1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2014 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2014 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #ifdef _KERNEL 133 #include <sys/vmsystm.h> 134 #include <vm/anon.h> 135 #include <sys/fs/swapnode.h> 136 #include <sys/dnlc.h> 137 #endif 138 #include <sys/callb.h> 139 #include <sys/kstat.h> 140 #include <zfs_fletcher.h> 141 142 #ifndef _KERNEL 143 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 144 boolean_t arc_watch = B_FALSE; 145 int arc_procfd; 146 #endif 147 148 static kmutex_t arc_reclaim_thr_lock; 149 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 150 static uint8_t arc_thread_exit; 151 152 uint_t arc_reduce_dnlc_percent = 3; 153 154 /* 155 * The number of iterations through arc_evict_*() before we 156 * drop & reacquire the lock. 157 */ 158 int arc_evict_iterations = 100; 159 160 /* number of seconds before growing cache again */ 161 static int arc_grow_retry = 60; 162 163 /* shift of arc_c for calculating both min and max arc_p */ 164 static int arc_p_min_shift = 4; 165 166 /* log2(fraction of arc to reclaim) */ 167 static int arc_shrink_shift = 7; 168 169 /* 170 * log2(fraction of ARC which must be free to allow growing). 171 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 172 * when reading a new block into the ARC, we will evict an equal-sized block 173 * from the ARC. 174 * 175 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 176 * we will still not allow it to grow. 177 */ 178 int arc_no_grow_shift = 5; 179 180 181 /* 182 * minimum lifespan of a prefetch block in clock ticks 183 * (initialized in arc_init()) 184 */ 185 static int arc_min_prefetch_lifespan; 186 187 /* 188 * If this percent of memory is free, don't throttle. 189 */ 190 int arc_lotsfree_percent = 10; 191 192 static int arc_dead; 193 194 /* 195 * The arc has filled available memory and has now warmed up. 196 */ 197 static boolean_t arc_warm; 198 199 /* 200 * These tunables are for performance analysis. 201 */ 202 uint64_t zfs_arc_max; 203 uint64_t zfs_arc_min; 204 uint64_t zfs_arc_meta_limit = 0; 205 uint64_t zfs_arc_meta_min = 0; 206 int zfs_arc_grow_retry = 0; 207 int zfs_arc_shrink_shift = 0; 208 int zfs_arc_p_min_shift = 0; 209 int zfs_disable_dup_eviction = 0; 210 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 211 212 /* 213 * Note that buffers can be in one of 6 states: 214 * ARC_anon - anonymous (discussed below) 215 * ARC_mru - recently used, currently cached 216 * ARC_mru_ghost - recentely used, no longer in cache 217 * ARC_mfu - frequently used, currently cached 218 * ARC_mfu_ghost - frequently used, no longer in cache 219 * ARC_l2c_only - exists in L2ARC but not other states 220 * When there are no active references to the buffer, they are 221 * are linked onto a list in one of these arc states. These are 222 * the only buffers that can be evicted or deleted. Within each 223 * state there are multiple lists, one for meta-data and one for 224 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 225 * etc.) is tracked separately so that it can be managed more 226 * explicitly: favored over data, limited explicitly. 227 * 228 * Anonymous buffers are buffers that are not associated with 229 * a DVA. These are buffers that hold dirty block copies 230 * before they are written to stable storage. By definition, 231 * they are "ref'd" and are considered part of arc_mru 232 * that cannot be freed. Generally, they will aquire a DVA 233 * as they are written and migrate onto the arc_mru list. 234 * 235 * The ARC_l2c_only state is for buffers that are in the second 236 * level ARC but no longer in any of the ARC_m* lists. The second 237 * level ARC itself may also contain buffers that are in any of 238 * the ARC_m* states - meaning that a buffer can exist in two 239 * places. The reason for the ARC_l2c_only state is to keep the 240 * buffer header in the hash table, so that reads that hit the 241 * second level ARC benefit from these fast lookups. 242 */ 243 244 typedef struct arc_state { 245 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */ 246 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 247 uint64_t arcs_size; /* total amount of data in this state */ 248 kmutex_t arcs_mtx; 249 } arc_state_t; 250 251 /* The 6 states: */ 252 static arc_state_t ARC_anon; 253 static arc_state_t ARC_mru; 254 static arc_state_t ARC_mru_ghost; 255 static arc_state_t ARC_mfu; 256 static arc_state_t ARC_mfu_ghost; 257 static arc_state_t ARC_l2c_only; 258 259 typedef struct arc_stats { 260 kstat_named_t arcstat_hits; 261 kstat_named_t arcstat_misses; 262 kstat_named_t arcstat_demand_data_hits; 263 kstat_named_t arcstat_demand_data_misses; 264 kstat_named_t arcstat_demand_metadata_hits; 265 kstat_named_t arcstat_demand_metadata_misses; 266 kstat_named_t arcstat_prefetch_data_hits; 267 kstat_named_t arcstat_prefetch_data_misses; 268 kstat_named_t arcstat_prefetch_metadata_hits; 269 kstat_named_t arcstat_prefetch_metadata_misses; 270 kstat_named_t arcstat_mru_hits; 271 kstat_named_t arcstat_mru_ghost_hits; 272 kstat_named_t arcstat_mfu_hits; 273 kstat_named_t arcstat_mfu_ghost_hits; 274 kstat_named_t arcstat_deleted; 275 kstat_named_t arcstat_recycle_miss; 276 /* 277 * Number of buffers that could not be evicted because the hash lock 278 * was held by another thread. The lock may not necessarily be held 279 * by something using the same buffer, since hash locks are shared 280 * by multiple buffers. 281 */ 282 kstat_named_t arcstat_mutex_miss; 283 /* 284 * Number of buffers skipped because they have I/O in progress, are 285 * indrect prefetch buffers that have not lived long enough, or are 286 * not from the spa we're trying to evict from. 287 */ 288 kstat_named_t arcstat_evict_skip; 289 kstat_named_t arcstat_evict_l2_cached; 290 kstat_named_t arcstat_evict_l2_eligible; 291 kstat_named_t arcstat_evict_l2_ineligible; 292 kstat_named_t arcstat_hash_elements; 293 kstat_named_t arcstat_hash_elements_max; 294 kstat_named_t arcstat_hash_collisions; 295 kstat_named_t arcstat_hash_chains; 296 kstat_named_t arcstat_hash_chain_max; 297 kstat_named_t arcstat_p; 298 kstat_named_t arcstat_c; 299 kstat_named_t arcstat_c_min; 300 kstat_named_t arcstat_c_max; 301 kstat_named_t arcstat_size; 302 /* 303 * Number of bytes consumed by internal ARC structures necessary 304 * for tracking purposes; these structures are not actually 305 * backed by ARC buffers. This includes arc_buf_hdr_t structures 306 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 307 * caches), and arc_buf_t structures (allocated via arc_buf_t 308 * cache). 309 */ 310 kstat_named_t arcstat_hdr_size; 311 /* 312 * Number of bytes consumed by ARC buffers of type equal to 313 * ARC_BUFC_DATA. This is generally consumed by buffers backing 314 * on disk user data (e.g. plain file contents). 315 */ 316 kstat_named_t arcstat_data_size; 317 /* 318 * Number of bytes consumed by ARC buffers of type equal to 319 * ARC_BUFC_METADATA. This is generally consumed by buffers 320 * backing on disk data that is used for internal ZFS 321 * structures (e.g. ZAP, dnode, indirect blocks, etc). 322 */ 323 kstat_named_t arcstat_metadata_size; 324 /* 325 * Number of bytes consumed by various buffers and structures 326 * not actually backed with ARC buffers. This includes bonus 327 * buffers (allocated directly via zio_buf_* functions), 328 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 329 * cache), and dnode_t structures (allocated via dnode_t cache). 330 */ 331 kstat_named_t arcstat_other_size; 332 /* 333 * Total number of bytes consumed by ARC buffers residing in the 334 * arc_anon state. This includes *all* buffers in the arc_anon 335 * state; e.g. data, metadata, evictable, and unevictable buffers 336 * are all included in this value. 337 */ 338 kstat_named_t arcstat_anon_size; 339 /* 340 * Number of bytes consumed by ARC buffers that meet the 341 * following criteria: backing buffers of type ARC_BUFC_DATA, 342 * residing in the arc_anon state, and are eligible for eviction 343 * (e.g. have no outstanding holds on the buffer). 344 */ 345 kstat_named_t arcstat_anon_evictable_data; 346 /* 347 * Number of bytes consumed by ARC buffers that meet the 348 * following criteria: backing buffers of type ARC_BUFC_METADATA, 349 * residing in the arc_anon state, and are eligible for eviction 350 * (e.g. have no outstanding holds on the buffer). 351 */ 352 kstat_named_t arcstat_anon_evictable_metadata; 353 /* 354 * Total number of bytes consumed by ARC buffers residing in the 355 * arc_mru state. This includes *all* buffers in the arc_mru 356 * state; e.g. data, metadata, evictable, and unevictable buffers 357 * are all included in this value. 358 */ 359 kstat_named_t arcstat_mru_size; 360 /* 361 * Number of bytes consumed by ARC buffers that meet the 362 * following criteria: backing buffers of type ARC_BUFC_DATA, 363 * residing in the arc_mru state, and are eligible for eviction 364 * (e.g. have no outstanding holds on the buffer). 365 */ 366 kstat_named_t arcstat_mru_evictable_data; 367 /* 368 * Number of bytes consumed by ARC buffers that meet the 369 * following criteria: backing buffers of type ARC_BUFC_METADATA, 370 * residing in the arc_mru state, and are eligible for eviction 371 * (e.g. have no outstanding holds on the buffer). 372 */ 373 kstat_named_t arcstat_mru_evictable_metadata; 374 /* 375 * Total number of bytes that *would have been* consumed by ARC 376 * buffers in the arc_mru_ghost state. The key thing to note 377 * here, is the fact that this size doesn't actually indicate 378 * RAM consumption. The ghost lists only consist of headers and 379 * don't actually have ARC buffers linked off of these headers. 380 * Thus, *if* the headers had associated ARC buffers, these 381 * buffers *would have* consumed this number of bytes. 382 */ 383 kstat_named_t arcstat_mru_ghost_size; 384 /* 385 * Number of bytes that *would have been* consumed by ARC 386 * buffers that are eligible for eviction, of type 387 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 388 */ 389 kstat_named_t arcstat_mru_ghost_evictable_data; 390 /* 391 * Number of bytes that *would have been* consumed by ARC 392 * buffers that are eligible for eviction, of type 393 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 394 */ 395 kstat_named_t arcstat_mru_ghost_evictable_metadata; 396 /* 397 * Total number of bytes consumed by ARC buffers residing in the 398 * arc_mfu state. This includes *all* buffers in the arc_mfu 399 * state; e.g. data, metadata, evictable, and unevictable buffers 400 * are all included in this value. 401 */ 402 kstat_named_t arcstat_mfu_size; 403 /* 404 * Number of bytes consumed by ARC buffers that are eligible for 405 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 406 * state. 407 */ 408 kstat_named_t arcstat_mfu_evictable_data; 409 /* 410 * Number of bytes consumed by ARC buffers that are eligible for 411 * eviction, of type ARC_BUFC_METADATA, and reside in the 412 * arc_mfu state. 413 */ 414 kstat_named_t arcstat_mfu_evictable_metadata; 415 /* 416 * Total number of bytes that *would have been* consumed by ARC 417 * buffers in the arc_mfu_ghost state. See the comment above 418 * arcstat_mru_ghost_size for more details. 419 */ 420 kstat_named_t arcstat_mfu_ghost_size; 421 /* 422 * Number of bytes that *would have been* consumed by ARC 423 * buffers that are eligible for eviction, of type 424 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 425 */ 426 kstat_named_t arcstat_mfu_ghost_evictable_data; 427 /* 428 * Number of bytes that *would have been* consumed by ARC 429 * buffers that are eligible for eviction, of type 430 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 431 */ 432 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 433 kstat_named_t arcstat_l2_hits; 434 kstat_named_t arcstat_l2_misses; 435 kstat_named_t arcstat_l2_feeds; 436 kstat_named_t arcstat_l2_rw_clash; 437 kstat_named_t arcstat_l2_read_bytes; 438 kstat_named_t arcstat_l2_write_bytes; 439 kstat_named_t arcstat_l2_writes_sent; 440 kstat_named_t arcstat_l2_writes_done; 441 kstat_named_t arcstat_l2_writes_error; 442 kstat_named_t arcstat_l2_writes_hdr_miss; 443 kstat_named_t arcstat_l2_evict_lock_retry; 444 kstat_named_t arcstat_l2_evict_reading; 445 kstat_named_t arcstat_l2_evict_l1cached; 446 kstat_named_t arcstat_l2_free_on_write; 447 kstat_named_t arcstat_l2_abort_lowmem; 448 kstat_named_t arcstat_l2_cksum_bad; 449 kstat_named_t arcstat_l2_io_error; 450 kstat_named_t arcstat_l2_size; 451 kstat_named_t arcstat_l2_asize; 452 kstat_named_t arcstat_l2_hdr_size; 453 kstat_named_t arcstat_l2_compress_successes; 454 kstat_named_t arcstat_l2_compress_zeros; 455 kstat_named_t arcstat_l2_compress_failures; 456 kstat_named_t arcstat_memory_throttle_count; 457 kstat_named_t arcstat_duplicate_buffers; 458 kstat_named_t arcstat_duplicate_buffers_size; 459 kstat_named_t arcstat_duplicate_reads; 460 kstat_named_t arcstat_meta_used; 461 kstat_named_t arcstat_meta_limit; 462 kstat_named_t arcstat_meta_max; 463 kstat_named_t arcstat_meta_min; 464 } arc_stats_t; 465 466 static arc_stats_t arc_stats = { 467 { "hits", KSTAT_DATA_UINT64 }, 468 { "misses", KSTAT_DATA_UINT64 }, 469 { "demand_data_hits", KSTAT_DATA_UINT64 }, 470 { "demand_data_misses", KSTAT_DATA_UINT64 }, 471 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 472 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 473 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 474 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 475 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 476 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 477 { "mru_hits", KSTAT_DATA_UINT64 }, 478 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 479 { "mfu_hits", KSTAT_DATA_UINT64 }, 480 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 481 { "deleted", KSTAT_DATA_UINT64 }, 482 { "recycle_miss", KSTAT_DATA_UINT64 }, 483 { "mutex_miss", KSTAT_DATA_UINT64 }, 484 { "evict_skip", KSTAT_DATA_UINT64 }, 485 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 486 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 487 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 488 { "hash_elements", KSTAT_DATA_UINT64 }, 489 { "hash_elements_max", KSTAT_DATA_UINT64 }, 490 { "hash_collisions", KSTAT_DATA_UINT64 }, 491 { "hash_chains", KSTAT_DATA_UINT64 }, 492 { "hash_chain_max", KSTAT_DATA_UINT64 }, 493 { "p", KSTAT_DATA_UINT64 }, 494 { "c", KSTAT_DATA_UINT64 }, 495 { "c_min", KSTAT_DATA_UINT64 }, 496 { "c_max", KSTAT_DATA_UINT64 }, 497 { "size", KSTAT_DATA_UINT64 }, 498 { "hdr_size", KSTAT_DATA_UINT64 }, 499 { "data_size", KSTAT_DATA_UINT64 }, 500 { "metadata_size", KSTAT_DATA_UINT64 }, 501 { "other_size", KSTAT_DATA_UINT64 }, 502 { "anon_size", KSTAT_DATA_UINT64 }, 503 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 504 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 505 { "mru_size", KSTAT_DATA_UINT64 }, 506 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 507 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 508 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 509 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 510 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 511 { "mfu_size", KSTAT_DATA_UINT64 }, 512 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 513 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 514 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 515 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 516 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 517 { "l2_hits", KSTAT_DATA_UINT64 }, 518 { "l2_misses", KSTAT_DATA_UINT64 }, 519 { "l2_feeds", KSTAT_DATA_UINT64 }, 520 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 521 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 522 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 523 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 524 { "l2_writes_done", KSTAT_DATA_UINT64 }, 525 { "l2_writes_error", KSTAT_DATA_UINT64 }, 526 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 527 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 528 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 529 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 530 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 531 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 532 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 533 { "l2_io_error", KSTAT_DATA_UINT64 }, 534 { "l2_size", KSTAT_DATA_UINT64 }, 535 { "l2_asize", KSTAT_DATA_UINT64 }, 536 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 537 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 538 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 539 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 540 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 541 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 542 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 543 { "duplicate_reads", KSTAT_DATA_UINT64 }, 544 { "arc_meta_used", KSTAT_DATA_UINT64 }, 545 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 546 { "arc_meta_max", KSTAT_DATA_UINT64 }, 547 { "arc_meta_min", KSTAT_DATA_UINT64 } 548 }; 549 550 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 551 552 #define ARCSTAT_INCR(stat, val) \ 553 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 554 555 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 556 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 557 558 #define ARCSTAT_MAX(stat, val) { \ 559 uint64_t m; \ 560 while ((val) > (m = arc_stats.stat.value.ui64) && \ 561 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 562 continue; \ 563 } 564 565 #define ARCSTAT_MAXSTAT(stat) \ 566 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 567 568 /* 569 * We define a macro to allow ARC hits/misses to be easily broken down by 570 * two separate conditions, giving a total of four different subtypes for 571 * each of hits and misses (so eight statistics total). 572 */ 573 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 574 if (cond1) { \ 575 if (cond2) { \ 576 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 577 } else { \ 578 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 579 } \ 580 } else { \ 581 if (cond2) { \ 582 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 583 } else { \ 584 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 585 } \ 586 } 587 588 kstat_t *arc_ksp; 589 static arc_state_t *arc_anon; 590 static arc_state_t *arc_mru; 591 static arc_state_t *arc_mru_ghost; 592 static arc_state_t *arc_mfu; 593 static arc_state_t *arc_mfu_ghost; 594 static arc_state_t *arc_l2c_only; 595 596 /* 597 * There are several ARC variables that are critical to export as kstats -- 598 * but we don't want to have to grovel around in the kstat whenever we wish to 599 * manipulate them. For these variables, we therefore define them to be in 600 * terms of the statistic variable. This assures that we are not introducing 601 * the possibility of inconsistency by having shadow copies of the variables, 602 * while still allowing the code to be readable. 603 */ 604 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 605 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 606 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 607 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 608 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 609 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 610 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 611 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 612 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 613 614 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 615 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 616 617 static int arc_no_grow; /* Don't try to grow cache size */ 618 static uint64_t arc_tempreserve; 619 static uint64_t arc_loaned_bytes; 620 621 typedef struct arc_callback arc_callback_t; 622 623 struct arc_callback { 624 void *acb_private; 625 arc_done_func_t *acb_done; 626 arc_buf_t *acb_buf; 627 zio_t *acb_zio_dummy; 628 arc_callback_t *acb_next; 629 }; 630 631 typedef struct arc_write_callback arc_write_callback_t; 632 633 struct arc_write_callback { 634 void *awcb_private; 635 arc_done_func_t *awcb_ready; 636 arc_done_func_t *awcb_physdone; 637 arc_done_func_t *awcb_done; 638 arc_buf_t *awcb_buf; 639 }; 640 641 /* 642 * ARC buffers are separated into multiple structs as a memory saving measure: 643 * - Common fields struct, always defined, and embedded within it: 644 * - L2-only fields, always allocated but undefined when not in L2ARC 645 * - L1-only fields, only allocated when in L1ARC 646 * 647 * Buffer in L1 Buffer only in L2 648 * +------------------------+ +------------------------+ 649 * | arc_buf_hdr_t | | arc_buf_hdr_t | 650 * | | | | 651 * | | | | 652 * | | | | 653 * +------------------------+ +------------------------+ 654 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 655 * | (undefined if L1-only) | | | 656 * +------------------------+ +------------------------+ 657 * | l1arc_buf_hdr_t | 658 * | | 659 * | | 660 * | | 661 * | | 662 * +------------------------+ 663 * 664 * Because it's possible for the L2ARC to become extremely large, we can wind 665 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 666 * is minimized by only allocating the fields necessary for an L1-cached buffer 667 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 668 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 669 * words in pointers. arc_hdr_realloc() is used to switch a header between 670 * these two allocation states. 671 */ 672 typedef struct l1arc_buf_hdr { 673 kmutex_t b_freeze_lock; 674 #ifdef ZFS_DEBUG 675 /* 676 * used for debugging wtih kmem_flags - by allocating and freeing 677 * b_thawed when the buffer is thawed, we get a record of the stack 678 * trace that thawed it. 679 */ 680 void *b_thawed; 681 #endif 682 683 arc_buf_t *b_buf; 684 uint32_t b_datacnt; 685 /* for waiting on writes to complete */ 686 kcondvar_t b_cv; 687 688 /* protected by arc state mutex */ 689 arc_state_t *b_state; 690 list_node_t b_arc_node; 691 692 /* updated atomically */ 693 clock_t b_arc_access; 694 695 /* self protecting */ 696 refcount_t b_refcnt; 697 698 arc_callback_t *b_acb; 699 /* temporary buffer holder for in-flight compressed data */ 700 void *b_tmp_cdata; 701 } l1arc_buf_hdr_t; 702 703 typedef struct l2arc_dev l2arc_dev_t; 704 705 typedef struct l2arc_buf_hdr { 706 /* protected by arc_buf_hdr mutex */ 707 l2arc_dev_t *b_dev; /* L2ARC device */ 708 uint64_t b_daddr; /* disk address, offset byte */ 709 /* real alloc'd buffer size depending on b_compress applied */ 710 int32_t b_asize; 711 712 list_node_t b_l2node; 713 } l2arc_buf_hdr_t; 714 715 struct arc_buf_hdr { 716 /* protected by hash lock */ 717 dva_t b_dva; 718 uint64_t b_birth; 719 /* 720 * Even though this checksum is only set/verified when a buffer is in 721 * the L1 cache, it needs to be in the set of common fields because it 722 * must be preserved from the time before a buffer is written out to 723 * L2ARC until after it is read back in. 724 */ 725 zio_cksum_t *b_freeze_cksum; 726 727 arc_buf_hdr_t *b_hash_next; 728 arc_flags_t b_flags; 729 730 /* immutable */ 731 int32_t b_size; 732 uint64_t b_spa; 733 734 /* L2ARC fields. Undefined when not in L2ARC. */ 735 l2arc_buf_hdr_t b_l2hdr; 736 /* L1ARC fields. Undefined when in l2arc_only state */ 737 l1arc_buf_hdr_t b_l1hdr; 738 }; 739 740 static arc_buf_t *arc_eviction_list; 741 static kmutex_t arc_eviction_mtx; 742 static arc_buf_hdr_t arc_eviction_hdr; 743 744 #define GHOST_STATE(state) \ 745 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 746 (state) == arc_l2c_only) 747 748 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 749 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 750 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 751 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 752 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 753 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 754 755 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 756 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 757 #define HDR_L2_READING(hdr) \ 758 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 759 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 760 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 761 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 762 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 763 764 #define HDR_ISTYPE_METADATA(hdr) \ 765 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 766 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 767 768 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 769 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 770 771 /* For storing compression mode in b_flags */ 772 #define HDR_COMPRESS_OFFSET 24 773 #define HDR_COMPRESS_NBITS 7 774 775 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 776 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 777 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 778 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 779 780 /* 781 * Other sizes 782 */ 783 784 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 785 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 786 787 /* 788 * Hash table routines 789 */ 790 791 #define HT_LOCK_PAD 64 792 793 struct ht_lock { 794 kmutex_t ht_lock; 795 #ifdef _KERNEL 796 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 797 #endif 798 }; 799 800 #define BUF_LOCKS 256 801 typedef struct buf_hash_table { 802 uint64_t ht_mask; 803 arc_buf_hdr_t **ht_table; 804 struct ht_lock ht_locks[BUF_LOCKS]; 805 } buf_hash_table_t; 806 807 static buf_hash_table_t buf_hash_table; 808 809 #define BUF_HASH_INDEX(spa, dva, birth) \ 810 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 811 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 812 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 813 #define HDR_LOCK(hdr) \ 814 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 815 816 uint64_t zfs_crc64_table[256]; 817 818 /* 819 * Level 2 ARC 820 */ 821 822 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 823 #define L2ARC_HEADROOM 2 /* num of writes */ 824 /* 825 * If we discover during ARC scan any buffers to be compressed, we boost 826 * our headroom for the next scanning cycle by this percentage multiple. 827 */ 828 #define L2ARC_HEADROOM_BOOST 200 829 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 830 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 831 832 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 833 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 834 835 /* L2ARC Performance Tunables */ 836 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 837 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 838 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 839 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 840 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 841 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 842 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 843 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 844 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 845 846 /* 847 * L2ARC Internals 848 */ 849 struct l2arc_dev { 850 vdev_t *l2ad_vdev; /* vdev */ 851 spa_t *l2ad_spa; /* spa */ 852 uint64_t l2ad_hand; /* next write location */ 853 uint64_t l2ad_start; /* first addr on device */ 854 uint64_t l2ad_end; /* last addr on device */ 855 uint64_t l2ad_evict; /* last addr eviction reached */ 856 boolean_t l2ad_first; /* first sweep through */ 857 boolean_t l2ad_writing; /* currently writing */ 858 kmutex_t l2ad_mtx; /* lock for buffer list */ 859 list_t l2ad_buflist; /* buffer list */ 860 list_node_t l2ad_node; /* device list node */ 861 }; 862 863 static list_t L2ARC_dev_list; /* device list */ 864 static list_t *l2arc_dev_list; /* device list pointer */ 865 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 866 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 867 static list_t L2ARC_free_on_write; /* free after write buf list */ 868 static list_t *l2arc_free_on_write; /* free after write list ptr */ 869 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 870 static uint64_t l2arc_ndev; /* number of devices */ 871 872 typedef struct l2arc_read_callback { 873 arc_buf_t *l2rcb_buf; /* read buffer */ 874 spa_t *l2rcb_spa; /* spa */ 875 blkptr_t l2rcb_bp; /* original blkptr */ 876 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 877 int l2rcb_flags; /* original flags */ 878 enum zio_compress l2rcb_compress; /* applied compress */ 879 } l2arc_read_callback_t; 880 881 typedef struct l2arc_write_callback { 882 l2arc_dev_t *l2wcb_dev; /* device info */ 883 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 884 } l2arc_write_callback_t; 885 886 typedef struct l2arc_data_free { 887 /* protected by l2arc_free_on_write_mtx */ 888 void *l2df_data; 889 size_t l2df_size; 890 void (*l2df_func)(void *, size_t); 891 list_node_t l2df_list_node; 892 } l2arc_data_free_t; 893 894 static kmutex_t l2arc_feed_thr_lock; 895 static kcondvar_t l2arc_feed_thr_cv; 896 static uint8_t l2arc_thread_exit; 897 898 static void arc_get_data_buf(arc_buf_t *); 899 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 900 static int arc_evict_needed(arc_buf_contents_t); 901 static void arc_evict_ghost(arc_state_t *, uint64_t, int64_t); 902 static void arc_buf_watch(arc_buf_t *); 903 904 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 905 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 906 907 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 908 static void l2arc_read_done(zio_t *); 909 910 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 911 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 912 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 913 914 static uint64_t 915 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 916 { 917 uint8_t *vdva = (uint8_t *)dva; 918 uint64_t crc = -1ULL; 919 int i; 920 921 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 922 923 for (i = 0; i < sizeof (dva_t); i++) 924 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 925 926 crc ^= (spa>>8) ^ birth; 927 928 return (crc); 929 } 930 931 #define BUF_EMPTY(buf) \ 932 ((buf)->b_dva.dva_word[0] == 0 && \ 933 (buf)->b_dva.dva_word[1] == 0) 934 935 #define BUF_EQUAL(spa, dva, birth, buf) \ 936 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 937 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 938 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 939 940 static void 941 buf_discard_identity(arc_buf_hdr_t *hdr) 942 { 943 hdr->b_dva.dva_word[0] = 0; 944 hdr->b_dva.dva_word[1] = 0; 945 hdr->b_birth = 0; 946 } 947 948 static arc_buf_hdr_t * 949 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 950 { 951 const dva_t *dva = BP_IDENTITY(bp); 952 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 953 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 954 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 955 arc_buf_hdr_t *hdr; 956 957 mutex_enter(hash_lock); 958 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 959 hdr = hdr->b_hash_next) { 960 if (BUF_EQUAL(spa, dva, birth, hdr)) { 961 *lockp = hash_lock; 962 return (hdr); 963 } 964 } 965 mutex_exit(hash_lock); 966 *lockp = NULL; 967 return (NULL); 968 } 969 970 /* 971 * Insert an entry into the hash table. If there is already an element 972 * equal to elem in the hash table, then the already existing element 973 * will be returned and the new element will not be inserted. 974 * Otherwise returns NULL. 975 * If lockp == NULL, the caller is assumed to already hold the hash lock. 976 */ 977 static arc_buf_hdr_t * 978 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 979 { 980 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 981 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 982 arc_buf_hdr_t *fhdr; 983 uint32_t i; 984 985 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 986 ASSERT(hdr->b_birth != 0); 987 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 988 989 if (lockp != NULL) { 990 *lockp = hash_lock; 991 mutex_enter(hash_lock); 992 } else { 993 ASSERT(MUTEX_HELD(hash_lock)); 994 } 995 996 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 997 fhdr = fhdr->b_hash_next, i++) { 998 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 999 return (fhdr); 1000 } 1001 1002 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1003 buf_hash_table.ht_table[idx] = hdr; 1004 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1005 1006 /* collect some hash table performance data */ 1007 if (i > 0) { 1008 ARCSTAT_BUMP(arcstat_hash_collisions); 1009 if (i == 1) 1010 ARCSTAT_BUMP(arcstat_hash_chains); 1011 1012 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1013 } 1014 1015 ARCSTAT_BUMP(arcstat_hash_elements); 1016 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1017 1018 return (NULL); 1019 } 1020 1021 static void 1022 buf_hash_remove(arc_buf_hdr_t *hdr) 1023 { 1024 arc_buf_hdr_t *fhdr, **hdrp; 1025 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1026 1027 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1028 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1029 1030 hdrp = &buf_hash_table.ht_table[idx]; 1031 while ((fhdr = *hdrp) != hdr) { 1032 ASSERT(fhdr != NULL); 1033 hdrp = &fhdr->b_hash_next; 1034 } 1035 *hdrp = hdr->b_hash_next; 1036 hdr->b_hash_next = NULL; 1037 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1038 1039 /* collect some hash table performance data */ 1040 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1041 1042 if (buf_hash_table.ht_table[idx] && 1043 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1044 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1045 } 1046 1047 /* 1048 * Global data structures and functions for the buf kmem cache. 1049 */ 1050 static kmem_cache_t *hdr_full_cache; 1051 static kmem_cache_t *hdr_l2only_cache; 1052 static kmem_cache_t *buf_cache; 1053 1054 static void 1055 buf_fini(void) 1056 { 1057 int i; 1058 1059 kmem_free(buf_hash_table.ht_table, 1060 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1061 for (i = 0; i < BUF_LOCKS; i++) 1062 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1063 kmem_cache_destroy(hdr_full_cache); 1064 kmem_cache_destroy(hdr_l2only_cache); 1065 kmem_cache_destroy(buf_cache); 1066 } 1067 1068 /* 1069 * Constructor callback - called when the cache is empty 1070 * and a new buf is requested. 1071 */ 1072 /* ARGSUSED */ 1073 static int 1074 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1075 { 1076 arc_buf_hdr_t *hdr = vbuf; 1077 1078 bzero(hdr, HDR_FULL_SIZE); 1079 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1080 refcount_create(&hdr->b_l1hdr.b_refcnt); 1081 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1082 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1083 1084 return (0); 1085 } 1086 1087 /* ARGSUSED */ 1088 static int 1089 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1090 { 1091 arc_buf_hdr_t *hdr = vbuf; 1092 1093 bzero(hdr, HDR_L2ONLY_SIZE); 1094 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1095 1096 return (0); 1097 } 1098 1099 /* ARGSUSED */ 1100 static int 1101 buf_cons(void *vbuf, void *unused, int kmflag) 1102 { 1103 arc_buf_t *buf = vbuf; 1104 1105 bzero(buf, sizeof (arc_buf_t)); 1106 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1107 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1108 1109 return (0); 1110 } 1111 1112 /* 1113 * Destructor callback - called when a cached buf is 1114 * no longer required. 1115 */ 1116 /* ARGSUSED */ 1117 static void 1118 hdr_full_dest(void *vbuf, void *unused) 1119 { 1120 arc_buf_hdr_t *hdr = vbuf; 1121 1122 ASSERT(BUF_EMPTY(hdr)); 1123 cv_destroy(&hdr->b_l1hdr.b_cv); 1124 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1125 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1126 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1127 } 1128 1129 /* ARGSUSED */ 1130 static void 1131 hdr_l2only_dest(void *vbuf, void *unused) 1132 { 1133 arc_buf_hdr_t *hdr = vbuf; 1134 1135 ASSERT(BUF_EMPTY(hdr)); 1136 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1137 } 1138 1139 /* ARGSUSED */ 1140 static void 1141 buf_dest(void *vbuf, void *unused) 1142 { 1143 arc_buf_t *buf = vbuf; 1144 1145 mutex_destroy(&buf->b_evict_lock); 1146 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1147 } 1148 1149 /* 1150 * Reclaim callback -- invoked when memory is low. 1151 */ 1152 /* ARGSUSED */ 1153 static void 1154 hdr_recl(void *unused) 1155 { 1156 dprintf("hdr_recl called\n"); 1157 /* 1158 * umem calls the reclaim func when we destroy the buf cache, 1159 * which is after we do arc_fini(). 1160 */ 1161 if (!arc_dead) 1162 cv_signal(&arc_reclaim_thr_cv); 1163 } 1164 1165 static void 1166 buf_init(void) 1167 { 1168 uint64_t *ct; 1169 uint64_t hsize = 1ULL << 12; 1170 int i, j; 1171 1172 /* 1173 * The hash table is big enough to fill all of physical memory 1174 * with an average block size of zfs_arc_average_blocksize (default 8K). 1175 * By default, the table will take up 1176 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1177 */ 1178 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1179 hsize <<= 1; 1180 retry: 1181 buf_hash_table.ht_mask = hsize - 1; 1182 buf_hash_table.ht_table = 1183 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1184 if (buf_hash_table.ht_table == NULL) { 1185 ASSERT(hsize > (1ULL << 8)); 1186 hsize >>= 1; 1187 goto retry; 1188 } 1189 1190 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1191 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1192 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1193 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1194 NULL, NULL, 0); 1195 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1196 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1197 1198 for (i = 0; i < 256; i++) 1199 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1200 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1201 1202 for (i = 0; i < BUF_LOCKS; i++) { 1203 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1204 NULL, MUTEX_DEFAULT, NULL); 1205 } 1206 } 1207 1208 /* 1209 * Transition between the two allocation states for the arc_buf_hdr struct. 1210 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1211 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1212 * version is used when a cache buffer is only in the L2ARC in order to reduce 1213 * memory usage. 1214 */ 1215 static arc_buf_hdr_t * 1216 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1217 { 1218 ASSERT(HDR_HAS_L2HDR(hdr)); 1219 1220 arc_buf_hdr_t *nhdr; 1221 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1222 1223 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1224 (old == hdr_l2only_cache && new == hdr_full_cache)); 1225 1226 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1227 1228 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1229 buf_hash_remove(hdr); 1230 1231 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1232 if (new == hdr_full_cache) { 1233 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1234 /* 1235 * arc_access and arc_change_state need to be aware that a 1236 * header has just come out of L2ARC, so we set its state to 1237 * l2c_only even though it's about to change. 1238 */ 1239 nhdr->b_l1hdr.b_state = arc_l2c_only; 1240 } else { 1241 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1242 ASSERT0(hdr->b_l1hdr.b_datacnt); 1243 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1244 /* 1245 * We might be removing the L1hdr of a buffer which was just 1246 * written out to L2ARC. If such a buffer is compressed then we 1247 * need to free its b_tmp_cdata before destroying the header. 1248 */ 1249 if (hdr->b_l1hdr.b_tmp_cdata != NULL && 1250 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 1251 l2arc_release_cdata_buf(hdr); 1252 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1253 } 1254 /* 1255 * The header has been reallocated so we need to re-insert it into any 1256 * lists it was on. 1257 */ 1258 (void) buf_hash_insert(nhdr, NULL); 1259 1260 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1261 1262 mutex_enter(&dev->l2ad_mtx); 1263 1264 /* 1265 * We must place the realloc'ed header back into the list at 1266 * the same spot. Otherwise, if it's placed earlier in the list, 1267 * l2arc_write_buffers() could find it during the function's 1268 * write phase, and try to write it out to the l2arc. 1269 */ 1270 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1271 list_remove(&dev->l2ad_buflist, hdr); 1272 1273 mutex_exit(&dev->l2ad_mtx); 1274 1275 buf_discard_identity(hdr); 1276 hdr->b_freeze_cksum = NULL; 1277 kmem_cache_free(old, hdr); 1278 1279 return (nhdr); 1280 } 1281 1282 1283 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1284 1285 static void 1286 arc_cksum_verify(arc_buf_t *buf) 1287 { 1288 zio_cksum_t zc; 1289 1290 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1291 return; 1292 1293 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1294 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1295 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1296 return; 1297 } 1298 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1299 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1300 panic("buffer modified while frozen!"); 1301 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1302 } 1303 1304 static int 1305 arc_cksum_equal(arc_buf_t *buf) 1306 { 1307 zio_cksum_t zc; 1308 int equal; 1309 1310 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1311 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1312 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1313 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1314 1315 return (equal); 1316 } 1317 1318 static void 1319 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1320 { 1321 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1322 return; 1323 1324 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1325 if (buf->b_hdr->b_freeze_cksum != NULL) { 1326 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1327 return; 1328 } 1329 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1330 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1331 buf->b_hdr->b_freeze_cksum); 1332 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1333 arc_buf_watch(buf); 1334 } 1335 1336 #ifndef _KERNEL 1337 typedef struct procctl { 1338 long cmd; 1339 prwatch_t prwatch; 1340 } procctl_t; 1341 #endif 1342 1343 /* ARGSUSED */ 1344 static void 1345 arc_buf_unwatch(arc_buf_t *buf) 1346 { 1347 #ifndef _KERNEL 1348 if (arc_watch) { 1349 int result; 1350 procctl_t ctl; 1351 ctl.cmd = PCWATCH; 1352 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1353 ctl.prwatch.pr_size = 0; 1354 ctl.prwatch.pr_wflags = 0; 1355 result = write(arc_procfd, &ctl, sizeof (ctl)); 1356 ASSERT3U(result, ==, sizeof (ctl)); 1357 } 1358 #endif 1359 } 1360 1361 /* ARGSUSED */ 1362 static void 1363 arc_buf_watch(arc_buf_t *buf) 1364 { 1365 #ifndef _KERNEL 1366 if (arc_watch) { 1367 int result; 1368 procctl_t ctl; 1369 ctl.cmd = PCWATCH; 1370 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1371 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1372 ctl.prwatch.pr_wflags = WA_WRITE; 1373 result = write(arc_procfd, &ctl, sizeof (ctl)); 1374 ASSERT3U(result, ==, sizeof (ctl)); 1375 } 1376 #endif 1377 } 1378 1379 static arc_buf_contents_t 1380 arc_buf_type(arc_buf_hdr_t *hdr) 1381 { 1382 if (HDR_ISTYPE_METADATA(hdr)) { 1383 return (ARC_BUFC_METADATA); 1384 } else { 1385 return (ARC_BUFC_DATA); 1386 } 1387 } 1388 1389 static uint32_t 1390 arc_bufc_to_flags(arc_buf_contents_t type) 1391 { 1392 switch (type) { 1393 case ARC_BUFC_DATA: 1394 /* metadata field is 0 if buffer contains normal data */ 1395 return (0); 1396 case ARC_BUFC_METADATA: 1397 return (ARC_FLAG_BUFC_METADATA); 1398 default: 1399 break; 1400 } 1401 panic("undefined ARC buffer type!"); 1402 return ((uint32_t)-1); 1403 } 1404 1405 void 1406 arc_buf_thaw(arc_buf_t *buf) 1407 { 1408 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1409 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1410 panic("modifying non-anon buffer!"); 1411 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1412 panic("modifying buffer while i/o in progress!"); 1413 arc_cksum_verify(buf); 1414 } 1415 1416 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1417 if (buf->b_hdr->b_freeze_cksum != NULL) { 1418 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1419 buf->b_hdr->b_freeze_cksum = NULL; 1420 } 1421 1422 #ifdef ZFS_DEBUG 1423 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1424 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1425 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1426 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1427 } 1428 #endif 1429 1430 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1431 1432 arc_buf_unwatch(buf); 1433 } 1434 1435 void 1436 arc_buf_freeze(arc_buf_t *buf) 1437 { 1438 kmutex_t *hash_lock; 1439 1440 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1441 return; 1442 1443 hash_lock = HDR_LOCK(buf->b_hdr); 1444 mutex_enter(hash_lock); 1445 1446 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1447 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1448 arc_cksum_compute(buf, B_FALSE); 1449 mutex_exit(hash_lock); 1450 1451 } 1452 1453 static void 1454 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1455 { 1456 ASSERT(HDR_HAS_L1HDR(hdr)); 1457 ASSERT(MUTEX_HELD(hash_lock)); 1458 arc_state_t *state = hdr->b_l1hdr.b_state; 1459 1460 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1461 (state != arc_anon)) { 1462 /* We don't use the L2-only state list. */ 1463 if (state != arc_l2c_only) { 1464 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1465 list_t *list = &state->arcs_list[arc_buf_type(hdr)]; 1466 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1467 1468 ASSERT(!MUTEX_HELD(&state->arcs_mtx)); 1469 mutex_enter(&state->arcs_mtx); 1470 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1471 list_remove(list, hdr); 1472 if (GHOST_STATE(state)) { 1473 ASSERT0(hdr->b_l1hdr.b_datacnt); 1474 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1475 delta = hdr->b_size; 1476 } 1477 ASSERT(delta > 0); 1478 ASSERT3U(*size, >=, delta); 1479 atomic_add_64(size, -delta); 1480 mutex_exit(&state->arcs_mtx); 1481 } 1482 /* remove the prefetch flag if we get a reference */ 1483 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1484 } 1485 } 1486 1487 static int 1488 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1489 { 1490 int cnt; 1491 arc_state_t *state = hdr->b_l1hdr.b_state; 1492 1493 ASSERT(HDR_HAS_L1HDR(hdr)); 1494 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1495 ASSERT(!GHOST_STATE(state)); 1496 1497 /* 1498 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1499 * check to prevent usage of the arc_l2c_only list. 1500 */ 1501 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1502 (state != arc_anon)) { 1503 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1504 1505 ASSERT(!MUTEX_HELD(&state->arcs_mtx)); 1506 mutex_enter(&state->arcs_mtx); 1507 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1508 list_insert_head(&state->arcs_list[arc_buf_type(hdr)], hdr); 1509 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1510 atomic_add_64(size, hdr->b_size * 1511 hdr->b_l1hdr.b_datacnt); 1512 mutex_exit(&state->arcs_mtx); 1513 } 1514 return (cnt); 1515 } 1516 1517 /* 1518 * Move the supplied buffer to the indicated state. The mutex 1519 * for the buffer must be held by the caller. 1520 */ 1521 static void 1522 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1523 kmutex_t *hash_lock) 1524 { 1525 arc_state_t *old_state; 1526 int64_t refcnt; 1527 uint32_t datacnt; 1528 uint64_t from_delta, to_delta; 1529 arc_buf_contents_t buftype = arc_buf_type(hdr); 1530 1531 /* 1532 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1533 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1534 * L1 hdr doesn't always exist when we change state to arc_anon before 1535 * destroying a header, in which case reallocating to add the L1 hdr is 1536 * pointless. 1537 */ 1538 if (HDR_HAS_L1HDR(hdr)) { 1539 old_state = hdr->b_l1hdr.b_state; 1540 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1541 datacnt = hdr->b_l1hdr.b_datacnt; 1542 } else { 1543 old_state = arc_l2c_only; 1544 refcnt = 0; 1545 datacnt = 0; 1546 } 1547 1548 ASSERT(MUTEX_HELD(hash_lock)); 1549 ASSERT3P(new_state, !=, old_state); 1550 ASSERT(refcnt == 0 || datacnt > 0); 1551 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1552 ASSERT(old_state != arc_anon || datacnt <= 1); 1553 1554 from_delta = to_delta = datacnt * hdr->b_size; 1555 1556 /* 1557 * If this buffer is evictable, transfer it from the 1558 * old state list to the new state list. 1559 */ 1560 if (refcnt == 0) { 1561 if (old_state != arc_anon && old_state != arc_l2c_only) { 1562 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx); 1563 uint64_t *size = &old_state->arcs_lsize[buftype]; 1564 1565 if (use_mutex) 1566 mutex_enter(&old_state->arcs_mtx); 1567 1568 ASSERT(HDR_HAS_L1HDR(hdr)); 1569 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1570 list_remove(&old_state->arcs_list[buftype], hdr); 1571 1572 /* 1573 * If prefetching out of the ghost cache, 1574 * we will have a non-zero datacnt. 1575 */ 1576 if (GHOST_STATE(old_state) && datacnt == 0) { 1577 /* ghost elements have a ghost size */ 1578 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1579 from_delta = hdr->b_size; 1580 } 1581 ASSERT3U(*size, >=, from_delta); 1582 atomic_add_64(size, -from_delta); 1583 1584 if (use_mutex) 1585 mutex_exit(&old_state->arcs_mtx); 1586 } 1587 if (new_state != arc_anon && new_state != arc_l2c_only) { 1588 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx); 1589 uint64_t *size = &new_state->arcs_lsize[buftype]; 1590 1591 /* 1592 * An L1 header always exists here, since if we're 1593 * moving to some L1-cached state (i.e. not l2c_only or 1594 * anonymous), we realloc the header to add an L1hdr 1595 * beforehand. 1596 */ 1597 ASSERT(HDR_HAS_L1HDR(hdr)); 1598 if (use_mutex) 1599 mutex_enter(&new_state->arcs_mtx); 1600 1601 list_insert_head(&new_state->arcs_list[buftype], hdr); 1602 1603 /* ghost elements have a ghost size */ 1604 if (GHOST_STATE(new_state)) { 1605 ASSERT0(datacnt); 1606 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1607 to_delta = hdr->b_size; 1608 } 1609 atomic_add_64(size, to_delta); 1610 1611 if (use_mutex) 1612 mutex_exit(&new_state->arcs_mtx); 1613 } 1614 } 1615 1616 ASSERT(!BUF_EMPTY(hdr)); 1617 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1618 buf_hash_remove(hdr); 1619 1620 /* adjust state sizes (ignore arc_l2c_only) */ 1621 if (to_delta && new_state != arc_l2c_only) 1622 atomic_add_64(&new_state->arcs_size, to_delta); 1623 if (from_delta && old_state != arc_l2c_only) { 1624 ASSERT3U(old_state->arcs_size, >=, from_delta); 1625 atomic_add_64(&old_state->arcs_size, -from_delta); 1626 } 1627 if (HDR_HAS_L1HDR(hdr)) 1628 hdr->b_l1hdr.b_state = new_state; 1629 1630 /* 1631 * L2 headers should never be on the L2 state list since they don't 1632 * have L1 headers allocated. 1633 */ 1634 ASSERT(list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1635 list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1636 } 1637 1638 void 1639 arc_space_consume(uint64_t space, arc_space_type_t type) 1640 { 1641 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1642 1643 switch (type) { 1644 case ARC_SPACE_DATA: 1645 ARCSTAT_INCR(arcstat_data_size, space); 1646 break; 1647 case ARC_SPACE_META: 1648 ARCSTAT_INCR(arcstat_metadata_size, space); 1649 break; 1650 case ARC_SPACE_OTHER: 1651 ARCSTAT_INCR(arcstat_other_size, space); 1652 break; 1653 case ARC_SPACE_HDRS: 1654 ARCSTAT_INCR(arcstat_hdr_size, space); 1655 break; 1656 case ARC_SPACE_L2HDRS: 1657 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1658 break; 1659 } 1660 1661 if (type != ARC_SPACE_DATA) 1662 ARCSTAT_INCR(arcstat_meta_used, space); 1663 1664 atomic_add_64(&arc_size, space); 1665 } 1666 1667 void 1668 arc_space_return(uint64_t space, arc_space_type_t type) 1669 { 1670 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1671 1672 switch (type) { 1673 case ARC_SPACE_DATA: 1674 ARCSTAT_INCR(arcstat_data_size, -space); 1675 break; 1676 case ARC_SPACE_META: 1677 ARCSTAT_INCR(arcstat_metadata_size, -space); 1678 break; 1679 case ARC_SPACE_OTHER: 1680 ARCSTAT_INCR(arcstat_other_size, -space); 1681 break; 1682 case ARC_SPACE_HDRS: 1683 ARCSTAT_INCR(arcstat_hdr_size, -space); 1684 break; 1685 case ARC_SPACE_L2HDRS: 1686 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1687 break; 1688 } 1689 1690 if (type != ARC_SPACE_DATA) { 1691 ASSERT(arc_meta_used >= space); 1692 if (arc_meta_max < arc_meta_used) 1693 arc_meta_max = arc_meta_used; 1694 ARCSTAT_INCR(arcstat_meta_used, -space); 1695 } 1696 1697 ASSERT(arc_size >= space); 1698 atomic_add_64(&arc_size, -space); 1699 } 1700 1701 arc_buf_t * 1702 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1703 { 1704 arc_buf_hdr_t *hdr; 1705 arc_buf_t *buf; 1706 1707 ASSERT3U(size, >, 0); 1708 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1709 ASSERT(BUF_EMPTY(hdr)); 1710 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1711 hdr->b_size = size; 1712 hdr->b_spa = spa_load_guid(spa); 1713 1714 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1715 buf->b_hdr = hdr; 1716 buf->b_data = NULL; 1717 buf->b_efunc = NULL; 1718 buf->b_private = NULL; 1719 buf->b_next = NULL; 1720 1721 hdr->b_flags = arc_bufc_to_flags(type); 1722 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1723 1724 hdr->b_l1hdr.b_buf = buf; 1725 hdr->b_l1hdr.b_state = arc_anon; 1726 hdr->b_l1hdr.b_arc_access = 0; 1727 hdr->b_l1hdr.b_datacnt = 1; 1728 1729 arc_get_data_buf(buf); 1730 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1731 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1732 1733 return (buf); 1734 } 1735 1736 static char *arc_onloan_tag = "onloan"; 1737 1738 /* 1739 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 1740 * flight data by arc_tempreserve_space() until they are "returned". Loaned 1741 * buffers must be returned to the arc before they can be used by the DMU or 1742 * freed. 1743 */ 1744 arc_buf_t * 1745 arc_loan_buf(spa_t *spa, int size) 1746 { 1747 arc_buf_t *buf; 1748 1749 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 1750 1751 atomic_add_64(&arc_loaned_bytes, size); 1752 return (buf); 1753 } 1754 1755 /* 1756 * Return a loaned arc buffer to the arc. 1757 */ 1758 void 1759 arc_return_buf(arc_buf_t *buf, void *tag) 1760 { 1761 arc_buf_hdr_t *hdr = buf->b_hdr; 1762 1763 ASSERT(buf->b_data != NULL); 1764 ASSERT(HDR_HAS_L1HDR(hdr)); 1765 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1766 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1767 1768 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 1769 } 1770 1771 /* Detach an arc_buf from a dbuf (tag) */ 1772 void 1773 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 1774 { 1775 arc_buf_hdr_t *hdr = buf->b_hdr; 1776 1777 ASSERT(buf->b_data != NULL); 1778 ASSERT(HDR_HAS_L1HDR(hdr)); 1779 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 1780 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 1781 buf->b_efunc = NULL; 1782 buf->b_private = NULL; 1783 1784 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 1785 } 1786 1787 static arc_buf_t * 1788 arc_buf_clone(arc_buf_t *from) 1789 { 1790 arc_buf_t *buf; 1791 arc_buf_hdr_t *hdr = from->b_hdr; 1792 uint64_t size = hdr->b_size; 1793 1794 ASSERT(HDR_HAS_L1HDR(hdr)); 1795 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 1796 1797 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1798 buf->b_hdr = hdr; 1799 buf->b_data = NULL; 1800 buf->b_efunc = NULL; 1801 buf->b_private = NULL; 1802 buf->b_next = hdr->b_l1hdr.b_buf; 1803 hdr->b_l1hdr.b_buf = buf; 1804 arc_get_data_buf(buf); 1805 bcopy(from->b_data, buf->b_data, size); 1806 1807 /* 1808 * This buffer already exists in the arc so create a duplicate 1809 * copy for the caller. If the buffer is associated with user data 1810 * then track the size and number of duplicates. These stats will be 1811 * updated as duplicate buffers are created and destroyed. 1812 */ 1813 if (HDR_ISTYPE_DATA(hdr)) { 1814 ARCSTAT_BUMP(arcstat_duplicate_buffers); 1815 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 1816 } 1817 hdr->b_l1hdr.b_datacnt += 1; 1818 return (buf); 1819 } 1820 1821 void 1822 arc_buf_add_ref(arc_buf_t *buf, void* tag) 1823 { 1824 arc_buf_hdr_t *hdr; 1825 kmutex_t *hash_lock; 1826 1827 /* 1828 * Check to see if this buffer is evicted. Callers 1829 * must verify b_data != NULL to know if the add_ref 1830 * was successful. 1831 */ 1832 mutex_enter(&buf->b_evict_lock); 1833 if (buf->b_data == NULL) { 1834 mutex_exit(&buf->b_evict_lock); 1835 return; 1836 } 1837 hash_lock = HDR_LOCK(buf->b_hdr); 1838 mutex_enter(hash_lock); 1839 hdr = buf->b_hdr; 1840 ASSERT(HDR_HAS_L1HDR(hdr)); 1841 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 1842 mutex_exit(&buf->b_evict_lock); 1843 1844 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 1845 hdr->b_l1hdr.b_state == arc_mfu); 1846 1847 add_reference(hdr, hash_lock, tag); 1848 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 1849 arc_access(hdr, hash_lock); 1850 mutex_exit(hash_lock); 1851 ARCSTAT_BUMP(arcstat_hits); 1852 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 1853 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 1854 data, metadata, hits); 1855 } 1856 1857 /* 1858 * Free the arc data buffer. If it is an l2arc write in progress, 1859 * the buffer is placed on l2arc_free_on_write to be freed later. 1860 */ 1861 static void 1862 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 1863 { 1864 arc_buf_hdr_t *hdr = buf->b_hdr; 1865 1866 if (HDR_L2_WRITING(hdr)) { 1867 l2arc_data_free_t *df; 1868 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 1869 df->l2df_data = buf->b_data; 1870 df->l2df_size = hdr->b_size; 1871 df->l2df_func = free_func; 1872 mutex_enter(&l2arc_free_on_write_mtx); 1873 list_insert_head(l2arc_free_on_write, df); 1874 mutex_exit(&l2arc_free_on_write_mtx); 1875 ARCSTAT_BUMP(arcstat_l2_free_on_write); 1876 } else { 1877 free_func(buf->b_data, hdr->b_size); 1878 } 1879 } 1880 1881 /* 1882 * Free up buf->b_data and if 'remove' is set, then pull the 1883 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 1884 */ 1885 static void 1886 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) 1887 { 1888 arc_buf_t **bufp; 1889 1890 /* free up data associated with the buf */ 1891 if (buf->b_data != NULL) { 1892 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 1893 uint64_t size = buf->b_hdr->b_size; 1894 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 1895 1896 arc_cksum_verify(buf); 1897 arc_buf_unwatch(buf); 1898 1899 if (!recycle) { 1900 if (type == ARC_BUFC_METADATA) { 1901 arc_buf_data_free(buf, zio_buf_free); 1902 arc_space_return(size, ARC_SPACE_META); 1903 } else { 1904 ASSERT(type == ARC_BUFC_DATA); 1905 arc_buf_data_free(buf, zio_data_buf_free); 1906 arc_space_return(size, ARC_SPACE_DATA); 1907 } 1908 } 1909 if (list_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 1910 uint64_t *cnt = &state->arcs_lsize[type]; 1911 1912 ASSERT(refcount_is_zero( 1913 &buf->b_hdr->b_l1hdr.b_refcnt)); 1914 ASSERT(state != arc_anon && state != arc_l2c_only); 1915 1916 ASSERT3U(*cnt, >=, size); 1917 atomic_add_64(cnt, -size); 1918 } 1919 ASSERT3U(state->arcs_size, >=, size); 1920 atomic_add_64(&state->arcs_size, -size); 1921 buf->b_data = NULL; 1922 1923 /* 1924 * If we're destroying a duplicate buffer make sure 1925 * that the appropriate statistics are updated. 1926 */ 1927 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 1928 HDR_ISTYPE_DATA(buf->b_hdr)) { 1929 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 1930 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 1931 } 1932 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 1933 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 1934 } 1935 1936 /* only remove the buf if requested */ 1937 if (!remove) 1938 return; 1939 1940 /* remove the buf from the hdr list */ 1941 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 1942 bufp = &(*bufp)->b_next) 1943 continue; 1944 *bufp = buf->b_next; 1945 buf->b_next = NULL; 1946 1947 ASSERT(buf->b_efunc == NULL); 1948 1949 /* clean up the buf */ 1950 buf->b_hdr = NULL; 1951 kmem_cache_free(buf_cache, buf); 1952 } 1953 1954 static void 1955 arc_hdr_destroy(arc_buf_hdr_t *hdr) 1956 { 1957 if (HDR_HAS_L1HDR(hdr)) { 1958 ASSERT(hdr->b_l1hdr.b_buf == NULL || 1959 hdr->b_l1hdr.b_datacnt > 0); 1960 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1961 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 1962 } 1963 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1964 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1965 1966 if (HDR_HAS_L2HDR(hdr)) { 1967 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 1968 boolean_t buflist_held = MUTEX_HELD(&l2hdr->b_dev->l2ad_mtx); 1969 1970 if (!buflist_held) { 1971 mutex_enter(&l2hdr->b_dev->l2ad_mtx); 1972 l2hdr = &hdr->b_l2hdr; 1973 } 1974 1975 list_remove(&l2hdr->b_dev->l2ad_buflist, hdr); 1976 1977 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 1978 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 1979 1980 if (!buflist_held) 1981 mutex_exit(&l2hdr->b_dev->l2ad_mtx); 1982 1983 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 1984 } 1985 1986 if (!BUF_EMPTY(hdr)) 1987 buf_discard_identity(hdr); 1988 1989 if (hdr->b_freeze_cksum != NULL) { 1990 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1991 hdr->b_freeze_cksum = NULL; 1992 } 1993 1994 if (HDR_HAS_L1HDR(hdr)) { 1995 while (hdr->b_l1hdr.b_buf) { 1996 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 1997 1998 if (buf->b_efunc != NULL) { 1999 mutex_enter(&arc_eviction_mtx); 2000 mutex_enter(&buf->b_evict_lock); 2001 ASSERT(buf->b_hdr != NULL); 2002 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2003 FALSE); 2004 hdr->b_l1hdr.b_buf = buf->b_next; 2005 buf->b_hdr = &arc_eviction_hdr; 2006 buf->b_next = arc_eviction_list; 2007 arc_eviction_list = buf; 2008 mutex_exit(&buf->b_evict_lock); 2009 mutex_exit(&arc_eviction_mtx); 2010 } else { 2011 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2012 TRUE); 2013 } 2014 } 2015 #ifdef ZFS_DEBUG 2016 if (hdr->b_l1hdr.b_thawed != NULL) { 2017 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2018 hdr->b_l1hdr.b_thawed = NULL; 2019 } 2020 #endif 2021 } 2022 2023 ASSERT3P(hdr->b_hash_next, ==, NULL); 2024 if (HDR_HAS_L1HDR(hdr)) { 2025 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 2026 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2027 kmem_cache_free(hdr_full_cache, hdr); 2028 } else { 2029 kmem_cache_free(hdr_l2only_cache, hdr); 2030 } 2031 } 2032 2033 void 2034 arc_buf_free(arc_buf_t *buf, void *tag) 2035 { 2036 arc_buf_hdr_t *hdr = buf->b_hdr; 2037 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2038 2039 ASSERT(buf->b_efunc == NULL); 2040 ASSERT(buf->b_data != NULL); 2041 2042 if (hashed) { 2043 kmutex_t *hash_lock = HDR_LOCK(hdr); 2044 2045 mutex_enter(hash_lock); 2046 hdr = buf->b_hdr; 2047 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2048 2049 (void) remove_reference(hdr, hash_lock, tag); 2050 if (hdr->b_l1hdr.b_datacnt > 1) { 2051 arc_buf_destroy(buf, FALSE, TRUE); 2052 } else { 2053 ASSERT(buf == hdr->b_l1hdr.b_buf); 2054 ASSERT(buf->b_efunc == NULL); 2055 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2056 } 2057 mutex_exit(hash_lock); 2058 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2059 int destroy_hdr; 2060 /* 2061 * We are in the middle of an async write. Don't destroy 2062 * this buffer unless the write completes before we finish 2063 * decrementing the reference count. 2064 */ 2065 mutex_enter(&arc_eviction_mtx); 2066 (void) remove_reference(hdr, NULL, tag); 2067 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2068 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2069 mutex_exit(&arc_eviction_mtx); 2070 if (destroy_hdr) 2071 arc_hdr_destroy(hdr); 2072 } else { 2073 if (remove_reference(hdr, NULL, tag) > 0) 2074 arc_buf_destroy(buf, FALSE, TRUE); 2075 else 2076 arc_hdr_destroy(hdr); 2077 } 2078 } 2079 2080 boolean_t 2081 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2082 { 2083 arc_buf_hdr_t *hdr = buf->b_hdr; 2084 kmutex_t *hash_lock = HDR_LOCK(hdr); 2085 boolean_t no_callback = (buf->b_efunc == NULL); 2086 2087 if (hdr->b_l1hdr.b_state == arc_anon) { 2088 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2089 arc_buf_free(buf, tag); 2090 return (no_callback); 2091 } 2092 2093 mutex_enter(hash_lock); 2094 hdr = buf->b_hdr; 2095 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2096 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2097 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2098 ASSERT(buf->b_data != NULL); 2099 2100 (void) remove_reference(hdr, hash_lock, tag); 2101 if (hdr->b_l1hdr.b_datacnt > 1) { 2102 if (no_callback) 2103 arc_buf_destroy(buf, FALSE, TRUE); 2104 } else if (no_callback) { 2105 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2106 ASSERT(buf->b_efunc == NULL); 2107 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2108 } 2109 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2110 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2111 mutex_exit(hash_lock); 2112 return (no_callback); 2113 } 2114 2115 int32_t 2116 arc_buf_size(arc_buf_t *buf) 2117 { 2118 return (buf->b_hdr->b_size); 2119 } 2120 2121 /* 2122 * Called from the DMU to determine if the current buffer should be 2123 * evicted. In order to ensure proper locking, the eviction must be initiated 2124 * from the DMU. Return true if the buffer is associated with user data and 2125 * duplicate buffers still exist. 2126 */ 2127 boolean_t 2128 arc_buf_eviction_needed(arc_buf_t *buf) 2129 { 2130 arc_buf_hdr_t *hdr; 2131 boolean_t evict_needed = B_FALSE; 2132 2133 if (zfs_disable_dup_eviction) 2134 return (B_FALSE); 2135 2136 mutex_enter(&buf->b_evict_lock); 2137 hdr = buf->b_hdr; 2138 if (hdr == NULL) { 2139 /* 2140 * We are in arc_do_user_evicts(); let that function 2141 * perform the eviction. 2142 */ 2143 ASSERT(buf->b_data == NULL); 2144 mutex_exit(&buf->b_evict_lock); 2145 return (B_FALSE); 2146 } else if (buf->b_data == NULL) { 2147 /* 2148 * We have already been added to the arc eviction list; 2149 * recommend eviction. 2150 */ 2151 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2152 mutex_exit(&buf->b_evict_lock); 2153 return (B_TRUE); 2154 } 2155 2156 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2157 evict_needed = B_TRUE; 2158 2159 mutex_exit(&buf->b_evict_lock); 2160 return (evict_needed); 2161 } 2162 2163 /* 2164 * Evict buffers from list until we've removed the specified number of 2165 * bytes. Move the removed buffers to the appropriate evict state. 2166 * If the recycle flag is set, then attempt to "recycle" a buffer: 2167 * - look for a buffer to evict that is `bytes' long. 2168 * - return the data block from this buffer rather than freeing it. 2169 * This flag is used by callers that are trying to make space for a 2170 * new buffer in a full arc cache. 2171 * 2172 * This function makes a "best effort". It skips over any buffers 2173 * it can't get a hash_lock on, and so may not catch all candidates. 2174 * It may also return without evicting as much space as requested. 2175 */ 2176 static void * 2177 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 2178 arc_buf_contents_t type) 2179 { 2180 arc_state_t *evicted_state; 2181 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 2182 arc_buf_hdr_t *hdr, *hdr_prev = NULL; 2183 kmutex_t *hash_lock; 2184 boolean_t have_lock; 2185 void *stolen = NULL; 2186 arc_buf_hdr_t marker = { 0 }; 2187 int count = 0; 2188 2189 ASSERT(state == arc_mru || state == arc_mfu); 2190 2191 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2192 2193 /* 2194 * The ghost list lock must be acquired first in order to prevent 2195 * a 3 party deadlock: 2196 * 2197 * - arc_evict_ghost acquires arc_*_ghost->arcs_mtx, followed by 2198 * l2ad_mtx in arc_hdr_realloc 2199 * - l2arc_write_buffers acquires l2ad_mtx, followed by arc_*->arcs_mtx 2200 * - arc_evict acquires arc_*_ghost->arcs_mtx, followed by 2201 * arc_*_ghost->arcs_mtx and forms a deadlock cycle. 2202 * 2203 * This situation is avoided by acquiring the ghost list lock first. 2204 */ 2205 mutex_enter(&evicted_state->arcs_mtx); 2206 mutex_enter(&state->arcs_mtx); 2207 2208 /* 2209 * Decide which "type" (data vs metadata) to recycle from. 2210 * 2211 * If we are over the metadata limit, recycle from metadata. 2212 * If we are under the metadata minimum, recycle from data. 2213 * Otherwise, recycle from whichever type has the oldest (least 2214 * recently accessed) header. 2215 */ 2216 if (recycle) { 2217 arc_buf_hdr_t *data_hdr = 2218 list_tail(&state->arcs_list[ARC_BUFC_DATA]); 2219 arc_buf_hdr_t *metadata_hdr = 2220 list_tail(&state->arcs_list[ARC_BUFC_METADATA]); 2221 arc_buf_contents_t realtype; 2222 2223 if (data_hdr == NULL) { 2224 realtype = ARC_BUFC_METADATA; 2225 } else if (metadata_hdr == NULL) { 2226 realtype = ARC_BUFC_DATA; 2227 } else if (arc_meta_used >= arc_meta_limit) { 2228 realtype = ARC_BUFC_METADATA; 2229 } else if (arc_meta_used <= arc_meta_min) { 2230 realtype = ARC_BUFC_DATA; 2231 } else if (HDR_HAS_L1HDR(data_hdr) && 2232 HDR_HAS_L1HDR(metadata_hdr) && 2233 data_hdr->b_l1hdr.b_arc_access < 2234 metadata_hdr->b_l1hdr.b_arc_access) { 2235 realtype = ARC_BUFC_DATA; 2236 } else { 2237 realtype = ARC_BUFC_METADATA; 2238 } 2239 if (realtype != type) { 2240 /* 2241 * If we want to evict from a different list, 2242 * we can not recycle, because DATA vs METADATA 2243 * buffers are segregated into different kmem 2244 * caches (and vmem arenas). 2245 */ 2246 type = realtype; 2247 recycle = B_FALSE; 2248 } 2249 } 2250 2251 list_t *list = &state->arcs_list[type]; 2252 2253 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2254 hdr_prev = list_prev(list, hdr); 2255 /* prefetch buffers have a minimum lifespan */ 2256 if (HDR_IO_IN_PROGRESS(hdr) || 2257 (spa && hdr->b_spa != spa) || 2258 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2259 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2260 arc_min_prefetch_lifespan)) { 2261 skipped++; 2262 continue; 2263 } 2264 /* "lookahead" for better eviction candidate */ 2265 if (recycle && hdr->b_size != bytes && 2266 hdr_prev && hdr_prev->b_size == bytes) 2267 continue; 2268 2269 /* ignore markers */ 2270 if (hdr->b_spa == 0) 2271 continue; 2272 2273 /* 2274 * It may take a long time to evict all the bufs requested. 2275 * To avoid blocking all arc activity, periodically drop 2276 * the arcs_mtx and give other threads a chance to run 2277 * before reacquiring the lock. 2278 * 2279 * If we are looking for a buffer to recycle, we are in 2280 * the hot code path, so don't sleep. 2281 */ 2282 if (!recycle && count++ > arc_evict_iterations) { 2283 list_insert_after(list, hdr, &marker); 2284 mutex_exit(&state->arcs_mtx); 2285 mutex_exit(&evicted_state->arcs_mtx); 2286 kpreempt(KPREEMPT_SYNC); 2287 mutex_enter(&evicted_state->arcs_mtx); 2288 mutex_enter(&state->arcs_mtx); 2289 hdr_prev = list_prev(list, &marker); 2290 list_remove(list, &marker); 2291 count = 0; 2292 continue; 2293 } 2294 2295 hash_lock = HDR_LOCK(hdr); 2296 have_lock = MUTEX_HELD(hash_lock); 2297 if (have_lock || mutex_tryenter(hash_lock)) { 2298 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2299 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2300 while (hdr->b_l1hdr.b_buf) { 2301 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2302 if (!mutex_tryenter(&buf->b_evict_lock)) { 2303 missed += 1; 2304 break; 2305 } 2306 if (buf->b_data != NULL) { 2307 bytes_evicted += hdr->b_size; 2308 if (recycle && 2309 arc_buf_type(hdr) == type && 2310 hdr->b_size == bytes && 2311 !HDR_L2_WRITING(hdr)) { 2312 stolen = buf->b_data; 2313 recycle = FALSE; 2314 } 2315 } 2316 if (buf->b_efunc != NULL) { 2317 mutex_enter(&arc_eviction_mtx); 2318 arc_buf_destroy(buf, 2319 buf->b_data == stolen, FALSE); 2320 hdr->b_l1hdr.b_buf = buf->b_next; 2321 buf->b_hdr = &arc_eviction_hdr; 2322 buf->b_next = arc_eviction_list; 2323 arc_eviction_list = buf; 2324 mutex_exit(&arc_eviction_mtx); 2325 mutex_exit(&buf->b_evict_lock); 2326 } else { 2327 mutex_exit(&buf->b_evict_lock); 2328 arc_buf_destroy(buf, 2329 buf->b_data == stolen, TRUE); 2330 } 2331 } 2332 2333 if (HDR_HAS_L2HDR(hdr)) { 2334 ARCSTAT_INCR(arcstat_evict_l2_cached, 2335 hdr->b_size); 2336 } else { 2337 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 2338 ARCSTAT_INCR(arcstat_evict_l2_eligible, 2339 hdr->b_size); 2340 } else { 2341 ARCSTAT_INCR( 2342 arcstat_evict_l2_ineligible, 2343 hdr->b_size); 2344 } 2345 } 2346 2347 if (hdr->b_l1hdr.b_datacnt == 0) { 2348 arc_change_state(evicted_state, hdr, hash_lock); 2349 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2350 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2351 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2352 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2353 } 2354 if (!have_lock) 2355 mutex_exit(hash_lock); 2356 if (bytes >= 0 && bytes_evicted >= bytes) 2357 break; 2358 } else { 2359 missed += 1; 2360 } 2361 } 2362 2363 mutex_exit(&state->arcs_mtx); 2364 mutex_exit(&evicted_state->arcs_mtx); 2365 2366 if (bytes_evicted < bytes) 2367 dprintf("only evicted %lld bytes from %x", 2368 (longlong_t)bytes_evicted, state); 2369 2370 if (skipped) 2371 ARCSTAT_INCR(arcstat_evict_skip, skipped); 2372 2373 if (missed) 2374 ARCSTAT_INCR(arcstat_mutex_miss, missed); 2375 2376 /* 2377 * Note: we have just evicted some data into the ghost state, 2378 * potentially putting the ghost size over the desired size. Rather 2379 * that evicting from the ghost list in this hot code path, leave 2380 * this chore to the arc_reclaim_thread(). 2381 */ 2382 2383 return (stolen); 2384 } 2385 2386 /* 2387 * Remove buffers from list until we've removed the specified number of 2388 * bytes. Destroy the buffers that are removed. 2389 */ 2390 static void 2391 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 2392 { 2393 arc_buf_hdr_t *hdr, *hdr_prev; 2394 arc_buf_hdr_t marker = { 0 }; 2395 list_t *list = &state->arcs_list[ARC_BUFC_DATA]; 2396 kmutex_t *hash_lock; 2397 uint64_t bytes_deleted = 0; 2398 uint64_t bufs_skipped = 0; 2399 int count = 0; 2400 2401 ASSERT(GHOST_STATE(state)); 2402 top: 2403 mutex_enter(&state->arcs_mtx); 2404 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2405 hdr_prev = list_prev(list, hdr); 2406 if (arc_buf_type(hdr) >= ARC_BUFC_NUMTYPES) 2407 panic("invalid hdr=%p", (void *)hdr); 2408 if (spa && hdr->b_spa != spa) 2409 continue; 2410 2411 /* ignore markers */ 2412 if (hdr->b_spa == 0) 2413 continue; 2414 2415 hash_lock = HDR_LOCK(hdr); 2416 /* caller may be trying to modify this buffer, skip it */ 2417 if (MUTEX_HELD(hash_lock)) 2418 continue; 2419 2420 /* 2421 * It may take a long time to evict all the bufs requested. 2422 * To avoid blocking all arc activity, periodically drop 2423 * the arcs_mtx and give other threads a chance to run 2424 * before reacquiring the lock. 2425 */ 2426 if (count++ > arc_evict_iterations) { 2427 list_insert_after(list, hdr, &marker); 2428 mutex_exit(&state->arcs_mtx); 2429 kpreempt(KPREEMPT_SYNC); 2430 mutex_enter(&state->arcs_mtx); 2431 hdr_prev = list_prev(list, &marker); 2432 list_remove(list, &marker); 2433 count = 0; 2434 continue; 2435 } 2436 if (mutex_tryenter(hash_lock)) { 2437 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2438 ASSERT(!HDR_HAS_L1HDR(hdr) || 2439 hdr->b_l1hdr.b_buf == NULL); 2440 ARCSTAT_BUMP(arcstat_deleted); 2441 bytes_deleted += hdr->b_size; 2442 2443 if (HDR_HAS_L2HDR(hdr)) { 2444 /* 2445 * This buffer is cached on the 2nd Level ARC; 2446 * don't destroy the header. 2447 */ 2448 arc_change_state(arc_l2c_only, hdr, hash_lock); 2449 /* 2450 * dropping from L1+L2 cached to L2-only, 2451 * realloc to remove the L1 header. 2452 */ 2453 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2454 hdr_l2only_cache); 2455 mutex_exit(hash_lock); 2456 } else { 2457 arc_change_state(arc_anon, hdr, hash_lock); 2458 mutex_exit(hash_lock); 2459 arc_hdr_destroy(hdr); 2460 } 2461 2462 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2463 if (bytes >= 0 && bytes_deleted >= bytes) 2464 break; 2465 } else if (bytes < 0) { 2466 /* 2467 * Insert a list marker and then wait for the 2468 * hash lock to become available. Once its 2469 * available, restart from where we left off. 2470 */ 2471 list_insert_after(list, hdr, &marker); 2472 mutex_exit(&state->arcs_mtx); 2473 mutex_enter(hash_lock); 2474 mutex_exit(hash_lock); 2475 mutex_enter(&state->arcs_mtx); 2476 hdr_prev = list_prev(list, &marker); 2477 list_remove(list, &marker); 2478 } else { 2479 bufs_skipped += 1; 2480 } 2481 2482 } 2483 mutex_exit(&state->arcs_mtx); 2484 2485 if (list == &state->arcs_list[ARC_BUFC_DATA] && 2486 (bytes < 0 || bytes_deleted < bytes)) { 2487 list = &state->arcs_list[ARC_BUFC_METADATA]; 2488 goto top; 2489 } 2490 2491 if (bufs_skipped) { 2492 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2493 ASSERT(bytes >= 0); 2494 } 2495 2496 if (bytes_deleted < bytes) 2497 dprintf("only deleted %lld bytes from %p", 2498 (longlong_t)bytes_deleted, state); 2499 } 2500 2501 static void 2502 arc_adjust(void) 2503 { 2504 int64_t adjustment, delta; 2505 2506 /* 2507 * Adjust MRU size 2508 */ 2509 2510 adjustment = MIN((int64_t)(arc_size - arc_c), 2511 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2512 arc_p)); 2513 2514 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2515 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2516 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA); 2517 adjustment -= delta; 2518 } 2519 2520 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2521 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2522 (void) arc_evict(arc_mru, NULL, delta, FALSE, 2523 ARC_BUFC_METADATA); 2524 } 2525 2526 /* 2527 * Adjust MFU size 2528 */ 2529 2530 adjustment = arc_size - arc_c; 2531 2532 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2533 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2534 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA); 2535 adjustment -= delta; 2536 } 2537 2538 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2539 int64_t delta = MIN(adjustment, 2540 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2541 (void) arc_evict(arc_mfu, NULL, delta, FALSE, 2542 ARC_BUFC_METADATA); 2543 } 2544 2545 /* 2546 * Adjust ghost lists 2547 */ 2548 2549 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2550 2551 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2552 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2553 arc_evict_ghost(arc_mru_ghost, NULL, delta); 2554 } 2555 2556 adjustment = 2557 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2558 2559 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2560 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2561 arc_evict_ghost(arc_mfu_ghost, NULL, delta); 2562 } 2563 } 2564 2565 static void 2566 arc_do_user_evicts(void) 2567 { 2568 mutex_enter(&arc_eviction_mtx); 2569 while (arc_eviction_list != NULL) { 2570 arc_buf_t *buf = arc_eviction_list; 2571 arc_eviction_list = buf->b_next; 2572 mutex_enter(&buf->b_evict_lock); 2573 buf->b_hdr = NULL; 2574 mutex_exit(&buf->b_evict_lock); 2575 mutex_exit(&arc_eviction_mtx); 2576 2577 if (buf->b_efunc != NULL) 2578 VERIFY0(buf->b_efunc(buf->b_private)); 2579 2580 buf->b_efunc = NULL; 2581 buf->b_private = NULL; 2582 kmem_cache_free(buf_cache, buf); 2583 mutex_enter(&arc_eviction_mtx); 2584 } 2585 mutex_exit(&arc_eviction_mtx); 2586 } 2587 2588 /* 2589 * Flush all *evictable* data from the cache for the given spa. 2590 * NOTE: this will not touch "active" (i.e. referenced) data. 2591 */ 2592 void 2593 arc_flush(spa_t *spa) 2594 { 2595 uint64_t guid = 0; 2596 2597 if (spa != NULL) 2598 guid = spa_load_guid(spa); 2599 2600 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) { 2601 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 2602 if (spa != NULL) 2603 break; 2604 } 2605 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) { 2606 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 2607 if (spa != NULL) 2608 break; 2609 } 2610 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) { 2611 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 2612 if (spa != NULL) 2613 break; 2614 } 2615 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) { 2616 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 2617 if (spa != NULL) 2618 break; 2619 } 2620 2621 arc_evict_ghost(arc_mru_ghost, guid, -1); 2622 arc_evict_ghost(arc_mfu_ghost, guid, -1); 2623 2624 mutex_enter(&arc_reclaim_thr_lock); 2625 arc_do_user_evicts(); 2626 mutex_exit(&arc_reclaim_thr_lock); 2627 ASSERT(spa || arc_eviction_list == NULL); 2628 } 2629 2630 void 2631 arc_shrink(int64_t to_free) 2632 { 2633 if (arc_c > arc_c_min) { 2634 2635 if (arc_c > arc_c_min + to_free) 2636 atomic_add_64(&arc_c, -to_free); 2637 else 2638 arc_c = arc_c_min; 2639 2640 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 2641 if (arc_c > arc_size) 2642 arc_c = MAX(arc_size, arc_c_min); 2643 if (arc_p > arc_c) 2644 arc_p = (arc_c >> 1); 2645 ASSERT(arc_c >= arc_c_min); 2646 ASSERT((int64_t)arc_p >= 0); 2647 } 2648 2649 if (arc_size > arc_c) 2650 arc_adjust(); 2651 } 2652 2653 typedef enum free_memory_reason_t { 2654 FMR_UNKNOWN, 2655 FMR_NEEDFREE, 2656 FMR_LOTSFREE, 2657 FMR_SWAPFS_MINFREE, 2658 FMR_PAGES_PP_MAXIMUM, 2659 FMR_HEAP_ARENA, 2660 FMR_ZIO_ARENA, 2661 } free_memory_reason_t; 2662 2663 int64_t last_free_memory; 2664 free_memory_reason_t last_free_reason; 2665 2666 /* 2667 * Additional reserve of pages for pp_reserve. 2668 */ 2669 int64_t arc_pages_pp_reserve = 64; 2670 2671 /* 2672 * Additional reserve of pages for swapfs. 2673 */ 2674 int64_t arc_swapfs_reserve = 64; 2675 2676 /* 2677 * Return the amount of memory that can be consumed before reclaim will be 2678 * needed. Positive if there is sufficient free memory, negative indicates 2679 * the amount of memory that needs to be freed up. 2680 */ 2681 static int64_t 2682 arc_available_memory(void) 2683 { 2684 int64_t lowest = INT64_MAX; 2685 int64_t n; 2686 free_memory_reason_t r = FMR_UNKNOWN; 2687 2688 #ifdef _KERNEL 2689 if (needfree > 0) { 2690 n = PAGESIZE * (-needfree); 2691 if (n < lowest) { 2692 lowest = n; 2693 r = FMR_NEEDFREE; 2694 } 2695 } 2696 2697 /* 2698 * check that we're out of range of the pageout scanner. It starts to 2699 * schedule paging if freemem is less than lotsfree and needfree. 2700 * lotsfree is the high-water mark for pageout, and needfree is the 2701 * number of needed free pages. We add extra pages here to make sure 2702 * the scanner doesn't start up while we're freeing memory. 2703 */ 2704 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 2705 if (n < lowest) { 2706 lowest = n; 2707 r = FMR_LOTSFREE; 2708 } 2709 2710 /* 2711 * check to make sure that swapfs has enough space so that anon 2712 * reservations can still succeed. anon_resvmem() checks that the 2713 * availrmem is greater than swapfs_minfree, and the number of reserved 2714 * swap pages. We also add a bit of extra here just to prevent 2715 * circumstances from getting really dire. 2716 */ 2717 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 2718 desfree - arc_swapfs_reserve); 2719 if (n < lowest) { 2720 lowest = n; 2721 r = FMR_SWAPFS_MINFREE; 2722 } 2723 2724 2725 /* 2726 * Check that we have enough availrmem that memory locking (e.g., via 2727 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 2728 * stores the number of pages that cannot be locked; when availrmem 2729 * drops below pages_pp_maximum, page locking mechanisms such as 2730 * page_pp_lock() will fail.) 2731 */ 2732 n = PAGESIZE * (availrmem - pages_pp_maximum - 2733 arc_pages_pp_reserve); 2734 if (n < lowest) { 2735 lowest = n; 2736 r = FMR_PAGES_PP_MAXIMUM; 2737 } 2738 2739 #if defined(__i386) 2740 /* 2741 * If we're on an i386 platform, it's possible that we'll exhaust the 2742 * kernel heap space before we ever run out of available physical 2743 * memory. Most checks of the size of the heap_area compare against 2744 * tune.t_minarmem, which is the minimum available real memory that we 2745 * can have in the system. However, this is generally fixed at 25 pages 2746 * which is so low that it's useless. In this comparison, we seek to 2747 * calculate the total heap-size, and reclaim if more than 3/4ths of the 2748 * heap is allocated. (Or, in the calculation, if less than 1/4th is 2749 * free) 2750 */ 2751 n = vmem_size(heap_arena, VMEM_FREE) - 2752 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 2753 if (n < lowest) { 2754 lowest = n; 2755 r = FMR_HEAP_ARENA; 2756 } 2757 #endif 2758 2759 /* 2760 * If zio data pages are being allocated out of a separate heap segment, 2761 * then enforce that the size of available vmem for this arena remains 2762 * above about 1/16th free. 2763 * 2764 * Note: The 1/16th arena free requirement was put in place 2765 * to aggressively evict memory from the arc in order to avoid 2766 * memory fragmentation issues. 2767 */ 2768 if (zio_arena != NULL) { 2769 n = vmem_size(zio_arena, VMEM_FREE) - 2770 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 2771 if (n < lowest) { 2772 lowest = n; 2773 r = FMR_ZIO_ARENA; 2774 } 2775 } 2776 #else 2777 /* Every 100 calls, free a small amount */ 2778 if (spa_get_random(100) == 0) 2779 lowest = -1024; 2780 #endif 2781 2782 last_free_memory = lowest; 2783 last_free_reason = r; 2784 2785 return (lowest); 2786 } 2787 2788 2789 /* 2790 * Determine if the system is under memory pressure and is asking 2791 * to reclaim memory. A return value of TRUE indicates that the system 2792 * is under memory pressure and that the arc should adjust accordingly. 2793 */ 2794 static boolean_t 2795 arc_reclaim_needed(void) 2796 { 2797 return (arc_available_memory() < 0); 2798 } 2799 2800 static void 2801 arc_kmem_reap_now(void) 2802 { 2803 size_t i; 2804 kmem_cache_t *prev_cache = NULL; 2805 kmem_cache_t *prev_data_cache = NULL; 2806 extern kmem_cache_t *zio_buf_cache[]; 2807 extern kmem_cache_t *zio_data_buf_cache[]; 2808 extern kmem_cache_t *range_seg_cache; 2809 2810 #ifdef _KERNEL 2811 if (arc_meta_used >= arc_meta_limit) { 2812 /* 2813 * We are exceeding our meta-data cache limit. 2814 * Purge some DNLC entries to release holds on meta-data. 2815 */ 2816 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 2817 } 2818 #if defined(__i386) 2819 /* 2820 * Reclaim unused memory from all kmem caches. 2821 */ 2822 kmem_reap(); 2823 #endif 2824 #endif 2825 2826 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 2827 if (zio_buf_cache[i] != prev_cache) { 2828 prev_cache = zio_buf_cache[i]; 2829 kmem_cache_reap_now(zio_buf_cache[i]); 2830 } 2831 if (zio_data_buf_cache[i] != prev_data_cache) { 2832 prev_data_cache = zio_data_buf_cache[i]; 2833 kmem_cache_reap_now(zio_data_buf_cache[i]); 2834 } 2835 } 2836 kmem_cache_reap_now(buf_cache); 2837 kmem_cache_reap_now(hdr_full_cache); 2838 kmem_cache_reap_now(hdr_l2only_cache); 2839 kmem_cache_reap_now(range_seg_cache); 2840 2841 if (zio_arena != NULL) { 2842 /* 2843 * Ask the vmem arena to reclaim unused memory from its 2844 * quantum caches. 2845 */ 2846 vmem_qcache_reap(zio_arena); 2847 } 2848 } 2849 2850 static void 2851 arc_reclaim_thread(void) 2852 { 2853 clock_t growtime = 0; 2854 callb_cpr_t cpr; 2855 2856 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 2857 2858 mutex_enter(&arc_reclaim_thr_lock); 2859 while (arc_thread_exit == 0) { 2860 int64_t free_memory = arc_available_memory(); 2861 if (free_memory < 0) { 2862 2863 arc_no_grow = B_TRUE; 2864 arc_warm = B_TRUE; 2865 2866 /* 2867 * Wait at least zfs_grow_retry (default 60) seconds 2868 * before considering growing. 2869 */ 2870 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 2871 2872 arc_kmem_reap_now(); 2873 2874 /* 2875 * If we are still low on memory, shrink the ARC 2876 * so that we have arc_shrink_min free space. 2877 */ 2878 free_memory = arc_available_memory(); 2879 2880 int64_t to_free = 2881 (arc_c >> arc_shrink_shift) - free_memory; 2882 if (to_free > 0) { 2883 #ifdef _KERNEL 2884 to_free = MAX(to_free, ptob(needfree)); 2885 #endif 2886 arc_shrink(to_free); 2887 } 2888 } else if (free_memory < arc_c >> arc_no_grow_shift) { 2889 arc_no_grow = B_TRUE; 2890 } else if (ddi_get_lbolt() >= growtime) { 2891 arc_no_grow = B_FALSE; 2892 } 2893 2894 arc_adjust(); 2895 2896 if (arc_eviction_list != NULL) 2897 arc_do_user_evicts(); 2898 2899 /* 2900 * This is necessary in order for the mdb ::arc dcmd to 2901 * show up to date information. Since the ::arc command 2902 * does not call the kstat's update function, without 2903 * this call, the command may show stale stats for the 2904 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 2905 * with this change, the data might be up to 1 second 2906 * out of date; but that should suffice. The arc_state_t 2907 * structures can be queried directly if more accurate 2908 * information is needed. 2909 */ 2910 if (arc_ksp != NULL) 2911 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 2912 2913 /* block until needed, or one second, whichever is shorter */ 2914 CALLB_CPR_SAFE_BEGIN(&cpr); 2915 (void) cv_timedwait(&arc_reclaim_thr_cv, 2916 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz)); 2917 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 2918 } 2919 2920 arc_thread_exit = 0; 2921 cv_broadcast(&arc_reclaim_thr_cv); 2922 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 2923 thread_exit(); 2924 } 2925 2926 /* 2927 * Adapt arc info given the number of bytes we are trying to add and 2928 * the state that we are comming from. This function is only called 2929 * when we are adding new content to the cache. 2930 */ 2931 static void 2932 arc_adapt(int bytes, arc_state_t *state) 2933 { 2934 int mult; 2935 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 2936 2937 if (state == arc_l2c_only) 2938 return; 2939 2940 ASSERT(bytes > 0); 2941 /* 2942 * Adapt the target size of the MRU list: 2943 * - if we just hit in the MRU ghost list, then increase 2944 * the target size of the MRU list. 2945 * - if we just hit in the MFU ghost list, then increase 2946 * the target size of the MFU list by decreasing the 2947 * target size of the MRU list. 2948 */ 2949 if (state == arc_mru_ghost) { 2950 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 2951 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 2952 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 2953 2954 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 2955 } else if (state == arc_mfu_ghost) { 2956 uint64_t delta; 2957 2958 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 2959 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 2960 mult = MIN(mult, 10); 2961 2962 delta = MIN(bytes * mult, arc_p); 2963 arc_p = MAX(arc_p_min, arc_p - delta); 2964 } 2965 ASSERT((int64_t)arc_p >= 0); 2966 2967 if (arc_reclaim_needed()) { 2968 cv_signal(&arc_reclaim_thr_cv); 2969 return; 2970 } 2971 2972 if (arc_no_grow) 2973 return; 2974 2975 if (arc_c >= arc_c_max) 2976 return; 2977 2978 /* 2979 * If we're within (2 * maxblocksize) bytes of the target 2980 * cache size, increment the target cache size 2981 */ 2982 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 2983 atomic_add_64(&arc_c, (int64_t)bytes); 2984 if (arc_c > arc_c_max) 2985 arc_c = arc_c_max; 2986 else if (state == arc_anon) 2987 atomic_add_64(&arc_p, (int64_t)bytes); 2988 if (arc_p > arc_c) 2989 arc_p = arc_c; 2990 } 2991 ASSERT((int64_t)arc_p >= 0); 2992 } 2993 2994 /* 2995 * Check if the cache has reached its limits and eviction is required 2996 * prior to insert. 2997 */ 2998 static int 2999 arc_evict_needed(arc_buf_contents_t type) 3000 { 3001 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 3002 return (1); 3003 3004 if (arc_reclaim_needed()) 3005 return (1); 3006 3007 return (arc_size > arc_c); 3008 } 3009 3010 /* 3011 * The buffer, supplied as the first argument, needs a data block. 3012 * So, if we are at cache max, determine which cache should be victimized. 3013 * We have the following cases: 3014 * 3015 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 3016 * In this situation if we're out of space, but the resident size of the MFU is 3017 * under the limit, victimize the MFU cache to satisfy this insertion request. 3018 * 3019 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 3020 * Here, we've used up all of the available space for the MRU, so we need to 3021 * evict from our own cache instead. Evict from the set of resident MRU 3022 * entries. 3023 * 3024 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 3025 * c minus p represents the MFU space in the cache, since p is the size of the 3026 * cache that is dedicated to the MRU. In this situation there's still space on 3027 * the MFU side, so the MRU side needs to be victimized. 3028 * 3029 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 3030 * MFU's resident set is consuming more space than it has been allotted. In 3031 * this situation, we must victimize our own cache, the MFU, for this insertion. 3032 */ 3033 static void 3034 arc_get_data_buf(arc_buf_t *buf) 3035 { 3036 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3037 uint64_t size = buf->b_hdr->b_size; 3038 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3039 3040 arc_adapt(size, state); 3041 3042 /* 3043 * We have not yet reached cache maximum size, 3044 * just allocate a new buffer. 3045 */ 3046 if (!arc_evict_needed(type)) { 3047 if (type == ARC_BUFC_METADATA) { 3048 buf->b_data = zio_buf_alloc(size); 3049 arc_space_consume(size, ARC_SPACE_META); 3050 } else { 3051 ASSERT(type == ARC_BUFC_DATA); 3052 buf->b_data = zio_data_buf_alloc(size); 3053 arc_space_consume(size, ARC_SPACE_DATA); 3054 } 3055 goto out; 3056 } 3057 3058 /* 3059 * If we are prefetching from the mfu ghost list, this buffer 3060 * will end up on the mru list; so steal space from there. 3061 */ 3062 if (state == arc_mfu_ghost) 3063 state = HDR_PREFETCH(buf->b_hdr) ? arc_mru : arc_mfu; 3064 else if (state == arc_mru_ghost) 3065 state = arc_mru; 3066 3067 if (state == arc_mru || state == arc_anon) { 3068 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 3069 state = (arc_mfu->arcs_lsize[type] >= size && 3070 arc_p > mru_used) ? arc_mfu : arc_mru; 3071 } else { 3072 /* MFU cases */ 3073 uint64_t mfu_space = arc_c - arc_p; 3074 state = (arc_mru->arcs_lsize[type] >= size && 3075 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 3076 } 3077 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) { 3078 if (type == ARC_BUFC_METADATA) { 3079 buf->b_data = zio_buf_alloc(size); 3080 arc_space_consume(size, ARC_SPACE_META); 3081 } else { 3082 ASSERT(type == ARC_BUFC_DATA); 3083 buf->b_data = zio_data_buf_alloc(size); 3084 arc_space_consume(size, ARC_SPACE_DATA); 3085 } 3086 ARCSTAT_BUMP(arcstat_recycle_miss); 3087 } 3088 ASSERT(buf->b_data != NULL); 3089 out: 3090 /* 3091 * Update the state size. Note that ghost states have a 3092 * "ghost size" and so don't need to be updated. 3093 */ 3094 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3095 arc_buf_hdr_t *hdr = buf->b_hdr; 3096 3097 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_size, size); 3098 if (list_link_active(&hdr->b_l1hdr.b_arc_node)) { 3099 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3100 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3101 size); 3102 } 3103 /* 3104 * If we are growing the cache, and we are adding anonymous 3105 * data, and we have outgrown arc_p, update arc_p 3106 */ 3107 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3108 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 3109 arc_p = MIN(arc_c, arc_p + size); 3110 } 3111 } 3112 3113 /* 3114 * This routine is called whenever a buffer is accessed. 3115 * NOTE: the hash lock is dropped in this function. 3116 */ 3117 static void 3118 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3119 { 3120 clock_t now; 3121 3122 ASSERT(MUTEX_HELD(hash_lock)); 3123 ASSERT(HDR_HAS_L1HDR(hdr)); 3124 3125 if (hdr->b_l1hdr.b_state == arc_anon) { 3126 /* 3127 * This buffer is not in the cache, and does not 3128 * appear in our "ghost" list. Add the new buffer 3129 * to the MRU state. 3130 */ 3131 3132 ASSERT0(hdr->b_l1hdr.b_arc_access); 3133 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3134 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3135 arc_change_state(arc_mru, hdr, hash_lock); 3136 3137 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3138 now = ddi_get_lbolt(); 3139 3140 /* 3141 * If this buffer is here because of a prefetch, then either: 3142 * - clear the flag if this is a "referencing" read 3143 * (any subsequent access will bump this into the MFU state). 3144 * or 3145 * - move the buffer to the head of the list if this is 3146 * another prefetch (to make it less likely to be evicted). 3147 */ 3148 if (HDR_PREFETCH(hdr)) { 3149 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3150 ASSERT(list_link_active( 3151 &hdr->b_l1hdr.b_arc_node)); 3152 } else { 3153 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3154 ARCSTAT_BUMP(arcstat_mru_hits); 3155 } 3156 hdr->b_l1hdr.b_arc_access = now; 3157 return; 3158 } 3159 3160 /* 3161 * This buffer has been "accessed" only once so far, 3162 * but it is still in the cache. Move it to the MFU 3163 * state. 3164 */ 3165 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3166 /* 3167 * More than 125ms have passed since we 3168 * instantiated this buffer. Move it to the 3169 * most frequently used state. 3170 */ 3171 hdr->b_l1hdr.b_arc_access = now; 3172 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3173 arc_change_state(arc_mfu, hdr, hash_lock); 3174 } 3175 ARCSTAT_BUMP(arcstat_mru_hits); 3176 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3177 arc_state_t *new_state; 3178 /* 3179 * This buffer has been "accessed" recently, but 3180 * was evicted from the cache. Move it to the 3181 * MFU state. 3182 */ 3183 3184 if (HDR_PREFETCH(hdr)) { 3185 new_state = arc_mru; 3186 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3187 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3188 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3189 } else { 3190 new_state = arc_mfu; 3191 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3192 } 3193 3194 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3195 arc_change_state(new_state, hdr, hash_lock); 3196 3197 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3198 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3199 /* 3200 * This buffer has been accessed more than once and is 3201 * still in the cache. Keep it in the MFU state. 3202 * 3203 * NOTE: an add_reference() that occurred when we did 3204 * the arc_read() will have kicked this off the list. 3205 * If it was a prefetch, we will explicitly move it to 3206 * the head of the list now. 3207 */ 3208 if ((HDR_PREFETCH(hdr)) != 0) { 3209 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3210 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 3211 } 3212 ARCSTAT_BUMP(arcstat_mfu_hits); 3213 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3214 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3215 arc_state_t *new_state = arc_mfu; 3216 /* 3217 * This buffer has been accessed more than once but has 3218 * been evicted from the cache. Move it back to the 3219 * MFU state. 3220 */ 3221 3222 if (HDR_PREFETCH(hdr)) { 3223 /* 3224 * This is a prefetch access... 3225 * move this block back to the MRU state. 3226 */ 3227 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3228 new_state = arc_mru; 3229 } 3230 3231 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3232 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3233 arc_change_state(new_state, hdr, hash_lock); 3234 3235 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3236 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3237 /* 3238 * This buffer is on the 2nd Level ARC. 3239 */ 3240 3241 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3242 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3243 arc_change_state(arc_mfu, hdr, hash_lock); 3244 } else { 3245 ASSERT(!"invalid arc state"); 3246 } 3247 } 3248 3249 /* a generic arc_done_func_t which you can use */ 3250 /* ARGSUSED */ 3251 void 3252 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3253 { 3254 if (zio == NULL || zio->io_error == 0) 3255 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3256 VERIFY(arc_buf_remove_ref(buf, arg)); 3257 } 3258 3259 /* a generic arc_done_func_t */ 3260 void 3261 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3262 { 3263 arc_buf_t **bufp = arg; 3264 if (zio && zio->io_error) { 3265 VERIFY(arc_buf_remove_ref(buf, arg)); 3266 *bufp = NULL; 3267 } else { 3268 *bufp = buf; 3269 ASSERT(buf->b_data); 3270 } 3271 } 3272 3273 static void 3274 arc_read_done(zio_t *zio) 3275 { 3276 arc_buf_hdr_t *hdr; 3277 arc_buf_t *buf; 3278 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3279 kmutex_t *hash_lock = NULL; 3280 arc_callback_t *callback_list, *acb; 3281 int freeable = FALSE; 3282 3283 buf = zio->io_private; 3284 hdr = buf->b_hdr; 3285 3286 /* 3287 * The hdr was inserted into hash-table and removed from lists 3288 * prior to starting I/O. We should find this header, since 3289 * it's in the hash table, and it should be legit since it's 3290 * not possible to evict it during the I/O. The only possible 3291 * reason for it not to be found is if we were freed during the 3292 * read. 3293 */ 3294 if (HDR_IN_HASH_TABLE(hdr)) { 3295 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3296 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3297 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3298 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3299 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3300 3301 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3302 &hash_lock); 3303 3304 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3305 hash_lock == NULL) || 3306 (found == hdr && 3307 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3308 (found == hdr && HDR_L2_READING(hdr))); 3309 } 3310 3311 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3312 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3313 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3314 3315 /* byteswap if necessary */ 3316 callback_list = hdr->b_l1hdr.b_acb; 3317 ASSERT(callback_list != NULL); 3318 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3319 dmu_object_byteswap_t bswap = 3320 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3321 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3322 byteswap_uint64_array : 3323 dmu_ot_byteswap[bswap].ob_func; 3324 func(buf->b_data, hdr->b_size); 3325 } 3326 3327 arc_cksum_compute(buf, B_FALSE); 3328 arc_buf_watch(buf); 3329 3330 if (hash_lock && zio->io_error == 0 && 3331 hdr->b_l1hdr.b_state == arc_anon) { 3332 /* 3333 * Only call arc_access on anonymous buffers. This is because 3334 * if we've issued an I/O for an evicted buffer, we've already 3335 * called arc_access (to prevent any simultaneous readers from 3336 * getting confused). 3337 */ 3338 arc_access(hdr, hash_lock); 3339 } 3340 3341 /* create copies of the data buffer for the callers */ 3342 abuf = buf; 3343 for (acb = callback_list; acb; acb = acb->acb_next) { 3344 if (acb->acb_done) { 3345 if (abuf == NULL) { 3346 ARCSTAT_BUMP(arcstat_duplicate_reads); 3347 abuf = arc_buf_clone(buf); 3348 } 3349 acb->acb_buf = abuf; 3350 abuf = NULL; 3351 } 3352 } 3353 hdr->b_l1hdr.b_acb = NULL; 3354 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3355 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3356 if (abuf == buf) { 3357 ASSERT(buf->b_efunc == NULL); 3358 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3359 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3360 } 3361 3362 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3363 callback_list != NULL); 3364 3365 if (zio->io_error != 0) { 3366 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3367 if (hdr->b_l1hdr.b_state != arc_anon) 3368 arc_change_state(arc_anon, hdr, hash_lock); 3369 if (HDR_IN_HASH_TABLE(hdr)) 3370 buf_hash_remove(hdr); 3371 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3372 } 3373 3374 /* 3375 * Broadcast before we drop the hash_lock to avoid the possibility 3376 * that the hdr (and hence the cv) might be freed before we get to 3377 * the cv_broadcast(). 3378 */ 3379 cv_broadcast(&hdr->b_l1hdr.b_cv); 3380 3381 if (hash_lock != NULL) { 3382 mutex_exit(hash_lock); 3383 } else { 3384 /* 3385 * This block was freed while we waited for the read to 3386 * complete. It has been removed from the hash table and 3387 * moved to the anonymous state (so that it won't show up 3388 * in the cache). 3389 */ 3390 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3391 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3392 } 3393 3394 /* execute each callback and free its structure */ 3395 while ((acb = callback_list) != NULL) { 3396 if (acb->acb_done) 3397 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3398 3399 if (acb->acb_zio_dummy != NULL) { 3400 acb->acb_zio_dummy->io_error = zio->io_error; 3401 zio_nowait(acb->acb_zio_dummy); 3402 } 3403 3404 callback_list = acb->acb_next; 3405 kmem_free(acb, sizeof (arc_callback_t)); 3406 } 3407 3408 if (freeable) 3409 arc_hdr_destroy(hdr); 3410 } 3411 3412 /* 3413 * "Read" the block at the specified DVA (in bp) via the 3414 * cache. If the block is found in the cache, invoke the provided 3415 * callback immediately and return. Note that the `zio' parameter 3416 * in the callback will be NULL in this case, since no IO was 3417 * required. If the block is not in the cache pass the read request 3418 * on to the spa with a substitute callback function, so that the 3419 * requested block will be added to the cache. 3420 * 3421 * If a read request arrives for a block that has a read in-progress, 3422 * either wait for the in-progress read to complete (and return the 3423 * results); or, if this is a read with a "done" func, add a record 3424 * to the read to invoke the "done" func when the read completes, 3425 * and return; or just return. 3426 * 3427 * arc_read_done() will invoke all the requested "done" functions 3428 * for readers of this block. 3429 */ 3430 int 3431 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3432 void *private, zio_priority_t priority, int zio_flags, 3433 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3434 { 3435 arc_buf_hdr_t *hdr = NULL; 3436 arc_buf_t *buf = NULL; 3437 kmutex_t *hash_lock = NULL; 3438 zio_t *rzio; 3439 uint64_t guid = spa_load_guid(spa); 3440 3441 ASSERT(!BP_IS_EMBEDDED(bp) || 3442 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3443 3444 top: 3445 if (!BP_IS_EMBEDDED(bp)) { 3446 /* 3447 * Embedded BP's have no DVA and require no I/O to "read". 3448 * Create an anonymous arc buf to back it. 3449 */ 3450 hdr = buf_hash_find(guid, bp, &hash_lock); 3451 } 3452 3453 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 3454 3455 *arc_flags |= ARC_FLAG_CACHED; 3456 3457 if (HDR_IO_IN_PROGRESS(hdr)) { 3458 3459 if (*arc_flags & ARC_FLAG_WAIT) { 3460 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 3461 mutex_exit(hash_lock); 3462 goto top; 3463 } 3464 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3465 3466 if (done) { 3467 arc_callback_t *acb = NULL; 3468 3469 acb = kmem_zalloc(sizeof (arc_callback_t), 3470 KM_SLEEP); 3471 acb->acb_done = done; 3472 acb->acb_private = private; 3473 if (pio != NULL) 3474 acb->acb_zio_dummy = zio_null(pio, 3475 spa, NULL, NULL, NULL, zio_flags); 3476 3477 ASSERT(acb->acb_done != NULL); 3478 acb->acb_next = hdr->b_l1hdr.b_acb; 3479 hdr->b_l1hdr.b_acb = acb; 3480 add_reference(hdr, hash_lock, private); 3481 mutex_exit(hash_lock); 3482 return (0); 3483 } 3484 mutex_exit(hash_lock); 3485 return (0); 3486 } 3487 3488 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3489 hdr->b_l1hdr.b_state == arc_mfu); 3490 3491 if (done) { 3492 add_reference(hdr, hash_lock, private); 3493 /* 3494 * If this block is already in use, create a new 3495 * copy of the data so that we will be guaranteed 3496 * that arc_release() will always succeed. 3497 */ 3498 buf = hdr->b_l1hdr.b_buf; 3499 ASSERT(buf); 3500 ASSERT(buf->b_data); 3501 if (HDR_BUF_AVAILABLE(hdr)) { 3502 ASSERT(buf->b_efunc == NULL); 3503 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3504 } else { 3505 buf = arc_buf_clone(buf); 3506 } 3507 3508 } else if (*arc_flags & ARC_FLAG_PREFETCH && 3509 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3510 hdr->b_flags |= ARC_FLAG_PREFETCH; 3511 } 3512 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 3513 arc_access(hdr, hash_lock); 3514 if (*arc_flags & ARC_FLAG_L2CACHE) 3515 hdr->b_flags |= ARC_FLAG_L2CACHE; 3516 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3517 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3518 mutex_exit(hash_lock); 3519 ARCSTAT_BUMP(arcstat_hits); 3520 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 3521 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 3522 data, metadata, hits); 3523 3524 if (done) 3525 done(NULL, buf, private); 3526 } else { 3527 uint64_t size = BP_GET_LSIZE(bp); 3528 arc_callback_t *acb; 3529 vdev_t *vd = NULL; 3530 uint64_t addr = 0; 3531 boolean_t devw = B_FALSE; 3532 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 3533 int32_t b_asize = 0; 3534 3535 if (hdr == NULL) { 3536 /* this block is not in the cache */ 3537 arc_buf_hdr_t *exists = NULL; 3538 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 3539 buf = arc_buf_alloc(spa, size, private, type); 3540 hdr = buf->b_hdr; 3541 if (!BP_IS_EMBEDDED(bp)) { 3542 hdr->b_dva = *BP_IDENTITY(bp); 3543 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 3544 exists = buf_hash_insert(hdr, &hash_lock); 3545 } 3546 if (exists != NULL) { 3547 /* somebody beat us to the hash insert */ 3548 mutex_exit(hash_lock); 3549 buf_discard_identity(hdr); 3550 (void) arc_buf_remove_ref(buf, private); 3551 goto top; /* restart the IO request */ 3552 } 3553 3554 /* if this is a prefetch, we don't have a reference */ 3555 if (*arc_flags & ARC_FLAG_PREFETCH) { 3556 (void) remove_reference(hdr, hash_lock, 3557 private); 3558 hdr->b_flags |= ARC_FLAG_PREFETCH; 3559 } 3560 if (*arc_flags & ARC_FLAG_L2CACHE) 3561 hdr->b_flags |= ARC_FLAG_L2CACHE; 3562 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3563 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3564 if (BP_GET_LEVEL(bp) > 0) 3565 hdr->b_flags |= ARC_FLAG_INDIRECT; 3566 } else { 3567 /* 3568 * This block is in the ghost cache. If it was L2-only 3569 * (and thus didn't have an L1 hdr), we realloc the 3570 * header to add an L1 hdr. 3571 */ 3572 if (!HDR_HAS_L1HDR(hdr)) { 3573 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 3574 hdr_full_cache); 3575 } 3576 3577 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 3578 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3579 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3580 ASSERT(hdr->b_l1hdr.b_buf == NULL); 3581 3582 /* if this is a prefetch, we don't have a reference */ 3583 if (*arc_flags & ARC_FLAG_PREFETCH) 3584 hdr->b_flags |= ARC_FLAG_PREFETCH; 3585 else 3586 add_reference(hdr, hash_lock, private); 3587 if (*arc_flags & ARC_FLAG_L2CACHE) 3588 hdr->b_flags |= ARC_FLAG_L2CACHE; 3589 if (*arc_flags & ARC_FLAG_L2COMPRESS) 3590 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 3591 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 3592 buf->b_hdr = hdr; 3593 buf->b_data = NULL; 3594 buf->b_efunc = NULL; 3595 buf->b_private = NULL; 3596 buf->b_next = NULL; 3597 hdr->b_l1hdr.b_buf = buf; 3598 ASSERT0(hdr->b_l1hdr.b_datacnt); 3599 hdr->b_l1hdr.b_datacnt = 1; 3600 arc_get_data_buf(buf); 3601 arc_access(hdr, hash_lock); 3602 } 3603 3604 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 3605 3606 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 3607 acb->acb_done = done; 3608 acb->acb_private = private; 3609 3610 ASSERT(hdr->b_l1hdr.b_acb == NULL); 3611 hdr->b_l1hdr.b_acb = acb; 3612 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 3613 3614 if (HDR_HAS_L2HDR(hdr) && 3615 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 3616 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 3617 addr = hdr->b_l2hdr.b_daddr; 3618 b_compress = HDR_GET_COMPRESS(hdr); 3619 b_asize = hdr->b_l2hdr.b_asize; 3620 /* 3621 * Lock out device removal. 3622 */ 3623 if (vdev_is_dead(vd) || 3624 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 3625 vd = NULL; 3626 } 3627 3628 if (hash_lock != NULL) 3629 mutex_exit(hash_lock); 3630 3631 /* 3632 * At this point, we have a level 1 cache miss. Try again in 3633 * L2ARC if possible. 3634 */ 3635 ASSERT3U(hdr->b_size, ==, size); 3636 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 3637 uint64_t, size, zbookmark_phys_t *, zb); 3638 ARCSTAT_BUMP(arcstat_misses); 3639 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 3640 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 3641 data, metadata, misses); 3642 3643 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 3644 /* 3645 * Read from the L2ARC if the following are true: 3646 * 1. The L2ARC vdev was previously cached. 3647 * 2. This buffer still has L2ARC metadata. 3648 * 3. This buffer isn't currently writing to the L2ARC. 3649 * 4. The L2ARC entry wasn't evicted, which may 3650 * also have invalidated the vdev. 3651 * 5. This isn't prefetch and l2arc_noprefetch is set. 3652 */ 3653 if (HDR_HAS_L2HDR(hdr) && 3654 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 3655 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 3656 l2arc_read_callback_t *cb; 3657 3658 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 3659 ARCSTAT_BUMP(arcstat_l2_hits); 3660 3661 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 3662 KM_SLEEP); 3663 cb->l2rcb_buf = buf; 3664 cb->l2rcb_spa = spa; 3665 cb->l2rcb_bp = *bp; 3666 cb->l2rcb_zb = *zb; 3667 cb->l2rcb_flags = zio_flags; 3668 cb->l2rcb_compress = b_compress; 3669 3670 ASSERT(addr >= VDEV_LABEL_START_SIZE && 3671 addr + size < vd->vdev_psize - 3672 VDEV_LABEL_END_SIZE); 3673 3674 /* 3675 * l2arc read. The SCL_L2ARC lock will be 3676 * released by l2arc_read_done(). 3677 * Issue a null zio if the underlying buffer 3678 * was squashed to zero size by compression. 3679 */ 3680 if (b_compress == ZIO_COMPRESS_EMPTY) { 3681 rzio = zio_null(pio, spa, vd, 3682 l2arc_read_done, cb, 3683 zio_flags | ZIO_FLAG_DONT_CACHE | 3684 ZIO_FLAG_CANFAIL | 3685 ZIO_FLAG_DONT_PROPAGATE | 3686 ZIO_FLAG_DONT_RETRY); 3687 } else { 3688 rzio = zio_read_phys(pio, vd, addr, 3689 b_asize, buf->b_data, 3690 ZIO_CHECKSUM_OFF, 3691 l2arc_read_done, cb, priority, 3692 zio_flags | ZIO_FLAG_DONT_CACHE | 3693 ZIO_FLAG_CANFAIL | 3694 ZIO_FLAG_DONT_PROPAGATE | 3695 ZIO_FLAG_DONT_RETRY, B_FALSE); 3696 } 3697 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 3698 zio_t *, rzio); 3699 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 3700 3701 if (*arc_flags & ARC_FLAG_NOWAIT) { 3702 zio_nowait(rzio); 3703 return (0); 3704 } 3705 3706 ASSERT(*arc_flags & ARC_FLAG_WAIT); 3707 if (zio_wait(rzio) == 0) 3708 return (0); 3709 3710 /* l2arc read error; goto zio_read() */ 3711 } else { 3712 DTRACE_PROBE1(l2arc__miss, 3713 arc_buf_hdr_t *, hdr); 3714 ARCSTAT_BUMP(arcstat_l2_misses); 3715 if (HDR_L2_WRITING(hdr)) 3716 ARCSTAT_BUMP(arcstat_l2_rw_clash); 3717 spa_config_exit(spa, SCL_L2ARC, vd); 3718 } 3719 } else { 3720 if (vd != NULL) 3721 spa_config_exit(spa, SCL_L2ARC, vd); 3722 if (l2arc_ndev != 0) { 3723 DTRACE_PROBE1(l2arc__miss, 3724 arc_buf_hdr_t *, hdr); 3725 ARCSTAT_BUMP(arcstat_l2_misses); 3726 } 3727 } 3728 3729 rzio = zio_read(pio, spa, bp, buf->b_data, size, 3730 arc_read_done, buf, priority, zio_flags, zb); 3731 3732 if (*arc_flags & ARC_FLAG_WAIT) 3733 return (zio_wait(rzio)); 3734 3735 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3736 zio_nowait(rzio); 3737 } 3738 return (0); 3739 } 3740 3741 void 3742 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 3743 { 3744 ASSERT(buf->b_hdr != NULL); 3745 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 3746 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 3747 func == NULL); 3748 ASSERT(buf->b_efunc == NULL); 3749 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 3750 3751 buf->b_efunc = func; 3752 buf->b_private = private; 3753 } 3754 3755 /* 3756 * Notify the arc that a block was freed, and thus will never be used again. 3757 */ 3758 void 3759 arc_freed(spa_t *spa, const blkptr_t *bp) 3760 { 3761 arc_buf_hdr_t *hdr; 3762 kmutex_t *hash_lock; 3763 uint64_t guid = spa_load_guid(spa); 3764 3765 ASSERT(!BP_IS_EMBEDDED(bp)); 3766 3767 hdr = buf_hash_find(guid, bp, &hash_lock); 3768 if (hdr == NULL) 3769 return; 3770 if (HDR_BUF_AVAILABLE(hdr)) { 3771 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3772 add_reference(hdr, hash_lock, FTAG); 3773 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3774 mutex_exit(hash_lock); 3775 3776 arc_release(buf, FTAG); 3777 (void) arc_buf_remove_ref(buf, FTAG); 3778 } else { 3779 mutex_exit(hash_lock); 3780 } 3781 3782 } 3783 3784 /* 3785 * Clear the user eviction callback set by arc_set_callback(), first calling 3786 * it if it exists. Because the presence of a callback keeps an arc_buf cached 3787 * clearing the callback may result in the arc_buf being destroyed. However, 3788 * it will not result in the *last* arc_buf being destroyed, hence the data 3789 * will remain cached in the ARC. We make a copy of the arc buffer here so 3790 * that we can process the callback without holding any locks. 3791 * 3792 * It's possible that the callback is already in the process of being cleared 3793 * by another thread. In this case we can not clear the callback. 3794 * 3795 * Returns B_TRUE if the callback was successfully called and cleared. 3796 */ 3797 boolean_t 3798 arc_clear_callback(arc_buf_t *buf) 3799 { 3800 arc_buf_hdr_t *hdr; 3801 kmutex_t *hash_lock; 3802 arc_evict_func_t *efunc = buf->b_efunc; 3803 void *private = buf->b_private; 3804 3805 mutex_enter(&buf->b_evict_lock); 3806 hdr = buf->b_hdr; 3807 if (hdr == NULL) { 3808 /* 3809 * We are in arc_do_user_evicts(). 3810 */ 3811 ASSERT(buf->b_data == NULL); 3812 mutex_exit(&buf->b_evict_lock); 3813 return (B_FALSE); 3814 } else if (buf->b_data == NULL) { 3815 /* 3816 * We are on the eviction list; process this buffer now 3817 * but let arc_do_user_evicts() do the reaping. 3818 */ 3819 buf->b_efunc = NULL; 3820 mutex_exit(&buf->b_evict_lock); 3821 VERIFY0(efunc(private)); 3822 return (B_TRUE); 3823 } 3824 hash_lock = HDR_LOCK(hdr); 3825 mutex_enter(hash_lock); 3826 hdr = buf->b_hdr; 3827 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3828 3829 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 3830 hdr->b_l1hdr.b_datacnt); 3831 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3832 hdr->b_l1hdr.b_state == arc_mfu); 3833 3834 buf->b_efunc = NULL; 3835 buf->b_private = NULL; 3836 3837 if (hdr->b_l1hdr.b_datacnt > 1) { 3838 mutex_exit(&buf->b_evict_lock); 3839 arc_buf_destroy(buf, FALSE, TRUE); 3840 } else { 3841 ASSERT(buf == hdr->b_l1hdr.b_buf); 3842 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3843 mutex_exit(&buf->b_evict_lock); 3844 } 3845 3846 mutex_exit(hash_lock); 3847 VERIFY0(efunc(private)); 3848 return (B_TRUE); 3849 } 3850 3851 /* 3852 * Release this buffer from the cache, making it an anonymous buffer. This 3853 * must be done after a read and prior to modifying the buffer contents. 3854 * If the buffer has more than one reference, we must make 3855 * a new hdr for the buffer. 3856 */ 3857 void 3858 arc_release(arc_buf_t *buf, void *tag) 3859 { 3860 arc_buf_hdr_t *hdr = buf->b_hdr; 3861 3862 /* 3863 * It would be nice to assert that if it's DMU metadata (level > 3864 * 0 || it's the dnode file), then it must be syncing context. 3865 * But we don't know that information at this level. 3866 */ 3867 3868 mutex_enter(&buf->b_evict_lock); 3869 3870 /* 3871 * We don't grab the hash lock prior to this check, because if 3872 * the buffer's header is in the arc_anon state, it won't be 3873 * linked into the hash table. 3874 */ 3875 if (hdr->b_l1hdr.b_state == arc_anon) { 3876 mutex_exit(&buf->b_evict_lock); 3877 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3878 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3879 ASSERT(!HDR_HAS_L2HDR(hdr)); 3880 ASSERT(BUF_EMPTY(hdr)); 3881 3882 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 3883 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 3884 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 3885 3886 ASSERT3P(buf->b_efunc, ==, NULL); 3887 ASSERT3P(buf->b_private, ==, NULL); 3888 3889 hdr->b_l1hdr.b_arc_access = 0; 3890 arc_buf_thaw(buf); 3891 3892 return; 3893 } 3894 3895 kmutex_t *hash_lock = HDR_LOCK(hdr); 3896 mutex_enter(hash_lock); 3897 3898 /* 3899 * This assignment is only valid as long as the hash_lock is 3900 * held, we must be careful not to reference state or the 3901 * b_state field after dropping the lock. 3902 */ 3903 arc_state_t *state = hdr->b_l1hdr.b_state; 3904 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3905 ASSERT3P(state, !=, arc_anon); 3906 3907 /* this buffer is not on any list */ 3908 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 3909 3910 if (HDR_HAS_L2HDR(hdr)) { 3911 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 3912 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 3913 3914 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 3915 list_remove(&hdr->b_l2hdr.b_dev->l2ad_buflist, hdr); 3916 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 3917 3918 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 3919 } 3920 3921 /* 3922 * Do we have more than one buf? 3923 */ 3924 if (hdr->b_l1hdr.b_datacnt > 1) { 3925 arc_buf_hdr_t *nhdr; 3926 arc_buf_t **bufp; 3927 uint64_t blksz = hdr->b_size; 3928 uint64_t spa = hdr->b_spa; 3929 arc_buf_contents_t type = arc_buf_type(hdr); 3930 uint32_t flags = hdr->b_flags; 3931 3932 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 3933 /* 3934 * Pull the data off of this hdr and attach it to 3935 * a new anonymous hdr. 3936 */ 3937 (void) remove_reference(hdr, hash_lock, tag); 3938 bufp = &hdr->b_l1hdr.b_buf; 3939 while (*bufp != buf) 3940 bufp = &(*bufp)->b_next; 3941 *bufp = buf->b_next; 3942 buf->b_next = NULL; 3943 3944 ASSERT3P(state, !=, arc_l2c_only); 3945 ASSERT3U(state->arcs_size, >=, hdr->b_size); 3946 atomic_add_64(&state->arcs_size, -hdr->b_size); 3947 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 3948 ASSERT3P(state, !=, arc_l2c_only); 3949 uint64_t *size = &state->arcs_lsize[type]; 3950 ASSERT3U(*size, >=, hdr->b_size); 3951 atomic_add_64(size, -hdr->b_size); 3952 } 3953 3954 /* 3955 * We're releasing a duplicate user data buffer, update 3956 * our statistics accordingly. 3957 */ 3958 if (HDR_ISTYPE_DATA(hdr)) { 3959 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 3960 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 3961 -hdr->b_size); 3962 } 3963 hdr->b_l1hdr.b_datacnt -= 1; 3964 arc_cksum_verify(buf); 3965 arc_buf_unwatch(buf); 3966 3967 mutex_exit(hash_lock); 3968 3969 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3970 nhdr->b_size = blksz; 3971 nhdr->b_spa = spa; 3972 3973 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 3974 nhdr->b_flags |= arc_bufc_to_flags(type); 3975 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 3976 3977 nhdr->b_l1hdr.b_buf = buf; 3978 nhdr->b_l1hdr.b_datacnt = 1; 3979 nhdr->b_l1hdr.b_state = arc_anon; 3980 nhdr->b_l1hdr.b_arc_access = 0; 3981 nhdr->b_freeze_cksum = NULL; 3982 3983 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 3984 buf->b_hdr = nhdr; 3985 mutex_exit(&buf->b_evict_lock); 3986 atomic_add_64(&arc_anon->arcs_size, blksz); 3987 } else { 3988 mutex_exit(&buf->b_evict_lock); 3989 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 3990 /* protected by hash lock */ 3991 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 3992 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3993 arc_change_state(arc_anon, hdr, hash_lock); 3994 hdr->b_l1hdr.b_arc_access = 0; 3995 mutex_exit(hash_lock); 3996 3997 buf_discard_identity(hdr); 3998 arc_buf_thaw(buf); 3999 } 4000 buf->b_efunc = NULL; 4001 buf->b_private = NULL; 4002 } 4003 4004 int 4005 arc_released(arc_buf_t *buf) 4006 { 4007 int released; 4008 4009 mutex_enter(&buf->b_evict_lock); 4010 released = (buf->b_data != NULL && 4011 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4012 mutex_exit(&buf->b_evict_lock); 4013 return (released); 4014 } 4015 4016 #ifdef ZFS_DEBUG 4017 int 4018 arc_referenced(arc_buf_t *buf) 4019 { 4020 int referenced; 4021 4022 mutex_enter(&buf->b_evict_lock); 4023 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4024 mutex_exit(&buf->b_evict_lock); 4025 return (referenced); 4026 } 4027 #endif 4028 4029 static void 4030 arc_write_ready(zio_t *zio) 4031 { 4032 arc_write_callback_t *callback = zio->io_private; 4033 arc_buf_t *buf = callback->awcb_buf; 4034 arc_buf_hdr_t *hdr = buf->b_hdr; 4035 4036 ASSERT(HDR_HAS_L1HDR(hdr)); 4037 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4038 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4039 callback->awcb_ready(zio, buf, callback->awcb_private); 4040 4041 /* 4042 * If the IO is already in progress, then this is a re-write 4043 * attempt, so we need to thaw and re-compute the cksum. 4044 * It is the responsibility of the callback to handle the 4045 * accounting for any re-write attempt. 4046 */ 4047 if (HDR_IO_IN_PROGRESS(hdr)) { 4048 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4049 if (hdr->b_freeze_cksum != NULL) { 4050 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4051 hdr->b_freeze_cksum = NULL; 4052 } 4053 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4054 } 4055 arc_cksum_compute(buf, B_FALSE); 4056 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4057 } 4058 4059 /* 4060 * The SPA calls this callback for each physical write that happens on behalf 4061 * of a logical write. See the comment in dbuf_write_physdone() for details. 4062 */ 4063 static void 4064 arc_write_physdone(zio_t *zio) 4065 { 4066 arc_write_callback_t *cb = zio->io_private; 4067 if (cb->awcb_physdone != NULL) 4068 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4069 } 4070 4071 static void 4072 arc_write_done(zio_t *zio) 4073 { 4074 arc_write_callback_t *callback = zio->io_private; 4075 arc_buf_t *buf = callback->awcb_buf; 4076 arc_buf_hdr_t *hdr = buf->b_hdr; 4077 4078 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4079 4080 if (zio->io_error == 0) { 4081 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4082 buf_discard_identity(hdr); 4083 } else { 4084 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4085 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4086 } 4087 } else { 4088 ASSERT(BUF_EMPTY(hdr)); 4089 } 4090 4091 /* 4092 * If the block to be written was all-zero or compressed enough to be 4093 * embedded in the BP, no write was performed so there will be no 4094 * dva/birth/checksum. The buffer must therefore remain anonymous 4095 * (and uncached). 4096 */ 4097 if (!BUF_EMPTY(hdr)) { 4098 arc_buf_hdr_t *exists; 4099 kmutex_t *hash_lock; 4100 4101 ASSERT(zio->io_error == 0); 4102 4103 arc_cksum_verify(buf); 4104 4105 exists = buf_hash_insert(hdr, &hash_lock); 4106 if (exists != NULL) { 4107 /* 4108 * This can only happen if we overwrite for 4109 * sync-to-convergence, because we remove 4110 * buffers from the hash table when we arc_free(). 4111 */ 4112 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4113 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4114 panic("bad overwrite, hdr=%p exists=%p", 4115 (void *)hdr, (void *)exists); 4116 ASSERT(refcount_is_zero( 4117 &exists->b_l1hdr.b_refcnt)); 4118 arc_change_state(arc_anon, exists, hash_lock); 4119 mutex_exit(hash_lock); 4120 arc_hdr_destroy(exists); 4121 exists = buf_hash_insert(hdr, &hash_lock); 4122 ASSERT3P(exists, ==, NULL); 4123 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4124 /* nopwrite */ 4125 ASSERT(zio->io_prop.zp_nopwrite); 4126 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4127 panic("bad nopwrite, hdr=%p exists=%p", 4128 (void *)hdr, (void *)exists); 4129 } else { 4130 /* Dedup */ 4131 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4132 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4133 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4134 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4135 } 4136 } 4137 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4138 /* if it's not anon, we are doing a scrub */ 4139 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4140 arc_access(hdr, hash_lock); 4141 mutex_exit(hash_lock); 4142 } else { 4143 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4144 } 4145 4146 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4147 callback->awcb_done(zio, buf, callback->awcb_private); 4148 4149 kmem_free(callback, sizeof (arc_write_callback_t)); 4150 } 4151 4152 zio_t * 4153 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4154 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4155 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4156 arc_done_func_t *done, void *private, zio_priority_t priority, 4157 int zio_flags, const zbookmark_phys_t *zb) 4158 { 4159 arc_buf_hdr_t *hdr = buf->b_hdr; 4160 arc_write_callback_t *callback; 4161 zio_t *zio; 4162 4163 ASSERT(ready != NULL); 4164 ASSERT(done != NULL); 4165 ASSERT(!HDR_IO_ERROR(hdr)); 4166 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4167 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4168 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4169 if (l2arc) 4170 hdr->b_flags |= ARC_FLAG_L2CACHE; 4171 if (l2arc_compress) 4172 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4173 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4174 callback->awcb_ready = ready; 4175 callback->awcb_physdone = physdone; 4176 callback->awcb_done = done; 4177 callback->awcb_private = private; 4178 callback->awcb_buf = buf; 4179 4180 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4181 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4182 priority, zio_flags, zb); 4183 4184 return (zio); 4185 } 4186 4187 static int 4188 arc_memory_throttle(uint64_t reserve, uint64_t txg) 4189 { 4190 #ifdef _KERNEL 4191 uint64_t available_memory = ptob(freemem); 4192 static uint64_t page_load = 0; 4193 static uint64_t last_txg = 0; 4194 4195 #if defined(__i386) 4196 available_memory = 4197 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 4198 #endif 4199 4200 if (freemem > physmem * arc_lotsfree_percent / 100) 4201 return (0); 4202 4203 if (txg > last_txg) { 4204 last_txg = txg; 4205 page_load = 0; 4206 } 4207 /* 4208 * If we are in pageout, we know that memory is already tight, 4209 * the arc is already going to be evicting, so we just want to 4210 * continue to let page writes occur as quickly as possible. 4211 */ 4212 if (curproc == proc_pageout) { 4213 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4214 return (SET_ERROR(ERESTART)); 4215 /* Note: reserve is inflated, so we deflate */ 4216 page_load += reserve / 8; 4217 return (0); 4218 } else if (page_load > 0 && arc_reclaim_needed()) { 4219 /* memory is low, delay before restarting */ 4220 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4221 return (SET_ERROR(EAGAIN)); 4222 } 4223 page_load = 0; 4224 #endif 4225 return (0); 4226 } 4227 4228 void 4229 arc_tempreserve_clear(uint64_t reserve) 4230 { 4231 atomic_add_64(&arc_tempreserve, -reserve); 4232 ASSERT((int64_t)arc_tempreserve >= 0); 4233 } 4234 4235 int 4236 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4237 { 4238 int error; 4239 uint64_t anon_size; 4240 4241 if (reserve > arc_c/4 && !arc_no_grow) 4242 arc_c = MIN(arc_c_max, reserve * 4); 4243 if (reserve > arc_c) 4244 return (SET_ERROR(ENOMEM)); 4245 4246 /* 4247 * Don't count loaned bufs as in flight dirty data to prevent long 4248 * network delays from blocking transactions that are ready to be 4249 * assigned to a txg. 4250 */ 4251 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 4252 4253 /* 4254 * Writes will, almost always, require additional memory allocations 4255 * in order to compress/encrypt/etc the data. We therefore need to 4256 * make sure that there is sufficient available memory for this. 4257 */ 4258 error = arc_memory_throttle(reserve, txg); 4259 if (error != 0) 4260 return (error); 4261 4262 /* 4263 * Throttle writes when the amount of dirty data in the cache 4264 * gets too large. We try to keep the cache less than half full 4265 * of dirty blocks so that our sync times don't grow too large. 4266 * Note: if two requests come in concurrently, we might let them 4267 * both succeed, when one of them should fail. Not a huge deal. 4268 */ 4269 4270 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4271 anon_size > arc_c / 4) { 4272 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4273 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4274 arc_tempreserve>>10, 4275 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4276 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4277 reserve>>10, arc_c>>10); 4278 return (SET_ERROR(ERESTART)); 4279 } 4280 atomic_add_64(&arc_tempreserve, reserve); 4281 return (0); 4282 } 4283 4284 static void 4285 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4286 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4287 { 4288 size->value.ui64 = state->arcs_size; 4289 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4290 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4291 } 4292 4293 static int 4294 arc_kstat_update(kstat_t *ksp, int rw) 4295 { 4296 arc_stats_t *as = ksp->ks_data; 4297 4298 if (rw == KSTAT_WRITE) { 4299 return (EACCES); 4300 } else { 4301 arc_kstat_update_state(arc_anon, 4302 &as->arcstat_anon_size, 4303 &as->arcstat_anon_evictable_data, 4304 &as->arcstat_anon_evictable_metadata); 4305 arc_kstat_update_state(arc_mru, 4306 &as->arcstat_mru_size, 4307 &as->arcstat_mru_evictable_data, 4308 &as->arcstat_mru_evictable_metadata); 4309 arc_kstat_update_state(arc_mru_ghost, 4310 &as->arcstat_mru_ghost_size, 4311 &as->arcstat_mru_ghost_evictable_data, 4312 &as->arcstat_mru_ghost_evictable_metadata); 4313 arc_kstat_update_state(arc_mfu, 4314 &as->arcstat_mfu_size, 4315 &as->arcstat_mfu_evictable_data, 4316 &as->arcstat_mfu_evictable_metadata); 4317 arc_kstat_update_state(arc_mfu_ghost, 4318 &as->arcstat_mfu_ghost_size, 4319 &as->arcstat_mfu_ghost_evictable_data, 4320 &as->arcstat_mfu_ghost_evictable_metadata); 4321 } 4322 4323 return (0); 4324 } 4325 4326 void 4327 arc_init(void) 4328 { 4329 /* 4330 * allmem is "all memory that we could possibly use". 4331 */ 4332 #ifdef _KERNEL 4333 uint64_t allmem = ptob(physmem - swapfs_minfree); 4334 #else 4335 uint64_t allmem = (physmem * PAGESIZE) / 2; 4336 #endif 4337 4338 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4339 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 4340 4341 /* Convert seconds to clock ticks */ 4342 arc_min_prefetch_lifespan = 1 * hz; 4343 4344 /* Start out with 1/8 of all memory */ 4345 arc_c = allmem / 8; 4346 4347 #ifdef _KERNEL 4348 /* 4349 * On architectures where the physical memory can be larger 4350 * than the addressable space (intel in 32-bit mode), we may 4351 * need to limit the cache to 1/8 of VM size. 4352 */ 4353 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4354 #endif 4355 4356 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 4357 arc_c_min = MAX(allmem / 32, 64 << 20); 4358 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 4359 if (allmem >= 1 << 30) 4360 arc_c_max = allmem - (1 << 30); 4361 else 4362 arc_c_max = arc_c_min; 4363 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 4364 4365 /* 4366 * Allow the tunables to override our calculations if they are 4367 * reasonable (ie. over 64MB) 4368 */ 4369 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 4370 arc_c_max = zfs_arc_max; 4371 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 4372 arc_c_min = zfs_arc_min; 4373 4374 arc_c = arc_c_max; 4375 arc_p = (arc_c >> 1); 4376 4377 /* limit meta-data to 1/4 of the arc capacity */ 4378 arc_meta_limit = arc_c_max / 4; 4379 4380 /* Allow the tunable to override if it is reasonable */ 4381 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4382 arc_meta_limit = zfs_arc_meta_limit; 4383 4384 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4385 arc_c_min = arc_meta_limit / 2; 4386 4387 if (zfs_arc_meta_min > 0) { 4388 arc_meta_min = zfs_arc_meta_min; 4389 } else { 4390 arc_meta_min = arc_c_min / 2; 4391 } 4392 4393 if (zfs_arc_grow_retry > 0) 4394 arc_grow_retry = zfs_arc_grow_retry; 4395 4396 if (zfs_arc_shrink_shift > 0) 4397 arc_shrink_shift = zfs_arc_shrink_shift; 4398 4399 /* 4400 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 4401 */ 4402 if (arc_no_grow_shift >= arc_shrink_shift) 4403 arc_no_grow_shift = arc_shrink_shift - 1; 4404 4405 if (zfs_arc_p_min_shift > 0) 4406 arc_p_min_shift = zfs_arc_p_min_shift; 4407 4408 /* if kmem_flags are set, lets try to use less memory */ 4409 if (kmem_debugging()) 4410 arc_c = arc_c / 2; 4411 if (arc_c < arc_c_min) 4412 arc_c = arc_c_min; 4413 4414 arc_anon = &ARC_anon; 4415 arc_mru = &ARC_mru; 4416 arc_mru_ghost = &ARC_mru_ghost; 4417 arc_mfu = &ARC_mfu; 4418 arc_mfu_ghost = &ARC_mfu_ghost; 4419 arc_l2c_only = &ARC_l2c_only; 4420 arc_size = 0; 4421 4422 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4423 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4424 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4425 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4426 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4427 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL); 4428 4429 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 4430 sizeof (arc_buf_hdr_t), 4431 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4432 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 4433 sizeof (arc_buf_hdr_t), 4434 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4435 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 4436 sizeof (arc_buf_hdr_t), 4437 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4438 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 4439 sizeof (arc_buf_hdr_t), 4440 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4441 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 4442 sizeof (arc_buf_hdr_t), 4443 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4444 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 4445 sizeof (arc_buf_hdr_t), 4446 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4447 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 4448 sizeof (arc_buf_hdr_t), 4449 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4450 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 4451 sizeof (arc_buf_hdr_t), 4452 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4453 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 4454 sizeof (arc_buf_hdr_t), 4455 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4456 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 4457 sizeof (arc_buf_hdr_t), 4458 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4459 4460 buf_init(); 4461 4462 arc_thread_exit = 0; 4463 arc_eviction_list = NULL; 4464 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 4465 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4466 4467 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4468 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4469 4470 if (arc_ksp != NULL) { 4471 arc_ksp->ks_data = &arc_stats; 4472 arc_ksp->ks_update = arc_kstat_update; 4473 kstat_install(arc_ksp); 4474 } 4475 4476 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 4477 TS_RUN, minclsyspri); 4478 4479 arc_dead = FALSE; 4480 arc_warm = B_FALSE; 4481 4482 /* 4483 * Calculate maximum amount of dirty data per pool. 4484 * 4485 * If it has been set by /etc/system, take that. 4486 * Otherwise, use a percentage of physical memory defined by 4487 * zfs_dirty_data_max_percent (default 10%) with a cap at 4488 * zfs_dirty_data_max_max (default 4GB). 4489 */ 4490 if (zfs_dirty_data_max == 0) { 4491 zfs_dirty_data_max = physmem * PAGESIZE * 4492 zfs_dirty_data_max_percent / 100; 4493 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 4494 zfs_dirty_data_max_max); 4495 } 4496 } 4497 4498 void 4499 arc_fini(void) 4500 { 4501 mutex_enter(&arc_reclaim_thr_lock); 4502 arc_thread_exit = 1; 4503 while (arc_thread_exit != 0) 4504 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 4505 mutex_exit(&arc_reclaim_thr_lock); 4506 4507 arc_flush(NULL); 4508 4509 arc_dead = TRUE; 4510 4511 if (arc_ksp != NULL) { 4512 kstat_delete(arc_ksp); 4513 arc_ksp = NULL; 4514 } 4515 4516 mutex_destroy(&arc_eviction_mtx); 4517 mutex_destroy(&arc_reclaim_thr_lock); 4518 cv_destroy(&arc_reclaim_thr_cv); 4519 4520 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 4521 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 4522 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 4523 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 4524 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 4525 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 4526 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 4527 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 4528 4529 mutex_destroy(&arc_anon->arcs_mtx); 4530 mutex_destroy(&arc_mru->arcs_mtx); 4531 mutex_destroy(&arc_mru_ghost->arcs_mtx); 4532 mutex_destroy(&arc_mfu->arcs_mtx); 4533 mutex_destroy(&arc_mfu_ghost->arcs_mtx); 4534 mutex_destroy(&arc_l2c_only->arcs_mtx); 4535 4536 buf_fini(); 4537 4538 ASSERT0(arc_loaned_bytes); 4539 } 4540 4541 /* 4542 * Level 2 ARC 4543 * 4544 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 4545 * It uses dedicated storage devices to hold cached data, which are populated 4546 * using large infrequent writes. The main role of this cache is to boost 4547 * the performance of random read workloads. The intended L2ARC devices 4548 * include short-stroked disks, solid state disks, and other media with 4549 * substantially faster read latency than disk. 4550 * 4551 * +-----------------------+ 4552 * | ARC | 4553 * +-----------------------+ 4554 * | ^ ^ 4555 * | | | 4556 * l2arc_feed_thread() arc_read() 4557 * | | | 4558 * | l2arc read | 4559 * V | | 4560 * +---------------+ | 4561 * | L2ARC | | 4562 * +---------------+ | 4563 * | ^ | 4564 * l2arc_write() | | 4565 * | | | 4566 * V | | 4567 * +-------+ +-------+ 4568 * | vdev | | vdev | 4569 * | cache | | cache | 4570 * +-------+ +-------+ 4571 * +=========+ .-----. 4572 * : L2ARC : |-_____-| 4573 * : devices : | Disks | 4574 * +=========+ `-_____-' 4575 * 4576 * Read requests are satisfied from the following sources, in order: 4577 * 4578 * 1) ARC 4579 * 2) vdev cache of L2ARC devices 4580 * 3) L2ARC devices 4581 * 4) vdev cache of disks 4582 * 5) disks 4583 * 4584 * Some L2ARC device types exhibit extremely slow write performance. 4585 * To accommodate for this there are some significant differences between 4586 * the L2ARC and traditional cache design: 4587 * 4588 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 4589 * the ARC behave as usual, freeing buffers and placing headers on ghost 4590 * lists. The ARC does not send buffers to the L2ARC during eviction as 4591 * this would add inflated write latencies for all ARC memory pressure. 4592 * 4593 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 4594 * It does this by periodically scanning buffers from the eviction-end of 4595 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 4596 * not already there. It scans until a headroom of buffers is satisfied, 4597 * which itself is a buffer for ARC eviction. If a compressible buffer is 4598 * found during scanning and selected for writing to an L2ARC device, we 4599 * temporarily boost scanning headroom during the next scan cycle to make 4600 * sure we adapt to compression effects (which might significantly reduce 4601 * the data volume we write to L2ARC). The thread that does this is 4602 * l2arc_feed_thread(), illustrated below; example sizes are included to 4603 * provide a better sense of ratio than this diagram: 4604 * 4605 * head --> tail 4606 * +---------------------+----------+ 4607 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 4608 * +---------------------+----------+ | o L2ARC eligible 4609 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 4610 * +---------------------+----------+ | 4611 * 15.9 Gbytes ^ 32 Mbytes | 4612 * headroom | 4613 * l2arc_feed_thread() 4614 * | 4615 * l2arc write hand <--[oooo]--' 4616 * | 8 Mbyte 4617 * | write max 4618 * V 4619 * +==============================+ 4620 * L2ARC dev |####|#|###|###| |####| ... | 4621 * +==============================+ 4622 * 32 Gbytes 4623 * 4624 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 4625 * evicted, then the L2ARC has cached a buffer much sooner than it probably 4626 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 4627 * safe to say that this is an uncommon case, since buffers at the end of 4628 * the ARC lists have moved there due to inactivity. 4629 * 4630 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 4631 * then the L2ARC simply misses copying some buffers. This serves as a 4632 * pressure valve to prevent heavy read workloads from both stalling the ARC 4633 * with waits and clogging the L2ARC with writes. This also helps prevent 4634 * the potential for the L2ARC to churn if it attempts to cache content too 4635 * quickly, such as during backups of the entire pool. 4636 * 4637 * 5. After system boot and before the ARC has filled main memory, there are 4638 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 4639 * lists can remain mostly static. Instead of searching from tail of these 4640 * lists as pictured, the l2arc_feed_thread() will search from the list heads 4641 * for eligible buffers, greatly increasing its chance of finding them. 4642 * 4643 * The L2ARC device write speed is also boosted during this time so that 4644 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 4645 * there are no L2ARC reads, and no fear of degrading read performance 4646 * through increased writes. 4647 * 4648 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 4649 * the vdev queue can aggregate them into larger and fewer writes. Each 4650 * device is written to in a rotor fashion, sweeping writes through 4651 * available space then repeating. 4652 * 4653 * 7. The L2ARC does not store dirty content. It never needs to flush 4654 * write buffers back to disk based storage. 4655 * 4656 * 8. If an ARC buffer is written (and dirtied) which also exists in the 4657 * L2ARC, the now stale L2ARC buffer is immediately dropped. 4658 * 4659 * The performance of the L2ARC can be tweaked by a number of tunables, which 4660 * may be necessary for different workloads: 4661 * 4662 * l2arc_write_max max write bytes per interval 4663 * l2arc_write_boost extra write bytes during device warmup 4664 * l2arc_noprefetch skip caching prefetched buffers 4665 * l2arc_headroom number of max device writes to precache 4666 * l2arc_headroom_boost when we find compressed buffers during ARC 4667 * scanning, we multiply headroom by this 4668 * percentage factor for the next scan cycle, 4669 * since more compressed buffers are likely to 4670 * be present 4671 * l2arc_feed_secs seconds between L2ARC writing 4672 * 4673 * Tunables may be removed or added as future performance improvements are 4674 * integrated, and also may become zpool properties. 4675 * 4676 * There are three key functions that control how the L2ARC warms up: 4677 * 4678 * l2arc_write_eligible() check if a buffer is eligible to cache 4679 * l2arc_write_size() calculate how much to write 4680 * l2arc_write_interval() calculate sleep delay between writes 4681 * 4682 * These three functions determine what to write, how much, and how quickly 4683 * to send writes. 4684 */ 4685 4686 static boolean_t 4687 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 4688 { 4689 /* 4690 * A buffer is *not* eligible for the L2ARC if it: 4691 * 1. belongs to a different spa. 4692 * 2. is already cached on the L2ARC. 4693 * 3. has an I/O in progress (it may be an incomplete read). 4694 * 4. is flagged not eligible (zfs property). 4695 */ 4696 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 4697 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr)) 4698 return (B_FALSE); 4699 4700 return (B_TRUE); 4701 } 4702 4703 static uint64_t 4704 l2arc_write_size(void) 4705 { 4706 uint64_t size; 4707 4708 /* 4709 * Make sure our globals have meaningful values in case the user 4710 * altered them. 4711 */ 4712 size = l2arc_write_max; 4713 if (size == 0) { 4714 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 4715 "be greater than zero, resetting it to the default (%d)", 4716 L2ARC_WRITE_SIZE); 4717 size = l2arc_write_max = L2ARC_WRITE_SIZE; 4718 } 4719 4720 if (arc_warm == B_FALSE) 4721 size += l2arc_write_boost; 4722 4723 return (size); 4724 4725 } 4726 4727 static clock_t 4728 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 4729 { 4730 clock_t interval, next, now; 4731 4732 /* 4733 * If the ARC lists are busy, increase our write rate; if the 4734 * lists are stale, idle back. This is achieved by checking 4735 * how much we previously wrote - if it was more than half of 4736 * what we wanted, schedule the next write much sooner. 4737 */ 4738 if (l2arc_feed_again && wrote > (wanted / 2)) 4739 interval = (hz * l2arc_feed_min_ms) / 1000; 4740 else 4741 interval = hz * l2arc_feed_secs; 4742 4743 now = ddi_get_lbolt(); 4744 next = MAX(now, MIN(now + interval, began + interval)); 4745 4746 return (next); 4747 } 4748 4749 /* 4750 * Cycle through L2ARC devices. This is how L2ARC load balances. 4751 * If a device is returned, this also returns holding the spa config lock. 4752 */ 4753 static l2arc_dev_t * 4754 l2arc_dev_get_next(void) 4755 { 4756 l2arc_dev_t *first, *next = NULL; 4757 4758 /* 4759 * Lock out the removal of spas (spa_namespace_lock), then removal 4760 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 4761 * both locks will be dropped and a spa config lock held instead. 4762 */ 4763 mutex_enter(&spa_namespace_lock); 4764 mutex_enter(&l2arc_dev_mtx); 4765 4766 /* if there are no vdevs, there is nothing to do */ 4767 if (l2arc_ndev == 0) 4768 goto out; 4769 4770 first = NULL; 4771 next = l2arc_dev_last; 4772 do { 4773 /* loop around the list looking for a non-faulted vdev */ 4774 if (next == NULL) { 4775 next = list_head(l2arc_dev_list); 4776 } else { 4777 next = list_next(l2arc_dev_list, next); 4778 if (next == NULL) 4779 next = list_head(l2arc_dev_list); 4780 } 4781 4782 /* if we have come back to the start, bail out */ 4783 if (first == NULL) 4784 first = next; 4785 else if (next == first) 4786 break; 4787 4788 } while (vdev_is_dead(next->l2ad_vdev)); 4789 4790 /* if we were unable to find any usable vdevs, return NULL */ 4791 if (vdev_is_dead(next->l2ad_vdev)) 4792 next = NULL; 4793 4794 l2arc_dev_last = next; 4795 4796 out: 4797 mutex_exit(&l2arc_dev_mtx); 4798 4799 /* 4800 * Grab the config lock to prevent the 'next' device from being 4801 * removed while we are writing to it. 4802 */ 4803 if (next != NULL) 4804 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 4805 mutex_exit(&spa_namespace_lock); 4806 4807 return (next); 4808 } 4809 4810 /* 4811 * Free buffers that were tagged for destruction. 4812 */ 4813 static void 4814 l2arc_do_free_on_write() 4815 { 4816 list_t *buflist; 4817 l2arc_data_free_t *df, *df_prev; 4818 4819 mutex_enter(&l2arc_free_on_write_mtx); 4820 buflist = l2arc_free_on_write; 4821 4822 for (df = list_tail(buflist); df; df = df_prev) { 4823 df_prev = list_prev(buflist, df); 4824 ASSERT(df->l2df_data != NULL); 4825 ASSERT(df->l2df_func != NULL); 4826 df->l2df_func(df->l2df_data, df->l2df_size); 4827 list_remove(buflist, df); 4828 kmem_free(df, sizeof (l2arc_data_free_t)); 4829 } 4830 4831 mutex_exit(&l2arc_free_on_write_mtx); 4832 } 4833 4834 /* 4835 * A write to a cache device has completed. Update all headers to allow 4836 * reads from these buffers to begin. 4837 */ 4838 static void 4839 l2arc_write_done(zio_t *zio) 4840 { 4841 l2arc_write_callback_t *cb; 4842 l2arc_dev_t *dev; 4843 list_t *buflist; 4844 arc_buf_hdr_t *head, *hdr, *hdr_prev; 4845 kmutex_t *hash_lock; 4846 int64_t bytes_dropped = 0; 4847 4848 cb = zio->io_private; 4849 ASSERT(cb != NULL); 4850 dev = cb->l2wcb_dev; 4851 ASSERT(dev != NULL); 4852 head = cb->l2wcb_head; 4853 ASSERT(head != NULL); 4854 buflist = &dev->l2ad_buflist; 4855 ASSERT(buflist != NULL); 4856 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 4857 l2arc_write_callback_t *, cb); 4858 4859 if (zio->io_error != 0) 4860 ARCSTAT_BUMP(arcstat_l2_writes_error); 4861 4862 mutex_enter(&dev->l2ad_mtx); 4863 4864 /* 4865 * All writes completed, or an error was hit. 4866 */ 4867 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 4868 hdr_prev = list_prev(buflist, hdr); 4869 4870 hash_lock = HDR_LOCK(hdr); 4871 if (!mutex_tryenter(hash_lock)) { 4872 /* 4873 * This buffer misses out. It may be in a stage 4874 * of eviction. Its ARC_FLAG_L2_WRITING flag will be 4875 * left set, denying reads to this buffer. 4876 */ 4877 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 4878 continue; 4879 } 4880 4881 /* 4882 * It's possible that this buffer got evicted from the L1 cache 4883 * before we grabbed the vdev + hash locks, in which case 4884 * arc_hdr_realloc freed b_tmp_cdata for us if it was allocated. 4885 * Only free the buffer if we still have an L1 hdr. 4886 */ 4887 if (HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_tmp_cdata != NULL && 4888 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 4889 l2arc_release_cdata_buf(hdr); 4890 4891 if (zio->io_error != 0) { 4892 /* 4893 * Error - drop L2ARC entry. 4894 */ 4895 list_remove(buflist, hdr); 4896 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 4897 4898 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 4899 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 4900 } 4901 4902 /* 4903 * Allow ARC to begin reads to this L2ARC entry. 4904 */ 4905 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 4906 4907 mutex_exit(hash_lock); 4908 } 4909 4910 atomic_inc_64(&l2arc_writes_done); 4911 list_remove(buflist, head); 4912 ASSERT(!HDR_HAS_L1HDR(head)); 4913 kmem_cache_free(hdr_l2only_cache, head); 4914 mutex_exit(&dev->l2ad_mtx); 4915 4916 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 4917 4918 l2arc_do_free_on_write(); 4919 4920 kmem_free(cb, sizeof (l2arc_write_callback_t)); 4921 } 4922 4923 /* 4924 * A read to a cache device completed. Validate buffer contents before 4925 * handing over to the regular ARC routines. 4926 */ 4927 static void 4928 l2arc_read_done(zio_t *zio) 4929 { 4930 l2arc_read_callback_t *cb; 4931 arc_buf_hdr_t *hdr; 4932 arc_buf_t *buf; 4933 kmutex_t *hash_lock; 4934 int equal; 4935 4936 ASSERT(zio->io_vd != NULL); 4937 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 4938 4939 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 4940 4941 cb = zio->io_private; 4942 ASSERT(cb != NULL); 4943 buf = cb->l2rcb_buf; 4944 ASSERT(buf != NULL); 4945 4946 hash_lock = HDR_LOCK(buf->b_hdr); 4947 mutex_enter(hash_lock); 4948 hdr = buf->b_hdr; 4949 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4950 4951 /* 4952 * If the buffer was compressed, decompress it first. 4953 */ 4954 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 4955 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 4956 ASSERT(zio->io_data != NULL); 4957 4958 /* 4959 * Check this survived the L2ARC journey. 4960 */ 4961 equal = arc_cksum_equal(buf); 4962 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 4963 mutex_exit(hash_lock); 4964 zio->io_private = buf; 4965 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 4966 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 4967 arc_read_done(zio); 4968 } else { 4969 mutex_exit(hash_lock); 4970 /* 4971 * Buffer didn't survive caching. Increment stats and 4972 * reissue to the original storage device. 4973 */ 4974 if (zio->io_error != 0) { 4975 ARCSTAT_BUMP(arcstat_l2_io_error); 4976 } else { 4977 zio->io_error = SET_ERROR(EIO); 4978 } 4979 if (!equal) 4980 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 4981 4982 /* 4983 * If there's no waiter, issue an async i/o to the primary 4984 * storage now. If there *is* a waiter, the caller must 4985 * issue the i/o in a context where it's OK to block. 4986 */ 4987 if (zio->io_waiter == NULL) { 4988 zio_t *pio = zio_unique_parent(zio); 4989 4990 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 4991 4992 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 4993 buf->b_data, zio->io_size, arc_read_done, buf, 4994 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 4995 } 4996 } 4997 4998 kmem_free(cb, sizeof (l2arc_read_callback_t)); 4999 } 5000 5001 /* 5002 * This is the list priority from which the L2ARC will search for pages to 5003 * cache. This is used within loops (0..3) to cycle through lists in the 5004 * desired order. This order can have a significant effect on cache 5005 * performance. 5006 * 5007 * Currently the metadata lists are hit first, MFU then MRU, followed by 5008 * the data lists. This function returns a locked list, and also returns 5009 * the lock pointer. 5010 */ 5011 static list_t * 5012 l2arc_list_locked(int list_num, kmutex_t **lock) 5013 { 5014 list_t *list = NULL; 5015 5016 ASSERT(list_num >= 0 && list_num <= 3); 5017 5018 switch (list_num) { 5019 case 0: 5020 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 5021 *lock = &arc_mfu->arcs_mtx; 5022 break; 5023 case 1: 5024 list = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 5025 *lock = &arc_mru->arcs_mtx; 5026 break; 5027 case 2: 5028 list = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 5029 *lock = &arc_mfu->arcs_mtx; 5030 break; 5031 case 3: 5032 list = &arc_mru->arcs_list[ARC_BUFC_DATA]; 5033 *lock = &arc_mru->arcs_mtx; 5034 break; 5035 } 5036 5037 ASSERT(!(MUTEX_HELD(*lock))); 5038 mutex_enter(*lock); 5039 return (list); 5040 } 5041 5042 /* 5043 * Evict buffers from the device write hand to the distance specified in 5044 * bytes. This distance may span populated buffers, it may span nothing. 5045 * This is clearing a region on the L2ARC device ready for writing. 5046 * If the 'all' boolean is set, every buffer is evicted. 5047 */ 5048 static void 5049 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5050 { 5051 list_t *buflist; 5052 arc_buf_hdr_t *hdr, *hdr_prev; 5053 kmutex_t *hash_lock; 5054 uint64_t taddr; 5055 int64_t bytes_evicted = 0; 5056 5057 buflist = &dev->l2ad_buflist; 5058 5059 if (!all && dev->l2ad_first) { 5060 /* 5061 * This is the first sweep through the device. There is 5062 * nothing to evict. 5063 */ 5064 return; 5065 } 5066 5067 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5068 /* 5069 * When nearing the end of the device, evict to the end 5070 * before the device write hand jumps to the start. 5071 */ 5072 taddr = dev->l2ad_end; 5073 } else { 5074 taddr = dev->l2ad_hand + distance; 5075 } 5076 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5077 uint64_t, taddr, boolean_t, all); 5078 5079 top: 5080 mutex_enter(&dev->l2ad_mtx); 5081 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5082 hdr_prev = list_prev(buflist, hdr); 5083 5084 hash_lock = HDR_LOCK(hdr); 5085 if (!mutex_tryenter(hash_lock)) { 5086 /* 5087 * Missed the hash lock. Retry. 5088 */ 5089 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5090 mutex_exit(&dev->l2ad_mtx); 5091 mutex_enter(hash_lock); 5092 mutex_exit(hash_lock); 5093 goto top; 5094 } 5095 5096 if (HDR_L2_WRITE_HEAD(hdr)) { 5097 /* 5098 * We hit a write head node. Leave it for 5099 * l2arc_write_done(). 5100 */ 5101 list_remove(buflist, hdr); 5102 mutex_exit(hash_lock); 5103 continue; 5104 } 5105 5106 if (!all && HDR_HAS_L2HDR(hdr) && 5107 (hdr->b_l2hdr.b_daddr > taddr || 5108 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5109 /* 5110 * We've evicted to the target address, 5111 * or the end of the device. 5112 */ 5113 mutex_exit(hash_lock); 5114 break; 5115 } 5116 5117 ASSERT(HDR_HAS_L2HDR(hdr)); 5118 if (!HDR_HAS_L1HDR(hdr)) { 5119 ASSERT(!HDR_L2_READING(hdr)); 5120 /* 5121 * This doesn't exist in the ARC. Destroy. 5122 * arc_hdr_destroy() will call list_remove() 5123 * and decrement arcstat_l2_size. 5124 */ 5125 arc_change_state(arc_anon, hdr, hash_lock); 5126 arc_hdr_destroy(hdr); 5127 } else { 5128 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5129 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5130 /* 5131 * Invalidate issued or about to be issued 5132 * reads, since we may be about to write 5133 * over this location. 5134 */ 5135 if (HDR_L2_READING(hdr)) { 5136 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5137 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5138 } 5139 5140 /* Tell ARC this no longer exists in L2ARC. */ 5141 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5142 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5143 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5144 list_remove(buflist, hdr); 5145 5146 /* This may have been leftover after a failed write. */ 5147 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5148 } 5149 mutex_exit(hash_lock); 5150 } 5151 mutex_exit(&dev->l2ad_mtx); 5152 5153 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0); 5154 dev->l2ad_evict = taddr; 5155 } 5156 5157 /* 5158 * Find and write ARC buffers to the L2ARC device. 5159 * 5160 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5161 * for reading until they have completed writing. 5162 * The headroom_boost is an in-out parameter used to maintain headroom boost 5163 * state between calls to this function. 5164 * 5165 * Returns the number of bytes actually written (which may be smaller than 5166 * the delta by which the device hand has changed due to alignment). 5167 */ 5168 static uint64_t 5169 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5170 boolean_t *headroom_boost) 5171 { 5172 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5173 list_t *list; 5174 uint64_t write_asize, write_psize, write_sz, headroom, 5175 buf_compress_minsz; 5176 void *buf_data; 5177 kmutex_t *list_lock; 5178 boolean_t full; 5179 l2arc_write_callback_t *cb; 5180 zio_t *pio, *wzio; 5181 uint64_t guid = spa_load_guid(spa); 5182 const boolean_t do_headroom_boost = *headroom_boost; 5183 5184 ASSERT(dev->l2ad_vdev != NULL); 5185 5186 /* Lower the flag now, we might want to raise it again later. */ 5187 *headroom_boost = B_FALSE; 5188 5189 pio = NULL; 5190 write_sz = write_asize = write_psize = 0; 5191 full = B_FALSE; 5192 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5193 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5194 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5195 5196 /* 5197 * We will want to try to compress buffers that are at least 2x the 5198 * device sector size. 5199 */ 5200 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5201 5202 /* 5203 * Copy buffers for L2ARC writing. 5204 */ 5205 mutex_enter(&dev->l2ad_mtx); 5206 for (int try = 0; try <= 3; try++) { 5207 uint64_t passed_sz = 0; 5208 5209 list = l2arc_list_locked(try, &list_lock); 5210 5211 /* 5212 * L2ARC fast warmup. 5213 * 5214 * Until the ARC is warm and starts to evict, read from the 5215 * head of the ARC lists rather than the tail. 5216 */ 5217 if (arc_warm == B_FALSE) 5218 hdr = list_head(list); 5219 else 5220 hdr = list_tail(list); 5221 5222 headroom = target_sz * l2arc_headroom; 5223 if (do_headroom_boost) 5224 headroom = (headroom * l2arc_headroom_boost) / 100; 5225 5226 for (; hdr; hdr = hdr_prev) { 5227 kmutex_t *hash_lock; 5228 uint64_t buf_sz; 5229 5230 if (arc_warm == B_FALSE) 5231 hdr_prev = list_next(list, hdr); 5232 else 5233 hdr_prev = list_prev(list, hdr); 5234 5235 hash_lock = HDR_LOCK(hdr); 5236 if (!mutex_tryenter(hash_lock)) { 5237 /* 5238 * Skip this buffer rather than waiting. 5239 */ 5240 continue; 5241 } 5242 5243 passed_sz += hdr->b_size; 5244 if (passed_sz > headroom) { 5245 /* 5246 * Searched too far. 5247 */ 5248 mutex_exit(hash_lock); 5249 break; 5250 } 5251 5252 if (!l2arc_write_eligible(guid, hdr)) { 5253 mutex_exit(hash_lock); 5254 continue; 5255 } 5256 5257 if ((write_sz + hdr->b_size) > target_sz) { 5258 full = B_TRUE; 5259 mutex_exit(hash_lock); 5260 break; 5261 } 5262 5263 if (pio == NULL) { 5264 /* 5265 * Insert a dummy header on the buflist so 5266 * l2arc_write_done() can find where the 5267 * write buffers begin without searching. 5268 */ 5269 list_insert_head(&dev->l2ad_buflist, head); 5270 5271 cb = kmem_alloc( 5272 sizeof (l2arc_write_callback_t), KM_SLEEP); 5273 cb->l2wcb_dev = dev; 5274 cb->l2wcb_head = head; 5275 pio = zio_root(spa, l2arc_write_done, cb, 5276 ZIO_FLAG_CANFAIL); 5277 } 5278 5279 /* 5280 * Create and add a new L2ARC header. 5281 */ 5282 hdr->b_l2hdr.b_dev = dev; 5283 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5284 /* 5285 * Temporarily stash the data buffer in b_tmp_cdata. 5286 * The subsequent write step will pick it up from 5287 * there. This is because can't access b_l1hdr.b_buf 5288 * without holding the hash_lock, which we in turn 5289 * can't access without holding the ARC list locks 5290 * (which we want to avoid during compression/writing). 5291 */ 5292 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5293 hdr->b_l2hdr.b_asize = hdr->b_size; 5294 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5295 5296 buf_sz = hdr->b_size; 5297 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5298 5299 list_insert_head(&dev->l2ad_buflist, hdr); 5300 5301 /* 5302 * Compute and store the buffer cksum before 5303 * writing. On debug the cksum is verified first. 5304 */ 5305 arc_cksum_verify(hdr->b_l1hdr.b_buf); 5306 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 5307 5308 mutex_exit(hash_lock); 5309 5310 write_sz += buf_sz; 5311 } 5312 5313 mutex_exit(list_lock); 5314 5315 if (full == B_TRUE) 5316 break; 5317 } 5318 5319 /* No buffers selected for writing? */ 5320 if (pio == NULL) { 5321 ASSERT0(write_sz); 5322 mutex_exit(&dev->l2ad_mtx); 5323 ASSERT(!HDR_HAS_L1HDR(head)); 5324 kmem_cache_free(hdr_l2only_cache, head); 5325 return (0); 5326 } 5327 5328 /* 5329 * Now start writing the buffers. We're starting at the write head 5330 * and work backwards, retracing the course of the buffer selector 5331 * loop above. 5332 */ 5333 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 5334 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 5335 uint64_t buf_sz; 5336 5337 /* 5338 * We shouldn't need to lock the buffer here, since we flagged 5339 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5340 * take care to only access its L2 cache parameters. In 5341 * particular, hdr->l1hdr.b_buf may be invalid by now due to 5342 * ARC eviction. 5343 */ 5344 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 5345 5346 if ((HDR_L2COMPRESS(hdr)) && 5347 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 5348 if (l2arc_compress_buf(hdr)) { 5349 /* 5350 * If compression succeeded, enable headroom 5351 * boost on the next scan cycle. 5352 */ 5353 *headroom_boost = B_TRUE; 5354 } 5355 } 5356 5357 /* 5358 * Pick up the buffer data we had previously stashed away 5359 * (and now potentially also compressed). 5360 */ 5361 buf_data = hdr->b_l1hdr.b_tmp_cdata; 5362 buf_sz = hdr->b_l2hdr.b_asize; 5363 5364 /* Compression may have squashed the buffer to zero length. */ 5365 if (buf_sz != 0) { 5366 uint64_t buf_p_sz; 5367 5368 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5369 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5370 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 5371 ZIO_FLAG_CANFAIL, B_FALSE); 5372 5373 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 5374 zio_t *, wzio); 5375 (void) zio_nowait(wzio); 5376 5377 write_asize += buf_sz; 5378 /* 5379 * Keep the clock hand suitably device-aligned. 5380 */ 5381 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5382 write_psize += buf_p_sz; 5383 dev->l2ad_hand += buf_p_sz; 5384 } 5385 } 5386 5387 mutex_exit(&dev->l2ad_mtx); 5388 5389 ASSERT3U(write_asize, <=, target_sz); 5390 ARCSTAT_BUMP(arcstat_l2_writes_sent); 5391 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 5392 ARCSTAT_INCR(arcstat_l2_size, write_sz); 5393 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 5394 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 5395 5396 /* 5397 * Bump device hand to the device start if it is approaching the end. 5398 * l2arc_evict() will already have evicted ahead for this case. 5399 */ 5400 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 5401 dev->l2ad_hand = dev->l2ad_start; 5402 dev->l2ad_evict = dev->l2ad_start; 5403 dev->l2ad_first = B_FALSE; 5404 } 5405 5406 dev->l2ad_writing = B_TRUE; 5407 (void) zio_wait(pio); 5408 dev->l2ad_writing = B_FALSE; 5409 5410 return (write_asize); 5411 } 5412 5413 /* 5414 * Compresses an L2ARC buffer. 5415 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 5416 * size in l2hdr->b_asize. This routine tries to compress the data and 5417 * depending on the compression result there are three possible outcomes: 5418 * *) The buffer was incompressible. The original l2hdr contents were left 5419 * untouched and are ready for writing to an L2 device. 5420 * *) The buffer was all-zeros, so there is no need to write it to an L2 5421 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 5422 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 5423 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 5424 * data buffer which holds the compressed data to be written, and b_asize 5425 * tells us how much data there is. b_compress is set to the appropriate 5426 * compression algorithm. Once writing is done, invoke 5427 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 5428 * 5429 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 5430 * buffer was incompressible). 5431 */ 5432 static boolean_t 5433 l2arc_compress_buf(arc_buf_hdr_t *hdr) 5434 { 5435 void *cdata; 5436 size_t csize, len, rounded; 5437 ASSERT(HDR_HAS_L2HDR(hdr)); 5438 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 5439 5440 ASSERT(HDR_HAS_L1HDR(hdr)); 5441 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 5442 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 5443 5444 len = l2hdr->b_asize; 5445 cdata = zio_data_buf_alloc(len); 5446 ASSERT3P(cdata, !=, NULL); 5447 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 5448 cdata, l2hdr->b_asize); 5449 5450 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 5451 if (rounded > csize) { 5452 bzero((char *)cdata + csize, rounded - csize); 5453 csize = rounded; 5454 } 5455 5456 if (csize == 0) { 5457 /* zero block, indicate that there's nothing to write */ 5458 zio_data_buf_free(cdata, len); 5459 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 5460 l2hdr->b_asize = 0; 5461 hdr->b_l1hdr.b_tmp_cdata = NULL; 5462 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 5463 return (B_TRUE); 5464 } else if (csize > 0 && csize < len) { 5465 /* 5466 * Compression succeeded, we'll keep the cdata around for 5467 * writing and release it afterwards. 5468 */ 5469 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 5470 l2hdr->b_asize = csize; 5471 hdr->b_l1hdr.b_tmp_cdata = cdata; 5472 ARCSTAT_BUMP(arcstat_l2_compress_successes); 5473 return (B_TRUE); 5474 } else { 5475 /* 5476 * Compression failed, release the compressed buffer. 5477 * l2hdr will be left unmodified. 5478 */ 5479 zio_data_buf_free(cdata, len); 5480 ARCSTAT_BUMP(arcstat_l2_compress_failures); 5481 return (B_FALSE); 5482 } 5483 } 5484 5485 /* 5486 * Decompresses a zio read back from an l2arc device. On success, the 5487 * underlying zio's io_data buffer is overwritten by the uncompressed 5488 * version. On decompression error (corrupt compressed stream), the 5489 * zio->io_error value is set to signal an I/O error. 5490 * 5491 * Please note that the compressed data stream is not checksummed, so 5492 * if the underlying device is experiencing data corruption, we may feed 5493 * corrupt data to the decompressor, so the decompressor needs to be 5494 * able to handle this situation (LZ4 does). 5495 */ 5496 static void 5497 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 5498 { 5499 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 5500 5501 if (zio->io_error != 0) { 5502 /* 5503 * An io error has occured, just restore the original io 5504 * size in preparation for a main pool read. 5505 */ 5506 zio->io_orig_size = zio->io_size = hdr->b_size; 5507 return; 5508 } 5509 5510 if (c == ZIO_COMPRESS_EMPTY) { 5511 /* 5512 * An empty buffer results in a null zio, which means we 5513 * need to fill its io_data after we're done restoring the 5514 * buffer's contents. 5515 */ 5516 ASSERT(hdr->b_l1hdr.b_buf != NULL); 5517 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 5518 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 5519 } else { 5520 ASSERT(zio->io_data != NULL); 5521 /* 5522 * We copy the compressed data from the start of the arc buffer 5523 * (the zio_read will have pulled in only what we need, the 5524 * rest is garbage which we will overwrite at decompression) 5525 * and then decompress back to the ARC data buffer. This way we 5526 * can minimize copying by simply decompressing back over the 5527 * original compressed data (rather than decompressing to an 5528 * aux buffer and then copying back the uncompressed buffer, 5529 * which is likely to be much larger). 5530 */ 5531 uint64_t csize; 5532 void *cdata; 5533 5534 csize = zio->io_size; 5535 cdata = zio_data_buf_alloc(csize); 5536 bcopy(zio->io_data, cdata, csize); 5537 if (zio_decompress_data(c, cdata, zio->io_data, csize, 5538 hdr->b_size) != 0) 5539 zio->io_error = EIO; 5540 zio_data_buf_free(cdata, csize); 5541 } 5542 5543 /* Restore the expected uncompressed IO size. */ 5544 zio->io_orig_size = zio->io_size = hdr->b_size; 5545 } 5546 5547 /* 5548 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 5549 * This buffer serves as a temporary holder of compressed data while 5550 * the buffer entry is being written to an l2arc device. Once that is 5551 * done, we can dispose of it. 5552 */ 5553 static void 5554 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 5555 { 5556 ASSERT(HDR_HAS_L1HDR(hdr)); 5557 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_EMPTY) { 5558 /* 5559 * If the data was compressed, then we've allocated a 5560 * temporary buffer for it, so now we need to release it. 5561 */ 5562 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 5563 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 5564 hdr->b_size); 5565 } 5566 hdr->b_l1hdr.b_tmp_cdata = NULL; 5567 } 5568 5569 /* 5570 * This thread feeds the L2ARC at regular intervals. This is the beating 5571 * heart of the L2ARC. 5572 */ 5573 static void 5574 l2arc_feed_thread(void) 5575 { 5576 callb_cpr_t cpr; 5577 l2arc_dev_t *dev; 5578 spa_t *spa; 5579 uint64_t size, wrote; 5580 clock_t begin, next = ddi_get_lbolt(); 5581 boolean_t headroom_boost = B_FALSE; 5582 5583 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 5584 5585 mutex_enter(&l2arc_feed_thr_lock); 5586 5587 while (l2arc_thread_exit == 0) { 5588 CALLB_CPR_SAFE_BEGIN(&cpr); 5589 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 5590 next); 5591 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 5592 next = ddi_get_lbolt() + hz; 5593 5594 /* 5595 * Quick check for L2ARC devices. 5596 */ 5597 mutex_enter(&l2arc_dev_mtx); 5598 if (l2arc_ndev == 0) { 5599 mutex_exit(&l2arc_dev_mtx); 5600 continue; 5601 } 5602 mutex_exit(&l2arc_dev_mtx); 5603 begin = ddi_get_lbolt(); 5604 5605 /* 5606 * This selects the next l2arc device to write to, and in 5607 * doing so the next spa to feed from: dev->l2ad_spa. This 5608 * will return NULL if there are now no l2arc devices or if 5609 * they are all faulted. 5610 * 5611 * If a device is returned, its spa's config lock is also 5612 * held to prevent device removal. l2arc_dev_get_next() 5613 * will grab and release l2arc_dev_mtx. 5614 */ 5615 if ((dev = l2arc_dev_get_next()) == NULL) 5616 continue; 5617 5618 spa = dev->l2ad_spa; 5619 ASSERT(spa != NULL); 5620 5621 /* 5622 * If the pool is read-only then force the feed thread to 5623 * sleep a little longer. 5624 */ 5625 if (!spa_writeable(spa)) { 5626 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 5627 spa_config_exit(spa, SCL_L2ARC, dev); 5628 continue; 5629 } 5630 5631 /* 5632 * Avoid contributing to memory pressure. 5633 */ 5634 if (arc_reclaim_needed()) { 5635 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 5636 spa_config_exit(spa, SCL_L2ARC, dev); 5637 continue; 5638 } 5639 5640 ARCSTAT_BUMP(arcstat_l2_feeds); 5641 5642 size = l2arc_write_size(); 5643 5644 /* 5645 * Evict L2ARC buffers that will be overwritten. 5646 */ 5647 l2arc_evict(dev, size, B_FALSE); 5648 5649 /* 5650 * Write ARC buffers. 5651 */ 5652 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 5653 5654 /* 5655 * Calculate interval between writes. 5656 */ 5657 next = l2arc_write_interval(begin, size, wrote); 5658 spa_config_exit(spa, SCL_L2ARC, dev); 5659 } 5660 5661 l2arc_thread_exit = 0; 5662 cv_broadcast(&l2arc_feed_thr_cv); 5663 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 5664 thread_exit(); 5665 } 5666 5667 boolean_t 5668 l2arc_vdev_present(vdev_t *vd) 5669 { 5670 l2arc_dev_t *dev; 5671 5672 mutex_enter(&l2arc_dev_mtx); 5673 for (dev = list_head(l2arc_dev_list); dev != NULL; 5674 dev = list_next(l2arc_dev_list, dev)) { 5675 if (dev->l2ad_vdev == vd) 5676 break; 5677 } 5678 mutex_exit(&l2arc_dev_mtx); 5679 5680 return (dev != NULL); 5681 } 5682 5683 /* 5684 * Add a vdev for use by the L2ARC. By this point the spa has already 5685 * validated the vdev and opened it. 5686 */ 5687 void 5688 l2arc_add_vdev(spa_t *spa, vdev_t *vd) 5689 { 5690 l2arc_dev_t *adddev; 5691 5692 ASSERT(!l2arc_vdev_present(vd)); 5693 5694 /* 5695 * Create a new l2arc device entry. 5696 */ 5697 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 5698 adddev->l2ad_spa = spa; 5699 adddev->l2ad_vdev = vd; 5700 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 5701 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 5702 adddev->l2ad_hand = adddev->l2ad_start; 5703 adddev->l2ad_evict = adddev->l2ad_start; 5704 adddev->l2ad_first = B_TRUE; 5705 adddev->l2ad_writing = B_FALSE; 5706 5707 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 5708 /* 5709 * This is a list of all ARC buffers that are still valid on the 5710 * device. 5711 */ 5712 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 5713 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 5714 5715 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 5716 5717 /* 5718 * Add device to global list 5719 */ 5720 mutex_enter(&l2arc_dev_mtx); 5721 list_insert_head(l2arc_dev_list, adddev); 5722 atomic_inc_64(&l2arc_ndev); 5723 mutex_exit(&l2arc_dev_mtx); 5724 } 5725 5726 /* 5727 * Remove a vdev from the L2ARC. 5728 */ 5729 void 5730 l2arc_remove_vdev(vdev_t *vd) 5731 { 5732 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 5733 5734 /* 5735 * Find the device by vdev 5736 */ 5737 mutex_enter(&l2arc_dev_mtx); 5738 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 5739 nextdev = list_next(l2arc_dev_list, dev); 5740 if (vd == dev->l2ad_vdev) { 5741 remdev = dev; 5742 break; 5743 } 5744 } 5745 ASSERT(remdev != NULL); 5746 5747 /* 5748 * Remove device from global list 5749 */ 5750 list_remove(l2arc_dev_list, remdev); 5751 l2arc_dev_last = NULL; /* may have been invalidated */ 5752 atomic_dec_64(&l2arc_ndev); 5753 mutex_exit(&l2arc_dev_mtx); 5754 5755 /* 5756 * Clear all buflists and ARC references. L2ARC device flush. 5757 */ 5758 l2arc_evict(remdev, 0, B_TRUE); 5759 list_destroy(&remdev->l2ad_buflist); 5760 mutex_destroy(&remdev->l2ad_mtx); 5761 kmem_free(remdev, sizeof (l2arc_dev_t)); 5762 } 5763 5764 void 5765 l2arc_init(void) 5766 { 5767 l2arc_thread_exit = 0; 5768 l2arc_ndev = 0; 5769 l2arc_writes_sent = 0; 5770 l2arc_writes_done = 0; 5771 5772 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 5773 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 5774 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 5775 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 5776 5777 l2arc_dev_list = &L2ARC_dev_list; 5778 l2arc_free_on_write = &L2ARC_free_on_write; 5779 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 5780 offsetof(l2arc_dev_t, l2ad_node)); 5781 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 5782 offsetof(l2arc_data_free_t, l2df_list_node)); 5783 } 5784 5785 void 5786 l2arc_fini(void) 5787 { 5788 /* 5789 * This is called from dmu_fini(), which is called from spa_fini(); 5790 * Because of this, we can assume that all l2arc devices have 5791 * already been removed when the pools themselves were removed. 5792 */ 5793 5794 l2arc_do_free_on_write(); 5795 5796 mutex_destroy(&l2arc_feed_thr_lock); 5797 cv_destroy(&l2arc_feed_thr_cv); 5798 mutex_destroy(&l2arc_dev_mtx); 5799 mutex_destroy(&l2arc_free_on_write_mtx); 5800 5801 list_destroy(l2arc_dev_list); 5802 list_destroy(l2arc_free_on_write); 5803 } 5804 5805 void 5806 l2arc_start(void) 5807 { 5808 if (!(spa_mode_global & FWRITE)) 5809 return; 5810 5811 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 5812 TS_RUN, minclsyspri); 5813 } 5814 5815 void 5816 l2arc_stop(void) 5817 { 5818 if (!(spa_mode_global & FWRITE)) 5819 return; 5820 5821 mutex_enter(&l2arc_feed_thr_lock); 5822 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 5823 l2arc_thread_exit = 1; 5824 while (l2arc_thread_exit != 0) 5825 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 5826 mutex_exit(&l2arc_feed_thr_lock); 5827 } 5828