1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #include <sys/multilist.h> 133 #ifdef _KERNEL 134 #include <sys/vmsystm.h> 135 #include <vm/anon.h> 136 #include <sys/fs/swapnode.h> 137 #include <sys/dnlc.h> 138 #endif 139 #include <sys/callb.h> 140 #include <sys/kstat.h> 141 #include <zfs_fletcher.h> 142 #include <sys/byteorder.h> 143 #include <sys/spa_impl.h> 144 145 #ifndef _KERNEL 146 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 147 boolean_t arc_watch = B_FALSE; 148 int arc_procfd; 149 #endif 150 151 static kmutex_t arc_reclaim_lock; 152 static kcondvar_t arc_reclaim_thread_cv; 153 static boolean_t arc_reclaim_thread_exit; 154 static kcondvar_t arc_reclaim_waiters_cv; 155 156 static kmutex_t arc_user_evicts_lock; 157 static kcondvar_t arc_user_evicts_cv; 158 static boolean_t arc_user_evicts_thread_exit; 159 160 uint_t arc_reduce_dnlc_percent = 3; 161 162 /* 163 * The number of headers to evict in arc_evict_state_impl() before 164 * dropping the sublist lock and evicting from another sublist. A lower 165 * value means we're more likely to evict the "correct" header (i.e. the 166 * oldest header in the arc state), but comes with higher overhead 167 * (i.e. more invocations of arc_evict_state_impl()). 168 */ 169 int zfs_arc_evict_batch_limit = 10; 170 171 /* 172 * The number of sublists used for each of the arc state lists. If this 173 * is not set to a suitable value by the user, it will be configured to 174 * the number of CPUs on the system in arc_init(). 175 */ 176 int zfs_arc_num_sublists_per_state = 0; 177 178 /* number of seconds before growing cache again */ 179 static int arc_grow_retry = 60; 180 181 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 182 int zfs_arc_overflow_shift = 8; 183 184 /* shift of arc_c for calculating both min and max arc_p */ 185 static int arc_p_min_shift = 4; 186 187 /* log2(fraction of arc to reclaim) */ 188 static int arc_shrink_shift = 7; 189 190 /* 191 * log2(fraction of ARC which must be free to allow growing). 192 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 193 * when reading a new block into the ARC, we will evict an equal-sized block 194 * from the ARC. 195 * 196 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 197 * we will still not allow it to grow. 198 */ 199 int arc_no_grow_shift = 5; 200 201 202 /* 203 * minimum lifespan of a prefetch block in clock ticks 204 * (initialized in arc_init()) 205 */ 206 static int arc_min_prefetch_lifespan; 207 208 /* 209 * If this percent of memory is free, don't throttle. 210 */ 211 int arc_lotsfree_percent = 10; 212 213 static int arc_dead; 214 215 /* 216 * The arc has filled available memory and has now warmed up. 217 */ 218 static boolean_t arc_warm; 219 220 /* 221 * These tunables are for performance analysis. 222 */ 223 uint64_t zfs_arc_max; 224 uint64_t zfs_arc_min; 225 uint64_t zfs_arc_meta_limit = 0; 226 uint64_t zfs_arc_meta_min = 0; 227 int zfs_arc_grow_retry = 0; 228 int zfs_arc_shrink_shift = 0; 229 int zfs_arc_p_min_shift = 0; 230 int zfs_disable_dup_eviction = 0; 231 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 232 233 /* 234 * Note that buffers can be in one of 6 states: 235 * ARC_anon - anonymous (discussed below) 236 * ARC_mru - recently used, currently cached 237 * ARC_mru_ghost - recentely used, no longer in cache 238 * ARC_mfu - frequently used, currently cached 239 * ARC_mfu_ghost - frequently used, no longer in cache 240 * ARC_l2c_only - exists in L2ARC but not other states 241 * When there are no active references to the buffer, they are 242 * are linked onto a list in one of these arc states. These are 243 * the only buffers that can be evicted or deleted. Within each 244 * state there are multiple lists, one for meta-data and one for 245 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 246 * etc.) is tracked separately so that it can be managed more 247 * explicitly: favored over data, limited explicitly. 248 * 249 * Anonymous buffers are buffers that are not associated with 250 * a DVA. These are buffers that hold dirty block copies 251 * before they are written to stable storage. By definition, 252 * they are "ref'd" and are considered part of arc_mru 253 * that cannot be freed. Generally, they will aquire a DVA 254 * as they are written and migrate onto the arc_mru list. 255 * 256 * The ARC_l2c_only state is for buffers that are in the second 257 * level ARC but no longer in any of the ARC_m* lists. The second 258 * level ARC itself may also contain buffers that are in any of 259 * the ARC_m* states - meaning that a buffer can exist in two 260 * places. The reason for the ARC_l2c_only state is to keep the 261 * buffer header in the hash table, so that reads that hit the 262 * second level ARC benefit from these fast lookups. 263 */ 264 265 typedef struct arc_state { 266 /* 267 * list of evictable buffers 268 */ 269 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 270 /* 271 * total amount of evictable data in this state 272 */ 273 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 274 /* 275 * total amount of data in this state; this includes: evictable, 276 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 277 */ 278 refcount_t arcs_size; 279 } arc_state_t; 280 281 /* The 6 states: */ 282 static arc_state_t ARC_anon; 283 static arc_state_t ARC_mru; 284 static arc_state_t ARC_mru_ghost; 285 static arc_state_t ARC_mfu; 286 static arc_state_t ARC_mfu_ghost; 287 static arc_state_t ARC_l2c_only; 288 289 typedef struct arc_stats { 290 kstat_named_t arcstat_hits; 291 kstat_named_t arcstat_misses; 292 kstat_named_t arcstat_demand_hits_data; 293 kstat_named_t arcstat_demand_misses_data; 294 kstat_named_t arcstat_demand_hits_metadata; 295 kstat_named_t arcstat_demand_misses_metadata; 296 kstat_named_t arcstat_prefetch_hits_data; 297 kstat_named_t arcstat_prefetch_misses_data; 298 kstat_named_t arcstat_prefetch_hits_metadata; 299 kstat_named_t arcstat_prefetch_misses_metadata; 300 kstat_named_t arcstat_mru_hits; 301 kstat_named_t arcstat_mru_ghost_hits; 302 kstat_named_t arcstat_mfu_hits; 303 kstat_named_t arcstat_mfu_ghost_hits; 304 kstat_named_t arcstat_deleted; 305 /* 306 * Number of buffers that could not be evicted because the hash lock 307 * was held by another thread. The lock may not necessarily be held 308 * by something using the same buffer, since hash locks are shared 309 * by multiple buffers. 310 */ 311 kstat_named_t arcstat_mutex_miss; 312 /* 313 * Number of buffers skipped because they have I/O in progress, are 314 * indrect prefetch buffers that have not lived long enough, or are 315 * not from the spa we're trying to evict from. 316 */ 317 kstat_named_t arcstat_evict_skip; 318 /* 319 * Number of times arc_evict_state() was unable to evict enough 320 * buffers to reach it's target amount. 321 */ 322 kstat_named_t arcstat_evict_not_enough; 323 kstat_named_t arcstat_evict_l2_cached; 324 kstat_named_t arcstat_evict_l2_eligible; 325 kstat_named_t arcstat_evict_l2_ineligible; 326 kstat_named_t arcstat_evict_l2_skip; 327 kstat_named_t arcstat_hash_elements; 328 kstat_named_t arcstat_hash_elements_max; 329 kstat_named_t arcstat_hash_collisions; 330 kstat_named_t arcstat_hash_chains; 331 kstat_named_t arcstat_hash_chain_max; 332 kstat_named_t arcstat_p; 333 kstat_named_t arcstat_c; 334 kstat_named_t arcstat_c_min; 335 kstat_named_t arcstat_c_max; 336 kstat_named_t arcstat_size; 337 /* 338 * Number of bytes consumed by internal ARC structures necessary 339 * for tracking purposes; these structures are not actually 340 * backed by ARC buffers. This includes arc_buf_hdr_t structures 341 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 342 * caches), and arc_buf_t structures (allocated via arc_buf_t 343 * cache). 344 */ 345 kstat_named_t arcstat_hdr_size; 346 /* 347 * Number of bytes consumed by ARC buffers of type equal to 348 * ARC_BUFC_DATA. This is generally consumed by buffers backing 349 * on disk user data (e.g. plain file contents). 350 */ 351 kstat_named_t arcstat_data_size; 352 /* 353 * Number of bytes consumed by ARC buffers of type equal to 354 * ARC_BUFC_METADATA. This is generally consumed by buffers 355 * backing on disk data that is used for internal ZFS 356 * structures (e.g. ZAP, dnode, indirect blocks, etc). 357 */ 358 kstat_named_t arcstat_metadata_size; 359 /* 360 * Number of bytes consumed by various buffers and structures 361 * not actually backed with ARC buffers. This includes bonus 362 * buffers (allocated directly via zio_buf_* functions), 363 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 364 * cache), and dnode_t structures (allocated via dnode_t cache). 365 */ 366 kstat_named_t arcstat_other_size; 367 /* 368 * Total number of bytes consumed by ARC buffers residing in the 369 * arc_anon state. This includes *all* buffers in the arc_anon 370 * state; e.g. data, metadata, evictable, and unevictable buffers 371 * are all included in this value. 372 */ 373 kstat_named_t arcstat_anon_size; 374 /* 375 * Number of bytes consumed by ARC buffers that meet the 376 * following criteria: backing buffers of type ARC_BUFC_DATA, 377 * residing in the arc_anon state, and are eligible for eviction 378 * (e.g. have no outstanding holds on the buffer). 379 */ 380 kstat_named_t arcstat_anon_evictable_data; 381 /* 382 * Number of bytes consumed by ARC buffers that meet the 383 * following criteria: backing buffers of type ARC_BUFC_METADATA, 384 * residing in the arc_anon state, and are eligible for eviction 385 * (e.g. have no outstanding holds on the buffer). 386 */ 387 kstat_named_t arcstat_anon_evictable_metadata; 388 /* 389 * Total number of bytes consumed by ARC buffers residing in the 390 * arc_mru state. This includes *all* buffers in the arc_mru 391 * state; e.g. data, metadata, evictable, and unevictable buffers 392 * are all included in this value. 393 */ 394 kstat_named_t arcstat_mru_size; 395 /* 396 * Number of bytes consumed by ARC buffers that meet the 397 * following criteria: backing buffers of type ARC_BUFC_DATA, 398 * residing in the arc_mru state, and are eligible for eviction 399 * (e.g. have no outstanding holds on the buffer). 400 */ 401 kstat_named_t arcstat_mru_evictable_data; 402 /* 403 * Number of bytes consumed by ARC buffers that meet the 404 * following criteria: backing buffers of type ARC_BUFC_METADATA, 405 * residing in the arc_mru state, and are eligible for eviction 406 * (e.g. have no outstanding holds on the buffer). 407 */ 408 kstat_named_t arcstat_mru_evictable_metadata; 409 /* 410 * Total number of bytes that *would have been* consumed by ARC 411 * buffers in the arc_mru_ghost state. The key thing to note 412 * here, is the fact that this size doesn't actually indicate 413 * RAM consumption. The ghost lists only consist of headers and 414 * don't actually have ARC buffers linked off of these headers. 415 * Thus, *if* the headers had associated ARC buffers, these 416 * buffers *would have* consumed this number of bytes. 417 */ 418 kstat_named_t arcstat_mru_ghost_size; 419 /* 420 * Number of bytes that *would have been* consumed by ARC 421 * buffers that are eligible for eviction, of type 422 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 423 */ 424 kstat_named_t arcstat_mru_ghost_evictable_data; 425 /* 426 * Number of bytes that *would have been* consumed by ARC 427 * buffers that are eligible for eviction, of type 428 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 429 */ 430 kstat_named_t arcstat_mru_ghost_evictable_metadata; 431 /* 432 * Total number of bytes consumed by ARC buffers residing in the 433 * arc_mfu state. This includes *all* buffers in the arc_mfu 434 * state; e.g. data, metadata, evictable, and unevictable buffers 435 * are all included in this value. 436 */ 437 kstat_named_t arcstat_mfu_size; 438 /* 439 * Number of bytes consumed by ARC buffers that are eligible for 440 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 441 * state. 442 */ 443 kstat_named_t arcstat_mfu_evictable_data; 444 /* 445 * Number of bytes consumed by ARC buffers that are eligible for 446 * eviction, of type ARC_BUFC_METADATA, and reside in the 447 * arc_mfu state. 448 */ 449 kstat_named_t arcstat_mfu_evictable_metadata; 450 /* 451 * Total number of bytes that *would have been* consumed by ARC 452 * buffers in the arc_mfu_ghost state. See the comment above 453 * arcstat_mru_ghost_size for more details. 454 */ 455 kstat_named_t arcstat_mfu_ghost_size; 456 /* 457 * Number of bytes that *would have been* consumed by ARC 458 * buffers that are eligible for eviction, of type 459 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 460 */ 461 kstat_named_t arcstat_mfu_ghost_evictable_data; 462 /* 463 * Number of bytes that *would have been* consumed by ARC 464 * buffers that are eligible for eviction, of type 465 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 466 */ 467 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 468 kstat_named_t arcstat_l2_hits; 469 kstat_named_t arcstat_l2_misses; 470 kstat_named_t arcstat_l2_feeds; 471 kstat_named_t arcstat_l2_rw_clash; 472 kstat_named_t arcstat_l2_read_bytes; 473 kstat_named_t arcstat_l2_write_bytes; 474 kstat_named_t arcstat_l2_writes_sent; 475 kstat_named_t arcstat_l2_writes_done; 476 kstat_named_t arcstat_l2_writes_error; 477 kstat_named_t arcstat_l2_writes_lock_retry; 478 kstat_named_t arcstat_l2_evict_lock_retry; 479 kstat_named_t arcstat_l2_evict_reading; 480 kstat_named_t arcstat_l2_evict_l1cached; 481 kstat_named_t arcstat_l2_free_on_write; 482 kstat_named_t arcstat_l2_cdata_free_on_write; 483 kstat_named_t arcstat_l2_abort_lowmem; 484 kstat_named_t arcstat_l2_cksum_bad; 485 kstat_named_t arcstat_l2_io_error; 486 kstat_named_t arcstat_l2_size; 487 kstat_named_t arcstat_l2_asize; 488 kstat_named_t arcstat_l2_hdr_size; 489 kstat_named_t arcstat_l2_compress_successes; 490 kstat_named_t arcstat_l2_compress_zeros; 491 kstat_named_t arcstat_l2_compress_failures; 492 kstat_named_t arcstat_l2_log_blk_writes; 493 kstat_named_t arcstat_l2_log_blk_avg_size; 494 kstat_named_t arcstat_l2_data_to_meta_ratio; 495 kstat_named_t arcstat_l2_rebuild_successes; 496 kstat_named_t arcstat_l2_rebuild_abort_unsupported; 497 kstat_named_t arcstat_l2_rebuild_abort_io_errors; 498 kstat_named_t arcstat_l2_rebuild_abort_cksum_errors; 499 kstat_named_t arcstat_l2_rebuild_abort_loop_errors; 500 kstat_named_t arcstat_l2_rebuild_abort_lowmem; 501 kstat_named_t arcstat_l2_rebuild_size; 502 kstat_named_t arcstat_l2_rebuild_bufs; 503 kstat_named_t arcstat_l2_rebuild_bufs_precached; 504 kstat_named_t arcstat_l2_rebuild_psize; 505 kstat_named_t arcstat_l2_rebuild_log_blks; 506 kstat_named_t arcstat_memory_throttle_count; 507 kstat_named_t arcstat_duplicate_buffers; 508 kstat_named_t arcstat_duplicate_buffers_size; 509 kstat_named_t arcstat_duplicate_reads; 510 kstat_named_t arcstat_meta_used; 511 kstat_named_t arcstat_meta_limit; 512 kstat_named_t arcstat_meta_max; 513 kstat_named_t arcstat_meta_min; 514 kstat_named_t arcstat_sync_wait_for_async; 515 kstat_named_t arcstat_demand_hit_predictive_prefetch; 516 } arc_stats_t; 517 518 static arc_stats_t arc_stats = { 519 { "hits", KSTAT_DATA_UINT64 }, 520 { "misses", KSTAT_DATA_UINT64 }, 521 { "demand_data_hits", KSTAT_DATA_UINT64 }, 522 { "demand_data_misses", KSTAT_DATA_UINT64 }, 523 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 524 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 525 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 526 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 527 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 528 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 529 { "mru_hits", KSTAT_DATA_UINT64 }, 530 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 531 { "mfu_hits", KSTAT_DATA_UINT64 }, 532 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 533 { "deleted", KSTAT_DATA_UINT64 }, 534 { "mutex_miss", KSTAT_DATA_UINT64 }, 535 { "evict_skip", KSTAT_DATA_UINT64 }, 536 { "evict_not_enough", KSTAT_DATA_UINT64 }, 537 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 538 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 539 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 540 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 541 { "hash_elements", KSTAT_DATA_UINT64 }, 542 { "hash_elements_max", KSTAT_DATA_UINT64 }, 543 { "hash_collisions", KSTAT_DATA_UINT64 }, 544 { "hash_chains", KSTAT_DATA_UINT64 }, 545 { "hash_chain_max", KSTAT_DATA_UINT64 }, 546 { "p", KSTAT_DATA_UINT64 }, 547 { "c", KSTAT_DATA_UINT64 }, 548 { "c_min", KSTAT_DATA_UINT64 }, 549 { "c_max", KSTAT_DATA_UINT64 }, 550 { "size", KSTAT_DATA_UINT64 }, 551 { "hdr_size", KSTAT_DATA_UINT64 }, 552 { "data_size", KSTAT_DATA_UINT64 }, 553 { "metadata_size", KSTAT_DATA_UINT64 }, 554 { "other_size", KSTAT_DATA_UINT64 }, 555 { "anon_size", KSTAT_DATA_UINT64 }, 556 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 557 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 558 { "mru_size", KSTAT_DATA_UINT64 }, 559 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 560 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 561 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 562 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 563 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 564 { "mfu_size", KSTAT_DATA_UINT64 }, 565 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 566 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 567 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 568 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 569 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 570 { "l2_hits", KSTAT_DATA_UINT64 }, 571 { "l2_misses", KSTAT_DATA_UINT64 }, 572 { "l2_feeds", KSTAT_DATA_UINT64 }, 573 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 574 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 575 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 576 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 577 { "l2_writes_done", KSTAT_DATA_UINT64 }, 578 { "l2_writes_error", KSTAT_DATA_UINT64 }, 579 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 580 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 581 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 582 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 583 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 584 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 585 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 586 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 587 { "l2_io_error", KSTAT_DATA_UINT64 }, 588 { "l2_size", KSTAT_DATA_UINT64 }, 589 { "l2_asize", KSTAT_DATA_UINT64 }, 590 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 591 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 592 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 593 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 594 { "l2_log_blk_writes", KSTAT_DATA_UINT64 }, 595 { "l2_log_blk_avg_size", KSTAT_DATA_UINT64 }, 596 { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 }, 597 { "l2_rebuild_successes", KSTAT_DATA_UINT64 }, 598 { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 }, 599 { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 }, 600 { "l2_rebuild_cksum_errors", KSTAT_DATA_UINT64 }, 601 { "l2_rebuild_loop_errors", KSTAT_DATA_UINT64 }, 602 { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 }, 603 { "l2_rebuild_size", KSTAT_DATA_UINT64 }, 604 { "l2_rebuild_bufs", KSTAT_DATA_UINT64 }, 605 { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 }, 606 { "l2_rebuild_psize", KSTAT_DATA_UINT64 }, 607 { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 }, 608 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 609 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 610 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 611 { "duplicate_reads", KSTAT_DATA_UINT64 }, 612 { "arc_meta_used", KSTAT_DATA_UINT64 }, 613 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 614 { "arc_meta_max", KSTAT_DATA_UINT64 }, 615 { "arc_meta_min", KSTAT_DATA_UINT64 }, 616 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 617 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 618 }; 619 620 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 621 622 #define ARCSTAT_INCR(stat, val) \ 623 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 624 625 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 626 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 627 628 #define ARCSTAT_MAX(stat, val) { \ 629 uint64_t m; \ 630 while ((val) > (m = arc_stats.stat.value.ui64) && \ 631 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 632 continue; \ 633 } 634 635 #define ARCSTAT_MAXSTAT(stat) \ 636 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 637 638 /* 639 * We define a macro to allow ARC hits/misses to be easily broken down by 640 * two separate conditions, giving a total of four different subtypes for 641 * each of hits and misses (so eight statistics total). 642 */ 643 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 644 if (cond1) { \ 645 if (cond2) { \ 646 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 647 } else { \ 648 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 649 } \ 650 } else { \ 651 if (cond2) { \ 652 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 653 } else { \ 654 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 655 } \ 656 } 657 658 /* 659 * This macro allows us to use kstats as floating averages. Each time we 660 * update this kstat, we first factor it and the update value by 661 * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall 662 * average. This macro assumes that integer loads and stores are atomic, but 663 * is not safe for multiple writers updating the kstat in parallel (only the 664 * last writer's update will remain). 665 */ 666 #define ARCSTAT_F_AVG_FACTOR 3 667 #define ARCSTAT_F_AVG(stat, value) \ 668 do { \ 669 uint64_t x = ARCSTAT(stat); \ 670 x = x - x / ARCSTAT_F_AVG_FACTOR + \ 671 (value) / ARCSTAT_F_AVG_FACTOR; \ 672 ARCSTAT(stat) = x; \ 673 _NOTE(CONSTCOND) \ 674 } while (0) 675 676 kstat_t *arc_ksp; 677 static arc_state_t *arc_anon; 678 static arc_state_t *arc_mru; 679 static arc_state_t *arc_mru_ghost; 680 static arc_state_t *arc_mfu; 681 static arc_state_t *arc_mfu_ghost; 682 static arc_state_t *arc_l2c_only; 683 684 /* 685 * There are several ARC variables that are critical to export as kstats -- 686 * but we don't want to have to grovel around in the kstat whenever we wish to 687 * manipulate them. For these variables, we therefore define them to be in 688 * terms of the statistic variable. This assures that we are not introducing 689 * the possibility of inconsistency by having shadow copies of the variables, 690 * while still allowing the code to be readable. 691 */ 692 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 693 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 694 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 695 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 696 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 697 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 698 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 699 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 700 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 701 702 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 703 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 704 705 static int arc_no_grow; /* Don't try to grow cache size */ 706 static uint64_t arc_tempreserve; 707 static uint64_t arc_loaned_bytes; 708 709 typedef struct arc_callback arc_callback_t; 710 711 struct arc_callback { 712 void *acb_private; 713 arc_done_func_t *acb_done; 714 arc_buf_t *acb_buf; 715 zio_t *acb_zio_dummy; 716 arc_callback_t *acb_next; 717 }; 718 719 typedef struct arc_write_callback arc_write_callback_t; 720 721 struct arc_write_callback { 722 void *awcb_private; 723 arc_done_func_t *awcb_ready; 724 arc_done_func_t *awcb_physdone; 725 arc_done_func_t *awcb_done; 726 arc_buf_t *awcb_buf; 727 }; 728 729 /* 730 * ARC buffers are separated into multiple structs as a memory saving measure: 731 * - Common fields struct, always defined, and embedded within it: 732 * - L2-only fields, always allocated but undefined when not in L2ARC 733 * - L1-only fields, only allocated when in L1ARC 734 * 735 * Buffer in L1 Buffer only in L2 736 * +------------------------+ +------------------------+ 737 * | arc_buf_hdr_t | | arc_buf_hdr_t | 738 * | | | | 739 * | | | | 740 * | | | | 741 * +------------------------+ +------------------------+ 742 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 743 * | (undefined if L1-only) | | | 744 * +------------------------+ +------------------------+ 745 * | l1arc_buf_hdr_t | 746 * | | 747 * | | 748 * | | 749 * | | 750 * +------------------------+ 751 * 752 * Because it's possible for the L2ARC to become extremely large, we can wind 753 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 754 * is minimized by only allocating the fields necessary for an L1-cached buffer 755 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 756 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 757 * words in pointers. arc_hdr_realloc() is used to switch a header between 758 * these two allocation states. 759 */ 760 typedef struct l1arc_buf_hdr { 761 kmutex_t b_freeze_lock; 762 #ifdef ZFS_DEBUG 763 /* 764 * used for debugging wtih kmem_flags - by allocating and freeing 765 * b_thawed when the buffer is thawed, we get a record of the stack 766 * trace that thawed it. 767 */ 768 void *b_thawed; 769 #endif 770 771 arc_buf_t *b_buf; 772 uint32_t b_datacnt; 773 /* for waiting on writes to complete */ 774 kcondvar_t b_cv; 775 776 /* protected by arc state mutex */ 777 arc_state_t *b_state; 778 multilist_node_t b_arc_node; 779 780 /* updated atomically */ 781 clock_t b_arc_access; 782 783 /* self protecting */ 784 refcount_t b_refcnt; 785 786 arc_callback_t *b_acb; 787 /* temporary buffer holder for in-flight compressed data */ 788 void *b_tmp_cdata; 789 } l1arc_buf_hdr_t; 790 791 typedef struct l2arc_dev l2arc_dev_t; 792 793 typedef struct l2arc_buf_hdr { 794 /* protected by arc_buf_hdr mutex */ 795 l2arc_dev_t *b_dev; /* L2ARC device */ 796 uint64_t b_daddr; /* disk address, offset byte */ 797 /* real alloc'd buffer size depending on b_compress applied */ 798 int32_t b_asize; 799 uint8_t b_compress; 800 801 list_node_t b_l2node; 802 } l2arc_buf_hdr_t; 803 804 struct arc_buf_hdr { 805 /* protected by hash lock */ 806 dva_t b_dva; 807 uint64_t b_birth; 808 /* 809 * Even though this checksum is only set/verified when a buffer is in 810 * the L1 cache, it needs to be in the set of common fields because it 811 * must be preserved from the time before a buffer is written out to 812 * L2ARC until after it is read back in. 813 */ 814 zio_cksum_t *b_freeze_cksum; 815 816 arc_buf_hdr_t *b_hash_next; 817 arc_flags_t b_flags; 818 819 /* immutable */ 820 int32_t b_size; 821 uint64_t b_spa; 822 823 /* L2ARC fields. Undefined when not in L2ARC. */ 824 l2arc_buf_hdr_t b_l2hdr; 825 /* L1ARC fields. Undefined when in l2arc_only state */ 826 l1arc_buf_hdr_t b_l1hdr; 827 }; 828 829 static arc_buf_t *arc_eviction_list; 830 static arc_buf_hdr_t arc_eviction_hdr; 831 832 #define GHOST_STATE(state) \ 833 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 834 (state) == arc_l2c_only) 835 836 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 837 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 838 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 839 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 840 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 841 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 842 843 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 844 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 845 #define HDR_L2_READING(hdr) \ 846 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 847 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 848 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 849 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 850 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 851 852 #define HDR_ISTYPE_METADATA(hdr) \ 853 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 854 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 855 856 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 857 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 858 859 /* 860 * Other sizes 861 */ 862 863 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 864 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 865 866 /* 867 * Hash table routines 868 */ 869 870 #define HT_LOCK_PAD 64 871 872 struct ht_lock { 873 kmutex_t ht_lock; 874 #ifdef _KERNEL 875 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 876 #endif 877 }; 878 879 #define BUF_LOCKS 256 880 typedef struct buf_hash_table { 881 uint64_t ht_mask; 882 arc_buf_hdr_t **ht_table; 883 struct ht_lock ht_locks[BUF_LOCKS]; 884 } buf_hash_table_t; 885 886 static buf_hash_table_t buf_hash_table; 887 888 #define BUF_HASH_INDEX(spa, dva, birth) \ 889 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 890 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 891 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 892 #define HDR_LOCK(hdr) \ 893 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 894 895 uint64_t zfs_crc64_table[256]; 896 897 /* 898 * Level 2 ARC 899 */ 900 901 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 902 #define L2ARC_HEADROOM 2 /* num of writes */ 903 /* 904 * If we discover during ARC scan any buffers to be compressed, we boost 905 * our headroom for the next scanning cycle by this percentage multiple. 906 */ 907 #define L2ARC_HEADROOM_BOOST 200 908 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 909 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 910 911 /* 912 * Used to distinguish headers that are being process by 913 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 914 * address. This can happen when the header is added to the l2arc's list 915 * of buffers to write in the first stage of l2arc_write_buffers(), but 916 * has not yet been written out which happens in the second stage of 917 * l2arc_write_buffers(). 918 */ 919 #define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 920 921 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 922 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 923 924 /* L2ARC Performance Tunables */ 925 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 926 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 927 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 928 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 929 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 930 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 931 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 932 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 933 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 934 935 static list_t L2ARC_dev_list; /* device list */ 936 static list_t *l2arc_dev_list; /* device list pointer */ 937 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 938 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 939 static list_t L2ARC_free_on_write; /* free after write buf list */ 940 static list_t *l2arc_free_on_write; /* free after write list ptr */ 941 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 942 static uint64_t l2arc_ndev; /* number of devices */ 943 944 typedef struct l2arc_read_callback { 945 arc_buf_t *l2rcb_buf; /* read buffer */ 946 spa_t *l2rcb_spa; /* spa */ 947 blkptr_t l2rcb_bp; /* original blkptr */ 948 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 949 int l2rcb_flags; /* original flags */ 950 enum zio_compress l2rcb_compress; /* applied compress */ 951 } l2arc_read_callback_t; 952 953 typedef struct l2arc_write_callback { 954 l2arc_dev_t *l2wcb_dev; /* device info */ 955 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 956 list_t l2wcb_log_blk_buflist; /* in-flight log blocks */ 957 } l2arc_write_callback_t; 958 959 typedef struct l2arc_data_free { 960 /* protected by l2arc_free_on_write_mtx */ 961 void *l2df_data; 962 size_t l2df_size; 963 void (*l2df_func)(void *, size_t); 964 list_node_t l2df_list_node; 965 } l2arc_data_free_t; 966 967 static kmutex_t l2arc_feed_thr_lock; 968 static kcondvar_t l2arc_feed_thr_cv; 969 static uint8_t l2arc_thread_exit; 970 971 static void arc_get_data_buf(arc_buf_t *); 972 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 973 static boolean_t arc_is_overflowing(); 974 static void arc_buf_watch(arc_buf_t *); 975 static void l2arc_read_done(zio_t *zio); 976 static l2arc_dev_t *l2arc_vdev_get(vdev_t *vd); 977 978 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 979 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 980 static arc_buf_contents_t arc_flags_to_bufc(uint32_t); 981 982 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 983 static void l2arc_read_done(zio_t *); 984 985 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 986 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 987 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 988 989 static void 990 arc_update_hit_stat(arc_buf_hdr_t *hdr, boolean_t hit) 991 { 992 boolean_t pf = !HDR_PREFETCH(hdr); 993 switch (arc_buf_type(hdr)) { 994 case ARC_BUFC_DATA: 995 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, data); 996 break; 997 case ARC_BUFC_METADATA: 998 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, 999 metadata); 1000 break; 1001 default: 1002 break; 1003 } 1004 } 1005 1006 enum { 1007 L2ARC_DEV_HDR_EVICT_FIRST = (1 << 0) /* mirror of l2ad_first */ 1008 }; 1009 1010 /* 1011 * Pointer used in persistent L2ARC (for pointing to log blocks & ARC buffers). 1012 */ 1013 typedef struct l2arc_log_blkptr { 1014 uint64_t lbp_daddr; /* device address of log */ 1015 /* 1016 * lbp_prop is the same format as the blk_prop in blkptr_t: 1017 * * logical size (in sectors) 1018 * * physical (compressed) size (in sectors) 1019 * * compression algorithm (we always LZ4-compress l2arc logs) 1020 * * checksum algorithm (used for lbp_cksum) 1021 * * object type & level (unused for now) 1022 */ 1023 uint64_t lbp_prop; 1024 zio_cksum_t lbp_cksum; /* fletcher4 of log */ 1025 } l2arc_log_blkptr_t; 1026 1027 /* 1028 * The persistent L2ARC device header. 1029 * Byte order of magic determines whether 64-bit bswap of fields is necessary. 1030 */ 1031 typedef struct l2arc_dev_hdr_phys { 1032 uint64_t dh_magic; /* L2ARC_DEV_HDR_MAGIC */ 1033 zio_cksum_t dh_self_cksum; /* fletcher4 of fields below */ 1034 1035 /* 1036 * Global L2ARC device state and metadata. 1037 */ 1038 uint64_t dh_spa_guid; 1039 uint64_t dh_alloc_space; /* vdev space alloc status */ 1040 uint64_t dh_flags; /* l2arc_dev_hdr_flags_t */ 1041 1042 /* 1043 * Start of log block chain. [0] -> newest log, [1] -> one older (used 1044 * for initiating prefetch). 1045 */ 1046 l2arc_log_blkptr_t dh_start_lbps[2]; 1047 1048 const uint64_t dh_pad[44]; /* pad to 512 bytes */ 1049 } l2arc_dev_hdr_phys_t; 1050 CTASSERT(sizeof (l2arc_dev_hdr_phys_t) == SPA_MINBLOCKSIZE); 1051 1052 /* 1053 * A single ARC buffer header entry in a l2arc_log_blk_phys_t. 1054 */ 1055 typedef struct l2arc_log_ent_phys { 1056 dva_t le_dva; /* dva of buffer */ 1057 uint64_t le_birth; /* birth txg of buffer */ 1058 zio_cksum_t le_freeze_cksum; 1059 /* 1060 * le_prop is the same format as the blk_prop in blkptr_t: 1061 * * logical size (in sectors) 1062 * * physical (compressed) size (in sectors) 1063 * * compression algorithm 1064 * * checksum algorithm (used for b_freeze_cksum) 1065 * * object type & level (used to restore arc_buf_contents_t) 1066 */ 1067 uint64_t le_prop; 1068 uint64_t le_daddr; /* buf location on l2dev */ 1069 const uint64_t le_pad[7]; /* resv'd for future use */ 1070 } l2arc_log_ent_phys_t; 1071 1072 /* 1073 * These design limits give us the following metadata overhead (before 1074 * compression): 1075 * avg_blk_sz overhead 1076 * 1k 12.51 % 1077 * 2k 6.26 % 1078 * 4k 3.13 % 1079 * 8k 1.56 % 1080 * 16k 0.78 % 1081 * 32k 0.39 % 1082 * 64k 0.20 % 1083 * 128k 0.10 % 1084 * Compression should be able to sequeeze these down by about a factor of 2x. 1085 */ 1086 #define L2ARC_LOG_BLK_SIZE (128 * 1024) /* 128k */ 1087 #define L2ARC_LOG_BLK_HEADER_LEN (128) 1088 #define L2ARC_LOG_BLK_ENTRIES /* 1023 entries */ \ 1089 ((L2ARC_LOG_BLK_SIZE - L2ARC_LOG_BLK_HEADER_LEN) / \ 1090 sizeof (l2arc_log_ent_phys_t)) 1091 /* 1092 * Maximum amount of data in an l2arc log block (used to terminate rebuilding 1093 * before we hit the write head and restore potentially corrupted blocks). 1094 */ 1095 #define L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE \ 1096 (SPA_MAXBLOCKSIZE * L2ARC_LOG_BLK_ENTRIES) 1097 /* 1098 * For the persistency and rebuild algorithms to operate reliably we need 1099 * the L2ARC device to at least be able to hold 3 full log blocks (otherwise 1100 * excessive log block looping might confuse the log chain end detection). 1101 * Under normal circumstances this is not a problem, since this is somewhere 1102 * around only 400 MB. 1103 */ 1104 #define L2ARC_PERSIST_MIN_SIZE (3 * L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE) 1105 1106 /* 1107 * A log block of up to 1023 ARC buffer log entries, chained into the 1108 * persistent L2ARC metadata linked list. Byte order of magic determines 1109 * whether 64-bit bswap of fields is necessary. 1110 */ 1111 typedef struct l2arc_log_blk_phys { 1112 /* Header - see L2ARC_LOG_BLK_HEADER_LEN above */ 1113 uint64_t lb_magic; /* L2ARC_LOG_BLK_MAGIC */ 1114 l2arc_log_blkptr_t lb_back2_lbp; /* back 2 steps in chain */ 1115 uint64_t lb_pad[9]; /* resv'd for future use */ 1116 /* Payload */ 1117 l2arc_log_ent_phys_t lb_entries[L2ARC_LOG_BLK_ENTRIES]; 1118 } l2arc_log_blk_phys_t; 1119 1120 CTASSERT(sizeof (l2arc_log_blk_phys_t) == L2ARC_LOG_BLK_SIZE); 1121 CTASSERT(offsetof(l2arc_log_blk_phys_t, lb_entries) - 1122 offsetof(l2arc_log_blk_phys_t, lb_magic) == L2ARC_LOG_BLK_HEADER_LEN); 1123 1124 /* 1125 * These structures hold in-flight l2arc_log_blk_phys_t's as they're being 1126 * written to the L2ARC device. They may be compressed, hence the uint8_t[]. 1127 */ 1128 typedef struct l2arc_log_blk_buf { 1129 uint8_t lbb_log_blk[sizeof (l2arc_log_blk_phys_t)]; 1130 list_node_t lbb_node; 1131 } l2arc_log_blk_buf_t; 1132 1133 /* Macros for the manipulation fields in the blk_prop format of blkptr_t */ 1134 #define BLKPROP_GET_LSIZE(_obj, _field) \ 1135 BF64_GET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1) 1136 #define BLKPROP_SET_LSIZE(_obj, _field, x) \ 1137 BF64_SET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1, x) 1138 #define BLKPROP_GET_PSIZE(_obj, _field) \ 1139 BF64_GET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 1) 1140 #define BLKPROP_SET_PSIZE(_obj, _field, x) \ 1141 BF64_SET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 1, x) 1142 #define BLKPROP_GET_COMPRESS(_obj, _field) \ 1143 BF64_GET((_obj)->_field, 32, 8) 1144 #define BLKPROP_SET_COMPRESS(_obj, _field, x) \ 1145 BF64_SET((_obj)->_field, 32, 8, x) 1146 #define BLKPROP_GET_CHECKSUM(_obj, _field) \ 1147 BF64_GET((_obj)->_field, 40, 8) 1148 #define BLKPROP_SET_CHECKSUM(_obj, _field, x) \ 1149 BF64_SET((_obj)->_field, 40, 8, x) 1150 #define BLKPROP_GET_TYPE(_obj, _field) \ 1151 BF64_GET((_obj)->_field, 48, 8) 1152 #define BLKPROP_SET_TYPE(_obj, _field, x) \ 1153 BF64_SET((_obj)->_field, 48, 8, x) 1154 1155 /* Macros for manipulating a l2arc_log_blkptr_t->lbp_prop field */ 1156 #define LBP_GET_LSIZE(_add) BLKPROP_GET_LSIZE(_add, lbp_prop) 1157 #define LBP_SET_LSIZE(_add, x) BLKPROP_SET_LSIZE(_add, lbp_prop, x) 1158 #define LBP_GET_PSIZE(_add) BLKPROP_GET_PSIZE(_add, lbp_prop) 1159 #define LBP_SET_PSIZE(_add, x) BLKPROP_SET_PSIZE(_add, lbp_prop, x) 1160 #define LBP_GET_COMPRESS(_add) BLKPROP_GET_COMPRESS(_add, lbp_prop) 1161 #define LBP_SET_COMPRESS(_add, x) BLKPROP_SET_COMPRESS(_add, lbp_prop, \ 1162 x) 1163 #define LBP_GET_CHECKSUM(_add) BLKPROP_GET_CHECKSUM(_add, lbp_prop) 1164 #define LBP_SET_CHECKSUM(_add, x) BLKPROP_SET_CHECKSUM(_add, lbp_prop, \ 1165 x) 1166 #define LBP_GET_TYPE(_add) BLKPROP_GET_TYPE(_add, lbp_prop) 1167 #define LBP_SET_TYPE(_add, x) BLKPROP_SET_TYPE(_add, lbp_prop, x) 1168 1169 /* Macros for manipulating a l2arc_log_ent_phys_t->le_prop field */ 1170 #define LE_GET_LSIZE(_le) BLKPROP_GET_LSIZE(_le, le_prop) 1171 #define LE_SET_LSIZE(_le, x) BLKPROP_SET_LSIZE(_le, le_prop, x) 1172 #define LE_GET_PSIZE(_le) BLKPROP_GET_PSIZE(_le, le_prop) 1173 #define LE_SET_PSIZE(_le, x) BLKPROP_SET_PSIZE(_le, le_prop, x) 1174 #define LE_GET_COMPRESS(_le) BLKPROP_GET_COMPRESS(_le, le_prop) 1175 #define LE_SET_COMPRESS(_le, x) BLKPROP_SET_COMPRESS(_le, le_prop, x) 1176 #define LE_GET_CHECKSUM(_le) BLKPROP_GET_CHECKSUM(_le, le_prop) 1177 #define LE_SET_CHECKSUM(_le, x) BLKPROP_SET_CHECKSUM(_le, le_prop, x) 1178 #define LE_GET_TYPE(_le) BLKPROP_GET_TYPE(_le, le_prop) 1179 #define LE_SET_TYPE(_le, x) BLKPROP_SET_TYPE(_le, le_prop, x) 1180 1181 #define PTR_SWAP(x, y) \ 1182 do { \ 1183 void *tmp = (x);\ 1184 x = y; \ 1185 y = tmp; \ 1186 _NOTE(CONSTCOND)\ 1187 } while (0) 1188 1189 #define L2ARC_DEV_HDR_MAGIC 0x5a46534341434845LLU /* ASCII: "ZFSCACHE" */ 1190 #define L2ARC_LOG_BLK_MAGIC 0x4c4f47424c4b4844LLU /* ASCII: "LOGBLKHD" */ 1191 1192 /* 1193 * Performance tuning of L2ARC persistency: 1194 * 1195 * l2arc_rebuild_enabled : Controls whether L2ARC device adds (either at 1196 * pool import or when adding one manually later) will attempt 1197 * to rebuild L2ARC buffer contents. In special circumstances, 1198 * the administrator may want to set this to B_FALSE, if they 1199 * are having trouble importing a pool or attaching an L2ARC 1200 * device (e.g. the L2ARC device is slow to read in stored log 1201 * metadata, or the metadata has become somehow 1202 * fragmented/unusable). 1203 */ 1204 boolean_t l2arc_rebuild_enabled = B_TRUE; 1205 1206 /* L2ARC persistency rebuild control routines. */ 1207 static void l2arc_dev_rebuild_start(l2arc_dev_t *dev); 1208 static int l2arc_rebuild(l2arc_dev_t *dev); 1209 1210 /* L2ARC persistency read I/O routines. */ 1211 static int l2arc_dev_hdr_read(l2arc_dev_t *dev); 1212 static int l2arc_log_blk_read(l2arc_dev_t *dev, 1213 const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp, 1214 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, 1215 uint8_t *this_lb_buf, uint8_t *next_lb_buf, 1216 zio_t *this_io, zio_t **next_io); 1217 static zio_t *l2arc_log_blk_prefetch(vdev_t *vd, 1218 const l2arc_log_blkptr_t *lp, uint8_t *lb_buf); 1219 static void l2arc_log_blk_prefetch_abort(zio_t *zio); 1220 1221 /* L2ARC persistency block restoration routines. */ 1222 static void l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid, 1223 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize); 1224 static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, 1225 l2arc_dev_t *dev, uint64_t guid); 1226 1227 /* L2ARC persistency write I/O routines. */ 1228 static void l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio); 1229 static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, 1230 l2arc_write_callback_t *cb); 1231 1232 /* L2ARC persistency auxilliary routines. */ 1233 static boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev, 1234 const l2arc_log_blkptr_t *lp); 1235 static void l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr, 1236 zio_cksum_t *cksum); 1237 static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev, 1238 const arc_buf_hdr_t *ab); 1239 static inline boolean_t l2arc_range_check_overlap(uint64_t bottom, 1240 uint64_t top, uint64_t check); 1241 1242 /* 1243 * L2ARC Internals 1244 */ 1245 struct l2arc_dev { 1246 vdev_t *l2ad_vdev; /* vdev */ 1247 spa_t *l2ad_spa; /* spa */ 1248 uint64_t l2ad_hand; /* next write location */ 1249 uint64_t l2ad_start; /* first addr on device */ 1250 uint64_t l2ad_end; /* last addr on device */ 1251 boolean_t l2ad_first; /* first sweep through */ 1252 boolean_t l2ad_writing; /* currently writing */ 1253 kmutex_t l2ad_mtx; /* lock for buffer list */ 1254 list_t l2ad_buflist; /* buffer list */ 1255 list_node_t l2ad_node; /* device list node */ 1256 refcount_t l2ad_alloc; /* allocated bytes */ 1257 l2arc_dev_hdr_phys_t *l2ad_dev_hdr; /* persistent device header */ 1258 uint64_t l2ad_dev_hdr_asize; /* aligned hdr size */ 1259 l2arc_log_blk_phys_t l2ad_log_blk; /* currently open log block */ 1260 int l2ad_log_ent_idx; /* index into cur log blk */ 1261 /* number of bytes in current log block's payload */ 1262 uint64_t l2ad_log_blk_payload_asize; 1263 /* flag indicating whether a rebuild is scheduled or is going on */ 1264 boolean_t l2ad_rebuild; 1265 boolean_t l2ad_rebuild_cancel; 1266 kt_did_t l2ad_rebuild_did; 1267 }; 1268 1269 static inline uint64_t 1270 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1271 { 1272 uint8_t *vdva = (uint8_t *)dva; 1273 uint64_t crc = -1ULL; 1274 int i; 1275 1276 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1277 1278 for (i = 0; i < sizeof (dva_t); i++) 1279 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1280 1281 crc ^= (spa>>8) ^ birth; 1282 1283 return (crc); 1284 } 1285 1286 #define BUF_EMPTY(buf) \ 1287 ((buf)->b_dva.dva_word[0] == 0 && \ 1288 (buf)->b_dva.dva_word[1] == 0) 1289 1290 #define BUF_EQUAL(spa, dva, birth, buf) \ 1291 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1292 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1293 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1294 1295 static void 1296 buf_discard_identity(arc_buf_hdr_t *hdr) 1297 { 1298 hdr->b_dva.dva_word[0] = 0; 1299 hdr->b_dva.dva_word[1] = 0; 1300 hdr->b_birth = 0; 1301 } 1302 1303 static arc_buf_hdr_t * 1304 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1305 { 1306 const dva_t *dva = BP_IDENTITY(bp); 1307 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1308 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1309 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1310 arc_buf_hdr_t *hdr; 1311 1312 mutex_enter(hash_lock); 1313 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1314 hdr = hdr->b_hash_next) { 1315 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1316 *lockp = hash_lock; 1317 return (hdr); 1318 } 1319 } 1320 mutex_exit(hash_lock); 1321 *lockp = NULL; 1322 return (NULL); 1323 } 1324 1325 /* 1326 * Insert an entry into the hash table. If there is already an element 1327 * equal to elem in the hash table, then the already existing element 1328 * will be returned and the new element will not be inserted. 1329 * Otherwise returns NULL. 1330 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1331 */ 1332 static arc_buf_hdr_t * 1333 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1334 { 1335 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1336 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1337 arc_buf_hdr_t *fhdr; 1338 uint32_t i; 1339 1340 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1341 ASSERT(hdr->b_birth != 0); 1342 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1343 1344 if (lockp != NULL) { 1345 *lockp = hash_lock; 1346 mutex_enter(hash_lock); 1347 } else { 1348 ASSERT(MUTEX_HELD(hash_lock)); 1349 } 1350 1351 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1352 fhdr = fhdr->b_hash_next, i++) { 1353 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1354 return (fhdr); 1355 } 1356 1357 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1358 buf_hash_table.ht_table[idx] = hdr; 1359 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1360 1361 /* collect some hash table performance data */ 1362 if (i > 0) { 1363 ARCSTAT_BUMP(arcstat_hash_collisions); 1364 if (i == 1) 1365 ARCSTAT_BUMP(arcstat_hash_chains); 1366 1367 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1368 } 1369 1370 ARCSTAT_BUMP(arcstat_hash_elements); 1371 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1372 1373 return (NULL); 1374 } 1375 1376 static void 1377 buf_hash_remove(arc_buf_hdr_t *hdr) 1378 { 1379 arc_buf_hdr_t *fhdr, **hdrp; 1380 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1381 1382 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1383 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1384 1385 hdrp = &buf_hash_table.ht_table[idx]; 1386 while ((fhdr = *hdrp) != hdr) { 1387 ASSERT(fhdr != NULL); 1388 hdrp = &fhdr->b_hash_next; 1389 } 1390 *hdrp = hdr->b_hash_next; 1391 hdr->b_hash_next = NULL; 1392 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1393 1394 /* collect some hash table performance data */ 1395 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1396 1397 if (buf_hash_table.ht_table[idx] && 1398 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1399 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1400 } 1401 1402 /* 1403 * Global data structures and functions for the buf kmem cache. 1404 */ 1405 static kmem_cache_t *hdr_full_cache; 1406 static kmem_cache_t *hdr_l2only_cache; 1407 static kmem_cache_t *buf_cache; 1408 1409 static void 1410 buf_fini(void) 1411 { 1412 int i; 1413 1414 kmem_free(buf_hash_table.ht_table, 1415 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1416 for (i = 0; i < BUF_LOCKS; i++) 1417 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1418 kmem_cache_destroy(hdr_full_cache); 1419 kmem_cache_destroy(hdr_l2only_cache); 1420 kmem_cache_destroy(buf_cache); 1421 } 1422 1423 /* 1424 * Constructor callback - called when the cache is empty 1425 * and a new buf is requested. 1426 */ 1427 /* ARGSUSED */ 1428 static int 1429 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1430 { 1431 arc_buf_hdr_t *hdr = vbuf; 1432 1433 bzero(hdr, HDR_FULL_SIZE); 1434 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1435 refcount_create(&hdr->b_l1hdr.b_refcnt); 1436 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1437 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1438 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1439 1440 return (0); 1441 } 1442 1443 /* ARGSUSED */ 1444 static int 1445 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1446 { 1447 arc_buf_hdr_t *hdr = vbuf; 1448 1449 bzero(hdr, HDR_L2ONLY_SIZE); 1450 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1451 1452 return (0); 1453 } 1454 1455 /* ARGSUSED */ 1456 static int 1457 buf_cons(void *vbuf, void *unused, int kmflag) 1458 { 1459 arc_buf_t *buf = vbuf; 1460 1461 bzero(buf, sizeof (arc_buf_t)); 1462 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1463 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1464 1465 return (0); 1466 } 1467 1468 /* 1469 * Destructor callback - called when a cached buf is 1470 * no longer required. 1471 */ 1472 /* ARGSUSED */ 1473 static void 1474 hdr_full_dest(void *vbuf, void *unused) 1475 { 1476 arc_buf_hdr_t *hdr = vbuf; 1477 1478 ASSERT(BUF_EMPTY(hdr)); 1479 cv_destroy(&hdr->b_l1hdr.b_cv); 1480 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1481 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1482 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1483 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1484 } 1485 1486 /* ARGSUSED */ 1487 static void 1488 hdr_l2only_dest(void *vbuf, void *unused) 1489 { 1490 arc_buf_hdr_t *hdr = vbuf; 1491 1492 ASSERT(BUF_EMPTY(hdr)); 1493 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1494 } 1495 1496 /* ARGSUSED */ 1497 static void 1498 buf_dest(void *vbuf, void *unused) 1499 { 1500 arc_buf_t *buf = vbuf; 1501 1502 mutex_destroy(&buf->b_evict_lock); 1503 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1504 } 1505 1506 /* 1507 * Reclaim callback -- invoked when memory is low. 1508 */ 1509 /* ARGSUSED */ 1510 static void 1511 hdr_recl(void *unused) 1512 { 1513 dprintf("hdr_recl called\n"); 1514 /* 1515 * umem calls the reclaim func when we destroy the buf cache, 1516 * which is after we do arc_fini(). 1517 */ 1518 if (!arc_dead) 1519 cv_signal(&arc_reclaim_thread_cv); 1520 } 1521 1522 static void 1523 buf_init(void) 1524 { 1525 uint64_t *ct; 1526 uint64_t hsize = 1ULL << 12; 1527 int i, j; 1528 1529 /* 1530 * The hash table is big enough to fill all of physical memory 1531 * with an average block size of zfs_arc_average_blocksize (default 8K). 1532 * By default, the table will take up 1533 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1534 */ 1535 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1536 hsize <<= 1; 1537 retry: 1538 buf_hash_table.ht_mask = hsize - 1; 1539 buf_hash_table.ht_table = 1540 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1541 if (buf_hash_table.ht_table == NULL) { 1542 ASSERT(hsize > (1ULL << 8)); 1543 hsize >>= 1; 1544 goto retry; 1545 } 1546 1547 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1548 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1549 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1550 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1551 NULL, NULL, 0); 1552 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1553 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1554 1555 for (i = 0; i < 256; i++) 1556 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1557 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1558 1559 for (i = 0; i < BUF_LOCKS; i++) { 1560 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1561 NULL, MUTEX_DEFAULT, NULL); 1562 } 1563 } 1564 1565 /* 1566 * Transition between the two allocation states for the arc_buf_hdr struct. 1567 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1568 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1569 * version is used when a cache buffer is only in the L2ARC in order to reduce 1570 * memory usage. 1571 */ 1572 static arc_buf_hdr_t * 1573 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1574 { 1575 ASSERT(HDR_HAS_L2HDR(hdr)); 1576 1577 arc_buf_hdr_t *nhdr; 1578 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1579 1580 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1581 (old == hdr_l2only_cache && new == hdr_full_cache)); 1582 1583 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1584 1585 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1586 buf_hash_remove(hdr); 1587 1588 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1589 1590 if (new == hdr_full_cache) { 1591 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1592 /* 1593 * arc_access and arc_change_state need to be aware that a 1594 * header has just come out of L2ARC, so we set its state to 1595 * l2c_only even though it's about to change. 1596 */ 1597 nhdr->b_l1hdr.b_state = arc_l2c_only; 1598 1599 /* Verify previous threads set to NULL before freeing */ 1600 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1601 } else { 1602 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1603 ASSERT0(hdr->b_l1hdr.b_datacnt); 1604 1605 /* 1606 * If we've reached here, We must have been called from 1607 * arc_evict_hdr(), as such we should have already been 1608 * removed from any ghost list we were previously on 1609 * (which protects us from racing with arc_evict_state), 1610 * thus no locking is needed during this check. 1611 */ 1612 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1613 1614 /* 1615 * A buffer must not be moved into the arc_l2c_only 1616 * state if it's not finished being written out to the 1617 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1618 * might try to be accessed, even though it was removed. 1619 */ 1620 VERIFY(!HDR_L2_WRITING(hdr)); 1621 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1622 1623 #ifdef ZFS_DEBUG 1624 if (hdr->b_l1hdr.b_thawed != NULL) { 1625 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1626 hdr->b_l1hdr.b_thawed = NULL; 1627 } 1628 #endif 1629 1630 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1631 } 1632 /* 1633 * The header has been reallocated so we need to re-insert it into any 1634 * lists it was on. 1635 */ 1636 (void) buf_hash_insert(nhdr, NULL); 1637 1638 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1639 1640 mutex_enter(&dev->l2ad_mtx); 1641 1642 /* 1643 * We must place the realloc'ed header back into the list at 1644 * the same spot. Otherwise, if it's placed earlier in the list, 1645 * l2arc_write_buffers() could find it during the function's 1646 * write phase, and try to write it out to the l2arc. 1647 */ 1648 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1649 list_remove(&dev->l2ad_buflist, hdr); 1650 1651 mutex_exit(&dev->l2ad_mtx); 1652 1653 /* 1654 * Since we're using the pointer address as the tag when 1655 * incrementing and decrementing the l2ad_alloc refcount, we 1656 * must remove the old pointer (that we're about to destroy) and 1657 * add the new pointer to the refcount. Otherwise we'd remove 1658 * the wrong pointer address when calling arc_hdr_destroy() later. 1659 */ 1660 1661 (void) refcount_remove_many(&dev->l2ad_alloc, 1662 hdr->b_l2hdr.b_asize, hdr); 1663 1664 (void) refcount_add_many(&dev->l2ad_alloc, 1665 nhdr->b_l2hdr.b_asize, nhdr); 1666 1667 buf_discard_identity(hdr); 1668 hdr->b_freeze_cksum = NULL; 1669 kmem_cache_free(old, hdr); 1670 1671 return (nhdr); 1672 } 1673 1674 1675 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1676 1677 static void 1678 arc_cksum_verify(arc_buf_t *buf) 1679 { 1680 zio_cksum_t zc; 1681 1682 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1683 return; 1684 1685 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1686 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1687 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1688 return; 1689 } 1690 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1691 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1692 panic("buffer modified while frozen!"); 1693 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1694 } 1695 1696 static int 1697 arc_cksum_equal(arc_buf_t *buf) 1698 { 1699 zio_cksum_t zc; 1700 int equal; 1701 1702 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1703 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1704 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1705 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1706 1707 return (equal); 1708 } 1709 1710 static void 1711 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1712 { 1713 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1714 return; 1715 1716 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1717 if (buf->b_hdr->b_freeze_cksum != NULL) { 1718 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1719 return; 1720 } 1721 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1722 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1723 NULL, buf->b_hdr->b_freeze_cksum); 1724 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1725 arc_buf_watch(buf); 1726 } 1727 1728 #ifndef _KERNEL 1729 typedef struct procctl { 1730 long cmd; 1731 prwatch_t prwatch; 1732 } procctl_t; 1733 #endif 1734 1735 /* ARGSUSED */ 1736 static void 1737 arc_buf_unwatch(arc_buf_t *buf) 1738 { 1739 #ifndef _KERNEL 1740 if (arc_watch) { 1741 int result; 1742 procctl_t ctl; 1743 ctl.cmd = PCWATCH; 1744 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1745 ctl.prwatch.pr_size = 0; 1746 ctl.prwatch.pr_wflags = 0; 1747 result = write(arc_procfd, &ctl, sizeof (ctl)); 1748 ASSERT3U(result, ==, sizeof (ctl)); 1749 } 1750 #endif 1751 } 1752 1753 /* ARGSUSED */ 1754 static void 1755 arc_buf_watch(arc_buf_t *buf) 1756 { 1757 #ifndef _KERNEL 1758 if (arc_watch) { 1759 int result; 1760 procctl_t ctl; 1761 ctl.cmd = PCWATCH; 1762 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1763 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1764 ctl.prwatch.pr_wflags = WA_WRITE; 1765 result = write(arc_procfd, &ctl, sizeof (ctl)); 1766 ASSERT3U(result, ==, sizeof (ctl)); 1767 } 1768 #endif 1769 } 1770 1771 static arc_buf_contents_t 1772 arc_buf_type(arc_buf_hdr_t *hdr) 1773 { 1774 if (HDR_ISTYPE_METADATA(hdr)) { 1775 return (ARC_BUFC_METADATA); 1776 } else { 1777 return (ARC_BUFC_DATA); 1778 } 1779 } 1780 1781 static uint32_t 1782 arc_bufc_to_flags(arc_buf_contents_t type) 1783 { 1784 switch (type) { 1785 case ARC_BUFC_DATA: 1786 /* metadata field is 0 if buffer contains normal data */ 1787 return (0); 1788 case ARC_BUFC_METADATA: 1789 return (ARC_FLAG_BUFC_METADATA); 1790 default: 1791 break; 1792 } 1793 panic("undefined ARC buffer type!"); 1794 return ((uint32_t)-1); 1795 } 1796 1797 static arc_buf_contents_t 1798 arc_flags_to_bufc(uint32_t flags) 1799 { 1800 if (flags & ARC_FLAG_BUFC_METADATA) 1801 return (ARC_BUFC_METADATA); 1802 return (ARC_BUFC_DATA); 1803 } 1804 1805 void 1806 arc_buf_thaw(arc_buf_t *buf) 1807 { 1808 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1809 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1810 panic("modifying non-anon buffer!"); 1811 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1812 panic("modifying buffer while i/o in progress!"); 1813 arc_cksum_verify(buf); 1814 } 1815 1816 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1817 if (buf->b_hdr->b_freeze_cksum != NULL) { 1818 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1819 buf->b_hdr->b_freeze_cksum = NULL; 1820 } 1821 1822 #ifdef ZFS_DEBUG 1823 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1824 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1825 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1826 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1827 } 1828 #endif 1829 1830 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1831 1832 arc_buf_unwatch(buf); 1833 } 1834 1835 void 1836 arc_buf_freeze(arc_buf_t *buf) 1837 { 1838 kmutex_t *hash_lock; 1839 1840 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1841 return; 1842 1843 hash_lock = HDR_LOCK(buf->b_hdr); 1844 mutex_enter(hash_lock); 1845 1846 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1847 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1848 arc_cksum_compute(buf, B_FALSE); 1849 mutex_exit(hash_lock); 1850 1851 } 1852 1853 static void 1854 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1855 { 1856 ASSERT(HDR_HAS_L1HDR(hdr)); 1857 ASSERT(MUTEX_HELD(hash_lock)); 1858 arc_state_t *state = hdr->b_l1hdr.b_state; 1859 1860 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1861 (state != arc_anon)) { 1862 /* We don't use the L2-only state list. */ 1863 if (state != arc_l2c_only) { 1864 arc_buf_contents_t type = arc_buf_type(hdr); 1865 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1866 multilist_t *list = &state->arcs_list[type]; 1867 uint64_t *size = &state->arcs_lsize[type]; 1868 1869 multilist_remove(list, hdr); 1870 1871 if (GHOST_STATE(state)) { 1872 ASSERT0(hdr->b_l1hdr.b_datacnt); 1873 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1874 delta = hdr->b_size; 1875 } 1876 ASSERT(delta > 0); 1877 ASSERT3U(*size, >=, delta); 1878 atomic_add_64(size, -delta); 1879 } 1880 /* remove the prefetch flag if we get a reference */ 1881 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1882 } 1883 } 1884 1885 static int 1886 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1887 { 1888 int cnt; 1889 arc_state_t *state = hdr->b_l1hdr.b_state; 1890 1891 ASSERT(HDR_HAS_L1HDR(hdr)); 1892 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1893 ASSERT(!GHOST_STATE(state)); 1894 1895 /* 1896 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1897 * check to prevent usage of the arc_l2c_only list. 1898 */ 1899 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1900 (state != arc_anon)) { 1901 arc_buf_contents_t type = arc_buf_type(hdr); 1902 multilist_t *list = &state->arcs_list[type]; 1903 uint64_t *size = &state->arcs_lsize[type]; 1904 1905 multilist_insert(list, hdr); 1906 1907 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1908 atomic_add_64(size, hdr->b_size * 1909 hdr->b_l1hdr.b_datacnt); 1910 } 1911 return (cnt); 1912 } 1913 1914 /* 1915 * Move the supplied buffer to the indicated state. The hash lock 1916 * for the buffer must be held by the caller. 1917 */ 1918 static void 1919 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1920 kmutex_t *hash_lock) 1921 { 1922 arc_state_t *old_state; 1923 int64_t refcnt; 1924 uint32_t datacnt; 1925 uint64_t from_delta, to_delta; 1926 arc_buf_contents_t buftype = arc_buf_type(hdr); 1927 1928 /* 1929 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1930 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1931 * L1 hdr doesn't always exist when we change state to arc_anon before 1932 * destroying a header, in which case reallocating to add the L1 hdr is 1933 * pointless. 1934 */ 1935 if (HDR_HAS_L1HDR(hdr)) { 1936 old_state = hdr->b_l1hdr.b_state; 1937 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1938 datacnt = hdr->b_l1hdr.b_datacnt; 1939 } else { 1940 old_state = arc_l2c_only; 1941 refcnt = 0; 1942 datacnt = 0; 1943 } 1944 1945 ASSERT(MUTEX_HELD(hash_lock)); 1946 ASSERT3P(new_state, !=, old_state); 1947 ASSERT(refcnt == 0 || datacnt > 0); 1948 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1949 ASSERT(old_state != arc_anon || datacnt <= 1); 1950 1951 from_delta = to_delta = datacnt * hdr->b_size; 1952 1953 /* 1954 * If this buffer is evictable, transfer it from the 1955 * old state list to the new state list. 1956 */ 1957 if (refcnt == 0) { 1958 if (old_state != arc_anon && old_state != arc_l2c_only) { 1959 uint64_t *size = &old_state->arcs_lsize[buftype]; 1960 1961 ASSERT(HDR_HAS_L1HDR(hdr)); 1962 multilist_remove(&old_state->arcs_list[buftype], hdr); 1963 1964 /* 1965 * If prefetching out of the ghost cache, 1966 * we will have a non-zero datacnt. 1967 */ 1968 if (GHOST_STATE(old_state) && datacnt == 0) { 1969 /* ghost elements have a ghost size */ 1970 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1971 from_delta = hdr->b_size; 1972 } 1973 ASSERT3U(*size, >=, from_delta); 1974 atomic_add_64(size, -from_delta); 1975 } 1976 if (new_state != arc_anon && new_state != arc_l2c_only) { 1977 uint64_t *size = &new_state->arcs_lsize[buftype]; 1978 1979 /* 1980 * An L1 header always exists here, since if we're 1981 * moving to some L1-cached state (i.e. not l2c_only or 1982 * anonymous), we realloc the header to add an L1hdr 1983 * beforehand. 1984 */ 1985 ASSERT(HDR_HAS_L1HDR(hdr)); 1986 multilist_insert(&new_state->arcs_list[buftype], hdr); 1987 1988 /* ghost elements have a ghost size */ 1989 if (GHOST_STATE(new_state)) { 1990 ASSERT0(datacnt); 1991 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1992 to_delta = hdr->b_size; 1993 } 1994 atomic_add_64(size, to_delta); 1995 } 1996 } 1997 1998 ASSERT(!BUF_EMPTY(hdr)); 1999 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2000 buf_hash_remove(hdr); 2001 2002 /* adjust state sizes (ignore arc_l2c_only) */ 2003 2004 if (to_delta && new_state != arc_l2c_only) { 2005 ASSERT(HDR_HAS_L1HDR(hdr)); 2006 if (GHOST_STATE(new_state)) { 2007 ASSERT0(datacnt); 2008 2009 /* 2010 * We moving a header to a ghost state, we first 2011 * remove all arc buffers. Thus, we'll have a 2012 * datacnt of zero, and no arc buffer to use for 2013 * the reference. As a result, we use the arc 2014 * header pointer for the reference. 2015 */ 2016 (void) refcount_add_many(&new_state->arcs_size, 2017 hdr->b_size, hdr); 2018 } else { 2019 ASSERT3U(datacnt, !=, 0); 2020 2021 /* 2022 * Each individual buffer holds a unique reference, 2023 * thus we must remove each of these references one 2024 * at a time. 2025 */ 2026 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2027 buf = buf->b_next) { 2028 (void) refcount_add_many(&new_state->arcs_size, 2029 hdr->b_size, buf); 2030 } 2031 } 2032 } 2033 2034 if (from_delta && old_state != arc_l2c_only) { 2035 ASSERT(HDR_HAS_L1HDR(hdr)); 2036 if (GHOST_STATE(old_state)) { 2037 /* 2038 * When moving a header off of a ghost state, 2039 * there's the possibility for datacnt to be 2040 * non-zero. This is because we first add the 2041 * arc buffer to the header prior to changing 2042 * the header's state. Since we used the header 2043 * for the reference when putting the header on 2044 * the ghost state, we must balance that and use 2045 * the header when removing off the ghost state 2046 * (even though datacnt is non zero). 2047 */ 2048 2049 IMPLY(datacnt == 0, new_state == arc_anon || 2050 new_state == arc_l2c_only); 2051 2052 (void) refcount_remove_many(&old_state->arcs_size, 2053 hdr->b_size, hdr); 2054 } else { 2055 ASSERT3P(datacnt, !=, 0); 2056 2057 /* 2058 * Each individual buffer holds a unique reference, 2059 * thus we must remove each of these references one 2060 * at a time. 2061 */ 2062 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2063 buf = buf->b_next) { 2064 (void) refcount_remove_many( 2065 &old_state->arcs_size, hdr->b_size, buf); 2066 } 2067 } 2068 } 2069 2070 if (HDR_HAS_L1HDR(hdr)) 2071 hdr->b_l1hdr.b_state = new_state; 2072 2073 /* 2074 * L2 headers should never be on the L2 state list since they don't 2075 * have L1 headers allocated. 2076 */ 2077 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2078 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2079 } 2080 2081 void 2082 arc_space_consume(uint64_t space, arc_space_type_t type) 2083 { 2084 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2085 2086 switch (type) { 2087 case ARC_SPACE_DATA: 2088 ARCSTAT_INCR(arcstat_data_size, space); 2089 break; 2090 case ARC_SPACE_META: 2091 ARCSTAT_INCR(arcstat_metadata_size, space); 2092 break; 2093 case ARC_SPACE_OTHER: 2094 ARCSTAT_INCR(arcstat_other_size, space); 2095 break; 2096 case ARC_SPACE_HDRS: 2097 ARCSTAT_INCR(arcstat_hdr_size, space); 2098 break; 2099 case ARC_SPACE_L2HDRS: 2100 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2101 break; 2102 } 2103 2104 if (type != ARC_SPACE_DATA) 2105 ARCSTAT_INCR(arcstat_meta_used, space); 2106 2107 atomic_add_64(&arc_size, space); 2108 } 2109 2110 void 2111 arc_space_return(uint64_t space, arc_space_type_t type) 2112 { 2113 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2114 2115 switch (type) { 2116 case ARC_SPACE_DATA: 2117 ARCSTAT_INCR(arcstat_data_size, -space); 2118 break; 2119 case ARC_SPACE_META: 2120 ARCSTAT_INCR(arcstat_metadata_size, -space); 2121 break; 2122 case ARC_SPACE_OTHER: 2123 ARCSTAT_INCR(arcstat_other_size, -space); 2124 break; 2125 case ARC_SPACE_HDRS: 2126 ARCSTAT_INCR(arcstat_hdr_size, -space); 2127 break; 2128 case ARC_SPACE_L2HDRS: 2129 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2130 break; 2131 } 2132 2133 if (type != ARC_SPACE_DATA) { 2134 ASSERT(arc_meta_used >= space); 2135 if (arc_meta_max < arc_meta_used) 2136 arc_meta_max = arc_meta_used; 2137 ARCSTAT_INCR(arcstat_meta_used, -space); 2138 } 2139 2140 ASSERT(arc_size >= space); 2141 atomic_add_64(&arc_size, -space); 2142 } 2143 2144 arc_buf_t * 2145 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2146 { 2147 arc_buf_hdr_t *hdr; 2148 arc_buf_t *buf; 2149 2150 ASSERT3U(size, >, 0); 2151 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2152 ASSERT(BUF_EMPTY(hdr)); 2153 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2154 hdr->b_size = size; 2155 hdr->b_spa = spa_load_guid(spa); 2156 2157 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2158 buf->b_hdr = hdr; 2159 buf->b_data = NULL; 2160 buf->b_efunc = NULL; 2161 buf->b_private = NULL; 2162 buf->b_next = NULL; 2163 2164 hdr->b_flags = arc_bufc_to_flags(type); 2165 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2166 2167 hdr->b_l1hdr.b_buf = buf; 2168 hdr->b_l1hdr.b_state = arc_anon; 2169 hdr->b_l1hdr.b_arc_access = 0; 2170 hdr->b_l1hdr.b_datacnt = 1; 2171 hdr->b_l1hdr.b_tmp_cdata = NULL; 2172 2173 arc_get_data_buf(buf); 2174 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2175 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2176 2177 return (buf); 2178 } 2179 2180 /* 2181 * Allocates an ARC buf header that's in an evicted & L2-cached state. 2182 * This is used during l2arc reconstruction to make empty ARC buffers 2183 * which circumvent the regular disk->arc->l2arc path and instead come 2184 * into being in the reverse order, i.e. l2arc->arc. 2185 */ 2186 arc_buf_hdr_t * 2187 arc_buf_alloc_l2only(uint64_t load_guid, int size, arc_buf_contents_t type, 2188 l2arc_dev_t *dev, dva_t dva, uint64_t daddr, int32_t asize, uint64_t birth, 2189 zio_cksum_t cksum, enum zio_compress compress) 2190 { 2191 arc_buf_hdr_t *hdr; 2192 2193 ASSERT3U(size, >, 0); 2194 hdr = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 2195 ASSERT(BUF_EMPTY(hdr)); 2196 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2197 hdr->b_dva = dva; 2198 hdr->b_birth = birth; 2199 hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 2200 bcopy(&cksum, hdr->b_freeze_cksum, sizeof (cksum)); 2201 hdr->b_flags = arc_bufc_to_flags(type); 2202 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 2203 hdr->b_size = size; 2204 hdr->b_spa = load_guid; 2205 2206 hdr->b_l2hdr.b_compress = compress; 2207 hdr->b_l2hdr.b_dev = dev; 2208 hdr->b_l2hdr.b_daddr = daddr; 2209 hdr->b_l2hdr.b_asize = asize; 2210 2211 return (hdr); 2212 } 2213 2214 static char *arc_onloan_tag = "onloan"; 2215 2216 /* 2217 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2218 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2219 * buffers must be returned to the arc before they can be used by the DMU or 2220 * freed. 2221 */ 2222 arc_buf_t * 2223 arc_loan_buf(spa_t *spa, int size) 2224 { 2225 arc_buf_t *buf; 2226 2227 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2228 2229 atomic_add_64(&arc_loaned_bytes, size); 2230 return (buf); 2231 } 2232 2233 /* 2234 * Return a loaned arc buffer to the arc. 2235 */ 2236 void 2237 arc_return_buf(arc_buf_t *buf, void *tag) 2238 { 2239 arc_buf_hdr_t *hdr = buf->b_hdr; 2240 2241 ASSERT(buf->b_data != NULL); 2242 ASSERT(HDR_HAS_L1HDR(hdr)); 2243 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2244 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2245 2246 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2247 } 2248 2249 /* Detach an arc_buf from a dbuf (tag) */ 2250 void 2251 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2252 { 2253 arc_buf_hdr_t *hdr = buf->b_hdr; 2254 2255 ASSERT(buf->b_data != NULL); 2256 ASSERT(HDR_HAS_L1HDR(hdr)); 2257 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2258 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2259 buf->b_efunc = NULL; 2260 buf->b_private = NULL; 2261 2262 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2263 } 2264 2265 static arc_buf_t * 2266 arc_buf_clone(arc_buf_t *from) 2267 { 2268 arc_buf_t *buf; 2269 arc_buf_hdr_t *hdr = from->b_hdr; 2270 uint64_t size = hdr->b_size; 2271 2272 ASSERT(HDR_HAS_L1HDR(hdr)); 2273 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2274 2275 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2276 buf->b_hdr = hdr; 2277 buf->b_data = NULL; 2278 buf->b_efunc = NULL; 2279 buf->b_private = NULL; 2280 buf->b_next = hdr->b_l1hdr.b_buf; 2281 hdr->b_l1hdr.b_buf = buf; 2282 arc_get_data_buf(buf); 2283 bcopy(from->b_data, buf->b_data, size); 2284 2285 /* 2286 * This buffer already exists in the arc so create a duplicate 2287 * copy for the caller. If the buffer is associated with user data 2288 * then track the size and number of duplicates. These stats will be 2289 * updated as duplicate buffers are created and destroyed. 2290 */ 2291 if (HDR_ISTYPE_DATA(hdr)) { 2292 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2293 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2294 } 2295 hdr->b_l1hdr.b_datacnt += 1; 2296 return (buf); 2297 } 2298 2299 void 2300 arc_buf_add_ref(arc_buf_t *buf, void* tag) 2301 { 2302 arc_buf_hdr_t *hdr; 2303 kmutex_t *hash_lock; 2304 2305 /* 2306 * Check to see if this buffer is evicted. Callers 2307 * must verify b_data != NULL to know if the add_ref 2308 * was successful. 2309 */ 2310 mutex_enter(&buf->b_evict_lock); 2311 if (buf->b_data == NULL) { 2312 mutex_exit(&buf->b_evict_lock); 2313 return; 2314 } 2315 hash_lock = HDR_LOCK(buf->b_hdr); 2316 mutex_enter(hash_lock); 2317 hdr = buf->b_hdr; 2318 ASSERT(HDR_HAS_L1HDR(hdr)); 2319 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2320 mutex_exit(&buf->b_evict_lock); 2321 2322 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2323 hdr->b_l1hdr.b_state == arc_mfu); 2324 2325 add_reference(hdr, hash_lock, tag); 2326 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2327 arc_access(hdr, hash_lock); 2328 mutex_exit(hash_lock); 2329 ARCSTAT_BUMP(arcstat_hits); 2330 arc_update_hit_stat(hdr, B_TRUE); 2331 } 2332 2333 static void 2334 arc_buf_free_on_write(void *data, size_t size, 2335 void (*free_func)(void *, size_t)) 2336 { 2337 l2arc_data_free_t *df; 2338 2339 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2340 df->l2df_data = data; 2341 df->l2df_size = size; 2342 df->l2df_func = free_func; 2343 mutex_enter(&l2arc_free_on_write_mtx); 2344 list_insert_head(l2arc_free_on_write, df); 2345 mutex_exit(&l2arc_free_on_write_mtx); 2346 } 2347 2348 /* 2349 * Free the arc data buffer. If it is an l2arc write in progress, 2350 * the buffer is placed on l2arc_free_on_write to be freed later. 2351 */ 2352 static void 2353 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2354 { 2355 arc_buf_hdr_t *hdr = buf->b_hdr; 2356 2357 if (HDR_L2_WRITING(hdr)) { 2358 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2359 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2360 } else { 2361 free_func(buf->b_data, hdr->b_size); 2362 } 2363 } 2364 2365 static void 2366 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2367 { 2368 ASSERT(HDR_HAS_L2HDR(hdr)); 2369 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2370 2371 /* 2372 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2373 * that doesn't exist, the header is in the arc_l2c_only state, 2374 * and there isn't anything to free (it's already been freed). 2375 */ 2376 if (!HDR_HAS_L1HDR(hdr)) 2377 return; 2378 2379 /* 2380 * The header isn't being written to the l2arc device, thus it 2381 * shouldn't have a b_tmp_cdata to free. 2382 */ 2383 if (!HDR_L2_WRITING(hdr)) { 2384 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2385 return; 2386 } 2387 2388 /* 2389 * The header does not have compression enabled. This can be due 2390 * to the buffer not being compressible, or because we're 2391 * freeing the buffer before the second phase of 2392 * l2arc_write_buffer() has started (which does the compression 2393 * step). In either case, b_tmp_cdata does not point to a 2394 * separately compressed buffer, so there's nothing to free (it 2395 * points to the same buffer as the arc_buf_t's b_data field). 2396 */ 2397 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) { 2398 hdr->b_l1hdr.b_tmp_cdata = NULL; 2399 return; 2400 } 2401 2402 /* 2403 * There's nothing to free since the buffer was all zero's and 2404 * compressed to a zero length buffer. 2405 */ 2406 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2407 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2408 return; 2409 } 2410 2411 ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress)); 2412 2413 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2414 hdr->b_size, zio_data_buf_free); 2415 2416 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2417 hdr->b_l1hdr.b_tmp_cdata = NULL; 2418 } 2419 2420 /* 2421 * Free up buf->b_data and if 'remove' is set, then pull the 2422 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2423 */ 2424 static void 2425 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2426 { 2427 arc_buf_t **bufp; 2428 2429 /* free up data associated with the buf */ 2430 if (buf->b_data != NULL) { 2431 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2432 uint64_t size = buf->b_hdr->b_size; 2433 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2434 2435 arc_cksum_verify(buf); 2436 arc_buf_unwatch(buf); 2437 2438 if (type == ARC_BUFC_METADATA) { 2439 arc_buf_data_free(buf, zio_buf_free); 2440 arc_space_return(size, ARC_SPACE_META); 2441 } else { 2442 ASSERT(type == ARC_BUFC_DATA); 2443 arc_buf_data_free(buf, zio_data_buf_free); 2444 arc_space_return(size, ARC_SPACE_DATA); 2445 } 2446 2447 /* protected by hash lock, if in the hash table */ 2448 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2449 uint64_t *cnt = &state->arcs_lsize[type]; 2450 2451 ASSERT(refcount_is_zero( 2452 &buf->b_hdr->b_l1hdr.b_refcnt)); 2453 ASSERT(state != arc_anon && state != arc_l2c_only); 2454 2455 ASSERT3U(*cnt, >=, size); 2456 atomic_add_64(cnt, -size); 2457 } 2458 2459 (void) refcount_remove_many(&state->arcs_size, size, buf); 2460 buf->b_data = NULL; 2461 2462 /* 2463 * If we're destroying a duplicate buffer make sure 2464 * that the appropriate statistics are updated. 2465 */ 2466 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2467 HDR_ISTYPE_DATA(buf->b_hdr)) { 2468 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2469 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2470 } 2471 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2472 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2473 } 2474 2475 /* only remove the buf if requested */ 2476 if (!remove) 2477 return; 2478 2479 /* remove the buf from the hdr list */ 2480 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2481 bufp = &(*bufp)->b_next) 2482 continue; 2483 *bufp = buf->b_next; 2484 buf->b_next = NULL; 2485 2486 ASSERT(buf->b_efunc == NULL); 2487 2488 /* clean up the buf */ 2489 buf->b_hdr = NULL; 2490 kmem_cache_free(buf_cache, buf); 2491 } 2492 2493 static void 2494 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2495 { 2496 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2497 l2arc_dev_t *dev = l2hdr->b_dev; 2498 2499 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2500 ASSERT(HDR_HAS_L2HDR(hdr)); 2501 2502 list_remove(&dev->l2ad_buflist, hdr); 2503 2504 /* 2505 * We don't want to leak the b_tmp_cdata buffer that was 2506 * allocated in l2arc_write_buffers() 2507 */ 2508 arc_buf_l2_cdata_free(hdr); 2509 2510 /* 2511 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2512 * this header is being processed by l2arc_write_buffers() (i.e. 2513 * it's in the first stage of l2arc_write_buffers()). 2514 * Re-affirming that truth here, just to serve as a reminder. If 2515 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2516 * may not have its HDR_L2_WRITING flag set. (the write may have 2517 * completed, in which case HDR_L2_WRITING will be false and the 2518 * b_daddr field will point to the address of the buffer on disk). 2519 */ 2520 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2521 2522 /* 2523 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2524 * l2arc_write_buffers(). Since we've just removed this header 2525 * from the l2arc buffer list, this header will never reach the 2526 * second stage of l2arc_write_buffers(), which increments the 2527 * accounting stats for this header. Thus, we must be careful 2528 * not to decrement them for this header either. 2529 */ 2530 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2531 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2532 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2533 2534 vdev_space_update(dev->l2ad_vdev, 2535 -l2hdr->b_asize, 0, 0); 2536 2537 (void) refcount_remove_many(&dev->l2ad_alloc, 2538 l2hdr->b_asize, hdr); 2539 } 2540 2541 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2542 } 2543 2544 static void 2545 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2546 { 2547 if (HDR_HAS_L1HDR(hdr)) { 2548 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2549 hdr->b_l1hdr.b_datacnt > 0); 2550 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2551 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2552 } 2553 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2554 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2555 2556 if (HDR_HAS_L2HDR(hdr)) { 2557 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2558 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2559 2560 if (!buflist_held) 2561 mutex_enter(&dev->l2ad_mtx); 2562 2563 /* 2564 * Even though we checked this conditional above, we 2565 * need to check this again now that we have the 2566 * l2ad_mtx. This is because we could be racing with 2567 * another thread calling l2arc_evict() which might have 2568 * destroyed this header's L2 portion as we were waiting 2569 * to acquire the l2ad_mtx. If that happens, we don't 2570 * want to re-destroy the header's L2 portion. 2571 */ 2572 if (HDR_HAS_L2HDR(hdr)) 2573 arc_hdr_l2hdr_destroy(hdr); 2574 2575 if (!buflist_held) 2576 mutex_exit(&dev->l2ad_mtx); 2577 } 2578 2579 if (!BUF_EMPTY(hdr)) 2580 buf_discard_identity(hdr); 2581 2582 if (hdr->b_freeze_cksum != NULL) { 2583 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2584 hdr->b_freeze_cksum = NULL; 2585 } 2586 2587 if (HDR_HAS_L1HDR(hdr)) { 2588 while (hdr->b_l1hdr.b_buf) { 2589 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2590 2591 if (buf->b_efunc != NULL) { 2592 mutex_enter(&arc_user_evicts_lock); 2593 mutex_enter(&buf->b_evict_lock); 2594 ASSERT(buf->b_hdr != NULL); 2595 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2596 hdr->b_l1hdr.b_buf = buf->b_next; 2597 buf->b_hdr = &arc_eviction_hdr; 2598 buf->b_next = arc_eviction_list; 2599 arc_eviction_list = buf; 2600 mutex_exit(&buf->b_evict_lock); 2601 cv_signal(&arc_user_evicts_cv); 2602 mutex_exit(&arc_user_evicts_lock); 2603 } else { 2604 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2605 } 2606 } 2607 #ifdef ZFS_DEBUG 2608 if (hdr->b_l1hdr.b_thawed != NULL) { 2609 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2610 hdr->b_l1hdr.b_thawed = NULL; 2611 } 2612 #endif 2613 } 2614 2615 ASSERT3P(hdr->b_hash_next, ==, NULL); 2616 if (HDR_HAS_L1HDR(hdr)) { 2617 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2618 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2619 kmem_cache_free(hdr_full_cache, hdr); 2620 } else { 2621 kmem_cache_free(hdr_l2only_cache, hdr); 2622 } 2623 } 2624 2625 void 2626 arc_buf_free(arc_buf_t *buf, void *tag) 2627 { 2628 arc_buf_hdr_t *hdr = buf->b_hdr; 2629 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2630 2631 ASSERT(buf->b_efunc == NULL); 2632 ASSERT(buf->b_data != NULL); 2633 2634 if (hashed) { 2635 kmutex_t *hash_lock = HDR_LOCK(hdr); 2636 2637 mutex_enter(hash_lock); 2638 hdr = buf->b_hdr; 2639 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2640 2641 (void) remove_reference(hdr, hash_lock, tag); 2642 if (hdr->b_l1hdr.b_datacnt > 1) { 2643 arc_buf_destroy(buf, TRUE); 2644 } else { 2645 ASSERT(buf == hdr->b_l1hdr.b_buf); 2646 ASSERT(buf->b_efunc == NULL); 2647 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2648 } 2649 mutex_exit(hash_lock); 2650 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2651 int destroy_hdr; 2652 /* 2653 * We are in the middle of an async write. Don't destroy 2654 * this buffer unless the write completes before we finish 2655 * decrementing the reference count. 2656 */ 2657 mutex_enter(&arc_user_evicts_lock); 2658 (void) remove_reference(hdr, NULL, tag); 2659 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2660 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2661 mutex_exit(&arc_user_evicts_lock); 2662 if (destroy_hdr) 2663 arc_hdr_destroy(hdr); 2664 } else { 2665 if (remove_reference(hdr, NULL, tag) > 0) 2666 arc_buf_destroy(buf, TRUE); 2667 else 2668 arc_hdr_destroy(hdr); 2669 } 2670 } 2671 2672 boolean_t 2673 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2674 { 2675 arc_buf_hdr_t *hdr = buf->b_hdr; 2676 kmutex_t *hash_lock = HDR_LOCK(hdr); 2677 boolean_t no_callback = (buf->b_efunc == NULL); 2678 2679 if (hdr->b_l1hdr.b_state == arc_anon) { 2680 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2681 arc_buf_free(buf, tag); 2682 return (no_callback); 2683 } 2684 2685 mutex_enter(hash_lock); 2686 hdr = buf->b_hdr; 2687 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2688 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2689 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2690 ASSERT(buf->b_data != NULL); 2691 2692 (void) remove_reference(hdr, hash_lock, tag); 2693 if (hdr->b_l1hdr.b_datacnt > 1) { 2694 if (no_callback) 2695 arc_buf_destroy(buf, TRUE); 2696 } else if (no_callback) { 2697 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2698 ASSERT(buf->b_efunc == NULL); 2699 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2700 } 2701 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2702 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2703 mutex_exit(hash_lock); 2704 return (no_callback); 2705 } 2706 2707 int32_t 2708 arc_buf_size(arc_buf_t *buf) 2709 { 2710 return (buf->b_hdr->b_size); 2711 } 2712 2713 /* 2714 * Called from the DMU to determine if the current buffer should be 2715 * evicted. In order to ensure proper locking, the eviction must be initiated 2716 * from the DMU. Return true if the buffer is associated with user data and 2717 * duplicate buffers still exist. 2718 */ 2719 boolean_t 2720 arc_buf_eviction_needed(arc_buf_t *buf) 2721 { 2722 arc_buf_hdr_t *hdr; 2723 boolean_t evict_needed = B_FALSE; 2724 2725 if (zfs_disable_dup_eviction) 2726 return (B_FALSE); 2727 2728 mutex_enter(&buf->b_evict_lock); 2729 hdr = buf->b_hdr; 2730 if (hdr == NULL) { 2731 /* 2732 * We are in arc_do_user_evicts(); let that function 2733 * perform the eviction. 2734 */ 2735 ASSERT(buf->b_data == NULL); 2736 mutex_exit(&buf->b_evict_lock); 2737 return (B_FALSE); 2738 } else if (buf->b_data == NULL) { 2739 /* 2740 * We have already been added to the arc eviction list; 2741 * recommend eviction. 2742 */ 2743 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2744 mutex_exit(&buf->b_evict_lock); 2745 return (B_TRUE); 2746 } 2747 2748 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2749 evict_needed = B_TRUE; 2750 2751 mutex_exit(&buf->b_evict_lock); 2752 return (evict_needed); 2753 } 2754 2755 /* 2756 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2757 * state of the header is dependent on it's state prior to entering this 2758 * function. The following transitions are possible: 2759 * 2760 * - arc_mru -> arc_mru_ghost 2761 * - arc_mfu -> arc_mfu_ghost 2762 * - arc_mru_ghost -> arc_l2c_only 2763 * - arc_mru_ghost -> deleted 2764 * - arc_mfu_ghost -> arc_l2c_only 2765 * - arc_mfu_ghost -> deleted 2766 */ 2767 static int64_t 2768 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2769 { 2770 arc_state_t *evicted_state, *state; 2771 int64_t bytes_evicted = 0; 2772 2773 ASSERT(MUTEX_HELD(hash_lock)); 2774 ASSERT(HDR_HAS_L1HDR(hdr)); 2775 2776 state = hdr->b_l1hdr.b_state; 2777 if (GHOST_STATE(state)) { 2778 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2779 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2780 2781 /* 2782 * l2arc_write_buffers() relies on a header's L1 portion 2783 * (i.e. it's b_tmp_cdata field) during it's write phase. 2784 * Thus, we cannot push a header onto the arc_l2c_only 2785 * state (removing it's L1 piece) until the header is 2786 * done being written to the l2arc. 2787 */ 2788 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2789 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2790 return (bytes_evicted); 2791 } 2792 2793 ARCSTAT_BUMP(arcstat_deleted); 2794 bytes_evicted += hdr->b_size; 2795 2796 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2797 2798 if (HDR_HAS_L2HDR(hdr)) { 2799 /* 2800 * This buffer is cached on the 2nd Level ARC; 2801 * don't destroy the header. 2802 */ 2803 arc_change_state(arc_l2c_only, hdr, hash_lock); 2804 /* 2805 * dropping from L1+L2 cached to L2-only, 2806 * realloc to remove the L1 header. 2807 */ 2808 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2809 hdr_l2only_cache); 2810 } else { 2811 arc_change_state(arc_anon, hdr, hash_lock); 2812 arc_hdr_destroy(hdr); 2813 } 2814 return (bytes_evicted); 2815 } 2816 2817 ASSERT(state == arc_mru || state == arc_mfu); 2818 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2819 2820 /* prefetch buffers have a minimum lifespan */ 2821 if (HDR_IO_IN_PROGRESS(hdr) || 2822 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2823 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2824 arc_min_prefetch_lifespan)) { 2825 ARCSTAT_BUMP(arcstat_evict_skip); 2826 return (bytes_evicted); 2827 } 2828 2829 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2830 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2831 while (hdr->b_l1hdr.b_buf) { 2832 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2833 if (!mutex_tryenter(&buf->b_evict_lock)) { 2834 ARCSTAT_BUMP(arcstat_mutex_miss); 2835 break; 2836 } 2837 if (buf->b_data != NULL) 2838 bytes_evicted += hdr->b_size; 2839 if (buf->b_efunc != NULL) { 2840 mutex_enter(&arc_user_evicts_lock); 2841 arc_buf_destroy(buf, FALSE); 2842 hdr->b_l1hdr.b_buf = buf->b_next; 2843 buf->b_hdr = &arc_eviction_hdr; 2844 buf->b_next = arc_eviction_list; 2845 arc_eviction_list = buf; 2846 cv_signal(&arc_user_evicts_cv); 2847 mutex_exit(&arc_user_evicts_lock); 2848 mutex_exit(&buf->b_evict_lock); 2849 } else { 2850 mutex_exit(&buf->b_evict_lock); 2851 arc_buf_destroy(buf, TRUE); 2852 } 2853 } 2854 2855 if (HDR_HAS_L2HDR(hdr)) { 2856 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2857 } else { 2858 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2859 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2860 else 2861 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2862 } 2863 2864 if (hdr->b_l1hdr.b_datacnt == 0) { 2865 arc_change_state(evicted_state, hdr, hash_lock); 2866 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2867 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2868 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2869 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2870 } 2871 2872 return (bytes_evicted); 2873 } 2874 2875 static uint64_t 2876 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2877 uint64_t spa, int64_t bytes) 2878 { 2879 multilist_sublist_t *mls; 2880 uint64_t bytes_evicted = 0; 2881 arc_buf_hdr_t *hdr; 2882 kmutex_t *hash_lock; 2883 int evict_count = 0; 2884 2885 ASSERT3P(marker, !=, NULL); 2886 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2887 2888 mls = multilist_sublist_lock(ml, idx); 2889 2890 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2891 hdr = multilist_sublist_prev(mls, marker)) { 2892 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2893 (evict_count >= zfs_arc_evict_batch_limit)) 2894 break; 2895 2896 /* 2897 * To keep our iteration location, move the marker 2898 * forward. Since we're not holding hdr's hash lock, we 2899 * must be very careful and not remove 'hdr' from the 2900 * sublist. Otherwise, other consumers might mistake the 2901 * 'hdr' as not being on a sublist when they call the 2902 * multilist_link_active() function (they all rely on 2903 * the hash lock protecting concurrent insertions and 2904 * removals). multilist_sublist_move_forward() was 2905 * specifically implemented to ensure this is the case 2906 * (only 'marker' will be removed and re-inserted). 2907 */ 2908 multilist_sublist_move_forward(mls, marker); 2909 2910 /* 2911 * The only case where the b_spa field should ever be 2912 * zero, is the marker headers inserted by 2913 * arc_evict_state(). It's possible for multiple threads 2914 * to be calling arc_evict_state() concurrently (e.g. 2915 * dsl_pool_close() and zio_inject_fault()), so we must 2916 * skip any markers we see from these other threads. 2917 */ 2918 if (hdr->b_spa == 0) 2919 continue; 2920 2921 /* we're only interested in evicting buffers of a certain spa */ 2922 if (spa != 0 && hdr->b_spa != spa) { 2923 ARCSTAT_BUMP(arcstat_evict_skip); 2924 continue; 2925 } 2926 2927 hash_lock = HDR_LOCK(hdr); 2928 2929 /* 2930 * We aren't calling this function from any code path 2931 * that would already be holding a hash lock, so we're 2932 * asserting on this assumption to be defensive in case 2933 * this ever changes. Without this check, it would be 2934 * possible to incorrectly increment arcstat_mutex_miss 2935 * below (e.g. if the code changed such that we called 2936 * this function with a hash lock held). 2937 */ 2938 ASSERT(!MUTEX_HELD(hash_lock)); 2939 2940 if (mutex_tryenter(hash_lock)) { 2941 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2942 mutex_exit(hash_lock); 2943 2944 bytes_evicted += evicted; 2945 2946 /* 2947 * If evicted is zero, arc_evict_hdr() must have 2948 * decided to skip this header, don't increment 2949 * evict_count in this case. 2950 */ 2951 if (evicted != 0) 2952 evict_count++; 2953 2954 /* 2955 * If arc_size isn't overflowing, signal any 2956 * threads that might happen to be waiting. 2957 * 2958 * For each header evicted, we wake up a single 2959 * thread. If we used cv_broadcast, we could 2960 * wake up "too many" threads causing arc_size 2961 * to significantly overflow arc_c; since 2962 * arc_get_data_buf() doesn't check for overflow 2963 * when it's woken up (it doesn't because it's 2964 * possible for the ARC to be overflowing while 2965 * full of un-evictable buffers, and the 2966 * function should proceed in this case). 2967 * 2968 * If threads are left sleeping, due to not 2969 * using cv_broadcast, they will be woken up 2970 * just before arc_reclaim_thread() sleeps. 2971 */ 2972 mutex_enter(&arc_reclaim_lock); 2973 if (!arc_is_overflowing()) 2974 cv_signal(&arc_reclaim_waiters_cv); 2975 mutex_exit(&arc_reclaim_lock); 2976 } else { 2977 ARCSTAT_BUMP(arcstat_mutex_miss); 2978 } 2979 } 2980 2981 multilist_sublist_unlock(mls); 2982 2983 return (bytes_evicted); 2984 } 2985 2986 /* 2987 * Evict buffers from the given arc state, until we've removed the 2988 * specified number of bytes. Move the removed buffers to the 2989 * appropriate evict state. 2990 * 2991 * This function makes a "best effort". It skips over any buffers 2992 * it can't get a hash_lock on, and so, may not catch all candidates. 2993 * It may also return without evicting as much space as requested. 2994 * 2995 * If bytes is specified using the special value ARC_EVICT_ALL, this 2996 * will evict all available (i.e. unlocked and evictable) buffers from 2997 * the given arc state; which is used by arc_flush(). 2998 */ 2999 static uint64_t 3000 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3001 arc_buf_contents_t type) 3002 { 3003 uint64_t total_evicted = 0; 3004 multilist_t *ml = &state->arcs_list[type]; 3005 int num_sublists; 3006 arc_buf_hdr_t **markers; 3007 3008 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3009 3010 num_sublists = multilist_get_num_sublists(ml); 3011 3012 /* 3013 * If we've tried to evict from each sublist, made some 3014 * progress, but still have not hit the target number of bytes 3015 * to evict, we want to keep trying. The markers allow us to 3016 * pick up where we left off for each individual sublist, rather 3017 * than starting from the tail each time. 3018 */ 3019 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3020 for (int i = 0; i < num_sublists; i++) { 3021 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3022 3023 /* 3024 * A b_spa of 0 is used to indicate that this header is 3025 * a marker. This fact is used in arc_adjust_type() and 3026 * arc_evict_state_impl(). 3027 */ 3028 markers[i]->b_spa = 0; 3029 3030 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3031 multilist_sublist_insert_tail(mls, markers[i]); 3032 multilist_sublist_unlock(mls); 3033 } 3034 3035 /* 3036 * While we haven't hit our target number of bytes to evict, or 3037 * we're evicting all available buffers. 3038 */ 3039 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3040 /* 3041 * Start eviction using a randomly selected sublist, 3042 * this is to try and evenly balance eviction across all 3043 * sublists. Always starting at the same sublist 3044 * (e.g. index 0) would cause evictions to favor certain 3045 * sublists over others. 3046 */ 3047 int sublist_idx = multilist_get_random_index(ml); 3048 uint64_t scan_evicted = 0; 3049 3050 for (int i = 0; i < num_sublists; i++) { 3051 uint64_t bytes_remaining; 3052 uint64_t bytes_evicted; 3053 3054 if (bytes == ARC_EVICT_ALL) 3055 bytes_remaining = ARC_EVICT_ALL; 3056 else if (total_evicted < bytes) 3057 bytes_remaining = bytes - total_evicted; 3058 else 3059 break; 3060 3061 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3062 markers[sublist_idx], spa, bytes_remaining); 3063 3064 scan_evicted += bytes_evicted; 3065 total_evicted += bytes_evicted; 3066 3067 /* we've reached the end, wrap to the beginning */ 3068 if (++sublist_idx >= num_sublists) 3069 sublist_idx = 0; 3070 } 3071 3072 /* 3073 * If we didn't evict anything during this scan, we have 3074 * no reason to believe we'll evict more during another 3075 * scan, so break the loop. 3076 */ 3077 if (scan_evicted == 0) { 3078 /* This isn't possible, let's make that obvious */ 3079 ASSERT3S(bytes, !=, 0); 3080 3081 /* 3082 * When bytes is ARC_EVICT_ALL, the only way to 3083 * break the loop is when scan_evicted is zero. 3084 * In that case, we actually have evicted enough, 3085 * so we don't want to increment the kstat. 3086 */ 3087 if (bytes != ARC_EVICT_ALL) { 3088 ASSERT3S(total_evicted, <, bytes); 3089 ARCSTAT_BUMP(arcstat_evict_not_enough); 3090 } 3091 3092 break; 3093 } 3094 } 3095 3096 for (int i = 0; i < num_sublists; i++) { 3097 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3098 multilist_sublist_remove(mls, markers[i]); 3099 multilist_sublist_unlock(mls); 3100 3101 kmem_cache_free(hdr_full_cache, markers[i]); 3102 } 3103 kmem_free(markers, sizeof (*markers) * num_sublists); 3104 3105 return (total_evicted); 3106 } 3107 3108 /* 3109 * Flush all "evictable" data of the given type from the arc state 3110 * specified. This will not evict any "active" buffers (i.e. referenced). 3111 * 3112 * When 'retry' is set to FALSE, the function will make a single pass 3113 * over the state and evict any buffers that it can. Since it doesn't 3114 * continually retry the eviction, it might end up leaving some buffers 3115 * in the ARC due to lock misses. 3116 * 3117 * When 'retry' is set to TRUE, the function will continually retry the 3118 * eviction until *all* evictable buffers have been removed from the 3119 * state. As a result, if concurrent insertions into the state are 3120 * allowed (e.g. if the ARC isn't shutting down), this function might 3121 * wind up in an infinite loop, continually trying to evict buffers. 3122 */ 3123 static uint64_t 3124 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3125 boolean_t retry) 3126 { 3127 uint64_t evicted = 0; 3128 3129 while (state->arcs_lsize[type] != 0) { 3130 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3131 3132 if (!retry) 3133 break; 3134 } 3135 3136 return (evicted); 3137 } 3138 3139 /* 3140 * Evict the specified number of bytes from the state specified, 3141 * restricting eviction to the spa and type given. This function 3142 * prevents us from trying to evict more from a state's list than 3143 * is "evictable", and to skip evicting altogether when passed a 3144 * negative value for "bytes". In contrast, arc_evict_state() will 3145 * evict everything it can, when passed a negative value for "bytes". 3146 */ 3147 static uint64_t 3148 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3149 arc_buf_contents_t type) 3150 { 3151 int64_t delta; 3152 3153 if (bytes > 0 && state->arcs_lsize[type] > 0) { 3154 delta = MIN(state->arcs_lsize[type], bytes); 3155 return (arc_evict_state(state, spa, delta, type)); 3156 } 3157 3158 return (0); 3159 } 3160 3161 /* 3162 * Evict metadata buffers from the cache, such that arc_meta_used is 3163 * capped by the arc_meta_limit tunable. 3164 */ 3165 static uint64_t 3166 arc_adjust_meta(void) 3167 { 3168 uint64_t total_evicted = 0; 3169 int64_t target; 3170 3171 /* 3172 * If we're over the meta limit, we want to evict enough 3173 * metadata to get back under the meta limit. We don't want to 3174 * evict so much that we drop the MRU below arc_p, though. If 3175 * we're over the meta limit more than we're over arc_p, we 3176 * evict some from the MRU here, and some from the MFU below. 3177 */ 3178 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3179 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3180 refcount_count(&arc_mru->arcs_size) - arc_p)); 3181 3182 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3183 3184 /* 3185 * Similar to the above, we want to evict enough bytes to get us 3186 * below the meta limit, but not so much as to drop us below the 3187 * space alloted to the MFU (which is defined as arc_c - arc_p). 3188 */ 3189 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3190 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3191 3192 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3193 3194 return (total_evicted); 3195 } 3196 3197 /* 3198 * Return the type of the oldest buffer in the given arc state 3199 * 3200 * This function will select a random sublist of type ARC_BUFC_DATA and 3201 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3202 * is compared, and the type which contains the "older" buffer will be 3203 * returned. 3204 */ 3205 static arc_buf_contents_t 3206 arc_adjust_type(arc_state_t *state) 3207 { 3208 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3209 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3210 int data_idx = multilist_get_random_index(data_ml); 3211 int meta_idx = multilist_get_random_index(meta_ml); 3212 multilist_sublist_t *data_mls; 3213 multilist_sublist_t *meta_mls; 3214 arc_buf_contents_t type; 3215 arc_buf_hdr_t *data_hdr; 3216 arc_buf_hdr_t *meta_hdr; 3217 3218 /* 3219 * We keep the sublist lock until we're finished, to prevent 3220 * the headers from being destroyed via arc_evict_state(). 3221 */ 3222 data_mls = multilist_sublist_lock(data_ml, data_idx); 3223 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3224 3225 /* 3226 * These two loops are to ensure we skip any markers that 3227 * might be at the tail of the lists due to arc_evict_state(). 3228 */ 3229 3230 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3231 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3232 if (data_hdr->b_spa != 0) 3233 break; 3234 } 3235 3236 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3237 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3238 if (meta_hdr->b_spa != 0) 3239 break; 3240 } 3241 3242 if (data_hdr == NULL && meta_hdr == NULL) { 3243 type = ARC_BUFC_DATA; 3244 } else if (data_hdr == NULL) { 3245 ASSERT3P(meta_hdr, !=, NULL); 3246 type = ARC_BUFC_METADATA; 3247 } else if (meta_hdr == NULL) { 3248 ASSERT3P(data_hdr, !=, NULL); 3249 type = ARC_BUFC_DATA; 3250 } else { 3251 ASSERT3P(data_hdr, !=, NULL); 3252 ASSERT3P(meta_hdr, !=, NULL); 3253 3254 /* The headers can't be on the sublist without an L1 header */ 3255 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3256 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3257 3258 if (data_hdr->b_l1hdr.b_arc_access < 3259 meta_hdr->b_l1hdr.b_arc_access) { 3260 type = ARC_BUFC_DATA; 3261 } else { 3262 type = ARC_BUFC_METADATA; 3263 } 3264 } 3265 3266 multilist_sublist_unlock(meta_mls); 3267 multilist_sublist_unlock(data_mls); 3268 3269 return (type); 3270 } 3271 3272 /* 3273 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3274 */ 3275 static uint64_t 3276 arc_adjust(void) 3277 { 3278 uint64_t total_evicted = 0; 3279 uint64_t bytes; 3280 int64_t target; 3281 3282 /* 3283 * If we're over arc_meta_limit, we want to correct that before 3284 * potentially evicting data buffers below. 3285 */ 3286 total_evicted += arc_adjust_meta(); 3287 3288 /* 3289 * Adjust MRU size 3290 * 3291 * If we're over the target cache size, we want to evict enough 3292 * from the list to get back to our target size. We don't want 3293 * to evict too much from the MRU, such that it drops below 3294 * arc_p. So, if we're over our target cache size more than 3295 * the MRU is over arc_p, we'll evict enough to get back to 3296 * arc_p here, and then evict more from the MFU below. 3297 */ 3298 target = MIN((int64_t)(arc_size - arc_c), 3299 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3300 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3301 3302 /* 3303 * If we're below arc_meta_min, always prefer to evict data. 3304 * Otherwise, try to satisfy the requested number of bytes to 3305 * evict from the type which contains older buffers; in an 3306 * effort to keep newer buffers in the cache regardless of their 3307 * type. If we cannot satisfy the number of bytes from this 3308 * type, spill over into the next type. 3309 */ 3310 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3311 arc_meta_used > arc_meta_min) { 3312 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3313 total_evicted += bytes; 3314 3315 /* 3316 * If we couldn't evict our target number of bytes from 3317 * metadata, we try to get the rest from data. 3318 */ 3319 target -= bytes; 3320 3321 total_evicted += 3322 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3323 } else { 3324 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3325 total_evicted += bytes; 3326 3327 /* 3328 * If we couldn't evict our target number of bytes from 3329 * data, we try to get the rest from metadata. 3330 */ 3331 target -= bytes; 3332 3333 total_evicted += 3334 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3335 } 3336 3337 /* 3338 * Adjust MFU size 3339 * 3340 * Now that we've tried to evict enough from the MRU to get its 3341 * size back to arc_p, if we're still above the target cache 3342 * size, we evict the rest from the MFU. 3343 */ 3344 target = arc_size - arc_c; 3345 3346 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3347 arc_meta_used > arc_meta_min) { 3348 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3349 total_evicted += bytes; 3350 3351 /* 3352 * If we couldn't evict our target number of bytes from 3353 * metadata, we try to get the rest from data. 3354 */ 3355 target -= bytes; 3356 3357 total_evicted += 3358 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3359 } else { 3360 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3361 total_evicted += bytes; 3362 3363 /* 3364 * If we couldn't evict our target number of bytes from 3365 * data, we try to get the rest from data. 3366 */ 3367 target -= bytes; 3368 3369 total_evicted += 3370 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3371 } 3372 3373 /* 3374 * Adjust ghost lists 3375 * 3376 * In addition to the above, the ARC also defines target values 3377 * for the ghost lists. The sum of the mru list and mru ghost 3378 * list should never exceed the target size of the cache, and 3379 * the sum of the mru list, mfu list, mru ghost list, and mfu 3380 * ghost list should never exceed twice the target size of the 3381 * cache. The following logic enforces these limits on the ghost 3382 * caches, and evicts from them as needed. 3383 */ 3384 target = refcount_count(&arc_mru->arcs_size) + 3385 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3386 3387 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3388 total_evicted += bytes; 3389 3390 target -= bytes; 3391 3392 total_evicted += 3393 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3394 3395 /* 3396 * We assume the sum of the mru list and mfu list is less than 3397 * or equal to arc_c (we enforced this above), which means we 3398 * can use the simpler of the two equations below: 3399 * 3400 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3401 * mru ghost + mfu ghost <= arc_c 3402 */ 3403 target = refcount_count(&arc_mru_ghost->arcs_size) + 3404 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3405 3406 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3407 total_evicted += bytes; 3408 3409 target -= bytes; 3410 3411 total_evicted += 3412 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3413 3414 return (total_evicted); 3415 } 3416 3417 static void 3418 arc_do_user_evicts(void) 3419 { 3420 mutex_enter(&arc_user_evicts_lock); 3421 while (arc_eviction_list != NULL) { 3422 arc_buf_t *buf = arc_eviction_list; 3423 arc_eviction_list = buf->b_next; 3424 mutex_enter(&buf->b_evict_lock); 3425 buf->b_hdr = NULL; 3426 mutex_exit(&buf->b_evict_lock); 3427 mutex_exit(&arc_user_evicts_lock); 3428 3429 if (buf->b_efunc != NULL) 3430 VERIFY0(buf->b_efunc(buf->b_private)); 3431 3432 buf->b_efunc = NULL; 3433 buf->b_private = NULL; 3434 kmem_cache_free(buf_cache, buf); 3435 mutex_enter(&arc_user_evicts_lock); 3436 } 3437 mutex_exit(&arc_user_evicts_lock); 3438 } 3439 3440 void 3441 arc_flush(spa_t *spa, boolean_t retry) 3442 { 3443 uint64_t guid = 0; 3444 3445 /* 3446 * If retry is TRUE, a spa must not be specified since we have 3447 * no good way to determine if all of a spa's buffers have been 3448 * evicted from an arc state. 3449 */ 3450 ASSERT(!retry || spa == 0); 3451 3452 if (spa != NULL) 3453 guid = spa_load_guid(spa); 3454 3455 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3456 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3457 3458 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3459 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3460 3461 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3462 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3463 3464 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3465 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3466 3467 arc_do_user_evicts(); 3468 ASSERT(spa || arc_eviction_list == NULL); 3469 } 3470 3471 void 3472 arc_shrink(int64_t to_free) 3473 { 3474 if (arc_c > arc_c_min) { 3475 3476 if (arc_c > arc_c_min + to_free) 3477 atomic_add_64(&arc_c, -to_free); 3478 else 3479 arc_c = arc_c_min; 3480 3481 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3482 if (arc_c > arc_size) 3483 arc_c = MAX(arc_size, arc_c_min); 3484 if (arc_p > arc_c) 3485 arc_p = (arc_c >> 1); 3486 ASSERT(arc_c >= arc_c_min); 3487 ASSERT((int64_t)arc_p >= 0); 3488 } 3489 3490 if (arc_size > arc_c) 3491 (void) arc_adjust(); 3492 } 3493 3494 typedef enum free_memory_reason_t { 3495 FMR_UNKNOWN, 3496 FMR_NEEDFREE, 3497 FMR_LOTSFREE, 3498 FMR_SWAPFS_MINFREE, 3499 FMR_PAGES_PP_MAXIMUM, 3500 FMR_HEAP_ARENA, 3501 FMR_ZIO_ARENA, 3502 } free_memory_reason_t; 3503 3504 int64_t last_free_memory; 3505 free_memory_reason_t last_free_reason; 3506 3507 /* 3508 * Additional reserve of pages for pp_reserve. 3509 */ 3510 int64_t arc_pages_pp_reserve = 64; 3511 3512 /* 3513 * Additional reserve of pages for swapfs. 3514 */ 3515 int64_t arc_swapfs_reserve = 64; 3516 3517 /* 3518 * Return the amount of memory that can be consumed before reclaim will be 3519 * needed. Positive if there is sufficient free memory, negative indicates 3520 * the amount of memory that needs to be freed up. 3521 */ 3522 static int64_t 3523 arc_available_memory(void) 3524 { 3525 int64_t lowest = INT64_MAX; 3526 int64_t n; 3527 free_memory_reason_t r = FMR_UNKNOWN; 3528 3529 #ifdef _KERNEL 3530 if (needfree > 0) { 3531 n = PAGESIZE * (-needfree); 3532 if (n < lowest) { 3533 lowest = n; 3534 r = FMR_NEEDFREE; 3535 } 3536 } 3537 3538 /* 3539 * check that we're out of range of the pageout scanner. It starts to 3540 * schedule paging if freemem is less than lotsfree and needfree. 3541 * lotsfree is the high-water mark for pageout, and needfree is the 3542 * number of needed free pages. We add extra pages here to make sure 3543 * the scanner doesn't start up while we're freeing memory. 3544 */ 3545 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3546 if (n < lowest) { 3547 lowest = n; 3548 r = FMR_LOTSFREE; 3549 } 3550 3551 /* 3552 * check to make sure that swapfs has enough space so that anon 3553 * reservations can still succeed. anon_resvmem() checks that the 3554 * availrmem is greater than swapfs_minfree, and the number of reserved 3555 * swap pages. We also add a bit of extra here just to prevent 3556 * circumstances from getting really dire. 3557 */ 3558 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3559 desfree - arc_swapfs_reserve); 3560 if (n < lowest) { 3561 lowest = n; 3562 r = FMR_SWAPFS_MINFREE; 3563 } 3564 3565 3566 /* 3567 * Check that we have enough availrmem that memory locking (e.g., via 3568 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3569 * stores the number of pages that cannot be locked; when availrmem 3570 * drops below pages_pp_maximum, page locking mechanisms such as 3571 * page_pp_lock() will fail.) 3572 */ 3573 n = PAGESIZE * (availrmem - pages_pp_maximum - 3574 arc_pages_pp_reserve); 3575 if (n < lowest) { 3576 lowest = n; 3577 r = FMR_PAGES_PP_MAXIMUM; 3578 } 3579 3580 #if defined(__i386) 3581 /* 3582 * If we're on an i386 platform, it's possible that we'll exhaust the 3583 * kernel heap space before we ever run out of available physical 3584 * memory. Most checks of the size of the heap_area compare against 3585 * tune.t_minarmem, which is the minimum available real memory that we 3586 * can have in the system. However, this is generally fixed at 25 pages 3587 * which is so low that it's useless. In this comparison, we seek to 3588 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3589 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3590 * free) 3591 */ 3592 n = vmem_size(heap_arena, VMEM_FREE) - 3593 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3594 if (n < lowest) { 3595 lowest = n; 3596 r = FMR_HEAP_ARENA; 3597 } 3598 #endif 3599 3600 /* 3601 * If zio data pages are being allocated out of a separate heap segment, 3602 * then enforce that the size of available vmem for this arena remains 3603 * above about 1/16th free. 3604 * 3605 * Note: The 1/16th arena free requirement was put in place 3606 * to aggressively evict memory from the arc in order to avoid 3607 * memory fragmentation issues. 3608 */ 3609 if (zio_arena != NULL) { 3610 n = vmem_size(zio_arena, VMEM_FREE) - 3611 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3612 if (n < lowest) { 3613 lowest = n; 3614 r = FMR_ZIO_ARENA; 3615 } 3616 } 3617 #else 3618 /* Every 100 calls, free a small amount */ 3619 if (spa_get_random(100) == 0) 3620 lowest = -1024; 3621 #endif 3622 3623 last_free_memory = lowest; 3624 last_free_reason = r; 3625 3626 return (lowest); 3627 } 3628 3629 3630 /* 3631 * Determine if the system is under memory pressure and is asking 3632 * to reclaim memory. A return value of TRUE indicates that the system 3633 * is under memory pressure and that the arc should adjust accordingly. 3634 */ 3635 static boolean_t 3636 arc_reclaim_needed(void) 3637 { 3638 return (arc_available_memory() < 0); 3639 } 3640 3641 static void 3642 arc_kmem_reap_now(void) 3643 { 3644 size_t i; 3645 kmem_cache_t *prev_cache = NULL; 3646 kmem_cache_t *prev_data_cache = NULL; 3647 extern kmem_cache_t *zio_buf_cache[]; 3648 extern kmem_cache_t *zio_data_buf_cache[]; 3649 extern kmem_cache_t *range_seg_cache; 3650 3651 #ifdef _KERNEL 3652 if (arc_meta_used >= arc_meta_limit) { 3653 /* 3654 * We are exceeding our meta-data cache limit. 3655 * Purge some DNLC entries to release holds on meta-data. 3656 */ 3657 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3658 } 3659 #if defined(__i386) 3660 /* 3661 * Reclaim unused memory from all kmem caches. 3662 */ 3663 kmem_reap(); 3664 #endif 3665 #endif 3666 3667 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3668 if (zio_buf_cache[i] != prev_cache) { 3669 prev_cache = zio_buf_cache[i]; 3670 kmem_cache_reap_now(zio_buf_cache[i]); 3671 } 3672 if (zio_data_buf_cache[i] != prev_data_cache) { 3673 prev_data_cache = zio_data_buf_cache[i]; 3674 kmem_cache_reap_now(zio_data_buf_cache[i]); 3675 } 3676 } 3677 kmem_cache_reap_now(buf_cache); 3678 kmem_cache_reap_now(hdr_full_cache); 3679 kmem_cache_reap_now(hdr_l2only_cache); 3680 kmem_cache_reap_now(range_seg_cache); 3681 3682 if (zio_arena != NULL) { 3683 /* 3684 * Ask the vmem arena to reclaim unused memory from its 3685 * quantum caches. 3686 */ 3687 vmem_qcache_reap(zio_arena); 3688 } 3689 } 3690 3691 /* 3692 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3693 * enough data and signal them to proceed. When this happens, the threads in 3694 * arc_get_data_buf() are sleeping while holding the hash lock for their 3695 * particular arc header. Thus, we must be careful to never sleep on a 3696 * hash lock in this thread. This is to prevent the following deadlock: 3697 * 3698 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3699 * waiting for the reclaim thread to signal it. 3700 * 3701 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3702 * fails, and goes to sleep forever. 3703 * 3704 * This possible deadlock is avoided by always acquiring a hash lock 3705 * using mutex_tryenter() from arc_reclaim_thread(). 3706 */ 3707 static void 3708 arc_reclaim_thread(void) 3709 { 3710 hrtime_t growtime = 0; 3711 callb_cpr_t cpr; 3712 3713 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3714 3715 mutex_enter(&arc_reclaim_lock); 3716 while (!arc_reclaim_thread_exit) { 3717 int64_t free_memory = arc_available_memory(); 3718 uint64_t evicted = 0; 3719 3720 mutex_exit(&arc_reclaim_lock); 3721 3722 if (free_memory < 0) { 3723 3724 arc_no_grow = B_TRUE; 3725 arc_warm = B_TRUE; 3726 3727 /* 3728 * Wait at least zfs_grow_retry (default 60) seconds 3729 * before considering growing. 3730 */ 3731 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 3732 3733 arc_kmem_reap_now(); 3734 3735 /* 3736 * If we are still low on memory, shrink the ARC 3737 * so that we have arc_shrink_min free space. 3738 */ 3739 free_memory = arc_available_memory(); 3740 3741 int64_t to_free = 3742 (arc_c >> arc_shrink_shift) - free_memory; 3743 if (to_free > 0) { 3744 #ifdef _KERNEL 3745 to_free = MAX(to_free, ptob(needfree)); 3746 #endif 3747 arc_shrink(to_free); 3748 } 3749 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3750 arc_no_grow = B_TRUE; 3751 } else if (gethrtime() >= growtime) { 3752 arc_no_grow = B_FALSE; 3753 } 3754 3755 evicted = arc_adjust(); 3756 3757 mutex_enter(&arc_reclaim_lock); 3758 3759 /* 3760 * If evicted is zero, we couldn't evict anything via 3761 * arc_adjust(). This could be due to hash lock 3762 * collisions, but more likely due to the majority of 3763 * arc buffers being unevictable. Therefore, even if 3764 * arc_size is above arc_c, another pass is unlikely to 3765 * be helpful and could potentially cause us to enter an 3766 * infinite loop. 3767 */ 3768 if (arc_size <= arc_c || evicted == 0) { 3769 /* 3770 * We're either no longer overflowing, or we 3771 * can't evict anything more, so we should wake 3772 * up any threads before we go to sleep. 3773 */ 3774 cv_broadcast(&arc_reclaim_waiters_cv); 3775 3776 /* 3777 * Block until signaled, or after one second (we 3778 * might need to perform arc_kmem_reap_now() 3779 * even if we aren't being signalled) 3780 */ 3781 CALLB_CPR_SAFE_BEGIN(&cpr); 3782 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 3783 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 3784 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3785 } 3786 } 3787 3788 arc_reclaim_thread_exit = FALSE; 3789 cv_broadcast(&arc_reclaim_thread_cv); 3790 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3791 thread_exit(); 3792 } 3793 3794 static void 3795 arc_user_evicts_thread(void) 3796 { 3797 callb_cpr_t cpr; 3798 3799 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3800 3801 mutex_enter(&arc_user_evicts_lock); 3802 while (!arc_user_evicts_thread_exit) { 3803 mutex_exit(&arc_user_evicts_lock); 3804 3805 arc_do_user_evicts(); 3806 3807 /* 3808 * This is necessary in order for the mdb ::arc dcmd to 3809 * show up to date information. Since the ::arc command 3810 * does not call the kstat's update function, without 3811 * this call, the command may show stale stats for the 3812 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3813 * with this change, the data might be up to 1 second 3814 * out of date; but that should suffice. The arc_state_t 3815 * structures can be queried directly if more accurate 3816 * information is needed. 3817 */ 3818 if (arc_ksp != NULL) 3819 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3820 3821 mutex_enter(&arc_user_evicts_lock); 3822 3823 /* 3824 * Block until signaled, or after one second (we need to 3825 * call the arc's kstat update function regularly). 3826 */ 3827 CALLB_CPR_SAFE_BEGIN(&cpr); 3828 (void) cv_timedwait(&arc_user_evicts_cv, 3829 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3830 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3831 } 3832 3833 arc_user_evicts_thread_exit = FALSE; 3834 cv_broadcast(&arc_user_evicts_cv); 3835 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3836 thread_exit(); 3837 } 3838 3839 /* 3840 * Adapt arc info given the number of bytes we are trying to add and 3841 * the state that we are comming from. This function is only called 3842 * when we are adding new content to the cache. 3843 */ 3844 static void 3845 arc_adapt(int bytes, arc_state_t *state) 3846 { 3847 int mult; 3848 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3849 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3850 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3851 3852 if (state == arc_l2c_only) 3853 return; 3854 3855 ASSERT(bytes > 0); 3856 /* 3857 * Adapt the target size of the MRU list: 3858 * - if we just hit in the MRU ghost list, then increase 3859 * the target size of the MRU list. 3860 * - if we just hit in the MFU ghost list, then increase 3861 * the target size of the MFU list by decreasing the 3862 * target size of the MRU list. 3863 */ 3864 if (state == arc_mru_ghost) { 3865 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3866 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3867 3868 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3869 } else if (state == arc_mfu_ghost) { 3870 uint64_t delta; 3871 3872 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3873 mult = MIN(mult, 10); 3874 3875 delta = MIN(bytes * mult, arc_p); 3876 arc_p = MAX(arc_p_min, arc_p - delta); 3877 } 3878 ASSERT((int64_t)arc_p >= 0); 3879 3880 if (arc_reclaim_needed()) { 3881 cv_signal(&arc_reclaim_thread_cv); 3882 return; 3883 } 3884 3885 if (arc_no_grow) 3886 return; 3887 3888 if (arc_c >= arc_c_max) 3889 return; 3890 3891 /* 3892 * If we're within (2 * maxblocksize) bytes of the target 3893 * cache size, increment the target cache size 3894 */ 3895 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3896 atomic_add_64(&arc_c, (int64_t)bytes); 3897 if (arc_c > arc_c_max) 3898 arc_c = arc_c_max; 3899 else if (state == arc_anon) 3900 atomic_add_64(&arc_p, (int64_t)bytes); 3901 if (arc_p > arc_c) 3902 arc_p = arc_c; 3903 } 3904 ASSERT((int64_t)arc_p >= 0); 3905 } 3906 3907 /* 3908 * Check if arc_size has grown past our upper threshold, determined by 3909 * zfs_arc_overflow_shift. 3910 */ 3911 static boolean_t 3912 arc_is_overflowing(void) 3913 { 3914 /* Always allow at least one block of overflow */ 3915 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3916 arc_c >> zfs_arc_overflow_shift); 3917 3918 return (arc_size >= arc_c + overflow); 3919 } 3920 3921 /* 3922 * The buffer, supplied as the first argument, needs a data block. If we 3923 * are hitting the hard limit for the cache size, we must sleep, waiting 3924 * for the eviction thread to catch up. If we're past the target size 3925 * but below the hard limit, we'll only signal the reclaim thread and 3926 * continue on. 3927 */ 3928 static void 3929 arc_get_data_buf(arc_buf_t *buf) 3930 { 3931 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3932 uint64_t size = buf->b_hdr->b_size; 3933 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3934 3935 arc_adapt(size, state); 3936 3937 /* 3938 * If arc_size is currently overflowing, and has grown past our 3939 * upper limit, we must be adding data faster than the evict 3940 * thread can evict. Thus, to ensure we don't compound the 3941 * problem by adding more data and forcing arc_size to grow even 3942 * further past it's target size, we halt and wait for the 3943 * eviction thread to catch up. 3944 * 3945 * It's also possible that the reclaim thread is unable to evict 3946 * enough buffers to get arc_size below the overflow limit (e.g. 3947 * due to buffers being un-evictable, or hash lock collisions). 3948 * In this case, we want to proceed regardless if we're 3949 * overflowing; thus we don't use a while loop here. 3950 */ 3951 if (arc_is_overflowing()) { 3952 mutex_enter(&arc_reclaim_lock); 3953 3954 /* 3955 * Now that we've acquired the lock, we may no longer be 3956 * over the overflow limit, lets check. 3957 * 3958 * We're ignoring the case of spurious wake ups. If that 3959 * were to happen, it'd let this thread consume an ARC 3960 * buffer before it should have (i.e. before we're under 3961 * the overflow limit and were signalled by the reclaim 3962 * thread). As long as that is a rare occurrence, it 3963 * shouldn't cause any harm. 3964 */ 3965 if (arc_is_overflowing()) { 3966 cv_signal(&arc_reclaim_thread_cv); 3967 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3968 } 3969 3970 mutex_exit(&arc_reclaim_lock); 3971 } 3972 3973 if (type == ARC_BUFC_METADATA) { 3974 buf->b_data = zio_buf_alloc(size); 3975 arc_space_consume(size, ARC_SPACE_META); 3976 } else { 3977 ASSERT(type == ARC_BUFC_DATA); 3978 buf->b_data = zio_data_buf_alloc(size); 3979 arc_space_consume(size, ARC_SPACE_DATA); 3980 } 3981 3982 /* 3983 * Update the state size. Note that ghost states have a 3984 * "ghost size" and so don't need to be updated. 3985 */ 3986 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3987 arc_buf_hdr_t *hdr = buf->b_hdr; 3988 arc_state_t *state = hdr->b_l1hdr.b_state; 3989 3990 (void) refcount_add_many(&state->arcs_size, size, buf); 3991 3992 /* 3993 * If this is reached via arc_read, the link is 3994 * protected by the hash lock. If reached via 3995 * arc_buf_alloc, the header should not be accessed by 3996 * any other thread. And, if reached via arc_read_done, 3997 * the hash lock will protect it if it's found in the 3998 * hash table; otherwise no other thread should be 3999 * trying to [add|remove]_reference it. 4000 */ 4001 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4002 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4003 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 4004 size); 4005 } 4006 /* 4007 * If we are growing the cache, and we are adding anonymous 4008 * data, and we have outgrown arc_p, update arc_p 4009 */ 4010 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4011 (refcount_count(&arc_anon->arcs_size) + 4012 refcount_count(&arc_mru->arcs_size) > arc_p)) 4013 arc_p = MIN(arc_c, arc_p + size); 4014 } 4015 } 4016 4017 /* 4018 * This routine is called whenever a buffer is accessed. 4019 * NOTE: the hash lock is dropped in this function. 4020 */ 4021 static void 4022 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4023 { 4024 clock_t now; 4025 4026 ASSERT(MUTEX_HELD(hash_lock)); 4027 ASSERT(HDR_HAS_L1HDR(hdr)); 4028 4029 if (hdr->b_l1hdr.b_state == arc_anon) { 4030 /* 4031 * This buffer is not in the cache, and does not 4032 * appear in our "ghost" list. Add the new buffer 4033 * to the MRU state. 4034 */ 4035 4036 ASSERT0(hdr->b_l1hdr.b_arc_access); 4037 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4038 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4039 arc_change_state(arc_mru, hdr, hash_lock); 4040 4041 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4042 now = ddi_get_lbolt(); 4043 4044 /* 4045 * If this buffer is here because of a prefetch, then either: 4046 * - clear the flag if this is a "referencing" read 4047 * (any subsequent access will bump this into the MFU state). 4048 * or 4049 * - move the buffer to the head of the list if this is 4050 * another prefetch (to make it less likely to be evicted). 4051 */ 4052 if (HDR_PREFETCH(hdr)) { 4053 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4054 /* link protected by hash lock */ 4055 ASSERT(multilist_link_active( 4056 &hdr->b_l1hdr.b_arc_node)); 4057 } else { 4058 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4059 ARCSTAT_BUMP(arcstat_mru_hits); 4060 } 4061 hdr->b_l1hdr.b_arc_access = now; 4062 return; 4063 } 4064 4065 /* 4066 * This buffer has been "accessed" only once so far, 4067 * but it is still in the cache. Move it to the MFU 4068 * state. 4069 */ 4070 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4071 /* 4072 * More than 125ms have passed since we 4073 * instantiated this buffer. Move it to the 4074 * most frequently used state. 4075 */ 4076 hdr->b_l1hdr.b_arc_access = now; 4077 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4078 arc_change_state(arc_mfu, hdr, hash_lock); 4079 } 4080 ARCSTAT_BUMP(arcstat_mru_hits); 4081 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4082 arc_state_t *new_state; 4083 /* 4084 * This buffer has been "accessed" recently, but 4085 * was evicted from the cache. Move it to the 4086 * MFU state. 4087 */ 4088 4089 if (HDR_PREFETCH(hdr)) { 4090 new_state = arc_mru; 4091 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4092 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4093 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4094 } else { 4095 new_state = arc_mfu; 4096 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4097 } 4098 4099 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4100 arc_change_state(new_state, hdr, hash_lock); 4101 4102 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4103 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4104 /* 4105 * This buffer has been accessed more than once and is 4106 * still in the cache. Keep it in the MFU state. 4107 * 4108 * NOTE: an add_reference() that occurred when we did 4109 * the arc_read() will have kicked this off the list. 4110 * If it was a prefetch, we will explicitly move it to 4111 * the head of the list now. 4112 */ 4113 if ((HDR_PREFETCH(hdr)) != 0) { 4114 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4115 /* link protected by hash_lock */ 4116 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4117 } 4118 ARCSTAT_BUMP(arcstat_mfu_hits); 4119 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4120 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4121 arc_state_t *new_state = arc_mfu; 4122 /* 4123 * This buffer has been accessed more than once but has 4124 * been evicted from the cache. Move it back to the 4125 * MFU state. 4126 */ 4127 4128 if (HDR_PREFETCH(hdr)) { 4129 /* 4130 * This is a prefetch access... 4131 * move this block back to the MRU state. 4132 */ 4133 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4134 new_state = arc_mru; 4135 } 4136 4137 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4138 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4139 arc_change_state(new_state, hdr, hash_lock); 4140 4141 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4142 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4143 /* 4144 * This buffer is on the 2nd Level ARC. 4145 */ 4146 4147 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4148 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4149 arc_change_state(arc_mfu, hdr, hash_lock); 4150 } else { 4151 ASSERT(!"invalid arc state"); 4152 } 4153 } 4154 4155 /* a generic arc_done_func_t which you can use */ 4156 /* ARGSUSED */ 4157 void 4158 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4159 { 4160 if (zio == NULL || zio->io_error == 0) 4161 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4162 VERIFY(arc_buf_remove_ref(buf, arg)); 4163 } 4164 4165 /* a generic arc_done_func_t */ 4166 void 4167 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4168 { 4169 arc_buf_t **bufp = arg; 4170 if (zio && zio->io_error) { 4171 VERIFY(arc_buf_remove_ref(buf, arg)); 4172 *bufp = NULL; 4173 } else { 4174 *bufp = buf; 4175 ASSERT(buf->b_data); 4176 } 4177 } 4178 4179 static void 4180 arc_read_done(zio_t *zio) 4181 { 4182 arc_buf_hdr_t *hdr; 4183 arc_buf_t *buf; 4184 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4185 kmutex_t *hash_lock = NULL; 4186 arc_callback_t *callback_list, *acb; 4187 int freeable = FALSE; 4188 4189 buf = zio->io_private; 4190 hdr = buf->b_hdr; 4191 4192 /* 4193 * The hdr was inserted into hash-table and removed from lists 4194 * prior to starting I/O. We should find this header, since 4195 * it's in the hash table, and it should be legit since it's 4196 * not possible to evict it during the I/O. The only possible 4197 * reason for it not to be found is if we were freed during the 4198 * read. 4199 */ 4200 if (HDR_IN_HASH_TABLE(hdr)) { 4201 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4202 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4203 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4204 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4205 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4206 4207 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4208 &hash_lock); 4209 4210 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4211 hash_lock == NULL) || 4212 (found == hdr && 4213 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4214 (found == hdr && HDR_L2_READING(hdr))); 4215 } 4216 4217 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4218 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4219 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4220 4221 /* byteswap if necessary */ 4222 callback_list = hdr->b_l1hdr.b_acb; 4223 ASSERT(callback_list != NULL); 4224 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4225 dmu_object_byteswap_t bswap = 4226 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4227 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4228 byteswap_uint64_array : 4229 dmu_ot_byteswap[bswap].ob_func; 4230 func(buf->b_data, hdr->b_size); 4231 } 4232 4233 arc_cksum_compute(buf, B_FALSE); 4234 arc_buf_watch(buf); 4235 4236 if (hash_lock && zio->io_error == 0 && 4237 hdr->b_l1hdr.b_state == arc_anon) { 4238 /* 4239 * Only call arc_access on anonymous buffers. This is because 4240 * if we've issued an I/O for an evicted buffer, we've already 4241 * called arc_access (to prevent any simultaneous readers from 4242 * getting confused). 4243 */ 4244 arc_access(hdr, hash_lock); 4245 } 4246 4247 /* create copies of the data buffer for the callers */ 4248 abuf = buf; 4249 for (acb = callback_list; acb; acb = acb->acb_next) { 4250 if (acb->acb_done) { 4251 if (abuf == NULL) { 4252 ARCSTAT_BUMP(arcstat_duplicate_reads); 4253 abuf = arc_buf_clone(buf); 4254 } 4255 acb->acb_buf = abuf; 4256 abuf = NULL; 4257 } 4258 } 4259 hdr->b_l1hdr.b_acb = NULL; 4260 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4261 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4262 if (abuf == buf) { 4263 ASSERT(buf->b_efunc == NULL); 4264 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4265 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4266 } 4267 4268 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4269 callback_list != NULL); 4270 4271 if (zio->io_error != 0) { 4272 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4273 if (hdr->b_l1hdr.b_state != arc_anon) 4274 arc_change_state(arc_anon, hdr, hash_lock); 4275 if (HDR_IN_HASH_TABLE(hdr)) 4276 buf_hash_remove(hdr); 4277 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4278 } 4279 4280 /* 4281 * Broadcast before we drop the hash_lock to avoid the possibility 4282 * that the hdr (and hence the cv) might be freed before we get to 4283 * the cv_broadcast(). 4284 */ 4285 cv_broadcast(&hdr->b_l1hdr.b_cv); 4286 4287 if (hash_lock != NULL) { 4288 mutex_exit(hash_lock); 4289 } else { 4290 /* 4291 * This block was freed while we waited for the read to 4292 * complete. It has been removed from the hash table and 4293 * moved to the anonymous state (so that it won't show up 4294 * in the cache). 4295 */ 4296 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4297 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4298 } 4299 4300 /* execute each callback and free its structure */ 4301 while ((acb = callback_list) != NULL) { 4302 if (acb->acb_done) 4303 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4304 4305 if (acb->acb_zio_dummy != NULL) { 4306 acb->acb_zio_dummy->io_error = zio->io_error; 4307 zio_nowait(acb->acb_zio_dummy); 4308 } 4309 4310 callback_list = acb->acb_next; 4311 kmem_free(acb, sizeof (arc_callback_t)); 4312 } 4313 4314 if (freeable) 4315 arc_hdr_destroy(hdr); 4316 } 4317 4318 /* 4319 * "Read" the block at the specified DVA (in bp) via the 4320 * cache. If the block is found in the cache, invoke the provided 4321 * callback immediately and return. Note that the `zio' parameter 4322 * in the callback will be NULL in this case, since no IO was 4323 * required. If the block is not in the cache pass the read request 4324 * on to the spa with a substitute callback function, so that the 4325 * requested block will be added to the cache. 4326 * 4327 * If a read request arrives for a block that has a read in-progress, 4328 * either wait for the in-progress read to complete (and return the 4329 * results); or, if this is a read with a "done" func, add a record 4330 * to the read to invoke the "done" func when the read completes, 4331 * and return; or just return. 4332 * 4333 * arc_read_done() will invoke all the requested "done" functions 4334 * for readers of this block. 4335 */ 4336 int 4337 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4338 void *private, zio_priority_t priority, int zio_flags, 4339 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4340 { 4341 arc_buf_hdr_t *hdr = NULL; 4342 arc_buf_t *buf = NULL; 4343 kmutex_t *hash_lock = NULL; 4344 zio_t *rzio; 4345 uint64_t guid = spa_load_guid(spa); 4346 4347 ASSERT(!BP_IS_EMBEDDED(bp) || 4348 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4349 4350 top: 4351 if (!BP_IS_EMBEDDED(bp)) { 4352 /* 4353 * Embedded BP's have no DVA and require no I/O to "read". 4354 * Create an anonymous arc buf to back it. 4355 */ 4356 hdr = buf_hash_find(guid, bp, &hash_lock); 4357 } 4358 4359 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4360 4361 *arc_flags |= ARC_FLAG_CACHED; 4362 4363 if (HDR_IO_IN_PROGRESS(hdr)) { 4364 4365 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4366 priority == ZIO_PRIORITY_SYNC_READ) { 4367 /* 4368 * This sync read must wait for an 4369 * in-progress async read (e.g. a predictive 4370 * prefetch). Async reads are queued 4371 * separately at the vdev_queue layer, so 4372 * this is a form of priority inversion. 4373 * Ideally, we would "inherit" the demand 4374 * i/o's priority by moving the i/o from 4375 * the async queue to the synchronous queue, 4376 * but there is currently no mechanism to do 4377 * so. Track this so that we can evaluate 4378 * the magnitude of this potential performance 4379 * problem. 4380 * 4381 * Note that if the prefetch i/o is already 4382 * active (has been issued to the device), 4383 * the prefetch improved performance, because 4384 * we issued it sooner than we would have 4385 * without the prefetch. 4386 */ 4387 DTRACE_PROBE1(arc__sync__wait__for__async, 4388 arc_buf_hdr_t *, hdr); 4389 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4390 } 4391 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4392 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4393 } 4394 4395 if (*arc_flags & ARC_FLAG_WAIT) { 4396 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4397 mutex_exit(hash_lock); 4398 goto top; 4399 } 4400 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4401 4402 if (done) { 4403 arc_callback_t *acb = NULL; 4404 4405 acb = kmem_zalloc(sizeof (arc_callback_t), 4406 KM_SLEEP); 4407 acb->acb_done = done; 4408 acb->acb_private = private; 4409 if (pio != NULL) 4410 acb->acb_zio_dummy = zio_null(pio, 4411 spa, NULL, NULL, NULL, zio_flags); 4412 4413 ASSERT(acb->acb_done != NULL); 4414 acb->acb_next = hdr->b_l1hdr.b_acb; 4415 hdr->b_l1hdr.b_acb = acb; 4416 add_reference(hdr, hash_lock, private); 4417 mutex_exit(hash_lock); 4418 return (0); 4419 } 4420 mutex_exit(hash_lock); 4421 return (0); 4422 } 4423 4424 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4425 hdr->b_l1hdr.b_state == arc_mfu); 4426 4427 if (done) { 4428 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4429 /* 4430 * This is a demand read which does not have to 4431 * wait for i/o because we did a predictive 4432 * prefetch i/o for it, which has completed. 4433 */ 4434 DTRACE_PROBE1( 4435 arc__demand__hit__predictive__prefetch, 4436 arc_buf_hdr_t *, hdr); 4437 ARCSTAT_BUMP( 4438 arcstat_demand_hit_predictive_prefetch); 4439 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4440 } 4441 add_reference(hdr, hash_lock, private); 4442 /* 4443 * If this block is already in use, create a new 4444 * copy of the data so that we will be guaranteed 4445 * that arc_release() will always succeed. 4446 */ 4447 buf = hdr->b_l1hdr.b_buf; 4448 ASSERT(buf); 4449 ASSERT(buf->b_data); 4450 if (HDR_BUF_AVAILABLE(hdr)) { 4451 ASSERT(buf->b_efunc == NULL); 4452 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4453 } else { 4454 buf = arc_buf_clone(buf); 4455 } 4456 4457 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4458 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4459 hdr->b_flags |= ARC_FLAG_PREFETCH; 4460 } 4461 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4462 arc_access(hdr, hash_lock); 4463 if (*arc_flags & ARC_FLAG_L2CACHE) 4464 hdr->b_flags |= ARC_FLAG_L2CACHE; 4465 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4466 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4467 mutex_exit(hash_lock); 4468 ARCSTAT_BUMP(arcstat_hits); 4469 arc_update_hit_stat(hdr, B_TRUE); 4470 4471 if (done) 4472 done(NULL, buf, private); 4473 } else { 4474 uint64_t size = BP_GET_LSIZE(bp); 4475 arc_callback_t *acb; 4476 vdev_t *vd = NULL; 4477 uint64_t addr = 0; 4478 boolean_t devw = B_FALSE; 4479 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4480 int32_t b_asize = 0; 4481 4482 if (hdr == NULL) { 4483 /* this block is not in the cache */ 4484 arc_buf_hdr_t *exists = NULL; 4485 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4486 buf = arc_buf_alloc(spa, size, private, type); 4487 hdr = buf->b_hdr; 4488 if (!BP_IS_EMBEDDED(bp)) { 4489 hdr->b_dva = *BP_IDENTITY(bp); 4490 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4491 exists = buf_hash_insert(hdr, &hash_lock); 4492 } 4493 if (exists != NULL) { 4494 /* somebody beat us to the hash insert */ 4495 mutex_exit(hash_lock); 4496 buf_discard_identity(hdr); 4497 (void) arc_buf_remove_ref(buf, private); 4498 goto top; /* restart the IO request */ 4499 } 4500 4501 /* 4502 * If there is a callback, we pass our reference to 4503 * it; otherwise we remove our reference. 4504 */ 4505 if (done == NULL) { 4506 (void) remove_reference(hdr, hash_lock, 4507 private); 4508 } 4509 if (*arc_flags & ARC_FLAG_PREFETCH) 4510 hdr->b_flags |= ARC_FLAG_PREFETCH; 4511 if (*arc_flags & ARC_FLAG_L2CACHE) 4512 hdr->b_flags |= ARC_FLAG_L2CACHE; 4513 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4514 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4515 if (BP_GET_LEVEL(bp) > 0) 4516 hdr->b_flags |= ARC_FLAG_INDIRECT; 4517 } else { 4518 /* 4519 * This block is in the ghost cache. If it was L2-only 4520 * (and thus didn't have an L1 hdr), we realloc the 4521 * header to add an L1 hdr. 4522 */ 4523 if (!HDR_HAS_L1HDR(hdr)) { 4524 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4525 hdr_full_cache); 4526 } 4527 4528 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4529 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4530 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4531 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4532 4533 /* 4534 * If there is a callback, we pass a reference to it. 4535 */ 4536 if (done != NULL) 4537 add_reference(hdr, hash_lock, private); 4538 if (*arc_flags & ARC_FLAG_PREFETCH) 4539 hdr->b_flags |= ARC_FLAG_PREFETCH; 4540 if (*arc_flags & ARC_FLAG_L2CACHE) 4541 hdr->b_flags |= ARC_FLAG_L2CACHE; 4542 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4543 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4544 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4545 buf->b_hdr = hdr; 4546 buf->b_data = NULL; 4547 buf->b_efunc = NULL; 4548 buf->b_private = NULL; 4549 buf->b_next = NULL; 4550 hdr->b_l1hdr.b_buf = buf; 4551 ASSERT0(hdr->b_l1hdr.b_datacnt); 4552 hdr->b_l1hdr.b_datacnt = 1; 4553 arc_get_data_buf(buf); 4554 arc_access(hdr, hash_lock); 4555 } 4556 4557 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4558 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4559 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4560 4561 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4562 acb->acb_done = done; 4563 acb->acb_private = private; 4564 4565 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4566 hdr->b_l1hdr.b_acb = acb; 4567 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4568 4569 if (HDR_HAS_L2HDR(hdr) && 4570 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4571 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4572 addr = hdr->b_l2hdr.b_daddr; 4573 b_compress = hdr->b_l2hdr.b_compress; 4574 b_asize = hdr->b_l2hdr.b_asize; 4575 /* 4576 * Lock out device removal. 4577 */ 4578 if (vdev_is_dead(vd) || 4579 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4580 vd = NULL; 4581 } 4582 4583 if (hash_lock != NULL) 4584 mutex_exit(hash_lock); 4585 4586 /* 4587 * At this point, we have a level 1 cache miss. Try again in 4588 * L2ARC if possible. 4589 */ 4590 ASSERT3U(hdr->b_size, ==, size); 4591 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4592 uint64_t, size, zbookmark_phys_t *, zb); 4593 ARCSTAT_BUMP(arcstat_misses); 4594 arc_update_hit_stat(hdr, B_FALSE); 4595 4596 if (priority == ZIO_PRIORITY_ASYNC_READ) 4597 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4598 else 4599 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4600 4601 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4602 /* 4603 * Read from the L2ARC if the following are true: 4604 * 1. The L2ARC vdev was previously cached. 4605 * 2. This buffer still has L2ARC metadata. 4606 * 3. This buffer isn't currently writing to the L2ARC. 4607 * 4. The L2ARC entry wasn't evicted, which may 4608 * also have invalidated the vdev. 4609 * 5. This isn't prefetch and l2arc_noprefetch is set. 4610 */ 4611 if (HDR_HAS_L2HDR(hdr) && 4612 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4613 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4614 l2arc_read_callback_t *cb; 4615 4616 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4617 ARCSTAT_BUMP(arcstat_l2_hits); 4618 4619 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4620 KM_SLEEP); 4621 cb->l2rcb_buf = buf; 4622 cb->l2rcb_spa = spa; 4623 cb->l2rcb_bp = *bp; 4624 cb->l2rcb_zb = *zb; 4625 cb->l2rcb_flags = zio_flags; 4626 cb->l2rcb_compress = b_compress; 4627 4628 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4629 addr + size < vd->vdev_psize - 4630 VDEV_LABEL_END_SIZE); 4631 4632 /* 4633 * l2arc read. The SCL_L2ARC lock will be 4634 * released by l2arc_read_done(). 4635 * Issue a null zio if the underlying buffer 4636 * was squashed to zero size by compression. 4637 */ 4638 if (b_compress == ZIO_COMPRESS_EMPTY) { 4639 rzio = zio_null(pio, spa, vd, 4640 l2arc_read_done, cb, 4641 zio_flags | ZIO_FLAG_DONT_CACHE | 4642 ZIO_FLAG_CANFAIL | 4643 ZIO_FLAG_DONT_PROPAGATE | 4644 ZIO_FLAG_DONT_RETRY); 4645 } else { 4646 rzio = zio_read_phys(pio, vd, addr, 4647 b_asize, buf->b_data, 4648 ZIO_CHECKSUM_OFF, 4649 l2arc_read_done, cb, priority, 4650 zio_flags | ZIO_FLAG_DONT_CACHE | 4651 ZIO_FLAG_CANFAIL | 4652 ZIO_FLAG_DONT_PROPAGATE | 4653 ZIO_FLAG_DONT_RETRY, B_FALSE); 4654 } 4655 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4656 zio_t *, rzio); 4657 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4658 4659 if (*arc_flags & ARC_FLAG_NOWAIT) { 4660 zio_nowait(rzio); 4661 return (0); 4662 } 4663 4664 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4665 if (zio_wait(rzio) == 0) 4666 return (0); 4667 4668 /* l2arc read error; goto zio_read() */ 4669 } else { 4670 DTRACE_PROBE1(l2arc__miss, 4671 arc_buf_hdr_t *, hdr); 4672 ARCSTAT_BUMP(arcstat_l2_misses); 4673 if (HDR_L2_WRITING(hdr)) 4674 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4675 spa_config_exit(spa, SCL_L2ARC, vd); 4676 } 4677 } else { 4678 if (vd != NULL) 4679 spa_config_exit(spa, SCL_L2ARC, vd); 4680 if (l2arc_ndev != 0) { 4681 DTRACE_PROBE1(l2arc__miss, 4682 arc_buf_hdr_t *, hdr); 4683 ARCSTAT_BUMP(arcstat_l2_misses); 4684 } 4685 } 4686 4687 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4688 arc_read_done, buf, priority, zio_flags, zb); 4689 4690 if (*arc_flags & ARC_FLAG_WAIT) 4691 return (zio_wait(rzio)); 4692 4693 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4694 zio_nowait(rzio); 4695 } 4696 return (0); 4697 } 4698 4699 void 4700 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4701 { 4702 ASSERT(buf->b_hdr != NULL); 4703 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4704 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4705 func == NULL); 4706 ASSERT(buf->b_efunc == NULL); 4707 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4708 4709 buf->b_efunc = func; 4710 buf->b_private = private; 4711 } 4712 4713 /* 4714 * Notify the arc that a block was freed, and thus will never be used again. 4715 */ 4716 void 4717 arc_freed(spa_t *spa, const blkptr_t *bp) 4718 { 4719 arc_buf_hdr_t *hdr; 4720 kmutex_t *hash_lock; 4721 uint64_t guid = spa_load_guid(spa); 4722 4723 ASSERT(!BP_IS_EMBEDDED(bp)); 4724 4725 hdr = buf_hash_find(guid, bp, &hash_lock); 4726 if (hdr == NULL) 4727 return; 4728 if (HDR_BUF_AVAILABLE(hdr)) { 4729 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4730 add_reference(hdr, hash_lock, FTAG); 4731 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4732 mutex_exit(hash_lock); 4733 4734 arc_release(buf, FTAG); 4735 (void) arc_buf_remove_ref(buf, FTAG); 4736 } else { 4737 mutex_exit(hash_lock); 4738 } 4739 4740 } 4741 4742 /* 4743 * Clear the user eviction callback set by arc_set_callback(), first calling 4744 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4745 * clearing the callback may result in the arc_buf being destroyed. However, 4746 * it will not result in the *last* arc_buf being destroyed, hence the data 4747 * will remain cached in the ARC. We make a copy of the arc buffer here so 4748 * that we can process the callback without holding any locks. 4749 * 4750 * It's possible that the callback is already in the process of being cleared 4751 * by another thread. In this case we can not clear the callback. 4752 * 4753 * Returns B_TRUE if the callback was successfully called and cleared. 4754 */ 4755 boolean_t 4756 arc_clear_callback(arc_buf_t *buf) 4757 { 4758 arc_buf_hdr_t *hdr; 4759 kmutex_t *hash_lock; 4760 arc_evict_func_t *efunc = buf->b_efunc; 4761 void *private = buf->b_private; 4762 4763 mutex_enter(&buf->b_evict_lock); 4764 hdr = buf->b_hdr; 4765 if (hdr == NULL) { 4766 /* 4767 * We are in arc_do_user_evicts(). 4768 */ 4769 ASSERT(buf->b_data == NULL); 4770 mutex_exit(&buf->b_evict_lock); 4771 return (B_FALSE); 4772 } else if (buf->b_data == NULL) { 4773 /* 4774 * We are on the eviction list; process this buffer now 4775 * but let arc_do_user_evicts() do the reaping. 4776 */ 4777 buf->b_efunc = NULL; 4778 mutex_exit(&buf->b_evict_lock); 4779 VERIFY0(efunc(private)); 4780 return (B_TRUE); 4781 } 4782 hash_lock = HDR_LOCK(hdr); 4783 mutex_enter(hash_lock); 4784 hdr = buf->b_hdr; 4785 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4786 4787 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4788 hdr->b_l1hdr.b_datacnt); 4789 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4790 hdr->b_l1hdr.b_state == arc_mfu); 4791 4792 buf->b_efunc = NULL; 4793 buf->b_private = NULL; 4794 4795 if (hdr->b_l1hdr.b_datacnt > 1) { 4796 mutex_exit(&buf->b_evict_lock); 4797 arc_buf_destroy(buf, TRUE); 4798 } else { 4799 ASSERT(buf == hdr->b_l1hdr.b_buf); 4800 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4801 mutex_exit(&buf->b_evict_lock); 4802 } 4803 4804 mutex_exit(hash_lock); 4805 VERIFY0(efunc(private)); 4806 return (B_TRUE); 4807 } 4808 4809 /* 4810 * Release this buffer from the cache, making it an anonymous buffer. This 4811 * must be done after a read and prior to modifying the buffer contents. 4812 * If the buffer has more than one reference, we must make 4813 * a new hdr for the buffer. 4814 */ 4815 void 4816 arc_release(arc_buf_t *buf, void *tag) 4817 { 4818 arc_buf_hdr_t *hdr = buf->b_hdr; 4819 4820 /* 4821 * It would be nice to assert that if it's DMU metadata (level > 4822 * 0 || it's the dnode file), then it must be syncing context. 4823 * But we don't know that information at this level. 4824 */ 4825 4826 mutex_enter(&buf->b_evict_lock); 4827 4828 ASSERT(HDR_HAS_L1HDR(hdr)); 4829 4830 /* 4831 * We don't grab the hash lock prior to this check, because if 4832 * the buffer's header is in the arc_anon state, it won't be 4833 * linked into the hash table. 4834 */ 4835 if (hdr->b_l1hdr.b_state == arc_anon) { 4836 mutex_exit(&buf->b_evict_lock); 4837 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4838 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4839 ASSERT(!HDR_HAS_L2HDR(hdr)); 4840 ASSERT(BUF_EMPTY(hdr)); 4841 4842 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4843 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4844 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4845 4846 ASSERT3P(buf->b_efunc, ==, NULL); 4847 ASSERT3P(buf->b_private, ==, NULL); 4848 4849 hdr->b_l1hdr.b_arc_access = 0; 4850 arc_buf_thaw(buf); 4851 4852 return; 4853 } 4854 4855 kmutex_t *hash_lock = HDR_LOCK(hdr); 4856 mutex_enter(hash_lock); 4857 4858 /* 4859 * This assignment is only valid as long as the hash_lock is 4860 * held, we must be careful not to reference state or the 4861 * b_state field after dropping the lock. 4862 */ 4863 arc_state_t *state = hdr->b_l1hdr.b_state; 4864 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4865 ASSERT3P(state, !=, arc_anon); 4866 4867 /* this buffer is not on any list */ 4868 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4869 4870 if (HDR_HAS_L2HDR(hdr)) { 4871 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4872 4873 /* 4874 * We have to recheck this conditional again now that 4875 * we're holding the l2ad_mtx to prevent a race with 4876 * another thread which might be concurrently calling 4877 * l2arc_evict(). In that case, l2arc_evict() might have 4878 * destroyed the header's L2 portion as we were waiting 4879 * to acquire the l2ad_mtx. 4880 */ 4881 if (HDR_HAS_L2HDR(hdr)) 4882 arc_hdr_l2hdr_destroy(hdr); 4883 4884 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4885 } 4886 4887 /* 4888 * Do we have more than one buf? 4889 */ 4890 if (hdr->b_l1hdr.b_datacnt > 1) { 4891 arc_buf_hdr_t *nhdr; 4892 arc_buf_t **bufp; 4893 uint64_t blksz = hdr->b_size; 4894 uint64_t spa = hdr->b_spa; 4895 arc_buf_contents_t type = arc_buf_type(hdr); 4896 uint32_t flags = hdr->b_flags; 4897 4898 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4899 /* 4900 * Pull the data off of this hdr and attach it to 4901 * a new anonymous hdr. 4902 */ 4903 (void) remove_reference(hdr, hash_lock, tag); 4904 bufp = &hdr->b_l1hdr.b_buf; 4905 while (*bufp != buf) 4906 bufp = &(*bufp)->b_next; 4907 *bufp = buf->b_next; 4908 buf->b_next = NULL; 4909 4910 ASSERT3P(state, !=, arc_l2c_only); 4911 4912 (void) refcount_remove_many( 4913 &state->arcs_size, hdr->b_size, buf); 4914 4915 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4916 ASSERT3P(state, !=, arc_l2c_only); 4917 uint64_t *size = &state->arcs_lsize[type]; 4918 ASSERT3U(*size, >=, hdr->b_size); 4919 atomic_add_64(size, -hdr->b_size); 4920 } 4921 4922 /* 4923 * We're releasing a duplicate user data buffer, update 4924 * our statistics accordingly. 4925 */ 4926 if (HDR_ISTYPE_DATA(hdr)) { 4927 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4928 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4929 -hdr->b_size); 4930 } 4931 hdr->b_l1hdr.b_datacnt -= 1; 4932 arc_cksum_verify(buf); 4933 arc_buf_unwatch(buf); 4934 4935 mutex_exit(hash_lock); 4936 4937 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4938 nhdr->b_size = blksz; 4939 nhdr->b_spa = spa; 4940 4941 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4942 nhdr->b_flags |= arc_bufc_to_flags(type); 4943 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4944 4945 nhdr->b_l1hdr.b_buf = buf; 4946 nhdr->b_l1hdr.b_datacnt = 1; 4947 nhdr->b_l1hdr.b_state = arc_anon; 4948 nhdr->b_l1hdr.b_arc_access = 0; 4949 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4950 nhdr->b_freeze_cksum = NULL; 4951 4952 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4953 buf->b_hdr = nhdr; 4954 mutex_exit(&buf->b_evict_lock); 4955 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4956 } else { 4957 mutex_exit(&buf->b_evict_lock); 4958 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4959 /* protected by hash lock, or hdr is on arc_anon */ 4960 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4961 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4962 arc_change_state(arc_anon, hdr, hash_lock); 4963 hdr->b_l1hdr.b_arc_access = 0; 4964 mutex_exit(hash_lock); 4965 4966 buf_discard_identity(hdr); 4967 arc_buf_thaw(buf); 4968 } 4969 buf->b_efunc = NULL; 4970 buf->b_private = NULL; 4971 } 4972 4973 int 4974 arc_released(arc_buf_t *buf) 4975 { 4976 int released; 4977 4978 mutex_enter(&buf->b_evict_lock); 4979 released = (buf->b_data != NULL && 4980 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4981 mutex_exit(&buf->b_evict_lock); 4982 return (released); 4983 } 4984 4985 #ifdef ZFS_DEBUG 4986 int 4987 arc_referenced(arc_buf_t *buf) 4988 { 4989 int referenced; 4990 4991 mutex_enter(&buf->b_evict_lock); 4992 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4993 mutex_exit(&buf->b_evict_lock); 4994 return (referenced); 4995 } 4996 #endif 4997 4998 static void 4999 arc_write_ready(zio_t *zio) 5000 { 5001 arc_write_callback_t *callback = zio->io_private; 5002 arc_buf_t *buf = callback->awcb_buf; 5003 arc_buf_hdr_t *hdr = buf->b_hdr; 5004 5005 ASSERT(HDR_HAS_L1HDR(hdr)); 5006 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5007 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5008 callback->awcb_ready(zio, buf, callback->awcb_private); 5009 5010 /* 5011 * If the IO is already in progress, then this is a re-write 5012 * attempt, so we need to thaw and re-compute the cksum. 5013 * It is the responsibility of the callback to handle the 5014 * accounting for any re-write attempt. 5015 */ 5016 if (HDR_IO_IN_PROGRESS(hdr)) { 5017 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 5018 if (hdr->b_freeze_cksum != NULL) { 5019 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 5020 hdr->b_freeze_cksum = NULL; 5021 } 5022 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 5023 } 5024 arc_cksum_compute(buf, B_FALSE); 5025 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 5026 } 5027 5028 /* 5029 * The SPA calls this callback for each physical write that happens on behalf 5030 * of a logical write. See the comment in dbuf_write_physdone() for details. 5031 */ 5032 static void 5033 arc_write_physdone(zio_t *zio) 5034 { 5035 arc_write_callback_t *cb = zio->io_private; 5036 if (cb->awcb_physdone != NULL) 5037 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5038 } 5039 5040 static void 5041 arc_write_done(zio_t *zio) 5042 { 5043 arc_write_callback_t *callback = zio->io_private; 5044 arc_buf_t *buf = callback->awcb_buf; 5045 arc_buf_hdr_t *hdr = buf->b_hdr; 5046 5047 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5048 5049 if (zio->io_error == 0) { 5050 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5051 buf_discard_identity(hdr); 5052 } else { 5053 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5054 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5055 } 5056 } else { 5057 ASSERT(BUF_EMPTY(hdr)); 5058 } 5059 5060 /* 5061 * If the block to be written was all-zero or compressed enough to be 5062 * embedded in the BP, no write was performed so there will be no 5063 * dva/birth/checksum. The buffer must therefore remain anonymous 5064 * (and uncached). 5065 */ 5066 if (!BUF_EMPTY(hdr)) { 5067 arc_buf_hdr_t *exists; 5068 kmutex_t *hash_lock; 5069 5070 ASSERT(zio->io_error == 0); 5071 5072 arc_cksum_verify(buf); 5073 5074 exists = buf_hash_insert(hdr, &hash_lock); 5075 if (exists != NULL) { 5076 /* 5077 * This can only happen if we overwrite for 5078 * sync-to-convergence, because we remove 5079 * buffers from the hash table when we arc_free(). 5080 */ 5081 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5082 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5083 panic("bad overwrite, hdr=%p exists=%p", 5084 (void *)hdr, (void *)exists); 5085 ASSERT(refcount_is_zero( 5086 &exists->b_l1hdr.b_refcnt)); 5087 arc_change_state(arc_anon, exists, hash_lock); 5088 mutex_exit(hash_lock); 5089 arc_hdr_destroy(exists); 5090 exists = buf_hash_insert(hdr, &hash_lock); 5091 ASSERT3P(exists, ==, NULL); 5092 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5093 /* nopwrite */ 5094 ASSERT(zio->io_prop.zp_nopwrite); 5095 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5096 panic("bad nopwrite, hdr=%p exists=%p", 5097 (void *)hdr, (void *)exists); 5098 } else { 5099 /* Dedup */ 5100 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5101 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5102 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5103 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5104 } 5105 } 5106 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5107 /* if it's not anon, we are doing a scrub */ 5108 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5109 arc_access(hdr, hash_lock); 5110 mutex_exit(hash_lock); 5111 } else { 5112 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5113 } 5114 5115 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5116 callback->awcb_done(zio, buf, callback->awcb_private); 5117 5118 kmem_free(callback, sizeof (arc_write_callback_t)); 5119 } 5120 5121 zio_t * 5122 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5123 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5124 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 5125 arc_done_func_t *done, void *private, zio_priority_t priority, 5126 int zio_flags, const zbookmark_phys_t *zb) 5127 { 5128 arc_buf_hdr_t *hdr = buf->b_hdr; 5129 arc_write_callback_t *callback; 5130 zio_t *zio; 5131 5132 ASSERT(ready != NULL); 5133 ASSERT(done != NULL); 5134 ASSERT(!HDR_IO_ERROR(hdr)); 5135 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5136 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5137 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5138 if (l2arc) 5139 hdr->b_flags |= ARC_FLAG_L2CACHE; 5140 if (l2arc_compress) 5141 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5142 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5143 callback->awcb_ready = ready; 5144 callback->awcb_physdone = physdone; 5145 callback->awcb_done = done; 5146 callback->awcb_private = private; 5147 callback->awcb_buf = buf; 5148 5149 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5150 arc_write_ready, arc_write_physdone, arc_write_done, callback, 5151 priority, zio_flags, zb); 5152 5153 return (zio); 5154 } 5155 5156 static int 5157 arc_memory_throttle(uint64_t reserve, uint64_t txg) 5158 { 5159 #ifdef _KERNEL 5160 uint64_t available_memory = ptob(freemem); 5161 static uint64_t page_load = 0; 5162 static uint64_t last_txg = 0; 5163 5164 #if defined(__i386) 5165 available_memory = 5166 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 5167 #endif 5168 5169 if (freemem > physmem * arc_lotsfree_percent / 100) 5170 return (0); 5171 5172 if (txg > last_txg) { 5173 last_txg = txg; 5174 page_load = 0; 5175 } 5176 /* 5177 * If we are in pageout, we know that memory is already tight, 5178 * the arc is already going to be evicting, so we just want to 5179 * continue to let page writes occur as quickly as possible. 5180 */ 5181 if (curproc == proc_pageout) { 5182 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5183 return (SET_ERROR(ERESTART)); 5184 /* Note: reserve is inflated, so we deflate */ 5185 page_load += reserve / 8; 5186 return (0); 5187 } else if (page_load > 0 && arc_reclaim_needed()) { 5188 /* memory is low, delay before restarting */ 5189 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5190 return (SET_ERROR(EAGAIN)); 5191 } 5192 page_load = 0; 5193 #endif 5194 return (0); 5195 } 5196 5197 void 5198 arc_tempreserve_clear(uint64_t reserve) 5199 { 5200 atomic_add_64(&arc_tempreserve, -reserve); 5201 ASSERT((int64_t)arc_tempreserve >= 0); 5202 } 5203 5204 int 5205 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5206 { 5207 int error; 5208 uint64_t anon_size; 5209 5210 if (reserve > arc_c/4 && !arc_no_grow) 5211 arc_c = MIN(arc_c_max, reserve * 4); 5212 if (reserve > arc_c) 5213 return (SET_ERROR(ENOMEM)); 5214 5215 /* 5216 * Don't count loaned bufs as in flight dirty data to prevent long 5217 * network delays from blocking transactions that are ready to be 5218 * assigned to a txg. 5219 */ 5220 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5221 arc_loaned_bytes), 0); 5222 5223 /* 5224 * Writes will, almost always, require additional memory allocations 5225 * in order to compress/encrypt/etc the data. We therefore need to 5226 * make sure that there is sufficient available memory for this. 5227 */ 5228 error = arc_memory_throttle(reserve, txg); 5229 if (error != 0) 5230 return (error); 5231 5232 /* 5233 * Throttle writes when the amount of dirty data in the cache 5234 * gets too large. We try to keep the cache less than half full 5235 * of dirty blocks so that our sync times don't grow too large. 5236 * Note: if two requests come in concurrently, we might let them 5237 * both succeed, when one of them should fail. Not a huge deal. 5238 */ 5239 5240 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5241 anon_size > arc_c / 4) { 5242 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5243 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5244 arc_tempreserve>>10, 5245 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5246 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5247 reserve>>10, arc_c>>10); 5248 return (SET_ERROR(ERESTART)); 5249 } 5250 atomic_add_64(&arc_tempreserve, reserve); 5251 return (0); 5252 } 5253 5254 static void 5255 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5256 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5257 { 5258 size->value.ui64 = refcount_count(&state->arcs_size); 5259 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5260 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5261 } 5262 5263 static int 5264 arc_kstat_update(kstat_t *ksp, int rw) 5265 { 5266 arc_stats_t *as = ksp->ks_data; 5267 5268 if (rw == KSTAT_WRITE) { 5269 return (EACCES); 5270 } else { 5271 arc_kstat_update_state(arc_anon, 5272 &as->arcstat_anon_size, 5273 &as->arcstat_anon_evictable_data, 5274 &as->arcstat_anon_evictable_metadata); 5275 arc_kstat_update_state(arc_mru, 5276 &as->arcstat_mru_size, 5277 &as->arcstat_mru_evictable_data, 5278 &as->arcstat_mru_evictable_metadata); 5279 arc_kstat_update_state(arc_mru_ghost, 5280 &as->arcstat_mru_ghost_size, 5281 &as->arcstat_mru_ghost_evictable_data, 5282 &as->arcstat_mru_ghost_evictable_metadata); 5283 arc_kstat_update_state(arc_mfu, 5284 &as->arcstat_mfu_size, 5285 &as->arcstat_mfu_evictable_data, 5286 &as->arcstat_mfu_evictable_metadata); 5287 arc_kstat_update_state(arc_mfu_ghost, 5288 &as->arcstat_mfu_ghost_size, 5289 &as->arcstat_mfu_ghost_evictable_data, 5290 &as->arcstat_mfu_ghost_evictable_metadata); 5291 } 5292 5293 return (0); 5294 } 5295 5296 /* 5297 * This function *must* return indices evenly distributed between all 5298 * sublists of the multilist. This is needed due to how the ARC eviction 5299 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5300 * distributed between all sublists and uses this assumption when 5301 * deciding which sublist to evict from and how much to evict from it. 5302 */ 5303 unsigned int 5304 arc_state_multilist_index_func(multilist_t *ml, void *obj) 5305 { 5306 arc_buf_hdr_t *hdr = obj; 5307 5308 /* 5309 * We rely on b_dva to generate evenly distributed index 5310 * numbers using buf_hash below. So, as an added precaution, 5311 * let's make sure we never add empty buffers to the arc lists. 5312 */ 5313 ASSERT(!BUF_EMPTY(hdr)); 5314 5315 /* 5316 * The assumption here, is the hash value for a given 5317 * arc_buf_hdr_t will remain constant throughout it's lifetime 5318 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5319 * Thus, we don't need to store the header's sublist index 5320 * on insertion, as this index can be recalculated on removal. 5321 * 5322 * Also, the low order bits of the hash value are thought to be 5323 * distributed evenly. Otherwise, in the case that the multilist 5324 * has a power of two number of sublists, each sublists' usage 5325 * would not be evenly distributed. 5326 */ 5327 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5328 multilist_get_num_sublists(ml)); 5329 } 5330 5331 void 5332 arc_init(void) 5333 { 5334 /* 5335 * allmem is "all memory that we could possibly use". 5336 */ 5337 #ifdef _KERNEL 5338 uint64_t allmem = ptob(physmem - swapfs_minfree); 5339 #else 5340 uint64_t allmem = (physmem * PAGESIZE) / 2; 5341 #endif 5342 5343 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5344 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5345 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5346 5347 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5348 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5349 5350 /* Convert seconds to clock ticks */ 5351 arc_min_prefetch_lifespan = 1 * hz; 5352 5353 /* Start out with 1/8 of all memory */ 5354 arc_c = allmem / 8; 5355 5356 #ifdef _KERNEL 5357 /* 5358 * On architectures where the physical memory can be larger 5359 * than the addressable space (intel in 32-bit mode), we may 5360 * need to limit the cache to 1/8 of VM size. 5361 */ 5362 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5363 #endif 5364 5365 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 5366 arc_c_min = MAX(allmem / 32, 64 << 20); 5367 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 5368 if (allmem >= 1 << 30) 5369 arc_c_max = allmem - (1 << 30); 5370 else 5371 arc_c_max = arc_c_min; 5372 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 5373 5374 /* 5375 * In userland, there's only the memory pressure that we artificially 5376 * create (see arc_available_memory()). Don't let arc_c get too 5377 * small, because it can cause transactions to be larger than 5378 * arc_c, causing arc_tempreserve_space() to fail. 5379 */ 5380 #ifndef _KERNEL 5381 arc_c_min = arc_c_max / 2; 5382 #endif 5383 5384 /* 5385 * Allow the tunables to override our calculations if they are 5386 * reasonable (ie. over 64MB) 5387 */ 5388 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 5389 arc_c_max = zfs_arc_max; 5390 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 5391 arc_c_min = zfs_arc_min; 5392 5393 arc_c = arc_c_max; 5394 arc_p = (arc_c >> 1); 5395 5396 /* limit meta-data to 1/4 of the arc capacity */ 5397 arc_meta_limit = arc_c_max / 4; 5398 5399 /* Allow the tunable to override if it is reasonable */ 5400 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5401 arc_meta_limit = zfs_arc_meta_limit; 5402 5403 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5404 arc_c_min = arc_meta_limit / 2; 5405 5406 if (zfs_arc_meta_min > 0) { 5407 arc_meta_min = zfs_arc_meta_min; 5408 } else { 5409 arc_meta_min = arc_c_min / 2; 5410 } 5411 5412 if (zfs_arc_grow_retry > 0) 5413 arc_grow_retry = zfs_arc_grow_retry; 5414 5415 if (zfs_arc_shrink_shift > 0) 5416 arc_shrink_shift = zfs_arc_shrink_shift; 5417 5418 /* 5419 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5420 */ 5421 if (arc_no_grow_shift >= arc_shrink_shift) 5422 arc_no_grow_shift = arc_shrink_shift - 1; 5423 5424 if (zfs_arc_p_min_shift > 0) 5425 arc_p_min_shift = zfs_arc_p_min_shift; 5426 5427 if (zfs_arc_num_sublists_per_state < 1) 5428 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 5429 5430 /* if kmem_flags are set, lets try to use less memory */ 5431 if (kmem_debugging()) 5432 arc_c = arc_c / 2; 5433 if (arc_c < arc_c_min) 5434 arc_c = arc_c_min; 5435 5436 arc_anon = &ARC_anon; 5437 arc_mru = &ARC_mru; 5438 arc_mru_ghost = &ARC_mru_ghost; 5439 arc_mfu = &ARC_mfu; 5440 arc_mfu_ghost = &ARC_mfu_ghost; 5441 arc_l2c_only = &ARC_l2c_only; 5442 arc_size = 0; 5443 5444 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5445 sizeof (arc_buf_hdr_t), 5446 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5447 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5448 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5449 sizeof (arc_buf_hdr_t), 5450 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5451 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5452 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5453 sizeof (arc_buf_hdr_t), 5454 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5455 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5456 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5457 sizeof (arc_buf_hdr_t), 5458 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5459 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5460 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5461 sizeof (arc_buf_hdr_t), 5462 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5463 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5464 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5465 sizeof (arc_buf_hdr_t), 5466 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5467 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5468 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5469 sizeof (arc_buf_hdr_t), 5470 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5471 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5472 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5473 sizeof (arc_buf_hdr_t), 5474 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5475 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5476 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5477 sizeof (arc_buf_hdr_t), 5478 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5479 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5480 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5481 sizeof (arc_buf_hdr_t), 5482 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5483 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5484 5485 refcount_create(&arc_anon->arcs_size); 5486 refcount_create(&arc_mru->arcs_size); 5487 refcount_create(&arc_mru_ghost->arcs_size); 5488 refcount_create(&arc_mfu->arcs_size); 5489 refcount_create(&arc_mfu_ghost->arcs_size); 5490 refcount_create(&arc_l2c_only->arcs_size); 5491 5492 buf_init(); 5493 5494 arc_reclaim_thread_exit = FALSE; 5495 arc_user_evicts_thread_exit = FALSE; 5496 arc_eviction_list = NULL; 5497 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5498 5499 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5500 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5501 5502 if (arc_ksp != NULL) { 5503 arc_ksp->ks_data = &arc_stats; 5504 arc_ksp->ks_update = arc_kstat_update; 5505 kstat_install(arc_ksp); 5506 } 5507 5508 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5509 TS_RUN, minclsyspri); 5510 5511 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5512 TS_RUN, minclsyspri); 5513 5514 arc_dead = FALSE; 5515 arc_warm = B_FALSE; 5516 5517 /* 5518 * Calculate maximum amount of dirty data per pool. 5519 * 5520 * If it has been set by /etc/system, take that. 5521 * Otherwise, use a percentage of physical memory defined by 5522 * zfs_dirty_data_max_percent (default 10%) with a cap at 5523 * zfs_dirty_data_max_max (default 4GB). 5524 */ 5525 if (zfs_dirty_data_max == 0) { 5526 zfs_dirty_data_max = physmem * PAGESIZE * 5527 zfs_dirty_data_max_percent / 100; 5528 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5529 zfs_dirty_data_max_max); 5530 } 5531 } 5532 5533 void 5534 arc_fini(void) 5535 { 5536 mutex_enter(&arc_reclaim_lock); 5537 arc_reclaim_thread_exit = TRUE; 5538 /* 5539 * The reclaim thread will set arc_reclaim_thread_exit back to 5540 * FALSE when it is finished exiting; we're waiting for that. 5541 */ 5542 while (arc_reclaim_thread_exit) { 5543 cv_signal(&arc_reclaim_thread_cv); 5544 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5545 } 5546 mutex_exit(&arc_reclaim_lock); 5547 5548 mutex_enter(&arc_user_evicts_lock); 5549 arc_user_evicts_thread_exit = TRUE; 5550 /* 5551 * The user evicts thread will set arc_user_evicts_thread_exit 5552 * to FALSE when it is finished exiting; we're waiting for that. 5553 */ 5554 while (arc_user_evicts_thread_exit) { 5555 cv_signal(&arc_user_evicts_cv); 5556 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5557 } 5558 mutex_exit(&arc_user_evicts_lock); 5559 5560 /* Use TRUE to ensure *all* buffers are evicted */ 5561 arc_flush(NULL, TRUE); 5562 5563 arc_dead = TRUE; 5564 5565 if (arc_ksp != NULL) { 5566 kstat_delete(arc_ksp); 5567 arc_ksp = NULL; 5568 } 5569 5570 mutex_destroy(&arc_reclaim_lock); 5571 cv_destroy(&arc_reclaim_thread_cv); 5572 cv_destroy(&arc_reclaim_waiters_cv); 5573 5574 mutex_destroy(&arc_user_evicts_lock); 5575 cv_destroy(&arc_user_evicts_cv); 5576 5577 refcount_destroy(&arc_anon->arcs_size); 5578 refcount_destroy(&arc_mru->arcs_size); 5579 refcount_destroy(&arc_mru_ghost->arcs_size); 5580 refcount_destroy(&arc_mfu->arcs_size); 5581 refcount_destroy(&arc_mfu_ghost->arcs_size); 5582 refcount_destroy(&arc_l2c_only->arcs_size); 5583 5584 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5585 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5586 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5587 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5588 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); 5589 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5590 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5591 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5592 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5593 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]); 5594 5595 buf_fini(); 5596 5597 ASSERT0(arc_loaned_bytes); 5598 } 5599 5600 /* 5601 * Level 2 ARC 5602 * 5603 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5604 * It uses dedicated storage devices to hold cached data, which are populated 5605 * using large infrequent writes. The main role of this cache is to boost 5606 * the performance of random read workloads. The intended L2ARC devices 5607 * include short-stroked disks, solid state disks, and other media with 5608 * substantially faster read latency than disk. 5609 * 5610 * +-----------------------+ 5611 * | ARC | 5612 * +-----------------------+ 5613 * | ^ ^ 5614 * | | | 5615 * l2arc_feed_thread() arc_read() 5616 * | | | 5617 * | l2arc read | 5618 * V | | 5619 * +---------------+ | 5620 * | L2ARC | | 5621 * +---------------+ | 5622 * | ^ | 5623 * l2arc_write() | | 5624 * | | | 5625 * V | | 5626 * +-------+ +-------+ 5627 * | vdev | | vdev | 5628 * | cache | | cache | 5629 * +-------+ +-------+ 5630 * +=========+ .-----. 5631 * : L2ARC : |-_____-| 5632 * : devices : | Disks | 5633 * +=========+ `-_____-' 5634 * 5635 * Read requests are satisfied from the following sources, in order: 5636 * 5637 * 1) ARC 5638 * 2) vdev cache of L2ARC devices 5639 * 3) L2ARC devices 5640 * 4) vdev cache of disks 5641 * 5) disks 5642 * 5643 * Some L2ARC device types exhibit extremely slow write performance. 5644 * To accommodate for this there are some significant differences between 5645 * the L2ARC and traditional cache design: 5646 * 5647 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5648 * the ARC behave as usual, freeing buffers and placing headers on ghost 5649 * lists. The ARC does not send buffers to the L2ARC during eviction as 5650 * this would add inflated write latencies for all ARC memory pressure. 5651 * 5652 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5653 * It does this by periodically scanning buffers from the eviction-end of 5654 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5655 * not already there. It scans until a headroom of buffers is satisfied, 5656 * which itself is a buffer for ARC eviction. If a compressible buffer is 5657 * found during scanning and selected for writing to an L2ARC device, we 5658 * temporarily boost scanning headroom during the next scan cycle to make 5659 * sure we adapt to compression effects (which might significantly reduce 5660 * the data volume we write to L2ARC). The thread that does this is 5661 * l2arc_feed_thread(), illustrated below; example sizes are included to 5662 * provide a better sense of ratio than this diagram: 5663 * 5664 * head --> tail 5665 * +---------------------+----------+ 5666 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5667 * +---------------------+----------+ | o L2ARC eligible 5668 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5669 * +---------------------+----------+ | 5670 * 15.9 Gbytes ^ 32 Mbytes | 5671 * headroom | 5672 * l2arc_feed_thread() 5673 * | 5674 * l2arc write hand <--[oooo]--' 5675 * | 8 Mbyte 5676 * | write max 5677 * V 5678 * +==============================+ 5679 * L2ARC dev |####|#|###|###| |####| ... | 5680 * +==============================+ 5681 * 32 Gbytes 5682 * 5683 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5684 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5685 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5686 * safe to say that this is an uncommon case, since buffers at the end of 5687 * the ARC lists have moved there due to inactivity. 5688 * 5689 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5690 * then the L2ARC simply misses copying some buffers. This serves as a 5691 * pressure valve to prevent heavy read workloads from both stalling the ARC 5692 * with waits and clogging the L2ARC with writes. This also helps prevent 5693 * the potential for the L2ARC to churn if it attempts to cache content too 5694 * quickly, such as during backups of the entire pool. 5695 * 5696 * 5. After system boot and before the ARC has filled main memory, there are 5697 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5698 * lists can remain mostly static. Instead of searching from tail of these 5699 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5700 * for eligible buffers, greatly increasing its chance of finding them. 5701 * 5702 * The L2ARC device write speed is also boosted during this time so that 5703 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5704 * there are no L2ARC reads, and no fear of degrading read performance 5705 * through increased writes. 5706 * 5707 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5708 * the vdev queue can aggregate them into larger and fewer writes. Each 5709 * device is written to in a rotor fashion, sweeping writes through 5710 * available space then repeating. 5711 * 5712 * 7. The L2ARC does not store dirty content. It never needs to flush 5713 * write buffers back to disk based storage. 5714 * 5715 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5716 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5717 * 5718 * The performance of the L2ARC can be tweaked by a number of tunables, which 5719 * may be necessary for different workloads: 5720 * 5721 * l2arc_write_max max write bytes per interval 5722 * l2arc_write_boost extra write bytes during device warmup 5723 * l2arc_noprefetch skip caching prefetched buffers 5724 * l2arc_headroom number of max device writes to precache 5725 * l2arc_headroom_boost when we find compressed buffers during ARC 5726 * scanning, we multiply headroom by this 5727 * percentage factor for the next scan cycle, 5728 * since more compressed buffers are likely to 5729 * be present 5730 * l2arc_feed_secs seconds between L2ARC writing 5731 * 5732 * Tunables may be removed or added as future performance improvements are 5733 * integrated, and also may become zpool properties. 5734 * 5735 * There are three key functions that control how the L2ARC warms up: 5736 * 5737 * l2arc_write_eligible() check if a buffer is eligible to cache 5738 * l2arc_write_size() calculate how much to write 5739 * l2arc_write_interval() calculate sleep delay between writes 5740 * 5741 * These three functions determine what to write, how much, and how quickly 5742 * to send writes. 5743 * 5744 * L2ARC persistency: 5745 * 5746 * When writing buffers to L2ARC, we periodically add some metadata to 5747 * make sure we can pick them up after reboot, thus dramatically reducing 5748 * the impact that any downtime has on the performance of storage systems 5749 * with large caches. 5750 * 5751 * The implementation works fairly simply by integrating the following two 5752 * modifications: 5753 * 5754 * *) Every now and then we mix in a piece of metadata (called a log block) 5755 * into the L2ARC write. This allows us to understand what's been written, 5756 * so that we can rebuild the arc_buf_hdr_t structures of the main ARC 5757 * buffers. The log block also includes a "2-back-reference" pointer to 5758 * he second-to-previous block, forming a back-linked list of blocks on 5759 * the L2ARC device. 5760 * 5761 * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device 5762 * for our header bookkeeping purposes. This contains a device header, 5763 * which contains our top-level reference structures. We update it each 5764 * time we write a new log block, so that we're able to locate it in the 5765 * L2ARC device. If this write results in an inconsistent device header 5766 * (e.g. due to power failure), we detect this by verifying the header's 5767 * checksum and simply drop the entries from L2ARC. 5768 * 5769 * Implementation diagram: 5770 * 5771 * +=== L2ARC device (not to scale) ======================================+ 5772 * | ___two newest log block pointers__.__________ | 5773 * | / \1 back \latest | 5774 * |.____/_. V V | 5775 * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---| 5776 * || hdr| ^ /^ /^ / / | 5777 * |+------+ ...--\-------/ \-----/--\------/ / | 5778 * | \--------------/ \--------------/ | 5779 * +======================================================================+ 5780 * 5781 * As can be seen on the diagram, rather than using a simple linked list, 5782 * we use a pair of linked lists with alternating elements. This is a 5783 * performance enhancement due to the fact that we only find out of the 5784 * address of the next log block access once the current block has been 5785 * completely read in. Obviously, this hurts performance, because we'd be 5786 * keeping the device's I/O queue at only a 1 operation deep, thus 5787 * incurring a large amount of I/O round-trip latency. Having two lists 5788 * allows us to "prefetch" two log blocks ahead of where we are currently 5789 * rebuilding L2ARC buffers. 5790 * 5791 * On-device data structures: 5792 * 5793 * L2ARC device header: l2arc_dev_hdr_phys_t 5794 * L2ARC log block: l2arc_log_blk_phys_t 5795 * 5796 * L2ARC reconstruction: 5797 * 5798 * When writing data, we simply write in the standard rotary fashion, 5799 * evicting buffers as we go and simply writing new data over them (writing 5800 * a new log block every now and then). This obviously means that once we 5801 * loop around the end of the device, we will start cutting into an already 5802 * committed log block (and its referenced data buffers), like so: 5803 * 5804 * current write head__ __old tail 5805 * \ / 5806 * V V 5807 * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |--> 5808 * ^ ^^^^^^^^^___________________________________ 5809 * | \ 5810 * <<nextwrite>> may overwrite this blk and/or its bufs --' 5811 * 5812 * When importing the pool, we detect this situation and use it to stop 5813 * our scanning process (see l2arc_rebuild). 5814 * 5815 * There is one significant caveat to consider when rebuilding ARC contents 5816 * from an L2ARC device: what about invalidated buffers? Given the above 5817 * construction, we cannot update blocks which we've already written to amend 5818 * them to remove buffers which were invalidated. Thus, during reconstruction, 5819 * we might be populating the cache with buffers for data that's not on the 5820 * main pool anymore, or may have been overwritten! 5821 * 5822 * As it turns out, this isn't a problem. Every arc_read request includes 5823 * both the DVA and, crucially, the birth TXG of the BP the caller is 5824 * looking for. So even if the cache were populated by completely rotten 5825 * blocks for data that had been long deleted and/or overwritten, we'll 5826 * never actually return bad data from the cache, since the DVA with the 5827 * birth TXG uniquely identify a block in space and time - once created, 5828 * a block is immutable on disk. The worst thing we have done is wasted 5829 * some time and memory at l2arc rebuild to reconstruct outdated ARC 5830 * entries that will get dropped from the l2arc as it is being updated 5831 * with new blocks. 5832 */ 5833 5834 static boolean_t 5835 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5836 { 5837 /* 5838 * A buffer is *not* eligible for the L2ARC if it: 5839 * 1. belongs to a different spa. 5840 * 2. is already cached on the L2ARC. 5841 * 3. has an I/O in progress (it may be an incomplete read). 5842 * 4. is flagged not eligible (zfs property). 5843 */ 5844 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5845 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 5846 return (B_FALSE); 5847 5848 return (B_TRUE); 5849 } 5850 5851 static uint64_t 5852 l2arc_write_size(void) 5853 { 5854 uint64_t size; 5855 5856 /* 5857 * Make sure our globals have meaningful values in case the user 5858 * altered them. 5859 */ 5860 size = l2arc_write_max; 5861 if (size == 0) { 5862 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5863 "be greater than zero, resetting it to the default (%d)", 5864 L2ARC_WRITE_SIZE); 5865 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5866 } 5867 5868 if (arc_warm == B_FALSE) 5869 size += l2arc_write_boost; 5870 5871 return (size); 5872 5873 } 5874 5875 static clock_t 5876 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5877 { 5878 clock_t interval, next, now; 5879 5880 /* 5881 * If the ARC lists are busy, increase our write rate; if the 5882 * lists are stale, idle back. This is achieved by checking 5883 * how much we previously wrote - if it was more than half of 5884 * what we wanted, schedule the next write much sooner. 5885 */ 5886 if (l2arc_feed_again && wrote > (wanted / 2)) 5887 interval = (hz * l2arc_feed_min_ms) / 1000; 5888 else 5889 interval = hz * l2arc_feed_secs; 5890 5891 now = ddi_get_lbolt(); 5892 next = MAX(now, MIN(now + interval, began + interval)); 5893 5894 return (next); 5895 } 5896 5897 /* 5898 * Cycle through L2ARC devices. This is how L2ARC load balances. 5899 * If a device is returned, this also returns holding the spa config lock. 5900 */ 5901 static l2arc_dev_t * 5902 l2arc_dev_get_next(void) 5903 { 5904 l2arc_dev_t *first, *next = NULL; 5905 5906 /* 5907 * Lock out the removal of spas (spa_namespace_lock), then removal 5908 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5909 * both locks will be dropped and a spa config lock held instead. 5910 */ 5911 mutex_enter(&spa_namespace_lock); 5912 mutex_enter(&l2arc_dev_mtx); 5913 5914 /* if there are no vdevs, there is nothing to do */ 5915 if (l2arc_ndev == 0) 5916 goto out; 5917 5918 first = NULL; 5919 next = l2arc_dev_last; 5920 do { 5921 /* loop around the list looking for a non-faulted vdev */ 5922 if (next == NULL) { 5923 next = list_head(l2arc_dev_list); 5924 } else { 5925 next = list_next(l2arc_dev_list, next); 5926 if (next == NULL) 5927 next = list_head(l2arc_dev_list); 5928 } 5929 5930 /* if we have come back to the start, bail out */ 5931 if (first == NULL) 5932 first = next; 5933 else if (next == first) 5934 break; 5935 5936 } while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild); 5937 5938 /* if we were unable to find any usable vdevs, return NULL */ 5939 if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild) 5940 next = NULL; 5941 5942 l2arc_dev_last = next; 5943 5944 out: 5945 mutex_exit(&l2arc_dev_mtx); 5946 5947 /* 5948 * Grab the config lock to prevent the 'next' device from being 5949 * removed while we are writing to it. 5950 */ 5951 if (next != NULL) 5952 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5953 mutex_exit(&spa_namespace_lock); 5954 5955 return (next); 5956 } 5957 5958 /* 5959 * Free buffers that were tagged for destruction. 5960 */ 5961 static void 5962 l2arc_do_free_on_write() 5963 { 5964 list_t *buflist; 5965 l2arc_data_free_t *df, *df_prev; 5966 5967 mutex_enter(&l2arc_free_on_write_mtx); 5968 buflist = l2arc_free_on_write; 5969 5970 for (df = list_tail(buflist); df; df = df_prev) { 5971 df_prev = list_prev(buflist, df); 5972 ASSERT(df->l2df_data != NULL); 5973 ASSERT(df->l2df_func != NULL); 5974 df->l2df_func(df->l2df_data, df->l2df_size); 5975 list_remove(buflist, df); 5976 kmem_free(df, sizeof (l2arc_data_free_t)); 5977 } 5978 5979 mutex_exit(&l2arc_free_on_write_mtx); 5980 } 5981 5982 /* 5983 * A write to a cache device has completed. Update all headers to allow 5984 * reads from these buffers to begin. 5985 */ 5986 static void 5987 l2arc_write_done(zio_t *zio) 5988 { 5989 l2arc_write_callback_t *cb; 5990 l2arc_dev_t *dev; 5991 list_t *buflist; 5992 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5993 kmutex_t *hash_lock; 5994 int64_t bytes_dropped = 0; 5995 l2arc_log_blk_buf_t *lb_buf; 5996 5997 cb = zio->io_private; 5998 ASSERT(cb != NULL); 5999 dev = cb->l2wcb_dev; 6000 ASSERT(dev != NULL); 6001 head = cb->l2wcb_head; 6002 ASSERT(head != NULL); 6003 buflist = &dev->l2ad_buflist; 6004 ASSERT(buflist != NULL); 6005 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6006 l2arc_write_callback_t *, cb); 6007 6008 if (zio->io_error != 0) 6009 ARCSTAT_BUMP(arcstat_l2_writes_error); 6010 6011 /* 6012 * All writes completed, or an error was hit. 6013 */ 6014 top: 6015 mutex_enter(&dev->l2ad_mtx); 6016 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 6017 hdr_prev = list_prev(buflist, hdr); 6018 6019 hash_lock = HDR_LOCK(hdr); 6020 6021 /* 6022 * We cannot use mutex_enter or else we can deadlock 6023 * with l2arc_write_buffers (due to swapping the order 6024 * the hash lock and l2ad_mtx are taken). 6025 */ 6026 if (!mutex_tryenter(hash_lock)) { 6027 /* 6028 * Missed the hash lock. We must retry so we 6029 * don't leave the ARC_FLAG_L2_WRITING bit set. 6030 */ 6031 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 6032 6033 /* 6034 * We don't want to rescan the headers we've 6035 * already marked as having been written out, so 6036 * we reinsert the head node so we can pick up 6037 * where we left off. 6038 */ 6039 list_remove(buflist, head); 6040 list_insert_after(buflist, hdr, head); 6041 6042 mutex_exit(&dev->l2ad_mtx); 6043 6044 /* 6045 * We wait for the hash lock to become available 6046 * to try and prevent busy waiting, and increase 6047 * the chance we'll be able to acquire the lock 6048 * the next time around. 6049 */ 6050 mutex_enter(hash_lock); 6051 mutex_exit(hash_lock); 6052 goto top; 6053 } 6054 6055 /* 6056 * We could not have been moved into the arc_l2c_only 6057 * state while in-flight due to our ARC_FLAG_L2_WRITING 6058 * bit being set. Let's just ensure that's being enforced. 6059 */ 6060 ASSERT(HDR_HAS_L1HDR(hdr)); 6061 6062 /* 6063 * We may have allocated a buffer for L2ARC compression, 6064 * we must release it to avoid leaking this data. 6065 */ 6066 l2arc_release_cdata_buf(hdr); 6067 6068 if (zio->io_error != 0) { 6069 /* 6070 * Error - drop L2ARC entry. 6071 */ 6072 list_remove(buflist, hdr); 6073 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 6074 6075 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 6076 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 6077 6078 bytes_dropped += hdr->b_l2hdr.b_asize; 6079 (void) refcount_remove_many(&dev->l2ad_alloc, 6080 hdr->b_l2hdr.b_asize, hdr); 6081 } 6082 6083 /* 6084 * Allow ARC to begin reads and ghost list evictions to 6085 * this L2ARC entry. 6086 */ 6087 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 6088 6089 mutex_exit(hash_lock); 6090 } 6091 6092 atomic_inc_64(&l2arc_writes_done); 6093 list_remove(buflist, head); 6094 ASSERT(!HDR_HAS_L1HDR(head)); 6095 kmem_cache_free(hdr_l2only_cache, head); 6096 mutex_exit(&dev->l2ad_mtx); 6097 6098 ASSERT(dev->l2ad_vdev != NULL); 6099 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6100 6101 l2arc_do_free_on_write(); 6102 6103 while ((lb_buf = list_remove_tail(&cb->l2wcb_log_blk_buflist)) != NULL) 6104 kmem_free(lb_buf, sizeof (*lb_buf)); 6105 list_destroy(&cb->l2wcb_log_blk_buflist); 6106 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6107 } 6108 6109 /* 6110 * A read to a cache device completed. Validate buffer contents before 6111 * handing over to the regular ARC routines. 6112 */ 6113 static void 6114 l2arc_read_done(zio_t *zio) 6115 { 6116 l2arc_read_callback_t *cb; 6117 arc_buf_hdr_t *hdr; 6118 arc_buf_t *buf; 6119 kmutex_t *hash_lock; 6120 int equal; 6121 6122 ASSERT(zio->io_vd != NULL); 6123 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6124 6125 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6126 6127 cb = zio->io_private; 6128 ASSERT(cb != NULL); 6129 buf = cb->l2rcb_buf; 6130 ASSERT(buf != NULL); 6131 6132 hash_lock = HDR_LOCK(buf->b_hdr); 6133 mutex_enter(hash_lock); 6134 hdr = buf->b_hdr; 6135 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6136 6137 /* 6138 * If the buffer was compressed, decompress it first. 6139 */ 6140 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6141 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6142 ASSERT(zio->io_data != NULL); 6143 ASSERT3U(zio->io_size, ==, hdr->b_size); 6144 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 6145 6146 /* 6147 * Check this survived the L2ARC journey. 6148 */ 6149 equal = arc_cksum_equal(buf); 6150 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6151 mutex_exit(hash_lock); 6152 zio->io_private = buf; 6153 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6154 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6155 arc_read_done(zio); 6156 } else { 6157 mutex_exit(hash_lock); 6158 /* 6159 * Buffer didn't survive caching. Increment stats and 6160 * reissue to the original storage device. 6161 */ 6162 if (zio->io_error != 0) { 6163 ARCSTAT_BUMP(arcstat_l2_io_error); 6164 } else { 6165 zio->io_error = SET_ERROR(EIO); 6166 } 6167 if (!equal) 6168 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6169 6170 /* 6171 * If there's no waiter, issue an async i/o to the primary 6172 * storage now. If there *is* a waiter, the caller must 6173 * issue the i/o in a context where it's OK to block. 6174 */ 6175 if (zio->io_waiter == NULL) { 6176 zio_t *pio = zio_unique_parent(zio); 6177 6178 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6179 6180 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6181 buf->b_data, hdr->b_size, arc_read_done, buf, 6182 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6183 } 6184 } 6185 6186 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6187 } 6188 6189 /* 6190 * This is the list priority from which the L2ARC will search for pages to 6191 * cache. This is used within loops (0..3) to cycle through lists in the 6192 * desired order. This order can have a significant effect on cache 6193 * performance. 6194 * 6195 * Currently the metadata lists are hit first, MFU then MRU, followed by 6196 * the data lists. This function returns a locked list, and also returns 6197 * the lock pointer. 6198 */ 6199 static multilist_sublist_t * 6200 l2arc_sublist_lock(int list_num) 6201 { 6202 multilist_t *ml = NULL; 6203 unsigned int idx; 6204 6205 ASSERT(list_num >= 0 && list_num <= 3); 6206 6207 switch (list_num) { 6208 case 0: 6209 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6210 break; 6211 case 1: 6212 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6213 break; 6214 case 2: 6215 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6216 break; 6217 case 3: 6218 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6219 break; 6220 } 6221 6222 /* 6223 * Return a randomly-selected sublist. This is acceptable 6224 * because the caller feeds only a little bit of data for each 6225 * call (8MB). Subsequent calls will result in different 6226 * sublists being selected. 6227 */ 6228 idx = multilist_get_random_index(ml); 6229 return (multilist_sublist_lock(ml, idx)); 6230 } 6231 6232 /* 6233 * Calculates the maximum overhead of L2ARC metadata log blocks for a given 6234 * L2ARC write size. l2arc_evict and l2arc_write_buffers need to include this 6235 * overhead in processing to make sure there is enough headroom available 6236 * when writing buffers. 6237 */ 6238 static inline uint64_t 6239 l2arc_log_blk_overhead(uint64_t write_sz) 6240 { 6241 return ((write_sz / SPA_MINBLOCKSIZE / L2ARC_LOG_BLK_ENTRIES) + 1) * 6242 L2ARC_LOG_BLK_SIZE; 6243 } 6244 6245 /* 6246 * Evict buffers from the device write hand to the distance specified in 6247 * bytes. This distance may span populated buffers, it may span nothing. 6248 * This is clearing a region on the L2ARC device ready for writing. 6249 * If the 'all' boolean is set, every buffer is evicted. 6250 */ 6251 static void 6252 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6253 { 6254 list_t *buflist; 6255 arc_buf_hdr_t *hdr, *hdr_prev; 6256 kmutex_t *hash_lock; 6257 uint64_t taddr; 6258 6259 buflist = &dev->l2ad_buflist; 6260 6261 if (!all && dev->l2ad_first) { 6262 /* 6263 * This is the first sweep through the device. There is 6264 * nothing to evict. 6265 */ 6266 return; 6267 } 6268 6269 /* 6270 * We need to add in the worst case scenario of log block overhead. 6271 */ 6272 distance += l2arc_log_blk_overhead(distance); 6273 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6274 /* 6275 * When nearing the end of the device, evict to the end 6276 * before the device write hand jumps to the start. 6277 */ 6278 taddr = dev->l2ad_end; 6279 } else { 6280 taddr = dev->l2ad_hand + distance; 6281 } 6282 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6283 uint64_t, taddr, boolean_t, all); 6284 6285 top: 6286 mutex_enter(&dev->l2ad_mtx); 6287 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6288 hdr_prev = list_prev(buflist, hdr); 6289 6290 hash_lock = HDR_LOCK(hdr); 6291 6292 /* 6293 * We cannot use mutex_enter or else we can deadlock 6294 * with l2arc_write_buffers (due to swapping the order 6295 * the hash lock and l2ad_mtx are taken). 6296 */ 6297 if (!mutex_tryenter(hash_lock)) { 6298 /* 6299 * Missed the hash lock. Retry. 6300 */ 6301 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6302 mutex_exit(&dev->l2ad_mtx); 6303 mutex_enter(hash_lock); 6304 mutex_exit(hash_lock); 6305 goto top; 6306 } 6307 6308 if (HDR_L2_WRITE_HEAD(hdr)) { 6309 /* 6310 * We hit a write head node. Leave it for 6311 * l2arc_write_done(). 6312 */ 6313 list_remove(buflist, hdr); 6314 mutex_exit(hash_lock); 6315 continue; 6316 } 6317 6318 if (!all && HDR_HAS_L2HDR(hdr) && 6319 (hdr->b_l2hdr.b_daddr > taddr || 6320 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6321 /* 6322 * We've evicted to the target address, 6323 * or the end of the device. 6324 */ 6325 mutex_exit(hash_lock); 6326 break; 6327 } 6328 6329 ASSERT(HDR_HAS_L2HDR(hdr)); 6330 if (!HDR_HAS_L1HDR(hdr)) { 6331 ASSERT(!HDR_L2_READING(hdr)); 6332 /* 6333 * This doesn't exist in the ARC. Destroy. 6334 * arc_hdr_destroy() will call list_remove() 6335 * and decrement arcstat_l2_size. 6336 */ 6337 arc_change_state(arc_anon, hdr, hash_lock); 6338 arc_hdr_destroy(hdr); 6339 } else { 6340 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6341 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6342 /* 6343 * Invalidate issued or about to be issued 6344 * reads, since we may be about to write 6345 * over this location. 6346 */ 6347 if (HDR_L2_READING(hdr)) { 6348 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6349 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6350 } 6351 6352 /* Ensure this header has finished being written */ 6353 ASSERT(!HDR_L2_WRITING(hdr)); 6354 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6355 6356 arc_hdr_l2hdr_destroy(hdr); 6357 } 6358 mutex_exit(hash_lock); 6359 } 6360 mutex_exit(&dev->l2ad_mtx); 6361 } 6362 6363 /* 6364 * Find and write ARC buffers to the L2ARC device. 6365 * 6366 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6367 * for reading until they have completed writing. 6368 * The headroom_boost is an in-out parameter used to maintain headroom boost 6369 * state between calls to this function. 6370 * 6371 * Returns the number of bytes actually written (which may be smaller than 6372 * the delta by which the device hand has changed due to alignment). 6373 */ 6374 static uint64_t 6375 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6376 boolean_t *headroom_boost) 6377 { 6378 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6379 uint64_t write_asize, write_sz, headroom, 6380 buf_compress_minsz; 6381 void *buf_data; 6382 boolean_t full; 6383 l2arc_write_callback_t *cb; 6384 zio_t *pio, *wzio; 6385 uint64_t guid = spa_load_guid(spa); 6386 const boolean_t do_headroom_boost = *headroom_boost; 6387 boolean_t dev_hdr_update = B_FALSE; 6388 6389 ASSERT(dev->l2ad_vdev != NULL); 6390 6391 /* Lower the flag now, we might want to raise it again later. */ 6392 *headroom_boost = B_FALSE; 6393 6394 pio = NULL; 6395 cb = NULL; 6396 write_sz = write_asize = 0; 6397 full = B_FALSE; 6398 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6399 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6400 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6401 6402 /* 6403 * We will want to try to compress buffers that are at least 2x the 6404 * device sector size. 6405 */ 6406 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6407 6408 /* 6409 * Copy buffers for L2ARC writing. 6410 */ 6411 for (int try = 0; try <= 3; try++) { 6412 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6413 uint64_t passed_sz = 0; 6414 6415 /* 6416 * L2ARC fast warmup. 6417 * 6418 * Until the ARC is warm and starts to evict, read from the 6419 * head of the ARC lists rather than the tail. 6420 */ 6421 if (arc_warm == B_FALSE) 6422 hdr = multilist_sublist_head(mls); 6423 else 6424 hdr = multilist_sublist_tail(mls); 6425 6426 headroom = target_sz * l2arc_headroom; 6427 if (do_headroom_boost) 6428 headroom = (headroom * l2arc_headroom_boost) / 100; 6429 6430 for (; hdr; hdr = hdr_prev) { 6431 kmutex_t *hash_lock; 6432 uint64_t buf_sz; 6433 uint64_t buf_a_sz; 6434 6435 if (arc_warm == B_FALSE) 6436 hdr_prev = multilist_sublist_next(mls, hdr); 6437 else 6438 hdr_prev = multilist_sublist_prev(mls, hdr); 6439 6440 hash_lock = HDR_LOCK(hdr); 6441 if (!mutex_tryenter(hash_lock)) { 6442 /* 6443 * Skip this buffer rather than waiting. 6444 */ 6445 continue; 6446 } 6447 6448 passed_sz += hdr->b_size; 6449 if (passed_sz > headroom) { 6450 /* 6451 * Searched too far. 6452 */ 6453 mutex_exit(hash_lock); 6454 break; 6455 } 6456 6457 if (!l2arc_write_eligible(guid, hdr)) { 6458 mutex_exit(hash_lock); 6459 continue; 6460 } 6461 6462 /* 6463 * Assume that the buffer is not going to be compressed 6464 * and could take more space on disk because of a larger 6465 * disk block size. 6466 */ 6467 buf_sz = hdr->b_size; 6468 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6469 6470 if ((write_asize + buf_a_sz) > target_sz) { 6471 full = B_TRUE; 6472 mutex_exit(hash_lock); 6473 break; 6474 } 6475 6476 if (pio == NULL) { 6477 /* 6478 * Insert a dummy header on the buflist so 6479 * l2arc_write_done() can find where the 6480 * write buffers begin without searching. 6481 */ 6482 mutex_enter(&dev->l2ad_mtx); 6483 list_insert_head(&dev->l2ad_buflist, head); 6484 mutex_exit(&dev->l2ad_mtx); 6485 6486 cb = kmem_zalloc( 6487 sizeof (l2arc_write_callback_t), KM_SLEEP); 6488 cb->l2wcb_dev = dev; 6489 cb->l2wcb_head = head; 6490 list_create(&cb->l2wcb_log_blk_buflist, 6491 sizeof (l2arc_log_blk_buf_t), 6492 offsetof(l2arc_log_blk_buf_t, lbb_node)); 6493 pio = zio_root(spa, l2arc_write_done, cb, 6494 ZIO_FLAG_CANFAIL); 6495 } 6496 6497 /* 6498 * Create and add a new L2ARC header. 6499 */ 6500 hdr->b_l2hdr.b_dev = dev; 6501 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6502 /* 6503 * Temporarily stash the data buffer in b_tmp_cdata. 6504 * The subsequent write step will pick it up from 6505 * there. This is because can't access b_l1hdr.b_buf 6506 * without holding the hash_lock, which we in turn 6507 * can't access without holding the ARC list locks 6508 * (which we want to avoid during compression/writing). 6509 */ 6510 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6511 hdr->b_l2hdr.b_asize = hdr->b_size; 6512 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6513 6514 /* 6515 * Explicitly set the b_daddr field to a known 6516 * value which means "invalid address". This 6517 * enables us to differentiate which stage of 6518 * l2arc_write_buffers() the particular header 6519 * is in (e.g. this loop, or the one below). 6520 * ARC_FLAG_L2_WRITING is not enough to make 6521 * this distinction, and we need to know in 6522 * order to do proper l2arc vdev accounting in 6523 * arc_release() and arc_hdr_destroy(). 6524 * 6525 * Note, we can't use a new flag to distinguish 6526 * the two stages because we don't hold the 6527 * header's hash_lock below, in the second stage 6528 * of this function. Thus, we can't simply 6529 * change the b_flags field to denote that the 6530 * IO has been sent. We can change the b_daddr 6531 * field of the L2 portion, though, since we'll 6532 * be holding the l2ad_mtx; which is why we're 6533 * using it to denote the header's state change. 6534 */ 6535 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6536 6537 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6538 6539 mutex_enter(&dev->l2ad_mtx); 6540 list_insert_head(&dev->l2ad_buflist, hdr); 6541 mutex_exit(&dev->l2ad_mtx); 6542 6543 /* 6544 * Compute and store the buffer cksum before 6545 * writing. On debug the cksum is verified first. 6546 */ 6547 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6548 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6549 6550 mutex_exit(hash_lock); 6551 6552 write_sz += buf_sz; 6553 write_asize += buf_a_sz; 6554 } 6555 6556 multilist_sublist_unlock(mls); 6557 6558 if (full == B_TRUE) 6559 break; 6560 } 6561 6562 /* No buffers selected for writing? */ 6563 if (pio == NULL) { 6564 ASSERT0(write_sz); 6565 ASSERT(!HDR_HAS_L1HDR(head)); 6566 kmem_cache_free(hdr_l2only_cache, head); 6567 return (0); 6568 } 6569 6570 mutex_enter(&dev->l2ad_mtx); 6571 6572 /* 6573 * Note that elsewhere in this file arcstat_l2_asize 6574 * and the used space on l2ad_vdev are updated using b_asize, 6575 * which is not necessarily rounded up to the device block size. 6576 * Too keep accounting consistent we do the same here as well: 6577 * stats_size accumulates the sum of b_asize of the written buffers, 6578 * while write_asize accumulates the sum of b_asize rounded up 6579 * to the device block size. 6580 * The latter sum is used only to validate the corectness of the code. 6581 */ 6582 uint64_t stats_size = 0; 6583 write_asize = 0; 6584 6585 /* 6586 * Now start writing the buffers. We're starting at the write head 6587 * and work backwards, retracing the course of the buffer selector 6588 * loop above. 6589 */ 6590 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6591 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6592 uint64_t buf_sz; 6593 6594 /* 6595 * We rely on the L1 portion of the header below, so 6596 * it's invalid for this header to have been evicted out 6597 * of the ghost cache, prior to being written out. The 6598 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6599 */ 6600 ASSERT(HDR_HAS_L1HDR(hdr)); 6601 6602 /* 6603 * We shouldn't need to lock the buffer here, since we flagged 6604 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6605 * take care to only access its L2 cache parameters. In 6606 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6607 * ARC eviction. 6608 */ 6609 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6610 6611 if ((HDR_L2COMPRESS(hdr)) && 6612 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 6613 if (l2arc_compress_buf(hdr)) { 6614 /* 6615 * If compression succeeded, enable headroom 6616 * boost on the next scan cycle. 6617 */ 6618 *headroom_boost = B_TRUE; 6619 } 6620 } 6621 6622 /* 6623 * Pick up the buffer data we had previously stashed away 6624 * (and now potentially also compressed). 6625 */ 6626 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6627 buf_sz = hdr->b_l2hdr.b_asize; 6628 6629 /* 6630 * We need to do this regardless if buf_sz is zero or 6631 * not, otherwise, when this l2hdr is evicted we'll 6632 * remove a reference that was never added. 6633 */ 6634 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6635 6636 /* Compression may have squashed the buffer to zero length. */ 6637 if (buf_sz != 0) { 6638 uint64_t buf_a_sz; 6639 6640 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6641 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6642 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6643 ZIO_FLAG_CANFAIL, B_FALSE); 6644 6645 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6646 zio_t *, wzio); 6647 (void) zio_nowait(wzio); 6648 6649 stats_size += buf_sz; 6650 6651 /* 6652 * Keep the clock hand suitably device-aligned. 6653 */ 6654 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6655 write_asize += buf_a_sz; 6656 dev->l2ad_hand += buf_a_sz; 6657 } 6658 6659 /* 6660 * Append buf info to current log and commit if full. 6661 * arcstat_l2_{size,asize} kstats are updated internally. 6662 */ 6663 if (l2arc_log_blk_insert(dev, hdr)) { 6664 l2arc_log_blk_commit(dev, pio, cb); 6665 dev_hdr_update = B_TRUE; 6666 } 6667 } 6668 6669 mutex_exit(&dev->l2ad_mtx); 6670 6671 /* 6672 * If we wrote any logs as part of this write, update dev hdr 6673 * to point to it. 6674 */ 6675 if (dev_hdr_update) 6676 l2arc_dev_hdr_update(dev, pio); 6677 6678 VERIFY3U(write_asize, <=, target_sz); 6679 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6680 ARCSTAT_INCR(arcstat_l2_write_bytes, stats_size); 6681 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6682 ARCSTAT_INCR(arcstat_l2_asize, stats_size); 6683 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6684 6685 /* 6686 * Bump device hand to the device start if it is approaching the end. 6687 * l2arc_evict() will already have evicted ahead for this case. 6688 */ 6689 if (dev->l2ad_hand + target_sz + l2arc_log_blk_overhead(target_sz) >= 6690 dev->l2ad_end) { 6691 dev->l2ad_hand = dev->l2ad_start; 6692 dev->l2ad_first = B_FALSE; 6693 } 6694 6695 dev->l2ad_writing = B_TRUE; 6696 (void) zio_wait(pio); 6697 dev->l2ad_writing = B_FALSE; 6698 6699 return (stats_size); 6700 } 6701 6702 /* 6703 * Compresses an L2ARC buffer. 6704 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6705 * size in l2hdr->b_asize. This routine tries to compress the data and 6706 * depending on the compression result there are three possible outcomes: 6707 * *) The buffer was incompressible. The original l2hdr contents were left 6708 * untouched and are ready for writing to an L2 device. 6709 * *) The buffer was all-zeros, so there is no need to write it to an L2 6710 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6711 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6712 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6713 * data buffer which holds the compressed data to be written, and b_asize 6714 * tells us how much data there is. b_compress is set to the appropriate 6715 * compression algorithm. Once writing is done, invoke 6716 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6717 * 6718 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6719 * buffer was incompressible). 6720 */ 6721 static boolean_t 6722 l2arc_compress_buf(arc_buf_hdr_t *hdr) 6723 { 6724 void *cdata; 6725 size_t csize, len, rounded; 6726 ASSERT(HDR_HAS_L2HDR(hdr)); 6727 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6728 6729 ASSERT(HDR_HAS_L1HDR(hdr)); 6730 ASSERT3S(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF); 6731 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6732 6733 len = l2hdr->b_asize; 6734 cdata = zio_data_buf_alloc(len); 6735 ASSERT3P(cdata, !=, NULL); 6736 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6737 cdata, l2hdr->b_asize); 6738 6739 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 6740 if (rounded > csize) { 6741 bzero((char *)cdata + csize, rounded - csize); 6742 csize = rounded; 6743 } 6744 6745 if (csize == 0) { 6746 /* zero block, indicate that there's nothing to write */ 6747 zio_data_buf_free(cdata, len); 6748 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6749 l2hdr->b_asize = 0; 6750 hdr->b_l1hdr.b_tmp_cdata = NULL; 6751 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6752 return (B_TRUE); 6753 } else if (csize > 0 && csize < len) { 6754 /* 6755 * Compression succeeded, we'll keep the cdata around for 6756 * writing and release it afterwards. 6757 */ 6758 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6759 l2hdr->b_asize = csize; 6760 hdr->b_l1hdr.b_tmp_cdata = cdata; 6761 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6762 return (B_TRUE); 6763 } else { 6764 /* 6765 * Compression failed, release the compressed buffer. 6766 * l2hdr will be left unmodified. 6767 */ 6768 zio_data_buf_free(cdata, len); 6769 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6770 return (B_FALSE); 6771 } 6772 } 6773 6774 /* 6775 * Decompresses a zio read back from an l2arc device. On success, the 6776 * underlying zio's io_data buffer is overwritten by the uncompressed 6777 * version. On decompression error (corrupt compressed stream), the 6778 * zio->io_error value is set to signal an I/O error. 6779 * 6780 * Please note that the compressed data stream is not checksummed, so 6781 * if the underlying device is experiencing data corruption, we may feed 6782 * corrupt data to the decompressor, so the decompressor needs to be 6783 * able to handle this situation (LZ4 does). 6784 */ 6785 static void 6786 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6787 { 6788 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6789 6790 if (zio->io_error != 0) { 6791 /* 6792 * An io error has occured, just restore the original io 6793 * size in preparation for a main pool read. 6794 */ 6795 zio->io_orig_size = zio->io_size = hdr->b_size; 6796 return; 6797 } 6798 6799 if (c == ZIO_COMPRESS_EMPTY) { 6800 /* 6801 * An empty buffer results in a null zio, which means we 6802 * need to fill its io_data after we're done restoring the 6803 * buffer's contents. 6804 */ 6805 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6806 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6807 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6808 } else { 6809 ASSERT(zio->io_data != NULL); 6810 /* 6811 * We copy the compressed data from the start of the arc buffer 6812 * (the zio_read will have pulled in only what we need, the 6813 * rest is garbage which we will overwrite at decompression) 6814 * and then decompress back to the ARC data buffer. This way we 6815 * can minimize copying by simply decompressing back over the 6816 * original compressed data (rather than decompressing to an 6817 * aux buffer and then copying back the uncompressed buffer, 6818 * which is likely to be much larger). 6819 */ 6820 uint64_t csize; 6821 void *cdata; 6822 6823 csize = zio->io_size; 6824 cdata = zio_data_buf_alloc(csize); 6825 bcopy(zio->io_data, cdata, csize); 6826 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6827 hdr->b_size) != 0) 6828 zio->io_error = EIO; 6829 zio_data_buf_free(cdata, csize); 6830 } 6831 6832 /* Restore the expected uncompressed IO size. */ 6833 zio->io_orig_size = zio->io_size = hdr->b_size; 6834 } 6835 6836 /* 6837 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6838 * This buffer serves as a temporary holder of compressed data while 6839 * the buffer entry is being written to an l2arc device. Once that is 6840 * done, we can dispose of it. 6841 */ 6842 static void 6843 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6844 { 6845 ASSERT(HDR_HAS_L2HDR(hdr)); 6846 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6847 6848 ASSERT(HDR_HAS_L1HDR(hdr)); 6849 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6850 6851 if (comp == ZIO_COMPRESS_OFF) { 6852 /* 6853 * In this case, b_tmp_cdata points to the same buffer 6854 * as the arc_buf_t's b_data field. We don't want to 6855 * free it, since the arc_buf_t will handle that. 6856 */ 6857 hdr->b_l1hdr.b_tmp_cdata = NULL; 6858 } else if (comp == ZIO_COMPRESS_EMPTY) { 6859 /* 6860 * In this case, b_tmp_cdata was compressed to an empty 6861 * buffer, thus there's nothing to free and b_tmp_cdata 6862 * should have been set to NULL in l2arc_write_buffers(). 6863 */ 6864 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6865 } else { 6866 /* 6867 * If the data was compressed, then we've allocated a 6868 * temporary buffer for it, so now we need to release it. 6869 */ 6870 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6871 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6872 hdr->b_size); 6873 hdr->b_l1hdr.b_tmp_cdata = NULL; 6874 } 6875 6876 } 6877 6878 /* 6879 * This thread feeds the L2ARC at regular intervals. This is the beating 6880 * heart of the L2ARC. 6881 */ 6882 static void 6883 l2arc_feed_thread(void) 6884 { 6885 callb_cpr_t cpr; 6886 l2arc_dev_t *dev; 6887 spa_t *spa; 6888 uint64_t size, wrote; 6889 clock_t begin, next = ddi_get_lbolt(); 6890 boolean_t headroom_boost = B_FALSE; 6891 6892 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6893 6894 mutex_enter(&l2arc_feed_thr_lock); 6895 6896 while (l2arc_thread_exit == 0) { 6897 CALLB_CPR_SAFE_BEGIN(&cpr); 6898 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6899 next); 6900 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6901 next = ddi_get_lbolt() + hz; 6902 6903 /* 6904 * Quick check for L2ARC devices. 6905 */ 6906 mutex_enter(&l2arc_dev_mtx); 6907 if (l2arc_ndev == 0) { 6908 mutex_exit(&l2arc_dev_mtx); 6909 continue; 6910 } 6911 mutex_exit(&l2arc_dev_mtx); 6912 begin = ddi_get_lbolt(); 6913 6914 /* 6915 * This selects the next l2arc device to write to, and in 6916 * doing so the next spa to feed from: dev->l2ad_spa. This 6917 * will return NULL if there are now no l2arc devices or if 6918 * they are all faulted. 6919 * 6920 * If a device is returned, its spa's config lock is also 6921 * held to prevent device removal. l2arc_dev_get_next() 6922 * will grab and release l2arc_dev_mtx. 6923 */ 6924 if ((dev = l2arc_dev_get_next()) == NULL) 6925 continue; 6926 6927 spa = dev->l2ad_spa; 6928 ASSERT(spa != NULL); 6929 6930 /* 6931 * If the pool is read-only then force the feed thread to 6932 * sleep a little longer. 6933 */ 6934 if (!spa_writeable(spa)) { 6935 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6936 spa_config_exit(spa, SCL_L2ARC, dev); 6937 continue; 6938 } 6939 6940 /* 6941 * Avoid contributing to memory pressure. 6942 */ 6943 if (arc_reclaim_needed()) { 6944 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6945 spa_config_exit(spa, SCL_L2ARC, dev); 6946 continue; 6947 } 6948 6949 ARCSTAT_BUMP(arcstat_l2_feeds); 6950 6951 size = l2arc_write_size(); 6952 6953 /* 6954 * Evict L2ARC buffers that will be overwritten. 6955 */ 6956 l2arc_evict(dev, size, B_FALSE); 6957 6958 /* 6959 * Write ARC buffers. 6960 */ 6961 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6962 6963 /* 6964 * Calculate interval between writes. 6965 */ 6966 next = l2arc_write_interval(begin, size, wrote); 6967 spa_config_exit(spa, SCL_L2ARC, dev); 6968 } 6969 6970 l2arc_thread_exit = 0; 6971 cv_broadcast(&l2arc_feed_thr_cv); 6972 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6973 thread_exit(); 6974 } 6975 6976 boolean_t 6977 l2arc_vdev_present(vdev_t *vd) 6978 { 6979 return (l2arc_vdev_get(vd) != NULL); 6980 } 6981 6982 /* 6983 * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if 6984 * the vdev_t isn't an L2ARC device. 6985 */ 6986 static l2arc_dev_t * 6987 l2arc_vdev_get(vdev_t *vd) 6988 { 6989 l2arc_dev_t *dev; 6990 boolean_t held = MUTEX_HELD(&l2arc_dev_mtx); 6991 6992 if (!held) 6993 mutex_enter(&l2arc_dev_mtx); 6994 for (dev = list_head(l2arc_dev_list); dev != NULL; 6995 dev = list_next(l2arc_dev_list, dev)) { 6996 if (dev->l2ad_vdev == vd) 6997 break; 6998 } 6999 if (!held) 7000 mutex_exit(&l2arc_dev_mtx); 7001 7002 return (dev); 7003 } 7004 7005 /* 7006 * Add a vdev for use by the L2ARC. By this point the spa has already 7007 * validated the vdev and opened it. The `rebuild' flag indicates whether 7008 * we should attempt an L2ARC persistency rebuild. 7009 */ 7010 void 7011 l2arc_add_vdev(spa_t *spa, vdev_t *vd, boolean_t rebuild) 7012 { 7013 l2arc_dev_t *adddev; 7014 7015 ASSERT(!l2arc_vdev_present(vd)); 7016 7017 /* 7018 * Create a new l2arc device entry. 7019 */ 7020 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7021 adddev->l2ad_spa = spa; 7022 adddev->l2ad_vdev = vd; 7023 /* leave extra size for an l2arc device header */ 7024 adddev->l2ad_dev_hdr_asize = MAX(sizeof (*adddev->l2ad_dev_hdr), 7025 1 << vd->vdev_ashift); 7026 adddev->l2ad_start = VDEV_LABEL_START_SIZE + adddev->l2ad_dev_hdr_asize; 7027 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7028 ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end); 7029 adddev->l2ad_hand = adddev->l2ad_start; 7030 adddev->l2ad_first = B_TRUE; 7031 adddev->l2ad_writing = B_FALSE; 7032 adddev->l2ad_dev_hdr = kmem_zalloc(adddev->l2ad_dev_hdr_asize, 7033 KM_SLEEP); 7034 7035 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7036 /* 7037 * This is a list of all ARC buffers that are still valid on the 7038 * device. 7039 */ 7040 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7041 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7042 7043 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7044 refcount_create(&adddev->l2ad_alloc); 7045 7046 /* 7047 * Add device to global list 7048 */ 7049 mutex_enter(&l2arc_dev_mtx); 7050 list_insert_head(l2arc_dev_list, adddev); 7051 atomic_inc_64(&l2arc_ndev); 7052 if (rebuild && l2arc_rebuild_enabled && 7053 adddev->l2ad_end - adddev->l2ad_start > L2ARC_PERSIST_MIN_SIZE) { 7054 /* 7055 * Just mark the device as pending for a rebuild. We won't 7056 * be starting a rebuild in line here as it would block pool 7057 * import. Instead spa_load_impl will hand that off to an 7058 * async task which will call l2arc_spa_rebuild_start. 7059 */ 7060 adddev->l2ad_rebuild = B_TRUE; 7061 } 7062 mutex_exit(&l2arc_dev_mtx); 7063 } 7064 7065 /* 7066 * Remove a vdev from the L2ARC. 7067 */ 7068 void 7069 l2arc_remove_vdev(vdev_t *vd) 7070 { 7071 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7072 7073 /* 7074 * Find the device by vdev 7075 */ 7076 mutex_enter(&l2arc_dev_mtx); 7077 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7078 nextdev = list_next(l2arc_dev_list, dev); 7079 if (vd == dev->l2ad_vdev) { 7080 remdev = dev; 7081 break; 7082 } 7083 } 7084 ASSERT(remdev != NULL); 7085 7086 /* 7087 * Cancel any ongoing or scheduled rebuild (race protection with 7088 * l2arc_spa_rebuild_start provided via l2arc_dev_mtx). 7089 */ 7090 remdev->l2ad_rebuild_cancel = B_TRUE; 7091 if (remdev->l2ad_rebuild_did != 0) { 7092 /* 7093 * N.B. it should be safe to thread_join with the rebuild 7094 * thread while holding l2arc_dev_mtx because it is not 7095 * accessed from anywhere in the l2arc rebuild code below 7096 * (except for l2arc_spa_rebuild_start, which is ok). 7097 */ 7098 thread_join(remdev->l2ad_rebuild_did); 7099 } 7100 7101 /* 7102 * Remove device from global list 7103 */ 7104 list_remove(l2arc_dev_list, remdev); 7105 l2arc_dev_last = NULL; /* may have been invalidated */ 7106 atomic_dec_64(&l2arc_ndev); 7107 mutex_exit(&l2arc_dev_mtx); 7108 7109 /* 7110 * Clear all buflists and ARC references. L2ARC device flush. 7111 */ 7112 l2arc_evict(remdev, 0, B_TRUE); 7113 list_destroy(&remdev->l2ad_buflist); 7114 mutex_destroy(&remdev->l2ad_mtx); 7115 refcount_destroy(&remdev->l2ad_alloc); 7116 kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize); 7117 kmem_free(remdev, sizeof (l2arc_dev_t)); 7118 } 7119 7120 void 7121 l2arc_init(void) 7122 { 7123 l2arc_thread_exit = 0; 7124 l2arc_ndev = 0; 7125 l2arc_writes_sent = 0; 7126 l2arc_writes_done = 0; 7127 7128 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7129 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7130 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7131 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7132 7133 l2arc_dev_list = &L2ARC_dev_list; 7134 l2arc_free_on_write = &L2ARC_free_on_write; 7135 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7136 offsetof(l2arc_dev_t, l2ad_node)); 7137 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7138 offsetof(l2arc_data_free_t, l2df_list_node)); 7139 } 7140 7141 void 7142 l2arc_fini(void) 7143 { 7144 /* 7145 * This is called from dmu_fini(), which is called from spa_fini(); 7146 * Because of this, we can assume that all l2arc devices have 7147 * already been removed when the pools themselves were removed. 7148 */ 7149 7150 l2arc_do_free_on_write(); 7151 7152 mutex_destroy(&l2arc_feed_thr_lock); 7153 cv_destroy(&l2arc_feed_thr_cv); 7154 mutex_destroy(&l2arc_dev_mtx); 7155 mutex_destroy(&l2arc_free_on_write_mtx); 7156 7157 list_destroy(l2arc_dev_list); 7158 list_destroy(l2arc_free_on_write); 7159 } 7160 7161 void 7162 l2arc_start(void) 7163 { 7164 if (!(spa_mode_global & FWRITE)) 7165 return; 7166 7167 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7168 TS_RUN, minclsyspri); 7169 } 7170 7171 void 7172 l2arc_stop(void) 7173 { 7174 if (!(spa_mode_global & FWRITE)) 7175 return; 7176 7177 mutex_enter(&l2arc_feed_thr_lock); 7178 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7179 l2arc_thread_exit = 1; 7180 while (l2arc_thread_exit != 0) 7181 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7182 mutex_exit(&l2arc_feed_thr_lock); 7183 } 7184 7185 /* 7186 * Punches out rebuild threads for the L2ARC devices in a spa. This should 7187 * be called after pool import from the spa async thread, since starting 7188 * these threads directly from spa_import() will make them part of the 7189 * "zpool import" context and delay process exit (and thus pool import). 7190 */ 7191 void 7192 l2arc_spa_rebuild_start(spa_t *spa) 7193 { 7194 /* 7195 * Locate the spa's l2arc devices and kick off rebuild threads. 7196 */ 7197 mutex_enter(&l2arc_dev_mtx); 7198 for (int i = 0; i < spa->spa_l2cache.sav_count; i++) { 7199 l2arc_dev_t *dev = 7200 l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]); 7201 ASSERT(dev != NULL); 7202 if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) { 7203 VERIFY3U(dev->l2ad_rebuild_did, ==, 0); 7204 #ifdef _KERNEL 7205 dev->l2ad_rebuild_did = thread_create(NULL, 0, 7206 l2arc_dev_rebuild_start, dev, 0, &p0, TS_RUN, 7207 minclsyspri)->t_did; 7208 #endif 7209 } 7210 } 7211 mutex_exit(&l2arc_dev_mtx); 7212 } 7213 7214 /* 7215 * Main entry point for L2ARC rebuilding. 7216 */ 7217 static void 7218 l2arc_dev_rebuild_start(l2arc_dev_t *dev) 7219 { 7220 if (!dev->l2ad_rebuild_cancel) { 7221 VERIFY(dev->l2ad_rebuild); 7222 (void) l2arc_rebuild(dev); 7223 dev->l2ad_rebuild = B_FALSE; 7224 } 7225 } 7226 7227 /* 7228 * This function implements the actual L2ARC metadata rebuild. It: 7229 * 7230 * 1) reads the device's header 7231 * 2) if a good device header is found, starts reading the log block chain 7232 * 3) restores each block's contents to memory (reconstructing arc_buf_hdr_t's) 7233 * 7234 * Operation stops under any of the following conditions: 7235 * 7236 * 1) We reach the end of the log blk chain (the back-reference in the blk is 7237 * invalid or loops over our starting point). 7238 * 2) We encounter *any* error condition (cksum errors, io errors, looped 7239 * blocks, etc.). 7240 */ 7241 static int 7242 l2arc_rebuild(l2arc_dev_t *dev) 7243 { 7244 vdev_t *vd = dev->l2ad_vdev; 7245 spa_t *spa = vd->vdev_spa; 7246 int err; 7247 l2arc_log_blk_phys_t *this_lb, *next_lb; 7248 uint8_t *this_lb_buf, *next_lb_buf; 7249 zio_t *this_io = NULL, *next_io = NULL; 7250 l2arc_log_blkptr_t lb_ptrs[2]; 7251 boolean_t first_pass, lock_held; 7252 uint64_t load_guid; 7253 7254 this_lb = kmem_zalloc(sizeof (*this_lb), KM_SLEEP); 7255 next_lb = kmem_zalloc(sizeof (*next_lb), KM_SLEEP); 7256 this_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP); 7257 next_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP); 7258 7259 /* 7260 * We prevent device removal while issuing reads to the device, 7261 * then during the rebuilding phases we drop this lock again so 7262 * that a spa_unload or device remove can be initiated - this is 7263 * safe, because the spa will signal us to stop before removing 7264 * our device and wait for us to stop. 7265 */ 7266 spa_config_enter(spa, SCL_L2ARC, vd, RW_READER); 7267 lock_held = B_TRUE; 7268 7269 load_guid = spa_load_guid(dev->l2ad_vdev->vdev_spa); 7270 /* 7271 * Device header processing phase. 7272 */ 7273 if ((err = l2arc_dev_hdr_read(dev)) != 0) { 7274 /* device header corrupted, start a new one */ 7275 bzero(dev->l2ad_dev_hdr, dev->l2ad_dev_hdr_asize); 7276 goto out; 7277 } 7278 7279 /* Retrieve the persistent L2ARC device state */ 7280 dev->l2ad_hand = vdev_psize_to_asize(dev->l2ad_vdev, 7281 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr + 7282 LBP_GET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0])); 7283 dev->l2ad_first = !!(dev->l2ad_dev_hdr->dh_flags & 7284 L2ARC_DEV_HDR_EVICT_FIRST); 7285 7286 /* Prepare the rebuild processing state */ 7287 bcopy(dev->l2ad_dev_hdr->dh_start_lbps, lb_ptrs, sizeof (lb_ptrs)); 7288 first_pass = B_TRUE; 7289 7290 /* Start the rebuild process */ 7291 for (;;) { 7292 if (!l2arc_log_blkptr_valid(dev, &lb_ptrs[0])) 7293 /* We hit an invalid block address, end the rebuild. */ 7294 break; 7295 7296 if ((err = l2arc_log_blk_read(dev, &lb_ptrs[0], &lb_ptrs[1], 7297 this_lb, next_lb, this_lb_buf, next_lb_buf, 7298 this_io, &next_io)) != 0) 7299 break; 7300 7301 spa_config_exit(spa, SCL_L2ARC, vd); 7302 lock_held = B_FALSE; 7303 7304 /* Protection against infinite loops of log blocks. */ 7305 if (l2arc_range_check_overlap(lb_ptrs[1].lbp_daddr, 7306 lb_ptrs[0].lbp_daddr, 7307 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) && 7308 !first_pass) { 7309 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_loop_errors); 7310 err = SET_ERROR(ELOOP); 7311 break; 7312 } 7313 7314 /* 7315 * Our memory pressure valve. If the system is running low 7316 * on memory, rather than swamping memory with new ARC buf 7317 * hdrs, we opt not to rebuild the L2ARC. At this point, 7318 * however, we have already set up our L2ARC dev to chain in 7319 * new metadata log blk, so the user may choose to re-add the 7320 * L2ARC dev at a later time to reconstruct it (when there's 7321 * less memory pressure). 7322 */ 7323 if (arc_reclaim_needed()) { 7324 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem); 7325 cmn_err(CE_NOTE, "System running low on memory, " 7326 "aborting L2ARC rebuild."); 7327 err = SET_ERROR(ENOMEM); 7328 break; 7329 } 7330 7331 /* 7332 * Now that we know that the next_lb checks out alright, we 7333 * can start reconstruction from this lb - we can be sure 7334 * that the L2ARC write hand has not yet reached any of our 7335 * buffers. 7336 */ 7337 l2arc_log_blk_restore(dev, load_guid, this_lb, 7338 LBP_GET_PSIZE(&lb_ptrs[0])); 7339 7340 /* 7341 * End of list detection. We can look ahead two steps in the 7342 * blk chain and if the 2nd blk from this_lb dips below the 7343 * initial chain starting point, then we know two things: 7344 * 1) it can't be valid, and 7345 * 2) the next_lb's ARC entries might have already been 7346 * partially overwritten and so we should stop before 7347 * we restore it 7348 */ 7349 if (l2arc_range_check_overlap( 7350 this_lb->lb_back2_lbp.lbp_daddr, lb_ptrs[0].lbp_daddr, 7351 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) && 7352 !first_pass) 7353 break; 7354 7355 /* log blk restored, continue with next one in the list */ 7356 lb_ptrs[0] = lb_ptrs[1]; 7357 lb_ptrs[1] = this_lb->lb_back2_lbp; 7358 PTR_SWAP(this_lb, next_lb); 7359 PTR_SWAP(this_lb_buf, next_lb_buf); 7360 this_io = next_io; 7361 next_io = NULL; 7362 first_pass = B_FALSE; 7363 7364 for (;;) { 7365 if (dev->l2ad_rebuild_cancel) { 7366 err = SET_ERROR(ECANCELED); 7367 goto out; 7368 } 7369 if (spa_config_tryenter(spa, SCL_L2ARC, vd, 7370 RW_READER)) { 7371 lock_held = B_TRUE; 7372 break; 7373 } 7374 /* 7375 * L2ARC config lock held by somebody in writer, 7376 * possibly due to them trying to remove us. They'll 7377 * likely to want us to shut down, so after a little 7378 * delay, we check l2ad_rebuild_cancel and retry 7379 * the lock again. 7380 */ 7381 delay(1); 7382 } 7383 } 7384 out: 7385 if (next_io != NULL) 7386 l2arc_log_blk_prefetch_abort(next_io); 7387 kmem_free(this_lb, sizeof (*this_lb)); 7388 kmem_free(next_lb, sizeof (*next_lb)); 7389 kmem_free(this_lb_buf, sizeof (l2arc_log_blk_phys_t)); 7390 kmem_free(next_lb_buf, sizeof (l2arc_log_blk_phys_t)); 7391 if (err == 0) 7392 ARCSTAT_BUMP(arcstat_l2_rebuild_successes); 7393 7394 if (lock_held) 7395 spa_config_exit(spa, SCL_L2ARC, vd); 7396 7397 return (err); 7398 } 7399 7400 /* 7401 * Attempts to read the device header on the provided L2ARC device and writes 7402 * it to `hdr'. On success, this function returns 0, otherwise the appropriate 7403 * error code is returned. 7404 */ 7405 static int 7406 l2arc_dev_hdr_read(l2arc_dev_t *dev) 7407 { 7408 int err; 7409 uint64_t guid; 7410 zio_cksum_t cksum; 7411 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr; 7412 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize; 7413 7414 guid = spa_guid(dev->l2ad_vdev->vdev_spa); 7415 7416 if ((err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev, 7417 VDEV_LABEL_START_SIZE, hdr_asize, hdr, 7418 ZIO_CHECKSUM_OFF, NULL, NULL, ZIO_PRIORITY_ASYNC_READ, 7419 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | 7420 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE))) != 0) { 7421 spa_config_exit(dev->l2ad_vdev->vdev_spa, SCL_L2ARC, 7422 dev->l2ad_vdev); 7423 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors); 7424 return (err); 7425 } 7426 7427 if (hdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC)) 7428 byteswap_uint64_array(hdr, sizeof (*hdr)); 7429 7430 if (hdr->dh_magic != L2ARC_DEV_HDR_MAGIC || hdr->dh_spa_guid != guid) { 7431 /* 7432 * Attempt to rebuild a device containing no actual dev hdr 7433 * or containing a header from some other pool. 7434 */ 7435 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported); 7436 return (SET_ERROR(ENOTSUP)); 7437 } 7438 7439 l2arc_dev_hdr_checksum(hdr, &cksum); 7440 if (!ZIO_CHECKSUM_EQUAL(hdr->dh_self_cksum, cksum)) { 7441 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors); 7442 return (SET_ERROR(EINVAL)); 7443 } 7444 7445 return (0); 7446 } 7447 7448 /* 7449 * Reads L2ARC log blocks from storage and validates their contents. 7450 * 7451 * This function implements a simple prefetcher to make sure that while 7452 * we're processing one buffer the L2ARC is already prefetching the next 7453 * one in the chain. 7454 * 7455 * The arguments this_lp and next_lp point to the current and next log blk 7456 * address in the block chain. Similarly, this_lb and next_lb hold the 7457 * l2arc_log_blk_phys_t's of the current and next L2ARC blk. The this_lb_buf 7458 * and next_lb_buf must be buffers of appropriate to hold a raw 7459 * l2arc_log_blk_phys_t (they are used as catch buffers for read ops prior 7460 * to buffer decompression). 7461 * 7462 * The `this_io' and `next_io' arguments are used for block prefetching. 7463 * When issuing the first blk IO during rebuild, you should pass NULL for 7464 * `this_io'. This function will then issue a sync IO to read the block and 7465 * also issue an async IO to fetch the next block in the block chain. The 7466 * prefetch IO is returned in `next_io'. On subsequent calls to this 7467 * function, pass the value returned in `next_io' from the previous call 7468 * as `this_io' and a fresh `next_io' pointer to hold the next prefetch IO. 7469 * Prior to the call, you should initialize your `next_io' pointer to be 7470 * NULL. If no prefetch IO was issued, the pointer is left set at NULL. 7471 * 7472 * On success, this function returns 0, otherwise it returns an appropriate 7473 * error code. On error the prefetching IO is aborted and cleared before 7474 * returning from this function. Therefore, if we return `success', the 7475 * caller can assume that we have taken care of cleanup of prefetch IOs. 7476 */ 7477 static int 7478 l2arc_log_blk_read(l2arc_dev_t *dev, 7479 const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp, 7480 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, 7481 uint8_t *this_lb_buf, uint8_t *next_lb_buf, 7482 zio_t *this_io, zio_t **next_io) 7483 { 7484 int err = 0; 7485 zio_cksum_t cksum; 7486 7487 ASSERT(this_lbp != NULL && next_lbp != NULL); 7488 ASSERT(this_lb != NULL && next_lb != NULL); 7489 ASSERT(this_lb_buf != NULL && next_lb_buf != NULL); 7490 ASSERT(next_io != NULL && *next_io == NULL); 7491 ASSERT(l2arc_log_blkptr_valid(dev, this_lbp)); 7492 7493 /* 7494 * Check to see if we have issued the IO for this log blk in a 7495 * previous run. If not, this is the first call, so issue it now. 7496 */ 7497 if (this_io == NULL) { 7498 this_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, this_lbp, 7499 this_lb_buf); 7500 } 7501 7502 /* 7503 * Peek to see if we can start issuing the next IO immediately. 7504 */ 7505 if (l2arc_log_blkptr_valid(dev, next_lbp)) { 7506 /* 7507 * Start issuing IO for the next log blk early - this 7508 * should help keep the L2ARC device busy while we 7509 * decompress and restore this log blk. 7510 */ 7511 *next_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, next_lbp, 7512 next_lb_buf); 7513 } 7514 7515 /* Wait for the IO to read this log block to complete */ 7516 if ((err = zio_wait(this_io)) != 0) { 7517 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors); 7518 goto cleanup; 7519 } 7520 7521 /* Make sure the buffer checks out */ 7522 fletcher_4_native(this_lb_buf, LBP_GET_PSIZE(this_lbp), NULL, &cksum); 7523 if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) { 7524 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors); 7525 err = SET_ERROR(EINVAL); 7526 goto cleanup; 7527 } 7528 7529 /* Now we can take our time decoding this buffer */ 7530 switch (LBP_GET_COMPRESS(this_lbp)) { 7531 case ZIO_COMPRESS_OFF: 7532 bcopy(this_lb_buf, this_lb, sizeof (*this_lb)); 7533 break; 7534 case ZIO_COMPRESS_LZ4: 7535 if ((err = zio_decompress_data(LBP_GET_COMPRESS(this_lbp), 7536 this_lb_buf, this_lb, LBP_GET_PSIZE(this_lbp), 7537 sizeof (*this_lb))) != 0) { 7538 err = SET_ERROR(EINVAL); 7539 goto cleanup; 7540 } 7541 break; 7542 default: 7543 err = SET_ERROR(EINVAL); 7544 goto cleanup; 7545 } 7546 if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC)) 7547 byteswap_uint64_array(this_lb, sizeof (*this_lb)); 7548 if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) { 7549 err = SET_ERROR(EINVAL); 7550 goto cleanup; 7551 } 7552 cleanup: 7553 /* Abort an in-flight prefetch I/O in case of error */ 7554 if (err != 0 && *next_io != NULL) { 7555 l2arc_log_blk_prefetch_abort(*next_io); 7556 *next_io = NULL; 7557 } 7558 return (err); 7559 } 7560 7561 /* 7562 * Restores the payload of a log blk to ARC. This creates empty ARC hdr 7563 * entries which only contain an l2arc hdr, essentially restoring the 7564 * buffers to their L2ARC evicted state. This function also updates space 7565 * usage on the L2ARC vdev to make sure it tracks restored buffers. 7566 */ 7567 static void 7568 l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid, 7569 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize) 7570 { 7571 uint64_t size = 0, psize = 0; 7572 7573 for (int i = L2ARC_LOG_BLK_ENTRIES - 1; i >= 0; i--) { 7574 /* 7575 * Restore goes in the reverse temporal direction to preserve 7576 * correct temporal ordering of buffers in the l2ad_buflist. 7577 * l2arc_hdr_restore also does a list_insert_tail instead of 7578 * list_insert_head on the l2ad_buflist: 7579 * 7580 * LIST l2ad_buflist LIST 7581 * HEAD <------ (time) ------ TAIL 7582 * direction +-----+-----+-----+-----+-----+ direction 7583 * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild 7584 * fill +-----+-----+-----+-----+-----+ 7585 * ^ ^ 7586 * | | 7587 * | | 7588 * l2arc_fill_thread l2arc_rebuild 7589 * places new bufs here restores bufs here 7590 * 7591 * This also works when the restored bufs get evicted at any 7592 * point during the rebuild. 7593 */ 7594 l2arc_hdr_restore(&lb->lb_entries[i], dev, load_guid); 7595 size += LE_GET_LSIZE(&lb->lb_entries[i]); 7596 psize += LE_GET_PSIZE(&lb->lb_entries[i]); 7597 } 7598 7599 /* 7600 * Record rebuild stats: 7601 * size In-memory size of restored buffer data in ARC 7602 * psize Physical size of restored buffers in the L2ARC 7603 * bufs # of ARC buffer headers restored 7604 * log_blks # of L2ARC log entries processed during restore 7605 */ 7606 ARCSTAT_INCR(arcstat_l2_rebuild_size, size); 7607 ARCSTAT_INCR(arcstat_l2_rebuild_psize, psize); 7608 ARCSTAT_INCR(arcstat_l2_rebuild_bufs, L2ARC_LOG_BLK_ENTRIES); 7609 ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks); 7610 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, lb_psize); 7611 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, psize / lb_psize); 7612 vdev_space_update(dev->l2ad_vdev, psize, 0, 0); 7613 } 7614 7615 /* 7616 * Restores a single ARC buf hdr from a log block. The ARC buffer is put 7617 * into a state indicating that it has been evicted to L2ARC. 7618 */ 7619 static void 7620 l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev, 7621 uint64_t load_guid) 7622 { 7623 arc_buf_hdr_t *hdr, *exists; 7624 kmutex_t *hash_lock; 7625 arc_buf_contents_t type = LE_GET_TYPE(le); 7626 7627 /* 7628 * Do all the allocation before grabbing any locks, this lets us 7629 * sleep if memory is full and we don't have to deal with failed 7630 * allocations. 7631 */ 7632 ASSERT(L2ARC_IS_VALID_COMPRESS(LE_GET_COMPRESS(le)) || 7633 LE_GET_COMPRESS(le) == ZIO_COMPRESS_OFF); 7634 hdr = arc_buf_alloc_l2only(load_guid, LE_GET_LSIZE(le), type, 7635 dev, le->le_dva, le->le_daddr, LE_GET_PSIZE(le), le->le_birth, 7636 le->le_freeze_cksum, LE_GET_COMPRESS(le)); 7637 if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET) { 7638 ARCSTAT_INCR(arcstat_l2_size, hdr->b_size); 7639 ARCSTAT_INCR(arcstat_l2_asize, hdr->b_l2hdr.b_asize); 7640 } 7641 7642 mutex_enter(&dev->l2ad_mtx); 7643 /* 7644 * We connect the l2hdr to the hdr only after the hdr is in the hash 7645 * table, otherwise the rest of the arc hdr manipulation machinery 7646 * might get confused. 7647 */ 7648 list_insert_tail(&dev->l2ad_buflist, hdr); 7649 (void) refcount_add_many(&dev->l2ad_alloc, hdr->b_l2hdr.b_asize, hdr); 7650 mutex_exit(&dev->l2ad_mtx); 7651 7652 exists = buf_hash_insert(hdr, &hash_lock); 7653 if (exists) { 7654 /* Buffer was already cached, no need to restore it. */ 7655 mutex_exit(hash_lock); 7656 arc_hdr_destroy(hdr); 7657 ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached); 7658 return; 7659 } 7660 7661 mutex_exit(hash_lock); 7662 } 7663 7664 /* 7665 * Starts an asynchronous read IO to read a log block. This is used in log 7666 * block reconstruction to start reading the next block before we are done 7667 * decoding and reconstructing the current block, to keep the l2arc device 7668 * nice and hot with read IO to process. 7669 * The returned zio will contain a newly allocated memory buffers for the IO 7670 * data which should then be freed by the caller once the zio is no longer 7671 * needed (i.e. due to it having completed). If you wish to abort this 7672 * zio, you should do so using l2arc_log_blk_prefetch_abort, which takes 7673 * care of disposing of the allocated buffers correctly. 7674 */ 7675 static zio_t * 7676 l2arc_log_blk_prefetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp, 7677 uint8_t *lb_buf) 7678 { 7679 uint32_t psize; 7680 zio_t *pio; 7681 7682 psize = LBP_GET_PSIZE(lbp); 7683 ASSERT(psize <= sizeof (l2arc_log_blk_phys_t)); 7684 pio = zio_root(vd->vdev_spa, NULL, NULL, ZIO_FLAG_DONT_CACHE | 7685 ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | 7686 ZIO_FLAG_DONT_RETRY); 7687 (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, psize, 7688 lb_buf, ZIO_CHECKSUM_OFF, NULL, NULL, ZIO_PRIORITY_ASYNC_READ, 7689 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | 7690 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE)); 7691 7692 return (pio); 7693 } 7694 7695 /* 7696 * Aborts a zio returned from l2arc_log_blk_prefetch and frees the data 7697 * buffers allocated for it. 7698 */ 7699 static void 7700 l2arc_log_blk_prefetch_abort(zio_t *zio) 7701 { 7702 (void) zio_wait(zio); 7703 } 7704 7705 /* 7706 * Creates a zio to update the device header on an l2arc device. The zio is 7707 * initiated as a child of `pio'. 7708 */ 7709 static void 7710 l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio) 7711 { 7712 zio_t *wzio; 7713 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr; 7714 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize; 7715 7716 hdr->dh_magic = L2ARC_DEV_HDR_MAGIC; 7717 hdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa); 7718 hdr->dh_alloc_space = refcount_count(&dev->l2ad_alloc); 7719 hdr->dh_flags = 0; 7720 if (dev->l2ad_first) 7721 hdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST; 7722 7723 /* checksum operation goes last */ 7724 l2arc_dev_hdr_checksum(hdr, &hdr->dh_self_cksum); 7725 7726 wzio = zio_write_phys(pio, dev->l2ad_vdev, VDEV_LABEL_START_SIZE, 7727 hdr_asize, hdr, ZIO_CHECKSUM_OFF, NULL, NULL, 7728 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE); 7729 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio); 7730 (void) zio_nowait(wzio); 7731 } 7732 7733 /* 7734 * Commits a log block to the L2ARC device. This routine is invoked from 7735 * l2arc_write_buffers when the log block fills up. 7736 * This function allocates some memory to temporarily hold the serialized 7737 * buffer to be written. This is then released in l2arc_write_done. 7738 */ 7739 static void 7740 l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, 7741 l2arc_write_callback_t *cb) 7742 { 7743 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; 7744 uint64_t psize, asize; 7745 l2arc_log_blk_buf_t *lb_buf; 7746 zio_t *wzio; 7747 7748 VERIFY(dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES); 7749 7750 /* link the buffer into the block chain */ 7751 lb->lb_back2_lbp = dev->l2ad_dev_hdr->dh_start_lbps[1]; 7752 lb->lb_magic = L2ARC_LOG_BLK_MAGIC; 7753 7754 /* try to compress the buffer */ 7755 lb_buf = kmem_zalloc(sizeof (*lb_buf), KM_SLEEP); 7756 list_insert_tail(&cb->l2wcb_log_blk_buflist, lb_buf); 7757 psize = zio_compress_data(ZIO_COMPRESS_LZ4, lb, lb_buf->lbb_log_blk, 7758 sizeof (*lb)); 7759 /* a log block is never entirely zero */ 7760 ASSERT(psize != 0); 7761 asize = vdev_psize_to_asize(dev->l2ad_vdev, psize); 7762 ASSERT(asize <= sizeof (lb_buf->lbb_log_blk)); 7763 7764 /* 7765 * Update the start log blk pointer in the device header to point 7766 * to the log block we're about to write. 7767 */ 7768 dev->l2ad_dev_hdr->dh_start_lbps[1] = 7769 dev->l2ad_dev_hdr->dh_start_lbps[0]; 7770 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand; 7771 _NOTE(CONSTCOND) 7772 LBP_SET_LSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], sizeof (*lb)); 7773 LBP_SET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], asize); 7774 LBP_SET_CHECKSUM(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7775 ZIO_CHECKSUM_FLETCHER_4); 7776 LBP_SET_TYPE(&dev->l2ad_dev_hdr->dh_start_lbps[0], 0); 7777 if (asize < sizeof (*lb)) { 7778 /* compression succeeded */ 7779 bzero(lb_buf->lbb_log_blk + psize, asize - psize); 7780 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7781 ZIO_COMPRESS_LZ4); 7782 } else { 7783 /* compression failed */ 7784 bcopy(lb, lb_buf->lbb_log_blk, sizeof (*lb)); 7785 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7786 ZIO_COMPRESS_OFF); 7787 } 7788 /* checksum what we're about to write */ 7789 fletcher_4_native(lb_buf->lbb_log_blk, asize, NULL, 7790 &dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_cksum); 7791 7792 /* perform the write itself */ 7793 CTASSERT(L2ARC_LOG_BLK_SIZE >= SPA_MINBLOCKSIZE && 7794 L2ARC_LOG_BLK_SIZE <= SPA_MAXBLOCKSIZE); 7795 wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand, 7796 asize, lb_buf->lbb_log_blk, ZIO_CHECKSUM_OFF, NULL, NULL, 7797 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE); 7798 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio); 7799 (void) zio_nowait(wzio); 7800 7801 dev->l2ad_hand += asize; 7802 vdev_space_update(dev->l2ad_vdev, asize, 0, 0); 7803 7804 /* bump the kstats */ 7805 ARCSTAT_INCR(arcstat_l2_write_bytes, asize); 7806 ARCSTAT_BUMP(arcstat_l2_log_blk_writes); 7807 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, asize); 7808 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, 7809 dev->l2ad_log_blk_payload_asize / asize); 7810 7811 /* start a new log block */ 7812 dev->l2ad_log_ent_idx = 0; 7813 dev->l2ad_log_blk_payload_asize = 0; 7814 } 7815 7816 /* 7817 * Validates an L2ARC log blk address to make sure that it can be read 7818 * from the provided L2ARC device. Returns B_TRUE if the address is 7819 * within the device's bounds, or B_FALSE if not. 7820 */ 7821 static boolean_t 7822 l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp) 7823 { 7824 uint64_t psize = LBP_GET_PSIZE(lbp); 7825 uint64_t end = lbp->lbp_daddr + psize; 7826 7827 /* 7828 * A log block is valid if all of the following conditions are true: 7829 * - it fits entirely between l2ad_start and l2ad_end 7830 * - it has a valid size 7831 */ 7832 return (lbp->lbp_daddr >= dev->l2ad_start && end <= dev->l2ad_end && 7833 psize > 0 && psize <= sizeof (l2arc_log_blk_phys_t)); 7834 } 7835 7836 /* 7837 * Computes the checksum of `hdr' and stores it in `cksum'. 7838 */ 7839 static void 7840 l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr, zio_cksum_t *cksum) 7841 { 7842 fletcher_4_native((uint8_t *)hdr + 7843 offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid), 7844 sizeof (*hdr) - offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid), 7845 NULL, cksum); 7846 } 7847 7848 /* 7849 * Inserts ARC buffer `ab' into the current L2ARC log blk on the device. 7850 * The buffer being inserted must be present in L2ARC. 7851 * Returns B_TRUE if the L2ARC log blk is full and needs to be committed 7852 * to L2ARC, or B_FALSE if it still has room for more ARC buffers. 7853 */ 7854 static boolean_t 7855 l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *ab) 7856 { 7857 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; 7858 l2arc_log_ent_phys_t *le; 7859 int index = dev->l2ad_log_ent_idx++; 7860 7861 ASSERT(index < L2ARC_LOG_BLK_ENTRIES); 7862 7863 le = &lb->lb_entries[index]; 7864 bzero(le, sizeof (*le)); 7865 le->le_dva = ab->b_dva; 7866 le->le_birth = ab->b_birth; 7867 le->le_daddr = ab->b_l2hdr.b_daddr; 7868 LE_SET_LSIZE(le, ab->b_size); 7869 LE_SET_PSIZE(le, ab->b_l2hdr.b_asize); 7870 LE_SET_COMPRESS(le, ab->b_l2hdr.b_compress); 7871 if (ab->b_l2hdr.b_compress != ZIO_COMPRESS_OFF) { 7872 ASSERT(L2ARC_IS_VALID_COMPRESS(ab->b_l2hdr.b_compress)); 7873 ASSERT(L2ARC_IS_VALID_COMPRESS(LE_GET_COMPRESS(le))); 7874 } 7875 le->le_freeze_cksum = *ab->b_freeze_cksum; 7876 LE_SET_CHECKSUM(le, ZIO_CHECKSUM_FLETCHER_2); 7877 LE_SET_TYPE(le, arc_flags_to_bufc(ab->b_flags)); 7878 dev->l2ad_log_blk_payload_asize += ab->b_l2hdr.b_asize; 7879 7880 return (dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES); 7881 } 7882 7883 /* 7884 * Checks whether a given L2ARC device address sits in a time-sequential 7885 * range. The trick here is that the L2ARC is a rotary buffer, so we can't 7886 * just do a range comparison, we need to handle the situation in which the 7887 * range wraps around the end of the L2ARC device. Arguments: 7888 * bottom Lower end of the range to check (written to earlier). 7889 * top Upper end of the range to check (written to later). 7890 * check The address for which we want to determine if it sits in 7891 * between the top and bottom. 7892 * 7893 * The 3-way conditional below represents the following cases: 7894 * 7895 * bottom < top : Sequentially ordered case: 7896 * <check>--------+-------------------+ 7897 * | (overlap here?) | 7898 * L2ARC dev V V 7899 * |---------------<bottom>============<top>--------------| 7900 * 7901 * bottom > top: Looped-around case: 7902 * <check>--------+------------------+ 7903 * | (overlap here?) | 7904 * L2ARC dev V V 7905 * |===============<top>---------------<bottom>===========| 7906 * ^ ^ 7907 * | (or here?) | 7908 * +---------------+---------<check> 7909 * 7910 * top == bottom : Just a single address comparison. 7911 */ 7912 static inline boolean_t 7913 l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check) 7914 { 7915 if (bottom < top) 7916 return (bottom <= check && check <= top); 7917 else if (bottom > top) 7918 return (check <= top || bottom <= check); 7919 else 7920 return (check == top); 7921 } 7922