697 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 6698 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 6699 6700 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 6701 arc_c_min = MAX(allmem / 32, arc_abs_min); 6702 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ 6703 if (allmem >= 1 << 30) 6704 arc_c_max = allmem - (1 << 30); 6705 else 6706 arc_c_max = arc_c_min; 6707 arc_c_max = MAX(allmem * 5 / 8, arc_c_max); 6708 6709 /* 6710 * In userland, there's only the memory pressure that we artificially 6711 * create (see arc_available_memory()). Don't let arc_c get too 6712 * small, because it can cause transactions to be larger than 6713 * arc_c, causing arc_tempreserve_space() to fail. 6714 */ 6715#ifndef _KERNEL 6716 arc_c_min = arc_c_max / 2; 6717#endif 6718 6719#ifdef _KERNEL 6720 /* 6721 * Allow the tunables to override our calculations if they are 6722 * reasonable. 6723 */ 6724 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { 6725 arc_c_max = zfs_arc_max; 6726 arc_c_min = MIN(arc_c_min, arc_c_max); 6727 } 6728 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6729 arc_c_min = zfs_arc_min; 6730#endif 6731 6732 arc_c = arc_c_max; 6733 arc_p = (arc_c >> 1); 6734 6735 /* limit meta-data to 1/4 of the arc capacity */ 6736 arc_meta_limit = arc_c_max / 4; 6737 6738#ifdef _KERNEL 6739 /* 6740 * Metadata is stored in the kernel's heap. Don't let us 6741 * use more than half the heap for the ARC. 6742 */ 6743 arc_meta_limit = MIN(arc_meta_limit, 6744 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 6745#endif 6746 6747 /* Allow the tunable to override if it is reasonable */ 6748 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6749 arc_meta_limit = zfs_arc_meta_limit; 6750 6751 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6752 arc_c_min = arc_meta_limit / 2; 6753 6754 if (zfs_arc_meta_min > 0) { 6755 arc_meta_min = zfs_arc_meta_min; 6756 } else { 6757 arc_meta_min = arc_c_min / 2; 6758 } 6759 6760 if (zfs_arc_grow_retry > 0) 6761 arc_grow_retry = zfs_arc_grow_retry; 6762 6763 if (zfs_arc_shrink_shift > 0) 6764 arc_shrink_shift = zfs_arc_shrink_shift; 6765 6766 if (zfs_arc_no_grow_shift > 0) 6767 arc_no_grow_shift = zfs_arc_no_grow_shift; 6768 /* 6769 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6770 */ 6771 if (arc_no_grow_shift >= arc_shrink_shift) 6772 arc_no_grow_shift = arc_shrink_shift - 1; 6773 6774 if (zfs_arc_p_min_shift > 0) 6775 arc_p_min_shift = zfs_arc_p_min_shift; 6776 6777 /* if kmem_flags are set, lets try to use less memory */ 6778 if (kmem_debugging()) 6779 arc_c = arc_c / 2; 6780 if (arc_c < arc_c_min) 6781 arc_c = arc_c_min; 6782 6783 zfs_arc_min = arc_c_min; 6784 zfs_arc_max = arc_c_max; 6785 6786 arc_state_init(); 6787 buf_init(); 6788 6789 arc_reclaim_thread_exit = B_FALSE; 6790 arc_dnlc_evicts_thread_exit = FALSE; 6791 6792 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6793 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6794 6795 if (arc_ksp != NULL) { 6796 arc_ksp->ks_data = &arc_stats; 6797 arc_ksp->ks_update = arc_kstat_update; 6798 kstat_install(arc_ksp); 6799 } 6800 6801 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6802 TS_RUN, minclsyspri); 6803 6804#ifdef _KERNEL 6805 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6806 EVENTHANDLER_PRI_FIRST); 6807#endif 6808 6809 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 6810 TS_RUN, minclsyspri); 6811 6812 arc_dead = B_FALSE; 6813 arc_warm = B_FALSE; 6814 6815 /* 6816 * Calculate maximum amount of dirty data per pool. 6817 * 6818 * If it has been set by /etc/system, take that. 6819 * Otherwise, use a percentage of physical memory defined by 6820 * zfs_dirty_data_max_percent (default 10%) with a cap at 6821 * zfs_dirty_data_max_max (default 4GB). 6822 */ 6823 if (zfs_dirty_data_max == 0) { 6824 zfs_dirty_data_max = ptob(physmem) * 6825 zfs_dirty_data_max_percent / 100; 6826 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6827 zfs_dirty_data_max_max); 6828 } 6829 6830#ifdef _KERNEL 6831 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6832 prefetch_tunable_set = 1; 6833 6834#ifdef __i386__ 6835 if (prefetch_tunable_set == 0) { 6836 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6837 "-- to enable,\n"); 6838 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6839 "to /boot/loader.conf.\n"); 6840 zfs_prefetch_disable = 1; 6841 } 6842#else 6843 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6844 prefetch_tunable_set == 0) { 6845 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6846 "than 4GB of RAM is present;\n" 6847 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6848 "to /boot/loader.conf.\n"); 6849 zfs_prefetch_disable = 1; 6850 } 6851#endif 6852 /* Warn about ZFS memory and address space requirements. */ 6853 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6854 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6855 "expect unstable behavior.\n"); 6856 } 6857 if (allmem < 512 * (1 << 20)) { 6858 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6859 "expect unstable behavior.\n"); 6860 printf(" Consider tuning vm.kmem_size and " 6861 "vm.kmem_size_max\n"); 6862 printf(" in /boot/loader.conf.\n"); 6863 } 6864#endif 6865} 6866 6867void 6868arc_fini(void) 6869{ 6870#ifdef _KERNEL 6871 if (arc_event_lowmem != NULL) 6872 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6873#endif 6874 6875 mutex_enter(&arc_reclaim_lock); 6876 arc_reclaim_thread_exit = B_TRUE; 6877 /* 6878 * The reclaim thread will set arc_reclaim_thread_exit back to 6879 * B_FALSE when it is finished exiting; we're waiting for that. 6880 */ 6881 while (arc_reclaim_thread_exit) { 6882 cv_signal(&arc_reclaim_thread_cv); 6883 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6884 } 6885 mutex_exit(&arc_reclaim_lock); 6886 6887 /* Use B_TRUE to ensure *all* buffers are evicted */ 6888 arc_flush(NULL, B_TRUE); 6889 6890 mutex_enter(&arc_dnlc_evicts_lock); 6891 arc_dnlc_evicts_thread_exit = TRUE; 6892 /* 6893 * The user evicts thread will set arc_user_evicts_thread_exit 6894 * to FALSE when it is finished exiting; we're waiting for that. 6895 */ 6896 while (arc_dnlc_evicts_thread_exit) { 6897 cv_signal(&arc_dnlc_evicts_cv); 6898 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 6899 } 6900 mutex_exit(&arc_dnlc_evicts_lock); 6901 6902 arc_dead = B_TRUE; 6903 6904 if (arc_ksp != NULL) { 6905 kstat_delete(arc_ksp); 6906 arc_ksp = NULL; 6907 } 6908 6909 mutex_destroy(&arc_reclaim_lock); 6910 cv_destroy(&arc_reclaim_thread_cv); 6911 cv_destroy(&arc_reclaim_waiters_cv); 6912 6913 mutex_destroy(&arc_dnlc_evicts_lock); 6914 cv_destroy(&arc_dnlc_evicts_cv); 6915 6916 arc_state_fini(); 6917 buf_fini(); 6918 6919 ASSERT0(arc_loaned_bytes); 6920} 6921 6922/* 6923 * Level 2 ARC 6924 * 6925 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6926 * It uses dedicated storage devices to hold cached data, which are populated 6927 * using large infrequent writes. The main role of this cache is to boost 6928 * the performance of random read workloads. The intended L2ARC devices 6929 * include short-stroked disks, solid state disks, and other media with 6930 * substantially faster read latency than disk. 6931 * 6932 * +-----------------------+ 6933 * | ARC | 6934 * +-----------------------+ 6935 * | ^ ^ 6936 * | | | 6937 * l2arc_feed_thread() arc_read() 6938 * | | | 6939 * | l2arc read | 6940 * V | | 6941 * +---------------+ | 6942 * | L2ARC | | 6943 * +---------------+ | 6944 * | ^ | 6945 * l2arc_write() | | 6946 * | | | 6947 * V | | 6948 * +-------+ +-------+ 6949 * | vdev | | vdev | 6950 * | cache | | cache | 6951 * +-------+ +-------+ 6952 * +=========+ .-----. 6953 * : L2ARC : |-_____-| 6954 * : devices : | Disks | 6955 * +=========+ `-_____-' 6956 * 6957 * Read requests are satisfied from the following sources, in order: 6958 * 6959 * 1) ARC 6960 * 2) vdev cache of L2ARC devices 6961 * 3) L2ARC devices 6962 * 4) vdev cache of disks 6963 * 5) disks 6964 * 6965 * Some L2ARC device types exhibit extremely slow write performance. 6966 * To accommodate for this there are some significant differences between 6967 * the L2ARC and traditional cache design: 6968 * 6969 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6970 * the ARC behave as usual, freeing buffers and placing headers on ghost 6971 * lists. The ARC does not send buffers to the L2ARC during eviction as 6972 * this would add inflated write latencies for all ARC memory pressure. 6973 * 6974 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6975 * It does this by periodically scanning buffers from the eviction-end of 6976 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6977 * not already there. It scans until a headroom of buffers is satisfied, 6978 * which itself is a buffer for ARC eviction. If a compressible buffer is 6979 * found during scanning and selected for writing to an L2ARC device, we 6980 * temporarily boost scanning headroom during the next scan cycle to make 6981 * sure we adapt to compression effects (which might significantly reduce 6982 * the data volume we write to L2ARC). The thread that does this is 6983 * l2arc_feed_thread(), illustrated below; example sizes are included to 6984 * provide a better sense of ratio than this diagram: 6985 * 6986 * head --> tail 6987 * +---------------------+----------+ 6988 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6989 * +---------------------+----------+ | o L2ARC eligible 6990 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6991 * +---------------------+----------+ | 6992 * 15.9 Gbytes ^ 32 Mbytes | 6993 * headroom | 6994 * l2arc_feed_thread() 6995 * | 6996 * l2arc write hand <--[oooo]--' 6997 * | 8 Mbyte 6998 * | write max 6999 * V 7000 * +==============================+ 7001 * L2ARC dev |####|#|###|###| |####| ... | 7002 * +==============================+ 7003 * 32 Gbytes 7004 * 7005 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 7006 * evicted, then the L2ARC has cached a buffer much sooner than it probably 7007 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 7008 * safe to say that this is an uncommon case, since buffers at the end of 7009 * the ARC lists have moved there due to inactivity. 7010 * 7011 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 7012 * then the L2ARC simply misses copying some buffers. This serves as a 7013 * pressure valve to prevent heavy read workloads from both stalling the ARC 7014 * with waits and clogging the L2ARC with writes. This also helps prevent 7015 * the potential for the L2ARC to churn if it attempts to cache content too 7016 * quickly, such as during backups of the entire pool. 7017 * 7018 * 5. After system boot and before the ARC has filled main memory, there are 7019 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 7020 * lists can remain mostly static. Instead of searching from tail of these 7021 * lists as pictured, the l2arc_feed_thread() will search from the list heads 7022 * for eligible buffers, greatly increasing its chance of finding them. 7023 * 7024 * The L2ARC device write speed is also boosted during this time so that 7025 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 7026 * there are no L2ARC reads, and no fear of degrading read performance 7027 * through increased writes. 7028 * 7029 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 7030 * the vdev queue can aggregate them into larger and fewer writes. Each 7031 * device is written to in a rotor fashion, sweeping writes through 7032 * available space then repeating. 7033 * 7034 * 7. The L2ARC does not store dirty content. It never needs to flush 7035 * write buffers back to disk based storage. 7036 * 7037 * 8. If an ARC buffer is written (and dirtied) which also exists in the 7038 * L2ARC, the now stale L2ARC buffer is immediately dropped. 7039 * 7040 * The performance of the L2ARC can be tweaked by a number of tunables, which 7041 * may be necessary for different workloads: 7042 * 7043 * l2arc_write_max max write bytes per interval 7044 * l2arc_write_boost extra write bytes during device warmup 7045 * l2arc_noprefetch skip caching prefetched buffers 7046 * l2arc_headroom number of max device writes to precache 7047 * l2arc_headroom_boost when we find compressed buffers during ARC 7048 * scanning, we multiply headroom by this 7049 * percentage factor for the next scan cycle, 7050 * since more compressed buffers are likely to 7051 * be present 7052 * l2arc_feed_secs seconds between L2ARC writing 7053 * 7054 * Tunables may be removed or added as future performance improvements are 7055 * integrated, and also may become zpool properties. 7056 * 7057 * There are three key functions that control how the L2ARC warms up: 7058 * 7059 * l2arc_write_eligible() check if a buffer is eligible to cache 7060 * l2arc_write_size() calculate how much to write 7061 * l2arc_write_interval() calculate sleep delay between writes 7062 * 7063 * These three functions determine what to write, how much, and how quickly 7064 * to send writes. 7065 */ 7066 7067static boolean_t 7068l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 7069{ 7070 /* 7071 * A buffer is *not* eligible for the L2ARC if it: 7072 * 1. belongs to a different spa. 7073 * 2. is already cached on the L2ARC. 7074 * 3. has an I/O in progress (it may be an incomplete read). 7075 * 4. is flagged not eligible (zfs property). 7076 */ 7077 if (hdr->b_spa != spa_guid) { 7078 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 7079 return (B_FALSE); 7080 } 7081 if (HDR_HAS_L2HDR(hdr)) { 7082 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 7083 return (B_FALSE); 7084 } 7085 if (HDR_IO_IN_PROGRESS(hdr)) { 7086 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 7087 return (B_FALSE); 7088 } 7089 if (!HDR_L2CACHE(hdr)) { 7090 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 7091 return (B_FALSE); 7092 } 7093 7094 return (B_TRUE); 7095} 7096 7097static uint64_t 7098l2arc_write_size(void) 7099{ 7100 uint64_t size; 7101 7102 /* 7103 * Make sure our globals have meaningful values in case the user 7104 * altered them. 7105 */ 7106 size = l2arc_write_max; 7107 if (size == 0) { 7108 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 7109 "be greater than zero, resetting it to the default (%d)", 7110 L2ARC_WRITE_SIZE); 7111 size = l2arc_write_max = L2ARC_WRITE_SIZE; 7112 } 7113 7114 if (arc_warm == B_FALSE) 7115 size += l2arc_write_boost; 7116 7117 return (size); 7118 7119} 7120 7121static clock_t 7122l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 7123{ 7124 clock_t interval, next, now; 7125 7126 /* 7127 * If the ARC lists are busy, increase our write rate; if the 7128 * lists are stale, idle back. This is achieved by checking 7129 * how much we previously wrote - if it was more than half of 7130 * what we wanted, schedule the next write much sooner. 7131 */ 7132 if (l2arc_feed_again && wrote > (wanted / 2)) 7133 interval = (hz * l2arc_feed_min_ms) / 1000; 7134 else 7135 interval = hz * l2arc_feed_secs; 7136 7137 now = ddi_get_lbolt(); 7138 next = MAX(now, MIN(now + interval, began + interval)); 7139 7140 return (next); 7141} 7142 7143/* 7144 * Cycle through L2ARC devices. This is how L2ARC load balances. 7145 * If a device is returned, this also returns holding the spa config lock. 7146 */ 7147static l2arc_dev_t * 7148l2arc_dev_get_next(void) 7149{ 7150 l2arc_dev_t *first, *next = NULL; 7151 7152 /* 7153 * Lock out the removal of spas (spa_namespace_lock), then removal 7154 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 7155 * both locks will be dropped and a spa config lock held instead. 7156 */ 7157 mutex_enter(&spa_namespace_lock); 7158 mutex_enter(&l2arc_dev_mtx); 7159 7160 /* if there are no vdevs, there is nothing to do */ 7161 if (l2arc_ndev == 0) 7162 goto out; 7163 7164 first = NULL; 7165 next = l2arc_dev_last; 7166 do { 7167 /* loop around the list looking for a non-faulted vdev */ 7168 if (next == NULL) { 7169 next = list_head(l2arc_dev_list); 7170 } else { 7171 next = list_next(l2arc_dev_list, next); 7172 if (next == NULL) 7173 next = list_head(l2arc_dev_list); 7174 } 7175 7176 /* if we have come back to the start, bail out */ 7177 if (first == NULL) 7178 first = next; 7179 else if (next == first) 7180 break; 7181 7182 } while (vdev_is_dead(next->l2ad_vdev)); 7183 7184 /* if we were unable to find any usable vdevs, return NULL */ 7185 if (vdev_is_dead(next->l2ad_vdev)) 7186 next = NULL; 7187 7188 l2arc_dev_last = next; 7189 7190out: 7191 mutex_exit(&l2arc_dev_mtx); 7192 7193 /* 7194 * Grab the config lock to prevent the 'next' device from being 7195 * removed while we are writing to it. 7196 */ 7197 if (next != NULL) 7198 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 7199 mutex_exit(&spa_namespace_lock); 7200 7201 return (next); 7202} 7203 7204/* 7205 * Free buffers that were tagged for destruction. 7206 */ 7207static void 7208l2arc_do_free_on_write() 7209{ 7210 list_t *buflist; 7211 l2arc_data_free_t *df, *df_prev; 7212 7213 mutex_enter(&l2arc_free_on_write_mtx); 7214 buflist = l2arc_free_on_write; 7215 7216 for (df = list_tail(buflist); df; df = df_prev) { 7217 df_prev = list_prev(buflist, df); 7218 ASSERT3P(df->l2df_abd, !=, NULL); 7219 abd_free(df->l2df_abd); 7220 list_remove(buflist, df); 7221 kmem_free(df, sizeof (l2arc_data_free_t)); 7222 } 7223 7224 mutex_exit(&l2arc_free_on_write_mtx); 7225} 7226 7227/* 7228 * A write to a cache device has completed. Update all headers to allow 7229 * reads from these buffers to begin. 7230 */ 7231static void 7232l2arc_write_done(zio_t *zio) 7233{ 7234 l2arc_write_callback_t *cb; 7235 l2arc_dev_t *dev; 7236 list_t *buflist; 7237 arc_buf_hdr_t *head, *hdr, *hdr_prev; 7238 kmutex_t *hash_lock; 7239 int64_t bytes_dropped = 0; 7240 7241 cb = zio->io_private; 7242 ASSERT3P(cb, !=, NULL); 7243 dev = cb->l2wcb_dev; 7244 ASSERT3P(dev, !=, NULL); 7245 head = cb->l2wcb_head; 7246 ASSERT3P(head, !=, NULL); 7247 buflist = &dev->l2ad_buflist; 7248 ASSERT3P(buflist, !=, NULL); 7249 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 7250 l2arc_write_callback_t *, cb); 7251 7252 if (zio->io_error != 0) 7253 ARCSTAT_BUMP(arcstat_l2_writes_error); 7254 7255 /* 7256 * All writes completed, or an error was hit. 7257 */ 7258top: 7259 mutex_enter(&dev->l2ad_mtx); 7260 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 7261 hdr_prev = list_prev(buflist, hdr); 7262 7263 hash_lock = HDR_LOCK(hdr); 7264 7265 /* 7266 * We cannot use mutex_enter or else we can deadlock 7267 * with l2arc_write_buffers (due to swapping the order 7268 * the hash lock and l2ad_mtx are taken). 7269 */ 7270 if (!mutex_tryenter(hash_lock)) { 7271 /* 7272 * Missed the hash lock. We must retry so we 7273 * don't leave the ARC_FLAG_L2_WRITING bit set. 7274 */ 7275 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 7276 7277 /* 7278 * We don't want to rescan the headers we've 7279 * already marked as having been written out, so 7280 * we reinsert the head node so we can pick up 7281 * where we left off. 7282 */ 7283 list_remove(buflist, head); 7284 list_insert_after(buflist, hdr, head); 7285 7286 mutex_exit(&dev->l2ad_mtx); 7287 7288 /* 7289 * We wait for the hash lock to become available 7290 * to try and prevent busy waiting, and increase 7291 * the chance we'll be able to acquire the lock 7292 * the next time around. 7293 */ 7294 mutex_enter(hash_lock); 7295 mutex_exit(hash_lock); 7296 goto top; 7297 } 7298 7299 /* 7300 * We could not have been moved into the arc_l2c_only 7301 * state while in-flight due to our ARC_FLAG_L2_WRITING 7302 * bit being set. Let's just ensure that's being enforced. 7303 */ 7304 ASSERT(HDR_HAS_L1HDR(hdr)); 7305 7306 if (zio->io_error != 0) { 7307 /* 7308 * Error - drop L2ARC entry. 7309 */ 7310 list_remove(buflist, hdr); 7311 l2arc_trim(hdr); 7312 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 7313 7314 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr)); 7315 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 7316 7317 bytes_dropped += arc_hdr_size(hdr); 7318 (void) refcount_remove_many(&dev->l2ad_alloc, 7319 arc_hdr_size(hdr), hdr); 7320 } 7321 7322 /* 7323 * Allow ARC to begin reads and ghost list evictions to 7324 * this L2ARC entry. 7325 */ 7326 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 7327 7328 mutex_exit(hash_lock); 7329 } 7330 7331 atomic_inc_64(&l2arc_writes_done); 7332 list_remove(buflist, head); 7333 ASSERT(!HDR_HAS_L1HDR(head)); 7334 kmem_cache_free(hdr_l2only_cache, head); 7335 mutex_exit(&dev->l2ad_mtx); 7336 7337 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 7338 7339 l2arc_do_free_on_write(); 7340 7341 kmem_free(cb, sizeof (l2arc_write_callback_t)); 7342} 7343 7344/* 7345 * A read to a cache device completed. Validate buffer contents before 7346 * handing over to the regular ARC routines. 7347 */ 7348static void 7349l2arc_read_done(zio_t *zio) 7350{ 7351 l2arc_read_callback_t *cb; 7352 arc_buf_hdr_t *hdr; 7353 kmutex_t *hash_lock; 7354 boolean_t valid_cksum; 7355 7356 ASSERT3P(zio->io_vd, !=, NULL); 7357 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 7358 7359 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 7360 7361 cb = zio->io_private; 7362 ASSERT3P(cb, !=, NULL); 7363 hdr = cb->l2rcb_hdr; 7364 ASSERT3P(hdr, !=, NULL); 7365 7366 hash_lock = HDR_LOCK(hdr); 7367 mutex_enter(hash_lock); 7368 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 7369 7370 /* 7371 * If the data was read into a temporary buffer, 7372 * move it and free the buffer. 7373 */ 7374 if (cb->l2rcb_abd != NULL) { 7375 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 7376 if (zio->io_error == 0) { 7377 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd, 7378 arc_hdr_size(hdr)); 7379 } 7380 7381 /* 7382 * The following must be done regardless of whether 7383 * there was an error: 7384 * - free the temporary buffer 7385 * - point zio to the real ARC buffer 7386 * - set zio size accordingly 7387 * These are required because zio is either re-used for 7388 * an I/O of the block in the case of the error 7389 * or the zio is passed to arc_read_done() and it 7390 * needs real data. 7391 */ 7392 abd_free(cb->l2rcb_abd); 7393 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 7394 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; 7395 } 7396 7397 ASSERT3P(zio->io_abd, !=, NULL); 7398 7399 /* 7400 * Check this survived the L2ARC journey. 7401 */ 7402 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); 7403 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 7404 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 7405 7406 valid_cksum = arc_cksum_is_equal(hdr, zio); 7407 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 7408 mutex_exit(hash_lock); 7409 zio->io_private = hdr; 7410 arc_read_done(zio); 7411 } else { 7412 mutex_exit(hash_lock); 7413 /* 7414 * Buffer didn't survive caching. Increment stats and 7415 * reissue to the original storage device. 7416 */ 7417 if (zio->io_error != 0) { 7418 ARCSTAT_BUMP(arcstat_l2_io_error); 7419 } else { 7420 zio->io_error = SET_ERROR(EIO); 7421 } 7422 if (!valid_cksum) 7423 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 7424 7425 /* 7426 * If there's no waiter, issue an async i/o to the primary 7427 * storage now. If there *is* a waiter, the caller must 7428 * issue the i/o in a context where it's OK to block. 7429 */ 7430 if (zio->io_waiter == NULL) { 7431 zio_t *pio = zio_unique_parent(zio); 7432 7433 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 7434 7435 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 7436 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, 7437 hdr, zio->io_priority, cb->l2rcb_flags, 7438 &cb->l2rcb_zb)); 7439 } 7440 } 7441 7442 kmem_free(cb, sizeof (l2arc_read_callback_t)); 7443} 7444 7445/* 7446 * This is the list priority from which the L2ARC will search for pages to 7447 * cache. This is used within loops (0..3) to cycle through lists in the 7448 * desired order. This order can have a significant effect on cache 7449 * performance. 7450 * 7451 * Currently the metadata lists are hit first, MFU then MRU, followed by 7452 * the data lists. This function returns a locked list, and also returns 7453 * the lock pointer. 7454 */ 7455static multilist_sublist_t * 7456l2arc_sublist_lock(int list_num) 7457{ 7458 multilist_t *ml = NULL; 7459 unsigned int idx; 7460 7461 ASSERT(list_num >= 0 && list_num <= 3); 7462 7463 switch (list_num) { 7464 case 0: 7465 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; 7466 break; 7467 case 1: 7468 ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; 7469 break; 7470 case 2: 7471 ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; 7472 break; 7473 case 3: 7474 ml = arc_mru->arcs_list[ARC_BUFC_DATA]; 7475 break; 7476 } 7477 7478 /* 7479 * Return a randomly-selected sublist. This is acceptable 7480 * because the caller feeds only a little bit of data for each 7481 * call (8MB). Subsequent calls will result in different 7482 * sublists being selected. 7483 */ 7484 idx = multilist_get_random_index(ml); 7485 return (multilist_sublist_lock(ml, idx)); 7486} 7487 7488/* 7489 * Evict buffers from the device write hand to the distance specified in 7490 * bytes. This distance may span populated buffers, it may span nothing. 7491 * This is clearing a region on the L2ARC device ready for writing. 7492 * If the 'all' boolean is set, every buffer is evicted. 7493 */ 7494static void 7495l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 7496{ 7497 list_t *buflist; 7498 arc_buf_hdr_t *hdr, *hdr_prev; 7499 kmutex_t *hash_lock; 7500 uint64_t taddr; 7501 7502 buflist = &dev->l2ad_buflist; 7503 7504 if (!all && dev->l2ad_first) { 7505 /* 7506 * This is the first sweep through the device. There is 7507 * nothing to evict. 7508 */ 7509 return; 7510 } 7511 7512 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 7513 /* 7514 * When nearing the end of the device, evict to the end 7515 * before the device write hand jumps to the start. 7516 */ 7517 taddr = dev->l2ad_end; 7518 } else { 7519 taddr = dev->l2ad_hand + distance; 7520 } 7521 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 7522 uint64_t, taddr, boolean_t, all); 7523 7524top: 7525 mutex_enter(&dev->l2ad_mtx); 7526 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 7527 hdr_prev = list_prev(buflist, hdr); 7528 7529 hash_lock = HDR_LOCK(hdr); 7530 7531 /* 7532 * We cannot use mutex_enter or else we can deadlock 7533 * with l2arc_write_buffers (due to swapping the order 7534 * the hash lock and l2ad_mtx are taken). 7535 */ 7536 if (!mutex_tryenter(hash_lock)) { 7537 /* 7538 * Missed the hash lock. Retry. 7539 */ 7540 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 7541 mutex_exit(&dev->l2ad_mtx); 7542 mutex_enter(hash_lock); 7543 mutex_exit(hash_lock); 7544 goto top; 7545 } 7546 7547 /* 7548 * A header can't be on this list if it doesn't have L2 header. 7549 */ 7550 ASSERT(HDR_HAS_L2HDR(hdr)); 7551 7552 /* Ensure this header has finished being written. */ 7553 ASSERT(!HDR_L2_WRITING(hdr)); 7554 ASSERT(!HDR_L2_WRITE_HEAD(hdr)); 7555 7556 if (!all && (hdr->b_l2hdr.b_daddr >= taddr || 7557 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 7558 /* 7559 * We've evicted to the target address, 7560 * or the end of the device. 7561 */ 7562 mutex_exit(hash_lock); 7563 break; 7564 } 7565 7566 if (!HDR_HAS_L1HDR(hdr)) { 7567 ASSERT(!HDR_L2_READING(hdr)); 7568 /* 7569 * This doesn't exist in the ARC. Destroy. 7570 * arc_hdr_destroy() will call list_remove() 7571 * and decrement arcstat_l2_lsize. 7572 */ 7573 arc_change_state(arc_anon, hdr, hash_lock); 7574 arc_hdr_destroy(hdr); 7575 } else { 7576 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 7577 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 7578 /* 7579 * Invalidate issued or about to be issued 7580 * reads, since we may be about to write 7581 * over this location. 7582 */ 7583 if (HDR_L2_READING(hdr)) { 7584 ARCSTAT_BUMP(arcstat_l2_evict_reading); 7585 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 7586 } 7587 7588 arc_hdr_l2hdr_destroy(hdr); 7589 } 7590 mutex_exit(hash_lock); 7591 } 7592 mutex_exit(&dev->l2ad_mtx); 7593} 7594 7595/* 7596 * Find and write ARC buffers to the L2ARC device. 7597 * 7598 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 7599 * for reading until they have completed writing. 7600 * The headroom_boost is an in-out parameter used to maintain headroom boost 7601 * state between calls to this function. 7602 * 7603 * Returns the number of bytes actually written (which may be smaller than 7604 * the delta by which the device hand has changed due to alignment). 7605 */ 7606static uint64_t 7607l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 7608{ 7609 arc_buf_hdr_t *hdr, *hdr_prev, *head; 7610 uint64_t write_asize, write_psize, write_lsize, headroom; 7611 boolean_t full; 7612 l2arc_write_callback_t *cb; 7613 zio_t *pio, *wzio; 7614 uint64_t guid = spa_load_guid(spa); 7615 int try; 7616 7617 ASSERT3P(dev->l2ad_vdev, !=, NULL); 7618 7619 pio = NULL; 7620 write_lsize = write_asize = write_psize = 0; 7621 full = B_FALSE; 7622 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 7623 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 7624 7625 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 7626 /* 7627 * Copy buffers for L2ARC writing. 7628 */ 7629 for (try = 0; try <= 3; try++) { 7630 multilist_sublist_t *mls = l2arc_sublist_lock(try); 7631 uint64_t passed_sz = 0; 7632 7633 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 7634 7635 /* 7636 * L2ARC fast warmup. 7637 * 7638 * Until the ARC is warm and starts to evict, read from the 7639 * head of the ARC lists rather than the tail. 7640 */ 7641 if (arc_warm == B_FALSE) 7642 hdr = multilist_sublist_head(mls); 7643 else 7644 hdr = multilist_sublist_tail(mls); 7645 if (hdr == NULL) 7646 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 7647 7648 headroom = target_sz * l2arc_headroom; 7649 if (zfs_compressed_arc_enabled) 7650 headroom = (headroom * l2arc_headroom_boost) / 100; 7651 7652 for (; hdr; hdr = hdr_prev) { 7653 kmutex_t *hash_lock; 7654 7655 if (arc_warm == B_FALSE) 7656 hdr_prev = multilist_sublist_next(mls, hdr); 7657 else 7658 hdr_prev = multilist_sublist_prev(mls, hdr); 7659 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 7660 HDR_GET_LSIZE(hdr)); 7661 7662 hash_lock = HDR_LOCK(hdr); 7663 if (!mutex_tryenter(hash_lock)) { 7664 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 7665 /* 7666 * Skip this buffer rather than waiting. 7667 */ 7668 continue; 7669 } 7670 7671 passed_sz += HDR_GET_LSIZE(hdr); 7672 if (passed_sz > headroom) { 7673 /* 7674 * Searched too far. 7675 */ 7676 mutex_exit(hash_lock); 7677 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 7678 break; 7679 } 7680 7681 if (!l2arc_write_eligible(guid, hdr)) { 7682 mutex_exit(hash_lock); 7683 continue; 7684 } 7685 7686 /* 7687 * We rely on the L1 portion of the header below, so 7688 * it's invalid for this header to have been evicted out 7689 * of the ghost cache, prior to being written out. The 7690 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 7691 */ 7692 ASSERT(HDR_HAS_L1HDR(hdr)); 7693 7694 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 7695 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 7696 ASSERT3U(arc_hdr_size(hdr), >, 0); 7697 uint64_t psize = arc_hdr_size(hdr); 7698 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 7699 psize); 7700 7701 if ((write_asize + asize) > target_sz) { 7702 full = B_TRUE; 7703 mutex_exit(hash_lock); 7704 ARCSTAT_BUMP(arcstat_l2_write_full); 7705 break; 7706 } 7707 7708 if (pio == NULL) { 7709 /* 7710 * Insert a dummy header on the buflist so 7711 * l2arc_write_done() can find where the 7712 * write buffers begin without searching. 7713 */ 7714 mutex_enter(&dev->l2ad_mtx); 7715 list_insert_head(&dev->l2ad_buflist, head); 7716 mutex_exit(&dev->l2ad_mtx); 7717 7718 cb = kmem_alloc( 7719 sizeof (l2arc_write_callback_t), KM_SLEEP); 7720 cb->l2wcb_dev = dev; 7721 cb->l2wcb_head = head; 7722 pio = zio_root(spa, l2arc_write_done, cb, 7723 ZIO_FLAG_CANFAIL); 7724 ARCSTAT_BUMP(arcstat_l2_write_pios); 7725 } 7726 7727 hdr->b_l2hdr.b_dev = dev; 7728 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 7729 arc_hdr_set_flags(hdr, 7730 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 7731 7732 mutex_enter(&dev->l2ad_mtx); 7733 list_insert_head(&dev->l2ad_buflist, hdr); 7734 mutex_exit(&dev->l2ad_mtx); 7735 7736 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr); 7737 7738 /* 7739 * Normally the L2ARC can use the hdr's data, but if 7740 * we're sharing data between the hdr and one of its 7741 * bufs, L2ARC needs its own copy of the data so that 7742 * the ZIO below can't race with the buf consumer. 7743 * Another case where we need to create a copy of the 7744 * data is when the buffer size is not device-aligned 7745 * and we need to pad the block to make it such. 7746 * That also keeps the clock hand suitably aligned. 7747 * 7748 * To ensure that the copy will be available for the 7749 * lifetime of the ZIO and be cleaned up afterwards, we 7750 * add it to the l2arc_free_on_write queue. 7751 */ 7752 abd_t *to_write; 7753 if (!HDR_SHARED_DATA(hdr) && psize == asize) { 7754 to_write = hdr->b_l1hdr.b_pabd; 7755 } else { 7756 to_write = abd_alloc_for_io(asize, 7757 HDR_ISTYPE_METADATA(hdr)); 7758 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize); 7759 if (asize != psize) { 7760 abd_zero_off(to_write, psize, 7761 asize - psize); 7762 } 7763 l2arc_free_abd_on_write(to_write, asize, 7764 arc_buf_type(hdr)); 7765 } 7766 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7767 hdr->b_l2hdr.b_daddr, asize, to_write, 7768 ZIO_CHECKSUM_OFF, NULL, hdr, 7769 ZIO_PRIORITY_ASYNC_WRITE, 7770 ZIO_FLAG_CANFAIL, B_FALSE); 7771 7772 write_lsize += HDR_GET_LSIZE(hdr); 7773 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7774 zio_t *, wzio); 7775 7776 write_psize += psize; 7777 write_asize += asize; 7778 dev->l2ad_hand += asize; 7779 7780 mutex_exit(hash_lock); 7781 7782 (void) zio_nowait(wzio); 7783 } 7784 7785 multilist_sublist_unlock(mls); 7786 7787 if (full == B_TRUE) 7788 break; 7789 } 7790 7791 /* No buffers selected for writing? */ 7792 if (pio == NULL) { 7793 ASSERT0(write_lsize); 7794 ASSERT(!HDR_HAS_L1HDR(head)); 7795 kmem_cache_free(hdr_l2only_cache, head); 7796 return (0); 7797 } 7798 7799 ASSERT3U(write_psize, <=, target_sz); 7800 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7801 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize); 7802 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize); 7803 ARCSTAT_INCR(arcstat_l2_psize, write_psize); 7804 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); 7805 7806 /* 7807 * Bump device hand to the device start if it is approaching the end. 7808 * l2arc_evict() will already have evicted ahead for this case. 7809 */ 7810 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7811 dev->l2ad_hand = dev->l2ad_start; 7812 dev->l2ad_first = B_FALSE; 7813 } 7814 7815 dev->l2ad_writing = B_TRUE; 7816 (void) zio_wait(pio); 7817 dev->l2ad_writing = B_FALSE; 7818 7819 return (write_asize); 7820} 7821 7822/* 7823 * This thread feeds the L2ARC at regular intervals. This is the beating 7824 * heart of the L2ARC. 7825 */ 7826/* ARGSUSED */ 7827static void 7828l2arc_feed_thread(void *unused __unused) 7829{ 7830 callb_cpr_t cpr; 7831 l2arc_dev_t *dev; 7832 spa_t *spa; 7833 uint64_t size, wrote; 7834 clock_t begin, next = ddi_get_lbolt(); 7835 7836 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7837 7838 mutex_enter(&l2arc_feed_thr_lock); 7839 7840 while (l2arc_thread_exit == 0) { 7841 CALLB_CPR_SAFE_BEGIN(&cpr); 7842 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7843 next - ddi_get_lbolt()); 7844 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7845 next = ddi_get_lbolt() + hz; 7846 7847 /* 7848 * Quick check for L2ARC devices. 7849 */ 7850 mutex_enter(&l2arc_dev_mtx); 7851 if (l2arc_ndev == 0) { 7852 mutex_exit(&l2arc_dev_mtx); 7853 continue; 7854 } 7855 mutex_exit(&l2arc_dev_mtx); 7856 begin = ddi_get_lbolt(); 7857 7858 /* 7859 * This selects the next l2arc device to write to, and in 7860 * doing so the next spa to feed from: dev->l2ad_spa. This 7861 * will return NULL if there are now no l2arc devices or if 7862 * they are all faulted. 7863 * 7864 * If a device is returned, its spa's config lock is also 7865 * held to prevent device removal. l2arc_dev_get_next() 7866 * will grab and release l2arc_dev_mtx. 7867 */ 7868 if ((dev = l2arc_dev_get_next()) == NULL) 7869 continue; 7870 7871 spa = dev->l2ad_spa; 7872 ASSERT3P(spa, !=, NULL); 7873 7874 /* 7875 * If the pool is read-only then force the feed thread to 7876 * sleep a little longer. 7877 */ 7878 if (!spa_writeable(spa)) { 7879 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7880 spa_config_exit(spa, SCL_L2ARC, dev); 7881 continue; 7882 } 7883 7884 /* 7885 * Avoid contributing to memory pressure. 7886 */ 7887 if (arc_reclaim_needed()) { 7888 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7889 spa_config_exit(spa, SCL_L2ARC, dev); 7890 continue; 7891 } 7892 7893 ARCSTAT_BUMP(arcstat_l2_feeds); 7894 7895 size = l2arc_write_size(); 7896 7897 /* 7898 * Evict L2ARC buffers that will be overwritten. 7899 */ 7900 l2arc_evict(dev, size, B_FALSE); 7901 7902 /* 7903 * Write ARC buffers. 7904 */ 7905 wrote = l2arc_write_buffers(spa, dev, size); 7906 7907 /* 7908 * Calculate interval between writes. 7909 */ 7910 next = l2arc_write_interval(begin, size, wrote); 7911 spa_config_exit(spa, SCL_L2ARC, dev); 7912 } 7913 7914 l2arc_thread_exit = 0; 7915 cv_broadcast(&l2arc_feed_thr_cv); 7916 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7917 thread_exit(); 7918} 7919 7920boolean_t 7921l2arc_vdev_present(vdev_t *vd) 7922{ 7923 l2arc_dev_t *dev; 7924 7925 mutex_enter(&l2arc_dev_mtx); 7926 for (dev = list_head(l2arc_dev_list); dev != NULL; 7927 dev = list_next(l2arc_dev_list, dev)) { 7928 if (dev->l2ad_vdev == vd) 7929 break; 7930 } 7931 mutex_exit(&l2arc_dev_mtx); 7932 7933 return (dev != NULL); 7934} 7935 7936/* 7937 * Add a vdev for use by the L2ARC. By this point the spa has already 7938 * validated the vdev and opened it. 7939 */ 7940void 7941l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7942{ 7943 l2arc_dev_t *adddev; 7944 7945 ASSERT(!l2arc_vdev_present(vd)); 7946 7947 vdev_ashift_optimize(vd); 7948 7949 /* 7950 * Create a new l2arc device entry. 7951 */ 7952 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7953 adddev->l2ad_spa = spa; 7954 adddev->l2ad_vdev = vd; 7955 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7956 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7957 adddev->l2ad_hand = adddev->l2ad_start; 7958 adddev->l2ad_first = B_TRUE; 7959 adddev->l2ad_writing = B_FALSE; 7960 7961 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7962 /* 7963 * This is a list of all ARC buffers that are still valid on the 7964 * device. 7965 */ 7966 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7967 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7968 7969 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7970 refcount_create(&adddev->l2ad_alloc); 7971 7972 /* 7973 * Add device to global list 7974 */ 7975 mutex_enter(&l2arc_dev_mtx); 7976 list_insert_head(l2arc_dev_list, adddev); 7977 atomic_inc_64(&l2arc_ndev); 7978 mutex_exit(&l2arc_dev_mtx); 7979} 7980 7981/* 7982 * Remove a vdev from the L2ARC. 7983 */ 7984void 7985l2arc_remove_vdev(vdev_t *vd) 7986{ 7987 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7988 7989 /* 7990 * Find the device by vdev 7991 */ 7992 mutex_enter(&l2arc_dev_mtx); 7993 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7994 nextdev = list_next(l2arc_dev_list, dev); 7995 if (vd == dev->l2ad_vdev) { 7996 remdev = dev; 7997 break; 7998 } 7999 } 8000 ASSERT3P(remdev, !=, NULL); 8001 8002 /* 8003 * Remove device from global list 8004 */ 8005 list_remove(l2arc_dev_list, remdev); 8006 l2arc_dev_last = NULL; /* may have been invalidated */ 8007 atomic_dec_64(&l2arc_ndev); 8008 mutex_exit(&l2arc_dev_mtx); 8009 8010 /* 8011 * Clear all buflists and ARC references. L2ARC device flush. 8012 */ 8013 l2arc_evict(remdev, 0, B_TRUE); 8014 list_destroy(&remdev->l2ad_buflist); 8015 mutex_destroy(&remdev->l2ad_mtx); 8016 refcount_destroy(&remdev->l2ad_alloc); 8017 kmem_free(remdev, sizeof (l2arc_dev_t)); 8018} 8019 8020void 8021l2arc_init(void) 8022{ 8023 l2arc_thread_exit = 0; 8024 l2arc_ndev = 0; 8025 l2arc_writes_sent = 0; 8026 l2arc_writes_done = 0; 8027 8028 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 8029 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 8030 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 8031 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 8032 8033 l2arc_dev_list = &L2ARC_dev_list; 8034 l2arc_free_on_write = &L2ARC_free_on_write; 8035 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 8036 offsetof(l2arc_dev_t, l2ad_node)); 8037 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 8038 offsetof(l2arc_data_free_t, l2df_list_node)); 8039} 8040 8041void 8042l2arc_fini(void) 8043{ 8044 /* 8045 * This is called from dmu_fini(), which is called from spa_fini(); 8046 * Because of this, we can assume that all l2arc devices have 8047 * already been removed when the pools themselves were removed. 8048 */ 8049 8050 l2arc_do_free_on_write(); 8051 8052 mutex_destroy(&l2arc_feed_thr_lock); 8053 cv_destroy(&l2arc_feed_thr_cv); 8054 mutex_destroy(&l2arc_dev_mtx); 8055 mutex_destroy(&l2arc_free_on_write_mtx); 8056 8057 list_destroy(l2arc_dev_list); 8058 list_destroy(l2arc_free_on_write); 8059} 8060 8061void 8062l2arc_start(void) 8063{ 8064 if (!(spa_mode_global & FWRITE)) 8065 return; 8066 8067 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 8068 TS_RUN, minclsyspri); 8069} 8070 8071void 8072l2arc_stop(void) 8073{ 8074 if (!(spa_mode_global & FWRITE)) 8075 return; 8076 8077 mutex_enter(&l2arc_feed_thr_lock); 8078 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 8079 l2arc_thread_exit = 1; 8080 while (l2arc_thread_exit != 0) 8081 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 8082 mutex_exit(&l2arc_feed_thr_lock); 8083} 8084