1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #include <sys/multilist.h> 133 #ifdef _KERNEL 134 #include <sys/vmsystm.h> 135 #include <vm/anon.h> 136 #include <sys/fs/swapnode.h> 137 #include <sys/dnlc.h> 138 #endif 139 #include <sys/callb.h> 140 #include <sys/kstat.h> 141 #include <zfs_fletcher.h> 142 143 #ifndef _KERNEL 144 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 145 boolean_t arc_watch = B_FALSE; 146 int arc_procfd; 147 #endif 148 149 static kmutex_t arc_reclaim_lock; 150 static kcondvar_t arc_reclaim_thread_cv; 151 static boolean_t arc_reclaim_thread_exit; 152 static kcondvar_t arc_reclaim_waiters_cv; 153 154 static kmutex_t arc_user_evicts_lock; 155 static kcondvar_t arc_user_evicts_cv; 156 static boolean_t arc_user_evicts_thread_exit; 157 158 uint_t arc_reduce_dnlc_percent = 3; 159 160 /* 161 * The number of headers to evict in arc_evict_state_impl() before 162 * dropping the sublist lock and evicting from another sublist. A lower 163 * value means we're more likely to evict the "correct" header (i.e. the 164 * oldest header in the arc state), but comes with higher overhead 165 * (i.e. more invocations of arc_evict_state_impl()). 166 */ 167 int zfs_arc_evict_batch_limit = 10; 168 169 /* 170 * The number of sublists used for each of the arc state lists. If this 171 * is not set to a suitable value by the user, it will be configured to 172 * the number of CPUs on the system in arc_init(). 173 */ 174 int zfs_arc_num_sublists_per_state = 0; 175 176 /* number of seconds before growing cache again */ 177 static int arc_grow_retry = 60; 178 179 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 180 int zfs_arc_overflow_shift = 8; 181 182 /* shift of arc_c for calculating both min and max arc_p */ 183 static int arc_p_min_shift = 4; 184 185 /* log2(fraction of arc to reclaim) */ 186 static int arc_shrink_shift = 7; 187 188 /* 189 * log2(fraction of ARC which must be free to allow growing). 190 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 191 * when reading a new block into the ARC, we will evict an equal-sized block 192 * from the ARC. 193 * 194 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 195 * we will still not allow it to grow. 196 */ 197 int arc_no_grow_shift = 5; 198 199 200 /* 201 * minimum lifespan of a prefetch block in clock ticks 202 * (initialized in arc_init()) 203 */ 204 static int arc_min_prefetch_lifespan; 205 206 /* 207 * If this percent of memory is free, don't throttle. 208 */ 209 int arc_lotsfree_percent = 10; 210 211 static int arc_dead; 212 213 /* 214 * The arc has filled available memory and has now warmed up. 215 */ 216 static boolean_t arc_warm; 217 218 /* 219 * These tunables are for performance analysis. 220 */ 221 uint64_t zfs_arc_max; 222 uint64_t zfs_arc_min; 223 uint64_t zfs_arc_meta_limit = 0; 224 uint64_t zfs_arc_meta_min = 0; 225 int zfs_arc_grow_retry = 0; 226 int zfs_arc_shrink_shift = 0; 227 int zfs_arc_p_min_shift = 0; 228 int zfs_disable_dup_eviction = 0; 229 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 230 231 /* 232 * Note that buffers can be in one of 6 states: 233 * ARC_anon - anonymous (discussed below) 234 * ARC_mru - recently used, currently cached 235 * ARC_mru_ghost - recentely used, no longer in cache 236 * ARC_mfu - frequently used, currently cached 237 * ARC_mfu_ghost - frequently used, no longer in cache 238 * ARC_l2c_only - exists in L2ARC but not other states 239 * When there are no active references to the buffer, they are 240 * are linked onto a list in one of these arc states. These are 241 * the only buffers that can be evicted or deleted. Within each 242 * state there are multiple lists, one for meta-data and one for 243 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 244 * etc.) is tracked separately so that it can be managed more 245 * explicitly: favored over data, limited explicitly. 246 * 247 * Anonymous buffers are buffers that are not associated with 248 * a DVA. These are buffers that hold dirty block copies 249 * before they are written to stable storage. By definition, 250 * they are "ref'd" and are considered part of arc_mru 251 * that cannot be freed. Generally, they will aquire a DVA 252 * as they are written and migrate onto the arc_mru list. 253 * 254 * The ARC_l2c_only state is for buffers that are in the second 255 * level ARC but no longer in any of the ARC_m* lists. The second 256 * level ARC itself may also contain buffers that are in any of 257 * the ARC_m* states - meaning that a buffer can exist in two 258 * places. The reason for the ARC_l2c_only state is to keep the 259 * buffer header in the hash table, so that reads that hit the 260 * second level ARC benefit from these fast lookups. 261 */ 262 263 typedef struct arc_state { 264 /* 265 * list of evictable buffers 266 */ 267 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 268 /* 269 * total amount of evictable data in this state 270 */ 271 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 272 /* 273 * total amount of data in this state; this includes: evictable, 274 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 275 */ 276 refcount_t arcs_size; 277 } arc_state_t; 278 279 /* The 6 states: */ 280 static arc_state_t ARC_anon; 281 static arc_state_t ARC_mru; 282 static arc_state_t ARC_mru_ghost; 283 static arc_state_t ARC_mfu; 284 static arc_state_t ARC_mfu_ghost; 285 static arc_state_t ARC_l2c_only; 286 287 typedef struct arc_stats { 288 kstat_named_t arcstat_hits; 289 kstat_named_t arcstat_misses; 290 kstat_named_t arcstat_demand_data_hits; 291 kstat_named_t arcstat_demand_data_misses; 292 kstat_named_t arcstat_demand_metadata_hits; 293 kstat_named_t arcstat_demand_metadata_misses; 294 kstat_named_t arcstat_prefetch_data_hits; 295 kstat_named_t arcstat_prefetch_data_misses; 296 kstat_named_t arcstat_prefetch_metadata_hits; 297 kstat_named_t arcstat_prefetch_metadata_misses; 298 kstat_named_t arcstat_mru_hits; 299 kstat_named_t arcstat_mru_ghost_hits; 300 kstat_named_t arcstat_mfu_hits; 301 kstat_named_t arcstat_mfu_ghost_hits; 302 kstat_named_t arcstat_deleted; 303 /* 304 * Number of buffers that could not be evicted because the hash lock 305 * was held by another thread. The lock may not necessarily be held 306 * by something using the same buffer, since hash locks are shared 307 * by multiple buffers. 308 */ 309 kstat_named_t arcstat_mutex_miss; 310 /* 311 * Number of buffers skipped because they have I/O in progress, are 312 * indrect prefetch buffers that have not lived long enough, or are 313 * not from the spa we're trying to evict from. 314 */ 315 kstat_named_t arcstat_evict_skip; 316 /* 317 * Number of times arc_evict_state() was unable to evict enough 318 * buffers to reach it's target amount. 319 */ 320 kstat_named_t arcstat_evict_not_enough; 321 kstat_named_t arcstat_evict_l2_cached; 322 kstat_named_t arcstat_evict_l2_eligible; 323 kstat_named_t arcstat_evict_l2_ineligible; 324 kstat_named_t arcstat_evict_l2_skip; 325 kstat_named_t arcstat_hash_elements; 326 kstat_named_t arcstat_hash_elements_max; 327 kstat_named_t arcstat_hash_collisions; 328 kstat_named_t arcstat_hash_chains; 329 kstat_named_t arcstat_hash_chain_max; 330 kstat_named_t arcstat_p; 331 kstat_named_t arcstat_c; 332 kstat_named_t arcstat_c_min; 333 kstat_named_t arcstat_c_max; 334 kstat_named_t arcstat_size; 335 /* 336 * Number of bytes consumed by internal ARC structures necessary 337 * for tracking purposes; these structures are not actually 338 * backed by ARC buffers. This includes arc_buf_hdr_t structures 339 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 340 * caches), and arc_buf_t structures (allocated via arc_buf_t 341 * cache). 342 */ 343 kstat_named_t arcstat_hdr_size; 344 /* 345 * Number of bytes consumed by ARC buffers of type equal to 346 * ARC_BUFC_DATA. This is generally consumed by buffers backing 347 * on disk user data (e.g. plain file contents). 348 */ 349 kstat_named_t arcstat_data_size; 350 /* 351 * Number of bytes consumed by ARC buffers of type equal to 352 * ARC_BUFC_METADATA. This is generally consumed by buffers 353 * backing on disk data that is used for internal ZFS 354 * structures (e.g. ZAP, dnode, indirect blocks, etc). 355 */ 356 kstat_named_t arcstat_metadata_size; 357 /* 358 * Number of bytes consumed by various buffers and structures 359 * not actually backed with ARC buffers. This includes bonus 360 * buffers (allocated directly via zio_buf_* functions), 361 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 362 * cache), and dnode_t structures (allocated via dnode_t cache). 363 */ 364 kstat_named_t arcstat_other_size; 365 /* 366 * Total number of bytes consumed by ARC buffers residing in the 367 * arc_anon state. This includes *all* buffers in the arc_anon 368 * state; e.g. data, metadata, evictable, and unevictable buffers 369 * are all included in this value. 370 */ 371 kstat_named_t arcstat_anon_size; 372 /* 373 * Number of bytes consumed by ARC buffers that meet the 374 * following criteria: backing buffers of type ARC_BUFC_DATA, 375 * residing in the arc_anon state, and are eligible for eviction 376 * (e.g. have no outstanding holds on the buffer). 377 */ 378 kstat_named_t arcstat_anon_evictable_data; 379 /* 380 * Number of bytes consumed by ARC buffers that meet the 381 * following criteria: backing buffers of type ARC_BUFC_METADATA, 382 * residing in the arc_anon state, and are eligible for eviction 383 * (e.g. have no outstanding holds on the buffer). 384 */ 385 kstat_named_t arcstat_anon_evictable_metadata; 386 /* 387 * Total number of bytes consumed by ARC buffers residing in the 388 * arc_mru state. This includes *all* buffers in the arc_mru 389 * state; e.g. data, metadata, evictable, and unevictable buffers 390 * are all included in this value. 391 */ 392 kstat_named_t arcstat_mru_size; 393 /* 394 * Number of bytes consumed by ARC buffers that meet the 395 * following criteria: backing buffers of type ARC_BUFC_DATA, 396 * residing in the arc_mru state, and are eligible for eviction 397 * (e.g. have no outstanding holds on the buffer). 398 */ 399 kstat_named_t arcstat_mru_evictable_data; 400 /* 401 * Number of bytes consumed by ARC buffers that meet the 402 * following criteria: backing buffers of type ARC_BUFC_METADATA, 403 * residing in the arc_mru state, and are eligible for eviction 404 * (e.g. have no outstanding holds on the buffer). 405 */ 406 kstat_named_t arcstat_mru_evictable_metadata; 407 /* 408 * Total number of bytes that *would have been* consumed by ARC 409 * buffers in the arc_mru_ghost state. The key thing to note 410 * here, is the fact that this size doesn't actually indicate 411 * RAM consumption. The ghost lists only consist of headers and 412 * don't actually have ARC buffers linked off of these headers. 413 * Thus, *if* the headers had associated ARC buffers, these 414 * buffers *would have* consumed this number of bytes. 415 */ 416 kstat_named_t arcstat_mru_ghost_size; 417 /* 418 * Number of bytes that *would have been* consumed by ARC 419 * buffers that are eligible for eviction, of type 420 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 421 */ 422 kstat_named_t arcstat_mru_ghost_evictable_data; 423 /* 424 * Number of bytes that *would have been* consumed by ARC 425 * buffers that are eligible for eviction, of type 426 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 427 */ 428 kstat_named_t arcstat_mru_ghost_evictable_metadata; 429 /* 430 * Total number of bytes consumed by ARC buffers residing in the 431 * arc_mfu state. This includes *all* buffers in the arc_mfu 432 * state; e.g. data, metadata, evictable, and unevictable buffers 433 * are all included in this value. 434 */ 435 kstat_named_t arcstat_mfu_size; 436 /* 437 * Number of bytes consumed by ARC buffers that are eligible for 438 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 439 * state. 440 */ 441 kstat_named_t arcstat_mfu_evictable_data; 442 /* 443 * Number of bytes consumed by ARC buffers that are eligible for 444 * eviction, of type ARC_BUFC_METADATA, and reside in the 445 * arc_mfu state. 446 */ 447 kstat_named_t arcstat_mfu_evictable_metadata; 448 /* 449 * Total number of bytes that *would have been* consumed by ARC 450 * buffers in the arc_mfu_ghost state. See the comment above 451 * arcstat_mru_ghost_size for more details. 452 */ 453 kstat_named_t arcstat_mfu_ghost_size; 454 /* 455 * Number of bytes that *would have been* consumed by ARC 456 * buffers that are eligible for eviction, of type 457 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 458 */ 459 kstat_named_t arcstat_mfu_ghost_evictable_data; 460 /* 461 * Number of bytes that *would have been* consumed by ARC 462 * buffers that are eligible for eviction, of type 463 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 464 */ 465 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 466 kstat_named_t arcstat_l2_hits; 467 kstat_named_t arcstat_l2_misses; 468 kstat_named_t arcstat_l2_feeds; 469 kstat_named_t arcstat_l2_rw_clash; 470 kstat_named_t arcstat_l2_read_bytes; 471 kstat_named_t arcstat_l2_write_bytes; 472 kstat_named_t arcstat_l2_writes_sent; 473 kstat_named_t arcstat_l2_writes_done; 474 kstat_named_t arcstat_l2_writes_error; 475 kstat_named_t arcstat_l2_writes_lock_retry; 476 kstat_named_t arcstat_l2_evict_lock_retry; 477 kstat_named_t arcstat_l2_evict_reading; 478 kstat_named_t arcstat_l2_evict_l1cached; 479 kstat_named_t arcstat_l2_free_on_write; 480 kstat_named_t arcstat_l2_cdata_free_on_write; 481 kstat_named_t arcstat_l2_abort_lowmem; 482 kstat_named_t arcstat_l2_cksum_bad; 483 kstat_named_t arcstat_l2_io_error; 484 kstat_named_t arcstat_l2_size; 485 kstat_named_t arcstat_l2_asize; 486 kstat_named_t arcstat_l2_hdr_size; 487 kstat_named_t arcstat_l2_compress_successes; 488 kstat_named_t arcstat_l2_compress_zeros; 489 kstat_named_t arcstat_l2_compress_failures; 490 kstat_named_t arcstat_memory_throttle_count; 491 kstat_named_t arcstat_duplicate_buffers; 492 kstat_named_t arcstat_duplicate_buffers_size; 493 kstat_named_t arcstat_duplicate_reads; 494 kstat_named_t arcstat_meta_used; 495 kstat_named_t arcstat_meta_limit; 496 kstat_named_t arcstat_meta_max; 497 kstat_named_t arcstat_meta_min; 498 } arc_stats_t; 499 500 static arc_stats_t arc_stats = { 501 { "hits", KSTAT_DATA_UINT64 }, 502 { "misses", KSTAT_DATA_UINT64 }, 503 { "demand_data_hits", KSTAT_DATA_UINT64 }, 504 { "demand_data_misses", KSTAT_DATA_UINT64 }, 505 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 506 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 507 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 508 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 509 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 510 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 511 { "mru_hits", KSTAT_DATA_UINT64 }, 512 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 513 { "mfu_hits", KSTAT_DATA_UINT64 }, 514 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 515 { "deleted", KSTAT_DATA_UINT64 }, 516 { "mutex_miss", KSTAT_DATA_UINT64 }, 517 { "evict_skip", KSTAT_DATA_UINT64 }, 518 { "evict_not_enough", KSTAT_DATA_UINT64 }, 519 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 520 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 521 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 522 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 523 { "hash_elements", KSTAT_DATA_UINT64 }, 524 { "hash_elements_max", KSTAT_DATA_UINT64 }, 525 { "hash_collisions", KSTAT_DATA_UINT64 }, 526 { "hash_chains", KSTAT_DATA_UINT64 }, 527 { "hash_chain_max", KSTAT_DATA_UINT64 }, 528 { "p", KSTAT_DATA_UINT64 }, 529 { "c", KSTAT_DATA_UINT64 }, 530 { "c_min", KSTAT_DATA_UINT64 }, 531 { "c_max", KSTAT_DATA_UINT64 }, 532 { "size", KSTAT_DATA_UINT64 }, 533 { "hdr_size", KSTAT_DATA_UINT64 }, 534 { "data_size", KSTAT_DATA_UINT64 }, 535 { "metadata_size", KSTAT_DATA_UINT64 }, 536 { "other_size", KSTAT_DATA_UINT64 }, 537 { "anon_size", KSTAT_DATA_UINT64 }, 538 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 539 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 540 { "mru_size", KSTAT_DATA_UINT64 }, 541 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 542 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 543 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 544 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 545 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 546 { "mfu_size", KSTAT_DATA_UINT64 }, 547 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 548 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 549 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 550 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 551 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 552 { "l2_hits", KSTAT_DATA_UINT64 }, 553 { "l2_misses", KSTAT_DATA_UINT64 }, 554 { "l2_feeds", KSTAT_DATA_UINT64 }, 555 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 556 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 557 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 558 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 559 { "l2_writes_done", KSTAT_DATA_UINT64 }, 560 { "l2_writes_error", KSTAT_DATA_UINT64 }, 561 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 562 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 563 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 564 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 565 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 566 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 567 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 568 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 569 { "l2_io_error", KSTAT_DATA_UINT64 }, 570 { "l2_size", KSTAT_DATA_UINT64 }, 571 { "l2_asize", KSTAT_DATA_UINT64 }, 572 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 573 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 574 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 575 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 576 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 577 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 578 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 579 { "duplicate_reads", KSTAT_DATA_UINT64 }, 580 { "arc_meta_used", KSTAT_DATA_UINT64 }, 581 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 582 { "arc_meta_max", KSTAT_DATA_UINT64 }, 583 { "arc_meta_min", KSTAT_DATA_UINT64 } 584 }; 585 586 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 587 588 #define ARCSTAT_INCR(stat, val) \ 589 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 590 591 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 592 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 593 594 #define ARCSTAT_MAX(stat, val) { \ 595 uint64_t m; \ 596 while ((val) > (m = arc_stats.stat.value.ui64) && \ 597 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 598 continue; \ 599 } 600 601 #define ARCSTAT_MAXSTAT(stat) \ 602 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 603 604 /* 605 * We define a macro to allow ARC hits/misses to be easily broken down by 606 * two separate conditions, giving a total of four different subtypes for 607 * each of hits and misses (so eight statistics total). 608 */ 609 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 610 if (cond1) { \ 611 if (cond2) { \ 612 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 613 } else { \ 614 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 615 } \ 616 } else { \ 617 if (cond2) { \ 618 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 619 } else { \ 620 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 621 } \ 622 } 623 624 kstat_t *arc_ksp; 625 static arc_state_t *arc_anon; 626 static arc_state_t *arc_mru; 627 static arc_state_t *arc_mru_ghost; 628 static arc_state_t *arc_mfu; 629 static arc_state_t *arc_mfu_ghost; 630 static arc_state_t *arc_l2c_only; 631 632 /* 633 * There are several ARC variables that are critical to export as kstats -- 634 * but we don't want to have to grovel around in the kstat whenever we wish to 635 * manipulate them. For these variables, we therefore define them to be in 636 * terms of the statistic variable. This assures that we are not introducing 637 * the possibility of inconsistency by having shadow copies of the variables, 638 * while still allowing the code to be readable. 639 */ 640 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 641 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 642 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 643 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 644 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 645 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 646 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 647 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 648 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 649 650 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 651 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 652 653 static int arc_no_grow; /* Don't try to grow cache size */ 654 static uint64_t arc_tempreserve; 655 static uint64_t arc_loaned_bytes; 656 657 typedef struct arc_callback arc_callback_t; 658 659 struct arc_callback { 660 void *acb_private; 661 arc_done_func_t *acb_done; 662 arc_buf_t *acb_buf; 663 zio_t *acb_zio_dummy; 664 arc_callback_t *acb_next; 665 }; 666 667 typedef struct arc_write_callback arc_write_callback_t; 668 669 struct arc_write_callback { 670 void *awcb_private; 671 arc_done_func_t *awcb_ready; 672 arc_done_func_t *awcb_physdone; 673 arc_done_func_t *awcb_done; 674 arc_buf_t *awcb_buf; 675 }; 676 677 /* 678 * ARC buffers are separated into multiple structs as a memory saving measure: 679 * - Common fields struct, always defined, and embedded within it: 680 * - L2-only fields, always allocated but undefined when not in L2ARC 681 * - L1-only fields, only allocated when in L1ARC 682 * 683 * Buffer in L1 Buffer only in L2 684 * +------------------------+ +------------------------+ 685 * | arc_buf_hdr_t | | arc_buf_hdr_t | 686 * | | | | 687 * | | | | 688 * | | | | 689 * +------------------------+ +------------------------+ 690 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 691 * | (undefined if L1-only) | | | 692 * +------------------------+ +------------------------+ 693 * | l1arc_buf_hdr_t | 694 * | | 695 * | | 696 * | | 697 * | | 698 * +------------------------+ 699 * 700 * Because it's possible for the L2ARC to become extremely large, we can wind 701 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 702 * is minimized by only allocating the fields necessary for an L1-cached buffer 703 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 704 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 705 * words in pointers. arc_hdr_realloc() is used to switch a header between 706 * these two allocation states. 707 */ 708 typedef struct l1arc_buf_hdr { 709 kmutex_t b_freeze_lock; 710 #ifdef ZFS_DEBUG 711 /* 712 * used for debugging wtih kmem_flags - by allocating and freeing 713 * b_thawed when the buffer is thawed, we get a record of the stack 714 * trace that thawed it. 715 */ 716 void *b_thawed; 717 #endif 718 719 arc_buf_t *b_buf; 720 uint32_t b_datacnt; 721 /* for waiting on writes to complete */ 722 kcondvar_t b_cv; 723 724 /* protected by arc state mutex */ 725 arc_state_t *b_state; 726 multilist_node_t b_arc_node; 727 728 /* updated atomically */ 729 clock_t b_arc_access; 730 731 /* self protecting */ 732 refcount_t b_refcnt; 733 734 arc_callback_t *b_acb; 735 /* temporary buffer holder for in-flight compressed data */ 736 void *b_tmp_cdata; 737 } l1arc_buf_hdr_t; 738 739 typedef struct l2arc_dev l2arc_dev_t; 740 741 typedef struct l2arc_buf_hdr { 742 /* protected by arc_buf_hdr mutex */ 743 l2arc_dev_t *b_dev; /* L2ARC device */ 744 uint64_t b_daddr; /* disk address, offset byte */ 745 /* real alloc'd buffer size depending on b_compress applied */ 746 int32_t b_asize; 747 748 list_node_t b_l2node; 749 } l2arc_buf_hdr_t; 750 751 struct arc_buf_hdr { 752 /* protected by hash lock */ 753 dva_t b_dva; 754 uint64_t b_birth; 755 /* 756 * Even though this checksum is only set/verified when a buffer is in 757 * the L1 cache, it needs to be in the set of common fields because it 758 * must be preserved from the time before a buffer is written out to 759 * L2ARC until after it is read back in. 760 */ 761 zio_cksum_t *b_freeze_cksum; 762 763 arc_buf_hdr_t *b_hash_next; 764 arc_flags_t b_flags; 765 766 /* immutable */ 767 int32_t b_size; 768 uint64_t b_spa; 769 770 /* L2ARC fields. Undefined when not in L2ARC. */ 771 l2arc_buf_hdr_t b_l2hdr; 772 /* L1ARC fields. Undefined when in l2arc_only state */ 773 l1arc_buf_hdr_t b_l1hdr; 774 }; 775 776 static arc_buf_t *arc_eviction_list; 777 static arc_buf_hdr_t arc_eviction_hdr; 778 779 #define GHOST_STATE(state) \ 780 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 781 (state) == arc_l2c_only) 782 783 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 784 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 785 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 786 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 787 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 788 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 789 790 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 791 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 792 #define HDR_L2_READING(hdr) \ 793 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 794 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 795 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 796 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 797 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 798 799 #define HDR_ISTYPE_METADATA(hdr) \ 800 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 801 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 802 803 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 804 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 805 806 /* For storing compression mode in b_flags */ 807 #define HDR_COMPRESS_OFFSET 24 808 #define HDR_COMPRESS_NBITS 7 809 810 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 811 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 812 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 813 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 814 815 /* 816 * Other sizes 817 */ 818 819 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 820 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 821 822 /* 823 * Hash table routines 824 */ 825 826 #define HT_LOCK_PAD 64 827 828 struct ht_lock { 829 kmutex_t ht_lock; 830 #ifdef _KERNEL 831 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 832 #endif 833 }; 834 835 #define BUF_LOCKS 256 836 typedef struct buf_hash_table { 837 uint64_t ht_mask; 838 arc_buf_hdr_t **ht_table; 839 struct ht_lock ht_locks[BUF_LOCKS]; 840 } buf_hash_table_t; 841 842 static buf_hash_table_t buf_hash_table; 843 844 #define BUF_HASH_INDEX(spa, dva, birth) \ 845 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 846 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 847 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 848 #define HDR_LOCK(hdr) \ 849 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 850 851 uint64_t zfs_crc64_table[256]; 852 853 /* 854 * Level 2 ARC 855 */ 856 857 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 858 #define L2ARC_HEADROOM 2 /* num of writes */ 859 /* 860 * If we discover during ARC scan any buffers to be compressed, we boost 861 * our headroom for the next scanning cycle by this percentage multiple. 862 */ 863 #define L2ARC_HEADROOM_BOOST 200 864 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 865 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 866 867 /* 868 * Used to distinguish headers that are being process by 869 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 870 * address. This can happen when the header is added to the l2arc's list 871 * of buffers to write in the first stage of l2arc_write_buffers(), but 872 * has not yet been written out which happens in the second stage of 873 * l2arc_write_buffers(). 874 */ 875 #define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 876 877 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 878 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 879 880 /* L2ARC Performance Tunables */ 881 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 882 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 883 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 884 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 885 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 886 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 887 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 888 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 889 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 890 891 /* 892 * L2ARC Internals 893 */ 894 struct l2arc_dev { 895 vdev_t *l2ad_vdev; /* vdev */ 896 spa_t *l2ad_spa; /* spa */ 897 uint64_t l2ad_hand; /* next write location */ 898 uint64_t l2ad_start; /* first addr on device */ 899 uint64_t l2ad_end; /* last addr on device */ 900 boolean_t l2ad_first; /* first sweep through */ 901 boolean_t l2ad_writing; /* currently writing */ 902 kmutex_t l2ad_mtx; /* lock for buffer list */ 903 list_t l2ad_buflist; /* buffer list */ 904 list_node_t l2ad_node; /* device list node */ 905 refcount_t l2ad_alloc; /* allocated bytes */ 906 }; 907 908 static list_t L2ARC_dev_list; /* device list */ 909 static list_t *l2arc_dev_list; /* device list pointer */ 910 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 911 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 912 static list_t L2ARC_free_on_write; /* free after write buf list */ 913 static list_t *l2arc_free_on_write; /* free after write list ptr */ 914 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 915 static uint64_t l2arc_ndev; /* number of devices */ 916 917 typedef struct l2arc_read_callback { 918 arc_buf_t *l2rcb_buf; /* read buffer */ 919 spa_t *l2rcb_spa; /* spa */ 920 blkptr_t l2rcb_bp; /* original blkptr */ 921 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 922 int l2rcb_flags; /* original flags */ 923 enum zio_compress l2rcb_compress; /* applied compress */ 924 } l2arc_read_callback_t; 925 926 typedef struct l2arc_write_callback { 927 l2arc_dev_t *l2wcb_dev; /* device info */ 928 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 929 } l2arc_write_callback_t; 930 931 typedef struct l2arc_data_free { 932 /* protected by l2arc_free_on_write_mtx */ 933 void *l2df_data; 934 size_t l2df_size; 935 void (*l2df_func)(void *, size_t); 936 list_node_t l2df_list_node; 937 } l2arc_data_free_t; 938 939 static kmutex_t l2arc_feed_thr_lock; 940 static kcondvar_t l2arc_feed_thr_cv; 941 static uint8_t l2arc_thread_exit; 942 943 static void arc_get_data_buf(arc_buf_t *); 944 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 945 static boolean_t arc_is_overflowing(); 946 static void arc_buf_watch(arc_buf_t *); 947 948 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 949 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 950 951 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 952 static void l2arc_read_done(zio_t *); 953 954 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 955 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 956 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 957 958 static uint64_t 959 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 960 { 961 uint8_t *vdva = (uint8_t *)dva; 962 uint64_t crc = -1ULL; 963 int i; 964 965 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 966 967 for (i = 0; i < sizeof (dva_t); i++) 968 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 969 970 crc ^= (spa>>8) ^ birth; 971 972 return (crc); 973 } 974 975 #define BUF_EMPTY(buf) \ 976 ((buf)->b_dva.dva_word[0] == 0 && \ 977 (buf)->b_dva.dva_word[1] == 0) 978 979 #define BUF_EQUAL(spa, dva, birth, buf) \ 980 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 981 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 982 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 983 984 static void 985 buf_discard_identity(arc_buf_hdr_t *hdr) 986 { 987 hdr->b_dva.dva_word[0] = 0; 988 hdr->b_dva.dva_word[1] = 0; 989 hdr->b_birth = 0; 990 } 991 992 static arc_buf_hdr_t * 993 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 994 { 995 const dva_t *dva = BP_IDENTITY(bp); 996 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 997 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 998 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 999 arc_buf_hdr_t *hdr; 1000 1001 mutex_enter(hash_lock); 1002 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1003 hdr = hdr->b_hash_next) { 1004 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1005 *lockp = hash_lock; 1006 return (hdr); 1007 } 1008 } 1009 mutex_exit(hash_lock); 1010 *lockp = NULL; 1011 return (NULL); 1012 } 1013 1014 /* 1015 * Insert an entry into the hash table. If there is already an element 1016 * equal to elem in the hash table, then the already existing element 1017 * will be returned and the new element will not be inserted. 1018 * Otherwise returns NULL. 1019 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1020 */ 1021 static arc_buf_hdr_t * 1022 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1023 { 1024 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1025 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1026 arc_buf_hdr_t *fhdr; 1027 uint32_t i; 1028 1029 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1030 ASSERT(hdr->b_birth != 0); 1031 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1032 1033 if (lockp != NULL) { 1034 *lockp = hash_lock; 1035 mutex_enter(hash_lock); 1036 } else { 1037 ASSERT(MUTEX_HELD(hash_lock)); 1038 } 1039 1040 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1041 fhdr = fhdr->b_hash_next, i++) { 1042 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1043 return (fhdr); 1044 } 1045 1046 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1047 buf_hash_table.ht_table[idx] = hdr; 1048 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1049 1050 /* collect some hash table performance data */ 1051 if (i > 0) { 1052 ARCSTAT_BUMP(arcstat_hash_collisions); 1053 if (i == 1) 1054 ARCSTAT_BUMP(arcstat_hash_chains); 1055 1056 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1057 } 1058 1059 ARCSTAT_BUMP(arcstat_hash_elements); 1060 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1061 1062 return (NULL); 1063 } 1064 1065 static void 1066 buf_hash_remove(arc_buf_hdr_t *hdr) 1067 { 1068 arc_buf_hdr_t *fhdr, **hdrp; 1069 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1070 1071 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1072 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1073 1074 hdrp = &buf_hash_table.ht_table[idx]; 1075 while ((fhdr = *hdrp) != hdr) { 1076 ASSERT(fhdr != NULL); 1077 hdrp = &fhdr->b_hash_next; 1078 } 1079 *hdrp = hdr->b_hash_next; 1080 hdr->b_hash_next = NULL; 1081 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1082 1083 /* collect some hash table performance data */ 1084 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1085 1086 if (buf_hash_table.ht_table[idx] && 1087 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1088 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1089 } 1090 1091 /* 1092 * Global data structures and functions for the buf kmem cache. 1093 */ 1094 static kmem_cache_t *hdr_full_cache; 1095 static kmem_cache_t *hdr_l2only_cache; 1096 static kmem_cache_t *buf_cache; 1097 1098 static void 1099 buf_fini(void) 1100 { 1101 int i; 1102 1103 kmem_free(buf_hash_table.ht_table, 1104 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1105 for (i = 0; i < BUF_LOCKS; i++) 1106 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1107 kmem_cache_destroy(hdr_full_cache); 1108 kmem_cache_destroy(hdr_l2only_cache); 1109 kmem_cache_destroy(buf_cache); 1110 } 1111 1112 /* 1113 * Constructor callback - called when the cache is empty 1114 * and a new buf is requested. 1115 */ 1116 /* ARGSUSED */ 1117 static int 1118 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1119 { 1120 arc_buf_hdr_t *hdr = vbuf; 1121 1122 bzero(hdr, HDR_FULL_SIZE); 1123 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1124 refcount_create(&hdr->b_l1hdr.b_refcnt); 1125 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1126 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1127 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1128 1129 return (0); 1130 } 1131 1132 /* ARGSUSED */ 1133 static int 1134 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1135 { 1136 arc_buf_hdr_t *hdr = vbuf; 1137 1138 bzero(hdr, HDR_L2ONLY_SIZE); 1139 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1140 1141 return (0); 1142 } 1143 1144 /* ARGSUSED */ 1145 static int 1146 buf_cons(void *vbuf, void *unused, int kmflag) 1147 { 1148 arc_buf_t *buf = vbuf; 1149 1150 bzero(buf, sizeof (arc_buf_t)); 1151 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1152 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1153 1154 return (0); 1155 } 1156 1157 /* 1158 * Destructor callback - called when a cached buf is 1159 * no longer required. 1160 */ 1161 /* ARGSUSED */ 1162 static void 1163 hdr_full_dest(void *vbuf, void *unused) 1164 { 1165 arc_buf_hdr_t *hdr = vbuf; 1166 1167 ASSERT(BUF_EMPTY(hdr)); 1168 cv_destroy(&hdr->b_l1hdr.b_cv); 1169 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1170 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1171 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1172 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1173 } 1174 1175 /* ARGSUSED */ 1176 static void 1177 hdr_l2only_dest(void *vbuf, void *unused) 1178 { 1179 arc_buf_hdr_t *hdr = vbuf; 1180 1181 ASSERT(BUF_EMPTY(hdr)); 1182 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1183 } 1184 1185 /* ARGSUSED */ 1186 static void 1187 buf_dest(void *vbuf, void *unused) 1188 { 1189 arc_buf_t *buf = vbuf; 1190 1191 mutex_destroy(&buf->b_evict_lock); 1192 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1193 } 1194 1195 /* 1196 * Reclaim callback -- invoked when memory is low. 1197 */ 1198 /* ARGSUSED */ 1199 static void 1200 hdr_recl(void *unused) 1201 { 1202 dprintf("hdr_recl called\n"); 1203 /* 1204 * umem calls the reclaim func when we destroy the buf cache, 1205 * which is after we do arc_fini(). 1206 */ 1207 if (!arc_dead) 1208 cv_signal(&arc_reclaim_thread_cv); 1209 } 1210 1211 static void 1212 buf_init(void) 1213 { 1214 uint64_t *ct; 1215 uint64_t hsize = 1ULL << 12; 1216 int i, j; 1217 1218 /* 1219 * The hash table is big enough to fill all of physical memory 1220 * with an average block size of zfs_arc_average_blocksize (default 8K). 1221 * By default, the table will take up 1222 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1223 */ 1224 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1225 hsize <<= 1; 1226 retry: 1227 buf_hash_table.ht_mask = hsize - 1; 1228 buf_hash_table.ht_table = 1229 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1230 if (buf_hash_table.ht_table == NULL) { 1231 ASSERT(hsize > (1ULL << 8)); 1232 hsize >>= 1; 1233 goto retry; 1234 } 1235 1236 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1237 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1238 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1239 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1240 NULL, NULL, 0); 1241 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1242 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1243 1244 for (i = 0; i < 256; i++) 1245 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1246 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1247 1248 for (i = 0; i < BUF_LOCKS; i++) { 1249 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1250 NULL, MUTEX_DEFAULT, NULL); 1251 } 1252 } 1253 1254 /* 1255 * Transition between the two allocation states for the arc_buf_hdr struct. 1256 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1257 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1258 * version is used when a cache buffer is only in the L2ARC in order to reduce 1259 * memory usage. 1260 */ 1261 static arc_buf_hdr_t * 1262 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1263 { 1264 ASSERT(HDR_HAS_L2HDR(hdr)); 1265 1266 arc_buf_hdr_t *nhdr; 1267 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1268 1269 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1270 (old == hdr_l2only_cache && new == hdr_full_cache)); 1271 1272 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1273 1274 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1275 buf_hash_remove(hdr); 1276 1277 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1278 1279 if (new == hdr_full_cache) { 1280 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1281 /* 1282 * arc_access and arc_change_state need to be aware that a 1283 * header has just come out of L2ARC, so we set its state to 1284 * l2c_only even though it's about to change. 1285 */ 1286 nhdr->b_l1hdr.b_state = arc_l2c_only; 1287 1288 /* Verify previous threads set to NULL before freeing */ 1289 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1290 } else { 1291 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1292 ASSERT0(hdr->b_l1hdr.b_datacnt); 1293 1294 /* 1295 * If we've reached here, We must have been called from 1296 * arc_evict_hdr(), as such we should have already been 1297 * removed from any ghost list we were previously on 1298 * (which protects us from racing with arc_evict_state), 1299 * thus no locking is needed during this check. 1300 */ 1301 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1302 1303 /* 1304 * A buffer must not be moved into the arc_l2c_only 1305 * state if it's not finished being written out to the 1306 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1307 * might try to be accessed, even though it was removed. 1308 */ 1309 VERIFY(!HDR_L2_WRITING(hdr)); 1310 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1311 1312 #ifdef ZFS_DEBUG 1313 if (hdr->b_l1hdr.b_thawed != NULL) 1314 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1315 hdr->b_l1hdr.b_thawed = NULL; 1316 #endif 1317 1318 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1319 } 1320 /* 1321 * The header has been reallocated so we need to re-insert it into any 1322 * lists it was on. 1323 */ 1324 (void) buf_hash_insert(nhdr, NULL); 1325 1326 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1327 1328 mutex_enter(&dev->l2ad_mtx); 1329 1330 /* 1331 * We must place the realloc'ed header back into the list at 1332 * the same spot. Otherwise, if it's placed earlier in the list, 1333 * l2arc_write_buffers() could find it during the function's 1334 * write phase, and try to write it out to the l2arc. 1335 */ 1336 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1337 list_remove(&dev->l2ad_buflist, hdr); 1338 1339 mutex_exit(&dev->l2ad_mtx); 1340 1341 /* 1342 * Since we're using the pointer address as the tag when 1343 * incrementing and decrementing the l2ad_alloc refcount, we 1344 * must remove the old pointer (that we're about to destroy) and 1345 * add the new pointer to the refcount. Otherwise we'd remove 1346 * the wrong pointer address when calling arc_hdr_destroy() later. 1347 */ 1348 1349 (void) refcount_remove_many(&dev->l2ad_alloc, 1350 hdr->b_l2hdr.b_asize, hdr); 1351 1352 (void) refcount_add_many(&dev->l2ad_alloc, 1353 nhdr->b_l2hdr.b_asize, nhdr); 1354 1355 buf_discard_identity(hdr); 1356 hdr->b_freeze_cksum = NULL; 1357 kmem_cache_free(old, hdr); 1358 1359 return (nhdr); 1360 } 1361 1362 1363 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1364 1365 static void 1366 arc_cksum_verify(arc_buf_t *buf) 1367 { 1368 zio_cksum_t zc; 1369 1370 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1371 return; 1372 1373 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1374 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1375 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1376 return; 1377 } 1378 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1379 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1380 panic("buffer modified while frozen!"); 1381 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1382 } 1383 1384 static int 1385 arc_cksum_equal(arc_buf_t *buf) 1386 { 1387 zio_cksum_t zc; 1388 int equal; 1389 1390 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1391 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1392 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1393 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1394 1395 return (equal); 1396 } 1397 1398 static void 1399 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1400 { 1401 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1402 return; 1403 1404 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1405 if (buf->b_hdr->b_freeze_cksum != NULL) { 1406 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1407 return; 1408 } 1409 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1410 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1411 buf->b_hdr->b_freeze_cksum); 1412 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1413 arc_buf_watch(buf); 1414 } 1415 1416 #ifndef _KERNEL 1417 typedef struct procctl { 1418 long cmd; 1419 prwatch_t prwatch; 1420 } procctl_t; 1421 #endif 1422 1423 /* ARGSUSED */ 1424 static void 1425 arc_buf_unwatch(arc_buf_t *buf) 1426 { 1427 #ifndef _KERNEL 1428 if (arc_watch) { 1429 int result; 1430 procctl_t ctl; 1431 ctl.cmd = PCWATCH; 1432 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1433 ctl.prwatch.pr_size = 0; 1434 ctl.prwatch.pr_wflags = 0; 1435 result = write(arc_procfd, &ctl, sizeof (ctl)); 1436 ASSERT3U(result, ==, sizeof (ctl)); 1437 } 1438 #endif 1439 } 1440 1441 /* ARGSUSED */ 1442 static void 1443 arc_buf_watch(arc_buf_t *buf) 1444 { 1445 #ifndef _KERNEL 1446 if (arc_watch) { 1447 int result; 1448 procctl_t ctl; 1449 ctl.cmd = PCWATCH; 1450 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1451 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1452 ctl.prwatch.pr_wflags = WA_WRITE; 1453 result = write(arc_procfd, &ctl, sizeof (ctl)); 1454 ASSERT3U(result, ==, sizeof (ctl)); 1455 } 1456 #endif 1457 } 1458 1459 static arc_buf_contents_t 1460 arc_buf_type(arc_buf_hdr_t *hdr) 1461 { 1462 if (HDR_ISTYPE_METADATA(hdr)) { 1463 return (ARC_BUFC_METADATA); 1464 } else { 1465 return (ARC_BUFC_DATA); 1466 } 1467 } 1468 1469 static uint32_t 1470 arc_bufc_to_flags(arc_buf_contents_t type) 1471 { 1472 switch (type) { 1473 case ARC_BUFC_DATA: 1474 /* metadata field is 0 if buffer contains normal data */ 1475 return (0); 1476 case ARC_BUFC_METADATA: 1477 return (ARC_FLAG_BUFC_METADATA); 1478 default: 1479 break; 1480 } 1481 panic("undefined ARC buffer type!"); 1482 return ((uint32_t)-1); 1483 } 1484 1485 void 1486 arc_buf_thaw(arc_buf_t *buf) 1487 { 1488 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1489 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1490 panic("modifying non-anon buffer!"); 1491 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1492 panic("modifying buffer while i/o in progress!"); 1493 arc_cksum_verify(buf); 1494 } 1495 1496 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1497 if (buf->b_hdr->b_freeze_cksum != NULL) { 1498 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1499 buf->b_hdr->b_freeze_cksum = NULL; 1500 } 1501 1502 #ifdef ZFS_DEBUG 1503 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1504 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1505 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1506 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1507 } 1508 #endif 1509 1510 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1511 1512 arc_buf_unwatch(buf); 1513 } 1514 1515 void 1516 arc_buf_freeze(arc_buf_t *buf) 1517 { 1518 kmutex_t *hash_lock; 1519 1520 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1521 return; 1522 1523 hash_lock = HDR_LOCK(buf->b_hdr); 1524 mutex_enter(hash_lock); 1525 1526 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1527 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1528 arc_cksum_compute(buf, B_FALSE); 1529 mutex_exit(hash_lock); 1530 1531 } 1532 1533 static void 1534 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1535 { 1536 ASSERT(HDR_HAS_L1HDR(hdr)); 1537 ASSERT(MUTEX_HELD(hash_lock)); 1538 arc_state_t *state = hdr->b_l1hdr.b_state; 1539 1540 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1541 (state != arc_anon)) { 1542 /* We don't use the L2-only state list. */ 1543 if (state != arc_l2c_only) { 1544 arc_buf_contents_t type = arc_buf_type(hdr); 1545 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1546 multilist_t *list = &state->arcs_list[type]; 1547 uint64_t *size = &state->arcs_lsize[type]; 1548 1549 multilist_remove(list, hdr); 1550 1551 if (GHOST_STATE(state)) { 1552 ASSERT0(hdr->b_l1hdr.b_datacnt); 1553 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1554 delta = hdr->b_size; 1555 } 1556 ASSERT(delta > 0); 1557 ASSERT3U(*size, >=, delta); 1558 atomic_add_64(size, -delta); 1559 } 1560 /* remove the prefetch flag if we get a reference */ 1561 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1562 } 1563 } 1564 1565 static int 1566 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1567 { 1568 int cnt; 1569 arc_state_t *state = hdr->b_l1hdr.b_state; 1570 1571 ASSERT(HDR_HAS_L1HDR(hdr)); 1572 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1573 ASSERT(!GHOST_STATE(state)); 1574 1575 /* 1576 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1577 * check to prevent usage of the arc_l2c_only list. 1578 */ 1579 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1580 (state != arc_anon)) { 1581 arc_buf_contents_t type = arc_buf_type(hdr); 1582 multilist_t *list = &state->arcs_list[type]; 1583 uint64_t *size = &state->arcs_lsize[type]; 1584 1585 multilist_insert(list, hdr); 1586 1587 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1588 atomic_add_64(size, hdr->b_size * 1589 hdr->b_l1hdr.b_datacnt); 1590 } 1591 return (cnt); 1592 } 1593 1594 /* 1595 * Move the supplied buffer to the indicated state. The hash lock 1596 * for the buffer must be held by the caller. 1597 */ 1598 static void 1599 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1600 kmutex_t *hash_lock) 1601 { 1602 arc_state_t *old_state; 1603 int64_t refcnt; 1604 uint32_t datacnt; 1605 uint64_t from_delta, to_delta; 1606 arc_buf_contents_t buftype = arc_buf_type(hdr); 1607 1608 /* 1609 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1610 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1611 * L1 hdr doesn't always exist when we change state to arc_anon before 1612 * destroying a header, in which case reallocating to add the L1 hdr is 1613 * pointless. 1614 */ 1615 if (HDR_HAS_L1HDR(hdr)) { 1616 old_state = hdr->b_l1hdr.b_state; 1617 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1618 datacnt = hdr->b_l1hdr.b_datacnt; 1619 } else { 1620 old_state = arc_l2c_only; 1621 refcnt = 0; 1622 datacnt = 0; 1623 } 1624 1625 ASSERT(MUTEX_HELD(hash_lock)); 1626 ASSERT3P(new_state, !=, old_state); 1627 ASSERT(refcnt == 0 || datacnt > 0); 1628 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1629 ASSERT(old_state != arc_anon || datacnt <= 1); 1630 1631 from_delta = to_delta = datacnt * hdr->b_size; 1632 1633 /* 1634 * If this buffer is evictable, transfer it from the 1635 * old state list to the new state list. 1636 */ 1637 if (refcnt == 0) { 1638 if (old_state != arc_anon && old_state != arc_l2c_only) { 1639 uint64_t *size = &old_state->arcs_lsize[buftype]; 1640 1641 ASSERT(HDR_HAS_L1HDR(hdr)); 1642 multilist_remove(&old_state->arcs_list[buftype], hdr); 1643 1644 /* 1645 * If prefetching out of the ghost cache, 1646 * we will have a non-zero datacnt. 1647 */ 1648 if (GHOST_STATE(old_state) && datacnt == 0) { 1649 /* ghost elements have a ghost size */ 1650 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1651 from_delta = hdr->b_size; 1652 } 1653 ASSERT3U(*size, >=, from_delta); 1654 atomic_add_64(size, -from_delta); 1655 } 1656 if (new_state != arc_anon && new_state != arc_l2c_only) { 1657 uint64_t *size = &new_state->arcs_lsize[buftype]; 1658 1659 /* 1660 * An L1 header always exists here, since if we're 1661 * moving to some L1-cached state (i.e. not l2c_only or 1662 * anonymous), we realloc the header to add an L1hdr 1663 * beforehand. 1664 */ 1665 ASSERT(HDR_HAS_L1HDR(hdr)); 1666 multilist_insert(&new_state->arcs_list[buftype], hdr); 1667 1668 /* ghost elements have a ghost size */ 1669 if (GHOST_STATE(new_state)) { 1670 ASSERT0(datacnt); 1671 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1672 to_delta = hdr->b_size; 1673 } 1674 atomic_add_64(size, to_delta); 1675 } 1676 } 1677 1678 ASSERT(!BUF_EMPTY(hdr)); 1679 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1680 buf_hash_remove(hdr); 1681 1682 /* adjust state sizes (ignore arc_l2c_only) */ 1683 1684 if (to_delta && new_state != arc_l2c_only) { 1685 ASSERT(HDR_HAS_L1HDR(hdr)); 1686 if (GHOST_STATE(new_state)) { 1687 ASSERT0(datacnt); 1688 1689 /* 1690 * We moving a header to a ghost state, we first 1691 * remove all arc buffers. Thus, we'll have a 1692 * datacnt of zero, and no arc buffer to use for 1693 * the reference. As a result, we use the arc 1694 * header pointer for the reference. 1695 */ 1696 (void) refcount_add_many(&new_state->arcs_size, 1697 hdr->b_size, hdr); 1698 } else { 1699 ASSERT3U(datacnt, !=, 0); 1700 1701 /* 1702 * Each individual buffer holds a unique reference, 1703 * thus we must remove each of these references one 1704 * at a time. 1705 */ 1706 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1707 buf = buf->b_next) { 1708 (void) refcount_add_many(&new_state->arcs_size, 1709 hdr->b_size, buf); 1710 } 1711 } 1712 } 1713 1714 if (from_delta && old_state != arc_l2c_only) { 1715 ASSERT(HDR_HAS_L1HDR(hdr)); 1716 if (GHOST_STATE(old_state)) { 1717 /* 1718 * When moving a header off of a ghost state, 1719 * there's the possibility for datacnt to be 1720 * non-zero. This is because we first add the 1721 * arc buffer to the header prior to changing 1722 * the header's state. Since we used the header 1723 * for the reference when putting the header on 1724 * the ghost state, we must balance that and use 1725 * the header when removing off the ghost state 1726 * (even though datacnt is non zero). 1727 */ 1728 1729 IMPLY(datacnt == 0, new_state == arc_anon || 1730 new_state == arc_l2c_only); 1731 1732 (void) refcount_remove_many(&old_state->arcs_size, 1733 hdr->b_size, hdr); 1734 } else { 1735 ASSERT3P(datacnt, !=, 0); 1736 1737 /* 1738 * Each individual buffer holds a unique reference, 1739 * thus we must remove each of these references one 1740 * at a time. 1741 */ 1742 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1743 buf = buf->b_next) { 1744 (void) refcount_remove_many( 1745 &old_state->arcs_size, hdr->b_size, buf); 1746 } 1747 } 1748 } 1749 1750 if (HDR_HAS_L1HDR(hdr)) 1751 hdr->b_l1hdr.b_state = new_state; 1752 1753 /* 1754 * L2 headers should never be on the L2 state list since they don't 1755 * have L1 headers allocated. 1756 */ 1757 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1758 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1759 } 1760 1761 void 1762 arc_space_consume(uint64_t space, arc_space_type_t type) 1763 { 1764 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1765 1766 switch (type) { 1767 case ARC_SPACE_DATA: 1768 ARCSTAT_INCR(arcstat_data_size, space); 1769 break; 1770 case ARC_SPACE_META: 1771 ARCSTAT_INCR(arcstat_metadata_size, space); 1772 break; 1773 case ARC_SPACE_OTHER: 1774 ARCSTAT_INCR(arcstat_other_size, space); 1775 break; 1776 case ARC_SPACE_HDRS: 1777 ARCSTAT_INCR(arcstat_hdr_size, space); 1778 break; 1779 case ARC_SPACE_L2HDRS: 1780 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1781 break; 1782 } 1783 1784 if (type != ARC_SPACE_DATA) 1785 ARCSTAT_INCR(arcstat_meta_used, space); 1786 1787 atomic_add_64(&arc_size, space); 1788 } 1789 1790 void 1791 arc_space_return(uint64_t space, arc_space_type_t type) 1792 { 1793 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1794 1795 switch (type) { 1796 case ARC_SPACE_DATA: 1797 ARCSTAT_INCR(arcstat_data_size, -space); 1798 break; 1799 case ARC_SPACE_META: 1800 ARCSTAT_INCR(arcstat_metadata_size, -space); 1801 break; 1802 case ARC_SPACE_OTHER: 1803 ARCSTAT_INCR(arcstat_other_size, -space); 1804 break; 1805 case ARC_SPACE_HDRS: 1806 ARCSTAT_INCR(arcstat_hdr_size, -space); 1807 break; 1808 case ARC_SPACE_L2HDRS: 1809 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1810 break; 1811 } 1812 1813 if (type != ARC_SPACE_DATA) { 1814 ASSERT(arc_meta_used >= space); 1815 if (arc_meta_max < arc_meta_used) 1816 arc_meta_max = arc_meta_used; 1817 ARCSTAT_INCR(arcstat_meta_used, -space); 1818 } 1819 1820 ASSERT(arc_size >= space); 1821 atomic_add_64(&arc_size, -space); 1822 } 1823 1824 arc_buf_t * 1825 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1826 { 1827 arc_buf_hdr_t *hdr; 1828 arc_buf_t *buf; 1829 1830 ASSERT3U(size, >, 0); 1831 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1832 ASSERT(BUF_EMPTY(hdr)); 1833 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1834 hdr->b_size = size; 1835 hdr->b_spa = spa_load_guid(spa); 1836 1837 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1838 buf->b_hdr = hdr; 1839 buf->b_data = NULL; 1840 buf->b_efunc = NULL; 1841 buf->b_private = NULL; 1842 buf->b_next = NULL; 1843 1844 hdr->b_flags = arc_bufc_to_flags(type); 1845 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1846 1847 hdr->b_l1hdr.b_buf = buf; 1848 hdr->b_l1hdr.b_state = arc_anon; 1849 hdr->b_l1hdr.b_arc_access = 0; 1850 hdr->b_l1hdr.b_datacnt = 1; 1851 hdr->b_l1hdr.b_tmp_cdata = NULL; 1852 1853 arc_get_data_buf(buf); 1854 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1855 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1856 1857 return (buf); 1858 } 1859 1860 static char *arc_onloan_tag = "onloan"; 1861 1862 /* 1863 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1864 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1865 * buffers must be returned to the arc before they can be used by the DMU or 1866 * freed. 1867 */ 1868 arc_buf_t * 1869 arc_loan_buf(spa_t *spa, int size) 1870 { 1871 arc_buf_t *buf; 1872 1873 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1874 1875 atomic_add_64(&arc_loaned_bytes, size); 1876 return (buf); 1877 } 1878 1879 /* 1880 * Return a loaned arc buffer to the arc. 1881 */ 1882 void 1883 arc_return_buf(arc_buf_t *buf, void *tag) 1884 { 1885 arc_buf_hdr_t *hdr = buf->b_hdr; 1886 1887 ASSERT(buf->b_data != NULL); 1888 ASSERT(HDR_HAS_L1HDR(hdr)); 1889 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1890 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1891 1892 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1893 } 1894 1895 /* Detach an arc_buf from a dbuf (tag) */ 1896 void 1897 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1898 { 1899 arc_buf_hdr_t *hdr = buf->b_hdr; 1900 1901 ASSERT(buf->b_data != NULL); 1902 ASSERT(HDR_HAS_L1HDR(hdr)); 1903 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1904 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 1905 buf->b_efunc = NULL; 1906 buf->b_private = NULL; 1907 1908 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1909 } 1910 1911 static arc_buf_t * 1912 arc_buf_clone(arc_buf_t *from) 1913 { 1914 arc_buf_t *buf; 1915 arc_buf_hdr_t *hdr = from->b_hdr; 1916 uint64_t size = hdr->b_size; 1917 1918 ASSERT(HDR_HAS_L1HDR(hdr)); 1919 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 1920 1921 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1922 buf->b_hdr = hdr; 1923 buf->b_data = NULL; 1924 buf->b_efunc = NULL; 1925 buf->b_private = NULL; 1926 buf->b_next = hdr->b_l1hdr.b_buf; 1927 hdr->b_l1hdr.b_buf = buf; 1928 arc_get_data_buf(buf); 1929 bcopy(from->b_data, buf->b_data, size); 1930 1931 /* 1932 * This buffer already exists in the arc so create a duplicate 1933 * copy for the caller. If the buffer is associated with user data 1934 * then track the size and number of duplicates. These stats will be 1935 * updated as duplicate buffers are created and destroyed. 1936 */ 1937 if (HDR_ISTYPE_DATA(hdr)) { 1938 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1939 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1940 } 1941 hdr->b_l1hdr.b_datacnt += 1; 1942 return (buf); 1943 } 1944 1945 void 1946 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1947 { 1948 arc_buf_hdr_t *hdr; 1949 kmutex_t *hash_lock; 1950 1951 /* 1952 * Check to see if this buffer is evicted. Callers 1953 * must verify b_data != NULL to know if the add_ref 1954 * was successful. 1955 */ 1956 mutex_enter(&buf->b_evict_lock); 1957 if (buf->b_data == NULL) { 1958 mutex_exit(&buf->b_evict_lock); 1959 return; 1960 } 1961 hash_lock = HDR_LOCK(buf->b_hdr); 1962 mutex_enter(hash_lock); 1963 hdr = buf->b_hdr; 1964 ASSERT(HDR_HAS_L1HDR(hdr)); 1965 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1966 mutex_exit(&buf->b_evict_lock); 1967 1968 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 1969 hdr->b_l1hdr.b_state == arc_mfu); 1970 1971 add_reference(hdr, hash_lock, tag); 1972 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1973 arc_access(hdr, hash_lock); 1974 mutex_exit(hash_lock); 1975 ARCSTAT_BUMP(arcstat_hits); 1976 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 1977 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 1978 data, metadata, hits); 1979 } 1980 1981 static void 1982 arc_buf_free_on_write(void *data, size_t size, 1983 void (*free_func)(void *, size_t)) 1984 { 1985 l2arc_data_free_t *df; 1986 1987 df = kmem_alloc(sizeof (*df), KM_SLEEP); 1988 df->l2df_data = data; 1989 df->l2df_size = size; 1990 df->l2df_func = free_func; 1991 mutex_enter(&l2arc_free_on_write_mtx); 1992 list_insert_head(l2arc_free_on_write, df); 1993 mutex_exit(&l2arc_free_on_write_mtx); 1994 } 1995 1996 /* 1997 * Free the arc data buffer. If it is an l2arc write in progress, 1998 * the buffer is placed on l2arc_free_on_write to be freed later. 1999 */ 2000 static void 2001 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2002 { 2003 arc_buf_hdr_t *hdr = buf->b_hdr; 2004 2005 if (HDR_L2_WRITING(hdr)) { 2006 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2007 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2008 } else { 2009 free_func(buf->b_data, hdr->b_size); 2010 } 2011 } 2012 2013 static void 2014 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2015 { 2016 ASSERT(HDR_HAS_L2HDR(hdr)); 2017 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2018 2019 /* 2020 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2021 * that doesn't exist, the header is in the arc_l2c_only state, 2022 * and there isn't anything to free (it's already been freed). 2023 */ 2024 if (!HDR_HAS_L1HDR(hdr)) 2025 return; 2026 2027 /* 2028 * The header isn't being written to the l2arc device, thus it 2029 * shouldn't have a b_tmp_cdata to free. 2030 */ 2031 if (!HDR_L2_WRITING(hdr)) { 2032 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2033 return; 2034 } 2035 2036 /* 2037 * The header does not have compression enabled. This can be due 2038 * to the buffer not being compressible, or because we're 2039 * freeing the buffer before the second phase of 2040 * l2arc_write_buffer() has started (which does the compression 2041 * step). In either case, b_tmp_cdata does not point to a 2042 * separately compressed buffer, so there's nothing to free (it 2043 * points to the same buffer as the arc_buf_t's b_data field). 2044 */ 2045 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 2046 hdr->b_l1hdr.b_tmp_cdata = NULL; 2047 return; 2048 } 2049 2050 /* 2051 * There's nothing to free since the buffer was all zero's and 2052 * compressed to a zero length buffer. 2053 */ 2054 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) { 2055 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2056 return; 2057 } 2058 2059 ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))); 2060 2061 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2062 hdr->b_size, zio_data_buf_free); 2063 2064 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2065 hdr->b_l1hdr.b_tmp_cdata = NULL; 2066 } 2067 2068 /* 2069 * Free up buf->b_data and if 'remove' is set, then pull the 2070 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2071 */ 2072 static void 2073 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2074 { 2075 arc_buf_t **bufp; 2076 2077 /* free up data associated with the buf */ 2078 if (buf->b_data != NULL) { 2079 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2080 uint64_t size = buf->b_hdr->b_size; 2081 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2082 2083 arc_cksum_verify(buf); 2084 arc_buf_unwatch(buf); 2085 2086 if (type == ARC_BUFC_METADATA) { 2087 arc_buf_data_free(buf, zio_buf_free); 2088 arc_space_return(size, ARC_SPACE_META); 2089 } else { 2090 ASSERT(type == ARC_BUFC_DATA); 2091 arc_buf_data_free(buf, zio_data_buf_free); 2092 arc_space_return(size, ARC_SPACE_DATA); 2093 } 2094 2095 /* protected by hash lock, if in the hash table */ 2096 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2097 uint64_t *cnt = &state->arcs_lsize[type]; 2098 2099 ASSERT(refcount_is_zero( 2100 &buf->b_hdr->b_l1hdr.b_refcnt)); 2101 ASSERT(state != arc_anon && state != arc_l2c_only); 2102 2103 ASSERT3U(*cnt, >=, size); 2104 atomic_add_64(cnt, -size); 2105 } 2106 2107 (void) refcount_remove_many(&state->arcs_size, size, buf); 2108 buf->b_data = NULL; 2109 2110 /* 2111 * If we're destroying a duplicate buffer make sure 2112 * that the appropriate statistics are updated. 2113 */ 2114 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2115 HDR_ISTYPE_DATA(buf->b_hdr)) { 2116 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2117 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2118 } 2119 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2120 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2121 } 2122 2123 /* only remove the buf if requested */ 2124 if (!remove) 2125 return; 2126 2127 /* remove the buf from the hdr list */ 2128 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2129 bufp = &(*bufp)->b_next) 2130 continue; 2131 *bufp = buf->b_next; 2132 buf->b_next = NULL; 2133 2134 ASSERT(buf->b_efunc == NULL); 2135 2136 /* clean up the buf */ 2137 buf->b_hdr = NULL; 2138 kmem_cache_free(buf_cache, buf); 2139 } 2140 2141 static void 2142 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2143 { 2144 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2145 l2arc_dev_t *dev = l2hdr->b_dev; 2146 2147 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2148 ASSERT(HDR_HAS_L2HDR(hdr)); 2149 2150 list_remove(&dev->l2ad_buflist, hdr); 2151 2152 /* 2153 * We don't want to leak the b_tmp_cdata buffer that was 2154 * allocated in l2arc_write_buffers() 2155 */ 2156 arc_buf_l2_cdata_free(hdr); 2157 2158 /* 2159 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2160 * this header is being processed by l2arc_write_buffers() (i.e. 2161 * it's in the first stage of l2arc_write_buffers()). 2162 * Re-affirming that truth here, just to serve as a reminder. If 2163 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2164 * may not have its HDR_L2_WRITING flag set. (the write may have 2165 * completed, in which case HDR_L2_WRITING will be false and the 2166 * b_daddr field will point to the address of the buffer on disk). 2167 */ 2168 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2169 2170 /* 2171 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2172 * l2arc_write_buffers(). Since we've just removed this header 2173 * from the l2arc buffer list, this header will never reach the 2174 * second stage of l2arc_write_buffers(), which increments the 2175 * accounting stats for this header. Thus, we must be careful 2176 * not to decrement them for this header either. 2177 */ 2178 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2179 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2180 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2181 2182 vdev_space_update(dev->l2ad_vdev, 2183 -l2hdr->b_asize, 0, 0); 2184 2185 (void) refcount_remove_many(&dev->l2ad_alloc, 2186 l2hdr->b_asize, hdr); 2187 } 2188 2189 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2190 } 2191 2192 static void 2193 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2194 { 2195 if (HDR_HAS_L1HDR(hdr)) { 2196 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2197 hdr->b_l1hdr.b_datacnt > 0); 2198 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2199 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2200 } 2201 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2202 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2203 2204 if (HDR_HAS_L2HDR(hdr)) { 2205 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2206 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2207 2208 if (!buflist_held) 2209 mutex_enter(&dev->l2ad_mtx); 2210 2211 /* 2212 * Even though we checked this conditional above, we 2213 * need to check this again now that we have the 2214 * l2ad_mtx. This is because we could be racing with 2215 * another thread calling l2arc_evict() which might have 2216 * destroyed this header's L2 portion as we were waiting 2217 * to acquire the l2ad_mtx. If that happens, we don't 2218 * want to re-destroy the header's L2 portion. 2219 */ 2220 if (HDR_HAS_L2HDR(hdr)) 2221 arc_hdr_l2hdr_destroy(hdr); 2222 2223 if (!buflist_held) 2224 mutex_exit(&dev->l2ad_mtx); 2225 } 2226 2227 if (!BUF_EMPTY(hdr)) 2228 buf_discard_identity(hdr); 2229 2230 if (hdr->b_freeze_cksum != NULL) { 2231 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2232 hdr->b_freeze_cksum = NULL; 2233 } 2234 2235 if (HDR_HAS_L1HDR(hdr)) { 2236 while (hdr->b_l1hdr.b_buf) { 2237 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2238 2239 if (buf->b_efunc != NULL) { 2240 mutex_enter(&arc_user_evicts_lock); 2241 mutex_enter(&buf->b_evict_lock); 2242 ASSERT(buf->b_hdr != NULL); 2243 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2244 hdr->b_l1hdr.b_buf = buf->b_next; 2245 buf->b_hdr = &arc_eviction_hdr; 2246 buf->b_next = arc_eviction_list; 2247 arc_eviction_list = buf; 2248 mutex_exit(&buf->b_evict_lock); 2249 cv_signal(&arc_user_evicts_cv); 2250 mutex_exit(&arc_user_evicts_lock); 2251 } else { 2252 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2253 } 2254 } 2255 #ifdef ZFS_DEBUG 2256 if (hdr->b_l1hdr.b_thawed != NULL) { 2257 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2258 hdr->b_l1hdr.b_thawed = NULL; 2259 } 2260 #endif 2261 } 2262 2263 ASSERT3P(hdr->b_hash_next, ==, NULL); 2264 if (HDR_HAS_L1HDR(hdr)) { 2265 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2266 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2267 kmem_cache_free(hdr_full_cache, hdr); 2268 } else { 2269 kmem_cache_free(hdr_l2only_cache, hdr); 2270 } 2271 } 2272 2273 void 2274 arc_buf_free(arc_buf_t *buf, void *tag) 2275 { 2276 arc_buf_hdr_t *hdr = buf->b_hdr; 2277 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2278 2279 ASSERT(buf->b_efunc == NULL); 2280 ASSERT(buf->b_data != NULL); 2281 2282 if (hashed) { 2283 kmutex_t *hash_lock = HDR_LOCK(hdr); 2284 2285 mutex_enter(hash_lock); 2286 hdr = buf->b_hdr; 2287 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2288 2289 (void) remove_reference(hdr, hash_lock, tag); 2290 if (hdr->b_l1hdr.b_datacnt > 1) { 2291 arc_buf_destroy(buf, TRUE); 2292 } else { 2293 ASSERT(buf == hdr->b_l1hdr.b_buf); 2294 ASSERT(buf->b_efunc == NULL); 2295 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2296 } 2297 mutex_exit(hash_lock); 2298 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2299 int destroy_hdr; 2300 /* 2301 * We are in the middle of an async write. Don't destroy 2302 * this buffer unless the write completes before we finish 2303 * decrementing the reference count. 2304 */ 2305 mutex_enter(&arc_user_evicts_lock); 2306 (void) remove_reference(hdr, NULL, tag); 2307 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2308 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2309 mutex_exit(&arc_user_evicts_lock); 2310 if (destroy_hdr) 2311 arc_hdr_destroy(hdr); 2312 } else { 2313 if (remove_reference(hdr, NULL, tag) > 0) 2314 arc_buf_destroy(buf, TRUE); 2315 else 2316 arc_hdr_destroy(hdr); 2317 } 2318 } 2319 2320 boolean_t 2321 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2322 { 2323 arc_buf_hdr_t *hdr = buf->b_hdr; 2324 kmutex_t *hash_lock = HDR_LOCK(hdr); 2325 boolean_t no_callback = (buf->b_efunc == NULL); 2326 2327 if (hdr->b_l1hdr.b_state == arc_anon) { 2328 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2329 arc_buf_free(buf, tag); 2330 return (no_callback); 2331 } 2332 2333 mutex_enter(hash_lock); 2334 hdr = buf->b_hdr; 2335 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2336 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2337 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2338 ASSERT(buf->b_data != NULL); 2339 2340 (void) remove_reference(hdr, hash_lock, tag); 2341 if (hdr->b_l1hdr.b_datacnt > 1) { 2342 if (no_callback) 2343 arc_buf_destroy(buf, TRUE); 2344 } else if (no_callback) { 2345 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2346 ASSERT(buf->b_efunc == NULL); 2347 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2348 } 2349 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2350 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2351 mutex_exit(hash_lock); 2352 return (no_callback); 2353 } 2354 2355 int32_t 2356 arc_buf_size(arc_buf_t *buf) 2357 { 2358 return (buf->b_hdr->b_size); 2359 } 2360 2361 /* 2362 * Called from the DMU to determine if the current buffer should be 2363 * evicted. In order to ensure proper locking, the eviction must be initiated 2364 * from the DMU. Return true if the buffer is associated with user data and 2365 * duplicate buffers still exist. 2366 */ 2367 boolean_t 2368 arc_buf_eviction_needed(arc_buf_t *buf) 2369 { 2370 arc_buf_hdr_t *hdr; 2371 boolean_t evict_needed = B_FALSE; 2372 2373 if (zfs_disable_dup_eviction) 2374 return (B_FALSE); 2375 2376 mutex_enter(&buf->b_evict_lock); 2377 hdr = buf->b_hdr; 2378 if (hdr == NULL) { 2379 /* 2380 * We are in arc_do_user_evicts(); let that function 2381 * perform the eviction. 2382 */ 2383 ASSERT(buf->b_data == NULL); 2384 mutex_exit(&buf->b_evict_lock); 2385 return (B_FALSE); 2386 } else if (buf->b_data == NULL) { 2387 /* 2388 * We have already been added to the arc eviction list; 2389 * recommend eviction. 2390 */ 2391 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2392 mutex_exit(&buf->b_evict_lock); 2393 return (B_TRUE); 2394 } 2395 2396 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2397 evict_needed = B_TRUE; 2398 2399 mutex_exit(&buf->b_evict_lock); 2400 return (evict_needed); 2401 } 2402 2403 /* 2404 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2405 * state of the header is dependent on it's state prior to entering this 2406 * function. The following transitions are possible: 2407 * 2408 * - arc_mru -> arc_mru_ghost 2409 * - arc_mfu -> arc_mfu_ghost 2410 * - arc_mru_ghost -> arc_l2c_only 2411 * - arc_mru_ghost -> deleted 2412 * - arc_mfu_ghost -> arc_l2c_only 2413 * - arc_mfu_ghost -> deleted 2414 */ 2415 static int64_t 2416 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2417 { 2418 arc_state_t *evicted_state, *state; 2419 int64_t bytes_evicted = 0; 2420 2421 ASSERT(MUTEX_HELD(hash_lock)); 2422 ASSERT(HDR_HAS_L1HDR(hdr)); 2423 2424 state = hdr->b_l1hdr.b_state; 2425 if (GHOST_STATE(state)) { 2426 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2427 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2428 2429 /* 2430 * l2arc_write_buffers() relies on a header's L1 portion 2431 * (i.e. it's b_tmp_cdata field) during it's write phase. 2432 * Thus, we cannot push a header onto the arc_l2c_only 2433 * state (removing it's L1 piece) until the header is 2434 * done being written to the l2arc. 2435 */ 2436 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2437 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2438 return (bytes_evicted); 2439 } 2440 2441 ARCSTAT_BUMP(arcstat_deleted); 2442 bytes_evicted += hdr->b_size; 2443 2444 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2445 2446 if (HDR_HAS_L2HDR(hdr)) { 2447 /* 2448 * This buffer is cached on the 2nd Level ARC; 2449 * don't destroy the header. 2450 */ 2451 arc_change_state(arc_l2c_only, hdr, hash_lock); 2452 /* 2453 * dropping from L1+L2 cached to L2-only, 2454 * realloc to remove the L1 header. 2455 */ 2456 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2457 hdr_l2only_cache); 2458 } else { 2459 arc_change_state(arc_anon, hdr, hash_lock); 2460 arc_hdr_destroy(hdr); 2461 } 2462 return (bytes_evicted); 2463 } 2464 2465 ASSERT(state == arc_mru || state == arc_mfu); 2466 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2467 2468 /* prefetch buffers have a minimum lifespan */ 2469 if (HDR_IO_IN_PROGRESS(hdr) || 2470 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2471 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2472 arc_min_prefetch_lifespan)) { 2473 ARCSTAT_BUMP(arcstat_evict_skip); 2474 return (bytes_evicted); 2475 } 2476 2477 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2478 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2479 while (hdr->b_l1hdr.b_buf) { 2480 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2481 if (!mutex_tryenter(&buf->b_evict_lock)) { 2482 ARCSTAT_BUMP(arcstat_mutex_miss); 2483 break; 2484 } 2485 if (buf->b_data != NULL) 2486 bytes_evicted += hdr->b_size; 2487 if (buf->b_efunc != NULL) { 2488 mutex_enter(&arc_user_evicts_lock); 2489 arc_buf_destroy(buf, FALSE); 2490 hdr->b_l1hdr.b_buf = buf->b_next; 2491 buf->b_hdr = &arc_eviction_hdr; 2492 buf->b_next = arc_eviction_list; 2493 arc_eviction_list = buf; 2494 cv_signal(&arc_user_evicts_cv); 2495 mutex_exit(&arc_user_evicts_lock); 2496 mutex_exit(&buf->b_evict_lock); 2497 } else { 2498 mutex_exit(&buf->b_evict_lock); 2499 arc_buf_destroy(buf, TRUE); 2500 } 2501 } 2502 2503 if (HDR_HAS_L2HDR(hdr)) { 2504 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2505 } else { 2506 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2507 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2508 else 2509 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2510 } 2511 2512 if (hdr->b_l1hdr.b_datacnt == 0) { 2513 arc_change_state(evicted_state, hdr, hash_lock); 2514 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2515 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2516 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2517 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2518 } 2519 2520 return (bytes_evicted); 2521 } 2522 2523 static uint64_t 2524 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2525 uint64_t spa, int64_t bytes) 2526 { 2527 multilist_sublist_t *mls; 2528 uint64_t bytes_evicted = 0; 2529 arc_buf_hdr_t *hdr; 2530 kmutex_t *hash_lock; 2531 int evict_count = 0; 2532 2533 ASSERT3P(marker, !=, NULL); 2534 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2535 2536 mls = multilist_sublist_lock(ml, idx); 2537 2538 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2539 hdr = multilist_sublist_prev(mls, marker)) { 2540 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2541 (evict_count >= zfs_arc_evict_batch_limit)) 2542 break; 2543 2544 /* 2545 * To keep our iteration location, move the marker 2546 * forward. Since we're not holding hdr's hash lock, we 2547 * must be very careful and not remove 'hdr' from the 2548 * sublist. Otherwise, other consumers might mistake the 2549 * 'hdr' as not being on a sublist when they call the 2550 * multilist_link_active() function (they all rely on 2551 * the hash lock protecting concurrent insertions and 2552 * removals). multilist_sublist_move_forward() was 2553 * specifically implemented to ensure this is the case 2554 * (only 'marker' will be removed and re-inserted). 2555 */ 2556 multilist_sublist_move_forward(mls, marker); 2557 2558 /* 2559 * The only case where the b_spa field should ever be 2560 * zero, is the marker headers inserted by 2561 * arc_evict_state(). It's possible for multiple threads 2562 * to be calling arc_evict_state() concurrently (e.g. 2563 * dsl_pool_close() and zio_inject_fault()), so we must 2564 * skip any markers we see from these other threads. 2565 */ 2566 if (hdr->b_spa == 0) 2567 continue; 2568 2569 /* we're only interested in evicting buffers of a certain spa */ 2570 if (spa != 0 && hdr->b_spa != spa) { 2571 ARCSTAT_BUMP(arcstat_evict_skip); 2572 continue; 2573 } 2574 2575 hash_lock = HDR_LOCK(hdr); 2576 2577 /* 2578 * We aren't calling this function from any code path 2579 * that would already be holding a hash lock, so we're 2580 * asserting on this assumption to be defensive in case 2581 * this ever changes. Without this check, it would be 2582 * possible to incorrectly increment arcstat_mutex_miss 2583 * below (e.g. if the code changed such that we called 2584 * this function with a hash lock held). 2585 */ 2586 ASSERT(!MUTEX_HELD(hash_lock)); 2587 2588 if (mutex_tryenter(hash_lock)) { 2589 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2590 mutex_exit(hash_lock); 2591 2592 bytes_evicted += evicted; 2593 2594 /* 2595 * If evicted is zero, arc_evict_hdr() must have 2596 * decided to skip this header, don't increment 2597 * evict_count in this case. 2598 */ 2599 if (evicted != 0) 2600 evict_count++; 2601 2602 /* 2603 * If arc_size isn't overflowing, signal any 2604 * threads that might happen to be waiting. 2605 * 2606 * For each header evicted, we wake up a single 2607 * thread. If we used cv_broadcast, we could 2608 * wake up "too many" threads causing arc_size 2609 * to significantly overflow arc_c; since 2610 * arc_get_data_buf() doesn't check for overflow 2611 * when it's woken up (it doesn't because it's 2612 * possible for the ARC to be overflowing while 2613 * full of un-evictable buffers, and the 2614 * function should proceed in this case). 2615 * 2616 * If threads are left sleeping, due to not 2617 * using cv_broadcast, they will be woken up 2618 * just before arc_reclaim_thread() sleeps. 2619 */ 2620 mutex_enter(&arc_reclaim_lock); 2621 if (!arc_is_overflowing()) 2622 cv_signal(&arc_reclaim_waiters_cv); 2623 mutex_exit(&arc_reclaim_lock); 2624 } else { 2625 ARCSTAT_BUMP(arcstat_mutex_miss); 2626 } 2627 } 2628 2629 multilist_sublist_unlock(mls); 2630 2631 return (bytes_evicted); 2632 } 2633 2634 /* 2635 * Evict buffers from the given arc state, until we've removed the 2636 * specified number of bytes. Move the removed buffers to the 2637 * appropriate evict state. 2638 * 2639 * This function makes a "best effort". It skips over any buffers 2640 * it can't get a hash_lock on, and so, may not catch all candidates. 2641 * It may also return without evicting as much space as requested. 2642 * 2643 * If bytes is specified using the special value ARC_EVICT_ALL, this 2644 * will evict all available (i.e. unlocked and evictable) buffers from 2645 * the given arc state; which is used by arc_flush(). 2646 */ 2647 static uint64_t 2648 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2649 arc_buf_contents_t type) 2650 { 2651 uint64_t total_evicted = 0; 2652 multilist_t *ml = &state->arcs_list[type]; 2653 int num_sublists; 2654 arc_buf_hdr_t **markers; 2655 2656 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2657 2658 num_sublists = multilist_get_num_sublists(ml); 2659 2660 /* 2661 * If we've tried to evict from each sublist, made some 2662 * progress, but still have not hit the target number of bytes 2663 * to evict, we want to keep trying. The markers allow us to 2664 * pick up where we left off for each individual sublist, rather 2665 * than starting from the tail each time. 2666 */ 2667 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2668 for (int i = 0; i < num_sublists; i++) { 2669 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2670 2671 /* 2672 * A b_spa of 0 is used to indicate that this header is 2673 * a marker. This fact is used in arc_adjust_type() and 2674 * arc_evict_state_impl(). 2675 */ 2676 markers[i]->b_spa = 0; 2677 2678 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2679 multilist_sublist_insert_tail(mls, markers[i]); 2680 multilist_sublist_unlock(mls); 2681 } 2682 2683 /* 2684 * While we haven't hit our target number of bytes to evict, or 2685 * we're evicting all available buffers. 2686 */ 2687 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2688 /* 2689 * Start eviction using a randomly selected sublist, 2690 * this is to try and evenly balance eviction across all 2691 * sublists. Always starting at the same sublist 2692 * (e.g. index 0) would cause evictions to favor certain 2693 * sublists over others. 2694 */ 2695 int sublist_idx = multilist_get_random_index(ml); 2696 uint64_t scan_evicted = 0; 2697 2698 for (int i = 0; i < num_sublists; i++) { 2699 uint64_t bytes_remaining; 2700 uint64_t bytes_evicted; 2701 2702 if (bytes == ARC_EVICT_ALL) 2703 bytes_remaining = ARC_EVICT_ALL; 2704 else if (total_evicted < bytes) 2705 bytes_remaining = bytes - total_evicted; 2706 else 2707 break; 2708 2709 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2710 markers[sublist_idx], spa, bytes_remaining); 2711 2712 scan_evicted += bytes_evicted; 2713 total_evicted += bytes_evicted; 2714 2715 /* we've reached the end, wrap to the beginning */ 2716 if (++sublist_idx >= num_sublists) 2717 sublist_idx = 0; 2718 } 2719 2720 /* 2721 * If we didn't evict anything during this scan, we have 2722 * no reason to believe we'll evict more during another 2723 * scan, so break the loop. 2724 */ 2725 if (scan_evicted == 0) { 2726 /* This isn't possible, let's make that obvious */ 2727 ASSERT3S(bytes, !=, 0); 2728 2729 /* 2730 * When bytes is ARC_EVICT_ALL, the only way to 2731 * break the loop is when scan_evicted is zero. 2732 * In that case, we actually have evicted enough, 2733 * so we don't want to increment the kstat. 2734 */ 2735 if (bytes != ARC_EVICT_ALL) { 2736 ASSERT3S(total_evicted, <, bytes); 2737 ARCSTAT_BUMP(arcstat_evict_not_enough); 2738 } 2739 2740 break; 2741 } 2742 } 2743 2744 for (int i = 0; i < num_sublists; i++) { 2745 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2746 multilist_sublist_remove(mls, markers[i]); 2747 multilist_sublist_unlock(mls); 2748 2749 kmem_cache_free(hdr_full_cache, markers[i]); 2750 } 2751 kmem_free(markers, sizeof (*markers) * num_sublists); 2752 2753 return (total_evicted); 2754 } 2755 2756 /* 2757 * Flush all "evictable" data of the given type from the arc state 2758 * specified. This will not evict any "active" buffers (i.e. referenced). 2759 * 2760 * When 'retry' is set to FALSE, the function will make a single pass 2761 * over the state and evict any buffers that it can. Since it doesn't 2762 * continually retry the eviction, it might end up leaving some buffers 2763 * in the ARC due to lock misses. 2764 * 2765 * When 'retry' is set to TRUE, the function will continually retry the 2766 * eviction until *all* evictable buffers have been removed from the 2767 * state. As a result, if concurrent insertions into the state are 2768 * allowed (e.g. if the ARC isn't shutting down), this function might 2769 * wind up in an infinite loop, continually trying to evict buffers. 2770 */ 2771 static uint64_t 2772 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2773 boolean_t retry) 2774 { 2775 uint64_t evicted = 0; 2776 2777 while (state->arcs_lsize[type] != 0) { 2778 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2779 2780 if (!retry) 2781 break; 2782 } 2783 2784 return (evicted); 2785 } 2786 2787 /* 2788 * Evict the specified number of bytes from the state specified, 2789 * restricting eviction to the spa and type given. This function 2790 * prevents us from trying to evict more from a state's list than 2791 * is "evictable", and to skip evicting altogether when passed a 2792 * negative value for "bytes". In contrast, arc_evict_state() will 2793 * evict everything it can, when passed a negative value for "bytes". 2794 */ 2795 static uint64_t 2796 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 2797 arc_buf_contents_t type) 2798 { 2799 int64_t delta; 2800 2801 if (bytes > 0 && state->arcs_lsize[type] > 0) { 2802 delta = MIN(state->arcs_lsize[type], bytes); 2803 return (arc_evict_state(state, spa, delta, type)); 2804 } 2805 2806 return (0); 2807 } 2808 2809 /* 2810 * Evict metadata buffers from the cache, such that arc_meta_used is 2811 * capped by the arc_meta_limit tunable. 2812 */ 2813 static uint64_t 2814 arc_adjust_meta(void) 2815 { 2816 uint64_t total_evicted = 0; 2817 int64_t target; 2818 2819 /* 2820 * If we're over the meta limit, we want to evict enough 2821 * metadata to get back under the meta limit. We don't want to 2822 * evict so much that we drop the MRU below arc_p, though. If 2823 * we're over the meta limit more than we're over arc_p, we 2824 * evict some from the MRU here, and some from the MFU below. 2825 */ 2826 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2827 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2828 refcount_count(&arc_mru->arcs_size) - arc_p)); 2829 2830 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2831 2832 /* 2833 * Similar to the above, we want to evict enough bytes to get us 2834 * below the meta limit, but not so much as to drop us below the 2835 * space alloted to the MFU (which is defined as arc_c - arc_p). 2836 */ 2837 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2838 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 2839 2840 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2841 2842 return (total_evicted); 2843 } 2844 2845 /* 2846 * Return the type of the oldest buffer in the given arc state 2847 * 2848 * This function will select a random sublist of type ARC_BUFC_DATA and 2849 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 2850 * is compared, and the type which contains the "older" buffer will be 2851 * returned. 2852 */ 2853 static arc_buf_contents_t 2854 arc_adjust_type(arc_state_t *state) 2855 { 2856 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 2857 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 2858 int data_idx = multilist_get_random_index(data_ml); 2859 int meta_idx = multilist_get_random_index(meta_ml); 2860 multilist_sublist_t *data_mls; 2861 multilist_sublist_t *meta_mls; 2862 arc_buf_contents_t type; 2863 arc_buf_hdr_t *data_hdr; 2864 arc_buf_hdr_t *meta_hdr; 2865 2866 /* 2867 * We keep the sublist lock until we're finished, to prevent 2868 * the headers from being destroyed via arc_evict_state(). 2869 */ 2870 data_mls = multilist_sublist_lock(data_ml, data_idx); 2871 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 2872 2873 /* 2874 * These two loops are to ensure we skip any markers that 2875 * might be at the tail of the lists due to arc_evict_state(). 2876 */ 2877 2878 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 2879 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 2880 if (data_hdr->b_spa != 0) 2881 break; 2882 } 2883 2884 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 2885 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 2886 if (meta_hdr->b_spa != 0) 2887 break; 2888 } 2889 2890 if (data_hdr == NULL && meta_hdr == NULL) { 2891 type = ARC_BUFC_DATA; 2892 } else if (data_hdr == NULL) { 2893 ASSERT3P(meta_hdr, !=, NULL); 2894 type = ARC_BUFC_METADATA; 2895 } else if (meta_hdr == NULL) { 2896 ASSERT3P(data_hdr, !=, NULL); 2897 type = ARC_BUFC_DATA; 2898 } else { 2899 ASSERT3P(data_hdr, !=, NULL); 2900 ASSERT3P(meta_hdr, !=, NULL); 2901 2902 /* The headers can't be on the sublist without an L1 header */ 2903 ASSERT(HDR_HAS_L1HDR(data_hdr)); 2904 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 2905 2906 if (data_hdr->b_l1hdr.b_arc_access < 2907 meta_hdr->b_l1hdr.b_arc_access) { 2908 type = ARC_BUFC_DATA; 2909 } else { 2910 type = ARC_BUFC_METADATA; 2911 } 2912 } 2913 2914 multilist_sublist_unlock(meta_mls); 2915 multilist_sublist_unlock(data_mls); 2916 2917 return (type); 2918 } 2919 2920 /* 2921 * Evict buffers from the cache, such that arc_size is capped by arc_c. 2922 */ 2923 static uint64_t 2924 arc_adjust(void) 2925 { 2926 uint64_t total_evicted = 0; 2927 uint64_t bytes; 2928 int64_t target; 2929 2930 /* 2931 * If we're over arc_meta_limit, we want to correct that before 2932 * potentially evicting data buffers below. 2933 */ 2934 total_evicted += arc_adjust_meta(); 2935 2936 /* 2937 * Adjust MRU size 2938 * 2939 * If we're over the target cache size, we want to evict enough 2940 * from the list to get back to our target size. We don't want 2941 * to evict too much from the MRU, such that it drops below 2942 * arc_p. So, if we're over our target cache size more than 2943 * the MRU is over arc_p, we'll evict enough to get back to 2944 * arc_p here, and then evict more from the MFU below. 2945 */ 2946 target = MIN((int64_t)(arc_size - arc_c), 2947 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2948 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 2949 2950 /* 2951 * If we're below arc_meta_min, always prefer to evict data. 2952 * Otherwise, try to satisfy the requested number of bytes to 2953 * evict from the type which contains older buffers; in an 2954 * effort to keep newer buffers in the cache regardless of their 2955 * type. If we cannot satisfy the number of bytes from this 2956 * type, spill over into the next type. 2957 */ 2958 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2959 arc_meta_used > arc_meta_min) { 2960 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2961 total_evicted += bytes; 2962 2963 /* 2964 * If we couldn't evict our target number of bytes from 2965 * metadata, we try to get the rest from data. 2966 */ 2967 target -= bytes; 2968 2969 total_evicted += 2970 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2971 } else { 2972 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2973 total_evicted += bytes; 2974 2975 /* 2976 * If we couldn't evict our target number of bytes from 2977 * data, we try to get the rest from metadata. 2978 */ 2979 target -= bytes; 2980 2981 total_evicted += 2982 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2983 } 2984 2985 /* 2986 * Adjust MFU size 2987 * 2988 * Now that we've tried to evict enough from the MRU to get its 2989 * size back to arc_p, if we're still above the target cache 2990 * size, we evict the rest from the MFU. 2991 */ 2992 target = arc_size - arc_c; 2993 2994 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 2995 arc_meta_used > arc_meta_min) { 2996 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2997 total_evicted += bytes; 2998 2999 /* 3000 * If we couldn't evict our target number of bytes from 3001 * metadata, we try to get the rest from data. 3002 */ 3003 target -= bytes; 3004 3005 total_evicted += 3006 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3007 } else { 3008 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3009 total_evicted += bytes; 3010 3011 /* 3012 * If we couldn't evict our target number of bytes from 3013 * data, we try to get the rest from data. 3014 */ 3015 target -= bytes; 3016 3017 total_evicted += 3018 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3019 } 3020 3021 /* 3022 * Adjust ghost lists 3023 * 3024 * In addition to the above, the ARC also defines target values 3025 * for the ghost lists. The sum of the mru list and mru ghost 3026 * list should never exceed the target size of the cache, and 3027 * the sum of the mru list, mfu list, mru ghost list, and mfu 3028 * ghost list should never exceed twice the target size of the 3029 * cache. The following logic enforces these limits on the ghost 3030 * caches, and evicts from them as needed. 3031 */ 3032 target = refcount_count(&arc_mru->arcs_size) + 3033 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3034 3035 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3036 total_evicted += bytes; 3037 3038 target -= bytes; 3039 3040 total_evicted += 3041 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3042 3043 /* 3044 * We assume the sum of the mru list and mfu list is less than 3045 * or equal to arc_c (we enforced this above), which means we 3046 * can use the simpler of the two equations below: 3047 * 3048 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3049 * mru ghost + mfu ghost <= arc_c 3050 */ 3051 target = refcount_count(&arc_mru_ghost->arcs_size) + 3052 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3053 3054 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3055 total_evicted += bytes; 3056 3057 target -= bytes; 3058 3059 total_evicted += 3060 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3061 3062 return (total_evicted); 3063 } 3064 3065 static void 3066 arc_do_user_evicts(void) 3067 { 3068 mutex_enter(&arc_user_evicts_lock); 3069 while (arc_eviction_list != NULL) { 3070 arc_buf_t *buf = arc_eviction_list; 3071 arc_eviction_list = buf->b_next; 3072 mutex_enter(&buf->b_evict_lock); 3073 buf->b_hdr = NULL; 3074 mutex_exit(&buf->b_evict_lock); 3075 mutex_exit(&arc_user_evicts_lock); 3076 3077 if (buf->b_efunc != NULL) 3078 VERIFY0(buf->b_efunc(buf->b_private)); 3079 3080 buf->b_efunc = NULL; 3081 buf->b_private = NULL; 3082 kmem_cache_free(buf_cache, buf); 3083 mutex_enter(&arc_user_evicts_lock); 3084 } 3085 mutex_exit(&arc_user_evicts_lock); 3086 } 3087 3088 void 3089 arc_flush(spa_t *spa, boolean_t retry) 3090 { 3091 uint64_t guid = 0; 3092 3093 /* 3094 * If retry is TRUE, a spa must not be specified since we have 3095 * no good way to determine if all of a spa's buffers have been 3096 * evicted from an arc state. 3097 */ 3098 ASSERT(!retry || spa == 0); 3099 3100 if (spa != NULL) 3101 guid = spa_load_guid(spa); 3102 3103 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3104 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3105 3106 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3107 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3108 3109 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3110 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3111 3112 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3113 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3114 3115 arc_do_user_evicts(); 3116 ASSERT(spa || arc_eviction_list == NULL); 3117 } 3118 3119 void 3120 arc_shrink(int64_t to_free) 3121 { 3122 if (arc_c > arc_c_min) { 3123 3124 if (arc_c > arc_c_min + to_free) 3125 atomic_add_64(&arc_c, -to_free); 3126 else 3127 arc_c = arc_c_min; 3128 3129 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3130 if (arc_c > arc_size) 3131 arc_c = MAX(arc_size, arc_c_min); 3132 if (arc_p > arc_c) 3133 arc_p = (arc_c >> 1); 3134 ASSERT(arc_c >= arc_c_min); 3135 ASSERT((int64_t)arc_p >= 0); 3136 } 3137 3138 if (arc_size > arc_c) 3139 (void) arc_adjust(); 3140 } 3141 3142 typedef enum free_memory_reason_t { 3143 FMR_UNKNOWN, 3144 FMR_NEEDFREE, 3145 FMR_LOTSFREE, 3146 FMR_SWAPFS_MINFREE, 3147 FMR_PAGES_PP_MAXIMUM, 3148 FMR_HEAP_ARENA, 3149 FMR_ZIO_ARENA, 3150 } free_memory_reason_t; 3151 3152 int64_t last_free_memory; 3153 free_memory_reason_t last_free_reason; 3154 3155 /* 3156 * Additional reserve of pages for pp_reserve. 3157 */ 3158 int64_t arc_pages_pp_reserve = 64; 3159 3160 /* 3161 * Additional reserve of pages for swapfs. 3162 */ 3163 int64_t arc_swapfs_reserve = 64; 3164 3165 /* 3166 * Return the amount of memory that can be consumed before reclaim will be 3167 * needed. Positive if there is sufficient free memory, negative indicates 3168 * the amount of memory that needs to be freed up. 3169 */ 3170 static int64_t 3171 arc_available_memory(void) 3172 { 3173 int64_t lowest = INT64_MAX; 3174 int64_t n; 3175 free_memory_reason_t r = FMR_UNKNOWN; 3176 3177 #ifdef _KERNEL 3178 if (needfree > 0) { 3179 n = PAGESIZE * (-needfree); 3180 if (n < lowest) { 3181 lowest = n; 3182 r = FMR_NEEDFREE; 3183 } 3184 } 3185 3186 /* 3187 * check that we're out of range of the pageout scanner. It starts to 3188 * schedule paging if freemem is less than lotsfree and needfree. 3189 * lotsfree is the high-water mark for pageout, and needfree is the 3190 * number of needed free pages. We add extra pages here to make sure 3191 * the scanner doesn't start up while we're freeing memory. 3192 */ 3193 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3194 if (n < lowest) { 3195 lowest = n; 3196 r = FMR_LOTSFREE; 3197 } 3198 3199 /* 3200 * check to make sure that swapfs has enough space so that anon 3201 * reservations can still succeed. anon_resvmem() checks that the 3202 * availrmem is greater than swapfs_minfree, and the number of reserved 3203 * swap pages. We also add a bit of extra here just to prevent 3204 * circumstances from getting really dire. 3205 */ 3206 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3207 desfree - arc_swapfs_reserve); 3208 if (n < lowest) { 3209 lowest = n; 3210 r = FMR_SWAPFS_MINFREE; 3211 } 3212 3213 3214 /* 3215 * Check that we have enough availrmem that memory locking (e.g., via 3216 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3217 * stores the number of pages that cannot be locked; when availrmem 3218 * drops below pages_pp_maximum, page locking mechanisms such as 3219 * page_pp_lock() will fail.) 3220 */ 3221 n = PAGESIZE * (availrmem - pages_pp_maximum - 3222 arc_pages_pp_reserve); 3223 if (n < lowest) { 3224 lowest = n; 3225 r = FMR_PAGES_PP_MAXIMUM; 3226 } 3227 3228 #if defined(__i386) 3229 /* 3230 * If we're on an i386 platform, it's possible that we'll exhaust the 3231 * kernel heap space before we ever run out of available physical 3232 * memory. Most checks of the size of the heap_area compare against 3233 * tune.t_minarmem, which is the minimum available real memory that we 3234 * can have in the system. However, this is generally fixed at 25 pages 3235 * which is so low that it's useless. In this comparison, we seek to 3236 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3237 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3238 * free) 3239 */ 3240 n = vmem_size(heap_arena, VMEM_FREE) - 3241 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3242 if (n < lowest) { 3243 lowest = n; 3244 r = FMR_HEAP_ARENA; 3245 } 3246 #endif 3247 3248 /* 3249 * If zio data pages are being allocated out of a separate heap segment, 3250 * then enforce that the size of available vmem for this arena remains 3251 * above about 1/16th free. 3252 * 3253 * Note: The 1/16th arena free requirement was put in place 3254 * to aggressively evict memory from the arc in order to avoid 3255 * memory fragmentation issues. 3256 */ 3257 if (zio_arena != NULL) { 3258 n = vmem_size(zio_arena, VMEM_FREE) - 3259 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3260 if (n < lowest) { 3261 lowest = n; 3262 r = FMR_ZIO_ARENA; 3263 } 3264 } 3265 #else 3266 /* Every 100 calls, free a small amount */ 3267 if (spa_get_random(100) == 0) 3268 lowest = -1024; 3269 #endif 3270 3271 last_free_memory = lowest; 3272 last_free_reason = r; 3273 3274 return (lowest); 3275 } 3276 3277 3278 /* 3279 * Determine if the system is under memory pressure and is asking 3280 * to reclaim memory. A return value of TRUE indicates that the system 3281 * is under memory pressure and that the arc should adjust accordingly. 3282 */ 3283 static boolean_t 3284 arc_reclaim_needed(void) 3285 { 3286 return (arc_available_memory() < 0); 3287 } 3288 3289 static void 3290 arc_kmem_reap_now(void) 3291 { 3292 size_t i; 3293 kmem_cache_t *prev_cache = NULL; 3294 kmem_cache_t *prev_data_cache = NULL; 3295 extern kmem_cache_t *zio_buf_cache[]; 3296 extern kmem_cache_t *zio_data_buf_cache[]; 3297 extern kmem_cache_t *range_seg_cache; 3298 3299 #ifdef _KERNEL 3300 if (arc_meta_used >= arc_meta_limit) { 3301 /* 3302 * We are exceeding our meta-data cache limit. 3303 * Purge some DNLC entries to release holds on meta-data. 3304 */ 3305 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3306 } 3307 #if defined(__i386) 3308 /* 3309 * Reclaim unused memory from all kmem caches. 3310 */ 3311 kmem_reap(); 3312 #endif 3313 #endif 3314 3315 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3316 if (zio_buf_cache[i] != prev_cache) { 3317 prev_cache = zio_buf_cache[i]; 3318 kmem_cache_reap_now(zio_buf_cache[i]); 3319 } 3320 if (zio_data_buf_cache[i] != prev_data_cache) { 3321 prev_data_cache = zio_data_buf_cache[i]; 3322 kmem_cache_reap_now(zio_data_buf_cache[i]); 3323 } 3324 } 3325 kmem_cache_reap_now(buf_cache); 3326 kmem_cache_reap_now(hdr_full_cache); 3327 kmem_cache_reap_now(hdr_l2only_cache); 3328 kmem_cache_reap_now(range_seg_cache); 3329 3330 if (zio_arena != NULL) { 3331 /* 3332 * Ask the vmem arena to reclaim unused memory from its 3333 * quantum caches. 3334 */ 3335 vmem_qcache_reap(zio_arena); 3336 } 3337 } 3338 3339 /* 3340 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3341 * enough data and signal them to proceed. When this happens, the threads in 3342 * arc_get_data_buf() are sleeping while holding the hash lock for their 3343 * particular arc header. Thus, we must be careful to never sleep on a 3344 * hash lock in this thread. This is to prevent the following deadlock: 3345 * 3346 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3347 * waiting for the reclaim thread to signal it. 3348 * 3349 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3350 * fails, and goes to sleep forever. 3351 * 3352 * This possible deadlock is avoided by always acquiring a hash lock 3353 * using mutex_tryenter() from arc_reclaim_thread(). 3354 */ 3355 static void 3356 arc_reclaim_thread(void) 3357 { 3358 clock_t growtime = 0; 3359 callb_cpr_t cpr; 3360 3361 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3362 3363 mutex_enter(&arc_reclaim_lock); 3364 while (!arc_reclaim_thread_exit) { 3365 int64_t free_memory = arc_available_memory(); 3366 uint64_t evicted = 0; 3367 3368 mutex_exit(&arc_reclaim_lock); 3369 3370 if (free_memory < 0) { 3371 3372 arc_no_grow = B_TRUE; 3373 arc_warm = B_TRUE; 3374 3375 /* 3376 * Wait at least zfs_grow_retry (default 60) seconds 3377 * before considering growing. 3378 */ 3379 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3380 3381 arc_kmem_reap_now(); 3382 3383 /* 3384 * If we are still low on memory, shrink the ARC 3385 * so that we have arc_shrink_min free space. 3386 */ 3387 free_memory = arc_available_memory(); 3388 3389 int64_t to_free = 3390 (arc_c >> arc_shrink_shift) - free_memory; 3391 if (to_free > 0) { 3392 #ifdef _KERNEL 3393 to_free = MAX(to_free, ptob(needfree)); 3394 #endif 3395 arc_shrink(to_free); 3396 } 3397 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3398 arc_no_grow = B_TRUE; 3399 } else if (ddi_get_lbolt() >= growtime) { 3400 arc_no_grow = B_FALSE; 3401 } 3402 3403 evicted = arc_adjust(); 3404 3405 mutex_enter(&arc_reclaim_lock); 3406 3407 /* 3408 * If evicted is zero, we couldn't evict anything via 3409 * arc_adjust(). This could be due to hash lock 3410 * collisions, but more likely due to the majority of 3411 * arc buffers being unevictable. Therefore, even if 3412 * arc_size is above arc_c, another pass is unlikely to 3413 * be helpful and could potentially cause us to enter an 3414 * infinite loop. 3415 */ 3416 if (arc_size <= arc_c || evicted == 0) { 3417 /* 3418 * We're either no longer overflowing, or we 3419 * can't evict anything more, so we should wake 3420 * up any threads before we go to sleep. 3421 */ 3422 cv_broadcast(&arc_reclaim_waiters_cv); 3423 3424 /* 3425 * Block until signaled, or after one second (we 3426 * might need to perform arc_kmem_reap_now() 3427 * even if we aren't being signalled) 3428 */ 3429 CALLB_CPR_SAFE_BEGIN(&cpr); 3430 (void) cv_timedwait(&arc_reclaim_thread_cv, 3431 &arc_reclaim_lock, ddi_get_lbolt() + hz); 3432 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3433 } 3434 } 3435 3436 arc_reclaim_thread_exit = FALSE; 3437 cv_broadcast(&arc_reclaim_thread_cv); 3438 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3439 thread_exit(); 3440 } 3441 3442 static void 3443 arc_user_evicts_thread(void) 3444 { 3445 callb_cpr_t cpr; 3446 3447 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3448 3449 mutex_enter(&arc_user_evicts_lock); 3450 while (!arc_user_evicts_thread_exit) { 3451 mutex_exit(&arc_user_evicts_lock); 3452 3453 arc_do_user_evicts(); 3454 3455 /* 3456 * This is necessary in order for the mdb ::arc dcmd to 3457 * show up to date information. Since the ::arc command 3458 * does not call the kstat's update function, without 3459 * this call, the command may show stale stats for the 3460 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3461 * with this change, the data might be up to 1 second 3462 * out of date; but that should suffice. The arc_state_t 3463 * structures can be queried directly if more accurate 3464 * information is needed. 3465 */ 3466 if (arc_ksp != NULL) 3467 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3468 3469 mutex_enter(&arc_user_evicts_lock); 3470 3471 /* 3472 * Block until signaled, or after one second (we need to 3473 * call the arc's kstat update function regularly). 3474 */ 3475 CALLB_CPR_SAFE_BEGIN(&cpr); 3476 (void) cv_timedwait(&arc_user_evicts_cv, 3477 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3478 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3479 } 3480 3481 arc_user_evicts_thread_exit = FALSE; 3482 cv_broadcast(&arc_user_evicts_cv); 3483 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3484 thread_exit(); 3485 } 3486 3487 /* 3488 * Adapt arc info given the number of bytes we are trying to add and 3489 * the state that we are comming from. This function is only called 3490 * when we are adding new content to the cache. 3491 */ 3492 static void 3493 arc_adapt(int bytes, arc_state_t *state) 3494 { 3495 int mult; 3496 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3497 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3498 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3499 3500 if (state == arc_l2c_only) 3501 return; 3502 3503 ASSERT(bytes > 0); 3504 /* 3505 * Adapt the target size of the MRU list: 3506 * - if we just hit in the MRU ghost list, then increase 3507 * the target size of the MRU list. 3508 * - if we just hit in the MFU ghost list, then increase 3509 * the target size of the MFU list by decreasing the 3510 * target size of the MRU list. 3511 */ 3512 if (state == arc_mru_ghost) { 3513 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3514 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3515 3516 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3517 } else if (state == arc_mfu_ghost) { 3518 uint64_t delta; 3519 3520 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3521 mult = MIN(mult, 10); 3522 3523 delta = MIN(bytes * mult, arc_p); 3524 arc_p = MAX(arc_p_min, arc_p - delta); 3525 } 3526 ASSERT((int64_t)arc_p >= 0); 3527 3528 if (arc_reclaim_needed()) { 3529 cv_signal(&arc_reclaim_thread_cv); 3530 return; 3531 } 3532 3533 if (arc_no_grow) 3534 return; 3535 3536 if (arc_c >= arc_c_max) 3537 return; 3538 3539 /* 3540 * If we're within (2 * maxblocksize) bytes of the target 3541 * cache size, increment the target cache size 3542 */ 3543 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3544 atomic_add_64(&arc_c, (int64_t)bytes); 3545 if (arc_c > arc_c_max) 3546 arc_c = arc_c_max; 3547 else if (state == arc_anon) 3548 atomic_add_64(&arc_p, (int64_t)bytes); 3549 if (arc_p > arc_c) 3550 arc_p = arc_c; 3551 } 3552 ASSERT((int64_t)arc_p >= 0); 3553 } 3554 3555 /* 3556 * Check if arc_size has grown past our upper threshold, determined by 3557 * zfs_arc_overflow_shift. 3558 */ 3559 static boolean_t 3560 arc_is_overflowing(void) 3561 { 3562 /* Always allow at least one block of overflow */ 3563 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3564 arc_c >> zfs_arc_overflow_shift); 3565 3566 return (arc_size >= arc_c + overflow); 3567 } 3568 3569 /* 3570 * The buffer, supplied as the first argument, needs a data block. If we 3571 * are hitting the hard limit for the cache size, we must sleep, waiting 3572 * for the eviction thread to catch up. If we're past the target size 3573 * but below the hard limit, we'll only signal the reclaim thread and 3574 * continue on. 3575 */ 3576 static void 3577 arc_get_data_buf(arc_buf_t *buf) 3578 { 3579 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3580 uint64_t size = buf->b_hdr->b_size; 3581 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3582 3583 arc_adapt(size, state); 3584 3585 /* 3586 * If arc_size is currently overflowing, and has grown past our 3587 * upper limit, we must be adding data faster than the evict 3588 * thread can evict. Thus, to ensure we don't compound the 3589 * problem by adding more data and forcing arc_size to grow even 3590 * further past it's target size, we halt and wait for the 3591 * eviction thread to catch up. 3592 * 3593 * It's also possible that the reclaim thread is unable to evict 3594 * enough buffers to get arc_size below the overflow limit (e.g. 3595 * due to buffers being un-evictable, or hash lock collisions). 3596 * In this case, we want to proceed regardless if we're 3597 * overflowing; thus we don't use a while loop here. 3598 */ 3599 if (arc_is_overflowing()) { 3600 mutex_enter(&arc_reclaim_lock); 3601 3602 /* 3603 * Now that we've acquired the lock, we may no longer be 3604 * over the overflow limit, lets check. 3605 * 3606 * We're ignoring the case of spurious wake ups. If that 3607 * were to happen, it'd let this thread consume an ARC 3608 * buffer before it should have (i.e. before we're under 3609 * the overflow limit and were signalled by the reclaim 3610 * thread). As long as that is a rare occurrence, it 3611 * shouldn't cause any harm. 3612 */ 3613 if (arc_is_overflowing()) { 3614 cv_signal(&arc_reclaim_thread_cv); 3615 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3616 } 3617 3618 mutex_exit(&arc_reclaim_lock); 3619 } 3620 3621 if (type == ARC_BUFC_METADATA) { 3622 buf->b_data = zio_buf_alloc(size); 3623 arc_space_consume(size, ARC_SPACE_META); 3624 } else { 3625 ASSERT(type == ARC_BUFC_DATA); 3626 buf->b_data = zio_data_buf_alloc(size); 3627 arc_space_consume(size, ARC_SPACE_DATA); 3628 } 3629 3630 /* 3631 * Update the state size. Note that ghost states have a 3632 * "ghost size" and so don't need to be updated. 3633 */ 3634 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3635 arc_buf_hdr_t *hdr = buf->b_hdr; 3636 arc_state_t *state = hdr->b_l1hdr.b_state; 3637 3638 (void) refcount_add_many(&state->arcs_size, size, buf); 3639 3640 /* 3641 * If this is reached via arc_read, the link is 3642 * protected by the hash lock. If reached via 3643 * arc_buf_alloc, the header should not be accessed by 3644 * any other thread. And, if reached via arc_read_done, 3645 * the hash lock will protect it if it's found in the 3646 * hash table; otherwise no other thread should be 3647 * trying to [add|remove]_reference it. 3648 */ 3649 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3650 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3651 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3652 size); 3653 } 3654 /* 3655 * If we are growing the cache, and we are adding anonymous 3656 * data, and we have outgrown arc_p, update arc_p 3657 */ 3658 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3659 (refcount_count(&arc_anon->arcs_size) + 3660 refcount_count(&arc_mru->arcs_size) > arc_p)) 3661 arc_p = MIN(arc_c, arc_p + size); 3662 } 3663 } 3664 3665 /* 3666 * This routine is called whenever a buffer is accessed. 3667 * NOTE: the hash lock is dropped in this function. 3668 */ 3669 static void 3670 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3671 { 3672 clock_t now; 3673 3674 ASSERT(MUTEX_HELD(hash_lock)); 3675 ASSERT(HDR_HAS_L1HDR(hdr)); 3676 3677 if (hdr->b_l1hdr.b_state == arc_anon) { 3678 /* 3679 * This buffer is not in the cache, and does not 3680 * appear in our "ghost" list. Add the new buffer 3681 * to the MRU state. 3682 */ 3683 3684 ASSERT0(hdr->b_l1hdr.b_arc_access); 3685 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3686 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3687 arc_change_state(arc_mru, hdr, hash_lock); 3688 3689 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3690 now = ddi_get_lbolt(); 3691 3692 /* 3693 * If this buffer is here because of a prefetch, then either: 3694 * - clear the flag if this is a "referencing" read 3695 * (any subsequent access will bump this into the MFU state). 3696 * or 3697 * - move the buffer to the head of the list if this is 3698 * another prefetch (to make it less likely to be evicted). 3699 */ 3700 if (HDR_PREFETCH(hdr)) { 3701 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3702 /* link protected by hash lock */ 3703 ASSERT(multilist_link_active( 3704 &hdr->b_l1hdr.b_arc_node)); 3705 } else { 3706 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3707 ARCSTAT_BUMP(arcstat_mru_hits); 3708 } 3709 hdr->b_l1hdr.b_arc_access = now; 3710 return; 3711 } 3712 3713 /* 3714 * This buffer has been "accessed" only once so far, 3715 * but it is still in the cache. Move it to the MFU 3716 * state. 3717 */ 3718 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3719 /* 3720 * More than 125ms have passed since we 3721 * instantiated this buffer. Move it to the 3722 * most frequently used state. 3723 */ 3724 hdr->b_l1hdr.b_arc_access = now; 3725 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3726 arc_change_state(arc_mfu, hdr, hash_lock); 3727 } 3728 ARCSTAT_BUMP(arcstat_mru_hits); 3729 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3730 arc_state_t *new_state; 3731 /* 3732 * This buffer has been "accessed" recently, but 3733 * was evicted from the cache. Move it to the 3734 * MFU state. 3735 */ 3736 3737 if (HDR_PREFETCH(hdr)) { 3738 new_state = arc_mru; 3739 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3740 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3741 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3742 } else { 3743 new_state = arc_mfu; 3744 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3745 } 3746 3747 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3748 arc_change_state(new_state, hdr, hash_lock); 3749 3750 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3751 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3752 /* 3753 * This buffer has been accessed more than once and is 3754 * still in the cache. Keep it in the MFU state. 3755 * 3756 * NOTE: an add_reference() that occurred when we did 3757 * the arc_read() will have kicked this off the list. 3758 * If it was a prefetch, we will explicitly move it to 3759 * the head of the list now. 3760 */ 3761 if ((HDR_PREFETCH(hdr)) != 0) { 3762 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3763 /* link protected by hash_lock */ 3764 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3765 } 3766 ARCSTAT_BUMP(arcstat_mfu_hits); 3767 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3768 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3769 arc_state_t *new_state = arc_mfu; 3770 /* 3771 * This buffer has been accessed more than once but has 3772 * been evicted from the cache. Move it back to the 3773 * MFU state. 3774 */ 3775 3776 if (HDR_PREFETCH(hdr)) { 3777 /* 3778 * This is a prefetch access... 3779 * move this block back to the MRU state. 3780 */ 3781 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3782 new_state = arc_mru; 3783 } 3784 3785 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3786 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3787 arc_change_state(new_state, hdr, hash_lock); 3788 3789 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3790 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3791 /* 3792 * This buffer is on the 2nd Level ARC. 3793 */ 3794 3795 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3796 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3797 arc_change_state(arc_mfu, hdr, hash_lock); 3798 } else { 3799 ASSERT(!"invalid arc state"); 3800 } 3801 } 3802 3803 /* a generic arc_done_func_t which you can use */ 3804 /* ARGSUSED */ 3805 void 3806 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3807 { 3808 if (zio == NULL || zio->io_error == 0) 3809 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3810 VERIFY(arc_buf_remove_ref(buf, arg)); 3811 } 3812 3813 /* a generic arc_done_func_t */ 3814 void 3815 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3816 { 3817 arc_buf_t **bufp = arg; 3818 if (zio && zio->io_error) { 3819 VERIFY(arc_buf_remove_ref(buf, arg)); 3820 *bufp = NULL; 3821 } else { 3822 *bufp = buf; 3823 ASSERT(buf->b_data); 3824 } 3825 } 3826 3827 static void 3828 arc_read_done(zio_t *zio) 3829 { 3830 arc_buf_hdr_t *hdr; 3831 arc_buf_t *buf; 3832 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3833 kmutex_t *hash_lock = NULL; 3834 arc_callback_t *callback_list, *acb; 3835 int freeable = FALSE; 3836 3837 buf = zio->io_private; 3838 hdr = buf->b_hdr; 3839 3840 /* 3841 * The hdr was inserted into hash-table and removed from lists 3842 * prior to starting I/O. We should find this header, since 3843 * it's in the hash table, and it should be legit since it's 3844 * not possible to evict it during the I/O. The only possible 3845 * reason for it not to be found is if we were freed during the 3846 * read. 3847 */ 3848 if (HDR_IN_HASH_TABLE(hdr)) { 3849 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3850 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3851 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3852 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3853 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3854 3855 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3856 &hash_lock); 3857 3858 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3859 hash_lock == NULL) || 3860 (found == hdr && 3861 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3862 (found == hdr && HDR_L2_READING(hdr))); 3863 } 3864 3865 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3866 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3867 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3868 3869 /* byteswap if necessary */ 3870 callback_list = hdr->b_l1hdr.b_acb; 3871 ASSERT(callback_list != NULL); 3872 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3873 dmu_object_byteswap_t bswap = 3874 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3875 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3876 byteswap_uint64_array : 3877 dmu_ot_byteswap[bswap].ob_func; 3878 func(buf->b_data, hdr->b_size); 3879 } 3880 3881 arc_cksum_compute(buf, B_FALSE); 3882 arc_buf_watch(buf); 3883 3884 if (hash_lock && zio->io_error == 0 && 3885 hdr->b_l1hdr.b_state == arc_anon) { 3886 /* 3887 * Only call arc_access on anonymous buffers. This is because 3888 * if we've issued an I/O for an evicted buffer, we've already 3889 * called arc_access (to prevent any simultaneous readers from 3890 * getting confused). 3891 */ 3892 arc_access(hdr, hash_lock); 3893 } 3894 3895 /* create copies of the data buffer for the callers */ 3896 abuf = buf; 3897 for (acb = callback_list; acb; acb = acb->acb_next) { 3898 if (acb->acb_done) { 3899 if (abuf == NULL) { 3900 ARCSTAT_BUMP(arcstat_duplicate_reads); 3901 abuf = arc_buf_clone(buf); 3902 } 3903 acb->acb_buf = abuf; 3904 abuf = NULL; 3905 } 3906 } 3907 hdr->b_l1hdr.b_acb = NULL; 3908 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3909 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3910 if (abuf == buf) { 3911 ASSERT(buf->b_efunc == NULL); 3912 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3913 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3914 } 3915 3916 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3917 callback_list != NULL); 3918 3919 if (zio->io_error != 0) { 3920 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3921 if (hdr->b_l1hdr.b_state != arc_anon) 3922 arc_change_state(arc_anon, hdr, hash_lock); 3923 if (HDR_IN_HASH_TABLE(hdr)) 3924 buf_hash_remove(hdr); 3925 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3926 } 3927 3928 /* 3929 * Broadcast before we drop the hash_lock to avoid the possibility 3930 * that the hdr (and hence the cv) might be freed before we get to 3931 * the cv_broadcast(). 3932 */ 3933 cv_broadcast(&hdr->b_l1hdr.b_cv); 3934 3935 if (hash_lock != NULL) { 3936 mutex_exit(hash_lock); 3937 } else { 3938 /* 3939 * This block was freed while we waited for the read to 3940 * complete. It has been removed from the hash table and 3941 * moved to the anonymous state (so that it won't show up 3942 * in the cache). 3943 */ 3944 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3945 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3946 } 3947 3948 /* execute each callback and free its structure */ 3949 while ((acb = callback_list) != NULL) { 3950 if (acb->acb_done) 3951 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3952 3953 if (acb->acb_zio_dummy != NULL) { 3954 acb->acb_zio_dummy->io_error = zio->io_error; 3955 zio_nowait(acb->acb_zio_dummy); 3956 } 3957 3958 callback_list = acb->acb_next; 3959 kmem_free(acb, sizeof (arc_callback_t)); 3960 } 3961 3962 if (freeable) 3963 arc_hdr_destroy(hdr); 3964 } 3965 3966 /* 3967 * "Read" the block at the specified DVA (in bp) via the 3968 * cache. If the block is found in the cache, invoke the provided 3969 * callback immediately and return. Note that the `zio' parameter 3970 * in the callback will be NULL in this case, since no IO was 3971 * required. If the block is not in the cache pass the read request 3972 * on to the spa with a substitute callback function, so that the 3973 * requested block will be added to the cache. 3974 * 3975 * If a read request arrives for a block that has a read in-progress, 3976 * either wait for the in-progress read to complete (and return the 3977 * results); or, if this is a read with a "done" func, add a record 3978 * to the read to invoke the "done" func when the read completes, 3979 * and return; or just return. 3980 * 3981 * arc_read_done() will invoke all the requested "done" functions 3982 * for readers of this block. 3983 */ 3984 int 3985 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3986 void *private, zio_priority_t priority, int zio_flags, 3987 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3988 { 3989 arc_buf_hdr_t *hdr = NULL; 3990 arc_buf_t *buf = NULL; 3991 kmutex_t *hash_lock = NULL; 3992 zio_t *rzio; 3993 uint64_t guid = spa_load_guid(spa); 3994 3995 ASSERT(!BP_IS_EMBEDDED(bp) || 3996 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3997 3998 top: 3999 if (!BP_IS_EMBEDDED(bp)) { 4000 /* 4001 * Embedded BP's have no DVA and require no I/O to "read". 4002 * Create an anonymous arc buf to back it. 4003 */ 4004 hdr = buf_hash_find(guid, bp, &hash_lock); 4005 } 4006 4007 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4008 4009 *arc_flags |= ARC_FLAG_CACHED; 4010 4011 if (HDR_IO_IN_PROGRESS(hdr)) { 4012 4013 if (*arc_flags & ARC_FLAG_WAIT) { 4014 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4015 mutex_exit(hash_lock); 4016 goto top; 4017 } 4018 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4019 4020 if (done) { 4021 arc_callback_t *acb = NULL; 4022 4023 acb = kmem_zalloc(sizeof (arc_callback_t), 4024 KM_SLEEP); 4025 acb->acb_done = done; 4026 acb->acb_private = private; 4027 if (pio != NULL) 4028 acb->acb_zio_dummy = zio_null(pio, 4029 spa, NULL, NULL, NULL, zio_flags); 4030 4031 ASSERT(acb->acb_done != NULL); 4032 acb->acb_next = hdr->b_l1hdr.b_acb; 4033 hdr->b_l1hdr.b_acb = acb; 4034 add_reference(hdr, hash_lock, private); 4035 mutex_exit(hash_lock); 4036 return (0); 4037 } 4038 mutex_exit(hash_lock); 4039 return (0); 4040 } 4041 4042 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4043 hdr->b_l1hdr.b_state == arc_mfu); 4044 4045 if (done) { 4046 add_reference(hdr, hash_lock, private); 4047 /* 4048 * If this block is already in use, create a new 4049 * copy of the data so that we will be guaranteed 4050 * that arc_release() will always succeed. 4051 */ 4052 buf = hdr->b_l1hdr.b_buf; 4053 ASSERT(buf); 4054 ASSERT(buf->b_data); 4055 if (HDR_BUF_AVAILABLE(hdr)) { 4056 ASSERT(buf->b_efunc == NULL); 4057 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4058 } else { 4059 buf = arc_buf_clone(buf); 4060 } 4061 4062 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4063 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4064 hdr->b_flags |= ARC_FLAG_PREFETCH; 4065 } 4066 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4067 arc_access(hdr, hash_lock); 4068 if (*arc_flags & ARC_FLAG_L2CACHE) 4069 hdr->b_flags |= ARC_FLAG_L2CACHE; 4070 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4071 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4072 mutex_exit(hash_lock); 4073 ARCSTAT_BUMP(arcstat_hits); 4074 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4075 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4076 data, metadata, hits); 4077 4078 if (done) 4079 done(NULL, buf, private); 4080 } else { 4081 uint64_t size = BP_GET_LSIZE(bp); 4082 arc_callback_t *acb; 4083 vdev_t *vd = NULL; 4084 uint64_t addr = 0; 4085 boolean_t devw = B_FALSE; 4086 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4087 int32_t b_asize = 0; 4088 4089 if (hdr == NULL) { 4090 /* this block is not in the cache */ 4091 arc_buf_hdr_t *exists = NULL; 4092 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4093 buf = arc_buf_alloc(spa, size, private, type); 4094 hdr = buf->b_hdr; 4095 if (!BP_IS_EMBEDDED(bp)) { 4096 hdr->b_dva = *BP_IDENTITY(bp); 4097 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4098 exists = buf_hash_insert(hdr, &hash_lock); 4099 } 4100 if (exists != NULL) { 4101 /* somebody beat us to the hash insert */ 4102 mutex_exit(hash_lock); 4103 buf_discard_identity(hdr); 4104 (void) arc_buf_remove_ref(buf, private); 4105 goto top; /* restart the IO request */ 4106 } 4107 4108 /* if this is a prefetch, we don't have a reference */ 4109 if (*arc_flags & ARC_FLAG_PREFETCH) { 4110 (void) remove_reference(hdr, hash_lock, 4111 private); 4112 hdr->b_flags |= ARC_FLAG_PREFETCH; 4113 } 4114 if (*arc_flags & ARC_FLAG_L2CACHE) 4115 hdr->b_flags |= ARC_FLAG_L2CACHE; 4116 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4117 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4118 if (BP_GET_LEVEL(bp) > 0) 4119 hdr->b_flags |= ARC_FLAG_INDIRECT; 4120 } else { 4121 /* 4122 * This block is in the ghost cache. If it was L2-only 4123 * (and thus didn't have an L1 hdr), we realloc the 4124 * header to add an L1 hdr. 4125 */ 4126 if (!HDR_HAS_L1HDR(hdr)) { 4127 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4128 hdr_full_cache); 4129 } 4130 4131 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4132 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4133 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4134 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4135 4136 /* if this is a prefetch, we don't have a reference */ 4137 if (*arc_flags & ARC_FLAG_PREFETCH) 4138 hdr->b_flags |= ARC_FLAG_PREFETCH; 4139 else 4140 add_reference(hdr, hash_lock, private); 4141 if (*arc_flags & ARC_FLAG_L2CACHE) 4142 hdr->b_flags |= ARC_FLAG_L2CACHE; 4143 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4144 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4145 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4146 buf->b_hdr = hdr; 4147 buf->b_data = NULL; 4148 buf->b_efunc = NULL; 4149 buf->b_private = NULL; 4150 buf->b_next = NULL; 4151 hdr->b_l1hdr.b_buf = buf; 4152 ASSERT0(hdr->b_l1hdr.b_datacnt); 4153 hdr->b_l1hdr.b_datacnt = 1; 4154 arc_get_data_buf(buf); 4155 arc_access(hdr, hash_lock); 4156 } 4157 4158 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4159 4160 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4161 acb->acb_done = done; 4162 acb->acb_private = private; 4163 4164 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4165 hdr->b_l1hdr.b_acb = acb; 4166 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4167 4168 if (HDR_HAS_L2HDR(hdr) && 4169 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4170 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4171 addr = hdr->b_l2hdr.b_daddr; 4172 b_compress = HDR_GET_COMPRESS(hdr); 4173 b_asize = hdr->b_l2hdr.b_asize; 4174 /* 4175 * Lock out device removal. 4176 */ 4177 if (vdev_is_dead(vd) || 4178 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4179 vd = NULL; 4180 } 4181 4182 if (hash_lock != NULL) 4183 mutex_exit(hash_lock); 4184 4185 /* 4186 * At this point, we have a level 1 cache miss. Try again in 4187 * L2ARC if possible. 4188 */ 4189 ASSERT3U(hdr->b_size, ==, size); 4190 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4191 uint64_t, size, zbookmark_phys_t *, zb); 4192 ARCSTAT_BUMP(arcstat_misses); 4193 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4194 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4195 data, metadata, misses); 4196 4197 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4198 /* 4199 * Read from the L2ARC if the following are true: 4200 * 1. The L2ARC vdev was previously cached. 4201 * 2. This buffer still has L2ARC metadata. 4202 * 3. This buffer isn't currently writing to the L2ARC. 4203 * 4. The L2ARC entry wasn't evicted, which may 4204 * also have invalidated the vdev. 4205 * 5. This isn't prefetch and l2arc_noprefetch is set. 4206 */ 4207 if (HDR_HAS_L2HDR(hdr) && 4208 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4209 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4210 l2arc_read_callback_t *cb; 4211 4212 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4213 ARCSTAT_BUMP(arcstat_l2_hits); 4214 4215 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4216 KM_SLEEP); 4217 cb->l2rcb_buf = buf; 4218 cb->l2rcb_spa = spa; 4219 cb->l2rcb_bp = *bp; 4220 cb->l2rcb_zb = *zb; 4221 cb->l2rcb_flags = zio_flags; 4222 cb->l2rcb_compress = b_compress; 4223 4224 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4225 addr + size < vd->vdev_psize - 4226 VDEV_LABEL_END_SIZE); 4227 4228 /* 4229 * l2arc read. The SCL_L2ARC lock will be 4230 * released by l2arc_read_done(). 4231 * Issue a null zio if the underlying buffer 4232 * was squashed to zero size by compression. 4233 */ 4234 if (b_compress == ZIO_COMPRESS_EMPTY) { 4235 rzio = zio_null(pio, spa, vd, 4236 l2arc_read_done, cb, 4237 zio_flags | ZIO_FLAG_DONT_CACHE | 4238 ZIO_FLAG_CANFAIL | 4239 ZIO_FLAG_DONT_PROPAGATE | 4240 ZIO_FLAG_DONT_RETRY); 4241 } else { 4242 rzio = zio_read_phys(pio, vd, addr, 4243 b_asize, buf->b_data, 4244 ZIO_CHECKSUM_OFF, 4245 l2arc_read_done, cb, priority, 4246 zio_flags | ZIO_FLAG_DONT_CACHE | 4247 ZIO_FLAG_CANFAIL | 4248 ZIO_FLAG_DONT_PROPAGATE | 4249 ZIO_FLAG_DONT_RETRY, B_FALSE); 4250 } 4251 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4252 zio_t *, rzio); 4253 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4254 4255 if (*arc_flags & ARC_FLAG_NOWAIT) { 4256 zio_nowait(rzio); 4257 return (0); 4258 } 4259 4260 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4261 if (zio_wait(rzio) == 0) 4262 return (0); 4263 4264 /* l2arc read error; goto zio_read() */ 4265 } else { 4266 DTRACE_PROBE1(l2arc__miss, 4267 arc_buf_hdr_t *, hdr); 4268 ARCSTAT_BUMP(arcstat_l2_misses); 4269 if (HDR_L2_WRITING(hdr)) 4270 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4271 spa_config_exit(spa, SCL_L2ARC, vd); 4272 } 4273 } else { 4274 if (vd != NULL) 4275 spa_config_exit(spa, SCL_L2ARC, vd); 4276 if (l2arc_ndev != 0) { 4277 DTRACE_PROBE1(l2arc__miss, 4278 arc_buf_hdr_t *, hdr); 4279 ARCSTAT_BUMP(arcstat_l2_misses); 4280 } 4281 } 4282 4283 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4284 arc_read_done, buf, priority, zio_flags, zb); 4285 4286 if (*arc_flags & ARC_FLAG_WAIT) 4287 return (zio_wait(rzio)); 4288 4289 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4290 zio_nowait(rzio); 4291 } 4292 return (0); 4293 } 4294 4295 void 4296 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4297 { 4298 ASSERT(buf->b_hdr != NULL); 4299 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4300 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4301 func == NULL); 4302 ASSERT(buf->b_efunc == NULL); 4303 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4304 4305 buf->b_efunc = func; 4306 buf->b_private = private; 4307 } 4308 4309 /* 4310 * Notify the arc that a block was freed, and thus will never be used again. 4311 */ 4312 void 4313 arc_freed(spa_t *spa, const blkptr_t *bp) 4314 { 4315 arc_buf_hdr_t *hdr; 4316 kmutex_t *hash_lock; 4317 uint64_t guid = spa_load_guid(spa); 4318 4319 ASSERT(!BP_IS_EMBEDDED(bp)); 4320 4321 hdr = buf_hash_find(guid, bp, &hash_lock); 4322 if (hdr == NULL) 4323 return; 4324 if (HDR_BUF_AVAILABLE(hdr)) { 4325 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4326 add_reference(hdr, hash_lock, FTAG); 4327 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4328 mutex_exit(hash_lock); 4329 4330 arc_release(buf, FTAG); 4331 (void) arc_buf_remove_ref(buf, FTAG); 4332 } else { 4333 mutex_exit(hash_lock); 4334 } 4335 4336 } 4337 4338 /* 4339 * Clear the user eviction callback set by arc_set_callback(), first calling 4340 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4341 * clearing the callback may result in the arc_buf being destroyed. However, 4342 * it will not result in the *last* arc_buf being destroyed, hence the data 4343 * will remain cached in the ARC. We make a copy of the arc buffer here so 4344 * that we can process the callback without holding any locks. 4345 * 4346 * It's possible that the callback is already in the process of being cleared 4347 * by another thread. In this case we can not clear the callback. 4348 * 4349 * Returns B_TRUE if the callback was successfully called and cleared. 4350 */ 4351 boolean_t 4352 arc_clear_callback(arc_buf_t *buf) 4353 { 4354 arc_buf_hdr_t *hdr; 4355 kmutex_t *hash_lock; 4356 arc_evict_func_t *efunc = buf->b_efunc; 4357 void *private = buf->b_private; 4358 4359 mutex_enter(&buf->b_evict_lock); 4360 hdr = buf->b_hdr; 4361 if (hdr == NULL) { 4362 /* 4363 * We are in arc_do_user_evicts(). 4364 */ 4365 ASSERT(buf->b_data == NULL); 4366 mutex_exit(&buf->b_evict_lock); 4367 return (B_FALSE); 4368 } else if (buf->b_data == NULL) { 4369 /* 4370 * We are on the eviction list; process this buffer now 4371 * but let arc_do_user_evicts() do the reaping. 4372 */ 4373 buf->b_efunc = NULL; 4374 mutex_exit(&buf->b_evict_lock); 4375 VERIFY0(efunc(private)); 4376 return (B_TRUE); 4377 } 4378 hash_lock = HDR_LOCK(hdr); 4379 mutex_enter(hash_lock); 4380 hdr = buf->b_hdr; 4381 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4382 4383 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4384 hdr->b_l1hdr.b_datacnt); 4385 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4386 hdr->b_l1hdr.b_state == arc_mfu); 4387 4388 buf->b_efunc = NULL; 4389 buf->b_private = NULL; 4390 4391 if (hdr->b_l1hdr.b_datacnt > 1) { 4392 mutex_exit(&buf->b_evict_lock); 4393 arc_buf_destroy(buf, TRUE); 4394 } else { 4395 ASSERT(buf == hdr->b_l1hdr.b_buf); 4396 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4397 mutex_exit(&buf->b_evict_lock); 4398 } 4399 4400 mutex_exit(hash_lock); 4401 VERIFY0(efunc(private)); 4402 return (B_TRUE); 4403 } 4404 4405 /* 4406 * Release this buffer from the cache, making it an anonymous buffer. This 4407 * must be done after a read and prior to modifying the buffer contents. 4408 * If the buffer has more than one reference, we must make 4409 * a new hdr for the buffer. 4410 */ 4411 void 4412 arc_release(arc_buf_t *buf, void *tag) 4413 { 4414 arc_buf_hdr_t *hdr = buf->b_hdr; 4415 4416 /* 4417 * It would be nice to assert that if it's DMU metadata (level > 4418 * 0 || it's the dnode file), then it must be syncing context. 4419 * But we don't know that information at this level. 4420 */ 4421 4422 mutex_enter(&buf->b_evict_lock); 4423 4424 ASSERT(HDR_HAS_L1HDR(hdr)); 4425 4426 /* 4427 * We don't grab the hash lock prior to this check, because if 4428 * the buffer's header is in the arc_anon state, it won't be 4429 * linked into the hash table. 4430 */ 4431 if (hdr->b_l1hdr.b_state == arc_anon) { 4432 mutex_exit(&buf->b_evict_lock); 4433 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4434 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4435 ASSERT(!HDR_HAS_L2HDR(hdr)); 4436 ASSERT(BUF_EMPTY(hdr)); 4437 4438 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4439 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4440 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4441 4442 ASSERT3P(buf->b_efunc, ==, NULL); 4443 ASSERT3P(buf->b_private, ==, NULL); 4444 4445 hdr->b_l1hdr.b_arc_access = 0; 4446 arc_buf_thaw(buf); 4447 4448 return; 4449 } 4450 4451 kmutex_t *hash_lock = HDR_LOCK(hdr); 4452 mutex_enter(hash_lock); 4453 4454 /* 4455 * This assignment is only valid as long as the hash_lock is 4456 * held, we must be careful not to reference state or the 4457 * b_state field after dropping the lock. 4458 */ 4459 arc_state_t *state = hdr->b_l1hdr.b_state; 4460 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4461 ASSERT3P(state, !=, arc_anon); 4462 4463 /* this buffer is not on any list */ 4464 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4465 4466 if (HDR_HAS_L2HDR(hdr)) { 4467 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4468 4469 /* 4470 * We have to recheck this conditional again now that 4471 * we're holding the l2ad_mtx to prevent a race with 4472 * another thread which might be concurrently calling 4473 * l2arc_evict(). In that case, l2arc_evict() might have 4474 * destroyed the header's L2 portion as we were waiting 4475 * to acquire the l2ad_mtx. 4476 */ 4477 if (HDR_HAS_L2HDR(hdr)) 4478 arc_hdr_l2hdr_destroy(hdr); 4479 4480 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4481 } 4482 4483 /* 4484 * Do we have more than one buf? 4485 */ 4486 if (hdr->b_l1hdr.b_datacnt > 1) { 4487 arc_buf_hdr_t *nhdr; 4488 arc_buf_t **bufp; 4489 uint64_t blksz = hdr->b_size; 4490 uint64_t spa = hdr->b_spa; 4491 arc_buf_contents_t type = arc_buf_type(hdr); 4492 uint32_t flags = hdr->b_flags; 4493 4494 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4495 /* 4496 * Pull the data off of this hdr and attach it to 4497 * a new anonymous hdr. 4498 */ 4499 (void) remove_reference(hdr, hash_lock, tag); 4500 bufp = &hdr->b_l1hdr.b_buf; 4501 while (*bufp != buf) 4502 bufp = &(*bufp)->b_next; 4503 *bufp = buf->b_next; 4504 buf->b_next = NULL; 4505 4506 ASSERT3P(state, !=, arc_l2c_only); 4507 4508 (void) refcount_remove_many( 4509 &state->arcs_size, hdr->b_size, buf); 4510 4511 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4512 ASSERT3P(state, !=, arc_l2c_only); 4513 uint64_t *size = &state->arcs_lsize[type]; 4514 ASSERT3U(*size, >=, hdr->b_size); 4515 atomic_add_64(size, -hdr->b_size); 4516 } 4517 4518 /* 4519 * We're releasing a duplicate user data buffer, update 4520 * our statistics accordingly. 4521 */ 4522 if (HDR_ISTYPE_DATA(hdr)) { 4523 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4524 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4525 -hdr->b_size); 4526 } 4527 hdr->b_l1hdr.b_datacnt -= 1; 4528 arc_cksum_verify(buf); 4529 arc_buf_unwatch(buf); 4530 4531 mutex_exit(hash_lock); 4532 4533 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4534 nhdr->b_size = blksz; 4535 nhdr->b_spa = spa; 4536 4537 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4538 nhdr->b_flags |= arc_bufc_to_flags(type); 4539 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4540 4541 nhdr->b_l1hdr.b_buf = buf; 4542 nhdr->b_l1hdr.b_datacnt = 1; 4543 nhdr->b_l1hdr.b_state = arc_anon; 4544 nhdr->b_l1hdr.b_arc_access = 0; 4545 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4546 nhdr->b_freeze_cksum = NULL; 4547 4548 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4549 buf->b_hdr = nhdr; 4550 mutex_exit(&buf->b_evict_lock); 4551 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4552 } else { 4553 mutex_exit(&buf->b_evict_lock); 4554 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4555 /* protected by hash lock, or hdr is on arc_anon */ 4556 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4557 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4558 arc_change_state(arc_anon, hdr, hash_lock); 4559 hdr->b_l1hdr.b_arc_access = 0; 4560 mutex_exit(hash_lock); 4561 4562 buf_discard_identity(hdr); 4563 arc_buf_thaw(buf); 4564 } 4565 buf->b_efunc = NULL; 4566 buf->b_private = NULL; 4567 } 4568 4569 int 4570 arc_released(arc_buf_t *buf) 4571 { 4572 int released; 4573 4574 mutex_enter(&buf->b_evict_lock); 4575 released = (buf->b_data != NULL && 4576 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4577 mutex_exit(&buf->b_evict_lock); 4578 return (released); 4579 } 4580 4581 #ifdef ZFS_DEBUG 4582 int 4583 arc_referenced(arc_buf_t *buf) 4584 { 4585 int referenced; 4586 4587 mutex_enter(&buf->b_evict_lock); 4588 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4589 mutex_exit(&buf->b_evict_lock); 4590 return (referenced); 4591 } 4592 #endif 4593 4594 static void 4595 arc_write_ready(zio_t *zio) 4596 { 4597 arc_write_callback_t *callback = zio->io_private; 4598 arc_buf_t *buf = callback->awcb_buf; 4599 arc_buf_hdr_t *hdr = buf->b_hdr; 4600 4601 ASSERT(HDR_HAS_L1HDR(hdr)); 4602 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4603 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4604 callback->awcb_ready(zio, buf, callback->awcb_private); 4605 4606 /* 4607 * If the IO is already in progress, then this is a re-write 4608 * attempt, so we need to thaw and re-compute the cksum. 4609 * It is the responsibility of the callback to handle the 4610 * accounting for any re-write attempt. 4611 */ 4612 if (HDR_IO_IN_PROGRESS(hdr)) { 4613 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4614 if (hdr->b_freeze_cksum != NULL) { 4615 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4616 hdr->b_freeze_cksum = NULL; 4617 } 4618 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4619 } 4620 arc_cksum_compute(buf, B_FALSE); 4621 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4622 } 4623 4624 /* 4625 * The SPA calls this callback for each physical write that happens on behalf 4626 * of a logical write. See the comment in dbuf_write_physdone() for details. 4627 */ 4628 static void 4629 arc_write_physdone(zio_t *zio) 4630 { 4631 arc_write_callback_t *cb = zio->io_private; 4632 if (cb->awcb_physdone != NULL) 4633 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4634 } 4635 4636 static void 4637 arc_write_done(zio_t *zio) 4638 { 4639 arc_write_callback_t *callback = zio->io_private; 4640 arc_buf_t *buf = callback->awcb_buf; 4641 arc_buf_hdr_t *hdr = buf->b_hdr; 4642 4643 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4644 4645 if (zio->io_error == 0) { 4646 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4647 buf_discard_identity(hdr); 4648 } else { 4649 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4650 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4651 } 4652 } else { 4653 ASSERT(BUF_EMPTY(hdr)); 4654 } 4655 4656 /* 4657 * If the block to be written was all-zero or compressed enough to be 4658 * embedded in the BP, no write was performed so there will be no 4659 * dva/birth/checksum. The buffer must therefore remain anonymous 4660 * (and uncached). 4661 */ 4662 if (!BUF_EMPTY(hdr)) { 4663 arc_buf_hdr_t *exists; 4664 kmutex_t *hash_lock; 4665 4666 ASSERT(zio->io_error == 0); 4667 4668 arc_cksum_verify(buf); 4669 4670 exists = buf_hash_insert(hdr, &hash_lock); 4671 if (exists != NULL) { 4672 /* 4673 * This can only happen if we overwrite for 4674 * sync-to-convergence, because we remove 4675 * buffers from the hash table when we arc_free(). 4676 */ 4677 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4678 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4679 panic("bad overwrite, hdr=%p exists=%p", 4680 (void *)hdr, (void *)exists); 4681 ASSERT(refcount_is_zero( 4682 &exists->b_l1hdr.b_refcnt)); 4683 arc_change_state(arc_anon, exists, hash_lock); 4684 mutex_exit(hash_lock); 4685 arc_hdr_destroy(exists); 4686 exists = buf_hash_insert(hdr, &hash_lock); 4687 ASSERT3P(exists, ==, NULL); 4688 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4689 /* nopwrite */ 4690 ASSERT(zio->io_prop.zp_nopwrite); 4691 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4692 panic("bad nopwrite, hdr=%p exists=%p", 4693 (void *)hdr, (void *)exists); 4694 } else { 4695 /* Dedup */ 4696 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4697 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4698 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4699 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4700 } 4701 } 4702 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4703 /* if it's not anon, we are doing a scrub */ 4704 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4705 arc_access(hdr, hash_lock); 4706 mutex_exit(hash_lock); 4707 } else { 4708 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4709 } 4710 4711 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4712 callback->awcb_done(zio, buf, callback->awcb_private); 4713 4714 kmem_free(callback, sizeof (arc_write_callback_t)); 4715 } 4716 4717 zio_t * 4718 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4719 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4720 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4721 arc_done_func_t *done, void *private, zio_priority_t priority, 4722 int zio_flags, const zbookmark_phys_t *zb) 4723 { 4724 arc_buf_hdr_t *hdr = buf->b_hdr; 4725 arc_write_callback_t *callback; 4726 zio_t *zio; 4727 4728 ASSERT(ready != NULL); 4729 ASSERT(done != NULL); 4730 ASSERT(!HDR_IO_ERROR(hdr)); 4731 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4732 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4733 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4734 if (l2arc) 4735 hdr->b_flags |= ARC_FLAG_L2CACHE; 4736 if (l2arc_compress) 4737 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4738 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4739 callback->awcb_ready = ready; 4740 callback->awcb_physdone = physdone; 4741 callback->awcb_done = done; 4742 callback->awcb_private = private; 4743 callback->awcb_buf = buf; 4744 4745 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4746 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4747 priority, zio_flags, zb); 4748 4749 return (zio); 4750 } 4751 4752 static int 4753 arc_memory_throttle(uint64_t reserve, uint64_t txg) 4754 { 4755 #ifdef _KERNEL 4756 uint64_t available_memory = ptob(freemem); 4757 static uint64_t page_load = 0; 4758 static uint64_t last_txg = 0; 4759 4760 #if defined(__i386) 4761 available_memory = 4762 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 4763 #endif 4764 4765 if (freemem > physmem * arc_lotsfree_percent / 100) 4766 return (0); 4767 4768 if (txg > last_txg) { 4769 last_txg = txg; 4770 page_load = 0; 4771 } 4772 /* 4773 * If we are in pageout, we know that memory is already tight, 4774 * the arc is already going to be evicting, so we just want to 4775 * continue to let page writes occur as quickly as possible. 4776 */ 4777 if (curproc == proc_pageout) { 4778 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4779 return (SET_ERROR(ERESTART)); 4780 /* Note: reserve is inflated, so we deflate */ 4781 page_load += reserve / 8; 4782 return (0); 4783 } else if (page_load > 0 && arc_reclaim_needed()) { 4784 /* memory is low, delay before restarting */ 4785 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4786 return (SET_ERROR(EAGAIN)); 4787 } 4788 page_load = 0; 4789 #endif 4790 return (0); 4791 } 4792 4793 void 4794 arc_tempreserve_clear(uint64_t reserve) 4795 { 4796 atomic_add_64(&arc_tempreserve, -reserve); 4797 ASSERT((int64_t)arc_tempreserve >= 0); 4798 } 4799 4800 int 4801 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4802 { 4803 int error; 4804 uint64_t anon_size; 4805 4806 if (reserve > arc_c/4 && !arc_no_grow) 4807 arc_c = MIN(arc_c_max, reserve * 4); 4808 if (reserve > arc_c) 4809 return (SET_ERROR(ENOMEM)); 4810 4811 /* 4812 * Don't count loaned bufs as in flight dirty data to prevent long 4813 * network delays from blocking transactions that are ready to be 4814 * assigned to a txg. 4815 */ 4816 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 4817 arc_loaned_bytes), 0); 4818 4819 /* 4820 * Writes will, almost always, require additional memory allocations 4821 * in order to compress/encrypt/etc the data. We therefore need to 4822 * make sure that there is sufficient available memory for this. 4823 */ 4824 error = arc_memory_throttle(reserve, txg); 4825 if (error != 0) 4826 return (error); 4827 4828 /* 4829 * Throttle writes when the amount of dirty data in the cache 4830 * gets too large. We try to keep the cache less than half full 4831 * of dirty blocks so that our sync times don't grow too large. 4832 * Note: if two requests come in concurrently, we might let them 4833 * both succeed, when one of them should fail. Not a huge deal. 4834 */ 4835 4836 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4837 anon_size > arc_c / 4) { 4838 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4839 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4840 arc_tempreserve>>10, 4841 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4842 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4843 reserve>>10, arc_c>>10); 4844 return (SET_ERROR(ERESTART)); 4845 } 4846 atomic_add_64(&arc_tempreserve, reserve); 4847 return (0); 4848 } 4849 4850 static void 4851 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4852 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4853 { 4854 size->value.ui64 = refcount_count(&state->arcs_size); 4855 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4856 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4857 } 4858 4859 static int 4860 arc_kstat_update(kstat_t *ksp, int rw) 4861 { 4862 arc_stats_t *as = ksp->ks_data; 4863 4864 if (rw == KSTAT_WRITE) { 4865 return (EACCES); 4866 } else { 4867 arc_kstat_update_state(arc_anon, 4868 &as->arcstat_anon_size, 4869 &as->arcstat_anon_evictable_data, 4870 &as->arcstat_anon_evictable_metadata); 4871 arc_kstat_update_state(arc_mru, 4872 &as->arcstat_mru_size, 4873 &as->arcstat_mru_evictable_data, 4874 &as->arcstat_mru_evictable_metadata); 4875 arc_kstat_update_state(arc_mru_ghost, 4876 &as->arcstat_mru_ghost_size, 4877 &as->arcstat_mru_ghost_evictable_data, 4878 &as->arcstat_mru_ghost_evictable_metadata); 4879 arc_kstat_update_state(arc_mfu, 4880 &as->arcstat_mfu_size, 4881 &as->arcstat_mfu_evictable_data, 4882 &as->arcstat_mfu_evictable_metadata); 4883 arc_kstat_update_state(arc_mfu_ghost, 4884 &as->arcstat_mfu_ghost_size, 4885 &as->arcstat_mfu_ghost_evictable_data, 4886 &as->arcstat_mfu_ghost_evictable_metadata); 4887 } 4888 4889 return (0); 4890 } 4891 4892 /* 4893 * This function *must* return indices evenly distributed between all 4894 * sublists of the multilist. This is needed due to how the ARC eviction 4895 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 4896 * distributed between all sublists and uses this assumption when 4897 * deciding which sublist to evict from and how much to evict from it. 4898 */ 4899 unsigned int 4900 arc_state_multilist_index_func(multilist_t *ml, void *obj) 4901 { 4902 arc_buf_hdr_t *hdr = obj; 4903 4904 /* 4905 * We rely on b_dva to generate evenly distributed index 4906 * numbers using buf_hash below. So, as an added precaution, 4907 * let's make sure we never add empty buffers to the arc lists. 4908 */ 4909 ASSERT(!BUF_EMPTY(hdr)); 4910 4911 /* 4912 * The assumption here, is the hash value for a given 4913 * arc_buf_hdr_t will remain constant throughout it's lifetime 4914 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 4915 * Thus, we don't need to store the header's sublist index 4916 * on insertion, as this index can be recalculated on removal. 4917 * 4918 * Also, the low order bits of the hash value are thought to be 4919 * distributed evenly. Otherwise, in the case that the multilist 4920 * has a power of two number of sublists, each sublists' usage 4921 * would not be evenly distributed. 4922 */ 4923 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 4924 multilist_get_num_sublists(ml)); 4925 } 4926 4927 void 4928 arc_init(void) 4929 { 4930 /* 4931 * allmem is "all memory that we could possibly use". 4932 */ 4933 #ifdef _KERNEL 4934 uint64_t allmem = ptob(physmem - swapfs_minfree); 4935 #else 4936 uint64_t allmem = (physmem * PAGESIZE) / 2; 4937 #endif 4938 4939 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 4940 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 4941 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 4942 4943 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 4944 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 4945 4946 /* Convert seconds to clock ticks */ 4947 arc_min_prefetch_lifespan = 1 * hz; 4948 4949 /* Start out with 1/8 of all memory */ 4950 arc_c = allmem / 8; 4951 4952 #ifdef _KERNEL 4953 /* 4954 * On architectures where the physical memory can be larger 4955 * than the addressable space (intel in 32-bit mode), we may 4956 * need to limit the cache to 1/8 of VM size. 4957 */ 4958 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4959 #endif 4960 4961 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 4962 arc_c_min = MAX(allmem / 32, 64 << 20); 4963 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 4964 if (allmem >= 1 << 30) 4965 arc_c_max = allmem - (1 << 30); 4966 else 4967 arc_c_max = arc_c_min; 4968 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 4969 4970 /* 4971 * Allow the tunables to override our calculations if they are 4972 * reasonable (ie. over 64MB) 4973 */ 4974 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 4975 arc_c_max = zfs_arc_max; 4976 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 4977 arc_c_min = zfs_arc_min; 4978 4979 arc_c = arc_c_max; 4980 arc_p = (arc_c >> 1); 4981 4982 /* limit meta-data to 1/4 of the arc capacity */ 4983 arc_meta_limit = arc_c_max / 4; 4984 4985 /* Allow the tunable to override if it is reasonable */ 4986 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4987 arc_meta_limit = zfs_arc_meta_limit; 4988 4989 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4990 arc_c_min = arc_meta_limit / 2; 4991 4992 if (zfs_arc_meta_min > 0) { 4993 arc_meta_min = zfs_arc_meta_min; 4994 } else { 4995 arc_meta_min = arc_c_min / 2; 4996 } 4997 4998 if (zfs_arc_grow_retry > 0) 4999 arc_grow_retry = zfs_arc_grow_retry; 5000 5001 if (zfs_arc_shrink_shift > 0) 5002 arc_shrink_shift = zfs_arc_shrink_shift; 5003 5004 /* 5005 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5006 */ 5007 if (arc_no_grow_shift >= arc_shrink_shift) 5008 arc_no_grow_shift = arc_shrink_shift - 1; 5009 5010 if (zfs_arc_p_min_shift > 0) 5011 arc_p_min_shift = zfs_arc_p_min_shift; 5012 5013 if (zfs_arc_num_sublists_per_state < 1) 5014 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 5015 5016 /* if kmem_flags are set, lets try to use less memory */ 5017 if (kmem_debugging()) 5018 arc_c = arc_c / 2; 5019 if (arc_c < arc_c_min) 5020 arc_c = arc_c_min; 5021 5022 arc_anon = &ARC_anon; 5023 arc_mru = &ARC_mru; 5024 arc_mru_ghost = &ARC_mru_ghost; 5025 arc_mfu = &ARC_mfu; 5026 arc_mfu_ghost = &ARC_mfu_ghost; 5027 arc_l2c_only = &ARC_l2c_only; 5028 arc_size = 0; 5029 5030 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5031 sizeof (arc_buf_hdr_t), 5032 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5033 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5034 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5035 sizeof (arc_buf_hdr_t), 5036 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5037 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5038 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5039 sizeof (arc_buf_hdr_t), 5040 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5041 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5042 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5043 sizeof (arc_buf_hdr_t), 5044 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5045 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5046 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5047 sizeof (arc_buf_hdr_t), 5048 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5049 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5050 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5051 sizeof (arc_buf_hdr_t), 5052 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5053 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5054 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5055 sizeof (arc_buf_hdr_t), 5056 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5057 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5058 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5059 sizeof (arc_buf_hdr_t), 5060 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5061 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5062 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5063 sizeof (arc_buf_hdr_t), 5064 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5065 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5066 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5067 sizeof (arc_buf_hdr_t), 5068 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5069 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5070 5071 refcount_create(&arc_anon->arcs_size); 5072 refcount_create(&arc_mru->arcs_size); 5073 refcount_create(&arc_mru_ghost->arcs_size); 5074 refcount_create(&arc_mfu->arcs_size); 5075 refcount_create(&arc_mfu_ghost->arcs_size); 5076 refcount_create(&arc_l2c_only->arcs_size); 5077 5078 buf_init(); 5079 5080 arc_reclaim_thread_exit = FALSE; 5081 arc_user_evicts_thread_exit = FALSE; 5082 arc_eviction_list = NULL; 5083 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5084 5085 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5086 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5087 5088 if (arc_ksp != NULL) { 5089 arc_ksp->ks_data = &arc_stats; 5090 arc_ksp->ks_update = arc_kstat_update; 5091 kstat_install(arc_ksp); 5092 } 5093 5094 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5095 TS_RUN, minclsyspri); 5096 5097 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5098 TS_RUN, minclsyspri); 5099 5100 arc_dead = FALSE; 5101 arc_warm = B_FALSE; 5102 5103 /* 5104 * Calculate maximum amount of dirty data per pool. 5105 * 5106 * If it has been set by /etc/system, take that. 5107 * Otherwise, use a percentage of physical memory defined by 5108 * zfs_dirty_data_max_percent (default 10%) with a cap at 5109 * zfs_dirty_data_max_max (default 4GB). 5110 */ 5111 if (zfs_dirty_data_max == 0) { 5112 zfs_dirty_data_max = physmem * PAGESIZE * 5113 zfs_dirty_data_max_percent / 100; 5114 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5115 zfs_dirty_data_max_max); 5116 } 5117 } 5118 5119 void 5120 arc_fini(void) 5121 { 5122 mutex_enter(&arc_reclaim_lock); 5123 arc_reclaim_thread_exit = TRUE; 5124 /* 5125 * The reclaim thread will set arc_reclaim_thread_exit back to 5126 * FALSE when it is finished exiting; we're waiting for that. 5127 */ 5128 while (arc_reclaim_thread_exit) { 5129 cv_signal(&arc_reclaim_thread_cv); 5130 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5131 } 5132 mutex_exit(&arc_reclaim_lock); 5133 5134 mutex_enter(&arc_user_evicts_lock); 5135 arc_user_evicts_thread_exit = TRUE; 5136 /* 5137 * The user evicts thread will set arc_user_evicts_thread_exit 5138 * to FALSE when it is finished exiting; we're waiting for that. 5139 */ 5140 while (arc_user_evicts_thread_exit) { 5141 cv_signal(&arc_user_evicts_cv); 5142 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5143 } 5144 mutex_exit(&arc_user_evicts_lock); 5145 5146 /* Use TRUE to ensure *all* buffers are evicted */ 5147 arc_flush(NULL, TRUE); 5148 5149 arc_dead = TRUE; 5150 5151 if (arc_ksp != NULL) { 5152 kstat_delete(arc_ksp); 5153 arc_ksp = NULL; 5154 } 5155 5156 mutex_destroy(&arc_reclaim_lock); 5157 cv_destroy(&arc_reclaim_thread_cv); 5158 cv_destroy(&arc_reclaim_waiters_cv); 5159 5160 mutex_destroy(&arc_user_evicts_lock); 5161 cv_destroy(&arc_user_evicts_cv); 5162 5163 refcount_destroy(&arc_anon->arcs_size); 5164 refcount_destroy(&arc_mru->arcs_size); 5165 refcount_destroy(&arc_mru_ghost->arcs_size); 5166 refcount_destroy(&arc_mfu->arcs_size); 5167 refcount_destroy(&arc_mfu_ghost->arcs_size); 5168 refcount_destroy(&arc_l2c_only->arcs_size); 5169 5170 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5171 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5172 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5173 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5174 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5175 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5176 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5177 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5178 5179 buf_fini(); 5180 5181 ASSERT0(arc_loaned_bytes); 5182 } 5183 5184 /* 5185 * Level 2 ARC 5186 * 5187 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5188 * It uses dedicated storage devices to hold cached data, which are populated 5189 * using large infrequent writes. The main role of this cache is to boost 5190 * the performance of random read workloads. The intended L2ARC devices 5191 * include short-stroked disks, solid state disks, and other media with 5192 * substantially faster read latency than disk. 5193 * 5194 * +-----------------------+ 5195 * | ARC | 5196 * +-----------------------+ 5197 * | ^ ^ 5198 * | | | 5199 * l2arc_feed_thread() arc_read() 5200 * | | | 5201 * | l2arc read | 5202 * V | | 5203 * +---------------+ | 5204 * | L2ARC | | 5205 * +---------------+ | 5206 * | ^ | 5207 * l2arc_write() | | 5208 * | | | 5209 * V | | 5210 * +-------+ +-------+ 5211 * | vdev | | vdev | 5212 * | cache | | cache | 5213 * +-------+ +-------+ 5214 * +=========+ .-----. 5215 * : L2ARC : |-_____-| 5216 * : devices : | Disks | 5217 * +=========+ `-_____-' 5218 * 5219 * Read requests are satisfied from the following sources, in order: 5220 * 5221 * 1) ARC 5222 * 2) vdev cache of L2ARC devices 5223 * 3) L2ARC devices 5224 * 4) vdev cache of disks 5225 * 5) disks 5226 * 5227 * Some L2ARC device types exhibit extremely slow write performance. 5228 * To accommodate for this there are some significant differences between 5229 * the L2ARC and traditional cache design: 5230 * 5231 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5232 * the ARC behave as usual, freeing buffers and placing headers on ghost 5233 * lists. The ARC does not send buffers to the L2ARC during eviction as 5234 * this would add inflated write latencies for all ARC memory pressure. 5235 * 5236 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5237 * It does this by periodically scanning buffers from the eviction-end of 5238 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5239 * not already there. It scans until a headroom of buffers is satisfied, 5240 * which itself is a buffer for ARC eviction. If a compressible buffer is 5241 * found during scanning and selected for writing to an L2ARC device, we 5242 * temporarily boost scanning headroom during the next scan cycle to make 5243 * sure we adapt to compression effects (which might significantly reduce 5244 * the data volume we write to L2ARC). The thread that does this is 5245 * l2arc_feed_thread(), illustrated below; example sizes are included to 5246 * provide a better sense of ratio than this diagram: 5247 * 5248 * head --> tail 5249 * +---------------------+----------+ 5250 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5251 * +---------------------+----------+ | o L2ARC eligible 5252 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5253 * +---------------------+----------+ | 5254 * 15.9 Gbytes ^ 32 Mbytes | 5255 * headroom | 5256 * l2arc_feed_thread() 5257 * | 5258 * l2arc write hand <--[oooo]--' 5259 * | 8 Mbyte 5260 * | write max 5261 * V 5262 * +==============================+ 5263 * L2ARC dev |####|#|###|###| |####| ... | 5264 * +==============================+ 5265 * 32 Gbytes 5266 * 5267 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5268 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5269 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5270 * safe to say that this is an uncommon case, since buffers at the end of 5271 * the ARC lists have moved there due to inactivity. 5272 * 5273 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5274 * then the L2ARC simply misses copying some buffers. This serves as a 5275 * pressure valve to prevent heavy read workloads from both stalling the ARC 5276 * with waits and clogging the L2ARC with writes. This also helps prevent 5277 * the potential for the L2ARC to churn if it attempts to cache content too 5278 * quickly, such as during backups of the entire pool. 5279 * 5280 * 5. After system boot and before the ARC has filled main memory, there are 5281 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5282 * lists can remain mostly static. Instead of searching from tail of these 5283 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5284 * for eligible buffers, greatly increasing its chance of finding them. 5285 * 5286 * The L2ARC device write speed is also boosted during this time so that 5287 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5288 * there are no L2ARC reads, and no fear of degrading read performance 5289 * through increased writes. 5290 * 5291 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5292 * the vdev queue can aggregate them into larger and fewer writes. Each 5293 * device is written to in a rotor fashion, sweeping writes through 5294 * available space then repeating. 5295 * 5296 * 7. The L2ARC does not store dirty content. It never needs to flush 5297 * write buffers back to disk based storage. 5298 * 5299 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5300 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5301 * 5302 * The performance of the L2ARC can be tweaked by a number of tunables, which 5303 * may be necessary for different workloads: 5304 * 5305 * l2arc_write_max max write bytes per interval 5306 * l2arc_write_boost extra write bytes during device warmup 5307 * l2arc_noprefetch skip caching prefetched buffers 5308 * l2arc_headroom number of max device writes to precache 5309 * l2arc_headroom_boost when we find compressed buffers during ARC 5310 * scanning, we multiply headroom by this 5311 * percentage factor for the next scan cycle, 5312 * since more compressed buffers are likely to 5313 * be present 5314 * l2arc_feed_secs seconds between L2ARC writing 5315 * 5316 * Tunables may be removed or added as future performance improvements are 5317 * integrated, and also may become zpool properties. 5318 * 5319 * There are three key functions that control how the L2ARC warms up: 5320 * 5321 * l2arc_write_eligible() check if a buffer is eligible to cache 5322 * l2arc_write_size() calculate how much to write 5323 * l2arc_write_interval() calculate sleep delay between writes 5324 * 5325 * These three functions determine what to write, how much, and how quickly 5326 * to send writes. 5327 */ 5328 5329 static boolean_t 5330 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5331 { 5332 /* 5333 * A buffer is *not* eligible for the L2ARC if it: 5334 * 1. belongs to a different spa. 5335 * 2. is already cached on the L2ARC. 5336 * 3. has an I/O in progress (it may be an incomplete read). 5337 * 4. is flagged not eligible (zfs property). 5338 */ 5339 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5340 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 5341 return (B_FALSE); 5342 5343 return (B_TRUE); 5344 } 5345 5346 static uint64_t 5347 l2arc_write_size(void) 5348 { 5349 uint64_t size; 5350 5351 /* 5352 * Make sure our globals have meaningful values in case the user 5353 * altered them. 5354 */ 5355 size = l2arc_write_max; 5356 if (size == 0) { 5357 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5358 "be greater than zero, resetting it to the default (%d)", 5359 L2ARC_WRITE_SIZE); 5360 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5361 } 5362 5363 if (arc_warm == B_FALSE) 5364 size += l2arc_write_boost; 5365 5366 return (size); 5367 5368 } 5369 5370 static clock_t 5371 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5372 { 5373 clock_t interval, next, now; 5374 5375 /* 5376 * If the ARC lists are busy, increase our write rate; if the 5377 * lists are stale, idle back. This is achieved by checking 5378 * how much we previously wrote - if it was more than half of 5379 * what we wanted, schedule the next write much sooner. 5380 */ 5381 if (l2arc_feed_again && wrote > (wanted / 2)) 5382 interval = (hz * l2arc_feed_min_ms) / 1000; 5383 else 5384 interval = hz * l2arc_feed_secs; 5385 5386 now = ddi_get_lbolt(); 5387 next = MAX(now, MIN(now + interval, began + interval)); 5388 5389 return (next); 5390 } 5391 5392 /* 5393 * Cycle through L2ARC devices. This is how L2ARC load balances. 5394 * If a device is returned, this also returns holding the spa config lock. 5395 */ 5396 static l2arc_dev_t * 5397 l2arc_dev_get_next(void) 5398 { 5399 l2arc_dev_t *first, *next = NULL; 5400 5401 /* 5402 * Lock out the removal of spas (spa_namespace_lock), then removal 5403 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5404 * both locks will be dropped and a spa config lock held instead. 5405 */ 5406 mutex_enter(&spa_namespace_lock); 5407 mutex_enter(&l2arc_dev_mtx); 5408 5409 /* if there are no vdevs, there is nothing to do */ 5410 if (l2arc_ndev == 0) 5411 goto out; 5412 5413 first = NULL; 5414 next = l2arc_dev_last; 5415 do { 5416 /* loop around the list looking for a non-faulted vdev */ 5417 if (next == NULL) { 5418 next = list_head(l2arc_dev_list); 5419 } else { 5420 next = list_next(l2arc_dev_list, next); 5421 if (next == NULL) 5422 next = list_head(l2arc_dev_list); 5423 } 5424 5425 /* if we have come back to the start, bail out */ 5426 if (first == NULL) 5427 first = next; 5428 else if (next == first) 5429 break; 5430 5431 } while (vdev_is_dead(next->l2ad_vdev)); 5432 5433 /* if we were unable to find any usable vdevs, return NULL */ 5434 if (vdev_is_dead(next->l2ad_vdev)) 5435 next = NULL; 5436 5437 l2arc_dev_last = next; 5438 5439 out: 5440 mutex_exit(&l2arc_dev_mtx); 5441 5442 /* 5443 * Grab the config lock to prevent the 'next' device from being 5444 * removed while we are writing to it. 5445 */ 5446 if (next != NULL) 5447 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5448 mutex_exit(&spa_namespace_lock); 5449 5450 return (next); 5451 } 5452 5453 /* 5454 * Free buffers that were tagged for destruction. 5455 */ 5456 static void 5457 l2arc_do_free_on_write() 5458 { 5459 list_t *buflist; 5460 l2arc_data_free_t *df, *df_prev; 5461 5462 mutex_enter(&l2arc_free_on_write_mtx); 5463 buflist = l2arc_free_on_write; 5464 5465 for (df = list_tail(buflist); df; df = df_prev) { 5466 df_prev = list_prev(buflist, df); 5467 ASSERT(df->l2df_data != NULL); 5468 ASSERT(df->l2df_func != NULL); 5469 df->l2df_func(df->l2df_data, df->l2df_size); 5470 list_remove(buflist, df); 5471 kmem_free(df, sizeof (l2arc_data_free_t)); 5472 } 5473 5474 mutex_exit(&l2arc_free_on_write_mtx); 5475 } 5476 5477 /* 5478 * A write to a cache device has completed. Update all headers to allow 5479 * reads from these buffers to begin. 5480 */ 5481 static void 5482 l2arc_write_done(zio_t *zio) 5483 { 5484 l2arc_write_callback_t *cb; 5485 l2arc_dev_t *dev; 5486 list_t *buflist; 5487 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5488 kmutex_t *hash_lock; 5489 int64_t bytes_dropped = 0; 5490 5491 cb = zio->io_private; 5492 ASSERT(cb != NULL); 5493 dev = cb->l2wcb_dev; 5494 ASSERT(dev != NULL); 5495 head = cb->l2wcb_head; 5496 ASSERT(head != NULL); 5497 buflist = &dev->l2ad_buflist; 5498 ASSERT(buflist != NULL); 5499 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5500 l2arc_write_callback_t *, cb); 5501 5502 if (zio->io_error != 0) 5503 ARCSTAT_BUMP(arcstat_l2_writes_error); 5504 5505 /* 5506 * All writes completed, or an error was hit. 5507 */ 5508 top: 5509 mutex_enter(&dev->l2ad_mtx); 5510 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5511 hdr_prev = list_prev(buflist, hdr); 5512 5513 hash_lock = HDR_LOCK(hdr); 5514 5515 /* 5516 * We cannot use mutex_enter or else we can deadlock 5517 * with l2arc_write_buffers (due to swapping the order 5518 * the hash lock and l2ad_mtx are taken). 5519 */ 5520 if (!mutex_tryenter(hash_lock)) { 5521 /* 5522 * Missed the hash lock. We must retry so we 5523 * don't leave the ARC_FLAG_L2_WRITING bit set. 5524 */ 5525 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5526 5527 /* 5528 * We don't want to rescan the headers we've 5529 * already marked as having been written out, so 5530 * we reinsert the head node so we can pick up 5531 * where we left off. 5532 */ 5533 list_remove(buflist, head); 5534 list_insert_after(buflist, hdr, head); 5535 5536 mutex_exit(&dev->l2ad_mtx); 5537 5538 /* 5539 * We wait for the hash lock to become available 5540 * to try and prevent busy waiting, and increase 5541 * the chance we'll be able to acquire the lock 5542 * the next time around. 5543 */ 5544 mutex_enter(hash_lock); 5545 mutex_exit(hash_lock); 5546 goto top; 5547 } 5548 5549 /* 5550 * We could not have been moved into the arc_l2c_only 5551 * state while in-flight due to our ARC_FLAG_L2_WRITING 5552 * bit being set. Let's just ensure that's being enforced. 5553 */ 5554 ASSERT(HDR_HAS_L1HDR(hdr)); 5555 5556 /* 5557 * We may have allocated a buffer for L2ARC compression, 5558 * we must release it to avoid leaking this data. 5559 */ 5560 l2arc_release_cdata_buf(hdr); 5561 5562 if (zio->io_error != 0) { 5563 /* 5564 * Error - drop L2ARC entry. 5565 */ 5566 list_remove(buflist, hdr); 5567 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5568 5569 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5570 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5571 5572 bytes_dropped += hdr->b_l2hdr.b_asize; 5573 (void) refcount_remove_many(&dev->l2ad_alloc, 5574 hdr->b_l2hdr.b_asize, hdr); 5575 } 5576 5577 /* 5578 * Allow ARC to begin reads and ghost list evictions to 5579 * this L2ARC entry. 5580 */ 5581 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5582 5583 mutex_exit(hash_lock); 5584 } 5585 5586 atomic_inc_64(&l2arc_writes_done); 5587 list_remove(buflist, head); 5588 ASSERT(!HDR_HAS_L1HDR(head)); 5589 kmem_cache_free(hdr_l2only_cache, head); 5590 mutex_exit(&dev->l2ad_mtx); 5591 5592 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5593 5594 l2arc_do_free_on_write(); 5595 5596 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5597 } 5598 5599 /* 5600 * A read to a cache device completed. Validate buffer contents before 5601 * handing over to the regular ARC routines. 5602 */ 5603 static void 5604 l2arc_read_done(zio_t *zio) 5605 { 5606 l2arc_read_callback_t *cb; 5607 arc_buf_hdr_t *hdr; 5608 arc_buf_t *buf; 5609 kmutex_t *hash_lock; 5610 int equal; 5611 5612 ASSERT(zio->io_vd != NULL); 5613 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5614 5615 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5616 5617 cb = zio->io_private; 5618 ASSERT(cb != NULL); 5619 buf = cb->l2rcb_buf; 5620 ASSERT(buf != NULL); 5621 5622 hash_lock = HDR_LOCK(buf->b_hdr); 5623 mutex_enter(hash_lock); 5624 hdr = buf->b_hdr; 5625 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5626 5627 /* 5628 * If the buffer was compressed, decompress it first. 5629 */ 5630 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5631 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5632 ASSERT(zio->io_data != NULL); 5633 5634 /* 5635 * Check this survived the L2ARC journey. 5636 */ 5637 equal = arc_cksum_equal(buf); 5638 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5639 mutex_exit(hash_lock); 5640 zio->io_private = buf; 5641 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5642 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5643 arc_read_done(zio); 5644 } else { 5645 mutex_exit(hash_lock); 5646 /* 5647 * Buffer didn't survive caching. Increment stats and 5648 * reissue to the original storage device. 5649 */ 5650 if (zio->io_error != 0) { 5651 ARCSTAT_BUMP(arcstat_l2_io_error); 5652 } else { 5653 zio->io_error = SET_ERROR(EIO); 5654 } 5655 if (!equal) 5656 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5657 5658 /* 5659 * If there's no waiter, issue an async i/o to the primary 5660 * storage now. If there *is* a waiter, the caller must 5661 * issue the i/o in a context where it's OK to block. 5662 */ 5663 if (zio->io_waiter == NULL) { 5664 zio_t *pio = zio_unique_parent(zio); 5665 5666 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5667 5668 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5669 buf->b_data, zio->io_size, arc_read_done, buf, 5670 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5671 } 5672 } 5673 5674 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5675 } 5676 5677 /* 5678 * This is the list priority from which the L2ARC will search for pages to 5679 * cache. This is used within loops (0..3) to cycle through lists in the 5680 * desired order. This order can have a significant effect on cache 5681 * performance. 5682 * 5683 * Currently the metadata lists are hit first, MFU then MRU, followed by 5684 * the data lists. This function returns a locked list, and also returns 5685 * the lock pointer. 5686 */ 5687 static multilist_sublist_t * 5688 l2arc_sublist_lock(int list_num) 5689 { 5690 multilist_t *ml = NULL; 5691 unsigned int idx; 5692 5693 ASSERT(list_num >= 0 && list_num <= 3); 5694 5695 switch (list_num) { 5696 case 0: 5697 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 5698 break; 5699 case 1: 5700 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 5701 break; 5702 case 2: 5703 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 5704 break; 5705 case 3: 5706 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 5707 break; 5708 } 5709 5710 /* 5711 * Return a randomly-selected sublist. This is acceptable 5712 * because the caller feeds only a little bit of data for each 5713 * call (8MB). Subsequent calls will result in different 5714 * sublists being selected. 5715 */ 5716 idx = multilist_get_random_index(ml); 5717 return (multilist_sublist_lock(ml, idx)); 5718 } 5719 5720 /* 5721 * Evict buffers from the device write hand to the distance specified in 5722 * bytes. This distance may span populated buffers, it may span nothing. 5723 * This is clearing a region on the L2ARC device ready for writing. 5724 * If the 'all' boolean is set, every buffer is evicted. 5725 */ 5726 static void 5727 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5728 { 5729 list_t *buflist; 5730 arc_buf_hdr_t *hdr, *hdr_prev; 5731 kmutex_t *hash_lock; 5732 uint64_t taddr; 5733 5734 buflist = &dev->l2ad_buflist; 5735 5736 if (!all && dev->l2ad_first) { 5737 /* 5738 * This is the first sweep through the device. There is 5739 * nothing to evict. 5740 */ 5741 return; 5742 } 5743 5744 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5745 /* 5746 * When nearing the end of the device, evict to the end 5747 * before the device write hand jumps to the start. 5748 */ 5749 taddr = dev->l2ad_end; 5750 } else { 5751 taddr = dev->l2ad_hand + distance; 5752 } 5753 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5754 uint64_t, taddr, boolean_t, all); 5755 5756 top: 5757 mutex_enter(&dev->l2ad_mtx); 5758 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5759 hdr_prev = list_prev(buflist, hdr); 5760 5761 hash_lock = HDR_LOCK(hdr); 5762 5763 /* 5764 * We cannot use mutex_enter or else we can deadlock 5765 * with l2arc_write_buffers (due to swapping the order 5766 * the hash lock and l2ad_mtx are taken). 5767 */ 5768 if (!mutex_tryenter(hash_lock)) { 5769 /* 5770 * Missed the hash lock. Retry. 5771 */ 5772 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5773 mutex_exit(&dev->l2ad_mtx); 5774 mutex_enter(hash_lock); 5775 mutex_exit(hash_lock); 5776 goto top; 5777 } 5778 5779 if (HDR_L2_WRITE_HEAD(hdr)) { 5780 /* 5781 * We hit a write head node. Leave it for 5782 * l2arc_write_done(). 5783 */ 5784 list_remove(buflist, hdr); 5785 mutex_exit(hash_lock); 5786 continue; 5787 } 5788 5789 if (!all && HDR_HAS_L2HDR(hdr) && 5790 (hdr->b_l2hdr.b_daddr > taddr || 5791 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5792 /* 5793 * We've evicted to the target address, 5794 * or the end of the device. 5795 */ 5796 mutex_exit(hash_lock); 5797 break; 5798 } 5799 5800 ASSERT(HDR_HAS_L2HDR(hdr)); 5801 if (!HDR_HAS_L1HDR(hdr)) { 5802 ASSERT(!HDR_L2_READING(hdr)); 5803 /* 5804 * This doesn't exist in the ARC. Destroy. 5805 * arc_hdr_destroy() will call list_remove() 5806 * and decrement arcstat_l2_size. 5807 */ 5808 arc_change_state(arc_anon, hdr, hash_lock); 5809 arc_hdr_destroy(hdr); 5810 } else { 5811 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5812 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5813 /* 5814 * Invalidate issued or about to be issued 5815 * reads, since we may be about to write 5816 * over this location. 5817 */ 5818 if (HDR_L2_READING(hdr)) { 5819 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5820 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5821 } 5822 5823 /* Ensure this header has finished being written */ 5824 ASSERT(!HDR_L2_WRITING(hdr)); 5825 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 5826 5827 arc_hdr_l2hdr_destroy(hdr); 5828 } 5829 mutex_exit(hash_lock); 5830 } 5831 mutex_exit(&dev->l2ad_mtx); 5832 } 5833 5834 /* 5835 * Find and write ARC buffers to the L2ARC device. 5836 * 5837 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5838 * for reading until they have completed writing. 5839 * The headroom_boost is an in-out parameter used to maintain headroom boost 5840 * state between calls to this function. 5841 * 5842 * Returns the number of bytes actually written (which may be smaller than 5843 * the delta by which the device hand has changed due to alignment). 5844 */ 5845 static uint64_t 5846 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5847 boolean_t *headroom_boost) 5848 { 5849 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5850 uint64_t write_asize, write_psize, write_sz, headroom, 5851 buf_compress_minsz; 5852 void *buf_data; 5853 boolean_t full; 5854 l2arc_write_callback_t *cb; 5855 zio_t *pio, *wzio; 5856 uint64_t guid = spa_load_guid(spa); 5857 const boolean_t do_headroom_boost = *headroom_boost; 5858 5859 ASSERT(dev->l2ad_vdev != NULL); 5860 5861 /* Lower the flag now, we might want to raise it again later. */ 5862 *headroom_boost = B_FALSE; 5863 5864 pio = NULL; 5865 write_sz = write_asize = write_psize = 0; 5866 full = B_FALSE; 5867 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5868 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5869 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5870 5871 /* 5872 * We will want to try to compress buffers that are at least 2x the 5873 * device sector size. 5874 */ 5875 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5876 5877 /* 5878 * Copy buffers for L2ARC writing. 5879 */ 5880 for (int try = 0; try <= 3; try++) { 5881 multilist_sublist_t *mls = l2arc_sublist_lock(try); 5882 uint64_t passed_sz = 0; 5883 5884 /* 5885 * L2ARC fast warmup. 5886 * 5887 * Until the ARC is warm and starts to evict, read from the 5888 * head of the ARC lists rather than the tail. 5889 */ 5890 if (arc_warm == B_FALSE) 5891 hdr = multilist_sublist_head(mls); 5892 else 5893 hdr = multilist_sublist_tail(mls); 5894 5895 headroom = target_sz * l2arc_headroom; 5896 if (do_headroom_boost) 5897 headroom = (headroom * l2arc_headroom_boost) / 100; 5898 5899 for (; hdr; hdr = hdr_prev) { 5900 kmutex_t *hash_lock; 5901 uint64_t buf_sz; 5902 5903 if (arc_warm == B_FALSE) 5904 hdr_prev = multilist_sublist_next(mls, hdr); 5905 else 5906 hdr_prev = multilist_sublist_prev(mls, hdr); 5907 5908 hash_lock = HDR_LOCK(hdr); 5909 if (!mutex_tryenter(hash_lock)) { 5910 /* 5911 * Skip this buffer rather than waiting. 5912 */ 5913 continue; 5914 } 5915 5916 passed_sz += hdr->b_size; 5917 if (passed_sz > headroom) { 5918 /* 5919 * Searched too far. 5920 */ 5921 mutex_exit(hash_lock); 5922 break; 5923 } 5924 5925 if (!l2arc_write_eligible(guid, hdr)) { 5926 mutex_exit(hash_lock); 5927 continue; 5928 } 5929 5930 if ((write_sz + hdr->b_size) > target_sz) { 5931 full = B_TRUE; 5932 mutex_exit(hash_lock); 5933 break; 5934 } 5935 5936 if (pio == NULL) { 5937 /* 5938 * Insert a dummy header on the buflist so 5939 * l2arc_write_done() can find where the 5940 * write buffers begin without searching. 5941 */ 5942 mutex_enter(&dev->l2ad_mtx); 5943 list_insert_head(&dev->l2ad_buflist, head); 5944 mutex_exit(&dev->l2ad_mtx); 5945 5946 cb = kmem_alloc( 5947 sizeof (l2arc_write_callback_t), KM_SLEEP); 5948 cb->l2wcb_dev = dev; 5949 cb->l2wcb_head = head; 5950 pio = zio_root(spa, l2arc_write_done, cb, 5951 ZIO_FLAG_CANFAIL); 5952 } 5953 5954 /* 5955 * Create and add a new L2ARC header. 5956 */ 5957 hdr->b_l2hdr.b_dev = dev; 5958 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5959 /* 5960 * Temporarily stash the data buffer in b_tmp_cdata. 5961 * The subsequent write step will pick it up from 5962 * there. This is because can't access b_l1hdr.b_buf 5963 * without holding the hash_lock, which we in turn 5964 * can't access without holding the ARC list locks 5965 * (which we want to avoid during compression/writing). 5966 */ 5967 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5968 hdr->b_l2hdr.b_asize = hdr->b_size; 5969 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5970 5971 /* 5972 * Explicitly set the b_daddr field to a known 5973 * value which means "invalid address". This 5974 * enables us to differentiate which stage of 5975 * l2arc_write_buffers() the particular header 5976 * is in (e.g. this loop, or the one below). 5977 * ARC_FLAG_L2_WRITING is not enough to make 5978 * this distinction, and we need to know in 5979 * order to do proper l2arc vdev accounting in 5980 * arc_release() and arc_hdr_destroy(). 5981 * 5982 * Note, we can't use a new flag to distinguish 5983 * the two stages because we don't hold the 5984 * header's hash_lock below, in the second stage 5985 * of this function. Thus, we can't simply 5986 * change the b_flags field to denote that the 5987 * IO has been sent. We can change the b_daddr 5988 * field of the L2 portion, though, since we'll 5989 * be holding the l2ad_mtx; which is why we're 5990 * using it to denote the header's state change. 5991 */ 5992 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 5993 5994 buf_sz = hdr->b_size; 5995 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5996 5997 mutex_enter(&dev->l2ad_mtx); 5998 list_insert_head(&dev->l2ad_buflist, hdr); 5999 mutex_exit(&dev->l2ad_mtx); 6000 6001 /* 6002 * Compute and store the buffer cksum before 6003 * writing. On debug the cksum is verified first. 6004 */ 6005 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6006 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6007 6008 mutex_exit(hash_lock); 6009 6010 write_sz += buf_sz; 6011 } 6012 6013 multilist_sublist_unlock(mls); 6014 6015 if (full == B_TRUE) 6016 break; 6017 } 6018 6019 /* No buffers selected for writing? */ 6020 if (pio == NULL) { 6021 ASSERT0(write_sz); 6022 ASSERT(!HDR_HAS_L1HDR(head)); 6023 kmem_cache_free(hdr_l2only_cache, head); 6024 return (0); 6025 } 6026 6027 mutex_enter(&dev->l2ad_mtx); 6028 6029 /* 6030 * Now start writing the buffers. We're starting at the write head 6031 * and work backwards, retracing the course of the buffer selector 6032 * loop above. 6033 */ 6034 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6035 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6036 uint64_t buf_sz; 6037 6038 /* 6039 * We rely on the L1 portion of the header below, so 6040 * it's invalid for this header to have been evicted out 6041 * of the ghost cache, prior to being written out. The 6042 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6043 */ 6044 ASSERT(HDR_HAS_L1HDR(hdr)); 6045 6046 /* 6047 * We shouldn't need to lock the buffer here, since we flagged 6048 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6049 * take care to only access its L2 cache parameters. In 6050 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6051 * ARC eviction. 6052 */ 6053 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6054 6055 if ((HDR_L2COMPRESS(hdr)) && 6056 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 6057 if (l2arc_compress_buf(hdr)) { 6058 /* 6059 * If compression succeeded, enable headroom 6060 * boost on the next scan cycle. 6061 */ 6062 *headroom_boost = B_TRUE; 6063 } 6064 } 6065 6066 /* 6067 * Pick up the buffer data we had previously stashed away 6068 * (and now potentially also compressed). 6069 */ 6070 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6071 buf_sz = hdr->b_l2hdr.b_asize; 6072 6073 /* 6074 * We need to do this regardless if buf_sz is zero or 6075 * not, otherwise, when this l2hdr is evicted we'll 6076 * remove a reference that was never added. 6077 */ 6078 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6079 6080 /* Compression may have squashed the buffer to zero length. */ 6081 if (buf_sz != 0) { 6082 uint64_t buf_p_sz; 6083 6084 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6085 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6086 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6087 ZIO_FLAG_CANFAIL, B_FALSE); 6088 6089 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6090 zio_t *, wzio); 6091 (void) zio_nowait(wzio); 6092 6093 write_asize += buf_sz; 6094 6095 /* 6096 * Keep the clock hand suitably device-aligned. 6097 */ 6098 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6099 write_psize += buf_p_sz; 6100 dev->l2ad_hand += buf_p_sz; 6101 } 6102 } 6103 6104 mutex_exit(&dev->l2ad_mtx); 6105 6106 ASSERT3U(write_asize, <=, target_sz); 6107 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6108 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6109 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6110 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6111 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6112 6113 /* 6114 * Bump device hand to the device start if it is approaching the end. 6115 * l2arc_evict() will already have evicted ahead for this case. 6116 */ 6117 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6118 dev->l2ad_hand = dev->l2ad_start; 6119 dev->l2ad_first = B_FALSE; 6120 } 6121 6122 dev->l2ad_writing = B_TRUE; 6123 (void) zio_wait(pio); 6124 dev->l2ad_writing = B_FALSE; 6125 6126 return (write_asize); 6127 } 6128 6129 /* 6130 * Compresses an L2ARC buffer. 6131 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6132 * size in l2hdr->b_asize. This routine tries to compress the data and 6133 * depending on the compression result there are three possible outcomes: 6134 * *) The buffer was incompressible. The original l2hdr contents were left 6135 * untouched and are ready for writing to an L2 device. 6136 * *) The buffer was all-zeros, so there is no need to write it to an L2 6137 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6138 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6139 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6140 * data buffer which holds the compressed data to be written, and b_asize 6141 * tells us how much data there is. b_compress is set to the appropriate 6142 * compression algorithm. Once writing is done, invoke 6143 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6144 * 6145 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6146 * buffer was incompressible). 6147 */ 6148 static boolean_t 6149 l2arc_compress_buf(arc_buf_hdr_t *hdr) 6150 { 6151 void *cdata; 6152 size_t csize, len, rounded; 6153 ASSERT(HDR_HAS_L2HDR(hdr)); 6154 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6155 6156 ASSERT(HDR_HAS_L1HDR(hdr)); 6157 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 6158 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6159 6160 len = l2hdr->b_asize; 6161 cdata = zio_data_buf_alloc(len); 6162 ASSERT3P(cdata, !=, NULL); 6163 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6164 cdata, l2hdr->b_asize); 6165 6166 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 6167 if (rounded > csize) { 6168 bzero((char *)cdata + csize, rounded - csize); 6169 csize = rounded; 6170 } 6171 6172 if (csize == 0) { 6173 /* zero block, indicate that there's nothing to write */ 6174 zio_data_buf_free(cdata, len); 6175 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 6176 l2hdr->b_asize = 0; 6177 hdr->b_l1hdr.b_tmp_cdata = NULL; 6178 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6179 return (B_TRUE); 6180 } else if (csize > 0 && csize < len) { 6181 /* 6182 * Compression succeeded, we'll keep the cdata around for 6183 * writing and release it afterwards. 6184 */ 6185 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 6186 l2hdr->b_asize = csize; 6187 hdr->b_l1hdr.b_tmp_cdata = cdata; 6188 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6189 return (B_TRUE); 6190 } else { 6191 /* 6192 * Compression failed, release the compressed buffer. 6193 * l2hdr will be left unmodified. 6194 */ 6195 zio_data_buf_free(cdata, len); 6196 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6197 return (B_FALSE); 6198 } 6199 } 6200 6201 /* 6202 * Decompresses a zio read back from an l2arc device. On success, the 6203 * underlying zio's io_data buffer is overwritten by the uncompressed 6204 * version. On decompression error (corrupt compressed stream), the 6205 * zio->io_error value is set to signal an I/O error. 6206 * 6207 * Please note that the compressed data stream is not checksummed, so 6208 * if the underlying device is experiencing data corruption, we may feed 6209 * corrupt data to the decompressor, so the decompressor needs to be 6210 * able to handle this situation (LZ4 does). 6211 */ 6212 static void 6213 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6214 { 6215 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6216 6217 if (zio->io_error != 0) { 6218 /* 6219 * An io error has occured, just restore the original io 6220 * size in preparation for a main pool read. 6221 */ 6222 zio->io_orig_size = zio->io_size = hdr->b_size; 6223 return; 6224 } 6225 6226 if (c == ZIO_COMPRESS_EMPTY) { 6227 /* 6228 * An empty buffer results in a null zio, which means we 6229 * need to fill its io_data after we're done restoring the 6230 * buffer's contents. 6231 */ 6232 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6233 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6234 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6235 } else { 6236 ASSERT(zio->io_data != NULL); 6237 /* 6238 * We copy the compressed data from the start of the arc buffer 6239 * (the zio_read will have pulled in only what we need, the 6240 * rest is garbage which we will overwrite at decompression) 6241 * and then decompress back to the ARC data buffer. This way we 6242 * can minimize copying by simply decompressing back over the 6243 * original compressed data (rather than decompressing to an 6244 * aux buffer and then copying back the uncompressed buffer, 6245 * which is likely to be much larger). 6246 */ 6247 uint64_t csize; 6248 void *cdata; 6249 6250 csize = zio->io_size; 6251 cdata = zio_data_buf_alloc(csize); 6252 bcopy(zio->io_data, cdata, csize); 6253 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6254 hdr->b_size) != 0) 6255 zio->io_error = EIO; 6256 zio_data_buf_free(cdata, csize); 6257 } 6258 6259 /* Restore the expected uncompressed IO size. */ 6260 zio->io_orig_size = zio->io_size = hdr->b_size; 6261 } 6262 6263 /* 6264 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6265 * This buffer serves as a temporary holder of compressed data while 6266 * the buffer entry is being written to an l2arc device. Once that is 6267 * done, we can dispose of it. 6268 */ 6269 static void 6270 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6271 { 6272 enum zio_compress comp = HDR_GET_COMPRESS(hdr); 6273 6274 ASSERT(HDR_HAS_L1HDR(hdr)); 6275 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6276 6277 if (comp == ZIO_COMPRESS_OFF) { 6278 /* 6279 * In this case, b_tmp_cdata points to the same buffer 6280 * as the arc_buf_t's b_data field. We don't want to 6281 * free it, since the arc_buf_t will handle that. 6282 */ 6283 hdr->b_l1hdr.b_tmp_cdata = NULL; 6284 } else if (comp == ZIO_COMPRESS_EMPTY) { 6285 /* 6286 * In this case, b_tmp_cdata was compressed to an empty 6287 * buffer, thus there's nothing to free and b_tmp_cdata 6288 * should have been set to NULL in l2arc_write_buffers(). 6289 */ 6290 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6291 } else { 6292 /* 6293 * If the data was compressed, then we've allocated a 6294 * temporary buffer for it, so now we need to release it. 6295 */ 6296 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6297 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6298 hdr->b_size); 6299 hdr->b_l1hdr.b_tmp_cdata = NULL; 6300 } 6301 6302 } 6303 6304 /* 6305 * This thread feeds the L2ARC at regular intervals. This is the beating 6306 * heart of the L2ARC. 6307 */ 6308 static void 6309 l2arc_feed_thread(void) 6310 { 6311 callb_cpr_t cpr; 6312 l2arc_dev_t *dev; 6313 spa_t *spa; 6314 uint64_t size, wrote; 6315 clock_t begin, next = ddi_get_lbolt(); 6316 boolean_t headroom_boost = B_FALSE; 6317 6318 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6319 6320 mutex_enter(&l2arc_feed_thr_lock); 6321 6322 while (l2arc_thread_exit == 0) { 6323 CALLB_CPR_SAFE_BEGIN(&cpr); 6324 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6325 next); 6326 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6327 next = ddi_get_lbolt() + hz; 6328 6329 /* 6330 * Quick check for L2ARC devices. 6331 */ 6332 mutex_enter(&l2arc_dev_mtx); 6333 if (l2arc_ndev == 0) { 6334 mutex_exit(&l2arc_dev_mtx); 6335 continue; 6336 } 6337 mutex_exit(&l2arc_dev_mtx); 6338 begin = ddi_get_lbolt(); 6339 6340 /* 6341 * This selects the next l2arc device to write to, and in 6342 * doing so the next spa to feed from: dev->l2ad_spa. This 6343 * will return NULL if there are now no l2arc devices or if 6344 * they are all faulted. 6345 * 6346 * If a device is returned, its spa's config lock is also 6347 * held to prevent device removal. l2arc_dev_get_next() 6348 * will grab and release l2arc_dev_mtx. 6349 */ 6350 if ((dev = l2arc_dev_get_next()) == NULL) 6351 continue; 6352 6353 spa = dev->l2ad_spa; 6354 ASSERT(spa != NULL); 6355 6356 /* 6357 * If the pool is read-only then force the feed thread to 6358 * sleep a little longer. 6359 */ 6360 if (!spa_writeable(spa)) { 6361 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6362 spa_config_exit(spa, SCL_L2ARC, dev); 6363 continue; 6364 } 6365 6366 /* 6367 * Avoid contributing to memory pressure. 6368 */ 6369 if (arc_reclaim_needed()) { 6370 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6371 spa_config_exit(spa, SCL_L2ARC, dev); 6372 continue; 6373 } 6374 6375 ARCSTAT_BUMP(arcstat_l2_feeds); 6376 6377 size = l2arc_write_size(); 6378 6379 /* 6380 * Evict L2ARC buffers that will be overwritten. 6381 */ 6382 l2arc_evict(dev, size, B_FALSE); 6383 6384 /* 6385 * Write ARC buffers. 6386 */ 6387 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6388 6389 /* 6390 * Calculate interval between writes. 6391 */ 6392 next = l2arc_write_interval(begin, size, wrote); 6393 spa_config_exit(spa, SCL_L2ARC, dev); 6394 } 6395 6396 l2arc_thread_exit = 0; 6397 cv_broadcast(&l2arc_feed_thr_cv); 6398 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6399 thread_exit(); 6400 } 6401 6402 boolean_t 6403 l2arc_vdev_present(vdev_t *vd) 6404 { 6405 l2arc_dev_t *dev; 6406 6407 mutex_enter(&l2arc_dev_mtx); 6408 for (dev = list_head(l2arc_dev_list); dev != NULL; 6409 dev = list_next(l2arc_dev_list, dev)) { 6410 if (dev->l2ad_vdev == vd) 6411 break; 6412 } 6413 mutex_exit(&l2arc_dev_mtx); 6414 6415 return (dev != NULL); 6416 } 6417 6418 /* 6419 * Add a vdev for use by the L2ARC. By this point the spa has already 6420 * validated the vdev and opened it. 6421 */ 6422 void 6423 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6424 { 6425 l2arc_dev_t *adddev; 6426 6427 ASSERT(!l2arc_vdev_present(vd)); 6428 6429 /* 6430 * Create a new l2arc device entry. 6431 */ 6432 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6433 adddev->l2ad_spa = spa; 6434 adddev->l2ad_vdev = vd; 6435 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6436 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6437 adddev->l2ad_hand = adddev->l2ad_start; 6438 adddev->l2ad_first = B_TRUE; 6439 adddev->l2ad_writing = B_FALSE; 6440 6441 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6442 /* 6443 * This is a list of all ARC buffers that are still valid on the 6444 * device. 6445 */ 6446 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6447 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6448 6449 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6450 refcount_create(&adddev->l2ad_alloc); 6451 6452 /* 6453 * Add device to global list 6454 */ 6455 mutex_enter(&l2arc_dev_mtx); 6456 list_insert_head(l2arc_dev_list, adddev); 6457 atomic_inc_64(&l2arc_ndev); 6458 mutex_exit(&l2arc_dev_mtx); 6459 } 6460 6461 /* 6462 * Remove a vdev from the L2ARC. 6463 */ 6464 void 6465 l2arc_remove_vdev(vdev_t *vd) 6466 { 6467 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6468 6469 /* 6470 * Find the device by vdev 6471 */ 6472 mutex_enter(&l2arc_dev_mtx); 6473 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6474 nextdev = list_next(l2arc_dev_list, dev); 6475 if (vd == dev->l2ad_vdev) { 6476 remdev = dev; 6477 break; 6478 } 6479 } 6480 ASSERT(remdev != NULL); 6481 6482 /* 6483 * Remove device from global list 6484 */ 6485 list_remove(l2arc_dev_list, remdev); 6486 l2arc_dev_last = NULL; /* may have been invalidated */ 6487 atomic_dec_64(&l2arc_ndev); 6488 mutex_exit(&l2arc_dev_mtx); 6489 6490 /* 6491 * Clear all buflists and ARC references. L2ARC device flush. 6492 */ 6493 l2arc_evict(remdev, 0, B_TRUE); 6494 list_destroy(&remdev->l2ad_buflist); 6495 mutex_destroy(&remdev->l2ad_mtx); 6496 refcount_destroy(&remdev->l2ad_alloc); 6497 kmem_free(remdev, sizeof (l2arc_dev_t)); 6498 } 6499 6500 void 6501 l2arc_init(void) 6502 { 6503 l2arc_thread_exit = 0; 6504 l2arc_ndev = 0; 6505 l2arc_writes_sent = 0; 6506 l2arc_writes_done = 0; 6507 6508 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6509 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6510 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6511 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6512 6513 l2arc_dev_list = &L2ARC_dev_list; 6514 l2arc_free_on_write = &L2ARC_free_on_write; 6515 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6516 offsetof(l2arc_dev_t, l2ad_node)); 6517 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6518 offsetof(l2arc_data_free_t, l2df_list_node)); 6519 } 6520 6521 void 6522 l2arc_fini(void) 6523 { 6524 /* 6525 * This is called from dmu_fini(), which is called from spa_fini(); 6526 * Because of this, we can assume that all l2arc devices have 6527 * already been removed when the pools themselves were removed. 6528 */ 6529 6530 l2arc_do_free_on_write(); 6531 6532 mutex_destroy(&l2arc_feed_thr_lock); 6533 cv_destroy(&l2arc_feed_thr_cv); 6534 mutex_destroy(&l2arc_dev_mtx); 6535 mutex_destroy(&l2arc_free_on_write_mtx); 6536 6537 list_destroy(l2arc_dev_list); 6538 list_destroy(l2arc_free_on_write); 6539 } 6540 6541 void 6542 l2arc_start(void) 6543 { 6544 if (!(spa_mode_global & FWRITE)) 6545 return; 6546 6547 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6548 TS_RUN, minclsyspri); 6549 } 6550 6551 void 6552 l2arc_stop(void) 6553 { 6554 if (!(spa_mode_global & FWRITE)) 6555 return; 6556 6557 mutex_enter(&l2arc_feed_thr_lock); 6558 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6559 l2arc_thread_exit = 1; 6560 while (l2arc_thread_exit != 0) 6561 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6562 mutex_exit(&l2arc_feed_thr_lock); 6563 }