arc.c revision 301873
156067Smarkm/* 256067Smarkm * CDDL HEADER START 3117728Smarkm * 4125261Sru * The contents of this file are subject to the terms of the 5233294Sstas * Common Development and Distribution License (the "License"). 6233294Sstas * You may not use this file except in compliance with the License. 7233294Sstas * 8117728Smarkm * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9117728Smarkm * or http://www.opensolaris.org/os/licensing. 1056067Smarkm * See the License for the specific language governing permissions 1156067Smarkm * and limitations under the License. 12125491Sru * 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/dnlc.h> 135#include <sys/racct.h> 136#endif 137#include <sys/callb.h> 138#include <sys/kstat.h> 139#include <sys/trim_map.h> 140#include <zfs_fletcher.h> 141#include <sys/sdt.h> 142 143#include <machine/vmparam.h> 144 145#ifdef illumos 146#ifndef _KERNEL 147/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 148boolean_t arc_watch = B_FALSE; 149int arc_procfd; 150#endif 151#endif /* illumos */ 152 153static kmutex_t arc_reclaim_lock; 154static kcondvar_t arc_reclaim_thread_cv; 155static boolean_t arc_reclaim_thread_exit; 156static kcondvar_t arc_reclaim_waiters_cv; 157 158static kmutex_t arc_user_evicts_lock; 159static kcondvar_t arc_user_evicts_cv; 160static boolean_t arc_user_evicts_thread_exit; 161 162uint_t arc_reduce_dnlc_percent = 3; 163 164/* 165 * The number of headers to evict in arc_evict_state_impl() before 166 * dropping the sublist lock and evicting from another sublist. A lower 167 * value means we're more likely to evict the "correct" header (i.e. the 168 * oldest header in the arc state), but comes with higher overhead 169 * (i.e. more invocations of arc_evict_state_impl()). 170 */ 171int zfs_arc_evict_batch_limit = 10; 172 173/* 174 * The number of sublists used for each of the arc state lists. If this 175 * is not set to a suitable value by the user, it will be configured to 176 * the number of CPUs on the system in arc_init(). 177 */ 178int zfs_arc_num_sublists_per_state = 0; 179 180/* number of seconds before growing cache again */ 181static int arc_grow_retry = 60; 182 183/* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 184int zfs_arc_overflow_shift = 8; 185 186/* shift of arc_c for calculating both min and max arc_p */ 187static int arc_p_min_shift = 4; 188 189/* log2(fraction of arc to reclaim) */ 190static int arc_shrink_shift = 7; 191 192/* 193 * log2(fraction of ARC which must be free to allow growing). 194 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 195 * when reading a new block into the ARC, we will evict an equal-sized block 196 * from the ARC. 197 * 198 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 199 * we will still not allow it to grow. 200 */ 201int arc_no_grow_shift = 5; 202 203 204/* 205 * minimum lifespan of a prefetch block in clock ticks 206 * (initialized in arc_init()) 207 */ 208static int arc_min_prefetch_lifespan; 209 210/* 211 * If this percent of memory is free, don't throttle. 212 */ 213int arc_lotsfree_percent = 10; 214 215static int arc_dead; 216extern boolean_t zfs_prefetch_disable; 217 218/* 219 * The arc has filled available memory and has now warmed up. 220 */ 221static boolean_t arc_warm; 222 223/* 224 * These tunables are for performance analysis. 225 */ 226uint64_t zfs_arc_max; 227uint64_t zfs_arc_min; 228uint64_t zfs_arc_meta_limit = 0; 229uint64_t zfs_arc_meta_min = 0; 230int zfs_arc_grow_retry = 0; 231int zfs_arc_shrink_shift = 0; 232int zfs_arc_p_min_shift = 0; 233int zfs_disable_dup_eviction = 0; 234uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 235u_int zfs_arc_free_target = 0; 236 237static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 238static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 239 240#ifdef _KERNEL 241static void 242arc_free_target_init(void *unused __unused) 243{ 244 245 zfs_arc_free_target = vm_pageout_wakeup_thresh; 246} 247SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 248 arc_free_target_init, NULL); 249 250TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 251TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 252TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 253SYSCTL_DECL(_vfs_zfs); 254SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 255 "Maximum ARC size"); 256SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 257 "Minimum ARC size"); 258SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 259 &zfs_arc_average_blocksize, 0, 260 "ARC average blocksize"); 261SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 262 &arc_shrink_shift, 0, 263 "log2(fraction of arc to reclaim)"); 264 265/* 266 * We don't have a tunable for arc_free_target due to the dependency on 267 * pagedaemon initialisation. 268 */ 269SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 270 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 271 sysctl_vfs_zfs_arc_free_target, "IU", 272 "Desired number of free pages below which ARC triggers reclaim"); 273 274static int 275sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 276{ 277 u_int val; 278 int err; 279 280 val = zfs_arc_free_target; 281 err = sysctl_handle_int(oidp, &val, 0, req); 282 if (err != 0 || req->newptr == NULL) 283 return (err); 284 285 if (val < minfree) 286 return (EINVAL); 287 if (val > vm_cnt.v_page_count) 288 return (EINVAL); 289 290 zfs_arc_free_target = val; 291 292 return (0); 293} 294 295/* 296 * Must be declared here, before the definition of corresponding kstat 297 * macro which uses the same names will confuse the compiler. 298 */ 299SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 300 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 301 sysctl_vfs_zfs_arc_meta_limit, "QU", 302 "ARC metadata limit"); 303#endif 304 305/* 306 * Note that buffers can be in one of 6 states: 307 * ARC_anon - anonymous (discussed below) 308 * ARC_mru - recently used, currently cached 309 * ARC_mru_ghost - recentely used, no longer in cache 310 * ARC_mfu - frequently used, currently cached 311 * ARC_mfu_ghost - frequently used, no longer in cache 312 * ARC_l2c_only - exists in L2ARC but not other states 313 * When there are no active references to the buffer, they are 314 * are linked onto a list in one of these arc states. These are 315 * the only buffers that can be evicted or deleted. Within each 316 * state there are multiple lists, one for meta-data and one for 317 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 318 * etc.) is tracked separately so that it can be managed more 319 * explicitly: favored over data, limited explicitly. 320 * 321 * Anonymous buffers are buffers that are not associated with 322 * a DVA. These are buffers that hold dirty block copies 323 * before they are written to stable storage. By definition, 324 * they are "ref'd" and are considered part of arc_mru 325 * that cannot be freed. Generally, they will aquire a DVA 326 * as they are written and migrate onto the arc_mru list. 327 * 328 * The ARC_l2c_only state is for buffers that are in the second 329 * level ARC but no longer in any of the ARC_m* lists. The second 330 * level ARC itself may also contain buffers that are in any of 331 * the ARC_m* states - meaning that a buffer can exist in two 332 * places. The reason for the ARC_l2c_only state is to keep the 333 * buffer header in the hash table, so that reads that hit the 334 * second level ARC benefit from these fast lookups. 335 */ 336 337typedef struct arc_state { 338 /* 339 * list of evictable buffers 340 */ 341 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 342 /* 343 * total amount of evictable data in this state 344 */ 345 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 346 /* 347 * total amount of data in this state; this includes: evictable, 348 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 349 */ 350 refcount_t arcs_size; 351} arc_state_t; 352 353/* The 6 states: */ 354static arc_state_t ARC_anon; 355static arc_state_t ARC_mru; 356static arc_state_t ARC_mru_ghost; 357static arc_state_t ARC_mfu; 358static arc_state_t ARC_mfu_ghost; 359static arc_state_t ARC_l2c_only; 360 361typedef struct arc_stats { 362 kstat_named_t arcstat_hits; 363 kstat_named_t arcstat_misses; 364 kstat_named_t arcstat_demand_data_hits; 365 kstat_named_t arcstat_demand_data_misses; 366 kstat_named_t arcstat_demand_metadata_hits; 367 kstat_named_t arcstat_demand_metadata_misses; 368 kstat_named_t arcstat_prefetch_data_hits; 369 kstat_named_t arcstat_prefetch_data_misses; 370 kstat_named_t arcstat_prefetch_metadata_hits; 371 kstat_named_t arcstat_prefetch_metadata_misses; 372 kstat_named_t arcstat_mru_hits; 373 kstat_named_t arcstat_mru_ghost_hits; 374 kstat_named_t arcstat_mfu_hits; 375 kstat_named_t arcstat_mfu_ghost_hits; 376 kstat_named_t arcstat_allocated; 377 kstat_named_t arcstat_deleted; 378 /* 379 * Number of buffers that could not be evicted because the hash lock 380 * was held by another thread. The lock may not necessarily be held 381 * by something using the same buffer, since hash locks are shared 382 * by multiple buffers. 383 */ 384 kstat_named_t arcstat_mutex_miss; 385 /* 386 * Number of buffers skipped because they have I/O in progress, are 387 * indrect prefetch buffers that have not lived long enough, or are 388 * not from the spa we're trying to evict from. 389 */ 390 kstat_named_t arcstat_evict_skip; 391 /* 392 * Number of times arc_evict_state() was unable to evict enough 393 * buffers to reach it's target amount. 394 */ 395 kstat_named_t arcstat_evict_not_enough; 396 kstat_named_t arcstat_evict_l2_cached; 397 kstat_named_t arcstat_evict_l2_eligible; 398 kstat_named_t arcstat_evict_l2_ineligible; 399 kstat_named_t arcstat_evict_l2_skip; 400 kstat_named_t arcstat_hash_elements; 401 kstat_named_t arcstat_hash_elements_max; 402 kstat_named_t arcstat_hash_collisions; 403 kstat_named_t arcstat_hash_chains; 404 kstat_named_t arcstat_hash_chain_max; 405 kstat_named_t arcstat_p; 406 kstat_named_t arcstat_c; 407 kstat_named_t arcstat_c_min; 408 kstat_named_t arcstat_c_max; 409 kstat_named_t arcstat_size; 410 /* 411 * Number of bytes consumed by internal ARC structures necessary 412 * for tracking purposes; these structures are not actually 413 * backed by ARC buffers. This includes arc_buf_hdr_t structures 414 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 415 * caches), and arc_buf_t structures (allocated via arc_buf_t 416 * cache). 417 */ 418 kstat_named_t arcstat_hdr_size; 419 /* 420 * Number of bytes consumed by ARC buffers of type equal to 421 * ARC_BUFC_DATA. This is generally consumed by buffers backing 422 * on disk user data (e.g. plain file contents). 423 */ 424 kstat_named_t arcstat_data_size; 425 /* 426 * Number of bytes consumed by ARC buffers of type equal to 427 * ARC_BUFC_METADATA. This is generally consumed by buffers 428 * backing on disk data that is used for internal ZFS 429 * structures (e.g. ZAP, dnode, indirect blocks, etc). 430 */ 431 kstat_named_t arcstat_metadata_size; 432 /* 433 * Number of bytes consumed by various buffers and structures 434 * not actually backed with ARC buffers. This includes bonus 435 * buffers (allocated directly via zio_buf_* functions), 436 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 437 * cache), and dnode_t structures (allocated via dnode_t cache). 438 */ 439 kstat_named_t arcstat_other_size; 440 /* 441 * Total number of bytes consumed by ARC buffers residing in the 442 * arc_anon state. This includes *all* buffers in the arc_anon 443 * state; e.g. data, metadata, evictable, and unevictable buffers 444 * are all included in this value. 445 */ 446 kstat_named_t arcstat_anon_size; 447 /* 448 * Number of bytes consumed by ARC buffers that meet the 449 * following criteria: backing buffers of type ARC_BUFC_DATA, 450 * residing in the arc_anon state, and are eligible for eviction 451 * (e.g. have no outstanding holds on the buffer). 452 */ 453 kstat_named_t arcstat_anon_evictable_data; 454 /* 455 * Number of bytes consumed by ARC buffers that meet the 456 * following criteria: backing buffers of type ARC_BUFC_METADATA, 457 * residing in the arc_anon state, and are eligible for eviction 458 * (e.g. have no outstanding holds on the buffer). 459 */ 460 kstat_named_t arcstat_anon_evictable_metadata; 461 /* 462 * Total number of bytes consumed by ARC buffers residing in the 463 * arc_mru state. This includes *all* buffers in the arc_mru 464 * state; e.g. data, metadata, evictable, and unevictable buffers 465 * are all included in this value. 466 */ 467 kstat_named_t arcstat_mru_size; 468 /* 469 * Number of bytes consumed by ARC buffers that meet the 470 * following criteria: backing buffers of type ARC_BUFC_DATA, 471 * residing in the arc_mru state, and are eligible for eviction 472 * (e.g. have no outstanding holds on the buffer). 473 */ 474 kstat_named_t arcstat_mru_evictable_data; 475 /* 476 * Number of bytes consumed by ARC buffers that meet the 477 * following criteria: backing buffers of type ARC_BUFC_METADATA, 478 * residing in the arc_mru state, and are eligible for eviction 479 * (e.g. have no outstanding holds on the buffer). 480 */ 481 kstat_named_t arcstat_mru_evictable_metadata; 482 /* 483 * Total number of bytes that *would have been* consumed by ARC 484 * buffers in the arc_mru_ghost state. The key thing to note 485 * here, is the fact that this size doesn't actually indicate 486 * RAM consumption. The ghost lists only consist of headers and 487 * don't actually have ARC buffers linked off of these headers. 488 * Thus, *if* the headers had associated ARC buffers, these 489 * buffers *would have* consumed this number of bytes. 490 */ 491 kstat_named_t arcstat_mru_ghost_size; 492 /* 493 * Number of bytes that *would have been* consumed by ARC 494 * buffers that are eligible for eviction, of type 495 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 496 */ 497 kstat_named_t arcstat_mru_ghost_evictable_data; 498 /* 499 * Number of bytes that *would have been* consumed by ARC 500 * buffers that are eligible for eviction, of type 501 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 502 */ 503 kstat_named_t arcstat_mru_ghost_evictable_metadata; 504 /* 505 * Total number of bytes consumed by ARC buffers residing in the 506 * arc_mfu state. This includes *all* buffers in the arc_mfu 507 * state; e.g. data, metadata, evictable, and unevictable buffers 508 * are all included in this value. 509 */ 510 kstat_named_t arcstat_mfu_size; 511 /* 512 * Number of bytes consumed by ARC buffers that are eligible for 513 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 514 * state. 515 */ 516 kstat_named_t arcstat_mfu_evictable_data; 517 /* 518 * Number of bytes consumed by ARC buffers that are eligible for 519 * eviction, of type ARC_BUFC_METADATA, and reside in the 520 * arc_mfu state. 521 */ 522 kstat_named_t arcstat_mfu_evictable_metadata; 523 /* 524 * Total number of bytes that *would have been* consumed by ARC 525 * buffers in the arc_mfu_ghost state. See the comment above 526 * arcstat_mru_ghost_size for more details. 527 */ 528 kstat_named_t arcstat_mfu_ghost_size; 529 /* 530 * Number of bytes that *would have been* consumed by ARC 531 * buffers that are eligible for eviction, of type 532 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 533 */ 534 kstat_named_t arcstat_mfu_ghost_evictable_data; 535 /* 536 * Number of bytes that *would have been* consumed by ARC 537 * buffers that are eligible for eviction, of type 538 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 539 */ 540 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 541 kstat_named_t arcstat_l2_hits; 542 kstat_named_t arcstat_l2_misses; 543 kstat_named_t arcstat_l2_feeds; 544 kstat_named_t arcstat_l2_rw_clash; 545 kstat_named_t arcstat_l2_read_bytes; 546 kstat_named_t arcstat_l2_write_bytes; 547 kstat_named_t arcstat_l2_writes_sent; 548 kstat_named_t arcstat_l2_writes_done; 549 kstat_named_t arcstat_l2_writes_error; 550 kstat_named_t arcstat_l2_writes_lock_retry; 551 kstat_named_t arcstat_l2_evict_lock_retry; 552 kstat_named_t arcstat_l2_evict_reading; 553 kstat_named_t arcstat_l2_evict_l1cached; 554 kstat_named_t arcstat_l2_free_on_write; 555 kstat_named_t arcstat_l2_cdata_free_on_write; 556 kstat_named_t arcstat_l2_abort_lowmem; 557 kstat_named_t arcstat_l2_cksum_bad; 558 kstat_named_t arcstat_l2_io_error; 559 kstat_named_t arcstat_l2_size; 560 kstat_named_t arcstat_l2_asize; 561 kstat_named_t arcstat_l2_hdr_size; 562 kstat_named_t arcstat_l2_compress_successes; 563 kstat_named_t arcstat_l2_compress_zeros; 564 kstat_named_t arcstat_l2_compress_failures; 565 kstat_named_t arcstat_l2_padding_needed; 566 kstat_named_t arcstat_l2_write_trylock_fail; 567 kstat_named_t arcstat_l2_write_passed_headroom; 568 kstat_named_t arcstat_l2_write_spa_mismatch; 569 kstat_named_t arcstat_l2_write_in_l2; 570 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 571 kstat_named_t arcstat_l2_write_not_cacheable; 572 kstat_named_t arcstat_l2_write_full; 573 kstat_named_t arcstat_l2_write_buffer_iter; 574 kstat_named_t arcstat_l2_write_pios; 575 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 576 kstat_named_t arcstat_l2_write_buffer_list_iter; 577 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 578 kstat_named_t arcstat_memory_throttle_count; 579 kstat_named_t arcstat_duplicate_buffers; 580 kstat_named_t arcstat_duplicate_buffers_size; 581 kstat_named_t arcstat_duplicate_reads; 582 kstat_named_t arcstat_meta_used; 583 kstat_named_t arcstat_meta_limit; 584 kstat_named_t arcstat_meta_max; 585 kstat_named_t arcstat_meta_min; 586 kstat_named_t arcstat_sync_wait_for_async; 587 kstat_named_t arcstat_demand_hit_predictive_prefetch; 588} arc_stats_t; 589 590static arc_stats_t arc_stats = { 591 { "hits", KSTAT_DATA_UINT64 }, 592 { "misses", KSTAT_DATA_UINT64 }, 593 { "demand_data_hits", KSTAT_DATA_UINT64 }, 594 { "demand_data_misses", KSTAT_DATA_UINT64 }, 595 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 596 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 597 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 598 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 599 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 600 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 601 { "mru_hits", KSTAT_DATA_UINT64 }, 602 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 603 { "mfu_hits", KSTAT_DATA_UINT64 }, 604 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 605 { "allocated", KSTAT_DATA_UINT64 }, 606 { "deleted", KSTAT_DATA_UINT64 }, 607 { "mutex_miss", KSTAT_DATA_UINT64 }, 608 { "evict_skip", KSTAT_DATA_UINT64 }, 609 { "evict_not_enough", KSTAT_DATA_UINT64 }, 610 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 611 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 612 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 613 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 614 { "hash_elements", KSTAT_DATA_UINT64 }, 615 { "hash_elements_max", KSTAT_DATA_UINT64 }, 616 { "hash_collisions", KSTAT_DATA_UINT64 }, 617 { "hash_chains", KSTAT_DATA_UINT64 }, 618 { "hash_chain_max", KSTAT_DATA_UINT64 }, 619 { "p", KSTAT_DATA_UINT64 }, 620 { "c", KSTAT_DATA_UINT64 }, 621 { "c_min", KSTAT_DATA_UINT64 }, 622 { "c_max", KSTAT_DATA_UINT64 }, 623 { "size", KSTAT_DATA_UINT64 }, 624 { "hdr_size", KSTAT_DATA_UINT64 }, 625 { "data_size", KSTAT_DATA_UINT64 }, 626 { "metadata_size", KSTAT_DATA_UINT64 }, 627 { "other_size", KSTAT_DATA_UINT64 }, 628 { "anon_size", KSTAT_DATA_UINT64 }, 629 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 630 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 631 { "mru_size", KSTAT_DATA_UINT64 }, 632 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 633 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 634 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 635 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 636 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 637 { "mfu_size", KSTAT_DATA_UINT64 }, 638 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 639 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 640 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 641 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 642 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 643 { "l2_hits", KSTAT_DATA_UINT64 }, 644 { "l2_misses", KSTAT_DATA_UINT64 }, 645 { "l2_feeds", KSTAT_DATA_UINT64 }, 646 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 647 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 648 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 649 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 650 { "l2_writes_done", KSTAT_DATA_UINT64 }, 651 { "l2_writes_error", KSTAT_DATA_UINT64 }, 652 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 653 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 654 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 655 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 656 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 657 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 658 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 659 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 660 { "l2_io_error", KSTAT_DATA_UINT64 }, 661 { "l2_size", KSTAT_DATA_UINT64 }, 662 { "l2_asize", KSTAT_DATA_UINT64 }, 663 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 664 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 665 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 666 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 667 { "l2_padding_needed", KSTAT_DATA_UINT64 }, 668 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 669 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 670 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 671 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 672 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 673 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 674 { "l2_write_full", KSTAT_DATA_UINT64 }, 675 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 676 { "l2_write_pios", KSTAT_DATA_UINT64 }, 677 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 678 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 679 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 680 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 681 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 682 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 683 { "duplicate_reads", KSTAT_DATA_UINT64 }, 684 { "arc_meta_used", KSTAT_DATA_UINT64 }, 685 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 686 { "arc_meta_max", KSTAT_DATA_UINT64 }, 687 { "arc_meta_min", KSTAT_DATA_UINT64 }, 688 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 689 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 690}; 691 692#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 693 694#define ARCSTAT_INCR(stat, val) \ 695 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 696 697#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 698#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 699 700#define ARCSTAT_MAX(stat, val) { \ 701 uint64_t m; \ 702 while ((val) > (m = arc_stats.stat.value.ui64) && \ 703 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 704 continue; \ 705} 706 707#define ARCSTAT_MAXSTAT(stat) \ 708 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 709 710/* 711 * We define a macro to allow ARC hits/misses to be easily broken down by 712 * two separate conditions, giving a total of four different subtypes for 713 * each of hits and misses (so eight statistics total). 714 */ 715#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 716 if (cond1) { \ 717 if (cond2) { \ 718 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 719 } else { \ 720 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 721 } \ 722 } else { \ 723 if (cond2) { \ 724 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 725 } else { \ 726 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 727 } \ 728 } 729 730kstat_t *arc_ksp; 731static arc_state_t *arc_anon; 732static arc_state_t *arc_mru; 733static arc_state_t *arc_mru_ghost; 734static arc_state_t *arc_mfu; 735static arc_state_t *arc_mfu_ghost; 736static arc_state_t *arc_l2c_only; 737 738/* 739 * There are several ARC variables that are critical to export as kstats -- 740 * but we don't want to have to grovel around in the kstat whenever we wish to 741 * manipulate them. For these variables, we therefore define them to be in 742 * terms of the statistic variable. This assures that we are not introducing 743 * the possibility of inconsistency by having shadow copies of the variables, 744 * while still allowing the code to be readable. 745 */ 746#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 747#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 748#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 749#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 750#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 751#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 752#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 753#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 754#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 755 756#define L2ARC_IS_VALID_COMPRESS(_c_) \ 757 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 758 759static int arc_no_grow; /* Don't try to grow cache size */ 760static uint64_t arc_tempreserve; 761static uint64_t arc_loaned_bytes; 762 763typedef struct arc_callback arc_callback_t; 764 765struct arc_callback { 766 void *acb_private; 767 arc_done_func_t *acb_done; 768 arc_buf_t *acb_buf; 769 zio_t *acb_zio_dummy; 770 arc_callback_t *acb_next; 771}; 772 773typedef struct arc_write_callback arc_write_callback_t; 774 775struct arc_write_callback { 776 void *awcb_private; 777 arc_done_func_t *awcb_ready; 778 arc_done_func_t *awcb_physdone; 779 arc_done_func_t *awcb_done; 780 arc_buf_t *awcb_buf; 781}; 782 783/* 784 * ARC buffers are separated into multiple structs as a memory saving measure: 785 * - Common fields struct, always defined, and embedded within it: 786 * - L2-only fields, always allocated but undefined when not in L2ARC 787 * - L1-only fields, only allocated when in L1ARC 788 * 789 * Buffer in L1 Buffer only in L2 790 * +------------------------+ +------------------------+ 791 * | arc_buf_hdr_t | | arc_buf_hdr_t | 792 * | | | | 793 * | | | | 794 * | | | | 795 * +------------------------+ +------------------------+ 796 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 797 * | (undefined if L1-only) | | | 798 * +------------------------+ +------------------------+ 799 * | l1arc_buf_hdr_t | 800 * | | 801 * | | 802 * | | 803 * | | 804 * +------------------------+ 805 * 806 * Because it's possible for the L2ARC to become extremely large, we can wind 807 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 808 * is minimized by only allocating the fields necessary for an L1-cached buffer 809 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 810 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 811 * words in pointers. arc_hdr_realloc() is used to switch a header between 812 * these two allocation states. 813 */ 814typedef struct l1arc_buf_hdr { 815 kmutex_t b_freeze_lock; 816#ifdef ZFS_DEBUG 817 /* 818 * used for debugging wtih kmem_flags - by allocating and freeing 819 * b_thawed when the buffer is thawed, we get a record of the stack 820 * trace that thawed it. 821 */ 822 void *b_thawed; 823#endif 824 825 arc_buf_t *b_buf; 826 uint32_t b_datacnt; 827 /* for waiting on writes to complete */ 828 kcondvar_t b_cv; 829 830 /* protected by arc state mutex */ 831 arc_state_t *b_state; 832 multilist_node_t b_arc_node; 833 834 /* updated atomically */ 835 clock_t b_arc_access; 836 837 /* self protecting */ 838 refcount_t b_refcnt; 839 840 arc_callback_t *b_acb; 841 /* temporary buffer holder for in-flight compressed or padded data */ 842 void *b_tmp_cdata; 843} l1arc_buf_hdr_t; 844 845typedef struct l2arc_dev l2arc_dev_t; 846 847typedef struct l2arc_buf_hdr { 848 /* protected by arc_buf_hdr mutex */ 849 l2arc_dev_t *b_dev; /* L2ARC device */ 850 uint64_t b_daddr; /* disk address, offset byte */ 851 /* real alloc'd buffer size depending on b_compress applied */ 852 int32_t b_asize; 853 uint8_t b_compress; 854 855 list_node_t b_l2node; 856} l2arc_buf_hdr_t; 857 858struct arc_buf_hdr { 859 /* protected by hash lock */ 860 dva_t b_dva; 861 uint64_t b_birth; 862 /* 863 * Even though this checksum is only set/verified when a buffer is in 864 * the L1 cache, it needs to be in the set of common fields because it 865 * must be preserved from the time before a buffer is written out to 866 * L2ARC until after it is read back in. 867 */ 868 zio_cksum_t *b_freeze_cksum; 869 870 arc_buf_hdr_t *b_hash_next; 871 arc_flags_t b_flags; 872 873 /* immutable */ 874 int32_t b_size; 875 uint64_t b_spa; 876 877 /* L2ARC fields. Undefined when not in L2ARC. */ 878 l2arc_buf_hdr_t b_l2hdr; 879 /* L1ARC fields. Undefined when in l2arc_only state */ 880 l1arc_buf_hdr_t b_l1hdr; 881}; 882 883#ifdef _KERNEL 884static int 885sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 886{ 887 uint64_t val; 888 int err; 889 890 val = arc_meta_limit; 891 err = sysctl_handle_64(oidp, &val, 0, req); 892 if (err != 0 || req->newptr == NULL) 893 return (err); 894 895 if (val <= 0 || val > arc_c_max) 896 return (EINVAL); 897 898 arc_meta_limit = val; 899 return (0); 900} 901#endif 902 903static arc_buf_t *arc_eviction_list; 904static arc_buf_hdr_t arc_eviction_hdr; 905 906#define GHOST_STATE(state) \ 907 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 908 (state) == arc_l2c_only) 909 910#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 911#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 912#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 913#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 914#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 915#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 916 917#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 918#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 919#define HDR_L2_READING(hdr) \ 920 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 921 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 922#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 923#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 924#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 925 926#define HDR_ISTYPE_METADATA(hdr) \ 927 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 928#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 929 930#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 931#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 932 933/* 934 * Other sizes 935 */ 936 937#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 938#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 939 940/* 941 * Hash table routines 942 */ 943 944#define HT_LOCK_PAD CACHE_LINE_SIZE 945 946struct ht_lock { 947 kmutex_t ht_lock; 948#ifdef _KERNEL 949 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 950#endif 951}; 952 953#define BUF_LOCKS 256 954typedef struct buf_hash_table { 955 uint64_t ht_mask; 956 arc_buf_hdr_t **ht_table; 957 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 958} buf_hash_table_t; 959 960static buf_hash_table_t buf_hash_table; 961 962#define BUF_HASH_INDEX(spa, dva, birth) \ 963 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 964#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 965#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 966#define HDR_LOCK(hdr) \ 967 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 968 969uint64_t zfs_crc64_table[256]; 970 971/* 972 * Level 2 ARC 973 */ 974 975#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 976#define L2ARC_HEADROOM 2 /* num of writes */ 977/* 978 * If we discover during ARC scan any buffers to be compressed, we boost 979 * our headroom for the next scanning cycle by this percentage multiple. 980 */ 981#define L2ARC_HEADROOM_BOOST 200 982#define L2ARC_FEED_SECS 1 /* caching interval secs */ 983#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 984 985/* 986 * Used to distinguish headers that are being process by 987 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 988 * address. This can happen when the header is added to the l2arc's list 989 * of buffers to write in the first stage of l2arc_write_buffers(), but 990 * has not yet been written out which happens in the second stage of 991 * l2arc_write_buffers(). 992 */ 993#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 994 995#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 996#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 997 998/* L2ARC Performance Tunables */ 999uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1000uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1001uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1002uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1003uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1004uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1005boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1006boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1007boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1008 1009SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1010 &l2arc_write_max, 0, "max write size"); 1011SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1012 &l2arc_write_boost, 0, "extra write during warmup"); 1013SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1014 &l2arc_headroom, 0, "number of dev writes"); 1015SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1016 &l2arc_feed_secs, 0, "interval seconds"); 1017SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1018 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1019 1020SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1021 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1022SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1023 &l2arc_feed_again, 0, "turbo warmup"); 1024SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1025 &l2arc_norw, 0, "no reads during writes"); 1026 1027SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1028 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1029SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1030 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1031SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1032 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1033 1034SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1035 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1036SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1037 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1038SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1039 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1040 1041SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1042 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1043SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1044 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1045 "size of metadata in mru ghost state"); 1046SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1047 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1048 "size of data in mru ghost state"); 1049 1050SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1051 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1052SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1053 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1054SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1055 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1056 1057SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1058 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1059SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1060 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1061 "size of metadata in mfu ghost state"); 1062SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1063 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1064 "size of data in mfu ghost state"); 1065 1066SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1067 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1068 1069/* 1070 * L2ARC Internals 1071 */ 1072struct l2arc_dev { 1073 vdev_t *l2ad_vdev; /* vdev */ 1074 spa_t *l2ad_spa; /* spa */ 1075 uint64_t l2ad_hand; /* next write location */ 1076 uint64_t l2ad_start; /* first addr on device */ 1077 uint64_t l2ad_end; /* last addr on device */ 1078 boolean_t l2ad_first; /* first sweep through */ 1079 boolean_t l2ad_writing; /* currently writing */ 1080 kmutex_t l2ad_mtx; /* lock for buffer list */ 1081 list_t l2ad_buflist; /* buffer list */ 1082 list_node_t l2ad_node; /* device list node */ 1083 refcount_t l2ad_alloc; /* allocated bytes */ 1084}; 1085 1086static list_t L2ARC_dev_list; /* device list */ 1087static list_t *l2arc_dev_list; /* device list pointer */ 1088static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1089static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1090static list_t L2ARC_free_on_write; /* free after write buf list */ 1091static list_t *l2arc_free_on_write; /* free after write list ptr */ 1092static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1093static uint64_t l2arc_ndev; /* number of devices */ 1094 1095typedef struct l2arc_read_callback { 1096 arc_buf_t *l2rcb_buf; /* read buffer */ 1097 spa_t *l2rcb_spa; /* spa */ 1098 blkptr_t l2rcb_bp; /* original blkptr */ 1099 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1100 int l2rcb_flags; /* original flags */ 1101 enum zio_compress l2rcb_compress; /* applied compress */ 1102 void *l2rcb_data; /* temporary buffer */ 1103} l2arc_read_callback_t; 1104 1105typedef struct l2arc_write_callback { 1106 l2arc_dev_t *l2wcb_dev; /* device info */ 1107 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1108} l2arc_write_callback_t; 1109 1110typedef struct l2arc_data_free { 1111 /* protected by l2arc_free_on_write_mtx */ 1112 void *l2df_data; 1113 size_t l2df_size; 1114 void (*l2df_func)(void *, size_t); 1115 list_node_t l2df_list_node; 1116} l2arc_data_free_t; 1117 1118static kmutex_t l2arc_feed_thr_lock; 1119static kcondvar_t l2arc_feed_thr_cv; 1120static uint8_t l2arc_thread_exit; 1121 1122static void arc_get_data_buf(arc_buf_t *); 1123static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1124static boolean_t arc_is_overflowing(); 1125static void arc_buf_watch(arc_buf_t *); 1126 1127static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1128static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1129 1130static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1131static void l2arc_read_done(zio_t *); 1132 1133static boolean_t l2arc_transform_buf(arc_buf_hdr_t *, boolean_t); 1134static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1135static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1136 1137static void 1138l2arc_trim(const arc_buf_hdr_t *hdr) 1139{ 1140 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1141 1142 ASSERT(HDR_HAS_L2HDR(hdr)); 1143 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1144 1145 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) 1146 return; 1147 if (hdr->b_l2hdr.b_asize != 0) { 1148 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1149 hdr->b_l2hdr.b_asize, 0); 1150 } else { 1151 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_EMPTY); 1152 } 1153} 1154 1155static uint64_t 1156buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1157{ 1158 uint8_t *vdva = (uint8_t *)dva; 1159 uint64_t crc = -1ULL; 1160 int i; 1161 1162 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1163 1164 for (i = 0; i < sizeof (dva_t); i++) 1165 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1166 1167 crc ^= (spa>>8) ^ birth; 1168 1169 return (crc); 1170} 1171 1172#define BUF_EMPTY(buf) \ 1173 ((buf)->b_dva.dva_word[0] == 0 && \ 1174 (buf)->b_dva.dva_word[1] == 0) 1175 1176#define BUF_EQUAL(spa, dva, birth, buf) \ 1177 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1178 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1179 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1180 1181static void 1182buf_discard_identity(arc_buf_hdr_t *hdr) 1183{ 1184 hdr->b_dva.dva_word[0] = 0; 1185 hdr->b_dva.dva_word[1] = 0; 1186 hdr->b_birth = 0; 1187} 1188 1189static arc_buf_hdr_t * 1190buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1191{ 1192 const dva_t *dva = BP_IDENTITY(bp); 1193 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1194 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1195 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1196 arc_buf_hdr_t *hdr; 1197 1198 mutex_enter(hash_lock); 1199 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1200 hdr = hdr->b_hash_next) { 1201 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1202 *lockp = hash_lock; 1203 return (hdr); 1204 } 1205 } 1206 mutex_exit(hash_lock); 1207 *lockp = NULL; 1208 return (NULL); 1209} 1210 1211/* 1212 * Insert an entry into the hash table. If there is already an element 1213 * equal to elem in the hash table, then the already existing element 1214 * will be returned and the new element will not be inserted. 1215 * Otherwise returns NULL. 1216 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1217 */ 1218static arc_buf_hdr_t * 1219buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1220{ 1221 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1222 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1223 arc_buf_hdr_t *fhdr; 1224 uint32_t i; 1225 1226 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1227 ASSERT(hdr->b_birth != 0); 1228 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1229 1230 if (lockp != NULL) { 1231 *lockp = hash_lock; 1232 mutex_enter(hash_lock); 1233 } else { 1234 ASSERT(MUTEX_HELD(hash_lock)); 1235 } 1236 1237 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1238 fhdr = fhdr->b_hash_next, i++) { 1239 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1240 return (fhdr); 1241 } 1242 1243 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1244 buf_hash_table.ht_table[idx] = hdr; 1245 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1246 1247 /* collect some hash table performance data */ 1248 if (i > 0) { 1249 ARCSTAT_BUMP(arcstat_hash_collisions); 1250 if (i == 1) 1251 ARCSTAT_BUMP(arcstat_hash_chains); 1252 1253 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1254 } 1255 1256 ARCSTAT_BUMP(arcstat_hash_elements); 1257 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1258 1259 return (NULL); 1260} 1261 1262static void 1263buf_hash_remove(arc_buf_hdr_t *hdr) 1264{ 1265 arc_buf_hdr_t *fhdr, **hdrp; 1266 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1267 1268 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1269 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1270 1271 hdrp = &buf_hash_table.ht_table[idx]; 1272 while ((fhdr = *hdrp) != hdr) { 1273 ASSERT(fhdr != NULL); 1274 hdrp = &fhdr->b_hash_next; 1275 } 1276 *hdrp = hdr->b_hash_next; 1277 hdr->b_hash_next = NULL; 1278 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1279 1280 /* collect some hash table performance data */ 1281 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1282 1283 if (buf_hash_table.ht_table[idx] && 1284 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1285 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1286} 1287 1288/* 1289 * Global data structures and functions for the buf kmem cache. 1290 */ 1291static kmem_cache_t *hdr_full_cache; 1292static kmem_cache_t *hdr_l2only_cache; 1293static kmem_cache_t *buf_cache; 1294 1295static void 1296buf_fini(void) 1297{ 1298 int i; 1299 1300 kmem_free(buf_hash_table.ht_table, 1301 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1302 for (i = 0; i < BUF_LOCKS; i++) 1303 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1304 kmem_cache_destroy(hdr_full_cache); 1305 kmem_cache_destroy(hdr_l2only_cache); 1306 kmem_cache_destroy(buf_cache); 1307} 1308 1309/* 1310 * Constructor callback - called when the cache is empty 1311 * and a new buf is requested. 1312 */ 1313/* ARGSUSED */ 1314static int 1315hdr_full_cons(void *vbuf, void *unused, int kmflag) 1316{ 1317 arc_buf_hdr_t *hdr = vbuf; 1318 1319 bzero(hdr, HDR_FULL_SIZE); 1320 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1321 refcount_create(&hdr->b_l1hdr.b_refcnt); 1322 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1323 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1324 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1325 1326 return (0); 1327} 1328 1329/* ARGSUSED */ 1330static int 1331hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1332{ 1333 arc_buf_hdr_t *hdr = vbuf; 1334 1335 bzero(hdr, HDR_L2ONLY_SIZE); 1336 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1337 1338 return (0); 1339} 1340 1341/* ARGSUSED */ 1342static int 1343buf_cons(void *vbuf, void *unused, int kmflag) 1344{ 1345 arc_buf_t *buf = vbuf; 1346 1347 bzero(buf, sizeof (arc_buf_t)); 1348 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1349 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1350 1351 return (0); 1352} 1353 1354/* 1355 * Destructor callback - called when a cached buf is 1356 * no longer required. 1357 */ 1358/* ARGSUSED */ 1359static void 1360hdr_full_dest(void *vbuf, void *unused) 1361{ 1362 arc_buf_hdr_t *hdr = vbuf; 1363 1364 ASSERT(BUF_EMPTY(hdr)); 1365 cv_destroy(&hdr->b_l1hdr.b_cv); 1366 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1367 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1368 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1369 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1370} 1371 1372/* ARGSUSED */ 1373static void 1374hdr_l2only_dest(void *vbuf, void *unused) 1375{ 1376 arc_buf_hdr_t *hdr = vbuf; 1377 1378 ASSERT(BUF_EMPTY(hdr)); 1379 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1380} 1381 1382/* ARGSUSED */ 1383static void 1384buf_dest(void *vbuf, void *unused) 1385{ 1386 arc_buf_t *buf = vbuf; 1387 1388 mutex_destroy(&buf->b_evict_lock); 1389 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1390} 1391 1392/* 1393 * Reclaim callback -- invoked when memory is low. 1394 */ 1395/* ARGSUSED */ 1396static void 1397hdr_recl(void *unused) 1398{ 1399 dprintf("hdr_recl called\n"); 1400 /* 1401 * umem calls the reclaim func when we destroy the buf cache, 1402 * which is after we do arc_fini(). 1403 */ 1404 if (!arc_dead) 1405 cv_signal(&arc_reclaim_thread_cv); 1406} 1407 1408static void 1409buf_init(void) 1410{ 1411 uint64_t *ct; 1412 uint64_t hsize = 1ULL << 12; 1413 int i, j; 1414 1415 /* 1416 * The hash table is big enough to fill all of physical memory 1417 * with an average block size of zfs_arc_average_blocksize (default 8K). 1418 * By default, the table will take up 1419 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1420 */ 1421 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1422 hsize <<= 1; 1423retry: 1424 buf_hash_table.ht_mask = hsize - 1; 1425 buf_hash_table.ht_table = 1426 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1427 if (buf_hash_table.ht_table == NULL) { 1428 ASSERT(hsize > (1ULL << 8)); 1429 hsize >>= 1; 1430 goto retry; 1431 } 1432 1433 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1434 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1435 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1436 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1437 NULL, NULL, 0); 1438 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1439 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1440 1441 for (i = 0; i < 256; i++) 1442 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1443 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1444 1445 for (i = 0; i < BUF_LOCKS; i++) { 1446 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1447 NULL, MUTEX_DEFAULT, NULL); 1448 } 1449} 1450 1451/* 1452 * Transition between the two allocation states for the arc_buf_hdr struct. 1453 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1454 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1455 * version is used when a cache buffer is only in the L2ARC in order to reduce 1456 * memory usage. 1457 */ 1458static arc_buf_hdr_t * 1459arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1460{ 1461 ASSERT(HDR_HAS_L2HDR(hdr)); 1462 1463 arc_buf_hdr_t *nhdr; 1464 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1465 1466 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1467 (old == hdr_l2only_cache && new == hdr_full_cache)); 1468 1469 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1470 1471 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1472 buf_hash_remove(hdr); 1473 1474 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1475 1476 if (new == hdr_full_cache) { 1477 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1478 /* 1479 * arc_access and arc_change_state need to be aware that a 1480 * header has just come out of L2ARC, so we set its state to 1481 * l2c_only even though it's about to change. 1482 */ 1483 nhdr->b_l1hdr.b_state = arc_l2c_only; 1484 1485 /* Verify previous threads set to NULL before freeing */ 1486 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1487 } else { 1488 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1489 ASSERT0(hdr->b_l1hdr.b_datacnt); 1490 1491 /* 1492 * If we've reached here, We must have been called from 1493 * arc_evict_hdr(), as such we should have already been 1494 * removed from any ghost list we were previously on 1495 * (which protects us from racing with arc_evict_state), 1496 * thus no locking is needed during this check. 1497 */ 1498 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1499 1500 /* 1501 * A buffer must not be moved into the arc_l2c_only 1502 * state if it's not finished being written out to the 1503 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1504 * might try to be accessed, even though it was removed. 1505 */ 1506 VERIFY(!HDR_L2_WRITING(hdr)); 1507 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1508 1509#ifdef ZFS_DEBUG 1510 if (hdr->b_l1hdr.b_thawed != NULL) { 1511 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1512 hdr->b_l1hdr.b_thawed = NULL; 1513 } 1514#endif 1515 1516 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1517 } 1518 /* 1519 * The header has been reallocated so we need to re-insert it into any 1520 * lists it was on. 1521 */ 1522 (void) buf_hash_insert(nhdr, NULL); 1523 1524 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1525 1526 mutex_enter(&dev->l2ad_mtx); 1527 1528 /* 1529 * We must place the realloc'ed header back into the list at 1530 * the same spot. Otherwise, if it's placed earlier in the list, 1531 * l2arc_write_buffers() could find it during the function's 1532 * write phase, and try to write it out to the l2arc. 1533 */ 1534 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1535 list_remove(&dev->l2ad_buflist, hdr); 1536 1537 mutex_exit(&dev->l2ad_mtx); 1538 1539 /* 1540 * Since we're using the pointer address as the tag when 1541 * incrementing and decrementing the l2ad_alloc refcount, we 1542 * must remove the old pointer (that we're about to destroy) and 1543 * add the new pointer to the refcount. Otherwise we'd remove 1544 * the wrong pointer address when calling arc_hdr_destroy() later. 1545 */ 1546 1547 (void) refcount_remove_many(&dev->l2ad_alloc, 1548 hdr->b_l2hdr.b_asize, hdr); 1549 1550 (void) refcount_add_many(&dev->l2ad_alloc, 1551 nhdr->b_l2hdr.b_asize, nhdr); 1552 1553 buf_discard_identity(hdr); 1554 hdr->b_freeze_cksum = NULL; 1555 kmem_cache_free(old, hdr); 1556 1557 return (nhdr); 1558} 1559 1560 1561#define ARC_MINTIME (hz>>4) /* 62 ms */ 1562 1563static void 1564arc_cksum_verify(arc_buf_t *buf) 1565{ 1566 zio_cksum_t zc; 1567 1568 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1569 return; 1570 1571 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1572 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1573 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1574 return; 1575 } 1576 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1577 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1578 panic("buffer modified while frozen!"); 1579 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1580} 1581 1582static int 1583arc_cksum_equal(arc_buf_t *buf) 1584{ 1585 zio_cksum_t zc; 1586 int equal; 1587 1588 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1589 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1590 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1591 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1592 1593 return (equal); 1594} 1595 1596static void 1597arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1598{ 1599 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1600 return; 1601 1602 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1603 if (buf->b_hdr->b_freeze_cksum != NULL) { 1604 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1605 return; 1606 } 1607 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1608 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1609 NULL, buf->b_hdr->b_freeze_cksum); 1610 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1611#ifdef illumos 1612 arc_buf_watch(buf); 1613#endif 1614} 1615 1616#ifdef illumos 1617#ifndef _KERNEL 1618typedef struct procctl { 1619 long cmd; 1620 prwatch_t prwatch; 1621} procctl_t; 1622#endif 1623 1624/* ARGSUSED */ 1625static void 1626arc_buf_unwatch(arc_buf_t *buf) 1627{ 1628#ifndef _KERNEL 1629 if (arc_watch) { 1630 int result; 1631 procctl_t ctl; 1632 ctl.cmd = PCWATCH; 1633 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1634 ctl.prwatch.pr_size = 0; 1635 ctl.prwatch.pr_wflags = 0; 1636 result = write(arc_procfd, &ctl, sizeof (ctl)); 1637 ASSERT3U(result, ==, sizeof (ctl)); 1638 } 1639#endif 1640} 1641 1642/* ARGSUSED */ 1643static void 1644arc_buf_watch(arc_buf_t *buf) 1645{ 1646#ifndef _KERNEL 1647 if (arc_watch) { 1648 int result; 1649 procctl_t ctl; 1650 ctl.cmd = PCWATCH; 1651 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1652 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1653 ctl.prwatch.pr_wflags = WA_WRITE; 1654 result = write(arc_procfd, &ctl, sizeof (ctl)); 1655 ASSERT3U(result, ==, sizeof (ctl)); 1656 } 1657#endif 1658} 1659#endif /* illumos */ 1660 1661static arc_buf_contents_t 1662arc_buf_type(arc_buf_hdr_t *hdr) 1663{ 1664 if (HDR_ISTYPE_METADATA(hdr)) { 1665 return (ARC_BUFC_METADATA); 1666 } else { 1667 return (ARC_BUFC_DATA); 1668 } 1669} 1670 1671static uint32_t 1672arc_bufc_to_flags(arc_buf_contents_t type) 1673{ 1674 switch (type) { 1675 case ARC_BUFC_DATA: 1676 /* metadata field is 0 if buffer contains normal data */ 1677 return (0); 1678 case ARC_BUFC_METADATA: 1679 return (ARC_FLAG_BUFC_METADATA); 1680 default: 1681 break; 1682 } 1683 panic("undefined ARC buffer type!"); 1684 return ((uint32_t)-1); 1685} 1686 1687void 1688arc_buf_thaw(arc_buf_t *buf) 1689{ 1690 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1691 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1692 panic("modifying non-anon buffer!"); 1693 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1694 panic("modifying buffer while i/o in progress!"); 1695 arc_cksum_verify(buf); 1696 } 1697 1698 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1699 if (buf->b_hdr->b_freeze_cksum != NULL) { 1700 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1701 buf->b_hdr->b_freeze_cksum = NULL; 1702 } 1703 1704#ifdef ZFS_DEBUG 1705 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1706 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1707 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1708 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1709 } 1710#endif 1711 1712 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1713 1714#ifdef illumos 1715 arc_buf_unwatch(buf); 1716#endif 1717} 1718 1719void 1720arc_buf_freeze(arc_buf_t *buf) 1721{ 1722 kmutex_t *hash_lock; 1723 1724 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1725 return; 1726 1727 hash_lock = HDR_LOCK(buf->b_hdr); 1728 mutex_enter(hash_lock); 1729 1730 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1731 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1732 arc_cksum_compute(buf, B_FALSE); 1733 mutex_exit(hash_lock); 1734 1735} 1736 1737static void 1738add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1739{ 1740 ASSERT(HDR_HAS_L1HDR(hdr)); 1741 ASSERT(MUTEX_HELD(hash_lock)); 1742 arc_state_t *state = hdr->b_l1hdr.b_state; 1743 1744 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1745 (state != arc_anon)) { 1746 /* We don't use the L2-only state list. */ 1747 if (state != arc_l2c_only) { 1748 arc_buf_contents_t type = arc_buf_type(hdr); 1749 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1750 multilist_t *list = &state->arcs_list[type]; 1751 uint64_t *size = &state->arcs_lsize[type]; 1752 1753 multilist_remove(list, hdr); 1754 1755 if (GHOST_STATE(state)) { 1756 ASSERT0(hdr->b_l1hdr.b_datacnt); 1757 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1758 delta = hdr->b_size; 1759 } 1760 ASSERT(delta > 0); 1761 ASSERT3U(*size, >=, delta); 1762 atomic_add_64(size, -delta); 1763 } 1764 /* remove the prefetch flag if we get a reference */ 1765 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1766 } 1767} 1768 1769static int 1770remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1771{ 1772 int cnt; 1773 arc_state_t *state = hdr->b_l1hdr.b_state; 1774 1775 ASSERT(HDR_HAS_L1HDR(hdr)); 1776 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1777 ASSERT(!GHOST_STATE(state)); 1778 1779 /* 1780 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1781 * check to prevent usage of the arc_l2c_only list. 1782 */ 1783 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1784 (state != arc_anon)) { 1785 arc_buf_contents_t type = arc_buf_type(hdr); 1786 multilist_t *list = &state->arcs_list[type]; 1787 uint64_t *size = &state->arcs_lsize[type]; 1788 1789 multilist_insert(list, hdr); 1790 1791 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1792 atomic_add_64(size, hdr->b_size * 1793 hdr->b_l1hdr.b_datacnt); 1794 } 1795 return (cnt); 1796} 1797 1798/* 1799 * Move the supplied buffer to the indicated state. The hash lock 1800 * for the buffer must be held by the caller. 1801 */ 1802static void 1803arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1804 kmutex_t *hash_lock) 1805{ 1806 arc_state_t *old_state; 1807 int64_t refcnt; 1808 uint32_t datacnt; 1809 uint64_t from_delta, to_delta; 1810 arc_buf_contents_t buftype = arc_buf_type(hdr); 1811 1812 /* 1813 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1814 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1815 * L1 hdr doesn't always exist when we change state to arc_anon before 1816 * destroying a header, in which case reallocating to add the L1 hdr is 1817 * pointless. 1818 */ 1819 if (HDR_HAS_L1HDR(hdr)) { 1820 old_state = hdr->b_l1hdr.b_state; 1821 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1822 datacnt = hdr->b_l1hdr.b_datacnt; 1823 } else { 1824 old_state = arc_l2c_only; 1825 refcnt = 0; 1826 datacnt = 0; 1827 } 1828 1829 ASSERT(MUTEX_HELD(hash_lock)); 1830 ASSERT3P(new_state, !=, old_state); 1831 ASSERT(refcnt == 0 || datacnt > 0); 1832 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1833 ASSERT(old_state != arc_anon || datacnt <= 1); 1834 1835 from_delta = to_delta = datacnt * hdr->b_size; 1836 1837 /* 1838 * If this buffer is evictable, transfer it from the 1839 * old state list to the new state list. 1840 */ 1841 if (refcnt == 0) { 1842 if (old_state != arc_anon && old_state != arc_l2c_only) { 1843 uint64_t *size = &old_state->arcs_lsize[buftype]; 1844 1845 ASSERT(HDR_HAS_L1HDR(hdr)); 1846 multilist_remove(&old_state->arcs_list[buftype], hdr); 1847 1848 /* 1849 * If prefetching out of the ghost cache, 1850 * we will have a non-zero datacnt. 1851 */ 1852 if (GHOST_STATE(old_state) && datacnt == 0) { 1853 /* ghost elements have a ghost size */ 1854 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1855 from_delta = hdr->b_size; 1856 } 1857 ASSERT3U(*size, >=, from_delta); 1858 atomic_add_64(size, -from_delta); 1859 } 1860 if (new_state != arc_anon && new_state != arc_l2c_only) { 1861 uint64_t *size = &new_state->arcs_lsize[buftype]; 1862 1863 /* 1864 * An L1 header always exists here, since if we're 1865 * moving to some L1-cached state (i.e. not l2c_only or 1866 * anonymous), we realloc the header to add an L1hdr 1867 * beforehand. 1868 */ 1869 ASSERT(HDR_HAS_L1HDR(hdr)); 1870 multilist_insert(&new_state->arcs_list[buftype], hdr); 1871 1872 /* ghost elements have a ghost size */ 1873 if (GHOST_STATE(new_state)) { 1874 ASSERT0(datacnt); 1875 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1876 to_delta = hdr->b_size; 1877 } 1878 atomic_add_64(size, to_delta); 1879 } 1880 } 1881 1882 ASSERT(!BUF_EMPTY(hdr)); 1883 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1884 buf_hash_remove(hdr); 1885 1886 /* adjust state sizes (ignore arc_l2c_only) */ 1887 1888 if (to_delta && new_state != arc_l2c_only) { 1889 ASSERT(HDR_HAS_L1HDR(hdr)); 1890 if (GHOST_STATE(new_state)) { 1891 ASSERT0(datacnt); 1892 1893 /* 1894 * We moving a header to a ghost state, we first 1895 * remove all arc buffers. Thus, we'll have a 1896 * datacnt of zero, and no arc buffer to use for 1897 * the reference. As a result, we use the arc 1898 * header pointer for the reference. 1899 */ 1900 (void) refcount_add_many(&new_state->arcs_size, 1901 hdr->b_size, hdr); 1902 } else { 1903 ASSERT3U(datacnt, !=, 0); 1904 1905 /* 1906 * Each individual buffer holds a unique reference, 1907 * thus we must remove each of these references one 1908 * at a time. 1909 */ 1910 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1911 buf = buf->b_next) { 1912 (void) refcount_add_many(&new_state->arcs_size, 1913 hdr->b_size, buf); 1914 } 1915 } 1916 } 1917 1918 if (from_delta && old_state != arc_l2c_only) { 1919 ASSERT(HDR_HAS_L1HDR(hdr)); 1920 if (GHOST_STATE(old_state)) { 1921 /* 1922 * When moving a header off of a ghost state, 1923 * there's the possibility for datacnt to be 1924 * non-zero. This is because we first add the 1925 * arc buffer to the header prior to changing 1926 * the header's state. Since we used the header 1927 * for the reference when putting the header on 1928 * the ghost state, we must balance that and use 1929 * the header when removing off the ghost state 1930 * (even though datacnt is non zero). 1931 */ 1932 1933 IMPLY(datacnt == 0, new_state == arc_anon || 1934 new_state == arc_l2c_only); 1935 1936 (void) refcount_remove_many(&old_state->arcs_size, 1937 hdr->b_size, hdr); 1938 } else { 1939 ASSERT3P(datacnt, !=, 0); 1940 1941 /* 1942 * Each individual buffer holds a unique reference, 1943 * thus we must remove each of these references one 1944 * at a time. 1945 */ 1946 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1947 buf = buf->b_next) { 1948 (void) refcount_remove_many( 1949 &old_state->arcs_size, hdr->b_size, buf); 1950 } 1951 } 1952 } 1953 1954 if (HDR_HAS_L1HDR(hdr)) 1955 hdr->b_l1hdr.b_state = new_state; 1956 1957 /* 1958 * L2 headers should never be on the L2 state list since they don't 1959 * have L1 headers allocated. 1960 */ 1961 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1962 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1963} 1964 1965void 1966arc_space_consume(uint64_t space, arc_space_type_t type) 1967{ 1968 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1969 1970 switch (type) { 1971 case ARC_SPACE_DATA: 1972 ARCSTAT_INCR(arcstat_data_size, space); 1973 break; 1974 case ARC_SPACE_META: 1975 ARCSTAT_INCR(arcstat_metadata_size, space); 1976 break; 1977 case ARC_SPACE_OTHER: 1978 ARCSTAT_INCR(arcstat_other_size, space); 1979 break; 1980 case ARC_SPACE_HDRS: 1981 ARCSTAT_INCR(arcstat_hdr_size, space); 1982 break; 1983 case ARC_SPACE_L2HDRS: 1984 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1985 break; 1986 } 1987 1988 if (type != ARC_SPACE_DATA) 1989 ARCSTAT_INCR(arcstat_meta_used, space); 1990 1991 atomic_add_64(&arc_size, space); 1992} 1993 1994void 1995arc_space_return(uint64_t space, arc_space_type_t type) 1996{ 1997 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1998 1999 switch (type) { 2000 case ARC_SPACE_DATA: 2001 ARCSTAT_INCR(arcstat_data_size, -space); 2002 break; 2003 case ARC_SPACE_META: 2004 ARCSTAT_INCR(arcstat_metadata_size, -space); 2005 break; 2006 case ARC_SPACE_OTHER: 2007 ARCSTAT_INCR(arcstat_other_size, -space); 2008 break; 2009 case ARC_SPACE_HDRS: 2010 ARCSTAT_INCR(arcstat_hdr_size, -space); 2011 break; 2012 case ARC_SPACE_L2HDRS: 2013 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2014 break; 2015 } 2016 2017 if (type != ARC_SPACE_DATA) { 2018 ASSERT(arc_meta_used >= space); 2019 if (arc_meta_max < arc_meta_used) 2020 arc_meta_max = arc_meta_used; 2021 ARCSTAT_INCR(arcstat_meta_used, -space); 2022 } 2023 2024 ASSERT(arc_size >= space); 2025 atomic_add_64(&arc_size, -space); 2026} 2027 2028arc_buf_t * 2029arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2030{ 2031 arc_buf_hdr_t *hdr; 2032 arc_buf_t *buf; 2033 2034 ASSERT3U(size, >, 0); 2035 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2036 ASSERT(BUF_EMPTY(hdr)); 2037 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2038 hdr->b_size = size; 2039 hdr->b_spa = spa_load_guid(spa); 2040 2041 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2042 buf->b_hdr = hdr; 2043 buf->b_data = NULL; 2044 buf->b_efunc = NULL; 2045 buf->b_private = NULL; 2046 buf->b_next = NULL; 2047 2048 hdr->b_flags = arc_bufc_to_flags(type); 2049 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2050 2051 hdr->b_l1hdr.b_buf = buf; 2052 hdr->b_l1hdr.b_state = arc_anon; 2053 hdr->b_l1hdr.b_arc_access = 0; 2054 hdr->b_l1hdr.b_datacnt = 1; 2055 hdr->b_l1hdr.b_tmp_cdata = NULL; 2056 2057 arc_get_data_buf(buf); 2058 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2059 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2060 2061 return (buf); 2062} 2063 2064static char *arc_onloan_tag = "onloan"; 2065 2066/* 2067 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2068 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2069 * buffers must be returned to the arc before they can be used by the DMU or 2070 * freed. 2071 */ 2072arc_buf_t * 2073arc_loan_buf(spa_t *spa, int size) 2074{ 2075 arc_buf_t *buf; 2076 2077 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2078 2079 atomic_add_64(&arc_loaned_bytes, size); 2080 return (buf); 2081} 2082 2083/* 2084 * Return a loaned arc buffer to the arc. 2085 */ 2086void 2087arc_return_buf(arc_buf_t *buf, void *tag) 2088{ 2089 arc_buf_hdr_t *hdr = buf->b_hdr; 2090 2091 ASSERT(buf->b_data != NULL); 2092 ASSERT(HDR_HAS_L1HDR(hdr)); 2093 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2094 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2095 2096 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2097} 2098 2099/* Detach an arc_buf from a dbuf (tag) */ 2100void 2101arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2102{ 2103 arc_buf_hdr_t *hdr = buf->b_hdr; 2104 2105 ASSERT(buf->b_data != NULL); 2106 ASSERT(HDR_HAS_L1HDR(hdr)); 2107 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2108 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2109 buf->b_efunc = NULL; 2110 buf->b_private = NULL; 2111 2112 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2113} 2114 2115static arc_buf_t * 2116arc_buf_clone(arc_buf_t *from) 2117{ 2118 arc_buf_t *buf; 2119 arc_buf_hdr_t *hdr = from->b_hdr; 2120 uint64_t size = hdr->b_size; 2121 2122 ASSERT(HDR_HAS_L1HDR(hdr)); 2123 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2124 2125 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2126 buf->b_hdr = hdr; 2127 buf->b_data = NULL; 2128 buf->b_efunc = NULL; 2129 buf->b_private = NULL; 2130 buf->b_next = hdr->b_l1hdr.b_buf; 2131 hdr->b_l1hdr.b_buf = buf; 2132 arc_get_data_buf(buf); 2133 bcopy(from->b_data, buf->b_data, size); 2134 2135 /* 2136 * This buffer already exists in the arc so create a duplicate 2137 * copy for the caller. If the buffer is associated with user data 2138 * then track the size and number of duplicates. These stats will be 2139 * updated as duplicate buffers are created and destroyed. 2140 */ 2141 if (HDR_ISTYPE_DATA(hdr)) { 2142 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2143 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2144 } 2145 hdr->b_l1hdr.b_datacnt += 1; 2146 return (buf); 2147} 2148 2149void 2150arc_buf_add_ref(arc_buf_t *buf, void* tag) 2151{ 2152 arc_buf_hdr_t *hdr; 2153 kmutex_t *hash_lock; 2154 2155 /* 2156 * Check to see if this buffer is evicted. Callers 2157 * must verify b_data != NULL to know if the add_ref 2158 * was successful. 2159 */ 2160 mutex_enter(&buf->b_evict_lock); 2161 if (buf->b_data == NULL) { 2162 mutex_exit(&buf->b_evict_lock); 2163 return; 2164 } 2165 hash_lock = HDR_LOCK(buf->b_hdr); 2166 mutex_enter(hash_lock); 2167 hdr = buf->b_hdr; 2168 ASSERT(HDR_HAS_L1HDR(hdr)); 2169 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2170 mutex_exit(&buf->b_evict_lock); 2171 2172 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2173 hdr->b_l1hdr.b_state == arc_mfu); 2174 2175 add_reference(hdr, hash_lock, tag); 2176 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2177 arc_access(hdr, hash_lock); 2178 mutex_exit(hash_lock); 2179 ARCSTAT_BUMP(arcstat_hits); 2180 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2181 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2182 data, metadata, hits); 2183} 2184 2185static void 2186arc_buf_free_on_write(void *data, size_t size, 2187 void (*free_func)(void *, size_t)) 2188{ 2189 l2arc_data_free_t *df; 2190 2191 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2192 df->l2df_data = data; 2193 df->l2df_size = size; 2194 df->l2df_func = free_func; 2195 mutex_enter(&l2arc_free_on_write_mtx); 2196 list_insert_head(l2arc_free_on_write, df); 2197 mutex_exit(&l2arc_free_on_write_mtx); 2198} 2199 2200/* 2201 * Free the arc data buffer. If it is an l2arc write in progress, 2202 * the buffer is placed on l2arc_free_on_write to be freed later. 2203 */ 2204static void 2205arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2206{ 2207 arc_buf_hdr_t *hdr = buf->b_hdr; 2208 2209 if (HDR_L2_WRITING(hdr)) { 2210 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2211 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2212 } else { 2213 free_func(buf->b_data, hdr->b_size); 2214 } 2215} 2216 2217static void 2218arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2219{ 2220 size_t align, asize, len; 2221 2222 ASSERT(HDR_HAS_L2HDR(hdr)); 2223 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2224 2225 /* 2226 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2227 * that doesn't exist, the header is in the arc_l2c_only state, 2228 * and there isn't anything to free (it's already been freed). 2229 */ 2230 if (!HDR_HAS_L1HDR(hdr)) 2231 return; 2232 2233 /* 2234 * The header isn't being written to the l2arc device, thus it 2235 * shouldn't have a b_tmp_cdata to free. 2236 */ 2237 if (!HDR_L2_WRITING(hdr)) { 2238 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2239 return; 2240 } 2241 2242 /* 2243 * The bufer has been chosen for writing to L2ARC, but it's 2244 * not being written just yet. In other words, 2245 * b_tmp_cdata points to exactly the same buffer as b_data, 2246 * l2arc_transform_buf hasn't been called. 2247 */ 2248 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) { 2249 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, 2250 hdr->b_l1hdr.b_buf->b_data); 2251 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_OFF); 2252 hdr->b_l1hdr.b_tmp_cdata = NULL; 2253 return; 2254 } 2255 2256 /* 2257 * There's nothing to free since the buffer was all zero's and 2258 * compressed to a zero length buffer. 2259 */ 2260 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2261 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2262 return; 2263 } 2264 2265 /* 2266 * Nothing to do if the temporary buffer was not required. 2267 */ 2268 if (hdr->b_l1hdr.b_tmp_cdata == NULL) 2269 return; 2270 2271 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2272 len = hdr->b_size; 2273 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 2274 asize = P2ROUNDUP(len, align); 2275 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, asize, 2276 zio_data_buf_free); 2277 hdr->b_l1hdr.b_tmp_cdata = NULL; 2278} 2279 2280/* 2281 * Free up buf->b_data and if 'remove' is set, then pull the 2282 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2283 */ 2284static void 2285arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2286{ 2287 arc_buf_t **bufp; 2288 2289 /* free up data associated with the buf */ 2290 if (buf->b_data != NULL) { 2291 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2292 uint64_t size = buf->b_hdr->b_size; 2293 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2294 2295 arc_cksum_verify(buf); 2296#ifdef illumos 2297 arc_buf_unwatch(buf); 2298#endif 2299 2300 if (type == ARC_BUFC_METADATA) { 2301 arc_buf_data_free(buf, zio_buf_free); 2302 arc_space_return(size, ARC_SPACE_META); 2303 } else { 2304 ASSERT(type == ARC_BUFC_DATA); 2305 arc_buf_data_free(buf, zio_data_buf_free); 2306 arc_space_return(size, ARC_SPACE_DATA); 2307 } 2308 2309 /* protected by hash lock, if in the hash table */ 2310 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2311 uint64_t *cnt = &state->arcs_lsize[type]; 2312 2313 ASSERT(refcount_is_zero( 2314 &buf->b_hdr->b_l1hdr.b_refcnt)); 2315 ASSERT(state != arc_anon && state != arc_l2c_only); 2316 2317 ASSERT3U(*cnt, >=, size); 2318 atomic_add_64(cnt, -size); 2319 } 2320 2321 (void) refcount_remove_many(&state->arcs_size, size, buf); 2322 buf->b_data = NULL; 2323 2324 /* 2325 * If we're destroying a duplicate buffer make sure 2326 * that the appropriate statistics are updated. 2327 */ 2328 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2329 HDR_ISTYPE_DATA(buf->b_hdr)) { 2330 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2331 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2332 } 2333 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2334 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2335 } 2336 2337 /* only remove the buf if requested */ 2338 if (!remove) 2339 return; 2340 2341 /* remove the buf from the hdr list */ 2342 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2343 bufp = &(*bufp)->b_next) 2344 continue; 2345 *bufp = buf->b_next; 2346 buf->b_next = NULL; 2347 2348 ASSERT(buf->b_efunc == NULL); 2349 2350 /* clean up the buf */ 2351 buf->b_hdr = NULL; 2352 kmem_cache_free(buf_cache, buf); 2353} 2354 2355static void 2356arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2357{ 2358 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2359 l2arc_dev_t *dev = l2hdr->b_dev; 2360 2361 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2362 ASSERT(HDR_HAS_L2HDR(hdr)); 2363 2364 list_remove(&dev->l2ad_buflist, hdr); 2365 2366 /* 2367 * We don't want to leak the b_tmp_cdata buffer that was 2368 * allocated in l2arc_write_buffers() 2369 */ 2370 arc_buf_l2_cdata_free(hdr); 2371 2372 /* 2373 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2374 * this header is being processed by l2arc_write_buffers() (i.e. 2375 * it's in the first stage of l2arc_write_buffers()). 2376 * Re-affirming that truth here, just to serve as a reminder. If 2377 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2378 * may not have its HDR_L2_WRITING flag set. (the write may have 2379 * completed, in which case HDR_L2_WRITING will be false and the 2380 * b_daddr field will point to the address of the buffer on disk). 2381 */ 2382 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2383 2384 /* 2385 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2386 * l2arc_write_buffers(). Since we've just removed this header 2387 * from the l2arc buffer list, this header will never reach the 2388 * second stage of l2arc_write_buffers(), which increments the 2389 * accounting stats for this header. Thus, we must be careful 2390 * not to decrement them for this header either. 2391 */ 2392 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2393 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2394 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2395 2396 vdev_space_update(dev->l2ad_vdev, 2397 -l2hdr->b_asize, 0, 0); 2398 2399 (void) refcount_remove_many(&dev->l2ad_alloc, 2400 l2hdr->b_asize, hdr); 2401 } 2402 2403 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2404} 2405 2406static void 2407arc_hdr_destroy(arc_buf_hdr_t *hdr) 2408{ 2409 if (HDR_HAS_L1HDR(hdr)) { 2410 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2411 hdr->b_l1hdr.b_datacnt > 0); 2412 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2413 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2414 } 2415 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2416 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2417 2418 if (HDR_HAS_L2HDR(hdr)) { 2419 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2420 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2421 2422 if (!buflist_held) 2423 mutex_enter(&dev->l2ad_mtx); 2424 2425 /* 2426 * Even though we checked this conditional above, we 2427 * need to check this again now that we have the 2428 * l2ad_mtx. This is because we could be racing with 2429 * another thread calling l2arc_evict() which might have 2430 * destroyed this header's L2 portion as we were waiting 2431 * to acquire the l2ad_mtx. If that happens, we don't 2432 * want to re-destroy the header's L2 portion. 2433 */ 2434 if (HDR_HAS_L2HDR(hdr)) { 2435 l2arc_trim(hdr); 2436 arc_hdr_l2hdr_destroy(hdr); 2437 } 2438 2439 if (!buflist_held) 2440 mutex_exit(&dev->l2ad_mtx); 2441 } 2442 2443 if (!BUF_EMPTY(hdr)) 2444 buf_discard_identity(hdr); 2445 2446 if (hdr->b_freeze_cksum != NULL) { 2447 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2448 hdr->b_freeze_cksum = NULL; 2449 } 2450 2451 if (HDR_HAS_L1HDR(hdr)) { 2452 while (hdr->b_l1hdr.b_buf) { 2453 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2454 2455 if (buf->b_efunc != NULL) { 2456 mutex_enter(&arc_user_evicts_lock); 2457 mutex_enter(&buf->b_evict_lock); 2458 ASSERT(buf->b_hdr != NULL); 2459 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2460 hdr->b_l1hdr.b_buf = buf->b_next; 2461 buf->b_hdr = &arc_eviction_hdr; 2462 buf->b_next = arc_eviction_list; 2463 arc_eviction_list = buf; 2464 mutex_exit(&buf->b_evict_lock); 2465 cv_signal(&arc_user_evicts_cv); 2466 mutex_exit(&arc_user_evicts_lock); 2467 } else { 2468 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2469 } 2470 } 2471#ifdef ZFS_DEBUG 2472 if (hdr->b_l1hdr.b_thawed != NULL) { 2473 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2474 hdr->b_l1hdr.b_thawed = NULL; 2475 } 2476#endif 2477 } 2478 2479 ASSERT3P(hdr->b_hash_next, ==, NULL); 2480 if (HDR_HAS_L1HDR(hdr)) { 2481 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2482 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2483 kmem_cache_free(hdr_full_cache, hdr); 2484 } else { 2485 kmem_cache_free(hdr_l2only_cache, hdr); 2486 } 2487} 2488 2489void 2490arc_buf_free(arc_buf_t *buf, void *tag) 2491{ 2492 arc_buf_hdr_t *hdr = buf->b_hdr; 2493 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2494 2495 ASSERT(buf->b_efunc == NULL); 2496 ASSERT(buf->b_data != NULL); 2497 2498 if (hashed) { 2499 kmutex_t *hash_lock = HDR_LOCK(hdr); 2500 2501 mutex_enter(hash_lock); 2502 hdr = buf->b_hdr; 2503 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2504 2505 (void) remove_reference(hdr, hash_lock, tag); 2506 if (hdr->b_l1hdr.b_datacnt > 1) { 2507 arc_buf_destroy(buf, TRUE); 2508 } else { 2509 ASSERT(buf == hdr->b_l1hdr.b_buf); 2510 ASSERT(buf->b_efunc == NULL); 2511 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2512 } 2513 mutex_exit(hash_lock); 2514 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2515 int destroy_hdr; 2516 /* 2517 * We are in the middle of an async write. Don't destroy 2518 * this buffer unless the write completes before we finish 2519 * decrementing the reference count. 2520 */ 2521 mutex_enter(&arc_user_evicts_lock); 2522 (void) remove_reference(hdr, NULL, tag); 2523 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2524 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2525 mutex_exit(&arc_user_evicts_lock); 2526 if (destroy_hdr) 2527 arc_hdr_destroy(hdr); 2528 } else { 2529 if (remove_reference(hdr, NULL, tag) > 0) 2530 arc_buf_destroy(buf, TRUE); 2531 else 2532 arc_hdr_destroy(hdr); 2533 } 2534} 2535 2536boolean_t 2537arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2538{ 2539 arc_buf_hdr_t *hdr = buf->b_hdr; 2540 kmutex_t *hash_lock = HDR_LOCK(hdr); 2541 boolean_t no_callback = (buf->b_efunc == NULL); 2542 2543 if (hdr->b_l1hdr.b_state == arc_anon) { 2544 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2545 arc_buf_free(buf, tag); 2546 return (no_callback); 2547 } 2548 2549 mutex_enter(hash_lock); 2550 hdr = buf->b_hdr; 2551 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2552 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2553 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2554 ASSERT(buf->b_data != NULL); 2555 2556 (void) remove_reference(hdr, hash_lock, tag); 2557 if (hdr->b_l1hdr.b_datacnt > 1) { 2558 if (no_callback) 2559 arc_buf_destroy(buf, TRUE); 2560 } else if (no_callback) { 2561 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2562 ASSERT(buf->b_efunc == NULL); 2563 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2564 } 2565 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2566 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2567 mutex_exit(hash_lock); 2568 return (no_callback); 2569} 2570 2571int32_t 2572arc_buf_size(arc_buf_t *buf) 2573{ 2574 return (buf->b_hdr->b_size); 2575} 2576 2577/* 2578 * Called from the DMU to determine if the current buffer should be 2579 * evicted. In order to ensure proper locking, the eviction must be initiated 2580 * from the DMU. Return true if the buffer is associated with user data and 2581 * duplicate buffers still exist. 2582 */ 2583boolean_t 2584arc_buf_eviction_needed(arc_buf_t *buf) 2585{ 2586 arc_buf_hdr_t *hdr; 2587 boolean_t evict_needed = B_FALSE; 2588 2589 if (zfs_disable_dup_eviction) 2590 return (B_FALSE); 2591 2592 mutex_enter(&buf->b_evict_lock); 2593 hdr = buf->b_hdr; 2594 if (hdr == NULL) { 2595 /* 2596 * We are in arc_do_user_evicts(); let that function 2597 * perform the eviction. 2598 */ 2599 ASSERT(buf->b_data == NULL); 2600 mutex_exit(&buf->b_evict_lock); 2601 return (B_FALSE); 2602 } else if (buf->b_data == NULL) { 2603 /* 2604 * We have already been added to the arc eviction list; 2605 * recommend eviction. 2606 */ 2607 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2608 mutex_exit(&buf->b_evict_lock); 2609 return (B_TRUE); 2610 } 2611 2612 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2613 evict_needed = B_TRUE; 2614 2615 mutex_exit(&buf->b_evict_lock); 2616 return (evict_needed); 2617} 2618 2619/* 2620 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2621 * state of the header is dependent on it's state prior to entering this 2622 * function. The following transitions are possible: 2623 * 2624 * - arc_mru -> arc_mru_ghost 2625 * - arc_mfu -> arc_mfu_ghost 2626 * - arc_mru_ghost -> arc_l2c_only 2627 * - arc_mru_ghost -> deleted 2628 * - arc_mfu_ghost -> arc_l2c_only 2629 * - arc_mfu_ghost -> deleted 2630 */ 2631static int64_t 2632arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2633{ 2634 arc_state_t *evicted_state, *state; 2635 int64_t bytes_evicted = 0; 2636 2637 ASSERT(MUTEX_HELD(hash_lock)); 2638 ASSERT(HDR_HAS_L1HDR(hdr)); 2639 2640 state = hdr->b_l1hdr.b_state; 2641 if (GHOST_STATE(state)) { 2642 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2643 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2644 2645 /* 2646 * l2arc_write_buffers() relies on a header's L1 portion 2647 * (i.e. it's b_tmp_cdata field) during it's write phase. 2648 * Thus, we cannot push a header onto the arc_l2c_only 2649 * state (removing it's L1 piece) until the header is 2650 * done being written to the l2arc. 2651 */ 2652 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2653 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2654 return (bytes_evicted); 2655 } 2656 2657 ARCSTAT_BUMP(arcstat_deleted); 2658 bytes_evicted += hdr->b_size; 2659 2660 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2661 2662 if (HDR_HAS_L2HDR(hdr)) { 2663 /* 2664 * This buffer is cached on the 2nd Level ARC; 2665 * don't destroy the header. 2666 */ 2667 arc_change_state(arc_l2c_only, hdr, hash_lock); 2668 /* 2669 * dropping from L1+L2 cached to L2-only, 2670 * realloc to remove the L1 header. 2671 */ 2672 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2673 hdr_l2only_cache); 2674 } else { 2675 arc_change_state(arc_anon, hdr, hash_lock); 2676 arc_hdr_destroy(hdr); 2677 } 2678 return (bytes_evicted); 2679 } 2680 2681 ASSERT(state == arc_mru || state == arc_mfu); 2682 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2683 2684 /* prefetch buffers have a minimum lifespan */ 2685 if (HDR_IO_IN_PROGRESS(hdr) || 2686 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2687 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2688 arc_min_prefetch_lifespan)) { 2689 ARCSTAT_BUMP(arcstat_evict_skip); 2690 return (bytes_evicted); 2691 } 2692 2693 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2694 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2695 while (hdr->b_l1hdr.b_buf) { 2696 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2697 if (!mutex_tryenter(&buf->b_evict_lock)) { 2698 ARCSTAT_BUMP(arcstat_mutex_miss); 2699 break; 2700 } 2701 if (buf->b_data != NULL) 2702 bytes_evicted += hdr->b_size; 2703 if (buf->b_efunc != NULL) { 2704 mutex_enter(&arc_user_evicts_lock); 2705 arc_buf_destroy(buf, FALSE); 2706 hdr->b_l1hdr.b_buf = buf->b_next; 2707 buf->b_hdr = &arc_eviction_hdr; 2708 buf->b_next = arc_eviction_list; 2709 arc_eviction_list = buf; 2710 cv_signal(&arc_user_evicts_cv); 2711 mutex_exit(&arc_user_evicts_lock); 2712 mutex_exit(&buf->b_evict_lock); 2713 } else { 2714 mutex_exit(&buf->b_evict_lock); 2715 arc_buf_destroy(buf, TRUE); 2716 } 2717 } 2718 2719 if (HDR_HAS_L2HDR(hdr)) { 2720 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2721 } else { 2722 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2723 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2724 else 2725 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2726 } 2727 2728 if (hdr->b_l1hdr.b_datacnt == 0) { 2729 arc_change_state(evicted_state, hdr, hash_lock); 2730 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2731 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2732 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2733 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2734 } 2735 2736 return (bytes_evicted); 2737} 2738 2739static uint64_t 2740arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2741 uint64_t spa, int64_t bytes) 2742{ 2743 multilist_sublist_t *mls; 2744 uint64_t bytes_evicted = 0; 2745 arc_buf_hdr_t *hdr; 2746 kmutex_t *hash_lock; 2747 int evict_count = 0; 2748 2749 ASSERT3P(marker, !=, NULL); 2750 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2751 2752 mls = multilist_sublist_lock(ml, idx); 2753 2754 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2755 hdr = multilist_sublist_prev(mls, marker)) { 2756 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2757 (evict_count >= zfs_arc_evict_batch_limit)) 2758 break; 2759 2760 /* 2761 * To keep our iteration location, move the marker 2762 * forward. Since we're not holding hdr's hash lock, we 2763 * must be very careful and not remove 'hdr' from the 2764 * sublist. Otherwise, other consumers might mistake the 2765 * 'hdr' as not being on a sublist when they call the 2766 * multilist_link_active() function (they all rely on 2767 * the hash lock protecting concurrent insertions and 2768 * removals). multilist_sublist_move_forward() was 2769 * specifically implemented to ensure this is the case 2770 * (only 'marker' will be removed and re-inserted). 2771 */ 2772 multilist_sublist_move_forward(mls, marker); 2773 2774 /* 2775 * The only case where the b_spa field should ever be 2776 * zero, is the marker headers inserted by 2777 * arc_evict_state(). It's possible for multiple threads 2778 * to be calling arc_evict_state() concurrently (e.g. 2779 * dsl_pool_close() and zio_inject_fault()), so we must 2780 * skip any markers we see from these other threads. 2781 */ 2782 if (hdr->b_spa == 0) 2783 continue; 2784 2785 /* we're only interested in evicting buffers of a certain spa */ 2786 if (spa != 0 && hdr->b_spa != spa) { 2787 ARCSTAT_BUMP(arcstat_evict_skip); 2788 continue; 2789 } 2790 2791 hash_lock = HDR_LOCK(hdr); 2792 2793 /* 2794 * We aren't calling this function from any code path 2795 * that would already be holding a hash lock, so we're 2796 * asserting on this assumption to be defensive in case 2797 * this ever changes. Without this check, it would be 2798 * possible to incorrectly increment arcstat_mutex_miss 2799 * below (e.g. if the code changed such that we called 2800 * this function with a hash lock held). 2801 */ 2802 ASSERT(!MUTEX_HELD(hash_lock)); 2803 2804 if (mutex_tryenter(hash_lock)) { 2805 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2806 mutex_exit(hash_lock); 2807 2808 bytes_evicted += evicted; 2809 2810 /* 2811 * If evicted is zero, arc_evict_hdr() must have 2812 * decided to skip this header, don't increment 2813 * evict_count in this case. 2814 */ 2815 if (evicted != 0) 2816 evict_count++; 2817 2818 /* 2819 * If arc_size isn't overflowing, signal any 2820 * threads that might happen to be waiting. 2821 * 2822 * For each header evicted, we wake up a single 2823 * thread. If we used cv_broadcast, we could 2824 * wake up "too many" threads causing arc_size 2825 * to significantly overflow arc_c; since 2826 * arc_get_data_buf() doesn't check for overflow 2827 * when it's woken up (it doesn't because it's 2828 * possible for the ARC to be overflowing while 2829 * full of un-evictable buffers, and the 2830 * function should proceed in this case). 2831 * 2832 * If threads are left sleeping, due to not 2833 * using cv_broadcast, they will be woken up 2834 * just before arc_reclaim_thread() sleeps. 2835 */ 2836 mutex_enter(&arc_reclaim_lock); 2837 if (!arc_is_overflowing()) 2838 cv_signal(&arc_reclaim_waiters_cv); 2839 mutex_exit(&arc_reclaim_lock); 2840 } else { 2841 ARCSTAT_BUMP(arcstat_mutex_miss); 2842 } 2843 } 2844 2845 multilist_sublist_unlock(mls); 2846 2847 return (bytes_evicted); 2848} 2849 2850/* 2851 * Evict buffers from the given arc state, until we've removed the 2852 * specified number of bytes. Move the removed buffers to the 2853 * appropriate evict state. 2854 * 2855 * This function makes a "best effort". It skips over any buffers 2856 * it can't get a hash_lock on, and so, may not catch all candidates. 2857 * It may also return without evicting as much space as requested. 2858 * 2859 * If bytes is specified using the special value ARC_EVICT_ALL, this 2860 * will evict all available (i.e. unlocked and evictable) buffers from 2861 * the given arc state; which is used by arc_flush(). 2862 */ 2863static uint64_t 2864arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2865 arc_buf_contents_t type) 2866{ 2867 uint64_t total_evicted = 0; 2868 multilist_t *ml = &state->arcs_list[type]; 2869 int num_sublists; 2870 arc_buf_hdr_t **markers; 2871 2872 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2873 2874 num_sublists = multilist_get_num_sublists(ml); 2875 2876 /* 2877 * If we've tried to evict from each sublist, made some 2878 * progress, but still have not hit the target number of bytes 2879 * to evict, we want to keep trying. The markers allow us to 2880 * pick up where we left off for each individual sublist, rather 2881 * than starting from the tail each time. 2882 */ 2883 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2884 for (int i = 0; i < num_sublists; i++) { 2885 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2886 2887 /* 2888 * A b_spa of 0 is used to indicate that this header is 2889 * a marker. This fact is used in arc_adjust_type() and 2890 * arc_evict_state_impl(). 2891 */ 2892 markers[i]->b_spa = 0; 2893 2894 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2895 multilist_sublist_insert_tail(mls, markers[i]); 2896 multilist_sublist_unlock(mls); 2897 } 2898 2899 /* 2900 * While we haven't hit our target number of bytes to evict, or 2901 * we're evicting all available buffers. 2902 */ 2903 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2904 /* 2905 * Start eviction using a randomly selected sublist, 2906 * this is to try and evenly balance eviction across all 2907 * sublists. Always starting at the same sublist 2908 * (e.g. index 0) would cause evictions to favor certain 2909 * sublists over others. 2910 */ 2911 int sublist_idx = multilist_get_random_index(ml); 2912 uint64_t scan_evicted = 0; 2913 2914 for (int i = 0; i < num_sublists; i++) { 2915 uint64_t bytes_remaining; 2916 uint64_t bytes_evicted; 2917 2918 if (bytes == ARC_EVICT_ALL) 2919 bytes_remaining = ARC_EVICT_ALL; 2920 else if (total_evicted < bytes) 2921 bytes_remaining = bytes - total_evicted; 2922 else 2923 break; 2924 2925 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2926 markers[sublist_idx], spa, bytes_remaining); 2927 2928 scan_evicted += bytes_evicted; 2929 total_evicted += bytes_evicted; 2930 2931 /* we've reached the end, wrap to the beginning */ 2932 if (++sublist_idx >= num_sublists) 2933 sublist_idx = 0; 2934 } 2935 2936 /* 2937 * If we didn't evict anything during this scan, we have 2938 * no reason to believe we'll evict more during another 2939 * scan, so break the loop. 2940 */ 2941 if (scan_evicted == 0) { 2942 /* This isn't possible, let's make that obvious */ 2943 ASSERT3S(bytes, !=, 0); 2944 2945 /* 2946 * When bytes is ARC_EVICT_ALL, the only way to 2947 * break the loop is when scan_evicted is zero. 2948 * In that case, we actually have evicted enough, 2949 * so we don't want to increment the kstat. 2950 */ 2951 if (bytes != ARC_EVICT_ALL) { 2952 ASSERT3S(total_evicted, <, bytes); 2953 ARCSTAT_BUMP(arcstat_evict_not_enough); 2954 } 2955 2956 break; 2957 } 2958 } 2959 2960 for (int i = 0; i < num_sublists; i++) { 2961 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2962 multilist_sublist_remove(mls, markers[i]); 2963 multilist_sublist_unlock(mls); 2964 2965 kmem_cache_free(hdr_full_cache, markers[i]); 2966 } 2967 kmem_free(markers, sizeof (*markers) * num_sublists); 2968 2969 return (total_evicted); 2970} 2971 2972/* 2973 * Flush all "evictable" data of the given type from the arc state 2974 * specified. This will not evict any "active" buffers (i.e. referenced). 2975 * 2976 * When 'retry' is set to FALSE, the function will make a single pass 2977 * over the state and evict any buffers that it can. Since it doesn't 2978 * continually retry the eviction, it might end up leaving some buffers 2979 * in the ARC due to lock misses. 2980 * 2981 * When 'retry' is set to TRUE, the function will continually retry the 2982 * eviction until *all* evictable buffers have been removed from the 2983 * state. As a result, if concurrent insertions into the state are 2984 * allowed (e.g. if the ARC isn't shutting down), this function might 2985 * wind up in an infinite loop, continually trying to evict buffers. 2986 */ 2987static uint64_t 2988arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2989 boolean_t retry) 2990{ 2991 uint64_t evicted = 0; 2992 2993 while (state->arcs_lsize[type] != 0) { 2994 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2995 2996 if (!retry) 2997 break; 2998 } 2999 3000 return (evicted); 3001} 3002 3003/* 3004 * Evict the specified number of bytes from the state specified, 3005 * restricting eviction to the spa and type given. This function 3006 * prevents us from trying to evict more from a state's list than 3007 * is "evictable", and to skip evicting altogether when passed a 3008 * negative value for "bytes". In contrast, arc_evict_state() will 3009 * evict everything it can, when passed a negative value for "bytes". 3010 */ 3011static uint64_t 3012arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3013 arc_buf_contents_t type) 3014{ 3015 int64_t delta; 3016 3017 if (bytes > 0 && state->arcs_lsize[type] > 0) { 3018 delta = MIN(state->arcs_lsize[type], bytes); 3019 return (arc_evict_state(state, spa, delta, type)); 3020 } 3021 3022 return (0); 3023} 3024 3025/* 3026 * Evict metadata buffers from the cache, such that arc_meta_used is 3027 * capped by the arc_meta_limit tunable. 3028 */ 3029static uint64_t 3030arc_adjust_meta(void) 3031{ 3032 uint64_t total_evicted = 0; 3033 int64_t target; 3034 3035 /* 3036 * If we're over the meta limit, we want to evict enough 3037 * metadata to get back under the meta limit. We don't want to 3038 * evict so much that we drop the MRU below arc_p, though. If 3039 * we're over the meta limit more than we're over arc_p, we 3040 * evict some from the MRU here, and some from the MFU below. 3041 */ 3042 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3043 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3044 refcount_count(&arc_mru->arcs_size) - arc_p)); 3045 3046 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3047 3048 /* 3049 * Similar to the above, we want to evict enough bytes to get us 3050 * below the meta limit, but not so much as to drop us below the 3051 * space alloted to the MFU (which is defined as arc_c - arc_p). 3052 */ 3053 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3054 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3055 3056 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3057 3058 return (total_evicted); 3059} 3060 3061/* 3062 * Return the type of the oldest buffer in the given arc state 3063 * 3064 * This function will select a random sublist of type ARC_BUFC_DATA and 3065 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3066 * is compared, and the type which contains the "older" buffer will be 3067 * returned. 3068 */ 3069static arc_buf_contents_t 3070arc_adjust_type(arc_state_t *state) 3071{ 3072 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3073 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3074 int data_idx = multilist_get_random_index(data_ml); 3075 int meta_idx = multilist_get_random_index(meta_ml); 3076 multilist_sublist_t *data_mls; 3077 multilist_sublist_t *meta_mls; 3078 arc_buf_contents_t type; 3079 arc_buf_hdr_t *data_hdr; 3080 arc_buf_hdr_t *meta_hdr; 3081 3082 /* 3083 * We keep the sublist lock until we're finished, to prevent 3084 * the headers from being destroyed via arc_evict_state(). 3085 */ 3086 data_mls = multilist_sublist_lock(data_ml, data_idx); 3087 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3088 3089 /* 3090 * These two loops are to ensure we skip any markers that 3091 * might be at the tail of the lists due to arc_evict_state(). 3092 */ 3093 3094 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3095 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3096 if (data_hdr->b_spa != 0) 3097 break; 3098 } 3099 3100 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3101 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3102 if (meta_hdr->b_spa != 0) 3103 break; 3104 } 3105 3106 if (data_hdr == NULL && meta_hdr == NULL) { 3107 type = ARC_BUFC_DATA; 3108 } else if (data_hdr == NULL) { 3109 ASSERT3P(meta_hdr, !=, NULL); 3110 type = ARC_BUFC_METADATA; 3111 } else if (meta_hdr == NULL) { 3112 ASSERT3P(data_hdr, !=, NULL); 3113 type = ARC_BUFC_DATA; 3114 } else { 3115 ASSERT3P(data_hdr, !=, NULL); 3116 ASSERT3P(meta_hdr, !=, NULL); 3117 3118 /* The headers can't be on the sublist without an L1 header */ 3119 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3120 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3121 3122 if (data_hdr->b_l1hdr.b_arc_access < 3123 meta_hdr->b_l1hdr.b_arc_access) { 3124 type = ARC_BUFC_DATA; 3125 } else { 3126 type = ARC_BUFC_METADATA; 3127 } 3128 } 3129 3130 multilist_sublist_unlock(meta_mls); 3131 multilist_sublist_unlock(data_mls); 3132 3133 return (type); 3134} 3135 3136/* 3137 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3138 */ 3139static uint64_t 3140arc_adjust(void) 3141{ 3142 uint64_t total_evicted = 0; 3143 uint64_t bytes; 3144 int64_t target; 3145 3146 /* 3147 * If we're over arc_meta_limit, we want to correct that before 3148 * potentially evicting data buffers below. 3149 */ 3150 total_evicted += arc_adjust_meta(); 3151 3152 /* 3153 * Adjust MRU size 3154 * 3155 * If we're over the target cache size, we want to evict enough 3156 * from the list to get back to our target size. We don't want 3157 * to evict too much from the MRU, such that it drops below 3158 * arc_p. So, if we're over our target cache size more than 3159 * the MRU is over arc_p, we'll evict enough to get back to 3160 * arc_p here, and then evict more from the MFU below. 3161 */ 3162 target = MIN((int64_t)(arc_size - arc_c), 3163 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3164 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3165 3166 /* 3167 * If we're below arc_meta_min, always prefer to evict data. 3168 * Otherwise, try to satisfy the requested number of bytes to 3169 * evict from the type which contains older buffers; in an 3170 * effort to keep newer buffers in the cache regardless of their 3171 * type. If we cannot satisfy the number of bytes from this 3172 * type, spill over into the next type. 3173 */ 3174 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3175 arc_meta_used > arc_meta_min) { 3176 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3177 total_evicted += bytes; 3178 3179 /* 3180 * If we couldn't evict our target number of bytes from 3181 * metadata, we try to get the rest from data. 3182 */ 3183 target -= bytes; 3184 3185 total_evicted += 3186 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3187 } else { 3188 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3189 total_evicted += bytes; 3190 3191 /* 3192 * If we couldn't evict our target number of bytes from 3193 * data, we try to get the rest from metadata. 3194 */ 3195 target -= bytes; 3196 3197 total_evicted += 3198 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3199 } 3200 3201 /* 3202 * Adjust MFU size 3203 * 3204 * Now that we've tried to evict enough from the MRU to get its 3205 * size back to arc_p, if we're still above the target cache 3206 * size, we evict the rest from the MFU. 3207 */ 3208 target = arc_size - arc_c; 3209 3210 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3211 arc_meta_used > arc_meta_min) { 3212 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3213 total_evicted += bytes; 3214 3215 /* 3216 * If we couldn't evict our target number of bytes from 3217 * metadata, we try to get the rest from data. 3218 */ 3219 target -= bytes; 3220 3221 total_evicted += 3222 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3223 } else { 3224 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3225 total_evicted += bytes; 3226 3227 /* 3228 * If we couldn't evict our target number of bytes from 3229 * data, we try to get the rest from data. 3230 */ 3231 target -= bytes; 3232 3233 total_evicted += 3234 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3235 } 3236 3237 /* 3238 * Adjust ghost lists 3239 * 3240 * In addition to the above, the ARC also defines target values 3241 * for the ghost lists. The sum of the mru list and mru ghost 3242 * list should never exceed the target size of the cache, and 3243 * the sum of the mru list, mfu list, mru ghost list, and mfu 3244 * ghost list should never exceed twice the target size of the 3245 * cache. The following logic enforces these limits on the ghost 3246 * caches, and evicts from them as needed. 3247 */ 3248 target = refcount_count(&arc_mru->arcs_size) + 3249 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3250 3251 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3252 total_evicted += bytes; 3253 3254 target -= bytes; 3255 3256 total_evicted += 3257 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3258 3259 /* 3260 * We assume the sum of the mru list and mfu list is less than 3261 * or equal to arc_c (we enforced this above), which means we 3262 * can use the simpler of the two equations below: 3263 * 3264 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3265 * mru ghost + mfu ghost <= arc_c 3266 */ 3267 target = refcount_count(&arc_mru_ghost->arcs_size) + 3268 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3269 3270 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3271 total_evicted += bytes; 3272 3273 target -= bytes; 3274 3275 total_evicted += 3276 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3277 3278 return (total_evicted); 3279} 3280 3281static void 3282arc_do_user_evicts(void) 3283{ 3284 mutex_enter(&arc_user_evicts_lock); 3285 while (arc_eviction_list != NULL) { 3286 arc_buf_t *buf = arc_eviction_list; 3287 arc_eviction_list = buf->b_next; 3288 mutex_enter(&buf->b_evict_lock); 3289 buf->b_hdr = NULL; 3290 mutex_exit(&buf->b_evict_lock); 3291 mutex_exit(&arc_user_evicts_lock); 3292 3293 if (buf->b_efunc != NULL) 3294 VERIFY0(buf->b_efunc(buf->b_private)); 3295 3296 buf->b_efunc = NULL; 3297 buf->b_private = NULL; 3298 kmem_cache_free(buf_cache, buf); 3299 mutex_enter(&arc_user_evicts_lock); 3300 } 3301 mutex_exit(&arc_user_evicts_lock); 3302} 3303 3304void 3305arc_flush(spa_t *spa, boolean_t retry) 3306{ 3307 uint64_t guid = 0; 3308 3309 /* 3310 * If retry is TRUE, a spa must not be specified since we have 3311 * no good way to determine if all of a spa's buffers have been 3312 * evicted from an arc state. 3313 */ 3314 ASSERT(!retry || spa == 0); 3315 3316 if (spa != NULL) 3317 guid = spa_load_guid(spa); 3318 3319 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3320 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3321 3322 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3323 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3324 3325 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3326 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3327 3328 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3329 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3330 3331 arc_do_user_evicts(); 3332 ASSERT(spa || arc_eviction_list == NULL); 3333} 3334 3335void 3336arc_shrink(int64_t to_free) 3337{ 3338 if (arc_c > arc_c_min) { 3339 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3340 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3341 if (arc_c > arc_c_min + to_free) 3342 atomic_add_64(&arc_c, -to_free); 3343 else 3344 arc_c = arc_c_min; 3345 3346 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3347 if (arc_c > arc_size) 3348 arc_c = MAX(arc_size, arc_c_min); 3349 if (arc_p > arc_c) 3350 arc_p = (arc_c >> 1); 3351 3352 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3353 arc_p); 3354 3355 ASSERT(arc_c >= arc_c_min); 3356 ASSERT((int64_t)arc_p >= 0); 3357 } 3358 3359 if (arc_size > arc_c) { 3360 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3361 uint64_t, arc_c); 3362 (void) arc_adjust(); 3363 } 3364} 3365 3366static long needfree = 0; 3367 3368typedef enum free_memory_reason_t { 3369 FMR_UNKNOWN, 3370 FMR_NEEDFREE, 3371 FMR_LOTSFREE, 3372 FMR_SWAPFS_MINFREE, 3373 FMR_PAGES_PP_MAXIMUM, 3374 FMR_HEAP_ARENA, 3375 FMR_ZIO_ARENA, 3376 FMR_ZIO_FRAG, 3377} free_memory_reason_t; 3378 3379int64_t last_free_memory; 3380free_memory_reason_t last_free_reason; 3381 3382/* 3383 * Additional reserve of pages for pp_reserve. 3384 */ 3385int64_t arc_pages_pp_reserve = 64; 3386 3387/* 3388 * Additional reserve of pages for swapfs. 3389 */ 3390int64_t arc_swapfs_reserve = 64; 3391 3392/* 3393 * Return the amount of memory that can be consumed before reclaim will be 3394 * needed. Positive if there is sufficient free memory, negative indicates 3395 * the amount of memory that needs to be freed up. 3396 */ 3397static int64_t 3398arc_available_memory(void) 3399{ 3400 int64_t lowest = INT64_MAX; 3401 int64_t n; 3402 free_memory_reason_t r = FMR_UNKNOWN; 3403 3404#ifdef _KERNEL 3405 if (needfree > 0) { 3406 n = PAGESIZE * (-needfree); 3407 if (n < lowest) { 3408 lowest = n; 3409 r = FMR_NEEDFREE; 3410 } 3411 } 3412 3413 /* 3414 * Cooperate with pagedaemon when it's time for it to scan 3415 * and reclaim some pages. 3416 */ 3417 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3418 if (n < lowest) { 3419 lowest = n; 3420 r = FMR_LOTSFREE; 3421 } 3422 3423#ifdef illumos 3424 /* 3425 * check that we're out of range of the pageout scanner. It starts to 3426 * schedule paging if freemem is less than lotsfree and needfree. 3427 * lotsfree is the high-water mark for pageout, and needfree is the 3428 * number of needed free pages. We add extra pages here to make sure 3429 * the scanner doesn't start up while we're freeing memory. 3430 */ 3431 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3432 if (n < lowest) { 3433 lowest = n; 3434 r = FMR_LOTSFREE; 3435 } 3436 3437 /* 3438 * check to make sure that swapfs has enough space so that anon 3439 * reservations can still succeed. anon_resvmem() checks that the 3440 * availrmem is greater than swapfs_minfree, and the number of reserved 3441 * swap pages. We also add a bit of extra here just to prevent 3442 * circumstances from getting really dire. 3443 */ 3444 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3445 desfree - arc_swapfs_reserve); 3446 if (n < lowest) { 3447 lowest = n; 3448 r = FMR_SWAPFS_MINFREE; 3449 } 3450 3451 3452 /* 3453 * Check that we have enough availrmem that memory locking (e.g., via 3454 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3455 * stores the number of pages that cannot be locked; when availrmem 3456 * drops below pages_pp_maximum, page locking mechanisms such as 3457 * page_pp_lock() will fail.) 3458 */ 3459 n = PAGESIZE * (availrmem - pages_pp_maximum - 3460 arc_pages_pp_reserve); 3461 if (n < lowest) { 3462 lowest = n; 3463 r = FMR_PAGES_PP_MAXIMUM; 3464 } 3465 3466#endif /* illumos */ 3467#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3468 /* 3469 * If we're on an i386 platform, it's possible that we'll exhaust the 3470 * kernel heap space before we ever run out of available physical 3471 * memory. Most checks of the size of the heap_area compare against 3472 * tune.t_minarmem, which is the minimum available real memory that we 3473 * can have in the system. However, this is generally fixed at 25 pages 3474 * which is so low that it's useless. In this comparison, we seek to 3475 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3476 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3477 * free) 3478 */ 3479 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3480 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3481 if (n < lowest) { 3482 lowest = n; 3483 r = FMR_HEAP_ARENA; 3484 } 3485#define zio_arena NULL 3486#else 3487#define zio_arena heap_arena 3488#endif 3489 3490 /* 3491 * If zio data pages are being allocated out of a separate heap segment, 3492 * then enforce that the size of available vmem for this arena remains 3493 * above about 1/16th free. 3494 * 3495 * Note: The 1/16th arena free requirement was put in place 3496 * to aggressively evict memory from the arc in order to avoid 3497 * memory fragmentation issues. 3498 */ 3499 if (zio_arena != NULL) { 3500 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3501 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3502 if (n < lowest) { 3503 lowest = n; 3504 r = FMR_ZIO_ARENA; 3505 } 3506 } 3507 3508 /* 3509 * Above limits know nothing about real level of KVA fragmentation. 3510 * Start aggressive reclamation if too little sequential KVA left. 3511 */ 3512 if (lowest > 0) { 3513 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3514 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3515 INT64_MAX; 3516 if (n < lowest) { 3517 lowest = n; 3518 r = FMR_ZIO_FRAG; 3519 } 3520 } 3521 3522#else /* _KERNEL */ 3523 /* Every 100 calls, free a small amount */ 3524 if (spa_get_random(100) == 0) 3525 lowest = -1024; 3526#endif /* _KERNEL */ 3527 3528 last_free_memory = lowest; 3529 last_free_reason = r; 3530 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3531 return (lowest); 3532} 3533 3534 3535/* 3536 * Determine if the system is under memory pressure and is asking 3537 * to reclaim memory. A return value of TRUE indicates that the system 3538 * is under memory pressure and that the arc should adjust accordingly. 3539 */ 3540static boolean_t 3541arc_reclaim_needed(void) 3542{ 3543 return (arc_available_memory() < 0); 3544} 3545 3546extern kmem_cache_t *zio_buf_cache[]; 3547extern kmem_cache_t *zio_data_buf_cache[]; 3548extern kmem_cache_t *range_seg_cache; 3549 3550static __noinline void 3551arc_kmem_reap_now(void) 3552{ 3553 size_t i; 3554 kmem_cache_t *prev_cache = NULL; 3555 kmem_cache_t *prev_data_cache = NULL; 3556 3557 DTRACE_PROBE(arc__kmem_reap_start); 3558#ifdef _KERNEL 3559 if (arc_meta_used >= arc_meta_limit) { 3560 /* 3561 * We are exceeding our meta-data cache limit. 3562 * Purge some DNLC entries to release holds on meta-data. 3563 */ 3564 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3565 } 3566#if defined(__i386) 3567 /* 3568 * Reclaim unused memory from all kmem caches. 3569 */ 3570 kmem_reap(); 3571#endif 3572#endif 3573 3574 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3575 if (zio_buf_cache[i] != prev_cache) { 3576 prev_cache = zio_buf_cache[i]; 3577 kmem_cache_reap_now(zio_buf_cache[i]); 3578 } 3579 if (zio_data_buf_cache[i] != prev_data_cache) { 3580 prev_data_cache = zio_data_buf_cache[i]; 3581 kmem_cache_reap_now(zio_data_buf_cache[i]); 3582 } 3583 } 3584 kmem_cache_reap_now(buf_cache); 3585 kmem_cache_reap_now(hdr_full_cache); 3586 kmem_cache_reap_now(hdr_l2only_cache); 3587 kmem_cache_reap_now(range_seg_cache); 3588 3589#ifdef illumos 3590 if (zio_arena != NULL) { 3591 /* 3592 * Ask the vmem arena to reclaim unused memory from its 3593 * quantum caches. 3594 */ 3595 vmem_qcache_reap(zio_arena); 3596 } 3597#endif 3598 DTRACE_PROBE(arc__kmem_reap_end); 3599} 3600 3601/* 3602 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3603 * enough data and signal them to proceed. When this happens, the threads in 3604 * arc_get_data_buf() are sleeping while holding the hash lock for their 3605 * particular arc header. Thus, we must be careful to never sleep on a 3606 * hash lock in this thread. This is to prevent the following deadlock: 3607 * 3608 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3609 * waiting for the reclaim thread to signal it. 3610 * 3611 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3612 * fails, and goes to sleep forever. 3613 * 3614 * This possible deadlock is avoided by always acquiring a hash lock 3615 * using mutex_tryenter() from arc_reclaim_thread(). 3616 */ 3617static void 3618arc_reclaim_thread(void *dummy __unused) 3619{ 3620 hrtime_t growtime = 0; 3621 callb_cpr_t cpr; 3622 3623 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3624 3625 mutex_enter(&arc_reclaim_lock); 3626 while (!arc_reclaim_thread_exit) { 3627 int64_t free_memory = arc_available_memory(); 3628 uint64_t evicted = 0; 3629 3630 mutex_exit(&arc_reclaim_lock); 3631 3632 if (free_memory < 0) { 3633 3634 arc_no_grow = B_TRUE; 3635 arc_warm = B_TRUE; 3636 3637 /* 3638 * Wait at least zfs_grow_retry (default 60) seconds 3639 * before considering growing. 3640 */ 3641 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 3642 3643 arc_kmem_reap_now(); 3644 3645 /* 3646 * If we are still low on memory, shrink the ARC 3647 * so that we have arc_shrink_min free space. 3648 */ 3649 free_memory = arc_available_memory(); 3650 3651 int64_t to_free = 3652 (arc_c >> arc_shrink_shift) - free_memory; 3653 if (to_free > 0) { 3654#ifdef _KERNEL 3655 to_free = MAX(to_free, ptob(needfree)); 3656#endif 3657 arc_shrink(to_free); 3658 } 3659 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3660 arc_no_grow = B_TRUE; 3661 } else if (gethrtime() >= growtime) { 3662 arc_no_grow = B_FALSE; 3663 } 3664 3665 evicted = arc_adjust(); 3666 3667 mutex_enter(&arc_reclaim_lock); 3668 3669 /* 3670 * If evicted is zero, we couldn't evict anything via 3671 * arc_adjust(). This could be due to hash lock 3672 * collisions, but more likely due to the majority of 3673 * arc buffers being unevictable. Therefore, even if 3674 * arc_size is above arc_c, another pass is unlikely to 3675 * be helpful and could potentially cause us to enter an 3676 * infinite loop. 3677 */ 3678 if (arc_size <= arc_c || evicted == 0) { 3679#ifdef _KERNEL 3680 needfree = 0; 3681#endif 3682 /* 3683 * We're either no longer overflowing, or we 3684 * can't evict anything more, so we should wake 3685 * up any threads before we go to sleep. 3686 */ 3687 cv_broadcast(&arc_reclaim_waiters_cv); 3688 3689 /* 3690 * Block until signaled, or after one second (we 3691 * might need to perform arc_kmem_reap_now() 3692 * even if we aren't being signalled) 3693 */ 3694 CALLB_CPR_SAFE_BEGIN(&cpr); 3695 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 3696 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 3697 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3698 } 3699 } 3700 3701 arc_reclaim_thread_exit = FALSE; 3702 cv_broadcast(&arc_reclaim_thread_cv); 3703 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3704 thread_exit(); 3705} 3706 3707static void 3708arc_user_evicts_thread(void *dummy __unused) 3709{ 3710 callb_cpr_t cpr; 3711 3712 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3713 3714 mutex_enter(&arc_user_evicts_lock); 3715 while (!arc_user_evicts_thread_exit) { 3716 mutex_exit(&arc_user_evicts_lock); 3717 3718 arc_do_user_evicts(); 3719 3720 /* 3721 * This is necessary in order for the mdb ::arc dcmd to 3722 * show up to date information. Since the ::arc command 3723 * does not call the kstat's update function, without 3724 * this call, the command may show stale stats for the 3725 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3726 * with this change, the data might be up to 1 second 3727 * out of date; but that should suffice. The arc_state_t 3728 * structures can be queried directly if more accurate 3729 * information is needed. 3730 */ 3731 if (arc_ksp != NULL) 3732 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3733 3734 mutex_enter(&arc_user_evicts_lock); 3735 3736 /* 3737 * Block until signaled, or after one second (we need to 3738 * call the arc's kstat update function regularly). 3739 */ 3740 CALLB_CPR_SAFE_BEGIN(&cpr); 3741 (void) cv_timedwait(&arc_user_evicts_cv, 3742 &arc_user_evicts_lock, hz); 3743 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3744 } 3745 3746 arc_user_evicts_thread_exit = FALSE; 3747 cv_broadcast(&arc_user_evicts_cv); 3748 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3749 thread_exit(); 3750} 3751 3752/* 3753 * Adapt arc info given the number of bytes we are trying to add and 3754 * the state that we are comming from. This function is only called 3755 * when we are adding new content to the cache. 3756 */ 3757static void 3758arc_adapt(int bytes, arc_state_t *state) 3759{ 3760 int mult; 3761 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3762 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3763 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3764 3765 if (state == arc_l2c_only) 3766 return; 3767 3768 ASSERT(bytes > 0); 3769 /* 3770 * Adapt the target size of the MRU list: 3771 * - if we just hit in the MRU ghost list, then increase 3772 * the target size of the MRU list. 3773 * - if we just hit in the MFU ghost list, then increase 3774 * the target size of the MFU list by decreasing the 3775 * target size of the MRU list. 3776 */ 3777 if (state == arc_mru_ghost) { 3778 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3779 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3780 3781 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3782 } else if (state == arc_mfu_ghost) { 3783 uint64_t delta; 3784 3785 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3786 mult = MIN(mult, 10); 3787 3788 delta = MIN(bytes * mult, arc_p); 3789 arc_p = MAX(arc_p_min, arc_p - delta); 3790 } 3791 ASSERT((int64_t)arc_p >= 0); 3792 3793 if (arc_reclaim_needed()) { 3794 cv_signal(&arc_reclaim_thread_cv); 3795 return; 3796 } 3797 3798 if (arc_no_grow) 3799 return; 3800 3801 if (arc_c >= arc_c_max) 3802 return; 3803 3804 /* 3805 * If we're within (2 * maxblocksize) bytes of the target 3806 * cache size, increment the target cache size 3807 */ 3808 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3809 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3810 atomic_add_64(&arc_c, (int64_t)bytes); 3811 if (arc_c > arc_c_max) 3812 arc_c = arc_c_max; 3813 else if (state == arc_anon) 3814 atomic_add_64(&arc_p, (int64_t)bytes); 3815 if (arc_p > arc_c) 3816 arc_p = arc_c; 3817 } 3818 ASSERT((int64_t)arc_p >= 0); 3819} 3820 3821/* 3822 * Check if arc_size has grown past our upper threshold, determined by 3823 * zfs_arc_overflow_shift. 3824 */ 3825static boolean_t 3826arc_is_overflowing(void) 3827{ 3828 /* Always allow at least one block of overflow */ 3829 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3830 arc_c >> zfs_arc_overflow_shift); 3831 3832 return (arc_size >= arc_c + overflow); 3833} 3834 3835/* 3836 * The buffer, supplied as the first argument, needs a data block. If we 3837 * are hitting the hard limit for the cache size, we must sleep, waiting 3838 * for the eviction thread to catch up. If we're past the target size 3839 * but below the hard limit, we'll only signal the reclaim thread and 3840 * continue on. 3841 */ 3842static void 3843arc_get_data_buf(arc_buf_t *buf) 3844{ 3845 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3846 uint64_t size = buf->b_hdr->b_size; 3847 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3848 3849 arc_adapt(size, state); 3850 3851 /* 3852 * If arc_size is currently overflowing, and has grown past our 3853 * upper limit, we must be adding data faster than the evict 3854 * thread can evict. Thus, to ensure we don't compound the 3855 * problem by adding more data and forcing arc_size to grow even 3856 * further past it's target size, we halt and wait for the 3857 * eviction thread to catch up. 3858 * 3859 * It's also possible that the reclaim thread is unable to evict 3860 * enough buffers to get arc_size below the overflow limit (e.g. 3861 * due to buffers being un-evictable, or hash lock collisions). 3862 * In this case, we want to proceed regardless if we're 3863 * overflowing; thus we don't use a while loop here. 3864 */ 3865 if (arc_is_overflowing()) { 3866 mutex_enter(&arc_reclaim_lock); 3867 3868 /* 3869 * Now that we've acquired the lock, we may no longer be 3870 * over the overflow limit, lets check. 3871 * 3872 * We're ignoring the case of spurious wake ups. If that 3873 * were to happen, it'd let this thread consume an ARC 3874 * buffer before it should have (i.e. before we're under 3875 * the overflow limit and were signalled by the reclaim 3876 * thread). As long as that is a rare occurrence, it 3877 * shouldn't cause any harm. 3878 */ 3879 if (arc_is_overflowing()) { 3880 cv_signal(&arc_reclaim_thread_cv); 3881 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3882 } 3883 3884 mutex_exit(&arc_reclaim_lock); 3885 } 3886 3887 if (type == ARC_BUFC_METADATA) { 3888 buf->b_data = zio_buf_alloc(size); 3889 arc_space_consume(size, ARC_SPACE_META); 3890 } else { 3891 ASSERT(type == ARC_BUFC_DATA); 3892 buf->b_data = zio_data_buf_alloc(size); 3893 arc_space_consume(size, ARC_SPACE_DATA); 3894 } 3895 3896 /* 3897 * Update the state size. Note that ghost states have a 3898 * "ghost size" and so don't need to be updated. 3899 */ 3900 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3901 arc_buf_hdr_t *hdr = buf->b_hdr; 3902 arc_state_t *state = hdr->b_l1hdr.b_state; 3903 3904 (void) refcount_add_many(&state->arcs_size, size, buf); 3905 3906 /* 3907 * If this is reached via arc_read, the link is 3908 * protected by the hash lock. If reached via 3909 * arc_buf_alloc, the header should not be accessed by 3910 * any other thread. And, if reached via arc_read_done, 3911 * the hash lock will protect it if it's found in the 3912 * hash table; otherwise no other thread should be 3913 * trying to [add|remove]_reference it. 3914 */ 3915 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3916 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3917 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3918 size); 3919 } 3920 /* 3921 * If we are growing the cache, and we are adding anonymous 3922 * data, and we have outgrown arc_p, update arc_p 3923 */ 3924 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3925 (refcount_count(&arc_anon->arcs_size) + 3926 refcount_count(&arc_mru->arcs_size) > arc_p)) 3927 arc_p = MIN(arc_c, arc_p + size); 3928 } 3929 ARCSTAT_BUMP(arcstat_allocated); 3930} 3931 3932/* 3933 * This routine is called whenever a buffer is accessed. 3934 * NOTE: the hash lock is dropped in this function. 3935 */ 3936static void 3937arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3938{ 3939 clock_t now; 3940 3941 ASSERT(MUTEX_HELD(hash_lock)); 3942 ASSERT(HDR_HAS_L1HDR(hdr)); 3943 3944 if (hdr->b_l1hdr.b_state == arc_anon) { 3945 /* 3946 * This buffer is not in the cache, and does not 3947 * appear in our "ghost" list. Add the new buffer 3948 * to the MRU state. 3949 */ 3950 3951 ASSERT0(hdr->b_l1hdr.b_arc_access); 3952 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3953 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3954 arc_change_state(arc_mru, hdr, hash_lock); 3955 3956 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3957 now = ddi_get_lbolt(); 3958 3959 /* 3960 * If this buffer is here because of a prefetch, then either: 3961 * - clear the flag if this is a "referencing" read 3962 * (any subsequent access will bump this into the MFU state). 3963 * or 3964 * - move the buffer to the head of the list if this is 3965 * another prefetch (to make it less likely to be evicted). 3966 */ 3967 if (HDR_PREFETCH(hdr)) { 3968 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3969 /* link protected by hash lock */ 3970 ASSERT(multilist_link_active( 3971 &hdr->b_l1hdr.b_arc_node)); 3972 } else { 3973 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3974 ARCSTAT_BUMP(arcstat_mru_hits); 3975 } 3976 hdr->b_l1hdr.b_arc_access = now; 3977 return; 3978 } 3979 3980 /* 3981 * This buffer has been "accessed" only once so far, 3982 * but it is still in the cache. Move it to the MFU 3983 * state. 3984 */ 3985 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3986 /* 3987 * More than 125ms have passed since we 3988 * instantiated this buffer. Move it to the 3989 * most frequently used state. 3990 */ 3991 hdr->b_l1hdr.b_arc_access = now; 3992 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3993 arc_change_state(arc_mfu, hdr, hash_lock); 3994 } 3995 ARCSTAT_BUMP(arcstat_mru_hits); 3996 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3997 arc_state_t *new_state; 3998 /* 3999 * This buffer has been "accessed" recently, but 4000 * was evicted from the cache. Move it to the 4001 * MFU state. 4002 */ 4003 4004 if (HDR_PREFETCH(hdr)) { 4005 new_state = arc_mru; 4006 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4007 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4008 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4009 } else { 4010 new_state = arc_mfu; 4011 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4012 } 4013 4014 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4015 arc_change_state(new_state, hdr, hash_lock); 4016 4017 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4018 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4019 /* 4020 * This buffer has been accessed more than once and is 4021 * still in the cache. Keep it in the MFU state. 4022 * 4023 * NOTE: an add_reference() that occurred when we did 4024 * the arc_read() will have kicked this off the list. 4025 * If it was a prefetch, we will explicitly move it to 4026 * the head of the list now. 4027 */ 4028 if ((HDR_PREFETCH(hdr)) != 0) { 4029 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4030 /* link protected by hash_lock */ 4031 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4032 } 4033 ARCSTAT_BUMP(arcstat_mfu_hits); 4034 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4035 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4036 arc_state_t *new_state = arc_mfu; 4037 /* 4038 * This buffer has been accessed more than once but has 4039 * been evicted from the cache. Move it back to the 4040 * MFU state. 4041 */ 4042 4043 if (HDR_PREFETCH(hdr)) { 4044 /* 4045 * This is a prefetch access... 4046 * move this block back to the MRU state. 4047 */ 4048 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4049 new_state = arc_mru; 4050 } 4051 4052 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4053 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4054 arc_change_state(new_state, hdr, hash_lock); 4055 4056 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4057 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4058 /* 4059 * This buffer is on the 2nd Level ARC. 4060 */ 4061 4062 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4063 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4064 arc_change_state(arc_mfu, hdr, hash_lock); 4065 } else { 4066 ASSERT(!"invalid arc state"); 4067 } 4068} 4069 4070/* a generic arc_done_func_t which you can use */ 4071/* ARGSUSED */ 4072void 4073arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4074{ 4075 if (zio == NULL || zio->io_error == 0) 4076 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4077 VERIFY(arc_buf_remove_ref(buf, arg)); 4078} 4079 4080/* a generic arc_done_func_t */ 4081void 4082arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4083{ 4084 arc_buf_t **bufp = arg; 4085 if (zio && zio->io_error) { 4086 VERIFY(arc_buf_remove_ref(buf, arg)); 4087 *bufp = NULL; 4088 } else { 4089 *bufp = buf; 4090 ASSERT(buf->b_data); 4091 } 4092} 4093 4094static void 4095arc_read_done(zio_t *zio) 4096{ 4097 arc_buf_hdr_t *hdr; 4098 arc_buf_t *buf; 4099 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4100 kmutex_t *hash_lock = NULL; 4101 arc_callback_t *callback_list, *acb; 4102 int freeable = FALSE; 4103 4104 buf = zio->io_private; 4105 hdr = buf->b_hdr; 4106 4107 /* 4108 * The hdr was inserted into hash-table and removed from lists 4109 * prior to starting I/O. We should find this header, since 4110 * it's in the hash table, and it should be legit since it's 4111 * not possible to evict it during the I/O. The only possible 4112 * reason for it not to be found is if we were freed during the 4113 * read. 4114 */ 4115 if (HDR_IN_HASH_TABLE(hdr)) { 4116 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4117 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4118 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4119 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4120 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4121 4122 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4123 &hash_lock); 4124 4125 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4126 hash_lock == NULL) || 4127 (found == hdr && 4128 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4129 (found == hdr && HDR_L2_READING(hdr))); 4130 } 4131 4132 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4133 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4134 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4135 4136 /* byteswap if necessary */ 4137 callback_list = hdr->b_l1hdr.b_acb; 4138 ASSERT(callback_list != NULL); 4139 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4140 dmu_object_byteswap_t bswap = 4141 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4142 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4143 byteswap_uint64_array : 4144 dmu_ot_byteswap[bswap].ob_func; 4145 func(buf->b_data, hdr->b_size); 4146 } 4147 4148 arc_cksum_compute(buf, B_FALSE); 4149#ifdef illumos 4150 arc_buf_watch(buf); 4151#endif 4152 4153 if (hash_lock && zio->io_error == 0 && 4154 hdr->b_l1hdr.b_state == arc_anon) { 4155 /* 4156 * Only call arc_access on anonymous buffers. This is because 4157 * if we've issued an I/O for an evicted buffer, we've already 4158 * called arc_access (to prevent any simultaneous readers from 4159 * getting confused). 4160 */ 4161 arc_access(hdr, hash_lock); 4162 } 4163 4164 /* create copies of the data buffer for the callers */ 4165 abuf = buf; 4166 for (acb = callback_list; acb; acb = acb->acb_next) { 4167 if (acb->acb_done) { 4168 if (abuf == NULL) { 4169 ARCSTAT_BUMP(arcstat_duplicate_reads); 4170 abuf = arc_buf_clone(buf); 4171 } 4172 acb->acb_buf = abuf; 4173 abuf = NULL; 4174 } 4175 } 4176 hdr->b_l1hdr.b_acb = NULL; 4177 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4178 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4179 if (abuf == buf) { 4180 ASSERT(buf->b_efunc == NULL); 4181 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4182 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4183 } 4184 4185 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4186 callback_list != NULL); 4187 4188 if (zio->io_error != 0) { 4189 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4190 if (hdr->b_l1hdr.b_state != arc_anon) 4191 arc_change_state(arc_anon, hdr, hash_lock); 4192 if (HDR_IN_HASH_TABLE(hdr)) 4193 buf_hash_remove(hdr); 4194 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4195 } 4196 4197 /* 4198 * Broadcast before we drop the hash_lock to avoid the possibility 4199 * that the hdr (and hence the cv) might be freed before we get to 4200 * the cv_broadcast(). 4201 */ 4202 cv_broadcast(&hdr->b_l1hdr.b_cv); 4203 4204 if (hash_lock != NULL) { 4205 mutex_exit(hash_lock); 4206 } else { 4207 /* 4208 * This block was freed while we waited for the read to 4209 * complete. It has been removed from the hash table and 4210 * moved to the anonymous state (so that it won't show up 4211 * in the cache). 4212 */ 4213 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4214 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4215 } 4216 4217 /* execute each callback and free its structure */ 4218 while ((acb = callback_list) != NULL) { 4219 if (acb->acb_done) 4220 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4221 4222 if (acb->acb_zio_dummy != NULL) { 4223 acb->acb_zio_dummy->io_error = zio->io_error; 4224 zio_nowait(acb->acb_zio_dummy); 4225 } 4226 4227 callback_list = acb->acb_next; 4228 kmem_free(acb, sizeof (arc_callback_t)); 4229 } 4230 4231 if (freeable) 4232 arc_hdr_destroy(hdr); 4233} 4234 4235/* 4236 * "Read" the block at the specified DVA (in bp) via the 4237 * cache. If the block is found in the cache, invoke the provided 4238 * callback immediately and return. Note that the `zio' parameter 4239 * in the callback will be NULL in this case, since no IO was 4240 * required. If the block is not in the cache pass the read request 4241 * on to the spa with a substitute callback function, so that the 4242 * requested block will be added to the cache. 4243 * 4244 * If a read request arrives for a block that has a read in-progress, 4245 * either wait for the in-progress read to complete (and return the 4246 * results); or, if this is a read with a "done" func, add a record 4247 * to the read to invoke the "done" func when the read completes, 4248 * and return; or just return. 4249 * 4250 * arc_read_done() will invoke all the requested "done" functions 4251 * for readers of this block. 4252 */ 4253int 4254arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4255 void *private, zio_priority_t priority, int zio_flags, 4256 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4257{ 4258 arc_buf_hdr_t *hdr = NULL; 4259 arc_buf_t *buf = NULL; 4260 kmutex_t *hash_lock = NULL; 4261 zio_t *rzio; 4262 uint64_t guid = spa_load_guid(spa); 4263 4264 ASSERT(!BP_IS_EMBEDDED(bp) || 4265 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4266 4267top: 4268 if (!BP_IS_EMBEDDED(bp)) { 4269 /* 4270 * Embedded BP's have no DVA and require no I/O to "read". 4271 * Create an anonymous arc buf to back it. 4272 */ 4273 hdr = buf_hash_find(guid, bp, &hash_lock); 4274 } 4275 4276 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4277 4278 *arc_flags |= ARC_FLAG_CACHED; 4279 4280 if (HDR_IO_IN_PROGRESS(hdr)) { 4281 4282 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4283 priority == ZIO_PRIORITY_SYNC_READ) { 4284 /* 4285 * This sync read must wait for an 4286 * in-progress async read (e.g. a predictive 4287 * prefetch). Async reads are queued 4288 * separately at the vdev_queue layer, so 4289 * this is a form of priority inversion. 4290 * Ideally, we would "inherit" the demand 4291 * i/o's priority by moving the i/o from 4292 * the async queue to the synchronous queue, 4293 * but there is currently no mechanism to do 4294 * so. Track this so that we can evaluate 4295 * the magnitude of this potential performance 4296 * problem. 4297 * 4298 * Note that if the prefetch i/o is already 4299 * active (has been issued to the device), 4300 * the prefetch improved performance, because 4301 * we issued it sooner than we would have 4302 * without the prefetch. 4303 */ 4304 DTRACE_PROBE1(arc__sync__wait__for__async, 4305 arc_buf_hdr_t *, hdr); 4306 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4307 } 4308 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4309 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4310 } 4311 4312 if (*arc_flags & ARC_FLAG_WAIT) { 4313 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4314 mutex_exit(hash_lock); 4315 goto top; 4316 } 4317 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4318 4319 if (done) { 4320 arc_callback_t *acb = NULL; 4321 4322 acb = kmem_zalloc(sizeof (arc_callback_t), 4323 KM_SLEEP); 4324 acb->acb_done = done; 4325 acb->acb_private = private; 4326 if (pio != NULL) 4327 acb->acb_zio_dummy = zio_null(pio, 4328 spa, NULL, NULL, NULL, zio_flags); 4329 4330 ASSERT(acb->acb_done != NULL); 4331 acb->acb_next = hdr->b_l1hdr.b_acb; 4332 hdr->b_l1hdr.b_acb = acb; 4333 add_reference(hdr, hash_lock, private); 4334 mutex_exit(hash_lock); 4335 return (0); 4336 } 4337 mutex_exit(hash_lock); 4338 return (0); 4339 } 4340 4341 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4342 hdr->b_l1hdr.b_state == arc_mfu); 4343 4344 if (done) { 4345 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4346 /* 4347 * This is a demand read which does not have to 4348 * wait for i/o because we did a predictive 4349 * prefetch i/o for it, which has completed. 4350 */ 4351 DTRACE_PROBE1( 4352 arc__demand__hit__predictive__prefetch, 4353 arc_buf_hdr_t *, hdr); 4354 ARCSTAT_BUMP( 4355 arcstat_demand_hit_predictive_prefetch); 4356 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4357 } 4358 add_reference(hdr, hash_lock, private); 4359 /* 4360 * If this block is already in use, create a new 4361 * copy of the data so that we will be guaranteed 4362 * that arc_release() will always succeed. 4363 */ 4364 buf = hdr->b_l1hdr.b_buf; 4365 ASSERT(buf); 4366 ASSERT(buf->b_data); 4367 if (HDR_BUF_AVAILABLE(hdr)) { 4368 ASSERT(buf->b_efunc == NULL); 4369 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4370 } else { 4371 buf = arc_buf_clone(buf); 4372 } 4373 4374 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4375 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4376 hdr->b_flags |= ARC_FLAG_PREFETCH; 4377 } 4378 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4379 arc_access(hdr, hash_lock); 4380 if (*arc_flags & ARC_FLAG_L2CACHE) 4381 hdr->b_flags |= ARC_FLAG_L2CACHE; 4382 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4383 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4384 mutex_exit(hash_lock); 4385 ARCSTAT_BUMP(arcstat_hits); 4386 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4387 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4388 data, metadata, hits); 4389 4390 if (done) 4391 done(NULL, buf, private); 4392 } else { 4393 uint64_t size = BP_GET_LSIZE(bp); 4394 arc_callback_t *acb; 4395 vdev_t *vd = NULL; 4396 uint64_t addr = 0; 4397 boolean_t devw = B_FALSE; 4398 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4399 int32_t b_asize = 0; 4400 4401 if (hdr == NULL) { 4402 /* this block is not in the cache */ 4403 arc_buf_hdr_t *exists = NULL; 4404 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4405 buf = arc_buf_alloc(spa, size, private, type); 4406 hdr = buf->b_hdr; 4407 if (!BP_IS_EMBEDDED(bp)) { 4408 hdr->b_dva = *BP_IDENTITY(bp); 4409 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4410 exists = buf_hash_insert(hdr, &hash_lock); 4411 } 4412 if (exists != NULL) { 4413 /* somebody beat us to the hash insert */ 4414 mutex_exit(hash_lock); 4415 buf_discard_identity(hdr); 4416 (void) arc_buf_remove_ref(buf, private); 4417 goto top; /* restart the IO request */ 4418 } 4419 4420 /* 4421 * If there is a callback, we pass our reference to 4422 * it; otherwise we remove our reference. 4423 */ 4424 if (done == NULL) { 4425 (void) remove_reference(hdr, hash_lock, 4426 private); 4427 } 4428 if (*arc_flags & ARC_FLAG_PREFETCH) 4429 hdr->b_flags |= ARC_FLAG_PREFETCH; 4430 if (*arc_flags & ARC_FLAG_L2CACHE) 4431 hdr->b_flags |= ARC_FLAG_L2CACHE; 4432 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4433 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4434 if (BP_GET_LEVEL(bp) > 0) 4435 hdr->b_flags |= ARC_FLAG_INDIRECT; 4436 } else { 4437 /* 4438 * This block is in the ghost cache. If it was L2-only 4439 * (and thus didn't have an L1 hdr), we realloc the 4440 * header to add an L1 hdr. 4441 */ 4442 if (!HDR_HAS_L1HDR(hdr)) { 4443 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4444 hdr_full_cache); 4445 } 4446 4447 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4448 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4449 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4450 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4451 4452 /* 4453 * If there is a callback, we pass a reference to it. 4454 */ 4455 if (done != NULL) 4456 add_reference(hdr, hash_lock, private); 4457 if (*arc_flags & ARC_FLAG_PREFETCH) 4458 hdr->b_flags |= ARC_FLAG_PREFETCH; 4459 if (*arc_flags & ARC_FLAG_L2CACHE) 4460 hdr->b_flags |= ARC_FLAG_L2CACHE; 4461 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4462 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4463 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4464 buf->b_hdr = hdr; 4465 buf->b_data = NULL; 4466 buf->b_efunc = NULL; 4467 buf->b_private = NULL; 4468 buf->b_next = NULL; 4469 hdr->b_l1hdr.b_buf = buf; 4470 ASSERT0(hdr->b_l1hdr.b_datacnt); 4471 hdr->b_l1hdr.b_datacnt = 1; 4472 arc_get_data_buf(buf); 4473 arc_access(hdr, hash_lock); 4474 } 4475 4476 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4477 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4478 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4479 4480 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4481 acb->acb_done = done; 4482 acb->acb_private = private; 4483 4484 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4485 hdr->b_l1hdr.b_acb = acb; 4486 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4487 4488 if (HDR_HAS_L2HDR(hdr) && 4489 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4490 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4491 addr = hdr->b_l2hdr.b_daddr; 4492 b_compress = hdr->b_l2hdr.b_compress; 4493 b_asize = hdr->b_l2hdr.b_asize; 4494 /* 4495 * Lock out device removal. 4496 */ 4497 if (vdev_is_dead(vd) || 4498 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4499 vd = NULL; 4500 } 4501 4502 if (hash_lock != NULL) 4503 mutex_exit(hash_lock); 4504 4505 /* 4506 * At this point, we have a level 1 cache miss. Try again in 4507 * L2ARC if possible. 4508 */ 4509 ASSERT3U(hdr->b_size, ==, size); 4510 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4511 uint64_t, size, zbookmark_phys_t *, zb); 4512 ARCSTAT_BUMP(arcstat_misses); 4513 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4514 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4515 data, metadata, misses); 4516#ifdef _KERNEL 4517#ifdef RACCT 4518 if (racct_enable) { 4519 PROC_LOCK(curproc); 4520 racct_add_force(curproc, RACCT_READBPS, size); 4521 racct_add_force(curproc, RACCT_READIOPS, 1); 4522 PROC_UNLOCK(curproc); 4523 } 4524#endif /* RACCT */ 4525 curthread->td_ru.ru_inblock++; 4526#endif 4527 4528 if (priority == ZIO_PRIORITY_ASYNC_READ) 4529 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4530 else 4531 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4532 4533 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4534 /* 4535 * Read from the L2ARC if the following are true: 4536 * 1. The L2ARC vdev was previously cached. 4537 * 2. This buffer still has L2ARC metadata. 4538 * 3. This buffer isn't currently writing to the L2ARC. 4539 * 4. The L2ARC entry wasn't evicted, which may 4540 * also have invalidated the vdev. 4541 * 5. This isn't prefetch and l2arc_noprefetch is set. 4542 */ 4543 if (HDR_HAS_L2HDR(hdr) && 4544 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4545 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4546 l2arc_read_callback_t *cb; 4547 void* b_data; 4548 4549 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4550 ARCSTAT_BUMP(arcstat_l2_hits); 4551 4552 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4553 KM_SLEEP); 4554 cb->l2rcb_buf = buf; 4555 cb->l2rcb_spa = spa; 4556 cb->l2rcb_bp = *bp; 4557 cb->l2rcb_zb = *zb; 4558 cb->l2rcb_flags = zio_flags; 4559 cb->l2rcb_compress = b_compress; 4560 if (b_asize > hdr->b_size) { 4561 ASSERT3U(b_compress, ==, 4562 ZIO_COMPRESS_OFF); 4563 b_data = zio_data_buf_alloc(b_asize); 4564 cb->l2rcb_data = b_data; 4565 } else { 4566 b_data = buf->b_data; 4567 } 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 ASSERT3U(b_asize, ==, 0); 4581 rzio = zio_null(pio, spa, vd, 4582 l2arc_read_done, cb, 4583 zio_flags | ZIO_FLAG_DONT_CACHE | 4584 ZIO_FLAG_CANFAIL | 4585 ZIO_FLAG_DONT_PROPAGATE | 4586 ZIO_FLAG_DONT_RETRY); 4587 } else { 4588 rzio = zio_read_phys(pio, vd, addr, 4589 b_asize, b_data, 4590 ZIO_CHECKSUM_OFF, 4591 l2arc_read_done, cb, priority, 4592 zio_flags | ZIO_FLAG_DONT_CACHE | 4593 ZIO_FLAG_CANFAIL | 4594 ZIO_FLAG_DONT_PROPAGATE | 4595 ZIO_FLAG_DONT_RETRY, B_FALSE); 4596 } 4597 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4598 zio_t *, rzio); 4599 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4600 4601 if (*arc_flags & ARC_FLAG_NOWAIT) { 4602 zio_nowait(rzio); 4603 return (0); 4604 } 4605 4606 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4607 if (zio_wait(rzio) == 0) 4608 return (0); 4609 4610 /* l2arc read error; goto zio_read() */ 4611 } else { 4612 DTRACE_PROBE1(l2arc__miss, 4613 arc_buf_hdr_t *, hdr); 4614 ARCSTAT_BUMP(arcstat_l2_misses); 4615 if (HDR_L2_WRITING(hdr)) 4616 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4617 spa_config_exit(spa, SCL_L2ARC, vd); 4618 } 4619 } else { 4620 if (vd != NULL) 4621 spa_config_exit(spa, SCL_L2ARC, vd); 4622 if (l2arc_ndev != 0) { 4623 DTRACE_PROBE1(l2arc__miss, 4624 arc_buf_hdr_t *, hdr); 4625 ARCSTAT_BUMP(arcstat_l2_misses); 4626 } 4627 } 4628 4629 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4630 arc_read_done, buf, priority, zio_flags, zb); 4631 4632 if (*arc_flags & ARC_FLAG_WAIT) 4633 return (zio_wait(rzio)); 4634 4635 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4636 zio_nowait(rzio); 4637 } 4638 return (0); 4639} 4640 4641void 4642arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4643{ 4644 ASSERT(buf->b_hdr != NULL); 4645 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4646 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4647 func == NULL); 4648 ASSERT(buf->b_efunc == NULL); 4649 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4650 4651 buf->b_efunc = func; 4652 buf->b_private = private; 4653} 4654 4655/* 4656 * Notify the arc that a block was freed, and thus will never be used again. 4657 */ 4658void 4659arc_freed(spa_t *spa, const blkptr_t *bp) 4660{ 4661 arc_buf_hdr_t *hdr; 4662 kmutex_t *hash_lock; 4663 uint64_t guid = spa_load_guid(spa); 4664 4665 ASSERT(!BP_IS_EMBEDDED(bp)); 4666 4667 hdr = buf_hash_find(guid, bp, &hash_lock); 4668 if (hdr == NULL) 4669 return; 4670 if (HDR_BUF_AVAILABLE(hdr)) { 4671 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4672 add_reference(hdr, hash_lock, FTAG); 4673 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4674 mutex_exit(hash_lock); 4675 4676 arc_release(buf, FTAG); 4677 (void) arc_buf_remove_ref(buf, FTAG); 4678 } else { 4679 mutex_exit(hash_lock); 4680 } 4681 4682} 4683 4684/* 4685 * Clear the user eviction callback set by arc_set_callback(), first calling 4686 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4687 * clearing the callback may result in the arc_buf being destroyed. However, 4688 * it will not result in the *last* arc_buf being destroyed, hence the data 4689 * will remain cached in the ARC. We make a copy of the arc buffer here so 4690 * that we can process the callback without holding any locks. 4691 * 4692 * It's possible that the callback is already in the process of being cleared 4693 * by another thread. In this case we can not clear the callback. 4694 * 4695 * Returns B_TRUE if the callback was successfully called and cleared. 4696 */ 4697boolean_t 4698arc_clear_callback(arc_buf_t *buf) 4699{ 4700 arc_buf_hdr_t *hdr; 4701 kmutex_t *hash_lock; 4702 arc_evict_func_t *efunc = buf->b_efunc; 4703 void *private = buf->b_private; 4704 4705 mutex_enter(&buf->b_evict_lock); 4706 hdr = buf->b_hdr; 4707 if (hdr == NULL) { 4708 /* 4709 * We are in arc_do_user_evicts(). 4710 */ 4711 ASSERT(buf->b_data == NULL); 4712 mutex_exit(&buf->b_evict_lock); 4713 return (B_FALSE); 4714 } else if (buf->b_data == NULL) { 4715 /* 4716 * We are on the eviction list; process this buffer now 4717 * but let arc_do_user_evicts() do the reaping. 4718 */ 4719 buf->b_efunc = NULL; 4720 mutex_exit(&buf->b_evict_lock); 4721 VERIFY0(efunc(private)); 4722 return (B_TRUE); 4723 } 4724 hash_lock = HDR_LOCK(hdr); 4725 mutex_enter(hash_lock); 4726 hdr = buf->b_hdr; 4727 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4728 4729 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4730 hdr->b_l1hdr.b_datacnt); 4731 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4732 hdr->b_l1hdr.b_state == arc_mfu); 4733 4734 buf->b_efunc = NULL; 4735 buf->b_private = NULL; 4736 4737 if (hdr->b_l1hdr.b_datacnt > 1) { 4738 mutex_exit(&buf->b_evict_lock); 4739 arc_buf_destroy(buf, TRUE); 4740 } else { 4741 ASSERT(buf == hdr->b_l1hdr.b_buf); 4742 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4743 mutex_exit(&buf->b_evict_lock); 4744 } 4745 4746 mutex_exit(hash_lock); 4747 VERIFY0(efunc(private)); 4748 return (B_TRUE); 4749} 4750 4751/* 4752 * Release this buffer from the cache, making it an anonymous buffer. This 4753 * must be done after a read and prior to modifying the buffer contents. 4754 * If the buffer has more than one reference, we must make 4755 * a new hdr for the buffer. 4756 */ 4757void 4758arc_release(arc_buf_t *buf, void *tag) 4759{ 4760 arc_buf_hdr_t *hdr = buf->b_hdr; 4761 4762 /* 4763 * It would be nice to assert that if it's DMU metadata (level > 4764 * 0 || it's the dnode file), then it must be syncing context. 4765 * But we don't know that information at this level. 4766 */ 4767 4768 mutex_enter(&buf->b_evict_lock); 4769 4770 ASSERT(HDR_HAS_L1HDR(hdr)); 4771 4772 /* 4773 * We don't grab the hash lock prior to this check, because if 4774 * the buffer's header is in the arc_anon state, it won't be 4775 * linked into the hash table. 4776 */ 4777 if (hdr->b_l1hdr.b_state == arc_anon) { 4778 mutex_exit(&buf->b_evict_lock); 4779 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4780 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4781 ASSERT(!HDR_HAS_L2HDR(hdr)); 4782 ASSERT(BUF_EMPTY(hdr)); 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 l2arc_trim(hdr); 4824 arc_hdr_l2hdr_destroy(hdr); 4825 } 4826 4827 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4828 } 4829 4830 /* 4831 * Do we have more than one buf? 4832 */ 4833 if (hdr->b_l1hdr.b_datacnt > 1) { 4834 arc_buf_hdr_t *nhdr; 4835 arc_buf_t **bufp; 4836 uint64_t blksz = hdr->b_size; 4837 uint64_t spa = hdr->b_spa; 4838 arc_buf_contents_t type = arc_buf_type(hdr); 4839 uint32_t flags = hdr->b_flags; 4840 4841 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4842 /* 4843 * Pull the data off of this hdr and attach it to 4844 * a new anonymous hdr. 4845 */ 4846 (void) remove_reference(hdr, hash_lock, tag); 4847 bufp = &hdr->b_l1hdr.b_buf; 4848 while (*bufp != buf) 4849 bufp = &(*bufp)->b_next; 4850 *bufp = buf->b_next; 4851 buf->b_next = NULL; 4852 4853 ASSERT3P(state, !=, arc_l2c_only); 4854 4855 (void) refcount_remove_many( 4856 &state->arcs_size, hdr->b_size, buf); 4857 4858 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4859 ASSERT3P(state, !=, arc_l2c_only); 4860 uint64_t *size = &state->arcs_lsize[type]; 4861 ASSERT3U(*size, >=, hdr->b_size); 4862 atomic_add_64(size, -hdr->b_size); 4863 } 4864 4865 /* 4866 * We're releasing a duplicate user data buffer, update 4867 * our statistics accordingly. 4868 */ 4869 if (HDR_ISTYPE_DATA(hdr)) { 4870 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4871 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4872 -hdr->b_size); 4873 } 4874 hdr->b_l1hdr.b_datacnt -= 1; 4875 arc_cksum_verify(buf); 4876#ifdef illumos 4877 arc_buf_unwatch(buf); 4878#endif 4879 4880 mutex_exit(hash_lock); 4881 4882 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4883 nhdr->b_size = blksz; 4884 nhdr->b_spa = spa; 4885 4886 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4887 nhdr->b_flags |= arc_bufc_to_flags(type); 4888 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4889 4890 nhdr->b_l1hdr.b_buf = buf; 4891 nhdr->b_l1hdr.b_datacnt = 1; 4892 nhdr->b_l1hdr.b_state = arc_anon; 4893 nhdr->b_l1hdr.b_arc_access = 0; 4894 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4895 nhdr->b_freeze_cksum = NULL; 4896 4897 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4898 buf->b_hdr = nhdr; 4899 mutex_exit(&buf->b_evict_lock); 4900 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4901 } else { 4902 mutex_exit(&buf->b_evict_lock); 4903 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4904 /* protected by hash lock, or hdr is on arc_anon */ 4905 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4906 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4907 arc_change_state(arc_anon, hdr, hash_lock); 4908 hdr->b_l1hdr.b_arc_access = 0; 4909 mutex_exit(hash_lock); 4910 4911 buf_discard_identity(hdr); 4912 arc_buf_thaw(buf); 4913 } 4914 buf->b_efunc = NULL; 4915 buf->b_private = NULL; 4916} 4917 4918int 4919arc_released(arc_buf_t *buf) 4920{ 4921 int released; 4922 4923 mutex_enter(&buf->b_evict_lock); 4924 released = (buf->b_data != NULL && 4925 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4926 mutex_exit(&buf->b_evict_lock); 4927 return (released); 4928} 4929 4930#ifdef ZFS_DEBUG 4931int 4932arc_referenced(arc_buf_t *buf) 4933{ 4934 int referenced; 4935 4936 mutex_enter(&buf->b_evict_lock); 4937 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4938 mutex_exit(&buf->b_evict_lock); 4939 return (referenced); 4940} 4941#endif 4942 4943static void 4944arc_write_ready(zio_t *zio) 4945{ 4946 arc_write_callback_t *callback = zio->io_private; 4947 arc_buf_t *buf = callback->awcb_buf; 4948 arc_buf_hdr_t *hdr = buf->b_hdr; 4949 4950 ASSERT(HDR_HAS_L1HDR(hdr)); 4951 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4952 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4953 callback->awcb_ready(zio, buf, callback->awcb_private); 4954 4955 /* 4956 * If the IO is already in progress, then this is a re-write 4957 * attempt, so we need to thaw and re-compute the cksum. 4958 * It is the responsibility of the callback to handle the 4959 * accounting for any re-write attempt. 4960 */ 4961 if (HDR_IO_IN_PROGRESS(hdr)) { 4962 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4963 if (hdr->b_freeze_cksum != NULL) { 4964 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4965 hdr->b_freeze_cksum = NULL; 4966 } 4967 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4968 } 4969 arc_cksum_compute(buf, B_FALSE); 4970 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4971} 4972 4973/* 4974 * The SPA calls this callback for each physical write that happens on behalf 4975 * of a logical write. See the comment in dbuf_write_physdone() for details. 4976 */ 4977static void 4978arc_write_physdone(zio_t *zio) 4979{ 4980 arc_write_callback_t *cb = zio->io_private; 4981 if (cb->awcb_physdone != NULL) 4982 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4983} 4984 4985static void 4986arc_write_done(zio_t *zio) 4987{ 4988 arc_write_callback_t *callback = zio->io_private; 4989 arc_buf_t *buf = callback->awcb_buf; 4990 arc_buf_hdr_t *hdr = buf->b_hdr; 4991 4992 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4993 4994 if (zio->io_error == 0) { 4995 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4996 buf_discard_identity(hdr); 4997 } else { 4998 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4999 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5000 } 5001 } else { 5002 ASSERT(BUF_EMPTY(hdr)); 5003 } 5004 5005 /* 5006 * If the block to be written was all-zero or compressed enough to be 5007 * embedded in the BP, no write was performed so there will be no 5008 * dva/birth/checksum. The buffer must therefore remain anonymous 5009 * (and uncached). 5010 */ 5011 if (!BUF_EMPTY(hdr)) { 5012 arc_buf_hdr_t *exists; 5013 kmutex_t *hash_lock; 5014 5015 ASSERT(zio->io_error == 0); 5016 5017 arc_cksum_verify(buf); 5018 5019 exists = buf_hash_insert(hdr, &hash_lock); 5020 if (exists != NULL) { 5021 /* 5022 * This can only happen if we overwrite for 5023 * sync-to-convergence, because we remove 5024 * buffers from the hash table when we arc_free(). 5025 */ 5026 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5027 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5028 panic("bad overwrite, hdr=%p exists=%p", 5029 (void *)hdr, (void *)exists); 5030 ASSERT(refcount_is_zero( 5031 &exists->b_l1hdr.b_refcnt)); 5032 arc_change_state(arc_anon, exists, hash_lock); 5033 mutex_exit(hash_lock); 5034 arc_hdr_destroy(exists); 5035 exists = buf_hash_insert(hdr, &hash_lock); 5036 ASSERT3P(exists, ==, NULL); 5037 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5038 /* nopwrite */ 5039 ASSERT(zio->io_prop.zp_nopwrite); 5040 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5041 panic("bad nopwrite, hdr=%p exists=%p", 5042 (void *)hdr, (void *)exists); 5043 } else { 5044 /* Dedup */ 5045 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5046 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5047 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5048 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5049 } 5050 } 5051 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5052 /* if it's not anon, we are doing a scrub */ 5053 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5054 arc_access(hdr, hash_lock); 5055 mutex_exit(hash_lock); 5056 } else { 5057 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5058 } 5059 5060 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5061 callback->awcb_done(zio, buf, callback->awcb_private); 5062 5063 kmem_free(callback, sizeof (arc_write_callback_t)); 5064} 5065 5066zio_t * 5067arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5068 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5069 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 5070 arc_done_func_t *done, void *private, zio_priority_t priority, 5071 int zio_flags, const zbookmark_phys_t *zb) 5072{ 5073 arc_buf_hdr_t *hdr = buf->b_hdr; 5074 arc_write_callback_t *callback; 5075 zio_t *zio; 5076 5077 ASSERT(ready != NULL); 5078 ASSERT(done != NULL); 5079 ASSERT(!HDR_IO_ERROR(hdr)); 5080 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5081 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5082 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5083 if (l2arc) 5084 hdr->b_flags |= ARC_FLAG_L2CACHE; 5085 if (l2arc_compress) 5086 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5087 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5088 callback->awcb_ready = ready; 5089 callback->awcb_physdone = physdone; 5090 callback->awcb_done = done; 5091 callback->awcb_private = private; 5092 callback->awcb_buf = buf; 5093 5094 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5095 arc_write_ready, arc_write_physdone, arc_write_done, callback, 5096 priority, zio_flags, zb); 5097 5098 return (zio); 5099} 5100 5101static int 5102arc_memory_throttle(uint64_t reserve, uint64_t txg) 5103{ 5104#ifdef _KERNEL 5105 uint64_t available_memory = ptob(freemem); 5106 static uint64_t page_load = 0; 5107 static uint64_t last_txg = 0; 5108 5109#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5110 available_memory = 5111 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5112#endif 5113 5114 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5115 return (0); 5116 5117 if (txg > last_txg) { 5118 last_txg = txg; 5119 page_load = 0; 5120 } 5121 /* 5122 * If we are in pageout, we know that memory is already tight, 5123 * the arc is already going to be evicting, so we just want to 5124 * continue to let page writes occur as quickly as possible. 5125 */ 5126 if (curproc == pageproc) { 5127 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5128 return (SET_ERROR(ERESTART)); 5129 /* Note: reserve is inflated, so we deflate */ 5130 page_load += reserve / 8; 5131 return (0); 5132 } else if (page_load > 0 && arc_reclaim_needed()) { 5133 /* memory is low, delay before restarting */ 5134 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5135 return (SET_ERROR(EAGAIN)); 5136 } 5137 page_load = 0; 5138#endif 5139 return (0); 5140} 5141 5142void 5143arc_tempreserve_clear(uint64_t reserve) 5144{ 5145 atomic_add_64(&arc_tempreserve, -reserve); 5146 ASSERT((int64_t)arc_tempreserve >= 0); 5147} 5148 5149int 5150arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5151{ 5152 int error; 5153 uint64_t anon_size; 5154 5155 if (reserve > arc_c/4 && !arc_no_grow) { 5156 arc_c = MIN(arc_c_max, reserve * 4); 5157 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5158 } 5159 if (reserve > arc_c) 5160 return (SET_ERROR(ENOMEM)); 5161 5162 /* 5163 * Don't count loaned bufs as in flight dirty data to prevent long 5164 * network delays from blocking transactions that are ready to be 5165 * assigned to a txg. 5166 */ 5167 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5168 arc_loaned_bytes), 0); 5169 5170 /* 5171 * Writes will, almost always, require additional memory allocations 5172 * in order to compress/encrypt/etc the data. We therefore need to 5173 * make sure that there is sufficient available memory for this. 5174 */ 5175 error = arc_memory_throttle(reserve, txg); 5176 if (error != 0) 5177 return (error); 5178 5179 /* 5180 * Throttle writes when the amount of dirty data in the cache 5181 * gets too large. We try to keep the cache less than half full 5182 * of dirty blocks so that our sync times don't grow too large. 5183 * Note: if two requests come in concurrently, we might let them 5184 * both succeed, when one of them should fail. Not a huge deal. 5185 */ 5186 5187 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5188 anon_size > arc_c / 4) { 5189 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5190 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5191 arc_tempreserve>>10, 5192 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5193 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5194 reserve>>10, arc_c>>10); 5195 return (SET_ERROR(ERESTART)); 5196 } 5197 atomic_add_64(&arc_tempreserve, reserve); 5198 return (0); 5199} 5200 5201static void 5202arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5203 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5204{ 5205 size->value.ui64 = refcount_count(&state->arcs_size); 5206 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5207 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5208} 5209 5210static int 5211arc_kstat_update(kstat_t *ksp, int rw) 5212{ 5213 arc_stats_t *as = ksp->ks_data; 5214 5215 if (rw == KSTAT_WRITE) { 5216 return (EACCES); 5217 } else { 5218 arc_kstat_update_state(arc_anon, 5219 &as->arcstat_anon_size, 5220 &as->arcstat_anon_evictable_data, 5221 &as->arcstat_anon_evictable_metadata); 5222 arc_kstat_update_state(arc_mru, 5223 &as->arcstat_mru_size, 5224 &as->arcstat_mru_evictable_data, 5225 &as->arcstat_mru_evictable_metadata); 5226 arc_kstat_update_state(arc_mru_ghost, 5227 &as->arcstat_mru_ghost_size, 5228 &as->arcstat_mru_ghost_evictable_data, 5229 &as->arcstat_mru_ghost_evictable_metadata); 5230 arc_kstat_update_state(arc_mfu, 5231 &as->arcstat_mfu_size, 5232 &as->arcstat_mfu_evictable_data, 5233 &as->arcstat_mfu_evictable_metadata); 5234 arc_kstat_update_state(arc_mfu_ghost, 5235 &as->arcstat_mfu_ghost_size, 5236 &as->arcstat_mfu_ghost_evictable_data, 5237 &as->arcstat_mfu_ghost_evictable_metadata); 5238 } 5239 5240 return (0); 5241} 5242 5243/* 5244 * This function *must* return indices evenly distributed between all 5245 * sublists of the multilist. This is needed due to how the ARC eviction 5246 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5247 * distributed between all sublists and uses this assumption when 5248 * deciding which sublist to evict from and how much to evict from it. 5249 */ 5250unsigned int 5251arc_state_multilist_index_func(multilist_t *ml, void *obj) 5252{ 5253 arc_buf_hdr_t *hdr = obj; 5254 5255 /* 5256 * We rely on b_dva to generate evenly distributed index 5257 * numbers using buf_hash below. So, as an added precaution, 5258 * let's make sure we never add empty buffers to the arc lists. 5259 */ 5260 ASSERT(!BUF_EMPTY(hdr)); 5261 5262 /* 5263 * The assumption here, is the hash value for a given 5264 * arc_buf_hdr_t will remain constant throughout it's lifetime 5265 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5266 * Thus, we don't need to store the header's sublist index 5267 * on insertion, as this index can be recalculated on removal. 5268 * 5269 * Also, the low order bits of the hash value are thought to be 5270 * distributed evenly. Otherwise, in the case that the multilist 5271 * has a power of two number of sublists, each sublists' usage 5272 * would not be evenly distributed. 5273 */ 5274 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5275 multilist_get_num_sublists(ml)); 5276} 5277 5278#ifdef _KERNEL 5279static eventhandler_tag arc_event_lowmem = NULL; 5280 5281static void 5282arc_lowmem(void *arg __unused, int howto __unused) 5283{ 5284 5285 mutex_enter(&arc_reclaim_lock); 5286 /* XXX: Memory deficit should be passed as argument. */ 5287 needfree = btoc(arc_c >> arc_shrink_shift); 5288 DTRACE_PROBE(arc__needfree); 5289 cv_signal(&arc_reclaim_thread_cv); 5290 5291 /* 5292 * It is unsafe to block here in arbitrary threads, because we can come 5293 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5294 * with ARC reclaim thread. 5295 */ 5296 if (curproc == pageproc) 5297 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5298 mutex_exit(&arc_reclaim_lock); 5299} 5300#endif 5301 5302void 5303arc_init(void) 5304{ 5305 int i, prefetch_tunable_set = 0; 5306 5307 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5308 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5309 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5310 5311 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5312 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5313 5314 /* Convert seconds to clock ticks */ 5315 arc_min_prefetch_lifespan = 1 * hz; 5316 5317 /* Start out with 1/8 of all memory */ 5318 arc_c = kmem_size() / 8; 5319 5320#ifdef illumos 5321#ifdef _KERNEL 5322 /* 5323 * On architectures where the physical memory can be larger 5324 * than the addressable space (intel in 32-bit mode), we may 5325 * need to limit the cache to 1/8 of VM size. 5326 */ 5327 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5328#endif 5329#endif /* illumos */ 5330 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 5331 arc_c_min = MAX(arc_c / 4, 16 << 20); 5332 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 5333 if (arc_c * 8 >= 1 << 30) 5334 arc_c_max = (arc_c * 8) - (1 << 30); 5335 else 5336 arc_c_max = arc_c_min; 5337 arc_c_max = MAX(arc_c * 5, arc_c_max); 5338 5339 /* 5340 * In userland, there's only the memory pressure that we artificially 5341 * create (see arc_available_memory()). Don't let arc_c get too 5342 * small, because it can cause transactions to be larger than 5343 * arc_c, causing arc_tempreserve_space() to fail. 5344 */ 5345#ifndef _KERNEL 5346 arc_c_min = arc_c_max / 2; 5347#endif 5348 5349#ifdef _KERNEL 5350 /* 5351 * Allow the tunables to override our calculations if they are 5352 * reasonable (ie. over 16MB) 5353 */ 5354 if (zfs_arc_max > 16 << 20 && zfs_arc_max < kmem_size()) 5355 arc_c_max = zfs_arc_max; 5356 if (zfs_arc_min > 16 << 20 && zfs_arc_min <= arc_c_max) 5357 arc_c_min = zfs_arc_min; 5358#endif 5359 5360 arc_c = arc_c_max; 5361 arc_p = (arc_c >> 1); 5362 5363 /* limit meta-data to 1/4 of the arc capacity */ 5364 arc_meta_limit = arc_c_max / 4; 5365 5366 /* Allow the tunable to override if it is reasonable */ 5367 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5368 arc_meta_limit = zfs_arc_meta_limit; 5369 5370 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5371 arc_c_min = arc_meta_limit / 2; 5372 5373 if (zfs_arc_meta_min > 0) { 5374 arc_meta_min = zfs_arc_meta_min; 5375 } else { 5376 arc_meta_min = arc_c_min / 2; 5377 } 5378 5379 if (zfs_arc_grow_retry > 0) 5380 arc_grow_retry = zfs_arc_grow_retry; 5381 5382 if (zfs_arc_shrink_shift > 0) 5383 arc_shrink_shift = zfs_arc_shrink_shift; 5384 5385 /* 5386 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5387 */ 5388 if (arc_no_grow_shift >= arc_shrink_shift) 5389 arc_no_grow_shift = arc_shrink_shift - 1; 5390 5391 if (zfs_arc_p_min_shift > 0) 5392 arc_p_min_shift = zfs_arc_p_min_shift; 5393 5394 if (zfs_arc_num_sublists_per_state < 1) 5395 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 5396 5397 /* if kmem_flags are set, lets try to use less memory */ 5398 if (kmem_debugging()) 5399 arc_c = arc_c / 2; 5400 if (arc_c < arc_c_min) 5401 arc_c = arc_c_min; 5402 5403 zfs_arc_min = arc_c_min; 5404 zfs_arc_max = arc_c_max; 5405 5406 arc_anon = &ARC_anon; 5407 arc_mru = &ARC_mru; 5408 arc_mru_ghost = &ARC_mru_ghost; 5409 arc_mfu = &ARC_mfu; 5410 arc_mfu_ghost = &ARC_mfu_ghost; 5411 arc_l2c_only = &ARC_l2c_only; 5412 arc_size = 0; 5413 5414 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5415 sizeof (arc_buf_hdr_t), 5416 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5417 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5418 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5419 sizeof (arc_buf_hdr_t), 5420 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5421 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5422 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5423 sizeof (arc_buf_hdr_t), 5424 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5425 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5426 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5427 sizeof (arc_buf_hdr_t), 5428 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5429 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5430 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5431 sizeof (arc_buf_hdr_t), 5432 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5433 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5434 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5435 sizeof (arc_buf_hdr_t), 5436 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5437 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5438 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5439 sizeof (arc_buf_hdr_t), 5440 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5441 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5442 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5443 sizeof (arc_buf_hdr_t), 5444 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5445 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5446 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5447 sizeof (arc_buf_hdr_t), 5448 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5449 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5450 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5451 sizeof (arc_buf_hdr_t), 5452 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5453 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5454 5455 refcount_create(&arc_anon->arcs_size); 5456 refcount_create(&arc_mru->arcs_size); 5457 refcount_create(&arc_mru_ghost->arcs_size); 5458 refcount_create(&arc_mfu->arcs_size); 5459 refcount_create(&arc_mfu_ghost->arcs_size); 5460 refcount_create(&arc_l2c_only->arcs_size); 5461 5462 buf_init(); 5463 5464 arc_reclaim_thread_exit = FALSE; 5465 arc_user_evicts_thread_exit = FALSE; 5466 arc_eviction_list = NULL; 5467 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5468 5469 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5470 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5471 5472 if (arc_ksp != NULL) { 5473 arc_ksp->ks_data = &arc_stats; 5474 arc_ksp->ks_update = arc_kstat_update; 5475 kstat_install(arc_ksp); 5476 } 5477 5478 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5479 TS_RUN, minclsyspri); 5480 5481#ifdef _KERNEL 5482 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5483 EVENTHANDLER_PRI_FIRST); 5484#endif 5485 5486 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5487 TS_RUN, minclsyspri); 5488 5489 arc_dead = FALSE; 5490 arc_warm = B_FALSE; 5491 5492 /* 5493 * Calculate maximum amount of dirty data per pool. 5494 * 5495 * If it has been set by /etc/system, take that. 5496 * Otherwise, use a percentage of physical memory defined by 5497 * zfs_dirty_data_max_percent (default 10%) with a cap at 5498 * zfs_dirty_data_max_max (default 4GB). 5499 */ 5500 if (zfs_dirty_data_max == 0) { 5501 zfs_dirty_data_max = ptob(physmem) * 5502 zfs_dirty_data_max_percent / 100; 5503 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5504 zfs_dirty_data_max_max); 5505 } 5506 5507#ifdef _KERNEL 5508 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5509 prefetch_tunable_set = 1; 5510 5511#ifdef __i386__ 5512 if (prefetch_tunable_set == 0) { 5513 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5514 "-- to enable,\n"); 5515 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5516 "to /boot/loader.conf.\n"); 5517 zfs_prefetch_disable = 1; 5518 } 5519#else 5520 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5521 prefetch_tunable_set == 0) { 5522 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5523 "than 4GB of RAM is present;\n" 5524 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5525 "to /boot/loader.conf.\n"); 5526 zfs_prefetch_disable = 1; 5527 } 5528#endif 5529 /* Warn about ZFS memory and address space requirements. */ 5530 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5531 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5532 "expect unstable behavior.\n"); 5533 } 5534 if (kmem_size() < 512 * (1 << 20)) { 5535 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5536 "expect unstable behavior.\n"); 5537 printf(" Consider tuning vm.kmem_size and " 5538 "vm.kmem_size_max\n"); 5539 printf(" in /boot/loader.conf.\n"); 5540 } 5541#endif 5542} 5543 5544void 5545arc_fini(void) 5546{ 5547 mutex_enter(&arc_reclaim_lock); 5548 arc_reclaim_thread_exit = TRUE; 5549 /* 5550 * The reclaim thread will set arc_reclaim_thread_exit back to 5551 * FALSE when it is finished exiting; we're waiting for that. 5552 */ 5553 while (arc_reclaim_thread_exit) { 5554 cv_signal(&arc_reclaim_thread_cv); 5555 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5556 } 5557 mutex_exit(&arc_reclaim_lock); 5558 5559 mutex_enter(&arc_user_evicts_lock); 5560 arc_user_evicts_thread_exit = TRUE; 5561 /* 5562 * The user evicts thread will set arc_user_evicts_thread_exit 5563 * to FALSE when it is finished exiting; we're waiting for that. 5564 */ 5565 while (arc_user_evicts_thread_exit) { 5566 cv_signal(&arc_user_evicts_cv); 5567 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5568 } 5569 mutex_exit(&arc_user_evicts_lock); 5570 5571 /* Use TRUE to ensure *all* buffers are evicted */ 5572 arc_flush(NULL, TRUE); 5573 5574 arc_dead = TRUE; 5575 5576 if (arc_ksp != NULL) { 5577 kstat_delete(arc_ksp); 5578 arc_ksp = NULL; 5579 } 5580 5581 mutex_destroy(&arc_reclaim_lock); 5582 cv_destroy(&arc_reclaim_thread_cv); 5583 cv_destroy(&arc_reclaim_waiters_cv); 5584 5585 mutex_destroy(&arc_user_evicts_lock); 5586 cv_destroy(&arc_user_evicts_cv); 5587 5588 refcount_destroy(&arc_anon->arcs_size); 5589 refcount_destroy(&arc_mru->arcs_size); 5590 refcount_destroy(&arc_mru_ghost->arcs_size); 5591 refcount_destroy(&arc_mfu->arcs_size); 5592 refcount_destroy(&arc_mfu_ghost->arcs_size); 5593 refcount_destroy(&arc_l2c_only->arcs_size); 5594 5595 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5596 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5597 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5598 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5599 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); 5600 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5601 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5602 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5603 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5604 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]); 5605 5606 buf_fini(); 5607 5608 ASSERT0(arc_loaned_bytes); 5609 5610#ifdef _KERNEL 5611 if (arc_event_lowmem != NULL) 5612 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5613#endif 5614} 5615 5616/* 5617 * Level 2 ARC 5618 * 5619 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5620 * It uses dedicated storage devices to hold cached data, which are populated 5621 * using large infrequent writes. The main role of this cache is to boost 5622 * the performance of random read workloads. The intended L2ARC devices 5623 * include short-stroked disks, solid state disks, and other media with 5624 * substantially faster read latency than disk. 5625 * 5626 * +-----------------------+ 5627 * | ARC | 5628 * +-----------------------+ 5629 * | ^ ^ 5630 * | | | 5631 * l2arc_feed_thread() arc_read() 5632 * | | | 5633 * | l2arc read | 5634 * V | | 5635 * +---------------+ | 5636 * | L2ARC | | 5637 * +---------------+ | 5638 * | ^ | 5639 * l2arc_write() | | 5640 * | | | 5641 * V | | 5642 * +-------+ +-------+ 5643 * | vdev | | vdev | 5644 * | cache | | cache | 5645 * +-------+ +-------+ 5646 * +=========+ .-----. 5647 * : L2ARC : |-_____-| 5648 * : devices : | Disks | 5649 * +=========+ `-_____-' 5650 * 5651 * Read requests are satisfied from the following sources, in order: 5652 * 5653 * 1) ARC 5654 * 2) vdev cache of L2ARC devices 5655 * 3) L2ARC devices 5656 * 4) vdev cache of disks 5657 * 5) disks 5658 * 5659 * Some L2ARC device types exhibit extremely slow write performance. 5660 * To accommodate for this there are some significant differences between 5661 * the L2ARC and traditional cache design: 5662 * 5663 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5664 * the ARC behave as usual, freeing buffers and placing headers on ghost 5665 * lists. The ARC does not send buffers to the L2ARC during eviction as 5666 * this would add inflated write latencies for all ARC memory pressure. 5667 * 5668 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5669 * It does this by periodically scanning buffers from the eviction-end of 5670 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5671 * not already there. It scans until a headroom of buffers is satisfied, 5672 * which itself is a buffer for ARC eviction. If a compressible buffer is 5673 * found during scanning and selected for writing to an L2ARC device, we 5674 * temporarily boost scanning headroom during the next scan cycle to make 5675 * sure we adapt to compression effects (which might significantly reduce 5676 * the data volume we write to L2ARC). The thread that does this is 5677 * l2arc_feed_thread(), illustrated below; example sizes are included to 5678 * provide a better sense of ratio than this diagram: 5679 * 5680 * head --> tail 5681 * +---------------------+----------+ 5682 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5683 * +---------------------+----------+ | o L2ARC eligible 5684 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5685 * +---------------------+----------+ | 5686 * 15.9 Gbytes ^ 32 Mbytes | 5687 * headroom | 5688 * l2arc_feed_thread() 5689 * | 5690 * l2arc write hand <--[oooo]--' 5691 * | 8 Mbyte 5692 * | write max 5693 * V 5694 * +==============================+ 5695 * L2ARC dev |####|#|###|###| |####| ... | 5696 * +==============================+ 5697 * 32 Gbytes 5698 * 5699 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5700 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5701 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5702 * safe to say that this is an uncommon case, since buffers at the end of 5703 * the ARC lists have moved there due to inactivity. 5704 * 5705 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5706 * then the L2ARC simply misses copying some buffers. This serves as a 5707 * pressure valve to prevent heavy read workloads from both stalling the ARC 5708 * with waits and clogging the L2ARC with writes. This also helps prevent 5709 * the potential for the L2ARC to churn if it attempts to cache content too 5710 * quickly, such as during backups of the entire pool. 5711 * 5712 * 5. After system boot and before the ARC has filled main memory, there are 5713 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5714 * lists can remain mostly static. Instead of searching from tail of these 5715 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5716 * for eligible buffers, greatly increasing its chance of finding them. 5717 * 5718 * The L2ARC device write speed is also boosted during this time so that 5719 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5720 * there are no L2ARC reads, and no fear of degrading read performance 5721 * through increased writes. 5722 * 5723 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5724 * the vdev queue can aggregate them into larger and fewer writes. Each 5725 * device is written to in a rotor fashion, sweeping writes through 5726 * available space then repeating. 5727 * 5728 * 7. The L2ARC does not store dirty content. It never needs to flush 5729 * write buffers back to disk based storage. 5730 * 5731 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5732 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5733 * 5734 * The performance of the L2ARC can be tweaked by a number of tunables, which 5735 * may be necessary for different workloads: 5736 * 5737 * l2arc_write_max max write bytes per interval 5738 * l2arc_write_boost extra write bytes during device warmup 5739 * l2arc_noprefetch skip caching prefetched buffers 5740 * l2arc_headroom number of max device writes to precache 5741 * l2arc_headroom_boost when we find compressed buffers during ARC 5742 * scanning, we multiply headroom by this 5743 * percentage factor for the next scan cycle, 5744 * since more compressed buffers are likely to 5745 * be present 5746 * l2arc_feed_secs seconds between L2ARC writing 5747 * 5748 * Tunables may be removed or added as future performance improvements are 5749 * integrated, and also may become zpool properties. 5750 * 5751 * There are three key functions that control how the L2ARC warms up: 5752 * 5753 * l2arc_write_eligible() check if a buffer is eligible to cache 5754 * l2arc_write_size() calculate how much to write 5755 * l2arc_write_interval() calculate sleep delay between writes 5756 * 5757 * These three functions determine what to write, how much, and how quickly 5758 * to send writes. 5759 */ 5760 5761static boolean_t 5762l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5763{ 5764 /* 5765 * A buffer is *not* eligible for the L2ARC if it: 5766 * 1. belongs to a different spa. 5767 * 2. is already cached on the L2ARC. 5768 * 3. has an I/O in progress (it may be an incomplete read). 5769 * 4. is flagged not eligible (zfs property). 5770 */ 5771 if (hdr->b_spa != spa_guid) { 5772 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5773 return (B_FALSE); 5774 } 5775 if (HDR_HAS_L2HDR(hdr)) { 5776 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5777 return (B_FALSE); 5778 } 5779 if (HDR_IO_IN_PROGRESS(hdr)) { 5780 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5781 return (B_FALSE); 5782 } 5783 if (!HDR_L2CACHE(hdr)) { 5784 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5785 return (B_FALSE); 5786 } 5787 5788 return (B_TRUE); 5789} 5790 5791static uint64_t 5792l2arc_write_size(void) 5793{ 5794 uint64_t size; 5795 5796 /* 5797 * Make sure our globals have meaningful values in case the user 5798 * altered them. 5799 */ 5800 size = l2arc_write_max; 5801 if (size == 0) { 5802 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5803 "be greater than zero, resetting it to the default (%d)", 5804 L2ARC_WRITE_SIZE); 5805 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5806 } 5807 5808 if (arc_warm == B_FALSE) 5809 size += l2arc_write_boost; 5810 5811 return (size); 5812 5813} 5814 5815static clock_t 5816l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5817{ 5818 clock_t interval, next, now; 5819 5820 /* 5821 * If the ARC lists are busy, increase our write rate; if the 5822 * lists are stale, idle back. This is achieved by checking 5823 * how much we previously wrote - if it was more than half of 5824 * what we wanted, schedule the next write much sooner. 5825 */ 5826 if (l2arc_feed_again && wrote > (wanted / 2)) 5827 interval = (hz * l2arc_feed_min_ms) / 1000; 5828 else 5829 interval = hz * l2arc_feed_secs; 5830 5831 now = ddi_get_lbolt(); 5832 next = MAX(now, MIN(now + interval, began + interval)); 5833 5834 return (next); 5835} 5836 5837/* 5838 * Cycle through L2ARC devices. This is how L2ARC load balances. 5839 * If a device is returned, this also returns holding the spa config lock. 5840 */ 5841static l2arc_dev_t * 5842l2arc_dev_get_next(void) 5843{ 5844 l2arc_dev_t *first, *next = NULL; 5845 5846 /* 5847 * Lock out the removal of spas (spa_namespace_lock), then removal 5848 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5849 * both locks will be dropped and a spa config lock held instead. 5850 */ 5851 mutex_enter(&spa_namespace_lock); 5852 mutex_enter(&l2arc_dev_mtx); 5853 5854 /* if there are no vdevs, there is nothing to do */ 5855 if (l2arc_ndev == 0) 5856 goto out; 5857 5858 first = NULL; 5859 next = l2arc_dev_last; 5860 do { 5861 /* loop around the list looking for a non-faulted vdev */ 5862 if (next == NULL) { 5863 next = list_head(l2arc_dev_list); 5864 } else { 5865 next = list_next(l2arc_dev_list, next); 5866 if (next == NULL) 5867 next = list_head(l2arc_dev_list); 5868 } 5869 5870 /* if we have come back to the start, bail out */ 5871 if (first == NULL) 5872 first = next; 5873 else if (next == first) 5874 break; 5875 5876 } while (vdev_is_dead(next->l2ad_vdev)); 5877 5878 /* if we were unable to find any usable vdevs, return NULL */ 5879 if (vdev_is_dead(next->l2ad_vdev)) 5880 next = NULL; 5881 5882 l2arc_dev_last = next; 5883 5884out: 5885 mutex_exit(&l2arc_dev_mtx); 5886 5887 /* 5888 * Grab the config lock to prevent the 'next' device from being 5889 * removed while we are writing to it. 5890 */ 5891 if (next != NULL) 5892 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5893 mutex_exit(&spa_namespace_lock); 5894 5895 return (next); 5896} 5897 5898/* 5899 * Free buffers that were tagged for destruction. 5900 */ 5901static void 5902l2arc_do_free_on_write() 5903{ 5904 list_t *buflist; 5905 l2arc_data_free_t *df, *df_prev; 5906 5907 mutex_enter(&l2arc_free_on_write_mtx); 5908 buflist = l2arc_free_on_write; 5909 5910 for (df = list_tail(buflist); df; df = df_prev) { 5911 df_prev = list_prev(buflist, df); 5912 ASSERT(df->l2df_data != NULL); 5913 ASSERT(df->l2df_func != NULL); 5914 df->l2df_func(df->l2df_data, df->l2df_size); 5915 list_remove(buflist, df); 5916 kmem_free(df, sizeof (l2arc_data_free_t)); 5917 } 5918 5919 mutex_exit(&l2arc_free_on_write_mtx); 5920} 5921 5922/* 5923 * A write to a cache device has completed. Update all headers to allow 5924 * reads from these buffers to begin. 5925 */ 5926static void 5927l2arc_write_done(zio_t *zio) 5928{ 5929 l2arc_write_callback_t *cb; 5930 l2arc_dev_t *dev; 5931 list_t *buflist; 5932 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5933 kmutex_t *hash_lock; 5934 int64_t bytes_dropped = 0; 5935 5936 cb = zio->io_private; 5937 ASSERT(cb != NULL); 5938 dev = cb->l2wcb_dev; 5939 ASSERT(dev != NULL); 5940 head = cb->l2wcb_head; 5941 ASSERT(head != NULL); 5942 buflist = &dev->l2ad_buflist; 5943 ASSERT(buflist != NULL); 5944 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5945 l2arc_write_callback_t *, cb); 5946 5947 if (zio->io_error != 0) 5948 ARCSTAT_BUMP(arcstat_l2_writes_error); 5949 5950 /* 5951 * All writes completed, or an error was hit. 5952 */ 5953top: 5954 mutex_enter(&dev->l2ad_mtx); 5955 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5956 hdr_prev = list_prev(buflist, hdr); 5957 5958 hash_lock = HDR_LOCK(hdr); 5959 5960 /* 5961 * We cannot use mutex_enter or else we can deadlock 5962 * with l2arc_write_buffers (due to swapping the order 5963 * the hash lock and l2ad_mtx are taken). 5964 */ 5965 if (!mutex_tryenter(hash_lock)) { 5966 /* 5967 * Missed the hash lock. We must retry so we 5968 * don't leave the ARC_FLAG_L2_WRITING bit set. 5969 */ 5970 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5971 5972 /* 5973 * We don't want to rescan the headers we've 5974 * already marked as having been written out, so 5975 * we reinsert the head node so we can pick up 5976 * where we left off. 5977 */ 5978 list_remove(buflist, head); 5979 list_insert_after(buflist, hdr, head); 5980 5981 mutex_exit(&dev->l2ad_mtx); 5982 5983 /* 5984 * We wait for the hash lock to become available 5985 * to try and prevent busy waiting, and increase 5986 * the chance we'll be able to acquire the lock 5987 * the next time around. 5988 */ 5989 mutex_enter(hash_lock); 5990 mutex_exit(hash_lock); 5991 goto top; 5992 } 5993 5994 /* 5995 * We could not have been moved into the arc_l2c_only 5996 * state while in-flight due to our ARC_FLAG_L2_WRITING 5997 * bit being set. Let's just ensure that's being enforced. 5998 */ 5999 ASSERT(HDR_HAS_L1HDR(hdr)); 6000 6001 /* 6002 * We may have allocated a buffer for L2ARC compression, 6003 * we must release it to avoid leaking this data. 6004 */ 6005 l2arc_release_cdata_buf(hdr); 6006 6007 if (zio->io_error != 0) { 6008 /* 6009 * Error - drop L2ARC entry. 6010 */ 6011 list_remove(buflist, hdr); 6012 l2arc_trim(hdr); 6013 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 6014 6015 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 6016 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 6017 6018 bytes_dropped += hdr->b_l2hdr.b_asize; 6019 (void) refcount_remove_many(&dev->l2ad_alloc, 6020 hdr->b_l2hdr.b_asize, hdr); 6021 } 6022 6023 /* 6024 * Allow ARC to begin reads and ghost list evictions to 6025 * this L2ARC entry. 6026 */ 6027 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 6028 6029 mutex_exit(hash_lock); 6030 } 6031 6032 atomic_inc_64(&l2arc_writes_done); 6033 list_remove(buflist, head); 6034 ASSERT(!HDR_HAS_L1HDR(head)); 6035 kmem_cache_free(hdr_l2only_cache, head); 6036 mutex_exit(&dev->l2ad_mtx); 6037 6038 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6039 6040 l2arc_do_free_on_write(); 6041 6042 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6043} 6044 6045/* 6046 * A read to a cache device completed. Validate buffer contents before 6047 * handing over to the regular ARC routines. 6048 */ 6049static void 6050l2arc_read_done(zio_t *zio) 6051{ 6052 l2arc_read_callback_t *cb; 6053 arc_buf_hdr_t *hdr; 6054 arc_buf_t *buf; 6055 kmutex_t *hash_lock; 6056 int equal; 6057 6058 ASSERT(zio->io_vd != NULL); 6059 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6060 6061 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6062 6063 cb = zio->io_private; 6064 ASSERT(cb != NULL); 6065 buf = cb->l2rcb_buf; 6066 ASSERT(buf != NULL); 6067 6068 hash_lock = HDR_LOCK(buf->b_hdr); 6069 mutex_enter(hash_lock); 6070 hdr = buf->b_hdr; 6071 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6072 6073 /* 6074 * If the data was read into a temporary buffer, 6075 * move it and free the buffer. 6076 */ 6077 if (cb->l2rcb_data != NULL) { 6078 ASSERT3U(hdr->b_size, <, zio->io_size); 6079 ASSERT3U(cb->l2rcb_compress, ==, ZIO_COMPRESS_OFF); 6080 if (zio->io_error == 0) 6081 bcopy(cb->l2rcb_data, buf->b_data, hdr->b_size); 6082 6083 /* 6084 * The following must be done regardless of whether 6085 * there was an error: 6086 * - free the temporary buffer 6087 * - point zio to the real ARC buffer 6088 * - set zio size accordingly 6089 * These are required because zio is either re-used for 6090 * an I/O of the block in the case of the error 6091 * or the zio is passed to arc_read_done() and it 6092 * needs real data. 6093 */ 6094 zio_data_buf_free(cb->l2rcb_data, zio->io_size); 6095 zio->io_size = zio->io_orig_size = hdr->b_size; 6096 zio->io_data = zio->io_orig_data = buf->b_data; 6097 } 6098 6099 /* 6100 * If the buffer was compressed, decompress it first. 6101 */ 6102 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6103 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6104 ASSERT(zio->io_data != NULL); 6105 ASSERT3U(zio->io_size, ==, hdr->b_size); 6106 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 6107 6108 /* 6109 * Check this survived the L2ARC journey. 6110 */ 6111 equal = arc_cksum_equal(buf); 6112 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6113 mutex_exit(hash_lock); 6114 zio->io_private = buf; 6115 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6116 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6117 arc_read_done(zio); 6118 } else { 6119 mutex_exit(hash_lock); 6120 /* 6121 * Buffer didn't survive caching. Increment stats and 6122 * reissue to the original storage device. 6123 */ 6124 if (zio->io_error != 0) { 6125 ARCSTAT_BUMP(arcstat_l2_io_error); 6126 } else { 6127 zio->io_error = SET_ERROR(EIO); 6128 } 6129 if (!equal) 6130 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6131 6132 /* 6133 * If there's no waiter, issue an async i/o to the primary 6134 * storage now. If there *is* a waiter, the caller must 6135 * issue the i/o in a context where it's OK to block. 6136 */ 6137 if (zio->io_waiter == NULL) { 6138 zio_t *pio = zio_unique_parent(zio); 6139 6140 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6141 6142 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6143 buf->b_data, hdr->b_size, arc_read_done, buf, 6144 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6145 } 6146 } 6147 6148 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6149} 6150 6151/* 6152 * This is the list priority from which the L2ARC will search for pages to 6153 * cache. This is used within loops (0..3) to cycle through lists in the 6154 * desired order. This order can have a significant effect on cache 6155 * performance. 6156 * 6157 * Currently the metadata lists are hit first, MFU then MRU, followed by 6158 * the data lists. This function returns a locked list, and also returns 6159 * the lock pointer. 6160 */ 6161static multilist_sublist_t * 6162l2arc_sublist_lock(int list_num) 6163{ 6164 multilist_t *ml = NULL; 6165 unsigned int idx; 6166 6167 ASSERT(list_num >= 0 && list_num <= 3); 6168 6169 switch (list_num) { 6170 case 0: 6171 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6172 break; 6173 case 1: 6174 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6175 break; 6176 case 2: 6177 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6178 break; 6179 case 3: 6180 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6181 break; 6182 } 6183 6184 /* 6185 * Return a randomly-selected sublist. This is acceptable 6186 * because the caller feeds only a little bit of data for each 6187 * call (8MB). Subsequent calls will result in different 6188 * sublists being selected. 6189 */ 6190 idx = multilist_get_random_index(ml); 6191 return (multilist_sublist_lock(ml, idx)); 6192} 6193 6194/* 6195 * Evict buffers from the device write hand to the distance specified in 6196 * bytes. This distance may span populated buffers, it may span nothing. 6197 * This is clearing a region on the L2ARC device ready for writing. 6198 * If the 'all' boolean is set, every buffer is evicted. 6199 */ 6200static void 6201l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6202{ 6203 list_t *buflist; 6204 arc_buf_hdr_t *hdr, *hdr_prev; 6205 kmutex_t *hash_lock; 6206 uint64_t taddr; 6207 6208 buflist = &dev->l2ad_buflist; 6209 6210 if (!all && dev->l2ad_first) { 6211 /* 6212 * This is the first sweep through the device. There is 6213 * nothing to evict. 6214 */ 6215 return; 6216 } 6217 6218 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6219 /* 6220 * When nearing the end of the device, evict to the end 6221 * before the device write hand jumps to the start. 6222 */ 6223 taddr = dev->l2ad_end; 6224 } else { 6225 taddr = dev->l2ad_hand + distance; 6226 } 6227 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6228 uint64_t, taddr, boolean_t, all); 6229 6230top: 6231 mutex_enter(&dev->l2ad_mtx); 6232 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6233 hdr_prev = list_prev(buflist, hdr); 6234 6235 hash_lock = HDR_LOCK(hdr); 6236 6237 /* 6238 * We cannot use mutex_enter or else we can deadlock 6239 * with l2arc_write_buffers (due to swapping the order 6240 * the hash lock and l2ad_mtx are taken). 6241 */ 6242 if (!mutex_tryenter(hash_lock)) { 6243 /* 6244 * Missed the hash lock. Retry. 6245 */ 6246 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6247 mutex_exit(&dev->l2ad_mtx); 6248 mutex_enter(hash_lock); 6249 mutex_exit(hash_lock); 6250 goto top; 6251 } 6252 6253 if (HDR_L2_WRITE_HEAD(hdr)) { 6254 /* 6255 * We hit a write head node. Leave it for 6256 * l2arc_write_done(). 6257 */ 6258 list_remove(buflist, hdr); 6259 mutex_exit(hash_lock); 6260 continue; 6261 } 6262 6263 if (!all && HDR_HAS_L2HDR(hdr) && 6264 (hdr->b_l2hdr.b_daddr > taddr || 6265 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6266 /* 6267 * We've evicted to the target address, 6268 * or the end of the device. 6269 */ 6270 mutex_exit(hash_lock); 6271 break; 6272 } 6273 6274 ASSERT(HDR_HAS_L2HDR(hdr)); 6275 if (!HDR_HAS_L1HDR(hdr)) { 6276 ASSERT(!HDR_L2_READING(hdr)); 6277 /* 6278 * This doesn't exist in the ARC. Destroy. 6279 * arc_hdr_destroy() will call list_remove() 6280 * and decrement arcstat_l2_size. 6281 */ 6282 arc_change_state(arc_anon, hdr, hash_lock); 6283 arc_hdr_destroy(hdr); 6284 } else { 6285 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6286 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6287 /* 6288 * Invalidate issued or about to be issued 6289 * reads, since we may be about to write 6290 * over this location. 6291 */ 6292 if (HDR_L2_READING(hdr)) { 6293 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6294 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6295 } 6296 6297 /* Ensure this header has finished being written */ 6298 ASSERT(!HDR_L2_WRITING(hdr)); 6299 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6300 6301 arc_hdr_l2hdr_destroy(hdr); 6302 } 6303 mutex_exit(hash_lock); 6304 } 6305 mutex_exit(&dev->l2ad_mtx); 6306} 6307 6308/* 6309 * Find and write ARC buffers to the L2ARC device. 6310 * 6311 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6312 * for reading until they have completed writing. 6313 * The headroom_boost is an in-out parameter used to maintain headroom boost 6314 * state between calls to this function. 6315 * 6316 * Returns the number of bytes actually written (which may be smaller than 6317 * the delta by which the device hand has changed due to alignment). 6318 */ 6319static uint64_t 6320l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6321 boolean_t *headroom_boost) 6322{ 6323 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6324 uint64_t write_asize, write_sz, headroom, 6325 buf_compress_minsz; 6326 void *buf_data; 6327 boolean_t full; 6328 l2arc_write_callback_t *cb; 6329 zio_t *pio, *wzio; 6330 uint64_t guid = spa_load_guid(spa); 6331 const boolean_t do_headroom_boost = *headroom_boost; 6332 int try; 6333 6334 ASSERT(dev->l2ad_vdev != NULL); 6335 6336 /* Lower the flag now, we might want to raise it again later. */ 6337 *headroom_boost = B_FALSE; 6338 6339 pio = NULL; 6340 write_sz = write_asize = 0; 6341 full = B_FALSE; 6342 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6343 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6344 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6345 6346 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6347 /* 6348 * We will want to try to compress buffers that are at least 2x the 6349 * device sector size. 6350 */ 6351 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6352 6353 /* 6354 * Copy buffers for L2ARC writing. 6355 */ 6356 for (try = 0; try <= 3; try++) { 6357 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6358 uint64_t passed_sz = 0; 6359 6360 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6361 6362 /* 6363 * L2ARC fast warmup. 6364 * 6365 * Until the ARC is warm and starts to evict, read from the 6366 * head of the ARC lists rather than the tail. 6367 */ 6368 if (arc_warm == B_FALSE) 6369 hdr = multilist_sublist_head(mls); 6370 else 6371 hdr = multilist_sublist_tail(mls); 6372 if (hdr == NULL) 6373 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6374 6375 headroom = target_sz * l2arc_headroom; 6376 if (do_headroom_boost) 6377 headroom = (headroom * l2arc_headroom_boost) / 100; 6378 6379 for (; hdr; hdr = hdr_prev) { 6380 kmutex_t *hash_lock; 6381 uint64_t buf_sz; 6382 uint64_t buf_a_sz; 6383 size_t align; 6384 6385 if (arc_warm == B_FALSE) 6386 hdr_prev = multilist_sublist_next(mls, hdr); 6387 else 6388 hdr_prev = multilist_sublist_prev(mls, hdr); 6389 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 6390 6391 hash_lock = HDR_LOCK(hdr); 6392 if (!mutex_tryenter(hash_lock)) { 6393 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 6394 /* 6395 * Skip this buffer rather than waiting. 6396 */ 6397 continue; 6398 } 6399 6400 passed_sz += hdr->b_size; 6401 if (passed_sz > headroom) { 6402 /* 6403 * Searched too far. 6404 */ 6405 mutex_exit(hash_lock); 6406 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 6407 break; 6408 } 6409 6410 if (!l2arc_write_eligible(guid, hdr)) { 6411 mutex_exit(hash_lock); 6412 continue; 6413 } 6414 6415 /* 6416 * Assume that the buffer is not going to be compressed 6417 * and could take more space on disk because of a larger 6418 * disk block size. 6419 */ 6420 buf_sz = hdr->b_size; 6421 align = (size_t)1 << dev->l2ad_vdev->vdev_ashift; 6422 buf_a_sz = P2ROUNDUP(buf_sz, align); 6423 6424 if ((write_asize + buf_a_sz) > target_sz) { 6425 full = B_TRUE; 6426 mutex_exit(hash_lock); 6427 ARCSTAT_BUMP(arcstat_l2_write_full); 6428 break; 6429 } 6430 6431 if (pio == NULL) { 6432 /* 6433 * Insert a dummy header on the buflist so 6434 * l2arc_write_done() can find where the 6435 * write buffers begin without searching. 6436 */ 6437 mutex_enter(&dev->l2ad_mtx); 6438 list_insert_head(&dev->l2ad_buflist, head); 6439 mutex_exit(&dev->l2ad_mtx); 6440 6441 cb = kmem_alloc( 6442 sizeof (l2arc_write_callback_t), KM_SLEEP); 6443 cb->l2wcb_dev = dev; 6444 cb->l2wcb_head = head; 6445 pio = zio_root(spa, l2arc_write_done, cb, 6446 ZIO_FLAG_CANFAIL); 6447 ARCSTAT_BUMP(arcstat_l2_write_pios); 6448 } 6449 6450 /* 6451 * Create and add a new L2ARC header. 6452 */ 6453 hdr->b_l2hdr.b_dev = dev; 6454 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6455 /* 6456 * Temporarily stash the data buffer in b_tmp_cdata. 6457 * The subsequent write step will pick it up from 6458 * there. This is because can't access b_l1hdr.b_buf 6459 * without holding the hash_lock, which we in turn 6460 * can't access without holding the ARC list locks 6461 * (which we want to avoid during compression/writing). 6462 */ 6463 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6464 hdr->b_l2hdr.b_asize = hdr->b_size; 6465 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6466 6467 /* 6468 * Explicitly set the b_daddr field to a known 6469 * value which means "invalid address". This 6470 * enables us to differentiate which stage of 6471 * l2arc_write_buffers() the particular header 6472 * is in (e.g. this loop, or the one below). 6473 * ARC_FLAG_L2_WRITING is not enough to make 6474 * this distinction, and we need to know in 6475 * order to do proper l2arc vdev accounting in 6476 * arc_release() and arc_hdr_destroy(). 6477 * 6478 * Note, we can't use a new flag to distinguish 6479 * the two stages because we don't hold the 6480 * header's hash_lock below, in the second stage 6481 * of this function. Thus, we can't simply 6482 * change the b_flags field to denote that the 6483 * IO has been sent. We can change the b_daddr 6484 * field of the L2 portion, though, since we'll 6485 * be holding the l2ad_mtx; which is why we're 6486 * using it to denote the header's state change. 6487 */ 6488 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6489 6490 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6491 6492 mutex_enter(&dev->l2ad_mtx); 6493 list_insert_head(&dev->l2ad_buflist, hdr); 6494 mutex_exit(&dev->l2ad_mtx); 6495 6496 /* 6497 * Compute and store the buffer cksum before 6498 * writing. On debug the cksum is verified first. 6499 */ 6500 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6501 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6502 6503 mutex_exit(hash_lock); 6504 6505 write_sz += buf_sz; 6506 write_asize += buf_a_sz; 6507 } 6508 6509 multilist_sublist_unlock(mls); 6510 6511 if (full == B_TRUE) 6512 break; 6513 } 6514 6515 /* No buffers selected for writing? */ 6516 if (pio == NULL) { 6517 ASSERT0(write_sz); 6518 ASSERT(!HDR_HAS_L1HDR(head)); 6519 kmem_cache_free(hdr_l2only_cache, head); 6520 return (0); 6521 } 6522 6523 mutex_enter(&dev->l2ad_mtx); 6524 6525 /* 6526 * Now start writing the buffers. We're starting at the write head 6527 * and work backwards, retracing the course of the buffer selector 6528 * loop above. 6529 */ 6530 write_asize = 0; 6531 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6532 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6533 uint64_t buf_sz; 6534 boolean_t compress; 6535 6536 /* 6537 * We rely on the L1 portion of the header below, so 6538 * it's invalid for this header to have been evicted out 6539 * of the ghost cache, prior to being written out. The 6540 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6541 */ 6542 ASSERT(HDR_HAS_L1HDR(hdr)); 6543 6544 /* 6545 * We shouldn't need to lock the buffer here, since we flagged 6546 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6547 * take care to only access its L2 cache parameters. In 6548 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6549 * ARC eviction. 6550 */ 6551 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6552 6553 /* 6554 * Save a pointer to the original buffer data we had previously 6555 * stashed away. 6556 */ 6557 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6558 6559 compress = HDR_L2COMPRESS(hdr) && 6560 hdr->b_l2hdr.b_asize >= buf_compress_minsz; 6561 if (l2arc_transform_buf(hdr, compress)) { 6562 /* 6563 * If compression succeeded, enable headroom 6564 * boost on the next scan cycle. 6565 */ 6566 *headroom_boost = B_TRUE; 6567 } 6568 6569 /* 6570 * Get the new buffer size that accounts for compression 6571 * and padding. 6572 */ 6573 buf_sz = hdr->b_l2hdr.b_asize; 6574 6575 /* 6576 * We need to do this regardless if buf_sz is zero or 6577 * not, otherwise, when this l2hdr is evicted we'll 6578 * remove a reference that was never added. 6579 */ 6580 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6581 6582 /* Compression may have squashed the buffer to zero length. */ 6583 if (buf_sz != 0) { 6584 /* 6585 * If the data was padded or compressed, then it 6586 * it is in a new buffer. 6587 */ 6588 if (hdr->b_l1hdr.b_tmp_cdata != NULL) 6589 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6590 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6591 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6592 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6593 ZIO_FLAG_CANFAIL, B_FALSE); 6594 6595 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6596 zio_t *, wzio); 6597 (void) zio_nowait(wzio); 6598 6599 write_asize += buf_sz; 6600 dev->l2ad_hand += buf_sz; 6601 } 6602 } 6603 6604 mutex_exit(&dev->l2ad_mtx); 6605 6606 ASSERT3U(write_asize, <=, target_sz); 6607 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6608 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6609 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6610 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6611 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6612 6613 /* 6614 * Bump device hand to the device start if it is approaching the end. 6615 * l2arc_evict() will already have evicted ahead for this case. 6616 */ 6617 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6618 dev->l2ad_hand = dev->l2ad_start; 6619 dev->l2ad_first = B_FALSE; 6620 } 6621 6622 dev->l2ad_writing = B_TRUE; 6623 (void) zio_wait(pio); 6624 dev->l2ad_writing = B_FALSE; 6625 6626 return (write_asize); 6627} 6628 6629/* 6630 * Transforms, possibly compresses and pads, an L2ARC buffer. 6631 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6632 * size in l2hdr->b_asize. This routine tries to compress the data and 6633 * depending on the compression result there are three possible outcomes: 6634 * *) The buffer was incompressible. The buffer size was already ashift aligned. 6635 * The original hdr contents were left untouched except for b_tmp_cdata, 6636 * which is reset to NULL. The caller must keep a pointer to the original 6637 * data. 6638 * *) The buffer was incompressible. The buffer size was not ashift aligned. 6639 * b_tmp_cdata was replaced with a temporary data buffer which holds a padded 6640 * (aligned) copy of the data. Once writing is done, invoke 6641 * l2arc_release_cdata_buf on this hdr to free the temporary buffer. 6642 * *) The buffer was all-zeros, so there is no need to write it to an L2 6643 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6644 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6645 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6646 * data buffer which holds the compressed data to be written, and b_asize 6647 * tells us how much data there is. b_compress is set to the appropriate 6648 * compression algorithm. Once writing is done, invoke 6649 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6650 * 6651 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6652 * buffer was incompressible). 6653 */ 6654static boolean_t 6655l2arc_transform_buf(arc_buf_hdr_t *hdr, boolean_t compress) 6656{ 6657 void *cdata; 6658 size_t align, asize, csize, len, rounded; 6659 6660 ASSERT(HDR_HAS_L2HDR(hdr)); 6661 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6662 6663 ASSERT(HDR_HAS_L1HDR(hdr)); 6664 ASSERT3S(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF); 6665 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6666 6667 len = l2hdr->b_asize; 6668 align = (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift; 6669 asize = P2ROUNDUP(len, align); 6670 cdata = zio_data_buf_alloc(asize); 6671 ASSERT3P(cdata, !=, NULL); 6672 if (compress) 6673 csize = zio_compress_data(ZIO_COMPRESS_LZ4, 6674 hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6675 else 6676 csize = len; 6677 6678 if (csize == 0) { 6679 /* zero block, indicate that there's nothing to write */ 6680 zio_data_buf_free(cdata, asize); 6681 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6682 l2hdr->b_asize = 0; 6683 hdr->b_l1hdr.b_tmp_cdata = NULL; 6684 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6685 return (B_TRUE); 6686 } 6687 6688 rounded = P2ROUNDUP(csize, align); 6689 ASSERT3U(rounded, <=, asize); 6690 if (rounded < len) { 6691 /* 6692 * Compression succeeded, we'll keep the cdata around for 6693 * writing and release it afterwards. 6694 */ 6695 if (rounded > csize) { 6696 bzero((char *)cdata + csize, rounded - csize); 6697 csize = rounded; 6698 } 6699 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6700 l2hdr->b_asize = csize; 6701 hdr->b_l1hdr.b_tmp_cdata = cdata; 6702 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6703 return (B_TRUE); 6704 } else { 6705 /* 6706 * Compression did not save space. 6707 */ 6708 if (P2PHASE(len, align) != 0) { 6709 /* 6710 * Use compression buffer for a copy of data padded to 6711 * the proper size. Compression algorithm remains set 6712 * to ZIO_COMPRESS_OFF. 6713 */ 6714 ASSERT3U(len, <, asize); 6715 bcopy(hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6716 bzero((char *)cdata + len, asize - len); 6717 l2hdr->b_asize = asize; 6718 hdr->b_l1hdr.b_tmp_cdata = cdata; 6719 ARCSTAT_BUMP(arcstat_l2_padding_needed); 6720 } else { 6721 ASSERT3U(len, ==, asize); 6722 /* 6723 * The original buffer is good as is, 6724 * release the compressed buffer. 6725 * l2hdr will be left unmodified except for b_tmp_cdata. 6726 */ 6727 zio_data_buf_free(cdata, asize); 6728 hdr->b_l1hdr.b_tmp_cdata = NULL; 6729 } 6730 if (compress) 6731 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6732 return (B_FALSE); 6733 } 6734} 6735 6736/* 6737 * Decompresses a zio read back from an l2arc device. On success, the 6738 * underlying zio's io_data buffer is overwritten by the uncompressed 6739 * version. On decompression error (corrupt compressed stream), the 6740 * zio->io_error value is set to signal an I/O error. 6741 * 6742 * Please note that the compressed data stream is not checksummed, so 6743 * if the underlying device is experiencing data corruption, we may feed 6744 * corrupt data to the decompressor, so the decompressor needs to be 6745 * able to handle this situation (LZ4 does). 6746 */ 6747static void 6748l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6749{ 6750 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6751 6752 if (zio->io_error != 0) { 6753 /* 6754 * An io error has occured, just restore the original io 6755 * size in preparation for a main pool read. 6756 */ 6757 zio->io_orig_size = zio->io_size = hdr->b_size; 6758 return; 6759 } 6760 6761 if (c == ZIO_COMPRESS_EMPTY) { 6762 /* 6763 * An empty buffer results in a null zio, which means we 6764 * need to fill its io_data after we're done restoring the 6765 * buffer's contents. 6766 */ 6767 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6768 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6769 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6770 } else { 6771 ASSERT(zio->io_data != NULL); 6772 /* 6773 * We copy the compressed data from the start of the arc buffer 6774 * (the zio_read will have pulled in only what we need, the 6775 * rest is garbage which we will overwrite at decompression) 6776 * and then decompress back to the ARC data buffer. This way we 6777 * can minimize copying by simply decompressing back over the 6778 * original compressed data (rather than decompressing to an 6779 * aux buffer and then copying back the uncompressed buffer, 6780 * which is likely to be much larger). 6781 */ 6782 uint64_t csize; 6783 void *cdata; 6784 6785 csize = zio->io_size; 6786 cdata = zio_data_buf_alloc(csize); 6787 bcopy(zio->io_data, cdata, csize); 6788 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6789 hdr->b_size) != 0) 6790 zio->io_error = EIO; 6791 zio_data_buf_free(cdata, csize); 6792 } 6793 6794 /* Restore the expected uncompressed IO size. */ 6795 zio->io_orig_size = zio->io_size = hdr->b_size; 6796} 6797 6798/* 6799 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6800 * This buffer serves as a temporary holder of compressed or padded data while 6801 * the buffer entry is being written to an l2arc device. Once that is 6802 * done, we can dispose of it. 6803 */ 6804static void 6805l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6806{ 6807 size_t align, asize, len; 6808 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6809 6810 ASSERT(HDR_HAS_L2HDR(hdr)); 6811 ASSERT(HDR_HAS_L1HDR(hdr)); 6812 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6813 6814 if (hdr->b_l1hdr.b_tmp_cdata != NULL) { 6815 ASSERT(comp != ZIO_COMPRESS_EMPTY); 6816 len = hdr->b_size; 6817 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 6818 asize = P2ROUNDUP(len, align); 6819 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, asize); 6820 hdr->b_l1hdr.b_tmp_cdata = NULL; 6821 } else { 6822 ASSERT(comp == ZIO_COMPRESS_OFF || comp == ZIO_COMPRESS_EMPTY); 6823 } 6824} 6825 6826/* 6827 * This thread feeds the L2ARC at regular intervals. This is the beating 6828 * heart of the L2ARC. 6829 */ 6830static void 6831l2arc_feed_thread(void *dummy __unused) 6832{ 6833 callb_cpr_t cpr; 6834 l2arc_dev_t *dev; 6835 spa_t *spa; 6836 uint64_t size, wrote; 6837 clock_t begin, next = ddi_get_lbolt(); 6838 boolean_t headroom_boost = B_FALSE; 6839 6840 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6841 6842 mutex_enter(&l2arc_feed_thr_lock); 6843 6844 while (l2arc_thread_exit == 0) { 6845 CALLB_CPR_SAFE_BEGIN(&cpr); 6846 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6847 next - ddi_get_lbolt()); 6848 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6849 next = ddi_get_lbolt() + hz; 6850 6851 /* 6852 * Quick check for L2ARC devices. 6853 */ 6854 mutex_enter(&l2arc_dev_mtx); 6855 if (l2arc_ndev == 0) { 6856 mutex_exit(&l2arc_dev_mtx); 6857 continue; 6858 } 6859 mutex_exit(&l2arc_dev_mtx); 6860 begin = ddi_get_lbolt(); 6861 6862 /* 6863 * This selects the next l2arc device to write to, and in 6864 * doing so the next spa to feed from: dev->l2ad_spa. This 6865 * will return NULL if there are now no l2arc devices or if 6866 * they are all faulted. 6867 * 6868 * If a device is returned, its spa's config lock is also 6869 * held to prevent device removal. l2arc_dev_get_next() 6870 * will grab and release l2arc_dev_mtx. 6871 */ 6872 if ((dev = l2arc_dev_get_next()) == NULL) 6873 continue; 6874 6875 spa = dev->l2ad_spa; 6876 ASSERT(spa != NULL); 6877 6878 /* 6879 * If the pool is read-only then force the feed thread to 6880 * sleep a little longer. 6881 */ 6882 if (!spa_writeable(spa)) { 6883 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6884 spa_config_exit(spa, SCL_L2ARC, dev); 6885 continue; 6886 } 6887 6888 /* 6889 * Avoid contributing to memory pressure. 6890 */ 6891 if (arc_reclaim_needed()) { 6892 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6893 spa_config_exit(spa, SCL_L2ARC, dev); 6894 continue; 6895 } 6896 6897 ARCSTAT_BUMP(arcstat_l2_feeds); 6898 6899 size = l2arc_write_size(); 6900 6901 /* 6902 * Evict L2ARC buffers that will be overwritten. 6903 */ 6904 l2arc_evict(dev, size, B_FALSE); 6905 6906 /* 6907 * Write ARC buffers. 6908 */ 6909 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6910 6911 /* 6912 * Calculate interval between writes. 6913 */ 6914 next = l2arc_write_interval(begin, size, wrote); 6915 spa_config_exit(spa, SCL_L2ARC, dev); 6916 } 6917 6918 l2arc_thread_exit = 0; 6919 cv_broadcast(&l2arc_feed_thr_cv); 6920 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6921 thread_exit(); 6922} 6923 6924boolean_t 6925l2arc_vdev_present(vdev_t *vd) 6926{ 6927 l2arc_dev_t *dev; 6928 6929 mutex_enter(&l2arc_dev_mtx); 6930 for (dev = list_head(l2arc_dev_list); dev != NULL; 6931 dev = list_next(l2arc_dev_list, dev)) { 6932 if (dev->l2ad_vdev == vd) 6933 break; 6934 } 6935 mutex_exit(&l2arc_dev_mtx); 6936 6937 return (dev != NULL); 6938} 6939 6940/* 6941 * Add a vdev for use by the L2ARC. By this point the spa has already 6942 * validated the vdev and opened it. 6943 */ 6944void 6945l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6946{ 6947 l2arc_dev_t *adddev; 6948 6949 ASSERT(!l2arc_vdev_present(vd)); 6950 6951 vdev_ashift_optimize(vd); 6952 6953 /* 6954 * Create a new l2arc device entry. 6955 */ 6956 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6957 adddev->l2ad_spa = spa; 6958 adddev->l2ad_vdev = vd; 6959 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6960 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6961 adddev->l2ad_hand = adddev->l2ad_start; 6962 adddev->l2ad_first = B_TRUE; 6963 adddev->l2ad_writing = B_FALSE; 6964 6965 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6966 /* 6967 * This is a list of all ARC buffers that are still valid on the 6968 * device. 6969 */ 6970 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6971 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6972 6973 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6974 refcount_create(&adddev->l2ad_alloc); 6975 6976 /* 6977 * Add device to global list 6978 */ 6979 mutex_enter(&l2arc_dev_mtx); 6980 list_insert_head(l2arc_dev_list, adddev); 6981 atomic_inc_64(&l2arc_ndev); 6982 mutex_exit(&l2arc_dev_mtx); 6983} 6984 6985/* 6986 * Remove a vdev from the L2ARC. 6987 */ 6988void 6989l2arc_remove_vdev(vdev_t *vd) 6990{ 6991 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6992 6993 /* 6994 * Find the device by vdev 6995 */ 6996 mutex_enter(&l2arc_dev_mtx); 6997 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6998 nextdev = list_next(l2arc_dev_list, dev); 6999 if (vd == dev->l2ad_vdev) { 7000 remdev = dev; 7001 break; 7002 } 7003 } 7004 ASSERT(remdev != NULL); 7005 7006 /* 7007 * Remove device from global list 7008 */ 7009 list_remove(l2arc_dev_list, remdev); 7010 l2arc_dev_last = NULL; /* may have been invalidated */ 7011 atomic_dec_64(&l2arc_ndev); 7012 mutex_exit(&l2arc_dev_mtx); 7013 7014 /* 7015 * Clear all buflists and ARC references. L2ARC device flush. 7016 */ 7017 l2arc_evict(remdev, 0, B_TRUE); 7018 list_destroy(&remdev->l2ad_buflist); 7019 mutex_destroy(&remdev->l2ad_mtx); 7020 refcount_destroy(&remdev->l2ad_alloc); 7021 kmem_free(remdev, sizeof (l2arc_dev_t)); 7022} 7023 7024void 7025l2arc_init(void) 7026{ 7027 l2arc_thread_exit = 0; 7028 l2arc_ndev = 0; 7029 l2arc_writes_sent = 0; 7030 l2arc_writes_done = 0; 7031 7032 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7033 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7034 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7035 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7036 7037 l2arc_dev_list = &L2ARC_dev_list; 7038 l2arc_free_on_write = &L2ARC_free_on_write; 7039 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7040 offsetof(l2arc_dev_t, l2ad_node)); 7041 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7042 offsetof(l2arc_data_free_t, l2df_list_node)); 7043} 7044 7045void 7046l2arc_fini(void) 7047{ 7048 /* 7049 * This is called from dmu_fini(), which is called from spa_fini(); 7050 * Because of this, we can assume that all l2arc devices have 7051 * already been removed when the pools themselves were removed. 7052 */ 7053 7054 l2arc_do_free_on_write(); 7055 7056 mutex_destroy(&l2arc_feed_thr_lock); 7057 cv_destroy(&l2arc_feed_thr_cv); 7058 mutex_destroy(&l2arc_dev_mtx); 7059 mutex_destroy(&l2arc_free_on_write_mtx); 7060 7061 list_destroy(l2arc_dev_list); 7062 list_destroy(l2arc_free_on_write); 7063} 7064 7065void 7066l2arc_start(void) 7067{ 7068 if (!(spa_mode_global & FWRITE)) 7069 return; 7070 7071 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7072 TS_RUN, minclsyspri); 7073} 7074 7075void 7076l2arc_stop(void) 7077{ 7078 if (!(spa_mode_global & FWRITE)) 7079 return; 7080 7081 mutex_enter(&l2arc_feed_thr_lock); 7082 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7083 l2arc_thread_exit = 1; 7084 while (l2arc_thread_exit != 0) 7085 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7086 mutex_exit(&l2arc_feed_thr_lock); 7087} 7088