1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2014 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2014 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the 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 uint64_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 } arc_stats_t; 499 500 static arc_stats_t arc_stats = { 501 { "hits", KSTAT_DATA_UINT64 }, 502 { "misses", KSTAT_DATA_UINT64 }, 503 { "demand_data_hits", KSTAT_DATA_UINT64 }, 504 { "demand_data_misses", KSTAT_DATA_UINT64 }, 505 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 506 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 507 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 508 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 509 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 510 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 511 { "mru_hits", KSTAT_DATA_UINT64 }, 512 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 513 { "mfu_hits", KSTAT_DATA_UINT64 }, 514 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 515 { "deleted", KSTAT_DATA_UINT64 }, 516 { "mutex_miss", KSTAT_DATA_UINT64 }, 517 { "evict_skip", KSTAT_DATA_UINT64 }, 518 { "evict_not_enough", KSTAT_DATA_UINT64 }, 519 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 520 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 521 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 522 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 523 { "hash_elements", KSTAT_DATA_UINT64 }, 524 { "hash_elements_max", KSTAT_DATA_UINT64 }, 525 { "hash_collisions", KSTAT_DATA_UINT64 }, 526 { "hash_chains", KSTAT_DATA_UINT64 }, 527 { "hash_chain_max", KSTAT_DATA_UINT64 }, 528 { "p", KSTAT_DATA_UINT64 }, 529 { "c", KSTAT_DATA_UINT64 }, 530 { "c_min", KSTAT_DATA_UINT64 }, 531 { "c_max", KSTAT_DATA_UINT64 }, 532 { "size", KSTAT_DATA_UINT64 }, 533 { "hdr_size", KSTAT_DATA_UINT64 }, 534 { "data_size", KSTAT_DATA_UINT64 }, 535 { "metadata_size", KSTAT_DATA_UINT64 }, 536 { "other_size", KSTAT_DATA_UINT64 }, 537 { "anon_size", KSTAT_DATA_UINT64 }, 538 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 539 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 540 { "mru_size", KSTAT_DATA_UINT64 }, 541 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 542 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 543 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 544 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 545 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 546 { "mfu_size", KSTAT_DATA_UINT64 }, 547 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 548 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 549 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 550 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 551 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 552 { "l2_hits", KSTAT_DATA_UINT64 }, 553 { "l2_misses", KSTAT_DATA_UINT64 }, 554 { "l2_feeds", KSTAT_DATA_UINT64 }, 555 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 556 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 557 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 558 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 559 { "l2_writes_done", KSTAT_DATA_UINT64 }, 560 { "l2_writes_error", KSTAT_DATA_UINT64 }, 561 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 562 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 563 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 564 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 565 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 566 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 567 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 568 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 569 { "l2_io_error", KSTAT_DATA_UINT64 }, 570 { "l2_size", KSTAT_DATA_UINT64 }, 571 { "l2_asize", KSTAT_DATA_UINT64 }, 572 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 573 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 574 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 575 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 576 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 577 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 578 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 579 { "duplicate_reads", KSTAT_DATA_UINT64 }, 580 { "arc_meta_used", KSTAT_DATA_UINT64 }, 581 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 582 { "arc_meta_max", KSTAT_DATA_UINT64 }, 583 { "arc_meta_min", KSTAT_DATA_UINT64 } 584 }; 585 586 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 587 588 #define ARCSTAT_INCR(stat, val) \ 589 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 590 591 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 592 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 593 594 #define ARCSTAT_MAX(stat, val) { \ 595 uint64_t m; \ 596 while ((val) > (m = arc_stats.stat.value.ui64) && \ 597 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 598 continue; \ 599 } 600 601 #define ARCSTAT_MAXSTAT(stat) \ 602 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 603 604 /* 605 * We define a macro to allow ARC hits/misses to be easily broken down by 606 * two separate conditions, giving a total of four different subtypes for 607 * each of hits and misses (so eight statistics total). 608 */ 609 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 610 if (cond1) { \ 611 if (cond2) { \ 612 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 613 } else { \ 614 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 615 } \ 616 } else { \ 617 if (cond2) { \ 618 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 619 } else { \ 620 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 621 } \ 622 } 623 624 kstat_t *arc_ksp; 625 static arc_state_t *arc_anon; 626 static arc_state_t *arc_mru; 627 static arc_state_t *arc_mru_ghost; 628 static arc_state_t *arc_mfu; 629 static arc_state_t *arc_mfu_ghost; 630 static arc_state_t *arc_l2c_only; 631 632 /* 633 * There are several ARC variables that are critical to export as kstats -- 634 * but we don't want to have to grovel around in the kstat whenever we wish to 635 * manipulate them. For these variables, we therefore define them to be in 636 * terms of the statistic variable. This assures that we are not introducing 637 * the possibility of inconsistency by having shadow copies of the variables, 638 * while still allowing the code to be readable. 639 */ 640 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 641 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 642 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 643 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 644 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 645 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 646 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 647 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 648 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 649 650 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 651 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 652 653 static int arc_no_grow; /* Don't try to grow cache size */ 654 static uint64_t arc_tempreserve; 655 static uint64_t arc_loaned_bytes; 656 657 typedef struct arc_callback arc_callback_t; 658 659 struct arc_callback { 660 void *acb_private; 661 arc_done_func_t *acb_done; 662 arc_buf_t *acb_buf; 663 zio_t *acb_zio_dummy; 664 arc_callback_t *acb_next; 665 }; 666 667 typedef struct arc_write_callback arc_write_callback_t; 668 669 struct arc_write_callback { 670 void *awcb_private; 671 arc_done_func_t *awcb_ready; 672 arc_done_func_t *awcb_physdone; 673 arc_done_func_t *awcb_done; 674 arc_buf_t *awcb_buf; 675 }; 676 677 /* 678 * ARC buffers are separated into multiple structs as a memory saving measure: 679 * - Common fields struct, always defined, and embedded within it: 680 * - L2-only fields, always allocated but undefined when not in L2ARC 681 * - L1-only fields, only allocated when in L1ARC 682 * 683 * Buffer in L1 Buffer only in L2 684 * +------------------------+ +------------------------+ 685 * | arc_buf_hdr_t | | arc_buf_hdr_t | 686 * | | | | 687 * | | | | 688 * | | | | 689 * +------------------------+ +------------------------+ 690 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 691 * | (undefined if L1-only) | | | 692 * +------------------------+ +------------------------+ 693 * | l1arc_buf_hdr_t | 694 * | | 695 * | | 696 * | | 697 * | | 698 * +------------------------+ 699 * 700 * Because it's possible for the L2ARC to become extremely large, we can wind 701 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 702 * is minimized by only allocating the fields necessary for an L1-cached buffer 703 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 704 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 705 * words in pointers. arc_hdr_realloc() is used to switch a header between 706 * these two allocation states. 707 */ 708 typedef struct l1arc_buf_hdr { 709 kmutex_t b_freeze_lock; 710 #ifdef ZFS_DEBUG 711 /* 712 * used for debugging wtih kmem_flags - by allocating and freeing 713 * b_thawed when the buffer is thawed, we get a record of the stack 714 * trace that thawed it. 715 */ 716 void *b_thawed; 717 #endif 718 719 arc_buf_t *b_buf; 720 uint32_t b_datacnt; 721 /* for waiting on writes to complete */ 722 kcondvar_t b_cv; 723 724 /* protected by arc state mutex */ 725 arc_state_t *b_state; 726 multilist_node_t b_arc_node; 727 728 /* updated atomically */ 729 clock_t b_arc_access; 730 731 /* self protecting */ 732 refcount_t b_refcnt; 733 734 arc_callback_t *b_acb; 735 /* temporary buffer holder for in-flight compressed data */ 736 void *b_tmp_cdata; 737 } l1arc_buf_hdr_t; 738 739 typedef struct l2arc_dev l2arc_dev_t; 740 741 typedef struct l2arc_buf_hdr { 742 /* protected by arc_buf_hdr mutex */ 743 l2arc_dev_t *b_dev; /* L2ARC device */ 744 uint64_t b_daddr; /* disk address, offset byte */ 745 /* real alloc'd buffer size depending on b_compress applied */ 746 int32_t b_asize; 747 748 list_node_t b_l2node; 749 } l2arc_buf_hdr_t; 750 751 struct arc_buf_hdr { 752 /* protected by hash lock */ 753 dva_t b_dva; 754 uint64_t b_birth; 755 /* 756 * Even though this checksum is only set/verified when a buffer is in 757 * the L1 cache, it needs to be in the set of common fields because it 758 * must be preserved from the time before a buffer is written out to 759 * L2ARC until after it is read back in. 760 */ 761 zio_cksum_t *b_freeze_cksum; 762 763 arc_buf_hdr_t *b_hash_next; 764 arc_flags_t b_flags; 765 766 /* immutable */ 767 int32_t b_size; 768 uint64_t b_spa; 769 770 /* L2ARC fields. Undefined when not in L2ARC. */ 771 l2arc_buf_hdr_t b_l2hdr; 772 /* L1ARC fields. Undefined when in l2arc_only state */ 773 l1arc_buf_hdr_t b_l1hdr; 774 }; 775 776 static arc_buf_t *arc_eviction_list; 777 static arc_buf_hdr_t arc_eviction_hdr; 778 779 #define GHOST_STATE(state) \ 780 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 781 (state) == arc_l2c_only) 782 783 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 784 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 785 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 786 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 787 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 788 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 789 790 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 791 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 792 #define HDR_L2_READING(hdr) \ 793 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 794 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 795 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 796 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 797 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 798 799 #define HDR_ISTYPE_METADATA(hdr) \ 800 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 801 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 802 803 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 804 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 805 806 /* For storing compression mode in b_flags */ 807 #define HDR_COMPRESS_OFFSET 24 808 #define HDR_COMPRESS_NBITS 7 809 810 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 811 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 812 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 813 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 814 815 /* 816 * Other sizes 817 */ 818 819 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 820 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 821 822 /* 823 * Hash table routines 824 */ 825 826 #define HT_LOCK_PAD 64 827 828 struct ht_lock { 829 kmutex_t ht_lock; 830 #ifdef _KERNEL 831 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 832 #endif 833 }; 834 835 #define BUF_LOCKS 256 836 typedef struct buf_hash_table { 837 uint64_t ht_mask; 838 arc_buf_hdr_t **ht_table; 839 struct ht_lock ht_locks[BUF_LOCKS]; 840 } buf_hash_table_t; 841 842 static buf_hash_table_t buf_hash_table; 843 844 #define BUF_HASH_INDEX(spa, dva, birth) \ 845 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 846 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 847 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 848 #define HDR_LOCK(hdr) \ 849 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 850 851 uint64_t zfs_crc64_table[256]; 852 853 /* 854 * Level 2 ARC 855 */ 856 857 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 858 #define L2ARC_HEADROOM 2 /* num of writes */ 859 /* 860 * If we discover during ARC scan any buffers to be compressed, we boost 861 * our headroom for the next scanning cycle by this percentage multiple. 862 */ 863 #define L2ARC_HEADROOM_BOOST 200 864 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 865 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 866 867 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 868 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 869 870 /* L2ARC Performance Tunables */ 871 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 872 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 873 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 874 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 875 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 876 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 877 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 878 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 879 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 880 881 /* 882 * L2ARC Internals 883 */ 884 struct l2arc_dev { 885 vdev_t *l2ad_vdev; /* vdev */ 886 spa_t *l2ad_spa; /* spa */ 887 uint64_t l2ad_hand; /* next write location */ 888 uint64_t l2ad_start; /* first addr on device */ 889 uint64_t l2ad_end; /* last addr on device */ 890 uint64_t l2ad_evict; /* last addr eviction reached */ 891 boolean_t l2ad_first; /* first sweep through */ 892 boolean_t l2ad_writing; /* currently writing */ 893 kmutex_t l2ad_mtx; /* lock for buffer list */ 894 list_t l2ad_buflist; /* buffer list */ 895 list_node_t l2ad_node; /* device list node */ 896 }; 897 898 static list_t L2ARC_dev_list; /* device list */ 899 static list_t *l2arc_dev_list; /* device list pointer */ 900 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 901 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 902 static list_t L2ARC_free_on_write; /* free after write buf list */ 903 static list_t *l2arc_free_on_write; /* free after write list ptr */ 904 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 905 static uint64_t l2arc_ndev; /* number of devices */ 906 907 typedef struct l2arc_read_callback { 908 arc_buf_t *l2rcb_buf; /* read buffer */ 909 spa_t *l2rcb_spa; /* spa */ 910 blkptr_t l2rcb_bp; /* original blkptr */ 911 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 912 int l2rcb_flags; /* original flags */ 913 enum zio_compress l2rcb_compress; /* applied compress */ 914 } l2arc_read_callback_t; 915 916 typedef struct l2arc_write_callback { 917 l2arc_dev_t *l2wcb_dev; /* device info */ 918 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 919 } l2arc_write_callback_t; 920 921 typedef struct l2arc_data_free { 922 /* protected by l2arc_free_on_write_mtx */ 923 void *l2df_data; 924 size_t l2df_size; 925 void (*l2df_func)(void *, size_t); 926 list_node_t l2df_list_node; 927 } l2arc_data_free_t; 928 929 static kmutex_t l2arc_feed_thr_lock; 930 static kcondvar_t l2arc_feed_thr_cv; 931 static uint8_t l2arc_thread_exit; 932 933 static void arc_get_data_buf(arc_buf_t *); 934 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 935 static boolean_t arc_is_overflowing(); 936 static void arc_buf_watch(arc_buf_t *); 937 938 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 939 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 940 941 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 942 static void l2arc_read_done(zio_t *); 943 944 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 945 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 946 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 947 948 static uint64_t 949 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 950 { 951 uint8_t *vdva = (uint8_t *)dva; 952 uint64_t crc = -1ULL; 953 int i; 954 955 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 956 957 for (i = 0; i < sizeof (dva_t); i++) 958 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 959 960 crc ^= (spa>>8) ^ birth; 961 962 return (crc); 963 } 964 965 #define BUF_EMPTY(buf) \ 966 ((buf)->b_dva.dva_word[0] == 0 && \ 967 (buf)->b_dva.dva_word[1] == 0) 968 969 #define BUF_EQUAL(spa, dva, birth, buf) \ 970 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 971 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 972 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 973 974 static void 975 buf_discard_identity(arc_buf_hdr_t *hdr) 976 { 977 hdr->b_dva.dva_word[0] = 0; 978 hdr->b_dva.dva_word[1] = 0; 979 hdr->b_birth = 0; 980 } 981 982 static arc_buf_hdr_t * 983 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 984 { 985 const dva_t *dva = BP_IDENTITY(bp); 986 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 987 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 988 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 989 arc_buf_hdr_t *hdr; 990 991 mutex_enter(hash_lock); 992 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 993 hdr = hdr->b_hash_next) { 994 if (BUF_EQUAL(spa, dva, birth, hdr)) { 995 *lockp = hash_lock; 996 return (hdr); 997 } 998 } 999 mutex_exit(hash_lock); 1000 *lockp = NULL; 1001 return (NULL); 1002 } 1003 1004 /* 1005 * Insert an entry into the hash table. If there is already an element 1006 * equal to elem in the hash table, then the already existing element 1007 * will be returned and the new element will not be inserted. 1008 * Otherwise returns NULL. 1009 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1010 */ 1011 static arc_buf_hdr_t * 1012 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1013 { 1014 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1015 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1016 arc_buf_hdr_t *fhdr; 1017 uint32_t i; 1018 1019 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1020 ASSERT(hdr->b_birth != 0); 1021 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1022 1023 if (lockp != NULL) { 1024 *lockp = hash_lock; 1025 mutex_enter(hash_lock); 1026 } else { 1027 ASSERT(MUTEX_HELD(hash_lock)); 1028 } 1029 1030 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1031 fhdr = fhdr->b_hash_next, i++) { 1032 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1033 return (fhdr); 1034 } 1035 1036 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1037 buf_hash_table.ht_table[idx] = hdr; 1038 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1039 1040 /* collect some hash table performance data */ 1041 if (i > 0) { 1042 ARCSTAT_BUMP(arcstat_hash_collisions); 1043 if (i == 1) 1044 ARCSTAT_BUMP(arcstat_hash_chains); 1045 1046 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1047 } 1048 1049 ARCSTAT_BUMP(arcstat_hash_elements); 1050 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1051 1052 return (NULL); 1053 } 1054 1055 static void 1056 buf_hash_remove(arc_buf_hdr_t *hdr) 1057 { 1058 arc_buf_hdr_t *fhdr, **hdrp; 1059 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1060 1061 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1062 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1063 1064 hdrp = &buf_hash_table.ht_table[idx]; 1065 while ((fhdr = *hdrp) != hdr) { 1066 ASSERT(fhdr != NULL); 1067 hdrp = &fhdr->b_hash_next; 1068 } 1069 *hdrp = hdr->b_hash_next; 1070 hdr->b_hash_next = NULL; 1071 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1072 1073 /* collect some hash table performance data */ 1074 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1075 1076 if (buf_hash_table.ht_table[idx] && 1077 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1078 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1079 } 1080 1081 /* 1082 * Global data structures and functions for the buf kmem cache. 1083 */ 1084 static kmem_cache_t *hdr_full_cache; 1085 static kmem_cache_t *hdr_l2only_cache; 1086 static kmem_cache_t *buf_cache; 1087 1088 static void 1089 buf_fini(void) 1090 { 1091 int i; 1092 1093 kmem_free(buf_hash_table.ht_table, 1094 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1095 for (i = 0; i < BUF_LOCKS; i++) 1096 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1097 kmem_cache_destroy(hdr_full_cache); 1098 kmem_cache_destroy(hdr_l2only_cache); 1099 kmem_cache_destroy(buf_cache); 1100 } 1101 1102 /* 1103 * Constructor callback - called when the cache is empty 1104 * and a new buf is requested. 1105 */ 1106 /* ARGSUSED */ 1107 static int 1108 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1109 { 1110 arc_buf_hdr_t *hdr = vbuf; 1111 1112 bzero(hdr, HDR_FULL_SIZE); 1113 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1114 refcount_create(&hdr->b_l1hdr.b_refcnt); 1115 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1116 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1117 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1118 1119 return (0); 1120 } 1121 1122 /* ARGSUSED */ 1123 static int 1124 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1125 { 1126 arc_buf_hdr_t *hdr = vbuf; 1127 1128 bzero(hdr, HDR_L2ONLY_SIZE); 1129 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1130 1131 return (0); 1132 } 1133 1134 /* ARGSUSED */ 1135 static int 1136 buf_cons(void *vbuf, void *unused, int kmflag) 1137 { 1138 arc_buf_t *buf = vbuf; 1139 1140 bzero(buf, sizeof (arc_buf_t)); 1141 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1142 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1143 1144 return (0); 1145 } 1146 1147 /* 1148 * Destructor callback - called when a cached buf is 1149 * no longer required. 1150 */ 1151 /* ARGSUSED */ 1152 static void 1153 hdr_full_dest(void *vbuf, void *unused) 1154 { 1155 arc_buf_hdr_t *hdr = vbuf; 1156 1157 ASSERT(BUF_EMPTY(hdr)); 1158 cv_destroy(&hdr->b_l1hdr.b_cv); 1159 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1160 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1161 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1162 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1163 } 1164 1165 /* ARGSUSED */ 1166 static void 1167 hdr_l2only_dest(void *vbuf, void *unused) 1168 { 1169 arc_buf_hdr_t *hdr = vbuf; 1170 1171 ASSERT(BUF_EMPTY(hdr)); 1172 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1173 } 1174 1175 /* ARGSUSED */ 1176 static void 1177 buf_dest(void *vbuf, void *unused) 1178 { 1179 arc_buf_t *buf = vbuf; 1180 1181 mutex_destroy(&buf->b_evict_lock); 1182 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1183 } 1184 1185 /* 1186 * Reclaim callback -- invoked when memory is low. 1187 */ 1188 /* ARGSUSED */ 1189 static void 1190 hdr_recl(void *unused) 1191 { 1192 dprintf("hdr_recl called\n"); 1193 /* 1194 * umem calls the reclaim func when we destroy the buf cache, 1195 * which is after we do arc_fini(). 1196 */ 1197 if (!arc_dead) 1198 cv_signal(&arc_reclaim_thread_cv); 1199 } 1200 1201 static void 1202 buf_init(void) 1203 { 1204 uint64_t *ct; 1205 uint64_t hsize = 1ULL << 12; 1206 int i, j; 1207 1208 /* 1209 * The hash table is big enough to fill all of physical memory 1210 * with an average block size of zfs_arc_average_blocksize (default 8K). 1211 * By default, the table will take up 1212 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1213 */ 1214 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1215 hsize <<= 1; 1216 retry: 1217 buf_hash_table.ht_mask = hsize - 1; 1218 buf_hash_table.ht_table = 1219 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1220 if (buf_hash_table.ht_table == NULL) { 1221 ASSERT(hsize > (1ULL << 8)); 1222 hsize >>= 1; 1223 goto retry; 1224 } 1225 1226 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1227 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1228 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1229 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1230 NULL, NULL, 0); 1231 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1232 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1233 1234 for (i = 0; i < 256; i++) 1235 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1236 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1237 1238 for (i = 0; i < BUF_LOCKS; i++) { 1239 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1240 NULL, MUTEX_DEFAULT, NULL); 1241 } 1242 } 1243 1244 /* 1245 * Transition between the two allocation states for the arc_buf_hdr struct. 1246 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1247 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1248 * version is used when a cache buffer is only in the L2ARC in order to reduce 1249 * memory usage. 1250 */ 1251 static arc_buf_hdr_t * 1252 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1253 { 1254 ASSERT(HDR_HAS_L2HDR(hdr)); 1255 1256 arc_buf_hdr_t *nhdr; 1257 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1258 1259 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1260 (old == hdr_l2only_cache && new == hdr_full_cache)); 1261 1262 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1263 1264 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1265 buf_hash_remove(hdr); 1266 1267 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1268 if (new == hdr_full_cache) { 1269 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1270 /* 1271 * arc_access and arc_change_state need to be aware that a 1272 * header has just come out of L2ARC, so we set its state to 1273 * l2c_only even though it's about to change. 1274 */ 1275 nhdr->b_l1hdr.b_state = arc_l2c_only; 1276 1277 /* Verify previous threads set to NULL before freeing */ 1278 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1279 } else { 1280 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1281 ASSERT0(hdr->b_l1hdr.b_datacnt); 1282 1283 /* 1284 * If we've reached here, We must have been called from 1285 * arc_evict_hdr(), as such we should have already been 1286 * removed from any ghost list we were previously on 1287 * (which protects us from racing with arc_evict_state), 1288 * thus no locking is needed during this check. 1289 */ 1290 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1291 1292 /* 1293 * A buffer must not be moved into the arc_l2c_only 1294 * state if it's not finished being written out to the 1295 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1296 * might try to be accessed, even though it was removed. 1297 */ 1298 VERIFY(!HDR_L2_WRITING(hdr)); 1299 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1300 1301 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1302 } 1303 /* 1304 * The header has been reallocated so we need to re-insert it into any 1305 * lists it was on. 1306 */ 1307 (void) buf_hash_insert(nhdr, NULL); 1308 1309 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1310 1311 mutex_enter(&dev->l2ad_mtx); 1312 1313 /* 1314 * We must place the realloc'ed header back into the list at 1315 * the same spot. Otherwise, if it's placed earlier in the list, 1316 * l2arc_write_buffers() could find it during the function's 1317 * write phase, and try to write it out to the l2arc. 1318 */ 1319 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1320 list_remove(&dev->l2ad_buflist, hdr); 1321 1322 mutex_exit(&dev->l2ad_mtx); 1323 1324 buf_discard_identity(hdr); 1325 hdr->b_freeze_cksum = NULL; 1326 kmem_cache_free(old, hdr); 1327 1328 return (nhdr); 1329 } 1330 1331 1332 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1333 1334 static void 1335 arc_cksum_verify(arc_buf_t *buf) 1336 { 1337 zio_cksum_t zc; 1338 1339 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1340 return; 1341 1342 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1343 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1344 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1345 return; 1346 } 1347 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1348 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1349 panic("buffer modified while frozen!"); 1350 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1351 } 1352 1353 static int 1354 arc_cksum_equal(arc_buf_t *buf) 1355 { 1356 zio_cksum_t zc; 1357 int equal; 1358 1359 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1360 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1361 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1362 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1363 1364 return (equal); 1365 } 1366 1367 static void 1368 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1369 { 1370 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1371 return; 1372 1373 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1374 if (buf->b_hdr->b_freeze_cksum != NULL) { 1375 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1376 return; 1377 } 1378 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1379 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1380 buf->b_hdr->b_freeze_cksum); 1381 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1382 arc_buf_watch(buf); 1383 } 1384 1385 #ifndef _KERNEL 1386 typedef struct procctl { 1387 long cmd; 1388 prwatch_t prwatch; 1389 } procctl_t; 1390 #endif 1391 1392 /* ARGSUSED */ 1393 static void 1394 arc_buf_unwatch(arc_buf_t *buf) 1395 { 1396 #ifndef _KERNEL 1397 if (arc_watch) { 1398 int result; 1399 procctl_t ctl; 1400 ctl.cmd = PCWATCH; 1401 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1402 ctl.prwatch.pr_size = 0; 1403 ctl.prwatch.pr_wflags = 0; 1404 result = write(arc_procfd, &ctl, sizeof (ctl)); 1405 ASSERT3U(result, ==, sizeof (ctl)); 1406 } 1407 #endif 1408 } 1409 1410 /* ARGSUSED */ 1411 static void 1412 arc_buf_watch(arc_buf_t *buf) 1413 { 1414 #ifndef _KERNEL 1415 if (arc_watch) { 1416 int result; 1417 procctl_t ctl; 1418 ctl.cmd = PCWATCH; 1419 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1420 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1421 ctl.prwatch.pr_wflags = WA_WRITE; 1422 result = write(arc_procfd, &ctl, sizeof (ctl)); 1423 ASSERT3U(result, ==, sizeof (ctl)); 1424 } 1425 #endif 1426 } 1427 1428 static arc_buf_contents_t 1429 arc_buf_type(arc_buf_hdr_t *hdr) 1430 { 1431 if (HDR_ISTYPE_METADATA(hdr)) { 1432 return (ARC_BUFC_METADATA); 1433 } else { 1434 return (ARC_BUFC_DATA); 1435 } 1436 } 1437 1438 static uint32_t 1439 arc_bufc_to_flags(arc_buf_contents_t type) 1440 { 1441 switch (type) { 1442 case ARC_BUFC_DATA: 1443 /* metadata field is 0 if buffer contains normal data */ 1444 return (0); 1445 case ARC_BUFC_METADATA: 1446 return (ARC_FLAG_BUFC_METADATA); 1447 default: 1448 break; 1449 } 1450 panic("undefined ARC buffer type!"); 1451 return ((uint32_t)-1); 1452 } 1453 1454 void 1455 arc_buf_thaw(arc_buf_t *buf) 1456 { 1457 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1458 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1459 panic("modifying non-anon buffer!"); 1460 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1461 panic("modifying buffer while i/o in progress!"); 1462 arc_cksum_verify(buf); 1463 } 1464 1465 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1466 if (buf->b_hdr->b_freeze_cksum != NULL) { 1467 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1468 buf->b_hdr->b_freeze_cksum = NULL; 1469 } 1470 1471 #ifdef ZFS_DEBUG 1472 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1473 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1474 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1475 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1476 } 1477 #endif 1478 1479 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1480 1481 arc_buf_unwatch(buf); 1482 } 1483 1484 void 1485 arc_buf_freeze(arc_buf_t *buf) 1486 { 1487 kmutex_t *hash_lock; 1488 1489 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1490 return; 1491 1492 hash_lock = HDR_LOCK(buf->b_hdr); 1493 mutex_enter(hash_lock); 1494 1495 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1496 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1497 arc_cksum_compute(buf, B_FALSE); 1498 mutex_exit(hash_lock); 1499 1500 } 1501 1502 static void 1503 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1504 { 1505 ASSERT(HDR_HAS_L1HDR(hdr)); 1506 ASSERT(MUTEX_HELD(hash_lock)); 1507 arc_state_t *state = hdr->b_l1hdr.b_state; 1508 1509 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1510 (state != arc_anon)) { 1511 /* We don't use the L2-only state list. */ 1512 if (state != arc_l2c_only) { 1513 arc_buf_contents_t type = arc_buf_type(hdr); 1514 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1515 multilist_t *list = &state->arcs_list[type]; 1516 uint64_t *size = &state->arcs_lsize[type]; 1517 1518 multilist_remove(list, hdr); 1519 1520 if (GHOST_STATE(state)) { 1521 ASSERT0(hdr->b_l1hdr.b_datacnt); 1522 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1523 delta = hdr->b_size; 1524 } 1525 ASSERT(delta > 0); 1526 ASSERT3U(*size, >=, delta); 1527 atomic_add_64(size, -delta); 1528 } 1529 /* remove the prefetch flag if we get a reference */ 1530 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1531 } 1532 } 1533 1534 static int 1535 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1536 { 1537 int cnt; 1538 arc_state_t *state = hdr->b_l1hdr.b_state; 1539 1540 ASSERT(HDR_HAS_L1HDR(hdr)); 1541 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1542 ASSERT(!GHOST_STATE(state)); 1543 1544 /* 1545 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1546 * check to prevent usage of the arc_l2c_only list. 1547 */ 1548 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1549 (state != arc_anon)) { 1550 arc_buf_contents_t type = arc_buf_type(hdr); 1551 multilist_t *list = &state->arcs_list[type]; 1552 uint64_t *size = &state->arcs_lsize[type]; 1553 1554 multilist_insert(list, hdr); 1555 1556 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1557 atomic_add_64(size, hdr->b_size * 1558 hdr->b_l1hdr.b_datacnt); 1559 } 1560 return (cnt); 1561 } 1562 1563 /* 1564 * Move the supplied buffer to the indicated state. The hash lock 1565 * for the buffer must be held by the caller. 1566 */ 1567 static void 1568 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1569 kmutex_t *hash_lock) 1570 { 1571 arc_state_t *old_state; 1572 int64_t refcnt; 1573 uint32_t datacnt; 1574 uint64_t from_delta, to_delta; 1575 arc_buf_contents_t buftype = arc_buf_type(hdr); 1576 1577 /* 1578 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1579 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1580 * L1 hdr doesn't always exist when we change state to arc_anon before 1581 * destroying a header, in which case reallocating to add the L1 hdr is 1582 * pointless. 1583 */ 1584 if (HDR_HAS_L1HDR(hdr)) { 1585 old_state = hdr->b_l1hdr.b_state; 1586 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1587 datacnt = hdr->b_l1hdr.b_datacnt; 1588 } else { 1589 old_state = arc_l2c_only; 1590 refcnt = 0; 1591 datacnt = 0; 1592 } 1593 1594 ASSERT(MUTEX_HELD(hash_lock)); 1595 ASSERT3P(new_state, !=, old_state); 1596 ASSERT(refcnt == 0 || datacnt > 0); 1597 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1598 ASSERT(old_state != arc_anon || datacnt <= 1); 1599 1600 from_delta = to_delta = datacnt * hdr->b_size; 1601 1602 /* 1603 * If this buffer is evictable, transfer it from the 1604 * old state list to the new state list. 1605 */ 1606 if (refcnt == 0) { 1607 if (old_state != arc_anon && old_state != arc_l2c_only) { 1608 uint64_t *size = &old_state->arcs_lsize[buftype]; 1609 1610 ASSERT(HDR_HAS_L1HDR(hdr)); 1611 multilist_remove(&old_state->arcs_list[buftype], hdr); 1612 1613 /* 1614 * If prefetching out of the ghost cache, 1615 * we will have a non-zero datacnt. 1616 */ 1617 if (GHOST_STATE(old_state) && datacnt == 0) { 1618 /* ghost elements have a ghost size */ 1619 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1620 from_delta = hdr->b_size; 1621 } 1622 ASSERT3U(*size, >=, from_delta); 1623 atomic_add_64(size, -from_delta); 1624 } 1625 if (new_state != arc_anon && new_state != arc_l2c_only) { 1626 uint64_t *size = &new_state->arcs_lsize[buftype]; 1627 1628 /* 1629 * An L1 header always exists here, since if we're 1630 * moving to some L1-cached state (i.e. not l2c_only or 1631 * anonymous), we realloc the header to add an L1hdr 1632 * beforehand. 1633 */ 1634 ASSERT(HDR_HAS_L1HDR(hdr)); 1635 multilist_insert(&new_state->arcs_list[buftype], hdr); 1636 1637 /* ghost elements have a ghost size */ 1638 if (GHOST_STATE(new_state)) { 1639 ASSERT0(datacnt); 1640 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1641 to_delta = hdr->b_size; 1642 } 1643 atomic_add_64(size, to_delta); 1644 } 1645 } 1646 1647 ASSERT(!BUF_EMPTY(hdr)); 1648 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1649 buf_hash_remove(hdr); 1650 1651 /* adjust state sizes (ignore arc_l2c_only) */ 1652 if (to_delta && new_state != arc_l2c_only) 1653 atomic_add_64(&new_state->arcs_size, to_delta); 1654 if (from_delta && old_state != arc_l2c_only) { 1655 ASSERT3U(old_state->arcs_size, >=, from_delta); 1656 atomic_add_64(&old_state->arcs_size, -from_delta); 1657 } 1658 if (HDR_HAS_L1HDR(hdr)) 1659 hdr->b_l1hdr.b_state = new_state; 1660 1661 /* 1662 * L2 headers should never be on the L2 state list since they don't 1663 * have L1 headers allocated. 1664 */ 1665 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1666 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1667 } 1668 1669 void 1670 arc_space_consume(uint64_t space, arc_space_type_t type) 1671 { 1672 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1673 1674 switch (type) { 1675 case ARC_SPACE_DATA: 1676 ARCSTAT_INCR(arcstat_data_size, space); 1677 break; 1678 case ARC_SPACE_META: 1679 ARCSTAT_INCR(arcstat_metadata_size, space); 1680 break; 1681 case ARC_SPACE_OTHER: 1682 ARCSTAT_INCR(arcstat_other_size, space); 1683 break; 1684 case ARC_SPACE_HDRS: 1685 ARCSTAT_INCR(arcstat_hdr_size, space); 1686 break; 1687 case ARC_SPACE_L2HDRS: 1688 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1689 break; 1690 } 1691 1692 if (type != ARC_SPACE_DATA) 1693 ARCSTAT_INCR(arcstat_meta_used, space); 1694 1695 atomic_add_64(&arc_size, space); 1696 } 1697 1698 void 1699 arc_space_return(uint64_t space, arc_space_type_t type) 1700 { 1701 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1702 1703 switch (type) { 1704 case ARC_SPACE_DATA: 1705 ARCSTAT_INCR(arcstat_data_size, -space); 1706 break; 1707 case ARC_SPACE_META: 1708 ARCSTAT_INCR(arcstat_metadata_size, -space); 1709 break; 1710 case ARC_SPACE_OTHER: 1711 ARCSTAT_INCR(arcstat_other_size, -space); 1712 break; 1713 case ARC_SPACE_HDRS: 1714 ARCSTAT_INCR(arcstat_hdr_size, -space); 1715 break; 1716 case ARC_SPACE_L2HDRS: 1717 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1718 break; 1719 } 1720 1721 if (type != ARC_SPACE_DATA) { 1722 ASSERT(arc_meta_used >= space); 1723 if (arc_meta_max < arc_meta_used) 1724 arc_meta_max = arc_meta_used; 1725 ARCSTAT_INCR(arcstat_meta_used, -space); 1726 } 1727 1728 ASSERT(arc_size >= space); 1729 atomic_add_64(&arc_size, -space); 1730 } 1731 1732 arc_buf_t * 1733 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1734 { 1735 arc_buf_hdr_t *hdr; 1736 arc_buf_t *buf; 1737 1738 ASSERT3U(size, >, 0); 1739 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1740 ASSERT(BUF_EMPTY(hdr)); 1741 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1742 hdr->b_size = size; 1743 hdr->b_spa = spa_load_guid(spa); 1744 1745 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1746 buf->b_hdr = hdr; 1747 buf->b_data = NULL; 1748 buf->b_efunc = NULL; 1749 buf->b_private = NULL; 1750 buf->b_next = NULL; 1751 1752 hdr->b_flags = arc_bufc_to_flags(type); 1753 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1754 1755 hdr->b_l1hdr.b_buf = buf; 1756 hdr->b_l1hdr.b_state = arc_anon; 1757 hdr->b_l1hdr.b_arc_access = 0; 1758 hdr->b_l1hdr.b_datacnt = 1; 1759 hdr->b_l1hdr.b_tmp_cdata = NULL; 1760 1761 arc_get_data_buf(buf); 1762 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1763 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1764 1765 return (buf); 1766 } 1767 1768 static char *arc_onloan_tag = "onloan"; 1769 1770 /* 1771 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1772 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1773 * buffers must be returned to the arc before they can be used by the DMU or 1774 * freed. 1775 */ 1776 arc_buf_t * 1777 arc_loan_buf(spa_t *spa, int size) 1778 { 1779 arc_buf_t *buf; 1780 1781 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1782 1783 atomic_add_64(&arc_loaned_bytes, size); 1784 return (buf); 1785 } 1786 1787 /* 1788 * Return a loaned arc buffer to the arc. 1789 */ 1790 void 1791 arc_return_buf(arc_buf_t *buf, void *tag) 1792 { 1793 arc_buf_hdr_t *hdr = buf->b_hdr; 1794 1795 ASSERT(buf->b_data != NULL); 1796 ASSERT(HDR_HAS_L1HDR(hdr)); 1797 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1798 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1799 1800 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1801 } 1802 1803 /* Detach an arc_buf from a dbuf (tag) */ 1804 void 1805 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1806 { 1807 arc_buf_hdr_t *hdr = buf->b_hdr; 1808 1809 ASSERT(buf->b_data != NULL); 1810 ASSERT(HDR_HAS_L1HDR(hdr)); 1811 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1812 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 1813 buf->b_efunc = NULL; 1814 buf->b_private = NULL; 1815 1816 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1817 } 1818 1819 static arc_buf_t * 1820 arc_buf_clone(arc_buf_t *from) 1821 { 1822 arc_buf_t *buf; 1823 arc_buf_hdr_t *hdr = from->b_hdr; 1824 uint64_t size = hdr->b_size; 1825 1826 ASSERT(HDR_HAS_L1HDR(hdr)); 1827 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 1828 1829 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1830 buf->b_hdr = hdr; 1831 buf->b_data = NULL; 1832 buf->b_efunc = NULL; 1833 buf->b_private = NULL; 1834 buf->b_next = hdr->b_l1hdr.b_buf; 1835 hdr->b_l1hdr.b_buf = buf; 1836 arc_get_data_buf(buf); 1837 bcopy(from->b_data, buf->b_data, size); 1838 1839 /* 1840 * This buffer already exists in the arc so create a duplicate 1841 * copy for the caller. If the buffer is associated with user data 1842 * then track the size and number of duplicates. These stats will be 1843 * updated as duplicate buffers are created and destroyed. 1844 */ 1845 if (HDR_ISTYPE_DATA(hdr)) { 1846 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1847 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1848 } 1849 hdr->b_l1hdr.b_datacnt += 1; 1850 return (buf); 1851 } 1852 1853 void 1854 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1855 { 1856 arc_buf_hdr_t *hdr; 1857 kmutex_t *hash_lock; 1858 1859 /* 1860 * Check to see if this buffer is evicted. Callers 1861 * must verify b_data != NULL to know if the add_ref 1862 * was successful. 1863 */ 1864 mutex_enter(&buf->b_evict_lock); 1865 if (buf->b_data == NULL) { 1866 mutex_exit(&buf->b_evict_lock); 1867 return; 1868 } 1869 hash_lock = HDR_LOCK(buf->b_hdr); 1870 mutex_enter(hash_lock); 1871 hdr = buf->b_hdr; 1872 ASSERT(HDR_HAS_L1HDR(hdr)); 1873 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1874 mutex_exit(&buf->b_evict_lock); 1875 1876 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 1877 hdr->b_l1hdr.b_state == arc_mfu); 1878 1879 add_reference(hdr, hash_lock, tag); 1880 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1881 arc_access(hdr, hash_lock); 1882 mutex_exit(hash_lock); 1883 ARCSTAT_BUMP(arcstat_hits); 1884 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 1885 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 1886 data, metadata, hits); 1887 } 1888 1889 static void 1890 arc_buf_free_on_write(void *data, size_t size, 1891 void (*free_func)(void *, size_t)) 1892 { 1893 l2arc_data_free_t *df; 1894 1895 df = kmem_alloc(sizeof (*df), KM_SLEEP); 1896 df->l2df_data = data; 1897 df->l2df_size = size; 1898 df->l2df_func = free_func; 1899 mutex_enter(&l2arc_free_on_write_mtx); 1900 list_insert_head(l2arc_free_on_write, df); 1901 mutex_exit(&l2arc_free_on_write_mtx); 1902 } 1903 1904 /* 1905 * Free the arc data buffer. If it is an l2arc write in progress, 1906 * the buffer is placed on l2arc_free_on_write to be freed later. 1907 */ 1908 static void 1909 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1910 { 1911 arc_buf_hdr_t *hdr = buf->b_hdr; 1912 1913 if (HDR_L2_WRITING(hdr)) { 1914 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 1915 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1916 } else { 1917 free_func(buf->b_data, hdr->b_size); 1918 } 1919 } 1920 1921 static void 1922 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 1923 { 1924 ASSERT(HDR_HAS_L2HDR(hdr)); 1925 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 1926 1927 /* 1928 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 1929 * that doesn't exist, the header is in the arc_l2c_only state, 1930 * and there isn't anything to free (it's already been freed). 1931 */ 1932 if (!HDR_HAS_L1HDR(hdr)) 1933 return; 1934 1935 /* 1936 * The header isn't being written to the l2arc device, thus it 1937 * shouldn't have a b_tmp_cdata to free. 1938 */ 1939 if (!HDR_L2_WRITING(hdr)) { 1940 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1941 return; 1942 } 1943 1944 /* 1945 * The header does not have compression enabled. This can be due 1946 * to the buffer not being compressible, or because we're 1947 * freeing the buffer before the second phase of 1948 * l2arc_write_buffer() has started (which does the compression 1949 * step). In either case, b_tmp_cdata does not point to a 1950 * separately compressed buffer, so there's nothing to free (it 1951 * points to the same buffer as the arc_buf_t's b_data field). 1952 */ 1953 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 1954 hdr->b_l1hdr.b_tmp_cdata = NULL; 1955 return; 1956 } 1957 1958 /* 1959 * There's nothing to free since the buffer was all zero's and 1960 * compressed to a zero length buffer. 1961 */ 1962 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) { 1963 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1964 return; 1965 } 1966 1967 ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))); 1968 1969 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 1970 hdr->b_size, zio_data_buf_free); 1971 1972 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 1973 hdr->b_l1hdr.b_tmp_cdata = NULL; 1974 } 1975 1976 /* 1977 * Free up buf->b_data and if 'remove' is set, then pull the 1978 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 1979 */ 1980 static void 1981 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 1982 { 1983 arc_buf_t **bufp; 1984 1985 /* free up data associated with the buf */ 1986 if (buf->b_data != NULL) { 1987 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 1988 uint64_t size = buf->b_hdr->b_size; 1989 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 1990 1991 arc_cksum_verify(buf); 1992 arc_buf_unwatch(buf); 1993 1994 if (type == ARC_BUFC_METADATA) { 1995 arc_buf_data_free(buf, zio_buf_free); 1996 arc_space_return(size, ARC_SPACE_META); 1997 } else { 1998 ASSERT(type == ARC_BUFC_DATA); 1999 arc_buf_data_free(buf, zio_data_buf_free); 2000 arc_space_return(size, ARC_SPACE_DATA); 2001 } 2002 2003 /* protected by hash lock, if in the hash table */ 2004 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2005 uint64_t *cnt = &state->arcs_lsize[type]; 2006 2007 ASSERT(refcount_is_zero( 2008 &buf->b_hdr->b_l1hdr.b_refcnt)); 2009 ASSERT(state != arc_anon && state != arc_l2c_only); 2010 2011 ASSERT3U(*cnt, >=, size); 2012 atomic_add_64(cnt, -size); 2013 } 2014 ASSERT3U(state->arcs_size, >=, size); 2015 atomic_add_64(&state->arcs_size, -size); 2016 buf->b_data = NULL; 2017 2018 /* 2019 * If we're destroying a duplicate buffer make sure 2020 * that the appropriate statistics are updated. 2021 */ 2022 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2023 HDR_ISTYPE_DATA(buf->b_hdr)) { 2024 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2025 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2026 } 2027 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2028 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2029 } 2030 2031 /* only remove the buf if requested */ 2032 if (!remove) 2033 return; 2034 2035 /* remove the buf from the hdr list */ 2036 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2037 bufp = &(*bufp)->b_next) 2038 continue; 2039 *bufp = buf->b_next; 2040 buf->b_next = NULL; 2041 2042 ASSERT(buf->b_efunc == NULL); 2043 2044 /* clean up the buf */ 2045 buf->b_hdr = NULL; 2046 kmem_cache_free(buf_cache, buf); 2047 } 2048 2049 static void 2050 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2051 { 2052 if (HDR_HAS_L1HDR(hdr)) { 2053 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2054 hdr->b_l1hdr.b_datacnt > 0); 2055 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2056 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2057 } 2058 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2059 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2060 2061 if (HDR_HAS_L2HDR(hdr)) { 2062 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2063 boolean_t buflist_held = MUTEX_HELD(&l2hdr->b_dev->l2ad_mtx); 2064 2065 if (!buflist_held) { 2066 mutex_enter(&l2hdr->b_dev->l2ad_mtx); 2067 l2hdr = &hdr->b_l2hdr; 2068 } 2069 2070 list_remove(&l2hdr->b_dev->l2ad_buflist, hdr); 2071 2072 /* 2073 * We don't want to leak the b_tmp_cdata buffer that was 2074 * allocated in l2arc_write_buffers() 2075 */ 2076 arc_buf_l2_cdata_free(hdr); 2077 2078 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2079 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2080 2081 if (!buflist_held) 2082 mutex_exit(&l2hdr->b_dev->l2ad_mtx); 2083 2084 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2085 } 2086 2087 if (!BUF_EMPTY(hdr)) 2088 buf_discard_identity(hdr); 2089 2090 if (hdr->b_freeze_cksum != NULL) { 2091 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2092 hdr->b_freeze_cksum = NULL; 2093 } 2094 2095 if (HDR_HAS_L1HDR(hdr)) { 2096 while (hdr->b_l1hdr.b_buf) { 2097 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2098 2099 if (buf->b_efunc != NULL) { 2100 mutex_enter(&arc_user_evicts_lock); 2101 mutex_enter(&buf->b_evict_lock); 2102 ASSERT(buf->b_hdr != NULL); 2103 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2104 hdr->b_l1hdr.b_buf = buf->b_next; 2105 buf->b_hdr = &arc_eviction_hdr; 2106 buf->b_next = arc_eviction_list; 2107 arc_eviction_list = buf; 2108 mutex_exit(&buf->b_evict_lock); 2109 cv_signal(&arc_user_evicts_cv); 2110 mutex_exit(&arc_user_evicts_lock); 2111 } else { 2112 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2113 } 2114 } 2115 #ifdef ZFS_DEBUG 2116 if (hdr->b_l1hdr.b_thawed != NULL) { 2117 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2118 hdr->b_l1hdr.b_thawed = NULL; 2119 } 2120 #endif 2121 } 2122 2123 ASSERT3P(hdr->b_hash_next, ==, NULL); 2124 if (HDR_HAS_L1HDR(hdr)) { 2125 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2126 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2127 kmem_cache_free(hdr_full_cache, hdr); 2128 } else { 2129 kmem_cache_free(hdr_l2only_cache, hdr); 2130 } 2131 } 2132 2133 void 2134 arc_buf_free(arc_buf_t *buf, void *tag) 2135 { 2136 arc_buf_hdr_t *hdr = buf->b_hdr; 2137 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2138 2139 ASSERT(buf->b_efunc == NULL); 2140 ASSERT(buf->b_data != NULL); 2141 2142 if (hashed) { 2143 kmutex_t *hash_lock = HDR_LOCK(hdr); 2144 2145 mutex_enter(hash_lock); 2146 hdr = buf->b_hdr; 2147 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2148 2149 (void) remove_reference(hdr, hash_lock, tag); 2150 if (hdr->b_l1hdr.b_datacnt > 1) { 2151 arc_buf_destroy(buf, TRUE); 2152 } else { 2153 ASSERT(buf == hdr->b_l1hdr.b_buf); 2154 ASSERT(buf->b_efunc == NULL); 2155 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2156 } 2157 mutex_exit(hash_lock); 2158 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2159 int destroy_hdr; 2160 /* 2161 * We are in the middle of an async write. Don't destroy 2162 * this buffer unless the write completes before we finish 2163 * decrementing the reference count. 2164 */ 2165 mutex_enter(&arc_user_evicts_lock); 2166 (void) remove_reference(hdr, NULL, tag); 2167 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2168 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2169 mutex_exit(&arc_user_evicts_lock); 2170 if (destroy_hdr) 2171 arc_hdr_destroy(hdr); 2172 } else { 2173 if (remove_reference(hdr, NULL, tag) > 0) 2174 arc_buf_destroy(buf, TRUE); 2175 else 2176 arc_hdr_destroy(hdr); 2177 } 2178 } 2179 2180 boolean_t 2181 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2182 { 2183 arc_buf_hdr_t *hdr = buf->b_hdr; 2184 kmutex_t *hash_lock = HDR_LOCK(hdr); 2185 boolean_t no_callback = (buf->b_efunc == NULL); 2186 2187 if (hdr->b_l1hdr.b_state == arc_anon) { 2188 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2189 arc_buf_free(buf, tag); 2190 return (no_callback); 2191 } 2192 2193 mutex_enter(hash_lock); 2194 hdr = buf->b_hdr; 2195 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2196 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2197 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2198 ASSERT(buf->b_data != NULL); 2199 2200 (void) remove_reference(hdr, hash_lock, tag); 2201 if (hdr->b_l1hdr.b_datacnt > 1) { 2202 if (no_callback) 2203 arc_buf_destroy(buf, TRUE); 2204 } else if (no_callback) { 2205 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2206 ASSERT(buf->b_efunc == NULL); 2207 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2208 } 2209 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2210 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2211 mutex_exit(hash_lock); 2212 return (no_callback); 2213 } 2214 2215 int32_t 2216 arc_buf_size(arc_buf_t *buf) 2217 { 2218 return (buf->b_hdr->b_size); 2219 } 2220 2221 /* 2222 * Called from the DMU to determine if the current buffer should be 2223 * evicted. In order to ensure proper locking, the eviction must be initiated 2224 * from the DMU. Return true if the buffer is associated with user data and 2225 * duplicate buffers still exist. 2226 */ 2227 boolean_t 2228 arc_buf_eviction_needed(arc_buf_t *buf) 2229 { 2230 arc_buf_hdr_t *hdr; 2231 boolean_t evict_needed = B_FALSE; 2232 2233 if (zfs_disable_dup_eviction) 2234 return (B_FALSE); 2235 2236 mutex_enter(&buf->b_evict_lock); 2237 hdr = buf->b_hdr; 2238 if (hdr == NULL) { 2239 /* 2240 * We are in arc_do_user_evicts(); let that function 2241 * perform the eviction. 2242 */ 2243 ASSERT(buf->b_data == NULL); 2244 mutex_exit(&buf->b_evict_lock); 2245 return (B_FALSE); 2246 } else if (buf->b_data == NULL) { 2247 /* 2248 * We have already been added to the arc eviction list; 2249 * recommend eviction. 2250 */ 2251 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2252 mutex_exit(&buf->b_evict_lock); 2253 return (B_TRUE); 2254 } 2255 2256 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2257 evict_needed = B_TRUE; 2258 2259 mutex_exit(&buf->b_evict_lock); 2260 return (evict_needed); 2261 } 2262 2263 /* 2264 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2265 * state of the header is dependent on it's state prior to entering this 2266 * function. The following transitions are possible: 2267 * 2268 * - arc_mru -> arc_mru_ghost 2269 * - arc_mfu -> arc_mfu_ghost 2270 * - arc_mru_ghost -> arc_l2c_only 2271 * - arc_mru_ghost -> deleted 2272 * - arc_mfu_ghost -> arc_l2c_only 2273 * - arc_mfu_ghost -> deleted 2274 */ 2275 static int64_t 2276 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2277 { 2278 arc_state_t *evicted_state, *state; 2279 int64_t bytes_evicted = 0; 2280 2281 ASSERT(MUTEX_HELD(hash_lock)); 2282 ASSERT(HDR_HAS_L1HDR(hdr)); 2283 2284 state = hdr->b_l1hdr.b_state; 2285 if (GHOST_STATE(state)) { 2286 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2287 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2288 2289 /* 2290 * l2arc_write_buffers() relies on a header's L1 portion 2291 * (i.e. it's b_tmp_cdata field) during it's write phase. 2292 * Thus, we cannot push a header onto the arc_l2c_only 2293 * state (removing it's L1 piece) until the header is 2294 * done being written to the l2arc. 2295 */ 2296 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2297 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2298 return (bytes_evicted); 2299 } 2300 2301 ARCSTAT_BUMP(arcstat_deleted); 2302 bytes_evicted += hdr->b_size; 2303 2304 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2305 2306 if (HDR_HAS_L2HDR(hdr)) { 2307 /* 2308 * This buffer is cached on the 2nd Level ARC; 2309 * don't destroy the header. 2310 */ 2311 arc_change_state(arc_l2c_only, hdr, hash_lock); 2312 /* 2313 * dropping from L1+L2 cached to L2-only, 2314 * realloc to remove the L1 header. 2315 */ 2316 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2317 hdr_l2only_cache); 2318 } else { 2319 arc_change_state(arc_anon, hdr, hash_lock); 2320 arc_hdr_destroy(hdr); 2321 } 2322 return (bytes_evicted); 2323 } 2324 2325 ASSERT(state == arc_mru || state == arc_mfu); 2326 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2327 2328 /* prefetch buffers have a minimum lifespan */ 2329 if (HDR_IO_IN_PROGRESS(hdr) || 2330 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2331 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2332 arc_min_prefetch_lifespan)) { 2333 ARCSTAT_BUMP(arcstat_evict_skip); 2334 return (bytes_evicted); 2335 } 2336 2337 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2338 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2339 while (hdr->b_l1hdr.b_buf) { 2340 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2341 if (!mutex_tryenter(&buf->b_evict_lock)) { 2342 ARCSTAT_BUMP(arcstat_mutex_miss); 2343 break; 2344 } 2345 if (buf->b_data != NULL) 2346 bytes_evicted += hdr->b_size; 2347 if (buf->b_efunc != NULL) { 2348 mutex_enter(&arc_user_evicts_lock); 2349 arc_buf_destroy(buf, FALSE); 2350 hdr->b_l1hdr.b_buf = buf->b_next; 2351 buf->b_hdr = &arc_eviction_hdr; 2352 buf->b_next = arc_eviction_list; 2353 arc_eviction_list = buf; 2354 cv_signal(&arc_user_evicts_cv); 2355 mutex_exit(&arc_user_evicts_lock); 2356 mutex_exit(&buf->b_evict_lock); 2357 } else { 2358 mutex_exit(&buf->b_evict_lock); 2359 arc_buf_destroy(buf, TRUE); 2360 } 2361 } 2362 2363 if (HDR_HAS_L2HDR(hdr)) { 2364 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2365 } else { 2366 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2367 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2368 else 2369 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2370 } 2371 2372 if (hdr->b_l1hdr.b_datacnt == 0) { 2373 arc_change_state(evicted_state, hdr, hash_lock); 2374 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2375 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2376 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2377 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2378 } 2379 2380 return (bytes_evicted); 2381 } 2382 2383 static uint64_t 2384 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2385 uint64_t spa, int64_t bytes) 2386 { 2387 multilist_sublist_t *mls; 2388 uint64_t bytes_evicted = 0; 2389 arc_buf_hdr_t *hdr; 2390 kmutex_t *hash_lock; 2391 int evict_count = 0; 2392 2393 ASSERT3P(marker, !=, NULL); 2394 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2395 2396 mls = multilist_sublist_lock(ml, idx); 2397 2398 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2399 hdr = multilist_sublist_prev(mls, marker)) { 2400 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2401 (evict_count >= zfs_arc_evict_batch_limit)) 2402 break; 2403 2404 /* 2405 * To keep our iteration location, move the marker 2406 * forward. Since we're not holding hdr's hash lock, we 2407 * must be very careful and not remove 'hdr' from the 2408 * sublist. Otherwise, other consumers might mistake the 2409 * 'hdr' as not being on a sublist when they call the 2410 * multilist_link_active() function (they all rely on 2411 * the hash lock protecting concurrent insertions and 2412 * removals). multilist_sublist_move_forward() was 2413 * specifically implemented to ensure this is the case 2414 * (only 'marker' will be removed and re-inserted). 2415 */ 2416 multilist_sublist_move_forward(mls, marker); 2417 2418 /* 2419 * The only case where the b_spa field should ever be 2420 * zero, is the marker headers inserted by 2421 * arc_evict_state(). It's possible for multiple threads 2422 * to be calling arc_evict_state() concurrently (e.g. 2423 * dsl_pool_close() and zio_inject_fault()), so we must 2424 * skip any markers we see from these other threads. 2425 */ 2426 if (hdr->b_spa == 0) 2427 continue; 2428 2429 /* we're only interested in evicting buffers of a certain spa */ 2430 if (spa != 0 && hdr->b_spa != spa) { 2431 ARCSTAT_BUMP(arcstat_evict_skip); 2432 continue; 2433 } 2434 2435 hash_lock = HDR_LOCK(hdr); 2436 2437 /* 2438 * We aren't calling this function from any code path 2439 * that would already be holding a hash lock, so we're 2440 * asserting on this assumption to be defensive in case 2441 * this ever changes. Without this check, it would be 2442 * possible to incorrectly increment arcstat_mutex_miss 2443 * below (e.g. if the code changed such that we called 2444 * this function with a hash lock held). 2445 */ 2446 ASSERT(!MUTEX_HELD(hash_lock)); 2447 2448 if (mutex_tryenter(hash_lock)) { 2449 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2450 mutex_exit(hash_lock); 2451 2452 bytes_evicted += evicted; 2453 2454 /* 2455 * If evicted is zero, arc_evict_hdr() must have 2456 * decided to skip this header, don't increment 2457 * evict_count in this case. 2458 */ 2459 if (evicted != 0) 2460 evict_count++; 2461 2462 /* 2463 * If arc_size isn't overflowing, signal any 2464 * threads that might happen to be waiting. 2465 * 2466 * For each header evicted, we wake up a single 2467 * thread. If we used cv_broadcast, we could 2468 * wake up "too many" threads causing arc_size 2469 * to significantly overflow arc_c; since 2470 * arc_get_data_buf() doesn't check for overflow 2471 * when it's woken up (it doesn't because it's 2472 * possible for the ARC to be overflowing while 2473 * full of un-evictable buffers, and the 2474 * function should proceed in this case). 2475 * 2476 * If threads are left sleeping, due to not 2477 * using cv_broadcast, they will be woken up 2478 * just before arc_reclaim_thread() sleeps. 2479 */ 2480 mutex_enter(&arc_reclaim_lock); 2481 if (!arc_is_overflowing()) 2482 cv_signal(&arc_reclaim_waiters_cv); 2483 mutex_exit(&arc_reclaim_lock); 2484 } else { 2485 ARCSTAT_BUMP(arcstat_mutex_miss); 2486 } 2487 } 2488 2489 multilist_sublist_unlock(mls); 2490 2491 return (bytes_evicted); 2492 } 2493 2494 /* 2495 * Evict buffers from the given arc state, until we've removed the 2496 * specified number of bytes. Move the removed buffers to the 2497 * appropriate evict state. 2498 * 2499 * This function makes a "best effort". It skips over any buffers 2500 * it can't get a hash_lock on, and so, may not catch all candidates. 2501 * It may also return without evicting as much space as requested. 2502 * 2503 * If bytes is specified using the special value ARC_EVICT_ALL, this 2504 * will evict all available (i.e. unlocked and evictable) buffers from 2505 * the given arc state; which is used by arc_flush(). 2506 */ 2507 static uint64_t 2508 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2509 arc_buf_contents_t type) 2510 { 2511 uint64_t total_evicted = 0; 2512 multilist_t *ml = &state->arcs_list[type]; 2513 int num_sublists; 2514 arc_buf_hdr_t **markers; 2515 2516 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2517 2518 num_sublists = multilist_get_num_sublists(ml); 2519 2520 /* 2521 * If we've tried to evict from each sublist, made some 2522 * progress, but still have not hit the target number of bytes 2523 * to evict, we want to keep trying. The markers allow us to 2524 * pick up where we left off for each individual sublist, rather 2525 * than starting from the tail each time. 2526 */ 2527 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2528 for (int i = 0; i < num_sublists; i++) { 2529 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2530 2531 /* 2532 * A b_spa of 0 is used to indicate that this header is 2533 * a marker. This fact is used in arc_adjust_type() and 2534 * arc_evict_state_impl(). 2535 */ 2536 markers[i]->b_spa = 0; 2537 2538 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2539 multilist_sublist_insert_tail(mls, markers[i]); 2540 multilist_sublist_unlock(mls); 2541 } 2542 2543 /* 2544 * While we haven't hit our target number of bytes to evict, or 2545 * we're evicting all available buffers. 2546 */ 2547 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2548 /* 2549 * Start eviction using a randomly selected sublist, 2550 * this is to try and evenly balance eviction across all 2551 * sublists. Always starting at the same sublist 2552 * (e.g. index 0) would cause evictions to favor certain 2553 * sublists over others. 2554 */ 2555 int sublist_idx = multilist_get_random_index(ml); 2556 uint64_t scan_evicted = 0; 2557 2558 for (int i = 0; i < num_sublists; i++) { 2559 uint64_t bytes_remaining; 2560 uint64_t bytes_evicted; 2561 2562 if (bytes == ARC_EVICT_ALL) 2563 bytes_remaining = ARC_EVICT_ALL; 2564 else if (total_evicted < bytes) 2565 bytes_remaining = bytes - total_evicted; 2566 else 2567 break; 2568 2569 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2570 markers[sublist_idx], spa, bytes_remaining); 2571 2572 scan_evicted += bytes_evicted; 2573 total_evicted += bytes_evicted; 2574 2575 /* we've reached the end, wrap to the beginning */ 2576 if (++sublist_idx >= num_sublists) 2577 sublist_idx = 0; 2578 } 2579 2580 /* 2581 * If we didn't evict anything during this scan, we have 2582 * no reason to believe we'll evict more during another 2583 * scan, so break the loop. 2584 */ 2585 if (scan_evicted == 0) { 2586 /* This isn't possible, let's make that obvious */ 2587 ASSERT3S(bytes, !=, 0); 2588 2589 /* 2590 * When bytes is ARC_EVICT_ALL, the only way to 2591 * break the loop is when scan_evicted is zero. 2592 * In that case, we actually have evicted enough, 2593 * so we don't want to increment the kstat. 2594 */ 2595 if (bytes != ARC_EVICT_ALL) { 2596 ASSERT3S(total_evicted, <, bytes); 2597 ARCSTAT_BUMP(arcstat_evict_not_enough); 2598 } 2599 2600 break; 2601 } 2602 } 2603 2604 for (int i = 0; i < num_sublists; i++) { 2605 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2606 multilist_sublist_remove(mls, markers[i]); 2607 multilist_sublist_unlock(mls); 2608 2609 kmem_cache_free(hdr_full_cache, markers[i]); 2610 } 2611 kmem_free(markers, sizeof (*markers) * num_sublists); 2612 2613 return (total_evicted); 2614 } 2615 2616 /* 2617 * Flush all "evictable" data of the given type from the arc state 2618 * specified. This will not evict any "active" buffers (i.e. referenced). 2619 * 2620 * When 'retry' is set to FALSE, the function will make a single pass 2621 * over the state and evict any buffers that it can. Since it doesn't 2622 * continually retry the eviction, it might end up leaving some buffers 2623 * in the ARC due to lock misses. 2624 * 2625 * When 'retry' is set to TRUE, the function will continually retry the 2626 * eviction until *all* evictable buffers have been removed from the 2627 * state. As a result, if concurrent insertions into the state are 2628 * allowed (e.g. if the ARC isn't shutting down), this function might 2629 * wind up in an infinite loop, continually trying to evict buffers. 2630 */ 2631 static uint64_t 2632 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2633 boolean_t retry) 2634 { 2635 uint64_t evicted = 0; 2636 2637 while (state->arcs_lsize[type] != 0) { 2638 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2639 2640 if (!retry) 2641 break; 2642 } 2643 2644 return (evicted); 2645 } 2646 2647 /* 2648 * Evict the specified number of bytes from the state specified, 2649 * restricting eviction to the spa and type given. This function 2650 * prevents us from trying to evict more from a state's list than 2651 * is "evictable", and to skip evicting altogether when passed a 2652 * negative value for "bytes". In contrast, arc_evict_state() will 2653 * evict everything it can, when passed a negative value for "bytes". 2654 */ 2655 static uint64_t 2656 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 2657 arc_buf_contents_t type) 2658 { 2659 int64_t delta; 2660 2661 if (bytes > 0 && state->arcs_lsize[type] > 0) { 2662 delta = MIN(state->arcs_lsize[type], bytes); 2663 return (arc_evict_state(state, spa, delta, type)); 2664 } 2665 2666 return (0); 2667 } 2668 2669 /* 2670 * Evict metadata buffers from the cache, such that arc_meta_used is 2671 * capped by the arc_meta_limit tunable. 2672 */ 2673 static uint64_t 2674 arc_adjust_meta(void) 2675 { 2676 uint64_t total_evicted = 0; 2677 int64_t target; 2678 2679 /* 2680 * If we're over the meta limit, we want to evict enough 2681 * metadata to get back under the meta limit. We don't want to 2682 * evict so much that we drop the MRU below arc_p, though. If 2683 * we're over the meta limit more than we're over arc_p, we 2684 * evict some from the MRU here, and some from the MFU below. 2685 */ 2686 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2687 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size - arc_p)); 2688 2689 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2690 2691 /* 2692 * Similar to the above, we want to evict enough bytes to get us 2693 * below the meta limit, but not so much as to drop us below the 2694 * space alloted to the MFU (which is defined as arc_c - arc_p). 2695 */ 2696 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2697 (int64_t)(arc_mfu->arcs_size - (arc_c - arc_p))); 2698 2699 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2700 2701 return (total_evicted); 2702 } 2703 2704 /* 2705 * Return the type of the oldest buffer in the given arc state 2706 * 2707 * This function will select a random sublist of type ARC_BUFC_DATA and 2708 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 2709 * is compared, and the type which contains the "older" buffer will be 2710 * returned. 2711 */ 2712 static arc_buf_contents_t 2713 arc_adjust_type(arc_state_t *state) 2714 { 2715 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 2716 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 2717 int data_idx = multilist_get_random_index(data_ml); 2718 int meta_idx = multilist_get_random_index(meta_ml); 2719 multilist_sublist_t *data_mls; 2720 multilist_sublist_t *meta_mls; 2721 arc_buf_contents_t type; 2722 arc_buf_hdr_t *data_hdr; 2723 arc_buf_hdr_t *meta_hdr; 2724 2725 /* 2726 * We keep the sublist lock until we're finished, to prevent 2727 * the headers from being destroyed via arc_evict_state(). 2728 */ 2729 data_mls = multilist_sublist_lock(data_ml, data_idx); 2730 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 2731 2732 /* 2733 * These two loops are to ensure we skip any markers that 2734 * might be at the tail of the lists due to arc_evict_state(). 2735 */ 2736 2737 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 2738 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 2739 if (data_hdr->b_spa != 0) 2740 break; 2741 } 2742 2743 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 2744 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 2745 if (meta_hdr->b_spa != 0) 2746 break; 2747 } 2748 2749 if (data_hdr == NULL && meta_hdr == NULL) { 2750 type = ARC_BUFC_DATA; 2751 } else if (data_hdr == NULL) { 2752 ASSERT3P(meta_hdr, !=, NULL); 2753 type = ARC_BUFC_METADATA; 2754 } else if (meta_hdr == NULL) { 2755 ASSERT3P(data_hdr, !=, NULL); 2756 type = ARC_BUFC_DATA; 2757 } else { 2758 ASSERT3P(data_hdr, !=, NULL); 2759 ASSERT3P(meta_hdr, !=, NULL); 2760 2761 /* The headers can't be on the sublist without an L1 header */ 2762 ASSERT(HDR_HAS_L1HDR(data_hdr)); 2763 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 2764 2765 if (data_hdr->b_l1hdr.b_arc_access < 2766 meta_hdr->b_l1hdr.b_arc_access) { 2767 type = ARC_BUFC_DATA; 2768 } else { 2769 type = ARC_BUFC_METADATA; 2770 } 2771 } 2772 2773 multilist_sublist_unlock(meta_mls); 2774 multilist_sublist_unlock(data_mls); 2775 2776 return (type); 2777 } 2778 2779 /* 2780 * Evict buffers from the cache, such that arc_size is capped by arc_c. 2781 */ 2782 static uint64_t 2783 arc_adjust(void) 2784 { 2785 uint64_t total_evicted = 0; 2786 uint64_t bytes; 2787 int64_t target; 2788 2789 /* 2790 * If we're over arc_meta_limit, we want to correct that before 2791 * potentially evicting data buffers below. 2792 */ 2793 total_evicted += arc_adjust_meta(); 2794 2795 /* 2796 * Adjust MRU size 2797 * 2798 * If we're over the target cache size, we want to evict enough 2799 * from the list to get back to our target size. We don't want 2800 * to evict too much from the MRU, such that it drops below 2801 * arc_p. So, if we're over our target cache size more than 2802 * the MRU is over arc_p, we'll evict enough to get back to 2803 * arc_p here, and then evict more from the MFU below. 2804 */ 2805 target = MIN((int64_t)(arc_size - arc_c), 2806 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2807 arc_p)); 2808 2809 /* 2810 * If we're below arc_meta_min, always prefer to evict data. 2811 * Otherwise, try to satisfy the requested number of bytes to 2812 * evict from the type which contains older buffers; in an 2813 * effort to keep newer buffers in the cache regardless of their 2814 * type. If we cannot satisfy the number of bytes from this 2815 * type, spill over into the next type. 2816 */ 2817 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2818 arc_meta_used > arc_meta_min) { 2819 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2820 total_evicted += bytes; 2821 2822 /* 2823 * If we couldn't evict our target number of bytes from 2824 * metadata, we try to get the rest from data. 2825 */ 2826 target -= bytes; 2827 2828 total_evicted += 2829 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2830 } else { 2831 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2832 total_evicted += bytes; 2833 2834 /* 2835 * If we couldn't evict our target number of bytes from 2836 * data, we try to get the rest from metadata. 2837 */ 2838 target -= bytes; 2839 2840 total_evicted += 2841 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2842 } 2843 2844 /* 2845 * Adjust MFU size 2846 * 2847 * Now that we've tried to evict enough from the MRU to get its 2848 * size back to arc_p, if we're still above the target cache 2849 * size, we evict the rest from the MFU. 2850 */ 2851 target = arc_size - arc_c; 2852 2853 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2854 arc_meta_used > arc_meta_min) { 2855 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2856 total_evicted += bytes; 2857 2858 /* 2859 * If we couldn't evict our target number of bytes from 2860 * metadata, we try to get the rest from data. 2861 */ 2862 target -= bytes; 2863 2864 total_evicted += 2865 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 2866 } else { 2867 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 2868 total_evicted += bytes; 2869 2870 /* 2871 * If we couldn't evict our target number of bytes from 2872 * data, we try to get the rest from data. 2873 */ 2874 target -= bytes; 2875 2876 total_evicted += 2877 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2878 } 2879 2880 /* 2881 * Adjust ghost lists 2882 * 2883 * In addition to the above, the ARC also defines target values 2884 * for the ghost lists. The sum of the mru list and mru ghost 2885 * list should never exceed the target size of the cache, and 2886 * the sum of the mru list, mfu list, mru ghost list, and mfu 2887 * ghost list should never exceed twice the target size of the 2888 * cache. The following logic enforces these limits on the ghost 2889 * caches, and evicts from them as needed. 2890 */ 2891 target = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2892 2893 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 2894 total_evicted += bytes; 2895 2896 target -= bytes; 2897 2898 total_evicted += 2899 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 2900 2901 /* 2902 * We assume the sum of the mru list and mfu list is less than 2903 * or equal to arc_c (we enforced this above), which means we 2904 * can use the simpler of the two equations below: 2905 * 2906 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 2907 * mru ghost + mfu ghost <= arc_c 2908 */ 2909 target = arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2910 2911 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 2912 total_evicted += bytes; 2913 2914 target -= bytes; 2915 2916 total_evicted += 2917 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 2918 2919 return (total_evicted); 2920 } 2921 2922 static void 2923 arc_do_user_evicts(void) 2924 { 2925 mutex_enter(&arc_user_evicts_lock); 2926 while (arc_eviction_list != NULL) { 2927 arc_buf_t *buf = arc_eviction_list; 2928 arc_eviction_list = buf->b_next; 2929 mutex_enter(&buf->b_evict_lock); 2930 buf->b_hdr = NULL; 2931 mutex_exit(&buf->b_evict_lock); 2932 mutex_exit(&arc_user_evicts_lock); 2933 2934 if (buf->b_efunc != NULL) 2935 VERIFY0(buf->b_efunc(buf->b_private)); 2936 2937 buf->b_efunc = NULL; 2938 buf->b_private = NULL; 2939 kmem_cache_free(buf_cache, buf); 2940 mutex_enter(&arc_user_evicts_lock); 2941 } 2942 mutex_exit(&arc_user_evicts_lock); 2943 } 2944 2945 void 2946 arc_flush(spa_t *spa, boolean_t retry) 2947 { 2948 uint64_t guid = 0; 2949 2950 /* 2951 * If retry is TRUE, a spa must not be specified since we have 2952 * no good way to determine if all of a spa's buffers have been 2953 * evicted from an arc state. 2954 */ 2955 ASSERT(!retry || spa == 0); 2956 2957 if (spa != NULL) 2958 guid = spa_load_guid(spa); 2959 2960 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 2961 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 2962 2963 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 2964 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 2965 2966 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 2967 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 2968 2969 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 2970 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 2971 2972 arc_do_user_evicts(); 2973 ASSERT(spa || arc_eviction_list == NULL); 2974 } 2975 2976 void 2977 arc_shrink(int64_t to_free) 2978 { 2979 if (arc_c > arc_c_min) { 2980 2981 if (arc_c > arc_c_min + to_free) 2982 atomic_add_64(&arc_c, -to_free); 2983 else 2984 arc_c = arc_c_min; 2985 2986 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2987 if (arc_c > arc_size) 2988 arc_c = MAX(arc_size, arc_c_min); 2989 if (arc_p > arc_c) 2990 arc_p = (arc_c >> 1); 2991 ASSERT(arc_c >= arc_c_min); 2992 ASSERT((int64_t)arc_p >= 0); 2993 } 2994 2995 if (arc_size > arc_c) 2996 (void) arc_adjust(); 2997 } 2998 2999 typedef enum free_memory_reason_t { 3000 FMR_UNKNOWN, 3001 FMR_NEEDFREE, 3002 FMR_LOTSFREE, 3003 FMR_SWAPFS_MINFREE, 3004 FMR_PAGES_PP_MAXIMUM, 3005 FMR_HEAP_ARENA, 3006 FMR_ZIO_ARENA, 3007 } free_memory_reason_t; 3008 3009 int64_t last_free_memory; 3010 free_memory_reason_t last_free_reason; 3011 3012 /* 3013 * Additional reserve of pages for pp_reserve. 3014 */ 3015 int64_t arc_pages_pp_reserve = 64; 3016 3017 /* 3018 * Additional reserve of pages for swapfs. 3019 */ 3020 int64_t arc_swapfs_reserve = 64; 3021 3022 /* 3023 * Return the amount of memory that can be consumed before reclaim will be 3024 * needed. Positive if there is sufficient free memory, negative indicates 3025 * the amount of memory that needs to be freed up. 3026 */ 3027 static int64_t 3028 arc_available_memory(void) 3029 { 3030 int64_t lowest = INT64_MAX; 3031 int64_t n; 3032 free_memory_reason_t r = FMR_UNKNOWN; 3033 3034 #ifdef _KERNEL 3035 if (needfree > 0) { 3036 n = PAGESIZE * (-needfree); 3037 if (n < lowest) { 3038 lowest = n; 3039 r = FMR_NEEDFREE; 3040 } 3041 } 3042 3043 /* 3044 * check that we're out of range of the pageout scanner. It starts to 3045 * schedule paging if freemem is less than lotsfree and needfree. 3046 * lotsfree is the high-water mark for pageout, and needfree is the 3047 * number of needed free pages. We add extra pages here to make sure 3048 * the scanner doesn't start up while we're freeing memory. 3049 */ 3050 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3051 if (n < lowest) { 3052 lowest = n; 3053 r = FMR_LOTSFREE; 3054 } 3055 3056 /* 3057 * check to make sure that swapfs has enough space so that anon 3058 * reservations can still succeed. anon_resvmem() checks that the 3059 * availrmem is greater than swapfs_minfree, and the number of reserved 3060 * swap pages. We also add a bit of extra here just to prevent 3061 * circumstances from getting really dire. 3062 */ 3063 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3064 desfree - arc_swapfs_reserve); 3065 if (n < lowest) { 3066 lowest = n; 3067 r = FMR_SWAPFS_MINFREE; 3068 } 3069 3070 3071 /* 3072 * Check that we have enough availrmem that memory locking (e.g., via 3073 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3074 * stores the number of pages that cannot be locked; when availrmem 3075 * drops below pages_pp_maximum, page locking mechanisms such as 3076 * page_pp_lock() will fail.) 3077 */ 3078 n = PAGESIZE * (availrmem - pages_pp_maximum - 3079 arc_pages_pp_reserve); 3080 if (n < lowest) { 3081 lowest = n; 3082 r = FMR_PAGES_PP_MAXIMUM; 3083 } 3084 3085 #if defined(__i386) 3086 /* 3087 * If we're on an i386 platform, it's possible that we'll exhaust the 3088 * kernel heap space before we ever run out of available physical 3089 * memory. Most checks of the size of the heap_area compare against 3090 * tune.t_minarmem, which is the minimum available real memory that we 3091 * can have in the system. However, this is generally fixed at 25 pages 3092 * which is so low that it's useless. In this comparison, we seek to 3093 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3094 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3095 * free) 3096 */ 3097 n = vmem_size(heap_arena, VMEM_FREE) - 3098 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3099 if (n < lowest) { 3100 lowest = n; 3101 r = FMR_HEAP_ARENA; 3102 } 3103 #endif 3104 3105 /* 3106 * If zio data pages are being allocated out of a separate heap segment, 3107 * then enforce that the size of available vmem for this arena remains 3108 * above about 1/16th free. 3109 * 3110 * Note: The 1/16th arena free requirement was put in place 3111 * to aggressively evict memory from the arc in order to avoid 3112 * memory fragmentation issues. 3113 */ 3114 if (zio_arena != NULL) { 3115 n = vmem_size(zio_arena, VMEM_FREE) - 3116 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3117 if (n < lowest) { 3118 lowest = n; 3119 r = FMR_ZIO_ARENA; 3120 } 3121 } 3122 #else 3123 /* Every 100 calls, free a small amount */ 3124 if (spa_get_random(100) == 0) 3125 lowest = -1024; 3126 #endif 3127 3128 last_free_memory = lowest; 3129 last_free_reason = r; 3130 3131 return (lowest); 3132 } 3133 3134 3135 /* 3136 * Determine if the system is under memory pressure and is asking 3137 * to reclaim memory. A return value of TRUE indicates that the system 3138 * is under memory pressure and that the arc should adjust accordingly. 3139 */ 3140 static boolean_t 3141 arc_reclaim_needed(void) 3142 { 3143 return (arc_available_memory() < 0); 3144 } 3145 3146 static void 3147 arc_kmem_reap_now(void) 3148 { 3149 size_t i; 3150 kmem_cache_t *prev_cache = NULL; 3151 kmem_cache_t *prev_data_cache = NULL; 3152 extern kmem_cache_t *zio_buf_cache[]; 3153 extern kmem_cache_t *zio_data_buf_cache[]; 3154 extern kmem_cache_t *range_seg_cache; 3155 3156 #ifdef _KERNEL 3157 if (arc_meta_used >= arc_meta_limit) { 3158 /* 3159 * We are exceeding our meta-data cache limit. 3160 * Purge some DNLC entries to release holds on meta-data. 3161 */ 3162 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3163 } 3164 #if defined(__i386) 3165 /* 3166 * Reclaim unused memory from all kmem caches. 3167 */ 3168 kmem_reap(); 3169 #endif 3170 #endif 3171 3172 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3173 if (zio_buf_cache[i] != prev_cache) { 3174 prev_cache = zio_buf_cache[i]; 3175 kmem_cache_reap_now(zio_buf_cache[i]); 3176 } 3177 if (zio_data_buf_cache[i] != prev_data_cache) { 3178 prev_data_cache = zio_data_buf_cache[i]; 3179 kmem_cache_reap_now(zio_data_buf_cache[i]); 3180 } 3181 } 3182 kmem_cache_reap_now(buf_cache); 3183 kmem_cache_reap_now(hdr_full_cache); 3184 kmem_cache_reap_now(hdr_l2only_cache); 3185 kmem_cache_reap_now(range_seg_cache); 3186 3187 if (zio_arena != NULL) { 3188 /* 3189 * Ask the vmem arena to reclaim unused memory from its 3190 * quantum caches. 3191 */ 3192 vmem_qcache_reap(zio_arena); 3193 } 3194 } 3195 3196 /* 3197 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3198 * enough data and signal them to proceed. When this happens, the threads in 3199 * arc_get_data_buf() are sleeping while holding the hash lock for their 3200 * particular arc header. Thus, we must be careful to never sleep on a 3201 * hash lock in this thread. This is to prevent the following deadlock: 3202 * 3203 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3204 * waiting for the reclaim thread to signal it. 3205 * 3206 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3207 * fails, and goes to sleep forever. 3208 * 3209 * This possible deadlock is avoided by always acquiring a hash lock 3210 * using mutex_tryenter() from arc_reclaim_thread(). 3211 */ 3212 static void 3213 arc_reclaim_thread(void) 3214 { 3215 clock_t growtime = 0; 3216 callb_cpr_t cpr; 3217 3218 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3219 3220 mutex_enter(&arc_reclaim_lock); 3221 while (!arc_reclaim_thread_exit) { 3222 int64_t free_memory = arc_available_memory(); 3223 uint64_t evicted = 0; 3224 3225 mutex_exit(&arc_reclaim_lock); 3226 3227 if (free_memory < 0) { 3228 3229 arc_no_grow = B_TRUE; 3230 arc_warm = B_TRUE; 3231 3232 /* 3233 * Wait at least zfs_grow_retry (default 60) seconds 3234 * before considering growing. 3235 */ 3236 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3237 3238 arc_kmem_reap_now(); 3239 3240 /* 3241 * If we are still low on memory, shrink the ARC 3242 * so that we have arc_shrink_min free space. 3243 */ 3244 free_memory = arc_available_memory(); 3245 3246 int64_t to_free = 3247 (arc_c >> arc_shrink_shift) - free_memory; 3248 if (to_free > 0) { 3249 #ifdef _KERNEL 3250 to_free = MAX(to_free, ptob(needfree)); 3251 #endif 3252 arc_shrink(to_free); 3253 } 3254 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3255 arc_no_grow = B_TRUE; 3256 } else if (ddi_get_lbolt() >= growtime) { 3257 arc_no_grow = B_FALSE; 3258 } 3259 3260 evicted = arc_adjust(); 3261 3262 mutex_enter(&arc_reclaim_lock); 3263 3264 /* 3265 * If evicted is zero, we couldn't evict anything via 3266 * arc_adjust(). This could be due to hash lock 3267 * collisions, but more likely due to the majority of 3268 * arc buffers being unevictable. Therefore, even if 3269 * arc_size is above arc_c, another pass is unlikely to 3270 * be helpful and could potentially cause us to enter an 3271 * infinite loop. 3272 */ 3273 if (arc_size <= arc_c || evicted == 0) { 3274 /* 3275 * We're either no longer overflowing, or we 3276 * can't evict anything more, so we should wake 3277 * up any threads before we go to sleep. 3278 */ 3279 cv_broadcast(&arc_reclaim_waiters_cv); 3280 3281 /* 3282 * Block until signaled, or after one second (we 3283 * might need to perform arc_kmem_reap_now() 3284 * even if we aren't being signalled) 3285 */ 3286 CALLB_CPR_SAFE_BEGIN(&cpr); 3287 (void) cv_timedwait(&arc_reclaim_thread_cv, 3288 &arc_reclaim_lock, ddi_get_lbolt() + hz); 3289 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3290 } 3291 } 3292 3293 arc_reclaim_thread_exit = FALSE; 3294 cv_broadcast(&arc_reclaim_thread_cv); 3295 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3296 thread_exit(); 3297 } 3298 3299 static void 3300 arc_user_evicts_thread(void) 3301 { 3302 callb_cpr_t cpr; 3303 3304 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3305 3306 mutex_enter(&arc_user_evicts_lock); 3307 while (!arc_user_evicts_thread_exit) { 3308 mutex_exit(&arc_user_evicts_lock); 3309 3310 arc_do_user_evicts(); 3311 3312 /* 3313 * This is necessary in order for the mdb ::arc dcmd to 3314 * show up to date information. Since the ::arc command 3315 * does not call the kstat's update function, without 3316 * this call, the command may show stale stats for the 3317 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3318 * with this change, the data might be up to 1 second 3319 * out of date; but that should suffice. The arc_state_t 3320 * structures can be queried directly if more accurate 3321 * information is needed. 3322 */ 3323 if (arc_ksp != NULL) 3324 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3325 3326 mutex_enter(&arc_user_evicts_lock); 3327 3328 /* 3329 * Block until signaled, or after one second (we need to 3330 * call the arc's kstat update function regularly). 3331 */ 3332 CALLB_CPR_SAFE_BEGIN(&cpr); 3333 (void) cv_timedwait(&arc_user_evicts_cv, 3334 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3335 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3336 } 3337 3338 arc_user_evicts_thread_exit = FALSE; 3339 cv_broadcast(&arc_user_evicts_cv); 3340 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3341 thread_exit(); 3342 } 3343 3344 /* 3345 * Adapt arc info given the number of bytes we are trying to add and 3346 * the state that we are comming from. This function is only called 3347 * when we are adding new content to the cache. 3348 */ 3349 static void 3350 arc_adapt(int bytes, arc_state_t *state) 3351 { 3352 int mult; 3353 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3354 3355 if (state == arc_l2c_only) 3356 return; 3357 3358 ASSERT(bytes > 0); 3359 /* 3360 * Adapt the target size of the MRU list: 3361 * - if we just hit in the MRU ghost list, then increase 3362 * the target size of the MRU list. 3363 * - if we just hit in the MFU ghost list, then increase 3364 * the target size of the MFU list by decreasing the 3365 * target size of the MRU list. 3366 */ 3367 if (state == arc_mru_ghost) { 3368 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 3369 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 3370 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3371 3372 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3373 } else if (state == arc_mfu_ghost) { 3374 uint64_t delta; 3375 3376 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 3377 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 3378 mult = MIN(mult, 10); 3379 3380 delta = MIN(bytes * mult, arc_p); 3381 arc_p = MAX(arc_p_min, arc_p - delta); 3382 } 3383 ASSERT((int64_t)arc_p >= 0); 3384 3385 if (arc_reclaim_needed()) { 3386 cv_signal(&arc_reclaim_thread_cv); 3387 return; 3388 } 3389 3390 if (arc_no_grow) 3391 return; 3392 3393 if (arc_c >= arc_c_max) 3394 return; 3395 3396 /* 3397 * If we're within (2 * maxblocksize) bytes of the target 3398 * cache size, increment the target cache size 3399 */ 3400 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3401 atomic_add_64(&arc_c, (int64_t)bytes); 3402 if (arc_c > arc_c_max) 3403 arc_c = arc_c_max; 3404 else if (state == arc_anon) 3405 atomic_add_64(&arc_p, (int64_t)bytes); 3406 if (arc_p > arc_c) 3407 arc_p = arc_c; 3408 } 3409 ASSERT((int64_t)arc_p >= 0); 3410 } 3411 3412 /* 3413 * Check if arc_size has grown past our upper threshold, determined by 3414 * zfs_arc_overflow_shift. 3415 */ 3416 static boolean_t 3417 arc_is_overflowing(void) 3418 { 3419 /* Always allow at least one block of overflow */ 3420 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3421 arc_c >> zfs_arc_overflow_shift); 3422 3423 return (arc_size >= arc_c + overflow); 3424 } 3425 3426 /* 3427 * The buffer, supplied as the first argument, needs a data block. If we 3428 * are hitting the hard limit for the cache size, we must sleep, waiting 3429 * for the eviction thread to catch up. If we're past the target size 3430 * but below the hard limit, we'll only signal the reclaim thread and 3431 * continue on. 3432 */ 3433 static void 3434 arc_get_data_buf(arc_buf_t *buf) 3435 { 3436 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3437 uint64_t size = buf->b_hdr->b_size; 3438 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3439 3440 arc_adapt(size, state); 3441 3442 /* 3443 * If arc_size is currently overflowing, and has grown past our 3444 * upper limit, we must be adding data faster than the evict 3445 * thread can evict. Thus, to ensure we don't compound the 3446 * problem by adding more data and forcing arc_size to grow even 3447 * further past it's target size, we halt and wait for the 3448 * eviction thread to catch up. 3449 * 3450 * It's also possible that the reclaim thread is unable to evict 3451 * enough buffers to get arc_size below the overflow limit (e.g. 3452 * due to buffers being un-evictable, or hash lock collisions). 3453 * In this case, we want to proceed regardless if we're 3454 * overflowing; thus we don't use a while loop here. 3455 */ 3456 if (arc_is_overflowing()) { 3457 mutex_enter(&arc_reclaim_lock); 3458 3459 /* 3460 * Now that we've acquired the lock, we may no longer be 3461 * over the overflow limit, lets check. 3462 * 3463 * We're ignoring the case of spurious wake ups. If that 3464 * were to happen, it'd let this thread consume an ARC 3465 * buffer before it should have (i.e. before we're under 3466 * the overflow limit and were signalled by the reclaim 3467 * thread). As long as that is a rare occurrence, it 3468 * shouldn't cause any harm. 3469 */ 3470 if (arc_is_overflowing()) { 3471 cv_signal(&arc_reclaim_thread_cv); 3472 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3473 } 3474 3475 mutex_exit(&arc_reclaim_lock); 3476 } 3477 3478 if (type == ARC_BUFC_METADATA) { 3479 buf->b_data = zio_buf_alloc(size); 3480 arc_space_consume(size, ARC_SPACE_META); 3481 } else { 3482 ASSERT(type == ARC_BUFC_DATA); 3483 buf->b_data = zio_data_buf_alloc(size); 3484 arc_space_consume(size, ARC_SPACE_DATA); 3485 } 3486 3487 /* 3488 * Update the state size. Note that ghost states have a 3489 * "ghost size" and so don't need to be updated. 3490 */ 3491 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3492 arc_buf_hdr_t *hdr = buf->b_hdr; 3493 3494 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_size, size); 3495 3496 /* 3497 * If this is reached via arc_read, the link is 3498 * protected by the hash lock. If reached via 3499 * arc_buf_alloc, the header should not be accessed by 3500 * any other thread. And, if reached via arc_read_done, 3501 * the hash lock will protect it if it's found in the 3502 * hash table; otherwise no other thread should be 3503 * trying to [add|remove]_reference it. 3504 */ 3505 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3506 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3507 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3508 size); 3509 } 3510 /* 3511 * If we are growing the cache, and we are adding anonymous 3512 * data, and we have outgrown arc_p, update arc_p 3513 */ 3514 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3515 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 3516 arc_p = MIN(arc_c, arc_p + size); 3517 } 3518 } 3519 3520 /* 3521 * This routine is called whenever a buffer is accessed. 3522 * NOTE: the hash lock is dropped in this function. 3523 */ 3524 static void 3525 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3526 { 3527 clock_t now; 3528 3529 ASSERT(MUTEX_HELD(hash_lock)); 3530 ASSERT(HDR_HAS_L1HDR(hdr)); 3531 3532 if (hdr->b_l1hdr.b_state == arc_anon) { 3533 /* 3534 * This buffer is not in the cache, and does not 3535 * appear in our "ghost" list. Add the new buffer 3536 * to the MRU state. 3537 */ 3538 3539 ASSERT0(hdr->b_l1hdr.b_arc_access); 3540 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3541 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3542 arc_change_state(arc_mru, hdr, hash_lock); 3543 3544 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3545 now = ddi_get_lbolt(); 3546 3547 /* 3548 * If this buffer is here because of a prefetch, then either: 3549 * - clear the flag if this is a "referencing" read 3550 * (any subsequent access will bump this into the MFU state). 3551 * or 3552 * - move the buffer to the head of the list if this is 3553 * another prefetch (to make it less likely to be evicted). 3554 */ 3555 if (HDR_PREFETCH(hdr)) { 3556 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3557 /* link protected by hash lock */ 3558 ASSERT(multilist_link_active( 3559 &hdr->b_l1hdr.b_arc_node)); 3560 } else { 3561 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3562 ARCSTAT_BUMP(arcstat_mru_hits); 3563 } 3564 hdr->b_l1hdr.b_arc_access = now; 3565 return; 3566 } 3567 3568 /* 3569 * This buffer has been "accessed" only once so far, 3570 * but it is still in the cache. Move it to the MFU 3571 * state. 3572 */ 3573 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3574 /* 3575 * More than 125ms have passed since we 3576 * instantiated this buffer. Move it to the 3577 * most frequently used state. 3578 */ 3579 hdr->b_l1hdr.b_arc_access = now; 3580 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3581 arc_change_state(arc_mfu, hdr, hash_lock); 3582 } 3583 ARCSTAT_BUMP(arcstat_mru_hits); 3584 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3585 arc_state_t *new_state; 3586 /* 3587 * This buffer has been "accessed" recently, but 3588 * was evicted from the cache. Move it to the 3589 * MFU state. 3590 */ 3591 3592 if (HDR_PREFETCH(hdr)) { 3593 new_state = arc_mru; 3594 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3595 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3596 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3597 } else { 3598 new_state = arc_mfu; 3599 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3600 } 3601 3602 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3603 arc_change_state(new_state, hdr, hash_lock); 3604 3605 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3606 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3607 /* 3608 * This buffer has been accessed more than once and is 3609 * still in the cache. Keep it in the MFU state. 3610 * 3611 * NOTE: an add_reference() that occurred when we did 3612 * the arc_read() will have kicked this off the list. 3613 * If it was a prefetch, we will explicitly move it to 3614 * the head of the list now. 3615 */ 3616 if ((HDR_PREFETCH(hdr)) != 0) { 3617 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3618 /* link protected by hash_lock */ 3619 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3620 } 3621 ARCSTAT_BUMP(arcstat_mfu_hits); 3622 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3623 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3624 arc_state_t *new_state = arc_mfu; 3625 /* 3626 * This buffer has been accessed more than once but has 3627 * been evicted from the cache. Move it back to the 3628 * MFU state. 3629 */ 3630 3631 if (HDR_PREFETCH(hdr)) { 3632 /* 3633 * This is a prefetch access... 3634 * move this block back to the MRU state. 3635 */ 3636 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3637 new_state = arc_mru; 3638 } 3639 3640 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3641 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3642 arc_change_state(new_state, hdr, hash_lock); 3643 3644 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3645 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3646 /* 3647 * This buffer is on the 2nd Level ARC. 3648 */ 3649 3650 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3651 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3652 arc_change_state(arc_mfu, hdr, hash_lock); 3653 } else { 3654 ASSERT(!"invalid arc state"); 3655 } 3656 } 3657 3658 /* a generic arc_done_func_t which you can use */ 3659 /* ARGSUSED */ 3660 void 3661 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3662 { 3663 if (zio == NULL || zio->io_error == 0) 3664 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3665 VERIFY(arc_buf_remove_ref(buf, arg)); 3666 } 3667 3668 /* a generic arc_done_func_t */ 3669 void 3670 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3671 { 3672 arc_buf_t **bufp = arg; 3673 if (zio && zio->io_error) { 3674 VERIFY(arc_buf_remove_ref(buf, arg)); 3675 *bufp = NULL; 3676 } else { 3677 *bufp = buf; 3678 ASSERT(buf->b_data); 3679 } 3680 } 3681 3682 static void 3683 arc_read_done(zio_t *zio) 3684 { 3685 arc_buf_hdr_t *hdr; 3686 arc_buf_t *buf; 3687 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3688 kmutex_t *hash_lock = NULL; 3689 arc_callback_t *callback_list, *acb; 3690 int freeable = FALSE; 3691 3692 buf = zio->io_private; 3693 hdr = buf->b_hdr; 3694 3695 /* 3696 * The hdr was inserted into hash-table and removed from lists 3697 * prior to starting I/O. We should find this header, since 3698 * it's in the hash table, and it should be legit since it's 3699 * not possible to evict it during the I/O. The only possible 3700 * reason for it not to be found is if we were freed during the 3701 * read. 3702 */ 3703 if (HDR_IN_HASH_TABLE(hdr)) { 3704 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3705 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3706 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3707 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3708 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3709 3710 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3711 &hash_lock); 3712 3713 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3714 hash_lock == NULL) || 3715 (found == hdr && 3716 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3717 (found == hdr && HDR_L2_READING(hdr))); 3718 } 3719 3720 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3721 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3722 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3723 3724 /* byteswap if necessary */ 3725 callback_list = hdr->b_l1hdr.b_acb; 3726 ASSERT(callback_list != NULL); 3727 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3728 dmu_object_byteswap_t bswap = 3729 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3730 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3731 byteswap_uint64_array : 3732 dmu_ot_byteswap[bswap].ob_func; 3733 func(buf->b_data, hdr->b_size); 3734 } 3735 3736 arc_cksum_compute(buf, B_FALSE); 3737 arc_buf_watch(buf); 3738 3739 if (hash_lock && zio->io_error == 0 && 3740 hdr->b_l1hdr.b_state == arc_anon) { 3741 /* 3742 * Only call arc_access on anonymous buffers. This is because 3743 * if we've issued an I/O for an evicted buffer, we've already 3744 * called arc_access (to prevent any simultaneous readers from 3745 * getting confused). 3746 */ 3747 arc_access(hdr, hash_lock); 3748 } 3749 3750 /* create copies of the data buffer for the callers */ 3751 abuf = buf; 3752 for (acb = callback_list; acb; acb = acb->acb_next) { 3753 if (acb->acb_done) { 3754 if (abuf == NULL) { 3755 ARCSTAT_BUMP(arcstat_duplicate_reads); 3756 abuf = arc_buf_clone(buf); 3757 } 3758 acb->acb_buf = abuf; 3759 abuf = NULL; 3760 } 3761 } 3762 hdr->b_l1hdr.b_acb = NULL; 3763 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3764 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3765 if (abuf == buf) { 3766 ASSERT(buf->b_efunc == NULL); 3767 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3768 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3769 } 3770 3771 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3772 callback_list != NULL); 3773 3774 if (zio->io_error != 0) { 3775 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3776 if (hdr->b_l1hdr.b_state != arc_anon) 3777 arc_change_state(arc_anon, hdr, hash_lock); 3778 if (HDR_IN_HASH_TABLE(hdr)) 3779 buf_hash_remove(hdr); 3780 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3781 } 3782 3783 /* 3784 * Broadcast before we drop the hash_lock to avoid the possibility 3785 * that the hdr (and hence the cv) might be freed before we get to 3786 * the cv_broadcast(). 3787 */ 3788 cv_broadcast(&hdr->b_l1hdr.b_cv); 3789 3790 if (hash_lock != NULL) { 3791 mutex_exit(hash_lock); 3792 } else { 3793 /* 3794 * This block was freed while we waited for the read to 3795 * complete. It has been removed from the hash table and 3796 * moved to the anonymous state (so that it won't show up 3797 * in the cache). 3798 */ 3799 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3800 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3801 } 3802 3803 /* execute each callback and free its structure */ 3804 while ((acb = callback_list) != NULL) { 3805 if (acb->acb_done) 3806 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3807 3808 if (acb->acb_zio_dummy != NULL) { 3809 acb->acb_zio_dummy->io_error = zio->io_error; 3810 zio_nowait(acb->acb_zio_dummy); 3811 } 3812 3813 callback_list = acb->acb_next; 3814 kmem_free(acb, sizeof (arc_callback_t)); 3815 } 3816 3817 if (freeable) 3818 arc_hdr_destroy(hdr); 3819 } 3820 3821 /* 3822 * "Read" the block at the specified DVA (in bp) via the 3823 * cache. If the block is found in the cache, invoke the provided 3824 * callback immediately and return. Note that the `zio' parameter 3825 * in the callback will be NULL in this case, since no IO was 3826 * required. If the block is not in the cache pass the read request 3827 * on to the spa with a substitute callback function, so that the 3828 * requested block will be added to the cache. 3829 * 3830 * If a read request arrives for a block that has a read in-progress, 3831 * either wait for the in-progress read to complete (and return the 3832 * results); or, if this is a read with a "done" func, add a record 3833 * to the read to invoke the "done" func when the read completes, 3834 * and return; or just return. 3835 * 3836 * arc_read_done() will invoke all the requested "done" functions 3837 * for readers of this block. 3838 */ 3839 int 3840 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3841 void *private, zio_priority_t priority, int zio_flags, 3842 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3843 { 3844 arc_buf_hdr_t *hdr = NULL; 3845 arc_buf_t *buf = NULL; 3846 kmutex_t *hash_lock = NULL; 3847 zio_t *rzio; 3848 uint64_t guid = spa_load_guid(spa); 3849 3850 ASSERT(!BP_IS_EMBEDDED(bp) || 3851 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3852 3853 top: 3854 if (!BP_IS_EMBEDDED(bp)) { 3855 /* 3856 * Embedded BP's have no DVA and require no I/O to "read". 3857 * Create an anonymous arc buf to back it. 3858 */ 3859 hdr = buf_hash_find(guid, bp, &hash_lock); 3860 } 3861 3862 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 3863 3864 *arc_flags |= ARC_FLAG_CACHED; 3865 3866 if (HDR_IO_IN_PROGRESS(hdr)) { 3867 3868 if (*arc_flags & ARC_FLAG_WAIT) { 3869 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 3870 mutex_exit(hash_lock); 3871 goto top; 3872 } 3873 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3874 3875 if (done) { 3876 arc_callback_t *acb = NULL; 3877 3878 acb = kmem_zalloc(sizeof (arc_callback_t), 3879 KM_SLEEP); 3880 acb->acb_done = done; 3881 acb->acb_private = private; 3882 if (pio != NULL) 3883 acb->acb_zio_dummy = zio_null(pio, 3884 spa, NULL, NULL, NULL, zio_flags); 3885 3886 ASSERT(acb->acb_done != NULL); 3887 acb->acb_next = hdr->b_l1hdr.b_acb; 3888 hdr->b_l1hdr.b_acb = acb; 3889 add_reference(hdr, hash_lock, private); 3890 mutex_exit(hash_lock); 3891 return (0); 3892 } 3893 mutex_exit(hash_lock); 3894 return (0); 3895 } 3896 3897 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3898 hdr->b_l1hdr.b_state == arc_mfu); 3899 3900 if (done) { 3901 add_reference(hdr, hash_lock, private); 3902 /* 3903 * If this block is already in use, create a new 3904 * copy of the data so that we will be guaranteed 3905 * that arc_release() will always succeed. 3906 */ 3907 buf = hdr->b_l1hdr.b_buf; 3908 ASSERT(buf); 3909 ASSERT(buf->b_data); 3910 if (HDR_BUF_AVAILABLE(hdr)) { 3911 ASSERT(buf->b_efunc == NULL); 3912 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3913 } else { 3914 buf = arc_buf_clone(buf); 3915 } 3916 3917 } else if (*arc_flags & ARC_FLAG_PREFETCH && 3918 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3919 hdr->b_flags |= ARC_FLAG_PREFETCH; 3920 } 3921 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 3922 arc_access(hdr, hash_lock); 3923 if (*arc_flags & ARC_FLAG_L2CACHE) 3924 hdr->b_flags |= ARC_FLAG_L2CACHE; 3925 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3926 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3927 mutex_exit(hash_lock); 3928 ARCSTAT_BUMP(arcstat_hits); 3929 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 3930 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 3931 data, metadata, hits); 3932 3933 if (done) 3934 done(NULL, buf, private); 3935 } else { 3936 uint64_t size = BP_GET_LSIZE(bp); 3937 arc_callback_t *acb; 3938 vdev_t *vd = NULL; 3939 uint64_t addr = 0; 3940 boolean_t devw = B_FALSE; 3941 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 3942 int32_t b_asize = 0; 3943 3944 if (hdr == NULL) { 3945 /* this block is not in the cache */ 3946 arc_buf_hdr_t *exists = NULL; 3947 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 3948 buf = arc_buf_alloc(spa, size, private, type); 3949 hdr = buf->b_hdr; 3950 if (!BP_IS_EMBEDDED(bp)) { 3951 hdr->b_dva = *BP_IDENTITY(bp); 3952 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 3953 exists = buf_hash_insert(hdr, &hash_lock); 3954 } 3955 if (exists != NULL) { 3956 /* somebody beat us to the hash insert */ 3957 mutex_exit(hash_lock); 3958 buf_discard_identity(hdr); 3959 (void) arc_buf_remove_ref(buf, private); 3960 goto top; /* restart the IO request */ 3961 } 3962 3963 /* if this is a prefetch, we don't have a reference */ 3964 if (*arc_flags & ARC_FLAG_PREFETCH) { 3965 (void) remove_reference(hdr, hash_lock, 3966 private); 3967 hdr->b_flags |= ARC_FLAG_PREFETCH; 3968 } 3969 if (*arc_flags & ARC_FLAG_L2CACHE) 3970 hdr->b_flags |= ARC_FLAG_L2CACHE; 3971 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3972 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3973 if (BP_GET_LEVEL(bp) > 0) 3974 hdr->b_flags |= ARC_FLAG_INDIRECT; 3975 } else { 3976 /* 3977 * This block is in the ghost cache. If it was L2-only 3978 * (and thus didn't have an L1 hdr), we realloc the 3979 * header to add an L1 hdr. 3980 */ 3981 if (!HDR_HAS_L1HDR(hdr)) { 3982 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 3983 hdr_full_cache); 3984 } 3985 3986 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 3987 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3988 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3989 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3990 3991 /* if this is a prefetch, we don't have a reference */ 3992 if (*arc_flags & ARC_FLAG_PREFETCH) 3993 hdr->b_flags |= ARC_FLAG_PREFETCH; 3994 else 3995 add_reference(hdr, hash_lock, private); 3996 if (*arc_flags & ARC_FLAG_L2CACHE) 3997 hdr->b_flags |= ARC_FLAG_L2CACHE; 3998 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3999 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4000 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4001 buf->b_hdr = hdr; 4002 buf->b_data = NULL; 4003 buf->b_efunc = NULL; 4004 buf->b_private = NULL; 4005 buf->b_next = NULL; 4006 hdr->b_l1hdr.b_buf = buf; 4007 ASSERT0(hdr->b_l1hdr.b_datacnt); 4008 hdr->b_l1hdr.b_datacnt = 1; 4009 arc_get_data_buf(buf); 4010 arc_access(hdr, hash_lock); 4011 } 4012 4013 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4014 4015 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4016 acb->acb_done = done; 4017 acb->acb_private = private; 4018 4019 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4020 hdr->b_l1hdr.b_acb = acb; 4021 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4022 4023 if (HDR_HAS_L2HDR(hdr) && 4024 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4025 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4026 addr = hdr->b_l2hdr.b_daddr; 4027 b_compress = HDR_GET_COMPRESS(hdr); 4028 b_asize = hdr->b_l2hdr.b_asize; 4029 /* 4030 * Lock out device removal. 4031 */ 4032 if (vdev_is_dead(vd) || 4033 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4034 vd = NULL; 4035 } 4036 4037 if (hash_lock != NULL) 4038 mutex_exit(hash_lock); 4039 4040 /* 4041 * At this point, we have a level 1 cache miss. Try again in 4042 * L2ARC if possible. 4043 */ 4044 ASSERT3U(hdr->b_size, ==, size); 4045 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4046 uint64_t, size, zbookmark_phys_t *, zb); 4047 ARCSTAT_BUMP(arcstat_misses); 4048 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4049 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4050 data, metadata, misses); 4051 4052 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4053 /* 4054 * Read from the L2ARC if the following are true: 4055 * 1. The L2ARC vdev was previously cached. 4056 * 2. This buffer still has L2ARC metadata. 4057 * 3. This buffer isn't currently writing to the L2ARC. 4058 * 4. The L2ARC entry wasn't evicted, which may 4059 * also have invalidated the vdev. 4060 * 5. This isn't prefetch and l2arc_noprefetch is set. 4061 */ 4062 if (HDR_HAS_L2HDR(hdr) && 4063 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4064 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4065 l2arc_read_callback_t *cb; 4066 4067 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4068 ARCSTAT_BUMP(arcstat_l2_hits); 4069 4070 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4071 KM_SLEEP); 4072 cb->l2rcb_buf = buf; 4073 cb->l2rcb_spa = spa; 4074 cb->l2rcb_bp = *bp; 4075 cb->l2rcb_zb = *zb; 4076 cb->l2rcb_flags = zio_flags; 4077 cb->l2rcb_compress = b_compress; 4078 4079 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4080 addr + size < vd->vdev_psize - 4081 VDEV_LABEL_END_SIZE); 4082 4083 /* 4084 * l2arc read. The SCL_L2ARC lock will be 4085 * released by l2arc_read_done(). 4086 * Issue a null zio if the underlying buffer 4087 * was squashed to zero size by compression. 4088 */ 4089 if (b_compress == ZIO_COMPRESS_EMPTY) { 4090 rzio = zio_null(pio, spa, vd, 4091 l2arc_read_done, cb, 4092 zio_flags | ZIO_FLAG_DONT_CACHE | 4093 ZIO_FLAG_CANFAIL | 4094 ZIO_FLAG_DONT_PROPAGATE | 4095 ZIO_FLAG_DONT_RETRY); 4096 } else { 4097 rzio = zio_read_phys(pio, vd, addr, 4098 b_asize, buf->b_data, 4099 ZIO_CHECKSUM_OFF, 4100 l2arc_read_done, cb, priority, 4101 zio_flags | ZIO_FLAG_DONT_CACHE | 4102 ZIO_FLAG_CANFAIL | 4103 ZIO_FLAG_DONT_PROPAGATE | 4104 ZIO_FLAG_DONT_RETRY, B_FALSE); 4105 } 4106 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4107 zio_t *, rzio); 4108 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4109 4110 if (*arc_flags & ARC_FLAG_NOWAIT) { 4111 zio_nowait(rzio); 4112 return (0); 4113 } 4114 4115 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4116 if (zio_wait(rzio) == 0) 4117 return (0); 4118 4119 /* l2arc read error; goto zio_read() */ 4120 } else { 4121 DTRACE_PROBE1(l2arc__miss, 4122 arc_buf_hdr_t *, hdr); 4123 ARCSTAT_BUMP(arcstat_l2_misses); 4124 if (HDR_L2_WRITING(hdr)) 4125 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4126 spa_config_exit(spa, SCL_L2ARC, vd); 4127 } 4128 } else { 4129 if (vd != NULL) 4130 spa_config_exit(spa, SCL_L2ARC, vd); 4131 if (l2arc_ndev != 0) { 4132 DTRACE_PROBE1(l2arc__miss, 4133 arc_buf_hdr_t *, hdr); 4134 ARCSTAT_BUMP(arcstat_l2_misses); 4135 } 4136 } 4137 4138 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4139 arc_read_done, buf, priority, zio_flags, zb); 4140 4141 if (*arc_flags & ARC_FLAG_WAIT) 4142 return (zio_wait(rzio)); 4143 4144 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4145 zio_nowait(rzio); 4146 } 4147 return (0); 4148 } 4149 4150 void 4151 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4152 { 4153 ASSERT(buf->b_hdr != NULL); 4154 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4155 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4156 func == NULL); 4157 ASSERT(buf->b_efunc == NULL); 4158 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4159 4160 buf->b_efunc = func; 4161 buf->b_private = private; 4162 } 4163 4164 /* 4165 * Notify the arc that a block was freed, and thus will never be used again. 4166 */ 4167 void 4168 arc_freed(spa_t *spa, const blkptr_t *bp) 4169 { 4170 arc_buf_hdr_t *hdr; 4171 kmutex_t *hash_lock; 4172 uint64_t guid = spa_load_guid(spa); 4173 4174 ASSERT(!BP_IS_EMBEDDED(bp)); 4175 4176 hdr = buf_hash_find(guid, bp, &hash_lock); 4177 if (hdr == NULL) 4178 return; 4179 if (HDR_BUF_AVAILABLE(hdr)) { 4180 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4181 add_reference(hdr, hash_lock, FTAG); 4182 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4183 mutex_exit(hash_lock); 4184 4185 arc_release(buf, FTAG); 4186 (void) arc_buf_remove_ref(buf, FTAG); 4187 } else { 4188 mutex_exit(hash_lock); 4189 } 4190 4191 } 4192 4193 /* 4194 * Clear the user eviction callback set by arc_set_callback(), first calling 4195 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4196 * clearing the callback may result in the arc_buf being destroyed. However, 4197 * it will not result in the *last* arc_buf being destroyed, hence the data 4198 * will remain cached in the ARC. We make a copy of the arc buffer here so 4199 * that we can process the callback without holding any locks. 4200 * 4201 * It's possible that the callback is already in the process of being cleared 4202 * by another thread. In this case we can not clear the callback. 4203 * 4204 * Returns B_TRUE if the callback was successfully called and cleared. 4205 */ 4206 boolean_t 4207 arc_clear_callback(arc_buf_t *buf) 4208 { 4209 arc_buf_hdr_t *hdr; 4210 kmutex_t *hash_lock; 4211 arc_evict_func_t *efunc = buf->b_efunc; 4212 void *private = buf->b_private; 4213 4214 mutex_enter(&buf->b_evict_lock); 4215 hdr = buf->b_hdr; 4216 if (hdr == NULL) { 4217 /* 4218 * We are in arc_do_user_evicts(). 4219 */ 4220 ASSERT(buf->b_data == NULL); 4221 mutex_exit(&buf->b_evict_lock); 4222 return (B_FALSE); 4223 } else if (buf->b_data == NULL) { 4224 /* 4225 * We are on the eviction list; process this buffer now 4226 * but let arc_do_user_evicts() do the reaping. 4227 */ 4228 buf->b_efunc = NULL; 4229 mutex_exit(&buf->b_evict_lock); 4230 VERIFY0(efunc(private)); 4231 return (B_TRUE); 4232 } 4233 hash_lock = HDR_LOCK(hdr); 4234 mutex_enter(hash_lock); 4235 hdr = buf->b_hdr; 4236 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4237 4238 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4239 hdr->b_l1hdr.b_datacnt); 4240 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4241 hdr->b_l1hdr.b_state == arc_mfu); 4242 4243 buf->b_efunc = NULL; 4244 buf->b_private = NULL; 4245 4246 if (hdr->b_l1hdr.b_datacnt > 1) { 4247 mutex_exit(&buf->b_evict_lock); 4248 arc_buf_destroy(buf, TRUE); 4249 } else { 4250 ASSERT(buf == hdr->b_l1hdr.b_buf); 4251 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4252 mutex_exit(&buf->b_evict_lock); 4253 } 4254 4255 mutex_exit(hash_lock); 4256 VERIFY0(efunc(private)); 4257 return (B_TRUE); 4258 } 4259 4260 /* 4261 * Release this buffer from the cache, making it an anonymous buffer. This 4262 * must be done after a read and prior to modifying the buffer contents. 4263 * If the buffer has more than one reference, we must make 4264 * a new hdr for the buffer. 4265 */ 4266 void 4267 arc_release(arc_buf_t *buf, void *tag) 4268 { 4269 arc_buf_hdr_t *hdr = buf->b_hdr; 4270 4271 /* 4272 * It would be nice to assert that if it's DMU metadata (level > 4273 * 0 || it's the dnode file), then it must be syncing context. 4274 * But we don't know that information at this level. 4275 */ 4276 4277 mutex_enter(&buf->b_evict_lock); 4278 4279 ASSERT(HDR_HAS_L1HDR(hdr)); 4280 4281 /* 4282 * We don't grab the hash lock prior to this check, because if 4283 * the buffer's header is in the arc_anon state, it won't be 4284 * linked into the hash table. 4285 */ 4286 if (hdr->b_l1hdr.b_state == arc_anon) { 4287 mutex_exit(&buf->b_evict_lock); 4288 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4289 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4290 ASSERT(!HDR_HAS_L2HDR(hdr)); 4291 ASSERT(BUF_EMPTY(hdr)); 4292 4293 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4294 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4295 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4296 4297 ASSERT3P(buf->b_efunc, ==, NULL); 4298 ASSERT3P(buf->b_private, ==, NULL); 4299 4300 hdr->b_l1hdr.b_arc_access = 0; 4301 arc_buf_thaw(buf); 4302 4303 return; 4304 } 4305 4306 kmutex_t *hash_lock = HDR_LOCK(hdr); 4307 mutex_enter(hash_lock); 4308 4309 /* 4310 * This assignment is only valid as long as the hash_lock is 4311 * held, we must be careful not to reference state or the 4312 * b_state field after dropping the lock. 4313 */ 4314 arc_state_t *state = hdr->b_l1hdr.b_state; 4315 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4316 ASSERT3P(state, !=, arc_anon); 4317 4318 /* this buffer is not on any list */ 4319 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4320 4321 if (HDR_HAS_L2HDR(hdr)) { 4322 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 4323 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 4324 4325 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4326 list_remove(&hdr->b_l2hdr.b_dev->l2ad_buflist, hdr); 4327 4328 /* 4329 * We don't want to leak the b_tmp_cdata buffer that was 4330 * allocated in l2arc_write_buffers() 4331 */ 4332 arc_buf_l2_cdata_free(hdr); 4333 4334 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4335 4336 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 4337 } 4338 4339 /* 4340 * Do we have more than one buf? 4341 */ 4342 if (hdr->b_l1hdr.b_datacnt > 1) { 4343 arc_buf_hdr_t *nhdr; 4344 arc_buf_t **bufp; 4345 uint64_t blksz = hdr->b_size; 4346 uint64_t spa = hdr->b_spa; 4347 arc_buf_contents_t type = arc_buf_type(hdr); 4348 uint32_t flags = hdr->b_flags; 4349 4350 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4351 /* 4352 * Pull the data off of this hdr and attach it to 4353 * a new anonymous hdr. 4354 */ 4355 (void) remove_reference(hdr, hash_lock, tag); 4356 bufp = &hdr->b_l1hdr.b_buf; 4357 while (*bufp != buf) 4358 bufp = &(*bufp)->b_next; 4359 *bufp = buf->b_next; 4360 buf->b_next = NULL; 4361 4362 ASSERT3P(state, !=, arc_l2c_only); 4363 ASSERT3U(state->arcs_size, >=, hdr->b_size); 4364 atomic_add_64(&state->arcs_size, -hdr->b_size); 4365 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4366 ASSERT3P(state, !=, arc_l2c_only); 4367 uint64_t *size = &state->arcs_lsize[type]; 4368 ASSERT3U(*size, >=, hdr->b_size); 4369 atomic_add_64(size, -hdr->b_size); 4370 } 4371 4372 /* 4373 * We're releasing a duplicate user data buffer, update 4374 * our statistics accordingly. 4375 */ 4376 if (HDR_ISTYPE_DATA(hdr)) { 4377 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4378 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4379 -hdr->b_size); 4380 } 4381 hdr->b_l1hdr.b_datacnt -= 1; 4382 arc_cksum_verify(buf); 4383 arc_buf_unwatch(buf); 4384 4385 mutex_exit(hash_lock); 4386 4387 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4388 nhdr->b_size = blksz; 4389 nhdr->b_spa = spa; 4390 4391 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4392 nhdr->b_flags |= arc_bufc_to_flags(type); 4393 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4394 4395 nhdr->b_l1hdr.b_buf = buf; 4396 nhdr->b_l1hdr.b_datacnt = 1; 4397 nhdr->b_l1hdr.b_state = arc_anon; 4398 nhdr->b_l1hdr.b_arc_access = 0; 4399 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4400 nhdr->b_freeze_cksum = NULL; 4401 4402 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4403 buf->b_hdr = nhdr; 4404 mutex_exit(&buf->b_evict_lock); 4405 atomic_add_64(&arc_anon->arcs_size, blksz); 4406 } else { 4407 mutex_exit(&buf->b_evict_lock); 4408 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4409 /* protected by hash lock, or hdr is on arc_anon */ 4410 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4411 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4412 arc_change_state(arc_anon, hdr, hash_lock); 4413 hdr->b_l1hdr.b_arc_access = 0; 4414 mutex_exit(hash_lock); 4415 4416 buf_discard_identity(hdr); 4417 arc_buf_thaw(buf); 4418 } 4419 buf->b_efunc = NULL; 4420 buf->b_private = NULL; 4421 } 4422 4423 int 4424 arc_released(arc_buf_t *buf) 4425 { 4426 int released; 4427 4428 mutex_enter(&buf->b_evict_lock); 4429 released = (buf->b_data != NULL && 4430 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4431 mutex_exit(&buf->b_evict_lock); 4432 return (released); 4433 } 4434 4435 #ifdef ZFS_DEBUG 4436 int 4437 arc_referenced(arc_buf_t *buf) 4438 { 4439 int referenced; 4440 4441 mutex_enter(&buf->b_evict_lock); 4442 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4443 mutex_exit(&buf->b_evict_lock); 4444 return (referenced); 4445 } 4446 #endif 4447 4448 static void 4449 arc_write_ready(zio_t *zio) 4450 { 4451 arc_write_callback_t *callback = zio->io_private; 4452 arc_buf_t *buf = callback->awcb_buf; 4453 arc_buf_hdr_t *hdr = buf->b_hdr; 4454 4455 ASSERT(HDR_HAS_L1HDR(hdr)); 4456 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4457 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4458 callback->awcb_ready(zio, buf, callback->awcb_private); 4459 4460 /* 4461 * If the IO is already in progress, then this is a re-write 4462 * attempt, so we need to thaw and re-compute the cksum. 4463 * It is the responsibility of the callback to handle the 4464 * accounting for any re-write attempt. 4465 */ 4466 if (HDR_IO_IN_PROGRESS(hdr)) { 4467 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4468 if (hdr->b_freeze_cksum != NULL) { 4469 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4470 hdr->b_freeze_cksum = NULL; 4471 } 4472 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4473 } 4474 arc_cksum_compute(buf, B_FALSE); 4475 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4476 } 4477 4478 /* 4479 * The SPA calls this callback for each physical write that happens on behalf 4480 * of a logical write. See the comment in dbuf_write_physdone() for details. 4481 */ 4482 static void 4483 arc_write_physdone(zio_t *zio) 4484 { 4485 arc_write_callback_t *cb = zio->io_private; 4486 if (cb->awcb_physdone != NULL) 4487 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4488 } 4489 4490 static void 4491 arc_write_done(zio_t *zio) 4492 { 4493 arc_write_callback_t *callback = zio->io_private; 4494 arc_buf_t *buf = callback->awcb_buf; 4495 arc_buf_hdr_t *hdr = buf->b_hdr; 4496 4497 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4498 4499 if (zio->io_error == 0) { 4500 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4501 buf_discard_identity(hdr); 4502 } else { 4503 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4504 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4505 } 4506 } else { 4507 ASSERT(BUF_EMPTY(hdr)); 4508 } 4509 4510 /* 4511 * If the block to be written was all-zero or compressed enough to be 4512 * embedded in the BP, no write was performed so there will be no 4513 * dva/birth/checksum. The buffer must therefore remain anonymous 4514 * (and uncached). 4515 */ 4516 if (!BUF_EMPTY(hdr)) { 4517 arc_buf_hdr_t *exists; 4518 kmutex_t *hash_lock; 4519 4520 ASSERT(zio->io_error == 0); 4521 4522 arc_cksum_verify(buf); 4523 4524 exists = buf_hash_insert(hdr, &hash_lock); 4525 if (exists != NULL) { 4526 /* 4527 * This can only happen if we overwrite for 4528 * sync-to-convergence, because we remove 4529 * buffers from the hash table when we arc_free(). 4530 */ 4531 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4532 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4533 panic("bad overwrite, hdr=%p exists=%p", 4534 (void *)hdr, (void *)exists); 4535 ASSERT(refcount_is_zero( 4536 &exists->b_l1hdr.b_refcnt)); 4537 arc_change_state(arc_anon, exists, hash_lock); 4538 mutex_exit(hash_lock); 4539 arc_hdr_destroy(exists); 4540 exists = buf_hash_insert(hdr, &hash_lock); 4541 ASSERT3P(exists, ==, NULL); 4542 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4543 /* nopwrite */ 4544 ASSERT(zio->io_prop.zp_nopwrite); 4545 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4546 panic("bad nopwrite, hdr=%p exists=%p", 4547 (void *)hdr, (void *)exists); 4548 } else { 4549 /* Dedup */ 4550 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4551 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4552 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4553 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4554 } 4555 } 4556 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4557 /* if it's not anon, we are doing a scrub */ 4558 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4559 arc_access(hdr, hash_lock); 4560 mutex_exit(hash_lock); 4561 } else { 4562 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4563 } 4564 4565 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4566 callback->awcb_done(zio, buf, callback->awcb_private); 4567 4568 kmem_free(callback, sizeof (arc_write_callback_t)); 4569 } 4570 4571 zio_t * 4572 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4573 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4574 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4575 arc_done_func_t *done, void *private, zio_priority_t priority, 4576 int zio_flags, const zbookmark_phys_t *zb) 4577 { 4578 arc_buf_hdr_t *hdr = buf->b_hdr; 4579 arc_write_callback_t *callback; 4580 zio_t *zio; 4581 4582 ASSERT(ready != NULL); 4583 ASSERT(done != NULL); 4584 ASSERT(!HDR_IO_ERROR(hdr)); 4585 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4586 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4587 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4588 if (l2arc) 4589 hdr->b_flags |= ARC_FLAG_L2CACHE; 4590 if (l2arc_compress) 4591 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4592 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4593 callback->awcb_ready = ready; 4594 callback->awcb_physdone = physdone; 4595 callback->awcb_done = done; 4596 callback->awcb_private = private; 4597 callback->awcb_buf = buf; 4598 4599 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4600 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4601 priority, zio_flags, zb); 4602 4603 return (zio); 4604 } 4605 4606 static int 4607 arc_memory_throttle(uint64_t reserve, uint64_t txg) 4608 { 4609 #ifdef _KERNEL 4610 uint64_t available_memory = ptob(freemem); 4611 static uint64_t page_load = 0; 4612 static uint64_t last_txg = 0; 4613 4614 #if defined(__i386) 4615 available_memory = 4616 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 4617 #endif 4618 4619 if (freemem > physmem * arc_lotsfree_percent / 100) 4620 return (0); 4621 4622 if (txg > last_txg) { 4623 last_txg = txg; 4624 page_load = 0; 4625 } 4626 /* 4627 * If we are in pageout, we know that memory is already tight, 4628 * the arc is already going to be evicting, so we just want to 4629 * continue to let page writes occur as quickly as possible. 4630 */ 4631 if (curproc == proc_pageout) { 4632 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4633 return (SET_ERROR(ERESTART)); 4634 /* Note: reserve is inflated, so we deflate */ 4635 page_load += reserve / 8; 4636 return (0); 4637 } else if (page_load > 0 && arc_reclaim_needed()) { 4638 /* memory is low, delay before restarting */ 4639 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4640 return (SET_ERROR(EAGAIN)); 4641 } 4642 page_load = 0; 4643 #endif 4644 return (0); 4645 } 4646 4647 void 4648 arc_tempreserve_clear(uint64_t reserve) 4649 { 4650 atomic_add_64(&arc_tempreserve, -reserve); 4651 ASSERT((int64_t)arc_tempreserve >= 0); 4652 } 4653 4654 int 4655 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4656 { 4657 int error; 4658 uint64_t anon_size; 4659 4660 if (reserve > arc_c/4 && !arc_no_grow) 4661 arc_c = MIN(arc_c_max, reserve * 4); 4662 if (reserve > arc_c) 4663 return (SET_ERROR(ENOMEM)); 4664 4665 /* 4666 * Don't count loaned bufs as in flight dirty data to prevent long 4667 * network delays from blocking transactions that are ready to be 4668 * assigned to a txg. 4669 */ 4670 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 4671 4672 /* 4673 * Writes will, almost always, require additional memory allocations 4674 * in order to compress/encrypt/etc the data. We therefore need to 4675 * make sure that there is sufficient available memory for this. 4676 */ 4677 error = arc_memory_throttle(reserve, txg); 4678 if (error != 0) 4679 return (error); 4680 4681 /* 4682 * Throttle writes when the amount of dirty data in the cache 4683 * gets too large. We try to keep the cache less than half full 4684 * of dirty blocks so that our sync times don't grow too large. 4685 * Note: if two requests come in concurrently, we might let them 4686 * both succeed, when one of them should fail. Not a huge deal. 4687 */ 4688 4689 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4690 anon_size > arc_c / 4) { 4691 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4692 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4693 arc_tempreserve>>10, 4694 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4695 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4696 reserve>>10, arc_c>>10); 4697 return (SET_ERROR(ERESTART)); 4698 } 4699 atomic_add_64(&arc_tempreserve, reserve); 4700 return (0); 4701 } 4702 4703 static void 4704 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4705 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4706 { 4707 size->value.ui64 = state->arcs_size; 4708 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4709 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4710 } 4711 4712 static int 4713 arc_kstat_update(kstat_t *ksp, int rw) 4714 { 4715 arc_stats_t *as = ksp->ks_data; 4716 4717 if (rw == KSTAT_WRITE) { 4718 return (EACCES); 4719 } else { 4720 arc_kstat_update_state(arc_anon, 4721 &as->arcstat_anon_size, 4722 &as->arcstat_anon_evictable_data, 4723 &as->arcstat_anon_evictable_metadata); 4724 arc_kstat_update_state(arc_mru, 4725 &as->arcstat_mru_size, 4726 &as->arcstat_mru_evictable_data, 4727 &as->arcstat_mru_evictable_metadata); 4728 arc_kstat_update_state(arc_mru_ghost, 4729 &as->arcstat_mru_ghost_size, 4730 &as->arcstat_mru_ghost_evictable_data, 4731 &as->arcstat_mru_ghost_evictable_metadata); 4732 arc_kstat_update_state(arc_mfu, 4733 &as->arcstat_mfu_size, 4734 &as->arcstat_mfu_evictable_data, 4735 &as->arcstat_mfu_evictable_metadata); 4736 arc_kstat_update_state(arc_mfu_ghost, 4737 &as->arcstat_mfu_ghost_size, 4738 &as->arcstat_mfu_ghost_evictable_data, 4739 &as->arcstat_mfu_ghost_evictable_metadata); 4740 } 4741 4742 return (0); 4743 } 4744 4745 /* 4746 * This function *must* return indices evenly distributed between all 4747 * sublists of the multilist. This is needed due to how the ARC eviction 4748 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 4749 * distributed between all sublists and uses this assumption when 4750 * deciding which sublist to evict from and how much to evict from it. 4751 */ 4752 unsigned int 4753 arc_state_multilist_index_func(multilist_t *ml, void *obj) 4754 { 4755 arc_buf_hdr_t *hdr = obj; 4756 4757 /* 4758 * We rely on b_dva to generate evenly distributed index 4759 * numbers using buf_hash below. So, as an added precaution, 4760 * let's make sure we never add empty buffers to the arc lists. 4761 */ 4762 ASSERT(!BUF_EMPTY(hdr)); 4763 4764 /* 4765 * The assumption here, is the hash value for a given 4766 * arc_buf_hdr_t will remain constant throughout it's lifetime 4767 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 4768 * Thus, we don't need to store the header's sublist index 4769 * on insertion, as this index can be recalculated on removal. 4770 * 4771 * Also, the low order bits of the hash value are thought to be 4772 * distributed evenly. Otherwise, in the case that the multilist 4773 * has a power of two number of sublists, each sublists' usage 4774 * would not be evenly distributed. 4775 */ 4776 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 4777 multilist_get_num_sublists(ml)); 4778 } 4779 4780 void 4781 arc_init(void) 4782 { 4783 /* 4784 * allmem is "all memory that we could possibly use". 4785 */ 4786 #ifdef _KERNEL 4787 uint64_t allmem = ptob(physmem - swapfs_minfree); 4788 #else 4789 uint64_t allmem = (physmem * PAGESIZE) / 2; 4790 #endif 4791 4792 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 4793 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 4794 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 4795 4796 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 4797 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 4798 4799 /* Convert seconds to clock ticks */ 4800 arc_min_prefetch_lifespan = 1 * hz; 4801 4802 /* Start out with 1/8 of all memory */ 4803 arc_c = allmem / 8; 4804 4805 #ifdef _KERNEL 4806 /* 4807 * On architectures where the physical memory can be larger 4808 * than the addressable space (intel in 32-bit mode), we may 4809 * need to limit the cache to 1/8 of VM size. 4810 */ 4811 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4812 #endif 4813 4814 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 4815 arc_c_min = MAX(allmem / 32, 64 << 20); 4816 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 4817 if (allmem >= 1 << 30) 4818 arc_c_max = allmem - (1 << 30); 4819 else 4820 arc_c_max = arc_c_min; 4821 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 4822 4823 /* 4824 * Allow the tunables to override our calculations if they are 4825 * reasonable (ie. over 64MB) 4826 */ 4827 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 4828 arc_c_max = zfs_arc_max; 4829 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 4830 arc_c_min = zfs_arc_min; 4831 4832 arc_c = arc_c_max; 4833 arc_p = (arc_c >> 1); 4834 4835 /* limit meta-data to 1/4 of the arc capacity */ 4836 arc_meta_limit = arc_c_max / 4; 4837 4838 /* Allow the tunable to override if it is reasonable */ 4839 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4840 arc_meta_limit = zfs_arc_meta_limit; 4841 4842 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4843 arc_c_min = arc_meta_limit / 2; 4844 4845 if (zfs_arc_meta_min > 0) { 4846 arc_meta_min = zfs_arc_meta_min; 4847 } else { 4848 arc_meta_min = arc_c_min / 2; 4849 } 4850 4851 if (zfs_arc_grow_retry > 0) 4852 arc_grow_retry = zfs_arc_grow_retry; 4853 4854 if (zfs_arc_shrink_shift > 0) 4855 arc_shrink_shift = zfs_arc_shrink_shift; 4856 4857 /* 4858 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 4859 */ 4860 if (arc_no_grow_shift >= arc_shrink_shift) 4861 arc_no_grow_shift = arc_shrink_shift - 1; 4862 4863 if (zfs_arc_p_min_shift > 0) 4864 arc_p_min_shift = zfs_arc_p_min_shift; 4865 4866 if (zfs_arc_num_sublists_per_state < 1) 4867 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 4868 4869 /* if kmem_flags are set, lets try to use less memory */ 4870 if (kmem_debugging()) 4871 arc_c = arc_c / 2; 4872 if (arc_c < arc_c_min) 4873 arc_c = arc_c_min; 4874 4875 arc_anon = &ARC_anon; 4876 arc_mru = &ARC_mru; 4877 arc_mru_ghost = &ARC_mru_ghost; 4878 arc_mfu = &ARC_mfu; 4879 arc_mfu_ghost = &ARC_mfu_ghost; 4880 arc_l2c_only = &ARC_l2c_only; 4881 arc_size = 0; 4882 4883 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 4884 sizeof (arc_buf_hdr_t), 4885 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4886 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4887 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 4888 sizeof (arc_buf_hdr_t), 4889 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4890 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4891 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 4892 sizeof (arc_buf_hdr_t), 4893 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4894 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4895 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 4896 sizeof (arc_buf_hdr_t), 4897 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4898 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4899 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 4900 sizeof (arc_buf_hdr_t), 4901 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4902 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4903 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 4904 sizeof (arc_buf_hdr_t), 4905 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4906 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4907 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 4908 sizeof (arc_buf_hdr_t), 4909 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4910 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4911 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 4912 sizeof (arc_buf_hdr_t), 4913 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4914 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4915 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 4916 sizeof (arc_buf_hdr_t), 4917 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4918 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4919 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 4920 sizeof (arc_buf_hdr_t), 4921 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4922 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4923 4924 buf_init(); 4925 4926 arc_reclaim_thread_exit = FALSE; 4927 arc_user_evicts_thread_exit = FALSE; 4928 arc_eviction_list = NULL; 4929 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4930 4931 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4932 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4933 4934 if (arc_ksp != NULL) { 4935 arc_ksp->ks_data = &arc_stats; 4936 arc_ksp->ks_update = arc_kstat_update; 4937 kstat_install(arc_ksp); 4938 } 4939 4940 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 4941 TS_RUN, minclsyspri); 4942 4943 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 4944 TS_RUN, minclsyspri); 4945 4946 arc_dead = FALSE; 4947 arc_warm = B_FALSE; 4948 4949 /* 4950 * Calculate maximum amount of dirty data per pool. 4951 * 4952 * If it has been set by /etc/system, take that. 4953 * Otherwise, use a percentage of physical memory defined by 4954 * zfs_dirty_data_max_percent (default 10%) with a cap at 4955 * zfs_dirty_data_max_max (default 4GB). 4956 */ 4957 if (zfs_dirty_data_max == 0) { 4958 zfs_dirty_data_max = physmem * PAGESIZE * 4959 zfs_dirty_data_max_percent / 100; 4960 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 4961 zfs_dirty_data_max_max); 4962 } 4963 } 4964 4965 void 4966 arc_fini(void) 4967 { 4968 mutex_enter(&arc_reclaim_lock); 4969 arc_reclaim_thread_exit = TRUE; 4970 /* 4971 * The reclaim thread will set arc_reclaim_thread_exit back to 4972 * FALSE when it is finished exiting; we're waiting for that. 4973 */ 4974 while (arc_reclaim_thread_exit) { 4975 cv_signal(&arc_reclaim_thread_cv); 4976 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 4977 } 4978 mutex_exit(&arc_reclaim_lock); 4979 4980 mutex_enter(&arc_user_evicts_lock); 4981 arc_user_evicts_thread_exit = TRUE; 4982 /* 4983 * The user evicts thread will set arc_user_evicts_thread_exit 4984 * to FALSE when it is finished exiting; we're waiting for that. 4985 */ 4986 while (arc_user_evicts_thread_exit) { 4987 cv_signal(&arc_user_evicts_cv); 4988 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 4989 } 4990 mutex_exit(&arc_user_evicts_lock); 4991 4992 /* Use TRUE to ensure *all* buffers are evicted */ 4993 arc_flush(NULL, TRUE); 4994 4995 arc_dead = TRUE; 4996 4997 if (arc_ksp != NULL) { 4998 kstat_delete(arc_ksp); 4999 arc_ksp = NULL; 5000 } 5001 5002 mutex_destroy(&arc_reclaim_lock); 5003 cv_destroy(&arc_reclaim_thread_cv); 5004 cv_destroy(&arc_reclaim_waiters_cv); 5005 5006 mutex_destroy(&arc_user_evicts_lock); 5007 cv_destroy(&arc_user_evicts_cv); 5008 5009 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5010 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5011 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5012 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5013 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5014 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5015 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5016 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5017 5018 buf_fini(); 5019 5020 ASSERT0(arc_loaned_bytes); 5021 } 5022 5023 /* 5024 * Level 2 ARC 5025 * 5026 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5027 * It uses dedicated storage devices to hold cached data, which are populated 5028 * using large infrequent writes. The main role of this cache is to boost 5029 * the performance of random read workloads. The intended L2ARC devices 5030 * include short-stroked disks, solid state disks, and other media with 5031 * substantially faster read latency than disk. 5032 * 5033 * +-----------------------+ 5034 * | ARC | 5035 * +-----------------------+ 5036 * | ^ ^ 5037 * | | | 5038 * l2arc_feed_thread() arc_read() 5039 * | | | 5040 * | l2arc read | 5041 * V | | 5042 * +---------------+ | 5043 * | L2ARC | | 5044 * +---------------+ | 5045 * | ^ | 5046 * l2arc_write() | | 5047 * | | | 5048 * V | | 5049 * +-------+ +-------+ 5050 * | vdev | | vdev | 5051 * | cache | | cache | 5052 * +-------+ +-------+ 5053 * +=========+ .-----. 5054 * : L2ARC : |-_____-| 5055 * : devices : | Disks | 5056 * +=========+ `-_____-' 5057 * 5058 * Read requests are satisfied from the following sources, in order: 5059 * 5060 * 1) ARC 5061 * 2) vdev cache of L2ARC devices 5062 * 3) L2ARC devices 5063 * 4) vdev cache of disks 5064 * 5) disks 5065 * 5066 * Some L2ARC device types exhibit extremely slow write performance. 5067 * To accommodate for this there are some significant differences between 5068 * the L2ARC and traditional cache design: 5069 * 5070 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5071 * the ARC behave as usual, freeing buffers and placing headers on ghost 5072 * lists. The ARC does not send buffers to the L2ARC during eviction as 5073 * this would add inflated write latencies for all ARC memory pressure. 5074 * 5075 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5076 * It does this by periodically scanning buffers from the eviction-end of 5077 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5078 * not already there. It scans until a headroom of buffers is satisfied, 5079 * which itself is a buffer for ARC eviction. If a compressible buffer is 5080 * found during scanning and selected for writing to an L2ARC device, we 5081 * temporarily boost scanning headroom during the next scan cycle to make 5082 * sure we adapt to compression effects (which might significantly reduce 5083 * the data volume we write to L2ARC). The thread that does this is 5084 * l2arc_feed_thread(), illustrated below; example sizes are included to 5085 * provide a better sense of ratio than this diagram: 5086 * 5087 * head --> tail 5088 * +---------------------+----------+ 5089 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5090 * +---------------------+----------+ | o L2ARC eligible 5091 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5092 * +---------------------+----------+ | 5093 * 15.9 Gbytes ^ 32 Mbytes | 5094 * headroom | 5095 * l2arc_feed_thread() 5096 * | 5097 * l2arc write hand <--[oooo]--' 5098 * | 8 Mbyte 5099 * | write max 5100 * V 5101 * +==============================+ 5102 * L2ARC dev |####|#|###|###| |####| ... | 5103 * +==============================+ 5104 * 32 Gbytes 5105 * 5106 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5107 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5108 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5109 * safe to say that this is an uncommon case, since buffers at the end of 5110 * the ARC lists have moved there due to inactivity. 5111 * 5112 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5113 * then the L2ARC simply misses copying some buffers. This serves as a 5114 * pressure valve to prevent heavy read workloads from both stalling the ARC 5115 * with waits and clogging the L2ARC with writes. This also helps prevent 5116 * the potential for the L2ARC to churn if it attempts to cache content too 5117 * quickly, such as during backups of the entire pool. 5118 * 5119 * 5. After system boot and before the ARC has filled main memory, there are 5120 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5121 * lists can remain mostly static. Instead of searching from tail of these 5122 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5123 * for eligible buffers, greatly increasing its chance of finding them. 5124 * 5125 * The L2ARC device write speed is also boosted during this time so that 5126 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5127 * there are no L2ARC reads, and no fear of degrading read performance 5128 * through increased writes. 5129 * 5130 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5131 * the vdev queue can aggregate them into larger and fewer writes. Each 5132 * device is written to in a rotor fashion, sweeping writes through 5133 * available space then repeating. 5134 * 5135 * 7. The L2ARC does not store dirty content. It never needs to flush 5136 * write buffers back to disk based storage. 5137 * 5138 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5139 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5140 * 5141 * The performance of the L2ARC can be tweaked by a number of tunables, which 5142 * may be necessary for different workloads: 5143 * 5144 * l2arc_write_max max write bytes per interval 5145 * l2arc_write_boost extra write bytes during device warmup 5146 * l2arc_noprefetch skip caching prefetched buffers 5147 * l2arc_headroom number of max device writes to precache 5148 * l2arc_headroom_boost when we find compressed buffers during ARC 5149 * scanning, we multiply headroom by this 5150 * percentage factor for the next scan cycle, 5151 * since more compressed buffers are likely to 5152 * be present 5153 * l2arc_feed_secs seconds between L2ARC writing 5154 * 5155 * Tunables may be removed or added as future performance improvements are 5156 * integrated, and also may become zpool properties. 5157 * 5158 * There are three key functions that control how the L2ARC warms up: 5159 * 5160 * l2arc_write_eligible() check if a buffer is eligible to cache 5161 * l2arc_write_size() calculate how much to write 5162 * l2arc_write_interval() calculate sleep delay between writes 5163 * 5164 * These three functions determine what to write, how much, and how quickly 5165 * to send writes. 5166 */ 5167 5168 static boolean_t 5169 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5170 { 5171 /* 5172 * A buffer is *not* eligible for the L2ARC if it: 5173 * 1. belongs to a different spa. 5174 * 2. is already cached on the L2ARC. 5175 * 3. has an I/O in progress (it may be an incomplete read). 5176 * 4. is flagged not eligible (zfs property). 5177 */ 5178 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5179 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 5180 return (B_FALSE); 5181 5182 return (B_TRUE); 5183 } 5184 5185 static uint64_t 5186 l2arc_write_size(void) 5187 { 5188 uint64_t size; 5189 5190 /* 5191 * Make sure our globals have meaningful values in case the user 5192 * altered them. 5193 */ 5194 size = l2arc_write_max; 5195 if (size == 0) { 5196 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5197 "be greater than zero, resetting it to the default (%d)", 5198 L2ARC_WRITE_SIZE); 5199 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5200 } 5201 5202 if (arc_warm == B_FALSE) 5203 size += l2arc_write_boost; 5204 5205 return (size); 5206 5207 } 5208 5209 static clock_t 5210 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5211 { 5212 clock_t interval, next, now; 5213 5214 /* 5215 * If the ARC lists are busy, increase our write rate; if the 5216 * lists are stale, idle back. This is achieved by checking 5217 * how much we previously wrote - if it was more than half of 5218 * what we wanted, schedule the next write much sooner. 5219 */ 5220 if (l2arc_feed_again && wrote > (wanted / 2)) 5221 interval = (hz * l2arc_feed_min_ms) / 1000; 5222 else 5223 interval = hz * l2arc_feed_secs; 5224 5225 now = ddi_get_lbolt(); 5226 next = MAX(now, MIN(now + interval, began + interval)); 5227 5228 return (next); 5229 } 5230 5231 /* 5232 * Cycle through L2ARC devices. This is how L2ARC load balances. 5233 * If a device is returned, this also returns holding the spa config lock. 5234 */ 5235 static l2arc_dev_t * 5236 l2arc_dev_get_next(void) 5237 { 5238 l2arc_dev_t *first, *next = NULL; 5239 5240 /* 5241 * Lock out the removal of spas (spa_namespace_lock), then removal 5242 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5243 * both locks will be dropped and a spa config lock held instead. 5244 */ 5245 mutex_enter(&spa_namespace_lock); 5246 mutex_enter(&l2arc_dev_mtx); 5247 5248 /* if there are no vdevs, there is nothing to do */ 5249 if (l2arc_ndev == 0) 5250 goto out; 5251 5252 first = NULL; 5253 next = l2arc_dev_last; 5254 do { 5255 /* loop around the list looking for a non-faulted vdev */ 5256 if (next == NULL) { 5257 next = list_head(l2arc_dev_list); 5258 } else { 5259 next = list_next(l2arc_dev_list, next); 5260 if (next == NULL) 5261 next = list_head(l2arc_dev_list); 5262 } 5263 5264 /* if we have come back to the start, bail out */ 5265 if (first == NULL) 5266 first = next; 5267 else if (next == first) 5268 break; 5269 5270 } while (vdev_is_dead(next->l2ad_vdev)); 5271 5272 /* if we were unable to find any usable vdevs, return NULL */ 5273 if (vdev_is_dead(next->l2ad_vdev)) 5274 next = NULL; 5275 5276 l2arc_dev_last = next; 5277 5278 out: 5279 mutex_exit(&l2arc_dev_mtx); 5280 5281 /* 5282 * Grab the config lock to prevent the 'next' device from being 5283 * removed while we are writing to it. 5284 */ 5285 if (next != NULL) 5286 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5287 mutex_exit(&spa_namespace_lock); 5288 5289 return (next); 5290 } 5291 5292 /* 5293 * Free buffers that were tagged for destruction. 5294 */ 5295 static void 5296 l2arc_do_free_on_write() 5297 { 5298 list_t *buflist; 5299 l2arc_data_free_t *df, *df_prev; 5300 5301 mutex_enter(&l2arc_free_on_write_mtx); 5302 buflist = l2arc_free_on_write; 5303 5304 for (df = list_tail(buflist); df; df = df_prev) { 5305 df_prev = list_prev(buflist, df); 5306 ASSERT(df->l2df_data != NULL); 5307 ASSERT(df->l2df_func != NULL); 5308 df->l2df_func(df->l2df_data, df->l2df_size); 5309 list_remove(buflist, df); 5310 kmem_free(df, sizeof (l2arc_data_free_t)); 5311 } 5312 5313 mutex_exit(&l2arc_free_on_write_mtx); 5314 } 5315 5316 /* 5317 * A write to a cache device has completed. Update all headers to allow 5318 * reads from these buffers to begin. 5319 */ 5320 static void 5321 l2arc_write_done(zio_t *zio) 5322 { 5323 l2arc_write_callback_t *cb; 5324 l2arc_dev_t *dev; 5325 list_t *buflist; 5326 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5327 kmutex_t *hash_lock; 5328 int64_t bytes_dropped = 0; 5329 5330 cb = zio->io_private; 5331 ASSERT(cb != NULL); 5332 dev = cb->l2wcb_dev; 5333 ASSERT(dev != NULL); 5334 head = cb->l2wcb_head; 5335 ASSERT(head != NULL); 5336 buflist = &dev->l2ad_buflist; 5337 ASSERT(buflist != NULL); 5338 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5339 l2arc_write_callback_t *, cb); 5340 5341 if (zio->io_error != 0) 5342 ARCSTAT_BUMP(arcstat_l2_writes_error); 5343 5344 /* 5345 * All writes completed, or an error was hit. 5346 */ 5347 top: 5348 mutex_enter(&dev->l2ad_mtx); 5349 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5350 hdr_prev = list_prev(buflist, hdr); 5351 5352 hash_lock = HDR_LOCK(hdr); 5353 5354 /* 5355 * We cannot use mutex_enter or else we can deadlock 5356 * with l2arc_write_buffers (due to swapping the order 5357 * the hash lock and l2ad_mtx are taken). 5358 */ 5359 if (!mutex_tryenter(hash_lock)) { 5360 /* 5361 * Missed the hash lock. We must retry so we 5362 * don't leave the ARC_FLAG_L2_WRITING bit set. 5363 */ 5364 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5365 5366 /* 5367 * We don't want to rescan the headers we've 5368 * already marked as having been written out, so 5369 * we reinsert the head node so we can pick up 5370 * where we left off. 5371 */ 5372 list_remove(buflist, head); 5373 list_insert_after(buflist, hdr, head); 5374 5375 mutex_exit(&dev->l2ad_mtx); 5376 5377 /* 5378 * We wait for the hash lock to become available 5379 * to try and prevent busy waiting, and increase 5380 * the chance we'll be able to acquire the lock 5381 * the next time around. 5382 */ 5383 mutex_enter(hash_lock); 5384 mutex_exit(hash_lock); 5385 goto top; 5386 } 5387 5388 /* 5389 * We could not have been moved into the arc_l2c_only 5390 * state while in-flight due to our ARC_FLAG_L2_WRITING 5391 * bit being set. Let's just ensure that's being enforced. 5392 */ 5393 ASSERT(HDR_HAS_L1HDR(hdr)); 5394 5395 /* 5396 * We may have allocated a buffer for L2ARC compression, 5397 * we must release it to avoid leaking this data. 5398 */ 5399 l2arc_release_cdata_buf(hdr); 5400 5401 if (zio->io_error != 0) { 5402 /* 5403 * Error - drop L2ARC entry. 5404 */ 5405 list_remove(buflist, hdr); 5406 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5407 5408 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5409 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5410 } 5411 5412 /* 5413 * Allow ARC to begin reads and ghost list evictions to 5414 * this L2ARC entry. 5415 */ 5416 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5417 5418 mutex_exit(hash_lock); 5419 } 5420 5421 atomic_inc_64(&l2arc_writes_done); 5422 list_remove(buflist, head); 5423 ASSERT(!HDR_HAS_L1HDR(head)); 5424 kmem_cache_free(hdr_l2only_cache, head); 5425 mutex_exit(&dev->l2ad_mtx); 5426 5427 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5428 5429 l2arc_do_free_on_write(); 5430 5431 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5432 } 5433 5434 /* 5435 * A read to a cache device completed. Validate buffer contents before 5436 * handing over to the regular ARC routines. 5437 */ 5438 static void 5439 l2arc_read_done(zio_t *zio) 5440 { 5441 l2arc_read_callback_t *cb; 5442 arc_buf_hdr_t *hdr; 5443 arc_buf_t *buf; 5444 kmutex_t *hash_lock; 5445 int equal; 5446 5447 ASSERT(zio->io_vd != NULL); 5448 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5449 5450 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5451 5452 cb = zio->io_private; 5453 ASSERT(cb != NULL); 5454 buf = cb->l2rcb_buf; 5455 ASSERT(buf != NULL); 5456 5457 hash_lock = HDR_LOCK(buf->b_hdr); 5458 mutex_enter(hash_lock); 5459 hdr = buf->b_hdr; 5460 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5461 5462 /* 5463 * If the buffer was compressed, decompress it first. 5464 */ 5465 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5466 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5467 ASSERT(zio->io_data != NULL); 5468 5469 /* 5470 * Check this survived the L2ARC journey. 5471 */ 5472 equal = arc_cksum_equal(buf); 5473 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5474 mutex_exit(hash_lock); 5475 zio->io_private = buf; 5476 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5477 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5478 arc_read_done(zio); 5479 } else { 5480 mutex_exit(hash_lock); 5481 /* 5482 * Buffer didn't survive caching. Increment stats and 5483 * reissue to the original storage device. 5484 */ 5485 if (zio->io_error != 0) { 5486 ARCSTAT_BUMP(arcstat_l2_io_error); 5487 } else { 5488 zio->io_error = SET_ERROR(EIO); 5489 } 5490 if (!equal) 5491 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5492 5493 /* 5494 * If there's no waiter, issue an async i/o to the primary 5495 * storage now. If there *is* a waiter, the caller must 5496 * issue the i/o in a context where it's OK to block. 5497 */ 5498 if (zio->io_waiter == NULL) { 5499 zio_t *pio = zio_unique_parent(zio); 5500 5501 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5502 5503 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5504 buf->b_data, zio->io_size, arc_read_done, buf, 5505 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5506 } 5507 } 5508 5509 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5510 } 5511 5512 /* 5513 * This is the list priority from which the L2ARC will search for pages to 5514 * cache. This is used within loops (0..3) to cycle through lists in the 5515 * desired order. This order can have a significant effect on cache 5516 * performance. 5517 * 5518 * Currently the metadata lists are hit first, MFU then MRU, followed by 5519 * the data lists. This function returns a locked list, and also returns 5520 * the lock pointer. 5521 */ 5522 static multilist_sublist_t * 5523 l2arc_sublist_lock(int list_num) 5524 { 5525 multilist_t *ml = NULL; 5526 unsigned int idx; 5527 5528 ASSERT(list_num >= 0 && list_num <= 3); 5529 5530 switch (list_num) { 5531 case 0: 5532 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 5533 break; 5534 case 1: 5535 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 5536 break; 5537 case 2: 5538 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 5539 break; 5540 case 3: 5541 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 5542 break; 5543 } 5544 5545 /* 5546 * Return a randomly-selected sublist. This is acceptable 5547 * because the caller feeds only a little bit of data for each 5548 * call (8MB). Subsequent calls will result in different 5549 * sublists being selected. 5550 */ 5551 idx = multilist_get_random_index(ml); 5552 return (multilist_sublist_lock(ml, idx)); 5553 } 5554 5555 /* 5556 * Evict buffers from the device write hand to the distance specified in 5557 * bytes. This distance may span populated buffers, it may span nothing. 5558 * This is clearing a region on the L2ARC device ready for writing. 5559 * If the 'all' boolean is set, every buffer is evicted. 5560 */ 5561 static void 5562 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5563 { 5564 list_t *buflist; 5565 arc_buf_hdr_t *hdr, *hdr_prev; 5566 kmutex_t *hash_lock; 5567 uint64_t taddr; 5568 int64_t bytes_evicted = 0; 5569 5570 buflist = &dev->l2ad_buflist; 5571 5572 if (!all && dev->l2ad_first) { 5573 /* 5574 * This is the first sweep through the device. There is 5575 * nothing to evict. 5576 */ 5577 return; 5578 } 5579 5580 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5581 /* 5582 * When nearing the end of the device, evict to the end 5583 * before the device write hand jumps to the start. 5584 */ 5585 taddr = dev->l2ad_end; 5586 } else { 5587 taddr = dev->l2ad_hand + distance; 5588 } 5589 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5590 uint64_t, taddr, boolean_t, all); 5591 5592 top: 5593 mutex_enter(&dev->l2ad_mtx); 5594 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5595 hdr_prev = list_prev(buflist, hdr); 5596 5597 hash_lock = HDR_LOCK(hdr); 5598 5599 /* 5600 * We cannot use mutex_enter or else we can deadlock 5601 * with l2arc_write_buffers (due to swapping the order 5602 * the hash lock and l2ad_mtx are taken). 5603 */ 5604 if (!mutex_tryenter(hash_lock)) { 5605 /* 5606 * Missed the hash lock. Retry. 5607 */ 5608 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5609 mutex_exit(&dev->l2ad_mtx); 5610 mutex_enter(hash_lock); 5611 mutex_exit(hash_lock); 5612 goto top; 5613 } 5614 5615 if (HDR_L2_WRITE_HEAD(hdr)) { 5616 /* 5617 * We hit a write head node. Leave it for 5618 * l2arc_write_done(). 5619 */ 5620 list_remove(buflist, hdr); 5621 mutex_exit(hash_lock); 5622 continue; 5623 } 5624 5625 if (!all && HDR_HAS_L2HDR(hdr) && 5626 (hdr->b_l2hdr.b_daddr > taddr || 5627 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5628 /* 5629 * We've evicted to the target address, 5630 * or the end of the device. 5631 */ 5632 mutex_exit(hash_lock); 5633 break; 5634 } 5635 5636 ASSERT(HDR_HAS_L2HDR(hdr)); 5637 if (!HDR_HAS_L1HDR(hdr)) { 5638 ASSERT(!HDR_L2_READING(hdr)); 5639 /* 5640 * This doesn't exist in the ARC. Destroy. 5641 * arc_hdr_destroy() will call list_remove() 5642 * and decrement arcstat_l2_size. 5643 */ 5644 arc_change_state(arc_anon, hdr, hash_lock); 5645 arc_hdr_destroy(hdr); 5646 } else { 5647 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5648 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5649 /* 5650 * Invalidate issued or about to be issued 5651 * reads, since we may be about to write 5652 * over this location. 5653 */ 5654 if (HDR_L2_READING(hdr)) { 5655 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5656 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5657 } 5658 5659 /* Tell ARC this no longer exists in L2ARC. */ 5660 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5661 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5662 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5663 list_remove(buflist, hdr); 5664 5665 /* Ensure this header has finished being written */ 5666 ASSERT(!HDR_L2_WRITING(hdr)); 5667 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 5668 } 5669 mutex_exit(hash_lock); 5670 } 5671 mutex_exit(&dev->l2ad_mtx); 5672 5673 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 5674 dev->l2ad_evict = taddr; 5675 } 5676 5677 /* 5678 * Find and write ARC buffers to the L2ARC device. 5679 * 5680 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5681 * for reading until they have completed writing. 5682 * The headroom_boost is an in-out parameter used to maintain headroom boost 5683 * state between calls to this function. 5684 * 5685 * Returns the number of bytes actually written (which may be smaller than 5686 * the delta by which the device hand has changed due to alignment). 5687 */ 5688 static uint64_t 5689 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5690 boolean_t *headroom_boost) 5691 { 5692 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5693 uint64_t write_asize, write_psize, write_sz, headroom, 5694 buf_compress_minsz; 5695 void *buf_data; 5696 boolean_t full; 5697 l2arc_write_callback_t *cb; 5698 zio_t *pio, *wzio; 5699 uint64_t guid = spa_load_guid(spa); 5700 const boolean_t do_headroom_boost = *headroom_boost; 5701 5702 ASSERT(dev->l2ad_vdev != NULL); 5703 5704 /* Lower the flag now, we might want to raise it again later. */ 5705 *headroom_boost = B_FALSE; 5706 5707 pio = NULL; 5708 write_sz = write_asize = write_psize = 0; 5709 full = B_FALSE; 5710 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5711 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5712 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5713 5714 /* 5715 * We will want to try to compress buffers that are at least 2x the 5716 * device sector size. 5717 */ 5718 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5719 5720 /* 5721 * Copy buffers for L2ARC writing. 5722 */ 5723 for (int try = 0; try <= 3; try++) { 5724 multilist_sublist_t *mls = l2arc_sublist_lock(try); 5725 uint64_t passed_sz = 0; 5726 5727 /* 5728 * L2ARC fast warmup. 5729 * 5730 * Until the ARC is warm and starts to evict, read from the 5731 * head of the ARC lists rather than the tail. 5732 */ 5733 if (arc_warm == B_FALSE) 5734 hdr = multilist_sublist_head(mls); 5735 else 5736 hdr = multilist_sublist_tail(mls); 5737 5738 headroom = target_sz * l2arc_headroom; 5739 if (do_headroom_boost) 5740 headroom = (headroom * l2arc_headroom_boost) / 100; 5741 5742 for (; hdr; hdr = hdr_prev) { 5743 kmutex_t *hash_lock; 5744 uint64_t buf_sz; 5745 5746 if (arc_warm == B_FALSE) 5747 hdr_prev = multilist_sublist_next(mls, hdr); 5748 else 5749 hdr_prev = multilist_sublist_prev(mls, hdr); 5750 5751 hash_lock = HDR_LOCK(hdr); 5752 if (!mutex_tryenter(hash_lock)) { 5753 /* 5754 * Skip this buffer rather than waiting. 5755 */ 5756 continue; 5757 } 5758 5759 passed_sz += hdr->b_size; 5760 if (passed_sz > headroom) { 5761 /* 5762 * Searched too far. 5763 */ 5764 mutex_exit(hash_lock); 5765 break; 5766 } 5767 5768 if (!l2arc_write_eligible(guid, hdr)) { 5769 mutex_exit(hash_lock); 5770 continue; 5771 } 5772 5773 if ((write_sz + hdr->b_size) > target_sz) { 5774 full = B_TRUE; 5775 mutex_exit(hash_lock); 5776 break; 5777 } 5778 5779 if (pio == NULL) { 5780 /* 5781 * Insert a dummy header on the buflist so 5782 * l2arc_write_done() can find where the 5783 * write buffers begin without searching. 5784 */ 5785 mutex_enter(&dev->l2ad_mtx); 5786 list_insert_head(&dev->l2ad_buflist, head); 5787 mutex_exit(&dev->l2ad_mtx); 5788 5789 cb = kmem_alloc( 5790 sizeof (l2arc_write_callback_t), KM_SLEEP); 5791 cb->l2wcb_dev = dev; 5792 cb->l2wcb_head = head; 5793 pio = zio_root(spa, l2arc_write_done, cb, 5794 ZIO_FLAG_CANFAIL); 5795 } 5796 5797 /* 5798 * Create and add a new L2ARC header. 5799 */ 5800 hdr->b_l2hdr.b_dev = dev; 5801 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5802 /* 5803 * Temporarily stash the data buffer in b_tmp_cdata. 5804 * The subsequent write step will pick it up from 5805 * there. This is because can't access b_l1hdr.b_buf 5806 * without holding the hash_lock, which we in turn 5807 * can't access without holding the ARC list locks 5808 * (which we want to avoid during compression/writing). 5809 */ 5810 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5811 hdr->b_l2hdr.b_asize = hdr->b_size; 5812 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5813 5814 buf_sz = hdr->b_size; 5815 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5816 5817 mutex_enter(&dev->l2ad_mtx); 5818 list_insert_head(&dev->l2ad_buflist, hdr); 5819 mutex_exit(&dev->l2ad_mtx); 5820 5821 /* 5822 * Compute and store the buffer cksum before 5823 * writing. On debug the cksum is verified first. 5824 */ 5825 arc_cksum_verify(hdr->b_l1hdr.b_buf); 5826 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 5827 5828 mutex_exit(hash_lock); 5829 5830 write_sz += buf_sz; 5831 } 5832 5833 multilist_sublist_unlock(mls); 5834 5835 if (full == B_TRUE) 5836 break; 5837 } 5838 5839 /* No buffers selected for writing? */ 5840 if (pio == NULL) { 5841 ASSERT0(write_sz); 5842 ASSERT(!HDR_HAS_L1HDR(head)); 5843 kmem_cache_free(hdr_l2only_cache, head); 5844 return (0); 5845 } 5846 5847 mutex_enter(&dev->l2ad_mtx); 5848 5849 /* 5850 * Now start writing the buffers. We're starting at the write head 5851 * and work backwards, retracing the course of the buffer selector 5852 * loop above. 5853 */ 5854 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 5855 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 5856 uint64_t buf_sz; 5857 5858 /* 5859 * We rely on the L1 portion of the header below, so 5860 * it's invalid for this header to have been evicted out 5861 * of the ghost cache, prior to being written out. The 5862 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 5863 */ 5864 ASSERT(HDR_HAS_L1HDR(hdr)); 5865 5866 /* 5867 * We shouldn't need to lock the buffer here, since we flagged 5868 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5869 * take care to only access its L2 cache parameters. In 5870 * particular, hdr->l1hdr.b_buf may be invalid by now due to 5871 * ARC eviction. 5872 */ 5873 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 5874 5875 if ((HDR_L2COMPRESS(hdr)) && 5876 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 5877 if (l2arc_compress_buf(hdr)) { 5878 /* 5879 * If compression succeeded, enable headroom 5880 * boost on the next scan cycle. 5881 */ 5882 *headroom_boost = B_TRUE; 5883 } 5884 } 5885 5886 /* 5887 * Pick up the buffer data we had previously stashed away 5888 * (and now potentially also compressed). 5889 */ 5890 buf_data = hdr->b_l1hdr.b_tmp_cdata; 5891 buf_sz = hdr->b_l2hdr.b_asize; 5892 5893 /* Compression may have squashed the buffer to zero length. */ 5894 if (buf_sz != 0) { 5895 uint64_t buf_p_sz; 5896 5897 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5898 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5899 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 5900 ZIO_FLAG_CANFAIL, B_FALSE); 5901 5902 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 5903 zio_t *, wzio); 5904 (void) zio_nowait(wzio); 5905 5906 write_asize += buf_sz; 5907 /* 5908 * Keep the clock hand suitably device-aligned. 5909 */ 5910 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5911 write_psize += buf_p_sz; 5912 dev->l2ad_hand += buf_p_sz; 5913 } 5914 } 5915 5916 mutex_exit(&dev->l2ad_mtx); 5917 5918 ASSERT3U(write_asize, <=, target_sz); 5919 ARCSTAT_BUMP(arcstat_l2_writes_sent); 5920 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 5921 ARCSTAT_INCR(arcstat_l2_size, write_sz); 5922 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 5923 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 5924 5925 /* 5926 * Bump device hand to the device start if it is approaching the end. 5927 * l2arc_evict() will already have evicted ahead for this case. 5928 */ 5929 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 5930 dev->l2ad_hand = dev->l2ad_start; 5931 dev->l2ad_evict = dev->l2ad_start; 5932 dev->l2ad_first = B_FALSE; 5933 } 5934 5935 dev->l2ad_writing = B_TRUE; 5936 (void) zio_wait(pio); 5937 dev->l2ad_writing = B_FALSE; 5938 5939 return (write_asize); 5940 } 5941 5942 /* 5943 * Compresses an L2ARC buffer. 5944 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 5945 * size in l2hdr->b_asize. This routine tries to compress the data and 5946 * depending on the compression result there are three possible outcomes: 5947 * *) The buffer was incompressible. The original l2hdr contents were left 5948 * untouched and are ready for writing to an L2 device. 5949 * *) The buffer was all-zeros, so there is no need to write it to an L2 5950 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 5951 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 5952 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 5953 * data buffer which holds the compressed data to be written, and b_asize 5954 * tells us how much data there is. b_compress is set to the appropriate 5955 * compression algorithm. Once writing is done, invoke 5956 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 5957 * 5958 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 5959 * buffer was incompressible). 5960 */ 5961 static boolean_t 5962 l2arc_compress_buf(arc_buf_hdr_t *hdr) 5963 { 5964 void *cdata; 5965 size_t csize, len, rounded; 5966 ASSERT(HDR_HAS_L2HDR(hdr)); 5967 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 5968 5969 ASSERT(HDR_HAS_L1HDR(hdr)); 5970 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 5971 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 5972 5973 len = l2hdr->b_asize; 5974 cdata = zio_data_buf_alloc(len); 5975 ASSERT3P(cdata, !=, NULL); 5976 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 5977 cdata, l2hdr->b_asize); 5978 5979 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 5980 if (rounded > csize) { 5981 bzero((char *)cdata + csize, rounded - csize); 5982 csize = rounded; 5983 } 5984 5985 if (csize == 0) { 5986 /* zero block, indicate that there's nothing to write */ 5987 zio_data_buf_free(cdata, len); 5988 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 5989 l2hdr->b_asize = 0; 5990 hdr->b_l1hdr.b_tmp_cdata = NULL; 5991 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 5992 return (B_TRUE); 5993 } else if (csize > 0 && csize < len) { 5994 /* 5995 * Compression succeeded, we'll keep the cdata around for 5996 * writing and release it afterwards. 5997 */ 5998 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 5999 l2hdr->b_asize = csize; 6000 hdr->b_l1hdr.b_tmp_cdata = cdata; 6001 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6002 return (B_TRUE); 6003 } else { 6004 /* 6005 * Compression failed, release the compressed buffer. 6006 * l2hdr will be left unmodified. 6007 */ 6008 zio_data_buf_free(cdata, len); 6009 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6010 return (B_FALSE); 6011 } 6012 } 6013 6014 /* 6015 * Decompresses a zio read back from an l2arc device. On success, the 6016 * underlying zio's io_data buffer is overwritten by the uncompressed 6017 * version. On decompression error (corrupt compressed stream), the 6018 * zio->io_error value is set to signal an I/O error. 6019 * 6020 * Please note that the compressed data stream is not checksummed, so 6021 * if the underlying device is experiencing data corruption, we may feed 6022 * corrupt data to the decompressor, so the decompressor needs to be 6023 * able to handle this situation (LZ4 does). 6024 */ 6025 static void 6026 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6027 { 6028 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6029 6030 if (zio->io_error != 0) { 6031 /* 6032 * An io error has occured, just restore the original io 6033 * size in preparation for a main pool read. 6034 */ 6035 zio->io_orig_size = zio->io_size = hdr->b_size; 6036 return; 6037 } 6038 6039 if (c == ZIO_COMPRESS_EMPTY) { 6040 /* 6041 * An empty buffer results in a null zio, which means we 6042 * need to fill its io_data after we're done restoring the 6043 * buffer's contents. 6044 */ 6045 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6046 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6047 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6048 } else { 6049 ASSERT(zio->io_data != NULL); 6050 /* 6051 * We copy the compressed data from the start of the arc buffer 6052 * (the zio_read will have pulled in only what we need, the 6053 * rest is garbage which we will overwrite at decompression) 6054 * and then decompress back to the ARC data buffer. This way we 6055 * can minimize copying by simply decompressing back over the 6056 * original compressed data (rather than decompressing to an 6057 * aux buffer and then copying back the uncompressed buffer, 6058 * which is likely to be much larger). 6059 */ 6060 uint64_t csize; 6061 void *cdata; 6062 6063 csize = zio->io_size; 6064 cdata = zio_data_buf_alloc(csize); 6065 bcopy(zio->io_data, cdata, csize); 6066 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6067 hdr->b_size) != 0) 6068 zio->io_error = EIO; 6069 zio_data_buf_free(cdata, csize); 6070 } 6071 6072 /* Restore the expected uncompressed IO size. */ 6073 zio->io_orig_size = zio->io_size = hdr->b_size; 6074 } 6075 6076 /* 6077 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6078 * This buffer serves as a temporary holder of compressed data while 6079 * the buffer entry is being written to an l2arc device. Once that is 6080 * done, we can dispose of it. 6081 */ 6082 static void 6083 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6084 { 6085 enum zio_compress comp = HDR_GET_COMPRESS(hdr); 6086 6087 ASSERT(HDR_HAS_L1HDR(hdr)); 6088 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6089 6090 if (comp == ZIO_COMPRESS_OFF) { 6091 /* 6092 * In this case, b_tmp_cdata points to the same buffer 6093 * as the arc_buf_t's b_data field. We don't want to 6094 * free it, since the arc_buf_t will handle that. 6095 */ 6096 hdr->b_l1hdr.b_tmp_cdata = NULL; 6097 } else if (comp == ZIO_COMPRESS_EMPTY) { 6098 /* 6099 * In this case, b_tmp_cdata was compressed to an empty 6100 * buffer, thus there's nothing to free and b_tmp_cdata 6101 * should have been set to NULL in l2arc_write_buffers(). 6102 */ 6103 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6104 } else { 6105 /* 6106 * If the data was compressed, then we've allocated a 6107 * temporary buffer for it, so now we need to release it. 6108 */ 6109 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6110 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6111 hdr->b_size); 6112 hdr->b_l1hdr.b_tmp_cdata = NULL; 6113 } 6114 6115 } 6116 6117 /* 6118 * This thread feeds the L2ARC at regular intervals. This is the beating 6119 * heart of the L2ARC. 6120 */ 6121 static void 6122 l2arc_feed_thread(void) 6123 { 6124 callb_cpr_t cpr; 6125 l2arc_dev_t *dev; 6126 spa_t *spa; 6127 uint64_t size, wrote; 6128 clock_t begin, next = ddi_get_lbolt(); 6129 boolean_t headroom_boost = B_FALSE; 6130 6131 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6132 6133 mutex_enter(&l2arc_feed_thr_lock); 6134 6135 while (l2arc_thread_exit == 0) { 6136 CALLB_CPR_SAFE_BEGIN(&cpr); 6137 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6138 next); 6139 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6140 next = ddi_get_lbolt() + hz; 6141 6142 /* 6143 * Quick check for L2ARC devices. 6144 */ 6145 mutex_enter(&l2arc_dev_mtx); 6146 if (l2arc_ndev == 0) { 6147 mutex_exit(&l2arc_dev_mtx); 6148 continue; 6149 } 6150 mutex_exit(&l2arc_dev_mtx); 6151 begin = ddi_get_lbolt(); 6152 6153 /* 6154 * This selects the next l2arc device to write to, and in 6155 * doing so the next spa to feed from: dev->l2ad_spa. This 6156 * will return NULL if there are now no l2arc devices or if 6157 * they are all faulted. 6158 * 6159 * If a device is returned, its spa's config lock is also 6160 * held to prevent device removal. l2arc_dev_get_next() 6161 * will grab and release l2arc_dev_mtx. 6162 */ 6163 if ((dev = l2arc_dev_get_next()) == NULL) 6164 continue; 6165 6166 spa = dev->l2ad_spa; 6167 ASSERT(spa != NULL); 6168 6169 /* 6170 * If the pool is read-only then force the feed thread to 6171 * sleep a little longer. 6172 */ 6173 if (!spa_writeable(spa)) { 6174 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6175 spa_config_exit(spa, SCL_L2ARC, dev); 6176 continue; 6177 } 6178 6179 /* 6180 * Avoid contributing to memory pressure. 6181 */ 6182 if (arc_reclaim_needed()) { 6183 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6184 spa_config_exit(spa, SCL_L2ARC, dev); 6185 continue; 6186 } 6187 6188 ARCSTAT_BUMP(arcstat_l2_feeds); 6189 6190 size = l2arc_write_size(); 6191 6192 /* 6193 * Evict L2ARC buffers that will be overwritten. 6194 */ 6195 l2arc_evict(dev, size, B_FALSE); 6196 6197 /* 6198 * Write ARC buffers. 6199 */ 6200 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6201 6202 /* 6203 * Calculate interval between writes. 6204 */ 6205 next = l2arc_write_interval(begin, size, wrote); 6206 spa_config_exit(spa, SCL_L2ARC, dev); 6207 } 6208 6209 l2arc_thread_exit = 0; 6210 cv_broadcast(&l2arc_feed_thr_cv); 6211 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6212 thread_exit(); 6213 } 6214 6215 boolean_t 6216 l2arc_vdev_present(vdev_t *vd) 6217 { 6218 l2arc_dev_t *dev; 6219 6220 mutex_enter(&l2arc_dev_mtx); 6221 for (dev = list_head(l2arc_dev_list); dev != NULL; 6222 dev = list_next(l2arc_dev_list, dev)) { 6223 if (dev->l2ad_vdev == vd) 6224 break; 6225 } 6226 mutex_exit(&l2arc_dev_mtx); 6227 6228 return (dev != NULL); 6229 } 6230 6231 /* 6232 * Add a vdev for use by the L2ARC. By this point the spa has already 6233 * validated the vdev and opened it. 6234 */ 6235 void 6236 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6237 { 6238 l2arc_dev_t *adddev; 6239 6240 ASSERT(!l2arc_vdev_present(vd)); 6241 6242 /* 6243 * Create a new l2arc device entry. 6244 */ 6245 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6246 adddev->l2ad_spa = spa; 6247 adddev->l2ad_vdev = vd; 6248 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6249 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6250 adddev->l2ad_hand = adddev->l2ad_start; 6251 adddev->l2ad_evict = adddev->l2ad_start; 6252 adddev->l2ad_first = B_TRUE; 6253 adddev->l2ad_writing = B_FALSE; 6254 6255 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6256 /* 6257 * This is a list of all ARC buffers that are still valid on the 6258 * device. 6259 */ 6260 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6261 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6262 6263 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6264 6265 /* 6266 * Add device to global list 6267 */ 6268 mutex_enter(&l2arc_dev_mtx); 6269 list_insert_head(l2arc_dev_list, adddev); 6270 atomic_inc_64(&l2arc_ndev); 6271 mutex_exit(&l2arc_dev_mtx); 6272 } 6273 6274 /* 6275 * Remove a vdev from the L2ARC. 6276 */ 6277 void 6278 l2arc_remove_vdev(vdev_t *vd) 6279 { 6280 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6281 6282 /* 6283 * Find the device by vdev 6284 */ 6285 mutex_enter(&l2arc_dev_mtx); 6286 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6287 nextdev = list_next(l2arc_dev_list, dev); 6288 if (vd == dev->l2ad_vdev) { 6289 remdev = dev; 6290 break; 6291 } 6292 } 6293 ASSERT(remdev != NULL); 6294 6295 /* 6296 * Remove device from global list 6297 */ 6298 list_remove(l2arc_dev_list, remdev); 6299 l2arc_dev_last = NULL; /* may have been invalidated */ 6300 atomic_dec_64(&l2arc_ndev); 6301 mutex_exit(&l2arc_dev_mtx); 6302 6303 /* 6304 * Clear all buflists and ARC references. L2ARC device flush. 6305 */ 6306 l2arc_evict(remdev, 0, B_TRUE); 6307 list_destroy(&remdev->l2ad_buflist); 6308 mutex_destroy(&remdev->l2ad_mtx); 6309 kmem_free(remdev, sizeof (l2arc_dev_t)); 6310 } 6311 6312 void 6313 l2arc_init(void) 6314 { 6315 l2arc_thread_exit = 0; 6316 l2arc_ndev = 0; 6317 l2arc_writes_sent = 0; 6318 l2arc_writes_done = 0; 6319 6320 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6321 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6322 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6323 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6324 6325 l2arc_dev_list = &L2ARC_dev_list; 6326 l2arc_free_on_write = &L2ARC_free_on_write; 6327 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6328 offsetof(l2arc_dev_t, l2ad_node)); 6329 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6330 offsetof(l2arc_data_free_t, l2df_list_node)); 6331 } 6332 6333 void 6334 l2arc_fini(void) 6335 { 6336 /* 6337 * This is called from dmu_fini(), which is called from spa_fini(); 6338 * Because of this, we can assume that all l2arc devices have 6339 * already been removed when the pools themselves were removed. 6340 */ 6341 6342 l2arc_do_free_on_write(); 6343 6344 mutex_destroy(&l2arc_feed_thr_lock); 6345 cv_destroy(&l2arc_feed_thr_cv); 6346 mutex_destroy(&l2arc_dev_mtx); 6347 mutex_destroy(&l2arc_free_on_write_mtx); 6348 6349 list_destroy(l2arc_dev_list); 6350 list_destroy(l2arc_free_on_write); 6351 } 6352 6353 void 6354 l2arc_start(void) 6355 { 6356 if (!(spa_mode_global & FWRITE)) 6357 return; 6358 6359 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6360 TS_RUN, minclsyspri); 6361 } 6362 6363 void 6364 l2arc_stop(void) 6365 { 6366 if (!(spa_mode_global & FWRITE)) 6367 return; 6368 6369 mutex_enter(&l2arc_feed_thr_lock); 6370 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6371 l2arc_thread_exit = 1; 6372 while (l2arc_thread_exit != 0) 6373 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6374 mutex_exit(&l2arc_feed_thr_lock); 6375 } 6376