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 2014 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #include <sys/multilist.h> 133 #ifdef _KERNEL 134 #include <sys/vmsystm.h> 135 #include <vm/anon.h> 136 #include <sys/fs/swapnode.h> 137 #include <sys/dnlc.h> 138 #endif 139 #include <sys/callb.h> 140 #include <sys/kstat.h> 141 #include <zfs_fletcher.h> 142 143 #ifndef _KERNEL 144 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 145 boolean_t arc_watch = B_FALSE; 146 int arc_procfd; 147 #endif 148 149 static kmutex_t arc_reclaim_lock; 150 static kcondvar_t arc_reclaim_thread_cv; 151 static boolean_t arc_reclaim_thread_exit; 152 static kcondvar_t arc_reclaim_waiters_cv; 153 154 static kmutex_t arc_user_evicts_lock; 155 static kcondvar_t arc_user_evicts_cv; 156 static boolean_t arc_user_evicts_thread_exit; 157 158 uint_t arc_reduce_dnlc_percent = 3; 159 160 /* 161 * The number of headers to evict in arc_evict_state_impl() before 162 * dropping the sublist lock and evicting from another sublist. A lower 163 * value means we're more likely to evict the "correct" header (i.e. the 164 * oldest header in the arc state), but comes with higher overhead 165 * (i.e. more invocations of arc_evict_state_impl()). 166 */ 167 int zfs_arc_evict_batch_limit = 10; 168 169 /* 170 * The number of sublists used for each of the arc state lists. If this 171 * is not set to a suitable value by the user, it will be configured to 172 * the number of CPUs on the system in arc_init(). 173 */ 174 int zfs_arc_num_sublists_per_state = 0; 175 176 /* number of seconds before growing cache again */ 177 static int arc_grow_retry = 60; 178 179 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 180 int zfs_arc_overflow_shift = 8; 181 182 /* shift of arc_c for calculating both min and max arc_p */ 183 static int arc_p_min_shift = 4; 184 185 /* log2(fraction of arc to reclaim) */ 186 static int arc_shrink_shift = 7; 187 188 /* 189 * log2(fraction of ARC which must be free to allow growing). 190 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 191 * when reading a new block into the ARC, we will evict an equal-sized block 192 * from the ARC. 193 * 194 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 195 * we will still not allow it to grow. 196 */ 197 int arc_no_grow_shift = 5; 198 199 200 /* 201 * minimum lifespan of a prefetch block in clock ticks 202 * (initialized in arc_init()) 203 */ 204 static int arc_min_prefetch_lifespan; 205 206 /* 207 * If this percent of memory is free, don't throttle. 208 */ 209 int arc_lotsfree_percent = 10; 210 211 static int arc_dead; 212 213 /* 214 * The arc has filled available memory and has now warmed up. 215 */ 216 static boolean_t arc_warm; 217 218 /* 219 * These tunables are for performance analysis. 220 */ 221 uint64_t zfs_arc_max; 222 uint64_t zfs_arc_min; 223 uint64_t zfs_arc_meta_limit = 0; 224 uint64_t zfs_arc_meta_min = 0; 225 int zfs_arc_grow_retry = 0; 226 int zfs_arc_shrink_shift = 0; 227 int zfs_arc_p_min_shift = 0; 228 int zfs_disable_dup_eviction = 0; 229 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 230 231 /* 232 * Note that buffers can be in one of 6 states: 233 * ARC_anon - anonymous (discussed below) 234 * ARC_mru - recently used, currently cached 235 * ARC_mru_ghost - recentely used, no longer in cache 236 * ARC_mfu - frequently used, currently cached 237 * ARC_mfu_ghost - frequently used, no longer in cache 238 * ARC_l2c_only - exists in L2ARC but not other states 239 * When there are no active references to the buffer, they are 240 * are linked onto a list in one of these arc states. These are 241 * the only buffers that can be evicted or deleted. Within each 242 * state there are multiple lists, one for meta-data and one for 243 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 244 * etc.) is tracked separately so that it can be managed more 245 * explicitly: favored over data, limited explicitly. 246 * 247 * Anonymous buffers are buffers that are not associated with 248 * a DVA. These are buffers that hold dirty block copies 249 * before they are written to stable storage. By definition, 250 * they are "ref'd" and are considered part of arc_mru 251 * that cannot be freed. Generally, they will aquire a DVA 252 * as they are written and migrate onto the arc_mru list. 253 * 254 * The ARC_l2c_only state is for buffers that are in the second 255 * level ARC but no longer in any of the ARC_m* lists. The second 256 * level ARC itself may also contain buffers that are in any of 257 * the ARC_m* states - meaning that a buffer can exist in two 258 * places. The reason for the ARC_l2c_only state is to keep the 259 * buffer header in the hash table, so that reads that hit the 260 * second level ARC benefit from these fast lookups. 261 */ 262 263 typedef struct arc_state { 264 /* 265 * list of evictable buffers 266 */ 267 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 268 /* 269 * total amount of evictable data in this state 270 */ 271 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 272 /* 273 * total amount of data in this state; this includes: evictable, 274 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 275 */ 276 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 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 868 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 869 870 /* L2ARC Performance Tunables */ 871 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 872 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 873 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 874 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 875 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 876 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 877 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 878 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 879 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 880 881 /* 882 * L2ARC Internals 883 */ 884 struct l2arc_dev { 885 vdev_t *l2ad_vdev; /* vdev */ 886 spa_t *l2ad_spa; /* spa */ 887 uint64_t l2ad_hand; /* next write location */ 888 uint64_t l2ad_start; /* first addr on device */ 889 uint64_t l2ad_end; /* last addr on device */ 890 uint64_t l2ad_evict; /* last addr eviction reached */ 891 boolean_t l2ad_first; /* first sweep through */ 892 boolean_t l2ad_writing; /* currently writing */ 893 kmutex_t l2ad_mtx; /* lock for buffer list */ 894 list_t l2ad_buflist; /* buffer list */ 895 list_node_t l2ad_node; /* device list node */ 896 }; 897 898 static list_t L2ARC_dev_list; /* device list */ 899 static list_t *l2arc_dev_list; /* device list pointer */ 900 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 901 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 902 static list_t L2ARC_free_on_write; /* free after write buf list */ 903 static list_t *l2arc_free_on_write; /* free after write list ptr */ 904 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 905 static uint64_t l2arc_ndev; /* number of devices */ 906 907 typedef struct l2arc_read_callback { 908 arc_buf_t *l2rcb_buf; /* read buffer */ 909 spa_t *l2rcb_spa; /* spa */ 910 blkptr_t l2rcb_bp; /* original blkptr */ 911 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 912 int l2rcb_flags; /* original flags */ 913 enum zio_compress l2rcb_compress; /* applied compress */ 914 } l2arc_read_callback_t; 915 916 typedef struct l2arc_write_callback { 917 l2arc_dev_t *l2wcb_dev; /* device info */ 918 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 919 } l2arc_write_callback_t; 920 921 typedef struct l2arc_data_free { 922 /* protected by l2arc_free_on_write_mtx */ 923 void *l2df_data; 924 size_t l2df_size; 925 void (*l2df_func)(void *, size_t); 926 list_node_t l2df_list_node; 927 } l2arc_data_free_t; 928 929 static kmutex_t l2arc_feed_thr_lock; 930 static kcondvar_t l2arc_feed_thr_cv; 931 static uint8_t l2arc_thread_exit; 932 933 static void arc_get_data_buf(arc_buf_t *); 934 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 935 static boolean_t arc_is_overflowing(); 936 static void arc_buf_watch(arc_buf_t *); 937 938 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 939 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 940 941 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 942 static void l2arc_read_done(zio_t *); 943 944 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 945 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 946 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 947 948 static uint64_t 949 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 950 { 951 uint8_t *vdva = (uint8_t *)dva; 952 uint64_t crc = -1ULL; 953 int i; 954 955 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 956 957 for (i = 0; i < sizeof (dva_t); i++) 958 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 959 960 crc ^= (spa>>8) ^ birth; 961 962 return (crc); 963 } 964 965 #define BUF_EMPTY(buf) \ 966 ((buf)->b_dva.dva_word[0] == 0 && \ 967 (buf)->b_dva.dva_word[1] == 0) 968 969 #define BUF_EQUAL(spa, dva, birth, buf) \ 970 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 971 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 972 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 973 974 static void 975 buf_discard_identity(arc_buf_hdr_t *hdr) 976 { 977 hdr->b_dva.dva_word[0] = 0; 978 hdr->b_dva.dva_word[1] = 0; 979 hdr->b_birth = 0; 980 } 981 982 static arc_buf_hdr_t * 983 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 984 { 985 const dva_t *dva = BP_IDENTITY(bp); 986 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 987 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 988 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 989 arc_buf_hdr_t *hdr; 990 991 mutex_enter(hash_lock); 992 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 993 hdr = hdr->b_hash_next) { 994 if (BUF_EQUAL(spa, dva, birth, hdr)) { 995 *lockp = hash_lock; 996 return (hdr); 997 } 998 } 999 mutex_exit(hash_lock); 1000 *lockp = NULL; 1001 return (NULL); 1002 } 1003 1004 /* 1005 * Insert an entry into the hash table. If there is already an element 1006 * equal to elem in the hash table, then the already existing element 1007 * will be returned and the new element will not be inserted. 1008 * Otherwise returns NULL. 1009 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1010 */ 1011 static arc_buf_hdr_t * 1012 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1013 { 1014 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1015 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1016 arc_buf_hdr_t *fhdr; 1017 uint32_t i; 1018 1019 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1020 ASSERT(hdr->b_birth != 0); 1021 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1022 1023 if (lockp != NULL) { 1024 *lockp = hash_lock; 1025 mutex_enter(hash_lock); 1026 } else { 1027 ASSERT(MUTEX_HELD(hash_lock)); 1028 } 1029 1030 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1031 fhdr = fhdr->b_hash_next, i++) { 1032 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1033 return (fhdr); 1034 } 1035 1036 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1037 buf_hash_table.ht_table[idx] = hdr; 1038 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1039 1040 /* collect some hash table performance data */ 1041 if (i > 0) { 1042 ARCSTAT_BUMP(arcstat_hash_collisions); 1043 if (i == 1) 1044 ARCSTAT_BUMP(arcstat_hash_chains); 1045 1046 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1047 } 1048 1049 ARCSTAT_BUMP(arcstat_hash_elements); 1050 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1051 1052 return (NULL); 1053 } 1054 1055 static void 1056 buf_hash_remove(arc_buf_hdr_t *hdr) 1057 { 1058 arc_buf_hdr_t *fhdr, **hdrp; 1059 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1060 1061 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1062 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1063 1064 hdrp = &buf_hash_table.ht_table[idx]; 1065 while ((fhdr = *hdrp) != hdr) { 1066 ASSERT(fhdr != NULL); 1067 hdrp = &fhdr->b_hash_next; 1068 } 1069 *hdrp = hdr->b_hash_next; 1070 hdr->b_hash_next = NULL; 1071 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1072 1073 /* collect some hash table performance data */ 1074 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1075 1076 if (buf_hash_table.ht_table[idx] && 1077 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1078 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1079 } 1080 1081 /* 1082 * Global data structures and functions for the buf kmem cache. 1083 */ 1084 static kmem_cache_t *hdr_full_cache; 1085 static kmem_cache_t *hdr_l2only_cache; 1086 static kmem_cache_t *buf_cache; 1087 1088 static void 1089 buf_fini(void) 1090 { 1091 int i; 1092 1093 kmem_free(buf_hash_table.ht_table, 1094 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1095 for (i = 0; i < BUF_LOCKS; i++) 1096 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1097 kmem_cache_destroy(hdr_full_cache); 1098 kmem_cache_destroy(hdr_l2only_cache); 1099 kmem_cache_destroy(buf_cache); 1100 } 1101 1102 /* 1103 * Constructor callback - called when the cache is empty 1104 * and a new buf is requested. 1105 */ 1106 /* ARGSUSED */ 1107 static int 1108 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1109 { 1110 arc_buf_hdr_t *hdr = vbuf; 1111 1112 bzero(hdr, HDR_FULL_SIZE); 1113 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1114 refcount_create(&hdr->b_l1hdr.b_refcnt); 1115 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1116 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1117 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1118 1119 return (0); 1120 } 1121 1122 /* ARGSUSED */ 1123 static int 1124 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1125 { 1126 arc_buf_hdr_t *hdr = vbuf; 1127 1128 bzero(hdr, HDR_L2ONLY_SIZE); 1129 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1130 1131 return (0); 1132 } 1133 1134 /* ARGSUSED */ 1135 static int 1136 buf_cons(void *vbuf, void *unused, int kmflag) 1137 { 1138 arc_buf_t *buf = vbuf; 1139 1140 bzero(buf, sizeof (arc_buf_t)); 1141 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1142 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1143 1144 return (0); 1145 } 1146 1147 /* 1148 * Destructor callback - called when a cached buf is 1149 * no longer required. 1150 */ 1151 /* ARGSUSED */ 1152 static void 1153 hdr_full_dest(void *vbuf, void *unused) 1154 { 1155 arc_buf_hdr_t *hdr = vbuf; 1156 1157 ASSERT(BUF_EMPTY(hdr)); 1158 cv_destroy(&hdr->b_l1hdr.b_cv); 1159 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1160 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1161 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1162 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1163 } 1164 1165 /* ARGSUSED */ 1166 static void 1167 hdr_l2only_dest(void *vbuf, void *unused) 1168 { 1169 arc_buf_hdr_t *hdr = vbuf; 1170 1171 ASSERT(BUF_EMPTY(hdr)); 1172 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1173 } 1174 1175 /* ARGSUSED */ 1176 static void 1177 buf_dest(void *vbuf, void *unused) 1178 { 1179 arc_buf_t *buf = vbuf; 1180 1181 mutex_destroy(&buf->b_evict_lock); 1182 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1183 } 1184 1185 /* 1186 * Reclaim callback -- invoked when memory is low. 1187 */ 1188 /* ARGSUSED */ 1189 static void 1190 hdr_recl(void *unused) 1191 { 1192 dprintf("hdr_recl called\n"); 1193 /* 1194 * umem calls the reclaim func when we destroy the buf cache, 1195 * which is after we do arc_fini(). 1196 */ 1197 if (!arc_dead) 1198 cv_signal(&arc_reclaim_thread_cv); 1199 } 1200 1201 static void 1202 buf_init(void) 1203 { 1204 uint64_t *ct; 1205 uint64_t hsize = 1ULL << 12; 1206 int i, j; 1207 1208 /* 1209 * The hash table is big enough to fill all of physical memory 1210 * with an average block size of zfs_arc_average_blocksize (default 8K). 1211 * By default, the table will take up 1212 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1213 */ 1214 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1215 hsize <<= 1; 1216 retry: 1217 buf_hash_table.ht_mask = hsize - 1; 1218 buf_hash_table.ht_table = 1219 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1220 if (buf_hash_table.ht_table == NULL) { 1221 ASSERT(hsize > (1ULL << 8)); 1222 hsize >>= 1; 1223 goto retry; 1224 } 1225 1226 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1227 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1228 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1229 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1230 NULL, NULL, 0); 1231 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1232 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1233 1234 for (i = 0; i < 256; i++) 1235 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1236 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1237 1238 for (i = 0; i < BUF_LOCKS; i++) { 1239 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1240 NULL, MUTEX_DEFAULT, NULL); 1241 } 1242 } 1243 1244 /* 1245 * Transition between the two allocation states for the arc_buf_hdr struct. 1246 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1247 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1248 * version is used when a cache buffer is only in the L2ARC in order to reduce 1249 * memory usage. 1250 */ 1251 static arc_buf_hdr_t * 1252 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1253 { 1254 ASSERT(HDR_HAS_L2HDR(hdr)); 1255 1256 arc_buf_hdr_t *nhdr; 1257 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1258 1259 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1260 (old == hdr_l2only_cache && new == hdr_full_cache)); 1261 1262 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1263 1264 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1265 buf_hash_remove(hdr); 1266 1267 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1268 if (new == hdr_full_cache) { 1269 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1270 /* 1271 * arc_access and arc_change_state need to be aware that a 1272 * header has just come out of L2ARC, so we set its state to 1273 * l2c_only even though it's about to change. 1274 */ 1275 nhdr->b_l1hdr.b_state = arc_l2c_only; 1276 1277 /* Verify previous threads set to NULL before freeing */ 1278 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1279 } else { 1280 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1281 ASSERT0(hdr->b_l1hdr.b_datacnt); 1282 1283 /* 1284 * If we've reached here, We must have been called from 1285 * arc_evict_hdr(), as such we should have already been 1286 * removed from any ghost list we were previously on 1287 * (which protects us from racing with arc_evict_state), 1288 * thus no locking is needed during this check. 1289 */ 1290 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1291 1292 /* 1293 * A buffer must not be moved into the arc_l2c_only 1294 * state if it's not finished being written out to the 1295 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1296 * might try to be accessed, even though it was removed. 1297 */ 1298 VERIFY(!HDR_L2_WRITING(hdr)); 1299 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1300 1301 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1302 } 1303 /* 1304 * The header has been reallocated so we need to re-insert it into any 1305 * lists it was on. 1306 */ 1307 (void) buf_hash_insert(nhdr, NULL); 1308 1309 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1310 1311 mutex_enter(&dev->l2ad_mtx); 1312 1313 /* 1314 * We must place the realloc'ed header back into the list at 1315 * the same spot. Otherwise, if it's placed earlier in the list, 1316 * l2arc_write_buffers() could find it during the function's 1317 * write phase, and try to write it out to the l2arc. 1318 */ 1319 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1320 list_remove(&dev->l2ad_buflist, hdr); 1321 1322 mutex_exit(&dev->l2ad_mtx); 1323 1324 buf_discard_identity(hdr); 1325 hdr->b_freeze_cksum = NULL; 1326 kmem_cache_free(old, hdr); 1327 1328 return (nhdr); 1329 } 1330 1331 1332 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1333 1334 static void 1335 arc_cksum_verify(arc_buf_t *buf) 1336 { 1337 zio_cksum_t zc; 1338 1339 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1340 return; 1341 1342 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1343 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1344 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1345 return; 1346 } 1347 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1348 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1349 panic("buffer modified while frozen!"); 1350 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1351 } 1352 1353 static int 1354 arc_cksum_equal(arc_buf_t *buf) 1355 { 1356 zio_cksum_t zc; 1357 int equal; 1358 1359 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1360 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1361 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1362 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1363 1364 return (equal); 1365 } 1366 1367 static void 1368 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1369 { 1370 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1371 return; 1372 1373 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1374 if (buf->b_hdr->b_freeze_cksum != NULL) { 1375 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1376 return; 1377 } 1378 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1379 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1380 buf->b_hdr->b_freeze_cksum); 1381 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1382 arc_buf_watch(buf); 1383 } 1384 1385 #ifndef _KERNEL 1386 typedef struct procctl { 1387 long cmd; 1388 prwatch_t prwatch; 1389 } procctl_t; 1390 #endif 1391 1392 /* ARGSUSED */ 1393 static void 1394 arc_buf_unwatch(arc_buf_t *buf) 1395 { 1396 #ifndef _KERNEL 1397 if (arc_watch) { 1398 int result; 1399 procctl_t ctl; 1400 ctl.cmd = PCWATCH; 1401 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1402 ctl.prwatch.pr_size = 0; 1403 ctl.prwatch.pr_wflags = 0; 1404 result = write(arc_procfd, &ctl, sizeof (ctl)); 1405 ASSERT3U(result, ==, sizeof (ctl)); 1406 } 1407 #endif 1408 } 1409 1410 /* ARGSUSED */ 1411 static void 1412 arc_buf_watch(arc_buf_t *buf) 1413 { 1414 #ifndef _KERNEL 1415 if (arc_watch) { 1416 int result; 1417 procctl_t ctl; 1418 ctl.cmd = PCWATCH; 1419 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1420 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1421 ctl.prwatch.pr_wflags = WA_WRITE; 1422 result = write(arc_procfd, &ctl, sizeof (ctl)); 1423 ASSERT3U(result, ==, sizeof (ctl)); 1424 } 1425 #endif 1426 } 1427 1428 static arc_buf_contents_t 1429 arc_buf_type(arc_buf_hdr_t *hdr) 1430 { 1431 if (HDR_ISTYPE_METADATA(hdr)) { 1432 return (ARC_BUFC_METADATA); 1433 } else { 1434 return (ARC_BUFC_DATA); 1435 } 1436 } 1437 1438 static uint32_t 1439 arc_bufc_to_flags(arc_buf_contents_t type) 1440 { 1441 switch (type) { 1442 case ARC_BUFC_DATA: 1443 /* metadata field is 0 if buffer contains normal data */ 1444 return (0); 1445 case ARC_BUFC_METADATA: 1446 return (ARC_FLAG_BUFC_METADATA); 1447 default: 1448 break; 1449 } 1450 panic("undefined ARC buffer type!"); 1451 return ((uint32_t)-1); 1452 } 1453 1454 void 1455 arc_buf_thaw(arc_buf_t *buf) 1456 { 1457 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1458 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1459 panic("modifying non-anon buffer!"); 1460 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1461 panic("modifying buffer while i/o in progress!"); 1462 arc_cksum_verify(buf); 1463 } 1464 1465 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1466 if (buf->b_hdr->b_freeze_cksum != NULL) { 1467 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1468 buf->b_hdr->b_freeze_cksum = NULL; 1469 } 1470 1471 #ifdef ZFS_DEBUG 1472 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1473 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1474 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1475 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1476 } 1477 #endif 1478 1479 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1480 1481 arc_buf_unwatch(buf); 1482 } 1483 1484 void 1485 arc_buf_freeze(arc_buf_t *buf) 1486 { 1487 kmutex_t *hash_lock; 1488 1489 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1490 return; 1491 1492 hash_lock = HDR_LOCK(buf->b_hdr); 1493 mutex_enter(hash_lock); 1494 1495 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1496 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1497 arc_cksum_compute(buf, B_FALSE); 1498 mutex_exit(hash_lock); 1499 1500 } 1501 1502 static void 1503 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1504 { 1505 ASSERT(HDR_HAS_L1HDR(hdr)); 1506 ASSERT(MUTEX_HELD(hash_lock)); 1507 arc_state_t *state = hdr->b_l1hdr.b_state; 1508 1509 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1510 (state != arc_anon)) { 1511 /* We don't use the L2-only state list. */ 1512 if (state != arc_l2c_only) { 1513 arc_buf_contents_t type = arc_buf_type(hdr); 1514 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1515 multilist_t *list = &state->arcs_list[type]; 1516 uint64_t *size = &state->arcs_lsize[type]; 1517 1518 multilist_remove(list, hdr); 1519 1520 if (GHOST_STATE(state)) { 1521 ASSERT0(hdr->b_l1hdr.b_datacnt); 1522 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1523 delta = hdr->b_size; 1524 } 1525 ASSERT(delta > 0); 1526 ASSERT3U(*size, >=, delta); 1527 atomic_add_64(size, -delta); 1528 } 1529 /* remove the prefetch flag if we get a reference */ 1530 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1531 } 1532 } 1533 1534 static int 1535 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1536 { 1537 int cnt; 1538 arc_state_t *state = hdr->b_l1hdr.b_state; 1539 1540 ASSERT(HDR_HAS_L1HDR(hdr)); 1541 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1542 ASSERT(!GHOST_STATE(state)); 1543 1544 /* 1545 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1546 * check to prevent usage of the arc_l2c_only list. 1547 */ 1548 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1549 (state != arc_anon)) { 1550 arc_buf_contents_t type = arc_buf_type(hdr); 1551 multilist_t *list = &state->arcs_list[type]; 1552 uint64_t *size = &state->arcs_lsize[type]; 1553 1554 multilist_insert(list, hdr); 1555 1556 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1557 atomic_add_64(size, hdr->b_size * 1558 hdr->b_l1hdr.b_datacnt); 1559 } 1560 return (cnt); 1561 } 1562 1563 /* 1564 * Move the supplied buffer to the indicated state. The hash lock 1565 * for the buffer must be held by the caller. 1566 */ 1567 static void 1568 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1569 kmutex_t *hash_lock) 1570 { 1571 arc_state_t *old_state; 1572 int64_t refcnt; 1573 uint32_t datacnt; 1574 uint64_t from_delta, to_delta; 1575 arc_buf_contents_t buftype = arc_buf_type(hdr); 1576 1577 /* 1578 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1579 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1580 * L1 hdr doesn't always exist when we change state to arc_anon before 1581 * destroying a header, in which case reallocating to add the L1 hdr is 1582 * pointless. 1583 */ 1584 if (HDR_HAS_L1HDR(hdr)) { 1585 old_state = hdr->b_l1hdr.b_state; 1586 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1587 datacnt = hdr->b_l1hdr.b_datacnt; 1588 } else { 1589 old_state = arc_l2c_only; 1590 refcnt = 0; 1591 datacnt = 0; 1592 } 1593 1594 ASSERT(MUTEX_HELD(hash_lock)); 1595 ASSERT3P(new_state, !=, old_state); 1596 ASSERT(refcnt == 0 || datacnt > 0); 1597 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1598 ASSERT(old_state != arc_anon || datacnt <= 1); 1599 1600 from_delta = to_delta = datacnt * hdr->b_size; 1601 1602 /* 1603 * If this buffer is evictable, transfer it from the 1604 * old state list to the new state list. 1605 */ 1606 if (refcnt == 0) { 1607 if (old_state != arc_anon && old_state != arc_l2c_only) { 1608 uint64_t *size = &old_state->arcs_lsize[buftype]; 1609 1610 ASSERT(HDR_HAS_L1HDR(hdr)); 1611 multilist_remove(&old_state->arcs_list[buftype], hdr); 1612 1613 /* 1614 * If prefetching out of the ghost cache, 1615 * we will have a non-zero datacnt. 1616 */ 1617 if (GHOST_STATE(old_state) && datacnt == 0) { 1618 /* ghost elements have a ghost size */ 1619 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1620 from_delta = hdr->b_size; 1621 } 1622 ASSERT3U(*size, >=, from_delta); 1623 atomic_add_64(size, -from_delta); 1624 } 1625 if (new_state != arc_anon && new_state != arc_l2c_only) { 1626 uint64_t *size = &new_state->arcs_lsize[buftype]; 1627 1628 /* 1629 * An L1 header always exists here, since if we're 1630 * moving to some L1-cached state (i.e. not l2c_only or 1631 * anonymous), we realloc the header to add an L1hdr 1632 * beforehand. 1633 */ 1634 ASSERT(HDR_HAS_L1HDR(hdr)); 1635 multilist_insert(&new_state->arcs_list[buftype], hdr); 1636 1637 /* ghost elements have a ghost size */ 1638 if (GHOST_STATE(new_state)) { 1639 ASSERT0(datacnt); 1640 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1641 to_delta = hdr->b_size; 1642 } 1643 atomic_add_64(size, to_delta); 1644 } 1645 } 1646 1647 ASSERT(!BUF_EMPTY(hdr)); 1648 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1649 buf_hash_remove(hdr); 1650 1651 /* adjust state sizes (ignore arc_l2c_only) */ 1652 1653 if (to_delta && new_state != arc_l2c_only) { 1654 ASSERT(HDR_HAS_L1HDR(hdr)); 1655 if (GHOST_STATE(new_state)) { 1656 ASSERT0(datacnt); 1657 1658 /* 1659 * We moving a header to a ghost state, we first 1660 * remove all arc buffers. Thus, we'll have a 1661 * datacnt of zero, and no arc buffer to use for 1662 * the reference. As a result, we use the arc 1663 * header pointer for the reference. 1664 */ 1665 (void) refcount_add_many(&new_state->arcs_size, 1666 hdr->b_size, hdr); 1667 } else { 1668 ASSERT3U(datacnt, !=, 0); 1669 1670 /* 1671 * Each individual buffer holds a unique reference, 1672 * thus we must remove each of these references one 1673 * at a time. 1674 */ 1675 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1676 buf = buf->b_next) { 1677 (void) refcount_add_many(&new_state->arcs_size, 1678 hdr->b_size, buf); 1679 } 1680 } 1681 } 1682 1683 if (from_delta && old_state != arc_l2c_only) { 1684 ASSERT(HDR_HAS_L1HDR(hdr)); 1685 if (GHOST_STATE(old_state)) { 1686 /* 1687 * When moving a header off of a ghost state, 1688 * there's the possibility for datacnt to be 1689 * non-zero. This is because we first add the 1690 * arc buffer to the header prior to changing 1691 * the header's state. Since we used the header 1692 * for the reference when putting the header on 1693 * the ghost state, we must balance that and use 1694 * the header when removing off the ghost state 1695 * (even though datacnt is non zero). 1696 */ 1697 1698 IMPLY(datacnt == 0, new_state == arc_anon || 1699 new_state == arc_l2c_only); 1700 1701 (void) refcount_remove_many(&old_state->arcs_size, 1702 hdr->b_size, hdr); 1703 } else { 1704 ASSERT3P(datacnt, !=, 0); 1705 1706 /* 1707 * Each individual buffer holds a unique reference, 1708 * thus we must remove each of these references one 1709 * at a time. 1710 */ 1711 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1712 buf = buf->b_next) { 1713 (void) refcount_remove_many( 1714 &old_state->arcs_size, hdr->b_size, buf); 1715 } 1716 } 1717 } 1718 1719 if (HDR_HAS_L1HDR(hdr)) 1720 hdr->b_l1hdr.b_state = new_state; 1721 1722 /* 1723 * L2 headers should never be on the L2 state list since they don't 1724 * have L1 headers allocated. 1725 */ 1726 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1727 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1728 } 1729 1730 void 1731 arc_space_consume(uint64_t space, arc_space_type_t type) 1732 { 1733 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1734 1735 switch (type) { 1736 case ARC_SPACE_DATA: 1737 ARCSTAT_INCR(arcstat_data_size, space); 1738 break; 1739 case ARC_SPACE_META: 1740 ARCSTAT_INCR(arcstat_metadata_size, space); 1741 break; 1742 case ARC_SPACE_OTHER: 1743 ARCSTAT_INCR(arcstat_other_size, space); 1744 break; 1745 case ARC_SPACE_HDRS: 1746 ARCSTAT_INCR(arcstat_hdr_size, space); 1747 break; 1748 case ARC_SPACE_L2HDRS: 1749 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1750 break; 1751 } 1752 1753 if (type != ARC_SPACE_DATA) 1754 ARCSTAT_INCR(arcstat_meta_used, space); 1755 1756 atomic_add_64(&arc_size, space); 1757 } 1758 1759 void 1760 arc_space_return(uint64_t space, arc_space_type_t type) 1761 { 1762 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1763 1764 switch (type) { 1765 case ARC_SPACE_DATA: 1766 ARCSTAT_INCR(arcstat_data_size, -space); 1767 break; 1768 case ARC_SPACE_META: 1769 ARCSTAT_INCR(arcstat_metadata_size, -space); 1770 break; 1771 case ARC_SPACE_OTHER: 1772 ARCSTAT_INCR(arcstat_other_size, -space); 1773 break; 1774 case ARC_SPACE_HDRS: 1775 ARCSTAT_INCR(arcstat_hdr_size, -space); 1776 break; 1777 case ARC_SPACE_L2HDRS: 1778 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1779 break; 1780 } 1781 1782 if (type != ARC_SPACE_DATA) { 1783 ASSERT(arc_meta_used >= space); 1784 if (arc_meta_max < arc_meta_used) 1785 arc_meta_max = arc_meta_used; 1786 ARCSTAT_INCR(arcstat_meta_used, -space); 1787 } 1788 1789 ASSERT(arc_size >= space); 1790 atomic_add_64(&arc_size, -space); 1791 } 1792 1793 arc_buf_t * 1794 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1795 { 1796 arc_buf_hdr_t *hdr; 1797 arc_buf_t *buf; 1798 1799 ASSERT3U(size, >, 0); 1800 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1801 ASSERT(BUF_EMPTY(hdr)); 1802 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1803 hdr->b_size = size; 1804 hdr->b_spa = spa_load_guid(spa); 1805 1806 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1807 buf->b_hdr = hdr; 1808 buf->b_data = NULL; 1809 buf->b_efunc = NULL; 1810 buf->b_private = NULL; 1811 buf->b_next = NULL; 1812 1813 hdr->b_flags = arc_bufc_to_flags(type); 1814 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1815 1816 hdr->b_l1hdr.b_buf = buf; 1817 hdr->b_l1hdr.b_state = arc_anon; 1818 hdr->b_l1hdr.b_arc_access = 0; 1819 hdr->b_l1hdr.b_datacnt = 1; 1820 hdr->b_l1hdr.b_tmp_cdata = NULL; 1821 1822 arc_get_data_buf(buf); 1823 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1824 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1825 1826 return (buf); 1827 } 1828 1829 static char *arc_onloan_tag = "onloan"; 1830 1831 /* 1832 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1833 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1834 * buffers must be returned to the arc before they can be used by the DMU or 1835 * freed. 1836 */ 1837 arc_buf_t * 1838 arc_loan_buf(spa_t *spa, int size) 1839 { 1840 arc_buf_t *buf; 1841 1842 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1843 1844 atomic_add_64(&arc_loaned_bytes, size); 1845 return (buf); 1846 } 1847 1848 /* 1849 * Return a loaned arc buffer to the arc. 1850 */ 1851 void 1852 arc_return_buf(arc_buf_t *buf, void *tag) 1853 { 1854 arc_buf_hdr_t *hdr = buf->b_hdr; 1855 1856 ASSERT(buf->b_data != NULL); 1857 ASSERT(HDR_HAS_L1HDR(hdr)); 1858 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1859 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1860 1861 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1862 } 1863 1864 /* Detach an arc_buf from a dbuf (tag) */ 1865 void 1866 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1867 { 1868 arc_buf_hdr_t *hdr = buf->b_hdr; 1869 1870 ASSERT(buf->b_data != NULL); 1871 ASSERT(HDR_HAS_L1HDR(hdr)); 1872 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1873 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 1874 buf->b_efunc = NULL; 1875 buf->b_private = NULL; 1876 1877 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1878 } 1879 1880 static arc_buf_t * 1881 arc_buf_clone(arc_buf_t *from) 1882 { 1883 arc_buf_t *buf; 1884 arc_buf_hdr_t *hdr = from->b_hdr; 1885 uint64_t size = hdr->b_size; 1886 1887 ASSERT(HDR_HAS_L1HDR(hdr)); 1888 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 1889 1890 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1891 buf->b_hdr = hdr; 1892 buf->b_data = NULL; 1893 buf->b_efunc = NULL; 1894 buf->b_private = NULL; 1895 buf->b_next = hdr->b_l1hdr.b_buf; 1896 hdr->b_l1hdr.b_buf = buf; 1897 arc_get_data_buf(buf); 1898 bcopy(from->b_data, buf->b_data, size); 1899 1900 /* 1901 * This buffer already exists in the arc so create a duplicate 1902 * copy for the caller. If the buffer is associated with user data 1903 * then track the size and number of duplicates. These stats will be 1904 * updated as duplicate buffers are created and destroyed. 1905 */ 1906 if (HDR_ISTYPE_DATA(hdr)) { 1907 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1908 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1909 } 1910 hdr->b_l1hdr.b_datacnt += 1; 1911 return (buf); 1912 } 1913 1914 void 1915 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1916 { 1917 arc_buf_hdr_t *hdr; 1918 kmutex_t *hash_lock; 1919 1920 /* 1921 * Check to see if this buffer is evicted. Callers 1922 * must verify b_data != NULL to know if the add_ref 1923 * was successful. 1924 */ 1925 mutex_enter(&buf->b_evict_lock); 1926 if (buf->b_data == NULL) { 1927 mutex_exit(&buf->b_evict_lock); 1928 return; 1929 } 1930 hash_lock = HDR_LOCK(buf->b_hdr); 1931 mutex_enter(hash_lock); 1932 hdr = buf->b_hdr; 1933 ASSERT(HDR_HAS_L1HDR(hdr)); 1934 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1935 mutex_exit(&buf->b_evict_lock); 1936 1937 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 1938 hdr->b_l1hdr.b_state == arc_mfu); 1939 1940 add_reference(hdr, hash_lock, tag); 1941 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1942 arc_access(hdr, hash_lock); 1943 mutex_exit(hash_lock); 1944 ARCSTAT_BUMP(arcstat_hits); 1945 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 1946 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 1947 data, metadata, hits); 1948 } 1949 1950 static void 1951 arc_buf_free_on_write(void *data, size_t size, 1952 void (*free_func)(void *, size_t)) 1953 { 1954 l2arc_data_free_t *df; 1955 1956 df = kmem_alloc(sizeof (*df), KM_SLEEP); 1957 df->l2df_data = data; 1958 df->l2df_size = size; 1959 df->l2df_func = free_func; 1960 mutex_enter(&l2arc_free_on_write_mtx); 1961 list_insert_head(l2arc_free_on_write, df); 1962 mutex_exit(&l2arc_free_on_write_mtx); 1963 } 1964 1965 /* 1966 * Free the arc data buffer. If it is an l2arc write in progress, 1967 * the buffer is placed on l2arc_free_on_write to be freed later. 1968 */ 1969 static void 1970 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1971 { 1972 arc_buf_hdr_t *hdr = buf->b_hdr; 1973 1974 if (HDR_L2_WRITING(hdr)) { 1975 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 1976 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1977 } else { 1978 free_func(buf->b_data, hdr->b_size); 1979 } 1980 } 1981 1982 static void 1983 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 1984 { 1985 ASSERT(HDR_HAS_L2HDR(hdr)); 1986 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 1987 1988 /* 1989 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 1990 * that doesn't exist, the header is in the arc_l2c_only state, 1991 * and there isn't anything to free (it's already been freed). 1992 */ 1993 if (!HDR_HAS_L1HDR(hdr)) 1994 return; 1995 1996 /* 1997 * The header isn't being written to the l2arc device, thus it 1998 * shouldn't have a b_tmp_cdata to free. 1999 */ 2000 if (!HDR_L2_WRITING(hdr)) { 2001 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2002 return; 2003 } 2004 2005 /* 2006 * The header does not have compression enabled. This can be due 2007 * to the buffer not being compressible, or because we're 2008 * freeing the buffer before the second phase of 2009 * l2arc_write_buffer() has started (which does the compression 2010 * step). In either case, b_tmp_cdata does not point to a 2011 * separately compressed buffer, so there's nothing to free (it 2012 * points to the same buffer as the arc_buf_t's b_data field). 2013 */ 2014 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 2015 hdr->b_l1hdr.b_tmp_cdata = NULL; 2016 return; 2017 } 2018 2019 /* 2020 * There's nothing to free since the buffer was all zero's and 2021 * compressed to a zero length buffer. 2022 */ 2023 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) { 2024 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2025 return; 2026 } 2027 2028 ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))); 2029 2030 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2031 hdr->b_size, zio_data_buf_free); 2032 2033 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2034 hdr->b_l1hdr.b_tmp_cdata = NULL; 2035 } 2036 2037 /* 2038 * Free up buf->b_data and if 'remove' is set, then pull the 2039 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2040 */ 2041 static void 2042 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2043 { 2044 arc_buf_t **bufp; 2045 2046 /* free up data associated with the buf */ 2047 if (buf->b_data != NULL) { 2048 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2049 uint64_t size = buf->b_hdr->b_size; 2050 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2051 2052 arc_cksum_verify(buf); 2053 arc_buf_unwatch(buf); 2054 2055 if (type == ARC_BUFC_METADATA) { 2056 arc_buf_data_free(buf, zio_buf_free); 2057 arc_space_return(size, ARC_SPACE_META); 2058 } else { 2059 ASSERT(type == ARC_BUFC_DATA); 2060 arc_buf_data_free(buf, zio_data_buf_free); 2061 arc_space_return(size, ARC_SPACE_DATA); 2062 } 2063 2064 /* protected by hash lock, if in the hash table */ 2065 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2066 uint64_t *cnt = &state->arcs_lsize[type]; 2067 2068 ASSERT(refcount_is_zero( 2069 &buf->b_hdr->b_l1hdr.b_refcnt)); 2070 ASSERT(state != arc_anon && state != arc_l2c_only); 2071 2072 ASSERT3U(*cnt, >=, size); 2073 atomic_add_64(cnt, -size); 2074 } 2075 2076 (void) refcount_remove_many(&state->arcs_size, size, buf); 2077 buf->b_data = NULL; 2078 2079 /* 2080 * If we're destroying a duplicate buffer make sure 2081 * that the appropriate statistics are updated. 2082 */ 2083 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2084 HDR_ISTYPE_DATA(buf->b_hdr)) { 2085 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2086 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2087 } 2088 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2089 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2090 } 2091 2092 /* only remove the buf if requested */ 2093 if (!remove) 2094 return; 2095 2096 /* remove the buf from the hdr list */ 2097 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2098 bufp = &(*bufp)->b_next) 2099 continue; 2100 *bufp = buf->b_next; 2101 buf->b_next = NULL; 2102 2103 ASSERT(buf->b_efunc == NULL); 2104 2105 /* clean up the buf */ 2106 buf->b_hdr = NULL; 2107 kmem_cache_free(buf_cache, buf); 2108 } 2109 2110 static void 2111 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2112 { 2113 if (HDR_HAS_L1HDR(hdr)) { 2114 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2115 hdr->b_l1hdr.b_datacnt > 0); 2116 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2117 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2118 } 2119 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2120 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2121 2122 if (HDR_HAS_L2HDR(hdr)) { 2123 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2124 boolean_t buflist_held = MUTEX_HELD(&l2hdr->b_dev->l2ad_mtx); 2125 2126 if (!buflist_held) { 2127 mutex_enter(&l2hdr->b_dev->l2ad_mtx); 2128 l2hdr = &hdr->b_l2hdr; 2129 } 2130 2131 list_remove(&l2hdr->b_dev->l2ad_buflist, hdr); 2132 2133 /* 2134 * We don't want to leak the b_tmp_cdata buffer that was 2135 * allocated in l2arc_write_buffers() 2136 */ 2137 arc_buf_l2_cdata_free(hdr); 2138 2139 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2140 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2141 2142 if (!buflist_held) 2143 mutex_exit(&l2hdr->b_dev->l2ad_mtx); 2144 2145 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2146 } 2147 2148 if (!BUF_EMPTY(hdr)) 2149 buf_discard_identity(hdr); 2150 2151 if (hdr->b_freeze_cksum != NULL) { 2152 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2153 hdr->b_freeze_cksum = NULL; 2154 } 2155 2156 if (HDR_HAS_L1HDR(hdr)) { 2157 while (hdr->b_l1hdr.b_buf) { 2158 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2159 2160 if (buf->b_efunc != NULL) { 2161 mutex_enter(&arc_user_evicts_lock); 2162 mutex_enter(&buf->b_evict_lock); 2163 ASSERT(buf->b_hdr != NULL); 2164 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2165 hdr->b_l1hdr.b_buf = buf->b_next; 2166 buf->b_hdr = &arc_eviction_hdr; 2167 buf->b_next = arc_eviction_list; 2168 arc_eviction_list = buf; 2169 mutex_exit(&buf->b_evict_lock); 2170 cv_signal(&arc_user_evicts_cv); 2171 mutex_exit(&arc_user_evicts_lock); 2172 } else { 2173 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2174 } 2175 } 2176 #ifdef ZFS_DEBUG 2177 if (hdr->b_l1hdr.b_thawed != NULL) { 2178 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2179 hdr->b_l1hdr.b_thawed = NULL; 2180 } 2181 #endif 2182 } 2183 2184 ASSERT3P(hdr->b_hash_next, ==, NULL); 2185 if (HDR_HAS_L1HDR(hdr)) { 2186 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2187 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2188 kmem_cache_free(hdr_full_cache, hdr); 2189 } else { 2190 kmem_cache_free(hdr_l2only_cache, hdr); 2191 } 2192 } 2193 2194 void 2195 arc_buf_free(arc_buf_t *buf, void *tag) 2196 { 2197 arc_buf_hdr_t *hdr = buf->b_hdr; 2198 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2199 2200 ASSERT(buf->b_efunc == NULL); 2201 ASSERT(buf->b_data != NULL); 2202 2203 if (hashed) { 2204 kmutex_t *hash_lock = HDR_LOCK(hdr); 2205 2206 mutex_enter(hash_lock); 2207 hdr = buf->b_hdr; 2208 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2209 2210 (void) remove_reference(hdr, hash_lock, tag); 2211 if (hdr->b_l1hdr.b_datacnt > 1) { 2212 arc_buf_destroy(buf, TRUE); 2213 } else { 2214 ASSERT(buf == hdr->b_l1hdr.b_buf); 2215 ASSERT(buf->b_efunc == NULL); 2216 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2217 } 2218 mutex_exit(hash_lock); 2219 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2220 int destroy_hdr; 2221 /* 2222 * We are in the middle of an async write. Don't destroy 2223 * this buffer unless the write completes before we finish 2224 * decrementing the reference count. 2225 */ 2226 mutex_enter(&arc_user_evicts_lock); 2227 (void) remove_reference(hdr, NULL, tag); 2228 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2229 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2230 mutex_exit(&arc_user_evicts_lock); 2231 if (destroy_hdr) 2232 arc_hdr_destroy(hdr); 2233 } else { 2234 if (remove_reference(hdr, NULL, tag) > 0) 2235 arc_buf_destroy(buf, TRUE); 2236 else 2237 arc_hdr_destroy(hdr); 2238 } 2239 } 2240 2241 boolean_t 2242 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2243 { 2244 arc_buf_hdr_t *hdr = buf->b_hdr; 2245 kmutex_t *hash_lock = HDR_LOCK(hdr); 2246 boolean_t no_callback = (buf->b_efunc == NULL); 2247 2248 if (hdr->b_l1hdr.b_state == arc_anon) { 2249 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2250 arc_buf_free(buf, tag); 2251 return (no_callback); 2252 } 2253 2254 mutex_enter(hash_lock); 2255 hdr = buf->b_hdr; 2256 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2257 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2258 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2259 ASSERT(buf->b_data != NULL); 2260 2261 (void) remove_reference(hdr, hash_lock, tag); 2262 if (hdr->b_l1hdr.b_datacnt > 1) { 2263 if (no_callback) 2264 arc_buf_destroy(buf, TRUE); 2265 } else if (no_callback) { 2266 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2267 ASSERT(buf->b_efunc == NULL); 2268 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2269 } 2270 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2271 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2272 mutex_exit(hash_lock); 2273 return (no_callback); 2274 } 2275 2276 int32_t 2277 arc_buf_size(arc_buf_t *buf) 2278 { 2279 return (buf->b_hdr->b_size); 2280 } 2281 2282 /* 2283 * Called from the DMU to determine if the current buffer should be 2284 * evicted. In order to ensure proper locking, the eviction must be initiated 2285 * from the DMU. Return true if the buffer is associated with user data and 2286 * duplicate buffers still exist. 2287 */ 2288 boolean_t 2289 arc_buf_eviction_needed(arc_buf_t *buf) 2290 { 2291 arc_buf_hdr_t *hdr; 2292 boolean_t evict_needed = B_FALSE; 2293 2294 if (zfs_disable_dup_eviction) 2295 return (B_FALSE); 2296 2297 mutex_enter(&buf->b_evict_lock); 2298 hdr = buf->b_hdr; 2299 if (hdr == NULL) { 2300 /* 2301 * We are in arc_do_user_evicts(); let that function 2302 * perform the eviction. 2303 */ 2304 ASSERT(buf->b_data == NULL); 2305 mutex_exit(&buf->b_evict_lock); 2306 return (B_FALSE); 2307 } else if (buf->b_data == NULL) { 2308 /* 2309 * We have already been added to the arc eviction list; 2310 * recommend eviction. 2311 */ 2312 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2313 mutex_exit(&buf->b_evict_lock); 2314 return (B_TRUE); 2315 } 2316 2317 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2318 evict_needed = B_TRUE; 2319 2320 mutex_exit(&buf->b_evict_lock); 2321 return (evict_needed); 2322 } 2323 2324 /* 2325 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2326 * state of the header is dependent on it's state prior to entering this 2327 * function. The following transitions are possible: 2328 * 2329 * - arc_mru -> arc_mru_ghost 2330 * - arc_mfu -> arc_mfu_ghost 2331 * - arc_mru_ghost -> arc_l2c_only 2332 * - arc_mru_ghost -> deleted 2333 * - arc_mfu_ghost -> arc_l2c_only 2334 * - arc_mfu_ghost -> deleted 2335 */ 2336 static int64_t 2337 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2338 { 2339 arc_state_t *evicted_state, *state; 2340 int64_t bytes_evicted = 0; 2341 2342 ASSERT(MUTEX_HELD(hash_lock)); 2343 ASSERT(HDR_HAS_L1HDR(hdr)); 2344 2345 state = hdr->b_l1hdr.b_state; 2346 if (GHOST_STATE(state)) { 2347 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2348 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2349 2350 /* 2351 * l2arc_write_buffers() relies on a header's L1 portion 2352 * (i.e. it's b_tmp_cdata field) during it's write phase. 2353 * Thus, we cannot push a header onto the arc_l2c_only 2354 * state (removing it's L1 piece) until the header is 2355 * done being written to the l2arc. 2356 */ 2357 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2358 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2359 return (bytes_evicted); 2360 } 2361 2362 ARCSTAT_BUMP(arcstat_deleted); 2363 bytes_evicted += hdr->b_size; 2364 2365 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2366 2367 if (HDR_HAS_L2HDR(hdr)) { 2368 /* 2369 * This buffer is cached on the 2nd Level ARC; 2370 * don't destroy the header. 2371 */ 2372 arc_change_state(arc_l2c_only, hdr, hash_lock); 2373 /* 2374 * dropping from L1+L2 cached to L2-only, 2375 * realloc to remove the L1 header. 2376 */ 2377 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2378 hdr_l2only_cache); 2379 } else { 2380 arc_change_state(arc_anon, hdr, hash_lock); 2381 arc_hdr_destroy(hdr); 2382 } 2383 return (bytes_evicted); 2384 } 2385 2386 ASSERT(state == arc_mru || state == arc_mfu); 2387 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2388 2389 /* prefetch buffers have a minimum lifespan */ 2390 if (HDR_IO_IN_PROGRESS(hdr) || 2391 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2392 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2393 arc_min_prefetch_lifespan)) { 2394 ARCSTAT_BUMP(arcstat_evict_skip); 2395 return (bytes_evicted); 2396 } 2397 2398 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2399 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2400 while (hdr->b_l1hdr.b_buf) { 2401 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2402 if (!mutex_tryenter(&buf->b_evict_lock)) { 2403 ARCSTAT_BUMP(arcstat_mutex_miss); 2404 break; 2405 } 2406 if (buf->b_data != NULL) 2407 bytes_evicted += hdr->b_size; 2408 if (buf->b_efunc != NULL) { 2409 mutex_enter(&arc_user_evicts_lock); 2410 arc_buf_destroy(buf, FALSE); 2411 hdr->b_l1hdr.b_buf = buf->b_next; 2412 buf->b_hdr = &arc_eviction_hdr; 2413 buf->b_next = arc_eviction_list; 2414 arc_eviction_list = buf; 2415 cv_signal(&arc_user_evicts_cv); 2416 mutex_exit(&arc_user_evicts_lock); 2417 mutex_exit(&buf->b_evict_lock); 2418 } else { 2419 mutex_exit(&buf->b_evict_lock); 2420 arc_buf_destroy(buf, TRUE); 2421 } 2422 } 2423 2424 if (HDR_HAS_L2HDR(hdr)) { 2425 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2426 } else { 2427 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2428 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2429 else 2430 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2431 } 2432 2433 if (hdr->b_l1hdr.b_datacnt == 0) { 2434 arc_change_state(evicted_state, hdr, hash_lock); 2435 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2436 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2437 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2438 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2439 } 2440 2441 return (bytes_evicted); 2442 } 2443 2444 static uint64_t 2445 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2446 uint64_t spa, int64_t bytes) 2447 { 2448 multilist_sublist_t *mls; 2449 uint64_t bytes_evicted = 0; 2450 arc_buf_hdr_t *hdr; 2451 kmutex_t *hash_lock; 2452 int evict_count = 0; 2453 2454 ASSERT3P(marker, !=, NULL); 2455 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2456 2457 mls = multilist_sublist_lock(ml, idx); 2458 2459 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2460 hdr = multilist_sublist_prev(mls, marker)) { 2461 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2462 (evict_count >= zfs_arc_evict_batch_limit)) 2463 break; 2464 2465 /* 2466 * To keep our iteration location, move the marker 2467 * forward. Since we're not holding hdr's hash lock, we 2468 * must be very careful and not remove 'hdr' from the 2469 * sublist. Otherwise, other consumers might mistake the 2470 * 'hdr' as not being on a sublist when they call the 2471 * multilist_link_active() function (they all rely on 2472 * the hash lock protecting concurrent insertions and 2473 * removals). multilist_sublist_move_forward() was 2474 * specifically implemented to ensure this is the case 2475 * (only 'marker' will be removed and re-inserted). 2476 */ 2477 multilist_sublist_move_forward(mls, marker); 2478 2479 /* 2480 * The only case where the b_spa field should ever be 2481 * zero, is the marker headers inserted by 2482 * arc_evict_state(). It's possible for multiple threads 2483 * to be calling arc_evict_state() concurrently (e.g. 2484 * dsl_pool_close() and zio_inject_fault()), so we must 2485 * skip any markers we see from these other threads. 2486 */ 2487 if (hdr->b_spa == 0) 2488 continue; 2489 2490 /* we're only interested in evicting buffers of a certain spa */ 2491 if (spa != 0 && hdr->b_spa != spa) { 2492 ARCSTAT_BUMP(arcstat_evict_skip); 2493 continue; 2494 } 2495 2496 hash_lock = HDR_LOCK(hdr); 2497 2498 /* 2499 * We aren't calling this function from any code path 2500 * that would already be holding a hash lock, so we're 2501 * asserting on this assumption to be defensive in case 2502 * this ever changes. Without this check, it would be 2503 * possible to incorrectly increment arcstat_mutex_miss 2504 * below (e.g. if the code changed such that we called 2505 * this function with a hash lock held). 2506 */ 2507 ASSERT(!MUTEX_HELD(hash_lock)); 2508 2509 if (mutex_tryenter(hash_lock)) { 2510 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2511 mutex_exit(hash_lock); 2512 2513 bytes_evicted += evicted; 2514 2515 /* 2516 * If evicted is zero, arc_evict_hdr() must have 2517 * decided to skip this header, don't increment 2518 * evict_count in this case. 2519 */ 2520 if (evicted != 0) 2521 evict_count++; 2522 2523 /* 2524 * If arc_size isn't overflowing, signal any 2525 * threads that might happen to be waiting. 2526 * 2527 * For each header evicted, we wake up a single 2528 * thread. If we used cv_broadcast, we could 2529 * wake up "too many" threads causing arc_size 2530 * to significantly overflow arc_c; since 2531 * arc_get_data_buf() doesn't check for overflow 2532 * when it's woken up (it doesn't because it's 2533 * possible for the ARC to be overflowing while 2534 * full of un-evictable buffers, and the 2535 * function should proceed in this case). 2536 * 2537 * If threads are left sleeping, due to not 2538 * using cv_broadcast, they will be woken up 2539 * just before arc_reclaim_thread() sleeps. 2540 */ 2541 mutex_enter(&arc_reclaim_lock); 2542 if (!arc_is_overflowing()) 2543 cv_signal(&arc_reclaim_waiters_cv); 2544 mutex_exit(&arc_reclaim_lock); 2545 } else { 2546 ARCSTAT_BUMP(arcstat_mutex_miss); 2547 } 2548 } 2549 2550 multilist_sublist_unlock(mls); 2551 2552 return (bytes_evicted); 2553 } 2554 2555 /* 2556 * Evict buffers from the given arc state, until we've removed the 2557 * specified number of bytes. Move the removed buffers to the 2558 * appropriate evict state. 2559 * 2560 * This function makes a "best effort". It skips over any buffers 2561 * it can't get a hash_lock on, and so, may not catch all candidates. 2562 * It may also return without evicting as much space as requested. 2563 * 2564 * If bytes is specified using the special value ARC_EVICT_ALL, this 2565 * will evict all available (i.e. unlocked and evictable) buffers from 2566 * the given arc state; which is used by arc_flush(). 2567 */ 2568 static uint64_t 2569 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2570 arc_buf_contents_t type) 2571 { 2572 uint64_t total_evicted = 0; 2573 multilist_t *ml = &state->arcs_list[type]; 2574 int num_sublists; 2575 arc_buf_hdr_t **markers; 2576 2577 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2578 2579 num_sublists = multilist_get_num_sublists(ml); 2580 2581 /* 2582 * If we've tried to evict from each sublist, made some 2583 * progress, but still have not hit the target number of bytes 2584 * to evict, we want to keep trying. The markers allow us to 2585 * pick up where we left off for each individual sublist, rather 2586 * than starting from the tail each time. 2587 */ 2588 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2589 for (int i = 0; i < num_sublists; i++) { 2590 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2591 2592 /* 2593 * A b_spa of 0 is used to indicate that this header is 2594 * a marker. This fact is used in arc_adjust_type() and 2595 * arc_evict_state_impl(). 2596 */ 2597 markers[i]->b_spa = 0; 2598 2599 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2600 multilist_sublist_insert_tail(mls, markers[i]); 2601 multilist_sublist_unlock(mls); 2602 } 2603 2604 /* 2605 * While we haven't hit our target number of bytes to evict, or 2606 * we're evicting all available buffers. 2607 */ 2608 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2609 /* 2610 * Start eviction using a randomly selected sublist, 2611 * this is to try and evenly balance eviction across all 2612 * sublists. Always starting at the same sublist 2613 * (e.g. index 0) would cause evictions to favor certain 2614 * sublists over others. 2615 */ 2616 int sublist_idx = multilist_get_random_index(ml); 2617 uint64_t scan_evicted = 0; 2618 2619 for (int i = 0; i < num_sublists; i++) { 2620 uint64_t bytes_remaining; 2621 uint64_t bytes_evicted; 2622 2623 if (bytes == ARC_EVICT_ALL) 2624 bytes_remaining = ARC_EVICT_ALL; 2625 else if (total_evicted < bytes) 2626 bytes_remaining = bytes - total_evicted; 2627 else 2628 break; 2629 2630 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2631 markers[sublist_idx], spa, bytes_remaining); 2632 2633 scan_evicted += bytes_evicted; 2634 total_evicted += bytes_evicted; 2635 2636 /* we've reached the end, wrap to the beginning */ 2637 if (++sublist_idx >= num_sublists) 2638 sublist_idx = 0; 2639 } 2640 2641 /* 2642 * If we didn't evict anything during this scan, we have 2643 * no reason to believe we'll evict more during another 2644 * scan, so break the loop. 2645 */ 2646 if (scan_evicted == 0) { 2647 /* This isn't possible, let's make that obvious */ 2648 ASSERT3S(bytes, !=, 0); 2649 2650 /* 2651 * When bytes is ARC_EVICT_ALL, the only way to 2652 * break the loop is when scan_evicted is zero. 2653 * In that case, we actually have evicted enough, 2654 * so we don't want to increment the kstat. 2655 */ 2656 if (bytes != ARC_EVICT_ALL) { 2657 ASSERT3S(total_evicted, <, bytes); 2658 ARCSTAT_BUMP(arcstat_evict_not_enough); 2659 } 2660 2661 break; 2662 } 2663 } 2664 2665 for (int i = 0; i < num_sublists; i++) { 2666 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2667 multilist_sublist_remove(mls, markers[i]); 2668 multilist_sublist_unlock(mls); 2669 2670 kmem_cache_free(hdr_full_cache, markers[i]); 2671 } 2672 kmem_free(markers, sizeof (*markers) * num_sublists); 2673 2674 return (total_evicted); 2675 } 2676 2677 /* 2678 * Flush all "evictable" data of the given type from the arc state 2679 * specified. This will not evict any "active" buffers (i.e. referenced). 2680 * 2681 * When 'retry' is set to FALSE, the function will make a single pass 2682 * over the state and evict any buffers that it can. Since it doesn't 2683 * continually retry the eviction, it might end up leaving some buffers 2684 * in the ARC due to lock misses. 2685 * 2686 * When 'retry' is set to TRUE, the function will continually retry the 2687 * eviction until *all* evictable buffers have been removed from the 2688 * state. As a result, if concurrent insertions into the state are 2689 * allowed (e.g. if the ARC isn't shutting down), this function might 2690 * wind up in an infinite loop, continually trying to evict buffers. 2691 */ 2692 static uint64_t 2693 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2694 boolean_t retry) 2695 { 2696 uint64_t evicted = 0; 2697 2698 while (state->arcs_lsize[type] != 0) { 2699 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2700 2701 if (!retry) 2702 break; 2703 } 2704 2705 return (evicted); 2706 } 2707 2708 /* 2709 * Evict the specified number of bytes from the state specified, 2710 * restricting eviction to the spa and type given. This function 2711 * prevents us from trying to evict more from a state's list than 2712 * is "evictable", and to skip evicting altogether when passed a 2713 * negative value for "bytes". In contrast, arc_evict_state() will 2714 * evict everything it can, when passed a negative value for "bytes". 2715 */ 2716 static uint64_t 2717 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 2718 arc_buf_contents_t type) 2719 { 2720 int64_t delta; 2721 2722 if (bytes > 0 && state->arcs_lsize[type] > 0) { 2723 delta = MIN(state->arcs_lsize[type], bytes); 2724 return (arc_evict_state(state, spa, delta, type)); 2725 } 2726 2727 return (0); 2728 } 2729 2730 /* 2731 * Evict metadata buffers from the cache, such that arc_meta_used is 2732 * capped by the arc_meta_limit tunable. 2733 */ 2734 static uint64_t 2735 arc_adjust_meta(void) 2736 { 2737 uint64_t total_evicted = 0; 2738 int64_t target; 2739 2740 /* 2741 * If we're over the meta limit, we want to evict enough 2742 * metadata to get back under the meta limit. We don't want to 2743 * evict so much that we drop the MRU below arc_p, though. If 2744 * we're over the meta limit more than we're over arc_p, we 2745 * evict some from the MRU here, and some from the MFU below. 2746 */ 2747 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2748 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2749 refcount_count(&arc_mru->arcs_size) - arc_p)); 2750 2751 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2752 2753 /* 2754 * Similar to the above, we want to evict enough bytes to get us 2755 * below the meta limit, but not so much as to drop us below the 2756 * space alloted to the MFU (which is defined as arc_c - arc_p). 2757 */ 2758 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 2759 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 2760 2761 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2762 2763 return (total_evicted); 2764 } 2765 2766 /* 2767 * Return the type of the oldest buffer in the given arc state 2768 * 2769 * This function will select a random sublist of type ARC_BUFC_DATA and 2770 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 2771 * is compared, and the type which contains the "older" buffer will be 2772 * returned. 2773 */ 2774 static arc_buf_contents_t 2775 arc_adjust_type(arc_state_t *state) 2776 { 2777 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 2778 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 2779 int data_idx = multilist_get_random_index(data_ml); 2780 int meta_idx = multilist_get_random_index(meta_ml); 2781 multilist_sublist_t *data_mls; 2782 multilist_sublist_t *meta_mls; 2783 arc_buf_contents_t type; 2784 arc_buf_hdr_t *data_hdr; 2785 arc_buf_hdr_t *meta_hdr; 2786 2787 /* 2788 * We keep the sublist lock until we're finished, to prevent 2789 * the headers from being destroyed via arc_evict_state(). 2790 */ 2791 data_mls = multilist_sublist_lock(data_ml, data_idx); 2792 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 2793 2794 /* 2795 * These two loops are to ensure we skip any markers that 2796 * might be at the tail of the lists due to arc_evict_state(). 2797 */ 2798 2799 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 2800 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 2801 if (data_hdr->b_spa != 0) 2802 break; 2803 } 2804 2805 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 2806 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 2807 if (meta_hdr->b_spa != 0) 2808 break; 2809 } 2810 2811 if (data_hdr == NULL && meta_hdr == NULL) { 2812 type = ARC_BUFC_DATA; 2813 } else if (data_hdr == NULL) { 2814 ASSERT3P(meta_hdr, !=, NULL); 2815 type = ARC_BUFC_METADATA; 2816 } else if (meta_hdr == NULL) { 2817 ASSERT3P(data_hdr, !=, NULL); 2818 type = ARC_BUFC_DATA; 2819 } else { 2820 ASSERT3P(data_hdr, !=, NULL); 2821 ASSERT3P(meta_hdr, !=, NULL); 2822 2823 /* The headers can't be on the sublist without an L1 header */ 2824 ASSERT(HDR_HAS_L1HDR(data_hdr)); 2825 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 2826 2827 if (data_hdr->b_l1hdr.b_arc_access < 2828 meta_hdr->b_l1hdr.b_arc_access) { 2829 type = ARC_BUFC_DATA; 2830 } else { 2831 type = ARC_BUFC_METADATA; 2832 } 2833 } 2834 2835 multilist_sublist_unlock(meta_mls); 2836 multilist_sublist_unlock(data_mls); 2837 2838 return (type); 2839 } 2840 2841 /* 2842 * Evict buffers from the cache, such that arc_size is capped by arc_c. 2843 */ 2844 static uint64_t 2845 arc_adjust(void) 2846 { 2847 uint64_t total_evicted = 0; 2848 uint64_t bytes; 2849 int64_t target; 2850 2851 /* 2852 * If we're over arc_meta_limit, we want to correct that before 2853 * potentially evicting data buffers below. 2854 */ 2855 total_evicted += arc_adjust_meta(); 2856 2857 /* 2858 * Adjust MRU size 2859 * 2860 * If we're over the target cache size, we want to evict enough 2861 * from the list to get back to our target size. We don't want 2862 * to evict too much from the MRU, such that it drops below 2863 * arc_p. So, if we're over our target cache size more than 2864 * the MRU is over arc_p, we'll evict enough to get back to 2865 * arc_p here, and then evict more from the MFU below. 2866 */ 2867 target = MIN((int64_t)(arc_size - arc_c), 2868 (int64_t)(refcount_count(&arc_anon->arcs_size) + 2869 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 2870 2871 /* 2872 * If we're below arc_meta_min, always prefer to evict data. 2873 * Otherwise, try to satisfy the requested number of bytes to 2874 * evict from the type which contains older buffers; in an 2875 * effort to keep newer buffers in the cache regardless of their 2876 * type. If we cannot satisfy the number of bytes from this 2877 * type, spill over into the next type. 2878 */ 2879 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2880 arc_meta_used > arc_meta_min) { 2881 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2882 total_evicted += bytes; 2883 2884 /* 2885 * If we couldn't evict our target number of bytes from 2886 * metadata, we try to get the rest from data. 2887 */ 2888 target -= bytes; 2889 2890 total_evicted += 2891 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2892 } else { 2893 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 2894 total_evicted += bytes; 2895 2896 /* 2897 * If we couldn't evict our target number of bytes from 2898 * data, we try to get the rest from metadata. 2899 */ 2900 target -= bytes; 2901 2902 total_evicted += 2903 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 2904 } 2905 2906 /* 2907 * Adjust MFU size 2908 * 2909 * Now that we've tried to evict enough from the MRU to get its 2910 * size back to arc_p, if we're still above the target cache 2911 * size, we evict the rest from the MFU. 2912 */ 2913 target = arc_size - arc_c; 2914 2915 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 2916 arc_meta_used > arc_meta_min) { 2917 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2918 total_evicted += bytes; 2919 2920 /* 2921 * If we couldn't evict our target number of bytes from 2922 * metadata, we try to get the rest from data. 2923 */ 2924 target -= bytes; 2925 2926 total_evicted += 2927 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 2928 } else { 2929 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 2930 total_evicted += bytes; 2931 2932 /* 2933 * If we couldn't evict our target number of bytes from 2934 * data, we try to get the rest from data. 2935 */ 2936 target -= bytes; 2937 2938 total_evicted += 2939 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 2940 } 2941 2942 /* 2943 * Adjust ghost lists 2944 * 2945 * In addition to the above, the ARC also defines target values 2946 * for the ghost lists. The sum of the mru list and mru ghost 2947 * list should never exceed the target size of the cache, and 2948 * the sum of the mru list, mfu list, mru ghost list, and mfu 2949 * ghost list should never exceed twice the target size of the 2950 * cache. The following logic enforces these limits on the ghost 2951 * caches, and evicts from them as needed. 2952 */ 2953 target = refcount_count(&arc_mru->arcs_size) + 2954 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 2955 2956 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 2957 total_evicted += bytes; 2958 2959 target -= bytes; 2960 2961 total_evicted += 2962 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 2963 2964 /* 2965 * We assume the sum of the mru list and mfu list is less than 2966 * or equal to arc_c (we enforced this above), which means we 2967 * can use the simpler of the two equations below: 2968 * 2969 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 2970 * mru ghost + mfu ghost <= arc_c 2971 */ 2972 target = refcount_count(&arc_mru_ghost->arcs_size) + 2973 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 2974 2975 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 2976 total_evicted += bytes; 2977 2978 target -= bytes; 2979 2980 total_evicted += 2981 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 2982 2983 return (total_evicted); 2984 } 2985 2986 static void 2987 arc_do_user_evicts(void) 2988 { 2989 mutex_enter(&arc_user_evicts_lock); 2990 while (arc_eviction_list != NULL) { 2991 arc_buf_t *buf = arc_eviction_list; 2992 arc_eviction_list = buf->b_next; 2993 mutex_enter(&buf->b_evict_lock); 2994 buf->b_hdr = NULL; 2995 mutex_exit(&buf->b_evict_lock); 2996 mutex_exit(&arc_user_evicts_lock); 2997 2998 if (buf->b_efunc != NULL) 2999 VERIFY0(buf->b_efunc(buf->b_private)); 3000 3001 buf->b_efunc = NULL; 3002 buf->b_private = NULL; 3003 kmem_cache_free(buf_cache, buf); 3004 mutex_enter(&arc_user_evicts_lock); 3005 } 3006 mutex_exit(&arc_user_evicts_lock); 3007 } 3008 3009 void 3010 arc_flush(spa_t *spa, boolean_t retry) 3011 { 3012 uint64_t guid = 0; 3013 3014 /* 3015 * If retry is TRUE, a spa must not be specified since we have 3016 * no good way to determine if all of a spa's buffers have been 3017 * evicted from an arc state. 3018 */ 3019 ASSERT(!retry || spa == 0); 3020 3021 if (spa != NULL) 3022 guid = spa_load_guid(spa); 3023 3024 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3025 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3026 3027 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3028 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3029 3030 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3031 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3032 3033 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3034 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3035 3036 arc_do_user_evicts(); 3037 ASSERT(spa || arc_eviction_list == NULL); 3038 } 3039 3040 void 3041 arc_shrink(int64_t to_free) 3042 { 3043 if (arc_c > arc_c_min) { 3044 3045 if (arc_c > arc_c_min + to_free) 3046 atomic_add_64(&arc_c, -to_free); 3047 else 3048 arc_c = arc_c_min; 3049 3050 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3051 if (arc_c > arc_size) 3052 arc_c = MAX(arc_size, arc_c_min); 3053 if (arc_p > arc_c) 3054 arc_p = (arc_c >> 1); 3055 ASSERT(arc_c >= arc_c_min); 3056 ASSERT((int64_t)arc_p >= 0); 3057 } 3058 3059 if (arc_size > arc_c) 3060 (void) arc_adjust(); 3061 } 3062 3063 typedef enum free_memory_reason_t { 3064 FMR_UNKNOWN, 3065 FMR_NEEDFREE, 3066 FMR_LOTSFREE, 3067 FMR_SWAPFS_MINFREE, 3068 FMR_PAGES_PP_MAXIMUM, 3069 FMR_HEAP_ARENA, 3070 FMR_ZIO_ARENA, 3071 } free_memory_reason_t; 3072 3073 int64_t last_free_memory; 3074 free_memory_reason_t last_free_reason; 3075 3076 /* 3077 * Additional reserve of pages for pp_reserve. 3078 */ 3079 int64_t arc_pages_pp_reserve = 64; 3080 3081 /* 3082 * Additional reserve of pages for swapfs. 3083 */ 3084 int64_t arc_swapfs_reserve = 64; 3085 3086 /* 3087 * Return the amount of memory that can be consumed before reclaim will be 3088 * needed. Positive if there is sufficient free memory, negative indicates 3089 * the amount of memory that needs to be freed up. 3090 */ 3091 static int64_t 3092 arc_available_memory(void) 3093 { 3094 int64_t lowest = INT64_MAX; 3095 int64_t n; 3096 free_memory_reason_t r = FMR_UNKNOWN; 3097 3098 #ifdef _KERNEL 3099 if (needfree > 0) { 3100 n = PAGESIZE * (-needfree); 3101 if (n < lowest) { 3102 lowest = n; 3103 r = FMR_NEEDFREE; 3104 } 3105 } 3106 3107 /* 3108 * check that we're out of range of the pageout scanner. It starts to 3109 * schedule paging if freemem is less than lotsfree and needfree. 3110 * lotsfree is the high-water mark for pageout, and needfree is the 3111 * number of needed free pages. We add extra pages here to make sure 3112 * the scanner doesn't start up while we're freeing memory. 3113 */ 3114 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3115 if (n < lowest) { 3116 lowest = n; 3117 r = FMR_LOTSFREE; 3118 } 3119 3120 /* 3121 * check to make sure that swapfs has enough space so that anon 3122 * reservations can still succeed. anon_resvmem() checks that the 3123 * availrmem is greater than swapfs_minfree, and the number of reserved 3124 * swap pages. We also add a bit of extra here just to prevent 3125 * circumstances from getting really dire. 3126 */ 3127 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3128 desfree - arc_swapfs_reserve); 3129 if (n < lowest) { 3130 lowest = n; 3131 r = FMR_SWAPFS_MINFREE; 3132 } 3133 3134 3135 /* 3136 * Check that we have enough availrmem that memory locking (e.g., via 3137 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3138 * stores the number of pages that cannot be locked; when availrmem 3139 * drops below pages_pp_maximum, page locking mechanisms such as 3140 * page_pp_lock() will fail.) 3141 */ 3142 n = PAGESIZE * (availrmem - pages_pp_maximum - 3143 arc_pages_pp_reserve); 3144 if (n < lowest) { 3145 lowest = n; 3146 r = FMR_PAGES_PP_MAXIMUM; 3147 } 3148 3149 #if defined(__i386) 3150 /* 3151 * If we're on an i386 platform, it's possible that we'll exhaust the 3152 * kernel heap space before we ever run out of available physical 3153 * memory. Most checks of the size of the heap_area compare against 3154 * tune.t_minarmem, which is the minimum available real memory that we 3155 * can have in the system. However, this is generally fixed at 25 pages 3156 * which is so low that it's useless. In this comparison, we seek to 3157 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3158 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3159 * free) 3160 */ 3161 n = vmem_size(heap_arena, VMEM_FREE) - 3162 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3163 if (n < lowest) { 3164 lowest = n; 3165 r = FMR_HEAP_ARENA; 3166 } 3167 #endif 3168 3169 /* 3170 * If zio data pages are being allocated out of a separate heap segment, 3171 * then enforce that the size of available vmem for this arena remains 3172 * above about 1/16th free. 3173 * 3174 * Note: The 1/16th arena free requirement was put in place 3175 * to aggressively evict memory from the arc in order to avoid 3176 * memory fragmentation issues. 3177 */ 3178 if (zio_arena != NULL) { 3179 n = vmem_size(zio_arena, VMEM_FREE) - 3180 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3181 if (n < lowest) { 3182 lowest = n; 3183 r = FMR_ZIO_ARENA; 3184 } 3185 } 3186 #else 3187 /* Every 100 calls, free a small amount */ 3188 if (spa_get_random(100) == 0) 3189 lowest = -1024; 3190 #endif 3191 3192 last_free_memory = lowest; 3193 last_free_reason = r; 3194 3195 return (lowest); 3196 } 3197 3198 3199 /* 3200 * Determine if the system is under memory pressure and is asking 3201 * to reclaim memory. A return value of TRUE indicates that the system 3202 * is under memory pressure and that the arc should adjust accordingly. 3203 */ 3204 static boolean_t 3205 arc_reclaim_needed(void) 3206 { 3207 return (arc_available_memory() < 0); 3208 } 3209 3210 static void 3211 arc_kmem_reap_now(void) 3212 { 3213 size_t i; 3214 kmem_cache_t *prev_cache = NULL; 3215 kmem_cache_t *prev_data_cache = NULL; 3216 extern kmem_cache_t *zio_buf_cache[]; 3217 extern kmem_cache_t *zio_data_buf_cache[]; 3218 extern kmem_cache_t *range_seg_cache; 3219 3220 #ifdef _KERNEL 3221 if (arc_meta_used >= arc_meta_limit) { 3222 /* 3223 * We are exceeding our meta-data cache limit. 3224 * Purge some DNLC entries to release holds on meta-data. 3225 */ 3226 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3227 } 3228 #if defined(__i386) 3229 /* 3230 * Reclaim unused memory from all kmem caches. 3231 */ 3232 kmem_reap(); 3233 #endif 3234 #endif 3235 3236 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3237 if (zio_buf_cache[i] != prev_cache) { 3238 prev_cache = zio_buf_cache[i]; 3239 kmem_cache_reap_now(zio_buf_cache[i]); 3240 } 3241 if (zio_data_buf_cache[i] != prev_data_cache) { 3242 prev_data_cache = zio_data_buf_cache[i]; 3243 kmem_cache_reap_now(zio_data_buf_cache[i]); 3244 } 3245 } 3246 kmem_cache_reap_now(buf_cache); 3247 kmem_cache_reap_now(hdr_full_cache); 3248 kmem_cache_reap_now(hdr_l2only_cache); 3249 kmem_cache_reap_now(range_seg_cache); 3250 3251 if (zio_arena != NULL) { 3252 /* 3253 * Ask the vmem arena to reclaim unused memory from its 3254 * quantum caches. 3255 */ 3256 vmem_qcache_reap(zio_arena); 3257 } 3258 } 3259 3260 /* 3261 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3262 * enough data and signal them to proceed. When this happens, the threads in 3263 * arc_get_data_buf() are sleeping while holding the hash lock for their 3264 * particular arc header. Thus, we must be careful to never sleep on a 3265 * hash lock in this thread. This is to prevent the following deadlock: 3266 * 3267 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3268 * waiting for the reclaim thread to signal it. 3269 * 3270 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3271 * fails, and goes to sleep forever. 3272 * 3273 * This possible deadlock is avoided by always acquiring a hash lock 3274 * using mutex_tryenter() from arc_reclaim_thread(). 3275 */ 3276 static void 3277 arc_reclaim_thread(void) 3278 { 3279 clock_t growtime = 0; 3280 callb_cpr_t cpr; 3281 3282 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3283 3284 mutex_enter(&arc_reclaim_lock); 3285 while (!arc_reclaim_thread_exit) { 3286 int64_t free_memory = arc_available_memory(); 3287 uint64_t evicted = 0; 3288 3289 mutex_exit(&arc_reclaim_lock); 3290 3291 if (free_memory < 0) { 3292 3293 arc_no_grow = B_TRUE; 3294 arc_warm = B_TRUE; 3295 3296 /* 3297 * Wait at least zfs_grow_retry (default 60) seconds 3298 * before considering growing. 3299 */ 3300 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3301 3302 arc_kmem_reap_now(); 3303 3304 /* 3305 * If we are still low on memory, shrink the ARC 3306 * so that we have arc_shrink_min free space. 3307 */ 3308 free_memory = arc_available_memory(); 3309 3310 int64_t to_free = 3311 (arc_c >> arc_shrink_shift) - free_memory; 3312 if (to_free > 0) { 3313 #ifdef _KERNEL 3314 to_free = MAX(to_free, ptob(needfree)); 3315 #endif 3316 arc_shrink(to_free); 3317 } 3318 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3319 arc_no_grow = B_TRUE; 3320 } else if (ddi_get_lbolt() >= growtime) { 3321 arc_no_grow = B_FALSE; 3322 } 3323 3324 evicted = arc_adjust(); 3325 3326 mutex_enter(&arc_reclaim_lock); 3327 3328 /* 3329 * If evicted is zero, we couldn't evict anything via 3330 * arc_adjust(). This could be due to hash lock 3331 * collisions, but more likely due to the majority of 3332 * arc buffers being unevictable. Therefore, even if 3333 * arc_size is above arc_c, another pass is unlikely to 3334 * be helpful and could potentially cause us to enter an 3335 * infinite loop. 3336 */ 3337 if (arc_size <= arc_c || evicted == 0) { 3338 /* 3339 * We're either no longer overflowing, or we 3340 * can't evict anything more, so we should wake 3341 * up any threads before we go to sleep. 3342 */ 3343 cv_broadcast(&arc_reclaim_waiters_cv); 3344 3345 /* 3346 * Block until signaled, or after one second (we 3347 * might need to perform arc_kmem_reap_now() 3348 * even if we aren't being signalled) 3349 */ 3350 CALLB_CPR_SAFE_BEGIN(&cpr); 3351 (void) cv_timedwait(&arc_reclaim_thread_cv, 3352 &arc_reclaim_lock, ddi_get_lbolt() + hz); 3353 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3354 } 3355 } 3356 3357 arc_reclaim_thread_exit = FALSE; 3358 cv_broadcast(&arc_reclaim_thread_cv); 3359 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3360 thread_exit(); 3361 } 3362 3363 static void 3364 arc_user_evicts_thread(void) 3365 { 3366 callb_cpr_t cpr; 3367 3368 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3369 3370 mutex_enter(&arc_user_evicts_lock); 3371 while (!arc_user_evicts_thread_exit) { 3372 mutex_exit(&arc_user_evicts_lock); 3373 3374 arc_do_user_evicts(); 3375 3376 /* 3377 * This is necessary in order for the mdb ::arc dcmd to 3378 * show up to date information. Since the ::arc command 3379 * does not call the kstat's update function, without 3380 * this call, the command may show stale stats for the 3381 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3382 * with this change, the data might be up to 1 second 3383 * out of date; but that should suffice. The arc_state_t 3384 * structures can be queried directly if more accurate 3385 * information is needed. 3386 */ 3387 if (arc_ksp != NULL) 3388 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3389 3390 mutex_enter(&arc_user_evicts_lock); 3391 3392 /* 3393 * Block until signaled, or after one second (we need to 3394 * call the arc's kstat update function regularly). 3395 */ 3396 CALLB_CPR_SAFE_BEGIN(&cpr); 3397 (void) cv_timedwait(&arc_user_evicts_cv, 3398 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3399 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3400 } 3401 3402 arc_user_evicts_thread_exit = FALSE; 3403 cv_broadcast(&arc_user_evicts_cv); 3404 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3405 thread_exit(); 3406 } 3407 3408 /* 3409 * Adapt arc info given the number of bytes we are trying to add and 3410 * the state that we are comming from. This function is only called 3411 * when we are adding new content to the cache. 3412 */ 3413 static void 3414 arc_adapt(int bytes, arc_state_t *state) 3415 { 3416 int mult; 3417 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3418 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3419 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3420 3421 if (state == arc_l2c_only) 3422 return; 3423 3424 ASSERT(bytes > 0); 3425 /* 3426 * Adapt the target size of the MRU list: 3427 * - if we just hit in the MRU ghost list, then increase 3428 * the target size of the MRU list. 3429 * - if we just hit in the MFU ghost list, then increase 3430 * the target size of the MFU list by decreasing the 3431 * target size of the MRU list. 3432 */ 3433 if (state == arc_mru_ghost) { 3434 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3435 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3436 3437 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3438 } else if (state == arc_mfu_ghost) { 3439 uint64_t delta; 3440 3441 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3442 mult = MIN(mult, 10); 3443 3444 delta = MIN(bytes * mult, arc_p); 3445 arc_p = MAX(arc_p_min, arc_p - delta); 3446 } 3447 ASSERT((int64_t)arc_p >= 0); 3448 3449 if (arc_reclaim_needed()) { 3450 cv_signal(&arc_reclaim_thread_cv); 3451 return; 3452 } 3453 3454 if (arc_no_grow) 3455 return; 3456 3457 if (arc_c >= arc_c_max) 3458 return; 3459 3460 /* 3461 * If we're within (2 * maxblocksize) bytes of the target 3462 * cache size, increment the target cache size 3463 */ 3464 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3465 atomic_add_64(&arc_c, (int64_t)bytes); 3466 if (arc_c > arc_c_max) 3467 arc_c = arc_c_max; 3468 else if (state == arc_anon) 3469 atomic_add_64(&arc_p, (int64_t)bytes); 3470 if (arc_p > arc_c) 3471 arc_p = arc_c; 3472 } 3473 ASSERT((int64_t)arc_p >= 0); 3474 } 3475 3476 /* 3477 * Check if arc_size has grown past our upper threshold, determined by 3478 * zfs_arc_overflow_shift. 3479 */ 3480 static boolean_t 3481 arc_is_overflowing(void) 3482 { 3483 /* Always allow at least one block of overflow */ 3484 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3485 arc_c >> zfs_arc_overflow_shift); 3486 3487 return (arc_size >= arc_c + overflow); 3488 } 3489 3490 /* 3491 * The buffer, supplied as the first argument, needs a data block. If we 3492 * are hitting the hard limit for the cache size, we must sleep, waiting 3493 * for the eviction thread to catch up. If we're past the target size 3494 * but below the hard limit, we'll only signal the reclaim thread and 3495 * continue on. 3496 */ 3497 static void 3498 arc_get_data_buf(arc_buf_t *buf) 3499 { 3500 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3501 uint64_t size = buf->b_hdr->b_size; 3502 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3503 3504 arc_adapt(size, state); 3505 3506 /* 3507 * If arc_size is currently overflowing, and has grown past our 3508 * upper limit, we must be adding data faster than the evict 3509 * thread can evict. Thus, to ensure we don't compound the 3510 * problem by adding more data and forcing arc_size to grow even 3511 * further past it's target size, we halt and wait for the 3512 * eviction thread to catch up. 3513 * 3514 * It's also possible that the reclaim thread is unable to evict 3515 * enough buffers to get arc_size below the overflow limit (e.g. 3516 * due to buffers being un-evictable, or hash lock collisions). 3517 * In this case, we want to proceed regardless if we're 3518 * overflowing; thus we don't use a while loop here. 3519 */ 3520 if (arc_is_overflowing()) { 3521 mutex_enter(&arc_reclaim_lock); 3522 3523 /* 3524 * Now that we've acquired the lock, we may no longer be 3525 * over the overflow limit, lets check. 3526 * 3527 * We're ignoring the case of spurious wake ups. If that 3528 * were to happen, it'd let this thread consume an ARC 3529 * buffer before it should have (i.e. before we're under 3530 * the overflow limit and were signalled by the reclaim 3531 * thread). As long as that is a rare occurrence, it 3532 * shouldn't cause any harm. 3533 */ 3534 if (arc_is_overflowing()) { 3535 cv_signal(&arc_reclaim_thread_cv); 3536 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3537 } 3538 3539 mutex_exit(&arc_reclaim_lock); 3540 } 3541 3542 if (type == ARC_BUFC_METADATA) { 3543 buf->b_data = zio_buf_alloc(size); 3544 arc_space_consume(size, ARC_SPACE_META); 3545 } else { 3546 ASSERT(type == ARC_BUFC_DATA); 3547 buf->b_data = zio_data_buf_alloc(size); 3548 arc_space_consume(size, ARC_SPACE_DATA); 3549 } 3550 3551 /* 3552 * Update the state size. Note that ghost states have a 3553 * "ghost size" and so don't need to be updated. 3554 */ 3555 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3556 arc_buf_hdr_t *hdr = buf->b_hdr; 3557 arc_state_t *state = hdr->b_l1hdr.b_state; 3558 3559 (void) refcount_add_many(&state->arcs_size, size, buf); 3560 3561 /* 3562 * If this is reached via arc_read, the link is 3563 * protected by the hash lock. If reached via 3564 * arc_buf_alloc, the header should not be accessed by 3565 * any other thread. And, if reached via arc_read_done, 3566 * the hash lock will protect it if it's found in the 3567 * hash table; otherwise no other thread should be 3568 * trying to [add|remove]_reference it. 3569 */ 3570 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3571 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3572 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3573 size); 3574 } 3575 /* 3576 * If we are growing the cache, and we are adding anonymous 3577 * data, and we have outgrown arc_p, update arc_p 3578 */ 3579 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3580 (refcount_count(&arc_anon->arcs_size) + 3581 refcount_count(&arc_mru->arcs_size) > arc_p)) 3582 arc_p = MIN(arc_c, arc_p + size); 3583 } 3584 } 3585 3586 /* 3587 * This routine is called whenever a buffer is accessed. 3588 * NOTE: the hash lock is dropped in this function. 3589 */ 3590 static void 3591 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3592 { 3593 clock_t now; 3594 3595 ASSERT(MUTEX_HELD(hash_lock)); 3596 ASSERT(HDR_HAS_L1HDR(hdr)); 3597 3598 if (hdr->b_l1hdr.b_state == arc_anon) { 3599 /* 3600 * This buffer is not in the cache, and does not 3601 * appear in our "ghost" list. Add the new buffer 3602 * to the MRU state. 3603 */ 3604 3605 ASSERT0(hdr->b_l1hdr.b_arc_access); 3606 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3607 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3608 arc_change_state(arc_mru, hdr, hash_lock); 3609 3610 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3611 now = ddi_get_lbolt(); 3612 3613 /* 3614 * If this buffer is here because of a prefetch, then either: 3615 * - clear the flag if this is a "referencing" read 3616 * (any subsequent access will bump this into the MFU state). 3617 * or 3618 * - move the buffer to the head of the list if this is 3619 * another prefetch (to make it less likely to be evicted). 3620 */ 3621 if (HDR_PREFETCH(hdr)) { 3622 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3623 /* link protected by hash lock */ 3624 ASSERT(multilist_link_active( 3625 &hdr->b_l1hdr.b_arc_node)); 3626 } else { 3627 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3628 ARCSTAT_BUMP(arcstat_mru_hits); 3629 } 3630 hdr->b_l1hdr.b_arc_access = now; 3631 return; 3632 } 3633 3634 /* 3635 * This buffer has been "accessed" only once so far, 3636 * but it is still in the cache. Move it to the MFU 3637 * state. 3638 */ 3639 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3640 /* 3641 * More than 125ms have passed since we 3642 * instantiated this buffer. Move it to the 3643 * most frequently used state. 3644 */ 3645 hdr->b_l1hdr.b_arc_access = now; 3646 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3647 arc_change_state(arc_mfu, hdr, hash_lock); 3648 } 3649 ARCSTAT_BUMP(arcstat_mru_hits); 3650 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3651 arc_state_t *new_state; 3652 /* 3653 * This buffer has been "accessed" recently, but 3654 * was evicted from the cache. Move it to the 3655 * MFU state. 3656 */ 3657 3658 if (HDR_PREFETCH(hdr)) { 3659 new_state = arc_mru; 3660 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3661 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3662 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3663 } else { 3664 new_state = arc_mfu; 3665 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3666 } 3667 3668 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3669 arc_change_state(new_state, hdr, hash_lock); 3670 3671 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3672 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3673 /* 3674 * This buffer has been accessed more than once and is 3675 * still in the cache. Keep it in the MFU state. 3676 * 3677 * NOTE: an add_reference() that occurred when we did 3678 * the arc_read() will have kicked this off the list. 3679 * If it was a prefetch, we will explicitly move it to 3680 * the head of the list now. 3681 */ 3682 if ((HDR_PREFETCH(hdr)) != 0) { 3683 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3684 /* link protected by hash_lock */ 3685 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3686 } 3687 ARCSTAT_BUMP(arcstat_mfu_hits); 3688 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3689 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3690 arc_state_t *new_state = arc_mfu; 3691 /* 3692 * This buffer has been accessed more than once but has 3693 * been evicted from the cache. Move it back to the 3694 * MFU state. 3695 */ 3696 3697 if (HDR_PREFETCH(hdr)) { 3698 /* 3699 * This is a prefetch access... 3700 * move this block back to the MRU state. 3701 */ 3702 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3703 new_state = arc_mru; 3704 } 3705 3706 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3707 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3708 arc_change_state(new_state, hdr, hash_lock); 3709 3710 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3711 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3712 /* 3713 * This buffer is on the 2nd Level ARC. 3714 */ 3715 3716 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3717 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3718 arc_change_state(arc_mfu, hdr, hash_lock); 3719 } else { 3720 ASSERT(!"invalid arc state"); 3721 } 3722 } 3723 3724 /* a generic arc_done_func_t which you can use */ 3725 /* ARGSUSED */ 3726 void 3727 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3728 { 3729 if (zio == NULL || zio->io_error == 0) 3730 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3731 VERIFY(arc_buf_remove_ref(buf, arg)); 3732 } 3733 3734 /* a generic arc_done_func_t */ 3735 void 3736 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3737 { 3738 arc_buf_t **bufp = arg; 3739 if (zio && zio->io_error) { 3740 VERIFY(arc_buf_remove_ref(buf, arg)); 3741 *bufp = NULL; 3742 } else { 3743 *bufp = buf; 3744 ASSERT(buf->b_data); 3745 } 3746 } 3747 3748 static void 3749 arc_read_done(zio_t *zio) 3750 { 3751 arc_buf_hdr_t *hdr; 3752 arc_buf_t *buf; 3753 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3754 kmutex_t *hash_lock = NULL; 3755 arc_callback_t *callback_list, *acb; 3756 int freeable = FALSE; 3757 3758 buf = zio->io_private; 3759 hdr = buf->b_hdr; 3760 3761 /* 3762 * The hdr was inserted into hash-table and removed from lists 3763 * prior to starting I/O. We should find this header, since 3764 * it's in the hash table, and it should be legit since it's 3765 * not possible to evict it during the I/O. The only possible 3766 * reason for it not to be found is if we were freed during the 3767 * read. 3768 */ 3769 if (HDR_IN_HASH_TABLE(hdr)) { 3770 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3771 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3772 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3773 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3774 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3775 3776 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3777 &hash_lock); 3778 3779 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3780 hash_lock == NULL) || 3781 (found == hdr && 3782 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3783 (found == hdr && HDR_L2_READING(hdr))); 3784 } 3785 3786 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3787 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3788 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3789 3790 /* byteswap if necessary */ 3791 callback_list = hdr->b_l1hdr.b_acb; 3792 ASSERT(callback_list != NULL); 3793 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3794 dmu_object_byteswap_t bswap = 3795 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3796 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3797 byteswap_uint64_array : 3798 dmu_ot_byteswap[bswap].ob_func; 3799 func(buf->b_data, hdr->b_size); 3800 } 3801 3802 arc_cksum_compute(buf, B_FALSE); 3803 arc_buf_watch(buf); 3804 3805 if (hash_lock && zio->io_error == 0 && 3806 hdr->b_l1hdr.b_state == arc_anon) { 3807 /* 3808 * Only call arc_access on anonymous buffers. This is because 3809 * if we've issued an I/O for an evicted buffer, we've already 3810 * called arc_access (to prevent any simultaneous readers from 3811 * getting confused). 3812 */ 3813 arc_access(hdr, hash_lock); 3814 } 3815 3816 /* create copies of the data buffer for the callers */ 3817 abuf = buf; 3818 for (acb = callback_list; acb; acb = acb->acb_next) { 3819 if (acb->acb_done) { 3820 if (abuf == NULL) { 3821 ARCSTAT_BUMP(arcstat_duplicate_reads); 3822 abuf = arc_buf_clone(buf); 3823 } 3824 acb->acb_buf = abuf; 3825 abuf = NULL; 3826 } 3827 } 3828 hdr->b_l1hdr.b_acb = NULL; 3829 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3830 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3831 if (abuf == buf) { 3832 ASSERT(buf->b_efunc == NULL); 3833 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3834 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3835 } 3836 3837 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3838 callback_list != NULL); 3839 3840 if (zio->io_error != 0) { 3841 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3842 if (hdr->b_l1hdr.b_state != arc_anon) 3843 arc_change_state(arc_anon, hdr, hash_lock); 3844 if (HDR_IN_HASH_TABLE(hdr)) 3845 buf_hash_remove(hdr); 3846 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3847 } 3848 3849 /* 3850 * Broadcast before we drop the hash_lock to avoid the possibility 3851 * that the hdr (and hence the cv) might be freed before we get to 3852 * the cv_broadcast(). 3853 */ 3854 cv_broadcast(&hdr->b_l1hdr.b_cv); 3855 3856 if (hash_lock != NULL) { 3857 mutex_exit(hash_lock); 3858 } else { 3859 /* 3860 * This block was freed while we waited for the read to 3861 * complete. It has been removed from the hash table and 3862 * moved to the anonymous state (so that it won't show up 3863 * in the cache). 3864 */ 3865 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3866 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3867 } 3868 3869 /* execute each callback and free its structure */ 3870 while ((acb = callback_list) != NULL) { 3871 if (acb->acb_done) 3872 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3873 3874 if (acb->acb_zio_dummy != NULL) { 3875 acb->acb_zio_dummy->io_error = zio->io_error; 3876 zio_nowait(acb->acb_zio_dummy); 3877 } 3878 3879 callback_list = acb->acb_next; 3880 kmem_free(acb, sizeof (arc_callback_t)); 3881 } 3882 3883 if (freeable) 3884 arc_hdr_destroy(hdr); 3885 } 3886 3887 /* 3888 * "Read" the block at the specified DVA (in bp) via the 3889 * cache. If the block is found in the cache, invoke the provided 3890 * callback immediately and return. Note that the `zio' parameter 3891 * in the callback will be NULL in this case, since no IO was 3892 * required. If the block is not in the cache pass the read request 3893 * on to the spa with a substitute callback function, so that the 3894 * requested block will be added to the cache. 3895 * 3896 * If a read request arrives for a block that has a read in-progress, 3897 * either wait for the in-progress read to complete (and return the 3898 * results); or, if this is a read with a "done" func, add a record 3899 * to the read to invoke the "done" func when the read completes, 3900 * and return; or just return. 3901 * 3902 * arc_read_done() will invoke all the requested "done" functions 3903 * for readers of this block. 3904 */ 3905 int 3906 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3907 void *private, zio_priority_t priority, int zio_flags, 3908 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3909 { 3910 arc_buf_hdr_t *hdr = NULL; 3911 arc_buf_t *buf = NULL; 3912 kmutex_t *hash_lock = NULL; 3913 zio_t *rzio; 3914 uint64_t guid = spa_load_guid(spa); 3915 3916 ASSERT(!BP_IS_EMBEDDED(bp) || 3917 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3918 3919 top: 3920 if (!BP_IS_EMBEDDED(bp)) { 3921 /* 3922 * Embedded BP's have no DVA and require no I/O to "read". 3923 * Create an anonymous arc buf to back it. 3924 */ 3925 hdr = buf_hash_find(guid, bp, &hash_lock); 3926 } 3927 3928 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 3929 3930 *arc_flags |= ARC_FLAG_CACHED; 3931 3932 if (HDR_IO_IN_PROGRESS(hdr)) { 3933 3934 if (*arc_flags & ARC_FLAG_WAIT) { 3935 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 3936 mutex_exit(hash_lock); 3937 goto top; 3938 } 3939 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3940 3941 if (done) { 3942 arc_callback_t *acb = NULL; 3943 3944 acb = kmem_zalloc(sizeof (arc_callback_t), 3945 KM_SLEEP); 3946 acb->acb_done = done; 3947 acb->acb_private = private; 3948 if (pio != NULL) 3949 acb->acb_zio_dummy = zio_null(pio, 3950 spa, NULL, NULL, NULL, zio_flags); 3951 3952 ASSERT(acb->acb_done != NULL); 3953 acb->acb_next = hdr->b_l1hdr.b_acb; 3954 hdr->b_l1hdr.b_acb = acb; 3955 add_reference(hdr, hash_lock, private); 3956 mutex_exit(hash_lock); 3957 return (0); 3958 } 3959 mutex_exit(hash_lock); 3960 return (0); 3961 } 3962 3963 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3964 hdr->b_l1hdr.b_state == arc_mfu); 3965 3966 if (done) { 3967 add_reference(hdr, hash_lock, private); 3968 /* 3969 * If this block is already in use, create a new 3970 * copy of the data so that we will be guaranteed 3971 * that arc_release() will always succeed. 3972 */ 3973 buf = hdr->b_l1hdr.b_buf; 3974 ASSERT(buf); 3975 ASSERT(buf->b_data); 3976 if (HDR_BUF_AVAILABLE(hdr)) { 3977 ASSERT(buf->b_efunc == NULL); 3978 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3979 } else { 3980 buf = arc_buf_clone(buf); 3981 } 3982 3983 } else if (*arc_flags & ARC_FLAG_PREFETCH && 3984 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3985 hdr->b_flags |= ARC_FLAG_PREFETCH; 3986 } 3987 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 3988 arc_access(hdr, hash_lock); 3989 if (*arc_flags & ARC_FLAG_L2CACHE) 3990 hdr->b_flags |= ARC_FLAG_L2CACHE; 3991 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3992 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3993 mutex_exit(hash_lock); 3994 ARCSTAT_BUMP(arcstat_hits); 3995 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 3996 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 3997 data, metadata, hits); 3998 3999 if (done) 4000 done(NULL, buf, private); 4001 } else { 4002 uint64_t size = BP_GET_LSIZE(bp); 4003 arc_callback_t *acb; 4004 vdev_t *vd = NULL; 4005 uint64_t addr = 0; 4006 boolean_t devw = B_FALSE; 4007 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4008 int32_t b_asize = 0; 4009 4010 if (hdr == NULL) { 4011 /* this block is not in the cache */ 4012 arc_buf_hdr_t *exists = NULL; 4013 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4014 buf = arc_buf_alloc(spa, size, private, type); 4015 hdr = buf->b_hdr; 4016 if (!BP_IS_EMBEDDED(bp)) { 4017 hdr->b_dva = *BP_IDENTITY(bp); 4018 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4019 exists = buf_hash_insert(hdr, &hash_lock); 4020 } 4021 if (exists != NULL) { 4022 /* somebody beat us to the hash insert */ 4023 mutex_exit(hash_lock); 4024 buf_discard_identity(hdr); 4025 (void) arc_buf_remove_ref(buf, private); 4026 goto top; /* restart the IO request */ 4027 } 4028 4029 /* if this is a prefetch, we don't have a reference */ 4030 if (*arc_flags & ARC_FLAG_PREFETCH) { 4031 (void) remove_reference(hdr, hash_lock, 4032 private); 4033 hdr->b_flags |= ARC_FLAG_PREFETCH; 4034 } 4035 if (*arc_flags & ARC_FLAG_L2CACHE) 4036 hdr->b_flags |= ARC_FLAG_L2CACHE; 4037 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4038 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4039 if (BP_GET_LEVEL(bp) > 0) 4040 hdr->b_flags |= ARC_FLAG_INDIRECT; 4041 } else { 4042 /* 4043 * This block is in the ghost cache. If it was L2-only 4044 * (and thus didn't have an L1 hdr), we realloc the 4045 * header to add an L1 hdr. 4046 */ 4047 if (!HDR_HAS_L1HDR(hdr)) { 4048 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4049 hdr_full_cache); 4050 } 4051 4052 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4053 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4054 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4055 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4056 4057 /* if this is a prefetch, we don't have a reference */ 4058 if (*arc_flags & ARC_FLAG_PREFETCH) 4059 hdr->b_flags |= ARC_FLAG_PREFETCH; 4060 else 4061 add_reference(hdr, hash_lock, private); 4062 if (*arc_flags & ARC_FLAG_L2CACHE) 4063 hdr->b_flags |= ARC_FLAG_L2CACHE; 4064 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4065 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4066 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4067 buf->b_hdr = hdr; 4068 buf->b_data = NULL; 4069 buf->b_efunc = NULL; 4070 buf->b_private = NULL; 4071 buf->b_next = NULL; 4072 hdr->b_l1hdr.b_buf = buf; 4073 ASSERT0(hdr->b_l1hdr.b_datacnt); 4074 hdr->b_l1hdr.b_datacnt = 1; 4075 arc_get_data_buf(buf); 4076 arc_access(hdr, hash_lock); 4077 } 4078 4079 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4080 4081 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4082 acb->acb_done = done; 4083 acb->acb_private = private; 4084 4085 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4086 hdr->b_l1hdr.b_acb = acb; 4087 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4088 4089 if (HDR_HAS_L2HDR(hdr) && 4090 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4091 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4092 addr = hdr->b_l2hdr.b_daddr; 4093 b_compress = HDR_GET_COMPRESS(hdr); 4094 b_asize = hdr->b_l2hdr.b_asize; 4095 /* 4096 * Lock out device removal. 4097 */ 4098 if (vdev_is_dead(vd) || 4099 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4100 vd = NULL; 4101 } 4102 4103 if (hash_lock != NULL) 4104 mutex_exit(hash_lock); 4105 4106 /* 4107 * At this point, we have a level 1 cache miss. Try again in 4108 * L2ARC if possible. 4109 */ 4110 ASSERT3U(hdr->b_size, ==, size); 4111 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4112 uint64_t, size, zbookmark_phys_t *, zb); 4113 ARCSTAT_BUMP(arcstat_misses); 4114 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4115 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4116 data, metadata, misses); 4117 4118 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4119 /* 4120 * Read from the L2ARC if the following are true: 4121 * 1. The L2ARC vdev was previously cached. 4122 * 2. This buffer still has L2ARC metadata. 4123 * 3. This buffer isn't currently writing to the L2ARC. 4124 * 4. The L2ARC entry wasn't evicted, which may 4125 * also have invalidated the vdev. 4126 * 5. This isn't prefetch and l2arc_noprefetch is set. 4127 */ 4128 if (HDR_HAS_L2HDR(hdr) && 4129 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4130 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4131 l2arc_read_callback_t *cb; 4132 4133 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4134 ARCSTAT_BUMP(arcstat_l2_hits); 4135 4136 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4137 KM_SLEEP); 4138 cb->l2rcb_buf = buf; 4139 cb->l2rcb_spa = spa; 4140 cb->l2rcb_bp = *bp; 4141 cb->l2rcb_zb = *zb; 4142 cb->l2rcb_flags = zio_flags; 4143 cb->l2rcb_compress = b_compress; 4144 4145 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4146 addr + size < vd->vdev_psize - 4147 VDEV_LABEL_END_SIZE); 4148 4149 /* 4150 * l2arc read. The SCL_L2ARC lock will be 4151 * released by l2arc_read_done(). 4152 * Issue a null zio if the underlying buffer 4153 * was squashed to zero size by compression. 4154 */ 4155 if (b_compress == ZIO_COMPRESS_EMPTY) { 4156 rzio = zio_null(pio, spa, vd, 4157 l2arc_read_done, cb, 4158 zio_flags | ZIO_FLAG_DONT_CACHE | 4159 ZIO_FLAG_CANFAIL | 4160 ZIO_FLAG_DONT_PROPAGATE | 4161 ZIO_FLAG_DONT_RETRY); 4162 } else { 4163 rzio = zio_read_phys(pio, vd, addr, 4164 b_asize, buf->b_data, 4165 ZIO_CHECKSUM_OFF, 4166 l2arc_read_done, cb, priority, 4167 zio_flags | ZIO_FLAG_DONT_CACHE | 4168 ZIO_FLAG_CANFAIL | 4169 ZIO_FLAG_DONT_PROPAGATE | 4170 ZIO_FLAG_DONT_RETRY, B_FALSE); 4171 } 4172 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4173 zio_t *, rzio); 4174 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4175 4176 if (*arc_flags & ARC_FLAG_NOWAIT) { 4177 zio_nowait(rzio); 4178 return (0); 4179 } 4180 4181 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4182 if (zio_wait(rzio) == 0) 4183 return (0); 4184 4185 /* l2arc read error; goto zio_read() */ 4186 } else { 4187 DTRACE_PROBE1(l2arc__miss, 4188 arc_buf_hdr_t *, hdr); 4189 ARCSTAT_BUMP(arcstat_l2_misses); 4190 if (HDR_L2_WRITING(hdr)) 4191 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4192 spa_config_exit(spa, SCL_L2ARC, vd); 4193 } 4194 } else { 4195 if (vd != NULL) 4196 spa_config_exit(spa, SCL_L2ARC, vd); 4197 if (l2arc_ndev != 0) { 4198 DTRACE_PROBE1(l2arc__miss, 4199 arc_buf_hdr_t *, hdr); 4200 ARCSTAT_BUMP(arcstat_l2_misses); 4201 } 4202 } 4203 4204 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4205 arc_read_done, buf, priority, zio_flags, zb); 4206 4207 if (*arc_flags & ARC_FLAG_WAIT) 4208 return (zio_wait(rzio)); 4209 4210 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4211 zio_nowait(rzio); 4212 } 4213 return (0); 4214 } 4215 4216 void 4217 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4218 { 4219 ASSERT(buf->b_hdr != NULL); 4220 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4221 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4222 func == NULL); 4223 ASSERT(buf->b_efunc == NULL); 4224 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4225 4226 buf->b_efunc = func; 4227 buf->b_private = private; 4228 } 4229 4230 /* 4231 * Notify the arc that a block was freed, and thus will never be used again. 4232 */ 4233 void 4234 arc_freed(spa_t *spa, const blkptr_t *bp) 4235 { 4236 arc_buf_hdr_t *hdr; 4237 kmutex_t *hash_lock; 4238 uint64_t guid = spa_load_guid(spa); 4239 4240 ASSERT(!BP_IS_EMBEDDED(bp)); 4241 4242 hdr = buf_hash_find(guid, bp, &hash_lock); 4243 if (hdr == NULL) 4244 return; 4245 if (HDR_BUF_AVAILABLE(hdr)) { 4246 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4247 add_reference(hdr, hash_lock, FTAG); 4248 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4249 mutex_exit(hash_lock); 4250 4251 arc_release(buf, FTAG); 4252 (void) arc_buf_remove_ref(buf, FTAG); 4253 } else { 4254 mutex_exit(hash_lock); 4255 } 4256 4257 } 4258 4259 /* 4260 * Clear the user eviction callback set by arc_set_callback(), first calling 4261 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4262 * clearing the callback may result in the arc_buf being destroyed. However, 4263 * it will not result in the *last* arc_buf being destroyed, hence the data 4264 * will remain cached in the ARC. We make a copy of the arc buffer here so 4265 * that we can process the callback without holding any locks. 4266 * 4267 * It's possible that the callback is already in the process of being cleared 4268 * by another thread. In this case we can not clear the callback. 4269 * 4270 * Returns B_TRUE if the callback was successfully called and cleared. 4271 */ 4272 boolean_t 4273 arc_clear_callback(arc_buf_t *buf) 4274 { 4275 arc_buf_hdr_t *hdr; 4276 kmutex_t *hash_lock; 4277 arc_evict_func_t *efunc = buf->b_efunc; 4278 void *private = buf->b_private; 4279 4280 mutex_enter(&buf->b_evict_lock); 4281 hdr = buf->b_hdr; 4282 if (hdr == NULL) { 4283 /* 4284 * We are in arc_do_user_evicts(). 4285 */ 4286 ASSERT(buf->b_data == NULL); 4287 mutex_exit(&buf->b_evict_lock); 4288 return (B_FALSE); 4289 } else if (buf->b_data == NULL) { 4290 /* 4291 * We are on the eviction list; process this buffer now 4292 * but let arc_do_user_evicts() do the reaping. 4293 */ 4294 buf->b_efunc = NULL; 4295 mutex_exit(&buf->b_evict_lock); 4296 VERIFY0(efunc(private)); 4297 return (B_TRUE); 4298 } 4299 hash_lock = HDR_LOCK(hdr); 4300 mutex_enter(hash_lock); 4301 hdr = buf->b_hdr; 4302 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4303 4304 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4305 hdr->b_l1hdr.b_datacnt); 4306 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4307 hdr->b_l1hdr.b_state == arc_mfu); 4308 4309 buf->b_efunc = NULL; 4310 buf->b_private = NULL; 4311 4312 if (hdr->b_l1hdr.b_datacnt > 1) { 4313 mutex_exit(&buf->b_evict_lock); 4314 arc_buf_destroy(buf, TRUE); 4315 } else { 4316 ASSERT(buf == hdr->b_l1hdr.b_buf); 4317 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4318 mutex_exit(&buf->b_evict_lock); 4319 } 4320 4321 mutex_exit(hash_lock); 4322 VERIFY0(efunc(private)); 4323 return (B_TRUE); 4324 } 4325 4326 /* 4327 * Release this buffer from the cache, making it an anonymous buffer. This 4328 * must be done after a read and prior to modifying the buffer contents. 4329 * If the buffer has more than one reference, we must make 4330 * a new hdr for the buffer. 4331 */ 4332 void 4333 arc_release(arc_buf_t *buf, void *tag) 4334 { 4335 arc_buf_hdr_t *hdr = buf->b_hdr; 4336 4337 /* 4338 * It would be nice to assert that if it's DMU metadata (level > 4339 * 0 || it's the dnode file), then it must be syncing context. 4340 * But we don't know that information at this level. 4341 */ 4342 4343 mutex_enter(&buf->b_evict_lock); 4344 4345 ASSERT(HDR_HAS_L1HDR(hdr)); 4346 4347 /* 4348 * We don't grab the hash lock prior to this check, because if 4349 * the buffer's header is in the arc_anon state, it won't be 4350 * linked into the hash table. 4351 */ 4352 if (hdr->b_l1hdr.b_state == arc_anon) { 4353 mutex_exit(&buf->b_evict_lock); 4354 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4355 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4356 ASSERT(!HDR_HAS_L2HDR(hdr)); 4357 ASSERT(BUF_EMPTY(hdr)); 4358 4359 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4360 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4361 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4362 4363 ASSERT3P(buf->b_efunc, ==, NULL); 4364 ASSERT3P(buf->b_private, ==, NULL); 4365 4366 hdr->b_l1hdr.b_arc_access = 0; 4367 arc_buf_thaw(buf); 4368 4369 return; 4370 } 4371 4372 kmutex_t *hash_lock = HDR_LOCK(hdr); 4373 mutex_enter(hash_lock); 4374 4375 /* 4376 * This assignment is only valid as long as the hash_lock is 4377 * held, we must be careful not to reference state or the 4378 * b_state field after dropping the lock. 4379 */ 4380 arc_state_t *state = hdr->b_l1hdr.b_state; 4381 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4382 ASSERT3P(state, !=, arc_anon); 4383 4384 /* this buffer is not on any list */ 4385 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4386 4387 if (HDR_HAS_L2HDR(hdr)) { 4388 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 4389 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 4390 4391 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4392 list_remove(&hdr->b_l2hdr.b_dev->l2ad_buflist, hdr); 4393 4394 /* 4395 * We don't want to leak the b_tmp_cdata buffer that was 4396 * allocated in l2arc_write_buffers() 4397 */ 4398 arc_buf_l2_cdata_free(hdr); 4399 4400 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4401 4402 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 4403 } 4404 4405 /* 4406 * Do we have more than one buf? 4407 */ 4408 if (hdr->b_l1hdr.b_datacnt > 1) { 4409 arc_buf_hdr_t *nhdr; 4410 arc_buf_t **bufp; 4411 uint64_t blksz = hdr->b_size; 4412 uint64_t spa = hdr->b_spa; 4413 arc_buf_contents_t type = arc_buf_type(hdr); 4414 uint32_t flags = hdr->b_flags; 4415 4416 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4417 /* 4418 * Pull the data off of this hdr and attach it to 4419 * a new anonymous hdr. 4420 */ 4421 (void) remove_reference(hdr, hash_lock, tag); 4422 bufp = &hdr->b_l1hdr.b_buf; 4423 while (*bufp != buf) 4424 bufp = &(*bufp)->b_next; 4425 *bufp = buf->b_next; 4426 buf->b_next = NULL; 4427 4428 ASSERT3P(state, !=, arc_l2c_only); 4429 4430 (void) refcount_remove_many( 4431 &state->arcs_size, hdr->b_size, buf); 4432 4433 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4434 ASSERT3P(state, !=, arc_l2c_only); 4435 uint64_t *size = &state->arcs_lsize[type]; 4436 ASSERT3U(*size, >=, hdr->b_size); 4437 atomic_add_64(size, -hdr->b_size); 4438 } 4439 4440 /* 4441 * We're releasing a duplicate user data buffer, update 4442 * our statistics accordingly. 4443 */ 4444 if (HDR_ISTYPE_DATA(hdr)) { 4445 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4446 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4447 -hdr->b_size); 4448 } 4449 hdr->b_l1hdr.b_datacnt -= 1; 4450 arc_cksum_verify(buf); 4451 arc_buf_unwatch(buf); 4452 4453 mutex_exit(hash_lock); 4454 4455 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4456 nhdr->b_size = blksz; 4457 nhdr->b_spa = spa; 4458 4459 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4460 nhdr->b_flags |= arc_bufc_to_flags(type); 4461 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4462 4463 nhdr->b_l1hdr.b_buf = buf; 4464 nhdr->b_l1hdr.b_datacnt = 1; 4465 nhdr->b_l1hdr.b_state = arc_anon; 4466 nhdr->b_l1hdr.b_arc_access = 0; 4467 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4468 nhdr->b_freeze_cksum = NULL; 4469 4470 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4471 buf->b_hdr = nhdr; 4472 mutex_exit(&buf->b_evict_lock); 4473 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4474 } else { 4475 mutex_exit(&buf->b_evict_lock); 4476 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4477 /* protected by hash lock, or hdr is on arc_anon */ 4478 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4479 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4480 arc_change_state(arc_anon, hdr, hash_lock); 4481 hdr->b_l1hdr.b_arc_access = 0; 4482 mutex_exit(hash_lock); 4483 4484 buf_discard_identity(hdr); 4485 arc_buf_thaw(buf); 4486 } 4487 buf->b_efunc = NULL; 4488 buf->b_private = NULL; 4489 } 4490 4491 int 4492 arc_released(arc_buf_t *buf) 4493 { 4494 int released; 4495 4496 mutex_enter(&buf->b_evict_lock); 4497 released = (buf->b_data != NULL && 4498 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4499 mutex_exit(&buf->b_evict_lock); 4500 return (released); 4501 } 4502 4503 #ifdef ZFS_DEBUG 4504 int 4505 arc_referenced(arc_buf_t *buf) 4506 { 4507 int referenced; 4508 4509 mutex_enter(&buf->b_evict_lock); 4510 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4511 mutex_exit(&buf->b_evict_lock); 4512 return (referenced); 4513 } 4514 #endif 4515 4516 static void 4517 arc_write_ready(zio_t *zio) 4518 { 4519 arc_write_callback_t *callback = zio->io_private; 4520 arc_buf_t *buf = callback->awcb_buf; 4521 arc_buf_hdr_t *hdr = buf->b_hdr; 4522 4523 ASSERT(HDR_HAS_L1HDR(hdr)); 4524 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4525 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4526 callback->awcb_ready(zio, buf, callback->awcb_private); 4527 4528 /* 4529 * If the IO is already in progress, then this is a re-write 4530 * attempt, so we need to thaw and re-compute the cksum. 4531 * It is the responsibility of the callback to handle the 4532 * accounting for any re-write attempt. 4533 */ 4534 if (HDR_IO_IN_PROGRESS(hdr)) { 4535 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4536 if (hdr->b_freeze_cksum != NULL) { 4537 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4538 hdr->b_freeze_cksum = NULL; 4539 } 4540 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4541 } 4542 arc_cksum_compute(buf, B_FALSE); 4543 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4544 } 4545 4546 /* 4547 * The SPA calls this callback for each physical write that happens on behalf 4548 * of a logical write. See the comment in dbuf_write_physdone() for details. 4549 */ 4550 static void 4551 arc_write_physdone(zio_t *zio) 4552 { 4553 arc_write_callback_t *cb = zio->io_private; 4554 if (cb->awcb_physdone != NULL) 4555 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4556 } 4557 4558 static void 4559 arc_write_done(zio_t *zio) 4560 { 4561 arc_write_callback_t *callback = zio->io_private; 4562 arc_buf_t *buf = callback->awcb_buf; 4563 arc_buf_hdr_t *hdr = buf->b_hdr; 4564 4565 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4566 4567 if (zio->io_error == 0) { 4568 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4569 buf_discard_identity(hdr); 4570 } else { 4571 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4572 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4573 } 4574 } else { 4575 ASSERT(BUF_EMPTY(hdr)); 4576 } 4577 4578 /* 4579 * If the block to be written was all-zero or compressed enough to be 4580 * embedded in the BP, no write was performed so there will be no 4581 * dva/birth/checksum. The buffer must therefore remain anonymous 4582 * (and uncached). 4583 */ 4584 if (!BUF_EMPTY(hdr)) { 4585 arc_buf_hdr_t *exists; 4586 kmutex_t *hash_lock; 4587 4588 ASSERT(zio->io_error == 0); 4589 4590 arc_cksum_verify(buf); 4591 4592 exists = buf_hash_insert(hdr, &hash_lock); 4593 if (exists != NULL) { 4594 /* 4595 * This can only happen if we overwrite for 4596 * sync-to-convergence, because we remove 4597 * buffers from the hash table when we arc_free(). 4598 */ 4599 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4600 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4601 panic("bad overwrite, hdr=%p exists=%p", 4602 (void *)hdr, (void *)exists); 4603 ASSERT(refcount_is_zero( 4604 &exists->b_l1hdr.b_refcnt)); 4605 arc_change_state(arc_anon, exists, hash_lock); 4606 mutex_exit(hash_lock); 4607 arc_hdr_destroy(exists); 4608 exists = buf_hash_insert(hdr, &hash_lock); 4609 ASSERT3P(exists, ==, NULL); 4610 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4611 /* nopwrite */ 4612 ASSERT(zio->io_prop.zp_nopwrite); 4613 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4614 panic("bad nopwrite, hdr=%p exists=%p", 4615 (void *)hdr, (void *)exists); 4616 } else { 4617 /* Dedup */ 4618 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4619 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4620 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4621 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4622 } 4623 } 4624 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4625 /* if it's not anon, we are doing a scrub */ 4626 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4627 arc_access(hdr, hash_lock); 4628 mutex_exit(hash_lock); 4629 } else { 4630 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4631 } 4632 4633 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4634 callback->awcb_done(zio, buf, callback->awcb_private); 4635 4636 kmem_free(callback, sizeof (arc_write_callback_t)); 4637 } 4638 4639 zio_t * 4640 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4641 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4642 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4643 arc_done_func_t *done, void *private, zio_priority_t priority, 4644 int zio_flags, const zbookmark_phys_t *zb) 4645 { 4646 arc_buf_hdr_t *hdr = buf->b_hdr; 4647 arc_write_callback_t *callback; 4648 zio_t *zio; 4649 4650 ASSERT(ready != NULL); 4651 ASSERT(done != NULL); 4652 ASSERT(!HDR_IO_ERROR(hdr)); 4653 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4654 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4655 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4656 if (l2arc) 4657 hdr->b_flags |= ARC_FLAG_L2CACHE; 4658 if (l2arc_compress) 4659 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4660 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4661 callback->awcb_ready = ready; 4662 callback->awcb_physdone = physdone; 4663 callback->awcb_done = done; 4664 callback->awcb_private = private; 4665 callback->awcb_buf = buf; 4666 4667 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4668 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4669 priority, zio_flags, zb); 4670 4671 return (zio); 4672 } 4673 4674 static int 4675 arc_memory_throttle(uint64_t reserve, uint64_t txg) 4676 { 4677 #ifdef _KERNEL 4678 uint64_t available_memory = ptob(freemem); 4679 static uint64_t page_load = 0; 4680 static uint64_t last_txg = 0; 4681 4682 #if defined(__i386) 4683 available_memory = 4684 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 4685 #endif 4686 4687 if (freemem > physmem * arc_lotsfree_percent / 100) 4688 return (0); 4689 4690 if (txg > last_txg) { 4691 last_txg = txg; 4692 page_load = 0; 4693 } 4694 /* 4695 * If we are in pageout, we know that memory is already tight, 4696 * the arc is already going to be evicting, so we just want to 4697 * continue to let page writes occur as quickly as possible. 4698 */ 4699 if (curproc == proc_pageout) { 4700 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4701 return (SET_ERROR(ERESTART)); 4702 /* Note: reserve is inflated, so we deflate */ 4703 page_load += reserve / 8; 4704 return (0); 4705 } else if (page_load > 0 && arc_reclaim_needed()) { 4706 /* memory is low, delay before restarting */ 4707 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4708 return (SET_ERROR(EAGAIN)); 4709 } 4710 page_load = 0; 4711 #endif 4712 return (0); 4713 } 4714 4715 void 4716 arc_tempreserve_clear(uint64_t reserve) 4717 { 4718 atomic_add_64(&arc_tempreserve, -reserve); 4719 ASSERT((int64_t)arc_tempreserve >= 0); 4720 } 4721 4722 int 4723 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4724 { 4725 int error; 4726 uint64_t anon_size; 4727 4728 if (reserve > arc_c/4 && !arc_no_grow) 4729 arc_c = MIN(arc_c_max, reserve * 4); 4730 if (reserve > arc_c) 4731 return (SET_ERROR(ENOMEM)); 4732 4733 /* 4734 * Don't count loaned bufs as in flight dirty data to prevent long 4735 * network delays from blocking transactions that are ready to be 4736 * assigned to a txg. 4737 */ 4738 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 4739 arc_loaned_bytes), 0); 4740 4741 /* 4742 * Writes will, almost always, require additional memory allocations 4743 * in order to compress/encrypt/etc the data. We therefore need to 4744 * make sure that there is sufficient available memory for this. 4745 */ 4746 error = arc_memory_throttle(reserve, txg); 4747 if (error != 0) 4748 return (error); 4749 4750 /* 4751 * Throttle writes when the amount of dirty data in the cache 4752 * gets too large. We try to keep the cache less than half full 4753 * of dirty blocks so that our sync times don't grow too large. 4754 * Note: if two requests come in concurrently, we might let them 4755 * both succeed, when one of them should fail. Not a huge deal. 4756 */ 4757 4758 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4759 anon_size > arc_c / 4) { 4760 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4761 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4762 arc_tempreserve>>10, 4763 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4764 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4765 reserve>>10, arc_c>>10); 4766 return (SET_ERROR(ERESTART)); 4767 } 4768 atomic_add_64(&arc_tempreserve, reserve); 4769 return (0); 4770 } 4771 4772 static void 4773 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4774 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4775 { 4776 size->value.ui64 = refcount_count(&state->arcs_size); 4777 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4778 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4779 } 4780 4781 static int 4782 arc_kstat_update(kstat_t *ksp, int rw) 4783 { 4784 arc_stats_t *as = ksp->ks_data; 4785 4786 if (rw == KSTAT_WRITE) { 4787 return (EACCES); 4788 } else { 4789 arc_kstat_update_state(arc_anon, 4790 &as->arcstat_anon_size, 4791 &as->arcstat_anon_evictable_data, 4792 &as->arcstat_anon_evictable_metadata); 4793 arc_kstat_update_state(arc_mru, 4794 &as->arcstat_mru_size, 4795 &as->arcstat_mru_evictable_data, 4796 &as->arcstat_mru_evictable_metadata); 4797 arc_kstat_update_state(arc_mru_ghost, 4798 &as->arcstat_mru_ghost_size, 4799 &as->arcstat_mru_ghost_evictable_data, 4800 &as->arcstat_mru_ghost_evictable_metadata); 4801 arc_kstat_update_state(arc_mfu, 4802 &as->arcstat_mfu_size, 4803 &as->arcstat_mfu_evictable_data, 4804 &as->arcstat_mfu_evictable_metadata); 4805 arc_kstat_update_state(arc_mfu_ghost, 4806 &as->arcstat_mfu_ghost_size, 4807 &as->arcstat_mfu_ghost_evictable_data, 4808 &as->arcstat_mfu_ghost_evictable_metadata); 4809 } 4810 4811 return (0); 4812 } 4813 4814 /* 4815 * This function *must* return indices evenly distributed between all 4816 * sublists of the multilist. This is needed due to how the ARC eviction 4817 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 4818 * distributed between all sublists and uses this assumption when 4819 * deciding which sublist to evict from and how much to evict from it. 4820 */ 4821 unsigned int 4822 arc_state_multilist_index_func(multilist_t *ml, void *obj) 4823 { 4824 arc_buf_hdr_t *hdr = obj; 4825 4826 /* 4827 * We rely on b_dva to generate evenly distributed index 4828 * numbers using buf_hash below. So, as an added precaution, 4829 * let's make sure we never add empty buffers to the arc lists. 4830 */ 4831 ASSERT(!BUF_EMPTY(hdr)); 4832 4833 /* 4834 * The assumption here, is the hash value for a given 4835 * arc_buf_hdr_t will remain constant throughout it's lifetime 4836 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 4837 * Thus, we don't need to store the header's sublist index 4838 * on insertion, as this index can be recalculated on removal. 4839 * 4840 * Also, the low order bits of the hash value are thought to be 4841 * distributed evenly. Otherwise, in the case that the multilist 4842 * has a power of two number of sublists, each sublists' usage 4843 * would not be evenly distributed. 4844 */ 4845 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 4846 multilist_get_num_sublists(ml)); 4847 } 4848 4849 void 4850 arc_init(void) 4851 { 4852 /* 4853 * allmem is "all memory that we could possibly use". 4854 */ 4855 #ifdef _KERNEL 4856 uint64_t allmem = ptob(physmem - swapfs_minfree); 4857 #else 4858 uint64_t allmem = (physmem * PAGESIZE) / 2; 4859 #endif 4860 4861 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 4862 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 4863 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 4864 4865 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 4866 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 4867 4868 /* Convert seconds to clock ticks */ 4869 arc_min_prefetch_lifespan = 1 * hz; 4870 4871 /* Start out with 1/8 of all memory */ 4872 arc_c = allmem / 8; 4873 4874 #ifdef _KERNEL 4875 /* 4876 * On architectures where the physical memory can be larger 4877 * than the addressable space (intel in 32-bit mode), we may 4878 * need to limit the cache to 1/8 of VM size. 4879 */ 4880 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4881 #endif 4882 4883 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 4884 arc_c_min = MAX(allmem / 32, 64 << 20); 4885 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 4886 if (allmem >= 1 << 30) 4887 arc_c_max = allmem - (1 << 30); 4888 else 4889 arc_c_max = arc_c_min; 4890 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 4891 4892 /* 4893 * Allow the tunables to override our calculations if they are 4894 * reasonable (ie. over 64MB) 4895 */ 4896 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 4897 arc_c_max = zfs_arc_max; 4898 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 4899 arc_c_min = zfs_arc_min; 4900 4901 arc_c = arc_c_max; 4902 arc_p = (arc_c >> 1); 4903 4904 /* limit meta-data to 1/4 of the arc capacity */ 4905 arc_meta_limit = arc_c_max / 4; 4906 4907 /* Allow the tunable to override if it is reasonable */ 4908 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4909 arc_meta_limit = zfs_arc_meta_limit; 4910 4911 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4912 arc_c_min = arc_meta_limit / 2; 4913 4914 if (zfs_arc_meta_min > 0) { 4915 arc_meta_min = zfs_arc_meta_min; 4916 } else { 4917 arc_meta_min = arc_c_min / 2; 4918 } 4919 4920 if (zfs_arc_grow_retry > 0) 4921 arc_grow_retry = zfs_arc_grow_retry; 4922 4923 if (zfs_arc_shrink_shift > 0) 4924 arc_shrink_shift = zfs_arc_shrink_shift; 4925 4926 /* 4927 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 4928 */ 4929 if (arc_no_grow_shift >= arc_shrink_shift) 4930 arc_no_grow_shift = arc_shrink_shift - 1; 4931 4932 if (zfs_arc_p_min_shift > 0) 4933 arc_p_min_shift = zfs_arc_p_min_shift; 4934 4935 if (zfs_arc_num_sublists_per_state < 1) 4936 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 4937 4938 /* if kmem_flags are set, lets try to use less memory */ 4939 if (kmem_debugging()) 4940 arc_c = arc_c / 2; 4941 if (arc_c < arc_c_min) 4942 arc_c = arc_c_min; 4943 4944 arc_anon = &ARC_anon; 4945 arc_mru = &ARC_mru; 4946 arc_mru_ghost = &ARC_mru_ghost; 4947 arc_mfu = &ARC_mfu; 4948 arc_mfu_ghost = &ARC_mfu_ghost; 4949 arc_l2c_only = &ARC_l2c_only; 4950 arc_size = 0; 4951 4952 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 4953 sizeof (arc_buf_hdr_t), 4954 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4955 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4956 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 4957 sizeof (arc_buf_hdr_t), 4958 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4959 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4960 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 4961 sizeof (arc_buf_hdr_t), 4962 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4963 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4964 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 4965 sizeof (arc_buf_hdr_t), 4966 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4967 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4968 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 4969 sizeof (arc_buf_hdr_t), 4970 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4971 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4972 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 4973 sizeof (arc_buf_hdr_t), 4974 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4975 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4976 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 4977 sizeof (arc_buf_hdr_t), 4978 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4979 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4980 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 4981 sizeof (arc_buf_hdr_t), 4982 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4983 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4984 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 4985 sizeof (arc_buf_hdr_t), 4986 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4987 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4988 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 4989 sizeof (arc_buf_hdr_t), 4990 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 4991 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 4992 4993 refcount_create(&arc_anon->arcs_size); 4994 refcount_create(&arc_mru->arcs_size); 4995 refcount_create(&arc_mru_ghost->arcs_size); 4996 refcount_create(&arc_mfu->arcs_size); 4997 refcount_create(&arc_mfu_ghost->arcs_size); 4998 refcount_create(&arc_l2c_only->arcs_size); 4999 5000 buf_init(); 5001 5002 arc_reclaim_thread_exit = FALSE; 5003 arc_user_evicts_thread_exit = FALSE; 5004 arc_eviction_list = NULL; 5005 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5006 5007 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5008 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5009 5010 if (arc_ksp != NULL) { 5011 arc_ksp->ks_data = &arc_stats; 5012 arc_ksp->ks_update = arc_kstat_update; 5013 kstat_install(arc_ksp); 5014 } 5015 5016 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5017 TS_RUN, minclsyspri); 5018 5019 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5020 TS_RUN, minclsyspri); 5021 5022 arc_dead = FALSE; 5023 arc_warm = B_FALSE; 5024 5025 /* 5026 * Calculate maximum amount of dirty data per pool. 5027 * 5028 * If it has been set by /etc/system, take that. 5029 * Otherwise, use a percentage of physical memory defined by 5030 * zfs_dirty_data_max_percent (default 10%) with a cap at 5031 * zfs_dirty_data_max_max (default 4GB). 5032 */ 5033 if (zfs_dirty_data_max == 0) { 5034 zfs_dirty_data_max = physmem * PAGESIZE * 5035 zfs_dirty_data_max_percent / 100; 5036 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5037 zfs_dirty_data_max_max); 5038 } 5039 } 5040 5041 void 5042 arc_fini(void) 5043 { 5044 mutex_enter(&arc_reclaim_lock); 5045 arc_reclaim_thread_exit = TRUE; 5046 /* 5047 * The reclaim thread will set arc_reclaim_thread_exit back to 5048 * FALSE when it is finished exiting; we're waiting for that. 5049 */ 5050 while (arc_reclaim_thread_exit) { 5051 cv_signal(&arc_reclaim_thread_cv); 5052 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5053 } 5054 mutex_exit(&arc_reclaim_lock); 5055 5056 mutex_enter(&arc_user_evicts_lock); 5057 arc_user_evicts_thread_exit = TRUE; 5058 /* 5059 * The user evicts thread will set arc_user_evicts_thread_exit 5060 * to FALSE when it is finished exiting; we're waiting for that. 5061 */ 5062 while (arc_user_evicts_thread_exit) { 5063 cv_signal(&arc_user_evicts_cv); 5064 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5065 } 5066 mutex_exit(&arc_user_evicts_lock); 5067 5068 /* Use TRUE to ensure *all* buffers are evicted */ 5069 arc_flush(NULL, TRUE); 5070 5071 arc_dead = TRUE; 5072 5073 if (arc_ksp != NULL) { 5074 kstat_delete(arc_ksp); 5075 arc_ksp = NULL; 5076 } 5077 5078 mutex_destroy(&arc_reclaim_lock); 5079 cv_destroy(&arc_reclaim_thread_cv); 5080 cv_destroy(&arc_reclaim_waiters_cv); 5081 5082 mutex_destroy(&arc_user_evicts_lock); 5083 cv_destroy(&arc_user_evicts_cv); 5084 5085 refcount_destroy(&arc_anon->arcs_size); 5086 refcount_destroy(&arc_mru->arcs_size); 5087 refcount_destroy(&arc_mru_ghost->arcs_size); 5088 refcount_destroy(&arc_mfu->arcs_size); 5089 refcount_destroy(&arc_mfu_ghost->arcs_size); 5090 refcount_destroy(&arc_l2c_only->arcs_size); 5091 5092 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5093 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5094 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5095 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5096 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5097 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5098 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5099 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5100 5101 buf_fini(); 5102 5103 ASSERT0(arc_loaned_bytes); 5104 } 5105 5106 /* 5107 * Level 2 ARC 5108 * 5109 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5110 * It uses dedicated storage devices to hold cached data, which are populated 5111 * using large infrequent writes. The main role of this cache is to boost 5112 * the performance of random read workloads. The intended L2ARC devices 5113 * include short-stroked disks, solid state disks, and other media with 5114 * substantially faster read latency than disk. 5115 * 5116 * +-----------------------+ 5117 * | ARC | 5118 * +-----------------------+ 5119 * | ^ ^ 5120 * | | | 5121 * l2arc_feed_thread() arc_read() 5122 * | | | 5123 * | l2arc read | 5124 * V | | 5125 * +---------------+ | 5126 * | L2ARC | | 5127 * +---------------+ | 5128 * | ^ | 5129 * l2arc_write() | | 5130 * | | | 5131 * V | | 5132 * +-------+ +-------+ 5133 * | vdev | | vdev | 5134 * | cache | | cache | 5135 * +-------+ +-------+ 5136 * +=========+ .-----. 5137 * : L2ARC : |-_____-| 5138 * : devices : | Disks | 5139 * +=========+ `-_____-' 5140 * 5141 * Read requests are satisfied from the following sources, in order: 5142 * 5143 * 1) ARC 5144 * 2) vdev cache of L2ARC devices 5145 * 3) L2ARC devices 5146 * 4) vdev cache of disks 5147 * 5) disks 5148 * 5149 * Some L2ARC device types exhibit extremely slow write performance. 5150 * To accommodate for this there are some significant differences between 5151 * the L2ARC and traditional cache design: 5152 * 5153 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5154 * the ARC behave as usual, freeing buffers and placing headers on ghost 5155 * lists. The ARC does not send buffers to the L2ARC during eviction as 5156 * this would add inflated write latencies for all ARC memory pressure. 5157 * 5158 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5159 * It does this by periodically scanning buffers from the eviction-end of 5160 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5161 * not already there. It scans until a headroom of buffers is satisfied, 5162 * which itself is a buffer for ARC eviction. If a compressible buffer is 5163 * found during scanning and selected for writing to an L2ARC device, we 5164 * temporarily boost scanning headroom during the next scan cycle to make 5165 * sure we adapt to compression effects (which might significantly reduce 5166 * the data volume we write to L2ARC). The thread that does this is 5167 * l2arc_feed_thread(), illustrated below; example sizes are included to 5168 * provide a better sense of ratio than this diagram: 5169 * 5170 * head --> tail 5171 * +---------------------+----------+ 5172 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5173 * +---------------------+----------+ | o L2ARC eligible 5174 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5175 * +---------------------+----------+ | 5176 * 15.9 Gbytes ^ 32 Mbytes | 5177 * headroom | 5178 * l2arc_feed_thread() 5179 * | 5180 * l2arc write hand <--[oooo]--' 5181 * | 8 Mbyte 5182 * | write max 5183 * V 5184 * +==============================+ 5185 * L2ARC dev |####|#|###|###| |####| ... | 5186 * +==============================+ 5187 * 32 Gbytes 5188 * 5189 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5190 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5191 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5192 * safe to say that this is an uncommon case, since buffers at the end of 5193 * the ARC lists have moved there due to inactivity. 5194 * 5195 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5196 * then the L2ARC simply misses copying some buffers. This serves as a 5197 * pressure valve to prevent heavy read workloads from both stalling the ARC 5198 * with waits and clogging the L2ARC with writes. This also helps prevent 5199 * the potential for the L2ARC to churn if it attempts to cache content too 5200 * quickly, such as during backups of the entire pool. 5201 * 5202 * 5. After system boot and before the ARC has filled main memory, there are 5203 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5204 * lists can remain mostly static. Instead of searching from tail of these 5205 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5206 * for eligible buffers, greatly increasing its chance of finding them. 5207 * 5208 * The L2ARC device write speed is also boosted during this time so that 5209 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5210 * there are no L2ARC reads, and no fear of degrading read performance 5211 * through increased writes. 5212 * 5213 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5214 * the vdev queue can aggregate them into larger and fewer writes. Each 5215 * device is written to in a rotor fashion, sweeping writes through 5216 * available space then repeating. 5217 * 5218 * 7. The L2ARC does not store dirty content. It never needs to flush 5219 * write buffers back to disk based storage. 5220 * 5221 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5222 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5223 * 5224 * The performance of the L2ARC can be tweaked by a number of tunables, which 5225 * may be necessary for different workloads: 5226 * 5227 * l2arc_write_max max write bytes per interval 5228 * l2arc_write_boost extra write bytes during device warmup 5229 * l2arc_noprefetch skip caching prefetched buffers 5230 * l2arc_headroom number of max device writes to precache 5231 * l2arc_headroom_boost when we find compressed buffers during ARC 5232 * scanning, we multiply headroom by this 5233 * percentage factor for the next scan cycle, 5234 * since more compressed buffers are likely to 5235 * be present 5236 * l2arc_feed_secs seconds between L2ARC writing 5237 * 5238 * Tunables may be removed or added as future performance improvements are 5239 * integrated, and also may become zpool properties. 5240 * 5241 * There are three key functions that control how the L2ARC warms up: 5242 * 5243 * l2arc_write_eligible() check if a buffer is eligible to cache 5244 * l2arc_write_size() calculate how much to write 5245 * l2arc_write_interval() calculate sleep delay between writes 5246 * 5247 * These three functions determine what to write, how much, and how quickly 5248 * to send writes. 5249 */ 5250 5251 static boolean_t 5252 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5253 { 5254 /* 5255 * A buffer is *not* eligible for the L2ARC if it: 5256 * 1. belongs to a different spa. 5257 * 2. is already cached on the L2ARC. 5258 * 3. has an I/O in progress (it may be an incomplete read). 5259 * 4. is flagged not eligible (zfs property). 5260 */ 5261 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5262 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 5263 return (B_FALSE); 5264 5265 return (B_TRUE); 5266 } 5267 5268 static uint64_t 5269 l2arc_write_size(void) 5270 { 5271 uint64_t size; 5272 5273 /* 5274 * Make sure our globals have meaningful values in case the user 5275 * altered them. 5276 */ 5277 size = l2arc_write_max; 5278 if (size == 0) { 5279 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5280 "be greater than zero, resetting it to the default (%d)", 5281 L2ARC_WRITE_SIZE); 5282 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5283 } 5284 5285 if (arc_warm == B_FALSE) 5286 size += l2arc_write_boost; 5287 5288 return (size); 5289 5290 } 5291 5292 static clock_t 5293 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5294 { 5295 clock_t interval, next, now; 5296 5297 /* 5298 * If the ARC lists are busy, increase our write rate; if the 5299 * lists are stale, idle back. This is achieved by checking 5300 * how much we previously wrote - if it was more than half of 5301 * what we wanted, schedule the next write much sooner. 5302 */ 5303 if (l2arc_feed_again && wrote > (wanted / 2)) 5304 interval = (hz * l2arc_feed_min_ms) / 1000; 5305 else 5306 interval = hz * l2arc_feed_secs; 5307 5308 now = ddi_get_lbolt(); 5309 next = MAX(now, MIN(now + interval, began + interval)); 5310 5311 return (next); 5312 } 5313 5314 /* 5315 * Cycle through L2ARC devices. This is how L2ARC load balances. 5316 * If a device is returned, this also returns holding the spa config lock. 5317 */ 5318 static l2arc_dev_t * 5319 l2arc_dev_get_next(void) 5320 { 5321 l2arc_dev_t *first, *next = NULL; 5322 5323 /* 5324 * Lock out the removal of spas (spa_namespace_lock), then removal 5325 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5326 * both locks will be dropped and a spa config lock held instead. 5327 */ 5328 mutex_enter(&spa_namespace_lock); 5329 mutex_enter(&l2arc_dev_mtx); 5330 5331 /* if there are no vdevs, there is nothing to do */ 5332 if (l2arc_ndev == 0) 5333 goto out; 5334 5335 first = NULL; 5336 next = l2arc_dev_last; 5337 do { 5338 /* loop around the list looking for a non-faulted vdev */ 5339 if (next == NULL) { 5340 next = list_head(l2arc_dev_list); 5341 } else { 5342 next = list_next(l2arc_dev_list, next); 5343 if (next == NULL) 5344 next = list_head(l2arc_dev_list); 5345 } 5346 5347 /* if we have come back to the start, bail out */ 5348 if (first == NULL) 5349 first = next; 5350 else if (next == first) 5351 break; 5352 5353 } while (vdev_is_dead(next->l2ad_vdev)); 5354 5355 /* if we were unable to find any usable vdevs, return NULL */ 5356 if (vdev_is_dead(next->l2ad_vdev)) 5357 next = NULL; 5358 5359 l2arc_dev_last = next; 5360 5361 out: 5362 mutex_exit(&l2arc_dev_mtx); 5363 5364 /* 5365 * Grab the config lock to prevent the 'next' device from being 5366 * removed while we are writing to it. 5367 */ 5368 if (next != NULL) 5369 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5370 mutex_exit(&spa_namespace_lock); 5371 5372 return (next); 5373 } 5374 5375 /* 5376 * Free buffers that were tagged for destruction. 5377 */ 5378 static void 5379 l2arc_do_free_on_write() 5380 { 5381 list_t *buflist; 5382 l2arc_data_free_t *df, *df_prev; 5383 5384 mutex_enter(&l2arc_free_on_write_mtx); 5385 buflist = l2arc_free_on_write; 5386 5387 for (df = list_tail(buflist); df; df = df_prev) { 5388 df_prev = list_prev(buflist, df); 5389 ASSERT(df->l2df_data != NULL); 5390 ASSERT(df->l2df_func != NULL); 5391 df->l2df_func(df->l2df_data, df->l2df_size); 5392 list_remove(buflist, df); 5393 kmem_free(df, sizeof (l2arc_data_free_t)); 5394 } 5395 5396 mutex_exit(&l2arc_free_on_write_mtx); 5397 } 5398 5399 /* 5400 * A write to a cache device has completed. Update all headers to allow 5401 * reads from these buffers to begin. 5402 */ 5403 static void 5404 l2arc_write_done(zio_t *zio) 5405 { 5406 l2arc_write_callback_t *cb; 5407 l2arc_dev_t *dev; 5408 list_t *buflist; 5409 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5410 kmutex_t *hash_lock; 5411 int64_t bytes_dropped = 0; 5412 5413 cb = zio->io_private; 5414 ASSERT(cb != NULL); 5415 dev = cb->l2wcb_dev; 5416 ASSERT(dev != NULL); 5417 head = cb->l2wcb_head; 5418 ASSERT(head != NULL); 5419 buflist = &dev->l2ad_buflist; 5420 ASSERT(buflist != NULL); 5421 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5422 l2arc_write_callback_t *, cb); 5423 5424 if (zio->io_error != 0) 5425 ARCSTAT_BUMP(arcstat_l2_writes_error); 5426 5427 /* 5428 * All writes completed, or an error was hit. 5429 */ 5430 top: 5431 mutex_enter(&dev->l2ad_mtx); 5432 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5433 hdr_prev = list_prev(buflist, hdr); 5434 5435 hash_lock = HDR_LOCK(hdr); 5436 5437 /* 5438 * We cannot use mutex_enter or else we can deadlock 5439 * with l2arc_write_buffers (due to swapping the order 5440 * the hash lock and l2ad_mtx are taken). 5441 */ 5442 if (!mutex_tryenter(hash_lock)) { 5443 /* 5444 * Missed the hash lock. We must retry so we 5445 * don't leave the ARC_FLAG_L2_WRITING bit set. 5446 */ 5447 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5448 5449 /* 5450 * We don't want to rescan the headers we've 5451 * already marked as having been written out, so 5452 * we reinsert the head node so we can pick up 5453 * where we left off. 5454 */ 5455 list_remove(buflist, head); 5456 list_insert_after(buflist, hdr, head); 5457 5458 mutex_exit(&dev->l2ad_mtx); 5459 5460 /* 5461 * We wait for the hash lock to become available 5462 * to try and prevent busy waiting, and increase 5463 * the chance we'll be able to acquire the lock 5464 * the next time around. 5465 */ 5466 mutex_enter(hash_lock); 5467 mutex_exit(hash_lock); 5468 goto top; 5469 } 5470 5471 /* 5472 * We could not have been moved into the arc_l2c_only 5473 * state while in-flight due to our ARC_FLAG_L2_WRITING 5474 * bit being set. Let's just ensure that's being enforced. 5475 */ 5476 ASSERT(HDR_HAS_L1HDR(hdr)); 5477 5478 /* 5479 * We may have allocated a buffer for L2ARC compression, 5480 * we must release it to avoid leaking this data. 5481 */ 5482 l2arc_release_cdata_buf(hdr); 5483 5484 if (zio->io_error != 0) { 5485 /* 5486 * Error - drop L2ARC entry. 5487 */ 5488 list_remove(buflist, hdr); 5489 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5490 5491 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5492 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5493 } 5494 5495 /* 5496 * Allow ARC to begin reads and ghost list evictions to 5497 * this L2ARC entry. 5498 */ 5499 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5500 5501 mutex_exit(hash_lock); 5502 } 5503 5504 atomic_inc_64(&l2arc_writes_done); 5505 list_remove(buflist, head); 5506 ASSERT(!HDR_HAS_L1HDR(head)); 5507 kmem_cache_free(hdr_l2only_cache, head); 5508 mutex_exit(&dev->l2ad_mtx); 5509 5510 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5511 5512 l2arc_do_free_on_write(); 5513 5514 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5515 } 5516 5517 /* 5518 * A read to a cache device completed. Validate buffer contents before 5519 * handing over to the regular ARC routines. 5520 */ 5521 static void 5522 l2arc_read_done(zio_t *zio) 5523 { 5524 l2arc_read_callback_t *cb; 5525 arc_buf_hdr_t *hdr; 5526 arc_buf_t *buf; 5527 kmutex_t *hash_lock; 5528 int equal; 5529 5530 ASSERT(zio->io_vd != NULL); 5531 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5532 5533 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5534 5535 cb = zio->io_private; 5536 ASSERT(cb != NULL); 5537 buf = cb->l2rcb_buf; 5538 ASSERT(buf != NULL); 5539 5540 hash_lock = HDR_LOCK(buf->b_hdr); 5541 mutex_enter(hash_lock); 5542 hdr = buf->b_hdr; 5543 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5544 5545 /* 5546 * If the buffer was compressed, decompress it first. 5547 */ 5548 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5549 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5550 ASSERT(zio->io_data != NULL); 5551 5552 /* 5553 * Check this survived the L2ARC journey. 5554 */ 5555 equal = arc_cksum_equal(buf); 5556 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5557 mutex_exit(hash_lock); 5558 zio->io_private = buf; 5559 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5560 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5561 arc_read_done(zio); 5562 } else { 5563 mutex_exit(hash_lock); 5564 /* 5565 * Buffer didn't survive caching. Increment stats and 5566 * reissue to the original storage device. 5567 */ 5568 if (zio->io_error != 0) { 5569 ARCSTAT_BUMP(arcstat_l2_io_error); 5570 } else { 5571 zio->io_error = SET_ERROR(EIO); 5572 } 5573 if (!equal) 5574 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5575 5576 /* 5577 * If there's no waiter, issue an async i/o to the primary 5578 * storage now. If there *is* a waiter, the caller must 5579 * issue the i/o in a context where it's OK to block. 5580 */ 5581 if (zio->io_waiter == NULL) { 5582 zio_t *pio = zio_unique_parent(zio); 5583 5584 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5585 5586 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5587 buf->b_data, zio->io_size, arc_read_done, buf, 5588 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5589 } 5590 } 5591 5592 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5593 } 5594 5595 /* 5596 * This is the list priority from which the L2ARC will search for pages to 5597 * cache. This is used within loops (0..3) to cycle through lists in the 5598 * desired order. This order can have a significant effect on cache 5599 * performance. 5600 * 5601 * Currently the metadata lists are hit first, MFU then MRU, followed by 5602 * the data lists. This function returns a locked list, and also returns 5603 * the lock pointer. 5604 */ 5605 static multilist_sublist_t * 5606 l2arc_sublist_lock(int list_num) 5607 { 5608 multilist_t *ml = NULL; 5609 unsigned int idx; 5610 5611 ASSERT(list_num >= 0 && list_num <= 3); 5612 5613 switch (list_num) { 5614 case 0: 5615 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 5616 break; 5617 case 1: 5618 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 5619 break; 5620 case 2: 5621 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 5622 break; 5623 case 3: 5624 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 5625 break; 5626 } 5627 5628 /* 5629 * Return a randomly-selected sublist. This is acceptable 5630 * because the caller feeds only a little bit of data for each 5631 * call (8MB). Subsequent calls will result in different 5632 * sublists being selected. 5633 */ 5634 idx = multilist_get_random_index(ml); 5635 return (multilist_sublist_lock(ml, idx)); 5636 } 5637 5638 /* 5639 * Evict buffers from the device write hand to the distance specified in 5640 * bytes. This distance may span populated buffers, it may span nothing. 5641 * This is clearing a region on the L2ARC device ready for writing. 5642 * If the 'all' boolean is set, every buffer is evicted. 5643 */ 5644 static void 5645 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5646 { 5647 list_t *buflist; 5648 arc_buf_hdr_t *hdr, *hdr_prev; 5649 kmutex_t *hash_lock; 5650 uint64_t taddr; 5651 int64_t bytes_evicted = 0; 5652 5653 buflist = &dev->l2ad_buflist; 5654 5655 if (!all && dev->l2ad_first) { 5656 /* 5657 * This is the first sweep through the device. There is 5658 * nothing to evict. 5659 */ 5660 return; 5661 } 5662 5663 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5664 /* 5665 * When nearing the end of the device, evict to the end 5666 * before the device write hand jumps to the start. 5667 */ 5668 taddr = dev->l2ad_end; 5669 } else { 5670 taddr = dev->l2ad_hand + distance; 5671 } 5672 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5673 uint64_t, taddr, boolean_t, all); 5674 5675 top: 5676 mutex_enter(&dev->l2ad_mtx); 5677 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5678 hdr_prev = list_prev(buflist, hdr); 5679 5680 hash_lock = HDR_LOCK(hdr); 5681 5682 /* 5683 * We cannot use mutex_enter or else we can deadlock 5684 * with l2arc_write_buffers (due to swapping the order 5685 * the hash lock and l2ad_mtx are taken). 5686 */ 5687 if (!mutex_tryenter(hash_lock)) { 5688 /* 5689 * Missed the hash lock. Retry. 5690 */ 5691 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5692 mutex_exit(&dev->l2ad_mtx); 5693 mutex_enter(hash_lock); 5694 mutex_exit(hash_lock); 5695 goto top; 5696 } 5697 5698 if (HDR_L2_WRITE_HEAD(hdr)) { 5699 /* 5700 * We hit a write head node. Leave it for 5701 * l2arc_write_done(). 5702 */ 5703 list_remove(buflist, hdr); 5704 mutex_exit(hash_lock); 5705 continue; 5706 } 5707 5708 if (!all && HDR_HAS_L2HDR(hdr) && 5709 (hdr->b_l2hdr.b_daddr > taddr || 5710 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5711 /* 5712 * We've evicted to the target address, 5713 * or the end of the device. 5714 */ 5715 mutex_exit(hash_lock); 5716 break; 5717 } 5718 5719 ASSERT(HDR_HAS_L2HDR(hdr)); 5720 if (!HDR_HAS_L1HDR(hdr)) { 5721 ASSERT(!HDR_L2_READING(hdr)); 5722 /* 5723 * This doesn't exist in the ARC. Destroy. 5724 * arc_hdr_destroy() will call list_remove() 5725 * and decrement arcstat_l2_size. 5726 */ 5727 arc_change_state(arc_anon, hdr, hash_lock); 5728 arc_hdr_destroy(hdr); 5729 } else { 5730 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5731 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5732 /* 5733 * Invalidate issued or about to be issued 5734 * reads, since we may be about to write 5735 * over this location. 5736 */ 5737 if (HDR_L2_READING(hdr)) { 5738 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5739 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5740 } 5741 5742 /* Tell ARC this no longer exists in L2ARC. */ 5743 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5744 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5745 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5746 list_remove(buflist, hdr); 5747 5748 /* Ensure this header has finished being written */ 5749 ASSERT(!HDR_L2_WRITING(hdr)); 5750 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 5751 } 5752 mutex_exit(hash_lock); 5753 } 5754 mutex_exit(&dev->l2ad_mtx); 5755 5756 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 5757 dev->l2ad_evict = taddr; 5758 } 5759 5760 /* 5761 * Find and write ARC buffers to the L2ARC device. 5762 * 5763 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5764 * for reading until they have completed writing. 5765 * The headroom_boost is an in-out parameter used to maintain headroom boost 5766 * state between calls to this function. 5767 * 5768 * Returns the number of bytes actually written (which may be smaller than 5769 * the delta by which the device hand has changed due to alignment). 5770 */ 5771 static uint64_t 5772 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5773 boolean_t *headroom_boost) 5774 { 5775 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5776 uint64_t write_asize, write_psize, write_sz, headroom, 5777 buf_compress_minsz; 5778 void *buf_data; 5779 boolean_t full; 5780 l2arc_write_callback_t *cb; 5781 zio_t *pio, *wzio; 5782 uint64_t guid = spa_load_guid(spa); 5783 const boolean_t do_headroom_boost = *headroom_boost; 5784 5785 ASSERT(dev->l2ad_vdev != NULL); 5786 5787 /* Lower the flag now, we might want to raise it again later. */ 5788 *headroom_boost = B_FALSE; 5789 5790 pio = NULL; 5791 write_sz = write_asize = write_psize = 0; 5792 full = B_FALSE; 5793 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5794 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5795 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5796 5797 /* 5798 * We will want to try to compress buffers that are at least 2x the 5799 * device sector size. 5800 */ 5801 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5802 5803 /* 5804 * Copy buffers for L2ARC writing. 5805 */ 5806 for (int try = 0; try <= 3; try++) { 5807 multilist_sublist_t *mls = l2arc_sublist_lock(try); 5808 uint64_t passed_sz = 0; 5809 5810 /* 5811 * L2ARC fast warmup. 5812 * 5813 * Until the ARC is warm and starts to evict, read from the 5814 * head of the ARC lists rather than the tail. 5815 */ 5816 if (arc_warm == B_FALSE) 5817 hdr = multilist_sublist_head(mls); 5818 else 5819 hdr = multilist_sublist_tail(mls); 5820 5821 headroom = target_sz * l2arc_headroom; 5822 if (do_headroom_boost) 5823 headroom = (headroom * l2arc_headroom_boost) / 100; 5824 5825 for (; hdr; hdr = hdr_prev) { 5826 kmutex_t *hash_lock; 5827 uint64_t buf_sz; 5828 5829 if (arc_warm == B_FALSE) 5830 hdr_prev = multilist_sublist_next(mls, hdr); 5831 else 5832 hdr_prev = multilist_sublist_prev(mls, hdr); 5833 5834 hash_lock = HDR_LOCK(hdr); 5835 if (!mutex_tryenter(hash_lock)) { 5836 /* 5837 * Skip this buffer rather than waiting. 5838 */ 5839 continue; 5840 } 5841 5842 passed_sz += hdr->b_size; 5843 if (passed_sz > headroom) { 5844 /* 5845 * Searched too far. 5846 */ 5847 mutex_exit(hash_lock); 5848 break; 5849 } 5850 5851 if (!l2arc_write_eligible(guid, hdr)) { 5852 mutex_exit(hash_lock); 5853 continue; 5854 } 5855 5856 if ((write_sz + hdr->b_size) > target_sz) { 5857 full = B_TRUE; 5858 mutex_exit(hash_lock); 5859 break; 5860 } 5861 5862 if (pio == NULL) { 5863 /* 5864 * Insert a dummy header on the buflist so 5865 * l2arc_write_done() can find where the 5866 * write buffers begin without searching. 5867 */ 5868 mutex_enter(&dev->l2ad_mtx); 5869 list_insert_head(&dev->l2ad_buflist, head); 5870 mutex_exit(&dev->l2ad_mtx); 5871 5872 cb = kmem_alloc( 5873 sizeof (l2arc_write_callback_t), KM_SLEEP); 5874 cb->l2wcb_dev = dev; 5875 cb->l2wcb_head = head; 5876 pio = zio_root(spa, l2arc_write_done, cb, 5877 ZIO_FLAG_CANFAIL); 5878 } 5879 5880 /* 5881 * Create and add a new L2ARC header. 5882 */ 5883 hdr->b_l2hdr.b_dev = dev; 5884 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5885 /* 5886 * Temporarily stash the data buffer in b_tmp_cdata. 5887 * The subsequent write step will pick it up from 5888 * there. This is because can't access b_l1hdr.b_buf 5889 * without holding the hash_lock, which we in turn 5890 * can't access without holding the ARC list locks 5891 * (which we want to avoid during compression/writing). 5892 */ 5893 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5894 hdr->b_l2hdr.b_asize = hdr->b_size; 5895 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5896 5897 buf_sz = hdr->b_size; 5898 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5899 5900 mutex_enter(&dev->l2ad_mtx); 5901 list_insert_head(&dev->l2ad_buflist, hdr); 5902 mutex_exit(&dev->l2ad_mtx); 5903 5904 /* 5905 * Compute and store the buffer cksum before 5906 * writing. On debug the cksum is verified first. 5907 */ 5908 arc_cksum_verify(hdr->b_l1hdr.b_buf); 5909 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 5910 5911 mutex_exit(hash_lock); 5912 5913 write_sz += buf_sz; 5914 } 5915 5916 multilist_sublist_unlock(mls); 5917 5918 if (full == B_TRUE) 5919 break; 5920 } 5921 5922 /* No buffers selected for writing? */ 5923 if (pio == NULL) { 5924 ASSERT0(write_sz); 5925 ASSERT(!HDR_HAS_L1HDR(head)); 5926 kmem_cache_free(hdr_l2only_cache, head); 5927 return (0); 5928 } 5929 5930 mutex_enter(&dev->l2ad_mtx); 5931 5932 /* 5933 * Now start writing the buffers. We're starting at the write head 5934 * and work backwards, retracing the course of the buffer selector 5935 * loop above. 5936 */ 5937 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 5938 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 5939 uint64_t buf_sz; 5940 5941 /* 5942 * We rely on the L1 portion of the header below, so 5943 * it's invalid for this header to have been evicted out 5944 * of the ghost cache, prior to being written out. The 5945 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 5946 */ 5947 ASSERT(HDR_HAS_L1HDR(hdr)); 5948 5949 /* 5950 * We shouldn't need to lock the buffer here, since we flagged 5951 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5952 * take care to only access its L2 cache parameters. In 5953 * particular, hdr->l1hdr.b_buf may be invalid by now due to 5954 * ARC eviction. 5955 */ 5956 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 5957 5958 if ((HDR_L2COMPRESS(hdr)) && 5959 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 5960 if (l2arc_compress_buf(hdr)) { 5961 /* 5962 * If compression succeeded, enable headroom 5963 * boost on the next scan cycle. 5964 */ 5965 *headroom_boost = B_TRUE; 5966 } 5967 } 5968 5969 /* 5970 * Pick up the buffer data we had previously stashed away 5971 * (and now potentially also compressed). 5972 */ 5973 buf_data = hdr->b_l1hdr.b_tmp_cdata; 5974 buf_sz = hdr->b_l2hdr.b_asize; 5975 5976 /* Compression may have squashed the buffer to zero length. */ 5977 if (buf_sz != 0) { 5978 uint64_t buf_p_sz; 5979 5980 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5981 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5982 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 5983 ZIO_FLAG_CANFAIL, B_FALSE); 5984 5985 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 5986 zio_t *, wzio); 5987 (void) zio_nowait(wzio); 5988 5989 write_asize += buf_sz; 5990 /* 5991 * Keep the clock hand suitably device-aligned. 5992 */ 5993 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5994 write_psize += buf_p_sz; 5995 dev->l2ad_hand += buf_p_sz; 5996 } 5997 } 5998 5999 mutex_exit(&dev->l2ad_mtx); 6000 6001 ASSERT3U(write_asize, <=, target_sz); 6002 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6003 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6004 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6005 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6006 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6007 6008 /* 6009 * Bump device hand to the device start if it is approaching the end. 6010 * l2arc_evict() will already have evicted ahead for this case. 6011 */ 6012 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6013 dev->l2ad_hand = dev->l2ad_start; 6014 dev->l2ad_evict = dev->l2ad_start; 6015 dev->l2ad_first = B_FALSE; 6016 } 6017 6018 dev->l2ad_writing = B_TRUE; 6019 (void) zio_wait(pio); 6020 dev->l2ad_writing = B_FALSE; 6021 6022 return (write_asize); 6023 } 6024 6025 /* 6026 * Compresses an L2ARC buffer. 6027 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6028 * size in l2hdr->b_asize. This routine tries to compress the data and 6029 * depending on the compression result there are three possible outcomes: 6030 * *) The buffer was incompressible. The original l2hdr contents were left 6031 * untouched and are ready for writing to an L2 device. 6032 * *) The buffer was all-zeros, so there is no need to write it to an L2 6033 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6034 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6035 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6036 * data buffer which holds the compressed data to be written, and b_asize 6037 * tells us how much data there is. b_compress is set to the appropriate 6038 * compression algorithm. Once writing is done, invoke 6039 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6040 * 6041 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6042 * buffer was incompressible). 6043 */ 6044 static boolean_t 6045 l2arc_compress_buf(arc_buf_hdr_t *hdr) 6046 { 6047 void *cdata; 6048 size_t csize, len, rounded; 6049 ASSERT(HDR_HAS_L2HDR(hdr)); 6050 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6051 6052 ASSERT(HDR_HAS_L1HDR(hdr)); 6053 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 6054 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6055 6056 len = l2hdr->b_asize; 6057 cdata = zio_data_buf_alloc(len); 6058 ASSERT3P(cdata, !=, NULL); 6059 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6060 cdata, l2hdr->b_asize); 6061 6062 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 6063 if (rounded > csize) { 6064 bzero((char *)cdata + csize, rounded - csize); 6065 csize = rounded; 6066 } 6067 6068 if (csize == 0) { 6069 /* zero block, indicate that there's nothing to write */ 6070 zio_data_buf_free(cdata, len); 6071 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 6072 l2hdr->b_asize = 0; 6073 hdr->b_l1hdr.b_tmp_cdata = NULL; 6074 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6075 return (B_TRUE); 6076 } else if (csize > 0 && csize < len) { 6077 /* 6078 * Compression succeeded, we'll keep the cdata around for 6079 * writing and release it afterwards. 6080 */ 6081 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 6082 l2hdr->b_asize = csize; 6083 hdr->b_l1hdr.b_tmp_cdata = cdata; 6084 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6085 return (B_TRUE); 6086 } else { 6087 /* 6088 * Compression failed, release the compressed buffer. 6089 * l2hdr will be left unmodified. 6090 */ 6091 zio_data_buf_free(cdata, len); 6092 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6093 return (B_FALSE); 6094 } 6095 } 6096 6097 /* 6098 * Decompresses a zio read back from an l2arc device. On success, the 6099 * underlying zio's io_data buffer is overwritten by the uncompressed 6100 * version. On decompression error (corrupt compressed stream), the 6101 * zio->io_error value is set to signal an I/O error. 6102 * 6103 * Please note that the compressed data stream is not checksummed, so 6104 * if the underlying device is experiencing data corruption, we may feed 6105 * corrupt data to the decompressor, so the decompressor needs to be 6106 * able to handle this situation (LZ4 does). 6107 */ 6108 static void 6109 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6110 { 6111 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6112 6113 if (zio->io_error != 0) { 6114 /* 6115 * An io error has occured, just restore the original io 6116 * size in preparation for a main pool read. 6117 */ 6118 zio->io_orig_size = zio->io_size = hdr->b_size; 6119 return; 6120 } 6121 6122 if (c == ZIO_COMPRESS_EMPTY) { 6123 /* 6124 * An empty buffer results in a null zio, which means we 6125 * need to fill its io_data after we're done restoring the 6126 * buffer's contents. 6127 */ 6128 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6129 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6130 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6131 } else { 6132 ASSERT(zio->io_data != NULL); 6133 /* 6134 * We copy the compressed data from the start of the arc buffer 6135 * (the zio_read will have pulled in only what we need, the 6136 * rest is garbage which we will overwrite at decompression) 6137 * and then decompress back to the ARC data buffer. This way we 6138 * can minimize copying by simply decompressing back over the 6139 * original compressed data (rather than decompressing to an 6140 * aux buffer and then copying back the uncompressed buffer, 6141 * which is likely to be much larger). 6142 */ 6143 uint64_t csize; 6144 void *cdata; 6145 6146 csize = zio->io_size; 6147 cdata = zio_data_buf_alloc(csize); 6148 bcopy(zio->io_data, cdata, csize); 6149 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6150 hdr->b_size) != 0) 6151 zio->io_error = EIO; 6152 zio_data_buf_free(cdata, csize); 6153 } 6154 6155 /* Restore the expected uncompressed IO size. */ 6156 zio->io_orig_size = zio->io_size = hdr->b_size; 6157 } 6158 6159 /* 6160 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6161 * This buffer serves as a temporary holder of compressed data while 6162 * the buffer entry is being written to an l2arc device. Once that is 6163 * done, we can dispose of it. 6164 */ 6165 static void 6166 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6167 { 6168 enum zio_compress comp = HDR_GET_COMPRESS(hdr); 6169 6170 ASSERT(HDR_HAS_L1HDR(hdr)); 6171 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6172 6173 if (comp == ZIO_COMPRESS_OFF) { 6174 /* 6175 * In this case, b_tmp_cdata points to the same buffer 6176 * as the arc_buf_t's b_data field. We don't want to 6177 * free it, since the arc_buf_t will handle that. 6178 */ 6179 hdr->b_l1hdr.b_tmp_cdata = NULL; 6180 } else if (comp == ZIO_COMPRESS_EMPTY) { 6181 /* 6182 * In this case, b_tmp_cdata was compressed to an empty 6183 * buffer, thus there's nothing to free and b_tmp_cdata 6184 * should have been set to NULL in l2arc_write_buffers(). 6185 */ 6186 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6187 } else { 6188 /* 6189 * If the data was compressed, then we've allocated a 6190 * temporary buffer for it, so now we need to release it. 6191 */ 6192 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6193 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6194 hdr->b_size); 6195 hdr->b_l1hdr.b_tmp_cdata = NULL; 6196 } 6197 6198 } 6199 6200 /* 6201 * This thread feeds the L2ARC at regular intervals. This is the beating 6202 * heart of the L2ARC. 6203 */ 6204 static void 6205 l2arc_feed_thread(void) 6206 { 6207 callb_cpr_t cpr; 6208 l2arc_dev_t *dev; 6209 spa_t *spa; 6210 uint64_t size, wrote; 6211 clock_t begin, next = ddi_get_lbolt(); 6212 boolean_t headroom_boost = B_FALSE; 6213 6214 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6215 6216 mutex_enter(&l2arc_feed_thr_lock); 6217 6218 while (l2arc_thread_exit == 0) { 6219 CALLB_CPR_SAFE_BEGIN(&cpr); 6220 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6221 next); 6222 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6223 next = ddi_get_lbolt() + hz; 6224 6225 /* 6226 * Quick check for L2ARC devices. 6227 */ 6228 mutex_enter(&l2arc_dev_mtx); 6229 if (l2arc_ndev == 0) { 6230 mutex_exit(&l2arc_dev_mtx); 6231 continue; 6232 } 6233 mutex_exit(&l2arc_dev_mtx); 6234 begin = ddi_get_lbolt(); 6235 6236 /* 6237 * This selects the next l2arc device to write to, and in 6238 * doing so the next spa to feed from: dev->l2ad_spa. This 6239 * will return NULL if there are now no l2arc devices or if 6240 * they are all faulted. 6241 * 6242 * If a device is returned, its spa's config lock is also 6243 * held to prevent device removal. l2arc_dev_get_next() 6244 * will grab and release l2arc_dev_mtx. 6245 */ 6246 if ((dev = l2arc_dev_get_next()) == NULL) 6247 continue; 6248 6249 spa = dev->l2ad_spa; 6250 ASSERT(spa != NULL); 6251 6252 /* 6253 * If the pool is read-only then force the feed thread to 6254 * sleep a little longer. 6255 */ 6256 if (!spa_writeable(spa)) { 6257 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6258 spa_config_exit(spa, SCL_L2ARC, dev); 6259 continue; 6260 } 6261 6262 /* 6263 * Avoid contributing to memory pressure. 6264 */ 6265 if (arc_reclaim_needed()) { 6266 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6267 spa_config_exit(spa, SCL_L2ARC, dev); 6268 continue; 6269 } 6270 6271 ARCSTAT_BUMP(arcstat_l2_feeds); 6272 6273 size = l2arc_write_size(); 6274 6275 /* 6276 * Evict L2ARC buffers that will be overwritten. 6277 */ 6278 l2arc_evict(dev, size, B_FALSE); 6279 6280 /* 6281 * Write ARC buffers. 6282 */ 6283 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6284 6285 /* 6286 * Calculate interval between writes. 6287 */ 6288 next = l2arc_write_interval(begin, size, wrote); 6289 spa_config_exit(spa, SCL_L2ARC, dev); 6290 } 6291 6292 l2arc_thread_exit = 0; 6293 cv_broadcast(&l2arc_feed_thr_cv); 6294 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6295 thread_exit(); 6296 } 6297 6298 boolean_t 6299 l2arc_vdev_present(vdev_t *vd) 6300 { 6301 l2arc_dev_t *dev; 6302 6303 mutex_enter(&l2arc_dev_mtx); 6304 for (dev = list_head(l2arc_dev_list); dev != NULL; 6305 dev = list_next(l2arc_dev_list, dev)) { 6306 if (dev->l2ad_vdev == vd) 6307 break; 6308 } 6309 mutex_exit(&l2arc_dev_mtx); 6310 6311 return (dev != NULL); 6312 } 6313 6314 /* 6315 * Add a vdev for use by the L2ARC. By this point the spa has already 6316 * validated the vdev and opened it. 6317 */ 6318 void 6319 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6320 { 6321 l2arc_dev_t *adddev; 6322 6323 ASSERT(!l2arc_vdev_present(vd)); 6324 6325 /* 6326 * Create a new l2arc device entry. 6327 */ 6328 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6329 adddev->l2ad_spa = spa; 6330 adddev->l2ad_vdev = vd; 6331 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6332 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6333 adddev->l2ad_hand = adddev->l2ad_start; 6334 adddev->l2ad_evict = adddev->l2ad_start; 6335 adddev->l2ad_first = B_TRUE; 6336 adddev->l2ad_writing = B_FALSE; 6337 6338 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6339 /* 6340 * This is a list of all ARC buffers that are still valid on the 6341 * device. 6342 */ 6343 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6344 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6345 6346 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6347 6348 /* 6349 * Add device to global list 6350 */ 6351 mutex_enter(&l2arc_dev_mtx); 6352 list_insert_head(l2arc_dev_list, adddev); 6353 atomic_inc_64(&l2arc_ndev); 6354 mutex_exit(&l2arc_dev_mtx); 6355 } 6356 6357 /* 6358 * Remove a vdev from the L2ARC. 6359 */ 6360 void 6361 l2arc_remove_vdev(vdev_t *vd) 6362 { 6363 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6364 6365 /* 6366 * Find the device by vdev 6367 */ 6368 mutex_enter(&l2arc_dev_mtx); 6369 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6370 nextdev = list_next(l2arc_dev_list, dev); 6371 if (vd == dev->l2ad_vdev) { 6372 remdev = dev; 6373 break; 6374 } 6375 } 6376 ASSERT(remdev != NULL); 6377 6378 /* 6379 * Remove device from global list 6380 */ 6381 list_remove(l2arc_dev_list, remdev); 6382 l2arc_dev_last = NULL; /* may have been invalidated */ 6383 atomic_dec_64(&l2arc_ndev); 6384 mutex_exit(&l2arc_dev_mtx); 6385 6386 /* 6387 * Clear all buflists and ARC references. L2ARC device flush. 6388 */ 6389 l2arc_evict(remdev, 0, B_TRUE); 6390 list_destroy(&remdev->l2ad_buflist); 6391 mutex_destroy(&remdev->l2ad_mtx); 6392 kmem_free(remdev, sizeof (l2arc_dev_t)); 6393 } 6394 6395 void 6396 l2arc_init(void) 6397 { 6398 l2arc_thread_exit = 0; 6399 l2arc_ndev = 0; 6400 l2arc_writes_sent = 0; 6401 l2arc_writes_done = 0; 6402 6403 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6404 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6405 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6406 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6407 6408 l2arc_dev_list = &L2ARC_dev_list; 6409 l2arc_free_on_write = &L2ARC_free_on_write; 6410 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6411 offsetof(l2arc_dev_t, l2ad_node)); 6412 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6413 offsetof(l2arc_data_free_t, l2df_list_node)); 6414 } 6415 6416 void 6417 l2arc_fini(void) 6418 { 6419 /* 6420 * This is called from dmu_fini(), which is called from spa_fini(); 6421 * Because of this, we can assume that all l2arc devices have 6422 * already been removed when the pools themselves were removed. 6423 */ 6424 6425 l2arc_do_free_on_write(); 6426 6427 mutex_destroy(&l2arc_feed_thr_lock); 6428 cv_destroy(&l2arc_feed_thr_cv); 6429 mutex_destroy(&l2arc_dev_mtx); 6430 mutex_destroy(&l2arc_free_on_write_mtx); 6431 6432 list_destroy(l2arc_dev_list); 6433 list_destroy(l2arc_free_on_write); 6434 } 6435 6436 void 6437 l2arc_start(void) 6438 { 6439 if (!(spa_mode_global & FWRITE)) 6440 return; 6441 6442 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6443 TS_RUN, minclsyspri); 6444 } 6445 6446 void 6447 l2arc_stop(void) 6448 { 6449 if (!(spa_mode_global & FWRITE)) 6450 return; 6451 6452 mutex_enter(&l2arc_feed_thr_lock); 6453 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6454 l2arc_thread_exit = 1; 6455 while (l2arc_thread_exit != 0) 6456 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6457 mutex_exit(&l2arc_feed_thr_lock); 6458 } 6459