1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29 /* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74 /* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123 #include <sys/spa.h> 124 #include <sys/zio.h> 125 #include <sys/zio_compress.h> 126 #include <sys/zfs_context.h> 127 #include <sys/arc.h> 128 #include <sys/refcount.h> 129 #include <sys/vdev.h> 130 #include <sys/vdev_impl.h> 131 #include <sys/dsl_pool.h> 132 #include <sys/multilist.h> 133 #ifdef _KERNEL 134 #include <sys/vmsystm.h> 135 #include <vm/anon.h> 136 #include <sys/fs/swapnode.h> 137 #include <sys/dnlc.h> 138 #endif 139 #include <sys/callb.h> 140 #include <sys/kstat.h> 141 #include <zfs_fletcher.h> 142 #include <sys/byteorder.h> 143 #include <sys/spa_impl.h> 144 #include <sys/zfs_ioctl.h> 145 146 #ifndef _KERNEL 147 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 148 boolean_t arc_watch = B_FALSE; 149 int arc_procfd; 150 #endif 151 152 static kmutex_t arc_reclaim_lock; 153 static kcondvar_t arc_reclaim_thread_cv; 154 static boolean_t arc_reclaim_thread_exit; 155 static kcondvar_t arc_reclaim_waiters_cv; 156 157 static kmutex_t arc_user_evicts_lock; 158 static kcondvar_t arc_user_evicts_cv; 159 static boolean_t arc_user_evicts_thread_exit; 160 161 uint_t arc_reduce_dnlc_percent = 3; 162 163 /* 164 * The number of headers to evict in arc_evict_state_impl() before 165 * dropping the sublist lock and evicting from another sublist. A lower 166 * value means we're more likely to evict the "correct" header (i.e. the 167 * oldest header in the arc state), but comes with higher overhead 168 * (i.e. more invocations of arc_evict_state_impl()). 169 */ 170 int zfs_arc_evict_batch_limit = 10; 171 172 /* 173 * The number of sublists used for each of the arc state lists. If this 174 * is not set to a suitable value by the user, it will be configured to 175 * the number of CPUs on the system in arc_init(). 176 */ 177 int zfs_arc_num_sublists_per_state = 0; 178 179 /* number of seconds before growing cache again */ 180 static int arc_grow_retry = 60; 181 182 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 183 int zfs_arc_overflow_shift = 8; 184 185 /* shift of arc_c for calculating both min and max arc_p */ 186 static int arc_p_min_shift = 4; 187 188 /* log2(fraction of arc to reclaim) */ 189 static int arc_shrink_shift = 7; 190 191 /* 192 * log2(fraction of ARC which must be free to allow growing). 193 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 194 * when reading a new block into the ARC, we will evict an equal-sized block 195 * from the ARC. 196 * 197 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 198 * we will still not allow it to grow. 199 */ 200 int arc_no_grow_shift = 5; 201 202 203 /* 204 * minimum lifespan of a prefetch block in clock ticks 205 * (initialized in arc_init()) 206 */ 207 static int arc_min_prefetch_lifespan; 208 209 /* 210 * If this percent of memory is free, don't throttle. 211 */ 212 int arc_lotsfree_percent = 10; 213 214 static int arc_dead; 215 216 /* 217 * The arc has filled available memory and has now warmed up. 218 */ 219 static boolean_t arc_warm; 220 221 /* 222 * These tunables are for performance analysis. 223 */ 224 uint64_t zfs_arc_max; 225 uint64_t zfs_arc_min; 226 uint64_t zfs_arc_meta_limit = 0; 227 uint64_t zfs_arc_meta_min = 0; 228 int zfs_arc_grow_retry = 0; 229 int zfs_arc_shrink_shift = 0; 230 int zfs_arc_p_min_shift = 0; 231 int zfs_disable_dup_eviction = 0; 232 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 233 234 /* 235 * Note that buffers can be in one of 6 states: 236 * ARC_anon - anonymous (discussed below) 237 * ARC_mru - recently used, currently cached 238 * ARC_mru_ghost - recentely used, no longer in cache 239 * ARC_mfu - frequently used, currently cached 240 * ARC_mfu_ghost - frequently used, no longer in cache 241 * ARC_l2c_only - exists in L2ARC but not other states 242 * When there are no active references to the buffer, they are 243 * are linked onto a list in one of these arc states. These are 244 * the only buffers that can be evicted or deleted. Within each 245 * state there are multiple lists, one for meta-data and one for 246 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 247 * etc.) is tracked separately so that it can be managed more 248 * explicitly: favored over data, limited explicitly. 249 * 250 * Anonymous buffers are buffers that are not associated with 251 * a DVA. These are buffers that hold dirty block copies 252 * before they are written to stable storage. By definition, 253 * they are "ref'd" and are considered part of arc_mru 254 * that cannot be freed. Generally, they will aquire a DVA 255 * as they are written and migrate onto the arc_mru list. 256 * 257 * The ARC_l2c_only state is for buffers that are in the second 258 * level ARC but no longer in any of the ARC_m* lists. The second 259 * level ARC itself may also contain buffers that are in any of 260 * the ARC_m* states - meaning that a buffer can exist in two 261 * places. The reason for the ARC_l2c_only state is to keep the 262 * buffer header in the hash table, so that reads that hit the 263 * second level ARC benefit from these fast lookups. 264 */ 265 266 typedef struct arc_state { 267 /* 268 * list of evictable buffers 269 */ 270 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 271 /* 272 * total amount of evictable data in this state 273 */ 274 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 275 /* 276 * total amount of data in this state; this includes: evictable, 277 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 278 */ 279 refcount_t arcs_size; 280 } arc_state_t; 281 282 /* The 6 states: */ 283 static arc_state_t ARC_anon; 284 static arc_state_t ARC_mru; 285 static arc_state_t ARC_mru_ghost; 286 static arc_state_t ARC_mfu; 287 static arc_state_t ARC_mfu_ghost; 288 static arc_state_t ARC_l2c_only; 289 290 typedef struct arc_stats { 291 kstat_named_t arcstat_hits; 292 kstat_named_t arcstat_misses; 293 kstat_named_t arcstat_demand_hits_data; 294 kstat_named_t arcstat_demand_misses_data; 295 kstat_named_t arcstat_demand_hits_metadata; 296 kstat_named_t arcstat_demand_misses_metadata; 297 kstat_named_t arcstat_prefetch_hits_data; 298 kstat_named_t arcstat_prefetch_misses_data; 299 kstat_named_t arcstat_prefetch_hits_metadata; 300 kstat_named_t arcstat_prefetch_misses_metadata; 301 kstat_named_t arcstat_mru_hits; 302 kstat_named_t arcstat_mru_ghost_hits; 303 kstat_named_t arcstat_mfu_hits; 304 kstat_named_t arcstat_mfu_ghost_hits; 305 kstat_named_t arcstat_deleted; 306 /* 307 * Number of buffers that could not be evicted because the hash lock 308 * was held by another thread. The lock may not necessarily be held 309 * by something using the same buffer, since hash locks are shared 310 * by multiple buffers. 311 */ 312 kstat_named_t arcstat_mutex_miss; 313 /* 314 * Number of buffers skipped because they have I/O in progress, are 315 * indrect prefetch buffers that have not lived long enough, or are 316 * not from the spa we're trying to evict from. 317 */ 318 kstat_named_t arcstat_evict_skip; 319 /* 320 * Number of times arc_evict_state() was unable to evict enough 321 * buffers to reach it's target amount. 322 */ 323 kstat_named_t arcstat_evict_not_enough; 324 kstat_named_t arcstat_evict_l2_cached; 325 kstat_named_t arcstat_evict_l2_eligible; 326 kstat_named_t arcstat_evict_l2_ineligible; 327 kstat_named_t arcstat_evict_l2_skip; 328 kstat_named_t arcstat_hash_elements; 329 kstat_named_t arcstat_hash_elements_max; 330 kstat_named_t arcstat_hash_collisions; 331 kstat_named_t arcstat_hash_chains; 332 kstat_named_t arcstat_hash_chain_max; 333 kstat_named_t arcstat_p; 334 kstat_named_t arcstat_c; 335 kstat_named_t arcstat_c_min; 336 kstat_named_t arcstat_c_max; 337 kstat_named_t arcstat_size; 338 /* 339 * Number of bytes consumed by internal ARC structures necessary 340 * for tracking purposes; these structures are not actually 341 * backed by ARC buffers. This includes arc_buf_hdr_t structures 342 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 343 * caches), and arc_buf_t structures (allocated via arc_buf_t 344 * cache). 345 */ 346 kstat_named_t arcstat_hdr_size; 347 /* 348 * Number of bytes consumed by ARC buffers of type equal to 349 * ARC_BUFC_DATA. This is generally consumed by buffers backing 350 * on disk user data (e.g. plain file contents). 351 */ 352 kstat_named_t arcstat_data_size; 353 /* 354 * Number of bytes consumed by ARC buffers of type equal to 355 * ARC_BUFC_METADATA. This is generally consumed by buffers 356 * backing on disk data that is used for internal ZFS 357 * structures (e.g. ZAP, dnode, indirect blocks, etc). 358 */ 359 kstat_named_t arcstat_metadata_size; 360 /* 361 * Number of bytes consumed by various buffers and structures 362 * not actually backed with ARC buffers. This includes bonus 363 * buffers (allocated directly via zio_buf_* functions), 364 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 365 * cache), and dnode_t structures (allocated via dnode_t cache). 366 */ 367 kstat_named_t arcstat_other_size; 368 /* 369 * Total number of bytes consumed by ARC buffers residing in the 370 * arc_anon state. This includes *all* buffers in the arc_anon 371 * state; e.g. data, metadata, evictable, and unevictable buffers 372 * are all included in this value. 373 */ 374 kstat_named_t arcstat_anon_size; 375 /* 376 * Number of bytes consumed by ARC buffers that meet the 377 * following criteria: backing buffers of type ARC_BUFC_DATA, 378 * residing in the arc_anon state, and are eligible for eviction 379 * (e.g. have no outstanding holds on the buffer). 380 */ 381 kstat_named_t arcstat_anon_evictable_data; 382 /* 383 * Number of bytes consumed by ARC buffers that meet the 384 * following criteria: backing buffers of type ARC_BUFC_METADATA, 385 * residing in the arc_anon state, and are eligible for eviction 386 * (e.g. have no outstanding holds on the buffer). 387 */ 388 kstat_named_t arcstat_anon_evictable_metadata; 389 /* 390 * Total number of bytes consumed by ARC buffers residing in the 391 * arc_mru state. This includes *all* buffers in the arc_mru 392 * state; e.g. data, metadata, evictable, and unevictable buffers 393 * are all included in this value. 394 */ 395 kstat_named_t arcstat_mru_size; 396 /* 397 * Number of bytes consumed by ARC buffers that meet the 398 * following criteria: backing buffers of type ARC_BUFC_DATA, 399 * residing in the arc_mru state, and are eligible for eviction 400 * (e.g. have no outstanding holds on the buffer). 401 */ 402 kstat_named_t arcstat_mru_evictable_data; 403 /* 404 * Number of bytes consumed by ARC buffers that meet the 405 * following criteria: backing buffers of type ARC_BUFC_METADATA, 406 * residing in the arc_mru state, and are eligible for eviction 407 * (e.g. have no outstanding holds on the buffer). 408 */ 409 kstat_named_t arcstat_mru_evictable_metadata; 410 /* 411 * Total number of bytes that *would have been* consumed by ARC 412 * buffers in the arc_mru_ghost state. The key thing to note 413 * here, is the fact that this size doesn't actually indicate 414 * RAM consumption. The ghost lists only consist of headers and 415 * don't actually have ARC buffers linked off of these headers. 416 * Thus, *if* the headers had associated ARC buffers, these 417 * buffers *would have* consumed this number of bytes. 418 */ 419 kstat_named_t arcstat_mru_ghost_size; 420 /* 421 * Number of bytes that *would have been* consumed by ARC 422 * buffers that are eligible for eviction, of type 423 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 424 */ 425 kstat_named_t arcstat_mru_ghost_evictable_data; 426 /* 427 * Number of bytes that *would have been* consumed by ARC 428 * buffers that are eligible for eviction, of type 429 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 430 */ 431 kstat_named_t arcstat_mru_ghost_evictable_metadata; 432 /* 433 * Total number of bytes consumed by ARC buffers residing in the 434 * arc_mfu state. This includes *all* buffers in the arc_mfu 435 * state; e.g. data, metadata, evictable, and unevictable buffers 436 * are all included in this value. 437 */ 438 kstat_named_t arcstat_mfu_size; 439 /* 440 * Number of bytes consumed by ARC buffers that are eligible for 441 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 442 * state. 443 */ 444 kstat_named_t arcstat_mfu_evictable_data; 445 /* 446 * Number of bytes consumed by ARC buffers that are eligible for 447 * eviction, of type ARC_BUFC_METADATA, and reside in the 448 * arc_mfu state. 449 */ 450 kstat_named_t arcstat_mfu_evictable_metadata; 451 /* 452 * Total number of bytes that *would have been* consumed by ARC 453 * buffers in the arc_mfu_ghost state. See the comment above 454 * arcstat_mru_ghost_size for more details. 455 */ 456 kstat_named_t arcstat_mfu_ghost_size; 457 /* 458 * Number of bytes that *would have been* consumed by ARC 459 * buffers that are eligible for eviction, of type 460 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 461 */ 462 kstat_named_t arcstat_mfu_ghost_evictable_data; 463 /* 464 * Number of bytes that *would have been* consumed by ARC 465 * buffers that are eligible for eviction, of type 466 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 467 */ 468 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 469 kstat_named_t arcstat_l2_hits; 470 kstat_named_t arcstat_l2_misses; 471 kstat_named_t arcstat_l2_feeds; 472 kstat_named_t arcstat_l2_rw_clash; 473 kstat_named_t arcstat_l2_read_bytes; 474 kstat_named_t arcstat_l2_write_bytes; 475 kstat_named_t arcstat_l2_writes_sent; 476 kstat_named_t arcstat_l2_writes_done; 477 kstat_named_t arcstat_l2_writes_error; 478 kstat_named_t arcstat_l2_writes_lock_retry; 479 kstat_named_t arcstat_l2_evict_lock_retry; 480 kstat_named_t arcstat_l2_evict_reading; 481 kstat_named_t arcstat_l2_evict_l1cached; 482 kstat_named_t arcstat_l2_free_on_write; 483 kstat_named_t arcstat_l2_cdata_free_on_write; 484 kstat_named_t arcstat_l2_abort_lowmem; 485 kstat_named_t arcstat_l2_cksum_bad; 486 kstat_named_t arcstat_l2_io_error; 487 kstat_named_t arcstat_l2_size; 488 kstat_named_t arcstat_l2_asize; 489 kstat_named_t arcstat_l2_hdr_size; 490 kstat_named_t arcstat_l2_compress_successes; 491 kstat_named_t arcstat_l2_compress_zeros; 492 kstat_named_t arcstat_l2_compress_failures; 493 kstat_named_t arcstat_l2_log_blk_writes; 494 kstat_named_t arcstat_l2_log_blk_avg_size; 495 kstat_named_t arcstat_l2_data_to_meta_ratio; 496 kstat_named_t arcstat_l2_rebuild_successes; 497 kstat_named_t arcstat_l2_rebuild_abort_unsupported; 498 kstat_named_t arcstat_l2_rebuild_abort_io_errors; 499 kstat_named_t arcstat_l2_rebuild_abort_cksum_errors; 500 kstat_named_t arcstat_l2_rebuild_abort_loop_errors; 501 kstat_named_t arcstat_l2_rebuild_abort_lowmem; 502 kstat_named_t arcstat_l2_rebuild_size; 503 kstat_named_t arcstat_l2_rebuild_bufs; 504 kstat_named_t arcstat_l2_rebuild_bufs_precached; 505 kstat_named_t arcstat_l2_rebuild_psize; 506 kstat_named_t arcstat_l2_rebuild_log_blks; 507 kstat_named_t arcstat_memory_throttle_count; 508 kstat_named_t arcstat_duplicate_buffers; 509 kstat_named_t arcstat_duplicate_buffers_size; 510 kstat_named_t arcstat_duplicate_reads; 511 kstat_named_t arcstat_meta_used; 512 kstat_named_t arcstat_meta_limit; 513 kstat_named_t arcstat_meta_max; 514 kstat_named_t arcstat_meta_min; 515 } arc_stats_t; 516 517 static arc_stats_t arc_stats = { 518 { "hits", KSTAT_DATA_UINT64 }, 519 { "misses", KSTAT_DATA_UINT64 }, 520 { "demand_data_hits", KSTAT_DATA_UINT64 }, 521 { "demand_data_misses", KSTAT_DATA_UINT64 }, 522 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 523 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 524 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 525 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 526 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 527 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 528 { "mru_hits", KSTAT_DATA_UINT64 }, 529 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 530 { "mfu_hits", KSTAT_DATA_UINT64 }, 531 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 532 { "deleted", KSTAT_DATA_UINT64 }, 533 { "mutex_miss", KSTAT_DATA_UINT64 }, 534 { "evict_skip", KSTAT_DATA_UINT64 }, 535 { "evict_not_enough", KSTAT_DATA_UINT64 }, 536 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 537 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 538 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 539 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 540 { "hash_elements", KSTAT_DATA_UINT64 }, 541 { "hash_elements_max", KSTAT_DATA_UINT64 }, 542 { "hash_collisions", KSTAT_DATA_UINT64 }, 543 { "hash_chains", KSTAT_DATA_UINT64 }, 544 { "hash_chain_max", KSTAT_DATA_UINT64 }, 545 { "p", KSTAT_DATA_UINT64 }, 546 { "c", KSTAT_DATA_UINT64 }, 547 { "c_min", KSTAT_DATA_UINT64 }, 548 { "c_max", KSTAT_DATA_UINT64 }, 549 { "size", KSTAT_DATA_UINT64 }, 550 { "hdr_size", KSTAT_DATA_UINT64 }, 551 { "data_size", KSTAT_DATA_UINT64 }, 552 { "metadata_size", KSTAT_DATA_UINT64 }, 553 { "other_size", KSTAT_DATA_UINT64 }, 554 { "anon_size", KSTAT_DATA_UINT64 }, 555 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 556 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 557 { "mru_size", KSTAT_DATA_UINT64 }, 558 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 559 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 560 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 561 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 562 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 563 { "mfu_size", KSTAT_DATA_UINT64 }, 564 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 565 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 566 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 567 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 568 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 569 { "l2_hits", KSTAT_DATA_UINT64 }, 570 { "l2_misses", KSTAT_DATA_UINT64 }, 571 { "l2_feeds", KSTAT_DATA_UINT64 }, 572 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 573 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 574 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 575 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 576 { "l2_writes_done", KSTAT_DATA_UINT64 }, 577 { "l2_writes_error", KSTAT_DATA_UINT64 }, 578 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 579 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 580 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 581 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 582 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 583 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 584 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 585 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 586 { "l2_io_error", KSTAT_DATA_UINT64 }, 587 { "l2_size", KSTAT_DATA_UINT64 }, 588 { "l2_asize", KSTAT_DATA_UINT64 }, 589 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 590 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 591 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 592 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 593 { "l2_log_blk_writes", KSTAT_DATA_UINT64 }, 594 { "l2_log_blk_avg_size", KSTAT_DATA_UINT64 }, 595 { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 }, 596 { "l2_rebuild_successes", KSTAT_DATA_UINT64 }, 597 { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 }, 598 { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 }, 599 { "l2_rebuild_cksum_errors", KSTAT_DATA_UINT64 }, 600 { "l2_rebuild_loop_errors", KSTAT_DATA_UINT64 }, 601 { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 }, 602 { "l2_rebuild_size", KSTAT_DATA_UINT64 }, 603 { "l2_rebuild_bufs", KSTAT_DATA_UINT64 }, 604 { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 }, 605 { "l2_rebuild_psize", KSTAT_DATA_UINT64 }, 606 { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 }, 607 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 608 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 609 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 610 { "duplicate_reads", KSTAT_DATA_UINT64 }, 611 { "arc_meta_used", KSTAT_DATA_UINT64 }, 612 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 613 { "arc_meta_max", KSTAT_DATA_UINT64 }, 614 { "arc_meta_min", KSTAT_DATA_UINT64 } 615 }; 616 617 #define ARCSTAT(stat) (arc_stats.stat.value.ui64) 618 619 #define ARCSTAT_INCR(stat, val) \ 620 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 621 622 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 623 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 624 625 #define ARCSTAT_MAX(stat, val) { \ 626 uint64_t m; \ 627 while ((val) > (m = arc_stats.stat.value.ui64) && \ 628 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 629 continue; \ 630 } 631 632 #define ARCSTAT_MAXSTAT(stat) \ 633 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 634 635 /* 636 * We define a macro to allow ARC hits/misses to be easily broken down by 637 * two separate conditions, giving a total of four different subtypes for 638 * each of hits and misses (so eight statistics total). 639 */ 640 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 641 if (cond1) { \ 642 if (cond2) { \ 643 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 644 } else { \ 645 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 646 } \ 647 } else { \ 648 if (cond2) { \ 649 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 650 } else { \ 651 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 652 } \ 653 } 654 655 /* 656 * This macro allows us to use kstats as floating averages. Each time we 657 * update this kstat, we first factor it and the update value by 658 * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall 659 * average. This macro assumes that integer loads and stores are atomic, but 660 * is not safe for multiple writers updating the kstat in parallel (only the 661 * last writer's update will remain). 662 */ 663 #define ARCSTAT_F_AVG_FACTOR 3 664 #define ARCSTAT_F_AVG(stat, value) \ 665 do { \ 666 uint64_t x = ARCSTAT(stat); \ 667 x = x - x / ARCSTAT_F_AVG_FACTOR + \ 668 (value) / ARCSTAT_F_AVG_FACTOR; \ 669 ARCSTAT(stat) = x; \ 670 _NOTE(CONSTCOND) \ 671 } while (0) 672 673 kstat_t *arc_ksp; 674 static arc_state_t *arc_anon; 675 static arc_state_t *arc_mru; 676 static arc_state_t *arc_mru_ghost; 677 static arc_state_t *arc_mfu; 678 static arc_state_t *arc_mfu_ghost; 679 static arc_state_t *arc_l2c_only; 680 681 /* 682 * There are several ARC variables that are critical to export as kstats -- 683 * but we don't want to have to grovel around in the kstat whenever we wish to 684 * manipulate them. For these variables, we therefore define them to be in 685 * terms of the statistic variable. This assures that we are not introducing 686 * the possibility of inconsistency by having shadow copies of the variables, 687 * while still allowing the code to be readable. 688 */ 689 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 690 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 691 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 692 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 693 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 694 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 695 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 696 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 697 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 698 699 #define L2ARC_IS_VALID_COMPRESS(_c_) \ 700 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 701 702 static int arc_no_grow; /* Don't try to grow cache size */ 703 static uint64_t arc_tempreserve; 704 static uint64_t arc_loaned_bytes; 705 706 typedef struct arc_callback arc_callback_t; 707 708 struct arc_callback { 709 void *acb_private; 710 arc_done_func_t *acb_done; 711 arc_buf_t *acb_buf; 712 zio_t *acb_zio_dummy; 713 arc_callback_t *acb_next; 714 }; 715 716 typedef struct arc_write_callback arc_write_callback_t; 717 718 struct arc_write_callback { 719 void *awcb_private; 720 arc_done_func_t *awcb_ready; 721 arc_done_func_t *awcb_physdone; 722 arc_done_func_t *awcb_done; 723 arc_buf_t *awcb_buf; 724 }; 725 726 /* 727 * ARC buffers are separated into multiple structs as a memory saving measure: 728 * - Common fields struct, always defined, and embedded within it: 729 * - L2-only fields, always allocated but undefined when not in L2ARC 730 * - L1-only fields, only allocated when in L1ARC 731 * 732 * Buffer in L1 Buffer only in L2 733 * +------------------------+ +------------------------+ 734 * | arc_buf_hdr_t | | arc_buf_hdr_t | 735 * | | | | 736 * | | | | 737 * | | | | 738 * +------------------------+ +------------------------+ 739 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 740 * | (undefined if L1-only) | | | 741 * +------------------------+ +------------------------+ 742 * | l1arc_buf_hdr_t | 743 * | | 744 * | | 745 * | | 746 * | | 747 * +------------------------+ 748 * 749 * Because it's possible for the L2ARC to become extremely large, we can wind 750 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 751 * is minimized by only allocating the fields necessary for an L1-cached buffer 752 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 753 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 754 * words in pointers. arc_hdr_realloc() is used to switch a header between 755 * these two allocation states. 756 */ 757 typedef struct l1arc_buf_hdr { 758 kmutex_t b_freeze_lock; 759 #ifdef ZFS_DEBUG 760 /* 761 * used for debugging wtih kmem_flags - by allocating and freeing 762 * b_thawed when the buffer is thawed, we get a record of the stack 763 * trace that thawed it. 764 */ 765 void *b_thawed; 766 #endif 767 768 arc_buf_t *b_buf; 769 uint32_t b_datacnt; 770 /* for waiting on writes to complete */ 771 kcondvar_t b_cv; 772 773 /* protected by arc state mutex */ 774 arc_state_t *b_state; 775 multilist_node_t b_arc_node; 776 777 /* updated atomically */ 778 clock_t b_arc_access; 779 780 /* self protecting */ 781 refcount_t b_refcnt; 782 783 arc_callback_t *b_acb; 784 /* temporary buffer holder for in-flight compressed data */ 785 void *b_tmp_cdata; 786 } l1arc_buf_hdr_t; 787 788 typedef struct l2arc_dev l2arc_dev_t; 789 790 typedef struct l2arc_buf_hdr { 791 /* protected by arc_buf_hdr mutex */ 792 l2arc_dev_t *b_dev; /* L2ARC device */ 793 uint64_t b_daddr; /* disk address, offset byte */ 794 /* real alloc'd buffer size depending on b_compress applied */ 795 int32_t b_asize; 796 uint8_t b_compress; 797 798 list_node_t b_l2node; 799 } l2arc_buf_hdr_t; 800 801 struct arc_buf_hdr { 802 /* protected by hash lock */ 803 dva_t b_dva; 804 uint64_t b_birth; 805 /* 806 * Even though this checksum is only set/verified when a buffer is in 807 * the L1 cache, it needs to be in the set of common fields because it 808 * must be preserved from the time before a buffer is written out to 809 * L2ARC until after it is read back in. 810 */ 811 zio_cksum_t *b_freeze_cksum; 812 813 arc_buf_hdr_t *b_hash_next; 814 arc_flags_t b_flags; 815 816 /* immutable */ 817 int32_t b_size; 818 uint64_t b_spa; 819 820 /* L2ARC fields. Undefined when not in L2ARC. */ 821 l2arc_buf_hdr_t b_l2hdr; 822 /* L1ARC fields. Undefined when in l2arc_only state */ 823 l1arc_buf_hdr_t b_l1hdr; 824 }; 825 826 static arc_buf_t *arc_eviction_list; 827 static arc_buf_hdr_t arc_eviction_hdr; 828 829 #define GHOST_STATE(state) \ 830 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 831 (state) == arc_l2c_only) 832 833 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 834 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 835 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 836 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 837 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 838 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 839 840 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 841 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 842 #define HDR_L2_READING(hdr) \ 843 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 844 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 845 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 846 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 847 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 848 849 #define HDR_ISTYPE_METADATA(hdr) \ 850 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 851 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 852 853 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 854 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 855 856 /* 857 * Other sizes 858 */ 859 860 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 861 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 862 863 /* 864 * Hash table routines 865 */ 866 867 #define HT_LOCK_PAD 64 868 869 struct ht_lock { 870 kmutex_t ht_lock; 871 #ifdef _KERNEL 872 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 873 #endif 874 }; 875 876 #define BUF_LOCKS 256 877 typedef struct buf_hash_table { 878 uint64_t ht_mask; 879 arc_buf_hdr_t **ht_table; 880 struct ht_lock ht_locks[BUF_LOCKS]; 881 } buf_hash_table_t; 882 883 static buf_hash_table_t buf_hash_table; 884 885 #define BUF_HASH_INDEX(spa, dva, birth) \ 886 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 887 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 888 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 889 #define HDR_LOCK(hdr) \ 890 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 891 892 uint64_t zfs_crc64_table[256]; 893 894 /* 895 * Level 2 ARC 896 */ 897 898 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 899 #define L2ARC_HEADROOM 2 /* num of writes */ 900 /* 901 * If we discover during ARC scan any buffers to be compressed, we boost 902 * our headroom for the next scanning cycle by this percentage multiple. 903 */ 904 #define L2ARC_HEADROOM_BOOST 200 905 #define L2ARC_FEED_SECS 1 /* caching interval secs */ 906 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 907 908 /* 909 * Used to distinguish headers that are being process by 910 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 911 * address. This can happen when the header is added to the l2arc's list 912 * of buffers to write in the first stage of l2arc_write_buffers(), but 913 * has not yet been written out which happens in the second stage of 914 * l2arc_write_buffers(). 915 */ 916 #define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 917 918 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 919 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 920 921 /* L2ARC Performance Tunables */ 922 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 923 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 924 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 925 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 926 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 927 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 928 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 929 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 930 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 931 932 static list_t L2ARC_dev_list; /* device list */ 933 static list_t *l2arc_dev_list; /* device list pointer */ 934 static kmutex_t l2arc_dev_mtx; /* device list mutex */ 935 static l2arc_dev_t *l2arc_dev_last; /* last device used */ 936 static list_t L2ARC_free_on_write; /* free after write buf list */ 937 static list_t *l2arc_free_on_write; /* free after write list ptr */ 938 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 939 static uint64_t l2arc_ndev; /* number of devices */ 940 941 typedef struct l2arc_read_callback { 942 arc_buf_t *l2rcb_buf; /* read buffer */ 943 spa_t *l2rcb_spa; /* spa */ 944 blkptr_t l2rcb_bp; /* original blkptr */ 945 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 946 int l2rcb_flags; /* original flags */ 947 enum zio_compress l2rcb_compress; /* applied compress */ 948 } l2arc_read_callback_t; 949 950 typedef struct l2arc_write_callback { 951 l2arc_dev_t *l2wcb_dev; /* device info */ 952 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 953 list_t l2wcb_log_blk_buflist; /* in-flight log blocks */ 954 } l2arc_write_callback_t; 955 956 typedef struct l2arc_data_free { 957 /* protected by l2arc_free_on_write_mtx */ 958 void *l2df_data; 959 size_t l2df_size; 960 void (*l2df_func)(void *, size_t); 961 list_node_t l2df_list_node; 962 } l2arc_data_free_t; 963 964 static kmutex_t l2arc_feed_thr_lock; 965 static kcondvar_t l2arc_feed_thr_cv; 966 static uint8_t l2arc_thread_exit; 967 968 static void arc_get_data_buf(arc_buf_t *); 969 static void arc_access(arc_buf_hdr_t *, kmutex_t *); 970 static boolean_t arc_is_overflowing(); 971 static void arc_buf_watch(arc_buf_t *); 972 static void l2arc_read_done(zio_t *zio); 973 static l2arc_dev_t *l2arc_vdev_get(vdev_t *vd); 974 975 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 976 static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 977 static arc_buf_contents_t arc_flags_to_bufc(uint32_t); 978 979 static boolean_t l2arc_write_eligible(uint64_t, uint64_t, arc_buf_hdr_t *); 980 static void l2arc_read_done(zio_t *); 981 982 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 983 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 984 static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 985 986 static void 987 arc_update_hit_stat(arc_buf_hdr_t *hdr, boolean_t hit) 988 { 989 boolean_t pf = !HDR_PREFETCH(hdr); 990 switch (arc_buf_type(hdr)) { 991 case ARC_BUFC_DATA: 992 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, data); 993 break; 994 case ARC_BUFC_METADATA: 995 ARCSTAT_CONDSTAT(pf, demand, prefetch, hit, hits, misses, 996 metadata); 997 break; 998 default: 999 break; 1000 } 1001 } 1002 1003 enum { 1004 L2ARC_DEV_HDR_EVICT_FIRST = (1 << 0) /* mirror of l2ad_first */ 1005 }; 1006 1007 /* 1008 * Pointer used in persistent L2ARC (for pointing to log blocks & ARC buffers). 1009 */ 1010 typedef struct l2arc_log_blkptr { 1011 uint64_t lbp_daddr; /* device address of log */ 1012 /* 1013 * lbp_prop is the same format as the blk_prop in blkptr_t: 1014 * * logical size (in sectors) 1015 * * physical (compressed) size (in sectors) 1016 * * compression algorithm (we always LZ4-compress l2arc logs) 1017 * * checksum algorithm (used for lbp_cksum) 1018 * * object type & level (unused for now) 1019 */ 1020 uint64_t lbp_prop; 1021 zio_cksum_t lbp_cksum; /* fletcher4 of log */ 1022 } l2arc_log_blkptr_t; 1023 1024 /* 1025 * The persistent L2ARC device header. 1026 * Byte order of magic determines whether 64-bit bswap of fields is necessary. 1027 */ 1028 typedef struct l2arc_dev_hdr_phys { 1029 uint64_t dh_magic; /* L2ARC_DEV_HDR_MAGIC */ 1030 zio_cksum_t dh_self_cksum; /* fletcher4 of fields below */ 1031 1032 /* 1033 * Global L2ARC device state and metadata. 1034 */ 1035 uint64_t dh_spa_guid; 1036 uint64_t dh_alloc_space; /* vdev space alloc status */ 1037 uint64_t dh_flags; /* l2arc_dev_hdr_flags_t */ 1038 1039 /* 1040 * Start of log block chain. [0] -> newest log, [1] -> one older (used 1041 * for initiating prefetch). 1042 */ 1043 l2arc_log_blkptr_t dh_start_lbps[2]; 1044 1045 const uint64_t dh_pad[44]; /* pad to 512 bytes */ 1046 } l2arc_dev_hdr_phys_t; 1047 CTASSERT(sizeof (l2arc_dev_hdr_phys_t) == SPA_MINBLOCKSIZE); 1048 1049 /* 1050 * A single ARC buffer header entry in a l2arc_log_blk_phys_t. 1051 */ 1052 typedef struct l2arc_log_ent_phys { 1053 dva_t le_dva; /* dva of buffer */ 1054 uint64_t le_birth; /* birth txg of buffer */ 1055 zio_cksum_t le_freeze_cksum; 1056 /* 1057 * le_prop is the same format as the blk_prop in blkptr_t: 1058 * * logical size (in sectors) 1059 * * physical (compressed) size (in sectors) 1060 * * compression algorithm 1061 * * checksum algorithm (used for b_freeze_cksum) 1062 * * object type & level (used to restore arc_buf_contents_t) 1063 */ 1064 uint64_t le_prop; 1065 uint64_t le_daddr; /* buf location on l2dev */ 1066 const uint64_t le_pad[7]; /* resv'd for future use */ 1067 } l2arc_log_ent_phys_t; 1068 1069 /* 1070 * These design limits give us the following metadata overhead (before 1071 * compression): 1072 * avg_blk_sz overhead 1073 * 1k 12.51 % 1074 * 2k 6.26 % 1075 * 4k 3.13 % 1076 * 8k 1.56 % 1077 * 16k 0.78 % 1078 * 32k 0.39 % 1079 * 64k 0.20 % 1080 * 128k 0.10 % 1081 * Compression should be able to sequeeze these down by about a factor of 2x. 1082 */ 1083 #define L2ARC_LOG_BLK_SIZE (128 * 1024) /* 128k */ 1084 #define L2ARC_LOG_BLK_HEADER_LEN (128) 1085 #define L2ARC_LOG_BLK_ENTRIES /* 1023 entries */ \ 1086 ((L2ARC_LOG_BLK_SIZE - L2ARC_LOG_BLK_HEADER_LEN) / \ 1087 sizeof (l2arc_log_ent_phys_t)) 1088 /* 1089 * Maximum amount of data in an l2arc log block (used to terminate rebuilding 1090 * before we hit the write head and restore potentially corrupted blocks). 1091 */ 1092 #define L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE \ 1093 (SPA_MAXBLOCKSIZE * L2ARC_LOG_BLK_ENTRIES) 1094 /* 1095 * For the persistency and rebuild algorithms to operate reliably we need 1096 * the L2ARC device to at least be able to hold 3 full log blocks (otherwise 1097 * excessive log block looping might confuse the log chain end detection). 1098 * Under normal circumstances this is not a problem, since this is somewhere 1099 * around only 400 MB. 1100 */ 1101 #define L2ARC_PERSIST_MIN_SIZE (3 * L2ARC_LOG_BLK_MAX_PAYLOAD_SIZE) 1102 1103 /* 1104 * A log block of up to 1023 ARC buffer log entries, chained into the 1105 * persistent L2ARC metadata linked list. Byte order of magic determines 1106 * whether 64-bit bswap of fields is necessary. 1107 */ 1108 typedef struct l2arc_log_blk_phys { 1109 /* Header - see L2ARC_LOG_BLK_HEADER_LEN above */ 1110 uint64_t lb_magic; /* L2ARC_LOG_BLK_MAGIC */ 1111 l2arc_log_blkptr_t lb_back2_lbp; /* back 2 steps in chain */ 1112 uint64_t lb_pad[9]; /* resv'd for future use */ 1113 /* Payload */ 1114 l2arc_log_ent_phys_t lb_entries[L2ARC_LOG_BLK_ENTRIES]; 1115 } l2arc_log_blk_phys_t; 1116 1117 CTASSERT(sizeof (l2arc_log_blk_phys_t) == L2ARC_LOG_BLK_SIZE); 1118 CTASSERT(offsetof(l2arc_log_blk_phys_t, lb_entries) - 1119 offsetof(l2arc_log_blk_phys_t, lb_magic) == L2ARC_LOG_BLK_HEADER_LEN); 1120 1121 /* 1122 * These structures hold in-flight l2arc_log_blk_phys_t's as they're being 1123 * written to the L2ARC device. They may be compressed, hence the uint8_t[]. 1124 */ 1125 typedef struct l2arc_log_blk_buf { 1126 uint8_t lbb_log_blk[sizeof (l2arc_log_blk_phys_t)]; 1127 list_node_t lbb_node; 1128 } l2arc_log_blk_buf_t; 1129 1130 /* Macros for the manipulation fields in the blk_prop format of blkptr_t */ 1131 #define BLKPROP_GET_LSIZE(_obj, _field) \ 1132 BF64_GET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1) 1133 #define BLKPROP_SET_LSIZE(_obj, _field, x) \ 1134 BF64_SET_SB((_obj)->_field, 0, 16, SPA_MINBLOCKSHIFT, 1, x) 1135 #define BLKPROP_GET_PSIZE(_obj, _field) \ 1136 BF64_GET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 1) 1137 #define BLKPROP_SET_PSIZE(_obj, _field, x) \ 1138 BF64_SET_SB((_obj)->_field, 16, 16, SPA_MINBLOCKSHIFT, 1, x) 1139 #define BLKPROP_GET_COMPRESS(_obj, _field) \ 1140 BF64_GET((_obj)->_field, 32, 8) 1141 #define BLKPROP_SET_COMPRESS(_obj, _field, x) \ 1142 BF64_SET((_obj)->_field, 32, 8, x) 1143 #define BLKPROP_GET_CHECKSUM(_obj, _field) \ 1144 BF64_GET((_obj)->_field, 40, 8) 1145 #define BLKPROP_SET_CHECKSUM(_obj, _field, x) \ 1146 BF64_SET((_obj)->_field, 40, 8, x) 1147 #define BLKPROP_GET_TYPE(_obj, _field) \ 1148 BF64_GET((_obj)->_field, 48, 8) 1149 #define BLKPROP_SET_TYPE(_obj, _field, x) \ 1150 BF64_SET((_obj)->_field, 48, 8, x) 1151 1152 /* Macros for manipulating a l2arc_log_blkptr_t->lbp_prop field */ 1153 #define LBP_GET_LSIZE(_add) BLKPROP_GET_LSIZE(_add, lbp_prop) 1154 #define LBP_SET_LSIZE(_add, x) BLKPROP_SET_LSIZE(_add, lbp_prop, x) 1155 #define LBP_GET_PSIZE(_add) BLKPROP_GET_PSIZE(_add, lbp_prop) 1156 #define LBP_SET_PSIZE(_add, x) BLKPROP_SET_PSIZE(_add, lbp_prop, x) 1157 #define LBP_GET_COMPRESS(_add) BLKPROP_GET_COMPRESS(_add, lbp_prop) 1158 #define LBP_SET_COMPRESS(_add, x) BLKPROP_SET_COMPRESS(_add, lbp_prop, \ 1159 x) 1160 #define LBP_GET_CHECKSUM(_add) BLKPROP_GET_CHECKSUM(_add, lbp_prop) 1161 #define LBP_SET_CHECKSUM(_add, x) BLKPROP_SET_CHECKSUM(_add, lbp_prop, \ 1162 x) 1163 #define LBP_GET_TYPE(_add) BLKPROP_GET_TYPE(_add, lbp_prop) 1164 #define LBP_SET_TYPE(_add, x) BLKPROP_SET_TYPE(_add, lbp_prop, x) 1165 1166 /* Macros for manipulating a l2arc_log_ent_phys_t->le_prop field */ 1167 #define LE_GET_LSIZE(_le) BLKPROP_GET_LSIZE(_le, le_prop) 1168 #define LE_SET_LSIZE(_le, x) BLKPROP_SET_LSIZE(_le, le_prop, x) 1169 #define LE_GET_PSIZE(_le) BLKPROP_GET_PSIZE(_le, le_prop) 1170 #define LE_SET_PSIZE(_le, x) BLKPROP_SET_PSIZE(_le, le_prop, x) 1171 #define LE_GET_COMPRESS(_le) BLKPROP_GET_COMPRESS(_le, le_prop) 1172 #define LE_SET_COMPRESS(_le, x) BLKPROP_SET_COMPRESS(_le, le_prop, x) 1173 #define LE_GET_CHECKSUM(_le) BLKPROP_GET_CHECKSUM(_le, le_prop) 1174 #define LE_SET_CHECKSUM(_le, x) BLKPROP_SET_CHECKSUM(_le, le_prop, x) 1175 #define LE_GET_TYPE(_le) BLKPROP_GET_TYPE(_le, le_prop) 1176 #define LE_SET_TYPE(_le, x) BLKPROP_SET_TYPE(_le, le_prop, x) 1177 1178 #define PTR_SWAP(x, y) \ 1179 do { \ 1180 void *tmp = (x);\ 1181 x = y; \ 1182 y = tmp; \ 1183 _NOTE(CONSTCOND)\ 1184 } while (0) 1185 1186 #define L2ARC_DEV_HDR_MAGIC 0x5a46534341434845LLU /* ASCII: "ZFSCACHE" */ 1187 #define L2ARC_LOG_BLK_MAGIC 0x4c4f47424c4b4844LLU /* ASCII: "LOGBLKHD" */ 1188 1189 /* 1190 * Performance tuning of L2ARC persistency: 1191 * 1192 * l2arc_rebuild_enabled : Controls whether L2ARC device adds (either at 1193 * pool import or when adding one manually later) will attempt 1194 * to rebuild L2ARC buffer contents. In special circumstances, 1195 * the administrator may want to set this to B_FALSE, if they 1196 * are having trouble importing a pool or attaching an L2ARC 1197 * device (e.g. the L2ARC device is slow to read in stored log 1198 * metadata, or the metadata has become somehow 1199 * fragmented/unusable). 1200 */ 1201 boolean_t l2arc_rebuild_enabled = B_TRUE; 1202 1203 /* L2ARC persistency rebuild control routines. */ 1204 static void l2arc_dev_rebuild_start(l2arc_dev_t *dev); 1205 static int l2arc_rebuild(l2arc_dev_t *dev); 1206 1207 /* L2ARC persistency read I/O routines. */ 1208 static int l2arc_dev_hdr_read(l2arc_dev_t *dev); 1209 static int l2arc_log_blk_read(l2arc_dev_t *dev, 1210 const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp, 1211 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, 1212 uint8_t *this_lb_buf, uint8_t *next_lb_buf, 1213 zio_t *this_io, zio_t **next_io); 1214 static zio_t *l2arc_log_blk_prefetch(vdev_t *vd, 1215 const l2arc_log_blkptr_t *lp, uint8_t *lb_buf); 1216 static void l2arc_log_blk_prefetch_abort(zio_t *zio); 1217 1218 /* L2ARC persistency block restoration routines. */ 1219 static void l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid, 1220 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize); 1221 static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, 1222 l2arc_dev_t *dev, uint64_t guid); 1223 1224 /* L2ARC persistency write I/O routines. */ 1225 static void l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio); 1226 static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, 1227 l2arc_write_callback_t *cb); 1228 1229 /* L2ARC persistency auxilliary routines. */ 1230 static boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev, 1231 const l2arc_log_blkptr_t *lp); 1232 static void l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr, 1233 zio_cksum_t *cksum); 1234 static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev, 1235 const arc_buf_hdr_t *ab); 1236 static inline boolean_t l2arc_range_check_overlap(uint64_t bottom, 1237 uint64_t top, uint64_t check); 1238 1239 /* 1240 * L2ARC Internals 1241 */ 1242 struct l2arc_dev { 1243 vdev_t *l2ad_vdev; /* vdev */ 1244 spa_t *l2ad_spa; /* spa */ 1245 uint64_t l2ad_hand; /* next write location */ 1246 uint64_t l2ad_start; /* first addr on device */ 1247 uint64_t l2ad_end; /* last addr on device */ 1248 boolean_t l2ad_first; /* first sweep through */ 1249 boolean_t l2ad_writing; /* currently writing */ 1250 kmutex_t l2ad_mtx; /* lock for buffer list */ 1251 list_t l2ad_buflist; /* buffer list */ 1252 list_node_t l2ad_node; /* device list node */ 1253 refcount_t l2ad_alloc; /* allocated bytes */ 1254 l2arc_dev_hdr_phys_t *l2ad_dev_hdr; /* persistent device header */ 1255 uint64_t l2ad_dev_hdr_asize; /* aligned hdr size */ 1256 l2arc_log_blk_phys_t l2ad_log_blk; /* currently open log block */ 1257 int l2ad_log_ent_idx; /* index into cur log blk */ 1258 /* number of bytes in current log block's payload */ 1259 uint64_t l2ad_log_blk_payload_asize; 1260 /* flag indicating whether a rebuild is scheduled or is going on */ 1261 boolean_t l2ad_rebuild; 1262 boolean_t l2ad_rebuild_cancel; 1263 kt_did_t l2ad_rebuild_did; 1264 }; 1265 1266 static inline uint64_t 1267 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1268 { 1269 uint8_t *vdva = (uint8_t *)dva; 1270 uint64_t crc = -1ULL; 1271 int i; 1272 1273 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1274 1275 for (i = 0; i < sizeof (dva_t); i++) 1276 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1277 1278 crc ^= (spa>>8) ^ birth; 1279 1280 return (crc); 1281 } 1282 1283 #define BUF_EMPTY(buf) \ 1284 ((buf)->b_dva.dva_word[0] == 0 && \ 1285 (buf)->b_dva.dva_word[1] == 0) 1286 1287 #define BUF_EQUAL(spa, dva, birth, buf) \ 1288 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1289 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1290 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1291 1292 static void 1293 buf_discard_identity(arc_buf_hdr_t *hdr) 1294 { 1295 hdr->b_dva.dva_word[0] = 0; 1296 hdr->b_dva.dva_word[1] = 0; 1297 hdr->b_birth = 0; 1298 } 1299 1300 static arc_buf_hdr_t * 1301 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1302 { 1303 const dva_t *dva = BP_IDENTITY(bp); 1304 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1305 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1306 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1307 arc_buf_hdr_t *hdr; 1308 1309 mutex_enter(hash_lock); 1310 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1311 hdr = hdr->b_hash_next) { 1312 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1313 *lockp = hash_lock; 1314 return (hdr); 1315 } 1316 } 1317 mutex_exit(hash_lock); 1318 *lockp = NULL; 1319 return (NULL); 1320 } 1321 1322 /* 1323 * Insert an entry into the hash table. If there is already an element 1324 * equal to elem in the hash table, then the already existing element 1325 * will be returned and the new element will not be inserted. 1326 * Otherwise returns NULL. 1327 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1328 */ 1329 static arc_buf_hdr_t * 1330 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1331 { 1332 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1333 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1334 arc_buf_hdr_t *fhdr; 1335 uint32_t i; 1336 1337 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1338 ASSERT(hdr->b_birth != 0); 1339 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1340 1341 if (lockp != NULL) { 1342 *lockp = hash_lock; 1343 mutex_enter(hash_lock); 1344 } else { 1345 ASSERT(MUTEX_HELD(hash_lock)); 1346 } 1347 1348 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1349 fhdr = fhdr->b_hash_next, i++) { 1350 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1351 return (fhdr); 1352 } 1353 1354 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1355 buf_hash_table.ht_table[idx] = hdr; 1356 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1357 1358 /* collect some hash table performance data */ 1359 if (i > 0) { 1360 ARCSTAT_BUMP(arcstat_hash_collisions); 1361 if (i == 1) 1362 ARCSTAT_BUMP(arcstat_hash_chains); 1363 1364 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1365 } 1366 1367 ARCSTAT_BUMP(arcstat_hash_elements); 1368 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1369 1370 return (NULL); 1371 } 1372 1373 static void 1374 buf_hash_remove(arc_buf_hdr_t *hdr) 1375 { 1376 arc_buf_hdr_t *fhdr, **hdrp; 1377 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1378 1379 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1380 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1381 1382 hdrp = &buf_hash_table.ht_table[idx]; 1383 while ((fhdr = *hdrp) != hdr) { 1384 ASSERT(fhdr != NULL); 1385 hdrp = &fhdr->b_hash_next; 1386 } 1387 *hdrp = hdr->b_hash_next; 1388 hdr->b_hash_next = NULL; 1389 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1390 1391 /* collect some hash table performance data */ 1392 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1393 1394 if (buf_hash_table.ht_table[idx] && 1395 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1396 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1397 } 1398 1399 /* 1400 * Global data structures and functions for the buf kmem cache. 1401 */ 1402 static kmem_cache_t *hdr_full_cache; 1403 static kmem_cache_t *hdr_l2only_cache; 1404 static kmem_cache_t *buf_cache; 1405 1406 static void 1407 buf_fini(void) 1408 { 1409 int i; 1410 1411 kmem_free(buf_hash_table.ht_table, 1412 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1413 for (i = 0; i < BUF_LOCKS; i++) 1414 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1415 kmem_cache_destroy(hdr_full_cache); 1416 kmem_cache_destroy(hdr_l2only_cache); 1417 kmem_cache_destroy(buf_cache); 1418 } 1419 1420 /* 1421 * Constructor callback - called when the cache is empty 1422 * and a new buf is requested. 1423 */ 1424 /* ARGSUSED */ 1425 static int 1426 hdr_full_cons(void *vbuf, void *unused, int kmflag) 1427 { 1428 arc_buf_hdr_t *hdr = vbuf; 1429 1430 bzero(hdr, HDR_FULL_SIZE); 1431 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1432 refcount_create(&hdr->b_l1hdr.b_refcnt); 1433 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1434 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1435 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1436 1437 return (0); 1438 } 1439 1440 /* ARGSUSED */ 1441 static int 1442 hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1443 { 1444 arc_buf_hdr_t *hdr = vbuf; 1445 1446 bzero(hdr, HDR_L2ONLY_SIZE); 1447 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1448 1449 return (0); 1450 } 1451 1452 /* ARGSUSED */ 1453 static int 1454 buf_cons(void *vbuf, void *unused, int kmflag) 1455 { 1456 arc_buf_t *buf = vbuf; 1457 1458 bzero(buf, sizeof (arc_buf_t)); 1459 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1460 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1461 1462 return (0); 1463 } 1464 1465 /* 1466 * Destructor callback - called when a cached buf is 1467 * no longer required. 1468 */ 1469 /* ARGSUSED */ 1470 static void 1471 hdr_full_dest(void *vbuf, void *unused) 1472 { 1473 arc_buf_hdr_t *hdr = vbuf; 1474 1475 ASSERT(BUF_EMPTY(hdr)); 1476 cv_destroy(&hdr->b_l1hdr.b_cv); 1477 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1478 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1479 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1480 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1481 } 1482 1483 /* ARGSUSED */ 1484 static void 1485 hdr_l2only_dest(void *vbuf, void *unused) 1486 { 1487 arc_buf_hdr_t *hdr = vbuf; 1488 1489 ASSERT(BUF_EMPTY(hdr)); 1490 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1491 } 1492 1493 /* ARGSUSED */ 1494 static void 1495 buf_dest(void *vbuf, void *unused) 1496 { 1497 arc_buf_t *buf = vbuf; 1498 1499 mutex_destroy(&buf->b_evict_lock); 1500 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1501 } 1502 1503 /* 1504 * Reclaim callback -- invoked when memory is low. 1505 */ 1506 /* ARGSUSED */ 1507 static void 1508 hdr_recl(void *unused) 1509 { 1510 dprintf("hdr_recl called\n"); 1511 /* 1512 * umem calls the reclaim func when we destroy the buf cache, 1513 * which is after we do arc_fini(). 1514 */ 1515 if (!arc_dead) 1516 cv_signal(&arc_reclaim_thread_cv); 1517 } 1518 1519 static void 1520 buf_init(void) 1521 { 1522 uint64_t *ct; 1523 uint64_t hsize = 1ULL << 12; 1524 int i, j; 1525 1526 /* 1527 * The hash table is big enough to fill all of physical memory 1528 * with an average block size of zfs_arc_average_blocksize (default 8K). 1529 * By default, the table will take up 1530 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1531 */ 1532 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE) 1533 hsize <<= 1; 1534 retry: 1535 buf_hash_table.ht_mask = hsize - 1; 1536 buf_hash_table.ht_table = 1537 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1538 if (buf_hash_table.ht_table == NULL) { 1539 ASSERT(hsize > (1ULL << 8)); 1540 hsize >>= 1; 1541 goto retry; 1542 } 1543 1544 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1545 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1546 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1547 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1548 NULL, NULL, 0); 1549 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1550 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1551 1552 for (i = 0; i < 256; i++) 1553 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1554 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1555 1556 for (i = 0; i < BUF_LOCKS; i++) { 1557 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1558 NULL, MUTEX_DEFAULT, NULL); 1559 } 1560 } 1561 1562 /* 1563 * Transition between the two allocation states for the arc_buf_hdr struct. 1564 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1565 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1566 * version is used when a cache buffer is only in the L2ARC in order to reduce 1567 * memory usage. 1568 */ 1569 static arc_buf_hdr_t * 1570 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1571 { 1572 ASSERT(HDR_HAS_L2HDR(hdr)); 1573 1574 arc_buf_hdr_t *nhdr; 1575 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1576 1577 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1578 (old == hdr_l2only_cache && new == hdr_full_cache)); 1579 1580 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1581 1582 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1583 buf_hash_remove(hdr); 1584 1585 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1586 1587 if (new == hdr_full_cache) { 1588 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1589 /* 1590 * arc_access and arc_change_state need to be aware that a 1591 * header has just come out of L2ARC, so we set its state to 1592 * l2c_only even though it's about to change. 1593 */ 1594 nhdr->b_l1hdr.b_state = arc_l2c_only; 1595 1596 /* Verify previous threads set to NULL before freeing */ 1597 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1598 } else { 1599 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1600 ASSERT0(hdr->b_l1hdr.b_datacnt); 1601 1602 /* 1603 * If we've reached here, We must have been called from 1604 * arc_evict_hdr(), as such we should have already been 1605 * removed from any ghost list we were previously on 1606 * (which protects us from racing with arc_evict_state), 1607 * thus no locking is needed during this check. 1608 */ 1609 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1610 1611 /* 1612 * A buffer must not be moved into the arc_l2c_only 1613 * state if it's not finished being written out to the 1614 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1615 * might try to be accessed, even though it was removed. 1616 */ 1617 VERIFY(!HDR_L2_WRITING(hdr)); 1618 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1619 1620 #ifdef ZFS_DEBUG 1621 if (hdr->b_l1hdr.b_thawed != NULL) { 1622 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1623 hdr->b_l1hdr.b_thawed = NULL; 1624 } 1625 #endif 1626 1627 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1628 } 1629 /* 1630 * The header has been reallocated so we need to re-insert it into any 1631 * lists it was on. 1632 */ 1633 (void) buf_hash_insert(nhdr, NULL); 1634 1635 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1636 1637 mutex_enter(&dev->l2ad_mtx); 1638 1639 /* 1640 * We must place the realloc'ed header back into the list at 1641 * the same spot. Otherwise, if it's placed earlier in the list, 1642 * l2arc_write_buffers() could find it during the function's 1643 * write phase, and try to write it out to the l2arc. 1644 */ 1645 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1646 list_remove(&dev->l2ad_buflist, hdr); 1647 1648 mutex_exit(&dev->l2ad_mtx); 1649 1650 /* 1651 * Since we're using the pointer address as the tag when 1652 * incrementing and decrementing the l2ad_alloc refcount, we 1653 * must remove the old pointer (that we're about to destroy) and 1654 * add the new pointer to the refcount. Otherwise we'd remove 1655 * the wrong pointer address when calling arc_hdr_destroy() later. 1656 */ 1657 1658 (void) refcount_remove_many(&dev->l2ad_alloc, 1659 hdr->b_l2hdr.b_asize, hdr); 1660 1661 (void) refcount_add_many(&dev->l2ad_alloc, 1662 nhdr->b_l2hdr.b_asize, nhdr); 1663 1664 buf_discard_identity(hdr); 1665 hdr->b_freeze_cksum = NULL; 1666 kmem_cache_free(old, hdr); 1667 1668 return (nhdr); 1669 } 1670 1671 1672 #define ARC_MINTIME (hz>>4) /* 62 ms */ 1673 1674 static void 1675 arc_cksum_verify(arc_buf_t *buf) 1676 { 1677 zio_cksum_t zc; 1678 1679 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1680 return; 1681 1682 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1683 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1684 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1685 return; 1686 } 1687 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1688 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1689 panic("buffer modified while frozen!"); 1690 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1691 } 1692 1693 static int 1694 arc_cksum_equal(arc_buf_t *buf) 1695 { 1696 zio_cksum_t zc; 1697 int equal; 1698 1699 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1700 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1701 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1702 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1703 1704 return (equal); 1705 } 1706 1707 static void 1708 arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1709 { 1710 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1711 return; 1712 1713 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1714 if (buf->b_hdr->b_freeze_cksum != NULL) { 1715 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1716 return; 1717 } 1718 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1719 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1720 buf->b_hdr->b_freeze_cksum); 1721 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1722 arc_buf_watch(buf); 1723 } 1724 1725 #ifndef _KERNEL 1726 typedef struct procctl { 1727 long cmd; 1728 prwatch_t prwatch; 1729 } procctl_t; 1730 #endif 1731 1732 /* ARGSUSED */ 1733 static void 1734 arc_buf_unwatch(arc_buf_t *buf) 1735 { 1736 #ifndef _KERNEL 1737 if (arc_watch) { 1738 int result; 1739 procctl_t ctl; 1740 ctl.cmd = PCWATCH; 1741 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1742 ctl.prwatch.pr_size = 0; 1743 ctl.prwatch.pr_wflags = 0; 1744 result = write(arc_procfd, &ctl, sizeof (ctl)); 1745 ASSERT3U(result, ==, sizeof (ctl)); 1746 } 1747 #endif 1748 } 1749 1750 /* ARGSUSED */ 1751 static void 1752 arc_buf_watch(arc_buf_t *buf) 1753 { 1754 #ifndef _KERNEL 1755 if (arc_watch) { 1756 int result; 1757 procctl_t ctl; 1758 ctl.cmd = PCWATCH; 1759 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1760 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1761 ctl.prwatch.pr_wflags = WA_WRITE; 1762 result = write(arc_procfd, &ctl, sizeof (ctl)); 1763 ASSERT3U(result, ==, sizeof (ctl)); 1764 } 1765 #endif 1766 } 1767 1768 static arc_buf_contents_t 1769 arc_buf_type(arc_buf_hdr_t *hdr) 1770 { 1771 if (HDR_ISTYPE_METADATA(hdr)) { 1772 return (ARC_BUFC_METADATA); 1773 } else { 1774 return (ARC_BUFC_DATA); 1775 } 1776 } 1777 1778 static uint32_t 1779 arc_bufc_to_flags(arc_buf_contents_t type) 1780 { 1781 switch (type) { 1782 case ARC_BUFC_DATA: 1783 /* metadata field is 0 if buffer contains normal data */ 1784 return (0); 1785 case ARC_BUFC_METADATA: 1786 return (ARC_FLAG_BUFC_METADATA); 1787 default: 1788 break; 1789 } 1790 panic("undefined ARC buffer type!"); 1791 return ((uint32_t)-1); 1792 } 1793 1794 static arc_buf_contents_t 1795 arc_flags_to_bufc(uint32_t flags) 1796 { 1797 if (flags & ARC_FLAG_BUFC_METADATA) 1798 return (ARC_BUFC_METADATA); 1799 return (ARC_BUFC_DATA); 1800 } 1801 1802 void 1803 arc_buf_thaw(arc_buf_t *buf) 1804 { 1805 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1806 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1807 panic("modifying non-anon buffer!"); 1808 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1809 panic("modifying buffer while i/o in progress!"); 1810 arc_cksum_verify(buf); 1811 } 1812 1813 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1814 if (buf->b_hdr->b_freeze_cksum != NULL) { 1815 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1816 buf->b_hdr->b_freeze_cksum = NULL; 1817 } 1818 1819 #ifdef ZFS_DEBUG 1820 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1821 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1822 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1823 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1824 } 1825 #endif 1826 1827 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1828 1829 arc_buf_unwatch(buf); 1830 } 1831 1832 void 1833 arc_buf_freeze(arc_buf_t *buf) 1834 { 1835 kmutex_t *hash_lock; 1836 1837 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1838 return; 1839 1840 hash_lock = HDR_LOCK(buf->b_hdr); 1841 mutex_enter(hash_lock); 1842 1843 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1844 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1845 arc_cksum_compute(buf, B_FALSE); 1846 mutex_exit(hash_lock); 1847 1848 } 1849 1850 static void 1851 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1852 { 1853 ASSERT(HDR_HAS_L1HDR(hdr)); 1854 ASSERT(MUTEX_HELD(hash_lock)); 1855 arc_state_t *state = hdr->b_l1hdr.b_state; 1856 1857 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1858 (state != arc_anon)) { 1859 /* We don't use the L2-only state list. */ 1860 if (state != arc_l2c_only) { 1861 arc_buf_contents_t type = arc_buf_type(hdr); 1862 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1863 multilist_t *list = &state->arcs_list[type]; 1864 uint64_t *size = &state->arcs_lsize[type]; 1865 1866 multilist_remove(list, hdr); 1867 1868 if (GHOST_STATE(state)) { 1869 ASSERT0(hdr->b_l1hdr.b_datacnt); 1870 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1871 delta = hdr->b_size; 1872 } 1873 ASSERT(delta > 0); 1874 ASSERT3U(*size, >=, delta); 1875 atomic_add_64(size, -delta); 1876 } 1877 /* remove the prefetch flag if we get a reference */ 1878 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1879 } 1880 } 1881 1882 static int 1883 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1884 { 1885 int cnt; 1886 arc_state_t *state = hdr->b_l1hdr.b_state; 1887 1888 ASSERT(HDR_HAS_L1HDR(hdr)); 1889 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1890 ASSERT(!GHOST_STATE(state)); 1891 1892 /* 1893 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1894 * check to prevent usage of the arc_l2c_only list. 1895 */ 1896 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1897 (state != arc_anon)) { 1898 arc_buf_contents_t type = arc_buf_type(hdr); 1899 multilist_t *list = &state->arcs_list[type]; 1900 uint64_t *size = &state->arcs_lsize[type]; 1901 1902 multilist_insert(list, hdr); 1903 1904 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1905 atomic_add_64(size, hdr->b_size * 1906 hdr->b_l1hdr.b_datacnt); 1907 } 1908 return (cnt); 1909 } 1910 1911 /* 1912 * Move the supplied buffer to the indicated state. The hash lock 1913 * for the buffer must be held by the caller. 1914 */ 1915 static void 1916 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1917 kmutex_t *hash_lock) 1918 { 1919 arc_state_t *old_state; 1920 int64_t refcnt; 1921 uint32_t datacnt; 1922 uint64_t from_delta, to_delta; 1923 arc_buf_contents_t buftype = arc_buf_type(hdr); 1924 1925 /* 1926 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1927 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1928 * L1 hdr doesn't always exist when we change state to arc_anon before 1929 * destroying a header, in which case reallocating to add the L1 hdr is 1930 * pointless. 1931 */ 1932 if (HDR_HAS_L1HDR(hdr)) { 1933 old_state = hdr->b_l1hdr.b_state; 1934 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1935 datacnt = hdr->b_l1hdr.b_datacnt; 1936 } else { 1937 old_state = arc_l2c_only; 1938 refcnt = 0; 1939 datacnt = 0; 1940 } 1941 1942 ASSERT(MUTEX_HELD(hash_lock)); 1943 ASSERT3P(new_state, !=, old_state); 1944 ASSERT(refcnt == 0 || datacnt > 0); 1945 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1946 ASSERT(old_state != arc_anon || datacnt <= 1); 1947 1948 from_delta = to_delta = datacnt * hdr->b_size; 1949 1950 /* 1951 * If this buffer is evictable, transfer it from the 1952 * old state list to the new state list. 1953 */ 1954 if (refcnt == 0) { 1955 if (old_state != arc_anon && old_state != arc_l2c_only) { 1956 uint64_t *size = &old_state->arcs_lsize[buftype]; 1957 1958 ASSERT(HDR_HAS_L1HDR(hdr)); 1959 multilist_remove(&old_state->arcs_list[buftype], hdr); 1960 1961 /* 1962 * If prefetching out of the ghost cache, 1963 * we will have a non-zero datacnt. 1964 */ 1965 if (GHOST_STATE(old_state) && datacnt == 0) { 1966 /* ghost elements have a ghost size */ 1967 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1968 from_delta = hdr->b_size; 1969 } 1970 ASSERT3U(*size, >=, from_delta); 1971 atomic_add_64(size, -from_delta); 1972 } 1973 if (new_state != arc_anon && new_state != arc_l2c_only) { 1974 uint64_t *size = &new_state->arcs_lsize[buftype]; 1975 1976 /* 1977 * An L1 header always exists here, since if we're 1978 * moving to some L1-cached state (i.e. not l2c_only or 1979 * anonymous), we realloc the header to add an L1hdr 1980 * beforehand. 1981 */ 1982 ASSERT(HDR_HAS_L1HDR(hdr)); 1983 multilist_insert(&new_state->arcs_list[buftype], hdr); 1984 1985 /* ghost elements have a ghost size */ 1986 if (GHOST_STATE(new_state)) { 1987 ASSERT0(datacnt); 1988 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1989 to_delta = hdr->b_size; 1990 } 1991 atomic_add_64(size, to_delta); 1992 } 1993 } 1994 1995 ASSERT(!BUF_EMPTY(hdr)); 1996 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1997 buf_hash_remove(hdr); 1998 1999 /* adjust state sizes (ignore arc_l2c_only) */ 2000 2001 if (to_delta && new_state != arc_l2c_only) { 2002 ASSERT(HDR_HAS_L1HDR(hdr)); 2003 if (GHOST_STATE(new_state)) { 2004 ASSERT0(datacnt); 2005 2006 /* 2007 * We moving a header to a ghost state, we first 2008 * remove all arc buffers. Thus, we'll have a 2009 * datacnt of zero, and no arc buffer to use for 2010 * the reference. As a result, we use the arc 2011 * header pointer for the reference. 2012 */ 2013 (void) refcount_add_many(&new_state->arcs_size, 2014 hdr->b_size, hdr); 2015 } else { 2016 ASSERT3U(datacnt, !=, 0); 2017 2018 /* 2019 * Each individual buffer holds a unique reference, 2020 * thus we must remove each of these references one 2021 * at a time. 2022 */ 2023 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2024 buf = buf->b_next) { 2025 (void) refcount_add_many(&new_state->arcs_size, 2026 hdr->b_size, buf); 2027 } 2028 } 2029 } 2030 2031 if (from_delta && old_state != arc_l2c_only) { 2032 ASSERT(HDR_HAS_L1HDR(hdr)); 2033 if (GHOST_STATE(old_state)) { 2034 /* 2035 * When moving a header off of a ghost state, 2036 * there's the possibility for datacnt to be 2037 * non-zero. This is because we first add the 2038 * arc buffer to the header prior to changing 2039 * the header's state. Since we used the header 2040 * for the reference when putting the header on 2041 * the ghost state, we must balance that and use 2042 * the header when removing off the ghost state 2043 * (even though datacnt is non zero). 2044 */ 2045 2046 IMPLY(datacnt == 0, new_state == arc_anon || 2047 new_state == arc_l2c_only); 2048 2049 (void) refcount_remove_many(&old_state->arcs_size, 2050 hdr->b_size, hdr); 2051 } else { 2052 ASSERT3P(datacnt, !=, 0); 2053 2054 /* 2055 * Each individual buffer holds a unique reference, 2056 * thus we must remove each of these references one 2057 * at a time. 2058 */ 2059 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2060 buf = buf->b_next) { 2061 (void) refcount_remove_many( 2062 &old_state->arcs_size, hdr->b_size, buf); 2063 } 2064 } 2065 } 2066 2067 if (HDR_HAS_L1HDR(hdr)) 2068 hdr->b_l1hdr.b_state = new_state; 2069 2070 /* 2071 * L2 headers should never be on the L2 state list since they don't 2072 * have L1 headers allocated. 2073 */ 2074 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2075 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2076 } 2077 2078 void 2079 arc_space_consume(uint64_t space, arc_space_type_t type) 2080 { 2081 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2082 2083 switch (type) { 2084 case ARC_SPACE_DATA: 2085 ARCSTAT_INCR(arcstat_data_size, space); 2086 break; 2087 case ARC_SPACE_META: 2088 ARCSTAT_INCR(arcstat_metadata_size, space); 2089 break; 2090 case ARC_SPACE_OTHER: 2091 ARCSTAT_INCR(arcstat_other_size, space); 2092 break; 2093 case ARC_SPACE_HDRS: 2094 ARCSTAT_INCR(arcstat_hdr_size, space); 2095 break; 2096 case ARC_SPACE_L2HDRS: 2097 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2098 break; 2099 } 2100 2101 if (type != ARC_SPACE_DATA) 2102 ARCSTAT_INCR(arcstat_meta_used, space); 2103 2104 atomic_add_64(&arc_size, space); 2105 } 2106 2107 void 2108 arc_space_return(uint64_t space, arc_space_type_t type) 2109 { 2110 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2111 2112 switch (type) { 2113 case ARC_SPACE_DATA: 2114 ARCSTAT_INCR(arcstat_data_size, -space); 2115 break; 2116 case ARC_SPACE_META: 2117 ARCSTAT_INCR(arcstat_metadata_size, -space); 2118 break; 2119 case ARC_SPACE_OTHER: 2120 ARCSTAT_INCR(arcstat_other_size, -space); 2121 break; 2122 case ARC_SPACE_HDRS: 2123 ARCSTAT_INCR(arcstat_hdr_size, -space); 2124 break; 2125 case ARC_SPACE_L2HDRS: 2126 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2127 break; 2128 } 2129 2130 if (type != ARC_SPACE_DATA) { 2131 ASSERT(arc_meta_used >= space); 2132 if (arc_meta_max < arc_meta_used) 2133 arc_meta_max = arc_meta_used; 2134 ARCSTAT_INCR(arcstat_meta_used, -space); 2135 } 2136 2137 ASSERT(arc_size >= space); 2138 atomic_add_64(&arc_size, -space); 2139 } 2140 2141 arc_buf_t * 2142 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2143 { 2144 arc_buf_hdr_t *hdr; 2145 arc_buf_t *buf; 2146 2147 ASSERT3U(size, >, 0); 2148 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2149 ASSERT(BUF_EMPTY(hdr)); 2150 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2151 hdr->b_size = size; 2152 hdr->b_spa = spa_load_guid(spa); 2153 2154 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2155 buf->b_hdr = hdr; 2156 buf->b_data = NULL; 2157 buf->b_efunc = NULL; 2158 buf->b_private = NULL; 2159 buf->b_next = NULL; 2160 2161 hdr->b_flags = arc_bufc_to_flags(type); 2162 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2163 2164 hdr->b_l1hdr.b_buf = buf; 2165 hdr->b_l1hdr.b_state = arc_anon; 2166 hdr->b_l1hdr.b_arc_access = 0; 2167 hdr->b_l1hdr.b_datacnt = 1; 2168 hdr->b_l1hdr.b_tmp_cdata = NULL; 2169 2170 arc_get_data_buf(buf); 2171 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2172 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2173 2174 return (buf); 2175 } 2176 2177 /* 2178 * Allocates an ARC buf header that's in an evicted & L2-cached state. 2179 * This is used during l2arc reconstruction to make empty ARC buffers 2180 * which circumvent the regular disk->arc->l2arc path and instead come 2181 * into being in the reverse order, i.e. l2arc->arc. 2182 */ 2183 arc_buf_hdr_t * 2184 arc_buf_alloc_l2only(uint64_t load_guid, int size, arc_buf_contents_t type, 2185 l2arc_dev_t *dev, dva_t dva, uint64_t daddr, int32_t asize, uint64_t birth, 2186 zio_cksum_t cksum, enum zio_compress compress) 2187 { 2188 arc_buf_hdr_t *hdr; 2189 2190 ASSERT3U(size, >, 0); 2191 hdr = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 2192 ASSERT(BUF_EMPTY(hdr)); 2193 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2194 hdr->b_dva = dva; 2195 hdr->b_birth = birth; 2196 hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 2197 bcopy(&cksum, hdr->b_freeze_cksum, sizeof (cksum)); 2198 hdr->b_flags = arc_bufc_to_flags(type); 2199 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 2200 hdr->b_size = size; 2201 hdr->b_spa = load_guid; 2202 2203 hdr->b_l2hdr.b_compress = compress; 2204 hdr->b_l2hdr.b_dev = dev; 2205 hdr->b_l2hdr.b_daddr = daddr; 2206 hdr->b_l2hdr.b_asize = asize; 2207 2208 return (hdr); 2209 } 2210 2211 static char *arc_onloan_tag = "onloan"; 2212 2213 /* 2214 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2215 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2216 * buffers must be returned to the arc before they can be used by the DMU or 2217 * freed. 2218 */ 2219 arc_buf_t * 2220 arc_loan_buf(spa_t *spa, int size) 2221 { 2222 arc_buf_t *buf; 2223 2224 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2225 2226 atomic_add_64(&arc_loaned_bytes, size); 2227 return (buf); 2228 } 2229 2230 /* 2231 * Return a loaned arc buffer to the arc. 2232 */ 2233 void 2234 arc_return_buf(arc_buf_t *buf, void *tag) 2235 { 2236 arc_buf_hdr_t *hdr = buf->b_hdr; 2237 2238 ASSERT(buf->b_data != NULL); 2239 ASSERT(HDR_HAS_L1HDR(hdr)); 2240 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2241 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2242 2243 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2244 } 2245 2246 /* Detach an arc_buf from a dbuf (tag) */ 2247 void 2248 arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2249 { 2250 arc_buf_hdr_t *hdr = buf->b_hdr; 2251 2252 ASSERT(buf->b_data != NULL); 2253 ASSERT(HDR_HAS_L1HDR(hdr)); 2254 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2255 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2256 buf->b_efunc = NULL; 2257 buf->b_private = NULL; 2258 2259 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2260 } 2261 2262 static arc_buf_t * 2263 arc_buf_clone(arc_buf_t *from) 2264 { 2265 arc_buf_t *buf; 2266 arc_buf_hdr_t *hdr = from->b_hdr; 2267 uint64_t size = hdr->b_size; 2268 2269 ASSERT(HDR_HAS_L1HDR(hdr)); 2270 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2271 2272 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2273 buf->b_hdr = hdr; 2274 buf->b_data = NULL; 2275 buf->b_efunc = NULL; 2276 buf->b_private = NULL; 2277 buf->b_next = hdr->b_l1hdr.b_buf; 2278 hdr->b_l1hdr.b_buf = buf; 2279 arc_get_data_buf(buf); 2280 bcopy(from->b_data, buf->b_data, size); 2281 2282 /* 2283 * This buffer already exists in the arc so create a duplicate 2284 * copy for the caller. If the buffer is associated with user data 2285 * then track the size and number of duplicates. These stats will be 2286 * updated as duplicate buffers are created and destroyed. 2287 */ 2288 if (HDR_ISTYPE_DATA(hdr)) { 2289 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2290 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2291 } 2292 hdr->b_l1hdr.b_datacnt += 1; 2293 return (buf); 2294 } 2295 2296 void 2297 arc_buf_add_ref(arc_buf_t *buf, void* tag) 2298 { 2299 arc_buf_hdr_t *hdr; 2300 kmutex_t *hash_lock; 2301 2302 /* 2303 * Check to see if this buffer is evicted. Callers 2304 * must verify b_data != NULL to know if the add_ref 2305 * was successful. 2306 */ 2307 mutex_enter(&buf->b_evict_lock); 2308 if (buf->b_data == NULL) { 2309 mutex_exit(&buf->b_evict_lock); 2310 return; 2311 } 2312 hash_lock = HDR_LOCK(buf->b_hdr); 2313 mutex_enter(hash_lock); 2314 hdr = buf->b_hdr; 2315 ASSERT(HDR_HAS_L1HDR(hdr)); 2316 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2317 mutex_exit(&buf->b_evict_lock); 2318 2319 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2320 hdr->b_l1hdr.b_state == arc_mfu); 2321 2322 add_reference(hdr, hash_lock, tag); 2323 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2324 arc_access(hdr, hash_lock); 2325 mutex_exit(hash_lock); 2326 ARCSTAT_BUMP(arcstat_hits); 2327 arc_update_hit_stat(hdr, B_TRUE); 2328 } 2329 2330 static void 2331 arc_buf_free_on_write(void *data, size_t size, 2332 void (*free_func)(void *, size_t)) 2333 { 2334 l2arc_data_free_t *df; 2335 2336 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2337 df->l2df_data = data; 2338 df->l2df_size = size; 2339 df->l2df_func = free_func; 2340 mutex_enter(&l2arc_free_on_write_mtx); 2341 list_insert_head(l2arc_free_on_write, df); 2342 mutex_exit(&l2arc_free_on_write_mtx); 2343 } 2344 2345 /* 2346 * Free the arc data buffer. If it is an l2arc write in progress, 2347 * the buffer is placed on l2arc_free_on_write to be freed later. 2348 */ 2349 static void 2350 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2351 { 2352 arc_buf_hdr_t *hdr = buf->b_hdr; 2353 2354 if (HDR_L2_WRITING(hdr)) { 2355 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2356 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2357 } else { 2358 free_func(buf->b_data, hdr->b_size); 2359 } 2360 } 2361 2362 static void 2363 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2364 { 2365 ASSERT(HDR_HAS_L2HDR(hdr)); 2366 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2367 2368 /* 2369 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2370 * that doesn't exist, the header is in the arc_l2c_only state, 2371 * and there isn't anything to free (it's already been freed). 2372 */ 2373 if (!HDR_HAS_L1HDR(hdr)) 2374 return; 2375 2376 /* 2377 * The header isn't being written to the l2arc device, thus it 2378 * shouldn't have a b_tmp_cdata to free. 2379 */ 2380 if (!HDR_L2_WRITING(hdr)) { 2381 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2382 return; 2383 } 2384 2385 /* 2386 * The header does not have compression enabled. This can be due 2387 * to the buffer not being compressible, or because we're 2388 * freeing the buffer before the second phase of 2389 * l2arc_write_buffer() has started (which does the compression 2390 * step). In either case, b_tmp_cdata does not point to a 2391 * separately compressed buffer, so there's nothing to free (it 2392 * points to the same buffer as the arc_buf_t's b_data field). 2393 */ 2394 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) { 2395 hdr->b_l1hdr.b_tmp_cdata = NULL; 2396 return; 2397 } 2398 2399 /* 2400 * There's nothing to free since the buffer was all zero's and 2401 * compressed to a zero length buffer. 2402 */ 2403 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2404 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2405 return; 2406 } 2407 2408 ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress)); 2409 2410 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2411 hdr->b_size, zio_data_buf_free); 2412 2413 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2414 hdr->b_l1hdr.b_tmp_cdata = NULL; 2415 } 2416 2417 /* 2418 * Free up buf->b_data and if 'remove' is set, then pull the 2419 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2420 */ 2421 static void 2422 arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2423 { 2424 arc_buf_t **bufp; 2425 2426 /* free up data associated with the buf */ 2427 if (buf->b_data != NULL) { 2428 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2429 uint64_t size = buf->b_hdr->b_size; 2430 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2431 2432 arc_cksum_verify(buf); 2433 arc_buf_unwatch(buf); 2434 2435 if (type == ARC_BUFC_METADATA) { 2436 arc_buf_data_free(buf, zio_buf_free); 2437 arc_space_return(size, ARC_SPACE_META); 2438 } else { 2439 ASSERT(type == ARC_BUFC_DATA); 2440 arc_buf_data_free(buf, zio_data_buf_free); 2441 arc_space_return(size, ARC_SPACE_DATA); 2442 } 2443 2444 /* protected by hash lock, if in the hash table */ 2445 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2446 uint64_t *cnt = &state->arcs_lsize[type]; 2447 2448 ASSERT(refcount_is_zero( 2449 &buf->b_hdr->b_l1hdr.b_refcnt)); 2450 ASSERT(state != arc_anon && state != arc_l2c_only); 2451 2452 ASSERT3U(*cnt, >=, size); 2453 atomic_add_64(cnt, -size); 2454 } 2455 2456 (void) refcount_remove_many(&state->arcs_size, size, buf); 2457 buf->b_data = NULL; 2458 2459 /* 2460 * If we're destroying a duplicate buffer make sure 2461 * that the appropriate statistics are updated. 2462 */ 2463 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2464 HDR_ISTYPE_DATA(buf->b_hdr)) { 2465 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2466 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2467 } 2468 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2469 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2470 } 2471 2472 /* only remove the buf if requested */ 2473 if (!remove) 2474 return; 2475 2476 /* remove the buf from the hdr list */ 2477 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2478 bufp = &(*bufp)->b_next) 2479 continue; 2480 *bufp = buf->b_next; 2481 buf->b_next = NULL; 2482 2483 ASSERT(buf->b_efunc == NULL); 2484 2485 /* clean up the buf */ 2486 buf->b_hdr = NULL; 2487 kmem_cache_free(buf_cache, buf); 2488 } 2489 2490 static void 2491 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2492 { 2493 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2494 l2arc_dev_t *dev = l2hdr->b_dev; 2495 2496 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2497 ASSERT(HDR_HAS_L2HDR(hdr)); 2498 2499 list_remove(&dev->l2ad_buflist, hdr); 2500 2501 /* 2502 * We don't want to leak the b_tmp_cdata buffer that was 2503 * allocated in l2arc_write_buffers() 2504 */ 2505 arc_buf_l2_cdata_free(hdr); 2506 2507 /* 2508 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2509 * this header is being processed by l2arc_write_buffers() (i.e. 2510 * it's in the first stage of l2arc_write_buffers()). 2511 * Re-affirming that truth here, just to serve as a reminder. If 2512 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2513 * may not have its HDR_L2_WRITING flag set. (the write may have 2514 * completed, in which case HDR_L2_WRITING will be false and the 2515 * b_daddr field will point to the address of the buffer on disk). 2516 */ 2517 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2518 2519 /* 2520 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2521 * l2arc_write_buffers(). Since we've just removed this header 2522 * from the l2arc buffer list, this header will never reach the 2523 * second stage of l2arc_write_buffers(), which increments the 2524 * accounting stats for this header. Thus, we must be careful 2525 * not to decrement them for this header either. 2526 */ 2527 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2528 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2529 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2530 2531 vdev_space_update(dev->l2ad_vdev, 2532 -l2hdr->b_asize, 0, 0); 2533 2534 (void) refcount_remove_many(&dev->l2ad_alloc, 2535 l2hdr->b_asize, hdr); 2536 } 2537 2538 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2539 } 2540 2541 static void 2542 arc_hdr_destroy(arc_buf_hdr_t *hdr) 2543 { 2544 if (HDR_HAS_L1HDR(hdr)) { 2545 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2546 hdr->b_l1hdr.b_datacnt > 0); 2547 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2548 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2549 } 2550 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2551 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2552 2553 if (HDR_HAS_L2HDR(hdr)) { 2554 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2555 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2556 2557 if (!buflist_held) 2558 mutex_enter(&dev->l2ad_mtx); 2559 2560 /* 2561 * Even though we checked this conditional above, we 2562 * need to check this again now that we have the 2563 * l2ad_mtx. This is because we could be racing with 2564 * another thread calling l2arc_evict() which might have 2565 * destroyed this header's L2 portion as we were waiting 2566 * to acquire the l2ad_mtx. If that happens, we don't 2567 * want to re-destroy the header's L2 portion. 2568 */ 2569 if (HDR_HAS_L2HDR(hdr)) 2570 arc_hdr_l2hdr_destroy(hdr); 2571 2572 if (!buflist_held) 2573 mutex_exit(&dev->l2ad_mtx); 2574 } 2575 2576 if (!BUF_EMPTY(hdr)) 2577 buf_discard_identity(hdr); 2578 2579 if (hdr->b_freeze_cksum != NULL) { 2580 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2581 hdr->b_freeze_cksum = NULL; 2582 } 2583 2584 if (HDR_HAS_L1HDR(hdr)) { 2585 while (hdr->b_l1hdr.b_buf) { 2586 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2587 2588 if (buf->b_efunc != NULL) { 2589 mutex_enter(&arc_user_evicts_lock); 2590 mutex_enter(&buf->b_evict_lock); 2591 ASSERT(buf->b_hdr != NULL); 2592 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2593 hdr->b_l1hdr.b_buf = buf->b_next; 2594 buf->b_hdr = &arc_eviction_hdr; 2595 buf->b_next = arc_eviction_list; 2596 arc_eviction_list = buf; 2597 mutex_exit(&buf->b_evict_lock); 2598 cv_signal(&arc_user_evicts_cv); 2599 mutex_exit(&arc_user_evicts_lock); 2600 } else { 2601 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2602 } 2603 } 2604 #ifdef ZFS_DEBUG 2605 if (hdr->b_l1hdr.b_thawed != NULL) { 2606 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2607 hdr->b_l1hdr.b_thawed = NULL; 2608 } 2609 #endif 2610 } 2611 2612 ASSERT3P(hdr->b_hash_next, ==, NULL); 2613 if (HDR_HAS_L1HDR(hdr)) { 2614 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2615 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2616 kmem_cache_free(hdr_full_cache, hdr); 2617 } else { 2618 kmem_cache_free(hdr_l2only_cache, hdr); 2619 } 2620 } 2621 2622 void 2623 arc_buf_free(arc_buf_t *buf, void *tag) 2624 { 2625 arc_buf_hdr_t *hdr = buf->b_hdr; 2626 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2627 2628 ASSERT(buf->b_efunc == NULL); 2629 ASSERT(buf->b_data != NULL); 2630 2631 if (hashed) { 2632 kmutex_t *hash_lock = HDR_LOCK(hdr); 2633 2634 mutex_enter(hash_lock); 2635 hdr = buf->b_hdr; 2636 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2637 2638 (void) remove_reference(hdr, hash_lock, tag); 2639 if (hdr->b_l1hdr.b_datacnt > 1) { 2640 arc_buf_destroy(buf, TRUE); 2641 } else { 2642 ASSERT(buf == hdr->b_l1hdr.b_buf); 2643 ASSERT(buf->b_efunc == NULL); 2644 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2645 } 2646 mutex_exit(hash_lock); 2647 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2648 int destroy_hdr; 2649 /* 2650 * We are in the middle of an async write. Don't destroy 2651 * this buffer unless the write completes before we finish 2652 * decrementing the reference count. 2653 */ 2654 mutex_enter(&arc_user_evicts_lock); 2655 (void) remove_reference(hdr, NULL, tag); 2656 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2657 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2658 mutex_exit(&arc_user_evicts_lock); 2659 if (destroy_hdr) 2660 arc_hdr_destroy(hdr); 2661 } else { 2662 if (remove_reference(hdr, NULL, tag) > 0) 2663 arc_buf_destroy(buf, TRUE); 2664 else 2665 arc_hdr_destroy(hdr); 2666 } 2667 } 2668 2669 boolean_t 2670 arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2671 { 2672 arc_buf_hdr_t *hdr = buf->b_hdr; 2673 kmutex_t *hash_lock = HDR_LOCK(hdr); 2674 boolean_t no_callback = (buf->b_efunc == NULL); 2675 2676 if (hdr->b_l1hdr.b_state == arc_anon) { 2677 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2678 arc_buf_free(buf, tag); 2679 return (no_callback); 2680 } 2681 2682 mutex_enter(hash_lock); 2683 hdr = buf->b_hdr; 2684 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2685 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2686 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2687 ASSERT(buf->b_data != NULL); 2688 2689 (void) remove_reference(hdr, hash_lock, tag); 2690 if (hdr->b_l1hdr.b_datacnt > 1) { 2691 if (no_callback) 2692 arc_buf_destroy(buf, TRUE); 2693 } else if (no_callback) { 2694 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2695 ASSERT(buf->b_efunc == NULL); 2696 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2697 } 2698 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2699 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2700 mutex_exit(hash_lock); 2701 return (no_callback); 2702 } 2703 2704 int32_t 2705 arc_buf_size(arc_buf_t *buf) 2706 { 2707 return (buf->b_hdr->b_size); 2708 } 2709 2710 /* 2711 * Called from the DMU to determine if the current buffer should be 2712 * evicted. In order to ensure proper locking, the eviction must be initiated 2713 * from the DMU. Return true if the buffer is associated with user data and 2714 * duplicate buffers still exist. 2715 */ 2716 boolean_t 2717 arc_buf_eviction_needed(arc_buf_t *buf) 2718 { 2719 arc_buf_hdr_t *hdr; 2720 boolean_t evict_needed = B_FALSE; 2721 2722 if (zfs_disable_dup_eviction) 2723 return (B_FALSE); 2724 2725 mutex_enter(&buf->b_evict_lock); 2726 hdr = buf->b_hdr; 2727 if (hdr == NULL) { 2728 /* 2729 * We are in arc_do_user_evicts(); let that function 2730 * perform the eviction. 2731 */ 2732 ASSERT(buf->b_data == NULL); 2733 mutex_exit(&buf->b_evict_lock); 2734 return (B_FALSE); 2735 } else if (buf->b_data == NULL) { 2736 /* 2737 * We have already been added to the arc eviction list; 2738 * recommend eviction. 2739 */ 2740 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2741 mutex_exit(&buf->b_evict_lock); 2742 return (B_TRUE); 2743 } 2744 2745 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2746 evict_needed = B_TRUE; 2747 2748 mutex_exit(&buf->b_evict_lock); 2749 return (evict_needed); 2750 } 2751 2752 /* 2753 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2754 * state of the header is dependent on it's state prior to entering this 2755 * function. The following transitions are possible: 2756 * 2757 * - arc_mru -> arc_mru_ghost 2758 * - arc_mfu -> arc_mfu_ghost 2759 * - arc_mru_ghost -> arc_l2c_only 2760 * - arc_mru_ghost -> deleted 2761 * - arc_mfu_ghost -> arc_l2c_only 2762 * - arc_mfu_ghost -> deleted 2763 */ 2764 static int64_t 2765 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2766 { 2767 arc_state_t *evicted_state, *state; 2768 int64_t bytes_evicted = 0; 2769 2770 ASSERT(MUTEX_HELD(hash_lock)); 2771 ASSERT(HDR_HAS_L1HDR(hdr)); 2772 2773 state = hdr->b_l1hdr.b_state; 2774 if (GHOST_STATE(state)) { 2775 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2776 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2777 2778 /* 2779 * l2arc_write_buffers() relies on a header's L1 portion 2780 * (i.e. it's b_tmp_cdata field) during it's write phase. 2781 * Thus, we cannot push a header onto the arc_l2c_only 2782 * state (removing it's L1 piece) until the header is 2783 * done being written to the l2arc. 2784 */ 2785 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2786 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2787 return (bytes_evicted); 2788 } 2789 2790 ARCSTAT_BUMP(arcstat_deleted); 2791 bytes_evicted += hdr->b_size; 2792 2793 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2794 2795 if (HDR_HAS_L2HDR(hdr)) { 2796 /* 2797 * This buffer is cached on the 2nd Level ARC; 2798 * don't destroy the header. 2799 */ 2800 arc_change_state(arc_l2c_only, hdr, hash_lock); 2801 /* 2802 * dropping from L1+L2 cached to L2-only, 2803 * realloc to remove the L1 header. 2804 */ 2805 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2806 hdr_l2only_cache); 2807 } else { 2808 arc_change_state(arc_anon, hdr, hash_lock); 2809 arc_hdr_destroy(hdr); 2810 } 2811 return (bytes_evicted); 2812 } 2813 2814 ASSERT(state == arc_mru || state == arc_mfu); 2815 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2816 2817 /* prefetch buffers have a minimum lifespan */ 2818 if (HDR_IO_IN_PROGRESS(hdr) || 2819 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2820 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2821 arc_min_prefetch_lifespan)) { 2822 ARCSTAT_BUMP(arcstat_evict_skip); 2823 return (bytes_evicted); 2824 } 2825 2826 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2827 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2828 while (hdr->b_l1hdr.b_buf) { 2829 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2830 if (!mutex_tryenter(&buf->b_evict_lock)) { 2831 ARCSTAT_BUMP(arcstat_mutex_miss); 2832 break; 2833 } 2834 if (buf->b_data != NULL) 2835 bytes_evicted += hdr->b_size; 2836 if (buf->b_efunc != NULL) { 2837 mutex_enter(&arc_user_evicts_lock); 2838 arc_buf_destroy(buf, FALSE); 2839 hdr->b_l1hdr.b_buf = buf->b_next; 2840 buf->b_hdr = &arc_eviction_hdr; 2841 buf->b_next = arc_eviction_list; 2842 arc_eviction_list = buf; 2843 cv_signal(&arc_user_evicts_cv); 2844 mutex_exit(&arc_user_evicts_lock); 2845 mutex_exit(&buf->b_evict_lock); 2846 } else { 2847 mutex_exit(&buf->b_evict_lock); 2848 arc_buf_destroy(buf, TRUE); 2849 } 2850 } 2851 2852 if (HDR_HAS_L2HDR(hdr)) { 2853 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2854 } else { 2855 if (l2arc_write_eligible(hdr->b_spa, UINT64_MAX, hdr)) 2856 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2857 else 2858 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2859 } 2860 2861 if (hdr->b_l1hdr.b_datacnt == 0) { 2862 arc_change_state(evicted_state, hdr, hash_lock); 2863 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2864 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2865 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2866 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2867 } 2868 2869 return (bytes_evicted); 2870 } 2871 2872 static uint64_t 2873 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2874 uint64_t spa, int64_t bytes) 2875 { 2876 multilist_sublist_t *mls; 2877 uint64_t bytes_evicted = 0; 2878 arc_buf_hdr_t *hdr; 2879 kmutex_t *hash_lock; 2880 int evict_count = 0; 2881 2882 ASSERT3P(marker, !=, NULL); 2883 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2884 2885 mls = multilist_sublist_lock(ml, idx); 2886 2887 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2888 hdr = multilist_sublist_prev(mls, marker)) { 2889 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2890 (evict_count >= zfs_arc_evict_batch_limit)) 2891 break; 2892 2893 /* 2894 * To keep our iteration location, move the marker 2895 * forward. Since we're not holding hdr's hash lock, we 2896 * must be very careful and not remove 'hdr' from the 2897 * sublist. Otherwise, other consumers might mistake the 2898 * 'hdr' as not being on a sublist when they call the 2899 * multilist_link_active() function (they all rely on 2900 * the hash lock protecting concurrent insertions and 2901 * removals). multilist_sublist_move_forward() was 2902 * specifically implemented to ensure this is the case 2903 * (only 'marker' will be removed and re-inserted). 2904 */ 2905 multilist_sublist_move_forward(mls, marker); 2906 2907 /* 2908 * The only case where the b_spa field should ever be 2909 * zero, is the marker headers inserted by 2910 * arc_evict_state(). It's possible for multiple threads 2911 * to be calling arc_evict_state() concurrently (e.g. 2912 * dsl_pool_close() and zio_inject_fault()), so we must 2913 * skip any markers we see from these other threads. 2914 */ 2915 if (hdr->b_spa == 0) 2916 continue; 2917 2918 /* we're only interested in evicting buffers of a certain spa */ 2919 if (spa != 0 && hdr->b_spa != spa) { 2920 ARCSTAT_BUMP(arcstat_evict_skip); 2921 continue; 2922 } 2923 2924 hash_lock = HDR_LOCK(hdr); 2925 2926 /* 2927 * We aren't calling this function from any code path 2928 * that would already be holding a hash lock, so we're 2929 * asserting on this assumption to be defensive in case 2930 * this ever changes. Without this check, it would be 2931 * possible to incorrectly increment arcstat_mutex_miss 2932 * below (e.g. if the code changed such that we called 2933 * this function with a hash lock held). 2934 */ 2935 ASSERT(!MUTEX_HELD(hash_lock)); 2936 2937 if (mutex_tryenter(hash_lock)) { 2938 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2939 mutex_exit(hash_lock); 2940 2941 bytes_evicted += evicted; 2942 2943 /* 2944 * If evicted is zero, arc_evict_hdr() must have 2945 * decided to skip this header, don't increment 2946 * evict_count in this case. 2947 */ 2948 if (evicted != 0) 2949 evict_count++; 2950 2951 /* 2952 * If arc_size isn't overflowing, signal any 2953 * threads that might happen to be waiting. 2954 * 2955 * For each header evicted, we wake up a single 2956 * thread. If we used cv_broadcast, we could 2957 * wake up "too many" threads causing arc_size 2958 * to significantly overflow arc_c; since 2959 * arc_get_data_buf() doesn't check for overflow 2960 * when it's woken up (it doesn't because it's 2961 * possible for the ARC to be overflowing while 2962 * full of un-evictable buffers, and the 2963 * function should proceed in this case). 2964 * 2965 * If threads are left sleeping, due to not 2966 * using cv_broadcast, they will be woken up 2967 * just before arc_reclaim_thread() sleeps. 2968 */ 2969 mutex_enter(&arc_reclaim_lock); 2970 if (!arc_is_overflowing()) 2971 cv_signal(&arc_reclaim_waiters_cv); 2972 mutex_exit(&arc_reclaim_lock); 2973 } else { 2974 ARCSTAT_BUMP(arcstat_mutex_miss); 2975 } 2976 } 2977 2978 multilist_sublist_unlock(mls); 2979 2980 return (bytes_evicted); 2981 } 2982 2983 /* 2984 * Evict buffers from the given arc state, until we've removed the 2985 * specified number of bytes. Move the removed buffers to the 2986 * appropriate evict state. 2987 * 2988 * This function makes a "best effort". It skips over any buffers 2989 * it can't get a hash_lock on, and so, may not catch all candidates. 2990 * It may also return without evicting as much space as requested. 2991 * 2992 * If bytes is specified using the special value ARC_EVICT_ALL, this 2993 * will evict all available (i.e. unlocked and evictable) buffers from 2994 * the given arc state; which is used by arc_flush(). 2995 */ 2996 static uint64_t 2997 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2998 arc_buf_contents_t type) 2999 { 3000 uint64_t total_evicted = 0; 3001 multilist_t *ml = &state->arcs_list[type]; 3002 int num_sublists; 3003 arc_buf_hdr_t **markers; 3004 3005 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3006 3007 num_sublists = multilist_get_num_sublists(ml); 3008 3009 /* 3010 * If we've tried to evict from each sublist, made some 3011 * progress, but still have not hit the target number of bytes 3012 * to evict, we want to keep trying. The markers allow us to 3013 * pick up where we left off for each individual sublist, rather 3014 * than starting from the tail each time. 3015 */ 3016 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3017 for (int i = 0; i < num_sublists; i++) { 3018 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3019 3020 /* 3021 * A b_spa of 0 is used to indicate that this header is 3022 * a marker. This fact is used in arc_adjust_type() and 3023 * arc_evict_state_impl(). 3024 */ 3025 markers[i]->b_spa = 0; 3026 3027 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3028 multilist_sublist_insert_tail(mls, markers[i]); 3029 multilist_sublist_unlock(mls); 3030 } 3031 3032 /* 3033 * While we haven't hit our target number of bytes to evict, or 3034 * we're evicting all available buffers. 3035 */ 3036 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3037 /* 3038 * Start eviction using a randomly selected sublist, 3039 * this is to try and evenly balance eviction across all 3040 * sublists. Always starting at the same sublist 3041 * (e.g. index 0) would cause evictions to favor certain 3042 * sublists over others. 3043 */ 3044 int sublist_idx = multilist_get_random_index(ml); 3045 uint64_t scan_evicted = 0; 3046 3047 for (int i = 0; i < num_sublists; i++) { 3048 uint64_t bytes_remaining; 3049 uint64_t bytes_evicted; 3050 3051 if (bytes == ARC_EVICT_ALL) 3052 bytes_remaining = ARC_EVICT_ALL; 3053 else if (total_evicted < bytes) 3054 bytes_remaining = bytes - total_evicted; 3055 else 3056 break; 3057 3058 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3059 markers[sublist_idx], spa, bytes_remaining); 3060 3061 scan_evicted += bytes_evicted; 3062 total_evicted += bytes_evicted; 3063 3064 /* we've reached the end, wrap to the beginning */ 3065 if (++sublist_idx >= num_sublists) 3066 sublist_idx = 0; 3067 } 3068 3069 /* 3070 * If we didn't evict anything during this scan, we have 3071 * no reason to believe we'll evict more during another 3072 * scan, so break the loop. 3073 */ 3074 if (scan_evicted == 0) { 3075 /* This isn't possible, let's make that obvious */ 3076 ASSERT3S(bytes, !=, 0); 3077 3078 /* 3079 * When bytes is ARC_EVICT_ALL, the only way to 3080 * break the loop is when scan_evicted is zero. 3081 * In that case, we actually have evicted enough, 3082 * so we don't want to increment the kstat. 3083 */ 3084 if (bytes != ARC_EVICT_ALL) { 3085 ASSERT3S(total_evicted, <, bytes); 3086 ARCSTAT_BUMP(arcstat_evict_not_enough); 3087 } 3088 3089 break; 3090 } 3091 } 3092 3093 for (int i = 0; i < num_sublists; i++) { 3094 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3095 multilist_sublist_remove(mls, markers[i]); 3096 multilist_sublist_unlock(mls); 3097 3098 kmem_cache_free(hdr_full_cache, markers[i]); 3099 } 3100 kmem_free(markers, sizeof (*markers) * num_sublists); 3101 3102 return (total_evicted); 3103 } 3104 3105 /* 3106 * Flush all "evictable" data of the given type from the arc state 3107 * specified. This will not evict any "active" buffers (i.e. referenced). 3108 * 3109 * When 'retry' is set to FALSE, the function will make a single pass 3110 * over the state and evict any buffers that it can. Since it doesn't 3111 * continually retry the eviction, it might end up leaving some buffers 3112 * in the ARC due to lock misses. 3113 * 3114 * When 'retry' is set to TRUE, the function will continually retry the 3115 * eviction until *all* evictable buffers have been removed from the 3116 * state. As a result, if concurrent insertions into the state are 3117 * allowed (e.g. if the ARC isn't shutting down), this function might 3118 * wind up in an infinite loop, continually trying to evict buffers. 3119 */ 3120 static uint64_t 3121 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3122 boolean_t retry) 3123 { 3124 uint64_t evicted = 0; 3125 3126 while (state->arcs_lsize[type] != 0) { 3127 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3128 3129 if (!retry) 3130 break; 3131 } 3132 3133 return (evicted); 3134 } 3135 3136 /* 3137 * Evict the specified number of bytes from the state specified, 3138 * restricting eviction to the spa and type given. This function 3139 * prevents us from trying to evict more from a state's list than 3140 * is "evictable", and to skip evicting altogether when passed a 3141 * negative value for "bytes". In contrast, arc_evict_state() will 3142 * evict everything it can, when passed a negative value for "bytes". 3143 */ 3144 static uint64_t 3145 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3146 arc_buf_contents_t type) 3147 { 3148 int64_t delta; 3149 3150 if (bytes > 0 && state->arcs_lsize[type] > 0) { 3151 delta = MIN(state->arcs_lsize[type], bytes); 3152 return (arc_evict_state(state, spa, delta, type)); 3153 } 3154 3155 return (0); 3156 } 3157 3158 /* 3159 * Evict metadata buffers from the cache, such that arc_meta_used is 3160 * capped by the arc_meta_limit tunable. 3161 */ 3162 static uint64_t 3163 arc_adjust_meta(void) 3164 { 3165 uint64_t total_evicted = 0; 3166 int64_t target; 3167 3168 /* 3169 * If we're over the meta limit, we want to evict enough 3170 * metadata to get back under the meta limit. We don't want to 3171 * evict so much that we drop the MRU below arc_p, though. If 3172 * we're over the meta limit more than we're over arc_p, we 3173 * evict some from the MRU here, and some from the MFU below. 3174 */ 3175 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3176 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3177 refcount_count(&arc_mru->arcs_size) - arc_p)); 3178 3179 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3180 3181 /* 3182 * Similar to the above, we want to evict enough bytes to get us 3183 * below the meta limit, but not so much as to drop us below the 3184 * space alloted to the MFU (which is defined as arc_c - arc_p). 3185 */ 3186 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3187 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3188 3189 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3190 3191 return (total_evicted); 3192 } 3193 3194 /* 3195 * Return the type of the oldest buffer in the given arc state 3196 * 3197 * This function will select a random sublist of type ARC_BUFC_DATA and 3198 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3199 * is compared, and the type which contains the "older" buffer will be 3200 * returned. 3201 */ 3202 static arc_buf_contents_t 3203 arc_adjust_type(arc_state_t *state) 3204 { 3205 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3206 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3207 int data_idx = multilist_get_random_index(data_ml); 3208 int meta_idx = multilist_get_random_index(meta_ml); 3209 multilist_sublist_t *data_mls; 3210 multilist_sublist_t *meta_mls; 3211 arc_buf_contents_t type; 3212 arc_buf_hdr_t *data_hdr; 3213 arc_buf_hdr_t *meta_hdr; 3214 3215 /* 3216 * We keep the sublist lock until we're finished, to prevent 3217 * the headers from being destroyed via arc_evict_state(). 3218 */ 3219 data_mls = multilist_sublist_lock(data_ml, data_idx); 3220 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3221 3222 /* 3223 * These two loops are to ensure we skip any markers that 3224 * might be at the tail of the lists due to arc_evict_state(). 3225 */ 3226 3227 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3228 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3229 if (data_hdr->b_spa != 0) 3230 break; 3231 } 3232 3233 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3234 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3235 if (meta_hdr->b_spa != 0) 3236 break; 3237 } 3238 3239 if (data_hdr == NULL && meta_hdr == NULL) { 3240 type = ARC_BUFC_DATA; 3241 } else if (data_hdr == NULL) { 3242 ASSERT3P(meta_hdr, !=, NULL); 3243 type = ARC_BUFC_METADATA; 3244 } else if (meta_hdr == NULL) { 3245 ASSERT3P(data_hdr, !=, NULL); 3246 type = ARC_BUFC_DATA; 3247 } else { 3248 ASSERT3P(data_hdr, !=, NULL); 3249 ASSERT3P(meta_hdr, !=, NULL); 3250 3251 /* The headers can't be on the sublist without an L1 header */ 3252 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3253 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3254 3255 if (data_hdr->b_l1hdr.b_arc_access < 3256 meta_hdr->b_l1hdr.b_arc_access) { 3257 type = ARC_BUFC_DATA; 3258 } else { 3259 type = ARC_BUFC_METADATA; 3260 } 3261 } 3262 3263 multilist_sublist_unlock(meta_mls); 3264 multilist_sublist_unlock(data_mls); 3265 3266 return (type); 3267 } 3268 3269 /* 3270 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3271 */ 3272 static uint64_t 3273 arc_adjust(void) 3274 { 3275 uint64_t total_evicted = 0; 3276 uint64_t bytes; 3277 int64_t target; 3278 3279 /* 3280 * If we're over arc_meta_limit, we want to correct that before 3281 * potentially evicting data buffers below. 3282 */ 3283 total_evicted += arc_adjust_meta(); 3284 3285 /* 3286 * Adjust MRU size 3287 * 3288 * If we're over the target cache size, we want to evict enough 3289 * from the list to get back to our target size. We don't want 3290 * to evict too much from the MRU, such that it drops below 3291 * arc_p. So, if we're over our target cache size more than 3292 * the MRU is over arc_p, we'll evict enough to get back to 3293 * arc_p here, and then evict more from the MFU below. 3294 */ 3295 target = MIN((int64_t)(arc_size - arc_c), 3296 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3297 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3298 3299 /* 3300 * If we're below arc_meta_min, always prefer to evict data. 3301 * Otherwise, try to satisfy the requested number of bytes to 3302 * evict from the type which contains older buffers; in an 3303 * effort to keep newer buffers in the cache regardless of their 3304 * type. If we cannot satisfy the number of bytes from this 3305 * type, spill over into the next type. 3306 */ 3307 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3308 arc_meta_used > arc_meta_min) { 3309 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3310 total_evicted += bytes; 3311 3312 /* 3313 * If we couldn't evict our target number of bytes from 3314 * metadata, we try to get the rest from data. 3315 */ 3316 target -= bytes; 3317 3318 total_evicted += 3319 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3320 } else { 3321 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3322 total_evicted += bytes; 3323 3324 /* 3325 * If we couldn't evict our target number of bytes from 3326 * data, we try to get the rest from metadata. 3327 */ 3328 target -= bytes; 3329 3330 total_evicted += 3331 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3332 } 3333 3334 /* 3335 * Adjust MFU size 3336 * 3337 * Now that we've tried to evict enough from the MRU to get its 3338 * size back to arc_p, if we're still above the target cache 3339 * size, we evict the rest from the MFU. 3340 */ 3341 target = arc_size - arc_c; 3342 3343 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3344 arc_meta_used > arc_meta_min) { 3345 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3346 total_evicted += bytes; 3347 3348 /* 3349 * If we couldn't evict our target number of bytes from 3350 * metadata, we try to get the rest from data. 3351 */ 3352 target -= bytes; 3353 3354 total_evicted += 3355 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3356 } else { 3357 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3358 total_evicted += bytes; 3359 3360 /* 3361 * If we couldn't evict our target number of bytes from 3362 * data, we try to get the rest from data. 3363 */ 3364 target -= bytes; 3365 3366 total_evicted += 3367 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3368 } 3369 3370 /* 3371 * Adjust ghost lists 3372 * 3373 * In addition to the above, the ARC also defines target values 3374 * for the ghost lists. The sum of the mru list and mru ghost 3375 * list should never exceed the target size of the cache, and 3376 * the sum of the mru list, mfu list, mru ghost list, and mfu 3377 * ghost list should never exceed twice the target size of the 3378 * cache. The following logic enforces these limits on the ghost 3379 * caches, and evicts from them as needed. 3380 */ 3381 target = refcount_count(&arc_mru->arcs_size) + 3382 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3383 3384 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3385 total_evicted += bytes; 3386 3387 target -= bytes; 3388 3389 total_evicted += 3390 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3391 3392 /* 3393 * We assume the sum of the mru list and mfu list is less than 3394 * or equal to arc_c (we enforced this above), which means we 3395 * can use the simpler of the two equations below: 3396 * 3397 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3398 * mru ghost + mfu ghost <= arc_c 3399 */ 3400 target = refcount_count(&arc_mru_ghost->arcs_size) + 3401 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3402 3403 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3404 total_evicted += bytes; 3405 3406 target -= bytes; 3407 3408 total_evicted += 3409 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3410 3411 return (total_evicted); 3412 } 3413 3414 static void 3415 arc_do_user_evicts(void) 3416 { 3417 mutex_enter(&arc_user_evicts_lock); 3418 while (arc_eviction_list != NULL) { 3419 arc_buf_t *buf = arc_eviction_list; 3420 arc_eviction_list = buf->b_next; 3421 mutex_enter(&buf->b_evict_lock); 3422 buf->b_hdr = NULL; 3423 mutex_exit(&buf->b_evict_lock); 3424 mutex_exit(&arc_user_evicts_lock); 3425 3426 if (buf->b_efunc != NULL) 3427 VERIFY0(buf->b_efunc(buf->b_private)); 3428 3429 buf->b_efunc = NULL; 3430 buf->b_private = NULL; 3431 kmem_cache_free(buf_cache, buf); 3432 mutex_enter(&arc_user_evicts_lock); 3433 } 3434 mutex_exit(&arc_user_evicts_lock); 3435 } 3436 3437 void 3438 arc_flush(spa_t *spa, boolean_t retry) 3439 { 3440 uint64_t guid = 0; 3441 3442 /* 3443 * If retry is TRUE, a spa must not be specified since we have 3444 * no good way to determine if all of a spa's buffers have been 3445 * evicted from an arc state. 3446 */ 3447 ASSERT(!retry || spa == 0); 3448 3449 if (spa != NULL) 3450 guid = spa_load_guid(spa); 3451 3452 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3453 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3454 3455 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3456 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3457 3458 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3459 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3460 3461 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3462 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3463 3464 arc_do_user_evicts(); 3465 ASSERT(spa || arc_eviction_list == NULL); 3466 } 3467 3468 void 3469 arc_shrink(int64_t to_free) 3470 { 3471 if (arc_c > arc_c_min) { 3472 3473 if (arc_c > arc_c_min + to_free) 3474 atomic_add_64(&arc_c, -to_free); 3475 else 3476 arc_c = arc_c_min; 3477 3478 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3479 if (arc_c > arc_size) 3480 arc_c = MAX(arc_size, arc_c_min); 3481 if (arc_p > arc_c) 3482 arc_p = (arc_c >> 1); 3483 ASSERT(arc_c >= arc_c_min); 3484 ASSERT((int64_t)arc_p >= 0); 3485 } 3486 3487 if (arc_size > arc_c) 3488 (void) arc_adjust(); 3489 } 3490 3491 typedef enum free_memory_reason_t { 3492 FMR_UNKNOWN, 3493 FMR_NEEDFREE, 3494 FMR_LOTSFREE, 3495 FMR_SWAPFS_MINFREE, 3496 FMR_PAGES_PP_MAXIMUM, 3497 FMR_HEAP_ARENA, 3498 FMR_ZIO_ARENA, 3499 } free_memory_reason_t; 3500 3501 int64_t last_free_memory; 3502 free_memory_reason_t last_free_reason; 3503 3504 /* 3505 * Additional reserve of pages for pp_reserve. 3506 */ 3507 int64_t arc_pages_pp_reserve = 64; 3508 3509 /* 3510 * Additional reserve of pages for swapfs. 3511 */ 3512 int64_t arc_swapfs_reserve = 64; 3513 3514 /* 3515 * Return the amount of memory that can be consumed before reclaim will be 3516 * needed. Positive if there is sufficient free memory, negative indicates 3517 * the amount of memory that needs to be freed up. 3518 */ 3519 static int64_t 3520 arc_available_memory(void) 3521 { 3522 int64_t lowest = INT64_MAX; 3523 int64_t n; 3524 free_memory_reason_t r = FMR_UNKNOWN; 3525 3526 #ifdef _KERNEL 3527 if (needfree > 0) { 3528 n = PAGESIZE * (-needfree); 3529 if (n < lowest) { 3530 lowest = n; 3531 r = FMR_NEEDFREE; 3532 } 3533 } 3534 3535 /* 3536 * check that we're out of range of the pageout scanner. It starts to 3537 * schedule paging if freemem is less than lotsfree and needfree. 3538 * lotsfree is the high-water mark for pageout, and needfree is the 3539 * number of needed free pages. We add extra pages here to make sure 3540 * the scanner doesn't start up while we're freeing memory. 3541 */ 3542 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3543 if (n < lowest) { 3544 lowest = n; 3545 r = FMR_LOTSFREE; 3546 } 3547 3548 /* 3549 * check to make sure that swapfs has enough space so that anon 3550 * reservations can still succeed. anon_resvmem() checks that the 3551 * availrmem is greater than swapfs_minfree, and the number of reserved 3552 * swap pages. We also add a bit of extra here just to prevent 3553 * circumstances from getting really dire. 3554 */ 3555 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3556 desfree - arc_swapfs_reserve); 3557 if (n < lowest) { 3558 lowest = n; 3559 r = FMR_SWAPFS_MINFREE; 3560 } 3561 3562 3563 /* 3564 * Check that we have enough availrmem that memory locking (e.g., via 3565 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3566 * stores the number of pages that cannot be locked; when availrmem 3567 * drops below pages_pp_maximum, page locking mechanisms such as 3568 * page_pp_lock() will fail.) 3569 */ 3570 n = PAGESIZE * (availrmem - pages_pp_maximum - 3571 arc_pages_pp_reserve); 3572 if (n < lowest) { 3573 lowest = n; 3574 r = FMR_PAGES_PP_MAXIMUM; 3575 } 3576 3577 #if defined(__i386) 3578 /* 3579 * If we're on an i386 platform, it's possible that we'll exhaust the 3580 * kernel heap space before we ever run out of available physical 3581 * memory. Most checks of the size of the heap_area compare against 3582 * tune.t_minarmem, which is the minimum available real memory that we 3583 * can have in the system. However, this is generally fixed at 25 pages 3584 * which is so low that it's useless. In this comparison, we seek to 3585 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3586 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3587 * free) 3588 */ 3589 n = vmem_size(heap_arena, VMEM_FREE) - 3590 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3591 if (n < lowest) { 3592 lowest = n; 3593 r = FMR_HEAP_ARENA; 3594 } 3595 #endif 3596 3597 /* 3598 * If zio data pages are being allocated out of a separate heap segment, 3599 * then enforce that the size of available vmem for this arena remains 3600 * above about 1/16th free. 3601 * 3602 * Note: The 1/16th arena free requirement was put in place 3603 * to aggressively evict memory from the arc in order to avoid 3604 * memory fragmentation issues. 3605 */ 3606 if (zio_arena != NULL) { 3607 n = vmem_size(zio_arena, VMEM_FREE) - 3608 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3609 if (n < lowest) { 3610 lowest = n; 3611 r = FMR_ZIO_ARENA; 3612 } 3613 } 3614 #else 3615 /* Every 100 calls, free a small amount */ 3616 if (spa_get_random(100) == 0) 3617 lowest = -1024; 3618 #endif 3619 3620 last_free_memory = lowest; 3621 last_free_reason = r; 3622 3623 return (lowest); 3624 } 3625 3626 3627 /* 3628 * Determine if the system is under memory pressure and is asking 3629 * to reclaim memory. A return value of TRUE indicates that the system 3630 * is under memory pressure and that the arc should adjust accordingly. 3631 */ 3632 static boolean_t 3633 arc_reclaim_needed(void) 3634 { 3635 return (arc_available_memory() < 0); 3636 } 3637 3638 static void 3639 arc_kmem_reap_now(void) 3640 { 3641 size_t i; 3642 kmem_cache_t *prev_cache = NULL; 3643 kmem_cache_t *prev_data_cache = NULL; 3644 extern kmem_cache_t *zio_buf_cache[]; 3645 extern kmem_cache_t *zio_data_buf_cache[]; 3646 extern kmem_cache_t *range_seg_cache; 3647 3648 #ifdef _KERNEL 3649 if (arc_meta_used >= arc_meta_limit) { 3650 /* 3651 * We are exceeding our meta-data cache limit. 3652 * Purge some DNLC entries to release holds on meta-data. 3653 */ 3654 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3655 } 3656 #if defined(__i386) 3657 /* 3658 * Reclaim unused memory from all kmem caches. 3659 */ 3660 kmem_reap(); 3661 #endif 3662 #endif 3663 3664 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3665 if (zio_buf_cache[i] != prev_cache) { 3666 prev_cache = zio_buf_cache[i]; 3667 kmem_cache_reap_now(zio_buf_cache[i]); 3668 } 3669 if (zio_data_buf_cache[i] != prev_data_cache) { 3670 prev_data_cache = zio_data_buf_cache[i]; 3671 kmem_cache_reap_now(zio_data_buf_cache[i]); 3672 } 3673 } 3674 kmem_cache_reap_now(buf_cache); 3675 kmem_cache_reap_now(hdr_full_cache); 3676 kmem_cache_reap_now(hdr_l2only_cache); 3677 kmem_cache_reap_now(range_seg_cache); 3678 3679 if (zio_arena != NULL) { 3680 /* 3681 * Ask the vmem arena to reclaim unused memory from its 3682 * quantum caches. 3683 */ 3684 vmem_qcache_reap(zio_arena); 3685 } 3686 } 3687 3688 /* 3689 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3690 * enough data and signal them to proceed. When this happens, the threads in 3691 * arc_get_data_buf() are sleeping while holding the hash lock for their 3692 * particular arc header. Thus, we must be careful to never sleep on a 3693 * hash lock in this thread. This is to prevent the following deadlock: 3694 * 3695 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3696 * waiting for the reclaim thread to signal it. 3697 * 3698 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3699 * fails, and goes to sleep forever. 3700 * 3701 * This possible deadlock is avoided by always acquiring a hash lock 3702 * using mutex_tryenter() from arc_reclaim_thread(). 3703 */ 3704 static void 3705 arc_reclaim_thread(void) 3706 { 3707 clock_t growtime = 0; 3708 callb_cpr_t cpr; 3709 3710 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3711 3712 mutex_enter(&arc_reclaim_lock); 3713 while (!arc_reclaim_thread_exit) { 3714 int64_t free_memory = arc_available_memory(); 3715 uint64_t evicted = 0; 3716 3717 mutex_exit(&arc_reclaim_lock); 3718 3719 if (free_memory < 0) { 3720 3721 arc_no_grow = B_TRUE; 3722 arc_warm = B_TRUE; 3723 3724 /* 3725 * Wait at least zfs_grow_retry (default 60) seconds 3726 * before considering growing. 3727 */ 3728 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3729 3730 arc_kmem_reap_now(); 3731 3732 /* 3733 * If we are still low on memory, shrink the ARC 3734 * so that we have arc_shrink_min free space. 3735 */ 3736 free_memory = arc_available_memory(); 3737 3738 int64_t to_free = 3739 (arc_c >> arc_shrink_shift) - free_memory; 3740 if (to_free > 0) { 3741 #ifdef _KERNEL 3742 to_free = MAX(to_free, ptob(needfree)); 3743 #endif 3744 arc_shrink(to_free); 3745 } 3746 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3747 arc_no_grow = B_TRUE; 3748 } else if (ddi_get_lbolt() >= growtime) { 3749 arc_no_grow = B_FALSE; 3750 } 3751 3752 evicted = arc_adjust(); 3753 3754 mutex_enter(&arc_reclaim_lock); 3755 3756 /* 3757 * If evicted is zero, we couldn't evict anything via 3758 * arc_adjust(). This could be due to hash lock 3759 * collisions, but more likely due to the majority of 3760 * arc buffers being unevictable. Therefore, even if 3761 * arc_size is above arc_c, another pass is unlikely to 3762 * be helpful and could potentially cause us to enter an 3763 * infinite loop. 3764 */ 3765 if (arc_size <= arc_c || evicted == 0) { 3766 /* 3767 * We're either no longer overflowing, or we 3768 * can't evict anything more, so we should wake 3769 * up any threads before we go to sleep. 3770 */ 3771 cv_broadcast(&arc_reclaim_waiters_cv); 3772 3773 /* 3774 * Block until signaled, or after one second (we 3775 * might need to perform arc_kmem_reap_now() 3776 * even if we aren't being signalled) 3777 */ 3778 CALLB_CPR_SAFE_BEGIN(&cpr); 3779 (void) cv_timedwait(&arc_reclaim_thread_cv, 3780 &arc_reclaim_lock, ddi_get_lbolt() + hz); 3781 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3782 } 3783 } 3784 3785 arc_reclaim_thread_exit = FALSE; 3786 cv_broadcast(&arc_reclaim_thread_cv); 3787 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3788 thread_exit(); 3789 } 3790 3791 static void 3792 arc_user_evicts_thread(void) 3793 { 3794 callb_cpr_t cpr; 3795 3796 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3797 3798 mutex_enter(&arc_user_evicts_lock); 3799 while (!arc_user_evicts_thread_exit) { 3800 mutex_exit(&arc_user_evicts_lock); 3801 3802 arc_do_user_evicts(); 3803 3804 /* 3805 * This is necessary in order for the mdb ::arc dcmd to 3806 * show up to date information. Since the ::arc command 3807 * does not call the kstat's update function, without 3808 * this call, the command may show stale stats for the 3809 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3810 * with this change, the data might be up to 1 second 3811 * out of date; but that should suffice. The arc_state_t 3812 * structures can be queried directly if more accurate 3813 * information is needed. 3814 */ 3815 if (arc_ksp != NULL) 3816 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3817 3818 mutex_enter(&arc_user_evicts_lock); 3819 3820 /* 3821 * Block until signaled, or after one second (we need to 3822 * call the arc's kstat update function regularly). 3823 */ 3824 CALLB_CPR_SAFE_BEGIN(&cpr); 3825 (void) cv_timedwait(&arc_user_evicts_cv, 3826 &arc_user_evicts_lock, ddi_get_lbolt() + hz); 3827 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3828 } 3829 3830 arc_user_evicts_thread_exit = FALSE; 3831 cv_broadcast(&arc_user_evicts_cv); 3832 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3833 thread_exit(); 3834 } 3835 3836 /* 3837 * Adapt arc info given the number of bytes we are trying to add and 3838 * the state that we are comming from. This function is only called 3839 * when we are adding new content to the cache. 3840 */ 3841 static void 3842 arc_adapt(int bytes, arc_state_t *state) 3843 { 3844 int mult; 3845 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3846 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3847 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3848 3849 if (state == arc_l2c_only) 3850 return; 3851 3852 ASSERT(bytes > 0); 3853 /* 3854 * Adapt the target size of the MRU list: 3855 * - if we just hit in the MRU ghost list, then increase 3856 * the target size of the MRU list. 3857 * - if we just hit in the MFU ghost list, then increase 3858 * the target size of the MFU list by decreasing the 3859 * target size of the MRU list. 3860 */ 3861 if (state == arc_mru_ghost) { 3862 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3863 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3864 3865 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3866 } else if (state == arc_mfu_ghost) { 3867 uint64_t delta; 3868 3869 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3870 mult = MIN(mult, 10); 3871 3872 delta = MIN(bytes * mult, arc_p); 3873 arc_p = MAX(arc_p_min, arc_p - delta); 3874 } 3875 ASSERT((int64_t)arc_p >= 0); 3876 3877 if (arc_reclaim_needed()) { 3878 cv_signal(&arc_reclaim_thread_cv); 3879 return; 3880 } 3881 3882 if (arc_no_grow) 3883 return; 3884 3885 if (arc_c >= arc_c_max) 3886 return; 3887 3888 /* 3889 * If we're within (2 * maxblocksize) bytes of the target 3890 * cache size, increment the target cache size 3891 */ 3892 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3893 atomic_add_64(&arc_c, (int64_t)bytes); 3894 if (arc_c > arc_c_max) 3895 arc_c = arc_c_max; 3896 else if (state == arc_anon) 3897 atomic_add_64(&arc_p, (int64_t)bytes); 3898 if (arc_p > arc_c) 3899 arc_p = arc_c; 3900 } 3901 ASSERT((int64_t)arc_p >= 0); 3902 } 3903 3904 /* 3905 * Check if arc_size has grown past our upper threshold, determined by 3906 * zfs_arc_overflow_shift. 3907 */ 3908 static boolean_t 3909 arc_is_overflowing(void) 3910 { 3911 /* Always allow at least one block of overflow */ 3912 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3913 arc_c >> zfs_arc_overflow_shift); 3914 3915 return (arc_size >= arc_c + overflow); 3916 } 3917 3918 /* 3919 * The buffer, supplied as the first argument, needs a data block. If we 3920 * are hitting the hard limit for the cache size, we must sleep, waiting 3921 * for the eviction thread to catch up. If we're past the target size 3922 * but below the hard limit, we'll only signal the reclaim thread and 3923 * continue on. 3924 */ 3925 static void 3926 arc_get_data_buf(arc_buf_t *buf) 3927 { 3928 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3929 uint64_t size = buf->b_hdr->b_size; 3930 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3931 3932 arc_adapt(size, state); 3933 3934 /* 3935 * If arc_size is currently overflowing, and has grown past our 3936 * upper limit, we must be adding data faster than the evict 3937 * thread can evict. Thus, to ensure we don't compound the 3938 * problem by adding more data and forcing arc_size to grow even 3939 * further past it's target size, we halt and wait for the 3940 * eviction thread to catch up. 3941 * 3942 * It's also possible that the reclaim thread is unable to evict 3943 * enough buffers to get arc_size below the overflow limit (e.g. 3944 * due to buffers being un-evictable, or hash lock collisions). 3945 * In this case, we want to proceed regardless if we're 3946 * overflowing; thus we don't use a while loop here. 3947 */ 3948 if (arc_is_overflowing()) { 3949 mutex_enter(&arc_reclaim_lock); 3950 3951 /* 3952 * Now that we've acquired the lock, we may no longer be 3953 * over the overflow limit, lets check. 3954 * 3955 * We're ignoring the case of spurious wake ups. If that 3956 * were to happen, it'd let this thread consume an ARC 3957 * buffer before it should have (i.e. before we're under 3958 * the overflow limit and were signalled by the reclaim 3959 * thread). As long as that is a rare occurrence, it 3960 * shouldn't cause any harm. 3961 */ 3962 if (arc_is_overflowing()) { 3963 cv_signal(&arc_reclaim_thread_cv); 3964 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3965 } 3966 3967 mutex_exit(&arc_reclaim_lock); 3968 } 3969 3970 if (type == ARC_BUFC_METADATA) { 3971 buf->b_data = zio_buf_alloc(size); 3972 arc_space_consume(size, ARC_SPACE_META); 3973 } else { 3974 ASSERT(type == ARC_BUFC_DATA); 3975 buf->b_data = zio_data_buf_alloc(size); 3976 arc_space_consume(size, ARC_SPACE_DATA); 3977 } 3978 3979 /* 3980 * Update the state size. Note that ghost states have a 3981 * "ghost size" and so don't need to be updated. 3982 */ 3983 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3984 arc_buf_hdr_t *hdr = buf->b_hdr; 3985 arc_state_t *state = hdr->b_l1hdr.b_state; 3986 3987 (void) refcount_add_many(&state->arcs_size, size, buf); 3988 3989 /* 3990 * If this is reached via arc_read, the link is 3991 * protected by the hash lock. If reached via 3992 * arc_buf_alloc, the header should not be accessed by 3993 * any other thread. And, if reached via arc_read_done, 3994 * the hash lock will protect it if it's found in the 3995 * hash table; otherwise no other thread should be 3996 * trying to [add|remove]_reference it. 3997 */ 3998 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3999 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4000 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 4001 size); 4002 } 4003 /* 4004 * If we are growing the cache, and we are adding anonymous 4005 * data, and we have outgrown arc_p, update arc_p 4006 */ 4007 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4008 (refcount_count(&arc_anon->arcs_size) + 4009 refcount_count(&arc_mru->arcs_size) > arc_p)) 4010 arc_p = MIN(arc_c, arc_p + size); 4011 } 4012 } 4013 4014 /* 4015 * This routine is called whenever a buffer is accessed. 4016 * NOTE: the hash lock is dropped in this function. 4017 */ 4018 static void 4019 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4020 { 4021 clock_t now; 4022 4023 ASSERT(MUTEX_HELD(hash_lock)); 4024 ASSERT(HDR_HAS_L1HDR(hdr)); 4025 4026 if (hdr->b_l1hdr.b_state == arc_anon) { 4027 /* 4028 * This buffer is not in the cache, and does not 4029 * appear in our "ghost" list. Add the new buffer 4030 * to the MRU state. 4031 */ 4032 4033 ASSERT0(hdr->b_l1hdr.b_arc_access); 4034 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4035 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4036 arc_change_state(arc_mru, hdr, hash_lock); 4037 4038 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4039 now = ddi_get_lbolt(); 4040 4041 /* 4042 * If this buffer is here because of a prefetch, then either: 4043 * - clear the flag if this is a "referencing" read 4044 * (any subsequent access will bump this into the MFU state). 4045 * or 4046 * - move the buffer to the head of the list if this is 4047 * another prefetch (to make it less likely to be evicted). 4048 */ 4049 if (HDR_PREFETCH(hdr)) { 4050 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4051 /* link protected by hash lock */ 4052 ASSERT(multilist_link_active( 4053 &hdr->b_l1hdr.b_arc_node)); 4054 } else { 4055 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4056 ARCSTAT_BUMP(arcstat_mru_hits); 4057 } 4058 hdr->b_l1hdr.b_arc_access = now; 4059 return; 4060 } 4061 4062 /* 4063 * This buffer has been "accessed" only once so far, 4064 * but it is still in the cache. Move it to the MFU 4065 * state. 4066 */ 4067 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4068 /* 4069 * More than 125ms have passed since we 4070 * instantiated this buffer. Move it to the 4071 * most frequently used state. 4072 */ 4073 hdr->b_l1hdr.b_arc_access = now; 4074 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4075 arc_change_state(arc_mfu, hdr, hash_lock); 4076 } 4077 ARCSTAT_BUMP(arcstat_mru_hits); 4078 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4079 arc_state_t *new_state; 4080 /* 4081 * This buffer has been "accessed" recently, but 4082 * was evicted from the cache. Move it to the 4083 * MFU state. 4084 */ 4085 4086 if (HDR_PREFETCH(hdr)) { 4087 new_state = arc_mru; 4088 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4089 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4090 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4091 } else { 4092 new_state = arc_mfu; 4093 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4094 } 4095 4096 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4097 arc_change_state(new_state, hdr, hash_lock); 4098 4099 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4100 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4101 /* 4102 * This buffer has been accessed more than once and is 4103 * still in the cache. Keep it in the MFU state. 4104 * 4105 * NOTE: an add_reference() that occurred when we did 4106 * the arc_read() will have kicked this off the list. 4107 * If it was a prefetch, we will explicitly move it to 4108 * the head of the list now. 4109 */ 4110 if ((HDR_PREFETCH(hdr)) != 0) { 4111 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4112 /* link protected by hash_lock */ 4113 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4114 } 4115 ARCSTAT_BUMP(arcstat_mfu_hits); 4116 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4117 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4118 arc_state_t *new_state = arc_mfu; 4119 /* 4120 * This buffer has been accessed more than once but has 4121 * been evicted from the cache. Move it back to the 4122 * MFU state. 4123 */ 4124 4125 if (HDR_PREFETCH(hdr)) { 4126 /* 4127 * This is a prefetch access... 4128 * move this block back to the MRU state. 4129 */ 4130 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4131 new_state = arc_mru; 4132 } 4133 4134 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4135 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4136 arc_change_state(new_state, hdr, hash_lock); 4137 4138 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4139 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4140 /* 4141 * This buffer is on the 2nd Level ARC. 4142 */ 4143 4144 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4145 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4146 arc_change_state(arc_mfu, hdr, hash_lock); 4147 } else { 4148 ASSERT(!"invalid arc state"); 4149 } 4150 } 4151 4152 /* a generic arc_done_func_t which you can use */ 4153 /* ARGSUSED */ 4154 void 4155 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4156 { 4157 if (zio == NULL || zio->io_error == 0) 4158 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4159 VERIFY(arc_buf_remove_ref(buf, arg)); 4160 } 4161 4162 /* a generic arc_done_func_t */ 4163 void 4164 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4165 { 4166 arc_buf_t **bufp = arg; 4167 if (zio && zio->io_error) { 4168 VERIFY(arc_buf_remove_ref(buf, arg)); 4169 *bufp = NULL; 4170 } else { 4171 *bufp = buf; 4172 ASSERT(buf->b_data); 4173 } 4174 } 4175 4176 static void 4177 arc_read_done(zio_t *zio) 4178 { 4179 arc_buf_hdr_t *hdr; 4180 arc_buf_t *buf; 4181 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4182 kmutex_t *hash_lock = NULL; 4183 arc_callback_t *callback_list, *acb; 4184 int freeable = FALSE; 4185 4186 buf = zio->io_private; 4187 hdr = buf->b_hdr; 4188 4189 /* 4190 * The hdr was inserted into hash-table and removed from lists 4191 * prior to starting I/O. We should find this header, since 4192 * it's in the hash table, and it should be legit since it's 4193 * not possible to evict it during the I/O. The only possible 4194 * reason for it not to be found is if we were freed during the 4195 * read. 4196 */ 4197 if (HDR_IN_HASH_TABLE(hdr)) { 4198 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4199 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4200 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4201 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4202 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4203 4204 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4205 &hash_lock); 4206 4207 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4208 hash_lock == NULL) || 4209 (found == hdr && 4210 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4211 (found == hdr && HDR_L2_READING(hdr))); 4212 } 4213 4214 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4215 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4216 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4217 4218 /* byteswap if necessary */ 4219 callback_list = hdr->b_l1hdr.b_acb; 4220 ASSERT(callback_list != NULL); 4221 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4222 dmu_object_byteswap_t bswap = 4223 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4224 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4225 byteswap_uint64_array : 4226 dmu_ot_byteswap[bswap].ob_func; 4227 func(buf->b_data, hdr->b_size); 4228 } 4229 4230 arc_cksum_compute(buf, B_FALSE); 4231 arc_buf_watch(buf); 4232 4233 if (hash_lock && zio->io_error == 0 && 4234 hdr->b_l1hdr.b_state == arc_anon) { 4235 /* 4236 * Only call arc_access on anonymous buffers. This is because 4237 * if we've issued an I/O for an evicted buffer, we've already 4238 * called arc_access (to prevent any simultaneous readers from 4239 * getting confused). 4240 */ 4241 arc_access(hdr, hash_lock); 4242 } 4243 4244 /* create copies of the data buffer for the callers */ 4245 abuf = buf; 4246 for (acb = callback_list; acb; acb = acb->acb_next) { 4247 if (acb->acb_done) { 4248 if (abuf == NULL) { 4249 ARCSTAT_BUMP(arcstat_duplicate_reads); 4250 abuf = arc_buf_clone(buf); 4251 } 4252 acb->acb_buf = abuf; 4253 abuf = NULL; 4254 } 4255 } 4256 hdr->b_l1hdr.b_acb = NULL; 4257 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4258 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4259 if (abuf == buf) { 4260 ASSERT(buf->b_efunc == NULL); 4261 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4262 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4263 } 4264 4265 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4266 callback_list != NULL); 4267 4268 if (zio->io_error != 0) { 4269 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4270 if (hdr->b_l1hdr.b_state != arc_anon) 4271 arc_change_state(arc_anon, hdr, hash_lock); 4272 if (HDR_IN_HASH_TABLE(hdr)) 4273 buf_hash_remove(hdr); 4274 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4275 } 4276 4277 /* 4278 * Broadcast before we drop the hash_lock to avoid the possibility 4279 * that the hdr (and hence the cv) might be freed before we get to 4280 * the cv_broadcast(). 4281 */ 4282 cv_broadcast(&hdr->b_l1hdr.b_cv); 4283 4284 if (hash_lock != NULL) { 4285 mutex_exit(hash_lock); 4286 } else { 4287 /* 4288 * This block was freed while we waited for the read to 4289 * complete. It has been removed from the hash table and 4290 * moved to the anonymous state (so that it won't show up 4291 * in the cache). 4292 */ 4293 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4294 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4295 } 4296 4297 /* execute each callback and free its structure */ 4298 while ((acb = callback_list) != NULL) { 4299 if (acb->acb_done) 4300 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4301 4302 if (acb->acb_zio_dummy != NULL) { 4303 acb->acb_zio_dummy->io_error = zio->io_error; 4304 zio_nowait(acb->acb_zio_dummy); 4305 } 4306 4307 callback_list = acb->acb_next; 4308 kmem_free(acb, sizeof (arc_callback_t)); 4309 } 4310 4311 if (freeable) 4312 arc_hdr_destroy(hdr); 4313 } 4314 4315 /* 4316 * "Read" the block at the specified DVA (in bp) via the 4317 * cache. If the block is found in the cache, invoke the provided 4318 * callback immediately and return. Note that the `zio' parameter 4319 * in the callback will be NULL in this case, since no IO was 4320 * required. If the block is not in the cache pass the read request 4321 * on to the spa with a substitute callback function, so that the 4322 * requested block will be added to the cache. 4323 * 4324 * If a read request arrives for a block that has a read in-progress, 4325 * either wait for the in-progress read to complete (and return the 4326 * results); or, if this is a read with a "done" func, add a record 4327 * to the read to invoke the "done" func when the read completes, 4328 * and return; or just return. 4329 * 4330 * arc_read_done() will invoke all the requested "done" functions 4331 * for readers of this block. 4332 */ 4333 int 4334 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4335 void *private, zio_priority_t priority, int zio_flags, 4336 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4337 { 4338 arc_buf_hdr_t *hdr = NULL; 4339 arc_buf_t *buf = NULL; 4340 kmutex_t *hash_lock = NULL; 4341 zio_t *rzio; 4342 uint64_t guid = spa_load_guid(spa); 4343 4344 ASSERT(!BP_IS_EMBEDDED(bp) || 4345 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4346 4347 top: 4348 if (!BP_IS_EMBEDDED(bp)) { 4349 /* 4350 * Embedded BP's have no DVA and require no I/O to "read". 4351 * Create an anonymous arc buf to back it. 4352 */ 4353 hdr = buf_hash_find(guid, bp, &hash_lock); 4354 } 4355 4356 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4357 4358 *arc_flags |= ARC_FLAG_CACHED; 4359 4360 if (HDR_IO_IN_PROGRESS(hdr)) { 4361 4362 if (*arc_flags & ARC_FLAG_WAIT) { 4363 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4364 mutex_exit(hash_lock); 4365 goto top; 4366 } 4367 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4368 4369 if (done) { 4370 arc_callback_t *acb = NULL; 4371 4372 acb = kmem_zalloc(sizeof (arc_callback_t), 4373 KM_SLEEP); 4374 acb->acb_done = done; 4375 acb->acb_private = private; 4376 if (pio != NULL) 4377 acb->acb_zio_dummy = zio_null(pio, 4378 spa, NULL, NULL, NULL, zio_flags); 4379 4380 ASSERT(acb->acb_done != NULL); 4381 acb->acb_next = hdr->b_l1hdr.b_acb; 4382 hdr->b_l1hdr.b_acb = acb; 4383 add_reference(hdr, hash_lock, private); 4384 mutex_exit(hash_lock); 4385 return (0); 4386 } 4387 mutex_exit(hash_lock); 4388 return (0); 4389 } 4390 4391 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4392 hdr->b_l1hdr.b_state == arc_mfu); 4393 4394 if (done) { 4395 add_reference(hdr, hash_lock, private); 4396 /* 4397 * If this block is already in use, create a new 4398 * copy of the data so that we will be guaranteed 4399 * that arc_release() will always succeed. 4400 */ 4401 buf = hdr->b_l1hdr.b_buf; 4402 ASSERT(buf); 4403 ASSERT(buf->b_data); 4404 if (HDR_BUF_AVAILABLE(hdr)) { 4405 ASSERT(buf->b_efunc == NULL); 4406 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4407 } else { 4408 buf = arc_buf_clone(buf); 4409 } 4410 4411 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4412 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4413 hdr->b_flags |= ARC_FLAG_PREFETCH; 4414 } 4415 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4416 arc_access(hdr, hash_lock); 4417 if (*arc_flags & ARC_FLAG_L2CACHE) 4418 hdr->b_flags |= ARC_FLAG_L2CACHE; 4419 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4420 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4421 mutex_exit(hash_lock); 4422 ARCSTAT_BUMP(arcstat_hits); 4423 arc_update_hit_stat(hdr, B_TRUE); 4424 4425 if (done) 4426 done(NULL, buf, private); 4427 } else { 4428 uint64_t size = BP_GET_LSIZE(bp); 4429 arc_callback_t *acb; 4430 vdev_t *vd = NULL; 4431 uint64_t addr = 0; 4432 boolean_t devw = B_FALSE; 4433 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4434 int32_t b_asize = 0; 4435 4436 if (hdr == NULL) { 4437 /* this block is not in the cache */ 4438 arc_buf_hdr_t *exists = NULL; 4439 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4440 buf = arc_buf_alloc(spa, size, private, type); 4441 hdr = buf->b_hdr; 4442 if (!BP_IS_EMBEDDED(bp)) { 4443 hdr->b_dva = *BP_IDENTITY(bp); 4444 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4445 exists = buf_hash_insert(hdr, &hash_lock); 4446 } 4447 if (exists != NULL) { 4448 /* somebody beat us to the hash insert */ 4449 mutex_exit(hash_lock); 4450 buf_discard_identity(hdr); 4451 (void) arc_buf_remove_ref(buf, private); 4452 goto top; /* restart the IO request */ 4453 } 4454 4455 /* if this is a prefetch, we don't have a reference */ 4456 if (*arc_flags & ARC_FLAG_PREFETCH) { 4457 (void) remove_reference(hdr, hash_lock, 4458 private); 4459 hdr->b_flags |= ARC_FLAG_PREFETCH; 4460 } 4461 if (*arc_flags & ARC_FLAG_L2CACHE) 4462 hdr->b_flags |= ARC_FLAG_L2CACHE; 4463 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4464 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4465 if (BP_GET_LEVEL(bp) > 0) 4466 hdr->b_flags |= ARC_FLAG_INDIRECT; 4467 } else { 4468 /* 4469 * This block is in the ghost cache. If it was L2-only 4470 * (and thus didn't have an L1 hdr), we realloc the 4471 * header to add an L1 hdr. 4472 */ 4473 if (!HDR_HAS_L1HDR(hdr)) { 4474 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4475 hdr_full_cache); 4476 } 4477 4478 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4479 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4480 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4481 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4482 4483 /* if this is a prefetch, we don't have a reference */ 4484 if (*arc_flags & ARC_FLAG_PREFETCH) 4485 hdr->b_flags |= ARC_FLAG_PREFETCH; 4486 else 4487 add_reference(hdr, hash_lock, private); 4488 if (*arc_flags & ARC_FLAG_L2CACHE) 4489 hdr->b_flags |= ARC_FLAG_L2CACHE; 4490 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4491 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4492 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4493 buf->b_hdr = hdr; 4494 buf->b_data = NULL; 4495 buf->b_efunc = NULL; 4496 buf->b_private = NULL; 4497 buf->b_next = NULL; 4498 hdr->b_l1hdr.b_buf = buf; 4499 ASSERT0(hdr->b_l1hdr.b_datacnt); 4500 hdr->b_l1hdr.b_datacnt = 1; 4501 arc_get_data_buf(buf); 4502 arc_access(hdr, hash_lock); 4503 } 4504 4505 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4506 4507 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4508 acb->acb_done = done; 4509 acb->acb_private = private; 4510 4511 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4512 hdr->b_l1hdr.b_acb = acb; 4513 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4514 4515 if (HDR_HAS_L2HDR(hdr) && 4516 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4517 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4518 addr = hdr->b_l2hdr.b_daddr; 4519 b_compress = hdr->b_l2hdr.b_compress; 4520 b_asize = hdr->b_l2hdr.b_asize; 4521 /* 4522 * Lock out device removal. 4523 */ 4524 if (vdev_is_dead(vd) || 4525 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4526 vd = NULL; 4527 } 4528 4529 if (hash_lock != NULL) 4530 mutex_exit(hash_lock); 4531 4532 /* 4533 * At this point, we have a level 1 cache miss. Try again in 4534 * L2ARC if possible. 4535 */ 4536 ASSERT3U(hdr->b_size, ==, size); 4537 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4538 uint64_t, size, zbookmark_phys_t *, zb); 4539 ARCSTAT_BUMP(arcstat_misses); 4540 arc_update_hit_stat(hdr, B_FALSE); 4541 4542 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4543 /* 4544 * Read from the L2ARC if the following are true: 4545 * 1. The L2ARC vdev was previously cached. 4546 * 2. This buffer still has L2ARC metadata. 4547 * 3. This buffer isn't currently writing to the L2ARC. 4548 * 4. The L2ARC entry wasn't evicted, which may 4549 * also have invalidated the vdev. 4550 * 5. This isn't prefetch and l2arc_noprefetch is set. 4551 */ 4552 if (HDR_HAS_L2HDR(hdr) && 4553 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4554 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4555 l2arc_read_callback_t *cb; 4556 4557 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4558 ARCSTAT_BUMP(arcstat_l2_hits); 4559 4560 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4561 KM_SLEEP); 4562 cb->l2rcb_buf = buf; 4563 cb->l2rcb_spa = spa; 4564 cb->l2rcb_bp = *bp; 4565 cb->l2rcb_zb = *zb; 4566 cb->l2rcb_flags = zio_flags; 4567 cb->l2rcb_compress = b_compress; 4568 4569 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4570 addr + size < vd->vdev_psize - 4571 VDEV_LABEL_END_SIZE); 4572 4573 /* 4574 * l2arc read. The SCL_L2ARC lock will be 4575 * released by l2arc_read_done(). 4576 * Issue a null zio if the underlying buffer 4577 * was squashed to zero size by compression. 4578 */ 4579 if (b_compress == ZIO_COMPRESS_EMPTY) { 4580 rzio = zio_null(pio, spa, vd, 4581 l2arc_read_done, cb, 4582 zio_flags | ZIO_FLAG_DONT_CACHE | 4583 ZIO_FLAG_CANFAIL | 4584 ZIO_FLAG_DONT_PROPAGATE | 4585 ZIO_FLAG_DONT_RETRY); 4586 } else { 4587 rzio = zio_read_phys(pio, vd, addr, 4588 b_asize, buf->b_data, 4589 ZIO_CHECKSUM_OFF, 4590 l2arc_read_done, cb, priority, 4591 zio_flags | ZIO_FLAG_DONT_CACHE | 4592 ZIO_FLAG_CANFAIL | 4593 ZIO_FLAG_DONT_PROPAGATE | 4594 ZIO_FLAG_DONT_RETRY, B_FALSE); 4595 } 4596 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4597 zio_t *, rzio); 4598 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4599 4600 if (*arc_flags & ARC_FLAG_NOWAIT) { 4601 zio_nowait(rzio); 4602 return (0); 4603 } 4604 4605 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4606 if (zio_wait(rzio) == 0) 4607 return (0); 4608 4609 /* l2arc read error; goto zio_read() */ 4610 } else { 4611 DTRACE_PROBE1(l2arc__miss, 4612 arc_buf_hdr_t *, hdr); 4613 ARCSTAT_BUMP(arcstat_l2_misses); 4614 if (HDR_L2_WRITING(hdr)) 4615 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4616 spa_config_exit(spa, SCL_L2ARC, vd); 4617 } 4618 } else { 4619 if (vd != NULL) 4620 spa_config_exit(spa, SCL_L2ARC, vd); 4621 if (l2arc_ndev != 0) { 4622 DTRACE_PROBE1(l2arc__miss, 4623 arc_buf_hdr_t *, hdr); 4624 ARCSTAT_BUMP(arcstat_l2_misses); 4625 } 4626 } 4627 4628 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4629 arc_read_done, buf, priority, zio_flags, zb); 4630 4631 if (*arc_flags & ARC_FLAG_WAIT) 4632 return (zio_wait(rzio)); 4633 4634 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4635 zio_nowait(rzio); 4636 } 4637 return (0); 4638 } 4639 4640 void 4641 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4642 { 4643 ASSERT(buf->b_hdr != NULL); 4644 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4645 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4646 func == NULL); 4647 ASSERT(buf->b_efunc == NULL); 4648 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4649 4650 buf->b_efunc = func; 4651 buf->b_private = private; 4652 } 4653 4654 /* 4655 * Notify the arc that a block was freed, and thus will never be used again. 4656 */ 4657 void 4658 arc_freed(spa_t *spa, const blkptr_t *bp) 4659 { 4660 arc_buf_hdr_t *hdr; 4661 kmutex_t *hash_lock; 4662 uint64_t guid = spa_load_guid(spa); 4663 4664 ASSERT(!BP_IS_EMBEDDED(bp)); 4665 4666 hdr = buf_hash_find(guid, bp, &hash_lock); 4667 if (hdr == NULL) 4668 return; 4669 if (HDR_BUF_AVAILABLE(hdr)) { 4670 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4671 add_reference(hdr, hash_lock, FTAG); 4672 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4673 mutex_exit(hash_lock); 4674 4675 arc_release(buf, FTAG); 4676 (void) arc_buf_remove_ref(buf, FTAG); 4677 } else { 4678 mutex_exit(hash_lock); 4679 } 4680 4681 } 4682 4683 /* 4684 * Clear the user eviction callback set by arc_set_callback(), first calling 4685 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4686 * clearing the callback may result in the arc_buf being destroyed. However, 4687 * it will not result in the *last* arc_buf being destroyed, hence the data 4688 * will remain cached in the ARC. We make a copy of the arc buffer here so 4689 * that we can process the callback without holding any locks. 4690 * 4691 * It's possible that the callback is already in the process of being cleared 4692 * by another thread. In this case we can not clear the callback. 4693 * 4694 * Returns B_TRUE if the callback was successfully called and cleared. 4695 */ 4696 boolean_t 4697 arc_clear_callback(arc_buf_t *buf) 4698 { 4699 arc_buf_hdr_t *hdr; 4700 kmutex_t *hash_lock; 4701 arc_evict_func_t *efunc = buf->b_efunc; 4702 void *private = buf->b_private; 4703 4704 mutex_enter(&buf->b_evict_lock); 4705 hdr = buf->b_hdr; 4706 if (hdr == NULL) { 4707 /* 4708 * We are in arc_do_user_evicts(). 4709 */ 4710 ASSERT(buf->b_data == NULL); 4711 mutex_exit(&buf->b_evict_lock); 4712 return (B_FALSE); 4713 } else if (buf->b_data == NULL) { 4714 /* 4715 * We are on the eviction list; process this buffer now 4716 * but let arc_do_user_evicts() do the reaping. 4717 */ 4718 buf->b_efunc = NULL; 4719 mutex_exit(&buf->b_evict_lock); 4720 VERIFY0(efunc(private)); 4721 return (B_TRUE); 4722 } 4723 hash_lock = HDR_LOCK(hdr); 4724 mutex_enter(hash_lock); 4725 hdr = buf->b_hdr; 4726 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4727 4728 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4729 hdr->b_l1hdr.b_datacnt); 4730 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4731 hdr->b_l1hdr.b_state == arc_mfu); 4732 4733 buf->b_efunc = NULL; 4734 buf->b_private = NULL; 4735 4736 if (hdr->b_l1hdr.b_datacnt > 1) { 4737 mutex_exit(&buf->b_evict_lock); 4738 arc_buf_destroy(buf, TRUE); 4739 } else { 4740 ASSERT(buf == hdr->b_l1hdr.b_buf); 4741 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4742 mutex_exit(&buf->b_evict_lock); 4743 } 4744 4745 mutex_exit(hash_lock); 4746 VERIFY0(efunc(private)); 4747 return (B_TRUE); 4748 } 4749 4750 /* 4751 * Release this buffer from the cache, making it an anonymous buffer. This 4752 * must be done after a read and prior to modifying the buffer contents. 4753 * If the buffer has more than one reference, we must make 4754 * a new hdr for the buffer. 4755 */ 4756 void 4757 arc_release(arc_buf_t *buf, void *tag) 4758 { 4759 arc_buf_hdr_t *hdr = buf->b_hdr; 4760 4761 /* 4762 * It would be nice to assert that if it's DMU metadata (level > 4763 * 0 || it's the dnode file), then it must be syncing context. 4764 * But we don't know that information at this level. 4765 */ 4766 4767 mutex_enter(&buf->b_evict_lock); 4768 4769 ASSERT(HDR_HAS_L1HDR(hdr)); 4770 4771 /* 4772 * We don't grab the hash lock prior to this check, because if 4773 * the buffer's header is in the arc_anon state, it won't be 4774 * linked into the hash table. 4775 */ 4776 if (hdr->b_l1hdr.b_state == arc_anon) { 4777 mutex_exit(&buf->b_evict_lock); 4778 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4779 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4780 ASSERT(!HDR_HAS_L2HDR(hdr)); 4781 ASSERT(BUF_EMPTY(hdr)); 4782 4783 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4784 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4785 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4786 4787 ASSERT3P(buf->b_efunc, ==, NULL); 4788 ASSERT3P(buf->b_private, ==, NULL); 4789 4790 hdr->b_l1hdr.b_arc_access = 0; 4791 arc_buf_thaw(buf); 4792 4793 return; 4794 } 4795 4796 kmutex_t *hash_lock = HDR_LOCK(hdr); 4797 mutex_enter(hash_lock); 4798 4799 /* 4800 * This assignment is only valid as long as the hash_lock is 4801 * held, we must be careful not to reference state or the 4802 * b_state field after dropping the lock. 4803 */ 4804 arc_state_t *state = hdr->b_l1hdr.b_state; 4805 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4806 ASSERT3P(state, !=, arc_anon); 4807 4808 /* this buffer is not on any list */ 4809 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4810 4811 if (HDR_HAS_L2HDR(hdr)) { 4812 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4813 4814 /* 4815 * We have to recheck this conditional again now that 4816 * we're holding the l2ad_mtx to prevent a race with 4817 * another thread which might be concurrently calling 4818 * l2arc_evict(). In that case, l2arc_evict() might have 4819 * destroyed the header's L2 portion as we were waiting 4820 * to acquire the l2ad_mtx. 4821 */ 4822 if (HDR_HAS_L2HDR(hdr)) 4823 arc_hdr_l2hdr_destroy(hdr); 4824 4825 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4826 } 4827 4828 /* 4829 * Do we have more than one buf? 4830 */ 4831 if (hdr->b_l1hdr.b_datacnt > 1) { 4832 arc_buf_hdr_t *nhdr; 4833 arc_buf_t **bufp; 4834 uint64_t blksz = hdr->b_size; 4835 uint64_t spa = hdr->b_spa; 4836 arc_buf_contents_t type = arc_buf_type(hdr); 4837 uint32_t flags = hdr->b_flags; 4838 4839 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4840 /* 4841 * Pull the data off of this hdr and attach it to 4842 * a new anonymous hdr. 4843 */ 4844 (void) remove_reference(hdr, hash_lock, tag); 4845 bufp = &hdr->b_l1hdr.b_buf; 4846 while (*bufp != buf) 4847 bufp = &(*bufp)->b_next; 4848 *bufp = buf->b_next; 4849 buf->b_next = NULL; 4850 4851 ASSERT3P(state, !=, arc_l2c_only); 4852 4853 (void) refcount_remove_many( 4854 &state->arcs_size, hdr->b_size, buf); 4855 4856 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4857 ASSERT3P(state, !=, arc_l2c_only); 4858 uint64_t *size = &state->arcs_lsize[type]; 4859 ASSERT3U(*size, >=, hdr->b_size); 4860 atomic_add_64(size, -hdr->b_size); 4861 } 4862 4863 /* 4864 * We're releasing a duplicate user data buffer, update 4865 * our statistics accordingly. 4866 */ 4867 if (HDR_ISTYPE_DATA(hdr)) { 4868 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4869 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4870 -hdr->b_size); 4871 } 4872 hdr->b_l1hdr.b_datacnt -= 1; 4873 arc_cksum_verify(buf); 4874 arc_buf_unwatch(buf); 4875 4876 mutex_exit(hash_lock); 4877 4878 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4879 nhdr->b_size = blksz; 4880 nhdr->b_spa = spa; 4881 4882 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4883 nhdr->b_flags |= arc_bufc_to_flags(type); 4884 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4885 4886 nhdr->b_l1hdr.b_buf = buf; 4887 nhdr->b_l1hdr.b_datacnt = 1; 4888 nhdr->b_l1hdr.b_state = arc_anon; 4889 nhdr->b_l1hdr.b_arc_access = 0; 4890 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4891 nhdr->b_freeze_cksum = NULL; 4892 4893 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4894 buf->b_hdr = nhdr; 4895 mutex_exit(&buf->b_evict_lock); 4896 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4897 } else { 4898 mutex_exit(&buf->b_evict_lock); 4899 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4900 /* protected by hash lock, or hdr is on arc_anon */ 4901 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4902 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4903 arc_change_state(arc_anon, hdr, hash_lock); 4904 hdr->b_l1hdr.b_arc_access = 0; 4905 mutex_exit(hash_lock); 4906 4907 buf_discard_identity(hdr); 4908 arc_buf_thaw(buf); 4909 } 4910 buf->b_efunc = NULL; 4911 buf->b_private = NULL; 4912 } 4913 4914 int 4915 arc_released(arc_buf_t *buf) 4916 { 4917 int released; 4918 4919 mutex_enter(&buf->b_evict_lock); 4920 released = (buf->b_data != NULL && 4921 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4922 mutex_exit(&buf->b_evict_lock); 4923 return (released); 4924 } 4925 4926 #ifdef ZFS_DEBUG 4927 int 4928 arc_referenced(arc_buf_t *buf) 4929 { 4930 int referenced; 4931 4932 mutex_enter(&buf->b_evict_lock); 4933 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4934 mutex_exit(&buf->b_evict_lock); 4935 return (referenced); 4936 } 4937 #endif 4938 4939 static void 4940 arc_write_ready(zio_t *zio) 4941 { 4942 arc_write_callback_t *callback = zio->io_private; 4943 arc_buf_t *buf = callback->awcb_buf; 4944 arc_buf_hdr_t *hdr = buf->b_hdr; 4945 4946 ASSERT(HDR_HAS_L1HDR(hdr)); 4947 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4948 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4949 callback->awcb_ready(zio, buf, callback->awcb_private); 4950 4951 /* 4952 * If the IO is already in progress, then this is a re-write 4953 * attempt, so we need to thaw and re-compute the cksum. 4954 * It is the responsibility of the callback to handle the 4955 * accounting for any re-write attempt. 4956 */ 4957 if (HDR_IO_IN_PROGRESS(hdr)) { 4958 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4959 if (hdr->b_freeze_cksum != NULL) { 4960 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4961 hdr->b_freeze_cksum = NULL; 4962 } 4963 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4964 } 4965 arc_cksum_compute(buf, B_FALSE); 4966 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4967 } 4968 4969 /* 4970 * The SPA calls this callback for each physical write that happens on behalf 4971 * of a logical write. See the comment in dbuf_write_physdone() for details. 4972 */ 4973 static void 4974 arc_write_physdone(zio_t *zio) 4975 { 4976 arc_write_callback_t *cb = zio->io_private; 4977 if (cb->awcb_physdone != NULL) 4978 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4979 } 4980 4981 static void 4982 arc_write_done(zio_t *zio) 4983 { 4984 arc_write_callback_t *callback = zio->io_private; 4985 arc_buf_t *buf = callback->awcb_buf; 4986 arc_buf_hdr_t *hdr = buf->b_hdr; 4987 4988 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4989 4990 if (zio->io_error == 0) { 4991 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4992 buf_discard_identity(hdr); 4993 } else { 4994 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4995 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4996 } 4997 } else { 4998 ASSERT(BUF_EMPTY(hdr)); 4999 } 5000 5001 /* 5002 * If the block to be written was all-zero or compressed enough to be 5003 * embedded in the BP, no write was performed so there will be no 5004 * dva/birth/checksum. The buffer must therefore remain anonymous 5005 * (and uncached). 5006 */ 5007 if (!BUF_EMPTY(hdr)) { 5008 arc_buf_hdr_t *exists; 5009 kmutex_t *hash_lock; 5010 5011 ASSERT(zio->io_error == 0); 5012 5013 arc_cksum_verify(buf); 5014 5015 exists = buf_hash_insert(hdr, &hash_lock); 5016 if (exists != NULL) { 5017 /* 5018 * This can only happen if we overwrite for 5019 * sync-to-convergence, because we remove 5020 * buffers from the hash table when we arc_free(). 5021 */ 5022 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5023 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5024 panic("bad overwrite, hdr=%p exists=%p", 5025 (void *)hdr, (void *)exists); 5026 ASSERT(refcount_is_zero( 5027 &exists->b_l1hdr.b_refcnt)); 5028 arc_change_state(arc_anon, exists, hash_lock); 5029 mutex_exit(hash_lock); 5030 arc_hdr_destroy(exists); 5031 exists = buf_hash_insert(hdr, &hash_lock); 5032 ASSERT3P(exists, ==, NULL); 5033 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5034 /* nopwrite */ 5035 ASSERT(zio->io_prop.zp_nopwrite); 5036 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5037 panic("bad nopwrite, hdr=%p exists=%p", 5038 (void *)hdr, (void *)exists); 5039 } else { 5040 /* Dedup */ 5041 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5042 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5043 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5044 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5045 } 5046 } 5047 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5048 /* if it's not anon, we are doing a scrub */ 5049 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5050 arc_access(hdr, hash_lock); 5051 mutex_exit(hash_lock); 5052 } else { 5053 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5054 } 5055 5056 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5057 callback->awcb_done(zio, buf, callback->awcb_private); 5058 5059 kmem_free(callback, sizeof (arc_write_callback_t)); 5060 } 5061 5062 zio_t * 5063 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5064 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5065 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 5066 arc_done_func_t *done, void *private, zio_priority_t priority, 5067 int zio_flags, const zbookmark_phys_t *zb) 5068 { 5069 arc_buf_hdr_t *hdr = buf->b_hdr; 5070 arc_write_callback_t *callback; 5071 zio_t *zio; 5072 5073 ASSERT(ready != NULL); 5074 ASSERT(done != NULL); 5075 ASSERT(!HDR_IO_ERROR(hdr)); 5076 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5077 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5078 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5079 if (l2arc) 5080 hdr->b_flags |= ARC_FLAG_L2CACHE; 5081 if (l2arc_compress) 5082 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5083 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5084 callback->awcb_ready = ready; 5085 callback->awcb_physdone = physdone; 5086 callback->awcb_done = done; 5087 callback->awcb_private = private; 5088 callback->awcb_buf = buf; 5089 5090 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5091 arc_write_ready, arc_write_physdone, arc_write_done, callback, 5092 priority, zio_flags, zb); 5093 5094 return (zio); 5095 } 5096 5097 static int 5098 arc_memory_throttle(uint64_t reserve, uint64_t txg) 5099 { 5100 #ifdef _KERNEL 5101 uint64_t available_memory = ptob(freemem); 5102 static uint64_t page_load = 0; 5103 static uint64_t last_txg = 0; 5104 5105 #if defined(__i386) 5106 available_memory = 5107 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE)); 5108 #endif 5109 5110 if (freemem > physmem * arc_lotsfree_percent / 100) 5111 return (0); 5112 5113 if (txg > last_txg) { 5114 last_txg = txg; 5115 page_load = 0; 5116 } 5117 /* 5118 * If we are in pageout, we know that memory is already tight, 5119 * the arc is already going to be evicting, so we just want to 5120 * continue to let page writes occur as quickly as possible. 5121 */ 5122 if (curproc == proc_pageout) { 5123 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5124 return (SET_ERROR(ERESTART)); 5125 /* Note: reserve is inflated, so we deflate */ 5126 page_load += reserve / 8; 5127 return (0); 5128 } else if (page_load > 0 && arc_reclaim_needed()) { 5129 /* memory is low, delay before restarting */ 5130 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5131 return (SET_ERROR(EAGAIN)); 5132 } 5133 page_load = 0; 5134 #endif 5135 return (0); 5136 } 5137 5138 void 5139 arc_tempreserve_clear(uint64_t reserve) 5140 { 5141 atomic_add_64(&arc_tempreserve, -reserve); 5142 ASSERT((int64_t)arc_tempreserve >= 0); 5143 } 5144 5145 int 5146 arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5147 { 5148 int error; 5149 uint64_t anon_size; 5150 5151 if (reserve > arc_c/4 && !arc_no_grow) 5152 arc_c = MIN(arc_c_max, reserve * 4); 5153 if (reserve > arc_c) 5154 return (SET_ERROR(ENOMEM)); 5155 5156 /* 5157 * Don't count loaned bufs as in flight dirty data to prevent long 5158 * network delays from blocking transactions that are ready to be 5159 * assigned to a txg. 5160 */ 5161 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5162 arc_loaned_bytes), 0); 5163 5164 /* 5165 * Writes will, almost always, require additional memory allocations 5166 * in order to compress/encrypt/etc the data. We therefore need to 5167 * make sure that there is sufficient available memory for this. 5168 */ 5169 error = arc_memory_throttle(reserve, txg); 5170 if (error != 0) 5171 return (error); 5172 5173 /* 5174 * Throttle writes when the amount of dirty data in the cache 5175 * gets too large. We try to keep the cache less than half full 5176 * of dirty blocks so that our sync times don't grow too large. 5177 * Note: if two requests come in concurrently, we might let them 5178 * both succeed, when one of them should fail. Not a huge deal. 5179 */ 5180 5181 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5182 anon_size > arc_c / 4) { 5183 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5184 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5185 arc_tempreserve>>10, 5186 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5187 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5188 reserve>>10, arc_c>>10); 5189 return (SET_ERROR(ERESTART)); 5190 } 5191 atomic_add_64(&arc_tempreserve, reserve); 5192 return (0); 5193 } 5194 5195 static void 5196 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5197 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5198 { 5199 size->value.ui64 = refcount_count(&state->arcs_size); 5200 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5201 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5202 } 5203 5204 static int 5205 arc_kstat_update(kstat_t *ksp, int rw) 5206 { 5207 arc_stats_t *as = ksp->ks_data; 5208 5209 if (rw == KSTAT_WRITE) { 5210 return (EACCES); 5211 } else { 5212 arc_kstat_update_state(arc_anon, 5213 &as->arcstat_anon_size, 5214 &as->arcstat_anon_evictable_data, 5215 &as->arcstat_anon_evictable_metadata); 5216 arc_kstat_update_state(arc_mru, 5217 &as->arcstat_mru_size, 5218 &as->arcstat_mru_evictable_data, 5219 &as->arcstat_mru_evictable_metadata); 5220 arc_kstat_update_state(arc_mru_ghost, 5221 &as->arcstat_mru_ghost_size, 5222 &as->arcstat_mru_ghost_evictable_data, 5223 &as->arcstat_mru_ghost_evictable_metadata); 5224 arc_kstat_update_state(arc_mfu, 5225 &as->arcstat_mfu_size, 5226 &as->arcstat_mfu_evictable_data, 5227 &as->arcstat_mfu_evictable_metadata); 5228 arc_kstat_update_state(arc_mfu_ghost, 5229 &as->arcstat_mfu_ghost_size, 5230 &as->arcstat_mfu_ghost_evictable_data, 5231 &as->arcstat_mfu_ghost_evictable_metadata); 5232 } 5233 5234 return (0); 5235 } 5236 5237 /* 5238 * This function *must* return indices evenly distributed between all 5239 * sublists of the multilist. This is needed due to how the ARC eviction 5240 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5241 * distributed between all sublists and uses this assumption when 5242 * deciding which sublist to evict from and how much to evict from it. 5243 */ 5244 unsigned int 5245 arc_state_multilist_index_func(multilist_t *ml, void *obj) 5246 { 5247 arc_buf_hdr_t *hdr = obj; 5248 5249 /* 5250 * We rely on b_dva to generate evenly distributed index 5251 * numbers using buf_hash below. So, as an added precaution, 5252 * let's make sure we never add empty buffers to the arc lists. 5253 */ 5254 ASSERT(!BUF_EMPTY(hdr)); 5255 5256 /* 5257 * The assumption here, is the hash value for a given 5258 * arc_buf_hdr_t will remain constant throughout it's lifetime 5259 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5260 * Thus, we don't need to store the header's sublist index 5261 * on insertion, as this index can be recalculated on removal. 5262 * 5263 * Also, the low order bits of the hash value are thought to be 5264 * distributed evenly. Otherwise, in the case that the multilist 5265 * has a power of two number of sublists, each sublists' usage 5266 * would not be evenly distributed. 5267 */ 5268 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5269 multilist_get_num_sublists(ml)); 5270 } 5271 5272 void 5273 arc_init(void) 5274 { 5275 /* 5276 * allmem is "all memory that we could possibly use". 5277 */ 5278 #ifdef _KERNEL 5279 uint64_t allmem = ptob(physmem - swapfs_minfree); 5280 #else 5281 uint64_t allmem = (physmem * PAGESIZE) / 2; 5282 #endif 5283 5284 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5285 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5286 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5287 5288 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5289 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5290 5291 /* Convert seconds to clock ticks */ 5292 arc_min_prefetch_lifespan = 1 * hz; 5293 5294 /* Start out with 1/8 of all memory */ 5295 arc_c = allmem / 8; 5296 5297 #ifdef _KERNEL 5298 /* 5299 * On architectures where the physical memory can be larger 5300 * than the addressable space (intel in 32-bit mode), we may 5301 * need to limit the cache to 1/8 of VM size. 5302 */ 5303 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5304 #endif 5305 5306 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */ 5307 arc_c_min = MAX(allmem / 32, 64 << 20); 5308 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */ 5309 if (allmem >= 1 << 30) 5310 arc_c_max = allmem - (1 << 30); 5311 else 5312 arc_c_max = arc_c_min; 5313 arc_c_max = MAX(allmem * 3 / 4, arc_c_max); 5314 5315 /* 5316 * Allow the tunables to override our calculations if they are 5317 * reasonable (ie. over 64MB) 5318 */ 5319 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) 5320 arc_c_max = zfs_arc_max; 5321 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max) 5322 arc_c_min = zfs_arc_min; 5323 5324 arc_c = arc_c_max; 5325 arc_p = (arc_c >> 1); 5326 5327 /* limit meta-data to 1/4 of the arc capacity */ 5328 arc_meta_limit = arc_c_max / 4; 5329 5330 /* Allow the tunable to override if it is reasonable */ 5331 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5332 arc_meta_limit = zfs_arc_meta_limit; 5333 5334 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5335 arc_c_min = arc_meta_limit / 2; 5336 5337 if (zfs_arc_meta_min > 0) { 5338 arc_meta_min = zfs_arc_meta_min; 5339 } else { 5340 arc_meta_min = arc_c_min / 2; 5341 } 5342 5343 if (zfs_arc_grow_retry > 0) 5344 arc_grow_retry = zfs_arc_grow_retry; 5345 5346 if (zfs_arc_shrink_shift > 0) 5347 arc_shrink_shift = zfs_arc_shrink_shift; 5348 5349 /* 5350 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5351 */ 5352 if (arc_no_grow_shift >= arc_shrink_shift) 5353 arc_no_grow_shift = arc_shrink_shift - 1; 5354 5355 if (zfs_arc_p_min_shift > 0) 5356 arc_p_min_shift = zfs_arc_p_min_shift; 5357 5358 if (zfs_arc_num_sublists_per_state < 1) 5359 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1); 5360 5361 /* if kmem_flags are set, lets try to use less memory */ 5362 if (kmem_debugging()) 5363 arc_c = arc_c / 2; 5364 if (arc_c < arc_c_min) 5365 arc_c = arc_c_min; 5366 5367 arc_anon = &ARC_anon; 5368 arc_mru = &ARC_mru; 5369 arc_mru_ghost = &ARC_mru_ghost; 5370 arc_mfu = &ARC_mfu; 5371 arc_mfu_ghost = &ARC_mfu_ghost; 5372 arc_l2c_only = &ARC_l2c_only; 5373 arc_size = 0; 5374 5375 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5376 sizeof (arc_buf_hdr_t), 5377 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5378 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5379 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5380 sizeof (arc_buf_hdr_t), 5381 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5382 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5383 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5384 sizeof (arc_buf_hdr_t), 5385 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5386 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5387 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5388 sizeof (arc_buf_hdr_t), 5389 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5390 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5391 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5392 sizeof (arc_buf_hdr_t), 5393 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5394 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5395 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5396 sizeof (arc_buf_hdr_t), 5397 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5398 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5399 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5400 sizeof (arc_buf_hdr_t), 5401 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5402 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5403 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5404 sizeof (arc_buf_hdr_t), 5405 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5406 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5407 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5408 sizeof (arc_buf_hdr_t), 5409 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5410 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5411 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5412 sizeof (arc_buf_hdr_t), 5413 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5414 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5415 5416 refcount_create(&arc_anon->arcs_size); 5417 refcount_create(&arc_mru->arcs_size); 5418 refcount_create(&arc_mru_ghost->arcs_size); 5419 refcount_create(&arc_mfu->arcs_size); 5420 refcount_create(&arc_mfu_ghost->arcs_size); 5421 refcount_create(&arc_l2c_only->arcs_size); 5422 5423 buf_init(); 5424 5425 arc_reclaim_thread_exit = FALSE; 5426 arc_user_evicts_thread_exit = FALSE; 5427 arc_eviction_list = NULL; 5428 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5429 5430 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5431 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5432 5433 if (arc_ksp != NULL) { 5434 arc_ksp->ks_data = &arc_stats; 5435 arc_ksp->ks_update = arc_kstat_update; 5436 kstat_install(arc_ksp); 5437 } 5438 5439 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5440 TS_RUN, minclsyspri); 5441 5442 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5443 TS_RUN, minclsyspri); 5444 5445 arc_dead = FALSE; 5446 arc_warm = B_FALSE; 5447 5448 /* 5449 * Calculate maximum amount of dirty data per pool. 5450 * 5451 * If it has been set by /etc/system, take that. 5452 * Otherwise, use a percentage of physical memory defined by 5453 * zfs_dirty_data_max_percent (default 10%) with a cap at 5454 * zfs_dirty_data_max_max (default 4GB). 5455 */ 5456 if (zfs_dirty_data_max == 0) { 5457 zfs_dirty_data_max = physmem * PAGESIZE * 5458 zfs_dirty_data_max_percent / 100; 5459 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5460 zfs_dirty_data_max_max); 5461 } 5462 } 5463 5464 void 5465 arc_fini(void) 5466 { 5467 mutex_enter(&arc_reclaim_lock); 5468 arc_reclaim_thread_exit = TRUE; 5469 /* 5470 * The reclaim thread will set arc_reclaim_thread_exit back to 5471 * FALSE when it is finished exiting; we're waiting for that. 5472 */ 5473 while (arc_reclaim_thread_exit) { 5474 cv_signal(&arc_reclaim_thread_cv); 5475 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5476 } 5477 mutex_exit(&arc_reclaim_lock); 5478 5479 mutex_enter(&arc_user_evicts_lock); 5480 arc_user_evicts_thread_exit = TRUE; 5481 /* 5482 * The user evicts thread will set arc_user_evicts_thread_exit 5483 * to FALSE when it is finished exiting; we're waiting for that. 5484 */ 5485 while (arc_user_evicts_thread_exit) { 5486 cv_signal(&arc_user_evicts_cv); 5487 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5488 } 5489 mutex_exit(&arc_user_evicts_lock); 5490 5491 /* Use TRUE to ensure *all* buffers are evicted */ 5492 arc_flush(NULL, TRUE); 5493 5494 arc_dead = TRUE; 5495 5496 if (arc_ksp != NULL) { 5497 kstat_delete(arc_ksp); 5498 arc_ksp = NULL; 5499 } 5500 5501 mutex_destroy(&arc_reclaim_lock); 5502 cv_destroy(&arc_reclaim_thread_cv); 5503 cv_destroy(&arc_reclaim_waiters_cv); 5504 5505 mutex_destroy(&arc_user_evicts_lock); 5506 cv_destroy(&arc_user_evicts_cv); 5507 5508 refcount_destroy(&arc_anon->arcs_size); 5509 refcount_destroy(&arc_mru->arcs_size); 5510 refcount_destroy(&arc_mru_ghost->arcs_size); 5511 refcount_destroy(&arc_mfu->arcs_size); 5512 refcount_destroy(&arc_mfu_ghost->arcs_size); 5513 refcount_destroy(&arc_l2c_only->arcs_size); 5514 5515 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5516 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5517 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5518 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5519 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5520 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5521 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5522 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5523 5524 buf_fini(); 5525 5526 ASSERT0(arc_loaned_bytes); 5527 } 5528 5529 /* 5530 * Level 2 ARC 5531 * 5532 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5533 * It uses dedicated storage devices to hold cached data, which are populated 5534 * using large infrequent writes. The main role of this cache is to boost 5535 * the performance of random read workloads. The intended L2ARC devices 5536 * include short-stroked disks, solid state disks, and other media with 5537 * substantially faster read latency than disk. 5538 * 5539 * +-----------------------+ 5540 * | ARC | 5541 * +-----------------------+ 5542 * | ^ ^ 5543 * | | | 5544 * l2arc_feed_thread() arc_read() 5545 * | | | 5546 * | l2arc read | 5547 * V | | 5548 * +---------------+ | 5549 * | L2ARC | | 5550 * +---------------+ | 5551 * | ^ | 5552 * l2arc_write() | | 5553 * | | | 5554 * V | | 5555 * +-------+ +-------+ 5556 * | vdev | | vdev | 5557 * | cache | | cache | 5558 * +-------+ +-------+ 5559 * +=========+ .-----. 5560 * : L2ARC : |-_____-| 5561 * : devices : | Disks | 5562 * +=========+ `-_____-' 5563 * 5564 * Read requests are satisfied from the following sources, in order: 5565 * 5566 * 1) ARC 5567 * 2) vdev cache of L2ARC devices 5568 * 3) L2ARC devices 5569 * 4) vdev cache of disks 5570 * 5) disks 5571 * 5572 * Some L2ARC device types exhibit extremely slow write performance. 5573 * To accommodate for this there are some significant differences between 5574 * the L2ARC and traditional cache design: 5575 * 5576 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5577 * the ARC behave as usual, freeing buffers and placing headers on ghost 5578 * lists. The ARC does not send buffers to the L2ARC during eviction as 5579 * this would add inflated write latencies for all ARC memory pressure. 5580 * 5581 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5582 * It does this by periodically scanning buffers from the eviction-end of 5583 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5584 * not already there. It scans until a headroom of buffers is satisfied, 5585 * which itself is a buffer for ARC eviction. If a compressible buffer is 5586 * found during scanning and selected for writing to an L2ARC device, we 5587 * temporarily boost scanning headroom during the next scan cycle to make 5588 * sure we adapt to compression effects (which might significantly reduce 5589 * the data volume we write to L2ARC). The thread that does this is 5590 * l2arc_feed_thread(), illustrated below; example sizes are included to 5591 * provide a better sense of ratio than this diagram: 5592 * 5593 * head --> tail 5594 * +---------------------+----------+ 5595 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5596 * +---------------------+----------+ | o L2ARC eligible 5597 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5598 * +---------------------+----------+ | 5599 * 15.9 Gbytes ^ 32 Mbytes | 5600 * headroom | 5601 * l2arc_feed_thread() 5602 * | 5603 * l2arc write hand <--[oooo]--' 5604 * | 8 Mbyte 5605 * | write max 5606 * V 5607 * +==============================+ 5608 * L2ARC dev |####|#|###|###| |####| ... | 5609 * +==============================+ 5610 * 32 Gbytes 5611 * 5612 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5613 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5614 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5615 * safe to say that this is an uncommon case, since buffers at the end of 5616 * the ARC lists have moved there due to inactivity. 5617 * 5618 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5619 * then the L2ARC simply misses copying some buffers. This serves as a 5620 * pressure valve to prevent heavy read workloads from both stalling the ARC 5621 * with waits and clogging the L2ARC with writes. This also helps prevent 5622 * the potential for the L2ARC to churn if it attempts to cache content too 5623 * quickly, such as during backups of the entire pool. 5624 * 5625 * 5. After system boot and before the ARC has filled main memory, there are 5626 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5627 * lists can remain mostly static. Instead of searching from tail of these 5628 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5629 * for eligible buffers, greatly increasing its chance of finding them. 5630 * 5631 * The L2ARC device write speed is also boosted during this time so that 5632 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5633 * there are no L2ARC reads, and no fear of degrading read performance 5634 * through increased writes. 5635 * 5636 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5637 * the vdev queue can aggregate them into larger and fewer writes. Each 5638 * device is written to in a rotor fashion, sweeping writes through 5639 * available space then repeating. 5640 * 5641 * 7. The L2ARC does not store dirty content. It never needs to flush 5642 * write buffers back to disk based storage. 5643 * 5644 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5645 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5646 * 5647 * The performance of the L2ARC can be tweaked by a number of tunables, which 5648 * may be necessary for different workloads: 5649 * 5650 * l2arc_write_max max write bytes per interval 5651 * l2arc_write_boost extra write bytes during device warmup 5652 * l2arc_noprefetch skip caching prefetched buffers 5653 * l2arc_headroom number of max device writes to precache 5654 * l2arc_headroom_boost when we find compressed buffers during ARC 5655 * scanning, we multiply headroom by this 5656 * percentage factor for the next scan cycle, 5657 * since more compressed buffers are likely to 5658 * be present 5659 * l2arc_feed_secs seconds between L2ARC writing 5660 * 5661 * Tunables may be removed or added as future performance improvements are 5662 * integrated, and also may become zpool properties. 5663 * 5664 * There are three key functions that control how the L2ARC warms up: 5665 * 5666 * l2arc_write_eligible() check if a buffer is eligible to cache 5667 * l2arc_write_size() calculate how much to write 5668 * l2arc_write_interval() calculate sleep delay between writes 5669 * 5670 * These three functions determine what to write, how much, and how quickly 5671 * to send writes. 5672 * 5673 * L2ARC persistency: 5674 * 5675 * When writing buffers to L2ARC, we periodically add some metadata to 5676 * make sure we can pick them up after reboot, thus dramatically reducing 5677 * the impact that any downtime has on the performance of storage systems 5678 * with large caches. 5679 * 5680 * The implementation works fairly simply by integrating the following two 5681 * modifications: 5682 * 5683 * *) Every now and then we mix in a piece of metadata (called a log block) 5684 * into the L2ARC write. This allows us to understand what's been written, 5685 * so that we can rebuild the arc_buf_hdr_t structures of the main ARC 5686 * buffers. The log block also includes a "2-back-reference" pointer to 5687 * he second-to-previous block, forming a back-linked list of blocks on 5688 * the L2ARC device. 5689 * 5690 * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device 5691 * for our header bookkeeping purposes. This contains a device header, 5692 * which contains our top-level reference structures. We update it each 5693 * time we write a new log block, so that we're able to locate it in the 5694 * L2ARC device. If this write results in an inconsistent device header 5695 * (e.g. due to power failure), we detect this by verifying the header's 5696 * checksum and simply drop the entries from L2ARC. 5697 * 5698 * Implementation diagram: 5699 * 5700 * +=== L2ARC device (not to scale) ======================================+ 5701 * | ___two newest log block pointers__.__________ | 5702 * | / \1 back \latest | 5703 * |.____/_. V V | 5704 * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---| 5705 * || hdr| ^ /^ /^ / / | 5706 * |+------+ ...--\-------/ \-----/--\------/ / | 5707 * | \--------------/ \--------------/ | 5708 * +======================================================================+ 5709 * 5710 * As can be seen on the diagram, rather than using a simple linked list, 5711 * we use a pair of linked lists with alternating elements. This is a 5712 * performance enhancement due to the fact that we only find out of the 5713 * address of the next log block access once the current block has been 5714 * completely read in. Obviously, this hurts performance, because we'd be 5715 * keeping the device's I/O queue at only a 1 operation deep, thus 5716 * incurring a large amount of I/O round-trip latency. Having two lists 5717 * allows us to "prefetch" two log blocks ahead of where we are currently 5718 * rebuilding L2ARC buffers. 5719 * 5720 * On-device data structures: 5721 * 5722 * L2ARC device header: l2arc_dev_hdr_phys_t 5723 * L2ARC log block: l2arc_log_blk_phys_t 5724 * 5725 * L2ARC reconstruction: 5726 * 5727 * When writing data, we simply write in the standard rotary fashion, 5728 * evicting buffers as we go and simply writing new data over them (writing 5729 * a new log block every now and then). This obviously means that once we 5730 * loop around the end of the device, we will start cutting into an already 5731 * committed log block (and its referenced data buffers), like so: 5732 * 5733 * current write head__ __old tail 5734 * \ / 5735 * V V 5736 * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |--> 5737 * ^ ^^^^^^^^^___________________________________ 5738 * | \ 5739 * <<nextwrite>> may overwrite this blk and/or its bufs --' 5740 * 5741 * When importing the pool, we detect this situation and use it to stop 5742 * our scanning process (see l2arc_rebuild). 5743 * 5744 * There is one significant caveat to consider when rebuilding ARC contents 5745 * from an L2ARC device: what about invalidated buffers? Given the above 5746 * construction, we cannot update blocks which we've already written to amend 5747 * them to remove buffers which were invalidated. Thus, during reconstruction, 5748 * we might be populating the cache with buffers for data that's not on the 5749 * main pool anymore, or may have been overwritten! 5750 * 5751 * As it turns out, this isn't a problem. Every arc_read request includes 5752 * both the DVA and, crucially, the birth TXG of the BP the caller is 5753 * looking for. So even if the cache were populated by completely rotten 5754 * blocks for data that had been long deleted and/or overwritten, we'll 5755 * never actually return bad data from the cache, since the DVA with the 5756 * birth TXG uniquely identify a block in space and time - once created, 5757 * a block is immutable on disk. The worst thing we have done is wasted 5758 * some time and memory at l2arc rebuild to reconstruct outdated ARC 5759 * entries that will get dropped from the l2arc as it is being updated 5760 * with new blocks. 5761 */ 5762 5763 static boolean_t 5764 l2arc_write_eligible(uint64_t spa_guid, uint64_t sync_txg, arc_buf_hdr_t *hdr) 5765 { 5766 /* 5767 * A buffer is *not* eligible for the L2ARC if it: 5768 * 1. belongs to a different spa. 5769 * 2. is already cached on the L2ARC. 5770 * 3. has an I/O in progress (it may be an incomplete read). 5771 * 4. is flagged not eligible (zfs property). 5772 * 5. is part of the syncing txg (and thus subject to change). 5773 */ 5774 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) || 5775 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr) || 5776 hdr->b_birth >= sync_txg) 5777 return (B_FALSE); 5778 5779 return (B_TRUE); 5780 } 5781 5782 static uint64_t 5783 l2arc_write_size(void) 5784 { 5785 uint64_t size; 5786 5787 /* 5788 * Make sure our globals have meaningful values in case the user 5789 * altered them. 5790 */ 5791 size = l2arc_write_max; 5792 if (size == 0) { 5793 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5794 "be greater than zero, resetting it to the default (%d)", 5795 L2ARC_WRITE_SIZE); 5796 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5797 } 5798 5799 if (arc_warm == B_FALSE) 5800 size += l2arc_write_boost; 5801 5802 return (size); 5803 5804 } 5805 5806 static clock_t 5807 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5808 { 5809 clock_t interval, next, now; 5810 5811 /* 5812 * If the ARC lists are busy, increase our write rate; if the 5813 * lists are stale, idle back. This is achieved by checking 5814 * how much we previously wrote - if it was more than half of 5815 * what we wanted, schedule the next write much sooner. 5816 */ 5817 if (l2arc_feed_again && wrote > (wanted / 2)) 5818 interval = (hz * l2arc_feed_min_ms) / 1000; 5819 else 5820 interval = hz * l2arc_feed_secs; 5821 5822 now = ddi_get_lbolt(); 5823 next = MAX(now, MIN(now + interval, began + interval)); 5824 5825 return (next); 5826 } 5827 5828 /* 5829 * Cycle through L2ARC devices. This is how L2ARC load balances. 5830 * If a device is returned, this also returns holding the spa config lock. 5831 */ 5832 static l2arc_dev_t * 5833 l2arc_dev_get_next(void) 5834 { 5835 l2arc_dev_t *first, *next = NULL; 5836 5837 /* 5838 * Lock out the removal of spas (spa_namespace_lock), then removal 5839 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5840 * both locks will be dropped and a spa config lock held instead. 5841 */ 5842 mutex_enter(&spa_namespace_lock); 5843 mutex_enter(&l2arc_dev_mtx); 5844 5845 /* if there are no vdevs, there is nothing to do */ 5846 if (l2arc_ndev == 0) 5847 goto out; 5848 5849 first = NULL; 5850 next = l2arc_dev_last; 5851 do { 5852 /* loop around the list looking for a non-faulted vdev */ 5853 if (next == NULL) { 5854 next = list_head(l2arc_dev_list); 5855 } else { 5856 next = list_next(l2arc_dev_list, next); 5857 if (next == NULL) 5858 next = list_head(l2arc_dev_list); 5859 } 5860 5861 /* if we have come back to the start, bail out */ 5862 if (first == NULL) 5863 first = next; 5864 else if (next == first) 5865 break; 5866 5867 } while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild); 5868 5869 /* if we were unable to find any usable vdevs, return NULL */ 5870 if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild) 5871 next = NULL; 5872 5873 l2arc_dev_last = next; 5874 5875 out: 5876 mutex_exit(&l2arc_dev_mtx); 5877 5878 /* 5879 * Grab the config lock to prevent the 'next' device from being 5880 * removed while we are writing to it. 5881 */ 5882 if (next != NULL) 5883 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5884 mutex_exit(&spa_namespace_lock); 5885 5886 return (next); 5887 } 5888 5889 /* 5890 * Free buffers that were tagged for destruction. 5891 */ 5892 static void 5893 l2arc_do_free_on_write() 5894 { 5895 list_t *buflist; 5896 l2arc_data_free_t *df, *df_prev; 5897 5898 mutex_enter(&l2arc_free_on_write_mtx); 5899 buflist = l2arc_free_on_write; 5900 5901 for (df = list_tail(buflist); df; df = df_prev) { 5902 df_prev = list_prev(buflist, df); 5903 ASSERT(df->l2df_data != NULL); 5904 ASSERT(df->l2df_func != NULL); 5905 df->l2df_func(df->l2df_data, df->l2df_size); 5906 list_remove(buflist, df); 5907 kmem_free(df, sizeof (l2arc_data_free_t)); 5908 } 5909 5910 mutex_exit(&l2arc_free_on_write_mtx); 5911 } 5912 5913 /* 5914 * A write to a cache device has completed. Update all headers to allow 5915 * reads from these buffers to begin. 5916 */ 5917 static void 5918 l2arc_write_done(zio_t *zio) 5919 { 5920 l2arc_write_callback_t *cb; 5921 l2arc_dev_t *dev; 5922 list_t *buflist; 5923 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5924 kmutex_t *hash_lock; 5925 int64_t bytes_dropped = 0; 5926 l2arc_log_blk_buf_t *lb_buf; 5927 5928 cb = zio->io_private; 5929 ASSERT(cb != NULL); 5930 dev = cb->l2wcb_dev; 5931 ASSERT(dev != NULL); 5932 head = cb->l2wcb_head; 5933 ASSERT(head != NULL); 5934 buflist = &dev->l2ad_buflist; 5935 ASSERT(buflist != NULL); 5936 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5937 l2arc_write_callback_t *, cb); 5938 5939 if (zio->io_error != 0) 5940 ARCSTAT_BUMP(arcstat_l2_writes_error); 5941 5942 /* 5943 * All writes completed, or an error was hit. 5944 */ 5945 top: 5946 mutex_enter(&dev->l2ad_mtx); 5947 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5948 hdr_prev = list_prev(buflist, hdr); 5949 5950 hash_lock = HDR_LOCK(hdr); 5951 5952 /* 5953 * We cannot use mutex_enter or else we can deadlock 5954 * with l2arc_write_buffers (due to swapping the order 5955 * the hash lock and l2ad_mtx are taken). 5956 */ 5957 if (!mutex_tryenter(hash_lock)) { 5958 /* 5959 * Missed the hash lock. We must retry so we 5960 * don't leave the ARC_FLAG_L2_WRITING bit set. 5961 */ 5962 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5963 5964 /* 5965 * We don't want to rescan the headers we've 5966 * already marked as having been written out, so 5967 * we reinsert the head node so we can pick up 5968 * where we left off. 5969 */ 5970 list_remove(buflist, head); 5971 list_insert_after(buflist, hdr, head); 5972 5973 mutex_exit(&dev->l2ad_mtx); 5974 5975 /* 5976 * We wait for the hash lock to become available 5977 * to try and prevent busy waiting, and increase 5978 * the chance we'll be able to acquire the lock 5979 * the next time around. 5980 */ 5981 mutex_enter(hash_lock); 5982 mutex_exit(hash_lock); 5983 goto top; 5984 } 5985 5986 /* 5987 * We could not have been moved into the arc_l2c_only 5988 * state while in-flight due to our ARC_FLAG_L2_WRITING 5989 * bit being set. Let's just ensure that's being enforced. 5990 */ 5991 ASSERT(HDR_HAS_L1HDR(hdr)); 5992 5993 /* 5994 * We may have allocated a buffer for L2ARC compression, 5995 * we must release it to avoid leaking this data. 5996 */ 5997 l2arc_release_cdata_buf(hdr); 5998 5999 if (zio->io_error != 0) { 6000 /* 6001 * Error - drop L2ARC entry. 6002 */ 6003 list_remove(buflist, hdr); 6004 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 6005 6006 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 6007 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 6008 6009 bytes_dropped += hdr->b_l2hdr.b_asize; 6010 (void) refcount_remove_many(&dev->l2ad_alloc, 6011 hdr->b_l2hdr.b_asize, hdr); 6012 } 6013 6014 /* 6015 * Allow ARC to begin reads and ghost list evictions to 6016 * this L2ARC entry. 6017 */ 6018 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 6019 6020 mutex_exit(hash_lock); 6021 } 6022 6023 atomic_inc_64(&l2arc_writes_done); 6024 list_remove(buflist, head); 6025 ASSERT(!HDR_HAS_L1HDR(head)); 6026 kmem_cache_free(hdr_l2only_cache, head); 6027 mutex_exit(&dev->l2ad_mtx); 6028 6029 ASSERT(dev->l2ad_vdev != NULL); 6030 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6031 6032 l2arc_do_free_on_write(); 6033 6034 while ((lb_buf = list_remove_tail(&cb->l2wcb_log_blk_buflist)) != NULL) 6035 kmem_free(lb_buf, sizeof (*lb_buf)); 6036 list_destroy(&cb->l2wcb_log_blk_buflist); 6037 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6038 } 6039 6040 /* 6041 * A read to a cache device completed. Validate buffer contents before 6042 * handing over to the regular ARC routines. 6043 */ 6044 static void 6045 l2arc_read_done(zio_t *zio) 6046 { 6047 l2arc_read_callback_t *cb; 6048 arc_buf_hdr_t *hdr; 6049 arc_buf_t *buf; 6050 kmutex_t *hash_lock; 6051 int equal; 6052 6053 ASSERT(zio->io_vd != NULL); 6054 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6055 6056 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6057 6058 cb = zio->io_private; 6059 ASSERT(cb != NULL); 6060 buf = cb->l2rcb_buf; 6061 ASSERT(buf != NULL); 6062 6063 hash_lock = HDR_LOCK(buf->b_hdr); 6064 mutex_enter(hash_lock); 6065 hdr = buf->b_hdr; 6066 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6067 6068 /* 6069 * If the buffer was compressed, decompress it first. 6070 */ 6071 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6072 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6073 ASSERT(zio->io_data != NULL); 6074 ASSERT3U(zio->io_size, ==, hdr->b_size); 6075 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 6076 6077 /* 6078 * Check this survived the L2ARC journey. 6079 */ 6080 equal = arc_cksum_equal(buf); 6081 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6082 mutex_exit(hash_lock); 6083 zio->io_private = buf; 6084 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6085 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6086 arc_read_done(zio); 6087 } else { 6088 mutex_exit(hash_lock); 6089 /* 6090 * Buffer didn't survive caching. Increment stats and 6091 * reissue to the original storage device. 6092 */ 6093 if (zio->io_error != 0) { 6094 ARCSTAT_BUMP(arcstat_l2_io_error); 6095 } else { 6096 zio->io_error = SET_ERROR(EIO); 6097 } 6098 if (!equal) 6099 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6100 6101 /* 6102 * If there's no waiter, issue an async i/o to the primary 6103 * storage now. If there *is* a waiter, the caller must 6104 * issue the i/o in a context where it's OK to block. 6105 */ 6106 if (zio->io_waiter == NULL) { 6107 zio_t *pio = zio_unique_parent(zio); 6108 6109 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6110 6111 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6112 buf->b_data, hdr->b_size, arc_read_done, buf, 6113 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6114 } 6115 } 6116 6117 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6118 } 6119 6120 /* 6121 * This is the list priority from which the L2ARC will search for pages to 6122 * cache. This is used within loops (0..3) to cycle through lists in the 6123 * desired order. This order can have a significant effect on cache 6124 * performance. 6125 * 6126 * Currently the metadata lists are hit first, MFU then MRU, followed by 6127 * the data lists. This function returns a locked list, and also returns 6128 * the lock pointer. 6129 */ 6130 static multilist_sublist_t * 6131 l2arc_sublist_lock(int list_num) 6132 { 6133 multilist_t *ml = NULL; 6134 unsigned int idx; 6135 6136 ASSERT(list_num >= 0 && list_num <= 3); 6137 6138 switch (list_num) { 6139 case 0: 6140 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6141 break; 6142 case 1: 6143 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6144 break; 6145 case 2: 6146 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6147 break; 6148 case 3: 6149 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6150 break; 6151 } 6152 6153 /* 6154 * Return a randomly-selected sublist. This is acceptable 6155 * because the caller feeds only a little bit of data for each 6156 * call (8MB). Subsequent calls will result in different 6157 * sublists being selected. 6158 */ 6159 idx = multilist_get_random_index(ml); 6160 return (multilist_sublist_lock(ml, idx)); 6161 } 6162 6163 /* 6164 * Calculates the maximum overhead of L2ARC metadata log blocks for a given 6165 * L2ARC write size. l2arc_evict and l2arc_write_buffers need to include this 6166 * overhead in processing to make sure there is enough headroom available 6167 * when writing buffers. 6168 */ 6169 static inline uint64_t 6170 l2arc_log_blk_overhead(uint64_t write_sz) 6171 { 6172 return ((write_sz / SPA_MINBLOCKSIZE / L2ARC_LOG_BLK_ENTRIES) + 1) * 6173 L2ARC_LOG_BLK_SIZE; 6174 } 6175 6176 /* 6177 * Evict buffers from the device write hand to the distance specified in 6178 * bytes. This distance may span populated buffers, it may span nothing. 6179 * This is clearing a region on the L2ARC device ready for writing. 6180 * If the 'all' boolean is set, every buffer is evicted. 6181 */ 6182 static void 6183 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6184 { 6185 list_t *buflist; 6186 arc_buf_hdr_t *hdr, *hdr_prev; 6187 kmutex_t *hash_lock; 6188 uint64_t taddr; 6189 6190 buflist = &dev->l2ad_buflist; 6191 6192 if (!all && dev->l2ad_first) { 6193 /* 6194 * This is the first sweep through the device. There is 6195 * nothing to evict. 6196 */ 6197 return; 6198 } 6199 6200 /* 6201 * We need to add in the worst case scenario of log block overhead. 6202 */ 6203 distance += l2arc_log_blk_overhead(distance); 6204 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6205 /* 6206 * When nearing the end of the device, evict to the end 6207 * before the device write hand jumps to the start. 6208 */ 6209 taddr = dev->l2ad_end; 6210 } else { 6211 taddr = dev->l2ad_hand + distance; 6212 } 6213 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6214 uint64_t, taddr, boolean_t, all); 6215 6216 top: 6217 mutex_enter(&dev->l2ad_mtx); 6218 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6219 hdr_prev = list_prev(buflist, hdr); 6220 6221 hash_lock = HDR_LOCK(hdr); 6222 6223 /* 6224 * We cannot use mutex_enter or else we can deadlock 6225 * with l2arc_write_buffers (due to swapping the order 6226 * the hash lock and l2ad_mtx are taken). 6227 */ 6228 if (!mutex_tryenter(hash_lock)) { 6229 /* 6230 * Missed the hash lock. Retry. 6231 */ 6232 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6233 mutex_exit(&dev->l2ad_mtx); 6234 mutex_enter(hash_lock); 6235 mutex_exit(hash_lock); 6236 goto top; 6237 } 6238 6239 if (HDR_L2_WRITE_HEAD(hdr)) { 6240 /* 6241 * We hit a write head node. Leave it for 6242 * l2arc_write_done(). 6243 */ 6244 list_remove(buflist, hdr); 6245 mutex_exit(hash_lock); 6246 continue; 6247 } 6248 6249 if (!all && HDR_HAS_L2HDR(hdr) && 6250 (hdr->b_l2hdr.b_daddr > taddr || 6251 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6252 /* 6253 * We've evicted to the target address, 6254 * or the end of the device. 6255 */ 6256 mutex_exit(hash_lock); 6257 break; 6258 } 6259 6260 ASSERT(HDR_HAS_L2HDR(hdr)); 6261 if (!HDR_HAS_L1HDR(hdr)) { 6262 ASSERT(!HDR_L2_READING(hdr)); 6263 /* 6264 * This doesn't exist in the ARC. Destroy. 6265 * arc_hdr_destroy() will call list_remove() 6266 * and decrement arcstat_l2_size. 6267 */ 6268 arc_change_state(arc_anon, hdr, hash_lock); 6269 arc_hdr_destroy(hdr); 6270 } else { 6271 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6272 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6273 /* 6274 * Invalidate issued or about to be issued 6275 * reads, since we may be about to write 6276 * over this location. 6277 */ 6278 if (HDR_L2_READING(hdr)) { 6279 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6280 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6281 } 6282 6283 /* Ensure this header has finished being written */ 6284 ASSERT(!HDR_L2_WRITING(hdr)); 6285 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6286 6287 arc_hdr_l2hdr_destroy(hdr); 6288 } 6289 mutex_exit(hash_lock); 6290 } 6291 mutex_exit(&dev->l2ad_mtx); 6292 } 6293 6294 /* 6295 * Find and write ARC buffers to the L2ARC device. 6296 * 6297 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6298 * for reading until they have completed writing. 6299 * The headroom_boost is an in-out parameter used to maintain headroom boost 6300 * state between calls to this function. 6301 * 6302 * Returns the number of bytes actually written (which may be smaller than 6303 * the delta by which the device hand has changed due to alignment). 6304 */ 6305 static uint64_t 6306 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6307 boolean_t *headroom_boost) 6308 { 6309 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6310 uint64_t headroom, buf_compress_minsz; 6311 /* 6312 * We must carefully track the space we deal with here: 6313 * - write_size: sum of the size of all buffers to be written 6314 * without compression or inter-buffer alignment applied. 6315 * This size is added to arcstat_l2_size, because subsequent 6316 * eviction of buffers decrements this kstat by only the 6317 * buffer's b_size (which doesn't take alignment into account). 6318 * - write_asize: sum of the size of all buffers to be written 6319 * without compression, but WITH inter-buffer alignment applied. 6320 * This size is used to estimate the maximum number of bytes 6321 * we could take up on the device and is thus used to gauge how 6322 * close we are to hitting target_sz. 6323 * - write_comp_size: sum of the size of all buffers to be written 6324 * WITH compression but WITHOUT inter-buffer alignment applied. 6325 * Similarly to write_size, this is used with the 6326 * arcstat_l2_asize kstat. It is also the sum of the actual 6327 * number bytes sent to zio_write_phys. 6328 * - write_comp_asize: sum of the size of all buffers to be written 6329 * WITH compression and inter-buffer alignment applied. 6330 * This is the actual number of bytes taken up on the device 6331 * and so this is the actual amount by which we adjusted the 6332 * l2ad_hand and is also used in vdev_space_update(). 6333 */ 6334 uint64_t write_size, write_asize; /* uncompressed */ 6335 uint64_t write_comp_size, write_comp_asize; /* compressed */ 6336 void *buf_data; 6337 boolean_t full; 6338 l2arc_write_callback_t *cb; 6339 zio_t *pio, *wzio; 6340 uint64_t guid = spa_load_guid(spa); 6341 uint64_t sync_txg = spa_syncing_txg(spa); 6342 const boolean_t do_headroom_boost = *headroom_boost; 6343 boolean_t dev_hdr_update = B_FALSE; 6344 6345 ASSERT(dev->l2ad_vdev != NULL); 6346 6347 /* Lower the flag now, we might want to raise it again later. */ 6348 *headroom_boost = B_FALSE; 6349 6350 pio = NULL; 6351 cb = NULL; 6352 write_size = write_asize = 0; 6353 write_comp_size = write_comp_asize = 0; 6354 full = B_FALSE; 6355 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6356 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6357 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6358 6359 /* 6360 * We will want to try to compress buffers that are at least 2x the 6361 * device sector size. 6362 */ 6363 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6364 6365 /* 6366 * Copy buffers for L2ARC writing. 6367 */ 6368 for (int try = 0; try <= 3; try++) { 6369 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6370 uint64_t passed_sz = 0; 6371 6372 /* 6373 * L2ARC fast warmup. 6374 * 6375 * Until the ARC is warm and starts to evict, read from the 6376 * head of the ARC lists rather than the tail. 6377 */ 6378 if (arc_warm == B_FALSE) 6379 hdr = multilist_sublist_head(mls); 6380 else 6381 hdr = multilist_sublist_tail(mls); 6382 6383 headroom = target_sz * l2arc_headroom; 6384 if (do_headroom_boost) 6385 headroom = (headroom * l2arc_headroom_boost) / 100; 6386 6387 for (; hdr; hdr = hdr_prev) { 6388 kmutex_t *hash_lock; 6389 uint64_t buf_size, buf_asize; 6390 6391 if (arc_warm == B_FALSE) 6392 hdr_prev = multilist_sublist_next(mls, hdr); 6393 else 6394 hdr_prev = multilist_sublist_prev(mls, hdr); 6395 6396 hash_lock = HDR_LOCK(hdr); 6397 if (!mutex_tryenter(hash_lock)) { 6398 /* 6399 * Skip this buffer rather than waiting. 6400 */ 6401 continue; 6402 } 6403 6404 /* 6405 * When examining whether we've met our write target, 6406 * we use psize_to_asize to account for inter-block 6407 * gaps due to different physical sector size on 6408 * L2ARC device. 6409 */ 6410 buf_size = hdr->b_size; 6411 buf_asize = vdev_psize_to_asize(dev->l2ad_vdev, 6412 hdr->b_size); 6413 passed_sz += buf_size; 6414 if (passed_sz > headroom) { 6415 /* 6416 * Searched too far. 6417 */ 6418 mutex_exit(hash_lock); 6419 break; 6420 } 6421 6422 if (!l2arc_write_eligible(guid, sync_txg, hdr)) { 6423 mutex_exit(hash_lock); 6424 continue; 6425 } 6426 6427 if (write_asize + buf_asize > target_sz) { 6428 full = B_TRUE; 6429 mutex_exit(hash_lock); 6430 break; 6431 } 6432 6433 if (pio == NULL) { 6434 /* 6435 * Insert a dummy header on the buflist so 6436 * l2arc_write_done() can find where the 6437 * write buffers begin without searching. 6438 */ 6439 mutex_enter(&dev->l2ad_mtx); 6440 list_insert_head(&dev->l2ad_buflist, head); 6441 mutex_exit(&dev->l2ad_mtx); 6442 6443 cb = kmem_zalloc( 6444 sizeof (l2arc_write_callback_t), KM_SLEEP); 6445 cb->l2wcb_dev = dev; 6446 cb->l2wcb_head = head; 6447 list_create(&cb->l2wcb_log_blk_buflist, 6448 sizeof (l2arc_log_blk_buf_t), 6449 offsetof(l2arc_log_blk_buf_t, lbb_node)); 6450 pio = zio_root(spa, l2arc_write_done, cb, 6451 ZIO_FLAG_CANFAIL); 6452 } 6453 6454 /* 6455 * Create and add a new L2ARC header. 6456 */ 6457 hdr->b_l2hdr.b_dev = dev; 6458 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6459 /* 6460 * Temporarily stash the data buffer in b_tmp_cdata. 6461 * The subsequent write step will pick it up from 6462 * there. This is because can't access b_l1hdr.b_buf 6463 * without holding the hash_lock, which we in turn 6464 * can't access without holding the ARC list locks 6465 * (which we want to avoid during compression/writing). 6466 */ 6467 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6468 hdr->b_l2hdr.b_asize = hdr->b_size; 6469 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6470 6471 /* 6472 * Explicitly set the b_daddr field to a known 6473 * value which means "invalid address". This 6474 * enables us to differentiate which stage of 6475 * l2arc_write_buffers() the particular header 6476 * is in (e.g. this loop, or the one below). 6477 * ARC_FLAG_L2_WRITING is not enough to make 6478 * this distinction, and we need to know in 6479 * order to do proper l2arc vdev accounting in 6480 * arc_release() and arc_hdr_destroy(). 6481 * 6482 * Note, we can't use a new flag to distinguish 6483 * the two stages because we don't hold the 6484 * header's hash_lock below, in the second stage 6485 * of this function. Thus, we can't simply 6486 * change the b_flags field to denote that the 6487 * IO has been sent. We can change the b_daddr 6488 * field of the L2 portion, though, since we'll 6489 * be holding the l2ad_mtx; which is why we're 6490 * using it to denote the header's state change. 6491 */ 6492 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6493 6494 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6495 6496 mutex_enter(&dev->l2ad_mtx); 6497 list_insert_head(&dev->l2ad_buflist, hdr); 6498 mutex_exit(&dev->l2ad_mtx); 6499 6500 /* 6501 * Compute and store the buffer cksum before 6502 * writing. On debug the cksum is verified first. 6503 */ 6504 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6505 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6506 6507 mutex_exit(hash_lock); 6508 6509 write_size += buf_size; 6510 write_asize += buf_asize; 6511 } 6512 6513 multilist_sublist_unlock(mls); 6514 6515 if (full == B_TRUE) 6516 break; 6517 } 6518 6519 /* No buffers selected for writing? */ 6520 if (pio == NULL) { 6521 ASSERT0(write_size); 6522 ASSERT(!HDR_HAS_L1HDR(head)); 6523 kmem_cache_free(hdr_l2only_cache, head); 6524 return (0); 6525 } 6526 6527 mutex_enter(&dev->l2ad_mtx); 6528 6529 /* 6530 * Now start writing the buffers. We're starting at the write head 6531 * and work backwards, retracing the course of the buffer selector 6532 * loop above. 6533 */ 6534 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6535 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6536 uint64_t buf_comp_size; 6537 6538 /* 6539 * We rely on the L1 portion of the header below, so 6540 * it's invalid for this header to have been evicted out 6541 * of the ghost cache, prior to being written out. The 6542 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6543 */ 6544 ASSERT(HDR_HAS_L1HDR(hdr)); 6545 6546 /* 6547 * We shouldn't need to lock the buffer here, since we flagged 6548 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6549 * take care to only access its L2 cache parameters. In 6550 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6551 * ARC eviction. 6552 */ 6553 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6554 6555 if ((HDR_L2COMPRESS(hdr)) && 6556 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 6557 if (l2arc_compress_buf(hdr)) { 6558 /* 6559 * If compression succeeded, enable headroom 6560 * boost on the next scan cycle. 6561 */ 6562 *headroom_boost = B_TRUE; 6563 } 6564 } 6565 6566 /* 6567 * Pick up the buffer data we had previously stashed away 6568 * (and now potentially also compressed). 6569 */ 6570 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6571 buf_comp_size = hdr->b_l2hdr.b_asize; 6572 6573 /* 6574 * We need to do this regardless if buf_comp_size is zero or 6575 * not, otherwise, when this l2hdr is evicted we'll 6576 * remove a reference that was never added. 6577 */ 6578 (void) refcount_add_many(&dev->l2ad_alloc, buf_comp_size, hdr); 6579 6580 /* Compression may have squashed the buffer to zero length. */ 6581 if (buf_comp_size != 0) { 6582 uint64_t buf_comp_asize; 6583 6584 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6585 dev->l2ad_hand, buf_comp_size, buf_data, 6586 ZIO_CHECKSUM_OFF, NULL, NULL, 6587 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, 6588 B_FALSE); 6589 6590 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6591 zio_t *, wzio); 6592 (void) zio_nowait(wzio); 6593 6594 write_comp_size += buf_comp_size; 6595 /* 6596 * Keep the clock hand suitably device-aligned. 6597 */ 6598 buf_comp_asize = vdev_psize_to_asize(dev->l2ad_vdev, 6599 buf_comp_size); 6600 write_comp_asize += buf_comp_asize; 6601 dev->l2ad_hand += buf_comp_asize; 6602 } 6603 6604 /* 6605 * Append buf info to current log and commit if full. 6606 * arcstat_l2_{size,asize} kstats are updated internally. 6607 */ 6608 if (l2arc_log_blk_insert(dev, hdr)) { 6609 l2arc_log_blk_commit(dev, pio, cb); 6610 dev_hdr_update = B_TRUE; 6611 } 6612 } 6613 6614 mutex_exit(&dev->l2ad_mtx); 6615 6616 /* 6617 * If we wrote any logs as part of this write, update dev hdr 6618 * to point to it. 6619 */ 6620 if (dev_hdr_update) 6621 l2arc_dev_hdr_update(dev, pio); 6622 6623 VERIFY3U(write_asize, <=, target_sz); 6624 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6625 ARCSTAT_INCR(arcstat_l2_write_bytes, write_comp_size); 6626 ARCSTAT_INCR(arcstat_l2_size, write_size); 6627 ARCSTAT_INCR(arcstat_l2_asize, write_comp_size); 6628 vdev_space_update(dev->l2ad_vdev, write_comp_asize, 0, 0); 6629 6630 /* 6631 * Bump device hand to the device start if it is approaching the end. 6632 * l2arc_evict() will already have evicted ahead for this case. 6633 */ 6634 if (dev->l2ad_hand + target_sz + l2arc_log_blk_overhead(target_sz) >= 6635 dev->l2ad_end) { 6636 dev->l2ad_hand = dev->l2ad_start; 6637 dev->l2ad_first = B_FALSE; 6638 } 6639 6640 dev->l2ad_writing = B_TRUE; 6641 (void) zio_wait(pio); 6642 dev->l2ad_writing = B_FALSE; 6643 6644 return (write_comp_size); 6645 } 6646 6647 /* 6648 * Compresses an L2ARC buffer. 6649 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6650 * size in l2hdr->b_asize. This routine tries to compress the data and 6651 * depending on the compression result there are three possible outcomes: 6652 * *) The buffer was incompressible. The original l2hdr contents were left 6653 * untouched and are ready for writing to an L2 device. 6654 * *) The buffer was all-zeros, so there is no need to write it to an L2 6655 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6656 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6657 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6658 * data buffer which holds the compressed data to be written, and b_asize 6659 * tells us how much data there is. b_compress is set to the appropriate 6660 * compression algorithm. Once writing is done, invoke 6661 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6662 * 6663 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6664 * buffer was incompressible). 6665 */ 6666 static boolean_t 6667 l2arc_compress_buf(arc_buf_hdr_t *hdr) 6668 { 6669 void *cdata; 6670 size_t csize, len, rounded; 6671 ASSERT(HDR_HAS_L2HDR(hdr)); 6672 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6673 6674 ASSERT(HDR_HAS_L1HDR(hdr)); 6675 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF); 6676 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6677 6678 len = l2hdr->b_asize; 6679 cdata = zio_data_buf_alloc(len); 6680 ASSERT3P(cdata, !=, NULL); 6681 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6682 cdata, l2hdr->b_asize); 6683 6684 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE); 6685 if (rounded > csize) { 6686 bzero((char *)cdata + csize, rounded - csize); 6687 csize = rounded; 6688 } 6689 6690 if (csize == 0) { 6691 /* zero block, indicate that there's nothing to write */ 6692 zio_data_buf_free(cdata, len); 6693 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6694 l2hdr->b_asize = 0; 6695 hdr->b_l1hdr.b_tmp_cdata = NULL; 6696 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6697 return (B_TRUE); 6698 } else if (csize > 0 && csize < len) { 6699 /* 6700 * Compression succeeded, we'll keep the cdata around for 6701 * writing and release it afterwards. 6702 */ 6703 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6704 l2hdr->b_asize = csize; 6705 hdr->b_l1hdr.b_tmp_cdata = cdata; 6706 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6707 return (B_TRUE); 6708 } else { 6709 /* 6710 * Compression failed, release the compressed buffer. 6711 * l2hdr will be left unmodified. 6712 */ 6713 zio_data_buf_free(cdata, len); 6714 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6715 return (B_FALSE); 6716 } 6717 } 6718 6719 /* 6720 * Decompresses a zio read back from an l2arc device. On success, the 6721 * underlying zio's io_data buffer is overwritten by the uncompressed 6722 * version. On decompression error (corrupt compressed stream), the 6723 * zio->io_error value is set to signal an I/O error. 6724 * 6725 * Please note that the compressed data stream is not checksummed, so 6726 * if the underlying device is experiencing data corruption, we may feed 6727 * corrupt data to the decompressor, so the decompressor needs to be 6728 * able to handle this situation (LZ4 does). 6729 */ 6730 static void 6731 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6732 { 6733 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6734 6735 if (zio->io_error != 0) { 6736 /* 6737 * An io error has occured, just restore the original io 6738 * size in preparation for a main pool read. 6739 */ 6740 zio->io_orig_size = zio->io_size = hdr->b_size; 6741 return; 6742 } 6743 6744 if (c == ZIO_COMPRESS_EMPTY) { 6745 /* 6746 * An empty buffer results in a null zio, which means we 6747 * need to fill its io_data after we're done restoring the 6748 * buffer's contents. 6749 */ 6750 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6751 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6752 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6753 } else { 6754 ASSERT(zio->io_data != NULL); 6755 /* 6756 * We copy the compressed data from the start of the arc buffer 6757 * (the zio_read will have pulled in only what we need, the 6758 * rest is garbage which we will overwrite at decompression) 6759 * and then decompress back to the ARC data buffer. This way we 6760 * can minimize copying by simply decompressing back over the 6761 * original compressed data (rather than decompressing to an 6762 * aux buffer and then copying back the uncompressed buffer, 6763 * which is likely to be much larger). 6764 */ 6765 uint64_t csize; 6766 void *cdata; 6767 6768 csize = zio->io_size; 6769 cdata = zio_data_buf_alloc(csize); 6770 bcopy(zio->io_data, cdata, csize); 6771 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6772 hdr->b_size) != 0) 6773 zio->io_error = EIO; 6774 zio_data_buf_free(cdata, csize); 6775 } 6776 6777 /* Restore the expected uncompressed IO size. */ 6778 zio->io_orig_size = zio->io_size = hdr->b_size; 6779 } 6780 6781 /* 6782 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6783 * This buffer serves as a temporary holder of compressed data while 6784 * the buffer entry is being written to an l2arc device. Once that is 6785 * done, we can dispose of it. 6786 */ 6787 static void 6788 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6789 { 6790 ASSERT(HDR_HAS_L2HDR(hdr)); 6791 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6792 6793 ASSERT(HDR_HAS_L1HDR(hdr)); 6794 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6795 6796 if (comp == ZIO_COMPRESS_OFF) { 6797 /* 6798 * In this case, b_tmp_cdata points to the same buffer 6799 * as the arc_buf_t's b_data field. We don't want to 6800 * free it, since the arc_buf_t will handle that. 6801 */ 6802 hdr->b_l1hdr.b_tmp_cdata = NULL; 6803 } else if (comp == ZIO_COMPRESS_EMPTY) { 6804 /* 6805 * In this case, b_tmp_cdata was compressed to an empty 6806 * buffer, thus there's nothing to free and b_tmp_cdata 6807 * should have been set to NULL in l2arc_write_buffers(). 6808 */ 6809 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6810 } else { 6811 /* 6812 * If the data was compressed, then we've allocated a 6813 * temporary buffer for it, so now we need to release it. 6814 */ 6815 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6816 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6817 hdr->b_size); 6818 hdr->b_l1hdr.b_tmp_cdata = NULL; 6819 } 6820 6821 } 6822 6823 /* 6824 * This thread feeds the L2ARC at regular intervals. This is the beating 6825 * heart of the L2ARC. 6826 */ 6827 static void 6828 l2arc_feed_thread(void) 6829 { 6830 callb_cpr_t cpr; 6831 l2arc_dev_t *dev; 6832 spa_t *spa; 6833 uint64_t size, wrote; 6834 clock_t begin, next = ddi_get_lbolt(); 6835 boolean_t headroom_boost = B_FALSE; 6836 6837 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6838 6839 mutex_enter(&l2arc_feed_thr_lock); 6840 6841 while (l2arc_thread_exit == 0) { 6842 CALLB_CPR_SAFE_BEGIN(&cpr); 6843 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6844 next); 6845 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6846 next = ddi_get_lbolt() + hz; 6847 6848 /* 6849 * Quick check for L2ARC devices. 6850 */ 6851 mutex_enter(&l2arc_dev_mtx); 6852 if (l2arc_ndev == 0) { 6853 mutex_exit(&l2arc_dev_mtx); 6854 continue; 6855 } 6856 mutex_exit(&l2arc_dev_mtx); 6857 begin = ddi_get_lbolt(); 6858 6859 /* 6860 * This selects the next l2arc device to write to, and in 6861 * doing so the next spa to feed from: dev->l2ad_spa. This 6862 * will return NULL if there are now no l2arc devices or if 6863 * they are all faulted. 6864 * 6865 * If a device is returned, its spa's config lock is also 6866 * held to prevent device removal. l2arc_dev_get_next() 6867 * will grab and release l2arc_dev_mtx. 6868 */ 6869 if ((dev = l2arc_dev_get_next()) == NULL) 6870 continue; 6871 6872 spa = dev->l2ad_spa; 6873 ASSERT(spa != NULL); 6874 6875 /* 6876 * If the pool is read-only then force the feed thread to 6877 * sleep a little longer. 6878 */ 6879 if (!spa_writeable(spa)) { 6880 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6881 spa_config_exit(spa, SCL_L2ARC, dev); 6882 continue; 6883 } 6884 6885 /* 6886 * Avoid contributing to memory pressure. 6887 */ 6888 if (arc_reclaim_needed()) { 6889 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6890 spa_config_exit(spa, SCL_L2ARC, dev); 6891 continue; 6892 } 6893 6894 ARCSTAT_BUMP(arcstat_l2_feeds); 6895 6896 size = l2arc_write_size(); 6897 6898 /* 6899 * Evict L2ARC buffers that will be overwritten. 6900 */ 6901 l2arc_evict(dev, size, B_FALSE); 6902 6903 /* 6904 * Write ARC buffers. 6905 */ 6906 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6907 6908 /* 6909 * Calculate interval between writes. 6910 */ 6911 next = l2arc_write_interval(begin, size, wrote); 6912 spa_config_exit(spa, SCL_L2ARC, dev); 6913 } 6914 6915 l2arc_thread_exit = 0; 6916 cv_broadcast(&l2arc_feed_thr_cv); 6917 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6918 thread_exit(); 6919 } 6920 6921 boolean_t 6922 l2arc_vdev_present(vdev_t *vd) 6923 { 6924 return (l2arc_vdev_get(vd) != NULL); 6925 } 6926 6927 /* 6928 * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if 6929 * the vdev_t isn't an L2ARC device. 6930 */ 6931 static l2arc_dev_t * 6932 l2arc_vdev_get(vdev_t *vd) 6933 { 6934 l2arc_dev_t *dev; 6935 boolean_t held = MUTEX_HELD(&l2arc_dev_mtx); 6936 6937 if (!held) 6938 mutex_enter(&l2arc_dev_mtx); 6939 for (dev = list_head(l2arc_dev_list); dev != NULL; 6940 dev = list_next(l2arc_dev_list, dev)) { 6941 if (dev->l2ad_vdev == vd) 6942 break; 6943 } 6944 if (!held) 6945 mutex_exit(&l2arc_dev_mtx); 6946 6947 return (dev); 6948 } 6949 6950 /* 6951 * Add a vdev for use by the L2ARC. By this point the spa has already 6952 * validated the vdev and opened it. The `rebuild' flag indicates whether 6953 * we should attempt an L2ARC persistency rebuild. 6954 */ 6955 void 6956 l2arc_add_vdev(spa_t *spa, vdev_t *vd, boolean_t rebuild) 6957 { 6958 l2arc_dev_t *adddev; 6959 6960 ASSERT(!l2arc_vdev_present(vd)); 6961 6962 /* 6963 * Create a new l2arc device entry. 6964 */ 6965 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6966 adddev->l2ad_spa = spa; 6967 adddev->l2ad_vdev = vd; 6968 /* leave extra size for an l2arc device header */ 6969 adddev->l2ad_dev_hdr_asize = MAX(sizeof (*adddev->l2ad_dev_hdr), 6970 1 << vd->vdev_ashift); 6971 adddev->l2ad_start = VDEV_LABEL_START_SIZE + adddev->l2ad_dev_hdr_asize; 6972 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6973 ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end); 6974 adddev->l2ad_hand = adddev->l2ad_start; 6975 adddev->l2ad_first = B_TRUE; 6976 adddev->l2ad_writing = B_FALSE; 6977 adddev->l2ad_dev_hdr = kmem_zalloc(adddev->l2ad_dev_hdr_asize, 6978 KM_SLEEP); 6979 6980 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6981 /* 6982 * This is a list of all ARC buffers that are still valid on the 6983 * device. 6984 */ 6985 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6986 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6987 6988 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6989 refcount_create(&adddev->l2ad_alloc); 6990 6991 /* 6992 * Add device to global list 6993 */ 6994 mutex_enter(&l2arc_dev_mtx); 6995 list_insert_head(l2arc_dev_list, adddev); 6996 atomic_inc_64(&l2arc_ndev); 6997 if (rebuild && l2arc_rebuild_enabled && 6998 adddev->l2ad_end - adddev->l2ad_start > L2ARC_PERSIST_MIN_SIZE) { 6999 /* 7000 * Just mark the device as pending for a rebuild. We won't 7001 * be starting a rebuild in line here as it would block pool 7002 * import. Instead spa_load_impl will hand that off to an 7003 * async task which will call l2arc_spa_rebuild_start. 7004 */ 7005 adddev->l2ad_rebuild = B_TRUE; 7006 } 7007 mutex_exit(&l2arc_dev_mtx); 7008 } 7009 7010 /* 7011 * Remove a vdev from the L2ARC. 7012 */ 7013 void 7014 l2arc_remove_vdev(vdev_t *vd) 7015 { 7016 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7017 7018 /* 7019 * Find the device by vdev 7020 */ 7021 mutex_enter(&l2arc_dev_mtx); 7022 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7023 nextdev = list_next(l2arc_dev_list, dev); 7024 if (vd == dev->l2ad_vdev) { 7025 remdev = dev; 7026 break; 7027 } 7028 } 7029 ASSERT(remdev != NULL); 7030 7031 /* 7032 * Cancel any ongoing or scheduled rebuild (race protection with 7033 * l2arc_spa_rebuild_start provided via l2arc_dev_mtx). 7034 */ 7035 remdev->l2ad_rebuild_cancel = B_TRUE; 7036 if (remdev->l2ad_rebuild_did != 0) { 7037 /* 7038 * N.B. it should be safe to thread_join with the rebuild 7039 * thread while holding l2arc_dev_mtx because it is not 7040 * accessed from anywhere in the l2arc rebuild code below 7041 * (except for l2arc_spa_rebuild_start, which is ok). 7042 */ 7043 thread_join(remdev->l2ad_rebuild_did); 7044 } 7045 7046 /* 7047 * Remove device from global list 7048 */ 7049 list_remove(l2arc_dev_list, remdev); 7050 l2arc_dev_last = NULL; /* may have been invalidated */ 7051 atomic_dec_64(&l2arc_ndev); 7052 mutex_exit(&l2arc_dev_mtx); 7053 7054 /* 7055 * Clear all buflists and ARC references. L2ARC device flush. 7056 */ 7057 l2arc_evict(remdev, 0, B_TRUE); 7058 list_destroy(&remdev->l2ad_buflist); 7059 mutex_destroy(&remdev->l2ad_mtx); 7060 refcount_destroy(&remdev->l2ad_alloc); 7061 kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize); 7062 kmem_free(remdev, sizeof (l2arc_dev_t)); 7063 } 7064 7065 void 7066 l2arc_init(void) 7067 { 7068 l2arc_thread_exit = 0; 7069 l2arc_ndev = 0; 7070 l2arc_writes_sent = 0; 7071 l2arc_writes_done = 0; 7072 7073 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7074 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7075 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7076 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7077 7078 l2arc_dev_list = &L2ARC_dev_list; 7079 l2arc_free_on_write = &L2ARC_free_on_write; 7080 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7081 offsetof(l2arc_dev_t, l2ad_node)); 7082 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7083 offsetof(l2arc_data_free_t, l2df_list_node)); 7084 } 7085 7086 void 7087 l2arc_fini(void) 7088 { 7089 /* 7090 * This is called from dmu_fini(), which is called from spa_fini(); 7091 * Because of this, we can assume that all l2arc devices have 7092 * already been removed when the pools themselves were removed. 7093 */ 7094 7095 l2arc_do_free_on_write(); 7096 7097 mutex_destroy(&l2arc_feed_thr_lock); 7098 cv_destroy(&l2arc_feed_thr_cv); 7099 mutex_destroy(&l2arc_dev_mtx); 7100 mutex_destroy(&l2arc_free_on_write_mtx); 7101 7102 list_destroy(l2arc_dev_list); 7103 list_destroy(l2arc_free_on_write); 7104 } 7105 7106 void 7107 l2arc_start(void) 7108 { 7109 if (!(spa_mode_global & FWRITE)) 7110 return; 7111 7112 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7113 TS_RUN, minclsyspri); 7114 } 7115 7116 void 7117 l2arc_stop(void) 7118 { 7119 if (!(spa_mode_global & FWRITE)) 7120 return; 7121 7122 mutex_enter(&l2arc_feed_thr_lock); 7123 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7124 l2arc_thread_exit = 1; 7125 while (l2arc_thread_exit != 0) 7126 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7127 mutex_exit(&l2arc_feed_thr_lock); 7128 } 7129 7130 /* 7131 * Punches out rebuild threads for the L2ARC devices in a spa. This should 7132 * be called after pool import from the spa async thread, since starting 7133 * these threads directly from spa_import() will make them part of the 7134 * "zpool import" context and delay process exit (and thus pool import). 7135 */ 7136 void 7137 l2arc_spa_rebuild_start(spa_t *spa) 7138 { 7139 /* 7140 * Locate the spa's l2arc devices and kick off rebuild threads. 7141 */ 7142 mutex_enter(&l2arc_dev_mtx); 7143 for (int i = 0; i < spa->spa_l2cache.sav_count; i++) { 7144 l2arc_dev_t *dev = 7145 l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]); 7146 ASSERT(dev != NULL); 7147 if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) { 7148 VERIFY3U(dev->l2ad_rebuild_did, ==, 0); 7149 #ifdef _KERNEL 7150 dev->l2ad_rebuild_did = thread_create(NULL, 0, 7151 l2arc_dev_rebuild_start, dev, 0, &p0, TS_RUN, 7152 minclsyspri)->t_did; 7153 #endif 7154 } 7155 } 7156 mutex_exit(&l2arc_dev_mtx); 7157 } 7158 7159 /* 7160 * Main entry point for L2ARC rebuilding. 7161 */ 7162 static void 7163 l2arc_dev_rebuild_start(l2arc_dev_t *dev) 7164 { 7165 if (!dev->l2ad_rebuild_cancel) { 7166 VERIFY(dev->l2ad_rebuild); 7167 (void) l2arc_rebuild(dev); 7168 dev->l2ad_rebuild = B_FALSE; 7169 } 7170 } 7171 7172 /* 7173 * This function implements the actual L2ARC metadata rebuild. It: 7174 * 7175 * 1) reads the device's header 7176 * 2) if a good device header is found, starts reading the log block chain 7177 * 3) restores each block's contents to memory (reconstructing arc_buf_hdr_t's) 7178 * 7179 * Operation stops under any of the following conditions: 7180 * 7181 * 1) We reach the end of the log blk chain (the back-reference in the blk is 7182 * invalid or loops over our starting point). 7183 * 2) We encounter *any* error condition (cksum errors, io errors, looped 7184 * blocks, etc.). 7185 */ 7186 static int 7187 l2arc_rebuild(l2arc_dev_t *dev) 7188 { 7189 vdev_t *vd = dev->l2ad_vdev; 7190 spa_t *spa = vd->vdev_spa; 7191 int err; 7192 l2arc_log_blk_phys_t *this_lb, *next_lb; 7193 uint8_t *this_lb_buf, *next_lb_buf; 7194 zio_t *this_io = NULL, *next_io = NULL; 7195 l2arc_log_blkptr_t lb_ptrs[2]; 7196 boolean_t first_pass, lock_held; 7197 uint64_t load_guid; 7198 7199 this_lb = kmem_zalloc(sizeof (*this_lb), KM_SLEEP); 7200 next_lb = kmem_zalloc(sizeof (*next_lb), KM_SLEEP); 7201 this_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP); 7202 next_lb_buf = kmem_zalloc(sizeof (l2arc_log_blk_phys_t), KM_SLEEP); 7203 7204 /* 7205 * We prevent device removal while issuing reads to the device, 7206 * then during the rebuilding phases we drop this lock again so 7207 * that a spa_unload or device remove can be initiated - this is 7208 * safe, because the spa will signal us to stop before removing 7209 * our device and wait for us to stop. 7210 */ 7211 spa_config_enter(spa, SCL_L2ARC, vd, RW_READER); 7212 lock_held = B_TRUE; 7213 7214 load_guid = spa_load_guid(dev->l2ad_vdev->vdev_spa); 7215 /* 7216 * Device header processing phase. 7217 */ 7218 if ((err = l2arc_dev_hdr_read(dev)) != 0) { 7219 /* device header corrupted, start a new one */ 7220 bzero(dev->l2ad_dev_hdr, dev->l2ad_dev_hdr_asize); 7221 goto out; 7222 } 7223 7224 /* Retrieve the persistent L2ARC device state */ 7225 dev->l2ad_hand = vdev_psize_to_asize(dev->l2ad_vdev, 7226 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr + 7227 LBP_GET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0])); 7228 dev->l2ad_first = !!(dev->l2ad_dev_hdr->dh_flags & 7229 L2ARC_DEV_HDR_EVICT_FIRST); 7230 7231 /* Prepare the rebuild processing state */ 7232 bcopy(dev->l2ad_dev_hdr->dh_start_lbps, lb_ptrs, sizeof (lb_ptrs)); 7233 first_pass = B_TRUE; 7234 7235 /* Start the rebuild process */ 7236 for (;;) { 7237 if (!l2arc_log_blkptr_valid(dev, &lb_ptrs[0])) 7238 /* We hit an invalid block address, end the rebuild. */ 7239 break; 7240 7241 if ((err = l2arc_log_blk_read(dev, &lb_ptrs[0], &lb_ptrs[1], 7242 this_lb, next_lb, this_lb_buf, next_lb_buf, 7243 this_io, &next_io)) != 0) 7244 break; 7245 7246 spa_config_exit(spa, SCL_L2ARC, vd); 7247 lock_held = B_FALSE; 7248 7249 /* Protection against infinite loops of log blocks. */ 7250 if (l2arc_range_check_overlap(lb_ptrs[1].lbp_daddr, 7251 lb_ptrs[0].lbp_daddr, 7252 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) && 7253 !first_pass) { 7254 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_loop_errors); 7255 err = SET_ERROR(ELOOP); 7256 break; 7257 } 7258 7259 /* 7260 * Our memory pressure valve. If the system is running low 7261 * on memory, rather than swamping memory with new ARC buf 7262 * hdrs, we opt not to rebuild the L2ARC. At this point, 7263 * however, we have already set up our L2ARC dev to chain in 7264 * new metadata log blk, so the user may choose to re-add the 7265 * L2ARC dev at a later time to reconstruct it (when there's 7266 * less memory pressure). 7267 */ 7268 if (arc_reclaim_needed()) { 7269 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem); 7270 cmn_err(CE_NOTE, "System running low on memory, " 7271 "aborting L2ARC rebuild."); 7272 err = SET_ERROR(ENOMEM); 7273 break; 7274 } 7275 7276 /* 7277 * Now that we know that the next_lb checks out alright, we 7278 * can start reconstruction from this lb - we can be sure 7279 * that the L2ARC write hand has not yet reached any of our 7280 * buffers. 7281 */ 7282 l2arc_log_blk_restore(dev, load_guid, this_lb, 7283 LBP_GET_PSIZE(&lb_ptrs[0])); 7284 7285 /* 7286 * End of list detection. We can look ahead two steps in the 7287 * blk chain and if the 2nd blk from this_lb dips below the 7288 * initial chain starting point, then we know two things: 7289 * 1) it can't be valid, and 7290 * 2) the next_lb's ARC entries might have already been 7291 * partially overwritten and so we should stop before 7292 * we restore it 7293 */ 7294 if (l2arc_range_check_overlap( 7295 this_lb->lb_back2_lbp.lbp_daddr, lb_ptrs[0].lbp_daddr, 7296 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr) && 7297 !first_pass) 7298 break; 7299 7300 /* log blk restored, continue with next one in the list */ 7301 lb_ptrs[0] = lb_ptrs[1]; 7302 lb_ptrs[1] = this_lb->lb_back2_lbp; 7303 PTR_SWAP(this_lb, next_lb); 7304 PTR_SWAP(this_lb_buf, next_lb_buf); 7305 this_io = next_io; 7306 next_io = NULL; 7307 first_pass = B_FALSE; 7308 7309 for (;;) { 7310 if (dev->l2ad_rebuild_cancel) { 7311 err = SET_ERROR(ECANCELED); 7312 goto out; 7313 } 7314 if (spa_config_tryenter(spa, SCL_L2ARC, vd, 7315 RW_READER)) { 7316 lock_held = B_TRUE; 7317 break; 7318 } 7319 /* 7320 * L2ARC config lock held by somebody in writer, 7321 * possibly due to them trying to remove us. They'll 7322 * likely to want us to shut down, so after a little 7323 * delay, we check l2ad_rebuild_cancel and retry 7324 * the lock again. 7325 */ 7326 delay(1); 7327 } 7328 } 7329 out: 7330 if (next_io != NULL) 7331 l2arc_log_blk_prefetch_abort(next_io); 7332 kmem_free(this_lb, sizeof (*this_lb)); 7333 kmem_free(next_lb, sizeof (*next_lb)); 7334 kmem_free(this_lb_buf, sizeof (l2arc_log_blk_phys_t)); 7335 kmem_free(next_lb_buf, sizeof (l2arc_log_blk_phys_t)); 7336 if (err == 0) 7337 ARCSTAT_BUMP(arcstat_l2_rebuild_successes); 7338 7339 if (lock_held) 7340 spa_config_exit(spa, SCL_L2ARC, vd); 7341 7342 return (err); 7343 } 7344 7345 /* 7346 * Attempts to read the device header on the provided L2ARC device and writes 7347 * it to `hdr'. On success, this function returns 0, otherwise the appropriate 7348 * error code is returned. 7349 */ 7350 static int 7351 l2arc_dev_hdr_read(l2arc_dev_t *dev) 7352 { 7353 int err; 7354 uint64_t guid; 7355 zio_cksum_t cksum; 7356 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr; 7357 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize; 7358 7359 guid = spa_guid(dev->l2ad_vdev->vdev_spa); 7360 7361 if ((err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev, 7362 VDEV_LABEL_START_SIZE, hdr_asize, hdr, 7363 ZIO_CHECKSUM_OFF, NULL, NULL, ZIO_PRIORITY_ASYNC_READ, 7364 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | 7365 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE))) != 0) { 7366 spa_config_exit(dev->l2ad_vdev->vdev_spa, SCL_L2ARC, 7367 dev->l2ad_vdev); 7368 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors); 7369 return (err); 7370 } 7371 7372 if (hdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC)) 7373 byteswap_uint64_array(hdr, sizeof (*hdr)); 7374 7375 if (hdr->dh_magic != L2ARC_DEV_HDR_MAGIC || hdr->dh_spa_guid != guid) { 7376 /* 7377 * Attempt to rebuild a device containing no actual dev hdr 7378 * or containing a header from some other pool. 7379 */ 7380 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported); 7381 return (SET_ERROR(ENOTSUP)); 7382 } 7383 7384 l2arc_dev_hdr_checksum(hdr, &cksum); 7385 if (!ZIO_CHECKSUM_EQUAL(hdr->dh_self_cksum, cksum)) { 7386 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors); 7387 return (SET_ERROR(EINVAL)); 7388 } 7389 7390 return (0); 7391 } 7392 7393 /* 7394 * Reads L2ARC log blocks from storage and validates their contents. 7395 * 7396 * This function implements a simple prefetcher to make sure that while 7397 * we're processing one buffer the L2ARC is already prefetching the next 7398 * one in the chain. 7399 * 7400 * The arguments this_lp and next_lp point to the current and next log blk 7401 * address in the block chain. Similarly, this_lb and next_lb hold the 7402 * l2arc_log_blk_phys_t's of the current and next L2ARC blk. The this_lb_buf 7403 * and next_lb_buf must be buffers of appropriate to hold a raw 7404 * l2arc_log_blk_phys_t (they are used as catch buffers for read ops prior 7405 * to buffer decompression). 7406 * 7407 * The `this_io' and `next_io' arguments are used for block prefetching. 7408 * When issuing the first blk IO during rebuild, you should pass NULL for 7409 * `this_io'. This function will then issue a sync IO to read the block and 7410 * also issue an async IO to fetch the next block in the block chain. The 7411 * prefetch IO is returned in `next_io'. On subsequent calls to this 7412 * function, pass the value returned in `next_io' from the previous call 7413 * as `this_io' and a fresh `next_io' pointer to hold the next prefetch IO. 7414 * Prior to the call, you should initialize your `next_io' pointer to be 7415 * NULL. If no prefetch IO was issued, the pointer is left set at NULL. 7416 * 7417 * On success, this function returns 0, otherwise it returns an appropriate 7418 * error code. On error the prefetching IO is aborted and cleared before 7419 * returning from this function. Therefore, if we return `success', the 7420 * caller can assume that we have taken care of cleanup of prefetch IOs. 7421 */ 7422 static int 7423 l2arc_log_blk_read(l2arc_dev_t *dev, 7424 const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp, 7425 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb, 7426 uint8_t *this_lb_buf, uint8_t *next_lb_buf, 7427 zio_t *this_io, zio_t **next_io) 7428 { 7429 int err = 0; 7430 zio_cksum_t cksum; 7431 7432 ASSERT(this_lbp != NULL && next_lbp != NULL); 7433 ASSERT(this_lb != NULL && next_lb != NULL); 7434 ASSERT(this_lb_buf != NULL && next_lb_buf != NULL); 7435 ASSERT(next_io != NULL && *next_io == NULL); 7436 ASSERT(l2arc_log_blkptr_valid(dev, this_lbp)); 7437 7438 /* 7439 * Check to see if we have issued the IO for this log blk in a 7440 * previous run. If not, this is the first call, so issue it now. 7441 */ 7442 if (this_io == NULL) { 7443 this_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, this_lbp, 7444 this_lb_buf); 7445 } 7446 7447 /* 7448 * Peek to see if we can start issuing the next IO immediately. 7449 */ 7450 if (l2arc_log_blkptr_valid(dev, next_lbp)) { 7451 /* 7452 * Start issuing IO for the next log blk early - this 7453 * should help keep the L2ARC device busy while we 7454 * decompress and restore this log blk. 7455 */ 7456 *next_io = l2arc_log_blk_prefetch(dev->l2ad_vdev, next_lbp, 7457 next_lb_buf); 7458 } 7459 7460 /* Wait for the IO to read this log block to complete */ 7461 if ((err = zio_wait(this_io)) != 0) { 7462 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors); 7463 goto cleanup; 7464 } 7465 7466 /* Make sure the buffer checks out */ 7467 fletcher_4_native(this_lb_buf, LBP_GET_PSIZE(this_lbp), &cksum); 7468 if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) { 7469 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_errors); 7470 err = SET_ERROR(EINVAL); 7471 goto cleanup; 7472 } 7473 7474 /* Now we can take our time decoding this buffer */ 7475 switch (LBP_GET_COMPRESS(this_lbp)) { 7476 case ZIO_COMPRESS_OFF: 7477 bcopy(this_lb_buf, this_lb, sizeof (*this_lb)); 7478 break; 7479 case ZIO_COMPRESS_LZ4: 7480 if ((err = zio_decompress_data(LBP_GET_COMPRESS(this_lbp), 7481 this_lb_buf, this_lb, LBP_GET_PSIZE(this_lbp), 7482 sizeof (*this_lb))) != 0) { 7483 err = SET_ERROR(EINVAL); 7484 goto cleanup; 7485 } 7486 break; 7487 default: 7488 err = SET_ERROR(EINVAL); 7489 goto cleanup; 7490 } 7491 if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC)) 7492 byteswap_uint64_array(this_lb, sizeof (*this_lb)); 7493 if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) { 7494 err = SET_ERROR(EINVAL); 7495 goto cleanup; 7496 } 7497 cleanup: 7498 /* Abort an in-flight prefetch I/O in case of error */ 7499 if (err != 0 && *next_io != NULL) { 7500 l2arc_log_blk_prefetch_abort(*next_io); 7501 *next_io = NULL; 7502 } 7503 return (err); 7504 } 7505 7506 /* 7507 * Restores the payload of a log blk to ARC. This creates empty ARC hdr 7508 * entries which only contain an l2arc hdr, essentially restoring the 7509 * buffers to their L2ARC evicted state. This function also updates space 7510 * usage on the L2ARC vdev to make sure it tracks restored buffers. 7511 */ 7512 static void 7513 l2arc_log_blk_restore(l2arc_dev_t *dev, uint64_t load_guid, 7514 const l2arc_log_blk_phys_t *lb, uint64_t lb_psize) 7515 { 7516 uint64_t size = 0, psize = 0; 7517 7518 for (int i = L2ARC_LOG_BLK_ENTRIES - 1; i >= 0; i--) { 7519 /* 7520 * Restore goes in the reverse temporal direction to preserve 7521 * correct temporal ordering of buffers in the l2ad_buflist. 7522 * l2arc_hdr_restore also does a list_insert_tail instead of 7523 * list_insert_head on the l2ad_buflist: 7524 * 7525 * LIST l2ad_buflist LIST 7526 * HEAD <------ (time) ------ TAIL 7527 * direction +-----+-----+-----+-----+-----+ direction 7528 * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild 7529 * fill +-----+-----+-----+-----+-----+ 7530 * ^ ^ 7531 * | | 7532 * | | 7533 * l2arc_fill_thread l2arc_rebuild 7534 * places new bufs here restores bufs here 7535 * 7536 * This also works when the restored bufs get evicted at any 7537 * point during the rebuild. 7538 */ 7539 l2arc_hdr_restore(&lb->lb_entries[i], dev, load_guid); 7540 size += LE_GET_LSIZE(&lb->lb_entries[i]); 7541 psize += LE_GET_PSIZE(&lb->lb_entries[i]); 7542 } 7543 7544 /* 7545 * Record rebuild stats: 7546 * size In-memory size of restored buffer data in ARC 7547 * psize Physical size of restored buffers in the L2ARC 7548 * bufs # of ARC buffer headers restored 7549 * log_blks # of L2ARC log entries processed during restore 7550 */ 7551 ARCSTAT_INCR(arcstat_l2_rebuild_size, size); 7552 ARCSTAT_INCR(arcstat_l2_rebuild_psize, psize); 7553 ARCSTAT_INCR(arcstat_l2_rebuild_bufs, L2ARC_LOG_BLK_ENTRIES); 7554 ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks); 7555 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, lb_psize); 7556 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, psize / lb_psize); 7557 vdev_space_update(dev->l2ad_vdev, psize, 0, 0); 7558 } 7559 7560 /* 7561 * Restores a single ARC buf hdr from a log block. The ARC buffer is put 7562 * into a state indicating that it has been evicted to L2ARC. 7563 */ 7564 static void 7565 l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev, 7566 uint64_t load_guid) 7567 { 7568 arc_buf_hdr_t *hdr, *exists; 7569 kmutex_t *hash_lock; 7570 arc_buf_contents_t type = LE_GET_TYPE(le); 7571 7572 /* 7573 * Do all the allocation before grabbing any locks, this lets us 7574 * sleep if memory is full and we don't have to deal with failed 7575 * allocations. 7576 */ 7577 ASSERT(L2ARC_IS_VALID_COMPRESS(LE_GET_COMPRESS(le)) || 7578 LE_GET_COMPRESS(le) == ZIO_COMPRESS_OFF); 7579 hdr = arc_buf_alloc_l2only(load_guid, LE_GET_LSIZE(le), type, 7580 dev, le->le_dva, le->le_daddr, LE_GET_PSIZE(le), le->le_birth, 7581 le->le_freeze_cksum, LE_GET_COMPRESS(le)); 7582 if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET) { 7583 ARCSTAT_INCR(arcstat_l2_size, hdr->b_size); 7584 ARCSTAT_INCR(arcstat_l2_asize, hdr->b_l2hdr.b_asize); 7585 } 7586 7587 mutex_enter(&dev->l2ad_mtx); 7588 /* 7589 * We connect the l2hdr to the hdr only after the hdr is in the hash 7590 * table, otherwise the rest of the arc hdr manipulation machinery 7591 * might get confused. 7592 */ 7593 list_insert_tail(&dev->l2ad_buflist, hdr); 7594 (void) refcount_add_many(&dev->l2ad_alloc, hdr->b_l2hdr.b_asize, hdr); 7595 mutex_exit(&dev->l2ad_mtx); 7596 7597 exists = buf_hash_insert(hdr, &hash_lock); 7598 if (exists) { 7599 /* Buffer was already cached, no need to restore it. */ 7600 mutex_exit(hash_lock); 7601 arc_hdr_destroy(hdr); 7602 ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached); 7603 return; 7604 } 7605 7606 mutex_exit(hash_lock); 7607 } 7608 7609 /* 7610 * Starts an asynchronous read IO to read a log block. This is used in log 7611 * block reconstruction to start reading the next block before we are done 7612 * decoding and reconstructing the current block, to keep the l2arc device 7613 * nice and hot with read IO to process. 7614 * The returned zio will contain a newly allocated memory buffers for the IO 7615 * data which should then be freed by the caller once the zio is no longer 7616 * needed (i.e. due to it having completed). If you wish to abort this 7617 * zio, you should do so using l2arc_log_blk_prefetch_abort, which takes 7618 * care of disposing of the allocated buffers correctly. 7619 */ 7620 static zio_t * 7621 l2arc_log_blk_prefetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp, 7622 uint8_t *lb_buf) 7623 { 7624 uint32_t psize; 7625 zio_t *pio; 7626 7627 psize = LBP_GET_PSIZE(lbp); 7628 ASSERT(psize <= sizeof (l2arc_log_blk_phys_t)); 7629 pio = zio_root(vd->vdev_spa, NULL, NULL, ZIO_FLAG_DONT_CACHE | 7630 ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | 7631 ZIO_FLAG_DONT_RETRY); 7632 (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, psize, 7633 lb_buf, ZIO_CHECKSUM_OFF, NULL, NULL, ZIO_PRIORITY_ASYNC_READ, 7634 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | 7635 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE)); 7636 7637 return (pio); 7638 } 7639 7640 /* 7641 * Aborts a zio returned from l2arc_log_blk_prefetch and frees the data 7642 * buffers allocated for it. 7643 */ 7644 static void 7645 l2arc_log_blk_prefetch_abort(zio_t *zio) 7646 { 7647 (void) zio_wait(zio); 7648 } 7649 7650 /* 7651 * Creates a zio to update the device header on an l2arc device. The zio is 7652 * initiated as a child of `pio'. 7653 */ 7654 static void 7655 l2arc_dev_hdr_update(l2arc_dev_t *dev, zio_t *pio) 7656 { 7657 zio_t *wzio; 7658 l2arc_dev_hdr_phys_t *hdr = dev->l2ad_dev_hdr; 7659 const uint64_t hdr_asize = dev->l2ad_dev_hdr_asize; 7660 7661 hdr->dh_magic = L2ARC_DEV_HDR_MAGIC; 7662 hdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa); 7663 hdr->dh_alloc_space = refcount_count(&dev->l2ad_alloc); 7664 hdr->dh_flags = 0; 7665 if (dev->l2ad_first) 7666 hdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST; 7667 7668 /* checksum operation goes last */ 7669 l2arc_dev_hdr_checksum(hdr, &hdr->dh_self_cksum); 7670 7671 wzio = zio_write_phys(pio, dev->l2ad_vdev, VDEV_LABEL_START_SIZE, 7672 hdr_asize, hdr, ZIO_CHECKSUM_OFF, NULL, NULL, 7673 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE); 7674 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio); 7675 (void) zio_nowait(wzio); 7676 } 7677 7678 /* 7679 * Commits a log block to the L2ARC device. This routine is invoked from 7680 * l2arc_write_buffers when the log block fills up. 7681 * This function allocates some memory to temporarily hold the serialized 7682 * buffer to be written. This is then released in l2arc_write_done. 7683 */ 7684 static void 7685 l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, 7686 l2arc_write_callback_t *cb) 7687 { 7688 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; 7689 uint64_t psize, asize; 7690 l2arc_log_blk_buf_t *lb_buf; 7691 zio_t *wzio; 7692 7693 VERIFY(dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES); 7694 7695 /* link the buffer into the block chain */ 7696 lb->lb_back2_lbp = dev->l2ad_dev_hdr->dh_start_lbps[1]; 7697 lb->lb_magic = L2ARC_LOG_BLK_MAGIC; 7698 7699 /* try to compress the buffer */ 7700 lb_buf = kmem_zalloc(sizeof (*lb_buf), KM_SLEEP); 7701 list_insert_tail(&cb->l2wcb_log_blk_buflist, lb_buf); 7702 psize = zio_compress_data(ZIO_COMPRESS_LZ4, lb, lb_buf->lbb_log_blk, 7703 sizeof (*lb)); 7704 /* a log block is never entirely zero */ 7705 ASSERT(psize != 0); 7706 asize = vdev_psize_to_asize(dev->l2ad_vdev, psize); 7707 ASSERT(asize <= sizeof (lb_buf->lbb_log_blk)); 7708 7709 /* 7710 * Update the start log blk pointer in the device header to point 7711 * to the log block we're about to write. 7712 */ 7713 dev->l2ad_dev_hdr->dh_start_lbps[1] = 7714 dev->l2ad_dev_hdr->dh_start_lbps[0]; 7715 dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand; 7716 _NOTE(CONSTCOND) 7717 LBP_SET_LSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], sizeof (*lb)); 7718 LBP_SET_PSIZE(&dev->l2ad_dev_hdr->dh_start_lbps[0], asize); 7719 LBP_SET_CHECKSUM(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7720 ZIO_CHECKSUM_FLETCHER_4); 7721 LBP_SET_TYPE(&dev->l2ad_dev_hdr->dh_start_lbps[0], 0); 7722 if (asize < sizeof (*lb)) { 7723 /* compression succeeded */ 7724 bzero(lb_buf->lbb_log_blk + psize, asize - psize); 7725 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7726 ZIO_COMPRESS_LZ4); 7727 } else { 7728 /* compression failed */ 7729 bcopy(lb, lb_buf->lbb_log_blk, sizeof (*lb)); 7730 LBP_SET_COMPRESS(&dev->l2ad_dev_hdr->dh_start_lbps[0], 7731 ZIO_COMPRESS_OFF); 7732 } 7733 /* checksum what we're about to write */ 7734 fletcher_4_native(lb_buf->lbb_log_blk, asize, 7735 &dev->l2ad_dev_hdr->dh_start_lbps[0].lbp_cksum); 7736 7737 /* perform the write itself */ 7738 CTASSERT(L2ARC_LOG_BLK_SIZE >= SPA_MINBLOCKSIZE && 7739 L2ARC_LOG_BLK_SIZE <= SPA_MAXBLOCKSIZE); 7740 wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand, 7741 asize, lb_buf->lbb_log_blk, ZIO_CHECKSUM_OFF, NULL, NULL, 7742 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE); 7743 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio); 7744 (void) zio_nowait(wzio); 7745 7746 dev->l2ad_hand += asize; 7747 vdev_space_update(dev->l2ad_vdev, asize, 0, 0); 7748 7749 /* bump the kstats */ 7750 ARCSTAT_INCR(arcstat_l2_write_bytes, asize); 7751 ARCSTAT_BUMP(arcstat_l2_log_blk_writes); 7752 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_size, asize); 7753 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, 7754 dev->l2ad_log_blk_payload_asize / asize); 7755 7756 /* start a new log block */ 7757 dev->l2ad_log_ent_idx = 0; 7758 dev->l2ad_log_blk_payload_asize = 0; 7759 } 7760 7761 /* 7762 * Validates an L2ARC log blk address to make sure that it can be read 7763 * from the provided L2ARC device. Returns B_TRUE if the address is 7764 * within the device's bounds, or B_FALSE if not. 7765 */ 7766 static boolean_t 7767 l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp) 7768 { 7769 uint64_t psize = LBP_GET_PSIZE(lbp); 7770 uint64_t end = lbp->lbp_daddr + psize; 7771 7772 /* 7773 * A log block is valid if all of the following conditions are true: 7774 * - it fits entirely between l2ad_start and l2ad_end 7775 * - it has a valid size 7776 */ 7777 return (lbp->lbp_daddr >= dev->l2ad_start && end <= dev->l2ad_end && 7778 psize > 0 && psize <= sizeof (l2arc_log_blk_phys_t)); 7779 } 7780 7781 /* 7782 * Computes the checksum of `hdr' and stores it in `cksum'. 7783 */ 7784 static void 7785 l2arc_dev_hdr_checksum(const l2arc_dev_hdr_phys_t *hdr, zio_cksum_t *cksum) 7786 { 7787 fletcher_4_native((uint8_t *)hdr + 7788 offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid), 7789 sizeof (*hdr) - offsetof(l2arc_dev_hdr_phys_t, dh_spa_guid), 7790 cksum); 7791 } 7792 7793 /* 7794 * Inserts ARC buffer `ab' into the current L2ARC log blk on the device. 7795 * The buffer being inserted must be present in L2ARC. 7796 * Returns B_TRUE if the L2ARC log blk is full and needs to be committed 7797 * to L2ARC, or B_FALSE if it still has room for more ARC buffers. 7798 */ 7799 static boolean_t 7800 l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *ab) 7801 { 7802 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk; 7803 l2arc_log_ent_phys_t *le; 7804 int index = dev->l2ad_log_ent_idx++; 7805 7806 ASSERT(index < L2ARC_LOG_BLK_ENTRIES); 7807 7808 le = &lb->lb_entries[index]; 7809 bzero(le, sizeof (*le)); 7810 le->le_dva = ab->b_dva; 7811 le->le_birth = ab->b_birth; 7812 le->le_daddr = ab->b_l2hdr.b_daddr; 7813 LE_SET_LSIZE(le, ab->b_size); 7814 LE_SET_PSIZE(le, ab->b_l2hdr.b_asize); 7815 LE_SET_COMPRESS(le, ab->b_l2hdr.b_compress); 7816 if (ab->b_l2hdr.b_compress != ZIO_COMPRESS_OFF) { 7817 ASSERT(L2ARC_IS_VALID_COMPRESS(ab->b_l2hdr.b_compress)); 7818 ASSERT(L2ARC_IS_VALID_COMPRESS(LE_GET_COMPRESS(le))); 7819 } 7820 le->le_freeze_cksum = *ab->b_freeze_cksum; 7821 LE_SET_CHECKSUM(le, ZIO_CHECKSUM_FLETCHER_2); 7822 LE_SET_TYPE(le, arc_flags_to_bufc(ab->b_flags)); 7823 dev->l2ad_log_blk_payload_asize += ab->b_l2hdr.b_asize; 7824 7825 return (dev->l2ad_log_ent_idx == L2ARC_LOG_BLK_ENTRIES); 7826 } 7827 7828 /* 7829 * Checks whether a given L2ARC device address sits in a time-sequential 7830 * range. The trick here is that the L2ARC is a rotary buffer, so we can't 7831 * just do a range comparison, we need to handle the situation in which the 7832 * range wraps around the end of the L2ARC device. Arguments: 7833 * bottom Lower end of the range to check (written to earlier). 7834 * top Upper end of the range to check (written to later). 7835 * check The address for which we want to determine if it sits in 7836 * between the top and bottom. 7837 * 7838 * The 3-way conditional below represents the following cases: 7839 * 7840 * bottom < top : Sequentially ordered case: 7841 * <check>--------+-------------------+ 7842 * | (overlap here?) | 7843 * L2ARC dev V V 7844 * |---------------<bottom>============<top>--------------| 7845 * 7846 * bottom > top: Looped-around case: 7847 * <check>--------+------------------+ 7848 * | (overlap here?) | 7849 * L2ARC dev V V 7850 * |===============<top>---------------<bottom>===========| 7851 * ^ ^ 7852 * | (or here?) | 7853 * +---------------+---------<check> 7854 * 7855 * top == bottom : Just a single address comparison. 7856 */ 7857 static inline boolean_t 7858 l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check) 7859 { 7860 if (bottom < top) 7861 return (bottom <= check && check <= top); 7862 else if (bottom > top) 7863 return (check <= top || bottom <= check); 7864 else 7865 return (check == top); 7866 } 7867 7868 /* 7869 * dump arc cache to user mode for debugging purposes 7870 */ 7871 static void 7872 arc_dump_entry(arc_buf_hdr_t *entry, arc_info_t *outp) 7873 { 7874 outp->ai_dva = entry->b_dva; 7875 outp->ai_birth = entry->b_birth; 7876 outp->ai_flags = entry->b_flags; 7877 outp->ai_spa = entry->b_spa; 7878 outp->ai_size = entry->b_size; 7879 if (HDR_HAS_L1HDR(entry)) { 7880 arc_state_t *state = entry->b_l1hdr.b_state; 7881 if (state == arc_anon) 7882 outp->ai_state = AIS_ANON; 7883 else if (state == arc_mru) 7884 outp->ai_state = AIS_MRU; 7885 else if (state == arc_mru_ghost) 7886 outp->ai_state = AIS_MRU_GHOST; 7887 else if (state == arc_mfu) 7888 outp->ai_state = AIS_MFU; 7889 else if (state == arc_mfu_ghost) 7890 outp->ai_state = AIS_MFU_GHOST; 7891 else if (state == arc_l2c_only) 7892 outp->ai_state = AIS_L2C_ONLY; 7893 else 7894 outp->ai_state = AIS_UNKNOWN; 7895 } else { 7896 outp->ai_state = AIS_NO_L1HDR; 7897 } 7898 } 7899 7900 int 7901 arc_dump(int start_bucket, void *buf, size_t bufsize, size_t *returned_bytes) 7902 { 7903 int i; 7904 arc_info_t *outp = buf + sizeof(arc_info_hdr_t); 7905 arc_info_t *maxp = buf + bufsize; 7906 arc_info_hdr_t *aih = buf; 7907 size_t nbuckets = buf_hash_table.ht_mask + 1; 7908 size_t bph = nbuckets / BUF_LOCKS; /* buckets per hash */ 7909 kmutex_t *last_lock = NULL; 7910 7911 if (bufsize < sizeof(arc_info_hdr_t)) 7912 return (ENOMEM); 7913 7914 aih->aih_buckets = nbuckets; 7915 aih->aih_buf_locks = BUF_LOCKS; 7916 7917 ASSERT(start_bucket >= 0); 7918 ASSERT(start_bucket < nbuckets); 7919 7920 for (i = start_bucket; i < nbuckets; ++i) { 7921 kmutex_t *hash_lock; 7922 arc_buf_hdr_t *entry; 7923 arc_info_t *dryrun = outp; 7924 int bucket; 7925 7926 /* 7927 * transform index. We want to enumerate the buckets in an 7928 * order that allows us to keep the mutex as long as possible 7929 */ 7930 bucket = (i / bph) + (i % bph) * BUF_LOCKS; 7931 7932 hash_lock = BUF_HASH_LOCK(bucket); 7933 if (hash_lock != last_lock) { 7934 if (last_lock) 7935 mutex_exit(last_lock); 7936 mutex_enter(hash_lock); 7937 } 7938 last_lock = hash_lock; 7939 /* count entries to see if they will fit */ 7940 entry = buf_hash_table.ht_table[bucket]; 7941 while (entry != NULL) { 7942 ++dryrun; 7943 entry = entry->b_hash_next; 7944 } 7945 if (dryrun > maxp) { 7946 break; 7947 } 7948 /* actually copy entries */ 7949 entry = buf_hash_table.ht_table[bucket]; 7950 while (entry != NULL) { 7951 arc_dump_entry(entry, outp); 7952 ++outp; 7953 entry = entry->b_hash_next; 7954 } 7955 } 7956 if (last_lock) 7957 mutex_exit(last_lock); 7958 7959 *returned_bytes = (void *)outp - buf; 7960 aih->aih_entries = (*returned_bytes - sizeof(*aih)) / sizeof(*outp); 7961 7962 if (i <= buf_hash_table.ht_mask) 7963 aih->aih_next = i; 7964 else 7965 aih->aih_next = 0; 7966 7967 return (0); 7968 } 7969