1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 24 * Copyright (c) 2012 by Delphix. All rights reserved. 25 */ 26 27 /* 28 * DVA-based Adjustable Replacement Cache 29 * 30 * While much of the theory of operation used here is 31 * based on the self-tuning, low overhead replacement cache 32 * presented by Megiddo and Modha at FAST 2003, there are some 33 * significant differences: 34 * 35 * 1. The Megiddo and Modha model assumes any page is evictable. 36 * Pages in its cache cannot be "locked" into memory. This makes 37 * the eviction algorithm simple: evict the last page in the list. 38 * This also make the performance characteristics easy to reason 39 * about. Our cache is not so simple. At any given moment, some 40 * subset of the blocks in the cache are un-evictable because we 41 * have handed out a reference to them. Blocks are only evictable 42 * when there are no external references active. This makes 43 * eviction far more problematic: we choose to evict the evictable 44 * blocks that are the "lowest" in the list. 45 * 46 * There are times when it is not possible to evict the requested 47 * space. In these circumstances we are unable to adjust the cache 48 * size. To prevent the cache growing unbounded at these times we 49 * implement a "cache throttle" that slows the flow of new data 50 * into the cache until we can make space available. 51 * 52 * 2. The Megiddo and Modha model assumes a fixed cache size. 53 * Pages are evicted when the cache is full and there is a cache 54 * miss. Our model has a variable sized cache. It grows with 55 * high use, but also tries to react to memory pressure from the 56 * operating system: decreasing its size when system memory is 57 * tight. 58 * 59 * 3. The Megiddo and Modha model assumes a fixed page size. All 60 * elements of the cache are therefor exactly the same size. So 61 * when adjusting the cache size following a cache miss, its simply 62 * a matter of choosing a single page to evict. In our model, we 63 * have variable sized cache blocks (rangeing from 512 bytes to 64 * 128K bytes). We therefor choose a set of blocks to evict to make 65 * space for a cache miss that approximates as closely as possible 66 * the space used by the new block. 67 * 68 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 69 * by N. Megiddo & D. Modha, FAST 2003 70 */ 71 72 /* 73 * The locking model: 74 * 75 * A new reference to a cache buffer can be obtained in two 76 * ways: 1) via a hash table lookup using the DVA as a key, 77 * or 2) via one of the ARC lists. The arc_read() interface 78 * uses method 1, while the internal arc algorithms for 79 * adjusting the cache use method 2. We therefor provide two 80 * types of locks: 1) the hash table lock array, and 2) the 81 * arc list locks. 82 * 83 * Buffers do not have their own mutexes, rather they rely on the 84 * hash table mutexes for the bulk of their protection (i.e. most 85 * fields in the arc_buf_hdr_t are protected by these mutexes). 86 * 87 * buf_hash_find() returns the appropriate mutex (held) when it 88 * locates the requested buffer in the hash table. It returns 89 * NULL for the mutex if the buffer was not in the table. 90 * 91 * buf_hash_remove() expects the appropriate hash mutex to be 92 * already held before it is invoked. 93 * 94 * Each arc state also has a mutex which is used to protect the 95 * buffer list associated with the state. When attempting to 96 * obtain a hash table lock while holding an arc list lock you 97 * must use: mutex_tryenter() to avoid deadlock. Also note that 98 * the active state mutex must be held before the ghost state mutex. 99 * 100 * Arc buffers may have an associated eviction callback function. 101 * This function will be invoked prior to removing the buffer (e.g. 102 * in arc_do_user_evicts()). Note however that the data associated 103 * with the buffer may be evicted prior to the callback. The callback 104 * must be made with *no locks held* (to prevent deadlock). Additionally, 105 * the users of callbacks must ensure that their private data is 106 * protected from simultaneous callbacks from arc_buf_evict() 107 * and arc_do_user_evicts(). 108 * 109 * Note that the majority of the performance stats are manipulated 110 * with atomic operations. 111 * 112 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following: 113 * 114 * - L2ARC buflist creation 115 * - L2ARC buflist eviction 116 * - L2ARC write completion, which walks L2ARC buflists 117 * - ARC header destruction, as it removes from L2ARC buflists 118 * - ARC header release, as it removes from L2ARC buflists 119 */ 120 121 #include <sys/spa.h> 122 #include <sys/zio.h> 123 #include <sys/zfs_context.h> 124 #include <sys/arc.h> 125 #include <sys/refcount.h> 126 #include <sys/vdev.h> 127 #include <sys/vdev_impl.h> 128 #ifdef _KERNEL 129 #include <sys/vmsystm.h> 130 #include <vm/anon.h> 131 #include <sys/fs/swapnode.h> 132 #include <sys/dnlc.h> 133 #endif 134 #include <sys/callb.h> 135 #include <sys/kstat.h> 136 #include <zfs_fletcher.h> 137 138 #ifndef _KERNEL 139 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 140 boolean_t arc_watch = B_FALSE; 141 int arc_procfd; 142 #endif 143 144 static kmutex_t arc_reclaim_thr_lock; 145 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 146 static uint8_t arc_thread_exit; 147 148 extern int zfs_write_limit_shift; 149 extern uint64_t zfs_write_limit_max; 150 extern kmutex_t zfs_write_limit_lock; 151 152 #define ARC_REDUCE_DNLC_PERCENT 3 153 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT; 154 155 typedef enum arc_reclaim_strategy { 156 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ 157 ARC_RECLAIM_CONS /* Conservative reclaim strategy */ 158 } arc_reclaim_strategy_t; 159 160 /* number of seconds before growing cache again */ 161 static int arc_grow_retry = 60; 162 163 /* shift of arc_c for calculating both min and max arc_p */ 164 static int arc_p_min_shift = 4; 165 166 /* log2(fraction of arc to reclaim) */ 167 static int arc_shrink_shift = 5; 168 169 /* 170 * minimum lifespan of a prefetch block in clock ticks 171 * (initialized in arc_init()) 172 */ 173 static int arc_min_prefetch_lifespan; 174 175 static int arc_dead; 176 177 /* 178 * The arc has filled available memory and has now warmed up. 179 */ 180 static boolean_t arc_warm; 181 182 /* 183 * These tunables are for performance analysis. 184 */ 185 uint64_t zfs_arc_max; 186 uint64_t zfs_arc_min; 187 uint64_t zfs_arc_meta_limit = 0; 188 int zfs_arc_grow_retry = 0; 189 int zfs_arc_shrink_shift = 0; 190 int zfs_arc_p_min_shift = 0; 191 int zfs_disable_dup_eviction = 0; 192 193 /* 194 * Note that buffers can be in one of 6 states: 195 * ARC_anon - anonymous (discussed below) 196 * ARC_mru - recently used, currently cached 197 * ARC_mru_ghost - recentely used, no longer in cache 198 * ARC_mfu - frequently used, currently cached 199 * ARC_mfu_ghost - frequently used, no longer in cache 200 * ARC_l2c_only - exists in L2ARC but not other states 201 * When there are no active references to the buffer, they are 202 * are linked onto a list in one of these arc states. These are 203 * the only buffers that can be evicted or deleted. Within each 204 * state there are multiple lists, one for meta-data and one for 205 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 206 * etc.) is tracked separately so that it can be managed more 207 * explicitly: favored over data, limited explicitly. 208 * 209 * Anonymous buffers are buffers that are not associated with 210 * a DVA. These are buffers that hold dirty block copies 211 * before they are written to stable storage. By definition, 212 * they are "ref'd" and are considered part of arc_mru 213 * that cannot be freed. Generally, they will aquire a DVA 214 * as they are written and migrate onto the arc_mru list. 215 * 216 * The ARC_l2c_only state is for buffers that are in the second 217 * level ARC but no longer in any of the ARC_m* lists. The second 218 * level ARC itself may also contain buffers that are in any of 219 * the ARC_m* states - meaning that a buffer can exist in two 220 * places. The reason for the ARC_l2c_only state is to keep the 221 * buffer header in the hash table, so that reads that hit the 222 * second level ARC benefit from these fast lookups. 223 */ 224 225 typedef struct arc_state { 226 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */ 227 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 228 uint64_t arcs_size; /* total amount of data in this state */ 229 kmutex_t arcs_mtx; 230 } arc_state_t; 231 232 /* The 6 states: */ 233 static arc_state_t ARC_anon; 234 static arc_state_t ARC_mru; 235 static arc_state_t ARC_mru_ghost; 236 static arc_state_t ARC_mfu; 237 static arc_state_t ARC_mfu_ghost; 238 static arc_state_t ARC_l2c_only; 239 240 typedef struct arc_stats { 241 kstat_named_t arcstat_hits; 242 kstat_named_t arcstat_misses; 243 kstat_named_t arcstat_demand_data_hits; 244 kstat_named_t arcstat_demand_data_misses; 245 kstat_named_t arcstat_demand_metadata_hits; 246 kstat_named_t arcstat_demand_metadata_misses; 247 kstat_named_t arcstat_prefetch_data_hits; 248 kstat_named_t arcstat_prefetch_data_misses; 249 kstat_named_t arcstat_prefetch_metadata_hits; 250 kstat_named_t arcstat_prefetch_metadata_misses; 251 kstat_named_t arcstat_mru_hits; 252 kstat_named_t arcstat_mru_ghost_hits; 253 kstat_named_t arcstat_mfu_hits; 254 kstat_named_t arcstat_mfu_ghost_hits; 255 kstat_named_t arcstat_deleted; 256 kstat_named_t arcstat_recycle_miss; 257 kstat_named_t arcstat_mutex_miss; 258 kstat_named_t arcstat_evict_skip; 259 kstat_named_t arcstat_evict_l2_cached; 260 kstat_named_t arcstat_evict_l2_eligible; 261 kstat_named_t arcstat_evict_l2_ineligible; 262 kstat_named_t arcstat_hash_elements; 263 kstat_named_t arcstat_hash_elements_max; 264 kstat_named_t arcstat_hash_collisions; 265 kstat_named_t arcstat_hash_chains; 266 kstat_named_t arcstat_hash_chain_max; 267 kstat_named_t arcstat_p; 268 kstat_named_t arcstat_c; 269 kstat_named_t arcstat_c_min; 270 kstat_named_t arcstat_c_max; 271 kstat_named_t arcstat_size; 272 kstat_named_t arcstat_hdr_size; 273 kstat_named_t arcstat_data_size; 274 kstat_named_t arcstat_other_size; 275 kstat_named_t arcstat_l2_hits; 276 kstat_named_t arcstat_l2_misses; 277 kstat_named_t arcstat_l2_feeds; 278 kstat_named_t arcstat_l2_rw_clash; 279 kstat_named_t arcstat_l2_read_bytes; 280 kstat_named_t arcstat_l2_write_bytes; 281 kstat_named_t arcstat_l2_writes_sent; 282 kstat_named_t arcstat_l2_writes_done; 283 kstat_named_t arcstat_l2_writes_error; 284 kstat_named_t arcstat_l2_writes_hdr_miss; 285 kstat_named_t arcstat_l2_evict_lock_retry; 286 kstat_named_t arcstat_l2_evict_reading; 287 kstat_named_t arcstat_l2_free_on_write; 288 kstat_named_t arcstat_l2_abort_lowmem; 289 kstat_named_t arcstat_l2_cksum_bad; 290 kstat_named_t arcstat_l2_io_error; 291 kstat_named_t arcstat_l2_size; 292 kstat_named_t arcstat_l2_hdr_size; 293 kstat_named_t arcstat_memory_throttle_count; 294 kstat_named_t arcstat_duplicate_buffers; 295 kstat_named_t arcstat_duplicate_buffers_size; 296 kstat_named_t arcstat_duplicate_reads; 297 } arc_stats_t; 298 299 static arc_stats_t arc_stats = { 300 { "hits", KSTAT_DATA_UINT64 }, 301 { "misses", KSTAT_DATA_UINT64 }, 302 { "demand_data_hits", KSTAT_DATA_UINT64 }, 303 { "demand_data_misses", KSTAT_DATA_UINT64 }, 304 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 305 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 306 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 307 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 308 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 309 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 310 { "mru_hits", KSTAT_DATA_UINT64 }, 311 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 312 { "mfu_hits", KSTAT_DATA_UINT64 }, 313 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 314 { "deleted", KSTAT_DATA_UINT64 }, 315 { "recycle_miss", KSTAT_DATA_UINT64 }, 316 { "mutex_miss", KSTAT_DATA_UINT64 }, 317 { "evict_skip", KSTAT_DATA_UINT64 }, 318 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 319 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 320 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 321 { "hash_elements", KSTAT_DATA_UINT64 }, 322 { "hash_elements_max", KSTAT_DATA_UINT64 }, 323 { "hash_collisions", KSTAT_DATA_UINT64 }, 324 { "hash_chains", KSTAT_DATA_UINT64 }, 325 { "hash_chain_max", KSTAT_DATA_UINT64 }, 326 { "p", KSTAT_DATA_UINT64 }, 327 { "c", KSTAT_DATA_UINT64 }, 328 { "c_min", KSTAT_DATA_UINT64 }, 329 { "c_max", KSTAT_DATA_UINT64 }, 330 { "size", KSTAT_DATA_UINT64 }, 331 { "hdr_size", KSTAT_DATA_UINT64 }, 332 { "data_size", KSTAT_DATA_UINT64 }, 333 { "other_size", KSTAT_DATA_UINT64 }, 334 { "l2_hits", KSTAT_DATA_UINT64 }, 335 { "l2_misses", KSTAT_DATA_UINT64 }, 336 { "l2_feeds", KSTAT_DATA_UINT64 }, 337 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 338 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 339 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 340 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 341 { "l2_writes_done", KSTAT_DATA_UINT64 }, 342 { "l2_writes_error", KSTAT_DATA_UINT64 }, 343 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 344 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 345 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 346 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 347 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 348 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 349 { "l2_io_error", KSTAT_DATA_UINT64 }, 350 { "l2_size", KSTAT_DATA_UINT64 }, 351 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 352 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 353 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 354 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 355 { "duplicate_reads", KSTAT_DATA_UINT64 } 356 }; 357 358 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 359 360 #define ARCSTAT_INCR(stat, val) \ 361 atomic_add_64(&arc_stats.stat.value.ui64, (val)); 362 363 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 364 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 365 366 #define ARCSTAT_MAX(stat, val) { \ 367 uint64_t m; \ 368 while ((val) > (m = arc_stats.stat.value.ui64) && \ 369 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 370 continue; \ 371 } 372 373 #define ARCSTAT_MAXSTAT(stat) \ 374 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 375 376 /* 377 * We define a macro to allow ARC hits/misses to be easily broken down by 378 * two separate conditions, giving a total of four different subtypes for 379 * each of hits and misses (so eight statistics total). 380 */ 381 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 382 if (cond1) { \ 383 if (cond2) { \ 384 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 385 } else { \ 386 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 387 } \ 388 } else { \ 389 if (cond2) { \ 390 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 391 } else { \ 392 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 393 } \ 394 } 395 396 kstat_t *arc_ksp; 397 static arc_state_t *arc_anon; 398 static arc_state_t *arc_mru; 399 static arc_state_t *arc_mru_ghost; 400 static arc_state_t *arc_mfu; 401 static arc_state_t *arc_mfu_ghost; 402 static arc_state_t *arc_l2c_only; 403 404 /* 405 * There are several ARC variables that are critical to export as kstats -- 406 * but we don't want to have to grovel around in the kstat whenever we wish to 407 * manipulate them. For these variables, we therefore define them to be in 408 * terms of the statistic variable. This assures that we are not introducing 409 * the possibility of inconsistency by having shadow copies of the variables, 410 * while still allowing the code to be readable. 411 */ 412 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 413 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 414 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 415 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 416 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 417 418 static int arc_no_grow; /* Don't try to grow cache size */ 419 static uint64_t arc_tempreserve; 420 static uint64_t arc_loaned_bytes; 421 static uint64_t arc_meta_used; 422 static uint64_t arc_meta_limit; 423 static uint64_t arc_meta_max = 0; 424 425 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; 426 427 typedef struct arc_callback arc_callback_t; 428 429 struct arc_callback { 430 void *acb_private; 431 arc_done_func_t *acb_done; 432 arc_buf_t *acb_buf; 433 zio_t *acb_zio_dummy; 434 arc_callback_t *acb_next; 435 }; 436 437 typedef struct arc_write_callback arc_write_callback_t; 438 439 struct arc_write_callback { 440 void *awcb_private; 441 arc_done_func_t *awcb_ready; 442 arc_done_func_t *awcb_done; 443 arc_buf_t *awcb_buf; 444 }; 445 446 struct arc_buf_hdr { 447 /* protected by hash lock */ 448 dva_t b_dva; 449 uint64_t b_birth; 450 uint64_t b_cksum0; 451 452 kmutex_t b_freeze_lock; 453 zio_cksum_t *b_freeze_cksum; 454 void *b_thawed; 455 456 arc_buf_hdr_t *b_hash_next; 457 arc_buf_t *b_buf; 458 uint32_t b_flags; 459 uint32_t b_datacnt; 460 461 arc_callback_t *b_acb; 462 kcondvar_t b_cv; 463 464 /* immutable */ 465 arc_buf_contents_t b_type; 466 uint64_t b_size; 467 uint64_t b_spa; 468 469 /* protected by arc state mutex */ 470 arc_state_t *b_state; 471 list_node_t b_arc_node; 472 473 /* updated atomically */ 474 clock_t b_arc_access; 475 476 /* self protecting */ 477 refcount_t b_refcnt; 478 479 l2arc_buf_hdr_t *b_l2hdr; 480 list_node_t b_l2node; 481 }; 482 483 static arc_buf_t *arc_eviction_list; 484 static kmutex_t arc_eviction_mtx; 485 static arc_buf_hdr_t arc_eviction_hdr; 486 static void arc_get_data_buf(arc_buf_t *buf); 487 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock); 488 static int arc_evict_needed(arc_buf_contents_t type); 489 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes); 490 static void arc_buf_watch(arc_buf_t *buf); 491 492 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab); 493 494 #define GHOST_STATE(state) \ 495 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 496 (state) == arc_l2c_only) 497 498 /* 499 * Private ARC flags. These flags are private ARC only flags that will show up 500 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can 501 * be passed in as arc_flags in things like arc_read. However, these flags 502 * should never be passed and should only be set by ARC code. When adding new 503 * public flags, make sure not to smash the private ones. 504 */ 505 506 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */ 507 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */ 508 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */ 509 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */ 510 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */ 511 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */ 512 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */ 513 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */ 514 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */ 515 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */ 516 517 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE) 518 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS) 519 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR) 520 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH) 521 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ) 522 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE) 523 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS) 524 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE) 525 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \ 526 (hdr)->b_l2hdr != NULL) 527 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING) 528 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED) 529 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD) 530 531 /* 532 * Other sizes 533 */ 534 535 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 536 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t)) 537 538 /* 539 * Hash table routines 540 */ 541 542 #define HT_LOCK_PAD 64 543 544 struct ht_lock { 545 kmutex_t ht_lock; 546 #ifdef _KERNEL 547 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 548 #endif 549 }; 550 551 #define BUF_LOCKS 256 552 typedef struct buf_hash_table { 553 uint64_t ht_mask; 554 arc_buf_hdr_t **ht_table; 555 struct ht_lock ht_locks[BUF_LOCKS]; 556 } buf_hash_table_t; 557 558 static buf_hash_table_t buf_hash_table; 559 560 #define BUF_HASH_INDEX(spa, dva, birth) \ 561 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 562 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 563 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 564 #define HDR_LOCK(hdr) \ 565 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 566 567 uint64_t zfs_crc64_table[256]; 568 569 /* 570 * Level 2 ARC 571 */ 572 573 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 574 #define L2ARC_HEADROOM 2 /* num of writes */ 575 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 576 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 577 578 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 579 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 580 581 /* 582 * L2ARC Performance Tunables 583 */ 584 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 585 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 586 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 587 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 588 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 589 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 590 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 591 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 592 593 /* 594 * L2ARC Internals 595 */ 596 typedef struct l2arc_dev { 597 vdev_t *l2ad_vdev; /* vdev */ 598 spa_t *l2ad_spa; /* spa */ 599 uint64_t l2ad_hand; /* next write location */ 600 uint64_t l2ad_write; /* desired write size, bytes */ 601 uint64_t l2ad_boost; /* warmup write boost, bytes */ 602 uint64_t l2ad_start; /* first addr on device */ 603 uint64_t l2ad_end; /* last addr on device */ 604 uint64_t l2ad_evict; /* last addr eviction reached */ 605 boolean_t l2ad_first; /* first sweep through */ 606 boolean_t l2ad_writing; /* currently writing */ 607 list_t *l2ad_buflist; /* buffer list */ 608 list_node_t l2ad_node; /* device list node */ 609 } l2arc_dev_t; 610 611 static list_t L2ARC_dev_list; /* device list */ 612 static list_t *l2arc_dev_list; /* device list pointer */ 613 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 614 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 615 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */ 616 static list_t L2ARC_free_on_write; /* free after write buf list */ 617 static list_t *l2arc_free_on_write; /* free after write list ptr */ 618 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 619 static uint64_t l2arc_ndev; /* number of devices */ 620 621 typedef struct l2arc_read_callback { 622 arc_buf_t *l2rcb_buf; /* read buffer */ 623 spa_t *l2rcb_spa; /* spa */ 624 blkptr_t l2rcb_bp; /* original blkptr */ 625 zbookmark_t l2rcb_zb; /* original bookmark */ 626 int l2rcb_flags; /* original flags */ 627 } l2arc_read_callback_t; 628 629 typedef struct l2arc_write_callback { 630 l2arc_dev_t *l2wcb_dev; /* device info */ 631 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 632 } l2arc_write_callback_t; 633 634 struct l2arc_buf_hdr { 635 /* protected by arc_buf_hdr mutex */ 636 l2arc_dev_t *b_dev; /* L2ARC device */ 637 uint64_t b_daddr; /* disk address, offset byte */ 638 }; 639 640 typedef struct l2arc_data_free { 641 /* protected by l2arc_free_on_write_mtx */ 642 void *l2df_data; 643 size_t l2df_size; 644 void (*l2df_func)(void *, size_t); 645 list_node_t l2df_list_node; 646 } l2arc_data_free_t; 647 648 static kmutex_t l2arc_feed_thr_lock; 649 static kcondvar_t l2arc_feed_thr_cv; 650 static uint8_t l2arc_thread_exit; 651 652 static void l2arc_read_done(zio_t *zio); 653 static void l2arc_hdr_stat_add(void); 654 static void l2arc_hdr_stat_remove(void); 655 656 static uint64_t 657 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 658 { 659 uint8_t *vdva = (uint8_t *)dva; 660 uint64_t crc = -1ULL; 661 int i; 662 663 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 664 665 for (i = 0; i < sizeof (dva_t); i++) 666 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 667 668 crc ^= (spa>>8) ^ birth; 669 670 return (crc); 671 } 672 673 #define BUF_EMPTY(buf) \ 674 ((buf)->b_dva.dva_word[0] == 0 && \ 675 (buf)->b_dva.dva_word[1] == 0 && \ 676 (buf)->b_birth == 0) 677 678 #define BUF_EQUAL(spa, dva, birth, buf) \ 679 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 680 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 681 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 682 683 static void 684 buf_discard_identity(arc_buf_hdr_t *hdr) 685 { 686 hdr->b_dva.dva_word[0] = 0; 687 hdr->b_dva.dva_word[1] = 0; 688 hdr->b_birth = 0; 689 hdr->b_cksum0 = 0; 690 } 691 692 static arc_buf_hdr_t * 693 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp) 694 { 695 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 696 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 697 arc_buf_hdr_t *buf; 698 699 mutex_enter(hash_lock); 700 for (buf = buf_hash_table.ht_table[idx]; buf != NULL; 701 buf = buf->b_hash_next) { 702 if (BUF_EQUAL(spa, dva, birth, buf)) { 703 *lockp = hash_lock; 704 return (buf); 705 } 706 } 707 mutex_exit(hash_lock); 708 *lockp = NULL; 709 return (NULL); 710 } 711 712 /* 713 * Insert an entry into the hash table. If there is already an element 714 * equal to elem in the hash table, then the already existing element 715 * will be returned and the new element will not be inserted. 716 * Otherwise returns NULL. 717 */ 718 static arc_buf_hdr_t * 719 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp) 720 { 721 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 722 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 723 arc_buf_hdr_t *fbuf; 724 uint32_t i; 725 726 ASSERT(!HDR_IN_HASH_TABLE(buf)); 727 *lockp = hash_lock; 728 mutex_enter(hash_lock); 729 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL; 730 fbuf = fbuf->b_hash_next, i++) { 731 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf)) 732 return (fbuf); 733 } 734 735 buf->b_hash_next = buf_hash_table.ht_table[idx]; 736 buf_hash_table.ht_table[idx] = buf; 737 buf->b_flags |= ARC_IN_HASH_TABLE; 738 739 /* collect some hash table performance data */ 740 if (i > 0) { 741 ARCSTAT_BUMP(arcstat_hash_collisions); 742 if (i == 1) 743 ARCSTAT_BUMP(arcstat_hash_chains); 744 745 ARCSTAT_MAX(arcstat_hash_chain_max, i); 746 } 747 748 ARCSTAT_BUMP(arcstat_hash_elements); 749 ARCSTAT_MAXSTAT(arcstat_hash_elements); 750 751 return (NULL); 752 } 753 754 static void 755 buf_hash_remove(arc_buf_hdr_t *buf) 756 { 757 arc_buf_hdr_t *fbuf, **bufp; 758 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 759 760 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 761 ASSERT(HDR_IN_HASH_TABLE(buf)); 762 763 bufp = &buf_hash_table.ht_table[idx]; 764 while ((fbuf = *bufp) != buf) { 765 ASSERT(fbuf != NULL); 766 bufp = &fbuf->b_hash_next; 767 } 768 *bufp = buf->b_hash_next; 769 buf->b_hash_next = NULL; 770 buf->b_flags &= ~ARC_IN_HASH_TABLE; 771 772 /* collect some hash table performance data */ 773 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 774 775 if (buf_hash_table.ht_table[idx] && 776 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 777 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 778 } 779 780 /* 781 * Global data structures and functions for the buf kmem cache. 782 */ 783 static kmem_cache_t *hdr_cache; 784 static kmem_cache_t *buf_cache; 785 786 static void 787 buf_fini(void) 788 { 789 int i; 790 791 kmem_free(buf_hash_table.ht_table, 792 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 793 for (i = 0; i < BUF_LOCKS; i++) 794 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 795 kmem_cache_destroy(hdr_cache); 796 kmem_cache_destroy(buf_cache); 797 } 798 799 /* 800 * Constructor callback - called when the cache is empty 801 * and a new buf is requested. 802 */ 803 /* ARGSUSED */ 804 static int 805 hdr_cons(void *vbuf, void *unused, int kmflag) 806 { 807 arc_buf_hdr_t *buf = vbuf; 808 809 bzero(buf, sizeof (arc_buf_hdr_t)); 810 refcount_create(&buf->b_refcnt); 811 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL); 812 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 813 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 814 815 return (0); 816 } 817 818 /* ARGSUSED */ 819 static int 820 buf_cons(void *vbuf, void *unused, int kmflag) 821 { 822 arc_buf_t *buf = vbuf; 823 824 bzero(buf, sizeof (arc_buf_t)); 825 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 826 rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL); 827 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 828 829 return (0); 830 } 831 832 /* 833 * Destructor callback - called when a cached buf is 834 * no longer required. 835 */ 836 /* ARGSUSED */ 837 static void 838 hdr_dest(void *vbuf, void *unused) 839 { 840 arc_buf_hdr_t *buf = vbuf; 841 842 ASSERT(BUF_EMPTY(buf)); 843 refcount_destroy(&buf->b_refcnt); 844 cv_destroy(&buf->b_cv); 845 mutex_destroy(&buf->b_freeze_lock); 846 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 847 } 848 849 /* ARGSUSED */ 850 static void 851 buf_dest(void *vbuf, void *unused) 852 { 853 arc_buf_t *buf = vbuf; 854 855 mutex_destroy(&buf->b_evict_lock); 856 rw_destroy(&buf->b_data_lock); 857 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 858 } 859 860 /* 861 * Reclaim callback -- invoked when memory is low. 862 */ 863 /* ARGSUSED */ 864 static void 865 hdr_recl(void *unused) 866 { 867 dprintf("hdr_recl called\n"); 868 /* 869 * umem calls the reclaim func when we destroy the buf cache, 870 * which is after we do arc_fini(). 871 */ 872 if (!arc_dead) 873 cv_signal(&arc_reclaim_thr_cv); 874 } 875 876 static void 877 buf_init(void) 878 { 879 uint64_t *ct; 880 uint64_t hsize = 1ULL << 12; 881 int i, j; 882 883 /* 884 * The hash table is big enough to fill all of physical memory 885 * with an average 64K block size. The table will take up 886 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers). 887 */ 888 while (hsize * 65536 < physmem * PAGESIZE) 889 hsize <<= 1; 890 retry: 891 buf_hash_table.ht_mask = hsize - 1; 892 buf_hash_table.ht_table = 893 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 894 if (buf_hash_table.ht_table == NULL) { 895 ASSERT(hsize > (1ULL << 8)); 896 hsize >>= 1; 897 goto retry; 898 } 899 900 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t), 901 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0); 902 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 903 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 904 905 for (i = 0; i < 256; i++) 906 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 907 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 908 909 for (i = 0; i < BUF_LOCKS; i++) { 910 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 911 NULL, MUTEX_DEFAULT, NULL); 912 } 913 } 914 915 #define ARC_MINTIME (hz>>4) /* 62 ms */ 916 917 static void 918 arc_cksum_verify(arc_buf_t *buf) 919 { 920 zio_cksum_t zc; 921 922 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 923 return; 924 925 mutex_enter(&buf->b_hdr->b_freeze_lock); 926 if (buf->b_hdr->b_freeze_cksum == NULL || 927 (buf->b_hdr->b_flags & ARC_IO_ERROR)) { 928 mutex_exit(&buf->b_hdr->b_freeze_lock); 929 return; 930 } 931 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 932 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 933 panic("buffer modified while frozen!"); 934 mutex_exit(&buf->b_hdr->b_freeze_lock); 935 } 936 937 static int 938 arc_cksum_equal(arc_buf_t *buf) 939 { 940 zio_cksum_t zc; 941 int equal; 942 943 mutex_enter(&buf->b_hdr->b_freeze_lock); 944 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 945 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 946 mutex_exit(&buf->b_hdr->b_freeze_lock); 947 948 return (equal); 949 } 950 951 static void 952 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 953 { 954 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 955 return; 956 957 mutex_enter(&buf->b_hdr->b_freeze_lock); 958 if (buf->b_hdr->b_freeze_cksum != NULL) { 959 mutex_exit(&buf->b_hdr->b_freeze_lock); 960 return; 961 } 962 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 963 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 964 buf->b_hdr->b_freeze_cksum); 965 mutex_exit(&buf->b_hdr->b_freeze_lock); 966 arc_buf_watch(buf); 967 } 968 969 #ifndef _KERNEL 970 typedef struct procctl { 971 long cmd; 972 prwatch_t prwatch; 973 } procctl_t; 974 #endif 975 976 /* ARGSUSED */ 977 static void 978 arc_buf_unwatch(arc_buf_t *buf) 979 { 980 #ifndef _KERNEL 981 if (arc_watch) { 982 int result; 983 procctl_t ctl; 984 ctl.cmd = PCWATCH; 985 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 986 ctl.prwatch.pr_size = 0; 987 ctl.prwatch.pr_wflags = 0; 988 result = write(arc_procfd, &ctl, sizeof (ctl)); 989 ASSERT3U(result, ==, sizeof (ctl)); 990 } 991 #endif 992 } 993 994 /* ARGSUSED */ 995 static void 996 arc_buf_watch(arc_buf_t *buf) 997 { 998 #ifndef _KERNEL 999 if (arc_watch) { 1000 int result; 1001 procctl_t ctl; 1002 ctl.cmd = PCWATCH; 1003 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1004 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1005 ctl.prwatch.pr_wflags = WA_WRITE; 1006 result = write(arc_procfd, &ctl, sizeof (ctl)); 1007 ASSERT3U(result, ==, sizeof (ctl)); 1008 } 1009 #endif 1010 } 1011 1012 void 1013 arc_buf_thaw(arc_buf_t *buf) 1014 { 1015 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1016 if (buf->b_hdr->b_state != arc_anon) 1017 panic("modifying non-anon buffer!"); 1018 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS) 1019 panic("modifying buffer while i/o in progress!"); 1020 arc_cksum_verify(buf); 1021 } 1022 1023 mutex_enter(&buf->b_hdr->b_freeze_lock); 1024 if (buf->b_hdr->b_freeze_cksum != NULL) { 1025 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1026 buf->b_hdr->b_freeze_cksum = NULL; 1027 } 1028 1029 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1030 if (buf->b_hdr->b_thawed) 1031 kmem_free(buf->b_hdr->b_thawed, 1); 1032 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP); 1033 } 1034 1035 mutex_exit(&buf->b_hdr->b_freeze_lock); 1036 1037 arc_buf_unwatch(buf); 1038 } 1039 1040 void 1041 arc_buf_freeze(arc_buf_t *buf) 1042 { 1043 kmutex_t *hash_lock; 1044 1045 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1046 return; 1047 1048 hash_lock = HDR_LOCK(buf->b_hdr); 1049 mutex_enter(hash_lock); 1050 1051 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1052 buf->b_hdr->b_state == arc_anon); 1053 arc_cksum_compute(buf, B_FALSE); 1054 mutex_exit(hash_lock); 1055 1056 } 1057 1058 static void 1059 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1060 { 1061 ASSERT(MUTEX_HELD(hash_lock)); 1062 1063 if ((refcount_add(&ab->b_refcnt, tag) == 1) && 1064 (ab->b_state != arc_anon)) { 1065 uint64_t delta = ab->b_size * ab->b_datacnt; 1066 list_t *list = &ab->b_state->arcs_list[ab->b_type]; 1067 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type]; 1068 1069 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx)); 1070 mutex_enter(&ab->b_state->arcs_mtx); 1071 ASSERT(list_link_active(&ab->b_arc_node)); 1072 list_remove(list, ab); 1073 if (GHOST_STATE(ab->b_state)) { 1074 ASSERT0(ab->b_datacnt); 1075 ASSERT3P(ab->b_buf, ==, NULL); 1076 delta = ab->b_size; 1077 } 1078 ASSERT(delta > 0); 1079 ASSERT3U(*size, >=, delta); 1080 atomic_add_64(size, -delta); 1081 mutex_exit(&ab->b_state->arcs_mtx); 1082 /* remove the prefetch flag if we get a reference */ 1083 if (ab->b_flags & ARC_PREFETCH) 1084 ab->b_flags &= ~ARC_PREFETCH; 1085 } 1086 } 1087 1088 static int 1089 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1090 { 1091 int cnt; 1092 arc_state_t *state = ab->b_state; 1093 1094 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1095 ASSERT(!GHOST_STATE(state)); 1096 1097 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) && 1098 (state != arc_anon)) { 1099 uint64_t *size = &state->arcs_lsize[ab->b_type]; 1100 1101 ASSERT(!MUTEX_HELD(&state->arcs_mtx)); 1102 mutex_enter(&state->arcs_mtx); 1103 ASSERT(!list_link_active(&ab->b_arc_node)); 1104 list_insert_head(&state->arcs_list[ab->b_type], ab); 1105 ASSERT(ab->b_datacnt > 0); 1106 atomic_add_64(size, ab->b_size * ab->b_datacnt); 1107 mutex_exit(&state->arcs_mtx); 1108 } 1109 return (cnt); 1110 } 1111 1112 /* 1113 * Move the supplied buffer to the indicated state. The mutex 1114 * for the buffer must be held by the caller. 1115 */ 1116 static void 1117 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock) 1118 { 1119 arc_state_t *old_state = ab->b_state; 1120 int64_t refcnt = refcount_count(&ab->b_refcnt); 1121 uint64_t from_delta, to_delta; 1122 1123 ASSERT(MUTEX_HELD(hash_lock)); 1124 ASSERT(new_state != old_state); 1125 ASSERT(refcnt == 0 || ab->b_datacnt > 0); 1126 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state)); 1127 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon); 1128 1129 from_delta = to_delta = ab->b_datacnt * ab->b_size; 1130 1131 /* 1132 * If this buffer is evictable, transfer it from the 1133 * old state list to the new state list. 1134 */ 1135 if (refcnt == 0) { 1136 if (old_state != arc_anon) { 1137 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx); 1138 uint64_t *size = &old_state->arcs_lsize[ab->b_type]; 1139 1140 if (use_mutex) 1141 mutex_enter(&old_state->arcs_mtx); 1142 1143 ASSERT(list_link_active(&ab->b_arc_node)); 1144 list_remove(&old_state->arcs_list[ab->b_type], ab); 1145 1146 /* 1147 * If prefetching out of the ghost cache, 1148 * we will have a non-zero datacnt. 1149 */ 1150 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) { 1151 /* ghost elements have a ghost size */ 1152 ASSERT(ab->b_buf == NULL); 1153 from_delta = ab->b_size; 1154 } 1155 ASSERT3U(*size, >=, from_delta); 1156 atomic_add_64(size, -from_delta); 1157 1158 if (use_mutex) 1159 mutex_exit(&old_state->arcs_mtx); 1160 } 1161 if (new_state != arc_anon) { 1162 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx); 1163 uint64_t *size = &new_state->arcs_lsize[ab->b_type]; 1164 1165 if (use_mutex) 1166 mutex_enter(&new_state->arcs_mtx); 1167 1168 list_insert_head(&new_state->arcs_list[ab->b_type], ab); 1169 1170 /* ghost elements have a ghost size */ 1171 if (GHOST_STATE(new_state)) { 1172 ASSERT(ab->b_datacnt == 0); 1173 ASSERT(ab->b_buf == NULL); 1174 to_delta = ab->b_size; 1175 } 1176 atomic_add_64(size, to_delta); 1177 1178 if (use_mutex) 1179 mutex_exit(&new_state->arcs_mtx); 1180 } 1181 } 1182 1183 ASSERT(!BUF_EMPTY(ab)); 1184 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab)) 1185 buf_hash_remove(ab); 1186 1187 /* adjust state sizes */ 1188 if (to_delta) 1189 atomic_add_64(&new_state->arcs_size, to_delta); 1190 if (from_delta) { 1191 ASSERT3U(old_state->arcs_size, >=, from_delta); 1192 atomic_add_64(&old_state->arcs_size, -from_delta); 1193 } 1194 ab->b_state = new_state; 1195 1196 /* adjust l2arc hdr stats */ 1197 if (new_state == arc_l2c_only) 1198 l2arc_hdr_stat_add(); 1199 else if (old_state == arc_l2c_only) 1200 l2arc_hdr_stat_remove(); 1201 } 1202 1203 void 1204 arc_space_consume(uint64_t space, arc_space_type_t type) 1205 { 1206 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1207 1208 switch (type) { 1209 case ARC_SPACE_DATA: 1210 ARCSTAT_INCR(arcstat_data_size, space); 1211 break; 1212 case ARC_SPACE_OTHER: 1213 ARCSTAT_INCR(arcstat_other_size, space); 1214 break; 1215 case ARC_SPACE_HDRS: 1216 ARCSTAT_INCR(arcstat_hdr_size, space); 1217 break; 1218 case ARC_SPACE_L2HDRS: 1219 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1220 break; 1221 } 1222 1223 atomic_add_64(&arc_meta_used, space); 1224 atomic_add_64(&arc_size, space); 1225 } 1226 1227 void 1228 arc_space_return(uint64_t space, arc_space_type_t type) 1229 { 1230 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1231 1232 switch (type) { 1233 case ARC_SPACE_DATA: 1234 ARCSTAT_INCR(arcstat_data_size, -space); 1235 break; 1236 case ARC_SPACE_OTHER: 1237 ARCSTAT_INCR(arcstat_other_size, -space); 1238 break; 1239 case ARC_SPACE_HDRS: 1240 ARCSTAT_INCR(arcstat_hdr_size, -space); 1241 break; 1242 case ARC_SPACE_L2HDRS: 1243 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1244 break; 1245 } 1246 1247 ASSERT(arc_meta_used >= space); 1248 if (arc_meta_max < arc_meta_used) 1249 arc_meta_max = arc_meta_used; 1250 atomic_add_64(&arc_meta_used, -space); 1251 ASSERT(arc_size >= space); 1252 atomic_add_64(&arc_size, -space); 1253 } 1254 1255 void * 1256 arc_data_buf_alloc(uint64_t size) 1257 { 1258 if (arc_evict_needed(ARC_BUFC_DATA)) 1259 cv_signal(&arc_reclaim_thr_cv); 1260 atomic_add_64(&arc_size, size); 1261 return (zio_data_buf_alloc(size)); 1262 } 1263 1264 void 1265 arc_data_buf_free(void *buf, uint64_t size) 1266 { 1267 zio_data_buf_free(buf, size); 1268 ASSERT(arc_size >= size); 1269 atomic_add_64(&arc_size, -size); 1270 } 1271 1272 arc_buf_t * 1273 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type) 1274 { 1275 arc_buf_hdr_t *hdr; 1276 arc_buf_t *buf; 1277 1278 ASSERT3U(size, >, 0); 1279 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 1280 ASSERT(BUF_EMPTY(hdr)); 1281 hdr->b_size = size; 1282 hdr->b_type = type; 1283 hdr->b_spa = spa_load_guid(spa); 1284 hdr->b_state = arc_anon; 1285 hdr->b_arc_access = 0; 1286 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1287 buf->b_hdr = hdr; 1288 buf->b_data = NULL; 1289 buf->b_efunc = NULL; 1290 buf->b_private = NULL; 1291 buf->b_next = NULL; 1292 hdr->b_buf = buf; 1293 arc_get_data_buf(buf); 1294 hdr->b_datacnt = 1; 1295 hdr->b_flags = 0; 1296 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1297 (void) refcount_add(&hdr->b_refcnt, tag); 1298 1299 return (buf); 1300 } 1301 1302 static char *arc_onloan_tag = "onloan"; 1303 1304 /* 1305 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1306 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1307 * buffers must be returned to the arc before they can be used by the DMU or 1308 * freed. 1309 */ 1310 arc_buf_t * 1311 arc_loan_buf(spa_t *spa, int size) 1312 { 1313 arc_buf_t *buf; 1314 1315 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1316 1317 atomic_add_64(&arc_loaned_bytes, size); 1318 return (buf); 1319 } 1320 1321 /* 1322 * Return a loaned arc buffer to the arc. 1323 */ 1324 void 1325 arc_return_buf(arc_buf_t *buf, void *tag) 1326 { 1327 arc_buf_hdr_t *hdr = buf->b_hdr; 1328 1329 ASSERT(buf->b_data != NULL); 1330 (void) refcount_add(&hdr->b_refcnt, tag); 1331 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag); 1332 1333 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1334 } 1335 1336 /* Detach an arc_buf from a dbuf (tag) */ 1337 void 1338 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1339 { 1340 arc_buf_hdr_t *hdr; 1341 1342 ASSERT(buf->b_data != NULL); 1343 hdr = buf->b_hdr; 1344 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag); 1345 (void) refcount_remove(&hdr->b_refcnt, tag); 1346 buf->b_efunc = NULL; 1347 buf->b_private = NULL; 1348 1349 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1350 } 1351 1352 static arc_buf_t * 1353 arc_buf_clone(arc_buf_t *from) 1354 { 1355 arc_buf_t *buf; 1356 arc_buf_hdr_t *hdr = from->b_hdr; 1357 uint64_t size = hdr->b_size; 1358 1359 ASSERT(hdr->b_state != arc_anon); 1360 1361 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1362 buf->b_hdr = hdr; 1363 buf->b_data = NULL; 1364 buf->b_efunc = NULL; 1365 buf->b_private = NULL; 1366 buf->b_next = hdr->b_buf; 1367 hdr->b_buf = buf; 1368 arc_get_data_buf(buf); 1369 bcopy(from->b_data, buf->b_data, size); 1370 1371 /* 1372 * This buffer already exists in the arc so create a duplicate 1373 * copy for the caller. If the buffer is associated with user data 1374 * then track the size and number of duplicates. These stats will be 1375 * updated as duplicate buffers are created and destroyed. 1376 */ 1377 if (hdr->b_type == ARC_BUFC_DATA) { 1378 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1379 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1380 } 1381 hdr->b_datacnt += 1; 1382 return (buf); 1383 } 1384 1385 void 1386 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1387 { 1388 arc_buf_hdr_t *hdr; 1389 kmutex_t *hash_lock; 1390 1391 /* 1392 * Check to see if this buffer is evicted. Callers 1393 * must verify b_data != NULL to know if the add_ref 1394 * was successful. 1395 */ 1396 mutex_enter(&buf->b_evict_lock); 1397 if (buf->b_data == NULL) { 1398 mutex_exit(&buf->b_evict_lock); 1399 return; 1400 } 1401 hash_lock = HDR_LOCK(buf->b_hdr); 1402 mutex_enter(hash_lock); 1403 hdr = buf->b_hdr; 1404 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1405 mutex_exit(&buf->b_evict_lock); 1406 1407 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 1408 add_reference(hdr, hash_lock, tag); 1409 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1410 arc_access(hdr, hash_lock); 1411 mutex_exit(hash_lock); 1412 ARCSTAT_BUMP(arcstat_hits); 1413 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 1414 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 1415 data, metadata, hits); 1416 } 1417 1418 /* 1419 * Free the arc data buffer. If it is an l2arc write in progress, 1420 * the buffer is placed on l2arc_free_on_write to be freed later. 1421 */ 1422 static void 1423 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1424 { 1425 arc_buf_hdr_t *hdr = buf->b_hdr; 1426 1427 if (HDR_L2_WRITING(hdr)) { 1428 l2arc_data_free_t *df; 1429 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1430 df->l2df_data = buf->b_data; 1431 df->l2df_size = hdr->b_size; 1432 df->l2df_func = free_func; 1433 mutex_enter(&l2arc_free_on_write_mtx); 1434 list_insert_head(l2arc_free_on_write, df); 1435 mutex_exit(&l2arc_free_on_write_mtx); 1436 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1437 } else { 1438 free_func(buf->b_data, hdr->b_size); 1439 } 1440 } 1441 1442 static void 1443 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all) 1444 { 1445 arc_buf_t **bufp; 1446 1447 /* free up data associated with the buf */ 1448 if (buf->b_data) { 1449 arc_state_t *state = buf->b_hdr->b_state; 1450 uint64_t size = buf->b_hdr->b_size; 1451 arc_buf_contents_t type = buf->b_hdr->b_type; 1452 1453 arc_cksum_verify(buf); 1454 arc_buf_unwatch(buf); 1455 1456 if (!recycle) { 1457 if (type == ARC_BUFC_METADATA) { 1458 arc_buf_data_free(buf, zio_buf_free); 1459 arc_space_return(size, ARC_SPACE_DATA); 1460 } else { 1461 ASSERT(type == ARC_BUFC_DATA); 1462 arc_buf_data_free(buf, zio_data_buf_free); 1463 ARCSTAT_INCR(arcstat_data_size, -size); 1464 atomic_add_64(&arc_size, -size); 1465 } 1466 } 1467 if (list_link_active(&buf->b_hdr->b_arc_node)) { 1468 uint64_t *cnt = &state->arcs_lsize[type]; 1469 1470 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt)); 1471 ASSERT(state != arc_anon); 1472 1473 ASSERT3U(*cnt, >=, size); 1474 atomic_add_64(cnt, -size); 1475 } 1476 ASSERT3U(state->arcs_size, >=, size); 1477 atomic_add_64(&state->arcs_size, -size); 1478 buf->b_data = NULL; 1479 1480 /* 1481 * If we're destroying a duplicate buffer make sure 1482 * that the appropriate statistics are updated. 1483 */ 1484 if (buf->b_hdr->b_datacnt > 1 && 1485 buf->b_hdr->b_type == ARC_BUFC_DATA) { 1486 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1487 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1488 } 1489 ASSERT(buf->b_hdr->b_datacnt > 0); 1490 buf->b_hdr->b_datacnt -= 1; 1491 } 1492 1493 /* only remove the buf if requested */ 1494 if (!all) 1495 return; 1496 1497 /* remove the buf from the hdr list */ 1498 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next) 1499 continue; 1500 *bufp = buf->b_next; 1501 buf->b_next = NULL; 1502 1503 ASSERT(buf->b_efunc == NULL); 1504 1505 /* clean up the buf */ 1506 buf->b_hdr = NULL; 1507 kmem_cache_free(buf_cache, buf); 1508 } 1509 1510 static void 1511 arc_hdr_destroy(arc_buf_hdr_t *hdr) 1512 { 1513 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1514 ASSERT3P(hdr->b_state, ==, arc_anon); 1515 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1516 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1517 1518 if (l2hdr != NULL) { 1519 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx); 1520 /* 1521 * To prevent arc_free() and l2arc_evict() from 1522 * attempting to free the same buffer at the same time, 1523 * a FREE_IN_PROGRESS flag is given to arc_free() to 1524 * give it priority. l2arc_evict() can't destroy this 1525 * header while we are waiting on l2arc_buflist_mtx. 1526 * 1527 * The hdr may be removed from l2ad_buflist before we 1528 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked. 1529 */ 1530 if (!buflist_held) { 1531 mutex_enter(&l2arc_buflist_mtx); 1532 l2hdr = hdr->b_l2hdr; 1533 } 1534 1535 if (l2hdr != NULL) { 1536 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 1537 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1538 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 1539 if (hdr->b_state == arc_l2c_only) 1540 l2arc_hdr_stat_remove(); 1541 hdr->b_l2hdr = NULL; 1542 } 1543 1544 if (!buflist_held) 1545 mutex_exit(&l2arc_buflist_mtx); 1546 } 1547 1548 if (!BUF_EMPTY(hdr)) { 1549 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1550 buf_discard_identity(hdr); 1551 } 1552 while (hdr->b_buf) { 1553 arc_buf_t *buf = hdr->b_buf; 1554 1555 if (buf->b_efunc) { 1556 mutex_enter(&arc_eviction_mtx); 1557 mutex_enter(&buf->b_evict_lock); 1558 ASSERT(buf->b_hdr != NULL); 1559 arc_buf_destroy(hdr->b_buf, FALSE, FALSE); 1560 hdr->b_buf = buf->b_next; 1561 buf->b_hdr = &arc_eviction_hdr; 1562 buf->b_next = arc_eviction_list; 1563 arc_eviction_list = buf; 1564 mutex_exit(&buf->b_evict_lock); 1565 mutex_exit(&arc_eviction_mtx); 1566 } else { 1567 arc_buf_destroy(hdr->b_buf, FALSE, TRUE); 1568 } 1569 } 1570 if (hdr->b_freeze_cksum != NULL) { 1571 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1572 hdr->b_freeze_cksum = NULL; 1573 } 1574 if (hdr->b_thawed) { 1575 kmem_free(hdr->b_thawed, 1); 1576 hdr->b_thawed = NULL; 1577 } 1578 1579 ASSERT(!list_link_active(&hdr->b_arc_node)); 1580 ASSERT3P(hdr->b_hash_next, ==, NULL); 1581 ASSERT3P(hdr->b_acb, ==, NULL); 1582 kmem_cache_free(hdr_cache, hdr); 1583 } 1584 1585 void 1586 arc_buf_free(arc_buf_t *buf, void *tag) 1587 { 1588 arc_buf_hdr_t *hdr = buf->b_hdr; 1589 int hashed = hdr->b_state != arc_anon; 1590 1591 ASSERT(buf->b_efunc == NULL); 1592 ASSERT(buf->b_data != NULL); 1593 1594 if (hashed) { 1595 kmutex_t *hash_lock = HDR_LOCK(hdr); 1596 1597 mutex_enter(hash_lock); 1598 hdr = buf->b_hdr; 1599 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1600 1601 (void) remove_reference(hdr, hash_lock, tag); 1602 if (hdr->b_datacnt > 1) { 1603 arc_buf_destroy(buf, FALSE, TRUE); 1604 } else { 1605 ASSERT(buf == hdr->b_buf); 1606 ASSERT(buf->b_efunc == NULL); 1607 hdr->b_flags |= ARC_BUF_AVAILABLE; 1608 } 1609 mutex_exit(hash_lock); 1610 } else if (HDR_IO_IN_PROGRESS(hdr)) { 1611 int destroy_hdr; 1612 /* 1613 * We are in the middle of an async write. Don't destroy 1614 * this buffer unless the write completes before we finish 1615 * decrementing the reference count. 1616 */ 1617 mutex_enter(&arc_eviction_mtx); 1618 (void) remove_reference(hdr, NULL, tag); 1619 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1620 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 1621 mutex_exit(&arc_eviction_mtx); 1622 if (destroy_hdr) 1623 arc_hdr_destroy(hdr); 1624 } else { 1625 if (remove_reference(hdr, NULL, tag) > 0) 1626 arc_buf_destroy(buf, FALSE, TRUE); 1627 else 1628 arc_hdr_destroy(hdr); 1629 } 1630 } 1631 1632 int 1633 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 1634 { 1635 arc_buf_hdr_t *hdr = buf->b_hdr; 1636 kmutex_t *hash_lock = HDR_LOCK(hdr); 1637 int no_callback = (buf->b_efunc == NULL); 1638 1639 if (hdr->b_state == arc_anon) { 1640 ASSERT(hdr->b_datacnt == 1); 1641 arc_buf_free(buf, tag); 1642 return (no_callback); 1643 } 1644 1645 mutex_enter(hash_lock); 1646 hdr = buf->b_hdr; 1647 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1648 ASSERT(hdr->b_state != arc_anon); 1649 ASSERT(buf->b_data != NULL); 1650 1651 (void) remove_reference(hdr, hash_lock, tag); 1652 if (hdr->b_datacnt > 1) { 1653 if (no_callback) 1654 arc_buf_destroy(buf, FALSE, TRUE); 1655 } else if (no_callback) { 1656 ASSERT(hdr->b_buf == buf && buf->b_next == NULL); 1657 ASSERT(buf->b_efunc == NULL); 1658 hdr->b_flags |= ARC_BUF_AVAILABLE; 1659 } 1660 ASSERT(no_callback || hdr->b_datacnt > 1 || 1661 refcount_is_zero(&hdr->b_refcnt)); 1662 mutex_exit(hash_lock); 1663 return (no_callback); 1664 } 1665 1666 int 1667 arc_buf_size(arc_buf_t *buf) 1668 { 1669 return (buf->b_hdr->b_size); 1670 } 1671 1672 /* 1673 * Called from the DMU to determine if the current buffer should be 1674 * evicted. In order to ensure proper locking, the eviction must be initiated 1675 * from the DMU. Return true if the buffer is associated with user data and 1676 * duplicate buffers still exist. 1677 */ 1678 boolean_t 1679 arc_buf_eviction_needed(arc_buf_t *buf) 1680 { 1681 arc_buf_hdr_t *hdr; 1682 boolean_t evict_needed = B_FALSE; 1683 1684 if (zfs_disable_dup_eviction) 1685 return (B_FALSE); 1686 1687 mutex_enter(&buf->b_evict_lock); 1688 hdr = buf->b_hdr; 1689 if (hdr == NULL) { 1690 /* 1691 * We are in arc_do_user_evicts(); let that function 1692 * perform the eviction. 1693 */ 1694 ASSERT(buf->b_data == NULL); 1695 mutex_exit(&buf->b_evict_lock); 1696 return (B_FALSE); 1697 } else if (buf->b_data == NULL) { 1698 /* 1699 * We have already been added to the arc eviction list; 1700 * recommend eviction. 1701 */ 1702 ASSERT3P(hdr, ==, &arc_eviction_hdr); 1703 mutex_exit(&buf->b_evict_lock); 1704 return (B_TRUE); 1705 } 1706 1707 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) 1708 evict_needed = B_TRUE; 1709 1710 mutex_exit(&buf->b_evict_lock); 1711 return (evict_needed); 1712 } 1713 1714 /* 1715 * Evict buffers from list until we've removed the specified number of 1716 * bytes. Move the removed buffers to the appropriate evict state. 1717 * If the recycle flag is set, then attempt to "recycle" a buffer: 1718 * - look for a buffer to evict that is `bytes' long. 1719 * - return the data block from this buffer rather than freeing it. 1720 * This flag is used by callers that are trying to make space for a 1721 * new buffer in a full arc cache. 1722 * 1723 * This function makes a "best effort". It skips over any buffers 1724 * it can't get a hash_lock on, and so may not catch all candidates. 1725 * It may also return without evicting as much space as requested. 1726 */ 1727 static void * 1728 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 1729 arc_buf_contents_t type) 1730 { 1731 arc_state_t *evicted_state; 1732 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 1733 arc_buf_hdr_t *ab, *ab_prev = NULL; 1734 list_t *list = &state->arcs_list[type]; 1735 kmutex_t *hash_lock; 1736 boolean_t have_lock; 1737 void *stolen = NULL; 1738 1739 ASSERT(state == arc_mru || state == arc_mfu); 1740 1741 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 1742 1743 mutex_enter(&state->arcs_mtx); 1744 mutex_enter(&evicted_state->arcs_mtx); 1745 1746 for (ab = list_tail(list); ab; ab = ab_prev) { 1747 ab_prev = list_prev(list, ab); 1748 /* prefetch buffers have a minimum lifespan */ 1749 if (HDR_IO_IN_PROGRESS(ab) || 1750 (spa && ab->b_spa != spa) || 1751 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) && 1752 ddi_get_lbolt() - ab->b_arc_access < 1753 arc_min_prefetch_lifespan)) { 1754 skipped++; 1755 continue; 1756 } 1757 /* "lookahead" for better eviction candidate */ 1758 if (recycle && ab->b_size != bytes && 1759 ab_prev && ab_prev->b_size == bytes) 1760 continue; 1761 hash_lock = HDR_LOCK(ab); 1762 have_lock = MUTEX_HELD(hash_lock); 1763 if (have_lock || mutex_tryenter(hash_lock)) { 1764 ASSERT0(refcount_count(&ab->b_refcnt)); 1765 ASSERT(ab->b_datacnt > 0); 1766 while (ab->b_buf) { 1767 arc_buf_t *buf = ab->b_buf; 1768 if (!mutex_tryenter(&buf->b_evict_lock)) { 1769 missed += 1; 1770 break; 1771 } 1772 if (buf->b_data) { 1773 bytes_evicted += ab->b_size; 1774 if (recycle && ab->b_type == type && 1775 ab->b_size == bytes && 1776 !HDR_L2_WRITING(ab)) { 1777 stolen = buf->b_data; 1778 recycle = FALSE; 1779 } 1780 } 1781 if (buf->b_efunc) { 1782 mutex_enter(&arc_eviction_mtx); 1783 arc_buf_destroy(buf, 1784 buf->b_data == stolen, FALSE); 1785 ab->b_buf = buf->b_next; 1786 buf->b_hdr = &arc_eviction_hdr; 1787 buf->b_next = arc_eviction_list; 1788 arc_eviction_list = buf; 1789 mutex_exit(&arc_eviction_mtx); 1790 mutex_exit(&buf->b_evict_lock); 1791 } else { 1792 mutex_exit(&buf->b_evict_lock); 1793 arc_buf_destroy(buf, 1794 buf->b_data == stolen, TRUE); 1795 } 1796 } 1797 1798 if (ab->b_l2hdr) { 1799 ARCSTAT_INCR(arcstat_evict_l2_cached, 1800 ab->b_size); 1801 } else { 1802 if (l2arc_write_eligible(ab->b_spa, ab)) { 1803 ARCSTAT_INCR(arcstat_evict_l2_eligible, 1804 ab->b_size); 1805 } else { 1806 ARCSTAT_INCR( 1807 arcstat_evict_l2_ineligible, 1808 ab->b_size); 1809 } 1810 } 1811 1812 if (ab->b_datacnt == 0) { 1813 arc_change_state(evicted_state, ab, hash_lock); 1814 ASSERT(HDR_IN_HASH_TABLE(ab)); 1815 ab->b_flags |= ARC_IN_HASH_TABLE; 1816 ab->b_flags &= ~ARC_BUF_AVAILABLE; 1817 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab); 1818 } 1819 if (!have_lock) 1820 mutex_exit(hash_lock); 1821 if (bytes >= 0 && bytes_evicted >= bytes) 1822 break; 1823 } else { 1824 missed += 1; 1825 } 1826 } 1827 1828 mutex_exit(&evicted_state->arcs_mtx); 1829 mutex_exit(&state->arcs_mtx); 1830 1831 if (bytes_evicted < bytes) 1832 dprintf("only evicted %lld bytes from %x", 1833 (longlong_t)bytes_evicted, state); 1834 1835 if (skipped) 1836 ARCSTAT_INCR(arcstat_evict_skip, skipped); 1837 1838 if (missed) 1839 ARCSTAT_INCR(arcstat_mutex_miss, missed); 1840 1841 /* 1842 * We have just evicted some date into the ghost state, make 1843 * sure we also adjust the ghost state size if necessary. 1844 */ 1845 if (arc_no_grow && 1846 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) { 1847 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size + 1848 arc_mru_ghost->arcs_size - arc_c; 1849 1850 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) { 1851 int64_t todelete = 1852 MIN(arc_mru_ghost->arcs_lsize[type], mru_over); 1853 arc_evict_ghost(arc_mru_ghost, NULL, todelete); 1854 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) { 1855 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type], 1856 arc_mru_ghost->arcs_size + 1857 arc_mfu_ghost->arcs_size - arc_c); 1858 arc_evict_ghost(arc_mfu_ghost, NULL, todelete); 1859 } 1860 } 1861 1862 return (stolen); 1863 } 1864 1865 /* 1866 * Remove buffers from list until we've removed the specified number of 1867 * bytes. Destroy the buffers that are removed. 1868 */ 1869 static void 1870 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 1871 { 1872 arc_buf_hdr_t *ab, *ab_prev; 1873 arc_buf_hdr_t marker = { 0 }; 1874 list_t *list = &state->arcs_list[ARC_BUFC_DATA]; 1875 kmutex_t *hash_lock; 1876 uint64_t bytes_deleted = 0; 1877 uint64_t bufs_skipped = 0; 1878 1879 ASSERT(GHOST_STATE(state)); 1880 top: 1881 mutex_enter(&state->arcs_mtx); 1882 for (ab = list_tail(list); ab; ab = ab_prev) { 1883 ab_prev = list_prev(list, ab); 1884 if (spa && ab->b_spa != spa) 1885 continue; 1886 1887 /* ignore markers */ 1888 if (ab->b_spa == 0) 1889 continue; 1890 1891 hash_lock = HDR_LOCK(ab); 1892 /* caller may be trying to modify this buffer, skip it */ 1893 if (MUTEX_HELD(hash_lock)) 1894 continue; 1895 if (mutex_tryenter(hash_lock)) { 1896 ASSERT(!HDR_IO_IN_PROGRESS(ab)); 1897 ASSERT(ab->b_buf == NULL); 1898 ARCSTAT_BUMP(arcstat_deleted); 1899 bytes_deleted += ab->b_size; 1900 1901 if (ab->b_l2hdr != NULL) { 1902 /* 1903 * This buffer is cached on the 2nd Level ARC; 1904 * don't destroy the header. 1905 */ 1906 arc_change_state(arc_l2c_only, ab, hash_lock); 1907 mutex_exit(hash_lock); 1908 } else { 1909 arc_change_state(arc_anon, ab, hash_lock); 1910 mutex_exit(hash_lock); 1911 arc_hdr_destroy(ab); 1912 } 1913 1914 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab); 1915 if (bytes >= 0 && bytes_deleted >= bytes) 1916 break; 1917 } else if (bytes < 0) { 1918 /* 1919 * Insert a list marker and then wait for the 1920 * hash lock to become available. Once its 1921 * available, restart from where we left off. 1922 */ 1923 list_insert_after(list, ab, &marker); 1924 mutex_exit(&state->arcs_mtx); 1925 mutex_enter(hash_lock); 1926 mutex_exit(hash_lock); 1927 mutex_enter(&state->arcs_mtx); 1928 ab_prev = list_prev(list, &marker); 1929 list_remove(list, &marker); 1930 } else 1931 bufs_skipped += 1; 1932 } 1933 mutex_exit(&state->arcs_mtx); 1934 1935 if (list == &state->arcs_list[ARC_BUFC_DATA] && 1936 (bytes < 0 || bytes_deleted < bytes)) { 1937 list = &state->arcs_list[ARC_BUFC_METADATA]; 1938 goto top; 1939 } 1940 1941 if (bufs_skipped) { 1942 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 1943 ASSERT(bytes >= 0); 1944 } 1945 1946 if (bytes_deleted < bytes) 1947 dprintf("only deleted %lld bytes from %p", 1948 (longlong_t)bytes_deleted, state); 1949 } 1950 1951 static void 1952 arc_adjust(void) 1953 { 1954 int64_t adjustment, delta; 1955 1956 /* 1957 * Adjust MRU size 1958 */ 1959 1960 adjustment = MIN((int64_t)(arc_size - arc_c), 1961 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 1962 arc_p)); 1963 1964 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 1965 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 1966 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA); 1967 adjustment -= delta; 1968 } 1969 1970 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 1971 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 1972 (void) arc_evict(arc_mru, NULL, delta, FALSE, 1973 ARC_BUFC_METADATA); 1974 } 1975 1976 /* 1977 * Adjust MFU size 1978 */ 1979 1980 adjustment = arc_size - arc_c; 1981 1982 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 1983 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 1984 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA); 1985 adjustment -= delta; 1986 } 1987 1988 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 1989 int64_t delta = MIN(adjustment, 1990 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 1991 (void) arc_evict(arc_mfu, NULL, delta, FALSE, 1992 ARC_BUFC_METADATA); 1993 } 1994 1995 /* 1996 * Adjust ghost lists 1997 */ 1998 1999 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2000 2001 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2002 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2003 arc_evict_ghost(arc_mru_ghost, NULL, delta); 2004 } 2005 2006 adjustment = 2007 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2008 2009 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2010 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2011 arc_evict_ghost(arc_mfu_ghost, NULL, delta); 2012 } 2013 } 2014 2015 static void 2016 arc_do_user_evicts(void) 2017 { 2018 mutex_enter(&arc_eviction_mtx); 2019 while (arc_eviction_list != NULL) { 2020 arc_buf_t *buf = arc_eviction_list; 2021 arc_eviction_list = buf->b_next; 2022 mutex_enter(&buf->b_evict_lock); 2023 buf->b_hdr = NULL; 2024 mutex_exit(&buf->b_evict_lock); 2025 mutex_exit(&arc_eviction_mtx); 2026 2027 if (buf->b_efunc != NULL) 2028 VERIFY(buf->b_efunc(buf) == 0); 2029 2030 buf->b_efunc = NULL; 2031 buf->b_private = NULL; 2032 kmem_cache_free(buf_cache, buf); 2033 mutex_enter(&arc_eviction_mtx); 2034 } 2035 mutex_exit(&arc_eviction_mtx); 2036 } 2037 2038 /* 2039 * Flush all *evictable* data from the cache for the given spa. 2040 * NOTE: this will not touch "active" (i.e. referenced) data. 2041 */ 2042 void 2043 arc_flush(spa_t *spa) 2044 { 2045 uint64_t guid = 0; 2046 2047 if (spa) 2048 guid = spa_load_guid(spa); 2049 2050 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) { 2051 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2052 if (spa) 2053 break; 2054 } 2055 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) { 2056 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2057 if (spa) 2058 break; 2059 } 2060 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) { 2061 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2062 if (spa) 2063 break; 2064 } 2065 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) { 2066 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2067 if (spa) 2068 break; 2069 } 2070 2071 arc_evict_ghost(arc_mru_ghost, guid, -1); 2072 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2073 2074 mutex_enter(&arc_reclaim_thr_lock); 2075 arc_do_user_evicts(); 2076 mutex_exit(&arc_reclaim_thr_lock); 2077 ASSERT(spa || arc_eviction_list == NULL); 2078 } 2079 2080 void 2081 arc_shrink(void) 2082 { 2083 if (arc_c > arc_c_min) { 2084 uint64_t to_free; 2085 2086 #ifdef _KERNEL 2087 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree)); 2088 #else 2089 to_free = arc_c >> arc_shrink_shift; 2090 #endif 2091 if (arc_c > arc_c_min + to_free) 2092 atomic_add_64(&arc_c, -to_free); 2093 else 2094 arc_c = arc_c_min; 2095 2096 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2097 if (arc_c > arc_size) 2098 arc_c = MAX(arc_size, arc_c_min); 2099 if (arc_p > arc_c) 2100 arc_p = (arc_c >> 1); 2101 ASSERT(arc_c >= arc_c_min); 2102 ASSERT((int64_t)arc_p >= 0); 2103 } 2104 2105 if (arc_size > arc_c) 2106 arc_adjust(); 2107 } 2108 2109 /* 2110 * Determine if the system is under memory pressure and is asking 2111 * to reclaim memory. A return value of 1 indicates that the system 2112 * is under memory pressure and that the arc should adjust accordingly. 2113 */ 2114 static int 2115 arc_reclaim_needed(void) 2116 { 2117 uint64_t extra; 2118 2119 #ifdef _KERNEL 2120 2121 if (needfree) 2122 return (1); 2123 2124 /* 2125 * take 'desfree' extra pages, so we reclaim sooner, rather than later 2126 */ 2127 extra = desfree; 2128 2129 /* 2130 * check that we're out of range of the pageout scanner. It starts to 2131 * schedule paging if freemem is less than lotsfree and needfree. 2132 * lotsfree is the high-water mark for pageout, and needfree is the 2133 * number of needed free pages. We add extra pages here to make sure 2134 * the scanner doesn't start up while we're freeing memory. 2135 */ 2136 if (freemem < lotsfree + needfree + extra) 2137 return (1); 2138 2139 /* 2140 * check to make sure that swapfs has enough space so that anon 2141 * reservations can still succeed. anon_resvmem() checks that the 2142 * availrmem is greater than swapfs_minfree, and the number of reserved 2143 * swap pages. We also add a bit of extra here just to prevent 2144 * circumstances from getting really dire. 2145 */ 2146 if (availrmem < swapfs_minfree + swapfs_reserve + extra) 2147 return (1); 2148 2149 #if defined(__i386) 2150 /* 2151 * If we're on an i386 platform, it's possible that we'll exhaust the 2152 * kernel heap space before we ever run out of available physical 2153 * memory. Most checks of the size of the heap_area compare against 2154 * tune.t_minarmem, which is the minimum available real memory that we 2155 * can have in the system. However, this is generally fixed at 25 pages 2156 * which is so low that it's useless. In this comparison, we seek to 2157 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2158 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2159 * free) 2160 */ 2161 if (vmem_size(heap_arena, VMEM_FREE) < 2162 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) 2163 return (1); 2164 #endif 2165 2166 /* 2167 * If zio data pages are being allocated out of a separate heap segment, 2168 * then enforce that the size of available vmem for this arena remains 2169 * above about 1/16th free. 2170 * 2171 * Note: The 1/16th arena free requirement was put in place 2172 * to aggressively evict memory from the arc in order to avoid 2173 * memory fragmentation issues. 2174 */ 2175 if (zio_arena != NULL && 2176 vmem_size(zio_arena, VMEM_FREE) < 2177 (vmem_size(zio_arena, VMEM_ALLOC) >> 4)) 2178 return (1); 2179 #else 2180 if (spa_get_random(100) == 0) 2181 return (1); 2182 #endif 2183 return (0); 2184 } 2185 2186 static void 2187 arc_kmem_reap_now(arc_reclaim_strategy_t strat) 2188 { 2189 size_t i; 2190 kmem_cache_t *prev_cache = NULL; 2191 kmem_cache_t *prev_data_cache = NULL; 2192 extern kmem_cache_t *zio_buf_cache[]; 2193 extern kmem_cache_t *zio_data_buf_cache[]; 2194 2195 #ifdef _KERNEL 2196 if (arc_meta_used >= arc_meta_limit) { 2197 /* 2198 * We are exceeding our meta-data cache limit. 2199 * Purge some DNLC entries to release holds on meta-data. 2200 */ 2201 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2202 } 2203 #if defined(__i386) 2204 /* 2205 * Reclaim unused memory from all kmem caches. 2206 */ 2207 kmem_reap(); 2208 #endif 2209 #endif 2210 2211 /* 2212 * An aggressive reclamation will shrink the cache size as well as 2213 * reap free buffers from the arc kmem caches. 2214 */ 2215 if (strat == ARC_RECLAIM_AGGR) 2216 arc_shrink(); 2217 2218 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2219 if (zio_buf_cache[i] != prev_cache) { 2220 prev_cache = zio_buf_cache[i]; 2221 kmem_cache_reap_now(zio_buf_cache[i]); 2222 } 2223 if (zio_data_buf_cache[i] != prev_data_cache) { 2224 prev_data_cache = zio_data_buf_cache[i]; 2225 kmem_cache_reap_now(zio_data_buf_cache[i]); 2226 } 2227 } 2228 kmem_cache_reap_now(buf_cache); 2229 kmem_cache_reap_now(hdr_cache); 2230 2231 /* 2232 * Ask the vmem areana to reclaim unused memory from its 2233 * quantum caches. 2234 */ 2235 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR) 2236 vmem_qcache_reap(zio_arena); 2237 } 2238 2239 static void 2240 arc_reclaim_thread(void) 2241 { 2242 clock_t growtime = 0; 2243 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS; 2244 callb_cpr_t cpr; 2245 2246 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2247 2248 mutex_enter(&arc_reclaim_thr_lock); 2249 while (arc_thread_exit == 0) { 2250 if (arc_reclaim_needed()) { 2251 2252 if (arc_no_grow) { 2253 if (last_reclaim == ARC_RECLAIM_CONS) { 2254 last_reclaim = ARC_RECLAIM_AGGR; 2255 } else { 2256 last_reclaim = ARC_RECLAIM_CONS; 2257 } 2258 } else { 2259 arc_no_grow = TRUE; 2260 last_reclaim = ARC_RECLAIM_AGGR; 2261 membar_producer(); 2262 } 2263 2264 /* reset the growth delay for every reclaim */ 2265 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2266 2267 arc_kmem_reap_now(last_reclaim); 2268 arc_warm = B_TRUE; 2269 2270 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { 2271 arc_no_grow = FALSE; 2272 } 2273 2274 arc_adjust(); 2275 2276 if (arc_eviction_list != NULL) 2277 arc_do_user_evicts(); 2278 2279 /* block until needed, or one second, whichever is shorter */ 2280 CALLB_CPR_SAFE_BEGIN(&cpr); 2281 (void) cv_timedwait(&arc_reclaim_thr_cv, 2282 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz)); 2283 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2284 } 2285 2286 arc_thread_exit = 0; 2287 cv_broadcast(&arc_reclaim_thr_cv); 2288 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2289 thread_exit(); 2290 } 2291 2292 /* 2293 * Adapt arc info given the number of bytes we are trying to add and 2294 * the state that we are comming from. This function is only called 2295 * when we are adding new content to the cache. 2296 */ 2297 static void 2298 arc_adapt(int bytes, arc_state_t *state) 2299 { 2300 int mult; 2301 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2302 2303 if (state == arc_l2c_only) 2304 return; 2305 2306 ASSERT(bytes > 0); 2307 /* 2308 * Adapt the target size of the MRU list: 2309 * - if we just hit in the MRU ghost list, then increase 2310 * the target size of the MRU list. 2311 * - if we just hit in the MFU ghost list, then increase 2312 * the target size of the MFU list by decreasing the 2313 * target size of the MRU list. 2314 */ 2315 if (state == arc_mru_ghost) { 2316 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2317 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2318 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2319 2320 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2321 } else if (state == arc_mfu_ghost) { 2322 uint64_t delta; 2323 2324 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2325 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2326 mult = MIN(mult, 10); 2327 2328 delta = MIN(bytes * mult, arc_p); 2329 arc_p = MAX(arc_p_min, arc_p - delta); 2330 } 2331 ASSERT((int64_t)arc_p >= 0); 2332 2333 if (arc_reclaim_needed()) { 2334 cv_signal(&arc_reclaim_thr_cv); 2335 return; 2336 } 2337 2338 if (arc_no_grow) 2339 return; 2340 2341 if (arc_c >= arc_c_max) 2342 return; 2343 2344 /* 2345 * If we're within (2 * maxblocksize) bytes of the target 2346 * cache size, increment the target cache size 2347 */ 2348 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2349 atomic_add_64(&arc_c, (int64_t)bytes); 2350 if (arc_c > arc_c_max) 2351 arc_c = arc_c_max; 2352 else if (state == arc_anon) 2353 atomic_add_64(&arc_p, (int64_t)bytes); 2354 if (arc_p > arc_c) 2355 arc_p = arc_c; 2356 } 2357 ASSERT((int64_t)arc_p >= 0); 2358 } 2359 2360 /* 2361 * Check if the cache has reached its limits and eviction is required 2362 * prior to insert. 2363 */ 2364 static int 2365 arc_evict_needed(arc_buf_contents_t type) 2366 { 2367 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 2368 return (1); 2369 2370 if (arc_reclaim_needed()) 2371 return (1); 2372 2373 return (arc_size > arc_c); 2374 } 2375 2376 /* 2377 * The buffer, supplied as the first argument, needs a data block. 2378 * So, if we are at cache max, determine which cache should be victimized. 2379 * We have the following cases: 2380 * 2381 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 2382 * In this situation if we're out of space, but the resident size of the MFU is 2383 * under the limit, victimize the MFU cache to satisfy this insertion request. 2384 * 2385 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 2386 * Here, we've used up all of the available space for the MRU, so we need to 2387 * evict from our own cache instead. Evict from the set of resident MRU 2388 * entries. 2389 * 2390 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 2391 * c minus p represents the MFU space in the cache, since p is the size of the 2392 * cache that is dedicated to the MRU. In this situation there's still space on 2393 * the MFU side, so the MRU side needs to be victimized. 2394 * 2395 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 2396 * MFU's resident set is consuming more space than it has been allotted. In 2397 * this situation, we must victimize our own cache, the MFU, for this insertion. 2398 */ 2399 static void 2400 arc_get_data_buf(arc_buf_t *buf) 2401 { 2402 arc_state_t *state = buf->b_hdr->b_state; 2403 uint64_t size = buf->b_hdr->b_size; 2404 arc_buf_contents_t type = buf->b_hdr->b_type; 2405 2406 arc_adapt(size, state); 2407 2408 /* 2409 * We have not yet reached cache maximum size, 2410 * just allocate a new buffer. 2411 */ 2412 if (!arc_evict_needed(type)) { 2413 if (type == ARC_BUFC_METADATA) { 2414 buf->b_data = zio_buf_alloc(size); 2415 arc_space_consume(size, ARC_SPACE_DATA); 2416 } else { 2417 ASSERT(type == ARC_BUFC_DATA); 2418 buf->b_data = zio_data_buf_alloc(size); 2419 ARCSTAT_INCR(arcstat_data_size, size); 2420 atomic_add_64(&arc_size, size); 2421 } 2422 goto out; 2423 } 2424 2425 /* 2426 * If we are prefetching from the mfu ghost list, this buffer 2427 * will end up on the mru list; so steal space from there. 2428 */ 2429 if (state == arc_mfu_ghost) 2430 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu; 2431 else if (state == arc_mru_ghost) 2432 state = arc_mru; 2433 2434 if (state == arc_mru || state == arc_anon) { 2435 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 2436 state = (arc_mfu->arcs_lsize[type] >= size && 2437 arc_p > mru_used) ? arc_mfu : arc_mru; 2438 } else { 2439 /* MFU cases */ 2440 uint64_t mfu_space = arc_c - arc_p; 2441 state = (arc_mru->arcs_lsize[type] >= size && 2442 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 2443 } 2444 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) { 2445 if (type == ARC_BUFC_METADATA) { 2446 buf->b_data = zio_buf_alloc(size); 2447 arc_space_consume(size, ARC_SPACE_DATA); 2448 } else { 2449 ASSERT(type == ARC_BUFC_DATA); 2450 buf->b_data = zio_data_buf_alloc(size); 2451 ARCSTAT_INCR(arcstat_data_size, size); 2452 atomic_add_64(&arc_size, size); 2453 } 2454 ARCSTAT_BUMP(arcstat_recycle_miss); 2455 } 2456 ASSERT(buf->b_data != NULL); 2457 out: 2458 /* 2459 * Update the state size. Note that ghost states have a 2460 * "ghost size" and so don't need to be updated. 2461 */ 2462 if (!GHOST_STATE(buf->b_hdr->b_state)) { 2463 arc_buf_hdr_t *hdr = buf->b_hdr; 2464 2465 atomic_add_64(&hdr->b_state->arcs_size, size); 2466 if (list_link_active(&hdr->b_arc_node)) { 2467 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 2468 atomic_add_64(&hdr->b_state->arcs_lsize[type], size); 2469 } 2470 /* 2471 * If we are growing the cache, and we are adding anonymous 2472 * data, and we have outgrown arc_p, update arc_p 2473 */ 2474 if (arc_size < arc_c && hdr->b_state == arc_anon && 2475 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 2476 arc_p = MIN(arc_c, arc_p + size); 2477 } 2478 } 2479 2480 /* 2481 * This routine is called whenever a buffer is accessed. 2482 * NOTE: the hash lock is dropped in this function. 2483 */ 2484 static void 2485 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock) 2486 { 2487 clock_t now; 2488 2489 ASSERT(MUTEX_HELD(hash_lock)); 2490 2491 if (buf->b_state == arc_anon) { 2492 /* 2493 * This buffer is not in the cache, and does not 2494 * appear in our "ghost" list. Add the new buffer 2495 * to the MRU state. 2496 */ 2497 2498 ASSERT(buf->b_arc_access == 0); 2499 buf->b_arc_access = ddi_get_lbolt(); 2500 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2501 arc_change_state(arc_mru, buf, hash_lock); 2502 2503 } else if (buf->b_state == arc_mru) { 2504 now = ddi_get_lbolt(); 2505 2506 /* 2507 * If this buffer is here because of a prefetch, then either: 2508 * - clear the flag if this is a "referencing" read 2509 * (any subsequent access will bump this into the MFU state). 2510 * or 2511 * - move the buffer to the head of the list if this is 2512 * another prefetch (to make it less likely to be evicted). 2513 */ 2514 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2515 if (refcount_count(&buf->b_refcnt) == 0) { 2516 ASSERT(list_link_active(&buf->b_arc_node)); 2517 } else { 2518 buf->b_flags &= ~ARC_PREFETCH; 2519 ARCSTAT_BUMP(arcstat_mru_hits); 2520 } 2521 buf->b_arc_access = now; 2522 return; 2523 } 2524 2525 /* 2526 * This buffer has been "accessed" only once so far, 2527 * but it is still in the cache. Move it to the MFU 2528 * state. 2529 */ 2530 if (now > buf->b_arc_access + ARC_MINTIME) { 2531 /* 2532 * More than 125ms have passed since we 2533 * instantiated this buffer. Move it to the 2534 * most frequently used state. 2535 */ 2536 buf->b_arc_access = now; 2537 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2538 arc_change_state(arc_mfu, buf, hash_lock); 2539 } 2540 ARCSTAT_BUMP(arcstat_mru_hits); 2541 } else if (buf->b_state == arc_mru_ghost) { 2542 arc_state_t *new_state; 2543 /* 2544 * This buffer has been "accessed" recently, but 2545 * was evicted from the cache. Move it to the 2546 * MFU state. 2547 */ 2548 2549 if (buf->b_flags & ARC_PREFETCH) { 2550 new_state = arc_mru; 2551 if (refcount_count(&buf->b_refcnt) > 0) 2552 buf->b_flags &= ~ARC_PREFETCH; 2553 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2554 } else { 2555 new_state = arc_mfu; 2556 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2557 } 2558 2559 buf->b_arc_access = ddi_get_lbolt(); 2560 arc_change_state(new_state, buf, hash_lock); 2561 2562 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 2563 } else if (buf->b_state == arc_mfu) { 2564 /* 2565 * This buffer has been accessed more than once and is 2566 * still in the cache. Keep it in the MFU state. 2567 * 2568 * NOTE: an add_reference() that occurred when we did 2569 * the arc_read() will have kicked this off the list. 2570 * If it was a prefetch, we will explicitly move it to 2571 * the head of the list now. 2572 */ 2573 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2574 ASSERT(refcount_count(&buf->b_refcnt) == 0); 2575 ASSERT(list_link_active(&buf->b_arc_node)); 2576 } 2577 ARCSTAT_BUMP(arcstat_mfu_hits); 2578 buf->b_arc_access = ddi_get_lbolt(); 2579 } else if (buf->b_state == arc_mfu_ghost) { 2580 arc_state_t *new_state = arc_mfu; 2581 /* 2582 * This buffer has been accessed more than once but has 2583 * been evicted from the cache. Move it back to the 2584 * MFU state. 2585 */ 2586 2587 if (buf->b_flags & ARC_PREFETCH) { 2588 /* 2589 * This is a prefetch access... 2590 * move this block back to the MRU state. 2591 */ 2592 ASSERT0(refcount_count(&buf->b_refcnt)); 2593 new_state = arc_mru; 2594 } 2595 2596 buf->b_arc_access = ddi_get_lbolt(); 2597 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2598 arc_change_state(new_state, buf, hash_lock); 2599 2600 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 2601 } else if (buf->b_state == arc_l2c_only) { 2602 /* 2603 * This buffer is on the 2nd Level ARC. 2604 */ 2605 2606 buf->b_arc_access = ddi_get_lbolt(); 2607 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2608 arc_change_state(arc_mfu, buf, hash_lock); 2609 } else { 2610 ASSERT(!"invalid arc state"); 2611 } 2612 } 2613 2614 /* a generic arc_done_func_t which you can use */ 2615 /* ARGSUSED */ 2616 void 2617 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 2618 { 2619 if (zio == NULL || zio->io_error == 0) 2620 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 2621 VERIFY(arc_buf_remove_ref(buf, arg) == 1); 2622 } 2623 2624 /* a generic arc_done_func_t */ 2625 void 2626 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 2627 { 2628 arc_buf_t **bufp = arg; 2629 if (zio && zio->io_error) { 2630 VERIFY(arc_buf_remove_ref(buf, arg) == 1); 2631 *bufp = NULL; 2632 } else { 2633 *bufp = buf; 2634 ASSERT(buf->b_data); 2635 } 2636 } 2637 2638 static void 2639 arc_read_done(zio_t *zio) 2640 { 2641 arc_buf_hdr_t *hdr, *found; 2642 arc_buf_t *buf; 2643 arc_buf_t *abuf; /* buffer we're assigning to callback */ 2644 kmutex_t *hash_lock; 2645 arc_callback_t *callback_list, *acb; 2646 int freeable = FALSE; 2647 2648 buf = zio->io_private; 2649 hdr = buf->b_hdr; 2650 2651 /* 2652 * The hdr was inserted into hash-table and removed from lists 2653 * prior to starting I/O. We should find this header, since 2654 * it's in the hash table, and it should be legit since it's 2655 * not possible to evict it during the I/O. The only possible 2656 * reason for it not to be found is if we were freed during the 2657 * read. 2658 */ 2659 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth, 2660 &hash_lock); 2661 2662 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) || 2663 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 2664 (found == hdr && HDR_L2_READING(hdr))); 2665 2666 hdr->b_flags &= ~ARC_L2_EVICTED; 2667 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH)) 2668 hdr->b_flags &= ~ARC_L2CACHE; 2669 2670 /* byteswap if necessary */ 2671 callback_list = hdr->b_acb; 2672 ASSERT(callback_list != NULL); 2673 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 2674 dmu_object_byteswap_t bswap = 2675 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 2676 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 2677 byteswap_uint64_array : 2678 dmu_ot_byteswap[bswap].ob_func; 2679 func(buf->b_data, hdr->b_size); 2680 } 2681 2682 arc_cksum_compute(buf, B_FALSE); 2683 arc_buf_watch(buf); 2684 2685 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) { 2686 /* 2687 * Only call arc_access on anonymous buffers. This is because 2688 * if we've issued an I/O for an evicted buffer, we've already 2689 * called arc_access (to prevent any simultaneous readers from 2690 * getting confused). 2691 */ 2692 arc_access(hdr, hash_lock); 2693 } 2694 2695 /* create copies of the data buffer for the callers */ 2696 abuf = buf; 2697 for (acb = callback_list; acb; acb = acb->acb_next) { 2698 if (acb->acb_done) { 2699 if (abuf == NULL) { 2700 ARCSTAT_BUMP(arcstat_duplicate_reads); 2701 abuf = arc_buf_clone(buf); 2702 } 2703 acb->acb_buf = abuf; 2704 abuf = NULL; 2705 } 2706 } 2707 hdr->b_acb = NULL; 2708 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 2709 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 2710 if (abuf == buf) { 2711 ASSERT(buf->b_efunc == NULL); 2712 ASSERT(hdr->b_datacnt == 1); 2713 hdr->b_flags |= ARC_BUF_AVAILABLE; 2714 } 2715 2716 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL); 2717 2718 if (zio->io_error != 0) { 2719 hdr->b_flags |= ARC_IO_ERROR; 2720 if (hdr->b_state != arc_anon) 2721 arc_change_state(arc_anon, hdr, hash_lock); 2722 if (HDR_IN_HASH_TABLE(hdr)) 2723 buf_hash_remove(hdr); 2724 freeable = refcount_is_zero(&hdr->b_refcnt); 2725 } 2726 2727 /* 2728 * Broadcast before we drop the hash_lock to avoid the possibility 2729 * that the hdr (and hence the cv) might be freed before we get to 2730 * the cv_broadcast(). 2731 */ 2732 cv_broadcast(&hdr->b_cv); 2733 2734 if (hash_lock) { 2735 mutex_exit(hash_lock); 2736 } else { 2737 /* 2738 * This block was freed while we waited for the read to 2739 * complete. It has been removed from the hash table and 2740 * moved to the anonymous state (so that it won't show up 2741 * in the cache). 2742 */ 2743 ASSERT3P(hdr->b_state, ==, arc_anon); 2744 freeable = refcount_is_zero(&hdr->b_refcnt); 2745 } 2746 2747 /* execute each callback and free its structure */ 2748 while ((acb = callback_list) != NULL) { 2749 if (acb->acb_done) 2750 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 2751 2752 if (acb->acb_zio_dummy != NULL) { 2753 acb->acb_zio_dummy->io_error = zio->io_error; 2754 zio_nowait(acb->acb_zio_dummy); 2755 } 2756 2757 callback_list = acb->acb_next; 2758 kmem_free(acb, sizeof (arc_callback_t)); 2759 } 2760 2761 if (freeable) 2762 arc_hdr_destroy(hdr); 2763 } 2764 2765 /* 2766 * "Read" the block at the specified DVA (in bp) via the 2767 * cache. If the block is found in the cache, invoke the provided 2768 * callback immediately and return. Note that the `zio' parameter 2769 * in the callback will be NULL in this case, since no IO was 2770 * required. If the block is not in the cache pass the read request 2771 * on to the spa with a substitute callback function, so that the 2772 * requested block will be added to the cache. 2773 * 2774 * If a read request arrives for a block that has a read in-progress, 2775 * either wait for the in-progress read to complete (and return the 2776 * results); or, if this is a read with a "done" func, add a record 2777 * to the read to invoke the "done" func when the read completes, 2778 * and return; or just return. 2779 * 2780 * arc_read_done() will invoke all the requested "done" functions 2781 * for readers of this block. 2782 * 2783 * Normal callers should use arc_read and pass the arc buffer and offset 2784 * for the bp. But if you know you don't need locking, you can use 2785 * arc_read_bp. 2786 */ 2787 int 2788 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf, 2789 arc_done_func_t *done, void *private, int priority, int zio_flags, 2790 uint32_t *arc_flags, const zbookmark_t *zb) 2791 { 2792 int err; 2793 2794 if (pbuf == NULL) { 2795 /* 2796 * XXX This happens from traverse callback funcs, for 2797 * the objset_phys_t block. 2798 */ 2799 return (arc_read_nolock(pio, spa, bp, done, private, priority, 2800 zio_flags, arc_flags, zb)); 2801 } 2802 2803 ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt)); 2804 ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size); 2805 rw_enter(&pbuf->b_data_lock, RW_READER); 2806 2807 err = arc_read_nolock(pio, spa, bp, done, private, priority, 2808 zio_flags, arc_flags, zb); 2809 rw_exit(&pbuf->b_data_lock); 2810 2811 return (err); 2812 } 2813 2814 int 2815 arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp, 2816 arc_done_func_t *done, void *private, int priority, int zio_flags, 2817 uint32_t *arc_flags, const zbookmark_t *zb) 2818 { 2819 arc_buf_hdr_t *hdr; 2820 arc_buf_t *buf; 2821 kmutex_t *hash_lock; 2822 zio_t *rzio; 2823 uint64_t guid = spa_load_guid(spa); 2824 2825 top: 2826 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp), 2827 &hash_lock); 2828 if (hdr && hdr->b_datacnt > 0) { 2829 2830 *arc_flags |= ARC_CACHED; 2831 2832 if (HDR_IO_IN_PROGRESS(hdr)) { 2833 2834 if (*arc_flags & ARC_WAIT) { 2835 cv_wait(&hdr->b_cv, hash_lock); 2836 mutex_exit(hash_lock); 2837 goto top; 2838 } 2839 ASSERT(*arc_flags & ARC_NOWAIT); 2840 2841 if (done) { 2842 arc_callback_t *acb = NULL; 2843 2844 acb = kmem_zalloc(sizeof (arc_callback_t), 2845 KM_SLEEP); 2846 acb->acb_done = done; 2847 acb->acb_private = private; 2848 if (pio != NULL) 2849 acb->acb_zio_dummy = zio_null(pio, 2850 spa, NULL, NULL, NULL, zio_flags); 2851 2852 ASSERT(acb->acb_done != NULL); 2853 acb->acb_next = hdr->b_acb; 2854 hdr->b_acb = acb; 2855 add_reference(hdr, hash_lock, private); 2856 mutex_exit(hash_lock); 2857 return (0); 2858 } 2859 mutex_exit(hash_lock); 2860 return (0); 2861 } 2862 2863 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 2864 2865 if (done) { 2866 add_reference(hdr, hash_lock, private); 2867 /* 2868 * If this block is already in use, create a new 2869 * copy of the data so that we will be guaranteed 2870 * that arc_release() will always succeed. 2871 */ 2872 buf = hdr->b_buf; 2873 ASSERT(buf); 2874 ASSERT(buf->b_data); 2875 if (HDR_BUF_AVAILABLE(hdr)) { 2876 ASSERT(buf->b_efunc == NULL); 2877 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 2878 } else { 2879 buf = arc_buf_clone(buf); 2880 } 2881 2882 } else if (*arc_flags & ARC_PREFETCH && 2883 refcount_count(&hdr->b_refcnt) == 0) { 2884 hdr->b_flags |= ARC_PREFETCH; 2885 } 2886 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2887 arc_access(hdr, hash_lock); 2888 if (*arc_flags & ARC_L2CACHE) 2889 hdr->b_flags |= ARC_L2CACHE; 2890 mutex_exit(hash_lock); 2891 ARCSTAT_BUMP(arcstat_hits); 2892 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 2893 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 2894 data, metadata, hits); 2895 2896 if (done) 2897 done(NULL, buf, private); 2898 } else { 2899 uint64_t size = BP_GET_LSIZE(bp); 2900 arc_callback_t *acb; 2901 vdev_t *vd = NULL; 2902 uint64_t addr; 2903 boolean_t devw = B_FALSE; 2904 2905 if (hdr == NULL) { 2906 /* this block is not in the cache */ 2907 arc_buf_hdr_t *exists; 2908 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 2909 buf = arc_buf_alloc(spa, size, private, type); 2910 hdr = buf->b_hdr; 2911 hdr->b_dva = *BP_IDENTITY(bp); 2912 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 2913 hdr->b_cksum0 = bp->blk_cksum.zc_word[0]; 2914 exists = buf_hash_insert(hdr, &hash_lock); 2915 if (exists) { 2916 /* somebody beat us to the hash insert */ 2917 mutex_exit(hash_lock); 2918 buf_discard_identity(hdr); 2919 (void) arc_buf_remove_ref(buf, private); 2920 goto top; /* restart the IO request */ 2921 } 2922 /* if this is a prefetch, we don't have a reference */ 2923 if (*arc_flags & ARC_PREFETCH) { 2924 (void) remove_reference(hdr, hash_lock, 2925 private); 2926 hdr->b_flags |= ARC_PREFETCH; 2927 } 2928 if (*arc_flags & ARC_L2CACHE) 2929 hdr->b_flags |= ARC_L2CACHE; 2930 if (BP_GET_LEVEL(bp) > 0) 2931 hdr->b_flags |= ARC_INDIRECT; 2932 } else { 2933 /* this block is in the ghost cache */ 2934 ASSERT(GHOST_STATE(hdr->b_state)); 2935 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2936 ASSERT0(refcount_count(&hdr->b_refcnt)); 2937 ASSERT(hdr->b_buf == NULL); 2938 2939 /* if this is a prefetch, we don't have a reference */ 2940 if (*arc_flags & ARC_PREFETCH) 2941 hdr->b_flags |= ARC_PREFETCH; 2942 else 2943 add_reference(hdr, hash_lock, private); 2944 if (*arc_flags & ARC_L2CACHE) 2945 hdr->b_flags |= ARC_L2CACHE; 2946 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2947 buf->b_hdr = hdr; 2948 buf->b_data = NULL; 2949 buf->b_efunc = NULL; 2950 buf->b_private = NULL; 2951 buf->b_next = NULL; 2952 hdr->b_buf = buf; 2953 ASSERT(hdr->b_datacnt == 0); 2954 hdr->b_datacnt = 1; 2955 arc_get_data_buf(buf); 2956 arc_access(hdr, hash_lock); 2957 } 2958 2959 ASSERT(!GHOST_STATE(hdr->b_state)); 2960 2961 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 2962 acb->acb_done = done; 2963 acb->acb_private = private; 2964 2965 ASSERT(hdr->b_acb == NULL); 2966 hdr->b_acb = acb; 2967 hdr->b_flags |= ARC_IO_IN_PROGRESS; 2968 2969 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL && 2970 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) { 2971 devw = hdr->b_l2hdr->b_dev->l2ad_writing; 2972 addr = hdr->b_l2hdr->b_daddr; 2973 /* 2974 * Lock out device removal. 2975 */ 2976 if (vdev_is_dead(vd) || 2977 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 2978 vd = NULL; 2979 } 2980 2981 mutex_exit(hash_lock); 2982 2983 ASSERT3U(hdr->b_size, ==, size); 2984 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 2985 uint64_t, size, zbookmark_t *, zb); 2986 ARCSTAT_BUMP(arcstat_misses); 2987 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 2988 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 2989 data, metadata, misses); 2990 2991 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 2992 /* 2993 * Read from the L2ARC if the following are true: 2994 * 1. The L2ARC vdev was previously cached. 2995 * 2. This buffer still has L2ARC metadata. 2996 * 3. This buffer isn't currently writing to the L2ARC. 2997 * 4. The L2ARC entry wasn't evicted, which may 2998 * also have invalidated the vdev. 2999 * 5. This isn't prefetch and l2arc_noprefetch is set. 3000 */ 3001 if (hdr->b_l2hdr != NULL && 3002 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3003 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3004 l2arc_read_callback_t *cb; 3005 3006 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3007 ARCSTAT_BUMP(arcstat_l2_hits); 3008 3009 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3010 KM_SLEEP); 3011 cb->l2rcb_buf = buf; 3012 cb->l2rcb_spa = spa; 3013 cb->l2rcb_bp = *bp; 3014 cb->l2rcb_zb = *zb; 3015 cb->l2rcb_flags = zio_flags; 3016 3017 /* 3018 * l2arc read. The SCL_L2ARC lock will be 3019 * released by l2arc_read_done(). 3020 */ 3021 rzio = zio_read_phys(pio, vd, addr, size, 3022 buf->b_data, ZIO_CHECKSUM_OFF, 3023 l2arc_read_done, cb, priority, zio_flags | 3024 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | 3025 ZIO_FLAG_DONT_PROPAGATE | 3026 ZIO_FLAG_DONT_RETRY, B_FALSE); 3027 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3028 zio_t *, rzio); 3029 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 3030 3031 if (*arc_flags & ARC_NOWAIT) { 3032 zio_nowait(rzio); 3033 return (0); 3034 } 3035 3036 ASSERT(*arc_flags & ARC_WAIT); 3037 if (zio_wait(rzio) == 0) 3038 return (0); 3039 3040 /* l2arc read error; goto zio_read() */ 3041 } else { 3042 DTRACE_PROBE1(l2arc__miss, 3043 arc_buf_hdr_t *, hdr); 3044 ARCSTAT_BUMP(arcstat_l2_misses); 3045 if (HDR_L2_WRITING(hdr)) 3046 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3047 spa_config_exit(spa, SCL_L2ARC, vd); 3048 } 3049 } else { 3050 if (vd != NULL) 3051 spa_config_exit(spa, SCL_L2ARC, vd); 3052 if (l2arc_ndev != 0) { 3053 DTRACE_PROBE1(l2arc__miss, 3054 arc_buf_hdr_t *, hdr); 3055 ARCSTAT_BUMP(arcstat_l2_misses); 3056 } 3057 } 3058 3059 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3060 arc_read_done, buf, priority, zio_flags, zb); 3061 3062 if (*arc_flags & ARC_WAIT) 3063 return (zio_wait(rzio)); 3064 3065 ASSERT(*arc_flags & ARC_NOWAIT); 3066 zio_nowait(rzio); 3067 } 3068 return (0); 3069 } 3070 3071 void 3072 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3073 { 3074 ASSERT(buf->b_hdr != NULL); 3075 ASSERT(buf->b_hdr->b_state != arc_anon); 3076 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL); 3077 ASSERT(buf->b_efunc == NULL); 3078 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3079 3080 buf->b_efunc = func; 3081 buf->b_private = private; 3082 } 3083 3084 /* 3085 * This is used by the DMU to let the ARC know that a buffer is 3086 * being evicted, so the ARC should clean up. If this arc buf 3087 * is not yet in the evicted state, it will be put there. 3088 */ 3089 int 3090 arc_buf_evict(arc_buf_t *buf) 3091 { 3092 arc_buf_hdr_t *hdr; 3093 kmutex_t *hash_lock; 3094 arc_buf_t **bufp; 3095 3096 mutex_enter(&buf->b_evict_lock); 3097 hdr = buf->b_hdr; 3098 if (hdr == NULL) { 3099 /* 3100 * We are in arc_do_user_evicts(). 3101 */ 3102 ASSERT(buf->b_data == NULL); 3103 mutex_exit(&buf->b_evict_lock); 3104 return (0); 3105 } else if (buf->b_data == NULL) { 3106 arc_buf_t copy = *buf; /* structure assignment */ 3107 /* 3108 * We are on the eviction list; process this buffer now 3109 * but let arc_do_user_evicts() do the reaping. 3110 */ 3111 buf->b_efunc = NULL; 3112 mutex_exit(&buf->b_evict_lock); 3113 VERIFY(copy.b_efunc(©) == 0); 3114 return (1); 3115 } 3116 hash_lock = HDR_LOCK(hdr); 3117 mutex_enter(hash_lock); 3118 hdr = buf->b_hdr; 3119 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3120 3121 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt); 3122 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3123 3124 /* 3125 * Pull this buffer off of the hdr 3126 */ 3127 bufp = &hdr->b_buf; 3128 while (*bufp != buf) 3129 bufp = &(*bufp)->b_next; 3130 *bufp = buf->b_next; 3131 3132 ASSERT(buf->b_data != NULL); 3133 arc_buf_destroy(buf, FALSE, FALSE); 3134 3135 if (hdr->b_datacnt == 0) { 3136 arc_state_t *old_state = hdr->b_state; 3137 arc_state_t *evicted_state; 3138 3139 ASSERT(hdr->b_buf == NULL); 3140 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 3141 3142 evicted_state = 3143 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3144 3145 mutex_enter(&old_state->arcs_mtx); 3146 mutex_enter(&evicted_state->arcs_mtx); 3147 3148 arc_change_state(evicted_state, hdr, hash_lock); 3149 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3150 hdr->b_flags |= ARC_IN_HASH_TABLE; 3151 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3152 3153 mutex_exit(&evicted_state->arcs_mtx); 3154 mutex_exit(&old_state->arcs_mtx); 3155 } 3156 mutex_exit(hash_lock); 3157 mutex_exit(&buf->b_evict_lock); 3158 3159 VERIFY(buf->b_efunc(buf) == 0); 3160 buf->b_efunc = NULL; 3161 buf->b_private = NULL; 3162 buf->b_hdr = NULL; 3163 buf->b_next = NULL; 3164 kmem_cache_free(buf_cache, buf); 3165 return (1); 3166 } 3167 3168 /* 3169 * Release this buffer from the cache. This must be done 3170 * after a read and prior to modifying the buffer contents. 3171 * If the buffer has more than one reference, we must make 3172 * a new hdr for the buffer. 3173 */ 3174 void 3175 arc_release(arc_buf_t *buf, void *tag) 3176 { 3177 arc_buf_hdr_t *hdr; 3178 kmutex_t *hash_lock = NULL; 3179 l2arc_buf_hdr_t *l2hdr; 3180 uint64_t buf_size; 3181 3182 /* 3183 * It would be nice to assert that if it's DMU metadata (level > 3184 * 0 || it's the dnode file), then it must be syncing context. 3185 * But we don't know that information at this level. 3186 */ 3187 3188 mutex_enter(&buf->b_evict_lock); 3189 hdr = buf->b_hdr; 3190 3191 /* this buffer is not on any list */ 3192 ASSERT(refcount_count(&hdr->b_refcnt) > 0); 3193 3194 if (hdr->b_state == arc_anon) { 3195 /* this buffer is already released */ 3196 ASSERT(buf->b_efunc == NULL); 3197 } else { 3198 hash_lock = HDR_LOCK(hdr); 3199 mutex_enter(hash_lock); 3200 hdr = buf->b_hdr; 3201 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3202 } 3203 3204 l2hdr = hdr->b_l2hdr; 3205 if (l2hdr) { 3206 mutex_enter(&l2arc_buflist_mtx); 3207 hdr->b_l2hdr = NULL; 3208 buf_size = hdr->b_size; 3209 } 3210 3211 /* 3212 * Do we have more than one buf? 3213 */ 3214 if (hdr->b_datacnt > 1) { 3215 arc_buf_hdr_t *nhdr; 3216 arc_buf_t **bufp; 3217 uint64_t blksz = hdr->b_size; 3218 uint64_t spa = hdr->b_spa; 3219 arc_buf_contents_t type = hdr->b_type; 3220 uint32_t flags = hdr->b_flags; 3221 3222 ASSERT(hdr->b_buf != buf || buf->b_next != NULL); 3223 /* 3224 * Pull the data off of this hdr and attach it to 3225 * a new anonymous hdr. 3226 */ 3227 (void) remove_reference(hdr, hash_lock, tag); 3228 bufp = &hdr->b_buf; 3229 while (*bufp != buf) 3230 bufp = &(*bufp)->b_next; 3231 *bufp = buf->b_next; 3232 buf->b_next = NULL; 3233 3234 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size); 3235 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size); 3236 if (refcount_is_zero(&hdr->b_refcnt)) { 3237 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 3238 ASSERT3U(*size, >=, hdr->b_size); 3239 atomic_add_64(size, -hdr->b_size); 3240 } 3241 3242 /* 3243 * We're releasing a duplicate user data buffer, update 3244 * our statistics accordingly. 3245 */ 3246 if (hdr->b_type == ARC_BUFC_DATA) { 3247 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3248 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3249 -hdr->b_size); 3250 } 3251 hdr->b_datacnt -= 1; 3252 arc_cksum_verify(buf); 3253 arc_buf_unwatch(buf); 3254 3255 mutex_exit(hash_lock); 3256 3257 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 3258 nhdr->b_size = blksz; 3259 nhdr->b_spa = spa; 3260 nhdr->b_type = type; 3261 nhdr->b_buf = buf; 3262 nhdr->b_state = arc_anon; 3263 nhdr->b_arc_access = 0; 3264 nhdr->b_flags = flags & ARC_L2_WRITING; 3265 nhdr->b_l2hdr = NULL; 3266 nhdr->b_datacnt = 1; 3267 nhdr->b_freeze_cksum = NULL; 3268 (void) refcount_add(&nhdr->b_refcnt, tag); 3269 buf->b_hdr = nhdr; 3270 mutex_exit(&buf->b_evict_lock); 3271 atomic_add_64(&arc_anon->arcs_size, blksz); 3272 } else { 3273 mutex_exit(&buf->b_evict_lock); 3274 ASSERT(refcount_count(&hdr->b_refcnt) == 1); 3275 ASSERT(!list_link_active(&hdr->b_arc_node)); 3276 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3277 if (hdr->b_state != arc_anon) 3278 arc_change_state(arc_anon, hdr, hash_lock); 3279 hdr->b_arc_access = 0; 3280 if (hash_lock) 3281 mutex_exit(hash_lock); 3282 3283 buf_discard_identity(hdr); 3284 arc_buf_thaw(buf); 3285 } 3286 buf->b_efunc = NULL; 3287 buf->b_private = NULL; 3288 3289 if (l2hdr) { 3290 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 3291 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 3292 ARCSTAT_INCR(arcstat_l2_size, -buf_size); 3293 mutex_exit(&l2arc_buflist_mtx); 3294 } 3295 } 3296 3297 /* 3298 * Release this buffer. If it does not match the provided BP, fill it 3299 * with that block's contents. 3300 */ 3301 /* ARGSUSED */ 3302 int 3303 arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa, 3304 zbookmark_t *zb) 3305 { 3306 arc_release(buf, tag); 3307 return (0); 3308 } 3309 3310 int 3311 arc_released(arc_buf_t *buf) 3312 { 3313 int released; 3314 3315 mutex_enter(&buf->b_evict_lock); 3316 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon); 3317 mutex_exit(&buf->b_evict_lock); 3318 return (released); 3319 } 3320 3321 int 3322 arc_has_callback(arc_buf_t *buf) 3323 { 3324 int callback; 3325 3326 mutex_enter(&buf->b_evict_lock); 3327 callback = (buf->b_efunc != NULL); 3328 mutex_exit(&buf->b_evict_lock); 3329 return (callback); 3330 } 3331 3332 #ifdef ZFS_DEBUG 3333 int 3334 arc_referenced(arc_buf_t *buf) 3335 { 3336 int referenced; 3337 3338 mutex_enter(&buf->b_evict_lock); 3339 referenced = (refcount_count(&buf->b_hdr->b_refcnt)); 3340 mutex_exit(&buf->b_evict_lock); 3341 return (referenced); 3342 } 3343 #endif 3344 3345 static void 3346 arc_write_ready(zio_t *zio) 3347 { 3348 arc_write_callback_t *callback = zio->io_private; 3349 arc_buf_t *buf = callback->awcb_buf; 3350 arc_buf_hdr_t *hdr = buf->b_hdr; 3351 3352 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt)); 3353 callback->awcb_ready(zio, buf, callback->awcb_private); 3354 3355 /* 3356 * If the IO is already in progress, then this is a re-write 3357 * attempt, so we need to thaw and re-compute the cksum. 3358 * It is the responsibility of the callback to handle the 3359 * accounting for any re-write attempt. 3360 */ 3361 if (HDR_IO_IN_PROGRESS(hdr)) { 3362 mutex_enter(&hdr->b_freeze_lock); 3363 if (hdr->b_freeze_cksum != NULL) { 3364 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 3365 hdr->b_freeze_cksum = NULL; 3366 } 3367 mutex_exit(&hdr->b_freeze_lock); 3368 } 3369 arc_cksum_compute(buf, B_FALSE); 3370 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3371 } 3372 3373 static void 3374 arc_write_done(zio_t *zio) 3375 { 3376 arc_write_callback_t *callback = zio->io_private; 3377 arc_buf_t *buf = callback->awcb_buf; 3378 arc_buf_hdr_t *hdr = buf->b_hdr; 3379 3380 ASSERT(hdr->b_acb == NULL); 3381 3382 if (zio->io_error == 0) { 3383 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 3384 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 3385 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0]; 3386 } else { 3387 ASSERT(BUF_EMPTY(hdr)); 3388 } 3389 3390 /* 3391 * If the block to be written was all-zero, we may have 3392 * compressed it away. In this case no write was performed 3393 * so there will be no dva/birth/checksum. The buffer must 3394 * therefore remain anonymous (and uncached). 3395 */ 3396 if (!BUF_EMPTY(hdr)) { 3397 arc_buf_hdr_t *exists; 3398 kmutex_t *hash_lock; 3399 3400 ASSERT(zio->io_error == 0); 3401 3402 arc_cksum_verify(buf); 3403 3404 exists = buf_hash_insert(hdr, &hash_lock); 3405 if (exists) { 3406 /* 3407 * This can only happen if we overwrite for 3408 * sync-to-convergence, because we remove 3409 * buffers from the hash table when we arc_free(). 3410 */ 3411 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 3412 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3413 panic("bad overwrite, hdr=%p exists=%p", 3414 (void *)hdr, (void *)exists); 3415 ASSERT(refcount_is_zero(&exists->b_refcnt)); 3416 arc_change_state(arc_anon, exists, hash_lock); 3417 mutex_exit(hash_lock); 3418 arc_hdr_destroy(exists); 3419 exists = buf_hash_insert(hdr, &hash_lock); 3420 ASSERT3P(exists, ==, NULL); 3421 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 3422 /* nopwrite */ 3423 ASSERT(zio->io_prop.zp_nopwrite); 3424 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3425 panic("bad nopwrite, hdr=%p exists=%p", 3426 (void *)hdr, (void *)exists); 3427 } else { 3428 /* Dedup */ 3429 ASSERT(hdr->b_datacnt == 1); 3430 ASSERT(hdr->b_state == arc_anon); 3431 ASSERT(BP_GET_DEDUP(zio->io_bp)); 3432 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 3433 } 3434 } 3435 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3436 /* if it's not anon, we are doing a scrub */ 3437 if (!exists && hdr->b_state == arc_anon) 3438 arc_access(hdr, hash_lock); 3439 mutex_exit(hash_lock); 3440 } else { 3441 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3442 } 3443 3444 ASSERT(!refcount_is_zero(&hdr->b_refcnt)); 3445 callback->awcb_done(zio, buf, callback->awcb_private); 3446 3447 kmem_free(callback, sizeof (arc_write_callback_t)); 3448 } 3449 3450 zio_t * 3451 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 3452 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp, 3453 arc_done_func_t *ready, arc_done_func_t *done, void *private, 3454 int priority, int zio_flags, const zbookmark_t *zb) 3455 { 3456 arc_buf_hdr_t *hdr = buf->b_hdr; 3457 arc_write_callback_t *callback; 3458 zio_t *zio; 3459 3460 ASSERT(ready != NULL); 3461 ASSERT(done != NULL); 3462 ASSERT(!HDR_IO_ERROR(hdr)); 3463 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0); 3464 ASSERT(hdr->b_acb == NULL); 3465 if (l2arc) 3466 hdr->b_flags |= ARC_L2CACHE; 3467 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 3468 callback->awcb_ready = ready; 3469 callback->awcb_done = done; 3470 callback->awcb_private = private; 3471 callback->awcb_buf = buf; 3472 3473 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 3474 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb); 3475 3476 return (zio); 3477 } 3478 3479 static int 3480 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg) 3481 { 3482 #ifdef _KERNEL 3483 uint64_t available_memory = ptob(freemem); 3484 static uint64_t page_load = 0; 3485 static uint64_t last_txg = 0; 3486 3487 #if defined(__i386) 3488 available_memory = 3489 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 3490 #endif 3491 if (available_memory >= zfs_write_limit_max) 3492 return (0); 3493 3494 if (txg > last_txg) { 3495 last_txg = txg; 3496 page_load = 0; 3497 } 3498 /* 3499 * If we are in pageout, we know that memory is already tight, 3500 * the arc is already going to be evicting, so we just want to 3501 * continue to let page writes occur as quickly as possible. 3502 */ 3503 if (curproc == proc_pageout) { 3504 if (page_load > MAX(ptob(minfree), available_memory) / 4) 3505 return (ERESTART); 3506 /* Note: reserve is inflated, so we deflate */ 3507 page_load += reserve / 8; 3508 return (0); 3509 } else if (page_load > 0 && arc_reclaim_needed()) { 3510 /* memory is low, delay before restarting */ 3511 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3512 return (EAGAIN); 3513 } 3514 page_load = 0; 3515 3516 if (arc_size > arc_c_min) { 3517 uint64_t evictable_memory = 3518 arc_mru->arcs_lsize[ARC_BUFC_DATA] + 3519 arc_mru->arcs_lsize[ARC_BUFC_METADATA] + 3520 arc_mfu->arcs_lsize[ARC_BUFC_DATA] + 3521 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]; 3522 available_memory += MIN(evictable_memory, arc_size - arc_c_min); 3523 } 3524 3525 if (inflight_data > available_memory / 4) { 3526 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3527 return (ERESTART); 3528 } 3529 #endif 3530 return (0); 3531 } 3532 3533 void 3534 arc_tempreserve_clear(uint64_t reserve) 3535 { 3536 atomic_add_64(&arc_tempreserve, -reserve); 3537 ASSERT((int64_t)arc_tempreserve >= 0); 3538 } 3539 3540 int 3541 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 3542 { 3543 int error; 3544 uint64_t anon_size; 3545 3546 #ifdef ZFS_DEBUG 3547 /* 3548 * Once in a while, fail for no reason. Everything should cope. 3549 */ 3550 if (spa_get_random(10000) == 0) { 3551 dprintf("forcing random failure\n"); 3552 return (ERESTART); 3553 } 3554 #endif 3555 if (reserve > arc_c/4 && !arc_no_grow) 3556 arc_c = MIN(arc_c_max, reserve * 4); 3557 if (reserve > arc_c) 3558 return (ENOMEM); 3559 3560 /* 3561 * Don't count loaned bufs as in flight dirty data to prevent long 3562 * network delays from blocking transactions that are ready to be 3563 * assigned to a txg. 3564 */ 3565 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 3566 3567 /* 3568 * Writes will, almost always, require additional memory allocations 3569 * in order to compress/encrypt/etc the data. We therefor need to 3570 * make sure that there is sufficient available memory for this. 3571 */ 3572 if (error = arc_memory_throttle(reserve, anon_size, txg)) 3573 return (error); 3574 3575 /* 3576 * Throttle writes when the amount of dirty data in the cache 3577 * gets too large. We try to keep the cache less than half full 3578 * of dirty blocks so that our sync times don't grow too large. 3579 * Note: if two requests come in concurrently, we might let them 3580 * both succeed, when one of them should fail. Not a huge deal. 3581 */ 3582 3583 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 3584 anon_size > arc_c / 4) { 3585 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 3586 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 3587 arc_tempreserve>>10, 3588 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 3589 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 3590 reserve>>10, arc_c>>10); 3591 return (ERESTART); 3592 } 3593 atomic_add_64(&arc_tempreserve, reserve); 3594 return (0); 3595 } 3596 3597 void 3598 arc_init(void) 3599 { 3600 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 3601 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 3602 3603 /* Convert seconds to clock ticks */ 3604 arc_min_prefetch_lifespan = 1 * hz; 3605 3606 /* Start out with 1/8 of all memory */ 3607 arc_c = physmem * PAGESIZE / 8; 3608 3609 #ifdef _KERNEL 3610 /* 3611 * On architectures where the physical memory can be larger 3612 * than the addressable space (intel in 32-bit mode), we may 3613 * need to limit the cache to 1/8 of VM size. 3614 */ 3615 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 3616 #endif 3617 3618 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 3619 arc_c_min = MAX(arc_c / 4, 64<<20); 3620 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 3621 if (arc_c * 8 >= 1<<30) 3622 arc_c_max = (arc_c * 8) - (1<<30); 3623 else 3624 arc_c_max = arc_c_min; 3625 arc_c_max = MAX(arc_c * 6, arc_c_max); 3626 3627 /* 3628 * Allow the tunables to override our calculations if they are 3629 * reasonable (ie. over 64MB) 3630 */ 3631 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE) 3632 arc_c_max = zfs_arc_max; 3633 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max) 3634 arc_c_min = zfs_arc_min; 3635 3636 arc_c = arc_c_max; 3637 arc_p = (arc_c >> 1); 3638 3639 /* limit meta-data to 1/4 of the arc capacity */ 3640 arc_meta_limit = arc_c_max / 4; 3641 3642 /* Allow the tunable to override if it is reasonable */ 3643 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 3644 arc_meta_limit = zfs_arc_meta_limit; 3645 3646 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 3647 arc_c_min = arc_meta_limit / 2; 3648 3649 if (zfs_arc_grow_retry > 0) 3650 arc_grow_retry = zfs_arc_grow_retry; 3651 3652 if (zfs_arc_shrink_shift > 0) 3653 arc_shrink_shift = zfs_arc_shrink_shift; 3654 3655 if (zfs_arc_p_min_shift > 0) 3656 arc_p_min_shift = zfs_arc_p_min_shift; 3657 3658 /* if kmem_flags are set, lets try to use less memory */ 3659 if (kmem_debugging()) 3660 arc_c = arc_c / 2; 3661 if (arc_c < arc_c_min) 3662 arc_c = arc_c_min; 3663 3664 arc_anon = &ARC_anon; 3665 arc_mru = &ARC_mru; 3666 arc_mru_ghost = &ARC_mru_ghost; 3667 arc_mfu = &ARC_mfu; 3668 arc_mfu_ghost = &ARC_mfu_ghost; 3669 arc_l2c_only = &ARC_l2c_only; 3670 arc_size = 0; 3671 3672 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3673 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3674 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3675 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3676 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3677 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3678 3679 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 3680 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3681 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 3682 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3683 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 3684 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3685 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 3686 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3687 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 3688 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3689 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 3690 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3691 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 3692 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3693 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 3694 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3695 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 3696 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3697 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 3698 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3699 3700 buf_init(); 3701 3702 arc_thread_exit = 0; 3703 arc_eviction_list = NULL; 3704 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 3705 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 3706 3707 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 3708 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 3709 3710 if (arc_ksp != NULL) { 3711 arc_ksp->ks_data = &arc_stats; 3712 kstat_install(arc_ksp); 3713 } 3714 3715 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 3716 TS_RUN, minclsyspri); 3717 3718 arc_dead = FALSE; 3719 arc_warm = B_FALSE; 3720 3721 if (zfs_write_limit_max == 0) 3722 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift; 3723 else 3724 zfs_write_limit_shift = 0; 3725 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL); 3726 } 3727 3728 void 3729 arc_fini(void) 3730 { 3731 mutex_enter(&arc_reclaim_thr_lock); 3732 arc_thread_exit = 1; 3733 while (arc_thread_exit != 0) 3734 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 3735 mutex_exit(&arc_reclaim_thr_lock); 3736 3737 arc_flush(NULL); 3738 3739 arc_dead = TRUE; 3740 3741 if (arc_ksp != NULL) { 3742 kstat_delete(arc_ksp); 3743 arc_ksp = NULL; 3744 } 3745 3746 mutex_destroy(&arc_eviction_mtx); 3747 mutex_destroy(&arc_reclaim_thr_lock); 3748 cv_destroy(&arc_reclaim_thr_cv); 3749 3750 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 3751 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 3752 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 3753 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 3754 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 3755 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 3756 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 3757 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 3758 3759 mutex_destroy(&arc_anon->arcs_mtx); 3760 mutex_destroy(&arc_mru->arcs_mtx); 3761 mutex_destroy(&arc_mru_ghost->arcs_mtx); 3762 mutex_destroy(&arc_mfu->arcs_mtx); 3763 mutex_destroy(&arc_mfu_ghost->arcs_mtx); 3764 mutex_destroy(&arc_l2c_only->arcs_mtx); 3765 3766 mutex_destroy(&zfs_write_limit_lock); 3767 3768 buf_fini(); 3769 3770 ASSERT(arc_loaned_bytes == 0); 3771 } 3772 3773 /* 3774 * Level 2 ARC 3775 * 3776 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 3777 * It uses dedicated storage devices to hold cached data, which are populated 3778 * using large infrequent writes. The main role of this cache is to boost 3779 * the performance of random read workloads. The intended L2ARC devices 3780 * include short-stroked disks, solid state disks, and other media with 3781 * substantially faster read latency than disk. 3782 * 3783 * +-----------------------+ 3784 * | ARC | 3785 * +-----------------------+ 3786 * | ^ ^ 3787 * | | | 3788 * l2arc_feed_thread() arc_read() 3789 * | | | 3790 * | l2arc read | 3791 * V | | 3792 * +---------------+ | 3793 * | L2ARC | | 3794 * +---------------+ | 3795 * | ^ | 3796 * l2arc_write() | | 3797 * | | | 3798 * V | | 3799 * +-------+ +-------+ 3800 * | vdev | | vdev | 3801 * | cache | | cache | 3802 * +-------+ +-------+ 3803 * +=========+ .-----. 3804 * : L2ARC : |-_____-| 3805 * : devices : | Disks | 3806 * +=========+ `-_____-' 3807 * 3808 * Read requests are satisfied from the following sources, in order: 3809 * 3810 * 1) ARC 3811 * 2) vdev cache of L2ARC devices 3812 * 3) L2ARC devices 3813 * 4) vdev cache of disks 3814 * 5) disks 3815 * 3816 * Some L2ARC device types exhibit extremely slow write performance. 3817 * To accommodate for this there are some significant differences between 3818 * the L2ARC and traditional cache design: 3819 * 3820 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 3821 * the ARC behave as usual, freeing buffers and placing headers on ghost 3822 * lists. The ARC does not send buffers to the L2ARC during eviction as 3823 * this would add inflated write latencies for all ARC memory pressure. 3824 * 3825 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 3826 * It does this by periodically scanning buffers from the eviction-end of 3827 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 3828 * not already there. It scans until a headroom of buffers is satisfied, 3829 * which itself is a buffer for ARC eviction. The thread that does this is 3830 * l2arc_feed_thread(), illustrated below; example sizes are included to 3831 * provide a better sense of ratio than this diagram: 3832 * 3833 * head --> tail 3834 * +---------------------+----------+ 3835 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 3836 * +---------------------+----------+ | o L2ARC eligible 3837 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 3838 * +---------------------+----------+ | 3839 * 15.9 Gbytes ^ 32 Mbytes | 3840 * headroom | 3841 * l2arc_feed_thread() 3842 * | 3843 * l2arc write hand <--[oooo]--' 3844 * | 8 Mbyte 3845 * | write max 3846 * V 3847 * +==============================+ 3848 * L2ARC dev |####|#|###|###| |####| ... | 3849 * +==============================+ 3850 * 32 Gbytes 3851 * 3852 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 3853 * evicted, then the L2ARC has cached a buffer much sooner than it probably 3854 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 3855 * safe to say that this is an uncommon case, since buffers at the end of 3856 * the ARC lists have moved there due to inactivity. 3857 * 3858 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 3859 * then the L2ARC simply misses copying some buffers. This serves as a 3860 * pressure valve to prevent heavy read workloads from both stalling the ARC 3861 * with waits and clogging the L2ARC with writes. This also helps prevent 3862 * the potential for the L2ARC to churn if it attempts to cache content too 3863 * quickly, such as during backups of the entire pool. 3864 * 3865 * 5. After system boot and before the ARC has filled main memory, there are 3866 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 3867 * lists can remain mostly static. Instead of searching from tail of these 3868 * lists as pictured, the l2arc_feed_thread() will search from the list heads 3869 * for eligible buffers, greatly increasing its chance of finding them. 3870 * 3871 * The L2ARC device write speed is also boosted during this time so that 3872 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 3873 * there are no L2ARC reads, and no fear of degrading read performance 3874 * through increased writes. 3875 * 3876 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 3877 * the vdev queue can aggregate them into larger and fewer writes. Each 3878 * device is written to in a rotor fashion, sweeping writes through 3879 * available space then repeating. 3880 * 3881 * 7. The L2ARC does not store dirty content. It never needs to flush 3882 * write buffers back to disk based storage. 3883 * 3884 * 8. If an ARC buffer is written (and dirtied) which also exists in the 3885 * L2ARC, the now stale L2ARC buffer is immediately dropped. 3886 * 3887 * The performance of the L2ARC can be tweaked by a number of tunables, which 3888 * may be necessary for different workloads: 3889 * 3890 * l2arc_write_max max write bytes per interval 3891 * l2arc_write_boost extra write bytes during device warmup 3892 * l2arc_noprefetch skip caching prefetched buffers 3893 * l2arc_headroom number of max device writes to precache 3894 * l2arc_feed_secs seconds between L2ARC writing 3895 * 3896 * Tunables may be removed or added as future performance improvements are 3897 * integrated, and also may become zpool properties. 3898 * 3899 * There are three key functions that control how the L2ARC warms up: 3900 * 3901 * l2arc_write_eligible() check if a buffer is eligible to cache 3902 * l2arc_write_size() calculate how much to write 3903 * l2arc_write_interval() calculate sleep delay between writes 3904 * 3905 * These three functions determine what to write, how much, and how quickly 3906 * to send writes. 3907 */ 3908 3909 static boolean_t 3910 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab) 3911 { 3912 /* 3913 * A buffer is *not* eligible for the L2ARC if it: 3914 * 1. belongs to a different spa. 3915 * 2. is already cached on the L2ARC. 3916 * 3. has an I/O in progress (it may be an incomplete read). 3917 * 4. is flagged not eligible (zfs property). 3918 */ 3919 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL || 3920 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab)) 3921 return (B_FALSE); 3922 3923 return (B_TRUE); 3924 } 3925 3926 static uint64_t 3927 l2arc_write_size(l2arc_dev_t *dev) 3928 { 3929 uint64_t size; 3930 3931 size = dev->l2ad_write; 3932 3933 if (arc_warm == B_FALSE) 3934 size += dev->l2ad_boost; 3935 3936 return (size); 3937 3938 } 3939 3940 static clock_t 3941 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 3942 { 3943 clock_t interval, next, now; 3944 3945 /* 3946 * If the ARC lists are busy, increase our write rate; if the 3947 * lists are stale, idle back. This is achieved by checking 3948 * how much we previously wrote - if it was more than half of 3949 * what we wanted, schedule the next write much sooner. 3950 */ 3951 if (l2arc_feed_again && wrote > (wanted / 2)) 3952 interval = (hz * l2arc_feed_min_ms) / 1000; 3953 else 3954 interval = hz * l2arc_feed_secs; 3955 3956 now = ddi_get_lbolt(); 3957 next = MAX(now, MIN(now + interval, began + interval)); 3958 3959 return (next); 3960 } 3961 3962 static void 3963 l2arc_hdr_stat_add(void) 3964 { 3965 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE); 3966 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE); 3967 } 3968 3969 static void 3970 l2arc_hdr_stat_remove(void) 3971 { 3972 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE)); 3973 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE); 3974 } 3975 3976 /* 3977 * Cycle through L2ARC devices. This is how L2ARC load balances. 3978 * If a device is returned, this also returns holding the spa config lock. 3979 */ 3980 static l2arc_dev_t * 3981 l2arc_dev_get_next(void) 3982 { 3983 l2arc_dev_t *first, *next = NULL; 3984 3985 /* 3986 * Lock out the removal of spas (spa_namespace_lock), then removal 3987 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 3988 * both locks will be dropped and a spa config lock held instead. 3989 */ 3990 mutex_enter(&spa_namespace_lock); 3991 mutex_enter(&l2arc_dev_mtx); 3992 3993 /* if there are no vdevs, there is nothing to do */ 3994 if (l2arc_ndev == 0) 3995 goto out; 3996 3997 first = NULL; 3998 next = l2arc_dev_last; 3999 do { 4000 /* loop around the list looking for a non-faulted vdev */ 4001 if (next == NULL) { 4002 next = list_head(l2arc_dev_list); 4003 } else { 4004 next = list_next(l2arc_dev_list, next); 4005 if (next == NULL) 4006 next = list_head(l2arc_dev_list); 4007 } 4008 4009 /* if we have come back to the start, bail out */ 4010 if (first == NULL) 4011 first = next; 4012 else if (next == first) 4013 break; 4014 4015 } while (vdev_is_dead(next->l2ad_vdev)); 4016 4017 /* if we were unable to find any usable vdevs, return NULL */ 4018 if (vdev_is_dead(next->l2ad_vdev)) 4019 next = NULL; 4020 4021 l2arc_dev_last = next; 4022 4023 out: 4024 mutex_exit(&l2arc_dev_mtx); 4025 4026 /* 4027 * Grab the config lock to prevent the 'next' device from being 4028 * removed while we are writing to it. 4029 */ 4030 if (next != NULL) 4031 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4032 mutex_exit(&spa_namespace_lock); 4033 4034 return (next); 4035 } 4036 4037 /* 4038 * Free buffers that were tagged for destruction. 4039 */ 4040 static void 4041 l2arc_do_free_on_write() 4042 { 4043 list_t *buflist; 4044 l2arc_data_free_t *df, *df_prev; 4045 4046 mutex_enter(&l2arc_free_on_write_mtx); 4047 buflist = l2arc_free_on_write; 4048 4049 for (df = list_tail(buflist); df; df = df_prev) { 4050 df_prev = list_prev(buflist, df); 4051 ASSERT(df->l2df_data != NULL); 4052 ASSERT(df->l2df_func != NULL); 4053 df->l2df_func(df->l2df_data, df->l2df_size); 4054 list_remove(buflist, df); 4055 kmem_free(df, sizeof (l2arc_data_free_t)); 4056 } 4057 4058 mutex_exit(&l2arc_free_on_write_mtx); 4059 } 4060 4061 /* 4062 * A write to a cache device has completed. Update all headers to allow 4063 * reads from these buffers to begin. 4064 */ 4065 static void 4066 l2arc_write_done(zio_t *zio) 4067 { 4068 l2arc_write_callback_t *cb; 4069 l2arc_dev_t *dev; 4070 list_t *buflist; 4071 arc_buf_hdr_t *head, *ab, *ab_prev; 4072 l2arc_buf_hdr_t *abl2; 4073 kmutex_t *hash_lock; 4074 4075 cb = zio->io_private; 4076 ASSERT(cb != NULL); 4077 dev = cb->l2wcb_dev; 4078 ASSERT(dev != NULL); 4079 head = cb->l2wcb_head; 4080 ASSERT(head != NULL); 4081 buflist = dev->l2ad_buflist; 4082 ASSERT(buflist != NULL); 4083 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4084 l2arc_write_callback_t *, cb); 4085 4086 if (zio->io_error != 0) 4087 ARCSTAT_BUMP(arcstat_l2_writes_error); 4088 4089 mutex_enter(&l2arc_buflist_mtx); 4090 4091 /* 4092 * All writes completed, or an error was hit. 4093 */ 4094 for (ab = list_prev(buflist, head); ab; ab = ab_prev) { 4095 ab_prev = list_prev(buflist, ab); 4096 4097 hash_lock = HDR_LOCK(ab); 4098 if (!mutex_tryenter(hash_lock)) { 4099 /* 4100 * This buffer misses out. It may be in a stage 4101 * of eviction. Its ARC_L2_WRITING flag will be 4102 * left set, denying reads to this buffer. 4103 */ 4104 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4105 continue; 4106 } 4107 4108 if (zio->io_error != 0) { 4109 /* 4110 * Error - drop L2ARC entry. 4111 */ 4112 list_remove(buflist, ab); 4113 abl2 = ab->b_l2hdr; 4114 ab->b_l2hdr = NULL; 4115 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4116 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4117 } 4118 4119 /* 4120 * Allow ARC to begin reads to this L2ARC entry. 4121 */ 4122 ab->b_flags &= ~ARC_L2_WRITING; 4123 4124 mutex_exit(hash_lock); 4125 } 4126 4127 atomic_inc_64(&l2arc_writes_done); 4128 list_remove(buflist, head); 4129 kmem_cache_free(hdr_cache, head); 4130 mutex_exit(&l2arc_buflist_mtx); 4131 4132 l2arc_do_free_on_write(); 4133 4134 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4135 } 4136 4137 /* 4138 * A read to a cache device completed. Validate buffer contents before 4139 * handing over to the regular ARC routines. 4140 */ 4141 static void 4142 l2arc_read_done(zio_t *zio) 4143 { 4144 l2arc_read_callback_t *cb; 4145 arc_buf_hdr_t *hdr; 4146 arc_buf_t *buf; 4147 kmutex_t *hash_lock; 4148 int equal; 4149 4150 ASSERT(zio->io_vd != NULL); 4151 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4152 4153 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4154 4155 cb = zio->io_private; 4156 ASSERT(cb != NULL); 4157 buf = cb->l2rcb_buf; 4158 ASSERT(buf != NULL); 4159 4160 hash_lock = HDR_LOCK(buf->b_hdr); 4161 mutex_enter(hash_lock); 4162 hdr = buf->b_hdr; 4163 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4164 4165 /* 4166 * Check this survived the L2ARC journey. 4167 */ 4168 equal = arc_cksum_equal(buf); 4169 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4170 mutex_exit(hash_lock); 4171 zio->io_private = buf; 4172 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4173 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4174 arc_read_done(zio); 4175 } else { 4176 mutex_exit(hash_lock); 4177 /* 4178 * Buffer didn't survive caching. Increment stats and 4179 * reissue to the original storage device. 4180 */ 4181 if (zio->io_error != 0) { 4182 ARCSTAT_BUMP(arcstat_l2_io_error); 4183 } else { 4184 zio->io_error = EIO; 4185 } 4186 if (!equal) 4187 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4188 4189 /* 4190 * If there's no waiter, issue an async i/o to the primary 4191 * storage now. If there *is* a waiter, the caller must 4192 * issue the i/o in a context where it's OK to block. 4193 */ 4194 if (zio->io_waiter == NULL) { 4195 zio_t *pio = zio_unique_parent(zio); 4196 4197 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4198 4199 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4200 buf->b_data, zio->io_size, arc_read_done, buf, 4201 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4202 } 4203 } 4204 4205 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4206 } 4207 4208 /* 4209 * This is the list priority from which the L2ARC will search for pages to 4210 * cache. This is used within loops (0..3) to cycle through lists in the 4211 * desired order. This order can have a significant effect on cache 4212 * performance. 4213 * 4214 * Currently the metadata lists are hit first, MFU then MRU, followed by 4215 * the data lists. This function returns a locked list, and also returns 4216 * the lock pointer. 4217 */ 4218 static list_t * 4219 l2arc_list_locked(int list_num, kmutex_t **lock) 4220 { 4221 list_t *list; 4222 4223 ASSERT(list_num >= 0 && list_num <= 3); 4224 4225 switch (list_num) { 4226 case 0: 4227 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 4228 *lock = &arc_mfu->arcs_mtx; 4229 break; 4230 case 1: 4231 list = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 4232 *lock = &arc_mru->arcs_mtx; 4233 break; 4234 case 2: 4235 list = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 4236 *lock = &arc_mfu->arcs_mtx; 4237 break; 4238 case 3: 4239 list = &arc_mru->arcs_list[ARC_BUFC_DATA]; 4240 *lock = &arc_mru->arcs_mtx; 4241 break; 4242 } 4243 4244 ASSERT(!(MUTEX_HELD(*lock))); 4245 mutex_enter(*lock); 4246 return (list); 4247 } 4248 4249 /* 4250 * Evict buffers from the device write hand to the distance specified in 4251 * bytes. This distance may span populated buffers, it may span nothing. 4252 * This is clearing a region on the L2ARC device ready for writing. 4253 * If the 'all' boolean is set, every buffer is evicted. 4254 */ 4255 static void 4256 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 4257 { 4258 list_t *buflist; 4259 l2arc_buf_hdr_t *abl2; 4260 arc_buf_hdr_t *ab, *ab_prev; 4261 kmutex_t *hash_lock; 4262 uint64_t taddr; 4263 4264 buflist = dev->l2ad_buflist; 4265 4266 if (buflist == NULL) 4267 return; 4268 4269 if (!all && dev->l2ad_first) { 4270 /* 4271 * This is the first sweep through the device. There is 4272 * nothing to evict. 4273 */ 4274 return; 4275 } 4276 4277 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 4278 /* 4279 * When nearing the end of the device, evict to the end 4280 * before the device write hand jumps to the start. 4281 */ 4282 taddr = dev->l2ad_end; 4283 } else { 4284 taddr = dev->l2ad_hand + distance; 4285 } 4286 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 4287 uint64_t, taddr, boolean_t, all); 4288 4289 top: 4290 mutex_enter(&l2arc_buflist_mtx); 4291 for (ab = list_tail(buflist); ab; ab = ab_prev) { 4292 ab_prev = list_prev(buflist, ab); 4293 4294 hash_lock = HDR_LOCK(ab); 4295 if (!mutex_tryenter(hash_lock)) { 4296 /* 4297 * Missed the hash lock. Retry. 4298 */ 4299 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 4300 mutex_exit(&l2arc_buflist_mtx); 4301 mutex_enter(hash_lock); 4302 mutex_exit(hash_lock); 4303 goto top; 4304 } 4305 4306 if (HDR_L2_WRITE_HEAD(ab)) { 4307 /* 4308 * We hit a write head node. Leave it for 4309 * l2arc_write_done(). 4310 */ 4311 list_remove(buflist, ab); 4312 mutex_exit(hash_lock); 4313 continue; 4314 } 4315 4316 if (!all && ab->b_l2hdr != NULL && 4317 (ab->b_l2hdr->b_daddr > taddr || 4318 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) { 4319 /* 4320 * We've evicted to the target address, 4321 * or the end of the device. 4322 */ 4323 mutex_exit(hash_lock); 4324 break; 4325 } 4326 4327 if (HDR_FREE_IN_PROGRESS(ab)) { 4328 /* 4329 * Already on the path to destruction. 4330 */ 4331 mutex_exit(hash_lock); 4332 continue; 4333 } 4334 4335 if (ab->b_state == arc_l2c_only) { 4336 ASSERT(!HDR_L2_READING(ab)); 4337 /* 4338 * This doesn't exist in the ARC. Destroy. 4339 * arc_hdr_destroy() will call list_remove() 4340 * and decrement arcstat_l2_size. 4341 */ 4342 arc_change_state(arc_anon, ab, hash_lock); 4343 arc_hdr_destroy(ab); 4344 } else { 4345 /* 4346 * Invalidate issued or about to be issued 4347 * reads, since we may be about to write 4348 * over this location. 4349 */ 4350 if (HDR_L2_READING(ab)) { 4351 ARCSTAT_BUMP(arcstat_l2_evict_reading); 4352 ab->b_flags |= ARC_L2_EVICTED; 4353 } 4354 4355 /* 4356 * Tell ARC this no longer exists in L2ARC. 4357 */ 4358 if (ab->b_l2hdr != NULL) { 4359 abl2 = ab->b_l2hdr; 4360 ab->b_l2hdr = NULL; 4361 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4362 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4363 } 4364 list_remove(buflist, ab); 4365 4366 /* 4367 * This may have been leftover after a 4368 * failed write. 4369 */ 4370 ab->b_flags &= ~ARC_L2_WRITING; 4371 } 4372 mutex_exit(hash_lock); 4373 } 4374 mutex_exit(&l2arc_buflist_mtx); 4375 4376 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0); 4377 dev->l2ad_evict = taddr; 4378 } 4379 4380 /* 4381 * Find and write ARC buffers to the L2ARC device. 4382 * 4383 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid 4384 * for reading until they have completed writing. 4385 */ 4386 static uint64_t 4387 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 4388 { 4389 arc_buf_hdr_t *ab, *ab_prev, *head; 4390 l2arc_buf_hdr_t *hdrl2; 4391 list_t *list; 4392 uint64_t passed_sz, write_sz, buf_sz, headroom; 4393 void *buf_data; 4394 kmutex_t *hash_lock, *list_lock; 4395 boolean_t have_lock, full; 4396 l2arc_write_callback_t *cb; 4397 zio_t *pio, *wzio; 4398 uint64_t guid = spa_load_guid(spa); 4399 4400 ASSERT(dev->l2ad_vdev != NULL); 4401 4402 pio = NULL; 4403 write_sz = 0; 4404 full = B_FALSE; 4405 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 4406 head->b_flags |= ARC_L2_WRITE_HEAD; 4407 4408 /* 4409 * Copy buffers for L2ARC writing. 4410 */ 4411 mutex_enter(&l2arc_buflist_mtx); 4412 for (int try = 0; try <= 3; try++) { 4413 list = l2arc_list_locked(try, &list_lock); 4414 passed_sz = 0; 4415 4416 /* 4417 * L2ARC fast warmup. 4418 * 4419 * Until the ARC is warm and starts to evict, read from the 4420 * head of the ARC lists rather than the tail. 4421 */ 4422 headroom = target_sz * l2arc_headroom; 4423 if (arc_warm == B_FALSE) 4424 ab = list_head(list); 4425 else 4426 ab = list_tail(list); 4427 4428 for (; ab; ab = ab_prev) { 4429 if (arc_warm == B_FALSE) 4430 ab_prev = list_next(list, ab); 4431 else 4432 ab_prev = list_prev(list, ab); 4433 4434 hash_lock = HDR_LOCK(ab); 4435 have_lock = MUTEX_HELD(hash_lock); 4436 if (!have_lock && !mutex_tryenter(hash_lock)) { 4437 /* 4438 * Skip this buffer rather than waiting. 4439 */ 4440 continue; 4441 } 4442 4443 passed_sz += ab->b_size; 4444 if (passed_sz > headroom) { 4445 /* 4446 * Searched too far. 4447 */ 4448 mutex_exit(hash_lock); 4449 break; 4450 } 4451 4452 if (!l2arc_write_eligible(guid, ab)) { 4453 mutex_exit(hash_lock); 4454 continue; 4455 } 4456 4457 if ((write_sz + ab->b_size) > target_sz) { 4458 full = B_TRUE; 4459 mutex_exit(hash_lock); 4460 break; 4461 } 4462 4463 if (pio == NULL) { 4464 /* 4465 * Insert a dummy header on the buflist so 4466 * l2arc_write_done() can find where the 4467 * write buffers begin without searching. 4468 */ 4469 list_insert_head(dev->l2ad_buflist, head); 4470 4471 cb = kmem_alloc( 4472 sizeof (l2arc_write_callback_t), KM_SLEEP); 4473 cb->l2wcb_dev = dev; 4474 cb->l2wcb_head = head; 4475 pio = zio_root(spa, l2arc_write_done, cb, 4476 ZIO_FLAG_CANFAIL); 4477 } 4478 4479 /* 4480 * Create and add a new L2ARC header. 4481 */ 4482 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP); 4483 hdrl2->b_dev = dev; 4484 hdrl2->b_daddr = dev->l2ad_hand; 4485 4486 ab->b_flags |= ARC_L2_WRITING; 4487 ab->b_l2hdr = hdrl2; 4488 list_insert_head(dev->l2ad_buflist, ab); 4489 buf_data = ab->b_buf->b_data; 4490 buf_sz = ab->b_size; 4491 4492 /* 4493 * Compute and store the buffer cksum before 4494 * writing. On debug the cksum is verified first. 4495 */ 4496 arc_cksum_verify(ab->b_buf); 4497 arc_cksum_compute(ab->b_buf, B_TRUE); 4498 4499 mutex_exit(hash_lock); 4500 4501 wzio = zio_write_phys(pio, dev->l2ad_vdev, 4502 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 4503 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 4504 ZIO_FLAG_CANFAIL, B_FALSE); 4505 4506 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 4507 zio_t *, wzio); 4508 (void) zio_nowait(wzio); 4509 4510 /* 4511 * Keep the clock hand suitably device-aligned. 4512 */ 4513 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 4514 4515 write_sz += buf_sz; 4516 dev->l2ad_hand += buf_sz; 4517 } 4518 4519 mutex_exit(list_lock); 4520 4521 if (full == B_TRUE) 4522 break; 4523 } 4524 mutex_exit(&l2arc_buflist_mtx); 4525 4526 if (pio == NULL) { 4527 ASSERT0(write_sz); 4528 kmem_cache_free(hdr_cache, head); 4529 return (0); 4530 } 4531 4532 ASSERT3U(write_sz, <=, target_sz); 4533 ARCSTAT_BUMP(arcstat_l2_writes_sent); 4534 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz); 4535 ARCSTAT_INCR(arcstat_l2_size, write_sz); 4536 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0); 4537 4538 /* 4539 * Bump device hand to the device start if it is approaching the end. 4540 * l2arc_evict() will already have evicted ahead for this case. 4541 */ 4542 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 4543 vdev_space_update(dev->l2ad_vdev, 4544 dev->l2ad_end - dev->l2ad_hand, 0, 0); 4545 dev->l2ad_hand = dev->l2ad_start; 4546 dev->l2ad_evict = dev->l2ad_start; 4547 dev->l2ad_first = B_FALSE; 4548 } 4549 4550 dev->l2ad_writing = B_TRUE; 4551 (void) zio_wait(pio); 4552 dev->l2ad_writing = B_FALSE; 4553 4554 return (write_sz); 4555 } 4556 4557 /* 4558 * This thread feeds the L2ARC at regular intervals. This is the beating 4559 * heart of the L2ARC. 4560 */ 4561 static void 4562 l2arc_feed_thread(void) 4563 { 4564 callb_cpr_t cpr; 4565 l2arc_dev_t *dev; 4566 spa_t *spa; 4567 uint64_t size, wrote; 4568 clock_t begin, next = ddi_get_lbolt(); 4569 4570 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 4571 4572 mutex_enter(&l2arc_feed_thr_lock); 4573 4574 while (l2arc_thread_exit == 0) { 4575 CALLB_CPR_SAFE_BEGIN(&cpr); 4576 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 4577 next); 4578 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 4579 next = ddi_get_lbolt() + hz; 4580 4581 /* 4582 * Quick check for L2ARC devices. 4583 */ 4584 mutex_enter(&l2arc_dev_mtx); 4585 if (l2arc_ndev == 0) { 4586 mutex_exit(&l2arc_dev_mtx); 4587 continue; 4588 } 4589 mutex_exit(&l2arc_dev_mtx); 4590 begin = ddi_get_lbolt(); 4591 4592 /* 4593 * This selects the next l2arc device to write to, and in 4594 * doing so the next spa to feed from: dev->l2ad_spa. This 4595 * will return NULL if there are now no l2arc devices or if 4596 * they are all faulted. 4597 * 4598 * If a device is returned, its spa's config lock is also 4599 * held to prevent device removal. l2arc_dev_get_next() 4600 * will grab and release l2arc_dev_mtx. 4601 */ 4602 if ((dev = l2arc_dev_get_next()) == NULL) 4603 continue; 4604 4605 spa = dev->l2ad_spa; 4606 ASSERT(spa != NULL); 4607 4608 /* 4609 * If the pool is read-only then force the feed thread to 4610 * sleep a little longer. 4611 */ 4612 if (!spa_writeable(spa)) { 4613 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 4614 spa_config_exit(spa, SCL_L2ARC, dev); 4615 continue; 4616 } 4617 4618 /* 4619 * Avoid contributing to memory pressure. 4620 */ 4621 if (arc_reclaim_needed()) { 4622 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 4623 spa_config_exit(spa, SCL_L2ARC, dev); 4624 continue; 4625 } 4626 4627 ARCSTAT_BUMP(arcstat_l2_feeds); 4628 4629 size = l2arc_write_size(dev); 4630 4631 /* 4632 * Evict L2ARC buffers that will be overwritten. 4633 */ 4634 l2arc_evict(dev, size, B_FALSE); 4635 4636 /* 4637 * Write ARC buffers. 4638 */ 4639 wrote = l2arc_write_buffers(spa, dev, size); 4640 4641 /* 4642 * Calculate interval between writes. 4643 */ 4644 next = l2arc_write_interval(begin, size, wrote); 4645 spa_config_exit(spa, SCL_L2ARC, dev); 4646 } 4647 4648 l2arc_thread_exit = 0; 4649 cv_broadcast(&l2arc_feed_thr_cv); 4650 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 4651 thread_exit(); 4652 } 4653 4654 boolean_t 4655 l2arc_vdev_present(vdev_t *vd) 4656 { 4657 l2arc_dev_t *dev; 4658 4659 mutex_enter(&l2arc_dev_mtx); 4660 for (dev = list_head(l2arc_dev_list); dev != NULL; 4661 dev = list_next(l2arc_dev_list, dev)) { 4662 if (dev->l2ad_vdev == vd) 4663 break; 4664 } 4665 mutex_exit(&l2arc_dev_mtx); 4666 4667 return (dev != NULL); 4668 } 4669 4670 /* 4671 * Add a vdev for use by the L2ARC. By this point the spa has already 4672 * validated the vdev and opened it. 4673 */ 4674 void 4675 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 4676 { 4677 l2arc_dev_t *adddev; 4678 4679 ASSERT(!l2arc_vdev_present(vd)); 4680 4681 /* 4682 * Create a new l2arc device entry. 4683 */ 4684 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 4685 adddev->l2ad_spa = spa; 4686 adddev->l2ad_vdev = vd; 4687 adddev->l2ad_write = l2arc_write_max; 4688 adddev->l2ad_boost = l2arc_write_boost; 4689 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 4690 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 4691 adddev->l2ad_hand = adddev->l2ad_start; 4692 adddev->l2ad_evict = adddev->l2ad_start; 4693 adddev->l2ad_first = B_TRUE; 4694 adddev->l2ad_writing = B_FALSE; 4695 ASSERT3U(adddev->l2ad_write, >, 0); 4696 4697 /* 4698 * This is a list of all ARC buffers that are still valid on the 4699 * device. 4700 */ 4701 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP); 4702 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 4703 offsetof(arc_buf_hdr_t, b_l2node)); 4704 4705 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 4706 4707 /* 4708 * Add device to global list 4709 */ 4710 mutex_enter(&l2arc_dev_mtx); 4711 list_insert_head(l2arc_dev_list, adddev); 4712 atomic_inc_64(&l2arc_ndev); 4713 mutex_exit(&l2arc_dev_mtx); 4714 } 4715 4716 /* 4717 * Remove a vdev from the L2ARC. 4718 */ 4719 void 4720 l2arc_remove_vdev(vdev_t *vd) 4721 { 4722 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 4723 4724 /* 4725 * Find the device by vdev 4726 */ 4727 mutex_enter(&l2arc_dev_mtx); 4728 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 4729 nextdev = list_next(l2arc_dev_list, dev); 4730 if (vd == dev->l2ad_vdev) { 4731 remdev = dev; 4732 break; 4733 } 4734 } 4735 ASSERT(remdev != NULL); 4736 4737 /* 4738 * Remove device from global list 4739 */ 4740 list_remove(l2arc_dev_list, remdev); 4741 l2arc_dev_last = NULL; /* may have been invalidated */ 4742 atomic_dec_64(&l2arc_ndev); 4743 mutex_exit(&l2arc_dev_mtx); 4744 4745 /* 4746 * Clear all buflists and ARC references. L2ARC device flush. 4747 */ 4748 l2arc_evict(remdev, 0, B_TRUE); 4749 list_destroy(remdev->l2ad_buflist); 4750 kmem_free(remdev->l2ad_buflist, sizeof (list_t)); 4751 kmem_free(remdev, sizeof (l2arc_dev_t)); 4752 } 4753 4754 void 4755 l2arc_init(void) 4756 { 4757 l2arc_thread_exit = 0; 4758 l2arc_ndev = 0; 4759 l2arc_writes_sent = 0; 4760 l2arc_writes_done = 0; 4761 4762 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4763 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 4764 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 4765 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL); 4766 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 4767 4768 l2arc_dev_list = &L2ARC_dev_list; 4769 l2arc_free_on_write = &L2ARC_free_on_write; 4770 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 4771 offsetof(l2arc_dev_t, l2ad_node)); 4772 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 4773 offsetof(l2arc_data_free_t, l2df_list_node)); 4774 } 4775 4776 void 4777 l2arc_fini(void) 4778 { 4779 /* 4780 * This is called from dmu_fini(), which is called from spa_fini(); 4781 * Because of this, we can assume that all l2arc devices have 4782 * already been removed when the pools themselves were removed. 4783 */ 4784 4785 l2arc_do_free_on_write(); 4786 4787 mutex_destroy(&l2arc_feed_thr_lock); 4788 cv_destroy(&l2arc_feed_thr_cv); 4789 mutex_destroy(&l2arc_dev_mtx); 4790 mutex_destroy(&l2arc_buflist_mtx); 4791 mutex_destroy(&l2arc_free_on_write_mtx); 4792 4793 list_destroy(l2arc_dev_list); 4794 list_destroy(l2arc_free_on_write); 4795 } 4796 4797 void 4798 l2arc_start(void) 4799 { 4800 if (!(spa_mode_global & FWRITE)) 4801 return; 4802 4803 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 4804 TS_RUN, minclsyspri); 4805 } 4806 4807 void 4808 l2arc_stop(void) 4809 { 4810 if (!(spa_mode_global & FWRITE)) 4811 return; 4812 4813 mutex_enter(&l2arc_feed_thr_lock); 4814 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 4815 l2arc_thread_exit = 1; 4816 while (l2arc_thread_exit != 0) 4817 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 4818 mutex_exit(&l2arc_feed_thr_lock); 4819 } 4820