1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2014 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2014 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #ifdef _KERNEL 133 #include <sys/vmsystm.h> 134 #include <vm/anon.h> 135 #include <sys/fs/swapnode.h> 136 #include <sys/dnlc.h> 137 #endif 138 #include <sys/callb.h> 139 #include <sys/kstat.h> 140 #include <zfs_fletcher.h> 141 142 #ifndef _KERNEL 143 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 144 boolean_t arc_watch = B_FALSE; 145 int arc_procfd; 146 #endif 147 148 static kmutex_t arc_reclaim_thr_lock; 149 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 150 static uint8_t arc_thread_exit; 151 152 #define ARC_REDUCE_DNLC_PERCENT 3 153 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT; 154 155 typedef enum arc_reclaim_strategy { 156 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ 157 ARC_RECLAIM_CONS /* Conservative reclaim strategy */ 158 } arc_reclaim_strategy_t; 159 160 /* 161 * The number of iterations through arc_evict_*() before we 162 * drop & reacquire the lock. 163 */ 164 int arc_evict_iterations = 100; 165 166 /* number of seconds before growing cache again */ 167 static int arc_grow_retry = 60; 168 169 /* shift of arc_c for calculating both min and max arc_p */ 170 static int arc_p_min_shift = 4; 171 172 /* log2(fraction of arc to reclaim) */ 173 static int arc_shrink_shift = 5; 174 175 /* 176 * minimum lifespan of a prefetch block in clock ticks 177 * (initialized in arc_init()) 178 */ 179 static int arc_min_prefetch_lifespan; 180 181 /* 182 * If this percent of memory is free, don't throttle. 183 */ 184 int arc_lotsfree_percent = 10; 185 186 static int arc_dead; 187 188 /* 189 * The arc has filled available memory and has now warmed up. 190 */ 191 static boolean_t arc_warm; 192 193 /* 194 * These tunables are for performance analysis. 195 */ 196 uint64_t zfs_arc_max; 197 uint64_t zfs_arc_min; 198 uint64_t zfs_arc_meta_limit = 0; 199 int zfs_arc_grow_retry = 0; 200 int zfs_arc_shrink_shift = 0; 201 int zfs_arc_p_min_shift = 0; 202 int zfs_disable_dup_eviction = 0; 203 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 204 205 /* 206 * Note that buffers can be in one of 6 states: 207 * ARC_anon - anonymous (discussed below) 208 * ARC_mru - recently used, currently cached 209 * ARC_mru_ghost - recentely used, no longer in cache 210 * ARC_mfu - frequently used, currently cached 211 * ARC_mfu_ghost - frequently used, no longer in cache 212 * ARC_l2c_only - exists in L2ARC but not other states 213 * When there are no active references to the buffer, they are 214 * are linked onto a list in one of these arc states. These are 215 * the only buffers that can be evicted or deleted. Within each 216 * state there are multiple lists, one for meta-data and one for 217 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 218 * etc.) is tracked separately so that it can be managed more 219 * explicitly: favored over data, limited explicitly. 220 * 221 * Anonymous buffers are buffers that are not associated with 222 * a DVA. These are buffers that hold dirty block copies 223 * before they are written to stable storage. By definition, 224 * they are "ref'd" and are considered part of arc_mru 225 * that cannot be freed. Generally, they will aquire a DVA 226 * as they are written and migrate onto the arc_mru list. 227 * 228 * The ARC_l2c_only state is for buffers that are in the second 229 * level ARC but no longer in any of the ARC_m* lists. The second 230 * level ARC itself may also contain buffers that are in any of 231 * the ARC_m* states - meaning that a buffer can exist in two 232 * places. The reason for the ARC_l2c_only state is to keep the 233 * buffer header in the hash table, so that reads that hit the 234 * second level ARC benefit from these fast lookups. 235 */ 236 237 typedef struct arc_state { 238 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */ 239 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 240 uint64_t arcs_size; /* total amount of data in this state */ 241 kmutex_t arcs_mtx; 242 } arc_state_t; 243 244 /* The 6 states: */ 245 static arc_state_t ARC_anon; 246 static arc_state_t ARC_mru; 247 static arc_state_t ARC_mru_ghost; 248 static arc_state_t ARC_mfu; 249 static arc_state_t ARC_mfu_ghost; 250 static arc_state_t ARC_l2c_only; 251 252 typedef struct arc_stats { 253 kstat_named_t arcstat_hits; 254 kstat_named_t arcstat_misses; 255 kstat_named_t arcstat_demand_data_hits; 256 kstat_named_t arcstat_demand_data_misses; 257 kstat_named_t arcstat_demand_metadata_hits; 258 kstat_named_t arcstat_demand_metadata_misses; 259 kstat_named_t arcstat_prefetch_data_hits; 260 kstat_named_t arcstat_prefetch_data_misses; 261 kstat_named_t arcstat_prefetch_metadata_hits; 262 kstat_named_t arcstat_prefetch_metadata_misses; 263 kstat_named_t arcstat_mru_hits; 264 kstat_named_t arcstat_mru_ghost_hits; 265 kstat_named_t arcstat_mfu_hits; 266 kstat_named_t arcstat_mfu_ghost_hits; 267 kstat_named_t arcstat_deleted; 268 kstat_named_t arcstat_recycle_miss; 269 /* 270 * Number of buffers that could not be evicted because the hash lock 271 * was held by another thread. The lock may not necessarily be held 272 * by something using the same buffer, since hash locks are shared 273 * by multiple buffers. 274 */ 275 kstat_named_t arcstat_mutex_miss; 276 /* 277 * Number of buffers skipped because they have I/O in progress, are 278 * indrect prefetch buffers that have not lived long enough, or are 279 * not from the spa we're trying to evict from. 280 */ 281 kstat_named_t arcstat_evict_skip; 282 kstat_named_t arcstat_evict_l2_cached; 283 kstat_named_t arcstat_evict_l2_eligible; 284 kstat_named_t arcstat_evict_l2_ineligible; 285 kstat_named_t arcstat_hash_elements; 286 kstat_named_t arcstat_hash_elements_max; 287 kstat_named_t arcstat_hash_collisions; 288 kstat_named_t arcstat_hash_chains; 289 kstat_named_t arcstat_hash_chain_max; 290 kstat_named_t arcstat_p; 291 kstat_named_t arcstat_c; 292 kstat_named_t arcstat_c_min; 293 kstat_named_t arcstat_c_max; 294 kstat_named_t arcstat_size; 295 kstat_named_t arcstat_hdr_size; 296 kstat_named_t arcstat_data_size; 297 kstat_named_t arcstat_other_size; 298 kstat_named_t arcstat_l2_hits; 299 kstat_named_t arcstat_l2_misses; 300 kstat_named_t arcstat_l2_feeds; 301 kstat_named_t arcstat_l2_rw_clash; 302 kstat_named_t arcstat_l2_read_bytes; 303 kstat_named_t arcstat_l2_write_bytes; 304 kstat_named_t arcstat_l2_writes_sent; 305 kstat_named_t arcstat_l2_writes_done; 306 kstat_named_t arcstat_l2_writes_error; 307 kstat_named_t arcstat_l2_writes_hdr_miss; 308 kstat_named_t arcstat_l2_evict_lock_retry; 309 kstat_named_t arcstat_l2_evict_reading; 310 kstat_named_t arcstat_l2_free_on_write; 311 kstat_named_t arcstat_l2_abort_lowmem; 312 kstat_named_t arcstat_l2_cksum_bad; 313 kstat_named_t arcstat_l2_io_error; 314 kstat_named_t arcstat_l2_size; 315 kstat_named_t arcstat_l2_asize; 316 kstat_named_t arcstat_l2_hdr_size; 317 kstat_named_t arcstat_l2_compress_successes; 318 kstat_named_t arcstat_l2_compress_zeros; 319 kstat_named_t arcstat_l2_compress_failures; 320 kstat_named_t arcstat_memory_throttle_count; 321 kstat_named_t arcstat_duplicate_buffers; 322 kstat_named_t arcstat_duplicate_buffers_size; 323 kstat_named_t arcstat_duplicate_reads; 324 kstat_named_t arcstat_meta_used; 325 kstat_named_t arcstat_meta_limit; 326 kstat_named_t arcstat_meta_max; 327 } arc_stats_t; 328 329 static arc_stats_t arc_stats = { 330 { "hits", KSTAT_DATA_UINT64 }, 331 { "misses", KSTAT_DATA_UINT64 }, 332 { "demand_data_hits", KSTAT_DATA_UINT64 }, 333 { "demand_data_misses", KSTAT_DATA_UINT64 }, 334 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 335 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 336 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 337 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 338 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 339 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 340 { "mru_hits", KSTAT_DATA_UINT64 }, 341 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 342 { "mfu_hits", KSTAT_DATA_UINT64 }, 343 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 344 { "deleted", KSTAT_DATA_UINT64 }, 345 { "recycle_miss", KSTAT_DATA_UINT64 }, 346 { "mutex_miss", KSTAT_DATA_UINT64 }, 347 { "evict_skip", KSTAT_DATA_UINT64 }, 348 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 349 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 350 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 351 { "hash_elements", KSTAT_DATA_UINT64 }, 352 { "hash_elements_max", KSTAT_DATA_UINT64 }, 353 { "hash_collisions", KSTAT_DATA_UINT64 }, 354 { "hash_chains", KSTAT_DATA_UINT64 }, 355 { "hash_chain_max", KSTAT_DATA_UINT64 }, 356 { "p", KSTAT_DATA_UINT64 }, 357 { "c", KSTAT_DATA_UINT64 }, 358 { "c_min", KSTAT_DATA_UINT64 }, 359 { "c_max", KSTAT_DATA_UINT64 }, 360 { "size", KSTAT_DATA_UINT64 }, 361 { "hdr_size", KSTAT_DATA_UINT64 }, 362 { "data_size", KSTAT_DATA_UINT64 }, 363 { "other_size", KSTAT_DATA_UINT64 }, 364 { "l2_hits", KSTAT_DATA_UINT64 }, 365 { "l2_misses", KSTAT_DATA_UINT64 }, 366 { "l2_feeds", KSTAT_DATA_UINT64 }, 367 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 368 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 369 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 370 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 371 { "l2_writes_done", KSTAT_DATA_UINT64 }, 372 { "l2_writes_error", KSTAT_DATA_UINT64 }, 373 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 374 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 375 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 376 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 377 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 378 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 379 { "l2_io_error", KSTAT_DATA_UINT64 }, 380 { "l2_size", KSTAT_DATA_UINT64 }, 381 { "l2_asize", KSTAT_DATA_UINT64 }, 382 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 383 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 384 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 385 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 386 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 387 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 388 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 389 { "duplicate_reads", KSTAT_DATA_UINT64 }, 390 { "arc_meta_used", KSTAT_DATA_UINT64 }, 391 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 392 { "arc_meta_max", KSTAT_DATA_UINT64 } 393 }; 394 395 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 396 397 #define ARCSTAT_INCR(stat, val) \ 398 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 399 400 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 401 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 402 403 #define ARCSTAT_MAX(stat, val) { \ 404 uint64_t m; \ 405 while ((val) > (m = arc_stats.stat.value.ui64) && \ 406 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 407 continue; \ 408 } 409 410 #define ARCSTAT_MAXSTAT(stat) \ 411 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 412 413 /* 414 * We define a macro to allow ARC hits/misses to be easily broken down by 415 * two separate conditions, giving a total of four different subtypes for 416 * each of hits and misses (so eight statistics total). 417 */ 418 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 419 if (cond1) { \ 420 if (cond2) { \ 421 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 422 } else { \ 423 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 424 } \ 425 } else { \ 426 if (cond2) { \ 427 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 428 } else { \ 429 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 430 } \ 431 } 432 433 kstat_t *arc_ksp; 434 static arc_state_t *arc_anon; 435 static arc_state_t *arc_mru; 436 static arc_state_t *arc_mru_ghost; 437 static arc_state_t *arc_mfu; 438 static arc_state_t *arc_mfu_ghost; 439 static arc_state_t *arc_l2c_only; 440 441 /* 442 * There are several ARC variables that are critical to export as kstats -- 443 * but we don't want to have to grovel around in the kstat whenever we wish to 444 * manipulate them. For these variables, we therefore define them to be in 445 * terms of the statistic variable. This assures that we are not introducing 446 * the possibility of inconsistency by having shadow copies of the variables, 447 * while still allowing the code to be readable. 448 */ 449 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 450 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 451 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 452 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 453 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 454 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 455 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 456 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 457 458 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 459 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 460 461 static int arc_no_grow; /* Don't try to grow cache size */ 462 static uint64_t arc_tempreserve; 463 static uint64_t arc_loaned_bytes; 464 465 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; 466 467 typedef struct arc_callback arc_callback_t; 468 469 struct arc_callback { 470 void *acb_private; 471 arc_done_func_t *acb_done; 472 arc_buf_t *acb_buf; 473 zio_t *acb_zio_dummy; 474 arc_callback_t *acb_next; 475 }; 476 477 typedef struct arc_write_callback arc_write_callback_t; 478 479 struct arc_write_callback { 480 void *awcb_private; 481 arc_done_func_t *awcb_ready; 482 arc_done_func_t *awcb_physdone; 483 arc_done_func_t *awcb_done; 484 arc_buf_t *awcb_buf; 485 }; 486 487 struct arc_buf_hdr { 488 /* protected by hash lock */ 489 dva_t b_dva; 490 uint64_t b_birth; 491 uint64_t b_cksum0; 492 493 kmutex_t b_freeze_lock; 494 zio_cksum_t *b_freeze_cksum; 495 void *b_thawed; 496 497 arc_buf_hdr_t *b_hash_next; 498 arc_buf_t *b_buf; 499 uint32_t b_flags; 500 uint32_t b_datacnt; 501 502 arc_callback_t *b_acb; 503 kcondvar_t b_cv; 504 505 /* immutable */ 506 arc_buf_contents_t b_type; 507 uint64_t b_size; 508 uint64_t b_spa; 509 510 /* protected by arc state mutex */ 511 arc_state_t *b_state; 512 list_node_t b_arc_node; 513 514 /* updated atomically */ 515 clock_t b_arc_access; 516 517 /* self protecting */ 518 refcount_t b_refcnt; 519 520 l2arc_buf_hdr_t *b_l2hdr; 521 list_node_t b_l2node; 522 }; 523 524 static arc_buf_t *arc_eviction_list; 525 static kmutex_t arc_eviction_mtx; 526 static arc_buf_hdr_t arc_eviction_hdr; 527 static void arc_get_data_buf(arc_buf_t *buf); 528 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock); 529 static int arc_evict_needed(arc_buf_contents_t type); 530 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes); 531 static void arc_buf_watch(arc_buf_t *buf); 532 533 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab); 534 535 #define GHOST_STATE(state) \ 536 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 537 (state) == arc_l2c_only) 538 539 /* 540 * Private ARC flags. These flags are private ARC only flags that will show up 541 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can 542 * be passed in as arc_flags in things like arc_read. However, these flags 543 * should never be passed and should only be set by ARC code. When adding new 544 * public flags, make sure not to smash the private ones. 545 */ 546 547 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */ 548 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */ 549 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */ 550 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */ 551 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */ 552 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */ 553 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */ 554 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */ 555 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */ 556 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */ 557 558 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE) 559 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS) 560 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR) 561 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH) 562 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ) 563 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE) 564 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS) 565 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE) 566 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \ 567 (hdr)->b_l2hdr != NULL) 568 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING) 569 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED) 570 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD) 571 572 /* 573 * Other sizes 574 */ 575 576 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 577 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t)) 578 579 /* 580 * Hash table routines 581 */ 582 583 #define HT_LOCK_PAD 64 584 585 struct ht_lock { 586 kmutex_t ht_lock; 587 #ifdef _KERNEL 588 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 589 #endif 590 }; 591 592 #define BUF_LOCKS 256 593 typedef struct buf_hash_table { 594 uint64_t ht_mask; 595 arc_buf_hdr_t **ht_table; 596 struct ht_lock ht_locks[BUF_LOCKS]; 597 } buf_hash_table_t; 598 599 static buf_hash_table_t buf_hash_table; 600 601 #define BUF_HASH_INDEX(spa, dva, birth) \ 602 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 603 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 604 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 605 #define HDR_LOCK(hdr) \ 606 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 607 608 uint64_t zfs_crc64_table[256]; 609 610 /* 611 * Level 2 ARC 612 */ 613 614 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 615 #define L2ARC_HEADROOM 2 /* num of writes */ 616 /* 617 * If we discover during ARC scan any buffers to be compressed, we boost 618 * our headroom for the next scanning cycle by this percentage multiple. 619 */ 620 #define L2ARC_HEADROOM_BOOST 200 621 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 622 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 623 624 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 625 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 626 627 /* L2ARC Performance Tunables */ 628 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 629 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 630 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 631 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 632 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 633 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 634 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 635 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 636 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 637 638 /* 639 * L2ARC Internals 640 */ 641 typedef struct l2arc_dev { 642 vdev_t *l2ad_vdev; /* vdev */ 643 spa_t *l2ad_spa; /* spa */ 644 uint64_t l2ad_hand; /* next write location */ 645 uint64_t l2ad_start; /* first addr on device */ 646 uint64_t l2ad_end; /* last addr on device */ 647 uint64_t l2ad_evict; /* last addr eviction reached */ 648 boolean_t l2ad_first; /* first sweep through */ 649 boolean_t l2ad_writing; /* currently writing */ 650 list_t *l2ad_buflist; /* buffer list */ 651 list_node_t l2ad_node; /* device list node */ 652 } l2arc_dev_t; 653 654 static list_t L2ARC_dev_list; /* device list */ 655 static list_t *l2arc_dev_list; /* device list pointer */ 656 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 657 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 658 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */ 659 static list_t L2ARC_free_on_write; /* free after write buf list */ 660 static list_t *l2arc_free_on_write; /* free after write list ptr */ 661 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 662 static uint64_t l2arc_ndev; /* number of devices */ 663 664 typedef struct l2arc_read_callback { 665 arc_buf_t *l2rcb_buf; /* read buffer */ 666 spa_t *l2rcb_spa; /* spa */ 667 blkptr_t l2rcb_bp; /* original blkptr */ 668 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 669 int l2rcb_flags; /* original flags */ 670 enum zio_compress l2rcb_compress; /* applied compress */ 671 } l2arc_read_callback_t; 672 673 typedef struct l2arc_write_callback { 674 l2arc_dev_t *l2wcb_dev; /* device info */ 675 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 676 } l2arc_write_callback_t; 677 678 struct l2arc_buf_hdr { 679 /* protected by arc_buf_hdr mutex */ 680 l2arc_dev_t *b_dev; /* L2ARC device */ 681 uint64_t b_daddr; /* disk address, offset byte */ 682 /* compression applied to buffer data */ 683 enum zio_compress b_compress; 684 /* real alloc'd buffer size depending on b_compress applied */ 685 int b_asize; 686 /* temporary buffer holder for in-flight compressed data */ 687 void *b_tmp_cdata; 688 }; 689 690 typedef struct l2arc_data_free { 691 /* protected by l2arc_free_on_write_mtx */ 692 void *l2df_data; 693 size_t l2df_size; 694 void (*l2df_func)(void *, size_t); 695 list_node_t l2df_list_node; 696 } l2arc_data_free_t; 697 698 static kmutex_t l2arc_feed_thr_lock; 699 static kcondvar_t l2arc_feed_thr_cv; 700 static uint8_t l2arc_thread_exit; 701 702 static void l2arc_read_done(zio_t *zio); 703 static void l2arc_hdr_stat_add(void); 704 static void l2arc_hdr_stat_remove(void); 705 706 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr); 707 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, 708 enum zio_compress c); 709 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab); 710 711 static uint64_t 712 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 713 { 714 uint8_t *vdva = (uint8_t *)dva; 715 uint64_t crc = -1ULL; 716 int i; 717 718 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 719 720 for (i = 0; i < sizeof (dva_t); i++) 721 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 722 723 crc ^= (spa>>8) ^ birth; 724 725 return (crc); 726 } 727 728 #define BUF_EMPTY(buf) \ 729 ((buf)->b_dva.dva_word[0] == 0 && \ 730 (buf)->b_dva.dva_word[1] == 0 && \ 731 (buf)->b_cksum0 == 0) 732 733 #define BUF_EQUAL(spa, dva, birth, buf) \ 734 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 735 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 736 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 737 738 static void 739 buf_discard_identity(arc_buf_hdr_t *hdr) 740 { 741 hdr->b_dva.dva_word[0] = 0; 742 hdr->b_dva.dva_word[1] = 0; 743 hdr->b_birth = 0; 744 hdr->b_cksum0 = 0; 745 } 746 747 static arc_buf_hdr_t * 748 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 749 { 750 const dva_t *dva = BP_IDENTITY(bp); 751 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 752 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 753 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 754 arc_buf_hdr_t *buf; 755 756 mutex_enter(hash_lock); 757 for (buf = buf_hash_table.ht_table[idx]; buf != NULL; 758 buf = buf->b_hash_next) { 759 if (BUF_EQUAL(spa, dva, birth, buf)) { 760 *lockp = hash_lock; 761 return (buf); 762 } 763 } 764 mutex_exit(hash_lock); 765 *lockp = NULL; 766 return (NULL); 767 } 768 769 /* 770 * Insert an entry into the hash table. If there is already an element 771 * equal to elem in the hash table, then the already existing element 772 * will be returned and the new element will not be inserted. 773 * Otherwise returns NULL. 774 */ 775 static arc_buf_hdr_t * 776 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp) 777 { 778 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 779 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 780 arc_buf_hdr_t *fbuf; 781 uint32_t i; 782 783 ASSERT(!DVA_IS_EMPTY(&buf->b_dva)); 784 ASSERT(buf->b_birth != 0); 785 ASSERT(!HDR_IN_HASH_TABLE(buf)); 786 *lockp = hash_lock; 787 mutex_enter(hash_lock); 788 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL; 789 fbuf = fbuf->b_hash_next, i++) { 790 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf)) 791 return (fbuf); 792 } 793 794 buf->b_hash_next = buf_hash_table.ht_table[idx]; 795 buf_hash_table.ht_table[idx] = buf; 796 buf->b_flags |= ARC_IN_HASH_TABLE; 797 798 /* collect some hash table performance data */ 799 if (i > 0) { 800 ARCSTAT_BUMP(arcstat_hash_collisions); 801 if (i == 1) 802 ARCSTAT_BUMP(arcstat_hash_chains); 803 804 ARCSTAT_MAX(arcstat_hash_chain_max, i); 805 } 806 807 ARCSTAT_BUMP(arcstat_hash_elements); 808 ARCSTAT_MAXSTAT(arcstat_hash_elements); 809 810 return (NULL); 811 } 812 813 static void 814 buf_hash_remove(arc_buf_hdr_t *buf) 815 { 816 arc_buf_hdr_t *fbuf, **bufp; 817 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth); 818 819 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 820 ASSERT(HDR_IN_HASH_TABLE(buf)); 821 822 bufp = &buf_hash_table.ht_table[idx]; 823 while ((fbuf = *bufp) != buf) { 824 ASSERT(fbuf != NULL); 825 bufp = &fbuf->b_hash_next; 826 } 827 *bufp = buf->b_hash_next; 828 buf->b_hash_next = NULL; 829 buf->b_flags &= ~ARC_IN_HASH_TABLE; 830 831 /* collect some hash table performance data */ 832 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 833 834 if (buf_hash_table.ht_table[idx] && 835 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 836 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 837 } 838 839 /* 840 * Global data structures and functions for the buf kmem cache. 841 */ 842 static kmem_cache_t *hdr_cache; 843 static kmem_cache_t *buf_cache; 844 845 static void 846 buf_fini(void) 847 { 848 int i; 849 850 kmem_free(buf_hash_table.ht_table, 851 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 852 for (i = 0; i < BUF_LOCKS; i++) 853 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 854 kmem_cache_destroy(hdr_cache); 855 kmem_cache_destroy(buf_cache); 856 } 857 858 /* 859 * Constructor callback - called when the cache is empty 860 * and a new buf is requested. 861 */ 862 /* ARGSUSED */ 863 static int 864 hdr_cons(void *vbuf, void *unused, int kmflag) 865 { 866 arc_buf_hdr_t *buf = vbuf; 867 868 bzero(buf, sizeof (arc_buf_hdr_t)); 869 refcount_create(&buf->b_refcnt); 870 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL); 871 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 872 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 873 874 return (0); 875 } 876 877 /* ARGSUSED */ 878 static int 879 buf_cons(void *vbuf, void *unused, int kmflag) 880 { 881 arc_buf_t *buf = vbuf; 882 883 bzero(buf, sizeof (arc_buf_t)); 884 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 885 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 886 887 return (0); 888 } 889 890 /* 891 * Destructor callback - called when a cached buf is 892 * no longer required. 893 */ 894 /* ARGSUSED */ 895 static void 896 hdr_dest(void *vbuf, void *unused) 897 { 898 arc_buf_hdr_t *buf = vbuf; 899 900 ASSERT(BUF_EMPTY(buf)); 901 refcount_destroy(&buf->b_refcnt); 902 cv_destroy(&buf->b_cv); 903 mutex_destroy(&buf->b_freeze_lock); 904 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 905 } 906 907 /* ARGSUSED */ 908 static void 909 buf_dest(void *vbuf, void *unused) 910 { 911 arc_buf_t *buf = vbuf; 912 913 mutex_destroy(&buf->b_evict_lock); 914 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 915 } 916 917 /* 918 * Reclaim callback -- invoked when memory is low. 919 */ 920 /* ARGSUSED */ 921 static void 922 hdr_recl(void *unused) 923 { 924 dprintf("hdr_recl called\n"); 925 /* 926 * umem calls the reclaim func when we destroy the buf cache, 927 * which is after we do arc_fini(). 928 */ 929 if (!arc_dead) 930 cv_signal(&arc_reclaim_thr_cv); 931 } 932 933 static void 934 buf_init(void) 935 { 936 uint64_t *ct; 937 uint64_t hsize = 1ULL << 12; 938 int i, j; 939 940 /* 941 * The hash table is big enough to fill all of physical memory 942 * with an average block size of zfs_arc_average_blocksize (default 8K). 943 * By default, the table will take up 944 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 945 */ 946 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 947 hsize <<= 1; 948 retry: 949 buf_hash_table.ht_mask = hsize - 1; 950 buf_hash_table.ht_table = 951 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 952 if (buf_hash_table.ht_table == NULL) { 953 ASSERT(hsize > (1ULL << 8)); 954 hsize >>= 1; 955 goto retry; 956 } 957 958 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t), 959 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0); 960 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 961 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 962 963 for (i = 0; i < 256; i++) 964 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 965 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 966 967 for (i = 0; i < BUF_LOCKS; i++) { 968 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 969 NULL, MUTEX_DEFAULT, NULL); 970 } 971 } 972 973 #define ARC_MINTIME (hz>>4) /* 62 ms */ 974 975 static void 976 arc_cksum_verify(arc_buf_t *buf) 977 { 978 zio_cksum_t zc; 979 980 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 981 return; 982 983 mutex_enter(&buf->b_hdr->b_freeze_lock); 984 if (buf->b_hdr->b_freeze_cksum == NULL || 985 (buf->b_hdr->b_flags & ARC_IO_ERROR)) { 986 mutex_exit(&buf->b_hdr->b_freeze_lock); 987 return; 988 } 989 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 990 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 991 panic("buffer modified while frozen!"); 992 mutex_exit(&buf->b_hdr->b_freeze_lock); 993 } 994 995 static int 996 arc_cksum_equal(arc_buf_t *buf) 997 { 998 zio_cksum_t zc; 999 int equal; 1000 1001 mutex_enter(&buf->b_hdr->b_freeze_lock); 1002 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1003 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1004 mutex_exit(&buf->b_hdr->b_freeze_lock); 1005 1006 return (equal); 1007 } 1008 1009 static void 1010 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1011 { 1012 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1013 return; 1014 1015 mutex_enter(&buf->b_hdr->b_freeze_lock); 1016 if (buf->b_hdr->b_freeze_cksum != NULL) { 1017 mutex_exit(&buf->b_hdr->b_freeze_lock); 1018 return; 1019 } 1020 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1021 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1022 buf->b_hdr->b_freeze_cksum); 1023 mutex_exit(&buf->b_hdr->b_freeze_lock); 1024 arc_buf_watch(buf); 1025 } 1026 1027 #ifndef _KERNEL 1028 typedef struct procctl { 1029 long cmd; 1030 prwatch_t prwatch; 1031 } procctl_t; 1032 #endif 1033 1034 /* ARGSUSED */ 1035 static void 1036 arc_buf_unwatch(arc_buf_t *buf) 1037 { 1038 #ifndef _KERNEL 1039 if (arc_watch) { 1040 int result; 1041 procctl_t ctl; 1042 ctl.cmd = PCWATCH; 1043 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1044 ctl.prwatch.pr_size = 0; 1045 ctl.prwatch.pr_wflags = 0; 1046 result = write(arc_procfd, &ctl, sizeof (ctl)); 1047 ASSERT3U(result, ==, sizeof (ctl)); 1048 } 1049 #endif 1050 } 1051 1052 /* ARGSUSED */ 1053 static void 1054 arc_buf_watch(arc_buf_t *buf) 1055 { 1056 #ifndef _KERNEL 1057 if (arc_watch) { 1058 int result; 1059 procctl_t ctl; 1060 ctl.cmd = PCWATCH; 1061 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1062 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1063 ctl.prwatch.pr_wflags = WA_WRITE; 1064 result = write(arc_procfd, &ctl, sizeof (ctl)); 1065 ASSERT3U(result, ==, sizeof (ctl)); 1066 } 1067 #endif 1068 } 1069 1070 void 1071 arc_buf_thaw(arc_buf_t *buf) 1072 { 1073 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1074 if (buf->b_hdr->b_state != arc_anon) 1075 panic("modifying non-anon buffer!"); 1076 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS) 1077 panic("modifying buffer while i/o in progress!"); 1078 arc_cksum_verify(buf); 1079 } 1080 1081 mutex_enter(&buf->b_hdr->b_freeze_lock); 1082 if (buf->b_hdr->b_freeze_cksum != NULL) { 1083 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1084 buf->b_hdr->b_freeze_cksum = NULL; 1085 } 1086 1087 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1088 if (buf->b_hdr->b_thawed) 1089 kmem_free(buf->b_hdr->b_thawed, 1); 1090 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP); 1091 } 1092 1093 mutex_exit(&buf->b_hdr->b_freeze_lock); 1094 1095 arc_buf_unwatch(buf); 1096 } 1097 1098 void 1099 arc_buf_freeze(arc_buf_t *buf) 1100 { 1101 kmutex_t *hash_lock; 1102 1103 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1104 return; 1105 1106 hash_lock = HDR_LOCK(buf->b_hdr); 1107 mutex_enter(hash_lock); 1108 1109 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1110 buf->b_hdr->b_state == arc_anon); 1111 arc_cksum_compute(buf, B_FALSE); 1112 mutex_exit(hash_lock); 1113 1114 } 1115 1116 static void 1117 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1118 { 1119 ASSERT(MUTEX_HELD(hash_lock)); 1120 1121 if ((refcount_add(&ab->b_refcnt, tag) == 1) && 1122 (ab->b_state != arc_anon)) { 1123 uint64_t delta = ab->b_size * ab->b_datacnt; 1124 list_t *list = &ab->b_state->arcs_list[ab->b_type]; 1125 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type]; 1126 1127 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx)); 1128 mutex_enter(&ab->b_state->arcs_mtx); 1129 ASSERT(list_link_active(&ab->b_arc_node)); 1130 list_remove(list, ab); 1131 if (GHOST_STATE(ab->b_state)) { 1132 ASSERT0(ab->b_datacnt); 1133 ASSERT3P(ab->b_buf, ==, NULL); 1134 delta = ab->b_size; 1135 } 1136 ASSERT(delta > 0); 1137 ASSERT3U(*size, >=, delta); 1138 atomic_add_64(size, -delta); 1139 mutex_exit(&ab->b_state->arcs_mtx); 1140 /* remove the prefetch flag if we get a reference */ 1141 if (ab->b_flags & ARC_PREFETCH) 1142 ab->b_flags &= ~ARC_PREFETCH; 1143 } 1144 } 1145 1146 static int 1147 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) 1148 { 1149 int cnt; 1150 arc_state_t *state = ab->b_state; 1151 1152 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1153 ASSERT(!GHOST_STATE(state)); 1154 1155 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) && 1156 (state != arc_anon)) { 1157 uint64_t *size = &state->arcs_lsize[ab->b_type]; 1158 1159 ASSERT(!MUTEX_HELD(&state->arcs_mtx)); 1160 mutex_enter(&state->arcs_mtx); 1161 ASSERT(!list_link_active(&ab->b_arc_node)); 1162 list_insert_head(&state->arcs_list[ab->b_type], ab); 1163 ASSERT(ab->b_datacnt > 0); 1164 atomic_add_64(size, ab->b_size * ab->b_datacnt); 1165 mutex_exit(&state->arcs_mtx); 1166 } 1167 return (cnt); 1168 } 1169 1170 /* 1171 * Move the supplied buffer to the indicated state. The mutex 1172 * for the buffer must be held by the caller. 1173 */ 1174 static void 1175 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock) 1176 { 1177 arc_state_t *old_state = ab->b_state; 1178 int64_t refcnt = refcount_count(&ab->b_refcnt); 1179 uint64_t from_delta, to_delta; 1180 1181 ASSERT(MUTEX_HELD(hash_lock)); 1182 ASSERT3P(new_state, !=, old_state); 1183 ASSERT(refcnt == 0 || ab->b_datacnt > 0); 1184 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state)); 1185 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon); 1186 1187 from_delta = to_delta = ab->b_datacnt * ab->b_size; 1188 1189 /* 1190 * If this buffer is evictable, transfer it from the 1191 * old state list to the new state list. 1192 */ 1193 if (refcnt == 0) { 1194 if (old_state != arc_anon) { 1195 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx); 1196 uint64_t *size = &old_state->arcs_lsize[ab->b_type]; 1197 1198 if (use_mutex) 1199 mutex_enter(&old_state->arcs_mtx); 1200 1201 ASSERT(list_link_active(&ab->b_arc_node)); 1202 list_remove(&old_state->arcs_list[ab->b_type], ab); 1203 1204 /* 1205 * If prefetching out of the ghost cache, 1206 * we will have a non-zero datacnt. 1207 */ 1208 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) { 1209 /* ghost elements have a ghost size */ 1210 ASSERT(ab->b_buf == NULL); 1211 from_delta = ab->b_size; 1212 } 1213 ASSERT3U(*size, >=, from_delta); 1214 atomic_add_64(size, -from_delta); 1215 1216 if (use_mutex) 1217 mutex_exit(&old_state->arcs_mtx); 1218 } 1219 if (new_state != arc_anon) { 1220 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx); 1221 uint64_t *size = &new_state->arcs_lsize[ab->b_type]; 1222 1223 if (use_mutex) 1224 mutex_enter(&new_state->arcs_mtx); 1225 1226 list_insert_head(&new_state->arcs_list[ab->b_type], ab); 1227 1228 /* ghost elements have a ghost size */ 1229 if (GHOST_STATE(new_state)) { 1230 ASSERT(ab->b_datacnt == 0); 1231 ASSERT(ab->b_buf == NULL); 1232 to_delta = ab->b_size; 1233 } 1234 atomic_add_64(size, to_delta); 1235 1236 if (use_mutex) 1237 mutex_exit(&new_state->arcs_mtx); 1238 } 1239 } 1240 1241 ASSERT(!BUF_EMPTY(ab)); 1242 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab)) 1243 buf_hash_remove(ab); 1244 1245 /* adjust state sizes */ 1246 if (to_delta) 1247 atomic_add_64(&new_state->arcs_size, to_delta); 1248 if (from_delta) { 1249 ASSERT3U(old_state->arcs_size, >=, from_delta); 1250 atomic_add_64(&old_state->arcs_size, -from_delta); 1251 } 1252 ab->b_state = new_state; 1253 1254 /* adjust l2arc hdr stats */ 1255 if (new_state == arc_l2c_only) 1256 l2arc_hdr_stat_add(); 1257 else if (old_state == arc_l2c_only) 1258 l2arc_hdr_stat_remove(); 1259 } 1260 1261 void 1262 arc_space_consume(uint64_t space, arc_space_type_t type) 1263 { 1264 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1265 1266 switch (type) { 1267 case ARC_SPACE_DATA: 1268 ARCSTAT_INCR(arcstat_data_size, space); 1269 break; 1270 case ARC_SPACE_OTHER: 1271 ARCSTAT_INCR(arcstat_other_size, space); 1272 break; 1273 case ARC_SPACE_HDRS: 1274 ARCSTAT_INCR(arcstat_hdr_size, space); 1275 break; 1276 case ARC_SPACE_L2HDRS: 1277 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1278 break; 1279 } 1280 1281 ARCSTAT_INCR(arcstat_meta_used, space); 1282 atomic_add_64(&arc_size, space); 1283 } 1284 1285 void 1286 arc_space_return(uint64_t space, arc_space_type_t type) 1287 { 1288 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1289 1290 switch (type) { 1291 case ARC_SPACE_DATA: 1292 ARCSTAT_INCR(arcstat_data_size, -space); 1293 break; 1294 case ARC_SPACE_OTHER: 1295 ARCSTAT_INCR(arcstat_other_size, -space); 1296 break; 1297 case ARC_SPACE_HDRS: 1298 ARCSTAT_INCR(arcstat_hdr_size, -space); 1299 break; 1300 case ARC_SPACE_L2HDRS: 1301 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1302 break; 1303 } 1304 1305 ASSERT(arc_meta_used >= space); 1306 if (arc_meta_max < arc_meta_used) 1307 arc_meta_max = arc_meta_used; 1308 ARCSTAT_INCR(arcstat_meta_used, -space); 1309 ASSERT(arc_size >= space); 1310 atomic_add_64(&arc_size, -space); 1311 } 1312 1313 void * 1314 arc_data_buf_alloc(uint64_t size) 1315 { 1316 if (arc_evict_needed(ARC_BUFC_DATA)) 1317 cv_signal(&arc_reclaim_thr_cv); 1318 atomic_add_64(&arc_size, size); 1319 return (zio_data_buf_alloc(size)); 1320 } 1321 1322 void 1323 arc_data_buf_free(void *buf, uint64_t size) 1324 { 1325 zio_data_buf_free(buf, size); 1326 ASSERT(arc_size >= size); 1327 atomic_add_64(&arc_size, -size); 1328 } 1329 1330 arc_buf_t * 1331 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type) 1332 { 1333 arc_buf_hdr_t *hdr; 1334 arc_buf_t *buf; 1335 1336 ASSERT3U(size, >, 0); 1337 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 1338 ASSERT(BUF_EMPTY(hdr)); 1339 hdr->b_size = size; 1340 hdr->b_type = type; 1341 hdr->b_spa = spa_load_guid(spa); 1342 hdr->b_state = arc_anon; 1343 hdr->b_arc_access = 0; 1344 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1345 buf->b_hdr = hdr; 1346 buf->b_data = NULL; 1347 buf->b_efunc = NULL; 1348 buf->b_private = NULL; 1349 buf->b_next = NULL; 1350 hdr->b_buf = buf; 1351 arc_get_data_buf(buf); 1352 hdr->b_datacnt = 1; 1353 hdr->b_flags = 0; 1354 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1355 (void) refcount_add(&hdr->b_refcnt, tag); 1356 1357 return (buf); 1358 } 1359 1360 static char *arc_onloan_tag = "onloan"; 1361 1362 /* 1363 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1364 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1365 * buffers must be returned to the arc before they can be used by the DMU or 1366 * freed. 1367 */ 1368 arc_buf_t * 1369 arc_loan_buf(spa_t *spa, int size) 1370 { 1371 arc_buf_t *buf; 1372 1373 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1374 1375 atomic_add_64(&arc_loaned_bytes, size); 1376 return (buf); 1377 } 1378 1379 /* 1380 * Return a loaned arc buffer to the arc. 1381 */ 1382 void 1383 arc_return_buf(arc_buf_t *buf, void *tag) 1384 { 1385 arc_buf_hdr_t *hdr = buf->b_hdr; 1386 1387 ASSERT(buf->b_data != NULL); 1388 (void) refcount_add(&hdr->b_refcnt, tag); 1389 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag); 1390 1391 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1392 } 1393 1394 /* Detach an arc_buf from a dbuf (tag) */ 1395 void 1396 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1397 { 1398 arc_buf_hdr_t *hdr; 1399 1400 ASSERT(buf->b_data != NULL); 1401 hdr = buf->b_hdr; 1402 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag); 1403 (void) refcount_remove(&hdr->b_refcnt, tag); 1404 buf->b_efunc = NULL; 1405 buf->b_private = NULL; 1406 1407 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1408 } 1409 1410 static arc_buf_t * 1411 arc_buf_clone(arc_buf_t *from) 1412 { 1413 arc_buf_t *buf; 1414 arc_buf_hdr_t *hdr = from->b_hdr; 1415 uint64_t size = hdr->b_size; 1416 1417 ASSERT(hdr->b_state != arc_anon); 1418 1419 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1420 buf->b_hdr = hdr; 1421 buf->b_data = NULL; 1422 buf->b_efunc = NULL; 1423 buf->b_private = NULL; 1424 buf->b_next = hdr->b_buf; 1425 hdr->b_buf = buf; 1426 arc_get_data_buf(buf); 1427 bcopy(from->b_data, buf->b_data, size); 1428 1429 /* 1430 * This buffer already exists in the arc so create a duplicate 1431 * copy for the caller. If the buffer is associated with user data 1432 * then track the size and number of duplicates. These stats will be 1433 * updated as duplicate buffers are created and destroyed. 1434 */ 1435 if (hdr->b_type == ARC_BUFC_DATA) { 1436 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1437 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1438 } 1439 hdr->b_datacnt += 1; 1440 return (buf); 1441 } 1442 1443 void 1444 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1445 { 1446 arc_buf_hdr_t *hdr; 1447 kmutex_t *hash_lock; 1448 1449 /* 1450 * Check to see if this buffer is evicted. Callers 1451 * must verify b_data != NULL to know if the add_ref 1452 * was successful. 1453 */ 1454 mutex_enter(&buf->b_evict_lock); 1455 if (buf->b_data == NULL) { 1456 mutex_exit(&buf->b_evict_lock); 1457 return; 1458 } 1459 hash_lock = HDR_LOCK(buf->b_hdr); 1460 mutex_enter(hash_lock); 1461 hdr = buf->b_hdr; 1462 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1463 mutex_exit(&buf->b_evict_lock); 1464 1465 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 1466 add_reference(hdr, hash_lock, tag); 1467 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1468 arc_access(hdr, hash_lock); 1469 mutex_exit(hash_lock); 1470 ARCSTAT_BUMP(arcstat_hits); 1471 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 1472 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 1473 data, metadata, hits); 1474 } 1475 1476 /* 1477 * Free the arc data buffer. If it is an l2arc write in progress, 1478 * the buffer is placed on l2arc_free_on_write to be freed later. 1479 */ 1480 static void 1481 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1482 { 1483 arc_buf_hdr_t *hdr = buf->b_hdr; 1484 1485 if (HDR_L2_WRITING(hdr)) { 1486 l2arc_data_free_t *df; 1487 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1488 df->l2df_data = buf->b_data; 1489 df->l2df_size = hdr->b_size; 1490 df->l2df_func = free_func; 1491 mutex_enter(&l2arc_free_on_write_mtx); 1492 list_insert_head(l2arc_free_on_write, df); 1493 mutex_exit(&l2arc_free_on_write_mtx); 1494 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1495 } else { 1496 free_func(buf->b_data, hdr->b_size); 1497 } 1498 } 1499 1500 /* 1501 * Free up buf->b_data and if 'remove' is set, then pull the 1502 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 1503 */ 1504 static void 1505 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) 1506 { 1507 arc_buf_t **bufp; 1508 1509 /* free up data associated with the buf */ 1510 if (buf->b_data) { 1511 arc_state_t *state = buf->b_hdr->b_state; 1512 uint64_t size = buf->b_hdr->b_size; 1513 arc_buf_contents_t type = buf->b_hdr->b_type; 1514 1515 arc_cksum_verify(buf); 1516 arc_buf_unwatch(buf); 1517 1518 if (!recycle) { 1519 if (type == ARC_BUFC_METADATA) { 1520 arc_buf_data_free(buf, zio_buf_free); 1521 arc_space_return(size, ARC_SPACE_DATA); 1522 } else { 1523 ASSERT(type == ARC_BUFC_DATA); 1524 arc_buf_data_free(buf, zio_data_buf_free); 1525 ARCSTAT_INCR(arcstat_data_size, -size); 1526 atomic_add_64(&arc_size, -size); 1527 } 1528 } 1529 if (list_link_active(&buf->b_hdr->b_arc_node)) { 1530 uint64_t *cnt = &state->arcs_lsize[type]; 1531 1532 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt)); 1533 ASSERT(state != arc_anon); 1534 1535 ASSERT3U(*cnt, >=, size); 1536 atomic_add_64(cnt, -size); 1537 } 1538 ASSERT3U(state->arcs_size, >=, size); 1539 atomic_add_64(&state->arcs_size, -size); 1540 buf->b_data = NULL; 1541 1542 /* 1543 * If we're destroying a duplicate buffer make sure 1544 * that the appropriate statistics are updated. 1545 */ 1546 if (buf->b_hdr->b_datacnt > 1 && 1547 buf->b_hdr->b_type == ARC_BUFC_DATA) { 1548 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1549 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1550 } 1551 ASSERT(buf->b_hdr->b_datacnt > 0); 1552 buf->b_hdr->b_datacnt -= 1; 1553 } 1554 1555 /* only remove the buf if requested */ 1556 if (!remove) 1557 return; 1558 1559 /* remove the buf from the hdr list */ 1560 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next) 1561 continue; 1562 *bufp = buf->b_next; 1563 buf->b_next = NULL; 1564 1565 ASSERT(buf->b_efunc == NULL); 1566 1567 /* clean up the buf */ 1568 buf->b_hdr = NULL; 1569 kmem_cache_free(buf_cache, buf); 1570 } 1571 1572 static void 1573 arc_hdr_destroy(arc_buf_hdr_t *hdr) 1574 { 1575 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1576 ASSERT3P(hdr->b_state, ==, arc_anon); 1577 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1578 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1579 1580 if (l2hdr != NULL) { 1581 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx); 1582 /* 1583 * To prevent arc_free() and l2arc_evict() from 1584 * attempting to free the same buffer at the same time, 1585 * a FREE_IN_PROGRESS flag is given to arc_free() to 1586 * give it priority. l2arc_evict() can't destroy this 1587 * header while we are waiting on l2arc_buflist_mtx. 1588 * 1589 * The hdr may be removed from l2ad_buflist before we 1590 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked. 1591 */ 1592 if (!buflist_held) { 1593 mutex_enter(&l2arc_buflist_mtx); 1594 l2hdr = hdr->b_l2hdr; 1595 } 1596 1597 if (l2hdr != NULL) { 1598 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 1599 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1600 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 1601 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 1602 -l2hdr->b_asize, 0, 0); 1603 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 1604 if (hdr->b_state == arc_l2c_only) 1605 l2arc_hdr_stat_remove(); 1606 hdr->b_l2hdr = NULL; 1607 } 1608 1609 if (!buflist_held) 1610 mutex_exit(&l2arc_buflist_mtx); 1611 } 1612 1613 if (!BUF_EMPTY(hdr)) { 1614 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1615 buf_discard_identity(hdr); 1616 } 1617 while (hdr->b_buf) { 1618 arc_buf_t *buf = hdr->b_buf; 1619 1620 if (buf->b_efunc) { 1621 mutex_enter(&arc_eviction_mtx); 1622 mutex_enter(&buf->b_evict_lock); 1623 ASSERT(buf->b_hdr != NULL); 1624 arc_buf_destroy(hdr->b_buf, FALSE, FALSE); 1625 hdr->b_buf = buf->b_next; 1626 buf->b_hdr = &arc_eviction_hdr; 1627 buf->b_next = arc_eviction_list; 1628 arc_eviction_list = buf; 1629 mutex_exit(&buf->b_evict_lock); 1630 mutex_exit(&arc_eviction_mtx); 1631 } else { 1632 arc_buf_destroy(hdr->b_buf, FALSE, TRUE); 1633 } 1634 } 1635 if (hdr->b_freeze_cksum != NULL) { 1636 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1637 hdr->b_freeze_cksum = NULL; 1638 } 1639 if (hdr->b_thawed) { 1640 kmem_free(hdr->b_thawed, 1); 1641 hdr->b_thawed = NULL; 1642 } 1643 1644 ASSERT(!list_link_active(&hdr->b_arc_node)); 1645 ASSERT3P(hdr->b_hash_next, ==, NULL); 1646 ASSERT3P(hdr->b_acb, ==, NULL); 1647 kmem_cache_free(hdr_cache, hdr); 1648 } 1649 1650 void 1651 arc_buf_free(arc_buf_t *buf, void *tag) 1652 { 1653 arc_buf_hdr_t *hdr = buf->b_hdr; 1654 int hashed = hdr->b_state != arc_anon; 1655 1656 ASSERT(buf->b_efunc == NULL); 1657 ASSERT(buf->b_data != NULL); 1658 1659 if (hashed) { 1660 kmutex_t *hash_lock = HDR_LOCK(hdr); 1661 1662 mutex_enter(hash_lock); 1663 hdr = buf->b_hdr; 1664 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1665 1666 (void) remove_reference(hdr, hash_lock, tag); 1667 if (hdr->b_datacnt > 1) { 1668 arc_buf_destroy(buf, FALSE, TRUE); 1669 } else { 1670 ASSERT(buf == hdr->b_buf); 1671 ASSERT(buf->b_efunc == NULL); 1672 hdr->b_flags |= ARC_BUF_AVAILABLE; 1673 } 1674 mutex_exit(hash_lock); 1675 } else if (HDR_IO_IN_PROGRESS(hdr)) { 1676 int destroy_hdr; 1677 /* 1678 * We are in the middle of an async write. Don't destroy 1679 * this buffer unless the write completes before we finish 1680 * decrementing the reference count. 1681 */ 1682 mutex_enter(&arc_eviction_mtx); 1683 (void) remove_reference(hdr, NULL, tag); 1684 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1685 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 1686 mutex_exit(&arc_eviction_mtx); 1687 if (destroy_hdr) 1688 arc_hdr_destroy(hdr); 1689 } else { 1690 if (remove_reference(hdr, NULL, tag) > 0) 1691 arc_buf_destroy(buf, FALSE, TRUE); 1692 else 1693 arc_hdr_destroy(hdr); 1694 } 1695 } 1696 1697 boolean_t 1698 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 1699 { 1700 arc_buf_hdr_t *hdr = buf->b_hdr; 1701 kmutex_t *hash_lock = HDR_LOCK(hdr); 1702 boolean_t no_callback = (buf->b_efunc == NULL); 1703 1704 if (hdr->b_state == arc_anon) { 1705 ASSERT(hdr->b_datacnt == 1); 1706 arc_buf_free(buf, tag); 1707 return (no_callback); 1708 } 1709 1710 mutex_enter(hash_lock); 1711 hdr = buf->b_hdr; 1712 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1713 ASSERT(hdr->b_state != arc_anon); 1714 ASSERT(buf->b_data != NULL); 1715 1716 (void) remove_reference(hdr, hash_lock, tag); 1717 if (hdr->b_datacnt > 1) { 1718 if (no_callback) 1719 arc_buf_destroy(buf, FALSE, TRUE); 1720 } else if (no_callback) { 1721 ASSERT(hdr->b_buf == buf && buf->b_next == NULL); 1722 ASSERT(buf->b_efunc == NULL); 1723 hdr->b_flags |= ARC_BUF_AVAILABLE; 1724 } 1725 ASSERT(no_callback || hdr->b_datacnt > 1 || 1726 refcount_is_zero(&hdr->b_refcnt)); 1727 mutex_exit(hash_lock); 1728 return (no_callback); 1729 } 1730 1731 int 1732 arc_buf_size(arc_buf_t *buf) 1733 { 1734 return (buf->b_hdr->b_size); 1735 } 1736 1737 /* 1738 * Called from the DMU to determine if the current buffer should be 1739 * evicted. In order to ensure proper locking, the eviction must be initiated 1740 * from the DMU. Return true if the buffer is associated with user data and 1741 * duplicate buffers still exist. 1742 */ 1743 boolean_t 1744 arc_buf_eviction_needed(arc_buf_t *buf) 1745 { 1746 arc_buf_hdr_t *hdr; 1747 boolean_t evict_needed = B_FALSE; 1748 1749 if (zfs_disable_dup_eviction) 1750 return (B_FALSE); 1751 1752 mutex_enter(&buf->b_evict_lock); 1753 hdr = buf->b_hdr; 1754 if (hdr == NULL) { 1755 /* 1756 * We are in arc_do_user_evicts(); let that function 1757 * perform the eviction. 1758 */ 1759 ASSERT(buf->b_data == NULL); 1760 mutex_exit(&buf->b_evict_lock); 1761 return (B_FALSE); 1762 } else if (buf->b_data == NULL) { 1763 /* 1764 * We have already been added to the arc eviction list; 1765 * recommend eviction. 1766 */ 1767 ASSERT3P(hdr, ==, &arc_eviction_hdr); 1768 mutex_exit(&buf->b_evict_lock); 1769 return (B_TRUE); 1770 } 1771 1772 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) 1773 evict_needed = B_TRUE; 1774 1775 mutex_exit(&buf->b_evict_lock); 1776 return (evict_needed); 1777 } 1778 1779 /* 1780 * Evict buffers from list until we've removed the specified number of 1781 * bytes. Move the removed buffers to the appropriate evict state. 1782 * If the recycle flag is set, then attempt to "recycle" a buffer: 1783 * - look for a buffer to evict that is `bytes' long. 1784 * - return the data block from this buffer rather than freeing it. 1785 * This flag is used by callers that are trying to make space for a 1786 * new buffer in a full arc cache. 1787 * 1788 * This function makes a "best effort". It skips over any buffers 1789 * it can't get a hash_lock on, and so may not catch all candidates. 1790 * It may also return without evicting as much space as requested. 1791 */ 1792 static void * 1793 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 1794 arc_buf_contents_t type) 1795 { 1796 arc_state_t *evicted_state; 1797 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 1798 arc_buf_hdr_t *ab, *ab_prev = NULL; 1799 list_t *list = &state->arcs_list[type]; 1800 kmutex_t *hash_lock; 1801 boolean_t have_lock; 1802 void *stolen = NULL; 1803 arc_buf_hdr_t marker = { 0 }; 1804 int count = 0; 1805 1806 ASSERT(state == arc_mru || state == arc_mfu); 1807 1808 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 1809 1810 mutex_enter(&state->arcs_mtx); 1811 mutex_enter(&evicted_state->arcs_mtx); 1812 1813 for (ab = list_tail(list); ab; ab = ab_prev) { 1814 ab_prev = list_prev(list, ab); 1815 /* prefetch buffers have a minimum lifespan */ 1816 if (HDR_IO_IN_PROGRESS(ab) || 1817 (spa && ab->b_spa != spa) || 1818 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) && 1819 ddi_get_lbolt() - ab->b_arc_access < 1820 arc_min_prefetch_lifespan)) { 1821 skipped++; 1822 continue; 1823 } 1824 /* "lookahead" for better eviction candidate */ 1825 if (recycle && ab->b_size != bytes && 1826 ab_prev && ab_prev->b_size == bytes) 1827 continue; 1828 1829 /* ignore markers */ 1830 if (ab->b_spa == 0) 1831 continue; 1832 1833 /* 1834 * It may take a long time to evict all the bufs requested. 1835 * To avoid blocking all arc activity, periodically drop 1836 * the arcs_mtx and give other threads a chance to run 1837 * before reacquiring the lock. 1838 * 1839 * If we are looking for a buffer to recycle, we are in 1840 * the hot code path, so don't sleep. 1841 */ 1842 if (!recycle && count++ > arc_evict_iterations) { 1843 list_insert_after(list, ab, &marker); 1844 mutex_exit(&evicted_state->arcs_mtx); 1845 mutex_exit(&state->arcs_mtx); 1846 kpreempt(KPREEMPT_SYNC); 1847 mutex_enter(&state->arcs_mtx); 1848 mutex_enter(&evicted_state->arcs_mtx); 1849 ab_prev = list_prev(list, &marker); 1850 list_remove(list, &marker); 1851 count = 0; 1852 continue; 1853 } 1854 1855 hash_lock = HDR_LOCK(ab); 1856 have_lock = MUTEX_HELD(hash_lock); 1857 if (have_lock || mutex_tryenter(hash_lock)) { 1858 ASSERT0(refcount_count(&ab->b_refcnt)); 1859 ASSERT(ab->b_datacnt > 0); 1860 while (ab->b_buf) { 1861 arc_buf_t *buf = ab->b_buf; 1862 if (!mutex_tryenter(&buf->b_evict_lock)) { 1863 missed += 1; 1864 break; 1865 } 1866 if (buf->b_data) { 1867 bytes_evicted += ab->b_size; 1868 if (recycle && ab->b_type == type && 1869 ab->b_size == bytes && 1870 !HDR_L2_WRITING(ab)) { 1871 stolen = buf->b_data; 1872 recycle = FALSE; 1873 } 1874 } 1875 if (buf->b_efunc) { 1876 mutex_enter(&arc_eviction_mtx); 1877 arc_buf_destroy(buf, 1878 buf->b_data == stolen, FALSE); 1879 ab->b_buf = buf->b_next; 1880 buf->b_hdr = &arc_eviction_hdr; 1881 buf->b_next = arc_eviction_list; 1882 arc_eviction_list = buf; 1883 mutex_exit(&arc_eviction_mtx); 1884 mutex_exit(&buf->b_evict_lock); 1885 } else { 1886 mutex_exit(&buf->b_evict_lock); 1887 arc_buf_destroy(buf, 1888 buf->b_data == stolen, TRUE); 1889 } 1890 } 1891 1892 if (ab->b_l2hdr) { 1893 ARCSTAT_INCR(arcstat_evict_l2_cached, 1894 ab->b_size); 1895 } else { 1896 if (l2arc_write_eligible(ab->b_spa, ab)) { 1897 ARCSTAT_INCR(arcstat_evict_l2_eligible, 1898 ab->b_size); 1899 } else { 1900 ARCSTAT_INCR( 1901 arcstat_evict_l2_ineligible, 1902 ab->b_size); 1903 } 1904 } 1905 1906 if (ab->b_datacnt == 0) { 1907 arc_change_state(evicted_state, ab, hash_lock); 1908 ASSERT(HDR_IN_HASH_TABLE(ab)); 1909 ab->b_flags |= ARC_IN_HASH_TABLE; 1910 ab->b_flags &= ~ARC_BUF_AVAILABLE; 1911 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab); 1912 } 1913 if (!have_lock) 1914 mutex_exit(hash_lock); 1915 if (bytes >= 0 && bytes_evicted >= bytes) 1916 break; 1917 } else { 1918 missed += 1; 1919 } 1920 } 1921 1922 mutex_exit(&evicted_state->arcs_mtx); 1923 mutex_exit(&state->arcs_mtx); 1924 1925 if (bytes_evicted < bytes) 1926 dprintf("only evicted %lld bytes from %x", 1927 (longlong_t)bytes_evicted, state); 1928 1929 if (skipped) 1930 ARCSTAT_INCR(arcstat_evict_skip, skipped); 1931 1932 if (missed) 1933 ARCSTAT_INCR(arcstat_mutex_miss, missed); 1934 1935 /* 1936 * Note: we have just evicted some data into the ghost state, 1937 * potentially putting the ghost size over the desired size. Rather 1938 * that evicting from the ghost list in this hot code path, leave 1939 * this chore to the arc_reclaim_thread(). 1940 */ 1941 1942 return (stolen); 1943 } 1944 1945 /* 1946 * Remove buffers from list until we've removed the specified number of 1947 * bytes. Destroy the buffers that are removed. 1948 */ 1949 static void 1950 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 1951 { 1952 arc_buf_hdr_t *ab, *ab_prev; 1953 arc_buf_hdr_t marker = { 0 }; 1954 list_t *list = &state->arcs_list[ARC_BUFC_DATA]; 1955 kmutex_t *hash_lock; 1956 uint64_t bytes_deleted = 0; 1957 uint64_t bufs_skipped = 0; 1958 int count = 0; 1959 1960 ASSERT(GHOST_STATE(state)); 1961 top: 1962 mutex_enter(&state->arcs_mtx); 1963 for (ab = list_tail(list); ab; ab = ab_prev) { 1964 ab_prev = list_prev(list, ab); 1965 if (ab->b_type > ARC_BUFC_NUMTYPES) 1966 panic("invalid ab=%p", (void *)ab); 1967 if (spa && ab->b_spa != spa) 1968 continue; 1969 1970 /* ignore markers */ 1971 if (ab->b_spa == 0) 1972 continue; 1973 1974 hash_lock = HDR_LOCK(ab); 1975 /* caller may be trying to modify this buffer, skip it */ 1976 if (MUTEX_HELD(hash_lock)) 1977 continue; 1978 1979 /* 1980 * It may take a long time to evict all the bufs requested. 1981 * To avoid blocking all arc activity, periodically drop 1982 * the arcs_mtx and give other threads a chance to run 1983 * before reacquiring the lock. 1984 */ 1985 if (count++ > arc_evict_iterations) { 1986 list_insert_after(list, ab, &marker); 1987 mutex_exit(&state->arcs_mtx); 1988 kpreempt(KPREEMPT_SYNC); 1989 mutex_enter(&state->arcs_mtx); 1990 ab_prev = list_prev(list, &marker); 1991 list_remove(list, &marker); 1992 count = 0; 1993 continue; 1994 } 1995 if (mutex_tryenter(hash_lock)) { 1996 ASSERT(!HDR_IO_IN_PROGRESS(ab)); 1997 ASSERT(ab->b_buf == NULL); 1998 ARCSTAT_BUMP(arcstat_deleted); 1999 bytes_deleted += ab->b_size; 2000 2001 if (ab->b_l2hdr != NULL) { 2002 /* 2003 * This buffer is cached on the 2nd Level ARC; 2004 * don't destroy the header. 2005 */ 2006 arc_change_state(arc_l2c_only, ab, hash_lock); 2007 mutex_exit(hash_lock); 2008 } else { 2009 arc_change_state(arc_anon, ab, hash_lock); 2010 mutex_exit(hash_lock); 2011 arc_hdr_destroy(ab); 2012 } 2013 2014 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab); 2015 if (bytes >= 0 && bytes_deleted >= bytes) 2016 break; 2017 } else if (bytes < 0) { 2018 /* 2019 * Insert a list marker and then wait for the 2020 * hash lock to become available. Once its 2021 * available, restart from where we left off. 2022 */ 2023 list_insert_after(list, ab, &marker); 2024 mutex_exit(&state->arcs_mtx); 2025 mutex_enter(hash_lock); 2026 mutex_exit(hash_lock); 2027 mutex_enter(&state->arcs_mtx); 2028 ab_prev = list_prev(list, &marker); 2029 list_remove(list, &marker); 2030 } else { 2031 bufs_skipped += 1; 2032 } 2033 2034 } 2035 mutex_exit(&state->arcs_mtx); 2036 2037 if (list == &state->arcs_list[ARC_BUFC_DATA] && 2038 (bytes < 0 || bytes_deleted < bytes)) { 2039 list = &state->arcs_list[ARC_BUFC_METADATA]; 2040 goto top; 2041 } 2042 2043 if (bufs_skipped) { 2044 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2045 ASSERT(bytes >= 0); 2046 } 2047 2048 if (bytes_deleted < bytes) 2049 dprintf("only deleted %lld bytes from %p", 2050 (longlong_t)bytes_deleted, state); 2051 } 2052 2053 static void 2054 arc_adjust(void) 2055 { 2056 int64_t adjustment, delta; 2057 2058 /* 2059 * Adjust MRU size 2060 */ 2061 2062 adjustment = MIN((int64_t)(arc_size - arc_c), 2063 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2064 arc_p)); 2065 2066 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2067 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2068 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA); 2069 adjustment -= delta; 2070 } 2071 2072 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2073 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2074 (void) arc_evict(arc_mru, NULL, delta, FALSE, 2075 ARC_BUFC_METADATA); 2076 } 2077 2078 /* 2079 * Adjust MFU size 2080 */ 2081 2082 adjustment = arc_size - arc_c; 2083 2084 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2085 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2086 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA); 2087 adjustment -= delta; 2088 } 2089 2090 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2091 int64_t delta = MIN(adjustment, 2092 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2093 (void) arc_evict(arc_mfu, NULL, delta, FALSE, 2094 ARC_BUFC_METADATA); 2095 } 2096 2097 /* 2098 * Adjust ghost lists 2099 */ 2100 2101 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2102 2103 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2104 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2105 arc_evict_ghost(arc_mru_ghost, NULL, delta); 2106 } 2107 2108 adjustment = 2109 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2110 2111 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2112 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2113 arc_evict_ghost(arc_mfu_ghost, NULL, delta); 2114 } 2115 } 2116 2117 static void 2118 arc_do_user_evicts(void) 2119 { 2120 mutex_enter(&arc_eviction_mtx); 2121 while (arc_eviction_list != NULL) { 2122 arc_buf_t *buf = arc_eviction_list; 2123 arc_eviction_list = buf->b_next; 2124 mutex_enter(&buf->b_evict_lock); 2125 buf->b_hdr = NULL; 2126 mutex_exit(&buf->b_evict_lock); 2127 mutex_exit(&arc_eviction_mtx); 2128 2129 if (buf->b_efunc != NULL) 2130 VERIFY0(buf->b_efunc(buf->b_private)); 2131 2132 buf->b_efunc = NULL; 2133 buf->b_private = NULL; 2134 kmem_cache_free(buf_cache, buf); 2135 mutex_enter(&arc_eviction_mtx); 2136 } 2137 mutex_exit(&arc_eviction_mtx); 2138 } 2139 2140 /* 2141 * Flush all *evictable* data from the cache for the given spa. 2142 * NOTE: this will not touch "active" (i.e. referenced) data. 2143 */ 2144 void 2145 arc_flush(spa_t *spa) 2146 { 2147 uint64_t guid = 0; 2148 2149 if (spa) 2150 guid = spa_load_guid(spa); 2151 2152 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) { 2153 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2154 if (spa) 2155 break; 2156 } 2157 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) { 2158 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2159 if (spa) 2160 break; 2161 } 2162 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) { 2163 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2164 if (spa) 2165 break; 2166 } 2167 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) { 2168 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2169 if (spa) 2170 break; 2171 } 2172 2173 arc_evict_ghost(arc_mru_ghost, guid, -1); 2174 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2175 2176 mutex_enter(&arc_reclaim_thr_lock); 2177 arc_do_user_evicts(); 2178 mutex_exit(&arc_reclaim_thr_lock); 2179 ASSERT(spa || arc_eviction_list == NULL); 2180 } 2181 2182 void 2183 arc_shrink(void) 2184 { 2185 if (arc_c > arc_c_min) { 2186 uint64_t to_free; 2187 2188 #ifdef _KERNEL 2189 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree)); 2190 #else 2191 to_free = arc_c >> arc_shrink_shift; 2192 #endif 2193 if (arc_c > arc_c_min + to_free) 2194 atomic_add_64(&arc_c, -to_free); 2195 else 2196 arc_c = arc_c_min; 2197 2198 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2199 if (arc_c > arc_size) 2200 arc_c = MAX(arc_size, arc_c_min); 2201 if (arc_p > arc_c) 2202 arc_p = (arc_c >> 1); 2203 ASSERT(arc_c >= arc_c_min); 2204 ASSERT((int64_t)arc_p >= 0); 2205 } 2206 2207 if (arc_size > arc_c) 2208 arc_adjust(); 2209 } 2210 2211 /* 2212 * Determine if the system is under memory pressure and is asking 2213 * to reclaim memory. A return value of 1 indicates that the system 2214 * is under memory pressure and that the arc should adjust accordingly. 2215 */ 2216 static int 2217 arc_reclaim_needed(void) 2218 { 2219 uint64_t extra; 2220 2221 #ifdef _KERNEL 2222 2223 if (needfree) 2224 return (1); 2225 2226 /* 2227 * take 'desfree' extra pages, so we reclaim sooner, rather than later 2228 */ 2229 extra = desfree; 2230 2231 /* 2232 * check that we're out of range of the pageout scanner. It starts to 2233 * schedule paging if freemem is less than lotsfree and needfree. 2234 * lotsfree is the high-water mark for pageout, and needfree is the 2235 * number of needed free pages. We add extra pages here to make sure 2236 * the scanner doesn't start up while we're freeing memory. 2237 */ 2238 if (freemem < lotsfree + needfree + extra) 2239 return (1); 2240 2241 /* 2242 * check to make sure that swapfs has enough space so that anon 2243 * reservations can still succeed. anon_resvmem() checks that the 2244 * availrmem is greater than swapfs_minfree, and the number of reserved 2245 * swap pages. We also add a bit of extra here just to prevent 2246 * circumstances from getting really dire. 2247 */ 2248 if (availrmem < swapfs_minfree + swapfs_reserve + extra) 2249 return (1); 2250 2251 /* 2252 * Check that we have enough availrmem that memory locking (e.g., via 2253 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 2254 * stores the number of pages that cannot be locked; when availrmem 2255 * drops below pages_pp_maximum, page locking mechanisms such as 2256 * page_pp_lock() will fail.) 2257 */ 2258 if (availrmem <= pages_pp_maximum) 2259 return (1); 2260 2261 #if defined(__i386) 2262 /* 2263 * If we're on an i386 platform, it's possible that we'll exhaust the 2264 * kernel heap space before we ever run out of available physical 2265 * memory. Most checks of the size of the heap_area compare against 2266 * tune.t_minarmem, which is the minimum available real memory that we 2267 * can have in the system. However, this is generally fixed at 25 pages 2268 * which is so low that it's useless. In this comparison, we seek to 2269 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2270 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2271 * free) 2272 */ 2273 if (vmem_size(heap_arena, VMEM_FREE) < 2274 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) 2275 return (1); 2276 #endif 2277 2278 /* 2279 * If zio data pages are being allocated out of a separate heap segment, 2280 * then enforce that the size of available vmem for this arena remains 2281 * above about 1/16th free. 2282 * 2283 * Note: The 1/16th arena free requirement was put in place 2284 * to aggressively evict memory from the arc in order to avoid 2285 * memory fragmentation issues. 2286 */ 2287 if (zio_arena != NULL && 2288 vmem_size(zio_arena, VMEM_FREE) < 2289 (vmem_size(zio_arena, VMEM_ALLOC) >> 4)) 2290 return (1); 2291 #else 2292 if (spa_get_random(100) == 0) 2293 return (1); 2294 #endif 2295 return (0); 2296 } 2297 2298 static void 2299 arc_kmem_reap_now(arc_reclaim_strategy_t strat) 2300 { 2301 size_t i; 2302 kmem_cache_t *prev_cache = NULL; 2303 kmem_cache_t *prev_data_cache = NULL; 2304 extern kmem_cache_t *zio_buf_cache[]; 2305 extern kmem_cache_t *zio_data_buf_cache[]; 2306 extern kmem_cache_t *range_seg_cache; 2307 2308 #ifdef _KERNEL 2309 if (arc_meta_used >= arc_meta_limit) { 2310 /* 2311 * We are exceeding our meta-data cache limit. 2312 * Purge some DNLC entries to release holds on meta-data. 2313 */ 2314 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2315 } 2316 #if defined(__i386) 2317 /* 2318 * Reclaim unused memory from all kmem caches. 2319 */ 2320 kmem_reap(); 2321 #endif 2322 #endif 2323 2324 /* 2325 * An aggressive reclamation will shrink the cache size as well as 2326 * reap free buffers from the arc kmem caches. 2327 */ 2328 if (strat == ARC_RECLAIM_AGGR) 2329 arc_shrink(); 2330 2331 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2332 if (zio_buf_cache[i] != prev_cache) { 2333 prev_cache = zio_buf_cache[i]; 2334 kmem_cache_reap_now(zio_buf_cache[i]); 2335 } 2336 if (zio_data_buf_cache[i] != prev_data_cache) { 2337 prev_data_cache = zio_data_buf_cache[i]; 2338 kmem_cache_reap_now(zio_data_buf_cache[i]); 2339 } 2340 } 2341 kmem_cache_reap_now(buf_cache); 2342 kmem_cache_reap_now(hdr_cache); 2343 kmem_cache_reap_now(range_seg_cache); 2344 2345 /* 2346 * Ask the vmem areana to reclaim unused memory from its 2347 * quantum caches. 2348 */ 2349 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR) 2350 vmem_qcache_reap(zio_arena); 2351 } 2352 2353 static void 2354 arc_reclaim_thread(void) 2355 { 2356 clock_t growtime = 0; 2357 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS; 2358 callb_cpr_t cpr; 2359 2360 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2361 2362 mutex_enter(&arc_reclaim_thr_lock); 2363 while (arc_thread_exit == 0) { 2364 if (arc_reclaim_needed()) { 2365 2366 if (arc_no_grow) { 2367 if (last_reclaim == ARC_RECLAIM_CONS) { 2368 last_reclaim = ARC_RECLAIM_AGGR; 2369 } else { 2370 last_reclaim = ARC_RECLAIM_CONS; 2371 } 2372 } else { 2373 arc_no_grow = TRUE; 2374 last_reclaim = ARC_RECLAIM_AGGR; 2375 membar_producer(); 2376 } 2377 2378 /* reset the growth delay for every reclaim */ 2379 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2380 2381 arc_kmem_reap_now(last_reclaim); 2382 arc_warm = B_TRUE; 2383 2384 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { 2385 arc_no_grow = FALSE; 2386 } 2387 2388 arc_adjust(); 2389 2390 if (arc_eviction_list != NULL) 2391 arc_do_user_evicts(); 2392 2393 /* block until needed, or one second, whichever is shorter */ 2394 CALLB_CPR_SAFE_BEGIN(&cpr); 2395 (void) cv_timedwait(&arc_reclaim_thr_cv, 2396 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz)); 2397 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2398 } 2399 2400 arc_thread_exit = 0; 2401 cv_broadcast(&arc_reclaim_thr_cv); 2402 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2403 thread_exit(); 2404 } 2405 2406 /* 2407 * Adapt arc info given the number of bytes we are trying to add and 2408 * the state that we are comming from. This function is only called 2409 * when we are adding new content to the cache. 2410 */ 2411 static void 2412 arc_adapt(int bytes, arc_state_t *state) 2413 { 2414 int mult; 2415 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2416 2417 if (state == arc_l2c_only) 2418 return; 2419 2420 ASSERT(bytes > 0); 2421 /* 2422 * Adapt the target size of the MRU list: 2423 * - if we just hit in the MRU ghost list, then increase 2424 * the target size of the MRU list. 2425 * - if we just hit in the MFU ghost list, then increase 2426 * the target size of the MFU list by decreasing the 2427 * target size of the MRU list. 2428 */ 2429 if (state == arc_mru_ghost) { 2430 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2431 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2432 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2433 2434 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2435 } else if (state == arc_mfu_ghost) { 2436 uint64_t delta; 2437 2438 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2439 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2440 mult = MIN(mult, 10); 2441 2442 delta = MIN(bytes * mult, arc_p); 2443 arc_p = MAX(arc_p_min, arc_p - delta); 2444 } 2445 ASSERT((int64_t)arc_p >= 0); 2446 2447 if (arc_reclaim_needed()) { 2448 cv_signal(&arc_reclaim_thr_cv); 2449 return; 2450 } 2451 2452 if (arc_no_grow) 2453 return; 2454 2455 if (arc_c >= arc_c_max) 2456 return; 2457 2458 /* 2459 * If we're within (2 * maxblocksize) bytes of the target 2460 * cache size, increment the target cache size 2461 */ 2462 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2463 atomic_add_64(&arc_c, (int64_t)bytes); 2464 if (arc_c > arc_c_max) 2465 arc_c = arc_c_max; 2466 else if (state == arc_anon) 2467 atomic_add_64(&arc_p, (int64_t)bytes); 2468 if (arc_p > arc_c) 2469 arc_p = arc_c; 2470 } 2471 ASSERT((int64_t)arc_p >= 0); 2472 } 2473 2474 /* 2475 * Check if the cache has reached its limits and eviction is required 2476 * prior to insert. 2477 */ 2478 static int 2479 arc_evict_needed(arc_buf_contents_t type) 2480 { 2481 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 2482 return (1); 2483 2484 if (arc_reclaim_needed()) 2485 return (1); 2486 2487 return (arc_size > arc_c); 2488 } 2489 2490 /* 2491 * The buffer, supplied as the first argument, needs a data block. 2492 * So, if we are at cache max, determine which cache should be victimized. 2493 * We have the following cases: 2494 * 2495 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 2496 * In this situation if we're out of space, but the resident size of the MFU is 2497 * under the limit, victimize the MFU cache to satisfy this insertion request. 2498 * 2499 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 2500 * Here, we've used up all of the available space for the MRU, so we need to 2501 * evict from our own cache instead. Evict from the set of resident MRU 2502 * entries. 2503 * 2504 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 2505 * c minus p represents the MFU space in the cache, since p is the size of the 2506 * cache that is dedicated to the MRU. In this situation there's still space on 2507 * the MFU side, so the MRU side needs to be victimized. 2508 * 2509 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 2510 * MFU's resident set is consuming more space than it has been allotted. In 2511 * this situation, we must victimize our own cache, the MFU, for this insertion. 2512 */ 2513 static void 2514 arc_get_data_buf(arc_buf_t *buf) 2515 { 2516 arc_state_t *state = buf->b_hdr->b_state; 2517 uint64_t size = buf->b_hdr->b_size; 2518 arc_buf_contents_t type = buf->b_hdr->b_type; 2519 2520 arc_adapt(size, state); 2521 2522 /* 2523 * We have not yet reached cache maximum size, 2524 * just allocate a new buffer. 2525 */ 2526 if (!arc_evict_needed(type)) { 2527 if (type == ARC_BUFC_METADATA) { 2528 buf->b_data = zio_buf_alloc(size); 2529 arc_space_consume(size, ARC_SPACE_DATA); 2530 } else { 2531 ASSERT(type == ARC_BUFC_DATA); 2532 buf->b_data = zio_data_buf_alloc(size); 2533 ARCSTAT_INCR(arcstat_data_size, size); 2534 atomic_add_64(&arc_size, size); 2535 } 2536 goto out; 2537 } 2538 2539 /* 2540 * If we are prefetching from the mfu ghost list, this buffer 2541 * will end up on the mru list; so steal space from there. 2542 */ 2543 if (state == arc_mfu_ghost) 2544 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu; 2545 else if (state == arc_mru_ghost) 2546 state = arc_mru; 2547 2548 if (state == arc_mru || state == arc_anon) { 2549 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 2550 state = (arc_mfu->arcs_lsize[type] >= size && 2551 arc_p > mru_used) ? arc_mfu : arc_mru; 2552 } else { 2553 /* MFU cases */ 2554 uint64_t mfu_space = arc_c - arc_p; 2555 state = (arc_mru->arcs_lsize[type] >= size && 2556 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 2557 } 2558 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) { 2559 if (type == ARC_BUFC_METADATA) { 2560 buf->b_data = zio_buf_alloc(size); 2561 arc_space_consume(size, ARC_SPACE_DATA); 2562 } else { 2563 ASSERT(type == ARC_BUFC_DATA); 2564 buf->b_data = zio_data_buf_alloc(size); 2565 ARCSTAT_INCR(arcstat_data_size, size); 2566 atomic_add_64(&arc_size, size); 2567 } 2568 ARCSTAT_BUMP(arcstat_recycle_miss); 2569 } 2570 ASSERT(buf->b_data != NULL); 2571 out: 2572 /* 2573 * Update the state size. Note that ghost states have a 2574 * "ghost size" and so don't need to be updated. 2575 */ 2576 if (!GHOST_STATE(buf->b_hdr->b_state)) { 2577 arc_buf_hdr_t *hdr = buf->b_hdr; 2578 2579 atomic_add_64(&hdr->b_state->arcs_size, size); 2580 if (list_link_active(&hdr->b_arc_node)) { 2581 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 2582 atomic_add_64(&hdr->b_state->arcs_lsize[type], size); 2583 } 2584 /* 2585 * If we are growing the cache, and we are adding anonymous 2586 * data, and we have outgrown arc_p, update arc_p 2587 */ 2588 if (arc_size < arc_c && hdr->b_state == arc_anon && 2589 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 2590 arc_p = MIN(arc_c, arc_p + size); 2591 } 2592 } 2593 2594 /* 2595 * This routine is called whenever a buffer is accessed. 2596 * NOTE: the hash lock is dropped in this function. 2597 */ 2598 static void 2599 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock) 2600 { 2601 clock_t now; 2602 2603 ASSERT(MUTEX_HELD(hash_lock)); 2604 2605 if (buf->b_state == arc_anon) { 2606 /* 2607 * This buffer is not in the cache, and does not 2608 * appear in our "ghost" list. Add the new buffer 2609 * to the MRU state. 2610 */ 2611 2612 ASSERT(buf->b_arc_access == 0); 2613 buf->b_arc_access = ddi_get_lbolt(); 2614 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2615 arc_change_state(arc_mru, buf, hash_lock); 2616 2617 } else if (buf->b_state == arc_mru) { 2618 now = ddi_get_lbolt(); 2619 2620 /* 2621 * If this buffer is here because of a prefetch, then either: 2622 * - clear the flag if this is a "referencing" read 2623 * (any subsequent access will bump this into the MFU state). 2624 * or 2625 * - move the buffer to the head of the list if this is 2626 * another prefetch (to make it less likely to be evicted). 2627 */ 2628 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2629 if (refcount_count(&buf->b_refcnt) == 0) { 2630 ASSERT(list_link_active(&buf->b_arc_node)); 2631 } else { 2632 buf->b_flags &= ~ARC_PREFETCH; 2633 ARCSTAT_BUMP(arcstat_mru_hits); 2634 } 2635 buf->b_arc_access = now; 2636 return; 2637 } 2638 2639 /* 2640 * This buffer has been "accessed" only once so far, 2641 * but it is still in the cache. Move it to the MFU 2642 * state. 2643 */ 2644 if (now > buf->b_arc_access + ARC_MINTIME) { 2645 /* 2646 * More than 125ms have passed since we 2647 * instantiated this buffer. Move it to the 2648 * most frequently used state. 2649 */ 2650 buf->b_arc_access = now; 2651 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2652 arc_change_state(arc_mfu, buf, hash_lock); 2653 } 2654 ARCSTAT_BUMP(arcstat_mru_hits); 2655 } else if (buf->b_state == arc_mru_ghost) { 2656 arc_state_t *new_state; 2657 /* 2658 * This buffer has been "accessed" recently, but 2659 * was evicted from the cache. Move it to the 2660 * MFU state. 2661 */ 2662 2663 if (buf->b_flags & ARC_PREFETCH) { 2664 new_state = arc_mru; 2665 if (refcount_count(&buf->b_refcnt) > 0) 2666 buf->b_flags &= ~ARC_PREFETCH; 2667 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf); 2668 } else { 2669 new_state = arc_mfu; 2670 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2671 } 2672 2673 buf->b_arc_access = ddi_get_lbolt(); 2674 arc_change_state(new_state, buf, hash_lock); 2675 2676 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 2677 } else if (buf->b_state == arc_mfu) { 2678 /* 2679 * This buffer has been accessed more than once and is 2680 * still in the cache. Keep it in the MFU state. 2681 * 2682 * NOTE: an add_reference() that occurred when we did 2683 * the arc_read() will have kicked this off the list. 2684 * If it was a prefetch, we will explicitly move it to 2685 * the head of the list now. 2686 */ 2687 if ((buf->b_flags & ARC_PREFETCH) != 0) { 2688 ASSERT(refcount_count(&buf->b_refcnt) == 0); 2689 ASSERT(list_link_active(&buf->b_arc_node)); 2690 } 2691 ARCSTAT_BUMP(arcstat_mfu_hits); 2692 buf->b_arc_access = ddi_get_lbolt(); 2693 } else if (buf->b_state == arc_mfu_ghost) { 2694 arc_state_t *new_state = arc_mfu; 2695 /* 2696 * This buffer has been accessed more than once but has 2697 * been evicted from the cache. Move it back to the 2698 * MFU state. 2699 */ 2700 2701 if (buf->b_flags & ARC_PREFETCH) { 2702 /* 2703 * This is a prefetch access... 2704 * move this block back to the MRU state. 2705 */ 2706 ASSERT0(refcount_count(&buf->b_refcnt)); 2707 new_state = arc_mru; 2708 } 2709 2710 buf->b_arc_access = ddi_get_lbolt(); 2711 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2712 arc_change_state(new_state, buf, hash_lock); 2713 2714 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 2715 } else if (buf->b_state == arc_l2c_only) { 2716 /* 2717 * This buffer is on the 2nd Level ARC. 2718 */ 2719 2720 buf->b_arc_access = ddi_get_lbolt(); 2721 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf); 2722 arc_change_state(arc_mfu, buf, hash_lock); 2723 } else { 2724 ASSERT(!"invalid arc state"); 2725 } 2726 } 2727 2728 /* a generic arc_done_func_t which you can use */ 2729 /* ARGSUSED */ 2730 void 2731 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 2732 { 2733 if (zio == NULL || zio->io_error == 0) 2734 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 2735 VERIFY(arc_buf_remove_ref(buf, arg)); 2736 } 2737 2738 /* a generic arc_done_func_t */ 2739 void 2740 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 2741 { 2742 arc_buf_t **bufp = arg; 2743 if (zio && zio->io_error) { 2744 VERIFY(arc_buf_remove_ref(buf, arg)); 2745 *bufp = NULL; 2746 } else { 2747 *bufp = buf; 2748 ASSERT(buf->b_data); 2749 } 2750 } 2751 2752 static void 2753 arc_read_done(zio_t *zio) 2754 { 2755 arc_buf_hdr_t *hdr; 2756 arc_buf_t *buf; 2757 arc_buf_t *abuf; /* buffer we're assigning to callback */ 2758 kmutex_t *hash_lock = NULL; 2759 arc_callback_t *callback_list, *acb; 2760 int freeable = FALSE; 2761 2762 buf = zio->io_private; 2763 hdr = buf->b_hdr; 2764 2765 /* 2766 * The hdr was inserted into hash-table and removed from lists 2767 * prior to starting I/O. We should find this header, since 2768 * it's in the hash table, and it should be legit since it's 2769 * not possible to evict it during the I/O. The only possible 2770 * reason for it not to be found is if we were freed during the 2771 * read. 2772 */ 2773 if (HDR_IN_HASH_TABLE(hdr)) { 2774 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 2775 ASSERT3U(hdr->b_dva.dva_word[0], ==, 2776 BP_IDENTITY(zio->io_bp)->dva_word[0]); 2777 ASSERT3U(hdr->b_dva.dva_word[1], ==, 2778 BP_IDENTITY(zio->io_bp)->dva_word[1]); 2779 2780 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 2781 &hash_lock); 2782 2783 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 2784 hash_lock == NULL) || 2785 (found == hdr && 2786 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 2787 (found == hdr && HDR_L2_READING(hdr))); 2788 } 2789 2790 hdr->b_flags &= ~ARC_L2_EVICTED; 2791 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH)) 2792 hdr->b_flags &= ~ARC_L2CACHE; 2793 2794 /* byteswap if necessary */ 2795 callback_list = hdr->b_acb; 2796 ASSERT(callback_list != NULL); 2797 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 2798 dmu_object_byteswap_t bswap = 2799 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 2800 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 2801 byteswap_uint64_array : 2802 dmu_ot_byteswap[bswap].ob_func; 2803 func(buf->b_data, hdr->b_size); 2804 } 2805 2806 arc_cksum_compute(buf, B_FALSE); 2807 arc_buf_watch(buf); 2808 2809 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) { 2810 /* 2811 * Only call arc_access on anonymous buffers. This is because 2812 * if we've issued an I/O for an evicted buffer, we've already 2813 * called arc_access (to prevent any simultaneous readers from 2814 * getting confused). 2815 */ 2816 arc_access(hdr, hash_lock); 2817 } 2818 2819 /* create copies of the data buffer for the callers */ 2820 abuf = buf; 2821 for (acb = callback_list; acb; acb = acb->acb_next) { 2822 if (acb->acb_done) { 2823 if (abuf == NULL) { 2824 ARCSTAT_BUMP(arcstat_duplicate_reads); 2825 abuf = arc_buf_clone(buf); 2826 } 2827 acb->acb_buf = abuf; 2828 abuf = NULL; 2829 } 2830 } 2831 hdr->b_acb = NULL; 2832 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 2833 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 2834 if (abuf == buf) { 2835 ASSERT(buf->b_efunc == NULL); 2836 ASSERT(hdr->b_datacnt == 1); 2837 hdr->b_flags |= ARC_BUF_AVAILABLE; 2838 } 2839 2840 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL); 2841 2842 if (zio->io_error != 0) { 2843 hdr->b_flags |= ARC_IO_ERROR; 2844 if (hdr->b_state != arc_anon) 2845 arc_change_state(arc_anon, hdr, hash_lock); 2846 if (HDR_IN_HASH_TABLE(hdr)) 2847 buf_hash_remove(hdr); 2848 freeable = refcount_is_zero(&hdr->b_refcnt); 2849 } 2850 2851 /* 2852 * Broadcast before we drop the hash_lock to avoid the possibility 2853 * that the hdr (and hence the cv) might be freed before we get to 2854 * the cv_broadcast(). 2855 */ 2856 cv_broadcast(&hdr->b_cv); 2857 2858 if (hash_lock) { 2859 mutex_exit(hash_lock); 2860 } else { 2861 /* 2862 * This block was freed while we waited for the read to 2863 * complete. It has been removed from the hash table and 2864 * moved to the anonymous state (so that it won't show up 2865 * in the cache). 2866 */ 2867 ASSERT3P(hdr->b_state, ==, arc_anon); 2868 freeable = refcount_is_zero(&hdr->b_refcnt); 2869 } 2870 2871 /* execute each callback and free its structure */ 2872 while ((acb = callback_list) != NULL) { 2873 if (acb->acb_done) 2874 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 2875 2876 if (acb->acb_zio_dummy != NULL) { 2877 acb->acb_zio_dummy->io_error = zio->io_error; 2878 zio_nowait(acb->acb_zio_dummy); 2879 } 2880 2881 callback_list = acb->acb_next; 2882 kmem_free(acb, sizeof (arc_callback_t)); 2883 } 2884 2885 if (freeable) 2886 arc_hdr_destroy(hdr); 2887 } 2888 2889 /* 2890 * "Read" the block at the specified DVA (in bp) via the 2891 * cache. If the block is found in the cache, invoke the provided 2892 * callback immediately and return. Note that the `zio' parameter 2893 * in the callback will be NULL in this case, since no IO was 2894 * required. If the block is not in the cache pass the read request 2895 * on to the spa with a substitute callback function, so that the 2896 * requested block will be added to the cache. 2897 * 2898 * If a read request arrives for a block that has a read in-progress, 2899 * either wait for the in-progress read to complete (and return the 2900 * results); or, if this is a read with a "done" func, add a record 2901 * to the read to invoke the "done" func when the read completes, 2902 * and return; or just return. 2903 * 2904 * arc_read_done() will invoke all the requested "done" functions 2905 * for readers of this block. 2906 */ 2907 int 2908 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 2909 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags, 2910 const zbookmark_phys_t *zb) 2911 { 2912 arc_buf_hdr_t *hdr = NULL; 2913 arc_buf_t *buf = NULL; 2914 kmutex_t *hash_lock = NULL; 2915 zio_t *rzio; 2916 uint64_t guid = spa_load_guid(spa); 2917 2918 ASSERT(!BP_IS_EMBEDDED(bp) || 2919 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 2920 2921 top: 2922 if (!BP_IS_EMBEDDED(bp)) { 2923 /* 2924 * Embedded BP's have no DVA and require no I/O to "read". 2925 * Create an anonymous arc buf to back it. 2926 */ 2927 hdr = buf_hash_find(guid, bp, &hash_lock); 2928 } 2929 2930 if (hdr != NULL && hdr->b_datacnt > 0) { 2931 2932 *arc_flags |= ARC_CACHED; 2933 2934 if (HDR_IO_IN_PROGRESS(hdr)) { 2935 2936 if (*arc_flags & ARC_WAIT) { 2937 cv_wait(&hdr->b_cv, hash_lock); 2938 mutex_exit(hash_lock); 2939 goto top; 2940 } 2941 ASSERT(*arc_flags & ARC_NOWAIT); 2942 2943 if (done) { 2944 arc_callback_t *acb = NULL; 2945 2946 acb = kmem_zalloc(sizeof (arc_callback_t), 2947 KM_SLEEP); 2948 acb->acb_done = done; 2949 acb->acb_private = private; 2950 if (pio != NULL) 2951 acb->acb_zio_dummy = zio_null(pio, 2952 spa, NULL, NULL, NULL, zio_flags); 2953 2954 ASSERT(acb->acb_done != NULL); 2955 acb->acb_next = hdr->b_acb; 2956 hdr->b_acb = acb; 2957 add_reference(hdr, hash_lock, private); 2958 mutex_exit(hash_lock); 2959 return (0); 2960 } 2961 mutex_exit(hash_lock); 2962 return (0); 2963 } 2964 2965 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 2966 2967 if (done) { 2968 add_reference(hdr, hash_lock, private); 2969 /* 2970 * If this block is already in use, create a new 2971 * copy of the data so that we will be guaranteed 2972 * that arc_release() will always succeed. 2973 */ 2974 buf = hdr->b_buf; 2975 ASSERT(buf); 2976 ASSERT(buf->b_data); 2977 if (HDR_BUF_AVAILABLE(hdr)) { 2978 ASSERT(buf->b_efunc == NULL); 2979 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 2980 } else { 2981 buf = arc_buf_clone(buf); 2982 } 2983 2984 } else if (*arc_flags & ARC_PREFETCH && 2985 refcount_count(&hdr->b_refcnt) == 0) { 2986 hdr->b_flags |= ARC_PREFETCH; 2987 } 2988 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2989 arc_access(hdr, hash_lock); 2990 if (*arc_flags & ARC_L2CACHE) 2991 hdr->b_flags |= ARC_L2CACHE; 2992 if (*arc_flags & ARC_L2COMPRESS) 2993 hdr->b_flags |= ARC_L2COMPRESS; 2994 mutex_exit(hash_lock); 2995 ARCSTAT_BUMP(arcstat_hits); 2996 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 2997 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 2998 data, metadata, hits); 2999 3000 if (done) 3001 done(NULL, buf, private); 3002 } else { 3003 uint64_t size = BP_GET_LSIZE(bp); 3004 arc_callback_t *acb; 3005 vdev_t *vd = NULL; 3006 uint64_t addr = 0; 3007 boolean_t devw = B_FALSE; 3008 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 3009 uint64_t b_asize = 0; 3010 3011 if (hdr == NULL) { 3012 /* this block is not in the cache */ 3013 arc_buf_hdr_t *exists = NULL; 3014 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 3015 buf = arc_buf_alloc(spa, size, private, type); 3016 hdr = buf->b_hdr; 3017 if (!BP_IS_EMBEDDED(bp)) { 3018 hdr->b_dva = *BP_IDENTITY(bp); 3019 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 3020 hdr->b_cksum0 = bp->blk_cksum.zc_word[0]; 3021 exists = buf_hash_insert(hdr, &hash_lock); 3022 } 3023 if (exists != NULL) { 3024 /* somebody beat us to the hash insert */ 3025 mutex_exit(hash_lock); 3026 buf_discard_identity(hdr); 3027 (void) arc_buf_remove_ref(buf, private); 3028 goto top; /* restart the IO request */ 3029 } 3030 /* if this is a prefetch, we don't have a reference */ 3031 if (*arc_flags & ARC_PREFETCH) { 3032 (void) remove_reference(hdr, hash_lock, 3033 private); 3034 hdr->b_flags |= ARC_PREFETCH; 3035 } 3036 if (*arc_flags & ARC_L2CACHE) 3037 hdr->b_flags |= ARC_L2CACHE; 3038 if (*arc_flags & ARC_L2COMPRESS) 3039 hdr->b_flags |= ARC_L2COMPRESS; 3040 if (BP_GET_LEVEL(bp) > 0) 3041 hdr->b_flags |= ARC_INDIRECT; 3042 } else { 3043 /* this block is in the ghost cache */ 3044 ASSERT(GHOST_STATE(hdr->b_state)); 3045 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3046 ASSERT0(refcount_count(&hdr->b_refcnt)); 3047 ASSERT(hdr->b_buf == NULL); 3048 3049 /* if this is a prefetch, we don't have a reference */ 3050 if (*arc_flags & ARC_PREFETCH) 3051 hdr->b_flags |= ARC_PREFETCH; 3052 else 3053 add_reference(hdr, hash_lock, private); 3054 if (*arc_flags & ARC_L2CACHE) 3055 hdr->b_flags |= ARC_L2CACHE; 3056 if (*arc_flags & ARC_L2COMPRESS) 3057 hdr->b_flags |= ARC_L2COMPRESS; 3058 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 3059 buf->b_hdr = hdr; 3060 buf->b_data = NULL; 3061 buf->b_efunc = NULL; 3062 buf->b_private = NULL; 3063 buf->b_next = NULL; 3064 hdr->b_buf = buf; 3065 ASSERT(hdr->b_datacnt == 0); 3066 hdr->b_datacnt = 1; 3067 arc_get_data_buf(buf); 3068 arc_access(hdr, hash_lock); 3069 } 3070 3071 ASSERT(!GHOST_STATE(hdr->b_state)); 3072 3073 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 3074 acb->acb_done = done; 3075 acb->acb_private = private; 3076 3077 ASSERT(hdr->b_acb == NULL); 3078 hdr->b_acb = acb; 3079 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3080 3081 if (hdr->b_l2hdr != NULL && 3082 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) { 3083 devw = hdr->b_l2hdr->b_dev->l2ad_writing; 3084 addr = hdr->b_l2hdr->b_daddr; 3085 b_compress = hdr->b_l2hdr->b_compress; 3086 b_asize = hdr->b_l2hdr->b_asize; 3087 /* 3088 * Lock out device removal. 3089 */ 3090 if (vdev_is_dead(vd) || 3091 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 3092 vd = NULL; 3093 } 3094 3095 if (hash_lock != NULL) 3096 mutex_exit(hash_lock); 3097 3098 /* 3099 * At this point, we have a level 1 cache miss. Try again in 3100 * L2ARC if possible. 3101 */ 3102 ASSERT3U(hdr->b_size, ==, size); 3103 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 3104 uint64_t, size, zbookmark_phys_t *, zb); 3105 ARCSTAT_BUMP(arcstat_misses); 3106 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH), 3107 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3108 data, metadata, misses); 3109 3110 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 3111 /* 3112 * Read from the L2ARC if the following are true: 3113 * 1. The L2ARC vdev was previously cached. 3114 * 2. This buffer still has L2ARC metadata. 3115 * 3. This buffer isn't currently writing to the L2ARC. 3116 * 4. The L2ARC entry wasn't evicted, which may 3117 * also have invalidated the vdev. 3118 * 5. This isn't prefetch and l2arc_noprefetch is set. 3119 */ 3120 if (hdr->b_l2hdr != NULL && 3121 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3122 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3123 l2arc_read_callback_t *cb; 3124 3125 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3126 ARCSTAT_BUMP(arcstat_l2_hits); 3127 3128 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3129 KM_SLEEP); 3130 cb->l2rcb_buf = buf; 3131 cb->l2rcb_spa = spa; 3132 cb->l2rcb_bp = *bp; 3133 cb->l2rcb_zb = *zb; 3134 cb->l2rcb_flags = zio_flags; 3135 cb->l2rcb_compress = b_compress; 3136 3137 ASSERT(addr >= VDEV_LABEL_START_SIZE && 3138 addr + size < vd->vdev_psize - 3139 VDEV_LABEL_END_SIZE); 3140 3141 /* 3142 * l2arc read. The SCL_L2ARC lock will be 3143 * released by l2arc_read_done(). 3144 * Issue a null zio if the underlying buffer 3145 * was squashed to zero size by compression. 3146 */ 3147 if (b_compress == ZIO_COMPRESS_EMPTY) { 3148 rzio = zio_null(pio, spa, vd, 3149 l2arc_read_done, cb, 3150 zio_flags | ZIO_FLAG_DONT_CACHE | 3151 ZIO_FLAG_CANFAIL | 3152 ZIO_FLAG_DONT_PROPAGATE | 3153 ZIO_FLAG_DONT_RETRY); 3154 } else { 3155 rzio = zio_read_phys(pio, vd, addr, 3156 b_asize, buf->b_data, 3157 ZIO_CHECKSUM_OFF, 3158 l2arc_read_done, cb, priority, 3159 zio_flags | ZIO_FLAG_DONT_CACHE | 3160 ZIO_FLAG_CANFAIL | 3161 ZIO_FLAG_DONT_PROPAGATE | 3162 ZIO_FLAG_DONT_RETRY, B_FALSE); 3163 } 3164 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3165 zio_t *, rzio); 3166 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 3167 3168 if (*arc_flags & ARC_NOWAIT) { 3169 zio_nowait(rzio); 3170 return (0); 3171 } 3172 3173 ASSERT(*arc_flags & ARC_WAIT); 3174 if (zio_wait(rzio) == 0) 3175 return (0); 3176 3177 /* l2arc read error; goto zio_read() */ 3178 } else { 3179 DTRACE_PROBE1(l2arc__miss, 3180 arc_buf_hdr_t *, hdr); 3181 ARCSTAT_BUMP(arcstat_l2_misses); 3182 if (HDR_L2_WRITING(hdr)) 3183 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3184 spa_config_exit(spa, SCL_L2ARC, vd); 3185 } 3186 } else { 3187 if (vd != NULL) 3188 spa_config_exit(spa, SCL_L2ARC, vd); 3189 if (l2arc_ndev != 0) { 3190 DTRACE_PROBE1(l2arc__miss, 3191 arc_buf_hdr_t *, hdr); 3192 ARCSTAT_BUMP(arcstat_l2_misses); 3193 } 3194 } 3195 3196 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3197 arc_read_done, buf, priority, zio_flags, zb); 3198 3199 if (*arc_flags & ARC_WAIT) 3200 return (zio_wait(rzio)); 3201 3202 ASSERT(*arc_flags & ARC_NOWAIT); 3203 zio_nowait(rzio); 3204 } 3205 return (0); 3206 } 3207 3208 void 3209 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3210 { 3211 ASSERT(buf->b_hdr != NULL); 3212 ASSERT(buf->b_hdr->b_state != arc_anon); 3213 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL); 3214 ASSERT(buf->b_efunc == NULL); 3215 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3216 3217 buf->b_efunc = func; 3218 buf->b_private = private; 3219 } 3220 3221 /* 3222 * Notify the arc that a block was freed, and thus will never be used again. 3223 */ 3224 void 3225 arc_freed(spa_t *spa, const blkptr_t *bp) 3226 { 3227 arc_buf_hdr_t *hdr; 3228 kmutex_t *hash_lock; 3229 uint64_t guid = spa_load_guid(spa); 3230 3231 ASSERT(!BP_IS_EMBEDDED(bp)); 3232 3233 hdr = buf_hash_find(guid, bp, &hash_lock); 3234 if (hdr == NULL) 3235 return; 3236 if (HDR_BUF_AVAILABLE(hdr)) { 3237 arc_buf_t *buf = hdr->b_buf; 3238 add_reference(hdr, hash_lock, FTAG); 3239 hdr->b_flags &= ~ARC_BUF_AVAILABLE; 3240 mutex_exit(hash_lock); 3241 3242 arc_release(buf, FTAG); 3243 (void) arc_buf_remove_ref(buf, FTAG); 3244 } else { 3245 mutex_exit(hash_lock); 3246 } 3247 3248 } 3249 3250 /* 3251 * Clear the user eviction callback set by arc_set_callback(), first calling 3252 * it if it exists. Because the presence of a callback keeps an arc_buf cached 3253 * clearing the callback may result in the arc_buf being destroyed. However, 3254 * it will not result in the *last* arc_buf being destroyed, hence the data 3255 * will remain cached in the ARC. We make a copy of the arc buffer here so 3256 * that we can process the callback without holding any locks. 3257 * 3258 * It's possible that the callback is already in the process of being cleared 3259 * by another thread. In this case we can not clear the callback. 3260 * 3261 * Returns B_TRUE if the callback was successfully called and cleared. 3262 */ 3263 boolean_t 3264 arc_clear_callback(arc_buf_t *buf) 3265 { 3266 arc_buf_hdr_t *hdr; 3267 kmutex_t *hash_lock; 3268 arc_evict_func_t *efunc = buf->b_efunc; 3269 void *private = buf->b_private; 3270 3271 mutex_enter(&buf->b_evict_lock); 3272 hdr = buf->b_hdr; 3273 if (hdr == NULL) { 3274 /* 3275 * We are in arc_do_user_evicts(). 3276 */ 3277 ASSERT(buf->b_data == NULL); 3278 mutex_exit(&buf->b_evict_lock); 3279 return (B_FALSE); 3280 } else if (buf->b_data == NULL) { 3281 /* 3282 * We are on the eviction list; process this buffer now 3283 * but let arc_do_user_evicts() do the reaping. 3284 */ 3285 buf->b_efunc = NULL; 3286 mutex_exit(&buf->b_evict_lock); 3287 VERIFY0(efunc(private)); 3288 return (B_TRUE); 3289 } 3290 hash_lock = HDR_LOCK(hdr); 3291 mutex_enter(hash_lock); 3292 hdr = buf->b_hdr; 3293 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3294 3295 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt); 3296 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3297 3298 buf->b_efunc = NULL; 3299 buf->b_private = NULL; 3300 3301 if (hdr->b_datacnt > 1) { 3302 mutex_exit(&buf->b_evict_lock); 3303 arc_buf_destroy(buf, FALSE, TRUE); 3304 } else { 3305 ASSERT(buf == hdr->b_buf); 3306 hdr->b_flags |= ARC_BUF_AVAILABLE; 3307 mutex_exit(&buf->b_evict_lock); 3308 } 3309 3310 mutex_exit(hash_lock); 3311 VERIFY0(efunc(private)); 3312 return (B_TRUE); 3313 } 3314 3315 /* 3316 * Release this buffer from the cache, making it an anonymous buffer. This 3317 * must be done after a read and prior to modifying the buffer contents. 3318 * If the buffer has more than one reference, we must make 3319 * a new hdr for the buffer. 3320 */ 3321 void 3322 arc_release(arc_buf_t *buf, void *tag) 3323 { 3324 arc_buf_hdr_t *hdr; 3325 kmutex_t *hash_lock = NULL; 3326 l2arc_buf_hdr_t *l2hdr; 3327 uint64_t buf_size; 3328 3329 /* 3330 * It would be nice to assert that if it's DMU metadata (level > 3331 * 0 || it's the dnode file), then it must be syncing context. 3332 * But we don't know that information at this level. 3333 */ 3334 3335 mutex_enter(&buf->b_evict_lock); 3336 hdr = buf->b_hdr; 3337 3338 /* this buffer is not on any list */ 3339 ASSERT(refcount_count(&hdr->b_refcnt) > 0); 3340 3341 if (hdr->b_state == arc_anon) { 3342 /* this buffer is already released */ 3343 ASSERT(buf->b_efunc == NULL); 3344 } else { 3345 hash_lock = HDR_LOCK(hdr); 3346 mutex_enter(hash_lock); 3347 hdr = buf->b_hdr; 3348 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3349 } 3350 3351 l2hdr = hdr->b_l2hdr; 3352 if (l2hdr) { 3353 mutex_enter(&l2arc_buflist_mtx); 3354 hdr->b_l2hdr = NULL; 3355 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 3356 } 3357 buf_size = hdr->b_size; 3358 3359 /* 3360 * Do we have more than one buf? 3361 */ 3362 if (hdr->b_datacnt > 1) { 3363 arc_buf_hdr_t *nhdr; 3364 arc_buf_t **bufp; 3365 uint64_t blksz = hdr->b_size; 3366 uint64_t spa = hdr->b_spa; 3367 arc_buf_contents_t type = hdr->b_type; 3368 uint32_t flags = hdr->b_flags; 3369 3370 ASSERT(hdr->b_buf != buf || buf->b_next != NULL); 3371 /* 3372 * Pull the data off of this hdr and attach it to 3373 * a new anonymous hdr. 3374 */ 3375 (void) remove_reference(hdr, hash_lock, tag); 3376 bufp = &hdr->b_buf; 3377 while (*bufp != buf) 3378 bufp = &(*bufp)->b_next; 3379 *bufp = buf->b_next; 3380 buf->b_next = NULL; 3381 3382 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size); 3383 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size); 3384 if (refcount_is_zero(&hdr->b_refcnt)) { 3385 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 3386 ASSERT3U(*size, >=, hdr->b_size); 3387 atomic_add_64(size, -hdr->b_size); 3388 } 3389 3390 /* 3391 * We're releasing a duplicate user data buffer, update 3392 * our statistics accordingly. 3393 */ 3394 if (hdr->b_type == ARC_BUFC_DATA) { 3395 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3396 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3397 -hdr->b_size); 3398 } 3399 hdr->b_datacnt -= 1; 3400 arc_cksum_verify(buf); 3401 arc_buf_unwatch(buf); 3402 3403 mutex_exit(hash_lock); 3404 3405 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 3406 nhdr->b_size = blksz; 3407 nhdr->b_spa = spa; 3408 nhdr->b_type = type; 3409 nhdr->b_buf = buf; 3410 nhdr->b_state = arc_anon; 3411 nhdr->b_arc_access = 0; 3412 nhdr->b_flags = flags & ARC_L2_WRITING; 3413 nhdr->b_l2hdr = NULL; 3414 nhdr->b_datacnt = 1; 3415 nhdr->b_freeze_cksum = NULL; 3416 (void) refcount_add(&nhdr->b_refcnt, tag); 3417 buf->b_hdr = nhdr; 3418 mutex_exit(&buf->b_evict_lock); 3419 atomic_add_64(&arc_anon->arcs_size, blksz); 3420 } else { 3421 mutex_exit(&buf->b_evict_lock); 3422 ASSERT(refcount_count(&hdr->b_refcnt) == 1); 3423 ASSERT(!list_link_active(&hdr->b_arc_node)); 3424 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3425 if (hdr->b_state != arc_anon) 3426 arc_change_state(arc_anon, hdr, hash_lock); 3427 hdr->b_arc_access = 0; 3428 if (hash_lock) 3429 mutex_exit(hash_lock); 3430 3431 buf_discard_identity(hdr); 3432 arc_buf_thaw(buf); 3433 } 3434 buf->b_efunc = NULL; 3435 buf->b_private = NULL; 3436 3437 if (l2hdr) { 3438 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 3439 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 3440 -l2hdr->b_asize, 0, 0); 3441 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 3442 ARCSTAT_INCR(arcstat_l2_size, -buf_size); 3443 mutex_exit(&l2arc_buflist_mtx); 3444 } 3445 } 3446 3447 int 3448 arc_released(arc_buf_t *buf) 3449 { 3450 int released; 3451 3452 mutex_enter(&buf->b_evict_lock); 3453 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon); 3454 mutex_exit(&buf->b_evict_lock); 3455 return (released); 3456 } 3457 3458 #ifdef ZFS_DEBUG 3459 int 3460 arc_referenced(arc_buf_t *buf) 3461 { 3462 int referenced; 3463 3464 mutex_enter(&buf->b_evict_lock); 3465 referenced = (refcount_count(&buf->b_hdr->b_refcnt)); 3466 mutex_exit(&buf->b_evict_lock); 3467 return (referenced); 3468 } 3469 #endif 3470 3471 static void 3472 arc_write_ready(zio_t *zio) 3473 { 3474 arc_write_callback_t *callback = zio->io_private; 3475 arc_buf_t *buf = callback->awcb_buf; 3476 arc_buf_hdr_t *hdr = buf->b_hdr; 3477 3478 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt)); 3479 callback->awcb_ready(zio, buf, callback->awcb_private); 3480 3481 /* 3482 * If the IO is already in progress, then this is a re-write 3483 * attempt, so we need to thaw and re-compute the cksum. 3484 * It is the responsibility of the callback to handle the 3485 * accounting for any re-write attempt. 3486 */ 3487 if (HDR_IO_IN_PROGRESS(hdr)) { 3488 mutex_enter(&hdr->b_freeze_lock); 3489 if (hdr->b_freeze_cksum != NULL) { 3490 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 3491 hdr->b_freeze_cksum = NULL; 3492 } 3493 mutex_exit(&hdr->b_freeze_lock); 3494 } 3495 arc_cksum_compute(buf, B_FALSE); 3496 hdr->b_flags |= ARC_IO_IN_PROGRESS; 3497 } 3498 3499 /* 3500 * The SPA calls this callback for each physical write that happens on behalf 3501 * of a logical write. See the comment in dbuf_write_physdone() for details. 3502 */ 3503 static void 3504 arc_write_physdone(zio_t *zio) 3505 { 3506 arc_write_callback_t *cb = zio->io_private; 3507 if (cb->awcb_physdone != NULL) 3508 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 3509 } 3510 3511 static void 3512 arc_write_done(zio_t *zio) 3513 { 3514 arc_write_callback_t *callback = zio->io_private; 3515 arc_buf_t *buf = callback->awcb_buf; 3516 arc_buf_hdr_t *hdr = buf->b_hdr; 3517 3518 ASSERT(hdr->b_acb == NULL); 3519 3520 if (zio->io_error == 0) { 3521 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 3522 buf_discard_identity(hdr); 3523 } else { 3524 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 3525 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 3526 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0]; 3527 } 3528 } else { 3529 ASSERT(BUF_EMPTY(hdr)); 3530 } 3531 3532 /* 3533 * If the block to be written was all-zero or compressed enough to be 3534 * embedded in the BP, no write was performed so there will be no 3535 * dva/birth/checksum. The buffer must therefore remain anonymous 3536 * (and uncached). 3537 */ 3538 if (!BUF_EMPTY(hdr)) { 3539 arc_buf_hdr_t *exists; 3540 kmutex_t *hash_lock; 3541 3542 ASSERT(zio->io_error == 0); 3543 3544 arc_cksum_verify(buf); 3545 3546 exists = buf_hash_insert(hdr, &hash_lock); 3547 if (exists) { 3548 /* 3549 * This can only happen if we overwrite for 3550 * sync-to-convergence, because we remove 3551 * buffers from the hash table when we arc_free(). 3552 */ 3553 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 3554 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3555 panic("bad overwrite, hdr=%p exists=%p", 3556 (void *)hdr, (void *)exists); 3557 ASSERT(refcount_is_zero(&exists->b_refcnt)); 3558 arc_change_state(arc_anon, exists, hash_lock); 3559 mutex_exit(hash_lock); 3560 arc_hdr_destroy(exists); 3561 exists = buf_hash_insert(hdr, &hash_lock); 3562 ASSERT3P(exists, ==, NULL); 3563 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 3564 /* nopwrite */ 3565 ASSERT(zio->io_prop.zp_nopwrite); 3566 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3567 panic("bad nopwrite, hdr=%p exists=%p", 3568 (void *)hdr, (void *)exists); 3569 } else { 3570 /* Dedup */ 3571 ASSERT(hdr->b_datacnt == 1); 3572 ASSERT(hdr->b_state == arc_anon); 3573 ASSERT(BP_GET_DEDUP(zio->io_bp)); 3574 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 3575 } 3576 } 3577 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3578 /* if it's not anon, we are doing a scrub */ 3579 if (!exists && hdr->b_state == arc_anon) 3580 arc_access(hdr, hash_lock); 3581 mutex_exit(hash_lock); 3582 } else { 3583 hdr->b_flags &= ~ARC_IO_IN_PROGRESS; 3584 } 3585 3586 ASSERT(!refcount_is_zero(&hdr->b_refcnt)); 3587 callback->awcb_done(zio, buf, callback->awcb_private); 3588 3589 kmem_free(callback, sizeof (arc_write_callback_t)); 3590 } 3591 3592 zio_t * 3593 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 3594 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 3595 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 3596 arc_done_func_t *done, void *private, zio_priority_t priority, 3597 int zio_flags, const zbookmark_phys_t *zb) 3598 { 3599 arc_buf_hdr_t *hdr = buf->b_hdr; 3600 arc_write_callback_t *callback; 3601 zio_t *zio; 3602 3603 ASSERT(ready != NULL); 3604 ASSERT(done != NULL); 3605 ASSERT(!HDR_IO_ERROR(hdr)); 3606 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0); 3607 ASSERT(hdr->b_acb == NULL); 3608 if (l2arc) 3609 hdr->b_flags |= ARC_L2CACHE; 3610 if (l2arc_compress) 3611 hdr->b_flags |= ARC_L2COMPRESS; 3612 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 3613 callback->awcb_ready = ready; 3614 callback->awcb_physdone = physdone; 3615 callback->awcb_done = done; 3616 callback->awcb_private = private; 3617 callback->awcb_buf = buf; 3618 3619 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 3620 arc_write_ready, arc_write_physdone, arc_write_done, callback, 3621 priority, zio_flags, zb); 3622 3623 return (zio); 3624 } 3625 3626 static int 3627 arc_memory_throttle(uint64_t reserve, uint64_t txg) 3628 { 3629 #ifdef _KERNEL 3630 uint64_t available_memory = ptob(freemem); 3631 static uint64_t page_load = 0; 3632 static uint64_t last_txg = 0; 3633 3634 #if defined(__i386) 3635 available_memory = 3636 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 3637 #endif 3638 3639 if (freemem > physmem * arc_lotsfree_percent / 100) 3640 return (0); 3641 3642 if (txg > last_txg) { 3643 last_txg = txg; 3644 page_load = 0; 3645 } 3646 /* 3647 * If we are in pageout, we know that memory is already tight, 3648 * the arc is already going to be evicting, so we just want to 3649 * continue to let page writes occur as quickly as possible. 3650 */ 3651 if (curproc == proc_pageout) { 3652 if (page_load > MAX(ptob(minfree), available_memory) / 4) 3653 return (SET_ERROR(ERESTART)); 3654 /* Note: reserve is inflated, so we deflate */ 3655 page_load += reserve / 8; 3656 return (0); 3657 } else if (page_load > 0 && arc_reclaim_needed()) { 3658 /* memory is low, delay before restarting */ 3659 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 3660 return (SET_ERROR(EAGAIN)); 3661 } 3662 page_load = 0; 3663 #endif 3664 return (0); 3665 } 3666 3667 void 3668 arc_tempreserve_clear(uint64_t reserve) 3669 { 3670 atomic_add_64(&arc_tempreserve, -reserve); 3671 ASSERT((int64_t)arc_tempreserve >= 0); 3672 } 3673 3674 int 3675 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 3676 { 3677 int error; 3678 uint64_t anon_size; 3679 3680 if (reserve > arc_c/4 && !arc_no_grow) 3681 arc_c = MIN(arc_c_max, reserve * 4); 3682 if (reserve > arc_c) 3683 return (SET_ERROR(ENOMEM)); 3684 3685 /* 3686 * Don't count loaned bufs as in flight dirty data to prevent long 3687 * network delays from blocking transactions that are ready to be 3688 * assigned to a txg. 3689 */ 3690 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 3691 3692 /* 3693 * Writes will, almost always, require additional memory allocations 3694 * in order to compress/encrypt/etc the data. We therefore need to 3695 * make sure that there is sufficient available memory for this. 3696 */ 3697 error = arc_memory_throttle(reserve, txg); 3698 if (error != 0) 3699 return (error); 3700 3701 /* 3702 * Throttle writes when the amount of dirty data in the cache 3703 * gets too large. We try to keep the cache less than half full 3704 * of dirty blocks so that our sync times don't grow too large. 3705 * Note: if two requests come in concurrently, we might let them 3706 * both succeed, when one of them should fail. Not a huge deal. 3707 */ 3708 3709 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 3710 anon_size > arc_c / 4) { 3711 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 3712 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 3713 arc_tempreserve>>10, 3714 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 3715 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 3716 reserve>>10, arc_c>>10); 3717 return (SET_ERROR(ERESTART)); 3718 } 3719 atomic_add_64(&arc_tempreserve, reserve); 3720 return (0); 3721 } 3722 3723 void 3724 arc_init(void) 3725 { 3726 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 3727 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 3728 3729 /* Convert seconds to clock ticks */ 3730 arc_min_prefetch_lifespan = 1 * hz; 3731 3732 /* Start out with 1/8 of all memory */ 3733 arc_c = physmem * PAGESIZE / 8; 3734 3735 #ifdef _KERNEL 3736 /* 3737 * On architectures where the physical memory can be larger 3738 * than the addressable space (intel in 32-bit mode), we may 3739 * need to limit the cache to 1/8 of VM size. 3740 */ 3741 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 3742 #endif 3743 3744 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 3745 arc_c_min = MAX(arc_c / 4, 64<<20); 3746 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 3747 if (arc_c * 8 >= 1<<30) 3748 arc_c_max = (arc_c * 8) - (1<<30); 3749 else 3750 arc_c_max = arc_c_min; 3751 arc_c_max = MAX(arc_c * 6, arc_c_max); 3752 3753 /* 3754 * Allow the tunables to override our calculations if they are 3755 * reasonable (ie. over 64MB) 3756 */ 3757 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE) 3758 arc_c_max = zfs_arc_max; 3759 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max) 3760 arc_c_min = zfs_arc_min; 3761 3762 arc_c = arc_c_max; 3763 arc_p = (arc_c >> 1); 3764 3765 /* limit meta-data to 1/4 of the arc capacity */ 3766 arc_meta_limit = arc_c_max / 4; 3767 3768 /* Allow the tunable to override if it is reasonable */ 3769 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 3770 arc_meta_limit = zfs_arc_meta_limit; 3771 3772 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 3773 arc_c_min = arc_meta_limit / 2; 3774 3775 if (zfs_arc_grow_retry > 0) 3776 arc_grow_retry = zfs_arc_grow_retry; 3777 3778 if (zfs_arc_shrink_shift > 0) 3779 arc_shrink_shift = zfs_arc_shrink_shift; 3780 3781 if (zfs_arc_p_min_shift > 0) 3782 arc_p_min_shift = zfs_arc_p_min_shift; 3783 3784 /* if kmem_flags are set, lets try to use less memory */ 3785 if (kmem_debugging()) 3786 arc_c = arc_c / 2; 3787 if (arc_c < arc_c_min) 3788 arc_c = arc_c_min; 3789 3790 arc_anon = &ARC_anon; 3791 arc_mru = &ARC_mru; 3792 arc_mru_ghost = &ARC_mru_ghost; 3793 arc_mfu = &ARC_mfu; 3794 arc_mfu_ghost = &ARC_mfu_ghost; 3795 arc_l2c_only = &ARC_l2c_only; 3796 arc_size = 0; 3797 3798 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3799 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3800 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3801 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3802 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3803 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 3804 3805 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 3806 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3807 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 3808 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3809 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 3810 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3811 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 3812 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3813 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 3814 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3815 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 3816 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3817 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 3818 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3819 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 3820 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3821 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 3822 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3823 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 3824 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 3825 3826 buf_init(); 3827 3828 arc_thread_exit = 0; 3829 arc_eviction_list = NULL; 3830 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 3831 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 3832 3833 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 3834 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 3835 3836 if (arc_ksp != NULL) { 3837 arc_ksp->ks_data = &arc_stats; 3838 kstat_install(arc_ksp); 3839 } 3840 3841 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 3842 TS_RUN, minclsyspri); 3843 3844 arc_dead = FALSE; 3845 arc_warm = B_FALSE; 3846 3847 /* 3848 * Calculate maximum amount of dirty data per pool. 3849 * 3850 * If it has been set by /etc/system, take that. 3851 * Otherwise, use a percentage of physical memory defined by 3852 * zfs_dirty_data_max_percent (default 10%) with a cap at 3853 * zfs_dirty_data_max_max (default 4GB). 3854 */ 3855 if (zfs_dirty_data_max == 0) { 3856 zfs_dirty_data_max = physmem * PAGESIZE * 3857 zfs_dirty_data_max_percent / 100; 3858 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 3859 zfs_dirty_data_max_max); 3860 } 3861 } 3862 3863 void 3864 arc_fini(void) 3865 { 3866 mutex_enter(&arc_reclaim_thr_lock); 3867 arc_thread_exit = 1; 3868 while (arc_thread_exit != 0) 3869 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 3870 mutex_exit(&arc_reclaim_thr_lock); 3871 3872 arc_flush(NULL); 3873 3874 arc_dead = TRUE; 3875 3876 if (arc_ksp != NULL) { 3877 kstat_delete(arc_ksp); 3878 arc_ksp = NULL; 3879 } 3880 3881 mutex_destroy(&arc_eviction_mtx); 3882 mutex_destroy(&arc_reclaim_thr_lock); 3883 cv_destroy(&arc_reclaim_thr_cv); 3884 3885 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 3886 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 3887 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 3888 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 3889 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 3890 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 3891 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 3892 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 3893 3894 mutex_destroy(&arc_anon->arcs_mtx); 3895 mutex_destroy(&arc_mru->arcs_mtx); 3896 mutex_destroy(&arc_mru_ghost->arcs_mtx); 3897 mutex_destroy(&arc_mfu->arcs_mtx); 3898 mutex_destroy(&arc_mfu_ghost->arcs_mtx); 3899 mutex_destroy(&arc_l2c_only->arcs_mtx); 3900 3901 buf_fini(); 3902 3903 ASSERT(arc_loaned_bytes == 0); 3904 } 3905 3906 /* 3907 * Level 2 ARC 3908 * 3909 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 3910 * It uses dedicated storage devices to hold cached data, which are populated 3911 * using large infrequent writes. The main role of this cache is to boost 3912 * the performance of random read workloads. The intended L2ARC devices 3913 * include short-stroked disks, solid state disks, and other media with 3914 * substantially faster read latency than disk. 3915 * 3916 * +-----------------------+ 3917 * | ARC | 3918 * +-----------------------+ 3919 * | ^ ^ 3920 * | | | 3921 * l2arc_feed_thread() arc_read() 3922 * | | | 3923 * | l2arc read | 3924 * V | | 3925 * +---------------+ | 3926 * | L2ARC | | 3927 * +---------------+ | 3928 * | ^ | 3929 * l2arc_write() | | 3930 * | | | 3931 * V | | 3932 * +-------+ +-------+ 3933 * | vdev | | vdev | 3934 * | cache | | cache | 3935 * +-------+ +-------+ 3936 * +=========+ .-----. 3937 * : L2ARC : |-_____-| 3938 * : devices : | Disks | 3939 * +=========+ `-_____-' 3940 * 3941 * Read requests are satisfied from the following sources, in order: 3942 * 3943 * 1) ARC 3944 * 2) vdev cache of L2ARC devices 3945 * 3) L2ARC devices 3946 * 4) vdev cache of disks 3947 * 5) disks 3948 * 3949 * Some L2ARC device types exhibit extremely slow write performance. 3950 * To accommodate for this there are some significant differences between 3951 * the L2ARC and traditional cache design: 3952 * 3953 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 3954 * the ARC behave as usual, freeing buffers and placing headers on ghost 3955 * lists. The ARC does not send buffers to the L2ARC during eviction as 3956 * this would add inflated write latencies for all ARC memory pressure. 3957 * 3958 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 3959 * It does this by periodically scanning buffers from the eviction-end of 3960 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 3961 * not already there. It scans until a headroom of buffers is satisfied, 3962 * which itself is a buffer for ARC eviction. If a compressible buffer is 3963 * found during scanning and selected for writing to an L2ARC device, we 3964 * temporarily boost scanning headroom during the next scan cycle to make 3965 * sure we adapt to compression effects (which might significantly reduce 3966 * the data volume we write to L2ARC). The thread that does this is 3967 * l2arc_feed_thread(), illustrated below; example sizes are included to 3968 * provide a better sense of ratio than this diagram: 3969 * 3970 * head --> tail 3971 * +---------------------+----------+ 3972 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 3973 * +---------------------+----------+ | o L2ARC eligible 3974 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 3975 * +---------------------+----------+ | 3976 * 15.9 Gbytes ^ 32 Mbytes | 3977 * headroom | 3978 * l2arc_feed_thread() 3979 * | 3980 * l2arc write hand <--[oooo]--' 3981 * | 8 Mbyte 3982 * | write max 3983 * V 3984 * +==============================+ 3985 * L2ARC dev |####|#|###|###| |####| ... | 3986 * +==============================+ 3987 * 32 Gbytes 3988 * 3989 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 3990 * evicted, then the L2ARC has cached a buffer much sooner than it probably 3991 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 3992 * safe to say that this is an uncommon case, since buffers at the end of 3993 * the ARC lists have moved there due to inactivity. 3994 * 3995 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 3996 * then the L2ARC simply misses copying some buffers. This serves as a 3997 * pressure valve to prevent heavy read workloads from both stalling the ARC 3998 * with waits and clogging the L2ARC with writes. This also helps prevent 3999 * the potential for the L2ARC to churn if it attempts to cache content too 4000 * quickly, such as during backups of the entire pool. 4001 * 4002 * 5. After system boot and before the ARC has filled main memory, there are 4003 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 4004 * lists can remain mostly static. Instead of searching from tail of these 4005 * lists as pictured, the l2arc_feed_thread() will search from the list heads 4006 * for eligible buffers, greatly increasing its chance of finding them. 4007 * 4008 * The L2ARC device write speed is also boosted during this time so that 4009 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 4010 * there are no L2ARC reads, and no fear of degrading read performance 4011 * through increased writes. 4012 * 4013 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 4014 * the vdev queue can aggregate them into larger and fewer writes. Each 4015 * device is written to in a rotor fashion, sweeping writes through 4016 * available space then repeating. 4017 * 4018 * 7. The L2ARC does not store dirty content. It never needs to flush 4019 * write buffers back to disk based storage. 4020 * 4021 * 8. If an ARC buffer is written (and dirtied) which also exists in the 4022 * L2ARC, the now stale L2ARC buffer is immediately dropped. 4023 * 4024 * The performance of the L2ARC can be tweaked by a number of tunables, which 4025 * may be necessary for different workloads: 4026 * 4027 * l2arc_write_max max write bytes per interval 4028 * l2arc_write_boost extra write bytes during device warmup 4029 * l2arc_noprefetch skip caching prefetched buffers 4030 * l2arc_headroom number of max device writes to precache 4031 * l2arc_headroom_boost when we find compressed buffers during ARC 4032 * scanning, we multiply headroom by this 4033 * percentage factor for the next scan cycle, 4034 * since more compressed buffers are likely to 4035 * be present 4036 * l2arc_feed_secs seconds between L2ARC writing 4037 * 4038 * Tunables may be removed or added as future performance improvements are 4039 * integrated, and also may become zpool properties. 4040 * 4041 * There are three key functions that control how the L2ARC warms up: 4042 * 4043 * l2arc_write_eligible() check if a buffer is eligible to cache 4044 * l2arc_write_size() calculate how much to write 4045 * l2arc_write_interval() calculate sleep delay between writes 4046 * 4047 * These three functions determine what to write, how much, and how quickly 4048 * to send writes. 4049 */ 4050 4051 static boolean_t 4052 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab) 4053 { 4054 /* 4055 * A buffer is *not* eligible for the L2ARC if it: 4056 * 1. belongs to a different spa. 4057 * 2. is already cached on the L2ARC. 4058 * 3. has an I/O in progress (it may be an incomplete read). 4059 * 4. is flagged not eligible (zfs property). 4060 */ 4061 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL || 4062 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab)) 4063 return (B_FALSE); 4064 4065 return (B_TRUE); 4066 } 4067 4068 static uint64_t 4069 l2arc_write_size(void) 4070 { 4071 uint64_t size; 4072 4073 /* 4074 * Make sure our globals have meaningful values in case the user 4075 * altered them. 4076 */ 4077 size = l2arc_write_max; 4078 if (size == 0) { 4079 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 4080 "be greater than zero, resetting it to the default (%d)", 4081 L2ARC_WRITE_SIZE); 4082 size = l2arc_write_max = L2ARC_WRITE_SIZE; 4083 } 4084 4085 if (arc_warm == B_FALSE) 4086 size += l2arc_write_boost; 4087 4088 return (size); 4089 4090 } 4091 4092 static clock_t 4093 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 4094 { 4095 clock_t interval, next, now; 4096 4097 /* 4098 * If the ARC lists are busy, increase our write rate; if the 4099 * lists are stale, idle back. This is achieved by checking 4100 * how much we previously wrote - if it was more than half of 4101 * what we wanted, schedule the next write much sooner. 4102 */ 4103 if (l2arc_feed_again && wrote > (wanted / 2)) 4104 interval = (hz * l2arc_feed_min_ms) / 1000; 4105 else 4106 interval = hz * l2arc_feed_secs; 4107 4108 now = ddi_get_lbolt(); 4109 next = MAX(now, MIN(now + interval, began + interval)); 4110 4111 return (next); 4112 } 4113 4114 static void 4115 l2arc_hdr_stat_add(void) 4116 { 4117 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE); 4118 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE); 4119 } 4120 4121 static void 4122 l2arc_hdr_stat_remove(void) 4123 { 4124 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE)); 4125 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE); 4126 } 4127 4128 /* 4129 * Cycle through L2ARC devices. This is how L2ARC load balances. 4130 * If a device is returned, this also returns holding the spa config lock. 4131 */ 4132 static l2arc_dev_t * 4133 l2arc_dev_get_next(void) 4134 { 4135 l2arc_dev_t *first, *next = NULL; 4136 4137 /* 4138 * Lock out the removal of spas (spa_namespace_lock), then removal 4139 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 4140 * both locks will be dropped and a spa config lock held instead. 4141 */ 4142 mutex_enter(&spa_namespace_lock); 4143 mutex_enter(&l2arc_dev_mtx); 4144 4145 /* if there are no vdevs, there is nothing to do */ 4146 if (l2arc_ndev == 0) 4147 goto out; 4148 4149 first = NULL; 4150 next = l2arc_dev_last; 4151 do { 4152 /* loop around the list looking for a non-faulted vdev */ 4153 if (next == NULL) { 4154 next = list_head(l2arc_dev_list); 4155 } else { 4156 next = list_next(l2arc_dev_list, next); 4157 if (next == NULL) 4158 next = list_head(l2arc_dev_list); 4159 } 4160 4161 /* if we have come back to the start, bail out */ 4162 if (first == NULL) 4163 first = next; 4164 else if (next == first) 4165 break; 4166 4167 } while (vdev_is_dead(next->l2ad_vdev)); 4168 4169 /* if we were unable to find any usable vdevs, return NULL */ 4170 if (vdev_is_dead(next->l2ad_vdev)) 4171 next = NULL; 4172 4173 l2arc_dev_last = next; 4174 4175 out: 4176 mutex_exit(&l2arc_dev_mtx); 4177 4178 /* 4179 * Grab the config lock to prevent the 'next' device from being 4180 * removed while we are writing to it. 4181 */ 4182 if (next != NULL) 4183 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4184 mutex_exit(&spa_namespace_lock); 4185 4186 return (next); 4187 } 4188 4189 /* 4190 * Free buffers that were tagged for destruction. 4191 */ 4192 static void 4193 l2arc_do_free_on_write() 4194 { 4195 list_t *buflist; 4196 l2arc_data_free_t *df, *df_prev; 4197 4198 mutex_enter(&l2arc_free_on_write_mtx); 4199 buflist = l2arc_free_on_write; 4200 4201 for (df = list_tail(buflist); df; df = df_prev) { 4202 df_prev = list_prev(buflist, df); 4203 ASSERT(df->l2df_data != NULL); 4204 ASSERT(df->l2df_func != NULL); 4205 df->l2df_func(df->l2df_data, df->l2df_size); 4206 list_remove(buflist, df); 4207 kmem_free(df, sizeof (l2arc_data_free_t)); 4208 } 4209 4210 mutex_exit(&l2arc_free_on_write_mtx); 4211 } 4212 4213 /* 4214 * A write to a cache device has completed. Update all headers to allow 4215 * reads from these buffers to begin. 4216 */ 4217 static void 4218 l2arc_write_done(zio_t *zio) 4219 { 4220 l2arc_write_callback_t *cb; 4221 l2arc_dev_t *dev; 4222 list_t *buflist; 4223 arc_buf_hdr_t *head, *ab, *ab_prev; 4224 l2arc_buf_hdr_t *abl2; 4225 kmutex_t *hash_lock; 4226 int64_t bytes_dropped = 0; 4227 4228 cb = zio->io_private; 4229 ASSERT(cb != NULL); 4230 dev = cb->l2wcb_dev; 4231 ASSERT(dev != NULL); 4232 head = cb->l2wcb_head; 4233 ASSERT(head != NULL); 4234 buflist = dev->l2ad_buflist; 4235 ASSERT(buflist != NULL); 4236 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4237 l2arc_write_callback_t *, cb); 4238 4239 if (zio->io_error != 0) 4240 ARCSTAT_BUMP(arcstat_l2_writes_error); 4241 4242 mutex_enter(&l2arc_buflist_mtx); 4243 4244 /* 4245 * All writes completed, or an error was hit. 4246 */ 4247 for (ab = list_prev(buflist, head); ab; ab = ab_prev) { 4248 ab_prev = list_prev(buflist, ab); 4249 abl2 = ab->b_l2hdr; 4250 4251 /* 4252 * Release the temporary compressed buffer as soon as possible. 4253 */ 4254 if (abl2->b_compress != ZIO_COMPRESS_OFF) 4255 l2arc_release_cdata_buf(ab); 4256 4257 hash_lock = HDR_LOCK(ab); 4258 if (!mutex_tryenter(hash_lock)) { 4259 /* 4260 * This buffer misses out. It may be in a stage 4261 * of eviction. Its ARC_L2_WRITING flag will be 4262 * left set, denying reads to this buffer. 4263 */ 4264 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4265 continue; 4266 } 4267 4268 if (zio->io_error != 0) { 4269 /* 4270 * Error - drop L2ARC entry. 4271 */ 4272 list_remove(buflist, ab); 4273 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4274 bytes_dropped += abl2->b_asize; 4275 ab->b_l2hdr = NULL; 4276 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4277 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4278 } 4279 4280 /* 4281 * Allow ARC to begin reads to this L2ARC entry. 4282 */ 4283 ab->b_flags &= ~ARC_L2_WRITING; 4284 4285 mutex_exit(hash_lock); 4286 } 4287 4288 atomic_inc_64(&l2arc_writes_done); 4289 list_remove(buflist, head); 4290 kmem_cache_free(hdr_cache, head); 4291 mutex_exit(&l2arc_buflist_mtx); 4292 4293 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 4294 4295 l2arc_do_free_on_write(); 4296 4297 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4298 } 4299 4300 /* 4301 * A read to a cache device completed. Validate buffer contents before 4302 * handing over to the regular ARC routines. 4303 */ 4304 static void 4305 l2arc_read_done(zio_t *zio) 4306 { 4307 l2arc_read_callback_t *cb; 4308 arc_buf_hdr_t *hdr; 4309 arc_buf_t *buf; 4310 kmutex_t *hash_lock; 4311 int equal; 4312 4313 ASSERT(zio->io_vd != NULL); 4314 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4315 4316 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4317 4318 cb = zio->io_private; 4319 ASSERT(cb != NULL); 4320 buf = cb->l2rcb_buf; 4321 ASSERT(buf != NULL); 4322 4323 hash_lock = HDR_LOCK(buf->b_hdr); 4324 mutex_enter(hash_lock); 4325 hdr = buf->b_hdr; 4326 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4327 4328 /* 4329 * If the buffer was compressed, decompress it first. 4330 */ 4331 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 4332 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 4333 ASSERT(zio->io_data != NULL); 4334 4335 /* 4336 * Check this survived the L2ARC journey. 4337 */ 4338 equal = arc_cksum_equal(buf); 4339 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4340 mutex_exit(hash_lock); 4341 zio->io_private = buf; 4342 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4343 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4344 arc_read_done(zio); 4345 } else { 4346 mutex_exit(hash_lock); 4347 /* 4348 * Buffer didn't survive caching. Increment stats and 4349 * reissue to the original storage device. 4350 */ 4351 if (zio->io_error != 0) { 4352 ARCSTAT_BUMP(arcstat_l2_io_error); 4353 } else { 4354 zio->io_error = SET_ERROR(EIO); 4355 } 4356 if (!equal) 4357 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4358 4359 /* 4360 * If there's no waiter, issue an async i/o to the primary 4361 * storage now. If there *is* a waiter, the caller must 4362 * issue the i/o in a context where it's OK to block. 4363 */ 4364 if (zio->io_waiter == NULL) { 4365 zio_t *pio = zio_unique_parent(zio); 4366 4367 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4368 4369 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4370 buf->b_data, zio->io_size, arc_read_done, buf, 4371 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4372 } 4373 } 4374 4375 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4376 } 4377 4378 /* 4379 * This is the list priority from which the L2ARC will search for pages to 4380 * cache. This is used within loops (0..3) to cycle through lists in the 4381 * desired order. This order can have a significant effect on cache 4382 * performance. 4383 * 4384 * Currently the metadata lists are hit first, MFU then MRU, followed by 4385 * the data lists. This function returns a locked list, and also returns 4386 * the lock pointer. 4387 */ 4388 static list_t * 4389 l2arc_list_locked(int list_num, kmutex_t **lock) 4390 { 4391 list_t *list = NULL; 4392 4393 ASSERT(list_num >= 0 && list_num <= 3); 4394 4395 switch (list_num) { 4396 case 0: 4397 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 4398 *lock = &arc_mfu->arcs_mtx; 4399 break; 4400 case 1: 4401 list = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 4402 *lock = &arc_mru->arcs_mtx; 4403 break; 4404 case 2: 4405 list = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 4406 *lock = &arc_mfu->arcs_mtx; 4407 break; 4408 case 3: 4409 list = &arc_mru->arcs_list[ARC_BUFC_DATA]; 4410 *lock = &arc_mru->arcs_mtx; 4411 break; 4412 } 4413 4414 ASSERT(!(MUTEX_HELD(*lock))); 4415 mutex_enter(*lock); 4416 return (list); 4417 } 4418 4419 /* 4420 * Evict buffers from the device write hand to the distance specified in 4421 * bytes. This distance may span populated buffers, it may span nothing. 4422 * This is clearing a region on the L2ARC device ready for writing. 4423 * If the 'all' boolean is set, every buffer is evicted. 4424 */ 4425 static void 4426 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 4427 { 4428 list_t *buflist; 4429 l2arc_buf_hdr_t *abl2; 4430 arc_buf_hdr_t *ab, *ab_prev; 4431 kmutex_t *hash_lock; 4432 uint64_t taddr; 4433 int64_t bytes_evicted = 0; 4434 4435 buflist = dev->l2ad_buflist; 4436 4437 if (buflist == NULL) 4438 return; 4439 4440 if (!all && dev->l2ad_first) { 4441 /* 4442 * This is the first sweep through the device. There is 4443 * nothing to evict. 4444 */ 4445 return; 4446 } 4447 4448 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 4449 /* 4450 * When nearing the end of the device, evict to the end 4451 * before the device write hand jumps to the start. 4452 */ 4453 taddr = dev->l2ad_end; 4454 } else { 4455 taddr = dev->l2ad_hand + distance; 4456 } 4457 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 4458 uint64_t, taddr, boolean_t, all); 4459 4460 top: 4461 mutex_enter(&l2arc_buflist_mtx); 4462 for (ab = list_tail(buflist); ab; ab = ab_prev) { 4463 ab_prev = list_prev(buflist, ab); 4464 4465 hash_lock = HDR_LOCK(ab); 4466 if (!mutex_tryenter(hash_lock)) { 4467 /* 4468 * Missed the hash lock. Retry. 4469 */ 4470 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 4471 mutex_exit(&l2arc_buflist_mtx); 4472 mutex_enter(hash_lock); 4473 mutex_exit(hash_lock); 4474 goto top; 4475 } 4476 4477 if (HDR_L2_WRITE_HEAD(ab)) { 4478 /* 4479 * We hit a write head node. Leave it for 4480 * l2arc_write_done(). 4481 */ 4482 list_remove(buflist, ab); 4483 mutex_exit(hash_lock); 4484 continue; 4485 } 4486 4487 if (!all && ab->b_l2hdr != NULL && 4488 (ab->b_l2hdr->b_daddr > taddr || 4489 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) { 4490 /* 4491 * We've evicted to the target address, 4492 * or the end of the device. 4493 */ 4494 mutex_exit(hash_lock); 4495 break; 4496 } 4497 4498 if (HDR_FREE_IN_PROGRESS(ab)) { 4499 /* 4500 * Already on the path to destruction. 4501 */ 4502 mutex_exit(hash_lock); 4503 continue; 4504 } 4505 4506 if (ab->b_state == arc_l2c_only) { 4507 ASSERT(!HDR_L2_READING(ab)); 4508 /* 4509 * This doesn't exist in the ARC. Destroy. 4510 * arc_hdr_destroy() will call list_remove() 4511 * and decrement arcstat_l2_size. 4512 */ 4513 arc_change_state(arc_anon, ab, hash_lock); 4514 arc_hdr_destroy(ab); 4515 } else { 4516 /* 4517 * Invalidate issued or about to be issued 4518 * reads, since we may be about to write 4519 * over this location. 4520 */ 4521 if (HDR_L2_READING(ab)) { 4522 ARCSTAT_BUMP(arcstat_l2_evict_reading); 4523 ab->b_flags |= ARC_L2_EVICTED; 4524 } 4525 4526 /* 4527 * Tell ARC this no longer exists in L2ARC. 4528 */ 4529 if (ab->b_l2hdr != NULL) { 4530 abl2 = ab->b_l2hdr; 4531 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4532 bytes_evicted += abl2->b_asize; 4533 ab->b_l2hdr = NULL; 4534 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4535 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); 4536 } 4537 list_remove(buflist, ab); 4538 4539 /* 4540 * This may have been leftover after a 4541 * failed write. 4542 */ 4543 ab->b_flags &= ~ARC_L2_WRITING; 4544 } 4545 mutex_exit(hash_lock); 4546 } 4547 mutex_exit(&l2arc_buflist_mtx); 4548 4549 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 4550 dev->l2ad_evict = taddr; 4551 } 4552 4553 /* 4554 * Find and write ARC buffers to the L2ARC device. 4555 * 4556 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid 4557 * for reading until they have completed writing. 4558 * The headroom_boost is an in-out parameter used to maintain headroom boost 4559 * state between calls to this function. 4560 * 4561 * Returns the number of bytes actually written (which may be smaller than 4562 * the delta by which the device hand has changed due to alignment). 4563 */ 4564 static uint64_t 4565 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 4566 boolean_t *headroom_boost) 4567 { 4568 arc_buf_hdr_t *ab, *ab_prev, *head; 4569 list_t *list; 4570 uint64_t write_asize, write_psize, write_sz, headroom, 4571 buf_compress_minsz; 4572 void *buf_data; 4573 kmutex_t *list_lock; 4574 boolean_t full; 4575 l2arc_write_callback_t *cb; 4576 zio_t *pio, *wzio; 4577 uint64_t guid = spa_load_guid(spa); 4578 const boolean_t do_headroom_boost = *headroom_boost; 4579 4580 ASSERT(dev->l2ad_vdev != NULL); 4581 4582 /* Lower the flag now, we might want to raise it again later. */ 4583 *headroom_boost = B_FALSE; 4584 4585 pio = NULL; 4586 write_sz = write_asize = write_psize = 0; 4587 full = B_FALSE; 4588 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 4589 head->b_flags |= ARC_L2_WRITE_HEAD; 4590 4591 /* 4592 * We will want to try to compress buffers that are at least 2x the 4593 * device sector size. 4594 */ 4595 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 4596 4597 /* 4598 * Copy buffers for L2ARC writing. 4599 */ 4600 mutex_enter(&l2arc_buflist_mtx); 4601 for (int try = 0; try <= 3; try++) { 4602 uint64_t passed_sz = 0; 4603 4604 list = l2arc_list_locked(try, &list_lock); 4605 4606 /* 4607 * L2ARC fast warmup. 4608 * 4609 * Until the ARC is warm and starts to evict, read from the 4610 * head of the ARC lists rather than the tail. 4611 */ 4612 if (arc_warm == B_FALSE) 4613 ab = list_head(list); 4614 else 4615 ab = list_tail(list); 4616 4617 headroom = target_sz * l2arc_headroom; 4618 if (do_headroom_boost) 4619 headroom = (headroom * l2arc_headroom_boost) / 100; 4620 4621 for (; ab; ab = ab_prev) { 4622 l2arc_buf_hdr_t *l2hdr; 4623 kmutex_t *hash_lock; 4624 uint64_t buf_sz; 4625 4626 if (arc_warm == B_FALSE) 4627 ab_prev = list_next(list, ab); 4628 else 4629 ab_prev = list_prev(list, ab); 4630 4631 hash_lock = HDR_LOCK(ab); 4632 if (!mutex_tryenter(hash_lock)) { 4633 /* 4634 * Skip this buffer rather than waiting. 4635 */ 4636 continue; 4637 } 4638 4639 passed_sz += ab->b_size; 4640 if (passed_sz > headroom) { 4641 /* 4642 * Searched too far. 4643 */ 4644 mutex_exit(hash_lock); 4645 break; 4646 } 4647 4648 if (!l2arc_write_eligible(guid, ab)) { 4649 mutex_exit(hash_lock); 4650 continue; 4651 } 4652 4653 if ((write_sz + ab->b_size) > target_sz) { 4654 full = B_TRUE; 4655 mutex_exit(hash_lock); 4656 break; 4657 } 4658 4659 if (pio == NULL) { 4660 /* 4661 * Insert a dummy header on the buflist so 4662 * l2arc_write_done() can find where the 4663 * write buffers begin without searching. 4664 */ 4665 list_insert_head(dev->l2ad_buflist, head); 4666 4667 cb = kmem_alloc( 4668 sizeof (l2arc_write_callback_t), KM_SLEEP); 4669 cb->l2wcb_dev = dev; 4670 cb->l2wcb_head = head; 4671 pio = zio_root(spa, l2arc_write_done, cb, 4672 ZIO_FLAG_CANFAIL); 4673 } 4674 4675 /* 4676 * Create and add a new L2ARC header. 4677 */ 4678 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP); 4679 l2hdr->b_dev = dev; 4680 ab->b_flags |= ARC_L2_WRITING; 4681 4682 /* 4683 * Temporarily stash the data buffer in b_tmp_cdata. 4684 * The subsequent write step will pick it up from 4685 * there. This is because can't access ab->b_buf 4686 * without holding the hash_lock, which we in turn 4687 * can't access without holding the ARC list locks 4688 * (which we want to avoid during compression/writing). 4689 */ 4690 l2hdr->b_compress = ZIO_COMPRESS_OFF; 4691 l2hdr->b_asize = ab->b_size; 4692 l2hdr->b_tmp_cdata = ab->b_buf->b_data; 4693 4694 buf_sz = ab->b_size; 4695 ab->b_l2hdr = l2hdr; 4696 4697 list_insert_head(dev->l2ad_buflist, ab); 4698 4699 /* 4700 * Compute and store the buffer cksum before 4701 * writing. On debug the cksum is verified first. 4702 */ 4703 arc_cksum_verify(ab->b_buf); 4704 arc_cksum_compute(ab->b_buf, B_TRUE); 4705 4706 mutex_exit(hash_lock); 4707 4708 write_sz += buf_sz; 4709 } 4710 4711 mutex_exit(list_lock); 4712 4713 if (full == B_TRUE) 4714 break; 4715 } 4716 4717 /* No buffers selected for writing? */ 4718 if (pio == NULL) { 4719 ASSERT0(write_sz); 4720 mutex_exit(&l2arc_buflist_mtx); 4721 kmem_cache_free(hdr_cache, head); 4722 return (0); 4723 } 4724 4725 /* 4726 * Now start writing the buffers. We're starting at the write head 4727 * and work backwards, retracing the course of the buffer selector 4728 * loop above. 4729 */ 4730 for (ab = list_prev(dev->l2ad_buflist, head); ab; 4731 ab = list_prev(dev->l2ad_buflist, ab)) { 4732 l2arc_buf_hdr_t *l2hdr; 4733 uint64_t buf_sz; 4734 4735 /* 4736 * We shouldn't need to lock the buffer here, since we flagged 4737 * it as ARC_L2_WRITING in the previous step, but we must take 4738 * care to only access its L2 cache parameters. In particular, 4739 * ab->b_buf may be invalid by now due to ARC eviction. 4740 */ 4741 l2hdr = ab->b_l2hdr; 4742 l2hdr->b_daddr = dev->l2ad_hand; 4743 4744 if ((ab->b_flags & ARC_L2COMPRESS) && 4745 l2hdr->b_asize >= buf_compress_minsz) { 4746 if (l2arc_compress_buf(l2hdr)) { 4747 /* 4748 * If compression succeeded, enable headroom 4749 * boost on the next scan cycle. 4750 */ 4751 *headroom_boost = B_TRUE; 4752 } 4753 } 4754 4755 /* 4756 * Pick up the buffer data we had previously stashed away 4757 * (and now potentially also compressed). 4758 */ 4759 buf_data = l2hdr->b_tmp_cdata; 4760 buf_sz = l2hdr->b_asize; 4761 4762 /* Compression may have squashed the buffer to zero length. */ 4763 if (buf_sz != 0) { 4764 uint64_t buf_p_sz; 4765 4766 wzio = zio_write_phys(pio, dev->l2ad_vdev, 4767 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 4768 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 4769 ZIO_FLAG_CANFAIL, B_FALSE); 4770 4771 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 4772 zio_t *, wzio); 4773 (void) zio_nowait(wzio); 4774 4775 write_asize += buf_sz; 4776 /* 4777 * Keep the clock hand suitably device-aligned. 4778 */ 4779 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 4780 write_psize += buf_p_sz; 4781 dev->l2ad_hand += buf_p_sz; 4782 } 4783 } 4784 4785 mutex_exit(&l2arc_buflist_mtx); 4786 4787 ASSERT3U(write_asize, <=, target_sz); 4788 ARCSTAT_BUMP(arcstat_l2_writes_sent); 4789 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 4790 ARCSTAT_INCR(arcstat_l2_size, write_sz); 4791 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 4792 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 4793 4794 /* 4795 * Bump device hand to the device start if it is approaching the end. 4796 * l2arc_evict() will already have evicted ahead for this case. 4797 */ 4798 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 4799 dev->l2ad_hand = dev->l2ad_start; 4800 dev->l2ad_evict = dev->l2ad_start; 4801 dev->l2ad_first = B_FALSE; 4802 } 4803 4804 dev->l2ad_writing = B_TRUE; 4805 (void) zio_wait(pio); 4806 dev->l2ad_writing = B_FALSE; 4807 4808 return (write_asize); 4809 } 4810 4811 /* 4812 * Compresses an L2ARC buffer. 4813 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its 4814 * size in l2hdr->b_asize. This routine tries to compress the data and 4815 * depending on the compression result there are three possible outcomes: 4816 * *) The buffer was incompressible. The original l2hdr contents were left 4817 * untouched and are ready for writing to an L2 device. 4818 * *) The buffer was all-zeros, so there is no need to write it to an L2 4819 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 4820 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 4821 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 4822 * data buffer which holds the compressed data to be written, and b_asize 4823 * tells us how much data there is. b_compress is set to the appropriate 4824 * compression algorithm. Once writing is done, invoke 4825 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 4826 * 4827 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 4828 * buffer was incompressible). 4829 */ 4830 static boolean_t 4831 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr) 4832 { 4833 void *cdata; 4834 size_t csize, len, rounded; 4835 4836 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF); 4837 ASSERT(l2hdr->b_tmp_cdata != NULL); 4838 4839 len = l2hdr->b_asize; 4840 cdata = zio_data_buf_alloc(len); 4841 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata, 4842 cdata, l2hdr->b_asize); 4843 4844 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 4845 if (rounded > csize) { 4846 bzero((char *)cdata + csize, rounded - csize); 4847 csize = rounded; 4848 } 4849 4850 if (csize == 0) { 4851 /* zero block, indicate that there's nothing to write */ 4852 zio_data_buf_free(cdata, len); 4853 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 4854 l2hdr->b_asize = 0; 4855 l2hdr->b_tmp_cdata = NULL; 4856 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 4857 return (B_TRUE); 4858 } else if (csize > 0 && csize < len) { 4859 /* 4860 * Compression succeeded, we'll keep the cdata around for 4861 * writing and release it afterwards. 4862 */ 4863 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 4864 l2hdr->b_asize = csize; 4865 l2hdr->b_tmp_cdata = cdata; 4866 ARCSTAT_BUMP(arcstat_l2_compress_successes); 4867 return (B_TRUE); 4868 } else { 4869 /* 4870 * Compression failed, release the compressed buffer. 4871 * l2hdr will be left unmodified. 4872 */ 4873 zio_data_buf_free(cdata, len); 4874 ARCSTAT_BUMP(arcstat_l2_compress_failures); 4875 return (B_FALSE); 4876 } 4877 } 4878 4879 /* 4880 * Decompresses a zio read back from an l2arc device. On success, the 4881 * underlying zio's io_data buffer is overwritten by the uncompressed 4882 * version. On decompression error (corrupt compressed stream), the 4883 * zio->io_error value is set to signal an I/O error. 4884 * 4885 * Please note that the compressed data stream is not checksummed, so 4886 * if the underlying device is experiencing data corruption, we may feed 4887 * corrupt data to the decompressor, so the decompressor needs to be 4888 * able to handle this situation (LZ4 does). 4889 */ 4890 static void 4891 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 4892 { 4893 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 4894 4895 if (zio->io_error != 0) { 4896 /* 4897 * An io error has occured, just restore the original io 4898 * size in preparation for a main pool read. 4899 */ 4900 zio->io_orig_size = zio->io_size = hdr->b_size; 4901 return; 4902 } 4903 4904 if (c == ZIO_COMPRESS_EMPTY) { 4905 /* 4906 * An empty buffer results in a null zio, which means we 4907 * need to fill its io_data after we're done restoring the 4908 * buffer's contents. 4909 */ 4910 ASSERT(hdr->b_buf != NULL); 4911 bzero(hdr->b_buf->b_data, hdr->b_size); 4912 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data; 4913 } else { 4914 ASSERT(zio->io_data != NULL); 4915 /* 4916 * We copy the compressed data from the start of the arc buffer 4917 * (the zio_read will have pulled in only what we need, the 4918 * rest is garbage which we will overwrite at decompression) 4919 * and then decompress back to the ARC data buffer. This way we 4920 * can minimize copying by simply decompressing back over the 4921 * original compressed data (rather than decompressing to an 4922 * aux buffer and then copying back the uncompressed buffer, 4923 * which is likely to be much larger). 4924 */ 4925 uint64_t csize; 4926 void *cdata; 4927 4928 csize = zio->io_size; 4929 cdata = zio_data_buf_alloc(csize); 4930 bcopy(zio->io_data, cdata, csize); 4931 if (zio_decompress_data(c, cdata, zio->io_data, csize, 4932 hdr->b_size) != 0) 4933 zio->io_error = EIO; 4934 zio_data_buf_free(cdata, csize); 4935 } 4936 4937 /* Restore the expected uncompressed IO size. */ 4938 zio->io_orig_size = zio->io_size = hdr->b_size; 4939 } 4940 4941 /* 4942 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 4943 * This buffer serves as a temporary holder of compressed data while 4944 * the buffer entry is being written to an l2arc device. Once that is 4945 * done, we can dispose of it. 4946 */ 4947 static void 4948 l2arc_release_cdata_buf(arc_buf_hdr_t *ab) 4949 { 4950 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr; 4951 4952 if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) { 4953 /* 4954 * If the data was compressed, then we've allocated a 4955 * temporary buffer for it, so now we need to release it. 4956 */ 4957 ASSERT(l2hdr->b_tmp_cdata != NULL); 4958 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size); 4959 } 4960 l2hdr->b_tmp_cdata = NULL; 4961 } 4962 4963 /* 4964 * This thread feeds the L2ARC at regular intervals. This is the beating 4965 * heart of the L2ARC. 4966 */ 4967 static void 4968 l2arc_feed_thread(void) 4969 { 4970 callb_cpr_t cpr; 4971 l2arc_dev_t *dev; 4972 spa_t *spa; 4973 uint64_t size, wrote; 4974 clock_t begin, next = ddi_get_lbolt(); 4975 boolean_t headroom_boost = B_FALSE; 4976 4977 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 4978 4979 mutex_enter(&l2arc_feed_thr_lock); 4980 4981 while (l2arc_thread_exit == 0) { 4982 CALLB_CPR_SAFE_BEGIN(&cpr); 4983 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 4984 next); 4985 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 4986 next = ddi_get_lbolt() + hz; 4987 4988 /* 4989 * Quick check for L2ARC devices. 4990 */ 4991 mutex_enter(&l2arc_dev_mtx); 4992 if (l2arc_ndev == 0) { 4993 mutex_exit(&l2arc_dev_mtx); 4994 continue; 4995 } 4996 mutex_exit(&l2arc_dev_mtx); 4997 begin = ddi_get_lbolt(); 4998 4999 /* 5000 * This selects the next l2arc device to write to, and in 5001 * doing so the next spa to feed from: dev->l2ad_spa. This 5002 * will return NULL if there are now no l2arc devices or if 5003 * they are all faulted. 5004 * 5005 * If a device is returned, its spa's config lock is also 5006 * held to prevent device removal. l2arc_dev_get_next() 5007 * will grab and release l2arc_dev_mtx. 5008 */ 5009 if ((dev = l2arc_dev_get_next()) == NULL) 5010 continue; 5011 5012 spa = dev->l2ad_spa; 5013 ASSERT(spa != NULL); 5014 5015 /* 5016 * If the pool is read-only then force the feed thread to 5017 * sleep a little longer. 5018 */ 5019 if (!spa_writeable(spa)) { 5020 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 5021 spa_config_exit(spa, SCL_L2ARC, dev); 5022 continue; 5023 } 5024 5025 /* 5026 * Avoid contributing to memory pressure. 5027 */ 5028 if (arc_reclaim_needed()) { 5029 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 5030 spa_config_exit(spa, SCL_L2ARC, dev); 5031 continue; 5032 } 5033 5034 ARCSTAT_BUMP(arcstat_l2_feeds); 5035 5036 size = l2arc_write_size(); 5037 5038 /* 5039 * Evict L2ARC buffers that will be overwritten. 5040 */ 5041 l2arc_evict(dev, size, B_FALSE); 5042 5043 /* 5044 * Write ARC buffers. 5045 */ 5046 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 5047 5048 /* 5049 * Calculate interval between writes. 5050 */ 5051 next = l2arc_write_interval(begin, size, wrote); 5052 spa_config_exit(spa, SCL_L2ARC, dev); 5053 } 5054 5055 l2arc_thread_exit = 0; 5056 cv_broadcast(&l2arc_feed_thr_cv); 5057 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 5058 thread_exit(); 5059 } 5060 5061 boolean_t 5062 l2arc_vdev_present(vdev_t *vd) 5063 { 5064 l2arc_dev_t *dev; 5065 5066 mutex_enter(&l2arc_dev_mtx); 5067 for (dev = list_head(l2arc_dev_list); dev != NULL; 5068 dev = list_next(l2arc_dev_list, dev)) { 5069 if (dev->l2ad_vdev == vd) 5070 break; 5071 } 5072 mutex_exit(&l2arc_dev_mtx); 5073 5074 return (dev != NULL); 5075 } 5076 5077 /* 5078 * Add a vdev for use by the L2ARC. By this point the spa has already 5079 * validated the vdev and opened it. 5080 */ 5081 void 5082 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 5083 { 5084 l2arc_dev_t *adddev; 5085 5086 ASSERT(!l2arc_vdev_present(vd)); 5087 5088 /* 5089 * Create a new l2arc device entry. 5090 */ 5091 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 5092 adddev->l2ad_spa = spa; 5093 adddev->l2ad_vdev = vd; 5094 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 5095 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 5096 adddev->l2ad_hand = adddev->l2ad_start; 5097 adddev->l2ad_evict = adddev->l2ad_start; 5098 adddev->l2ad_first = B_TRUE; 5099 adddev->l2ad_writing = B_FALSE; 5100 5101 /* 5102 * This is a list of all ARC buffers that are still valid on the 5103 * device. 5104 */ 5105 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP); 5106 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 5107 offsetof(arc_buf_hdr_t, b_l2node)); 5108 5109 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 5110 5111 /* 5112 * Add device to global list 5113 */ 5114 mutex_enter(&l2arc_dev_mtx); 5115 list_insert_head(l2arc_dev_list, adddev); 5116 atomic_inc_64(&l2arc_ndev); 5117 mutex_exit(&l2arc_dev_mtx); 5118 } 5119 5120 /* 5121 * Remove a vdev from the L2ARC. 5122 */ 5123 void 5124 l2arc_remove_vdev(vdev_t *vd) 5125 { 5126 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 5127 5128 /* 5129 * Find the device by vdev 5130 */ 5131 mutex_enter(&l2arc_dev_mtx); 5132 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 5133 nextdev = list_next(l2arc_dev_list, dev); 5134 if (vd == dev->l2ad_vdev) { 5135 remdev = dev; 5136 break; 5137 } 5138 } 5139 ASSERT(remdev != NULL); 5140 5141 /* 5142 * Remove device from global list 5143 */ 5144 list_remove(l2arc_dev_list, remdev); 5145 l2arc_dev_last = NULL; /* may have been invalidated */ 5146 atomic_dec_64(&l2arc_ndev); 5147 mutex_exit(&l2arc_dev_mtx); 5148 5149 /* 5150 * Clear all buflists and ARC references. L2ARC device flush. 5151 */ 5152 l2arc_evict(remdev, 0, B_TRUE); 5153 list_destroy(remdev->l2ad_buflist); 5154 kmem_free(remdev->l2ad_buflist, sizeof (list_t)); 5155 kmem_free(remdev, sizeof (l2arc_dev_t)); 5156 } 5157 5158 void 5159 l2arc_init(void) 5160 { 5161 l2arc_thread_exit = 0; 5162 l2arc_ndev = 0; 5163 l2arc_writes_sent = 0; 5164 l2arc_writes_done = 0; 5165 5166 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 5167 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 5168 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 5169 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL); 5170 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 5171 5172 l2arc_dev_list = &L2ARC_dev_list; 5173 l2arc_free_on_write = &L2ARC_free_on_write; 5174 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 5175 offsetof(l2arc_dev_t, l2ad_node)); 5176 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 5177 offsetof(l2arc_data_free_t, l2df_list_node)); 5178 } 5179 5180 void 5181 l2arc_fini(void) 5182 { 5183 /* 5184 * This is called from dmu_fini(), which is called from spa_fini(); 5185 * Because of this, we can assume that all l2arc devices have 5186 * already been removed when the pools themselves were removed. 5187 */ 5188 5189 l2arc_do_free_on_write(); 5190 5191 mutex_destroy(&l2arc_feed_thr_lock); 5192 cv_destroy(&l2arc_feed_thr_cv); 5193 mutex_destroy(&l2arc_dev_mtx); 5194 mutex_destroy(&l2arc_buflist_mtx); 5195 mutex_destroy(&l2arc_free_on_write_mtx); 5196 5197 list_destroy(l2arc_dev_list); 5198 list_destroy(l2arc_free_on_write); 5199 } 5200 5201 void 5202 l2arc_start(void) 5203 { 5204 if (!(spa_mode_global & FWRITE)) 5205 return; 5206 5207 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 5208 TS_RUN, minclsyspri); 5209 } 5210 5211 void 5212 l2arc_stop(void) 5213 { 5214 if (!(spa_mode_global & FWRITE)) 5215 return; 5216 5217 mutex_enter(&l2arc_feed_thr_lock); 5218 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 5219 l2arc_thread_exit = 1; 5220 while (l2arc_thread_exit != 0) 5221 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 5222 mutex_exit(&l2arc_feed_thr_lock); 5223 }