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, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev 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 #include <sys/multilist.h> 133 #ifdef _KERNEL 134 #include <sys/vmsystm.h> 135 #include <vm/anon.h> 136 #include <sys/fs/swapnode.h> 137 #include <sys/dnlc.h> 138 #endif 139 #include <sys/callb.h> 140 #include <sys/kstat.h> 141 #include <zfs_fletcher.h> 142 143 #ifndef _KERNEL 144 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 145 boolean_t arc_watch = B_FALSE; 146 int arc_procfd; 147 #endif 148 149 static kmutex_t arc_reclaim_lock; 150 static kcondvar_t arc_reclaim_thread_cv; 151 static boolean_t arc_reclaim_thread_exit; 152 static kcondvar_t arc_reclaim_waiters_cv; 153 154 static kmutex_t arc_user_evicts_lock; 155 static kcondvar_t arc_user_evicts_cv; 156 static boolean_t arc_user_evicts_thread_exit; 157 158 uint_t arc_reduce_dnlc_percent = 3; 159 160 /* 161 * The number of headers to evict in arc_evict_state_impl() before 162 * dropping the sublist lock and evicting from another sublist. A lower 163 * value means we're more likely to evict the "correct" header (i.e. the 164 * oldest header in the arc state), but comes with higher overhead 165 * (i.e. more invocations of arc_evict_state_impl()). 166 */ 167 int zfs_arc_evict_batch_limit = 10; 168 169 /* 170 * The number of sublists used for each of the arc state lists. If this 171 * is not set to a suitable value by the user, it will be configured to 172 * the number of CPUs on the system in arc_init(). 173 */ 174 int zfs_arc_num_sublists_per_state = 0; 175 176 /* number of seconds before growing cache again */ 177 static int arc_grow_retry = 60; 178 179 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 180 int zfs_arc_overflow_shift = 8; 181 182 /* shift of arc_c for calculating both min and max arc_p */ 183 static int arc_p_min_shift = 4; 184 185 /* log2(fraction of arc to reclaim) */ 186 static int arc_shrink_shift = 7; 187 188 /* 189 * log2(fraction of ARC which must be free to allow growing). 190 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 191 * when reading a new block into the ARC, we will evict an equal-sized block 192 * from the ARC. 193 * 194 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 195 * we will still not allow it to grow. 196 */ 197 int arc_no_grow_shift = 5; 198 199 200 /* 201 * minimum lifespan of a prefetch block in clock ticks 202 * (initialized in arc_init()) 203 */ 204 static int arc_min_prefetch_lifespan; 205 206 /* 207 * If this percent of memory is free, don't throttle. 208 */ 209 int arc_lotsfree_percent = 10; 210 211 static int arc_dead; 212 213 /* 214 * The arc has filled available memory and has now warmed up. 215 */ 216 static boolean_t arc_warm; 217 218 /* 219 * These tunables are for performance analysis. 220 */ 221 uint64_t zfs_arc_max; 222 uint64_t zfs_arc_min; 223 uint64_t zfs_arc_meta_limit = 0; 224 uint64_t zfs_arc_meta_min = 0; 225 int zfs_arc_grow_retry = 0; 226 int zfs_arc_shrink_shift = 0; 227 int zfs_arc_p_min_shift = 0; 228 int zfs_disable_dup_eviction = 0; 229 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 230 231 /* 232 * Note that buffers can be in one of 6 states: 233 * ARC_anon - anonymous (discussed below) 234 * ARC_mru - recently used, currently cached 235 * ARC_mru_ghost - recentely used, no longer in cache 236 * ARC_mfu - frequently used, currently cached 237 * ARC_mfu_ghost - frequently used, no longer in cache 238 * ARC_l2c_only - exists in L2ARC but not other states 239 * When there are no active references to the buffer, they are 240 * are linked onto a list in one of these arc states. These are 241 * the only buffers that can be evicted or deleted. Within each 242 * state there are multiple lists, one for meta-data and one for 243 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 244 * etc.) is tracked separately so that it can be managed more 245 * explicitly: favored over data, limited explicitly. 246 * 247 * Anonymous buffers are buffers that are not associated with 248 * a DVA. These are buffers that hold dirty block copies 249 * before they are written to stable storage. By definition, 250 * they are "ref'd" and are considered part of arc_mru 251 * that cannot be freed. Generally, they will aquire a DVA 252 * as they are written and migrate onto the arc_mru list. 253 * 254 * The ARC_l2c_only state is for buffers that are in the second 255 * level ARC but no longer in any of the ARC_m* lists. The second 256 * level ARC itself may also contain buffers that are in any of 257 * the ARC_m* states - meaning that a buffer can exist in two 258 * places. The reason for the ARC_l2c_only state is to keep the 259 * buffer header in the hash table, so that reads that hit the 260 * second level ARC benefit from these fast lookups. 261 */ 262 263 typedef struct arc_state { 264 /* 265 * list of evictable buffers 266 */ 267 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 268 /* 269 * total amount of evictable data in this state 270 */ 271 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 272 /* 273 * total amount of data in this state; this includes: evictable, 274 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 275 */ 276 refcount_t arcs_size; 277 } arc_state_t; 278 279 /* The 6 states: */ 280 static arc_state_t ARC_anon; 281 static arc_state_t ARC_mru; 282 static arc_state_t ARC_mru_ghost; 283 static arc_state_t ARC_mfu; 284 static arc_state_t ARC_mfu_ghost; 285 static arc_state_t ARC_l2c_only; 286 287 typedef struct arc_stats { 288 kstat_named_t arcstat_hits; 289 kstat_named_t arcstat_misses; 290 kstat_named_t arcstat_demand_data_hits; 291 kstat_named_t arcstat_demand_data_misses; 292 kstat_named_t arcstat_demand_metadata_hits; 293 kstat_named_t arcstat_demand_metadata_misses; 294 kstat_named_t arcstat_prefetch_data_hits; 295 kstat_named_t arcstat_prefetch_data_misses; 296 kstat_named_t arcstat_prefetch_metadata_hits; 297 kstat_named_t arcstat_prefetch_metadata_misses; 298 kstat_named_t arcstat_mru_hits; 299 kstat_named_t arcstat_mru_ghost_hits; 300 kstat_named_t arcstat_mfu_hits; 301 kstat_named_t arcstat_mfu_ghost_hits; 302 kstat_named_t arcstat_deleted; 303 /* 304 * Number of buffers that could not be evicted because the hash lock 305 * was held by another thread. The lock may not necessarily be held 306 * by something using the same buffer, since hash locks are shared 307 * by multiple buffers. 308 */ 309 kstat_named_t arcstat_mutex_miss; 310 /* 311 * Number of buffers skipped because they have I/O in progress, are 312 * indrect prefetch buffers that have not lived long enough, or are 313 * not from the spa we're trying to evict from. 314 */ 315 kstat_named_t arcstat_evict_skip; 316 /* 317 * Number of times arc_evict_state() was unable to evict enough 318 * buffers to reach it's target amount. 319 */ 320 kstat_named_t arcstat_evict_not_enough; 321 kstat_named_t arcstat_evict_l2_cached; 322 kstat_named_t arcstat_evict_l2_eligible; 323 kstat_named_t arcstat_evict_l2_ineligible; 324 kstat_named_t arcstat_evict_l2_skip; 325 kstat_named_t arcstat_hash_elements; 326 kstat_named_t arcstat_hash_elements_max; 327 kstat_named_t arcstat_hash_collisions; 328 kstat_named_t arcstat_hash_chains; 329 kstat_named_t arcstat_hash_chain_max; 330 kstat_named_t arcstat_p; 331 kstat_named_t arcstat_c; 332 kstat_named_t arcstat_c_min; 333 kstat_named_t arcstat_c_max; 334 kstat_named_t arcstat_size; 335 /* 336 * Number of bytes consumed by internal ARC structures necessary 337 * for tracking purposes; these structures are not actually 338 * backed by ARC buffers. This includes arc_buf_hdr_t structures 339 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 340 * caches), and arc_buf_t structures (allocated via arc_buf_t 341 * cache). 342 */ 343 kstat_named_t arcstat_hdr_size; 344 /* 345 * Number of bytes consumed by ARC buffers of type equal to 346 * ARC_BUFC_DATA. This is generally consumed by buffers backing 347 * on disk user data (e.g. plain file contents). 348 */ 349 kstat_named_t arcstat_data_size; 350 /* 351 * Number of bytes consumed by ARC buffers of type equal to 352 * ARC_BUFC_METADATA. This is generally consumed by buffers 353 * backing on disk data that is used for internal ZFS 354 * structures (e.g. ZAP, dnode, indirect blocks, etc). 355 */ 356 kstat_named_t arcstat_metadata_size; 357 /* 358 * Number of bytes consumed by various buffers and structures 359 * not actually backed with ARC buffers. This includes bonus 360 * buffers (allocated directly via zio_buf_* functions), 361 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 362 * cache), and dnode_t structures (allocated via dnode_t cache). 363 */ 364 kstat_named_t arcstat_other_size; 365 /* 366 * Total number of bytes consumed by ARC buffers residing in the 367 * arc_anon state. This includes *all* buffers in the arc_anon 368 * state; e.g. data, metadata, evictable, and unevictable buffers 369 * are all included in this value. 370 */ 371 kstat_named_t arcstat_anon_size; 372 /* 373 * Number of bytes consumed by ARC buffers that meet the 374 * following criteria: backing buffers of type ARC_BUFC_DATA, 375 * residing in the arc_anon state, and are eligible for eviction 376 * (e.g. have no outstanding holds on the buffer). 377 */ 378 kstat_named_t arcstat_anon_evictable_data; 379 /* 380 * Number of bytes consumed by ARC buffers that meet the 381 * following criteria: backing buffers of type ARC_BUFC_METADATA, 382 * residing in the arc_anon state, and are eligible for eviction 383 * (e.g. have no outstanding holds on the buffer). 384 */ 385 kstat_named_t arcstat_anon_evictable_metadata; 386 /* 387 * Total number of bytes consumed by ARC buffers residing in the 388 * arc_mru state. This includes *all* buffers in the arc_mru 389 * state; e.g. data, metadata, evictable, and unevictable buffers 390 * are all included in this value. 391 */ 392 kstat_named_t arcstat_mru_size; 393 /* 394 * Number of bytes consumed by ARC buffers that meet the 395 * following criteria: backing buffers of type ARC_BUFC_DATA, 396 * residing in the arc_mru state, and are eligible for eviction 397 * (e.g. have no outstanding holds on the buffer). 398 */ 399 kstat_named_t arcstat_mru_evictable_data; 400 /* 401 * Number of bytes consumed by ARC buffers that meet the 402 * following criteria: backing buffers of type ARC_BUFC_METADATA, 403 * residing in the arc_mru state, and are eligible for eviction 404 * (e.g. have no outstanding holds on the buffer). 405 */ 406 kstat_named_t arcstat_mru_evictable_metadata; 407 /* 408 * Total number of bytes that *would have been* consumed by ARC 409 * buffers in the arc_mru_ghost state. The key thing to note 410 * here, is the fact that this size doesn't actually indicate 411 * RAM consumption. The ghost lists only consist of headers and 412 * don't actually have ARC buffers linked off of these headers. 413 * Thus, *if* the headers had associated ARC buffers, these 414 * buffers *would have* consumed this number of bytes. 415 */ 416 kstat_named_t arcstat_mru_ghost_size; 417 /* 418 * Number of bytes that *would have been* consumed by ARC 419 * buffers that are eligible for eviction, of type 420 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 421 */ 422 kstat_named_t arcstat_mru_ghost_evictable_data; 423 /* 424 * Number of bytes that *would have been* consumed by ARC 425 * buffers that are eligible for eviction, of type 426 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 427 */ 428 kstat_named_t arcstat_mru_ghost_evictable_metadata; 429 /* 430 * Total number of bytes consumed by ARC buffers residing in the 431 * arc_mfu state. This includes *all* buffers in the arc_mfu 432 * state; e.g. data, metadata, evictable, and unevictable buffers 433 * are all included in this value. 434 */ 435 kstat_named_t arcstat_mfu_size; 436 /* 437 * Number of bytes consumed by ARC buffers that are eligible for 438 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 439 * state. 440 */ 441 kstat_named_t arcstat_mfu_evictable_data; 442 /* 443 * Number of bytes consumed by ARC buffers that are eligible for 444 * eviction, of type ARC_BUFC_METADATA, and reside in the 445 * arc_mfu state. 446 */ 447 kstat_named_t arcstat_mfu_evictable_metadata; 448 /* 449 * Total number of bytes that *would have been* consumed by ARC 450 * buffers in the arc_mfu_ghost state. See the comment above 451 * arcstat_mru_ghost_size for more details. 452 */ 453 kstat_named_t arcstat_mfu_ghost_size; 454 /* 455 * Number of bytes that *would have been* consumed by ARC 456 * buffers that are eligible for eviction, of type 457 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 458 */ 459 kstat_named_t arcstat_mfu_ghost_evictable_data; 460 /* 461 * Number of bytes that *would have been* consumed by ARC 462 * buffers that are eligible for eviction, of type 463 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 464 */ 465 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 466 kstat_named_t arcstat_l2_hits; 467 kstat_named_t arcstat_l2_misses; 468 kstat_named_t arcstat_l2_feeds; 469 kstat_named_t arcstat_l2_rw_clash; 470 kstat_named_t arcstat_l2_read_bytes; 471 kstat_named_t arcstat_l2_write_bytes; 472 kstat_named_t arcstat_l2_writes_sent; 473 kstat_named_t arcstat_l2_writes_done; 474 kstat_named_t arcstat_l2_writes_error; 475 kstat_named_t arcstat_l2_writes_lock_retry; 476 kstat_named_t arcstat_l2_evict_lock_retry; 477 kstat_named_t arcstat_l2_evict_reading; 478 kstat_named_t arcstat_l2_evict_l1cached; 479 kstat_named_t arcstat_l2_free_on_write; 480 kstat_named_t arcstat_l2_cdata_free_on_write; 481 kstat_named_t arcstat_l2_abort_lowmem; 482 kstat_named_t arcstat_l2_cksum_bad; 483 kstat_named_t arcstat_l2_io_error; 484 kstat_named_t arcstat_l2_size; 485 kstat_named_t arcstat_l2_asize; 486 kstat_named_t arcstat_l2_hdr_size; 487 kstat_named_t arcstat_l2_compress_successes; 488 kstat_named_t arcstat_l2_compress_zeros; 489 kstat_named_t arcstat_l2_compress_failures; 490 kstat_named_t arcstat_memory_throttle_count; 491 kstat_named_t arcstat_duplicate_buffers; 492 kstat_named_t arcstat_duplicate_buffers_size; 493 kstat_named_t arcstat_duplicate_reads; 494 kstat_named_t arcstat_meta_used; 495 kstat_named_t arcstat_meta_limit; 496 kstat_named_t arcstat_meta_max; 497 kstat_named_t arcstat_meta_min; 498 kstat_named_t arcstat_sync_wait_for_async; 499 kstat_named_t arcstat_demand_hit_predictive_prefetch; 500 } arc_stats_t; 501 502 static arc_stats_t arc_stats = { 503 { "hits", KSTAT_DATA_UINT64 }, 504 { "misses", KSTAT_DATA_UINT64 }, 505 { "demand_data_hits", KSTAT_DATA_UINT64 }, 506 { "demand_data_misses", KSTAT_DATA_UINT64 }, 507 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 508 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 509 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 510 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 511 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 512 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 513 { "mru_hits", KSTAT_DATA_UINT64 }, 514 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 515 { "mfu_hits", KSTAT_DATA_UINT64 }, 516 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 517 { "deleted", KSTAT_DATA_UINT64 }, 518 { "mutex_miss", KSTAT_DATA_UINT64 }, 519 { "evict_skip", KSTAT_DATA_UINT64 }, 520 { "evict_not_enough", KSTAT_DATA_UINT64 }, 521 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 522 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 523 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 524 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 525 { "hash_elements", KSTAT_DATA_UINT64 }, 526 { "hash_elements_max", KSTAT_DATA_UINT64 }, 527 { "hash_collisions", KSTAT_DATA_UINT64 }, 528 { "hash_chains", KSTAT_DATA_UINT64 }, 529 { "hash_chain_max", KSTAT_DATA_UINT64 }, 530 { "p", KSTAT_DATA_UINT64 }, 531 { "c", KSTAT_DATA_UINT64 }, 532 { "c_min", KSTAT_DATA_UINT64 }, 533 { "c_max", KSTAT_DATA_UINT64 }, 534 { "size", KSTAT_DATA_UINT64 }, 535 { "hdr_size", KSTAT_DATA_UINT64 }, 536 { "data_size", KSTAT_DATA_UINT64 }, 537 { "metadata_size", KSTAT_DATA_UINT64 }, 538 { "other_size", KSTAT_DATA_UINT64 }, 539 { "anon_size", KSTAT_DATA_UINT64 }, 540 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 541 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 542 { "mru_size", KSTAT_DATA_UINT64 }, 543 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 544 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 545 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 546 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 547 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 548 { "mfu_size", KSTAT_DATA_UINT64 }, 549 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 550 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 551 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 552 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 553 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 554 { "l2_hits", KSTAT_DATA_UINT64 }, 555 { "l2_misses", KSTAT_DATA_UINT64 }, 556 { "l2_feeds", KSTAT_DATA_UINT64 }, 557 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 558 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 559 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 560 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 561 { "l2_writes_done", KSTAT_DATA_UINT64 }, 562 { "l2_writes_error", KSTAT_DATA_UINT64 }, 563 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 564 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 565 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 566 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 567 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 568 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 569 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 570 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 571 { "l2_io_error", KSTAT_DATA_UINT64 }, 572 { "l2_size", KSTAT_DATA_UINT64 }, 573 { "l2_asize", KSTAT_DATA_UINT64 }, 574 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 575 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 576 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 577 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 578 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 579 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 580 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 581 { "duplicate_reads", KSTAT_DATA_UINT64 }, 582 { "arc_meta_used", KSTAT_DATA_UINT64 }, 583 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 584 { "arc_meta_max", KSTAT_DATA_UINT64 }, 585 { "arc_meta_min", KSTAT_DATA_UINT64 }, 586 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 587 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 588 }; 589 590 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 591 592 #define ARCSTAT_INCR(stat, val) \ 593 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 594 595 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 596 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 597 598 #define ARCSTAT_MAX(stat, val) { \ 599 uint64_t m; \ 600 while ((val) > (m = arc_stats.stat.value.ui64) && \ 601 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 602 continue; \ 603 } 604 605 #define ARCSTAT_MAXSTAT(stat) \ 606 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 607 608 /* 609 * We define a macro to allow ARC hits/misses to be easily broken down by 610 * two separate conditions, giving a total of four different subtypes for 611 * each of hits and misses (so eight statistics total). 612 */ 613 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 614 if (cond1) { \ 615 if (cond2) { \ 616 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 617 } else { \ 618 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 619 } \ 620 } else { \ 621 if (cond2) { \ 622 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 623 } else { \ 624 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 625 } \ 626 } 627 628 kstat_t *arc_ksp; 629 static arc_state_t *arc_anon; 630 static arc_state_t *arc_mru; 631 static arc_state_t *arc_mru_ghost; 632 static arc_state_t *arc_mfu; 633 static arc_state_t *arc_mfu_ghost; 634 static arc_state_t *arc_l2c_only; 635 636 /* 637 * There are several ARC variables that are critical to export as kstats -- 638 * but we don't want to have to grovel around in the kstat whenever we wish to 639 * manipulate them. For these variables, we therefore define them to be in 640 * terms of the statistic variable. This assures that we are not introducing 641 * the possibility of inconsistency by having shadow copies of the variables, 642 * while still allowing the code to be readable. 643 */ 644 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 645 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 646 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 647 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 648 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 649 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 650 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 651 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 652 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 653 654 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 655 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 656 657 static int arc_no_grow; /* Don't try to grow cache size */ 658 static uint64_t arc_tempreserve; 659 static uint64_t arc_loaned_bytes; 660 661 typedef struct arc_callback arc_callback_t; 662 663 struct arc_callback { 664 void *acb_private; 665 arc_done_func_t *acb_done; 666 arc_buf_t *acb_buf; 667 zio_t *acb_zio_dummy; 668 arc_callback_t *acb_next; 669 }; 670 671 typedef struct arc_write_callback arc_write_callback_t; 672 673 struct arc_write_callback { 674 void *awcb_private; 675 arc_done_func_t *awcb_ready; 676 arc_done_func_t *awcb_physdone; 677 arc_done_func_t *awcb_done; 678 arc_buf_t *awcb_buf; 679 }; 680 681 /* 682 * ARC buffers are separated into multiple structs as a memory saving measure: 683 * - Common fields struct, always defined, and embedded within it: 684 * - L2-only fields, always allocated but undefined when not in L2ARC 685 * - L1-only fields, only allocated when in L1ARC 686 * 687 * Buffer in L1 Buffer only in L2 688 * +------------------------+ +------------------------+ 689 * | arc_buf_hdr_t | | arc_buf_hdr_t | 690 * | | | | 691 * | | | | 692 * | | | | 693 * +------------------------+ +------------------------+ 694 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 695 * | (undefined if L1-only) | | | 696 * +------------------------+ +------------------------+ 697 * | l1arc_buf_hdr_t | 698 * | | 699 * | | 700 * | | 701 * | | 702 * +------------------------+ 703 * 704 * Because it's possible for the L2ARC to become extremely large, we can wind 705 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 706 * is minimized by only allocating the fields necessary for an L1-cached buffer 707 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 708 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 709 * words in pointers. arc_hdr_realloc() is used to switch a header between 710 * these two allocation states. 711 */ 712 typedef struct l1arc_buf_hdr { 713 kmutex_t b_freeze_lock; 714 #ifdef ZFS_DEBUG 715 /* 716 * used for debugging wtih kmem_flags - by allocating and freeing 717 * b_thawed when the buffer is thawed, we get a record of the stack 718 * trace that thawed it. 719 */ 720 void *b_thawed; 721 #endif 722 723 arc_buf_t *b_buf; 724 uint32_t b_datacnt; 725 /* for waiting on writes to complete */ 726 kcondvar_t b_cv; 727 728 /* protected by arc state mutex */ 729 arc_state_t *b_state; 730 multilist_node_t b_arc_node; 731 732 /* updated atomically */ 733 clock_t b_arc_access; 734 735 /* self protecting */ 736 refcount_t b_refcnt; 737 738 arc_callback_t *b_acb; 739 /* temporary buffer holder for in-flight compressed data */ 740 void *b_tmp_cdata; 741 } l1arc_buf_hdr_t; 742 743 typedef struct l2arc_dev l2arc_dev_t; 744 745 typedef struct l2arc_buf_hdr { 746 /* protected by arc_buf_hdr mutex */ 747 l2arc_dev_t *b_dev; /* L2ARC device */ 748 uint64_t b_daddr; /* disk address, offset byte */ 749 /* real alloc'd buffer size depending on b_compress applied */ 750 int32_t b_asize; 751 uint8_t b_compress; 752 753 list_node_t b_l2node; 754 } l2arc_buf_hdr_t; 755 756 struct arc_buf_hdr { 757 /* protected by hash lock */ 758 dva_t b_dva; 759 uint64_t b_birth; 760 /* 761 * Even though this checksum is only set/verified when a buffer is in 762 * the L1 cache, it needs to be in the set of common fields because it 763 * must be preserved from the time before a buffer is written out to 764 * L2ARC until after it is read back in. 765 */ 766 zio_cksum_t *b_freeze_cksum; 767 768 arc_buf_hdr_t *b_hash_next; 769 arc_flags_t b_flags; 770 771 /* immutable */ 772 int32_t b_size; 773 uint64_t b_spa; 774 775 /* L2ARC fields. Undefined when not in L2ARC. */ 776 l2arc_buf_hdr_t b_l2hdr; 777 /* L1ARC fields. Undefined when in l2arc_only state */ 778 l1arc_buf_hdr_t b_l1hdr; 779 }; 780 781 static arc_buf_t *arc_eviction_list; 782 static arc_buf_hdr_t arc_eviction_hdr; 783 784 #define GHOST_STATE(state) \ 785 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 786 (state) == arc_l2c_only) 787 788 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 789 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 790 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 791 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 792 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 793 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 794 795 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 796 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 797 #define HDR_L2_READING(hdr) \ 798 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 799 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 800 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 801 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 802 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 803 804 #define HDR_ISTYPE_METADATA(hdr) \ 805 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 806 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 807 808 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 809 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 810 811 /* 812 * Other sizes 813 */ 814 815 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 816 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 817 818 /* 819 * Hash table routines 820 */ 821 822 #define HT_LOCK_PAD 64 823 824 struct ht_lock { 825 kmutex_t ht_lock; 826 #ifdef _KERNEL 827 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 828 #endif 829 }; 830 831 #define BUF_LOCKS 256 832 typedef struct buf_hash_table { 833 uint64_t ht_mask; 834 arc_buf_hdr_t **ht_table; 835 struct ht_lock ht_locks[BUF_LOCKS]; 836 } buf_hash_table_t; 837 838 static buf_hash_table_t buf_hash_table; 839 840 #define BUF_HASH_INDEX(spa, dva, birth) \ 841 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 842 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 843 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 844 #define HDR_LOCK(hdr) \ 845 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 846 847 uint64_t zfs_crc64_table[256]; 848 849 /* 850 * Level 2 ARC 851 */ 852 853 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 854 #define L2ARC_HEADROOM 2 /* num of writes */ 855 /* 856 * If we discover during ARC scan any buffers to be compressed, we boost 857 * our headroom for the next scanning cycle by this percentage multiple. 858 */ 859 #define L2ARC_HEADROOM_BOOST 200 860 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 861 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 862 863 /* 864 * Used to distinguish headers that are being process by 865 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 866 * address. This can happen when the header is added to the l2arc's list 867 * of buffers to write in the first stage of l2arc_write_buffers(), but 868 * has not yet been written out which happens in the second stage of 869 * l2arc_write_buffers(). 870 */ 871 #define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 872 873 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 874 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 875 876 /* L2ARC Performance Tunables */ 877 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 878 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 879 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 880 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 881 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 882 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 883 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 884 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 885 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 886 887 /* 888 * L2ARC Internals 889 */ 890 struct l2arc_dev { 891 vdev_t *l2ad_vdev; /* vdev */ 892 spa_t *l2ad_spa; /* spa */ 893 uint64_t l2ad_hand; /* next write location */ 894 uint64_t l2ad_start; /* first addr on device */ 895 uint64_t l2ad_end; /* last addr on device */ 896 boolean_t l2ad_first; /* first sweep through */ 897 boolean_t l2ad_writing; /* currently writing */ 898 kmutex_t l2ad_mtx; /* lock for buffer list */ 899 list_t l2ad_buflist; /* buffer list */ 900 list_node_t l2ad_node; /* device list node */ 901 refcount_t l2ad_alloc; /* allocated bytes */ 902 }; 903 904 static list_t L2ARC_dev_list; /* device list */ 905 static list_t *l2arc_dev_list; /* device list pointer */ 906 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 907 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 908 static list_t L2ARC_free_on_write; /* free after write buf list */ 909 static list_t *l2arc_free_on_write; /* free after write list ptr */ 910 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 911 static uint64_t l2arc_ndev; /* number of devices */ 912 913 typedef struct l2arc_read_callback { 914 arc_buf_t *l2rcb_buf; /* read buffer */ 915 spa_t *l2rcb_spa; /* spa */ 916 blkptr_t l2rcb_bp; /* original blkptr */ 917 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 918 int l2rcb_flags; /* original flags */ 919 enum zio_compress l2rcb_compress; /* applied compress */ 920 } l2arc_read_callback_t; 921 922 typedef struct l2arc_write_callback { 923 l2arc_dev_t *l2wcb_dev; /* device info */ 924 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 925 } l2arc_write_callback_t; 926 927 typedef struct l2arc_data_free { 928 /* protected by l2arc_free_on_write_mtx */ 929 void *l2df_data; 930 size_t l2df_size; 931 void (*l2df_func)(void *, size_t); 932 list_node_t l2df_list_node; 933 } l2arc_data_free_t; 934 935 static kmutex_t l2arc_feed_thr_lock; 936 static kcondvar_t l2arc_feed_thr_cv; 937 static uint8_t l2arc_thread_exit; 938 939 static void arc_get_data_buf(arc_buf_t *); 940 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 941 static boolean_t arc_is_overflowing(); 942 static void arc_buf_watch(arc_buf_t *); 943 944 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 945 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 946 947 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 948 static void l2arc_read_done(zio_t *); 949 950 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 951 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 952 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 953 954 static uint64_t 955 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 956 { 957 uint8_t *vdva = (uint8_t *)dva; 958 uint64_t crc = -1ULL; 959 int i; 960 961 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 962 963 for (i = 0; i < sizeof (dva_t); i++) 964 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 965 966 crc ^= (spa>>8) ^ birth; 967 968 return (crc); 969 } 970 971 #define BUF_EMPTY(buf) \ 972 ((buf)->b_dva.dva_word[0] == 0 && \ 973 (buf)->b_dva.dva_word[1] == 0) 974 975 #define BUF_EQUAL(spa, dva, birth, buf) \ 976 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 977 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 978 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 979 980 static void 981 buf_discard_identity(arc_buf_hdr_t *hdr) 982 { 983 hdr->b_dva.dva_word[0] = 0; 984 hdr->b_dva.dva_word[1] = 0; 985 hdr->b_birth = 0; 986 } 987 988 static arc_buf_hdr_t * 989 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 990 { 991 const dva_t *dva = BP_IDENTITY(bp); 992 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 993 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 994 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 995 arc_buf_hdr_t *hdr; 996 997 mutex_enter(hash_lock); 998 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 999 hdr = hdr->b_hash_next) { 1000 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1001 *lockp = hash_lock; 1002 return (hdr); 1003 } 1004 } 1005 mutex_exit(hash_lock); 1006 *lockp = NULL; 1007 return (NULL); 1008 } 1009 1010 /* 1011 * Insert an entry into the hash table. If there is already an element 1012 * equal to elem in the hash table, then the already existing element 1013 * will be returned and the new element will not be inserted. 1014 * Otherwise returns NULL. 1015 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1016 */ 1017 static arc_buf_hdr_t * 1018 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1019 { 1020 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1021 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1022 arc_buf_hdr_t *fhdr; 1023 uint32_t i; 1024 1025 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1026 ASSERT(hdr->b_birth != 0); 1027 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1028 1029 if (lockp != NULL) { 1030 *lockp = hash_lock; 1031 mutex_enter(hash_lock); 1032 } else { 1033 ASSERT(MUTEX_HELD(hash_lock)); 1034 } 1035 1036 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1037 fhdr = fhdr->b_hash_next, i++) { 1038 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1039 return (fhdr); 1040 } 1041 1042 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1043 buf_hash_table.ht_table[idx] = hdr; 1044 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1045 1046 /* collect some hash table performance data */ 1047 if (i > 0) { 1048 ARCSTAT_BUMP(arcstat_hash_collisions); 1049 if (i == 1) 1050 ARCSTAT_BUMP(arcstat_hash_chains); 1051 1052 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1053 } 1054 1055 ARCSTAT_BUMP(arcstat_hash_elements); 1056 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1057 1058 return (NULL); 1059 } 1060 1061 static void 1062 buf_hash_remove(arc_buf_hdr_t *hdr) 1063 { 1064 arc_buf_hdr_t *fhdr, **hdrp; 1065 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1066 1067 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1068 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1069 1070 hdrp = &buf_hash_table.ht_table[idx]; 1071 while ((fhdr = *hdrp) != hdr) { 1072 ASSERT(fhdr != NULL); 1073 hdrp = &fhdr->b_hash_next; 1074 } 1075 *hdrp = hdr->b_hash_next; 1076 hdr->b_hash_next = NULL; 1077 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1078 1079 /* collect some hash table performance data */ 1080 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1081 1082 if (buf_hash_table.ht_table[idx] && 1083 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1084 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1085 } 1086 1087 /* 1088 * Global data structures and functions for the buf kmem cache. 1089 */ 1090 static kmem_cache_t *hdr_full_cache; 1091 static kmem_cache_t *hdr_l2only_cache; 1092 static kmem_cache_t *buf_cache; 1093 1094 static void 1095 buf_fini(void) 1096 { 1097 int i; 1098 1099 kmem_free(buf_hash_table.ht_table, 1100 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1101 for (i = 0; i < BUF_LOCKS; i++) 1102 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1103 kmem_cache_destroy(hdr_full_cache); 1104 kmem_cache_destroy(hdr_l2only_cache); 1105 kmem_cache_destroy(buf_cache); 1106 } 1107 1108 /* 1109 * Constructor callback - called when the cache is empty 1110 * and a new buf is requested. 1111 */ 1112 /* ARGSUSED */ 1113 static int 1114 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1115 { 1116 arc_buf_hdr_t *hdr = vbuf; 1117 1118 bzero(hdr, HDR_FULL_SIZE); 1119 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1120 refcount_create(&hdr->b_l1hdr.b_refcnt); 1121 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1122 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1123 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1124 1125 return (0); 1126 } 1127 1128 /* ARGSUSED */ 1129 static int 1130 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1131 { 1132 arc_buf_hdr_t *hdr = vbuf; 1133 1134 bzero(hdr, HDR_L2ONLY_SIZE); 1135 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1136 1137 return (0); 1138 } 1139 1140 /* ARGSUSED */ 1141 static int 1142 buf_cons(void *vbuf, void *unused, int kmflag) 1143 { 1144 arc_buf_t *buf = vbuf; 1145 1146 bzero(buf, sizeof (arc_buf_t)); 1147 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1148 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1149 1150 return (0); 1151 } 1152 1153 /* 1154 * Destructor callback - called when a cached buf is 1155 * no longer required. 1156 */ 1157 /* ARGSUSED */ 1158 static void 1159 hdr_full_dest(void *vbuf, void *unused) 1160 { 1161 arc_buf_hdr_t *hdr = vbuf; 1162 1163 ASSERT(BUF_EMPTY(hdr)); 1164 cv_destroy(&hdr->b_l1hdr.b_cv); 1165 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1166 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1167 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1168 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1169 } 1170 1171 /* ARGSUSED */ 1172 static void 1173 hdr_l2only_dest(void *vbuf, void *unused) 1174 { 1175 arc_buf_hdr_t *hdr = vbuf; 1176 1177 ASSERT(BUF_EMPTY(hdr)); 1178 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1179 } 1180 1181 /* ARGSUSED */ 1182 static void 1183 buf_dest(void *vbuf, void *unused) 1184 { 1185 arc_buf_t *buf = vbuf; 1186 1187 mutex_destroy(&buf->b_evict_lock); 1188 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1189 } 1190 1191 /* 1192 * Reclaim callback -- invoked when memory is low. 1193 */ 1194 /* ARGSUSED */ 1195 static void 1196 hdr_recl(void *unused) 1197 { 1198 dprintf("hdr_recl called\n"); 1199 /* 1200 * umem calls the reclaim func when we destroy the buf cache, 1201 * which is after we do arc_fini(). 1202 */ 1203 if (!arc_dead) 1204 cv_signal(&arc_reclaim_thread_cv); 1205 } 1206 1207 static void 1208 buf_init(void) 1209 { 1210 uint64_t *ct; 1211 uint64_t hsize = 1ULL << 12; 1212 int i, j; 1213 1214 /* 1215 * The hash table is big enough to fill all of physical memory 1216 * with an average block size of zfs_arc_average_blocksize (default 8K). 1217 * By default, the table will take up 1218 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1219 */ 1220 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1221 hsize <<= 1; 1222 retry: 1223 buf_hash_table.ht_mask = hsize - 1; 1224 buf_hash_table.ht_table = 1225 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1226 if (buf_hash_table.ht_table == NULL) { 1227 ASSERT(hsize > (1ULL << 8)); 1228 hsize >>= 1; 1229 goto retry; 1230 } 1231 1232 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1233 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1234 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1235 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1236 NULL, NULL, 0); 1237 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1238 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1239 1240 for (i = 0; i < 256; i++) 1241 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1242 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1243 1244 for (i = 0; i < BUF_LOCKS; i++) { 1245 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1246 NULL, MUTEX_DEFAULT, NULL); 1247 } 1248 } 1249 1250 /* 1251 * Transition between the two allocation states for the arc_buf_hdr struct. 1252 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1253 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1254 * version is used when a cache buffer is only in the L2ARC in order to reduce 1255 * memory usage. 1256 */ 1257 static arc_buf_hdr_t * 1258 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1259 { 1260 ASSERT(HDR_HAS_L2HDR(hdr)); 1261 1262 arc_buf_hdr_t *nhdr; 1263 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1264 1265 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1266 (old == hdr_l2only_cache && new == hdr_full_cache)); 1267 1268 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1269 1270 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1271 buf_hash_remove(hdr); 1272 1273 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1274 1275 if (new == hdr_full_cache) { 1276 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1277 /* 1278 * arc_access and arc_change_state need to be aware that a 1279 * header has just come out of L2ARC, so we set its state to 1280 * l2c_only even though it's about to change. 1281 */ 1282 nhdr->b_l1hdr.b_state = arc_l2c_only; 1283 1284 /* Verify previous threads set to NULL before freeing */ 1285 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1286 } else { 1287 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1288 ASSERT0(hdr->b_l1hdr.b_datacnt); 1289 1290 /* 1291 * If we've reached here, We must have been called from 1292 * arc_evict_hdr(), as such we should have already been 1293 * removed from any ghost list we were previously on 1294 * (which protects us from racing with arc_evict_state), 1295 * thus no locking is needed during this check. 1296 */ 1297 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1298 1299 /* 1300 * A buffer must not be moved into the arc_l2c_only 1301 * state if it's not finished being written out to the 1302 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1303 * might try to be accessed, even though it was removed. 1304 */ 1305 VERIFY(!HDR_L2_WRITING(hdr)); 1306 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1307 1308 #ifdef ZFS_DEBUG 1309 if (hdr->b_l1hdr.b_thawed != NULL) { 1310 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1311 hdr->b_l1hdr.b_thawed = NULL; 1312 } 1313 #endif 1314 1315 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1316 } 1317 /* 1318 * The header has been reallocated so we need to re-insert it into any 1319 * lists it was on. 1320 */ 1321 (void) buf_hash_insert(nhdr, NULL); 1322 1323 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1324 1325 mutex_enter(&dev->l2ad_mtx); 1326 1327 /* 1328 * We must place the realloc'ed header back into the list at 1329 * the same spot. Otherwise, if it's placed earlier in the list, 1330 * l2arc_write_buffers() could find it during the function's 1331 * write phase, and try to write it out to the l2arc. 1332 */ 1333 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1334 list_remove(&dev->l2ad_buflist, hdr); 1335 1336 mutex_exit(&dev->l2ad_mtx); 1337 1338 /* 1339 * Since we're using the pointer address as the tag when 1340 * incrementing and decrementing the l2ad_alloc refcount, we 1341 * must remove the old pointer (that we're about to destroy) and 1342 * add the new pointer to the refcount. Otherwise we'd remove 1343 * the wrong pointer address when calling arc_hdr_destroy() later. 1344 */ 1345 1346 (void) refcount_remove_many(&dev->l2ad_alloc, 1347 hdr->b_l2hdr.b_asize, hdr); 1348 1349 (void) refcount_add_many(&dev->l2ad_alloc, 1350 nhdr->b_l2hdr.b_asize, nhdr); 1351 1352 buf_discard_identity(hdr); 1353 hdr->b_freeze_cksum = NULL; 1354 kmem_cache_free(old, hdr); 1355 1356 return (nhdr); 1357 } 1358 1359 1360 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1361 1362 static void 1363 arc_cksum_verify(arc_buf_t *buf) 1364 { 1365 zio_cksum_t zc; 1366 1367 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1368 return; 1369 1370 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1371 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1372 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1373 return; 1374 } 1375 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1376 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1377 panic("buffer modified while frozen!"); 1378 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1379 } 1380 1381 static int 1382 arc_cksum_equal(arc_buf_t *buf) 1383 { 1384 zio_cksum_t zc; 1385 int equal; 1386 1387 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1388 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1389 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1390 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1391 1392 return (equal); 1393 } 1394 1395 static void 1396 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1397 { 1398 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1399 return; 1400 1401 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1402 if (buf->b_hdr->b_freeze_cksum != NULL) { 1403 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1404 return; 1405 } 1406 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1407 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1408 NULL, buf->b_hdr->b_freeze_cksum); 1409 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1410 arc_buf_watch(buf); 1411 } 1412 1413 #ifndef _KERNEL 1414 typedef struct procctl { 1415 long cmd; 1416 prwatch_t prwatch; 1417 } procctl_t; 1418 #endif 1419 1420 /* ARGSUSED */ 1421 static void 1422 arc_buf_unwatch(arc_buf_t *buf) 1423 { 1424 #ifndef _KERNEL 1425 if (arc_watch) { 1426 int result; 1427 procctl_t ctl; 1428 ctl.cmd = PCWATCH; 1429 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1430 ctl.prwatch.pr_size = 0; 1431 ctl.prwatch.pr_wflags = 0; 1432 result = write(arc_procfd, &ctl, sizeof (ctl)); 1433 ASSERT3U(result, ==, sizeof (ctl)); 1434 } 1435 #endif 1436 } 1437 1438 /* ARGSUSED */ 1439 static void 1440 arc_buf_watch(arc_buf_t *buf) 1441 { 1442 #ifndef _KERNEL 1443 if (arc_watch) { 1444 int result; 1445 procctl_t ctl; 1446 ctl.cmd = PCWATCH; 1447 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1448 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1449 ctl.prwatch.pr_wflags = WA_WRITE; 1450 result = write(arc_procfd, &ctl, sizeof (ctl)); 1451 ASSERT3U(result, ==, sizeof (ctl)); 1452 } 1453 #endif 1454 } 1455 1456 static arc_buf_contents_t 1457 arc_buf_type(arc_buf_hdr_t *hdr) 1458 { 1459 if (HDR_ISTYPE_METADATA(hdr)) { 1460 return (ARC_BUFC_METADATA); 1461 } else { 1462 return (ARC_BUFC_DATA); 1463 } 1464 } 1465 1466 static uint32_t 1467 arc_bufc_to_flags(arc_buf_contents_t type) 1468 { 1469 switch (type) { 1470 case ARC_BUFC_DATA: 1471 /* metadata field is 0 if buffer contains normal data */ 1472 return (0); 1473 case ARC_BUFC_METADATA: 1474 return (ARC_FLAG_BUFC_METADATA); 1475 default: 1476 break; 1477 } 1478 panic("undefined ARC buffer type!"); 1479 return ((uint32_t)-1); 1480 } 1481 1482 void 1483 arc_buf_thaw(arc_buf_t *buf) 1484 { 1485 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1486 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1487 panic("modifying non-anon buffer!"); 1488 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1489 panic("modifying buffer while i/o in progress!"); 1490 arc_cksum_verify(buf); 1491 } 1492 1493 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1494 if (buf->b_hdr->b_freeze_cksum != NULL) { 1495 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1496 buf->b_hdr->b_freeze_cksum = NULL; 1497 } 1498 1499 #ifdef ZFS_DEBUG 1500 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1501 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1502 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1503 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1504 } 1505 #endif 1506 1507 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1508 1509 arc_buf_unwatch(buf); 1510 } 1511 1512 void 1513 arc_buf_freeze(arc_buf_t *buf) 1514 { 1515 kmutex_t *hash_lock; 1516 1517 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1518 return; 1519 1520 hash_lock = HDR_LOCK(buf->b_hdr); 1521 mutex_enter(hash_lock); 1522 1523 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1524 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1525 arc_cksum_compute(buf, B_FALSE); 1526 mutex_exit(hash_lock); 1527 1528 } 1529 1530 static void 1531 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1532 { 1533 ASSERT(HDR_HAS_L1HDR(hdr)); 1534 ASSERT(MUTEX_HELD(hash_lock)); 1535 arc_state_t *state = hdr->b_l1hdr.b_state; 1536 1537 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1538 (state != arc_anon)) { 1539 /* We don't use the L2-only state list. */ 1540 if (state != arc_l2c_only) { 1541 arc_buf_contents_t type = arc_buf_type(hdr); 1542 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1543 multilist_t *list = &state->arcs_list[type]; 1544 uint64_t *size = &state->arcs_lsize[type]; 1545 1546 multilist_remove(list, hdr); 1547 1548 if (GHOST_STATE(state)) { 1549 ASSERT0(hdr->b_l1hdr.b_datacnt); 1550 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1551 delta = hdr->b_size; 1552 } 1553 ASSERT(delta > 0); 1554 ASSERT3U(*size, >=, delta); 1555 atomic_add_64(size, -delta); 1556 } 1557 /* remove the prefetch flag if we get a reference */ 1558 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1559 } 1560 } 1561 1562 static int 1563 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1564 { 1565 int cnt; 1566 arc_state_t *state = hdr->b_l1hdr.b_state; 1567 1568 ASSERT(HDR_HAS_L1HDR(hdr)); 1569 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1570 ASSERT(!GHOST_STATE(state)); 1571 1572 /* 1573 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1574 * check to prevent usage of the arc_l2c_only list. 1575 */ 1576 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1577 (state != arc_anon)) { 1578 arc_buf_contents_t type = arc_buf_type(hdr); 1579 multilist_t *list = &state->arcs_list[type]; 1580 uint64_t *size = &state->arcs_lsize[type]; 1581 1582 multilist_insert(list, hdr); 1583 1584 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1585 atomic_add_64(size, hdr->b_size * 1586 hdr->b_l1hdr.b_datacnt); 1587 } 1588 return (cnt); 1589 } 1590 1591 /* 1592 * Move the supplied buffer to the indicated state. The hash lock 1593 * for the buffer must be held by the caller. 1594 */ 1595 static void 1596 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1597 kmutex_t *hash_lock) 1598 { 1599 arc_state_t *old_state; 1600 int64_t refcnt; 1601 uint32_t datacnt; 1602 uint64_t from_delta, to_delta; 1603 arc_buf_contents_t buftype = arc_buf_type(hdr); 1604 1605 /* 1606 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1607 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1608 * L1 hdr doesn't always exist when we change state to arc_anon before 1609 * destroying a header, in which case reallocating to add the L1 hdr is 1610 * pointless. 1611 */ 1612 if (HDR_HAS_L1HDR(hdr)) { 1613 old_state = hdr->b_l1hdr.b_state; 1614 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1615 datacnt = hdr->b_l1hdr.b_datacnt; 1616 } else { 1617 old_state = arc_l2c_only; 1618 refcnt = 0; 1619 datacnt = 0; 1620 } 1621 1622 ASSERT(MUTEX_HELD(hash_lock)); 1623 ASSERT3P(new_state, !=, old_state); 1624 ASSERT(refcnt == 0 || datacnt > 0); 1625 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1626 ASSERT(old_state != arc_anon || datacnt <= 1); 1627 1628 from_delta = to_delta = datacnt * hdr->b_size; 1629 1630 /* 1631 * If this buffer is evictable, transfer it from the 1632 * old state list to the new state list. 1633 */ 1634 if (refcnt == 0) { 1635 if (old_state != arc_anon && old_state != arc_l2c_only) { 1636 uint64_t *size = &old_state->arcs_lsize[buftype]; 1637 1638 ASSERT(HDR_HAS_L1HDR(hdr)); 1639 multilist_remove(&old_state->arcs_list[buftype], hdr); 1640 1641 /* 1642 * If prefetching out of the ghost cache, 1643 * we will have a non-zero datacnt. 1644 */ 1645 if (GHOST_STATE(old_state) && datacnt == 0) { 1646 /* ghost elements have a ghost size */ 1647 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1648 from_delta = hdr->b_size; 1649 } 1650 ASSERT3U(*size, >=, from_delta); 1651 atomic_add_64(size, -from_delta); 1652 } 1653 if (new_state != arc_anon && new_state != arc_l2c_only) { 1654 uint64_t *size = &new_state->arcs_lsize[buftype]; 1655 1656 /* 1657 * An L1 header always exists here, since if we're 1658 * moving to some L1-cached state (i.e. not l2c_only or 1659 * anonymous), we realloc the header to add an L1hdr 1660 * beforehand. 1661 */ 1662 ASSERT(HDR_HAS_L1HDR(hdr)); 1663 multilist_insert(&new_state->arcs_list[buftype], hdr); 1664 1665 /* ghost elements have a ghost size */ 1666 if (GHOST_STATE(new_state)) { 1667 ASSERT0(datacnt); 1668 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1669 to_delta = hdr->b_size; 1670 } 1671 atomic_add_64(size, to_delta); 1672 } 1673 } 1674 1675 ASSERT(!BUF_EMPTY(hdr)); 1676 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1677 buf_hash_remove(hdr); 1678 1679 /* adjust state sizes (ignore arc_l2c_only) */ 1680 1681 if (to_delta && new_state != arc_l2c_only) { 1682 ASSERT(HDR_HAS_L1HDR(hdr)); 1683 if (GHOST_STATE(new_state)) { 1684 ASSERT0(datacnt); 1685 1686 /* 1687 * We moving a header to a ghost state, we first 1688 * remove all arc buffers. Thus, we'll have a 1689 * datacnt of zero, and no arc buffer to use for 1690 * the reference. As a result, we use the arc 1691 * header pointer for the reference. 1692 */ 1693 (void) refcount_add_many(&new_state->arcs_size, 1694 hdr->b_size, hdr); 1695 } else { 1696 ASSERT3U(datacnt, !=, 0); 1697 1698 /* 1699 * Each individual buffer holds a unique reference, 1700 * thus we must remove each of these references one 1701 * at a time. 1702 */ 1703 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1704 buf = buf->b_next) { 1705 (void) refcount_add_many(&new_state->arcs_size, 1706 hdr->b_size, buf); 1707 } 1708 } 1709 } 1710 1711 if (from_delta && old_state != arc_l2c_only) { 1712 ASSERT(HDR_HAS_L1HDR(hdr)); 1713 if (GHOST_STATE(old_state)) { 1714 /* 1715 * When moving a header off of a ghost state, 1716 * there's the possibility for datacnt to be 1717 * non-zero. This is because we first add the 1718 * arc buffer to the header prior to changing 1719 * the header's state. Since we used the header 1720 * for the reference when putting the header on 1721 * the ghost state, we must balance that and use 1722 * the header when removing off the ghost state 1723 * (even though datacnt is non zero). 1724 */ 1725 1726 IMPLY(datacnt == 0, new_state == arc_anon || 1727 new_state == arc_l2c_only); 1728 1729 (void) refcount_remove_many(&old_state->arcs_size, 1730 hdr->b_size, hdr); 1731 } else { 1732 ASSERT3P(datacnt, !=, 0); 1733 1734 /* 1735 * Each individual buffer holds a unique reference, 1736 * thus we must remove each of these references one 1737 * at a time. 1738 */ 1739 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1740 buf = buf->b_next) { 1741 (void) refcount_remove_many( 1742 &old_state->arcs_size, hdr->b_size, buf); 1743 } 1744 } 1745 } 1746 1747 if (HDR_HAS_L1HDR(hdr)) 1748 hdr->b_l1hdr.b_state = new_state; 1749 1750 /* 1751 * L2 headers should never be on the L2 state list since they don't 1752 * have L1 headers allocated. 1753 */ 1754 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1755 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1756 } 1757 1758 void 1759 arc_space_consume(uint64_t space, arc_space_type_t type) 1760 { 1761 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1762 1763 switch (type) { 1764 case ARC_SPACE_DATA: 1765 ARCSTAT_INCR(arcstat_data_size, space); 1766 break; 1767 case ARC_SPACE_META: 1768 ARCSTAT_INCR(arcstat_metadata_size, space); 1769 break; 1770 case ARC_SPACE_OTHER: 1771 ARCSTAT_INCR(arcstat_other_size, space); 1772 break; 1773 case ARC_SPACE_HDRS: 1774 ARCSTAT_INCR(arcstat_hdr_size, space); 1775 break; 1776 case ARC_SPACE_L2HDRS: 1777 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1778 break; 1779 } 1780 1781 if (type != ARC_SPACE_DATA) 1782 ARCSTAT_INCR(arcstat_meta_used, space); 1783 1784 atomic_add_64(&arc_size, space); 1785 } 1786 1787 void 1788 arc_space_return(uint64_t space, arc_space_type_t type) 1789 { 1790 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1791 1792 switch (type) { 1793 case ARC_SPACE_DATA: 1794 ARCSTAT_INCR(arcstat_data_size, -space); 1795 break; 1796 case ARC_SPACE_META: 1797 ARCSTAT_INCR(arcstat_metadata_size, -space); 1798 break; 1799 case ARC_SPACE_OTHER: 1800 ARCSTAT_INCR(arcstat_other_size, -space); 1801 break; 1802 case ARC_SPACE_HDRS: 1803 ARCSTAT_INCR(arcstat_hdr_size, -space); 1804 break; 1805 case ARC_SPACE_L2HDRS: 1806 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1807 break; 1808 } 1809 1810 if (type != ARC_SPACE_DATA) { 1811 ASSERT(arc_meta_used >= space); 1812 if (arc_meta_max < arc_meta_used) 1813 arc_meta_max = arc_meta_used; 1814 ARCSTAT_INCR(arcstat_meta_used, -space); 1815 } 1816 1817 ASSERT(arc_size >= space); 1818 atomic_add_64(&arc_size, -space); 1819 } 1820 1821 arc_buf_t * 1822 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1823 { 1824 arc_buf_hdr_t *hdr; 1825 arc_buf_t *buf; 1826 1827 ASSERT3U(size, >, 0); 1828 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1829 ASSERT(BUF_EMPTY(hdr)); 1830 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1831 hdr->b_size = size; 1832 hdr->b_spa = spa_load_guid(spa); 1833 1834 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1835 buf->b_hdr = hdr; 1836 buf->b_data = NULL; 1837 buf->b_efunc = NULL; 1838 buf->b_private = NULL; 1839 buf->b_next = NULL; 1840 1841 hdr->b_flags = arc_bufc_to_flags(type); 1842 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1843 1844 hdr->b_l1hdr.b_buf = buf; 1845 hdr->b_l1hdr.b_state = arc_anon; 1846 hdr->b_l1hdr.b_arc_access = 0; 1847 hdr->b_l1hdr.b_datacnt = 1; 1848 hdr->b_l1hdr.b_tmp_cdata = NULL; 1849 1850 arc_get_data_buf(buf); 1851 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1852 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1853 1854 return (buf); 1855 } 1856 1857 static char *arc_onloan_tag = "onloan"; 1858 1859 /* 1860 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1861 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1862 * buffers must be returned to the arc before they can be used by the DMU or 1863 * freed. 1864 */ 1865 arc_buf_t * 1866 arc_loan_buf(spa_t *spa, int size) 1867 { 1868 arc_buf_t *buf; 1869 1870 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1871 1872 atomic_add_64(&arc_loaned_bytes, size); 1873 return (buf); 1874 } 1875 1876 /* 1877 * Return a loaned arc buffer to the arc. 1878 */ 1879 void 1880 arc_return_buf(arc_buf_t *buf, void *tag) 1881 { 1882 arc_buf_hdr_t *hdr = buf->b_hdr; 1883 1884 ASSERT(buf->b_data != NULL); 1885 ASSERT(HDR_HAS_L1HDR(hdr)); 1886 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1887 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1888 1889 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1890 } 1891 1892 /* Detach an arc_buf from a dbuf (tag) */ 1893 void 1894 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1895 { 1896 arc_buf_hdr_t *hdr = buf->b_hdr; 1897 1898 ASSERT(buf->b_data != NULL); 1899 ASSERT(HDR_HAS_L1HDR(hdr)); 1900 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1901 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 1902 buf->b_efunc = NULL; 1903 buf->b_private = NULL; 1904 1905 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1906 } 1907 1908 static arc_buf_t * 1909 arc_buf_clone(arc_buf_t *from) 1910 { 1911 arc_buf_t *buf; 1912 arc_buf_hdr_t *hdr = from->b_hdr; 1913 uint64_t size = hdr->b_size; 1914 1915 ASSERT(HDR_HAS_L1HDR(hdr)); 1916 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 1917 1918 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1919 buf->b_hdr = hdr; 1920 buf->b_data = NULL; 1921 buf->b_efunc = NULL; 1922 buf->b_private = NULL; 1923 buf->b_next = hdr->b_l1hdr.b_buf; 1924 hdr->b_l1hdr.b_buf = buf; 1925 arc_get_data_buf(buf); 1926 bcopy(from->b_data, buf->b_data, size); 1927 1928 /* 1929 * This buffer already exists in the arc so create a duplicate 1930 * copy for the caller. If the buffer is associated with user data 1931 * then track the size and number of duplicates. These stats will be 1932 * updated as duplicate buffers are created and destroyed. 1933 */ 1934 if (HDR_ISTYPE_DATA(hdr)) { 1935 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1936 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1937 } 1938 hdr->b_l1hdr.b_datacnt += 1; 1939 return (buf); 1940 } 1941 1942 void 1943 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1944 { 1945 arc_buf_hdr_t *hdr; 1946 kmutex_t *hash_lock; 1947 1948 /* 1949 * Check to see if this buffer is evicted. Callers 1950 * must verify b_data != NULL to know if the add_ref 1951 * was successful. 1952 */ 1953 mutex_enter(&buf->b_evict_lock); 1954 if (buf->b_data == NULL) { 1955 mutex_exit(&buf->b_evict_lock); 1956 return; 1957 } 1958 hash_lock = HDR_LOCK(buf->b_hdr); 1959 mutex_enter(hash_lock); 1960 hdr = buf->b_hdr; 1961 ASSERT(HDR_HAS_L1HDR(hdr)); 1962 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1963 mutex_exit(&buf->b_evict_lock); 1964 1965 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 1966 hdr->b_l1hdr.b_state == arc_mfu); 1967 1968 add_reference(hdr, hash_lock, tag); 1969 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1970 arc_access(hdr, hash_lock); 1971 mutex_exit(hash_lock); 1972 ARCSTAT_BUMP(arcstat_hits); 1973 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 1974 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 1975 data, metadata, hits); 1976 } 1977 1978 static void 1979 arc_buf_free_on_write(void *data, size_t size, 1980 void (*free_func)(void *, size_t)) 1981 { 1982 l2arc_data_free_t *df; 1983 1984 df = kmem_alloc(sizeof (*df), KM_SLEEP); 1985 df->l2df_data = data; 1986 df->l2df_size = size; 1987 df->l2df_func = free_func; 1988 mutex_enter(&l2arc_free_on_write_mtx); 1989 list_insert_head(l2arc_free_on_write, df); 1990 mutex_exit(&l2arc_free_on_write_mtx); 1991 } 1992 1993 /* 1994 * Free the arc data buffer. If it is an l2arc write in progress, 1995 * the buffer is placed on l2arc_free_on_write to be freed later. 1996 */ 1997 static void 1998 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1999 { 2000 arc_buf_hdr_t *hdr = buf->b_hdr; 2001 2002 if (HDR_L2_WRITING(hdr)) { 2003 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2004 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2005 } else { 2006 free_func(buf->b_data, hdr->b_size); 2007 } 2008 } 2009 2010 static void 2011 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2012 { 2013 ASSERT(HDR_HAS_L2HDR(hdr)); 2014 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2015 2016 /* 2017 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2018 * that doesn't exist, the header is in the arc_l2c_only state, 2019 * and there isn't anything to free (it's already been freed). 2020 */ 2021 if (!HDR_HAS_L1HDR(hdr)) 2022 return; 2023 2024 /* 2025 * The header isn't being written to the l2arc device, thus it 2026 * shouldn't have a b_tmp_cdata to free. 2027 */ 2028 if (!HDR_L2_WRITING(hdr)) { 2029 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2030 return; 2031 } 2032 2033 /* 2034 * The header does not have compression enabled. This can be due 2035 * to the buffer not being compressible, or because we're 2036 * freeing the buffer before the second phase of 2037 * l2arc_write_buffer() has started (which does the compression 2038 * step). In either case, b_tmp_cdata does not point to a 2039 * separately compressed buffer, so there's nothing to free (it 2040 * points to the same buffer as the arc_buf_t's b_data field). 2041 */ 2042 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) { 2043 hdr->b_l1hdr.b_tmp_cdata = NULL; 2044 return; 2045 } 2046 2047 /* 2048 * There's nothing to free since the buffer was all zero's and 2049 * compressed to a zero length buffer. 2050 */ 2051 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2052 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2053 return; 2054 } 2055 2056 ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress)); 2057 2058 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2059 hdr->b_size, zio_data_buf_free); 2060 2061 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2062 hdr->b_l1hdr.b_tmp_cdata = NULL; 2063 } 2064 2065 /* 2066 * Free up buf->b_data and if 'remove' is set, then pull the 2067 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2068 */ 2069 static void 2070 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2071 { 2072 arc_buf_t **bufp; 2073 2074 /* free up data associated with the buf */ 2075 if (buf->b_data != NULL) { 2076 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2077 uint64_t size = buf->b_hdr->b_size; 2078 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2079 2080 arc_cksum_verify(buf); 2081 arc_buf_unwatch(buf); 2082 2083 if (type == ARC_BUFC_METADATA) { 2084 arc_buf_data_free(buf, zio_buf_free); 2085 arc_space_return(size, ARC_SPACE_META); 2086 } else { 2087 ASSERT(type == ARC_BUFC_DATA); 2088 arc_buf_data_free(buf, zio_data_buf_free); 2089 arc_space_return(size, ARC_SPACE_DATA); 2090 } 2091 2092 /* protected by hash lock, if in the hash table */ 2093 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2094 uint64_t *cnt = &state->arcs_lsize[type]; 2095 2096 ASSERT(refcount_is_zero( 2097 &buf->b_hdr->b_l1hdr.b_refcnt)); 2098 ASSERT(state != arc_anon && state != arc_l2c_only); 2099 2100 ASSERT3U(*cnt, >=, size); 2101 atomic_add_64(cnt, -size); 2102 } 2103 2104 (void) refcount_remove_many(&state->arcs_size, size, buf); 2105 buf->b_data = NULL; 2106 2107 /* 2108 * If we're destroying a duplicate buffer make sure 2109 * that the appropriate statistics are updated. 2110 */ 2111 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2112 HDR_ISTYPE_DATA(buf->b_hdr)) { 2113 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2114 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2115 } 2116 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2117 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2118 } 2119 2120 /* only remove the buf if requested */ 2121 if (!remove) 2122 return; 2123 2124 /* remove the buf from the hdr list */ 2125 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2126 bufp = &(*bufp)->b_next) 2127 continue; 2128 *bufp = buf->b_next; 2129 buf->b_next = NULL; 2130 2131 ASSERT(buf->b_efunc == NULL); 2132 2133 /* clean up the buf */ 2134 buf->b_hdr = NULL; 2135 kmem_cache_free(buf_cache, buf); 2136 } 2137 2138 static void 2139 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2140 { 2141 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2142 l2arc_dev_t *dev = l2hdr->b_dev; 2143 2144 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2145 ASSERT(HDR_HAS_L2HDR(hdr)); 2146 2147 list_remove(&dev->l2ad_buflist, hdr); 2148 2149 /* 2150 * We don't want to leak the b_tmp_cdata buffer that was 2151 * allocated in l2arc_write_buffers() 2152 */ 2153 arc_buf_l2_cdata_free(hdr); 2154 2155 /* 2156 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2157 * this header is being processed by l2arc_write_buffers() (i.e. 2158 * it's in the first stage of l2arc_write_buffers()). 2159 * Re-affirming that truth here, just to serve as a reminder. If 2160 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2161 * may not have its HDR_L2_WRITING flag set. (the write may have 2162 * completed, in which case HDR_L2_WRITING will be false and the 2163 * b_daddr field will point to the address of the buffer on disk). 2164 */ 2165 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2166 2167 /* 2168 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2169 * l2arc_write_buffers(). Since we've just removed this header 2170 * from the l2arc buffer list, this header will never reach the 2171 * second stage of l2arc_write_buffers(), which increments the 2172 * accounting stats for this header. Thus, we must be careful 2173 * not to decrement them for this header either. 2174 */ 2175 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2176 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2177 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2178 2179 vdev_space_update(dev->l2ad_vdev, 2180 -l2hdr->b_asize, 0, 0); 2181 2182 (void) refcount_remove_many(&dev->l2ad_alloc, 2183 l2hdr->b_asize, hdr); 2184 } 2185 2186 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2187 } 2188 2189 static void 2190 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2191 { 2192 if (HDR_HAS_L1HDR(hdr)) { 2193 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2194 hdr->b_l1hdr.b_datacnt > 0); 2195 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2196 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2197 } 2198 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2199 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2200 2201 if (HDR_HAS_L2HDR(hdr)) { 2202 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2203 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2204 2205 if (!buflist_held) 2206 mutex_enter(&dev->l2ad_mtx); 2207 2208 /* 2209 * Even though we checked this conditional above, we 2210 * need to check this again now that we have the 2211 * l2ad_mtx. This is because we could be racing with 2212 * another thread calling l2arc_evict() which might have 2213 * destroyed this header's L2 portion as we were waiting 2214 * to acquire the l2ad_mtx. If that happens, we don't 2215 * want to re-destroy the header's L2 portion. 2216 */ 2217 if (HDR_HAS_L2HDR(hdr)) 2218 arc_hdr_l2hdr_destroy(hdr); 2219 2220 if (!buflist_held) 2221 mutex_exit(&dev->l2ad_mtx); 2222 } 2223 2224 if (!BUF_EMPTY(hdr)) 2225 buf_discard_identity(hdr); 2226 2227 if (hdr->b_freeze_cksum != NULL) { 2228 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2229 hdr->b_freeze_cksum = NULL; 2230 } 2231 2232 if (HDR_HAS_L1HDR(hdr)) { 2233 while (hdr->b_l1hdr.b_buf) { 2234 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2235 2236 if (buf->b_efunc != NULL) { 2237 mutex_enter(&arc_user_evicts_lock); 2238 mutex_enter(&buf->b_evict_lock); 2239 ASSERT(buf->b_hdr != NULL); 2240 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2241 hdr->b_l1hdr.b_buf = buf->b_next; 2242 buf->b_hdr = &arc_eviction_hdr; 2243 buf->b_next = arc_eviction_list; 2244 arc_eviction_list = buf; 2245 mutex_exit(&buf->b_evict_lock); 2246 cv_signal(&arc_user_evicts_cv); 2247 mutex_exit(&arc_user_evicts_lock); 2248 } else { 2249 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2250 } 2251 } 2252 #ifdef ZFS_DEBUG 2253 if (hdr->b_l1hdr.b_thawed != NULL) { 2254 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2255 hdr->b_l1hdr.b_thawed = NULL; 2256 } 2257 #endif 2258 } 2259 2260 ASSERT3P(hdr->b_hash_next, ==, NULL); 2261 if (HDR_HAS_L1HDR(hdr)) { 2262 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2263 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2264 kmem_cache_free(hdr_full_cache, hdr); 2265 } else { 2266 kmem_cache_free(hdr_l2only_cache, hdr); 2267 } 2268 } 2269 2270 void 2271 arc_buf_free(arc_buf_t *buf, void *tag) 2272 { 2273 arc_buf_hdr_t *hdr = buf->b_hdr; 2274 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2275 2276 ASSERT(buf->b_efunc == NULL); 2277 ASSERT(buf->b_data != NULL); 2278 2279 if (hashed) { 2280 kmutex_t *hash_lock = HDR_LOCK(hdr); 2281 2282 mutex_enter(hash_lock); 2283 hdr = buf->b_hdr; 2284 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2285 2286 (void) remove_reference(hdr, hash_lock, tag); 2287 if (hdr->b_l1hdr.b_datacnt > 1) { 2288 arc_buf_destroy(buf, TRUE); 2289 } else { 2290 ASSERT(buf == hdr->b_l1hdr.b_buf); 2291 ASSERT(buf->b_efunc == NULL); 2292 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2293 } 2294 mutex_exit(hash_lock); 2295 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2296 int destroy_hdr; 2297 /* 2298 * We are in the middle of an async write. Don't destroy 2299 * this buffer unless the write completes before we finish 2300 * decrementing the reference count. 2301 */ 2302 mutex_enter(&arc_user_evicts_lock); 2303 (void) remove_reference(hdr, NULL, tag); 2304 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2305 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2306 mutex_exit(&arc_user_evicts_lock); 2307 if (destroy_hdr) 2308 arc_hdr_destroy(hdr); 2309 } else { 2310 if (remove_reference(hdr, NULL, tag) > 0) 2311 arc_buf_destroy(buf, TRUE); 2312 else 2313 arc_hdr_destroy(hdr); 2314 } 2315 } 2316 2317 boolean_t 2318 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2319 { 2320 arc_buf_hdr_t *hdr = buf->b_hdr; 2321 kmutex_t *hash_lock = HDR_LOCK(hdr); 2322 boolean_t no_callback = (buf->b_efunc == NULL); 2323 2324 if (hdr->b_l1hdr.b_state == arc_anon) { 2325 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2326 arc_buf_free(buf, tag); 2327 return (no_callback); 2328 } 2329 2330 mutex_enter(hash_lock); 2331 hdr = buf->b_hdr; 2332 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2333 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2334 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2335 ASSERT(buf->b_data != NULL); 2336 2337 (void) remove_reference(hdr, hash_lock, tag); 2338 if (hdr->b_l1hdr.b_datacnt > 1) { 2339 if (no_callback) 2340 arc_buf_destroy(buf, TRUE); 2341 } else if (no_callback) { 2342 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2343 ASSERT(buf->b_efunc == NULL); 2344 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2345 } 2346 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2347 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2348 mutex_exit(hash_lock); 2349 return (no_callback); 2350 } 2351 2352 int32_t 2353 arc_buf_size(arc_buf_t *buf) 2354 { 2355 return (buf->b_hdr->b_size); 2356 } 2357 2358 /* 2359 * Called from the DMU to determine if the current buffer should be 2360 * evicted. In order to ensure proper locking, the eviction must be initiated 2361 * from the DMU. Return true if the buffer is associated with user data and 2362 * duplicate buffers still exist. 2363 */ 2364 boolean_t 2365 arc_buf_eviction_needed(arc_buf_t *buf) 2366 { 2367 arc_buf_hdr_t *hdr; 2368 boolean_t evict_needed = B_FALSE; 2369 2370 if (zfs_disable_dup_eviction) 2371 return (B_FALSE); 2372 2373 mutex_enter(&buf->b_evict_lock); 2374 hdr = buf->b_hdr; 2375 if (hdr == NULL) { 2376 /* 2377 * We are in arc_do_user_evicts(); let that function 2378 * perform the eviction. 2379 */ 2380 ASSERT(buf->b_data == NULL); 2381 mutex_exit(&buf->b_evict_lock); 2382 return (B_FALSE); 2383 } else if (buf->b_data == NULL) { 2384 /* 2385 * We have already been added to the arc eviction list; 2386 * recommend eviction. 2387 */ 2388 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2389 mutex_exit(&buf->b_evict_lock); 2390 return (B_TRUE); 2391 } 2392 2393 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2394 evict_needed = B_TRUE; 2395 2396 mutex_exit(&buf->b_evict_lock); 2397 return (evict_needed); 2398 } 2399 2400 /* 2401 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2402 * state of the header is dependent on it's state prior to entering this 2403 * function. The following transitions are possible: 2404 * 2405 * - arc_mru -> arc_mru_ghost 2406 * - arc_mfu -> arc_mfu_ghost 2407 * - arc_mru_ghost -> arc_l2c_only 2408 * - arc_mru_ghost -> deleted 2409 * - arc_mfu_ghost -> arc_l2c_only 2410 * - arc_mfu_ghost -> deleted 2411 */ 2412 static int64_t 2413 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2414 { 2415 arc_state_t *evicted_state, *state; 2416 int64_t bytes_evicted = 0; 2417 2418 ASSERT(MUTEX_HELD(hash_lock)); 2419 ASSERT(HDR_HAS_L1HDR(hdr)); 2420 2421 state = hdr->b_l1hdr.b_state; 2422 if (GHOST_STATE(state)) { 2423 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2424 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2425 2426 /* 2427 * l2arc_write_buffers() relies on a header's L1 portion 2428 * (i.e. it's b_tmp_cdata field) during it's write phase. 2429 * Thus, we cannot push a header onto the arc_l2c_only 2430 * state (removing it's L1 piece) until the header is 2431 * done being written to the l2arc. 2432 */ 2433 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2434 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2435 return (bytes_evicted); 2436 } 2437 2438 ARCSTAT_BUMP(arcstat_deleted); 2439 bytes_evicted += hdr->b_size; 2440 2441 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2442 2443 if (HDR_HAS_L2HDR(hdr)) { 2444 /* 2445 * This buffer is cached on the 2nd Level ARC; 2446 * don't destroy the header. 2447 */ 2448 arc_change_state(arc_l2c_only, hdr, hash_lock); 2449 /* 2450 * dropping from L1+L2 cached to L2-only, 2451 * realloc to remove the L1 header. 2452 */ 2453 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2454 hdr_l2only_cache); 2455 } else { 2456 arc_change_state(arc_anon, hdr, hash_lock); 2457 arc_hdr_destroy(hdr); 2458 } 2459 return (bytes_evicted); 2460 } 2461 2462 ASSERT(state == arc_mru || state == arc_mfu); 2463 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2464 2465 /* prefetch buffers have a minimum lifespan */ 2466 if (HDR_IO_IN_PROGRESS(hdr) || 2467 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2468 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2469 arc_min_prefetch_lifespan)) { 2470 ARCSTAT_BUMP(arcstat_evict_skip); 2471 return (bytes_evicted); 2472 } 2473 2474 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2475 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2476 while (hdr->b_l1hdr.b_buf) { 2477 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2478 if (!mutex_tryenter(&buf->b_evict_lock)) { 2479 ARCSTAT_BUMP(arcstat_mutex_miss); 2480 break; 2481 } 2482 if (buf->b_data != NULL) 2483 bytes_evicted += hdr->b_size; 2484 if (buf->b_efunc != NULL) { 2485 mutex_enter(&arc_user_evicts_lock); 2486 arc_buf_destroy(buf, FALSE); 2487 hdr->b_l1hdr.b_buf = buf->b_next; 2488 buf->b_hdr = &arc_eviction_hdr; 2489 buf->b_next = arc_eviction_list; 2490 arc_eviction_list = buf; 2491 cv_signal(&arc_user_evicts_cv); 2492 mutex_exit(&arc_user_evicts_lock); 2493 mutex_exit(&buf->b_evict_lock); 2494 } else { 2495 mutex_exit(&buf->b_evict_lock); 2496 arc_buf_destroy(buf, TRUE); 2497 } 2498 } 2499 2500 if (HDR_HAS_L2HDR(hdr)) { 2501 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2502 } else { 2503 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2504 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2505 else 2506 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2507 } 2508 2509 if (hdr->b_l1hdr.b_datacnt == 0) { 2510 arc_change_state(evicted_state, hdr, hash_lock); 2511 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2512 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2513 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2514 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2515 } 2516 2517 return (bytes_evicted); 2518 } 2519 2520 static uint64_t 2521 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2522 uint64_t spa, int64_t bytes) 2523 { 2524 multilist_sublist_t *mls; 2525 uint64_t bytes_evicted = 0; 2526 arc_buf_hdr_t *hdr; 2527 kmutex_t *hash_lock; 2528 int evict_count = 0; 2529 2530 ASSERT3P(marker, !=, NULL); 2531 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2532 2533 mls = multilist_sublist_lock(ml, idx); 2534 2535 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2536 hdr = multilist_sublist_prev(mls, marker)) { 2537 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2538 (evict_count >= zfs_arc_evict_batch_limit)) 2539 break; 2540 2541 /* 2542 * To keep our iteration location, move the marker 2543 * forward. Since we're not holding hdr's hash lock, we 2544 * must be very careful and not remove 'hdr' from the 2545 * sublist. Otherwise, other consumers might mistake the 2546 * 'hdr' as not being on a sublist when they call the 2547 * multilist_link_active() function (they all rely on 2548 * the hash lock protecting concurrent insertions and 2549 * removals). multilist_sublist_move_forward() was 2550 * specifically implemented to ensure this is the case 2551 * (only 'marker' will be removed and re-inserted). 2552 */ 2553 multilist_sublist_move_forward(mls, marker); 2554 2555 /* 2556 * The only case where the b_spa field should ever be 2557 * zero, is the marker headers inserted by 2558 * arc_evict_state(). It's possible for multiple threads 2559 * to be calling arc_evict_state() concurrently (e.g. 2560 * dsl_pool_close() and zio_inject_fault()), so we must 2561 * skip any markers we see from these other threads. 2562 */ 2563 if (hdr->b_spa == 0) 2564 continue; 2565 2566 /* we're only interested in evicting buffers of a certain spa */ 2567 if (spa != 0 && hdr->b_spa != spa) { 2568 ARCSTAT_BUMP(arcstat_evict_skip); 2569 continue; 2570 } 2571 2572 hash_lock = HDR_LOCK(hdr); 2573 2574 /* 2575 * We aren't calling this function from any code path 2576 * that would already be holding a hash lock, so we're 2577 * asserting on this assumption to be defensive in case 2578 * this ever changes. Without this check, it would be 2579 * possible to incorrectly increment arcstat_mutex_miss 2580 * below (e.g. if the code changed such that we called 2581 * this function with a hash lock held). 2582 */ 2583 ASSERT(!MUTEX_HELD(hash_lock)); 2584 2585 if (mutex_tryenter(hash_lock)) { 2586 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2587 mutex_exit(hash_lock); 2588 2589 bytes_evicted += evicted; 2590 2591 /* 2592 * If evicted is zero, arc_evict_hdr() must have 2593 * decided to skip this header, don't increment 2594 * evict_count in this case. 2595 */ 2596 if (evicted != 0) 2597 evict_count++; 2598 2599 /* 2600 * If arc_size isn't overflowing, signal any 2601 * threads that might happen to be waiting. 2602 * 2603 * For each header evicted, we wake up a single 2604 * thread. If we used cv_broadcast, we could 2605 * wake up "too many" threads causing arc_size 2606 * to significantly overflow arc_c; since 2607 * arc_get_data_buf() doesn't check for overflow 2608 * when it's woken up (it doesn't because it's 2609 * possible for the ARC to be overflowing while 2610 * full of un-evictable buffers, and the 2611 * function should proceed in this case). 2612 * 2613 * If threads are left sleeping, due to not 2614 * using cv_broadcast, they will be woken up 2615 * just before arc_reclaim_thread() sleeps. 2616 */ 2617 mutex_enter(&arc_reclaim_lock); 2618 if (!arc_is_overflowing()) 2619 cv_signal(&arc_reclaim_waiters_cv); 2620 mutex_exit(&arc_reclaim_lock); 2621 } else { 2622 ARCSTAT_BUMP(arcstat_mutex_miss); 2623 } 2624 } 2625 2626 multilist_sublist_unlock(mls); 2627 2628 return (bytes_evicted); 2629 } 2630 2631 /* 2632 * Evict buffers from the given arc state, until we've removed the 2633 * specified number of bytes. Move the removed buffers to the 2634 * appropriate evict state. 2635 * 2636 * This function makes a "best effort". It skips over any buffers 2637 * it can't get a hash_lock on, and so, may not catch all candidates. 2638 * It may also return without evicting as much space as requested. 2639 * 2640 * If bytes is specified using the special value ARC_EVICT_ALL, this 2641 * will evict all available (i.e. unlocked and evictable) buffers from 2642 * the given arc state; which is used by arc_flush(). 2643 */ 2644 static uint64_t 2645 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2646 arc_buf_contents_t type) 2647 { 2648 uint64_t total_evicted = 0; 2649 multilist_t *ml = &state->arcs_list[type]; 2650 int num_sublists; 2651 arc_buf_hdr_t **markers; 2652 2653 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2654 2655 num_sublists = multilist_get_num_sublists(ml); 2656 2657 /* 2658 * If we've tried to evict from each sublist, made some 2659 * progress, but still have not hit the target number of bytes 2660 * to evict, we want to keep trying. The markers allow us to 2661 * pick up where we left off for each individual sublist, rather 2662 * than starting from the tail each time. 2663 */ 2664 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2665 for (int i = 0; i < num_sublists; i++) { 2666 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2667 2668 /* 2669 * A b_spa of 0 is used to indicate that this header is 2670 * a marker. This fact is used in arc_adjust_type() and 2671 * arc_evict_state_impl(). 2672 */ 2673 markers[i]->b_spa = 0; 2674 2675 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2676 multilist_sublist_insert_tail(mls, markers[i]); 2677 multilist_sublist_unlock(mls); 2678 } 2679 2680 /* 2681 * While we haven't hit our target number of bytes to evict, or 2682 * we're evicting all available buffers. 2683 */ 2684 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2685 /* 2686 * Start eviction using a randomly selected sublist, 2687 * this is to try and evenly balance eviction across all 2688 * sublists. Always starting at the same sublist 2689 * (e.g. index 0) would cause evictions to favor certain 2690 * sublists over others. 2691 */ 2692 int sublist_idx = multilist_get_random_index(ml); 2693 uint64_t scan_evicted = 0; 2694 2695 for (int i = 0; i < num_sublists; i++) { 2696 uint64_t bytes_remaining; 2697 uint64_t bytes_evicted; 2698 2699 if (bytes == ARC_EVICT_ALL) 2700 bytes_remaining = ARC_EVICT_ALL; 2701 else if (total_evicted < bytes) 2702 bytes_remaining = bytes - total_evicted; 2703 else 2704 break; 2705 2706 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2707 markers[sublist_idx], spa, bytes_remaining); 2708 2709 scan_evicted += bytes_evicted; 2710 total_evicted += bytes_evicted; 2711 2712 /* we've reached the end, wrap to the beginning */ 2713 if (++sublist_idx >= num_sublists) 2714 sublist_idx = 0; 2715 } 2716 2717 /* 2718 * If we didn't evict anything during this scan, we have 2719 * no reason to believe we'll evict more during another 2720 * scan, so break the loop. 2721 */ 2722 if (scan_evicted == 0) { 2723 /* This isn't possible, let's make that obvious */ 2724 ASSERT3S(bytes, !=, 0); 2725 2726 /* 2727 * When bytes is ARC_EVICT_ALL, the only way to 2728 * break the loop is when scan_evicted is zero. 2729 * In that case, we actually have evicted enough, 2730 * so we don't want to increment the kstat. 2731 */ 2732 if (bytes != ARC_EVICT_ALL) { 2733 ASSERT3S(total_evicted, <, bytes); 2734 ARCSTAT_BUMP(arcstat_evict_not_enough); 2735 } 2736 2737 break; 2738 } 2739 } 2740 2741 for (int i = 0; i < num_sublists; i++) { 2742 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2743 multilist_sublist_remove(mls, markers[i]); 2744 multilist_sublist_unlock(mls); 2745 2746 kmem_cache_free(hdr_full_cache, markers[i]); 2747 } 2748 kmem_free(markers, sizeof (*markers) * num_sublists); 2749 2750 return (total_evicted); 2751 } 2752 2753 /* 2754 * Flush all "evictable" data of the given type from the arc state 2755 * specified. This will not evict any "active" buffers (i.e. referenced). 2756 * 2757 * When 'retry' is set to FALSE, the function will make a single pass 2758 * over the state and evict any buffers that it can. Since it doesn't 2759 * continually retry the eviction, it might end up leaving some buffers 2760 * in the ARC due to lock misses. 2761 * 2762 * When 'retry' is set to TRUE, the function will continually retry the 2763 * eviction until *all* evictable buffers have been removed from the 2764 * state. As a result, if concurrent insertions into the state are 2765 * allowed (e.g. if the ARC isn't shutting down), this function might 2766 * wind up in an infinite loop, continually trying to evict buffers. 2767 */ 2768 static uint64_t 2769 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2770 boolean_t retry) 2771 { 2772 uint64_t evicted = 0; 2773 2774 while (state->arcs_lsize[type] != 0) { 2775 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2776 2777 if (!retry) 2778 break; 2779 } 2780 2781 return (evicted); 2782 } 2783 2784 /* 2785 * Evict the specified number of bytes from the state specified, 2786 * restricting eviction to the spa and type given. This function 2787 * prevents us from trying to evict more from a state's list than 2788 * is "evictable", and to skip evicting altogether when passed a 2789 * negative value for "bytes". In contrast, arc_evict_state() will 2790 * evict everything it can, when passed a negative value for "bytes". 2791 */ 2792 static uint64_t 2793 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 2794 arc_buf_contents_t type) 2795 { 2796 int64_t delta; 2797 2798 if (bytes > 0 && state->arcs_lsize[type] > 0) { 2799 delta = MIN(state->arcs_lsize[type], bytes); 2800 return (arc_evict_state(state, spa, delta, type)); 2801 } 2802 2803 return (0); 2804 } 2805 2806 /* 2807 * Evict metadata buffers from the cache, such that arc_meta_used is 2808 * capped by the arc_meta_limit tunable. 2809 */ 2810 static uint64_t 2811 arc_adjust_meta(void) 2812 { 2813 uint64_t total_evicted = 0; 2814 int64_t target; 2815 2816 /* 2817 * If we're over the meta limit, we want to evict enough 2818 * metadata to get back under the meta limit. We don't want to 2819 * evict so much that we drop the MRU below arc_p, though. If 2820 * we're over the meta limit more than we're over arc_p, we 2821 * evict some from the MRU here, and some from the MFU below. 2822 */ 2823 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2824 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2825 refcount_count(&arc_mru->arcs_size) - arc_p)); 2826 2827 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2828 2829 /* 2830 * Similar to the above, we want to evict enough bytes to get us 2831 * below the meta limit, but not so much as to drop us below the 2832 * space alloted to the MFU (which is defined as arc_c - arc_p). 2833 */ 2834 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2835 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 2836 2837 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2838 2839 return (total_evicted); 2840 } 2841 2842 /* 2843 * Return the type of the oldest buffer in the given arc state 2844 * 2845 * This function will select a random sublist of type ARC_BUFC_DATA and 2846 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 2847 * is compared, and the type which contains the "older" buffer will be 2848 * returned. 2849 */ 2850 static arc_buf_contents_t 2851 arc_adjust_type(arc_state_t *state) 2852 { 2853 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 2854 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 2855 int data_idx = multilist_get_random_index(data_ml); 2856 int meta_idx = multilist_get_random_index(meta_ml); 2857 multilist_sublist_t *data_mls; 2858 multilist_sublist_t *meta_mls; 2859 arc_buf_contents_t type; 2860 arc_buf_hdr_t *data_hdr; 2861 arc_buf_hdr_t *meta_hdr; 2862 2863 /* 2864 * We keep the sublist lock until we're finished, to prevent 2865 * the headers from being destroyed via arc_evict_state(). 2866 */ 2867 data_mls = multilist_sublist_lock(data_ml, data_idx); 2868 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 2869 2870 /* 2871 * These two loops are to ensure we skip any markers that 2872 * might be at the tail of the lists due to arc_evict_state(). 2873 */ 2874 2875 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 2876 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 2877 if (data_hdr->b_spa != 0) 2878 break; 2879 } 2880 2881 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 2882 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 2883 if (meta_hdr->b_spa != 0) 2884 break; 2885 } 2886 2887 if (data_hdr == NULL && meta_hdr == NULL) { 2888 type = ARC_BUFC_DATA; 2889 } else if (data_hdr == NULL) { 2890 ASSERT3P(meta_hdr, !=, NULL); 2891 type = ARC_BUFC_METADATA; 2892 } else if (meta_hdr == NULL) { 2893 ASSERT3P(data_hdr, !=, NULL); 2894 type = ARC_BUFC_DATA; 2895 } else { 2896 ASSERT3P(data_hdr, !=, NULL); 2897 ASSERT3P(meta_hdr, !=, NULL); 2898 2899 /* The headers can't be on the sublist without an L1 header */ 2900 ASSERT(HDR_HAS_L1HDR(data_hdr)); 2901 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 2902 2903 if (data_hdr->b_l1hdr.b_arc_access < 2904 meta_hdr->b_l1hdr.b_arc_access) { 2905 type = ARC_BUFC_DATA; 2906 } else { 2907 type = ARC_BUFC_METADATA; 2908 } 2909 } 2910 2911 multilist_sublist_unlock(meta_mls); 2912 multilist_sublist_unlock(data_mls); 2913 2914 return (type); 2915 } 2916 2917 /* 2918 * Evict buffers from the cache, such that arc_size is capped by arc_c. 2919 */ 2920 static uint64_t 2921 arc_adjust(void) 2922 { 2923 uint64_t total_evicted = 0; 2924 uint64_t bytes; 2925 int64_t target; 2926 2927 /* 2928 * If we're over arc_meta_limit, we want to correct that before 2929 * potentially evicting data buffers below. 2930 */ 2931 total_evicted += arc_adjust_meta(); 2932 2933 /* 2934 * Adjust MRU size 2935 * 2936 * If we're over the target cache size, we want to evict enough 2937 * from the list to get back to our target size. We don't want 2938 * to evict too much from the MRU, such that it drops below 2939 * arc_p. So, if we're over our target cache size more than 2940 * the MRU is over arc_p, we'll evict enough to get back to 2941 * arc_p here, and then evict more from the MFU below. 2942 */ 2943 target = MIN((int64_t)(arc_size - arc_c), 2944 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2945 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 2946 2947 /* 2948 * If we're below arc_meta_min, always prefer to evict data. 2949 * Otherwise, try to satisfy the requested number of bytes to 2950 * evict from the type which contains older buffers; in an 2951 * effort to keep newer buffers in the cache regardless of their 2952 * type. If we cannot satisfy the number of bytes from this 2953 * type, spill over into the next type. 2954 */ 2955 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2956 arc_meta_used > arc_meta_min) { 2957 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2958 total_evicted += bytes; 2959 2960 /* 2961 * If we couldn't evict our target number of bytes from 2962 * metadata, we try to get the rest from data. 2963 */ 2964 target -= bytes; 2965 2966 total_evicted += 2967 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2968 } else { 2969 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2970 total_evicted += bytes; 2971 2972 /* 2973 * If we couldn't evict our target number of bytes from 2974 * data, we try to get the rest from metadata. 2975 */ 2976 target -= bytes; 2977 2978 total_evicted += 2979 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2980 } 2981 2982 /* 2983 * Adjust MFU size 2984 * 2985 * Now that we've tried to evict enough from the MRU to get its 2986 * size back to arc_p, if we're still above the target cache 2987 * size, we evict the rest from the MFU. 2988 */ 2989 target = arc_size - arc_c; 2990 2991 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 2992 arc_meta_used > arc_meta_min) { 2993 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2994 total_evicted += bytes; 2995 2996 /* 2997 * If we couldn't evict our target number of bytes from 2998 * metadata, we try to get the rest from data. 2999 */ 3000 target -= bytes; 3001 3002 total_evicted += 3003 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3004 } else { 3005 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3006 total_evicted += bytes; 3007 3008 /* 3009 * If we couldn't evict our target number of bytes from 3010 * data, we try to get the rest from data. 3011 */ 3012 target -= bytes; 3013 3014 total_evicted += 3015 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3016 } 3017 3018 /* 3019 * Adjust ghost lists 3020 * 3021 * In addition to the above, the ARC also defines target values 3022 * for the ghost lists. The sum of the mru list and mru ghost 3023 * list should never exceed the target size of the cache, and 3024 * the sum of the mru list, mfu list, mru ghost list, and mfu 3025 * ghost list should never exceed twice the target size of the 3026 * cache. The following logic enforces these limits on the ghost 3027 * caches, and evicts from them as needed. 3028 */ 3029 target = refcount_count(&arc_mru->arcs_size) + 3030 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3031 3032 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3033 total_evicted += bytes; 3034 3035 target -= bytes; 3036 3037 total_evicted += 3038 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3039 3040 /* 3041 * We assume the sum of the mru list and mfu list is less than 3042 * or equal to arc_c (we enforced this above), which means we 3043 * can use the simpler of the two equations below: 3044 * 3045 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3046 * mru ghost + mfu ghost <= arc_c 3047 */ 3048 target = refcount_count(&arc_mru_ghost->arcs_size) + 3049 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3050 3051 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3052 total_evicted += bytes; 3053 3054 target -= bytes; 3055 3056 total_evicted += 3057 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3058 3059 return (total_evicted); 3060 } 3061 3062 static void 3063 arc_do_user_evicts(void) 3064 { 3065 mutex_enter(&arc_user_evicts_lock); 3066 while (arc_eviction_list != NULL) { 3067 arc_buf_t *buf = arc_eviction_list; 3068 arc_eviction_list = buf->b_next; 3069 mutex_enter(&buf->b_evict_lock); 3070 buf->b_hdr = NULL; 3071 mutex_exit(&buf->b_evict_lock); 3072 mutex_exit(&arc_user_evicts_lock); 3073 3074 if (buf->b_efunc != NULL) 3075 VERIFY0(buf->b_efunc(buf->b_private)); 3076 3077 buf->b_efunc = NULL; 3078 buf->b_private = NULL; 3079 kmem_cache_free(buf_cache, buf); 3080 mutex_enter(&arc_user_evicts_lock); 3081 } 3082 mutex_exit(&arc_user_evicts_lock); 3083 } 3084 3085 void 3086 arc_flush(spa_t *spa, boolean_t retry) 3087 { 3088 uint64_t guid = 0; 3089 3090 /* 3091 * If retry is TRUE, a spa must not be specified since we have 3092 * no good way to determine if all of a spa's buffers have been 3093 * evicted from an arc state. 3094 */ 3095 ASSERT(!retry || spa == 0); 3096 3097 if (spa != NULL) 3098 guid = spa_load_guid(spa); 3099 3100 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3101 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3102 3103 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3104 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3105 3106 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3107 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3108 3109 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3110 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3111 3112 arc_do_user_evicts(); 3113 ASSERT(spa || arc_eviction_list == NULL); 3114 } 3115 3116 void 3117 arc_shrink(int64_t to_free) 3118 { 3119 if (arc_c > arc_c_min) { 3120 3121 if (arc_c > arc_c_min + to_free) 3122 atomic_add_64(&arc_c, -to_free); 3123 else 3124 arc_c = arc_c_min; 3125 3126 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3127 if (arc_c > arc_size) 3128 arc_c = MAX(arc_size, arc_c_min); 3129 if (arc_p > arc_c) 3130 arc_p = (arc_c >> 1); 3131 ASSERT(arc_c >= arc_c_min); 3132 ASSERT((int64_t)arc_p >= 0); 3133 } 3134 3135 if (arc_size > arc_c) 3136 (void) arc_adjust(); 3137 } 3138 3139 typedef enum free_memory_reason_t { 3140 FMR_UNKNOWN, 3141 FMR_NEEDFREE, 3142 FMR_LOTSFREE, 3143 FMR_SWAPFS_MINFREE, 3144 FMR_PAGES_PP_MAXIMUM, 3145 FMR_HEAP_ARENA, 3146 FMR_ZIO_ARENA, 3147 } free_memory_reason_t; 3148 3149 int64_t last_free_memory; 3150 free_memory_reason_t last_free_reason; 3151 3152 /* 3153 * Additional reserve of pages for pp_reserve. 3154 */ 3155 int64_t arc_pages_pp_reserve = 64; 3156 3157 /* 3158 * Additional reserve of pages for swapfs. 3159 */ 3160 int64_t arc_swapfs_reserve = 64; 3161 3162 /* 3163 * Return the amount of memory that can be consumed before reclaim will be 3164 * needed. Positive if there is sufficient free memory, negative indicates 3165 * the amount of memory that needs to be freed up. 3166 */ 3167 static int64_t 3168 arc_available_memory(void) 3169 { 3170 int64_t lowest = INT64_MAX; 3171 int64_t n; 3172 free_memory_reason_t r = FMR_UNKNOWN; 3173 3174 #ifdef _KERNEL 3175 if (needfree > 0) { 3176 n = PAGESIZE * (-needfree); 3177 if (n < lowest) { 3178 lowest = n; 3179 r = FMR_NEEDFREE; 3180 } 3181 } 3182 3183 /* 3184 * check that we're out of range of the pageout scanner. It starts to 3185 * schedule paging if freemem is less than lotsfree and needfree. 3186 * lotsfree is the high-water mark for pageout, and needfree is the 3187 * number of needed free pages. We add extra pages here to make sure 3188 * the scanner doesn't start up while we're freeing memory. 3189 */ 3190 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3191 if (n < lowest) { 3192 lowest = n; 3193 r = FMR_LOTSFREE; 3194 } 3195 3196 /* 3197 * check to make sure that swapfs has enough space so that anon 3198 * reservations can still succeed. anon_resvmem() checks that the 3199 * availrmem is greater than swapfs_minfree, and the number of reserved 3200 * swap pages. We also add a bit of extra here just to prevent 3201 * circumstances from getting really dire. 3202 */ 3203 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3204 desfree - arc_swapfs_reserve); 3205 if (n < lowest) { 3206 lowest = n; 3207 r = FMR_SWAPFS_MINFREE; 3208 } 3209 3210 3211 /* 3212 * Check that we have enough availrmem that memory locking (e.g., via 3213 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3214 * stores the number of pages that cannot be locked; when availrmem 3215 * drops below pages_pp_maximum, page locking mechanisms such as 3216 * page_pp_lock() will fail.) 3217 */ 3218 n = PAGESIZE * (availrmem - pages_pp_maximum - 3219 arc_pages_pp_reserve); 3220 if (n < lowest) { 3221 lowest = n; 3222 r = FMR_PAGES_PP_MAXIMUM; 3223 } 3224 3225 #if defined(__i386) 3226 /* 3227 * If we're on an i386 platform, it's possible that we'll exhaust the 3228 * kernel heap space before we ever run out of available physical 3229 * memory. Most checks of the size of the heap_area compare against 3230 * tune.t_minarmem, which is the minimum available real memory that we 3231 * can have in the system. However, this is generally fixed at 25 pages 3232 * which is so low that it's useless. In this comparison, we seek to 3233 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3234 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3235 * free) 3236 */ 3237 n = vmem_size(heap_arena, VMEM_FREE) - 3238 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3239 if (n < lowest) { 3240 lowest = n; 3241 r = FMR_HEAP_ARENA; 3242 } 3243 #endif 3244 3245 /* 3246 * If zio data pages are being allocated out of a separate heap segment, 3247 * then enforce that the size of available vmem for this arena remains 3248 * above about 1/16th free. 3249 * 3250 * Note: The 1/16th arena free requirement was put in place 3251 * to aggressively evict memory from the arc in order to avoid 3252 * memory fragmentation issues. 3253 */ 3254 if (zio_arena != NULL) { 3255 n = vmem_size(zio_arena, VMEM_FREE) - 3256 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3257 if (n < lowest) { 3258 lowest = n; 3259 r = FMR_ZIO_ARENA; 3260 } 3261 } 3262 #else 3263 /* Every 100 calls, free a small amount */ 3264 if (spa_get_random(100) == 0) 3265 lowest = -1024; 3266 #endif 3267 3268 last_free_memory = lowest; 3269 last_free_reason = r; 3270 3271 return (lowest); 3272 } 3273 3274 3275 /* 3276 * Determine if the system is under memory pressure and is asking 3277 * to reclaim memory. A return value of TRUE indicates that the system 3278 * is under memory pressure and that the arc should adjust accordingly. 3279 */ 3280 static boolean_t 3281 arc_reclaim_needed(void) 3282 { 3283 return (arc_available_memory() < 0); 3284 } 3285 3286 static void 3287 arc_kmem_reap_now(void) 3288 { 3289 size_t i; 3290 kmem_cache_t *prev_cache = NULL; 3291 kmem_cache_t *prev_data_cache = NULL; 3292 extern kmem_cache_t *zio_buf_cache[]; 3293 extern kmem_cache_t *zio_data_buf_cache[]; 3294 extern kmem_cache_t *range_seg_cache; 3295 3296 #ifdef _KERNEL 3297 if (arc_meta_used >= arc_meta_limit) { 3298 /* 3299 * We are exceeding our meta-data cache limit. 3300 * Purge some DNLC entries to release holds on meta-data. 3301 */ 3302 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3303 } 3304 #if defined(__i386) 3305 /* 3306 * Reclaim unused memory from all kmem caches. 3307 */ 3308 kmem_reap(); 3309 #endif 3310 #endif 3311 3312 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3313 if (zio_buf_cache[i] != prev_cache) { 3314 prev_cache = zio_buf_cache[i]; 3315 kmem_cache_reap_now(zio_buf_cache[i]); 3316 } 3317 if (zio_data_buf_cache[i] != prev_data_cache) { 3318 prev_data_cache = zio_data_buf_cache[i]; 3319 kmem_cache_reap_now(zio_data_buf_cache[i]); 3320 } 3321 } 3322 kmem_cache_reap_now(buf_cache); 3323 kmem_cache_reap_now(hdr_full_cache); 3324 kmem_cache_reap_now(hdr_l2only_cache); 3325 kmem_cache_reap_now(range_seg_cache); 3326 3327 if (zio_arena != NULL) { 3328 /* 3329 * Ask the vmem arena to reclaim unused memory from its 3330 * quantum caches. 3331 */ 3332 vmem_qcache_reap(zio_arena); 3333 } 3334 } 3335 3336 /* 3337 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3338 * enough data and signal them to proceed. When this happens, the threads in 3339 * arc_get_data_buf() are sleeping while holding the hash lock for their 3340 * particular arc header. Thus, we must be careful to never sleep on a 3341 * hash lock in this thread. This is to prevent the following deadlock: 3342 * 3343 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3344 * waiting for the reclaim thread to signal it. 3345 * 3346 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3347 * fails, and goes to sleep forever. 3348 * 3349 * This possible deadlock is avoided by always acquiring a hash lock 3350 * using mutex_tryenter() from arc_reclaim_thread(). 3351 */ 3352 static void 3353 arc_reclaim_thread(void) 3354 { 3355 hrtime_t growtime = 0; 3356 callb_cpr_t cpr; 3357 3358 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3359 3360 mutex_enter(&arc_reclaim_lock); 3361 while (!arc_reclaim_thread_exit) { 3362 int64_t free_memory = arc_available_memory(); 3363 uint64_t evicted = 0; 3364 3365 mutex_exit(&arc_reclaim_lock); 3366 3367 if (free_memory < 0) { 3368 3369 arc_no_grow = B_TRUE; 3370 arc_warm = B_TRUE; 3371 3372 /* 3373 * Wait at least zfs_grow_retry (default 60) seconds 3374 * before considering growing. 3375 */ 3376 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 3377 3378 arc_kmem_reap_now(); 3379 3380 /* 3381 * If we are still low on memory, shrink the ARC 3382 * so that we have arc_shrink_min free space. 3383 */ 3384 free_memory = arc_available_memory(); 3385 3386 int64_t to_free = 3387 (arc_c >> arc_shrink_shift) - free_memory; 3388 if (to_free > 0) { 3389 #ifdef _KERNEL 3390 to_free = MAX(to_free, ptob(needfree)); 3391 #endif 3392 arc_shrink(to_free); 3393 } 3394 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3395 arc_no_grow = B_TRUE; 3396 } else if (gethrtime() >= growtime) { 3397 arc_no_grow = B_FALSE; 3398 } 3399 3400 evicted = arc_adjust(); 3401 3402 mutex_enter(&arc_reclaim_lock); 3403 3404 /* 3405 * If evicted is zero, we couldn't evict anything via 3406 * arc_adjust(). This could be due to hash lock 3407 * collisions, but more likely due to the majority of 3408 * arc buffers being unevictable. Therefore, even if 3409 * arc_size is above arc_c, another pass is unlikely to 3410 * be helpful and could potentially cause us to enter an 3411 * infinite loop. 3412 */ 3413 if (arc_size <= arc_c || evicted == 0) { 3414 /* 3415 * We're either no longer overflowing, or we 3416 * can't evict anything more, so we should wake 3417 * up any threads before we go to sleep. 3418 */ 3419 cv_broadcast(&arc_reclaim_waiters_cv); 3420 3421 /* 3422 * Block until signaled, or after one second (we 3423 * might need to perform arc_kmem_reap_now() 3424 * even if we aren't being signalled) 3425 */ 3426 CALLB_CPR_SAFE_BEGIN(&cpr); 3427 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 3428 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 3429 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3430 } 3431 } 3432 3433 arc_reclaim_thread_exit = FALSE; 3434 cv_broadcast(&arc_reclaim_thread_cv); 3435 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3436 thread_exit(); 3437 } 3438 3439 static void 3440 arc_user_evicts_thread(void) 3441 { 3442 callb_cpr_t cpr; 3443 3444 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3445 3446 mutex_enter(&arc_user_evicts_lock); 3447 while (!arc_user_evicts_thread_exit) { 3448 mutex_exit(&arc_user_evicts_lock); 3449 3450 arc_do_user_evicts(); 3451 3452 /* 3453 * This is necessary in order for the mdb ::arc dcmd to 3454 * show up to date information. Since the ::arc command 3455 * does not call the kstat's update function, without 3456 * this call, the command may show stale stats for the 3457 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3458 * with this change, the data might be up to 1 second 3459 * out of date; but that should suffice. The arc_state_t 3460 * structures can be queried directly if more accurate 3461 * information is needed. 3462 */ 3463 if (arc_ksp != NULL) 3464 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3465 3466 mutex_enter(&arc_user_evicts_lock); 3467 3468 /* 3469 * Block until signaled, or after one second (we need to 3470 * call the arc's kstat update function regularly). 3471 */ 3472 CALLB_CPR_SAFE_BEGIN(&cpr); 3473 (void) cv_timedwait(&arc_user_evicts_cv, 3474 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3475 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3476 } 3477 3478 arc_user_evicts_thread_exit = FALSE; 3479 cv_broadcast(&arc_user_evicts_cv); 3480 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3481 thread_exit(); 3482 } 3483 3484 /* 3485 * Adapt arc info given the number of bytes we are trying to add and 3486 * the state that we are comming from. This function is only called 3487 * when we are adding new content to the cache. 3488 */ 3489 static void 3490 arc_adapt(int bytes, arc_state_t *state) 3491 { 3492 int mult; 3493 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3494 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3495 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3496 3497 if (state == arc_l2c_only) 3498 return; 3499 3500 ASSERT(bytes > 0); 3501 /* 3502 * Adapt the target size of the MRU list: 3503 * - if we just hit in the MRU ghost list, then increase 3504 * the target size of the MRU list. 3505 * - if we just hit in the MFU ghost list, then increase 3506 * the target size of the MFU list by decreasing the 3507 * target size of the MRU list. 3508 */ 3509 if (state == arc_mru_ghost) { 3510 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3511 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3512 3513 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3514 } else if (state == arc_mfu_ghost) { 3515 uint64_t delta; 3516 3517 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3518 mult = MIN(mult, 10); 3519 3520 delta = MIN(bytes * mult, arc_p); 3521 arc_p = MAX(arc_p_min, arc_p - delta); 3522 } 3523 ASSERT((int64_t)arc_p >= 0); 3524 3525 if (arc_reclaim_needed()) { 3526 cv_signal(&arc_reclaim_thread_cv); 3527 return; 3528 } 3529 3530 if (arc_no_grow) 3531 return; 3532 3533 if (arc_c >= arc_c_max) 3534 return; 3535 3536 /* 3537 * If we're within (2 * maxblocksize) bytes of the target 3538 * cache size, increment the target cache size 3539 */ 3540 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3541 atomic_add_64(&arc_c, (int64_t)bytes); 3542 if (arc_c > arc_c_max) 3543 arc_c = arc_c_max; 3544 else if (state == arc_anon) 3545 atomic_add_64(&arc_p, (int64_t)bytes); 3546 if (arc_p > arc_c) 3547 arc_p = arc_c; 3548 } 3549 ASSERT((int64_t)arc_p >= 0); 3550 } 3551 3552 /* 3553 * Check if arc_size has grown past our upper threshold, determined by 3554 * zfs_arc_overflow_shift. 3555 */ 3556 static boolean_t 3557 arc_is_overflowing(void) 3558 { 3559 /* Always allow at least one block of overflow */ 3560 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3561 arc_c >> zfs_arc_overflow_shift); 3562 3563 return (arc_size >= arc_c + overflow); 3564 } 3565 3566 /* 3567 * The buffer, supplied as the first argument, needs a data block. If we 3568 * are hitting the hard limit for the cache size, we must sleep, waiting 3569 * for the eviction thread to catch up. If we're past the target size 3570 * but below the hard limit, we'll only signal the reclaim thread and 3571 * continue on. 3572 */ 3573 static void 3574 arc_get_data_buf(arc_buf_t *buf) 3575 { 3576 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3577 uint64_t size = buf->b_hdr->b_size; 3578 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3579 3580 arc_adapt(size, state); 3581 3582 /* 3583 * If arc_size is currently overflowing, and has grown past our 3584 * upper limit, we must be adding data faster than the evict 3585 * thread can evict. Thus, to ensure we don't compound the 3586 * problem by adding more data and forcing arc_size to grow even 3587 * further past it's target size, we halt and wait for the 3588 * eviction thread to catch up. 3589 * 3590 * It's also possible that the reclaim thread is unable to evict 3591 * enough buffers to get arc_size below the overflow limit (e.g. 3592 * due to buffers being un-evictable, or hash lock collisions). 3593 * In this case, we want to proceed regardless if we're 3594 * overflowing; thus we don't use a while loop here. 3595 */ 3596 if (arc_is_overflowing()) { 3597 mutex_enter(&arc_reclaim_lock); 3598 3599 /* 3600 * Now that we've acquired the lock, we may no longer be 3601 * over the overflow limit, lets check. 3602 * 3603 * We're ignoring the case of spurious wake ups. If that 3604 * were to happen, it'd let this thread consume an ARC 3605 * buffer before it should have (i.e. before we're under 3606 * the overflow limit and were signalled by the reclaim 3607 * thread). As long as that is a rare occurrence, it 3608 * shouldn't cause any harm. 3609 */ 3610 if (arc_is_overflowing()) { 3611 cv_signal(&arc_reclaim_thread_cv); 3612 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3613 } 3614 3615 mutex_exit(&arc_reclaim_lock); 3616 } 3617 3618 if (type == ARC_BUFC_METADATA) { 3619 buf->b_data = zio_buf_alloc(size); 3620 arc_space_consume(size, ARC_SPACE_META); 3621 } else { 3622 ASSERT(type == ARC_BUFC_DATA); 3623 buf->b_data = zio_data_buf_alloc(size); 3624 arc_space_consume(size, ARC_SPACE_DATA); 3625 } 3626 3627 /* 3628 * Update the state size. Note that ghost states have a 3629 * "ghost size" and so don't need to be updated. 3630 */ 3631 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3632 arc_buf_hdr_t *hdr = buf->b_hdr; 3633 arc_state_t *state = hdr->b_l1hdr.b_state; 3634 3635 (void) refcount_add_many(&state->arcs_size, size, buf); 3636 3637 /* 3638 * If this is reached via arc_read, the link is 3639 * protected by the hash lock. If reached via 3640 * arc_buf_alloc, the header should not be accessed by 3641 * any other thread. And, if reached via arc_read_done, 3642 * the hash lock will protect it if it's found in the 3643 * hash table; otherwise no other thread should be 3644 * trying to [add|remove]_reference it. 3645 */ 3646 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3647 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3648 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3649 size); 3650 } 3651 /* 3652 * If we are growing the cache, and we are adding anonymous 3653 * data, and we have outgrown arc_p, update arc_p 3654 */ 3655 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3656 (refcount_count(&arc_anon->arcs_size) + 3657 refcount_count(&arc_mru->arcs_size) > arc_p)) 3658 arc_p = MIN(arc_c, arc_p + size); 3659 } 3660 } 3661 3662 /* 3663 * This routine is called whenever a buffer is accessed. 3664 * NOTE: the hash lock is dropped in this function. 3665 */ 3666 static void 3667 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3668 { 3669 clock_t now; 3670 3671 ASSERT(MUTEX_HELD(hash_lock)); 3672 ASSERT(HDR_HAS_L1HDR(hdr)); 3673 3674 if (hdr->b_l1hdr.b_state == arc_anon) { 3675 /* 3676 * This buffer is not in the cache, and does not 3677 * appear in our "ghost" list. Add the new buffer 3678 * to the MRU state. 3679 */ 3680 3681 ASSERT0(hdr->b_l1hdr.b_arc_access); 3682 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3683 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3684 arc_change_state(arc_mru, hdr, hash_lock); 3685 3686 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3687 now = ddi_get_lbolt(); 3688 3689 /* 3690 * If this buffer is here because of a prefetch, then either: 3691 * - clear the flag if this is a "referencing" read 3692 * (any subsequent access will bump this into the MFU state). 3693 * or 3694 * - move the buffer to the head of the list if this is 3695 * another prefetch (to make it less likely to be evicted). 3696 */ 3697 if (HDR_PREFETCH(hdr)) { 3698 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3699 /* link protected by hash lock */ 3700 ASSERT(multilist_link_active( 3701 &hdr->b_l1hdr.b_arc_node)); 3702 } else { 3703 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3704 ARCSTAT_BUMP(arcstat_mru_hits); 3705 } 3706 hdr->b_l1hdr.b_arc_access = now; 3707 return; 3708 } 3709 3710 /* 3711 * This buffer has been "accessed" only once so far, 3712 * but it is still in the cache. Move it to the MFU 3713 * state. 3714 */ 3715 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3716 /* 3717 * More than 125ms have passed since we 3718 * instantiated this buffer. Move it to the 3719 * most frequently used state. 3720 */ 3721 hdr->b_l1hdr.b_arc_access = now; 3722 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3723 arc_change_state(arc_mfu, hdr, hash_lock); 3724 } 3725 ARCSTAT_BUMP(arcstat_mru_hits); 3726 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3727 arc_state_t *new_state; 3728 /* 3729 * This buffer has been "accessed" recently, but 3730 * was evicted from the cache. Move it to the 3731 * MFU state. 3732 */ 3733 3734 if (HDR_PREFETCH(hdr)) { 3735 new_state = arc_mru; 3736 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3737 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3738 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3739 } else { 3740 new_state = arc_mfu; 3741 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3742 } 3743 3744 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3745 arc_change_state(new_state, hdr, hash_lock); 3746 3747 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3748 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3749 /* 3750 * This buffer has been accessed more than once and is 3751 * still in the cache. Keep it in the MFU state. 3752 * 3753 * NOTE: an add_reference() that occurred when we did 3754 * the arc_read() will have kicked this off the list. 3755 * If it was a prefetch, we will explicitly move it to 3756 * the head of the list now. 3757 */ 3758 if ((HDR_PREFETCH(hdr)) != 0) { 3759 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3760 /* link protected by hash_lock */ 3761 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3762 } 3763 ARCSTAT_BUMP(arcstat_mfu_hits); 3764 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3765 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3766 arc_state_t *new_state = arc_mfu; 3767 /* 3768 * This buffer has been accessed more than once but has 3769 * been evicted from the cache. Move it back to the 3770 * MFU state. 3771 */ 3772 3773 if (HDR_PREFETCH(hdr)) { 3774 /* 3775 * This is a prefetch access... 3776 * move this block back to the MRU state. 3777 */ 3778 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3779 new_state = arc_mru; 3780 } 3781 3782 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3783 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3784 arc_change_state(new_state, hdr, hash_lock); 3785 3786 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3787 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3788 /* 3789 * This buffer is on the 2nd Level ARC. 3790 */ 3791 3792 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3793 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3794 arc_change_state(arc_mfu, hdr, hash_lock); 3795 } else { 3796 ASSERT(!"invalid arc state"); 3797 } 3798 } 3799 3800 /* a generic arc_done_func_t which you can use */ 3801 /* ARGSUSED */ 3802 void 3803 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3804 { 3805 if (zio == NULL || zio->io_error == 0) 3806 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3807 VERIFY(arc_buf_remove_ref(buf, arg)); 3808 } 3809 3810 /* a generic arc_done_func_t */ 3811 void 3812 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3813 { 3814 arc_buf_t **bufp = arg; 3815 if (zio && zio->io_error) { 3816 VERIFY(arc_buf_remove_ref(buf, arg)); 3817 *bufp = NULL; 3818 } else { 3819 *bufp = buf; 3820 ASSERT(buf->b_data); 3821 } 3822 } 3823 3824 static void 3825 arc_read_done(zio_t *zio) 3826 { 3827 arc_buf_hdr_t *hdr; 3828 arc_buf_t *buf; 3829 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3830 kmutex_t *hash_lock = NULL; 3831 arc_callback_t *callback_list, *acb; 3832 int freeable = FALSE; 3833 3834 buf = zio->io_private; 3835 hdr = buf->b_hdr; 3836 3837 /* 3838 * The hdr was inserted into hash-table and removed from lists 3839 * prior to starting I/O. We should find this header, since 3840 * it's in the hash table, and it should be legit since it's 3841 * not possible to evict it during the I/O. The only possible 3842 * reason for it not to be found is if we were freed during the 3843 * read. 3844 */ 3845 if (HDR_IN_HASH_TABLE(hdr)) { 3846 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3847 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3848 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3849 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3850 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3851 3852 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3853 &hash_lock); 3854 3855 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3856 hash_lock == NULL) || 3857 (found == hdr && 3858 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3859 (found == hdr && HDR_L2_READING(hdr))); 3860 } 3861 3862 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3863 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3864 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3865 3866 /* byteswap if necessary */ 3867 callback_list = hdr->b_l1hdr.b_acb; 3868 ASSERT(callback_list != NULL); 3869 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3870 dmu_object_byteswap_t bswap = 3871 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3872 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3873 byteswap_uint64_array : 3874 dmu_ot_byteswap[bswap].ob_func; 3875 func(buf->b_data, hdr->b_size); 3876 } 3877 3878 arc_cksum_compute(buf, B_FALSE); 3879 arc_buf_watch(buf); 3880 3881 if (hash_lock && zio->io_error == 0 && 3882 hdr->b_l1hdr.b_state == arc_anon) { 3883 /* 3884 * Only call arc_access on anonymous buffers. This is because 3885 * if we've issued an I/O for an evicted buffer, we've already 3886 * called arc_access (to prevent any simultaneous readers from 3887 * getting confused). 3888 */ 3889 arc_access(hdr, hash_lock); 3890 } 3891 3892 /* create copies of the data buffer for the callers */ 3893 abuf = buf; 3894 for (acb = callback_list; acb; acb = acb->acb_next) { 3895 if (acb->acb_done) { 3896 if (abuf == NULL) { 3897 ARCSTAT_BUMP(arcstat_duplicate_reads); 3898 abuf = arc_buf_clone(buf); 3899 } 3900 acb->acb_buf = abuf; 3901 abuf = NULL; 3902 } 3903 } 3904 hdr->b_l1hdr.b_acb = NULL; 3905 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3906 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3907 if (abuf == buf) { 3908 ASSERT(buf->b_efunc == NULL); 3909 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3910 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3911 } 3912 3913 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3914 callback_list != NULL); 3915 3916 if (zio->io_error != 0) { 3917 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3918 if (hdr->b_l1hdr.b_state != arc_anon) 3919 arc_change_state(arc_anon, hdr, hash_lock); 3920 if (HDR_IN_HASH_TABLE(hdr)) 3921 buf_hash_remove(hdr); 3922 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3923 } 3924 3925 /* 3926 * Broadcast before we drop the hash_lock to avoid the possibility 3927 * that the hdr (and hence the cv) might be freed before we get to 3928 * the cv_broadcast(). 3929 */ 3930 cv_broadcast(&hdr->b_l1hdr.b_cv); 3931 3932 if (hash_lock != NULL) { 3933 mutex_exit(hash_lock); 3934 } else { 3935 /* 3936 * This block was freed while we waited for the read to 3937 * complete. It has been removed from the hash table and 3938 * moved to the anonymous state (so that it won't show up 3939 * in the cache). 3940 */ 3941 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3942 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3943 } 3944 3945 /* execute each callback and free its structure */ 3946 while ((acb = callback_list) != NULL) { 3947 if (acb->acb_done) 3948 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3949 3950 if (acb->acb_zio_dummy != NULL) { 3951 acb->acb_zio_dummy->io_error = zio->io_error; 3952 zio_nowait(acb->acb_zio_dummy); 3953 } 3954 3955 callback_list = acb->acb_next; 3956 kmem_free(acb, sizeof (arc_callback_t)); 3957 } 3958 3959 if (freeable) 3960 arc_hdr_destroy(hdr); 3961 } 3962 3963 /* 3964 * "Read" the block at the specified DVA (in bp) via the 3965 * cache. If the block is found in the cache, invoke the provided 3966 * callback immediately and return. Note that the `zio' parameter 3967 * in the callback will be NULL in this case, since no IO was 3968 * required. If the block is not in the cache pass the read request 3969 * on to the spa with a substitute callback function, so that the 3970 * requested block will be added to the cache. 3971 * 3972 * If a read request arrives for a block that has a read in-progress, 3973 * either wait for the in-progress read to complete (and return the 3974 * results); or, if this is a read with a "done" func, add a record 3975 * to the read to invoke the "done" func when the read completes, 3976 * and return; or just return. 3977 * 3978 * arc_read_done() will invoke all the requested "done" functions 3979 * for readers of this block. 3980 */ 3981 int 3982 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3983 void *private, zio_priority_t priority, int zio_flags, 3984 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3985 { 3986 arc_buf_hdr_t *hdr = NULL; 3987 arc_buf_t *buf = NULL; 3988 kmutex_t *hash_lock = NULL; 3989 zio_t *rzio; 3990 uint64_t guid = spa_load_guid(spa); 3991 3992 ASSERT(!BP_IS_EMBEDDED(bp) || 3993 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3994 3995 top: 3996 if (!BP_IS_EMBEDDED(bp)) { 3997 /* 3998 * Embedded BP's have no DVA and require no I/O to "read". 3999 * Create an anonymous arc buf to back it. 4000 */ 4001 hdr = buf_hash_find(guid, bp, &hash_lock); 4002 } 4003 4004 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4005 4006 *arc_flags |= ARC_FLAG_CACHED; 4007 4008 if (HDR_IO_IN_PROGRESS(hdr)) { 4009 4010 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4011 priority == ZIO_PRIORITY_SYNC_READ) { 4012 /* 4013 * This sync read must wait for an 4014 * in-progress async read (e.g. a predictive 4015 * prefetch). Async reads are queued 4016 * separately at the vdev_queue layer, so 4017 * this is a form of priority inversion. 4018 * Ideally, we would "inherit" the demand 4019 * i/o's priority by moving the i/o from 4020 * the async queue to the synchronous queue, 4021 * but there is currently no mechanism to do 4022 * so. Track this so that we can evaluate 4023 * the magnitude of this potential performance 4024 * problem. 4025 * 4026 * Note that if the prefetch i/o is already 4027 * active (has been issued to the device), 4028 * the prefetch improved performance, because 4029 * we issued it sooner than we would have 4030 * without the prefetch. 4031 */ 4032 DTRACE_PROBE1(arc__sync__wait__for__async, 4033 arc_buf_hdr_t *, hdr); 4034 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4035 } 4036 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4037 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4038 } 4039 4040 if (*arc_flags & ARC_FLAG_WAIT) { 4041 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4042 mutex_exit(hash_lock); 4043 goto top; 4044 } 4045 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4046 4047 if (done) { 4048 arc_callback_t *acb = NULL; 4049 4050 acb = kmem_zalloc(sizeof (arc_callback_t), 4051 KM_SLEEP); 4052 acb->acb_done = done; 4053 acb->acb_private = private; 4054 if (pio != NULL) 4055 acb->acb_zio_dummy = zio_null(pio, 4056 spa, NULL, NULL, NULL, zio_flags); 4057 4058 ASSERT(acb->acb_done != NULL); 4059 acb->acb_next = hdr->b_l1hdr.b_acb; 4060 hdr->b_l1hdr.b_acb = acb; 4061 add_reference(hdr, hash_lock, private); 4062 mutex_exit(hash_lock); 4063 return (0); 4064 } 4065 mutex_exit(hash_lock); 4066 return (0); 4067 } 4068 4069 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4070 hdr->b_l1hdr.b_state == arc_mfu); 4071 4072 if (done) { 4073 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4074 /* 4075 * This is a demand read which does not have to 4076 * wait for i/o because we did a predictive 4077 * prefetch i/o for it, which has completed. 4078 */ 4079 DTRACE_PROBE1( 4080 arc__demand__hit__predictive__prefetch, 4081 arc_buf_hdr_t *, hdr); 4082 ARCSTAT_BUMP( 4083 arcstat_demand_hit_predictive_prefetch); 4084 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4085 } 4086 add_reference(hdr, hash_lock, private); 4087 /* 4088 * If this block is already in use, create a new 4089 * copy of the data so that we will be guaranteed 4090 * that arc_release() will always succeed. 4091 */ 4092 buf = hdr->b_l1hdr.b_buf; 4093 ASSERT(buf); 4094 ASSERT(buf->b_data); 4095 if (HDR_BUF_AVAILABLE(hdr)) { 4096 ASSERT(buf->b_efunc == NULL); 4097 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4098 } else { 4099 buf = arc_buf_clone(buf); 4100 } 4101 4102 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4103 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4104 hdr->b_flags |= ARC_FLAG_PREFETCH; 4105 } 4106 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4107 arc_access(hdr, hash_lock); 4108 if (*arc_flags & ARC_FLAG_L2CACHE) 4109 hdr->b_flags |= ARC_FLAG_L2CACHE; 4110 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4111 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4112 mutex_exit(hash_lock); 4113 ARCSTAT_BUMP(arcstat_hits); 4114 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4115 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4116 data, metadata, hits); 4117 4118 if (done) 4119 done(NULL, buf, private); 4120 } else { 4121 uint64_t size = BP_GET_LSIZE(bp); 4122 arc_callback_t *acb; 4123 vdev_t *vd = NULL; 4124 uint64_t addr = 0; 4125 boolean_t devw = B_FALSE; 4126 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4127 int32_t b_asize = 0; 4128 4129 if (hdr == NULL) { 4130 /* this block is not in the cache */ 4131 arc_buf_hdr_t *exists = NULL; 4132 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4133 buf = arc_buf_alloc(spa, size, private, type); 4134 hdr = buf->b_hdr; 4135 if (!BP_IS_EMBEDDED(bp)) { 4136 hdr->b_dva = *BP_IDENTITY(bp); 4137 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4138 exists = buf_hash_insert(hdr, &hash_lock); 4139 } 4140 if (exists != NULL) { 4141 /* somebody beat us to the hash insert */ 4142 mutex_exit(hash_lock); 4143 buf_discard_identity(hdr); 4144 (void) arc_buf_remove_ref(buf, private); 4145 goto top; /* restart the IO request */ 4146 } 4147 4148 /* 4149 * If there is a callback, we pass our reference to 4150 * it; otherwise we remove our reference. 4151 */ 4152 if (done == NULL) { 4153 (void) remove_reference(hdr, hash_lock, 4154 private); 4155 } 4156 if (*arc_flags & ARC_FLAG_PREFETCH) 4157 hdr->b_flags |= ARC_FLAG_PREFETCH; 4158 if (*arc_flags & ARC_FLAG_L2CACHE) 4159 hdr->b_flags |= ARC_FLAG_L2CACHE; 4160 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4161 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4162 if (BP_GET_LEVEL(bp) > 0) 4163 hdr->b_flags |= ARC_FLAG_INDIRECT; 4164 } else { 4165 /* 4166 * This block is in the ghost cache. If it was L2-only 4167 * (and thus didn't have an L1 hdr), we realloc the 4168 * header to add an L1 hdr. 4169 */ 4170 if (!HDR_HAS_L1HDR(hdr)) { 4171 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4172 hdr_full_cache); 4173 } 4174 4175 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4176 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4177 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4178 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4179 4180 /* 4181 * If there is a callback, we pass a reference to it. 4182 */ 4183 if (done != NULL) 4184 add_reference(hdr, hash_lock, private); 4185 if (*arc_flags & ARC_FLAG_PREFETCH) 4186 hdr->b_flags |= ARC_FLAG_PREFETCH; 4187 if (*arc_flags & ARC_FLAG_L2CACHE) 4188 hdr->b_flags |= ARC_FLAG_L2CACHE; 4189 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4190 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4191 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4192 buf->b_hdr = hdr; 4193 buf->b_data = NULL; 4194 buf->b_efunc = NULL; 4195 buf->b_private = NULL; 4196 buf->b_next = NULL; 4197 hdr->b_l1hdr.b_buf = buf; 4198 ASSERT0(hdr->b_l1hdr.b_datacnt); 4199 hdr->b_l1hdr.b_datacnt = 1; 4200 arc_get_data_buf(buf); 4201 arc_access(hdr, hash_lock); 4202 } 4203 4204 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4205 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4206 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4207 4208 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4209 acb->acb_done = done; 4210 acb->acb_private = private; 4211 4212 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4213 hdr->b_l1hdr.b_acb = acb; 4214 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4215 4216 if (HDR_HAS_L2HDR(hdr) && 4217 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4218 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4219 addr = hdr->b_l2hdr.b_daddr; 4220 b_compress = hdr->b_l2hdr.b_compress; 4221 b_asize = hdr->b_l2hdr.b_asize; 4222 /* 4223 * Lock out device removal. 4224 */ 4225 if (vdev_is_dead(vd) || 4226 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4227 vd = NULL; 4228 } 4229 4230 if (hash_lock != NULL) 4231 mutex_exit(hash_lock); 4232 4233 /* 4234 * At this point, we have a level 1 cache miss. Try again in 4235 * L2ARC if possible. 4236 */ 4237 ASSERT3U(hdr->b_size, ==, size); 4238 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4239 uint64_t, size, zbookmark_phys_t *, zb); 4240 ARCSTAT_BUMP(arcstat_misses); 4241 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4242 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4243 data, metadata, misses); 4244 4245 if (priority == ZIO_PRIORITY_ASYNC_READ) 4246 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4247 else 4248 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4249 4250 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4251 /* 4252 * Read from the L2ARC if the following are true: 4253 * 1. The L2ARC vdev was previously cached. 4254 * 2. This buffer still has L2ARC metadata. 4255 * 3. This buffer isn't currently writing to the L2ARC. 4256 * 4. The L2ARC entry wasn't evicted, which may 4257 * also have invalidated the vdev. 4258 * 5. This isn't prefetch and l2arc_noprefetch is set. 4259 */ 4260 if (HDR_HAS_L2HDR(hdr) && 4261 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4262 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4263 l2arc_read_callback_t *cb; 4264 4265 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4266 ARCSTAT_BUMP(arcstat_l2_hits); 4267 4268 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4269 KM_SLEEP); 4270 cb->l2rcb_buf = buf; 4271 cb->l2rcb_spa = spa; 4272 cb->l2rcb_bp = *bp; 4273 cb->l2rcb_zb = *zb; 4274 cb->l2rcb_flags = zio_flags; 4275 cb->l2rcb_compress = b_compress; 4276 4277 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4278 addr + size < vd->vdev_psize - 4279 VDEV_LABEL_END_SIZE); 4280 4281 /* 4282 * l2arc read. The SCL_L2ARC lock will be 4283 * released by l2arc_read_done(). 4284 * Issue a null zio if the underlying buffer 4285 * was squashed to zero size by compression. 4286 */ 4287 if (b_compress == ZIO_COMPRESS_EMPTY) { 4288 rzio = zio_null(pio, spa, vd, 4289 l2arc_read_done, cb, 4290 zio_flags | ZIO_FLAG_DONT_CACHE | 4291 ZIO_FLAG_CANFAIL | 4292 ZIO_FLAG_DONT_PROPAGATE | 4293 ZIO_FLAG_DONT_RETRY); 4294 } else { 4295 rzio = zio_read_phys(pio, vd, addr, 4296 b_asize, buf->b_data, 4297 ZIO_CHECKSUM_OFF, 4298 l2arc_read_done, cb, priority, 4299 zio_flags | ZIO_FLAG_DONT_CACHE | 4300 ZIO_FLAG_CANFAIL | 4301 ZIO_FLAG_DONT_PROPAGATE | 4302 ZIO_FLAG_DONT_RETRY, B_FALSE); 4303 } 4304 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4305 zio_t *, rzio); 4306 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4307 4308 if (*arc_flags & ARC_FLAG_NOWAIT) { 4309 zio_nowait(rzio); 4310 return (0); 4311 } 4312 4313 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4314 if (zio_wait(rzio) == 0) 4315 return (0); 4316 4317 /* l2arc read error; goto zio_read() */ 4318 } else { 4319 DTRACE_PROBE1(l2arc__miss, 4320 arc_buf_hdr_t *, hdr); 4321 ARCSTAT_BUMP(arcstat_l2_misses); 4322 if (HDR_L2_WRITING(hdr)) 4323 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4324 spa_config_exit(spa, SCL_L2ARC, vd); 4325 } 4326 } else { 4327 if (vd != NULL) 4328 spa_config_exit(spa, SCL_L2ARC, vd); 4329 if (l2arc_ndev != 0) { 4330 DTRACE_PROBE1(l2arc__miss, 4331 arc_buf_hdr_t *, hdr); 4332 ARCSTAT_BUMP(arcstat_l2_misses); 4333 } 4334 } 4335 4336 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4337 arc_read_done, buf, priority, zio_flags, zb); 4338 4339 if (*arc_flags & ARC_FLAG_WAIT) 4340 return (zio_wait(rzio)); 4341 4342 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4343 zio_nowait(rzio); 4344 } 4345 return (0); 4346 } 4347 4348 void 4349 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4350 { 4351 ASSERT(buf->b_hdr != NULL); 4352 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4353 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4354 func == NULL); 4355 ASSERT(buf->b_efunc == NULL); 4356 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4357 4358 buf->b_efunc = func; 4359 buf->b_private = private; 4360 } 4361 4362 /* 4363 * Notify the arc that a block was freed, and thus will never be used again. 4364 */ 4365 void 4366 arc_freed(spa_t *spa, const blkptr_t *bp) 4367 { 4368 arc_buf_hdr_t *hdr; 4369 kmutex_t *hash_lock; 4370 uint64_t guid = spa_load_guid(spa); 4371 4372 ASSERT(!BP_IS_EMBEDDED(bp)); 4373 4374 hdr = buf_hash_find(guid, bp, &hash_lock); 4375 if (hdr == NULL) 4376 return; 4377 if (HDR_BUF_AVAILABLE(hdr)) { 4378 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4379 add_reference(hdr, hash_lock, FTAG); 4380 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4381 mutex_exit(hash_lock); 4382 4383 arc_release(buf, FTAG); 4384 (void) arc_buf_remove_ref(buf, FTAG); 4385 } else { 4386 mutex_exit(hash_lock); 4387 } 4388 4389 } 4390 4391 /* 4392 * Clear the user eviction callback set by arc_set_callback(), first calling 4393 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4394 * clearing the callback may result in the arc_buf being destroyed. However, 4395 * it will not result in the *last* arc_buf being destroyed, hence the data 4396 * will remain cached in the ARC. We make a copy of the arc buffer here so 4397 * that we can process the callback without holding any locks. 4398 * 4399 * It's possible that the callback is already in the process of being cleared 4400 * by another thread. In this case we can not clear the callback. 4401 * 4402 * Returns B_TRUE if the callback was successfully called and cleared. 4403 */ 4404 boolean_t 4405 arc_clear_callback(arc_buf_t *buf) 4406 { 4407 arc_buf_hdr_t *hdr; 4408 kmutex_t *hash_lock; 4409 arc_evict_func_t *efunc = buf->b_efunc; 4410 void *private = buf->b_private; 4411 4412 mutex_enter(&buf->b_evict_lock); 4413 hdr = buf->b_hdr; 4414 if (hdr == NULL) { 4415 /* 4416 * We are in arc_do_user_evicts(). 4417 */ 4418 ASSERT(buf->b_data == NULL); 4419 mutex_exit(&buf->b_evict_lock); 4420 return (B_FALSE); 4421 } else if (buf->b_data == NULL) { 4422 /* 4423 * We are on the eviction list; process this buffer now 4424 * but let arc_do_user_evicts() do the reaping. 4425 */ 4426 buf->b_efunc = NULL; 4427 mutex_exit(&buf->b_evict_lock); 4428 VERIFY0(efunc(private)); 4429 return (B_TRUE); 4430 } 4431 hash_lock = HDR_LOCK(hdr); 4432 mutex_enter(hash_lock); 4433 hdr = buf->b_hdr; 4434 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4435 4436 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4437 hdr->b_l1hdr.b_datacnt); 4438 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4439 hdr->b_l1hdr.b_state == arc_mfu); 4440 4441 buf->b_efunc = NULL; 4442 buf->b_private = NULL; 4443 4444 if (hdr->b_l1hdr.b_datacnt > 1) { 4445 mutex_exit(&buf->b_evict_lock); 4446 arc_buf_destroy(buf, TRUE); 4447 } else { 4448 ASSERT(buf == hdr->b_l1hdr.b_buf); 4449 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4450 mutex_exit(&buf->b_evict_lock); 4451 } 4452 4453 mutex_exit(hash_lock); 4454 VERIFY0(efunc(private)); 4455 return (B_TRUE); 4456 } 4457 4458 /* 4459 * Release this buffer from the cache, making it an anonymous buffer. This 4460 * must be done after a read and prior to modifying the buffer contents. 4461 * If the buffer has more than one reference, we must make 4462 * a new hdr for the buffer. 4463 */ 4464 void 4465 arc_release(arc_buf_t *buf, void *tag) 4466 { 4467 arc_buf_hdr_t *hdr = buf->b_hdr; 4468 4469 /* 4470 * It would be nice to assert that if it's DMU metadata (level > 4471 * 0 || it's the dnode file), then it must be syncing context. 4472 * But we don't know that information at this level. 4473 */ 4474 4475 mutex_enter(&buf->b_evict_lock); 4476 4477 ASSERT(HDR_HAS_L1HDR(hdr)); 4478 4479 /* 4480 * We don't grab the hash lock prior to this check, because if 4481 * the buffer's header is in the arc_anon state, it won't be 4482 * linked into the hash table. 4483 */ 4484 if (hdr->b_l1hdr.b_state == arc_anon) { 4485 mutex_exit(&buf->b_evict_lock); 4486 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4487 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4488 ASSERT(!HDR_HAS_L2HDR(hdr)); 4489 ASSERT(BUF_EMPTY(hdr)); 4490 4491 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4492 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4493 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4494 4495 ASSERT3P(buf->b_efunc, ==, NULL); 4496 ASSERT3P(buf->b_private, ==, NULL); 4497 4498 hdr->b_l1hdr.b_arc_access = 0; 4499 arc_buf_thaw(buf); 4500 4501 return; 4502 } 4503 4504 kmutex_t *hash_lock = HDR_LOCK(hdr); 4505 mutex_enter(hash_lock); 4506 4507 /* 4508 * This assignment is only valid as long as the hash_lock is 4509 * held, we must be careful not to reference state or the 4510 * b_state field after dropping the lock. 4511 */ 4512 arc_state_t *state = hdr->b_l1hdr.b_state; 4513 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4514 ASSERT3P(state, !=, arc_anon); 4515 4516 /* this buffer is not on any list */ 4517 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4518 4519 if (HDR_HAS_L2HDR(hdr)) { 4520 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4521 4522 /* 4523 * We have to recheck this conditional again now that 4524 * we're holding the l2ad_mtx to prevent a race with 4525 * another thread which might be concurrently calling 4526 * l2arc_evict(). In that case, l2arc_evict() might have 4527 * destroyed the header's L2 portion as we were waiting 4528 * to acquire the l2ad_mtx. 4529 */ 4530 if (HDR_HAS_L2HDR(hdr)) 4531 arc_hdr_l2hdr_destroy(hdr); 4532 4533 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4534 } 4535 4536 /* 4537 * Do we have more than one buf? 4538 */ 4539 if (hdr->b_l1hdr.b_datacnt > 1) { 4540 arc_buf_hdr_t *nhdr; 4541 arc_buf_t **bufp; 4542 uint64_t blksz = hdr->b_size; 4543 uint64_t spa = hdr->b_spa; 4544 arc_buf_contents_t type = arc_buf_type(hdr); 4545 uint32_t flags = hdr->b_flags; 4546 4547 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4548 /* 4549 * Pull the data off of this hdr and attach it to 4550 * a new anonymous hdr. 4551 */ 4552 (void) remove_reference(hdr, hash_lock, tag); 4553 bufp = &hdr->b_l1hdr.b_buf; 4554 while (*bufp != buf) 4555 bufp = &(*bufp)->b_next; 4556 *bufp = buf->b_next; 4557 buf->b_next = NULL; 4558 4559 ASSERT3P(state, !=, arc_l2c_only); 4560 4561 (void) refcount_remove_many( 4562 &state->arcs_size, hdr->b_size, buf); 4563 4564 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4565 ASSERT3P(state, !=, arc_l2c_only); 4566 uint64_t *size = &state->arcs_lsize[type]; 4567 ASSERT3U(*size, >=, hdr->b_size); 4568 atomic_add_64(size, -hdr->b_size); 4569 } 4570 4571 /* 4572 * We're releasing a duplicate user data buffer, update 4573 * our statistics accordingly. 4574 */ 4575 if (HDR_ISTYPE_DATA(hdr)) { 4576 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4577 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4578 -hdr->b_size); 4579 } 4580 hdr->b_l1hdr.b_datacnt -= 1; 4581 arc_cksum_verify(buf); 4582 arc_buf_unwatch(buf); 4583 4584 mutex_exit(hash_lock); 4585 4586 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4587 nhdr->b_size = blksz; 4588 nhdr->b_spa = spa; 4589 4590 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4591 nhdr->b_flags |= arc_bufc_to_flags(type); 4592 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4593 4594 nhdr->b_l1hdr.b_buf = buf; 4595 nhdr->b_l1hdr.b_datacnt = 1; 4596 nhdr->b_l1hdr.b_state = arc_anon; 4597 nhdr->b_l1hdr.b_arc_access = 0; 4598 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4599 nhdr->b_freeze_cksum = NULL; 4600 4601 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4602 buf->b_hdr = nhdr; 4603 mutex_exit(&buf->b_evict_lock); 4604 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4605 } else { 4606 mutex_exit(&buf->b_evict_lock); 4607 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4608 /* protected by hash lock, or hdr is on arc_anon */ 4609 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4610 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4611 arc_change_state(arc_anon, hdr, hash_lock); 4612 hdr->b_l1hdr.b_arc_access = 0; 4613 mutex_exit(hash_lock); 4614 4615 buf_discard_identity(hdr); 4616 arc_buf_thaw(buf); 4617 } 4618 buf->b_efunc = NULL; 4619 buf->b_private = NULL; 4620 } 4621 4622 int 4623 arc_released(arc_buf_t *buf) 4624 { 4625 int released; 4626 4627 mutex_enter(&buf->b_evict_lock); 4628 released = (buf->b_data != NULL && 4629 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4630 mutex_exit(&buf->b_evict_lock); 4631 return (released); 4632 } 4633 4634 #ifdef ZFS_DEBUG 4635 int 4636 arc_referenced(arc_buf_t *buf) 4637 { 4638 int referenced; 4639 4640 mutex_enter(&buf->b_evict_lock); 4641 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4642 mutex_exit(&buf->b_evict_lock); 4643 return (referenced); 4644 } 4645 #endif 4646 4647 static void 4648 arc_write_ready(zio_t *zio) 4649 { 4650 arc_write_callback_t *callback = zio->io_private; 4651 arc_buf_t *buf = callback->awcb_buf; 4652 arc_buf_hdr_t *hdr = buf->b_hdr; 4653 4654 ASSERT(HDR_HAS_L1HDR(hdr)); 4655 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4656 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4657 callback->awcb_ready(zio, buf, callback->awcb_private); 4658 4659 /* 4660 * If the IO is already in progress, then this is a re-write 4661 * attempt, so we need to thaw and re-compute the cksum. 4662 * It is the responsibility of the callback to handle the 4663 * accounting for any re-write attempt. 4664 */ 4665 if (HDR_IO_IN_PROGRESS(hdr)) { 4666 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4667 if (hdr->b_freeze_cksum != NULL) { 4668 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4669 hdr->b_freeze_cksum = NULL; 4670 } 4671 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4672 } 4673 arc_cksum_compute(buf, B_FALSE); 4674 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4675 } 4676 4677 /* 4678 * The SPA calls this callback for each physical write that happens on behalf 4679 * of a logical write. See the comment in dbuf_write_physdone() for details. 4680 */ 4681 static void 4682 arc_write_physdone(zio_t *zio) 4683 { 4684 arc_write_callback_t *cb = zio->io_private; 4685 if (cb->awcb_physdone != NULL) 4686 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4687 } 4688 4689 static void 4690 arc_write_done(zio_t *zio) 4691 { 4692 arc_write_callback_t *callback = zio->io_private; 4693 arc_buf_t *buf = callback->awcb_buf; 4694 arc_buf_hdr_t *hdr = buf->b_hdr; 4695 4696 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4697 4698 if (zio->io_error == 0) { 4699 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4700 buf_discard_identity(hdr); 4701 } else { 4702 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4703 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4704 } 4705 } else { 4706 ASSERT(BUF_EMPTY(hdr)); 4707 } 4708 4709 /* 4710 * If the block to be written was all-zero or compressed enough to be 4711 * embedded in the BP, no write was performed so there will be no 4712 * dva/birth/checksum. The buffer must therefore remain anonymous 4713 * (and uncached). 4714 */ 4715 if (!BUF_EMPTY(hdr)) { 4716 arc_buf_hdr_t *exists; 4717 kmutex_t *hash_lock; 4718 4719 ASSERT(zio->io_error == 0); 4720 4721 arc_cksum_verify(buf); 4722 4723 exists = buf_hash_insert(hdr, &hash_lock); 4724 if (exists != NULL) { 4725 /* 4726 * This can only happen if we overwrite for 4727 * sync-to-convergence, because we remove 4728 * buffers from the hash table when we arc_free(). 4729 */ 4730 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4731 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4732 panic("bad overwrite, hdr=%p exists=%p", 4733 (void *)hdr, (void *)exists); 4734 ASSERT(refcount_is_zero( 4735 &exists->b_l1hdr.b_refcnt)); 4736 arc_change_state(arc_anon, exists, hash_lock); 4737 mutex_exit(hash_lock); 4738 arc_hdr_destroy(exists); 4739 exists = buf_hash_insert(hdr, &hash_lock); 4740 ASSERT3P(exists, ==, NULL); 4741 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4742 /* nopwrite */ 4743 ASSERT(zio->io_prop.zp_nopwrite); 4744 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4745 panic("bad nopwrite, hdr=%p exists=%p", 4746 (void *)hdr, (void *)exists); 4747 } else { 4748 /* Dedup */ 4749 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4750 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4751 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4752 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4753 } 4754 } 4755 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4756 /* if it's not anon, we are doing a scrub */ 4757 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4758 arc_access(hdr, hash_lock); 4759 mutex_exit(hash_lock); 4760 } else { 4761 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4762 } 4763 4764 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4765 callback->awcb_done(zio, buf, callback->awcb_private); 4766 4767 kmem_free(callback, sizeof (arc_write_callback_t)); 4768 } 4769 4770 zio_t * 4771 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4772 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4773 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4774 arc_done_func_t *done, void *private, zio_priority_t priority, 4775 int zio_flags, const zbookmark_phys_t *zb) 4776 { 4777 arc_buf_hdr_t *hdr = buf->b_hdr; 4778 arc_write_callback_t *callback; 4779 zio_t *zio; 4780 4781 ASSERT(ready != NULL); 4782 ASSERT(done != NULL); 4783 ASSERT(!HDR_IO_ERROR(hdr)); 4784 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4785 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4786 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4787 if (l2arc) 4788 hdr->b_flags |= ARC_FLAG_L2CACHE; 4789 if (l2arc_compress) 4790 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4791 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4792 callback->awcb_ready = ready; 4793 callback->awcb_physdone = physdone; 4794 callback->awcb_done = done; 4795 callback->awcb_private = private; 4796 callback->awcb_buf = buf; 4797 4798 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4799 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4800 priority, zio_flags, zb); 4801 4802 return (zio); 4803 } 4804 4805 static int 4806 arc_memory_throttle(uint64_t reserve, uint64_t txg) 4807 { 4808 #ifdef _KERNEL 4809 uint64_t available_memory = ptob(freemem); 4810 static uint64_t page_load = 0; 4811 static uint64_t last_txg = 0; 4812 4813 #if defined(__i386) 4814 available_memory = 4815 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 4816 #endif 4817 4818 if (freemem > physmem * arc_lotsfree_percent / 100) 4819 return (0); 4820 4821 if (txg > last_txg) { 4822 last_txg = txg; 4823 page_load = 0; 4824 } 4825 /* 4826 * If we are in pageout, we know that memory is already tight, 4827 * the arc is already going to be evicting, so we just want to 4828 * continue to let page writes occur as quickly as possible. 4829 */ 4830 if (curproc == proc_pageout) { 4831 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4832 return (SET_ERROR(ERESTART)); 4833 /* Note: reserve is inflated, so we deflate */ 4834 page_load += reserve / 8; 4835 return (0); 4836 } else if (page_load > 0 && arc_reclaim_needed()) { 4837 /* memory is low, delay before restarting */ 4838 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4839 return (SET_ERROR(EAGAIN)); 4840 } 4841 page_load = 0; 4842 #endif 4843 return (0); 4844 } 4845 4846 void 4847 arc_tempreserve_clear(uint64_t reserve) 4848 { 4849 atomic_add_64(&arc_tempreserve, -reserve); 4850 ASSERT((int64_t)arc_tempreserve >= 0); 4851 } 4852 4853 int 4854 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4855 { 4856 int error; 4857 uint64_t anon_size; 4858 4859 if (reserve > arc_c/4 && !arc_no_grow) 4860 arc_c = MIN(arc_c_max, reserve * 4); 4861 if (reserve > arc_c) 4862 return (SET_ERROR(ENOMEM)); 4863 4864 /* 4865 * Don't count loaned bufs as in flight dirty data to prevent long 4866 * network delays from blocking transactions that are ready to be 4867 * assigned to a txg. 4868 */ 4869 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 4870 arc_loaned_bytes), 0); 4871 4872 /* 4873 * Writes will, almost always, require additional memory allocations 4874 * in order to compress/encrypt/etc the data. We therefore need to 4875 * make sure that there is sufficient available memory for this. 4876 */ 4877 error = arc_memory_throttle(reserve, txg); 4878 if (error != 0) 4879 return (error); 4880 4881 /* 4882 * Throttle writes when the amount of dirty data in the cache 4883 * gets too large. We try to keep the cache less than half full 4884 * of dirty blocks so that our sync times don't grow too large. 4885 * Note: if two requests come in concurrently, we might let them 4886 * both succeed, when one of them should fail. Not a huge deal. 4887 */ 4888 4889 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4890 anon_size > arc_c / 4) { 4891 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4892 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4893 arc_tempreserve>>10, 4894 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4895 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4896 reserve>>10, arc_c>>10); 4897 return (SET_ERROR(ERESTART)); 4898 } 4899 atomic_add_64(&arc_tempreserve, reserve); 4900 return (0); 4901 } 4902 4903 static void 4904 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4905 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4906 { 4907 size->value.ui64 = refcount_count(&state->arcs_size); 4908 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4909 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4910 } 4911 4912 static int 4913 arc_kstat_update(kstat_t *ksp, int rw) 4914 { 4915 arc_stats_t *as = ksp->ks_data; 4916 4917 if (rw == KSTAT_WRITE) { 4918 return (EACCES); 4919 } else { 4920 arc_kstat_update_state(arc_anon, 4921 &as->arcstat_anon_size, 4922 &as->arcstat_anon_evictable_data, 4923 &as->arcstat_anon_evictable_metadata); 4924 arc_kstat_update_state(arc_mru, 4925 &as->arcstat_mru_size, 4926 &as->arcstat_mru_evictable_data, 4927 &as->arcstat_mru_evictable_metadata); 4928 arc_kstat_update_state(arc_mru_ghost, 4929 &as->arcstat_mru_ghost_size, 4930 &as->arcstat_mru_ghost_evictable_data, 4931 &as->arcstat_mru_ghost_evictable_metadata); 4932 arc_kstat_update_state(arc_mfu, 4933 &as->arcstat_mfu_size, 4934 &as->arcstat_mfu_evictable_data, 4935 &as->arcstat_mfu_evictable_metadata); 4936 arc_kstat_update_state(arc_mfu_ghost, 4937 &as->arcstat_mfu_ghost_size, 4938 &as->arcstat_mfu_ghost_evictable_data, 4939 &as->arcstat_mfu_ghost_evictable_metadata); 4940 } 4941 4942 return (0); 4943 } 4944 4945 /* 4946 * This function *must* return indices evenly distributed between all 4947 * sublists of the multilist. This is needed due to how the ARC eviction 4948 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 4949 * distributed between all sublists and uses this assumption when 4950 * deciding which sublist to evict from and how much to evict from it. 4951 */ 4952 unsigned int 4953 arc_state_multilist_index_func(multilist_t *ml, void *obj) 4954 { 4955 arc_buf_hdr_t *hdr = obj; 4956 4957 /* 4958 * We rely on b_dva to generate evenly distributed index 4959 * numbers using buf_hash below. So, as an added precaution, 4960 * let's make sure we never add empty buffers to the arc lists. 4961 */ 4962 ASSERT(!BUF_EMPTY(hdr)); 4963 4964 /* 4965 * The assumption here, is the hash value for a given 4966 * arc_buf_hdr_t will remain constant throughout it's lifetime 4967 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 4968 * Thus, we don't need to store the header's sublist index 4969 * on insertion, as this index can be recalculated on removal. 4970 * 4971 * Also, the low order bits of the hash value are thought to be 4972 * distributed evenly. Otherwise, in the case that the multilist 4973 * has a power of two number of sublists, each sublists' usage 4974 * would not be evenly distributed. 4975 */ 4976 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 4977 multilist_get_num_sublists(ml)); 4978 } 4979 4980 void 4981 arc_init(void) 4982 { 4983 /* 4984 * allmem is "all memory that we could possibly use". 4985 */ 4986 #ifdef _KERNEL 4987 uint64_t allmem = ptob(physmem - swapfs_minfree); 4988 #else 4989 uint64_t allmem = (physmem * PAGESIZE) / 2; 4990 #endif 4991 4992 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 4993 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 4994 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 4995 4996 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 4997 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 4998 4999 /* Convert seconds to clock ticks */ 5000 arc_min_prefetch_lifespan = 1 * hz; 5001 5002 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 5003 arc_c_min = MAX(allmem / 32, 64 << 20); 5004 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 5005 if (allmem >= 1 << 30) 5006 arc_c_max = allmem - (1 << 30); 5007 else 5008 arc_c_max = arc_c_min; 5009 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 5010 5011 /* 5012 * In userland, there's only the memory pressure that we artificially 5013 * create (see arc_available_memory()). Don't let arc_c get too 5014 * small, because it can cause transactions to be larger than 5015 * arc_c, causing arc_tempreserve_space() to fail. 5016 */ 5017 #ifndef _KERNEL 5018 arc_c_min = arc_c_max / 2; 5019 #endif 5020 5021 /* 5022 * Allow the tunables to override our calculations if they are 5023 * reasonable (ie. over 64MB) 5024 */ 5025 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 5026 arc_c_max = zfs_arc_max; 5027 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 5028 arc_c_min = zfs_arc_min; 5029 5030 arc_c = arc_c_max; 5031 arc_p = (arc_c >> 1); 5032 5033 /* limit meta-data to 1/4 of the arc capacity */ 5034 arc_meta_limit = arc_c_max / 4; 5035 5036 #ifdef _KERNEL 5037 /* 5038 * Metadata is stored in the kernel's heap. Don't let us 5039 * use more than half the heap for the ARC. 5040 */ 5041 arc_meta_limit = MIN(arc_meta_limit, 5042 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 5043 #endif 5044 5045 /* Allow the tunable to override if it is reasonable */ 5046 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5047 arc_meta_limit = zfs_arc_meta_limit; 5048 5049 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5050 arc_c_min = arc_meta_limit / 2; 5051 5052 if (zfs_arc_meta_min > 0) { 5053 arc_meta_min = zfs_arc_meta_min; 5054 } else { 5055 arc_meta_min = arc_c_min / 2; 5056 } 5057 5058 if (zfs_arc_grow_retry > 0) 5059 arc_grow_retry = zfs_arc_grow_retry; 5060 5061 if (zfs_arc_shrink_shift > 0) 5062 arc_shrink_shift = zfs_arc_shrink_shift; 5063 5064 /* 5065 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5066 */ 5067 if (arc_no_grow_shift >= arc_shrink_shift) 5068 arc_no_grow_shift = arc_shrink_shift - 1; 5069 5070 if (zfs_arc_p_min_shift > 0) 5071 arc_p_min_shift = zfs_arc_p_min_shift; 5072 5073 if (zfs_arc_num_sublists_per_state < 1) 5074 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 5075 5076 /* if kmem_flags are set, lets try to use less memory */ 5077 if (kmem_debugging()) 5078 arc_c = arc_c / 2; 5079 if (arc_c < arc_c_min) 5080 arc_c = arc_c_min; 5081 5082 arc_anon = &ARC_anon; 5083 arc_mru = &ARC_mru; 5084 arc_mru_ghost = &ARC_mru_ghost; 5085 arc_mfu = &ARC_mfu; 5086 arc_mfu_ghost = &ARC_mfu_ghost; 5087 arc_l2c_only = &ARC_l2c_only; 5088 arc_size = 0; 5089 5090 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5091 sizeof (arc_buf_hdr_t), 5092 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5093 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5094 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5095 sizeof (arc_buf_hdr_t), 5096 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5097 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5098 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5099 sizeof (arc_buf_hdr_t), 5100 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5101 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5102 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5103 sizeof (arc_buf_hdr_t), 5104 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5105 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5106 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5107 sizeof (arc_buf_hdr_t), 5108 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5109 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5110 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5111 sizeof (arc_buf_hdr_t), 5112 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5113 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5114 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5115 sizeof (arc_buf_hdr_t), 5116 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5117 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5118 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5119 sizeof (arc_buf_hdr_t), 5120 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5121 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5122 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5123 sizeof (arc_buf_hdr_t), 5124 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5125 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5126 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5127 sizeof (arc_buf_hdr_t), 5128 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5129 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5130 5131 refcount_create(&arc_anon->arcs_size); 5132 refcount_create(&arc_mru->arcs_size); 5133 refcount_create(&arc_mru_ghost->arcs_size); 5134 refcount_create(&arc_mfu->arcs_size); 5135 refcount_create(&arc_mfu_ghost->arcs_size); 5136 refcount_create(&arc_l2c_only->arcs_size); 5137 5138 buf_init(); 5139 5140 arc_reclaim_thread_exit = FALSE; 5141 arc_user_evicts_thread_exit = FALSE; 5142 arc_eviction_list = NULL; 5143 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5144 5145 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5146 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5147 5148 if (arc_ksp != NULL) { 5149 arc_ksp->ks_data = &arc_stats; 5150 arc_ksp->ks_update = arc_kstat_update; 5151 kstat_install(arc_ksp); 5152 } 5153 5154 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5155 TS_RUN, minclsyspri); 5156 5157 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5158 TS_RUN, minclsyspri); 5159 5160 arc_dead = FALSE; 5161 arc_warm = B_FALSE; 5162 5163 /* 5164 * Calculate maximum amount of dirty data per pool. 5165 * 5166 * If it has been set by /etc/system, take that. 5167 * Otherwise, use a percentage of physical memory defined by 5168 * zfs_dirty_data_max_percent (default 10%) with a cap at 5169 * zfs_dirty_data_max_max (default 4GB). 5170 */ 5171 if (zfs_dirty_data_max == 0) { 5172 zfs_dirty_data_max = physmem * PAGESIZE * 5173 zfs_dirty_data_max_percent / 100; 5174 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5175 zfs_dirty_data_max_max); 5176 } 5177 } 5178 5179 void 5180 arc_fini(void) 5181 { 5182 mutex_enter(&arc_reclaim_lock); 5183 arc_reclaim_thread_exit = TRUE; 5184 /* 5185 * The reclaim thread will set arc_reclaim_thread_exit back to 5186 * FALSE when it is finished exiting; we're waiting for that. 5187 */ 5188 while (arc_reclaim_thread_exit) { 5189 cv_signal(&arc_reclaim_thread_cv); 5190 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5191 } 5192 mutex_exit(&arc_reclaim_lock); 5193 5194 mutex_enter(&arc_user_evicts_lock); 5195 arc_user_evicts_thread_exit = TRUE; 5196 /* 5197 * The user evicts thread will set arc_user_evicts_thread_exit 5198 * to FALSE when it is finished exiting; we're waiting for that. 5199 */ 5200 while (arc_user_evicts_thread_exit) { 5201 cv_signal(&arc_user_evicts_cv); 5202 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5203 } 5204 mutex_exit(&arc_user_evicts_lock); 5205 5206 /* Use TRUE to ensure *all* buffers are evicted */ 5207 arc_flush(NULL, TRUE); 5208 5209 arc_dead = TRUE; 5210 5211 if (arc_ksp != NULL) { 5212 kstat_delete(arc_ksp); 5213 arc_ksp = NULL; 5214 } 5215 5216 mutex_destroy(&arc_reclaim_lock); 5217 cv_destroy(&arc_reclaim_thread_cv); 5218 cv_destroy(&arc_reclaim_waiters_cv); 5219 5220 mutex_destroy(&arc_user_evicts_lock); 5221 cv_destroy(&arc_user_evicts_cv); 5222 5223 refcount_destroy(&arc_anon->arcs_size); 5224 refcount_destroy(&arc_mru->arcs_size); 5225 refcount_destroy(&arc_mru_ghost->arcs_size); 5226 refcount_destroy(&arc_mfu->arcs_size); 5227 refcount_destroy(&arc_mfu_ghost->arcs_size); 5228 refcount_destroy(&arc_l2c_only->arcs_size); 5229 5230 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5231 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5232 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5233 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5234 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); 5235 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5236 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5237 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5238 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5239 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]); 5240 5241 buf_fini(); 5242 5243 ASSERT0(arc_loaned_bytes); 5244 } 5245 5246 /* 5247 * Level 2 ARC 5248 * 5249 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5250 * It uses dedicated storage devices to hold cached data, which are populated 5251 * using large infrequent writes. The main role of this cache is to boost 5252 * the performance of random read workloads. The intended L2ARC devices 5253 * include short-stroked disks, solid state disks, and other media with 5254 * substantially faster read latency than disk. 5255 * 5256 * +-----------------------+ 5257 * | ARC | 5258 * +-----------------------+ 5259 * | ^ ^ 5260 * | | | 5261 * l2arc_feed_thread() arc_read() 5262 * | | | 5263 * | l2arc read | 5264 * V | | 5265 * +---------------+ | 5266 * | L2ARC | | 5267 * +---------------+ | 5268 * | ^ | 5269 * l2arc_write() | | 5270 * | | | 5271 * V | | 5272 * +-------+ +-------+ 5273 * | vdev | | vdev | 5274 * | cache | | cache | 5275 * +-------+ +-------+ 5276 * +=========+ .-----. 5277 * : L2ARC : |-_____-| 5278 * : devices : | Disks | 5279 * +=========+ `-_____-' 5280 * 5281 * Read requests are satisfied from the following sources, in order: 5282 * 5283 * 1) ARC 5284 * 2) vdev cache of L2ARC devices 5285 * 3) L2ARC devices 5286 * 4) vdev cache of disks 5287 * 5) disks 5288 * 5289 * Some L2ARC device types exhibit extremely slow write performance. 5290 * To accommodate for this there are some significant differences between 5291 * the L2ARC and traditional cache design: 5292 * 5293 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5294 * the ARC behave as usual, freeing buffers and placing headers on ghost 5295 * lists. The ARC does not send buffers to the L2ARC during eviction as 5296 * this would add inflated write latencies for all ARC memory pressure. 5297 * 5298 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5299 * It does this by periodically scanning buffers from the eviction-end of 5300 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5301 * not already there. It scans until a headroom of buffers is satisfied, 5302 * which itself is a buffer for ARC eviction. If a compressible buffer is 5303 * found during scanning and selected for writing to an L2ARC device, we 5304 * temporarily boost scanning headroom during the next scan cycle to make 5305 * sure we adapt to compression effects (which might significantly reduce 5306 * the data volume we write to L2ARC). The thread that does this is 5307 * l2arc_feed_thread(), illustrated below; example sizes are included to 5308 * provide a better sense of ratio than this diagram: 5309 * 5310 * head --> tail 5311 * +---------------------+----------+ 5312 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5313 * +---------------------+----------+ | o L2ARC eligible 5314 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5315 * +---------------------+----------+ | 5316 * 15.9 Gbytes ^ 32 Mbytes | 5317 * headroom | 5318 * l2arc_feed_thread() 5319 * | 5320 * l2arc write hand <--[oooo]--' 5321 * | 8 Mbyte 5322 * | write max 5323 * V 5324 * +==============================+ 5325 * L2ARC dev |####|#|###|###| |####| ... | 5326 * +==============================+ 5327 * 32 Gbytes 5328 * 5329 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5330 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5331 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5332 * safe to say that this is an uncommon case, since buffers at the end of 5333 * the ARC lists have moved there due to inactivity. 5334 * 5335 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5336 * then the L2ARC simply misses copying some buffers. This serves as a 5337 * pressure valve to prevent heavy read workloads from both stalling the ARC 5338 * with waits and clogging the L2ARC with writes. This also helps prevent 5339 * the potential for the L2ARC to churn if it attempts to cache content too 5340 * quickly, such as during backups of the entire pool. 5341 * 5342 * 5. After system boot and before the ARC has filled main memory, there are 5343 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5344 * lists can remain mostly static. Instead of searching from tail of these 5345 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5346 * for eligible buffers, greatly increasing its chance of finding them. 5347 * 5348 * The L2ARC device write speed is also boosted during this time so that 5349 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5350 * there are no L2ARC reads, and no fear of degrading read performance 5351 * through increased writes. 5352 * 5353 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5354 * the vdev queue can aggregate them into larger and fewer writes. Each 5355 * device is written to in a rotor fashion, sweeping writes through 5356 * available space then repeating. 5357 * 5358 * 7. The L2ARC does not store dirty content. It never needs to flush 5359 * write buffers back to disk based storage. 5360 * 5361 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5362 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5363 * 5364 * The performance of the L2ARC can be tweaked by a number of tunables, which 5365 * may be necessary for different workloads: 5366 * 5367 * l2arc_write_max max write bytes per interval 5368 * l2arc_write_boost extra write bytes during device warmup 5369 * l2arc_noprefetch skip caching prefetched buffers 5370 * l2arc_headroom number of max device writes to precache 5371 * l2arc_headroom_boost when we find compressed buffers during ARC 5372 * scanning, we multiply headroom by this 5373 * percentage factor for the next scan cycle, 5374 * since more compressed buffers are likely to 5375 * be present 5376 * l2arc_feed_secs seconds between L2ARC writing 5377 * 5378 * Tunables may be removed or added as future performance improvements are 5379 * integrated, and also may become zpool properties. 5380 * 5381 * There are three key functions that control how the L2ARC warms up: 5382 * 5383 * l2arc_write_eligible() check if a buffer is eligible to cache 5384 * l2arc_write_size() calculate how much to write 5385 * l2arc_write_interval() calculate sleep delay between writes 5386 * 5387 * These three functions determine what to write, how much, and how quickly 5388 * to send writes. 5389 */ 5390 5391 static boolean_t 5392 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5393 { 5394 /* 5395 * A buffer is *not* eligible for the L2ARC if it: 5396 * 1. belongs to a different spa. 5397 * 2. is already cached on the L2ARC. 5398 * 3. has an I/O in progress (it may be an incomplete read). 5399 * 4. is flagged not eligible (zfs property). 5400 */ 5401 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5402 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 5403 return (B_FALSE); 5404 5405 return (B_TRUE); 5406 } 5407 5408 static uint64_t 5409 l2arc_write_size(void) 5410 { 5411 uint64_t size; 5412 5413 /* 5414 * Make sure our globals have meaningful values in case the user 5415 * altered them. 5416 */ 5417 size = l2arc_write_max; 5418 if (size == 0) { 5419 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5420 "be greater than zero, resetting it to the default (%d)", 5421 L2ARC_WRITE_SIZE); 5422 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5423 } 5424 5425 if (arc_warm == B_FALSE) 5426 size += l2arc_write_boost; 5427 5428 return (size); 5429 5430 } 5431 5432 static clock_t 5433 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5434 { 5435 clock_t interval, next, now; 5436 5437 /* 5438 * If the ARC lists are busy, increase our write rate; if the 5439 * lists are stale, idle back. This is achieved by checking 5440 * how much we previously wrote - if it was more than half of 5441 * what we wanted, schedule the next write much sooner. 5442 */ 5443 if (l2arc_feed_again && wrote > (wanted / 2)) 5444 interval = (hz * l2arc_feed_min_ms) / 1000; 5445 else 5446 interval = hz * l2arc_feed_secs; 5447 5448 now = ddi_get_lbolt(); 5449 next = MAX(now, MIN(now + interval, began + interval)); 5450 5451 return (next); 5452 } 5453 5454 /* 5455 * Cycle through L2ARC devices. This is how L2ARC load balances. 5456 * If a device is returned, this also returns holding the spa config lock. 5457 */ 5458 static l2arc_dev_t * 5459 l2arc_dev_get_next(void) 5460 { 5461 l2arc_dev_t *first, *next = NULL; 5462 5463 /* 5464 * Lock out the removal of spas (spa_namespace_lock), then removal 5465 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5466 * both locks will be dropped and a spa config lock held instead. 5467 */ 5468 mutex_enter(&spa_namespace_lock); 5469 mutex_enter(&l2arc_dev_mtx); 5470 5471 /* if there are no vdevs, there is nothing to do */ 5472 if (l2arc_ndev == 0) 5473 goto out; 5474 5475 first = NULL; 5476 next = l2arc_dev_last; 5477 do { 5478 /* loop around the list looking for a non-faulted vdev */ 5479 if (next == NULL) { 5480 next = list_head(l2arc_dev_list); 5481 } else { 5482 next = list_next(l2arc_dev_list, next); 5483 if (next == NULL) 5484 next = list_head(l2arc_dev_list); 5485 } 5486 5487 /* if we have come back to the start, bail out */ 5488 if (first == NULL) 5489 first = next; 5490 else if (next == first) 5491 break; 5492 5493 } while (vdev_is_dead(next->l2ad_vdev)); 5494 5495 /* if we were unable to find any usable vdevs, return NULL */ 5496 if (vdev_is_dead(next->l2ad_vdev)) 5497 next = NULL; 5498 5499 l2arc_dev_last = next; 5500 5501 out: 5502 mutex_exit(&l2arc_dev_mtx); 5503 5504 /* 5505 * Grab the config lock to prevent the 'next' device from being 5506 * removed while we are writing to it. 5507 */ 5508 if (next != NULL) 5509 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5510 mutex_exit(&spa_namespace_lock); 5511 5512 return (next); 5513 } 5514 5515 /* 5516 * Free buffers that were tagged for destruction. 5517 */ 5518 static void 5519 l2arc_do_free_on_write() 5520 { 5521 list_t *buflist; 5522 l2arc_data_free_t *df, *df_prev; 5523 5524 mutex_enter(&l2arc_free_on_write_mtx); 5525 buflist = l2arc_free_on_write; 5526 5527 for (df = list_tail(buflist); df; df = df_prev) { 5528 df_prev = list_prev(buflist, df); 5529 ASSERT(df->l2df_data != NULL); 5530 ASSERT(df->l2df_func != NULL); 5531 df->l2df_func(df->l2df_data, df->l2df_size); 5532 list_remove(buflist, df); 5533 kmem_free(df, sizeof (l2arc_data_free_t)); 5534 } 5535 5536 mutex_exit(&l2arc_free_on_write_mtx); 5537 } 5538 5539 /* 5540 * A write to a cache device has completed. Update all headers to allow 5541 * reads from these buffers to begin. 5542 */ 5543 static void 5544 l2arc_write_done(zio_t *zio) 5545 { 5546 l2arc_write_callback_t *cb; 5547 l2arc_dev_t *dev; 5548 list_t *buflist; 5549 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5550 kmutex_t *hash_lock; 5551 int64_t bytes_dropped = 0; 5552 5553 cb = zio->io_private; 5554 ASSERT(cb != NULL); 5555 dev = cb->l2wcb_dev; 5556 ASSERT(dev != NULL); 5557 head = cb->l2wcb_head; 5558 ASSERT(head != NULL); 5559 buflist = &dev->l2ad_buflist; 5560 ASSERT(buflist != NULL); 5561 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5562 l2arc_write_callback_t *, cb); 5563 5564 if (zio->io_error != 0) 5565 ARCSTAT_BUMP(arcstat_l2_writes_error); 5566 5567 /* 5568 * All writes completed, or an error was hit. 5569 */ 5570 top: 5571 mutex_enter(&dev->l2ad_mtx); 5572 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5573 hdr_prev = list_prev(buflist, hdr); 5574 5575 hash_lock = HDR_LOCK(hdr); 5576 5577 /* 5578 * We cannot use mutex_enter or else we can deadlock 5579 * with l2arc_write_buffers (due to swapping the order 5580 * the hash lock and l2ad_mtx are taken). 5581 */ 5582 if (!mutex_tryenter(hash_lock)) { 5583 /* 5584 * Missed the hash lock. We must retry so we 5585 * don't leave the ARC_FLAG_L2_WRITING bit set. 5586 */ 5587 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5588 5589 /* 5590 * We don't want to rescan the headers we've 5591 * already marked as having been written out, so 5592 * we reinsert the head node so we can pick up 5593 * where we left off. 5594 */ 5595 list_remove(buflist, head); 5596 list_insert_after(buflist, hdr, head); 5597 5598 mutex_exit(&dev->l2ad_mtx); 5599 5600 /* 5601 * We wait for the hash lock to become available 5602 * to try and prevent busy waiting, and increase 5603 * the chance we'll be able to acquire the lock 5604 * the next time around. 5605 */ 5606 mutex_enter(hash_lock); 5607 mutex_exit(hash_lock); 5608 goto top; 5609 } 5610 5611 /* 5612 * We could not have been moved into the arc_l2c_only 5613 * state while in-flight due to our ARC_FLAG_L2_WRITING 5614 * bit being set. Let's just ensure that's being enforced. 5615 */ 5616 ASSERT(HDR_HAS_L1HDR(hdr)); 5617 5618 /* 5619 * We may have allocated a buffer for L2ARC compression, 5620 * we must release it to avoid leaking this data. 5621 */ 5622 l2arc_release_cdata_buf(hdr); 5623 5624 if (zio->io_error != 0) { 5625 /* 5626 * Error - drop L2ARC entry. 5627 */ 5628 list_remove(buflist, hdr); 5629 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5630 5631 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5632 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5633 5634 bytes_dropped += hdr->b_l2hdr.b_asize; 5635 (void) refcount_remove_many(&dev->l2ad_alloc, 5636 hdr->b_l2hdr.b_asize, hdr); 5637 } 5638 5639 /* 5640 * Allow ARC to begin reads and ghost list evictions to 5641 * this L2ARC entry. 5642 */ 5643 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5644 5645 mutex_exit(hash_lock); 5646 } 5647 5648 atomic_inc_64(&l2arc_writes_done); 5649 list_remove(buflist, head); 5650 ASSERT(!HDR_HAS_L1HDR(head)); 5651 kmem_cache_free(hdr_l2only_cache, head); 5652 mutex_exit(&dev->l2ad_mtx); 5653 5654 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5655 5656 l2arc_do_free_on_write(); 5657 5658 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5659 } 5660 5661 /* 5662 * A read to a cache device completed. Validate buffer contents before 5663 * handing over to the regular ARC routines. 5664 */ 5665 static void 5666 l2arc_read_done(zio_t *zio) 5667 { 5668 l2arc_read_callback_t *cb; 5669 arc_buf_hdr_t *hdr; 5670 arc_buf_t *buf; 5671 kmutex_t *hash_lock; 5672 int equal; 5673 5674 ASSERT(zio->io_vd != NULL); 5675 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5676 5677 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5678 5679 cb = zio->io_private; 5680 ASSERT(cb != NULL); 5681 buf = cb->l2rcb_buf; 5682 ASSERT(buf != NULL); 5683 5684 hash_lock = HDR_LOCK(buf->b_hdr); 5685 mutex_enter(hash_lock); 5686 hdr = buf->b_hdr; 5687 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5688 5689 /* 5690 * If the buffer was compressed, decompress it first. 5691 */ 5692 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5693 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5694 ASSERT(zio->io_data != NULL); 5695 ASSERT3U(zio->io_size, ==, hdr->b_size); 5696 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 5697 5698 /* 5699 * Check this survived the L2ARC journey. 5700 */ 5701 equal = arc_cksum_equal(buf); 5702 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5703 mutex_exit(hash_lock); 5704 zio->io_private = buf; 5705 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5706 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5707 arc_read_done(zio); 5708 } else { 5709 mutex_exit(hash_lock); 5710 /* 5711 * Buffer didn't survive caching. Increment stats and 5712 * reissue to the original storage device. 5713 */ 5714 if (zio->io_error != 0) { 5715 ARCSTAT_BUMP(arcstat_l2_io_error); 5716 } else { 5717 zio->io_error = SET_ERROR(EIO); 5718 } 5719 if (!equal) 5720 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5721 5722 /* 5723 * If there's no waiter, issue an async i/o to the primary 5724 * storage now. If there *is* a waiter, the caller must 5725 * issue the i/o in a context where it's OK to block. 5726 */ 5727 if (zio->io_waiter == NULL) { 5728 zio_t *pio = zio_unique_parent(zio); 5729 5730 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5731 5732 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5733 buf->b_data, hdr->b_size, arc_read_done, buf, 5734 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5735 } 5736 } 5737 5738 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5739 } 5740 5741 /* 5742 * This is the list priority from which the L2ARC will search for pages to 5743 * cache. This is used within loops (0..3) to cycle through lists in the 5744 * desired order. This order can have a significant effect on cache 5745 * performance. 5746 * 5747 * Currently the metadata lists are hit first, MFU then MRU, followed by 5748 * the data lists. This function returns a locked list, and also returns 5749 * the lock pointer. 5750 */ 5751 static multilist_sublist_t * 5752 l2arc_sublist_lock(int list_num) 5753 { 5754 multilist_t *ml = NULL; 5755 unsigned int idx; 5756 5757 ASSERT(list_num >= 0 && list_num <= 3); 5758 5759 switch (list_num) { 5760 case 0: 5761 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 5762 break; 5763 case 1: 5764 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 5765 break; 5766 case 2: 5767 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 5768 break; 5769 case 3: 5770 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 5771 break; 5772 } 5773 5774 /* 5775 * Return a randomly-selected sublist. This is acceptable 5776 * because the caller feeds only a little bit of data for each 5777 * call (8MB). Subsequent calls will result in different 5778 * sublists being selected. 5779 */ 5780 idx = multilist_get_random_index(ml); 5781 return (multilist_sublist_lock(ml, idx)); 5782 } 5783 5784 /* 5785 * Evict buffers from the device write hand to the distance specified in 5786 * bytes. This distance may span populated buffers, it may span nothing. 5787 * This is clearing a region on the L2ARC device ready for writing. 5788 * If the 'all' boolean is set, every buffer is evicted. 5789 */ 5790 static void 5791 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5792 { 5793 list_t *buflist; 5794 arc_buf_hdr_t *hdr, *hdr_prev; 5795 kmutex_t *hash_lock; 5796 uint64_t taddr; 5797 5798 buflist = &dev->l2ad_buflist; 5799 5800 if (!all && dev->l2ad_first) { 5801 /* 5802 * This is the first sweep through the device. There is 5803 * nothing to evict. 5804 */ 5805 return; 5806 } 5807 5808 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5809 /* 5810 * When nearing the end of the device, evict to the end 5811 * before the device write hand jumps to the start. 5812 */ 5813 taddr = dev->l2ad_end; 5814 } else { 5815 taddr = dev->l2ad_hand + distance; 5816 } 5817 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5818 uint64_t, taddr, boolean_t, all); 5819 5820 top: 5821 mutex_enter(&dev->l2ad_mtx); 5822 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5823 hdr_prev = list_prev(buflist, hdr); 5824 5825 hash_lock = HDR_LOCK(hdr); 5826 5827 /* 5828 * We cannot use mutex_enter or else we can deadlock 5829 * with l2arc_write_buffers (due to swapping the order 5830 * the hash lock and l2ad_mtx are taken). 5831 */ 5832 if (!mutex_tryenter(hash_lock)) { 5833 /* 5834 * Missed the hash lock. Retry. 5835 */ 5836 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5837 mutex_exit(&dev->l2ad_mtx); 5838 mutex_enter(hash_lock); 5839 mutex_exit(hash_lock); 5840 goto top; 5841 } 5842 5843 if (HDR_L2_WRITE_HEAD(hdr)) { 5844 /* 5845 * We hit a write head node. Leave it for 5846 * l2arc_write_done(). 5847 */ 5848 list_remove(buflist, hdr); 5849 mutex_exit(hash_lock); 5850 continue; 5851 } 5852 5853 if (!all && HDR_HAS_L2HDR(hdr) && 5854 (hdr->b_l2hdr.b_daddr > taddr || 5855 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5856 /* 5857 * We've evicted to the target address, 5858 * or the end of the device. 5859 */ 5860 mutex_exit(hash_lock); 5861 break; 5862 } 5863 5864 ASSERT(HDR_HAS_L2HDR(hdr)); 5865 if (!HDR_HAS_L1HDR(hdr)) { 5866 ASSERT(!HDR_L2_READING(hdr)); 5867 /* 5868 * This doesn't exist in the ARC. Destroy. 5869 * arc_hdr_destroy() will call list_remove() 5870 * and decrement arcstat_l2_size. 5871 */ 5872 arc_change_state(arc_anon, hdr, hash_lock); 5873 arc_hdr_destroy(hdr); 5874 } else { 5875 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5876 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5877 /* 5878 * Invalidate issued or about to be issued 5879 * reads, since we may be about to write 5880 * over this location. 5881 */ 5882 if (HDR_L2_READING(hdr)) { 5883 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5884 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5885 } 5886 5887 /* Ensure this header has finished being written */ 5888 ASSERT(!HDR_L2_WRITING(hdr)); 5889 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 5890 5891 arc_hdr_l2hdr_destroy(hdr); 5892 } 5893 mutex_exit(hash_lock); 5894 } 5895 mutex_exit(&dev->l2ad_mtx); 5896 } 5897 5898 /* 5899 * Find and write ARC buffers to the L2ARC device. 5900 * 5901 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5902 * for reading until they have completed writing. 5903 * The headroom_boost is an in-out parameter used to maintain headroom boost 5904 * state between calls to this function. 5905 * 5906 * Returns the number of bytes actually written (which may be smaller than 5907 * the delta by which the device hand has changed due to alignment). 5908 */ 5909 static uint64_t 5910 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5911 boolean_t *headroom_boost) 5912 { 5913 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5914 uint64_t write_asize, write_sz, headroom, 5915 buf_compress_minsz; 5916 void *buf_data; 5917 boolean_t full; 5918 l2arc_write_callback_t *cb; 5919 zio_t *pio, *wzio; 5920 uint64_t guid = spa_load_guid(spa); 5921 const boolean_t do_headroom_boost = *headroom_boost; 5922 5923 ASSERT(dev->l2ad_vdev != NULL); 5924 5925 /* Lower the flag now, we might want to raise it again later. */ 5926 *headroom_boost = B_FALSE; 5927 5928 pio = NULL; 5929 write_sz = write_asize = 0; 5930 full = B_FALSE; 5931 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5932 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5933 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5934 5935 /* 5936 * We will want to try to compress buffers that are at least 2x the 5937 * device sector size. 5938 */ 5939 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5940 5941 /* 5942 * Copy buffers for L2ARC writing. 5943 */ 5944 for (int try = 0; try <= 3; try++) { 5945 multilist_sublist_t *mls = l2arc_sublist_lock(try); 5946 uint64_t passed_sz = 0; 5947 5948 /* 5949 * L2ARC fast warmup. 5950 * 5951 * Until the ARC is warm and starts to evict, read from the 5952 * head of the ARC lists rather than the tail. 5953 */ 5954 if (arc_warm == B_FALSE) 5955 hdr = multilist_sublist_head(mls); 5956 else 5957 hdr = multilist_sublist_tail(mls); 5958 5959 headroom = target_sz * l2arc_headroom; 5960 if (do_headroom_boost) 5961 headroom = (headroom * l2arc_headroom_boost) / 100; 5962 5963 for (; hdr; hdr = hdr_prev) { 5964 kmutex_t *hash_lock; 5965 uint64_t buf_sz; 5966 uint64_t buf_a_sz; 5967 5968 if (arc_warm == B_FALSE) 5969 hdr_prev = multilist_sublist_next(mls, hdr); 5970 else 5971 hdr_prev = multilist_sublist_prev(mls, hdr); 5972 5973 hash_lock = HDR_LOCK(hdr); 5974 if (!mutex_tryenter(hash_lock)) { 5975 /* 5976 * Skip this buffer rather than waiting. 5977 */ 5978 continue; 5979 } 5980 5981 passed_sz += hdr->b_size; 5982 if (passed_sz > headroom) { 5983 /* 5984 * Searched too far. 5985 */ 5986 mutex_exit(hash_lock); 5987 break; 5988 } 5989 5990 if (!l2arc_write_eligible(guid, hdr)) { 5991 mutex_exit(hash_lock); 5992 continue; 5993 } 5994 5995 /* 5996 * Assume that the buffer is not going to be compressed 5997 * and could take more space on disk because of a larger 5998 * disk block size. 5999 */ 6000 buf_sz = hdr->b_size; 6001 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6002 6003 if ((write_asize + buf_a_sz) > target_sz) { 6004 full = B_TRUE; 6005 mutex_exit(hash_lock); 6006 break; 6007 } 6008 6009 if (pio == NULL) { 6010 /* 6011 * Insert a dummy header on the buflist so 6012 * l2arc_write_done() can find where the 6013 * write buffers begin without searching. 6014 */ 6015 mutex_enter(&dev->l2ad_mtx); 6016 list_insert_head(&dev->l2ad_buflist, head); 6017 mutex_exit(&dev->l2ad_mtx); 6018 6019 cb = kmem_alloc( 6020 sizeof (l2arc_write_callback_t), KM_SLEEP); 6021 cb->l2wcb_dev = dev; 6022 cb->l2wcb_head = head; 6023 pio = zio_root(spa, l2arc_write_done, cb, 6024 ZIO_FLAG_CANFAIL); 6025 } 6026 6027 /* 6028 * Create and add a new L2ARC header. 6029 */ 6030 hdr->b_l2hdr.b_dev = dev; 6031 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6032 /* 6033 * Temporarily stash the data buffer in b_tmp_cdata. 6034 * The subsequent write step will pick it up from 6035 * there. This is because can't access b_l1hdr.b_buf 6036 * without holding the hash_lock, which we in turn 6037 * can't access without holding the ARC list locks 6038 * (which we want to avoid during compression/writing). 6039 */ 6040 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6041 hdr->b_l2hdr.b_asize = hdr->b_size; 6042 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6043 6044 /* 6045 * Explicitly set the b_daddr field to a known 6046 * value which means "invalid address". This 6047 * enables us to differentiate which stage of 6048 * l2arc_write_buffers() the particular header 6049 * is in (e.g. this loop, or the one below). 6050 * ARC_FLAG_L2_WRITING is not enough to make 6051 * this distinction, and we need to know in 6052 * order to do proper l2arc vdev accounting in 6053 * arc_release() and arc_hdr_destroy(). 6054 * 6055 * Note, we can't use a new flag to distinguish 6056 * the two stages because we don't hold the 6057 * header's hash_lock below, in the second stage 6058 * of this function. Thus, we can't simply 6059 * change the b_flags field to denote that the 6060 * IO has been sent. We can change the b_daddr 6061 * field of the L2 portion, though, since we'll 6062 * be holding the l2ad_mtx; which is why we're 6063 * using it to denote the header's state change. 6064 */ 6065 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6066 6067 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6068 6069 mutex_enter(&dev->l2ad_mtx); 6070 list_insert_head(&dev->l2ad_buflist, hdr); 6071 mutex_exit(&dev->l2ad_mtx); 6072 6073 /* 6074 * Compute and store the buffer cksum before 6075 * writing. On debug the cksum is verified first. 6076 */ 6077 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6078 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6079 6080 mutex_exit(hash_lock); 6081 6082 write_sz += buf_sz; 6083 write_asize += buf_a_sz; 6084 } 6085 6086 multilist_sublist_unlock(mls); 6087 6088 if (full == B_TRUE) 6089 break; 6090 } 6091 6092 /* No buffers selected for writing? */ 6093 if (pio == NULL) { 6094 ASSERT0(write_sz); 6095 ASSERT(!HDR_HAS_L1HDR(head)); 6096 kmem_cache_free(hdr_l2only_cache, head); 6097 return (0); 6098 } 6099 6100 mutex_enter(&dev->l2ad_mtx); 6101 6102 /* 6103 * Note that elsewhere in this file arcstat_l2_asize 6104 * and the used space on l2ad_vdev are updated using b_asize, 6105 * which is not necessarily rounded up to the device block size. 6106 * Too keep accounting consistent we do the same here as well: 6107 * stats_size accumulates the sum of b_asize of the written buffers, 6108 * while write_asize accumulates the sum of b_asize rounded up 6109 * to the device block size. 6110 * The latter sum is used only to validate the corectness of the code. 6111 */ 6112 uint64_t stats_size = 0; 6113 write_asize = 0; 6114 6115 /* 6116 * Now start writing the buffers. We're starting at the write head 6117 * and work backwards, retracing the course of the buffer selector 6118 * loop above. 6119 */ 6120 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6121 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6122 uint64_t buf_sz; 6123 6124 /* 6125 * We rely on the L1 portion of the header below, so 6126 * it's invalid for this header to have been evicted out 6127 * of the ghost cache, prior to being written out. The 6128 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6129 */ 6130 ASSERT(HDR_HAS_L1HDR(hdr)); 6131 6132 /* 6133 * We shouldn't need to lock the buffer here, since we flagged 6134 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6135 * take care to only access its L2 cache parameters. In 6136 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6137 * ARC eviction. 6138 */ 6139 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6140 6141 if ((HDR_L2COMPRESS(hdr)) && 6142 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 6143 if (l2arc_compress_buf(hdr)) { 6144 /* 6145 * If compression succeeded, enable headroom 6146 * boost on the next scan cycle. 6147 */ 6148 *headroom_boost = B_TRUE; 6149 } 6150 } 6151 6152 /* 6153 * Pick up the buffer data we had previously stashed away 6154 * (and now potentially also compressed). 6155 */ 6156 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6157 buf_sz = hdr->b_l2hdr.b_asize; 6158 6159 /* 6160 * We need to do this regardless if buf_sz is zero or 6161 * not, otherwise, when this l2hdr is evicted we'll 6162 * remove a reference that was never added. 6163 */ 6164 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6165 6166 /* Compression may have squashed the buffer to zero length. */ 6167 if (buf_sz != 0) { 6168 uint64_t buf_a_sz; 6169 6170 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6171 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6172 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6173 ZIO_FLAG_CANFAIL, B_FALSE); 6174 6175 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6176 zio_t *, wzio); 6177 (void) zio_nowait(wzio); 6178 6179 stats_size += buf_sz; 6180 6181 /* 6182 * Keep the clock hand suitably device-aligned. 6183 */ 6184 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6185 write_asize += buf_a_sz; 6186 dev->l2ad_hand += buf_a_sz; 6187 } 6188 } 6189 6190 mutex_exit(&dev->l2ad_mtx); 6191 6192 ASSERT3U(write_asize, <=, target_sz); 6193 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6194 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6195 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6196 ARCSTAT_INCR(arcstat_l2_asize, stats_size); 6197 vdev_space_update(dev->l2ad_vdev, stats_size, 0, 0); 6198 6199 /* 6200 * Bump device hand to the device start if it is approaching the end. 6201 * l2arc_evict() will already have evicted ahead for this case. 6202 */ 6203 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6204 dev->l2ad_hand = dev->l2ad_start; 6205 dev->l2ad_first = B_FALSE; 6206 } 6207 6208 dev->l2ad_writing = B_TRUE; 6209 (void) zio_wait(pio); 6210 dev->l2ad_writing = B_FALSE; 6211 6212 return (write_asize); 6213 } 6214 6215 /* 6216 * Compresses an L2ARC buffer. 6217 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6218 * size in l2hdr->b_asize. This routine tries to compress the data and 6219 * depending on the compression result there are three possible outcomes: 6220 * *) The buffer was incompressible. The original l2hdr contents were left 6221 * untouched and are ready for writing to an L2 device. 6222 * *) The buffer was all-zeros, so there is no need to write it to an L2 6223 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6224 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6225 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6226 * data buffer which holds the compressed data to be written, and b_asize 6227 * tells us how much data there is. b_compress is set to the appropriate 6228 * compression algorithm. Once writing is done, invoke 6229 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6230 * 6231 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6232 * buffer was incompressible). 6233 */ 6234 static boolean_t 6235 l2arc_compress_buf(arc_buf_hdr_t *hdr) 6236 { 6237 void *cdata; 6238 size_t csize, len, rounded; 6239 ASSERT(HDR_HAS_L2HDR(hdr)); 6240 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6241 6242 ASSERT(HDR_HAS_L1HDR(hdr)); 6243 ASSERT3S(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF); 6244 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6245 6246 len = l2hdr->b_asize; 6247 cdata = zio_data_buf_alloc(len); 6248 ASSERT3P(cdata, !=, NULL); 6249 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6250 cdata, l2hdr->b_asize); 6251 6252 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 6253 if (rounded > csize) { 6254 bzero((char *)cdata + csize, rounded - csize); 6255 csize = rounded; 6256 } 6257 6258 if (csize == 0) { 6259 /* zero block, indicate that there's nothing to write */ 6260 zio_data_buf_free(cdata, len); 6261 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6262 l2hdr->b_asize = 0; 6263 hdr->b_l1hdr.b_tmp_cdata = NULL; 6264 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6265 return (B_TRUE); 6266 } else if (csize > 0 && csize < len) { 6267 /* 6268 * Compression succeeded, we'll keep the cdata around for 6269 * writing and release it afterwards. 6270 */ 6271 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6272 l2hdr->b_asize = csize; 6273 hdr->b_l1hdr.b_tmp_cdata = cdata; 6274 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6275 return (B_TRUE); 6276 } else { 6277 /* 6278 * Compression failed, release the compressed buffer. 6279 * l2hdr will be left unmodified. 6280 */ 6281 zio_data_buf_free(cdata, len); 6282 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6283 return (B_FALSE); 6284 } 6285 } 6286 6287 /* 6288 * Decompresses a zio read back from an l2arc device. On success, the 6289 * underlying zio's io_data buffer is overwritten by the uncompressed 6290 * version. On decompression error (corrupt compressed stream), the 6291 * zio->io_error value is set to signal an I/O error. 6292 * 6293 * Please note that the compressed data stream is not checksummed, so 6294 * if the underlying device is experiencing data corruption, we may feed 6295 * corrupt data to the decompressor, so the decompressor needs to be 6296 * able to handle this situation (LZ4 does). 6297 */ 6298 static void 6299 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6300 { 6301 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6302 6303 if (zio->io_error != 0) { 6304 /* 6305 * An io error has occured, just restore the original io 6306 * size in preparation for a main pool read. 6307 */ 6308 zio->io_orig_size = zio->io_size = hdr->b_size; 6309 return; 6310 } 6311 6312 if (c == ZIO_COMPRESS_EMPTY) { 6313 /* 6314 * An empty buffer results in a null zio, which means we 6315 * need to fill its io_data after we're done restoring the 6316 * buffer's contents. 6317 */ 6318 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6319 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6320 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6321 } else { 6322 ASSERT(zio->io_data != NULL); 6323 /* 6324 * We copy the compressed data from the start of the arc buffer 6325 * (the zio_read will have pulled in only what we need, the 6326 * rest is garbage which we will overwrite at decompression) 6327 * and then decompress back to the ARC data buffer. This way we 6328 * can minimize copying by simply decompressing back over the 6329 * original compressed data (rather than decompressing to an 6330 * aux buffer and then copying back the uncompressed buffer, 6331 * which is likely to be much larger). 6332 */ 6333 uint64_t csize; 6334 void *cdata; 6335 6336 csize = zio->io_size; 6337 cdata = zio_data_buf_alloc(csize); 6338 bcopy(zio->io_data, cdata, csize); 6339 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6340 hdr->b_size) != 0) 6341 zio->io_error = EIO; 6342 zio_data_buf_free(cdata, csize); 6343 } 6344 6345 /* Restore the expected uncompressed IO size. */ 6346 zio->io_orig_size = zio->io_size = hdr->b_size; 6347 } 6348 6349 /* 6350 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6351 * This buffer serves as a temporary holder of compressed data while 6352 * the buffer entry is being written to an l2arc device. Once that is 6353 * done, we can dispose of it. 6354 */ 6355 static void 6356 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6357 { 6358 ASSERT(HDR_HAS_L2HDR(hdr)); 6359 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6360 6361 ASSERT(HDR_HAS_L1HDR(hdr)); 6362 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6363 6364 if (comp == ZIO_COMPRESS_OFF) { 6365 /* 6366 * In this case, b_tmp_cdata points to the same buffer 6367 * as the arc_buf_t's b_data field. We don't want to 6368 * free it, since the arc_buf_t will handle that. 6369 */ 6370 hdr->b_l1hdr.b_tmp_cdata = NULL; 6371 } else if (comp == ZIO_COMPRESS_EMPTY) { 6372 /* 6373 * In this case, b_tmp_cdata was compressed to an empty 6374 * buffer, thus there's nothing to free and b_tmp_cdata 6375 * should have been set to NULL in l2arc_write_buffers(). 6376 */ 6377 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6378 } else { 6379 /* 6380 * If the data was compressed, then we've allocated a 6381 * temporary buffer for it, so now we need to release it. 6382 */ 6383 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6384 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6385 hdr->b_size); 6386 hdr->b_l1hdr.b_tmp_cdata = NULL; 6387 } 6388 6389 } 6390 6391 /* 6392 * This thread feeds the L2ARC at regular intervals. This is the beating 6393 * heart of the L2ARC. 6394 */ 6395 static void 6396 l2arc_feed_thread(void) 6397 { 6398 callb_cpr_t cpr; 6399 l2arc_dev_t *dev; 6400 spa_t *spa; 6401 uint64_t size, wrote; 6402 clock_t begin, next = ddi_get_lbolt(); 6403 boolean_t headroom_boost = B_FALSE; 6404 6405 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6406 6407 mutex_enter(&l2arc_feed_thr_lock); 6408 6409 while (l2arc_thread_exit == 0) { 6410 CALLB_CPR_SAFE_BEGIN(&cpr); 6411 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6412 next); 6413 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6414 next = ddi_get_lbolt() + hz; 6415 6416 /* 6417 * Quick check for L2ARC devices. 6418 */ 6419 mutex_enter(&l2arc_dev_mtx); 6420 if (l2arc_ndev == 0) { 6421 mutex_exit(&l2arc_dev_mtx); 6422 continue; 6423 } 6424 mutex_exit(&l2arc_dev_mtx); 6425 begin = ddi_get_lbolt(); 6426 6427 /* 6428 * This selects the next l2arc device to write to, and in 6429 * doing so the next spa to feed from: dev->l2ad_spa. This 6430 * will return NULL if there are now no l2arc devices or if 6431 * they are all faulted. 6432 * 6433 * If a device is returned, its spa's config lock is also 6434 * held to prevent device removal. l2arc_dev_get_next() 6435 * will grab and release l2arc_dev_mtx. 6436 */ 6437 if ((dev = l2arc_dev_get_next()) == NULL) 6438 continue; 6439 6440 spa = dev->l2ad_spa; 6441 ASSERT(spa != NULL); 6442 6443 /* 6444 * If the pool is read-only then force the feed thread to 6445 * sleep a little longer. 6446 */ 6447 if (!spa_writeable(spa)) { 6448 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6449 spa_config_exit(spa, SCL_L2ARC, dev); 6450 continue; 6451 } 6452 6453 /* 6454 * Avoid contributing to memory pressure. 6455 */ 6456 if (arc_reclaim_needed()) { 6457 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6458 spa_config_exit(spa, SCL_L2ARC, dev); 6459 continue; 6460 } 6461 6462 ARCSTAT_BUMP(arcstat_l2_feeds); 6463 6464 size = l2arc_write_size(); 6465 6466 /* 6467 * Evict L2ARC buffers that will be overwritten. 6468 */ 6469 l2arc_evict(dev, size, B_FALSE); 6470 6471 /* 6472 * Write ARC buffers. 6473 */ 6474 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6475 6476 /* 6477 * Calculate interval between writes. 6478 */ 6479 next = l2arc_write_interval(begin, size, wrote); 6480 spa_config_exit(spa, SCL_L2ARC, dev); 6481 } 6482 6483 l2arc_thread_exit = 0; 6484 cv_broadcast(&l2arc_feed_thr_cv); 6485 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6486 thread_exit(); 6487 } 6488 6489 boolean_t 6490 l2arc_vdev_present(vdev_t *vd) 6491 { 6492 l2arc_dev_t *dev; 6493 6494 mutex_enter(&l2arc_dev_mtx); 6495 for (dev = list_head(l2arc_dev_list); dev != NULL; 6496 dev = list_next(l2arc_dev_list, dev)) { 6497 if (dev->l2ad_vdev == vd) 6498 break; 6499 } 6500 mutex_exit(&l2arc_dev_mtx); 6501 6502 return (dev != NULL); 6503 } 6504 6505 /* 6506 * Add a vdev for use by the L2ARC. By this point the spa has already 6507 * validated the vdev and opened it. 6508 */ 6509 void 6510 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6511 { 6512 l2arc_dev_t *adddev; 6513 6514 ASSERT(!l2arc_vdev_present(vd)); 6515 6516 /* 6517 * Create a new l2arc device entry. 6518 */ 6519 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6520 adddev->l2ad_spa = spa; 6521 adddev->l2ad_vdev = vd; 6522 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6523 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6524 adddev->l2ad_hand = adddev->l2ad_start; 6525 adddev->l2ad_first = B_TRUE; 6526 adddev->l2ad_writing = B_FALSE; 6527 6528 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6529 /* 6530 * This is a list of all ARC buffers that are still valid on the 6531 * device. 6532 */ 6533 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6534 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6535 6536 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6537 refcount_create(&adddev->l2ad_alloc); 6538 6539 /* 6540 * Add device to global list 6541 */ 6542 mutex_enter(&l2arc_dev_mtx); 6543 list_insert_head(l2arc_dev_list, adddev); 6544 atomic_inc_64(&l2arc_ndev); 6545 mutex_exit(&l2arc_dev_mtx); 6546 } 6547 6548 /* 6549 * Remove a vdev from the L2ARC. 6550 */ 6551 void 6552 l2arc_remove_vdev(vdev_t *vd) 6553 { 6554 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6555 6556 /* 6557 * Find the device by vdev 6558 */ 6559 mutex_enter(&l2arc_dev_mtx); 6560 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6561 nextdev = list_next(l2arc_dev_list, dev); 6562 if (vd == dev->l2ad_vdev) { 6563 remdev = dev; 6564 break; 6565 } 6566 } 6567 ASSERT(remdev != NULL); 6568 6569 /* 6570 * Remove device from global list 6571 */ 6572 list_remove(l2arc_dev_list, remdev); 6573 l2arc_dev_last = NULL; /* may have been invalidated */ 6574 atomic_dec_64(&l2arc_ndev); 6575 mutex_exit(&l2arc_dev_mtx); 6576 6577 /* 6578 * Clear all buflists and ARC references. L2ARC device flush. 6579 */ 6580 l2arc_evict(remdev, 0, B_TRUE); 6581 list_destroy(&remdev->l2ad_buflist); 6582 mutex_destroy(&remdev->l2ad_mtx); 6583 refcount_destroy(&remdev->l2ad_alloc); 6584 kmem_free(remdev, sizeof (l2arc_dev_t)); 6585 } 6586 6587 void 6588 l2arc_init(void) 6589 { 6590 l2arc_thread_exit = 0; 6591 l2arc_ndev = 0; 6592 l2arc_writes_sent = 0; 6593 l2arc_writes_done = 0; 6594 6595 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6596 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6597 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6598 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6599 6600 l2arc_dev_list = &L2ARC_dev_list; 6601 l2arc_free_on_write = &L2ARC_free_on_write; 6602 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6603 offsetof(l2arc_dev_t, l2ad_node)); 6604 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6605 offsetof(l2arc_data_free_t, l2df_list_node)); 6606 } 6607 6608 void 6609 l2arc_fini(void) 6610 { 6611 /* 6612 * This is called from dmu_fini(), which is called from spa_fini(); 6613 * Because of this, we can assume that all l2arc devices have 6614 * already been removed when the pools themselves were removed. 6615 */ 6616 6617 l2arc_do_free_on_write(); 6618 6619 mutex_destroy(&l2arc_feed_thr_lock); 6620 cv_destroy(&l2arc_feed_thr_cv); 6621 mutex_destroy(&l2arc_dev_mtx); 6622 mutex_destroy(&l2arc_free_on_write_mtx); 6623 6624 list_destroy(l2arc_dev_list); 6625 list_destroy(l2arc_free_on_write); 6626 } 6627 6628 void 6629 l2arc_start(void) 6630 { 6631 if (!(spa_mode_global & FWRITE)) 6632 return; 6633 6634 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6635 TS_RUN, minclsyspri); 6636 } 6637 6638 void 6639 l2arc_stop(void) 6640 { 6641 if (!(spa_mode_global & FWRITE)) 6642 return; 6643 6644 mutex_enter(&l2arc_feed_thr_lock); 6645 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6646 l2arc_thread_exit = 1; 6647 while (l2arc_thread_exit != 0) 6648 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6649 mutex_exit(&l2arc_feed_thr_lock); 6650 } 6651