arc.c revision 288594
1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29/* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74/* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123#include <sys/spa.h> 124#include <sys/zio.h> 125#include <sys/zio_compress.h> 126#include <sys/zfs_context.h> 127#include <sys/arc.h> 128#include <sys/refcount.h> 129#include <sys/vdev.h> 130#include <sys/vdev_impl.h> 131#include <sys/dsl_pool.h> 132#include <sys/multilist.h> 133#ifdef _KERNEL 134#include <sys/dnlc.h> 135#endif 136#include <sys/callb.h> 137#include <sys/kstat.h> 138#include <sys/trim_map.h> 139#include <zfs_fletcher.h> 140#include <sys/sdt.h> 141 142#include <vm/vm_pageout.h> 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_max", &zfs_arc_max); 251TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min); 252TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 253TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 254TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize); 255TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 256SYSCTL_DECL(_vfs_zfs); 257SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 258 "Maximum ARC size"); 259SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 260 "Minimum ARC size"); 261SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 262 &zfs_arc_average_blocksize, 0, 263 "ARC average blocksize"); 264SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 265 &arc_shrink_shift, 0, 266 "log2(fraction of arc to reclaim)"); 267 268/* 269 * We don't have a tunable for arc_free_target due to the dependency on 270 * pagedaemon initialisation. 271 */ 272SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 273 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 274 sysctl_vfs_zfs_arc_free_target, "IU", 275 "Desired number of free pages below which ARC triggers reclaim"); 276 277static int 278sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 279{ 280 u_int val; 281 int err; 282 283 val = zfs_arc_free_target; 284 err = sysctl_handle_int(oidp, &val, 0, req); 285 if (err != 0 || req->newptr == NULL) 286 return (err); 287 288 if (val < minfree) 289 return (EINVAL); 290 if (val > cnt.v_page_count) 291 return (EINVAL); 292 293 zfs_arc_free_target = val; 294 295 return (0); 296} 297 298/* 299 * Must be declared here, before the definition of corresponding kstat 300 * macro which uses the same names will confuse the compiler. 301 */ 302SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 303 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 304 sysctl_vfs_zfs_arc_meta_limit, "QU", 305 "ARC metadata limit"); 306#endif 307 308/* 309 * Note that buffers can be in one of 6 states: 310 * ARC_anon - anonymous (discussed below) 311 * ARC_mru - recently used, currently cached 312 * ARC_mru_ghost - recentely used, no longer in cache 313 * ARC_mfu - frequently used, currently cached 314 * ARC_mfu_ghost - frequently used, no longer in cache 315 * ARC_l2c_only - exists in L2ARC but not other states 316 * When there are no active references to the buffer, they are 317 * are linked onto a list in one of these arc states. These are 318 * the only buffers that can be evicted or deleted. Within each 319 * state there are multiple lists, one for meta-data and one for 320 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 321 * etc.) is tracked separately so that it can be managed more 322 * explicitly: favored over data, limited explicitly. 323 * 324 * Anonymous buffers are buffers that are not associated with 325 * a DVA. These are buffers that hold dirty block copies 326 * before they are written to stable storage. By definition, 327 * they are "ref'd" and are considered part of arc_mru 328 * that cannot be freed. Generally, they will aquire a DVA 329 * as they are written and migrate onto the arc_mru list. 330 * 331 * The ARC_l2c_only state is for buffers that are in the second 332 * level ARC but no longer in any of the ARC_m* lists. The second 333 * level ARC itself may also contain buffers that are in any of 334 * the ARC_m* states - meaning that a buffer can exist in two 335 * places. The reason for the ARC_l2c_only state is to keep the 336 * buffer header in the hash table, so that reads that hit the 337 * second level ARC benefit from these fast lookups. 338 */ 339 340typedef struct arc_state { 341 /* 342 * list of evictable buffers 343 */ 344 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 345 /* 346 * total amount of evictable data in this state 347 */ 348 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 349 /* 350 * total amount of data in this state; this includes: evictable, 351 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 352 */ 353 refcount_t arcs_size; 354} arc_state_t; 355 356/* The 6 states: */ 357static arc_state_t ARC_anon; 358static arc_state_t ARC_mru; 359static arc_state_t ARC_mru_ghost; 360static arc_state_t ARC_mfu; 361static arc_state_t ARC_mfu_ghost; 362static arc_state_t ARC_l2c_only; 363 364typedef struct arc_stats { 365 kstat_named_t arcstat_hits; 366 kstat_named_t arcstat_misses; 367 kstat_named_t arcstat_demand_data_hits; 368 kstat_named_t arcstat_demand_data_misses; 369 kstat_named_t arcstat_demand_metadata_hits; 370 kstat_named_t arcstat_demand_metadata_misses; 371 kstat_named_t arcstat_prefetch_data_hits; 372 kstat_named_t arcstat_prefetch_data_misses; 373 kstat_named_t arcstat_prefetch_metadata_hits; 374 kstat_named_t arcstat_prefetch_metadata_misses; 375 kstat_named_t arcstat_mru_hits; 376 kstat_named_t arcstat_mru_ghost_hits; 377 kstat_named_t arcstat_mfu_hits; 378 kstat_named_t arcstat_mfu_ghost_hits; 379 kstat_named_t arcstat_allocated; 380 kstat_named_t arcstat_deleted; 381 /* 382 * Number of buffers that could not be evicted because the hash lock 383 * was held by another thread. The lock may not necessarily be held 384 * by something using the same buffer, since hash locks are shared 385 * by multiple buffers. 386 */ 387 kstat_named_t arcstat_mutex_miss; 388 /* 389 * Number of buffers skipped because they have I/O in progress, are 390 * indrect prefetch buffers that have not lived long enough, or are 391 * not from the spa we're trying to evict from. 392 */ 393 kstat_named_t arcstat_evict_skip; 394 /* 395 * Number of times arc_evict_state() was unable to evict enough 396 * buffers to reach it's target amount. 397 */ 398 kstat_named_t arcstat_evict_not_enough; 399 kstat_named_t arcstat_evict_l2_cached; 400 kstat_named_t arcstat_evict_l2_eligible; 401 kstat_named_t arcstat_evict_l2_ineligible; 402 kstat_named_t arcstat_evict_l2_skip; 403 kstat_named_t arcstat_hash_elements; 404 kstat_named_t arcstat_hash_elements_max; 405 kstat_named_t arcstat_hash_collisions; 406 kstat_named_t arcstat_hash_chains; 407 kstat_named_t arcstat_hash_chain_max; 408 kstat_named_t arcstat_p; 409 kstat_named_t arcstat_c; 410 kstat_named_t arcstat_c_min; 411 kstat_named_t arcstat_c_max; 412 kstat_named_t arcstat_size; 413 /* 414 * Number of bytes consumed by internal ARC structures necessary 415 * for tracking purposes; these structures are not actually 416 * backed by ARC buffers. This includes arc_buf_hdr_t structures 417 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 418 * caches), and arc_buf_t structures (allocated via arc_buf_t 419 * cache). 420 */ 421 kstat_named_t arcstat_hdr_size; 422 /* 423 * Number of bytes consumed by ARC buffers of type equal to 424 * ARC_BUFC_DATA. This is generally consumed by buffers backing 425 * on disk user data (e.g. plain file contents). 426 */ 427 kstat_named_t arcstat_data_size; 428 /* 429 * Number of bytes consumed by ARC buffers of type equal to 430 * ARC_BUFC_METADATA. This is generally consumed by buffers 431 * backing on disk data that is used for internal ZFS 432 * structures (e.g. ZAP, dnode, indirect blocks, etc). 433 */ 434 kstat_named_t arcstat_metadata_size; 435 /* 436 * Number of bytes consumed by various buffers and structures 437 * not actually backed with ARC buffers. This includes bonus 438 * buffers (allocated directly via zio_buf_* functions), 439 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 440 * cache), and dnode_t structures (allocated via dnode_t cache). 441 */ 442 kstat_named_t arcstat_other_size; 443 /* 444 * Total number of bytes consumed by ARC buffers residing in the 445 * arc_anon state. This includes *all* buffers in the arc_anon 446 * state; e.g. data, metadata, evictable, and unevictable buffers 447 * are all included in this value. 448 */ 449 kstat_named_t arcstat_anon_size; 450 /* 451 * Number of bytes consumed by ARC buffers that meet the 452 * following criteria: backing buffers of type ARC_BUFC_DATA, 453 * residing in the arc_anon state, and are eligible for eviction 454 * (e.g. have no outstanding holds on the buffer). 455 */ 456 kstat_named_t arcstat_anon_evictable_data; 457 /* 458 * Number of bytes consumed by ARC buffers that meet the 459 * following criteria: backing buffers of type ARC_BUFC_METADATA, 460 * residing in the arc_anon state, and are eligible for eviction 461 * (e.g. have no outstanding holds on the buffer). 462 */ 463 kstat_named_t arcstat_anon_evictable_metadata; 464 /* 465 * Total number of bytes consumed by ARC buffers residing in the 466 * arc_mru state. This includes *all* buffers in the arc_mru 467 * state; e.g. data, metadata, evictable, and unevictable buffers 468 * are all included in this value. 469 */ 470 kstat_named_t arcstat_mru_size; 471 /* 472 * Number of bytes consumed by ARC buffers that meet the 473 * following criteria: backing buffers of type ARC_BUFC_DATA, 474 * residing in the arc_mru state, and are eligible for eviction 475 * (e.g. have no outstanding holds on the buffer). 476 */ 477 kstat_named_t arcstat_mru_evictable_data; 478 /* 479 * Number of bytes consumed by ARC buffers that meet the 480 * following criteria: backing buffers of type ARC_BUFC_METADATA, 481 * residing in the arc_mru state, and are eligible for eviction 482 * (e.g. have no outstanding holds on the buffer). 483 */ 484 kstat_named_t arcstat_mru_evictable_metadata; 485 /* 486 * Total number of bytes that *would have been* consumed by ARC 487 * buffers in the arc_mru_ghost state. The key thing to note 488 * here, is the fact that this size doesn't actually indicate 489 * RAM consumption. The ghost lists only consist of headers and 490 * don't actually have ARC buffers linked off of these headers. 491 * Thus, *if* the headers had associated ARC buffers, these 492 * buffers *would have* consumed this number of bytes. 493 */ 494 kstat_named_t arcstat_mru_ghost_size; 495 /* 496 * Number of bytes that *would have been* consumed by ARC 497 * buffers that are eligible for eviction, of type 498 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 499 */ 500 kstat_named_t arcstat_mru_ghost_evictable_data; 501 /* 502 * Number of bytes that *would have been* consumed by ARC 503 * buffers that are eligible for eviction, of type 504 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 505 */ 506 kstat_named_t arcstat_mru_ghost_evictable_metadata; 507 /* 508 * Total number of bytes consumed by ARC buffers residing in the 509 * arc_mfu state. This includes *all* buffers in the arc_mfu 510 * state; e.g. data, metadata, evictable, and unevictable buffers 511 * are all included in this value. 512 */ 513 kstat_named_t arcstat_mfu_size; 514 /* 515 * Number of bytes consumed by ARC buffers that are eligible for 516 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 517 * state. 518 */ 519 kstat_named_t arcstat_mfu_evictable_data; 520 /* 521 * Number of bytes consumed by ARC buffers that are eligible for 522 * eviction, of type ARC_BUFC_METADATA, and reside in the 523 * arc_mfu state. 524 */ 525 kstat_named_t arcstat_mfu_evictable_metadata; 526 /* 527 * Total number of bytes that *would have been* consumed by ARC 528 * buffers in the arc_mfu_ghost state. See the comment above 529 * arcstat_mru_ghost_size for more details. 530 */ 531 kstat_named_t arcstat_mfu_ghost_size; 532 /* 533 * Number of bytes that *would have been* consumed by ARC 534 * buffers that are eligible for eviction, of type 535 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 536 */ 537 kstat_named_t arcstat_mfu_ghost_evictable_data; 538 /* 539 * Number of bytes that *would have been* consumed by ARC 540 * buffers that are eligible for eviction, of type 541 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 542 */ 543 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 544 kstat_named_t arcstat_l2_hits; 545 kstat_named_t arcstat_l2_misses; 546 kstat_named_t arcstat_l2_feeds; 547 kstat_named_t arcstat_l2_rw_clash; 548 kstat_named_t arcstat_l2_read_bytes; 549 kstat_named_t arcstat_l2_write_bytes; 550 kstat_named_t arcstat_l2_writes_sent; 551 kstat_named_t arcstat_l2_writes_done; 552 kstat_named_t arcstat_l2_writes_error; 553 kstat_named_t arcstat_l2_writes_lock_retry; 554 kstat_named_t arcstat_l2_evict_lock_retry; 555 kstat_named_t arcstat_l2_evict_reading; 556 kstat_named_t arcstat_l2_evict_l1cached; 557 kstat_named_t arcstat_l2_free_on_write; 558 kstat_named_t arcstat_l2_cdata_free_on_write; 559 kstat_named_t arcstat_l2_abort_lowmem; 560 kstat_named_t arcstat_l2_cksum_bad; 561 kstat_named_t arcstat_l2_io_error; 562 kstat_named_t arcstat_l2_size; 563 kstat_named_t arcstat_l2_asize; 564 kstat_named_t arcstat_l2_hdr_size; 565 kstat_named_t arcstat_l2_compress_successes; 566 kstat_named_t arcstat_l2_compress_zeros; 567 kstat_named_t arcstat_l2_compress_failures; 568 kstat_named_t arcstat_l2_write_trylock_fail; 569 kstat_named_t arcstat_l2_write_passed_headroom; 570 kstat_named_t arcstat_l2_write_spa_mismatch; 571 kstat_named_t arcstat_l2_write_in_l2; 572 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 573 kstat_named_t arcstat_l2_write_not_cacheable; 574 kstat_named_t arcstat_l2_write_full; 575 kstat_named_t arcstat_l2_write_buffer_iter; 576 kstat_named_t arcstat_l2_write_pios; 577 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 578 kstat_named_t arcstat_l2_write_buffer_list_iter; 579 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 580 kstat_named_t arcstat_memory_throttle_count; 581 kstat_named_t arcstat_duplicate_buffers; 582 kstat_named_t arcstat_duplicate_buffers_size; 583 kstat_named_t arcstat_duplicate_reads; 584 kstat_named_t arcstat_meta_used; 585 kstat_named_t arcstat_meta_limit; 586 kstat_named_t arcstat_meta_max; 587 kstat_named_t arcstat_meta_min; 588 kstat_named_t arcstat_sync_wait_for_async; 589 kstat_named_t arcstat_demand_hit_predictive_prefetch; 590} arc_stats_t; 591 592static arc_stats_t arc_stats = { 593 { "hits", KSTAT_DATA_UINT64 }, 594 { "misses", KSTAT_DATA_UINT64 }, 595 { "demand_data_hits", KSTAT_DATA_UINT64 }, 596 { "demand_data_misses", KSTAT_DATA_UINT64 }, 597 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 598 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 599 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 600 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 601 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 602 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 603 { "mru_hits", KSTAT_DATA_UINT64 }, 604 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 605 { "mfu_hits", KSTAT_DATA_UINT64 }, 606 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 607 { "allocated", KSTAT_DATA_UINT64 }, 608 { "deleted", KSTAT_DATA_UINT64 }, 609 { "mutex_miss", KSTAT_DATA_UINT64 }, 610 { "evict_skip", KSTAT_DATA_UINT64 }, 611 { "evict_not_enough", KSTAT_DATA_UINT64 }, 612 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 613 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 614 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 615 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 616 { "hash_elements", KSTAT_DATA_UINT64 }, 617 { "hash_elements_max", KSTAT_DATA_UINT64 }, 618 { "hash_collisions", KSTAT_DATA_UINT64 }, 619 { "hash_chains", KSTAT_DATA_UINT64 }, 620 { "hash_chain_max", KSTAT_DATA_UINT64 }, 621 { "p", KSTAT_DATA_UINT64 }, 622 { "c", KSTAT_DATA_UINT64 }, 623 { "c_min", KSTAT_DATA_UINT64 }, 624 { "c_max", KSTAT_DATA_UINT64 }, 625 { "size", KSTAT_DATA_UINT64 }, 626 { "hdr_size", KSTAT_DATA_UINT64 }, 627 { "data_size", KSTAT_DATA_UINT64 }, 628 { "metadata_size", KSTAT_DATA_UINT64 }, 629 { "other_size", KSTAT_DATA_UINT64 }, 630 { "anon_size", KSTAT_DATA_UINT64 }, 631 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 632 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 633 { "mru_size", KSTAT_DATA_UINT64 }, 634 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 635 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 636 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 637 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 638 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 639 { "mfu_size", KSTAT_DATA_UINT64 }, 640 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 641 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 642 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 643 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 644 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 645 { "l2_hits", KSTAT_DATA_UINT64 }, 646 { "l2_misses", KSTAT_DATA_UINT64 }, 647 { "l2_feeds", KSTAT_DATA_UINT64 }, 648 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 649 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 650 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 651 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 652 { "l2_writes_done", KSTAT_DATA_UINT64 }, 653 { "l2_writes_error", KSTAT_DATA_UINT64 }, 654 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 655 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 656 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 657 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 658 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 659 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 660 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 661 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 662 { "l2_io_error", KSTAT_DATA_UINT64 }, 663 { "l2_size", KSTAT_DATA_UINT64 }, 664 { "l2_asize", KSTAT_DATA_UINT64 }, 665 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 666 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 667 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 668 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 669 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 670 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 671 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 672 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 673 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 674 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 675 { "l2_write_full", KSTAT_DATA_UINT64 }, 676 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 677 { "l2_write_pios", KSTAT_DATA_UINT64 }, 678 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 679 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 680 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 681 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 682 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 683 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 684 { "duplicate_reads", KSTAT_DATA_UINT64 }, 685 { "arc_meta_used", KSTAT_DATA_UINT64 }, 686 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 687 { "arc_meta_max", KSTAT_DATA_UINT64 }, 688 { "arc_meta_min", KSTAT_DATA_UINT64 }, 689 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 690 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 691}; 692 693#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 694 695#define ARCSTAT_INCR(stat, val) \ 696 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 697 698#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 699#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 700 701#define ARCSTAT_MAX(stat, val) { \ 702 uint64_t m; \ 703 while ((val) > (m = arc_stats.stat.value.ui64) && \ 704 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 705 continue; \ 706} 707 708#define ARCSTAT_MAXSTAT(stat) \ 709 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 710 711/* 712 * We define a macro to allow ARC hits/misses to be easily broken down by 713 * two separate conditions, giving a total of four different subtypes for 714 * each of hits and misses (so eight statistics total). 715 */ 716#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 717 if (cond1) { \ 718 if (cond2) { \ 719 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 720 } else { \ 721 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 722 } \ 723 } else { \ 724 if (cond2) { \ 725 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 726 } else { \ 727 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 728 } \ 729 } 730 731kstat_t *arc_ksp; 732static arc_state_t *arc_anon; 733static arc_state_t *arc_mru; 734static arc_state_t *arc_mru_ghost; 735static arc_state_t *arc_mfu; 736static arc_state_t *arc_mfu_ghost; 737static arc_state_t *arc_l2c_only; 738 739/* 740 * There are several ARC variables that are critical to export as kstats -- 741 * but we don't want to have to grovel around in the kstat whenever we wish to 742 * manipulate them. For these variables, we therefore define them to be in 743 * terms of the statistic variable. This assures that we are not introducing 744 * the possibility of inconsistency by having shadow copies of the variables, 745 * while still allowing the code to be readable. 746 */ 747#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 748#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 749#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 750#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 751#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 752#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 753#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 754#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 755#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 756 757#define L2ARC_IS_VALID_COMPRESS(_c_) \ 758 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 759 760static int arc_no_grow; /* Don't try to grow cache size */ 761static uint64_t arc_tempreserve; 762static uint64_t arc_loaned_bytes; 763 764typedef struct arc_callback arc_callback_t; 765 766struct arc_callback { 767 void *acb_private; 768 arc_done_func_t *acb_done; 769 arc_buf_t *acb_buf; 770 zio_t *acb_zio_dummy; 771 arc_callback_t *acb_next; 772}; 773 774typedef struct arc_write_callback arc_write_callback_t; 775 776struct arc_write_callback { 777 void *awcb_private; 778 arc_done_func_t *awcb_ready; 779 arc_done_func_t *awcb_physdone; 780 arc_done_func_t *awcb_done; 781 arc_buf_t *awcb_buf; 782}; 783 784/* 785 * ARC buffers are separated into multiple structs as a memory saving measure: 786 * - Common fields struct, always defined, and embedded within it: 787 * - L2-only fields, always allocated but undefined when not in L2ARC 788 * - L1-only fields, only allocated when in L1ARC 789 * 790 * Buffer in L1 Buffer only in L2 791 * +------------------------+ +------------------------+ 792 * | arc_buf_hdr_t | | arc_buf_hdr_t | 793 * | | | | 794 * | | | | 795 * | | | | 796 * +------------------------+ +------------------------+ 797 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 798 * | (undefined if L1-only) | | | 799 * +------------------------+ +------------------------+ 800 * | l1arc_buf_hdr_t | 801 * | | 802 * | | 803 * | | 804 * | | 805 * +------------------------+ 806 * 807 * Because it's possible for the L2ARC to become extremely large, we can wind 808 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 809 * is minimized by only allocating the fields necessary for an L1-cached buffer 810 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 811 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 812 * words in pointers. arc_hdr_realloc() is used to switch a header between 813 * these two allocation states. 814 */ 815typedef struct l1arc_buf_hdr { 816 kmutex_t b_freeze_lock; 817#ifdef ZFS_DEBUG 818 /* 819 * used for debugging wtih kmem_flags - by allocating and freeing 820 * b_thawed when the buffer is thawed, we get a record of the stack 821 * trace that thawed it. 822 */ 823 void *b_thawed; 824#endif 825 826 arc_buf_t *b_buf; 827 uint32_t b_datacnt; 828 /* for waiting on writes to complete */ 829 kcondvar_t b_cv; 830 831 /* protected by arc state mutex */ 832 arc_state_t *b_state; 833 multilist_node_t b_arc_node; 834 835 /* updated atomically */ 836 clock_t b_arc_access; 837 838 /* self protecting */ 839 refcount_t b_refcnt; 840 841 arc_callback_t *b_acb; 842 /* temporary buffer holder for in-flight compressed data */ 843 void *b_tmp_cdata; 844} l1arc_buf_hdr_t; 845 846typedef struct l2arc_dev l2arc_dev_t; 847 848typedef struct l2arc_buf_hdr { 849 /* protected by arc_buf_hdr mutex */ 850 l2arc_dev_t *b_dev; /* L2ARC device */ 851 uint64_t b_daddr; /* disk address, offset byte */ 852 /* real alloc'd buffer size depending on b_compress applied */ 853 int32_t b_asize; 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/* For storing compression mode in b_flags */ 934#define HDR_COMPRESS_OFFSET 24 935#define HDR_COMPRESS_NBITS 7 936 937#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 938 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 939#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 940 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 941 942/* 943 * Other sizes 944 */ 945 946#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 947#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 948 949/* 950 * Hash table routines 951 */ 952 953#define HT_LOCK_PAD CACHE_LINE_SIZE 954 955struct ht_lock { 956 kmutex_t ht_lock; 957#ifdef _KERNEL 958 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 959#endif 960}; 961 962#define BUF_LOCKS 256 963typedef struct buf_hash_table { 964 uint64_t ht_mask; 965 arc_buf_hdr_t **ht_table; 966 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 967} buf_hash_table_t; 968 969static buf_hash_table_t buf_hash_table; 970 971#define BUF_HASH_INDEX(spa, dva, birth) \ 972 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 973#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 974#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 975#define HDR_LOCK(hdr) \ 976 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 977 978uint64_t zfs_crc64_table[256]; 979 980/* 981 * Level 2 ARC 982 */ 983 984#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 985#define L2ARC_HEADROOM 2 /* num of writes */ 986/* 987 * If we discover during ARC scan any buffers to be compressed, we boost 988 * our headroom for the next scanning cycle by this percentage multiple. 989 */ 990#define L2ARC_HEADROOM_BOOST 200 991#define L2ARC_FEED_SECS 1 /* caching interval secs */ 992#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 993 994/* 995 * Used to distinguish headers that are being process by 996 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 997 * address. This can happen when the header is added to the l2arc's list 998 * of buffers to write in the first stage of l2arc_write_buffers(), but 999 * has not yet been written out which happens in the second stage of 1000 * l2arc_write_buffers(). 1001 */ 1002#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 1003 1004#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1005#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1006 1007/* L2ARC Performance Tunables */ 1008uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1009uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1010uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1011uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1012uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1013uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1014boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1015boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1016boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1017 1018SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1019 &l2arc_write_max, 0, "max write size"); 1020SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1021 &l2arc_write_boost, 0, "extra write during warmup"); 1022SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1023 &l2arc_headroom, 0, "number of dev writes"); 1024SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1025 &l2arc_feed_secs, 0, "interval seconds"); 1026SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1027 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1028 1029SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1030 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1031SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1032 &l2arc_feed_again, 0, "turbo warmup"); 1033SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1034 &l2arc_norw, 0, "no reads during writes"); 1035 1036SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1037 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1038SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1039 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1040SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1041 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1042 1043SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1044 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1045SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1046 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1047SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1048 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1049 1050SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1051 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1052SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1053 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1054 "size of metadata in mru ghost state"); 1055SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1056 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1057 "size of data in mru ghost state"); 1058 1059SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1060 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1061SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1062 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1063SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1064 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1065 1066SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1067 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1068SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1069 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1070 "size of metadata in mfu ghost state"); 1071SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1072 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1073 "size of data in mfu ghost state"); 1074 1075SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1076 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1077 1078/* 1079 * L2ARC Internals 1080 */ 1081struct l2arc_dev { 1082 vdev_t *l2ad_vdev; /* vdev */ 1083 spa_t *l2ad_spa; /* spa */ 1084 uint64_t l2ad_hand; /* next write location */ 1085 uint64_t l2ad_start; /* first addr on device */ 1086 uint64_t l2ad_end; /* last addr on device */ 1087 boolean_t l2ad_first; /* first sweep through */ 1088 boolean_t l2ad_writing; /* currently writing */ 1089 kmutex_t l2ad_mtx; /* lock for buffer list */ 1090 list_t l2ad_buflist; /* buffer list */ 1091 list_node_t l2ad_node; /* device list node */ 1092 refcount_t l2ad_alloc; /* allocated bytes */ 1093}; 1094 1095static list_t L2ARC_dev_list; /* device list */ 1096static list_t *l2arc_dev_list; /* device list pointer */ 1097static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1098static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1099static list_t L2ARC_free_on_write; /* free after write buf list */ 1100static list_t *l2arc_free_on_write; /* free after write list ptr */ 1101static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1102static uint64_t l2arc_ndev; /* number of devices */ 1103 1104typedef struct l2arc_read_callback { 1105 arc_buf_t *l2rcb_buf; /* read buffer */ 1106 spa_t *l2rcb_spa; /* spa */ 1107 blkptr_t l2rcb_bp; /* original blkptr */ 1108 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1109 int l2rcb_flags; /* original flags */ 1110 enum zio_compress l2rcb_compress; /* applied compress */ 1111} l2arc_read_callback_t; 1112 1113typedef struct l2arc_write_callback { 1114 l2arc_dev_t *l2wcb_dev; /* device info */ 1115 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1116} l2arc_write_callback_t; 1117 1118typedef struct l2arc_data_free { 1119 /* protected by l2arc_free_on_write_mtx */ 1120 void *l2df_data; 1121 size_t l2df_size; 1122 void (*l2df_func)(void *, size_t); 1123 list_node_t l2df_list_node; 1124} l2arc_data_free_t; 1125 1126static kmutex_t l2arc_feed_thr_lock; 1127static kcondvar_t l2arc_feed_thr_cv; 1128static uint8_t l2arc_thread_exit; 1129 1130static void arc_get_data_buf(arc_buf_t *); 1131static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1132static boolean_t arc_is_overflowing(); 1133static void arc_buf_watch(arc_buf_t *); 1134 1135static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1136static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1137 1138static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1139static void l2arc_read_done(zio_t *); 1140 1141static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 1142static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1143static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1144 1145static uint64_t 1146buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1147{ 1148 uint8_t *vdva = (uint8_t *)dva; 1149 uint64_t crc = -1ULL; 1150 int i; 1151 1152 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1153 1154 for (i = 0; i < sizeof (dva_t); i++) 1155 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1156 1157 crc ^= (spa>>8) ^ birth; 1158 1159 return (crc); 1160} 1161 1162#define BUF_EMPTY(buf) \ 1163 ((buf)->b_dva.dva_word[0] == 0 && \ 1164 (buf)->b_dva.dva_word[1] == 0) 1165 1166#define BUF_EQUAL(spa, dva, birth, buf) \ 1167 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1168 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1169 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1170 1171static void 1172buf_discard_identity(arc_buf_hdr_t *hdr) 1173{ 1174 hdr->b_dva.dva_word[0] = 0; 1175 hdr->b_dva.dva_word[1] = 0; 1176 hdr->b_birth = 0; 1177} 1178 1179static arc_buf_hdr_t * 1180buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1181{ 1182 const dva_t *dva = BP_IDENTITY(bp); 1183 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1184 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1185 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1186 arc_buf_hdr_t *hdr; 1187 1188 mutex_enter(hash_lock); 1189 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1190 hdr = hdr->b_hash_next) { 1191 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1192 *lockp = hash_lock; 1193 return (hdr); 1194 } 1195 } 1196 mutex_exit(hash_lock); 1197 *lockp = NULL; 1198 return (NULL); 1199} 1200 1201/* 1202 * Insert an entry into the hash table. If there is already an element 1203 * equal to elem in the hash table, then the already existing element 1204 * will be returned and the new element will not be inserted. 1205 * Otherwise returns NULL. 1206 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1207 */ 1208static arc_buf_hdr_t * 1209buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1210{ 1211 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1212 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1213 arc_buf_hdr_t *fhdr; 1214 uint32_t i; 1215 1216 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1217 ASSERT(hdr->b_birth != 0); 1218 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1219 1220 if (lockp != NULL) { 1221 *lockp = hash_lock; 1222 mutex_enter(hash_lock); 1223 } else { 1224 ASSERT(MUTEX_HELD(hash_lock)); 1225 } 1226 1227 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1228 fhdr = fhdr->b_hash_next, i++) { 1229 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1230 return (fhdr); 1231 } 1232 1233 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1234 buf_hash_table.ht_table[idx] = hdr; 1235 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1236 1237 /* collect some hash table performance data */ 1238 if (i > 0) { 1239 ARCSTAT_BUMP(arcstat_hash_collisions); 1240 if (i == 1) 1241 ARCSTAT_BUMP(arcstat_hash_chains); 1242 1243 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1244 } 1245 1246 ARCSTAT_BUMP(arcstat_hash_elements); 1247 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1248 1249 return (NULL); 1250} 1251 1252static void 1253buf_hash_remove(arc_buf_hdr_t *hdr) 1254{ 1255 arc_buf_hdr_t *fhdr, **hdrp; 1256 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1257 1258 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1259 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1260 1261 hdrp = &buf_hash_table.ht_table[idx]; 1262 while ((fhdr = *hdrp) != hdr) { 1263 ASSERT(fhdr != NULL); 1264 hdrp = &fhdr->b_hash_next; 1265 } 1266 *hdrp = hdr->b_hash_next; 1267 hdr->b_hash_next = NULL; 1268 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1269 1270 /* collect some hash table performance data */ 1271 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1272 1273 if (buf_hash_table.ht_table[idx] && 1274 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1275 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1276} 1277 1278/* 1279 * Global data structures and functions for the buf kmem cache. 1280 */ 1281static kmem_cache_t *hdr_full_cache; 1282static kmem_cache_t *hdr_l2only_cache; 1283static kmem_cache_t *buf_cache; 1284 1285static void 1286buf_fini(void) 1287{ 1288 int i; 1289 1290 kmem_free(buf_hash_table.ht_table, 1291 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1292 for (i = 0; i < BUF_LOCKS; i++) 1293 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1294 kmem_cache_destroy(hdr_full_cache); 1295 kmem_cache_destroy(hdr_l2only_cache); 1296 kmem_cache_destroy(buf_cache); 1297} 1298 1299/* 1300 * Constructor callback - called when the cache is empty 1301 * and a new buf is requested. 1302 */ 1303/* ARGSUSED */ 1304static int 1305hdr_full_cons(void *vbuf, void *unused, int kmflag) 1306{ 1307 arc_buf_hdr_t *hdr = vbuf; 1308 1309 bzero(hdr, HDR_FULL_SIZE); 1310 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1311 refcount_create(&hdr->b_l1hdr.b_refcnt); 1312 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1313 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1314 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1315 1316 return (0); 1317} 1318 1319/* ARGSUSED */ 1320static int 1321hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1322{ 1323 arc_buf_hdr_t *hdr = vbuf; 1324 1325 bzero(hdr, HDR_L2ONLY_SIZE); 1326 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1327 1328 return (0); 1329} 1330 1331/* ARGSUSED */ 1332static int 1333buf_cons(void *vbuf, void *unused, int kmflag) 1334{ 1335 arc_buf_t *buf = vbuf; 1336 1337 bzero(buf, sizeof (arc_buf_t)); 1338 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1339 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1340 1341 return (0); 1342} 1343 1344/* 1345 * Destructor callback - called when a cached buf is 1346 * no longer required. 1347 */ 1348/* ARGSUSED */ 1349static void 1350hdr_full_dest(void *vbuf, void *unused) 1351{ 1352 arc_buf_hdr_t *hdr = vbuf; 1353 1354 ASSERT(BUF_EMPTY(hdr)); 1355 cv_destroy(&hdr->b_l1hdr.b_cv); 1356 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1357 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1358 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1359 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1360} 1361 1362/* ARGSUSED */ 1363static void 1364hdr_l2only_dest(void *vbuf, void *unused) 1365{ 1366 arc_buf_hdr_t *hdr = vbuf; 1367 1368 ASSERT(BUF_EMPTY(hdr)); 1369 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1370} 1371 1372/* ARGSUSED */ 1373static void 1374buf_dest(void *vbuf, void *unused) 1375{ 1376 arc_buf_t *buf = vbuf; 1377 1378 mutex_destroy(&buf->b_evict_lock); 1379 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1380} 1381 1382/* 1383 * Reclaim callback -- invoked when memory is low. 1384 */ 1385/* ARGSUSED */ 1386static void 1387hdr_recl(void *unused) 1388{ 1389 dprintf("hdr_recl called\n"); 1390 /* 1391 * umem calls the reclaim func when we destroy the buf cache, 1392 * which is after we do arc_fini(). 1393 */ 1394 if (!arc_dead) 1395 cv_signal(&arc_reclaim_thread_cv); 1396} 1397 1398static void 1399buf_init(void) 1400{ 1401 uint64_t *ct; 1402 uint64_t hsize = 1ULL << 12; 1403 int i, j; 1404 1405 /* 1406 * The hash table is big enough to fill all of physical memory 1407 * with an average block size of zfs_arc_average_blocksize (default 8K). 1408 * By default, the table will take up 1409 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1410 */ 1411 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1412 hsize <<= 1; 1413retry: 1414 buf_hash_table.ht_mask = hsize - 1; 1415 buf_hash_table.ht_table = 1416 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1417 if (buf_hash_table.ht_table == NULL) { 1418 ASSERT(hsize > (1ULL << 8)); 1419 hsize >>= 1; 1420 goto retry; 1421 } 1422 1423 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1424 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1425 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1426 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1427 NULL, NULL, 0); 1428 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1429 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1430 1431 for (i = 0; i < 256; i++) 1432 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1433 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1434 1435 for (i = 0; i < BUF_LOCKS; i++) { 1436 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1437 NULL, MUTEX_DEFAULT, NULL); 1438 } 1439} 1440 1441/* 1442 * Transition between the two allocation states for the arc_buf_hdr struct. 1443 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1444 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1445 * version is used when a cache buffer is only in the L2ARC in order to reduce 1446 * memory usage. 1447 */ 1448static arc_buf_hdr_t * 1449arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1450{ 1451 ASSERT(HDR_HAS_L2HDR(hdr)); 1452 1453 arc_buf_hdr_t *nhdr; 1454 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1455 1456 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1457 (old == hdr_l2only_cache && new == hdr_full_cache)); 1458 1459 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1460 1461 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1462 buf_hash_remove(hdr); 1463 1464 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1465 1466 if (new == hdr_full_cache) { 1467 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1468 /* 1469 * arc_access and arc_change_state need to be aware that a 1470 * header has just come out of L2ARC, so we set its state to 1471 * l2c_only even though it's about to change. 1472 */ 1473 nhdr->b_l1hdr.b_state = arc_l2c_only; 1474 1475 /* Verify previous threads set to NULL before freeing */ 1476 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1477 } else { 1478 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1479 ASSERT0(hdr->b_l1hdr.b_datacnt); 1480 1481 /* 1482 * If we've reached here, We must have been called from 1483 * arc_evict_hdr(), as such we should have already been 1484 * removed from any ghost list we were previously on 1485 * (which protects us from racing with arc_evict_state), 1486 * thus no locking is needed during this check. 1487 */ 1488 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1489 1490 /* 1491 * A buffer must not be moved into the arc_l2c_only 1492 * state if it's not finished being written out to the 1493 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1494 * might try to be accessed, even though it was removed. 1495 */ 1496 VERIFY(!HDR_L2_WRITING(hdr)); 1497 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1498 1499 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1500 } 1501 /* 1502 * The header has been reallocated so we need to re-insert it into any 1503 * lists it was on. 1504 */ 1505 (void) buf_hash_insert(nhdr, NULL); 1506 1507 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1508 1509 mutex_enter(&dev->l2ad_mtx); 1510 1511 /* 1512 * We must place the realloc'ed header back into the list at 1513 * the same spot. Otherwise, if it's placed earlier in the list, 1514 * l2arc_write_buffers() could find it during the function's 1515 * write phase, and try to write it out to the l2arc. 1516 */ 1517 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1518 list_remove(&dev->l2ad_buflist, hdr); 1519 1520 mutex_exit(&dev->l2ad_mtx); 1521 1522 /* 1523 * Since we're using the pointer address as the tag when 1524 * incrementing and decrementing the l2ad_alloc refcount, we 1525 * must remove the old pointer (that we're about to destroy) and 1526 * add the new pointer to the refcount. Otherwise we'd remove 1527 * the wrong pointer address when calling arc_hdr_destroy() later. 1528 */ 1529 1530 (void) refcount_remove_many(&dev->l2ad_alloc, 1531 hdr->b_l2hdr.b_asize, hdr); 1532 1533 (void) refcount_add_many(&dev->l2ad_alloc, 1534 nhdr->b_l2hdr.b_asize, nhdr); 1535 1536 buf_discard_identity(hdr); 1537 hdr->b_freeze_cksum = NULL; 1538 kmem_cache_free(old, hdr); 1539 1540 return (nhdr); 1541} 1542 1543 1544#define ARC_MINTIME (hz>>4) /* 62 ms */ 1545 1546static void 1547arc_cksum_verify(arc_buf_t *buf) 1548{ 1549 zio_cksum_t zc; 1550 1551 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1552 return; 1553 1554 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1555 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1556 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1557 return; 1558 } 1559 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1560 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1561 panic("buffer modified while frozen!"); 1562 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1563} 1564 1565static int 1566arc_cksum_equal(arc_buf_t *buf) 1567{ 1568 zio_cksum_t zc; 1569 int equal; 1570 1571 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1572 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1573 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1574 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1575 1576 return (equal); 1577} 1578 1579static void 1580arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1581{ 1582 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1583 return; 1584 1585 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1586 if (buf->b_hdr->b_freeze_cksum != NULL) { 1587 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1588 return; 1589 } 1590 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1591 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1592 buf->b_hdr->b_freeze_cksum); 1593 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1594#ifdef illumos 1595 arc_buf_watch(buf); 1596#endif /* illumos */ 1597} 1598 1599#ifdef illumos 1600#ifndef _KERNEL 1601typedef struct procctl { 1602 long cmd; 1603 prwatch_t prwatch; 1604} procctl_t; 1605#endif 1606 1607/* ARGSUSED */ 1608static void 1609arc_buf_unwatch(arc_buf_t *buf) 1610{ 1611#ifndef _KERNEL 1612 if (arc_watch) { 1613 int result; 1614 procctl_t ctl; 1615 ctl.cmd = PCWATCH; 1616 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1617 ctl.prwatch.pr_size = 0; 1618 ctl.prwatch.pr_wflags = 0; 1619 result = write(arc_procfd, &ctl, sizeof (ctl)); 1620 ASSERT3U(result, ==, sizeof (ctl)); 1621 } 1622#endif 1623} 1624 1625/* ARGSUSED */ 1626static void 1627arc_buf_watch(arc_buf_t *buf) 1628{ 1629#ifndef _KERNEL 1630 if (arc_watch) { 1631 int result; 1632 procctl_t ctl; 1633 ctl.cmd = PCWATCH; 1634 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1635 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1636 ctl.prwatch.pr_wflags = WA_WRITE; 1637 result = write(arc_procfd, &ctl, sizeof (ctl)); 1638 ASSERT3U(result, ==, sizeof (ctl)); 1639 } 1640#endif 1641} 1642#endif /* illumos */ 1643 1644static arc_buf_contents_t 1645arc_buf_type(arc_buf_hdr_t *hdr) 1646{ 1647 if (HDR_ISTYPE_METADATA(hdr)) { 1648 return (ARC_BUFC_METADATA); 1649 } else { 1650 return (ARC_BUFC_DATA); 1651 } 1652} 1653 1654static uint32_t 1655arc_bufc_to_flags(arc_buf_contents_t type) 1656{ 1657 switch (type) { 1658 case ARC_BUFC_DATA: 1659 /* metadata field is 0 if buffer contains normal data */ 1660 return (0); 1661 case ARC_BUFC_METADATA: 1662 return (ARC_FLAG_BUFC_METADATA); 1663 default: 1664 break; 1665 } 1666 panic("undefined ARC buffer type!"); 1667 return ((uint32_t)-1); 1668} 1669 1670void 1671arc_buf_thaw(arc_buf_t *buf) 1672{ 1673 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1674 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1675 panic("modifying non-anon buffer!"); 1676 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1677 panic("modifying buffer while i/o in progress!"); 1678 arc_cksum_verify(buf); 1679 } 1680 1681 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1682 if (buf->b_hdr->b_freeze_cksum != NULL) { 1683 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1684 buf->b_hdr->b_freeze_cksum = NULL; 1685 } 1686 1687#ifdef ZFS_DEBUG 1688 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1689 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1690 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1691 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1692 } 1693#endif 1694 1695 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1696 1697#ifdef illumos 1698 arc_buf_unwatch(buf); 1699#endif /* illumos */ 1700} 1701 1702void 1703arc_buf_freeze(arc_buf_t *buf) 1704{ 1705 kmutex_t *hash_lock; 1706 1707 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1708 return; 1709 1710 hash_lock = HDR_LOCK(buf->b_hdr); 1711 mutex_enter(hash_lock); 1712 1713 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1714 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1715 arc_cksum_compute(buf, B_FALSE); 1716 mutex_exit(hash_lock); 1717 1718} 1719 1720static void 1721add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1722{ 1723 ASSERT(HDR_HAS_L1HDR(hdr)); 1724 ASSERT(MUTEX_HELD(hash_lock)); 1725 arc_state_t *state = hdr->b_l1hdr.b_state; 1726 1727 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1728 (state != arc_anon)) { 1729 /* We don't use the L2-only state list. */ 1730 if (state != arc_l2c_only) { 1731 arc_buf_contents_t type = arc_buf_type(hdr); 1732 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1733 multilist_t *list = &state->arcs_list[type]; 1734 uint64_t *size = &state->arcs_lsize[type]; 1735 1736 multilist_remove(list, hdr); 1737 1738 if (GHOST_STATE(state)) { 1739 ASSERT0(hdr->b_l1hdr.b_datacnt); 1740 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1741 delta = hdr->b_size; 1742 } 1743 ASSERT(delta > 0); 1744 ASSERT3U(*size, >=, delta); 1745 atomic_add_64(size, -delta); 1746 } 1747 /* remove the prefetch flag if we get a reference */ 1748 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1749 } 1750} 1751 1752static int 1753remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1754{ 1755 int cnt; 1756 arc_state_t *state = hdr->b_l1hdr.b_state; 1757 1758 ASSERT(HDR_HAS_L1HDR(hdr)); 1759 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1760 ASSERT(!GHOST_STATE(state)); 1761 1762 /* 1763 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1764 * check to prevent usage of the arc_l2c_only list. 1765 */ 1766 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1767 (state != arc_anon)) { 1768 arc_buf_contents_t type = arc_buf_type(hdr); 1769 multilist_t *list = &state->arcs_list[type]; 1770 uint64_t *size = &state->arcs_lsize[type]; 1771 1772 multilist_insert(list, hdr); 1773 1774 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1775 atomic_add_64(size, hdr->b_size * 1776 hdr->b_l1hdr.b_datacnt); 1777 } 1778 return (cnt); 1779} 1780 1781/* 1782 * Move the supplied buffer to the indicated state. The hash lock 1783 * for the buffer must be held by the caller. 1784 */ 1785static void 1786arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1787 kmutex_t *hash_lock) 1788{ 1789 arc_state_t *old_state; 1790 int64_t refcnt; 1791 uint32_t datacnt; 1792 uint64_t from_delta, to_delta; 1793 arc_buf_contents_t buftype = arc_buf_type(hdr); 1794 1795 /* 1796 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1797 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1798 * L1 hdr doesn't always exist when we change state to arc_anon before 1799 * destroying a header, in which case reallocating to add the L1 hdr is 1800 * pointless. 1801 */ 1802 if (HDR_HAS_L1HDR(hdr)) { 1803 old_state = hdr->b_l1hdr.b_state; 1804 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1805 datacnt = hdr->b_l1hdr.b_datacnt; 1806 } else { 1807 old_state = arc_l2c_only; 1808 refcnt = 0; 1809 datacnt = 0; 1810 } 1811 1812 ASSERT(MUTEX_HELD(hash_lock)); 1813 ASSERT3P(new_state, !=, old_state); 1814 ASSERT(refcnt == 0 || datacnt > 0); 1815 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1816 ASSERT(old_state != arc_anon || datacnt <= 1); 1817 1818 from_delta = to_delta = datacnt * hdr->b_size; 1819 1820 /* 1821 * If this buffer is evictable, transfer it from the 1822 * old state list to the new state list. 1823 */ 1824 if (refcnt == 0) { 1825 if (old_state != arc_anon && old_state != arc_l2c_only) { 1826 uint64_t *size = &old_state->arcs_lsize[buftype]; 1827 1828 ASSERT(HDR_HAS_L1HDR(hdr)); 1829 multilist_remove(&old_state->arcs_list[buftype], hdr); 1830 1831 /* 1832 * If prefetching out of the ghost cache, 1833 * we will have a non-zero datacnt. 1834 */ 1835 if (GHOST_STATE(old_state) && datacnt == 0) { 1836 /* ghost elements have a ghost size */ 1837 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1838 from_delta = hdr->b_size; 1839 } 1840 ASSERT3U(*size, >=, from_delta); 1841 atomic_add_64(size, -from_delta); 1842 } 1843 if (new_state != arc_anon && new_state != arc_l2c_only) { 1844 uint64_t *size = &new_state->arcs_lsize[buftype]; 1845 1846 /* 1847 * An L1 header always exists here, since if we're 1848 * moving to some L1-cached state (i.e. not l2c_only or 1849 * anonymous), we realloc the header to add an L1hdr 1850 * beforehand. 1851 */ 1852 ASSERT(HDR_HAS_L1HDR(hdr)); 1853 multilist_insert(&new_state->arcs_list[buftype], hdr); 1854 1855 /* ghost elements have a ghost size */ 1856 if (GHOST_STATE(new_state)) { 1857 ASSERT0(datacnt); 1858 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1859 to_delta = hdr->b_size; 1860 } 1861 atomic_add_64(size, to_delta); 1862 } 1863 } 1864 1865 ASSERT(!BUF_EMPTY(hdr)); 1866 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1867 buf_hash_remove(hdr); 1868 1869 /* adjust state sizes (ignore arc_l2c_only) */ 1870 1871 if (to_delta && new_state != arc_l2c_only) { 1872 ASSERT(HDR_HAS_L1HDR(hdr)); 1873 if (GHOST_STATE(new_state)) { 1874 ASSERT0(datacnt); 1875 1876 /* 1877 * We moving a header to a ghost state, we first 1878 * remove all arc buffers. Thus, we'll have a 1879 * datacnt of zero, and no arc buffer to use for 1880 * the reference. As a result, we use the arc 1881 * header pointer for the reference. 1882 */ 1883 (void) refcount_add_many(&new_state->arcs_size, 1884 hdr->b_size, hdr); 1885 } else { 1886 ASSERT3U(datacnt, !=, 0); 1887 1888 /* 1889 * Each individual buffer holds a unique reference, 1890 * thus we must remove each of these references one 1891 * at a time. 1892 */ 1893 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1894 buf = buf->b_next) { 1895 (void) refcount_add_many(&new_state->arcs_size, 1896 hdr->b_size, buf); 1897 } 1898 } 1899 } 1900 1901 if (from_delta && old_state != arc_l2c_only) { 1902 ASSERT(HDR_HAS_L1HDR(hdr)); 1903 if (GHOST_STATE(old_state)) { 1904 /* 1905 * When moving a header off of a ghost state, 1906 * there's the possibility for datacnt to be 1907 * non-zero. This is because we first add the 1908 * arc buffer to the header prior to changing 1909 * the header's state. Since we used the header 1910 * for the reference when putting the header on 1911 * the ghost state, we must balance that and use 1912 * the header when removing off the ghost state 1913 * (even though datacnt is non zero). 1914 */ 1915 1916 IMPLY(datacnt == 0, new_state == arc_anon || 1917 new_state == arc_l2c_only); 1918 1919 (void) refcount_remove_many(&old_state->arcs_size, 1920 hdr->b_size, hdr); 1921 } else { 1922 ASSERT3P(datacnt, !=, 0); 1923 1924 /* 1925 * Each individual buffer holds a unique reference, 1926 * thus we must remove each of these references one 1927 * at a time. 1928 */ 1929 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1930 buf = buf->b_next) { 1931 (void) refcount_remove_many( 1932 &old_state->arcs_size, hdr->b_size, buf); 1933 } 1934 } 1935 } 1936 1937 if (HDR_HAS_L1HDR(hdr)) 1938 hdr->b_l1hdr.b_state = new_state; 1939 1940 /* 1941 * L2 headers should never be on the L2 state list since they don't 1942 * have L1 headers allocated. 1943 */ 1944 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1945 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1946} 1947 1948void 1949arc_space_consume(uint64_t space, arc_space_type_t type) 1950{ 1951 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1952 1953 switch (type) { 1954 case ARC_SPACE_DATA: 1955 ARCSTAT_INCR(arcstat_data_size, space); 1956 break; 1957 case ARC_SPACE_META: 1958 ARCSTAT_INCR(arcstat_metadata_size, space); 1959 break; 1960 case ARC_SPACE_OTHER: 1961 ARCSTAT_INCR(arcstat_other_size, space); 1962 break; 1963 case ARC_SPACE_HDRS: 1964 ARCSTAT_INCR(arcstat_hdr_size, space); 1965 break; 1966 case ARC_SPACE_L2HDRS: 1967 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1968 break; 1969 } 1970 1971 if (type != ARC_SPACE_DATA) 1972 ARCSTAT_INCR(arcstat_meta_used, space); 1973 1974 atomic_add_64(&arc_size, space); 1975} 1976 1977void 1978arc_space_return(uint64_t space, arc_space_type_t type) 1979{ 1980 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1981 1982 switch (type) { 1983 case ARC_SPACE_DATA: 1984 ARCSTAT_INCR(arcstat_data_size, -space); 1985 break; 1986 case ARC_SPACE_META: 1987 ARCSTAT_INCR(arcstat_metadata_size, -space); 1988 break; 1989 case ARC_SPACE_OTHER: 1990 ARCSTAT_INCR(arcstat_other_size, -space); 1991 break; 1992 case ARC_SPACE_HDRS: 1993 ARCSTAT_INCR(arcstat_hdr_size, -space); 1994 break; 1995 case ARC_SPACE_L2HDRS: 1996 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1997 break; 1998 } 1999 2000 if (type != ARC_SPACE_DATA) { 2001 ASSERT(arc_meta_used >= space); 2002 if (arc_meta_max < arc_meta_used) 2003 arc_meta_max = arc_meta_used; 2004 ARCSTAT_INCR(arcstat_meta_used, -space); 2005 } 2006 2007 ASSERT(arc_size >= space); 2008 atomic_add_64(&arc_size, -space); 2009} 2010 2011arc_buf_t * 2012arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2013{ 2014 arc_buf_hdr_t *hdr; 2015 arc_buf_t *buf; 2016 2017 ASSERT3U(size, >, 0); 2018 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2019 ASSERT(BUF_EMPTY(hdr)); 2020 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2021 hdr->b_size = size; 2022 hdr->b_spa = spa_load_guid(spa); 2023 2024 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2025 buf->b_hdr = hdr; 2026 buf->b_data = NULL; 2027 buf->b_efunc = NULL; 2028 buf->b_private = NULL; 2029 buf->b_next = NULL; 2030 2031 hdr->b_flags = arc_bufc_to_flags(type); 2032 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2033 2034 hdr->b_l1hdr.b_buf = buf; 2035 hdr->b_l1hdr.b_state = arc_anon; 2036 hdr->b_l1hdr.b_arc_access = 0; 2037 hdr->b_l1hdr.b_datacnt = 1; 2038 hdr->b_l1hdr.b_tmp_cdata = NULL; 2039 2040 arc_get_data_buf(buf); 2041 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2042 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2043 2044 return (buf); 2045} 2046 2047static char *arc_onloan_tag = "onloan"; 2048 2049/* 2050 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2051 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2052 * buffers must be returned to the arc before they can be used by the DMU or 2053 * freed. 2054 */ 2055arc_buf_t * 2056arc_loan_buf(spa_t *spa, int size) 2057{ 2058 arc_buf_t *buf; 2059 2060 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2061 2062 atomic_add_64(&arc_loaned_bytes, size); 2063 return (buf); 2064} 2065 2066/* 2067 * Return a loaned arc buffer to the arc. 2068 */ 2069void 2070arc_return_buf(arc_buf_t *buf, void *tag) 2071{ 2072 arc_buf_hdr_t *hdr = buf->b_hdr; 2073 2074 ASSERT(buf->b_data != NULL); 2075 ASSERT(HDR_HAS_L1HDR(hdr)); 2076 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2077 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2078 2079 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2080} 2081 2082/* Detach an arc_buf from a dbuf (tag) */ 2083void 2084arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2085{ 2086 arc_buf_hdr_t *hdr = buf->b_hdr; 2087 2088 ASSERT(buf->b_data != NULL); 2089 ASSERT(HDR_HAS_L1HDR(hdr)); 2090 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2091 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2092 buf->b_efunc = NULL; 2093 buf->b_private = NULL; 2094 2095 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2096} 2097 2098static arc_buf_t * 2099arc_buf_clone(arc_buf_t *from) 2100{ 2101 arc_buf_t *buf; 2102 arc_buf_hdr_t *hdr = from->b_hdr; 2103 uint64_t size = hdr->b_size; 2104 2105 ASSERT(HDR_HAS_L1HDR(hdr)); 2106 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2107 2108 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2109 buf->b_hdr = hdr; 2110 buf->b_data = NULL; 2111 buf->b_efunc = NULL; 2112 buf->b_private = NULL; 2113 buf->b_next = hdr->b_l1hdr.b_buf; 2114 hdr->b_l1hdr.b_buf = buf; 2115 arc_get_data_buf(buf); 2116 bcopy(from->b_data, buf->b_data, size); 2117 2118 /* 2119 * This buffer already exists in the arc so create a duplicate 2120 * copy for the caller. If the buffer is associated with user data 2121 * then track the size and number of duplicates. These stats will be 2122 * updated as duplicate buffers are created and destroyed. 2123 */ 2124 if (HDR_ISTYPE_DATA(hdr)) { 2125 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2126 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2127 } 2128 hdr->b_l1hdr.b_datacnt += 1; 2129 return (buf); 2130} 2131 2132void 2133arc_buf_add_ref(arc_buf_t *buf, void* tag) 2134{ 2135 arc_buf_hdr_t *hdr; 2136 kmutex_t *hash_lock; 2137 2138 /* 2139 * Check to see if this buffer is evicted. Callers 2140 * must verify b_data != NULL to know if the add_ref 2141 * was successful. 2142 */ 2143 mutex_enter(&buf->b_evict_lock); 2144 if (buf->b_data == NULL) { 2145 mutex_exit(&buf->b_evict_lock); 2146 return; 2147 } 2148 hash_lock = HDR_LOCK(buf->b_hdr); 2149 mutex_enter(hash_lock); 2150 hdr = buf->b_hdr; 2151 ASSERT(HDR_HAS_L1HDR(hdr)); 2152 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2153 mutex_exit(&buf->b_evict_lock); 2154 2155 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2156 hdr->b_l1hdr.b_state == arc_mfu); 2157 2158 add_reference(hdr, hash_lock, tag); 2159 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2160 arc_access(hdr, hash_lock); 2161 mutex_exit(hash_lock); 2162 ARCSTAT_BUMP(arcstat_hits); 2163 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2164 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2165 data, metadata, hits); 2166} 2167 2168static void 2169arc_buf_free_on_write(void *data, size_t size, 2170 void (*free_func)(void *, size_t)) 2171{ 2172 l2arc_data_free_t *df; 2173 2174 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2175 df->l2df_data = data; 2176 df->l2df_size = size; 2177 df->l2df_func = free_func; 2178 mutex_enter(&l2arc_free_on_write_mtx); 2179 list_insert_head(l2arc_free_on_write, df); 2180 mutex_exit(&l2arc_free_on_write_mtx); 2181} 2182 2183/* 2184 * Free the arc data buffer. If it is an l2arc write in progress, 2185 * the buffer is placed on l2arc_free_on_write to be freed later. 2186 */ 2187static void 2188arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2189{ 2190 arc_buf_hdr_t *hdr = buf->b_hdr; 2191 2192 if (HDR_L2_WRITING(hdr)) { 2193 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2194 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2195 } else { 2196 free_func(buf->b_data, hdr->b_size); 2197 } 2198} 2199 2200static void 2201arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2202{ 2203 ASSERT(HDR_HAS_L2HDR(hdr)); 2204 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2205 2206 /* 2207 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2208 * that doesn't exist, the header is in the arc_l2c_only state, 2209 * and there isn't anything to free (it's already been freed). 2210 */ 2211 if (!HDR_HAS_L1HDR(hdr)) 2212 return; 2213 2214 /* 2215 * The header isn't being written to the l2arc device, thus it 2216 * shouldn't have a b_tmp_cdata to free. 2217 */ 2218 if (!HDR_L2_WRITING(hdr)) { 2219 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2220 return; 2221 } 2222 2223 /* 2224 * The header does not have compression enabled. This can be due 2225 * to the buffer not being compressible, or because we're 2226 * freeing the buffer before the second phase of 2227 * l2arc_write_buffer() has started (which does the compression 2228 * step). In either case, b_tmp_cdata does not point to a 2229 * separately compressed buffer, so there's nothing to free (it 2230 * points to the same buffer as the arc_buf_t's b_data field). 2231 */ 2232 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 2233 hdr->b_l1hdr.b_tmp_cdata = NULL; 2234 return; 2235 } 2236 2237 /* 2238 * There's nothing to free since the buffer was all zero's and 2239 * compressed to a zero length buffer. 2240 */ 2241 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) { 2242 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2243 return; 2244 } 2245 2246 ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))); 2247 2248 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, 2249 hdr->b_size, zio_data_buf_free); 2250 2251 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2252 hdr->b_l1hdr.b_tmp_cdata = NULL; 2253} 2254 2255/* 2256 * Free up buf->b_data and if 'remove' is set, then pull the 2257 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2258 */ 2259static void 2260arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2261{ 2262 arc_buf_t **bufp; 2263 2264 /* free up data associated with the buf */ 2265 if (buf->b_data != NULL) { 2266 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2267 uint64_t size = buf->b_hdr->b_size; 2268 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2269 2270 arc_cksum_verify(buf); 2271#ifdef illumos 2272 arc_buf_unwatch(buf); 2273#endif /* illumos */ 2274 2275 if (type == ARC_BUFC_METADATA) { 2276 arc_buf_data_free(buf, zio_buf_free); 2277 arc_space_return(size, ARC_SPACE_META); 2278 } else { 2279 ASSERT(type == ARC_BUFC_DATA); 2280 arc_buf_data_free(buf, zio_data_buf_free); 2281 arc_space_return(size, ARC_SPACE_DATA); 2282 } 2283 2284 /* protected by hash lock, if in the hash table */ 2285 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2286 uint64_t *cnt = &state->arcs_lsize[type]; 2287 2288 ASSERT(refcount_is_zero( 2289 &buf->b_hdr->b_l1hdr.b_refcnt)); 2290 ASSERT(state != arc_anon && state != arc_l2c_only); 2291 2292 ASSERT3U(*cnt, >=, size); 2293 atomic_add_64(cnt, -size); 2294 } 2295 2296 (void) refcount_remove_many(&state->arcs_size, size, buf); 2297 buf->b_data = NULL; 2298 2299 /* 2300 * If we're destroying a duplicate buffer make sure 2301 * that the appropriate statistics are updated. 2302 */ 2303 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2304 HDR_ISTYPE_DATA(buf->b_hdr)) { 2305 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2306 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2307 } 2308 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2309 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2310 } 2311 2312 /* only remove the buf if requested */ 2313 if (!remove) 2314 return; 2315 2316 /* remove the buf from the hdr list */ 2317 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2318 bufp = &(*bufp)->b_next) 2319 continue; 2320 *bufp = buf->b_next; 2321 buf->b_next = NULL; 2322 2323 ASSERT(buf->b_efunc == NULL); 2324 2325 /* clean up the buf */ 2326 buf->b_hdr = NULL; 2327 kmem_cache_free(buf_cache, buf); 2328} 2329 2330static void 2331arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2332{ 2333 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2334 l2arc_dev_t *dev = l2hdr->b_dev; 2335 2336 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2337 ASSERT(HDR_HAS_L2HDR(hdr)); 2338 2339 list_remove(&dev->l2ad_buflist, hdr); 2340 2341 /* 2342 * We don't want to leak the b_tmp_cdata buffer that was 2343 * allocated in l2arc_write_buffers() 2344 */ 2345 arc_buf_l2_cdata_free(hdr); 2346 2347 /* 2348 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2349 * this header is being processed by l2arc_write_buffers() (i.e. 2350 * it's in the first stage of l2arc_write_buffers()). 2351 * Re-affirming that truth here, just to serve as a reminder. If 2352 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2353 * may not have its HDR_L2_WRITING flag set. (the write may have 2354 * completed, in which case HDR_L2_WRITING will be false and the 2355 * b_daddr field will point to the address of the buffer on disk). 2356 */ 2357 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2358 2359 /* 2360 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2361 * l2arc_write_buffers(). Since we've just removed this header 2362 * from the l2arc buffer list, this header will never reach the 2363 * second stage of l2arc_write_buffers(), which increments the 2364 * accounting stats for this header. Thus, we must be careful 2365 * not to decrement them for this header either. 2366 */ 2367 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2368 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2369 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2370 2371 vdev_space_update(dev->l2ad_vdev, 2372 -l2hdr->b_asize, 0, 0); 2373 2374 (void) refcount_remove_many(&dev->l2ad_alloc, 2375 l2hdr->b_asize, hdr); 2376 } 2377 2378 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2379} 2380 2381static void 2382arc_hdr_destroy(arc_buf_hdr_t *hdr) 2383{ 2384 if (HDR_HAS_L1HDR(hdr)) { 2385 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2386 hdr->b_l1hdr.b_datacnt > 0); 2387 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2388 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2389 } 2390 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2391 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2392 2393 if (HDR_HAS_L2HDR(hdr)) { 2394 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2395 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2396 2397 if (!buflist_held) 2398 mutex_enter(&dev->l2ad_mtx); 2399 2400 /* 2401 * Even though we checked this conditional above, we 2402 * need to check this again now that we have the 2403 * l2ad_mtx. This is because we could be racing with 2404 * another thread calling l2arc_evict() which might have 2405 * destroyed this header's L2 portion as we were waiting 2406 * to acquire the l2ad_mtx. If that happens, we don't 2407 * want to re-destroy the header's L2 portion. 2408 */ 2409 if (HDR_HAS_L2HDR(hdr)) { 2410 if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET) 2411 trim_map_free(dev->l2ad_vdev, 2412 hdr->b_l2hdr.b_daddr, 2413 hdr->b_l2hdr.b_asize, 0); 2414 arc_hdr_l2hdr_destroy(hdr); 2415 } 2416 2417 if (!buflist_held) 2418 mutex_exit(&dev->l2ad_mtx); 2419 } 2420 2421 if (!BUF_EMPTY(hdr)) 2422 buf_discard_identity(hdr); 2423 2424 if (hdr->b_freeze_cksum != NULL) { 2425 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2426 hdr->b_freeze_cksum = NULL; 2427 } 2428 2429 if (HDR_HAS_L1HDR(hdr)) { 2430 while (hdr->b_l1hdr.b_buf) { 2431 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2432 2433 if (buf->b_efunc != NULL) { 2434 mutex_enter(&arc_user_evicts_lock); 2435 mutex_enter(&buf->b_evict_lock); 2436 ASSERT(buf->b_hdr != NULL); 2437 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2438 hdr->b_l1hdr.b_buf = buf->b_next; 2439 buf->b_hdr = &arc_eviction_hdr; 2440 buf->b_next = arc_eviction_list; 2441 arc_eviction_list = buf; 2442 mutex_exit(&buf->b_evict_lock); 2443 cv_signal(&arc_user_evicts_cv); 2444 mutex_exit(&arc_user_evicts_lock); 2445 } else { 2446 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2447 } 2448 } 2449#ifdef ZFS_DEBUG 2450 if (hdr->b_l1hdr.b_thawed != NULL) { 2451 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2452 hdr->b_l1hdr.b_thawed = NULL; 2453 } 2454#endif 2455 } 2456 2457 ASSERT3P(hdr->b_hash_next, ==, NULL); 2458 if (HDR_HAS_L1HDR(hdr)) { 2459 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2460 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2461 kmem_cache_free(hdr_full_cache, hdr); 2462 } else { 2463 kmem_cache_free(hdr_l2only_cache, hdr); 2464 } 2465} 2466 2467void 2468arc_buf_free(arc_buf_t *buf, void *tag) 2469{ 2470 arc_buf_hdr_t *hdr = buf->b_hdr; 2471 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2472 2473 ASSERT(buf->b_efunc == NULL); 2474 ASSERT(buf->b_data != NULL); 2475 2476 if (hashed) { 2477 kmutex_t *hash_lock = HDR_LOCK(hdr); 2478 2479 mutex_enter(hash_lock); 2480 hdr = buf->b_hdr; 2481 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2482 2483 (void) remove_reference(hdr, hash_lock, tag); 2484 if (hdr->b_l1hdr.b_datacnt > 1) { 2485 arc_buf_destroy(buf, TRUE); 2486 } else { 2487 ASSERT(buf == hdr->b_l1hdr.b_buf); 2488 ASSERT(buf->b_efunc == NULL); 2489 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2490 } 2491 mutex_exit(hash_lock); 2492 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2493 int destroy_hdr; 2494 /* 2495 * We are in the middle of an async write. Don't destroy 2496 * this buffer unless the write completes before we finish 2497 * decrementing the reference count. 2498 */ 2499 mutex_enter(&arc_user_evicts_lock); 2500 (void) remove_reference(hdr, NULL, tag); 2501 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2502 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2503 mutex_exit(&arc_user_evicts_lock); 2504 if (destroy_hdr) 2505 arc_hdr_destroy(hdr); 2506 } else { 2507 if (remove_reference(hdr, NULL, tag) > 0) 2508 arc_buf_destroy(buf, TRUE); 2509 else 2510 arc_hdr_destroy(hdr); 2511 } 2512} 2513 2514boolean_t 2515arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2516{ 2517 arc_buf_hdr_t *hdr = buf->b_hdr; 2518 kmutex_t *hash_lock = HDR_LOCK(hdr); 2519 boolean_t no_callback = (buf->b_efunc == NULL); 2520 2521 if (hdr->b_l1hdr.b_state == arc_anon) { 2522 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2523 arc_buf_free(buf, tag); 2524 return (no_callback); 2525 } 2526 2527 mutex_enter(hash_lock); 2528 hdr = buf->b_hdr; 2529 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2530 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2531 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2532 ASSERT(buf->b_data != NULL); 2533 2534 (void) remove_reference(hdr, hash_lock, tag); 2535 if (hdr->b_l1hdr.b_datacnt > 1) { 2536 if (no_callback) 2537 arc_buf_destroy(buf, TRUE); 2538 } else if (no_callback) { 2539 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2540 ASSERT(buf->b_efunc == NULL); 2541 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2542 } 2543 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2544 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2545 mutex_exit(hash_lock); 2546 return (no_callback); 2547} 2548 2549int32_t 2550arc_buf_size(arc_buf_t *buf) 2551{ 2552 return (buf->b_hdr->b_size); 2553} 2554 2555/* 2556 * Called from the DMU to determine if the current buffer should be 2557 * evicted. In order to ensure proper locking, the eviction must be initiated 2558 * from the DMU. Return true if the buffer is associated with user data and 2559 * duplicate buffers still exist. 2560 */ 2561boolean_t 2562arc_buf_eviction_needed(arc_buf_t *buf) 2563{ 2564 arc_buf_hdr_t *hdr; 2565 boolean_t evict_needed = B_FALSE; 2566 2567 if (zfs_disable_dup_eviction) 2568 return (B_FALSE); 2569 2570 mutex_enter(&buf->b_evict_lock); 2571 hdr = buf->b_hdr; 2572 if (hdr == NULL) { 2573 /* 2574 * We are in arc_do_user_evicts(); let that function 2575 * perform the eviction. 2576 */ 2577 ASSERT(buf->b_data == NULL); 2578 mutex_exit(&buf->b_evict_lock); 2579 return (B_FALSE); 2580 } else if (buf->b_data == NULL) { 2581 /* 2582 * We have already been added to the arc eviction list; 2583 * recommend eviction. 2584 */ 2585 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2586 mutex_exit(&buf->b_evict_lock); 2587 return (B_TRUE); 2588 } 2589 2590 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2591 evict_needed = B_TRUE; 2592 2593 mutex_exit(&buf->b_evict_lock); 2594 return (evict_needed); 2595} 2596 2597/* 2598 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2599 * state of the header is dependent on it's state prior to entering this 2600 * function. The following transitions are possible: 2601 * 2602 * - arc_mru -> arc_mru_ghost 2603 * - arc_mfu -> arc_mfu_ghost 2604 * - arc_mru_ghost -> arc_l2c_only 2605 * - arc_mru_ghost -> deleted 2606 * - arc_mfu_ghost -> arc_l2c_only 2607 * - arc_mfu_ghost -> deleted 2608 */ 2609static int64_t 2610arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2611{ 2612 arc_state_t *evicted_state, *state; 2613 int64_t bytes_evicted = 0; 2614 2615 ASSERT(MUTEX_HELD(hash_lock)); 2616 ASSERT(HDR_HAS_L1HDR(hdr)); 2617 2618 state = hdr->b_l1hdr.b_state; 2619 if (GHOST_STATE(state)) { 2620 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2621 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2622 2623 /* 2624 * l2arc_write_buffers() relies on a header's L1 portion 2625 * (i.e. it's b_tmp_cdata field) during it's write phase. 2626 * Thus, we cannot push a header onto the arc_l2c_only 2627 * state (removing it's L1 piece) until the header is 2628 * done being written to the l2arc. 2629 */ 2630 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2631 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2632 return (bytes_evicted); 2633 } 2634 2635 ARCSTAT_BUMP(arcstat_deleted); 2636 bytes_evicted += hdr->b_size; 2637 2638 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2639 2640 if (HDR_HAS_L2HDR(hdr)) { 2641 /* 2642 * This buffer is cached on the 2nd Level ARC; 2643 * don't destroy the header. 2644 */ 2645 arc_change_state(arc_l2c_only, hdr, hash_lock); 2646 /* 2647 * dropping from L1+L2 cached to L2-only, 2648 * realloc to remove the L1 header. 2649 */ 2650 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2651 hdr_l2only_cache); 2652 } else { 2653 arc_change_state(arc_anon, hdr, hash_lock); 2654 arc_hdr_destroy(hdr); 2655 } 2656 return (bytes_evicted); 2657 } 2658 2659 ASSERT(state == arc_mru || state == arc_mfu); 2660 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2661 2662 /* prefetch buffers have a minimum lifespan */ 2663 if (HDR_IO_IN_PROGRESS(hdr) || 2664 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2665 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2666 arc_min_prefetch_lifespan)) { 2667 ARCSTAT_BUMP(arcstat_evict_skip); 2668 return (bytes_evicted); 2669 } 2670 2671 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2672 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2673 while (hdr->b_l1hdr.b_buf) { 2674 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2675 if (!mutex_tryenter(&buf->b_evict_lock)) { 2676 ARCSTAT_BUMP(arcstat_mutex_miss); 2677 break; 2678 } 2679 if (buf->b_data != NULL) 2680 bytes_evicted += hdr->b_size; 2681 if (buf->b_efunc != NULL) { 2682 mutex_enter(&arc_user_evicts_lock); 2683 arc_buf_destroy(buf, FALSE); 2684 hdr->b_l1hdr.b_buf = buf->b_next; 2685 buf->b_hdr = &arc_eviction_hdr; 2686 buf->b_next = arc_eviction_list; 2687 arc_eviction_list = buf; 2688 cv_signal(&arc_user_evicts_cv); 2689 mutex_exit(&arc_user_evicts_lock); 2690 mutex_exit(&buf->b_evict_lock); 2691 } else { 2692 mutex_exit(&buf->b_evict_lock); 2693 arc_buf_destroy(buf, TRUE); 2694 } 2695 } 2696 2697 if (HDR_HAS_L2HDR(hdr)) { 2698 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2699 } else { 2700 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2701 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2702 else 2703 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2704 } 2705 2706 if (hdr->b_l1hdr.b_datacnt == 0) { 2707 arc_change_state(evicted_state, hdr, hash_lock); 2708 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2709 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2710 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2711 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2712 } 2713 2714 return (bytes_evicted); 2715} 2716 2717static uint64_t 2718arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2719 uint64_t spa, int64_t bytes) 2720{ 2721 multilist_sublist_t *mls; 2722 uint64_t bytes_evicted = 0; 2723 arc_buf_hdr_t *hdr; 2724 kmutex_t *hash_lock; 2725 int evict_count = 0; 2726 2727 ASSERT3P(marker, !=, NULL); 2728 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2729 2730 mls = multilist_sublist_lock(ml, idx); 2731 2732 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2733 hdr = multilist_sublist_prev(mls, marker)) { 2734 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2735 (evict_count >= zfs_arc_evict_batch_limit)) 2736 break; 2737 2738 /* 2739 * To keep our iteration location, move the marker 2740 * forward. Since we're not holding hdr's hash lock, we 2741 * must be very careful and not remove 'hdr' from the 2742 * sublist. Otherwise, other consumers might mistake the 2743 * 'hdr' as not being on a sublist when they call the 2744 * multilist_link_active() function (they all rely on 2745 * the hash lock protecting concurrent insertions and 2746 * removals). multilist_sublist_move_forward() was 2747 * specifically implemented to ensure this is the case 2748 * (only 'marker' will be removed and re-inserted). 2749 */ 2750 multilist_sublist_move_forward(mls, marker); 2751 2752 /* 2753 * The only case where the b_spa field should ever be 2754 * zero, is the marker headers inserted by 2755 * arc_evict_state(). It's possible for multiple threads 2756 * to be calling arc_evict_state() concurrently (e.g. 2757 * dsl_pool_close() and zio_inject_fault()), so we must 2758 * skip any markers we see from these other threads. 2759 */ 2760 if (hdr->b_spa == 0) 2761 continue; 2762 2763 /* we're only interested in evicting buffers of a certain spa */ 2764 if (spa != 0 && hdr->b_spa != spa) { 2765 ARCSTAT_BUMP(arcstat_evict_skip); 2766 continue; 2767 } 2768 2769 hash_lock = HDR_LOCK(hdr); 2770 2771 /* 2772 * We aren't calling this function from any code path 2773 * that would already be holding a hash lock, so we're 2774 * asserting on this assumption to be defensive in case 2775 * this ever changes. Without this check, it would be 2776 * possible to incorrectly increment arcstat_mutex_miss 2777 * below (e.g. if the code changed such that we called 2778 * this function with a hash lock held). 2779 */ 2780 ASSERT(!MUTEX_HELD(hash_lock)); 2781 2782 if (mutex_tryenter(hash_lock)) { 2783 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2784 mutex_exit(hash_lock); 2785 2786 bytes_evicted += evicted; 2787 2788 /* 2789 * If evicted is zero, arc_evict_hdr() must have 2790 * decided to skip this header, don't increment 2791 * evict_count in this case. 2792 */ 2793 if (evicted != 0) 2794 evict_count++; 2795 2796 /* 2797 * If arc_size isn't overflowing, signal any 2798 * threads that might happen to be waiting. 2799 * 2800 * For each header evicted, we wake up a single 2801 * thread. If we used cv_broadcast, we could 2802 * wake up "too many" threads causing arc_size 2803 * to significantly overflow arc_c; since 2804 * arc_get_data_buf() doesn't check for overflow 2805 * when it's woken up (it doesn't because it's 2806 * possible for the ARC to be overflowing while 2807 * full of un-evictable buffers, and the 2808 * function should proceed in this case). 2809 * 2810 * If threads are left sleeping, due to not 2811 * using cv_broadcast, they will be woken up 2812 * just before arc_reclaim_thread() sleeps. 2813 */ 2814 mutex_enter(&arc_reclaim_lock); 2815 if (!arc_is_overflowing()) 2816 cv_signal(&arc_reclaim_waiters_cv); 2817 mutex_exit(&arc_reclaim_lock); 2818 } else { 2819 ARCSTAT_BUMP(arcstat_mutex_miss); 2820 } 2821 } 2822 2823 multilist_sublist_unlock(mls); 2824 2825 return (bytes_evicted); 2826} 2827 2828/* 2829 * Evict buffers from the given arc state, until we've removed the 2830 * specified number of bytes. Move the removed buffers to the 2831 * appropriate evict state. 2832 * 2833 * This function makes a "best effort". It skips over any buffers 2834 * it can't get a hash_lock on, and so, may not catch all candidates. 2835 * It may also return without evicting as much space as requested. 2836 * 2837 * If bytes is specified using the special value ARC_EVICT_ALL, this 2838 * will evict all available (i.e. unlocked and evictable) buffers from 2839 * the given arc state; which is used by arc_flush(). 2840 */ 2841static uint64_t 2842arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2843 arc_buf_contents_t type) 2844{ 2845 uint64_t total_evicted = 0; 2846 multilist_t *ml = &state->arcs_list[type]; 2847 int num_sublists; 2848 arc_buf_hdr_t **markers; 2849 2850 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2851 2852 num_sublists = multilist_get_num_sublists(ml); 2853 2854 /* 2855 * If we've tried to evict from each sublist, made some 2856 * progress, but still have not hit the target number of bytes 2857 * to evict, we want to keep trying. The markers allow us to 2858 * pick up where we left off for each individual sublist, rather 2859 * than starting from the tail each time. 2860 */ 2861 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2862 for (int i = 0; i < num_sublists; i++) { 2863 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2864 2865 /* 2866 * A b_spa of 0 is used to indicate that this header is 2867 * a marker. This fact is used in arc_adjust_type() and 2868 * arc_evict_state_impl(). 2869 */ 2870 markers[i]->b_spa = 0; 2871 2872 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2873 multilist_sublist_insert_tail(mls, markers[i]); 2874 multilist_sublist_unlock(mls); 2875 } 2876 2877 /* 2878 * While we haven't hit our target number of bytes to evict, or 2879 * we're evicting all available buffers. 2880 */ 2881 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2882 /* 2883 * Start eviction using a randomly selected sublist, 2884 * this is to try and evenly balance eviction across all 2885 * sublists. Always starting at the same sublist 2886 * (e.g. index 0) would cause evictions to favor certain 2887 * sublists over others. 2888 */ 2889 int sublist_idx = multilist_get_random_index(ml); 2890 uint64_t scan_evicted = 0; 2891 2892 for (int i = 0; i < num_sublists; i++) { 2893 uint64_t bytes_remaining; 2894 uint64_t bytes_evicted; 2895 2896 if (bytes == ARC_EVICT_ALL) 2897 bytes_remaining = ARC_EVICT_ALL; 2898 else if (total_evicted < bytes) 2899 bytes_remaining = bytes - total_evicted; 2900 else 2901 break; 2902 2903 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 2904 markers[sublist_idx], spa, bytes_remaining); 2905 2906 scan_evicted += bytes_evicted; 2907 total_evicted += bytes_evicted; 2908 2909 /* we've reached the end, wrap to the beginning */ 2910 if (++sublist_idx >= num_sublists) 2911 sublist_idx = 0; 2912 } 2913 2914 /* 2915 * If we didn't evict anything during this scan, we have 2916 * no reason to believe we'll evict more during another 2917 * scan, so break the loop. 2918 */ 2919 if (scan_evicted == 0) { 2920 /* This isn't possible, let's make that obvious */ 2921 ASSERT3S(bytes, !=, 0); 2922 2923 /* 2924 * When bytes is ARC_EVICT_ALL, the only way to 2925 * break the loop is when scan_evicted is zero. 2926 * In that case, we actually have evicted enough, 2927 * so we don't want to increment the kstat. 2928 */ 2929 if (bytes != ARC_EVICT_ALL) { 2930 ASSERT3S(total_evicted, <, bytes); 2931 ARCSTAT_BUMP(arcstat_evict_not_enough); 2932 } 2933 2934 break; 2935 } 2936 } 2937 2938 for (int i = 0; i < num_sublists; i++) { 2939 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2940 multilist_sublist_remove(mls, markers[i]); 2941 multilist_sublist_unlock(mls); 2942 2943 kmem_cache_free(hdr_full_cache, markers[i]); 2944 } 2945 kmem_free(markers, sizeof (*markers) * num_sublists); 2946 2947 return (total_evicted); 2948} 2949 2950/* 2951 * Flush all "evictable" data of the given type from the arc state 2952 * specified. This will not evict any "active" buffers (i.e. referenced). 2953 * 2954 * When 'retry' is set to FALSE, the function will make a single pass 2955 * over the state and evict any buffers that it can. Since it doesn't 2956 * continually retry the eviction, it might end up leaving some buffers 2957 * in the ARC due to lock misses. 2958 * 2959 * When 'retry' is set to TRUE, the function will continually retry the 2960 * eviction until *all* evictable buffers have been removed from the 2961 * state. As a result, if concurrent insertions into the state are 2962 * allowed (e.g. if the ARC isn't shutting down), this function might 2963 * wind up in an infinite loop, continually trying to evict buffers. 2964 */ 2965static uint64_t 2966arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 2967 boolean_t retry) 2968{ 2969 uint64_t evicted = 0; 2970 2971 while (state->arcs_lsize[type] != 0) { 2972 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 2973 2974 if (!retry) 2975 break; 2976 } 2977 2978 return (evicted); 2979} 2980 2981/* 2982 * Evict the specified number of bytes from the state specified, 2983 * restricting eviction to the spa and type given. This function 2984 * prevents us from trying to evict more from a state's list than 2985 * is "evictable", and to skip evicting altogether when passed a 2986 * negative value for "bytes". In contrast, arc_evict_state() will 2987 * evict everything it can, when passed a negative value for "bytes". 2988 */ 2989static uint64_t 2990arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 2991 arc_buf_contents_t type) 2992{ 2993 int64_t delta; 2994 2995 if (bytes > 0 && state->arcs_lsize[type] > 0) { 2996 delta = MIN(state->arcs_lsize[type], bytes); 2997 return (arc_evict_state(state, spa, delta, type)); 2998 } 2999 3000 return (0); 3001} 3002 3003/* 3004 * Evict metadata buffers from the cache, such that arc_meta_used is 3005 * capped by the arc_meta_limit tunable. 3006 */ 3007static uint64_t 3008arc_adjust_meta(void) 3009{ 3010 uint64_t total_evicted = 0; 3011 int64_t target; 3012 3013 /* 3014 * If we're over the meta limit, we want to evict enough 3015 * metadata to get back under the meta limit. We don't want to 3016 * evict so much that we drop the MRU below arc_p, though. If 3017 * we're over the meta limit more than we're over arc_p, we 3018 * evict some from the MRU here, and some from the MFU below. 3019 */ 3020 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3021 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3022 refcount_count(&arc_mru->arcs_size) - arc_p)); 3023 3024 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3025 3026 /* 3027 * Similar to the above, we want to evict enough bytes to get us 3028 * below the meta limit, but not so much as to drop us below the 3029 * space alloted to the MFU (which is defined as arc_c - arc_p). 3030 */ 3031 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3032 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3033 3034 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3035 3036 return (total_evicted); 3037} 3038 3039/* 3040 * Return the type of the oldest buffer in the given arc state 3041 * 3042 * This function will select a random sublist of type ARC_BUFC_DATA and 3043 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3044 * is compared, and the type which contains the "older" buffer will be 3045 * returned. 3046 */ 3047static arc_buf_contents_t 3048arc_adjust_type(arc_state_t *state) 3049{ 3050 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3051 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3052 int data_idx = multilist_get_random_index(data_ml); 3053 int meta_idx = multilist_get_random_index(meta_ml); 3054 multilist_sublist_t *data_mls; 3055 multilist_sublist_t *meta_mls; 3056 arc_buf_contents_t type; 3057 arc_buf_hdr_t *data_hdr; 3058 arc_buf_hdr_t *meta_hdr; 3059 3060 /* 3061 * We keep the sublist lock until we're finished, to prevent 3062 * the headers from being destroyed via arc_evict_state(). 3063 */ 3064 data_mls = multilist_sublist_lock(data_ml, data_idx); 3065 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3066 3067 /* 3068 * These two loops are to ensure we skip any markers that 3069 * might be at the tail of the lists due to arc_evict_state(). 3070 */ 3071 3072 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3073 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3074 if (data_hdr->b_spa != 0) 3075 break; 3076 } 3077 3078 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3079 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3080 if (meta_hdr->b_spa != 0) 3081 break; 3082 } 3083 3084 if (data_hdr == NULL && meta_hdr == NULL) { 3085 type = ARC_BUFC_DATA; 3086 } else if (data_hdr == NULL) { 3087 ASSERT3P(meta_hdr, !=, NULL); 3088 type = ARC_BUFC_METADATA; 3089 } else if (meta_hdr == NULL) { 3090 ASSERT3P(data_hdr, !=, NULL); 3091 type = ARC_BUFC_DATA; 3092 } else { 3093 ASSERT3P(data_hdr, !=, NULL); 3094 ASSERT3P(meta_hdr, !=, NULL); 3095 3096 /* The headers can't be on the sublist without an L1 header */ 3097 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3098 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3099 3100 if (data_hdr->b_l1hdr.b_arc_access < 3101 meta_hdr->b_l1hdr.b_arc_access) { 3102 type = ARC_BUFC_DATA; 3103 } else { 3104 type = ARC_BUFC_METADATA; 3105 } 3106 } 3107 3108 multilist_sublist_unlock(meta_mls); 3109 multilist_sublist_unlock(data_mls); 3110 3111 return (type); 3112} 3113 3114/* 3115 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3116 */ 3117static uint64_t 3118arc_adjust(void) 3119{ 3120 uint64_t total_evicted = 0; 3121 uint64_t bytes; 3122 int64_t target; 3123 3124 /* 3125 * If we're over arc_meta_limit, we want to correct that before 3126 * potentially evicting data buffers below. 3127 */ 3128 total_evicted += arc_adjust_meta(); 3129 3130 /* 3131 * Adjust MRU size 3132 * 3133 * If we're over the target cache size, we want to evict enough 3134 * from the list to get back to our target size. We don't want 3135 * to evict too much from the MRU, such that it drops below 3136 * arc_p. So, if we're over our target cache size more than 3137 * the MRU is over arc_p, we'll evict enough to get back to 3138 * arc_p here, and then evict more from the MFU below. 3139 */ 3140 target = MIN((int64_t)(arc_size - arc_c), 3141 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3142 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3143 3144 /* 3145 * If we're below arc_meta_min, always prefer to evict data. 3146 * Otherwise, try to satisfy the requested number of bytes to 3147 * evict from the type which contains older buffers; in an 3148 * effort to keep newer buffers in the cache regardless of their 3149 * type. If we cannot satisfy the number of bytes from this 3150 * type, spill over into the next type. 3151 */ 3152 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3153 arc_meta_used > arc_meta_min) { 3154 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3155 total_evicted += bytes; 3156 3157 /* 3158 * If we couldn't evict our target number of bytes from 3159 * metadata, we try to get the rest from data. 3160 */ 3161 target -= bytes; 3162 3163 total_evicted += 3164 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3165 } else { 3166 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3167 total_evicted += bytes; 3168 3169 /* 3170 * If we couldn't evict our target number of bytes from 3171 * data, we try to get the rest from metadata. 3172 */ 3173 target -= bytes; 3174 3175 total_evicted += 3176 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3177 } 3178 3179 /* 3180 * Adjust MFU size 3181 * 3182 * Now that we've tried to evict enough from the MRU to get its 3183 * size back to arc_p, if we're still above the target cache 3184 * size, we evict the rest from the MFU. 3185 */ 3186 target = arc_size - arc_c; 3187 3188 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3189 arc_meta_used > arc_meta_min) { 3190 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3191 total_evicted += bytes; 3192 3193 /* 3194 * If we couldn't evict our target number of bytes from 3195 * metadata, we try to get the rest from data. 3196 */ 3197 target -= bytes; 3198 3199 total_evicted += 3200 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3201 } else { 3202 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3203 total_evicted += bytes; 3204 3205 /* 3206 * If we couldn't evict our target number of bytes from 3207 * data, we try to get the rest from data. 3208 */ 3209 target -= bytes; 3210 3211 total_evicted += 3212 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3213 } 3214 3215 /* 3216 * Adjust ghost lists 3217 * 3218 * In addition to the above, the ARC also defines target values 3219 * for the ghost lists. The sum of the mru list and mru ghost 3220 * list should never exceed the target size of the cache, and 3221 * the sum of the mru list, mfu list, mru ghost list, and mfu 3222 * ghost list should never exceed twice the target size of the 3223 * cache. The following logic enforces these limits on the ghost 3224 * caches, and evicts from them as needed. 3225 */ 3226 target = refcount_count(&arc_mru->arcs_size) + 3227 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3228 3229 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3230 total_evicted += bytes; 3231 3232 target -= bytes; 3233 3234 total_evicted += 3235 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3236 3237 /* 3238 * We assume the sum of the mru list and mfu list is less than 3239 * or equal to arc_c (we enforced this above), which means we 3240 * can use the simpler of the two equations below: 3241 * 3242 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3243 * mru ghost + mfu ghost <= arc_c 3244 */ 3245 target = refcount_count(&arc_mru_ghost->arcs_size) + 3246 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3247 3248 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3249 total_evicted += bytes; 3250 3251 target -= bytes; 3252 3253 total_evicted += 3254 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3255 3256 return (total_evicted); 3257} 3258 3259static void 3260arc_do_user_evicts(void) 3261{ 3262 mutex_enter(&arc_user_evicts_lock); 3263 while (arc_eviction_list != NULL) { 3264 arc_buf_t *buf = arc_eviction_list; 3265 arc_eviction_list = buf->b_next; 3266 mutex_enter(&buf->b_evict_lock); 3267 buf->b_hdr = NULL; 3268 mutex_exit(&buf->b_evict_lock); 3269 mutex_exit(&arc_user_evicts_lock); 3270 3271 if (buf->b_efunc != NULL) 3272 VERIFY0(buf->b_efunc(buf->b_private)); 3273 3274 buf->b_efunc = NULL; 3275 buf->b_private = NULL; 3276 kmem_cache_free(buf_cache, buf); 3277 mutex_enter(&arc_user_evicts_lock); 3278 } 3279 mutex_exit(&arc_user_evicts_lock); 3280} 3281 3282void 3283arc_flush(spa_t *spa, boolean_t retry) 3284{ 3285 uint64_t guid = 0; 3286 3287 /* 3288 * If retry is TRUE, a spa must not be specified since we have 3289 * no good way to determine if all of a spa's buffers have been 3290 * evicted from an arc state. 3291 */ 3292 ASSERT(!retry || spa == 0); 3293 3294 if (spa != NULL) 3295 guid = spa_load_guid(spa); 3296 3297 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3298 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3299 3300 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3301 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3302 3303 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3304 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3305 3306 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3307 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3308 3309 arc_do_user_evicts(); 3310 ASSERT(spa || arc_eviction_list == NULL); 3311} 3312 3313void 3314arc_shrink(int64_t to_free) 3315{ 3316 if (arc_c > arc_c_min) { 3317 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3318 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3319 if (arc_c > arc_c_min + to_free) 3320 atomic_add_64(&arc_c, -to_free); 3321 else 3322 arc_c = arc_c_min; 3323 3324 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3325 if (arc_c > arc_size) 3326 arc_c = MAX(arc_size, arc_c_min); 3327 if (arc_p > arc_c) 3328 arc_p = (arc_c >> 1); 3329 3330 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3331 arc_p); 3332 3333 ASSERT(arc_c >= arc_c_min); 3334 ASSERT((int64_t)arc_p >= 0); 3335 } 3336 3337 if (arc_size > arc_c) { 3338 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3339 uint64_t, arc_c); 3340 (void) arc_adjust(); 3341 } 3342} 3343 3344static long needfree = 0; 3345 3346typedef enum free_memory_reason_t { 3347 FMR_UNKNOWN, 3348 FMR_NEEDFREE, 3349 FMR_LOTSFREE, 3350 FMR_SWAPFS_MINFREE, 3351 FMR_PAGES_PP_MAXIMUM, 3352 FMR_HEAP_ARENA, 3353 FMR_ZIO_ARENA, 3354 FMR_ZIO_FRAG, 3355} free_memory_reason_t; 3356 3357int64_t last_free_memory; 3358free_memory_reason_t last_free_reason; 3359 3360/* 3361 * Additional reserve of pages for pp_reserve. 3362 */ 3363int64_t arc_pages_pp_reserve = 64; 3364 3365/* 3366 * Additional reserve of pages for swapfs. 3367 */ 3368int64_t arc_swapfs_reserve = 64; 3369 3370/* 3371 * Return the amount of memory that can be consumed before reclaim will be 3372 * needed. Positive if there is sufficient free memory, negative indicates 3373 * the amount of memory that needs to be freed up. 3374 */ 3375static int64_t 3376arc_available_memory(void) 3377{ 3378 int64_t lowest = INT64_MAX; 3379 int64_t n; 3380 free_memory_reason_t r = FMR_UNKNOWN; 3381 3382#ifdef _KERNEL 3383 if (needfree > 0) { 3384 n = PAGESIZE * (-needfree); 3385 if (n < lowest) { 3386 lowest = n; 3387 r = FMR_NEEDFREE; 3388 } 3389 } 3390 3391 /* 3392 * Cooperate with pagedaemon when it's time for it to scan 3393 * and reclaim some pages. 3394 */ 3395 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3396 if (n < lowest) { 3397 lowest = n; 3398 r = FMR_LOTSFREE; 3399 } 3400 3401#ifdef sun 3402 /* 3403 * check that we're out of range of the pageout scanner. It starts to 3404 * schedule paging if freemem is less than lotsfree and needfree. 3405 * lotsfree is the high-water mark for pageout, and needfree is the 3406 * number of needed free pages. We add extra pages here to make sure 3407 * the scanner doesn't start up while we're freeing memory. 3408 */ 3409 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3410 if (n < lowest) { 3411 lowest = n; 3412 r = FMR_LOTSFREE; 3413 } 3414 3415 /* 3416 * check to make sure that swapfs has enough space so that anon 3417 * reservations can still succeed. anon_resvmem() checks that the 3418 * availrmem is greater than swapfs_minfree, and the number of reserved 3419 * swap pages. We also add a bit of extra here just to prevent 3420 * circumstances from getting really dire. 3421 */ 3422 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3423 desfree - arc_swapfs_reserve); 3424 if (n < lowest) { 3425 lowest = n; 3426 r = FMR_SWAPFS_MINFREE; 3427 } 3428 3429 3430 /* 3431 * Check that we have enough availrmem that memory locking (e.g., via 3432 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3433 * stores the number of pages that cannot be locked; when availrmem 3434 * drops below pages_pp_maximum, page locking mechanisms such as 3435 * page_pp_lock() will fail.) 3436 */ 3437 n = PAGESIZE * (availrmem - pages_pp_maximum - 3438 arc_pages_pp_reserve); 3439 if (n < lowest) { 3440 lowest = n; 3441 r = FMR_PAGES_PP_MAXIMUM; 3442 } 3443 3444#endif /* sun */ 3445#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3446 /* 3447 * If we're on an i386 platform, it's possible that we'll exhaust the 3448 * kernel heap space before we ever run out of available physical 3449 * memory. Most checks of the size of the heap_area compare against 3450 * tune.t_minarmem, which is the minimum available real memory that we 3451 * can have in the system. However, this is generally fixed at 25 pages 3452 * which is so low that it's useless. In this comparison, we seek to 3453 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3454 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3455 * free) 3456 */ 3457 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3458 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3459 if (n < lowest) { 3460 lowest = n; 3461 r = FMR_HEAP_ARENA; 3462 } 3463#define zio_arena NULL 3464#else 3465#define zio_arena heap_arena 3466#endif 3467 3468 /* 3469 * If zio data pages are being allocated out of a separate heap segment, 3470 * then enforce that the size of available vmem for this arena remains 3471 * above about 1/16th free. 3472 * 3473 * Note: The 1/16th arena free requirement was put in place 3474 * to aggressively evict memory from the arc in order to avoid 3475 * memory fragmentation issues. 3476 */ 3477 if (zio_arena != NULL) { 3478 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3479 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3480 if (n < lowest) { 3481 lowest = n; 3482 r = FMR_ZIO_ARENA; 3483 } 3484 } 3485 3486 /* 3487 * Above limits know nothing about real level of KVA fragmentation. 3488 * Start aggressive reclamation if too little sequential KVA left. 3489 */ 3490 if (lowest > 0) { 3491 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3492 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3493 INT64_MAX; 3494 if (n < lowest) { 3495 lowest = n; 3496 r = FMR_ZIO_FRAG; 3497 } 3498 } 3499 3500#else /* _KERNEL */ 3501 /* Every 100 calls, free a small amount */ 3502 if (spa_get_random(100) == 0) 3503 lowest = -1024; 3504#endif /* _KERNEL */ 3505 3506 last_free_memory = lowest; 3507 last_free_reason = r; 3508 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3509 return (lowest); 3510} 3511 3512 3513/* 3514 * Determine if the system is under memory pressure and is asking 3515 * to reclaim memory. A return value of TRUE indicates that the system 3516 * is under memory pressure and that the arc should adjust accordingly. 3517 */ 3518static boolean_t 3519arc_reclaim_needed(void) 3520{ 3521 return (arc_available_memory() < 0); 3522} 3523 3524extern kmem_cache_t *zio_buf_cache[]; 3525extern kmem_cache_t *zio_data_buf_cache[]; 3526extern kmem_cache_t *range_seg_cache; 3527 3528static __noinline void 3529arc_kmem_reap_now(void) 3530{ 3531 size_t i; 3532 kmem_cache_t *prev_cache = NULL; 3533 kmem_cache_t *prev_data_cache = NULL; 3534 3535 DTRACE_PROBE(arc__kmem_reap_start); 3536#ifdef _KERNEL 3537 if (arc_meta_used >= arc_meta_limit) { 3538 /* 3539 * We are exceeding our meta-data cache limit. 3540 * Purge some DNLC entries to release holds on meta-data. 3541 */ 3542 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3543 } 3544#if defined(__i386) 3545 /* 3546 * Reclaim unused memory from all kmem caches. 3547 */ 3548 kmem_reap(); 3549#endif 3550#endif 3551 3552 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3553 if (zio_buf_cache[i] != prev_cache) { 3554 prev_cache = zio_buf_cache[i]; 3555 kmem_cache_reap_now(zio_buf_cache[i]); 3556 } 3557 if (zio_data_buf_cache[i] != prev_data_cache) { 3558 prev_data_cache = zio_data_buf_cache[i]; 3559 kmem_cache_reap_now(zio_data_buf_cache[i]); 3560 } 3561 } 3562 kmem_cache_reap_now(buf_cache); 3563 kmem_cache_reap_now(hdr_full_cache); 3564 kmem_cache_reap_now(hdr_l2only_cache); 3565 kmem_cache_reap_now(range_seg_cache); 3566 3567#ifdef sun 3568 if (zio_arena != NULL) { 3569 /* 3570 * Ask the vmem arena to reclaim unused memory from its 3571 * quantum caches. 3572 */ 3573 vmem_qcache_reap(zio_arena); 3574 } 3575#endif 3576 DTRACE_PROBE(arc__kmem_reap_end); 3577} 3578 3579/* 3580 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3581 * enough data and signal them to proceed. When this happens, the threads in 3582 * arc_get_data_buf() are sleeping while holding the hash lock for their 3583 * particular arc header. Thus, we must be careful to never sleep on a 3584 * hash lock in this thread. This is to prevent the following deadlock: 3585 * 3586 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3587 * waiting for the reclaim thread to signal it. 3588 * 3589 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3590 * fails, and goes to sleep forever. 3591 * 3592 * This possible deadlock is avoided by always acquiring a hash lock 3593 * using mutex_tryenter() from arc_reclaim_thread(). 3594 */ 3595static void 3596arc_reclaim_thread(void *dummy __unused) 3597{ 3598 clock_t growtime = 0; 3599 callb_cpr_t cpr; 3600 3601 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3602 3603 mutex_enter(&arc_reclaim_lock); 3604 while (!arc_reclaim_thread_exit) { 3605 int64_t free_memory = arc_available_memory(); 3606 uint64_t evicted = 0; 3607 3608 mutex_exit(&arc_reclaim_lock); 3609 3610 if (free_memory < 0) { 3611 3612 arc_no_grow = B_TRUE; 3613 arc_warm = B_TRUE; 3614 3615 /* 3616 * Wait at least zfs_grow_retry (default 60) seconds 3617 * before considering growing. 3618 */ 3619 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3620 3621 arc_kmem_reap_now(); 3622 3623 /* 3624 * If we are still low on memory, shrink the ARC 3625 * so that we have arc_shrink_min free space. 3626 */ 3627 free_memory = arc_available_memory(); 3628 3629 int64_t to_free = 3630 (arc_c >> arc_shrink_shift) - free_memory; 3631 if (to_free > 0) { 3632#ifdef _KERNEL 3633 to_free = MAX(to_free, ptob(needfree)); 3634#endif 3635 arc_shrink(to_free); 3636 } 3637 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3638 arc_no_grow = B_TRUE; 3639 } else if (ddi_get_lbolt() >= growtime) { 3640 arc_no_grow = B_FALSE; 3641 } 3642 3643 evicted = arc_adjust(); 3644 3645 mutex_enter(&arc_reclaim_lock); 3646 3647 /* 3648 * If evicted is zero, we couldn't evict anything via 3649 * arc_adjust(). This could be due to hash lock 3650 * collisions, but more likely due to the majority of 3651 * arc buffers being unevictable. Therefore, even if 3652 * arc_size is above arc_c, another pass is unlikely to 3653 * be helpful and could potentially cause us to enter an 3654 * infinite loop. 3655 */ 3656 if (arc_size <= arc_c || evicted == 0) { 3657#ifdef _KERNEL 3658 needfree = 0; 3659#endif 3660 /* 3661 * We're either no longer overflowing, or we 3662 * can't evict anything more, so we should wake 3663 * up any threads before we go to sleep. 3664 */ 3665 cv_broadcast(&arc_reclaim_waiters_cv); 3666 3667 /* 3668 * Block until signaled, or after one second (we 3669 * might need to perform arc_kmem_reap_now() 3670 * even if we aren't being signalled) 3671 */ 3672 CALLB_CPR_SAFE_BEGIN(&cpr); 3673 (void) cv_timedwait(&arc_reclaim_thread_cv, 3674 &arc_reclaim_lock, hz); 3675 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3676 } 3677 } 3678 3679 arc_reclaim_thread_exit = FALSE; 3680 cv_broadcast(&arc_reclaim_thread_cv); 3681 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3682 thread_exit(); 3683} 3684 3685static void 3686arc_user_evicts_thread(void *dummy __unused) 3687{ 3688 callb_cpr_t cpr; 3689 3690 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3691 3692 mutex_enter(&arc_user_evicts_lock); 3693 while (!arc_user_evicts_thread_exit) { 3694 mutex_exit(&arc_user_evicts_lock); 3695 3696 arc_do_user_evicts(); 3697 3698 /* 3699 * This is necessary in order for the mdb ::arc dcmd to 3700 * show up to date information. Since the ::arc command 3701 * does not call the kstat's update function, without 3702 * this call, the command may show stale stats for the 3703 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3704 * with this change, the data might be up to 1 second 3705 * out of date; but that should suffice. The arc_state_t 3706 * structures can be queried directly if more accurate 3707 * information is needed. 3708 */ 3709 if (arc_ksp != NULL) 3710 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3711 3712 mutex_enter(&arc_user_evicts_lock); 3713 3714 /* 3715 * Block until signaled, or after one second (we need to 3716 * call the arc's kstat update function regularly). 3717 */ 3718 CALLB_CPR_SAFE_BEGIN(&cpr); 3719 (void) cv_timedwait(&arc_user_evicts_cv, 3720 &arc_user_evicts_lock, hz); 3721 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3722 } 3723 3724 arc_user_evicts_thread_exit = FALSE; 3725 cv_broadcast(&arc_user_evicts_cv); 3726 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3727 thread_exit(); 3728} 3729 3730/* 3731 * Adapt arc info given the number of bytes we are trying to add and 3732 * the state that we are comming from. This function is only called 3733 * when we are adding new content to the cache. 3734 */ 3735static void 3736arc_adapt(int bytes, arc_state_t *state) 3737{ 3738 int mult; 3739 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3740 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3741 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3742 3743 if (state == arc_l2c_only) 3744 return; 3745 3746 ASSERT(bytes > 0); 3747 /* 3748 * Adapt the target size of the MRU list: 3749 * - if we just hit in the MRU ghost list, then increase 3750 * the target size of the MRU list. 3751 * - if we just hit in the MFU ghost list, then increase 3752 * the target size of the MFU list by decreasing the 3753 * target size of the MRU list. 3754 */ 3755 if (state == arc_mru_ghost) { 3756 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3757 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3758 3759 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3760 } else if (state == arc_mfu_ghost) { 3761 uint64_t delta; 3762 3763 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3764 mult = MIN(mult, 10); 3765 3766 delta = MIN(bytes * mult, arc_p); 3767 arc_p = MAX(arc_p_min, arc_p - delta); 3768 } 3769 ASSERT((int64_t)arc_p >= 0); 3770 3771 if (arc_reclaim_needed()) { 3772 cv_signal(&arc_reclaim_thread_cv); 3773 return; 3774 } 3775 3776 if (arc_no_grow) 3777 return; 3778 3779 if (arc_c >= arc_c_max) 3780 return; 3781 3782 /* 3783 * If we're within (2 * maxblocksize) bytes of the target 3784 * cache size, increment the target cache size 3785 */ 3786 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3787 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3788 atomic_add_64(&arc_c, (int64_t)bytes); 3789 if (arc_c > arc_c_max) 3790 arc_c = arc_c_max; 3791 else if (state == arc_anon) 3792 atomic_add_64(&arc_p, (int64_t)bytes); 3793 if (arc_p > arc_c) 3794 arc_p = arc_c; 3795 } 3796 ASSERT((int64_t)arc_p >= 0); 3797} 3798 3799/* 3800 * Check if arc_size has grown past our upper threshold, determined by 3801 * zfs_arc_overflow_shift. 3802 */ 3803static boolean_t 3804arc_is_overflowing(void) 3805{ 3806 /* Always allow at least one block of overflow */ 3807 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3808 arc_c >> zfs_arc_overflow_shift); 3809 3810 return (arc_size >= arc_c + overflow); 3811} 3812 3813/* 3814 * The buffer, supplied as the first argument, needs a data block. If we 3815 * are hitting the hard limit for the cache size, we must sleep, waiting 3816 * for the eviction thread to catch up. If we're past the target size 3817 * but below the hard limit, we'll only signal the reclaim thread and 3818 * continue on. 3819 */ 3820static void 3821arc_get_data_buf(arc_buf_t *buf) 3822{ 3823 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3824 uint64_t size = buf->b_hdr->b_size; 3825 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3826 3827 arc_adapt(size, state); 3828 3829 /* 3830 * If arc_size is currently overflowing, and has grown past our 3831 * upper limit, we must be adding data faster than the evict 3832 * thread can evict. Thus, to ensure we don't compound the 3833 * problem by adding more data and forcing arc_size to grow even 3834 * further past it's target size, we halt and wait for the 3835 * eviction thread to catch up. 3836 * 3837 * It's also possible that the reclaim thread is unable to evict 3838 * enough buffers to get arc_size below the overflow limit (e.g. 3839 * due to buffers being un-evictable, or hash lock collisions). 3840 * In this case, we want to proceed regardless if we're 3841 * overflowing; thus we don't use a while loop here. 3842 */ 3843 if (arc_is_overflowing()) { 3844 mutex_enter(&arc_reclaim_lock); 3845 3846 /* 3847 * Now that we've acquired the lock, we may no longer be 3848 * over the overflow limit, lets check. 3849 * 3850 * We're ignoring the case of spurious wake ups. If that 3851 * were to happen, it'd let this thread consume an ARC 3852 * buffer before it should have (i.e. before we're under 3853 * the overflow limit and were signalled by the reclaim 3854 * thread). As long as that is a rare occurrence, it 3855 * shouldn't cause any harm. 3856 */ 3857 if (arc_is_overflowing()) { 3858 cv_signal(&arc_reclaim_thread_cv); 3859 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3860 } 3861 3862 mutex_exit(&arc_reclaim_lock); 3863 } 3864 3865 if (type == ARC_BUFC_METADATA) { 3866 buf->b_data = zio_buf_alloc(size); 3867 arc_space_consume(size, ARC_SPACE_META); 3868 } else { 3869 ASSERT(type == ARC_BUFC_DATA); 3870 buf->b_data = zio_data_buf_alloc(size); 3871 arc_space_consume(size, ARC_SPACE_DATA); 3872 } 3873 3874 /* 3875 * Update the state size. Note that ghost states have a 3876 * "ghost size" and so don't need to be updated. 3877 */ 3878 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3879 arc_buf_hdr_t *hdr = buf->b_hdr; 3880 arc_state_t *state = hdr->b_l1hdr.b_state; 3881 3882 (void) refcount_add_many(&state->arcs_size, size, buf); 3883 3884 /* 3885 * If this is reached via arc_read, the link is 3886 * protected by the hash lock. If reached via 3887 * arc_buf_alloc, the header should not be accessed by 3888 * any other thread. And, if reached via arc_read_done, 3889 * the hash lock will protect it if it's found in the 3890 * hash table; otherwise no other thread should be 3891 * trying to [add|remove]_reference it. 3892 */ 3893 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3894 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3895 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3896 size); 3897 } 3898 /* 3899 * If we are growing the cache, and we are adding anonymous 3900 * data, and we have outgrown arc_p, update arc_p 3901 */ 3902 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3903 (refcount_count(&arc_anon->arcs_size) + 3904 refcount_count(&arc_mru->arcs_size) > arc_p)) 3905 arc_p = MIN(arc_c, arc_p + size); 3906 } 3907 ARCSTAT_BUMP(arcstat_allocated); 3908} 3909 3910/* 3911 * This routine is called whenever a buffer is accessed. 3912 * NOTE: the hash lock is dropped in this function. 3913 */ 3914static void 3915arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3916{ 3917 clock_t now; 3918 3919 ASSERT(MUTEX_HELD(hash_lock)); 3920 ASSERT(HDR_HAS_L1HDR(hdr)); 3921 3922 if (hdr->b_l1hdr.b_state == arc_anon) { 3923 /* 3924 * This buffer is not in the cache, and does not 3925 * appear in our "ghost" list. Add the new buffer 3926 * to the MRU state. 3927 */ 3928 3929 ASSERT0(hdr->b_l1hdr.b_arc_access); 3930 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3931 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3932 arc_change_state(arc_mru, hdr, hash_lock); 3933 3934 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3935 now = ddi_get_lbolt(); 3936 3937 /* 3938 * If this buffer is here because of a prefetch, then either: 3939 * - clear the flag if this is a "referencing" read 3940 * (any subsequent access will bump this into the MFU state). 3941 * or 3942 * - move the buffer to the head of the list if this is 3943 * another prefetch (to make it less likely to be evicted). 3944 */ 3945 if (HDR_PREFETCH(hdr)) { 3946 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3947 /* link protected by hash lock */ 3948 ASSERT(multilist_link_active( 3949 &hdr->b_l1hdr.b_arc_node)); 3950 } else { 3951 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3952 ARCSTAT_BUMP(arcstat_mru_hits); 3953 } 3954 hdr->b_l1hdr.b_arc_access = now; 3955 return; 3956 } 3957 3958 /* 3959 * This buffer has been "accessed" only once so far, 3960 * but it is still in the cache. Move it to the MFU 3961 * state. 3962 */ 3963 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3964 /* 3965 * More than 125ms have passed since we 3966 * instantiated this buffer. Move it to the 3967 * most frequently used state. 3968 */ 3969 hdr->b_l1hdr.b_arc_access = now; 3970 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3971 arc_change_state(arc_mfu, hdr, hash_lock); 3972 } 3973 ARCSTAT_BUMP(arcstat_mru_hits); 3974 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3975 arc_state_t *new_state; 3976 /* 3977 * This buffer has been "accessed" recently, but 3978 * was evicted from the cache. Move it to the 3979 * MFU state. 3980 */ 3981 3982 if (HDR_PREFETCH(hdr)) { 3983 new_state = arc_mru; 3984 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3985 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3986 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3987 } else { 3988 new_state = arc_mfu; 3989 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3990 } 3991 3992 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3993 arc_change_state(new_state, hdr, hash_lock); 3994 3995 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3996 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3997 /* 3998 * This buffer has been accessed more than once and is 3999 * still in the cache. Keep it in the MFU state. 4000 * 4001 * NOTE: an add_reference() that occurred when we did 4002 * the arc_read() will have kicked this off the list. 4003 * If it was a prefetch, we will explicitly move it to 4004 * the head of the list now. 4005 */ 4006 if ((HDR_PREFETCH(hdr)) != 0) { 4007 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4008 /* link protected by hash_lock */ 4009 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4010 } 4011 ARCSTAT_BUMP(arcstat_mfu_hits); 4012 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4013 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4014 arc_state_t *new_state = arc_mfu; 4015 /* 4016 * This buffer has been accessed more than once but has 4017 * been evicted from the cache. Move it back to the 4018 * MFU state. 4019 */ 4020 4021 if (HDR_PREFETCH(hdr)) { 4022 /* 4023 * This is a prefetch access... 4024 * move this block back to the MRU state. 4025 */ 4026 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4027 new_state = arc_mru; 4028 } 4029 4030 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4031 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4032 arc_change_state(new_state, hdr, hash_lock); 4033 4034 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4035 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4036 /* 4037 * This buffer is on the 2nd Level ARC. 4038 */ 4039 4040 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4041 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4042 arc_change_state(arc_mfu, hdr, hash_lock); 4043 } else { 4044 ASSERT(!"invalid arc state"); 4045 } 4046} 4047 4048/* a generic arc_done_func_t which you can use */ 4049/* ARGSUSED */ 4050void 4051arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4052{ 4053 if (zio == NULL || zio->io_error == 0) 4054 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4055 VERIFY(arc_buf_remove_ref(buf, arg)); 4056} 4057 4058/* a generic arc_done_func_t */ 4059void 4060arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4061{ 4062 arc_buf_t **bufp = arg; 4063 if (zio && zio->io_error) { 4064 VERIFY(arc_buf_remove_ref(buf, arg)); 4065 *bufp = NULL; 4066 } else { 4067 *bufp = buf; 4068 ASSERT(buf->b_data); 4069 } 4070} 4071 4072static void 4073arc_read_done(zio_t *zio) 4074{ 4075 arc_buf_hdr_t *hdr; 4076 arc_buf_t *buf; 4077 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4078 kmutex_t *hash_lock = NULL; 4079 arc_callback_t *callback_list, *acb; 4080 int freeable = FALSE; 4081 4082 buf = zio->io_private; 4083 hdr = buf->b_hdr; 4084 4085 /* 4086 * The hdr was inserted into hash-table and removed from lists 4087 * prior to starting I/O. We should find this header, since 4088 * it's in the hash table, and it should be legit since it's 4089 * not possible to evict it during the I/O. The only possible 4090 * reason for it not to be found is if we were freed during the 4091 * read. 4092 */ 4093 if (HDR_IN_HASH_TABLE(hdr)) { 4094 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4095 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4096 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4097 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4098 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4099 4100 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4101 &hash_lock); 4102 4103 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4104 hash_lock == NULL) || 4105 (found == hdr && 4106 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4107 (found == hdr && HDR_L2_READING(hdr))); 4108 } 4109 4110 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4111 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4112 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4113 4114 /* byteswap if necessary */ 4115 callback_list = hdr->b_l1hdr.b_acb; 4116 ASSERT(callback_list != NULL); 4117 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4118 dmu_object_byteswap_t bswap = 4119 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4120 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4121 byteswap_uint64_array : 4122 dmu_ot_byteswap[bswap].ob_func; 4123 func(buf->b_data, hdr->b_size); 4124 } 4125 4126 arc_cksum_compute(buf, B_FALSE); 4127#ifdef illumos 4128 arc_buf_watch(buf); 4129#endif /* illumos */ 4130 4131 if (hash_lock && zio->io_error == 0 && 4132 hdr->b_l1hdr.b_state == arc_anon) { 4133 /* 4134 * Only call arc_access on anonymous buffers. This is because 4135 * if we've issued an I/O for an evicted buffer, we've already 4136 * called arc_access (to prevent any simultaneous readers from 4137 * getting confused). 4138 */ 4139 arc_access(hdr, hash_lock); 4140 } 4141 4142 /* create copies of the data buffer for the callers */ 4143 abuf = buf; 4144 for (acb = callback_list; acb; acb = acb->acb_next) { 4145 if (acb->acb_done) { 4146 if (abuf == NULL) { 4147 ARCSTAT_BUMP(arcstat_duplicate_reads); 4148 abuf = arc_buf_clone(buf); 4149 } 4150 acb->acb_buf = abuf; 4151 abuf = NULL; 4152 } 4153 } 4154 hdr->b_l1hdr.b_acb = NULL; 4155 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4156 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4157 if (abuf == buf) { 4158 ASSERT(buf->b_efunc == NULL); 4159 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4160 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4161 } 4162 4163 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4164 callback_list != NULL); 4165 4166 if (zio->io_error != 0) { 4167 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4168 if (hdr->b_l1hdr.b_state != arc_anon) 4169 arc_change_state(arc_anon, hdr, hash_lock); 4170 if (HDR_IN_HASH_TABLE(hdr)) 4171 buf_hash_remove(hdr); 4172 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4173 } 4174 4175 /* 4176 * Broadcast before we drop the hash_lock to avoid the possibility 4177 * that the hdr (and hence the cv) might be freed before we get to 4178 * the cv_broadcast(). 4179 */ 4180 cv_broadcast(&hdr->b_l1hdr.b_cv); 4181 4182 if (hash_lock != NULL) { 4183 mutex_exit(hash_lock); 4184 } else { 4185 /* 4186 * This block was freed while we waited for the read to 4187 * complete. It has been removed from the hash table and 4188 * moved to the anonymous state (so that it won't show up 4189 * in the cache). 4190 */ 4191 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4192 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4193 } 4194 4195 /* execute each callback and free its structure */ 4196 while ((acb = callback_list) != NULL) { 4197 if (acb->acb_done) 4198 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4199 4200 if (acb->acb_zio_dummy != NULL) { 4201 acb->acb_zio_dummy->io_error = zio->io_error; 4202 zio_nowait(acb->acb_zio_dummy); 4203 } 4204 4205 callback_list = acb->acb_next; 4206 kmem_free(acb, sizeof (arc_callback_t)); 4207 } 4208 4209 if (freeable) 4210 arc_hdr_destroy(hdr); 4211} 4212 4213/* 4214 * "Read" the block at the specified DVA (in bp) via the 4215 * cache. If the block is found in the cache, invoke the provided 4216 * callback immediately and return. Note that the `zio' parameter 4217 * in the callback will be NULL in this case, since no IO was 4218 * required. If the block is not in the cache pass the read request 4219 * on to the spa with a substitute callback function, so that the 4220 * requested block will be added to the cache. 4221 * 4222 * If a read request arrives for a block that has a read in-progress, 4223 * either wait for the in-progress read to complete (and return the 4224 * results); or, if this is a read with a "done" func, add a record 4225 * to the read to invoke the "done" func when the read completes, 4226 * and return; or just return. 4227 * 4228 * arc_read_done() will invoke all the requested "done" functions 4229 * for readers of this block. 4230 */ 4231int 4232arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4233 void *private, zio_priority_t priority, int zio_flags, 4234 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4235{ 4236 arc_buf_hdr_t *hdr = NULL; 4237 arc_buf_t *buf = NULL; 4238 kmutex_t *hash_lock = NULL; 4239 zio_t *rzio; 4240 uint64_t guid = spa_load_guid(spa); 4241 4242 ASSERT(!BP_IS_EMBEDDED(bp) || 4243 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4244 4245top: 4246 if (!BP_IS_EMBEDDED(bp)) { 4247 /* 4248 * Embedded BP's have no DVA and require no I/O to "read". 4249 * Create an anonymous arc buf to back it. 4250 */ 4251 hdr = buf_hash_find(guid, bp, &hash_lock); 4252 } 4253 4254 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4255 4256 *arc_flags |= ARC_FLAG_CACHED; 4257 4258 if (HDR_IO_IN_PROGRESS(hdr)) { 4259 4260 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4261 priority == ZIO_PRIORITY_SYNC_READ) { 4262 /* 4263 * This sync read must wait for an 4264 * in-progress async read (e.g. a predictive 4265 * prefetch). Async reads are queued 4266 * separately at the vdev_queue layer, so 4267 * this is a form of priority inversion. 4268 * Ideally, we would "inherit" the demand 4269 * i/o's priority by moving the i/o from 4270 * the async queue to the synchronous queue, 4271 * but there is currently no mechanism to do 4272 * so. Track this so that we can evaluate 4273 * the magnitude of this potential performance 4274 * problem. 4275 * 4276 * Note that if the prefetch i/o is already 4277 * active (has been issued to the device), 4278 * the prefetch improved performance, because 4279 * we issued it sooner than we would have 4280 * without the prefetch. 4281 */ 4282 DTRACE_PROBE1(arc__sync__wait__for__async, 4283 arc_buf_hdr_t *, hdr); 4284 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4285 } 4286 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4287 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4288 } 4289 4290 if (*arc_flags & ARC_FLAG_WAIT) { 4291 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4292 mutex_exit(hash_lock); 4293 goto top; 4294 } 4295 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4296 4297 if (done) { 4298 arc_callback_t *acb = NULL; 4299 4300 acb = kmem_zalloc(sizeof (arc_callback_t), 4301 KM_SLEEP); 4302 acb->acb_done = done; 4303 acb->acb_private = private; 4304 if (pio != NULL) 4305 acb->acb_zio_dummy = zio_null(pio, 4306 spa, NULL, NULL, NULL, zio_flags); 4307 4308 ASSERT(acb->acb_done != NULL); 4309 acb->acb_next = hdr->b_l1hdr.b_acb; 4310 hdr->b_l1hdr.b_acb = acb; 4311 add_reference(hdr, hash_lock, private); 4312 mutex_exit(hash_lock); 4313 return (0); 4314 } 4315 mutex_exit(hash_lock); 4316 return (0); 4317 } 4318 4319 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4320 hdr->b_l1hdr.b_state == arc_mfu); 4321 4322 if (done) { 4323 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4324 /* 4325 * This is a demand read which does not have to 4326 * wait for i/o because we did a predictive 4327 * prefetch i/o for it, which has completed. 4328 */ 4329 DTRACE_PROBE1( 4330 arc__demand__hit__predictive__prefetch, 4331 arc_buf_hdr_t *, hdr); 4332 ARCSTAT_BUMP( 4333 arcstat_demand_hit_predictive_prefetch); 4334 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4335 } 4336 add_reference(hdr, hash_lock, private); 4337 /* 4338 * If this block is already in use, create a new 4339 * copy of the data so that we will be guaranteed 4340 * that arc_release() will always succeed. 4341 */ 4342 buf = hdr->b_l1hdr.b_buf; 4343 ASSERT(buf); 4344 ASSERT(buf->b_data); 4345 if (HDR_BUF_AVAILABLE(hdr)) { 4346 ASSERT(buf->b_efunc == NULL); 4347 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4348 } else { 4349 buf = arc_buf_clone(buf); 4350 } 4351 4352 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4353 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4354 hdr->b_flags |= ARC_FLAG_PREFETCH; 4355 } 4356 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4357 arc_access(hdr, hash_lock); 4358 if (*arc_flags & ARC_FLAG_L2CACHE) 4359 hdr->b_flags |= ARC_FLAG_L2CACHE; 4360 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4361 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4362 mutex_exit(hash_lock); 4363 ARCSTAT_BUMP(arcstat_hits); 4364 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4365 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4366 data, metadata, hits); 4367 4368 if (done) 4369 done(NULL, buf, private); 4370 } else { 4371 uint64_t size = BP_GET_LSIZE(bp); 4372 arc_callback_t *acb; 4373 vdev_t *vd = NULL; 4374 uint64_t addr = 0; 4375 boolean_t devw = B_FALSE; 4376 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4377 int32_t b_asize = 0; 4378 4379 if (hdr == NULL) { 4380 /* this block is not in the cache */ 4381 arc_buf_hdr_t *exists = NULL; 4382 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4383 buf = arc_buf_alloc(spa, size, private, type); 4384 hdr = buf->b_hdr; 4385 if (!BP_IS_EMBEDDED(bp)) { 4386 hdr->b_dva = *BP_IDENTITY(bp); 4387 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4388 exists = buf_hash_insert(hdr, &hash_lock); 4389 } 4390 if (exists != NULL) { 4391 /* somebody beat us to the hash insert */ 4392 mutex_exit(hash_lock); 4393 buf_discard_identity(hdr); 4394 (void) arc_buf_remove_ref(buf, private); 4395 goto top; /* restart the IO request */ 4396 } 4397 4398 /* 4399 * If there is a callback, we pass our reference to 4400 * it; otherwise we remove our reference. 4401 */ 4402 if (done == NULL) { 4403 (void) remove_reference(hdr, hash_lock, 4404 private); 4405 } 4406 if (*arc_flags & ARC_FLAG_PREFETCH) 4407 hdr->b_flags |= ARC_FLAG_PREFETCH; 4408 if (*arc_flags & ARC_FLAG_L2CACHE) 4409 hdr->b_flags |= ARC_FLAG_L2CACHE; 4410 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4411 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4412 if (BP_GET_LEVEL(bp) > 0) 4413 hdr->b_flags |= ARC_FLAG_INDIRECT; 4414 } else { 4415 /* 4416 * This block is in the ghost cache. If it was L2-only 4417 * (and thus didn't have an L1 hdr), we realloc the 4418 * header to add an L1 hdr. 4419 */ 4420 if (!HDR_HAS_L1HDR(hdr)) { 4421 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4422 hdr_full_cache); 4423 } 4424 4425 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4426 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4427 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4428 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4429 4430 /* 4431 * If there is a callback, we pass a reference to it. 4432 */ 4433 if (done != NULL) 4434 add_reference(hdr, hash_lock, private); 4435 if (*arc_flags & ARC_FLAG_PREFETCH) 4436 hdr->b_flags |= ARC_FLAG_PREFETCH; 4437 if (*arc_flags & ARC_FLAG_L2CACHE) 4438 hdr->b_flags |= ARC_FLAG_L2CACHE; 4439 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4440 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4441 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4442 buf->b_hdr = hdr; 4443 buf->b_data = NULL; 4444 buf->b_efunc = NULL; 4445 buf->b_private = NULL; 4446 buf->b_next = NULL; 4447 hdr->b_l1hdr.b_buf = buf; 4448 ASSERT0(hdr->b_l1hdr.b_datacnt); 4449 hdr->b_l1hdr.b_datacnt = 1; 4450 arc_get_data_buf(buf); 4451 arc_access(hdr, hash_lock); 4452 } 4453 4454 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4455 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4456 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4457 4458 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4459 acb->acb_done = done; 4460 acb->acb_private = private; 4461 4462 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4463 hdr->b_l1hdr.b_acb = acb; 4464 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4465 4466 if (HDR_HAS_L2HDR(hdr) && 4467 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4468 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4469 addr = hdr->b_l2hdr.b_daddr; 4470 b_compress = HDR_GET_COMPRESS(hdr); 4471 b_asize = hdr->b_l2hdr.b_asize; 4472 /* 4473 * Lock out device removal. 4474 */ 4475 if (vdev_is_dead(vd) || 4476 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4477 vd = NULL; 4478 } 4479 4480 if (hash_lock != NULL) 4481 mutex_exit(hash_lock); 4482 4483 /* 4484 * At this point, we have a level 1 cache miss. Try again in 4485 * L2ARC if possible. 4486 */ 4487 ASSERT3U(hdr->b_size, ==, size); 4488 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4489 uint64_t, size, zbookmark_phys_t *, zb); 4490 ARCSTAT_BUMP(arcstat_misses); 4491 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4492 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4493 data, metadata, misses); 4494#ifdef _KERNEL 4495 curthread->td_ru.ru_inblock++; 4496#endif 4497 4498 if (priority == ZIO_PRIORITY_ASYNC_READ) 4499 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4500 else 4501 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4502 4503 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4504 /* 4505 * Read from the L2ARC if the following are true: 4506 * 1. The L2ARC vdev was previously cached. 4507 * 2. This buffer still has L2ARC metadata. 4508 * 3. This buffer isn't currently writing to the L2ARC. 4509 * 4. The L2ARC entry wasn't evicted, which may 4510 * also have invalidated the vdev. 4511 * 5. This isn't prefetch and l2arc_noprefetch is set. 4512 */ 4513 if (HDR_HAS_L2HDR(hdr) && 4514 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4515 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4516 l2arc_read_callback_t *cb; 4517 4518 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4519 ARCSTAT_BUMP(arcstat_l2_hits); 4520 4521 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4522 KM_SLEEP); 4523 cb->l2rcb_buf = buf; 4524 cb->l2rcb_spa = spa; 4525 cb->l2rcb_bp = *bp; 4526 cb->l2rcb_zb = *zb; 4527 cb->l2rcb_flags = zio_flags; 4528 cb->l2rcb_compress = b_compress; 4529 4530 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4531 addr + size < vd->vdev_psize - 4532 VDEV_LABEL_END_SIZE); 4533 4534 /* 4535 * l2arc read. The SCL_L2ARC lock will be 4536 * released by l2arc_read_done(). 4537 * Issue a null zio if the underlying buffer 4538 * was squashed to zero size by compression. 4539 */ 4540 if (b_compress == ZIO_COMPRESS_EMPTY) { 4541 rzio = zio_null(pio, spa, vd, 4542 l2arc_read_done, cb, 4543 zio_flags | ZIO_FLAG_DONT_CACHE | 4544 ZIO_FLAG_CANFAIL | 4545 ZIO_FLAG_DONT_PROPAGATE | 4546 ZIO_FLAG_DONT_RETRY); 4547 } else { 4548 rzio = zio_read_phys(pio, vd, addr, 4549 b_asize, buf->b_data, 4550 ZIO_CHECKSUM_OFF, 4551 l2arc_read_done, cb, priority, 4552 zio_flags | ZIO_FLAG_DONT_CACHE | 4553 ZIO_FLAG_CANFAIL | 4554 ZIO_FLAG_DONT_PROPAGATE | 4555 ZIO_FLAG_DONT_RETRY, B_FALSE); 4556 } 4557 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4558 zio_t *, rzio); 4559 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4560 4561 if (*arc_flags & ARC_FLAG_NOWAIT) { 4562 zio_nowait(rzio); 4563 return (0); 4564 } 4565 4566 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4567 if (zio_wait(rzio) == 0) 4568 return (0); 4569 4570 /* l2arc read error; goto zio_read() */ 4571 } else { 4572 DTRACE_PROBE1(l2arc__miss, 4573 arc_buf_hdr_t *, hdr); 4574 ARCSTAT_BUMP(arcstat_l2_misses); 4575 if (HDR_L2_WRITING(hdr)) 4576 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4577 spa_config_exit(spa, SCL_L2ARC, vd); 4578 } 4579 } else { 4580 if (vd != NULL) 4581 spa_config_exit(spa, SCL_L2ARC, vd); 4582 if (l2arc_ndev != 0) { 4583 DTRACE_PROBE1(l2arc__miss, 4584 arc_buf_hdr_t *, hdr); 4585 ARCSTAT_BUMP(arcstat_l2_misses); 4586 } 4587 } 4588 4589 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4590 arc_read_done, buf, priority, zio_flags, zb); 4591 4592 if (*arc_flags & ARC_FLAG_WAIT) 4593 return (zio_wait(rzio)); 4594 4595 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4596 zio_nowait(rzio); 4597 } 4598 return (0); 4599} 4600 4601void 4602arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4603{ 4604 ASSERT(buf->b_hdr != NULL); 4605 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4606 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4607 func == NULL); 4608 ASSERT(buf->b_efunc == NULL); 4609 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4610 4611 buf->b_efunc = func; 4612 buf->b_private = private; 4613} 4614 4615/* 4616 * Notify the arc that a block was freed, and thus will never be used again. 4617 */ 4618void 4619arc_freed(spa_t *spa, const blkptr_t *bp) 4620{ 4621 arc_buf_hdr_t *hdr; 4622 kmutex_t *hash_lock; 4623 uint64_t guid = spa_load_guid(spa); 4624 4625 ASSERT(!BP_IS_EMBEDDED(bp)); 4626 4627 hdr = buf_hash_find(guid, bp, &hash_lock); 4628 if (hdr == NULL) 4629 return; 4630 if (HDR_BUF_AVAILABLE(hdr)) { 4631 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4632 add_reference(hdr, hash_lock, FTAG); 4633 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4634 mutex_exit(hash_lock); 4635 4636 arc_release(buf, FTAG); 4637 (void) arc_buf_remove_ref(buf, FTAG); 4638 } else { 4639 mutex_exit(hash_lock); 4640 } 4641 4642} 4643 4644/* 4645 * Clear the user eviction callback set by arc_set_callback(), first calling 4646 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4647 * clearing the callback may result in the arc_buf being destroyed. However, 4648 * it will not result in the *last* arc_buf being destroyed, hence the data 4649 * will remain cached in the ARC. We make a copy of the arc buffer here so 4650 * that we can process the callback without holding any locks. 4651 * 4652 * It's possible that the callback is already in the process of being cleared 4653 * by another thread. In this case we can not clear the callback. 4654 * 4655 * Returns B_TRUE if the callback was successfully called and cleared. 4656 */ 4657boolean_t 4658arc_clear_callback(arc_buf_t *buf) 4659{ 4660 arc_buf_hdr_t *hdr; 4661 kmutex_t *hash_lock; 4662 arc_evict_func_t *efunc = buf->b_efunc; 4663 void *private = buf->b_private; 4664 4665 mutex_enter(&buf->b_evict_lock); 4666 hdr = buf->b_hdr; 4667 if (hdr == NULL) { 4668 /* 4669 * We are in arc_do_user_evicts(). 4670 */ 4671 ASSERT(buf->b_data == NULL); 4672 mutex_exit(&buf->b_evict_lock); 4673 return (B_FALSE); 4674 } else if (buf->b_data == NULL) { 4675 /* 4676 * We are on the eviction list; process this buffer now 4677 * but let arc_do_user_evicts() do the reaping. 4678 */ 4679 buf->b_efunc = NULL; 4680 mutex_exit(&buf->b_evict_lock); 4681 VERIFY0(efunc(private)); 4682 return (B_TRUE); 4683 } 4684 hash_lock = HDR_LOCK(hdr); 4685 mutex_enter(hash_lock); 4686 hdr = buf->b_hdr; 4687 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4688 4689 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4690 hdr->b_l1hdr.b_datacnt); 4691 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4692 hdr->b_l1hdr.b_state == arc_mfu); 4693 4694 buf->b_efunc = NULL; 4695 buf->b_private = NULL; 4696 4697 if (hdr->b_l1hdr.b_datacnt > 1) { 4698 mutex_exit(&buf->b_evict_lock); 4699 arc_buf_destroy(buf, TRUE); 4700 } else { 4701 ASSERT(buf == hdr->b_l1hdr.b_buf); 4702 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4703 mutex_exit(&buf->b_evict_lock); 4704 } 4705 4706 mutex_exit(hash_lock); 4707 VERIFY0(efunc(private)); 4708 return (B_TRUE); 4709} 4710 4711/* 4712 * Release this buffer from the cache, making it an anonymous buffer. This 4713 * must be done after a read and prior to modifying the buffer contents. 4714 * If the buffer has more than one reference, we must make 4715 * a new hdr for the buffer. 4716 */ 4717void 4718arc_release(arc_buf_t *buf, void *tag) 4719{ 4720 arc_buf_hdr_t *hdr = buf->b_hdr; 4721 4722 /* 4723 * It would be nice to assert that if it's DMU metadata (level > 4724 * 0 || it's the dnode file), then it must be syncing context. 4725 * But we don't know that information at this level. 4726 */ 4727 4728 mutex_enter(&buf->b_evict_lock); 4729 4730 ASSERT(HDR_HAS_L1HDR(hdr)); 4731 4732 /* 4733 * We don't grab the hash lock prior to this check, because if 4734 * the buffer's header is in the arc_anon state, it won't be 4735 * linked into the hash table. 4736 */ 4737 if (hdr->b_l1hdr.b_state == arc_anon) { 4738 mutex_exit(&buf->b_evict_lock); 4739 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4740 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4741 ASSERT(!HDR_HAS_L2HDR(hdr)); 4742 ASSERT(BUF_EMPTY(hdr)); 4743 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4744 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4745 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4746 4747 ASSERT3P(buf->b_efunc, ==, NULL); 4748 ASSERT3P(buf->b_private, ==, NULL); 4749 4750 hdr->b_l1hdr.b_arc_access = 0; 4751 arc_buf_thaw(buf); 4752 4753 return; 4754 } 4755 4756 kmutex_t *hash_lock = HDR_LOCK(hdr); 4757 mutex_enter(hash_lock); 4758 4759 /* 4760 * This assignment is only valid as long as the hash_lock is 4761 * held, we must be careful not to reference state or the 4762 * b_state field after dropping the lock. 4763 */ 4764 arc_state_t *state = hdr->b_l1hdr.b_state; 4765 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4766 ASSERT3P(state, !=, arc_anon); 4767 4768 /* this buffer is not on any list */ 4769 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4770 4771 if (HDR_HAS_L2HDR(hdr)) { 4772 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4773 4774 /* 4775 * We have to recheck this conditional again now that 4776 * we're holding the l2ad_mtx to prevent a race with 4777 * another thread which might be concurrently calling 4778 * l2arc_evict(). In that case, l2arc_evict() might have 4779 * destroyed the header's L2 portion as we were waiting 4780 * to acquire the l2ad_mtx. 4781 */ 4782 if (HDR_HAS_L2HDR(hdr)) { 4783 if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET) 4784 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 4785 hdr->b_l2hdr.b_daddr, 4786 hdr->b_l2hdr.b_asize, 0); 4787 arc_hdr_l2hdr_destroy(hdr); 4788 } 4789 4790 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4791 } 4792 4793 /* 4794 * Do we have more than one buf? 4795 */ 4796 if (hdr->b_l1hdr.b_datacnt > 1) { 4797 arc_buf_hdr_t *nhdr; 4798 arc_buf_t **bufp; 4799 uint64_t blksz = hdr->b_size; 4800 uint64_t spa = hdr->b_spa; 4801 arc_buf_contents_t type = arc_buf_type(hdr); 4802 uint32_t flags = hdr->b_flags; 4803 4804 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4805 /* 4806 * Pull the data off of this hdr and attach it to 4807 * a new anonymous hdr. 4808 */ 4809 (void) remove_reference(hdr, hash_lock, tag); 4810 bufp = &hdr->b_l1hdr.b_buf; 4811 while (*bufp != buf) 4812 bufp = &(*bufp)->b_next; 4813 *bufp = buf->b_next; 4814 buf->b_next = NULL; 4815 4816 ASSERT3P(state, !=, arc_l2c_only); 4817 4818 (void) refcount_remove_many( 4819 &state->arcs_size, hdr->b_size, buf); 4820 4821 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4822 ASSERT3P(state, !=, arc_l2c_only); 4823 uint64_t *size = &state->arcs_lsize[type]; 4824 ASSERT3U(*size, >=, hdr->b_size); 4825 atomic_add_64(size, -hdr->b_size); 4826 } 4827 4828 /* 4829 * We're releasing a duplicate user data buffer, update 4830 * our statistics accordingly. 4831 */ 4832 if (HDR_ISTYPE_DATA(hdr)) { 4833 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4834 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4835 -hdr->b_size); 4836 } 4837 hdr->b_l1hdr.b_datacnt -= 1; 4838 arc_cksum_verify(buf); 4839#ifdef illumos 4840 arc_buf_unwatch(buf); 4841#endif /* illumos */ 4842 4843 mutex_exit(hash_lock); 4844 4845 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4846 nhdr->b_size = blksz; 4847 nhdr->b_spa = spa; 4848 4849 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4850 nhdr->b_flags |= arc_bufc_to_flags(type); 4851 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4852 4853 nhdr->b_l1hdr.b_buf = buf; 4854 nhdr->b_l1hdr.b_datacnt = 1; 4855 nhdr->b_l1hdr.b_state = arc_anon; 4856 nhdr->b_l1hdr.b_arc_access = 0; 4857 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4858 nhdr->b_freeze_cksum = NULL; 4859 4860 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4861 buf->b_hdr = nhdr; 4862 mutex_exit(&buf->b_evict_lock); 4863 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4864 } else { 4865 mutex_exit(&buf->b_evict_lock); 4866 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4867 /* protected by hash lock, or hdr is on arc_anon */ 4868 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4869 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4870 arc_change_state(arc_anon, hdr, hash_lock); 4871 hdr->b_l1hdr.b_arc_access = 0; 4872 mutex_exit(hash_lock); 4873 4874 buf_discard_identity(hdr); 4875 arc_buf_thaw(buf); 4876 } 4877 buf->b_efunc = NULL; 4878 buf->b_private = NULL; 4879} 4880 4881int 4882arc_released(arc_buf_t *buf) 4883{ 4884 int released; 4885 4886 mutex_enter(&buf->b_evict_lock); 4887 released = (buf->b_data != NULL && 4888 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4889 mutex_exit(&buf->b_evict_lock); 4890 return (released); 4891} 4892 4893#ifdef ZFS_DEBUG 4894int 4895arc_referenced(arc_buf_t *buf) 4896{ 4897 int referenced; 4898 4899 mutex_enter(&buf->b_evict_lock); 4900 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4901 mutex_exit(&buf->b_evict_lock); 4902 return (referenced); 4903} 4904#endif 4905 4906static void 4907arc_write_ready(zio_t *zio) 4908{ 4909 arc_write_callback_t *callback = zio->io_private; 4910 arc_buf_t *buf = callback->awcb_buf; 4911 arc_buf_hdr_t *hdr = buf->b_hdr; 4912 4913 ASSERT(HDR_HAS_L1HDR(hdr)); 4914 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4915 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4916 callback->awcb_ready(zio, buf, callback->awcb_private); 4917 4918 /* 4919 * If the IO is already in progress, then this is a re-write 4920 * attempt, so we need to thaw and re-compute the cksum. 4921 * It is the responsibility of the callback to handle the 4922 * accounting for any re-write attempt. 4923 */ 4924 if (HDR_IO_IN_PROGRESS(hdr)) { 4925 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4926 if (hdr->b_freeze_cksum != NULL) { 4927 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4928 hdr->b_freeze_cksum = NULL; 4929 } 4930 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4931 } 4932 arc_cksum_compute(buf, B_FALSE); 4933 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4934} 4935 4936/* 4937 * The SPA calls this callback for each physical write that happens on behalf 4938 * of a logical write. See the comment in dbuf_write_physdone() for details. 4939 */ 4940static void 4941arc_write_physdone(zio_t *zio) 4942{ 4943 arc_write_callback_t *cb = zio->io_private; 4944 if (cb->awcb_physdone != NULL) 4945 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4946} 4947 4948static void 4949arc_write_done(zio_t *zio) 4950{ 4951 arc_write_callback_t *callback = zio->io_private; 4952 arc_buf_t *buf = callback->awcb_buf; 4953 arc_buf_hdr_t *hdr = buf->b_hdr; 4954 4955 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4956 4957 if (zio->io_error == 0) { 4958 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4959 buf_discard_identity(hdr); 4960 } else { 4961 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4962 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4963 } 4964 } else { 4965 ASSERT(BUF_EMPTY(hdr)); 4966 } 4967 4968 /* 4969 * If the block to be written was all-zero or compressed enough to be 4970 * embedded in the BP, no write was performed so there will be no 4971 * dva/birth/checksum. The buffer must therefore remain anonymous 4972 * (and uncached). 4973 */ 4974 if (!BUF_EMPTY(hdr)) { 4975 arc_buf_hdr_t *exists; 4976 kmutex_t *hash_lock; 4977 4978 ASSERT(zio->io_error == 0); 4979 4980 arc_cksum_verify(buf); 4981 4982 exists = buf_hash_insert(hdr, &hash_lock); 4983 if (exists != NULL) { 4984 /* 4985 * This can only happen if we overwrite for 4986 * sync-to-convergence, because we remove 4987 * buffers from the hash table when we arc_free(). 4988 */ 4989 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4990 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4991 panic("bad overwrite, hdr=%p exists=%p", 4992 (void *)hdr, (void *)exists); 4993 ASSERT(refcount_is_zero( 4994 &exists->b_l1hdr.b_refcnt)); 4995 arc_change_state(arc_anon, exists, hash_lock); 4996 mutex_exit(hash_lock); 4997 arc_hdr_destroy(exists); 4998 exists = buf_hash_insert(hdr, &hash_lock); 4999 ASSERT3P(exists, ==, NULL); 5000 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5001 /* nopwrite */ 5002 ASSERT(zio->io_prop.zp_nopwrite); 5003 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5004 panic("bad nopwrite, hdr=%p exists=%p", 5005 (void *)hdr, (void *)exists); 5006 } else { 5007 /* Dedup */ 5008 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5009 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5010 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5011 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5012 } 5013 } 5014 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5015 /* if it's not anon, we are doing a scrub */ 5016 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5017 arc_access(hdr, hash_lock); 5018 mutex_exit(hash_lock); 5019 } else { 5020 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5021 } 5022 5023 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5024 callback->awcb_done(zio, buf, callback->awcb_private); 5025 5026 kmem_free(callback, sizeof (arc_write_callback_t)); 5027} 5028 5029zio_t * 5030arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5031 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5032 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 5033 arc_done_func_t *done, void *private, zio_priority_t priority, 5034 int zio_flags, const zbookmark_phys_t *zb) 5035{ 5036 arc_buf_hdr_t *hdr = buf->b_hdr; 5037 arc_write_callback_t *callback; 5038 zio_t *zio; 5039 5040 ASSERT(ready != NULL); 5041 ASSERT(done != NULL); 5042 ASSERT(!HDR_IO_ERROR(hdr)); 5043 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5044 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5045 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5046 if (l2arc) 5047 hdr->b_flags |= ARC_FLAG_L2CACHE; 5048 if (l2arc_compress) 5049 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5050 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5051 callback->awcb_ready = ready; 5052 callback->awcb_physdone = physdone; 5053 callback->awcb_done = done; 5054 callback->awcb_private = private; 5055 callback->awcb_buf = buf; 5056 5057 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5058 arc_write_ready, arc_write_physdone, arc_write_done, callback, 5059 priority, zio_flags, zb); 5060 5061 return (zio); 5062} 5063 5064static int 5065arc_memory_throttle(uint64_t reserve, uint64_t txg) 5066{ 5067#ifdef _KERNEL 5068 uint64_t available_memory = ptob(freemem); 5069 static uint64_t page_load = 0; 5070 static uint64_t last_txg = 0; 5071 5072#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5073 available_memory = 5074 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5075#endif 5076 5077 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5078 return (0); 5079 5080 if (txg > last_txg) { 5081 last_txg = txg; 5082 page_load = 0; 5083 } 5084 /* 5085 * If we are in pageout, we know that memory is already tight, 5086 * the arc is already going to be evicting, so we just want to 5087 * continue to let page writes occur as quickly as possible. 5088 */ 5089 if (curproc == pageproc) { 5090 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5091 return (SET_ERROR(ERESTART)); 5092 /* Note: reserve is inflated, so we deflate */ 5093 page_load += reserve / 8; 5094 return (0); 5095 } else if (page_load > 0 && arc_reclaim_needed()) { 5096 /* memory is low, delay before restarting */ 5097 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5098 return (SET_ERROR(EAGAIN)); 5099 } 5100 page_load = 0; 5101#endif 5102 return (0); 5103} 5104 5105void 5106arc_tempreserve_clear(uint64_t reserve) 5107{ 5108 atomic_add_64(&arc_tempreserve, -reserve); 5109 ASSERT((int64_t)arc_tempreserve >= 0); 5110} 5111 5112int 5113arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5114{ 5115 int error; 5116 uint64_t anon_size; 5117 5118 if (reserve > arc_c/4 && !arc_no_grow) { 5119 arc_c = MIN(arc_c_max, reserve * 4); 5120 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5121 } 5122 if (reserve > arc_c) 5123 return (SET_ERROR(ENOMEM)); 5124 5125 /* 5126 * Don't count loaned bufs as in flight dirty data to prevent long 5127 * network delays from blocking transactions that are ready to be 5128 * assigned to a txg. 5129 */ 5130 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5131 arc_loaned_bytes), 0); 5132 5133 /* 5134 * Writes will, almost always, require additional memory allocations 5135 * in order to compress/encrypt/etc the data. We therefore need to 5136 * make sure that there is sufficient available memory for this. 5137 */ 5138 error = arc_memory_throttle(reserve, txg); 5139 if (error != 0) 5140 return (error); 5141 5142 /* 5143 * Throttle writes when the amount of dirty data in the cache 5144 * gets too large. We try to keep the cache less than half full 5145 * of dirty blocks so that our sync times don't grow too large. 5146 * Note: if two requests come in concurrently, we might let them 5147 * both succeed, when one of them should fail. Not a huge deal. 5148 */ 5149 5150 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5151 anon_size > arc_c / 4) { 5152 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5153 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5154 arc_tempreserve>>10, 5155 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5156 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5157 reserve>>10, arc_c>>10); 5158 return (SET_ERROR(ERESTART)); 5159 } 5160 atomic_add_64(&arc_tempreserve, reserve); 5161 return (0); 5162} 5163 5164static void 5165arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5166 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5167{ 5168 size->value.ui64 = refcount_count(&state->arcs_size); 5169 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5170 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5171} 5172 5173static int 5174arc_kstat_update(kstat_t *ksp, int rw) 5175{ 5176 arc_stats_t *as = ksp->ks_data; 5177 5178 if (rw == KSTAT_WRITE) { 5179 return (EACCES); 5180 } else { 5181 arc_kstat_update_state(arc_anon, 5182 &as->arcstat_anon_size, 5183 &as->arcstat_anon_evictable_data, 5184 &as->arcstat_anon_evictable_metadata); 5185 arc_kstat_update_state(arc_mru, 5186 &as->arcstat_mru_size, 5187 &as->arcstat_mru_evictable_data, 5188 &as->arcstat_mru_evictable_metadata); 5189 arc_kstat_update_state(arc_mru_ghost, 5190 &as->arcstat_mru_ghost_size, 5191 &as->arcstat_mru_ghost_evictable_data, 5192 &as->arcstat_mru_ghost_evictable_metadata); 5193 arc_kstat_update_state(arc_mfu, 5194 &as->arcstat_mfu_size, 5195 &as->arcstat_mfu_evictable_data, 5196 &as->arcstat_mfu_evictable_metadata); 5197 arc_kstat_update_state(arc_mfu_ghost, 5198 &as->arcstat_mfu_ghost_size, 5199 &as->arcstat_mfu_ghost_evictable_data, 5200 &as->arcstat_mfu_ghost_evictable_metadata); 5201 } 5202 5203 return (0); 5204} 5205 5206/* 5207 * This function *must* return indices evenly distributed between all 5208 * sublists of the multilist. This is needed due to how the ARC eviction 5209 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5210 * distributed between all sublists and uses this assumption when 5211 * deciding which sublist to evict from and how much to evict from it. 5212 */ 5213unsigned int 5214arc_state_multilist_index_func(multilist_t *ml, void *obj) 5215{ 5216 arc_buf_hdr_t *hdr = obj; 5217 5218 /* 5219 * We rely on b_dva to generate evenly distributed index 5220 * numbers using buf_hash below. So, as an added precaution, 5221 * let's make sure we never add empty buffers to the arc lists. 5222 */ 5223 ASSERT(!BUF_EMPTY(hdr)); 5224 5225 /* 5226 * The assumption here, is the hash value for a given 5227 * arc_buf_hdr_t will remain constant throughout it's lifetime 5228 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5229 * Thus, we don't need to store the header's sublist index 5230 * on insertion, as this index can be recalculated on removal. 5231 * 5232 * Also, the low order bits of the hash value are thought to be 5233 * distributed evenly. Otherwise, in the case that the multilist 5234 * has a power of two number of sublists, each sublists' usage 5235 * would not be evenly distributed. 5236 */ 5237 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5238 multilist_get_num_sublists(ml)); 5239} 5240 5241#ifdef _KERNEL 5242static eventhandler_tag arc_event_lowmem = NULL; 5243 5244static void 5245arc_lowmem(void *arg __unused, int howto __unused) 5246{ 5247 5248 mutex_enter(&arc_reclaim_lock); 5249 /* XXX: Memory deficit should be passed as argument. */ 5250 needfree = btoc(arc_c >> arc_shrink_shift); 5251 DTRACE_PROBE(arc__needfree); 5252 cv_signal(&arc_reclaim_thread_cv); 5253 5254 /* 5255 * It is unsafe to block here in arbitrary threads, because we can come 5256 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5257 * with ARC reclaim thread. 5258 */ 5259 if (curproc == pageproc) 5260 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5261 mutex_exit(&arc_reclaim_lock); 5262} 5263#endif 5264 5265void 5266arc_init(void) 5267{ 5268 int i, prefetch_tunable_set = 0; 5269 5270 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5271 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5272 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5273 5274 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5275 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5276 5277 /* Convert seconds to clock ticks */ 5278 arc_min_prefetch_lifespan = 1 * hz; 5279 5280 /* Start out with 1/8 of all memory */ 5281 arc_c = kmem_size() / 8; 5282 5283#ifdef sun 5284#ifdef _KERNEL 5285 /* 5286 * On architectures where the physical memory can be larger 5287 * than the addressable space (intel in 32-bit mode), we may 5288 * need to limit the cache to 1/8 of VM size. 5289 */ 5290 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5291#endif 5292#endif /* sun */ 5293 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 5294 arc_c_min = MAX(arc_c / 4, 16 << 20); 5295 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 5296 if (arc_c * 8 >= 1 << 30) 5297 arc_c_max = (arc_c * 8) - (1 << 30); 5298 else 5299 arc_c_max = arc_c_min; 5300 arc_c_max = MAX(arc_c * 5, arc_c_max); 5301 5302#ifdef _KERNEL 5303 /* 5304 * Allow the tunables to override our calculations if they are 5305 * reasonable (ie. over 16MB) 5306 */ 5307 if (zfs_arc_max > 16 << 20 && zfs_arc_max < kmem_size()) 5308 arc_c_max = zfs_arc_max; 5309 if (zfs_arc_min > 16 << 20 && zfs_arc_min <= arc_c_max) 5310 arc_c_min = zfs_arc_min; 5311#endif 5312 5313 arc_c = arc_c_max; 5314 arc_p = (arc_c >> 1); 5315 5316 /* limit meta-data to 1/4 of the arc capacity */ 5317 arc_meta_limit = arc_c_max / 4; 5318 5319 /* Allow the tunable to override if it is reasonable */ 5320 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5321 arc_meta_limit = zfs_arc_meta_limit; 5322 5323 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5324 arc_c_min = arc_meta_limit / 2; 5325 5326 if (zfs_arc_meta_min > 0) { 5327 arc_meta_min = zfs_arc_meta_min; 5328 } else { 5329 arc_meta_min = arc_c_min / 2; 5330 } 5331 5332 if (zfs_arc_grow_retry > 0) 5333 arc_grow_retry = zfs_arc_grow_retry; 5334 5335 if (zfs_arc_shrink_shift > 0) 5336 arc_shrink_shift = zfs_arc_shrink_shift; 5337 5338 /* 5339 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5340 */ 5341 if (arc_no_grow_shift >= arc_shrink_shift) 5342 arc_no_grow_shift = arc_shrink_shift - 1; 5343 5344 if (zfs_arc_p_min_shift > 0) 5345 arc_p_min_shift = zfs_arc_p_min_shift; 5346 5347 if (zfs_arc_num_sublists_per_state < 1) 5348 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 5349 5350 /* if kmem_flags are set, lets try to use less memory */ 5351 if (kmem_debugging()) 5352 arc_c = arc_c / 2; 5353 if (arc_c < arc_c_min) 5354 arc_c = arc_c_min; 5355 5356 zfs_arc_min = arc_c_min; 5357 zfs_arc_max = arc_c_max; 5358 5359 arc_anon = &ARC_anon; 5360 arc_mru = &ARC_mru; 5361 arc_mru_ghost = &ARC_mru_ghost; 5362 arc_mfu = &ARC_mfu; 5363 arc_mfu_ghost = &ARC_mfu_ghost; 5364 arc_l2c_only = &ARC_l2c_only; 5365 arc_size = 0; 5366 5367 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5368 sizeof (arc_buf_hdr_t), 5369 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5370 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5371 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5372 sizeof (arc_buf_hdr_t), 5373 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5374 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5375 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5376 sizeof (arc_buf_hdr_t), 5377 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5378 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5379 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5380 sizeof (arc_buf_hdr_t), 5381 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5382 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5383 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5384 sizeof (arc_buf_hdr_t), 5385 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5386 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5387 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5388 sizeof (arc_buf_hdr_t), 5389 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5390 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5391 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5392 sizeof (arc_buf_hdr_t), 5393 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5394 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5395 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5396 sizeof (arc_buf_hdr_t), 5397 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5398 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5399 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5400 sizeof (arc_buf_hdr_t), 5401 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5402 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5403 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5404 sizeof (arc_buf_hdr_t), 5405 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5406 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5407 5408 refcount_create(&arc_anon->arcs_size); 5409 refcount_create(&arc_mru->arcs_size); 5410 refcount_create(&arc_mru_ghost->arcs_size); 5411 refcount_create(&arc_mfu->arcs_size); 5412 refcount_create(&arc_mfu_ghost->arcs_size); 5413 refcount_create(&arc_l2c_only->arcs_size); 5414 5415 buf_init(); 5416 5417 arc_reclaim_thread_exit = FALSE; 5418 arc_user_evicts_thread_exit = FALSE; 5419 arc_eviction_list = NULL; 5420 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5421 5422 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5423 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5424 5425 if (arc_ksp != NULL) { 5426 arc_ksp->ks_data = &arc_stats; 5427 arc_ksp->ks_update = arc_kstat_update; 5428 kstat_install(arc_ksp); 5429 } 5430 5431 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5432 TS_RUN, minclsyspri); 5433 5434#ifdef _KERNEL 5435 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5436 EVENTHANDLER_PRI_FIRST); 5437#endif 5438 5439 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5440 TS_RUN, minclsyspri); 5441 5442 arc_dead = FALSE; 5443 arc_warm = B_FALSE; 5444 5445 /* 5446 * Calculate maximum amount of dirty data per pool. 5447 * 5448 * If it has been set by /etc/system, take that. 5449 * Otherwise, use a percentage of physical memory defined by 5450 * zfs_dirty_data_max_percent (default 10%) with a cap at 5451 * zfs_dirty_data_max_max (default 4GB). 5452 */ 5453 if (zfs_dirty_data_max == 0) { 5454 zfs_dirty_data_max = ptob(physmem) * 5455 zfs_dirty_data_max_percent / 100; 5456 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5457 zfs_dirty_data_max_max); 5458 } 5459 5460#ifdef _KERNEL 5461 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5462 prefetch_tunable_set = 1; 5463 5464#ifdef __i386__ 5465 if (prefetch_tunable_set == 0) { 5466 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5467 "-- to enable,\n"); 5468 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5469 "to /boot/loader.conf.\n"); 5470 zfs_prefetch_disable = 1; 5471 } 5472#else 5473 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5474 prefetch_tunable_set == 0) { 5475 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5476 "than 4GB of RAM is present;\n" 5477 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5478 "to /boot/loader.conf.\n"); 5479 zfs_prefetch_disable = 1; 5480 } 5481#endif 5482 /* Warn about ZFS memory and address space requirements. */ 5483 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5484 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5485 "expect unstable behavior.\n"); 5486 } 5487 if (kmem_size() < 512 * (1 << 20)) { 5488 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5489 "expect unstable behavior.\n"); 5490 printf(" Consider tuning vm.kmem_size and " 5491 "vm.kmem_size_max\n"); 5492 printf(" in /boot/loader.conf.\n"); 5493 } 5494#endif 5495} 5496 5497void 5498arc_fini(void) 5499{ 5500 mutex_enter(&arc_reclaim_lock); 5501 arc_reclaim_thread_exit = TRUE; 5502 /* 5503 * The reclaim thread will set arc_reclaim_thread_exit back to 5504 * FALSE when it is finished exiting; we're waiting for that. 5505 */ 5506 while (arc_reclaim_thread_exit) { 5507 cv_signal(&arc_reclaim_thread_cv); 5508 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5509 } 5510 mutex_exit(&arc_reclaim_lock); 5511 5512 mutex_enter(&arc_user_evicts_lock); 5513 arc_user_evicts_thread_exit = TRUE; 5514 /* 5515 * The user evicts thread will set arc_user_evicts_thread_exit 5516 * to FALSE when it is finished exiting; we're waiting for that. 5517 */ 5518 while (arc_user_evicts_thread_exit) { 5519 cv_signal(&arc_user_evicts_cv); 5520 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5521 } 5522 mutex_exit(&arc_user_evicts_lock); 5523 5524 /* Use TRUE to ensure *all* buffers are evicted */ 5525 arc_flush(NULL, TRUE); 5526 5527 arc_dead = TRUE; 5528 5529 if (arc_ksp != NULL) { 5530 kstat_delete(arc_ksp); 5531 arc_ksp = NULL; 5532 } 5533 5534 mutex_destroy(&arc_reclaim_lock); 5535 cv_destroy(&arc_reclaim_thread_cv); 5536 cv_destroy(&arc_reclaim_waiters_cv); 5537 5538 mutex_destroy(&arc_user_evicts_lock); 5539 cv_destroy(&arc_user_evicts_cv); 5540 5541 refcount_destroy(&arc_anon->arcs_size); 5542 refcount_destroy(&arc_mru->arcs_size); 5543 refcount_destroy(&arc_mru_ghost->arcs_size); 5544 refcount_destroy(&arc_mfu->arcs_size); 5545 refcount_destroy(&arc_mfu_ghost->arcs_size); 5546 refcount_destroy(&arc_l2c_only->arcs_size); 5547 5548 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5549 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5550 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5551 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5552 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5553 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5554 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5555 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5556 5557 buf_fini(); 5558 5559 ASSERT0(arc_loaned_bytes); 5560 5561#ifdef _KERNEL 5562 if (arc_event_lowmem != NULL) 5563 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5564#endif 5565} 5566 5567/* 5568 * Level 2 ARC 5569 * 5570 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5571 * It uses dedicated storage devices to hold cached data, which are populated 5572 * using large infrequent writes. The main role of this cache is to boost 5573 * the performance of random read workloads. The intended L2ARC devices 5574 * include short-stroked disks, solid state disks, and other media with 5575 * substantially faster read latency than disk. 5576 * 5577 * +-----------------------+ 5578 * | ARC | 5579 * +-----------------------+ 5580 * | ^ ^ 5581 * | | | 5582 * l2arc_feed_thread() arc_read() 5583 * | | | 5584 * | l2arc read | 5585 * V | | 5586 * +---------------+ | 5587 * | L2ARC | | 5588 * +---------------+ | 5589 * | ^ | 5590 * l2arc_write() | | 5591 * | | | 5592 * V | | 5593 * +-------+ +-------+ 5594 * | vdev | | vdev | 5595 * | cache | | cache | 5596 * +-------+ +-------+ 5597 * +=========+ .-----. 5598 * : L2ARC : |-_____-| 5599 * : devices : | Disks | 5600 * +=========+ `-_____-' 5601 * 5602 * Read requests are satisfied from the following sources, in order: 5603 * 5604 * 1) ARC 5605 * 2) vdev cache of L2ARC devices 5606 * 3) L2ARC devices 5607 * 4) vdev cache of disks 5608 * 5) disks 5609 * 5610 * Some L2ARC device types exhibit extremely slow write performance. 5611 * To accommodate for this there are some significant differences between 5612 * the L2ARC and traditional cache design: 5613 * 5614 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5615 * the ARC behave as usual, freeing buffers and placing headers on ghost 5616 * lists. The ARC does not send buffers to the L2ARC during eviction as 5617 * this would add inflated write latencies for all ARC memory pressure. 5618 * 5619 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5620 * It does this by periodically scanning buffers from the eviction-end of 5621 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5622 * not already there. It scans until a headroom of buffers is satisfied, 5623 * which itself is a buffer for ARC eviction. If a compressible buffer is 5624 * found during scanning and selected for writing to an L2ARC device, we 5625 * temporarily boost scanning headroom during the next scan cycle to make 5626 * sure we adapt to compression effects (which might significantly reduce 5627 * the data volume we write to L2ARC). The thread that does this is 5628 * l2arc_feed_thread(), illustrated below; example sizes are included to 5629 * provide a better sense of ratio than this diagram: 5630 * 5631 * head --> tail 5632 * +---------------------+----------+ 5633 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5634 * +---------------------+----------+ | o L2ARC eligible 5635 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5636 * +---------------------+----------+ | 5637 * 15.9 Gbytes ^ 32 Mbytes | 5638 * headroom | 5639 * l2arc_feed_thread() 5640 * | 5641 * l2arc write hand <--[oooo]--' 5642 * | 8 Mbyte 5643 * | write max 5644 * V 5645 * +==============================+ 5646 * L2ARC dev |####|#|###|###| |####| ... | 5647 * +==============================+ 5648 * 32 Gbytes 5649 * 5650 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5651 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5652 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5653 * safe to say that this is an uncommon case, since buffers at the end of 5654 * the ARC lists have moved there due to inactivity. 5655 * 5656 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5657 * then the L2ARC simply misses copying some buffers. This serves as a 5658 * pressure valve to prevent heavy read workloads from both stalling the ARC 5659 * with waits and clogging the L2ARC with writes. This also helps prevent 5660 * the potential for the L2ARC to churn if it attempts to cache content too 5661 * quickly, such as during backups of the entire pool. 5662 * 5663 * 5. After system boot and before the ARC has filled main memory, there are 5664 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5665 * lists can remain mostly static. Instead of searching from tail of these 5666 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5667 * for eligible buffers, greatly increasing its chance of finding them. 5668 * 5669 * The L2ARC device write speed is also boosted during this time so that 5670 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5671 * there are no L2ARC reads, and no fear of degrading read performance 5672 * through increased writes. 5673 * 5674 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5675 * the vdev queue can aggregate them into larger and fewer writes. Each 5676 * device is written to in a rotor fashion, sweeping writes through 5677 * available space then repeating. 5678 * 5679 * 7. The L2ARC does not store dirty content. It never needs to flush 5680 * write buffers back to disk based storage. 5681 * 5682 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5683 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5684 * 5685 * The performance of the L2ARC can be tweaked by a number of tunables, which 5686 * may be necessary for different workloads: 5687 * 5688 * l2arc_write_max max write bytes per interval 5689 * l2arc_write_boost extra write bytes during device warmup 5690 * l2arc_noprefetch skip caching prefetched buffers 5691 * l2arc_headroom number of max device writes to precache 5692 * l2arc_headroom_boost when we find compressed buffers during ARC 5693 * scanning, we multiply headroom by this 5694 * percentage factor for the next scan cycle, 5695 * since more compressed buffers are likely to 5696 * be present 5697 * l2arc_feed_secs seconds between L2ARC writing 5698 * 5699 * Tunables may be removed or added as future performance improvements are 5700 * integrated, and also may become zpool properties. 5701 * 5702 * There are three key functions that control how the L2ARC warms up: 5703 * 5704 * l2arc_write_eligible() check if a buffer is eligible to cache 5705 * l2arc_write_size() calculate how much to write 5706 * l2arc_write_interval() calculate sleep delay between writes 5707 * 5708 * These three functions determine what to write, how much, and how quickly 5709 * to send writes. 5710 */ 5711 5712static boolean_t 5713l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5714{ 5715 /* 5716 * A buffer is *not* eligible for the L2ARC if it: 5717 * 1. belongs to a different spa. 5718 * 2. is already cached on the L2ARC. 5719 * 3. has an I/O in progress (it may be an incomplete read). 5720 * 4. is flagged not eligible (zfs property). 5721 */ 5722 if (hdr->b_spa != spa_guid) { 5723 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5724 return (B_FALSE); 5725 } 5726 if (HDR_HAS_L2HDR(hdr)) { 5727 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5728 return (B_FALSE); 5729 } 5730 if (HDR_IO_IN_PROGRESS(hdr)) { 5731 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5732 return (B_FALSE); 5733 } 5734 if (!HDR_L2CACHE(hdr)) { 5735 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5736 return (B_FALSE); 5737 } 5738 5739 return (B_TRUE); 5740} 5741 5742static uint64_t 5743l2arc_write_size(void) 5744{ 5745 uint64_t size; 5746 5747 /* 5748 * Make sure our globals have meaningful values in case the user 5749 * altered them. 5750 */ 5751 size = l2arc_write_max; 5752 if (size == 0) { 5753 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5754 "be greater than zero, resetting it to the default (%d)", 5755 L2ARC_WRITE_SIZE); 5756 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5757 } 5758 5759 if (arc_warm == B_FALSE) 5760 size += l2arc_write_boost; 5761 5762 return (size); 5763 5764} 5765 5766static clock_t 5767l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5768{ 5769 clock_t interval, next, now; 5770 5771 /* 5772 * If the ARC lists are busy, increase our write rate; if the 5773 * lists are stale, idle back. This is achieved by checking 5774 * how much we previously wrote - if it was more than half of 5775 * what we wanted, schedule the next write much sooner. 5776 */ 5777 if (l2arc_feed_again && wrote > (wanted / 2)) 5778 interval = (hz * l2arc_feed_min_ms) / 1000; 5779 else 5780 interval = hz * l2arc_feed_secs; 5781 5782 now = ddi_get_lbolt(); 5783 next = MAX(now, MIN(now + interval, began + interval)); 5784 5785 return (next); 5786} 5787 5788/* 5789 * Cycle through L2ARC devices. This is how L2ARC load balances. 5790 * If a device is returned, this also returns holding the spa config lock. 5791 */ 5792static l2arc_dev_t * 5793l2arc_dev_get_next(void) 5794{ 5795 l2arc_dev_t *first, *next = NULL; 5796 5797 /* 5798 * Lock out the removal of spas (spa_namespace_lock), then removal 5799 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5800 * both locks will be dropped and a spa config lock held instead. 5801 */ 5802 mutex_enter(&spa_namespace_lock); 5803 mutex_enter(&l2arc_dev_mtx); 5804 5805 /* if there are no vdevs, there is nothing to do */ 5806 if (l2arc_ndev == 0) 5807 goto out; 5808 5809 first = NULL; 5810 next = l2arc_dev_last; 5811 do { 5812 /* loop around the list looking for a non-faulted vdev */ 5813 if (next == NULL) { 5814 next = list_head(l2arc_dev_list); 5815 } else { 5816 next = list_next(l2arc_dev_list, next); 5817 if (next == NULL) 5818 next = list_head(l2arc_dev_list); 5819 } 5820 5821 /* if we have come back to the start, bail out */ 5822 if (first == NULL) 5823 first = next; 5824 else if (next == first) 5825 break; 5826 5827 } while (vdev_is_dead(next->l2ad_vdev)); 5828 5829 /* if we were unable to find any usable vdevs, return NULL */ 5830 if (vdev_is_dead(next->l2ad_vdev)) 5831 next = NULL; 5832 5833 l2arc_dev_last = next; 5834 5835out: 5836 mutex_exit(&l2arc_dev_mtx); 5837 5838 /* 5839 * Grab the config lock to prevent the 'next' device from being 5840 * removed while we are writing to it. 5841 */ 5842 if (next != NULL) 5843 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5844 mutex_exit(&spa_namespace_lock); 5845 5846 return (next); 5847} 5848 5849/* 5850 * Free buffers that were tagged for destruction. 5851 */ 5852static void 5853l2arc_do_free_on_write() 5854{ 5855 list_t *buflist; 5856 l2arc_data_free_t *df, *df_prev; 5857 5858 mutex_enter(&l2arc_free_on_write_mtx); 5859 buflist = l2arc_free_on_write; 5860 5861 for (df = list_tail(buflist); df; df = df_prev) { 5862 df_prev = list_prev(buflist, df); 5863 ASSERT(df->l2df_data != NULL); 5864 ASSERT(df->l2df_func != NULL); 5865 df->l2df_func(df->l2df_data, df->l2df_size); 5866 list_remove(buflist, df); 5867 kmem_free(df, sizeof (l2arc_data_free_t)); 5868 } 5869 5870 mutex_exit(&l2arc_free_on_write_mtx); 5871} 5872 5873/* 5874 * A write to a cache device has completed. Update all headers to allow 5875 * reads from these buffers to begin. 5876 */ 5877static void 5878l2arc_write_done(zio_t *zio) 5879{ 5880 l2arc_write_callback_t *cb; 5881 l2arc_dev_t *dev; 5882 list_t *buflist; 5883 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5884 kmutex_t *hash_lock; 5885 int64_t bytes_dropped = 0; 5886 5887 cb = zio->io_private; 5888 ASSERT(cb != NULL); 5889 dev = cb->l2wcb_dev; 5890 ASSERT(dev != NULL); 5891 head = cb->l2wcb_head; 5892 ASSERT(head != NULL); 5893 buflist = &dev->l2ad_buflist; 5894 ASSERT(buflist != NULL); 5895 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5896 l2arc_write_callback_t *, cb); 5897 5898 if (zio->io_error != 0) 5899 ARCSTAT_BUMP(arcstat_l2_writes_error); 5900 5901 /* 5902 * All writes completed, or an error was hit. 5903 */ 5904top: 5905 mutex_enter(&dev->l2ad_mtx); 5906 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5907 hdr_prev = list_prev(buflist, hdr); 5908 5909 hash_lock = HDR_LOCK(hdr); 5910 5911 /* 5912 * We cannot use mutex_enter or else we can deadlock 5913 * with l2arc_write_buffers (due to swapping the order 5914 * the hash lock and l2ad_mtx are taken). 5915 */ 5916 if (!mutex_tryenter(hash_lock)) { 5917 /* 5918 * Missed the hash lock. We must retry so we 5919 * don't leave the ARC_FLAG_L2_WRITING bit set. 5920 */ 5921 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 5922 5923 /* 5924 * We don't want to rescan the headers we've 5925 * already marked as having been written out, so 5926 * we reinsert the head node so we can pick up 5927 * where we left off. 5928 */ 5929 list_remove(buflist, head); 5930 list_insert_after(buflist, hdr, head); 5931 5932 mutex_exit(&dev->l2ad_mtx); 5933 5934 /* 5935 * We wait for the hash lock to become available 5936 * to try and prevent busy waiting, and increase 5937 * the chance we'll be able to acquire the lock 5938 * the next time around. 5939 */ 5940 mutex_enter(hash_lock); 5941 mutex_exit(hash_lock); 5942 goto top; 5943 } 5944 5945 /* 5946 * We could not have been moved into the arc_l2c_only 5947 * state while in-flight due to our ARC_FLAG_L2_WRITING 5948 * bit being set. Let's just ensure that's being enforced. 5949 */ 5950 ASSERT(HDR_HAS_L1HDR(hdr)); 5951 5952 /* 5953 * We may have allocated a buffer for L2ARC compression, 5954 * we must release it to avoid leaking this data. 5955 */ 5956 l2arc_release_cdata_buf(hdr); 5957 5958 if (zio->io_error != 0) { 5959 /* 5960 * Error - drop L2ARC entry. 5961 */ 5962 list_remove(buflist, hdr); 5963 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 5964 hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0); 5965 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5966 5967 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5968 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5969 5970 bytes_dropped += hdr->b_l2hdr.b_asize; 5971 (void) refcount_remove_many(&dev->l2ad_alloc, 5972 hdr->b_l2hdr.b_asize, hdr); 5973 } 5974 5975 /* 5976 * Allow ARC to begin reads and ghost list evictions to 5977 * this L2ARC entry. 5978 */ 5979 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5980 5981 mutex_exit(hash_lock); 5982 } 5983 5984 atomic_inc_64(&l2arc_writes_done); 5985 list_remove(buflist, head); 5986 ASSERT(!HDR_HAS_L1HDR(head)); 5987 kmem_cache_free(hdr_l2only_cache, head); 5988 mutex_exit(&dev->l2ad_mtx); 5989 5990 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5991 5992 l2arc_do_free_on_write(); 5993 5994 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5995} 5996 5997/* 5998 * A read to a cache device completed. Validate buffer contents before 5999 * handing over to the regular ARC routines. 6000 */ 6001static void 6002l2arc_read_done(zio_t *zio) 6003{ 6004 l2arc_read_callback_t *cb; 6005 arc_buf_hdr_t *hdr; 6006 arc_buf_t *buf; 6007 kmutex_t *hash_lock; 6008 int equal; 6009 6010 ASSERT(zio->io_vd != NULL); 6011 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6012 6013 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6014 6015 cb = zio->io_private; 6016 ASSERT(cb != NULL); 6017 buf = cb->l2rcb_buf; 6018 ASSERT(buf != NULL); 6019 6020 hash_lock = HDR_LOCK(buf->b_hdr); 6021 mutex_enter(hash_lock); 6022 hdr = buf->b_hdr; 6023 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6024 6025 /* 6026 * If the buffer was compressed, decompress it first. 6027 */ 6028 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6029 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6030 ASSERT(zio->io_data != NULL); 6031 6032 /* 6033 * Check this survived the L2ARC journey. 6034 */ 6035 equal = arc_cksum_equal(buf); 6036 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6037 mutex_exit(hash_lock); 6038 zio->io_private = buf; 6039 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6040 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6041 arc_read_done(zio); 6042 } else { 6043 mutex_exit(hash_lock); 6044 /* 6045 * Buffer didn't survive caching. Increment stats and 6046 * reissue to the original storage device. 6047 */ 6048 if (zio->io_error != 0) { 6049 ARCSTAT_BUMP(arcstat_l2_io_error); 6050 } else { 6051 zio->io_error = SET_ERROR(EIO); 6052 } 6053 if (!equal) 6054 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6055 6056 /* 6057 * If there's no waiter, issue an async i/o to the primary 6058 * storage now. If there *is* a waiter, the caller must 6059 * issue the i/o in a context where it's OK to block. 6060 */ 6061 if (zio->io_waiter == NULL) { 6062 zio_t *pio = zio_unique_parent(zio); 6063 6064 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6065 6066 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6067 buf->b_data, zio->io_size, arc_read_done, buf, 6068 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6069 } 6070 } 6071 6072 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6073} 6074 6075/* 6076 * This is the list priority from which the L2ARC will search for pages to 6077 * cache. This is used within loops (0..3) to cycle through lists in the 6078 * desired order. This order can have a significant effect on cache 6079 * performance. 6080 * 6081 * Currently the metadata lists are hit first, MFU then MRU, followed by 6082 * the data lists. This function returns a locked list, and also returns 6083 * the lock pointer. 6084 */ 6085static multilist_sublist_t * 6086l2arc_sublist_lock(int list_num) 6087{ 6088 multilist_t *ml = NULL; 6089 unsigned int idx; 6090 6091 ASSERT(list_num >= 0 && list_num <= 3); 6092 6093 switch (list_num) { 6094 case 0: 6095 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6096 break; 6097 case 1: 6098 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6099 break; 6100 case 2: 6101 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6102 break; 6103 case 3: 6104 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6105 break; 6106 } 6107 6108 /* 6109 * Return a randomly-selected sublist. This is acceptable 6110 * because the caller feeds only a little bit of data for each 6111 * call (8MB). Subsequent calls will result in different 6112 * sublists being selected. 6113 */ 6114 idx = multilist_get_random_index(ml); 6115 return (multilist_sublist_lock(ml, idx)); 6116} 6117 6118/* 6119 * Evict buffers from the device write hand to the distance specified in 6120 * bytes. This distance may span populated buffers, it may span nothing. 6121 * This is clearing a region on the L2ARC device ready for writing. 6122 * If the 'all' boolean is set, every buffer is evicted. 6123 */ 6124static void 6125l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6126{ 6127 list_t *buflist; 6128 arc_buf_hdr_t *hdr, *hdr_prev; 6129 kmutex_t *hash_lock; 6130 uint64_t taddr; 6131 6132 buflist = &dev->l2ad_buflist; 6133 6134 if (!all && dev->l2ad_first) { 6135 /* 6136 * This is the first sweep through the device. There is 6137 * nothing to evict. 6138 */ 6139 return; 6140 } 6141 6142 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6143 /* 6144 * When nearing the end of the device, evict to the end 6145 * before the device write hand jumps to the start. 6146 */ 6147 taddr = dev->l2ad_end; 6148 } else { 6149 taddr = dev->l2ad_hand + distance; 6150 } 6151 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6152 uint64_t, taddr, boolean_t, all); 6153 6154top: 6155 mutex_enter(&dev->l2ad_mtx); 6156 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6157 hdr_prev = list_prev(buflist, hdr); 6158 6159 hash_lock = HDR_LOCK(hdr); 6160 6161 /* 6162 * We cannot use mutex_enter or else we can deadlock 6163 * with l2arc_write_buffers (due to swapping the order 6164 * the hash lock and l2ad_mtx are taken). 6165 */ 6166 if (!mutex_tryenter(hash_lock)) { 6167 /* 6168 * Missed the hash lock. Retry. 6169 */ 6170 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6171 mutex_exit(&dev->l2ad_mtx); 6172 mutex_enter(hash_lock); 6173 mutex_exit(hash_lock); 6174 goto top; 6175 } 6176 6177 if (HDR_L2_WRITE_HEAD(hdr)) { 6178 /* 6179 * We hit a write head node. Leave it for 6180 * l2arc_write_done(). 6181 */ 6182 list_remove(buflist, hdr); 6183 mutex_exit(hash_lock); 6184 continue; 6185 } 6186 6187 if (!all && HDR_HAS_L2HDR(hdr) && 6188 (hdr->b_l2hdr.b_daddr > taddr || 6189 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6190 /* 6191 * We've evicted to the target address, 6192 * or the end of the device. 6193 */ 6194 mutex_exit(hash_lock); 6195 break; 6196 } 6197 6198 ASSERT(HDR_HAS_L2HDR(hdr)); 6199 if (!HDR_HAS_L1HDR(hdr)) { 6200 ASSERT(!HDR_L2_READING(hdr)); 6201 /* 6202 * This doesn't exist in the ARC. Destroy. 6203 * arc_hdr_destroy() will call list_remove() 6204 * and decrement arcstat_l2_size. 6205 */ 6206 arc_change_state(arc_anon, hdr, hash_lock); 6207 arc_hdr_destroy(hdr); 6208 } else { 6209 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6210 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6211 /* 6212 * Invalidate issued or about to be issued 6213 * reads, since we may be about to write 6214 * over this location. 6215 */ 6216 if (HDR_L2_READING(hdr)) { 6217 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6218 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6219 } 6220 6221 /* Ensure this header has finished being written */ 6222 ASSERT(!HDR_L2_WRITING(hdr)); 6223 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6224 6225 arc_hdr_l2hdr_destroy(hdr); 6226 } 6227 mutex_exit(hash_lock); 6228 } 6229 mutex_exit(&dev->l2ad_mtx); 6230} 6231 6232/* 6233 * Find and write ARC buffers to the L2ARC device. 6234 * 6235 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6236 * for reading until they have completed writing. 6237 * The headroom_boost is an in-out parameter used to maintain headroom boost 6238 * state between calls to this function. 6239 * 6240 * Returns the number of bytes actually written (which may be smaller than 6241 * the delta by which the device hand has changed due to alignment). 6242 */ 6243static uint64_t 6244l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6245 boolean_t *headroom_boost) 6246{ 6247 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6248 uint64_t write_asize, write_sz, headroom, buf_compress_minsz; 6249 void *buf_data; 6250 boolean_t full; 6251 l2arc_write_callback_t *cb; 6252 zio_t *pio, *wzio; 6253 uint64_t guid = spa_load_guid(spa); 6254 const boolean_t do_headroom_boost = *headroom_boost; 6255 int try; 6256 6257 ASSERT(dev->l2ad_vdev != NULL); 6258 6259 /* Lower the flag now, we might want to raise it again later. */ 6260 *headroom_boost = B_FALSE; 6261 6262 pio = NULL; 6263 write_sz = write_asize = 0; 6264 full = B_FALSE; 6265 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6266 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6267 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6268 6269 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6270 /* 6271 * We will want to try to compress buffers that are at least 2x the 6272 * device sector size. 6273 */ 6274 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6275 6276 /* 6277 * Copy buffers for L2ARC writing. 6278 */ 6279 for (try = 0; try <= 3; try++) { 6280 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6281 uint64_t passed_sz = 0; 6282 6283 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6284 6285 /* 6286 * L2ARC fast warmup. 6287 * 6288 * Until the ARC is warm and starts to evict, read from the 6289 * head of the ARC lists rather than the tail. 6290 */ 6291 if (arc_warm == B_FALSE) 6292 hdr = multilist_sublist_head(mls); 6293 else 6294 hdr = multilist_sublist_tail(mls); 6295 if (hdr == NULL) 6296 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6297 6298 headroom = target_sz * l2arc_headroom; 6299 if (do_headroom_boost) 6300 headroom = (headroom * l2arc_headroom_boost) / 100; 6301 6302 for (; hdr; hdr = hdr_prev) { 6303 kmutex_t *hash_lock; 6304 uint64_t buf_sz; 6305 uint64_t buf_a_sz; 6306 6307 if (arc_warm == B_FALSE) 6308 hdr_prev = multilist_sublist_next(mls, hdr); 6309 else 6310 hdr_prev = multilist_sublist_prev(mls, hdr); 6311 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 6312 6313 hash_lock = HDR_LOCK(hdr); 6314 if (!mutex_tryenter(hash_lock)) { 6315 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 6316 /* 6317 * Skip this buffer rather than waiting. 6318 */ 6319 continue; 6320 } 6321 6322 passed_sz += hdr->b_size; 6323 if (passed_sz > headroom) { 6324 /* 6325 * Searched too far. 6326 */ 6327 mutex_exit(hash_lock); 6328 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 6329 break; 6330 } 6331 6332 if (!l2arc_write_eligible(guid, hdr)) { 6333 mutex_exit(hash_lock); 6334 continue; 6335 } 6336 6337 /* 6338 * Assume that the buffer is not going to be compressed 6339 * and could take more space on disk because of a larger 6340 * disk block size. 6341 */ 6342 buf_sz = hdr->b_size; 6343 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6344 6345 if ((write_asize + buf_a_sz) > target_sz) { 6346 full = B_TRUE; 6347 mutex_exit(hash_lock); 6348 ARCSTAT_BUMP(arcstat_l2_write_full); 6349 break; 6350 } 6351 6352 if (pio == NULL) { 6353 /* 6354 * Insert a dummy header on the buflist so 6355 * l2arc_write_done() can find where the 6356 * write buffers begin without searching. 6357 */ 6358 mutex_enter(&dev->l2ad_mtx); 6359 list_insert_head(&dev->l2ad_buflist, head); 6360 mutex_exit(&dev->l2ad_mtx); 6361 6362 cb = kmem_alloc( 6363 sizeof (l2arc_write_callback_t), KM_SLEEP); 6364 cb->l2wcb_dev = dev; 6365 cb->l2wcb_head = head; 6366 pio = zio_root(spa, l2arc_write_done, cb, 6367 ZIO_FLAG_CANFAIL); 6368 ARCSTAT_BUMP(arcstat_l2_write_pios); 6369 } 6370 6371 /* 6372 * Create and add a new L2ARC header. 6373 */ 6374 hdr->b_l2hdr.b_dev = dev; 6375 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6376 /* 6377 * Temporarily stash the data buffer in b_tmp_cdata. 6378 * The subsequent write step will pick it up from 6379 * there. This is because can't access b_l1hdr.b_buf 6380 * without holding the hash_lock, which we in turn 6381 * can't access without holding the ARC list locks 6382 * (which we want to avoid during compression/writing). 6383 */ 6384 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 6385 hdr->b_l2hdr.b_asize = hdr->b_size; 6386 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6387 6388 /* 6389 * Explicitly set the b_daddr field to a known 6390 * value which means "invalid address". This 6391 * enables us to differentiate which stage of 6392 * l2arc_write_buffers() the particular header 6393 * is in (e.g. this loop, or the one below). 6394 * ARC_FLAG_L2_WRITING is not enough to make 6395 * this distinction, and we need to know in 6396 * order to do proper l2arc vdev accounting in 6397 * arc_release() and arc_hdr_destroy(). 6398 * 6399 * Note, we can't use a new flag to distinguish 6400 * the two stages because we don't hold the 6401 * header's hash_lock below, in the second stage 6402 * of this function. Thus, we can't simply 6403 * change the b_flags field to denote that the 6404 * IO has been sent. We can change the b_daddr 6405 * field of the L2 portion, though, since we'll 6406 * be holding the l2ad_mtx; which is why we're 6407 * using it to denote the header's state change. 6408 */ 6409 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6410 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6411 6412 mutex_enter(&dev->l2ad_mtx); 6413 list_insert_head(&dev->l2ad_buflist, hdr); 6414 mutex_exit(&dev->l2ad_mtx); 6415 6416 /* 6417 * Compute and store the buffer cksum before 6418 * writing. On debug the cksum is verified first. 6419 */ 6420 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6421 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6422 6423 mutex_exit(hash_lock); 6424 6425 write_sz += buf_sz; 6426 write_asize += buf_a_sz; 6427 } 6428 6429 multilist_sublist_unlock(mls); 6430 6431 if (full == B_TRUE) 6432 break; 6433 } 6434 6435 /* No buffers selected for writing? */ 6436 if (pio == NULL) { 6437 ASSERT0(write_sz); 6438 ASSERT(!HDR_HAS_L1HDR(head)); 6439 kmem_cache_free(hdr_l2only_cache, head); 6440 return (0); 6441 } 6442 6443 mutex_enter(&dev->l2ad_mtx); 6444 6445 /* 6446 * Note that elsewhere in this file arcstat_l2_asize 6447 * and the used space on l2ad_vdev are updated using b_asize, 6448 * which is not necessarily rounded up to the device block size. 6449 * Too keep accounting consistent we do the same here as well: 6450 * stats_size accumulates the sum of b_asize of the written buffers, 6451 * while write_asize accumulates the sum of b_asize rounded up 6452 * to the device block size. 6453 * The latter sum is used only to validate the corectness of the code. 6454 */ 6455 uint64_t stats_size = 0; 6456 write_asize = 0; 6457 6458 /* 6459 * Now start writing the buffers. We're starting at the write head 6460 * and work backwards, retracing the course of the buffer selector 6461 * loop above. 6462 */ 6463 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6464 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6465 uint64_t buf_sz; 6466 6467 /* 6468 * We rely on the L1 portion of the header below, so 6469 * it's invalid for this header to have been evicted out 6470 * of the ghost cache, prior to being written out. The 6471 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6472 */ 6473 ASSERT(HDR_HAS_L1HDR(hdr)); 6474 6475 /* 6476 * We shouldn't need to lock the buffer here, since we flagged 6477 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6478 * take care to only access its L2 cache parameters. In 6479 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6480 * ARC eviction. 6481 */ 6482 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6483 6484 if ((HDR_L2COMPRESS(hdr)) && 6485 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 6486 if (l2arc_compress_buf(hdr)) { 6487 /* 6488 * If compression succeeded, enable headroom 6489 * boost on the next scan cycle. 6490 */ 6491 *headroom_boost = B_TRUE; 6492 } 6493 } 6494 6495 /* 6496 * Pick up the buffer data we had previously stashed away 6497 * (and now potentially also compressed). 6498 */ 6499 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6500 buf_sz = hdr->b_l2hdr.b_asize; 6501 6502 /* 6503 * We need to do this regardless if buf_sz is zero or 6504 * not, otherwise, when this l2hdr is evicted we'll 6505 * remove a reference that was never added. 6506 */ 6507 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6508 6509 /* Compression may have squashed the buffer to zero length. */ 6510 if (buf_sz != 0) { 6511 uint64_t buf_a_sz; 6512 6513 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6514 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6515 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6516 ZIO_FLAG_CANFAIL, B_FALSE); 6517 6518 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6519 zio_t *, wzio); 6520 (void) zio_nowait(wzio); 6521 6522 stats_size += buf_sz; 6523 6524 /* 6525 * Keep the clock hand suitably device-aligned. 6526 */ 6527 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6528 write_asize += buf_a_sz; 6529 dev->l2ad_hand += buf_a_sz; 6530 } 6531 } 6532 6533 mutex_exit(&dev->l2ad_mtx); 6534 6535 ASSERT3U(write_asize, <=, target_sz); 6536 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6537 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6538 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6539 ARCSTAT_INCR(arcstat_l2_asize, stats_size); 6540 vdev_space_update(dev->l2ad_vdev, stats_size, 0, 0); 6541 6542 /* 6543 * Bump device hand to the device start if it is approaching the end. 6544 * l2arc_evict() will already have evicted ahead for this case. 6545 */ 6546 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6547 dev->l2ad_hand = dev->l2ad_start; 6548 dev->l2ad_first = B_FALSE; 6549 } 6550 6551 dev->l2ad_writing = B_TRUE; 6552 (void) zio_wait(pio); 6553 dev->l2ad_writing = B_FALSE; 6554 6555 return (write_asize); 6556} 6557 6558/* 6559 * Compresses an L2ARC buffer. 6560 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6561 * size in l2hdr->b_asize. This routine tries to compress the data and 6562 * depending on the compression result there are three possible outcomes: 6563 * *) The buffer was incompressible. The original l2hdr contents were left 6564 * untouched and are ready for writing to an L2 device. 6565 * *) The buffer was all-zeros, so there is no need to write it to an L2 6566 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6567 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6568 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6569 * data buffer which holds the compressed data to be written, and b_asize 6570 * tells us how much data there is. b_compress is set to the appropriate 6571 * compression algorithm. Once writing is done, invoke 6572 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6573 * 6574 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6575 * buffer was incompressible). 6576 */ 6577static boolean_t 6578l2arc_compress_buf(arc_buf_hdr_t *hdr) 6579{ 6580 void *cdata; 6581 size_t csize, len, rounded; 6582 ASSERT(HDR_HAS_L2HDR(hdr)); 6583 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6584 6585 ASSERT(HDR_HAS_L1HDR(hdr)); 6586 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 6587 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6588 6589 len = l2hdr->b_asize; 6590 cdata = zio_data_buf_alloc(len); 6591 ASSERT3P(cdata, !=, NULL); 6592 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6593 cdata, l2hdr->b_asize); 6594 6595 if (csize == 0) { 6596 /* zero block, indicate that there's nothing to write */ 6597 zio_data_buf_free(cdata, len); 6598 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 6599 l2hdr->b_asize = 0; 6600 hdr->b_l1hdr.b_tmp_cdata = NULL; 6601 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6602 return (B_TRUE); 6603 } 6604 6605 rounded = P2ROUNDUP(csize, 6606 (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift); 6607 if (rounded < len) { 6608 /* 6609 * Compression succeeded, we'll keep the cdata around for 6610 * writing and release it afterwards. 6611 */ 6612 if (rounded > csize) { 6613 bzero((char *)cdata + csize, rounded - csize); 6614 csize = rounded; 6615 } 6616 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 6617 l2hdr->b_asize = csize; 6618 hdr->b_l1hdr.b_tmp_cdata = cdata; 6619 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6620 return (B_TRUE); 6621 } else { 6622 /* 6623 * Compression failed, release the compressed buffer. 6624 * l2hdr will be left unmodified. 6625 */ 6626 zio_data_buf_free(cdata, len); 6627 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6628 return (B_FALSE); 6629 } 6630} 6631 6632/* 6633 * Decompresses a zio read back from an l2arc device. On success, the 6634 * underlying zio's io_data buffer is overwritten by the uncompressed 6635 * version. On decompression error (corrupt compressed stream), the 6636 * zio->io_error value is set to signal an I/O error. 6637 * 6638 * Please note that the compressed data stream is not checksummed, so 6639 * if the underlying device is experiencing data corruption, we may feed 6640 * corrupt data to the decompressor, so the decompressor needs to be 6641 * able to handle this situation (LZ4 does). 6642 */ 6643static void 6644l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6645{ 6646 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6647 6648 if (zio->io_error != 0) { 6649 /* 6650 * An io error has occured, just restore the original io 6651 * size in preparation for a main pool read. 6652 */ 6653 zio->io_orig_size = zio->io_size = hdr->b_size; 6654 return; 6655 } 6656 6657 if (c == ZIO_COMPRESS_EMPTY) { 6658 /* 6659 * An empty buffer results in a null zio, which means we 6660 * need to fill its io_data after we're done restoring the 6661 * buffer's contents. 6662 */ 6663 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6664 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6665 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6666 } else { 6667 ASSERT(zio->io_data != NULL); 6668 /* 6669 * We copy the compressed data from the start of the arc buffer 6670 * (the zio_read will have pulled in only what we need, the 6671 * rest is garbage which we will overwrite at decompression) 6672 * and then decompress back to the ARC data buffer. This way we 6673 * can minimize copying by simply decompressing back over the 6674 * original compressed data (rather than decompressing to an 6675 * aux buffer and then copying back the uncompressed buffer, 6676 * which is likely to be much larger). 6677 */ 6678 uint64_t csize; 6679 void *cdata; 6680 6681 csize = zio->io_size; 6682 cdata = zio_data_buf_alloc(csize); 6683 bcopy(zio->io_data, cdata, csize); 6684 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6685 hdr->b_size) != 0) 6686 zio->io_error = EIO; 6687 zio_data_buf_free(cdata, csize); 6688 } 6689 6690 /* Restore the expected uncompressed IO size. */ 6691 zio->io_orig_size = zio->io_size = hdr->b_size; 6692} 6693 6694/* 6695 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6696 * This buffer serves as a temporary holder of compressed data while 6697 * the buffer entry is being written to an l2arc device. Once that is 6698 * done, we can dispose of it. 6699 */ 6700static void 6701l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6702{ 6703 enum zio_compress comp = HDR_GET_COMPRESS(hdr); 6704 6705 ASSERT(HDR_HAS_L1HDR(hdr)); 6706 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6707 6708 if (comp == ZIO_COMPRESS_OFF) { 6709 /* 6710 * In this case, b_tmp_cdata points to the same buffer 6711 * as the arc_buf_t's b_data field. We don't want to 6712 * free it, since the arc_buf_t will handle that. 6713 */ 6714 hdr->b_l1hdr.b_tmp_cdata = NULL; 6715 } else if (comp == ZIO_COMPRESS_EMPTY) { 6716 /* 6717 * In this case, b_tmp_cdata was compressed to an empty 6718 * buffer, thus there's nothing to free and b_tmp_cdata 6719 * should have been set to NULL in l2arc_write_buffers(). 6720 */ 6721 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6722 } else { 6723 /* 6724 * If the data was compressed, then we've allocated a 6725 * temporary buffer for it, so now we need to release it. 6726 */ 6727 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6728 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6729 hdr->b_size); 6730 hdr->b_l1hdr.b_tmp_cdata = NULL; 6731 } 6732 6733} 6734 6735/* 6736 * This thread feeds the L2ARC at regular intervals. This is the beating 6737 * heart of the L2ARC. 6738 */ 6739static void 6740l2arc_feed_thread(void *dummy __unused) 6741{ 6742 callb_cpr_t cpr; 6743 l2arc_dev_t *dev; 6744 spa_t *spa; 6745 uint64_t size, wrote; 6746 clock_t begin, next = ddi_get_lbolt(); 6747 boolean_t headroom_boost = B_FALSE; 6748 6749 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6750 6751 mutex_enter(&l2arc_feed_thr_lock); 6752 6753 while (l2arc_thread_exit == 0) { 6754 CALLB_CPR_SAFE_BEGIN(&cpr); 6755 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6756 next - ddi_get_lbolt()); 6757 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6758 next = ddi_get_lbolt() + hz; 6759 6760 /* 6761 * Quick check for L2ARC devices. 6762 */ 6763 mutex_enter(&l2arc_dev_mtx); 6764 if (l2arc_ndev == 0) { 6765 mutex_exit(&l2arc_dev_mtx); 6766 continue; 6767 } 6768 mutex_exit(&l2arc_dev_mtx); 6769 begin = ddi_get_lbolt(); 6770 6771 /* 6772 * This selects the next l2arc device to write to, and in 6773 * doing so the next spa to feed from: dev->l2ad_spa. This 6774 * will return NULL if there are now no l2arc devices or if 6775 * they are all faulted. 6776 * 6777 * If a device is returned, its spa's config lock is also 6778 * held to prevent device removal. l2arc_dev_get_next() 6779 * will grab and release l2arc_dev_mtx. 6780 */ 6781 if ((dev = l2arc_dev_get_next()) == NULL) 6782 continue; 6783 6784 spa = dev->l2ad_spa; 6785 ASSERT(spa != NULL); 6786 6787 /* 6788 * If the pool is read-only then force the feed thread to 6789 * sleep a little longer. 6790 */ 6791 if (!spa_writeable(spa)) { 6792 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6793 spa_config_exit(spa, SCL_L2ARC, dev); 6794 continue; 6795 } 6796 6797 /* 6798 * Avoid contributing to memory pressure. 6799 */ 6800 if (arc_reclaim_needed()) { 6801 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6802 spa_config_exit(spa, SCL_L2ARC, dev); 6803 continue; 6804 } 6805 6806 ARCSTAT_BUMP(arcstat_l2_feeds); 6807 6808 size = l2arc_write_size(); 6809 6810 /* 6811 * Evict L2ARC buffers that will be overwritten. 6812 */ 6813 l2arc_evict(dev, size, B_FALSE); 6814 6815 /* 6816 * Write ARC buffers. 6817 */ 6818 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6819 6820 /* 6821 * Calculate interval between writes. 6822 */ 6823 next = l2arc_write_interval(begin, size, wrote); 6824 spa_config_exit(spa, SCL_L2ARC, dev); 6825 } 6826 6827 l2arc_thread_exit = 0; 6828 cv_broadcast(&l2arc_feed_thr_cv); 6829 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6830 thread_exit(); 6831} 6832 6833boolean_t 6834l2arc_vdev_present(vdev_t *vd) 6835{ 6836 l2arc_dev_t *dev; 6837 6838 mutex_enter(&l2arc_dev_mtx); 6839 for (dev = list_head(l2arc_dev_list); dev != NULL; 6840 dev = list_next(l2arc_dev_list, dev)) { 6841 if (dev->l2ad_vdev == vd) 6842 break; 6843 } 6844 mutex_exit(&l2arc_dev_mtx); 6845 6846 return (dev != NULL); 6847} 6848 6849/* 6850 * Add a vdev for use by the L2ARC. By this point the spa has already 6851 * validated the vdev and opened it. 6852 */ 6853void 6854l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6855{ 6856 l2arc_dev_t *adddev; 6857 6858 ASSERT(!l2arc_vdev_present(vd)); 6859 6860 vdev_ashift_optimize(vd); 6861 6862 /* 6863 * Create a new l2arc device entry. 6864 */ 6865 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6866 adddev->l2ad_spa = spa; 6867 adddev->l2ad_vdev = vd; 6868 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6869 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6870 adddev->l2ad_hand = adddev->l2ad_start; 6871 adddev->l2ad_first = B_TRUE; 6872 adddev->l2ad_writing = B_FALSE; 6873 6874 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6875 /* 6876 * This is a list of all ARC buffers that are still valid on the 6877 * device. 6878 */ 6879 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6880 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6881 6882 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6883 refcount_create(&adddev->l2ad_alloc); 6884 6885 /* 6886 * Add device to global list 6887 */ 6888 mutex_enter(&l2arc_dev_mtx); 6889 list_insert_head(l2arc_dev_list, adddev); 6890 atomic_inc_64(&l2arc_ndev); 6891 mutex_exit(&l2arc_dev_mtx); 6892} 6893 6894/* 6895 * Remove a vdev from the L2ARC. 6896 */ 6897void 6898l2arc_remove_vdev(vdev_t *vd) 6899{ 6900 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6901 6902 /* 6903 * Find the device by vdev 6904 */ 6905 mutex_enter(&l2arc_dev_mtx); 6906 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6907 nextdev = list_next(l2arc_dev_list, dev); 6908 if (vd == dev->l2ad_vdev) { 6909 remdev = dev; 6910 break; 6911 } 6912 } 6913 ASSERT(remdev != NULL); 6914 6915 /* 6916 * Remove device from global list 6917 */ 6918 list_remove(l2arc_dev_list, remdev); 6919 l2arc_dev_last = NULL; /* may have been invalidated */ 6920 atomic_dec_64(&l2arc_ndev); 6921 mutex_exit(&l2arc_dev_mtx); 6922 6923 /* 6924 * Clear all buflists and ARC references. L2ARC device flush. 6925 */ 6926 l2arc_evict(remdev, 0, B_TRUE); 6927 list_destroy(&remdev->l2ad_buflist); 6928 mutex_destroy(&remdev->l2ad_mtx); 6929 refcount_destroy(&remdev->l2ad_alloc); 6930 kmem_free(remdev, sizeof (l2arc_dev_t)); 6931} 6932 6933void 6934l2arc_init(void) 6935{ 6936 l2arc_thread_exit = 0; 6937 l2arc_ndev = 0; 6938 l2arc_writes_sent = 0; 6939 l2arc_writes_done = 0; 6940 6941 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6942 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6943 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6944 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6945 6946 l2arc_dev_list = &L2ARC_dev_list; 6947 l2arc_free_on_write = &L2ARC_free_on_write; 6948 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6949 offsetof(l2arc_dev_t, l2ad_node)); 6950 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6951 offsetof(l2arc_data_free_t, l2df_list_node)); 6952} 6953 6954void 6955l2arc_fini(void) 6956{ 6957 /* 6958 * This is called from dmu_fini(), which is called from spa_fini(); 6959 * Because of this, we can assume that all l2arc devices have 6960 * already been removed when the pools themselves were removed. 6961 */ 6962 6963 l2arc_do_free_on_write(); 6964 6965 mutex_destroy(&l2arc_feed_thr_lock); 6966 cv_destroy(&l2arc_feed_thr_cv); 6967 mutex_destroy(&l2arc_dev_mtx); 6968 mutex_destroy(&l2arc_free_on_write_mtx); 6969 6970 list_destroy(l2arc_dev_list); 6971 list_destroy(l2arc_free_on_write); 6972} 6973 6974void 6975l2arc_start(void) 6976{ 6977 if (!(spa_mode_global & FWRITE)) 6978 return; 6979 6980 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6981 TS_RUN, minclsyspri); 6982} 6983 6984void 6985l2arc_stop(void) 6986{ 6987 if (!(spa_mode_global & FWRITE)) 6988 return; 6989 6990 mutex_enter(&l2arc_feed_thr_lock); 6991 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6992 l2arc_thread_exit = 1; 6993 while (l2arc_thread_exit != 0) 6994 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6995 mutex_exit(&l2arc_feed_thr_lock); 6996} 6997