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