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.
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23 * Copyright (c) 2013 by Delphix. All rights reserved.
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23 * Copyright (c) 2011, 2014 by Delphix. All rights reserved. |
24 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 25 * Copyright 2014 Nexenta Systems, Inc. All rights reserved. 26 */ 27 28/* 29 * DVA-based Adjustable Replacement Cache 30 * 31 * While much of the theory of operation used here is 32 * based on the self-tuning, low overhead replacement cache 33 * presented by Megiddo and Modha at FAST 2003, there are some 34 * significant differences: 35 * 36 * 1. The Megiddo and Modha model assumes any page is evictable. 37 * Pages in its cache cannot be "locked" into memory. This makes 38 * the eviction algorithm simple: evict the last page in the list. 39 * This also make the performance characteristics easy to reason 40 * about. Our cache is not so simple. At any given moment, some 41 * subset of the blocks in the cache are un-evictable because we 42 * have handed out a reference to them. Blocks are only evictable 43 * when there are no external references active. This makes 44 * eviction far more problematic: we choose to evict the evictable 45 * blocks that are the "lowest" in the list. 46 * 47 * There are times when it is not possible to evict the requested 48 * space. In these circumstances we are unable to adjust the cache 49 * size. To prevent the cache growing unbounded at these times we 50 * implement a "cache throttle" that slows the flow of new data 51 * into the cache until we can make space available. 52 * 53 * 2. The Megiddo and Modha model assumes a fixed cache size. 54 * Pages are evicted when the cache is full and there is a cache 55 * miss. Our model has a variable sized cache. It grows with 56 * high use, but also tries to react to memory pressure from the 57 * operating system: decreasing its size when system memory is 58 * tight. 59 * 60 * 3. The Megiddo and Modha model assumes a fixed page size. All 61 * elements of the cache are therefore exactly the same size. So 62 * when adjusting the cache size following a cache miss, its simply 63 * a matter of choosing a single page to evict. In our model, we 64 * have variable sized cache blocks (rangeing from 512 bytes to 65 * 128K bytes). We therefore choose a set of blocks to evict to make 66 * space for a cache miss that approximates as closely as possible 67 * the space used by the new block. 68 * 69 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 70 * by N. Megiddo & D. Modha, FAST 2003 71 */ 72 73/* 74 * The locking model: 75 * 76 * A new reference to a cache buffer can be obtained in two 77 * ways: 1) via a hash table lookup using the DVA as a key, 78 * or 2) via one of the ARC lists. The arc_read() interface 79 * uses method 1, while the internal arc algorithms for 80 * adjusting the cache use method 2. We therefore provide two 81 * types of locks: 1) the hash table lock array, and 2) the 82 * arc list locks. 83 * 84 * Buffers do not have their own mutexs, rather they rely on the 85 * hash table mutexs for the bulk of their protection (i.e. most 86 * fields in the arc_buf_hdr_t are protected by these mutexs). 87 * 88 * buf_hash_find() returns the appropriate mutex (held) when it 89 * locates the requested buffer in the hash table. It returns 90 * NULL for the mutex if the buffer was not in the table. 91 * 92 * buf_hash_remove() expects the appropriate hash mutex to be 93 * already held before it is invoked. 94 * 95 * Each arc state also has a mutex which is used to protect the 96 * buffer list associated with the state. When attempting to 97 * obtain a hash table lock while holding an arc list lock you 98 * must use: mutex_tryenter() to avoid deadlock. Also note that 99 * the active state mutex must be held before the ghost state mutex. 100 * 101 * Arc buffers may have an associated eviction callback function. 102 * This function will be invoked prior to removing the buffer (e.g. 103 * in arc_do_user_evicts()). Note however that the data associated 104 * with the buffer may be evicted prior to the callback. The callback 105 * must be made with *no locks held* (to prevent deadlock). Additionally, 106 * the users of callbacks must ensure that their private data is 107 * protected from simultaneous callbacks from arc_buf_evict() 108 * and arc_do_user_evicts(). 109 * 110 * Note that the majority of the performance stats are manipulated 111 * with atomic operations. 112 * 113 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following: 114 * 115 * - L2ARC buflist creation 116 * - L2ARC buflist eviction 117 * - L2ARC write completion, which walks L2ARC buflists 118 * - ARC header destruction, as it removes from L2ARC buflists 119 * - ARC header release, as it removes from L2ARC buflists 120 */ 121 122#include <sys/spa.h> 123#include <sys/zio.h> 124#include <sys/zio_compress.h> 125#include <sys/zfs_context.h> 126#include <sys/arc.h> 127#include <sys/refcount.h> 128#include <sys/vdev.h> 129#include <sys/vdev_impl.h> 130#include <sys/dsl_pool.h> 131#ifdef _KERNEL 132#include <sys/dnlc.h> 133#endif 134#include <sys/callb.h> 135#include <sys/kstat.h> 136#include <sys/trim_map.h> 137#include <zfs_fletcher.h> 138#include <sys/sdt.h> 139 140#include <vm/vm_pageout.h> 141 142#ifdef illumos 143#ifndef _KERNEL 144/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 145boolean_t arc_watch = B_FALSE; 146int arc_procfd; 147#endif 148#endif /* illumos */ 149 150static kmutex_t arc_reclaim_thr_lock; 151static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 152static uint8_t arc_thread_exit; 153 154#define ARC_REDUCE_DNLC_PERCENT 3 155uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT; 156 157typedef enum arc_reclaim_strategy { 158 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ 159 ARC_RECLAIM_CONS /* Conservative reclaim strategy */ 160} arc_reclaim_strategy_t; 161 162/* 163 * The number of iterations through arc_evict_*() before we 164 * drop & reacquire the lock. 165 */ 166int arc_evict_iterations = 100; 167 168/* number of seconds before growing cache again */ 169static int arc_grow_retry = 60; 170 171/* shift of arc_c for calculating both min and max arc_p */ 172static int arc_p_min_shift = 4; 173 174/* log2(fraction of arc to reclaim) */ 175static int arc_shrink_shift = 5; 176 177/* 178 * minimum lifespan of a prefetch block in clock ticks 179 * (initialized in arc_init()) 180 */ 181static int arc_min_prefetch_lifespan; 182 183/* 184 * If this percent of memory is free, don't throttle. 185 */ 186int arc_lotsfree_percent = 10; 187 188static int arc_dead; 189extern int zfs_prefetch_disable; 190 191/* 192 * The arc has filled available memory and has now warmed up. 193 */ 194static boolean_t arc_warm; 195 196/* 197 * These tunables are for performance analysis. 198 */ 199uint64_t zfs_arc_max; 200uint64_t zfs_arc_min; 201uint64_t zfs_arc_meta_limit = 0; 202int zfs_arc_grow_retry = 0; 203int zfs_arc_shrink_shift = 0; 204int zfs_arc_p_min_shift = 0; 205int zfs_disable_dup_eviction = 0; 206 207TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 208SYSCTL_DECL(_vfs_zfs); 209SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 210 "Maximum ARC size"); 211SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 212 "Minimum ARC size"); 213 214/* 215 * Note that buffers can be in one of 6 states: 216 * ARC_anon - anonymous (discussed below) 217 * ARC_mru - recently used, currently cached 218 * ARC_mru_ghost - recentely used, no longer in cache 219 * ARC_mfu - frequently used, currently cached 220 * ARC_mfu_ghost - frequently used, no longer in cache 221 * ARC_l2c_only - exists in L2ARC but not other states 222 * When there are no active references to the buffer, they are 223 * are linked onto a list in one of these arc states. These are 224 * the only buffers that can be evicted or deleted. Within each 225 * state there are multiple lists, one for meta-data and one for 226 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 227 * etc.) is tracked separately so that it can be managed more 228 * explicitly: favored over data, limited explicitly. 229 * 230 * Anonymous buffers are buffers that are not associated with 231 * a DVA. These are buffers that hold dirty block copies 232 * before they are written to stable storage. By definition, 233 * they are "ref'd" and are considered part of arc_mru 234 * that cannot be freed. Generally, they will aquire a DVA 235 * as they are written and migrate onto the arc_mru list. 236 * 237 * The ARC_l2c_only state is for buffers that are in the second 238 * level ARC but no longer in any of the ARC_m* lists. The second 239 * level ARC itself may also contain buffers that are in any of 240 * the ARC_m* states - meaning that a buffer can exist in two 241 * places. The reason for the ARC_l2c_only state is to keep the 242 * buffer header in the hash table, so that reads that hit the 243 * second level ARC benefit from these fast lookups. 244 */ 245 246#define ARCS_LOCK_PAD CACHE_LINE_SIZE 247struct arcs_lock { 248 kmutex_t arcs_lock; 249#ifdef _KERNEL 250 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))]; 251#endif 252}; 253 254/* 255 * must be power of two for mask use to work 256 * 257 */ 258#define ARC_BUFC_NUMDATALISTS 16 259#define ARC_BUFC_NUMMETADATALISTS 16 260#define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS) 261 262typedef struct arc_state { 263 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 264 uint64_t arcs_size; /* total amount of data in this state */ 265 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */ 266 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE); 267} arc_state_t; 268 269#define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock)) 270 271/* The 6 states: */ 272static arc_state_t ARC_anon; 273static arc_state_t ARC_mru; 274static arc_state_t ARC_mru_ghost; 275static arc_state_t ARC_mfu; 276static arc_state_t ARC_mfu_ghost; 277static arc_state_t ARC_l2c_only; 278 279typedef struct arc_stats { 280 kstat_named_t arcstat_hits; 281 kstat_named_t arcstat_misses; 282 kstat_named_t arcstat_demand_data_hits; 283 kstat_named_t arcstat_demand_data_misses; 284 kstat_named_t arcstat_demand_metadata_hits; 285 kstat_named_t arcstat_demand_metadata_misses; 286 kstat_named_t arcstat_prefetch_data_hits; 287 kstat_named_t arcstat_prefetch_data_misses; 288 kstat_named_t arcstat_prefetch_metadata_hits; 289 kstat_named_t arcstat_prefetch_metadata_misses; 290 kstat_named_t arcstat_mru_hits; 291 kstat_named_t arcstat_mru_ghost_hits; 292 kstat_named_t arcstat_mfu_hits; 293 kstat_named_t arcstat_mfu_ghost_hits; 294 kstat_named_t arcstat_allocated; 295 kstat_named_t arcstat_deleted; 296 kstat_named_t arcstat_stolen; 297 kstat_named_t arcstat_recycle_miss; 298 /* 299 * Number of buffers that could not be evicted because the hash lock 300 * was held by another thread. The lock may not necessarily be held 301 * by something using the same buffer, since hash locks are shared 302 * by multiple buffers. 303 */ 304 kstat_named_t arcstat_mutex_miss; 305 /* 306 * Number of buffers skipped because they have I/O in progress, are 307 * indrect prefetch buffers that have not lived long enough, or are 308 * not from the spa we're trying to evict from. 309 */ 310 kstat_named_t arcstat_evict_skip; 311 kstat_named_t arcstat_evict_l2_cached; 312 kstat_named_t arcstat_evict_l2_eligible; 313 kstat_named_t arcstat_evict_l2_ineligible; 314 kstat_named_t arcstat_hash_elements; 315 kstat_named_t arcstat_hash_elements_max; 316 kstat_named_t arcstat_hash_collisions; 317 kstat_named_t arcstat_hash_chains; 318 kstat_named_t arcstat_hash_chain_max; 319 kstat_named_t arcstat_p; 320 kstat_named_t arcstat_c; 321 kstat_named_t arcstat_c_min; 322 kstat_named_t arcstat_c_max; 323 kstat_named_t arcstat_size; 324 kstat_named_t arcstat_hdr_size; 325 kstat_named_t arcstat_data_size; 326 kstat_named_t arcstat_other_size; 327 kstat_named_t arcstat_l2_hits; 328 kstat_named_t arcstat_l2_misses; 329 kstat_named_t arcstat_l2_feeds; 330 kstat_named_t arcstat_l2_rw_clash; 331 kstat_named_t arcstat_l2_read_bytes; 332 kstat_named_t arcstat_l2_write_bytes; 333 kstat_named_t arcstat_l2_writes_sent; 334 kstat_named_t arcstat_l2_writes_done; 335 kstat_named_t arcstat_l2_writes_error; 336 kstat_named_t arcstat_l2_writes_hdr_miss; 337 kstat_named_t arcstat_l2_evict_lock_retry; 338 kstat_named_t arcstat_l2_evict_reading; 339 kstat_named_t arcstat_l2_free_on_write; 340 kstat_named_t arcstat_l2_abort_lowmem; 341 kstat_named_t arcstat_l2_cksum_bad; 342 kstat_named_t arcstat_l2_io_error; 343 kstat_named_t arcstat_l2_size; 344 kstat_named_t arcstat_l2_asize; 345 kstat_named_t arcstat_l2_hdr_size; 346 kstat_named_t arcstat_l2_compress_successes; 347 kstat_named_t arcstat_l2_compress_zeros; 348 kstat_named_t arcstat_l2_compress_failures; 349 kstat_named_t arcstat_l2_write_trylock_fail; 350 kstat_named_t arcstat_l2_write_passed_headroom; 351 kstat_named_t arcstat_l2_write_spa_mismatch; 352 kstat_named_t arcstat_l2_write_in_l2; 353 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 354 kstat_named_t arcstat_l2_write_not_cacheable; 355 kstat_named_t arcstat_l2_write_full; 356 kstat_named_t arcstat_l2_write_buffer_iter; 357 kstat_named_t arcstat_l2_write_pios; 358 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 359 kstat_named_t arcstat_l2_write_buffer_list_iter; 360 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 361 kstat_named_t arcstat_memory_throttle_count; 362 kstat_named_t arcstat_duplicate_buffers; 363 kstat_named_t arcstat_duplicate_buffers_size; 364 kstat_named_t arcstat_duplicate_reads; 365} arc_stats_t; 366 367static arc_stats_t arc_stats = { 368 { "hits", KSTAT_DATA_UINT64 }, 369 { "misses", KSTAT_DATA_UINT64 }, 370 { "demand_data_hits", KSTAT_DATA_UINT64 }, 371 { "demand_data_misses", KSTAT_DATA_UINT64 }, 372 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 373 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 374 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 375 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 376 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 377 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 378 { "mru_hits", KSTAT_DATA_UINT64 }, 379 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 380 { "mfu_hits", KSTAT_DATA_UINT64 }, 381 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 382 { "allocated", KSTAT_DATA_UINT64 }, 383 { "deleted", KSTAT_DATA_UINT64 }, 384 { "stolen", KSTAT_DATA_UINT64 }, 385 { "recycle_miss", KSTAT_DATA_UINT64 }, 386 { "mutex_miss", KSTAT_DATA_UINT64 }, 387 { "evict_skip", KSTAT_DATA_UINT64 }, 388 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 389 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 390 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 391 { "hash_elements", KSTAT_DATA_UINT64 }, 392 { "hash_elements_max", KSTAT_DATA_UINT64 }, 393 { "hash_collisions", KSTAT_DATA_UINT64 }, 394 { "hash_chains", KSTAT_DATA_UINT64 }, 395 { "hash_chain_max", KSTAT_DATA_UINT64 }, 396 { "p", KSTAT_DATA_UINT64 }, 397 { "c", KSTAT_DATA_UINT64 }, 398 { "c_min", KSTAT_DATA_UINT64 }, 399 { "c_max", KSTAT_DATA_UINT64 }, 400 { "size", KSTAT_DATA_UINT64 }, 401 { "hdr_size", KSTAT_DATA_UINT64 }, 402 { "data_size", KSTAT_DATA_UINT64 }, 403 { "other_size", KSTAT_DATA_UINT64 }, 404 { "l2_hits", KSTAT_DATA_UINT64 }, 405 { "l2_misses", KSTAT_DATA_UINT64 }, 406 { "l2_feeds", KSTAT_DATA_UINT64 }, 407 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 408 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 409 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 410 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 411 { "l2_writes_done", KSTAT_DATA_UINT64 }, 412 { "l2_writes_error", KSTAT_DATA_UINT64 }, 413 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 414 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 415 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 416 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 417 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 418 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 419 { "l2_io_error", KSTAT_DATA_UINT64 }, 420 { "l2_size", KSTAT_DATA_UINT64 }, 421 { "l2_asize", KSTAT_DATA_UINT64 }, 422 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 423 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 424 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 425 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 426 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 427 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 428 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 429 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 430 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 431 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 432 { "l2_write_full", KSTAT_DATA_UINT64 }, 433 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 434 { "l2_write_pios", KSTAT_DATA_UINT64 }, 435 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 436 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 437 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 438 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 439 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 440 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 441 { "duplicate_reads", KSTAT_DATA_UINT64 } 442}; 443 444#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 445 446#define ARCSTAT_INCR(stat, val) \ 447 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 448 449#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 450#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 451 452#define ARCSTAT_MAX(stat, val) { \ 453 uint64_t m; \ 454 while ((val) > (m = arc_stats.stat.value.ui64) && \ 455 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 456 continue; \ 457} 458 459#define ARCSTAT_MAXSTAT(stat) \ 460 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 461 462/* 463 * We define a macro to allow ARC hits/misses to be easily broken down by 464 * two separate conditions, giving a total of four different subtypes for 465 * each of hits and misses (so eight statistics total). 466 */ 467#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 468 if (cond1) { \ 469 if (cond2) { \ 470 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 471 } else { \ 472 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 473 } \ 474 } else { \ 475 if (cond2) { \ 476 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 477 } else { \ 478 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 479 } \ 480 } 481 482kstat_t *arc_ksp; 483static arc_state_t *arc_anon; 484static arc_state_t *arc_mru; 485static arc_state_t *arc_mru_ghost; 486static arc_state_t *arc_mfu; 487static arc_state_t *arc_mfu_ghost; 488static arc_state_t *arc_l2c_only; 489 490/* 491 * There are several ARC variables that are critical to export as kstats -- 492 * but we don't want to have to grovel around in the kstat whenever we wish to 493 * manipulate them. For these variables, we therefore define them to be in 494 * terms of the statistic variable. This assures that we are not introducing 495 * the possibility of inconsistency by having shadow copies of the variables, 496 * while still allowing the code to be readable. 497 */ 498#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 499#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 500#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 501#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 502#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 503 504#define L2ARC_IS_VALID_COMPRESS(_c_) \ 505 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 506 507static int arc_no_grow; /* Don't try to grow cache size */ 508static uint64_t arc_tempreserve; 509static uint64_t arc_loaned_bytes; 510static uint64_t arc_meta_used; 511static uint64_t arc_meta_limit; 512static uint64_t arc_meta_max = 0; 513SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RD, &arc_meta_used, 0, 514 "ARC metadata used"); 515SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RW, &arc_meta_limit, 0, 516 "ARC metadata limit"); 517 518typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; 519 520typedef struct arc_callback arc_callback_t; 521 522struct arc_callback { 523 void *acb_private; 524 arc_done_func_t *acb_done; 525 arc_buf_t *acb_buf; 526 zio_t *acb_zio_dummy; 527 arc_callback_t *acb_next; 528}; 529 530typedef struct arc_write_callback arc_write_callback_t; 531 532struct arc_write_callback { 533 void *awcb_private; 534 arc_done_func_t *awcb_ready; 535 arc_done_func_t *awcb_physdone; 536 arc_done_func_t *awcb_done; 537 arc_buf_t *awcb_buf; 538}; 539 540struct arc_buf_hdr { 541 /* protected by hash lock */ 542 dva_t b_dva; 543 uint64_t b_birth; 544 uint64_t b_cksum0; 545 546 kmutex_t b_freeze_lock; 547 zio_cksum_t *b_freeze_cksum; 548 void *b_thawed; 549 550 arc_buf_hdr_t *b_hash_next; 551 arc_buf_t *b_buf; 552 uint32_t b_flags; 553 uint32_t b_datacnt; 554 555 arc_callback_t *b_acb; 556 kcondvar_t b_cv; 557 558 /* immutable */ 559 arc_buf_contents_t b_type; 560 uint64_t b_size; 561 uint64_t b_spa; 562 563 /* protected by arc state mutex */ 564 arc_state_t *b_state; 565 list_node_t b_arc_node; 566 567 /* updated atomically */ 568 clock_t b_arc_access; 569 570 /* self protecting */ 571 refcount_t b_refcnt; 572 573 l2arc_buf_hdr_t *b_l2hdr; 574 list_node_t b_l2node; 575}; 576 577static arc_buf_t *arc_eviction_list; 578static kmutex_t arc_eviction_mtx; 579static arc_buf_hdr_t arc_eviction_hdr; 580static void arc_get_data_buf(arc_buf_t *buf); 581static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock); 582static int arc_evict_needed(arc_buf_contents_t type); 583static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes); 584#ifdef illumos 585static void arc_buf_watch(arc_buf_t *buf); 586#endif /* illumos */ 587 588static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab); 589 590#define GHOST_STATE(state) \ 591 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 592 (state) == arc_l2c_only) 593 594/* 595 * Private ARC flags. These flags are private ARC only flags that will show up 596 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can 597 * be passed in as arc_flags in things like arc_read. However, these flags 598 * should never be passed and should only be set by ARC code. When adding new 599 * public flags, make sure not to smash the private ones. 600 */ 601 602#define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */ 603#define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */ 604#define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */ 605#define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */ 606#define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */ 607#define ARC_INDIRECT (1 << 14) /* this is an indirect block */ 608#define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */ 609#define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */ 610#define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */ 611#define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */ 612 613#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE) 614#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS) 615#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR) 616#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH) 617#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ) 618#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE) 619#define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS) 620#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE) 621#define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \ 622 (hdr)->b_l2hdr != NULL) 623#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING) 624#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED) 625#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD) 626 627/* 628 * Other sizes 629 */ 630 631#define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 632#define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t)) 633 634/* 635 * Hash table routines 636 */ 637 638#define HT_LOCK_PAD CACHE_LINE_SIZE 639 640struct ht_lock { 641 kmutex_t ht_lock; 642#ifdef _KERNEL 643 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 644#endif 645}; 646 647#define BUF_LOCKS 256 648typedef struct buf_hash_table { 649 uint64_t ht_mask; 650 arc_buf_hdr_t **ht_table; 651 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 652} buf_hash_table_t; 653 654static buf_hash_table_t buf_hash_table; 655 656#define BUF_HASH_INDEX(spa, dva, birth) \ 657 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 658#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 659#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 660#define HDR_LOCK(hdr) \ 661 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 662 663uint64_t zfs_crc64_table[256]; 664 665/* 666 * Level 2 ARC 667 */ 668 669#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 670#define L2ARC_HEADROOM 2 /* num of writes */ 671/* 672 * If we discover during ARC scan any buffers to be compressed, we boost 673 * our headroom for the next scanning cycle by this percentage multiple. 674 */ 675#define L2ARC_HEADROOM_BOOST 200 676#define L2ARC_FEED_SECS 1 /* caching interval secs */ 677#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 678 679#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 680#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 681 682/* L2ARC Performance Tunables */ 683uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 684uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 685uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 686uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 687uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 688uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 689boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 690boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 691boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 692 693SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 694 &l2arc_write_max, 0, "max write size"); 695SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 696 &l2arc_write_boost, 0, "extra write during warmup"); 697SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 698 &l2arc_headroom, 0, "number of dev writes"); 699SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 700 &l2arc_feed_secs, 0, "interval seconds"); 701SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 702 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 703 704SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 705 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 706SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 707 &l2arc_feed_again, 0, "turbo warmup"); 708SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 709 &l2arc_norw, 0, "no reads during writes"); 710 711SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 712 &ARC_anon.arcs_size, 0, "size of anonymous state"); 713SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 714 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 715SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 716 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 717 718SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 719 &ARC_mru.arcs_size, 0, "size of mru state"); 720SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 721 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 722SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 723 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 724 725SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 726 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state"); 727SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 728 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 729 "size of metadata in mru ghost state"); 730SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 731 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 732 "size of data in mru ghost state"); 733 734SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 735 &ARC_mfu.arcs_size, 0, "size of mfu state"); 736SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 737 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 738SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 739 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 740 741SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 742 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state"); 743SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 744 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 745 "size of metadata in mfu ghost state"); 746SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 747 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 748 "size of data in mfu ghost state"); 749 750SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 751 &ARC_l2c_only.arcs_size, 0, "size of mru state"); 752 753/* 754 * L2ARC Internals 755 */ 756typedef struct l2arc_dev { 757 vdev_t *l2ad_vdev; /* vdev */ 758 spa_t *l2ad_spa; /* spa */ 759 uint64_t l2ad_hand; /* next write location */ 760 uint64_t l2ad_start; /* first addr on device */ 761 uint64_t l2ad_end; /* last addr on device */ 762 uint64_t l2ad_evict; /* last addr eviction reached */ 763 boolean_t l2ad_first; /* first sweep through */ 764 boolean_t l2ad_writing; /* currently writing */ 765 list_t *l2ad_buflist; /* buffer list */ 766 list_node_t l2ad_node; /* device list node */ 767} l2arc_dev_t; 768 769static list_t L2ARC_dev_list; /* device list */ 770static list_t *l2arc_dev_list; /* device list pointer */ 771static kmutex_t l2arc_dev_mtx; /* device list mutex */ 772static l2arc_dev_t *l2arc_dev_last; /* last device used */ 773static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */ 774static list_t L2ARC_free_on_write; /* free after write buf list */ 775static list_t *l2arc_free_on_write; /* free after write list ptr */ 776static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 777static uint64_t l2arc_ndev; /* number of devices */ 778 779typedef struct l2arc_read_callback { 780 arc_buf_t *l2rcb_buf; /* read buffer */ 781 spa_t *l2rcb_spa; /* spa */ 782 blkptr_t l2rcb_bp; /* original blkptr */
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783 zbookmark_t l2rcb_zb; /* original bookmark */
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783 zbookmark_phys_t l2rcb_zb; /* original bookmark */ |
784 int l2rcb_flags; /* original flags */ 785 enum zio_compress l2rcb_compress; /* applied compress */ 786} l2arc_read_callback_t; 787 788typedef struct l2arc_write_callback { 789 l2arc_dev_t *l2wcb_dev; /* device info */ 790 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 791} l2arc_write_callback_t; 792 793struct l2arc_buf_hdr { 794 /* protected by arc_buf_hdr mutex */ 795 l2arc_dev_t *b_dev; /* L2ARC device */ 796 uint64_t b_daddr; /* disk address, offset byte */ 797 /* compression applied to buffer data */ 798 enum zio_compress b_compress; 799 /* real alloc'd buffer size depending on b_compress applied */ 800 int b_asize; 801 /* temporary buffer holder for in-flight compressed data */ 802 void *b_tmp_cdata; 803}; 804 805typedef struct l2arc_data_free { 806 /* protected by l2arc_free_on_write_mtx */ 807 void *l2df_data; 808 size_t l2df_size; 809 void (*l2df_func)(void *, size_t); 810 list_node_t l2df_list_node; 811} l2arc_data_free_t; 812 813static kmutex_t l2arc_feed_thr_lock; 814static kcondvar_t l2arc_feed_thr_cv; 815static uint8_t l2arc_thread_exit; 816 817static void l2arc_read_done(zio_t *zio); 818static void l2arc_hdr_stat_add(void); 819static void l2arc_hdr_stat_remove(void); 820 821static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr); 822static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, 823 enum zio_compress c); 824static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab); 825 826static uint64_t 827buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 828{ 829 uint8_t *vdva = (uint8_t *)dva; 830 uint64_t crc = -1ULL; 831 int i; 832 833 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 834 835 for (i = 0; i < sizeof (dva_t); i++) 836 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 837 838 crc ^= (spa>>8) ^ birth; 839 840 return (crc); 841} 842 843#define BUF_EMPTY(buf) \ 844 ((buf)->b_dva.dva_word[0] == 0 && \ 845 (buf)->b_dva.dva_word[1] == 0 && \ 846 (buf)->b_cksum0 == 0) 847 848#define BUF_EQUAL(spa, dva, birth, buf) \ 849 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 850 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 851 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 852 853static void 854buf_discard_identity(arc_buf_hdr_t *hdr) 855{ 856 hdr->b_dva.dva_word[0] = 0; 857 hdr->b_dva.dva_word[1] = 0; 858 hdr->b_birth = 0; 859 hdr->b_cksum0 = 0; 860} 861 862static arc_buf_hdr_t * 863buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 864{ 865 const dva_t *dva = BP_IDENTITY(bp); 866 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 867 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 868 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 869 arc_buf_hdr_t *buf; 870 871 mutex_enter(hash_lock); 872 for (buf = buf_hash_table.ht_table[idx]; buf != NULL; 873 buf = buf->b_hash_next) { 874 if (BUF_EQUAL(spa, dva, birth, buf)) { 875 *lockp = hash_lock; 876 return (buf); 877 } 878 } 879 mutex_exit(hash_lock); 880 *lockp = NULL; 881 return (NULL); 882} 883 884/* 885 * Insert an entry into the hash table. If there is already an element 886 * equal to elem in the hash table, then the already existing element 887 * will be returned and the new element will not be inserted. 888 * Otherwise returns NULL. 889 */ 890static arc_buf_hdr_t * 891buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp) 892{ 893 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 894 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 895 arc_buf_hdr_t *fbuf; 896 uint32_t i; 897 898 ASSERT(!DVA_IS_EMPTY(&buf->b_dva)); 899 ASSERT(buf->b_birth != 0); 900 ASSERT(!HDR_IN_HASH_TABLE(buf)); 901 *lockp = hash_lock; 902 mutex_enter(hash_lock); 903 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL; 904 fbuf = fbuf->b_hash_next, i++) { 905 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf)) 906 return (fbuf); 907 } 908 909 buf->b_hash_next = buf_hash_table.ht_table[idx]; 910 buf_hash_table.ht_table[idx] = buf; 911 buf->b_flags |= ARC_IN_HASH_TABLE; 912 913 /* collect some hash table performance data */ 914 if (i > 0) { 915 ARCSTAT_BUMP(arcstat_hash_collisions); 916 if (i == 1) 917 ARCSTAT_BUMP(arcstat_hash_chains); 918 919 ARCSTAT_MAX(arcstat_hash_chain_max, i); 920 } 921 922 ARCSTAT_BUMP(arcstat_hash_elements); 923 ARCSTAT_MAXSTAT(arcstat_hash_elements); 924 925 return (NULL); 926} 927 928static void 929buf_hash_remove(arc_buf_hdr_t *buf) 930{ 931 arc_buf_hdr_t *fbuf, **bufp; 932 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 933 934 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 935 ASSERT(HDR_IN_HASH_TABLE(buf)); 936 937 bufp = &buf_hash_table.ht_table[idx]; 938 while ((fbuf = *bufp) != buf) { 939 ASSERT(fbuf != NULL); 940 bufp = &fbuf->b_hash_next; 941 } 942 *bufp = buf->b_hash_next; 943 buf->b_hash_next = NULL; 944 buf->b_flags &= ~ARC_IN_HASH_TABLE; 945 946 /* collect some hash table performance data */ 947 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 948 949 if (buf_hash_table.ht_table[idx] && 950 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 951 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 952} 953 954/* 955 * Global data structures and functions for the buf kmem cache. 956 */ 957static kmem_cache_t *hdr_cache; 958static kmem_cache_t *buf_cache; 959 960static void 961buf_fini(void) 962{ 963 int i; 964 965 kmem_free(buf_hash_table.ht_table, 966 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 967 for (i = 0; i < BUF_LOCKS; i++) 968 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 969 kmem_cache_destroy(hdr_cache); 970 kmem_cache_destroy(buf_cache); 971} 972 973/* 974 * Constructor callback - called when the cache is empty 975 * and a new buf is requested. 976 */ 977/* ARGSUSED */ 978static int 979hdr_cons(void *vbuf, void *unused, int kmflag) 980{ 981 arc_buf_hdr_t *buf = vbuf; 982 983 bzero(buf, sizeof (arc_buf_hdr_t)); 984 refcount_create(&buf->b_refcnt); 985 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL); 986 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 987 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 988 989 return (0); 990} 991 992/* ARGSUSED */ 993static int 994buf_cons(void *vbuf, void *unused, int kmflag) 995{ 996 arc_buf_t *buf = vbuf; 997 998 bzero(buf, sizeof (arc_buf_t)); 999 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1000 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1001 1002 return (0); 1003} 1004 1005/* 1006 * Destructor callback - called when a cached buf is 1007 * no longer required. 1008 */ 1009/* ARGSUSED */ 1010static void 1011hdr_dest(void *vbuf, void *unused) 1012{ 1013 arc_buf_hdr_t *buf = vbuf; 1014 1015 ASSERT(BUF_EMPTY(buf)); 1016 refcount_destroy(&buf->b_refcnt); 1017 cv_destroy(&buf->b_cv); 1018 mutex_destroy(&buf->b_freeze_lock); 1019 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 1020} 1021 1022/* ARGSUSED */ 1023static void 1024buf_dest(void *vbuf, void *unused) 1025{ 1026 arc_buf_t *buf = vbuf; 1027 1028 mutex_destroy(&buf->b_evict_lock); 1029 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1030} 1031 1032/* 1033 * Reclaim callback -- invoked when memory is low. 1034 */ 1035/* ARGSUSED */ 1036static void 1037hdr_recl(void *unused) 1038{ 1039 dprintf("hdr_recl called\n"); 1040 /* 1041 * umem calls the reclaim func when we destroy the buf cache, 1042 * which is after we do arc_fini(). 1043 */ 1044 if (!arc_dead) 1045 cv_signal(&arc_reclaim_thr_cv); 1046} 1047 1048static void 1049buf_init(void) 1050{ 1051 uint64_t *ct; 1052 uint64_t hsize = 1ULL << 12; 1053 int i, j; 1054 1055 /* 1056 * The hash table is big enough to fill all of physical memory 1057 * with an average 64K block size. The table will take up 1058 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers). 1059 */ 1060 while (hsize * 65536 < (uint64_t)physmem * PAGESIZE) 1061 hsize <<= 1; 1062retry: 1063 buf_hash_table.ht_mask = hsize - 1; 1064 buf_hash_table.ht_table = 1065 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1066 if (buf_hash_table.ht_table == NULL) { 1067 ASSERT(hsize > (1ULL << 8)); 1068 hsize >>= 1; 1069 goto retry; 1070 } 1071 1072 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t), 1073 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0); 1074 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1075 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1076 1077 for (i = 0; i < 256; i++) 1078 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1079 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1080 1081 for (i = 0; i < BUF_LOCKS; i++) { 1082 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1083 NULL, MUTEX_DEFAULT, NULL); 1084 } 1085} 1086 1087#define ARC_MINTIME (hz>>4) /* 62 ms */ 1088 1089static void 1090arc_cksum_verify(arc_buf_t *buf) 1091{ 1092 zio_cksum_t zc; 1093 1094 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1095 return; 1096 1097 mutex_enter(&buf->b_hdr->b_freeze_lock); 1098 if (buf->b_hdr->b_freeze_cksum == NULL || 1099 (buf->b_hdr->b_flags & ARC_IO_ERROR)) { 1100 mutex_exit(&buf->b_hdr->b_freeze_lock); 1101 return; 1102 } 1103 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1104 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1105 panic("buffer modified while frozen!"); 1106 mutex_exit(&buf->b_hdr->b_freeze_lock); 1107} 1108 1109static int 1110arc_cksum_equal(arc_buf_t *buf) 1111{ 1112 zio_cksum_t zc; 1113 int equal; 1114 1115 mutex_enter(&buf->b_hdr->b_freeze_lock); 1116 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1117 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1118 mutex_exit(&buf->b_hdr->b_freeze_lock); 1119 1120 return (equal); 1121} 1122 1123static void 1124arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1125{ 1126 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1127 return; 1128 1129 mutex_enter(&buf->b_hdr->b_freeze_lock); 1130 if (buf->b_hdr->b_freeze_cksum != NULL) { 1131 mutex_exit(&buf->b_hdr->b_freeze_lock); 1132 return; 1133 } 1134 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1135 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1136 buf->b_hdr->b_freeze_cksum); 1137 mutex_exit(&buf->b_hdr->b_freeze_lock); 1138#ifdef illumos 1139 arc_buf_watch(buf); 1140#endif /* illumos */ 1141} 1142 1143#ifdef illumos 1144#ifndef _KERNEL 1145typedef struct procctl { 1146 long cmd; 1147 prwatch_t prwatch; 1148} procctl_t; 1149#endif 1150 1151/* ARGSUSED */ 1152static void 1153arc_buf_unwatch(arc_buf_t *buf) 1154{ 1155#ifndef _KERNEL 1156 if (arc_watch) { 1157 int result; 1158 procctl_t ctl; 1159 ctl.cmd = PCWATCH; 1160 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1161 ctl.prwatch.pr_size = 0; 1162 ctl.prwatch.pr_wflags = 0; 1163 result = write(arc_procfd, &ctl, sizeof (ctl)); 1164 ASSERT3U(result, ==, sizeof (ctl)); 1165 } 1166#endif 1167} 1168 1169/* ARGSUSED */ 1170static void 1171arc_buf_watch(arc_buf_t *buf) 1172{ 1173#ifndef _KERNEL 1174 if (arc_watch) { 1175 int result; 1176 procctl_t ctl; 1177 ctl.cmd = PCWATCH; 1178 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1179 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1180 ctl.prwatch.pr_wflags = WA_WRITE; 1181 result = write(arc_procfd, &ctl, sizeof (ctl)); 1182 ASSERT3U(result, ==, sizeof (ctl)); 1183 } 1184#endif 1185} 1186#endif /* illumos */ 1187 1188void 1189arc_buf_thaw(arc_buf_t *buf) 1190{ 1191 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1192 if (buf->b_hdr->b_state != arc_anon) 1193 panic("modifying non-anon buffer!"); 1194 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS) 1195 panic("modifying buffer while i/o in progress!"); 1196 arc_cksum_verify(buf); 1197 } 1198 1199 mutex_enter(&buf->b_hdr->b_freeze_lock); 1200 if (buf->b_hdr->b_freeze_cksum != NULL) { 1201 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1202 buf->b_hdr->b_freeze_cksum = NULL; 1203 } 1204 1205 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1206 if (buf->b_hdr->b_thawed) 1207 kmem_free(buf->b_hdr->b_thawed, 1); 1208 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP); 1209 } 1210 1211 mutex_exit(&buf->b_hdr->b_freeze_lock); 1212 1213#ifdef illumos 1214 arc_buf_unwatch(buf); 1215#endif /* illumos */ 1216} 1217 1218void 1219arc_buf_freeze(arc_buf_t *buf) 1220{ 1221 kmutex_t *hash_lock; 1222 1223 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1224 return; 1225 1226 hash_lock = HDR_LOCK(buf->b_hdr); 1227 mutex_enter(hash_lock); 1228 1229 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1230 buf->b_hdr->b_state == arc_anon); 1231 arc_cksum_compute(buf, B_FALSE); 1232 mutex_exit(hash_lock); 1233 1234} 1235 1236static void 1237get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock) 1238{ 1239 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth); 1240 1241 if (ab->b_type == ARC_BUFC_METADATA) 1242 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1); 1243 else { 1244 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1); 1245 buf_hashid += ARC_BUFC_NUMMETADATALISTS; 1246 } 1247 1248 *list = &state->arcs_lists[buf_hashid]; 1249 *lock = ARCS_LOCK(state, buf_hashid); 1250} 1251 1252 1253static void 1254add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1255{ 1256 ASSERT(MUTEX_HELD(hash_lock)); 1257 1258 if ((refcount_add(&ab->b_refcnt, tag) == 1) && 1259 (ab->b_state != arc_anon)) { 1260 uint64_t delta = ab->b_size * ab->b_datacnt; 1261 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type]; 1262 list_t *list; 1263 kmutex_t *lock; 1264 1265 get_buf_info(ab, ab->b_state, &list, &lock); 1266 ASSERT(!MUTEX_HELD(lock)); 1267 mutex_enter(lock); 1268 ASSERT(list_link_active(&ab->b_arc_node)); 1269 list_remove(list, ab); 1270 if (GHOST_STATE(ab->b_state)) { 1271 ASSERT0(ab->b_datacnt); 1272 ASSERT3P(ab->b_buf, ==, NULL); 1273 delta = ab->b_size; 1274 } 1275 ASSERT(delta > 0); 1276 ASSERT3U(*size, >=, delta); 1277 atomic_add_64(size, -delta); 1278 mutex_exit(lock); 1279 /* remove the prefetch flag if we get a reference */ 1280 if (ab->b_flags & ARC_PREFETCH) 1281 ab->b_flags &= ~ARC_PREFETCH; 1282 } 1283} 1284 1285static int 1286remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1287{ 1288 int cnt; 1289 arc_state_t *state = ab->b_state; 1290 1291 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1292 ASSERT(!GHOST_STATE(state)); 1293 1294 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) && 1295 (state != arc_anon)) { 1296 uint64_t *size = &state->arcs_lsize[ab->b_type]; 1297 list_t *list; 1298 kmutex_t *lock; 1299 1300 get_buf_info(ab, state, &list, &lock); 1301 ASSERT(!MUTEX_HELD(lock)); 1302 mutex_enter(lock); 1303 ASSERT(!list_link_active(&ab->b_arc_node)); 1304 list_insert_head(list, ab); 1305 ASSERT(ab->b_datacnt > 0); 1306 atomic_add_64(size, ab->b_size * ab->b_datacnt); 1307 mutex_exit(lock); 1308 } 1309 return (cnt); 1310} 1311 1312/* 1313 * Move the supplied buffer to the indicated state. The mutex 1314 * for the buffer must be held by the caller. 1315 */ 1316static void 1317arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock) 1318{ 1319 arc_state_t *old_state = ab->b_state; 1320 int64_t refcnt = refcount_count(&ab->b_refcnt); 1321 uint64_t from_delta, to_delta; 1322 list_t *list; 1323 kmutex_t *lock; 1324 1325 ASSERT(MUTEX_HELD(hash_lock)); 1326 ASSERT3P(new_state, !=, old_state); 1327 ASSERT(refcnt == 0 || ab->b_datacnt > 0); 1328 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state)); 1329 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon); 1330 1331 from_delta = to_delta = ab->b_datacnt * ab->b_size; 1332 1333 /* 1334 * If this buffer is evictable, transfer it from the 1335 * old state list to the new state list. 1336 */ 1337 if (refcnt == 0) { 1338 if (old_state != arc_anon) { 1339 int use_mutex; 1340 uint64_t *size = &old_state->arcs_lsize[ab->b_type]; 1341 1342 get_buf_info(ab, old_state, &list, &lock); 1343 use_mutex = !MUTEX_HELD(lock); 1344 if (use_mutex) 1345 mutex_enter(lock); 1346 1347 ASSERT(list_link_active(&ab->b_arc_node)); 1348 list_remove(list, ab); 1349 1350 /* 1351 * If prefetching out of the ghost cache, 1352 * we will have a non-zero datacnt. 1353 */ 1354 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) { 1355 /* ghost elements have a ghost size */ 1356 ASSERT(ab->b_buf == NULL); 1357 from_delta = ab->b_size; 1358 } 1359 ASSERT3U(*size, >=, from_delta); 1360 atomic_add_64(size, -from_delta); 1361 1362 if (use_mutex) 1363 mutex_exit(lock); 1364 } 1365 if (new_state != arc_anon) { 1366 int use_mutex; 1367 uint64_t *size = &new_state->arcs_lsize[ab->b_type]; 1368 1369 get_buf_info(ab, new_state, &list, &lock); 1370 use_mutex = !MUTEX_HELD(lock); 1371 if (use_mutex) 1372 mutex_enter(lock); 1373 1374 list_insert_head(list, ab); 1375 1376 /* ghost elements have a ghost size */ 1377 if (GHOST_STATE(new_state)) { 1378 ASSERT(ab->b_datacnt == 0); 1379 ASSERT(ab->b_buf == NULL); 1380 to_delta = ab->b_size; 1381 } 1382 atomic_add_64(size, to_delta); 1383 1384 if (use_mutex) 1385 mutex_exit(lock); 1386 } 1387 } 1388 1389 ASSERT(!BUF_EMPTY(ab)); 1390 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab)) 1391 buf_hash_remove(ab); 1392 1393 /* adjust state sizes */ 1394 if (to_delta) 1395 atomic_add_64(&new_state->arcs_size, to_delta); 1396 if (from_delta) { 1397 ASSERT3U(old_state->arcs_size, >=, from_delta); 1398 atomic_add_64(&old_state->arcs_size, -from_delta); 1399 } 1400 ab->b_state = new_state; 1401 1402 /* adjust l2arc hdr stats */ 1403 if (new_state == arc_l2c_only) 1404 l2arc_hdr_stat_add(); 1405 else if (old_state == arc_l2c_only) 1406 l2arc_hdr_stat_remove(); 1407} 1408 1409void 1410arc_space_consume(uint64_t space, arc_space_type_t type) 1411{ 1412 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1413 1414 switch (type) { 1415 case ARC_SPACE_DATA: 1416 ARCSTAT_INCR(arcstat_data_size, space); 1417 break; 1418 case ARC_SPACE_OTHER: 1419 ARCSTAT_INCR(arcstat_other_size, space); 1420 break; 1421 case ARC_SPACE_HDRS: 1422 ARCSTAT_INCR(arcstat_hdr_size, space); 1423 break; 1424 case ARC_SPACE_L2HDRS: 1425 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1426 break; 1427 } 1428 1429 atomic_add_64(&arc_meta_used, space); 1430 atomic_add_64(&arc_size, space); 1431} 1432 1433void 1434arc_space_return(uint64_t space, arc_space_type_t type) 1435{ 1436 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1437 1438 switch (type) { 1439 case ARC_SPACE_DATA: 1440 ARCSTAT_INCR(arcstat_data_size, -space); 1441 break; 1442 case ARC_SPACE_OTHER: 1443 ARCSTAT_INCR(arcstat_other_size, -space); 1444 break; 1445 case ARC_SPACE_HDRS: 1446 ARCSTAT_INCR(arcstat_hdr_size, -space); 1447 break; 1448 case ARC_SPACE_L2HDRS: 1449 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1450 break; 1451 } 1452 1453 ASSERT(arc_meta_used >= space); 1454 if (arc_meta_max < arc_meta_used) 1455 arc_meta_max = arc_meta_used; 1456 atomic_add_64(&arc_meta_used, -space); 1457 ASSERT(arc_size >= space); 1458 atomic_add_64(&arc_size, -space); 1459} 1460 1461void * 1462arc_data_buf_alloc(uint64_t size) 1463{ 1464 if (arc_evict_needed(ARC_BUFC_DATA)) 1465 cv_signal(&arc_reclaim_thr_cv); 1466 atomic_add_64(&arc_size, size); 1467 return (zio_data_buf_alloc(size)); 1468} 1469 1470void 1471arc_data_buf_free(void *buf, uint64_t size) 1472{ 1473 zio_data_buf_free(buf, size); 1474 ASSERT(arc_size >= size); 1475 atomic_add_64(&arc_size, -size); 1476} 1477 1478arc_buf_t * 1479arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type) 1480{ 1481 arc_buf_hdr_t *hdr; 1482 arc_buf_t *buf; 1483 1484 ASSERT3U(size, >, 0); 1485 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 1486 ASSERT(BUF_EMPTY(hdr)); 1487 hdr->b_size = size; 1488 hdr->b_type = type; 1489 hdr->b_spa = spa_load_guid(spa); 1490 hdr->b_state = arc_anon; 1491 hdr->b_arc_access = 0; 1492 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1493 buf->b_hdr = hdr; 1494 buf->b_data = NULL; 1495 buf->b_efunc = NULL; 1496 buf->b_private = NULL; 1497 buf->b_next = NULL; 1498 hdr->b_buf = buf; 1499 arc_get_data_buf(buf); 1500 hdr->b_datacnt = 1; 1501 hdr->b_flags = 0; 1502 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1503 (void) refcount_add(&hdr->b_refcnt, tag); 1504 1505 return (buf); 1506} 1507 1508static char *arc_onloan_tag = "onloan"; 1509 1510/* 1511 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1512 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1513 * buffers must be returned to the arc before they can be used by the DMU or 1514 * freed. 1515 */ 1516arc_buf_t * 1517arc_loan_buf(spa_t *spa, int size) 1518{ 1519 arc_buf_t *buf; 1520 1521 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1522 1523 atomic_add_64(&arc_loaned_bytes, size); 1524 return (buf); 1525} 1526 1527/* 1528 * Return a loaned arc buffer to the arc. 1529 */ 1530void 1531arc_return_buf(arc_buf_t *buf, void *tag) 1532{ 1533 arc_buf_hdr_t *hdr = buf->b_hdr; 1534 1535 ASSERT(buf->b_data != NULL); 1536 (void) refcount_add(&hdr->b_refcnt, tag); 1537 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag); 1538 1539 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1540} 1541 1542/* Detach an arc_buf from a dbuf (tag) */ 1543void 1544arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1545{ 1546 arc_buf_hdr_t *hdr; 1547 1548 ASSERT(buf->b_data != NULL); 1549 hdr = buf->b_hdr; 1550 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag); 1551 (void) refcount_remove(&hdr->b_refcnt, tag); 1552 buf->b_efunc = NULL; 1553 buf->b_private = NULL; 1554 1555 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1556} 1557 1558static arc_buf_t * 1559arc_buf_clone(arc_buf_t *from) 1560{ 1561 arc_buf_t *buf; 1562 arc_buf_hdr_t *hdr = from->b_hdr; 1563 uint64_t size = hdr->b_size; 1564 1565 ASSERT(hdr->b_state != arc_anon); 1566 1567 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1568 buf->b_hdr = hdr; 1569 buf->b_data = NULL; 1570 buf->b_efunc = NULL; 1571 buf->b_private = NULL; 1572 buf->b_next = hdr->b_buf; 1573 hdr->b_buf = buf; 1574 arc_get_data_buf(buf); 1575 bcopy(from->b_data, buf->b_data, size); 1576 1577 /* 1578 * This buffer already exists in the arc so create a duplicate 1579 * copy for the caller. If the buffer is associated with user data 1580 * then track the size and number of duplicates. These stats will be 1581 * updated as duplicate buffers are created and destroyed. 1582 */ 1583 if (hdr->b_type == ARC_BUFC_DATA) { 1584 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1585 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1586 } 1587 hdr->b_datacnt += 1; 1588 return (buf); 1589} 1590 1591void 1592arc_buf_add_ref(arc_buf_t *buf, void* tag) 1593{ 1594 arc_buf_hdr_t *hdr; 1595 kmutex_t *hash_lock; 1596 1597 /* 1598 * Check to see if this buffer is evicted. Callers 1599 * must verify b_data != NULL to know if the add_ref 1600 * was successful. 1601 */ 1602 mutex_enter(&buf->b_evict_lock); 1603 if (buf->b_data == NULL) { 1604 mutex_exit(&buf->b_evict_lock); 1605 return; 1606 } 1607 hash_lock = HDR_LOCK(buf->b_hdr); 1608 mutex_enter(hash_lock); 1609 hdr = buf->b_hdr; 1610 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1611 mutex_exit(&buf->b_evict_lock); 1612 1613 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 1614 add_reference(hdr, hash_lock, tag); 1615 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1616 arc_access(hdr, hash_lock); 1617 mutex_exit(hash_lock); 1618 ARCSTAT_BUMP(arcstat_hits); 1619 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 1620 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 1621 data, metadata, hits); 1622} 1623 1624/* 1625 * Free the arc data buffer. If it is an l2arc write in progress, 1626 * the buffer is placed on l2arc_free_on_write to be freed later. 1627 */ 1628static void 1629arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1630{ 1631 arc_buf_hdr_t *hdr = buf->b_hdr; 1632 1633 if (HDR_L2_WRITING(hdr)) { 1634 l2arc_data_free_t *df; 1635 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1636 df->l2df_data = buf->b_data; 1637 df->l2df_size = hdr->b_size; 1638 df->l2df_func = free_func; 1639 mutex_enter(&l2arc_free_on_write_mtx); 1640 list_insert_head(l2arc_free_on_write, df); 1641 mutex_exit(&l2arc_free_on_write_mtx); 1642 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1643 } else { 1644 free_func(buf->b_data, hdr->b_size); 1645 } 1646} 1647 1648static void 1649arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all) 1650{ 1651 arc_buf_t **bufp; 1652 1653 /* free up data associated with the buf */ 1654 if (buf->b_data) { 1655 arc_state_t *state = buf->b_hdr->b_state; 1656 uint64_t size = buf->b_hdr->b_size; 1657 arc_buf_contents_t type = buf->b_hdr->b_type; 1658 1659 arc_cksum_verify(buf); 1660#ifdef illumos 1661 arc_buf_unwatch(buf); 1662#endif /* illumos */ 1663 1664 if (!recycle) { 1665 if (type == ARC_BUFC_METADATA) { 1666 arc_buf_data_free(buf, zio_buf_free); 1667 arc_space_return(size, ARC_SPACE_DATA); 1668 } else { 1669 ASSERT(type == ARC_BUFC_DATA); 1670 arc_buf_data_free(buf, zio_data_buf_free); 1671 ARCSTAT_INCR(arcstat_data_size, -size); 1672 atomic_add_64(&arc_size, -size); 1673 } 1674 } 1675 if (list_link_active(&buf->b_hdr->b_arc_node)) { 1676 uint64_t *cnt = &state->arcs_lsize[type]; 1677 1678 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt)); 1679 ASSERT(state != arc_anon); 1680 1681 ASSERT3U(*cnt, >=, size); 1682 atomic_add_64(cnt, -size); 1683 } 1684 ASSERT3U(state->arcs_size, >=, size); 1685 atomic_add_64(&state->arcs_size, -size); 1686 buf->b_data = NULL; 1687 1688 /* 1689 * If we're destroying a duplicate buffer make sure 1690 * that the appropriate statistics are updated. 1691 */ 1692 if (buf->b_hdr->b_datacnt > 1 && 1693 buf->b_hdr->b_type == ARC_BUFC_DATA) { 1694 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1695 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1696 } 1697 ASSERT(buf->b_hdr->b_datacnt > 0); 1698 buf->b_hdr->b_datacnt -= 1; 1699 } 1700 1701 /* only remove the buf if requested */ 1702 if (!all) 1703 return; 1704 1705 /* remove the buf from the hdr list */ 1706 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next) 1707 continue; 1708 *bufp = buf->b_next; 1709 buf->b_next = NULL; 1710 1711 ASSERT(buf->b_efunc == NULL); 1712 1713 /* clean up the buf */ 1714 buf->b_hdr = NULL; 1715 kmem_cache_free(buf_cache, buf); 1716} 1717 1718static void 1719arc_hdr_destroy(arc_buf_hdr_t *hdr) 1720{ 1721 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1722 ASSERT3P(hdr->b_state, ==, arc_anon); 1723 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1724 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1725 1726 if (l2hdr != NULL) { 1727 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx); 1728 /* 1729 * To prevent arc_free() and l2arc_evict() from 1730 * attempting to free the same buffer at the same time, 1731 * a FREE_IN_PROGRESS flag is given to arc_free() to 1732 * give it priority. l2arc_evict() can't destroy this 1733 * header while we are waiting on l2arc_buflist_mtx. 1734 * 1735 * The hdr may be removed from l2ad_buflist before we 1736 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked. 1737 */ 1738 if (!buflist_held) { 1739 mutex_enter(&l2arc_buflist_mtx); 1740 l2hdr = hdr->b_l2hdr; 1741 } 1742 1743 if (l2hdr != NULL) { 1744 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr, 1745 hdr->b_size, 0); 1746 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 1747 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1748 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 1749 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 1750 -l2hdr->b_asize, 0, 0); 1751 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 1752 if (hdr->b_state == arc_l2c_only) 1753 l2arc_hdr_stat_remove(); 1754 hdr->b_l2hdr = NULL; 1755 } 1756 1757 if (!buflist_held) 1758 mutex_exit(&l2arc_buflist_mtx); 1759 } 1760 1761 if (!BUF_EMPTY(hdr)) { 1762 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1763 buf_discard_identity(hdr); 1764 } 1765 while (hdr->b_buf) { 1766 arc_buf_t *buf = hdr->b_buf; 1767 1768 if (buf->b_efunc) { 1769 mutex_enter(&arc_eviction_mtx); 1770 mutex_enter(&buf->b_evict_lock); 1771 ASSERT(buf->b_hdr != NULL); 1772 arc_buf_destroy(hdr->b_buf, FALSE, FALSE); 1773 hdr->b_buf = buf->b_next; 1774 buf->b_hdr = &arc_eviction_hdr; 1775 buf->b_next = arc_eviction_list; 1776 arc_eviction_list = buf; 1777 mutex_exit(&buf->b_evict_lock); 1778 mutex_exit(&arc_eviction_mtx); 1779 } else { 1780 arc_buf_destroy(hdr->b_buf, FALSE, TRUE); 1781 } 1782 } 1783 if (hdr->b_freeze_cksum != NULL) { 1784 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1785 hdr->b_freeze_cksum = NULL; 1786 } 1787 if (hdr->b_thawed) { 1788 kmem_free(hdr->b_thawed, 1); 1789 hdr->b_thawed = NULL; 1790 } 1791 1792 ASSERT(!list_link_active(&hdr->b_arc_node)); 1793 ASSERT3P(hdr->b_hash_next, ==, NULL); 1794 ASSERT3P(hdr->b_acb, ==, NULL); 1795 kmem_cache_free(hdr_cache, hdr); 1796} 1797 1798void 1799arc_buf_free(arc_buf_t *buf, void *tag) 1800{ 1801 arc_buf_hdr_t *hdr = buf->b_hdr; 1802 int hashed = hdr->b_state != arc_anon; 1803 1804 ASSERT(buf->b_efunc == NULL); 1805 ASSERT(buf->b_data != NULL); 1806 1807 if (hashed) { 1808 kmutex_t *hash_lock = HDR_LOCK(hdr); 1809 1810 mutex_enter(hash_lock); 1811 hdr = buf->b_hdr; 1812 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1813 1814 (void) remove_reference(hdr, hash_lock, tag); 1815 if (hdr->b_datacnt > 1) { 1816 arc_buf_destroy(buf, FALSE, TRUE); 1817 } else { 1818 ASSERT(buf == hdr->b_buf); 1819 ASSERT(buf->b_efunc == NULL); 1820 hdr->b_flags |= ARC_BUF_AVAILABLE; 1821 } 1822 mutex_exit(hash_lock); 1823 } else if (HDR_IO_IN_PROGRESS(hdr)) { 1824 int destroy_hdr; 1825 /* 1826 * We are in the middle of an async write. Don't destroy 1827 * this buffer unless the write completes before we finish 1828 * decrementing the reference count. 1829 */ 1830 mutex_enter(&arc_eviction_mtx); 1831 (void) remove_reference(hdr, NULL, tag); 1832 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1833 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 1834 mutex_exit(&arc_eviction_mtx); 1835 if (destroy_hdr) 1836 arc_hdr_destroy(hdr); 1837 } else { 1838 if (remove_reference(hdr, NULL, tag) > 0) 1839 arc_buf_destroy(buf, FALSE, TRUE); 1840 else 1841 arc_hdr_destroy(hdr); 1842 } 1843} 1844 1845boolean_t 1846arc_buf_remove_ref(arc_buf_t *buf, void* tag) 1847{ 1848 arc_buf_hdr_t *hdr = buf->b_hdr; 1849 kmutex_t *hash_lock = HDR_LOCK(hdr); 1850 boolean_t no_callback = (buf->b_efunc == NULL); 1851 1852 if (hdr->b_state == arc_anon) { 1853 ASSERT(hdr->b_datacnt == 1); 1854 arc_buf_free(buf, tag); 1855 return (no_callback); 1856 } 1857 1858 mutex_enter(hash_lock); 1859 hdr = buf->b_hdr; 1860 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1861 ASSERT(hdr->b_state != arc_anon); 1862 ASSERT(buf->b_data != NULL); 1863 1864 (void) remove_reference(hdr, hash_lock, tag); 1865 if (hdr->b_datacnt > 1) { 1866 if (no_callback) 1867 arc_buf_destroy(buf, FALSE, TRUE); 1868 } else if (no_callback) { 1869 ASSERT(hdr->b_buf == buf && buf->b_next == NULL); 1870 ASSERT(buf->b_efunc == NULL); 1871 hdr->b_flags |= ARC_BUF_AVAILABLE; 1872 } 1873 ASSERT(no_callback || hdr->b_datacnt > 1 || 1874 refcount_is_zero(&hdr->b_refcnt)); 1875 mutex_exit(hash_lock); 1876 return (no_callback); 1877} 1878 1879int 1880arc_buf_size(arc_buf_t *buf) 1881{ 1882 return (buf->b_hdr->b_size); 1883} 1884 1885/* 1886 * Called from the DMU to determine if the current buffer should be 1887 * evicted. In order to ensure proper locking, the eviction must be initiated 1888 * from the DMU. Return true if the buffer is associated with user data and 1889 * duplicate buffers still exist. 1890 */ 1891boolean_t 1892arc_buf_eviction_needed(arc_buf_t *buf) 1893{ 1894 arc_buf_hdr_t *hdr; 1895 boolean_t evict_needed = B_FALSE; 1896 1897 if (zfs_disable_dup_eviction) 1898 return (B_FALSE); 1899 1900 mutex_enter(&buf->b_evict_lock); 1901 hdr = buf->b_hdr; 1902 if (hdr == NULL) { 1903 /* 1904 * We are in arc_do_user_evicts(); let that function 1905 * perform the eviction. 1906 */ 1907 ASSERT(buf->b_data == NULL); 1908 mutex_exit(&buf->b_evict_lock); 1909 return (B_FALSE); 1910 } else if (buf->b_data == NULL) { 1911 /* 1912 * We have already been added to the arc eviction list; 1913 * recommend eviction. 1914 */ 1915 ASSERT3P(hdr, ==, &arc_eviction_hdr); 1916 mutex_exit(&buf->b_evict_lock); 1917 return (B_TRUE); 1918 } 1919 1920 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) 1921 evict_needed = B_TRUE; 1922 1923 mutex_exit(&buf->b_evict_lock); 1924 return (evict_needed); 1925} 1926 1927/* 1928 * Evict buffers from list until we've removed the specified number of 1929 * bytes. Move the removed buffers to the appropriate evict state. 1930 * If the recycle flag is set, then attempt to "recycle" a buffer: 1931 * - look for a buffer to evict that is `bytes' long. 1932 * - return the data block from this buffer rather than freeing it. 1933 * This flag is used by callers that are trying to make space for a 1934 * new buffer in a full arc cache. 1935 * 1936 * This function makes a "best effort". It skips over any buffers 1937 * it can't get a hash_lock on, and so may not catch all candidates. 1938 * It may also return without evicting as much space as requested. 1939 */ 1940static void * 1941arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 1942 arc_buf_contents_t type) 1943{ 1944 arc_state_t *evicted_state; 1945 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 1946 int64_t bytes_remaining; 1947 arc_buf_hdr_t *ab, *ab_prev = NULL; 1948 list_t *evicted_list, *list, *evicted_list_start, *list_start; 1949 kmutex_t *lock, *evicted_lock; 1950 kmutex_t *hash_lock; 1951 boolean_t have_lock; 1952 void *stolen = NULL; 1953 arc_buf_hdr_t marker = { 0 }; 1954 int count = 0; 1955 static int evict_metadata_offset, evict_data_offset; 1956 int i, idx, offset, list_count, lists; 1957 1958 ASSERT(state == arc_mru || state == arc_mfu); 1959 1960 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 1961 1962 if (type == ARC_BUFC_METADATA) { 1963 offset = 0; 1964 list_count = ARC_BUFC_NUMMETADATALISTS; 1965 list_start = &state->arcs_lists[0]; 1966 evicted_list_start = &evicted_state->arcs_lists[0]; 1967 idx = evict_metadata_offset; 1968 } else { 1969 offset = ARC_BUFC_NUMMETADATALISTS; 1970 list_start = &state->arcs_lists[offset]; 1971 evicted_list_start = &evicted_state->arcs_lists[offset]; 1972 list_count = ARC_BUFC_NUMDATALISTS; 1973 idx = evict_data_offset; 1974 } 1975 bytes_remaining = evicted_state->arcs_lsize[type]; 1976 lists = 0; 1977 1978evict_start: 1979 list = &list_start[idx]; 1980 evicted_list = &evicted_list_start[idx]; 1981 lock = ARCS_LOCK(state, (offset + idx)); 1982 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx)); 1983 1984 mutex_enter(lock); 1985 mutex_enter(evicted_lock); 1986 1987 for (ab = list_tail(list); ab; ab = ab_prev) { 1988 ab_prev = list_prev(list, ab); 1989 bytes_remaining -= (ab->b_size * ab->b_datacnt); 1990 /* prefetch buffers have a minimum lifespan */ 1991 if (HDR_IO_IN_PROGRESS(ab) || 1992 (spa && ab->b_spa != spa) || 1993 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) && 1994 ddi_get_lbolt() - ab->b_arc_access < 1995 arc_min_prefetch_lifespan)) { 1996 skipped++; 1997 continue; 1998 } 1999 /* "lookahead" for better eviction candidate */ 2000 if (recycle && ab->b_size != bytes && 2001 ab_prev && ab_prev->b_size == bytes) 2002 continue; 2003 2004 /* ignore markers */ 2005 if (ab->b_spa == 0) 2006 continue; 2007 2008 /* 2009 * It may take a long time to evict all the bufs requested. 2010 * To avoid blocking all arc activity, periodically drop 2011 * the arcs_mtx and give other threads a chance to run 2012 * before reacquiring the lock. 2013 * 2014 * If we are looking for a buffer to recycle, we are in 2015 * the hot code path, so don't sleep. 2016 */ 2017 if (!recycle && count++ > arc_evict_iterations) { 2018 list_insert_after(list, ab, &marker); 2019 mutex_exit(evicted_lock); 2020 mutex_exit(lock); 2021 kpreempt(KPREEMPT_SYNC); 2022 mutex_enter(lock); 2023 mutex_enter(evicted_lock); 2024 ab_prev = list_prev(list, &marker); 2025 list_remove(list, &marker); 2026 count = 0; 2027 continue; 2028 } 2029 2030 hash_lock = HDR_LOCK(ab); 2031 have_lock = MUTEX_HELD(hash_lock); 2032 if (have_lock || mutex_tryenter(hash_lock)) { 2033 ASSERT0(refcount_count(&ab->b_refcnt)); 2034 ASSERT(ab->b_datacnt > 0); 2035 while (ab->b_buf) { 2036 arc_buf_t *buf = ab->b_buf; 2037 if (!mutex_tryenter(&buf->b_evict_lock)) { 2038 missed += 1; 2039 break; 2040 } 2041 if (buf->b_data) { 2042 bytes_evicted += ab->b_size; 2043 if (recycle && ab->b_type == type && 2044 ab->b_size == bytes && 2045 !HDR_L2_WRITING(ab)) { 2046 stolen = buf->b_data; 2047 recycle = FALSE; 2048 } 2049 } 2050 if (buf->b_efunc) { 2051 mutex_enter(&arc_eviction_mtx); 2052 arc_buf_destroy(buf, 2053 buf->b_data == stolen, FALSE); 2054 ab->b_buf = buf->b_next; 2055 buf->b_hdr = &arc_eviction_hdr; 2056 buf->b_next = arc_eviction_list; 2057 arc_eviction_list = buf; 2058 mutex_exit(&arc_eviction_mtx); 2059 mutex_exit(&buf->b_evict_lock); 2060 } else { 2061 mutex_exit(&buf->b_evict_lock); 2062 arc_buf_destroy(buf, 2063 buf->b_data == stolen, TRUE); 2064 } 2065 } 2066 2067 if (ab->b_l2hdr) { 2068 ARCSTAT_INCR(arcstat_evict_l2_cached, 2069 ab->b_size); 2070 } else { 2071 if (l2arc_write_eligible(ab->b_spa, ab)) { 2072 ARCSTAT_INCR(arcstat_evict_l2_eligible, 2073 ab->b_size); 2074 } else { 2075 ARCSTAT_INCR( 2076 arcstat_evict_l2_ineligible, 2077 ab->b_size); 2078 } 2079 } 2080 2081 if (ab->b_datacnt == 0) { 2082 arc_change_state(evicted_state, ab, hash_lock); 2083 ASSERT(HDR_IN_HASH_TABLE(ab)); 2084 ab->b_flags |= ARC_IN_HASH_TABLE; 2085 ab->b_flags &= ~ARC_BUF_AVAILABLE; 2086 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab); 2087 } 2088 if (!have_lock) 2089 mutex_exit(hash_lock); 2090 if (bytes >= 0 && bytes_evicted >= bytes) 2091 break; 2092 if (bytes_remaining > 0) { 2093 mutex_exit(evicted_lock); 2094 mutex_exit(lock); 2095 idx = ((idx + 1) & (list_count - 1)); 2096 lists++; 2097 goto evict_start; 2098 } 2099 } else { 2100 missed += 1; 2101 } 2102 } 2103 2104 mutex_exit(evicted_lock); 2105 mutex_exit(lock); 2106 2107 idx = ((idx + 1) & (list_count - 1)); 2108 lists++; 2109 2110 if (bytes_evicted < bytes) { 2111 if (lists < list_count) 2112 goto evict_start; 2113 else 2114 dprintf("only evicted %lld bytes from %x", 2115 (longlong_t)bytes_evicted, state); 2116 } 2117 if (type == ARC_BUFC_METADATA) 2118 evict_metadata_offset = idx; 2119 else 2120 evict_data_offset = idx; 2121 2122 if (skipped) 2123 ARCSTAT_INCR(arcstat_evict_skip, skipped); 2124 2125 if (missed) 2126 ARCSTAT_INCR(arcstat_mutex_miss, missed); 2127 2128 /* 2129 * Note: we have just evicted some data into the ghost state, 2130 * potentially putting the ghost size over the desired size. Rather 2131 * that evicting from the ghost list in this hot code path, leave 2132 * this chore to the arc_reclaim_thread(). 2133 */ 2134 2135 if (stolen) 2136 ARCSTAT_BUMP(arcstat_stolen); 2137 return (stolen); 2138} 2139 2140/* 2141 * Remove buffers from list until we've removed the specified number of 2142 * bytes. Destroy the buffers that are removed. 2143 */ 2144static void 2145arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 2146{ 2147 arc_buf_hdr_t *ab, *ab_prev; 2148 arc_buf_hdr_t marker = { 0 }; 2149 list_t *list, *list_start; 2150 kmutex_t *hash_lock, *lock; 2151 uint64_t bytes_deleted = 0; 2152 uint64_t bufs_skipped = 0; 2153 int count = 0; 2154 static int evict_offset; 2155 int list_count, idx = evict_offset; 2156 int offset, lists = 0; 2157 2158 ASSERT(GHOST_STATE(state)); 2159 2160 /* 2161 * data lists come after metadata lists 2162 */ 2163 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS]; 2164 list_count = ARC_BUFC_NUMDATALISTS; 2165 offset = ARC_BUFC_NUMMETADATALISTS; 2166 2167evict_start: 2168 list = &list_start[idx]; 2169 lock = ARCS_LOCK(state, idx + offset); 2170 2171 mutex_enter(lock); 2172 for (ab = list_tail(list); ab; ab = ab_prev) { 2173 ab_prev = list_prev(list, ab); 2174 if (ab->b_type > ARC_BUFC_NUMTYPES) 2175 panic("invalid ab=%p", (void *)ab); 2176 if (spa && ab->b_spa != spa) 2177 continue; 2178 2179 /* ignore markers */ 2180 if (ab->b_spa == 0) 2181 continue; 2182 2183 hash_lock = HDR_LOCK(ab); 2184 /* caller may be trying to modify this buffer, skip it */ 2185 if (MUTEX_HELD(hash_lock)) 2186 continue; 2187 2188 /* 2189 * It may take a long time to evict all the bufs requested. 2190 * To avoid blocking all arc activity, periodically drop 2191 * the arcs_mtx and give other threads a chance to run 2192 * before reacquiring the lock. 2193 */ 2194 if (count++ > arc_evict_iterations) { 2195 list_insert_after(list, ab, &marker); 2196 mutex_exit(lock); 2197 kpreempt(KPREEMPT_SYNC); 2198 mutex_enter(lock); 2199 ab_prev = list_prev(list, &marker); 2200 list_remove(list, &marker); 2201 count = 0; 2202 continue; 2203 } 2204 if (mutex_tryenter(hash_lock)) { 2205 ASSERT(!HDR_IO_IN_PROGRESS(ab)); 2206 ASSERT(ab->b_buf == NULL); 2207 ARCSTAT_BUMP(arcstat_deleted); 2208 bytes_deleted += ab->b_size; 2209 2210 if (ab->b_l2hdr != NULL) { 2211 /* 2212 * This buffer is cached on the 2nd Level ARC; 2213 * don't destroy the header. 2214 */ 2215 arc_change_state(arc_l2c_only, ab, hash_lock); 2216 mutex_exit(hash_lock); 2217 } else { 2218 arc_change_state(arc_anon, ab, hash_lock); 2219 mutex_exit(hash_lock); 2220 arc_hdr_destroy(ab); 2221 } 2222 2223 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab); 2224 if (bytes >= 0 && bytes_deleted >= bytes) 2225 break; 2226 } else if (bytes < 0) { 2227 /* 2228 * Insert a list marker and then wait for the 2229 * hash lock to become available. Once its 2230 * available, restart from where we left off. 2231 */ 2232 list_insert_after(list, ab, &marker); 2233 mutex_exit(lock); 2234 mutex_enter(hash_lock); 2235 mutex_exit(hash_lock); 2236 mutex_enter(lock); 2237 ab_prev = list_prev(list, &marker); 2238 list_remove(list, &marker); 2239 } else { 2240 bufs_skipped += 1; 2241 } 2242 2243 } 2244 mutex_exit(lock); 2245 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1)); 2246 lists++; 2247 2248 if (lists < list_count) 2249 goto evict_start; 2250 2251 evict_offset = idx; 2252 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] && 2253 (bytes < 0 || bytes_deleted < bytes)) { 2254 list_start = &state->arcs_lists[0]; 2255 list_count = ARC_BUFC_NUMMETADATALISTS; 2256 offset = lists = 0; 2257 goto evict_start; 2258 } 2259 2260 if (bufs_skipped) { 2261 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2262 ASSERT(bytes >= 0); 2263 } 2264 2265 if (bytes_deleted < bytes) 2266 dprintf("only deleted %lld bytes from %p", 2267 (longlong_t)bytes_deleted, state); 2268} 2269 2270static void 2271arc_adjust(void) 2272{ 2273 int64_t adjustment, delta; 2274 2275 /* 2276 * Adjust MRU size 2277 */ 2278 2279 adjustment = MIN((int64_t)(arc_size - arc_c), 2280 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2281 arc_p)); 2282 2283 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2284 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2285 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA); 2286 adjustment -= delta; 2287 } 2288 2289 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2290 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2291 (void) arc_evict(arc_mru, 0, delta, FALSE, 2292 ARC_BUFC_METADATA); 2293 } 2294 2295 /* 2296 * Adjust MFU size 2297 */ 2298 2299 adjustment = arc_size - arc_c; 2300 2301 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2302 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2303 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA); 2304 adjustment -= delta; 2305 } 2306 2307 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2308 int64_t delta = MIN(adjustment, 2309 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2310 (void) arc_evict(arc_mfu, 0, delta, FALSE, 2311 ARC_BUFC_METADATA); 2312 } 2313 2314 /* 2315 * Adjust ghost lists 2316 */ 2317 2318 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2319 2320 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2321 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2322 arc_evict_ghost(arc_mru_ghost, 0, delta); 2323 } 2324 2325 adjustment = 2326 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2327 2328 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2329 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2330 arc_evict_ghost(arc_mfu_ghost, 0, delta); 2331 } 2332} 2333 2334static void 2335arc_do_user_evicts(void) 2336{ 2337 static arc_buf_t *tmp_arc_eviction_list; 2338 2339 /* 2340 * Move list over to avoid LOR 2341 */ 2342restart: 2343 mutex_enter(&arc_eviction_mtx); 2344 tmp_arc_eviction_list = arc_eviction_list; 2345 arc_eviction_list = NULL; 2346 mutex_exit(&arc_eviction_mtx); 2347 2348 while (tmp_arc_eviction_list != NULL) { 2349 arc_buf_t *buf = tmp_arc_eviction_list; 2350 tmp_arc_eviction_list = buf->b_next; 2351 mutex_enter(&buf->b_evict_lock); 2352 buf->b_hdr = NULL; 2353 mutex_exit(&buf->b_evict_lock); 2354 2355 if (buf->b_efunc != NULL) 2356 VERIFY(buf->b_efunc(buf) == 0); 2357 2358 buf->b_efunc = NULL; 2359 buf->b_private = NULL; 2360 kmem_cache_free(buf_cache, buf); 2361 } 2362 2363 if (arc_eviction_list != NULL) 2364 goto restart; 2365} 2366 2367/* 2368 * Flush all *evictable* data from the cache for the given spa. 2369 * NOTE: this will not touch "active" (i.e. referenced) data. 2370 */ 2371void 2372arc_flush(spa_t *spa) 2373{ 2374 uint64_t guid = 0; 2375 2376 if (spa) 2377 guid = spa_load_guid(spa); 2378 2379 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) { 2380 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2381 if (spa) 2382 break; 2383 } 2384 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) { 2385 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2386 if (spa) 2387 break; 2388 } 2389 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) { 2390 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2391 if (spa) 2392 break; 2393 } 2394 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) { 2395 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2396 if (spa) 2397 break; 2398 } 2399 2400 arc_evict_ghost(arc_mru_ghost, guid, -1); 2401 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2402 2403 mutex_enter(&arc_reclaim_thr_lock); 2404 arc_do_user_evicts(); 2405 mutex_exit(&arc_reclaim_thr_lock); 2406 ASSERT(spa || arc_eviction_list == NULL); 2407} 2408 2409void 2410arc_shrink(void) 2411{ 2412 if (arc_c > arc_c_min) { 2413 uint64_t to_free; 2414 2415#ifdef _KERNEL 2416 to_free = arc_c >> arc_shrink_shift; 2417#else 2418 to_free = arc_c >> arc_shrink_shift; 2419#endif 2420 if (arc_c > arc_c_min + to_free) 2421 atomic_add_64(&arc_c, -to_free); 2422 else 2423 arc_c = arc_c_min; 2424 2425 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2426 if (arc_c > arc_size) 2427 arc_c = MAX(arc_size, arc_c_min); 2428 if (arc_p > arc_c) 2429 arc_p = (arc_c >> 1); 2430 ASSERT(arc_c >= arc_c_min); 2431 ASSERT((int64_t)arc_p >= 0); 2432 } 2433 2434 if (arc_size > arc_c) 2435 arc_adjust(); 2436} 2437 2438static int needfree = 0; 2439 2440static int 2441arc_reclaim_needed(void) 2442{ 2443 2444#ifdef _KERNEL 2445 2446 if (needfree) 2447 return (1); 2448 2449 /* 2450 * Cooperate with pagedaemon when it's time for it to scan 2451 * and reclaim some pages. 2452 */ 2453 if (vm_paging_needed()) 2454 return (1); 2455 2456#ifdef sun 2457 /* 2458 * take 'desfree' extra pages, so we reclaim sooner, rather than later 2459 */ 2460 extra = desfree; 2461 2462 /* 2463 * check that we're out of range of the pageout scanner. It starts to 2464 * schedule paging if freemem is less than lotsfree and needfree. 2465 * lotsfree is the high-water mark for pageout, and needfree is the 2466 * number of needed free pages. We add extra pages here to make sure 2467 * the scanner doesn't start up while we're freeing memory. 2468 */ 2469 if (freemem < lotsfree + needfree + extra) 2470 return (1); 2471 2472 /* 2473 * check to make sure that swapfs has enough space so that anon 2474 * reservations can still succeed. anon_resvmem() checks that the 2475 * availrmem is greater than swapfs_minfree, and the number of reserved 2476 * swap pages. We also add a bit of extra here just to prevent 2477 * circumstances from getting really dire. 2478 */ 2479 if (availrmem < swapfs_minfree + swapfs_reserve + extra) 2480 return (1); 2481 2482#if defined(__i386) 2483 /* 2484 * If we're on an i386 platform, it's possible that we'll exhaust the 2485 * kernel heap space before we ever run out of available physical 2486 * memory. Most checks of the size of the heap_area compare against 2487 * tune.t_minarmem, which is the minimum available real memory that we 2488 * can have in the system. However, this is generally fixed at 25 pages 2489 * which is so low that it's useless. In this comparison, we seek to 2490 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2491 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2492 * free) 2493 */ 2494 if (btop(vmem_size(heap_arena, VMEM_FREE)) < 2495 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2)) 2496 return (1); 2497#endif 2498#else /* !sun */ 2499 if (kmem_used() > (kmem_size() * 3) / 4) 2500 return (1); 2501#endif /* sun */ 2502 2503#else 2504 if (spa_get_random(100) == 0) 2505 return (1); 2506#endif 2507 return (0); 2508} 2509 2510extern kmem_cache_t *zio_buf_cache[]; 2511extern kmem_cache_t *zio_data_buf_cache[]; 2512 2513static void 2514arc_kmem_reap_now(arc_reclaim_strategy_t strat) 2515{ 2516 size_t i; 2517 kmem_cache_t *prev_cache = NULL; 2518 kmem_cache_t *prev_data_cache = NULL; 2519 2520#ifdef _KERNEL 2521 if (arc_meta_used >= arc_meta_limit) { 2522 /* 2523 * We are exceeding our meta-data cache limit. 2524 * Purge some DNLC entries to release holds on meta-data. 2525 */ 2526 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2527 } 2528#if defined(__i386) 2529 /* 2530 * Reclaim unused memory from all kmem caches. 2531 */ 2532 kmem_reap(); 2533#endif 2534#endif 2535 2536 /* 2537 * An aggressive reclamation will shrink the cache size as well as 2538 * reap free buffers from the arc kmem caches. 2539 */ 2540 if (strat == ARC_RECLAIM_AGGR) 2541 arc_shrink(); 2542 2543 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2544 if (zio_buf_cache[i] != prev_cache) { 2545 prev_cache = zio_buf_cache[i]; 2546 kmem_cache_reap_now(zio_buf_cache[i]); 2547 } 2548 if (zio_data_buf_cache[i] != prev_data_cache) { 2549 prev_data_cache = zio_data_buf_cache[i]; 2550 kmem_cache_reap_now(zio_data_buf_cache[i]); 2551 } 2552 } 2553 kmem_cache_reap_now(buf_cache); 2554 kmem_cache_reap_now(hdr_cache); 2555} 2556 2557static void 2558arc_reclaim_thread(void *dummy __unused) 2559{ 2560 clock_t growtime = 0; 2561 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS; 2562 callb_cpr_t cpr; 2563 2564 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2565 2566 mutex_enter(&arc_reclaim_thr_lock); 2567 while (arc_thread_exit == 0) { 2568 if (arc_reclaim_needed()) { 2569 2570 if (arc_no_grow) { 2571 if (last_reclaim == ARC_RECLAIM_CONS) { 2572 last_reclaim = ARC_RECLAIM_AGGR; 2573 } else { 2574 last_reclaim = ARC_RECLAIM_CONS; 2575 } 2576 } else { 2577 arc_no_grow = TRUE; 2578 last_reclaim = ARC_RECLAIM_AGGR; 2579 membar_producer(); 2580 } 2581 2582 /* reset the growth delay for every reclaim */ 2583 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2584 2585 if (needfree && last_reclaim == ARC_RECLAIM_CONS) { 2586 /* 2587 * If needfree is TRUE our vm_lowmem hook 2588 * was called and in that case we must free some 2589 * memory, so switch to aggressive mode. 2590 */ 2591 arc_no_grow = TRUE; 2592 last_reclaim = ARC_RECLAIM_AGGR; 2593 } 2594 arc_kmem_reap_now(last_reclaim); 2595 arc_warm = B_TRUE; 2596 2597 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { 2598 arc_no_grow = FALSE; 2599 } 2600 2601 arc_adjust(); 2602 2603 if (arc_eviction_list != NULL) 2604 arc_do_user_evicts(); 2605 2606#ifdef _KERNEL 2607 if (needfree) { 2608 needfree = 0; 2609 wakeup(&needfree); 2610 } 2611#endif 2612 2613 /* block until needed, or one second, whichever is shorter */ 2614 CALLB_CPR_SAFE_BEGIN(&cpr); 2615 (void) cv_timedwait(&arc_reclaim_thr_cv, 2616 &arc_reclaim_thr_lock, hz); 2617 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2618 } 2619 2620 arc_thread_exit = 0; 2621 cv_broadcast(&arc_reclaim_thr_cv); 2622 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2623 thread_exit(); 2624} 2625 2626/* 2627 * Adapt arc info given the number of bytes we are trying to add and 2628 * the state that we are comming from. This function is only called 2629 * when we are adding new content to the cache. 2630 */ 2631static void 2632arc_adapt(int bytes, arc_state_t *state) 2633{ 2634 int mult; 2635 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2636 2637 if (state == arc_l2c_only) 2638 return; 2639 2640 ASSERT(bytes > 0); 2641 /* 2642 * Adapt the target size of the MRU list: 2643 * - if we just hit in the MRU ghost list, then increase 2644 * the target size of the MRU list. 2645 * - if we just hit in the MFU ghost list, then increase 2646 * the target size of the MFU list by decreasing the 2647 * target size of the MRU list. 2648 */ 2649 if (state == arc_mru_ghost) { 2650 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2651 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2652 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2653 2654 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2655 } else if (state == arc_mfu_ghost) { 2656 uint64_t delta; 2657 2658 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2659 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2660 mult = MIN(mult, 10); 2661 2662 delta = MIN(bytes * mult, arc_p); 2663 arc_p = MAX(arc_p_min, arc_p - delta); 2664 } 2665 ASSERT((int64_t)arc_p >= 0); 2666 2667 if (arc_reclaim_needed()) { 2668 cv_signal(&arc_reclaim_thr_cv); 2669 return; 2670 } 2671 2672 if (arc_no_grow) 2673 return; 2674 2675 if (arc_c >= arc_c_max) 2676 return; 2677 2678 /* 2679 * If we're within (2 * maxblocksize) bytes of the target 2680 * cache size, increment the target cache size 2681 */ 2682 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2683 atomic_add_64(&arc_c, (int64_t)bytes); 2684 if (arc_c > arc_c_max) 2685 arc_c = arc_c_max; 2686 else if (state == arc_anon) 2687 atomic_add_64(&arc_p, (int64_t)bytes); 2688 if (arc_p > arc_c) 2689 arc_p = arc_c; 2690 } 2691 ASSERT((int64_t)arc_p >= 0); 2692} 2693 2694/* 2695 * Check if the cache has reached its limits and eviction is required 2696 * prior to insert. 2697 */ 2698static int 2699arc_evict_needed(arc_buf_contents_t type) 2700{ 2701 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 2702 return (1); 2703 2704#ifdef sun 2705#ifdef _KERNEL 2706 /* 2707 * If zio data pages are being allocated out of a separate heap segment, 2708 * then enforce that the size of available vmem for this area remains 2709 * above about 1/32nd free. 2710 */ 2711 if (type == ARC_BUFC_DATA && zio_arena != NULL && 2712 vmem_size(zio_arena, VMEM_FREE) < 2713 (vmem_size(zio_arena, VMEM_ALLOC) >> 5)) 2714 return (1); 2715#endif 2716#endif /* sun */ 2717 2718 if (arc_reclaim_needed()) 2719 return (1); 2720 2721 return (arc_size > arc_c); 2722} 2723 2724/* 2725 * The buffer, supplied as the first argument, needs a data block. 2726 * So, if we are at cache max, determine which cache should be victimized. 2727 * We have the following cases: 2728 * 2729 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 2730 * In this situation if we're out of space, but the resident size of the MFU is 2731 * under the limit, victimize the MFU cache to satisfy this insertion request. 2732 * 2733 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 2734 * Here, we've used up all of the available space for the MRU, so we need to 2735 * evict from our own cache instead. Evict from the set of resident MRU 2736 * entries. 2737 * 2738 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 2739 * c minus p represents the MFU space in the cache, since p is the size of the 2740 * cache that is dedicated to the MRU. In this situation there's still space on 2741 * the MFU side, so the MRU side needs to be victimized. 2742 * 2743 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 2744 * MFU's resident set is consuming more space than it has been allotted. In 2745 * this situation, we must victimize our own cache, the MFU, for this insertion. 2746 */ 2747static void 2748arc_get_data_buf(arc_buf_t *buf) 2749{ 2750 arc_state_t *state = buf->b_hdr->b_state; 2751 uint64_t size = buf->b_hdr->b_size; 2752 arc_buf_contents_t type = buf->b_hdr->b_type; 2753 2754 arc_adapt(size, state); 2755 2756 /* 2757 * We have not yet reached cache maximum size, 2758 * just allocate a new buffer. 2759 */ 2760 if (!arc_evict_needed(type)) { 2761 if (type == ARC_BUFC_METADATA) { 2762 buf->b_data = zio_buf_alloc(size); 2763 arc_space_consume(size, ARC_SPACE_DATA); 2764 } else { 2765 ASSERT(type == ARC_BUFC_DATA); 2766 buf->b_data = zio_data_buf_alloc(size); 2767 ARCSTAT_INCR(arcstat_data_size, size); 2768 atomic_add_64(&arc_size, size); 2769 } 2770 goto out; 2771 } 2772 2773 /* 2774 * If we are prefetching from the mfu ghost list, this buffer 2775 * will end up on the mru list; so steal space from there. 2776 */ 2777 if (state == arc_mfu_ghost) 2778 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu; 2779 else if (state == arc_mru_ghost) 2780 state = arc_mru; 2781 2782 if (state == arc_mru || state == arc_anon) { 2783 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 2784 state = (arc_mfu->arcs_lsize[type] >= size && 2785 arc_p > mru_used) ? arc_mfu : arc_mru; 2786 } else { 2787 /* MFU cases */ 2788 uint64_t mfu_space = arc_c - arc_p; 2789 state = (arc_mru->arcs_lsize[type] >= size && 2790 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 2791 } 2792 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) { 2793 if (type == ARC_BUFC_METADATA) { 2794 buf->b_data = zio_buf_alloc(size); 2795 arc_space_consume(size, ARC_SPACE_DATA); 2796 } else { 2797 ASSERT(type == ARC_BUFC_DATA); 2798 buf->b_data = zio_data_buf_alloc(size); 2799 ARCSTAT_INCR(arcstat_data_size, size); 2800 atomic_add_64(&arc_size, size); 2801 } 2802 ARCSTAT_BUMP(arcstat_recycle_miss); 2803 } 2804 ASSERT(buf->b_data != NULL); 2805out: 2806 /* 2807 * Update the state size. Note that ghost states have a 2808 * "ghost size" and so don't need to be updated. 2809 */ 2810 if (!GHOST_STATE(buf->b_hdr->b_state)) { 2811 arc_buf_hdr_t *hdr = buf->b_hdr; 2812 2813 atomic_add_64(&hdr->b_state->arcs_size, size); 2814 if (list_link_active(&hdr->b_arc_node)) { 2815 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 2816 atomic_add_64(&hdr->b_state->arcs_lsize[type], size); 2817 } 2818 /* 2819 * If we are growing the cache, and we are adding anonymous 2820 * data, and we have outgrown arc_p, update arc_p 2821 */ 2822 if (arc_size < arc_c && hdr->b_state == arc_anon && 2823 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 2824 arc_p = MIN(arc_c, arc_p + size); 2825 } 2826 ARCSTAT_BUMP(arcstat_allocated); 2827} 2828 2829/* 2830 * This routine is called whenever a buffer is accessed. 2831 * NOTE: the hash lock is dropped in this function. 2832 */ 2833static void 2834arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock) 2835{ 2836 clock_t now; 2837 2838 ASSERT(MUTEX_HELD(hash_lock)); 2839 2840 if (buf->b_state == arc_anon) { 2841 /* 2842 * This buffer is not in the cache, and does not 2843 * appear in our "ghost" list. Add the new buffer 2844 * to the MRU state. 2845 */ 2846 2847 ASSERT(buf->b_arc_access == 0); 2848 buf->b_arc_access = ddi_get_lbolt(); 2849 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2850 arc_change_state(arc_mru, buf, hash_lock); 2851 2852 } else if (buf->b_state == arc_mru) { 2853 now = ddi_get_lbolt(); 2854 2855 /* 2856 * If this buffer is here because of a prefetch, then either: 2857 * - clear the flag if this is a "referencing" read 2858 * (any subsequent access will bump this into the MFU state). 2859 * or 2860 * - move the buffer to the head of the list if this is 2861 * another prefetch (to make it less likely to be evicted). 2862 */ 2863 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2864 if (refcount_count(&buf->b_refcnt) == 0) { 2865 ASSERT(list_link_active(&buf->b_arc_node)); 2866 } else { 2867 buf->b_flags &= ~ARC_PREFETCH; 2868 ARCSTAT_BUMP(arcstat_mru_hits); 2869 } 2870 buf->b_arc_access = now; 2871 return; 2872 } 2873 2874 /* 2875 * This buffer has been "accessed" only once so far, 2876 * but it is still in the cache. Move it to the MFU 2877 * state. 2878 */ 2879 if (now > buf->b_arc_access + ARC_MINTIME) { 2880 /* 2881 * More than 125ms have passed since we 2882 * instantiated this buffer. Move it to the 2883 * most frequently used state. 2884 */ 2885 buf->b_arc_access = now; 2886 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2887 arc_change_state(arc_mfu, buf, hash_lock); 2888 } 2889 ARCSTAT_BUMP(arcstat_mru_hits); 2890 } else if (buf->b_state == arc_mru_ghost) { 2891 arc_state_t *new_state; 2892 /* 2893 * This buffer has been "accessed" recently, but 2894 * was evicted from the cache. Move it to the 2895 * MFU state. 2896 */ 2897 2898 if (buf->b_flags & ARC_PREFETCH) { 2899 new_state = arc_mru; 2900 if (refcount_count(&buf->b_refcnt) > 0) 2901 buf->b_flags &= ~ARC_PREFETCH; 2902 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2903 } else { 2904 new_state = arc_mfu; 2905 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2906 } 2907 2908 buf->b_arc_access = ddi_get_lbolt(); 2909 arc_change_state(new_state, buf, hash_lock); 2910 2911 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 2912 } else if (buf->b_state == arc_mfu) { 2913 /* 2914 * This buffer has been accessed more than once and is 2915 * still in the cache. Keep it in the MFU state. 2916 * 2917 * NOTE: an add_reference() that occurred when we did 2918 * the arc_read() will have kicked this off the list. 2919 * If it was a prefetch, we will explicitly move it to 2920 * the head of the list now. 2921 */ 2922 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2923 ASSERT(refcount_count(&buf->b_refcnt) == 0); 2924 ASSERT(list_link_active(&buf->b_arc_node)); 2925 } 2926 ARCSTAT_BUMP(arcstat_mfu_hits); 2927 buf->b_arc_access = ddi_get_lbolt(); 2928 } else if (buf->b_state == arc_mfu_ghost) { 2929 arc_state_t *new_state = arc_mfu; 2930 /* 2931 * This buffer has been accessed more than once but has 2932 * been evicted from the cache. Move it back to the 2933 * MFU state. 2934 */ 2935 2936 if (buf->b_flags & ARC_PREFETCH) { 2937 /* 2938 * This is a prefetch access... 2939 * move this block back to the MRU state. 2940 */ 2941 ASSERT0(refcount_count(&buf->b_refcnt)); 2942 new_state = arc_mru; 2943 } 2944 2945 buf->b_arc_access = ddi_get_lbolt(); 2946 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2947 arc_change_state(new_state, buf, hash_lock); 2948 2949 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 2950 } else if (buf->b_state == arc_l2c_only) { 2951 /* 2952 * This buffer is on the 2nd Level ARC. 2953 */ 2954 2955 buf->b_arc_access = ddi_get_lbolt(); 2956 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2957 arc_change_state(arc_mfu, buf, hash_lock); 2958 } else { 2959 ASSERT(!"invalid arc state"); 2960 } 2961} 2962 2963/* a generic arc_done_func_t which you can use */ 2964/* ARGSUSED */ 2965void 2966arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 2967{ 2968 if (zio == NULL || zio->io_error == 0) 2969 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 2970 VERIFY(arc_buf_remove_ref(buf, arg)); 2971} 2972 2973/* a generic arc_done_func_t */ 2974void 2975arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 2976{ 2977 arc_buf_t **bufp = arg; 2978 if (zio && zio->io_error) { 2979 VERIFY(arc_buf_remove_ref(buf, arg)); 2980 *bufp = NULL; 2981 } else { 2982 *bufp = buf; 2983 ASSERT(buf->b_data); 2984 } 2985} 2986 2987static void 2988arc_read_done(zio_t *zio) 2989{ 2990 arc_buf_hdr_t *hdr; 2991 arc_buf_t *buf; 2992 arc_buf_t *abuf; /* buffer we're assigning to callback */ 2993 kmutex_t *hash_lock = NULL; 2994 arc_callback_t *callback_list, *acb; 2995 int freeable = FALSE; 2996 2997 buf = zio->io_private; 2998 hdr = buf->b_hdr; 2999 3000 /* 3001 * The hdr was inserted into hash-table and removed from lists 3002 * prior to starting I/O. We should find this header, since 3003 * it's in the hash table, and it should be legit since it's 3004 * not possible to evict it during the I/O. The only possible 3005 * reason for it not to be found is if we were freed during the 3006 * read. 3007 */ 3008 if (HDR_IN_HASH_TABLE(hdr)) { 3009 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3010 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3011 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3012 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3013 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3014 3015 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3016 &hash_lock); 3017 3018 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3019 hash_lock == NULL) || 3020 (found == hdr && 3021 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3022 (found == hdr && HDR_L2_READING(hdr))); 3023 } 3024 3025 hdr->b_flags &= ~ARC_L2_EVICTED; 3026 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH)) 3027 hdr->b_flags &= ~ARC_L2CACHE; 3028 3029 /* byteswap if necessary */ 3030 callback_list = hdr->b_acb; 3031 ASSERT(callback_list != NULL); 3032 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3033 dmu_object_byteswap_t bswap = 3034 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3035 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3036 byteswap_uint64_array : 3037 dmu_ot_byteswap[bswap].ob_func; 3038 func(buf->b_data, hdr->b_size); 3039 } 3040 3041 arc_cksum_compute(buf, B_FALSE); 3042#ifdef illumos 3043 arc_buf_watch(buf); 3044#endif /* illumos */ 3045 3046 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) { 3047 /* 3048 * Only call arc_access on anonymous buffers. This is because 3049 * if we've issued an I/O for an evicted buffer, we've already 3050 * called arc_access (to prevent any simultaneous readers from 3051 * getting confused). 3052 */ 3053 arc_access(hdr, hash_lock); 3054 } 3055 3056 /* create copies of the data buffer for the callers */ 3057 abuf = buf; 3058 for (acb = callback_list; acb; acb = acb->acb_next) { 3059 if (acb->acb_done) { 3060 if (abuf == NULL) { 3061 ARCSTAT_BUMP(arcstat_duplicate_reads); 3062 abuf = arc_buf_clone(buf); 3063 } 3064 acb->acb_buf = abuf; 3065 abuf = NULL; 3066 } 3067 } 3068 hdr->b_acb = NULL; 3069 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3070 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3071 if (abuf == buf) { 3072 ASSERT(buf->b_efunc == NULL); 3073 ASSERT(hdr->b_datacnt == 1); 3074 hdr->b_flags |= ARC_BUF_AVAILABLE; 3075 } 3076 3077 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL); 3078 3079 if (zio->io_error != 0) { 3080 hdr->b_flags |= ARC_IO_ERROR; 3081 if (hdr->b_state != arc_anon) 3082 arc_change_state(arc_anon, hdr, hash_lock); 3083 if (HDR_IN_HASH_TABLE(hdr)) 3084 buf_hash_remove(hdr); 3085 freeable = refcount_is_zero(&hdr->b_refcnt); 3086 } 3087 3088 /* 3089 * Broadcast before we drop the hash_lock to avoid the possibility 3090 * that the hdr (and hence the cv) might be freed before we get to 3091 * the cv_broadcast(). 3092 */ 3093 cv_broadcast(&hdr->b_cv); 3094 3095 if (hash_lock) { 3096 mutex_exit(hash_lock); 3097 } else { 3098 /* 3099 * This block was freed while we waited for the read to 3100 * complete. It has been removed from the hash table and 3101 * moved to the anonymous state (so that it won't show up 3102 * in the cache). 3103 */ 3104 ASSERT3P(hdr->b_state, ==, arc_anon); 3105 freeable = refcount_is_zero(&hdr->b_refcnt); 3106 } 3107 3108 /* execute each callback and free its structure */ 3109 while ((acb = callback_list) != NULL) { 3110 if (acb->acb_done) 3111 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3112 3113 if (acb->acb_zio_dummy != NULL) { 3114 acb->acb_zio_dummy->io_error = zio->io_error; 3115 zio_nowait(acb->acb_zio_dummy); 3116 } 3117 3118 callback_list = acb->acb_next; 3119 kmem_free(acb, sizeof (arc_callback_t)); 3120 } 3121 3122 if (freeable) 3123 arc_hdr_destroy(hdr); 3124} 3125 3126/* 3127 * "Read" the block block at the specified DVA (in bp) via the 3128 * cache. If the block is found in the cache, invoke the provided 3129 * callback immediately and return. Note that the `zio' parameter 3130 * in the callback will be NULL in this case, since no IO was 3131 * required. If the block is not in the cache pass the read request 3132 * on to the spa with a substitute callback function, so that the 3133 * requested block will be added to the cache. 3134 * 3135 * If a read request arrives for a block that has a read in-progress, 3136 * either wait for the in-progress read to complete (and return the 3137 * results); or, if this is a read with a "done" func, add a record 3138 * to the read to invoke the "done" func when the read completes, 3139 * and return; or just return. 3140 * 3141 * arc_read_done() will invoke all the requested "done" functions 3142 * for readers of this block. 3143 */ 3144int 3145arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3146 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
|
3147 const zbookmark_t *zb)
|
3147 const zbookmark_phys_t *zb) |
3148{ 3149 arc_buf_hdr_t *hdr = NULL; 3150 arc_buf_t *buf = NULL; 3151 kmutex_t *hash_lock = NULL; 3152 zio_t *rzio; 3153 uint64_t guid = spa_load_guid(spa); 3154 3155 ASSERT(!BP_IS_EMBEDDED(bp) || 3156 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3157 3158top: 3159 if (!BP_IS_EMBEDDED(bp)) { 3160 /* 3161 * Embedded BP's have no DVA and require no I/O to "read". 3162 * Create an anonymous arc buf to back it. 3163 */ 3164 hdr = buf_hash_find(guid, bp, &hash_lock); 3165 } 3166 3167 if (hdr != NULL && hdr->b_datacnt > 0) { 3168 3169 *arc_flags |= ARC_CACHED; 3170 3171 if (HDR_IO_IN_PROGRESS(hdr)) { 3172 3173 if (*arc_flags & ARC_WAIT) { 3174 cv_wait(&hdr->b_cv, hash_lock); 3175 mutex_exit(hash_lock); 3176 goto top; 3177 } 3178 ASSERT(*arc_flags & ARC_NOWAIT); 3179 3180 if (done) { 3181 arc_callback_t *acb = NULL; 3182 3183 acb = kmem_zalloc(sizeof (arc_callback_t), 3184 KM_SLEEP); 3185 acb->acb_done = done; 3186 acb->acb_private = private; 3187 if (pio != NULL) 3188 acb->acb_zio_dummy = zio_null(pio, 3189 spa, NULL, NULL, NULL, zio_flags); 3190 3191 ASSERT(acb->acb_done != NULL); 3192 acb->acb_next = hdr->b_acb; 3193 hdr->b_acb = acb; 3194 add_reference(hdr, hash_lock, private); 3195 mutex_exit(hash_lock); 3196 return (0); 3197 } 3198 mutex_exit(hash_lock); 3199 return (0); 3200 } 3201 3202 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3203 3204 if (done) { 3205 add_reference(hdr, hash_lock, private); 3206 /* 3207 * If this block is already in use, create a new 3208 * copy of the data so that we will be guaranteed 3209 * that arc_release() will always succeed. 3210 */ 3211 buf = hdr->b_buf; 3212 ASSERT(buf); 3213 ASSERT(buf->b_data); 3214 if (HDR_BUF_AVAILABLE(hdr)) { 3215 ASSERT(buf->b_efunc == NULL); 3216 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3217 } else { 3218 buf = arc_buf_clone(buf); 3219 } 3220 3221 } else if (*arc_flags & ARC_PREFETCH && 3222 refcount_count(&hdr->b_refcnt) == 0) { 3223 hdr->b_flags |= ARC_PREFETCH; 3224 } 3225 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 3226 arc_access(hdr, hash_lock); 3227 if (*arc_flags & ARC_L2CACHE) 3228 hdr->b_flags |= ARC_L2CACHE; 3229 if (*arc_flags & ARC_L2COMPRESS) 3230 hdr->b_flags |= ARC_L2COMPRESS; 3231 mutex_exit(hash_lock); 3232 ARCSTAT_BUMP(arcstat_hits); 3233 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 3234 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3235 data, metadata, hits); 3236 3237 if (done) 3238 done(NULL, buf, private); 3239 } else { 3240 uint64_t size = BP_GET_LSIZE(bp); 3241 arc_callback_t *acb; 3242 vdev_t *vd = NULL; 3243 uint64_t addr = 0; 3244 boolean_t devw = B_FALSE; 3245 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 3246 uint64_t b_asize = 0; 3247 3248 if (hdr == NULL) { 3249 /* this block is not in the cache */ 3250 arc_buf_hdr_t *exists = NULL; 3251 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 3252 buf = arc_buf_alloc(spa, size, private, type); 3253 hdr = buf->b_hdr; 3254 if (!BP_IS_EMBEDDED(bp)) { 3255 hdr->b_dva = *BP_IDENTITY(bp); 3256 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 3257 hdr->b_cksum0 = bp->blk_cksum.zc_word[0]; 3258 exists = buf_hash_insert(hdr, &hash_lock); 3259 } 3260 if (exists != NULL) { 3261 /* somebody beat us to the hash insert */ 3262 mutex_exit(hash_lock); 3263 buf_discard_identity(hdr); 3264 (void) arc_buf_remove_ref(buf, private); 3265 goto top; /* restart the IO request */ 3266 } 3267 /* if this is a prefetch, we don't have a reference */ 3268 if (*arc_flags & ARC_PREFETCH) { 3269 (void) remove_reference(hdr, hash_lock, 3270 private); 3271 hdr->b_flags |= ARC_PREFETCH; 3272 } 3273 if (*arc_flags & ARC_L2CACHE) 3274 hdr->b_flags |= ARC_L2CACHE; 3275 if (*arc_flags & ARC_L2COMPRESS) 3276 hdr->b_flags |= ARC_L2COMPRESS; 3277 if (BP_GET_LEVEL(bp) > 0) 3278 hdr->b_flags |= ARC_INDIRECT; 3279 } else { 3280 /* this block is in the ghost cache */ 3281 ASSERT(GHOST_STATE(hdr->b_state)); 3282 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3283 ASSERT0(refcount_count(&hdr->b_refcnt)); 3284 ASSERT(hdr->b_buf == NULL); 3285 3286 /* if this is a prefetch, we don't have a reference */ 3287 if (*arc_flags & ARC_PREFETCH) 3288 hdr->b_flags |= ARC_PREFETCH; 3289 else 3290 add_reference(hdr, hash_lock, private); 3291 if (*arc_flags & ARC_L2CACHE) 3292 hdr->b_flags |= ARC_L2CACHE; 3293 if (*arc_flags & ARC_L2COMPRESS) 3294 hdr->b_flags |= ARC_L2COMPRESS; 3295 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 3296 buf->b_hdr = hdr; 3297 buf->b_data = NULL; 3298 buf->b_efunc = NULL; 3299 buf->b_private = NULL; 3300 buf->b_next = NULL; 3301 hdr->b_buf = buf; 3302 ASSERT(hdr->b_datacnt == 0); 3303 hdr->b_datacnt = 1; 3304 arc_get_data_buf(buf); 3305 arc_access(hdr, hash_lock); 3306 } 3307 3308 ASSERT(!GHOST_STATE(hdr->b_state)); 3309 3310 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 3311 acb->acb_done = done; 3312 acb->acb_private = private; 3313 3314 ASSERT(hdr->b_acb == NULL); 3315 hdr->b_acb = acb; 3316 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3317 3318 if (hdr->b_l2hdr != NULL && 3319 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) { 3320 devw = hdr->b_l2hdr->b_dev->l2ad_writing; 3321 addr = hdr->b_l2hdr->b_daddr; 3322 b_compress = hdr->b_l2hdr->b_compress; 3323 b_asize = hdr->b_l2hdr->b_asize; 3324 /* 3325 * Lock out device removal. 3326 */ 3327 if (vdev_is_dead(vd) || 3328 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 3329 vd = NULL; 3330 } 3331 3332 if (hash_lock != NULL) 3333 mutex_exit(hash_lock); 3334 3335 /* 3336 * At this point, we have a level 1 cache miss. Try again in 3337 * L2ARC if possible. 3338 */ 3339 ASSERT3U(hdr->b_size, ==, size); 3340 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
|
3341 uint64_t, size, zbookmark_t *, zb);
|
3341 uint64_t, size, zbookmark_phys_t *, zb); |
3342 ARCSTAT_BUMP(arcstat_misses); 3343 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 3344 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3345 data, metadata, misses); 3346#ifdef _KERNEL 3347 curthread->td_ru.ru_inblock++; 3348#endif 3349 3350 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 3351 /* 3352 * Read from the L2ARC if the following are true: 3353 * 1. The L2ARC vdev was previously cached. 3354 * 2. This buffer still has L2ARC metadata. 3355 * 3. This buffer isn't currently writing to the L2ARC. 3356 * 4. The L2ARC entry wasn't evicted, which may 3357 * also have invalidated the vdev. 3358 * 5. This isn't prefetch and l2arc_noprefetch is set. 3359 */ 3360 if (hdr->b_l2hdr != NULL && 3361 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3362 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3363 l2arc_read_callback_t *cb; 3364 3365 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3366 ARCSTAT_BUMP(arcstat_l2_hits); 3367 3368 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3369 KM_SLEEP); 3370 cb->l2rcb_buf = buf; 3371 cb->l2rcb_spa = spa; 3372 cb->l2rcb_bp = *bp; 3373 cb->l2rcb_zb = *zb; 3374 cb->l2rcb_flags = zio_flags; 3375 cb->l2rcb_compress = b_compress; 3376 3377 ASSERT(addr >= VDEV_LABEL_START_SIZE && 3378 addr + size < vd->vdev_psize - 3379 VDEV_LABEL_END_SIZE); 3380 3381 /* 3382 * l2arc read. The SCL_L2ARC lock will be 3383 * released by l2arc_read_done(). 3384 * Issue a null zio if the underlying buffer 3385 * was squashed to zero size by compression. 3386 */ 3387 if (b_compress == ZIO_COMPRESS_EMPTY) { 3388 rzio = zio_null(pio, spa, vd, 3389 l2arc_read_done, cb, 3390 zio_flags | ZIO_FLAG_DONT_CACHE | 3391 ZIO_FLAG_CANFAIL | 3392 ZIO_FLAG_DONT_PROPAGATE | 3393 ZIO_FLAG_DONT_RETRY); 3394 } else { 3395 rzio = zio_read_phys(pio, vd, addr, 3396 b_asize, buf->b_data, 3397 ZIO_CHECKSUM_OFF, 3398 l2arc_read_done, cb, priority, 3399 zio_flags | ZIO_FLAG_DONT_CACHE | 3400 ZIO_FLAG_CANFAIL | 3401 ZIO_FLAG_DONT_PROPAGATE | 3402 ZIO_FLAG_DONT_RETRY, B_FALSE); 3403 } 3404 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3405 zio_t *, rzio); 3406 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 3407 3408 if (*arc_flags & ARC_NOWAIT) { 3409 zio_nowait(rzio); 3410 return (0); 3411 } 3412 3413 ASSERT(*arc_flags & ARC_WAIT); 3414 if (zio_wait(rzio) == 0) 3415 return (0); 3416 3417 /* l2arc read error; goto zio_read() */ 3418 } else { 3419 DTRACE_PROBE1(l2arc__miss, 3420 arc_buf_hdr_t *, hdr); 3421 ARCSTAT_BUMP(arcstat_l2_misses); 3422 if (HDR_L2_WRITING(hdr)) 3423 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3424 spa_config_exit(spa, SCL_L2ARC, vd); 3425 } 3426 } else { 3427 if (vd != NULL) 3428 spa_config_exit(spa, SCL_L2ARC, vd); 3429 if (l2arc_ndev != 0) { 3430 DTRACE_PROBE1(l2arc__miss, 3431 arc_buf_hdr_t *, hdr); 3432 ARCSTAT_BUMP(arcstat_l2_misses); 3433 } 3434 } 3435 3436 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3437 arc_read_done, buf, priority, zio_flags, zb); 3438 3439 if (*arc_flags & ARC_WAIT) 3440 return (zio_wait(rzio)); 3441 3442 ASSERT(*arc_flags & ARC_NOWAIT); 3443 zio_nowait(rzio); 3444 } 3445 return (0); 3446} 3447 3448void 3449arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3450{ 3451 ASSERT(buf->b_hdr != NULL); 3452 ASSERT(buf->b_hdr->b_state != arc_anon); 3453 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL); 3454 ASSERT(buf->b_efunc == NULL); 3455 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3456 3457 buf->b_efunc = func; 3458 buf->b_private = private; 3459} 3460 3461/* 3462 * Notify the arc that a block was freed, and thus will never be used again. 3463 */ 3464void 3465arc_freed(spa_t *spa, const blkptr_t *bp) 3466{ 3467 arc_buf_hdr_t *hdr; 3468 kmutex_t *hash_lock; 3469 uint64_t guid = spa_load_guid(spa); 3470 3471 ASSERT(!BP_IS_EMBEDDED(bp)); 3472 3473 hdr = buf_hash_find(guid, bp, &hash_lock); 3474 if (hdr == NULL) 3475 return; 3476 if (HDR_BUF_AVAILABLE(hdr)) { 3477 arc_buf_t *buf = hdr->b_buf; 3478 add_reference(hdr, hash_lock, FTAG); 3479 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3480 mutex_exit(hash_lock); 3481 3482 arc_release(buf, FTAG); 3483 (void) arc_buf_remove_ref(buf, FTAG); 3484 } else { 3485 mutex_exit(hash_lock); 3486 } 3487 3488} 3489 3490/* 3491 * This is used by the DMU to let the ARC know that a buffer is 3492 * being evicted, so the ARC should clean up. If this arc buf 3493 * is not yet in the evicted state, it will be put there. 3494 */ 3495int 3496arc_buf_evict(arc_buf_t *buf) 3497{ 3498 arc_buf_hdr_t *hdr; 3499 kmutex_t *hash_lock; 3500 arc_buf_t **bufp; 3501 list_t *list, *evicted_list; 3502 kmutex_t *lock, *evicted_lock; 3503 3504 mutex_enter(&buf->b_evict_lock); 3505 hdr = buf->b_hdr; 3506 if (hdr == NULL) { 3507 /* 3508 * We are in arc_do_user_evicts(). 3509 */ 3510 ASSERT(buf->b_data == NULL); 3511 mutex_exit(&buf->b_evict_lock); 3512 return (0); 3513 } else if (buf->b_data == NULL) { 3514 arc_buf_t copy = *buf; /* structure assignment */ 3515 /* 3516 * We are on the eviction list; process this buffer now 3517 * but let arc_do_user_evicts() do the reaping. 3518 */ 3519 buf->b_efunc = NULL; 3520 mutex_exit(&buf->b_evict_lock); 3521 VERIFY(copy.b_efunc(©) == 0); 3522 return (1); 3523 } 3524 hash_lock = HDR_LOCK(hdr); 3525 mutex_enter(hash_lock); 3526 hdr = buf->b_hdr; 3527 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3528 3529 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt); 3530 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3531 3532 /* 3533 * Pull this buffer off of the hdr 3534 */ 3535 bufp = &hdr->b_buf; 3536 while (*bufp != buf) 3537 bufp = &(*bufp)->b_next; 3538 *bufp = buf->b_next; 3539 3540 ASSERT(buf->b_data != NULL); 3541 arc_buf_destroy(buf, FALSE, FALSE); 3542 3543 if (hdr->b_datacnt == 0) { 3544 arc_state_t *old_state = hdr->b_state; 3545 arc_state_t *evicted_state; 3546 3547 ASSERT(hdr->b_buf == NULL); 3548 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 3549 3550 evicted_state = 3551 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3552 3553 get_buf_info(hdr, old_state, &list, &lock); 3554 get_buf_info(hdr, evicted_state, &evicted_list, &evicted_lock); 3555 mutex_enter(lock); 3556 mutex_enter(evicted_lock); 3557 3558 arc_change_state(evicted_state, hdr, hash_lock); 3559 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3560 hdr->b_flags |= ARC_IN_HASH_TABLE; 3561 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3562 3563 mutex_exit(evicted_lock); 3564 mutex_exit(lock); 3565 } 3566 mutex_exit(hash_lock); 3567 mutex_exit(&buf->b_evict_lock); 3568 3569 VERIFY(buf->b_efunc(buf) == 0); 3570 buf->b_efunc = NULL; 3571 buf->b_private = NULL; 3572 buf->b_hdr = NULL; 3573 buf->b_next = NULL; 3574 kmem_cache_free(buf_cache, buf); 3575 return (1); 3576} 3577 3578/* 3579 * Release this buffer from the cache, making it an anonymous buffer. This 3580 * must be done after a read and prior to modifying the buffer contents. 3581 * If the buffer has more than one reference, we must make 3582 * a new hdr for the buffer. 3583 */ 3584void 3585arc_release(arc_buf_t *buf, void *tag) 3586{ 3587 arc_buf_hdr_t *hdr; 3588 kmutex_t *hash_lock = NULL; 3589 l2arc_buf_hdr_t *l2hdr; 3590 uint64_t buf_size; 3591 3592 /* 3593 * It would be nice to assert that if it's DMU metadata (level > 3594 * 0 || it's the dnode file), then it must be syncing context. 3595 * But we don't know that information at this level. 3596 */ 3597 3598 mutex_enter(&buf->b_evict_lock); 3599 hdr = buf->b_hdr; 3600 3601 /* this buffer is not on any list */ 3602 ASSERT(refcount_count(&hdr->b_refcnt) > 0); 3603 3604 if (hdr->b_state == arc_anon) { 3605 /* this buffer is already released */ 3606 ASSERT(buf->b_efunc == NULL); 3607 } else { 3608 hash_lock = HDR_LOCK(hdr); 3609 mutex_enter(hash_lock); 3610 hdr = buf->b_hdr; 3611 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3612 } 3613 3614 l2hdr = hdr->b_l2hdr; 3615 if (l2hdr) { 3616 mutex_enter(&l2arc_buflist_mtx); 3617 hdr->b_l2hdr = NULL; 3618 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 3619 } 3620 buf_size = hdr->b_size; 3621 3622 /* 3623 * Do we have more than one buf? 3624 */ 3625 if (hdr->b_datacnt > 1) { 3626 arc_buf_hdr_t *nhdr; 3627 arc_buf_t **bufp; 3628 uint64_t blksz = hdr->b_size; 3629 uint64_t spa = hdr->b_spa; 3630 arc_buf_contents_t type = hdr->b_type; 3631 uint32_t flags = hdr->b_flags; 3632 3633 ASSERT(hdr->b_buf != buf || buf->b_next != NULL); 3634 /* 3635 * Pull the data off of this hdr and attach it to 3636 * a new anonymous hdr. 3637 */ 3638 (void) remove_reference(hdr, hash_lock, tag); 3639 bufp = &hdr->b_buf; 3640 while (*bufp != buf) 3641 bufp = &(*bufp)->b_next; 3642 *bufp = buf->b_next; 3643 buf->b_next = NULL; 3644 3645 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size); 3646 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size); 3647 if (refcount_is_zero(&hdr->b_refcnt)) { 3648 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 3649 ASSERT3U(*size, >=, hdr->b_size); 3650 atomic_add_64(size, -hdr->b_size); 3651 } 3652 3653 /* 3654 * We're releasing a duplicate user data buffer, update 3655 * our statistics accordingly. 3656 */ 3657 if (hdr->b_type == ARC_BUFC_DATA) { 3658 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3659 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3660 -hdr->b_size); 3661 } 3662 hdr->b_datacnt -= 1; 3663 arc_cksum_verify(buf); 3664#ifdef illumos 3665 arc_buf_unwatch(buf); 3666#endif /* illumos */ 3667 3668 mutex_exit(hash_lock); 3669 3670 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 3671 nhdr->b_size = blksz; 3672 nhdr->b_spa = spa; 3673 nhdr->b_type = type; 3674 nhdr->b_buf = buf; 3675 nhdr->b_state = arc_anon; 3676 nhdr->b_arc_access = 0; 3677 nhdr->b_flags = flags & ARC_L2_WRITING; 3678 nhdr->b_l2hdr = NULL; 3679 nhdr->b_datacnt = 1; 3680 nhdr->b_freeze_cksum = NULL; 3681 (void) refcount_add(&nhdr->b_refcnt, tag); 3682 buf->b_hdr = nhdr; 3683 mutex_exit(&buf->b_evict_lock); 3684 atomic_add_64(&arc_anon->arcs_size, blksz); 3685 } else { 3686 mutex_exit(&buf->b_evict_lock); 3687 ASSERT(refcount_count(&hdr->b_refcnt) == 1); 3688 ASSERT(!list_link_active(&hdr->b_arc_node)); 3689 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3690 if (hdr->b_state != arc_anon) 3691 arc_change_state(arc_anon, hdr, hash_lock); 3692 hdr->b_arc_access = 0; 3693 if (hash_lock) 3694 mutex_exit(hash_lock); 3695 3696 buf_discard_identity(hdr); 3697 arc_buf_thaw(buf); 3698 } 3699 buf->b_efunc = NULL; 3700 buf->b_private = NULL; 3701 3702 if (l2hdr) { 3703 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 3704 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 3705 -l2hdr->b_asize, 0, 0); 3706 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr, 3707 hdr->b_size, 0); 3708 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 3709 ARCSTAT_INCR(arcstat_l2_size, -buf_size); 3710 mutex_exit(&l2arc_buflist_mtx); 3711 } 3712} 3713 3714int 3715arc_released(arc_buf_t *buf) 3716{ 3717 int released; 3718 3719 mutex_enter(&buf->b_evict_lock); 3720 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon); 3721 mutex_exit(&buf->b_evict_lock); 3722 return (released); 3723} 3724 3725int 3726arc_has_callback(arc_buf_t *buf) 3727{ 3728 int callback; 3729 3730 mutex_enter(&buf->b_evict_lock); 3731 callback = (buf->b_efunc != NULL); 3732 mutex_exit(&buf->b_evict_lock); 3733 return (callback); 3734} 3735 3736#ifdef ZFS_DEBUG 3737int 3738arc_referenced(arc_buf_t *buf) 3739{ 3740 int referenced; 3741 3742 mutex_enter(&buf->b_evict_lock); 3743 referenced = (refcount_count(&buf->b_hdr->b_refcnt)); 3744 mutex_exit(&buf->b_evict_lock); 3745 return (referenced); 3746} 3747#endif 3748 3749static void 3750arc_write_ready(zio_t *zio) 3751{ 3752 arc_write_callback_t *callback = zio->io_private; 3753 arc_buf_t *buf = callback->awcb_buf; 3754 arc_buf_hdr_t *hdr = buf->b_hdr; 3755 3756 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt)); 3757 callback->awcb_ready(zio, buf, callback->awcb_private); 3758 3759 /* 3760 * If the IO is already in progress, then this is a re-write 3761 * attempt, so we need to thaw and re-compute the cksum. 3762 * It is the responsibility of the callback to handle the 3763 * accounting for any re-write attempt. 3764 */ 3765 if (HDR_IO_IN_PROGRESS(hdr)) { 3766 mutex_enter(&hdr->b_freeze_lock); 3767 if (hdr->b_freeze_cksum != NULL) { 3768 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 3769 hdr->b_freeze_cksum = NULL; 3770 } 3771 mutex_exit(&hdr->b_freeze_lock); 3772 } 3773 arc_cksum_compute(buf, B_FALSE); 3774 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3775} 3776 3777/* 3778 * The SPA calls this callback for each physical write that happens on behalf 3779 * of a logical write. See the comment in dbuf_write_physdone() for details. 3780 */ 3781static void 3782arc_write_physdone(zio_t *zio) 3783{ 3784 arc_write_callback_t *cb = zio->io_private; 3785 if (cb->awcb_physdone != NULL) 3786 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 3787} 3788 3789static void 3790arc_write_done(zio_t *zio) 3791{ 3792 arc_write_callback_t *callback = zio->io_private; 3793 arc_buf_t *buf = callback->awcb_buf; 3794 arc_buf_hdr_t *hdr = buf->b_hdr; 3795 3796 ASSERT(hdr->b_acb == NULL); 3797 3798 if (zio->io_error == 0) { 3799 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 3800 buf_discard_identity(hdr); 3801 } else { 3802 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 3803 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 3804 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0]; 3805 } 3806 } else { 3807 ASSERT(BUF_EMPTY(hdr)); 3808 } 3809 3810 /* 3811 * If the block to be written was all-zero or compressed enough to be 3812 * embedded in the BP, no write was performed so there will be no 3813 * dva/birth/checksum. The buffer must therefore remain anonymous 3814 * (and uncached). 3815 */ 3816 if (!BUF_EMPTY(hdr)) { 3817 arc_buf_hdr_t *exists; 3818 kmutex_t *hash_lock; 3819 3820 ASSERT(zio->io_error == 0); 3821 3822 arc_cksum_verify(buf); 3823 3824 exists = buf_hash_insert(hdr, &hash_lock); 3825 if (exists) { 3826 /* 3827 * This can only happen if we overwrite for 3828 * sync-to-convergence, because we remove 3829 * buffers from the hash table when we arc_free(). 3830 */ 3831 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 3832 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3833 panic("bad overwrite, hdr=%p exists=%p", 3834 (void *)hdr, (void *)exists); 3835 ASSERT(refcount_is_zero(&exists->b_refcnt)); 3836 arc_change_state(arc_anon, exists, hash_lock); 3837 mutex_exit(hash_lock); 3838 arc_hdr_destroy(exists); 3839 exists = buf_hash_insert(hdr, &hash_lock); 3840 ASSERT3P(exists, ==, NULL); 3841 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 3842 /* nopwrite */ 3843 ASSERT(zio->io_prop.zp_nopwrite); 3844 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3845 panic("bad nopwrite, hdr=%p exists=%p", 3846 (void *)hdr, (void *)exists); 3847 } else { 3848 /* Dedup */ 3849 ASSERT(hdr->b_datacnt == 1); 3850 ASSERT(hdr->b_state == arc_anon); 3851 ASSERT(BP_GET_DEDUP(zio->io_bp)); 3852 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 3853 } 3854 } 3855 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3856 /* if it's not anon, we are doing a scrub */ 3857 if (!exists && hdr->b_state == arc_anon) 3858 arc_access(hdr, hash_lock); 3859 mutex_exit(hash_lock); 3860 } else { 3861 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3862 } 3863 3864 ASSERT(!refcount_is_zero(&hdr->b_refcnt)); 3865 callback->awcb_done(zio, buf, callback->awcb_private); 3866 3867 kmem_free(callback, sizeof (arc_write_callback_t)); 3868} 3869 3870zio_t * 3871arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 3872 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 3873 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 3874 arc_done_func_t *done, void *private, zio_priority_t priority,
|
3875 int zio_flags, const zbookmark_t *zb)
|
3875 int zio_flags, const zbookmark_phys_t *zb) |
3876{ 3877 arc_buf_hdr_t *hdr = buf->b_hdr; 3878 arc_write_callback_t *callback; 3879 zio_t *zio; 3880 3881 ASSERT(ready != NULL); 3882 ASSERT(done != NULL); 3883 ASSERT(!HDR_IO_ERROR(hdr)); 3884 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0); 3885 ASSERT(hdr->b_acb == NULL); 3886 if (l2arc) 3887 hdr->b_flags |= ARC_L2CACHE; 3888 if (l2arc_compress) 3889 hdr->b_flags |= ARC_L2COMPRESS; 3890 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 3891 callback->awcb_ready = ready; 3892 callback->awcb_physdone = physdone; 3893 callback->awcb_done = done; 3894 callback->awcb_private = private; 3895 callback->awcb_buf = buf; 3896 3897 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 3898 arc_write_ready, arc_write_physdone, arc_write_done, callback, 3899 priority, zio_flags, zb); 3900 3901 return (zio); 3902} 3903 3904static int 3905arc_memory_throttle(uint64_t reserve, uint64_t txg) 3906{ 3907#ifdef _KERNEL 3908 uint64_t available_memory = 3909 ptoa((uintmax_t)vm_cnt.v_free_count + vm_cnt.v_cache_count); 3910 static uint64_t page_load = 0; 3911 static uint64_t last_txg = 0; 3912 3913#ifdef sun 3914#if defined(__i386) 3915 available_memory = 3916 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 3917#endif 3918#endif /* sun */ 3919 3920 if (vm_cnt.v_free_count + vm_cnt.v_cache_count > 3921 (uint64_t)physmem * arc_lotsfree_percent / 100) 3922 return (0); 3923 3924 if (txg > last_txg) { 3925 last_txg = txg; 3926 page_load = 0; 3927 } 3928 /* 3929 * If we are in pageout, we know that memory is already tight, 3930 * the arc is already going to be evicting, so we just want to 3931 * continue to let page writes occur as quickly as possible. 3932 */ 3933 if (curproc == pageproc) { 3934 if (page_load > available_memory / 4) 3935 return (SET_ERROR(ERESTART)); 3936 /* Note: reserve is inflated, so we deflate */ 3937 page_load += reserve / 8; 3938 return (0); 3939 } else if (page_load > 0 && arc_reclaim_needed()) { 3940 /* memory is low, delay before restarting */ 3941 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3942 return (SET_ERROR(EAGAIN)); 3943 } 3944 page_load = 0; 3945#endif 3946 return (0); 3947} 3948 3949void 3950arc_tempreserve_clear(uint64_t reserve) 3951{ 3952 atomic_add_64(&arc_tempreserve, -reserve); 3953 ASSERT((int64_t)arc_tempreserve >= 0); 3954} 3955 3956int 3957arc_tempreserve_space(uint64_t reserve, uint64_t txg) 3958{ 3959 int error; 3960 uint64_t anon_size; 3961 3962 if (reserve > arc_c/4 && !arc_no_grow) 3963 arc_c = MIN(arc_c_max, reserve * 4); 3964 if (reserve > arc_c) 3965 return (SET_ERROR(ENOMEM)); 3966 3967 /* 3968 * Don't count loaned bufs as in flight dirty data to prevent long 3969 * network delays from blocking transactions that are ready to be 3970 * assigned to a txg. 3971 */ 3972 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 3973 3974 /* 3975 * Writes will, almost always, require additional memory allocations 3976 * in order to compress/encrypt/etc the data. We therefore need to 3977 * make sure that there is sufficient available memory for this. 3978 */ 3979 error = arc_memory_throttle(reserve, txg); 3980 if (error != 0) 3981 return (error); 3982 3983 /* 3984 * Throttle writes when the amount of dirty data in the cache 3985 * gets too large. We try to keep the cache less than half full 3986 * of dirty blocks so that our sync times don't grow too large. 3987 * Note: if two requests come in concurrently, we might let them 3988 * both succeed, when one of them should fail. Not a huge deal. 3989 */ 3990 3991 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 3992 anon_size > arc_c / 4) { 3993 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 3994 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 3995 arc_tempreserve>>10, 3996 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 3997 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 3998 reserve>>10, arc_c>>10); 3999 return (SET_ERROR(ERESTART)); 4000 } 4001 atomic_add_64(&arc_tempreserve, reserve); 4002 return (0); 4003} 4004 4005static kmutex_t arc_lowmem_lock; 4006#ifdef _KERNEL 4007static eventhandler_tag arc_event_lowmem = NULL; 4008 4009static void 4010arc_lowmem(void *arg __unused, int howto __unused) 4011{ 4012 4013 /* Serialize access via arc_lowmem_lock. */ 4014 mutex_enter(&arc_lowmem_lock); 4015 mutex_enter(&arc_reclaim_thr_lock); 4016 needfree = 1; 4017 cv_signal(&arc_reclaim_thr_cv); 4018 4019 /* 4020 * It is unsafe to block here in arbitrary threads, because we can come 4021 * here from ARC itself and may hold ARC locks and thus risk a deadlock 4022 * with ARC reclaim thread. 4023 */ 4024 if (curproc == pageproc) { 4025 while (needfree) 4026 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0); 4027 } 4028 mutex_exit(&arc_reclaim_thr_lock); 4029 mutex_exit(&arc_lowmem_lock); 4030} 4031#endif 4032 4033void 4034arc_init(void) 4035{ 4036 int i, prefetch_tunable_set = 0; 4037 4038 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4039 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 4040 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL); 4041 4042 /* Convert seconds to clock ticks */ 4043 arc_min_prefetch_lifespan = 1 * hz; 4044 4045 /* Start out with 1/8 of all memory */ 4046 arc_c = kmem_size() / 8; 4047 4048#ifdef sun 4049#ifdef _KERNEL 4050 /* 4051 * On architectures where the physical memory can be larger 4052 * than the addressable space (intel in 32-bit mode), we may 4053 * need to limit the cache to 1/8 of VM size. 4054 */ 4055 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4056#endif 4057#endif /* sun */ 4058 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 4059 arc_c_min = MAX(arc_c / 4, 64<<18); 4060 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 4061 if (arc_c * 8 >= 1<<30) 4062 arc_c_max = (arc_c * 8) - (1<<30); 4063 else 4064 arc_c_max = arc_c_min; 4065 arc_c_max = MAX(arc_c * 5, arc_c_max); 4066 4067#ifdef _KERNEL 4068 /* 4069 * Allow the tunables to override our calculations if they are 4070 * reasonable (ie. over 16MB) 4071 */ 4072 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size()) 4073 arc_c_max = zfs_arc_max; 4074 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max) 4075 arc_c_min = zfs_arc_min; 4076#endif 4077 4078 arc_c = arc_c_max; 4079 arc_p = (arc_c >> 1); 4080 4081 /* limit meta-data to 1/4 of the arc capacity */ 4082 arc_meta_limit = arc_c_max / 4; 4083 4084 /* Allow the tunable to override if it is reasonable */ 4085 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4086 arc_meta_limit = zfs_arc_meta_limit; 4087 4088 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4089 arc_c_min = arc_meta_limit / 2; 4090 4091 if (zfs_arc_grow_retry > 0) 4092 arc_grow_retry = zfs_arc_grow_retry; 4093 4094 if (zfs_arc_shrink_shift > 0) 4095 arc_shrink_shift = zfs_arc_shrink_shift; 4096 4097 if (zfs_arc_p_min_shift > 0) 4098 arc_p_min_shift = zfs_arc_p_min_shift; 4099 4100 /* if kmem_flags are set, lets try to use less memory */ 4101 if (kmem_debugging()) 4102 arc_c = arc_c / 2; 4103 if (arc_c < arc_c_min) 4104 arc_c = arc_c_min; 4105 4106 zfs_arc_min = arc_c_min; 4107 zfs_arc_max = arc_c_max; 4108 4109 arc_anon = &ARC_anon; 4110 arc_mru = &ARC_mru; 4111 arc_mru_ghost = &ARC_mru_ghost; 4112 arc_mfu = &ARC_mfu; 4113 arc_mfu_ghost = &ARC_mfu_ghost; 4114 arc_l2c_only = &ARC_l2c_only; 4115 arc_size = 0; 4116 4117 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4118 mutex_init(&arc_anon->arcs_locks[i].arcs_lock, 4119 NULL, MUTEX_DEFAULT, NULL); 4120 mutex_init(&arc_mru->arcs_locks[i].arcs_lock, 4121 NULL, MUTEX_DEFAULT, NULL); 4122 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock, 4123 NULL, MUTEX_DEFAULT, NULL); 4124 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock, 4125 NULL, MUTEX_DEFAULT, NULL); 4126 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock, 4127 NULL, MUTEX_DEFAULT, NULL); 4128 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock, 4129 NULL, MUTEX_DEFAULT, NULL); 4130 4131 list_create(&arc_mru->arcs_lists[i], 4132 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4133 list_create(&arc_mru_ghost->arcs_lists[i], 4134 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4135 list_create(&arc_mfu->arcs_lists[i], 4136 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4137 list_create(&arc_mfu_ghost->arcs_lists[i], 4138 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4139 list_create(&arc_mfu_ghost->arcs_lists[i], 4140 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4141 list_create(&arc_l2c_only->arcs_lists[i], 4142 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4143 } 4144 4145 buf_init(); 4146 4147 arc_thread_exit = 0; 4148 arc_eviction_list = NULL; 4149 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 4150 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4151 4152 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4153 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4154 4155 if (arc_ksp != NULL) { 4156 arc_ksp->ks_data = &arc_stats; 4157 kstat_install(arc_ksp); 4158 } 4159 4160 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 4161 TS_RUN, minclsyspri); 4162 4163#ifdef _KERNEL 4164 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 4165 EVENTHANDLER_PRI_FIRST); 4166#endif 4167 4168 arc_dead = FALSE; 4169 arc_warm = B_FALSE; 4170 4171 /* 4172 * Calculate maximum amount of dirty data per pool. 4173 * 4174 * If it has been set by /etc/system, take that. 4175 * Otherwise, use a percentage of physical memory defined by 4176 * zfs_dirty_data_max_percent (default 10%) with a cap at 4177 * zfs_dirty_data_max_max (default 4GB). 4178 */ 4179 if (zfs_dirty_data_max == 0) { 4180 zfs_dirty_data_max = ptob(physmem) * 4181 zfs_dirty_data_max_percent / 100; 4182 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 4183 zfs_dirty_data_max_max); 4184 } 4185 4186#ifdef _KERNEL 4187 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 4188 prefetch_tunable_set = 1; 4189 4190#ifdef __i386__ 4191 if (prefetch_tunable_set == 0) { 4192 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 4193 "-- to enable,\n"); 4194 printf(" add \"vfs.zfs.prefetch_disable=0\" " 4195 "to /boot/loader.conf.\n"); 4196 zfs_prefetch_disable = 1; 4197 } 4198#else 4199 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 4200 prefetch_tunable_set == 0) { 4201 printf("ZFS NOTICE: Prefetch is disabled by default if less " 4202 "than 4GB of RAM is present;\n" 4203 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 4204 "to /boot/loader.conf.\n"); 4205 zfs_prefetch_disable = 1; 4206 } 4207#endif 4208 /* Warn about ZFS memory and address space requirements. */ 4209 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 4210 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 4211 "expect unstable behavior.\n"); 4212 } 4213 if (kmem_size() < 512 * (1 << 20)) { 4214 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 4215 "expect unstable behavior.\n"); 4216 printf(" Consider tuning vm.kmem_size and " 4217 "vm.kmem_size_max\n"); 4218 printf(" in /boot/loader.conf.\n"); 4219 } 4220#endif 4221} 4222 4223void 4224arc_fini(void) 4225{ 4226 int i; 4227 4228 mutex_enter(&arc_reclaim_thr_lock); 4229 arc_thread_exit = 1; 4230 cv_signal(&arc_reclaim_thr_cv); 4231 while (arc_thread_exit != 0) 4232 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 4233 mutex_exit(&arc_reclaim_thr_lock); 4234 4235 arc_flush(NULL); 4236 4237 arc_dead = TRUE; 4238 4239 if (arc_ksp != NULL) { 4240 kstat_delete(arc_ksp); 4241 arc_ksp = NULL; 4242 } 4243 4244 mutex_destroy(&arc_eviction_mtx); 4245 mutex_destroy(&arc_reclaim_thr_lock); 4246 cv_destroy(&arc_reclaim_thr_cv); 4247 4248 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4249 list_destroy(&arc_mru->arcs_lists[i]); 4250 list_destroy(&arc_mru_ghost->arcs_lists[i]); 4251 list_destroy(&arc_mfu->arcs_lists[i]); 4252 list_destroy(&arc_mfu_ghost->arcs_lists[i]); 4253 list_destroy(&arc_l2c_only->arcs_lists[i]); 4254 4255 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock); 4256 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock); 4257 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock); 4258 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock); 4259 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock); 4260 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock); 4261 } 4262 4263 buf_fini(); 4264 4265 ASSERT(arc_loaned_bytes == 0); 4266 4267 mutex_destroy(&arc_lowmem_lock); 4268#ifdef _KERNEL 4269 if (arc_event_lowmem != NULL) 4270 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 4271#endif 4272} 4273 4274/* 4275 * Level 2 ARC 4276 * 4277 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 4278 * It uses dedicated storage devices to hold cached data, which are populated 4279 * using large infrequent writes. The main role of this cache is to boost 4280 * the performance of random read workloads. The intended L2ARC devices 4281 * include short-stroked disks, solid state disks, and other media with 4282 * substantially faster read latency than disk. 4283 * 4284 * +-----------------------+ 4285 * | ARC | 4286 * +-----------------------+ 4287 * | ^ ^ 4288 * | | | 4289 * l2arc_feed_thread() arc_read() 4290 * | | | 4291 * | l2arc read | 4292 * V | | 4293 * +---------------+ | 4294 * | L2ARC | | 4295 * +---------------+ | 4296 * | ^ | 4297 * l2arc_write() | | 4298 * | | | 4299 * V | | 4300 * +-------+ +-------+ 4301 * | vdev | | vdev | 4302 * | cache | | cache | 4303 * +-------+ +-------+ 4304 * +=========+ .-----. 4305 * : L2ARC : |-_____-| 4306 * : devices : | Disks | 4307 * +=========+ `-_____-' 4308 * 4309 * Read requests are satisfied from the following sources, in order: 4310 * 4311 * 1) ARC 4312 * 2) vdev cache of L2ARC devices 4313 * 3) L2ARC devices 4314 * 4) vdev cache of disks 4315 * 5) disks 4316 * 4317 * Some L2ARC device types exhibit extremely slow write performance. 4318 * To accommodate for this there are some significant differences between 4319 * the L2ARC and traditional cache design: 4320 * 4321 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 4322 * the ARC behave as usual, freeing buffers and placing headers on ghost 4323 * lists. The ARC does not send buffers to the L2ARC during eviction as 4324 * this would add inflated write latencies for all ARC memory pressure. 4325 * 4326 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 4327 * It does this by periodically scanning buffers from the eviction-end of 4328 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 4329 * not already there. It scans until a headroom of buffers is satisfied, 4330 * which itself is a buffer for ARC eviction. If a compressible buffer is 4331 * found during scanning and selected for writing to an L2ARC device, we 4332 * temporarily boost scanning headroom during the next scan cycle to make 4333 * sure we adapt to compression effects (which might significantly reduce 4334 * the data volume we write to L2ARC). The thread that does this is 4335 * l2arc_feed_thread(), illustrated below; example sizes are included to 4336 * provide a better sense of ratio than this diagram: 4337 * 4338 * head --> tail 4339 * +---------------------+----------+ 4340 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 4341 * +---------------------+----------+ | o L2ARC eligible 4342 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 4343 * +---------------------+----------+ | 4344 * 15.9 Gbytes ^ 32 Mbytes | 4345 * headroom | 4346 * l2arc_feed_thread() 4347 * | 4348 * l2arc write hand <--[oooo]--' 4349 * | 8 Mbyte 4350 * | write max 4351 * V 4352 * +==============================+ 4353 * L2ARC dev |####|#|###|###| |####| ... | 4354 * +==============================+ 4355 * 32 Gbytes 4356 * 4357 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 4358 * evicted, then the L2ARC has cached a buffer much sooner than it probably 4359 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 4360 * safe to say that this is an uncommon case, since buffers at the end of 4361 * the ARC lists have moved there due to inactivity. 4362 * 4363 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 4364 * then the L2ARC simply misses copying some buffers. This serves as a 4365 * pressure valve to prevent heavy read workloads from both stalling the ARC 4366 * with waits and clogging the L2ARC with writes. This also helps prevent 4367 * the potential for the L2ARC to churn if it attempts to cache content too 4368 * quickly, such as during backups of the entire pool. 4369 * 4370 * 5. After system boot and before the ARC has filled main memory, there are 4371 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 4372 * lists can remain mostly static. Instead of searching from tail of these 4373 * lists as pictured, the l2arc_feed_thread() will search from the list heads 4374 * for eligible buffers, greatly increasing its chance of finding them. 4375 * 4376 * The L2ARC device write speed is also boosted during this time so that 4377 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 4378 * there are no L2ARC reads, and no fear of degrading read performance 4379 * through increased writes. 4380 * 4381 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 4382 * the vdev queue can aggregate them into larger and fewer writes. Each 4383 * device is written to in a rotor fashion, sweeping writes through 4384 * available space then repeating. 4385 * 4386 * 7. The L2ARC does not store dirty content. It never needs to flush 4387 * write buffers back to disk based storage. 4388 * 4389 * 8. If an ARC buffer is written (and dirtied) which also exists in the 4390 * L2ARC, the now stale L2ARC buffer is immediately dropped. 4391 * 4392 * The performance of the L2ARC can be tweaked by a number of tunables, which 4393 * may be necessary for different workloads: 4394 * 4395 * l2arc_write_max max write bytes per interval 4396 * l2arc_write_boost extra write bytes during device warmup 4397 * l2arc_noprefetch skip caching prefetched buffers 4398 * l2arc_headroom number of max device writes to precache 4399 * l2arc_headroom_boost when we find compressed buffers during ARC 4400 * scanning, we multiply headroom by this 4401 * percentage factor for the next scan cycle, 4402 * since more compressed buffers are likely to 4403 * be present 4404 * l2arc_feed_secs seconds between L2ARC writing 4405 * 4406 * Tunables may be removed or added as future performance improvements are 4407 * integrated, and also may become zpool properties. 4408 * 4409 * There are three key functions that control how the L2ARC warms up: 4410 * 4411 * l2arc_write_eligible() check if a buffer is eligible to cache 4412 * l2arc_write_size() calculate how much to write 4413 * l2arc_write_interval() calculate sleep delay between writes 4414 * 4415 * These three functions determine what to write, how much, and how quickly 4416 * to send writes. 4417 */ 4418 4419static boolean_t 4420l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab) 4421{ 4422 /* 4423 * A buffer is *not* eligible for the L2ARC if it: 4424 * 1. belongs to a different spa. 4425 * 2. is already cached on the L2ARC. 4426 * 3. has an I/O in progress (it may be an incomplete read). 4427 * 4. is flagged not eligible (zfs property). 4428 */ 4429 if (ab->b_spa != spa_guid) { 4430 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 4431 return (B_FALSE); 4432 } 4433 if (ab->b_l2hdr != NULL) { 4434 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 4435 return (B_FALSE); 4436 } 4437 if (HDR_IO_IN_PROGRESS(ab)) { 4438 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 4439 return (B_FALSE); 4440 } 4441 if (!HDR_L2CACHE(ab)) { 4442 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 4443 return (B_FALSE); 4444 } 4445 4446 return (B_TRUE); 4447} 4448 4449static uint64_t 4450l2arc_write_size(void) 4451{ 4452 uint64_t size; 4453 4454 /* 4455 * Make sure our globals have meaningful values in case the user 4456 * altered them. 4457 */ 4458 size = l2arc_write_max; 4459 if (size == 0) { 4460 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 4461 "be greater than zero, resetting it to the default (%d)", 4462 L2ARC_WRITE_SIZE); 4463 size = l2arc_write_max = L2ARC_WRITE_SIZE; 4464 } 4465 4466 if (arc_warm == B_FALSE) 4467 size += l2arc_write_boost; 4468 4469 return (size); 4470 4471} 4472 4473static clock_t 4474l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 4475{ 4476 clock_t interval, next, now; 4477 4478 /* 4479 * If the ARC lists are busy, increase our write rate; if the 4480 * lists are stale, idle back. This is achieved by checking 4481 * how much we previously wrote - if it was more than half of 4482 * what we wanted, schedule the next write much sooner. 4483 */ 4484 if (l2arc_feed_again && wrote > (wanted / 2)) 4485 interval = (hz * l2arc_feed_min_ms) / 1000; 4486 else 4487 interval = hz * l2arc_feed_secs; 4488 4489 now = ddi_get_lbolt(); 4490 next = MAX(now, MIN(now + interval, began + interval)); 4491 4492 return (next); 4493} 4494 4495static void 4496l2arc_hdr_stat_add(void) 4497{ 4498 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE); 4499 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE); 4500} 4501 4502static void 4503l2arc_hdr_stat_remove(void) 4504{ 4505 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE)); 4506 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE); 4507} 4508 4509/* 4510 * Cycle through L2ARC devices. This is how L2ARC load balances. 4511 * If a device is returned, this also returns holding the spa config lock. 4512 */ 4513static l2arc_dev_t * 4514l2arc_dev_get_next(void) 4515{ 4516 l2arc_dev_t *first, *next = NULL; 4517 4518 /* 4519 * Lock out the removal of spas (spa_namespace_lock), then removal 4520 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 4521 * both locks will be dropped and a spa config lock held instead. 4522 */ 4523 mutex_enter(&spa_namespace_lock); 4524 mutex_enter(&l2arc_dev_mtx); 4525 4526 /* if there are no vdevs, there is nothing to do */ 4527 if (l2arc_ndev == 0) 4528 goto out; 4529 4530 first = NULL; 4531 next = l2arc_dev_last; 4532 do { 4533 /* loop around the list looking for a non-faulted vdev */ 4534 if (next == NULL) { 4535 next = list_head(l2arc_dev_list); 4536 } else { 4537 next = list_next(l2arc_dev_list, next); 4538 if (next == NULL) 4539 next = list_head(l2arc_dev_list); 4540 } 4541 4542 /* if we have come back to the start, bail out */ 4543 if (first == NULL) 4544 first = next; 4545 else if (next == first) 4546 break; 4547 4548 } while (vdev_is_dead(next->l2ad_vdev)); 4549 4550 /* if we were unable to find any usable vdevs, return NULL */ 4551 if (vdev_is_dead(next->l2ad_vdev)) 4552 next = NULL; 4553 4554 l2arc_dev_last = next; 4555 4556out: 4557 mutex_exit(&l2arc_dev_mtx); 4558 4559 /* 4560 * Grab the config lock to prevent the 'next' device from being 4561 * removed while we are writing to it. 4562 */ 4563 if (next != NULL) 4564 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4565 mutex_exit(&spa_namespace_lock); 4566 4567 return (next); 4568} 4569 4570/* 4571 * Free buffers that were tagged for destruction. 4572 */ 4573static void 4574l2arc_do_free_on_write() 4575{ 4576 list_t *buflist; 4577 l2arc_data_free_t *df, *df_prev; 4578 4579 mutex_enter(&l2arc_free_on_write_mtx); 4580 buflist = l2arc_free_on_write; 4581 4582 for (df = list_tail(buflist); df; df = df_prev) { 4583 df_prev = list_prev(buflist, df); 4584 ASSERT(df->l2df_data != NULL); 4585 ASSERT(df->l2df_func != NULL); 4586 df->l2df_func(df->l2df_data, df->l2df_size); 4587 list_remove(buflist, df); 4588 kmem_free(df, sizeof (l2arc_data_free_t)); 4589 } 4590 4591 mutex_exit(&l2arc_free_on_write_mtx); 4592} 4593 4594/* 4595 * A write to a cache device has completed. Update all headers to allow 4596 * reads from these buffers to begin. 4597 */ 4598static void 4599l2arc_write_done(zio_t *zio) 4600{ 4601 l2arc_write_callback_t *cb; 4602 l2arc_dev_t *dev; 4603 list_t *buflist; 4604 arc_buf_hdr_t *head, *ab, *ab_prev; 4605 l2arc_buf_hdr_t *abl2; 4606 kmutex_t *hash_lock; 4607 int64_t bytes_dropped = 0; 4608 4609 cb = zio->io_private; 4610 ASSERT(cb != NULL); 4611 dev = cb->l2wcb_dev; 4612 ASSERT(dev != NULL); 4613 head = cb->l2wcb_head; 4614 ASSERT(head != NULL); 4615 buflist = dev->l2ad_buflist; 4616 ASSERT(buflist != NULL); 4617 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4618 l2arc_write_callback_t *, cb); 4619 4620 if (zio->io_error != 0) 4621 ARCSTAT_BUMP(arcstat_l2_writes_error); 4622 4623 mutex_enter(&l2arc_buflist_mtx); 4624 4625 /* 4626 * All writes completed, or an error was hit. 4627 */ 4628 for (ab = list_prev(buflist, head); ab; ab = ab_prev) { 4629 ab_prev = list_prev(buflist, ab); 4630 abl2 = ab->b_l2hdr; 4631 4632 /* 4633 * Release the temporary compressed buffer as soon as possible. 4634 */ 4635 if (abl2->b_compress != ZIO_COMPRESS_OFF) 4636 l2arc_release_cdata_buf(ab); 4637 4638 hash_lock = HDR_LOCK(ab); 4639 if (!mutex_tryenter(hash_lock)) { 4640 /* 4641 * This buffer misses out. It may be in a stage 4642 * of eviction. Its ARC_L2_WRITING flag will be 4643 * left set, denying reads to this buffer. 4644 */ 4645 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4646 continue; 4647 } 4648 4649 if (zio->io_error != 0) { 4650 /* 4651 * Error - drop L2ARC entry. 4652 */ 4653 list_remove(buflist, ab); 4654 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4655 bytes_dropped += abl2->b_asize; 4656 ab->b_l2hdr = NULL; 4657 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr, 4658 ab->b_size, 0); 4659 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4660 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4661 } 4662 4663 /* 4664 * Allow ARC to begin reads to this L2ARC entry. 4665 */ 4666 ab->b_flags &= ~ARC_L2_WRITING; 4667 4668 mutex_exit(hash_lock); 4669 } 4670 4671 atomic_inc_64(&l2arc_writes_done); 4672 list_remove(buflist, head); 4673 kmem_cache_free(hdr_cache, head); 4674 mutex_exit(&l2arc_buflist_mtx); 4675 4676 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 4677 4678 l2arc_do_free_on_write(); 4679 4680 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4681} 4682 4683/* 4684 * A read to a cache device completed. Validate buffer contents before 4685 * handing over to the regular ARC routines. 4686 */ 4687static void 4688l2arc_read_done(zio_t *zio) 4689{ 4690 l2arc_read_callback_t *cb; 4691 arc_buf_hdr_t *hdr; 4692 arc_buf_t *buf; 4693 kmutex_t *hash_lock; 4694 int equal; 4695 4696 ASSERT(zio->io_vd != NULL); 4697 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4698 4699 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4700 4701 cb = zio->io_private; 4702 ASSERT(cb != NULL); 4703 buf = cb->l2rcb_buf; 4704 ASSERT(buf != NULL); 4705 4706 hash_lock = HDR_LOCK(buf->b_hdr); 4707 mutex_enter(hash_lock); 4708 hdr = buf->b_hdr; 4709 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4710 4711 /* 4712 * If the buffer was compressed, decompress it first. 4713 */ 4714 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 4715 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 4716 ASSERT(zio->io_data != NULL); 4717 4718 /* 4719 * Check this survived the L2ARC journey. 4720 */ 4721 equal = arc_cksum_equal(buf); 4722 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4723 mutex_exit(hash_lock); 4724 zio->io_private = buf; 4725 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4726 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4727 arc_read_done(zio); 4728 } else { 4729 mutex_exit(hash_lock); 4730 /* 4731 * Buffer didn't survive caching. Increment stats and 4732 * reissue to the original storage device. 4733 */ 4734 if (zio->io_error != 0) { 4735 ARCSTAT_BUMP(arcstat_l2_io_error); 4736 } else { 4737 zio->io_error = SET_ERROR(EIO); 4738 } 4739 if (!equal) 4740 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4741 4742 /* 4743 * If there's no waiter, issue an async i/o to the primary 4744 * storage now. If there *is* a waiter, the caller must 4745 * issue the i/o in a context where it's OK to block. 4746 */ 4747 if (zio->io_waiter == NULL) { 4748 zio_t *pio = zio_unique_parent(zio); 4749 4750 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4751 4752 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4753 buf->b_data, zio->io_size, arc_read_done, buf, 4754 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4755 } 4756 } 4757 4758 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4759} 4760 4761/* 4762 * This is the list priority from which the L2ARC will search for pages to 4763 * cache. This is used within loops (0..3) to cycle through lists in the 4764 * desired order. This order can have a significant effect on cache 4765 * performance. 4766 * 4767 * Currently the metadata lists are hit first, MFU then MRU, followed by 4768 * the data lists. This function returns a locked list, and also returns 4769 * the lock pointer. 4770 */ 4771static list_t * 4772l2arc_list_locked(int list_num, kmutex_t **lock) 4773{ 4774 list_t *list = NULL; 4775 int idx; 4776 4777 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS); 4778 4779 if (list_num < ARC_BUFC_NUMMETADATALISTS) { 4780 idx = list_num; 4781 list = &arc_mfu->arcs_lists[idx]; 4782 *lock = ARCS_LOCK(arc_mfu, idx); 4783 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) { 4784 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 4785 list = &arc_mru->arcs_lists[idx]; 4786 *lock = ARCS_LOCK(arc_mru, idx); 4787 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 + 4788 ARC_BUFC_NUMDATALISTS)) { 4789 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 4790 list = &arc_mfu->arcs_lists[idx]; 4791 *lock = ARCS_LOCK(arc_mfu, idx); 4792 } else { 4793 idx = list_num - ARC_BUFC_NUMLISTS; 4794 list = &arc_mru->arcs_lists[idx]; 4795 *lock = ARCS_LOCK(arc_mru, idx); 4796 } 4797 4798 ASSERT(!(MUTEX_HELD(*lock))); 4799 mutex_enter(*lock); 4800 return (list); 4801} 4802 4803/* 4804 * Evict buffers from the device write hand to the distance specified in 4805 * bytes. This distance may span populated buffers, it may span nothing. 4806 * This is clearing a region on the L2ARC device ready for writing. 4807 * If the 'all' boolean is set, every buffer is evicted. 4808 */ 4809static void 4810l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 4811{ 4812 list_t *buflist; 4813 l2arc_buf_hdr_t *abl2; 4814 arc_buf_hdr_t *ab, *ab_prev; 4815 kmutex_t *hash_lock; 4816 uint64_t taddr; 4817 int64_t bytes_evicted = 0; 4818 4819 buflist = dev->l2ad_buflist; 4820 4821 if (buflist == NULL) 4822 return; 4823 4824 if (!all && dev->l2ad_first) { 4825 /* 4826 * This is the first sweep through the device. There is 4827 * nothing to evict. 4828 */ 4829 return; 4830 } 4831 4832 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 4833 /* 4834 * When nearing the end of the device, evict to the end 4835 * before the device write hand jumps to the start. 4836 */ 4837 taddr = dev->l2ad_end; 4838 } else { 4839 taddr = dev->l2ad_hand + distance; 4840 } 4841 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 4842 uint64_t, taddr, boolean_t, all); 4843 4844top: 4845 mutex_enter(&l2arc_buflist_mtx); 4846 for (ab = list_tail(buflist); ab; ab = ab_prev) { 4847 ab_prev = list_prev(buflist, ab); 4848 4849 hash_lock = HDR_LOCK(ab); 4850 if (!mutex_tryenter(hash_lock)) { 4851 /* 4852 * Missed the hash lock. Retry. 4853 */ 4854 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 4855 mutex_exit(&l2arc_buflist_mtx); 4856 mutex_enter(hash_lock); 4857 mutex_exit(hash_lock); 4858 goto top; 4859 } 4860 4861 if (HDR_L2_WRITE_HEAD(ab)) { 4862 /* 4863 * We hit a write head node. Leave it for 4864 * l2arc_write_done(). 4865 */ 4866 list_remove(buflist, ab); 4867 mutex_exit(hash_lock); 4868 continue; 4869 } 4870 4871 if (!all && ab->b_l2hdr != NULL && 4872 (ab->b_l2hdr->b_daddr > taddr || 4873 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) { 4874 /* 4875 * We've evicted to the target address, 4876 * or the end of the device. 4877 */ 4878 mutex_exit(hash_lock); 4879 break; 4880 } 4881 4882 if (HDR_FREE_IN_PROGRESS(ab)) { 4883 /* 4884 * Already on the path to destruction. 4885 */ 4886 mutex_exit(hash_lock); 4887 continue; 4888 } 4889 4890 if (ab->b_state == arc_l2c_only) { 4891 ASSERT(!HDR_L2_READING(ab)); 4892 /* 4893 * This doesn't exist in the ARC. Destroy. 4894 * arc_hdr_destroy() will call list_remove() 4895 * and decrement arcstat_l2_size. 4896 */ 4897 arc_change_state(arc_anon, ab, hash_lock); 4898 arc_hdr_destroy(ab); 4899 } else { 4900 /* 4901 * Invalidate issued or about to be issued 4902 * reads, since we may be about to write 4903 * over this location. 4904 */ 4905 if (HDR_L2_READING(ab)) { 4906 ARCSTAT_BUMP(arcstat_l2_evict_reading); 4907 ab->b_flags |= ARC_L2_EVICTED; 4908 } 4909 4910 /* 4911 * Tell ARC this no longer exists in L2ARC. 4912 */ 4913 if (ab->b_l2hdr != NULL) { 4914 abl2 = ab->b_l2hdr; 4915 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4916 bytes_evicted += abl2->b_asize; 4917 ab->b_l2hdr = NULL; 4918 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4919 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4920 } 4921 list_remove(buflist, ab); 4922 4923 /* 4924 * This may have been leftover after a 4925 * failed write. 4926 */ 4927 ab->b_flags &= ~ARC_L2_WRITING; 4928 } 4929 mutex_exit(hash_lock); 4930 } 4931 mutex_exit(&l2arc_buflist_mtx); 4932 4933 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 4934 dev->l2ad_evict = taddr; 4935} 4936 4937/* 4938 * Find and write ARC buffers to the L2ARC device. 4939 * 4940 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid 4941 * for reading until they have completed writing. 4942 * The headroom_boost is an in-out parameter used to maintain headroom boost 4943 * state between calls to this function. 4944 * 4945 * Returns the number of bytes actually written (which may be smaller than 4946 * the delta by which the device hand has changed due to alignment). 4947 */ 4948static uint64_t 4949l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 4950 boolean_t *headroom_boost) 4951{ 4952 arc_buf_hdr_t *ab, *ab_prev, *head; 4953 list_t *list; 4954 uint64_t write_asize, write_psize, write_sz, headroom, 4955 buf_compress_minsz; 4956 void *buf_data; 4957 kmutex_t *list_lock; 4958 boolean_t full; 4959 l2arc_write_callback_t *cb; 4960 zio_t *pio, *wzio; 4961 uint64_t guid = spa_load_guid(spa); 4962 const boolean_t do_headroom_boost = *headroom_boost; 4963 int try; 4964 4965 ASSERT(dev->l2ad_vdev != NULL); 4966 4967 /* Lower the flag now, we might want to raise it again later. */ 4968 *headroom_boost = B_FALSE; 4969 4970 pio = NULL; 4971 write_sz = write_asize = write_psize = 0; 4972 full = B_FALSE; 4973 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 4974 head->b_flags |= ARC_L2_WRITE_HEAD; 4975 4976 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 4977 /* 4978 * We will want to try to compress buffers that are at least 2x the 4979 * device sector size. 4980 */ 4981 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 4982 4983 /* 4984 * Copy buffers for L2ARC writing. 4985 */ 4986 mutex_enter(&l2arc_buflist_mtx); 4987 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) { 4988 uint64_t passed_sz = 0; 4989 4990 list = l2arc_list_locked(try, &list_lock); 4991 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 4992 4993 /* 4994 * L2ARC fast warmup. 4995 * 4996 * Until the ARC is warm and starts to evict, read from the 4997 * head of the ARC lists rather than the tail. 4998 */ 4999 if (arc_warm == B_FALSE) 5000 ab = list_head(list); 5001 else 5002 ab = list_tail(list); 5003 if (ab == NULL) 5004 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 5005 5006 headroom = target_sz * l2arc_headroom; 5007 if (do_headroom_boost) 5008 headroom = (headroom * l2arc_headroom_boost) / 100; 5009 5010 for (; ab; ab = ab_prev) { 5011 l2arc_buf_hdr_t *l2hdr; 5012 kmutex_t *hash_lock; 5013 uint64_t buf_sz; 5014 5015 if (arc_warm == B_FALSE) 5016 ab_prev = list_next(list, ab); 5017 else 5018 ab_prev = list_prev(list, ab); 5019 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size); 5020 5021 hash_lock = HDR_LOCK(ab); 5022 if (!mutex_tryenter(hash_lock)) { 5023 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 5024 /* 5025 * Skip this buffer rather than waiting. 5026 */ 5027 continue; 5028 } 5029 5030 passed_sz += ab->b_size; 5031 if (passed_sz > headroom) { 5032 /* 5033 * Searched too far. 5034 */ 5035 mutex_exit(hash_lock); 5036 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 5037 break; 5038 } 5039 5040 if (!l2arc_write_eligible(guid, ab)) { 5041 mutex_exit(hash_lock); 5042 continue; 5043 } 5044 5045 if ((write_sz + ab->b_size) > target_sz) { 5046 full = B_TRUE; 5047 mutex_exit(hash_lock); 5048 ARCSTAT_BUMP(arcstat_l2_write_full); 5049 break; 5050 } 5051 5052 if (pio == NULL) { 5053 /* 5054 * Insert a dummy header on the buflist so 5055 * l2arc_write_done() can find where the 5056 * write buffers begin without searching. 5057 */ 5058 list_insert_head(dev->l2ad_buflist, head); 5059 5060 cb = kmem_alloc( 5061 sizeof (l2arc_write_callback_t), KM_SLEEP); 5062 cb->l2wcb_dev = dev; 5063 cb->l2wcb_head = head; 5064 pio = zio_root(spa, l2arc_write_done, cb, 5065 ZIO_FLAG_CANFAIL); 5066 ARCSTAT_BUMP(arcstat_l2_write_pios); 5067 } 5068 5069 /* 5070 * Create and add a new L2ARC header. 5071 */ 5072 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP); 5073 l2hdr->b_dev = dev; 5074 ab->b_flags |= ARC_L2_WRITING; 5075 5076 /* 5077 * Temporarily stash the data buffer in b_tmp_cdata. 5078 * The subsequent write step will pick it up from 5079 * there. This is because can't access ab->b_buf 5080 * without holding the hash_lock, which we in turn 5081 * can't access without holding the ARC list locks 5082 * (which we want to avoid during compression/writing). 5083 */ 5084 l2hdr->b_compress = ZIO_COMPRESS_OFF; 5085 l2hdr->b_asize = ab->b_size; 5086 l2hdr->b_tmp_cdata = ab->b_buf->b_data; 5087 5088 buf_sz = ab->b_size; 5089 ab->b_l2hdr = l2hdr; 5090 5091 list_insert_head(dev->l2ad_buflist, ab); 5092 5093 /* 5094 * Compute and store the buffer cksum before 5095 * writing. On debug the cksum is verified first. 5096 */ 5097 arc_cksum_verify(ab->b_buf); 5098 arc_cksum_compute(ab->b_buf, B_TRUE); 5099 5100 mutex_exit(hash_lock); 5101 5102 write_sz += buf_sz; 5103 } 5104 5105 mutex_exit(list_lock); 5106 5107 if (full == B_TRUE) 5108 break; 5109 } 5110 5111 /* No buffers selected for writing? */ 5112 if (pio == NULL) { 5113 ASSERT0(write_sz); 5114 mutex_exit(&l2arc_buflist_mtx); 5115 kmem_cache_free(hdr_cache, head); 5116 return (0); 5117 } 5118 5119 /* 5120 * Now start writing the buffers. We're starting at the write head 5121 * and work backwards, retracing the course of the buffer selector 5122 * loop above. 5123 */ 5124 for (ab = list_prev(dev->l2ad_buflist, head); ab; 5125 ab = list_prev(dev->l2ad_buflist, ab)) { 5126 l2arc_buf_hdr_t *l2hdr; 5127 uint64_t buf_sz; 5128 5129 /* 5130 * We shouldn't need to lock the buffer here, since we flagged 5131 * it as ARC_L2_WRITING in the previous step, but we must take 5132 * care to only access its L2 cache parameters. In particular, 5133 * ab->b_buf may be invalid by now due to ARC eviction. 5134 */ 5135 l2hdr = ab->b_l2hdr; 5136 l2hdr->b_daddr = dev->l2ad_hand; 5137 5138 if ((ab->b_flags & ARC_L2COMPRESS) && 5139 l2hdr->b_asize >= buf_compress_minsz) { 5140 if (l2arc_compress_buf(l2hdr)) { 5141 /* 5142 * If compression succeeded, enable headroom 5143 * boost on the next scan cycle. 5144 */ 5145 *headroom_boost = B_TRUE; 5146 } 5147 } 5148 5149 /* 5150 * Pick up the buffer data we had previously stashed away 5151 * (and now potentially also compressed). 5152 */ 5153 buf_data = l2hdr->b_tmp_cdata; 5154 buf_sz = l2hdr->b_asize; 5155 5156 /* Compression may have squashed the buffer to zero length. */ 5157 if (buf_sz != 0) { 5158 uint64_t buf_p_sz; 5159 5160 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5161 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5162 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 5163 ZIO_FLAG_CANFAIL, B_FALSE); 5164 5165 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 5166 zio_t *, wzio); 5167 (void) zio_nowait(wzio); 5168 5169 write_asize += buf_sz; 5170 /* 5171 * Keep the clock hand suitably device-aligned. 5172 */ 5173 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5174 write_psize += buf_p_sz; 5175 dev->l2ad_hand += buf_p_sz; 5176 } 5177 } 5178 5179 mutex_exit(&l2arc_buflist_mtx); 5180 5181 ASSERT3U(write_asize, <=, target_sz); 5182 ARCSTAT_BUMP(arcstat_l2_writes_sent); 5183 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 5184 ARCSTAT_INCR(arcstat_l2_size, write_sz); 5185 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 5186 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 5187 5188 /* 5189 * Bump device hand to the device start if it is approaching the end. 5190 * l2arc_evict() will already have evicted ahead for this case. 5191 */ 5192 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 5193 dev->l2ad_hand = dev->l2ad_start; 5194 dev->l2ad_evict = dev->l2ad_start; 5195 dev->l2ad_first = B_FALSE; 5196 } 5197 5198 dev->l2ad_writing = B_TRUE; 5199 (void) zio_wait(pio); 5200 dev->l2ad_writing = B_FALSE; 5201 5202 return (write_asize); 5203} 5204 5205/* 5206 * Compresses an L2ARC buffer. 5207 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its 5208 * size in l2hdr->b_asize. This routine tries to compress the data and 5209 * depending on the compression result there are three possible outcomes: 5210 * *) The buffer was incompressible. The original l2hdr contents were left 5211 * untouched and are ready for writing to an L2 device. 5212 * *) The buffer was all-zeros, so there is no need to write it to an L2 5213 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 5214 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 5215 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 5216 * data buffer which holds the compressed data to be written, and b_asize 5217 * tells us how much data there is. b_compress is set to the appropriate 5218 * compression algorithm. Once writing is done, invoke 5219 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 5220 * 5221 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 5222 * buffer was incompressible). 5223 */ 5224static boolean_t 5225l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr) 5226{ 5227 void *cdata; 5228 size_t csize, len, rounded; 5229 5230 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF); 5231 ASSERT(l2hdr->b_tmp_cdata != NULL); 5232 5233 len = l2hdr->b_asize; 5234 cdata = zio_data_buf_alloc(len); 5235 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata, 5236 cdata, l2hdr->b_asize, (size_t)(1ULL << l2hdr->b_dev->l2ad_vdev->vdev_ashift)); 5237 5238 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 5239 if (rounded > csize) { 5240 bzero((char *)cdata + csize, rounded - csize); 5241 csize = rounded; 5242 } 5243 5244 if (csize == 0) { 5245 /* zero block, indicate that there's nothing to write */ 5246 zio_data_buf_free(cdata, len); 5247 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 5248 l2hdr->b_asize = 0; 5249 l2hdr->b_tmp_cdata = NULL; 5250 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 5251 return (B_TRUE); 5252 } else if (csize > 0 && csize < len) { 5253 /* 5254 * Compression succeeded, we'll keep the cdata around for 5255 * writing and release it afterwards. 5256 */ 5257 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 5258 l2hdr->b_asize = csize; 5259 l2hdr->b_tmp_cdata = cdata; 5260 ARCSTAT_BUMP(arcstat_l2_compress_successes); 5261 return (B_TRUE); 5262 } else { 5263 /* 5264 * Compression failed, release the compressed buffer. 5265 * l2hdr will be left unmodified. 5266 */ 5267 zio_data_buf_free(cdata, len); 5268 ARCSTAT_BUMP(arcstat_l2_compress_failures); 5269 return (B_FALSE); 5270 } 5271} 5272 5273/* 5274 * Decompresses a zio read back from an l2arc device. On success, the 5275 * underlying zio's io_data buffer is overwritten by the uncompressed 5276 * version. On decompression error (corrupt compressed stream), the 5277 * zio->io_error value is set to signal an I/O error. 5278 * 5279 * Please note that the compressed data stream is not checksummed, so 5280 * if the underlying device is experiencing data corruption, we may feed 5281 * corrupt data to the decompressor, so the decompressor needs to be 5282 * able to handle this situation (LZ4 does). 5283 */ 5284static void 5285l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 5286{ 5287 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 5288 5289 if (zio->io_error != 0) { 5290 /* 5291 * An io error has occured, just restore the original io 5292 * size in preparation for a main pool read. 5293 */ 5294 zio->io_orig_size = zio->io_size = hdr->b_size; 5295 return; 5296 } 5297 5298 if (c == ZIO_COMPRESS_EMPTY) { 5299 /* 5300 * An empty buffer results in a null zio, which means we 5301 * need to fill its io_data after we're done restoring the 5302 * buffer's contents. 5303 */ 5304 ASSERT(hdr->b_buf != NULL); 5305 bzero(hdr->b_buf->b_data, hdr->b_size); 5306 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data; 5307 } else { 5308 ASSERT(zio->io_data != NULL); 5309 /* 5310 * We copy the compressed data from the start of the arc buffer 5311 * (the zio_read will have pulled in only what we need, the 5312 * rest is garbage which we will overwrite at decompression) 5313 * and then decompress back to the ARC data buffer. This way we 5314 * can minimize copying by simply decompressing back over the 5315 * original compressed data (rather than decompressing to an 5316 * aux buffer and then copying back the uncompressed buffer, 5317 * which is likely to be much larger). 5318 */ 5319 uint64_t csize; 5320 void *cdata; 5321 5322 csize = zio->io_size; 5323 cdata = zio_data_buf_alloc(csize); 5324 bcopy(zio->io_data, cdata, csize); 5325 if (zio_decompress_data(c, cdata, zio->io_data, csize, 5326 hdr->b_size) != 0) 5327 zio->io_error = EIO; 5328 zio_data_buf_free(cdata, csize); 5329 } 5330 5331 /* Restore the expected uncompressed IO size. */ 5332 zio->io_orig_size = zio->io_size = hdr->b_size; 5333} 5334 5335/* 5336 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 5337 * This buffer serves as a temporary holder of compressed data while 5338 * the buffer entry is being written to an l2arc device. Once that is 5339 * done, we can dispose of it. 5340 */ 5341static void 5342l2arc_release_cdata_buf(arc_buf_hdr_t *ab) 5343{ 5344 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr; 5345 5346 if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) { 5347 /* 5348 * If the data was compressed, then we've allocated a 5349 * temporary buffer for it, so now we need to release it. 5350 */ 5351 ASSERT(l2hdr->b_tmp_cdata != NULL); 5352 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size); 5353 } 5354 l2hdr->b_tmp_cdata = NULL; 5355} 5356 5357/* 5358 * This thread feeds the L2ARC at regular intervals. This is the beating 5359 * heart of the L2ARC. 5360 */ 5361static void 5362l2arc_feed_thread(void *dummy __unused) 5363{ 5364 callb_cpr_t cpr; 5365 l2arc_dev_t *dev; 5366 spa_t *spa; 5367 uint64_t size, wrote; 5368 clock_t begin, next = ddi_get_lbolt(); 5369 boolean_t headroom_boost = B_FALSE; 5370 5371 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 5372 5373 mutex_enter(&l2arc_feed_thr_lock); 5374 5375 while (l2arc_thread_exit == 0) { 5376 CALLB_CPR_SAFE_BEGIN(&cpr); 5377 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 5378 next - ddi_get_lbolt()); 5379 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 5380 next = ddi_get_lbolt() + hz; 5381 5382 /* 5383 * Quick check for L2ARC devices. 5384 */ 5385 mutex_enter(&l2arc_dev_mtx); 5386 if (l2arc_ndev == 0) { 5387 mutex_exit(&l2arc_dev_mtx); 5388 continue; 5389 } 5390 mutex_exit(&l2arc_dev_mtx); 5391 begin = ddi_get_lbolt(); 5392 5393 /* 5394 * This selects the next l2arc device to write to, and in 5395 * doing so the next spa to feed from: dev->l2ad_spa. This 5396 * will return NULL if there are now no l2arc devices or if 5397 * they are all faulted. 5398 * 5399 * If a device is returned, its spa's config lock is also 5400 * held to prevent device removal. l2arc_dev_get_next() 5401 * will grab and release l2arc_dev_mtx. 5402 */ 5403 if ((dev = l2arc_dev_get_next()) == NULL) 5404 continue; 5405 5406 spa = dev->l2ad_spa; 5407 ASSERT(spa != NULL); 5408 5409 /* 5410 * If the pool is read-only then force the feed thread to 5411 * sleep a little longer. 5412 */ 5413 if (!spa_writeable(spa)) { 5414 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 5415 spa_config_exit(spa, SCL_L2ARC, dev); 5416 continue; 5417 } 5418 5419 /* 5420 * Avoid contributing to memory pressure. 5421 */ 5422 if (arc_reclaim_needed()) { 5423 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 5424 spa_config_exit(spa, SCL_L2ARC, dev); 5425 continue; 5426 } 5427 5428 ARCSTAT_BUMP(arcstat_l2_feeds); 5429 5430 size = l2arc_write_size(); 5431 5432 /* 5433 * Evict L2ARC buffers that will be overwritten. 5434 */ 5435 l2arc_evict(dev, size, B_FALSE); 5436 5437 /* 5438 * Write ARC buffers. 5439 */ 5440 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 5441 5442 /* 5443 * Calculate interval between writes. 5444 */ 5445 next = l2arc_write_interval(begin, size, wrote); 5446 spa_config_exit(spa, SCL_L2ARC, dev); 5447 } 5448 5449 l2arc_thread_exit = 0; 5450 cv_broadcast(&l2arc_feed_thr_cv); 5451 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 5452 thread_exit(); 5453} 5454 5455boolean_t 5456l2arc_vdev_present(vdev_t *vd) 5457{ 5458 l2arc_dev_t *dev; 5459 5460 mutex_enter(&l2arc_dev_mtx); 5461 for (dev = list_head(l2arc_dev_list); dev != NULL; 5462 dev = list_next(l2arc_dev_list, dev)) { 5463 if (dev->l2ad_vdev == vd) 5464 break; 5465 } 5466 mutex_exit(&l2arc_dev_mtx); 5467 5468 return (dev != NULL); 5469} 5470 5471/* 5472 * Add a vdev for use by the L2ARC. By this point the spa has already 5473 * validated the vdev and opened it. 5474 */ 5475void 5476l2arc_add_vdev(spa_t *spa, vdev_t *vd) 5477{ 5478 l2arc_dev_t *adddev; 5479 5480 ASSERT(!l2arc_vdev_present(vd)); 5481 5482 vdev_ashift_optimize(vd); 5483 5484 /* 5485 * Create a new l2arc device entry. 5486 */ 5487 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 5488 adddev->l2ad_spa = spa; 5489 adddev->l2ad_vdev = vd; 5490 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 5491 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 5492 adddev->l2ad_hand = adddev->l2ad_start; 5493 adddev->l2ad_evict = adddev->l2ad_start; 5494 adddev->l2ad_first = B_TRUE; 5495 adddev->l2ad_writing = B_FALSE; 5496 5497 /* 5498 * This is a list of all ARC buffers that are still valid on the 5499 * device. 5500 */ 5501 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP); 5502 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 5503 offsetof(arc_buf_hdr_t, b_l2node)); 5504 5505 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 5506 5507 /* 5508 * Add device to global list 5509 */ 5510 mutex_enter(&l2arc_dev_mtx); 5511 list_insert_head(l2arc_dev_list, adddev); 5512 atomic_inc_64(&l2arc_ndev); 5513 mutex_exit(&l2arc_dev_mtx); 5514} 5515 5516/* 5517 * Remove a vdev from the L2ARC. 5518 */ 5519void 5520l2arc_remove_vdev(vdev_t *vd) 5521{ 5522 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 5523 5524 /* 5525 * Find the device by vdev 5526 */ 5527 mutex_enter(&l2arc_dev_mtx); 5528 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 5529 nextdev = list_next(l2arc_dev_list, dev); 5530 if (vd == dev->l2ad_vdev) { 5531 remdev = dev; 5532 break; 5533 } 5534 } 5535 ASSERT(remdev != NULL); 5536 5537 /* 5538 * Remove device from global list 5539 */ 5540 list_remove(l2arc_dev_list, remdev); 5541 l2arc_dev_last = NULL; /* may have been invalidated */ 5542 atomic_dec_64(&l2arc_ndev); 5543 mutex_exit(&l2arc_dev_mtx); 5544 5545 /* 5546 * Clear all buflists and ARC references. L2ARC device flush. 5547 */ 5548 l2arc_evict(remdev, 0, B_TRUE); 5549 list_destroy(remdev->l2ad_buflist); 5550 kmem_free(remdev->l2ad_buflist, sizeof (list_t)); 5551 kmem_free(remdev, sizeof (l2arc_dev_t)); 5552} 5553 5554void 5555l2arc_init(void) 5556{ 5557 l2arc_thread_exit = 0; 5558 l2arc_ndev = 0; 5559 l2arc_writes_sent = 0; 5560 l2arc_writes_done = 0; 5561 5562 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 5563 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 5564 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 5565 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL); 5566 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 5567 5568 l2arc_dev_list = &L2ARC_dev_list; 5569 l2arc_free_on_write = &L2ARC_free_on_write; 5570 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 5571 offsetof(l2arc_dev_t, l2ad_node)); 5572 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 5573 offsetof(l2arc_data_free_t, l2df_list_node)); 5574} 5575 5576void 5577l2arc_fini(void) 5578{ 5579 /* 5580 * This is called from dmu_fini(), which is called from spa_fini(); 5581 * Because of this, we can assume that all l2arc devices have 5582 * already been removed when the pools themselves were removed. 5583 */ 5584 5585 l2arc_do_free_on_write(); 5586 5587 mutex_destroy(&l2arc_feed_thr_lock); 5588 cv_destroy(&l2arc_feed_thr_cv); 5589 mutex_destroy(&l2arc_dev_mtx); 5590 mutex_destroy(&l2arc_buflist_mtx); 5591 mutex_destroy(&l2arc_free_on_write_mtx); 5592 5593 list_destroy(l2arc_dev_list); 5594 list_destroy(l2arc_free_on_write); 5595} 5596 5597void 5598l2arc_start(void) 5599{ 5600 if (!(spa_mode_global & FWRITE)) 5601 return; 5602 5603 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 5604 TS_RUN, minclsyspri); 5605} 5606 5607void 5608l2arc_stop(void) 5609{ 5610 if (!(spa_mode_global & FWRITE)) 5611 return; 5612 5613 mutex_enter(&l2arc_feed_thr_lock); 5614 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 5615 l2arc_thread_exit = 1; 5616 while (l2arc_thread_exit != 0) 5617 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 5618 mutex_exit(&l2arc_feed_thr_lock); 5619}
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