arc.c revision 304139
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, 2016 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 <machine/vmparam.h> 143 144#ifdef illumos 145#ifndef _KERNEL 146/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 147boolean_t arc_watch = B_FALSE; 148int arc_procfd; 149#endif 150#endif /* illumos */ 151 152static kmutex_t arc_reclaim_lock; 153static kcondvar_t arc_reclaim_thread_cv; 154static boolean_t arc_reclaim_thread_exit; 155static kcondvar_t arc_reclaim_waiters_cv; 156 157static kmutex_t arc_user_evicts_lock; 158static kcondvar_t arc_user_evicts_cv; 159static boolean_t arc_user_evicts_thread_exit; 160 161uint_t arc_reduce_dnlc_percent = 3; 162 163/* 164 * The number of headers to evict in arc_evict_state_impl() before 165 * dropping the sublist lock and evicting from another sublist. A lower 166 * value means we're more likely to evict the "correct" header (i.e. the 167 * oldest header in the arc state), but comes with higher overhead 168 * (i.e. more invocations of arc_evict_state_impl()). 169 */ 170int zfs_arc_evict_batch_limit = 10; 171 172/* 173 * The number of sublists used for each of the arc state lists. If this 174 * is not set to a suitable value by the user, it will be configured to 175 * the number of CPUs on the system in arc_init(). 176 */ 177int zfs_arc_num_sublists_per_state = 0; 178 179/* number of seconds before growing cache again */ 180static int arc_grow_retry = 60; 181 182/* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 183int zfs_arc_overflow_shift = 8; 184 185/* shift of arc_c for calculating both min and max arc_p */ 186static int arc_p_min_shift = 4; 187 188/* log2(fraction of arc to reclaim) */ 189static int arc_shrink_shift = 7; 190 191/* 192 * log2(fraction of ARC which must be free to allow growing). 193 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 194 * when reading a new block into the ARC, we will evict an equal-sized block 195 * from the ARC. 196 * 197 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 198 * we will still not allow it to grow. 199 */ 200int arc_no_grow_shift = 5; 201 202 203/* 204 * minimum lifespan of a prefetch block in clock ticks 205 * (initialized in arc_init()) 206 */ 207static int arc_min_prefetch_lifespan; 208 209/* 210 * If this percent of memory is free, don't throttle. 211 */ 212int arc_lotsfree_percent = 10; 213 214static int arc_dead; 215extern boolean_t zfs_prefetch_disable; 216 217/* 218 * The arc has filled available memory and has now warmed up. 219 */ 220static boolean_t arc_warm; 221 222/* 223 * These tunables are for performance analysis. 224 */ 225uint64_t zfs_arc_max; 226uint64_t zfs_arc_min; 227uint64_t zfs_arc_meta_limit = 0; 228uint64_t zfs_arc_meta_min = 0; 229int zfs_arc_grow_retry = 0; 230int zfs_arc_shrink_shift = 0; 231int zfs_arc_p_min_shift = 0; 232int zfs_disable_dup_eviction = 0; 233uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 234u_int zfs_arc_free_target = 0; 235 236/* Absolute min for arc min / max is 16MB. */ 237static uint64_t arc_abs_min = 16 << 20; 238 239static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 240static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 241static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 242static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 243 244#if defined(__FreeBSD__) && defined(_KERNEL) 245static void 246arc_free_target_init(void *unused __unused) 247{ 248 249 zfs_arc_free_target = vm_pageout_wakeup_thresh; 250} 251SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 252 arc_free_target_init, NULL); 253 254TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max); 255TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min); 256TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 257TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 258TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize); 259TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 260SYSCTL_DECL(_vfs_zfs); 261SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 262 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 263SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 264 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 265SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 266 &zfs_arc_average_blocksize, 0, 267 "ARC average blocksize"); 268SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 269 &arc_shrink_shift, 0, 270 "log2(fraction of arc to reclaim)"); 271 272/* 273 * We don't have a tunable for arc_free_target due to the dependency on 274 * pagedaemon initialisation. 275 */ 276SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 277 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 278 sysctl_vfs_zfs_arc_free_target, "IU", 279 "Desired number of free pages below which ARC triggers reclaim"); 280 281static int 282sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 283{ 284 u_int val; 285 int err; 286 287 val = zfs_arc_free_target; 288 err = sysctl_handle_int(oidp, &val, 0, req); 289 if (err != 0 || req->newptr == NULL) 290 return (err); 291 292 if (val < minfree) 293 return (EINVAL); 294 if (val > cnt.v_page_count) 295 return (EINVAL); 296 297 zfs_arc_free_target = val; 298 299 return (0); 300} 301 302/* 303 * Must be declared here, before the definition of corresponding kstat 304 * macro which uses the same names will confuse the compiler. 305 */ 306SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 307 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 308 sysctl_vfs_zfs_arc_meta_limit, "QU", 309 "ARC metadata limit"); 310#endif 311 312/* 313 * Note that buffers can be in one of 6 states: 314 * ARC_anon - anonymous (discussed below) 315 * ARC_mru - recently used, currently cached 316 * ARC_mru_ghost - recentely used, no longer in cache 317 * ARC_mfu - frequently used, currently cached 318 * ARC_mfu_ghost - frequently used, no longer in cache 319 * ARC_l2c_only - exists in L2ARC but not other states 320 * When there are no active references to the buffer, they are 321 * are linked onto a list in one of these arc states. These are 322 * the only buffers that can be evicted or deleted. Within each 323 * state there are multiple lists, one for meta-data and one for 324 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 325 * etc.) is tracked separately so that it can be managed more 326 * explicitly: favored over data, limited explicitly. 327 * 328 * Anonymous buffers are buffers that are not associated with 329 * a DVA. These are buffers that hold dirty block copies 330 * before they are written to stable storage. By definition, 331 * they are "ref'd" and are considered part of arc_mru 332 * that cannot be freed. Generally, they will aquire a DVA 333 * as they are written and migrate onto the arc_mru list. 334 * 335 * The ARC_l2c_only state is for buffers that are in the second 336 * level ARC but no longer in any of the ARC_m* lists. The second 337 * level ARC itself may also contain buffers that are in any of 338 * the ARC_m* states - meaning that a buffer can exist in two 339 * places. The reason for the ARC_l2c_only state is to keep the 340 * buffer header in the hash table, so that reads that hit the 341 * second level ARC benefit from these fast lookups. 342 */ 343 344typedef struct arc_state { 345 /* 346 * list of evictable buffers 347 */ 348 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 349 /* 350 * total amount of evictable data in this state 351 */ 352 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; 353 /* 354 * total amount of data in this state; this includes: evictable, 355 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 356 */ 357 refcount_t arcs_size; 358} arc_state_t; 359 360/* The 6 states: */ 361static arc_state_t ARC_anon; 362static arc_state_t ARC_mru; 363static arc_state_t ARC_mru_ghost; 364static arc_state_t ARC_mfu; 365static arc_state_t ARC_mfu_ghost; 366static arc_state_t ARC_l2c_only; 367 368typedef struct arc_stats { 369 kstat_named_t arcstat_hits; 370 kstat_named_t arcstat_misses; 371 kstat_named_t arcstat_demand_data_hits; 372 kstat_named_t arcstat_demand_data_misses; 373 kstat_named_t arcstat_demand_metadata_hits; 374 kstat_named_t arcstat_demand_metadata_misses; 375 kstat_named_t arcstat_prefetch_data_hits; 376 kstat_named_t arcstat_prefetch_data_misses; 377 kstat_named_t arcstat_prefetch_metadata_hits; 378 kstat_named_t arcstat_prefetch_metadata_misses; 379 kstat_named_t arcstat_mru_hits; 380 kstat_named_t arcstat_mru_ghost_hits; 381 kstat_named_t arcstat_mfu_hits; 382 kstat_named_t arcstat_mfu_ghost_hits; 383 kstat_named_t arcstat_allocated; 384 kstat_named_t arcstat_deleted; 385 /* 386 * Number of buffers that could not be evicted because the hash lock 387 * was held by another thread. The lock may not necessarily be held 388 * by something using the same buffer, since hash locks are shared 389 * by multiple buffers. 390 */ 391 kstat_named_t arcstat_mutex_miss; 392 /* 393 * Number of buffers skipped because they have I/O in progress, are 394 * indrect prefetch buffers that have not lived long enough, or are 395 * not from the spa we're trying to evict from. 396 */ 397 kstat_named_t arcstat_evict_skip; 398 /* 399 * Number of times arc_evict_state() was unable to evict enough 400 * buffers to reach it's target amount. 401 */ 402 kstat_named_t arcstat_evict_not_enough; 403 kstat_named_t arcstat_evict_l2_cached; 404 kstat_named_t arcstat_evict_l2_eligible; 405 kstat_named_t arcstat_evict_l2_ineligible; 406 kstat_named_t arcstat_evict_l2_skip; 407 kstat_named_t arcstat_hash_elements; 408 kstat_named_t arcstat_hash_elements_max; 409 kstat_named_t arcstat_hash_collisions; 410 kstat_named_t arcstat_hash_chains; 411 kstat_named_t arcstat_hash_chain_max; 412 kstat_named_t arcstat_p; 413 kstat_named_t arcstat_c; 414 kstat_named_t arcstat_c_min; 415 kstat_named_t arcstat_c_max; 416 kstat_named_t arcstat_size; 417 /* 418 * Number of bytes consumed by internal ARC structures necessary 419 * for tracking purposes; these structures are not actually 420 * backed by ARC buffers. This includes arc_buf_hdr_t structures 421 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 422 * caches), and arc_buf_t structures (allocated via arc_buf_t 423 * cache). 424 */ 425 kstat_named_t arcstat_hdr_size; 426 /* 427 * Number of bytes consumed by ARC buffers of type equal to 428 * ARC_BUFC_DATA. This is generally consumed by buffers backing 429 * on disk user data (e.g. plain file contents). 430 */ 431 kstat_named_t arcstat_data_size; 432 /* 433 * Number of bytes consumed by ARC buffers of type equal to 434 * ARC_BUFC_METADATA. This is generally consumed by buffers 435 * backing on disk data that is used for internal ZFS 436 * structures (e.g. ZAP, dnode, indirect blocks, etc). 437 */ 438 kstat_named_t arcstat_metadata_size; 439 /* 440 * Number of bytes consumed by various buffers and structures 441 * not actually backed with ARC buffers. This includes bonus 442 * buffers (allocated directly via zio_buf_* functions), 443 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 444 * cache), and dnode_t structures (allocated via dnode_t cache). 445 */ 446 kstat_named_t arcstat_other_size; 447 /* 448 * Total number of bytes consumed by ARC buffers residing in the 449 * arc_anon state. This includes *all* buffers in the arc_anon 450 * state; e.g. data, metadata, evictable, and unevictable buffers 451 * are all included in this value. 452 */ 453 kstat_named_t arcstat_anon_size; 454 /* 455 * Number of bytes consumed by ARC buffers that meet the 456 * following criteria: backing buffers of type ARC_BUFC_DATA, 457 * residing in the arc_anon state, and are eligible for eviction 458 * (e.g. have no outstanding holds on the buffer). 459 */ 460 kstat_named_t arcstat_anon_evictable_data; 461 /* 462 * Number of bytes consumed by ARC buffers that meet the 463 * following criteria: backing buffers of type ARC_BUFC_METADATA, 464 * residing in the arc_anon state, and are eligible for eviction 465 * (e.g. have no outstanding holds on the buffer). 466 */ 467 kstat_named_t arcstat_anon_evictable_metadata; 468 /* 469 * Total number of bytes consumed by ARC buffers residing in the 470 * arc_mru state. This includes *all* buffers in the arc_mru 471 * state; e.g. data, metadata, evictable, and unevictable buffers 472 * are all included in this value. 473 */ 474 kstat_named_t arcstat_mru_size; 475 /* 476 * Number of bytes consumed by ARC buffers that meet the 477 * following criteria: backing buffers of type ARC_BUFC_DATA, 478 * residing in the arc_mru state, and are eligible for eviction 479 * (e.g. have no outstanding holds on the buffer). 480 */ 481 kstat_named_t arcstat_mru_evictable_data; 482 /* 483 * Number of bytes consumed by ARC buffers that meet the 484 * following criteria: backing buffers of type ARC_BUFC_METADATA, 485 * residing in the arc_mru state, and are eligible for eviction 486 * (e.g. have no outstanding holds on the buffer). 487 */ 488 kstat_named_t arcstat_mru_evictable_metadata; 489 /* 490 * Total number of bytes that *would have been* consumed by ARC 491 * buffers in the arc_mru_ghost state. The key thing to note 492 * here, is the fact that this size doesn't actually indicate 493 * RAM consumption. The ghost lists only consist of headers and 494 * don't actually have ARC buffers linked off of these headers. 495 * Thus, *if* the headers had associated ARC buffers, these 496 * buffers *would have* consumed this number of bytes. 497 */ 498 kstat_named_t arcstat_mru_ghost_size; 499 /* 500 * Number of bytes that *would have been* consumed by ARC 501 * buffers that are eligible for eviction, of type 502 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 503 */ 504 kstat_named_t arcstat_mru_ghost_evictable_data; 505 /* 506 * Number of bytes that *would have been* consumed by ARC 507 * buffers that are eligible for eviction, of type 508 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 509 */ 510 kstat_named_t arcstat_mru_ghost_evictable_metadata; 511 /* 512 * Total number of bytes consumed by ARC buffers residing in the 513 * arc_mfu state. This includes *all* buffers in the arc_mfu 514 * state; e.g. data, metadata, evictable, and unevictable buffers 515 * are all included in this value. 516 */ 517 kstat_named_t arcstat_mfu_size; 518 /* 519 * Number of bytes consumed by ARC buffers that are eligible for 520 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 521 * state. 522 */ 523 kstat_named_t arcstat_mfu_evictable_data; 524 /* 525 * Number of bytes consumed by ARC buffers that are eligible for 526 * eviction, of type ARC_BUFC_METADATA, and reside in the 527 * arc_mfu state. 528 */ 529 kstat_named_t arcstat_mfu_evictable_metadata; 530 /* 531 * Total number of bytes that *would have been* consumed by ARC 532 * buffers in the arc_mfu_ghost state. See the comment above 533 * arcstat_mru_ghost_size for more details. 534 */ 535 kstat_named_t arcstat_mfu_ghost_size; 536 /* 537 * Number of bytes that *would have been* consumed by ARC 538 * buffers that are eligible for eviction, of type 539 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 540 */ 541 kstat_named_t arcstat_mfu_ghost_evictable_data; 542 /* 543 * Number of bytes that *would have been* consumed by ARC 544 * buffers that are eligible for eviction, of type 545 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 546 */ 547 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 548 kstat_named_t arcstat_l2_hits; 549 kstat_named_t arcstat_l2_misses; 550 kstat_named_t arcstat_l2_feeds; 551 kstat_named_t arcstat_l2_rw_clash; 552 kstat_named_t arcstat_l2_read_bytes; 553 kstat_named_t arcstat_l2_write_bytes; 554 kstat_named_t arcstat_l2_writes_sent; 555 kstat_named_t arcstat_l2_writes_done; 556 kstat_named_t arcstat_l2_writes_error; 557 kstat_named_t arcstat_l2_writes_lock_retry; 558 kstat_named_t arcstat_l2_evict_lock_retry; 559 kstat_named_t arcstat_l2_evict_reading; 560 kstat_named_t arcstat_l2_evict_l1cached; 561 kstat_named_t arcstat_l2_free_on_write; 562 kstat_named_t arcstat_l2_cdata_free_on_write; 563 kstat_named_t arcstat_l2_abort_lowmem; 564 kstat_named_t arcstat_l2_cksum_bad; 565 kstat_named_t arcstat_l2_io_error; 566 kstat_named_t arcstat_l2_size; 567 kstat_named_t arcstat_l2_asize; 568 kstat_named_t arcstat_l2_hdr_size; 569 kstat_named_t arcstat_l2_compress_successes; 570 kstat_named_t arcstat_l2_compress_zeros; 571 kstat_named_t arcstat_l2_compress_failures; 572 kstat_named_t arcstat_l2_padding_needed; 573 kstat_named_t arcstat_l2_write_trylock_fail; 574 kstat_named_t arcstat_l2_write_passed_headroom; 575 kstat_named_t arcstat_l2_write_spa_mismatch; 576 kstat_named_t arcstat_l2_write_in_l2; 577 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 578 kstat_named_t arcstat_l2_write_not_cacheable; 579 kstat_named_t arcstat_l2_write_full; 580 kstat_named_t arcstat_l2_write_buffer_iter; 581 kstat_named_t arcstat_l2_write_pios; 582 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 583 kstat_named_t arcstat_l2_write_buffer_list_iter; 584 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 585 kstat_named_t arcstat_memory_throttle_count; 586 kstat_named_t arcstat_duplicate_buffers; 587 kstat_named_t arcstat_duplicate_buffers_size; 588 kstat_named_t arcstat_duplicate_reads; 589 kstat_named_t arcstat_meta_used; 590 kstat_named_t arcstat_meta_limit; 591 kstat_named_t arcstat_meta_max; 592 kstat_named_t arcstat_meta_min; 593 kstat_named_t arcstat_sync_wait_for_async; 594 kstat_named_t arcstat_demand_hit_predictive_prefetch; 595} arc_stats_t; 596 597static arc_stats_t arc_stats = { 598 { "hits", KSTAT_DATA_UINT64 }, 599 { "misses", KSTAT_DATA_UINT64 }, 600 { "demand_data_hits", KSTAT_DATA_UINT64 }, 601 { "demand_data_misses", KSTAT_DATA_UINT64 }, 602 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 603 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 604 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 605 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 606 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 607 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 608 { "mru_hits", KSTAT_DATA_UINT64 }, 609 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 610 { "mfu_hits", KSTAT_DATA_UINT64 }, 611 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 612 { "allocated", KSTAT_DATA_UINT64 }, 613 { "deleted", KSTAT_DATA_UINT64 }, 614 { "mutex_miss", KSTAT_DATA_UINT64 }, 615 { "evict_skip", KSTAT_DATA_UINT64 }, 616 { "evict_not_enough", KSTAT_DATA_UINT64 }, 617 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 618 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 619 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 620 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 621 { "hash_elements", KSTAT_DATA_UINT64 }, 622 { "hash_elements_max", KSTAT_DATA_UINT64 }, 623 { "hash_collisions", KSTAT_DATA_UINT64 }, 624 { "hash_chains", KSTAT_DATA_UINT64 }, 625 { "hash_chain_max", KSTAT_DATA_UINT64 }, 626 { "p", KSTAT_DATA_UINT64 }, 627 { "c", KSTAT_DATA_UINT64 }, 628 { "c_min", KSTAT_DATA_UINT64 }, 629 { "c_max", KSTAT_DATA_UINT64 }, 630 { "size", KSTAT_DATA_UINT64 }, 631 { "hdr_size", KSTAT_DATA_UINT64 }, 632 { "data_size", KSTAT_DATA_UINT64 }, 633 { "metadata_size", KSTAT_DATA_UINT64 }, 634 { "other_size", KSTAT_DATA_UINT64 }, 635 { "anon_size", KSTAT_DATA_UINT64 }, 636 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 637 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 638 { "mru_size", KSTAT_DATA_UINT64 }, 639 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 640 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 641 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 642 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 643 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 644 { "mfu_size", KSTAT_DATA_UINT64 }, 645 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 646 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 647 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 648 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 649 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 650 { "l2_hits", KSTAT_DATA_UINT64 }, 651 { "l2_misses", KSTAT_DATA_UINT64 }, 652 { "l2_feeds", KSTAT_DATA_UINT64 }, 653 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 654 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 655 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 656 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 657 { "l2_writes_done", KSTAT_DATA_UINT64 }, 658 { "l2_writes_error", KSTAT_DATA_UINT64 }, 659 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 660 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 661 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 662 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 663 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 664 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 665 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 666 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 667 { "l2_io_error", KSTAT_DATA_UINT64 }, 668 { "l2_size", KSTAT_DATA_UINT64 }, 669 { "l2_asize", KSTAT_DATA_UINT64 }, 670 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 671 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 672 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 673 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 674 { "l2_padding_needed", KSTAT_DATA_UINT64 }, 675 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 676 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 677 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 678 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 679 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 680 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 681 { "l2_write_full", KSTAT_DATA_UINT64 }, 682 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 683 { "l2_write_pios", KSTAT_DATA_UINT64 }, 684 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 685 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 686 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 687 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 688 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 689 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 690 { "duplicate_reads", KSTAT_DATA_UINT64 }, 691 { "arc_meta_used", KSTAT_DATA_UINT64 }, 692 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 693 { "arc_meta_max", KSTAT_DATA_UINT64 }, 694 { "arc_meta_min", KSTAT_DATA_UINT64 }, 695 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 696 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 697}; 698 699#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 700 701#define ARCSTAT_INCR(stat, val) \ 702 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 703 704#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 705#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 706 707#define ARCSTAT_MAX(stat, val) { \ 708 uint64_t m; \ 709 while ((val) > (m = arc_stats.stat.value.ui64) && \ 710 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 711 continue; \ 712} 713 714#define ARCSTAT_MAXSTAT(stat) \ 715 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 716 717/* 718 * We define a macro to allow ARC hits/misses to be easily broken down by 719 * two separate conditions, giving a total of four different subtypes for 720 * each of hits and misses (so eight statistics total). 721 */ 722#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 723 if (cond1) { \ 724 if (cond2) { \ 725 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 726 } else { \ 727 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 728 } \ 729 } else { \ 730 if (cond2) { \ 731 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 732 } else { \ 733 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 734 } \ 735 } 736 737kstat_t *arc_ksp; 738static arc_state_t *arc_anon; 739static arc_state_t *arc_mru; 740static arc_state_t *arc_mru_ghost; 741static arc_state_t *arc_mfu; 742static arc_state_t *arc_mfu_ghost; 743static arc_state_t *arc_l2c_only; 744 745/* 746 * There are several ARC variables that are critical to export as kstats -- 747 * but we don't want to have to grovel around in the kstat whenever we wish to 748 * manipulate them. For these variables, we therefore define them to be in 749 * terms of the statistic variable. This assures that we are not introducing 750 * the possibility of inconsistency by having shadow copies of the variables, 751 * while still allowing the code to be readable. 752 */ 753#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 754#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 755#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 756#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 757#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 758#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 759#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 760#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 761#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 762 763#define L2ARC_IS_VALID_COMPRESS(_c_) \ 764 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 765 766static int arc_no_grow; /* Don't try to grow cache size */ 767static uint64_t arc_tempreserve; 768static uint64_t arc_loaned_bytes; 769 770typedef struct arc_callback arc_callback_t; 771 772struct arc_callback { 773 void *acb_private; 774 arc_done_func_t *acb_done; 775 arc_buf_t *acb_buf; 776 zio_t *acb_zio_dummy; 777 arc_callback_t *acb_next; 778}; 779 780typedef struct arc_write_callback arc_write_callback_t; 781 782struct arc_write_callback { 783 void *awcb_private; 784 arc_done_func_t *awcb_ready; 785 arc_done_func_t *awcb_children_ready; 786 arc_done_func_t *awcb_physdone; 787 arc_done_func_t *awcb_done; 788 arc_buf_t *awcb_buf; 789}; 790 791/* 792 * ARC buffers are separated into multiple structs as a memory saving measure: 793 * - Common fields struct, always defined, and embedded within it: 794 * - L2-only fields, always allocated but undefined when not in L2ARC 795 * - L1-only fields, only allocated when in L1ARC 796 * 797 * Buffer in L1 Buffer only in L2 798 * +------------------------+ +------------------------+ 799 * | arc_buf_hdr_t | | arc_buf_hdr_t | 800 * | | | | 801 * | | | | 802 * | | | | 803 * +------------------------+ +------------------------+ 804 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 805 * | (undefined if L1-only) | | | 806 * +------------------------+ +------------------------+ 807 * | l1arc_buf_hdr_t | 808 * | | 809 * | | 810 * | | 811 * | | 812 * +------------------------+ 813 * 814 * Because it's possible for the L2ARC to become extremely large, we can wind 815 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 816 * is minimized by only allocating the fields necessary for an L1-cached buffer 817 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 818 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 819 * words in pointers. arc_hdr_realloc() is used to switch a header between 820 * these two allocation states. 821 */ 822typedef struct l1arc_buf_hdr { 823 kmutex_t b_freeze_lock; 824#ifdef ZFS_DEBUG 825 /* 826 * used for debugging wtih kmem_flags - by allocating and freeing 827 * b_thawed when the buffer is thawed, we get a record of the stack 828 * trace that thawed it. 829 */ 830 void *b_thawed; 831#endif 832 833 arc_buf_t *b_buf; 834 uint32_t b_datacnt; 835 /* for waiting on writes to complete */ 836 kcondvar_t b_cv; 837 838 /* protected by arc state mutex */ 839 arc_state_t *b_state; 840 multilist_node_t b_arc_node; 841 842 /* updated atomically */ 843 clock_t b_arc_access; 844 845 /* self protecting */ 846 refcount_t b_refcnt; 847 848 arc_callback_t *b_acb; 849 /* temporary buffer holder for in-flight compressed or padded data */ 850 void *b_tmp_cdata; 851} l1arc_buf_hdr_t; 852 853typedef struct l2arc_dev l2arc_dev_t; 854 855typedef struct l2arc_buf_hdr { 856 /* protected by arc_buf_hdr mutex */ 857 l2arc_dev_t *b_dev; /* L2ARC device */ 858 uint64_t b_daddr; /* disk address, offset byte */ 859 /* real alloc'd buffer size depending on b_compress applied */ 860 int32_t b_asize; 861 uint8_t b_compress; 862 863 list_node_t b_l2node; 864} l2arc_buf_hdr_t; 865 866struct arc_buf_hdr { 867 /* protected by hash lock */ 868 dva_t b_dva; 869 uint64_t b_birth; 870 /* 871 * Even though this checksum is only set/verified when a buffer is in 872 * the L1 cache, it needs to be in the set of common fields because it 873 * must be preserved from the time before a buffer is written out to 874 * L2ARC until after it is read back in. 875 */ 876 zio_cksum_t *b_freeze_cksum; 877 878 arc_buf_hdr_t *b_hash_next; 879 arc_flags_t b_flags; 880 881 /* immutable */ 882 int32_t b_size; 883 uint64_t b_spa; 884 885 /* L2ARC fields. Undefined when not in L2ARC. */ 886 l2arc_buf_hdr_t b_l2hdr; 887 /* L1ARC fields. Undefined when in l2arc_only state */ 888 l1arc_buf_hdr_t b_l1hdr; 889}; 890 891#if defined(__FreeBSD__) && defined(_KERNEL) 892static int 893sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 894{ 895 uint64_t val; 896 int err; 897 898 val = arc_meta_limit; 899 err = sysctl_handle_64(oidp, &val, 0, req); 900 if (err != 0 || req->newptr == NULL) 901 return (err); 902 903 if (val <= 0 || val > arc_c_max) 904 return (EINVAL); 905 906 arc_meta_limit = val; 907 return (0); 908} 909 910static int 911sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 912{ 913 uint64_t val; 914 int err; 915 916 val = zfs_arc_max; 917 err = sysctl_handle_64(oidp, &val, 0, req); 918 if (err != 0 || req->newptr == NULL) 919 return (err); 920 921 if (zfs_arc_max == 0) { 922 /* Loader tunable so blindly set */ 923 zfs_arc_max = val; 924 return (0); 925 } 926 927 if (val < arc_abs_min || val > kmem_size()) 928 return (EINVAL); 929 if (val < arc_c_min) 930 return (EINVAL); 931 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 932 return (EINVAL); 933 934 arc_c_max = val; 935 936 arc_c = arc_c_max; 937 arc_p = (arc_c >> 1); 938 939 if (zfs_arc_meta_limit == 0) { 940 /* limit meta-data to 1/4 of the arc capacity */ 941 arc_meta_limit = arc_c_max / 4; 942 } 943 944 /* if kmem_flags are set, lets try to use less memory */ 945 if (kmem_debugging()) 946 arc_c = arc_c / 2; 947 948 zfs_arc_max = arc_c; 949 950 return (0); 951} 952 953static int 954sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 955{ 956 uint64_t val; 957 int err; 958 959 val = zfs_arc_min; 960 err = sysctl_handle_64(oidp, &val, 0, req); 961 if (err != 0 || req->newptr == NULL) 962 return (err); 963 964 if (zfs_arc_min == 0) { 965 /* Loader tunable so blindly set */ 966 zfs_arc_min = val; 967 return (0); 968 } 969 970 if (val < arc_abs_min || val > arc_c_max) 971 return (EINVAL); 972 973 arc_c_min = val; 974 975 if (zfs_arc_meta_min == 0) 976 arc_meta_min = arc_c_min / 2; 977 978 if (arc_c < arc_c_min) 979 arc_c = arc_c_min; 980 981 zfs_arc_min = arc_c_min; 982 983 return (0); 984} 985#endif 986 987static arc_buf_t *arc_eviction_list; 988static arc_buf_hdr_t arc_eviction_hdr; 989 990#define GHOST_STATE(state) \ 991 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 992 (state) == arc_l2c_only) 993 994#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 995#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 996#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 997#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 998#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 999#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 1000 1001#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1002#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 1003#define HDR_L2_READING(hdr) \ 1004 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1005 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1006#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1007#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1008#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1009 1010#define HDR_ISTYPE_METADATA(hdr) \ 1011 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1012#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1013 1014#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1015#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1016 1017/* 1018 * Other sizes 1019 */ 1020 1021#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1022#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1023 1024/* 1025 * Hash table routines 1026 */ 1027 1028#define HT_LOCK_PAD CACHE_LINE_SIZE 1029 1030struct ht_lock { 1031 kmutex_t ht_lock; 1032#ifdef _KERNEL 1033 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1034#endif 1035}; 1036 1037#define BUF_LOCKS 256 1038typedef struct buf_hash_table { 1039 uint64_t ht_mask; 1040 arc_buf_hdr_t **ht_table; 1041 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1042} buf_hash_table_t; 1043 1044static buf_hash_table_t buf_hash_table; 1045 1046#define BUF_HASH_INDEX(spa, dva, birth) \ 1047 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1048#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1049#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1050#define HDR_LOCK(hdr) \ 1051 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1052 1053uint64_t zfs_crc64_table[256]; 1054 1055/* 1056 * Level 2 ARC 1057 */ 1058 1059#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1060#define L2ARC_HEADROOM 2 /* num of writes */ 1061/* 1062 * If we discover during ARC scan any buffers to be compressed, we boost 1063 * our headroom for the next scanning cycle by this percentage multiple. 1064 */ 1065#define L2ARC_HEADROOM_BOOST 200 1066#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1067#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1068 1069/* 1070 * Used to distinguish headers that are being process by 1071 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 1072 * address. This can happen when the header is added to the l2arc's list 1073 * of buffers to write in the first stage of l2arc_write_buffers(), but 1074 * has not yet been written out which happens in the second stage of 1075 * l2arc_write_buffers(). 1076 */ 1077#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 1078 1079#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1080#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1081 1082/* L2ARC Performance Tunables */ 1083uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1084uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1085uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1086uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1087uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1088uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1089boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1090boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1091boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1092 1093SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1094 &l2arc_write_max, 0, "max write size"); 1095SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1096 &l2arc_write_boost, 0, "extra write during warmup"); 1097SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1098 &l2arc_headroom, 0, "number of dev writes"); 1099SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1100 &l2arc_feed_secs, 0, "interval seconds"); 1101SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1102 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1103 1104SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1105 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1106SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1107 &l2arc_feed_again, 0, "turbo warmup"); 1108SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1109 &l2arc_norw, 0, "no reads during writes"); 1110 1111SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1112 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1113SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1114 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1115SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1116 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1117 1118SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1119 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1120SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1121 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1122SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1123 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1124 1125SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1126 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1127SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1128 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1129 "size of metadata in mru ghost state"); 1130SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1131 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1132 "size of data in mru ghost state"); 1133 1134SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1135 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1136SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1137 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1138SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1139 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1140 1141SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1142 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1143SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1144 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1145 "size of metadata in mfu ghost state"); 1146SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1147 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1148 "size of data in mfu ghost state"); 1149 1150SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1151 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1152 1153/* 1154 * L2ARC Internals 1155 */ 1156struct l2arc_dev { 1157 vdev_t *l2ad_vdev; /* vdev */ 1158 spa_t *l2ad_spa; /* spa */ 1159 uint64_t l2ad_hand; /* next write location */ 1160 uint64_t l2ad_start; /* first addr on device */ 1161 uint64_t l2ad_end; /* last addr on device */ 1162 boolean_t l2ad_first; /* first sweep through */ 1163 boolean_t l2ad_writing; /* currently writing */ 1164 kmutex_t l2ad_mtx; /* lock for buffer list */ 1165 list_t l2ad_buflist; /* buffer list */ 1166 list_node_t l2ad_node; /* device list node */ 1167 refcount_t l2ad_alloc; /* allocated bytes */ 1168}; 1169 1170static list_t L2ARC_dev_list; /* device list */ 1171static list_t *l2arc_dev_list; /* device list pointer */ 1172static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1173static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1174static list_t L2ARC_free_on_write; /* free after write buf list */ 1175static list_t *l2arc_free_on_write; /* free after write list ptr */ 1176static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1177static uint64_t l2arc_ndev; /* number of devices */ 1178 1179typedef struct l2arc_read_callback { 1180 arc_buf_t *l2rcb_buf; /* read buffer */ 1181 spa_t *l2rcb_spa; /* spa */ 1182 blkptr_t l2rcb_bp; /* original blkptr */ 1183 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1184 int l2rcb_flags; /* original flags */ 1185 enum zio_compress l2rcb_compress; /* applied compress */ 1186 void *l2rcb_data; /* temporary buffer */ 1187} l2arc_read_callback_t; 1188 1189typedef struct l2arc_write_callback { 1190 l2arc_dev_t *l2wcb_dev; /* device info */ 1191 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1192} l2arc_write_callback_t; 1193 1194typedef struct l2arc_data_free { 1195 /* protected by l2arc_free_on_write_mtx */ 1196 void *l2df_data; 1197 size_t l2df_size; 1198 void (*l2df_func)(void *, size_t); 1199 list_node_t l2df_list_node; 1200} l2arc_data_free_t; 1201 1202static kmutex_t l2arc_feed_thr_lock; 1203static kcondvar_t l2arc_feed_thr_cv; 1204static uint8_t l2arc_thread_exit; 1205 1206static void arc_get_data_buf(arc_buf_t *); 1207static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1208static boolean_t arc_is_overflowing(); 1209static void arc_buf_watch(arc_buf_t *); 1210 1211static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1212static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1213 1214static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1215static void l2arc_read_done(zio_t *); 1216 1217static boolean_t l2arc_transform_buf(arc_buf_hdr_t *, boolean_t); 1218static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1219static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1220 1221static void 1222l2arc_trim(const arc_buf_hdr_t *hdr) 1223{ 1224 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1225 1226 ASSERT(HDR_HAS_L2HDR(hdr)); 1227 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1228 1229 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) 1230 return; 1231 if (hdr->b_l2hdr.b_asize != 0) { 1232 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1233 hdr->b_l2hdr.b_asize, 0); 1234 } else { 1235 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_EMPTY); 1236 } 1237} 1238 1239static uint64_t 1240buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1241{ 1242 uint8_t *vdva = (uint8_t *)dva; 1243 uint64_t crc = -1ULL; 1244 int i; 1245 1246 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1247 1248 for (i = 0; i < sizeof (dva_t); i++) 1249 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1250 1251 crc ^= (spa>>8) ^ birth; 1252 1253 return (crc); 1254} 1255 1256#define BUF_EMPTY(buf) \ 1257 ((buf)->b_dva.dva_word[0] == 0 && \ 1258 (buf)->b_dva.dva_word[1] == 0) 1259 1260#define BUF_EQUAL(spa, dva, birth, buf) \ 1261 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1262 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1263 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1264 1265static void 1266buf_discard_identity(arc_buf_hdr_t *hdr) 1267{ 1268 hdr->b_dva.dva_word[0] = 0; 1269 hdr->b_dva.dva_word[1] = 0; 1270 hdr->b_birth = 0; 1271} 1272 1273static arc_buf_hdr_t * 1274buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1275{ 1276 const dva_t *dva = BP_IDENTITY(bp); 1277 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1278 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1279 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1280 arc_buf_hdr_t *hdr; 1281 1282 mutex_enter(hash_lock); 1283 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1284 hdr = hdr->b_hash_next) { 1285 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1286 *lockp = hash_lock; 1287 return (hdr); 1288 } 1289 } 1290 mutex_exit(hash_lock); 1291 *lockp = NULL; 1292 return (NULL); 1293} 1294 1295/* 1296 * Insert an entry into the hash table. If there is already an element 1297 * equal to elem in the hash table, then the already existing element 1298 * will be returned and the new element will not be inserted. 1299 * Otherwise returns NULL. 1300 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1301 */ 1302static arc_buf_hdr_t * 1303buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1304{ 1305 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1306 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1307 arc_buf_hdr_t *fhdr; 1308 uint32_t i; 1309 1310 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1311 ASSERT(hdr->b_birth != 0); 1312 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1313 1314 if (lockp != NULL) { 1315 *lockp = hash_lock; 1316 mutex_enter(hash_lock); 1317 } else { 1318 ASSERT(MUTEX_HELD(hash_lock)); 1319 } 1320 1321 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1322 fhdr = fhdr->b_hash_next, i++) { 1323 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1324 return (fhdr); 1325 } 1326 1327 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1328 buf_hash_table.ht_table[idx] = hdr; 1329 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1330 1331 /* collect some hash table performance data */ 1332 if (i > 0) { 1333 ARCSTAT_BUMP(arcstat_hash_collisions); 1334 if (i == 1) 1335 ARCSTAT_BUMP(arcstat_hash_chains); 1336 1337 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1338 } 1339 1340 ARCSTAT_BUMP(arcstat_hash_elements); 1341 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1342 1343 return (NULL); 1344} 1345 1346static void 1347buf_hash_remove(arc_buf_hdr_t *hdr) 1348{ 1349 arc_buf_hdr_t *fhdr, **hdrp; 1350 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1351 1352 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1353 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1354 1355 hdrp = &buf_hash_table.ht_table[idx]; 1356 while ((fhdr = *hdrp) != hdr) { 1357 ASSERT(fhdr != NULL); 1358 hdrp = &fhdr->b_hash_next; 1359 } 1360 *hdrp = hdr->b_hash_next; 1361 hdr->b_hash_next = NULL; 1362 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1363 1364 /* collect some hash table performance data */ 1365 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1366 1367 if (buf_hash_table.ht_table[idx] && 1368 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1369 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1370} 1371 1372/* 1373 * Global data structures and functions for the buf kmem cache. 1374 */ 1375static kmem_cache_t *hdr_full_cache; 1376static kmem_cache_t *hdr_l2only_cache; 1377static kmem_cache_t *buf_cache; 1378 1379static void 1380buf_fini(void) 1381{ 1382 int i; 1383 1384 kmem_free(buf_hash_table.ht_table, 1385 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1386 for (i = 0; i < BUF_LOCKS; i++) 1387 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1388 kmem_cache_destroy(hdr_full_cache); 1389 kmem_cache_destroy(hdr_l2only_cache); 1390 kmem_cache_destroy(buf_cache); 1391} 1392 1393/* 1394 * Constructor callback - called when the cache is empty 1395 * and a new buf is requested. 1396 */ 1397/* ARGSUSED */ 1398static int 1399hdr_full_cons(void *vbuf, void *unused, int kmflag) 1400{ 1401 arc_buf_hdr_t *hdr = vbuf; 1402 1403 bzero(hdr, HDR_FULL_SIZE); 1404 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1405 refcount_create(&hdr->b_l1hdr.b_refcnt); 1406 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1407 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1408 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1409 1410 return (0); 1411} 1412 1413/* ARGSUSED */ 1414static int 1415hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1416{ 1417 arc_buf_hdr_t *hdr = vbuf; 1418 1419 bzero(hdr, HDR_L2ONLY_SIZE); 1420 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1421 1422 return (0); 1423} 1424 1425/* ARGSUSED */ 1426static int 1427buf_cons(void *vbuf, void *unused, int kmflag) 1428{ 1429 arc_buf_t *buf = vbuf; 1430 1431 bzero(buf, sizeof (arc_buf_t)); 1432 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1433 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1434 1435 return (0); 1436} 1437 1438/* 1439 * Destructor callback - called when a cached buf is 1440 * no longer required. 1441 */ 1442/* ARGSUSED */ 1443static void 1444hdr_full_dest(void *vbuf, void *unused) 1445{ 1446 arc_buf_hdr_t *hdr = vbuf; 1447 1448 ASSERT(BUF_EMPTY(hdr)); 1449 cv_destroy(&hdr->b_l1hdr.b_cv); 1450 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1451 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1452 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1453 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1454} 1455 1456/* ARGSUSED */ 1457static void 1458hdr_l2only_dest(void *vbuf, void *unused) 1459{ 1460 arc_buf_hdr_t *hdr = vbuf; 1461 1462 ASSERT(BUF_EMPTY(hdr)); 1463 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1464} 1465 1466/* ARGSUSED */ 1467static void 1468buf_dest(void *vbuf, void *unused) 1469{ 1470 arc_buf_t *buf = vbuf; 1471 1472 mutex_destroy(&buf->b_evict_lock); 1473 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1474} 1475 1476/* 1477 * Reclaim callback -- invoked when memory is low. 1478 */ 1479/* ARGSUSED */ 1480static void 1481hdr_recl(void *unused) 1482{ 1483 dprintf("hdr_recl called\n"); 1484 /* 1485 * umem calls the reclaim func when we destroy the buf cache, 1486 * which is after we do arc_fini(). 1487 */ 1488 if (!arc_dead) 1489 cv_signal(&arc_reclaim_thread_cv); 1490} 1491 1492static void 1493buf_init(void) 1494{ 1495 uint64_t *ct; 1496 uint64_t hsize = 1ULL << 12; 1497 int i, j; 1498 1499 /* 1500 * The hash table is big enough to fill all of physical memory 1501 * with an average block size of zfs_arc_average_blocksize (default 8K). 1502 * By default, the table will take up 1503 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1504 */ 1505 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1506 hsize <<= 1; 1507retry: 1508 buf_hash_table.ht_mask = hsize - 1; 1509 buf_hash_table.ht_table = 1510 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1511 if (buf_hash_table.ht_table == NULL) { 1512 ASSERT(hsize > (1ULL << 8)); 1513 hsize >>= 1; 1514 goto retry; 1515 } 1516 1517 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1518 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1519 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1520 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1521 NULL, NULL, 0); 1522 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1523 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1524 1525 for (i = 0; i < 256; i++) 1526 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1527 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1528 1529 for (i = 0; i < BUF_LOCKS; i++) { 1530 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1531 NULL, MUTEX_DEFAULT, NULL); 1532 } 1533} 1534 1535/* 1536 * Transition between the two allocation states for the arc_buf_hdr struct. 1537 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1538 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1539 * version is used when a cache buffer is only in the L2ARC in order to reduce 1540 * memory usage. 1541 */ 1542static arc_buf_hdr_t * 1543arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1544{ 1545 ASSERT(HDR_HAS_L2HDR(hdr)); 1546 1547 arc_buf_hdr_t *nhdr; 1548 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1549 1550 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1551 (old == hdr_l2only_cache && new == hdr_full_cache)); 1552 1553 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1554 1555 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1556 buf_hash_remove(hdr); 1557 1558 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1559 1560 if (new == hdr_full_cache) { 1561 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1562 /* 1563 * arc_access and arc_change_state need to be aware that a 1564 * header has just come out of L2ARC, so we set its state to 1565 * l2c_only even though it's about to change. 1566 */ 1567 nhdr->b_l1hdr.b_state = arc_l2c_only; 1568 1569 /* Verify previous threads set to NULL before freeing */ 1570 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1571 } else { 1572 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1573 ASSERT0(hdr->b_l1hdr.b_datacnt); 1574 1575 /* 1576 * If we've reached here, We must have been called from 1577 * arc_evict_hdr(), as such we should have already been 1578 * removed from any ghost list we were previously on 1579 * (which protects us from racing with arc_evict_state), 1580 * thus no locking is needed during this check. 1581 */ 1582 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1583 1584 /* 1585 * A buffer must not be moved into the arc_l2c_only 1586 * state if it's not finished being written out to the 1587 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1588 * might try to be accessed, even though it was removed. 1589 */ 1590 VERIFY(!HDR_L2_WRITING(hdr)); 1591 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1592 1593#ifdef ZFS_DEBUG 1594 if (hdr->b_l1hdr.b_thawed != NULL) { 1595 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1596 hdr->b_l1hdr.b_thawed = NULL; 1597 } 1598#endif 1599 1600 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1601 } 1602 /* 1603 * The header has been reallocated so we need to re-insert it into any 1604 * lists it was on. 1605 */ 1606 (void) buf_hash_insert(nhdr, NULL); 1607 1608 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1609 1610 mutex_enter(&dev->l2ad_mtx); 1611 1612 /* 1613 * We must place the realloc'ed header back into the list at 1614 * the same spot. Otherwise, if it's placed earlier in the list, 1615 * l2arc_write_buffers() could find it during the function's 1616 * write phase, and try to write it out to the l2arc. 1617 */ 1618 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1619 list_remove(&dev->l2ad_buflist, hdr); 1620 1621 mutex_exit(&dev->l2ad_mtx); 1622 1623 /* 1624 * Since we're using the pointer address as the tag when 1625 * incrementing and decrementing the l2ad_alloc refcount, we 1626 * must remove the old pointer (that we're about to destroy) and 1627 * add the new pointer to the refcount. Otherwise we'd remove 1628 * the wrong pointer address when calling arc_hdr_destroy() later. 1629 */ 1630 1631 (void) refcount_remove_many(&dev->l2ad_alloc, 1632 hdr->b_l2hdr.b_asize, hdr); 1633 1634 (void) refcount_add_many(&dev->l2ad_alloc, 1635 nhdr->b_l2hdr.b_asize, nhdr); 1636 1637 buf_discard_identity(hdr); 1638 hdr->b_freeze_cksum = NULL; 1639 kmem_cache_free(old, hdr); 1640 1641 return (nhdr); 1642} 1643 1644 1645#define ARC_MINTIME (hz>>4) /* 62 ms */ 1646 1647static void 1648arc_cksum_verify(arc_buf_t *buf) 1649{ 1650 zio_cksum_t zc; 1651 1652 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1653 return; 1654 1655 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1656 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1657 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1658 return; 1659 } 1660 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1661 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1662 panic("buffer modified while frozen!"); 1663 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1664} 1665 1666static int 1667arc_cksum_equal(arc_buf_t *buf) 1668{ 1669 zio_cksum_t zc; 1670 int equal; 1671 1672 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1673 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1674 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1675 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1676 1677 return (equal); 1678} 1679 1680static void 1681arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1682{ 1683 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1684 return; 1685 1686 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1687 if (buf->b_hdr->b_freeze_cksum != NULL) { 1688 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1689 return; 1690 } 1691 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1692 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1693 NULL, buf->b_hdr->b_freeze_cksum); 1694 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1695#ifdef illumos 1696 arc_buf_watch(buf); 1697#endif 1698} 1699 1700#ifdef illumos 1701#ifndef _KERNEL 1702typedef struct procctl { 1703 long cmd; 1704 prwatch_t prwatch; 1705} procctl_t; 1706#endif 1707 1708/* ARGSUSED */ 1709static void 1710arc_buf_unwatch(arc_buf_t *buf) 1711{ 1712#ifndef _KERNEL 1713 if (arc_watch) { 1714 int result; 1715 procctl_t ctl; 1716 ctl.cmd = PCWATCH; 1717 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1718 ctl.prwatch.pr_size = 0; 1719 ctl.prwatch.pr_wflags = 0; 1720 result = write(arc_procfd, &ctl, sizeof (ctl)); 1721 ASSERT3U(result, ==, sizeof (ctl)); 1722 } 1723#endif 1724} 1725 1726/* ARGSUSED */ 1727static void 1728arc_buf_watch(arc_buf_t *buf) 1729{ 1730#ifndef _KERNEL 1731 if (arc_watch) { 1732 int result; 1733 procctl_t ctl; 1734 ctl.cmd = PCWATCH; 1735 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1736 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1737 ctl.prwatch.pr_wflags = WA_WRITE; 1738 result = write(arc_procfd, &ctl, sizeof (ctl)); 1739 ASSERT3U(result, ==, sizeof (ctl)); 1740 } 1741#endif 1742} 1743#endif /* illumos */ 1744 1745static arc_buf_contents_t 1746arc_buf_type(arc_buf_hdr_t *hdr) 1747{ 1748 if (HDR_ISTYPE_METADATA(hdr)) { 1749 return (ARC_BUFC_METADATA); 1750 } else { 1751 return (ARC_BUFC_DATA); 1752 } 1753} 1754 1755static uint32_t 1756arc_bufc_to_flags(arc_buf_contents_t type) 1757{ 1758 switch (type) { 1759 case ARC_BUFC_DATA: 1760 /* metadata field is 0 if buffer contains normal data */ 1761 return (0); 1762 case ARC_BUFC_METADATA: 1763 return (ARC_FLAG_BUFC_METADATA); 1764 default: 1765 break; 1766 } 1767 panic("undefined ARC buffer type!"); 1768 return ((uint32_t)-1); 1769} 1770 1771void 1772arc_buf_thaw(arc_buf_t *buf) 1773{ 1774 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1775 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1776 panic("modifying non-anon buffer!"); 1777 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1778 panic("modifying buffer while i/o in progress!"); 1779 arc_cksum_verify(buf); 1780 } 1781 1782 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1783 if (buf->b_hdr->b_freeze_cksum != NULL) { 1784 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1785 buf->b_hdr->b_freeze_cksum = NULL; 1786 } 1787 1788#ifdef ZFS_DEBUG 1789 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1790 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1791 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1792 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1793 } 1794#endif 1795 1796 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1797 1798#ifdef illumos 1799 arc_buf_unwatch(buf); 1800#endif 1801} 1802 1803void 1804arc_buf_freeze(arc_buf_t *buf) 1805{ 1806 kmutex_t *hash_lock; 1807 1808 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1809 return; 1810 1811 hash_lock = HDR_LOCK(buf->b_hdr); 1812 mutex_enter(hash_lock); 1813 1814 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1815 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1816 arc_cksum_compute(buf, B_FALSE); 1817 mutex_exit(hash_lock); 1818 1819} 1820 1821static void 1822add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1823{ 1824 ASSERT(HDR_HAS_L1HDR(hdr)); 1825 ASSERT(MUTEX_HELD(hash_lock)); 1826 arc_state_t *state = hdr->b_l1hdr.b_state; 1827 1828 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1829 (state != arc_anon)) { 1830 /* We don't use the L2-only state list. */ 1831 if (state != arc_l2c_only) { 1832 arc_buf_contents_t type = arc_buf_type(hdr); 1833 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1834 multilist_t *list = &state->arcs_list[type]; 1835 uint64_t *size = &state->arcs_lsize[type]; 1836 1837 multilist_remove(list, hdr); 1838 1839 if (GHOST_STATE(state)) { 1840 ASSERT0(hdr->b_l1hdr.b_datacnt); 1841 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1842 delta = hdr->b_size; 1843 } 1844 ASSERT(delta > 0); 1845 ASSERT3U(*size, >=, delta); 1846 atomic_add_64(size, -delta); 1847 } 1848 /* remove the prefetch flag if we get a reference */ 1849 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1850 } 1851} 1852 1853static int 1854remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1855{ 1856 int cnt; 1857 arc_state_t *state = hdr->b_l1hdr.b_state; 1858 1859 ASSERT(HDR_HAS_L1HDR(hdr)); 1860 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1861 ASSERT(!GHOST_STATE(state)); 1862 1863 /* 1864 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1865 * check to prevent usage of the arc_l2c_only list. 1866 */ 1867 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1868 (state != arc_anon)) { 1869 arc_buf_contents_t type = arc_buf_type(hdr); 1870 multilist_t *list = &state->arcs_list[type]; 1871 uint64_t *size = &state->arcs_lsize[type]; 1872 1873 multilist_insert(list, hdr); 1874 1875 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1876 atomic_add_64(size, hdr->b_size * 1877 hdr->b_l1hdr.b_datacnt); 1878 } 1879 return (cnt); 1880} 1881 1882/* 1883 * Move the supplied buffer to the indicated state. The hash lock 1884 * for the buffer must be held by the caller. 1885 */ 1886static void 1887arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1888 kmutex_t *hash_lock) 1889{ 1890 arc_state_t *old_state; 1891 int64_t refcnt; 1892 uint32_t datacnt; 1893 uint64_t from_delta, to_delta; 1894 arc_buf_contents_t buftype = arc_buf_type(hdr); 1895 1896 /* 1897 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1898 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1899 * L1 hdr doesn't always exist when we change state to arc_anon before 1900 * destroying a header, in which case reallocating to add the L1 hdr is 1901 * pointless. 1902 */ 1903 if (HDR_HAS_L1HDR(hdr)) { 1904 old_state = hdr->b_l1hdr.b_state; 1905 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1906 datacnt = hdr->b_l1hdr.b_datacnt; 1907 } else { 1908 old_state = arc_l2c_only; 1909 refcnt = 0; 1910 datacnt = 0; 1911 } 1912 1913 ASSERT(MUTEX_HELD(hash_lock)); 1914 ASSERT3P(new_state, !=, old_state); 1915 ASSERT(refcnt == 0 || datacnt > 0); 1916 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1917 ASSERT(old_state != arc_anon || datacnt <= 1); 1918 1919 from_delta = to_delta = datacnt * hdr->b_size; 1920 1921 /* 1922 * If this buffer is evictable, transfer it from the 1923 * old state list to the new state list. 1924 */ 1925 if (refcnt == 0) { 1926 if (old_state != arc_anon && old_state != arc_l2c_only) { 1927 uint64_t *size = &old_state->arcs_lsize[buftype]; 1928 1929 ASSERT(HDR_HAS_L1HDR(hdr)); 1930 multilist_remove(&old_state->arcs_list[buftype], hdr); 1931 1932 /* 1933 * If prefetching out of the ghost cache, 1934 * we will have a non-zero datacnt. 1935 */ 1936 if (GHOST_STATE(old_state) && datacnt == 0) { 1937 /* ghost elements have a ghost size */ 1938 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1939 from_delta = hdr->b_size; 1940 } 1941 ASSERT3U(*size, >=, from_delta); 1942 atomic_add_64(size, -from_delta); 1943 } 1944 if (new_state != arc_anon && new_state != arc_l2c_only) { 1945 uint64_t *size = &new_state->arcs_lsize[buftype]; 1946 1947 /* 1948 * An L1 header always exists here, since if we're 1949 * moving to some L1-cached state (i.e. not l2c_only or 1950 * anonymous), we realloc the header to add an L1hdr 1951 * beforehand. 1952 */ 1953 ASSERT(HDR_HAS_L1HDR(hdr)); 1954 multilist_insert(&new_state->arcs_list[buftype], hdr); 1955 1956 /* ghost elements have a ghost size */ 1957 if (GHOST_STATE(new_state)) { 1958 ASSERT0(datacnt); 1959 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1960 to_delta = hdr->b_size; 1961 } 1962 atomic_add_64(size, to_delta); 1963 } 1964 } 1965 1966 ASSERT(!BUF_EMPTY(hdr)); 1967 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1968 buf_hash_remove(hdr); 1969 1970 /* adjust state sizes (ignore arc_l2c_only) */ 1971 1972 if (to_delta && new_state != arc_l2c_only) { 1973 ASSERT(HDR_HAS_L1HDR(hdr)); 1974 if (GHOST_STATE(new_state)) { 1975 ASSERT0(datacnt); 1976 1977 /* 1978 * We moving a header to a ghost state, we first 1979 * remove all arc buffers. Thus, we'll have a 1980 * datacnt of zero, and no arc buffer to use for 1981 * the reference. As a result, we use the arc 1982 * header pointer for the reference. 1983 */ 1984 (void) refcount_add_many(&new_state->arcs_size, 1985 hdr->b_size, hdr); 1986 } else { 1987 ASSERT3U(datacnt, !=, 0); 1988 1989 /* 1990 * Each individual buffer holds a unique reference, 1991 * thus we must remove each of these references one 1992 * at a time. 1993 */ 1994 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1995 buf = buf->b_next) { 1996 (void) refcount_add_many(&new_state->arcs_size, 1997 hdr->b_size, buf); 1998 } 1999 } 2000 } 2001 2002 if (from_delta && old_state != arc_l2c_only) { 2003 ASSERT(HDR_HAS_L1HDR(hdr)); 2004 if (GHOST_STATE(old_state)) { 2005 /* 2006 * When moving a header off of a ghost state, 2007 * there's the possibility for datacnt to be 2008 * non-zero. This is because we first add the 2009 * arc buffer to the header prior to changing 2010 * the header's state. Since we used the header 2011 * for the reference when putting the header on 2012 * the ghost state, we must balance that and use 2013 * the header when removing off the ghost state 2014 * (even though datacnt is non zero). 2015 */ 2016 2017 IMPLY(datacnt == 0, new_state == arc_anon || 2018 new_state == arc_l2c_only); 2019 2020 (void) refcount_remove_many(&old_state->arcs_size, 2021 hdr->b_size, hdr); 2022 } else { 2023 ASSERT3P(datacnt, !=, 0); 2024 2025 /* 2026 * Each individual buffer holds a unique reference, 2027 * thus we must remove each of these references one 2028 * at a time. 2029 */ 2030 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2031 buf = buf->b_next) { 2032 (void) refcount_remove_many( 2033 &old_state->arcs_size, hdr->b_size, buf); 2034 } 2035 } 2036 } 2037 2038 if (HDR_HAS_L1HDR(hdr)) 2039 hdr->b_l1hdr.b_state = new_state; 2040 2041 /* 2042 * L2 headers should never be on the L2 state list since they don't 2043 * have L1 headers allocated. 2044 */ 2045 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2046 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2047} 2048 2049void 2050arc_space_consume(uint64_t space, arc_space_type_t type) 2051{ 2052 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2053 2054 switch (type) { 2055 case ARC_SPACE_DATA: 2056 ARCSTAT_INCR(arcstat_data_size, space); 2057 break; 2058 case ARC_SPACE_META: 2059 ARCSTAT_INCR(arcstat_metadata_size, space); 2060 break; 2061 case ARC_SPACE_OTHER: 2062 ARCSTAT_INCR(arcstat_other_size, space); 2063 break; 2064 case ARC_SPACE_HDRS: 2065 ARCSTAT_INCR(arcstat_hdr_size, space); 2066 break; 2067 case ARC_SPACE_L2HDRS: 2068 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2069 break; 2070 } 2071 2072 if (type != ARC_SPACE_DATA) 2073 ARCSTAT_INCR(arcstat_meta_used, space); 2074 2075 atomic_add_64(&arc_size, space); 2076} 2077 2078void 2079arc_space_return(uint64_t space, arc_space_type_t type) 2080{ 2081 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2082 2083 switch (type) { 2084 case ARC_SPACE_DATA: 2085 ARCSTAT_INCR(arcstat_data_size, -space); 2086 break; 2087 case ARC_SPACE_META: 2088 ARCSTAT_INCR(arcstat_metadata_size, -space); 2089 break; 2090 case ARC_SPACE_OTHER: 2091 ARCSTAT_INCR(arcstat_other_size, -space); 2092 break; 2093 case ARC_SPACE_HDRS: 2094 ARCSTAT_INCR(arcstat_hdr_size, -space); 2095 break; 2096 case ARC_SPACE_L2HDRS: 2097 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2098 break; 2099 } 2100 2101 if (type != ARC_SPACE_DATA) { 2102 ASSERT(arc_meta_used >= space); 2103 if (arc_meta_max < arc_meta_used) 2104 arc_meta_max = arc_meta_used; 2105 ARCSTAT_INCR(arcstat_meta_used, -space); 2106 } 2107 2108 ASSERT(arc_size >= space); 2109 atomic_add_64(&arc_size, -space); 2110} 2111 2112arc_buf_t * 2113arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2114{ 2115 arc_buf_hdr_t *hdr; 2116 arc_buf_t *buf; 2117 2118 ASSERT3U(size, >, 0); 2119 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2120 ASSERT(BUF_EMPTY(hdr)); 2121 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2122 hdr->b_size = size; 2123 hdr->b_spa = spa_load_guid(spa); 2124 2125 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2126 buf->b_hdr = hdr; 2127 buf->b_data = NULL; 2128 buf->b_efunc = NULL; 2129 buf->b_private = NULL; 2130 buf->b_next = NULL; 2131 2132 hdr->b_flags = arc_bufc_to_flags(type); 2133 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2134 2135 hdr->b_l1hdr.b_buf = buf; 2136 hdr->b_l1hdr.b_state = arc_anon; 2137 hdr->b_l1hdr.b_arc_access = 0; 2138 hdr->b_l1hdr.b_datacnt = 1; 2139 hdr->b_l1hdr.b_tmp_cdata = NULL; 2140 2141 arc_get_data_buf(buf); 2142 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2143 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2144 2145 return (buf); 2146} 2147 2148static char *arc_onloan_tag = "onloan"; 2149 2150/* 2151 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2152 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2153 * buffers must be returned to the arc before they can be used by the DMU or 2154 * freed. 2155 */ 2156arc_buf_t * 2157arc_loan_buf(spa_t *spa, int size) 2158{ 2159 arc_buf_t *buf; 2160 2161 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2162 2163 atomic_add_64(&arc_loaned_bytes, size); 2164 return (buf); 2165} 2166 2167/* 2168 * Return a loaned arc buffer to the arc. 2169 */ 2170void 2171arc_return_buf(arc_buf_t *buf, void *tag) 2172{ 2173 arc_buf_hdr_t *hdr = buf->b_hdr; 2174 2175 ASSERT(buf->b_data != NULL); 2176 ASSERT(HDR_HAS_L1HDR(hdr)); 2177 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2178 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2179 2180 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2181} 2182 2183/* Detach an arc_buf from a dbuf (tag) */ 2184void 2185arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2186{ 2187 arc_buf_hdr_t *hdr = buf->b_hdr; 2188 2189 ASSERT(buf->b_data != NULL); 2190 ASSERT(HDR_HAS_L1HDR(hdr)); 2191 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2192 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2193 buf->b_efunc = NULL; 2194 buf->b_private = NULL; 2195 2196 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2197} 2198 2199static arc_buf_t * 2200arc_buf_clone(arc_buf_t *from) 2201{ 2202 arc_buf_t *buf; 2203 arc_buf_hdr_t *hdr = from->b_hdr; 2204 uint64_t size = hdr->b_size; 2205 2206 ASSERT(HDR_HAS_L1HDR(hdr)); 2207 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2208 2209 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2210 buf->b_hdr = hdr; 2211 buf->b_data = NULL; 2212 buf->b_efunc = NULL; 2213 buf->b_private = NULL; 2214 buf->b_next = hdr->b_l1hdr.b_buf; 2215 hdr->b_l1hdr.b_buf = buf; 2216 arc_get_data_buf(buf); 2217 bcopy(from->b_data, buf->b_data, size); 2218 2219 /* 2220 * This buffer already exists in the arc so create a duplicate 2221 * copy for the caller. If the buffer is associated with user data 2222 * then track the size and number of duplicates. These stats will be 2223 * updated as duplicate buffers are created and destroyed. 2224 */ 2225 if (HDR_ISTYPE_DATA(hdr)) { 2226 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2227 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2228 } 2229 hdr->b_l1hdr.b_datacnt += 1; 2230 return (buf); 2231} 2232 2233void 2234arc_buf_add_ref(arc_buf_t *buf, void* tag) 2235{ 2236 arc_buf_hdr_t *hdr; 2237 kmutex_t *hash_lock; 2238 2239 /* 2240 * Check to see if this buffer is evicted. Callers 2241 * must verify b_data != NULL to know if the add_ref 2242 * was successful. 2243 */ 2244 mutex_enter(&buf->b_evict_lock); 2245 if (buf->b_data == NULL) { 2246 mutex_exit(&buf->b_evict_lock); 2247 return; 2248 } 2249 hash_lock = HDR_LOCK(buf->b_hdr); 2250 mutex_enter(hash_lock); 2251 hdr = buf->b_hdr; 2252 ASSERT(HDR_HAS_L1HDR(hdr)); 2253 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2254 mutex_exit(&buf->b_evict_lock); 2255 2256 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2257 hdr->b_l1hdr.b_state == arc_mfu); 2258 2259 add_reference(hdr, hash_lock, tag); 2260 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2261 arc_access(hdr, hash_lock); 2262 mutex_exit(hash_lock); 2263 ARCSTAT_BUMP(arcstat_hits); 2264 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2265 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2266 data, metadata, hits); 2267} 2268 2269static void 2270arc_buf_free_on_write(void *data, size_t size, 2271 void (*free_func)(void *, size_t)) 2272{ 2273 l2arc_data_free_t *df; 2274 2275 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2276 df->l2df_data = data; 2277 df->l2df_size = size; 2278 df->l2df_func = free_func; 2279 mutex_enter(&l2arc_free_on_write_mtx); 2280 list_insert_head(l2arc_free_on_write, df); 2281 mutex_exit(&l2arc_free_on_write_mtx); 2282} 2283 2284/* 2285 * Free the arc data buffer. If it is an l2arc write in progress, 2286 * the buffer is placed on l2arc_free_on_write to be freed later. 2287 */ 2288static void 2289arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2290{ 2291 arc_buf_hdr_t *hdr = buf->b_hdr; 2292 2293 if (HDR_L2_WRITING(hdr)) { 2294 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2295 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2296 } else { 2297 free_func(buf->b_data, hdr->b_size); 2298 } 2299} 2300 2301static void 2302arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2303{ 2304 size_t align, asize, len; 2305 2306 ASSERT(HDR_HAS_L2HDR(hdr)); 2307 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2308 2309 /* 2310 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2311 * that doesn't exist, the header is in the arc_l2c_only state, 2312 * and there isn't anything to free (it's already been freed). 2313 */ 2314 if (!HDR_HAS_L1HDR(hdr)) 2315 return; 2316 2317 /* 2318 * The header isn't being written to the l2arc device, thus it 2319 * shouldn't have a b_tmp_cdata to free. 2320 */ 2321 if (!HDR_L2_WRITING(hdr)) { 2322 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2323 return; 2324 } 2325 2326 /* 2327 * The bufer has been chosen for writing to L2ARC, but it's 2328 * not being written just yet. In other words, 2329 * b_tmp_cdata points to exactly the same buffer as b_data, 2330 * l2arc_transform_buf hasn't been called. 2331 */ 2332 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) { 2333 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, 2334 hdr->b_l1hdr.b_buf->b_data); 2335 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_OFF); 2336 hdr->b_l1hdr.b_tmp_cdata = NULL; 2337 return; 2338 } 2339 2340 /* 2341 * There's nothing to free since the buffer was all zero's and 2342 * compressed to a zero length buffer. 2343 */ 2344 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2345 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2346 return; 2347 } 2348 2349 /* 2350 * Nothing to do if the temporary buffer was not required. 2351 */ 2352 if (hdr->b_l1hdr.b_tmp_cdata == NULL) 2353 return; 2354 2355 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2356 len = hdr->b_size; 2357 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 2358 asize = P2ROUNDUP(len, align); 2359 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, asize, 2360 zio_data_buf_free); 2361 hdr->b_l1hdr.b_tmp_cdata = NULL; 2362} 2363 2364/* 2365 * Free up buf->b_data and if 'remove' is set, then pull the 2366 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2367 */ 2368static void 2369arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2370{ 2371 arc_buf_t **bufp; 2372 2373 /* free up data associated with the buf */ 2374 if (buf->b_data != NULL) { 2375 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2376 uint64_t size = buf->b_hdr->b_size; 2377 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2378 2379 arc_cksum_verify(buf); 2380#ifdef illumos 2381 arc_buf_unwatch(buf); 2382#endif 2383 2384 if (type == ARC_BUFC_METADATA) { 2385 arc_buf_data_free(buf, zio_buf_free); 2386 arc_space_return(size, ARC_SPACE_META); 2387 } else { 2388 ASSERT(type == ARC_BUFC_DATA); 2389 arc_buf_data_free(buf, zio_data_buf_free); 2390 arc_space_return(size, ARC_SPACE_DATA); 2391 } 2392 2393 /* protected by hash lock, if in the hash table */ 2394 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2395 uint64_t *cnt = &state->arcs_lsize[type]; 2396 2397 ASSERT(refcount_is_zero( 2398 &buf->b_hdr->b_l1hdr.b_refcnt)); 2399 ASSERT(state != arc_anon && state != arc_l2c_only); 2400 2401 ASSERT3U(*cnt, >=, size); 2402 atomic_add_64(cnt, -size); 2403 } 2404 2405 (void) refcount_remove_many(&state->arcs_size, size, buf); 2406 buf->b_data = NULL; 2407 2408 /* 2409 * If we're destroying a duplicate buffer make sure 2410 * that the appropriate statistics are updated. 2411 */ 2412 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2413 HDR_ISTYPE_DATA(buf->b_hdr)) { 2414 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2415 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2416 } 2417 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2418 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2419 } 2420 2421 /* only remove the buf if requested */ 2422 if (!remove) 2423 return; 2424 2425 /* remove the buf from the hdr list */ 2426 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2427 bufp = &(*bufp)->b_next) 2428 continue; 2429 *bufp = buf->b_next; 2430 buf->b_next = NULL; 2431 2432 ASSERT(buf->b_efunc == NULL); 2433 2434 /* clean up the buf */ 2435 buf->b_hdr = NULL; 2436 kmem_cache_free(buf_cache, buf); 2437} 2438 2439static void 2440arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2441{ 2442 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2443 l2arc_dev_t *dev = l2hdr->b_dev; 2444 2445 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2446 ASSERT(HDR_HAS_L2HDR(hdr)); 2447 2448 list_remove(&dev->l2ad_buflist, hdr); 2449 2450 /* 2451 * We don't want to leak the b_tmp_cdata buffer that was 2452 * allocated in l2arc_write_buffers() 2453 */ 2454 arc_buf_l2_cdata_free(hdr); 2455 2456 /* 2457 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2458 * this header is being processed by l2arc_write_buffers() (i.e. 2459 * it's in the first stage of l2arc_write_buffers()). 2460 * Re-affirming that truth here, just to serve as a reminder. If 2461 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2462 * may not have its HDR_L2_WRITING flag set. (the write may have 2463 * completed, in which case HDR_L2_WRITING will be false and the 2464 * b_daddr field will point to the address of the buffer on disk). 2465 */ 2466 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2467 2468 /* 2469 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2470 * l2arc_write_buffers(). Since we've just removed this header 2471 * from the l2arc buffer list, this header will never reach the 2472 * second stage of l2arc_write_buffers(), which increments the 2473 * accounting stats for this header. Thus, we must be careful 2474 * not to decrement them for this header either. 2475 */ 2476 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2477 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2478 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2479 2480 vdev_space_update(dev->l2ad_vdev, 2481 -l2hdr->b_asize, 0, 0); 2482 2483 (void) refcount_remove_many(&dev->l2ad_alloc, 2484 l2hdr->b_asize, hdr); 2485 } 2486 2487 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2488} 2489 2490static void 2491arc_hdr_destroy(arc_buf_hdr_t *hdr) 2492{ 2493 if (HDR_HAS_L1HDR(hdr)) { 2494 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2495 hdr->b_l1hdr.b_datacnt > 0); 2496 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2497 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2498 } 2499 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2500 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2501 2502 if (HDR_HAS_L2HDR(hdr)) { 2503 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2504 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2505 2506 if (!buflist_held) 2507 mutex_enter(&dev->l2ad_mtx); 2508 2509 /* 2510 * Even though we checked this conditional above, we 2511 * need to check this again now that we have the 2512 * l2ad_mtx. This is because we could be racing with 2513 * another thread calling l2arc_evict() which might have 2514 * destroyed this header's L2 portion as we were waiting 2515 * to acquire the l2ad_mtx. If that happens, we don't 2516 * want to re-destroy the header's L2 portion. 2517 */ 2518 if (HDR_HAS_L2HDR(hdr)) { 2519 l2arc_trim(hdr); 2520 arc_hdr_l2hdr_destroy(hdr); 2521 } 2522 2523 if (!buflist_held) 2524 mutex_exit(&dev->l2ad_mtx); 2525 } 2526 2527 if (!BUF_EMPTY(hdr)) 2528 buf_discard_identity(hdr); 2529 2530 if (hdr->b_freeze_cksum != NULL) { 2531 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2532 hdr->b_freeze_cksum = NULL; 2533 } 2534 2535 if (HDR_HAS_L1HDR(hdr)) { 2536 while (hdr->b_l1hdr.b_buf) { 2537 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2538 2539 if (buf->b_efunc != NULL) { 2540 mutex_enter(&arc_user_evicts_lock); 2541 mutex_enter(&buf->b_evict_lock); 2542 ASSERT(buf->b_hdr != NULL); 2543 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2544 hdr->b_l1hdr.b_buf = buf->b_next; 2545 buf->b_hdr = &arc_eviction_hdr; 2546 buf->b_next = arc_eviction_list; 2547 arc_eviction_list = buf; 2548 mutex_exit(&buf->b_evict_lock); 2549 cv_signal(&arc_user_evicts_cv); 2550 mutex_exit(&arc_user_evicts_lock); 2551 } else { 2552 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2553 } 2554 } 2555#ifdef ZFS_DEBUG 2556 if (hdr->b_l1hdr.b_thawed != NULL) { 2557 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2558 hdr->b_l1hdr.b_thawed = NULL; 2559 } 2560#endif 2561 } 2562 2563 ASSERT3P(hdr->b_hash_next, ==, NULL); 2564 if (HDR_HAS_L1HDR(hdr)) { 2565 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2566 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2567 kmem_cache_free(hdr_full_cache, hdr); 2568 } else { 2569 kmem_cache_free(hdr_l2only_cache, hdr); 2570 } 2571} 2572 2573void 2574arc_buf_free(arc_buf_t *buf, void *tag) 2575{ 2576 arc_buf_hdr_t *hdr = buf->b_hdr; 2577 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2578 2579 ASSERT(buf->b_efunc == NULL); 2580 ASSERT(buf->b_data != NULL); 2581 2582 if (hashed) { 2583 kmutex_t *hash_lock = HDR_LOCK(hdr); 2584 2585 mutex_enter(hash_lock); 2586 hdr = buf->b_hdr; 2587 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2588 2589 (void) remove_reference(hdr, hash_lock, tag); 2590 if (hdr->b_l1hdr.b_datacnt > 1) { 2591 arc_buf_destroy(buf, TRUE); 2592 } else { 2593 ASSERT(buf == hdr->b_l1hdr.b_buf); 2594 ASSERT(buf->b_efunc == NULL); 2595 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2596 } 2597 mutex_exit(hash_lock); 2598 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2599 int destroy_hdr; 2600 /* 2601 * We are in the middle of an async write. Don't destroy 2602 * this buffer unless the write completes before we finish 2603 * decrementing the reference count. 2604 */ 2605 mutex_enter(&arc_user_evicts_lock); 2606 (void) remove_reference(hdr, NULL, tag); 2607 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2608 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2609 mutex_exit(&arc_user_evicts_lock); 2610 if (destroy_hdr) 2611 arc_hdr_destroy(hdr); 2612 } else { 2613 if (remove_reference(hdr, NULL, tag) > 0) 2614 arc_buf_destroy(buf, TRUE); 2615 else 2616 arc_hdr_destroy(hdr); 2617 } 2618} 2619 2620boolean_t 2621arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2622{ 2623 arc_buf_hdr_t *hdr = buf->b_hdr; 2624 kmutex_t *hash_lock = HDR_LOCK(hdr); 2625 boolean_t no_callback = (buf->b_efunc == NULL); 2626 2627 if (hdr->b_l1hdr.b_state == arc_anon) { 2628 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2629 arc_buf_free(buf, tag); 2630 return (no_callback); 2631 } 2632 2633 mutex_enter(hash_lock); 2634 hdr = buf->b_hdr; 2635 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2636 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2637 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2638 ASSERT(buf->b_data != NULL); 2639 2640 (void) remove_reference(hdr, hash_lock, tag); 2641 if (hdr->b_l1hdr.b_datacnt > 1) { 2642 if (no_callback) 2643 arc_buf_destroy(buf, TRUE); 2644 } else if (no_callback) { 2645 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2646 ASSERT(buf->b_efunc == NULL); 2647 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2648 } 2649 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2650 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2651 mutex_exit(hash_lock); 2652 return (no_callback); 2653} 2654 2655int32_t 2656arc_buf_size(arc_buf_t *buf) 2657{ 2658 return (buf->b_hdr->b_size); 2659} 2660 2661/* 2662 * Called from the DMU to determine if the current buffer should be 2663 * evicted. In order to ensure proper locking, the eviction must be initiated 2664 * from the DMU. Return true if the buffer is associated with user data and 2665 * duplicate buffers still exist. 2666 */ 2667boolean_t 2668arc_buf_eviction_needed(arc_buf_t *buf) 2669{ 2670 arc_buf_hdr_t *hdr; 2671 boolean_t evict_needed = B_FALSE; 2672 2673 if (zfs_disable_dup_eviction) 2674 return (B_FALSE); 2675 2676 mutex_enter(&buf->b_evict_lock); 2677 hdr = buf->b_hdr; 2678 if (hdr == NULL) { 2679 /* 2680 * We are in arc_do_user_evicts(); let that function 2681 * perform the eviction. 2682 */ 2683 ASSERT(buf->b_data == NULL); 2684 mutex_exit(&buf->b_evict_lock); 2685 return (B_FALSE); 2686 } else if (buf->b_data == NULL) { 2687 /* 2688 * We have already been added to the arc eviction list; 2689 * recommend eviction. 2690 */ 2691 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2692 mutex_exit(&buf->b_evict_lock); 2693 return (B_TRUE); 2694 } 2695 2696 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2697 evict_needed = B_TRUE; 2698 2699 mutex_exit(&buf->b_evict_lock); 2700 return (evict_needed); 2701} 2702 2703/* 2704 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2705 * state of the header is dependent on it's state prior to entering this 2706 * function. The following transitions are possible: 2707 * 2708 * - arc_mru -> arc_mru_ghost 2709 * - arc_mfu -> arc_mfu_ghost 2710 * - arc_mru_ghost -> arc_l2c_only 2711 * - arc_mru_ghost -> deleted 2712 * - arc_mfu_ghost -> arc_l2c_only 2713 * - arc_mfu_ghost -> deleted 2714 */ 2715static int64_t 2716arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2717{ 2718 arc_state_t *evicted_state, *state; 2719 int64_t bytes_evicted = 0; 2720 2721 ASSERT(MUTEX_HELD(hash_lock)); 2722 ASSERT(HDR_HAS_L1HDR(hdr)); 2723 2724 state = hdr->b_l1hdr.b_state; 2725 if (GHOST_STATE(state)) { 2726 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2727 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2728 2729 /* 2730 * l2arc_write_buffers() relies on a header's L1 portion 2731 * (i.e. it's b_tmp_cdata field) during it's write phase. 2732 * Thus, we cannot push a header onto the arc_l2c_only 2733 * state (removing it's L1 piece) until the header is 2734 * done being written to the l2arc. 2735 */ 2736 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2737 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2738 return (bytes_evicted); 2739 } 2740 2741 ARCSTAT_BUMP(arcstat_deleted); 2742 bytes_evicted += hdr->b_size; 2743 2744 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2745 2746 if (HDR_HAS_L2HDR(hdr)) { 2747 /* 2748 * This buffer is cached on the 2nd Level ARC; 2749 * don't destroy the header. 2750 */ 2751 arc_change_state(arc_l2c_only, hdr, hash_lock); 2752 /* 2753 * dropping from L1+L2 cached to L2-only, 2754 * realloc to remove the L1 header. 2755 */ 2756 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2757 hdr_l2only_cache); 2758 } else { 2759 arc_change_state(arc_anon, hdr, hash_lock); 2760 arc_hdr_destroy(hdr); 2761 } 2762 return (bytes_evicted); 2763 } 2764 2765 ASSERT(state == arc_mru || state == arc_mfu); 2766 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2767 2768 /* prefetch buffers have a minimum lifespan */ 2769 if (HDR_IO_IN_PROGRESS(hdr) || 2770 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2771 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2772 arc_min_prefetch_lifespan)) { 2773 ARCSTAT_BUMP(arcstat_evict_skip); 2774 return (bytes_evicted); 2775 } 2776 2777 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2778 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2779 while (hdr->b_l1hdr.b_buf) { 2780 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2781 if (!mutex_tryenter(&buf->b_evict_lock)) { 2782 ARCSTAT_BUMP(arcstat_mutex_miss); 2783 break; 2784 } 2785 if (buf->b_data != NULL) 2786 bytes_evicted += hdr->b_size; 2787 if (buf->b_efunc != NULL) { 2788 mutex_enter(&arc_user_evicts_lock); 2789 arc_buf_destroy(buf, FALSE); 2790 hdr->b_l1hdr.b_buf = buf->b_next; 2791 buf->b_hdr = &arc_eviction_hdr; 2792 buf->b_next = arc_eviction_list; 2793 arc_eviction_list = buf; 2794 cv_signal(&arc_user_evicts_cv); 2795 mutex_exit(&arc_user_evicts_lock); 2796 mutex_exit(&buf->b_evict_lock); 2797 } else { 2798 mutex_exit(&buf->b_evict_lock); 2799 arc_buf_destroy(buf, TRUE); 2800 } 2801 } 2802 2803 if (HDR_HAS_L2HDR(hdr)) { 2804 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2805 } else { 2806 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2807 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2808 else 2809 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2810 } 2811 2812 if (hdr->b_l1hdr.b_datacnt == 0) { 2813 arc_change_state(evicted_state, hdr, hash_lock); 2814 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2815 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2816 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2817 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2818 } 2819 2820 return (bytes_evicted); 2821} 2822 2823static uint64_t 2824arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2825 uint64_t spa, int64_t bytes) 2826{ 2827 multilist_sublist_t *mls; 2828 uint64_t bytes_evicted = 0; 2829 arc_buf_hdr_t *hdr; 2830 kmutex_t *hash_lock; 2831 int evict_count = 0; 2832 2833 ASSERT3P(marker, !=, NULL); 2834 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2835 2836 mls = multilist_sublist_lock(ml, idx); 2837 2838 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2839 hdr = multilist_sublist_prev(mls, marker)) { 2840 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2841 (evict_count >= zfs_arc_evict_batch_limit)) 2842 break; 2843 2844 /* 2845 * To keep our iteration location, move the marker 2846 * forward. Since we're not holding hdr's hash lock, we 2847 * must be very careful and not remove 'hdr' from the 2848 * sublist. Otherwise, other consumers might mistake the 2849 * 'hdr' as not being on a sublist when they call the 2850 * multilist_link_active() function (they all rely on 2851 * the hash lock protecting concurrent insertions and 2852 * removals). multilist_sublist_move_forward() was 2853 * specifically implemented to ensure this is the case 2854 * (only 'marker' will be removed and re-inserted). 2855 */ 2856 multilist_sublist_move_forward(mls, marker); 2857 2858 /* 2859 * The only case where the b_spa field should ever be 2860 * zero, is the marker headers inserted by 2861 * arc_evict_state(). It's possible for multiple threads 2862 * to be calling arc_evict_state() concurrently (e.g. 2863 * dsl_pool_close() and zio_inject_fault()), so we must 2864 * skip any markers we see from these other threads. 2865 */ 2866 if (hdr->b_spa == 0) 2867 continue; 2868 2869 /* we're only interested in evicting buffers of a certain spa */ 2870 if (spa != 0 && hdr->b_spa != spa) { 2871 ARCSTAT_BUMP(arcstat_evict_skip); 2872 continue; 2873 } 2874 2875 hash_lock = HDR_LOCK(hdr); 2876 2877 /* 2878 * We aren't calling this function from any code path 2879 * that would already be holding a hash lock, so we're 2880 * asserting on this assumption to be defensive in case 2881 * this ever changes. Without this check, it would be 2882 * possible to incorrectly increment arcstat_mutex_miss 2883 * below (e.g. if the code changed such that we called 2884 * this function with a hash lock held). 2885 */ 2886 ASSERT(!MUTEX_HELD(hash_lock)); 2887 2888 if (mutex_tryenter(hash_lock)) { 2889 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2890 mutex_exit(hash_lock); 2891 2892 bytes_evicted += evicted; 2893 2894 /* 2895 * If evicted is zero, arc_evict_hdr() must have 2896 * decided to skip this header, don't increment 2897 * evict_count in this case. 2898 */ 2899 if (evicted != 0) 2900 evict_count++; 2901 2902 /* 2903 * If arc_size isn't overflowing, signal any 2904 * threads that might happen to be waiting. 2905 * 2906 * For each header evicted, we wake up a single 2907 * thread. If we used cv_broadcast, we could 2908 * wake up "too many" threads causing arc_size 2909 * to significantly overflow arc_c; since 2910 * arc_get_data_buf() doesn't check for overflow 2911 * when it's woken up (it doesn't because it's 2912 * possible for the ARC to be overflowing while 2913 * full of un-evictable buffers, and the 2914 * function should proceed in this case). 2915 * 2916 * If threads are left sleeping, due to not 2917 * using cv_broadcast, they will be woken up 2918 * just before arc_reclaim_thread() sleeps. 2919 */ 2920 mutex_enter(&arc_reclaim_lock); 2921 if (!arc_is_overflowing()) 2922 cv_signal(&arc_reclaim_waiters_cv); 2923 mutex_exit(&arc_reclaim_lock); 2924 } else { 2925 ARCSTAT_BUMP(arcstat_mutex_miss); 2926 } 2927 } 2928 2929 multilist_sublist_unlock(mls); 2930 2931 return (bytes_evicted); 2932} 2933 2934/* 2935 * Evict buffers from the given arc state, until we've removed the 2936 * specified number of bytes. Move the removed buffers to the 2937 * appropriate evict state. 2938 * 2939 * This function makes a "best effort". It skips over any buffers 2940 * it can't get a hash_lock on, and so, may not catch all candidates. 2941 * It may also return without evicting as much space as requested. 2942 * 2943 * If bytes is specified using the special value ARC_EVICT_ALL, this 2944 * will evict all available (i.e. unlocked and evictable) buffers from 2945 * the given arc state; which is used by arc_flush(). 2946 */ 2947static uint64_t 2948arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2949 arc_buf_contents_t type) 2950{ 2951 uint64_t total_evicted = 0; 2952 multilist_t *ml = &state->arcs_list[type]; 2953 int num_sublists; 2954 arc_buf_hdr_t **markers; 2955 2956 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2957 2958 num_sublists = multilist_get_num_sublists(ml); 2959 2960 /* 2961 * If we've tried to evict from each sublist, made some 2962 * progress, but still have not hit the target number of bytes 2963 * to evict, we want to keep trying. The markers allow us to 2964 * pick up where we left off for each individual sublist, rather 2965 * than starting from the tail each time. 2966 */ 2967 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2968 for (int i = 0; i < num_sublists; i++) { 2969 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2970 2971 /* 2972 * A b_spa of 0 is used to indicate that this header is 2973 * a marker. This fact is used in arc_adjust_type() and 2974 * arc_evict_state_impl(). 2975 */ 2976 markers[i]->b_spa = 0; 2977 2978 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2979 multilist_sublist_insert_tail(mls, markers[i]); 2980 multilist_sublist_unlock(mls); 2981 } 2982 2983 /* 2984 * While we haven't hit our target number of bytes to evict, or 2985 * we're evicting all available buffers. 2986 */ 2987 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2988 /* 2989 * Start eviction using a randomly selected sublist, 2990 * this is to try and evenly balance eviction across all 2991 * sublists. Always starting at the same sublist 2992 * (e.g. index 0) would cause evictions to favor certain 2993 * sublists over others. 2994 */ 2995 int sublist_idx = multilist_get_random_index(ml); 2996 uint64_t scan_evicted = 0; 2997 2998 for (int i = 0; i < num_sublists; i++) { 2999 uint64_t bytes_remaining; 3000 uint64_t bytes_evicted; 3001 3002 if (bytes == ARC_EVICT_ALL) 3003 bytes_remaining = ARC_EVICT_ALL; 3004 else if (total_evicted < bytes) 3005 bytes_remaining = bytes - total_evicted; 3006 else 3007 break; 3008 3009 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3010 markers[sublist_idx], spa, bytes_remaining); 3011 3012 scan_evicted += bytes_evicted; 3013 total_evicted += bytes_evicted; 3014 3015 /* we've reached the end, wrap to the beginning */ 3016 if (++sublist_idx >= num_sublists) 3017 sublist_idx = 0; 3018 } 3019 3020 /* 3021 * If we didn't evict anything during this scan, we have 3022 * no reason to believe we'll evict more during another 3023 * scan, so break the loop. 3024 */ 3025 if (scan_evicted == 0) { 3026 /* This isn't possible, let's make that obvious */ 3027 ASSERT3S(bytes, !=, 0); 3028 3029 /* 3030 * When bytes is ARC_EVICT_ALL, the only way to 3031 * break the loop is when scan_evicted is zero. 3032 * In that case, we actually have evicted enough, 3033 * so we don't want to increment the kstat. 3034 */ 3035 if (bytes != ARC_EVICT_ALL) { 3036 ASSERT3S(total_evicted, <, bytes); 3037 ARCSTAT_BUMP(arcstat_evict_not_enough); 3038 } 3039 3040 break; 3041 } 3042 } 3043 3044 for (int i = 0; i < num_sublists; i++) { 3045 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3046 multilist_sublist_remove(mls, markers[i]); 3047 multilist_sublist_unlock(mls); 3048 3049 kmem_cache_free(hdr_full_cache, markers[i]); 3050 } 3051 kmem_free(markers, sizeof (*markers) * num_sublists); 3052 3053 return (total_evicted); 3054} 3055 3056/* 3057 * Flush all "evictable" data of the given type from the arc state 3058 * specified. This will not evict any "active" buffers (i.e. referenced). 3059 * 3060 * When 'retry' is set to FALSE, the function will make a single pass 3061 * over the state and evict any buffers that it can. Since it doesn't 3062 * continually retry the eviction, it might end up leaving some buffers 3063 * in the ARC due to lock misses. 3064 * 3065 * When 'retry' is set to TRUE, the function will continually retry the 3066 * eviction until *all* evictable buffers have been removed from the 3067 * state. As a result, if concurrent insertions into the state are 3068 * allowed (e.g. if the ARC isn't shutting down), this function might 3069 * wind up in an infinite loop, continually trying to evict buffers. 3070 */ 3071static uint64_t 3072arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3073 boolean_t retry) 3074{ 3075 uint64_t evicted = 0; 3076 3077 while (state->arcs_lsize[type] != 0) { 3078 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3079 3080 if (!retry) 3081 break; 3082 } 3083 3084 return (evicted); 3085} 3086 3087/* 3088 * Evict the specified number of bytes from the state specified, 3089 * restricting eviction to the spa and type given. This function 3090 * prevents us from trying to evict more from a state's list than 3091 * is "evictable", and to skip evicting altogether when passed a 3092 * negative value for "bytes". In contrast, arc_evict_state() will 3093 * evict everything it can, when passed a negative value for "bytes". 3094 */ 3095static uint64_t 3096arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3097 arc_buf_contents_t type) 3098{ 3099 int64_t delta; 3100 3101 if (bytes > 0 && state->arcs_lsize[type] > 0) { 3102 delta = MIN(state->arcs_lsize[type], bytes); 3103 return (arc_evict_state(state, spa, delta, type)); 3104 } 3105 3106 return (0); 3107} 3108 3109/* 3110 * Evict metadata buffers from the cache, such that arc_meta_used is 3111 * capped by the arc_meta_limit tunable. 3112 */ 3113static uint64_t 3114arc_adjust_meta(void) 3115{ 3116 uint64_t total_evicted = 0; 3117 int64_t target; 3118 3119 /* 3120 * If we're over the meta limit, we want to evict enough 3121 * metadata to get back under the meta limit. We don't want to 3122 * evict so much that we drop the MRU below arc_p, though. If 3123 * we're over the meta limit more than we're over arc_p, we 3124 * evict some from the MRU here, and some from the MFU below. 3125 */ 3126 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3127 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3128 refcount_count(&arc_mru->arcs_size) - arc_p)); 3129 3130 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3131 3132 /* 3133 * Similar to the above, we want to evict enough bytes to get us 3134 * below the meta limit, but not so much as to drop us below the 3135 * space alloted to the MFU (which is defined as arc_c - arc_p). 3136 */ 3137 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3138 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3139 3140 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3141 3142 return (total_evicted); 3143} 3144 3145/* 3146 * Return the type of the oldest buffer in the given arc state 3147 * 3148 * This function will select a random sublist of type ARC_BUFC_DATA and 3149 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3150 * is compared, and the type which contains the "older" buffer will be 3151 * returned. 3152 */ 3153static arc_buf_contents_t 3154arc_adjust_type(arc_state_t *state) 3155{ 3156 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3157 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3158 int data_idx = multilist_get_random_index(data_ml); 3159 int meta_idx = multilist_get_random_index(meta_ml); 3160 multilist_sublist_t *data_mls; 3161 multilist_sublist_t *meta_mls; 3162 arc_buf_contents_t type; 3163 arc_buf_hdr_t *data_hdr; 3164 arc_buf_hdr_t *meta_hdr; 3165 3166 /* 3167 * We keep the sublist lock until we're finished, to prevent 3168 * the headers from being destroyed via arc_evict_state(). 3169 */ 3170 data_mls = multilist_sublist_lock(data_ml, data_idx); 3171 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3172 3173 /* 3174 * These two loops are to ensure we skip any markers that 3175 * might be at the tail of the lists due to arc_evict_state(). 3176 */ 3177 3178 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3179 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3180 if (data_hdr->b_spa != 0) 3181 break; 3182 } 3183 3184 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3185 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3186 if (meta_hdr->b_spa != 0) 3187 break; 3188 } 3189 3190 if (data_hdr == NULL && meta_hdr == NULL) { 3191 type = ARC_BUFC_DATA; 3192 } else if (data_hdr == NULL) { 3193 ASSERT3P(meta_hdr, !=, NULL); 3194 type = ARC_BUFC_METADATA; 3195 } else if (meta_hdr == NULL) { 3196 ASSERT3P(data_hdr, !=, NULL); 3197 type = ARC_BUFC_DATA; 3198 } else { 3199 ASSERT3P(data_hdr, !=, NULL); 3200 ASSERT3P(meta_hdr, !=, NULL); 3201 3202 /* The headers can't be on the sublist without an L1 header */ 3203 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3204 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3205 3206 if (data_hdr->b_l1hdr.b_arc_access < 3207 meta_hdr->b_l1hdr.b_arc_access) { 3208 type = ARC_BUFC_DATA; 3209 } else { 3210 type = ARC_BUFC_METADATA; 3211 } 3212 } 3213 3214 multilist_sublist_unlock(meta_mls); 3215 multilist_sublist_unlock(data_mls); 3216 3217 return (type); 3218} 3219 3220/* 3221 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3222 */ 3223static uint64_t 3224arc_adjust(void) 3225{ 3226 uint64_t total_evicted = 0; 3227 uint64_t bytes; 3228 int64_t target; 3229 3230 /* 3231 * If we're over arc_meta_limit, we want to correct that before 3232 * potentially evicting data buffers below. 3233 */ 3234 total_evicted += arc_adjust_meta(); 3235 3236 /* 3237 * Adjust MRU size 3238 * 3239 * If we're over the target cache size, we want to evict enough 3240 * from the list to get back to our target size. We don't want 3241 * to evict too much from the MRU, such that it drops below 3242 * arc_p. So, if we're over our target cache size more than 3243 * the MRU is over arc_p, we'll evict enough to get back to 3244 * arc_p here, and then evict more from the MFU below. 3245 */ 3246 target = MIN((int64_t)(arc_size - arc_c), 3247 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3248 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3249 3250 /* 3251 * If we're below arc_meta_min, always prefer to evict data. 3252 * Otherwise, try to satisfy the requested number of bytes to 3253 * evict from the type which contains older buffers; in an 3254 * effort to keep newer buffers in the cache regardless of their 3255 * type. If we cannot satisfy the number of bytes from this 3256 * type, spill over into the next type. 3257 */ 3258 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3259 arc_meta_used > arc_meta_min) { 3260 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3261 total_evicted += bytes; 3262 3263 /* 3264 * If we couldn't evict our target number of bytes from 3265 * metadata, we try to get the rest from data. 3266 */ 3267 target -= bytes; 3268 3269 total_evicted += 3270 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3271 } else { 3272 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3273 total_evicted += bytes; 3274 3275 /* 3276 * If we couldn't evict our target number of bytes from 3277 * data, we try to get the rest from metadata. 3278 */ 3279 target -= bytes; 3280 3281 total_evicted += 3282 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3283 } 3284 3285 /* 3286 * Adjust MFU size 3287 * 3288 * Now that we've tried to evict enough from the MRU to get its 3289 * size back to arc_p, if we're still above the target cache 3290 * size, we evict the rest from the MFU. 3291 */ 3292 target = arc_size - arc_c; 3293 3294 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3295 arc_meta_used > arc_meta_min) { 3296 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3297 total_evicted += bytes; 3298 3299 /* 3300 * If we couldn't evict our target number of bytes from 3301 * metadata, we try to get the rest from data. 3302 */ 3303 target -= bytes; 3304 3305 total_evicted += 3306 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3307 } else { 3308 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3309 total_evicted += bytes; 3310 3311 /* 3312 * If we couldn't evict our target number of bytes from 3313 * data, we try to get the rest from data. 3314 */ 3315 target -= bytes; 3316 3317 total_evicted += 3318 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3319 } 3320 3321 /* 3322 * Adjust ghost lists 3323 * 3324 * In addition to the above, the ARC also defines target values 3325 * for the ghost lists. The sum of the mru list and mru ghost 3326 * list should never exceed the target size of the cache, and 3327 * the sum of the mru list, mfu list, mru ghost list, and mfu 3328 * ghost list should never exceed twice the target size of the 3329 * cache. The following logic enforces these limits on the ghost 3330 * caches, and evicts from them as needed. 3331 */ 3332 target = refcount_count(&arc_mru->arcs_size) + 3333 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3334 3335 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3336 total_evicted += bytes; 3337 3338 target -= bytes; 3339 3340 total_evicted += 3341 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3342 3343 /* 3344 * We assume the sum of the mru list and mfu list is less than 3345 * or equal to arc_c (we enforced this above), which means we 3346 * can use the simpler of the two equations below: 3347 * 3348 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3349 * mru ghost + mfu ghost <= arc_c 3350 */ 3351 target = refcount_count(&arc_mru_ghost->arcs_size) + 3352 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3353 3354 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3355 total_evicted += bytes; 3356 3357 target -= bytes; 3358 3359 total_evicted += 3360 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3361 3362 return (total_evicted); 3363} 3364 3365static void 3366arc_do_user_evicts(void) 3367{ 3368 mutex_enter(&arc_user_evicts_lock); 3369 while (arc_eviction_list != NULL) { 3370 arc_buf_t *buf = arc_eviction_list; 3371 arc_eviction_list = buf->b_next; 3372 mutex_enter(&buf->b_evict_lock); 3373 buf->b_hdr = NULL; 3374 mutex_exit(&buf->b_evict_lock); 3375 mutex_exit(&arc_user_evicts_lock); 3376 3377 if (buf->b_efunc != NULL) 3378 VERIFY0(buf->b_efunc(buf->b_private)); 3379 3380 buf->b_efunc = NULL; 3381 buf->b_private = NULL; 3382 kmem_cache_free(buf_cache, buf); 3383 mutex_enter(&arc_user_evicts_lock); 3384 } 3385 mutex_exit(&arc_user_evicts_lock); 3386} 3387 3388void 3389arc_flush(spa_t *spa, boolean_t retry) 3390{ 3391 uint64_t guid = 0; 3392 3393 /* 3394 * If retry is TRUE, a spa must not be specified since we have 3395 * no good way to determine if all of a spa's buffers have been 3396 * evicted from an arc state. 3397 */ 3398 ASSERT(!retry || spa == 0); 3399 3400 if (spa != NULL) 3401 guid = spa_load_guid(spa); 3402 3403 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3404 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3405 3406 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3407 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3408 3409 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3410 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3411 3412 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3413 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3414 3415 arc_do_user_evicts(); 3416 ASSERT(spa || arc_eviction_list == NULL); 3417} 3418 3419void 3420arc_shrink(int64_t to_free) 3421{ 3422 if (arc_c > arc_c_min) { 3423 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3424 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3425 if (arc_c > arc_c_min + to_free) 3426 atomic_add_64(&arc_c, -to_free); 3427 else 3428 arc_c = arc_c_min; 3429 3430 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3431 if (arc_c > arc_size) 3432 arc_c = MAX(arc_size, arc_c_min); 3433 if (arc_p > arc_c) 3434 arc_p = (arc_c >> 1); 3435 3436 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3437 arc_p); 3438 3439 ASSERT(arc_c >= arc_c_min); 3440 ASSERT((int64_t)arc_p >= 0); 3441 } 3442 3443 if (arc_size > arc_c) { 3444 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3445 uint64_t, arc_c); 3446 (void) arc_adjust(); 3447 } 3448} 3449 3450static long needfree = 0; 3451 3452typedef enum free_memory_reason_t { 3453 FMR_UNKNOWN, 3454 FMR_NEEDFREE, 3455 FMR_LOTSFREE, 3456 FMR_SWAPFS_MINFREE, 3457 FMR_PAGES_PP_MAXIMUM, 3458 FMR_HEAP_ARENA, 3459 FMR_ZIO_ARENA, 3460 FMR_ZIO_FRAG, 3461} free_memory_reason_t; 3462 3463int64_t last_free_memory; 3464free_memory_reason_t last_free_reason; 3465 3466/* 3467 * Additional reserve of pages for pp_reserve. 3468 */ 3469int64_t arc_pages_pp_reserve = 64; 3470 3471/* 3472 * Additional reserve of pages for swapfs. 3473 */ 3474int64_t arc_swapfs_reserve = 64; 3475 3476/* 3477 * Return the amount of memory that can be consumed before reclaim will be 3478 * needed. Positive if there is sufficient free memory, negative indicates 3479 * the amount of memory that needs to be freed up. 3480 */ 3481static int64_t 3482arc_available_memory(void) 3483{ 3484 int64_t lowest = INT64_MAX; 3485 int64_t n; 3486 free_memory_reason_t r = FMR_UNKNOWN; 3487 3488#ifdef _KERNEL 3489 if (needfree > 0) { 3490 n = PAGESIZE * (-needfree); 3491 if (n < lowest) { 3492 lowest = n; 3493 r = FMR_NEEDFREE; 3494 } 3495 } 3496 3497 /* 3498 * Cooperate with pagedaemon when it's time for it to scan 3499 * and reclaim some pages. 3500 */ 3501 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3502 if (n < lowest) { 3503 lowest = n; 3504 r = FMR_LOTSFREE; 3505 } 3506 3507#ifdef illumos 3508 /* 3509 * check that we're out of range of the pageout scanner. It starts to 3510 * schedule paging if freemem is less than lotsfree and needfree. 3511 * lotsfree is the high-water mark for pageout, and needfree is the 3512 * number of needed free pages. We add extra pages here to make sure 3513 * the scanner doesn't start up while we're freeing memory. 3514 */ 3515 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3516 if (n < lowest) { 3517 lowest = n; 3518 r = FMR_LOTSFREE; 3519 } 3520 3521 /* 3522 * check to make sure that swapfs has enough space so that anon 3523 * reservations can still succeed. anon_resvmem() checks that the 3524 * availrmem is greater than swapfs_minfree, and the number of reserved 3525 * swap pages. We also add a bit of extra here just to prevent 3526 * circumstances from getting really dire. 3527 */ 3528 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3529 desfree - arc_swapfs_reserve); 3530 if (n < lowest) { 3531 lowest = n; 3532 r = FMR_SWAPFS_MINFREE; 3533 } 3534 3535 3536 /* 3537 * Check that we have enough availrmem that memory locking (e.g., via 3538 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3539 * stores the number of pages that cannot be locked; when availrmem 3540 * drops below pages_pp_maximum, page locking mechanisms such as 3541 * page_pp_lock() will fail.) 3542 */ 3543 n = PAGESIZE * (availrmem - pages_pp_maximum - 3544 arc_pages_pp_reserve); 3545 if (n < lowest) { 3546 lowest = n; 3547 r = FMR_PAGES_PP_MAXIMUM; 3548 } 3549 3550#endif /* illumos */ 3551#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3552 /* 3553 * If we're on an i386 platform, it's possible that we'll exhaust the 3554 * kernel heap space before we ever run out of available physical 3555 * memory. Most checks of the size of the heap_area compare against 3556 * tune.t_minarmem, which is the minimum available real memory that we 3557 * can have in the system. However, this is generally fixed at 25 pages 3558 * which is so low that it's useless. In this comparison, we seek to 3559 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3560 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3561 * free) 3562 */ 3563 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3564 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3565 if (n < lowest) { 3566 lowest = n; 3567 r = FMR_HEAP_ARENA; 3568 } 3569#define zio_arena NULL 3570#else 3571#define zio_arena heap_arena 3572#endif 3573 3574 /* 3575 * If zio data pages are being allocated out of a separate heap segment, 3576 * then enforce that the size of available vmem for this arena remains 3577 * above about 1/16th free. 3578 * 3579 * Note: The 1/16th arena free requirement was put in place 3580 * to aggressively evict memory from the arc in order to avoid 3581 * memory fragmentation issues. 3582 */ 3583 if (zio_arena != NULL) { 3584 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3585 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3586 if (n < lowest) { 3587 lowest = n; 3588 r = FMR_ZIO_ARENA; 3589 } 3590 } 3591 3592 /* 3593 * Above limits know nothing about real level of KVA fragmentation. 3594 * Start aggressive reclamation if too little sequential KVA left. 3595 */ 3596 if (lowest > 0) { 3597 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3598 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3599 INT64_MAX; 3600 if (n < lowest) { 3601 lowest = n; 3602 r = FMR_ZIO_FRAG; 3603 } 3604 } 3605 3606#else /* _KERNEL */ 3607 /* Every 100 calls, free a small amount */ 3608 if (spa_get_random(100) == 0) 3609 lowest = -1024; 3610#endif /* _KERNEL */ 3611 3612 last_free_memory = lowest; 3613 last_free_reason = r; 3614 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3615 return (lowest); 3616} 3617 3618 3619/* 3620 * Determine if the system is under memory pressure and is asking 3621 * to reclaim memory. A return value of TRUE indicates that the system 3622 * is under memory pressure and that the arc should adjust accordingly. 3623 */ 3624static boolean_t 3625arc_reclaim_needed(void) 3626{ 3627 return (arc_available_memory() < 0); 3628} 3629 3630extern kmem_cache_t *zio_buf_cache[]; 3631extern kmem_cache_t *zio_data_buf_cache[]; 3632extern kmem_cache_t *range_seg_cache; 3633 3634static __noinline void 3635arc_kmem_reap_now(void) 3636{ 3637 size_t i; 3638 kmem_cache_t *prev_cache = NULL; 3639 kmem_cache_t *prev_data_cache = NULL; 3640 3641 DTRACE_PROBE(arc__kmem_reap_start); 3642#ifdef _KERNEL 3643 if (arc_meta_used >= arc_meta_limit) { 3644 /* 3645 * We are exceeding our meta-data cache limit. 3646 * Purge some DNLC entries to release holds on meta-data. 3647 */ 3648 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3649 } 3650#if defined(__i386) 3651 /* 3652 * Reclaim unused memory from all kmem caches. 3653 */ 3654 kmem_reap(); 3655#endif 3656#endif 3657 3658 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3659 if (zio_buf_cache[i] != prev_cache) { 3660 prev_cache = zio_buf_cache[i]; 3661 kmem_cache_reap_now(zio_buf_cache[i]); 3662 } 3663 if (zio_data_buf_cache[i] != prev_data_cache) { 3664 prev_data_cache = zio_data_buf_cache[i]; 3665 kmem_cache_reap_now(zio_data_buf_cache[i]); 3666 } 3667 } 3668 kmem_cache_reap_now(buf_cache); 3669 kmem_cache_reap_now(hdr_full_cache); 3670 kmem_cache_reap_now(hdr_l2only_cache); 3671 kmem_cache_reap_now(range_seg_cache); 3672 3673#ifdef illumos 3674 if (zio_arena != NULL) { 3675 /* 3676 * Ask the vmem arena to reclaim unused memory from its 3677 * quantum caches. 3678 */ 3679 vmem_qcache_reap(zio_arena); 3680 } 3681#endif 3682 DTRACE_PROBE(arc__kmem_reap_end); 3683} 3684 3685/* 3686 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3687 * enough data and signal them to proceed. When this happens, the threads in 3688 * arc_get_data_buf() are sleeping while holding the hash lock for their 3689 * particular arc header. Thus, we must be careful to never sleep on a 3690 * hash lock in this thread. This is to prevent the following deadlock: 3691 * 3692 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3693 * waiting for the reclaim thread to signal it. 3694 * 3695 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3696 * fails, and goes to sleep forever. 3697 * 3698 * This possible deadlock is avoided by always acquiring a hash lock 3699 * using mutex_tryenter() from arc_reclaim_thread(). 3700 */ 3701static void 3702arc_reclaim_thread(void *dummy __unused) 3703{ 3704 hrtime_t growtime = 0; 3705 callb_cpr_t cpr; 3706 3707 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3708 3709 mutex_enter(&arc_reclaim_lock); 3710 while (!arc_reclaim_thread_exit) { 3711 int64_t free_memory = arc_available_memory(); 3712 uint64_t evicted = 0; 3713 3714 mutex_exit(&arc_reclaim_lock); 3715 3716 if (free_memory < 0) { 3717 3718 arc_no_grow = B_TRUE; 3719 arc_warm = B_TRUE; 3720 3721 /* 3722 * Wait at least zfs_grow_retry (default 60) seconds 3723 * before considering growing. 3724 */ 3725 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 3726 3727 arc_kmem_reap_now(); 3728 3729 /* 3730 * If we are still low on memory, shrink the ARC 3731 * so that we have arc_shrink_min free space. 3732 */ 3733 free_memory = arc_available_memory(); 3734 3735 int64_t to_free = 3736 (arc_c >> arc_shrink_shift) - free_memory; 3737 if (to_free > 0) { 3738#ifdef _KERNEL 3739 to_free = MAX(to_free, ptob(needfree)); 3740#endif 3741 arc_shrink(to_free); 3742 } 3743 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3744 arc_no_grow = B_TRUE; 3745 } else if (gethrtime() >= growtime) { 3746 arc_no_grow = B_FALSE; 3747 } 3748 3749 evicted = arc_adjust(); 3750 3751 mutex_enter(&arc_reclaim_lock); 3752 3753 /* 3754 * If evicted is zero, we couldn't evict anything via 3755 * arc_adjust(). This could be due to hash lock 3756 * collisions, but more likely due to the majority of 3757 * arc buffers being unevictable. Therefore, even if 3758 * arc_size is above arc_c, another pass is unlikely to 3759 * be helpful and could potentially cause us to enter an 3760 * infinite loop. 3761 */ 3762 if (arc_size <= arc_c || evicted == 0) { 3763#ifdef _KERNEL 3764 needfree = 0; 3765#endif 3766 /* 3767 * We're either no longer overflowing, or we 3768 * can't evict anything more, so we should wake 3769 * up any threads before we go to sleep. 3770 */ 3771 cv_broadcast(&arc_reclaim_waiters_cv); 3772 3773 /* 3774 * Block until signaled, or after one second (we 3775 * might need to perform arc_kmem_reap_now() 3776 * even if we aren't being signalled) 3777 */ 3778 CALLB_CPR_SAFE_BEGIN(&cpr); 3779 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 3780 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 3781 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3782 } 3783 } 3784 3785 arc_reclaim_thread_exit = FALSE; 3786 cv_broadcast(&arc_reclaim_thread_cv); 3787 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3788 thread_exit(); 3789} 3790 3791static void 3792arc_user_evicts_thread(void *dummy __unused) 3793{ 3794 callb_cpr_t cpr; 3795 3796 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3797 3798 mutex_enter(&arc_user_evicts_lock); 3799 while (!arc_user_evicts_thread_exit) { 3800 mutex_exit(&arc_user_evicts_lock); 3801 3802 arc_do_user_evicts(); 3803 3804 /* 3805 * This is necessary in order for the mdb ::arc dcmd to 3806 * show up to date information. Since the ::arc command 3807 * does not call the kstat's update function, without 3808 * this call, the command may show stale stats for the 3809 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3810 * with this change, the data might be up to 1 second 3811 * out of date; but that should suffice. The arc_state_t 3812 * structures can be queried directly if more accurate 3813 * information is needed. 3814 */ 3815 if (arc_ksp != NULL) 3816 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3817 3818 mutex_enter(&arc_user_evicts_lock); 3819 3820 /* 3821 * Block until signaled, or after one second (we need to 3822 * call the arc's kstat update function regularly). 3823 */ 3824 CALLB_CPR_SAFE_BEGIN(&cpr); 3825 (void) cv_timedwait(&arc_user_evicts_cv, 3826 &arc_user_evicts_lock, hz); 3827 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3828 } 3829 3830 arc_user_evicts_thread_exit = FALSE; 3831 cv_broadcast(&arc_user_evicts_cv); 3832 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3833 thread_exit(); 3834} 3835 3836/* 3837 * Adapt arc info given the number of bytes we are trying to add and 3838 * the state that we are comming from. This function is only called 3839 * when we are adding new content to the cache. 3840 */ 3841static void 3842arc_adapt(int bytes, arc_state_t *state) 3843{ 3844 int mult; 3845 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3846 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3847 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3848 3849 if (state == arc_l2c_only) 3850 return; 3851 3852 ASSERT(bytes > 0); 3853 /* 3854 * Adapt the target size of the MRU list: 3855 * - if we just hit in the MRU ghost list, then increase 3856 * the target size of the MRU list. 3857 * - if we just hit in the MFU ghost list, then increase 3858 * the target size of the MFU list by decreasing the 3859 * target size of the MRU list. 3860 */ 3861 if (state == arc_mru_ghost) { 3862 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3863 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3864 3865 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3866 } else if (state == arc_mfu_ghost) { 3867 uint64_t delta; 3868 3869 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3870 mult = MIN(mult, 10); 3871 3872 delta = MIN(bytes * mult, arc_p); 3873 arc_p = MAX(arc_p_min, arc_p - delta); 3874 } 3875 ASSERT((int64_t)arc_p >= 0); 3876 3877 if (arc_reclaim_needed()) { 3878 cv_signal(&arc_reclaim_thread_cv); 3879 return; 3880 } 3881 3882 if (arc_no_grow) 3883 return; 3884 3885 if (arc_c >= arc_c_max) 3886 return; 3887 3888 /* 3889 * If we're within (2 * maxblocksize) bytes of the target 3890 * cache size, increment the target cache size 3891 */ 3892 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3893 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3894 atomic_add_64(&arc_c, (int64_t)bytes); 3895 if (arc_c > arc_c_max) 3896 arc_c = arc_c_max; 3897 else if (state == arc_anon) 3898 atomic_add_64(&arc_p, (int64_t)bytes); 3899 if (arc_p > arc_c) 3900 arc_p = arc_c; 3901 } 3902 ASSERT((int64_t)arc_p >= 0); 3903} 3904 3905/* 3906 * Check if arc_size has grown past our upper threshold, determined by 3907 * zfs_arc_overflow_shift. 3908 */ 3909static boolean_t 3910arc_is_overflowing(void) 3911{ 3912 /* Always allow at least one block of overflow */ 3913 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3914 arc_c >> zfs_arc_overflow_shift); 3915 3916 return (arc_size >= arc_c + overflow); 3917} 3918 3919/* 3920 * The buffer, supplied as the first argument, needs a data block. If we 3921 * are hitting the hard limit for the cache size, we must sleep, waiting 3922 * for the eviction thread to catch up. If we're past the target size 3923 * but below the hard limit, we'll only signal the reclaim thread and 3924 * continue on. 3925 */ 3926static void 3927arc_get_data_buf(arc_buf_t *buf) 3928{ 3929 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3930 uint64_t size = buf->b_hdr->b_size; 3931 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3932 3933 arc_adapt(size, state); 3934 3935 /* 3936 * If arc_size is currently overflowing, and has grown past our 3937 * upper limit, we must be adding data faster than the evict 3938 * thread can evict. Thus, to ensure we don't compound the 3939 * problem by adding more data and forcing arc_size to grow even 3940 * further past it's target size, we halt and wait for the 3941 * eviction thread to catch up. 3942 * 3943 * It's also possible that the reclaim thread is unable to evict 3944 * enough buffers to get arc_size below the overflow limit (e.g. 3945 * due to buffers being un-evictable, or hash lock collisions). 3946 * In this case, we want to proceed regardless if we're 3947 * overflowing; thus we don't use a while loop here. 3948 */ 3949 if (arc_is_overflowing()) { 3950 mutex_enter(&arc_reclaim_lock); 3951 3952 /* 3953 * Now that we've acquired the lock, we may no longer be 3954 * over the overflow limit, lets check. 3955 * 3956 * We're ignoring the case of spurious wake ups. If that 3957 * were to happen, it'd let this thread consume an ARC 3958 * buffer before it should have (i.e. before we're under 3959 * the overflow limit and were signalled by the reclaim 3960 * thread). As long as that is a rare occurrence, it 3961 * shouldn't cause any harm. 3962 */ 3963 if (arc_is_overflowing()) { 3964 cv_signal(&arc_reclaim_thread_cv); 3965 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3966 } 3967 3968 mutex_exit(&arc_reclaim_lock); 3969 } 3970 3971 if (type == ARC_BUFC_METADATA) { 3972 buf->b_data = zio_buf_alloc(size); 3973 arc_space_consume(size, ARC_SPACE_META); 3974 } else { 3975 ASSERT(type == ARC_BUFC_DATA); 3976 buf->b_data = zio_data_buf_alloc(size); 3977 arc_space_consume(size, ARC_SPACE_DATA); 3978 } 3979 3980 /* 3981 * Update the state size. Note that ghost states have a 3982 * "ghost size" and so don't need to be updated. 3983 */ 3984 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3985 arc_buf_hdr_t *hdr = buf->b_hdr; 3986 arc_state_t *state = hdr->b_l1hdr.b_state; 3987 3988 (void) refcount_add_many(&state->arcs_size, size, buf); 3989 3990 /* 3991 * If this is reached via arc_read, the link is 3992 * protected by the hash lock. If reached via 3993 * arc_buf_alloc, the header should not be accessed by 3994 * any other thread. And, if reached via arc_read_done, 3995 * the hash lock will protect it if it's found in the 3996 * hash table; otherwise no other thread should be 3997 * trying to [add|remove]_reference it. 3998 */ 3999 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4000 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4001 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 4002 size); 4003 } 4004 /* 4005 * If we are growing the cache, and we are adding anonymous 4006 * data, and we have outgrown arc_p, update arc_p 4007 */ 4008 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4009 (refcount_count(&arc_anon->arcs_size) + 4010 refcount_count(&arc_mru->arcs_size) > arc_p)) 4011 arc_p = MIN(arc_c, arc_p + size); 4012 } 4013 ARCSTAT_BUMP(arcstat_allocated); 4014} 4015 4016/* 4017 * This routine is called whenever a buffer is accessed. 4018 * NOTE: the hash lock is dropped in this function. 4019 */ 4020static void 4021arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4022{ 4023 clock_t now; 4024 4025 ASSERT(MUTEX_HELD(hash_lock)); 4026 ASSERT(HDR_HAS_L1HDR(hdr)); 4027 4028 if (hdr->b_l1hdr.b_state == arc_anon) { 4029 /* 4030 * This buffer is not in the cache, and does not 4031 * appear in our "ghost" list. Add the new buffer 4032 * to the MRU state. 4033 */ 4034 4035 ASSERT0(hdr->b_l1hdr.b_arc_access); 4036 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4037 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4038 arc_change_state(arc_mru, hdr, hash_lock); 4039 4040 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4041 now = ddi_get_lbolt(); 4042 4043 /* 4044 * If this buffer is here because of a prefetch, then either: 4045 * - clear the flag if this is a "referencing" read 4046 * (any subsequent access will bump this into the MFU state). 4047 * or 4048 * - move the buffer to the head of the list if this is 4049 * another prefetch (to make it less likely to be evicted). 4050 */ 4051 if (HDR_PREFETCH(hdr)) { 4052 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4053 /* link protected by hash lock */ 4054 ASSERT(multilist_link_active( 4055 &hdr->b_l1hdr.b_arc_node)); 4056 } else { 4057 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4058 ARCSTAT_BUMP(arcstat_mru_hits); 4059 } 4060 hdr->b_l1hdr.b_arc_access = now; 4061 return; 4062 } 4063 4064 /* 4065 * This buffer has been "accessed" only once so far, 4066 * but it is still in the cache. Move it to the MFU 4067 * state. 4068 */ 4069 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4070 /* 4071 * More than 125ms have passed since we 4072 * instantiated this buffer. Move it to the 4073 * most frequently used state. 4074 */ 4075 hdr->b_l1hdr.b_arc_access = now; 4076 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4077 arc_change_state(arc_mfu, hdr, hash_lock); 4078 } 4079 ARCSTAT_BUMP(arcstat_mru_hits); 4080 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4081 arc_state_t *new_state; 4082 /* 4083 * This buffer has been "accessed" recently, but 4084 * was evicted from the cache. Move it to the 4085 * MFU state. 4086 */ 4087 4088 if (HDR_PREFETCH(hdr)) { 4089 new_state = arc_mru; 4090 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4091 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4092 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4093 } else { 4094 new_state = arc_mfu; 4095 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4096 } 4097 4098 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4099 arc_change_state(new_state, hdr, hash_lock); 4100 4101 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4102 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4103 /* 4104 * This buffer has been accessed more than once and is 4105 * still in the cache. Keep it in the MFU state. 4106 * 4107 * NOTE: an add_reference() that occurred when we did 4108 * the arc_read() will have kicked this off the list. 4109 * If it was a prefetch, we will explicitly move it to 4110 * the head of the list now. 4111 */ 4112 if ((HDR_PREFETCH(hdr)) != 0) { 4113 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4114 /* link protected by hash_lock */ 4115 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4116 } 4117 ARCSTAT_BUMP(arcstat_mfu_hits); 4118 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4119 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4120 arc_state_t *new_state = arc_mfu; 4121 /* 4122 * This buffer has been accessed more than once but has 4123 * been evicted from the cache. Move it back to the 4124 * MFU state. 4125 */ 4126 4127 if (HDR_PREFETCH(hdr)) { 4128 /* 4129 * This is a prefetch access... 4130 * move this block back to the MRU state. 4131 */ 4132 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4133 new_state = arc_mru; 4134 } 4135 4136 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4137 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4138 arc_change_state(new_state, hdr, hash_lock); 4139 4140 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4141 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4142 /* 4143 * This buffer is on the 2nd Level ARC. 4144 */ 4145 4146 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4147 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4148 arc_change_state(arc_mfu, hdr, hash_lock); 4149 } else { 4150 ASSERT(!"invalid arc state"); 4151 } 4152} 4153 4154/* a generic arc_done_func_t which you can use */ 4155/* ARGSUSED */ 4156void 4157arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4158{ 4159 if (zio == NULL || zio->io_error == 0) 4160 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4161 VERIFY(arc_buf_remove_ref(buf, arg)); 4162} 4163 4164/* a generic arc_done_func_t */ 4165void 4166arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4167{ 4168 arc_buf_t **bufp = arg; 4169 if (zio && zio->io_error) { 4170 VERIFY(arc_buf_remove_ref(buf, arg)); 4171 *bufp = NULL; 4172 } else { 4173 *bufp = buf; 4174 ASSERT(buf->b_data); 4175 } 4176} 4177 4178static void 4179arc_read_done(zio_t *zio) 4180{ 4181 arc_buf_hdr_t *hdr; 4182 arc_buf_t *buf; 4183 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4184 kmutex_t *hash_lock = NULL; 4185 arc_callback_t *callback_list, *acb; 4186 int freeable = FALSE; 4187 4188 buf = zio->io_private; 4189 hdr = buf->b_hdr; 4190 4191 /* 4192 * The hdr was inserted into hash-table and removed from lists 4193 * prior to starting I/O. We should find this header, since 4194 * it's in the hash table, and it should be legit since it's 4195 * not possible to evict it during the I/O. The only possible 4196 * reason for it not to be found is if we were freed during the 4197 * read. 4198 */ 4199 if (HDR_IN_HASH_TABLE(hdr)) { 4200 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4201 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4202 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4203 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4204 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4205 4206 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4207 &hash_lock); 4208 4209 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4210 hash_lock == NULL) || 4211 (found == hdr && 4212 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4213 (found == hdr && HDR_L2_READING(hdr))); 4214 } 4215 4216 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4217 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4218 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4219 4220 /* byteswap if necessary */ 4221 callback_list = hdr->b_l1hdr.b_acb; 4222 ASSERT(callback_list != NULL); 4223 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4224 dmu_object_byteswap_t bswap = 4225 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4226 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4227 byteswap_uint64_array : 4228 dmu_ot_byteswap[bswap].ob_func; 4229 func(buf->b_data, hdr->b_size); 4230 } 4231 4232 arc_cksum_compute(buf, B_FALSE); 4233#ifdef illumos 4234 arc_buf_watch(buf); 4235#endif 4236 4237 if (hash_lock && zio->io_error == 0 && 4238 hdr->b_l1hdr.b_state == arc_anon) { 4239 /* 4240 * Only call arc_access on anonymous buffers. This is because 4241 * if we've issued an I/O for an evicted buffer, we've already 4242 * called arc_access (to prevent any simultaneous readers from 4243 * getting confused). 4244 */ 4245 arc_access(hdr, hash_lock); 4246 } 4247 4248 /* create copies of the data buffer for the callers */ 4249 abuf = buf; 4250 for (acb = callback_list; acb; acb = acb->acb_next) { 4251 if (acb->acb_done) { 4252 if (abuf == NULL) { 4253 ARCSTAT_BUMP(arcstat_duplicate_reads); 4254 abuf = arc_buf_clone(buf); 4255 } 4256 acb->acb_buf = abuf; 4257 abuf = NULL; 4258 } 4259 } 4260 hdr->b_l1hdr.b_acb = NULL; 4261 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4262 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4263 if (abuf == buf) { 4264 ASSERT(buf->b_efunc == NULL); 4265 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4266 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4267 } 4268 4269 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4270 callback_list != NULL); 4271 4272 if (zio->io_error != 0) { 4273 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4274 if (hdr->b_l1hdr.b_state != arc_anon) 4275 arc_change_state(arc_anon, hdr, hash_lock); 4276 if (HDR_IN_HASH_TABLE(hdr)) 4277 buf_hash_remove(hdr); 4278 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4279 } 4280 4281 /* 4282 * Broadcast before we drop the hash_lock to avoid the possibility 4283 * that the hdr (and hence the cv) might be freed before we get to 4284 * the cv_broadcast(). 4285 */ 4286 cv_broadcast(&hdr->b_l1hdr.b_cv); 4287 4288 if (hash_lock != NULL) { 4289 mutex_exit(hash_lock); 4290 } else { 4291 /* 4292 * This block was freed while we waited for the read to 4293 * complete. It has been removed from the hash table and 4294 * moved to the anonymous state (so that it won't show up 4295 * in the cache). 4296 */ 4297 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4298 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4299 } 4300 4301 /* execute each callback and free its structure */ 4302 while ((acb = callback_list) != NULL) { 4303 if (acb->acb_done) 4304 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4305 4306 if (acb->acb_zio_dummy != NULL) { 4307 acb->acb_zio_dummy->io_error = zio->io_error; 4308 zio_nowait(acb->acb_zio_dummy); 4309 } 4310 4311 callback_list = acb->acb_next; 4312 kmem_free(acb, sizeof (arc_callback_t)); 4313 } 4314 4315 if (freeable) 4316 arc_hdr_destroy(hdr); 4317} 4318 4319/* 4320 * "Read" the block at the specified DVA (in bp) via the 4321 * cache. If the block is found in the cache, invoke the provided 4322 * callback immediately and return. Note that the `zio' parameter 4323 * in the callback will be NULL in this case, since no IO was 4324 * required. If the block is not in the cache pass the read request 4325 * on to the spa with a substitute callback function, so that the 4326 * requested block will be added to the cache. 4327 * 4328 * If a read request arrives for a block that has a read in-progress, 4329 * either wait for the in-progress read to complete (and return the 4330 * results); or, if this is a read with a "done" func, add a record 4331 * to the read to invoke the "done" func when the read completes, 4332 * and return; or just return. 4333 * 4334 * arc_read_done() will invoke all the requested "done" functions 4335 * for readers of this block. 4336 */ 4337int 4338arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4339 void *private, zio_priority_t priority, int zio_flags, 4340 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4341{ 4342 arc_buf_hdr_t *hdr = NULL; 4343 arc_buf_t *buf = NULL; 4344 kmutex_t *hash_lock = NULL; 4345 zio_t *rzio; 4346 uint64_t guid = spa_load_guid(spa); 4347 4348 ASSERT(!BP_IS_EMBEDDED(bp) || 4349 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4350 4351top: 4352 if (!BP_IS_EMBEDDED(bp)) { 4353 /* 4354 * Embedded BP's have no DVA and require no I/O to "read". 4355 * Create an anonymous arc buf to back it. 4356 */ 4357 hdr = buf_hash_find(guid, bp, &hash_lock); 4358 } 4359 4360 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4361 4362 *arc_flags |= ARC_FLAG_CACHED; 4363 4364 if (HDR_IO_IN_PROGRESS(hdr)) { 4365 4366 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4367 priority == ZIO_PRIORITY_SYNC_READ) { 4368 /* 4369 * This sync read must wait for an 4370 * in-progress async read (e.g. a predictive 4371 * prefetch). Async reads are queued 4372 * separately at the vdev_queue layer, so 4373 * this is a form of priority inversion. 4374 * Ideally, we would "inherit" the demand 4375 * i/o's priority by moving the i/o from 4376 * the async queue to the synchronous queue, 4377 * but there is currently no mechanism to do 4378 * so. Track this so that we can evaluate 4379 * the magnitude of this potential performance 4380 * problem. 4381 * 4382 * Note that if the prefetch i/o is already 4383 * active (has been issued to the device), 4384 * the prefetch improved performance, because 4385 * we issued it sooner than we would have 4386 * without the prefetch. 4387 */ 4388 DTRACE_PROBE1(arc__sync__wait__for__async, 4389 arc_buf_hdr_t *, hdr); 4390 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4391 } 4392 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4393 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4394 } 4395 4396 if (*arc_flags & ARC_FLAG_WAIT) { 4397 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4398 mutex_exit(hash_lock); 4399 goto top; 4400 } 4401 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4402 4403 if (done) { 4404 arc_callback_t *acb = NULL; 4405 4406 acb = kmem_zalloc(sizeof (arc_callback_t), 4407 KM_SLEEP); 4408 acb->acb_done = done; 4409 acb->acb_private = private; 4410 if (pio != NULL) 4411 acb->acb_zio_dummy = zio_null(pio, 4412 spa, NULL, NULL, NULL, zio_flags); 4413 4414 ASSERT(acb->acb_done != NULL); 4415 acb->acb_next = hdr->b_l1hdr.b_acb; 4416 hdr->b_l1hdr.b_acb = acb; 4417 add_reference(hdr, hash_lock, private); 4418 mutex_exit(hash_lock); 4419 return (0); 4420 } 4421 mutex_exit(hash_lock); 4422 return (0); 4423 } 4424 4425 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4426 hdr->b_l1hdr.b_state == arc_mfu); 4427 4428 if (done) { 4429 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4430 /* 4431 * This is a demand read which does not have to 4432 * wait for i/o because we did a predictive 4433 * prefetch i/o for it, which has completed. 4434 */ 4435 DTRACE_PROBE1( 4436 arc__demand__hit__predictive__prefetch, 4437 arc_buf_hdr_t *, hdr); 4438 ARCSTAT_BUMP( 4439 arcstat_demand_hit_predictive_prefetch); 4440 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4441 } 4442 add_reference(hdr, hash_lock, private); 4443 /* 4444 * If this block is already in use, create a new 4445 * copy of the data so that we will be guaranteed 4446 * that arc_release() will always succeed. 4447 */ 4448 buf = hdr->b_l1hdr.b_buf; 4449 ASSERT(buf); 4450 ASSERT(buf->b_data); 4451 if (HDR_BUF_AVAILABLE(hdr)) { 4452 ASSERT(buf->b_efunc == NULL); 4453 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4454 } else { 4455 buf = arc_buf_clone(buf); 4456 } 4457 4458 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4459 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4460 hdr->b_flags |= ARC_FLAG_PREFETCH; 4461 } 4462 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4463 arc_access(hdr, hash_lock); 4464 if (*arc_flags & ARC_FLAG_L2CACHE) 4465 hdr->b_flags |= ARC_FLAG_L2CACHE; 4466 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4467 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4468 mutex_exit(hash_lock); 4469 ARCSTAT_BUMP(arcstat_hits); 4470 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4471 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4472 data, metadata, hits); 4473 4474 if (done) 4475 done(NULL, buf, private); 4476 } else { 4477 uint64_t size = BP_GET_LSIZE(bp); 4478 arc_callback_t *acb; 4479 vdev_t *vd = NULL; 4480 uint64_t addr = 0; 4481 boolean_t devw = B_FALSE; 4482 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4483 int32_t b_asize = 0; 4484 4485 if (hdr == NULL) { 4486 /* this block is not in the cache */ 4487 arc_buf_hdr_t *exists = NULL; 4488 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4489 buf = arc_buf_alloc(spa, size, private, type); 4490 hdr = buf->b_hdr; 4491 if (!BP_IS_EMBEDDED(bp)) { 4492 hdr->b_dva = *BP_IDENTITY(bp); 4493 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4494 exists = buf_hash_insert(hdr, &hash_lock); 4495 } 4496 if (exists != NULL) { 4497 /* somebody beat us to the hash insert */ 4498 mutex_exit(hash_lock); 4499 buf_discard_identity(hdr); 4500 (void) arc_buf_remove_ref(buf, private); 4501 goto top; /* restart the IO request */ 4502 } 4503 4504 /* 4505 * If there is a callback, we pass our reference to 4506 * it; otherwise we remove our reference. 4507 */ 4508 if (done == NULL) { 4509 (void) remove_reference(hdr, hash_lock, 4510 private); 4511 } 4512 if (*arc_flags & ARC_FLAG_PREFETCH) 4513 hdr->b_flags |= ARC_FLAG_PREFETCH; 4514 if (*arc_flags & ARC_FLAG_L2CACHE) 4515 hdr->b_flags |= ARC_FLAG_L2CACHE; 4516 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4517 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4518 if (BP_GET_LEVEL(bp) > 0) 4519 hdr->b_flags |= ARC_FLAG_INDIRECT; 4520 } else { 4521 /* 4522 * This block is in the ghost cache. If it was L2-only 4523 * (and thus didn't have an L1 hdr), we realloc the 4524 * header to add an L1 hdr. 4525 */ 4526 if (!HDR_HAS_L1HDR(hdr)) { 4527 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4528 hdr_full_cache); 4529 } 4530 4531 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4532 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4533 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4534 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4535 4536 /* 4537 * If there is a callback, we pass a reference to it. 4538 */ 4539 if (done != NULL) 4540 add_reference(hdr, hash_lock, private); 4541 if (*arc_flags & ARC_FLAG_PREFETCH) 4542 hdr->b_flags |= ARC_FLAG_PREFETCH; 4543 if (*arc_flags & ARC_FLAG_L2CACHE) 4544 hdr->b_flags |= ARC_FLAG_L2CACHE; 4545 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4546 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4547 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4548 buf->b_hdr = hdr; 4549 buf->b_data = NULL; 4550 buf->b_efunc = NULL; 4551 buf->b_private = NULL; 4552 buf->b_next = NULL; 4553 hdr->b_l1hdr.b_buf = buf; 4554 ASSERT0(hdr->b_l1hdr.b_datacnt); 4555 hdr->b_l1hdr.b_datacnt = 1; 4556 arc_get_data_buf(buf); 4557 arc_access(hdr, hash_lock); 4558 } 4559 4560 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4561 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4562 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4563 4564 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4565 acb->acb_done = done; 4566 acb->acb_private = private; 4567 4568 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4569 hdr->b_l1hdr.b_acb = acb; 4570 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4571 4572 if (HDR_HAS_L2HDR(hdr) && 4573 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4574 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4575 addr = hdr->b_l2hdr.b_daddr; 4576 b_compress = hdr->b_l2hdr.b_compress; 4577 b_asize = hdr->b_l2hdr.b_asize; 4578 /* 4579 * Lock out device removal. 4580 */ 4581 if (vdev_is_dead(vd) || 4582 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4583 vd = NULL; 4584 } 4585 4586 if (hash_lock != NULL) 4587 mutex_exit(hash_lock); 4588 4589 /* 4590 * At this point, we have a level 1 cache miss. Try again in 4591 * L2ARC if possible. 4592 */ 4593 ASSERT3U(hdr->b_size, ==, size); 4594 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4595 uint64_t, size, zbookmark_phys_t *, zb); 4596 ARCSTAT_BUMP(arcstat_misses); 4597 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4598 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4599 data, metadata, misses); 4600#ifdef _KERNEL 4601 curthread->td_ru.ru_inblock++; 4602#endif 4603 4604 if (priority == ZIO_PRIORITY_ASYNC_READ) 4605 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4606 else 4607 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4608 4609 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4610 /* 4611 * Read from the L2ARC if the following are true: 4612 * 1. The L2ARC vdev was previously cached. 4613 * 2. This buffer still has L2ARC metadata. 4614 * 3. This buffer isn't currently writing to the L2ARC. 4615 * 4. The L2ARC entry wasn't evicted, which may 4616 * also have invalidated the vdev. 4617 * 5. This isn't prefetch and l2arc_noprefetch is set. 4618 */ 4619 if (HDR_HAS_L2HDR(hdr) && 4620 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4621 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4622 l2arc_read_callback_t *cb; 4623 void* b_data; 4624 4625 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4626 ARCSTAT_BUMP(arcstat_l2_hits); 4627 4628 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4629 KM_SLEEP); 4630 cb->l2rcb_buf = buf; 4631 cb->l2rcb_spa = spa; 4632 cb->l2rcb_bp = *bp; 4633 cb->l2rcb_zb = *zb; 4634 cb->l2rcb_flags = zio_flags; 4635 cb->l2rcb_compress = b_compress; 4636 if (b_asize > hdr->b_size) { 4637 ASSERT3U(b_compress, ==, 4638 ZIO_COMPRESS_OFF); 4639 b_data = zio_data_buf_alloc(b_asize); 4640 cb->l2rcb_data = b_data; 4641 } else { 4642 b_data = buf->b_data; 4643 } 4644 4645 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4646 addr + size < vd->vdev_psize - 4647 VDEV_LABEL_END_SIZE); 4648 4649 /* 4650 * l2arc read. The SCL_L2ARC lock will be 4651 * released by l2arc_read_done(). 4652 * Issue a null zio if the underlying buffer 4653 * was squashed to zero size by compression. 4654 */ 4655 if (b_compress == ZIO_COMPRESS_EMPTY) { 4656 ASSERT3U(b_asize, ==, 0); 4657 rzio = zio_null(pio, spa, vd, 4658 l2arc_read_done, cb, 4659 zio_flags | ZIO_FLAG_DONT_CACHE | 4660 ZIO_FLAG_CANFAIL | 4661 ZIO_FLAG_DONT_PROPAGATE | 4662 ZIO_FLAG_DONT_RETRY); 4663 } else { 4664 rzio = zio_read_phys(pio, vd, addr, 4665 b_asize, b_data, 4666 ZIO_CHECKSUM_OFF, 4667 l2arc_read_done, cb, priority, 4668 zio_flags | ZIO_FLAG_DONT_CACHE | 4669 ZIO_FLAG_CANFAIL | 4670 ZIO_FLAG_DONT_PROPAGATE | 4671 ZIO_FLAG_DONT_RETRY, B_FALSE); 4672 } 4673 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4674 zio_t *, rzio); 4675 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4676 4677 if (*arc_flags & ARC_FLAG_NOWAIT) { 4678 zio_nowait(rzio); 4679 return (0); 4680 } 4681 4682 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4683 if (zio_wait(rzio) == 0) 4684 return (0); 4685 4686 /* l2arc read error; goto zio_read() */ 4687 } else { 4688 DTRACE_PROBE1(l2arc__miss, 4689 arc_buf_hdr_t *, hdr); 4690 ARCSTAT_BUMP(arcstat_l2_misses); 4691 if (HDR_L2_WRITING(hdr)) 4692 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4693 spa_config_exit(spa, SCL_L2ARC, vd); 4694 } 4695 } else { 4696 if (vd != NULL) 4697 spa_config_exit(spa, SCL_L2ARC, vd); 4698 if (l2arc_ndev != 0) { 4699 DTRACE_PROBE1(l2arc__miss, 4700 arc_buf_hdr_t *, hdr); 4701 ARCSTAT_BUMP(arcstat_l2_misses); 4702 } 4703 } 4704 4705 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4706 arc_read_done, buf, priority, zio_flags, zb); 4707 4708 if (*arc_flags & ARC_FLAG_WAIT) 4709 return (zio_wait(rzio)); 4710 4711 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4712 zio_nowait(rzio); 4713 } 4714 return (0); 4715} 4716 4717void 4718arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4719{ 4720 ASSERT(buf->b_hdr != NULL); 4721 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4722 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4723 func == NULL); 4724 ASSERT(buf->b_efunc == NULL); 4725 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4726 4727 buf->b_efunc = func; 4728 buf->b_private = private; 4729} 4730 4731/* 4732 * Notify the arc that a block was freed, and thus will never be used again. 4733 */ 4734void 4735arc_freed(spa_t *spa, const blkptr_t *bp) 4736{ 4737 arc_buf_hdr_t *hdr; 4738 kmutex_t *hash_lock; 4739 uint64_t guid = spa_load_guid(spa); 4740 4741 ASSERT(!BP_IS_EMBEDDED(bp)); 4742 4743 hdr = buf_hash_find(guid, bp, &hash_lock); 4744 if (hdr == NULL) 4745 return; 4746 if (HDR_BUF_AVAILABLE(hdr)) { 4747 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4748 add_reference(hdr, hash_lock, FTAG); 4749 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4750 mutex_exit(hash_lock); 4751 4752 arc_release(buf, FTAG); 4753 (void) arc_buf_remove_ref(buf, FTAG); 4754 } else { 4755 mutex_exit(hash_lock); 4756 } 4757 4758} 4759 4760/* 4761 * Clear the user eviction callback set by arc_set_callback(), first calling 4762 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4763 * clearing the callback may result in the arc_buf being destroyed. However, 4764 * it will not result in the *last* arc_buf being destroyed, hence the data 4765 * will remain cached in the ARC. We make a copy of the arc buffer here so 4766 * that we can process the callback without holding any locks. 4767 * 4768 * It's possible that the callback is already in the process of being cleared 4769 * by another thread. In this case we can not clear the callback. 4770 * 4771 * Returns B_TRUE if the callback was successfully called and cleared. 4772 */ 4773boolean_t 4774arc_clear_callback(arc_buf_t *buf) 4775{ 4776 arc_buf_hdr_t *hdr; 4777 kmutex_t *hash_lock; 4778 arc_evict_func_t *efunc = buf->b_efunc; 4779 void *private = buf->b_private; 4780 4781 mutex_enter(&buf->b_evict_lock); 4782 hdr = buf->b_hdr; 4783 if (hdr == NULL) { 4784 /* 4785 * We are in arc_do_user_evicts(). 4786 */ 4787 ASSERT(buf->b_data == NULL); 4788 mutex_exit(&buf->b_evict_lock); 4789 return (B_FALSE); 4790 } else if (buf->b_data == NULL) { 4791 /* 4792 * We are on the eviction list; process this buffer now 4793 * but let arc_do_user_evicts() do the reaping. 4794 */ 4795 buf->b_efunc = NULL; 4796 mutex_exit(&buf->b_evict_lock); 4797 VERIFY0(efunc(private)); 4798 return (B_TRUE); 4799 } 4800 hash_lock = HDR_LOCK(hdr); 4801 mutex_enter(hash_lock); 4802 hdr = buf->b_hdr; 4803 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4804 4805 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4806 hdr->b_l1hdr.b_datacnt); 4807 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4808 hdr->b_l1hdr.b_state == arc_mfu); 4809 4810 buf->b_efunc = NULL; 4811 buf->b_private = NULL; 4812 4813 if (hdr->b_l1hdr.b_datacnt > 1) { 4814 mutex_exit(&buf->b_evict_lock); 4815 arc_buf_destroy(buf, TRUE); 4816 } else { 4817 ASSERT(buf == hdr->b_l1hdr.b_buf); 4818 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4819 mutex_exit(&buf->b_evict_lock); 4820 } 4821 4822 mutex_exit(hash_lock); 4823 VERIFY0(efunc(private)); 4824 return (B_TRUE); 4825} 4826 4827/* 4828 * Release this buffer from the cache, making it an anonymous buffer. This 4829 * must be done after a read and prior to modifying the buffer contents. 4830 * If the buffer has more than one reference, we must make 4831 * a new hdr for the buffer. 4832 */ 4833void 4834arc_release(arc_buf_t *buf, void *tag) 4835{ 4836 arc_buf_hdr_t *hdr = buf->b_hdr; 4837 4838 /* 4839 * It would be nice to assert that if it's DMU metadata (level > 4840 * 0 || it's the dnode file), then it must be syncing context. 4841 * But we don't know that information at this level. 4842 */ 4843 4844 mutex_enter(&buf->b_evict_lock); 4845 4846 ASSERT(HDR_HAS_L1HDR(hdr)); 4847 4848 /* 4849 * We don't grab the hash lock prior to this check, because if 4850 * the buffer's header is in the arc_anon state, it won't be 4851 * linked into the hash table. 4852 */ 4853 if (hdr->b_l1hdr.b_state == arc_anon) { 4854 mutex_exit(&buf->b_evict_lock); 4855 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4856 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4857 ASSERT(!HDR_HAS_L2HDR(hdr)); 4858 ASSERT(BUF_EMPTY(hdr)); 4859 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4860 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4861 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4862 4863 ASSERT3P(buf->b_efunc, ==, NULL); 4864 ASSERT3P(buf->b_private, ==, NULL); 4865 4866 hdr->b_l1hdr.b_arc_access = 0; 4867 arc_buf_thaw(buf); 4868 4869 return; 4870 } 4871 4872 kmutex_t *hash_lock = HDR_LOCK(hdr); 4873 mutex_enter(hash_lock); 4874 4875 /* 4876 * This assignment is only valid as long as the hash_lock is 4877 * held, we must be careful not to reference state or the 4878 * b_state field after dropping the lock. 4879 */ 4880 arc_state_t *state = hdr->b_l1hdr.b_state; 4881 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4882 ASSERT3P(state, !=, arc_anon); 4883 4884 /* this buffer is not on any list */ 4885 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4886 4887 if (HDR_HAS_L2HDR(hdr)) { 4888 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4889 4890 /* 4891 * We have to recheck this conditional again now that 4892 * we're holding the l2ad_mtx to prevent a race with 4893 * another thread which might be concurrently calling 4894 * l2arc_evict(). In that case, l2arc_evict() might have 4895 * destroyed the header's L2 portion as we were waiting 4896 * to acquire the l2ad_mtx. 4897 */ 4898 if (HDR_HAS_L2HDR(hdr)) { 4899 l2arc_trim(hdr); 4900 arc_hdr_l2hdr_destroy(hdr); 4901 } 4902 4903 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4904 } 4905 4906 /* 4907 * Do we have more than one buf? 4908 */ 4909 if (hdr->b_l1hdr.b_datacnt > 1) { 4910 arc_buf_hdr_t *nhdr; 4911 arc_buf_t **bufp; 4912 uint64_t blksz = hdr->b_size; 4913 uint64_t spa = hdr->b_spa; 4914 arc_buf_contents_t type = arc_buf_type(hdr); 4915 uint32_t flags = hdr->b_flags; 4916 4917 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4918 /* 4919 * Pull the data off of this hdr and attach it to 4920 * a new anonymous hdr. 4921 */ 4922 (void) remove_reference(hdr, hash_lock, tag); 4923 bufp = &hdr->b_l1hdr.b_buf; 4924 while (*bufp != buf) 4925 bufp = &(*bufp)->b_next; 4926 *bufp = buf->b_next; 4927 buf->b_next = NULL; 4928 4929 ASSERT3P(state, !=, arc_l2c_only); 4930 4931 (void) refcount_remove_many( 4932 &state->arcs_size, hdr->b_size, buf); 4933 4934 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4935 ASSERT3P(state, !=, arc_l2c_only); 4936 uint64_t *size = &state->arcs_lsize[type]; 4937 ASSERT3U(*size, >=, hdr->b_size); 4938 atomic_add_64(size, -hdr->b_size); 4939 } 4940 4941 /* 4942 * We're releasing a duplicate user data buffer, update 4943 * our statistics accordingly. 4944 */ 4945 if (HDR_ISTYPE_DATA(hdr)) { 4946 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4947 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4948 -hdr->b_size); 4949 } 4950 hdr->b_l1hdr.b_datacnt -= 1; 4951 arc_cksum_verify(buf); 4952#ifdef illumos 4953 arc_buf_unwatch(buf); 4954#endif 4955 4956 mutex_exit(hash_lock); 4957 4958 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4959 nhdr->b_size = blksz; 4960 nhdr->b_spa = spa; 4961 4962 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4963 nhdr->b_flags |= arc_bufc_to_flags(type); 4964 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4965 4966 nhdr->b_l1hdr.b_buf = buf; 4967 nhdr->b_l1hdr.b_datacnt = 1; 4968 nhdr->b_l1hdr.b_state = arc_anon; 4969 nhdr->b_l1hdr.b_arc_access = 0; 4970 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4971 nhdr->b_freeze_cksum = NULL; 4972 4973 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4974 buf->b_hdr = nhdr; 4975 mutex_exit(&buf->b_evict_lock); 4976 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4977 } else { 4978 mutex_exit(&buf->b_evict_lock); 4979 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4980 /* protected by hash lock, or hdr is on arc_anon */ 4981 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4982 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4983 arc_change_state(arc_anon, hdr, hash_lock); 4984 hdr->b_l1hdr.b_arc_access = 0; 4985 mutex_exit(hash_lock); 4986 4987 buf_discard_identity(hdr); 4988 arc_buf_thaw(buf); 4989 } 4990 buf->b_efunc = NULL; 4991 buf->b_private = NULL; 4992} 4993 4994int 4995arc_released(arc_buf_t *buf) 4996{ 4997 int released; 4998 4999 mutex_enter(&buf->b_evict_lock); 5000 released = (buf->b_data != NULL && 5001 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5002 mutex_exit(&buf->b_evict_lock); 5003 return (released); 5004} 5005 5006#ifdef ZFS_DEBUG 5007int 5008arc_referenced(arc_buf_t *buf) 5009{ 5010 int referenced; 5011 5012 mutex_enter(&buf->b_evict_lock); 5013 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5014 mutex_exit(&buf->b_evict_lock); 5015 return (referenced); 5016} 5017#endif 5018 5019static void 5020arc_write_ready(zio_t *zio) 5021{ 5022 arc_write_callback_t *callback = zio->io_private; 5023 arc_buf_t *buf = callback->awcb_buf; 5024 arc_buf_hdr_t *hdr = buf->b_hdr; 5025 5026 ASSERT(HDR_HAS_L1HDR(hdr)); 5027 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5028 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5029 callback->awcb_ready(zio, buf, callback->awcb_private); 5030 5031 /* 5032 * If the IO is already in progress, then this is a re-write 5033 * attempt, so we need to thaw and re-compute the cksum. 5034 * It is the responsibility of the callback to handle the 5035 * accounting for any re-write attempt. 5036 */ 5037 if (HDR_IO_IN_PROGRESS(hdr)) { 5038 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 5039 if (hdr->b_freeze_cksum != NULL) { 5040 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 5041 hdr->b_freeze_cksum = NULL; 5042 } 5043 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 5044 } 5045 arc_cksum_compute(buf, B_FALSE); 5046 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 5047} 5048 5049static void 5050arc_write_children_ready(zio_t *zio) 5051{ 5052 arc_write_callback_t *callback = zio->io_private; 5053 arc_buf_t *buf = callback->awcb_buf; 5054 5055 callback->awcb_children_ready(zio, buf, callback->awcb_private); 5056} 5057 5058/* 5059 * The SPA calls this callback for each physical write that happens on behalf 5060 * of a logical write. See the comment in dbuf_write_physdone() for details. 5061 */ 5062static void 5063arc_write_physdone(zio_t *zio) 5064{ 5065 arc_write_callback_t *cb = zio->io_private; 5066 if (cb->awcb_physdone != NULL) 5067 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5068} 5069 5070static void 5071arc_write_done(zio_t *zio) 5072{ 5073 arc_write_callback_t *callback = zio->io_private; 5074 arc_buf_t *buf = callback->awcb_buf; 5075 arc_buf_hdr_t *hdr = buf->b_hdr; 5076 5077 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5078 5079 if (zio->io_error == 0) { 5080 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5081 buf_discard_identity(hdr); 5082 } else { 5083 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5084 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5085 } 5086 } else { 5087 ASSERT(BUF_EMPTY(hdr)); 5088 } 5089 5090 /* 5091 * If the block to be written was all-zero or compressed enough to be 5092 * embedded in the BP, no write was performed so there will be no 5093 * dva/birth/checksum. The buffer must therefore remain anonymous 5094 * (and uncached). 5095 */ 5096 if (!BUF_EMPTY(hdr)) { 5097 arc_buf_hdr_t *exists; 5098 kmutex_t *hash_lock; 5099 5100 ASSERT(zio->io_error == 0); 5101 5102 arc_cksum_verify(buf); 5103 5104 exists = buf_hash_insert(hdr, &hash_lock); 5105 if (exists != NULL) { 5106 /* 5107 * This can only happen if we overwrite for 5108 * sync-to-convergence, because we remove 5109 * buffers from the hash table when we arc_free(). 5110 */ 5111 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5112 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5113 panic("bad overwrite, hdr=%p exists=%p", 5114 (void *)hdr, (void *)exists); 5115 ASSERT(refcount_is_zero( 5116 &exists->b_l1hdr.b_refcnt)); 5117 arc_change_state(arc_anon, exists, hash_lock); 5118 mutex_exit(hash_lock); 5119 arc_hdr_destroy(exists); 5120 exists = buf_hash_insert(hdr, &hash_lock); 5121 ASSERT3P(exists, ==, NULL); 5122 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5123 /* nopwrite */ 5124 ASSERT(zio->io_prop.zp_nopwrite); 5125 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5126 panic("bad nopwrite, hdr=%p exists=%p", 5127 (void *)hdr, (void *)exists); 5128 } else { 5129 /* Dedup */ 5130 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5131 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5132 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5133 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5134 } 5135 } 5136 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5137 /* if it's not anon, we are doing a scrub */ 5138 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5139 arc_access(hdr, hash_lock); 5140 mutex_exit(hash_lock); 5141 } else { 5142 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5143 } 5144 5145 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5146 callback->awcb_done(zio, buf, callback->awcb_private); 5147 5148 kmem_free(callback, sizeof (arc_write_callback_t)); 5149} 5150 5151zio_t * 5152arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5153 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5154 const zio_prop_t *zp, arc_done_func_t *ready, 5155 arc_done_func_t *children_ready, arc_done_func_t *physdone, 5156 arc_done_func_t *done, void *private, zio_priority_t priority, 5157 int zio_flags, const zbookmark_phys_t *zb) 5158{ 5159 arc_buf_hdr_t *hdr = buf->b_hdr; 5160 arc_write_callback_t *callback; 5161 zio_t *zio; 5162 5163 ASSERT(ready != NULL); 5164 ASSERT(done != NULL); 5165 ASSERT(!HDR_IO_ERROR(hdr)); 5166 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5167 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5168 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5169 if (l2arc) 5170 hdr->b_flags |= ARC_FLAG_L2CACHE; 5171 if (l2arc_compress) 5172 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5173 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5174 callback->awcb_ready = ready; 5175 callback->awcb_children_ready = children_ready; 5176 callback->awcb_physdone = physdone; 5177 callback->awcb_done = done; 5178 callback->awcb_private = private; 5179 callback->awcb_buf = buf; 5180 5181 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5182 arc_write_ready, 5183 (children_ready != NULL) ? arc_write_children_ready : NULL, 5184 arc_write_physdone, arc_write_done, callback, 5185 priority, zio_flags, zb); 5186 5187 return (zio); 5188} 5189 5190static int 5191arc_memory_throttle(uint64_t reserve, uint64_t txg) 5192{ 5193#ifdef _KERNEL 5194 uint64_t available_memory = ptob(freemem); 5195 static uint64_t page_load = 0; 5196 static uint64_t last_txg = 0; 5197 5198#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5199 available_memory = 5200 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5201#endif 5202 5203 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5204 return (0); 5205 5206 if (txg > last_txg) { 5207 last_txg = txg; 5208 page_load = 0; 5209 } 5210 /* 5211 * If we are in pageout, we know that memory is already tight, 5212 * the arc is already going to be evicting, so we just want to 5213 * continue to let page writes occur as quickly as possible. 5214 */ 5215 if (curproc == pageproc) { 5216 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5217 return (SET_ERROR(ERESTART)); 5218 /* Note: reserve is inflated, so we deflate */ 5219 page_load += reserve / 8; 5220 return (0); 5221 } else if (page_load > 0 && arc_reclaim_needed()) { 5222 /* memory is low, delay before restarting */ 5223 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5224 return (SET_ERROR(EAGAIN)); 5225 } 5226 page_load = 0; 5227#endif 5228 return (0); 5229} 5230 5231void 5232arc_tempreserve_clear(uint64_t reserve) 5233{ 5234 atomic_add_64(&arc_tempreserve, -reserve); 5235 ASSERT((int64_t)arc_tempreserve >= 0); 5236} 5237 5238int 5239arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5240{ 5241 int error; 5242 uint64_t anon_size; 5243 5244 if (reserve > arc_c/4 && !arc_no_grow) { 5245 arc_c = MIN(arc_c_max, reserve * 4); 5246 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5247 } 5248 if (reserve > arc_c) 5249 return (SET_ERROR(ENOMEM)); 5250 5251 /* 5252 * Don't count loaned bufs as in flight dirty data to prevent long 5253 * network delays from blocking transactions that are ready to be 5254 * assigned to a txg. 5255 */ 5256 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5257 arc_loaned_bytes), 0); 5258 5259 /* 5260 * Writes will, almost always, require additional memory allocations 5261 * in order to compress/encrypt/etc the data. We therefore need to 5262 * make sure that there is sufficient available memory for this. 5263 */ 5264 error = arc_memory_throttle(reserve, txg); 5265 if (error != 0) 5266 return (error); 5267 5268 /* 5269 * Throttle writes when the amount of dirty data in the cache 5270 * gets too large. We try to keep the cache less than half full 5271 * of dirty blocks so that our sync times don't grow too large. 5272 * Note: if two requests come in concurrently, we might let them 5273 * both succeed, when one of them should fail. Not a huge deal. 5274 */ 5275 5276 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5277 anon_size > arc_c / 4) { 5278 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5279 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5280 arc_tempreserve>>10, 5281 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5282 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5283 reserve>>10, arc_c>>10); 5284 return (SET_ERROR(ERESTART)); 5285 } 5286 atomic_add_64(&arc_tempreserve, reserve); 5287 return (0); 5288} 5289 5290static void 5291arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5292 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5293{ 5294 size->value.ui64 = refcount_count(&state->arcs_size); 5295 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5296 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5297} 5298 5299static int 5300arc_kstat_update(kstat_t *ksp, int rw) 5301{ 5302 arc_stats_t *as = ksp->ks_data; 5303 5304 if (rw == KSTAT_WRITE) { 5305 return (EACCES); 5306 } else { 5307 arc_kstat_update_state(arc_anon, 5308 &as->arcstat_anon_size, 5309 &as->arcstat_anon_evictable_data, 5310 &as->arcstat_anon_evictable_metadata); 5311 arc_kstat_update_state(arc_mru, 5312 &as->arcstat_mru_size, 5313 &as->arcstat_mru_evictable_data, 5314 &as->arcstat_mru_evictable_metadata); 5315 arc_kstat_update_state(arc_mru_ghost, 5316 &as->arcstat_mru_ghost_size, 5317 &as->arcstat_mru_ghost_evictable_data, 5318 &as->arcstat_mru_ghost_evictable_metadata); 5319 arc_kstat_update_state(arc_mfu, 5320 &as->arcstat_mfu_size, 5321 &as->arcstat_mfu_evictable_data, 5322 &as->arcstat_mfu_evictable_metadata); 5323 arc_kstat_update_state(arc_mfu_ghost, 5324 &as->arcstat_mfu_ghost_size, 5325 &as->arcstat_mfu_ghost_evictable_data, 5326 &as->arcstat_mfu_ghost_evictable_metadata); 5327 } 5328 5329 return (0); 5330} 5331 5332/* 5333 * This function *must* return indices evenly distributed between all 5334 * sublists of the multilist. This is needed due to how the ARC eviction 5335 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5336 * distributed between all sublists and uses this assumption when 5337 * deciding which sublist to evict from and how much to evict from it. 5338 */ 5339unsigned int 5340arc_state_multilist_index_func(multilist_t *ml, void *obj) 5341{ 5342 arc_buf_hdr_t *hdr = obj; 5343 5344 /* 5345 * We rely on b_dva to generate evenly distributed index 5346 * numbers using buf_hash below. So, as an added precaution, 5347 * let's make sure we never add empty buffers to the arc lists. 5348 */ 5349 ASSERT(!BUF_EMPTY(hdr)); 5350 5351 /* 5352 * The assumption here, is the hash value for a given 5353 * arc_buf_hdr_t will remain constant throughout it's lifetime 5354 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5355 * Thus, we don't need to store the header's sublist index 5356 * on insertion, as this index can be recalculated on removal. 5357 * 5358 * Also, the low order bits of the hash value are thought to be 5359 * distributed evenly. Otherwise, in the case that the multilist 5360 * has a power of two number of sublists, each sublists' usage 5361 * would not be evenly distributed. 5362 */ 5363 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5364 multilist_get_num_sublists(ml)); 5365} 5366 5367#ifdef _KERNEL 5368static eventhandler_tag arc_event_lowmem = NULL; 5369 5370static void 5371arc_lowmem(void *arg __unused, int howto __unused) 5372{ 5373 5374 mutex_enter(&arc_reclaim_lock); 5375 /* XXX: Memory deficit should be passed as argument. */ 5376 needfree = btoc(arc_c >> arc_shrink_shift); 5377 DTRACE_PROBE(arc__needfree); 5378 cv_signal(&arc_reclaim_thread_cv); 5379 5380 /* 5381 * It is unsafe to block here in arbitrary threads, because we can come 5382 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5383 * with ARC reclaim thread. 5384 */ 5385 if (curproc == pageproc) 5386 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5387 mutex_exit(&arc_reclaim_lock); 5388} 5389#endif 5390 5391void 5392arc_init(void) 5393{ 5394 int i, prefetch_tunable_set = 0; 5395 5396 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5397 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5398 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5399 5400 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5401 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5402 5403 /* Convert seconds to clock ticks */ 5404 arc_min_prefetch_lifespan = 1 * hz; 5405 5406 /* Start out with 1/8 of all memory */ 5407 arc_c = kmem_size() / 8; 5408 5409#ifdef illumos 5410#ifdef _KERNEL 5411 /* 5412 * On architectures where the physical memory can be larger 5413 * than the addressable space (intel in 32-bit mode), we may 5414 * need to limit the cache to 1/8 of VM size. 5415 */ 5416 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5417#endif 5418#endif /* illumos */ 5419 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 5420 arc_c_min = MAX(arc_c / 4, arc_abs_min); 5421 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 5422 if (arc_c * 8 >= 1 << 30) 5423 arc_c_max = (arc_c * 8) - (1 << 30); 5424 else 5425 arc_c_max = arc_c_min; 5426 arc_c_max = MAX(arc_c * 5, arc_c_max); 5427 5428 /* 5429 * In userland, there's only the memory pressure that we artificially 5430 * create (see arc_available_memory()). Don't let arc_c get too 5431 * small, because it can cause transactions to be larger than 5432 * arc_c, causing arc_tempreserve_space() to fail. 5433 */ 5434#ifndef _KERNEL 5435 arc_c_min = arc_c_max / 2; 5436#endif 5437 5438#ifdef _KERNEL 5439 /* 5440 * Allow the tunables to override our calculations if they are 5441 * reasonable. 5442 */ 5443 if (zfs_arc_max > arc_abs_min && zfs_arc_max < kmem_size()) 5444 arc_c_max = zfs_arc_max; 5445 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 5446 arc_c_min = zfs_arc_min; 5447#endif 5448 5449 arc_c = arc_c_max; 5450 arc_p = (arc_c >> 1); 5451 5452 /* limit meta-data to 1/4 of the arc capacity */ 5453 arc_meta_limit = arc_c_max / 4; 5454 5455 /* Allow the tunable to override if it is reasonable */ 5456 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5457 arc_meta_limit = zfs_arc_meta_limit; 5458 5459 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5460 arc_c_min = arc_meta_limit / 2; 5461 5462 if (zfs_arc_meta_min > 0) { 5463 arc_meta_min = zfs_arc_meta_min; 5464 } else { 5465 arc_meta_min = arc_c_min / 2; 5466 } 5467 5468 if (zfs_arc_grow_retry > 0) 5469 arc_grow_retry = zfs_arc_grow_retry; 5470 5471 if (zfs_arc_shrink_shift > 0) 5472 arc_shrink_shift = zfs_arc_shrink_shift; 5473 5474 /* 5475 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5476 */ 5477 if (arc_no_grow_shift >= arc_shrink_shift) 5478 arc_no_grow_shift = arc_shrink_shift - 1; 5479 5480 if (zfs_arc_p_min_shift > 0) 5481 arc_p_min_shift = zfs_arc_p_min_shift; 5482 5483 if (zfs_arc_num_sublists_per_state < 1) 5484 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 5485 5486 /* if kmem_flags are set, lets try to use less memory */ 5487 if (kmem_debugging()) 5488 arc_c = arc_c / 2; 5489 if (arc_c < arc_c_min) 5490 arc_c = arc_c_min; 5491 5492 zfs_arc_min = arc_c_min; 5493 zfs_arc_max = arc_c_max; 5494 5495 arc_anon = &ARC_anon; 5496 arc_mru = &ARC_mru; 5497 arc_mru_ghost = &ARC_mru_ghost; 5498 arc_mfu = &ARC_mfu; 5499 arc_mfu_ghost = &ARC_mfu_ghost; 5500 arc_l2c_only = &ARC_l2c_only; 5501 arc_size = 0; 5502 5503 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5504 sizeof (arc_buf_hdr_t), 5505 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5506 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5507 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5508 sizeof (arc_buf_hdr_t), 5509 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5510 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5511 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5512 sizeof (arc_buf_hdr_t), 5513 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5514 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5515 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5516 sizeof (arc_buf_hdr_t), 5517 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5518 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5519 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5520 sizeof (arc_buf_hdr_t), 5521 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5522 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5523 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5524 sizeof (arc_buf_hdr_t), 5525 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5526 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5527 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5528 sizeof (arc_buf_hdr_t), 5529 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5530 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5531 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5532 sizeof (arc_buf_hdr_t), 5533 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5534 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5535 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5536 sizeof (arc_buf_hdr_t), 5537 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5538 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5539 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5540 sizeof (arc_buf_hdr_t), 5541 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5542 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5543 5544 refcount_create(&arc_anon->arcs_size); 5545 refcount_create(&arc_mru->arcs_size); 5546 refcount_create(&arc_mru_ghost->arcs_size); 5547 refcount_create(&arc_mfu->arcs_size); 5548 refcount_create(&arc_mfu_ghost->arcs_size); 5549 refcount_create(&arc_l2c_only->arcs_size); 5550 5551 buf_init(); 5552 5553 arc_reclaim_thread_exit = FALSE; 5554 arc_user_evicts_thread_exit = FALSE; 5555 arc_eviction_list = NULL; 5556 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5557 5558 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5559 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5560 5561 if (arc_ksp != NULL) { 5562 arc_ksp->ks_data = &arc_stats; 5563 arc_ksp->ks_update = arc_kstat_update; 5564 kstat_install(arc_ksp); 5565 } 5566 5567 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5568 TS_RUN, minclsyspri); 5569 5570#ifdef _KERNEL 5571 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5572 EVENTHANDLER_PRI_FIRST); 5573#endif 5574 5575 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5576 TS_RUN, minclsyspri); 5577 5578 arc_dead = FALSE; 5579 arc_warm = B_FALSE; 5580 5581 /* 5582 * Calculate maximum amount of dirty data per pool. 5583 * 5584 * If it has been set by /etc/system, take that. 5585 * Otherwise, use a percentage of physical memory defined by 5586 * zfs_dirty_data_max_percent (default 10%) with a cap at 5587 * zfs_dirty_data_max_max (default 4GB). 5588 */ 5589 if (zfs_dirty_data_max == 0) { 5590 zfs_dirty_data_max = ptob(physmem) * 5591 zfs_dirty_data_max_percent / 100; 5592 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5593 zfs_dirty_data_max_max); 5594 } 5595 5596#ifdef _KERNEL 5597 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5598 prefetch_tunable_set = 1; 5599 5600#ifdef __i386__ 5601 if (prefetch_tunable_set == 0) { 5602 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5603 "-- to enable,\n"); 5604 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5605 "to /boot/loader.conf.\n"); 5606 zfs_prefetch_disable = 1; 5607 } 5608#else 5609 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5610 prefetch_tunable_set == 0) { 5611 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5612 "than 4GB of RAM is present;\n" 5613 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5614 "to /boot/loader.conf.\n"); 5615 zfs_prefetch_disable = 1; 5616 } 5617#endif 5618 /* Warn about ZFS memory and address space requirements. */ 5619 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5620 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5621 "expect unstable behavior.\n"); 5622 } 5623 if (kmem_size() < 512 * (1 << 20)) { 5624 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5625 "expect unstable behavior.\n"); 5626 printf(" Consider tuning vm.kmem_size and " 5627 "vm.kmem_size_max\n"); 5628 printf(" in /boot/loader.conf.\n"); 5629 } 5630#endif 5631} 5632 5633void 5634arc_fini(void) 5635{ 5636 mutex_enter(&arc_reclaim_lock); 5637 arc_reclaim_thread_exit = TRUE; 5638 /* 5639 * The reclaim thread will set arc_reclaim_thread_exit back to 5640 * FALSE when it is finished exiting; we're waiting for that. 5641 */ 5642 while (arc_reclaim_thread_exit) { 5643 cv_signal(&arc_reclaim_thread_cv); 5644 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5645 } 5646 mutex_exit(&arc_reclaim_lock); 5647 5648 mutex_enter(&arc_user_evicts_lock); 5649 arc_user_evicts_thread_exit = TRUE; 5650 /* 5651 * The user evicts thread will set arc_user_evicts_thread_exit 5652 * to FALSE when it is finished exiting; we're waiting for that. 5653 */ 5654 while (arc_user_evicts_thread_exit) { 5655 cv_signal(&arc_user_evicts_cv); 5656 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5657 } 5658 mutex_exit(&arc_user_evicts_lock); 5659 5660 /* Use TRUE to ensure *all* buffers are evicted */ 5661 arc_flush(NULL, TRUE); 5662 5663 arc_dead = TRUE; 5664 5665 if (arc_ksp != NULL) { 5666 kstat_delete(arc_ksp); 5667 arc_ksp = NULL; 5668 } 5669 5670 mutex_destroy(&arc_reclaim_lock); 5671 cv_destroy(&arc_reclaim_thread_cv); 5672 cv_destroy(&arc_reclaim_waiters_cv); 5673 5674 mutex_destroy(&arc_user_evicts_lock); 5675 cv_destroy(&arc_user_evicts_cv); 5676 5677 refcount_destroy(&arc_anon->arcs_size); 5678 refcount_destroy(&arc_mru->arcs_size); 5679 refcount_destroy(&arc_mru_ghost->arcs_size); 5680 refcount_destroy(&arc_mfu->arcs_size); 5681 refcount_destroy(&arc_mfu_ghost->arcs_size); 5682 refcount_destroy(&arc_l2c_only->arcs_size); 5683 5684 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5685 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5686 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5687 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5688 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); 5689 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5690 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5691 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5692 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5693 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]); 5694 5695 buf_fini(); 5696 5697 ASSERT0(arc_loaned_bytes); 5698 5699#ifdef _KERNEL 5700 if (arc_event_lowmem != NULL) 5701 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5702#endif 5703} 5704 5705/* 5706 * Level 2 ARC 5707 * 5708 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5709 * It uses dedicated storage devices to hold cached data, which are populated 5710 * using large infrequent writes. The main role of this cache is to boost 5711 * the performance of random read workloads. The intended L2ARC devices 5712 * include short-stroked disks, solid state disks, and other media with 5713 * substantially faster read latency than disk. 5714 * 5715 * +-----------------------+ 5716 * | ARC | 5717 * +-----------------------+ 5718 * | ^ ^ 5719 * | | | 5720 * l2arc_feed_thread() arc_read() 5721 * | | | 5722 * | l2arc read | 5723 * V | | 5724 * +---------------+ | 5725 * | L2ARC | | 5726 * +---------------+ | 5727 * | ^ | 5728 * l2arc_write() | | 5729 * | | | 5730 * V | | 5731 * +-------+ +-------+ 5732 * | vdev | | vdev | 5733 * | cache | | cache | 5734 * +-------+ +-------+ 5735 * +=========+ .-----. 5736 * : L2ARC : |-_____-| 5737 * : devices : | Disks | 5738 * +=========+ `-_____-' 5739 * 5740 * Read requests are satisfied from the following sources, in order: 5741 * 5742 * 1) ARC 5743 * 2) vdev cache of L2ARC devices 5744 * 3) L2ARC devices 5745 * 4) vdev cache of disks 5746 * 5) disks 5747 * 5748 * Some L2ARC device types exhibit extremely slow write performance. 5749 * To accommodate for this there are some significant differences between 5750 * the L2ARC and traditional cache design: 5751 * 5752 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5753 * the ARC behave as usual, freeing buffers and placing headers on ghost 5754 * lists. The ARC does not send buffers to the L2ARC during eviction as 5755 * this would add inflated write latencies for all ARC memory pressure. 5756 * 5757 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5758 * It does this by periodically scanning buffers from the eviction-end of 5759 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5760 * not already there. It scans until a headroom of buffers is satisfied, 5761 * which itself is a buffer for ARC eviction. If a compressible buffer is 5762 * found during scanning and selected for writing to an L2ARC device, we 5763 * temporarily boost scanning headroom during the next scan cycle to make 5764 * sure we adapt to compression effects (which might significantly reduce 5765 * the data volume we write to L2ARC). The thread that does this is 5766 * l2arc_feed_thread(), illustrated below; example sizes are included to 5767 * provide a better sense of ratio than this diagram: 5768 * 5769 * head --> tail 5770 * +---------------------+----------+ 5771 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5772 * +---------------------+----------+ | o L2ARC eligible 5773 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5774 * +---------------------+----------+ | 5775 * 15.9 Gbytes ^ 32 Mbytes | 5776 * headroom | 5777 * l2arc_feed_thread() 5778 * | 5779 * l2arc write hand <--[oooo]--' 5780 * | 8 Mbyte 5781 * | write max 5782 * V 5783 * +==============================+ 5784 * L2ARC dev |####|#|###|###| |####| ... | 5785 * +==============================+ 5786 * 32 Gbytes 5787 * 5788 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5789 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5790 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5791 * safe to say that this is an uncommon case, since buffers at the end of 5792 * the ARC lists have moved there due to inactivity. 5793 * 5794 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5795 * then the L2ARC simply misses copying some buffers. This serves as a 5796 * pressure valve to prevent heavy read workloads from both stalling the ARC 5797 * with waits and clogging the L2ARC with writes. This also helps prevent 5798 * the potential for the L2ARC to churn if it attempts to cache content too 5799 * quickly, such as during backups of the entire pool. 5800 * 5801 * 5. After system boot and before the ARC has filled main memory, there are 5802 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5803 * lists can remain mostly static. Instead of searching from tail of these 5804 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5805 * for eligible buffers, greatly increasing its chance of finding them. 5806 * 5807 * The L2ARC device write speed is also boosted during this time so that 5808 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5809 * there are no L2ARC reads, and no fear of degrading read performance 5810 * through increased writes. 5811 * 5812 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5813 * the vdev queue can aggregate them into larger and fewer writes. Each 5814 * device is written to in a rotor fashion, sweeping writes through 5815 * available space then repeating. 5816 * 5817 * 7. The L2ARC does not store dirty content. It never needs to flush 5818 * write buffers back to disk based storage. 5819 * 5820 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5821 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5822 * 5823 * The performance of the L2ARC can be tweaked by a number of tunables, which 5824 * may be necessary for different workloads: 5825 * 5826 * l2arc_write_max max write bytes per interval 5827 * l2arc_write_boost extra write bytes during device warmup 5828 * l2arc_noprefetch skip caching prefetched buffers 5829 * l2arc_headroom number of max device writes to precache 5830 * l2arc_headroom_boost when we find compressed buffers during ARC 5831 * scanning, we multiply headroom by this 5832 * percentage factor for the next scan cycle, 5833 * since more compressed buffers are likely to 5834 * be present 5835 * l2arc_feed_secs seconds between L2ARC writing 5836 * 5837 * Tunables may be removed or added as future performance improvements are 5838 * integrated, and also may become zpool properties. 5839 * 5840 * There are three key functions that control how the L2ARC warms up: 5841 * 5842 * l2arc_write_eligible() check if a buffer is eligible to cache 5843 * l2arc_write_size() calculate how much to write 5844 * l2arc_write_interval() calculate sleep delay between writes 5845 * 5846 * These three functions determine what to write, how much, and how quickly 5847 * to send writes. 5848 */ 5849 5850static boolean_t 5851l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5852{ 5853 /* 5854 * A buffer is *not* eligible for the L2ARC if it: 5855 * 1. belongs to a different spa. 5856 * 2. is already cached on the L2ARC. 5857 * 3. has an I/O in progress (it may be an incomplete read). 5858 * 4. is flagged not eligible (zfs property). 5859 */ 5860 if (hdr->b_spa != spa_guid) { 5861 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5862 return (B_FALSE); 5863 } 5864 if (HDR_HAS_L2HDR(hdr)) { 5865 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5866 return (B_FALSE); 5867 } 5868 if (HDR_IO_IN_PROGRESS(hdr)) { 5869 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5870 return (B_FALSE); 5871 } 5872 if (!HDR_L2CACHE(hdr)) { 5873 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5874 return (B_FALSE); 5875 } 5876 5877 return (B_TRUE); 5878} 5879 5880static uint64_t 5881l2arc_write_size(void) 5882{ 5883 uint64_t size; 5884 5885 /* 5886 * Make sure our globals have meaningful values in case the user 5887 * altered them. 5888 */ 5889 size = l2arc_write_max; 5890 if (size == 0) { 5891 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5892 "be greater than zero, resetting it to the default (%d)", 5893 L2ARC_WRITE_SIZE); 5894 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5895 } 5896 5897 if (arc_warm == B_FALSE) 5898 size += l2arc_write_boost; 5899 5900 return (size); 5901 5902} 5903 5904static clock_t 5905l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5906{ 5907 clock_t interval, next, now; 5908 5909 /* 5910 * If the ARC lists are busy, increase our write rate; if the 5911 * lists are stale, idle back. This is achieved by checking 5912 * how much we previously wrote - if it was more than half of 5913 * what we wanted, schedule the next write much sooner. 5914 */ 5915 if (l2arc_feed_again && wrote > (wanted / 2)) 5916 interval = (hz * l2arc_feed_min_ms) / 1000; 5917 else 5918 interval = hz * l2arc_feed_secs; 5919 5920 now = ddi_get_lbolt(); 5921 next = MAX(now, MIN(now + interval, began + interval)); 5922 5923 return (next); 5924} 5925 5926/* 5927 * Cycle through L2ARC devices. This is how L2ARC load balances. 5928 * If a device is returned, this also returns holding the spa config lock. 5929 */ 5930static l2arc_dev_t * 5931l2arc_dev_get_next(void) 5932{ 5933 l2arc_dev_t *first, *next = NULL; 5934 5935 /* 5936 * Lock out the removal of spas (spa_namespace_lock), then removal 5937 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5938 * both locks will be dropped and a spa config lock held instead. 5939 */ 5940 mutex_enter(&spa_namespace_lock); 5941 mutex_enter(&l2arc_dev_mtx); 5942 5943 /* if there are no vdevs, there is nothing to do */ 5944 if (l2arc_ndev == 0) 5945 goto out; 5946 5947 first = NULL; 5948 next = l2arc_dev_last; 5949 do { 5950 /* loop around the list looking for a non-faulted vdev */ 5951 if (next == NULL) { 5952 next = list_head(l2arc_dev_list); 5953 } else { 5954 next = list_next(l2arc_dev_list, next); 5955 if (next == NULL) 5956 next = list_head(l2arc_dev_list); 5957 } 5958 5959 /* if we have come back to the start, bail out */ 5960 if (first == NULL) 5961 first = next; 5962 else if (next == first) 5963 break; 5964 5965 } while (vdev_is_dead(next->l2ad_vdev)); 5966 5967 /* if we were unable to find any usable vdevs, return NULL */ 5968 if (vdev_is_dead(next->l2ad_vdev)) 5969 next = NULL; 5970 5971 l2arc_dev_last = next; 5972 5973out: 5974 mutex_exit(&l2arc_dev_mtx); 5975 5976 /* 5977 * Grab the config lock to prevent the 'next' device from being 5978 * removed while we are writing to it. 5979 */ 5980 if (next != NULL) 5981 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5982 mutex_exit(&spa_namespace_lock); 5983 5984 return (next); 5985} 5986 5987/* 5988 * Free buffers that were tagged for destruction. 5989 */ 5990static void 5991l2arc_do_free_on_write() 5992{ 5993 list_t *buflist; 5994 l2arc_data_free_t *df, *df_prev; 5995 5996 mutex_enter(&l2arc_free_on_write_mtx); 5997 buflist = l2arc_free_on_write; 5998 5999 for (df = list_tail(buflist); df; df = df_prev) { 6000 df_prev = list_prev(buflist, df); 6001 ASSERT(df->l2df_data != NULL); 6002 ASSERT(df->l2df_func != NULL); 6003 df->l2df_func(df->l2df_data, df->l2df_size); 6004 list_remove(buflist, df); 6005 kmem_free(df, sizeof (l2arc_data_free_t)); 6006 } 6007 6008 mutex_exit(&l2arc_free_on_write_mtx); 6009} 6010 6011/* 6012 * A write to a cache device has completed. Update all headers to allow 6013 * reads from these buffers to begin. 6014 */ 6015static void 6016l2arc_write_done(zio_t *zio) 6017{ 6018 l2arc_write_callback_t *cb; 6019 l2arc_dev_t *dev; 6020 list_t *buflist; 6021 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6022 kmutex_t *hash_lock; 6023 int64_t bytes_dropped = 0; 6024 6025 cb = zio->io_private; 6026 ASSERT(cb != NULL); 6027 dev = cb->l2wcb_dev; 6028 ASSERT(dev != NULL); 6029 head = cb->l2wcb_head; 6030 ASSERT(head != NULL); 6031 buflist = &dev->l2ad_buflist; 6032 ASSERT(buflist != NULL); 6033 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6034 l2arc_write_callback_t *, cb); 6035 6036 if (zio->io_error != 0) 6037 ARCSTAT_BUMP(arcstat_l2_writes_error); 6038 6039 /* 6040 * All writes completed, or an error was hit. 6041 */ 6042top: 6043 mutex_enter(&dev->l2ad_mtx); 6044 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 6045 hdr_prev = list_prev(buflist, hdr); 6046 6047 hash_lock = HDR_LOCK(hdr); 6048 6049 /* 6050 * We cannot use mutex_enter or else we can deadlock 6051 * with l2arc_write_buffers (due to swapping the order 6052 * the hash lock and l2ad_mtx are taken). 6053 */ 6054 if (!mutex_tryenter(hash_lock)) { 6055 /* 6056 * Missed the hash lock. We must retry so we 6057 * don't leave the ARC_FLAG_L2_WRITING bit set. 6058 */ 6059 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 6060 6061 /* 6062 * We don't want to rescan the headers we've 6063 * already marked as having been written out, so 6064 * we reinsert the head node so we can pick up 6065 * where we left off. 6066 */ 6067 list_remove(buflist, head); 6068 list_insert_after(buflist, hdr, head); 6069 6070 mutex_exit(&dev->l2ad_mtx); 6071 6072 /* 6073 * We wait for the hash lock to become available 6074 * to try and prevent busy waiting, and increase 6075 * the chance we'll be able to acquire the lock 6076 * the next time around. 6077 */ 6078 mutex_enter(hash_lock); 6079 mutex_exit(hash_lock); 6080 goto top; 6081 } 6082 6083 /* 6084 * We could not have been moved into the arc_l2c_only 6085 * state while in-flight due to our ARC_FLAG_L2_WRITING 6086 * bit being set. Let's just ensure that's being enforced. 6087 */ 6088 ASSERT(HDR_HAS_L1HDR(hdr)); 6089 6090 /* 6091 * We may have allocated a buffer for L2ARC compression, 6092 * we must release it to avoid leaking this data. 6093 */ 6094 l2arc_release_cdata_buf(hdr); 6095 6096 if (zio->io_error != 0) { 6097 /* 6098 * Error - drop L2ARC entry. 6099 */ 6100 list_remove(buflist, hdr); 6101 l2arc_trim(hdr); 6102 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 6103 6104 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 6105 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 6106 6107 bytes_dropped += hdr->b_l2hdr.b_asize; 6108 (void) refcount_remove_many(&dev->l2ad_alloc, 6109 hdr->b_l2hdr.b_asize, hdr); 6110 } 6111 6112 /* 6113 * Allow ARC to begin reads and ghost list evictions to 6114 * this L2ARC entry. 6115 */ 6116 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 6117 6118 mutex_exit(hash_lock); 6119 } 6120 6121 atomic_inc_64(&l2arc_writes_done); 6122 list_remove(buflist, head); 6123 ASSERT(!HDR_HAS_L1HDR(head)); 6124 kmem_cache_free(hdr_l2only_cache, head); 6125 mutex_exit(&dev->l2ad_mtx); 6126 6127 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6128 6129 l2arc_do_free_on_write(); 6130 6131 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6132} 6133 6134/* 6135 * A read to a cache device completed. Validate buffer contents before 6136 * handing over to the regular ARC routines. 6137 */ 6138static void 6139l2arc_read_done(zio_t *zio) 6140{ 6141 l2arc_read_callback_t *cb; 6142 arc_buf_hdr_t *hdr; 6143 arc_buf_t *buf; 6144 kmutex_t *hash_lock; 6145 int equal; 6146 6147 ASSERT(zio->io_vd != NULL); 6148 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6149 6150 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6151 6152 cb = zio->io_private; 6153 ASSERT(cb != NULL); 6154 buf = cb->l2rcb_buf; 6155 ASSERT(buf != NULL); 6156 6157 hash_lock = HDR_LOCK(buf->b_hdr); 6158 mutex_enter(hash_lock); 6159 hdr = buf->b_hdr; 6160 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6161 6162 /* 6163 * If the data was read into a temporary buffer, 6164 * move it and free the buffer. 6165 */ 6166 if (cb->l2rcb_data != NULL) { 6167 ASSERT3U(hdr->b_size, <, zio->io_size); 6168 ASSERT3U(cb->l2rcb_compress, ==, ZIO_COMPRESS_OFF); 6169 if (zio->io_error == 0) 6170 bcopy(cb->l2rcb_data, buf->b_data, hdr->b_size); 6171 6172 /* 6173 * The following must be done regardless of whether 6174 * there was an error: 6175 * - free the temporary buffer 6176 * - point zio to the real ARC buffer 6177 * - set zio size accordingly 6178 * These are required because zio is either re-used for 6179 * an I/O of the block in the case of the error 6180 * or the zio is passed to arc_read_done() and it 6181 * needs real data. 6182 */ 6183 zio_data_buf_free(cb->l2rcb_data, zio->io_size); 6184 zio->io_size = zio->io_orig_size = hdr->b_size; 6185 zio->io_data = zio->io_orig_data = buf->b_data; 6186 } 6187 6188 /* 6189 * If the buffer was compressed, decompress it first. 6190 */ 6191 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6192 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6193 ASSERT(zio->io_data != NULL); 6194 ASSERT3U(zio->io_size, ==, hdr->b_size); 6195 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 6196 6197 /* 6198 * Check this survived the L2ARC journey. 6199 */ 6200 equal = arc_cksum_equal(buf); 6201 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6202 mutex_exit(hash_lock); 6203 zio->io_private = buf; 6204 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6205 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6206 arc_read_done(zio); 6207 } else { 6208 mutex_exit(hash_lock); 6209 /* 6210 * Buffer didn't survive caching. Increment stats and 6211 * reissue to the original storage device. 6212 */ 6213 if (zio->io_error != 0) { 6214 ARCSTAT_BUMP(arcstat_l2_io_error); 6215 } else { 6216 zio->io_error = SET_ERROR(EIO); 6217 } 6218 if (!equal) 6219 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6220 6221 /* 6222 * If there's no waiter, issue an async i/o to the primary 6223 * storage now. If there *is* a waiter, the caller must 6224 * issue the i/o in a context where it's OK to block. 6225 */ 6226 if (zio->io_waiter == NULL) { 6227 zio_t *pio = zio_unique_parent(zio); 6228 6229 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6230 6231 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6232 buf->b_data, hdr->b_size, arc_read_done, buf, 6233 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6234 } 6235 } 6236 6237 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6238} 6239 6240/* 6241 * This is the list priority from which the L2ARC will search for pages to 6242 * cache. This is used within loops (0..3) to cycle through lists in the 6243 * desired order. This order can have a significant effect on cache 6244 * performance. 6245 * 6246 * Currently the metadata lists are hit first, MFU then MRU, followed by 6247 * the data lists. This function returns a locked list, and also returns 6248 * the lock pointer. 6249 */ 6250static multilist_sublist_t * 6251l2arc_sublist_lock(int list_num) 6252{ 6253 multilist_t *ml = NULL; 6254 unsigned int idx; 6255 6256 ASSERT(list_num >= 0 && list_num <= 3); 6257 6258 switch (list_num) { 6259 case 0: 6260 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6261 break; 6262 case 1: 6263 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6264 break; 6265 case 2: 6266 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6267 break; 6268 case 3: 6269 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6270 break; 6271 } 6272 6273 /* 6274 * Return a randomly-selected sublist. This is acceptable 6275 * because the caller feeds only a little bit of data for each 6276 * call (8MB). Subsequent calls will result in different 6277 * sublists being selected. 6278 */ 6279 idx = multilist_get_random_index(ml); 6280 return (multilist_sublist_lock(ml, idx)); 6281} 6282 6283/* 6284 * Evict buffers from the device write hand to the distance specified in 6285 * bytes. This distance may span populated buffers, it may span nothing. 6286 * This is clearing a region on the L2ARC device ready for writing. 6287 * If the 'all' boolean is set, every buffer is evicted. 6288 */ 6289static void 6290l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6291{ 6292 list_t *buflist; 6293 arc_buf_hdr_t *hdr, *hdr_prev; 6294 kmutex_t *hash_lock; 6295 uint64_t taddr; 6296 6297 buflist = &dev->l2ad_buflist; 6298 6299 if (!all && dev->l2ad_first) { 6300 /* 6301 * This is the first sweep through the device. There is 6302 * nothing to evict. 6303 */ 6304 return; 6305 } 6306 6307 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6308 /* 6309 * When nearing the end of the device, evict to the end 6310 * before the device write hand jumps to the start. 6311 */ 6312 taddr = dev->l2ad_end; 6313 } else { 6314 taddr = dev->l2ad_hand + distance; 6315 } 6316 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6317 uint64_t, taddr, boolean_t, all); 6318 6319top: 6320 mutex_enter(&dev->l2ad_mtx); 6321 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6322 hdr_prev = list_prev(buflist, hdr); 6323 6324 hash_lock = HDR_LOCK(hdr); 6325 6326 /* 6327 * We cannot use mutex_enter or else we can deadlock 6328 * with l2arc_write_buffers (due to swapping the order 6329 * the hash lock and l2ad_mtx are taken). 6330 */ 6331 if (!mutex_tryenter(hash_lock)) { 6332 /* 6333 * Missed the hash lock. Retry. 6334 */ 6335 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6336 mutex_exit(&dev->l2ad_mtx); 6337 mutex_enter(hash_lock); 6338 mutex_exit(hash_lock); 6339 goto top; 6340 } 6341 6342 if (HDR_L2_WRITE_HEAD(hdr)) { 6343 /* 6344 * We hit a write head node. Leave it for 6345 * l2arc_write_done(). 6346 */ 6347 list_remove(buflist, hdr); 6348 mutex_exit(hash_lock); 6349 continue; 6350 } 6351 6352 if (!all && HDR_HAS_L2HDR(hdr) && 6353 (hdr->b_l2hdr.b_daddr > taddr || 6354 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6355 /* 6356 * We've evicted to the target address, 6357 * or the end of the device. 6358 */ 6359 mutex_exit(hash_lock); 6360 break; 6361 } 6362 6363 ASSERT(HDR_HAS_L2HDR(hdr)); 6364 if (!HDR_HAS_L1HDR(hdr)) { 6365 ASSERT(!HDR_L2_READING(hdr)); 6366 /* 6367 * This doesn't exist in the ARC. Destroy. 6368 * arc_hdr_destroy() will call list_remove() 6369 * and decrement arcstat_l2_size. 6370 */ 6371 arc_change_state(arc_anon, hdr, hash_lock); 6372 arc_hdr_destroy(hdr); 6373 } else { 6374 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6375 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6376 /* 6377 * Invalidate issued or about to be issued 6378 * reads, since we may be about to write 6379 * over this location. 6380 */ 6381 if (HDR_L2_READING(hdr)) { 6382 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6383 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6384 } 6385 6386 /* Ensure this header has finished being written */ 6387 ASSERT(!HDR_L2_WRITING(hdr)); 6388 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6389 6390 arc_hdr_l2hdr_destroy(hdr); 6391 } 6392 mutex_exit(hash_lock); 6393 } 6394 mutex_exit(&dev->l2ad_mtx); 6395} 6396 6397/* 6398 * Find and write ARC buffers to the L2ARC device. 6399 * 6400 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6401 * for reading until they have completed writing. 6402 * The headroom_boost is an in-out parameter used to maintain headroom boost 6403 * state between calls to this function. 6404 * 6405 * Returns the number of bytes actually written (which may be smaller than 6406 * the delta by which the device hand has changed due to alignment). 6407 */ 6408static uint64_t 6409l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6410 boolean_t *headroom_boost) 6411{ 6412 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6413 uint64_t write_asize, write_sz, headroom, 6414 buf_compress_minsz; 6415 void *buf_data; 6416 boolean_t full; 6417 l2arc_write_callback_t *cb; 6418 zio_t *pio, *wzio; 6419 uint64_t guid = spa_load_guid(spa); 6420 const boolean_t do_headroom_boost = *headroom_boost; 6421 int try; 6422 6423 ASSERT(dev->l2ad_vdev != NULL); 6424 6425 /* Lower the flag now, we might want to raise it again later. */ 6426 *headroom_boost = B_FALSE; 6427 6428 pio = NULL; 6429 write_sz = write_asize = 0; 6430 full = B_FALSE; 6431 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6432 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6433 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6434 6435 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6436 /* 6437 * We will want to try to compress buffers that are at least 2x the 6438 * device sector size. 6439 */ 6440 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6441 6442 /* 6443 * Copy buffers for L2ARC writing. 6444 */ 6445 for (try = 0; try <= 3; try++) { 6446 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6447 uint64_t passed_sz = 0; 6448 6449 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6450 6451 /* 6452 * L2ARC fast warmup. 6453 * 6454 * Until the ARC is warm and starts to evict, read from the 6455 * head of the ARC lists rather than the tail. 6456 */ 6457 if (arc_warm == B_FALSE) 6458 hdr = multilist_sublist_head(mls); 6459 else 6460 hdr = multilist_sublist_tail(mls); 6461 if (hdr == NULL) 6462 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6463 6464 headroom = target_sz * l2arc_headroom; 6465 if (do_headroom_boost) 6466 headroom = (headroom * l2arc_headroom_boost) / 100; 6467 6468 for (; hdr; hdr = hdr_prev) { 6469 kmutex_t *hash_lock; 6470 uint64_t buf_sz; 6471 uint64_t buf_a_sz; 6472 size_t align; 6473 6474 if (arc_warm == B_FALSE) 6475 hdr_prev = multilist_sublist_next(mls, hdr); 6476 else 6477 hdr_prev = multilist_sublist_prev(mls, hdr); 6478 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 6479 6480 hash_lock = HDR_LOCK(hdr); 6481 if (!mutex_tryenter(hash_lock)) { 6482 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 6483 /* 6484 * Skip this buffer rather than waiting. 6485 */ 6486 continue; 6487 } 6488 6489 passed_sz += hdr->b_size; 6490 if (passed_sz > headroom) { 6491 /* 6492 * Searched too far. 6493 */ 6494 mutex_exit(hash_lock); 6495 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 6496 break; 6497 } 6498 6499 if (!l2arc_write_eligible(guid, hdr)) { 6500 mutex_exit(hash_lock); 6501 continue; 6502 } 6503 6504 /* 6505 * Assume that the buffer is not going to be compressed 6506 * and could take more space on disk because of a larger 6507 * disk block size. 6508 */ 6509 buf_sz = hdr->b_size; 6510 align = (size_t)1 << dev->l2ad_vdev->vdev_ashift; 6511 buf_a_sz = P2ROUNDUP(buf_sz, align); 6512 6513 if ((write_asize + buf_a_sz) > target_sz) { 6514 full = B_TRUE; 6515 mutex_exit(hash_lock); 6516 ARCSTAT_BUMP(arcstat_l2_write_full); 6517 break; 6518 } 6519 6520 if (pio == NULL) { 6521 /* 6522 * Insert a dummy header on the buflist so 6523 * l2arc_write_done() can find where the 6524 * write buffers begin without searching. 6525 */ 6526 mutex_enter(&dev->l2ad_mtx); 6527 list_insert_head(&dev->l2ad_buflist, head); 6528 mutex_exit(&dev->l2ad_mtx); 6529 6530 cb = kmem_alloc( 6531 sizeof (l2arc_write_callback_t), KM_SLEEP); 6532 cb->l2wcb_dev = dev; 6533 cb->l2wcb_head = head; 6534 pio = zio_root(spa, l2arc_write_done, cb, 6535 ZIO_FLAG_CANFAIL); 6536 ARCSTAT_BUMP(arcstat_l2_write_pios); 6537 } 6538 6539 /* 6540 * Create and add a new L2ARC header. 6541 */ 6542 hdr->b_l2hdr.b_dev = dev; 6543 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6544 /* 6545 * Temporarily stash the data buffer in b_tmp_cdata. 6546 * The subsequent write step will pick it up from 6547 * there. This is because can't access b_l1hdr.b_buf 6548 * without holding the hash_lock, which we in turn 6549 * can't access without holding the ARC list locks 6550 * (which we want to avoid during compression/writing). 6551 */ 6552 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6553 hdr->b_l2hdr.b_asize = hdr->b_size; 6554 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6555 6556 /* 6557 * Explicitly set the b_daddr field to a known 6558 * value which means "invalid address". This 6559 * enables us to differentiate which stage of 6560 * l2arc_write_buffers() the particular header 6561 * is in (e.g. this loop, or the one below). 6562 * ARC_FLAG_L2_WRITING is not enough to make 6563 * this distinction, and we need to know in 6564 * order to do proper l2arc vdev accounting in 6565 * arc_release() and arc_hdr_destroy(). 6566 * 6567 * Note, we can't use a new flag to distinguish 6568 * the two stages because we don't hold the 6569 * header's hash_lock below, in the second stage 6570 * of this function. Thus, we can't simply 6571 * change the b_flags field to denote that the 6572 * IO has been sent. We can change the b_daddr 6573 * field of the L2 portion, though, since we'll 6574 * be holding the l2ad_mtx; which is why we're 6575 * using it to denote the header's state change. 6576 */ 6577 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6578 6579 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6580 6581 mutex_enter(&dev->l2ad_mtx); 6582 list_insert_head(&dev->l2ad_buflist, hdr); 6583 mutex_exit(&dev->l2ad_mtx); 6584 6585 /* 6586 * Compute and store the buffer cksum before 6587 * writing. On debug the cksum is verified first. 6588 */ 6589 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6590 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6591 6592 mutex_exit(hash_lock); 6593 6594 write_sz += buf_sz; 6595 write_asize += buf_a_sz; 6596 } 6597 6598 multilist_sublist_unlock(mls); 6599 6600 if (full == B_TRUE) 6601 break; 6602 } 6603 6604 /* No buffers selected for writing? */ 6605 if (pio == NULL) { 6606 ASSERT0(write_sz); 6607 ASSERT(!HDR_HAS_L1HDR(head)); 6608 kmem_cache_free(hdr_l2only_cache, head); 6609 return (0); 6610 } 6611 6612 mutex_enter(&dev->l2ad_mtx); 6613 6614 /* 6615 * Now start writing the buffers. We're starting at the write head 6616 * and work backwards, retracing the course of the buffer selector 6617 * loop above. 6618 */ 6619 write_asize = 0; 6620 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6621 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6622 uint64_t buf_sz; 6623 boolean_t compress; 6624 6625 /* 6626 * We rely on the L1 portion of the header below, so 6627 * it's invalid for this header to have been evicted out 6628 * of the ghost cache, prior to being written out. The 6629 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6630 */ 6631 ASSERT(HDR_HAS_L1HDR(hdr)); 6632 6633 /* 6634 * We shouldn't need to lock the buffer here, since we flagged 6635 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6636 * take care to only access its L2 cache parameters. In 6637 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6638 * ARC eviction. 6639 */ 6640 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6641 6642 /* 6643 * Save a pointer to the original buffer data we had previously 6644 * stashed away. 6645 */ 6646 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6647 6648 compress = HDR_L2COMPRESS(hdr) && 6649 hdr->b_l2hdr.b_asize >= buf_compress_minsz; 6650 if (l2arc_transform_buf(hdr, compress)) { 6651 /* 6652 * If compression succeeded, enable headroom 6653 * boost on the next scan cycle. 6654 */ 6655 *headroom_boost = B_TRUE; 6656 } 6657 6658 /* 6659 * Get the new buffer size that accounts for compression 6660 * and padding. 6661 */ 6662 buf_sz = hdr->b_l2hdr.b_asize; 6663 6664 /* 6665 * We need to do this regardless if buf_sz is zero or 6666 * not, otherwise, when this l2hdr is evicted we'll 6667 * remove a reference that was never added. 6668 */ 6669 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6670 6671 /* Compression may have squashed the buffer to zero length. */ 6672 if (buf_sz != 0) { 6673 /* 6674 * If the data was padded or compressed, then it 6675 * it is in a new buffer. 6676 */ 6677 if (hdr->b_l1hdr.b_tmp_cdata != NULL) 6678 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6679 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6680 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6681 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6682 ZIO_FLAG_CANFAIL, B_FALSE); 6683 6684 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6685 zio_t *, wzio); 6686 (void) zio_nowait(wzio); 6687 6688 write_asize += buf_sz; 6689 dev->l2ad_hand += buf_sz; 6690 } 6691 } 6692 6693 mutex_exit(&dev->l2ad_mtx); 6694 6695 ASSERT3U(write_asize, <=, target_sz); 6696 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6697 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6698 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6699 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6700 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6701 6702 /* 6703 * Bump device hand to the device start if it is approaching the end. 6704 * l2arc_evict() will already have evicted ahead for this case. 6705 */ 6706 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6707 dev->l2ad_hand = dev->l2ad_start; 6708 dev->l2ad_first = B_FALSE; 6709 } 6710 6711 dev->l2ad_writing = B_TRUE; 6712 (void) zio_wait(pio); 6713 dev->l2ad_writing = B_FALSE; 6714 6715 return (write_asize); 6716} 6717 6718/* 6719 * Transforms, possibly compresses and pads, an L2ARC buffer. 6720 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6721 * size in l2hdr->b_asize. This routine tries to compress the data and 6722 * depending on the compression result there are three possible outcomes: 6723 * *) The buffer was incompressible. The buffer size was already ashift aligned. 6724 * The original hdr contents were left untouched except for b_tmp_cdata, 6725 * which is reset to NULL. The caller must keep a pointer to the original 6726 * data. 6727 * *) The buffer was incompressible. The buffer size was not ashift aligned. 6728 * b_tmp_cdata was replaced with a temporary data buffer which holds a padded 6729 * (aligned) copy of the data. Once writing is done, invoke 6730 * l2arc_release_cdata_buf on this hdr to free the temporary buffer. 6731 * *) The buffer was all-zeros, so there is no need to write it to an L2 6732 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6733 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6734 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6735 * data buffer which holds the compressed data to be written, and b_asize 6736 * tells us how much data there is. b_compress is set to the appropriate 6737 * compression algorithm. Once writing is done, invoke 6738 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6739 * 6740 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6741 * buffer was incompressible). 6742 */ 6743static boolean_t 6744l2arc_transform_buf(arc_buf_hdr_t *hdr, boolean_t compress) 6745{ 6746 void *cdata; 6747 size_t align, asize, csize, len, rounded; 6748 6749 ASSERT(HDR_HAS_L2HDR(hdr)); 6750 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6751 6752 ASSERT(HDR_HAS_L1HDR(hdr)); 6753 ASSERT3S(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF); 6754 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6755 6756 len = l2hdr->b_asize; 6757 align = (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift; 6758 asize = P2ROUNDUP(len, align); 6759 cdata = zio_data_buf_alloc(asize); 6760 ASSERT3P(cdata, !=, NULL); 6761 if (compress) 6762 csize = zio_compress_data(ZIO_COMPRESS_LZ4, 6763 hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6764 else 6765 csize = len; 6766 6767 if (csize == 0) { 6768 /* zero block, indicate that there's nothing to write */ 6769 zio_data_buf_free(cdata, asize); 6770 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6771 l2hdr->b_asize = 0; 6772 hdr->b_l1hdr.b_tmp_cdata = NULL; 6773 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6774 return (B_TRUE); 6775 } 6776 6777 rounded = P2ROUNDUP(csize, align); 6778 ASSERT3U(rounded, <=, asize); 6779 if (rounded < len) { 6780 /* 6781 * Compression succeeded, we'll keep the cdata around for 6782 * writing and release it afterwards. 6783 */ 6784 if (rounded > csize) { 6785 bzero((char *)cdata + csize, rounded - csize); 6786 csize = rounded; 6787 } 6788 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6789 l2hdr->b_asize = csize; 6790 hdr->b_l1hdr.b_tmp_cdata = cdata; 6791 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6792 return (B_TRUE); 6793 } else { 6794 /* 6795 * Compression did not save space. 6796 */ 6797 if (P2PHASE(len, align) != 0) { 6798 /* 6799 * Use compression buffer for a copy of data padded to 6800 * the proper size. Compression algorithm remains set 6801 * to ZIO_COMPRESS_OFF. 6802 */ 6803 ASSERT3U(len, <, asize); 6804 bcopy(hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6805 bzero((char *)cdata + len, asize - len); 6806 l2hdr->b_asize = asize; 6807 hdr->b_l1hdr.b_tmp_cdata = cdata; 6808 ARCSTAT_BUMP(arcstat_l2_padding_needed); 6809 } else { 6810 ASSERT3U(len, ==, asize); 6811 /* 6812 * The original buffer is good as is, 6813 * release the compressed buffer. 6814 * l2hdr will be left unmodified except for b_tmp_cdata. 6815 */ 6816 zio_data_buf_free(cdata, asize); 6817 hdr->b_l1hdr.b_tmp_cdata = NULL; 6818 } 6819 if (compress) 6820 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6821 return (B_FALSE); 6822 } 6823} 6824 6825/* 6826 * Decompresses a zio read back from an l2arc device. On success, the 6827 * underlying zio's io_data buffer is overwritten by the uncompressed 6828 * version. On decompression error (corrupt compressed stream), the 6829 * zio->io_error value is set to signal an I/O error. 6830 * 6831 * Please note that the compressed data stream is not checksummed, so 6832 * if the underlying device is experiencing data corruption, we may feed 6833 * corrupt data to the decompressor, so the decompressor needs to be 6834 * able to handle this situation (LZ4 does). 6835 */ 6836static void 6837l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6838{ 6839 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6840 6841 if (zio->io_error != 0) { 6842 /* 6843 * An io error has occured, just restore the original io 6844 * size in preparation for a main pool read. 6845 */ 6846 zio->io_orig_size = zio->io_size = hdr->b_size; 6847 return; 6848 } 6849 6850 if (c == ZIO_COMPRESS_EMPTY) { 6851 /* 6852 * An empty buffer results in a null zio, which means we 6853 * need to fill its io_data after we're done restoring the 6854 * buffer's contents. 6855 */ 6856 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6857 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6858 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6859 } else { 6860 ASSERT(zio->io_data != NULL); 6861 /* 6862 * We copy the compressed data from the start of the arc buffer 6863 * (the zio_read will have pulled in only what we need, the 6864 * rest is garbage which we will overwrite at decompression) 6865 * and then decompress back to the ARC data buffer. This way we 6866 * can minimize copying by simply decompressing back over the 6867 * original compressed data (rather than decompressing to an 6868 * aux buffer and then copying back the uncompressed buffer, 6869 * which is likely to be much larger). 6870 */ 6871 uint64_t csize; 6872 void *cdata; 6873 6874 csize = zio->io_size; 6875 cdata = zio_data_buf_alloc(csize); 6876 bcopy(zio->io_data, cdata, csize); 6877 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6878 hdr->b_size) != 0) 6879 zio->io_error = EIO; 6880 zio_data_buf_free(cdata, csize); 6881 } 6882 6883 /* Restore the expected uncompressed IO size. */ 6884 zio->io_orig_size = zio->io_size = hdr->b_size; 6885} 6886 6887/* 6888 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6889 * This buffer serves as a temporary holder of compressed or padded data while 6890 * the buffer entry is being written to an l2arc device. Once that is 6891 * done, we can dispose of it. 6892 */ 6893static void 6894l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6895{ 6896 size_t align, asize, len; 6897 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6898 6899 ASSERT(HDR_HAS_L2HDR(hdr)); 6900 ASSERT(HDR_HAS_L1HDR(hdr)); 6901 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6902 6903 if (hdr->b_l1hdr.b_tmp_cdata != NULL) { 6904 ASSERT(comp != ZIO_COMPRESS_EMPTY); 6905 len = hdr->b_size; 6906 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 6907 asize = P2ROUNDUP(len, align); 6908 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, asize); 6909 hdr->b_l1hdr.b_tmp_cdata = NULL; 6910 } else { 6911 ASSERT(comp == ZIO_COMPRESS_OFF || comp == ZIO_COMPRESS_EMPTY); 6912 } 6913} 6914 6915/* 6916 * This thread feeds the L2ARC at regular intervals. This is the beating 6917 * heart of the L2ARC. 6918 */ 6919static void 6920l2arc_feed_thread(void *dummy __unused) 6921{ 6922 callb_cpr_t cpr; 6923 l2arc_dev_t *dev; 6924 spa_t *spa; 6925 uint64_t size, wrote; 6926 clock_t begin, next = ddi_get_lbolt(); 6927 boolean_t headroom_boost = B_FALSE; 6928 6929 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6930 6931 mutex_enter(&l2arc_feed_thr_lock); 6932 6933 while (l2arc_thread_exit == 0) { 6934 CALLB_CPR_SAFE_BEGIN(&cpr); 6935 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6936 next - ddi_get_lbolt()); 6937 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6938 next = ddi_get_lbolt() + hz; 6939 6940 /* 6941 * Quick check for L2ARC devices. 6942 */ 6943 mutex_enter(&l2arc_dev_mtx); 6944 if (l2arc_ndev == 0) { 6945 mutex_exit(&l2arc_dev_mtx); 6946 continue; 6947 } 6948 mutex_exit(&l2arc_dev_mtx); 6949 begin = ddi_get_lbolt(); 6950 6951 /* 6952 * This selects the next l2arc device to write to, and in 6953 * doing so the next spa to feed from: dev->l2ad_spa. This 6954 * will return NULL if there are now no l2arc devices or if 6955 * they are all faulted. 6956 * 6957 * If a device is returned, its spa's config lock is also 6958 * held to prevent device removal. l2arc_dev_get_next() 6959 * will grab and release l2arc_dev_mtx. 6960 */ 6961 if ((dev = l2arc_dev_get_next()) == NULL) 6962 continue; 6963 6964 spa = dev->l2ad_spa; 6965 ASSERT(spa != NULL); 6966 6967 /* 6968 * If the pool is read-only then force the feed thread to 6969 * sleep a little longer. 6970 */ 6971 if (!spa_writeable(spa)) { 6972 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6973 spa_config_exit(spa, SCL_L2ARC, dev); 6974 continue; 6975 } 6976 6977 /* 6978 * Avoid contributing to memory pressure. 6979 */ 6980 if (arc_reclaim_needed()) { 6981 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6982 spa_config_exit(spa, SCL_L2ARC, dev); 6983 continue; 6984 } 6985 6986 ARCSTAT_BUMP(arcstat_l2_feeds); 6987 6988 size = l2arc_write_size(); 6989 6990 /* 6991 * Evict L2ARC buffers that will be overwritten. 6992 */ 6993 l2arc_evict(dev, size, B_FALSE); 6994 6995 /* 6996 * Write ARC buffers. 6997 */ 6998 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6999 7000 /* 7001 * Calculate interval between writes. 7002 */ 7003 next = l2arc_write_interval(begin, size, wrote); 7004 spa_config_exit(spa, SCL_L2ARC, dev); 7005 } 7006 7007 l2arc_thread_exit = 0; 7008 cv_broadcast(&l2arc_feed_thr_cv); 7009 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7010 thread_exit(); 7011} 7012 7013boolean_t 7014l2arc_vdev_present(vdev_t *vd) 7015{ 7016 l2arc_dev_t *dev; 7017 7018 mutex_enter(&l2arc_dev_mtx); 7019 for (dev = list_head(l2arc_dev_list); dev != NULL; 7020 dev = list_next(l2arc_dev_list, dev)) { 7021 if (dev->l2ad_vdev == vd) 7022 break; 7023 } 7024 mutex_exit(&l2arc_dev_mtx); 7025 7026 return (dev != NULL); 7027} 7028 7029/* 7030 * Add a vdev for use by the L2ARC. By this point the spa has already 7031 * validated the vdev and opened it. 7032 */ 7033void 7034l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7035{ 7036 l2arc_dev_t *adddev; 7037 7038 ASSERT(!l2arc_vdev_present(vd)); 7039 7040 vdev_ashift_optimize(vd); 7041 7042 /* 7043 * Create a new l2arc device entry. 7044 */ 7045 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7046 adddev->l2ad_spa = spa; 7047 adddev->l2ad_vdev = vd; 7048 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7049 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7050 adddev->l2ad_hand = adddev->l2ad_start; 7051 adddev->l2ad_first = B_TRUE; 7052 adddev->l2ad_writing = B_FALSE; 7053 7054 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7055 /* 7056 * This is a list of all ARC buffers that are still valid on the 7057 * device. 7058 */ 7059 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7060 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7061 7062 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7063 refcount_create(&adddev->l2ad_alloc); 7064 7065 /* 7066 * Add device to global list 7067 */ 7068 mutex_enter(&l2arc_dev_mtx); 7069 list_insert_head(l2arc_dev_list, adddev); 7070 atomic_inc_64(&l2arc_ndev); 7071 mutex_exit(&l2arc_dev_mtx); 7072} 7073 7074/* 7075 * Remove a vdev from the L2ARC. 7076 */ 7077void 7078l2arc_remove_vdev(vdev_t *vd) 7079{ 7080 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7081 7082 /* 7083 * Find the device by vdev 7084 */ 7085 mutex_enter(&l2arc_dev_mtx); 7086 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7087 nextdev = list_next(l2arc_dev_list, dev); 7088 if (vd == dev->l2ad_vdev) { 7089 remdev = dev; 7090 break; 7091 } 7092 } 7093 ASSERT(remdev != NULL); 7094 7095 /* 7096 * Remove device from global list 7097 */ 7098 list_remove(l2arc_dev_list, remdev); 7099 l2arc_dev_last = NULL; /* may have been invalidated */ 7100 atomic_dec_64(&l2arc_ndev); 7101 mutex_exit(&l2arc_dev_mtx); 7102 7103 /* 7104 * Clear all buflists and ARC references. L2ARC device flush. 7105 */ 7106 l2arc_evict(remdev, 0, B_TRUE); 7107 list_destroy(&remdev->l2ad_buflist); 7108 mutex_destroy(&remdev->l2ad_mtx); 7109 refcount_destroy(&remdev->l2ad_alloc); 7110 kmem_free(remdev, sizeof (l2arc_dev_t)); 7111} 7112 7113void 7114l2arc_init(void) 7115{ 7116 l2arc_thread_exit = 0; 7117 l2arc_ndev = 0; 7118 l2arc_writes_sent = 0; 7119 l2arc_writes_done = 0; 7120 7121 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7122 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7123 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7124 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7125 7126 l2arc_dev_list = &L2ARC_dev_list; 7127 l2arc_free_on_write = &L2ARC_free_on_write; 7128 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7129 offsetof(l2arc_dev_t, l2ad_node)); 7130 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7131 offsetof(l2arc_data_free_t, l2df_list_node)); 7132} 7133 7134void 7135l2arc_fini(void) 7136{ 7137 /* 7138 * This is called from dmu_fini(), which is called from spa_fini(); 7139 * Because of this, we can assume that all l2arc devices have 7140 * already been removed when the pools themselves were removed. 7141 */ 7142 7143 l2arc_do_free_on_write(); 7144 7145 mutex_destroy(&l2arc_feed_thr_lock); 7146 cv_destroy(&l2arc_feed_thr_cv); 7147 mutex_destroy(&l2arc_dev_mtx); 7148 mutex_destroy(&l2arc_free_on_write_mtx); 7149 7150 list_destroy(l2arc_dev_list); 7151 list_destroy(l2arc_free_on_write); 7152} 7153 7154void 7155l2arc_start(void) 7156{ 7157 if (!(spa_mode_global & FWRITE)) 7158 return; 7159 7160 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7161 TS_RUN, minclsyspri); 7162} 7163 7164void 7165l2arc_stop(void) 7166{ 7167 if (!(spa_mode_global & FWRITE)) 7168 return; 7169 7170 mutex_enter(&l2arc_feed_thr_lock); 7171 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7172 l2arc_thread_exit = 1; 7173 while (l2arc_thread_exit != 0) 7174 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7175 mutex_exit(&l2arc_feed_thr_lock); 7176} 7177