arc.c revision 288536
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 mutexs, rather they rely on the 86 * hash table mutexs for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexs). 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/dnlc.h> 134#endif 135#include <sys/callb.h> 136#include <sys/kstat.h> 137#include <sys/trim_map.h> 138#include <zfs_fletcher.h> 139#include <sys/sdt.h> 140 141#include <vm/vm_pageout.h> 142#include <machine/vmparam.h> 143 144#ifdef illumos 145#ifndef _KERNEL 146/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 147boolean_t arc_watch = B_FALSE; 148int arc_procfd; 149#endif 150#endif /* illumos */ 151 152static kmutex_t arc_reclaim_thr_lock; 153static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 154static uint8_t arc_thread_exit; 155 156#define ARC_REDUCE_DNLC_PERCENT 3 157uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT; 158 159typedef enum arc_reclaim_strategy { 160 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */ 161 ARC_RECLAIM_CONS /* Conservative reclaim strategy */ 162} arc_reclaim_strategy_t; 163 164/* 165 * The number of iterations through arc_evict_*() before we 166 * drop & reacquire the lock. 167 */ 168int arc_evict_iterations = 100; 169 170/* number of seconds before growing cache again */ 171static int arc_grow_retry = 60; 172 173/* shift of arc_c for calculating both min and max arc_p */ 174static int arc_p_min_shift = 4; 175 176/* log2(fraction of arc to reclaim) */ 177static int arc_shrink_shift = 5; 178 179/* 180 * minimum lifespan of a prefetch block in clock ticks 181 * (initialized in arc_init()) 182 */ 183static int arc_min_prefetch_lifespan; 184 185/* 186 * If this percent of memory is free, don't throttle. 187 */ 188int arc_lotsfree_percent = 10; 189 190static int arc_dead; 191extern int zfs_prefetch_disable; 192 193/* 194 * The arc has filled available memory and has now warmed up. 195 */ 196static boolean_t arc_warm; 197 198uint64_t zfs_arc_max; 199uint64_t zfs_arc_min; 200uint64_t zfs_arc_meta_limit = 0; 201uint64_t zfs_arc_meta_min = 0; 202int zfs_arc_grow_retry = 0; 203int zfs_arc_shrink_shift = 0; 204int zfs_arc_p_min_shift = 0; 205int zfs_disable_dup_eviction = 0; 206uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 207u_int zfs_arc_free_target = 0; 208 209static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 210static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 211 212#ifdef _KERNEL 213static void 214arc_free_target_init(void *unused __unused) 215{ 216 217 zfs_arc_free_target = vm_pageout_wakeup_thresh; 218} 219SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 220 arc_free_target_init, NULL); 221 222TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max); 223TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min); 224TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 225TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 226TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize); 227TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 228SYSCTL_DECL(_vfs_zfs); 229SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 230 "Maximum ARC size"); 231SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 232 "Minimum ARC size"); 233SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 234 &zfs_arc_average_blocksize, 0, 235 "ARC average blocksize"); 236SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 237 &arc_shrink_shift, 0, 238 "log2(fraction of arc to reclaim)"); 239 240/* 241 * We don't have a tunable for arc_free_target due to the dependency on 242 * pagedaemon initialisation. 243 */ 244SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 245 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 246 sysctl_vfs_zfs_arc_free_target, "IU", 247 "Desired number of free pages below which ARC triggers reclaim"); 248 249static int 250sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 251{ 252 u_int val; 253 int err; 254 255 val = zfs_arc_free_target; 256 err = sysctl_handle_int(oidp, &val, 0, req); 257 if (err != 0 || req->newptr == NULL) 258 return (err); 259 260 if (val < minfree) 261 return (EINVAL); 262 if (val > cnt.v_page_count) 263 return (EINVAL); 264 265 zfs_arc_free_target = val; 266 267 return (0); 268} 269 270/* 271 * Must be declared here, before the definition of corresponding kstat 272 * macro which uses the same names will confuse the compiler. 273 */ 274SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 275 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 276 sysctl_vfs_zfs_arc_meta_limit, "QU", 277 "ARC metadata limit"); 278#endif 279 280/* 281 * Note that buffers can be in one of 6 states: 282 * ARC_anon - anonymous (discussed below) 283 * ARC_mru - recently used, currently cached 284 * ARC_mru_ghost - recentely used, no longer in cache 285 * ARC_mfu - frequently used, currently cached 286 * ARC_mfu_ghost - frequently used, no longer in cache 287 * ARC_l2c_only - exists in L2ARC but not other states 288 * When there are no active references to the buffer, they are 289 * are linked onto a list in one of these arc states. These are 290 * the only buffers that can be evicted or deleted. Within each 291 * state there are multiple lists, one for meta-data and one for 292 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 293 * etc.) is tracked separately so that it can be managed more 294 * explicitly: favored over data, limited explicitly. 295 * 296 * Anonymous buffers are buffers that are not associated with 297 * a DVA. These are buffers that hold dirty block copies 298 * before they are written to stable storage. By definition, 299 * they are "ref'd" and are considered part of arc_mru 300 * that cannot be freed. Generally, they will aquire a DVA 301 * as they are written and migrate onto the arc_mru list. 302 * 303 * The ARC_l2c_only state is for buffers that are in the second 304 * level ARC but no longer in any of the ARC_m* lists. The second 305 * level ARC itself may also contain buffers that are in any of 306 * the ARC_m* states - meaning that a buffer can exist in two 307 * places. The reason for the ARC_l2c_only state is to keep the 308 * buffer header in the hash table, so that reads that hit the 309 * second level ARC benefit from these fast lookups. 310 */ 311 312#define ARCS_LOCK_PAD CACHE_LINE_SIZE 313struct arcs_lock { 314 kmutex_t arcs_lock; 315#ifdef _KERNEL 316 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))]; 317#endif 318}; 319 320/* 321 * must be power of two for mask use to work 322 * 323 */ 324#define ARC_BUFC_NUMDATALISTS 16 325#define ARC_BUFC_NUMMETADATALISTS 16 326#define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS) 327 328typedef struct arc_state { 329 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 330 uint64_t arcs_size; /* total amount of data in this state */ 331 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */ 332 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE); 333} arc_state_t; 334 335#define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock)) 336 337/* The 6 states: */ 338static arc_state_t ARC_anon; 339static arc_state_t ARC_mru; 340static arc_state_t ARC_mru_ghost; 341static arc_state_t ARC_mfu; 342static arc_state_t ARC_mfu_ghost; 343static arc_state_t ARC_l2c_only; 344 345typedef struct arc_stats { 346 kstat_named_t arcstat_hits; 347 kstat_named_t arcstat_misses; 348 kstat_named_t arcstat_demand_data_hits; 349 kstat_named_t arcstat_demand_data_misses; 350 kstat_named_t arcstat_demand_metadata_hits; 351 kstat_named_t arcstat_demand_metadata_misses; 352 kstat_named_t arcstat_prefetch_data_hits; 353 kstat_named_t arcstat_prefetch_data_misses; 354 kstat_named_t arcstat_prefetch_metadata_hits; 355 kstat_named_t arcstat_prefetch_metadata_misses; 356 kstat_named_t arcstat_mru_hits; 357 kstat_named_t arcstat_mru_ghost_hits; 358 kstat_named_t arcstat_mfu_hits; 359 kstat_named_t arcstat_mfu_ghost_hits; 360 kstat_named_t arcstat_allocated; 361 kstat_named_t arcstat_deleted; 362 kstat_named_t arcstat_stolen; 363 kstat_named_t arcstat_recycle_miss; 364 /* 365 * Number of buffers that could not be evicted because the hash lock 366 * was held by another thread. The lock may not necessarily be held 367 * by something using the same buffer, since hash locks are shared 368 * by multiple buffers. 369 */ 370 kstat_named_t arcstat_mutex_miss; 371 /* 372 * Number of buffers skipped because they have I/O in progress, are 373 * indrect prefetch buffers that have not lived long enough, or are 374 * not from the spa we're trying to evict from. 375 */ 376 kstat_named_t arcstat_evict_skip; 377 kstat_named_t arcstat_evict_l2_cached; 378 kstat_named_t arcstat_evict_l2_eligible; 379 kstat_named_t arcstat_evict_l2_ineligible; 380 kstat_named_t arcstat_hash_elements; 381 kstat_named_t arcstat_hash_elements_max; 382 kstat_named_t arcstat_hash_collisions; 383 kstat_named_t arcstat_hash_chains; 384 kstat_named_t arcstat_hash_chain_max; 385 kstat_named_t arcstat_p; 386 kstat_named_t arcstat_c; 387 kstat_named_t arcstat_c_min; 388 kstat_named_t arcstat_c_max; 389 kstat_named_t arcstat_size; 390 kstat_named_t arcstat_hdr_size; 391 kstat_named_t arcstat_data_size; 392 kstat_named_t arcstat_other_size; 393 kstat_named_t arcstat_l2_hits; 394 kstat_named_t arcstat_l2_misses; 395 kstat_named_t arcstat_l2_feeds; 396 kstat_named_t arcstat_l2_rw_clash; 397 kstat_named_t arcstat_l2_read_bytes; 398 kstat_named_t arcstat_l2_write_bytes; 399 kstat_named_t arcstat_l2_writes_sent; 400 kstat_named_t arcstat_l2_writes_done; 401 kstat_named_t arcstat_l2_writes_error; 402 kstat_named_t arcstat_l2_writes_hdr_miss; 403 kstat_named_t arcstat_l2_evict_lock_retry; 404 kstat_named_t arcstat_l2_evict_reading; 405 kstat_named_t arcstat_l2_free_on_write; 406 kstat_named_t arcstat_l2_cdata_free_on_write; 407 kstat_named_t arcstat_l2_abort_lowmem; 408 kstat_named_t arcstat_l2_cksum_bad; 409 kstat_named_t arcstat_l2_io_error; 410 kstat_named_t arcstat_l2_size; 411 kstat_named_t arcstat_l2_asize; 412 kstat_named_t arcstat_l2_hdr_size; 413 kstat_named_t arcstat_l2_compress_successes; 414 kstat_named_t arcstat_l2_compress_zeros; 415 kstat_named_t arcstat_l2_compress_failures; 416 kstat_named_t arcstat_l2_write_trylock_fail; 417 kstat_named_t arcstat_l2_write_passed_headroom; 418 kstat_named_t arcstat_l2_write_spa_mismatch; 419 kstat_named_t arcstat_l2_write_in_l2; 420 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 421 kstat_named_t arcstat_l2_write_not_cacheable; 422 kstat_named_t arcstat_l2_write_full; 423 kstat_named_t arcstat_l2_write_buffer_iter; 424 kstat_named_t arcstat_l2_write_pios; 425 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 426 kstat_named_t arcstat_l2_write_buffer_list_iter; 427 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 428 kstat_named_t arcstat_memory_throttle_count; 429 kstat_named_t arcstat_duplicate_buffers; 430 kstat_named_t arcstat_duplicate_buffers_size; 431 kstat_named_t arcstat_duplicate_reads; 432 kstat_named_t arcstat_meta_used; 433 kstat_named_t arcstat_meta_limit; 434 kstat_named_t arcstat_meta_max; 435 kstat_named_t arcstat_meta_min; 436} arc_stats_t; 437 438static arc_stats_t arc_stats = { 439 { "hits", KSTAT_DATA_UINT64 }, 440 { "misses", KSTAT_DATA_UINT64 }, 441 { "demand_data_hits", KSTAT_DATA_UINT64 }, 442 { "demand_data_misses", KSTAT_DATA_UINT64 }, 443 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 444 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 445 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 446 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 447 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 448 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 449 { "mru_hits", KSTAT_DATA_UINT64 }, 450 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 451 { "mfu_hits", KSTAT_DATA_UINT64 }, 452 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 453 { "allocated", KSTAT_DATA_UINT64 }, 454 { "deleted", KSTAT_DATA_UINT64 }, 455 { "stolen", KSTAT_DATA_UINT64 }, 456 { "recycle_miss", KSTAT_DATA_UINT64 }, 457 { "mutex_miss", KSTAT_DATA_UINT64 }, 458 { "evict_skip", KSTAT_DATA_UINT64 }, 459 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 460 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 461 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 462 { "hash_elements", KSTAT_DATA_UINT64 }, 463 { "hash_elements_max", KSTAT_DATA_UINT64 }, 464 { "hash_collisions", KSTAT_DATA_UINT64 }, 465 { "hash_chains", KSTAT_DATA_UINT64 }, 466 { "hash_chain_max", KSTAT_DATA_UINT64 }, 467 { "p", KSTAT_DATA_UINT64 }, 468 { "c", KSTAT_DATA_UINT64 }, 469 { "c_min", KSTAT_DATA_UINT64 }, 470 { "c_max", KSTAT_DATA_UINT64 }, 471 { "size", KSTAT_DATA_UINT64 }, 472 { "hdr_size", KSTAT_DATA_UINT64 }, 473 { "data_size", KSTAT_DATA_UINT64 }, 474 { "other_size", KSTAT_DATA_UINT64 }, 475 { "l2_hits", KSTAT_DATA_UINT64 }, 476 { "l2_misses", KSTAT_DATA_UINT64 }, 477 { "l2_feeds", KSTAT_DATA_UINT64 }, 478 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 479 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 480 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 481 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 482 { "l2_writes_done", KSTAT_DATA_UINT64 }, 483 { "l2_writes_error", KSTAT_DATA_UINT64 }, 484 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 485 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 486 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 487 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 488 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 489 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 490 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 491 { "l2_io_error", KSTAT_DATA_UINT64 }, 492 { "l2_size", KSTAT_DATA_UINT64 }, 493 { "l2_asize", KSTAT_DATA_UINT64 }, 494 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 495 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 496 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 497 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 498 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 499 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 500 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 501 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 502 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 503 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 504 { "l2_write_full", KSTAT_DATA_UINT64 }, 505 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 506 { "l2_write_pios", KSTAT_DATA_UINT64 }, 507 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 508 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 509 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 510 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 511 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 512 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 513 { "duplicate_reads", KSTAT_DATA_UINT64 }, 514 { "arc_meta_used", KSTAT_DATA_UINT64 }, 515 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 516 { "arc_meta_max", KSTAT_DATA_UINT64 }, 517 { "arc_meta_min", KSTAT_DATA_UINT64 } 518}; 519 520#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 521 522#define ARCSTAT_INCR(stat, val) \ 523 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 524 525#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 526#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 527 528#define ARCSTAT_MAX(stat, val) { \ 529 uint64_t m; \ 530 while ((val) > (m = arc_stats.stat.value.ui64) && \ 531 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 532 continue; \ 533} 534 535#define ARCSTAT_MAXSTAT(stat) \ 536 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 537 538/* 539 * We define a macro to allow ARC hits/misses to be easily broken down by 540 * two separate conditions, giving a total of four different subtypes for 541 * each of hits and misses (so eight statistics total). 542 */ 543#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 544 if (cond1) { \ 545 if (cond2) { \ 546 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 547 } else { \ 548 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 549 } \ 550 } else { \ 551 if (cond2) { \ 552 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 553 } else { \ 554 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 555 } \ 556 } 557 558kstat_t *arc_ksp; 559static arc_state_t *arc_anon; 560static arc_state_t *arc_mru; 561static arc_state_t *arc_mru_ghost; 562static arc_state_t *arc_mfu; 563static arc_state_t *arc_mfu_ghost; 564static arc_state_t *arc_l2c_only; 565 566/* 567 * There are several ARC variables that are critical to export as kstats -- 568 * but we don't want to have to grovel around in the kstat whenever we wish to 569 * manipulate them. For these variables, we therefore define them to be in 570 * terms of the statistic variable. This assures that we are not introducing 571 * the possibility of inconsistency by having shadow copies of the variables, 572 * while still allowing the code to be readable. 573 */ 574#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 575#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 576#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 577#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 578#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 579#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 580#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 581#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 582#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 583 584#define L2ARC_IS_VALID_COMPRESS(_c_) \ 585 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 586 587static int arc_no_grow; /* Don't try to grow cache size */ 588static uint64_t arc_tempreserve; 589static uint64_t arc_loaned_bytes; 590 591typedef struct l2arc_buf_hdr l2arc_buf_hdr_t; 592 593typedef struct arc_callback arc_callback_t; 594 595struct arc_callback { 596 void *acb_private; 597 arc_done_func_t *acb_done; 598 arc_buf_t *acb_buf; 599 zio_t *acb_zio_dummy; 600 arc_callback_t *acb_next; 601}; 602 603typedef struct arc_write_callback arc_write_callback_t; 604 605struct arc_write_callback { 606 void *awcb_private; 607 arc_done_func_t *awcb_ready; 608 arc_done_func_t *awcb_physdone; 609 arc_done_func_t *awcb_done; 610 arc_buf_t *awcb_buf; 611}; 612 613struct arc_buf_hdr { 614 /* protected by hash lock */ 615 dva_t b_dva; 616 uint64_t b_birth; 617 uint64_t b_cksum0; 618 619 kmutex_t b_freeze_lock; 620 zio_cksum_t *b_freeze_cksum; 621 void *b_thawed; 622 623 arc_buf_hdr_t *b_hash_next; 624 arc_buf_t *b_buf; 625 arc_flags_t b_flags; 626 uint32_t b_datacnt; 627 628 arc_callback_t *b_acb; 629 kcondvar_t b_cv; 630 631 /* immutable */ 632 arc_buf_contents_t b_type; 633 uint64_t b_size; 634 uint64_t b_spa; 635 636 /* protected by arc state mutex */ 637 arc_state_t *b_state; 638 list_node_t b_arc_node; 639 640 /* updated atomically */ 641 clock_t b_arc_access; 642 643 /* self protecting */ 644 refcount_t b_refcnt; 645 646 l2arc_buf_hdr_t *b_l2hdr; 647 list_node_t b_l2node; 648}; 649 650#ifdef _KERNEL 651static int 652sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 653{ 654 uint64_t val; 655 int err; 656 657 val = arc_meta_limit; 658 err = sysctl_handle_64(oidp, &val, 0, req); 659 if (err != 0 || req->newptr == NULL) 660 return (err); 661 662 if (val <= 0 || val > arc_c_max) 663 return (EINVAL); 664 665 arc_meta_limit = val; 666 return (0); 667} 668#endif 669 670static arc_buf_t *arc_eviction_list; 671static kmutex_t arc_eviction_mtx; 672static arc_buf_hdr_t arc_eviction_hdr; 673 674#define GHOST_STATE(state) \ 675 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 676 (state) == arc_l2c_only) 677 678#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 679#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 680#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 681#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 682#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 683#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 684#define HDR_FREE_IN_PROGRESS(hdr) \ 685 ((hdr)->b_flags & ARC_FLAG_FREE_IN_PROGRESS) 686#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 687#define HDR_L2_READING(hdr) \ 688 ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS && \ 689 (hdr)->b_l2hdr != NULL) 690#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 691#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 692#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 693 694/* 695 * Other sizes 696 */ 697 698#define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 699#define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t)) 700 701/* 702 * Hash table routines 703 */ 704 705#define HT_LOCK_PAD CACHE_LINE_SIZE 706 707struct ht_lock { 708 kmutex_t ht_lock; 709#ifdef _KERNEL 710 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 711#endif 712}; 713 714#define BUF_LOCKS 256 715typedef struct buf_hash_table { 716 uint64_t ht_mask; 717 arc_buf_hdr_t **ht_table; 718 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 719} buf_hash_table_t; 720 721static buf_hash_table_t buf_hash_table; 722 723#define BUF_HASH_INDEX(spa, dva, birth) \ 724 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 725#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 726#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 727#define HDR_LOCK(hdr) \ 728 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 729 730uint64_t zfs_crc64_table[256]; 731 732/* 733 * Level 2 ARC 734 */ 735 736#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 737#define L2ARC_HEADROOM 2 /* num of writes */ 738/* 739 * If we discover during ARC scan any buffers to be compressed, we boost 740 * our headroom for the next scanning cycle by this percentage multiple. 741 */ 742#define L2ARC_HEADROOM_BOOST 200 743#define L2ARC_FEED_SECS 1 /* caching interval secs */ 744#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 745 746#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 747#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 748 749/* L2ARC Performance Tunables */ 750uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 751uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 752uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 753uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 754uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 755uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 756boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 757boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 758boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 759 760SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 761 &l2arc_write_max, 0, "max write size"); 762SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 763 &l2arc_write_boost, 0, "extra write during warmup"); 764SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 765 &l2arc_headroom, 0, "number of dev writes"); 766SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 767 &l2arc_feed_secs, 0, "interval seconds"); 768SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 769 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 770 771SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 772 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 773SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 774 &l2arc_feed_again, 0, "turbo warmup"); 775SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 776 &l2arc_norw, 0, "no reads during writes"); 777 778SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 779 &ARC_anon.arcs_size, 0, "size of anonymous state"); 780SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 781 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 782SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 783 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 784 785SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 786 &ARC_mru.arcs_size, 0, "size of mru state"); 787SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 788 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 789SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 790 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 791 792SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 793 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state"); 794SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 795 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 796 "size of metadata in mru ghost state"); 797SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 798 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 799 "size of data in mru ghost state"); 800 801SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 802 &ARC_mfu.arcs_size, 0, "size of mfu state"); 803SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 804 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 805SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 806 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 807 808SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 809 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state"); 810SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 811 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 812 "size of metadata in mfu ghost state"); 813SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 814 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 815 "size of data in mfu ghost state"); 816 817SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 818 &ARC_l2c_only.arcs_size, 0, "size of mru state"); 819 820/* 821 * L2ARC Internals 822 */ 823typedef struct l2arc_dev { 824 vdev_t *l2ad_vdev; /* vdev */ 825 spa_t *l2ad_spa; /* spa */ 826 uint64_t l2ad_hand; /* next write location */ 827 uint64_t l2ad_start; /* first addr on device */ 828 uint64_t l2ad_end; /* last addr on device */ 829 uint64_t l2ad_evict; /* last addr eviction reached */ 830 boolean_t l2ad_first; /* first sweep through */ 831 boolean_t l2ad_writing; /* currently writing */ 832 list_t *l2ad_buflist; /* buffer list */ 833 list_node_t l2ad_node; /* device list node */ 834} l2arc_dev_t; 835 836static list_t L2ARC_dev_list; /* device list */ 837static list_t *l2arc_dev_list; /* device list pointer */ 838static kmutex_t l2arc_dev_mtx; /* device list mutex */ 839static l2arc_dev_t *l2arc_dev_last; /* last device used */ 840static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */ 841static list_t L2ARC_free_on_write; /* free after write buf list */ 842static list_t *l2arc_free_on_write; /* free after write list ptr */ 843static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 844static uint64_t l2arc_ndev; /* number of devices */ 845 846typedef struct l2arc_read_callback { 847 arc_buf_t *l2rcb_buf; /* read buffer */ 848 spa_t *l2rcb_spa; /* spa */ 849 blkptr_t l2rcb_bp; /* original blkptr */ 850 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 851 int l2rcb_flags; /* original flags */ 852 enum zio_compress l2rcb_compress; /* applied compress */ 853} l2arc_read_callback_t; 854 855typedef struct l2arc_write_callback { 856 l2arc_dev_t *l2wcb_dev; /* device info */ 857 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 858} l2arc_write_callback_t; 859 860struct l2arc_buf_hdr { 861 /* protected by arc_buf_hdr mutex */ 862 l2arc_dev_t *b_dev; /* L2ARC device */ 863 uint64_t b_daddr; /* disk address, offset byte */ 864 /* compression applied to buffer data */ 865 enum zio_compress b_compress; 866 /* real alloc'd buffer size depending on b_compress applied */ 867 int b_asize; 868 /* temporary buffer holder for in-flight compressed data */ 869 void *b_tmp_cdata; 870}; 871 872typedef struct l2arc_data_free { 873 /* protected by l2arc_free_on_write_mtx */ 874 void *l2df_data; 875 size_t l2df_size; 876 void (*l2df_func)(void *, size_t); 877 list_node_t l2df_list_node; 878} l2arc_data_free_t; 879 880static kmutex_t l2arc_feed_thr_lock; 881static kcondvar_t l2arc_feed_thr_cv; 882static uint8_t l2arc_thread_exit; 883 884static void arc_get_data_buf(arc_buf_t *); 885static void arc_access(arc_buf_hdr_t *, kmutex_t *); 886static int arc_evict_needed(arc_buf_contents_t); 887static void arc_evict_ghost(arc_state_t *, uint64_t, int64_t); 888static void arc_buf_watch(arc_buf_t *); 889 890static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 891static void l2arc_read_done(zio_t *); 892static void l2arc_hdr_stat_add(void); 893static void l2arc_hdr_stat_remove(void); 894 895static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *); 896static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 897static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 898 899static uint64_t 900buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 901{ 902 uint8_t *vdva = (uint8_t *)dva; 903 uint64_t crc = -1ULL; 904 int i; 905 906 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 907 908 for (i = 0; i < sizeof (dva_t); i++) 909 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 910 911 crc ^= (spa>>8) ^ birth; 912 913 return (crc); 914} 915 916#define BUF_EMPTY(buf) \ 917 ((buf)->b_dva.dva_word[0] == 0 && \ 918 (buf)->b_dva.dva_word[1] == 0 && \ 919 (buf)->b_cksum0 == 0) 920 921#define BUF_EQUAL(spa, dva, birth, buf) \ 922 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 923 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 924 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 925 926static void 927buf_discard_identity(arc_buf_hdr_t *hdr) 928{ 929 hdr->b_dva.dva_word[0] = 0; 930 hdr->b_dva.dva_word[1] = 0; 931 hdr->b_birth = 0; 932 hdr->b_cksum0 = 0; 933} 934 935static arc_buf_hdr_t * 936buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 937{ 938 const dva_t *dva = BP_IDENTITY(bp); 939 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 940 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 941 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 942 arc_buf_hdr_t *hdr; 943 944 mutex_enter(hash_lock); 945 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 946 hdr = hdr->b_hash_next) { 947 if (BUF_EQUAL(spa, dva, birth, hdr)) { 948 *lockp = hash_lock; 949 return (hdr); 950 } 951 } 952 mutex_exit(hash_lock); 953 *lockp = NULL; 954 return (NULL); 955} 956 957/* 958 * Insert an entry into the hash table. If there is already an element 959 * equal to elem in the hash table, then the already existing element 960 * will be returned and the new element will not be inserted. 961 * Otherwise returns NULL. 962 */ 963static arc_buf_hdr_t * 964buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 965{ 966 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 967 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 968 arc_buf_hdr_t *fhdr; 969 uint32_t i; 970 971 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 972 ASSERT(hdr->b_birth != 0); 973 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 974 *lockp = hash_lock; 975 mutex_enter(hash_lock); 976 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 977 fhdr = fhdr->b_hash_next, i++) { 978 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 979 return (fhdr); 980 } 981 982 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 983 buf_hash_table.ht_table[idx] = hdr; 984 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 985 986 /* collect some hash table performance data */ 987 if (i > 0) { 988 ARCSTAT_BUMP(arcstat_hash_collisions); 989 if (i == 1) 990 ARCSTAT_BUMP(arcstat_hash_chains); 991 992 ARCSTAT_MAX(arcstat_hash_chain_max, i); 993 } 994 995 ARCSTAT_BUMP(arcstat_hash_elements); 996 ARCSTAT_MAXSTAT(arcstat_hash_elements); 997 998 return (NULL); 999} 1000 1001static void 1002buf_hash_remove(arc_buf_hdr_t *hdr) 1003{ 1004 arc_buf_hdr_t *fhdr, **hdrp; 1005 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1006 1007 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1008 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1009 1010 hdrp = &buf_hash_table.ht_table[idx]; 1011 while ((fhdr = *hdrp) != hdr) { 1012 ASSERT(fhdr != NULL); 1013 hdrp = &fhdr->b_hash_next; 1014 } 1015 *hdrp = hdr->b_hash_next; 1016 hdr->b_hash_next = NULL; 1017 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1018 1019 /* collect some hash table performance data */ 1020 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1021 1022 if (buf_hash_table.ht_table[idx] && 1023 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1024 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1025} 1026 1027/* 1028 * Global data structures and functions for the buf kmem cache. 1029 */ 1030static kmem_cache_t *hdr_cache; 1031static kmem_cache_t *buf_cache; 1032 1033static void 1034buf_fini(void) 1035{ 1036 int i; 1037 1038 kmem_free(buf_hash_table.ht_table, 1039 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1040 for (i = 0; i < BUF_LOCKS; i++) 1041 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1042 kmem_cache_destroy(hdr_cache); 1043 kmem_cache_destroy(buf_cache); 1044} 1045 1046/* 1047 * Constructor callback - called when the cache is empty 1048 * and a new buf is requested. 1049 */ 1050/* ARGSUSED */ 1051static int 1052hdr_cons(void *vbuf, void *unused, int kmflag) 1053{ 1054 arc_buf_hdr_t *hdr = vbuf; 1055 1056 bzero(hdr, sizeof (arc_buf_hdr_t)); 1057 refcount_create(&hdr->b_refcnt); 1058 cv_init(&hdr->b_cv, NULL, CV_DEFAULT, NULL); 1059 mutex_init(&hdr->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1060 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 1061 1062 return (0); 1063} 1064 1065/* ARGSUSED */ 1066static int 1067buf_cons(void *vbuf, void *unused, int kmflag) 1068{ 1069 arc_buf_t *buf = vbuf; 1070 1071 bzero(buf, sizeof (arc_buf_t)); 1072 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1073 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1074 1075 return (0); 1076} 1077 1078/* 1079 * Destructor callback - called when a cached buf is 1080 * no longer required. 1081 */ 1082/* ARGSUSED */ 1083static void 1084hdr_dest(void *vbuf, void *unused) 1085{ 1086 arc_buf_hdr_t *hdr = vbuf; 1087 1088 ASSERT(BUF_EMPTY(hdr)); 1089 refcount_destroy(&hdr->b_refcnt); 1090 cv_destroy(&hdr->b_cv); 1091 mutex_destroy(&hdr->b_freeze_lock); 1092 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS); 1093} 1094 1095/* ARGSUSED */ 1096static void 1097buf_dest(void *vbuf, void *unused) 1098{ 1099 arc_buf_t *buf = vbuf; 1100 1101 mutex_destroy(&buf->b_evict_lock); 1102 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1103} 1104 1105/* 1106 * Reclaim callback -- invoked when memory is low. 1107 */ 1108/* ARGSUSED */ 1109static void 1110hdr_recl(void *unused) 1111{ 1112 dprintf("hdr_recl called\n"); 1113 /* 1114 * umem calls the reclaim func when we destroy the buf cache, 1115 * which is after we do arc_fini(). 1116 */ 1117 if (!arc_dead) 1118 cv_signal(&arc_reclaim_thr_cv); 1119} 1120 1121static void 1122buf_init(void) 1123{ 1124 uint64_t *ct; 1125 uint64_t hsize = 1ULL << 12; 1126 int i, j; 1127 1128 /* 1129 * The hash table is big enough to fill all of physical memory 1130 * with an average block size of zfs_arc_average_blocksize (default 8K). 1131 * By default, the table will take up 1132 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1133 */ 1134 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1135 hsize <<= 1; 1136retry: 1137 buf_hash_table.ht_mask = hsize - 1; 1138 buf_hash_table.ht_table = 1139 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1140 if (buf_hash_table.ht_table == NULL) { 1141 ASSERT(hsize > (1ULL << 8)); 1142 hsize >>= 1; 1143 goto retry; 1144 } 1145 1146 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t), 1147 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0); 1148 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1149 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1150 1151 for (i = 0; i < 256; i++) 1152 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1153 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1154 1155 for (i = 0; i < BUF_LOCKS; i++) { 1156 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1157 NULL, MUTEX_DEFAULT, NULL); 1158 } 1159} 1160 1161#define ARC_MINTIME (hz>>4) /* 62 ms */ 1162 1163static void 1164arc_cksum_verify(arc_buf_t *buf) 1165{ 1166 zio_cksum_t zc; 1167 1168 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1169 return; 1170 1171 mutex_enter(&buf->b_hdr->b_freeze_lock); 1172 if (buf->b_hdr->b_freeze_cksum == NULL || 1173 (buf->b_hdr->b_flags & ARC_FLAG_IO_ERROR)) { 1174 mutex_exit(&buf->b_hdr->b_freeze_lock); 1175 return; 1176 } 1177 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1178 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1179 panic("buffer modified while frozen!"); 1180 mutex_exit(&buf->b_hdr->b_freeze_lock); 1181} 1182 1183static int 1184arc_cksum_equal(arc_buf_t *buf) 1185{ 1186 zio_cksum_t zc; 1187 int equal; 1188 1189 mutex_enter(&buf->b_hdr->b_freeze_lock); 1190 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1191 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1192 mutex_exit(&buf->b_hdr->b_freeze_lock); 1193 1194 return (equal); 1195} 1196 1197static void 1198arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1199{ 1200 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1201 return; 1202 1203 mutex_enter(&buf->b_hdr->b_freeze_lock); 1204 if (buf->b_hdr->b_freeze_cksum != NULL) { 1205 mutex_exit(&buf->b_hdr->b_freeze_lock); 1206 return; 1207 } 1208 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1209 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1210 buf->b_hdr->b_freeze_cksum); 1211 mutex_exit(&buf->b_hdr->b_freeze_lock); 1212#ifdef illumos 1213 arc_buf_watch(buf); 1214#endif /* illumos */ 1215} 1216 1217#ifdef illumos 1218#ifndef _KERNEL 1219typedef struct procctl { 1220 long cmd; 1221 prwatch_t prwatch; 1222} procctl_t; 1223#endif 1224 1225/* ARGSUSED */ 1226static void 1227arc_buf_unwatch(arc_buf_t *buf) 1228{ 1229#ifndef _KERNEL 1230 if (arc_watch) { 1231 int result; 1232 procctl_t ctl; 1233 ctl.cmd = PCWATCH; 1234 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1235 ctl.prwatch.pr_size = 0; 1236 ctl.prwatch.pr_wflags = 0; 1237 result = write(arc_procfd, &ctl, sizeof (ctl)); 1238 ASSERT3U(result, ==, sizeof (ctl)); 1239 } 1240#endif 1241} 1242 1243/* ARGSUSED */ 1244static void 1245arc_buf_watch(arc_buf_t *buf) 1246{ 1247#ifndef _KERNEL 1248 if (arc_watch) { 1249 int result; 1250 procctl_t ctl; 1251 ctl.cmd = PCWATCH; 1252 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1253 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1254 ctl.prwatch.pr_wflags = WA_WRITE; 1255 result = write(arc_procfd, &ctl, sizeof (ctl)); 1256 ASSERT3U(result, ==, sizeof (ctl)); 1257 } 1258#endif 1259} 1260#endif /* illumos */ 1261 1262void 1263arc_buf_thaw(arc_buf_t *buf) 1264{ 1265 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1266 if (buf->b_hdr->b_state != arc_anon) 1267 panic("modifying non-anon buffer!"); 1268 if (buf->b_hdr->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1269 panic("modifying buffer while i/o in progress!"); 1270 arc_cksum_verify(buf); 1271 } 1272 1273 mutex_enter(&buf->b_hdr->b_freeze_lock); 1274 if (buf->b_hdr->b_freeze_cksum != NULL) { 1275 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1276 buf->b_hdr->b_freeze_cksum = NULL; 1277 } 1278 1279 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1280 if (buf->b_hdr->b_thawed) 1281 kmem_free(buf->b_hdr->b_thawed, 1); 1282 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP); 1283 } 1284 1285 mutex_exit(&buf->b_hdr->b_freeze_lock); 1286 1287#ifdef illumos 1288 arc_buf_unwatch(buf); 1289#endif /* illumos */ 1290} 1291 1292void 1293arc_buf_freeze(arc_buf_t *buf) 1294{ 1295 kmutex_t *hash_lock; 1296 1297 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1298 return; 1299 1300 hash_lock = HDR_LOCK(buf->b_hdr); 1301 mutex_enter(hash_lock); 1302 1303 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1304 buf->b_hdr->b_state == arc_anon); 1305 arc_cksum_compute(buf, B_FALSE); 1306 mutex_exit(hash_lock); 1307 1308} 1309 1310static void 1311get_buf_info(arc_buf_hdr_t *hdr, arc_state_t *state, list_t **list, kmutex_t **lock) 1312{ 1313 uint64_t buf_hashid = buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1314 1315 if (hdr->b_type == ARC_BUFC_METADATA) 1316 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1); 1317 else { 1318 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1); 1319 buf_hashid += ARC_BUFC_NUMMETADATALISTS; 1320 } 1321 1322 *list = &state->arcs_lists[buf_hashid]; 1323 *lock = ARCS_LOCK(state, buf_hashid); 1324} 1325 1326 1327static void 1328add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1329{ 1330 ASSERT(MUTEX_HELD(hash_lock)); 1331 1332 if ((refcount_add(&hdr->b_refcnt, tag) == 1) && 1333 (hdr->b_state != arc_anon)) { 1334 uint64_t delta = hdr->b_size * hdr->b_datacnt; 1335 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 1336 list_t *list; 1337 kmutex_t *lock; 1338 1339 get_buf_info(hdr, hdr->b_state, &list, &lock); 1340 ASSERT(!MUTEX_HELD(lock)); 1341 mutex_enter(lock); 1342 ASSERT(list_link_active(&hdr->b_arc_node)); 1343 list_remove(list, hdr); 1344 if (GHOST_STATE(hdr->b_state)) { 1345 ASSERT0(hdr->b_datacnt); 1346 ASSERT3P(hdr->b_buf, ==, NULL); 1347 delta = hdr->b_size; 1348 } 1349 ASSERT(delta > 0); 1350 ASSERT3U(*size, >=, delta); 1351 atomic_add_64(size, -delta); 1352 mutex_exit(lock); 1353 /* remove the prefetch flag if we get a reference */ 1354 if (hdr->b_flags & ARC_FLAG_PREFETCH) 1355 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1356 } 1357} 1358 1359static int 1360remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1361{ 1362 int cnt; 1363 arc_state_t *state = hdr->b_state; 1364 1365 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1366 ASSERT(!GHOST_STATE(state)); 1367 1368 if (((cnt = refcount_remove(&hdr->b_refcnt, tag)) == 0) && 1369 (state != arc_anon)) { 1370 uint64_t *size = &state->arcs_lsize[hdr->b_type]; 1371 list_t *list; 1372 kmutex_t *lock; 1373 1374 get_buf_info(hdr, state, &list, &lock); 1375 ASSERT(!MUTEX_HELD(lock)); 1376 mutex_enter(lock); 1377 ASSERT(!list_link_active(&hdr->b_arc_node)); 1378 list_insert_head(list, hdr); 1379 ASSERT(hdr->b_datacnt > 0); 1380 atomic_add_64(size, hdr->b_size * hdr->b_datacnt); 1381 mutex_exit(lock); 1382 } 1383 return (cnt); 1384} 1385 1386/* 1387 * Move the supplied buffer to the indicated state. The mutex 1388 * for the buffer must be held by the caller. 1389 */ 1390static void 1391arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1392 kmutex_t *hash_lock) 1393{ 1394 arc_state_t *old_state = hdr->b_state; 1395 int64_t refcnt = refcount_count(&hdr->b_refcnt); 1396 uint64_t from_delta, to_delta; 1397 list_t *list; 1398 kmutex_t *lock; 1399 1400 ASSERT(MUTEX_HELD(hash_lock)); 1401 ASSERT3P(new_state, !=, old_state); 1402 ASSERT(refcnt == 0 || hdr->b_datacnt > 0); 1403 ASSERT(hdr->b_datacnt == 0 || !GHOST_STATE(new_state)); 1404 ASSERT(hdr->b_datacnt <= 1 || old_state != arc_anon); 1405 1406 from_delta = to_delta = hdr->b_datacnt * hdr->b_size; 1407 1408 /* 1409 * If this buffer is evictable, transfer it from the 1410 * old state list to the new state list. 1411 */ 1412 if (refcnt == 0) { 1413 if (old_state != arc_anon) { 1414 int use_mutex; 1415 uint64_t *size = &old_state->arcs_lsize[hdr->b_type]; 1416 1417 get_buf_info(hdr, old_state, &list, &lock); 1418 use_mutex = !MUTEX_HELD(lock); 1419 if (use_mutex) 1420 mutex_enter(lock); 1421 1422 ASSERT(list_link_active(&hdr->b_arc_node)); 1423 list_remove(list, hdr); 1424 1425 /* 1426 * If prefetching out of the ghost cache, 1427 * we will have a non-zero datacnt. 1428 */ 1429 if (GHOST_STATE(old_state) && hdr->b_datacnt == 0) { 1430 /* ghost elements have a ghost size */ 1431 ASSERT(hdr->b_buf == NULL); 1432 from_delta = hdr->b_size; 1433 } 1434 ASSERT3U(*size, >=, from_delta); 1435 atomic_add_64(size, -from_delta); 1436 1437 if (use_mutex) 1438 mutex_exit(lock); 1439 } 1440 if (new_state != arc_anon) { 1441 int use_mutex; 1442 uint64_t *size = &new_state->arcs_lsize[hdr->b_type]; 1443 1444 get_buf_info(hdr, new_state, &list, &lock); 1445 use_mutex = !MUTEX_HELD(lock); 1446 if (use_mutex) 1447 mutex_enter(lock); 1448 1449 list_insert_head(list, hdr); 1450 1451 /* ghost elements have a ghost size */ 1452 if (GHOST_STATE(new_state)) { 1453 ASSERT(hdr->b_datacnt == 0); 1454 ASSERT(hdr->b_buf == NULL); 1455 to_delta = hdr->b_size; 1456 } 1457 atomic_add_64(size, to_delta); 1458 1459 if (use_mutex) 1460 mutex_exit(lock); 1461 } 1462 } 1463 1464 ASSERT(!BUF_EMPTY(hdr)); 1465 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1466 buf_hash_remove(hdr); 1467 1468 /* adjust state sizes */ 1469 if (to_delta) 1470 atomic_add_64(&new_state->arcs_size, to_delta); 1471 if (from_delta) { 1472 ASSERT3U(old_state->arcs_size, >=, from_delta); 1473 atomic_add_64(&old_state->arcs_size, -from_delta); 1474 } 1475 hdr->b_state = new_state; 1476 1477 /* adjust l2arc hdr stats */ 1478 if (new_state == arc_l2c_only) 1479 l2arc_hdr_stat_add(); 1480 else if (old_state == arc_l2c_only) 1481 l2arc_hdr_stat_remove(); 1482} 1483 1484void 1485arc_space_consume(uint64_t space, arc_space_type_t type) 1486{ 1487 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1488 1489 switch (type) { 1490 case ARC_SPACE_DATA: 1491 ARCSTAT_INCR(arcstat_data_size, space); 1492 break; 1493 case ARC_SPACE_OTHER: 1494 ARCSTAT_INCR(arcstat_other_size, space); 1495 break; 1496 case ARC_SPACE_HDRS: 1497 ARCSTAT_INCR(arcstat_hdr_size, space); 1498 break; 1499 case ARC_SPACE_L2HDRS: 1500 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1501 break; 1502 } 1503 1504 ARCSTAT_INCR(arcstat_meta_used, space); 1505 atomic_add_64(&arc_size, space); 1506} 1507 1508void 1509arc_space_return(uint64_t space, arc_space_type_t type) 1510{ 1511 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1512 1513 switch (type) { 1514 case ARC_SPACE_DATA: 1515 ARCSTAT_INCR(arcstat_data_size, -space); 1516 break; 1517 case ARC_SPACE_OTHER: 1518 ARCSTAT_INCR(arcstat_other_size, -space); 1519 break; 1520 case ARC_SPACE_HDRS: 1521 ARCSTAT_INCR(arcstat_hdr_size, -space); 1522 break; 1523 case ARC_SPACE_L2HDRS: 1524 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1525 break; 1526 } 1527 1528 ASSERT(arc_meta_used >= space); 1529 if (arc_meta_max < arc_meta_used) 1530 arc_meta_max = arc_meta_used; 1531 ARCSTAT_INCR(arcstat_meta_used, -space); 1532 ASSERT(arc_size >= space); 1533 atomic_add_64(&arc_size, -space); 1534} 1535 1536arc_buf_t * 1537arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type) 1538{ 1539 arc_buf_hdr_t *hdr; 1540 arc_buf_t *buf; 1541 1542 ASSERT3U(size, >, 0); 1543 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 1544 ASSERT(BUF_EMPTY(hdr)); 1545 hdr->b_size = size; 1546 hdr->b_type = type; 1547 hdr->b_spa = spa_load_guid(spa); 1548 hdr->b_state = arc_anon; 1549 hdr->b_arc_access = 0; 1550 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1551 buf->b_hdr = hdr; 1552 buf->b_data = NULL; 1553 buf->b_efunc = NULL; 1554 buf->b_private = NULL; 1555 buf->b_next = NULL; 1556 hdr->b_buf = buf; 1557 arc_get_data_buf(buf); 1558 hdr->b_datacnt = 1; 1559 hdr->b_flags = 0; 1560 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1561 (void) refcount_add(&hdr->b_refcnt, tag); 1562 1563 return (buf); 1564} 1565 1566static char *arc_onloan_tag = "onloan"; 1567 1568/* 1569 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1570 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1571 * buffers must be returned to the arc before they can be used by the DMU or 1572 * freed. 1573 */ 1574arc_buf_t * 1575arc_loan_buf(spa_t *spa, int size) 1576{ 1577 arc_buf_t *buf; 1578 1579 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1580 1581 atomic_add_64(&arc_loaned_bytes, size); 1582 return (buf); 1583} 1584 1585/* 1586 * Return a loaned arc buffer to the arc. 1587 */ 1588void 1589arc_return_buf(arc_buf_t *buf, void *tag) 1590{ 1591 arc_buf_hdr_t *hdr = buf->b_hdr; 1592 1593 ASSERT(buf->b_data != NULL); 1594 (void) refcount_add(&hdr->b_refcnt, tag); 1595 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag); 1596 1597 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1598} 1599 1600/* Detach an arc_buf from a dbuf (tag) */ 1601void 1602arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1603{ 1604 arc_buf_hdr_t *hdr; 1605 1606 ASSERT(buf->b_data != NULL); 1607 hdr = buf->b_hdr; 1608 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag); 1609 (void) refcount_remove(&hdr->b_refcnt, tag); 1610 buf->b_efunc = NULL; 1611 buf->b_private = NULL; 1612 1613 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1614} 1615 1616static arc_buf_t * 1617arc_buf_clone(arc_buf_t *from) 1618{ 1619 arc_buf_t *buf; 1620 arc_buf_hdr_t *hdr = from->b_hdr; 1621 uint64_t size = hdr->b_size; 1622 1623 ASSERT(hdr->b_state != arc_anon); 1624 1625 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1626 buf->b_hdr = hdr; 1627 buf->b_data = NULL; 1628 buf->b_efunc = NULL; 1629 buf->b_private = NULL; 1630 buf->b_next = hdr->b_buf; 1631 hdr->b_buf = buf; 1632 arc_get_data_buf(buf); 1633 bcopy(from->b_data, buf->b_data, size); 1634 1635 /* 1636 * This buffer already exists in the arc so create a duplicate 1637 * copy for the caller. If the buffer is associated with user data 1638 * then track the size and number of duplicates. These stats will be 1639 * updated as duplicate buffers are created and destroyed. 1640 */ 1641 if (hdr->b_type == ARC_BUFC_DATA) { 1642 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1643 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1644 } 1645 hdr->b_datacnt += 1; 1646 return (buf); 1647} 1648 1649void 1650arc_buf_add_ref(arc_buf_t *buf, void* tag) 1651{ 1652 arc_buf_hdr_t *hdr; 1653 kmutex_t *hash_lock; 1654 1655 /* 1656 * Check to see if this buffer is evicted. Callers 1657 * must verify b_data != NULL to know if the add_ref 1658 * was successful. 1659 */ 1660 mutex_enter(&buf->b_evict_lock); 1661 if (buf->b_data == NULL) { 1662 mutex_exit(&buf->b_evict_lock); 1663 return; 1664 } 1665 hash_lock = HDR_LOCK(buf->b_hdr); 1666 mutex_enter(hash_lock); 1667 hdr = buf->b_hdr; 1668 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1669 mutex_exit(&buf->b_evict_lock); 1670 1671 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 1672 add_reference(hdr, hash_lock, tag); 1673 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1674 arc_access(hdr, hash_lock); 1675 mutex_exit(hash_lock); 1676 ARCSTAT_BUMP(arcstat_hits); 1677 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH), 1678 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 1679 data, metadata, hits); 1680} 1681 1682static void 1683arc_buf_free_on_write(void *data, size_t size, 1684 void (*free_func)(void *, size_t)) 1685{ 1686 l2arc_data_free_t *df; 1687 1688 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1689 df->l2df_data = data; 1690 df->l2df_size = size; 1691 df->l2df_func = free_func; 1692 mutex_enter(&l2arc_free_on_write_mtx); 1693 list_insert_head(l2arc_free_on_write, df); 1694 mutex_exit(&l2arc_free_on_write_mtx); 1695} 1696 1697/* 1698 * Free the arc data buffer. If it is an l2arc write in progress, 1699 * the buffer is placed on l2arc_free_on_write to be freed later. 1700 */ 1701static void 1702arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1703{ 1704 arc_buf_hdr_t *hdr = buf->b_hdr; 1705 1706 if (HDR_L2_WRITING(hdr)) { 1707 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 1708 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1709 } else { 1710 free_func(buf->b_data, hdr->b_size); 1711 } 1712} 1713 1714/* 1715 * Free up buf->b_data and if 'remove' is set, then pull the 1716 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 1717 */ 1718static void 1719arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 1720{ 1721 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1722 1723 ASSERT(MUTEX_HELD(&l2arc_buflist_mtx)); 1724 1725 if (l2hdr->b_tmp_cdata == NULL) 1726 return; 1727 1728 ASSERT(HDR_L2_WRITING(hdr)); 1729 arc_buf_free_on_write(l2hdr->b_tmp_cdata, hdr->b_size, 1730 zio_data_buf_free); 1731 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 1732 l2hdr->b_tmp_cdata = NULL; 1733} 1734 1735static void 1736arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) 1737{ 1738 arc_buf_t **bufp; 1739 1740 /* free up data associated with the buf */ 1741 if (buf->b_data) { 1742 arc_state_t *state = buf->b_hdr->b_state; 1743 uint64_t size = buf->b_hdr->b_size; 1744 arc_buf_contents_t type = buf->b_hdr->b_type; 1745 1746 arc_cksum_verify(buf); 1747#ifdef illumos 1748 arc_buf_unwatch(buf); 1749#endif /* illumos */ 1750 1751 if (!recycle) { 1752 if (type == ARC_BUFC_METADATA) { 1753 arc_buf_data_free(buf, zio_buf_free); 1754 arc_space_return(size, ARC_SPACE_DATA); 1755 } else { 1756 ASSERT(type == ARC_BUFC_DATA); 1757 arc_buf_data_free(buf, zio_data_buf_free); 1758 ARCSTAT_INCR(arcstat_data_size, -size); 1759 atomic_add_64(&arc_size, -size); 1760 } 1761 } 1762 if (list_link_active(&buf->b_hdr->b_arc_node)) { 1763 uint64_t *cnt = &state->arcs_lsize[type]; 1764 1765 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt)); 1766 ASSERT(state != arc_anon); 1767 1768 ASSERT3U(*cnt, >=, size); 1769 atomic_add_64(cnt, -size); 1770 } 1771 ASSERT3U(state->arcs_size, >=, size); 1772 atomic_add_64(&state->arcs_size, -size); 1773 buf->b_data = NULL; 1774 1775 /* 1776 * If we're destroying a duplicate buffer make sure 1777 * that the appropriate statistics are updated. 1778 */ 1779 if (buf->b_hdr->b_datacnt > 1 && 1780 buf->b_hdr->b_type == ARC_BUFC_DATA) { 1781 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1782 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1783 } 1784 ASSERT(buf->b_hdr->b_datacnt > 0); 1785 buf->b_hdr->b_datacnt -= 1; 1786 } 1787 1788 /* only remove the buf if requested */ 1789 if (!remove) 1790 return; 1791 1792 /* remove the buf from the hdr list */ 1793 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next) 1794 continue; 1795 *bufp = buf->b_next; 1796 buf->b_next = NULL; 1797 1798 ASSERT(buf->b_efunc == NULL); 1799 1800 /* clean up the buf */ 1801 buf->b_hdr = NULL; 1802 kmem_cache_free(buf_cache, buf); 1803} 1804 1805static void 1806arc_hdr_destroy(arc_buf_hdr_t *hdr) 1807{ 1808 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1809 ASSERT3P(hdr->b_state, ==, arc_anon); 1810 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1811 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 1812 1813 if (l2hdr != NULL) { 1814 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx); 1815 /* 1816 * To prevent arc_free() and l2arc_evict() from 1817 * attempting to free the same buffer at the same time, 1818 * a FREE_IN_PROGRESS flag is given to arc_free() to 1819 * give it priority. l2arc_evict() can't destroy this 1820 * header while we are waiting on l2arc_buflist_mtx. 1821 * 1822 * The hdr may be removed from l2ad_buflist before we 1823 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked. 1824 */ 1825 if (!buflist_held) { 1826 mutex_enter(&l2arc_buflist_mtx); 1827 l2hdr = hdr->b_l2hdr; 1828 } 1829 1830 if (l2hdr != NULL) { 1831 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr, 1832 l2hdr->b_asize, 0); 1833 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 1834 arc_buf_l2_cdata_free(hdr); 1835 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1836 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 1837 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 1838 -l2hdr->b_asize, 0, 0); 1839 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 1840 if (hdr->b_state == arc_l2c_only) 1841 l2arc_hdr_stat_remove(); 1842 hdr->b_l2hdr = NULL; 1843 } 1844 1845 if (!buflist_held) 1846 mutex_exit(&l2arc_buflist_mtx); 1847 } 1848 1849 if (!BUF_EMPTY(hdr)) { 1850 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1851 buf_discard_identity(hdr); 1852 } 1853 while (hdr->b_buf) { 1854 arc_buf_t *buf = hdr->b_buf; 1855 1856 if (buf->b_efunc) { 1857 mutex_enter(&arc_eviction_mtx); 1858 mutex_enter(&buf->b_evict_lock); 1859 ASSERT(buf->b_hdr != NULL); 1860 arc_buf_destroy(hdr->b_buf, FALSE, FALSE); 1861 hdr->b_buf = buf->b_next; 1862 buf->b_hdr = &arc_eviction_hdr; 1863 buf->b_next = arc_eviction_list; 1864 arc_eviction_list = buf; 1865 mutex_exit(&buf->b_evict_lock); 1866 mutex_exit(&arc_eviction_mtx); 1867 } else { 1868 arc_buf_destroy(hdr->b_buf, FALSE, TRUE); 1869 } 1870 } 1871 if (hdr->b_freeze_cksum != NULL) { 1872 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1873 hdr->b_freeze_cksum = NULL; 1874 } 1875 if (hdr->b_thawed) { 1876 kmem_free(hdr->b_thawed, 1); 1877 hdr->b_thawed = NULL; 1878 } 1879 1880 ASSERT(!list_link_active(&hdr->b_arc_node)); 1881 ASSERT3P(hdr->b_hash_next, ==, NULL); 1882 ASSERT3P(hdr->b_acb, ==, NULL); 1883 kmem_cache_free(hdr_cache, hdr); 1884} 1885 1886void 1887arc_buf_free(arc_buf_t *buf, void *tag) 1888{ 1889 arc_buf_hdr_t *hdr = buf->b_hdr; 1890 int hashed = hdr->b_state != arc_anon; 1891 1892 ASSERT(buf->b_efunc == NULL); 1893 ASSERT(buf->b_data != NULL); 1894 1895 if (hashed) { 1896 kmutex_t *hash_lock = HDR_LOCK(hdr); 1897 1898 mutex_enter(hash_lock); 1899 hdr = buf->b_hdr; 1900 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1901 1902 (void) remove_reference(hdr, hash_lock, tag); 1903 if (hdr->b_datacnt > 1) { 1904 arc_buf_destroy(buf, FALSE, TRUE); 1905 } else { 1906 ASSERT(buf == hdr->b_buf); 1907 ASSERT(buf->b_efunc == NULL); 1908 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 1909 } 1910 mutex_exit(hash_lock); 1911 } else if (HDR_IO_IN_PROGRESS(hdr)) { 1912 int destroy_hdr; 1913 /* 1914 * We are in the middle of an async write. Don't destroy 1915 * this buffer unless the write completes before we finish 1916 * decrementing the reference count. 1917 */ 1918 mutex_enter(&arc_eviction_mtx); 1919 (void) remove_reference(hdr, NULL, tag); 1920 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 1921 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 1922 mutex_exit(&arc_eviction_mtx); 1923 if (destroy_hdr) 1924 arc_hdr_destroy(hdr); 1925 } else { 1926 if (remove_reference(hdr, NULL, tag) > 0) 1927 arc_buf_destroy(buf, FALSE, TRUE); 1928 else 1929 arc_hdr_destroy(hdr); 1930 } 1931} 1932 1933boolean_t 1934arc_buf_remove_ref(arc_buf_t *buf, void* tag) 1935{ 1936 arc_buf_hdr_t *hdr = buf->b_hdr; 1937 kmutex_t *hash_lock = HDR_LOCK(hdr); 1938 boolean_t no_callback = (buf->b_efunc == NULL); 1939 1940 if (hdr->b_state == arc_anon) { 1941 ASSERT(hdr->b_datacnt == 1); 1942 arc_buf_free(buf, tag); 1943 return (no_callback); 1944 } 1945 1946 mutex_enter(hash_lock); 1947 hdr = buf->b_hdr; 1948 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1949 ASSERT(hdr->b_state != arc_anon); 1950 ASSERT(buf->b_data != NULL); 1951 1952 (void) remove_reference(hdr, hash_lock, tag); 1953 if (hdr->b_datacnt > 1) { 1954 if (no_callback) 1955 arc_buf_destroy(buf, FALSE, TRUE); 1956 } else if (no_callback) { 1957 ASSERT(hdr->b_buf == buf && buf->b_next == NULL); 1958 ASSERT(buf->b_efunc == NULL); 1959 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 1960 } 1961 ASSERT(no_callback || hdr->b_datacnt > 1 || 1962 refcount_is_zero(&hdr->b_refcnt)); 1963 mutex_exit(hash_lock); 1964 return (no_callback); 1965} 1966 1967int 1968arc_buf_size(arc_buf_t *buf) 1969{ 1970 return (buf->b_hdr->b_size); 1971} 1972 1973/* 1974 * Called from the DMU to determine if the current buffer should be 1975 * evicted. In order to ensure proper locking, the eviction must be initiated 1976 * from the DMU. Return true if the buffer is associated with user data and 1977 * duplicate buffers still exist. 1978 */ 1979boolean_t 1980arc_buf_eviction_needed(arc_buf_t *buf) 1981{ 1982 arc_buf_hdr_t *hdr; 1983 boolean_t evict_needed = B_FALSE; 1984 1985 if (zfs_disable_dup_eviction) 1986 return (B_FALSE); 1987 1988 mutex_enter(&buf->b_evict_lock); 1989 hdr = buf->b_hdr; 1990 if (hdr == NULL) { 1991 /* 1992 * We are in arc_do_user_evicts(); let that function 1993 * perform the eviction. 1994 */ 1995 ASSERT(buf->b_data == NULL); 1996 mutex_exit(&buf->b_evict_lock); 1997 return (B_FALSE); 1998 } else if (buf->b_data == NULL) { 1999 /* 2000 * We have already been added to the arc eviction list; 2001 * recommend eviction. 2002 */ 2003 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2004 mutex_exit(&buf->b_evict_lock); 2005 return (B_TRUE); 2006 } 2007 2008 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA) 2009 evict_needed = B_TRUE; 2010 2011 mutex_exit(&buf->b_evict_lock); 2012 return (evict_needed); 2013} 2014 2015/* 2016 * Evict buffers from list until we've removed the specified number of 2017 * bytes. Move the removed buffers to the appropriate evict state. 2018 * If the recycle flag is set, then attempt to "recycle" a buffer: 2019 * - look for a buffer to evict that is `bytes' long. 2020 * - return the data block from this buffer rather than freeing it. 2021 * This flag is used by callers that are trying to make space for a 2022 * new buffer in a full arc cache. 2023 * 2024 * This function makes a "best effort". It skips over any buffers 2025 * it can't get a hash_lock on, and so may not catch all candidates. 2026 * It may also return without evicting as much space as requested. 2027 */ 2028static void * 2029arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 2030 arc_buf_contents_t type) 2031{ 2032 arc_state_t *evicted_state; 2033 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 2034 int64_t bytes_remaining; 2035 arc_buf_hdr_t *hdr, *hdr_prev = NULL; 2036 list_t *evicted_list, *list, *evicted_list_start, *list_start; 2037 kmutex_t *lock, *evicted_lock; 2038 kmutex_t *hash_lock; 2039 boolean_t have_lock; 2040 void *stolen = NULL; 2041 arc_buf_hdr_t marker = { 0 }; 2042 int count = 0; 2043 static int evict_metadata_offset, evict_data_offset; 2044 int i, idx, offset, list_count, lists; 2045 2046 ASSERT(state == arc_mru || state == arc_mfu); 2047 2048 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2049 2050 /* 2051 * Decide which "type" (data vs metadata) to recycle from. 2052 * 2053 * If we are over the metadata limit, recycle from metadata. 2054 * If we are under the metadata minimum, recycle from data. 2055 * Otherwise, recycle from whichever type has the oldest (least 2056 * recently accessed) header. This is not yet implemented. 2057 */ 2058 if (recycle) { 2059 arc_buf_contents_t realtype; 2060 if (state->arcs_lsize[ARC_BUFC_DATA] == 0) { 2061 realtype = ARC_BUFC_METADATA; 2062 } else if (state->arcs_lsize[ARC_BUFC_METADATA] == 0) { 2063 realtype = ARC_BUFC_DATA; 2064 } else if (arc_meta_used >= arc_meta_limit) { 2065 realtype = ARC_BUFC_METADATA; 2066 } else if (arc_meta_used <= arc_meta_min) { 2067 realtype = ARC_BUFC_DATA; 2068 } else { 2069#ifdef illumos 2070 if (data_hdr->b_arc_access < 2071 metadata_hdr->b_arc_access) { 2072 realtype = ARC_BUFC_DATA; 2073 } else { 2074 realtype = ARC_BUFC_METADATA; 2075 } 2076#else 2077 /* TODO */ 2078 realtype = type; 2079#endif 2080 } 2081 if (realtype != type) { 2082 /* 2083 * If we want to evict from a different list, 2084 * we can not recycle, because DATA vs METADATA 2085 * buffers are segregated into different kmem 2086 * caches (and vmem arenas). 2087 */ 2088 type = realtype; 2089 recycle = B_FALSE; 2090 } 2091 } 2092 2093 if (type == ARC_BUFC_METADATA) { 2094 offset = 0; 2095 list_count = ARC_BUFC_NUMMETADATALISTS; 2096 list_start = &state->arcs_lists[0]; 2097 evicted_list_start = &evicted_state->arcs_lists[0]; 2098 idx = evict_metadata_offset; 2099 } else { 2100 offset = ARC_BUFC_NUMMETADATALISTS; 2101 list_start = &state->arcs_lists[offset]; 2102 evicted_list_start = &evicted_state->arcs_lists[offset]; 2103 list_count = ARC_BUFC_NUMDATALISTS; 2104 idx = evict_data_offset; 2105 } 2106 bytes_remaining = evicted_state->arcs_lsize[type]; 2107 lists = 0; 2108 2109evict_start: 2110 list = &list_start[idx]; 2111 evicted_list = &evicted_list_start[idx]; 2112 lock = ARCS_LOCK(state, (offset + idx)); 2113 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx)); 2114 2115 mutex_enter(lock); 2116 mutex_enter(evicted_lock); 2117 2118 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2119 hdr_prev = list_prev(list, hdr); 2120 bytes_remaining -= (hdr->b_size * hdr->b_datacnt); 2121 /* prefetch buffers have a minimum lifespan */ 2122 if (HDR_IO_IN_PROGRESS(hdr) || 2123 (spa && hdr->b_spa != spa) || 2124 (hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT) && 2125 ddi_get_lbolt() - hdr->b_arc_access < 2126 arc_min_prefetch_lifespan)) { 2127 skipped++; 2128 continue; 2129 } 2130 /* "lookahead" for better eviction candidate */ 2131 if (recycle && hdr->b_size != bytes && 2132 hdr_prev && hdr_prev->b_size == bytes) 2133 continue; 2134 2135 /* ignore markers */ 2136 if (hdr->b_spa == 0) 2137 continue; 2138 2139 /* 2140 * It may take a long time to evict all the bufs requested. 2141 * To avoid blocking all arc activity, periodically drop 2142 * the arcs_mtx and give other threads a chance to run 2143 * before reacquiring the lock. 2144 * 2145 * If we are looking for a buffer to recycle, we are in 2146 * the hot code path, so don't sleep. 2147 */ 2148 if (!recycle && count++ > arc_evict_iterations) { 2149 list_insert_after(list, hdr, &marker); 2150 mutex_exit(evicted_lock); 2151 mutex_exit(lock); 2152 kpreempt(KPREEMPT_SYNC); 2153 mutex_enter(lock); 2154 mutex_enter(evicted_lock); 2155 hdr_prev = list_prev(list, &marker); 2156 list_remove(list, &marker); 2157 count = 0; 2158 continue; 2159 } 2160 2161 hash_lock = HDR_LOCK(hdr); 2162 have_lock = MUTEX_HELD(hash_lock); 2163 if (have_lock || mutex_tryenter(hash_lock)) { 2164 ASSERT0(refcount_count(&hdr->b_refcnt)); 2165 ASSERT(hdr->b_datacnt > 0); 2166 while (hdr->b_buf) { 2167 arc_buf_t *buf = hdr->b_buf; 2168 if (!mutex_tryenter(&buf->b_evict_lock)) { 2169 missed += 1; 2170 break; 2171 } 2172 if (buf->b_data) { 2173 bytes_evicted += hdr->b_size; 2174 if (recycle && hdr->b_type == type && 2175 hdr->b_size == bytes && 2176 !HDR_L2_WRITING(hdr)) { 2177 stolen = buf->b_data; 2178 recycle = FALSE; 2179 } 2180 } 2181 if (buf->b_efunc) { 2182 mutex_enter(&arc_eviction_mtx); 2183 arc_buf_destroy(buf, 2184 buf->b_data == stolen, FALSE); 2185 hdr->b_buf = buf->b_next; 2186 buf->b_hdr = &arc_eviction_hdr; 2187 buf->b_next = arc_eviction_list; 2188 arc_eviction_list = buf; 2189 mutex_exit(&arc_eviction_mtx); 2190 mutex_exit(&buf->b_evict_lock); 2191 } else { 2192 mutex_exit(&buf->b_evict_lock); 2193 arc_buf_destroy(buf, 2194 buf->b_data == stolen, TRUE); 2195 } 2196 } 2197 2198 if (hdr->b_l2hdr) { 2199 ARCSTAT_INCR(arcstat_evict_l2_cached, 2200 hdr->b_size); 2201 } else { 2202 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 2203 ARCSTAT_INCR(arcstat_evict_l2_eligible, 2204 hdr->b_size); 2205 } else { 2206 ARCSTAT_INCR( 2207 arcstat_evict_l2_ineligible, 2208 hdr->b_size); 2209 } 2210 } 2211 2212 if (hdr->b_datacnt == 0) { 2213 arc_change_state(evicted_state, hdr, hash_lock); 2214 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2215 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2216 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2217 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2218 } 2219 if (!have_lock) 2220 mutex_exit(hash_lock); 2221 if (bytes >= 0 && bytes_evicted >= bytes) 2222 break; 2223 if (bytes_remaining > 0) { 2224 mutex_exit(evicted_lock); 2225 mutex_exit(lock); 2226 idx = ((idx + 1) & (list_count - 1)); 2227 lists++; 2228 goto evict_start; 2229 } 2230 } else { 2231 missed += 1; 2232 } 2233 } 2234 2235 mutex_exit(evicted_lock); 2236 mutex_exit(lock); 2237 2238 idx = ((idx + 1) & (list_count - 1)); 2239 lists++; 2240 2241 if (bytes_evicted < bytes) { 2242 if (lists < list_count) 2243 goto evict_start; 2244 else 2245 dprintf("only evicted %lld bytes from %x", 2246 (longlong_t)bytes_evicted, state); 2247 } 2248 if (type == ARC_BUFC_METADATA) 2249 evict_metadata_offset = idx; 2250 else 2251 evict_data_offset = idx; 2252 2253 if (skipped) 2254 ARCSTAT_INCR(arcstat_evict_skip, skipped); 2255 2256 if (missed) 2257 ARCSTAT_INCR(arcstat_mutex_miss, missed); 2258 2259 /* 2260 * Note: we have just evicted some data into the ghost state, 2261 * potentially putting the ghost size over the desired size. Rather 2262 * that evicting from the ghost list in this hot code path, leave 2263 * this chore to the arc_reclaim_thread(). 2264 */ 2265 2266 if (stolen) 2267 ARCSTAT_BUMP(arcstat_stolen); 2268 return (stolen); 2269} 2270 2271/* 2272 * Remove buffers from list until we've removed the specified number of 2273 * bytes. Destroy the buffers that are removed. 2274 */ 2275static void 2276arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 2277{ 2278 arc_buf_hdr_t *hdr, *hdr_prev; 2279 arc_buf_hdr_t marker = { 0 }; 2280 list_t *list, *list_start; 2281 kmutex_t *hash_lock, *lock; 2282 uint64_t bytes_deleted = 0; 2283 uint64_t bufs_skipped = 0; 2284 int count = 0; 2285 static int evict_offset; 2286 int list_count, idx = evict_offset; 2287 int offset, lists = 0; 2288 2289 ASSERT(GHOST_STATE(state)); 2290 2291 /* 2292 * data lists come after metadata lists 2293 */ 2294 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS]; 2295 list_count = ARC_BUFC_NUMDATALISTS; 2296 offset = ARC_BUFC_NUMMETADATALISTS; 2297 2298evict_start: 2299 list = &list_start[idx]; 2300 lock = ARCS_LOCK(state, idx + offset); 2301 2302 mutex_enter(lock); 2303 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2304 hdr_prev = list_prev(list, hdr); 2305 if (hdr->b_type > ARC_BUFC_NUMTYPES) 2306 panic("invalid hdr=%p", (void *)hdr); 2307 if (spa && hdr->b_spa != spa) 2308 continue; 2309 2310 /* ignore markers */ 2311 if (hdr->b_spa == 0) 2312 continue; 2313 2314 hash_lock = HDR_LOCK(hdr); 2315 /* caller may be trying to modify this buffer, skip it */ 2316 if (MUTEX_HELD(hash_lock)) 2317 continue; 2318 2319 /* 2320 * It may take a long time to evict all the bufs requested. 2321 * To avoid blocking all arc activity, periodically drop 2322 * the arcs_mtx and give other threads a chance to run 2323 * before reacquiring the lock. 2324 */ 2325 if (count++ > arc_evict_iterations) { 2326 list_insert_after(list, hdr, &marker); 2327 mutex_exit(lock); 2328 kpreempt(KPREEMPT_SYNC); 2329 mutex_enter(lock); 2330 hdr_prev = list_prev(list, &marker); 2331 list_remove(list, &marker); 2332 count = 0; 2333 continue; 2334 } 2335 if (mutex_tryenter(hash_lock)) { 2336 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2337 ASSERT(hdr->b_buf == NULL); 2338 ARCSTAT_BUMP(arcstat_deleted); 2339 bytes_deleted += hdr->b_size; 2340 2341 if (hdr->b_l2hdr != NULL) { 2342 /* 2343 * This buffer is cached on the 2nd Level ARC; 2344 * don't destroy the header. 2345 */ 2346 arc_change_state(arc_l2c_only, hdr, hash_lock); 2347 mutex_exit(hash_lock); 2348 } else { 2349 arc_change_state(arc_anon, hdr, hash_lock); 2350 mutex_exit(hash_lock); 2351 arc_hdr_destroy(hdr); 2352 } 2353 2354 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2355 if (bytes >= 0 && bytes_deleted >= bytes) 2356 break; 2357 } else if (bytes < 0) { 2358 /* 2359 * Insert a list marker and then wait for the 2360 * hash lock to become available. Once its 2361 * available, restart from where we left off. 2362 */ 2363 list_insert_after(list, hdr, &marker); 2364 mutex_exit(lock); 2365 mutex_enter(hash_lock); 2366 mutex_exit(hash_lock); 2367 mutex_enter(lock); 2368 hdr_prev = list_prev(list, &marker); 2369 list_remove(list, &marker); 2370 } else { 2371 bufs_skipped += 1; 2372 } 2373 2374 } 2375 mutex_exit(lock); 2376 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1)); 2377 lists++; 2378 2379 if (lists < list_count) 2380 goto evict_start; 2381 2382 evict_offset = idx; 2383 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] && 2384 (bytes < 0 || bytes_deleted < bytes)) { 2385 list_start = &state->arcs_lists[0]; 2386 list_count = ARC_BUFC_NUMMETADATALISTS; 2387 offset = lists = 0; 2388 goto evict_start; 2389 } 2390 2391 if (bufs_skipped) { 2392 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2393 ASSERT(bytes >= 0); 2394 } 2395 2396 if (bytes_deleted < bytes) 2397 dprintf("only deleted %lld bytes from %p", 2398 (longlong_t)bytes_deleted, state); 2399} 2400 2401static void 2402arc_adjust(void) 2403{ 2404 int64_t adjustment, delta; 2405 2406 /* 2407 * Adjust MRU size 2408 */ 2409 2410 adjustment = MIN((int64_t)(arc_size - arc_c), 2411 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2412 arc_p)); 2413 2414 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2415 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2416 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA); 2417 adjustment -= delta; 2418 } 2419 2420 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2421 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2422 (void) arc_evict(arc_mru, 0, delta, FALSE, 2423 ARC_BUFC_METADATA); 2424 } 2425 2426 /* 2427 * Adjust MFU size 2428 */ 2429 2430 adjustment = arc_size - arc_c; 2431 2432 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2433 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2434 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA); 2435 adjustment -= delta; 2436 } 2437 2438 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2439 int64_t delta = MIN(adjustment, 2440 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2441 (void) arc_evict(arc_mfu, 0, delta, FALSE, 2442 ARC_BUFC_METADATA); 2443 } 2444 2445 /* 2446 * Adjust ghost lists 2447 */ 2448 2449 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2450 2451 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2452 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2453 arc_evict_ghost(arc_mru_ghost, 0, delta); 2454 } 2455 2456 adjustment = 2457 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2458 2459 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2460 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2461 arc_evict_ghost(arc_mfu_ghost, 0, delta); 2462 } 2463} 2464 2465static void 2466arc_do_user_evicts(void) 2467{ 2468 static arc_buf_t *tmp_arc_eviction_list; 2469 2470 /* 2471 * Move list over to avoid LOR 2472 */ 2473restart: 2474 mutex_enter(&arc_eviction_mtx); 2475 tmp_arc_eviction_list = arc_eviction_list; 2476 arc_eviction_list = NULL; 2477 mutex_exit(&arc_eviction_mtx); 2478 2479 while (tmp_arc_eviction_list != NULL) { 2480 arc_buf_t *buf = tmp_arc_eviction_list; 2481 tmp_arc_eviction_list = buf->b_next; 2482 mutex_enter(&buf->b_evict_lock); 2483 buf->b_hdr = NULL; 2484 mutex_exit(&buf->b_evict_lock); 2485 2486 if (buf->b_efunc != NULL) 2487 VERIFY0(buf->b_efunc(buf->b_private)); 2488 2489 buf->b_efunc = NULL; 2490 buf->b_private = NULL; 2491 kmem_cache_free(buf_cache, buf); 2492 } 2493 2494 if (arc_eviction_list != NULL) 2495 goto restart; 2496} 2497 2498/* 2499 * Flush all *evictable* data from the cache for the given spa. 2500 * NOTE: this will not touch "active" (i.e. referenced) data. 2501 */ 2502void 2503arc_flush(spa_t *spa) 2504{ 2505 uint64_t guid = 0; 2506 2507 if (spa) 2508 guid = spa_load_guid(spa); 2509 2510 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) { 2511 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2512 if (spa) 2513 break; 2514 } 2515 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) { 2516 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2517 if (spa) 2518 break; 2519 } 2520 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) { 2521 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2522 if (spa) 2523 break; 2524 } 2525 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) { 2526 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2527 if (spa) 2528 break; 2529 } 2530 2531 arc_evict_ghost(arc_mru_ghost, guid, -1); 2532 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2533 2534 mutex_enter(&arc_reclaim_thr_lock); 2535 arc_do_user_evicts(); 2536 mutex_exit(&arc_reclaim_thr_lock); 2537 ASSERT(spa || arc_eviction_list == NULL); 2538} 2539 2540void 2541arc_shrink(void) 2542{ 2543 2544 if (arc_c > arc_c_min) { 2545 uint64_t to_free; 2546 2547 to_free = arc_c >> arc_shrink_shift; 2548 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 2549 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 2550 if (arc_c > arc_c_min + to_free) 2551 atomic_add_64(&arc_c, -to_free); 2552 else 2553 arc_c = arc_c_min; 2554 2555 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2556 if (arc_c > arc_size) 2557 arc_c = MAX(arc_size, arc_c_min); 2558 if (arc_p > arc_c) 2559 arc_p = (arc_c >> 1); 2560 2561 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 2562 arc_p); 2563 2564 ASSERT(arc_c >= arc_c_min); 2565 ASSERT((int64_t)arc_p >= 0); 2566 } 2567 2568 if (arc_size > arc_c) { 2569 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 2570 uint64_t, arc_c); 2571 arc_adjust(); 2572 } 2573} 2574 2575static int needfree = 0; 2576 2577static int 2578arc_reclaim_needed(void) 2579{ 2580 2581#ifdef _KERNEL 2582 2583 if (needfree) { 2584 DTRACE_PROBE(arc__reclaim_needfree); 2585 return (1); 2586 } 2587 2588 /* 2589 * Cooperate with pagedaemon when it's time for it to scan 2590 * and reclaim some pages. 2591 */ 2592 if (freemem < zfs_arc_free_target) { 2593 DTRACE_PROBE2(arc__reclaim_freemem, uint64_t, 2594 freemem, uint64_t, zfs_arc_free_target); 2595 return (1); 2596 } 2597 2598#ifdef sun 2599 /* 2600 * take 'desfree' extra pages, so we reclaim sooner, rather than later 2601 */ 2602 extra = desfree; 2603 2604 /* 2605 * check that we're out of range of the pageout scanner. It starts to 2606 * schedule paging if freemem is less than lotsfree and needfree. 2607 * lotsfree is the high-water mark for pageout, and needfree is the 2608 * number of needed free pages. We add extra pages here to make sure 2609 * the scanner doesn't start up while we're freeing memory. 2610 */ 2611 if (freemem < lotsfree + needfree + extra) 2612 return (1); 2613 2614 /* 2615 * check to make sure that swapfs has enough space so that anon 2616 * reservations can still succeed. anon_resvmem() checks that the 2617 * availrmem is greater than swapfs_minfree, and the number of reserved 2618 * swap pages. We also add a bit of extra here just to prevent 2619 * circumstances from getting really dire. 2620 */ 2621 if (availrmem < swapfs_minfree + swapfs_reserve + extra) 2622 return (1); 2623 2624 /* 2625 * Check that we have enough availrmem that memory locking (e.g., via 2626 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 2627 * stores the number of pages that cannot be locked; when availrmem 2628 * drops below pages_pp_maximum, page locking mechanisms such as 2629 * page_pp_lock() will fail.) 2630 */ 2631 if (availrmem <= pages_pp_maximum) 2632 return (1); 2633 2634#endif /* sun */ 2635#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 2636 /* 2637 * If we're on an i386 platform, it's possible that we'll exhaust the 2638 * kernel heap space before we ever run out of available physical 2639 * memory. Most checks of the size of the heap_area compare against 2640 * tune.t_minarmem, which is the minimum available real memory that we 2641 * can have in the system. However, this is generally fixed at 25 pages 2642 * which is so low that it's useless. In this comparison, we seek to 2643 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2644 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2645 * free) 2646 */ 2647 if (vmem_size(heap_arena, VMEM_FREE) < 2648 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) { 2649 DTRACE_PROBE2(arc__reclaim_used, uint64_t, 2650 vmem_size(heap_arena, VMEM_FREE), uint64_t, 2651 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2); 2652 return (1); 2653 } 2654#define zio_arena NULL 2655#else 2656#define zio_arena heap_arena 2657#endif 2658 2659 /* 2660 * If zio data pages are being allocated out of a separate heap segment, 2661 * then enforce that the size of available vmem for this arena remains 2662 * above about 1/16th free. 2663 * 2664 * Note: The 1/16th arena free requirement was put in place 2665 * to aggressively evict memory from the arc in order to avoid 2666 * memory fragmentation issues. 2667 */ 2668 if (zio_arena != NULL && 2669 vmem_size(zio_arena, VMEM_FREE) < 2670 (vmem_size(zio_arena, VMEM_ALLOC) >> 4)) 2671 return (1); 2672 2673 /* 2674 * Above limits know nothing about real level of KVA fragmentation. 2675 * Start aggressive reclamation if too little sequential KVA left. 2676 */ 2677 if (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) { 2678 DTRACE_PROBE2(arc__reclaim_maxfree, uint64_t, 2679 vmem_size(heap_arena, VMEM_MAXFREE), 2680 uint64_t, zfs_max_recordsize); 2681 return (1); 2682 } 2683 2684#else /* _KERNEL */ 2685 if (spa_get_random(100) == 0) 2686 return (1); 2687#endif /* _KERNEL */ 2688 DTRACE_PROBE(arc__reclaim_no); 2689 2690 return (0); 2691} 2692 2693extern kmem_cache_t *zio_buf_cache[]; 2694extern kmem_cache_t *zio_data_buf_cache[]; 2695extern kmem_cache_t *range_seg_cache; 2696 2697static __noinline void 2698arc_kmem_reap_now(arc_reclaim_strategy_t strat) 2699{ 2700 size_t i; 2701 kmem_cache_t *prev_cache = NULL; 2702 kmem_cache_t *prev_data_cache = NULL; 2703 2704 DTRACE_PROBE(arc__kmem_reap_start); 2705#ifdef _KERNEL 2706 if (arc_meta_used >= arc_meta_limit) { 2707 /* 2708 * We are exceeding our meta-data cache limit. 2709 * Purge some DNLC entries to release holds on meta-data. 2710 */ 2711 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2712 } 2713#if defined(__i386) 2714 /* 2715 * Reclaim unused memory from all kmem caches. 2716 */ 2717 kmem_reap(); 2718#endif 2719#endif 2720 2721 /* 2722 * An aggressive reclamation will shrink the cache size as well as 2723 * reap free buffers from the arc kmem caches. 2724 */ 2725 if (strat == ARC_RECLAIM_AGGR) 2726 arc_shrink(); 2727 2728 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2729 if (zio_buf_cache[i] != prev_cache) { 2730 prev_cache = zio_buf_cache[i]; 2731 kmem_cache_reap_now(zio_buf_cache[i]); 2732 } 2733 if (zio_data_buf_cache[i] != prev_data_cache) { 2734 prev_data_cache = zio_data_buf_cache[i]; 2735 kmem_cache_reap_now(zio_data_buf_cache[i]); 2736 } 2737 } 2738 kmem_cache_reap_now(buf_cache); 2739 kmem_cache_reap_now(hdr_cache); 2740 kmem_cache_reap_now(range_seg_cache); 2741 2742#ifdef sun 2743 /* 2744 * Ask the vmem arena to reclaim unused memory from its 2745 * quantum caches. 2746 */ 2747 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR) 2748 vmem_qcache_reap(zio_arena); 2749#endif 2750 DTRACE_PROBE(arc__kmem_reap_end); 2751} 2752 2753static void 2754arc_reclaim_thread(void *dummy __unused) 2755{ 2756 clock_t growtime = 0; 2757 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS; 2758 callb_cpr_t cpr; 2759 2760 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2761 2762 mutex_enter(&arc_reclaim_thr_lock); 2763 while (arc_thread_exit == 0) { 2764 if (arc_reclaim_needed()) { 2765 2766 if (arc_no_grow) { 2767 if (last_reclaim == ARC_RECLAIM_CONS) { 2768 DTRACE_PROBE(arc__reclaim_aggr_no_grow); 2769 last_reclaim = ARC_RECLAIM_AGGR; 2770 } else { 2771 last_reclaim = ARC_RECLAIM_CONS; 2772 } 2773 } else { 2774 arc_no_grow = TRUE; 2775 last_reclaim = ARC_RECLAIM_AGGR; 2776 DTRACE_PROBE(arc__reclaim_aggr); 2777 membar_producer(); 2778 } 2779 2780 /* reset the growth delay for every reclaim */ 2781 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2782 2783 if (needfree && last_reclaim == ARC_RECLAIM_CONS) { 2784 /* 2785 * If needfree is TRUE our vm_lowmem hook 2786 * was called and in that case we must free some 2787 * memory, so switch to aggressive mode. 2788 */ 2789 arc_no_grow = TRUE; 2790 last_reclaim = ARC_RECLAIM_AGGR; 2791 } 2792 arc_kmem_reap_now(last_reclaim); 2793 arc_warm = B_TRUE; 2794 2795 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) { 2796 arc_no_grow = FALSE; 2797 } 2798 2799 arc_adjust(); 2800 2801 if (arc_eviction_list != NULL) 2802 arc_do_user_evicts(); 2803 2804#ifdef _KERNEL 2805 if (needfree) { 2806 needfree = 0; 2807 wakeup(&needfree); 2808 } 2809#endif 2810 2811 /* block until needed, or one second, whichever is shorter */ 2812 CALLB_CPR_SAFE_BEGIN(&cpr); 2813 (void) cv_timedwait(&arc_reclaim_thr_cv, 2814 &arc_reclaim_thr_lock, hz); 2815 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2816 } 2817 2818 arc_thread_exit = 0; 2819 cv_broadcast(&arc_reclaim_thr_cv); 2820 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2821 thread_exit(); 2822} 2823 2824/* 2825 * Adapt arc info given the number of bytes we are trying to add and 2826 * the state that we are comming from. This function is only called 2827 * when we are adding new content to the cache. 2828 */ 2829static void 2830arc_adapt(int bytes, arc_state_t *state) 2831{ 2832 int mult; 2833 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2834 2835 if (state == arc_l2c_only) 2836 return; 2837 2838 ASSERT(bytes > 0); 2839 /* 2840 * Adapt the target size of the MRU list: 2841 * - if we just hit in the MRU ghost list, then increase 2842 * the target size of the MRU list. 2843 * - if we just hit in the MFU ghost list, then increase 2844 * the target size of the MFU list by decreasing the 2845 * target size of the MRU list. 2846 */ 2847 if (state == arc_mru_ghost) { 2848 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2849 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2850 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2851 2852 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2853 } else if (state == arc_mfu_ghost) { 2854 uint64_t delta; 2855 2856 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2857 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2858 mult = MIN(mult, 10); 2859 2860 delta = MIN(bytes * mult, arc_p); 2861 arc_p = MAX(arc_p_min, arc_p - delta); 2862 } 2863 ASSERT((int64_t)arc_p >= 0); 2864 2865 if (arc_reclaim_needed()) { 2866 cv_signal(&arc_reclaim_thr_cv); 2867 return; 2868 } 2869 2870 if (arc_no_grow) 2871 return; 2872 2873 if (arc_c >= arc_c_max) 2874 return; 2875 2876 /* 2877 * If we're within (2 * maxblocksize) bytes of the target 2878 * cache size, increment the target cache size 2879 */ 2880 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2881 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 2882 atomic_add_64(&arc_c, (int64_t)bytes); 2883 if (arc_c > arc_c_max) 2884 arc_c = arc_c_max; 2885 else if (state == arc_anon) 2886 atomic_add_64(&arc_p, (int64_t)bytes); 2887 if (arc_p > arc_c) 2888 arc_p = arc_c; 2889 } 2890 ASSERT((int64_t)arc_p >= 0); 2891} 2892 2893/* 2894 * Check if the cache has reached its limits and eviction is required 2895 * prior to insert. 2896 */ 2897static int 2898arc_evict_needed(arc_buf_contents_t type) 2899{ 2900 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 2901 return (1); 2902 2903 if (arc_reclaim_needed()) 2904 return (1); 2905 2906 return (arc_size > arc_c); 2907} 2908 2909/* 2910 * The buffer, supplied as the first argument, needs a data block. 2911 * So, if we are at cache max, determine which cache should be victimized. 2912 * We have the following cases: 2913 * 2914 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 2915 * In this situation if we're out of space, but the resident size of the MFU is 2916 * under the limit, victimize the MFU cache to satisfy this insertion request. 2917 * 2918 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 2919 * Here, we've used up all of the available space for the MRU, so we need to 2920 * evict from our own cache instead. Evict from the set of resident MRU 2921 * entries. 2922 * 2923 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 2924 * c minus p represents the MFU space in the cache, since p is the size of the 2925 * cache that is dedicated to the MRU. In this situation there's still space on 2926 * the MFU side, so the MRU side needs to be victimized. 2927 * 2928 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 2929 * MFU's resident set is consuming more space than it has been allotted. In 2930 * this situation, we must victimize our own cache, the MFU, for this insertion. 2931 */ 2932static void 2933arc_get_data_buf(arc_buf_t *buf) 2934{ 2935 arc_state_t *state = buf->b_hdr->b_state; 2936 uint64_t size = buf->b_hdr->b_size; 2937 arc_buf_contents_t type = buf->b_hdr->b_type; 2938 2939 arc_adapt(size, state); 2940 2941 /* 2942 * We have not yet reached cache maximum size, 2943 * just allocate a new buffer. 2944 */ 2945 if (!arc_evict_needed(type)) { 2946 if (type == ARC_BUFC_METADATA) { 2947 buf->b_data = zio_buf_alloc(size); 2948 arc_space_consume(size, ARC_SPACE_DATA); 2949 } else { 2950 ASSERT(type == ARC_BUFC_DATA); 2951 buf->b_data = zio_data_buf_alloc(size); 2952 ARCSTAT_INCR(arcstat_data_size, size); 2953 atomic_add_64(&arc_size, size); 2954 } 2955 goto out; 2956 } 2957 2958 /* 2959 * If we are prefetching from the mfu ghost list, this buffer 2960 * will end up on the mru list; so steal space from there. 2961 */ 2962 if (state == arc_mfu_ghost) 2963 state = buf->b_hdr->b_flags & ARC_FLAG_PREFETCH ? 2964 arc_mru : arc_mfu; 2965 else if (state == arc_mru_ghost) 2966 state = arc_mru; 2967 2968 if (state == arc_mru || state == arc_anon) { 2969 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 2970 state = (arc_mfu->arcs_lsize[type] >= size && 2971 arc_p > mru_used) ? arc_mfu : arc_mru; 2972 } else { 2973 /* MFU cases */ 2974 uint64_t mfu_space = arc_c - arc_p; 2975 state = (arc_mru->arcs_lsize[type] >= size && 2976 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 2977 } 2978 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) { 2979 if (type == ARC_BUFC_METADATA) { 2980 buf->b_data = zio_buf_alloc(size); 2981 arc_space_consume(size, ARC_SPACE_DATA); 2982 } else { 2983 ASSERT(type == ARC_BUFC_DATA); 2984 buf->b_data = zio_data_buf_alloc(size); 2985 ARCSTAT_INCR(arcstat_data_size, size); 2986 atomic_add_64(&arc_size, size); 2987 } 2988 ARCSTAT_BUMP(arcstat_recycle_miss); 2989 } 2990 ASSERT(buf->b_data != NULL); 2991out: 2992 /* 2993 * Update the state size. Note that ghost states have a 2994 * "ghost size" and so don't need to be updated. 2995 */ 2996 if (!GHOST_STATE(buf->b_hdr->b_state)) { 2997 arc_buf_hdr_t *hdr = buf->b_hdr; 2998 2999 atomic_add_64(&hdr->b_state->arcs_size, size); 3000 if (list_link_active(&hdr->b_arc_node)) { 3001 ASSERT(refcount_is_zero(&hdr->b_refcnt)); 3002 atomic_add_64(&hdr->b_state->arcs_lsize[type], size); 3003 } 3004 /* 3005 * If we are growing the cache, and we are adding anonymous 3006 * data, and we have outgrown arc_p, update arc_p 3007 */ 3008 if (arc_size < arc_c && hdr->b_state == arc_anon && 3009 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 3010 arc_p = MIN(arc_c, arc_p + size); 3011 } 3012 ARCSTAT_BUMP(arcstat_allocated); 3013} 3014 3015/* 3016 * This routine is called whenever a buffer is accessed. 3017 * NOTE: the hash lock is dropped in this function. 3018 */ 3019static void 3020arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3021{ 3022 clock_t now; 3023 3024 ASSERT(MUTEX_HELD(hash_lock)); 3025 3026 if (hdr->b_state == arc_anon) { 3027 /* 3028 * This buffer is not in the cache, and does not 3029 * appear in our "ghost" list. Add the new buffer 3030 * to the MRU state. 3031 */ 3032 3033 ASSERT(hdr->b_arc_access == 0); 3034 hdr->b_arc_access = ddi_get_lbolt(); 3035 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3036 arc_change_state(arc_mru, hdr, hash_lock); 3037 3038 } else if (hdr->b_state == arc_mru) { 3039 now = ddi_get_lbolt(); 3040 3041 /* 3042 * If this buffer is here because of a prefetch, then either: 3043 * - clear the flag if this is a "referencing" read 3044 * (any subsequent access will bump this into the MFU state). 3045 * or 3046 * - move the buffer to the head of the list if this is 3047 * another prefetch (to make it less likely to be evicted). 3048 */ 3049 if ((hdr->b_flags & ARC_FLAG_PREFETCH) != 0) { 3050 if (refcount_count(&hdr->b_refcnt) == 0) { 3051 ASSERT(list_link_active(&hdr->b_arc_node)); 3052 } else { 3053 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3054 ARCSTAT_BUMP(arcstat_mru_hits); 3055 } 3056 hdr->b_arc_access = now; 3057 return; 3058 } 3059 3060 /* 3061 * This buffer has been "accessed" only once so far, 3062 * but it is still in the cache. Move it to the MFU 3063 * state. 3064 */ 3065 if (now > hdr->b_arc_access + ARC_MINTIME) { 3066 /* 3067 * More than 125ms have passed since we 3068 * instantiated this buffer. Move it to the 3069 * most frequently used state. 3070 */ 3071 hdr->b_arc_access = now; 3072 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3073 arc_change_state(arc_mfu, hdr, hash_lock); 3074 } 3075 ARCSTAT_BUMP(arcstat_mru_hits); 3076 } else if (hdr->b_state == arc_mru_ghost) { 3077 arc_state_t *new_state; 3078 /* 3079 * This buffer has been "accessed" recently, but 3080 * was evicted from the cache. Move it to the 3081 * MFU state. 3082 */ 3083 3084 if (hdr->b_flags & ARC_FLAG_PREFETCH) { 3085 new_state = arc_mru; 3086 if (refcount_count(&hdr->b_refcnt) > 0) 3087 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3088 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3089 } else { 3090 new_state = arc_mfu; 3091 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3092 } 3093 3094 hdr->b_arc_access = ddi_get_lbolt(); 3095 arc_change_state(new_state, hdr, hash_lock); 3096 3097 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3098 } else if (hdr->b_state == arc_mfu) { 3099 /* 3100 * This buffer has been accessed more than once and is 3101 * still in the cache. Keep it in the MFU state. 3102 * 3103 * NOTE: an add_reference() that occurred when we did 3104 * the arc_read() will have kicked this off the list. 3105 * If it was a prefetch, we will explicitly move it to 3106 * the head of the list now. 3107 */ 3108 if ((hdr->b_flags & ARC_FLAG_PREFETCH) != 0) { 3109 ASSERT(refcount_count(&hdr->b_refcnt) == 0); 3110 ASSERT(list_link_active(&hdr->b_arc_node)); 3111 } 3112 ARCSTAT_BUMP(arcstat_mfu_hits); 3113 hdr->b_arc_access = ddi_get_lbolt(); 3114 } else if (hdr->b_state == arc_mfu_ghost) { 3115 arc_state_t *new_state = arc_mfu; 3116 /* 3117 * This buffer has been accessed more than once but has 3118 * been evicted from the cache. Move it back to the 3119 * MFU state. 3120 */ 3121 3122 if (hdr->b_flags & ARC_FLAG_PREFETCH) { 3123 /* 3124 * This is a prefetch access... 3125 * move this block back to the MRU state. 3126 */ 3127 ASSERT0(refcount_count(&hdr->b_refcnt)); 3128 new_state = arc_mru; 3129 } 3130 3131 hdr->b_arc_access = ddi_get_lbolt(); 3132 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3133 arc_change_state(new_state, hdr, hash_lock); 3134 3135 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3136 } else if (hdr->b_state == arc_l2c_only) { 3137 /* 3138 * This buffer is on the 2nd Level ARC. 3139 */ 3140 3141 hdr->b_arc_access = ddi_get_lbolt(); 3142 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3143 arc_change_state(arc_mfu, hdr, hash_lock); 3144 } else { 3145 ASSERT(!"invalid arc state"); 3146 } 3147} 3148 3149/* a generic arc_done_func_t which you can use */ 3150/* ARGSUSED */ 3151void 3152arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3153{ 3154 if (zio == NULL || zio->io_error == 0) 3155 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3156 VERIFY(arc_buf_remove_ref(buf, arg)); 3157} 3158 3159/* a generic arc_done_func_t */ 3160void 3161arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3162{ 3163 arc_buf_t **bufp = arg; 3164 if (zio && zio->io_error) { 3165 VERIFY(arc_buf_remove_ref(buf, arg)); 3166 *bufp = NULL; 3167 } else { 3168 *bufp = buf; 3169 ASSERT(buf->b_data); 3170 } 3171} 3172 3173static void 3174arc_read_done(zio_t *zio) 3175{ 3176 arc_buf_hdr_t *hdr; 3177 arc_buf_t *buf; 3178 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3179 kmutex_t *hash_lock = NULL; 3180 arc_callback_t *callback_list, *acb; 3181 int freeable = FALSE; 3182 3183 buf = zio->io_private; 3184 hdr = buf->b_hdr; 3185 3186 /* 3187 * The hdr was inserted into hash-table and removed from lists 3188 * prior to starting I/O. We should find this header, since 3189 * it's in the hash table, and it should be legit since it's 3190 * not possible to evict it during the I/O. The only possible 3191 * reason for it not to be found is if we were freed during the 3192 * read. 3193 */ 3194 if (HDR_IN_HASH_TABLE(hdr)) { 3195 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3196 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3197 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3198 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3199 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3200 3201 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3202 &hash_lock); 3203 3204 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3205 hash_lock == NULL) || 3206 (found == hdr && 3207 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3208 (found == hdr && HDR_L2_READING(hdr))); 3209 } 3210 3211 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3212 if (l2arc_noprefetch && (hdr->b_flags & ARC_FLAG_PREFETCH)) 3213 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3214 3215 /* byteswap if necessary */ 3216 callback_list = hdr->b_acb; 3217 ASSERT(callback_list != NULL); 3218 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3219 dmu_object_byteswap_t bswap = 3220 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3221 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3222 byteswap_uint64_array : 3223 dmu_ot_byteswap[bswap].ob_func; 3224 func(buf->b_data, hdr->b_size); 3225 } 3226 3227 arc_cksum_compute(buf, B_FALSE); 3228#ifdef illumos 3229 arc_buf_watch(buf); 3230#endif /* illumos */ 3231 3232 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) { 3233 /* 3234 * Only call arc_access on anonymous buffers. This is because 3235 * if we've issued an I/O for an evicted buffer, we've already 3236 * called arc_access (to prevent any simultaneous readers from 3237 * getting confused). 3238 */ 3239 arc_access(hdr, hash_lock); 3240 } 3241 3242 /* create copies of the data buffer for the callers */ 3243 abuf = buf; 3244 for (acb = callback_list; acb; acb = acb->acb_next) { 3245 if (acb->acb_done) { 3246 if (abuf == NULL) { 3247 ARCSTAT_BUMP(arcstat_duplicate_reads); 3248 abuf = arc_buf_clone(buf); 3249 } 3250 acb->acb_buf = abuf; 3251 abuf = NULL; 3252 } 3253 } 3254 hdr->b_acb = NULL; 3255 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3256 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3257 if (abuf == buf) { 3258 ASSERT(buf->b_efunc == NULL); 3259 ASSERT(hdr->b_datacnt == 1); 3260 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3261 } 3262 3263 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL); 3264 3265 if (zio->io_error != 0) { 3266 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3267 if (hdr->b_state != arc_anon) 3268 arc_change_state(arc_anon, hdr, hash_lock); 3269 if (HDR_IN_HASH_TABLE(hdr)) 3270 buf_hash_remove(hdr); 3271 freeable = refcount_is_zero(&hdr->b_refcnt); 3272 } 3273 3274 /* 3275 * Broadcast before we drop the hash_lock to avoid the possibility 3276 * that the hdr (and hence the cv) might be freed before we get to 3277 * the cv_broadcast(). 3278 */ 3279 cv_broadcast(&hdr->b_cv); 3280 3281 if (hash_lock) { 3282 mutex_exit(hash_lock); 3283 } else { 3284 /* 3285 * This block was freed while we waited for the read to 3286 * complete. It has been removed from the hash table and 3287 * moved to the anonymous state (so that it won't show up 3288 * in the cache). 3289 */ 3290 ASSERT3P(hdr->b_state, ==, arc_anon); 3291 freeable = refcount_is_zero(&hdr->b_refcnt); 3292 } 3293 3294 /* execute each callback and free its structure */ 3295 while ((acb = callback_list) != NULL) { 3296 if (acb->acb_done) 3297 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3298 3299 if (acb->acb_zio_dummy != NULL) { 3300 acb->acb_zio_dummy->io_error = zio->io_error; 3301 zio_nowait(acb->acb_zio_dummy); 3302 } 3303 3304 callback_list = acb->acb_next; 3305 kmem_free(acb, sizeof (arc_callback_t)); 3306 } 3307 3308 if (freeable) 3309 arc_hdr_destroy(hdr); 3310} 3311 3312/* 3313 * "Read" the block block at the specified DVA (in bp) via the 3314 * cache. If the block is found in the cache, invoke the provided 3315 * callback immediately and return. Note that the `zio' parameter 3316 * in the callback will be NULL in this case, since no IO was 3317 * required. If the block is not in the cache pass the read request 3318 * on to the spa with a substitute callback function, so that the 3319 * requested block will be added to the cache. 3320 * 3321 * If a read request arrives for a block that has a read in-progress, 3322 * either wait for the in-progress read to complete (and return the 3323 * results); or, if this is a read with a "done" func, add a record 3324 * to the read to invoke the "done" func when the read completes, 3325 * and return; or just return. 3326 * 3327 * arc_read_done() will invoke all the requested "done" functions 3328 * for readers of this block. 3329 */ 3330int 3331arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3332 void *private, zio_priority_t priority, int zio_flags, 3333 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3334{ 3335 arc_buf_hdr_t *hdr = NULL; 3336 arc_buf_t *buf = NULL; 3337 kmutex_t *hash_lock = NULL; 3338 zio_t *rzio; 3339 uint64_t guid = spa_load_guid(spa); 3340 3341 ASSERT(!BP_IS_EMBEDDED(bp) || 3342 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3343 3344top: 3345 if (!BP_IS_EMBEDDED(bp)) { 3346 /* 3347 * Embedded BP's have no DVA and require no I/O to "read". 3348 * Create an anonymous arc buf to back it. 3349 */ 3350 hdr = buf_hash_find(guid, bp, &hash_lock); 3351 } 3352 3353 if (hdr != NULL && hdr->b_datacnt > 0) { 3354 3355 *arc_flags |= ARC_FLAG_CACHED; 3356 3357 if (HDR_IO_IN_PROGRESS(hdr)) { 3358 3359 if (*arc_flags & ARC_FLAG_WAIT) { 3360 cv_wait(&hdr->b_cv, hash_lock); 3361 mutex_exit(hash_lock); 3362 goto top; 3363 } 3364 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3365 3366 if (done) { 3367 arc_callback_t *acb = NULL; 3368 3369 acb = kmem_zalloc(sizeof (arc_callback_t), 3370 KM_SLEEP); 3371 acb->acb_done = done; 3372 acb->acb_private = private; 3373 if (pio != NULL) 3374 acb->acb_zio_dummy = zio_null(pio, 3375 spa, NULL, NULL, NULL, zio_flags); 3376 3377 ASSERT(acb->acb_done != NULL); 3378 acb->acb_next = hdr->b_acb; 3379 hdr->b_acb = acb; 3380 add_reference(hdr, hash_lock, private); 3381 mutex_exit(hash_lock); 3382 return (0); 3383 } 3384 mutex_exit(hash_lock); 3385 return (0); 3386 } 3387 3388 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3389 3390 if (done) { 3391 add_reference(hdr, hash_lock, private); 3392 /* 3393 * If this block is already in use, create a new 3394 * copy of the data so that we will be guaranteed 3395 * that arc_release() will always succeed. 3396 */ 3397 buf = hdr->b_buf; 3398 ASSERT(buf); 3399 ASSERT(buf->b_data); 3400 if (HDR_BUF_AVAILABLE(hdr)) { 3401 ASSERT(buf->b_efunc == NULL); 3402 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3403 } else { 3404 buf = arc_buf_clone(buf); 3405 } 3406 3407 } else if (*arc_flags & ARC_FLAG_PREFETCH && 3408 refcount_count(&hdr->b_refcnt) == 0) { 3409 hdr->b_flags |= ARC_FLAG_PREFETCH; 3410 } 3411 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 3412 arc_access(hdr, hash_lock); 3413 if (*arc_flags & ARC_FLAG_L2CACHE) 3414 hdr->b_flags |= ARC_FLAG_L2CACHE; 3415 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3416 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3417 mutex_exit(hash_lock); 3418 ARCSTAT_BUMP(arcstat_hits); 3419 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH), 3420 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3421 data, metadata, hits); 3422 3423 if (done) 3424 done(NULL, buf, private); 3425 } else { 3426 uint64_t size = BP_GET_LSIZE(bp); 3427 arc_callback_t *acb; 3428 vdev_t *vd = NULL; 3429 uint64_t addr = 0; 3430 boolean_t devw = B_FALSE; 3431 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 3432 uint64_t b_asize = 0; 3433 3434 if (hdr == NULL) { 3435 /* this block is not in the cache */ 3436 arc_buf_hdr_t *exists = NULL; 3437 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 3438 buf = arc_buf_alloc(spa, size, private, type); 3439 hdr = buf->b_hdr; 3440 if (!BP_IS_EMBEDDED(bp)) { 3441 hdr->b_dva = *BP_IDENTITY(bp); 3442 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 3443 hdr->b_cksum0 = bp->blk_cksum.zc_word[0]; 3444 exists = buf_hash_insert(hdr, &hash_lock); 3445 } 3446 if (exists != NULL) { 3447 /* somebody beat us to the hash insert */ 3448 mutex_exit(hash_lock); 3449 buf_discard_identity(hdr); 3450 (void) arc_buf_remove_ref(buf, private); 3451 goto top; /* restart the IO request */ 3452 } 3453 3454 /* if this is a prefetch, we don't have a reference */ 3455 if (*arc_flags & ARC_FLAG_PREFETCH) { 3456 (void) remove_reference(hdr, hash_lock, 3457 private); 3458 hdr->b_flags |= ARC_FLAG_PREFETCH; 3459 } 3460 if (*arc_flags & ARC_FLAG_L2CACHE) 3461 hdr->b_flags |= ARC_FLAG_L2CACHE; 3462 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3463 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3464 if (BP_GET_LEVEL(bp) > 0) 3465 hdr->b_flags |= ARC_FLAG_INDIRECT; 3466 } else { 3467 /* this block is in the ghost cache */ 3468 ASSERT(GHOST_STATE(hdr->b_state)); 3469 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3470 ASSERT0(refcount_count(&hdr->b_refcnt)); 3471 ASSERT(hdr->b_buf == NULL); 3472 3473 /* if this is a prefetch, we don't have a reference */ 3474 if (*arc_flags & ARC_FLAG_PREFETCH) 3475 hdr->b_flags |= ARC_FLAG_PREFETCH; 3476 else 3477 add_reference(hdr, hash_lock, private); 3478 if (*arc_flags & ARC_FLAG_L2CACHE) 3479 hdr->b_flags |= ARC_FLAG_L2CACHE; 3480 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3481 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3482 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 3483 buf->b_hdr = hdr; 3484 buf->b_data = NULL; 3485 buf->b_efunc = NULL; 3486 buf->b_private = NULL; 3487 buf->b_next = NULL; 3488 hdr->b_buf = buf; 3489 ASSERT(hdr->b_datacnt == 0); 3490 hdr->b_datacnt = 1; 3491 arc_get_data_buf(buf); 3492 arc_access(hdr, hash_lock); 3493 } 3494 3495 ASSERT(!GHOST_STATE(hdr->b_state)); 3496 3497 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 3498 acb->acb_done = done; 3499 acb->acb_private = private; 3500 3501 ASSERT(hdr->b_acb == NULL); 3502 hdr->b_acb = acb; 3503 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 3504 3505 if (hdr->b_l2hdr != NULL && 3506 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) { 3507 devw = hdr->b_l2hdr->b_dev->l2ad_writing; 3508 addr = hdr->b_l2hdr->b_daddr; 3509 b_compress = hdr->b_l2hdr->b_compress; 3510 b_asize = hdr->b_l2hdr->b_asize; 3511 /* 3512 * Lock out device removal. 3513 */ 3514 if (vdev_is_dead(vd) || 3515 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 3516 vd = NULL; 3517 } 3518 3519 if (hash_lock != NULL) 3520 mutex_exit(hash_lock); 3521 3522 /* 3523 * At this point, we have a level 1 cache miss. Try again in 3524 * L2ARC if possible. 3525 */ 3526 ASSERT3U(hdr->b_size, ==, size); 3527 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 3528 uint64_t, size, zbookmark_phys_t *, zb); 3529 ARCSTAT_BUMP(arcstat_misses); 3530 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH), 3531 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA, 3532 data, metadata, misses); 3533#ifdef _KERNEL 3534 curthread->td_ru.ru_inblock++; 3535#endif 3536 3537 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 3538 /* 3539 * Read from the L2ARC if the following are true: 3540 * 1. The L2ARC vdev was previously cached. 3541 * 2. This buffer still has L2ARC metadata. 3542 * 3. This buffer isn't currently writing to the L2ARC. 3543 * 4. The L2ARC entry wasn't evicted, which may 3544 * also have invalidated the vdev. 3545 * 5. This isn't prefetch and l2arc_noprefetch is set. 3546 */ 3547 if (hdr->b_l2hdr != NULL && 3548 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3549 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3550 l2arc_read_callback_t *cb; 3551 3552 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3553 ARCSTAT_BUMP(arcstat_l2_hits); 3554 3555 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3556 KM_SLEEP); 3557 cb->l2rcb_buf = buf; 3558 cb->l2rcb_spa = spa; 3559 cb->l2rcb_bp = *bp; 3560 cb->l2rcb_zb = *zb; 3561 cb->l2rcb_flags = zio_flags; 3562 cb->l2rcb_compress = b_compress; 3563 3564 ASSERT(addr >= VDEV_LABEL_START_SIZE && 3565 addr + size < vd->vdev_psize - 3566 VDEV_LABEL_END_SIZE); 3567 3568 /* 3569 * l2arc read. The SCL_L2ARC lock will be 3570 * released by l2arc_read_done(). 3571 * Issue a null zio if the underlying buffer 3572 * was squashed to zero size by compression. 3573 */ 3574 if (b_compress == ZIO_COMPRESS_EMPTY) { 3575 rzio = zio_null(pio, spa, vd, 3576 l2arc_read_done, cb, 3577 zio_flags | ZIO_FLAG_DONT_CACHE | 3578 ZIO_FLAG_CANFAIL | 3579 ZIO_FLAG_DONT_PROPAGATE | 3580 ZIO_FLAG_DONT_RETRY); 3581 } else { 3582 rzio = zio_read_phys(pio, vd, addr, 3583 b_asize, buf->b_data, 3584 ZIO_CHECKSUM_OFF, 3585 l2arc_read_done, cb, priority, 3586 zio_flags | ZIO_FLAG_DONT_CACHE | 3587 ZIO_FLAG_CANFAIL | 3588 ZIO_FLAG_DONT_PROPAGATE | 3589 ZIO_FLAG_DONT_RETRY, B_FALSE); 3590 } 3591 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3592 zio_t *, rzio); 3593 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 3594 3595 if (*arc_flags & ARC_FLAG_NOWAIT) { 3596 zio_nowait(rzio); 3597 return (0); 3598 } 3599 3600 ASSERT(*arc_flags & ARC_FLAG_WAIT); 3601 if (zio_wait(rzio) == 0) 3602 return (0); 3603 3604 /* l2arc read error; goto zio_read() */ 3605 } else { 3606 DTRACE_PROBE1(l2arc__miss, 3607 arc_buf_hdr_t *, hdr); 3608 ARCSTAT_BUMP(arcstat_l2_misses); 3609 if (HDR_L2_WRITING(hdr)) 3610 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3611 spa_config_exit(spa, SCL_L2ARC, vd); 3612 } 3613 } else { 3614 if (vd != NULL) 3615 spa_config_exit(spa, SCL_L2ARC, vd); 3616 if (l2arc_ndev != 0) { 3617 DTRACE_PROBE1(l2arc__miss, 3618 arc_buf_hdr_t *, hdr); 3619 ARCSTAT_BUMP(arcstat_l2_misses); 3620 } 3621 } 3622 3623 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3624 arc_read_done, buf, priority, zio_flags, zb); 3625 3626 if (*arc_flags & ARC_FLAG_WAIT) 3627 return (zio_wait(rzio)); 3628 3629 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3630 zio_nowait(rzio); 3631 } 3632 return (0); 3633} 3634 3635void 3636arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3637{ 3638 ASSERT(buf->b_hdr != NULL); 3639 ASSERT(buf->b_hdr->b_state != arc_anon); 3640 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL); 3641 ASSERT(buf->b_efunc == NULL); 3642 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3643 3644 buf->b_efunc = func; 3645 buf->b_private = private; 3646} 3647 3648/* 3649 * Notify the arc that a block was freed, and thus will never be used again. 3650 */ 3651void 3652arc_freed(spa_t *spa, const blkptr_t *bp) 3653{ 3654 arc_buf_hdr_t *hdr; 3655 kmutex_t *hash_lock; 3656 uint64_t guid = spa_load_guid(spa); 3657 3658 ASSERT(!BP_IS_EMBEDDED(bp)); 3659 3660 hdr = buf_hash_find(guid, bp, &hash_lock); 3661 if (hdr == NULL) 3662 return; 3663 if (HDR_BUF_AVAILABLE(hdr)) { 3664 arc_buf_t *buf = hdr->b_buf; 3665 add_reference(hdr, hash_lock, FTAG); 3666 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3667 mutex_exit(hash_lock); 3668 3669 arc_release(buf, FTAG); 3670 (void) arc_buf_remove_ref(buf, FTAG); 3671 } else { 3672 mutex_exit(hash_lock); 3673 } 3674 3675} 3676 3677/* 3678 * Clear the user eviction callback set by arc_set_callback(), first calling 3679 * it if it exists. Because the presence of a callback keeps an arc_buf cached 3680 * clearing the callback may result in the arc_buf being destroyed. However, 3681 * it will not result in the *last* arc_buf being destroyed, hence the data 3682 * will remain cached in the ARC. We make a copy of the arc buffer here so 3683 * that we can process the callback without holding any locks. 3684 * 3685 * It's possible that the callback is already in the process of being cleared 3686 * by another thread. In this case we can not clear the callback. 3687 * 3688 * Returns B_TRUE if the callback was successfully called and cleared. 3689 */ 3690boolean_t 3691arc_clear_callback(arc_buf_t *buf) 3692{ 3693 arc_buf_hdr_t *hdr; 3694 kmutex_t *hash_lock; 3695 arc_evict_func_t *efunc = buf->b_efunc; 3696 void *private = buf->b_private; 3697 list_t *list, *evicted_list; 3698 kmutex_t *lock, *evicted_lock; 3699 3700 mutex_enter(&buf->b_evict_lock); 3701 hdr = buf->b_hdr; 3702 if (hdr == NULL) { 3703 /* 3704 * We are in arc_do_user_evicts(). 3705 */ 3706 ASSERT(buf->b_data == NULL); 3707 mutex_exit(&buf->b_evict_lock); 3708 return (B_FALSE); 3709 } else if (buf->b_data == NULL) { 3710 /* 3711 * We are on the eviction list; process this buffer now 3712 * but let arc_do_user_evicts() do the reaping. 3713 */ 3714 buf->b_efunc = NULL; 3715 mutex_exit(&buf->b_evict_lock); 3716 VERIFY0(efunc(private)); 3717 return (B_TRUE); 3718 } 3719 hash_lock = HDR_LOCK(hdr); 3720 mutex_enter(hash_lock); 3721 hdr = buf->b_hdr; 3722 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3723 3724 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt); 3725 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu); 3726 3727 buf->b_efunc = NULL; 3728 buf->b_private = NULL; 3729 3730 if (hdr->b_datacnt > 1) { 3731 mutex_exit(&buf->b_evict_lock); 3732 arc_buf_destroy(buf, FALSE, TRUE); 3733 } else { 3734 ASSERT(buf == hdr->b_buf); 3735 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3736 mutex_exit(&buf->b_evict_lock); 3737 } 3738 3739 mutex_exit(hash_lock); 3740 VERIFY0(efunc(private)); 3741 return (B_TRUE); 3742} 3743 3744/* 3745 * Release this buffer from the cache, making it an anonymous buffer. This 3746 * must be done after a read and prior to modifying the buffer contents. 3747 * If the buffer has more than one reference, we must make 3748 * a new hdr for the buffer. 3749 */ 3750void 3751arc_release(arc_buf_t *buf, void *tag) 3752{ 3753 arc_buf_hdr_t *hdr; 3754 kmutex_t *hash_lock = NULL; 3755 l2arc_buf_hdr_t *l2hdr; 3756 uint64_t buf_size; 3757 3758 /* 3759 * It would be nice to assert that if it's DMU metadata (level > 3760 * 0 || it's the dnode file), then it must be syncing context. 3761 * But we don't know that information at this level. 3762 */ 3763 3764 mutex_enter(&buf->b_evict_lock); 3765 hdr = buf->b_hdr; 3766 3767 /* this buffer is not on any list */ 3768 ASSERT(refcount_count(&hdr->b_refcnt) > 0); 3769 3770 if (hdr->b_state == arc_anon) { 3771 /* this buffer is already released */ 3772 ASSERT(buf->b_efunc == NULL); 3773 } else { 3774 hash_lock = HDR_LOCK(hdr); 3775 mutex_enter(hash_lock); 3776 hdr = buf->b_hdr; 3777 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3778 } 3779 3780 l2hdr = hdr->b_l2hdr; 3781 if (l2hdr) { 3782 mutex_enter(&l2arc_buflist_mtx); 3783 arc_buf_l2_cdata_free(hdr); 3784 hdr->b_l2hdr = NULL; 3785 list_remove(l2hdr->b_dev->l2ad_buflist, hdr); 3786 } 3787 buf_size = hdr->b_size; 3788 3789 /* 3790 * Do we have more than one buf? 3791 */ 3792 if (hdr->b_datacnt > 1) { 3793 arc_buf_hdr_t *nhdr; 3794 arc_buf_t **bufp; 3795 uint64_t blksz = hdr->b_size; 3796 uint64_t spa = hdr->b_spa; 3797 arc_buf_contents_t type = hdr->b_type; 3798 uint32_t flags = hdr->b_flags; 3799 3800 ASSERT(hdr->b_buf != buf || buf->b_next != NULL); 3801 /* 3802 * Pull the data off of this hdr and attach it to 3803 * a new anonymous hdr. 3804 */ 3805 (void) remove_reference(hdr, hash_lock, tag); 3806 bufp = &hdr->b_buf; 3807 while (*bufp != buf) 3808 bufp = &(*bufp)->b_next; 3809 *bufp = buf->b_next; 3810 buf->b_next = NULL; 3811 3812 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size); 3813 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size); 3814 if (refcount_is_zero(&hdr->b_refcnt)) { 3815 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type]; 3816 ASSERT3U(*size, >=, hdr->b_size); 3817 atomic_add_64(size, -hdr->b_size); 3818 } 3819 3820 /* 3821 * We're releasing a duplicate user data buffer, update 3822 * our statistics accordingly. 3823 */ 3824 if (hdr->b_type == ARC_BUFC_DATA) { 3825 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3826 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3827 -hdr->b_size); 3828 } 3829 hdr->b_datacnt -= 1; 3830 arc_cksum_verify(buf); 3831#ifdef illumos 3832 arc_buf_unwatch(buf); 3833#endif /* illumos */ 3834 3835 mutex_exit(hash_lock); 3836 3837 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 3838 nhdr->b_size = blksz; 3839 nhdr->b_spa = spa; 3840 nhdr->b_type = type; 3841 nhdr->b_buf = buf; 3842 nhdr->b_state = arc_anon; 3843 nhdr->b_arc_access = 0; 3844 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 3845 nhdr->b_l2hdr = NULL; 3846 nhdr->b_datacnt = 1; 3847 nhdr->b_freeze_cksum = NULL; 3848 (void) refcount_add(&nhdr->b_refcnt, tag); 3849 buf->b_hdr = nhdr; 3850 mutex_exit(&buf->b_evict_lock); 3851 atomic_add_64(&arc_anon->arcs_size, blksz); 3852 } else { 3853 mutex_exit(&buf->b_evict_lock); 3854 ASSERT(refcount_count(&hdr->b_refcnt) == 1); 3855 ASSERT(!list_link_active(&hdr->b_arc_node)); 3856 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3857 if (hdr->b_state != arc_anon) 3858 arc_change_state(arc_anon, hdr, hash_lock); 3859 hdr->b_arc_access = 0; 3860 if (hash_lock) 3861 mutex_exit(hash_lock); 3862 3863 buf_discard_identity(hdr); 3864 arc_buf_thaw(buf); 3865 } 3866 buf->b_efunc = NULL; 3867 buf->b_private = NULL; 3868 3869 if (l2hdr) { 3870 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 3871 vdev_space_update(l2hdr->b_dev->l2ad_vdev, 3872 -l2hdr->b_asize, 0, 0); 3873 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr, 3874 l2hdr->b_asize, 0); 3875 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t)); 3876 ARCSTAT_INCR(arcstat_l2_size, -buf_size); 3877 mutex_exit(&l2arc_buflist_mtx); 3878 } 3879} 3880 3881int 3882arc_released(arc_buf_t *buf) 3883{ 3884 int released; 3885 3886 mutex_enter(&buf->b_evict_lock); 3887 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon); 3888 mutex_exit(&buf->b_evict_lock); 3889 return (released); 3890} 3891 3892#ifdef ZFS_DEBUG 3893int 3894arc_referenced(arc_buf_t *buf) 3895{ 3896 int referenced; 3897 3898 mutex_enter(&buf->b_evict_lock); 3899 referenced = (refcount_count(&buf->b_hdr->b_refcnt)); 3900 mutex_exit(&buf->b_evict_lock); 3901 return (referenced); 3902} 3903#endif 3904 3905static void 3906arc_write_ready(zio_t *zio) 3907{ 3908 arc_write_callback_t *callback = zio->io_private; 3909 arc_buf_t *buf = callback->awcb_buf; 3910 arc_buf_hdr_t *hdr = buf->b_hdr; 3911 3912 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt)); 3913 callback->awcb_ready(zio, buf, callback->awcb_private); 3914 3915 /* 3916 * If the IO is already in progress, then this is a re-write 3917 * attempt, so we need to thaw and re-compute the cksum. 3918 * It is the responsibility of the callback to handle the 3919 * accounting for any re-write attempt. 3920 */ 3921 if (HDR_IO_IN_PROGRESS(hdr)) { 3922 mutex_enter(&hdr->b_freeze_lock); 3923 if (hdr->b_freeze_cksum != NULL) { 3924 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 3925 hdr->b_freeze_cksum = NULL; 3926 } 3927 mutex_exit(&hdr->b_freeze_lock); 3928 } 3929 arc_cksum_compute(buf, B_FALSE); 3930 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 3931} 3932 3933/* 3934 * The SPA calls this callback for each physical write that happens on behalf 3935 * of a logical write. See the comment in dbuf_write_physdone() for details. 3936 */ 3937static void 3938arc_write_physdone(zio_t *zio) 3939{ 3940 arc_write_callback_t *cb = zio->io_private; 3941 if (cb->awcb_physdone != NULL) 3942 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 3943} 3944 3945static void 3946arc_write_done(zio_t *zio) 3947{ 3948 arc_write_callback_t *callback = zio->io_private; 3949 arc_buf_t *buf = callback->awcb_buf; 3950 arc_buf_hdr_t *hdr = buf->b_hdr; 3951 3952 ASSERT(hdr->b_acb == NULL); 3953 3954 if (zio->io_error == 0) { 3955 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 3956 buf_discard_identity(hdr); 3957 } else { 3958 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 3959 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 3960 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0]; 3961 } 3962 } else { 3963 ASSERT(BUF_EMPTY(hdr)); 3964 } 3965 3966 /* 3967 * If the block to be written was all-zero or compressed enough to be 3968 * embedded in the BP, no write was performed so there will be no 3969 * dva/birth/checksum. The buffer must therefore remain anonymous 3970 * (and uncached). 3971 */ 3972 if (!BUF_EMPTY(hdr)) { 3973 arc_buf_hdr_t *exists; 3974 kmutex_t *hash_lock; 3975 3976 ASSERT(zio->io_error == 0); 3977 3978 arc_cksum_verify(buf); 3979 3980 exists = buf_hash_insert(hdr, &hash_lock); 3981 if (exists) { 3982 /* 3983 * This can only happen if we overwrite for 3984 * sync-to-convergence, because we remove 3985 * buffers from the hash table when we arc_free(). 3986 */ 3987 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 3988 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 3989 panic("bad overwrite, hdr=%p exists=%p", 3990 (void *)hdr, (void *)exists); 3991 ASSERT(refcount_is_zero(&exists->b_refcnt)); 3992 arc_change_state(arc_anon, exists, hash_lock); 3993 mutex_exit(hash_lock); 3994 arc_hdr_destroy(exists); 3995 exists = buf_hash_insert(hdr, &hash_lock); 3996 ASSERT3P(exists, ==, NULL); 3997 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 3998 /* nopwrite */ 3999 ASSERT(zio->io_prop.zp_nopwrite); 4000 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4001 panic("bad nopwrite, hdr=%p exists=%p", 4002 (void *)hdr, (void *)exists); 4003 } else { 4004 /* Dedup */ 4005 ASSERT(hdr->b_datacnt == 1); 4006 ASSERT(hdr->b_state == arc_anon); 4007 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4008 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4009 } 4010 } 4011 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4012 /* if it's not anon, we are doing a scrub */ 4013 if (!exists && hdr->b_state == arc_anon) 4014 arc_access(hdr, hash_lock); 4015 mutex_exit(hash_lock); 4016 } else { 4017 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4018 } 4019 4020 ASSERT(!refcount_is_zero(&hdr->b_refcnt)); 4021 callback->awcb_done(zio, buf, callback->awcb_private); 4022 4023 kmem_free(callback, sizeof (arc_write_callback_t)); 4024} 4025 4026zio_t * 4027arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4028 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4029 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4030 arc_done_func_t *done, void *private, zio_priority_t priority, 4031 int zio_flags, const zbookmark_phys_t *zb) 4032{ 4033 arc_buf_hdr_t *hdr = buf->b_hdr; 4034 arc_write_callback_t *callback; 4035 zio_t *zio; 4036 4037 ASSERT(ready != NULL); 4038 ASSERT(done != NULL); 4039 ASSERT(!HDR_IO_ERROR(hdr)); 4040 ASSERT((hdr->b_flags & ARC_FLAG_IO_IN_PROGRESS) == 0); 4041 ASSERT(hdr->b_acb == NULL); 4042 if (l2arc) 4043 hdr->b_flags |= ARC_FLAG_L2CACHE; 4044 if (l2arc_compress) 4045 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4046 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4047 callback->awcb_ready = ready; 4048 callback->awcb_physdone = physdone; 4049 callback->awcb_done = done; 4050 callback->awcb_private = private; 4051 callback->awcb_buf = buf; 4052 4053 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4054 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4055 priority, zio_flags, zb); 4056 4057 return (zio); 4058} 4059 4060static int 4061arc_memory_throttle(uint64_t reserve, uint64_t txg) 4062{ 4063#ifdef _KERNEL 4064 uint64_t available_memory = ptob(freemem); 4065 static uint64_t page_load = 0; 4066 static uint64_t last_txg = 0; 4067 4068#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4069 available_memory = 4070 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 4071#endif 4072 4073 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 4074 return (0); 4075 4076 if (txg > last_txg) { 4077 last_txg = txg; 4078 page_load = 0; 4079 } 4080 /* 4081 * If we are in pageout, we know that memory is already tight, 4082 * the arc is already going to be evicting, so we just want to 4083 * continue to let page writes occur as quickly as possible. 4084 */ 4085 if (curproc == pageproc) { 4086 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4087 return (SET_ERROR(ERESTART)); 4088 /* Note: reserve is inflated, so we deflate */ 4089 page_load += reserve / 8; 4090 return (0); 4091 } else if (page_load > 0 && arc_reclaim_needed()) { 4092 /* memory is low, delay before restarting */ 4093 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4094 return (SET_ERROR(EAGAIN)); 4095 } 4096 page_load = 0; 4097#endif 4098 return (0); 4099} 4100 4101void 4102arc_tempreserve_clear(uint64_t reserve) 4103{ 4104 atomic_add_64(&arc_tempreserve, -reserve); 4105 ASSERT((int64_t)arc_tempreserve >= 0); 4106} 4107 4108int 4109arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4110{ 4111 int error; 4112 uint64_t anon_size; 4113 4114 if (reserve > arc_c/4 && !arc_no_grow) { 4115 arc_c = MIN(arc_c_max, reserve * 4); 4116 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 4117 } 4118 if (reserve > arc_c) 4119 return (SET_ERROR(ENOMEM)); 4120 4121 /* 4122 * Don't count loaned bufs as in flight dirty data to prevent long 4123 * network delays from blocking transactions that are ready to be 4124 * assigned to a txg. 4125 */ 4126 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 4127 4128 /* 4129 * Writes will, almost always, require additional memory allocations 4130 * in order to compress/encrypt/etc the data. We therefore need to 4131 * make sure that there is sufficient available memory for this. 4132 */ 4133 error = arc_memory_throttle(reserve, txg); 4134 if (error != 0) 4135 return (error); 4136 4137 /* 4138 * Throttle writes when the amount of dirty data in the cache 4139 * gets too large. We try to keep the cache less than half full 4140 * of dirty blocks so that our sync times don't grow too large. 4141 * Note: if two requests come in concurrently, we might let them 4142 * both succeed, when one of them should fail. Not a huge deal. 4143 */ 4144 4145 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4146 anon_size > arc_c / 4) { 4147 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4148 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4149 arc_tempreserve>>10, 4150 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4151 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4152 reserve>>10, arc_c>>10); 4153 return (SET_ERROR(ERESTART)); 4154 } 4155 atomic_add_64(&arc_tempreserve, reserve); 4156 return (0); 4157} 4158 4159static kmutex_t arc_lowmem_lock; 4160#ifdef _KERNEL 4161static eventhandler_tag arc_event_lowmem = NULL; 4162 4163static void 4164arc_lowmem(void *arg __unused, int howto __unused) 4165{ 4166 4167 /* Serialize access via arc_lowmem_lock. */ 4168 mutex_enter(&arc_lowmem_lock); 4169 mutex_enter(&arc_reclaim_thr_lock); 4170 needfree = 1; 4171 DTRACE_PROBE(arc__needfree); 4172 cv_signal(&arc_reclaim_thr_cv); 4173 4174 /* 4175 * It is unsafe to block here in arbitrary threads, because we can come 4176 * here from ARC itself and may hold ARC locks and thus risk a deadlock 4177 * with ARC reclaim thread. 4178 */ 4179 if (curproc == pageproc) { 4180 while (needfree) 4181 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0); 4182 } 4183 mutex_exit(&arc_reclaim_thr_lock); 4184 mutex_exit(&arc_lowmem_lock); 4185} 4186#endif 4187 4188void 4189arc_init(void) 4190{ 4191 int i, prefetch_tunable_set = 0; 4192 4193 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4194 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 4195 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL); 4196 4197 /* Convert seconds to clock ticks */ 4198 arc_min_prefetch_lifespan = 1 * hz; 4199 4200 /* Start out with 1/8 of all memory */ 4201 arc_c = kmem_size() / 8; 4202 4203#ifdef sun 4204#ifdef _KERNEL 4205 /* 4206 * On architectures where the physical memory can be larger 4207 * than the addressable space (intel in 32-bit mode), we may 4208 * need to limit the cache to 1/8 of VM size. 4209 */ 4210 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4211#endif 4212#endif /* sun */ 4213 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 4214 arc_c_min = MAX(arc_c / 4, 16 << 20); 4215 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 4216 if (arc_c * 8 >= 1 << 30) 4217 arc_c_max = (arc_c * 8) - (1 << 30); 4218 else 4219 arc_c_max = arc_c_min; 4220 arc_c_max = MAX(arc_c * 5, arc_c_max); 4221 4222#ifdef _KERNEL 4223 /* 4224 * Allow the tunables to override our calculations if they are 4225 * reasonable (ie. over 16MB) 4226 */ 4227 if (zfs_arc_max > 16 << 20 && zfs_arc_max < kmem_size()) 4228 arc_c_max = zfs_arc_max; 4229 if (zfs_arc_min > 16 << 20 && zfs_arc_min <= arc_c_max) 4230 arc_c_min = zfs_arc_min; 4231#endif 4232 4233 arc_c = arc_c_max; 4234 arc_p = (arc_c >> 1); 4235 4236 /* limit meta-data to 1/4 of the arc capacity */ 4237 arc_meta_limit = arc_c_max / 4; 4238 4239 /* Allow the tunable to override if it is reasonable */ 4240 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4241 arc_meta_limit = zfs_arc_meta_limit; 4242 4243 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4244 arc_c_min = arc_meta_limit / 2; 4245 4246 if (zfs_arc_meta_min > 0) { 4247 arc_meta_min = zfs_arc_meta_min; 4248 } else { 4249 arc_meta_min = arc_c_min / 2; 4250 } 4251 4252 if (zfs_arc_grow_retry > 0) 4253 arc_grow_retry = zfs_arc_grow_retry; 4254 4255 if (zfs_arc_shrink_shift > 0) 4256 arc_shrink_shift = zfs_arc_shrink_shift; 4257 4258 if (zfs_arc_p_min_shift > 0) 4259 arc_p_min_shift = zfs_arc_p_min_shift; 4260 4261 /* if kmem_flags are set, lets try to use less memory */ 4262 if (kmem_debugging()) 4263 arc_c = arc_c / 2; 4264 if (arc_c < arc_c_min) 4265 arc_c = arc_c_min; 4266 4267 zfs_arc_min = arc_c_min; 4268 zfs_arc_max = arc_c_max; 4269 4270 arc_anon = &ARC_anon; 4271 arc_mru = &ARC_mru; 4272 arc_mru_ghost = &ARC_mru_ghost; 4273 arc_mfu = &ARC_mfu; 4274 arc_mfu_ghost = &ARC_mfu_ghost; 4275 arc_l2c_only = &ARC_l2c_only; 4276 arc_size = 0; 4277 4278 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4279 mutex_init(&arc_anon->arcs_locks[i].arcs_lock, 4280 NULL, MUTEX_DEFAULT, NULL); 4281 mutex_init(&arc_mru->arcs_locks[i].arcs_lock, 4282 NULL, MUTEX_DEFAULT, NULL); 4283 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock, 4284 NULL, MUTEX_DEFAULT, NULL); 4285 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock, 4286 NULL, MUTEX_DEFAULT, NULL); 4287 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock, 4288 NULL, MUTEX_DEFAULT, NULL); 4289 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock, 4290 NULL, MUTEX_DEFAULT, NULL); 4291 4292 list_create(&arc_mru->arcs_lists[i], 4293 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4294 list_create(&arc_mru_ghost->arcs_lists[i], 4295 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4296 list_create(&arc_mfu->arcs_lists[i], 4297 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4298 list_create(&arc_mfu_ghost->arcs_lists[i], 4299 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4300 list_create(&arc_mfu_ghost->arcs_lists[i], 4301 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4302 list_create(&arc_l2c_only->arcs_lists[i], 4303 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); 4304 } 4305 4306 buf_init(); 4307 4308 arc_thread_exit = 0; 4309 arc_eviction_list = NULL; 4310 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 4311 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4312 4313 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4314 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4315 4316 if (arc_ksp != NULL) { 4317 arc_ksp->ks_data = &arc_stats; 4318 kstat_install(arc_ksp); 4319 } 4320 4321 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 4322 TS_RUN, minclsyspri); 4323 4324#ifdef _KERNEL 4325 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 4326 EVENTHANDLER_PRI_FIRST); 4327#endif 4328 4329 arc_dead = FALSE; 4330 arc_warm = B_FALSE; 4331 4332 /* 4333 * Calculate maximum amount of dirty data per pool. 4334 * 4335 * If it has been set by /etc/system, take that. 4336 * Otherwise, use a percentage of physical memory defined by 4337 * zfs_dirty_data_max_percent (default 10%) with a cap at 4338 * zfs_dirty_data_max_max (default 4GB). 4339 */ 4340 if (zfs_dirty_data_max == 0) { 4341 zfs_dirty_data_max = ptob(physmem) * 4342 zfs_dirty_data_max_percent / 100; 4343 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 4344 zfs_dirty_data_max_max); 4345 } 4346 4347#ifdef _KERNEL 4348 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 4349 prefetch_tunable_set = 1; 4350 4351#ifdef __i386__ 4352 if (prefetch_tunable_set == 0) { 4353 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 4354 "-- to enable,\n"); 4355 printf(" add \"vfs.zfs.prefetch_disable=0\" " 4356 "to /boot/loader.conf.\n"); 4357 zfs_prefetch_disable = 1; 4358 } 4359#else 4360 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 4361 prefetch_tunable_set == 0) { 4362 printf("ZFS NOTICE: Prefetch is disabled by default if less " 4363 "than 4GB of RAM is present;\n" 4364 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 4365 "to /boot/loader.conf.\n"); 4366 zfs_prefetch_disable = 1; 4367 } 4368#endif 4369 /* Warn about ZFS memory and address space requirements. */ 4370 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 4371 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 4372 "expect unstable behavior.\n"); 4373 } 4374 if (kmem_size() < 512 * (1 << 20)) { 4375 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 4376 "expect unstable behavior.\n"); 4377 printf(" Consider tuning vm.kmem_size and " 4378 "vm.kmem_size_max\n"); 4379 printf(" in /boot/loader.conf.\n"); 4380 } 4381#endif 4382} 4383 4384void 4385arc_fini(void) 4386{ 4387 int i; 4388 4389 mutex_enter(&arc_reclaim_thr_lock); 4390 arc_thread_exit = 1; 4391 cv_signal(&arc_reclaim_thr_cv); 4392 while (arc_thread_exit != 0) 4393 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 4394 mutex_exit(&arc_reclaim_thr_lock); 4395 4396 arc_flush(NULL); 4397 4398 arc_dead = TRUE; 4399 4400 if (arc_ksp != NULL) { 4401 kstat_delete(arc_ksp); 4402 arc_ksp = NULL; 4403 } 4404 4405 mutex_destroy(&arc_eviction_mtx); 4406 mutex_destroy(&arc_reclaim_thr_lock); 4407 cv_destroy(&arc_reclaim_thr_cv); 4408 4409 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4410 list_destroy(&arc_mru->arcs_lists[i]); 4411 list_destroy(&arc_mru_ghost->arcs_lists[i]); 4412 list_destroy(&arc_mfu->arcs_lists[i]); 4413 list_destroy(&arc_mfu_ghost->arcs_lists[i]); 4414 list_destroy(&arc_l2c_only->arcs_lists[i]); 4415 4416 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock); 4417 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock); 4418 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock); 4419 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock); 4420 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock); 4421 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock); 4422 } 4423 4424 buf_fini(); 4425 4426 ASSERT(arc_loaned_bytes == 0); 4427 4428 mutex_destroy(&arc_lowmem_lock); 4429#ifdef _KERNEL 4430 if (arc_event_lowmem != NULL) 4431 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 4432#endif 4433} 4434 4435/* 4436 * Level 2 ARC 4437 * 4438 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 4439 * It uses dedicated storage devices to hold cached data, which are populated 4440 * using large infrequent writes. The main role of this cache is to boost 4441 * the performance of random read workloads. The intended L2ARC devices 4442 * include short-stroked disks, solid state disks, and other media with 4443 * substantially faster read latency than disk. 4444 * 4445 * +-----------------------+ 4446 * | ARC | 4447 * +-----------------------+ 4448 * | ^ ^ 4449 * | | | 4450 * l2arc_feed_thread() arc_read() 4451 * | | | 4452 * | l2arc read | 4453 * V | | 4454 * +---------------+ | 4455 * | L2ARC | | 4456 * +---------------+ | 4457 * | ^ | 4458 * l2arc_write() | | 4459 * | | | 4460 * V | | 4461 * +-------+ +-------+ 4462 * | vdev | | vdev | 4463 * | cache | | cache | 4464 * +-------+ +-------+ 4465 * +=========+ .-----. 4466 * : L2ARC : |-_____-| 4467 * : devices : | Disks | 4468 * +=========+ `-_____-' 4469 * 4470 * Read requests are satisfied from the following sources, in order: 4471 * 4472 * 1) ARC 4473 * 2) vdev cache of L2ARC devices 4474 * 3) L2ARC devices 4475 * 4) vdev cache of disks 4476 * 5) disks 4477 * 4478 * Some L2ARC device types exhibit extremely slow write performance. 4479 * To accommodate for this there are some significant differences between 4480 * the L2ARC and traditional cache design: 4481 * 4482 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 4483 * the ARC behave as usual, freeing buffers and placing headers on ghost 4484 * lists. The ARC does not send buffers to the L2ARC during eviction as 4485 * this would add inflated write latencies for all ARC memory pressure. 4486 * 4487 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 4488 * It does this by periodically scanning buffers from the eviction-end of 4489 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 4490 * not already there. It scans until a headroom of buffers is satisfied, 4491 * which itself is a buffer for ARC eviction. If a compressible buffer is 4492 * found during scanning and selected for writing to an L2ARC device, we 4493 * temporarily boost scanning headroom during the next scan cycle to make 4494 * sure we adapt to compression effects (which might significantly reduce 4495 * the data volume we write to L2ARC). The thread that does this is 4496 * l2arc_feed_thread(), illustrated below; example sizes are included to 4497 * provide a better sense of ratio than this diagram: 4498 * 4499 * head --> tail 4500 * +---------------------+----------+ 4501 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 4502 * +---------------------+----------+ | o L2ARC eligible 4503 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 4504 * +---------------------+----------+ | 4505 * 15.9 Gbytes ^ 32 Mbytes | 4506 * headroom | 4507 * l2arc_feed_thread() 4508 * | 4509 * l2arc write hand <--[oooo]--' 4510 * | 8 Mbyte 4511 * | write max 4512 * V 4513 * +==============================+ 4514 * L2ARC dev |####|#|###|###| |####| ... | 4515 * +==============================+ 4516 * 32 Gbytes 4517 * 4518 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 4519 * evicted, then the L2ARC has cached a buffer much sooner than it probably 4520 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 4521 * safe to say that this is an uncommon case, since buffers at the end of 4522 * the ARC lists have moved there due to inactivity. 4523 * 4524 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 4525 * then the L2ARC simply misses copying some buffers. This serves as a 4526 * pressure valve to prevent heavy read workloads from both stalling the ARC 4527 * with waits and clogging the L2ARC with writes. This also helps prevent 4528 * the potential for the L2ARC to churn if it attempts to cache content too 4529 * quickly, such as during backups of the entire pool. 4530 * 4531 * 5. After system boot and before the ARC has filled main memory, there are 4532 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 4533 * lists can remain mostly static. Instead of searching from tail of these 4534 * lists as pictured, the l2arc_feed_thread() will search from the list heads 4535 * for eligible buffers, greatly increasing its chance of finding them. 4536 * 4537 * The L2ARC device write speed is also boosted during this time so that 4538 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 4539 * there are no L2ARC reads, and no fear of degrading read performance 4540 * through increased writes. 4541 * 4542 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 4543 * the vdev queue can aggregate them into larger and fewer writes. Each 4544 * device is written to in a rotor fashion, sweeping writes through 4545 * available space then repeating. 4546 * 4547 * 7. The L2ARC does not store dirty content. It never needs to flush 4548 * write buffers back to disk based storage. 4549 * 4550 * 8. If an ARC buffer is written (and dirtied) which also exists in the 4551 * L2ARC, the now stale L2ARC buffer is immediately dropped. 4552 * 4553 * The performance of the L2ARC can be tweaked by a number of tunables, which 4554 * may be necessary for different workloads: 4555 * 4556 * l2arc_write_max max write bytes per interval 4557 * l2arc_write_boost extra write bytes during device warmup 4558 * l2arc_noprefetch skip caching prefetched buffers 4559 * l2arc_headroom number of max device writes to precache 4560 * l2arc_headroom_boost when we find compressed buffers during ARC 4561 * scanning, we multiply headroom by this 4562 * percentage factor for the next scan cycle, 4563 * since more compressed buffers are likely to 4564 * be present 4565 * l2arc_feed_secs seconds between L2ARC writing 4566 * 4567 * Tunables may be removed or added as future performance improvements are 4568 * integrated, and also may become zpool properties. 4569 * 4570 * There are three key functions that control how the L2ARC warms up: 4571 * 4572 * l2arc_write_eligible() check if a buffer is eligible to cache 4573 * l2arc_write_size() calculate how much to write 4574 * l2arc_write_interval() calculate sleep delay between writes 4575 * 4576 * These three functions determine what to write, how much, and how quickly 4577 * to send writes. 4578 */ 4579 4580static boolean_t 4581l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 4582{ 4583 /* 4584 * A buffer is *not* eligible for the L2ARC if it: 4585 * 1. belongs to a different spa. 4586 * 2. is already cached on the L2ARC. 4587 * 3. has an I/O in progress (it may be an incomplete read). 4588 * 4. is flagged not eligible (zfs property). 4589 */ 4590 if (hdr->b_spa != spa_guid) { 4591 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 4592 return (B_FALSE); 4593 } 4594 if (hdr->b_l2hdr != NULL) { 4595 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 4596 return (B_FALSE); 4597 } 4598 if (HDR_IO_IN_PROGRESS(hdr)) { 4599 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 4600 return (B_FALSE); 4601 } 4602 if (!HDR_L2CACHE(hdr)) { 4603 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 4604 return (B_FALSE); 4605 } 4606 4607 return (B_TRUE); 4608} 4609 4610static uint64_t 4611l2arc_write_size(void) 4612{ 4613 uint64_t size; 4614 4615 /* 4616 * Make sure our globals have meaningful values in case the user 4617 * altered them. 4618 */ 4619 size = l2arc_write_max; 4620 if (size == 0) { 4621 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 4622 "be greater than zero, resetting it to the default (%d)", 4623 L2ARC_WRITE_SIZE); 4624 size = l2arc_write_max = L2ARC_WRITE_SIZE; 4625 } 4626 4627 if (arc_warm == B_FALSE) 4628 size += l2arc_write_boost; 4629 4630 return (size); 4631 4632} 4633 4634static clock_t 4635l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 4636{ 4637 clock_t interval, next, now; 4638 4639 /* 4640 * If the ARC lists are busy, increase our write rate; if the 4641 * lists are stale, idle back. This is achieved by checking 4642 * how much we previously wrote - if it was more than half of 4643 * what we wanted, schedule the next write much sooner. 4644 */ 4645 if (l2arc_feed_again && wrote > (wanted / 2)) 4646 interval = (hz * l2arc_feed_min_ms) / 1000; 4647 else 4648 interval = hz * l2arc_feed_secs; 4649 4650 now = ddi_get_lbolt(); 4651 next = MAX(now, MIN(now + interval, began + interval)); 4652 4653 return (next); 4654} 4655 4656static void 4657l2arc_hdr_stat_add(void) 4658{ 4659 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE); 4660 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE); 4661} 4662 4663static void 4664l2arc_hdr_stat_remove(void) 4665{ 4666 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE)); 4667 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE); 4668} 4669 4670/* 4671 * Cycle through L2ARC devices. This is how L2ARC load balances. 4672 * If a device is returned, this also returns holding the spa config lock. 4673 */ 4674static l2arc_dev_t * 4675l2arc_dev_get_next(void) 4676{ 4677 l2arc_dev_t *first, *next = NULL; 4678 4679 /* 4680 * Lock out the removal of spas (spa_namespace_lock), then removal 4681 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 4682 * both locks will be dropped and a spa config lock held instead. 4683 */ 4684 mutex_enter(&spa_namespace_lock); 4685 mutex_enter(&l2arc_dev_mtx); 4686 4687 /* if there are no vdevs, there is nothing to do */ 4688 if (l2arc_ndev == 0) 4689 goto out; 4690 4691 first = NULL; 4692 next = l2arc_dev_last; 4693 do { 4694 /* loop around the list looking for a non-faulted vdev */ 4695 if (next == NULL) { 4696 next = list_head(l2arc_dev_list); 4697 } else { 4698 next = list_next(l2arc_dev_list, next); 4699 if (next == NULL) 4700 next = list_head(l2arc_dev_list); 4701 } 4702 4703 /* if we have come back to the start, bail out */ 4704 if (first == NULL) 4705 first = next; 4706 else if (next == first) 4707 break; 4708 4709 } while (vdev_is_dead(next->l2ad_vdev)); 4710 4711 /* if we were unable to find any usable vdevs, return NULL */ 4712 if (vdev_is_dead(next->l2ad_vdev)) 4713 next = NULL; 4714 4715 l2arc_dev_last = next; 4716 4717out: 4718 mutex_exit(&l2arc_dev_mtx); 4719 4720 /* 4721 * Grab the config lock to prevent the 'next' device from being 4722 * removed while we are writing to it. 4723 */ 4724 if (next != NULL) 4725 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4726 mutex_exit(&spa_namespace_lock); 4727 4728 return (next); 4729} 4730 4731/* 4732 * Free buffers that were tagged for destruction. 4733 */ 4734static void 4735l2arc_do_free_on_write() 4736{ 4737 list_t *buflist; 4738 l2arc_data_free_t *df, *df_prev; 4739 4740 mutex_enter(&l2arc_free_on_write_mtx); 4741 buflist = l2arc_free_on_write; 4742 4743 for (df = list_tail(buflist); df; df = df_prev) { 4744 df_prev = list_prev(buflist, df); 4745 ASSERT(df->l2df_data != NULL); 4746 ASSERT(df->l2df_func != NULL); 4747 df->l2df_func(df->l2df_data, df->l2df_size); 4748 list_remove(buflist, df); 4749 kmem_free(df, sizeof (l2arc_data_free_t)); 4750 } 4751 4752 mutex_exit(&l2arc_free_on_write_mtx); 4753} 4754 4755/* 4756 * A write to a cache device has completed. Update all headers to allow 4757 * reads from these buffers to begin. 4758 */ 4759static void 4760l2arc_write_done(zio_t *zio) 4761{ 4762 l2arc_write_callback_t *cb; 4763 l2arc_dev_t *dev; 4764 list_t *buflist; 4765 arc_buf_hdr_t *head, *hdr, *hdr_prev; 4766 l2arc_buf_hdr_t *abl2; 4767 kmutex_t *hash_lock; 4768 int64_t bytes_dropped = 0; 4769 4770 cb = zio->io_private; 4771 ASSERT(cb != NULL); 4772 dev = cb->l2wcb_dev; 4773 ASSERT(dev != NULL); 4774 head = cb->l2wcb_head; 4775 ASSERT(head != NULL); 4776 buflist = dev->l2ad_buflist; 4777 ASSERT(buflist != NULL); 4778 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4779 l2arc_write_callback_t *, cb); 4780 4781 if (zio->io_error != 0) 4782 ARCSTAT_BUMP(arcstat_l2_writes_error); 4783 4784 mutex_enter(&l2arc_buflist_mtx); 4785 4786 /* 4787 * All writes completed, or an error was hit. 4788 */ 4789 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 4790 hdr_prev = list_prev(buflist, hdr); 4791 abl2 = hdr->b_l2hdr; 4792 4793 /* 4794 * Release the temporary compressed buffer as soon as possible. 4795 */ 4796 if (abl2->b_compress != ZIO_COMPRESS_OFF) 4797 l2arc_release_cdata_buf(hdr); 4798 4799 hash_lock = HDR_LOCK(hdr); 4800 if (!mutex_tryenter(hash_lock)) { 4801 /* 4802 * This buffer misses out. It may be in a stage 4803 * of eviction. Its ARC_L2_WRITING flag will be 4804 * left set, denying reads to this buffer. 4805 */ 4806 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4807 continue; 4808 } 4809 4810 if (zio->io_error != 0) { 4811 /* 4812 * Error - drop L2ARC entry. 4813 */ 4814 list_remove(buflist, hdr); 4815 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 4816 bytes_dropped += abl2->b_asize; 4817 hdr->b_l2hdr = NULL; 4818 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr, 4819 abl2->b_asize, 0); 4820 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 4821 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 4822 } 4823 4824 /* 4825 * Allow ARC to begin reads to this L2ARC entry. 4826 */ 4827 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 4828 4829 mutex_exit(hash_lock); 4830 } 4831 4832 atomic_inc_64(&l2arc_writes_done); 4833 list_remove(buflist, head); 4834 kmem_cache_free(hdr_cache, head); 4835 mutex_exit(&l2arc_buflist_mtx); 4836 4837 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 4838 4839 l2arc_do_free_on_write(); 4840 4841 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4842} 4843 4844/* 4845 * A read to a cache device completed. Validate buffer contents before 4846 * handing over to the regular ARC routines. 4847 */ 4848static void 4849l2arc_read_done(zio_t *zio) 4850{ 4851 l2arc_read_callback_t *cb; 4852 arc_buf_hdr_t *hdr; 4853 arc_buf_t *buf; 4854 kmutex_t *hash_lock; 4855 int equal; 4856 4857 ASSERT(zio->io_vd != NULL); 4858 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4859 4860 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4861 4862 cb = zio->io_private; 4863 ASSERT(cb != NULL); 4864 buf = cb->l2rcb_buf; 4865 ASSERT(buf != NULL); 4866 4867 hash_lock = HDR_LOCK(buf->b_hdr); 4868 mutex_enter(hash_lock); 4869 hdr = buf->b_hdr; 4870 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4871 4872 /* 4873 * If the buffer was compressed, decompress it first. 4874 */ 4875 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 4876 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 4877 ASSERT(zio->io_data != NULL); 4878 4879 /* 4880 * Check this survived the L2ARC journey. 4881 */ 4882 equal = arc_cksum_equal(buf); 4883 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4884 mutex_exit(hash_lock); 4885 zio->io_private = buf; 4886 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4887 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4888 arc_read_done(zio); 4889 } else { 4890 mutex_exit(hash_lock); 4891 /* 4892 * Buffer didn't survive caching. Increment stats and 4893 * reissue to the original storage device. 4894 */ 4895 if (zio->io_error != 0) { 4896 ARCSTAT_BUMP(arcstat_l2_io_error); 4897 } else { 4898 zio->io_error = SET_ERROR(EIO); 4899 } 4900 if (!equal) 4901 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4902 4903 /* 4904 * If there's no waiter, issue an async i/o to the primary 4905 * storage now. If there *is* a waiter, the caller must 4906 * issue the i/o in a context where it's OK to block. 4907 */ 4908 if (zio->io_waiter == NULL) { 4909 zio_t *pio = zio_unique_parent(zio); 4910 4911 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4912 4913 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4914 buf->b_data, zio->io_size, arc_read_done, buf, 4915 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4916 } 4917 } 4918 4919 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4920} 4921 4922/* 4923 * This is the list priority from which the L2ARC will search for pages to 4924 * cache. This is used within loops (0..3) to cycle through lists in the 4925 * desired order. This order can have a significant effect on cache 4926 * performance. 4927 * 4928 * Currently the metadata lists are hit first, MFU then MRU, followed by 4929 * the data lists. This function returns a locked list, and also returns 4930 * the lock pointer. 4931 */ 4932static list_t * 4933l2arc_list_locked(int list_num, kmutex_t **lock) 4934{ 4935 list_t *list = NULL; 4936 int idx; 4937 4938 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS); 4939 4940 if (list_num < ARC_BUFC_NUMMETADATALISTS) { 4941 idx = list_num; 4942 list = &arc_mfu->arcs_lists[idx]; 4943 *lock = ARCS_LOCK(arc_mfu, idx); 4944 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) { 4945 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 4946 list = &arc_mru->arcs_lists[idx]; 4947 *lock = ARCS_LOCK(arc_mru, idx); 4948 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 + 4949 ARC_BUFC_NUMDATALISTS)) { 4950 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 4951 list = &arc_mfu->arcs_lists[idx]; 4952 *lock = ARCS_LOCK(arc_mfu, idx); 4953 } else { 4954 idx = list_num - ARC_BUFC_NUMLISTS; 4955 list = &arc_mru->arcs_lists[idx]; 4956 *lock = ARCS_LOCK(arc_mru, idx); 4957 } 4958 4959 ASSERT(!(MUTEX_HELD(*lock))); 4960 mutex_enter(*lock); 4961 return (list); 4962} 4963 4964/* 4965 * Evict buffers from the device write hand to the distance specified in 4966 * bytes. This distance may span populated buffers, it may span nothing. 4967 * This is clearing a region on the L2ARC device ready for writing. 4968 * If the 'all' boolean is set, every buffer is evicted. 4969 */ 4970static void 4971l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 4972{ 4973 list_t *buflist; 4974 l2arc_buf_hdr_t *abl2; 4975 arc_buf_hdr_t *hdr, *hdr_prev; 4976 kmutex_t *hash_lock; 4977 uint64_t taddr; 4978 int64_t bytes_evicted = 0; 4979 4980 buflist = dev->l2ad_buflist; 4981 4982 if (buflist == NULL) 4983 return; 4984 4985 if (!all && dev->l2ad_first) { 4986 /* 4987 * This is the first sweep through the device. There is 4988 * nothing to evict. 4989 */ 4990 return; 4991 } 4992 4993 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 4994 /* 4995 * When nearing the end of the device, evict to the end 4996 * before the device write hand jumps to the start. 4997 */ 4998 taddr = dev->l2ad_end; 4999 } else { 5000 taddr = dev->l2ad_hand + distance; 5001 } 5002 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5003 uint64_t, taddr, boolean_t, all); 5004 5005top: 5006 mutex_enter(&l2arc_buflist_mtx); 5007 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5008 hdr_prev = list_prev(buflist, hdr); 5009 5010 hash_lock = HDR_LOCK(hdr); 5011 if (!mutex_tryenter(hash_lock)) { 5012 /* 5013 * Missed the hash lock. Retry. 5014 */ 5015 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5016 mutex_exit(&l2arc_buflist_mtx); 5017 mutex_enter(hash_lock); 5018 mutex_exit(hash_lock); 5019 goto top; 5020 } 5021 5022 if (HDR_L2_WRITE_HEAD(hdr)) { 5023 /* 5024 * We hit a write head node. Leave it for 5025 * l2arc_write_done(). 5026 */ 5027 list_remove(buflist, hdr); 5028 mutex_exit(hash_lock); 5029 continue; 5030 } 5031 5032 if (!all && hdr->b_l2hdr != NULL && 5033 (hdr->b_l2hdr->b_daddr > taddr || 5034 hdr->b_l2hdr->b_daddr < dev->l2ad_hand)) { 5035 /* 5036 * We've evicted to the target address, 5037 * or the end of the device. 5038 */ 5039 mutex_exit(hash_lock); 5040 break; 5041 } 5042 5043 if (HDR_FREE_IN_PROGRESS(hdr)) { 5044 /* 5045 * Already on the path to destruction. 5046 */ 5047 mutex_exit(hash_lock); 5048 continue; 5049 } 5050 5051 if (hdr->b_state == arc_l2c_only) { 5052 ASSERT(!HDR_L2_READING(hdr)); 5053 /* 5054 * This doesn't exist in the ARC. Destroy. 5055 * arc_hdr_destroy() will call list_remove() 5056 * and decrement arcstat_l2_size. 5057 */ 5058 arc_change_state(arc_anon, hdr, hash_lock); 5059 arc_hdr_destroy(hdr); 5060 } else { 5061 /* 5062 * Invalidate issued or about to be issued 5063 * reads, since we may be about to write 5064 * over this location. 5065 */ 5066 if (HDR_L2_READING(hdr)) { 5067 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5068 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5069 } 5070 5071 /* 5072 * Tell ARC this no longer exists in L2ARC. 5073 */ 5074 if (hdr->b_l2hdr != NULL) { 5075 abl2 = hdr->b_l2hdr; 5076 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); 5077 bytes_evicted += abl2->b_asize; 5078 hdr->b_l2hdr = NULL; 5079 /* 5080 * We are destroying l2hdr, so ensure that 5081 * its compressed buffer, if any, is not leaked. 5082 */ 5083 ASSERT(abl2->b_tmp_cdata == NULL); 5084 kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); 5085 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5086 } 5087 list_remove(buflist, hdr); 5088 5089 /* 5090 * This may have been leftover after a 5091 * failed write. 5092 */ 5093 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5094 } 5095 mutex_exit(hash_lock); 5096 } 5097 mutex_exit(&l2arc_buflist_mtx); 5098 5099 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 5100 dev->l2ad_evict = taddr; 5101} 5102 5103/* 5104 * Find and write ARC buffers to the L2ARC device. 5105 * 5106 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5107 * for reading until they have completed writing. 5108 * The headroom_boost is an in-out parameter used to maintain headroom boost 5109 * state between calls to this function. 5110 * 5111 * Returns the number of bytes actually written (which may be smaller than 5112 * the delta by which the device hand has changed due to alignment). 5113 */ 5114static uint64_t 5115l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5116 boolean_t *headroom_boost) 5117{ 5118 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5119 list_t *list; 5120 uint64_t write_asize, write_sz, headroom, buf_compress_minsz; 5121 void *buf_data; 5122 kmutex_t *list_lock; 5123 boolean_t full; 5124 l2arc_write_callback_t *cb; 5125 zio_t *pio, *wzio; 5126 uint64_t guid = spa_load_guid(spa); 5127 const boolean_t do_headroom_boost = *headroom_boost; 5128 int try; 5129 5130 ASSERT(dev->l2ad_vdev != NULL); 5131 5132 /* Lower the flag now, we might want to raise it again later. */ 5133 *headroom_boost = B_FALSE; 5134 5135 pio = NULL; 5136 write_sz = write_asize = 0; 5137 full = B_FALSE; 5138 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE); 5139 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5140 5141 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 5142 /* 5143 * We will want to try to compress buffers that are at least 2x the 5144 * device sector size. 5145 */ 5146 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5147 5148 /* 5149 * Copy buffers for L2ARC writing. 5150 */ 5151 mutex_enter(&l2arc_buflist_mtx); 5152 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) { 5153 uint64_t passed_sz = 0; 5154 5155 list = l2arc_list_locked(try, &list_lock); 5156 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 5157 5158 /* 5159 * L2ARC fast warmup. 5160 * 5161 * Until the ARC is warm and starts to evict, read from the 5162 * head of the ARC lists rather than the tail. 5163 */ 5164 if (arc_warm == B_FALSE) 5165 hdr = list_head(list); 5166 else 5167 hdr = list_tail(list); 5168 if (hdr == NULL) 5169 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 5170 5171 headroom = target_sz * l2arc_headroom * 2 / ARC_BUFC_NUMLISTS; 5172 if (do_headroom_boost) 5173 headroom = (headroom * l2arc_headroom_boost) / 100; 5174 5175 for (; hdr; hdr = hdr_prev) { 5176 l2arc_buf_hdr_t *l2hdr; 5177 kmutex_t *hash_lock; 5178 uint64_t buf_sz; 5179 uint64_t buf_a_sz; 5180 5181 if (arc_warm == B_FALSE) 5182 hdr_prev = list_next(list, hdr); 5183 else 5184 hdr_prev = list_prev(list, hdr); 5185 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 5186 5187 hash_lock = HDR_LOCK(hdr); 5188 if (!mutex_tryenter(hash_lock)) { 5189 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 5190 /* 5191 * Skip this buffer rather than waiting. 5192 */ 5193 continue; 5194 } 5195 5196 passed_sz += hdr->b_size; 5197 if (passed_sz > headroom) { 5198 /* 5199 * Searched too far. 5200 */ 5201 mutex_exit(hash_lock); 5202 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 5203 break; 5204 } 5205 5206 if (!l2arc_write_eligible(guid, hdr)) { 5207 mutex_exit(hash_lock); 5208 continue; 5209 } 5210 5211 /* 5212 * Assume that the buffer is not going to be compressed 5213 * and could take more space on disk because of a larger 5214 * disk block size. 5215 */ 5216 buf_sz = hdr->b_size; 5217 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5218 5219 if ((write_asize + buf_a_sz) > target_sz) { 5220 full = B_TRUE; 5221 mutex_exit(hash_lock); 5222 ARCSTAT_BUMP(arcstat_l2_write_full); 5223 break; 5224 } 5225 5226 if (pio == NULL) { 5227 /* 5228 * Insert a dummy header on the buflist so 5229 * l2arc_write_done() can find where the 5230 * write buffers begin without searching. 5231 */ 5232 list_insert_head(dev->l2ad_buflist, head); 5233 5234 cb = kmem_alloc( 5235 sizeof (l2arc_write_callback_t), KM_SLEEP); 5236 cb->l2wcb_dev = dev; 5237 cb->l2wcb_head = head; 5238 pio = zio_root(spa, l2arc_write_done, cb, 5239 ZIO_FLAG_CANFAIL); 5240 ARCSTAT_BUMP(arcstat_l2_write_pios); 5241 } 5242 5243 /* 5244 * Create and add a new L2ARC header. 5245 */ 5246 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP); 5247 l2hdr->b_dev = dev; 5248 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5249 5250 /* 5251 * Temporarily stash the data buffer in b_tmp_cdata. 5252 * The subsequent write step will pick it up from 5253 * there. This is because can't access hdr->b_buf 5254 * without holding the hash_lock, which we in turn 5255 * can't access without holding the ARC list locks 5256 * (which we want to avoid during compression/writing). 5257 */ 5258 l2hdr->b_compress = ZIO_COMPRESS_OFF; 5259 l2hdr->b_asize = hdr->b_size; 5260 l2hdr->b_tmp_cdata = hdr->b_buf->b_data; 5261 5262 hdr->b_l2hdr = l2hdr; 5263 5264 list_insert_head(dev->l2ad_buflist, hdr); 5265 5266 /* 5267 * Compute and store the buffer cksum before 5268 * writing. On debug the cksum is verified first. 5269 */ 5270 arc_cksum_verify(hdr->b_buf); 5271 arc_cksum_compute(hdr->b_buf, B_TRUE); 5272 5273 mutex_exit(hash_lock); 5274 5275 write_sz += buf_sz; 5276 write_asize += buf_a_sz; 5277 } 5278 5279 mutex_exit(list_lock); 5280 5281 if (full == B_TRUE) 5282 break; 5283 } 5284 5285 /* No buffers selected for writing? */ 5286 if (pio == NULL) { 5287 ASSERT0(write_sz); 5288 mutex_exit(&l2arc_buflist_mtx); 5289 kmem_cache_free(hdr_cache, head); 5290 return (0); 5291 } 5292 5293 /* 5294 * Note that elsewhere in this file arcstat_l2_asize 5295 * and the used space on l2ad_vdev are updated using b_asize, 5296 * which is not necessarily rounded up to the device block size. 5297 * Too keep accounting consistent we do the same here as well: 5298 * stats_size accumulates the sum of b_asize of the written buffers, 5299 * while write_asize accumulates the sum of b_asize rounded up 5300 * to the device block size. 5301 * The latter sum is used only to validate the corectness of the code. 5302 */ 5303 uint64_t stats_size = 0; 5304 write_asize = 0; 5305 5306 /* 5307 * Now start writing the buffers. We're starting at the write head 5308 * and work backwards, retracing the course of the buffer selector 5309 * loop above. 5310 */ 5311 for (hdr = list_prev(dev->l2ad_buflist, head); hdr; 5312 hdr = list_prev(dev->l2ad_buflist, hdr)) { 5313 l2arc_buf_hdr_t *l2hdr; 5314 uint64_t buf_sz; 5315 5316 /* 5317 * We shouldn't need to lock the buffer here, since we flagged 5318 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5319 * take care to only access its L2 cache parameters. In 5320 * particular, hdr->b_buf may be invalid by now due to 5321 * ARC eviction. 5322 */ 5323 l2hdr = hdr->b_l2hdr; 5324 l2hdr->b_daddr = dev->l2ad_hand; 5325 5326 if ((hdr->b_flags & ARC_FLAG_L2COMPRESS) && 5327 l2hdr->b_asize >= buf_compress_minsz) { 5328 if (l2arc_compress_buf(l2hdr)) { 5329 /* 5330 * If compression succeeded, enable headroom 5331 * boost on the next scan cycle. 5332 */ 5333 *headroom_boost = B_TRUE; 5334 } 5335 } 5336 5337 /* 5338 * Pick up the buffer data we had previously stashed away 5339 * (and now potentially also compressed). 5340 */ 5341 buf_data = l2hdr->b_tmp_cdata; 5342 buf_sz = l2hdr->b_asize; 5343 5344 /* 5345 * If the data has not been compressed, then clear b_tmp_cdata 5346 * to make sure that it points only to a temporary compression 5347 * buffer. 5348 */ 5349 if (!L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress)) 5350 l2hdr->b_tmp_cdata = NULL; 5351 5352 /* Compression may have squashed the buffer to zero length. */ 5353 if (buf_sz != 0) { 5354 uint64_t buf_a_sz; 5355 5356 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5357 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5358 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 5359 ZIO_FLAG_CANFAIL, B_FALSE); 5360 5361 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 5362 zio_t *, wzio); 5363 (void) zio_nowait(wzio); 5364 5365 stats_size += buf_sz; 5366 /* 5367 * Keep the clock hand suitably device-aligned. 5368 */ 5369 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5370 write_asize += buf_a_sz; 5371 dev->l2ad_hand += buf_a_sz; 5372 } 5373 } 5374 5375 mutex_exit(&l2arc_buflist_mtx); 5376 5377 ASSERT3U(write_asize, <=, target_sz); 5378 ARCSTAT_BUMP(arcstat_l2_writes_sent); 5379 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 5380 ARCSTAT_INCR(arcstat_l2_size, write_sz); 5381 ARCSTAT_INCR(arcstat_l2_asize, stats_size); 5382 vdev_space_update(dev->l2ad_vdev, stats_size, 0, 0); 5383 5384 /* 5385 * Bump device hand to the device start if it is approaching the end. 5386 * l2arc_evict() will already have evicted ahead for this case. 5387 */ 5388 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 5389 dev->l2ad_hand = dev->l2ad_start; 5390 dev->l2ad_evict = dev->l2ad_start; 5391 dev->l2ad_first = B_FALSE; 5392 } 5393 5394 dev->l2ad_writing = B_TRUE; 5395 (void) zio_wait(pio); 5396 dev->l2ad_writing = B_FALSE; 5397 5398 return (write_asize); 5399} 5400 5401/* 5402 * Compresses an L2ARC buffer. 5403 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its 5404 * size in l2hdr->b_asize. This routine tries to compress the data and 5405 * depending on the compression result there are three possible outcomes: 5406 * *) The buffer was incompressible. The original l2hdr contents were left 5407 * untouched and are ready for writing to an L2 device. 5408 * *) The buffer was all-zeros, so there is no need to write it to an L2 5409 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 5410 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 5411 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 5412 * data buffer which holds the compressed data to be written, and b_asize 5413 * tells us how much data there is. b_compress is set to the appropriate 5414 * compression algorithm. Once writing is done, invoke 5415 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 5416 * 5417 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 5418 * buffer was incompressible). 5419 */ 5420static boolean_t 5421l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr) 5422{ 5423 void *cdata; 5424 size_t csize, len, rounded; 5425 5426 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF); 5427 ASSERT(l2hdr->b_tmp_cdata != NULL); 5428 5429 len = l2hdr->b_asize; 5430 cdata = zio_data_buf_alloc(len); 5431 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata, 5432 cdata, l2hdr->b_asize); 5433 5434 if (csize == 0) { 5435 /* zero block, indicate that there's nothing to write */ 5436 zio_data_buf_free(cdata, len); 5437 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 5438 l2hdr->b_asize = 0; 5439 l2hdr->b_tmp_cdata = NULL; 5440 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 5441 return (B_TRUE); 5442 } 5443 5444 rounded = P2ROUNDUP(csize, 5445 (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift); 5446 if (rounded < len) { 5447 /* 5448 * Compression succeeded, we'll keep the cdata around for 5449 * writing and release it afterwards. 5450 */ 5451 if (rounded > csize) { 5452 bzero((char *)cdata + csize, rounded - csize); 5453 csize = rounded; 5454 } 5455 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 5456 l2hdr->b_asize = csize; 5457 l2hdr->b_tmp_cdata = cdata; 5458 ARCSTAT_BUMP(arcstat_l2_compress_successes); 5459 return (B_TRUE); 5460 } else { 5461 /* 5462 * Compression failed, release the compressed buffer. 5463 * l2hdr will be left unmodified. 5464 */ 5465 zio_data_buf_free(cdata, len); 5466 ARCSTAT_BUMP(arcstat_l2_compress_failures); 5467 return (B_FALSE); 5468 } 5469} 5470 5471/* 5472 * Decompresses a zio read back from an l2arc device. On success, the 5473 * underlying zio's io_data buffer is overwritten by the uncompressed 5474 * version. On decompression error (corrupt compressed stream), the 5475 * zio->io_error value is set to signal an I/O error. 5476 * 5477 * Please note that the compressed data stream is not checksummed, so 5478 * if the underlying device is experiencing data corruption, we may feed 5479 * corrupt data to the decompressor, so the decompressor needs to be 5480 * able to handle this situation (LZ4 does). 5481 */ 5482static void 5483l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 5484{ 5485 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 5486 5487 if (zio->io_error != 0) { 5488 /* 5489 * An io error has occured, just restore the original io 5490 * size in preparation for a main pool read. 5491 */ 5492 zio->io_orig_size = zio->io_size = hdr->b_size; 5493 return; 5494 } 5495 5496 if (c == ZIO_COMPRESS_EMPTY) { 5497 /* 5498 * An empty buffer results in a null zio, which means we 5499 * need to fill its io_data after we're done restoring the 5500 * buffer's contents. 5501 */ 5502 ASSERT(hdr->b_buf != NULL); 5503 bzero(hdr->b_buf->b_data, hdr->b_size); 5504 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data; 5505 } else { 5506 ASSERT(zio->io_data != NULL); 5507 /* 5508 * We copy the compressed data from the start of the arc buffer 5509 * (the zio_read will have pulled in only what we need, the 5510 * rest is garbage which we will overwrite at decompression) 5511 * and then decompress back to the ARC data buffer. This way we 5512 * can minimize copying by simply decompressing back over the 5513 * original compressed data (rather than decompressing to an 5514 * aux buffer and then copying back the uncompressed buffer, 5515 * which is likely to be much larger). 5516 */ 5517 uint64_t csize; 5518 void *cdata; 5519 5520 csize = zio->io_size; 5521 cdata = zio_data_buf_alloc(csize); 5522 bcopy(zio->io_data, cdata, csize); 5523 if (zio_decompress_data(c, cdata, zio->io_data, csize, 5524 hdr->b_size) != 0) 5525 zio->io_error = EIO; 5526 zio_data_buf_free(cdata, csize); 5527 } 5528 5529 /* Restore the expected uncompressed IO size. */ 5530 zio->io_orig_size = zio->io_size = hdr->b_size; 5531} 5532 5533/* 5534 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 5535 * This buffer serves as a temporary holder of compressed data while 5536 * the buffer entry is being written to an l2arc device. Once that is 5537 * done, we can dispose of it. 5538 */ 5539static void 5540l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 5541{ 5542 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; 5543 5544 ASSERT(L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress)); 5545 if (l2hdr->b_compress != ZIO_COMPRESS_EMPTY) { 5546 /* 5547 * If the data was compressed, then we've allocated a 5548 * temporary buffer for it, so now we need to release it. 5549 */ 5550 ASSERT(l2hdr->b_tmp_cdata != NULL); 5551 zio_data_buf_free(l2hdr->b_tmp_cdata, hdr->b_size); 5552 l2hdr->b_tmp_cdata = NULL; 5553 } else { 5554 ASSERT(l2hdr->b_tmp_cdata == NULL); 5555 } 5556} 5557 5558/* 5559 * This thread feeds the L2ARC at regular intervals. This is the beating 5560 * heart of the L2ARC. 5561 */ 5562static void 5563l2arc_feed_thread(void *dummy __unused) 5564{ 5565 callb_cpr_t cpr; 5566 l2arc_dev_t *dev; 5567 spa_t *spa; 5568 uint64_t size, wrote; 5569 clock_t begin, next = ddi_get_lbolt(); 5570 boolean_t headroom_boost = B_FALSE; 5571 5572 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 5573 5574 mutex_enter(&l2arc_feed_thr_lock); 5575 5576 while (l2arc_thread_exit == 0) { 5577 CALLB_CPR_SAFE_BEGIN(&cpr); 5578 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 5579 next - ddi_get_lbolt()); 5580 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 5581 next = ddi_get_lbolt() + hz; 5582 5583 /* 5584 * Quick check for L2ARC devices. 5585 */ 5586 mutex_enter(&l2arc_dev_mtx); 5587 if (l2arc_ndev == 0) { 5588 mutex_exit(&l2arc_dev_mtx); 5589 continue; 5590 } 5591 mutex_exit(&l2arc_dev_mtx); 5592 begin = ddi_get_lbolt(); 5593 5594 /* 5595 * This selects the next l2arc device to write to, and in 5596 * doing so the next spa to feed from: dev->l2ad_spa. This 5597 * will return NULL if there are now no l2arc devices or if 5598 * they are all faulted. 5599 * 5600 * If a device is returned, its spa's config lock is also 5601 * held to prevent device removal. l2arc_dev_get_next() 5602 * will grab and release l2arc_dev_mtx. 5603 */ 5604 if ((dev = l2arc_dev_get_next()) == NULL) 5605 continue; 5606 5607 spa = dev->l2ad_spa; 5608 ASSERT(spa != NULL); 5609 5610 /* 5611 * If the pool is read-only then force the feed thread to 5612 * sleep a little longer. 5613 */ 5614 if (!spa_writeable(spa)) { 5615 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 5616 spa_config_exit(spa, SCL_L2ARC, dev); 5617 continue; 5618 } 5619 5620 /* 5621 * Avoid contributing to memory pressure. 5622 */ 5623 if (arc_reclaim_needed()) { 5624 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 5625 spa_config_exit(spa, SCL_L2ARC, dev); 5626 continue; 5627 } 5628 5629 ARCSTAT_BUMP(arcstat_l2_feeds); 5630 5631 size = l2arc_write_size(); 5632 5633 /* 5634 * Evict L2ARC buffers that will be overwritten. 5635 */ 5636 l2arc_evict(dev, size, B_FALSE); 5637 5638 /* 5639 * Write ARC buffers. 5640 */ 5641 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 5642 5643 /* 5644 * Calculate interval between writes. 5645 */ 5646 next = l2arc_write_interval(begin, size, wrote); 5647 spa_config_exit(spa, SCL_L2ARC, dev); 5648 } 5649 5650 l2arc_thread_exit = 0; 5651 cv_broadcast(&l2arc_feed_thr_cv); 5652 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 5653 thread_exit(); 5654} 5655 5656boolean_t 5657l2arc_vdev_present(vdev_t *vd) 5658{ 5659 l2arc_dev_t *dev; 5660 5661 mutex_enter(&l2arc_dev_mtx); 5662 for (dev = list_head(l2arc_dev_list); dev != NULL; 5663 dev = list_next(l2arc_dev_list, dev)) { 5664 if (dev->l2ad_vdev == vd) 5665 break; 5666 } 5667 mutex_exit(&l2arc_dev_mtx); 5668 5669 return (dev != NULL); 5670} 5671 5672/* 5673 * Add a vdev for use by the L2ARC. By this point the spa has already 5674 * validated the vdev and opened it. 5675 */ 5676void 5677l2arc_add_vdev(spa_t *spa, vdev_t *vd) 5678{ 5679 l2arc_dev_t *adddev; 5680 5681 ASSERT(!l2arc_vdev_present(vd)); 5682 5683 vdev_ashift_optimize(vd); 5684 5685 /* 5686 * Create a new l2arc device entry. 5687 */ 5688 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 5689 adddev->l2ad_spa = spa; 5690 adddev->l2ad_vdev = vd; 5691 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 5692 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 5693 adddev->l2ad_hand = adddev->l2ad_start; 5694 adddev->l2ad_evict = adddev->l2ad_start; 5695 adddev->l2ad_first = B_TRUE; 5696 adddev->l2ad_writing = B_FALSE; 5697 5698 /* 5699 * This is a list of all ARC buffers that are still valid on the 5700 * device. 5701 */ 5702 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP); 5703 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 5704 offsetof(arc_buf_hdr_t, b_l2node)); 5705 5706 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 5707 5708 /* 5709 * Add device to global list 5710 */ 5711 mutex_enter(&l2arc_dev_mtx); 5712 list_insert_head(l2arc_dev_list, adddev); 5713 atomic_inc_64(&l2arc_ndev); 5714 mutex_exit(&l2arc_dev_mtx); 5715} 5716 5717/* 5718 * Remove a vdev from the L2ARC. 5719 */ 5720void 5721l2arc_remove_vdev(vdev_t *vd) 5722{ 5723 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 5724 5725 /* 5726 * Find the device by vdev 5727 */ 5728 mutex_enter(&l2arc_dev_mtx); 5729 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 5730 nextdev = list_next(l2arc_dev_list, dev); 5731 if (vd == dev->l2ad_vdev) { 5732 remdev = dev; 5733 break; 5734 } 5735 } 5736 ASSERT(remdev != NULL); 5737 5738 /* 5739 * Remove device from global list 5740 */ 5741 list_remove(l2arc_dev_list, remdev); 5742 l2arc_dev_last = NULL; /* may have been invalidated */ 5743 atomic_dec_64(&l2arc_ndev); 5744 mutex_exit(&l2arc_dev_mtx); 5745 5746 /* 5747 * Clear all buflists and ARC references. L2ARC device flush. 5748 */ 5749 l2arc_evict(remdev, 0, B_TRUE); 5750 list_destroy(remdev->l2ad_buflist); 5751 kmem_free(remdev->l2ad_buflist, sizeof (list_t)); 5752 kmem_free(remdev, sizeof (l2arc_dev_t)); 5753} 5754 5755void 5756l2arc_init(void) 5757{ 5758 l2arc_thread_exit = 0; 5759 l2arc_ndev = 0; 5760 l2arc_writes_sent = 0; 5761 l2arc_writes_done = 0; 5762 5763 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 5764 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 5765 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 5766 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL); 5767 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 5768 5769 l2arc_dev_list = &L2ARC_dev_list; 5770 l2arc_free_on_write = &L2ARC_free_on_write; 5771 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 5772 offsetof(l2arc_dev_t, l2ad_node)); 5773 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 5774 offsetof(l2arc_data_free_t, l2df_list_node)); 5775} 5776 5777void 5778l2arc_fini(void) 5779{ 5780 /* 5781 * This is called from dmu_fini(), which is called from spa_fini(); 5782 * Because of this, we can assume that all l2arc devices have 5783 * already been removed when the pools themselves were removed. 5784 */ 5785 5786 l2arc_do_free_on_write(); 5787 5788 mutex_destroy(&l2arc_feed_thr_lock); 5789 cv_destroy(&l2arc_feed_thr_cv); 5790 mutex_destroy(&l2arc_dev_mtx); 5791 mutex_destroy(&l2arc_buflist_mtx); 5792 mutex_destroy(&l2arc_free_on_write_mtx); 5793 5794 list_destroy(l2arc_dev_list); 5795 list_destroy(l2arc_free_on_write); 5796} 5797 5798void 5799l2arc_start(void) 5800{ 5801 if (!(spa_mode_global & FWRITE)) 5802 return; 5803 5804 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 5805 TS_RUN, minclsyspri); 5806} 5807 5808void 5809l2arc_stop(void) 5810{ 5811 if (!(spa_mode_global & FWRITE)) 5812 return; 5813 5814 mutex_enter(&l2arc_feed_thr_lock); 5815 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 5816 l2arc_thread_exit = 1; 5817 while (l2arc_thread_exit != 0) 5818 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 5819 mutex_exit(&l2arc_feed_thr_lock); 5820} 5821