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) 2013 by Delphix. All rights reserved. 25 * Copyright (c) 2013 by Saso Kiselkov. All rights reserved. 26 */ 27 28 /* 29 * DVA-based Adjustable Replacement Cache 30 * 31 * While much of the theory of operation used here is 32 * based on the self-tuning, low overhead replacement cache 33 * presented by Megiddo and Modha at FAST 2003, there are some 34 * significant differences: 35 * 36 * 1. The Megiddo and Modha model assumes any page is evictable. 37 * Pages in its cache cannot be "locked" into memory. This makes 38 * the eviction algorithm simple: evict the last page in the list. 39 * This also make the performance characteristics easy to reason 40 * about. Our cache is not so simple. At any given moment, some 41 * subset of the blocks in the cache are un-evictable because we 42 * have handed out a reference to them. Blocks are only evictable 43 * when there are no external references active. This makes 44 * eviction far more problematic: we choose to evict the evictable 45 * blocks that are the "lowest" in the list. 46 * 47 * There are times when it is not possible to evict the requested 48 * space. In these circumstances we are unable to adjust the cache 49 * size. To prevent the cache growing unbounded at these times we 50 * implement a "cache throttle" that slows the flow of new data 51 * into the cache until we can make space available. 52 * 53 * 2. The Megiddo and Modha model assumes a fixed cache size. 54 * Pages are evicted when the cache is full and there is a cache 55 * miss. Our model has a variable sized cache. It grows with 56 * high use, but also tries to react to memory pressure from the 57 * operating system: decreasing its size when system memory is 58 * tight. 59 * 60 * 3. The Megiddo and Modha model assumes a fixed page size. All 61 * elements of the cache are therefore exactly the same size. So 62 * when adjusting the cache size following a cache miss, its simply 63 * a matter of choosing a single page to evict. In our model, we 64 * have variable sized cache blocks (rangeing from 512 bytes to 65 * 128K bytes). We therefore choose a set of blocks to evict to make 66 * space for a cache miss that approximates as closely as possible 67 * the space used by the new block. 68 * 69 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 70 * by N. Megiddo & D. Modha, FAST 2003 71 */ 72 73 /* 74 * The locking model: 75 * 76 * A new reference to a cache buffer can be obtained in two 77 * ways: 1) via a hash table lookup using the DVA as a key, 78 * or 2) via one of the ARC lists. The arc_read() interface 79 * uses method 1, while the internal arc algorithms for 80 * adjusting the cache use method 2. We therefore provide two 81 * types of locks: 1) the hash table lock array, and 2) the 82 * arc list locks. 83 * 84 * Buffers do not have their own mutexes, rather they rely on the 85 * hash table mutexes for the bulk of their protection (i.e. most 86 * fields in the arc_buf_hdr_t are protected by these mutexes). 87 * 88 * buf_hash_find() returns the appropriate mutex (held) when it 89 * locates the requested buffer in the hash table. It returns 90 * NULL for the mutex if the buffer was not in the table. 91 * 92 * buf_hash_remove() expects the appropriate hash mutex to be 93 * already held before it is invoked. 94 * 95 * Each arc state also has a mutex which is used to protect the 96 * buffer list associated with the state. When attempting to 97 * obtain a hash table lock while holding an arc list lock you 98 * must use: mutex_tryenter() to avoid deadlock. Also note that 99 * the active state mutex must be held before the ghost state mutex. 100 * 101 * Arc buffers may have an associated eviction callback function. 102 * This function will be invoked prior to removing the buffer (e.g. 103 * in arc_do_user_evicts()). Note however that the data associated 104 * with the buffer may be evicted prior to the callback. The callback 105 * must be made with *no locks held* (to prevent deadlock). Additionally, 106 * the users of callbacks must ensure that their private data is 107 * protected from simultaneous callbacks from arc_buf_evict() 108 * and arc_do_user_evicts(). 109 * 110 * Note that the majority of the performance stats are manipulated 111 * with atomic operations. 112 * 113 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following: 114 * 115 * - L2ARC buflist creation 116 * - L2ARC buflist eviction 117 * - L2ARC write completion, which walks L2ARC buflists 118 * - ARC header destruction, as it removes from L2ARC buflists 119 * - ARC header release, as it removes from L2ARC buflists 120 */ 121 122 #include <sys/spa.h> 123 #include <sys/zio.h> 124 #include <sys/zio_compress.h> 125 #include <sys/zfs_context.h> 126 #include <sys/arc.h> 127 #include <sys/refcount.h> 128 #include <sys/vdev.h> 129 #include <sys/vdev_impl.h> 130 #ifdef _KERNEL 131 #include <sys/vmsystm.h> 132 #include <vm/anon.h> 133 #include <sys/fs/swapnode.h> 134 #include <sys/dnlc.h> 135 #endif 136 #include <sys/callb.h> 137 #include <sys/kstat.h> 138 #include <zfs_fletcher.h> 139 140 #ifndef _KERNEL 141 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 142 boolean_t arc_watch = B_FALSE; 143 int arc_procfd; 144 #endif 145 146 static kmutex_t arc_reclaim_thr_lock; 147 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 148 static uint8_t arc_thread_exit; 149 150 extern int zfs_write_limit_shift; 151 extern uint64_t zfs_write_limit_max; 152 extern kmutex_t zfs_write_limit_lock; 153 154 #define ARC_REDUCE_DNLC_PERCENT 3 155 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT; 156 157 typedef enum arc_reclaim_strategy { 158 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ 159 ARC_RECLAIM_CONS /* Conservative reclaim strategy */ 160 } arc_reclaim_strategy_t; 161 162 /* number of seconds before growing cache again */ 163 static int arc_grow_retry = 60; 164 165 /* shift of arc_c for calculating both min and max arc_p */ 166 static int arc_p_min_shift = 4; 167 168 /* log2(fraction of arc to reclaim) */ 169 static int arc_shrink_shift = 5; 170 171 /* 172 * minimum lifespan of a prefetch block in clock ticks 173 * (initialized in arc_init()) 174 */ 175 static int arc_min_prefetch_lifespan; 176 177 static int arc_dead; 178 179 /* 180 * The arc has filled available memory and has now warmed up. 181 */ 182 static boolean_t arc_warm; 183 184 /* 185 * These tunables are for performance analysis. 186 */ 187 uint64_t zfs_arc_max; 188 uint64_t zfs_arc_min; 189 uint64_t zfs_arc_meta_limit = 0; 190 int zfs_arc_grow_retry = 0; 191 int zfs_arc_shrink_shift = 0; 192 int zfs_arc_p_min_shift = 0; 193 int zfs_disable_dup_eviction = 0; 194 195 /* 196 * Note that buffers can be in one of 6 states: 197 * ARC_anon - anonymous (discussed below) 198 * ARC_mru - recently used, currently cached 199 * ARC_mru_ghost - recentely used, no longer in cache 200 * ARC_mfu - frequently used, currently cached 201 * ARC_mfu_ghost - frequently used, no longer in cache 202 * ARC_l2c_only - exists in L2ARC but not other states 203 * When there are no active references to the buffer, they are 204 * are linked onto a list in one of these arc states. These are 205 * the only buffers that can be evicted or deleted. Within each 206 * state there are multiple lists, one for meta-data and one for 207 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 208 * etc.) is tracked separately so that it can be managed more 209 * explicitly: favored over data, limited explicitly. 210 * 211 * Anonymous buffers are buffers that are not associated with 212 * a DVA. These are buffers that hold dirty block copies 213 * before they are written to stable storage. By definition, 214 * they are "ref'd" and are considered part of arc_mru 215 * that cannot be freed. Generally, they will aquire a DVA 216 * as they are written and migrate onto the arc_mru list. 217 * 218 * The ARC_l2c_only state is for buffers that are in the second 219 * level ARC but no longer in any of the ARC_m* lists. The second 220 * level ARC itself may also contain buffers that are in any of 221 * the ARC_m* states - meaning that a buffer can exist in two 222 * places. The reason for the ARC_l2c_only state is to keep the 223 * buffer header in the hash table, so that reads that hit the 224 * second level ARC benefit from these fast lookups. 225 */ 226 227 typedef struct arc_state { 228 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */ 229 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 230 uint64_t arcs_size; /* total amount of data in this state */ 231 kmutex_t arcs_mtx; 232 } arc_state_t; 233 234 /* The 6 states: */ 235 static arc_state_t ARC_anon; 236 static arc_state_t ARC_mru; 237 static arc_state_t ARC_mru_ghost; 238 static arc_state_t ARC_mfu; 239 static arc_state_t ARC_mfu_ghost; 240 static arc_state_t ARC_l2c_only; 241 242 typedef struct arc_stats { 243 kstat_named_t arcstat_hits; 244 kstat_named_t arcstat_misses; 245 kstat_named_t arcstat_demand_data_hits; 246 kstat_named_t arcstat_demand_data_misses; 247 kstat_named_t arcstat_demand_metadata_hits; 248 kstat_named_t arcstat_demand_metadata_misses; 249 kstat_named_t arcstat_prefetch_data_hits; 250 kstat_named_t arcstat_prefetch_data_misses; 251 kstat_named_t arcstat_prefetch_metadata_hits; 252 kstat_named_t arcstat_prefetch_metadata_misses; 253 kstat_named_t arcstat_mru_hits; 254 kstat_named_t arcstat_mru_ghost_hits; 255 kstat_named_t arcstat_mfu_hits; 256 kstat_named_t arcstat_mfu_ghost_hits; 257 kstat_named_t arcstat_deleted; 258 kstat_named_t arcstat_recycle_miss; 259 /* 260 * Number of buffers that could not be evicted because the hash lock 261 * was held by another thread. The lock may not necessarily be held 262 * by something using the same buffer, since hash locks are shared 263 * by multiple buffers. 264 */ 265 kstat_named_t arcstat_mutex_miss; 266 /* 267 * Number of buffers skipped because they have I/O in progress, are 268 * indrect prefetch buffers that have not lived long enough, or are 269 * not from the spa we're trying to evict from. 270 */ 271 kstat_named_t arcstat_evict_skip; 272 kstat_named_t arcstat_evict_l2_cached; 273 kstat_named_t arcstat_evict_l2_eligible; 274 kstat_named_t arcstat_evict_l2_ineligible; 275 kstat_named_t arcstat_hash_elements; 276 kstat_named_t arcstat_hash_elements_max; 277 kstat_named_t arcstat_hash_collisions; 278 kstat_named_t arcstat_hash_chains; 279 kstat_named_t arcstat_hash_chain_max; 280 kstat_named_t arcstat_p; 281 kstat_named_t arcstat_c; 282 kstat_named_t arcstat_c_min; 283 kstat_named_t arcstat_c_max; 284 kstat_named_t arcstat_size; 285 kstat_named_t arcstat_hdr_size; 286 kstat_named_t arcstat_data_size; 287 kstat_named_t arcstat_other_size; 288 kstat_named_t arcstat_l2_hits; 289 kstat_named_t arcstat_l2_misses; 290 kstat_named_t arcstat_l2_feeds; 291 kstat_named_t arcstat_l2_rw_clash; 292 kstat_named_t arcstat_l2_read_bytes; 293 kstat_named_t arcstat_l2_write_bytes; 294 kstat_named_t arcstat_l2_writes_sent; 295 kstat_named_t arcstat_l2_writes_done; 296 kstat_named_t arcstat_l2_writes_error; 297 kstat_named_t arcstat_l2_writes_hdr_miss; 298 kstat_named_t arcstat_l2_evict_lock_retry; 299 kstat_named_t arcstat_l2_evict_reading; 300 kstat_named_t arcstat_l2_free_on_write; 301 kstat_named_t arcstat_l2_abort_lowmem; 302 kstat_named_t arcstat_l2_cksum_bad; 303 kstat_named_t arcstat_l2_io_error; 304 kstat_named_t arcstat_l2_size; 305 kstat_named_t arcstat_l2_asize; 306 kstat_named_t arcstat_l2_hdr_size; 307 kstat_named_t arcstat_l2_compress_successes; 308 kstat_named_t arcstat_l2_compress_zeros; 309 kstat_named_t arcstat_l2_compress_failures; 310 kstat_named_t arcstat_memory_throttle_count; 311 kstat_named_t arcstat_duplicate_buffers; 312 kstat_named_t arcstat_duplicate_buffers_size; 313 kstat_named_t arcstat_duplicate_reads; 314 kstat_named_t arcstat_meta_used; 315 kstat_named_t arcstat_meta_limit; 316 kstat_named_t arcstat_meta_max; 317 } arc_stats_t; 318 319 static arc_stats_t arc_stats = { 320 { "hits", KSTAT_DATA_UINT64 }, 321 { "misses", KSTAT_DATA_UINT64 }, 322 { "demand_data_hits", KSTAT_DATA_UINT64 }, 323 { "demand_data_misses", KSTAT_DATA_UINT64 }, 324 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 325 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 326 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 327 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 328 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 329 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 330 { "mru_hits", KSTAT_DATA_UINT64 }, 331 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 332 { "mfu_hits", KSTAT_DATA_UINT64 }, 333 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 334 { "deleted", KSTAT_DATA_UINT64 }, 335 { "recycle_miss", KSTAT_DATA_UINT64 }, 336 { "mutex_miss", KSTAT_DATA_UINT64 }, 337 { "evict_skip", KSTAT_DATA_UINT64 }, 338 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 339 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 340 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 341 { "hash_elements", KSTAT_DATA_UINT64 }, 342 { "hash_elements_max", KSTAT_DATA_UINT64 }, 343 { "hash_collisions", KSTAT_DATA_UINT64 }, 344 { "hash_chains", KSTAT_DATA_UINT64 }, 345 { "hash_chain_max", KSTAT_DATA_UINT64 }, 346 { "p", KSTAT_DATA_UINT64 }, 347 { "c", KSTAT_DATA_UINT64 }, 348 { "c_min", KSTAT_DATA_UINT64 }, 349 { "c_max", KSTAT_DATA_UINT64 }, 350 { "size", KSTAT_DATA_UINT64 }, 351 { "hdr_size", KSTAT_DATA_UINT64 }, 352 { "data_size", KSTAT_DATA_UINT64 }, 353 { "other_size", KSTAT_DATA_UINT64 }, 354 { "l2_hits", KSTAT_DATA_UINT64 }, 355 { "l2_misses", KSTAT_DATA_UINT64 }, 356 { "l2_feeds", KSTAT_DATA_UINT64 }, 357 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 358 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 359 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 360 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 361 { "l2_writes_done", KSTAT_DATA_UINT64 }, 362 { "l2_writes_error", KSTAT_DATA_UINT64 }, 363 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 364 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 365 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 366 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 367 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 368 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 369 { "l2_io_error", KSTAT_DATA_UINT64 }, 370 { "l2_size", KSTAT_DATA_UINT64 }, 371 { "l2_asize", KSTAT_DATA_UINT64 }, 372 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 373 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 374 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 375 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 376 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 377 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 378 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 379 { "duplicate_reads", KSTAT_DATA_UINT64 }, 380 { "arc_meta_used", KSTAT_DATA_UINT64 }, 381 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 382 { "arc_meta_max", KSTAT_DATA_UINT64 } 383 }; 384 385 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 386 387 #define ARCSTAT_INCR(stat, val) \ 388 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 389 390 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 391 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 392 393 #define ARCSTAT_MAX(stat, val) { \ 394 uint64_t m; \ 395 while ((val) > (m = arc_stats.stat.value.ui64) && \ 396 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 397 continue; \ 398 } 399 400 #define ARCSTAT_MAXSTAT(stat) \ 401 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 402 403 /* 404 * We define a macro to allow ARC hits/misses to be easily broken down by 405 * two separate conditions, giving a total of four different subtypes for 406 * each of hits and misses (so eight statistics total). 407 */ 408 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 409 if (cond1) { \ 410 if (cond2) { \ 411 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 412 } else { \ 413 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 414 } \ 415 } else { \ 416 if (cond2) { \ 417 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 418 } else { \ 419 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 420 } \ 421 } 422 423 kstat_t *arc_ksp; 424 static arc_state_t *arc_anon; 425 static arc_state_t *arc_mru; 426 static arc_state_t *arc_mru_ghost; 427 static arc_state_t *arc_mfu; 428 static arc_state_t *arc_mfu_ghost; 429 static arc_state_t *arc_l2c_only; 430 431 /* 432 * There are several ARC variables that are critical to export as kstats -- 433 * but we don't want to have to grovel around in the kstat whenever we wish to 434 * manipulate them. For these variables, we therefore define them to be in 435 * terms of the statistic variable. This assures that we are not introducing 436 * the possibility of inconsistency by having shadow copies of the variables, 437 * while still allowing the code to be readable. 438 */ 439 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 440 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 441 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 442 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 443 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 444 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 445 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 446 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 447 448 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 449 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 450 451 static int arc_no_grow; /* Don't try to grow cache size */ 452 static uint64_t arc_tempreserve; 453 static uint64_t arc_loaned_bytes; 454 455 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; 456 457 typedef struct arc_callback arc_callback_t; 458 459 struct arc_callback { 460 void *acb_private; 461 arc_done_func_t *acb_done; 462 arc_buf_t *acb_buf; 463 zio_t *acb_zio_dummy; 464 arc_callback_t *acb_next; 465 }; 466 467 typedef struct arc_write_callback arc_write_callback_t; 468 469 struct arc_write_callback { 470 void *awcb_private; 471 arc_done_func_t *awcb_ready; 472 arc_done_func_t *awcb_done; 473 arc_buf_t *awcb_buf; 474 }; 475 476 struct arc_buf_hdr { 477 /* protected by hash lock */ 478 dva_t b_dva; 479 uint64_t b_birth; 480 uint64_t b_cksum0; 481 482 kmutex_t b_freeze_lock; 483 zio_cksum_t *b_freeze_cksum; 484 void *b_thawed; 485 486 arc_buf_hdr_t *b_hash_next; 487 arc_buf_t *b_buf; 488 uint32_t b_flags; 489 uint32_t b_datacnt; 490 491 arc_callback_t *b_acb; 492 kcondvar_t b_cv; 493 494 /* immutable */ 495 arc_buf_contents_t b_type; 496 uint64_t b_size; 497 uint64_t b_spa; 498 499 /* protected by arc state mutex */ 500 arc_state_t *b_state; 501 list_node_t b_arc_node; 502 503 /* updated atomically */ 504 clock_t b_arc_access; 505 506 /* self protecting */ 507 refcount_t b_refcnt; 508 509 l2arc_buf_hdr_t *b_l2hdr; 510 list_node_t b_l2node; 511 }; 512 513 static arc_buf_t *arc_eviction_list; 514 static kmutex_t arc_eviction_mtx; 515 static arc_buf_hdr_t arc_eviction_hdr; 516 static void arc_get_data_buf(arc_buf_t *buf); 517 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock); 518 static int arc_evict_needed(arc_buf_contents_t type); 519 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes); 520 static void arc_buf_watch(arc_buf_t *buf); 521 522 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab); 523 524 #define GHOST_STATE(state) \ 525 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 526 (state) == arc_l2c_only) 527 528 /* 529 * Private ARC flags. These flags are private ARC only flags that will show up 530 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can 531 * be passed in as arc_flags in things like arc_read. However, these flags 532 * should never be passed and should only be set by ARC code. When adding new 533 * public flags, make sure not to smash the private ones. 534 */ 535 536 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */ 537 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */ 538 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */ 539 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */ 540 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */ 541 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */ 542 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */ 543 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */ 544 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */ 545 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */ 546 547 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE) 548 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS) 549 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR) 550 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH) 551 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ) 552 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE) 553 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS) 554 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE) 555 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \ 556 (hdr)->b_l2hdr != NULL) 557 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING) 558 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED) 559 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD) 560 561 /* 562 * Other sizes 563 */ 564 565 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 566 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t)) 567 568 /* 569 * Hash table routines 570 */ 571 572 #define HT_LOCK_PAD 64 573 574 struct ht_lock { 575 kmutex_t ht_lock; 576 #ifdef _KERNEL 577 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 578 #endif 579 }; 580 581 #define BUF_LOCKS 256 582 typedef struct buf_hash_table { 583 uint64_t ht_mask; 584 arc_buf_hdr_t **ht_table; 585 struct ht_lock ht_locks[BUF_LOCKS]; 586 } buf_hash_table_t; 587 588 static buf_hash_table_t buf_hash_table; 589 590 #define BUF_HASH_INDEX(spa, dva, birth) \ 591 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 592 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 593 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 594 #define HDR_LOCK(hdr) \ 595 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 596 597 uint64_t zfs_crc64_table[256]; 598 599 /* 600 * Level 2 ARC 601 */ 602 603 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 604 #define L2ARC_HEADROOM 2 /* num of writes */ 605 /* 606 * If we discover during ARC scan any buffers to be compressed, we boost 607 * our headroom for the next scanning cycle by this percentage multiple. 608 */ 609 #define L2ARC_HEADROOM_BOOST 200 610 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 611 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 612 613 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 614 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 615 616 /* L2ARC Performance Tunables */ 617 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 618 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 619 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 620 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 621 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 622 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 623 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 624 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 625 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 626 627 /* 628 * L2ARC Internals 629 */ 630 typedef struct l2arc_dev { 631 vdev_t *l2ad_vdev; /* vdev */ 632 spa_t *l2ad_spa; /* spa */ 633 uint64_t l2ad_hand; /* next write location */ 634 uint64_t l2ad_start; /* first addr on device */ 635 uint64_t l2ad_end; /* last addr on device */ 636 uint64_t l2ad_evict; /* last addr eviction reached */ 637 boolean_t l2ad_first; /* first sweep through */ 638 boolean_t l2ad_writing; /* currently writing */ 639 list_t *l2ad_buflist; /* buffer list */ 640 list_node_t l2ad_node; /* device list node */ 641 } l2arc_dev_t; 642 643 static list_t L2ARC_dev_list; /* device list */ 644 static list_t *l2arc_dev_list; /* device list pointer */ 645 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 646 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 647 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */ 648 static list_t L2ARC_free_on_write; /* free after write buf list */ 649 static list_t *l2arc_free_on_write; /* free after write list ptr */ 650 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 651 static uint64_t l2arc_ndev; /* number of devices */ 652 653 typedef struct l2arc_read_callback { 654 arc_buf_t *l2rcb_buf; /* read buffer */ 655 spa_t *l2rcb_spa; /* spa */ 656 blkptr_t l2rcb_bp; /* original blkptr */ 657 zbookmark_t l2rcb_zb; /* original bookmark */ 658 int l2rcb_flags; /* original flags */ 659 enum zio_compress l2rcb_compress; /* applied compress */ 660 } l2arc_read_callback_t; 661 662 typedef struct l2arc_write_callback { 663 l2arc_dev_t *l2wcb_dev; /* device info */ 664 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 665 } l2arc_write_callback_t; 666 667 struct l2arc_buf_hdr { 668 /* protected by arc_buf_hdr mutex */ 669 l2arc_dev_t *b_dev; /* L2ARC device */ 670 uint64_t b_daddr; /* disk address, offset byte */ 671 /* compression applied to buffer data */ 672 enum zio_compress b_compress; 673 /* real alloc'd buffer size depending on b_compress applied */ 674 int b_asize; 675 /* temporary buffer holder for in-flight compressed data */ 676 void *b_tmp_cdata; 677 }; 678 679 typedef struct l2arc_data_free { 680 /* protected by l2arc_free_on_write_mtx */ 681 void *l2df_data; 682 size_t l2df_size; 683 void (*l2df_func)(void *, size_t); 684 list_node_t l2df_list_node; 685 } l2arc_data_free_t; 686 687 static kmutex_t l2arc_feed_thr_lock; 688 static kcondvar_t l2arc_feed_thr_cv; 689 static uint8_t l2arc_thread_exit; 690 691 static void l2arc_read_done(zio_t *zio); 692 static void l2arc_hdr_stat_add(void); 693 static void l2arc_hdr_stat_remove(void); 694 695 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr); 696 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, 697 enum zio_compress c); 698 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab); 699 700 static uint64_t 701 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 702 { 703 uint8_t *vdva = (uint8_t *)dva; 704 uint64_t crc = -1ULL; 705 int i; 706 707 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 708 709 for (i = 0; i < sizeof (dva_t); i++) 710 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 711 712 crc ^= (spa>>8) ^ birth; 713 714 return (crc); 715 } 716 717 #define BUF_EMPTY(buf) \ 718 ((buf)->b_dva.dva_word[0] == 0 && \ 719 (buf)->b_dva.dva_word[1] == 0 && \ 720 (buf)->b_birth == 0) 721 722 #define BUF_EQUAL(spa, dva, birth, buf) \ 723 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 724 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 725 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 726 727 static void 728 buf_discard_identity(arc_buf_hdr_t *hdr) 729 { 730 hdr->b_dva.dva_word[0] = 0; 731 hdr->b_dva.dva_word[1] = 0; 732 hdr->b_birth = 0; 733 hdr->b_cksum0 = 0; 734 } 735 736 static arc_buf_hdr_t * 737 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp) 738 { 739 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 740 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 741 arc_buf_hdr_t *buf; 742 743 mutex_enter(hash_lock); 744 for (buf = buf_hash_table.ht_table[idx]; buf != NULL; 745 buf = buf->b_hash_next) { 746 if (BUF_EQUAL(spa, dva, birth, buf)) { 747 *lockp = hash_lock; 748 return (buf); 749 } 750 } 751 mutex_exit(hash_lock); 752 *lockp = NULL; 753 return (NULL); 754 } 755 756 /* 757 * Insert an entry into the hash table. If there is already an element 758 * equal to elem in the hash table, then the already existing element 759 * will be returned and the new element will not be inserted. 760 * Otherwise returns NULL. 761 */ 762 static arc_buf_hdr_t * 763 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp) 764 { 765 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 766 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 767 arc_buf_hdr_t *fbuf; 768 uint32_t i; 769 770 ASSERT(!HDR_IN_HASH_TABLE(buf)); 771 *lockp = hash_lock; 772 mutex_enter(hash_lock); 773 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL; 774 fbuf = fbuf->b_hash_next, i++) { 775 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf)) 776 return (fbuf); 777 } 778 779 buf->b_hash_next = buf_hash_table.ht_table[idx]; 780 buf_hash_table.ht_table[idx] = buf; 781 buf->b_flags |= ARC_IN_HASH_TABLE; 782 783 /* collect some hash table performance data */ 784 if (i > 0) { 785 ARCSTAT_BUMP(arcstat_hash_collisions); 786 if (i == 1) 787 ARCSTAT_BUMP(arcstat_hash_chains); 788 789 ARCSTAT_MAX(arcstat_hash_chain_max, i); 790 } 791 792 ARCSTAT_BUMP(arcstat_hash_elements); 793 ARCSTAT_MAXSTAT(arcstat_hash_elements); 794 795 return (NULL); 796 } 797 798 static void 799 buf_hash_remove(arc_buf_hdr_t *buf) 800 { 801 arc_buf_hdr_t *fbuf, **bufp; 802 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 803 804 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 805 ASSERT(HDR_IN_HASH_TABLE(buf)); 806 807 bufp = &buf_hash_table.ht_table[idx]; 808 while ((fbuf = *bufp) != buf) { 809 ASSERT(fbuf != NULL); 810 bufp = &fbuf->b_hash_next; 811 } 812 *bufp = buf->b_hash_next; 813 buf->b_hash_next = NULL; 814 buf->b_flags &= ~ARC_IN_HASH_TABLE; 815 816 /* collect some hash table performance data */ 817 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 818 819 if (buf_hash_table.ht_table[idx] && 820 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 821 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 822 } 823 824 /* 825 * Global data structures and functions for the buf kmem cache. 826 */ 827 static kmem_cache_t *hdr_cache; 828 static kmem_cache_t *buf_cache; 829 830 static void 831 buf_fini(void) 832 { 833 int i; 834 835 kmem_free(buf_hash_table.ht_table, 836 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 837 for (i = 0; i < BUF_LOCKS; i++) 838 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 839 kmem_cache_destroy(hdr_cache); 840 kmem_cache_destroy(buf_cache); 841 } 842 843 /* 844 * Constructor callback - called when the cache is empty 845 * and a new buf is requested. 846 */ 847 /* ARGSUSED */ 848 static int 849 hdr_cons(void *vbuf, void *unused, int kmflag) 850 { 851 arc_buf_hdr_t *buf = vbuf; 852 853 bzero(buf, sizeof (arc_buf_hdr_t)); 854 refcount_create(&buf->b_refcnt); 855 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL); 856 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 857 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 858 859 return (0); 860 } 861 862 /* ARGSUSED */ 863 static int 864 buf_cons(void *vbuf, void *unused, int kmflag) 865 { 866 arc_buf_t *buf = vbuf; 867 868 bzero(buf, sizeof (arc_buf_t)); 869 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 870 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 871 872 return (0); 873 } 874 875 /* 876 * Destructor callback - called when a cached buf is 877 * no longer required. 878 */ 879 /* ARGSUSED */ 880 static void 881 hdr_dest(void *vbuf, void *unused) 882 { 883 arc_buf_hdr_t *buf = vbuf; 884 885 ASSERT(BUF_EMPTY(buf)); 886 refcount_destroy(&buf->b_refcnt); 887 cv_destroy(&buf->b_cv); 888 mutex_destroy(&buf->b_freeze_lock); 889 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 890 } 891 892 /* ARGSUSED */ 893 static void 894 buf_dest(void *vbuf, void *unused) 895 { 896 arc_buf_t *buf = vbuf; 897 898 mutex_destroy(&buf->b_evict_lock); 899 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 900 } 901 902 /* 903 * Reclaim callback -- invoked when memory is low. 904 */ 905 /* ARGSUSED */ 906 static void 907 hdr_recl(void *unused) 908 { 909 dprintf("hdr_recl called\n"); 910 /* 911 * umem calls the reclaim func when we destroy the buf cache, 912 * which is after we do arc_fini(). 913 */ 914 if (!arc_dead) 915 cv_signal(&arc_reclaim_thr_cv); 916 } 917 918 static void 919 buf_init(void) 920 { 921 uint64_t *ct; 922 uint64_t hsize = 1ULL << 12; 923 int i, j; 924 925 /* 926 * The hash table is big enough to fill all of physical memory 927 * with an average 64K block size. The table will take up 928 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers). 929 */ 930 while (hsize * 65536 < physmem * PAGESIZE) 931 hsize <<= 1; 932 retry: 933 buf_hash_table.ht_mask = hsize - 1; 934 buf_hash_table.ht_table = 935 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 936 if (buf_hash_table.ht_table == NULL) { 937 ASSERT(hsize > (1ULL << 8)); 938 hsize >>= 1; 939 goto retry; 940 } 941 942 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t), 943 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0); 944 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 945 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 946 947 for (i = 0; i < 256; i++) 948 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 949 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 950 951 for (i = 0; i < BUF_LOCKS; i++) { 952 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 953 NULL, MUTEX_DEFAULT, NULL); 954 } 955 } 956 957 #define ARC_MINTIME (hz>>4) /* 62 ms */ 958 959 static void 960 arc_cksum_verify(arc_buf_t *buf) 961 { 962 zio_cksum_t zc; 963 964 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 965 return; 966 967 mutex_enter(&buf->b_hdr->b_freeze_lock); 968 if (buf->b_hdr->b_freeze_cksum == NULL || 969 (buf->b_hdr->b_flags & ARC_IO_ERROR)) { 970 mutex_exit(&buf->b_hdr->b_freeze_lock); 971 return; 972 } 973 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 974 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 975 panic("buffer modified while frozen!"); 976 mutex_exit(&buf->b_hdr->b_freeze_lock); 977 } 978 979 static int 980 arc_cksum_equal(arc_buf_t *buf) 981 { 982 zio_cksum_t zc; 983 int equal; 984 985 mutex_enter(&buf->b_hdr->b_freeze_lock); 986 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 987 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 988 mutex_exit(&buf->b_hdr->b_freeze_lock); 989 990 return (equal); 991 } 992 993 static void 994 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 995 { 996 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 997 return; 998 999 mutex_enter(&buf->b_hdr->b_freeze_lock); 1000 if (buf->b_hdr->b_freeze_cksum != NULL) { 1001 mutex_exit(&buf->b_hdr->b_freeze_lock); 1002 return; 1003 } 1004 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1005 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1006 buf->b_hdr->b_freeze_cksum); 1007 mutex_exit(&buf->b_hdr->b_freeze_lock); 1008 arc_buf_watch(buf); 1009 } 1010 1011 #ifndef _KERNEL 1012 typedef struct procctl { 1013 long cmd; 1014 prwatch_t prwatch; 1015 } procctl_t; 1016 #endif 1017 1018 /* ARGSUSED */ 1019 static void 1020 arc_buf_unwatch(arc_buf_t *buf) 1021 { 1022 #ifndef _KERNEL 1023 if (arc_watch) { 1024 int result; 1025 procctl_t ctl; 1026 ctl.cmd = PCWATCH; 1027 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1028 ctl.prwatch.pr_size = 0; 1029 ctl.prwatch.pr_wflags = 0; 1030 result = write(arc_procfd, &ctl, sizeof (ctl)); 1031 ASSERT3U(result, ==, sizeof (ctl)); 1032 } 1033 #endif 1034 } 1035 1036 /* ARGSUSED */ 1037 static void 1038 arc_buf_watch(arc_buf_t *buf) 1039 { 1040 #ifndef _KERNEL 1041 if (arc_watch) { 1042 int result; 1043 procctl_t ctl; 1044 ctl.cmd = PCWATCH; 1045 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1046 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1047 ctl.prwatch.pr_wflags = WA_WRITE; 1048 result = write(arc_procfd, &ctl, sizeof (ctl)); 1049 ASSERT3U(result, ==, sizeof (ctl)); 1050 } 1051 #endif 1052 } 1053 1054 void 1055 arc_buf_thaw(arc_buf_t *buf) 1056 { 1057 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1058 if (buf->b_hdr->b_state != arc_anon) 1059 panic("modifying non-anon buffer!"); 1060 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS) 1061 panic("modifying buffer while i/o in progress!"); 1062 arc_cksum_verify(buf); 1063 } 1064 1065 mutex_enter(&buf->b_hdr->b_freeze_lock); 1066 if (buf->b_hdr->b_freeze_cksum != NULL) { 1067 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1068 buf->b_hdr->b_freeze_cksum = NULL; 1069 } 1070 1071 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1072 if (buf->b_hdr->b_thawed) 1073 kmem_free(buf->b_hdr->b_thawed, 1); 1074 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP); 1075 } 1076 1077 mutex_exit(&buf->b_hdr->b_freeze_lock); 1078 1079 arc_buf_unwatch(buf); 1080 } 1081 1082 void 1083 arc_buf_freeze(arc_buf_t *buf) 1084 { 1085 kmutex_t *hash_lock; 1086 1087 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1088 return; 1089 1090 hash_lock = HDR_LOCK(buf->b_hdr); 1091 mutex_enter(hash_lock); 1092 1093 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1094 buf->b_hdr->b_state == arc_anon); 1095 arc_cksum_compute(buf, B_FALSE); 1096 mutex_exit(hash_lock); 1097 1098 } 1099 1100 static void 1101 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1102 { 1103 ASSERT(MUTEX_HELD(hash_lock)); 1104 1105 if ((refcount_add(&ab->b_refcnt, tag) == 1) && 1106 (ab->b_state != arc_anon)) { 1107 uint64_t delta = ab->b_size * ab->b_datacnt; 1108 list_t *list = &ab->b_state->arcs_list[ab->b_type]; 1109 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type]; 1110 1111 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx)); 1112 mutex_enter(&ab->b_state->arcs_mtx); 1113 ASSERT(list_link_active(&ab->b_arc_node)); 1114 list_remove(list, ab); 1115 if (GHOST_STATE(ab->b_state)) { 1116 ASSERT0(ab->b_datacnt); 1117 ASSERT3P(ab->b_buf, ==, NULL); 1118 delta = ab->b_size; 1119 } 1120 ASSERT(delta > 0); 1121 ASSERT3U(*size, >=, delta); 1122 atomic_add_64(size, -delta); 1123 mutex_exit(&ab->b_state->arcs_mtx); 1124 /* remove the prefetch flag if we get a reference */ 1125 if (ab->b_flags & ARC_PREFETCH) 1126 ab->b_flags &= ~ARC_PREFETCH; 1127 } 1128 } 1129 1130 static int 1131 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1132 { 1133 int cnt; 1134 arc_state_t *state = ab->b_state; 1135 1136 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1137 ASSERT(!GHOST_STATE(state)); 1138 1139 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) && 1140 (state != arc_anon)) { 1141 uint64_t *size = &state->arcs_lsize[ab->b_type]; 1142 1143 ASSERT(!MUTEX_HELD(&state->arcs_mtx)); 1144 mutex_enter(&state->arcs_mtx); 1145 ASSERT(!list_link_active(&ab->b_arc_node)); 1146 list_insert_head(&state->arcs_list[ab->b_type], ab); 1147 ASSERT(ab->b_datacnt > 0); 1148 atomic_add_64(size, ab->b_size * ab->b_datacnt); 1149 mutex_exit(&state->arcs_mtx); 1150 } 1151 return (cnt); 1152 } 1153 1154 /* 1155 * Move the supplied buffer to the indicated state. The mutex 1156 * for the buffer must be held by the caller. 1157 */ 1158 static void 1159 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock) 1160 { 1161 arc_state_t *old_state = ab->b_state; 1162 int64_t refcnt = refcount_count(&ab->b_refcnt); 1163 uint64_t from_delta, to_delta; 1164 1165 ASSERT(MUTEX_HELD(hash_lock)); 1166 ASSERT(new_state != old_state); 1167 ASSERT(refcnt == 0 || ab->b_datacnt > 0); 1168 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state)); 1169 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon); 1170 1171 from_delta = to_delta = ab->b_datacnt * ab->b_size; 1172 1173 /* 1174 * If this buffer is evictable, transfer it from the 1175 * old state list to the new state list. 1176 */ 1177 if (refcnt == 0) { 1178 if (old_state != arc_anon) { 1179 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx); 1180 uint64_t *size = &old_state->arcs_lsize[ab->b_type]; 1181 1182 if (use_mutex) 1183 mutex_enter(&old_state->arcs_mtx); 1184 1185 ASSERT(list_link_active(&ab->b_arc_node)); 1186 list_remove(&old_state->arcs_list[ab->b_type], ab); 1187 1188 /* 1189 * If prefetching out of the ghost cache, 1190 * we will have a non-zero datacnt. 1191 */ 1192 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) { 1193 /* ghost elements have a ghost size */ 1194 ASSERT(ab->b_buf == NULL); 1195 from_delta = ab->b_size; 1196 } 1197 ASSERT3U(*size, >=, from_delta); 1198 atomic_add_64(size, -from_delta); 1199 1200 if (use_mutex) 1201 mutex_exit(&old_state->arcs_mtx); 1202 } 1203 if (new_state != arc_anon) { 1204 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx); 1205 uint64_t *size = &new_state->arcs_lsize[ab->b_type]; 1206 1207 if (use_mutex) 1208 mutex_enter(&new_state->arcs_mtx); 1209 1210 list_insert_head(&new_state->arcs_list[ab->b_type], ab); 1211 1212 /* ghost elements have a ghost size */ 1213 if (GHOST_STATE(new_state)) { 1214 ASSERT(ab->b_datacnt == 0); 1215 ASSERT(ab->b_buf == NULL); 1216 to_delta = ab->b_size; 1217 } 1218 atomic_add_64(size, to_delta); 1219 1220 if (use_mutex) 1221 mutex_exit(&new_state->arcs_mtx); 1222 } 1223 } 1224 1225 ASSERT(!BUF_EMPTY(ab)); 1226 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab)) 1227 buf_hash_remove(ab); 1228 1229 /* adjust state sizes */ 1230 if (to_delta) 1231 atomic_add_64(&new_state->arcs_size, to_delta); 1232 if (from_delta) { 1233 ASSERT3U(old_state->arcs_size, >=, from_delta); 1234 atomic_add_64(&old_state->arcs_size, -from_delta); 1235 } 1236 ab->b_state = new_state; 1237 1238 /* adjust l2arc hdr stats */ 1239 if (new_state == arc_l2c_only) 1240 l2arc_hdr_stat_add(); 1241 else if (old_state == arc_l2c_only) 1242 l2arc_hdr_stat_remove(); 1243 } 1244 1245 void 1246 arc_space_consume(uint64_t space, arc_space_type_t type) 1247 { 1248 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1249 1250 switch (type) { 1251 case ARC_SPACE_DATA: 1252 ARCSTAT_INCR(arcstat_data_size, space); 1253 break; 1254 case ARC_SPACE_OTHER: 1255 ARCSTAT_INCR(arcstat_other_size, space); 1256 break; 1257 case ARC_SPACE_HDRS: 1258 ARCSTAT_INCR(arcstat_hdr_size, space); 1259 break; 1260 case ARC_SPACE_L2HDRS: 1261 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1262 break; 1263 } 1264 1265 ARCSTAT_INCR(arcstat_meta_used, space); 1266 atomic_add_64(&arc_size, space); 1267 } 1268 1269 void 1270 arc_space_return(uint64_t space, arc_space_type_t type) 1271 { 1272 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1273 1274 switch (type) { 1275 case ARC_SPACE_DATA: 1276 ARCSTAT_INCR(arcstat_data_size, -space); 1277 break; 1278 case ARC_SPACE_OTHER: 1279 ARCSTAT_INCR(arcstat_other_size, -space); 1280 break; 1281 case ARC_SPACE_HDRS: 1282 ARCSTAT_INCR(arcstat_hdr_size, -space); 1283 break; 1284 case ARC_SPACE_L2HDRS: 1285 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1286 break; 1287 } 1288 1289 ASSERT(arc_meta_used >= space); 1290 if (arc_meta_max < arc_meta_used) 1291 arc_meta_max = arc_meta_used; 1292 ARCSTAT_INCR(arcstat_meta_used, -space); 1293 ASSERT(arc_size >= space); 1294 atomic_add_64(&arc_size, -space); 1295 } 1296 1297 void * 1298 arc_data_buf_alloc(uint64_t size) 1299 { 1300 if (arc_evict_needed(ARC_BUFC_DATA)) 1301 cv_signal(&arc_reclaim_thr_cv); 1302 atomic_add_64(&arc_size, size); 1303 return (zio_data_buf_alloc(size)); 1304 } 1305 1306 void 1307 arc_data_buf_free(void *buf, uint64_t size) 1308 { 1309 zio_data_buf_free(buf, size); 1310 ASSERT(arc_size >= size); 1311 atomic_add_64(&arc_size, -size); 1312 } 1313 1314 arc_buf_t * 1315 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type) 1316 { 1317 arc_buf_hdr_t *hdr; 1318 arc_buf_t *buf; 1319 1320 ASSERT3U(size, >, 0); 1321 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 1322 ASSERT(BUF_EMPTY(hdr)); 1323 hdr->b_size = size; 1324 hdr->b_type = type; 1325 hdr->b_spa = spa_load_guid(spa); 1326 hdr->b_state = arc_anon; 1327 hdr->b_arc_access = 0; 1328 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1329 buf->b_hdr = hdr; 1330 buf->b_data = NULL; 1331 buf->b_efunc = NULL; 1332 buf->b_private = NULL; 1333 buf->b_next = NULL; 1334 hdr->b_buf = buf; 1335 arc_get_data_buf(buf); 1336 hdr->b_datacnt = 1; 1337 hdr->b_flags = 0; 1338 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1339 (void) refcount_add(&hdr->b_refcnt, tag); 1340 1341 return (buf); 1342 } 1343 1344 static char *arc_onloan_tag = "onloan"; 1345 1346 /* 1347 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1348 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1349 * buffers must be returned to the arc before they can be used by the DMU or 1350 * freed. 1351 */ 1352 arc_buf_t * 1353 arc_loan_buf(spa_t *spa, int size) 1354 { 1355 arc_buf_t *buf; 1356 1357 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1358 1359 atomic_add_64(&arc_loaned_bytes, size); 1360 return (buf); 1361 } 1362 1363 /* 1364 * Return a loaned arc buffer to the arc. 1365 */ 1366 void 1367 arc_return_buf(arc_buf_t *buf, void *tag) 1368 { 1369 arc_buf_hdr_t *hdr = buf->b_hdr; 1370 1371 ASSERT(buf->b_data != NULL); 1372 (void) refcount_add(&hdr->b_refcnt, tag); 1373 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag); 1374 1375 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1376 } 1377 1378 /* Detach an arc_buf from a dbuf (tag) */ 1379 void 1380 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1381 { 1382 arc_buf_hdr_t *hdr; 1383 1384 ASSERT(buf->b_data != NULL); 1385 hdr = buf->b_hdr; 1386 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag); 1387 (void) refcount_remove(&hdr->b_refcnt, tag); 1388 buf->b_efunc = NULL; 1389 buf->b_private = NULL; 1390 1391 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1392 } 1393 1394 static arc_buf_t * 1395 arc_buf_clone(arc_buf_t *from) 1396 { 1397 arc_buf_t *buf; 1398 arc_buf_hdr_t *hdr = from->b_hdr; 1399 uint64_t size = hdr->b_size; 1400 1401 ASSERT(hdr->b_state != arc_anon); 1402 1403 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1404 buf->b_hdr = hdr; 1405 buf->b_data = NULL; 1406 buf->b_efunc = NULL; 1407 buf->b_private = NULL; 1408 buf->b_next = hdr->b_buf; 1409 hdr->b_buf = buf; 1410 arc_get_data_buf(buf); 1411 bcopy(from->b_data, buf->b_data, size); 1412 1413 /* 1414 * This buffer already exists in the arc so create a duplicate 1415 * copy for the caller. If the buffer is associated with user data 1416 * then track the size and number of duplicates. These stats will be 1417 * updated as duplicate buffers are created and destroyed. 1418 */ 1419 if (hdr->b_type == ARC_BUFC_DATA) { 1420 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1421 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1422 } 1423 hdr->b_datacnt += 1; 1424 return (buf); 1425 } 1426 1427 void 1428 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1429 { 1430 arc_buf_hdr_t *hdr; 1431 kmutex_t *hash_lock; 1432 1433 /* 1434 * Check to see if this buffer is evicted. Callers 1435 * must verify b_data != NULL to know if the add_ref 1436 * was successful. 1437 */ 1438 mutex_enter(&buf->b_evict_lock); 1439 if (buf->b_data == NULL) { 1440 mutex_exit(&buf->b_evict_lock); 1441 return; 1442 } 1443 hash_lock = HDR_LOCK(buf->b_hdr); 1444 mutex_enter(hash_lock); 1445 hdr = buf->b_hdr; 1446 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1447 mutex_exit(&buf->b_evict_lock); 1448 1449 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 1450 add_reference(hdr, hash_lock, tag); 1451 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1452 arc_access(hdr, hash_lock); 1453 mutex_exit(hash_lock); 1454 ARCSTAT_BUMP(arcstat_hits); 1455 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 1456 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 1457 data, metadata, hits); 1458 } 1459 1460 /* 1461 * Free the arc data buffer. If it is an l2arc write in progress, 1462 * the buffer is placed on l2arc_free_on_write to be freed later. 1463 */ 1464 static void 1465 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1466 { 1467 arc_buf_hdr_t *hdr = buf->b_hdr; 1468 1469 if (HDR_L2_WRITING(hdr)) { 1470 l2arc_data_free_t *df; 1471 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1472 df->l2df_data = buf->b_data; 1473 df->l2df_size = hdr->b_size; 1474 df->l2df_func = free_func; 1475 mutex_enter(&l2arc_free_on_write_mtx); 1476 list_insert_head(l2arc_free_on_write, df); 1477 mutex_exit(&l2arc_free_on_write_mtx); 1478 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1479 } else { 1480 free_func(buf->b_data, hdr->b_size); 1481 } 1482 } 1483 1484 static void 1485 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all) 1486 { 1487 arc_buf_t **bufp; 1488 1489 /* free up data associated with the buf */ 1490 if (buf->b_data) { 1491 arc_state_t *state = buf->b_hdr->b_state; 1492 uint64_t size = buf->b_hdr->b_size; 1493 arc_buf_contents_t type = buf->b_hdr->b_type; 1494 1495 arc_cksum_verify(buf); 1496 arc_buf_unwatch(buf); 1497 1498 if (!recycle) { 1499 if (type == ARC_BUFC_METADATA) { 1500 arc_buf_data_free(buf, zio_buf_free); 1501 arc_space_return(size, ARC_SPACE_DATA); 1502 } else { 1503 ASSERT(type == ARC_BUFC_DATA); 1504 arc_buf_data_free(buf, zio_data_buf_free); 1505 ARCSTAT_INCR(arcstat_data_size, -size); 1506 atomic_add_64(&arc_size, -size); 1507 } 1508 } 1509 if (list_link_active(&buf->b_hdr->b_arc_node)) { 1510 uint64_t *cnt = &state->arcs_lsize[type]; 1511 1512 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt)); 1513 ASSERT(state != arc_anon); 1514 1515 ASSERT3U(*cnt, >=, size); 1516 atomic_add_64(cnt, -size); 1517 } 1518 ASSERT3U(state->arcs_size, >=, size); 1519 atomic_add_64(&state->arcs_size, -size); 1520 buf->b_data = NULL; 1521 1522 /* 1523 * If we're destroying a duplicate buffer make sure 1524 * that the appropriate statistics are updated. 1525 */ 1526 if (buf->b_hdr->b_datacnt > 1 && 1527 buf->b_hdr->b_type == ARC_BUFC_DATA) { 1528 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1529 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1530 } 1531 ASSERT(buf->b_hdr->b_datacnt > 0); 1532 buf->b_hdr->b_datacnt -= 1; 1533 } 1534 1535 /* only remove the buf if requested */ 1536 if (!all) 1537 return; 1538 1539 /* remove the buf from the hdr list */ 1540 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next) 1541 continue; 1542 *bufp = buf->b_next; 1543 buf->b_next = NULL; 1544 1545 ASSERT(buf->b_efunc == NULL); 1546 1547 /* clean up the buf */ 1548 buf->b_hdr = NULL; 1549 kmem_cache_free(buf_cache, buf); 1550 } 1551 1552 static void 1553 arc_hdr_destroy(arc_buf_hdr_t *hdr) 1554 { 1555 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1556 ASSERT3P(hdr->b_state, ==, arc_anon); 1557 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1558 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1559 1560 if (l2hdr != NULL) { 1561 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx); 1562 /* 1563 * To prevent arc_free() and l2arc_evict() from 1564 * attempting to free the same buffer at the same time, 1565 * a FREE_IN_PROGRESS flag is given to arc_free() to 1566 * give it priority. l2arc_evict() can't destroy this 1567 * header while we are waiting on l2arc_buflist_mtx. 1568 * 1569 * The hdr may be removed from l2ad_buflist before we 1570 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked. 1571 */ 1572 if (!buflist_held) { 1573 mutex_enter(&l2arc_buflist_mtx); 1574 l2hdr = hdr->b_l2hdr; 1575 } 1576 1577 if (l2hdr != NULL) { 1578 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 1579 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1580 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 1581 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 1582 if (hdr->b_state == arc_l2c_only) 1583 l2arc_hdr_stat_remove(); 1584 hdr->b_l2hdr = NULL; 1585 } 1586 1587 if (!buflist_held) 1588 mutex_exit(&l2arc_buflist_mtx); 1589 } 1590 1591 if (!BUF_EMPTY(hdr)) { 1592 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1593 buf_discard_identity(hdr); 1594 } 1595 while (hdr->b_buf) { 1596 arc_buf_t *buf = hdr->b_buf; 1597 1598 if (buf->b_efunc) { 1599 mutex_enter(&arc_eviction_mtx); 1600 mutex_enter(&buf->b_evict_lock); 1601 ASSERT(buf->b_hdr != NULL); 1602 arc_buf_destroy(hdr->b_buf, FALSE, FALSE); 1603 hdr->b_buf = buf->b_next; 1604 buf->b_hdr = &arc_eviction_hdr; 1605 buf->b_next = arc_eviction_list; 1606 arc_eviction_list = buf; 1607 mutex_exit(&buf->b_evict_lock); 1608 mutex_exit(&arc_eviction_mtx); 1609 } else { 1610 arc_buf_destroy(hdr->b_buf, FALSE, TRUE); 1611 } 1612 } 1613 if (hdr->b_freeze_cksum != NULL) { 1614 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1615 hdr->b_freeze_cksum = NULL; 1616 } 1617 if (hdr->b_thawed) { 1618 kmem_free(hdr->b_thawed, 1); 1619 hdr->b_thawed = NULL; 1620 } 1621 1622 ASSERT(!list_link_active(&hdr->b_arc_node)); 1623 ASSERT3P(hdr->b_hash_next, ==, NULL); 1624 ASSERT3P(hdr->b_acb, ==, NULL); 1625 kmem_cache_free(hdr_cache, hdr); 1626 } 1627 1628 void 1629 arc_buf_free(arc_buf_t *buf, void *tag) 1630 { 1631 arc_buf_hdr_t *hdr = buf->b_hdr; 1632 int hashed = hdr->b_state != arc_anon; 1633 1634 ASSERT(buf->b_efunc == NULL); 1635 ASSERT(buf->b_data != NULL); 1636 1637 if (hashed) { 1638 kmutex_t *hash_lock = HDR_LOCK(hdr); 1639 1640 mutex_enter(hash_lock); 1641 hdr = buf->b_hdr; 1642 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1643 1644 (void) remove_reference(hdr, hash_lock, tag); 1645 if (hdr->b_datacnt > 1) { 1646 arc_buf_destroy(buf, FALSE, TRUE); 1647 } else { 1648 ASSERT(buf == hdr->b_buf); 1649 ASSERT(buf->b_efunc == NULL); 1650 hdr->b_flags |= ARC_BUF_AVAILABLE; 1651 } 1652 mutex_exit(hash_lock); 1653 } else if (HDR_IO_IN_PROGRESS(hdr)) { 1654 int destroy_hdr; 1655 /* 1656 * We are in the middle of an async write. Don't destroy 1657 * this buffer unless the write completes before we finish 1658 * decrementing the reference count. 1659 */ 1660 mutex_enter(&arc_eviction_mtx); 1661 (void) remove_reference(hdr, NULL, tag); 1662 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1663 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 1664 mutex_exit(&arc_eviction_mtx); 1665 if (destroy_hdr) 1666 arc_hdr_destroy(hdr); 1667 } else { 1668 if (remove_reference(hdr, NULL, tag) > 0) 1669 arc_buf_destroy(buf, FALSE, TRUE); 1670 else 1671 arc_hdr_destroy(hdr); 1672 } 1673 } 1674 1675 boolean_t 1676 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 1677 { 1678 arc_buf_hdr_t *hdr = buf->b_hdr; 1679 kmutex_t *hash_lock = HDR_LOCK(hdr); 1680 boolean_t no_callback = (buf->b_efunc == NULL); 1681 1682 if (hdr->b_state == arc_anon) { 1683 ASSERT(hdr->b_datacnt == 1); 1684 arc_buf_free(buf, tag); 1685 return (no_callback); 1686 } 1687 1688 mutex_enter(hash_lock); 1689 hdr = buf->b_hdr; 1690 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1691 ASSERT(hdr->b_state != arc_anon); 1692 ASSERT(buf->b_data != NULL); 1693 1694 (void) remove_reference(hdr, hash_lock, tag); 1695 if (hdr->b_datacnt > 1) { 1696 if (no_callback) 1697 arc_buf_destroy(buf, FALSE, TRUE); 1698 } else if (no_callback) { 1699 ASSERT(hdr->b_buf == buf && buf->b_next == NULL); 1700 ASSERT(buf->b_efunc == NULL); 1701 hdr->b_flags |= ARC_BUF_AVAILABLE; 1702 } 1703 ASSERT(no_callback || hdr->b_datacnt > 1 || 1704 refcount_is_zero(&hdr->b_refcnt)); 1705 mutex_exit(hash_lock); 1706 return (no_callback); 1707 } 1708 1709 int 1710 arc_buf_size(arc_buf_t *buf) 1711 { 1712 return (buf->b_hdr->b_size); 1713 } 1714 1715 /* 1716 * Called from the DMU to determine if the current buffer should be 1717 * evicted. In order to ensure proper locking, the eviction must be initiated 1718 * from the DMU. Return true if the buffer is associated with user data and 1719 * duplicate buffers still exist. 1720 */ 1721 boolean_t 1722 arc_buf_eviction_needed(arc_buf_t *buf) 1723 { 1724 arc_buf_hdr_t *hdr; 1725 boolean_t evict_needed = B_FALSE; 1726 1727 if (zfs_disable_dup_eviction) 1728 return (B_FALSE); 1729 1730 mutex_enter(&buf->b_evict_lock); 1731 hdr = buf->b_hdr; 1732 if (hdr == NULL) { 1733 /* 1734 * We are in arc_do_user_evicts(); let that function 1735 * perform the eviction. 1736 */ 1737 ASSERT(buf->b_data == NULL); 1738 mutex_exit(&buf->b_evict_lock); 1739 return (B_FALSE); 1740 } else if (buf->b_data == NULL) { 1741 /* 1742 * We have already been added to the arc eviction list; 1743 * recommend eviction. 1744 */ 1745 ASSERT3P(hdr, ==, &arc_eviction_hdr); 1746 mutex_exit(&buf->b_evict_lock); 1747 return (B_TRUE); 1748 } 1749 1750 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) 1751 evict_needed = B_TRUE; 1752 1753 mutex_exit(&buf->b_evict_lock); 1754 return (evict_needed); 1755 } 1756 1757 /* 1758 * Evict buffers from list until we've removed the specified number of 1759 * bytes. Move the removed buffers to the appropriate evict state. 1760 * If the recycle flag is set, then attempt to "recycle" a buffer: 1761 * - look for a buffer to evict that is `bytes' long. 1762 * - return the data block from this buffer rather than freeing it. 1763 * This flag is used by callers that are trying to make space for a 1764 * new buffer in a full arc cache. 1765 * 1766 * This function makes a "best effort". It skips over any buffers 1767 * it can't get a hash_lock on, and so may not catch all candidates. 1768 * It may also return without evicting as much space as requested. 1769 */ 1770 static void * 1771 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 1772 arc_buf_contents_t type) 1773 { 1774 arc_state_t *evicted_state; 1775 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 1776 arc_buf_hdr_t *ab, *ab_prev = NULL; 1777 list_t *list = &state->arcs_list[type]; 1778 kmutex_t *hash_lock; 1779 boolean_t have_lock; 1780 void *stolen = NULL; 1781 1782 ASSERT(state == arc_mru || state == arc_mfu); 1783 1784 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 1785 1786 mutex_enter(&state->arcs_mtx); 1787 mutex_enter(&evicted_state->arcs_mtx); 1788 1789 for (ab = list_tail(list); ab; ab = ab_prev) { 1790 ab_prev = list_prev(list, ab); 1791 /* prefetch buffers have a minimum lifespan */ 1792 if (HDR_IO_IN_PROGRESS(ab) || 1793 (spa && ab->b_spa != spa) || 1794 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) && 1795 ddi_get_lbolt() - ab->b_arc_access < 1796 arc_min_prefetch_lifespan)) { 1797 skipped++; 1798 continue; 1799 } 1800 /* "lookahead" for better eviction candidate */ 1801 if (recycle && ab->b_size != bytes && 1802 ab_prev && ab_prev->b_size == bytes) 1803 continue; 1804 hash_lock = HDR_LOCK(ab); 1805 have_lock = MUTEX_HELD(hash_lock); 1806 if (have_lock || mutex_tryenter(hash_lock)) { 1807 ASSERT0(refcount_count(&ab->b_refcnt)); 1808 ASSERT(ab->b_datacnt > 0); 1809 while (ab->b_buf) { 1810 arc_buf_t *buf = ab->b_buf; 1811 if (!mutex_tryenter(&buf->b_evict_lock)) { 1812 missed += 1; 1813 break; 1814 } 1815 if (buf->b_data) { 1816 bytes_evicted += ab->b_size; 1817 if (recycle && ab->b_type == type && 1818 ab->b_size == bytes && 1819 !HDR_L2_WRITING(ab)) { 1820 stolen = buf->b_data; 1821 recycle = FALSE; 1822 } 1823 } 1824 if (buf->b_efunc) { 1825 mutex_enter(&arc_eviction_mtx); 1826 arc_buf_destroy(buf, 1827 buf->b_data == stolen, FALSE); 1828 ab->b_buf = buf->b_next; 1829 buf->b_hdr = &arc_eviction_hdr; 1830 buf->b_next = arc_eviction_list; 1831 arc_eviction_list = buf; 1832 mutex_exit(&arc_eviction_mtx); 1833 mutex_exit(&buf->b_evict_lock); 1834 } else { 1835 mutex_exit(&buf->b_evict_lock); 1836 arc_buf_destroy(buf, 1837 buf->b_data == stolen, TRUE); 1838 } 1839 } 1840 1841 if (ab->b_l2hdr) { 1842 ARCSTAT_INCR(arcstat_evict_l2_cached, 1843 ab->b_size); 1844 } else { 1845 if (l2arc_write_eligible(ab->b_spa, ab)) { 1846 ARCSTAT_INCR(arcstat_evict_l2_eligible, 1847 ab->b_size); 1848 } else { 1849 ARCSTAT_INCR( 1850 arcstat_evict_l2_ineligible, 1851 ab->b_size); 1852 } 1853 } 1854 1855 if (ab->b_datacnt == 0) { 1856 arc_change_state(evicted_state, ab, hash_lock); 1857 ASSERT(HDR_IN_HASH_TABLE(ab)); 1858 ab->b_flags |= ARC_IN_HASH_TABLE; 1859 ab->b_flags &= ~ARC_BUF_AVAILABLE; 1860 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab); 1861 } 1862 if (!have_lock) 1863 mutex_exit(hash_lock); 1864 if (bytes >= 0 && bytes_evicted >= bytes) 1865 break; 1866 } else { 1867 missed += 1; 1868 } 1869 } 1870 1871 mutex_exit(&evicted_state->arcs_mtx); 1872 mutex_exit(&state->arcs_mtx); 1873 1874 if (bytes_evicted < bytes) 1875 dprintf("only evicted %lld bytes from %x", 1876 (longlong_t)bytes_evicted, state); 1877 1878 if (skipped) 1879 ARCSTAT_INCR(arcstat_evict_skip, skipped); 1880 1881 if (missed) 1882 ARCSTAT_INCR(arcstat_mutex_miss, missed); 1883 1884 /* 1885 * We have just evicted some data into the ghost state, make 1886 * sure we also adjust the ghost state size if necessary. 1887 */ 1888 if (arc_no_grow && 1889 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) { 1890 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size + 1891 arc_mru_ghost->arcs_size - arc_c; 1892 1893 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) { 1894 int64_t todelete = 1895 MIN(arc_mru_ghost->arcs_lsize[type], mru_over); 1896 arc_evict_ghost(arc_mru_ghost, NULL, todelete); 1897 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) { 1898 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type], 1899 arc_mru_ghost->arcs_size + 1900 arc_mfu_ghost->arcs_size - arc_c); 1901 arc_evict_ghost(arc_mfu_ghost, NULL, todelete); 1902 } 1903 } 1904 1905 return (stolen); 1906 } 1907 1908 /* 1909 * Remove buffers from list until we've removed the specified number of 1910 * bytes. Destroy the buffers that are removed. 1911 */ 1912 static void 1913 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 1914 { 1915 arc_buf_hdr_t *ab, *ab_prev; 1916 arc_buf_hdr_t marker = { 0 }; 1917 list_t *list = &state->arcs_list[ARC_BUFC_DATA]; 1918 kmutex_t *hash_lock; 1919 uint64_t bytes_deleted = 0; 1920 uint64_t bufs_skipped = 0; 1921 1922 ASSERT(GHOST_STATE(state)); 1923 top: 1924 mutex_enter(&state->arcs_mtx); 1925 for (ab = list_tail(list); ab; ab = ab_prev) { 1926 ab_prev = list_prev(list, ab); 1927 if (spa && ab->b_spa != spa) 1928 continue; 1929 1930 /* ignore markers */ 1931 if (ab->b_spa == 0) 1932 continue; 1933 1934 hash_lock = HDR_LOCK(ab); 1935 /* caller may be trying to modify this buffer, skip it */ 1936 if (MUTEX_HELD(hash_lock)) 1937 continue; 1938 if (mutex_tryenter(hash_lock)) { 1939 ASSERT(!HDR_IO_IN_PROGRESS(ab)); 1940 ASSERT(ab->b_buf == NULL); 1941 ARCSTAT_BUMP(arcstat_deleted); 1942 bytes_deleted += ab->b_size; 1943 1944 if (ab->b_l2hdr != NULL) { 1945 /* 1946 * This buffer is cached on the 2nd Level ARC; 1947 * don't destroy the header. 1948 */ 1949 arc_change_state(arc_l2c_only, ab, hash_lock); 1950 mutex_exit(hash_lock); 1951 } else { 1952 arc_change_state(arc_anon, ab, hash_lock); 1953 mutex_exit(hash_lock); 1954 arc_hdr_destroy(ab); 1955 } 1956 1957 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab); 1958 if (bytes >= 0 && bytes_deleted >= bytes) 1959 break; 1960 } else if (bytes < 0) { 1961 /* 1962 * Insert a list marker and then wait for the 1963 * hash lock to become available. Once its 1964 * available, restart from where we left off. 1965 */ 1966 list_insert_after(list, ab, &marker); 1967 mutex_exit(&state->arcs_mtx); 1968 mutex_enter(hash_lock); 1969 mutex_exit(hash_lock); 1970 mutex_enter(&state->arcs_mtx); 1971 ab_prev = list_prev(list, &marker); 1972 list_remove(list, &marker); 1973 } else 1974 bufs_skipped += 1; 1975 } 1976 mutex_exit(&state->arcs_mtx); 1977 1978 if (list == &state->arcs_list[ARC_BUFC_DATA] && 1979 (bytes < 0 || bytes_deleted < bytes)) { 1980 list = &state->arcs_list[ARC_BUFC_METADATA]; 1981 goto top; 1982 } 1983 1984 if (bufs_skipped) { 1985 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 1986 ASSERT(bytes >= 0); 1987 } 1988 1989 if (bytes_deleted < bytes) 1990 dprintf("only deleted %lld bytes from %p", 1991 (longlong_t)bytes_deleted, state); 1992 } 1993 1994 static void 1995 arc_adjust(void) 1996 { 1997 int64_t adjustment, delta; 1998 1999 /* 2000 * Adjust MRU size 2001 */ 2002 2003 adjustment = MIN((int64_t)(arc_size - arc_c), 2004 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2005 arc_p)); 2006 2007 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2008 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2009 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA); 2010 adjustment -= delta; 2011 } 2012 2013 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2014 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2015 (void) arc_evict(arc_mru, NULL, delta, FALSE, 2016 ARC_BUFC_METADATA); 2017 } 2018 2019 /* 2020 * Adjust MFU size 2021 */ 2022 2023 adjustment = arc_size - arc_c; 2024 2025 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2026 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2027 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA); 2028 adjustment -= delta; 2029 } 2030 2031 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2032 int64_t delta = MIN(adjustment, 2033 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2034 (void) arc_evict(arc_mfu, NULL, delta, FALSE, 2035 ARC_BUFC_METADATA); 2036 } 2037 2038 /* 2039 * Adjust ghost lists 2040 */ 2041 2042 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2043 2044 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2045 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2046 arc_evict_ghost(arc_mru_ghost, NULL, delta); 2047 } 2048 2049 adjustment = 2050 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2051 2052 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2053 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2054 arc_evict_ghost(arc_mfu_ghost, NULL, delta); 2055 } 2056 } 2057 2058 static void 2059 arc_do_user_evicts(void) 2060 { 2061 mutex_enter(&arc_eviction_mtx); 2062 while (arc_eviction_list != NULL) { 2063 arc_buf_t *buf = arc_eviction_list; 2064 arc_eviction_list = buf->b_next; 2065 mutex_enter(&buf->b_evict_lock); 2066 buf->b_hdr = NULL; 2067 mutex_exit(&buf->b_evict_lock); 2068 mutex_exit(&arc_eviction_mtx); 2069 2070 if (buf->b_efunc != NULL) 2071 VERIFY(buf->b_efunc(buf) == 0); 2072 2073 buf->b_efunc = NULL; 2074 buf->b_private = NULL; 2075 kmem_cache_free(buf_cache, buf); 2076 mutex_enter(&arc_eviction_mtx); 2077 } 2078 mutex_exit(&arc_eviction_mtx); 2079 } 2080 2081 /* 2082 * Flush all *evictable* data from the cache for the given spa. 2083 * NOTE: this will not touch "active" (i.e. referenced) data. 2084 */ 2085 void 2086 arc_flush(spa_t *spa) 2087 { 2088 uint64_t guid = 0; 2089 2090 if (spa) 2091 guid = spa_load_guid(spa); 2092 2093 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) { 2094 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2095 if (spa) 2096 break; 2097 } 2098 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) { 2099 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2100 if (spa) 2101 break; 2102 } 2103 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) { 2104 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2105 if (spa) 2106 break; 2107 } 2108 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) { 2109 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2110 if (spa) 2111 break; 2112 } 2113 2114 arc_evict_ghost(arc_mru_ghost, guid, -1); 2115 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2116 2117 mutex_enter(&arc_reclaim_thr_lock); 2118 arc_do_user_evicts(); 2119 mutex_exit(&arc_reclaim_thr_lock); 2120 ASSERT(spa || arc_eviction_list == NULL); 2121 } 2122 2123 void 2124 arc_shrink(void) 2125 { 2126 if (arc_c > arc_c_min) { 2127 uint64_t to_free; 2128 2129 #ifdef _KERNEL 2130 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree)); 2131 #else 2132 to_free = arc_c >> arc_shrink_shift; 2133 #endif 2134 if (arc_c > arc_c_min + to_free) 2135 atomic_add_64(&arc_c, -to_free); 2136 else 2137 arc_c = arc_c_min; 2138 2139 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2140 if (arc_c > arc_size) 2141 arc_c = MAX(arc_size, arc_c_min); 2142 if (arc_p > arc_c) 2143 arc_p = (arc_c >> 1); 2144 ASSERT(arc_c >= arc_c_min); 2145 ASSERT((int64_t)arc_p >= 0); 2146 } 2147 2148 if (arc_size > arc_c) 2149 arc_adjust(); 2150 } 2151 2152 /* 2153 * Determine if the system is under memory pressure and is asking 2154 * to reclaim memory. A return value of 1 indicates that the system 2155 * is under memory pressure and that the arc should adjust accordingly. 2156 */ 2157 static int 2158 arc_reclaim_needed(void) 2159 { 2160 uint64_t extra; 2161 2162 #ifdef _KERNEL 2163 2164 if (needfree) 2165 return (1); 2166 2167 /* 2168 * take 'desfree' extra pages, so we reclaim sooner, rather than later 2169 */ 2170 extra = desfree; 2171 2172 /* 2173 * check that we're out of range of the pageout scanner. It starts to 2174 * schedule paging if freemem is less than lotsfree and needfree. 2175 * lotsfree is the high-water mark for pageout, and needfree is the 2176 * number of needed free pages. We add extra pages here to make sure 2177 * the scanner doesn't start up while we're freeing memory. 2178 */ 2179 if (freemem < lotsfree + needfree + extra) 2180 return (1); 2181 2182 /* 2183 * check to make sure that swapfs has enough space so that anon 2184 * reservations can still succeed. anon_resvmem() checks that the 2185 * availrmem is greater than swapfs_minfree, and the number of reserved 2186 * swap pages. We also add a bit of extra here just to prevent 2187 * circumstances from getting really dire. 2188 */ 2189 if (availrmem < swapfs_minfree + swapfs_reserve + extra) 2190 return (1); 2191 2192 #if defined(__i386) 2193 /* 2194 * If we're on an i386 platform, it's possible that we'll exhaust the 2195 * kernel heap space before we ever run out of available physical 2196 * memory. Most checks of the size of the heap_area compare against 2197 * tune.t_minarmem, which is the minimum available real memory that we 2198 * can have in the system. However, this is generally fixed at 25 pages 2199 * which is so low that it's useless. In this comparison, we seek to 2200 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2201 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2202 * free) 2203 */ 2204 if (vmem_size(heap_arena, VMEM_FREE) < 2205 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) 2206 return (1); 2207 #endif 2208 2209 /* 2210 * If zio data pages are being allocated out of a separate heap segment, 2211 * then enforce that the size of available vmem for this arena remains 2212 * above about 1/16th free. 2213 * 2214 * Note: The 1/16th arena free requirement was put in place 2215 * to aggressively evict memory from the arc in order to avoid 2216 * memory fragmentation issues. 2217 */ 2218 if (zio_arena != NULL && 2219 vmem_size(zio_arena, VMEM_FREE) < 2220 (vmem_size(zio_arena, VMEM_ALLOC) >> 4)) 2221 return (1); 2222 #else 2223 if (spa_get_random(100) == 0) 2224 return (1); 2225 #endif 2226 return (0); 2227 } 2228 2229 static void 2230 arc_kmem_reap_now(arc_reclaim_strategy_t strat) 2231 { 2232 size_t i; 2233 kmem_cache_t *prev_cache = NULL; 2234 kmem_cache_t *prev_data_cache = NULL; 2235 extern kmem_cache_t *zio_buf_cache[]; 2236 extern kmem_cache_t *zio_data_buf_cache[]; 2237 2238 #ifdef _KERNEL 2239 if (arc_meta_used >= arc_meta_limit) { 2240 /* 2241 * We are exceeding our meta-data cache limit. 2242 * Purge some DNLC entries to release holds on meta-data. 2243 */ 2244 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2245 } 2246 #if defined(__i386) 2247 /* 2248 * Reclaim unused memory from all kmem caches. 2249 */ 2250 kmem_reap(); 2251 #endif 2252 #endif 2253 2254 /* 2255 * An aggressive reclamation will shrink the cache size as well as 2256 * reap free buffers from the arc kmem caches. 2257 */ 2258 if (strat == ARC_RECLAIM_AGGR) 2259 arc_shrink(); 2260 2261 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2262 if (zio_buf_cache[i] != prev_cache) { 2263 prev_cache = zio_buf_cache[i]; 2264 kmem_cache_reap_now(zio_buf_cache[i]); 2265 } 2266 if (zio_data_buf_cache[i] != prev_data_cache) { 2267 prev_data_cache = zio_data_buf_cache[i]; 2268 kmem_cache_reap_now(zio_data_buf_cache[i]); 2269 } 2270 } 2271 kmem_cache_reap_now(buf_cache); 2272 kmem_cache_reap_now(hdr_cache); 2273 2274 /* 2275 * Ask the vmem areana to reclaim unused memory from its 2276 * quantum caches. 2277 */ 2278 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR) 2279 vmem_qcache_reap(zio_arena); 2280 } 2281 2282 static void 2283 arc_reclaim_thread(void) 2284 { 2285 clock_t growtime = 0; 2286 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS; 2287 callb_cpr_t cpr; 2288 2289 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2290 2291 mutex_enter(&arc_reclaim_thr_lock); 2292 while (arc_thread_exit == 0) { 2293 if (arc_reclaim_needed()) { 2294 2295 if (arc_no_grow) { 2296 if (last_reclaim == ARC_RECLAIM_CONS) { 2297 last_reclaim = ARC_RECLAIM_AGGR; 2298 } else { 2299 last_reclaim = ARC_RECLAIM_CONS; 2300 } 2301 } else { 2302 arc_no_grow = TRUE; 2303 last_reclaim = ARC_RECLAIM_AGGR; 2304 membar_producer(); 2305 } 2306 2307 /* reset the growth delay for every reclaim */ 2308 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2309 2310 arc_kmem_reap_now(last_reclaim); 2311 arc_warm = B_TRUE; 2312 2313 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { 2314 arc_no_grow = FALSE; 2315 } 2316 2317 arc_adjust(); 2318 2319 if (arc_eviction_list != NULL) 2320 arc_do_user_evicts(); 2321 2322 /* block until needed, or one second, whichever is shorter */ 2323 CALLB_CPR_SAFE_BEGIN(&cpr); 2324 (void) cv_timedwait(&arc_reclaim_thr_cv, 2325 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz)); 2326 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2327 } 2328 2329 arc_thread_exit = 0; 2330 cv_broadcast(&arc_reclaim_thr_cv); 2331 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2332 thread_exit(); 2333 } 2334 2335 /* 2336 * Adapt arc info given the number of bytes we are trying to add and 2337 * the state that we are comming from. This function is only called 2338 * when we are adding new content to the cache. 2339 */ 2340 static void 2341 arc_adapt(int bytes, arc_state_t *state) 2342 { 2343 int mult; 2344 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2345 2346 if (state == arc_l2c_only) 2347 return; 2348 2349 ASSERT(bytes > 0); 2350 /* 2351 * Adapt the target size of the MRU list: 2352 * - if we just hit in the MRU ghost list, then increase 2353 * the target size of the MRU list. 2354 * - if we just hit in the MFU ghost list, then increase 2355 * the target size of the MFU list by decreasing the 2356 * target size of the MRU list. 2357 */ 2358 if (state == arc_mru_ghost) { 2359 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2360 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2361 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2362 2363 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2364 } else if (state == arc_mfu_ghost) { 2365 uint64_t delta; 2366 2367 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2368 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2369 mult = MIN(mult, 10); 2370 2371 delta = MIN(bytes * mult, arc_p); 2372 arc_p = MAX(arc_p_min, arc_p - delta); 2373 } 2374 ASSERT((int64_t)arc_p >= 0); 2375 2376 if (arc_reclaim_needed()) { 2377 cv_signal(&arc_reclaim_thr_cv); 2378 return; 2379 } 2380 2381 if (arc_no_grow) 2382 return; 2383 2384 if (arc_c >= arc_c_max) 2385 return; 2386 2387 /* 2388 * If we're within (2 * maxblocksize) bytes of the target 2389 * cache size, increment the target cache size 2390 */ 2391 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2392 atomic_add_64(&arc_c, (int64_t)bytes); 2393 if (arc_c > arc_c_max) 2394 arc_c = arc_c_max; 2395 else if (state == arc_anon) 2396 atomic_add_64(&arc_p, (int64_t)bytes); 2397 if (arc_p > arc_c) 2398 arc_p = arc_c; 2399 } 2400 ASSERT((int64_t)arc_p >= 0); 2401 } 2402 2403 /* 2404 * Check if the cache has reached its limits and eviction is required 2405 * prior to insert. 2406 */ 2407 static int 2408 arc_evict_needed(arc_buf_contents_t type) 2409 { 2410 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 2411 return (1); 2412 2413 if (arc_reclaim_needed()) 2414 return (1); 2415 2416 return (arc_size > arc_c); 2417 } 2418 2419 /* 2420 * The buffer, supplied as the first argument, needs a data block. 2421 * So, if we are at cache max, determine which cache should be victimized. 2422 * We have the following cases: 2423 * 2424 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 2425 * In this situation if we're out of space, but the resident size of the MFU is 2426 * under the limit, victimize the MFU cache to satisfy this insertion request. 2427 * 2428 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 2429 * Here, we've used up all of the available space for the MRU, so we need to 2430 * evict from our own cache instead. Evict from the set of resident MRU 2431 * entries. 2432 * 2433 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 2434 * c minus p represents the MFU space in the cache, since p is the size of the 2435 * cache that is dedicated to the MRU. In this situation there's still space on 2436 * the MFU side, so the MRU side needs to be victimized. 2437 * 2438 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 2439 * MFU's resident set is consuming more space than it has been allotted. In 2440 * this situation, we must victimize our own cache, the MFU, for this insertion. 2441 */ 2442 static void 2443 arc_get_data_buf(arc_buf_t *buf) 2444 { 2445 arc_state_t *state = buf->b_hdr->b_state; 2446 uint64_t size = buf->b_hdr->b_size; 2447 arc_buf_contents_t type = buf->b_hdr->b_type; 2448 2449 arc_adapt(size, state); 2450 2451 /* 2452 * We have not yet reached cache maximum size, 2453 * just allocate a new buffer. 2454 */ 2455 if (!arc_evict_needed(type)) { 2456 if (type == ARC_BUFC_METADATA) { 2457 buf->b_data = zio_buf_alloc(size); 2458 arc_space_consume(size, ARC_SPACE_DATA); 2459 } else { 2460 ASSERT(type == ARC_BUFC_DATA); 2461 buf->b_data = zio_data_buf_alloc(size); 2462 ARCSTAT_INCR(arcstat_data_size, size); 2463 atomic_add_64(&arc_size, size); 2464 } 2465 goto out; 2466 } 2467 2468 /* 2469 * If we are prefetching from the mfu ghost list, this buffer 2470 * will end up on the mru list; so steal space from there. 2471 */ 2472 if (state == arc_mfu_ghost) 2473 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu; 2474 else if (state == arc_mru_ghost) 2475 state = arc_mru; 2476 2477 if (state == arc_mru || state == arc_anon) { 2478 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 2479 state = (arc_mfu->arcs_lsize[type] >= size && 2480 arc_p > mru_used) ? arc_mfu : arc_mru; 2481 } else { 2482 /* MFU cases */ 2483 uint64_t mfu_space = arc_c - arc_p; 2484 state = (arc_mru->arcs_lsize[type] >= size && 2485 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 2486 } 2487 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) { 2488 if (type == ARC_BUFC_METADATA) { 2489 buf->b_data = zio_buf_alloc(size); 2490 arc_space_consume(size, ARC_SPACE_DATA); 2491 } else { 2492 ASSERT(type == ARC_BUFC_DATA); 2493 buf->b_data = zio_data_buf_alloc(size); 2494 ARCSTAT_INCR(arcstat_data_size, size); 2495 atomic_add_64(&arc_size, size); 2496 } 2497 ARCSTAT_BUMP(arcstat_recycle_miss); 2498 } 2499 ASSERT(buf->b_data != NULL); 2500 out: 2501 /* 2502 * Update the state size. Note that ghost states have a 2503 * "ghost size" and so don't need to be updated. 2504 */ 2505 if (!GHOST_STATE(buf->b_hdr->b_state)) { 2506 arc_buf_hdr_t *hdr = buf->b_hdr; 2507 2508 atomic_add_64(&hdr->b_state->arcs_size, size); 2509 if (list_link_active(&hdr->b_arc_node)) { 2510 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 2511 atomic_add_64(&hdr->b_state->arcs_lsize[type], size); 2512 } 2513 /* 2514 * If we are growing the cache, and we are adding anonymous 2515 * data, and we have outgrown arc_p, update arc_p 2516 */ 2517 if (arc_size < arc_c && hdr->b_state == arc_anon && 2518 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 2519 arc_p = MIN(arc_c, arc_p + size); 2520 } 2521 } 2522 2523 /* 2524 * This routine is called whenever a buffer is accessed. 2525 * NOTE: the hash lock is dropped in this function. 2526 */ 2527 static void 2528 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock) 2529 { 2530 clock_t now; 2531 2532 ASSERT(MUTEX_HELD(hash_lock)); 2533 2534 if (buf->b_state == arc_anon) { 2535 /* 2536 * This buffer is not in the cache, and does not 2537 * appear in our "ghost" list. Add the new buffer 2538 * to the MRU state. 2539 */ 2540 2541 ASSERT(buf->b_arc_access == 0); 2542 buf->b_arc_access = ddi_get_lbolt(); 2543 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2544 arc_change_state(arc_mru, buf, hash_lock); 2545 2546 } else if (buf->b_state == arc_mru) { 2547 now = ddi_get_lbolt(); 2548 2549 /* 2550 * If this buffer is here because of a prefetch, then either: 2551 * - clear the flag if this is a "referencing" read 2552 * (any subsequent access will bump this into the MFU state). 2553 * or 2554 * - move the buffer to the head of the list if this is 2555 * another prefetch (to make it less likely to be evicted). 2556 */ 2557 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2558 if (refcount_count(&buf->b_refcnt) == 0) { 2559 ASSERT(list_link_active(&buf->b_arc_node)); 2560 } else { 2561 buf->b_flags &= ~ARC_PREFETCH; 2562 ARCSTAT_BUMP(arcstat_mru_hits); 2563 } 2564 buf->b_arc_access = now; 2565 return; 2566 } 2567 2568 /* 2569 * This buffer has been "accessed" only once so far, 2570 * but it is still in the cache. Move it to the MFU 2571 * state. 2572 */ 2573 if (now > buf->b_arc_access + ARC_MINTIME) { 2574 /* 2575 * More than 125ms have passed since we 2576 * instantiated this buffer. Move it to the 2577 * most frequently used state. 2578 */ 2579 buf->b_arc_access = now; 2580 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2581 arc_change_state(arc_mfu, buf, hash_lock); 2582 } 2583 ARCSTAT_BUMP(arcstat_mru_hits); 2584 } else if (buf->b_state == arc_mru_ghost) { 2585 arc_state_t *new_state; 2586 /* 2587 * This buffer has been "accessed" recently, but 2588 * was evicted from the cache. Move it to the 2589 * MFU state. 2590 */ 2591 2592 if (buf->b_flags & ARC_PREFETCH) { 2593 new_state = arc_mru; 2594 if (refcount_count(&buf->b_refcnt) > 0) 2595 buf->b_flags &= ~ARC_PREFETCH; 2596 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2597 } else { 2598 new_state = arc_mfu; 2599 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2600 } 2601 2602 buf->b_arc_access = ddi_get_lbolt(); 2603 arc_change_state(new_state, buf, hash_lock); 2604 2605 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 2606 } else if (buf->b_state == arc_mfu) { 2607 /* 2608 * This buffer has been accessed more than once and is 2609 * still in the cache. Keep it in the MFU state. 2610 * 2611 * NOTE: an add_reference() that occurred when we did 2612 * the arc_read() will have kicked this off the list. 2613 * If it was a prefetch, we will explicitly move it to 2614 * the head of the list now. 2615 */ 2616 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2617 ASSERT(refcount_count(&buf->b_refcnt) == 0); 2618 ASSERT(list_link_active(&buf->b_arc_node)); 2619 } 2620 ARCSTAT_BUMP(arcstat_mfu_hits); 2621 buf->b_arc_access = ddi_get_lbolt(); 2622 } else if (buf->b_state == arc_mfu_ghost) { 2623 arc_state_t *new_state = arc_mfu; 2624 /* 2625 * This buffer has been accessed more than once but has 2626 * been evicted from the cache. Move it back to the 2627 * MFU state. 2628 */ 2629 2630 if (buf->b_flags & ARC_PREFETCH) { 2631 /* 2632 * This is a prefetch access... 2633 * move this block back to the MRU state. 2634 */ 2635 ASSERT0(refcount_count(&buf->b_refcnt)); 2636 new_state = arc_mru; 2637 } 2638 2639 buf->b_arc_access = ddi_get_lbolt(); 2640 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2641 arc_change_state(new_state, buf, hash_lock); 2642 2643 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 2644 } else if (buf->b_state == arc_l2c_only) { 2645 /* 2646 * This buffer is on the 2nd Level ARC. 2647 */ 2648 2649 buf->b_arc_access = ddi_get_lbolt(); 2650 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2651 arc_change_state(arc_mfu, buf, hash_lock); 2652 } else { 2653 ASSERT(!"invalid arc state"); 2654 } 2655 } 2656 2657 /* a generic arc_done_func_t which you can use */ 2658 /* ARGSUSED */ 2659 void 2660 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 2661 { 2662 if (zio == NULL || zio->io_error == 0) 2663 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 2664 VERIFY(arc_buf_remove_ref(buf, arg)); 2665 } 2666 2667 /* a generic arc_done_func_t */ 2668 void 2669 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 2670 { 2671 arc_buf_t **bufp = arg; 2672 if (zio && zio->io_error) { 2673 VERIFY(arc_buf_remove_ref(buf, arg)); 2674 *bufp = NULL; 2675 } else { 2676 *bufp = buf; 2677 ASSERT(buf->b_data); 2678 } 2679 } 2680 2681 static void 2682 arc_read_done(zio_t *zio) 2683 { 2684 arc_buf_hdr_t *hdr, *found; 2685 arc_buf_t *buf; 2686 arc_buf_t *abuf; /* buffer we're assigning to callback */ 2687 kmutex_t *hash_lock; 2688 arc_callback_t *callback_list, *acb; 2689 int freeable = FALSE; 2690 2691 buf = zio->io_private; 2692 hdr = buf->b_hdr; 2693 2694 /* 2695 * The hdr was inserted into hash-table and removed from lists 2696 * prior to starting I/O. We should find this header, since 2697 * it's in the hash table, and it should be legit since it's 2698 * not possible to evict it during the I/O. The only possible 2699 * reason for it not to be found is if we were freed during the 2700 * read. 2701 */ 2702 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth, 2703 &hash_lock); 2704 2705 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) || 2706 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 2707 (found == hdr && HDR_L2_READING(hdr))); 2708 2709 hdr->b_flags &= ~ARC_L2_EVICTED; 2710 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH)) 2711 hdr->b_flags &= ~ARC_L2CACHE; 2712 2713 /* byteswap if necessary */ 2714 callback_list = hdr->b_acb; 2715 ASSERT(callback_list != NULL); 2716 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 2717 dmu_object_byteswap_t bswap = 2718 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 2719 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 2720 byteswap_uint64_array : 2721 dmu_ot_byteswap[bswap].ob_func; 2722 func(buf->b_data, hdr->b_size); 2723 } 2724 2725 arc_cksum_compute(buf, B_FALSE); 2726 arc_buf_watch(buf); 2727 2728 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) { 2729 /* 2730 * Only call arc_access on anonymous buffers. This is because 2731 * if we've issued an I/O for an evicted buffer, we've already 2732 * called arc_access (to prevent any simultaneous readers from 2733 * getting confused). 2734 */ 2735 arc_access(hdr, hash_lock); 2736 } 2737 2738 /* create copies of the data buffer for the callers */ 2739 abuf = buf; 2740 for (acb = callback_list; acb; acb = acb->acb_next) { 2741 if (acb->acb_done) { 2742 if (abuf == NULL) { 2743 ARCSTAT_BUMP(arcstat_duplicate_reads); 2744 abuf = arc_buf_clone(buf); 2745 } 2746 acb->acb_buf = abuf; 2747 abuf = NULL; 2748 } 2749 } 2750 hdr->b_acb = NULL; 2751 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 2752 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 2753 if (abuf == buf) { 2754 ASSERT(buf->b_efunc == NULL); 2755 ASSERT(hdr->b_datacnt == 1); 2756 hdr->b_flags |= ARC_BUF_AVAILABLE; 2757 } 2758 2759 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL); 2760 2761 if (zio->io_error != 0) { 2762 hdr->b_flags |= ARC_IO_ERROR; 2763 if (hdr->b_state != arc_anon) 2764 arc_change_state(arc_anon, hdr, hash_lock); 2765 if (HDR_IN_HASH_TABLE(hdr)) 2766 buf_hash_remove(hdr); 2767 freeable = refcount_is_zero(&hdr->b_refcnt); 2768 } 2769 2770 /* 2771 * Broadcast before we drop the hash_lock to avoid the possibility 2772 * that the hdr (and hence the cv) might be freed before we get to 2773 * the cv_broadcast(). 2774 */ 2775 cv_broadcast(&hdr->b_cv); 2776 2777 if (hash_lock) { 2778 mutex_exit(hash_lock); 2779 } else { 2780 /* 2781 * This block was freed while we waited for the read to 2782 * complete. It has been removed from the hash table and 2783 * moved to the anonymous state (so that it won't show up 2784 * in the cache). 2785 */ 2786 ASSERT3P(hdr->b_state, ==, arc_anon); 2787 freeable = refcount_is_zero(&hdr->b_refcnt); 2788 } 2789 2790 /* execute each callback and free its structure */ 2791 while ((acb = callback_list) != NULL) { 2792 if (acb->acb_done) 2793 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 2794 2795 if (acb->acb_zio_dummy != NULL) { 2796 acb->acb_zio_dummy->io_error = zio->io_error; 2797 zio_nowait(acb->acb_zio_dummy); 2798 } 2799 2800 callback_list = acb->acb_next; 2801 kmem_free(acb, sizeof (arc_callback_t)); 2802 } 2803 2804 if (freeable) 2805 arc_hdr_destroy(hdr); 2806 } 2807 2808 /* 2809 * "Read" the block at the specified DVA (in bp) via the 2810 * cache. If the block is found in the cache, invoke the provided 2811 * callback immediately and return. Note that the `zio' parameter 2812 * in the callback will be NULL in this case, since no IO was 2813 * required. If the block is not in the cache pass the read request 2814 * on to the spa with a substitute callback function, so that the 2815 * requested block will be added to the cache. 2816 * 2817 * If a read request arrives for a block that has a read in-progress, 2818 * either wait for the in-progress read to complete (and return the 2819 * results); or, if this is a read with a "done" func, add a record 2820 * to the read to invoke the "done" func when the read completes, 2821 * and return; or just return. 2822 * 2823 * arc_read_done() will invoke all the requested "done" functions 2824 * for readers of this block. 2825 */ 2826 int 2827 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 2828 void *private, int priority, int zio_flags, uint32_t *arc_flags, 2829 const zbookmark_t *zb) 2830 { 2831 arc_buf_hdr_t *hdr; 2832 arc_buf_t *buf = NULL; 2833 kmutex_t *hash_lock; 2834 zio_t *rzio; 2835 uint64_t guid = spa_load_guid(spa); 2836 2837 top: 2838 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp), 2839 &hash_lock); 2840 if (hdr && hdr->b_datacnt > 0) { 2841 2842 *arc_flags |= ARC_CACHED; 2843 2844 if (HDR_IO_IN_PROGRESS(hdr)) { 2845 2846 if (*arc_flags & ARC_WAIT) { 2847 cv_wait(&hdr->b_cv, hash_lock); 2848 mutex_exit(hash_lock); 2849 goto top; 2850 } 2851 ASSERT(*arc_flags & ARC_NOWAIT); 2852 2853 if (done) { 2854 arc_callback_t *acb = NULL; 2855 2856 acb = kmem_zalloc(sizeof (arc_callback_t), 2857 KM_SLEEP); 2858 acb->acb_done = done; 2859 acb->acb_private = private; 2860 if (pio != NULL) 2861 acb->acb_zio_dummy = zio_null(pio, 2862 spa, NULL, NULL, NULL, zio_flags); 2863 2864 ASSERT(acb->acb_done != NULL); 2865 acb->acb_next = hdr->b_acb; 2866 hdr->b_acb = acb; 2867 add_reference(hdr, hash_lock, private); 2868 mutex_exit(hash_lock); 2869 return (0); 2870 } 2871 mutex_exit(hash_lock); 2872 return (0); 2873 } 2874 2875 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 2876 2877 if (done) { 2878 add_reference(hdr, hash_lock, private); 2879 /* 2880 * If this block is already in use, create a new 2881 * copy of the data so that we will be guaranteed 2882 * that arc_release() will always succeed. 2883 */ 2884 buf = hdr->b_buf; 2885 ASSERT(buf); 2886 ASSERT(buf->b_data); 2887 if (HDR_BUF_AVAILABLE(hdr)) { 2888 ASSERT(buf->b_efunc == NULL); 2889 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 2890 } else { 2891 buf = arc_buf_clone(buf); 2892 } 2893 2894 } else if (*arc_flags & ARC_PREFETCH && 2895 refcount_count(&hdr->b_refcnt) == 0) { 2896 hdr->b_flags |= ARC_PREFETCH; 2897 } 2898 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2899 arc_access(hdr, hash_lock); 2900 if (*arc_flags & ARC_L2CACHE) 2901 hdr->b_flags |= ARC_L2CACHE; 2902 if (*arc_flags & ARC_L2COMPRESS) 2903 hdr->b_flags |= ARC_L2COMPRESS; 2904 mutex_exit(hash_lock); 2905 ARCSTAT_BUMP(arcstat_hits); 2906 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 2907 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 2908 data, metadata, hits); 2909 2910 if (done) 2911 done(NULL, buf, private); 2912 } else { 2913 uint64_t size = BP_GET_LSIZE(bp); 2914 arc_callback_t *acb; 2915 vdev_t *vd = NULL; 2916 uint64_t addr = 0; 2917 boolean_t devw = B_FALSE; 2918 2919 if (hdr == NULL) { 2920 /* this block is not in the cache */ 2921 arc_buf_hdr_t *exists; 2922 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 2923 buf = arc_buf_alloc(spa, size, private, type); 2924 hdr = buf->b_hdr; 2925 hdr->b_dva = *BP_IDENTITY(bp); 2926 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 2927 hdr->b_cksum0 = bp->blk_cksum.zc_word[0]; 2928 exists = buf_hash_insert(hdr, &hash_lock); 2929 if (exists) { 2930 /* somebody beat us to the hash insert */ 2931 mutex_exit(hash_lock); 2932 buf_discard_identity(hdr); 2933 (void) arc_buf_remove_ref(buf, private); 2934 goto top; /* restart the IO request */ 2935 } 2936 /* if this is a prefetch, we don't have a reference */ 2937 if (*arc_flags & ARC_PREFETCH) { 2938 (void) remove_reference(hdr, hash_lock, 2939 private); 2940 hdr->b_flags |= ARC_PREFETCH; 2941 } 2942 if (*arc_flags & ARC_L2CACHE) 2943 hdr->b_flags |= ARC_L2CACHE; 2944 if (*arc_flags & ARC_L2COMPRESS) 2945 hdr->b_flags |= ARC_L2COMPRESS; 2946 if (BP_GET_LEVEL(bp) > 0) 2947 hdr->b_flags |= ARC_INDIRECT; 2948 } else { 2949 /* this block is in the ghost cache */ 2950 ASSERT(GHOST_STATE(hdr->b_state)); 2951 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2952 ASSERT0(refcount_count(&hdr->b_refcnt)); 2953 ASSERT(hdr->b_buf == NULL); 2954 2955 /* if this is a prefetch, we don't have a reference */ 2956 if (*arc_flags & ARC_PREFETCH) 2957 hdr->b_flags |= ARC_PREFETCH; 2958 else 2959 add_reference(hdr, hash_lock, private); 2960 if (*arc_flags & ARC_L2CACHE) 2961 hdr->b_flags |= ARC_L2CACHE; 2962 if (*arc_flags & ARC_L2COMPRESS) 2963 hdr->b_flags |= ARC_L2COMPRESS; 2964 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2965 buf->b_hdr = hdr; 2966 buf->b_data = NULL; 2967 buf->b_efunc = NULL; 2968 buf->b_private = NULL; 2969 buf->b_next = NULL; 2970 hdr->b_buf = buf; 2971 ASSERT(hdr->b_datacnt == 0); 2972 hdr->b_datacnt = 1; 2973 arc_get_data_buf(buf); 2974 arc_access(hdr, hash_lock); 2975 } 2976 2977 ASSERT(!GHOST_STATE(hdr->b_state)); 2978 2979 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 2980 acb->acb_done = done; 2981 acb->acb_private = private; 2982 2983 ASSERT(hdr->b_acb == NULL); 2984 hdr->b_acb = acb; 2985 hdr->b_flags |= ARC_IO_IN_PROGRESS; 2986 2987 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL && 2988 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) { 2989 devw = hdr->b_l2hdr->b_dev->l2ad_writing; 2990 addr = hdr->b_l2hdr->b_daddr; 2991 /* 2992 * Lock out device removal. 2993 */ 2994 if (vdev_is_dead(vd) || 2995 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 2996 vd = NULL; 2997 } 2998 2999 mutex_exit(hash_lock); 3000 3001 /* 3002 * At this point, we have a level 1 cache miss. Try again in 3003 * L2ARC if possible. 3004 */ 3005 ASSERT3U(hdr->b_size, ==, size); 3006 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 3007 uint64_t, size, zbookmark_t *, zb); 3008 ARCSTAT_BUMP(arcstat_misses); 3009 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 3010 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3011 data, metadata, misses); 3012 3013 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 3014 /* 3015 * Read from the L2ARC if the following are true: 3016 * 1. The L2ARC vdev was previously cached. 3017 * 2. This buffer still has L2ARC metadata. 3018 * 3. This buffer isn't currently writing to the L2ARC. 3019 * 4. The L2ARC entry wasn't evicted, which may 3020 * also have invalidated the vdev. 3021 * 5. This isn't prefetch and l2arc_noprefetch is set. 3022 */ 3023 if (hdr->b_l2hdr != NULL && 3024 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3025 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3026 l2arc_read_callback_t *cb; 3027 3028 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3029 ARCSTAT_BUMP(arcstat_l2_hits); 3030 3031 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3032 KM_SLEEP); 3033 cb->l2rcb_buf = buf; 3034 cb->l2rcb_spa = spa; 3035 cb->l2rcb_bp = *bp; 3036 cb->l2rcb_zb = *zb; 3037 cb->l2rcb_flags = zio_flags; 3038 cb->l2rcb_compress = hdr->b_l2hdr->b_compress; 3039 3040 ASSERT(addr >= VDEV_LABEL_START_SIZE && 3041 addr + size < vd->vdev_psize - 3042 VDEV_LABEL_END_SIZE); 3043 3044 /* 3045 * l2arc read. The SCL_L2ARC lock will be 3046 * released by l2arc_read_done(). 3047 * Issue a null zio if the underlying buffer 3048 * was squashed to zero size by compression. 3049 */ 3050 if (hdr->b_l2hdr->b_compress == 3051 ZIO_COMPRESS_EMPTY) { 3052 rzio = zio_null(pio, spa, vd, 3053 l2arc_read_done, cb, 3054 zio_flags | ZIO_FLAG_DONT_CACHE | 3055 ZIO_FLAG_CANFAIL | 3056 ZIO_FLAG_DONT_PROPAGATE | 3057 ZIO_FLAG_DONT_RETRY); 3058 } else { 3059 rzio = zio_read_phys(pio, vd, addr, 3060 hdr->b_l2hdr->b_asize, 3061 buf->b_data, ZIO_CHECKSUM_OFF, 3062 l2arc_read_done, cb, priority, 3063 zio_flags | ZIO_FLAG_DONT_CACHE | 3064 ZIO_FLAG_CANFAIL | 3065 ZIO_FLAG_DONT_PROPAGATE | 3066 ZIO_FLAG_DONT_RETRY, B_FALSE); 3067 } 3068 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3069 zio_t *, rzio); 3070 ARCSTAT_INCR(arcstat_l2_read_bytes, 3071 hdr->b_l2hdr->b_asize); 3072 3073 if (*arc_flags & ARC_NOWAIT) { 3074 zio_nowait(rzio); 3075 return (0); 3076 } 3077 3078 ASSERT(*arc_flags & ARC_WAIT); 3079 if (zio_wait(rzio) == 0) 3080 return (0); 3081 3082 /* l2arc read error; goto zio_read() */ 3083 } else { 3084 DTRACE_PROBE1(l2arc__miss, 3085 arc_buf_hdr_t *, hdr); 3086 ARCSTAT_BUMP(arcstat_l2_misses); 3087 if (HDR_L2_WRITING(hdr)) 3088 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3089 spa_config_exit(spa, SCL_L2ARC, vd); 3090 } 3091 } else { 3092 if (vd != NULL) 3093 spa_config_exit(spa, SCL_L2ARC, vd); 3094 if (l2arc_ndev != 0) { 3095 DTRACE_PROBE1(l2arc__miss, 3096 arc_buf_hdr_t *, hdr); 3097 ARCSTAT_BUMP(arcstat_l2_misses); 3098 } 3099 } 3100 3101 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3102 arc_read_done, buf, priority, zio_flags, zb); 3103 3104 if (*arc_flags & ARC_WAIT) 3105 return (zio_wait(rzio)); 3106 3107 ASSERT(*arc_flags & ARC_NOWAIT); 3108 zio_nowait(rzio); 3109 } 3110 return (0); 3111 } 3112 3113 void 3114 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3115 { 3116 ASSERT(buf->b_hdr != NULL); 3117 ASSERT(buf->b_hdr->b_state != arc_anon); 3118 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL); 3119 ASSERT(buf->b_efunc == NULL); 3120 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3121 3122 buf->b_efunc = func; 3123 buf->b_private = private; 3124 } 3125 3126 /* 3127 * Notify the arc that a block was freed, and thus will never be used again. 3128 */ 3129 void 3130 arc_freed(spa_t *spa, const blkptr_t *bp) 3131 { 3132 arc_buf_hdr_t *hdr; 3133 kmutex_t *hash_lock; 3134 uint64_t guid = spa_load_guid(spa); 3135 3136 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp), 3137 &hash_lock); 3138 if (hdr == NULL) 3139 return; 3140 if (HDR_BUF_AVAILABLE(hdr)) { 3141 arc_buf_t *buf = hdr->b_buf; 3142 add_reference(hdr, hash_lock, FTAG); 3143 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3144 mutex_exit(hash_lock); 3145 3146 arc_release(buf, FTAG); 3147 (void) arc_buf_remove_ref(buf, FTAG); 3148 } else { 3149 mutex_exit(hash_lock); 3150 } 3151 3152 } 3153 3154 /* 3155 * This is used by the DMU to let the ARC know that a buffer is 3156 * being evicted, so the ARC should clean up. If this arc buf 3157 * is not yet in the evicted state, it will be put there. 3158 */ 3159 int 3160 arc_buf_evict(arc_buf_t *buf) 3161 { 3162 arc_buf_hdr_t *hdr; 3163 kmutex_t *hash_lock; 3164 arc_buf_t **bufp; 3165 3166 mutex_enter(&buf->b_evict_lock); 3167 hdr = buf->b_hdr; 3168 if (hdr == NULL) { 3169 /* 3170 * We are in arc_do_user_evicts(). 3171 */ 3172 ASSERT(buf->b_data == NULL); 3173 mutex_exit(&buf->b_evict_lock); 3174 return (0); 3175 } else if (buf->b_data == NULL) { 3176 arc_buf_t copy = *buf; /* structure assignment */ 3177 /* 3178 * We are on the eviction list; process this buffer now 3179 * but let arc_do_user_evicts() do the reaping. 3180 */ 3181 buf->b_efunc = NULL; 3182 mutex_exit(&buf->b_evict_lock); 3183 VERIFY(copy.b_efunc(©) == 0); 3184 return (1); 3185 } 3186 hash_lock = HDR_LOCK(hdr); 3187 mutex_enter(hash_lock); 3188 hdr = buf->b_hdr; 3189 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3190 3191 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt); 3192 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3193 3194 /* 3195 * Pull this buffer off of the hdr 3196 */ 3197 bufp = &hdr->b_buf; 3198 while (*bufp != buf) 3199 bufp = &(*bufp)->b_next; 3200 *bufp = buf->b_next; 3201 3202 ASSERT(buf->b_data != NULL); 3203 arc_buf_destroy(buf, FALSE, FALSE); 3204 3205 if (hdr->b_datacnt == 0) { 3206 arc_state_t *old_state = hdr->b_state; 3207 arc_state_t *evicted_state; 3208 3209 ASSERT(hdr->b_buf == NULL); 3210 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 3211 3212 evicted_state = 3213 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3214 3215 mutex_enter(&old_state->arcs_mtx); 3216 mutex_enter(&evicted_state->arcs_mtx); 3217 3218 arc_change_state(evicted_state, hdr, hash_lock); 3219 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3220 hdr->b_flags |= ARC_IN_HASH_TABLE; 3221 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3222 3223 mutex_exit(&evicted_state->arcs_mtx); 3224 mutex_exit(&old_state->arcs_mtx); 3225 } 3226 mutex_exit(hash_lock); 3227 mutex_exit(&buf->b_evict_lock); 3228 3229 VERIFY(buf->b_efunc(buf) == 0); 3230 buf->b_efunc = NULL; 3231 buf->b_private = NULL; 3232 buf->b_hdr = NULL; 3233 buf->b_next = NULL; 3234 kmem_cache_free(buf_cache, buf); 3235 return (1); 3236 } 3237 3238 /* 3239 * Release this buffer from the cache, making it an anonymous buffer. This 3240 * must be done after a read and prior to modifying the buffer contents. 3241 * If the buffer has more than one reference, we must make 3242 * a new hdr for the buffer. 3243 */ 3244 void 3245 arc_release(arc_buf_t *buf, void *tag) 3246 { 3247 arc_buf_hdr_t *hdr; 3248 kmutex_t *hash_lock = NULL; 3249 l2arc_buf_hdr_t *l2hdr; 3250 uint64_t buf_size; 3251 3252 /* 3253 * It would be nice to assert that if it's DMU metadata (level > 3254 * 0 || it's the dnode file), then it must be syncing context. 3255 * But we don't know that information at this level. 3256 */ 3257 3258 mutex_enter(&buf->b_evict_lock); 3259 hdr = buf->b_hdr; 3260 3261 /* this buffer is not on any list */ 3262 ASSERT(refcount_count(&hdr->b_refcnt) > 0); 3263 3264 if (hdr->b_state == arc_anon) { 3265 /* this buffer is already released */ 3266 ASSERT(buf->b_efunc == NULL); 3267 } else { 3268 hash_lock = HDR_LOCK(hdr); 3269 mutex_enter(hash_lock); 3270 hdr = buf->b_hdr; 3271 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3272 } 3273 3274 l2hdr = hdr->b_l2hdr; 3275 if (l2hdr) { 3276 mutex_enter(&l2arc_buflist_mtx); 3277 hdr->b_l2hdr = NULL; 3278 } 3279 buf_size = hdr->b_size; 3280 3281 /* 3282 * Do we have more than one buf? 3283 */ 3284 if (hdr->b_datacnt > 1) { 3285 arc_buf_hdr_t *nhdr; 3286 arc_buf_t **bufp; 3287 uint64_t blksz = hdr->b_size; 3288 uint64_t spa = hdr->b_spa; 3289 arc_buf_contents_t type = hdr->b_type; 3290 uint32_t flags = hdr->b_flags; 3291 3292 ASSERT(hdr->b_buf != buf || buf->b_next != NULL); 3293 /* 3294 * Pull the data off of this hdr and attach it to 3295 * a new anonymous hdr. 3296 */ 3297 (void) remove_reference(hdr, hash_lock, tag); 3298 bufp = &hdr->b_buf; 3299 while (*bufp != buf) 3300 bufp = &(*bufp)->b_next; 3301 *bufp = buf->b_next; 3302 buf->b_next = NULL; 3303 3304 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size); 3305 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size); 3306 if (refcount_is_zero(&hdr->b_refcnt)) { 3307 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 3308 ASSERT3U(*size, >=, hdr->b_size); 3309 atomic_add_64(size, -hdr->b_size); 3310 } 3311 3312 /* 3313 * We're releasing a duplicate user data buffer, update 3314 * our statistics accordingly. 3315 */ 3316 if (hdr->b_type == ARC_BUFC_DATA) { 3317 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3318 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3319 -hdr->b_size); 3320 } 3321 hdr->b_datacnt -= 1; 3322 arc_cksum_verify(buf); 3323 arc_buf_unwatch(buf); 3324 3325 mutex_exit(hash_lock); 3326 3327 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 3328 nhdr->b_size = blksz; 3329 nhdr->b_spa = spa; 3330 nhdr->b_type = type; 3331 nhdr->b_buf = buf; 3332 nhdr->b_state = arc_anon; 3333 nhdr->b_arc_access = 0; 3334 nhdr->b_flags = flags & ARC_L2_WRITING; 3335 nhdr->b_l2hdr = NULL; 3336 nhdr->b_datacnt = 1; 3337 nhdr->b_freeze_cksum = NULL; 3338 (void) refcount_add(&nhdr->b_refcnt, tag); 3339 buf->b_hdr = nhdr; 3340 mutex_exit(&buf->b_evict_lock); 3341 atomic_add_64(&arc_anon->arcs_size, blksz); 3342 } else { 3343 mutex_exit(&buf->b_evict_lock); 3344 ASSERT(refcount_count(&hdr->b_refcnt) == 1); 3345 ASSERT(!list_link_active(&hdr->b_arc_node)); 3346 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3347 if (hdr->b_state != arc_anon) 3348 arc_change_state(arc_anon, hdr, hash_lock); 3349 hdr->b_arc_access = 0; 3350 if (hash_lock) 3351 mutex_exit(hash_lock); 3352 3353 buf_discard_identity(hdr); 3354 arc_buf_thaw(buf); 3355 } 3356 buf->b_efunc = NULL; 3357 buf->b_private = NULL; 3358 3359 if (l2hdr) { 3360 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 3361 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 3362 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 3363 ARCSTAT_INCR(arcstat_l2_size, -buf_size); 3364 mutex_exit(&l2arc_buflist_mtx); 3365 } 3366 } 3367 3368 int 3369 arc_released(arc_buf_t *buf) 3370 { 3371 int released; 3372 3373 mutex_enter(&buf->b_evict_lock); 3374 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon); 3375 mutex_exit(&buf->b_evict_lock); 3376 return (released); 3377 } 3378 3379 int 3380 arc_has_callback(arc_buf_t *buf) 3381 { 3382 int callback; 3383 3384 mutex_enter(&buf->b_evict_lock); 3385 callback = (buf->b_efunc != NULL); 3386 mutex_exit(&buf->b_evict_lock); 3387 return (callback); 3388 } 3389 3390 #ifdef ZFS_DEBUG 3391 int 3392 arc_referenced(arc_buf_t *buf) 3393 { 3394 int referenced; 3395 3396 mutex_enter(&buf->b_evict_lock); 3397 referenced = (refcount_count(&buf->b_hdr->b_refcnt)); 3398 mutex_exit(&buf->b_evict_lock); 3399 return (referenced); 3400 } 3401 #endif 3402 3403 static void 3404 arc_write_ready(zio_t *zio) 3405 { 3406 arc_write_callback_t *callback = zio->io_private; 3407 arc_buf_t *buf = callback->awcb_buf; 3408 arc_buf_hdr_t *hdr = buf->b_hdr; 3409 3410 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt)); 3411 callback->awcb_ready(zio, buf, callback->awcb_private); 3412 3413 /* 3414 * If the IO is already in progress, then this is a re-write 3415 * attempt, so we need to thaw and re-compute the cksum. 3416 * It is the responsibility of the callback to handle the 3417 * accounting for any re-write attempt. 3418 */ 3419 if (HDR_IO_IN_PROGRESS(hdr)) { 3420 mutex_enter(&hdr->b_freeze_lock); 3421 if (hdr->b_freeze_cksum != NULL) { 3422 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 3423 hdr->b_freeze_cksum = NULL; 3424 } 3425 mutex_exit(&hdr->b_freeze_lock); 3426 } 3427 arc_cksum_compute(buf, B_FALSE); 3428 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3429 } 3430 3431 static void 3432 arc_write_done(zio_t *zio) 3433 { 3434 arc_write_callback_t *callback = zio->io_private; 3435 arc_buf_t *buf = callback->awcb_buf; 3436 arc_buf_hdr_t *hdr = buf->b_hdr; 3437 3438 ASSERT(hdr->b_acb == NULL); 3439 3440 if (zio->io_error == 0) { 3441 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 3442 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 3443 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0]; 3444 } else { 3445 ASSERT(BUF_EMPTY(hdr)); 3446 } 3447 3448 /* 3449 * If the block to be written was all-zero, we may have 3450 * compressed it away. In this case no write was performed 3451 * so there will be no dva/birth/checksum. The buffer must 3452 * therefore remain anonymous (and uncached). 3453 */ 3454 if (!BUF_EMPTY(hdr)) { 3455 arc_buf_hdr_t *exists; 3456 kmutex_t *hash_lock; 3457 3458 ASSERT(zio->io_error == 0); 3459 3460 arc_cksum_verify(buf); 3461 3462 exists = buf_hash_insert(hdr, &hash_lock); 3463 if (exists) { 3464 /* 3465 * This can only happen if we overwrite for 3466 * sync-to-convergence, because we remove 3467 * buffers from the hash table when we arc_free(). 3468 */ 3469 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 3470 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3471 panic("bad overwrite, hdr=%p exists=%p", 3472 (void *)hdr, (void *)exists); 3473 ASSERT(refcount_is_zero(&exists->b_refcnt)); 3474 arc_change_state(arc_anon, exists, hash_lock); 3475 mutex_exit(hash_lock); 3476 arc_hdr_destroy(exists); 3477 exists = buf_hash_insert(hdr, &hash_lock); 3478 ASSERT3P(exists, ==, NULL); 3479 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 3480 /* nopwrite */ 3481 ASSERT(zio->io_prop.zp_nopwrite); 3482 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3483 panic("bad nopwrite, hdr=%p exists=%p", 3484 (void *)hdr, (void *)exists); 3485 } else { 3486 /* Dedup */ 3487 ASSERT(hdr->b_datacnt == 1); 3488 ASSERT(hdr->b_state == arc_anon); 3489 ASSERT(BP_GET_DEDUP(zio->io_bp)); 3490 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 3491 } 3492 } 3493 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3494 /* if it's not anon, we are doing a scrub */ 3495 if (!exists && hdr->b_state == arc_anon) 3496 arc_access(hdr, hash_lock); 3497 mutex_exit(hash_lock); 3498 } else { 3499 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3500 } 3501 3502 ASSERT(!refcount_is_zero(&hdr->b_refcnt)); 3503 callback->awcb_done(zio, buf, callback->awcb_private); 3504 3505 kmem_free(callback, sizeof (arc_write_callback_t)); 3506 } 3507 3508 zio_t * 3509 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 3510 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 3511 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *done, 3512 void *private, int priority, int zio_flags, const zbookmark_t *zb) 3513 { 3514 arc_buf_hdr_t *hdr = buf->b_hdr; 3515 arc_write_callback_t *callback; 3516 zio_t *zio; 3517 3518 ASSERT(ready != NULL); 3519 ASSERT(done != NULL); 3520 ASSERT(!HDR_IO_ERROR(hdr)); 3521 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0); 3522 ASSERT(hdr->b_acb == NULL); 3523 if (l2arc) 3524 hdr->b_flags |= ARC_L2CACHE; 3525 if (l2arc_compress) 3526 hdr->b_flags |= ARC_L2COMPRESS; 3527 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 3528 callback->awcb_ready = ready; 3529 callback->awcb_done = done; 3530 callback->awcb_private = private; 3531 callback->awcb_buf = buf; 3532 3533 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 3534 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb); 3535 3536 return (zio); 3537 } 3538 3539 static int 3540 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg) 3541 { 3542 #ifdef _KERNEL 3543 uint64_t available_memory = ptob(freemem); 3544 static uint64_t page_load = 0; 3545 static uint64_t last_txg = 0; 3546 3547 #if defined(__i386) 3548 available_memory = 3549 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 3550 #endif 3551 if (available_memory >= zfs_write_limit_max) 3552 return (0); 3553 3554 if (txg > last_txg) { 3555 last_txg = txg; 3556 page_load = 0; 3557 } 3558 /* 3559 * If we are in pageout, we know that memory is already tight, 3560 * the arc is already going to be evicting, so we just want to 3561 * continue to let page writes occur as quickly as possible. 3562 */ 3563 if (curproc == proc_pageout) { 3564 if (page_load > MAX(ptob(minfree), available_memory) / 4) 3565 return (SET_ERROR(ERESTART)); 3566 /* Note: reserve is inflated, so we deflate */ 3567 page_load += reserve / 8; 3568 return (0); 3569 } else if (page_load > 0 && arc_reclaim_needed()) { 3570 /* memory is low, delay before restarting */ 3571 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3572 return (SET_ERROR(EAGAIN)); 3573 } 3574 page_load = 0; 3575 3576 if (arc_size > arc_c_min) { 3577 uint64_t evictable_memory = 3578 arc_mru->arcs_lsize[ARC_BUFC_DATA] + 3579 arc_mru->arcs_lsize[ARC_BUFC_METADATA] + 3580 arc_mfu->arcs_lsize[ARC_BUFC_DATA] + 3581 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]; 3582 available_memory += MIN(evictable_memory, arc_size - arc_c_min); 3583 } 3584 3585 if (inflight_data > available_memory / 4) { 3586 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3587 return (SET_ERROR(ERESTART)); 3588 } 3589 #endif 3590 return (0); 3591 } 3592 3593 void 3594 arc_tempreserve_clear(uint64_t reserve) 3595 { 3596 atomic_add_64(&arc_tempreserve, -reserve); 3597 ASSERT((int64_t)arc_tempreserve >= 0); 3598 } 3599 3600 int 3601 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 3602 { 3603 int error; 3604 uint64_t anon_size; 3605 3606 #ifdef ZFS_DEBUG 3607 /* 3608 * Once in a while, fail for no reason. Everything should cope. 3609 */ 3610 if (spa_get_random(10000) == 0) { 3611 dprintf("forcing random failure\n"); 3612 return (SET_ERROR(ERESTART)); 3613 } 3614 #endif 3615 if (reserve > arc_c/4 && !arc_no_grow) 3616 arc_c = MIN(arc_c_max, reserve * 4); 3617 if (reserve > arc_c) 3618 return (SET_ERROR(ENOMEM)); 3619 3620 /* 3621 * Don't count loaned bufs as in flight dirty data to prevent long 3622 * network delays from blocking transactions that are ready to be 3623 * assigned to a txg. 3624 */ 3625 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 3626 3627 /* 3628 * Writes will, almost always, require additional memory allocations 3629 * in order to compress/encrypt/etc the data. We therefore need to 3630 * make sure that there is sufficient available memory for this. 3631 */ 3632 if (error = arc_memory_throttle(reserve, anon_size, txg)) 3633 return (error); 3634 3635 /* 3636 * Throttle writes when the amount of dirty data in the cache 3637 * gets too large. We try to keep the cache less than half full 3638 * of dirty blocks so that our sync times don't grow too large. 3639 * Note: if two requests come in concurrently, we might let them 3640 * both succeed, when one of them should fail. Not a huge deal. 3641 */ 3642 3643 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 3644 anon_size > arc_c / 4) { 3645 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 3646 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 3647 arc_tempreserve>>10, 3648 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 3649 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 3650 reserve>>10, arc_c>>10); 3651 return (SET_ERROR(ERESTART)); 3652 } 3653 atomic_add_64(&arc_tempreserve, reserve); 3654 return (0); 3655 } 3656 3657 void 3658 arc_init(void) 3659 { 3660 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 3661 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 3662 3663 /* Convert seconds to clock ticks */ 3664 arc_min_prefetch_lifespan = 1 * hz; 3665 3666 /* Start out with 1/8 of all memory */ 3667 arc_c = physmem * PAGESIZE / 8; 3668 3669 #ifdef _KERNEL 3670 /* 3671 * On architectures where the physical memory can be larger 3672 * than the addressable space (intel in 32-bit mode), we may 3673 * need to limit the cache to 1/8 of VM size. 3674 */ 3675 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 3676 #endif 3677 3678 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 3679 arc_c_min = MAX(arc_c / 4, 64<<20); 3680 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 3681 if (arc_c * 8 >= 1<<30) 3682 arc_c_max = (arc_c * 8) - (1<<30); 3683 else 3684 arc_c_max = arc_c_min; 3685 arc_c_max = MAX(arc_c * 6, arc_c_max); 3686 3687 /* 3688 * Allow the tunables to override our calculations if they are 3689 * reasonable (ie. over 64MB) 3690 */ 3691 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE) 3692 arc_c_max = zfs_arc_max; 3693 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max) 3694 arc_c_min = zfs_arc_min; 3695 3696 arc_c = arc_c_max; 3697 arc_p = (arc_c >> 1); 3698 3699 /* limit meta-data to 1/4 of the arc capacity */ 3700 arc_meta_limit = arc_c_max / 4; 3701 3702 /* Allow the tunable to override if it is reasonable */ 3703 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 3704 arc_meta_limit = zfs_arc_meta_limit; 3705 3706 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 3707 arc_c_min = arc_meta_limit / 2; 3708 3709 if (zfs_arc_grow_retry > 0) 3710 arc_grow_retry = zfs_arc_grow_retry; 3711 3712 if (zfs_arc_shrink_shift > 0) 3713 arc_shrink_shift = zfs_arc_shrink_shift; 3714 3715 if (zfs_arc_p_min_shift > 0) 3716 arc_p_min_shift = zfs_arc_p_min_shift; 3717 3718 /* if kmem_flags are set, lets try to use less memory */ 3719 if (kmem_debugging()) 3720 arc_c = arc_c / 2; 3721 if (arc_c < arc_c_min) 3722 arc_c = arc_c_min; 3723 3724 arc_anon = &ARC_anon; 3725 arc_mru = &ARC_mru; 3726 arc_mru_ghost = &ARC_mru_ghost; 3727 arc_mfu = &ARC_mfu; 3728 arc_mfu_ghost = &ARC_mfu_ghost; 3729 arc_l2c_only = &ARC_l2c_only; 3730 arc_size = 0; 3731 3732 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3733 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3734 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3735 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3736 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3737 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3738 3739 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 3740 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3741 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 3742 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3743 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 3744 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3745 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 3746 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3747 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 3748 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3749 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 3750 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3751 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 3752 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3753 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 3754 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3755 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 3756 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3757 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 3758 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3759 3760 buf_init(); 3761 3762 arc_thread_exit = 0; 3763 arc_eviction_list = NULL; 3764 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 3765 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 3766 3767 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 3768 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 3769 3770 if (arc_ksp != NULL) { 3771 arc_ksp->ks_data = &arc_stats; 3772 kstat_install(arc_ksp); 3773 } 3774 3775 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 3776 TS_RUN, minclsyspri); 3777 3778 arc_dead = FALSE; 3779 arc_warm = B_FALSE; 3780 3781 if (zfs_write_limit_max == 0) 3782 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift; 3783 else 3784 zfs_write_limit_shift = 0; 3785 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL); 3786 } 3787 3788 void 3789 arc_fini(void) 3790 { 3791 mutex_enter(&arc_reclaim_thr_lock); 3792 arc_thread_exit = 1; 3793 while (arc_thread_exit != 0) 3794 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 3795 mutex_exit(&arc_reclaim_thr_lock); 3796 3797 arc_flush(NULL); 3798 3799 arc_dead = TRUE; 3800 3801 if (arc_ksp != NULL) { 3802 kstat_delete(arc_ksp); 3803 arc_ksp = NULL; 3804 } 3805 3806 mutex_destroy(&arc_eviction_mtx); 3807 mutex_destroy(&arc_reclaim_thr_lock); 3808 cv_destroy(&arc_reclaim_thr_cv); 3809 3810 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 3811 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 3812 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 3813 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 3814 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 3815 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 3816 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 3817 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 3818 3819 mutex_destroy(&arc_anon->arcs_mtx); 3820 mutex_destroy(&arc_mru->arcs_mtx); 3821 mutex_destroy(&arc_mru_ghost->arcs_mtx); 3822 mutex_destroy(&arc_mfu->arcs_mtx); 3823 mutex_destroy(&arc_mfu_ghost->arcs_mtx); 3824 mutex_destroy(&arc_l2c_only->arcs_mtx); 3825 3826 mutex_destroy(&zfs_write_limit_lock); 3827 3828 buf_fini(); 3829 3830 ASSERT(arc_loaned_bytes == 0); 3831 } 3832 3833 /* 3834 * Level 2 ARC 3835 * 3836 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 3837 * It uses dedicated storage devices to hold cached data, which are populated 3838 * using large infrequent writes. The main role of this cache is to boost 3839 * the performance of random read workloads. The intended L2ARC devices 3840 * include short-stroked disks, solid state disks, and other media with 3841 * substantially faster read latency than disk. 3842 * 3843 * +-----------------------+ 3844 * | ARC | 3845 * +-----------------------+ 3846 * | ^ ^ 3847 * | | | 3848 * l2arc_feed_thread() arc_read() 3849 * | | | 3850 * | l2arc read | 3851 * V | | 3852 * +---------------+ | 3853 * | L2ARC | | 3854 * +---------------+ | 3855 * | ^ | 3856 * l2arc_write() | | 3857 * | | | 3858 * V | | 3859 * +-------+ +-------+ 3860 * | vdev | | vdev | 3861 * | cache | | cache | 3862 * +-------+ +-------+ 3863 * +=========+ .-----. 3864 * : L2ARC : |-_____-| 3865 * : devices : | Disks | 3866 * +=========+ `-_____-' 3867 * 3868 * Read requests are satisfied from the following sources, in order: 3869 * 3870 * 1) ARC 3871 * 2) vdev cache of L2ARC devices 3872 * 3) L2ARC devices 3873 * 4) vdev cache of disks 3874 * 5) disks 3875 * 3876 * Some L2ARC device types exhibit extremely slow write performance. 3877 * To accommodate for this there are some significant differences between 3878 * the L2ARC and traditional cache design: 3879 * 3880 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 3881 * the ARC behave as usual, freeing buffers and placing headers on ghost 3882 * lists. The ARC does not send buffers to the L2ARC during eviction as 3883 * this would add inflated write latencies for all ARC memory pressure. 3884 * 3885 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 3886 * It does this by periodically scanning buffers from the eviction-end of 3887 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 3888 * not already there. It scans until a headroom of buffers is satisfied, 3889 * which itself is a buffer for ARC eviction. If a compressible buffer is 3890 * found during scanning and selected for writing to an L2ARC device, we 3891 * temporarily boost scanning headroom during the next scan cycle to make 3892 * sure we adapt to compression effects (which might significantly reduce 3893 * the data volume we write to L2ARC). The thread that does this is 3894 * l2arc_feed_thread(), illustrated below; example sizes are included to 3895 * provide a better sense of ratio than this diagram: 3896 * 3897 * head --> tail 3898 * +---------------------+----------+ 3899 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 3900 * +---------------------+----------+ | o L2ARC eligible 3901 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 3902 * +---------------------+----------+ | 3903 * 15.9 Gbytes ^ 32 Mbytes | 3904 * headroom | 3905 * l2arc_feed_thread() 3906 * | 3907 * l2arc write hand <--[oooo]--' 3908 * | 8 Mbyte 3909 * | write max 3910 * V 3911 * +==============================+ 3912 * L2ARC dev |####|#|###|###| |####| ... | 3913 * +==============================+ 3914 * 32 Gbytes 3915 * 3916 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 3917 * evicted, then the L2ARC has cached a buffer much sooner than it probably 3918 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 3919 * safe to say that this is an uncommon case, since buffers at the end of 3920 * the ARC lists have moved there due to inactivity. 3921 * 3922 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 3923 * then the L2ARC simply misses copying some buffers. This serves as a 3924 * pressure valve to prevent heavy read workloads from both stalling the ARC 3925 * with waits and clogging the L2ARC with writes. This also helps prevent 3926 * the potential for the L2ARC to churn if it attempts to cache content too 3927 * quickly, such as during backups of the entire pool. 3928 * 3929 * 5. After system boot and before the ARC has filled main memory, there are 3930 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 3931 * lists can remain mostly static. Instead of searching from tail of these 3932 * lists as pictured, the l2arc_feed_thread() will search from the list heads 3933 * for eligible buffers, greatly increasing its chance of finding them. 3934 * 3935 * The L2ARC device write speed is also boosted during this time so that 3936 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 3937 * there are no L2ARC reads, and no fear of degrading read performance 3938 * through increased writes. 3939 * 3940 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 3941 * the vdev queue can aggregate them into larger and fewer writes. Each 3942 * device is written to in a rotor fashion, sweeping writes through 3943 * available space then repeating. 3944 * 3945 * 7. The L2ARC does not store dirty content. It never needs to flush 3946 * write buffers back to disk based storage. 3947 * 3948 * 8. If an ARC buffer is written (and dirtied) which also exists in the 3949 * L2ARC, the now stale L2ARC buffer is immediately dropped. 3950 * 3951 * The performance of the L2ARC can be tweaked by a number of tunables, which 3952 * may be necessary for different workloads: 3953 * 3954 * l2arc_write_max max write bytes per interval 3955 * l2arc_write_boost extra write bytes during device warmup 3956 * l2arc_noprefetch skip caching prefetched buffers 3957 * l2arc_headroom number of max device writes to precache 3958 * l2arc_headroom_boost when we find compressed buffers during ARC 3959 * scanning, we multiply headroom by this 3960 * percentage factor for the next scan cycle, 3961 * since more compressed buffers are likely to 3962 * be present 3963 * l2arc_feed_secs seconds between L2ARC writing 3964 * 3965 * Tunables may be removed or added as future performance improvements are 3966 * integrated, and also may become zpool properties. 3967 * 3968 * There are three key functions that control how the L2ARC warms up: 3969 * 3970 * l2arc_write_eligible() check if a buffer is eligible to cache 3971 * l2arc_write_size() calculate how much to write 3972 * l2arc_write_interval() calculate sleep delay between writes 3973 * 3974 * These three functions determine what to write, how much, and how quickly 3975 * to send writes. 3976 */ 3977 3978 static boolean_t 3979 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab) 3980 { 3981 /* 3982 * A buffer is *not* eligible for the L2ARC if it: 3983 * 1. belongs to a different spa. 3984 * 2. is already cached on the L2ARC. 3985 * 3. has an I/O in progress (it may be an incomplete read). 3986 * 4. is flagged not eligible (zfs property). 3987 */ 3988 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL || 3989 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab)) 3990 return (B_FALSE); 3991 3992 return (B_TRUE); 3993 } 3994 3995 static uint64_t 3996 l2arc_write_size(void) 3997 { 3998 uint64_t size; 3999 4000 /* 4001 * Make sure our globals have meaningful values in case the user 4002 * altered them. 4003 */ 4004 size = l2arc_write_max; 4005 if (size == 0) { 4006 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 4007 "be greater than zero, resetting it to the default (%d)", 4008 L2ARC_WRITE_SIZE); 4009 size = l2arc_write_max = L2ARC_WRITE_SIZE; 4010 } 4011 4012 if (arc_warm == B_FALSE) 4013 size += l2arc_write_boost; 4014 4015 return (size); 4016 4017 } 4018 4019 static clock_t 4020 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 4021 { 4022 clock_t interval, next, now; 4023 4024 /* 4025 * If the ARC lists are busy, increase our write rate; if the 4026 * lists are stale, idle back. This is achieved by checking 4027 * how much we previously wrote - if it was more than half of 4028 * what we wanted, schedule the next write much sooner. 4029 */ 4030 if (l2arc_feed_again && wrote > (wanted / 2)) 4031 interval = (hz * l2arc_feed_min_ms) / 1000; 4032 else 4033 interval = hz * l2arc_feed_secs; 4034 4035 now = ddi_get_lbolt(); 4036 next = MAX(now, MIN(now + interval, began + interval)); 4037 4038 return (next); 4039 } 4040 4041 static void 4042 l2arc_hdr_stat_add(void) 4043 { 4044 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE); 4045 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE); 4046 } 4047 4048 static void 4049 l2arc_hdr_stat_remove(void) 4050 { 4051 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE)); 4052 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE); 4053 } 4054 4055 /* 4056 * Cycle through L2ARC devices. This is how L2ARC load balances. 4057 * If a device is returned, this also returns holding the spa config lock. 4058 */ 4059 static l2arc_dev_t * 4060 l2arc_dev_get_next(void) 4061 { 4062 l2arc_dev_t *first, *next = NULL; 4063 4064 /* 4065 * Lock out the removal of spas (spa_namespace_lock), then removal 4066 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 4067 * both locks will be dropped and a spa config lock held instead. 4068 */ 4069 mutex_enter(&spa_namespace_lock); 4070 mutex_enter(&l2arc_dev_mtx); 4071 4072 /* if there are no vdevs, there is nothing to do */ 4073 if (l2arc_ndev == 0) 4074 goto out; 4075 4076 first = NULL; 4077 next = l2arc_dev_last; 4078 do { 4079 /* loop around the list looking for a non-faulted vdev */ 4080 if (next == NULL) { 4081 next = list_head(l2arc_dev_list); 4082 } else { 4083 next = list_next(l2arc_dev_list, next); 4084 if (next == NULL) 4085 next = list_head(l2arc_dev_list); 4086 } 4087 4088 /* if we have come back to the start, bail out */ 4089 if (first == NULL) 4090 first = next; 4091 else if (next == first) 4092 break; 4093 4094 } while (vdev_is_dead(next->l2ad_vdev)); 4095 4096 /* if we were unable to find any usable vdevs, return NULL */ 4097 if (vdev_is_dead(next->l2ad_vdev)) 4098 next = NULL; 4099 4100 l2arc_dev_last = next; 4101 4102 out: 4103 mutex_exit(&l2arc_dev_mtx); 4104 4105 /* 4106 * Grab the config lock to prevent the 'next' device from being 4107 * removed while we are writing to it. 4108 */ 4109 if (next != NULL) 4110 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4111 mutex_exit(&spa_namespace_lock); 4112 4113 return (next); 4114 } 4115 4116 /* 4117 * Free buffers that were tagged for destruction. 4118 */ 4119 static void 4120 l2arc_do_free_on_write() 4121 { 4122 list_t *buflist; 4123 l2arc_data_free_t *df, *df_prev; 4124 4125 mutex_enter(&l2arc_free_on_write_mtx); 4126 buflist = l2arc_free_on_write; 4127 4128 for (df = list_tail(buflist); df; df = df_prev) { 4129 df_prev = list_prev(buflist, df); 4130 ASSERT(df->l2df_data != NULL); 4131 ASSERT(df->l2df_func != NULL); 4132 df->l2df_func(df->l2df_data, df->l2df_size); 4133 list_remove(buflist, df); 4134 kmem_free(df, sizeof (l2arc_data_free_t)); 4135 } 4136 4137 mutex_exit(&l2arc_free_on_write_mtx); 4138 } 4139 4140 /* 4141 * A write to a cache device has completed. Update all headers to allow 4142 * reads from these buffers to begin. 4143 */ 4144 static void 4145 l2arc_write_done(zio_t *zio) 4146 { 4147 l2arc_write_callback_t *cb; 4148 l2arc_dev_t *dev; 4149 list_t *buflist; 4150 arc_buf_hdr_t *head, *ab, *ab_prev; 4151 l2arc_buf_hdr_t *abl2; 4152 kmutex_t *hash_lock; 4153 4154 cb = zio->io_private; 4155 ASSERT(cb != NULL); 4156 dev = cb->l2wcb_dev; 4157 ASSERT(dev != NULL); 4158 head = cb->l2wcb_head; 4159 ASSERT(head != NULL); 4160 buflist = dev->l2ad_buflist; 4161 ASSERT(buflist != NULL); 4162 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4163 l2arc_write_callback_t *, cb); 4164 4165 if (zio->io_error != 0) 4166 ARCSTAT_BUMP(arcstat_l2_writes_error); 4167 4168 mutex_enter(&l2arc_buflist_mtx); 4169 4170 /* 4171 * All writes completed, or an error was hit. 4172 */ 4173 for (ab = list_prev(buflist, head); ab; ab = ab_prev) { 4174 ab_prev = list_prev(buflist, ab); 4175 4176 hash_lock = HDR_LOCK(ab); 4177 if (!mutex_tryenter(hash_lock)) { 4178 /* 4179 * This buffer misses out. It may be in a stage 4180 * of eviction. Its ARC_L2_WRITING flag will be 4181 * left set, denying reads to this buffer. 4182 */ 4183 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4184 continue; 4185 } 4186 4187 abl2 = ab->b_l2hdr; 4188 4189 /* 4190 * Release the temporary compressed buffer as soon as possible. 4191 */ 4192 if (abl2->b_compress != ZIO_COMPRESS_OFF) 4193 l2arc_release_cdata_buf(ab); 4194 4195 if (zio->io_error != 0) { 4196 /* 4197 * Error - drop L2ARC entry. 4198 */ 4199 list_remove(buflist, ab); 4200 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4201 ab->b_l2hdr = NULL; 4202 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4203 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4204 } 4205 4206 /* 4207 * Allow ARC to begin reads to this L2ARC entry. 4208 */ 4209 ab->b_flags &= ~ARC_L2_WRITING; 4210 4211 mutex_exit(hash_lock); 4212 } 4213 4214 atomic_inc_64(&l2arc_writes_done); 4215 list_remove(buflist, head); 4216 kmem_cache_free(hdr_cache, head); 4217 mutex_exit(&l2arc_buflist_mtx); 4218 4219 l2arc_do_free_on_write(); 4220 4221 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4222 } 4223 4224 /* 4225 * A read to a cache device completed. Validate buffer contents before 4226 * handing over to the regular ARC routines. 4227 */ 4228 static void 4229 l2arc_read_done(zio_t *zio) 4230 { 4231 l2arc_read_callback_t *cb; 4232 arc_buf_hdr_t *hdr; 4233 arc_buf_t *buf; 4234 kmutex_t *hash_lock; 4235 int equal; 4236 4237 ASSERT(zio->io_vd != NULL); 4238 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4239 4240 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4241 4242 cb = zio->io_private; 4243 ASSERT(cb != NULL); 4244 buf = cb->l2rcb_buf; 4245 ASSERT(buf != NULL); 4246 4247 hash_lock = HDR_LOCK(buf->b_hdr); 4248 mutex_enter(hash_lock); 4249 hdr = buf->b_hdr; 4250 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4251 4252 /* 4253 * If the buffer was compressed, decompress it first. 4254 */ 4255 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 4256 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 4257 ASSERT(zio->io_data != NULL); 4258 4259 /* 4260 * Check this survived the L2ARC journey. 4261 */ 4262 equal = arc_cksum_equal(buf); 4263 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4264 mutex_exit(hash_lock); 4265 zio->io_private = buf; 4266 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4267 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4268 arc_read_done(zio); 4269 } else { 4270 mutex_exit(hash_lock); 4271 /* 4272 * Buffer didn't survive caching. Increment stats and 4273 * reissue to the original storage device. 4274 */ 4275 if (zio->io_error != 0) { 4276 ARCSTAT_BUMP(arcstat_l2_io_error); 4277 } else { 4278 zio->io_error = SET_ERROR(EIO); 4279 } 4280 if (!equal) 4281 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4282 4283 /* 4284 * If there's no waiter, issue an async i/o to the primary 4285 * storage now. If there *is* a waiter, the caller must 4286 * issue the i/o in a context where it's OK to block. 4287 */ 4288 if (zio->io_waiter == NULL) { 4289 zio_t *pio = zio_unique_parent(zio); 4290 4291 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4292 4293 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4294 buf->b_data, zio->io_size, arc_read_done, buf, 4295 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4296 } 4297 } 4298 4299 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4300 } 4301 4302 /* 4303 * This is the list priority from which the L2ARC will search for pages to 4304 * cache. This is used within loops (0..3) to cycle through lists in the 4305 * desired order. This order can have a significant effect on cache 4306 * performance. 4307 * 4308 * Currently the metadata lists are hit first, MFU then MRU, followed by 4309 * the data lists. This function returns a locked list, and also returns 4310 * the lock pointer. 4311 */ 4312 static list_t * 4313 l2arc_list_locked(int list_num, kmutex_t **lock) 4314 { 4315 list_t *list = NULL; 4316 4317 ASSERT(list_num >= 0 && list_num <= 3); 4318 4319 switch (list_num) { 4320 case 0: 4321 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 4322 *lock = &arc_mfu->arcs_mtx; 4323 break; 4324 case 1: 4325 list = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 4326 *lock = &arc_mru->arcs_mtx; 4327 break; 4328 case 2: 4329 list = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 4330 *lock = &arc_mfu->arcs_mtx; 4331 break; 4332 case 3: 4333 list = &arc_mru->arcs_list[ARC_BUFC_DATA]; 4334 *lock = &arc_mru->arcs_mtx; 4335 break; 4336 } 4337 4338 ASSERT(!(MUTEX_HELD(*lock))); 4339 mutex_enter(*lock); 4340 return (list); 4341 } 4342 4343 /* 4344 * Evict buffers from the device write hand to the distance specified in 4345 * bytes. This distance may span populated buffers, it may span nothing. 4346 * This is clearing a region on the L2ARC device ready for writing. 4347 * If the 'all' boolean is set, every buffer is evicted. 4348 */ 4349 static void 4350 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 4351 { 4352 list_t *buflist; 4353 l2arc_buf_hdr_t *abl2; 4354 arc_buf_hdr_t *ab, *ab_prev; 4355 kmutex_t *hash_lock; 4356 uint64_t taddr; 4357 4358 buflist = dev->l2ad_buflist; 4359 4360 if (buflist == NULL) 4361 return; 4362 4363 if (!all && dev->l2ad_first) { 4364 /* 4365 * This is the first sweep through the device. There is 4366 * nothing to evict. 4367 */ 4368 return; 4369 } 4370 4371 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 4372 /* 4373 * When nearing the end of the device, evict to the end 4374 * before the device write hand jumps to the start. 4375 */ 4376 taddr = dev->l2ad_end; 4377 } else { 4378 taddr = dev->l2ad_hand + distance; 4379 } 4380 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 4381 uint64_t, taddr, boolean_t, all); 4382 4383 top: 4384 mutex_enter(&l2arc_buflist_mtx); 4385 for (ab = list_tail(buflist); ab; ab = ab_prev) { 4386 ab_prev = list_prev(buflist, ab); 4387 4388 hash_lock = HDR_LOCK(ab); 4389 if (!mutex_tryenter(hash_lock)) { 4390 /* 4391 * Missed the hash lock. Retry. 4392 */ 4393 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 4394 mutex_exit(&l2arc_buflist_mtx); 4395 mutex_enter(hash_lock); 4396 mutex_exit(hash_lock); 4397 goto top; 4398 } 4399 4400 if (HDR_L2_WRITE_HEAD(ab)) { 4401 /* 4402 * We hit a write head node. Leave it for 4403 * l2arc_write_done(). 4404 */ 4405 list_remove(buflist, ab); 4406 mutex_exit(hash_lock); 4407 continue; 4408 } 4409 4410 if (!all && ab->b_l2hdr != NULL && 4411 (ab->b_l2hdr->b_daddr > taddr || 4412 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) { 4413 /* 4414 * We've evicted to the target address, 4415 * or the end of the device. 4416 */ 4417 mutex_exit(hash_lock); 4418 break; 4419 } 4420 4421 if (HDR_FREE_IN_PROGRESS(ab)) { 4422 /* 4423 * Already on the path to destruction. 4424 */ 4425 mutex_exit(hash_lock); 4426 continue; 4427 } 4428 4429 if (ab->b_state == arc_l2c_only) { 4430 ASSERT(!HDR_L2_READING(ab)); 4431 /* 4432 * This doesn't exist in the ARC. Destroy. 4433 * arc_hdr_destroy() will call list_remove() 4434 * and decrement arcstat_l2_size. 4435 */ 4436 arc_change_state(arc_anon, ab, hash_lock); 4437 arc_hdr_destroy(ab); 4438 } else { 4439 /* 4440 * Invalidate issued or about to be issued 4441 * reads, since we may be about to write 4442 * over this location. 4443 */ 4444 if (HDR_L2_READING(ab)) { 4445 ARCSTAT_BUMP(arcstat_l2_evict_reading); 4446 ab->b_flags |= ARC_L2_EVICTED; 4447 } 4448 4449 /* 4450 * Tell ARC this no longer exists in L2ARC. 4451 */ 4452 if (ab->b_l2hdr != NULL) { 4453 abl2 = ab->b_l2hdr; 4454 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4455 ab->b_l2hdr = NULL; 4456 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4457 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4458 } 4459 list_remove(buflist, ab); 4460 4461 /* 4462 * This may have been leftover after a 4463 * failed write. 4464 */ 4465 ab->b_flags &= ~ARC_L2_WRITING; 4466 } 4467 mutex_exit(hash_lock); 4468 } 4469 mutex_exit(&l2arc_buflist_mtx); 4470 4471 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0); 4472 dev->l2ad_evict = taddr; 4473 } 4474 4475 /* 4476 * Find and write ARC buffers to the L2ARC device. 4477 * 4478 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid 4479 * for reading until they have completed writing. 4480 * The headroom_boost is an in-out parameter used to maintain headroom boost 4481 * state between calls to this function. 4482 * 4483 * Returns the number of bytes actually written (which may be smaller than 4484 * the delta by which the device hand has changed due to alignment). 4485 */ 4486 static uint64_t 4487 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 4488 boolean_t *headroom_boost) 4489 { 4490 arc_buf_hdr_t *ab, *ab_prev, *head; 4491 list_t *list; 4492 uint64_t write_asize, write_psize, write_sz, headroom, 4493 buf_compress_minsz; 4494 void *buf_data; 4495 kmutex_t *list_lock; 4496 boolean_t full; 4497 l2arc_write_callback_t *cb; 4498 zio_t *pio, *wzio; 4499 uint64_t guid = spa_load_guid(spa); 4500 const boolean_t do_headroom_boost = *headroom_boost; 4501 4502 ASSERT(dev->l2ad_vdev != NULL); 4503 4504 /* Lower the flag now, we might want to raise it again later. */ 4505 *headroom_boost = B_FALSE; 4506 4507 pio = NULL; 4508 write_sz = write_asize = write_psize = 0; 4509 full = B_FALSE; 4510 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 4511 head->b_flags |= ARC_L2_WRITE_HEAD; 4512 4513 /* 4514 * We will want to try to compress buffers that are at least 2x the 4515 * device sector size. 4516 */ 4517 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 4518 4519 /* 4520 * Copy buffers for L2ARC writing. 4521 */ 4522 mutex_enter(&l2arc_buflist_mtx); 4523 for (int try = 0; try <= 3; try++) { 4524 uint64_t passed_sz = 0; 4525 4526 list = l2arc_list_locked(try, &list_lock); 4527 4528 /* 4529 * L2ARC fast warmup. 4530 * 4531 * Until the ARC is warm and starts to evict, read from the 4532 * head of the ARC lists rather than the tail. 4533 */ 4534 if (arc_warm == B_FALSE) 4535 ab = list_head(list); 4536 else 4537 ab = list_tail(list); 4538 4539 headroom = target_sz * l2arc_headroom; 4540 if (do_headroom_boost) 4541 headroom = (headroom * l2arc_headroom_boost) / 100; 4542 4543 for (; ab; ab = ab_prev) { 4544 l2arc_buf_hdr_t *l2hdr; 4545 kmutex_t *hash_lock; 4546 uint64_t buf_sz; 4547 4548 if (arc_warm == B_FALSE) 4549 ab_prev = list_next(list, ab); 4550 else 4551 ab_prev = list_prev(list, ab); 4552 4553 hash_lock = HDR_LOCK(ab); 4554 if (!mutex_tryenter(hash_lock)) { 4555 /* 4556 * Skip this buffer rather than waiting. 4557 */ 4558 continue; 4559 } 4560 4561 passed_sz += ab->b_size; 4562 if (passed_sz > headroom) { 4563 /* 4564 * Searched too far. 4565 */ 4566 mutex_exit(hash_lock); 4567 break; 4568 } 4569 4570 if (!l2arc_write_eligible(guid, ab)) { 4571 mutex_exit(hash_lock); 4572 continue; 4573 } 4574 4575 if ((write_sz + ab->b_size) > target_sz) { 4576 full = B_TRUE; 4577 mutex_exit(hash_lock); 4578 break; 4579 } 4580 4581 if (pio == NULL) { 4582 /* 4583 * Insert a dummy header on the buflist so 4584 * l2arc_write_done() can find where the 4585 * write buffers begin without searching. 4586 */ 4587 list_insert_head(dev->l2ad_buflist, head); 4588 4589 cb = kmem_alloc( 4590 sizeof (l2arc_write_callback_t), KM_SLEEP); 4591 cb->l2wcb_dev = dev; 4592 cb->l2wcb_head = head; 4593 pio = zio_root(spa, l2arc_write_done, cb, 4594 ZIO_FLAG_CANFAIL); 4595 } 4596 4597 /* 4598 * Create and add a new L2ARC header. 4599 */ 4600 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP); 4601 l2hdr->b_dev = dev; 4602 ab->b_flags |= ARC_L2_WRITING; 4603 4604 /* 4605 * Temporarily stash the data buffer in b_tmp_cdata. 4606 * The subsequent write step will pick it up from 4607 * there. This is because can't access ab->b_buf 4608 * without holding the hash_lock, which we in turn 4609 * can't access without holding the ARC list locks 4610 * (which we want to avoid during compression/writing). 4611 */ 4612 l2hdr->b_compress = ZIO_COMPRESS_OFF; 4613 l2hdr->b_asize = ab->b_size; 4614 l2hdr->b_tmp_cdata = ab->b_buf->b_data; 4615 4616 buf_sz = ab->b_size; 4617 ab->b_l2hdr = l2hdr; 4618 4619 list_insert_head(dev->l2ad_buflist, ab); 4620 4621 /* 4622 * Compute and store the buffer cksum before 4623 * writing. On debug the cksum is verified first. 4624 */ 4625 arc_cksum_verify(ab->b_buf); 4626 arc_cksum_compute(ab->b_buf, B_TRUE); 4627 4628 mutex_exit(hash_lock); 4629 4630 write_sz += buf_sz; 4631 } 4632 4633 mutex_exit(list_lock); 4634 4635 if (full == B_TRUE) 4636 break; 4637 } 4638 4639 /* No buffers selected for writing? */ 4640 if (pio == NULL) { 4641 ASSERT0(write_sz); 4642 mutex_exit(&l2arc_buflist_mtx); 4643 kmem_cache_free(hdr_cache, head); 4644 return (0); 4645 } 4646 4647 /* 4648 * Now start writing the buffers. We're starting at the write head 4649 * and work backwards, retracing the course of the buffer selector 4650 * loop above. 4651 */ 4652 for (ab = list_prev(dev->l2ad_buflist, head); ab; 4653 ab = list_prev(dev->l2ad_buflist, ab)) { 4654 l2arc_buf_hdr_t *l2hdr; 4655 uint64_t buf_sz; 4656 4657 /* 4658 * We shouldn't need to lock the buffer here, since we flagged 4659 * it as ARC_L2_WRITING in the previous step, but we must take 4660 * care to only access its L2 cache parameters. In particular, 4661 * ab->b_buf may be invalid by now due to ARC eviction. 4662 */ 4663 l2hdr = ab->b_l2hdr; 4664 l2hdr->b_daddr = dev->l2ad_hand; 4665 4666 if ((ab->b_flags & ARC_L2COMPRESS) && 4667 l2hdr->b_asize >= buf_compress_minsz) { 4668 if (l2arc_compress_buf(l2hdr)) { 4669 /* 4670 * If compression succeeded, enable headroom 4671 * boost on the next scan cycle. 4672 */ 4673 *headroom_boost = B_TRUE; 4674 } 4675 } 4676 4677 /* 4678 * Pick up the buffer data we had previously stashed away 4679 * (and now potentially also compressed). 4680 */ 4681 buf_data = l2hdr->b_tmp_cdata; 4682 buf_sz = l2hdr->b_asize; 4683 4684 /* Compression may have squashed the buffer to zero length. */ 4685 if (buf_sz != 0) { 4686 uint64_t buf_p_sz; 4687 4688 wzio = zio_write_phys(pio, dev->l2ad_vdev, 4689 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 4690 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 4691 ZIO_FLAG_CANFAIL, B_FALSE); 4692 4693 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 4694 zio_t *, wzio); 4695 (void) zio_nowait(wzio); 4696 4697 write_asize += buf_sz; 4698 /* 4699 * Keep the clock hand suitably device-aligned. 4700 */ 4701 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 4702 write_psize += buf_p_sz; 4703 dev->l2ad_hand += buf_p_sz; 4704 } 4705 } 4706 4707 mutex_exit(&l2arc_buflist_mtx); 4708 4709 ASSERT3U(write_asize, <=, target_sz); 4710 ARCSTAT_BUMP(arcstat_l2_writes_sent); 4711 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 4712 ARCSTAT_INCR(arcstat_l2_size, write_sz); 4713 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 4714 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); 4715 4716 /* 4717 * Bump device hand to the device start if it is approaching the end. 4718 * l2arc_evict() will already have evicted ahead for this case. 4719 */ 4720 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 4721 vdev_space_update(dev->l2ad_vdev, 4722 dev->l2ad_end - dev->l2ad_hand, 0, 0); 4723 dev->l2ad_hand = dev->l2ad_start; 4724 dev->l2ad_evict = dev->l2ad_start; 4725 dev->l2ad_first = B_FALSE; 4726 } 4727 4728 dev->l2ad_writing = B_TRUE; 4729 (void) zio_wait(pio); 4730 dev->l2ad_writing = B_FALSE; 4731 4732 return (write_asize); 4733 } 4734 4735 /* 4736 * Compresses an L2ARC buffer. 4737 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its 4738 * size in l2hdr->b_asize. This routine tries to compress the data and 4739 * depending on the compression result there are three possible outcomes: 4740 * *) The buffer was incompressible. The original l2hdr contents were left 4741 * untouched and are ready for writing to an L2 device. 4742 * *) The buffer was all-zeros, so there is no need to write it to an L2 4743 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 4744 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 4745 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 4746 * data buffer which holds the compressed data to be written, and b_asize 4747 * tells us how much data there is. b_compress is set to the appropriate 4748 * compression algorithm. Once writing is done, invoke 4749 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 4750 * 4751 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 4752 * buffer was incompressible). 4753 */ 4754 static boolean_t 4755 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr) 4756 { 4757 void *cdata; 4758 size_t csize, len; 4759 4760 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF); 4761 ASSERT(l2hdr->b_tmp_cdata != NULL); 4762 4763 len = l2hdr->b_asize; 4764 cdata = zio_data_buf_alloc(len); 4765 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata, 4766 cdata, l2hdr->b_asize); 4767 4768 if (csize == 0) { 4769 /* zero block, indicate that there's nothing to write */ 4770 zio_data_buf_free(cdata, len); 4771 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 4772 l2hdr->b_asize = 0; 4773 l2hdr->b_tmp_cdata = NULL; 4774 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 4775 return (B_TRUE); 4776 } else if (csize > 0 && csize < len) { 4777 /* 4778 * Compression succeeded, we'll keep the cdata around for 4779 * writing and release it afterwards. 4780 */ 4781 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 4782 l2hdr->b_asize = csize; 4783 l2hdr->b_tmp_cdata = cdata; 4784 ARCSTAT_BUMP(arcstat_l2_compress_successes); 4785 return (B_TRUE); 4786 } else { 4787 /* 4788 * Compression failed, release the compressed buffer. 4789 * l2hdr will be left unmodified. 4790 */ 4791 zio_data_buf_free(cdata, len); 4792 ARCSTAT_BUMP(arcstat_l2_compress_failures); 4793 return (B_FALSE); 4794 } 4795 } 4796 4797 /* 4798 * Decompresses a zio read back from an l2arc device. On success, the 4799 * underlying zio's io_data buffer is overwritten by the uncompressed 4800 * version. On decompression error (corrupt compressed stream), the 4801 * zio->io_error value is set to signal an I/O error. 4802 * 4803 * Please note that the compressed data stream is not checksummed, so 4804 * if the underlying device is experiencing data corruption, we may feed 4805 * corrupt data to the decompressor, so the decompressor needs to be 4806 * able to handle this situation (LZ4 does). 4807 */ 4808 static void 4809 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 4810 { 4811 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 4812 4813 if (zio->io_error != 0) { 4814 /* 4815 * An io error has occured, just restore the original io 4816 * size in preparation for a main pool read. 4817 */ 4818 zio->io_orig_size = zio->io_size = hdr->b_size; 4819 return; 4820 } 4821 4822 if (c == ZIO_COMPRESS_EMPTY) { 4823 /* 4824 * An empty buffer results in a null zio, which means we 4825 * need to fill its io_data after we're done restoring the 4826 * buffer's contents. 4827 */ 4828 ASSERT(hdr->b_buf != NULL); 4829 bzero(hdr->b_buf->b_data, hdr->b_size); 4830 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data; 4831 } else { 4832 ASSERT(zio->io_data != NULL); 4833 /* 4834 * We copy the compressed data from the start of the arc buffer 4835 * (the zio_read will have pulled in only what we need, the 4836 * rest is garbage which we will overwrite at decompression) 4837 * and then decompress back to the ARC data buffer. This way we 4838 * can minimize copying by simply decompressing back over the 4839 * original compressed data (rather than decompressing to an 4840 * aux buffer and then copying back the uncompressed buffer, 4841 * which is likely to be much larger). 4842 */ 4843 uint64_t csize; 4844 void *cdata; 4845 4846 csize = zio->io_size; 4847 cdata = zio_data_buf_alloc(csize); 4848 bcopy(zio->io_data, cdata, csize); 4849 if (zio_decompress_data(c, cdata, zio->io_data, csize, 4850 hdr->b_size) != 0) 4851 zio->io_error = EIO; 4852 zio_data_buf_free(cdata, csize); 4853 } 4854 4855 /* Restore the expected uncompressed IO size. */ 4856 zio->io_orig_size = zio->io_size = hdr->b_size; 4857 } 4858 4859 /* 4860 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 4861 * This buffer serves as a temporary holder of compressed data while 4862 * the buffer entry is being written to an l2arc device. Once that is 4863 * done, we can dispose of it. 4864 */ 4865 static void 4866 l2arc_release_cdata_buf(arc_buf_hdr_t *ab) 4867 { 4868 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr; 4869 4870 if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) { 4871 /* 4872 * If the data was compressed, then we've allocated a 4873 * temporary buffer for it, so now we need to release it. 4874 */ 4875 ASSERT(l2hdr->b_tmp_cdata != NULL); 4876 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size); 4877 } 4878 l2hdr->b_tmp_cdata = NULL; 4879 } 4880 4881 /* 4882 * This thread feeds the L2ARC at regular intervals. This is the beating 4883 * heart of the L2ARC. 4884 */ 4885 static void 4886 l2arc_feed_thread(void) 4887 { 4888 callb_cpr_t cpr; 4889 l2arc_dev_t *dev; 4890 spa_t *spa; 4891 uint64_t size, wrote; 4892 clock_t begin, next = ddi_get_lbolt(); 4893 boolean_t headroom_boost = B_FALSE; 4894 4895 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 4896 4897 mutex_enter(&l2arc_feed_thr_lock); 4898 4899 while (l2arc_thread_exit == 0) { 4900 CALLB_CPR_SAFE_BEGIN(&cpr); 4901 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 4902 next); 4903 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 4904 next = ddi_get_lbolt() + hz; 4905 4906 /* 4907 * Quick check for L2ARC devices. 4908 */ 4909 mutex_enter(&l2arc_dev_mtx); 4910 if (l2arc_ndev == 0) { 4911 mutex_exit(&l2arc_dev_mtx); 4912 continue; 4913 } 4914 mutex_exit(&l2arc_dev_mtx); 4915 begin = ddi_get_lbolt(); 4916 4917 /* 4918 * This selects the next l2arc device to write to, and in 4919 * doing so the next spa to feed from: dev->l2ad_spa. This 4920 * will return NULL if there are now no l2arc devices or if 4921 * they are all faulted. 4922 * 4923 * If a device is returned, its spa's config lock is also 4924 * held to prevent device removal. l2arc_dev_get_next() 4925 * will grab and release l2arc_dev_mtx. 4926 */ 4927 if ((dev = l2arc_dev_get_next()) == NULL) 4928 continue; 4929 4930 spa = dev->l2ad_spa; 4931 ASSERT(spa != NULL); 4932 4933 /* 4934 * If the pool is read-only then force the feed thread to 4935 * sleep a little longer. 4936 */ 4937 if (!spa_writeable(spa)) { 4938 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 4939 spa_config_exit(spa, SCL_L2ARC, dev); 4940 continue; 4941 } 4942 4943 /* 4944 * Avoid contributing to memory pressure. 4945 */ 4946 if (arc_reclaim_needed()) { 4947 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 4948 spa_config_exit(spa, SCL_L2ARC, dev); 4949 continue; 4950 } 4951 4952 ARCSTAT_BUMP(arcstat_l2_feeds); 4953 4954 size = l2arc_write_size(); 4955 4956 /* 4957 * Evict L2ARC buffers that will be overwritten. 4958 */ 4959 l2arc_evict(dev, size, B_FALSE); 4960 4961 /* 4962 * Write ARC buffers. 4963 */ 4964 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 4965 4966 /* 4967 * Calculate interval between writes. 4968 */ 4969 next = l2arc_write_interval(begin, size, wrote); 4970 spa_config_exit(spa, SCL_L2ARC, dev); 4971 } 4972 4973 l2arc_thread_exit = 0; 4974 cv_broadcast(&l2arc_feed_thr_cv); 4975 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 4976 thread_exit(); 4977 } 4978 4979 boolean_t 4980 l2arc_vdev_present(vdev_t *vd) 4981 { 4982 l2arc_dev_t *dev; 4983 4984 mutex_enter(&l2arc_dev_mtx); 4985 for (dev = list_head(l2arc_dev_list); dev != NULL; 4986 dev = list_next(l2arc_dev_list, dev)) { 4987 if (dev->l2ad_vdev == vd) 4988 break; 4989 } 4990 mutex_exit(&l2arc_dev_mtx); 4991 4992 return (dev != NULL); 4993 } 4994 4995 /* 4996 * Add a vdev for use by the L2ARC. By this point the spa has already 4997 * validated the vdev and opened it. 4998 */ 4999 void 5000 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 5001 { 5002 l2arc_dev_t *adddev; 5003 5004 ASSERT(!l2arc_vdev_present(vd)); 5005 5006 /* 5007 * Create a new l2arc device entry. 5008 */ 5009 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 5010 adddev->l2ad_spa = spa; 5011 adddev->l2ad_vdev = vd; 5012 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 5013 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 5014 adddev->l2ad_hand = adddev->l2ad_start; 5015 adddev->l2ad_evict = adddev->l2ad_start; 5016 adddev->l2ad_first = B_TRUE; 5017 adddev->l2ad_writing = B_FALSE; 5018 5019 /* 5020 * This is a list of all ARC buffers that are still valid on the 5021 * device. 5022 */ 5023 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP); 5024 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 5025 offsetof(arc_buf_hdr_t, b_l2node)); 5026 5027 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 5028 5029 /* 5030 * Add device to global list 5031 */ 5032 mutex_enter(&l2arc_dev_mtx); 5033 list_insert_head(l2arc_dev_list, adddev); 5034 atomic_inc_64(&l2arc_ndev); 5035 mutex_exit(&l2arc_dev_mtx); 5036 } 5037 5038 /* 5039 * Remove a vdev from the L2ARC. 5040 */ 5041 void 5042 l2arc_remove_vdev(vdev_t *vd) 5043 { 5044 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 5045 5046 /* 5047 * Find the device by vdev 5048 */ 5049 mutex_enter(&l2arc_dev_mtx); 5050 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 5051 nextdev = list_next(l2arc_dev_list, dev); 5052 if (vd == dev->l2ad_vdev) { 5053 remdev = dev; 5054 break; 5055 } 5056 } 5057 ASSERT(remdev != NULL); 5058 5059 /* 5060 * Remove device from global list 5061 */ 5062 list_remove(l2arc_dev_list, remdev); 5063 l2arc_dev_last = NULL; /* may have been invalidated */ 5064 atomic_dec_64(&l2arc_ndev); 5065 mutex_exit(&l2arc_dev_mtx); 5066 5067 /* 5068 * Clear all buflists and ARC references. L2ARC device flush. 5069 */ 5070 l2arc_evict(remdev, 0, B_TRUE); 5071 list_destroy(remdev->l2ad_buflist); 5072 kmem_free(remdev->l2ad_buflist, sizeof (list_t)); 5073 kmem_free(remdev, sizeof (l2arc_dev_t)); 5074 } 5075 5076 void 5077 l2arc_init(void) 5078 { 5079 l2arc_thread_exit = 0; 5080 l2arc_ndev = 0; 5081 l2arc_writes_sent = 0; 5082 l2arc_writes_done = 0; 5083 5084 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 5085 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 5086 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 5087 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL); 5088 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 5089 5090 l2arc_dev_list = &L2ARC_dev_list; 5091 l2arc_free_on_write = &L2ARC_free_on_write; 5092 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 5093 offsetof(l2arc_dev_t, l2ad_node)); 5094 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 5095 offsetof(l2arc_data_free_t, l2df_list_node)); 5096 } 5097 5098 void 5099 l2arc_fini(void) 5100 { 5101 /* 5102 * This is called from dmu_fini(), which is called from spa_fini(); 5103 * Because of this, we can assume that all l2arc devices have 5104 * already been removed when the pools themselves were removed. 5105 */ 5106 5107 l2arc_do_free_on_write(); 5108 5109 mutex_destroy(&l2arc_feed_thr_lock); 5110 cv_destroy(&l2arc_feed_thr_cv); 5111 mutex_destroy(&l2arc_dev_mtx); 5112 mutex_destroy(&l2arc_buflist_mtx); 5113 mutex_destroy(&l2arc_free_on_write_mtx); 5114 5115 list_destroy(l2arc_dev_list); 5116 list_destroy(l2arc_free_on_write); 5117 } 5118 5119 void 5120 l2arc_start(void) 5121 { 5122 if (!(spa_mode_global & FWRITE)) 5123 return; 5124 5125 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 5126 TS_RUN, minclsyspri); 5127 } 5128 5129 void 5130 l2arc_stop(void) 5131 { 5132 if (!(spa_mode_global & FWRITE)) 5133 return; 5134 5135 mutex_enter(&l2arc_feed_thr_lock); 5136 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 5137 l2arc_thread_exit = 1; 5138 while (l2arc_thread_exit != 0) 5139 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 5140 mutex_exit(&l2arc_feed_thr_lock); 5141 }