arc.c revision 332551
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, 2017 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 = 1000; 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 arc_min_prefetch_lifespan; 343 344/* 345 * If this percent of memory is free, don't throttle. 346 */ 347int arc_lotsfree_percent = 10; 348 349static int arc_dead; 350extern boolean_t zfs_prefetch_disable; 351 352/* 353 * The arc has filled available memory and has now warmed up. 354 */ 355static boolean_t arc_warm; 356 357/* 358 * log2 fraction of the zio arena to keep free. 359 */ 360int arc_zio_arena_free_shift = 2; 361 362/* 363 * These tunables are for performance analysis. 364 */ 365uint64_t zfs_arc_max; 366uint64_t zfs_arc_min; 367uint64_t zfs_arc_meta_limit = 0; 368uint64_t zfs_arc_meta_min = 0; 369int zfs_arc_grow_retry = 0; 370int zfs_arc_shrink_shift = 0; 371int zfs_arc_no_grow_shift = 0; 372int zfs_arc_p_min_shift = 0; 373uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 374u_int zfs_arc_free_target = 0; 375 376/* Absolute min for arc min / max is 16MB. */ 377static uint64_t arc_abs_min = 16 << 20; 378 379boolean_t zfs_compressed_arc_enabled = B_TRUE; 380 381static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 382static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 383static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 384static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 385static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS); 386 387#if defined(__FreeBSD__) && defined(_KERNEL) 388static void 389arc_free_target_init(void *unused __unused) 390{ 391 392 zfs_arc_free_target = vm_pageout_wakeup_thresh; 393} 394SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 395 arc_free_target_init, NULL); 396 397TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 398TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 399TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 400TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry); 401TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift); 402SYSCTL_DECL(_vfs_zfs); 403SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 404 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 405SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 406 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 407SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN, 408 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U", 409 "log2(fraction of ARC which must be free to allow growing)"); 410SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 411 &zfs_arc_average_blocksize, 0, 412 "ARC average blocksize"); 413SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 414 &arc_shrink_shift, 0, 415 "log2(fraction of arc to reclaim)"); 416SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW, 417 &arc_grow_retry, 0, 418 "Wait in seconds before considering growing ARC"); 419SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 420 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC"); 421 422/* 423 * We don't have a tunable for arc_free_target due to the dependency on 424 * pagedaemon initialisation. 425 */ 426SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 427 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 428 sysctl_vfs_zfs_arc_free_target, "IU", 429 "Desired number of free pages below which ARC triggers reclaim"); 430 431static int 432sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 433{ 434 u_int val; 435 int err; 436 437 val = zfs_arc_free_target; 438 err = sysctl_handle_int(oidp, &val, 0, req); 439 if (err != 0 || req->newptr == NULL) 440 return (err); 441 442 if (val < minfree) 443 return (EINVAL); 444 if (val > vm_cnt.v_page_count) 445 return (EINVAL); 446 447 zfs_arc_free_target = val; 448 449 return (0); 450} 451 452/* 453 * Must be declared here, before the definition of corresponding kstat 454 * macro which uses the same names will confuse the compiler. 455 */ 456SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 457 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 458 sysctl_vfs_zfs_arc_meta_limit, "QU", 459 "ARC metadata limit"); 460#endif 461 462/* 463 * Note that buffers can be in one of 6 states: 464 * ARC_anon - anonymous (discussed below) 465 * ARC_mru - recently used, currently cached 466 * ARC_mru_ghost - recentely used, no longer in cache 467 * ARC_mfu - frequently used, currently cached 468 * ARC_mfu_ghost - frequently used, no longer in cache 469 * ARC_l2c_only - exists in L2ARC but not other states 470 * When there are no active references to the buffer, they are 471 * are linked onto a list in one of these arc states. These are 472 * the only buffers that can be evicted or deleted. Within each 473 * state there are multiple lists, one for meta-data and one for 474 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 475 * etc.) is tracked separately so that it can be managed more 476 * explicitly: favored over data, limited explicitly. 477 * 478 * Anonymous buffers are buffers that are not associated with 479 * a DVA. These are buffers that hold dirty block copies 480 * before they are written to stable storage. By definition, 481 * they are "ref'd" and are considered part of arc_mru 482 * that cannot be freed. Generally, they will aquire a DVA 483 * as they are written and migrate onto the arc_mru list. 484 * 485 * The ARC_l2c_only state is for buffers that are in the second 486 * level ARC but no longer in any of the ARC_m* lists. The second 487 * level ARC itself may also contain buffers that are in any of 488 * the ARC_m* states - meaning that a buffer can exist in two 489 * places. The reason for the ARC_l2c_only state is to keep the 490 * buffer header in the hash table, so that reads that hit the 491 * second level ARC benefit from these fast lookups. 492 */ 493 494typedef struct arc_state { 495 /* 496 * list of evictable buffers 497 */ 498 multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; 499 /* 500 * total amount of evictable data in this state 501 */ 502 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 503 /* 504 * total amount of data in this state; this includes: evictable, 505 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 506 */ 507 refcount_t arcs_size; 508} arc_state_t; 509 510/* The 6 states: */ 511static arc_state_t ARC_anon; 512static arc_state_t ARC_mru; 513static arc_state_t ARC_mru_ghost; 514static arc_state_t ARC_mfu; 515static arc_state_t ARC_mfu_ghost; 516static arc_state_t ARC_l2c_only; 517 518typedef struct arc_stats { 519 kstat_named_t arcstat_hits; 520 kstat_named_t arcstat_misses; 521 kstat_named_t arcstat_demand_data_hits; 522 kstat_named_t arcstat_demand_data_misses; 523 kstat_named_t arcstat_demand_metadata_hits; 524 kstat_named_t arcstat_demand_metadata_misses; 525 kstat_named_t arcstat_prefetch_data_hits; 526 kstat_named_t arcstat_prefetch_data_misses; 527 kstat_named_t arcstat_prefetch_metadata_hits; 528 kstat_named_t arcstat_prefetch_metadata_misses; 529 kstat_named_t arcstat_mru_hits; 530 kstat_named_t arcstat_mru_ghost_hits; 531 kstat_named_t arcstat_mfu_hits; 532 kstat_named_t arcstat_mfu_ghost_hits; 533 kstat_named_t arcstat_allocated; 534 kstat_named_t arcstat_deleted; 535 /* 536 * Number of buffers that could not be evicted because the hash lock 537 * was held by another thread. The lock may not necessarily be held 538 * by something using the same buffer, since hash locks are shared 539 * by multiple buffers. 540 */ 541 kstat_named_t arcstat_mutex_miss; 542 /* 543 * Number of buffers skipped because they have I/O in progress, are 544 * indrect prefetch buffers that have not lived long enough, or are 545 * not from the spa we're trying to evict from. 546 */ 547 kstat_named_t arcstat_evict_skip; 548 /* 549 * Number of times arc_evict_state() was unable to evict enough 550 * buffers to reach it's target amount. 551 */ 552 kstat_named_t arcstat_evict_not_enough; 553 kstat_named_t arcstat_evict_l2_cached; 554 kstat_named_t arcstat_evict_l2_eligible; 555 kstat_named_t arcstat_evict_l2_ineligible; 556 kstat_named_t arcstat_evict_l2_skip; 557 kstat_named_t arcstat_hash_elements; 558 kstat_named_t arcstat_hash_elements_max; 559 kstat_named_t arcstat_hash_collisions; 560 kstat_named_t arcstat_hash_chains; 561 kstat_named_t arcstat_hash_chain_max; 562 kstat_named_t arcstat_p; 563 kstat_named_t arcstat_c; 564 kstat_named_t arcstat_c_min; 565 kstat_named_t arcstat_c_max; 566 /* Not updated directly; only synced in arc_kstat_update. */ 567 kstat_named_t arcstat_size; 568 /* 569 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. 570 * Note that the compressed bytes may match the uncompressed bytes 571 * if the block is either not compressed or compressed arc is disabled. 572 */ 573 kstat_named_t arcstat_compressed_size; 574 /* 575 * Uncompressed size of the data stored in b_pabd. If compressed 576 * arc is disabled then this value will be identical to the stat 577 * above. 578 */ 579 kstat_named_t arcstat_uncompressed_size; 580 /* 581 * Number of bytes stored in all the arc_buf_t's. This is classified 582 * as "overhead" since this data is typically short-lived and will 583 * be evicted from the arc when it becomes unreferenced unless the 584 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 585 * values have been set (see comment in dbuf.c for more information). 586 */ 587 kstat_named_t arcstat_overhead_size; 588 /* 589 * Number of bytes consumed by internal ARC structures necessary 590 * for tracking purposes; these structures are not actually 591 * backed by ARC buffers. This includes arc_buf_hdr_t structures 592 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 593 * caches), and arc_buf_t structures (allocated via arc_buf_t 594 * cache). 595 * Not updated directly; only synced in arc_kstat_update. 596 */ 597 kstat_named_t arcstat_hdr_size; 598 /* 599 * Number of bytes consumed by ARC buffers of type equal to 600 * ARC_BUFC_DATA. This is generally consumed by buffers backing 601 * on disk user data (e.g. plain file contents). 602 * Not updated directly; only synced in arc_kstat_update. 603 */ 604 kstat_named_t arcstat_data_size; 605 /* 606 * Number of bytes consumed by ARC buffers of type equal to 607 * ARC_BUFC_METADATA. This is generally consumed by buffers 608 * backing on disk data that is used for internal ZFS 609 * structures (e.g. ZAP, dnode, indirect blocks, etc). 610 * Not updated directly; only synced in arc_kstat_update. 611 */ 612 kstat_named_t arcstat_metadata_size; 613 /* 614 * Number of bytes consumed by various buffers and structures 615 * not actually backed with ARC buffers. This includes bonus 616 * buffers (allocated directly via zio_buf_* functions), 617 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 618 * cache), and dnode_t structures (allocated via dnode_t cache). 619 * Not updated directly; only synced in arc_kstat_update. 620 */ 621 kstat_named_t arcstat_other_size; 622 /* 623 * Total number of bytes consumed by ARC buffers residing in the 624 * arc_anon state. This includes *all* buffers in the arc_anon 625 * state; e.g. data, metadata, evictable, and unevictable buffers 626 * are all included in this value. 627 * Not updated directly; only synced in arc_kstat_update. 628 */ 629 kstat_named_t arcstat_anon_size; 630 /* 631 * Number of bytes consumed by ARC buffers that meet the 632 * following criteria: backing buffers of type ARC_BUFC_DATA, 633 * residing in the arc_anon state, and are eligible for eviction 634 * (e.g. have no outstanding holds on the buffer). 635 * Not updated directly; only synced in arc_kstat_update. 636 */ 637 kstat_named_t arcstat_anon_evictable_data; 638 /* 639 * Number of bytes consumed by ARC buffers that meet the 640 * following criteria: backing buffers of type ARC_BUFC_METADATA, 641 * residing in the arc_anon state, and are eligible for eviction 642 * (e.g. have no outstanding holds on the buffer). 643 * Not updated directly; only synced in arc_kstat_update. 644 */ 645 kstat_named_t arcstat_anon_evictable_metadata; 646 /* 647 * Total number of bytes consumed by ARC buffers residing in the 648 * arc_mru state. This includes *all* buffers in the arc_mru 649 * state; e.g. data, metadata, evictable, and unevictable buffers 650 * are all included in this value. 651 * Not updated directly; only synced in arc_kstat_update. 652 */ 653 kstat_named_t arcstat_mru_size; 654 /* 655 * Number of bytes consumed by ARC buffers that meet the 656 * following criteria: backing buffers of type ARC_BUFC_DATA, 657 * residing in the arc_mru state, and are eligible for eviction 658 * (e.g. have no outstanding holds on the buffer). 659 * Not updated directly; only synced in arc_kstat_update. 660 */ 661 kstat_named_t arcstat_mru_evictable_data; 662 /* 663 * Number of bytes consumed by ARC buffers that meet the 664 * following criteria: backing buffers of type ARC_BUFC_METADATA, 665 * residing in the arc_mru state, and are eligible for eviction 666 * (e.g. have no outstanding holds on the buffer). 667 * Not updated directly; only synced in arc_kstat_update. 668 */ 669 kstat_named_t arcstat_mru_evictable_metadata; 670 /* 671 * Total number of bytes that *would have been* consumed by ARC 672 * buffers in the arc_mru_ghost state. The key thing to note 673 * here, is the fact that this size doesn't actually indicate 674 * RAM consumption. The ghost lists only consist of headers and 675 * don't actually have ARC buffers linked off of these headers. 676 * Thus, *if* the headers had associated ARC buffers, these 677 * buffers *would have* consumed this number of bytes. 678 * Not updated directly; only synced in arc_kstat_update. 679 */ 680 kstat_named_t arcstat_mru_ghost_size; 681 /* 682 * Number of bytes that *would have been* consumed by ARC 683 * buffers that are eligible for eviction, of type 684 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 685 * Not updated directly; only synced in arc_kstat_update. 686 */ 687 kstat_named_t arcstat_mru_ghost_evictable_data; 688 /* 689 * Number of bytes that *would have been* consumed by ARC 690 * buffers that are eligible for eviction, of type 691 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 692 * Not updated directly; only synced in arc_kstat_update. 693 */ 694 kstat_named_t arcstat_mru_ghost_evictable_metadata; 695 /* 696 * Total number of bytes consumed by ARC buffers residing in the 697 * arc_mfu state. This includes *all* buffers in the arc_mfu 698 * state; e.g. data, metadata, evictable, and unevictable buffers 699 * are all included in this value. 700 * Not updated directly; only synced in arc_kstat_update. 701 */ 702 kstat_named_t arcstat_mfu_size; 703 /* 704 * Number of bytes consumed by ARC buffers that are eligible for 705 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 706 * state. 707 * Not updated directly; only synced in arc_kstat_update. 708 */ 709 kstat_named_t arcstat_mfu_evictable_data; 710 /* 711 * Number of bytes consumed by ARC buffers that are eligible for 712 * eviction, of type ARC_BUFC_METADATA, and reside in the 713 * arc_mfu state. 714 * Not updated directly; only synced in arc_kstat_update. 715 */ 716 kstat_named_t arcstat_mfu_evictable_metadata; 717 /* 718 * Total number of bytes that *would have been* consumed by ARC 719 * buffers in the arc_mfu_ghost state. See the comment above 720 * arcstat_mru_ghost_size for more details. 721 * Not updated directly; only synced in arc_kstat_update. 722 */ 723 kstat_named_t arcstat_mfu_ghost_size; 724 /* 725 * Number of bytes that *would have been* consumed by ARC 726 * buffers that are eligible for eviction, of type 727 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 728 * Not updated directly; only synced in arc_kstat_update. 729 */ 730 kstat_named_t arcstat_mfu_ghost_evictable_data; 731 /* 732 * Number of bytes that *would have been* consumed by ARC 733 * buffers that are eligible for eviction, of type 734 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 735 * Not updated directly; only synced in arc_kstat_update. 736 */ 737 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 738 kstat_named_t arcstat_l2_hits; 739 kstat_named_t arcstat_l2_misses; 740 kstat_named_t arcstat_l2_feeds; 741 kstat_named_t arcstat_l2_rw_clash; 742 kstat_named_t arcstat_l2_read_bytes; 743 kstat_named_t arcstat_l2_write_bytes; 744 kstat_named_t arcstat_l2_writes_sent; 745 kstat_named_t arcstat_l2_writes_done; 746 kstat_named_t arcstat_l2_writes_error; 747 kstat_named_t arcstat_l2_writes_lock_retry; 748 kstat_named_t arcstat_l2_evict_lock_retry; 749 kstat_named_t arcstat_l2_evict_reading; 750 kstat_named_t arcstat_l2_evict_l1cached; 751 kstat_named_t arcstat_l2_free_on_write; 752 kstat_named_t arcstat_l2_abort_lowmem; 753 kstat_named_t arcstat_l2_cksum_bad; 754 kstat_named_t arcstat_l2_io_error; 755 kstat_named_t arcstat_l2_lsize; 756 kstat_named_t arcstat_l2_psize; 757 /* Not updated directly; only synced in arc_kstat_update. */ 758 kstat_named_t arcstat_l2_hdr_size; 759 kstat_named_t arcstat_l2_write_trylock_fail; 760 kstat_named_t arcstat_l2_write_passed_headroom; 761 kstat_named_t arcstat_l2_write_spa_mismatch; 762 kstat_named_t arcstat_l2_write_in_l2; 763 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 764 kstat_named_t arcstat_l2_write_not_cacheable; 765 kstat_named_t arcstat_l2_write_full; 766 kstat_named_t arcstat_l2_write_buffer_iter; 767 kstat_named_t arcstat_l2_write_pios; 768 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 769 kstat_named_t arcstat_l2_write_buffer_list_iter; 770 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 771 kstat_named_t arcstat_memory_throttle_count; 772 /* Not updated directly; only synced in arc_kstat_update. */ 773 kstat_named_t arcstat_meta_used; 774 kstat_named_t arcstat_meta_limit; 775 kstat_named_t arcstat_meta_max; 776 kstat_named_t arcstat_meta_min; 777 kstat_named_t arcstat_sync_wait_for_async; 778 kstat_named_t arcstat_demand_hit_predictive_prefetch; 779} arc_stats_t; 780 781static arc_stats_t arc_stats = { 782 { "hits", KSTAT_DATA_UINT64 }, 783 { "misses", KSTAT_DATA_UINT64 }, 784 { "demand_data_hits", KSTAT_DATA_UINT64 }, 785 { "demand_data_misses", KSTAT_DATA_UINT64 }, 786 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 787 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 788 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 789 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 790 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 791 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 792 { "mru_hits", KSTAT_DATA_UINT64 }, 793 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 794 { "mfu_hits", KSTAT_DATA_UINT64 }, 795 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 796 { "allocated", KSTAT_DATA_UINT64 }, 797 { "deleted", KSTAT_DATA_UINT64 }, 798 { "mutex_miss", KSTAT_DATA_UINT64 }, 799 { "evict_skip", KSTAT_DATA_UINT64 }, 800 { "evict_not_enough", KSTAT_DATA_UINT64 }, 801 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 802 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 803 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 804 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 805 { "hash_elements", KSTAT_DATA_UINT64 }, 806 { "hash_elements_max", KSTAT_DATA_UINT64 }, 807 { "hash_collisions", KSTAT_DATA_UINT64 }, 808 { "hash_chains", KSTAT_DATA_UINT64 }, 809 { "hash_chain_max", KSTAT_DATA_UINT64 }, 810 { "p", KSTAT_DATA_UINT64 }, 811 { "c", KSTAT_DATA_UINT64 }, 812 { "c_min", KSTAT_DATA_UINT64 }, 813 { "c_max", KSTAT_DATA_UINT64 }, 814 { "size", KSTAT_DATA_UINT64 }, 815 { "compressed_size", KSTAT_DATA_UINT64 }, 816 { "uncompressed_size", KSTAT_DATA_UINT64 }, 817 { "overhead_size", KSTAT_DATA_UINT64 }, 818 { "hdr_size", KSTAT_DATA_UINT64 }, 819 { "data_size", KSTAT_DATA_UINT64 }, 820 { "metadata_size", KSTAT_DATA_UINT64 }, 821 { "other_size", KSTAT_DATA_UINT64 }, 822 { "anon_size", KSTAT_DATA_UINT64 }, 823 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 824 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 825 { "mru_size", KSTAT_DATA_UINT64 }, 826 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 827 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 828 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 829 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 830 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 831 { "mfu_size", KSTAT_DATA_UINT64 }, 832 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 833 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 834 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 835 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 836 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 837 { "l2_hits", KSTAT_DATA_UINT64 }, 838 { "l2_misses", KSTAT_DATA_UINT64 }, 839 { "l2_feeds", KSTAT_DATA_UINT64 }, 840 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 841 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 842 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 843 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 844 { "l2_writes_done", KSTAT_DATA_UINT64 }, 845 { "l2_writes_error", KSTAT_DATA_UINT64 }, 846 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 847 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 848 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 849 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 850 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 851 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 852 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 853 { "l2_io_error", KSTAT_DATA_UINT64 }, 854 { "l2_size", KSTAT_DATA_UINT64 }, 855 { "l2_asize", KSTAT_DATA_UINT64 }, 856 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 857 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 858 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 859 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 860 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 861 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 862 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 863 { "l2_write_full", KSTAT_DATA_UINT64 }, 864 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 865 { "l2_write_pios", KSTAT_DATA_UINT64 }, 866 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 867 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 868 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 869 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 870 { "arc_meta_used", KSTAT_DATA_UINT64 }, 871 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 872 { "arc_meta_max", KSTAT_DATA_UINT64 }, 873 { "arc_meta_min", KSTAT_DATA_UINT64 }, 874 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 875 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 876}; 877 878#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 879 880#define ARCSTAT_INCR(stat, val) \ 881 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 882 883#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 884#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 885 886#define ARCSTAT_MAX(stat, val) { \ 887 uint64_t m; \ 888 while ((val) > (m = arc_stats.stat.value.ui64) && \ 889 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 890 continue; \ 891} 892 893#define ARCSTAT_MAXSTAT(stat) \ 894 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 895 896/* 897 * We define a macro to allow ARC hits/misses to be easily broken down by 898 * two separate conditions, giving a total of four different subtypes for 899 * each of hits and misses (so eight statistics total). 900 */ 901#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 902 if (cond1) { \ 903 if (cond2) { \ 904 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 905 } else { \ 906 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 907 } \ 908 } else { \ 909 if (cond2) { \ 910 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 911 } else { \ 912 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 913 } \ 914 } 915 916kstat_t *arc_ksp; 917static arc_state_t *arc_anon; 918static arc_state_t *arc_mru; 919static arc_state_t *arc_mru_ghost; 920static arc_state_t *arc_mfu; 921static arc_state_t *arc_mfu_ghost; 922static arc_state_t *arc_l2c_only; 923 924/* 925 * There are several ARC variables that are critical to export as kstats -- 926 * but we don't want to have to grovel around in the kstat whenever we wish to 927 * manipulate them. For these variables, we therefore define them to be in 928 * terms of the statistic variable. This assures that we are not introducing 929 * the possibility of inconsistency by having shadow copies of the variables, 930 * while still allowing the code to be readable. 931 */ 932#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 933#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 934#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 935#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 936#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 937#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 938#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 939 940/* compressed size of entire arc */ 941#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 942/* uncompressed size of entire arc */ 943#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 944/* number of bytes in the arc from arc_buf_t's */ 945#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 946 947/* 948 * There are also some ARC variables that we want to export, but that are 949 * updated so often that having the canonical representation be the statistic 950 * variable causes a performance bottleneck. We want to use aggsum_t's for these 951 * instead, but still be able to export the kstat in the same way as before. 952 * The solution is to always use the aggsum version, except in the kstat update 953 * callback. 954 */ 955aggsum_t arc_size; 956aggsum_t arc_meta_used; 957aggsum_t astat_data_size; 958aggsum_t astat_metadata_size; 959aggsum_t astat_hdr_size; 960aggsum_t astat_other_size; 961aggsum_t astat_l2_hdr_size; 962 963static int arc_no_grow; /* Don't try to grow cache size */ 964static uint64_t arc_tempreserve; 965static uint64_t arc_loaned_bytes; 966 967typedef struct arc_callback arc_callback_t; 968 969struct arc_callback { 970 void *acb_private; 971 arc_done_func_t *acb_done; 972 arc_buf_t *acb_buf; 973 boolean_t acb_compressed; 974 zio_t *acb_zio_dummy; 975 arc_callback_t *acb_next; 976}; 977 978typedef struct arc_write_callback arc_write_callback_t; 979 980struct arc_write_callback { 981 void *awcb_private; 982 arc_done_func_t *awcb_ready; 983 arc_done_func_t *awcb_children_ready; 984 arc_done_func_t *awcb_physdone; 985 arc_done_func_t *awcb_done; 986 arc_buf_t *awcb_buf; 987}; 988 989/* 990 * ARC buffers are separated into multiple structs as a memory saving measure: 991 * - Common fields struct, always defined, and embedded within it: 992 * - L2-only fields, always allocated but undefined when not in L2ARC 993 * - L1-only fields, only allocated when in L1ARC 994 * 995 * Buffer in L1 Buffer only in L2 996 * +------------------------+ +------------------------+ 997 * | arc_buf_hdr_t | | arc_buf_hdr_t | 998 * | | | | 999 * | | | | 1000 * | | | | 1001 * +------------------------+ +------------------------+ 1002 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 1003 * | (undefined if L1-only) | | | 1004 * +------------------------+ +------------------------+ 1005 * | l1arc_buf_hdr_t | 1006 * | | 1007 * | | 1008 * | | 1009 * | | 1010 * +------------------------+ 1011 * 1012 * Because it's possible for the L2ARC to become extremely large, we can wind 1013 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 1014 * is minimized by only allocating the fields necessary for an L1-cached buffer 1015 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 1016 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 1017 * words in pointers. arc_hdr_realloc() is used to switch a header between 1018 * these two allocation states. 1019 */ 1020typedef struct l1arc_buf_hdr { 1021 kmutex_t b_freeze_lock; 1022 zio_cksum_t *b_freeze_cksum; 1023#ifdef ZFS_DEBUG 1024 /* 1025 * Used for debugging with kmem_flags - by allocating and freeing 1026 * b_thawed when the buffer is thawed, we get a record of the stack 1027 * trace that thawed it. 1028 */ 1029 void *b_thawed; 1030#endif 1031 1032 arc_buf_t *b_buf; 1033 uint32_t b_bufcnt; 1034 /* for waiting on writes to complete */ 1035 kcondvar_t b_cv; 1036 uint8_t b_byteswap; 1037 1038 /* protected by arc state mutex */ 1039 arc_state_t *b_state; 1040 multilist_node_t b_arc_node; 1041 1042 /* updated atomically */ 1043 clock_t b_arc_access; 1044 1045 /* self protecting */ 1046 refcount_t b_refcnt; 1047 1048 arc_callback_t *b_acb; 1049 abd_t *b_pabd; 1050} l1arc_buf_hdr_t; 1051 1052typedef struct l2arc_dev l2arc_dev_t; 1053 1054typedef struct l2arc_buf_hdr { 1055 /* protected by arc_buf_hdr mutex */ 1056 l2arc_dev_t *b_dev; /* L2ARC device */ 1057 uint64_t b_daddr; /* disk address, offset byte */ 1058 1059 list_node_t b_l2node; 1060} l2arc_buf_hdr_t; 1061 1062struct arc_buf_hdr { 1063 /* protected by hash lock */ 1064 dva_t b_dva; 1065 uint64_t b_birth; 1066 1067 arc_buf_contents_t b_type; 1068 arc_buf_hdr_t *b_hash_next; 1069 arc_flags_t b_flags; 1070 1071 /* 1072 * This field stores the size of the data buffer after 1073 * compression, and is set in the arc's zio completion handlers. 1074 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1075 * 1076 * While the block pointers can store up to 32MB in their psize 1077 * field, we can only store up to 32MB minus 512B. This is due 1078 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1079 * a field of zeros represents 512B in the bp). We can't use a 1080 * bias of 1 since we need to reserve a psize of zero, here, to 1081 * represent holes and embedded blocks. 1082 * 1083 * This isn't a problem in practice, since the maximum size of a 1084 * buffer is limited to 16MB, so we never need to store 32MB in 1085 * this field. Even in the upstream illumos code base, the 1086 * maximum size of a buffer is limited to 16MB. 1087 */ 1088 uint16_t b_psize; 1089 1090 /* 1091 * This field stores the size of the data buffer before 1092 * compression, and cannot change once set. It is in units 1093 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1094 */ 1095 uint16_t b_lsize; /* immutable */ 1096 uint64_t b_spa; /* immutable */ 1097 1098 /* L2ARC fields. Undefined when not in L2ARC. */ 1099 l2arc_buf_hdr_t b_l2hdr; 1100 /* L1ARC fields. Undefined when in l2arc_only state */ 1101 l1arc_buf_hdr_t b_l1hdr; 1102}; 1103 1104#if defined(__FreeBSD__) && defined(_KERNEL) 1105static int 1106sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1107{ 1108 uint64_t val; 1109 int err; 1110 1111 val = arc_meta_limit; 1112 err = sysctl_handle_64(oidp, &val, 0, req); 1113 if (err != 0 || req->newptr == NULL) 1114 return (err); 1115 1116 if (val <= 0 || val > arc_c_max) 1117 return (EINVAL); 1118 1119 arc_meta_limit = val; 1120 return (0); 1121} 1122 1123static int 1124sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS) 1125{ 1126 uint32_t val; 1127 int err; 1128 1129 val = arc_no_grow_shift; 1130 err = sysctl_handle_32(oidp, &val, 0, req); 1131 if (err != 0 || req->newptr == NULL) 1132 return (err); 1133 1134 if (val >= arc_shrink_shift) 1135 return (EINVAL); 1136 1137 arc_no_grow_shift = val; 1138 return (0); 1139} 1140 1141static int 1142sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1143{ 1144 uint64_t val; 1145 int err; 1146 1147 val = zfs_arc_max; 1148 err = sysctl_handle_64(oidp, &val, 0, req); 1149 if (err != 0 || req->newptr == NULL) 1150 return (err); 1151 1152 if (zfs_arc_max == 0) { 1153 /* Loader tunable so blindly set */ 1154 zfs_arc_max = val; 1155 return (0); 1156 } 1157 1158 if (val < arc_abs_min || val > kmem_size()) 1159 return (EINVAL); 1160 if (val < arc_c_min) 1161 return (EINVAL); 1162 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1163 return (EINVAL); 1164 1165 arc_c_max = val; 1166 1167 arc_c = arc_c_max; 1168 arc_p = (arc_c >> 1); 1169 1170 if (zfs_arc_meta_limit == 0) { 1171 /* limit meta-data to 1/4 of the arc capacity */ 1172 arc_meta_limit = arc_c_max / 4; 1173 } 1174 1175 /* if kmem_flags are set, lets try to use less memory */ 1176 if (kmem_debugging()) 1177 arc_c = arc_c / 2; 1178 1179 zfs_arc_max = arc_c; 1180 1181 return (0); 1182} 1183 1184static int 1185sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1186{ 1187 uint64_t val; 1188 int err; 1189 1190 val = zfs_arc_min; 1191 err = sysctl_handle_64(oidp, &val, 0, req); 1192 if (err != 0 || req->newptr == NULL) 1193 return (err); 1194 1195 if (zfs_arc_min == 0) { 1196 /* Loader tunable so blindly set */ 1197 zfs_arc_min = val; 1198 return (0); 1199 } 1200 1201 if (val < arc_abs_min || val > arc_c_max) 1202 return (EINVAL); 1203 1204 arc_c_min = val; 1205 1206 if (zfs_arc_meta_min == 0) 1207 arc_meta_min = arc_c_min / 2; 1208 1209 if (arc_c < arc_c_min) 1210 arc_c = arc_c_min; 1211 1212 zfs_arc_min = arc_c_min; 1213 1214 return (0); 1215} 1216#endif 1217 1218#define GHOST_STATE(state) \ 1219 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1220 (state) == arc_l2c_only) 1221 1222#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1223#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1224#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1225#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1226#define HDR_COMPRESSION_ENABLED(hdr) \ 1227 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1228 1229#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1230#define HDR_L2_READING(hdr) \ 1231 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1232 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1233#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1234#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1235#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1236#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1237 1238#define HDR_ISTYPE_METADATA(hdr) \ 1239 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1240#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1241 1242#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1243#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1244 1245/* For storing compression mode in b_flags */ 1246#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1247 1248#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1249 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1250#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1251 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1252 1253#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1254#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) 1255#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) 1256 1257/* 1258 * Other sizes 1259 */ 1260 1261#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1262#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1263 1264/* 1265 * Hash table routines 1266 */ 1267 1268#define HT_LOCK_PAD CACHE_LINE_SIZE 1269 1270struct ht_lock { 1271 kmutex_t ht_lock; 1272#ifdef _KERNEL 1273 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1274#endif 1275}; 1276 1277#define BUF_LOCKS 256 1278typedef struct buf_hash_table { 1279 uint64_t ht_mask; 1280 arc_buf_hdr_t **ht_table; 1281 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1282} buf_hash_table_t; 1283 1284static buf_hash_table_t buf_hash_table; 1285 1286#define BUF_HASH_INDEX(spa, dva, birth) \ 1287 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1288#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1289#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1290#define HDR_LOCK(hdr) \ 1291 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1292 1293uint64_t zfs_crc64_table[256]; 1294 1295/* 1296 * Level 2 ARC 1297 */ 1298 1299#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1300#define L2ARC_HEADROOM 2 /* num of writes */ 1301/* 1302 * If we discover during ARC scan any buffers to be compressed, we boost 1303 * our headroom for the next scanning cycle by this percentage multiple. 1304 */ 1305#define L2ARC_HEADROOM_BOOST 200 1306#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1307#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1308 1309#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1310#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1311 1312/* L2ARC Performance Tunables */ 1313uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1314uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1315uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1316uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1317uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1318uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1319boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1320boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1321boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1322 1323SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1324 &l2arc_write_max, 0, "max write size"); 1325SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1326 &l2arc_write_boost, 0, "extra write during warmup"); 1327SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1328 &l2arc_headroom, 0, "number of dev writes"); 1329SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1330 &l2arc_feed_secs, 0, "interval seconds"); 1331SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1332 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1333 1334SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1335 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1336SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1337 &l2arc_feed_again, 0, "turbo warmup"); 1338SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1339 &l2arc_norw, 0, "no reads during writes"); 1340 1341SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1342 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1343SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1344 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1345 "size of anonymous state"); 1346SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1347 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1348 "size of anonymous state"); 1349 1350SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1351 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1352SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1353 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1354 "size of metadata in mru state"); 1355SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1356 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1357 "size of data in mru state"); 1358 1359SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1360 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1361SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1362 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1363 "size of metadata in mru ghost state"); 1364SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1365 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1366 "size of data in mru ghost state"); 1367 1368SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1369 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1370SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1371 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1372 "size of metadata in mfu state"); 1373SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1374 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1375 "size of data in mfu state"); 1376 1377SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1378 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1379SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1380 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1381 "size of metadata in mfu ghost state"); 1382SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1383 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1384 "size of data in mfu ghost state"); 1385 1386SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1387 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1388 1389/* 1390 * L2ARC Internals 1391 */ 1392struct l2arc_dev { 1393 vdev_t *l2ad_vdev; /* vdev */ 1394 spa_t *l2ad_spa; /* spa */ 1395 uint64_t l2ad_hand; /* next write location */ 1396 uint64_t l2ad_start; /* first addr on device */ 1397 uint64_t l2ad_end; /* last addr on device */ 1398 boolean_t l2ad_first; /* first sweep through */ 1399 boolean_t l2ad_writing; /* currently writing */ 1400 kmutex_t l2ad_mtx; /* lock for buffer list */ 1401 list_t l2ad_buflist; /* buffer list */ 1402 list_node_t l2ad_node; /* device list node */ 1403 refcount_t l2ad_alloc; /* allocated bytes */ 1404}; 1405 1406static list_t L2ARC_dev_list; /* device list */ 1407static list_t *l2arc_dev_list; /* device list pointer */ 1408static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1409static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1410static list_t L2ARC_free_on_write; /* free after write buf list */ 1411static list_t *l2arc_free_on_write; /* free after write list ptr */ 1412static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1413static uint64_t l2arc_ndev; /* number of devices */ 1414 1415typedef struct l2arc_read_callback { 1416 arc_buf_hdr_t *l2rcb_hdr; /* read header */ 1417 blkptr_t l2rcb_bp; /* original blkptr */ 1418 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1419 int l2rcb_flags; /* original flags */ 1420 abd_t *l2rcb_abd; /* temporary buffer */ 1421} l2arc_read_callback_t; 1422 1423typedef struct l2arc_write_callback { 1424 l2arc_dev_t *l2wcb_dev; /* device info */ 1425 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1426} l2arc_write_callback_t; 1427 1428typedef struct l2arc_data_free { 1429 /* protected by l2arc_free_on_write_mtx */ 1430 abd_t *l2df_abd; 1431 size_t l2df_size; 1432 arc_buf_contents_t l2df_type; 1433 list_node_t l2df_list_node; 1434} l2arc_data_free_t; 1435 1436static kmutex_t l2arc_feed_thr_lock; 1437static kcondvar_t l2arc_feed_thr_cv; 1438static uint8_t l2arc_thread_exit; 1439 1440static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *); 1441static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1442static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *); 1443static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); 1444static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1445static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); 1446static void arc_hdr_free_pabd(arc_buf_hdr_t *); 1447static void arc_hdr_alloc_pabd(arc_buf_hdr_t *); 1448static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1449static boolean_t arc_is_overflowing(); 1450static void arc_buf_watch(arc_buf_t *); 1451 1452static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1453static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1454static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1455static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1456 1457static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1458static void l2arc_read_done(zio_t *); 1459 1460static void 1461l2arc_trim(const arc_buf_hdr_t *hdr) 1462{ 1463 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1464 1465 ASSERT(HDR_HAS_L2HDR(hdr)); 1466 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1467 1468 if (HDR_GET_PSIZE(hdr) != 0) { 1469 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1470 HDR_GET_PSIZE(hdr), 0); 1471 } 1472} 1473 1474/* 1475 * We use Cityhash for this. It's fast, and has good hash properties without 1476 * requiring any large static buffers. 1477 */ 1478static uint64_t 1479buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1480{ 1481 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth)); 1482} 1483 1484#define HDR_EMPTY(hdr) \ 1485 ((hdr)->b_dva.dva_word[0] == 0 && \ 1486 (hdr)->b_dva.dva_word[1] == 0) 1487 1488#define HDR_EQUAL(spa, dva, birth, hdr) \ 1489 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1490 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1491 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1492 1493static void 1494buf_discard_identity(arc_buf_hdr_t *hdr) 1495{ 1496 hdr->b_dva.dva_word[0] = 0; 1497 hdr->b_dva.dva_word[1] = 0; 1498 hdr->b_birth = 0; 1499} 1500 1501static arc_buf_hdr_t * 1502buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1503{ 1504 const dva_t *dva = BP_IDENTITY(bp); 1505 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1506 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1507 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1508 arc_buf_hdr_t *hdr; 1509 1510 mutex_enter(hash_lock); 1511 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1512 hdr = hdr->b_hash_next) { 1513 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1514 *lockp = hash_lock; 1515 return (hdr); 1516 } 1517 } 1518 mutex_exit(hash_lock); 1519 *lockp = NULL; 1520 return (NULL); 1521} 1522 1523/* 1524 * Insert an entry into the hash table. If there is already an element 1525 * equal to elem in the hash table, then the already existing element 1526 * will be returned and the new element will not be inserted. 1527 * Otherwise returns NULL. 1528 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1529 */ 1530static arc_buf_hdr_t * 1531buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1532{ 1533 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1534 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1535 arc_buf_hdr_t *fhdr; 1536 uint32_t i; 1537 1538 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1539 ASSERT(hdr->b_birth != 0); 1540 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1541 1542 if (lockp != NULL) { 1543 *lockp = hash_lock; 1544 mutex_enter(hash_lock); 1545 } else { 1546 ASSERT(MUTEX_HELD(hash_lock)); 1547 } 1548 1549 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1550 fhdr = fhdr->b_hash_next, i++) { 1551 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1552 return (fhdr); 1553 } 1554 1555 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1556 buf_hash_table.ht_table[idx] = hdr; 1557 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1558 1559 /* collect some hash table performance data */ 1560 if (i > 0) { 1561 ARCSTAT_BUMP(arcstat_hash_collisions); 1562 if (i == 1) 1563 ARCSTAT_BUMP(arcstat_hash_chains); 1564 1565 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1566 } 1567 1568 ARCSTAT_BUMP(arcstat_hash_elements); 1569 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1570 1571 return (NULL); 1572} 1573 1574static void 1575buf_hash_remove(arc_buf_hdr_t *hdr) 1576{ 1577 arc_buf_hdr_t *fhdr, **hdrp; 1578 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1579 1580 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1581 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1582 1583 hdrp = &buf_hash_table.ht_table[idx]; 1584 while ((fhdr = *hdrp) != hdr) { 1585 ASSERT3P(fhdr, !=, NULL); 1586 hdrp = &fhdr->b_hash_next; 1587 } 1588 *hdrp = hdr->b_hash_next; 1589 hdr->b_hash_next = NULL; 1590 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1591 1592 /* collect some hash table performance data */ 1593 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1594 1595 if (buf_hash_table.ht_table[idx] && 1596 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1597 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1598} 1599 1600/* 1601 * Global data structures and functions for the buf kmem cache. 1602 */ 1603static kmem_cache_t *hdr_full_cache; 1604static kmem_cache_t *hdr_l2only_cache; 1605static kmem_cache_t *buf_cache; 1606 1607static void 1608buf_fini(void) 1609{ 1610 int i; 1611 1612 kmem_free(buf_hash_table.ht_table, 1613 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1614 for (i = 0; i < BUF_LOCKS; i++) 1615 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1616 kmem_cache_destroy(hdr_full_cache); 1617 kmem_cache_destroy(hdr_l2only_cache); 1618 kmem_cache_destroy(buf_cache); 1619} 1620 1621/* 1622 * Constructor callback - called when the cache is empty 1623 * and a new buf is requested. 1624 */ 1625/* ARGSUSED */ 1626static int 1627hdr_full_cons(void *vbuf, void *unused, int kmflag) 1628{ 1629 arc_buf_hdr_t *hdr = vbuf; 1630 1631 bzero(hdr, HDR_FULL_SIZE); 1632 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1633 refcount_create(&hdr->b_l1hdr.b_refcnt); 1634 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1635 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1636 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1637 1638 return (0); 1639} 1640 1641/* ARGSUSED */ 1642static int 1643hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1644{ 1645 arc_buf_hdr_t *hdr = vbuf; 1646 1647 bzero(hdr, HDR_L2ONLY_SIZE); 1648 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1649 1650 return (0); 1651} 1652 1653/* ARGSUSED */ 1654static int 1655buf_cons(void *vbuf, void *unused, int kmflag) 1656{ 1657 arc_buf_t *buf = vbuf; 1658 1659 bzero(buf, sizeof (arc_buf_t)); 1660 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1661 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1662 1663 return (0); 1664} 1665 1666/* 1667 * Destructor callback - called when a cached buf is 1668 * no longer required. 1669 */ 1670/* ARGSUSED */ 1671static void 1672hdr_full_dest(void *vbuf, void *unused) 1673{ 1674 arc_buf_hdr_t *hdr = vbuf; 1675 1676 ASSERT(HDR_EMPTY(hdr)); 1677 cv_destroy(&hdr->b_l1hdr.b_cv); 1678 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1679 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1680 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1681 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1682} 1683 1684/* ARGSUSED */ 1685static void 1686hdr_l2only_dest(void *vbuf, void *unused) 1687{ 1688 arc_buf_hdr_t *hdr = vbuf; 1689 1690 ASSERT(HDR_EMPTY(hdr)); 1691 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1692} 1693 1694/* ARGSUSED */ 1695static void 1696buf_dest(void *vbuf, void *unused) 1697{ 1698 arc_buf_t *buf = vbuf; 1699 1700 mutex_destroy(&buf->b_evict_lock); 1701 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1702} 1703 1704/* 1705 * Reclaim callback -- invoked when memory is low. 1706 */ 1707/* ARGSUSED */ 1708static void 1709hdr_recl(void *unused) 1710{ 1711 dprintf("hdr_recl called\n"); 1712 /* 1713 * umem calls the reclaim func when we destroy the buf cache, 1714 * which is after we do arc_fini(). 1715 */ 1716 if (!arc_dead) 1717 cv_signal(&arc_reclaim_thread_cv); 1718} 1719 1720static void 1721buf_init(void) 1722{ 1723 uint64_t *ct; 1724 uint64_t hsize = 1ULL << 12; 1725 int i, j; 1726 1727 /* 1728 * The hash table is big enough to fill all of physical memory 1729 * with an average block size of zfs_arc_average_blocksize (default 8K). 1730 * By default, the table will take up 1731 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1732 */ 1733 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1734 hsize <<= 1; 1735retry: 1736 buf_hash_table.ht_mask = hsize - 1; 1737 buf_hash_table.ht_table = 1738 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1739 if (buf_hash_table.ht_table == NULL) { 1740 ASSERT(hsize > (1ULL << 8)); 1741 hsize >>= 1; 1742 goto retry; 1743 } 1744 1745 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1746 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1747 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1748 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1749 NULL, NULL, 0); 1750 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1751 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1752 1753 for (i = 0; i < 256; i++) 1754 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1755 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1756 1757 for (i = 0; i < BUF_LOCKS; i++) { 1758 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1759 NULL, MUTEX_DEFAULT, NULL); 1760 } 1761} 1762 1763/* 1764 * This is the size that the buf occupies in memory. If the buf is compressed, 1765 * it will correspond to the compressed size. You should use this method of 1766 * getting the buf size unless you explicitly need the logical size. 1767 */ 1768int32_t 1769arc_buf_size(arc_buf_t *buf) 1770{ 1771 return (ARC_BUF_COMPRESSED(buf) ? 1772 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); 1773} 1774 1775int32_t 1776arc_buf_lsize(arc_buf_t *buf) 1777{ 1778 return (HDR_GET_LSIZE(buf->b_hdr)); 1779} 1780 1781enum zio_compress 1782arc_get_compression(arc_buf_t *buf) 1783{ 1784 return (ARC_BUF_COMPRESSED(buf) ? 1785 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); 1786} 1787 1788#define ARC_MINTIME (hz>>4) /* 62 ms */ 1789 1790static inline boolean_t 1791arc_buf_is_shared(arc_buf_t *buf) 1792{ 1793 boolean_t shared = (buf->b_data != NULL && 1794 buf->b_hdr->b_l1hdr.b_pabd != NULL && 1795 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && 1796 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); 1797 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1798 IMPLY(shared, ARC_BUF_SHARED(buf)); 1799 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); 1800 1801 /* 1802 * It would be nice to assert arc_can_share() too, but the "hdr isn't 1803 * already being shared" requirement prevents us from doing that. 1804 */ 1805 1806 return (shared); 1807} 1808 1809/* 1810 * Free the checksum associated with this header. If there is no checksum, this 1811 * is a no-op. 1812 */ 1813static inline void 1814arc_cksum_free(arc_buf_hdr_t *hdr) 1815{ 1816 ASSERT(HDR_HAS_L1HDR(hdr)); 1817 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1818 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1819 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1820 hdr->b_l1hdr.b_freeze_cksum = NULL; 1821 } 1822 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1823} 1824 1825/* 1826 * Return true iff at least one of the bufs on hdr is not compressed. 1827 */ 1828static boolean_t 1829arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) 1830{ 1831 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { 1832 if (!ARC_BUF_COMPRESSED(b)) { 1833 return (B_TRUE); 1834 } 1835 } 1836 return (B_FALSE); 1837} 1838 1839/* 1840 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data 1841 * matches the checksum that is stored in the hdr. If there is no checksum, 1842 * or if the buf is compressed, this is a no-op. 1843 */ 1844static void 1845arc_cksum_verify(arc_buf_t *buf) 1846{ 1847 arc_buf_hdr_t *hdr = buf->b_hdr; 1848 zio_cksum_t zc; 1849 1850 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1851 return; 1852 1853 if (ARC_BUF_COMPRESSED(buf)) { 1854 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 1855 arc_hdr_has_uncompressed_buf(hdr)); 1856 return; 1857 } 1858 1859 ASSERT(HDR_HAS_L1HDR(hdr)); 1860 1861 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1862 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1863 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1864 return; 1865 } 1866 1867 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); 1868 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1869 panic("buffer modified while frozen!"); 1870 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1871} 1872 1873static boolean_t 1874arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1875{ 1876 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1877 boolean_t valid_cksum; 1878 1879 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1880 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1881 1882 /* 1883 * We rely on the blkptr's checksum to determine if the block 1884 * is valid or not. When compressed arc is enabled, the l2arc 1885 * writes the block to the l2arc just as it appears in the pool. 1886 * This allows us to use the blkptr's checksum to validate the 1887 * data that we just read off of the l2arc without having to store 1888 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1889 * arc is disabled, then the data written to the l2arc is always 1890 * uncompressed and won't match the block as it exists in the main 1891 * pool. When this is the case, we must first compress it if it is 1892 * compressed on the main pool before we can validate the checksum. 1893 */ 1894 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1895 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1896 uint64_t lsize = HDR_GET_LSIZE(hdr); 1897 uint64_t csize; 1898 1899 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE); 1900 csize = zio_compress_data(compress, zio->io_abd, 1901 abd_to_buf(cdata), lsize); 1902 1903 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1904 if (csize < HDR_GET_PSIZE(hdr)) { 1905 /* 1906 * Compressed blocks are always a multiple of the 1907 * smallest ashift in the pool. Ideally, we would 1908 * like to round up the csize to the next 1909 * spa_min_ashift but that value may have changed 1910 * since the block was last written. Instead, 1911 * we rely on the fact that the hdr's psize 1912 * was set to the psize of the block when it was 1913 * last written. We set the csize to that value 1914 * and zero out any part that should not contain 1915 * data. 1916 */ 1917 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize); 1918 csize = HDR_GET_PSIZE(hdr); 1919 } 1920 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL); 1921 } 1922 1923 /* 1924 * Block pointers always store the checksum for the logical data. 1925 * If the block pointer has the gang bit set, then the checksum 1926 * it represents is for the reconstituted data and not for an 1927 * individual gang member. The zio pipeline, however, must be able to 1928 * determine the checksum of each of the gang constituents so it 1929 * treats the checksum comparison differently than what we need 1930 * for l2arc blocks. This prevents us from using the 1931 * zio_checksum_error() interface directly. Instead we must call the 1932 * zio_checksum_error_impl() so that we can ensure the checksum is 1933 * generated using the correct checksum algorithm and accounts for the 1934 * logical I/O size and not just a gang fragment. 1935 */ 1936 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1937 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, 1938 zio->io_offset, NULL) == 0); 1939 zio_pop_transforms(zio); 1940 return (valid_cksum); 1941} 1942 1943/* 1944 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a 1945 * checksum and attaches it to the buf's hdr so that we can ensure that the buf 1946 * isn't modified later on. If buf is compressed or there is already a checksum 1947 * on the hdr, this is a no-op (we only checksum uncompressed bufs). 1948 */ 1949static void 1950arc_cksum_compute(arc_buf_t *buf) 1951{ 1952 arc_buf_hdr_t *hdr = buf->b_hdr; 1953 1954 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1955 return; 1956 1957 ASSERT(HDR_HAS_L1HDR(hdr)); 1958 1959 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1960 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1961 ASSERT(arc_hdr_has_uncompressed_buf(hdr)); 1962 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1963 return; 1964 } else if (ARC_BUF_COMPRESSED(buf)) { 1965 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1966 return; 1967 } 1968 1969 ASSERT(!ARC_BUF_COMPRESSED(buf)); 1970 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1971 KM_SLEEP); 1972 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, 1973 hdr->b_l1hdr.b_freeze_cksum); 1974 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1975#ifdef illumos 1976 arc_buf_watch(buf); 1977#endif 1978} 1979 1980#ifdef illumos 1981#ifndef _KERNEL 1982typedef struct procctl { 1983 long cmd; 1984 prwatch_t prwatch; 1985} procctl_t; 1986#endif 1987 1988/* ARGSUSED */ 1989static void 1990arc_buf_unwatch(arc_buf_t *buf) 1991{ 1992#ifndef _KERNEL 1993 if (arc_watch) { 1994 int result; 1995 procctl_t ctl; 1996 ctl.cmd = PCWATCH; 1997 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1998 ctl.prwatch.pr_size = 0; 1999 ctl.prwatch.pr_wflags = 0; 2000 result = write(arc_procfd, &ctl, sizeof (ctl)); 2001 ASSERT3U(result, ==, sizeof (ctl)); 2002 } 2003#endif 2004} 2005 2006/* ARGSUSED */ 2007static void 2008arc_buf_watch(arc_buf_t *buf) 2009{ 2010#ifndef _KERNEL 2011 if (arc_watch) { 2012 int result; 2013 procctl_t ctl; 2014 ctl.cmd = PCWATCH; 2015 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 2016 ctl.prwatch.pr_size = arc_buf_size(buf); 2017 ctl.prwatch.pr_wflags = WA_WRITE; 2018 result = write(arc_procfd, &ctl, sizeof (ctl)); 2019 ASSERT3U(result, ==, sizeof (ctl)); 2020 } 2021#endif 2022} 2023#endif /* illumos */ 2024 2025static arc_buf_contents_t 2026arc_buf_type(arc_buf_hdr_t *hdr) 2027{ 2028 arc_buf_contents_t type; 2029 if (HDR_ISTYPE_METADATA(hdr)) { 2030 type = ARC_BUFC_METADATA; 2031 } else { 2032 type = ARC_BUFC_DATA; 2033 } 2034 VERIFY3U(hdr->b_type, ==, type); 2035 return (type); 2036} 2037 2038boolean_t 2039arc_is_metadata(arc_buf_t *buf) 2040{ 2041 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); 2042} 2043 2044static uint32_t 2045arc_bufc_to_flags(arc_buf_contents_t type) 2046{ 2047 switch (type) { 2048 case ARC_BUFC_DATA: 2049 /* metadata field is 0 if buffer contains normal data */ 2050 return (0); 2051 case ARC_BUFC_METADATA: 2052 return (ARC_FLAG_BUFC_METADATA); 2053 default: 2054 break; 2055 } 2056 panic("undefined ARC buffer type!"); 2057 return ((uint32_t)-1); 2058} 2059 2060void 2061arc_buf_thaw(arc_buf_t *buf) 2062{ 2063 arc_buf_hdr_t *hdr = buf->b_hdr; 2064 2065 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2066 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2067 2068 arc_cksum_verify(buf); 2069 2070 /* 2071 * Compressed buffers do not manipulate the b_freeze_cksum or 2072 * allocate b_thawed. 2073 */ 2074 if (ARC_BUF_COMPRESSED(buf)) { 2075 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2076 arc_hdr_has_uncompressed_buf(hdr)); 2077 return; 2078 } 2079 2080 ASSERT(HDR_HAS_L1HDR(hdr)); 2081 arc_cksum_free(hdr); 2082 2083 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 2084#ifdef ZFS_DEBUG 2085 if (zfs_flags & ZFS_DEBUG_MODIFY) { 2086 if (hdr->b_l1hdr.b_thawed != NULL) 2087 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2088 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 2089 } 2090#endif 2091 2092 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2093 2094#ifdef illumos 2095 arc_buf_unwatch(buf); 2096#endif 2097} 2098 2099void 2100arc_buf_freeze(arc_buf_t *buf) 2101{ 2102 arc_buf_hdr_t *hdr = buf->b_hdr; 2103 kmutex_t *hash_lock; 2104 2105 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2106 return; 2107 2108 if (ARC_BUF_COMPRESSED(buf)) { 2109 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2110 arc_hdr_has_uncompressed_buf(hdr)); 2111 return; 2112 } 2113 2114 hash_lock = HDR_LOCK(hdr); 2115 mutex_enter(hash_lock); 2116 2117 ASSERT(HDR_HAS_L1HDR(hdr)); 2118 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 2119 hdr->b_l1hdr.b_state == arc_anon); 2120 arc_cksum_compute(buf); 2121 mutex_exit(hash_lock); 2122} 2123 2124/* 2125 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 2126 * the following functions should be used to ensure that the flags are 2127 * updated in a thread-safe way. When manipulating the flags either 2128 * the hash_lock must be held or the hdr must be undiscoverable. This 2129 * ensures that we're not racing with any other threads when updating 2130 * the flags. 2131 */ 2132static inline void 2133arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2134{ 2135 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2136 hdr->b_flags |= flags; 2137} 2138 2139static inline void 2140arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2141{ 2142 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2143 hdr->b_flags &= ~flags; 2144} 2145 2146/* 2147 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 2148 * done in a special way since we have to clear and set bits 2149 * at the same time. Consumers that wish to set the compression bits 2150 * must use this function to ensure that the flags are updated in 2151 * thread-safe manner. 2152 */ 2153static void 2154arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 2155{ 2156 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2157 2158 /* 2159 * Holes and embedded blocks will always have a psize = 0 so 2160 * we ignore the compression of the blkptr and set the 2161 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 2162 * Holes and embedded blocks remain anonymous so we don't 2163 * want to uncompress them. Mark them as uncompressed. 2164 */ 2165 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 2166 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2167 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 2168 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 2169 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2170 } else { 2171 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2172 HDR_SET_COMPRESS(hdr, cmp); 2173 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2174 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2175 } 2176} 2177 2178/* 2179 * Looks for another buf on the same hdr which has the data decompressed, copies 2180 * from it, and returns true. If no such buf exists, returns false. 2181 */ 2182static boolean_t 2183arc_buf_try_copy_decompressed_data(arc_buf_t *buf) 2184{ 2185 arc_buf_hdr_t *hdr = buf->b_hdr; 2186 boolean_t copied = B_FALSE; 2187 2188 ASSERT(HDR_HAS_L1HDR(hdr)); 2189 ASSERT3P(buf->b_data, !=, NULL); 2190 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2191 2192 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; 2193 from = from->b_next) { 2194 /* can't use our own data buffer */ 2195 if (from == buf) { 2196 continue; 2197 } 2198 2199 if (!ARC_BUF_COMPRESSED(from)) { 2200 bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); 2201 copied = B_TRUE; 2202 break; 2203 } 2204 } 2205 2206 /* 2207 * There were no decompressed bufs, so there should not be a 2208 * checksum on the hdr either. 2209 */ 2210 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); 2211 2212 return (copied); 2213} 2214 2215/* 2216 * Given a buf that has a data buffer attached to it, this function will 2217 * efficiently fill the buf with data of the specified compression setting from 2218 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr 2219 * are already sharing a data buf, no copy is performed. 2220 * 2221 * If the buf is marked as compressed but uncompressed data was requested, this 2222 * will allocate a new data buffer for the buf, remove that flag, and fill the 2223 * buf with uncompressed data. You can't request a compressed buf on a hdr with 2224 * uncompressed data, and (since we haven't added support for it yet) if you 2225 * want compressed data your buf must already be marked as compressed and have 2226 * the correct-sized data buffer. 2227 */ 2228static int 2229arc_buf_fill(arc_buf_t *buf, boolean_t compressed) 2230{ 2231 arc_buf_hdr_t *hdr = buf->b_hdr; 2232 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 2233 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2234 2235 ASSERT3P(buf->b_data, !=, NULL); 2236 IMPLY(compressed, hdr_compressed); 2237 IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); 2238 2239 if (hdr_compressed == compressed) { 2240 if (!arc_buf_is_shared(buf)) { 2241 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, 2242 arc_buf_size(buf)); 2243 } 2244 } else { 2245 ASSERT(hdr_compressed); 2246 ASSERT(!compressed); 2247 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2248 2249 /* 2250 * If the buf is sharing its data with the hdr, unlink it and 2251 * allocate a new data buffer for the buf. 2252 */ 2253 if (arc_buf_is_shared(buf)) { 2254 ASSERT(ARC_BUF_COMPRESSED(buf)); 2255 2256 /* We need to give the buf it's own b_data */ 2257 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2258 buf->b_data = 2259 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2260 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2261 2262 /* Previously overhead was 0; just add new overhead */ 2263 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2264 } else if (ARC_BUF_COMPRESSED(buf)) { 2265 /* We need to reallocate the buf's b_data */ 2266 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), 2267 buf); 2268 buf->b_data = 2269 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2270 2271 /* We increased the size of b_data; update overhead */ 2272 ARCSTAT_INCR(arcstat_overhead_size, 2273 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); 2274 } 2275 2276 /* 2277 * Regardless of the buf's previous compression settings, it 2278 * should not be compressed at the end of this function. 2279 */ 2280 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; 2281 2282 /* 2283 * Try copying the data from another buf which already has a 2284 * decompressed version. If that's not possible, it's time to 2285 * bite the bullet and decompress the data from the hdr. 2286 */ 2287 if (arc_buf_try_copy_decompressed_data(buf)) { 2288 /* Skip byteswapping and checksumming (already done) */ 2289 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); 2290 return (0); 2291 } else { 2292 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2293 hdr->b_l1hdr.b_pabd, buf->b_data, 2294 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2295 2296 /* 2297 * Absent hardware errors or software bugs, this should 2298 * be impossible, but log it anyway so we can debug it. 2299 */ 2300 if (error != 0) { 2301 zfs_dbgmsg( 2302 "hdr %p, compress %d, psize %d, lsize %d", 2303 hdr, HDR_GET_COMPRESS(hdr), 2304 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2305 return (SET_ERROR(EIO)); 2306 } 2307 } 2308 } 2309 2310 /* Byteswap the buf's data if necessary */ 2311 if (bswap != DMU_BSWAP_NUMFUNCS) { 2312 ASSERT(!HDR_SHARED_DATA(hdr)); 2313 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2314 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2315 } 2316 2317 /* Compute the hdr's checksum if necessary */ 2318 arc_cksum_compute(buf); 2319 2320 return (0); 2321} 2322 2323int 2324arc_decompress(arc_buf_t *buf) 2325{ 2326 return (arc_buf_fill(buf, B_FALSE)); 2327} 2328 2329/* 2330 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. 2331 */ 2332static uint64_t 2333arc_hdr_size(arc_buf_hdr_t *hdr) 2334{ 2335 uint64_t size; 2336 2337 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2338 HDR_GET_PSIZE(hdr) > 0) { 2339 size = HDR_GET_PSIZE(hdr); 2340 } else { 2341 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2342 size = HDR_GET_LSIZE(hdr); 2343 } 2344 return (size); 2345} 2346 2347/* 2348 * Increment the amount of evictable space in the arc_state_t's refcount. 2349 * We account for the space used by the hdr and the arc buf individually 2350 * so that we can add and remove them from the refcount individually. 2351 */ 2352static void 2353arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2354{ 2355 arc_buf_contents_t type = arc_buf_type(hdr); 2356 2357 ASSERT(HDR_HAS_L1HDR(hdr)); 2358 2359 if (GHOST_STATE(state)) { 2360 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2361 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2362 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2363 (void) refcount_add_many(&state->arcs_esize[type], 2364 HDR_GET_LSIZE(hdr), hdr); 2365 return; 2366 } 2367 2368 ASSERT(!GHOST_STATE(state)); 2369 if (hdr->b_l1hdr.b_pabd != NULL) { 2370 (void) refcount_add_many(&state->arcs_esize[type], 2371 arc_hdr_size(hdr), hdr); 2372 } 2373 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2374 buf = buf->b_next) { 2375 if (arc_buf_is_shared(buf)) 2376 continue; 2377 (void) refcount_add_many(&state->arcs_esize[type], 2378 arc_buf_size(buf), buf); 2379 } 2380} 2381 2382/* 2383 * Decrement the amount of evictable space in the arc_state_t's refcount. 2384 * We account for the space used by the hdr and the arc buf individually 2385 * so that we can add and remove them from the refcount individually. 2386 */ 2387static void 2388arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2389{ 2390 arc_buf_contents_t type = arc_buf_type(hdr); 2391 2392 ASSERT(HDR_HAS_L1HDR(hdr)); 2393 2394 if (GHOST_STATE(state)) { 2395 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2396 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2397 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2398 (void) refcount_remove_many(&state->arcs_esize[type], 2399 HDR_GET_LSIZE(hdr), hdr); 2400 return; 2401 } 2402 2403 ASSERT(!GHOST_STATE(state)); 2404 if (hdr->b_l1hdr.b_pabd != NULL) { 2405 (void) refcount_remove_many(&state->arcs_esize[type], 2406 arc_hdr_size(hdr), hdr); 2407 } 2408 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2409 buf = buf->b_next) { 2410 if (arc_buf_is_shared(buf)) 2411 continue; 2412 (void) refcount_remove_many(&state->arcs_esize[type], 2413 arc_buf_size(buf), buf); 2414 } 2415} 2416 2417/* 2418 * Add a reference to this hdr indicating that someone is actively 2419 * referencing that memory. When the refcount transitions from 0 to 1, 2420 * we remove it from the respective arc_state_t list to indicate that 2421 * it is not evictable. 2422 */ 2423static void 2424add_reference(arc_buf_hdr_t *hdr, void *tag) 2425{ 2426 ASSERT(HDR_HAS_L1HDR(hdr)); 2427 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2428 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2429 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2430 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2431 } 2432 2433 arc_state_t *state = hdr->b_l1hdr.b_state; 2434 2435 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2436 (state != arc_anon)) { 2437 /* We don't use the L2-only state list. */ 2438 if (state != arc_l2c_only) { 2439 multilist_remove(state->arcs_list[arc_buf_type(hdr)], 2440 hdr); 2441 arc_evictable_space_decrement(hdr, state); 2442 } 2443 /* remove the prefetch flag if we get a reference */ 2444 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2445 } 2446} 2447 2448/* 2449 * Remove a reference from this hdr. When the reference transitions from 2450 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2451 * list making it eligible for eviction. 2452 */ 2453static int 2454remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2455{ 2456 int cnt; 2457 arc_state_t *state = hdr->b_l1hdr.b_state; 2458 2459 ASSERT(HDR_HAS_L1HDR(hdr)); 2460 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2461 ASSERT(!GHOST_STATE(state)); 2462 2463 /* 2464 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2465 * check to prevent usage of the arc_l2c_only list. 2466 */ 2467 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2468 (state != arc_anon)) { 2469 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); 2470 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2471 arc_evictable_space_increment(hdr, state); 2472 } 2473 return (cnt); 2474} 2475 2476/* 2477 * Move the supplied buffer to the indicated state. The hash lock 2478 * for the buffer must be held by the caller. 2479 */ 2480static void 2481arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2482 kmutex_t *hash_lock) 2483{ 2484 arc_state_t *old_state; 2485 int64_t refcnt; 2486 uint32_t bufcnt; 2487 boolean_t update_old, update_new; 2488 arc_buf_contents_t buftype = arc_buf_type(hdr); 2489 2490 /* 2491 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2492 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2493 * L1 hdr doesn't always exist when we change state to arc_anon before 2494 * destroying a header, in which case reallocating to add the L1 hdr is 2495 * pointless. 2496 */ 2497 if (HDR_HAS_L1HDR(hdr)) { 2498 old_state = hdr->b_l1hdr.b_state; 2499 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2500 bufcnt = hdr->b_l1hdr.b_bufcnt; 2501 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); 2502 } else { 2503 old_state = arc_l2c_only; 2504 refcnt = 0; 2505 bufcnt = 0; 2506 update_old = B_FALSE; 2507 } 2508 update_new = update_old; 2509 2510 ASSERT(MUTEX_HELD(hash_lock)); 2511 ASSERT3P(new_state, !=, old_state); 2512 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2513 ASSERT(old_state != arc_anon || bufcnt <= 1); 2514 2515 /* 2516 * If this buffer is evictable, transfer it from the 2517 * old state list to the new state list. 2518 */ 2519 if (refcnt == 0) { 2520 if (old_state != arc_anon && old_state != arc_l2c_only) { 2521 ASSERT(HDR_HAS_L1HDR(hdr)); 2522 multilist_remove(old_state->arcs_list[buftype], hdr); 2523 2524 if (GHOST_STATE(old_state)) { 2525 ASSERT0(bufcnt); 2526 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2527 update_old = B_TRUE; 2528 } 2529 arc_evictable_space_decrement(hdr, old_state); 2530 } 2531 if (new_state != arc_anon && new_state != arc_l2c_only) { 2532 2533 /* 2534 * An L1 header always exists here, since if we're 2535 * moving to some L1-cached state (i.e. not l2c_only or 2536 * anonymous), we realloc the header to add an L1hdr 2537 * beforehand. 2538 */ 2539 ASSERT(HDR_HAS_L1HDR(hdr)); 2540 multilist_insert(new_state->arcs_list[buftype], hdr); 2541 2542 if (GHOST_STATE(new_state)) { 2543 ASSERT0(bufcnt); 2544 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2545 update_new = B_TRUE; 2546 } 2547 arc_evictable_space_increment(hdr, new_state); 2548 } 2549 } 2550 2551 ASSERT(!HDR_EMPTY(hdr)); 2552 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2553 buf_hash_remove(hdr); 2554 2555 /* adjust state sizes (ignore arc_l2c_only) */ 2556 2557 if (update_new && new_state != arc_l2c_only) { 2558 ASSERT(HDR_HAS_L1HDR(hdr)); 2559 if (GHOST_STATE(new_state)) { 2560 ASSERT0(bufcnt); 2561 2562 /* 2563 * When moving a header to a ghost state, we first 2564 * remove all arc buffers. Thus, we'll have a 2565 * bufcnt of zero, and no arc buffer to use for 2566 * the reference. As a result, we use the arc 2567 * header pointer for the reference. 2568 */ 2569 (void) refcount_add_many(&new_state->arcs_size, 2570 HDR_GET_LSIZE(hdr), hdr); 2571 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2572 } else { 2573 uint32_t buffers = 0; 2574 2575 /* 2576 * Each individual buffer holds a unique reference, 2577 * thus we must remove each of these references one 2578 * at a time. 2579 */ 2580 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2581 buf = buf->b_next) { 2582 ASSERT3U(bufcnt, !=, 0); 2583 buffers++; 2584 2585 /* 2586 * When the arc_buf_t is sharing the data 2587 * block with the hdr, the owner of the 2588 * reference belongs to the hdr. Only 2589 * add to the refcount if the arc_buf_t is 2590 * not shared. 2591 */ 2592 if (arc_buf_is_shared(buf)) 2593 continue; 2594 2595 (void) refcount_add_many(&new_state->arcs_size, 2596 arc_buf_size(buf), buf); 2597 } 2598 ASSERT3U(bufcnt, ==, buffers); 2599 2600 if (hdr->b_l1hdr.b_pabd != NULL) { 2601 (void) refcount_add_many(&new_state->arcs_size, 2602 arc_hdr_size(hdr), hdr); 2603 } else { 2604 ASSERT(GHOST_STATE(old_state)); 2605 } 2606 } 2607 } 2608 2609 if (update_old && old_state != arc_l2c_only) { 2610 ASSERT(HDR_HAS_L1HDR(hdr)); 2611 if (GHOST_STATE(old_state)) { 2612 ASSERT0(bufcnt); 2613 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2614 2615 /* 2616 * When moving a header off of a ghost state, 2617 * the header will not contain any arc buffers. 2618 * We use the arc header pointer for the reference 2619 * which is exactly what we did when we put the 2620 * header on the ghost state. 2621 */ 2622 2623 (void) refcount_remove_many(&old_state->arcs_size, 2624 HDR_GET_LSIZE(hdr), hdr); 2625 } else { 2626 uint32_t buffers = 0; 2627 2628 /* 2629 * Each individual buffer holds a unique reference, 2630 * thus we must remove each of these references one 2631 * at a time. 2632 */ 2633 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2634 buf = buf->b_next) { 2635 ASSERT3U(bufcnt, !=, 0); 2636 buffers++; 2637 2638 /* 2639 * When the arc_buf_t is sharing the data 2640 * block with the hdr, the owner of the 2641 * reference belongs to the hdr. Only 2642 * add to the refcount if the arc_buf_t is 2643 * not shared. 2644 */ 2645 if (arc_buf_is_shared(buf)) 2646 continue; 2647 2648 (void) refcount_remove_many( 2649 &old_state->arcs_size, arc_buf_size(buf), 2650 buf); 2651 } 2652 ASSERT3U(bufcnt, ==, buffers); 2653 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2654 (void) refcount_remove_many( 2655 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2656 } 2657 } 2658 2659 if (HDR_HAS_L1HDR(hdr)) 2660 hdr->b_l1hdr.b_state = new_state; 2661 2662 /* 2663 * L2 headers should never be on the L2 state list since they don't 2664 * have L1 headers allocated. 2665 */ 2666 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2667 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2668} 2669 2670void 2671arc_space_consume(uint64_t space, arc_space_type_t type) 2672{ 2673 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2674 2675 switch (type) { 2676 case ARC_SPACE_DATA: 2677 aggsum_add(&astat_data_size, space); 2678 break; 2679 case ARC_SPACE_META: 2680 aggsum_add(&astat_metadata_size, space); 2681 break; 2682 case ARC_SPACE_OTHER: 2683 aggsum_add(&astat_other_size, space); 2684 break; 2685 case ARC_SPACE_HDRS: 2686 aggsum_add(&astat_hdr_size, space); 2687 break; 2688 case ARC_SPACE_L2HDRS: 2689 aggsum_add(&astat_l2_hdr_size, space); 2690 break; 2691 } 2692 2693 if (type != ARC_SPACE_DATA) 2694 aggsum_add(&arc_meta_used, space); 2695 2696 aggsum_add(&arc_size, space); 2697} 2698 2699void 2700arc_space_return(uint64_t space, arc_space_type_t type) 2701{ 2702 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2703 2704 switch (type) { 2705 case ARC_SPACE_DATA: 2706 aggsum_add(&astat_data_size, -space); 2707 break; 2708 case ARC_SPACE_META: 2709 aggsum_add(&astat_metadata_size, -space); 2710 break; 2711 case ARC_SPACE_OTHER: 2712 aggsum_add(&astat_other_size, -space); 2713 break; 2714 case ARC_SPACE_HDRS: 2715 aggsum_add(&astat_hdr_size, -space); 2716 break; 2717 case ARC_SPACE_L2HDRS: 2718 aggsum_add(&astat_l2_hdr_size, -space); 2719 break; 2720 } 2721 2722 if (type != ARC_SPACE_DATA) { 2723 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0); 2724 /* 2725 * We use the upper bound here rather than the precise value 2726 * because the arc_meta_max value doesn't need to be 2727 * precise. It's only consumed by humans via arcstats. 2728 */ 2729 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used)) 2730 arc_meta_max = aggsum_upper_bound(&arc_meta_used); 2731 aggsum_add(&arc_meta_used, -space); 2732 } 2733 2734 ASSERT(aggsum_compare(&arc_size, space) >= 0); 2735 aggsum_add(&arc_size, -space); 2736} 2737 2738/* 2739 * Given a hdr and a buf, returns whether that buf can share its b_data buffer 2740 * with the hdr's b_pabd. 2741 */ 2742static boolean_t 2743arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2744{ 2745 /* 2746 * The criteria for sharing a hdr's data are: 2747 * 1. the hdr's compression matches the buf's compression 2748 * 2. the hdr doesn't need to be byteswapped 2749 * 3. the hdr isn't already being shared 2750 * 4. the buf is either compressed or it is the last buf in the hdr list 2751 * 2752 * Criterion #4 maintains the invariant that shared uncompressed 2753 * bufs must be the final buf in the hdr's b_buf list. Reading this, you 2754 * might ask, "if a compressed buf is allocated first, won't that be the 2755 * last thing in the list?", but in that case it's impossible to create 2756 * a shared uncompressed buf anyway (because the hdr must be compressed 2757 * to have the compressed buf). You might also think that #3 is 2758 * sufficient to make this guarantee, however it's possible 2759 * (specifically in the rare L2ARC write race mentioned in 2760 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that 2761 * is sharable, but wasn't at the time of its allocation. Rather than 2762 * allow a new shared uncompressed buf to be created and then shuffle 2763 * the list around to make it the last element, this simply disallows 2764 * sharing if the new buf isn't the first to be added. 2765 */ 2766 ASSERT3P(buf->b_hdr, ==, hdr); 2767 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; 2768 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; 2769 return (buf_compressed == hdr_compressed && 2770 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2771 !HDR_SHARED_DATA(hdr) && 2772 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); 2773} 2774 2775/* 2776 * Allocate a buf for this hdr. If you care about the data that's in the hdr, 2777 * or if you want a compressed buffer, pass those flags in. Returns 0 if the 2778 * copy was made successfully, or an error code otherwise. 2779 */ 2780static int 2781arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed, 2782 boolean_t fill, arc_buf_t **ret) 2783{ 2784 arc_buf_t *buf; 2785 2786 ASSERT(HDR_HAS_L1HDR(hdr)); 2787 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2788 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2789 hdr->b_type == ARC_BUFC_METADATA); 2790 ASSERT3P(ret, !=, NULL); 2791 ASSERT3P(*ret, ==, NULL); 2792 2793 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2794 buf->b_hdr = hdr; 2795 buf->b_data = NULL; 2796 buf->b_next = hdr->b_l1hdr.b_buf; 2797 buf->b_flags = 0; 2798 2799 add_reference(hdr, tag); 2800 2801 /* 2802 * We're about to change the hdr's b_flags. We must either 2803 * hold the hash_lock or be undiscoverable. 2804 */ 2805 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2806 2807 /* 2808 * Only honor requests for compressed bufs if the hdr is actually 2809 * compressed. 2810 */ 2811 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 2812 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; 2813 2814 /* 2815 * If the hdr's data can be shared then we share the data buffer and 2816 * set the appropriate bit in the hdr's b_flags to indicate the hdr is 2817 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new 2818 * buffer to store the buf's data. 2819 * 2820 * There are two additional restrictions here because we're sharing 2821 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be 2822 * actively involved in an L2ARC write, because if this buf is used by 2823 * an arc_write() then the hdr's data buffer will be released when the 2824 * write completes, even though the L2ARC write might still be using it. 2825 * Second, the hdr's ABD must be linear so that the buf's user doesn't 2826 * need to be ABD-aware. 2827 */ 2828 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && 2829 abd_is_linear(hdr->b_l1hdr.b_pabd); 2830 2831 /* Set up b_data and sharing */ 2832 if (can_share) { 2833 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); 2834 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2835 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2836 } else { 2837 buf->b_data = 2838 arc_get_data_buf(hdr, arc_buf_size(buf), buf); 2839 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2840 } 2841 VERIFY3P(buf->b_data, !=, NULL); 2842 2843 hdr->b_l1hdr.b_buf = buf; 2844 hdr->b_l1hdr.b_bufcnt += 1; 2845 2846 /* 2847 * If the user wants the data from the hdr, we need to either copy or 2848 * decompress the data. 2849 */ 2850 if (fill) { 2851 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); 2852 } 2853 2854 return (0); 2855} 2856 2857static char *arc_onloan_tag = "onloan"; 2858 2859static inline void 2860arc_loaned_bytes_update(int64_t delta) 2861{ 2862 atomic_add_64(&arc_loaned_bytes, delta); 2863 2864 /* assert that it did not wrap around */ 2865 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 2866} 2867 2868/* 2869 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2870 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2871 * buffers must be returned to the arc before they can be used by the DMU or 2872 * freed. 2873 */ 2874arc_buf_t * 2875arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) 2876{ 2877 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, 2878 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); 2879 2880 arc_loaned_bytes_update(arc_buf_size(buf)); 2881 2882 return (buf); 2883} 2884 2885arc_buf_t * 2886arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, 2887 enum zio_compress compression_type) 2888{ 2889 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, 2890 psize, lsize, compression_type); 2891 2892 arc_loaned_bytes_update(arc_buf_size(buf)); 2893 2894 return (buf); 2895} 2896 2897 2898/* 2899 * Return a loaned arc buffer to the arc. 2900 */ 2901void 2902arc_return_buf(arc_buf_t *buf, void *tag) 2903{ 2904 arc_buf_hdr_t *hdr = buf->b_hdr; 2905 2906 ASSERT3P(buf->b_data, !=, NULL); 2907 ASSERT(HDR_HAS_L1HDR(hdr)); 2908 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2909 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2910 2911 arc_loaned_bytes_update(-arc_buf_size(buf)); 2912} 2913 2914/* Detach an arc_buf from a dbuf (tag) */ 2915void 2916arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2917{ 2918 arc_buf_hdr_t *hdr = buf->b_hdr; 2919 2920 ASSERT3P(buf->b_data, !=, NULL); 2921 ASSERT(HDR_HAS_L1HDR(hdr)); 2922 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2923 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2924 2925 arc_loaned_bytes_update(arc_buf_size(buf)); 2926} 2927 2928static void 2929l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) 2930{ 2931 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2932 2933 df->l2df_abd = abd; 2934 df->l2df_size = size; 2935 df->l2df_type = type; 2936 mutex_enter(&l2arc_free_on_write_mtx); 2937 list_insert_head(l2arc_free_on_write, df); 2938 mutex_exit(&l2arc_free_on_write_mtx); 2939} 2940 2941static void 2942arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2943{ 2944 arc_state_t *state = hdr->b_l1hdr.b_state; 2945 arc_buf_contents_t type = arc_buf_type(hdr); 2946 uint64_t size = arc_hdr_size(hdr); 2947 2948 /* protected by hash lock, if in the hash table */ 2949 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2950 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2951 ASSERT(state != arc_anon && state != arc_l2c_only); 2952 2953 (void) refcount_remove_many(&state->arcs_esize[type], 2954 size, hdr); 2955 } 2956 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2957 if (type == ARC_BUFC_METADATA) { 2958 arc_space_return(size, ARC_SPACE_META); 2959 } else { 2960 ASSERT(type == ARC_BUFC_DATA); 2961 arc_space_return(size, ARC_SPACE_DATA); 2962 } 2963 2964 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); 2965} 2966 2967/* 2968 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2969 * data buffer, we transfer the refcount ownership to the hdr and update 2970 * the appropriate kstats. 2971 */ 2972static void 2973arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2974{ 2975 arc_state_t *state = hdr->b_l1hdr.b_state; 2976 2977 ASSERT(arc_can_share(hdr, buf)); 2978 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2979 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2980 2981 /* 2982 * Start sharing the data buffer. We transfer the 2983 * refcount ownership to the hdr since it always owns 2984 * the refcount whenever an arc_buf_t is shared. 2985 */ 2986 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 2987 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); 2988 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, 2989 HDR_ISTYPE_METADATA(hdr)); 2990 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2991 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2992 2993 /* 2994 * Since we've transferred ownership to the hdr we need 2995 * to increment its compressed and uncompressed kstats and 2996 * decrement the overhead size. 2997 */ 2998 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2999 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3000 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf)); 3001} 3002 3003static void 3004arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3005{ 3006 arc_state_t *state = hdr->b_l1hdr.b_state; 3007 3008 ASSERT(arc_buf_is_shared(buf)); 3009 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3010 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3011 3012 /* 3013 * We are no longer sharing this buffer so we need 3014 * to transfer its ownership to the rightful owner. 3015 */ 3016 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 3017 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3018 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); 3019 abd_put(hdr->b_l1hdr.b_pabd); 3020 hdr->b_l1hdr.b_pabd = NULL; 3021 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 3022 3023 /* 3024 * Since the buffer is no longer shared between 3025 * the arc buf and the hdr, count it as overhead. 3026 */ 3027 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3028 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3029 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 3030} 3031 3032/* 3033 * Remove an arc_buf_t from the hdr's buf list and return the last 3034 * arc_buf_t on the list. If no buffers remain on the list then return 3035 * NULL. 3036 */ 3037static arc_buf_t * 3038arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) 3039{ 3040 ASSERT(HDR_HAS_L1HDR(hdr)); 3041 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3042 3043 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; 3044 arc_buf_t *lastbuf = NULL; 3045 3046 /* 3047 * Remove the buf from the hdr list and locate the last 3048 * remaining buffer on the list. 3049 */ 3050 while (*bufp != NULL) { 3051 if (*bufp == buf) 3052 *bufp = buf->b_next; 3053 3054 /* 3055 * If we've removed a buffer in the middle of 3056 * the list then update the lastbuf and update 3057 * bufp. 3058 */ 3059 if (*bufp != NULL) { 3060 lastbuf = *bufp; 3061 bufp = &(*bufp)->b_next; 3062 } 3063 } 3064 buf->b_next = NULL; 3065 ASSERT3P(lastbuf, !=, buf); 3066 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); 3067 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); 3068 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); 3069 3070 return (lastbuf); 3071} 3072 3073/* 3074 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's 3075 * list and free it. 3076 */ 3077static void 3078arc_buf_destroy_impl(arc_buf_t *buf) 3079{ 3080 arc_buf_hdr_t *hdr = buf->b_hdr; 3081 3082 /* 3083 * Free up the data associated with the buf but only if we're not 3084 * sharing this with the hdr. If we are sharing it with the hdr, the 3085 * hdr is responsible for doing the free. 3086 */ 3087 if (buf->b_data != NULL) { 3088 /* 3089 * We're about to change the hdr's b_flags. We must either 3090 * hold the hash_lock or be undiscoverable. 3091 */ 3092 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3093 3094 arc_cksum_verify(buf); 3095#ifdef illumos 3096 arc_buf_unwatch(buf); 3097#endif 3098 3099 if (arc_buf_is_shared(buf)) { 3100 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3101 } else { 3102 uint64_t size = arc_buf_size(buf); 3103 arc_free_data_buf(hdr, buf->b_data, size, buf); 3104 ARCSTAT_INCR(arcstat_overhead_size, -size); 3105 } 3106 buf->b_data = NULL; 3107 3108 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3109 hdr->b_l1hdr.b_bufcnt -= 1; 3110 } 3111 3112 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 3113 3114 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { 3115 /* 3116 * If the current arc_buf_t is sharing its data buffer with the 3117 * hdr, then reassign the hdr's b_pabd to share it with the new 3118 * buffer at the end of the list. The shared buffer is always 3119 * the last one on the hdr's buffer list. 3120 * 3121 * There is an equivalent case for compressed bufs, but since 3122 * they aren't guaranteed to be the last buf in the list and 3123 * that is an exceedingly rare case, we just allow that space be 3124 * wasted temporarily. 3125 */ 3126 if (lastbuf != NULL) { 3127 /* Only one buf can be shared at once */ 3128 VERIFY(!arc_buf_is_shared(lastbuf)); 3129 /* hdr is uncompressed so can't have compressed buf */ 3130 VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); 3131 3132 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3133 arc_hdr_free_pabd(hdr); 3134 3135 /* 3136 * We must setup a new shared block between the 3137 * last buffer and the hdr. The data would have 3138 * been allocated by the arc buf so we need to transfer 3139 * ownership to the hdr since it's now being shared. 3140 */ 3141 arc_share_buf(hdr, lastbuf); 3142 } 3143 } else if (HDR_SHARED_DATA(hdr)) { 3144 /* 3145 * Uncompressed shared buffers are always at the end 3146 * of the list. Compressed buffers don't have the 3147 * same requirements. This makes it hard to 3148 * simply assert that the lastbuf is shared so 3149 * we rely on the hdr's compression flags to determine 3150 * if we have a compressed, shared buffer. 3151 */ 3152 ASSERT3P(lastbuf, !=, NULL); 3153 ASSERT(arc_buf_is_shared(lastbuf) || 3154 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 3155 } 3156 3157 /* 3158 * Free the checksum if we're removing the last uncompressed buf from 3159 * this hdr. 3160 */ 3161 if (!arc_hdr_has_uncompressed_buf(hdr)) { 3162 arc_cksum_free(hdr); 3163 } 3164 3165 /* clean up the buf */ 3166 buf->b_hdr = NULL; 3167 kmem_cache_free(buf_cache, buf); 3168} 3169 3170static void 3171arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr) 3172{ 3173 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 3174 ASSERT(HDR_HAS_L1HDR(hdr)); 3175 ASSERT(!HDR_SHARED_DATA(hdr)); 3176 3177 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3178 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr); 3179 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3180 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3181 3182 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3183 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3184} 3185 3186static void 3187arc_hdr_free_pabd(arc_buf_hdr_t *hdr) 3188{ 3189 ASSERT(HDR_HAS_L1HDR(hdr)); 3190 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3191 3192 /* 3193 * If the hdr is currently being written to the l2arc then 3194 * we defer freeing the data by adding it to the l2arc_free_on_write 3195 * list. The l2arc will free the data once it's finished 3196 * writing it to the l2arc device. 3197 */ 3198 if (HDR_L2_WRITING(hdr)) { 3199 arc_hdr_free_on_write(hdr); 3200 ARCSTAT_BUMP(arcstat_l2_free_on_write); 3201 } else { 3202 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, 3203 arc_hdr_size(hdr), hdr); 3204 } 3205 hdr->b_l1hdr.b_pabd = NULL; 3206 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3207 3208 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3209 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3210} 3211 3212static arc_buf_hdr_t * 3213arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 3214 enum zio_compress compression_type, arc_buf_contents_t type) 3215{ 3216 arc_buf_hdr_t *hdr; 3217 3218 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 3219 3220 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3221 ASSERT(HDR_EMPTY(hdr)); 3222 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3223 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 3224 HDR_SET_PSIZE(hdr, psize); 3225 HDR_SET_LSIZE(hdr, lsize); 3226 hdr->b_spa = spa; 3227 hdr->b_type = type; 3228 hdr->b_flags = 0; 3229 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 3230 arc_hdr_set_compress(hdr, compression_type); 3231 3232 hdr->b_l1hdr.b_state = arc_anon; 3233 hdr->b_l1hdr.b_arc_access = 0; 3234 hdr->b_l1hdr.b_bufcnt = 0; 3235 hdr->b_l1hdr.b_buf = NULL; 3236 3237 /* 3238 * Allocate the hdr's buffer. This will contain either 3239 * the compressed or uncompressed data depending on the block 3240 * it references and compressed arc enablement. 3241 */ 3242 arc_hdr_alloc_pabd(hdr); 3243 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3244 3245 return (hdr); 3246} 3247 3248/* 3249 * Transition between the two allocation states for the arc_buf_hdr struct. 3250 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 3251 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 3252 * version is used when a cache buffer is only in the L2ARC in order to reduce 3253 * memory usage. 3254 */ 3255static arc_buf_hdr_t * 3256arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 3257{ 3258 ASSERT(HDR_HAS_L2HDR(hdr)); 3259 3260 arc_buf_hdr_t *nhdr; 3261 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3262 3263 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 3264 (old == hdr_l2only_cache && new == hdr_full_cache)); 3265 3266 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 3267 3268 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 3269 buf_hash_remove(hdr); 3270 3271 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 3272 3273 if (new == hdr_full_cache) { 3274 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3275 /* 3276 * arc_access and arc_change_state need to be aware that a 3277 * header has just come out of L2ARC, so we set its state to 3278 * l2c_only even though it's about to change. 3279 */ 3280 nhdr->b_l1hdr.b_state = arc_l2c_only; 3281 3282 /* Verify previous threads set to NULL before freeing */ 3283 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); 3284 } else { 3285 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3286 ASSERT0(hdr->b_l1hdr.b_bufcnt); 3287 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3288 3289 /* 3290 * If we've reached here, We must have been called from 3291 * arc_evict_hdr(), as such we should have already been 3292 * removed from any ghost list we were previously on 3293 * (which protects us from racing with arc_evict_state), 3294 * thus no locking is needed during this check. 3295 */ 3296 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3297 3298 /* 3299 * A buffer must not be moved into the arc_l2c_only 3300 * state if it's not finished being written out to the 3301 * l2arc device. Otherwise, the b_l1hdr.b_pabd field 3302 * might try to be accessed, even though it was removed. 3303 */ 3304 VERIFY(!HDR_L2_WRITING(hdr)); 3305 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3306 3307#ifdef ZFS_DEBUG 3308 if (hdr->b_l1hdr.b_thawed != NULL) { 3309 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3310 hdr->b_l1hdr.b_thawed = NULL; 3311 } 3312#endif 3313 3314 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3315 } 3316 /* 3317 * The header has been reallocated so we need to re-insert it into any 3318 * lists it was on. 3319 */ 3320 (void) buf_hash_insert(nhdr, NULL); 3321 3322 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 3323 3324 mutex_enter(&dev->l2ad_mtx); 3325 3326 /* 3327 * We must place the realloc'ed header back into the list at 3328 * the same spot. Otherwise, if it's placed earlier in the list, 3329 * l2arc_write_buffers() could find it during the function's 3330 * write phase, and try to write it out to the l2arc. 3331 */ 3332 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 3333 list_remove(&dev->l2ad_buflist, hdr); 3334 3335 mutex_exit(&dev->l2ad_mtx); 3336 3337 /* 3338 * Since we're using the pointer address as the tag when 3339 * incrementing and decrementing the l2ad_alloc refcount, we 3340 * must remove the old pointer (that we're about to destroy) and 3341 * add the new pointer to the refcount. Otherwise we'd remove 3342 * the wrong pointer address when calling arc_hdr_destroy() later. 3343 */ 3344 3345 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 3346 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 3347 3348 buf_discard_identity(hdr); 3349 kmem_cache_free(old, hdr); 3350 3351 return (nhdr); 3352} 3353 3354/* 3355 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 3356 * The buf is returned thawed since we expect the consumer to modify it. 3357 */ 3358arc_buf_t * 3359arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) 3360{ 3361 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 3362 ZIO_COMPRESS_OFF, type); 3363 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3364 3365 arc_buf_t *buf = NULL; 3366 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf)); 3367 arc_buf_thaw(buf); 3368 3369 return (buf); 3370} 3371 3372/* 3373 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this 3374 * for bufs containing metadata. 3375 */ 3376arc_buf_t * 3377arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, 3378 enum zio_compress compression_type) 3379{ 3380 ASSERT3U(lsize, >, 0); 3381 ASSERT3U(lsize, >=, psize); 3382 ASSERT(compression_type > ZIO_COMPRESS_OFF); 3383 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); 3384 3385 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 3386 compression_type, ARC_BUFC_DATA); 3387 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3388 3389 arc_buf_t *buf = NULL; 3390 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf)); 3391 arc_buf_thaw(buf); 3392 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3393 3394 if (!arc_buf_is_shared(buf)) { 3395 /* 3396 * To ensure that the hdr has the correct data in it if we call 3397 * arc_decompress() on this buf before it's been written to 3398 * disk, it's easiest if we just set up sharing between the 3399 * buf and the hdr. 3400 */ 3401 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); 3402 arc_hdr_free_pabd(hdr); 3403 arc_share_buf(hdr, buf); 3404 } 3405 3406 return (buf); 3407} 3408 3409static void 3410arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 3411{ 3412 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 3413 l2arc_dev_t *dev = l2hdr->b_dev; 3414 uint64_t psize = arc_hdr_size(hdr); 3415 3416 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 3417 ASSERT(HDR_HAS_L2HDR(hdr)); 3418 3419 list_remove(&dev->l2ad_buflist, hdr); 3420 3421 ARCSTAT_INCR(arcstat_l2_psize, -psize); 3422 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 3423 3424 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0); 3425 3426 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr); 3427 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3428} 3429 3430static void 3431arc_hdr_destroy(arc_buf_hdr_t *hdr) 3432{ 3433 if (HDR_HAS_L1HDR(hdr)) { 3434 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3435 hdr->b_l1hdr.b_bufcnt > 0); 3436 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3437 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3438 } 3439 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3440 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3441 3442 if (!HDR_EMPTY(hdr)) 3443 buf_discard_identity(hdr); 3444 3445 if (HDR_HAS_L2HDR(hdr)) { 3446 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3447 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3448 3449 if (!buflist_held) 3450 mutex_enter(&dev->l2ad_mtx); 3451 3452 /* 3453 * Even though we checked this conditional above, we 3454 * need to check this again now that we have the 3455 * l2ad_mtx. This is because we could be racing with 3456 * another thread calling l2arc_evict() which might have 3457 * destroyed this header's L2 portion as we were waiting 3458 * to acquire the l2ad_mtx. If that happens, we don't 3459 * want to re-destroy the header's L2 portion. 3460 */ 3461 if (HDR_HAS_L2HDR(hdr)) { 3462 l2arc_trim(hdr); 3463 arc_hdr_l2hdr_destroy(hdr); 3464 } 3465 3466 if (!buflist_held) 3467 mutex_exit(&dev->l2ad_mtx); 3468 } 3469 3470 if (HDR_HAS_L1HDR(hdr)) { 3471 arc_cksum_free(hdr); 3472 3473 while (hdr->b_l1hdr.b_buf != NULL) 3474 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); 3475 3476#ifdef ZFS_DEBUG 3477 if (hdr->b_l1hdr.b_thawed != NULL) { 3478 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3479 hdr->b_l1hdr.b_thawed = NULL; 3480 } 3481#endif 3482 3483 if (hdr->b_l1hdr.b_pabd != NULL) { 3484 arc_hdr_free_pabd(hdr); 3485 } 3486 } 3487 3488 ASSERT3P(hdr->b_hash_next, ==, NULL); 3489 if (HDR_HAS_L1HDR(hdr)) { 3490 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3491 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3492 kmem_cache_free(hdr_full_cache, hdr); 3493 } else { 3494 kmem_cache_free(hdr_l2only_cache, hdr); 3495 } 3496} 3497 3498void 3499arc_buf_destroy(arc_buf_t *buf, void* tag) 3500{ 3501 arc_buf_hdr_t *hdr = buf->b_hdr; 3502 kmutex_t *hash_lock = HDR_LOCK(hdr); 3503 3504 if (hdr->b_l1hdr.b_state == arc_anon) { 3505 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3506 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3507 VERIFY0(remove_reference(hdr, NULL, tag)); 3508 arc_hdr_destroy(hdr); 3509 return; 3510 } 3511 3512 mutex_enter(hash_lock); 3513 ASSERT3P(hdr, ==, buf->b_hdr); 3514 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3515 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3516 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3517 ASSERT3P(buf->b_data, !=, NULL); 3518 3519 (void) remove_reference(hdr, hash_lock, tag); 3520 arc_buf_destroy_impl(buf); 3521 mutex_exit(hash_lock); 3522} 3523 3524/* 3525 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3526 * state of the header is dependent on it's state prior to entering this 3527 * function. The following transitions are possible: 3528 * 3529 * - arc_mru -> arc_mru_ghost 3530 * - arc_mfu -> arc_mfu_ghost 3531 * - arc_mru_ghost -> arc_l2c_only 3532 * - arc_mru_ghost -> deleted 3533 * - arc_mfu_ghost -> arc_l2c_only 3534 * - arc_mfu_ghost -> deleted 3535 */ 3536static int64_t 3537arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3538{ 3539 arc_state_t *evicted_state, *state; 3540 int64_t bytes_evicted = 0; 3541 3542 ASSERT(MUTEX_HELD(hash_lock)); 3543 ASSERT(HDR_HAS_L1HDR(hdr)); 3544 3545 state = hdr->b_l1hdr.b_state; 3546 if (GHOST_STATE(state)) { 3547 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3548 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3549 3550 /* 3551 * l2arc_write_buffers() relies on a header's L1 portion 3552 * (i.e. its b_pabd field) during it's write phase. 3553 * Thus, we cannot push a header onto the arc_l2c_only 3554 * state (removing it's L1 piece) until the header is 3555 * done being written to the l2arc. 3556 */ 3557 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3558 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3559 return (bytes_evicted); 3560 } 3561 3562 ARCSTAT_BUMP(arcstat_deleted); 3563 bytes_evicted += HDR_GET_LSIZE(hdr); 3564 3565 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3566 3567 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3568 if (HDR_HAS_L2HDR(hdr)) { 3569 /* 3570 * This buffer is cached on the 2nd Level ARC; 3571 * don't destroy the header. 3572 */ 3573 arc_change_state(arc_l2c_only, hdr, hash_lock); 3574 /* 3575 * dropping from L1+L2 cached to L2-only, 3576 * realloc to remove the L1 header. 3577 */ 3578 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3579 hdr_l2only_cache); 3580 } else { 3581 arc_change_state(arc_anon, hdr, hash_lock); 3582 arc_hdr_destroy(hdr); 3583 } 3584 return (bytes_evicted); 3585 } 3586 3587 ASSERT(state == arc_mru || state == arc_mfu); 3588 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3589 3590 /* prefetch buffers have a minimum lifespan */ 3591 if (HDR_IO_IN_PROGRESS(hdr) || 3592 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3593 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 3594 arc_min_prefetch_lifespan)) { 3595 ARCSTAT_BUMP(arcstat_evict_skip); 3596 return (bytes_evicted); 3597 } 3598 3599 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3600 while (hdr->b_l1hdr.b_buf) { 3601 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3602 if (!mutex_tryenter(&buf->b_evict_lock)) { 3603 ARCSTAT_BUMP(arcstat_mutex_miss); 3604 break; 3605 } 3606 if (buf->b_data != NULL) 3607 bytes_evicted += HDR_GET_LSIZE(hdr); 3608 mutex_exit(&buf->b_evict_lock); 3609 arc_buf_destroy_impl(buf); 3610 } 3611 3612 if (HDR_HAS_L2HDR(hdr)) { 3613 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3614 } else { 3615 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3616 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3617 HDR_GET_LSIZE(hdr)); 3618 } else { 3619 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3620 HDR_GET_LSIZE(hdr)); 3621 } 3622 } 3623 3624 if (hdr->b_l1hdr.b_bufcnt == 0) { 3625 arc_cksum_free(hdr); 3626 3627 bytes_evicted += arc_hdr_size(hdr); 3628 3629 /* 3630 * If this hdr is being evicted and has a compressed 3631 * buffer then we discard it here before we change states. 3632 * This ensures that the accounting is updated correctly 3633 * in arc_free_data_impl(). 3634 */ 3635 arc_hdr_free_pabd(hdr); 3636 3637 arc_change_state(evicted_state, hdr, hash_lock); 3638 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3639 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3640 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3641 } 3642 3643 return (bytes_evicted); 3644} 3645 3646static uint64_t 3647arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3648 uint64_t spa, int64_t bytes) 3649{ 3650 multilist_sublist_t *mls; 3651 uint64_t bytes_evicted = 0; 3652 arc_buf_hdr_t *hdr; 3653 kmutex_t *hash_lock; 3654 int evict_count = 0; 3655 3656 ASSERT3P(marker, !=, NULL); 3657 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3658 3659 mls = multilist_sublist_lock(ml, idx); 3660 3661 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3662 hdr = multilist_sublist_prev(mls, marker)) { 3663 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3664 (evict_count >= zfs_arc_evict_batch_limit)) 3665 break; 3666 3667 /* 3668 * To keep our iteration location, move the marker 3669 * forward. Since we're not holding hdr's hash lock, we 3670 * must be very careful and not remove 'hdr' from the 3671 * sublist. Otherwise, other consumers might mistake the 3672 * 'hdr' as not being on a sublist when they call the 3673 * multilist_link_active() function (they all rely on 3674 * the hash lock protecting concurrent insertions and 3675 * removals). multilist_sublist_move_forward() was 3676 * specifically implemented to ensure this is the case 3677 * (only 'marker' will be removed and re-inserted). 3678 */ 3679 multilist_sublist_move_forward(mls, marker); 3680 3681 /* 3682 * The only case where the b_spa field should ever be 3683 * zero, is the marker headers inserted by 3684 * arc_evict_state(). It's possible for multiple threads 3685 * to be calling arc_evict_state() concurrently (e.g. 3686 * dsl_pool_close() and zio_inject_fault()), so we must 3687 * skip any markers we see from these other threads. 3688 */ 3689 if (hdr->b_spa == 0) 3690 continue; 3691 3692 /* we're only interested in evicting buffers of a certain spa */ 3693 if (spa != 0 && hdr->b_spa != spa) { 3694 ARCSTAT_BUMP(arcstat_evict_skip); 3695 continue; 3696 } 3697 3698 hash_lock = HDR_LOCK(hdr); 3699 3700 /* 3701 * We aren't calling this function from any code path 3702 * that would already be holding a hash lock, so we're 3703 * asserting on this assumption to be defensive in case 3704 * this ever changes. Without this check, it would be 3705 * possible to incorrectly increment arcstat_mutex_miss 3706 * below (e.g. if the code changed such that we called 3707 * this function with a hash lock held). 3708 */ 3709 ASSERT(!MUTEX_HELD(hash_lock)); 3710 3711 if (mutex_tryenter(hash_lock)) { 3712 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3713 mutex_exit(hash_lock); 3714 3715 bytes_evicted += evicted; 3716 3717 /* 3718 * If evicted is zero, arc_evict_hdr() must have 3719 * decided to skip this header, don't increment 3720 * evict_count in this case. 3721 */ 3722 if (evicted != 0) 3723 evict_count++; 3724 3725 /* 3726 * If arc_size isn't overflowing, signal any 3727 * threads that might happen to be waiting. 3728 * 3729 * For each header evicted, we wake up a single 3730 * thread. If we used cv_broadcast, we could 3731 * wake up "too many" threads causing arc_size 3732 * to significantly overflow arc_c; since 3733 * arc_get_data_impl() doesn't check for overflow 3734 * when it's woken up (it doesn't because it's 3735 * possible for the ARC to be overflowing while 3736 * full of un-evictable buffers, and the 3737 * function should proceed in this case). 3738 * 3739 * If threads are left sleeping, due to not 3740 * using cv_broadcast, they will be woken up 3741 * just before arc_reclaim_thread() sleeps. 3742 */ 3743 mutex_enter(&arc_reclaim_lock); 3744 if (!arc_is_overflowing()) 3745 cv_signal(&arc_reclaim_waiters_cv); 3746 mutex_exit(&arc_reclaim_lock); 3747 } else { 3748 ARCSTAT_BUMP(arcstat_mutex_miss); 3749 } 3750 } 3751 3752 multilist_sublist_unlock(mls); 3753 3754 return (bytes_evicted); 3755} 3756 3757/* 3758 * Evict buffers from the given arc state, until we've removed the 3759 * specified number of bytes. Move the removed buffers to the 3760 * appropriate evict state. 3761 * 3762 * This function makes a "best effort". It skips over any buffers 3763 * it can't get a hash_lock on, and so, may not catch all candidates. 3764 * It may also return without evicting as much space as requested. 3765 * 3766 * If bytes is specified using the special value ARC_EVICT_ALL, this 3767 * will evict all available (i.e. unlocked and evictable) buffers from 3768 * the given arc state; which is used by arc_flush(). 3769 */ 3770static uint64_t 3771arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3772 arc_buf_contents_t type) 3773{ 3774 uint64_t total_evicted = 0; 3775 multilist_t *ml = state->arcs_list[type]; 3776 int num_sublists; 3777 arc_buf_hdr_t **markers; 3778 3779 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3780 3781 num_sublists = multilist_get_num_sublists(ml); 3782 3783 /* 3784 * If we've tried to evict from each sublist, made some 3785 * progress, but still have not hit the target number of bytes 3786 * to evict, we want to keep trying. The markers allow us to 3787 * pick up where we left off for each individual sublist, rather 3788 * than starting from the tail each time. 3789 */ 3790 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3791 for (int i = 0; i < num_sublists; i++) { 3792 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3793 3794 /* 3795 * A b_spa of 0 is used to indicate that this header is 3796 * a marker. This fact is used in arc_adjust_type() and 3797 * arc_evict_state_impl(). 3798 */ 3799 markers[i]->b_spa = 0; 3800 3801 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3802 multilist_sublist_insert_tail(mls, markers[i]); 3803 multilist_sublist_unlock(mls); 3804 } 3805 3806 /* 3807 * While we haven't hit our target number of bytes to evict, or 3808 * we're evicting all available buffers. 3809 */ 3810 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3811 /* 3812 * Start eviction using a randomly selected sublist, 3813 * this is to try and evenly balance eviction across all 3814 * sublists. Always starting at the same sublist 3815 * (e.g. index 0) would cause evictions to favor certain 3816 * sublists over others. 3817 */ 3818 int sublist_idx = multilist_get_random_index(ml); 3819 uint64_t scan_evicted = 0; 3820 3821 for (int i = 0; i < num_sublists; i++) { 3822 uint64_t bytes_remaining; 3823 uint64_t bytes_evicted; 3824 3825 if (bytes == ARC_EVICT_ALL) 3826 bytes_remaining = ARC_EVICT_ALL; 3827 else if (total_evicted < bytes) 3828 bytes_remaining = bytes - total_evicted; 3829 else 3830 break; 3831 3832 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3833 markers[sublist_idx], spa, bytes_remaining); 3834 3835 scan_evicted += bytes_evicted; 3836 total_evicted += bytes_evicted; 3837 3838 /* we've reached the end, wrap to the beginning */ 3839 if (++sublist_idx >= num_sublists) 3840 sublist_idx = 0; 3841 } 3842 3843 /* 3844 * If we didn't evict anything during this scan, we have 3845 * no reason to believe we'll evict more during another 3846 * scan, so break the loop. 3847 */ 3848 if (scan_evicted == 0) { 3849 /* This isn't possible, let's make that obvious */ 3850 ASSERT3S(bytes, !=, 0); 3851 3852 /* 3853 * When bytes is ARC_EVICT_ALL, the only way to 3854 * break the loop is when scan_evicted is zero. 3855 * In that case, we actually have evicted enough, 3856 * so we don't want to increment the kstat. 3857 */ 3858 if (bytes != ARC_EVICT_ALL) { 3859 ASSERT3S(total_evicted, <, bytes); 3860 ARCSTAT_BUMP(arcstat_evict_not_enough); 3861 } 3862 3863 break; 3864 } 3865 } 3866 3867 for (int i = 0; i < num_sublists; i++) { 3868 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3869 multilist_sublist_remove(mls, markers[i]); 3870 multilist_sublist_unlock(mls); 3871 3872 kmem_cache_free(hdr_full_cache, markers[i]); 3873 } 3874 kmem_free(markers, sizeof (*markers) * num_sublists); 3875 3876 return (total_evicted); 3877} 3878 3879/* 3880 * Flush all "evictable" data of the given type from the arc state 3881 * specified. This will not evict any "active" buffers (i.e. referenced). 3882 * 3883 * When 'retry' is set to B_FALSE, the function will make a single pass 3884 * over the state and evict any buffers that it can. Since it doesn't 3885 * continually retry the eviction, it might end up leaving some buffers 3886 * in the ARC due to lock misses. 3887 * 3888 * When 'retry' is set to B_TRUE, the function will continually retry the 3889 * eviction until *all* evictable buffers have been removed from the 3890 * state. As a result, if concurrent insertions into the state are 3891 * allowed (e.g. if the ARC isn't shutting down), this function might 3892 * wind up in an infinite loop, continually trying to evict buffers. 3893 */ 3894static uint64_t 3895arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3896 boolean_t retry) 3897{ 3898 uint64_t evicted = 0; 3899 3900 while (refcount_count(&state->arcs_esize[type]) != 0) { 3901 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3902 3903 if (!retry) 3904 break; 3905 } 3906 3907 return (evicted); 3908} 3909 3910/* 3911 * Evict the specified number of bytes from the state specified, 3912 * restricting eviction to the spa and type given. This function 3913 * prevents us from trying to evict more from a state's list than 3914 * is "evictable", and to skip evicting altogether when passed a 3915 * negative value for "bytes". In contrast, arc_evict_state() will 3916 * evict everything it can, when passed a negative value for "bytes". 3917 */ 3918static uint64_t 3919arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3920 arc_buf_contents_t type) 3921{ 3922 int64_t delta; 3923 3924 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3925 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3926 return (arc_evict_state(state, spa, delta, type)); 3927 } 3928 3929 return (0); 3930} 3931 3932/* 3933 * Evict metadata buffers from the cache, such that arc_meta_used is 3934 * capped by the arc_meta_limit tunable. 3935 */ 3936static uint64_t 3937arc_adjust_meta(uint64_t meta_used) 3938{ 3939 uint64_t total_evicted = 0; 3940 int64_t target; 3941 3942 /* 3943 * If we're over the meta limit, we want to evict enough 3944 * metadata to get back under the meta limit. We don't want to 3945 * evict so much that we drop the MRU below arc_p, though. If 3946 * we're over the meta limit more than we're over arc_p, we 3947 * evict some from the MRU here, and some from the MFU below. 3948 */ 3949 target = MIN((int64_t)(meta_used - arc_meta_limit), 3950 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3951 refcount_count(&arc_mru->arcs_size) - arc_p)); 3952 3953 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3954 3955 /* 3956 * Similar to the above, we want to evict enough bytes to get us 3957 * below the meta limit, but not so much as to drop us below the 3958 * space allotted to the MFU (which is defined as arc_c - arc_p). 3959 */ 3960 target = MIN((int64_t)(meta_used - arc_meta_limit), 3961 (int64_t)(refcount_count(&arc_mfu->arcs_size) - 3962 (arc_c - arc_p))); 3963 3964 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3965 3966 return (total_evicted); 3967} 3968 3969/* 3970 * Return the type of the oldest buffer in the given arc state 3971 * 3972 * This function will select a random sublist of type ARC_BUFC_DATA and 3973 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3974 * is compared, and the type which contains the "older" buffer will be 3975 * returned. 3976 */ 3977static arc_buf_contents_t 3978arc_adjust_type(arc_state_t *state) 3979{ 3980 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; 3981 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; 3982 int data_idx = multilist_get_random_index(data_ml); 3983 int meta_idx = multilist_get_random_index(meta_ml); 3984 multilist_sublist_t *data_mls; 3985 multilist_sublist_t *meta_mls; 3986 arc_buf_contents_t type; 3987 arc_buf_hdr_t *data_hdr; 3988 arc_buf_hdr_t *meta_hdr; 3989 3990 /* 3991 * We keep the sublist lock until we're finished, to prevent 3992 * the headers from being destroyed via arc_evict_state(). 3993 */ 3994 data_mls = multilist_sublist_lock(data_ml, data_idx); 3995 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3996 3997 /* 3998 * These two loops are to ensure we skip any markers that 3999 * might be at the tail of the lists due to arc_evict_state(). 4000 */ 4001 4002 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 4003 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 4004 if (data_hdr->b_spa != 0) 4005 break; 4006 } 4007 4008 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 4009 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 4010 if (meta_hdr->b_spa != 0) 4011 break; 4012 } 4013 4014 if (data_hdr == NULL && meta_hdr == NULL) { 4015 type = ARC_BUFC_DATA; 4016 } else if (data_hdr == NULL) { 4017 ASSERT3P(meta_hdr, !=, NULL); 4018 type = ARC_BUFC_METADATA; 4019 } else if (meta_hdr == NULL) { 4020 ASSERT3P(data_hdr, !=, NULL); 4021 type = ARC_BUFC_DATA; 4022 } else { 4023 ASSERT3P(data_hdr, !=, NULL); 4024 ASSERT3P(meta_hdr, !=, NULL); 4025 4026 /* The headers can't be on the sublist without an L1 header */ 4027 ASSERT(HDR_HAS_L1HDR(data_hdr)); 4028 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 4029 4030 if (data_hdr->b_l1hdr.b_arc_access < 4031 meta_hdr->b_l1hdr.b_arc_access) { 4032 type = ARC_BUFC_DATA; 4033 } else { 4034 type = ARC_BUFC_METADATA; 4035 } 4036 } 4037 4038 multilist_sublist_unlock(meta_mls); 4039 multilist_sublist_unlock(data_mls); 4040 4041 return (type); 4042} 4043 4044/* 4045 * Evict buffers from the cache, such that arc_size is capped by arc_c. 4046 */ 4047static uint64_t 4048arc_adjust(void) 4049{ 4050 uint64_t total_evicted = 0; 4051 uint64_t bytes; 4052 int64_t target; 4053 uint64_t asize = aggsum_value(&arc_size); 4054 uint64_t ameta = aggsum_value(&arc_meta_used); 4055 4056 /* 4057 * If we're over arc_meta_limit, we want to correct that before 4058 * potentially evicting data buffers below. 4059 */ 4060 total_evicted += arc_adjust_meta(ameta); 4061 4062 /* 4063 * Adjust MRU size 4064 * 4065 * If we're over the target cache size, we want to evict enough 4066 * from the list to get back to our target size. We don't want 4067 * to evict too much from the MRU, such that it drops below 4068 * arc_p. So, if we're over our target cache size more than 4069 * the MRU is over arc_p, we'll evict enough to get back to 4070 * arc_p here, and then evict more from the MFU below. 4071 */ 4072 target = MIN((int64_t)(asize - arc_c), 4073 (int64_t)(refcount_count(&arc_anon->arcs_size) + 4074 refcount_count(&arc_mru->arcs_size) + ameta - arc_p)); 4075 4076 /* 4077 * If we're below arc_meta_min, always prefer to evict data. 4078 * Otherwise, try to satisfy the requested number of bytes to 4079 * evict from the type which contains older buffers; in an 4080 * effort to keep newer buffers in the cache regardless of their 4081 * type. If we cannot satisfy the number of bytes from this 4082 * type, spill over into the next type. 4083 */ 4084 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 4085 ameta > arc_meta_min) { 4086 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4087 total_evicted += bytes; 4088 4089 /* 4090 * If we couldn't evict our target number of bytes from 4091 * metadata, we try to get the rest from data. 4092 */ 4093 target -= bytes; 4094 4095 total_evicted += 4096 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4097 } else { 4098 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4099 total_evicted += bytes; 4100 4101 /* 4102 * If we couldn't evict our target number of bytes from 4103 * data, we try to get the rest from metadata. 4104 */ 4105 target -= bytes; 4106 4107 total_evicted += 4108 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4109 } 4110 4111 /* 4112 * Adjust MFU size 4113 * 4114 * Now that we've tried to evict enough from the MRU to get its 4115 * size back to arc_p, if we're still above the target cache 4116 * size, we evict the rest from the MFU. 4117 */ 4118 target = asize - arc_c; 4119 4120 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 4121 ameta > arc_meta_min) { 4122 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4123 total_evicted += bytes; 4124 4125 /* 4126 * If we couldn't evict our target number of bytes from 4127 * metadata, we try to get the rest from data. 4128 */ 4129 target -= bytes; 4130 4131 total_evicted += 4132 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4133 } else { 4134 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4135 total_evicted += bytes; 4136 4137 /* 4138 * If we couldn't evict our target number of bytes from 4139 * data, we try to get the rest from data. 4140 */ 4141 target -= bytes; 4142 4143 total_evicted += 4144 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4145 } 4146 4147 /* 4148 * Adjust ghost lists 4149 * 4150 * In addition to the above, the ARC also defines target values 4151 * for the ghost lists. The sum of the mru list and mru ghost 4152 * list should never exceed the target size of the cache, and 4153 * the sum of the mru list, mfu list, mru ghost list, and mfu 4154 * ghost list should never exceed twice the target size of the 4155 * cache. The following logic enforces these limits on the ghost 4156 * caches, and evicts from them as needed. 4157 */ 4158 target = refcount_count(&arc_mru->arcs_size) + 4159 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 4160 4161 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 4162 total_evicted += bytes; 4163 4164 target -= bytes; 4165 4166 total_evicted += 4167 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 4168 4169 /* 4170 * We assume the sum of the mru list and mfu list is less than 4171 * or equal to arc_c (we enforced this above), which means we 4172 * can use the simpler of the two equations below: 4173 * 4174 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 4175 * mru ghost + mfu ghost <= arc_c 4176 */ 4177 target = refcount_count(&arc_mru_ghost->arcs_size) + 4178 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 4179 4180 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 4181 total_evicted += bytes; 4182 4183 target -= bytes; 4184 4185 total_evicted += 4186 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 4187 4188 return (total_evicted); 4189} 4190 4191void 4192arc_flush(spa_t *spa, boolean_t retry) 4193{ 4194 uint64_t guid = 0; 4195 4196 /* 4197 * If retry is B_TRUE, a spa must not be specified since we have 4198 * no good way to determine if all of a spa's buffers have been 4199 * evicted from an arc state. 4200 */ 4201 ASSERT(!retry || spa == 0); 4202 4203 if (spa != NULL) 4204 guid = spa_load_guid(spa); 4205 4206 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 4207 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 4208 4209 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 4210 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 4211 4212 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 4213 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 4214 4215 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 4216 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 4217} 4218 4219void 4220arc_shrink(int64_t to_free) 4221{ 4222 uint64_t asize = aggsum_value(&arc_size); 4223 if (arc_c > arc_c_min) { 4224 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 4225 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 4226 if (arc_c > arc_c_min + to_free) 4227 atomic_add_64(&arc_c, -to_free); 4228 else 4229 arc_c = arc_c_min; 4230 4231 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 4232 if (asize < arc_c) 4233 arc_c = MAX(asize, arc_c_min); 4234 if (arc_p > arc_c) 4235 arc_p = (arc_c >> 1); 4236 4237 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 4238 arc_p); 4239 4240 ASSERT(arc_c >= arc_c_min); 4241 ASSERT((int64_t)arc_p >= 0); 4242 } 4243 4244 if (asize > arc_c) { 4245 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize, 4246 uint64_t, arc_c); 4247 (void) arc_adjust(); 4248 } 4249} 4250 4251typedef enum free_memory_reason_t { 4252 FMR_UNKNOWN, 4253 FMR_NEEDFREE, 4254 FMR_LOTSFREE, 4255 FMR_SWAPFS_MINFREE, 4256 FMR_PAGES_PP_MAXIMUM, 4257 FMR_HEAP_ARENA, 4258 FMR_ZIO_ARENA, 4259 FMR_ZIO_FRAG, 4260} free_memory_reason_t; 4261 4262int64_t last_free_memory; 4263free_memory_reason_t last_free_reason; 4264 4265/* 4266 * Additional reserve of pages for pp_reserve. 4267 */ 4268int64_t arc_pages_pp_reserve = 64; 4269 4270/* 4271 * Additional reserve of pages for swapfs. 4272 */ 4273int64_t arc_swapfs_reserve = 64; 4274 4275/* 4276 * Return the amount of memory that can be consumed before reclaim will be 4277 * needed. Positive if there is sufficient free memory, negative indicates 4278 * the amount of memory that needs to be freed up. 4279 */ 4280static int64_t 4281arc_available_memory(void) 4282{ 4283 int64_t lowest = INT64_MAX; 4284 int64_t n; 4285 free_memory_reason_t r = FMR_UNKNOWN; 4286 4287#ifdef _KERNEL 4288#ifdef __FreeBSD__ 4289 /* 4290 * Cooperate with pagedaemon when it's time for it to scan 4291 * and reclaim some pages. 4292 */ 4293 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 4294 if (n < lowest) { 4295 lowest = n; 4296 r = FMR_LOTSFREE; 4297 } 4298 4299#else 4300 if (needfree > 0) { 4301 n = PAGESIZE * (-needfree); 4302 if (n < lowest) { 4303 lowest = n; 4304 r = FMR_NEEDFREE; 4305 } 4306 } 4307 4308 /* 4309 * check that we're out of range of the pageout scanner. It starts to 4310 * schedule paging if freemem is less than lotsfree and needfree. 4311 * lotsfree is the high-water mark for pageout, and needfree is the 4312 * number of needed free pages. We add extra pages here to make sure 4313 * the scanner doesn't start up while we're freeing memory. 4314 */ 4315 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 4316 if (n < lowest) { 4317 lowest = n; 4318 r = FMR_LOTSFREE; 4319 } 4320 4321 /* 4322 * check to make sure that swapfs has enough space so that anon 4323 * reservations can still succeed. anon_resvmem() checks that the 4324 * availrmem is greater than swapfs_minfree, and the number of reserved 4325 * swap pages. We also add a bit of extra here just to prevent 4326 * circumstances from getting really dire. 4327 */ 4328 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 4329 desfree - arc_swapfs_reserve); 4330 if (n < lowest) { 4331 lowest = n; 4332 r = FMR_SWAPFS_MINFREE; 4333 } 4334 4335 4336 /* 4337 * Check that we have enough availrmem that memory locking (e.g., via 4338 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 4339 * stores the number of pages that cannot be locked; when availrmem 4340 * drops below pages_pp_maximum, page locking mechanisms such as 4341 * page_pp_lock() will fail.) 4342 */ 4343 n = PAGESIZE * (availrmem - pages_pp_maximum - 4344 arc_pages_pp_reserve); 4345 if (n < lowest) { 4346 lowest = n; 4347 r = FMR_PAGES_PP_MAXIMUM; 4348 } 4349 4350#endif /* __FreeBSD__ */ 4351#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4352 /* 4353 * If we're on an i386 platform, it's possible that we'll exhaust the 4354 * kernel heap space before we ever run out of available physical 4355 * memory. Most checks of the size of the heap_area compare against 4356 * tune.t_minarmem, which is the minimum available real memory that we 4357 * can have in the system. However, this is generally fixed at 25 pages 4358 * which is so low that it's useless. In this comparison, we seek to 4359 * calculate the total heap-size, and reclaim if more than 3/4ths of the 4360 * heap is allocated. (Or, in the calculation, if less than 1/4th is 4361 * free) 4362 */ 4363 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 4364 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 4365 if (n < lowest) { 4366 lowest = n; 4367 r = FMR_HEAP_ARENA; 4368 } 4369#define zio_arena NULL 4370#else 4371#define zio_arena heap_arena 4372#endif 4373 4374 /* 4375 * If zio data pages are being allocated out of a separate heap segment, 4376 * then enforce that the size of available vmem for this arena remains 4377 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free. 4378 * 4379 * Note that reducing the arc_zio_arena_free_shift keeps more virtual 4380 * memory (in the zio_arena) free, which can avoid memory 4381 * fragmentation issues. 4382 */ 4383 if (zio_arena != NULL) { 4384 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 4385 (vmem_size(zio_arena, VMEM_ALLOC) >> 4386 arc_zio_arena_free_shift); 4387 if (n < lowest) { 4388 lowest = n; 4389 r = FMR_ZIO_ARENA; 4390 } 4391 } 4392 4393 /* 4394 * Above limits know nothing about real level of KVA fragmentation. 4395 * Start aggressive reclamation if too little sequential KVA left. 4396 */ 4397 if (lowest > 0) { 4398 n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ? 4399 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 4400 INT64_MAX; 4401 if (n < lowest) { 4402 lowest = n; 4403 r = FMR_ZIO_FRAG; 4404 } 4405 } 4406 4407#else /* _KERNEL */ 4408 /* Every 100 calls, free a small amount */ 4409 if (spa_get_random(100) == 0) 4410 lowest = -1024; 4411#endif /* _KERNEL */ 4412 4413 last_free_memory = lowest; 4414 last_free_reason = r; 4415 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 4416 return (lowest); 4417} 4418 4419 4420/* 4421 * Determine if the system is under memory pressure and is asking 4422 * to reclaim memory. A return value of B_TRUE indicates that the system 4423 * is under memory pressure and that the arc should adjust accordingly. 4424 */ 4425static boolean_t 4426arc_reclaim_needed(void) 4427{ 4428 return (arc_available_memory() < 0); 4429} 4430 4431extern kmem_cache_t *zio_buf_cache[]; 4432extern kmem_cache_t *zio_data_buf_cache[]; 4433extern kmem_cache_t *range_seg_cache; 4434extern kmem_cache_t *abd_chunk_cache; 4435 4436static __noinline void 4437arc_kmem_reap_now(void) 4438{ 4439 size_t i; 4440 kmem_cache_t *prev_cache = NULL; 4441 kmem_cache_t *prev_data_cache = NULL; 4442 4443 DTRACE_PROBE(arc__kmem_reap_start); 4444#ifdef _KERNEL 4445 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) { 4446 /* 4447 * We are exceeding our meta-data cache limit. 4448 * Purge some DNLC entries to release holds on meta-data. 4449 */ 4450 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4451 } 4452#if defined(__i386) 4453 /* 4454 * Reclaim unused memory from all kmem caches. 4455 */ 4456 kmem_reap(); 4457#endif 4458#endif 4459 4460 /* 4461 * If a kmem reap is already active, don't schedule more. We must 4462 * check for this because kmem_cache_reap_soon() won't actually 4463 * block on the cache being reaped (this is to prevent callers from 4464 * becoming implicitly blocked by a system-wide kmem reap -- which, 4465 * on a system with many, many full magazines, can take minutes). 4466 */ 4467 if (kmem_cache_reap_active()) 4468 return; 4469 4470 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4471 if (zio_buf_cache[i] != prev_cache) { 4472 prev_cache = zio_buf_cache[i]; 4473 kmem_cache_reap_soon(zio_buf_cache[i]); 4474 } 4475 if (zio_data_buf_cache[i] != prev_data_cache) { 4476 prev_data_cache = zio_data_buf_cache[i]; 4477 kmem_cache_reap_soon(zio_data_buf_cache[i]); 4478 } 4479 } 4480 kmem_cache_reap_soon(abd_chunk_cache); 4481 kmem_cache_reap_soon(buf_cache); 4482 kmem_cache_reap_soon(hdr_full_cache); 4483 kmem_cache_reap_soon(hdr_l2only_cache); 4484 kmem_cache_reap_soon(range_seg_cache); 4485 4486#ifdef illumos 4487 if (zio_arena != NULL) { 4488 /* 4489 * Ask the vmem arena to reclaim unused memory from its 4490 * quantum caches. 4491 */ 4492 vmem_qcache_reap(zio_arena); 4493 } 4494#endif 4495 DTRACE_PROBE(arc__kmem_reap_end); 4496} 4497 4498/* 4499 * Threads can block in arc_get_data_impl() waiting for this thread to evict 4500 * enough data and signal them to proceed. When this happens, the threads in 4501 * arc_get_data_impl() are sleeping while holding the hash lock for their 4502 * particular arc header. Thus, we must be careful to never sleep on a 4503 * hash lock in this thread. This is to prevent the following deadlock: 4504 * 4505 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L", 4506 * waiting for the reclaim thread to signal it. 4507 * 4508 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4509 * fails, and goes to sleep forever. 4510 * 4511 * This possible deadlock is avoided by always acquiring a hash lock 4512 * using mutex_tryenter() from arc_reclaim_thread(). 4513 */ 4514/* ARGSUSED */ 4515static void 4516arc_reclaim_thread(void *unused __unused) 4517{ 4518 hrtime_t growtime = 0; 4519 hrtime_t kmem_reap_time = 0; 4520 callb_cpr_t cpr; 4521 4522 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4523 4524 mutex_enter(&arc_reclaim_lock); 4525 while (!arc_reclaim_thread_exit) { 4526 uint64_t evicted = 0; 4527 4528 /* 4529 * This is necessary in order for the mdb ::arc dcmd to 4530 * show up to date information. Since the ::arc command 4531 * does not call the kstat's update function, without 4532 * this call, the command may show stale stats for the 4533 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4534 * with this change, the data might be up to 1 second 4535 * out of date; but that should suffice. The arc_state_t 4536 * structures can be queried directly if more accurate 4537 * information is needed. 4538 */ 4539 if (arc_ksp != NULL) 4540 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4541 4542 mutex_exit(&arc_reclaim_lock); 4543 4544 /* 4545 * We call arc_adjust() before (possibly) calling 4546 * arc_kmem_reap_now(), so that we can wake up 4547 * arc_get_data_impl() sooner. 4548 */ 4549 evicted = arc_adjust(); 4550 4551 int64_t free_memory = arc_available_memory(); 4552 if (free_memory < 0) { 4553 hrtime_t curtime = gethrtime(); 4554 arc_no_grow = B_TRUE; 4555 arc_warm = B_TRUE; 4556 4557 /* 4558 * Wait at least zfs_grow_retry (default 60) seconds 4559 * before considering growing. 4560 */ 4561 growtime = curtime + SEC2NSEC(arc_grow_retry); 4562 4563 /* 4564 * Wait at least arc_kmem_cache_reap_retry_ms 4565 * between arc_kmem_reap_now() calls. Without 4566 * this check it is possible to end up in a 4567 * situation where we spend lots of time 4568 * reaping caches, while we're near arc_c_min. 4569 */ 4570 if (curtime >= kmem_reap_time) { 4571 arc_kmem_reap_now(); 4572 kmem_reap_time = gethrtime() + 4573 MSEC2NSEC(arc_kmem_cache_reap_retry_ms); 4574 } 4575 4576 /* 4577 * If we are still low on memory, shrink the ARC 4578 * so that we have arc_shrink_min free space. 4579 */ 4580 free_memory = arc_available_memory(); 4581 4582 int64_t to_free = 4583 (arc_c >> arc_shrink_shift) - free_memory; 4584 if (to_free > 0) { 4585#ifdef _KERNEL 4586#ifdef illumos 4587 to_free = MAX(to_free, ptob(needfree)); 4588#endif 4589#endif 4590 arc_shrink(to_free); 4591 } 4592 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4593 arc_no_grow = B_TRUE; 4594 } else if (gethrtime() >= growtime) { 4595 arc_no_grow = B_FALSE; 4596 } 4597 4598 mutex_enter(&arc_reclaim_lock); 4599 4600 /* 4601 * If evicted is zero, we couldn't evict anything via 4602 * arc_adjust(). This could be due to hash lock 4603 * collisions, but more likely due to the majority of 4604 * arc buffers being unevictable. Therefore, even if 4605 * arc_size is above arc_c, another pass is unlikely to 4606 * be helpful and could potentially cause us to enter an 4607 * infinite loop. 4608 */ 4609 if (aggsum_compare(&arc_size, arc_c) <= 0|| evicted == 0) { 4610 /* 4611 * We're either no longer overflowing, or we 4612 * can't evict anything more, so we should wake 4613 * up any threads before we go to sleep. 4614 */ 4615 cv_broadcast(&arc_reclaim_waiters_cv); 4616 4617 /* 4618 * Block until signaled, or after one second (we 4619 * might need to perform arc_kmem_reap_now() 4620 * even if we aren't being signalled) 4621 */ 4622 CALLB_CPR_SAFE_BEGIN(&cpr); 4623 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4624 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4625 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4626 } 4627 } 4628 4629 arc_reclaim_thread_exit = B_FALSE; 4630 cv_broadcast(&arc_reclaim_thread_cv); 4631 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4632 thread_exit(); 4633} 4634 4635static u_int arc_dnlc_evicts_arg; 4636extern struct vfsops zfs_vfsops; 4637 4638static void 4639arc_dnlc_evicts_thread(void *dummy __unused) 4640{ 4641 callb_cpr_t cpr; 4642 u_int percent; 4643 4644 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 4645 4646 mutex_enter(&arc_dnlc_evicts_lock); 4647 while (!arc_dnlc_evicts_thread_exit) { 4648 CALLB_CPR_SAFE_BEGIN(&cpr); 4649 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 4650 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 4651 if (arc_dnlc_evicts_arg != 0) { 4652 percent = arc_dnlc_evicts_arg; 4653 mutex_exit(&arc_dnlc_evicts_lock); 4654#ifdef _KERNEL 4655 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 4656#endif 4657 mutex_enter(&arc_dnlc_evicts_lock); 4658 /* 4659 * Clear our token only after vnlru_free() 4660 * pass is done, to avoid false queueing of 4661 * the requests. 4662 */ 4663 arc_dnlc_evicts_arg = 0; 4664 } 4665 } 4666 arc_dnlc_evicts_thread_exit = FALSE; 4667 cv_broadcast(&arc_dnlc_evicts_cv); 4668 CALLB_CPR_EXIT(&cpr); 4669 thread_exit(); 4670} 4671 4672void 4673dnlc_reduce_cache(void *arg) 4674{ 4675 u_int percent; 4676 4677 percent = (u_int)(uintptr_t)arg; 4678 mutex_enter(&arc_dnlc_evicts_lock); 4679 if (arc_dnlc_evicts_arg == 0) { 4680 arc_dnlc_evicts_arg = percent; 4681 cv_broadcast(&arc_dnlc_evicts_cv); 4682 } 4683 mutex_exit(&arc_dnlc_evicts_lock); 4684} 4685 4686/* 4687 * Adapt arc info given the number of bytes we are trying to add and 4688 * the state that we are comming from. This function is only called 4689 * when we are adding new content to the cache. 4690 */ 4691static void 4692arc_adapt(int bytes, arc_state_t *state) 4693{ 4694 int mult; 4695 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4696 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4697 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4698 4699 if (state == arc_l2c_only) 4700 return; 4701 4702 ASSERT(bytes > 0); 4703 /* 4704 * Adapt the target size of the MRU list: 4705 * - if we just hit in the MRU ghost list, then increase 4706 * the target size of the MRU list. 4707 * - if we just hit in the MFU ghost list, then increase 4708 * the target size of the MFU list by decreasing the 4709 * target size of the MRU list. 4710 */ 4711 if (state == arc_mru_ghost) { 4712 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4713 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4714 4715 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4716 } else if (state == arc_mfu_ghost) { 4717 uint64_t delta; 4718 4719 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4720 mult = MIN(mult, 10); 4721 4722 delta = MIN(bytes * mult, arc_p); 4723 arc_p = MAX(arc_p_min, arc_p - delta); 4724 } 4725 ASSERT((int64_t)arc_p >= 0); 4726 4727 if (arc_reclaim_needed()) { 4728 cv_signal(&arc_reclaim_thread_cv); 4729 return; 4730 } 4731 4732 if (arc_no_grow) 4733 return; 4734 4735 if (arc_c >= arc_c_max) 4736 return; 4737 4738 /* 4739 * If we're within (2 * maxblocksize) bytes of the target 4740 * cache size, increment the target cache size 4741 */ 4742 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) > 4743 0) { 4744 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4745 atomic_add_64(&arc_c, (int64_t)bytes); 4746 if (arc_c > arc_c_max) 4747 arc_c = arc_c_max; 4748 else if (state == arc_anon) 4749 atomic_add_64(&arc_p, (int64_t)bytes); 4750 if (arc_p > arc_c) 4751 arc_p = arc_c; 4752 } 4753 ASSERT((int64_t)arc_p >= 0); 4754} 4755 4756/* 4757 * Check if arc_size has grown past our upper threshold, determined by 4758 * zfs_arc_overflow_shift. 4759 */ 4760static boolean_t 4761arc_is_overflowing(void) 4762{ 4763 /* Always allow at least one block of overflow */ 4764 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4765 arc_c >> zfs_arc_overflow_shift); 4766 4767 /* 4768 * We just compare the lower bound here for performance reasons. Our 4769 * primary goals are to make sure that the arc never grows without 4770 * bound, and that it can reach its maximum size. This check 4771 * accomplishes both goals. The maximum amount we could run over by is 4772 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block 4773 * in the ARC. In practice, that's in the tens of MB, which is low 4774 * enough to be safe. 4775 */ 4776 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow); 4777} 4778 4779static abd_t * 4780arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4781{ 4782 arc_buf_contents_t type = arc_buf_type(hdr); 4783 4784 arc_get_data_impl(hdr, size, tag); 4785 if (type == ARC_BUFC_METADATA) { 4786 return (abd_alloc(size, B_TRUE)); 4787 } else { 4788 ASSERT(type == ARC_BUFC_DATA); 4789 return (abd_alloc(size, B_FALSE)); 4790 } 4791} 4792 4793static void * 4794arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4795{ 4796 arc_buf_contents_t type = arc_buf_type(hdr); 4797 4798 arc_get_data_impl(hdr, size, tag); 4799 if (type == ARC_BUFC_METADATA) { 4800 return (zio_buf_alloc(size)); 4801 } else { 4802 ASSERT(type == ARC_BUFC_DATA); 4803 return (zio_data_buf_alloc(size)); 4804 } 4805} 4806 4807/* 4808 * Allocate a block and return it to the caller. If we are hitting the 4809 * hard limit for the cache size, we must sleep, waiting for the eviction 4810 * thread to catch up. If we're past the target size but below the hard 4811 * limit, we'll only signal the reclaim thread and continue on. 4812 */ 4813static void 4814arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4815{ 4816 arc_state_t *state = hdr->b_l1hdr.b_state; 4817 arc_buf_contents_t type = arc_buf_type(hdr); 4818 4819 arc_adapt(size, state); 4820 4821 /* 4822 * If arc_size is currently overflowing, and has grown past our 4823 * upper limit, we must be adding data faster than the evict 4824 * thread can evict. Thus, to ensure we don't compound the 4825 * problem by adding more data and forcing arc_size to grow even 4826 * further past it's target size, we halt and wait for the 4827 * eviction thread to catch up. 4828 * 4829 * It's also possible that the reclaim thread is unable to evict 4830 * enough buffers to get arc_size below the overflow limit (e.g. 4831 * due to buffers being un-evictable, or hash lock collisions). 4832 * In this case, we want to proceed regardless if we're 4833 * overflowing; thus we don't use a while loop here. 4834 */ 4835 if (arc_is_overflowing()) { 4836 mutex_enter(&arc_reclaim_lock); 4837 4838 /* 4839 * Now that we've acquired the lock, we may no longer be 4840 * over the overflow limit, lets check. 4841 * 4842 * We're ignoring the case of spurious wake ups. If that 4843 * were to happen, it'd let this thread consume an ARC 4844 * buffer before it should have (i.e. before we're under 4845 * the overflow limit and were signalled by the reclaim 4846 * thread). As long as that is a rare occurrence, it 4847 * shouldn't cause any harm. 4848 */ 4849 if (arc_is_overflowing()) { 4850 cv_signal(&arc_reclaim_thread_cv); 4851 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4852 } 4853 4854 mutex_exit(&arc_reclaim_lock); 4855 } 4856 4857 VERIFY3U(hdr->b_type, ==, type); 4858 if (type == ARC_BUFC_METADATA) { 4859 arc_space_consume(size, ARC_SPACE_META); 4860 } else { 4861 arc_space_consume(size, ARC_SPACE_DATA); 4862 } 4863 4864 /* 4865 * Update the state size. Note that ghost states have a 4866 * "ghost size" and so don't need to be updated. 4867 */ 4868 if (!GHOST_STATE(state)) { 4869 4870 (void) refcount_add_many(&state->arcs_size, size, tag); 4871 4872 /* 4873 * If this is reached via arc_read, the link is 4874 * protected by the hash lock. If reached via 4875 * arc_buf_alloc, the header should not be accessed by 4876 * any other thread. And, if reached via arc_read_done, 4877 * the hash lock will protect it if it's found in the 4878 * hash table; otherwise no other thread should be 4879 * trying to [add|remove]_reference it. 4880 */ 4881 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4882 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4883 (void) refcount_add_many(&state->arcs_esize[type], 4884 size, tag); 4885 } 4886 4887 /* 4888 * If we are growing the cache, and we are adding anonymous 4889 * data, and we have outgrown arc_p, update arc_p 4890 */ 4891 if (aggsum_compare(&arc_size, arc_c) < 0 && 4892 hdr->b_l1hdr.b_state == arc_anon && 4893 (refcount_count(&arc_anon->arcs_size) + 4894 refcount_count(&arc_mru->arcs_size) > arc_p)) 4895 arc_p = MIN(arc_c, arc_p + size); 4896 } 4897 ARCSTAT_BUMP(arcstat_allocated); 4898} 4899 4900static void 4901arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) 4902{ 4903 arc_free_data_impl(hdr, size, tag); 4904 abd_free(abd); 4905} 4906 4907static void 4908arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) 4909{ 4910 arc_buf_contents_t type = arc_buf_type(hdr); 4911 4912 arc_free_data_impl(hdr, size, tag); 4913 if (type == ARC_BUFC_METADATA) { 4914 zio_buf_free(buf, size); 4915 } else { 4916 ASSERT(type == ARC_BUFC_DATA); 4917 zio_data_buf_free(buf, size); 4918 } 4919} 4920 4921/* 4922 * Free the arc data buffer. 4923 */ 4924static void 4925arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4926{ 4927 arc_state_t *state = hdr->b_l1hdr.b_state; 4928 arc_buf_contents_t type = arc_buf_type(hdr); 4929 4930 /* protected by hash lock, if in the hash table */ 4931 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4932 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4933 ASSERT(state != arc_anon && state != arc_l2c_only); 4934 4935 (void) refcount_remove_many(&state->arcs_esize[type], 4936 size, tag); 4937 } 4938 (void) refcount_remove_many(&state->arcs_size, size, tag); 4939 4940 VERIFY3U(hdr->b_type, ==, type); 4941 if (type == ARC_BUFC_METADATA) { 4942 arc_space_return(size, ARC_SPACE_META); 4943 } else { 4944 ASSERT(type == ARC_BUFC_DATA); 4945 arc_space_return(size, ARC_SPACE_DATA); 4946 } 4947} 4948 4949/* 4950 * This routine is called whenever a buffer is accessed. 4951 * NOTE: the hash lock is dropped in this function. 4952 */ 4953static void 4954arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4955{ 4956 clock_t now; 4957 4958 ASSERT(MUTEX_HELD(hash_lock)); 4959 ASSERT(HDR_HAS_L1HDR(hdr)); 4960 4961 if (hdr->b_l1hdr.b_state == arc_anon) { 4962 /* 4963 * This buffer is not in the cache, and does not 4964 * appear in our "ghost" list. Add the new buffer 4965 * to the MRU state. 4966 */ 4967 4968 ASSERT0(hdr->b_l1hdr.b_arc_access); 4969 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4970 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4971 arc_change_state(arc_mru, hdr, hash_lock); 4972 4973 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4974 now = ddi_get_lbolt(); 4975 4976 /* 4977 * If this buffer is here because of a prefetch, then either: 4978 * - clear the flag if this is a "referencing" read 4979 * (any subsequent access will bump this into the MFU state). 4980 * or 4981 * - move the buffer to the head of the list if this is 4982 * another prefetch (to make it less likely to be evicted). 4983 */ 4984 if (HDR_PREFETCH(hdr)) { 4985 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4986 /* link protected by hash lock */ 4987 ASSERT(multilist_link_active( 4988 &hdr->b_l1hdr.b_arc_node)); 4989 } else { 4990 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4991 ARCSTAT_BUMP(arcstat_mru_hits); 4992 } 4993 hdr->b_l1hdr.b_arc_access = now; 4994 return; 4995 } 4996 4997 /* 4998 * This buffer has been "accessed" only once so far, 4999 * but it is still in the cache. Move it to the MFU 5000 * state. 5001 */ 5002 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 5003 /* 5004 * More than 125ms have passed since we 5005 * instantiated this buffer. Move it to the 5006 * most frequently used state. 5007 */ 5008 hdr->b_l1hdr.b_arc_access = now; 5009 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5010 arc_change_state(arc_mfu, hdr, hash_lock); 5011 } 5012 ARCSTAT_BUMP(arcstat_mru_hits); 5013 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 5014 arc_state_t *new_state; 5015 /* 5016 * This buffer has been "accessed" recently, but 5017 * was evicted from the cache. Move it to the 5018 * MFU state. 5019 */ 5020 5021 if (HDR_PREFETCH(hdr)) { 5022 new_state = arc_mru; 5023 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 5024 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 5025 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 5026 } else { 5027 new_state = arc_mfu; 5028 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5029 } 5030 5031 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5032 arc_change_state(new_state, hdr, hash_lock); 5033 5034 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 5035 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 5036 /* 5037 * This buffer has been accessed more than once and is 5038 * still in the cache. Keep it in the MFU state. 5039 * 5040 * NOTE: an add_reference() that occurred when we did 5041 * the arc_read() will have kicked this off the list. 5042 * If it was a prefetch, we will explicitly move it to 5043 * the head of the list now. 5044 */ 5045 if ((HDR_PREFETCH(hdr)) != 0) { 5046 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5047 /* link protected by hash_lock */ 5048 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5049 } 5050 ARCSTAT_BUMP(arcstat_mfu_hits); 5051 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5052 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 5053 arc_state_t *new_state = arc_mfu; 5054 /* 5055 * This buffer has been accessed more than once but has 5056 * been evicted from the cache. Move it back to the 5057 * MFU state. 5058 */ 5059 5060 if (HDR_PREFETCH(hdr)) { 5061 /* 5062 * This is a prefetch access... 5063 * move this block back to the MRU state. 5064 */ 5065 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 5066 new_state = arc_mru; 5067 } 5068 5069 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5070 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5071 arc_change_state(new_state, hdr, hash_lock); 5072 5073 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 5074 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 5075 /* 5076 * This buffer is on the 2nd Level ARC. 5077 */ 5078 5079 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 5080 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 5081 arc_change_state(arc_mfu, hdr, hash_lock); 5082 } else { 5083 ASSERT(!"invalid arc state"); 5084 } 5085} 5086 5087/* a generic arc_done_func_t which you can use */ 5088/* ARGSUSED */ 5089void 5090arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 5091{ 5092 if (zio == NULL || zio->io_error == 0) 5093 bcopy(buf->b_data, arg, arc_buf_size(buf)); 5094 arc_buf_destroy(buf, arg); 5095} 5096 5097/* a generic arc_done_func_t */ 5098void 5099arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 5100{ 5101 arc_buf_t **bufp = arg; 5102 if (zio && zio->io_error) { 5103 arc_buf_destroy(buf, arg); 5104 *bufp = NULL; 5105 } else { 5106 *bufp = buf; 5107 ASSERT(buf->b_data); 5108 } 5109} 5110 5111static void 5112arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 5113{ 5114 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 5115 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 5116 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 5117 } else { 5118 if (HDR_COMPRESSION_ENABLED(hdr)) { 5119 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 5120 BP_GET_COMPRESS(bp)); 5121 } 5122 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 5123 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 5124 } 5125} 5126 5127static void 5128arc_read_done(zio_t *zio) 5129{ 5130 arc_buf_hdr_t *hdr = zio->io_private; 5131 kmutex_t *hash_lock = NULL; 5132 arc_callback_t *callback_list; 5133 arc_callback_t *acb; 5134 boolean_t freeable = B_FALSE; 5135 boolean_t no_zio_error = (zio->io_error == 0); 5136 5137 /* 5138 * The hdr was inserted into hash-table and removed from lists 5139 * prior to starting I/O. We should find this header, since 5140 * it's in the hash table, and it should be legit since it's 5141 * not possible to evict it during the I/O. The only possible 5142 * reason for it not to be found is if we were freed during the 5143 * read. 5144 */ 5145 if (HDR_IN_HASH_TABLE(hdr)) { 5146 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 5147 ASSERT3U(hdr->b_dva.dva_word[0], ==, 5148 BP_IDENTITY(zio->io_bp)->dva_word[0]); 5149 ASSERT3U(hdr->b_dva.dva_word[1], ==, 5150 BP_IDENTITY(zio->io_bp)->dva_word[1]); 5151 5152 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 5153 &hash_lock); 5154 5155 ASSERT((found == hdr && 5156 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 5157 (found == hdr && HDR_L2_READING(hdr))); 5158 ASSERT3P(hash_lock, !=, NULL); 5159 } 5160 5161 if (no_zio_error) { 5162 /* byteswap if necessary */ 5163 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 5164 if (BP_GET_LEVEL(zio->io_bp) > 0) { 5165 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 5166 } else { 5167 hdr->b_l1hdr.b_byteswap = 5168 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 5169 } 5170 } else { 5171 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 5172 } 5173 } 5174 5175 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 5176 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 5177 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 5178 5179 callback_list = hdr->b_l1hdr.b_acb; 5180 ASSERT3P(callback_list, !=, NULL); 5181 5182 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) { 5183 /* 5184 * Only call arc_access on anonymous buffers. This is because 5185 * if we've issued an I/O for an evicted buffer, we've already 5186 * called arc_access (to prevent any simultaneous readers from 5187 * getting confused). 5188 */ 5189 arc_access(hdr, hash_lock); 5190 } 5191 5192 /* 5193 * If a read request has a callback (i.e. acb_done is not NULL), then we 5194 * make a buf containing the data according to the parameters which were 5195 * passed in. The implementation of arc_buf_alloc_impl() ensures that we 5196 * aren't needlessly decompressing the data multiple times. 5197 */ 5198 int callback_cnt = 0; 5199 for (acb = callback_list; acb != NULL; acb = acb->acb_next) { 5200 if (!acb->acb_done) 5201 continue; 5202 5203 /* This is a demand read since prefetches don't use callbacks */ 5204 callback_cnt++; 5205 5206 int error = arc_buf_alloc_impl(hdr, acb->acb_private, 5207 acb->acb_compressed, no_zio_error, &acb->acb_buf); 5208 if (no_zio_error) { 5209 zio->io_error = error; 5210 } 5211 } 5212 hdr->b_l1hdr.b_acb = NULL; 5213 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5214 if (callback_cnt == 0) { 5215 ASSERT(HDR_PREFETCH(hdr)); 5216 ASSERT0(hdr->b_l1hdr.b_bufcnt); 5217 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5218 } 5219 5220 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 5221 callback_list != NULL); 5222 5223 if (no_zio_error) { 5224 arc_hdr_verify(hdr, zio->io_bp); 5225 } else { 5226 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 5227 if (hdr->b_l1hdr.b_state != arc_anon) 5228 arc_change_state(arc_anon, hdr, hash_lock); 5229 if (HDR_IN_HASH_TABLE(hdr)) 5230 buf_hash_remove(hdr); 5231 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5232 } 5233 5234 /* 5235 * Broadcast before we drop the hash_lock to avoid the possibility 5236 * that the hdr (and hence the cv) might be freed before we get to 5237 * the cv_broadcast(). 5238 */ 5239 cv_broadcast(&hdr->b_l1hdr.b_cv); 5240 5241 if (hash_lock != NULL) { 5242 mutex_exit(hash_lock); 5243 } else { 5244 /* 5245 * This block was freed while we waited for the read to 5246 * complete. It has been removed from the hash table and 5247 * moved to the anonymous state (so that it won't show up 5248 * in the cache). 5249 */ 5250 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 5251 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5252 } 5253 5254 /* execute each callback and free its structure */ 5255 while ((acb = callback_list) != NULL) { 5256 if (acb->acb_done) 5257 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 5258 5259 if (acb->acb_zio_dummy != NULL) { 5260 acb->acb_zio_dummy->io_error = zio->io_error; 5261 zio_nowait(acb->acb_zio_dummy); 5262 } 5263 5264 callback_list = acb->acb_next; 5265 kmem_free(acb, sizeof (arc_callback_t)); 5266 } 5267 5268 if (freeable) 5269 arc_hdr_destroy(hdr); 5270} 5271 5272/* 5273 * "Read" the block at the specified DVA (in bp) via the 5274 * cache. If the block is found in the cache, invoke the provided 5275 * callback immediately and return. Note that the `zio' parameter 5276 * in the callback will be NULL in this case, since no IO was 5277 * required. If the block is not in the cache pass the read request 5278 * on to the spa with a substitute callback function, so that the 5279 * requested block will be added to the cache. 5280 * 5281 * If a read request arrives for a block that has a read in-progress, 5282 * either wait for the in-progress read to complete (and return the 5283 * results); or, if this is a read with a "done" func, add a record 5284 * to the read to invoke the "done" func when the read completes, 5285 * and return; or just return. 5286 * 5287 * arc_read_done() will invoke all the requested "done" functions 5288 * for readers of this block. 5289 */ 5290int 5291arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 5292 void *private, zio_priority_t priority, int zio_flags, 5293 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 5294{ 5295 arc_buf_hdr_t *hdr = NULL; 5296 kmutex_t *hash_lock = NULL; 5297 zio_t *rzio; 5298 uint64_t guid = spa_load_guid(spa); 5299 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0; 5300 5301 ASSERT(!BP_IS_EMBEDDED(bp) || 5302 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 5303 5304top: 5305 if (!BP_IS_EMBEDDED(bp)) { 5306 /* 5307 * Embedded BP's have no DVA and require no I/O to "read". 5308 * Create an anonymous arc buf to back it. 5309 */ 5310 hdr = buf_hash_find(guid, bp, &hash_lock); 5311 } 5312 5313 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { 5314 arc_buf_t *buf = NULL; 5315 *arc_flags |= ARC_FLAG_CACHED; 5316 5317 if (HDR_IO_IN_PROGRESS(hdr)) { 5318 5319 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 5320 priority == ZIO_PRIORITY_SYNC_READ) { 5321 /* 5322 * This sync read must wait for an 5323 * in-progress async read (e.g. a predictive 5324 * prefetch). Async reads are queued 5325 * separately at the vdev_queue layer, so 5326 * this is a form of priority inversion. 5327 * Ideally, we would "inherit" the demand 5328 * i/o's priority by moving the i/o from 5329 * the async queue to the synchronous queue, 5330 * but there is currently no mechanism to do 5331 * so. Track this so that we can evaluate 5332 * the magnitude of this potential performance 5333 * problem. 5334 * 5335 * Note that if the prefetch i/o is already 5336 * active (has been issued to the device), 5337 * the prefetch improved performance, because 5338 * we issued it sooner than we would have 5339 * without the prefetch. 5340 */ 5341 DTRACE_PROBE1(arc__sync__wait__for__async, 5342 arc_buf_hdr_t *, hdr); 5343 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 5344 } 5345 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5346 arc_hdr_clear_flags(hdr, 5347 ARC_FLAG_PREDICTIVE_PREFETCH); 5348 } 5349 5350 if (*arc_flags & ARC_FLAG_WAIT) { 5351 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 5352 mutex_exit(hash_lock); 5353 goto top; 5354 } 5355 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5356 5357 if (done) { 5358 arc_callback_t *acb = NULL; 5359 5360 acb = kmem_zalloc(sizeof (arc_callback_t), 5361 KM_SLEEP); 5362 acb->acb_done = done; 5363 acb->acb_private = private; 5364 acb->acb_compressed = compressed_read; 5365 if (pio != NULL) 5366 acb->acb_zio_dummy = zio_null(pio, 5367 spa, NULL, NULL, NULL, zio_flags); 5368 5369 ASSERT3P(acb->acb_done, !=, NULL); 5370 acb->acb_next = hdr->b_l1hdr.b_acb; 5371 hdr->b_l1hdr.b_acb = acb; 5372 mutex_exit(hash_lock); 5373 return (0); 5374 } 5375 mutex_exit(hash_lock); 5376 return (0); 5377 } 5378 5379 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5380 hdr->b_l1hdr.b_state == arc_mfu); 5381 5382 if (done) { 5383 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5384 /* 5385 * This is a demand read which does not have to 5386 * wait for i/o because we did a predictive 5387 * prefetch i/o for it, which has completed. 5388 */ 5389 DTRACE_PROBE1( 5390 arc__demand__hit__predictive__prefetch, 5391 arc_buf_hdr_t *, hdr); 5392 ARCSTAT_BUMP( 5393 arcstat_demand_hit_predictive_prefetch); 5394 arc_hdr_clear_flags(hdr, 5395 ARC_FLAG_PREDICTIVE_PREFETCH); 5396 } 5397 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 5398 5399 /* Get a buf with the desired data in it. */ 5400 VERIFY0(arc_buf_alloc_impl(hdr, private, 5401 compressed_read, B_TRUE, &buf)); 5402 } else if (*arc_flags & ARC_FLAG_PREFETCH && 5403 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5404 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5405 } 5406 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5407 arc_access(hdr, hash_lock); 5408 if (*arc_flags & ARC_FLAG_L2CACHE) 5409 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5410 mutex_exit(hash_lock); 5411 ARCSTAT_BUMP(arcstat_hits); 5412 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5413 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5414 data, metadata, hits); 5415 5416 if (done) 5417 done(NULL, buf, private); 5418 } else { 5419 uint64_t lsize = BP_GET_LSIZE(bp); 5420 uint64_t psize = BP_GET_PSIZE(bp); 5421 arc_callback_t *acb; 5422 vdev_t *vd = NULL; 5423 uint64_t addr = 0; 5424 boolean_t devw = B_FALSE; 5425 uint64_t size; 5426 5427 if (hdr == NULL) { 5428 /* this block is not in the cache */ 5429 arc_buf_hdr_t *exists = NULL; 5430 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 5431 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 5432 BP_GET_COMPRESS(bp), type); 5433 5434 if (!BP_IS_EMBEDDED(bp)) { 5435 hdr->b_dva = *BP_IDENTITY(bp); 5436 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 5437 exists = buf_hash_insert(hdr, &hash_lock); 5438 } 5439 if (exists != NULL) { 5440 /* somebody beat us to the hash insert */ 5441 mutex_exit(hash_lock); 5442 buf_discard_identity(hdr); 5443 arc_hdr_destroy(hdr); 5444 goto top; /* restart the IO request */ 5445 } 5446 } else { 5447 /* 5448 * This block is in the ghost cache. If it was L2-only 5449 * (and thus didn't have an L1 hdr), we realloc the 5450 * header to add an L1 hdr. 5451 */ 5452 if (!HDR_HAS_L1HDR(hdr)) { 5453 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 5454 hdr_full_cache); 5455 } 5456 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5457 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 5458 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5459 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5460 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 5461 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 5462 5463 /* 5464 * This is a delicate dance that we play here. 5465 * This hdr is in the ghost list so we access it 5466 * to move it out of the ghost list before we 5467 * initiate the read. If it's a prefetch then 5468 * it won't have a callback so we'll remove the 5469 * reference that arc_buf_alloc_impl() created. We 5470 * do this after we've called arc_access() to 5471 * avoid hitting an assert in remove_reference(). 5472 */ 5473 arc_access(hdr, hash_lock); 5474 arc_hdr_alloc_pabd(hdr); 5475 } 5476 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5477 size = arc_hdr_size(hdr); 5478 5479 /* 5480 * If compression is enabled on the hdr, then will do 5481 * RAW I/O and will store the compressed data in the hdr's 5482 * data block. Otherwise, the hdr's data block will contain 5483 * the uncompressed data. 5484 */ 5485 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5486 zio_flags |= ZIO_FLAG_RAW; 5487 } 5488 5489 if (*arc_flags & ARC_FLAG_PREFETCH) 5490 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5491 if (*arc_flags & ARC_FLAG_L2CACHE) 5492 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5493 if (BP_GET_LEVEL(bp) > 0) 5494 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5495 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5496 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5497 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5498 5499 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5500 acb->acb_done = done; 5501 acb->acb_private = private; 5502 acb->acb_compressed = compressed_read; 5503 5504 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5505 hdr->b_l1hdr.b_acb = acb; 5506 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5507 5508 if (HDR_HAS_L2HDR(hdr) && 5509 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5510 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5511 addr = hdr->b_l2hdr.b_daddr; 5512 /* 5513 * Lock out L2ARC device removal. 5514 */ 5515 if (vdev_is_dead(vd) || 5516 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 5517 vd = NULL; 5518 } 5519 5520 if (priority == ZIO_PRIORITY_ASYNC_READ) 5521 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5522 else 5523 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5524 5525 if (hash_lock != NULL) 5526 mutex_exit(hash_lock); 5527 5528 /* 5529 * At this point, we have a level 1 cache miss. Try again in 5530 * L2ARC if possible. 5531 */ 5532 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 5533 5534 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 5535 uint64_t, lsize, zbookmark_phys_t *, zb); 5536 ARCSTAT_BUMP(arcstat_misses); 5537 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5538 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5539 data, metadata, misses); 5540#ifdef _KERNEL 5541#ifdef RACCT 5542 if (racct_enable) { 5543 PROC_LOCK(curproc); 5544 racct_add_force(curproc, RACCT_READBPS, size); 5545 racct_add_force(curproc, RACCT_READIOPS, 1); 5546 PROC_UNLOCK(curproc); 5547 } 5548#endif /* RACCT */ 5549 curthread->td_ru.ru_inblock++; 5550#endif 5551 5552 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5553 /* 5554 * Read from the L2ARC if the following are true: 5555 * 1. The L2ARC vdev was previously cached. 5556 * 2. This buffer still has L2ARC metadata. 5557 * 3. This buffer isn't currently writing to the L2ARC. 5558 * 4. The L2ARC entry wasn't evicted, which may 5559 * also have invalidated the vdev. 5560 * 5. This isn't prefetch and l2arc_noprefetch is set. 5561 */ 5562 if (HDR_HAS_L2HDR(hdr) && 5563 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5564 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5565 l2arc_read_callback_t *cb; 5566 abd_t *abd; 5567 uint64_t asize; 5568 5569 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5570 ARCSTAT_BUMP(arcstat_l2_hits); 5571 5572 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5573 KM_SLEEP); 5574 cb->l2rcb_hdr = hdr; 5575 cb->l2rcb_bp = *bp; 5576 cb->l2rcb_zb = *zb; 5577 cb->l2rcb_flags = zio_flags; 5578 5579 asize = vdev_psize_to_asize(vd, size); 5580 if (asize != size) { 5581 abd = abd_alloc_for_io(asize, 5582 HDR_ISTYPE_METADATA(hdr)); 5583 cb->l2rcb_abd = abd; 5584 } else { 5585 abd = hdr->b_l1hdr.b_pabd; 5586 } 5587 5588 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5589 addr + asize <= vd->vdev_psize - 5590 VDEV_LABEL_END_SIZE); 5591 5592 /* 5593 * l2arc read. The SCL_L2ARC lock will be 5594 * released by l2arc_read_done(). 5595 * Issue a null zio if the underlying buffer 5596 * was squashed to zero size by compression. 5597 */ 5598 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5599 ZIO_COMPRESS_EMPTY); 5600 rzio = zio_read_phys(pio, vd, addr, 5601 asize, abd, 5602 ZIO_CHECKSUM_OFF, 5603 l2arc_read_done, cb, priority, 5604 zio_flags | ZIO_FLAG_DONT_CACHE | 5605 ZIO_FLAG_CANFAIL | 5606 ZIO_FLAG_DONT_PROPAGATE | 5607 ZIO_FLAG_DONT_RETRY, B_FALSE); 5608 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5609 zio_t *, rzio); 5610 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5611 5612 if (*arc_flags & ARC_FLAG_NOWAIT) { 5613 zio_nowait(rzio); 5614 return (0); 5615 } 5616 5617 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5618 if (zio_wait(rzio) == 0) 5619 return (0); 5620 5621 /* l2arc read error; goto zio_read() */ 5622 } else { 5623 DTRACE_PROBE1(l2arc__miss, 5624 arc_buf_hdr_t *, hdr); 5625 ARCSTAT_BUMP(arcstat_l2_misses); 5626 if (HDR_L2_WRITING(hdr)) 5627 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5628 spa_config_exit(spa, SCL_L2ARC, vd); 5629 } 5630 } else { 5631 if (vd != NULL) 5632 spa_config_exit(spa, SCL_L2ARC, vd); 5633 if (l2arc_ndev != 0) { 5634 DTRACE_PROBE1(l2arc__miss, 5635 arc_buf_hdr_t *, hdr); 5636 ARCSTAT_BUMP(arcstat_l2_misses); 5637 } 5638 } 5639 5640 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size, 5641 arc_read_done, hdr, priority, zio_flags, zb); 5642 5643 if (*arc_flags & ARC_FLAG_WAIT) 5644 return (zio_wait(rzio)); 5645 5646 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5647 zio_nowait(rzio); 5648 } 5649 return (0); 5650} 5651 5652/* 5653 * Notify the arc that a block was freed, and thus will never be used again. 5654 */ 5655void 5656arc_freed(spa_t *spa, const blkptr_t *bp) 5657{ 5658 arc_buf_hdr_t *hdr; 5659 kmutex_t *hash_lock; 5660 uint64_t guid = spa_load_guid(spa); 5661 5662 ASSERT(!BP_IS_EMBEDDED(bp)); 5663 5664 hdr = buf_hash_find(guid, bp, &hash_lock); 5665 if (hdr == NULL) 5666 return; 5667 5668 /* 5669 * We might be trying to free a block that is still doing I/O 5670 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5671 * dmu_sync-ed block). If this block is being prefetched, then it 5672 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5673 * until the I/O completes. A block may also have a reference if it is 5674 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5675 * have written the new block to its final resting place on disk but 5676 * without the dedup flag set. This would have left the hdr in the MRU 5677 * state and discoverable. When the txg finally syncs it detects that 5678 * the block was overridden in open context and issues an override I/O. 5679 * Since this is a dedup block, the override I/O will determine if the 5680 * block is already in the DDT. If so, then it will replace the io_bp 5681 * with the bp from the DDT and allow the I/O to finish. When the I/O 5682 * reaches the done callback, dbuf_write_override_done, it will 5683 * check to see if the io_bp and io_bp_override are identical. 5684 * If they are not, then it indicates that the bp was replaced with 5685 * the bp in the DDT and the override bp is freed. This allows 5686 * us to arrive here with a reference on a block that is being 5687 * freed. So if we have an I/O in progress, or a reference to 5688 * this hdr, then we don't destroy the hdr. 5689 */ 5690 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5691 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5692 arc_change_state(arc_anon, hdr, hash_lock); 5693 arc_hdr_destroy(hdr); 5694 mutex_exit(hash_lock); 5695 } else { 5696 mutex_exit(hash_lock); 5697 } 5698 5699} 5700 5701/* 5702 * Release this buffer from the cache, making it an anonymous buffer. This 5703 * must be done after a read and prior to modifying the buffer contents. 5704 * If the buffer has more than one reference, we must make 5705 * a new hdr for the buffer. 5706 */ 5707void 5708arc_release(arc_buf_t *buf, void *tag) 5709{ 5710 arc_buf_hdr_t *hdr = buf->b_hdr; 5711 5712 /* 5713 * It would be nice to assert that if it's DMU metadata (level > 5714 * 0 || it's the dnode file), then it must be syncing context. 5715 * But we don't know that information at this level. 5716 */ 5717 5718 mutex_enter(&buf->b_evict_lock); 5719 5720 ASSERT(HDR_HAS_L1HDR(hdr)); 5721 5722 /* 5723 * We don't grab the hash lock prior to this check, because if 5724 * the buffer's header is in the arc_anon state, it won't be 5725 * linked into the hash table. 5726 */ 5727 if (hdr->b_l1hdr.b_state == arc_anon) { 5728 mutex_exit(&buf->b_evict_lock); 5729 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5730 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5731 ASSERT(!HDR_HAS_L2HDR(hdr)); 5732 ASSERT(HDR_EMPTY(hdr)); 5733 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5734 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5735 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5736 5737 hdr->b_l1hdr.b_arc_access = 0; 5738 5739 /* 5740 * If the buf is being overridden then it may already 5741 * have a hdr that is not empty. 5742 */ 5743 buf_discard_identity(hdr); 5744 arc_buf_thaw(buf); 5745 5746 return; 5747 } 5748 5749 kmutex_t *hash_lock = HDR_LOCK(hdr); 5750 mutex_enter(hash_lock); 5751 5752 /* 5753 * This assignment is only valid as long as the hash_lock is 5754 * held, we must be careful not to reference state or the 5755 * b_state field after dropping the lock. 5756 */ 5757 arc_state_t *state = hdr->b_l1hdr.b_state; 5758 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5759 ASSERT3P(state, !=, arc_anon); 5760 5761 /* this buffer is not on any list */ 5762 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); 5763 5764 if (HDR_HAS_L2HDR(hdr)) { 5765 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5766 5767 /* 5768 * We have to recheck this conditional again now that 5769 * we're holding the l2ad_mtx to prevent a race with 5770 * another thread which might be concurrently calling 5771 * l2arc_evict(). In that case, l2arc_evict() might have 5772 * destroyed the header's L2 portion as we were waiting 5773 * to acquire the l2ad_mtx. 5774 */ 5775 if (HDR_HAS_L2HDR(hdr)) { 5776 l2arc_trim(hdr); 5777 arc_hdr_l2hdr_destroy(hdr); 5778 } 5779 5780 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5781 } 5782 5783 /* 5784 * Do we have more than one buf? 5785 */ 5786 if (hdr->b_l1hdr.b_bufcnt > 1) { 5787 arc_buf_hdr_t *nhdr; 5788 uint64_t spa = hdr->b_spa; 5789 uint64_t psize = HDR_GET_PSIZE(hdr); 5790 uint64_t lsize = HDR_GET_LSIZE(hdr); 5791 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5792 arc_buf_contents_t type = arc_buf_type(hdr); 5793 VERIFY3U(hdr->b_type, ==, type); 5794 5795 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5796 (void) remove_reference(hdr, hash_lock, tag); 5797 5798 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { 5799 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5800 ASSERT(ARC_BUF_LAST(buf)); 5801 } 5802 5803 /* 5804 * Pull the data off of this hdr and attach it to 5805 * a new anonymous hdr. Also find the last buffer 5806 * in the hdr's buffer list. 5807 */ 5808 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 5809 ASSERT3P(lastbuf, !=, NULL); 5810 5811 /* 5812 * If the current arc_buf_t and the hdr are sharing their data 5813 * buffer, then we must stop sharing that block. 5814 */ 5815 if (arc_buf_is_shared(buf)) { 5816 VERIFY(!arc_buf_is_shared(lastbuf)); 5817 5818 /* 5819 * First, sever the block sharing relationship between 5820 * buf and the arc_buf_hdr_t. 5821 */ 5822 arc_unshare_buf(hdr, buf); 5823 5824 /* 5825 * Now we need to recreate the hdr's b_pabd. Since we 5826 * have lastbuf handy, we try to share with it, but if 5827 * we can't then we allocate a new b_pabd and copy the 5828 * data from buf into it. 5829 */ 5830 if (arc_can_share(hdr, lastbuf)) { 5831 arc_share_buf(hdr, lastbuf); 5832 } else { 5833 arc_hdr_alloc_pabd(hdr); 5834 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, 5835 buf->b_data, psize); 5836 } 5837 VERIFY3P(lastbuf->b_data, !=, NULL); 5838 } else if (HDR_SHARED_DATA(hdr)) { 5839 /* 5840 * Uncompressed shared buffers are always at the end 5841 * of the list. Compressed buffers don't have the 5842 * same requirements. This makes it hard to 5843 * simply assert that the lastbuf is shared so 5844 * we rely on the hdr's compression flags to determine 5845 * if we have a compressed, shared buffer. 5846 */ 5847 ASSERT(arc_buf_is_shared(lastbuf) || 5848 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 5849 ASSERT(!ARC_BUF_SHARED(buf)); 5850 } 5851 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5852 ASSERT3P(state, !=, arc_l2c_only); 5853 5854 (void) refcount_remove_many(&state->arcs_size, 5855 arc_buf_size(buf), buf); 5856 5857 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5858 ASSERT3P(state, !=, arc_l2c_only); 5859 (void) refcount_remove_many(&state->arcs_esize[type], 5860 arc_buf_size(buf), buf); 5861 } 5862 5863 hdr->b_l1hdr.b_bufcnt -= 1; 5864 arc_cksum_verify(buf); 5865#ifdef illumos 5866 arc_buf_unwatch(buf); 5867#endif 5868 5869 mutex_exit(hash_lock); 5870 5871 /* 5872 * Allocate a new hdr. The new hdr will contain a b_pabd 5873 * buffer which will be freed in arc_write(). 5874 */ 5875 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 5876 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 5877 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 5878 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 5879 VERIFY3U(nhdr->b_type, ==, type); 5880 ASSERT(!HDR_SHARED_DATA(nhdr)); 5881 5882 nhdr->b_l1hdr.b_buf = buf; 5883 nhdr->b_l1hdr.b_bufcnt = 1; 5884 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 5885 buf->b_hdr = nhdr; 5886 5887 mutex_exit(&buf->b_evict_lock); 5888 (void) refcount_add_many(&arc_anon->arcs_size, 5889 arc_buf_size(buf), buf); 5890 } else { 5891 mutex_exit(&buf->b_evict_lock); 5892 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 5893 /* protected by hash lock, or hdr is on arc_anon */ 5894 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5895 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5896 arc_change_state(arc_anon, hdr, hash_lock); 5897 hdr->b_l1hdr.b_arc_access = 0; 5898 mutex_exit(hash_lock); 5899 5900 buf_discard_identity(hdr); 5901 arc_buf_thaw(buf); 5902 } 5903} 5904 5905int 5906arc_released(arc_buf_t *buf) 5907{ 5908 int released; 5909 5910 mutex_enter(&buf->b_evict_lock); 5911 released = (buf->b_data != NULL && 5912 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5913 mutex_exit(&buf->b_evict_lock); 5914 return (released); 5915} 5916 5917#ifdef ZFS_DEBUG 5918int 5919arc_referenced(arc_buf_t *buf) 5920{ 5921 int referenced; 5922 5923 mutex_enter(&buf->b_evict_lock); 5924 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5925 mutex_exit(&buf->b_evict_lock); 5926 return (referenced); 5927} 5928#endif 5929 5930static void 5931arc_write_ready(zio_t *zio) 5932{ 5933 arc_write_callback_t *callback = zio->io_private; 5934 arc_buf_t *buf = callback->awcb_buf; 5935 arc_buf_hdr_t *hdr = buf->b_hdr; 5936 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 5937 5938 ASSERT(HDR_HAS_L1HDR(hdr)); 5939 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5940 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 5941 5942 /* 5943 * If we're reexecuting this zio because the pool suspended, then 5944 * cleanup any state that was previously set the first time the 5945 * callback was invoked. 5946 */ 5947 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 5948 arc_cksum_free(hdr); 5949#ifdef illumos 5950 arc_buf_unwatch(buf); 5951#endif 5952 if (hdr->b_l1hdr.b_pabd != NULL) { 5953 if (arc_buf_is_shared(buf)) { 5954 arc_unshare_buf(hdr, buf); 5955 } else { 5956 arc_hdr_free_pabd(hdr); 5957 } 5958 } 5959 } 5960 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5961 ASSERT(!HDR_SHARED_DATA(hdr)); 5962 ASSERT(!arc_buf_is_shared(buf)); 5963 5964 callback->awcb_ready(zio, buf, callback->awcb_private); 5965 5966 if (HDR_IO_IN_PROGRESS(hdr)) 5967 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 5968 5969 arc_cksum_compute(buf); 5970 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5971 5972 enum zio_compress compress; 5973 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5974 compress = ZIO_COMPRESS_OFF; 5975 } else { 5976 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 5977 compress = BP_GET_COMPRESS(zio->io_bp); 5978 } 5979 HDR_SET_PSIZE(hdr, psize); 5980 arc_hdr_set_compress(hdr, compress); 5981 5982 5983 /* 5984 * Fill the hdr with data. If the hdr is compressed, the data we want 5985 * is available from the zio, otherwise we can take it from the buf. 5986 * 5987 * We might be able to share the buf's data with the hdr here. However, 5988 * doing so would cause the ARC to be full of linear ABDs if we write a 5989 * lot of shareable data. As a compromise, we check whether scattered 5990 * ABDs are allowed, and assume that if they are then the user wants 5991 * the ARC to be primarily filled with them regardless of the data being 5992 * written. Therefore, if they're allowed then we allocate one and copy 5993 * the data into it; otherwise, we share the data directly if we can. 5994 */ 5995 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { 5996 arc_hdr_alloc_pabd(hdr); 5997 5998 /* 5999 * Ideally, we would always copy the io_abd into b_pabd, but the 6000 * user may have disabled compressed ARC, thus we must check the 6001 * hdr's compression setting rather than the io_bp's. 6002 */ 6003 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 6004 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, 6005 ZIO_COMPRESS_OFF); 6006 ASSERT3U(psize, >, 0); 6007 6008 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); 6009 } else { 6010 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); 6011 6012 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, 6013 arc_buf_size(buf)); 6014 } 6015 } else { 6016 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); 6017 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); 6018 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 6019 6020 arc_share_buf(hdr, buf); 6021 } 6022 6023 arc_hdr_verify(hdr, zio->io_bp); 6024} 6025 6026static void 6027arc_write_children_ready(zio_t *zio) 6028{ 6029 arc_write_callback_t *callback = zio->io_private; 6030 arc_buf_t *buf = callback->awcb_buf; 6031 6032 callback->awcb_children_ready(zio, buf, callback->awcb_private); 6033} 6034 6035/* 6036 * The SPA calls this callback for each physical write that happens on behalf 6037 * of a logical write. See the comment in dbuf_write_physdone() for details. 6038 */ 6039static void 6040arc_write_physdone(zio_t *zio) 6041{ 6042 arc_write_callback_t *cb = zio->io_private; 6043 if (cb->awcb_physdone != NULL) 6044 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 6045} 6046 6047static void 6048arc_write_done(zio_t *zio) 6049{ 6050 arc_write_callback_t *callback = zio->io_private; 6051 arc_buf_t *buf = callback->awcb_buf; 6052 arc_buf_hdr_t *hdr = buf->b_hdr; 6053 6054 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6055 6056 if (zio->io_error == 0) { 6057 arc_hdr_verify(hdr, zio->io_bp); 6058 6059 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 6060 buf_discard_identity(hdr); 6061 } else { 6062 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 6063 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 6064 } 6065 } else { 6066 ASSERT(HDR_EMPTY(hdr)); 6067 } 6068 6069 /* 6070 * If the block to be written was all-zero or compressed enough to be 6071 * embedded in the BP, no write was performed so there will be no 6072 * dva/birth/checksum. The buffer must therefore remain anonymous 6073 * (and uncached). 6074 */ 6075 if (!HDR_EMPTY(hdr)) { 6076 arc_buf_hdr_t *exists; 6077 kmutex_t *hash_lock; 6078 6079 ASSERT3U(zio->io_error, ==, 0); 6080 6081 arc_cksum_verify(buf); 6082 6083 exists = buf_hash_insert(hdr, &hash_lock); 6084 if (exists != NULL) { 6085 /* 6086 * This can only happen if we overwrite for 6087 * sync-to-convergence, because we remove 6088 * buffers from the hash table when we arc_free(). 6089 */ 6090 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 6091 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6092 panic("bad overwrite, hdr=%p exists=%p", 6093 (void *)hdr, (void *)exists); 6094 ASSERT(refcount_is_zero( 6095 &exists->b_l1hdr.b_refcnt)); 6096 arc_change_state(arc_anon, exists, hash_lock); 6097 mutex_exit(hash_lock); 6098 arc_hdr_destroy(exists); 6099 exists = buf_hash_insert(hdr, &hash_lock); 6100 ASSERT3P(exists, ==, NULL); 6101 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 6102 /* nopwrite */ 6103 ASSERT(zio->io_prop.zp_nopwrite); 6104 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6105 panic("bad nopwrite, hdr=%p exists=%p", 6106 (void *)hdr, (void *)exists); 6107 } else { 6108 /* Dedup */ 6109 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 6110 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 6111 ASSERT(BP_GET_DEDUP(zio->io_bp)); 6112 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 6113 } 6114 } 6115 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6116 /* if it's not anon, we are doing a scrub */ 6117 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 6118 arc_access(hdr, hash_lock); 6119 mutex_exit(hash_lock); 6120 } else { 6121 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6122 } 6123 6124 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 6125 callback->awcb_done(zio, buf, callback->awcb_private); 6126 6127 abd_put(zio->io_abd); 6128 kmem_free(callback, sizeof (arc_write_callback_t)); 6129} 6130 6131zio_t * 6132arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 6133 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready, 6134 arc_done_func_t *children_ready, arc_done_func_t *physdone, 6135 arc_done_func_t *done, void *private, zio_priority_t priority, 6136 int zio_flags, const zbookmark_phys_t *zb) 6137{ 6138 arc_buf_hdr_t *hdr = buf->b_hdr; 6139 arc_write_callback_t *callback; 6140 zio_t *zio; 6141 zio_prop_t localprop = *zp; 6142 6143 ASSERT3P(ready, !=, NULL); 6144 ASSERT3P(done, !=, NULL); 6145 ASSERT(!HDR_IO_ERROR(hdr)); 6146 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6147 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6148 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 6149 if (l2arc) 6150 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 6151 if (ARC_BUF_COMPRESSED(buf)) { 6152 /* 6153 * We're writing a pre-compressed buffer. Make the 6154 * compression algorithm requested by the zio_prop_t match 6155 * the pre-compressed buffer's compression algorithm. 6156 */ 6157 localprop.zp_compress = HDR_GET_COMPRESS(hdr); 6158 6159 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); 6160 zio_flags |= ZIO_FLAG_RAW; 6161 } 6162 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 6163 callback->awcb_ready = ready; 6164 callback->awcb_children_ready = children_ready; 6165 callback->awcb_physdone = physdone; 6166 callback->awcb_done = done; 6167 callback->awcb_private = private; 6168 callback->awcb_buf = buf; 6169 6170 /* 6171 * The hdr's b_pabd is now stale, free it now. A new data block 6172 * will be allocated when the zio pipeline calls arc_write_ready(). 6173 */ 6174 if (hdr->b_l1hdr.b_pabd != NULL) { 6175 /* 6176 * If the buf is currently sharing the data block with 6177 * the hdr then we need to break that relationship here. 6178 * The hdr will remain with a NULL data pointer and the 6179 * buf will take sole ownership of the block. 6180 */ 6181 if (arc_buf_is_shared(buf)) { 6182 arc_unshare_buf(hdr, buf); 6183 } else { 6184 arc_hdr_free_pabd(hdr); 6185 } 6186 VERIFY3P(buf->b_data, !=, NULL); 6187 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 6188 } 6189 ASSERT(!arc_buf_is_shared(buf)); 6190 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6191 6192 zio = zio_write(pio, spa, txg, bp, 6193 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), 6194 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, 6195 (children_ready != NULL) ? arc_write_children_ready : NULL, 6196 arc_write_physdone, arc_write_done, callback, 6197 priority, zio_flags, zb); 6198 6199 return (zio); 6200} 6201 6202static int 6203arc_memory_throttle(uint64_t reserve, uint64_t txg) 6204{ 6205#ifdef _KERNEL 6206 uint64_t available_memory = ptob(freemem); 6207 static uint64_t page_load = 0; 6208 static uint64_t last_txg = 0; 6209 6210#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 6211 available_memory = 6212 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 6213#endif 6214 6215 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 6216 return (0); 6217 6218 if (txg > last_txg) { 6219 last_txg = txg; 6220 page_load = 0; 6221 } 6222 /* 6223 * If we are in pageout, we know that memory is already tight, 6224 * the arc is already going to be evicting, so we just want to 6225 * continue to let page writes occur as quickly as possible. 6226 */ 6227 if (curproc == pageproc) { 6228 if (page_load > MAX(ptob(minfree), available_memory) / 4) 6229 return (SET_ERROR(ERESTART)); 6230 /* Note: reserve is inflated, so we deflate */ 6231 page_load += reserve / 8; 6232 return (0); 6233 } else if (page_load > 0 && arc_reclaim_needed()) { 6234 /* memory is low, delay before restarting */ 6235 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 6236 return (SET_ERROR(EAGAIN)); 6237 } 6238 page_load = 0; 6239#endif 6240 return (0); 6241} 6242 6243void 6244arc_tempreserve_clear(uint64_t reserve) 6245{ 6246 atomic_add_64(&arc_tempreserve, -reserve); 6247 ASSERT((int64_t)arc_tempreserve >= 0); 6248} 6249 6250int 6251arc_tempreserve_space(uint64_t reserve, uint64_t txg) 6252{ 6253 int error; 6254 uint64_t anon_size; 6255 6256 if (reserve > arc_c/4 && !arc_no_grow) { 6257 arc_c = MIN(arc_c_max, reserve * 4); 6258 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 6259 } 6260 if (reserve > arc_c) 6261 return (SET_ERROR(ENOMEM)); 6262 6263 /* 6264 * Don't count loaned bufs as in flight dirty data to prevent long 6265 * network delays from blocking transactions that are ready to be 6266 * assigned to a txg. 6267 */ 6268 6269 /* assert that it has not wrapped around */ 6270 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 6271 6272 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 6273 arc_loaned_bytes), 0); 6274 6275 /* 6276 * Writes will, almost always, require additional memory allocations 6277 * in order to compress/encrypt/etc the data. We therefore need to 6278 * make sure that there is sufficient available memory for this. 6279 */ 6280 error = arc_memory_throttle(reserve, txg); 6281 if (error != 0) 6282 return (error); 6283 6284 /* 6285 * Throttle writes when the amount of dirty data in the cache 6286 * gets too large. We try to keep the cache less than half full 6287 * of dirty blocks so that our sync times don't grow too large. 6288 * Note: if two requests come in concurrently, we might let them 6289 * both succeed, when one of them should fail. Not a huge deal. 6290 */ 6291 6292 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 6293 anon_size > arc_c / 4) { 6294 uint64_t meta_esize = 6295 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6296 uint64_t data_esize = 6297 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6298 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 6299 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 6300 arc_tempreserve >> 10, meta_esize >> 10, 6301 data_esize >> 10, reserve >> 10, arc_c >> 10); 6302 return (SET_ERROR(ERESTART)); 6303 } 6304 atomic_add_64(&arc_tempreserve, reserve); 6305 return (0); 6306} 6307 6308static void 6309arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 6310 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 6311{ 6312 size->value.ui64 = refcount_count(&state->arcs_size); 6313 evict_data->value.ui64 = 6314 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 6315 evict_metadata->value.ui64 = 6316 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 6317} 6318 6319static int 6320arc_kstat_update(kstat_t *ksp, int rw) 6321{ 6322 arc_stats_t *as = ksp->ks_data; 6323 6324 if (rw == KSTAT_WRITE) { 6325 return (EACCES); 6326 } else { 6327 arc_kstat_update_state(arc_anon, 6328 &as->arcstat_anon_size, 6329 &as->arcstat_anon_evictable_data, 6330 &as->arcstat_anon_evictable_metadata); 6331 arc_kstat_update_state(arc_mru, 6332 &as->arcstat_mru_size, 6333 &as->arcstat_mru_evictable_data, 6334 &as->arcstat_mru_evictable_metadata); 6335 arc_kstat_update_state(arc_mru_ghost, 6336 &as->arcstat_mru_ghost_size, 6337 &as->arcstat_mru_ghost_evictable_data, 6338 &as->arcstat_mru_ghost_evictable_metadata); 6339 arc_kstat_update_state(arc_mfu, 6340 &as->arcstat_mfu_size, 6341 &as->arcstat_mfu_evictable_data, 6342 &as->arcstat_mfu_evictable_metadata); 6343 arc_kstat_update_state(arc_mfu_ghost, 6344 &as->arcstat_mfu_ghost_size, 6345 &as->arcstat_mfu_ghost_evictable_data, 6346 &as->arcstat_mfu_ghost_evictable_metadata); 6347 6348 ARCSTAT(arcstat_size) = aggsum_value(&arc_size); 6349 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used); 6350 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size); 6351 ARCSTAT(arcstat_metadata_size) = 6352 aggsum_value(&astat_metadata_size); 6353 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size); 6354 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_other_size); 6355 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size); 6356 } 6357 6358 return (0); 6359} 6360 6361/* 6362 * This function *must* return indices evenly distributed between all 6363 * sublists of the multilist. This is needed due to how the ARC eviction 6364 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 6365 * distributed between all sublists and uses this assumption when 6366 * deciding which sublist to evict from and how much to evict from it. 6367 */ 6368unsigned int 6369arc_state_multilist_index_func(multilist_t *ml, void *obj) 6370{ 6371 arc_buf_hdr_t *hdr = obj; 6372 6373 /* 6374 * We rely on b_dva to generate evenly distributed index 6375 * numbers using buf_hash below. So, as an added precaution, 6376 * let's make sure we never add empty buffers to the arc lists. 6377 */ 6378 ASSERT(!HDR_EMPTY(hdr)); 6379 6380 /* 6381 * The assumption here, is the hash value for a given 6382 * arc_buf_hdr_t will remain constant throughout it's lifetime 6383 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 6384 * Thus, we don't need to store the header's sublist index 6385 * on insertion, as this index can be recalculated on removal. 6386 * 6387 * Also, the low order bits of the hash value are thought to be 6388 * distributed evenly. Otherwise, in the case that the multilist 6389 * has a power of two number of sublists, each sublists' usage 6390 * would not be evenly distributed. 6391 */ 6392 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 6393 multilist_get_num_sublists(ml)); 6394} 6395 6396#ifdef _KERNEL 6397static eventhandler_tag arc_event_lowmem = NULL; 6398 6399static void 6400arc_lowmem(void *arg __unused, int howto __unused) 6401{ 6402 6403 mutex_enter(&arc_reclaim_lock); 6404 DTRACE_PROBE1(arc__needfree, int64_t, ((int64_t)freemem - zfs_arc_free_target) * PAGESIZE); 6405 cv_signal(&arc_reclaim_thread_cv); 6406 6407 /* 6408 * It is unsafe to block here in arbitrary threads, because we can come 6409 * here from ARC itself and may hold ARC locks and thus risk a deadlock 6410 * with ARC reclaim thread. 6411 */ 6412 if (curproc == pageproc) 6413 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 6414 mutex_exit(&arc_reclaim_lock); 6415} 6416#endif 6417 6418static void 6419arc_state_init(void) 6420{ 6421 arc_anon = &ARC_anon; 6422 arc_mru = &ARC_mru; 6423 arc_mru_ghost = &ARC_mru_ghost; 6424 arc_mfu = &ARC_mfu; 6425 arc_mfu_ghost = &ARC_mfu_ghost; 6426 arc_l2c_only = &ARC_l2c_only; 6427 6428 arc_mru->arcs_list[ARC_BUFC_METADATA] = 6429 multilist_create(sizeof (arc_buf_hdr_t), 6430 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6431 arc_state_multilist_index_func); 6432 arc_mru->arcs_list[ARC_BUFC_DATA] = 6433 multilist_create(sizeof (arc_buf_hdr_t), 6434 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6435 arc_state_multilist_index_func); 6436 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = 6437 multilist_create(sizeof (arc_buf_hdr_t), 6438 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6439 arc_state_multilist_index_func); 6440 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = 6441 multilist_create(sizeof (arc_buf_hdr_t), 6442 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6443 arc_state_multilist_index_func); 6444 arc_mfu->arcs_list[ARC_BUFC_METADATA] = 6445 multilist_create(sizeof (arc_buf_hdr_t), 6446 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6447 arc_state_multilist_index_func); 6448 arc_mfu->arcs_list[ARC_BUFC_DATA] = 6449 multilist_create(sizeof (arc_buf_hdr_t), 6450 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6451 arc_state_multilist_index_func); 6452 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = 6453 multilist_create(sizeof (arc_buf_hdr_t), 6454 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6455 arc_state_multilist_index_func); 6456 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = 6457 multilist_create(sizeof (arc_buf_hdr_t), 6458 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6459 arc_state_multilist_index_func); 6460 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = 6461 multilist_create(sizeof (arc_buf_hdr_t), 6462 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6463 arc_state_multilist_index_func); 6464 arc_l2c_only->arcs_list[ARC_BUFC_DATA] = 6465 multilist_create(sizeof (arc_buf_hdr_t), 6466 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6467 arc_state_multilist_index_func); 6468 6469 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6470 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6471 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6472 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6473 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6474 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6475 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6476 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6477 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6478 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6479 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6480 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6481 6482 refcount_create(&arc_anon->arcs_size); 6483 refcount_create(&arc_mru->arcs_size); 6484 refcount_create(&arc_mru_ghost->arcs_size); 6485 refcount_create(&arc_mfu->arcs_size); 6486 refcount_create(&arc_mfu_ghost->arcs_size); 6487 refcount_create(&arc_l2c_only->arcs_size); 6488 6489 aggsum_init(&arc_meta_used, 0); 6490 aggsum_init(&arc_size, 0); 6491 aggsum_init(&astat_data_size, 0); 6492 aggsum_init(&astat_metadata_size, 0); 6493 aggsum_init(&astat_hdr_size, 0); 6494 aggsum_init(&astat_other_size, 0); 6495 aggsum_init(&astat_l2_hdr_size, 0); 6496} 6497 6498static void 6499arc_state_fini(void) 6500{ 6501 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6502 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6503 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6504 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6505 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6506 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6507 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6508 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6509 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6510 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6511 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6512 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6513 6514 refcount_destroy(&arc_anon->arcs_size); 6515 refcount_destroy(&arc_mru->arcs_size); 6516 refcount_destroy(&arc_mru_ghost->arcs_size); 6517 refcount_destroy(&arc_mfu->arcs_size); 6518 refcount_destroy(&arc_mfu_ghost->arcs_size); 6519 refcount_destroy(&arc_l2c_only->arcs_size); 6520 6521 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); 6522 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 6523 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); 6524 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 6525 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); 6526 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 6527 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); 6528 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 6529} 6530 6531uint64_t 6532arc_max_bytes(void) 6533{ 6534 return (arc_c_max); 6535} 6536 6537void 6538arc_init(void) 6539{ 6540 int i, prefetch_tunable_set = 0; 6541 6542 /* 6543 * allmem is "all memory that we could possibly use". 6544 */ 6545#ifdef illumos 6546#ifdef _KERNEL 6547 uint64_t allmem = ptob(physmem - swapfs_minfree); 6548#else 6549 uint64_t allmem = (physmem * PAGESIZE) / 2; 6550#endif 6551#else 6552 uint64_t allmem = kmem_size(); 6553#endif 6554 6555 6556 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 6557 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 6558 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 6559 6560 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 6561 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 6562 6563 /* Convert seconds to clock ticks */ 6564 arc_min_prefetch_lifespan = 1 * hz; 6565 6566 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 6567 arc_c_min = MAX(allmem / 32, arc_abs_min); 6568 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ 6569 if (allmem >= 1 << 30) 6570 arc_c_max = allmem - (1 << 30); 6571 else 6572 arc_c_max = arc_c_min; 6573 arc_c_max = MAX(allmem * 5 / 8, arc_c_max); 6574 6575 /* 6576 * In userland, there's only the memory pressure that we artificially 6577 * create (see arc_available_memory()). Don't let arc_c get too 6578 * small, because it can cause transactions to be larger than 6579 * arc_c, causing arc_tempreserve_space() to fail. 6580 */ 6581#ifndef _KERNEL 6582 arc_c_min = arc_c_max / 2; 6583#endif 6584 6585#ifdef _KERNEL 6586 /* 6587 * Allow the tunables to override our calculations if they are 6588 * reasonable. 6589 */ 6590 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { 6591 arc_c_max = zfs_arc_max; 6592 arc_c_min = MIN(arc_c_min, arc_c_max); 6593 } 6594 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6595 arc_c_min = zfs_arc_min; 6596#endif 6597 6598 arc_c = arc_c_max; 6599 arc_p = (arc_c >> 1); 6600 6601 /* limit meta-data to 1/4 of the arc capacity */ 6602 arc_meta_limit = arc_c_max / 4; 6603 6604#ifdef _KERNEL 6605 /* 6606 * Metadata is stored in the kernel's heap. Don't let us 6607 * use more than half the heap for the ARC. 6608 */ 6609 arc_meta_limit = MIN(arc_meta_limit, 6610 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 6611#endif 6612 6613 /* Allow the tunable to override if it is reasonable */ 6614 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6615 arc_meta_limit = zfs_arc_meta_limit; 6616 6617 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6618 arc_c_min = arc_meta_limit / 2; 6619 6620 if (zfs_arc_meta_min > 0) { 6621 arc_meta_min = zfs_arc_meta_min; 6622 } else { 6623 arc_meta_min = arc_c_min / 2; 6624 } 6625 6626 if (zfs_arc_grow_retry > 0) 6627 arc_grow_retry = zfs_arc_grow_retry; 6628 6629 if (zfs_arc_shrink_shift > 0) 6630 arc_shrink_shift = zfs_arc_shrink_shift; 6631 6632 if (zfs_arc_no_grow_shift > 0) 6633 arc_no_grow_shift = zfs_arc_no_grow_shift; 6634 /* 6635 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6636 */ 6637 if (arc_no_grow_shift >= arc_shrink_shift) 6638 arc_no_grow_shift = arc_shrink_shift - 1; 6639 6640 if (zfs_arc_p_min_shift > 0) 6641 arc_p_min_shift = zfs_arc_p_min_shift; 6642 6643 /* if kmem_flags are set, lets try to use less memory */ 6644 if (kmem_debugging()) 6645 arc_c = arc_c / 2; 6646 if (arc_c < arc_c_min) 6647 arc_c = arc_c_min; 6648 6649 zfs_arc_min = arc_c_min; 6650 zfs_arc_max = arc_c_max; 6651 6652 arc_state_init(); 6653 buf_init(); 6654 6655 arc_reclaim_thread_exit = B_FALSE; 6656 arc_dnlc_evicts_thread_exit = FALSE; 6657 6658 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6659 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6660 6661 if (arc_ksp != NULL) { 6662 arc_ksp->ks_data = &arc_stats; 6663 arc_ksp->ks_update = arc_kstat_update; 6664 kstat_install(arc_ksp); 6665 } 6666 6667 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6668 TS_RUN, minclsyspri); 6669 6670#ifdef _KERNEL 6671 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6672 EVENTHANDLER_PRI_FIRST); 6673#endif 6674 6675 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 6676 TS_RUN, minclsyspri); 6677 6678 arc_dead = B_FALSE; 6679 arc_warm = B_FALSE; 6680 6681 /* 6682 * Calculate maximum amount of dirty data per pool. 6683 * 6684 * If it has been set by /etc/system, take that. 6685 * Otherwise, use a percentage of physical memory defined by 6686 * zfs_dirty_data_max_percent (default 10%) with a cap at 6687 * zfs_dirty_data_max_max (default 4GB). 6688 */ 6689 if (zfs_dirty_data_max == 0) { 6690 zfs_dirty_data_max = ptob(physmem) * 6691 zfs_dirty_data_max_percent / 100; 6692 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6693 zfs_dirty_data_max_max); 6694 } 6695 6696#ifdef _KERNEL 6697 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6698 prefetch_tunable_set = 1; 6699 6700#ifdef __i386__ 6701 if (prefetch_tunable_set == 0) { 6702 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6703 "-- to enable,\n"); 6704 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6705 "to /boot/loader.conf.\n"); 6706 zfs_prefetch_disable = 1; 6707 } 6708#else 6709 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6710 prefetch_tunable_set == 0) { 6711 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6712 "than 4GB of RAM is present;\n" 6713 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6714 "to /boot/loader.conf.\n"); 6715 zfs_prefetch_disable = 1; 6716 } 6717#endif 6718 /* Warn about ZFS memory and address space requirements. */ 6719 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6720 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6721 "expect unstable behavior.\n"); 6722 } 6723 if (allmem < 512 * (1 << 20)) { 6724 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6725 "expect unstable behavior.\n"); 6726 printf(" Consider tuning vm.kmem_size and " 6727 "vm.kmem_size_max\n"); 6728 printf(" in /boot/loader.conf.\n"); 6729 } 6730#endif 6731} 6732 6733void 6734arc_fini(void) 6735{ 6736#ifdef _KERNEL 6737 if (arc_event_lowmem != NULL) 6738 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6739#endif 6740 6741 mutex_enter(&arc_reclaim_lock); 6742 arc_reclaim_thread_exit = B_TRUE; 6743 /* 6744 * The reclaim thread will set arc_reclaim_thread_exit back to 6745 * B_FALSE when it is finished exiting; we're waiting for that. 6746 */ 6747 while (arc_reclaim_thread_exit) { 6748 cv_signal(&arc_reclaim_thread_cv); 6749 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6750 } 6751 mutex_exit(&arc_reclaim_lock); 6752 6753 /* Use B_TRUE to ensure *all* buffers are evicted */ 6754 arc_flush(NULL, B_TRUE); 6755 6756 mutex_enter(&arc_dnlc_evicts_lock); 6757 arc_dnlc_evicts_thread_exit = TRUE; 6758 /* 6759 * The user evicts thread will set arc_user_evicts_thread_exit 6760 * to FALSE when it is finished exiting; we're waiting for that. 6761 */ 6762 while (arc_dnlc_evicts_thread_exit) { 6763 cv_signal(&arc_dnlc_evicts_cv); 6764 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 6765 } 6766 mutex_exit(&arc_dnlc_evicts_lock); 6767 6768 arc_dead = B_TRUE; 6769 6770 if (arc_ksp != NULL) { 6771 kstat_delete(arc_ksp); 6772 arc_ksp = NULL; 6773 } 6774 6775 mutex_destroy(&arc_reclaim_lock); 6776 cv_destroy(&arc_reclaim_thread_cv); 6777 cv_destroy(&arc_reclaim_waiters_cv); 6778 6779 mutex_destroy(&arc_dnlc_evicts_lock); 6780 cv_destroy(&arc_dnlc_evicts_cv); 6781 6782 arc_state_fini(); 6783 buf_fini(); 6784 6785 ASSERT0(arc_loaned_bytes); 6786} 6787 6788/* 6789 * Level 2 ARC 6790 * 6791 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6792 * It uses dedicated storage devices to hold cached data, which are populated 6793 * using large infrequent writes. The main role of this cache is to boost 6794 * the performance of random read workloads. The intended L2ARC devices 6795 * include short-stroked disks, solid state disks, and other media with 6796 * substantially faster read latency than disk. 6797 * 6798 * +-----------------------+ 6799 * | ARC | 6800 * +-----------------------+ 6801 * | ^ ^ 6802 * | | | 6803 * l2arc_feed_thread() arc_read() 6804 * | | | 6805 * | l2arc read | 6806 * V | | 6807 * +---------------+ | 6808 * | L2ARC | | 6809 * +---------------+ | 6810 * | ^ | 6811 * l2arc_write() | | 6812 * | | | 6813 * V | | 6814 * +-------+ +-------+ 6815 * | vdev | | vdev | 6816 * | cache | | cache | 6817 * +-------+ +-------+ 6818 * +=========+ .-----. 6819 * : L2ARC : |-_____-| 6820 * : devices : | Disks | 6821 * +=========+ `-_____-' 6822 * 6823 * Read requests are satisfied from the following sources, in order: 6824 * 6825 * 1) ARC 6826 * 2) vdev cache of L2ARC devices 6827 * 3) L2ARC devices 6828 * 4) vdev cache of disks 6829 * 5) disks 6830 * 6831 * Some L2ARC device types exhibit extremely slow write performance. 6832 * To accommodate for this there are some significant differences between 6833 * the L2ARC and traditional cache design: 6834 * 6835 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6836 * the ARC behave as usual, freeing buffers and placing headers on ghost 6837 * lists. The ARC does not send buffers to the L2ARC during eviction as 6838 * this would add inflated write latencies for all ARC memory pressure. 6839 * 6840 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6841 * It does this by periodically scanning buffers from the eviction-end of 6842 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6843 * not already there. It scans until a headroom of buffers is satisfied, 6844 * which itself is a buffer for ARC eviction. If a compressible buffer is 6845 * found during scanning and selected for writing to an L2ARC device, we 6846 * temporarily boost scanning headroom during the next scan cycle to make 6847 * sure we adapt to compression effects (which might significantly reduce 6848 * the data volume we write to L2ARC). The thread that does this is 6849 * l2arc_feed_thread(), illustrated below; example sizes are included to 6850 * provide a better sense of ratio than this diagram: 6851 * 6852 * head --> tail 6853 * +---------------------+----------+ 6854 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6855 * +---------------------+----------+ | o L2ARC eligible 6856 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6857 * +---------------------+----------+ | 6858 * 15.9 Gbytes ^ 32 Mbytes | 6859 * headroom | 6860 * l2arc_feed_thread() 6861 * | 6862 * l2arc write hand <--[oooo]--' 6863 * | 8 Mbyte 6864 * | write max 6865 * V 6866 * +==============================+ 6867 * L2ARC dev |####|#|###|###| |####| ... | 6868 * +==============================+ 6869 * 32 Gbytes 6870 * 6871 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 6872 * evicted, then the L2ARC has cached a buffer much sooner than it probably 6873 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 6874 * safe to say that this is an uncommon case, since buffers at the end of 6875 * the ARC lists have moved there due to inactivity. 6876 * 6877 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 6878 * then the L2ARC simply misses copying some buffers. This serves as a 6879 * pressure valve to prevent heavy read workloads from both stalling the ARC 6880 * with waits and clogging the L2ARC with writes. This also helps prevent 6881 * the potential for the L2ARC to churn if it attempts to cache content too 6882 * quickly, such as during backups of the entire pool. 6883 * 6884 * 5. After system boot and before the ARC has filled main memory, there are 6885 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 6886 * lists can remain mostly static. Instead of searching from tail of these 6887 * lists as pictured, the l2arc_feed_thread() will search from the list heads 6888 * for eligible buffers, greatly increasing its chance of finding them. 6889 * 6890 * The L2ARC device write speed is also boosted during this time so that 6891 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 6892 * there are no L2ARC reads, and no fear of degrading read performance 6893 * through increased writes. 6894 * 6895 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 6896 * the vdev queue can aggregate them into larger and fewer writes. Each 6897 * device is written to in a rotor fashion, sweeping writes through 6898 * available space then repeating. 6899 * 6900 * 7. The L2ARC does not store dirty content. It never needs to flush 6901 * write buffers back to disk based storage. 6902 * 6903 * 8. If an ARC buffer is written (and dirtied) which also exists in the 6904 * L2ARC, the now stale L2ARC buffer is immediately dropped. 6905 * 6906 * The performance of the L2ARC can be tweaked by a number of tunables, which 6907 * may be necessary for different workloads: 6908 * 6909 * l2arc_write_max max write bytes per interval 6910 * l2arc_write_boost extra write bytes during device warmup 6911 * l2arc_noprefetch skip caching prefetched buffers 6912 * l2arc_headroom number of max device writes to precache 6913 * l2arc_headroom_boost when we find compressed buffers during ARC 6914 * scanning, we multiply headroom by this 6915 * percentage factor for the next scan cycle, 6916 * since more compressed buffers are likely to 6917 * be present 6918 * l2arc_feed_secs seconds between L2ARC writing 6919 * 6920 * Tunables may be removed or added as future performance improvements are 6921 * integrated, and also may become zpool properties. 6922 * 6923 * There are three key functions that control how the L2ARC warms up: 6924 * 6925 * l2arc_write_eligible() check if a buffer is eligible to cache 6926 * l2arc_write_size() calculate how much to write 6927 * l2arc_write_interval() calculate sleep delay between writes 6928 * 6929 * These three functions determine what to write, how much, and how quickly 6930 * to send writes. 6931 */ 6932 6933static boolean_t 6934l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 6935{ 6936 /* 6937 * A buffer is *not* eligible for the L2ARC if it: 6938 * 1. belongs to a different spa. 6939 * 2. is already cached on the L2ARC. 6940 * 3. has an I/O in progress (it may be an incomplete read). 6941 * 4. is flagged not eligible (zfs property). 6942 */ 6943 if (hdr->b_spa != spa_guid) { 6944 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 6945 return (B_FALSE); 6946 } 6947 if (HDR_HAS_L2HDR(hdr)) { 6948 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 6949 return (B_FALSE); 6950 } 6951 if (HDR_IO_IN_PROGRESS(hdr)) { 6952 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 6953 return (B_FALSE); 6954 } 6955 if (!HDR_L2CACHE(hdr)) { 6956 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 6957 return (B_FALSE); 6958 } 6959 6960 return (B_TRUE); 6961} 6962 6963static uint64_t 6964l2arc_write_size(void) 6965{ 6966 uint64_t size; 6967 6968 /* 6969 * Make sure our globals have meaningful values in case the user 6970 * altered them. 6971 */ 6972 size = l2arc_write_max; 6973 if (size == 0) { 6974 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 6975 "be greater than zero, resetting it to the default (%d)", 6976 L2ARC_WRITE_SIZE); 6977 size = l2arc_write_max = L2ARC_WRITE_SIZE; 6978 } 6979 6980 if (arc_warm == B_FALSE) 6981 size += l2arc_write_boost; 6982 6983 return (size); 6984 6985} 6986 6987static clock_t 6988l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 6989{ 6990 clock_t interval, next, now; 6991 6992 /* 6993 * If the ARC lists are busy, increase our write rate; if the 6994 * lists are stale, idle back. This is achieved by checking 6995 * how much we previously wrote - if it was more than half of 6996 * what we wanted, schedule the next write much sooner. 6997 */ 6998 if (l2arc_feed_again && wrote > (wanted / 2)) 6999 interval = (hz * l2arc_feed_min_ms) / 1000; 7000 else 7001 interval = hz * l2arc_feed_secs; 7002 7003 now = ddi_get_lbolt(); 7004 next = MAX(now, MIN(now + interval, began + interval)); 7005 7006 return (next); 7007} 7008 7009/* 7010 * Cycle through L2ARC devices. This is how L2ARC load balances. 7011 * If a device is returned, this also returns holding the spa config lock. 7012 */ 7013static l2arc_dev_t * 7014l2arc_dev_get_next(void) 7015{ 7016 l2arc_dev_t *first, *next = NULL; 7017 7018 /* 7019 * Lock out the removal of spas (spa_namespace_lock), then removal 7020 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 7021 * both locks will be dropped and a spa config lock held instead. 7022 */ 7023 mutex_enter(&spa_namespace_lock); 7024 mutex_enter(&l2arc_dev_mtx); 7025 7026 /* if there are no vdevs, there is nothing to do */ 7027 if (l2arc_ndev == 0) 7028 goto out; 7029 7030 first = NULL; 7031 next = l2arc_dev_last; 7032 do { 7033 /* loop around the list looking for a non-faulted vdev */ 7034 if (next == NULL) { 7035 next = list_head(l2arc_dev_list); 7036 } else { 7037 next = list_next(l2arc_dev_list, next); 7038 if (next == NULL) 7039 next = list_head(l2arc_dev_list); 7040 } 7041 7042 /* if we have come back to the start, bail out */ 7043 if (first == NULL) 7044 first = next; 7045 else if (next == first) 7046 break; 7047 7048 } while (vdev_is_dead(next->l2ad_vdev)); 7049 7050 /* if we were unable to find any usable vdevs, return NULL */ 7051 if (vdev_is_dead(next->l2ad_vdev)) 7052 next = NULL; 7053 7054 l2arc_dev_last = next; 7055 7056out: 7057 mutex_exit(&l2arc_dev_mtx); 7058 7059 /* 7060 * Grab the config lock to prevent the 'next' device from being 7061 * removed while we are writing to it. 7062 */ 7063 if (next != NULL) 7064 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 7065 mutex_exit(&spa_namespace_lock); 7066 7067 return (next); 7068} 7069 7070/* 7071 * Free buffers that were tagged for destruction. 7072 */ 7073static void 7074l2arc_do_free_on_write() 7075{ 7076 list_t *buflist; 7077 l2arc_data_free_t *df, *df_prev; 7078 7079 mutex_enter(&l2arc_free_on_write_mtx); 7080 buflist = l2arc_free_on_write; 7081 7082 for (df = list_tail(buflist); df; df = df_prev) { 7083 df_prev = list_prev(buflist, df); 7084 ASSERT3P(df->l2df_abd, !=, NULL); 7085 abd_free(df->l2df_abd); 7086 list_remove(buflist, df); 7087 kmem_free(df, sizeof (l2arc_data_free_t)); 7088 } 7089 7090 mutex_exit(&l2arc_free_on_write_mtx); 7091} 7092 7093/* 7094 * A write to a cache device has completed. Update all headers to allow 7095 * reads from these buffers to begin. 7096 */ 7097static void 7098l2arc_write_done(zio_t *zio) 7099{ 7100 l2arc_write_callback_t *cb; 7101 l2arc_dev_t *dev; 7102 list_t *buflist; 7103 arc_buf_hdr_t *head, *hdr, *hdr_prev; 7104 kmutex_t *hash_lock; 7105 int64_t bytes_dropped = 0; 7106 7107 cb = zio->io_private; 7108 ASSERT3P(cb, !=, NULL); 7109 dev = cb->l2wcb_dev; 7110 ASSERT3P(dev, !=, NULL); 7111 head = cb->l2wcb_head; 7112 ASSERT3P(head, !=, NULL); 7113 buflist = &dev->l2ad_buflist; 7114 ASSERT3P(buflist, !=, NULL); 7115 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 7116 l2arc_write_callback_t *, cb); 7117 7118 if (zio->io_error != 0) 7119 ARCSTAT_BUMP(arcstat_l2_writes_error); 7120 7121 /* 7122 * All writes completed, or an error was hit. 7123 */ 7124top: 7125 mutex_enter(&dev->l2ad_mtx); 7126 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 7127 hdr_prev = list_prev(buflist, hdr); 7128 7129 hash_lock = HDR_LOCK(hdr); 7130 7131 /* 7132 * We cannot use mutex_enter or else we can deadlock 7133 * with l2arc_write_buffers (due to swapping the order 7134 * the hash lock and l2ad_mtx are taken). 7135 */ 7136 if (!mutex_tryenter(hash_lock)) { 7137 /* 7138 * Missed the hash lock. We must retry so we 7139 * don't leave the ARC_FLAG_L2_WRITING bit set. 7140 */ 7141 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 7142 7143 /* 7144 * We don't want to rescan the headers we've 7145 * already marked as having been written out, so 7146 * we reinsert the head node so we can pick up 7147 * where we left off. 7148 */ 7149 list_remove(buflist, head); 7150 list_insert_after(buflist, hdr, head); 7151 7152 mutex_exit(&dev->l2ad_mtx); 7153 7154 /* 7155 * We wait for the hash lock to become available 7156 * to try and prevent busy waiting, and increase 7157 * the chance we'll be able to acquire the lock 7158 * the next time around. 7159 */ 7160 mutex_enter(hash_lock); 7161 mutex_exit(hash_lock); 7162 goto top; 7163 } 7164 7165 /* 7166 * We could not have been moved into the arc_l2c_only 7167 * state while in-flight due to our ARC_FLAG_L2_WRITING 7168 * bit being set. Let's just ensure that's being enforced. 7169 */ 7170 ASSERT(HDR_HAS_L1HDR(hdr)); 7171 7172 if (zio->io_error != 0) { 7173 /* 7174 * Error - drop L2ARC entry. 7175 */ 7176 list_remove(buflist, hdr); 7177 l2arc_trim(hdr); 7178 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 7179 7180 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr)); 7181 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 7182 7183 bytes_dropped += arc_hdr_size(hdr); 7184 (void) refcount_remove_many(&dev->l2ad_alloc, 7185 arc_hdr_size(hdr), hdr); 7186 } 7187 7188 /* 7189 * Allow ARC to begin reads and ghost list evictions to 7190 * this L2ARC entry. 7191 */ 7192 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 7193 7194 mutex_exit(hash_lock); 7195 } 7196 7197 atomic_inc_64(&l2arc_writes_done); 7198 list_remove(buflist, head); 7199 ASSERT(!HDR_HAS_L1HDR(head)); 7200 kmem_cache_free(hdr_l2only_cache, head); 7201 mutex_exit(&dev->l2ad_mtx); 7202 7203 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 7204 7205 l2arc_do_free_on_write(); 7206 7207 kmem_free(cb, sizeof (l2arc_write_callback_t)); 7208} 7209 7210/* 7211 * A read to a cache device completed. Validate buffer contents before 7212 * handing over to the regular ARC routines. 7213 */ 7214static void 7215l2arc_read_done(zio_t *zio) 7216{ 7217 l2arc_read_callback_t *cb; 7218 arc_buf_hdr_t *hdr; 7219 kmutex_t *hash_lock; 7220 boolean_t valid_cksum; 7221 7222 ASSERT3P(zio->io_vd, !=, NULL); 7223 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 7224 7225 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 7226 7227 cb = zio->io_private; 7228 ASSERT3P(cb, !=, NULL); 7229 hdr = cb->l2rcb_hdr; 7230 ASSERT3P(hdr, !=, NULL); 7231 7232 hash_lock = HDR_LOCK(hdr); 7233 mutex_enter(hash_lock); 7234 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 7235 7236 /* 7237 * If the data was read into a temporary buffer, 7238 * move it and free the buffer. 7239 */ 7240 if (cb->l2rcb_abd != NULL) { 7241 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 7242 if (zio->io_error == 0) { 7243 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd, 7244 arc_hdr_size(hdr)); 7245 } 7246 7247 /* 7248 * The following must be done regardless of whether 7249 * there was an error: 7250 * - free the temporary buffer 7251 * - point zio to the real ARC buffer 7252 * - set zio size accordingly 7253 * These are required because zio is either re-used for 7254 * an I/O of the block in the case of the error 7255 * or the zio is passed to arc_read_done() and it 7256 * needs real data. 7257 */ 7258 abd_free(cb->l2rcb_abd); 7259 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 7260 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; 7261 } 7262 7263 ASSERT3P(zio->io_abd, !=, NULL); 7264 7265 /* 7266 * Check this survived the L2ARC journey. 7267 */ 7268 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); 7269 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 7270 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 7271 7272 valid_cksum = arc_cksum_is_equal(hdr, zio); 7273 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 7274 mutex_exit(hash_lock); 7275 zio->io_private = hdr; 7276 arc_read_done(zio); 7277 } else { 7278 mutex_exit(hash_lock); 7279 /* 7280 * Buffer didn't survive caching. Increment stats and 7281 * reissue to the original storage device. 7282 */ 7283 if (zio->io_error != 0) { 7284 ARCSTAT_BUMP(arcstat_l2_io_error); 7285 } else { 7286 zio->io_error = SET_ERROR(EIO); 7287 } 7288 if (!valid_cksum) 7289 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 7290 7291 /* 7292 * If there's no waiter, issue an async i/o to the primary 7293 * storage now. If there *is* a waiter, the caller must 7294 * issue the i/o in a context where it's OK to block. 7295 */ 7296 if (zio->io_waiter == NULL) { 7297 zio_t *pio = zio_unique_parent(zio); 7298 7299 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 7300 7301 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 7302 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, 7303 hdr, zio->io_priority, cb->l2rcb_flags, 7304 &cb->l2rcb_zb)); 7305 } 7306 } 7307 7308 kmem_free(cb, sizeof (l2arc_read_callback_t)); 7309} 7310 7311/* 7312 * This is the list priority from which the L2ARC will search for pages to 7313 * cache. This is used within loops (0..3) to cycle through lists in the 7314 * desired order. This order can have a significant effect on cache 7315 * performance. 7316 * 7317 * Currently the metadata lists are hit first, MFU then MRU, followed by 7318 * the data lists. This function returns a locked list, and also returns 7319 * the lock pointer. 7320 */ 7321static multilist_sublist_t * 7322l2arc_sublist_lock(int list_num) 7323{ 7324 multilist_t *ml = NULL; 7325 unsigned int idx; 7326 7327 ASSERT(list_num >= 0 && list_num <= 3); 7328 7329 switch (list_num) { 7330 case 0: 7331 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; 7332 break; 7333 case 1: 7334 ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; 7335 break; 7336 case 2: 7337 ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; 7338 break; 7339 case 3: 7340 ml = arc_mru->arcs_list[ARC_BUFC_DATA]; 7341 break; 7342 } 7343 7344 /* 7345 * Return a randomly-selected sublist. This is acceptable 7346 * because the caller feeds only a little bit of data for each 7347 * call (8MB). Subsequent calls will result in different 7348 * sublists being selected. 7349 */ 7350 idx = multilist_get_random_index(ml); 7351 return (multilist_sublist_lock(ml, idx)); 7352} 7353 7354/* 7355 * Evict buffers from the device write hand to the distance specified in 7356 * bytes. This distance may span populated buffers, it may span nothing. 7357 * This is clearing a region on the L2ARC device ready for writing. 7358 * If the 'all' boolean is set, every buffer is evicted. 7359 */ 7360static void 7361l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 7362{ 7363 list_t *buflist; 7364 arc_buf_hdr_t *hdr, *hdr_prev; 7365 kmutex_t *hash_lock; 7366 uint64_t taddr; 7367 7368 buflist = &dev->l2ad_buflist; 7369 7370 if (!all && dev->l2ad_first) { 7371 /* 7372 * This is the first sweep through the device. There is 7373 * nothing to evict. 7374 */ 7375 return; 7376 } 7377 7378 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 7379 /* 7380 * When nearing the end of the device, evict to the end 7381 * before the device write hand jumps to the start. 7382 */ 7383 taddr = dev->l2ad_end; 7384 } else { 7385 taddr = dev->l2ad_hand + distance; 7386 } 7387 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 7388 uint64_t, taddr, boolean_t, all); 7389 7390top: 7391 mutex_enter(&dev->l2ad_mtx); 7392 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 7393 hdr_prev = list_prev(buflist, hdr); 7394 7395 hash_lock = HDR_LOCK(hdr); 7396 7397 /* 7398 * We cannot use mutex_enter or else we can deadlock 7399 * with l2arc_write_buffers (due to swapping the order 7400 * the hash lock and l2ad_mtx are taken). 7401 */ 7402 if (!mutex_tryenter(hash_lock)) { 7403 /* 7404 * Missed the hash lock. Retry. 7405 */ 7406 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 7407 mutex_exit(&dev->l2ad_mtx); 7408 mutex_enter(hash_lock); 7409 mutex_exit(hash_lock); 7410 goto top; 7411 } 7412 7413 /* 7414 * A header can't be on this list if it doesn't have L2 header. 7415 */ 7416 ASSERT(HDR_HAS_L2HDR(hdr)); 7417 7418 /* Ensure this header has finished being written. */ 7419 ASSERT(!HDR_L2_WRITING(hdr)); 7420 ASSERT(!HDR_L2_WRITE_HEAD(hdr)); 7421 7422 if (!all && (hdr->b_l2hdr.b_daddr >= taddr || 7423 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 7424 /* 7425 * We've evicted to the target address, 7426 * or the end of the device. 7427 */ 7428 mutex_exit(hash_lock); 7429 break; 7430 } 7431 7432 if (!HDR_HAS_L1HDR(hdr)) { 7433 ASSERT(!HDR_L2_READING(hdr)); 7434 /* 7435 * This doesn't exist in the ARC. Destroy. 7436 * arc_hdr_destroy() will call list_remove() 7437 * and decrement arcstat_l2_lsize. 7438 */ 7439 arc_change_state(arc_anon, hdr, hash_lock); 7440 arc_hdr_destroy(hdr); 7441 } else { 7442 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 7443 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 7444 /* 7445 * Invalidate issued or about to be issued 7446 * reads, since we may be about to write 7447 * over this location. 7448 */ 7449 if (HDR_L2_READING(hdr)) { 7450 ARCSTAT_BUMP(arcstat_l2_evict_reading); 7451 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 7452 } 7453 7454 arc_hdr_l2hdr_destroy(hdr); 7455 } 7456 mutex_exit(hash_lock); 7457 } 7458 mutex_exit(&dev->l2ad_mtx); 7459} 7460 7461/* 7462 * Find and write ARC buffers to the L2ARC device. 7463 * 7464 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 7465 * for reading until they have completed writing. 7466 * The headroom_boost is an in-out parameter used to maintain headroom boost 7467 * state between calls to this function. 7468 * 7469 * Returns the number of bytes actually written (which may be smaller than 7470 * the delta by which the device hand has changed due to alignment). 7471 */ 7472static uint64_t 7473l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 7474{ 7475 arc_buf_hdr_t *hdr, *hdr_prev, *head; 7476 uint64_t write_asize, write_psize, write_lsize, headroom; 7477 boolean_t full; 7478 l2arc_write_callback_t *cb; 7479 zio_t *pio, *wzio; 7480 uint64_t guid = spa_load_guid(spa); 7481 int try; 7482 7483 ASSERT3P(dev->l2ad_vdev, !=, NULL); 7484 7485 pio = NULL; 7486 write_lsize = write_asize = write_psize = 0; 7487 full = B_FALSE; 7488 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 7489 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 7490 7491 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 7492 /* 7493 * Copy buffers for L2ARC writing. 7494 */ 7495 for (try = 0; try <= 3; try++) { 7496 multilist_sublist_t *mls = l2arc_sublist_lock(try); 7497 uint64_t passed_sz = 0; 7498 7499 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 7500 7501 /* 7502 * L2ARC fast warmup. 7503 * 7504 * Until the ARC is warm and starts to evict, read from the 7505 * head of the ARC lists rather than the tail. 7506 */ 7507 if (arc_warm == B_FALSE) 7508 hdr = multilist_sublist_head(mls); 7509 else 7510 hdr = multilist_sublist_tail(mls); 7511 if (hdr == NULL) 7512 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 7513 7514 headroom = target_sz * l2arc_headroom; 7515 if (zfs_compressed_arc_enabled) 7516 headroom = (headroom * l2arc_headroom_boost) / 100; 7517 7518 for (; hdr; hdr = hdr_prev) { 7519 kmutex_t *hash_lock; 7520 7521 if (arc_warm == B_FALSE) 7522 hdr_prev = multilist_sublist_next(mls, hdr); 7523 else 7524 hdr_prev = multilist_sublist_prev(mls, hdr); 7525 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 7526 HDR_GET_LSIZE(hdr)); 7527 7528 hash_lock = HDR_LOCK(hdr); 7529 if (!mutex_tryenter(hash_lock)) { 7530 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 7531 /* 7532 * Skip this buffer rather than waiting. 7533 */ 7534 continue; 7535 } 7536 7537 passed_sz += HDR_GET_LSIZE(hdr); 7538 if (passed_sz > headroom) { 7539 /* 7540 * Searched too far. 7541 */ 7542 mutex_exit(hash_lock); 7543 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 7544 break; 7545 } 7546 7547 if (!l2arc_write_eligible(guid, hdr)) { 7548 mutex_exit(hash_lock); 7549 continue; 7550 } 7551 7552 /* 7553 * We rely on the L1 portion of the header below, so 7554 * it's invalid for this header to have been evicted out 7555 * of the ghost cache, prior to being written out. The 7556 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 7557 */ 7558 ASSERT(HDR_HAS_L1HDR(hdr)); 7559 7560 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 7561 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 7562 ASSERT3U(arc_hdr_size(hdr), >, 0); 7563 uint64_t psize = arc_hdr_size(hdr); 7564 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 7565 psize); 7566 7567 if ((write_asize + asize) > target_sz) { 7568 full = B_TRUE; 7569 mutex_exit(hash_lock); 7570 ARCSTAT_BUMP(arcstat_l2_write_full); 7571 break; 7572 } 7573 7574 if (pio == NULL) { 7575 /* 7576 * Insert a dummy header on the buflist so 7577 * l2arc_write_done() can find where the 7578 * write buffers begin without searching. 7579 */ 7580 mutex_enter(&dev->l2ad_mtx); 7581 list_insert_head(&dev->l2ad_buflist, head); 7582 mutex_exit(&dev->l2ad_mtx); 7583 7584 cb = kmem_alloc( 7585 sizeof (l2arc_write_callback_t), KM_SLEEP); 7586 cb->l2wcb_dev = dev; 7587 cb->l2wcb_head = head; 7588 pio = zio_root(spa, l2arc_write_done, cb, 7589 ZIO_FLAG_CANFAIL); 7590 ARCSTAT_BUMP(arcstat_l2_write_pios); 7591 } 7592 7593 hdr->b_l2hdr.b_dev = dev; 7594 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 7595 arc_hdr_set_flags(hdr, 7596 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 7597 7598 mutex_enter(&dev->l2ad_mtx); 7599 list_insert_head(&dev->l2ad_buflist, hdr); 7600 mutex_exit(&dev->l2ad_mtx); 7601 7602 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr); 7603 7604 /* 7605 * Normally the L2ARC can use the hdr's data, but if 7606 * we're sharing data between the hdr and one of its 7607 * bufs, L2ARC needs its own copy of the data so that 7608 * the ZIO below can't race with the buf consumer. 7609 * Another case where we need to create a copy of the 7610 * data is when the buffer size is not device-aligned 7611 * and we need to pad the block to make it such. 7612 * That also keeps the clock hand suitably aligned. 7613 * 7614 * To ensure that the copy will be available for the 7615 * lifetime of the ZIO and be cleaned up afterwards, we 7616 * add it to the l2arc_free_on_write queue. 7617 */ 7618 abd_t *to_write; 7619 if (!HDR_SHARED_DATA(hdr) && psize == asize) { 7620 to_write = hdr->b_l1hdr.b_pabd; 7621 } else { 7622 to_write = abd_alloc_for_io(asize, 7623 HDR_ISTYPE_METADATA(hdr)); 7624 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize); 7625 if (asize != psize) { 7626 abd_zero_off(to_write, psize, 7627 asize - psize); 7628 } 7629 l2arc_free_abd_on_write(to_write, asize, 7630 arc_buf_type(hdr)); 7631 } 7632 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7633 hdr->b_l2hdr.b_daddr, asize, to_write, 7634 ZIO_CHECKSUM_OFF, NULL, hdr, 7635 ZIO_PRIORITY_ASYNC_WRITE, 7636 ZIO_FLAG_CANFAIL, B_FALSE); 7637 7638 write_lsize += HDR_GET_LSIZE(hdr); 7639 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7640 zio_t *, wzio); 7641 7642 write_psize += psize; 7643 write_asize += asize; 7644 dev->l2ad_hand += asize; 7645 7646 mutex_exit(hash_lock); 7647 7648 (void) zio_nowait(wzio); 7649 } 7650 7651 multilist_sublist_unlock(mls); 7652 7653 if (full == B_TRUE) 7654 break; 7655 } 7656 7657 /* No buffers selected for writing? */ 7658 if (pio == NULL) { 7659 ASSERT0(write_lsize); 7660 ASSERT(!HDR_HAS_L1HDR(head)); 7661 kmem_cache_free(hdr_l2only_cache, head); 7662 return (0); 7663 } 7664 7665 ASSERT3U(write_psize, <=, target_sz); 7666 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7667 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize); 7668 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize); 7669 ARCSTAT_INCR(arcstat_l2_psize, write_psize); 7670 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); 7671 7672 /* 7673 * Bump device hand to the device start if it is approaching the end. 7674 * l2arc_evict() will already have evicted ahead for this case. 7675 */ 7676 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7677 dev->l2ad_hand = dev->l2ad_start; 7678 dev->l2ad_first = B_FALSE; 7679 } 7680 7681 dev->l2ad_writing = B_TRUE; 7682 (void) zio_wait(pio); 7683 dev->l2ad_writing = B_FALSE; 7684 7685 return (write_asize); 7686} 7687 7688/* 7689 * This thread feeds the L2ARC at regular intervals. This is the beating 7690 * heart of the L2ARC. 7691 */ 7692/* ARGSUSED */ 7693static void 7694l2arc_feed_thread(void *unused __unused) 7695{ 7696 callb_cpr_t cpr; 7697 l2arc_dev_t *dev; 7698 spa_t *spa; 7699 uint64_t size, wrote; 7700 clock_t begin, next = ddi_get_lbolt(); 7701 7702 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7703 7704 mutex_enter(&l2arc_feed_thr_lock); 7705 7706 while (l2arc_thread_exit == 0) { 7707 CALLB_CPR_SAFE_BEGIN(&cpr); 7708 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7709 next - ddi_get_lbolt()); 7710 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7711 next = ddi_get_lbolt() + hz; 7712 7713 /* 7714 * Quick check for L2ARC devices. 7715 */ 7716 mutex_enter(&l2arc_dev_mtx); 7717 if (l2arc_ndev == 0) { 7718 mutex_exit(&l2arc_dev_mtx); 7719 continue; 7720 } 7721 mutex_exit(&l2arc_dev_mtx); 7722 begin = ddi_get_lbolt(); 7723 7724 /* 7725 * This selects the next l2arc device to write to, and in 7726 * doing so the next spa to feed from: dev->l2ad_spa. This 7727 * will return NULL if there are now no l2arc devices or if 7728 * they are all faulted. 7729 * 7730 * If a device is returned, its spa's config lock is also 7731 * held to prevent device removal. l2arc_dev_get_next() 7732 * will grab and release l2arc_dev_mtx. 7733 */ 7734 if ((dev = l2arc_dev_get_next()) == NULL) 7735 continue; 7736 7737 spa = dev->l2ad_spa; 7738 ASSERT3P(spa, !=, NULL); 7739 7740 /* 7741 * If the pool is read-only then force the feed thread to 7742 * sleep a little longer. 7743 */ 7744 if (!spa_writeable(spa)) { 7745 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7746 spa_config_exit(spa, SCL_L2ARC, dev); 7747 continue; 7748 } 7749 7750 /* 7751 * Avoid contributing to memory pressure. 7752 */ 7753 if (arc_reclaim_needed()) { 7754 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7755 spa_config_exit(spa, SCL_L2ARC, dev); 7756 continue; 7757 } 7758 7759 ARCSTAT_BUMP(arcstat_l2_feeds); 7760 7761 size = l2arc_write_size(); 7762 7763 /* 7764 * Evict L2ARC buffers that will be overwritten. 7765 */ 7766 l2arc_evict(dev, size, B_FALSE); 7767 7768 /* 7769 * Write ARC buffers. 7770 */ 7771 wrote = l2arc_write_buffers(spa, dev, size); 7772 7773 /* 7774 * Calculate interval between writes. 7775 */ 7776 next = l2arc_write_interval(begin, size, wrote); 7777 spa_config_exit(spa, SCL_L2ARC, dev); 7778 } 7779 7780 l2arc_thread_exit = 0; 7781 cv_broadcast(&l2arc_feed_thr_cv); 7782 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7783 thread_exit(); 7784} 7785 7786boolean_t 7787l2arc_vdev_present(vdev_t *vd) 7788{ 7789 l2arc_dev_t *dev; 7790 7791 mutex_enter(&l2arc_dev_mtx); 7792 for (dev = list_head(l2arc_dev_list); dev != NULL; 7793 dev = list_next(l2arc_dev_list, dev)) { 7794 if (dev->l2ad_vdev == vd) 7795 break; 7796 } 7797 mutex_exit(&l2arc_dev_mtx); 7798 7799 return (dev != NULL); 7800} 7801 7802/* 7803 * Add a vdev for use by the L2ARC. By this point the spa has already 7804 * validated the vdev and opened it. 7805 */ 7806void 7807l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7808{ 7809 l2arc_dev_t *adddev; 7810 7811 ASSERT(!l2arc_vdev_present(vd)); 7812 7813 vdev_ashift_optimize(vd); 7814 7815 /* 7816 * Create a new l2arc device entry. 7817 */ 7818 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7819 adddev->l2ad_spa = spa; 7820 adddev->l2ad_vdev = vd; 7821 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7822 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7823 adddev->l2ad_hand = adddev->l2ad_start; 7824 adddev->l2ad_first = B_TRUE; 7825 adddev->l2ad_writing = B_FALSE; 7826 7827 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7828 /* 7829 * This is a list of all ARC buffers that are still valid on the 7830 * device. 7831 */ 7832 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7833 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7834 7835 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7836 refcount_create(&adddev->l2ad_alloc); 7837 7838 /* 7839 * Add device to global list 7840 */ 7841 mutex_enter(&l2arc_dev_mtx); 7842 list_insert_head(l2arc_dev_list, adddev); 7843 atomic_inc_64(&l2arc_ndev); 7844 mutex_exit(&l2arc_dev_mtx); 7845} 7846 7847/* 7848 * Remove a vdev from the L2ARC. 7849 */ 7850void 7851l2arc_remove_vdev(vdev_t *vd) 7852{ 7853 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7854 7855 /* 7856 * Find the device by vdev 7857 */ 7858 mutex_enter(&l2arc_dev_mtx); 7859 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7860 nextdev = list_next(l2arc_dev_list, dev); 7861 if (vd == dev->l2ad_vdev) { 7862 remdev = dev; 7863 break; 7864 } 7865 } 7866 ASSERT3P(remdev, !=, NULL); 7867 7868 /* 7869 * Remove device from global list 7870 */ 7871 list_remove(l2arc_dev_list, remdev); 7872 l2arc_dev_last = NULL; /* may have been invalidated */ 7873 atomic_dec_64(&l2arc_ndev); 7874 mutex_exit(&l2arc_dev_mtx); 7875 7876 /* 7877 * Clear all buflists and ARC references. L2ARC device flush. 7878 */ 7879 l2arc_evict(remdev, 0, B_TRUE); 7880 list_destroy(&remdev->l2ad_buflist); 7881 mutex_destroy(&remdev->l2ad_mtx); 7882 refcount_destroy(&remdev->l2ad_alloc); 7883 kmem_free(remdev, sizeof (l2arc_dev_t)); 7884} 7885 7886void 7887l2arc_init(void) 7888{ 7889 l2arc_thread_exit = 0; 7890 l2arc_ndev = 0; 7891 l2arc_writes_sent = 0; 7892 l2arc_writes_done = 0; 7893 7894 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7895 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7896 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7897 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7898 7899 l2arc_dev_list = &L2ARC_dev_list; 7900 l2arc_free_on_write = &L2ARC_free_on_write; 7901 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7902 offsetof(l2arc_dev_t, l2ad_node)); 7903 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7904 offsetof(l2arc_data_free_t, l2df_list_node)); 7905} 7906 7907void 7908l2arc_fini(void) 7909{ 7910 /* 7911 * This is called from dmu_fini(), which is called from spa_fini(); 7912 * Because of this, we can assume that all l2arc devices have 7913 * already been removed when the pools themselves were removed. 7914 */ 7915 7916 l2arc_do_free_on_write(); 7917 7918 mutex_destroy(&l2arc_feed_thr_lock); 7919 cv_destroy(&l2arc_feed_thr_cv); 7920 mutex_destroy(&l2arc_dev_mtx); 7921 mutex_destroy(&l2arc_free_on_write_mtx); 7922 7923 list_destroy(l2arc_dev_list); 7924 list_destroy(l2arc_free_on_write); 7925} 7926 7927void 7928l2arc_start(void) 7929{ 7930 if (!(spa_mode_global & FWRITE)) 7931 return; 7932 7933 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7934 TS_RUN, minclsyspri); 7935} 7936 7937void 7938l2arc_stop(void) 7939{ 7940 if (!(spa_mode_global & FWRITE)) 7941 return; 7942 7943 mutex_enter(&l2arc_feed_thr_lock); 7944 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7945 l2arc_thread_exit = 1; 7946 while (l2arc_thread_exit != 0) 7947 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7948 mutex_exit(&l2arc_feed_thr_lock); 7949} 7950