arc.c revision 302729
1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29/* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74/* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123#include <sys/spa.h> 124#include <sys/zio.h> 125#include <sys/zio_compress.h> 126#include <sys/zfs_context.h> 127#include <sys/arc.h> 128#include <sys/refcount.h> 129#include <sys/vdev.h> 130#include <sys/vdev_impl.h> 131#include <sys/dsl_pool.h> 132#include <sys/multilist.h> 133#ifdef _KERNEL 134#include <sys/dnlc.h> 135#endif 136#include <sys/callb.h> 137#include <sys/kstat.h> 138#include <sys/trim_map.h> 139#include <zfs_fletcher.h> 140#include <sys/sdt.h> 141 142#include <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_physdone; 786 arc_done_func_t *awcb_done; 787 arc_buf_t *awcb_buf; 788}; 789 790/* 791 * ARC buffers are separated into multiple structs as a memory saving measure: 792 * - Common fields struct, always defined, and embedded within it: 793 * - L2-only fields, always allocated but undefined when not in L2ARC 794 * - L1-only fields, only allocated when in L1ARC 795 * 796 * Buffer in L1 Buffer only in L2 797 * +------------------------+ +------------------------+ 798 * | arc_buf_hdr_t | | arc_buf_hdr_t | 799 * | | | | 800 * | | | | 801 * | | | | 802 * +------------------------+ +------------------------+ 803 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 804 * | (undefined if L1-only) | | | 805 * +------------------------+ +------------------------+ 806 * | l1arc_buf_hdr_t | 807 * | | 808 * | | 809 * | | 810 * | | 811 * +------------------------+ 812 * 813 * Because it's possible for the L2ARC to become extremely large, we can wind 814 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 815 * is minimized by only allocating the fields necessary for an L1-cached buffer 816 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 817 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 818 * words in pointers. arc_hdr_realloc() is used to switch a header between 819 * these two allocation states. 820 */ 821typedef struct l1arc_buf_hdr { 822 kmutex_t b_freeze_lock; 823#ifdef ZFS_DEBUG 824 /* 825 * used for debugging wtih kmem_flags - by allocating and freeing 826 * b_thawed when the buffer is thawed, we get a record of the stack 827 * trace that thawed it. 828 */ 829 void *b_thawed; 830#endif 831 832 arc_buf_t *b_buf; 833 uint32_t b_datacnt; 834 /* for waiting on writes to complete */ 835 kcondvar_t b_cv; 836 837 /* protected by arc state mutex */ 838 arc_state_t *b_state; 839 multilist_node_t b_arc_node; 840 841 /* updated atomically */ 842 clock_t b_arc_access; 843 844 /* self protecting */ 845 refcount_t b_refcnt; 846 847 arc_callback_t *b_acb; 848 /* temporary buffer holder for in-flight compressed or padded data */ 849 void *b_tmp_cdata; 850} l1arc_buf_hdr_t; 851 852typedef struct l2arc_dev l2arc_dev_t; 853 854typedef struct l2arc_buf_hdr { 855 /* protected by arc_buf_hdr mutex */ 856 l2arc_dev_t *b_dev; /* L2ARC device */ 857 uint64_t b_daddr; /* disk address, offset byte */ 858 /* real alloc'd buffer size depending on b_compress applied */ 859 int32_t b_asize; 860 uint8_t b_compress; 861 862 list_node_t b_l2node; 863} l2arc_buf_hdr_t; 864 865struct arc_buf_hdr { 866 /* protected by hash lock */ 867 dva_t b_dva; 868 uint64_t b_birth; 869 /* 870 * Even though this checksum is only set/verified when a buffer is in 871 * the L1 cache, it needs to be in the set of common fields because it 872 * must be preserved from the time before a buffer is written out to 873 * L2ARC until after it is read back in. 874 */ 875 zio_cksum_t *b_freeze_cksum; 876 877 arc_buf_hdr_t *b_hash_next; 878 arc_flags_t b_flags; 879 880 /* immutable */ 881 int32_t b_size; 882 uint64_t b_spa; 883 884 /* L2ARC fields. Undefined when not in L2ARC. */ 885 l2arc_buf_hdr_t b_l2hdr; 886 /* L1ARC fields. Undefined when in l2arc_only state */ 887 l1arc_buf_hdr_t b_l1hdr; 888}; 889 890#if defined(__FreeBSD__) && defined(_KERNEL) 891static int 892sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 893{ 894 uint64_t val; 895 int err; 896 897 val = arc_meta_limit; 898 err = sysctl_handle_64(oidp, &val, 0, req); 899 if (err != 0 || req->newptr == NULL) 900 return (err); 901 902 if (val <= 0 || val > arc_c_max) 903 return (EINVAL); 904 905 arc_meta_limit = val; 906 return (0); 907} 908 909static int 910sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 911{ 912 uint64_t val; 913 int err; 914 915 val = zfs_arc_max; 916 err = sysctl_handle_64(oidp, &val, 0, req); 917 if (err != 0 || req->newptr == NULL) 918 return (err); 919 920 if (zfs_arc_max == 0) { 921 /* Loader tunable so blindly set */ 922 zfs_arc_max = val; 923 return (0); 924 } 925 926 if (val < arc_abs_min || val > kmem_size()) 927 return (EINVAL); 928 if (val < arc_c_min) 929 return (EINVAL); 930 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 931 return (EINVAL); 932 933 arc_c_max = val; 934 935 arc_c = arc_c_max; 936 arc_p = (arc_c >> 1); 937 938 if (zfs_arc_meta_limit == 0) { 939 /* limit meta-data to 1/4 of the arc capacity */ 940 arc_meta_limit = arc_c_max / 4; 941 } 942 943 /* if kmem_flags are set, lets try to use less memory */ 944 if (kmem_debugging()) 945 arc_c = arc_c / 2; 946 947 zfs_arc_max = arc_c; 948 949 return (0); 950} 951 952static int 953sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 954{ 955 uint64_t val; 956 int err; 957 958 val = zfs_arc_min; 959 err = sysctl_handle_64(oidp, &val, 0, req); 960 if (err != 0 || req->newptr == NULL) 961 return (err); 962 963 if (zfs_arc_min == 0) { 964 /* Loader tunable so blindly set */ 965 zfs_arc_min = val; 966 return (0); 967 } 968 969 if (val < arc_abs_min || val > arc_c_max) 970 return (EINVAL); 971 972 arc_c_min = val; 973 974 if (zfs_arc_meta_min == 0) 975 arc_meta_min = arc_c_min / 2; 976 977 if (arc_c < arc_c_min) 978 arc_c = arc_c_min; 979 980 zfs_arc_min = arc_c_min; 981 982 return (0); 983} 984#endif 985 986static arc_buf_t *arc_eviction_list; 987static arc_buf_hdr_t arc_eviction_hdr; 988 989#define GHOST_STATE(state) \ 990 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 991 (state) == arc_l2c_only) 992 993#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 994#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 995#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 996#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 997#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 998#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 999 1000#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1001#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 1002#define HDR_L2_READING(hdr) \ 1003 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1004 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1005#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1006#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1007#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1008 1009#define HDR_ISTYPE_METADATA(hdr) \ 1010 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1011#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1012 1013#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1014#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1015 1016/* 1017 * Other sizes 1018 */ 1019 1020#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1021#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1022 1023/* 1024 * Hash table routines 1025 */ 1026 1027#define HT_LOCK_PAD CACHE_LINE_SIZE 1028 1029struct ht_lock { 1030 kmutex_t ht_lock; 1031#ifdef _KERNEL 1032 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1033#endif 1034}; 1035 1036#define BUF_LOCKS 256 1037typedef struct buf_hash_table { 1038 uint64_t ht_mask; 1039 arc_buf_hdr_t **ht_table; 1040 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1041} buf_hash_table_t; 1042 1043static buf_hash_table_t buf_hash_table; 1044 1045#define BUF_HASH_INDEX(spa, dva, birth) \ 1046 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1047#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1048#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1049#define HDR_LOCK(hdr) \ 1050 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1051 1052uint64_t zfs_crc64_table[256]; 1053 1054/* 1055 * Level 2 ARC 1056 */ 1057 1058#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1059#define L2ARC_HEADROOM 2 /* num of writes */ 1060/* 1061 * If we discover during ARC scan any buffers to be compressed, we boost 1062 * our headroom for the next scanning cycle by this percentage multiple. 1063 */ 1064#define L2ARC_HEADROOM_BOOST 200 1065#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1066#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1067 1068/* 1069 * Used to distinguish headers that are being process by 1070 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 1071 * address. This can happen when the header is added to the l2arc's list 1072 * of buffers to write in the first stage of l2arc_write_buffers(), but 1073 * has not yet been written out which happens in the second stage of 1074 * l2arc_write_buffers(). 1075 */ 1076#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 1077 1078#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1079#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1080 1081/* L2ARC Performance Tunables */ 1082uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1083uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1084uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1085uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1086uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1087uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1088boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1089boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1090boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1091 1092SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1093 &l2arc_write_max, 0, "max write size"); 1094SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1095 &l2arc_write_boost, 0, "extra write during warmup"); 1096SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1097 &l2arc_headroom, 0, "number of dev writes"); 1098SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1099 &l2arc_feed_secs, 0, "interval seconds"); 1100SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1101 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1102 1103SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1104 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1105SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1106 &l2arc_feed_again, 0, "turbo warmup"); 1107SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1108 &l2arc_norw, 0, "no reads during writes"); 1109 1110SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1111 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1112SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1113 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1114SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1115 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1116 1117SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1118 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1119SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1120 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1121SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1122 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1123 1124SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1125 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1126SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1127 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1128 "size of metadata in mru ghost state"); 1129SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1130 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1131 "size of data in mru ghost state"); 1132 1133SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1134 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1135SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1136 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1137SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1138 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1139 1140SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1141 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1142SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1143 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1144 "size of metadata in mfu ghost state"); 1145SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1146 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1147 "size of data in mfu ghost state"); 1148 1149SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1150 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1151 1152/* 1153 * L2ARC Internals 1154 */ 1155struct l2arc_dev { 1156 vdev_t *l2ad_vdev; /* vdev */ 1157 spa_t *l2ad_spa; /* spa */ 1158 uint64_t l2ad_hand; /* next write location */ 1159 uint64_t l2ad_start; /* first addr on device */ 1160 uint64_t l2ad_end; /* last addr on device */ 1161 boolean_t l2ad_first; /* first sweep through */ 1162 boolean_t l2ad_writing; /* currently writing */ 1163 kmutex_t l2ad_mtx; /* lock for buffer list */ 1164 list_t l2ad_buflist; /* buffer list */ 1165 list_node_t l2ad_node; /* device list node */ 1166 refcount_t l2ad_alloc; /* allocated bytes */ 1167}; 1168 1169static list_t L2ARC_dev_list; /* device list */ 1170static list_t *l2arc_dev_list; /* device list pointer */ 1171static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1172static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1173static list_t L2ARC_free_on_write; /* free after write buf list */ 1174static list_t *l2arc_free_on_write; /* free after write list ptr */ 1175static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1176static uint64_t l2arc_ndev; /* number of devices */ 1177 1178typedef struct l2arc_read_callback { 1179 arc_buf_t *l2rcb_buf; /* read buffer */ 1180 spa_t *l2rcb_spa; /* spa */ 1181 blkptr_t l2rcb_bp; /* original blkptr */ 1182 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1183 int l2rcb_flags; /* original flags */ 1184 enum zio_compress l2rcb_compress; /* applied compress */ 1185 void *l2rcb_data; /* temporary buffer */ 1186} l2arc_read_callback_t; 1187 1188typedef struct l2arc_write_callback { 1189 l2arc_dev_t *l2wcb_dev; /* device info */ 1190 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1191} l2arc_write_callback_t; 1192 1193typedef struct l2arc_data_free { 1194 /* protected by l2arc_free_on_write_mtx */ 1195 void *l2df_data; 1196 size_t l2df_size; 1197 void (*l2df_func)(void *, size_t); 1198 list_node_t l2df_list_node; 1199} l2arc_data_free_t; 1200 1201static kmutex_t l2arc_feed_thr_lock; 1202static kcondvar_t l2arc_feed_thr_cv; 1203static uint8_t l2arc_thread_exit; 1204 1205static void arc_get_data_buf(arc_buf_t *); 1206static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1207static boolean_t arc_is_overflowing(); 1208static void arc_buf_watch(arc_buf_t *); 1209 1210static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1211static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1212 1213static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1214static void l2arc_read_done(zio_t *); 1215 1216static boolean_t l2arc_transform_buf(arc_buf_hdr_t *, boolean_t); 1217static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1218static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1219 1220static void 1221l2arc_trim(const arc_buf_hdr_t *hdr) 1222{ 1223 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1224 1225 ASSERT(HDR_HAS_L2HDR(hdr)); 1226 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1227 1228 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) 1229 return; 1230 if (hdr->b_l2hdr.b_asize != 0) { 1231 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1232 hdr->b_l2hdr.b_asize, 0); 1233 } else { 1234 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_EMPTY); 1235 } 1236} 1237 1238static uint64_t 1239buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1240{ 1241 uint8_t *vdva = (uint8_t *)dva; 1242 uint64_t crc = -1ULL; 1243 int i; 1244 1245 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1246 1247 for (i = 0; i < sizeof (dva_t); i++) 1248 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1249 1250 crc ^= (spa>>8) ^ birth; 1251 1252 return (crc); 1253} 1254 1255#define BUF_EMPTY(buf) \ 1256 ((buf)->b_dva.dva_word[0] == 0 && \ 1257 (buf)->b_dva.dva_word[1] == 0) 1258 1259#define BUF_EQUAL(spa, dva, birth, buf) \ 1260 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1261 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1262 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1263 1264static void 1265buf_discard_identity(arc_buf_hdr_t *hdr) 1266{ 1267 hdr->b_dva.dva_word[0] = 0; 1268 hdr->b_dva.dva_word[1] = 0; 1269 hdr->b_birth = 0; 1270} 1271 1272static arc_buf_hdr_t * 1273buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1274{ 1275 const dva_t *dva = BP_IDENTITY(bp); 1276 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1277 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1278 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1279 arc_buf_hdr_t *hdr; 1280 1281 mutex_enter(hash_lock); 1282 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1283 hdr = hdr->b_hash_next) { 1284 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1285 *lockp = hash_lock; 1286 return (hdr); 1287 } 1288 } 1289 mutex_exit(hash_lock); 1290 *lockp = NULL; 1291 return (NULL); 1292} 1293 1294/* 1295 * Insert an entry into the hash table. If there is already an element 1296 * equal to elem in the hash table, then the already existing element 1297 * will be returned and the new element will not be inserted. 1298 * Otherwise returns NULL. 1299 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1300 */ 1301static arc_buf_hdr_t * 1302buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1303{ 1304 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1305 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1306 arc_buf_hdr_t *fhdr; 1307 uint32_t i; 1308 1309 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1310 ASSERT(hdr->b_birth != 0); 1311 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1312 1313 if (lockp != NULL) { 1314 *lockp = hash_lock; 1315 mutex_enter(hash_lock); 1316 } else { 1317 ASSERT(MUTEX_HELD(hash_lock)); 1318 } 1319 1320 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1321 fhdr = fhdr->b_hash_next, i++) { 1322 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1323 return (fhdr); 1324 } 1325 1326 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1327 buf_hash_table.ht_table[idx] = hdr; 1328 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1329 1330 /* collect some hash table performance data */ 1331 if (i > 0) { 1332 ARCSTAT_BUMP(arcstat_hash_collisions); 1333 if (i == 1) 1334 ARCSTAT_BUMP(arcstat_hash_chains); 1335 1336 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1337 } 1338 1339 ARCSTAT_BUMP(arcstat_hash_elements); 1340 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1341 1342 return (NULL); 1343} 1344 1345static void 1346buf_hash_remove(arc_buf_hdr_t *hdr) 1347{ 1348 arc_buf_hdr_t *fhdr, **hdrp; 1349 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1350 1351 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1352 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1353 1354 hdrp = &buf_hash_table.ht_table[idx]; 1355 while ((fhdr = *hdrp) != hdr) { 1356 ASSERT(fhdr != NULL); 1357 hdrp = &fhdr->b_hash_next; 1358 } 1359 *hdrp = hdr->b_hash_next; 1360 hdr->b_hash_next = NULL; 1361 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1362 1363 /* collect some hash table performance data */ 1364 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1365 1366 if (buf_hash_table.ht_table[idx] && 1367 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1368 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1369} 1370 1371/* 1372 * Global data structures and functions for the buf kmem cache. 1373 */ 1374static kmem_cache_t *hdr_full_cache; 1375static kmem_cache_t *hdr_l2only_cache; 1376static kmem_cache_t *buf_cache; 1377 1378static void 1379buf_fini(void) 1380{ 1381 int i; 1382 1383 kmem_free(buf_hash_table.ht_table, 1384 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1385 for (i = 0; i < BUF_LOCKS; i++) 1386 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1387 kmem_cache_destroy(hdr_full_cache); 1388 kmem_cache_destroy(hdr_l2only_cache); 1389 kmem_cache_destroy(buf_cache); 1390} 1391 1392/* 1393 * Constructor callback - called when the cache is empty 1394 * and a new buf is requested. 1395 */ 1396/* ARGSUSED */ 1397static int 1398hdr_full_cons(void *vbuf, void *unused, int kmflag) 1399{ 1400 arc_buf_hdr_t *hdr = vbuf; 1401 1402 bzero(hdr, HDR_FULL_SIZE); 1403 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1404 refcount_create(&hdr->b_l1hdr.b_refcnt); 1405 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1406 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1407 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1408 1409 return (0); 1410} 1411 1412/* ARGSUSED */ 1413static int 1414hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1415{ 1416 arc_buf_hdr_t *hdr = vbuf; 1417 1418 bzero(hdr, HDR_L2ONLY_SIZE); 1419 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1420 1421 return (0); 1422} 1423 1424/* ARGSUSED */ 1425static int 1426buf_cons(void *vbuf, void *unused, int kmflag) 1427{ 1428 arc_buf_t *buf = vbuf; 1429 1430 bzero(buf, sizeof (arc_buf_t)); 1431 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1432 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1433 1434 return (0); 1435} 1436 1437/* 1438 * Destructor callback - called when a cached buf is 1439 * no longer required. 1440 */ 1441/* ARGSUSED */ 1442static void 1443hdr_full_dest(void *vbuf, void *unused) 1444{ 1445 arc_buf_hdr_t *hdr = vbuf; 1446 1447 ASSERT(BUF_EMPTY(hdr)); 1448 cv_destroy(&hdr->b_l1hdr.b_cv); 1449 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1450 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1451 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1452 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1453} 1454 1455/* ARGSUSED */ 1456static void 1457hdr_l2only_dest(void *vbuf, void *unused) 1458{ 1459 arc_buf_hdr_t *hdr = vbuf; 1460 1461 ASSERT(BUF_EMPTY(hdr)); 1462 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1463} 1464 1465/* ARGSUSED */ 1466static void 1467buf_dest(void *vbuf, void *unused) 1468{ 1469 arc_buf_t *buf = vbuf; 1470 1471 mutex_destroy(&buf->b_evict_lock); 1472 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1473} 1474 1475/* 1476 * Reclaim callback -- invoked when memory is low. 1477 */ 1478/* ARGSUSED */ 1479static void 1480hdr_recl(void *unused) 1481{ 1482 dprintf("hdr_recl called\n"); 1483 /* 1484 * umem calls the reclaim func when we destroy the buf cache, 1485 * which is after we do arc_fini(). 1486 */ 1487 if (!arc_dead) 1488 cv_signal(&arc_reclaim_thread_cv); 1489} 1490 1491static void 1492buf_init(void) 1493{ 1494 uint64_t *ct; 1495 uint64_t hsize = 1ULL << 12; 1496 int i, j; 1497 1498 /* 1499 * The hash table is big enough to fill all of physical memory 1500 * with an average block size of zfs_arc_average_blocksize (default 8K). 1501 * By default, the table will take up 1502 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1503 */ 1504 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1505 hsize <<= 1; 1506retry: 1507 buf_hash_table.ht_mask = hsize - 1; 1508 buf_hash_table.ht_table = 1509 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1510 if (buf_hash_table.ht_table == NULL) { 1511 ASSERT(hsize > (1ULL << 8)); 1512 hsize >>= 1; 1513 goto retry; 1514 } 1515 1516 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1517 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1518 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1519 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1520 NULL, NULL, 0); 1521 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1522 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1523 1524 for (i = 0; i < 256; i++) 1525 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1526 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1527 1528 for (i = 0; i < BUF_LOCKS; i++) { 1529 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1530 NULL, MUTEX_DEFAULT, NULL); 1531 } 1532} 1533 1534/* 1535 * Transition between the two allocation states for the arc_buf_hdr struct. 1536 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1537 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1538 * version is used when a cache buffer is only in the L2ARC in order to reduce 1539 * memory usage. 1540 */ 1541static arc_buf_hdr_t * 1542arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1543{ 1544 ASSERT(HDR_HAS_L2HDR(hdr)); 1545 1546 arc_buf_hdr_t *nhdr; 1547 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1548 1549 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1550 (old == hdr_l2only_cache && new == hdr_full_cache)); 1551 1552 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1553 1554 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1555 buf_hash_remove(hdr); 1556 1557 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1558 1559 if (new == hdr_full_cache) { 1560 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1561 /* 1562 * arc_access and arc_change_state need to be aware that a 1563 * header has just come out of L2ARC, so we set its state to 1564 * l2c_only even though it's about to change. 1565 */ 1566 nhdr->b_l1hdr.b_state = arc_l2c_only; 1567 1568 /* Verify previous threads set to NULL before freeing */ 1569 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1570 } else { 1571 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1572 ASSERT0(hdr->b_l1hdr.b_datacnt); 1573 1574 /* 1575 * If we've reached here, We must have been called from 1576 * arc_evict_hdr(), as such we should have already been 1577 * removed from any ghost list we were previously on 1578 * (which protects us from racing with arc_evict_state), 1579 * thus no locking is needed during this check. 1580 */ 1581 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1582 1583 /* 1584 * A buffer must not be moved into the arc_l2c_only 1585 * state if it's not finished being written out to the 1586 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field 1587 * might try to be accessed, even though it was removed. 1588 */ 1589 VERIFY(!HDR_L2_WRITING(hdr)); 1590 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 1591 1592#ifdef ZFS_DEBUG 1593 if (hdr->b_l1hdr.b_thawed != NULL) { 1594 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1595 hdr->b_l1hdr.b_thawed = NULL; 1596 } 1597#endif 1598 1599 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1600 } 1601 /* 1602 * The header has been reallocated so we need to re-insert it into any 1603 * lists it was on. 1604 */ 1605 (void) buf_hash_insert(nhdr, NULL); 1606 1607 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1608 1609 mutex_enter(&dev->l2ad_mtx); 1610 1611 /* 1612 * We must place the realloc'ed header back into the list at 1613 * the same spot. Otherwise, if it's placed earlier in the list, 1614 * l2arc_write_buffers() could find it during the function's 1615 * write phase, and try to write it out to the l2arc. 1616 */ 1617 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1618 list_remove(&dev->l2ad_buflist, hdr); 1619 1620 mutex_exit(&dev->l2ad_mtx); 1621 1622 /* 1623 * Since we're using the pointer address as the tag when 1624 * incrementing and decrementing the l2ad_alloc refcount, we 1625 * must remove the old pointer (that we're about to destroy) and 1626 * add the new pointer to the refcount. Otherwise we'd remove 1627 * the wrong pointer address when calling arc_hdr_destroy() later. 1628 */ 1629 1630 (void) refcount_remove_many(&dev->l2ad_alloc, 1631 hdr->b_l2hdr.b_asize, hdr); 1632 1633 (void) refcount_add_many(&dev->l2ad_alloc, 1634 nhdr->b_l2hdr.b_asize, nhdr); 1635 1636 buf_discard_identity(hdr); 1637 hdr->b_freeze_cksum = NULL; 1638 kmem_cache_free(old, hdr); 1639 1640 return (nhdr); 1641} 1642 1643 1644#define ARC_MINTIME (hz>>4) /* 62 ms */ 1645 1646static void 1647arc_cksum_verify(arc_buf_t *buf) 1648{ 1649 zio_cksum_t zc; 1650 1651 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1652 return; 1653 1654 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1655 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1656 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1657 return; 1658 } 1659 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1660 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1661 panic("buffer modified while frozen!"); 1662 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1663} 1664 1665static int 1666arc_cksum_equal(arc_buf_t *buf) 1667{ 1668 zio_cksum_t zc; 1669 int equal; 1670 1671 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1672 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, NULL, &zc); 1673 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1674 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1675 1676 return (equal); 1677} 1678 1679static void 1680arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1681{ 1682 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1683 return; 1684 1685 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1686 if (buf->b_hdr->b_freeze_cksum != NULL) { 1687 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1688 return; 1689 } 1690 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1691 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1692 NULL, buf->b_hdr->b_freeze_cksum); 1693 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1694#ifdef illumos 1695 arc_buf_watch(buf); 1696#endif 1697} 1698 1699#ifdef illumos 1700#ifndef _KERNEL 1701typedef struct procctl { 1702 long cmd; 1703 prwatch_t prwatch; 1704} procctl_t; 1705#endif 1706 1707/* ARGSUSED */ 1708static void 1709arc_buf_unwatch(arc_buf_t *buf) 1710{ 1711#ifndef _KERNEL 1712 if (arc_watch) { 1713 int result; 1714 procctl_t ctl; 1715 ctl.cmd = PCWATCH; 1716 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1717 ctl.prwatch.pr_size = 0; 1718 ctl.prwatch.pr_wflags = 0; 1719 result = write(arc_procfd, &ctl, sizeof (ctl)); 1720 ASSERT3U(result, ==, sizeof (ctl)); 1721 } 1722#endif 1723} 1724 1725/* ARGSUSED */ 1726static void 1727arc_buf_watch(arc_buf_t *buf) 1728{ 1729#ifndef _KERNEL 1730 if (arc_watch) { 1731 int result; 1732 procctl_t ctl; 1733 ctl.cmd = PCWATCH; 1734 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1735 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1736 ctl.prwatch.pr_wflags = WA_WRITE; 1737 result = write(arc_procfd, &ctl, sizeof (ctl)); 1738 ASSERT3U(result, ==, sizeof (ctl)); 1739 } 1740#endif 1741} 1742#endif /* illumos */ 1743 1744static arc_buf_contents_t 1745arc_buf_type(arc_buf_hdr_t *hdr) 1746{ 1747 if (HDR_ISTYPE_METADATA(hdr)) { 1748 return (ARC_BUFC_METADATA); 1749 } else { 1750 return (ARC_BUFC_DATA); 1751 } 1752} 1753 1754static uint32_t 1755arc_bufc_to_flags(arc_buf_contents_t type) 1756{ 1757 switch (type) { 1758 case ARC_BUFC_DATA: 1759 /* metadata field is 0 if buffer contains normal data */ 1760 return (0); 1761 case ARC_BUFC_METADATA: 1762 return (ARC_FLAG_BUFC_METADATA); 1763 default: 1764 break; 1765 } 1766 panic("undefined ARC buffer type!"); 1767 return ((uint32_t)-1); 1768} 1769 1770void 1771arc_buf_thaw(arc_buf_t *buf) 1772{ 1773 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1774 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1775 panic("modifying non-anon buffer!"); 1776 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1777 panic("modifying buffer while i/o in progress!"); 1778 arc_cksum_verify(buf); 1779 } 1780 1781 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1782 if (buf->b_hdr->b_freeze_cksum != NULL) { 1783 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1784 buf->b_hdr->b_freeze_cksum = NULL; 1785 } 1786 1787#ifdef ZFS_DEBUG 1788 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1789 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1790 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1791 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1792 } 1793#endif 1794 1795 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1796 1797#ifdef illumos 1798 arc_buf_unwatch(buf); 1799#endif 1800} 1801 1802void 1803arc_buf_freeze(arc_buf_t *buf) 1804{ 1805 kmutex_t *hash_lock; 1806 1807 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1808 return; 1809 1810 hash_lock = HDR_LOCK(buf->b_hdr); 1811 mutex_enter(hash_lock); 1812 1813 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1814 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1815 arc_cksum_compute(buf, B_FALSE); 1816 mutex_exit(hash_lock); 1817 1818} 1819 1820static void 1821add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1822{ 1823 ASSERT(HDR_HAS_L1HDR(hdr)); 1824 ASSERT(MUTEX_HELD(hash_lock)); 1825 arc_state_t *state = hdr->b_l1hdr.b_state; 1826 1827 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1828 (state != arc_anon)) { 1829 /* We don't use the L2-only state list. */ 1830 if (state != arc_l2c_only) { 1831 arc_buf_contents_t type = arc_buf_type(hdr); 1832 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1833 multilist_t *list = &state->arcs_list[type]; 1834 uint64_t *size = &state->arcs_lsize[type]; 1835 1836 multilist_remove(list, hdr); 1837 1838 if (GHOST_STATE(state)) { 1839 ASSERT0(hdr->b_l1hdr.b_datacnt); 1840 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1841 delta = hdr->b_size; 1842 } 1843 ASSERT(delta > 0); 1844 ASSERT3U(*size, >=, delta); 1845 atomic_add_64(size, -delta); 1846 } 1847 /* remove the prefetch flag if we get a reference */ 1848 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1849 } 1850} 1851 1852static int 1853remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1854{ 1855 int cnt; 1856 arc_state_t *state = hdr->b_l1hdr.b_state; 1857 1858 ASSERT(HDR_HAS_L1HDR(hdr)); 1859 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1860 ASSERT(!GHOST_STATE(state)); 1861 1862 /* 1863 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1864 * check to prevent usage of the arc_l2c_only list. 1865 */ 1866 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1867 (state != arc_anon)) { 1868 arc_buf_contents_t type = arc_buf_type(hdr); 1869 multilist_t *list = &state->arcs_list[type]; 1870 uint64_t *size = &state->arcs_lsize[type]; 1871 1872 multilist_insert(list, hdr); 1873 1874 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1875 atomic_add_64(size, hdr->b_size * 1876 hdr->b_l1hdr.b_datacnt); 1877 } 1878 return (cnt); 1879} 1880 1881/* 1882 * Move the supplied buffer to the indicated state. The hash lock 1883 * for the buffer must be held by the caller. 1884 */ 1885static void 1886arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1887 kmutex_t *hash_lock) 1888{ 1889 arc_state_t *old_state; 1890 int64_t refcnt; 1891 uint32_t datacnt; 1892 uint64_t from_delta, to_delta; 1893 arc_buf_contents_t buftype = arc_buf_type(hdr); 1894 1895 /* 1896 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1897 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1898 * L1 hdr doesn't always exist when we change state to arc_anon before 1899 * destroying a header, in which case reallocating to add the L1 hdr is 1900 * pointless. 1901 */ 1902 if (HDR_HAS_L1HDR(hdr)) { 1903 old_state = hdr->b_l1hdr.b_state; 1904 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1905 datacnt = hdr->b_l1hdr.b_datacnt; 1906 } else { 1907 old_state = arc_l2c_only; 1908 refcnt = 0; 1909 datacnt = 0; 1910 } 1911 1912 ASSERT(MUTEX_HELD(hash_lock)); 1913 ASSERT3P(new_state, !=, old_state); 1914 ASSERT(refcnt == 0 || datacnt > 0); 1915 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1916 ASSERT(old_state != arc_anon || datacnt <= 1); 1917 1918 from_delta = to_delta = datacnt * hdr->b_size; 1919 1920 /* 1921 * If this buffer is evictable, transfer it from the 1922 * old state list to the new state list. 1923 */ 1924 if (refcnt == 0) { 1925 if (old_state != arc_anon && old_state != arc_l2c_only) { 1926 uint64_t *size = &old_state->arcs_lsize[buftype]; 1927 1928 ASSERT(HDR_HAS_L1HDR(hdr)); 1929 multilist_remove(&old_state->arcs_list[buftype], hdr); 1930 1931 /* 1932 * If prefetching out of the ghost cache, 1933 * we will have a non-zero datacnt. 1934 */ 1935 if (GHOST_STATE(old_state) && datacnt == 0) { 1936 /* ghost elements have a ghost size */ 1937 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1938 from_delta = hdr->b_size; 1939 } 1940 ASSERT3U(*size, >=, from_delta); 1941 atomic_add_64(size, -from_delta); 1942 } 1943 if (new_state != arc_anon && new_state != arc_l2c_only) { 1944 uint64_t *size = &new_state->arcs_lsize[buftype]; 1945 1946 /* 1947 * An L1 header always exists here, since if we're 1948 * moving to some L1-cached state (i.e. not l2c_only or 1949 * anonymous), we realloc the header to add an L1hdr 1950 * beforehand. 1951 */ 1952 ASSERT(HDR_HAS_L1HDR(hdr)); 1953 multilist_insert(&new_state->arcs_list[buftype], hdr); 1954 1955 /* ghost elements have a ghost size */ 1956 if (GHOST_STATE(new_state)) { 1957 ASSERT0(datacnt); 1958 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1959 to_delta = hdr->b_size; 1960 } 1961 atomic_add_64(size, to_delta); 1962 } 1963 } 1964 1965 ASSERT(!BUF_EMPTY(hdr)); 1966 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1967 buf_hash_remove(hdr); 1968 1969 /* adjust state sizes (ignore arc_l2c_only) */ 1970 1971 if (to_delta && new_state != arc_l2c_only) { 1972 ASSERT(HDR_HAS_L1HDR(hdr)); 1973 if (GHOST_STATE(new_state)) { 1974 ASSERT0(datacnt); 1975 1976 /* 1977 * We moving a header to a ghost state, we first 1978 * remove all arc buffers. Thus, we'll have a 1979 * datacnt of zero, and no arc buffer to use for 1980 * the reference. As a result, we use the arc 1981 * header pointer for the reference. 1982 */ 1983 (void) refcount_add_many(&new_state->arcs_size, 1984 hdr->b_size, hdr); 1985 } else { 1986 ASSERT3U(datacnt, !=, 0); 1987 1988 /* 1989 * Each individual buffer holds a unique reference, 1990 * thus we must remove each of these references one 1991 * at a time. 1992 */ 1993 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 1994 buf = buf->b_next) { 1995 (void) refcount_add_many(&new_state->arcs_size, 1996 hdr->b_size, buf); 1997 } 1998 } 1999 } 2000 2001 if (from_delta && old_state != arc_l2c_only) { 2002 ASSERT(HDR_HAS_L1HDR(hdr)); 2003 if (GHOST_STATE(old_state)) { 2004 /* 2005 * When moving a header off of a ghost state, 2006 * there's the possibility for datacnt to be 2007 * non-zero. This is because we first add the 2008 * arc buffer to the header prior to changing 2009 * the header's state. Since we used the header 2010 * for the reference when putting the header on 2011 * the ghost state, we must balance that and use 2012 * the header when removing off the ghost state 2013 * (even though datacnt is non zero). 2014 */ 2015 2016 IMPLY(datacnt == 0, new_state == arc_anon || 2017 new_state == arc_l2c_only); 2018 2019 (void) refcount_remove_many(&old_state->arcs_size, 2020 hdr->b_size, hdr); 2021 } else { 2022 ASSERT3P(datacnt, !=, 0); 2023 2024 /* 2025 * Each individual buffer holds a unique reference, 2026 * thus we must remove each of these references one 2027 * at a time. 2028 */ 2029 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2030 buf = buf->b_next) { 2031 (void) refcount_remove_many( 2032 &old_state->arcs_size, hdr->b_size, buf); 2033 } 2034 } 2035 } 2036 2037 if (HDR_HAS_L1HDR(hdr)) 2038 hdr->b_l1hdr.b_state = new_state; 2039 2040 /* 2041 * L2 headers should never be on the L2 state list since they don't 2042 * have L1 headers allocated. 2043 */ 2044 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2045 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2046} 2047 2048void 2049arc_space_consume(uint64_t space, arc_space_type_t type) 2050{ 2051 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2052 2053 switch (type) { 2054 case ARC_SPACE_DATA: 2055 ARCSTAT_INCR(arcstat_data_size, space); 2056 break; 2057 case ARC_SPACE_META: 2058 ARCSTAT_INCR(arcstat_metadata_size, space); 2059 break; 2060 case ARC_SPACE_OTHER: 2061 ARCSTAT_INCR(arcstat_other_size, space); 2062 break; 2063 case ARC_SPACE_HDRS: 2064 ARCSTAT_INCR(arcstat_hdr_size, space); 2065 break; 2066 case ARC_SPACE_L2HDRS: 2067 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2068 break; 2069 } 2070 2071 if (type != ARC_SPACE_DATA) 2072 ARCSTAT_INCR(arcstat_meta_used, space); 2073 2074 atomic_add_64(&arc_size, space); 2075} 2076 2077void 2078arc_space_return(uint64_t space, arc_space_type_t type) 2079{ 2080 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2081 2082 switch (type) { 2083 case ARC_SPACE_DATA: 2084 ARCSTAT_INCR(arcstat_data_size, -space); 2085 break; 2086 case ARC_SPACE_META: 2087 ARCSTAT_INCR(arcstat_metadata_size, -space); 2088 break; 2089 case ARC_SPACE_OTHER: 2090 ARCSTAT_INCR(arcstat_other_size, -space); 2091 break; 2092 case ARC_SPACE_HDRS: 2093 ARCSTAT_INCR(arcstat_hdr_size, -space); 2094 break; 2095 case ARC_SPACE_L2HDRS: 2096 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2097 break; 2098 } 2099 2100 if (type != ARC_SPACE_DATA) { 2101 ASSERT(arc_meta_used >= space); 2102 if (arc_meta_max < arc_meta_used) 2103 arc_meta_max = arc_meta_used; 2104 ARCSTAT_INCR(arcstat_meta_used, -space); 2105 } 2106 2107 ASSERT(arc_size >= space); 2108 atomic_add_64(&arc_size, -space); 2109} 2110 2111arc_buf_t * 2112arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2113{ 2114 arc_buf_hdr_t *hdr; 2115 arc_buf_t *buf; 2116 2117 ASSERT3U(size, >, 0); 2118 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2119 ASSERT(BUF_EMPTY(hdr)); 2120 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 2121 hdr->b_size = size; 2122 hdr->b_spa = spa_load_guid(spa); 2123 2124 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2125 buf->b_hdr = hdr; 2126 buf->b_data = NULL; 2127 buf->b_efunc = NULL; 2128 buf->b_private = NULL; 2129 buf->b_next = NULL; 2130 2131 hdr->b_flags = arc_bufc_to_flags(type); 2132 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 2133 2134 hdr->b_l1hdr.b_buf = buf; 2135 hdr->b_l1hdr.b_state = arc_anon; 2136 hdr->b_l1hdr.b_arc_access = 0; 2137 hdr->b_l1hdr.b_datacnt = 1; 2138 hdr->b_l1hdr.b_tmp_cdata = NULL; 2139 2140 arc_get_data_buf(buf); 2141 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2142 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2143 2144 return (buf); 2145} 2146 2147static char *arc_onloan_tag = "onloan"; 2148 2149/* 2150 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2151 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2152 * buffers must be returned to the arc before they can be used by the DMU or 2153 * freed. 2154 */ 2155arc_buf_t * 2156arc_loan_buf(spa_t *spa, int size) 2157{ 2158 arc_buf_t *buf; 2159 2160 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2161 2162 atomic_add_64(&arc_loaned_bytes, size); 2163 return (buf); 2164} 2165 2166/* 2167 * Return a loaned arc buffer to the arc. 2168 */ 2169void 2170arc_return_buf(arc_buf_t *buf, void *tag) 2171{ 2172 arc_buf_hdr_t *hdr = buf->b_hdr; 2173 2174 ASSERT(buf->b_data != NULL); 2175 ASSERT(HDR_HAS_L1HDR(hdr)); 2176 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2177 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2178 2179 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2180} 2181 2182/* Detach an arc_buf from a dbuf (tag) */ 2183void 2184arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2185{ 2186 arc_buf_hdr_t *hdr = buf->b_hdr; 2187 2188 ASSERT(buf->b_data != NULL); 2189 ASSERT(HDR_HAS_L1HDR(hdr)); 2190 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2191 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2192 buf->b_efunc = NULL; 2193 buf->b_private = NULL; 2194 2195 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2196} 2197 2198static arc_buf_t * 2199arc_buf_clone(arc_buf_t *from) 2200{ 2201 arc_buf_t *buf; 2202 arc_buf_hdr_t *hdr = from->b_hdr; 2203 uint64_t size = hdr->b_size; 2204 2205 ASSERT(HDR_HAS_L1HDR(hdr)); 2206 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2207 2208 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2209 buf->b_hdr = hdr; 2210 buf->b_data = NULL; 2211 buf->b_efunc = NULL; 2212 buf->b_private = NULL; 2213 buf->b_next = hdr->b_l1hdr.b_buf; 2214 hdr->b_l1hdr.b_buf = buf; 2215 arc_get_data_buf(buf); 2216 bcopy(from->b_data, buf->b_data, size); 2217 2218 /* 2219 * This buffer already exists in the arc so create a duplicate 2220 * copy for the caller. If the buffer is associated with user data 2221 * then track the size and number of duplicates. These stats will be 2222 * updated as duplicate buffers are created and destroyed. 2223 */ 2224 if (HDR_ISTYPE_DATA(hdr)) { 2225 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2226 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2227 } 2228 hdr->b_l1hdr.b_datacnt += 1; 2229 return (buf); 2230} 2231 2232void 2233arc_buf_add_ref(arc_buf_t *buf, void* tag) 2234{ 2235 arc_buf_hdr_t *hdr; 2236 kmutex_t *hash_lock; 2237 2238 /* 2239 * Check to see if this buffer is evicted. Callers 2240 * must verify b_data != NULL to know if the add_ref 2241 * was successful. 2242 */ 2243 mutex_enter(&buf->b_evict_lock); 2244 if (buf->b_data == NULL) { 2245 mutex_exit(&buf->b_evict_lock); 2246 return; 2247 } 2248 hash_lock = HDR_LOCK(buf->b_hdr); 2249 mutex_enter(hash_lock); 2250 hdr = buf->b_hdr; 2251 ASSERT(HDR_HAS_L1HDR(hdr)); 2252 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2253 mutex_exit(&buf->b_evict_lock); 2254 2255 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2256 hdr->b_l1hdr.b_state == arc_mfu); 2257 2258 add_reference(hdr, hash_lock, tag); 2259 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2260 arc_access(hdr, hash_lock); 2261 mutex_exit(hash_lock); 2262 ARCSTAT_BUMP(arcstat_hits); 2263 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2264 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2265 data, metadata, hits); 2266} 2267 2268static void 2269arc_buf_free_on_write(void *data, size_t size, 2270 void (*free_func)(void *, size_t)) 2271{ 2272 l2arc_data_free_t *df; 2273 2274 df = kmem_alloc(sizeof (*df), KM_SLEEP); 2275 df->l2df_data = data; 2276 df->l2df_size = size; 2277 df->l2df_func = free_func; 2278 mutex_enter(&l2arc_free_on_write_mtx); 2279 list_insert_head(l2arc_free_on_write, df); 2280 mutex_exit(&l2arc_free_on_write_mtx); 2281} 2282 2283/* 2284 * Free the arc data buffer. If it is an l2arc write in progress, 2285 * the buffer is placed on l2arc_free_on_write to be freed later. 2286 */ 2287static void 2288arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2289{ 2290 arc_buf_hdr_t *hdr = buf->b_hdr; 2291 2292 if (HDR_L2_WRITING(hdr)) { 2293 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2294 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2295 } else { 2296 free_func(buf->b_data, hdr->b_size); 2297 } 2298} 2299 2300static void 2301arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2302{ 2303 size_t align, asize, len; 2304 2305 ASSERT(HDR_HAS_L2HDR(hdr)); 2306 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2307 2308 /* 2309 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2310 * that doesn't exist, the header is in the arc_l2c_only state, 2311 * and there isn't anything to free (it's already been freed). 2312 */ 2313 if (!HDR_HAS_L1HDR(hdr)) 2314 return; 2315 2316 /* 2317 * The header isn't being written to the l2arc device, thus it 2318 * shouldn't have a b_tmp_cdata to free. 2319 */ 2320 if (!HDR_L2_WRITING(hdr)) { 2321 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2322 return; 2323 } 2324 2325 /* 2326 * The bufer has been chosen for writing to L2ARC, but it's 2327 * not being written just yet. In other words, 2328 * b_tmp_cdata points to exactly the same buffer as b_data, 2329 * l2arc_transform_buf hasn't been called. 2330 */ 2331 if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET) { 2332 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, 2333 hdr->b_l1hdr.b_buf->b_data); 2334 ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_OFF); 2335 hdr->b_l1hdr.b_tmp_cdata = NULL; 2336 return; 2337 } 2338 2339 /* 2340 * There's nothing to free since the buffer was all zero's and 2341 * compressed to a zero length buffer. 2342 */ 2343 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) { 2344 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 2345 return; 2346 } 2347 2348 /* 2349 * Nothing to do if the temporary buffer was not required. 2350 */ 2351 if (hdr->b_l1hdr.b_tmp_cdata == NULL) 2352 return; 2353 2354 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2355 len = hdr->b_size; 2356 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 2357 asize = P2ROUNDUP(len, align); 2358 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, asize, 2359 zio_data_buf_free); 2360 hdr->b_l1hdr.b_tmp_cdata = NULL; 2361} 2362 2363/* 2364 * Free up buf->b_data and if 'remove' is set, then pull the 2365 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2366 */ 2367static void 2368arc_buf_destroy(arc_buf_t *buf, boolean_t remove) 2369{ 2370 arc_buf_t **bufp; 2371 2372 /* free up data associated with the buf */ 2373 if (buf->b_data != NULL) { 2374 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2375 uint64_t size = buf->b_hdr->b_size; 2376 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2377 2378 arc_cksum_verify(buf); 2379#ifdef illumos 2380 arc_buf_unwatch(buf); 2381#endif 2382 2383 if (type == ARC_BUFC_METADATA) { 2384 arc_buf_data_free(buf, zio_buf_free); 2385 arc_space_return(size, ARC_SPACE_META); 2386 } else { 2387 ASSERT(type == ARC_BUFC_DATA); 2388 arc_buf_data_free(buf, zio_data_buf_free); 2389 arc_space_return(size, ARC_SPACE_DATA); 2390 } 2391 2392 /* protected by hash lock, if in the hash table */ 2393 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2394 uint64_t *cnt = &state->arcs_lsize[type]; 2395 2396 ASSERT(refcount_is_zero( 2397 &buf->b_hdr->b_l1hdr.b_refcnt)); 2398 ASSERT(state != arc_anon && state != arc_l2c_only); 2399 2400 ASSERT3U(*cnt, >=, size); 2401 atomic_add_64(cnt, -size); 2402 } 2403 2404 (void) refcount_remove_many(&state->arcs_size, size, buf); 2405 buf->b_data = NULL; 2406 2407 /* 2408 * If we're destroying a duplicate buffer make sure 2409 * that the appropriate statistics are updated. 2410 */ 2411 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2412 HDR_ISTYPE_DATA(buf->b_hdr)) { 2413 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2414 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2415 } 2416 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2417 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2418 } 2419 2420 /* only remove the buf if requested */ 2421 if (!remove) 2422 return; 2423 2424 /* remove the buf from the hdr list */ 2425 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2426 bufp = &(*bufp)->b_next) 2427 continue; 2428 *bufp = buf->b_next; 2429 buf->b_next = NULL; 2430 2431 ASSERT(buf->b_efunc == NULL); 2432 2433 /* clean up the buf */ 2434 buf->b_hdr = NULL; 2435 kmem_cache_free(buf_cache, buf); 2436} 2437 2438static void 2439arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2440{ 2441 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2442 l2arc_dev_t *dev = l2hdr->b_dev; 2443 2444 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2445 ASSERT(HDR_HAS_L2HDR(hdr)); 2446 2447 list_remove(&dev->l2ad_buflist, hdr); 2448 2449 /* 2450 * We don't want to leak the b_tmp_cdata buffer that was 2451 * allocated in l2arc_write_buffers() 2452 */ 2453 arc_buf_l2_cdata_free(hdr); 2454 2455 /* 2456 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2457 * this header is being processed by l2arc_write_buffers() (i.e. 2458 * it's in the first stage of l2arc_write_buffers()). 2459 * Re-affirming that truth here, just to serve as a reminder. If 2460 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2461 * may not have its HDR_L2_WRITING flag set. (the write may have 2462 * completed, in which case HDR_L2_WRITING will be false and the 2463 * b_daddr field will point to the address of the buffer on disk). 2464 */ 2465 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2466 2467 /* 2468 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2469 * l2arc_write_buffers(). Since we've just removed this header 2470 * from the l2arc buffer list, this header will never reach the 2471 * second stage of l2arc_write_buffers(), which increments the 2472 * accounting stats for this header. Thus, we must be careful 2473 * not to decrement them for this header either. 2474 */ 2475 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2476 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2477 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2478 2479 vdev_space_update(dev->l2ad_vdev, 2480 -l2hdr->b_asize, 0, 0); 2481 2482 (void) refcount_remove_many(&dev->l2ad_alloc, 2483 l2hdr->b_asize, hdr); 2484 } 2485 2486 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2487} 2488 2489static void 2490arc_hdr_destroy(arc_buf_hdr_t *hdr) 2491{ 2492 if (HDR_HAS_L1HDR(hdr)) { 2493 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2494 hdr->b_l1hdr.b_datacnt > 0); 2495 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2496 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2497 } 2498 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2499 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2500 2501 if (HDR_HAS_L2HDR(hdr)) { 2502 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2503 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2504 2505 if (!buflist_held) 2506 mutex_enter(&dev->l2ad_mtx); 2507 2508 /* 2509 * Even though we checked this conditional above, we 2510 * need to check this again now that we have the 2511 * l2ad_mtx. This is because we could be racing with 2512 * another thread calling l2arc_evict() which might have 2513 * destroyed this header's L2 portion as we were waiting 2514 * to acquire the l2ad_mtx. If that happens, we don't 2515 * want to re-destroy the header's L2 portion. 2516 */ 2517 if (HDR_HAS_L2HDR(hdr)) { 2518 l2arc_trim(hdr); 2519 arc_hdr_l2hdr_destroy(hdr); 2520 } 2521 2522 if (!buflist_held) 2523 mutex_exit(&dev->l2ad_mtx); 2524 } 2525 2526 if (!BUF_EMPTY(hdr)) 2527 buf_discard_identity(hdr); 2528 2529 if (hdr->b_freeze_cksum != NULL) { 2530 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2531 hdr->b_freeze_cksum = NULL; 2532 } 2533 2534 if (HDR_HAS_L1HDR(hdr)) { 2535 while (hdr->b_l1hdr.b_buf) { 2536 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2537 2538 if (buf->b_efunc != NULL) { 2539 mutex_enter(&arc_user_evicts_lock); 2540 mutex_enter(&buf->b_evict_lock); 2541 ASSERT(buf->b_hdr != NULL); 2542 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE); 2543 hdr->b_l1hdr.b_buf = buf->b_next; 2544 buf->b_hdr = &arc_eviction_hdr; 2545 buf->b_next = arc_eviction_list; 2546 arc_eviction_list = buf; 2547 mutex_exit(&buf->b_evict_lock); 2548 cv_signal(&arc_user_evicts_cv); 2549 mutex_exit(&arc_user_evicts_lock); 2550 } else { 2551 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE); 2552 } 2553 } 2554#ifdef ZFS_DEBUG 2555 if (hdr->b_l1hdr.b_thawed != NULL) { 2556 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2557 hdr->b_l1hdr.b_thawed = NULL; 2558 } 2559#endif 2560 } 2561 2562 ASSERT3P(hdr->b_hash_next, ==, NULL); 2563 if (HDR_HAS_L1HDR(hdr)) { 2564 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2565 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2566 kmem_cache_free(hdr_full_cache, hdr); 2567 } else { 2568 kmem_cache_free(hdr_l2only_cache, hdr); 2569 } 2570} 2571 2572void 2573arc_buf_free(arc_buf_t *buf, void *tag) 2574{ 2575 arc_buf_hdr_t *hdr = buf->b_hdr; 2576 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2577 2578 ASSERT(buf->b_efunc == NULL); 2579 ASSERT(buf->b_data != NULL); 2580 2581 if (hashed) { 2582 kmutex_t *hash_lock = HDR_LOCK(hdr); 2583 2584 mutex_enter(hash_lock); 2585 hdr = buf->b_hdr; 2586 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2587 2588 (void) remove_reference(hdr, hash_lock, tag); 2589 if (hdr->b_l1hdr.b_datacnt > 1) { 2590 arc_buf_destroy(buf, TRUE); 2591 } else { 2592 ASSERT(buf == hdr->b_l1hdr.b_buf); 2593 ASSERT(buf->b_efunc == NULL); 2594 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2595 } 2596 mutex_exit(hash_lock); 2597 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2598 int destroy_hdr; 2599 /* 2600 * We are in the middle of an async write. Don't destroy 2601 * this buffer unless the write completes before we finish 2602 * decrementing the reference count. 2603 */ 2604 mutex_enter(&arc_user_evicts_lock); 2605 (void) remove_reference(hdr, NULL, tag); 2606 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2607 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2608 mutex_exit(&arc_user_evicts_lock); 2609 if (destroy_hdr) 2610 arc_hdr_destroy(hdr); 2611 } else { 2612 if (remove_reference(hdr, NULL, tag) > 0) 2613 arc_buf_destroy(buf, TRUE); 2614 else 2615 arc_hdr_destroy(hdr); 2616 } 2617} 2618 2619boolean_t 2620arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2621{ 2622 arc_buf_hdr_t *hdr = buf->b_hdr; 2623 kmutex_t *hash_lock = HDR_LOCK(hdr); 2624 boolean_t no_callback = (buf->b_efunc == NULL); 2625 2626 if (hdr->b_l1hdr.b_state == arc_anon) { 2627 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2628 arc_buf_free(buf, tag); 2629 return (no_callback); 2630 } 2631 2632 mutex_enter(hash_lock); 2633 hdr = buf->b_hdr; 2634 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2635 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2636 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2637 ASSERT(buf->b_data != NULL); 2638 2639 (void) remove_reference(hdr, hash_lock, tag); 2640 if (hdr->b_l1hdr.b_datacnt > 1) { 2641 if (no_callback) 2642 arc_buf_destroy(buf, TRUE); 2643 } else if (no_callback) { 2644 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2645 ASSERT(buf->b_efunc == NULL); 2646 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2647 } 2648 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2649 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2650 mutex_exit(hash_lock); 2651 return (no_callback); 2652} 2653 2654int32_t 2655arc_buf_size(arc_buf_t *buf) 2656{ 2657 return (buf->b_hdr->b_size); 2658} 2659 2660/* 2661 * Called from the DMU to determine if the current buffer should be 2662 * evicted. In order to ensure proper locking, the eviction must be initiated 2663 * from the DMU. Return true if the buffer is associated with user data and 2664 * duplicate buffers still exist. 2665 */ 2666boolean_t 2667arc_buf_eviction_needed(arc_buf_t *buf) 2668{ 2669 arc_buf_hdr_t *hdr; 2670 boolean_t evict_needed = B_FALSE; 2671 2672 if (zfs_disable_dup_eviction) 2673 return (B_FALSE); 2674 2675 mutex_enter(&buf->b_evict_lock); 2676 hdr = buf->b_hdr; 2677 if (hdr == NULL) { 2678 /* 2679 * We are in arc_do_user_evicts(); let that function 2680 * perform the eviction. 2681 */ 2682 ASSERT(buf->b_data == NULL); 2683 mutex_exit(&buf->b_evict_lock); 2684 return (B_FALSE); 2685 } else if (buf->b_data == NULL) { 2686 /* 2687 * We have already been added to the arc eviction list; 2688 * recommend eviction. 2689 */ 2690 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2691 mutex_exit(&buf->b_evict_lock); 2692 return (B_TRUE); 2693 } 2694 2695 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2696 evict_needed = B_TRUE; 2697 2698 mutex_exit(&buf->b_evict_lock); 2699 return (evict_needed); 2700} 2701 2702/* 2703 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 2704 * state of the header is dependent on it's state prior to entering this 2705 * function. The following transitions are possible: 2706 * 2707 * - arc_mru -> arc_mru_ghost 2708 * - arc_mfu -> arc_mfu_ghost 2709 * - arc_mru_ghost -> arc_l2c_only 2710 * - arc_mru_ghost -> deleted 2711 * - arc_mfu_ghost -> arc_l2c_only 2712 * - arc_mfu_ghost -> deleted 2713 */ 2714static int64_t 2715arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 2716{ 2717 arc_state_t *evicted_state, *state; 2718 int64_t bytes_evicted = 0; 2719 2720 ASSERT(MUTEX_HELD(hash_lock)); 2721 ASSERT(HDR_HAS_L1HDR(hdr)); 2722 2723 state = hdr->b_l1hdr.b_state; 2724 if (GHOST_STATE(state)) { 2725 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2726 ASSERT(hdr->b_l1hdr.b_buf == NULL); 2727 2728 /* 2729 * l2arc_write_buffers() relies on a header's L1 portion 2730 * (i.e. it's b_tmp_cdata field) during it's write phase. 2731 * Thus, we cannot push a header onto the arc_l2c_only 2732 * state (removing it's L1 piece) until the header is 2733 * done being written to the l2arc. 2734 */ 2735 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 2736 ARCSTAT_BUMP(arcstat_evict_l2_skip); 2737 return (bytes_evicted); 2738 } 2739 2740 ARCSTAT_BUMP(arcstat_deleted); 2741 bytes_evicted += hdr->b_size; 2742 2743 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2744 2745 if (HDR_HAS_L2HDR(hdr)) { 2746 /* 2747 * This buffer is cached on the 2nd Level ARC; 2748 * don't destroy the header. 2749 */ 2750 arc_change_state(arc_l2c_only, hdr, hash_lock); 2751 /* 2752 * dropping from L1+L2 cached to L2-only, 2753 * realloc to remove the L1 header. 2754 */ 2755 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2756 hdr_l2only_cache); 2757 } else { 2758 arc_change_state(arc_anon, hdr, hash_lock); 2759 arc_hdr_destroy(hdr); 2760 } 2761 return (bytes_evicted); 2762 } 2763 2764 ASSERT(state == arc_mru || state == arc_mfu); 2765 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2766 2767 /* prefetch buffers have a minimum lifespan */ 2768 if (HDR_IO_IN_PROGRESS(hdr) || 2769 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2770 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2771 arc_min_prefetch_lifespan)) { 2772 ARCSTAT_BUMP(arcstat_evict_skip); 2773 return (bytes_evicted); 2774 } 2775 2776 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2777 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2778 while (hdr->b_l1hdr.b_buf) { 2779 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2780 if (!mutex_tryenter(&buf->b_evict_lock)) { 2781 ARCSTAT_BUMP(arcstat_mutex_miss); 2782 break; 2783 } 2784 if (buf->b_data != NULL) 2785 bytes_evicted += hdr->b_size; 2786 if (buf->b_efunc != NULL) { 2787 mutex_enter(&arc_user_evicts_lock); 2788 arc_buf_destroy(buf, FALSE); 2789 hdr->b_l1hdr.b_buf = buf->b_next; 2790 buf->b_hdr = &arc_eviction_hdr; 2791 buf->b_next = arc_eviction_list; 2792 arc_eviction_list = buf; 2793 cv_signal(&arc_user_evicts_cv); 2794 mutex_exit(&arc_user_evicts_lock); 2795 mutex_exit(&buf->b_evict_lock); 2796 } else { 2797 mutex_exit(&buf->b_evict_lock); 2798 arc_buf_destroy(buf, TRUE); 2799 } 2800 } 2801 2802 if (HDR_HAS_L2HDR(hdr)) { 2803 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size); 2804 } else { 2805 if (l2arc_write_eligible(hdr->b_spa, hdr)) 2806 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size); 2807 else 2808 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size); 2809 } 2810 2811 if (hdr->b_l1hdr.b_datacnt == 0) { 2812 arc_change_state(evicted_state, hdr, hash_lock); 2813 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2814 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2815 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2816 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2817 } 2818 2819 return (bytes_evicted); 2820} 2821 2822static uint64_t 2823arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 2824 uint64_t spa, int64_t bytes) 2825{ 2826 multilist_sublist_t *mls; 2827 uint64_t bytes_evicted = 0; 2828 arc_buf_hdr_t *hdr; 2829 kmutex_t *hash_lock; 2830 int evict_count = 0; 2831 2832 ASSERT3P(marker, !=, NULL); 2833 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2834 2835 mls = multilist_sublist_lock(ml, idx); 2836 2837 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 2838 hdr = multilist_sublist_prev(mls, marker)) { 2839 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 2840 (evict_count >= zfs_arc_evict_batch_limit)) 2841 break; 2842 2843 /* 2844 * To keep our iteration location, move the marker 2845 * forward. Since we're not holding hdr's hash lock, we 2846 * must be very careful and not remove 'hdr' from the 2847 * sublist. Otherwise, other consumers might mistake the 2848 * 'hdr' as not being on a sublist when they call the 2849 * multilist_link_active() function (they all rely on 2850 * the hash lock protecting concurrent insertions and 2851 * removals). multilist_sublist_move_forward() was 2852 * specifically implemented to ensure this is the case 2853 * (only 'marker' will be removed and re-inserted). 2854 */ 2855 multilist_sublist_move_forward(mls, marker); 2856 2857 /* 2858 * The only case where the b_spa field should ever be 2859 * zero, is the marker headers inserted by 2860 * arc_evict_state(). It's possible for multiple threads 2861 * to be calling arc_evict_state() concurrently (e.g. 2862 * dsl_pool_close() and zio_inject_fault()), so we must 2863 * skip any markers we see from these other threads. 2864 */ 2865 if (hdr->b_spa == 0) 2866 continue; 2867 2868 /* we're only interested in evicting buffers of a certain spa */ 2869 if (spa != 0 && hdr->b_spa != spa) { 2870 ARCSTAT_BUMP(arcstat_evict_skip); 2871 continue; 2872 } 2873 2874 hash_lock = HDR_LOCK(hdr); 2875 2876 /* 2877 * We aren't calling this function from any code path 2878 * that would already be holding a hash lock, so we're 2879 * asserting on this assumption to be defensive in case 2880 * this ever changes. Without this check, it would be 2881 * possible to incorrectly increment arcstat_mutex_miss 2882 * below (e.g. if the code changed such that we called 2883 * this function with a hash lock held). 2884 */ 2885 ASSERT(!MUTEX_HELD(hash_lock)); 2886 2887 if (mutex_tryenter(hash_lock)) { 2888 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 2889 mutex_exit(hash_lock); 2890 2891 bytes_evicted += evicted; 2892 2893 /* 2894 * If evicted is zero, arc_evict_hdr() must have 2895 * decided to skip this header, don't increment 2896 * evict_count in this case. 2897 */ 2898 if (evicted != 0) 2899 evict_count++; 2900 2901 /* 2902 * If arc_size isn't overflowing, signal any 2903 * threads that might happen to be waiting. 2904 * 2905 * For each header evicted, we wake up a single 2906 * thread. If we used cv_broadcast, we could 2907 * wake up "too many" threads causing arc_size 2908 * to significantly overflow arc_c; since 2909 * arc_get_data_buf() doesn't check for overflow 2910 * when it's woken up (it doesn't because it's 2911 * possible for the ARC to be overflowing while 2912 * full of un-evictable buffers, and the 2913 * function should proceed in this case). 2914 * 2915 * If threads are left sleeping, due to not 2916 * using cv_broadcast, they will be woken up 2917 * just before arc_reclaim_thread() sleeps. 2918 */ 2919 mutex_enter(&arc_reclaim_lock); 2920 if (!arc_is_overflowing()) 2921 cv_signal(&arc_reclaim_waiters_cv); 2922 mutex_exit(&arc_reclaim_lock); 2923 } else { 2924 ARCSTAT_BUMP(arcstat_mutex_miss); 2925 } 2926 } 2927 2928 multilist_sublist_unlock(mls); 2929 2930 return (bytes_evicted); 2931} 2932 2933/* 2934 * Evict buffers from the given arc state, until we've removed the 2935 * specified number of bytes. Move the removed buffers to the 2936 * appropriate evict state. 2937 * 2938 * This function makes a "best effort". It skips over any buffers 2939 * it can't get a hash_lock on, and so, may not catch all candidates. 2940 * It may also return without evicting as much space as requested. 2941 * 2942 * If bytes is specified using the special value ARC_EVICT_ALL, this 2943 * will evict all available (i.e. unlocked and evictable) buffers from 2944 * the given arc state; which is used by arc_flush(). 2945 */ 2946static uint64_t 2947arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 2948 arc_buf_contents_t type) 2949{ 2950 uint64_t total_evicted = 0; 2951 multilist_t *ml = &state->arcs_list[type]; 2952 int num_sublists; 2953 arc_buf_hdr_t **markers; 2954 2955 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 2956 2957 num_sublists = multilist_get_num_sublists(ml); 2958 2959 /* 2960 * If we've tried to evict from each sublist, made some 2961 * progress, but still have not hit the target number of bytes 2962 * to evict, we want to keep trying. The markers allow us to 2963 * pick up where we left off for each individual sublist, rather 2964 * than starting from the tail each time. 2965 */ 2966 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 2967 for (int i = 0; i < num_sublists; i++) { 2968 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 2969 2970 /* 2971 * A b_spa of 0 is used to indicate that this header is 2972 * a marker. This fact is used in arc_adjust_type() and 2973 * arc_evict_state_impl(). 2974 */ 2975 markers[i]->b_spa = 0; 2976 2977 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 2978 multilist_sublist_insert_tail(mls, markers[i]); 2979 multilist_sublist_unlock(mls); 2980 } 2981 2982 /* 2983 * While we haven't hit our target number of bytes to evict, or 2984 * we're evicting all available buffers. 2985 */ 2986 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 2987 /* 2988 * Start eviction using a randomly selected sublist, 2989 * this is to try and evenly balance eviction across all 2990 * sublists. Always starting at the same sublist 2991 * (e.g. index 0) would cause evictions to favor certain 2992 * sublists over others. 2993 */ 2994 int sublist_idx = multilist_get_random_index(ml); 2995 uint64_t scan_evicted = 0; 2996 2997 for (int i = 0; i < num_sublists; i++) { 2998 uint64_t bytes_remaining; 2999 uint64_t bytes_evicted; 3000 3001 if (bytes == ARC_EVICT_ALL) 3002 bytes_remaining = ARC_EVICT_ALL; 3003 else if (total_evicted < bytes) 3004 bytes_remaining = bytes - total_evicted; 3005 else 3006 break; 3007 3008 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3009 markers[sublist_idx], spa, bytes_remaining); 3010 3011 scan_evicted += bytes_evicted; 3012 total_evicted += bytes_evicted; 3013 3014 /* we've reached the end, wrap to the beginning */ 3015 if (++sublist_idx >= num_sublists) 3016 sublist_idx = 0; 3017 } 3018 3019 /* 3020 * If we didn't evict anything during this scan, we have 3021 * no reason to believe we'll evict more during another 3022 * scan, so break the loop. 3023 */ 3024 if (scan_evicted == 0) { 3025 /* This isn't possible, let's make that obvious */ 3026 ASSERT3S(bytes, !=, 0); 3027 3028 /* 3029 * When bytes is ARC_EVICT_ALL, the only way to 3030 * break the loop is when scan_evicted is zero. 3031 * In that case, we actually have evicted enough, 3032 * so we don't want to increment the kstat. 3033 */ 3034 if (bytes != ARC_EVICT_ALL) { 3035 ASSERT3S(total_evicted, <, bytes); 3036 ARCSTAT_BUMP(arcstat_evict_not_enough); 3037 } 3038 3039 break; 3040 } 3041 } 3042 3043 for (int i = 0; i < num_sublists; i++) { 3044 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3045 multilist_sublist_remove(mls, markers[i]); 3046 multilist_sublist_unlock(mls); 3047 3048 kmem_cache_free(hdr_full_cache, markers[i]); 3049 } 3050 kmem_free(markers, sizeof (*markers) * num_sublists); 3051 3052 return (total_evicted); 3053} 3054 3055/* 3056 * Flush all "evictable" data of the given type from the arc state 3057 * specified. This will not evict any "active" buffers (i.e. referenced). 3058 * 3059 * When 'retry' is set to FALSE, the function will make a single pass 3060 * over the state and evict any buffers that it can. Since it doesn't 3061 * continually retry the eviction, it might end up leaving some buffers 3062 * in the ARC due to lock misses. 3063 * 3064 * When 'retry' is set to TRUE, the function will continually retry the 3065 * eviction until *all* evictable buffers have been removed from the 3066 * state. As a result, if concurrent insertions into the state are 3067 * allowed (e.g. if the ARC isn't shutting down), this function might 3068 * wind up in an infinite loop, continually trying to evict buffers. 3069 */ 3070static uint64_t 3071arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3072 boolean_t retry) 3073{ 3074 uint64_t evicted = 0; 3075 3076 while (state->arcs_lsize[type] != 0) { 3077 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3078 3079 if (!retry) 3080 break; 3081 } 3082 3083 return (evicted); 3084} 3085 3086/* 3087 * Evict the specified number of bytes from the state specified, 3088 * restricting eviction to the spa and type given. This function 3089 * prevents us from trying to evict more from a state's list than 3090 * is "evictable", and to skip evicting altogether when passed a 3091 * negative value for "bytes". In contrast, arc_evict_state() will 3092 * evict everything it can, when passed a negative value for "bytes". 3093 */ 3094static uint64_t 3095arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3096 arc_buf_contents_t type) 3097{ 3098 int64_t delta; 3099 3100 if (bytes > 0 && state->arcs_lsize[type] > 0) { 3101 delta = MIN(state->arcs_lsize[type], bytes); 3102 return (arc_evict_state(state, spa, delta, type)); 3103 } 3104 3105 return (0); 3106} 3107 3108/* 3109 * Evict metadata buffers from the cache, such that arc_meta_used is 3110 * capped by the arc_meta_limit tunable. 3111 */ 3112static uint64_t 3113arc_adjust_meta(void) 3114{ 3115 uint64_t total_evicted = 0; 3116 int64_t target; 3117 3118 /* 3119 * If we're over the meta limit, we want to evict enough 3120 * metadata to get back under the meta limit. We don't want to 3121 * evict so much that we drop the MRU below arc_p, though. If 3122 * we're over the meta limit more than we're over arc_p, we 3123 * evict some from the MRU here, and some from the MFU below. 3124 */ 3125 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3126 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3127 refcount_count(&arc_mru->arcs_size) - arc_p)); 3128 3129 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3130 3131 /* 3132 * Similar to the above, we want to evict enough bytes to get us 3133 * below the meta limit, but not so much as to drop us below the 3134 * space alloted to the MFU (which is defined as arc_c - arc_p). 3135 */ 3136 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3137 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3138 3139 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3140 3141 return (total_evicted); 3142} 3143 3144/* 3145 * Return the type of the oldest buffer in the given arc state 3146 * 3147 * This function will select a random sublist of type ARC_BUFC_DATA and 3148 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3149 * is compared, and the type which contains the "older" buffer will be 3150 * returned. 3151 */ 3152static arc_buf_contents_t 3153arc_adjust_type(arc_state_t *state) 3154{ 3155 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3156 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3157 int data_idx = multilist_get_random_index(data_ml); 3158 int meta_idx = multilist_get_random_index(meta_ml); 3159 multilist_sublist_t *data_mls; 3160 multilist_sublist_t *meta_mls; 3161 arc_buf_contents_t type; 3162 arc_buf_hdr_t *data_hdr; 3163 arc_buf_hdr_t *meta_hdr; 3164 3165 /* 3166 * We keep the sublist lock until we're finished, to prevent 3167 * the headers from being destroyed via arc_evict_state(). 3168 */ 3169 data_mls = multilist_sublist_lock(data_ml, data_idx); 3170 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3171 3172 /* 3173 * These two loops are to ensure we skip any markers that 3174 * might be at the tail of the lists due to arc_evict_state(). 3175 */ 3176 3177 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3178 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3179 if (data_hdr->b_spa != 0) 3180 break; 3181 } 3182 3183 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3184 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3185 if (meta_hdr->b_spa != 0) 3186 break; 3187 } 3188 3189 if (data_hdr == NULL && meta_hdr == NULL) { 3190 type = ARC_BUFC_DATA; 3191 } else if (data_hdr == NULL) { 3192 ASSERT3P(meta_hdr, !=, NULL); 3193 type = ARC_BUFC_METADATA; 3194 } else if (meta_hdr == NULL) { 3195 ASSERT3P(data_hdr, !=, NULL); 3196 type = ARC_BUFC_DATA; 3197 } else { 3198 ASSERT3P(data_hdr, !=, NULL); 3199 ASSERT3P(meta_hdr, !=, NULL); 3200 3201 /* The headers can't be on the sublist without an L1 header */ 3202 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3203 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3204 3205 if (data_hdr->b_l1hdr.b_arc_access < 3206 meta_hdr->b_l1hdr.b_arc_access) { 3207 type = ARC_BUFC_DATA; 3208 } else { 3209 type = ARC_BUFC_METADATA; 3210 } 3211 } 3212 3213 multilist_sublist_unlock(meta_mls); 3214 multilist_sublist_unlock(data_mls); 3215 3216 return (type); 3217} 3218 3219/* 3220 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3221 */ 3222static uint64_t 3223arc_adjust(void) 3224{ 3225 uint64_t total_evicted = 0; 3226 uint64_t bytes; 3227 int64_t target; 3228 3229 /* 3230 * If we're over arc_meta_limit, we want to correct that before 3231 * potentially evicting data buffers below. 3232 */ 3233 total_evicted += arc_adjust_meta(); 3234 3235 /* 3236 * Adjust MRU size 3237 * 3238 * If we're over the target cache size, we want to evict enough 3239 * from the list to get back to our target size. We don't want 3240 * to evict too much from the MRU, such that it drops below 3241 * arc_p. So, if we're over our target cache size more than 3242 * the MRU is over arc_p, we'll evict enough to get back to 3243 * arc_p here, and then evict more from the MFU below. 3244 */ 3245 target = MIN((int64_t)(arc_size - arc_c), 3246 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3247 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3248 3249 /* 3250 * If we're below arc_meta_min, always prefer to evict data. 3251 * Otherwise, try to satisfy the requested number of bytes to 3252 * evict from the type which contains older buffers; in an 3253 * effort to keep newer buffers in the cache regardless of their 3254 * type. If we cannot satisfy the number of bytes from this 3255 * type, spill over into the next type. 3256 */ 3257 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3258 arc_meta_used > arc_meta_min) { 3259 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3260 total_evicted += bytes; 3261 3262 /* 3263 * If we couldn't evict our target number of bytes from 3264 * metadata, we try to get the rest from data. 3265 */ 3266 target -= bytes; 3267 3268 total_evicted += 3269 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3270 } else { 3271 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3272 total_evicted += bytes; 3273 3274 /* 3275 * If we couldn't evict our target number of bytes from 3276 * data, we try to get the rest from metadata. 3277 */ 3278 target -= bytes; 3279 3280 total_evicted += 3281 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3282 } 3283 3284 /* 3285 * Adjust MFU size 3286 * 3287 * Now that we've tried to evict enough from the MRU to get its 3288 * size back to arc_p, if we're still above the target cache 3289 * size, we evict the rest from the MFU. 3290 */ 3291 target = arc_size - arc_c; 3292 3293 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3294 arc_meta_used > arc_meta_min) { 3295 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3296 total_evicted += bytes; 3297 3298 /* 3299 * If we couldn't evict our target number of bytes from 3300 * metadata, we try to get the rest from data. 3301 */ 3302 target -= bytes; 3303 3304 total_evicted += 3305 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3306 } else { 3307 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3308 total_evicted += bytes; 3309 3310 /* 3311 * If we couldn't evict our target number of bytes from 3312 * data, we try to get the rest from data. 3313 */ 3314 target -= bytes; 3315 3316 total_evicted += 3317 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3318 } 3319 3320 /* 3321 * Adjust ghost lists 3322 * 3323 * In addition to the above, the ARC also defines target values 3324 * for the ghost lists. The sum of the mru list and mru ghost 3325 * list should never exceed the target size of the cache, and 3326 * the sum of the mru list, mfu list, mru ghost list, and mfu 3327 * ghost list should never exceed twice the target size of the 3328 * cache. The following logic enforces these limits on the ghost 3329 * caches, and evicts from them as needed. 3330 */ 3331 target = refcount_count(&arc_mru->arcs_size) + 3332 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3333 3334 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3335 total_evicted += bytes; 3336 3337 target -= bytes; 3338 3339 total_evicted += 3340 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3341 3342 /* 3343 * We assume the sum of the mru list and mfu list is less than 3344 * or equal to arc_c (we enforced this above), which means we 3345 * can use the simpler of the two equations below: 3346 * 3347 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3348 * mru ghost + mfu ghost <= arc_c 3349 */ 3350 target = refcount_count(&arc_mru_ghost->arcs_size) + 3351 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3352 3353 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3354 total_evicted += bytes; 3355 3356 target -= bytes; 3357 3358 total_evicted += 3359 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3360 3361 return (total_evicted); 3362} 3363 3364static void 3365arc_do_user_evicts(void) 3366{ 3367 mutex_enter(&arc_user_evicts_lock); 3368 while (arc_eviction_list != NULL) { 3369 arc_buf_t *buf = arc_eviction_list; 3370 arc_eviction_list = buf->b_next; 3371 mutex_enter(&buf->b_evict_lock); 3372 buf->b_hdr = NULL; 3373 mutex_exit(&buf->b_evict_lock); 3374 mutex_exit(&arc_user_evicts_lock); 3375 3376 if (buf->b_efunc != NULL) 3377 VERIFY0(buf->b_efunc(buf->b_private)); 3378 3379 buf->b_efunc = NULL; 3380 buf->b_private = NULL; 3381 kmem_cache_free(buf_cache, buf); 3382 mutex_enter(&arc_user_evicts_lock); 3383 } 3384 mutex_exit(&arc_user_evicts_lock); 3385} 3386 3387void 3388arc_flush(spa_t *spa, boolean_t retry) 3389{ 3390 uint64_t guid = 0; 3391 3392 /* 3393 * If retry is TRUE, a spa must not be specified since we have 3394 * no good way to determine if all of a spa's buffers have been 3395 * evicted from an arc state. 3396 */ 3397 ASSERT(!retry || spa == 0); 3398 3399 if (spa != NULL) 3400 guid = spa_load_guid(spa); 3401 3402 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3403 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3404 3405 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3406 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3407 3408 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3409 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3410 3411 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3412 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3413 3414 arc_do_user_evicts(); 3415 ASSERT(spa || arc_eviction_list == NULL); 3416} 3417 3418void 3419arc_shrink(int64_t to_free) 3420{ 3421 if (arc_c > arc_c_min) { 3422 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3423 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3424 if (arc_c > arc_c_min + to_free) 3425 atomic_add_64(&arc_c, -to_free); 3426 else 3427 arc_c = arc_c_min; 3428 3429 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3430 if (arc_c > arc_size) 3431 arc_c = MAX(arc_size, arc_c_min); 3432 if (arc_p > arc_c) 3433 arc_p = (arc_c >> 1); 3434 3435 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3436 arc_p); 3437 3438 ASSERT(arc_c >= arc_c_min); 3439 ASSERT((int64_t)arc_p >= 0); 3440 } 3441 3442 if (arc_size > arc_c) { 3443 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3444 uint64_t, arc_c); 3445 (void) arc_adjust(); 3446 } 3447} 3448 3449static long needfree = 0; 3450 3451typedef enum free_memory_reason_t { 3452 FMR_UNKNOWN, 3453 FMR_NEEDFREE, 3454 FMR_LOTSFREE, 3455 FMR_SWAPFS_MINFREE, 3456 FMR_PAGES_PP_MAXIMUM, 3457 FMR_HEAP_ARENA, 3458 FMR_ZIO_ARENA, 3459 FMR_ZIO_FRAG, 3460} free_memory_reason_t; 3461 3462int64_t last_free_memory; 3463free_memory_reason_t last_free_reason; 3464 3465/* 3466 * Additional reserve of pages for pp_reserve. 3467 */ 3468int64_t arc_pages_pp_reserve = 64; 3469 3470/* 3471 * Additional reserve of pages for swapfs. 3472 */ 3473int64_t arc_swapfs_reserve = 64; 3474 3475/* 3476 * Return the amount of memory that can be consumed before reclaim will be 3477 * needed. Positive if there is sufficient free memory, negative indicates 3478 * the amount of memory that needs to be freed up. 3479 */ 3480static int64_t 3481arc_available_memory(void) 3482{ 3483 int64_t lowest = INT64_MAX; 3484 int64_t n; 3485 free_memory_reason_t r = FMR_UNKNOWN; 3486 3487#ifdef _KERNEL 3488 if (needfree > 0) { 3489 n = PAGESIZE * (-needfree); 3490 if (n < lowest) { 3491 lowest = n; 3492 r = FMR_NEEDFREE; 3493 } 3494 } 3495 3496 /* 3497 * Cooperate with pagedaemon when it's time for it to scan 3498 * and reclaim some pages. 3499 */ 3500 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3501 if (n < lowest) { 3502 lowest = n; 3503 r = FMR_LOTSFREE; 3504 } 3505 3506#ifdef illumos 3507 /* 3508 * check that we're out of range of the pageout scanner. It starts to 3509 * schedule paging if freemem is less than lotsfree and needfree. 3510 * lotsfree is the high-water mark for pageout, and needfree is the 3511 * number of needed free pages. We add extra pages here to make sure 3512 * the scanner doesn't start up while we're freeing memory. 3513 */ 3514 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3515 if (n < lowest) { 3516 lowest = n; 3517 r = FMR_LOTSFREE; 3518 } 3519 3520 /* 3521 * check to make sure that swapfs has enough space so that anon 3522 * reservations can still succeed. anon_resvmem() checks that the 3523 * availrmem is greater than swapfs_minfree, and the number of reserved 3524 * swap pages. We also add a bit of extra here just to prevent 3525 * circumstances from getting really dire. 3526 */ 3527 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3528 desfree - arc_swapfs_reserve); 3529 if (n < lowest) { 3530 lowest = n; 3531 r = FMR_SWAPFS_MINFREE; 3532 } 3533 3534 3535 /* 3536 * Check that we have enough availrmem that memory locking (e.g., via 3537 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3538 * stores the number of pages that cannot be locked; when availrmem 3539 * drops below pages_pp_maximum, page locking mechanisms such as 3540 * page_pp_lock() will fail.) 3541 */ 3542 n = PAGESIZE * (availrmem - pages_pp_maximum - 3543 arc_pages_pp_reserve); 3544 if (n < lowest) { 3545 lowest = n; 3546 r = FMR_PAGES_PP_MAXIMUM; 3547 } 3548 3549#endif /* illumos */ 3550#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3551 /* 3552 * If we're on an i386 platform, it's possible that we'll exhaust the 3553 * kernel heap space before we ever run out of available physical 3554 * memory. Most checks of the size of the heap_area compare against 3555 * tune.t_minarmem, which is the minimum available real memory that we 3556 * can have in the system. However, this is generally fixed at 25 pages 3557 * which is so low that it's useless. In this comparison, we seek to 3558 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3559 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3560 * free) 3561 */ 3562 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3563 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3564 if (n < lowest) { 3565 lowest = n; 3566 r = FMR_HEAP_ARENA; 3567 } 3568#define zio_arena NULL 3569#else 3570#define zio_arena heap_arena 3571#endif 3572 3573 /* 3574 * If zio data pages are being allocated out of a separate heap segment, 3575 * then enforce that the size of available vmem for this arena remains 3576 * above about 1/16th free. 3577 * 3578 * Note: The 1/16th arena free requirement was put in place 3579 * to aggressively evict memory from the arc in order to avoid 3580 * memory fragmentation issues. 3581 */ 3582 if (zio_arena != NULL) { 3583 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3584 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3585 if (n < lowest) { 3586 lowest = n; 3587 r = FMR_ZIO_ARENA; 3588 } 3589 } 3590 3591 /* 3592 * Above limits know nothing about real level of KVA fragmentation. 3593 * Start aggressive reclamation if too little sequential KVA left. 3594 */ 3595 if (lowest > 0) { 3596 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3597 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3598 INT64_MAX; 3599 if (n < lowest) { 3600 lowest = n; 3601 r = FMR_ZIO_FRAG; 3602 } 3603 } 3604 3605#else /* _KERNEL */ 3606 /* Every 100 calls, free a small amount */ 3607 if (spa_get_random(100) == 0) 3608 lowest = -1024; 3609#endif /* _KERNEL */ 3610 3611 last_free_memory = lowest; 3612 last_free_reason = r; 3613 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3614 return (lowest); 3615} 3616 3617 3618/* 3619 * Determine if the system is under memory pressure and is asking 3620 * to reclaim memory. A return value of TRUE indicates that the system 3621 * is under memory pressure and that the arc should adjust accordingly. 3622 */ 3623static boolean_t 3624arc_reclaim_needed(void) 3625{ 3626 return (arc_available_memory() < 0); 3627} 3628 3629extern kmem_cache_t *zio_buf_cache[]; 3630extern kmem_cache_t *zio_data_buf_cache[]; 3631extern kmem_cache_t *range_seg_cache; 3632 3633static __noinline void 3634arc_kmem_reap_now(void) 3635{ 3636 size_t i; 3637 kmem_cache_t *prev_cache = NULL; 3638 kmem_cache_t *prev_data_cache = NULL; 3639 3640 DTRACE_PROBE(arc__kmem_reap_start); 3641#ifdef _KERNEL 3642 if (arc_meta_used >= arc_meta_limit) { 3643 /* 3644 * We are exceeding our meta-data cache limit. 3645 * Purge some DNLC entries to release holds on meta-data. 3646 */ 3647 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3648 } 3649#if defined(__i386) 3650 /* 3651 * Reclaim unused memory from all kmem caches. 3652 */ 3653 kmem_reap(); 3654#endif 3655#endif 3656 3657 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3658 if (zio_buf_cache[i] != prev_cache) { 3659 prev_cache = zio_buf_cache[i]; 3660 kmem_cache_reap_now(zio_buf_cache[i]); 3661 } 3662 if (zio_data_buf_cache[i] != prev_data_cache) { 3663 prev_data_cache = zio_data_buf_cache[i]; 3664 kmem_cache_reap_now(zio_data_buf_cache[i]); 3665 } 3666 } 3667 kmem_cache_reap_now(buf_cache); 3668 kmem_cache_reap_now(hdr_full_cache); 3669 kmem_cache_reap_now(hdr_l2only_cache); 3670 kmem_cache_reap_now(range_seg_cache); 3671 3672#ifdef illumos 3673 if (zio_arena != NULL) { 3674 /* 3675 * Ask the vmem arena to reclaim unused memory from its 3676 * quantum caches. 3677 */ 3678 vmem_qcache_reap(zio_arena); 3679 } 3680#endif 3681 DTRACE_PROBE(arc__kmem_reap_end); 3682} 3683 3684/* 3685 * Threads can block in arc_get_data_buf() waiting for this thread to evict 3686 * enough data and signal them to proceed. When this happens, the threads in 3687 * arc_get_data_buf() are sleeping while holding the hash lock for their 3688 * particular arc header. Thus, we must be careful to never sleep on a 3689 * hash lock in this thread. This is to prevent the following deadlock: 3690 * 3691 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 3692 * waiting for the reclaim thread to signal it. 3693 * 3694 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 3695 * fails, and goes to sleep forever. 3696 * 3697 * This possible deadlock is avoided by always acquiring a hash lock 3698 * using mutex_tryenter() from arc_reclaim_thread(). 3699 */ 3700static void 3701arc_reclaim_thread(void *dummy __unused) 3702{ 3703 hrtime_t growtime = 0; 3704 callb_cpr_t cpr; 3705 3706 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 3707 3708 mutex_enter(&arc_reclaim_lock); 3709 while (!arc_reclaim_thread_exit) { 3710 int64_t free_memory = arc_available_memory(); 3711 uint64_t evicted = 0; 3712 3713 mutex_exit(&arc_reclaim_lock); 3714 3715 if (free_memory < 0) { 3716 3717 arc_no_grow = B_TRUE; 3718 arc_warm = B_TRUE; 3719 3720 /* 3721 * Wait at least zfs_grow_retry (default 60) seconds 3722 * before considering growing. 3723 */ 3724 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 3725 3726 arc_kmem_reap_now(); 3727 3728 /* 3729 * If we are still low on memory, shrink the ARC 3730 * so that we have arc_shrink_min free space. 3731 */ 3732 free_memory = arc_available_memory(); 3733 3734 int64_t to_free = 3735 (arc_c >> arc_shrink_shift) - free_memory; 3736 if (to_free > 0) { 3737#ifdef _KERNEL 3738 to_free = MAX(to_free, ptob(needfree)); 3739#endif 3740 arc_shrink(to_free); 3741 } 3742 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3743 arc_no_grow = B_TRUE; 3744 } else if (gethrtime() >= growtime) { 3745 arc_no_grow = B_FALSE; 3746 } 3747 3748 evicted = arc_adjust(); 3749 3750 mutex_enter(&arc_reclaim_lock); 3751 3752 /* 3753 * If evicted is zero, we couldn't evict anything via 3754 * arc_adjust(). This could be due to hash lock 3755 * collisions, but more likely due to the majority of 3756 * arc buffers being unevictable. Therefore, even if 3757 * arc_size is above arc_c, another pass is unlikely to 3758 * be helpful and could potentially cause us to enter an 3759 * infinite loop. 3760 */ 3761 if (arc_size <= arc_c || evicted == 0) { 3762#ifdef _KERNEL 3763 needfree = 0; 3764#endif 3765 /* 3766 * We're either no longer overflowing, or we 3767 * can't evict anything more, so we should wake 3768 * up any threads before we go to sleep. 3769 */ 3770 cv_broadcast(&arc_reclaim_waiters_cv); 3771 3772 /* 3773 * Block until signaled, or after one second (we 3774 * might need to perform arc_kmem_reap_now() 3775 * even if we aren't being signalled) 3776 */ 3777 CALLB_CPR_SAFE_BEGIN(&cpr); 3778 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 3779 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 3780 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 3781 } 3782 } 3783 3784 arc_reclaim_thread_exit = FALSE; 3785 cv_broadcast(&arc_reclaim_thread_cv); 3786 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 3787 thread_exit(); 3788} 3789 3790static void 3791arc_user_evicts_thread(void *dummy __unused) 3792{ 3793 callb_cpr_t cpr; 3794 3795 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG); 3796 3797 mutex_enter(&arc_user_evicts_lock); 3798 while (!arc_user_evicts_thread_exit) { 3799 mutex_exit(&arc_user_evicts_lock); 3800 3801 arc_do_user_evicts(); 3802 3803 /* 3804 * This is necessary in order for the mdb ::arc dcmd to 3805 * show up to date information. Since the ::arc command 3806 * does not call the kstat's update function, without 3807 * this call, the command may show stale stats for the 3808 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3809 * with this change, the data might be up to 1 second 3810 * out of date; but that should suffice. The arc_state_t 3811 * structures can be queried directly if more accurate 3812 * information is needed. 3813 */ 3814 if (arc_ksp != NULL) 3815 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3816 3817 mutex_enter(&arc_user_evicts_lock); 3818 3819 /* 3820 * Block until signaled, or after one second (we need to 3821 * call the arc's kstat update function regularly). 3822 */ 3823 CALLB_CPR_SAFE_BEGIN(&cpr); 3824 (void) cv_timedwait(&arc_user_evicts_cv, 3825 &arc_user_evicts_lock, hz); 3826 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock); 3827 } 3828 3829 arc_user_evicts_thread_exit = FALSE; 3830 cv_broadcast(&arc_user_evicts_cv); 3831 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */ 3832 thread_exit(); 3833} 3834 3835/* 3836 * Adapt arc info given the number of bytes we are trying to add and 3837 * the state that we are comming from. This function is only called 3838 * when we are adding new content to the cache. 3839 */ 3840static void 3841arc_adapt(int bytes, arc_state_t *state) 3842{ 3843 int mult; 3844 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3845 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 3846 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 3847 3848 if (state == arc_l2c_only) 3849 return; 3850 3851 ASSERT(bytes > 0); 3852 /* 3853 * Adapt the target size of the MRU list: 3854 * - if we just hit in the MRU ghost list, then increase 3855 * the target size of the MRU list. 3856 * - if we just hit in the MFU ghost list, then increase 3857 * the target size of the MFU list by decreasing the 3858 * target size of the MRU list. 3859 */ 3860 if (state == arc_mru_ghost) { 3861 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 3862 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3863 3864 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3865 } else if (state == arc_mfu_ghost) { 3866 uint64_t delta; 3867 3868 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 3869 mult = MIN(mult, 10); 3870 3871 delta = MIN(bytes * mult, arc_p); 3872 arc_p = MAX(arc_p_min, arc_p - delta); 3873 } 3874 ASSERT((int64_t)arc_p >= 0); 3875 3876 if (arc_reclaim_needed()) { 3877 cv_signal(&arc_reclaim_thread_cv); 3878 return; 3879 } 3880 3881 if (arc_no_grow) 3882 return; 3883 3884 if (arc_c >= arc_c_max) 3885 return; 3886 3887 /* 3888 * If we're within (2 * maxblocksize) bytes of the target 3889 * cache size, increment the target cache size 3890 */ 3891 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3892 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3893 atomic_add_64(&arc_c, (int64_t)bytes); 3894 if (arc_c > arc_c_max) 3895 arc_c = arc_c_max; 3896 else if (state == arc_anon) 3897 atomic_add_64(&arc_p, (int64_t)bytes); 3898 if (arc_p > arc_c) 3899 arc_p = arc_c; 3900 } 3901 ASSERT((int64_t)arc_p >= 0); 3902} 3903 3904/* 3905 * Check if arc_size has grown past our upper threshold, determined by 3906 * zfs_arc_overflow_shift. 3907 */ 3908static boolean_t 3909arc_is_overflowing(void) 3910{ 3911 /* Always allow at least one block of overflow */ 3912 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 3913 arc_c >> zfs_arc_overflow_shift); 3914 3915 return (arc_size >= arc_c + overflow); 3916} 3917 3918/* 3919 * The buffer, supplied as the first argument, needs a data block. If we 3920 * are hitting the hard limit for the cache size, we must sleep, waiting 3921 * for the eviction thread to catch up. If we're past the target size 3922 * but below the hard limit, we'll only signal the reclaim thread and 3923 * continue on. 3924 */ 3925static void 3926arc_get_data_buf(arc_buf_t *buf) 3927{ 3928 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3929 uint64_t size = buf->b_hdr->b_size; 3930 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3931 3932 arc_adapt(size, state); 3933 3934 /* 3935 * If arc_size is currently overflowing, and has grown past our 3936 * upper limit, we must be adding data faster than the evict 3937 * thread can evict. Thus, to ensure we don't compound the 3938 * problem by adding more data and forcing arc_size to grow even 3939 * further past it's target size, we halt and wait for the 3940 * eviction thread to catch up. 3941 * 3942 * It's also possible that the reclaim thread is unable to evict 3943 * enough buffers to get arc_size below the overflow limit (e.g. 3944 * due to buffers being un-evictable, or hash lock collisions). 3945 * In this case, we want to proceed regardless if we're 3946 * overflowing; thus we don't use a while loop here. 3947 */ 3948 if (arc_is_overflowing()) { 3949 mutex_enter(&arc_reclaim_lock); 3950 3951 /* 3952 * Now that we've acquired the lock, we may no longer be 3953 * over the overflow limit, lets check. 3954 * 3955 * We're ignoring the case of spurious wake ups. If that 3956 * were to happen, it'd let this thread consume an ARC 3957 * buffer before it should have (i.e. before we're under 3958 * the overflow limit and were signalled by the reclaim 3959 * thread). As long as that is a rare occurrence, it 3960 * shouldn't cause any harm. 3961 */ 3962 if (arc_is_overflowing()) { 3963 cv_signal(&arc_reclaim_thread_cv); 3964 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 3965 } 3966 3967 mutex_exit(&arc_reclaim_lock); 3968 } 3969 3970 if (type == ARC_BUFC_METADATA) { 3971 buf->b_data = zio_buf_alloc(size); 3972 arc_space_consume(size, ARC_SPACE_META); 3973 } else { 3974 ASSERT(type == ARC_BUFC_DATA); 3975 buf->b_data = zio_data_buf_alloc(size); 3976 arc_space_consume(size, ARC_SPACE_DATA); 3977 } 3978 3979 /* 3980 * Update the state size. Note that ghost states have a 3981 * "ghost size" and so don't need to be updated. 3982 */ 3983 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3984 arc_buf_hdr_t *hdr = buf->b_hdr; 3985 arc_state_t *state = hdr->b_l1hdr.b_state; 3986 3987 (void) refcount_add_many(&state->arcs_size, size, buf); 3988 3989 /* 3990 * If this is reached via arc_read, the link is 3991 * protected by the hash lock. If reached via 3992 * arc_buf_alloc, the header should not be accessed by 3993 * any other thread. And, if reached via arc_read_done, 3994 * the hash lock will protect it if it's found in the 3995 * hash table; otherwise no other thread should be 3996 * trying to [add|remove]_reference it. 3997 */ 3998 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 3999 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4000 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 4001 size); 4002 } 4003 /* 4004 * If we are growing the cache, and we are adding anonymous 4005 * data, and we have outgrown arc_p, update arc_p 4006 */ 4007 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4008 (refcount_count(&arc_anon->arcs_size) + 4009 refcount_count(&arc_mru->arcs_size) > arc_p)) 4010 arc_p = MIN(arc_c, arc_p + size); 4011 } 4012 ARCSTAT_BUMP(arcstat_allocated); 4013} 4014 4015/* 4016 * This routine is called whenever a buffer is accessed. 4017 * NOTE: the hash lock is dropped in this function. 4018 */ 4019static void 4020arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4021{ 4022 clock_t now; 4023 4024 ASSERT(MUTEX_HELD(hash_lock)); 4025 ASSERT(HDR_HAS_L1HDR(hdr)); 4026 4027 if (hdr->b_l1hdr.b_state == arc_anon) { 4028 /* 4029 * This buffer is not in the cache, and does not 4030 * appear in our "ghost" list. Add the new buffer 4031 * to the MRU state. 4032 */ 4033 4034 ASSERT0(hdr->b_l1hdr.b_arc_access); 4035 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4036 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4037 arc_change_state(arc_mru, hdr, hash_lock); 4038 4039 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4040 now = ddi_get_lbolt(); 4041 4042 /* 4043 * If this buffer is here because of a prefetch, then either: 4044 * - clear the flag if this is a "referencing" read 4045 * (any subsequent access will bump this into the MFU state). 4046 * or 4047 * - move the buffer to the head of the list if this is 4048 * another prefetch (to make it less likely to be evicted). 4049 */ 4050 if (HDR_PREFETCH(hdr)) { 4051 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4052 /* link protected by hash lock */ 4053 ASSERT(multilist_link_active( 4054 &hdr->b_l1hdr.b_arc_node)); 4055 } else { 4056 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4057 ARCSTAT_BUMP(arcstat_mru_hits); 4058 } 4059 hdr->b_l1hdr.b_arc_access = now; 4060 return; 4061 } 4062 4063 /* 4064 * This buffer has been "accessed" only once so far, 4065 * but it is still in the cache. Move it to the MFU 4066 * state. 4067 */ 4068 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4069 /* 4070 * More than 125ms have passed since we 4071 * instantiated this buffer. Move it to the 4072 * most frequently used state. 4073 */ 4074 hdr->b_l1hdr.b_arc_access = now; 4075 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4076 arc_change_state(arc_mfu, hdr, hash_lock); 4077 } 4078 ARCSTAT_BUMP(arcstat_mru_hits); 4079 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4080 arc_state_t *new_state; 4081 /* 4082 * This buffer has been "accessed" recently, but 4083 * was evicted from the cache. Move it to the 4084 * MFU state. 4085 */ 4086 4087 if (HDR_PREFETCH(hdr)) { 4088 new_state = arc_mru; 4089 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4090 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 4091 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4092 } else { 4093 new_state = arc_mfu; 4094 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4095 } 4096 4097 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4098 arc_change_state(new_state, hdr, hash_lock); 4099 4100 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4101 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4102 /* 4103 * This buffer has been accessed more than once and is 4104 * still in the cache. Keep it in the MFU state. 4105 * 4106 * NOTE: an add_reference() that occurred when we did 4107 * the arc_read() will have kicked this off the list. 4108 * If it was a prefetch, we will explicitly move it to 4109 * the head of the list now. 4110 */ 4111 if ((HDR_PREFETCH(hdr)) != 0) { 4112 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4113 /* link protected by hash_lock */ 4114 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4115 } 4116 ARCSTAT_BUMP(arcstat_mfu_hits); 4117 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4118 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4119 arc_state_t *new_state = arc_mfu; 4120 /* 4121 * This buffer has been accessed more than once but has 4122 * been evicted from the cache. Move it back to the 4123 * MFU state. 4124 */ 4125 4126 if (HDR_PREFETCH(hdr)) { 4127 /* 4128 * This is a prefetch access... 4129 * move this block back to the MRU state. 4130 */ 4131 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4132 new_state = arc_mru; 4133 } 4134 4135 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4136 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4137 arc_change_state(new_state, hdr, hash_lock); 4138 4139 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4140 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4141 /* 4142 * This buffer is on the 2nd Level ARC. 4143 */ 4144 4145 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4146 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4147 arc_change_state(arc_mfu, hdr, hash_lock); 4148 } else { 4149 ASSERT(!"invalid arc state"); 4150 } 4151} 4152 4153/* a generic arc_done_func_t which you can use */ 4154/* ARGSUSED */ 4155void 4156arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4157{ 4158 if (zio == NULL || zio->io_error == 0) 4159 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 4160 VERIFY(arc_buf_remove_ref(buf, arg)); 4161} 4162 4163/* a generic arc_done_func_t */ 4164void 4165arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4166{ 4167 arc_buf_t **bufp = arg; 4168 if (zio && zio->io_error) { 4169 VERIFY(arc_buf_remove_ref(buf, arg)); 4170 *bufp = NULL; 4171 } else { 4172 *bufp = buf; 4173 ASSERT(buf->b_data); 4174 } 4175} 4176 4177static void 4178arc_read_done(zio_t *zio) 4179{ 4180 arc_buf_hdr_t *hdr; 4181 arc_buf_t *buf; 4182 arc_buf_t *abuf; /* buffer we're assigning to callback */ 4183 kmutex_t *hash_lock = NULL; 4184 arc_callback_t *callback_list, *acb; 4185 int freeable = FALSE; 4186 4187 buf = zio->io_private; 4188 hdr = buf->b_hdr; 4189 4190 /* 4191 * The hdr was inserted into hash-table and removed from lists 4192 * prior to starting I/O. We should find this header, since 4193 * it's in the hash table, and it should be legit since it's 4194 * not possible to evict it during the I/O. The only possible 4195 * reason for it not to be found is if we were freed during the 4196 * read. 4197 */ 4198 if (HDR_IN_HASH_TABLE(hdr)) { 4199 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4200 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4201 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4202 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4203 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4204 4205 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4206 &hash_lock); 4207 4208 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 4209 hash_lock == NULL) || 4210 (found == hdr && 4211 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4212 (found == hdr && HDR_L2_READING(hdr))); 4213 } 4214 4215 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 4216 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4217 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 4218 4219 /* byteswap if necessary */ 4220 callback_list = hdr->b_l1hdr.b_acb; 4221 ASSERT(callback_list != NULL); 4222 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 4223 dmu_object_byteswap_t bswap = 4224 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4225 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 4226 byteswap_uint64_array : 4227 dmu_ot_byteswap[bswap].ob_func; 4228 func(buf->b_data, hdr->b_size); 4229 } 4230 4231 arc_cksum_compute(buf, B_FALSE); 4232#ifdef illumos 4233 arc_buf_watch(buf); 4234#endif 4235 4236 if (hash_lock && zio->io_error == 0 && 4237 hdr->b_l1hdr.b_state == arc_anon) { 4238 /* 4239 * Only call arc_access on anonymous buffers. This is because 4240 * if we've issued an I/O for an evicted buffer, we've already 4241 * called arc_access (to prevent any simultaneous readers from 4242 * getting confused). 4243 */ 4244 arc_access(hdr, hash_lock); 4245 } 4246 4247 /* create copies of the data buffer for the callers */ 4248 abuf = buf; 4249 for (acb = callback_list; acb; acb = acb->acb_next) { 4250 if (acb->acb_done) { 4251 if (abuf == NULL) { 4252 ARCSTAT_BUMP(arcstat_duplicate_reads); 4253 abuf = arc_buf_clone(buf); 4254 } 4255 acb->acb_buf = abuf; 4256 abuf = NULL; 4257 } 4258 } 4259 hdr->b_l1hdr.b_acb = NULL; 4260 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4261 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 4262 if (abuf == buf) { 4263 ASSERT(buf->b_efunc == NULL); 4264 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4265 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4266 } 4267 4268 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4269 callback_list != NULL); 4270 4271 if (zio->io_error != 0) { 4272 hdr->b_flags |= ARC_FLAG_IO_ERROR; 4273 if (hdr->b_l1hdr.b_state != arc_anon) 4274 arc_change_state(arc_anon, hdr, hash_lock); 4275 if (HDR_IN_HASH_TABLE(hdr)) 4276 buf_hash_remove(hdr); 4277 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4278 } 4279 4280 /* 4281 * Broadcast before we drop the hash_lock to avoid the possibility 4282 * that the hdr (and hence the cv) might be freed before we get to 4283 * the cv_broadcast(). 4284 */ 4285 cv_broadcast(&hdr->b_l1hdr.b_cv); 4286 4287 if (hash_lock != NULL) { 4288 mutex_exit(hash_lock); 4289 } else { 4290 /* 4291 * This block was freed while we waited for the read to 4292 * complete. It has been removed from the hash table and 4293 * moved to the anonymous state (so that it won't show up 4294 * in the cache). 4295 */ 4296 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4297 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4298 } 4299 4300 /* execute each callback and free its structure */ 4301 while ((acb = callback_list) != NULL) { 4302 if (acb->acb_done) 4303 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4304 4305 if (acb->acb_zio_dummy != NULL) { 4306 acb->acb_zio_dummy->io_error = zio->io_error; 4307 zio_nowait(acb->acb_zio_dummy); 4308 } 4309 4310 callback_list = acb->acb_next; 4311 kmem_free(acb, sizeof (arc_callback_t)); 4312 } 4313 4314 if (freeable) 4315 arc_hdr_destroy(hdr); 4316} 4317 4318/* 4319 * "Read" the block at the specified DVA (in bp) via the 4320 * cache. If the block is found in the cache, invoke the provided 4321 * callback immediately and return. Note that the `zio' parameter 4322 * in the callback will be NULL in this case, since no IO was 4323 * required. If the block is not in the cache pass the read request 4324 * on to the spa with a substitute callback function, so that the 4325 * requested block will be added to the cache. 4326 * 4327 * If a read request arrives for a block that has a read in-progress, 4328 * either wait for the in-progress read to complete (and return the 4329 * results); or, if this is a read with a "done" func, add a record 4330 * to the read to invoke the "done" func when the read completes, 4331 * and return; or just return. 4332 * 4333 * arc_read_done() will invoke all the requested "done" functions 4334 * for readers of this block. 4335 */ 4336int 4337arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4338 void *private, zio_priority_t priority, int zio_flags, 4339 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4340{ 4341 arc_buf_hdr_t *hdr = NULL; 4342 arc_buf_t *buf = NULL; 4343 kmutex_t *hash_lock = NULL; 4344 zio_t *rzio; 4345 uint64_t guid = spa_load_guid(spa); 4346 4347 ASSERT(!BP_IS_EMBEDDED(bp) || 4348 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4349 4350top: 4351 if (!BP_IS_EMBEDDED(bp)) { 4352 /* 4353 * Embedded BP's have no DVA and require no I/O to "read". 4354 * Create an anonymous arc buf to back it. 4355 */ 4356 hdr = buf_hash_find(guid, bp, &hash_lock); 4357 } 4358 4359 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 4360 4361 *arc_flags |= ARC_FLAG_CACHED; 4362 4363 if (HDR_IO_IN_PROGRESS(hdr)) { 4364 4365 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4366 priority == ZIO_PRIORITY_SYNC_READ) { 4367 /* 4368 * This sync read must wait for an 4369 * in-progress async read (e.g. a predictive 4370 * prefetch). Async reads are queued 4371 * separately at the vdev_queue layer, so 4372 * this is a form of priority inversion. 4373 * Ideally, we would "inherit" the demand 4374 * i/o's priority by moving the i/o from 4375 * the async queue to the synchronous queue, 4376 * but there is currently no mechanism to do 4377 * so. Track this so that we can evaluate 4378 * the magnitude of this potential performance 4379 * problem. 4380 * 4381 * Note that if the prefetch i/o is already 4382 * active (has been issued to the device), 4383 * the prefetch improved performance, because 4384 * we issued it sooner than we would have 4385 * without the prefetch. 4386 */ 4387 DTRACE_PROBE1(arc__sync__wait__for__async, 4388 arc_buf_hdr_t *, hdr); 4389 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4390 } 4391 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4392 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4393 } 4394 4395 if (*arc_flags & ARC_FLAG_WAIT) { 4396 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4397 mutex_exit(hash_lock); 4398 goto top; 4399 } 4400 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4401 4402 if (done) { 4403 arc_callback_t *acb = NULL; 4404 4405 acb = kmem_zalloc(sizeof (arc_callback_t), 4406 KM_SLEEP); 4407 acb->acb_done = done; 4408 acb->acb_private = private; 4409 if (pio != NULL) 4410 acb->acb_zio_dummy = zio_null(pio, 4411 spa, NULL, NULL, NULL, zio_flags); 4412 4413 ASSERT(acb->acb_done != NULL); 4414 acb->acb_next = hdr->b_l1hdr.b_acb; 4415 hdr->b_l1hdr.b_acb = acb; 4416 add_reference(hdr, hash_lock, private); 4417 mutex_exit(hash_lock); 4418 return (0); 4419 } 4420 mutex_exit(hash_lock); 4421 return (0); 4422 } 4423 4424 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4425 hdr->b_l1hdr.b_state == arc_mfu); 4426 4427 if (done) { 4428 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4429 /* 4430 * This is a demand read which does not have to 4431 * wait for i/o because we did a predictive 4432 * prefetch i/o for it, which has completed. 4433 */ 4434 DTRACE_PROBE1( 4435 arc__demand__hit__predictive__prefetch, 4436 arc_buf_hdr_t *, hdr); 4437 ARCSTAT_BUMP( 4438 arcstat_demand_hit_predictive_prefetch); 4439 hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH; 4440 } 4441 add_reference(hdr, hash_lock, private); 4442 /* 4443 * If this block is already in use, create a new 4444 * copy of the data so that we will be guaranteed 4445 * that arc_release() will always succeed. 4446 */ 4447 buf = hdr->b_l1hdr.b_buf; 4448 ASSERT(buf); 4449 ASSERT(buf->b_data); 4450 if (HDR_BUF_AVAILABLE(hdr)) { 4451 ASSERT(buf->b_efunc == NULL); 4452 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4453 } else { 4454 buf = arc_buf_clone(buf); 4455 } 4456 4457 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4458 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4459 hdr->b_flags |= ARC_FLAG_PREFETCH; 4460 } 4461 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4462 arc_access(hdr, hash_lock); 4463 if (*arc_flags & ARC_FLAG_L2CACHE) 4464 hdr->b_flags |= ARC_FLAG_L2CACHE; 4465 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4466 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4467 mutex_exit(hash_lock); 4468 ARCSTAT_BUMP(arcstat_hits); 4469 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4470 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4471 data, metadata, hits); 4472 4473 if (done) 4474 done(NULL, buf, private); 4475 } else { 4476 uint64_t size = BP_GET_LSIZE(bp); 4477 arc_callback_t *acb; 4478 vdev_t *vd = NULL; 4479 uint64_t addr = 0; 4480 boolean_t devw = B_FALSE; 4481 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4482 int32_t b_asize = 0; 4483 4484 if (hdr == NULL) { 4485 /* this block is not in the cache */ 4486 arc_buf_hdr_t *exists = NULL; 4487 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4488 buf = arc_buf_alloc(spa, size, private, type); 4489 hdr = buf->b_hdr; 4490 if (!BP_IS_EMBEDDED(bp)) { 4491 hdr->b_dva = *BP_IDENTITY(bp); 4492 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4493 exists = buf_hash_insert(hdr, &hash_lock); 4494 } 4495 if (exists != NULL) { 4496 /* somebody beat us to the hash insert */ 4497 mutex_exit(hash_lock); 4498 buf_discard_identity(hdr); 4499 (void) arc_buf_remove_ref(buf, private); 4500 goto top; /* restart the IO request */ 4501 } 4502 4503 /* 4504 * If there is a callback, we pass our reference to 4505 * it; otherwise we remove our reference. 4506 */ 4507 if (done == NULL) { 4508 (void) remove_reference(hdr, hash_lock, 4509 private); 4510 } 4511 if (*arc_flags & ARC_FLAG_PREFETCH) 4512 hdr->b_flags |= ARC_FLAG_PREFETCH; 4513 if (*arc_flags & ARC_FLAG_L2CACHE) 4514 hdr->b_flags |= ARC_FLAG_L2CACHE; 4515 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4516 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4517 if (BP_GET_LEVEL(bp) > 0) 4518 hdr->b_flags |= ARC_FLAG_INDIRECT; 4519 } else { 4520 /* 4521 * This block is in the ghost cache. If it was L2-only 4522 * (and thus didn't have an L1 hdr), we realloc the 4523 * header to add an L1 hdr. 4524 */ 4525 if (!HDR_HAS_L1HDR(hdr)) { 4526 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4527 hdr_full_cache); 4528 } 4529 4530 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4531 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4532 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4533 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4534 4535 /* 4536 * If there is a callback, we pass a reference to it. 4537 */ 4538 if (done != NULL) 4539 add_reference(hdr, hash_lock, private); 4540 if (*arc_flags & ARC_FLAG_PREFETCH) 4541 hdr->b_flags |= ARC_FLAG_PREFETCH; 4542 if (*arc_flags & ARC_FLAG_L2CACHE) 4543 hdr->b_flags |= ARC_FLAG_L2CACHE; 4544 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4545 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4546 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4547 buf->b_hdr = hdr; 4548 buf->b_data = NULL; 4549 buf->b_efunc = NULL; 4550 buf->b_private = NULL; 4551 buf->b_next = NULL; 4552 hdr->b_l1hdr.b_buf = buf; 4553 ASSERT0(hdr->b_l1hdr.b_datacnt); 4554 hdr->b_l1hdr.b_datacnt = 1; 4555 arc_get_data_buf(buf); 4556 arc_access(hdr, hash_lock); 4557 } 4558 4559 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4560 hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH; 4561 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4562 4563 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4564 acb->acb_done = done; 4565 acb->acb_private = private; 4566 4567 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4568 hdr->b_l1hdr.b_acb = acb; 4569 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4570 4571 if (HDR_HAS_L2HDR(hdr) && 4572 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4573 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4574 addr = hdr->b_l2hdr.b_daddr; 4575 b_compress = hdr->b_l2hdr.b_compress; 4576 b_asize = hdr->b_l2hdr.b_asize; 4577 /* 4578 * Lock out device removal. 4579 */ 4580 if (vdev_is_dead(vd) || 4581 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4582 vd = NULL; 4583 } 4584 4585 if (hash_lock != NULL) 4586 mutex_exit(hash_lock); 4587 4588 /* 4589 * At this point, we have a level 1 cache miss. Try again in 4590 * L2ARC if possible. 4591 */ 4592 ASSERT3U(hdr->b_size, ==, size); 4593 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4594 uint64_t, size, zbookmark_phys_t *, zb); 4595 ARCSTAT_BUMP(arcstat_misses); 4596 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4597 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4598 data, metadata, misses); 4599#ifdef _KERNEL 4600 curthread->td_ru.ru_inblock++; 4601#endif 4602 4603 if (priority == ZIO_PRIORITY_ASYNC_READ) 4604 hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ; 4605 else 4606 hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ; 4607 4608 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4609 /* 4610 * Read from the L2ARC if the following are true: 4611 * 1. The L2ARC vdev was previously cached. 4612 * 2. This buffer still has L2ARC metadata. 4613 * 3. This buffer isn't currently writing to the L2ARC. 4614 * 4. The L2ARC entry wasn't evicted, which may 4615 * also have invalidated the vdev. 4616 * 5. This isn't prefetch and l2arc_noprefetch is set. 4617 */ 4618 if (HDR_HAS_L2HDR(hdr) && 4619 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4620 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4621 l2arc_read_callback_t *cb; 4622 void* b_data; 4623 4624 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4625 ARCSTAT_BUMP(arcstat_l2_hits); 4626 4627 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4628 KM_SLEEP); 4629 cb->l2rcb_buf = buf; 4630 cb->l2rcb_spa = spa; 4631 cb->l2rcb_bp = *bp; 4632 cb->l2rcb_zb = *zb; 4633 cb->l2rcb_flags = zio_flags; 4634 cb->l2rcb_compress = b_compress; 4635 if (b_asize > hdr->b_size) { 4636 ASSERT3U(b_compress, ==, 4637 ZIO_COMPRESS_OFF); 4638 b_data = zio_data_buf_alloc(b_asize); 4639 cb->l2rcb_data = b_data; 4640 } else { 4641 b_data = buf->b_data; 4642 } 4643 4644 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4645 addr + size < vd->vdev_psize - 4646 VDEV_LABEL_END_SIZE); 4647 4648 /* 4649 * l2arc read. The SCL_L2ARC lock will be 4650 * released by l2arc_read_done(). 4651 * Issue a null zio if the underlying buffer 4652 * was squashed to zero size by compression. 4653 */ 4654 if (b_compress == ZIO_COMPRESS_EMPTY) { 4655 ASSERT3U(b_asize, ==, 0); 4656 rzio = zio_null(pio, spa, vd, 4657 l2arc_read_done, cb, 4658 zio_flags | ZIO_FLAG_DONT_CACHE | 4659 ZIO_FLAG_CANFAIL | 4660 ZIO_FLAG_DONT_PROPAGATE | 4661 ZIO_FLAG_DONT_RETRY); 4662 } else { 4663 rzio = zio_read_phys(pio, vd, addr, 4664 b_asize, b_data, 4665 ZIO_CHECKSUM_OFF, 4666 l2arc_read_done, cb, priority, 4667 zio_flags | ZIO_FLAG_DONT_CACHE | 4668 ZIO_FLAG_CANFAIL | 4669 ZIO_FLAG_DONT_PROPAGATE | 4670 ZIO_FLAG_DONT_RETRY, B_FALSE); 4671 } 4672 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4673 zio_t *, rzio); 4674 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4675 4676 if (*arc_flags & ARC_FLAG_NOWAIT) { 4677 zio_nowait(rzio); 4678 return (0); 4679 } 4680 4681 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4682 if (zio_wait(rzio) == 0) 4683 return (0); 4684 4685 /* l2arc read error; goto zio_read() */ 4686 } else { 4687 DTRACE_PROBE1(l2arc__miss, 4688 arc_buf_hdr_t *, hdr); 4689 ARCSTAT_BUMP(arcstat_l2_misses); 4690 if (HDR_L2_WRITING(hdr)) 4691 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4692 spa_config_exit(spa, SCL_L2ARC, vd); 4693 } 4694 } else { 4695 if (vd != NULL) 4696 spa_config_exit(spa, SCL_L2ARC, vd); 4697 if (l2arc_ndev != 0) { 4698 DTRACE_PROBE1(l2arc__miss, 4699 arc_buf_hdr_t *, hdr); 4700 ARCSTAT_BUMP(arcstat_l2_misses); 4701 } 4702 } 4703 4704 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4705 arc_read_done, buf, priority, zio_flags, zb); 4706 4707 if (*arc_flags & ARC_FLAG_WAIT) 4708 return (zio_wait(rzio)); 4709 4710 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4711 zio_nowait(rzio); 4712 } 4713 return (0); 4714} 4715 4716void 4717arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4718{ 4719 ASSERT(buf->b_hdr != NULL); 4720 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4721 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4722 func == NULL); 4723 ASSERT(buf->b_efunc == NULL); 4724 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4725 4726 buf->b_efunc = func; 4727 buf->b_private = private; 4728} 4729 4730/* 4731 * Notify the arc that a block was freed, and thus will never be used again. 4732 */ 4733void 4734arc_freed(spa_t *spa, const blkptr_t *bp) 4735{ 4736 arc_buf_hdr_t *hdr; 4737 kmutex_t *hash_lock; 4738 uint64_t guid = spa_load_guid(spa); 4739 4740 ASSERT(!BP_IS_EMBEDDED(bp)); 4741 4742 hdr = buf_hash_find(guid, bp, &hash_lock); 4743 if (hdr == NULL) 4744 return; 4745 if (HDR_BUF_AVAILABLE(hdr)) { 4746 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4747 add_reference(hdr, hash_lock, FTAG); 4748 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4749 mutex_exit(hash_lock); 4750 4751 arc_release(buf, FTAG); 4752 (void) arc_buf_remove_ref(buf, FTAG); 4753 } else { 4754 mutex_exit(hash_lock); 4755 } 4756 4757} 4758 4759/* 4760 * Clear the user eviction callback set by arc_set_callback(), first calling 4761 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4762 * clearing the callback may result in the arc_buf being destroyed. However, 4763 * it will not result in the *last* arc_buf being destroyed, hence the data 4764 * will remain cached in the ARC. We make a copy of the arc buffer here so 4765 * that we can process the callback without holding any locks. 4766 * 4767 * It's possible that the callback is already in the process of being cleared 4768 * by another thread. In this case we can not clear the callback. 4769 * 4770 * Returns B_TRUE if the callback was successfully called and cleared. 4771 */ 4772boolean_t 4773arc_clear_callback(arc_buf_t *buf) 4774{ 4775 arc_buf_hdr_t *hdr; 4776 kmutex_t *hash_lock; 4777 arc_evict_func_t *efunc = buf->b_efunc; 4778 void *private = buf->b_private; 4779 4780 mutex_enter(&buf->b_evict_lock); 4781 hdr = buf->b_hdr; 4782 if (hdr == NULL) { 4783 /* 4784 * We are in arc_do_user_evicts(). 4785 */ 4786 ASSERT(buf->b_data == NULL); 4787 mutex_exit(&buf->b_evict_lock); 4788 return (B_FALSE); 4789 } else if (buf->b_data == NULL) { 4790 /* 4791 * We are on the eviction list; process this buffer now 4792 * but let arc_do_user_evicts() do the reaping. 4793 */ 4794 buf->b_efunc = NULL; 4795 mutex_exit(&buf->b_evict_lock); 4796 VERIFY0(efunc(private)); 4797 return (B_TRUE); 4798 } 4799 hash_lock = HDR_LOCK(hdr); 4800 mutex_enter(hash_lock); 4801 hdr = buf->b_hdr; 4802 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4803 4804 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4805 hdr->b_l1hdr.b_datacnt); 4806 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4807 hdr->b_l1hdr.b_state == arc_mfu); 4808 4809 buf->b_efunc = NULL; 4810 buf->b_private = NULL; 4811 4812 if (hdr->b_l1hdr.b_datacnt > 1) { 4813 mutex_exit(&buf->b_evict_lock); 4814 arc_buf_destroy(buf, TRUE); 4815 } else { 4816 ASSERT(buf == hdr->b_l1hdr.b_buf); 4817 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4818 mutex_exit(&buf->b_evict_lock); 4819 } 4820 4821 mutex_exit(hash_lock); 4822 VERIFY0(efunc(private)); 4823 return (B_TRUE); 4824} 4825 4826/* 4827 * Release this buffer from the cache, making it an anonymous buffer. This 4828 * must be done after a read and prior to modifying the buffer contents. 4829 * If the buffer has more than one reference, we must make 4830 * a new hdr for the buffer. 4831 */ 4832void 4833arc_release(arc_buf_t *buf, void *tag) 4834{ 4835 arc_buf_hdr_t *hdr = buf->b_hdr; 4836 4837 /* 4838 * It would be nice to assert that if it's DMU metadata (level > 4839 * 0 || it's the dnode file), then it must be syncing context. 4840 * But we don't know that information at this level. 4841 */ 4842 4843 mutex_enter(&buf->b_evict_lock); 4844 4845 ASSERT(HDR_HAS_L1HDR(hdr)); 4846 4847 /* 4848 * We don't grab the hash lock prior to this check, because if 4849 * the buffer's header is in the arc_anon state, it won't be 4850 * linked into the hash table. 4851 */ 4852 if (hdr->b_l1hdr.b_state == arc_anon) { 4853 mutex_exit(&buf->b_evict_lock); 4854 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4855 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4856 ASSERT(!HDR_HAS_L2HDR(hdr)); 4857 ASSERT(BUF_EMPTY(hdr)); 4858 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4859 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4860 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4861 4862 ASSERT3P(buf->b_efunc, ==, NULL); 4863 ASSERT3P(buf->b_private, ==, NULL); 4864 4865 hdr->b_l1hdr.b_arc_access = 0; 4866 arc_buf_thaw(buf); 4867 4868 return; 4869 } 4870 4871 kmutex_t *hash_lock = HDR_LOCK(hdr); 4872 mutex_enter(hash_lock); 4873 4874 /* 4875 * This assignment is only valid as long as the hash_lock is 4876 * held, we must be careful not to reference state or the 4877 * b_state field after dropping the lock. 4878 */ 4879 arc_state_t *state = hdr->b_l1hdr.b_state; 4880 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4881 ASSERT3P(state, !=, arc_anon); 4882 4883 /* this buffer is not on any list */ 4884 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4885 4886 if (HDR_HAS_L2HDR(hdr)) { 4887 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4888 4889 /* 4890 * We have to recheck this conditional again now that 4891 * we're holding the l2ad_mtx to prevent a race with 4892 * another thread which might be concurrently calling 4893 * l2arc_evict(). In that case, l2arc_evict() might have 4894 * destroyed the header's L2 portion as we were waiting 4895 * to acquire the l2ad_mtx. 4896 */ 4897 if (HDR_HAS_L2HDR(hdr)) { 4898 l2arc_trim(hdr); 4899 arc_hdr_l2hdr_destroy(hdr); 4900 } 4901 4902 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4903 } 4904 4905 /* 4906 * Do we have more than one buf? 4907 */ 4908 if (hdr->b_l1hdr.b_datacnt > 1) { 4909 arc_buf_hdr_t *nhdr; 4910 arc_buf_t **bufp; 4911 uint64_t blksz = hdr->b_size; 4912 uint64_t spa = hdr->b_spa; 4913 arc_buf_contents_t type = arc_buf_type(hdr); 4914 uint32_t flags = hdr->b_flags; 4915 4916 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4917 /* 4918 * Pull the data off of this hdr and attach it to 4919 * a new anonymous hdr. 4920 */ 4921 (void) remove_reference(hdr, hash_lock, tag); 4922 bufp = &hdr->b_l1hdr.b_buf; 4923 while (*bufp != buf) 4924 bufp = &(*bufp)->b_next; 4925 *bufp = buf->b_next; 4926 buf->b_next = NULL; 4927 4928 ASSERT3P(state, !=, arc_l2c_only); 4929 4930 (void) refcount_remove_many( 4931 &state->arcs_size, hdr->b_size, buf); 4932 4933 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4934 ASSERT3P(state, !=, arc_l2c_only); 4935 uint64_t *size = &state->arcs_lsize[type]; 4936 ASSERT3U(*size, >=, hdr->b_size); 4937 atomic_add_64(size, -hdr->b_size); 4938 } 4939 4940 /* 4941 * We're releasing a duplicate user data buffer, update 4942 * our statistics accordingly. 4943 */ 4944 if (HDR_ISTYPE_DATA(hdr)) { 4945 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4946 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4947 -hdr->b_size); 4948 } 4949 hdr->b_l1hdr.b_datacnt -= 1; 4950 arc_cksum_verify(buf); 4951#ifdef illumos 4952 arc_buf_unwatch(buf); 4953#endif 4954 4955 mutex_exit(hash_lock); 4956 4957 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4958 nhdr->b_size = blksz; 4959 nhdr->b_spa = spa; 4960 4961 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4962 nhdr->b_flags |= arc_bufc_to_flags(type); 4963 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4964 4965 nhdr->b_l1hdr.b_buf = buf; 4966 nhdr->b_l1hdr.b_datacnt = 1; 4967 nhdr->b_l1hdr.b_state = arc_anon; 4968 nhdr->b_l1hdr.b_arc_access = 0; 4969 nhdr->b_l1hdr.b_tmp_cdata = NULL; 4970 nhdr->b_freeze_cksum = NULL; 4971 4972 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4973 buf->b_hdr = nhdr; 4974 mutex_exit(&buf->b_evict_lock); 4975 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf); 4976 } else { 4977 mutex_exit(&buf->b_evict_lock); 4978 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4979 /* protected by hash lock, or hdr is on arc_anon */ 4980 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4981 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4982 arc_change_state(arc_anon, hdr, hash_lock); 4983 hdr->b_l1hdr.b_arc_access = 0; 4984 mutex_exit(hash_lock); 4985 4986 buf_discard_identity(hdr); 4987 arc_buf_thaw(buf); 4988 } 4989 buf->b_efunc = NULL; 4990 buf->b_private = NULL; 4991} 4992 4993int 4994arc_released(arc_buf_t *buf) 4995{ 4996 int released; 4997 4998 mutex_enter(&buf->b_evict_lock); 4999 released = (buf->b_data != NULL && 5000 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5001 mutex_exit(&buf->b_evict_lock); 5002 return (released); 5003} 5004 5005#ifdef ZFS_DEBUG 5006int 5007arc_referenced(arc_buf_t *buf) 5008{ 5009 int referenced; 5010 5011 mutex_enter(&buf->b_evict_lock); 5012 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5013 mutex_exit(&buf->b_evict_lock); 5014 return (referenced); 5015} 5016#endif 5017 5018static void 5019arc_write_ready(zio_t *zio) 5020{ 5021 arc_write_callback_t *callback = zio->io_private; 5022 arc_buf_t *buf = callback->awcb_buf; 5023 arc_buf_hdr_t *hdr = buf->b_hdr; 5024 5025 ASSERT(HDR_HAS_L1HDR(hdr)); 5026 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5027 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5028 callback->awcb_ready(zio, buf, callback->awcb_private); 5029 5030 /* 5031 * If the IO is already in progress, then this is a re-write 5032 * attempt, so we need to thaw and re-compute the cksum. 5033 * It is the responsibility of the callback to handle the 5034 * accounting for any re-write attempt. 5035 */ 5036 if (HDR_IO_IN_PROGRESS(hdr)) { 5037 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 5038 if (hdr->b_freeze_cksum != NULL) { 5039 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 5040 hdr->b_freeze_cksum = NULL; 5041 } 5042 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 5043 } 5044 arc_cksum_compute(buf, B_FALSE); 5045 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 5046} 5047 5048/* 5049 * The SPA calls this callback for each physical write that happens on behalf 5050 * of a logical write. See the comment in dbuf_write_physdone() for details. 5051 */ 5052static void 5053arc_write_physdone(zio_t *zio) 5054{ 5055 arc_write_callback_t *cb = zio->io_private; 5056 if (cb->awcb_physdone != NULL) 5057 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5058} 5059 5060static void 5061arc_write_done(zio_t *zio) 5062{ 5063 arc_write_callback_t *callback = zio->io_private; 5064 arc_buf_t *buf = callback->awcb_buf; 5065 arc_buf_hdr_t *hdr = buf->b_hdr; 5066 5067 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5068 5069 if (zio->io_error == 0) { 5070 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5071 buf_discard_identity(hdr); 5072 } else { 5073 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5074 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5075 } 5076 } else { 5077 ASSERT(BUF_EMPTY(hdr)); 5078 } 5079 5080 /* 5081 * If the block to be written was all-zero or compressed enough to be 5082 * embedded in the BP, no write was performed so there will be no 5083 * dva/birth/checksum. The buffer must therefore remain anonymous 5084 * (and uncached). 5085 */ 5086 if (!BUF_EMPTY(hdr)) { 5087 arc_buf_hdr_t *exists; 5088 kmutex_t *hash_lock; 5089 5090 ASSERT(zio->io_error == 0); 5091 5092 arc_cksum_verify(buf); 5093 5094 exists = buf_hash_insert(hdr, &hash_lock); 5095 if (exists != NULL) { 5096 /* 5097 * This can only happen if we overwrite for 5098 * sync-to-convergence, because we remove 5099 * buffers from the hash table when we arc_free(). 5100 */ 5101 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5102 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5103 panic("bad overwrite, hdr=%p exists=%p", 5104 (void *)hdr, (void *)exists); 5105 ASSERT(refcount_is_zero( 5106 &exists->b_l1hdr.b_refcnt)); 5107 arc_change_state(arc_anon, exists, hash_lock); 5108 mutex_exit(hash_lock); 5109 arc_hdr_destroy(exists); 5110 exists = buf_hash_insert(hdr, &hash_lock); 5111 ASSERT3P(exists, ==, NULL); 5112 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5113 /* nopwrite */ 5114 ASSERT(zio->io_prop.zp_nopwrite); 5115 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5116 panic("bad nopwrite, hdr=%p exists=%p", 5117 (void *)hdr, (void *)exists); 5118 } else { 5119 /* Dedup */ 5120 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 5121 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5122 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5123 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5124 } 5125 } 5126 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5127 /* if it's not anon, we are doing a scrub */ 5128 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5129 arc_access(hdr, hash_lock); 5130 mutex_exit(hash_lock); 5131 } else { 5132 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 5133 } 5134 5135 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5136 callback->awcb_done(zio, buf, callback->awcb_private); 5137 5138 kmem_free(callback, sizeof (arc_write_callback_t)); 5139} 5140 5141zio_t * 5142arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 5143 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 5144 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 5145 arc_done_func_t *done, void *private, zio_priority_t priority, 5146 int zio_flags, const zbookmark_phys_t *zb) 5147{ 5148 arc_buf_hdr_t *hdr = buf->b_hdr; 5149 arc_write_callback_t *callback; 5150 zio_t *zio; 5151 5152 ASSERT(ready != NULL); 5153 ASSERT(done != NULL); 5154 ASSERT(!HDR_IO_ERROR(hdr)); 5155 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5156 ASSERT(hdr->b_l1hdr.b_acb == NULL); 5157 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 5158 if (l2arc) 5159 hdr->b_flags |= ARC_FLAG_L2CACHE; 5160 if (l2arc_compress) 5161 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 5162 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5163 callback->awcb_ready = ready; 5164 callback->awcb_physdone = physdone; 5165 callback->awcb_done = done; 5166 callback->awcb_private = private; 5167 callback->awcb_buf = buf; 5168 5169 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 5170 arc_write_ready, arc_write_physdone, arc_write_done, callback, 5171 priority, zio_flags, zb); 5172 5173 return (zio); 5174} 5175 5176static int 5177arc_memory_throttle(uint64_t reserve, uint64_t txg) 5178{ 5179#ifdef _KERNEL 5180 uint64_t available_memory = ptob(freemem); 5181 static uint64_t page_load = 0; 5182 static uint64_t last_txg = 0; 5183 5184#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5185 available_memory = 5186 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5187#endif 5188 5189 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5190 return (0); 5191 5192 if (txg > last_txg) { 5193 last_txg = txg; 5194 page_load = 0; 5195 } 5196 /* 5197 * If we are in pageout, we know that memory is already tight, 5198 * the arc is already going to be evicting, so we just want to 5199 * continue to let page writes occur as quickly as possible. 5200 */ 5201 if (curproc == pageproc) { 5202 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5203 return (SET_ERROR(ERESTART)); 5204 /* Note: reserve is inflated, so we deflate */ 5205 page_load += reserve / 8; 5206 return (0); 5207 } else if (page_load > 0 && arc_reclaim_needed()) { 5208 /* memory is low, delay before restarting */ 5209 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5210 return (SET_ERROR(EAGAIN)); 5211 } 5212 page_load = 0; 5213#endif 5214 return (0); 5215} 5216 5217void 5218arc_tempreserve_clear(uint64_t reserve) 5219{ 5220 atomic_add_64(&arc_tempreserve, -reserve); 5221 ASSERT((int64_t)arc_tempreserve >= 0); 5222} 5223 5224int 5225arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5226{ 5227 int error; 5228 uint64_t anon_size; 5229 5230 if (reserve > arc_c/4 && !arc_no_grow) { 5231 arc_c = MIN(arc_c_max, reserve * 4); 5232 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5233 } 5234 if (reserve > arc_c) 5235 return (SET_ERROR(ENOMEM)); 5236 5237 /* 5238 * Don't count loaned bufs as in flight dirty data to prevent long 5239 * network delays from blocking transactions that are ready to be 5240 * assigned to a txg. 5241 */ 5242 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5243 arc_loaned_bytes), 0); 5244 5245 /* 5246 * Writes will, almost always, require additional memory allocations 5247 * in order to compress/encrypt/etc the data. We therefore need to 5248 * make sure that there is sufficient available memory for this. 5249 */ 5250 error = arc_memory_throttle(reserve, txg); 5251 if (error != 0) 5252 return (error); 5253 5254 /* 5255 * Throttle writes when the amount of dirty data in the cache 5256 * gets too large. We try to keep the cache less than half full 5257 * of dirty blocks so that our sync times don't grow too large. 5258 * Note: if two requests come in concurrently, we might let them 5259 * both succeed, when one of them should fail. Not a huge deal. 5260 */ 5261 5262 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5263 anon_size > arc_c / 4) { 5264 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5265 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5266 arc_tempreserve>>10, 5267 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 5268 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 5269 reserve>>10, arc_c>>10); 5270 return (SET_ERROR(ERESTART)); 5271 } 5272 atomic_add_64(&arc_tempreserve, reserve); 5273 return (0); 5274} 5275 5276static void 5277arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5278 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5279{ 5280 size->value.ui64 = refcount_count(&state->arcs_size); 5281 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 5282 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 5283} 5284 5285static int 5286arc_kstat_update(kstat_t *ksp, int rw) 5287{ 5288 arc_stats_t *as = ksp->ks_data; 5289 5290 if (rw == KSTAT_WRITE) { 5291 return (EACCES); 5292 } else { 5293 arc_kstat_update_state(arc_anon, 5294 &as->arcstat_anon_size, 5295 &as->arcstat_anon_evictable_data, 5296 &as->arcstat_anon_evictable_metadata); 5297 arc_kstat_update_state(arc_mru, 5298 &as->arcstat_mru_size, 5299 &as->arcstat_mru_evictable_data, 5300 &as->arcstat_mru_evictable_metadata); 5301 arc_kstat_update_state(arc_mru_ghost, 5302 &as->arcstat_mru_ghost_size, 5303 &as->arcstat_mru_ghost_evictable_data, 5304 &as->arcstat_mru_ghost_evictable_metadata); 5305 arc_kstat_update_state(arc_mfu, 5306 &as->arcstat_mfu_size, 5307 &as->arcstat_mfu_evictable_data, 5308 &as->arcstat_mfu_evictable_metadata); 5309 arc_kstat_update_state(arc_mfu_ghost, 5310 &as->arcstat_mfu_ghost_size, 5311 &as->arcstat_mfu_ghost_evictable_data, 5312 &as->arcstat_mfu_ghost_evictable_metadata); 5313 } 5314 5315 return (0); 5316} 5317 5318/* 5319 * This function *must* return indices evenly distributed between all 5320 * sublists of the multilist. This is needed due to how the ARC eviction 5321 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5322 * distributed between all sublists and uses this assumption when 5323 * deciding which sublist to evict from and how much to evict from it. 5324 */ 5325unsigned int 5326arc_state_multilist_index_func(multilist_t *ml, void *obj) 5327{ 5328 arc_buf_hdr_t *hdr = obj; 5329 5330 /* 5331 * We rely on b_dva to generate evenly distributed index 5332 * numbers using buf_hash below. So, as an added precaution, 5333 * let's make sure we never add empty buffers to the arc lists. 5334 */ 5335 ASSERT(!BUF_EMPTY(hdr)); 5336 5337 /* 5338 * The assumption here, is the hash value for a given 5339 * arc_buf_hdr_t will remain constant throughout it's lifetime 5340 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5341 * Thus, we don't need to store the header's sublist index 5342 * on insertion, as this index can be recalculated on removal. 5343 * 5344 * Also, the low order bits of the hash value are thought to be 5345 * distributed evenly. Otherwise, in the case that the multilist 5346 * has a power of two number of sublists, each sublists' usage 5347 * would not be evenly distributed. 5348 */ 5349 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5350 multilist_get_num_sublists(ml)); 5351} 5352 5353#ifdef _KERNEL 5354static eventhandler_tag arc_event_lowmem = NULL; 5355 5356static void 5357arc_lowmem(void *arg __unused, int howto __unused) 5358{ 5359 5360 mutex_enter(&arc_reclaim_lock); 5361 /* XXX: Memory deficit should be passed as argument. */ 5362 needfree = btoc(arc_c >> arc_shrink_shift); 5363 DTRACE_PROBE(arc__needfree); 5364 cv_signal(&arc_reclaim_thread_cv); 5365 5366 /* 5367 * It is unsafe to block here in arbitrary threads, because we can come 5368 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5369 * with ARC reclaim thread. 5370 */ 5371 if (curproc == pageproc) 5372 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5373 mutex_exit(&arc_reclaim_lock); 5374} 5375#endif 5376 5377void 5378arc_init(void) 5379{ 5380 int i, prefetch_tunable_set = 0; 5381 5382 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5383 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5384 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5385 5386 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 5387 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL); 5388 5389 /* Convert seconds to clock ticks */ 5390 arc_min_prefetch_lifespan = 1 * hz; 5391 5392 /* Start out with 1/8 of all memory */ 5393 arc_c = kmem_size() / 8; 5394 5395#ifdef illumos 5396#ifdef _KERNEL 5397 /* 5398 * On architectures where the physical memory can be larger 5399 * than the addressable space (intel in 32-bit mode), we may 5400 * need to limit the cache to 1/8 of VM size. 5401 */ 5402 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5403#endif 5404#endif /* illumos */ 5405 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 5406 arc_c_min = MAX(arc_c / 4, arc_abs_min); 5407 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 5408 if (arc_c * 8 >= 1 << 30) 5409 arc_c_max = (arc_c * 8) - (1 << 30); 5410 else 5411 arc_c_max = arc_c_min; 5412 arc_c_max = MAX(arc_c * 5, arc_c_max); 5413 5414 /* 5415 * In userland, there's only the memory pressure that we artificially 5416 * create (see arc_available_memory()). Don't let arc_c get too 5417 * small, because it can cause transactions to be larger than 5418 * arc_c, causing arc_tempreserve_space() to fail. 5419 */ 5420#ifndef _KERNEL 5421 arc_c_min = arc_c_max / 2; 5422#endif 5423 5424#ifdef _KERNEL 5425 /* 5426 * Allow the tunables to override our calculations if they are 5427 * reasonable. 5428 */ 5429 if (zfs_arc_max > arc_abs_min && zfs_arc_max < kmem_size()) 5430 arc_c_max = zfs_arc_max; 5431 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 5432 arc_c_min = zfs_arc_min; 5433#endif 5434 5435 arc_c = arc_c_max; 5436 arc_p = (arc_c >> 1); 5437 5438 /* limit meta-data to 1/4 of the arc capacity */ 5439 arc_meta_limit = arc_c_max / 4; 5440 5441 /* Allow the tunable to override if it is reasonable */ 5442 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 5443 arc_meta_limit = zfs_arc_meta_limit; 5444 5445 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 5446 arc_c_min = arc_meta_limit / 2; 5447 5448 if (zfs_arc_meta_min > 0) { 5449 arc_meta_min = zfs_arc_meta_min; 5450 } else { 5451 arc_meta_min = arc_c_min / 2; 5452 } 5453 5454 if (zfs_arc_grow_retry > 0) 5455 arc_grow_retry = zfs_arc_grow_retry; 5456 5457 if (zfs_arc_shrink_shift > 0) 5458 arc_shrink_shift = zfs_arc_shrink_shift; 5459 5460 /* 5461 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 5462 */ 5463 if (arc_no_grow_shift >= arc_shrink_shift) 5464 arc_no_grow_shift = arc_shrink_shift - 1; 5465 5466 if (zfs_arc_p_min_shift > 0) 5467 arc_p_min_shift = zfs_arc_p_min_shift; 5468 5469 if (zfs_arc_num_sublists_per_state < 1) 5470 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 5471 5472 /* if kmem_flags are set, lets try to use less memory */ 5473 if (kmem_debugging()) 5474 arc_c = arc_c / 2; 5475 if (arc_c < arc_c_min) 5476 arc_c = arc_c_min; 5477 5478 zfs_arc_min = arc_c_min; 5479 zfs_arc_max = arc_c_max; 5480 5481 arc_anon = &ARC_anon; 5482 arc_mru = &ARC_mru; 5483 arc_mru_ghost = &ARC_mru_ghost; 5484 arc_mfu = &ARC_mfu; 5485 arc_mfu_ghost = &ARC_mfu_ghost; 5486 arc_l2c_only = &ARC_l2c_only; 5487 arc_size = 0; 5488 5489 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5490 sizeof (arc_buf_hdr_t), 5491 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5492 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5493 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5494 sizeof (arc_buf_hdr_t), 5495 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5496 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5497 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5498 sizeof (arc_buf_hdr_t), 5499 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5500 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5501 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5502 sizeof (arc_buf_hdr_t), 5503 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5504 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5505 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5506 sizeof (arc_buf_hdr_t), 5507 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5508 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5509 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5510 sizeof (arc_buf_hdr_t), 5511 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5512 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5513 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5514 sizeof (arc_buf_hdr_t), 5515 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5516 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5517 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5518 sizeof (arc_buf_hdr_t), 5519 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5520 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5521 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5522 sizeof (arc_buf_hdr_t), 5523 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5524 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5525 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5526 sizeof (arc_buf_hdr_t), 5527 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5528 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5529 5530 refcount_create(&arc_anon->arcs_size); 5531 refcount_create(&arc_mru->arcs_size); 5532 refcount_create(&arc_mru_ghost->arcs_size); 5533 refcount_create(&arc_mfu->arcs_size); 5534 refcount_create(&arc_mfu_ghost->arcs_size); 5535 refcount_create(&arc_l2c_only->arcs_size); 5536 5537 buf_init(); 5538 5539 arc_reclaim_thread_exit = FALSE; 5540 arc_user_evicts_thread_exit = FALSE; 5541 arc_eviction_list = NULL; 5542 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 5543 5544 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 5545 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 5546 5547 if (arc_ksp != NULL) { 5548 arc_ksp->ks_data = &arc_stats; 5549 arc_ksp->ks_update = arc_kstat_update; 5550 kstat_install(arc_ksp); 5551 } 5552 5553 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5554 TS_RUN, minclsyspri); 5555 5556#ifdef _KERNEL 5557 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5558 EVENTHANDLER_PRI_FIRST); 5559#endif 5560 5561 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0, 5562 TS_RUN, minclsyspri); 5563 5564 arc_dead = FALSE; 5565 arc_warm = B_FALSE; 5566 5567 /* 5568 * Calculate maximum amount of dirty data per pool. 5569 * 5570 * If it has been set by /etc/system, take that. 5571 * Otherwise, use a percentage of physical memory defined by 5572 * zfs_dirty_data_max_percent (default 10%) with a cap at 5573 * zfs_dirty_data_max_max (default 4GB). 5574 */ 5575 if (zfs_dirty_data_max == 0) { 5576 zfs_dirty_data_max = ptob(physmem) * 5577 zfs_dirty_data_max_percent / 100; 5578 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5579 zfs_dirty_data_max_max); 5580 } 5581 5582#ifdef _KERNEL 5583 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5584 prefetch_tunable_set = 1; 5585 5586#ifdef __i386__ 5587 if (prefetch_tunable_set == 0) { 5588 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5589 "-- to enable,\n"); 5590 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5591 "to /boot/loader.conf.\n"); 5592 zfs_prefetch_disable = 1; 5593 } 5594#else 5595 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5596 prefetch_tunable_set == 0) { 5597 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5598 "than 4GB of RAM is present;\n" 5599 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5600 "to /boot/loader.conf.\n"); 5601 zfs_prefetch_disable = 1; 5602 } 5603#endif 5604 /* Warn about ZFS memory and address space requirements. */ 5605 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5606 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5607 "expect unstable behavior.\n"); 5608 } 5609 if (kmem_size() < 512 * (1 << 20)) { 5610 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5611 "expect unstable behavior.\n"); 5612 printf(" Consider tuning vm.kmem_size and " 5613 "vm.kmem_size_max\n"); 5614 printf(" in /boot/loader.conf.\n"); 5615 } 5616#endif 5617} 5618 5619void 5620arc_fini(void) 5621{ 5622 mutex_enter(&arc_reclaim_lock); 5623 arc_reclaim_thread_exit = TRUE; 5624 /* 5625 * The reclaim thread will set arc_reclaim_thread_exit back to 5626 * FALSE when it is finished exiting; we're waiting for that. 5627 */ 5628 while (arc_reclaim_thread_exit) { 5629 cv_signal(&arc_reclaim_thread_cv); 5630 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 5631 } 5632 mutex_exit(&arc_reclaim_lock); 5633 5634 mutex_enter(&arc_user_evicts_lock); 5635 arc_user_evicts_thread_exit = TRUE; 5636 /* 5637 * The user evicts thread will set arc_user_evicts_thread_exit 5638 * to FALSE when it is finished exiting; we're waiting for that. 5639 */ 5640 while (arc_user_evicts_thread_exit) { 5641 cv_signal(&arc_user_evicts_cv); 5642 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock); 5643 } 5644 mutex_exit(&arc_user_evicts_lock); 5645 5646 /* Use TRUE to ensure *all* buffers are evicted */ 5647 arc_flush(NULL, TRUE); 5648 5649 arc_dead = TRUE; 5650 5651 if (arc_ksp != NULL) { 5652 kstat_delete(arc_ksp); 5653 arc_ksp = NULL; 5654 } 5655 5656 mutex_destroy(&arc_reclaim_lock); 5657 cv_destroy(&arc_reclaim_thread_cv); 5658 cv_destroy(&arc_reclaim_waiters_cv); 5659 5660 mutex_destroy(&arc_user_evicts_lock); 5661 cv_destroy(&arc_user_evicts_cv); 5662 5663 refcount_destroy(&arc_anon->arcs_size); 5664 refcount_destroy(&arc_mru->arcs_size); 5665 refcount_destroy(&arc_mru_ghost->arcs_size); 5666 refcount_destroy(&arc_mfu->arcs_size); 5667 refcount_destroy(&arc_mfu_ghost->arcs_size); 5668 refcount_destroy(&arc_l2c_only->arcs_size); 5669 5670 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5671 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5672 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5673 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5674 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]); 5675 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5676 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5677 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5678 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5679 multilist_destroy(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]); 5680 5681 buf_fini(); 5682 5683 ASSERT0(arc_loaned_bytes); 5684 5685#ifdef _KERNEL 5686 if (arc_event_lowmem != NULL) 5687 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5688#endif 5689} 5690 5691/* 5692 * Level 2 ARC 5693 * 5694 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5695 * It uses dedicated storage devices to hold cached data, which are populated 5696 * using large infrequent writes. The main role of this cache is to boost 5697 * the performance of random read workloads. The intended L2ARC devices 5698 * include short-stroked disks, solid state disks, and other media with 5699 * substantially faster read latency than disk. 5700 * 5701 * +-----------------------+ 5702 * | ARC | 5703 * +-----------------------+ 5704 * | ^ ^ 5705 * | | | 5706 * l2arc_feed_thread() arc_read() 5707 * | | | 5708 * | l2arc read | 5709 * V | | 5710 * +---------------+ | 5711 * | L2ARC | | 5712 * +---------------+ | 5713 * | ^ | 5714 * l2arc_write() | | 5715 * | | | 5716 * V | | 5717 * +-------+ +-------+ 5718 * | vdev | | vdev | 5719 * | cache | | cache | 5720 * +-------+ +-------+ 5721 * +=========+ .-----. 5722 * : L2ARC : |-_____-| 5723 * : devices : | Disks | 5724 * +=========+ `-_____-' 5725 * 5726 * Read requests are satisfied from the following sources, in order: 5727 * 5728 * 1) ARC 5729 * 2) vdev cache of L2ARC devices 5730 * 3) L2ARC devices 5731 * 4) vdev cache of disks 5732 * 5) disks 5733 * 5734 * Some L2ARC device types exhibit extremely slow write performance. 5735 * To accommodate for this there are some significant differences between 5736 * the L2ARC and traditional cache design: 5737 * 5738 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5739 * the ARC behave as usual, freeing buffers and placing headers on ghost 5740 * lists. The ARC does not send buffers to the L2ARC during eviction as 5741 * this would add inflated write latencies for all ARC memory pressure. 5742 * 5743 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5744 * It does this by periodically scanning buffers from the eviction-end of 5745 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5746 * not already there. It scans until a headroom of buffers is satisfied, 5747 * which itself is a buffer for ARC eviction. If a compressible buffer is 5748 * found during scanning and selected for writing to an L2ARC device, we 5749 * temporarily boost scanning headroom during the next scan cycle to make 5750 * sure we adapt to compression effects (which might significantly reduce 5751 * the data volume we write to L2ARC). The thread that does this is 5752 * l2arc_feed_thread(), illustrated below; example sizes are included to 5753 * provide a better sense of ratio than this diagram: 5754 * 5755 * head --> tail 5756 * +---------------------+----------+ 5757 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5758 * +---------------------+----------+ | o L2ARC eligible 5759 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5760 * +---------------------+----------+ | 5761 * 15.9 Gbytes ^ 32 Mbytes | 5762 * headroom | 5763 * l2arc_feed_thread() 5764 * | 5765 * l2arc write hand <--[oooo]--' 5766 * | 8 Mbyte 5767 * | write max 5768 * V 5769 * +==============================+ 5770 * L2ARC dev |####|#|###|###| |####| ... | 5771 * +==============================+ 5772 * 32 Gbytes 5773 * 5774 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5775 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5776 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5777 * safe to say that this is an uncommon case, since buffers at the end of 5778 * the ARC lists have moved there due to inactivity. 5779 * 5780 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5781 * then the L2ARC simply misses copying some buffers. This serves as a 5782 * pressure valve to prevent heavy read workloads from both stalling the ARC 5783 * with waits and clogging the L2ARC with writes. This also helps prevent 5784 * the potential for the L2ARC to churn if it attempts to cache content too 5785 * quickly, such as during backups of the entire pool. 5786 * 5787 * 5. After system boot and before the ARC has filled main memory, there are 5788 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5789 * lists can remain mostly static. Instead of searching from tail of these 5790 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5791 * for eligible buffers, greatly increasing its chance of finding them. 5792 * 5793 * The L2ARC device write speed is also boosted during this time so that 5794 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5795 * there are no L2ARC reads, and no fear of degrading read performance 5796 * through increased writes. 5797 * 5798 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5799 * the vdev queue can aggregate them into larger and fewer writes. Each 5800 * device is written to in a rotor fashion, sweeping writes through 5801 * available space then repeating. 5802 * 5803 * 7. The L2ARC does not store dirty content. It never needs to flush 5804 * write buffers back to disk based storage. 5805 * 5806 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5807 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5808 * 5809 * The performance of the L2ARC can be tweaked by a number of tunables, which 5810 * may be necessary for different workloads: 5811 * 5812 * l2arc_write_max max write bytes per interval 5813 * l2arc_write_boost extra write bytes during device warmup 5814 * l2arc_noprefetch skip caching prefetched buffers 5815 * l2arc_headroom number of max device writes to precache 5816 * l2arc_headroom_boost when we find compressed buffers during ARC 5817 * scanning, we multiply headroom by this 5818 * percentage factor for the next scan cycle, 5819 * since more compressed buffers are likely to 5820 * be present 5821 * l2arc_feed_secs seconds between L2ARC writing 5822 * 5823 * Tunables may be removed or added as future performance improvements are 5824 * integrated, and also may become zpool properties. 5825 * 5826 * There are three key functions that control how the L2ARC warms up: 5827 * 5828 * l2arc_write_eligible() check if a buffer is eligible to cache 5829 * l2arc_write_size() calculate how much to write 5830 * l2arc_write_interval() calculate sleep delay between writes 5831 * 5832 * These three functions determine what to write, how much, and how quickly 5833 * to send writes. 5834 */ 5835 5836static boolean_t 5837l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5838{ 5839 /* 5840 * A buffer is *not* eligible for the L2ARC if it: 5841 * 1. belongs to a different spa. 5842 * 2. is already cached on the L2ARC. 5843 * 3. has an I/O in progress (it may be an incomplete read). 5844 * 4. is flagged not eligible (zfs property). 5845 */ 5846 if (hdr->b_spa != spa_guid) { 5847 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5848 return (B_FALSE); 5849 } 5850 if (HDR_HAS_L2HDR(hdr)) { 5851 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5852 return (B_FALSE); 5853 } 5854 if (HDR_IO_IN_PROGRESS(hdr)) { 5855 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5856 return (B_FALSE); 5857 } 5858 if (!HDR_L2CACHE(hdr)) { 5859 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5860 return (B_FALSE); 5861 } 5862 5863 return (B_TRUE); 5864} 5865 5866static uint64_t 5867l2arc_write_size(void) 5868{ 5869 uint64_t size; 5870 5871 /* 5872 * Make sure our globals have meaningful values in case the user 5873 * altered them. 5874 */ 5875 size = l2arc_write_max; 5876 if (size == 0) { 5877 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5878 "be greater than zero, resetting it to the default (%d)", 5879 L2ARC_WRITE_SIZE); 5880 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5881 } 5882 5883 if (arc_warm == B_FALSE) 5884 size += l2arc_write_boost; 5885 5886 return (size); 5887 5888} 5889 5890static clock_t 5891l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5892{ 5893 clock_t interval, next, now; 5894 5895 /* 5896 * If the ARC lists are busy, increase our write rate; if the 5897 * lists are stale, idle back. This is achieved by checking 5898 * how much we previously wrote - if it was more than half of 5899 * what we wanted, schedule the next write much sooner. 5900 */ 5901 if (l2arc_feed_again && wrote > (wanted / 2)) 5902 interval = (hz * l2arc_feed_min_ms) / 1000; 5903 else 5904 interval = hz * l2arc_feed_secs; 5905 5906 now = ddi_get_lbolt(); 5907 next = MAX(now, MIN(now + interval, began + interval)); 5908 5909 return (next); 5910} 5911 5912/* 5913 * Cycle through L2ARC devices. This is how L2ARC load balances. 5914 * If a device is returned, this also returns holding the spa config lock. 5915 */ 5916static l2arc_dev_t * 5917l2arc_dev_get_next(void) 5918{ 5919 l2arc_dev_t *first, *next = NULL; 5920 5921 /* 5922 * Lock out the removal of spas (spa_namespace_lock), then removal 5923 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5924 * both locks will be dropped and a spa config lock held instead. 5925 */ 5926 mutex_enter(&spa_namespace_lock); 5927 mutex_enter(&l2arc_dev_mtx); 5928 5929 /* if there are no vdevs, there is nothing to do */ 5930 if (l2arc_ndev == 0) 5931 goto out; 5932 5933 first = NULL; 5934 next = l2arc_dev_last; 5935 do { 5936 /* loop around the list looking for a non-faulted vdev */ 5937 if (next == NULL) { 5938 next = list_head(l2arc_dev_list); 5939 } else { 5940 next = list_next(l2arc_dev_list, next); 5941 if (next == NULL) 5942 next = list_head(l2arc_dev_list); 5943 } 5944 5945 /* if we have come back to the start, bail out */ 5946 if (first == NULL) 5947 first = next; 5948 else if (next == first) 5949 break; 5950 5951 } while (vdev_is_dead(next->l2ad_vdev)); 5952 5953 /* if we were unable to find any usable vdevs, return NULL */ 5954 if (vdev_is_dead(next->l2ad_vdev)) 5955 next = NULL; 5956 5957 l2arc_dev_last = next; 5958 5959out: 5960 mutex_exit(&l2arc_dev_mtx); 5961 5962 /* 5963 * Grab the config lock to prevent the 'next' device from being 5964 * removed while we are writing to it. 5965 */ 5966 if (next != NULL) 5967 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5968 mutex_exit(&spa_namespace_lock); 5969 5970 return (next); 5971} 5972 5973/* 5974 * Free buffers that were tagged for destruction. 5975 */ 5976static void 5977l2arc_do_free_on_write() 5978{ 5979 list_t *buflist; 5980 l2arc_data_free_t *df, *df_prev; 5981 5982 mutex_enter(&l2arc_free_on_write_mtx); 5983 buflist = l2arc_free_on_write; 5984 5985 for (df = list_tail(buflist); df; df = df_prev) { 5986 df_prev = list_prev(buflist, df); 5987 ASSERT(df->l2df_data != NULL); 5988 ASSERT(df->l2df_func != NULL); 5989 df->l2df_func(df->l2df_data, df->l2df_size); 5990 list_remove(buflist, df); 5991 kmem_free(df, sizeof (l2arc_data_free_t)); 5992 } 5993 5994 mutex_exit(&l2arc_free_on_write_mtx); 5995} 5996 5997/* 5998 * A write to a cache device has completed. Update all headers to allow 5999 * reads from these buffers to begin. 6000 */ 6001static void 6002l2arc_write_done(zio_t *zio) 6003{ 6004 l2arc_write_callback_t *cb; 6005 l2arc_dev_t *dev; 6006 list_t *buflist; 6007 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6008 kmutex_t *hash_lock; 6009 int64_t bytes_dropped = 0; 6010 6011 cb = zio->io_private; 6012 ASSERT(cb != NULL); 6013 dev = cb->l2wcb_dev; 6014 ASSERT(dev != NULL); 6015 head = cb->l2wcb_head; 6016 ASSERT(head != NULL); 6017 buflist = &dev->l2ad_buflist; 6018 ASSERT(buflist != NULL); 6019 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6020 l2arc_write_callback_t *, cb); 6021 6022 if (zio->io_error != 0) 6023 ARCSTAT_BUMP(arcstat_l2_writes_error); 6024 6025 /* 6026 * All writes completed, or an error was hit. 6027 */ 6028top: 6029 mutex_enter(&dev->l2ad_mtx); 6030 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 6031 hdr_prev = list_prev(buflist, hdr); 6032 6033 hash_lock = HDR_LOCK(hdr); 6034 6035 /* 6036 * We cannot use mutex_enter or else we can deadlock 6037 * with l2arc_write_buffers (due to swapping the order 6038 * the hash lock and l2ad_mtx are taken). 6039 */ 6040 if (!mutex_tryenter(hash_lock)) { 6041 /* 6042 * Missed the hash lock. We must retry so we 6043 * don't leave the ARC_FLAG_L2_WRITING bit set. 6044 */ 6045 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 6046 6047 /* 6048 * We don't want to rescan the headers we've 6049 * already marked as having been written out, so 6050 * we reinsert the head node so we can pick up 6051 * where we left off. 6052 */ 6053 list_remove(buflist, head); 6054 list_insert_after(buflist, hdr, head); 6055 6056 mutex_exit(&dev->l2ad_mtx); 6057 6058 /* 6059 * We wait for the hash lock to become available 6060 * to try and prevent busy waiting, and increase 6061 * the chance we'll be able to acquire the lock 6062 * the next time around. 6063 */ 6064 mutex_enter(hash_lock); 6065 mutex_exit(hash_lock); 6066 goto top; 6067 } 6068 6069 /* 6070 * We could not have been moved into the arc_l2c_only 6071 * state while in-flight due to our ARC_FLAG_L2_WRITING 6072 * bit being set. Let's just ensure that's being enforced. 6073 */ 6074 ASSERT(HDR_HAS_L1HDR(hdr)); 6075 6076 /* 6077 * We may have allocated a buffer for L2ARC compression, 6078 * we must release it to avoid leaking this data. 6079 */ 6080 l2arc_release_cdata_buf(hdr); 6081 6082 if (zio->io_error != 0) { 6083 /* 6084 * Error - drop L2ARC entry. 6085 */ 6086 list_remove(buflist, hdr); 6087 l2arc_trim(hdr); 6088 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 6089 6090 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 6091 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 6092 6093 bytes_dropped += hdr->b_l2hdr.b_asize; 6094 (void) refcount_remove_many(&dev->l2ad_alloc, 6095 hdr->b_l2hdr.b_asize, hdr); 6096 } 6097 6098 /* 6099 * Allow ARC to begin reads and ghost list evictions to 6100 * this L2ARC entry. 6101 */ 6102 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 6103 6104 mutex_exit(hash_lock); 6105 } 6106 6107 atomic_inc_64(&l2arc_writes_done); 6108 list_remove(buflist, head); 6109 ASSERT(!HDR_HAS_L1HDR(head)); 6110 kmem_cache_free(hdr_l2only_cache, head); 6111 mutex_exit(&dev->l2ad_mtx); 6112 6113 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6114 6115 l2arc_do_free_on_write(); 6116 6117 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6118} 6119 6120/* 6121 * A read to a cache device completed. Validate buffer contents before 6122 * handing over to the regular ARC routines. 6123 */ 6124static void 6125l2arc_read_done(zio_t *zio) 6126{ 6127 l2arc_read_callback_t *cb; 6128 arc_buf_hdr_t *hdr; 6129 arc_buf_t *buf; 6130 kmutex_t *hash_lock; 6131 int equal; 6132 6133 ASSERT(zio->io_vd != NULL); 6134 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6135 6136 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6137 6138 cb = zio->io_private; 6139 ASSERT(cb != NULL); 6140 buf = cb->l2rcb_buf; 6141 ASSERT(buf != NULL); 6142 6143 hash_lock = HDR_LOCK(buf->b_hdr); 6144 mutex_enter(hash_lock); 6145 hdr = buf->b_hdr; 6146 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6147 6148 /* 6149 * If the data was read into a temporary buffer, 6150 * move it and free the buffer. 6151 */ 6152 if (cb->l2rcb_data != NULL) { 6153 ASSERT3U(hdr->b_size, <, zio->io_size); 6154 ASSERT3U(cb->l2rcb_compress, ==, ZIO_COMPRESS_OFF); 6155 if (zio->io_error == 0) 6156 bcopy(cb->l2rcb_data, buf->b_data, hdr->b_size); 6157 6158 /* 6159 * The following must be done regardless of whether 6160 * there was an error: 6161 * - free the temporary buffer 6162 * - point zio to the real ARC buffer 6163 * - set zio size accordingly 6164 * These are required because zio is either re-used for 6165 * an I/O of the block in the case of the error 6166 * or the zio is passed to arc_read_done() and it 6167 * needs real data. 6168 */ 6169 zio_data_buf_free(cb->l2rcb_data, zio->io_size); 6170 zio->io_size = zio->io_orig_size = hdr->b_size; 6171 zio->io_data = zio->io_orig_data = buf->b_data; 6172 } 6173 6174 /* 6175 * If the buffer was compressed, decompress it first. 6176 */ 6177 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 6178 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 6179 ASSERT(zio->io_data != NULL); 6180 ASSERT3U(zio->io_size, ==, hdr->b_size); 6181 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size); 6182 6183 /* 6184 * Check this survived the L2ARC journey. 6185 */ 6186 equal = arc_cksum_equal(buf); 6187 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6188 mutex_exit(hash_lock); 6189 zio->io_private = buf; 6190 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6191 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6192 arc_read_done(zio); 6193 } else { 6194 mutex_exit(hash_lock); 6195 /* 6196 * Buffer didn't survive caching. Increment stats and 6197 * reissue to the original storage device. 6198 */ 6199 if (zio->io_error != 0) { 6200 ARCSTAT_BUMP(arcstat_l2_io_error); 6201 } else { 6202 zio->io_error = SET_ERROR(EIO); 6203 } 6204 if (!equal) 6205 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6206 6207 /* 6208 * If there's no waiter, issue an async i/o to the primary 6209 * storage now. If there *is* a waiter, the caller must 6210 * issue the i/o in a context where it's OK to block. 6211 */ 6212 if (zio->io_waiter == NULL) { 6213 zio_t *pio = zio_unique_parent(zio); 6214 6215 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6216 6217 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 6218 buf->b_data, hdr->b_size, arc_read_done, buf, 6219 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 6220 } 6221 } 6222 6223 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6224} 6225 6226/* 6227 * This is the list priority from which the L2ARC will search for pages to 6228 * cache. This is used within loops (0..3) to cycle through lists in the 6229 * desired order. This order can have a significant effect on cache 6230 * performance. 6231 * 6232 * Currently the metadata lists are hit first, MFU then MRU, followed by 6233 * the data lists. This function returns a locked list, and also returns 6234 * the lock pointer. 6235 */ 6236static multilist_sublist_t * 6237l2arc_sublist_lock(int list_num) 6238{ 6239 multilist_t *ml = NULL; 6240 unsigned int idx; 6241 6242 ASSERT(list_num >= 0 && list_num <= 3); 6243 6244 switch (list_num) { 6245 case 0: 6246 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6247 break; 6248 case 1: 6249 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6250 break; 6251 case 2: 6252 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6253 break; 6254 case 3: 6255 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6256 break; 6257 } 6258 6259 /* 6260 * Return a randomly-selected sublist. This is acceptable 6261 * because the caller feeds only a little bit of data for each 6262 * call (8MB). Subsequent calls will result in different 6263 * sublists being selected. 6264 */ 6265 idx = multilist_get_random_index(ml); 6266 return (multilist_sublist_lock(ml, idx)); 6267} 6268 6269/* 6270 * Evict buffers from the device write hand to the distance specified in 6271 * bytes. This distance may span populated buffers, it may span nothing. 6272 * This is clearing a region on the L2ARC device ready for writing. 6273 * If the 'all' boolean is set, every buffer is evicted. 6274 */ 6275static void 6276l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6277{ 6278 list_t *buflist; 6279 arc_buf_hdr_t *hdr, *hdr_prev; 6280 kmutex_t *hash_lock; 6281 uint64_t taddr; 6282 6283 buflist = &dev->l2ad_buflist; 6284 6285 if (!all && dev->l2ad_first) { 6286 /* 6287 * This is the first sweep through the device. There is 6288 * nothing to evict. 6289 */ 6290 return; 6291 } 6292 6293 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6294 /* 6295 * When nearing the end of the device, evict to the end 6296 * before the device write hand jumps to the start. 6297 */ 6298 taddr = dev->l2ad_end; 6299 } else { 6300 taddr = dev->l2ad_hand + distance; 6301 } 6302 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6303 uint64_t, taddr, boolean_t, all); 6304 6305top: 6306 mutex_enter(&dev->l2ad_mtx); 6307 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6308 hdr_prev = list_prev(buflist, hdr); 6309 6310 hash_lock = HDR_LOCK(hdr); 6311 6312 /* 6313 * We cannot use mutex_enter or else we can deadlock 6314 * with l2arc_write_buffers (due to swapping the order 6315 * the hash lock and l2ad_mtx are taken). 6316 */ 6317 if (!mutex_tryenter(hash_lock)) { 6318 /* 6319 * Missed the hash lock. Retry. 6320 */ 6321 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6322 mutex_exit(&dev->l2ad_mtx); 6323 mutex_enter(hash_lock); 6324 mutex_exit(hash_lock); 6325 goto top; 6326 } 6327 6328 if (HDR_L2_WRITE_HEAD(hdr)) { 6329 /* 6330 * We hit a write head node. Leave it for 6331 * l2arc_write_done(). 6332 */ 6333 list_remove(buflist, hdr); 6334 mutex_exit(hash_lock); 6335 continue; 6336 } 6337 6338 if (!all && HDR_HAS_L2HDR(hdr) && 6339 (hdr->b_l2hdr.b_daddr > taddr || 6340 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6341 /* 6342 * We've evicted to the target address, 6343 * or the end of the device. 6344 */ 6345 mutex_exit(hash_lock); 6346 break; 6347 } 6348 6349 ASSERT(HDR_HAS_L2HDR(hdr)); 6350 if (!HDR_HAS_L1HDR(hdr)) { 6351 ASSERT(!HDR_L2_READING(hdr)); 6352 /* 6353 * This doesn't exist in the ARC. Destroy. 6354 * arc_hdr_destroy() will call list_remove() 6355 * and decrement arcstat_l2_size. 6356 */ 6357 arc_change_state(arc_anon, hdr, hash_lock); 6358 arc_hdr_destroy(hdr); 6359 } else { 6360 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6361 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6362 /* 6363 * Invalidate issued or about to be issued 6364 * reads, since we may be about to write 6365 * over this location. 6366 */ 6367 if (HDR_L2_READING(hdr)) { 6368 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6369 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 6370 } 6371 6372 /* Ensure this header has finished being written */ 6373 ASSERT(!HDR_L2_WRITING(hdr)); 6374 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL); 6375 6376 arc_hdr_l2hdr_destroy(hdr); 6377 } 6378 mutex_exit(hash_lock); 6379 } 6380 mutex_exit(&dev->l2ad_mtx); 6381} 6382 6383/* 6384 * Find and write ARC buffers to the L2ARC device. 6385 * 6386 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6387 * for reading until they have completed writing. 6388 * The headroom_boost is an in-out parameter used to maintain headroom boost 6389 * state between calls to this function. 6390 * 6391 * Returns the number of bytes actually written (which may be smaller than 6392 * the delta by which the device hand has changed due to alignment). 6393 */ 6394static uint64_t 6395l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 6396 boolean_t *headroom_boost) 6397{ 6398 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6399 uint64_t write_asize, write_sz, headroom, 6400 buf_compress_minsz; 6401 void *buf_data; 6402 boolean_t full; 6403 l2arc_write_callback_t *cb; 6404 zio_t *pio, *wzio; 6405 uint64_t guid = spa_load_guid(spa); 6406 const boolean_t do_headroom_boost = *headroom_boost; 6407 int try; 6408 6409 ASSERT(dev->l2ad_vdev != NULL); 6410 6411 /* Lower the flag now, we might want to raise it again later. */ 6412 *headroom_boost = B_FALSE; 6413 6414 pio = NULL; 6415 write_sz = write_asize = 0; 6416 full = B_FALSE; 6417 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6418 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 6419 head->b_flags |= ARC_FLAG_HAS_L2HDR; 6420 6421 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6422 /* 6423 * We will want to try to compress buffers that are at least 2x the 6424 * device sector size. 6425 */ 6426 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 6427 6428 /* 6429 * Copy buffers for L2ARC writing. 6430 */ 6431 for (try = 0; try <= 3; try++) { 6432 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6433 uint64_t passed_sz = 0; 6434 6435 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6436 6437 /* 6438 * L2ARC fast warmup. 6439 * 6440 * Until the ARC is warm and starts to evict, read from the 6441 * head of the ARC lists rather than the tail. 6442 */ 6443 if (arc_warm == B_FALSE) 6444 hdr = multilist_sublist_head(mls); 6445 else 6446 hdr = multilist_sublist_tail(mls); 6447 if (hdr == NULL) 6448 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6449 6450 headroom = target_sz * l2arc_headroom; 6451 if (do_headroom_boost) 6452 headroom = (headroom * l2arc_headroom_boost) / 100; 6453 6454 for (; hdr; hdr = hdr_prev) { 6455 kmutex_t *hash_lock; 6456 uint64_t buf_sz; 6457 uint64_t buf_a_sz; 6458 size_t align; 6459 6460 if (arc_warm == B_FALSE) 6461 hdr_prev = multilist_sublist_next(mls, hdr); 6462 else 6463 hdr_prev = multilist_sublist_prev(mls, hdr); 6464 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 6465 6466 hash_lock = HDR_LOCK(hdr); 6467 if (!mutex_tryenter(hash_lock)) { 6468 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 6469 /* 6470 * Skip this buffer rather than waiting. 6471 */ 6472 continue; 6473 } 6474 6475 passed_sz += hdr->b_size; 6476 if (passed_sz > headroom) { 6477 /* 6478 * Searched too far. 6479 */ 6480 mutex_exit(hash_lock); 6481 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 6482 break; 6483 } 6484 6485 if (!l2arc_write_eligible(guid, hdr)) { 6486 mutex_exit(hash_lock); 6487 continue; 6488 } 6489 6490 /* 6491 * Assume that the buffer is not going to be compressed 6492 * and could take more space on disk because of a larger 6493 * disk block size. 6494 */ 6495 buf_sz = hdr->b_size; 6496 align = (size_t)1 << dev->l2ad_vdev->vdev_ashift; 6497 buf_a_sz = P2ROUNDUP(buf_sz, align); 6498 6499 if ((write_asize + buf_a_sz) > target_sz) { 6500 full = B_TRUE; 6501 mutex_exit(hash_lock); 6502 ARCSTAT_BUMP(arcstat_l2_write_full); 6503 break; 6504 } 6505 6506 if (pio == NULL) { 6507 /* 6508 * Insert a dummy header on the buflist so 6509 * l2arc_write_done() can find where the 6510 * write buffers begin without searching. 6511 */ 6512 mutex_enter(&dev->l2ad_mtx); 6513 list_insert_head(&dev->l2ad_buflist, head); 6514 mutex_exit(&dev->l2ad_mtx); 6515 6516 cb = kmem_alloc( 6517 sizeof (l2arc_write_callback_t), KM_SLEEP); 6518 cb->l2wcb_dev = dev; 6519 cb->l2wcb_head = head; 6520 pio = zio_root(spa, l2arc_write_done, cb, 6521 ZIO_FLAG_CANFAIL); 6522 ARCSTAT_BUMP(arcstat_l2_write_pios); 6523 } 6524 6525 /* 6526 * Create and add a new L2ARC header. 6527 */ 6528 hdr->b_l2hdr.b_dev = dev; 6529 hdr->b_flags |= ARC_FLAG_L2_WRITING; 6530 /* 6531 * Temporarily stash the data buffer in b_tmp_cdata. 6532 * The subsequent write step will pick it up from 6533 * there. This is because can't access b_l1hdr.b_buf 6534 * without holding the hash_lock, which we in turn 6535 * can't access without holding the ARC list locks 6536 * (which we want to avoid during compression/writing). 6537 */ 6538 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF; 6539 hdr->b_l2hdr.b_asize = hdr->b_size; 6540 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 6541 6542 /* 6543 * Explicitly set the b_daddr field to a known 6544 * value which means "invalid address". This 6545 * enables us to differentiate which stage of 6546 * l2arc_write_buffers() the particular header 6547 * is in (e.g. this loop, or the one below). 6548 * ARC_FLAG_L2_WRITING is not enough to make 6549 * this distinction, and we need to know in 6550 * order to do proper l2arc vdev accounting in 6551 * arc_release() and arc_hdr_destroy(). 6552 * 6553 * Note, we can't use a new flag to distinguish 6554 * the two stages because we don't hold the 6555 * header's hash_lock below, in the second stage 6556 * of this function. Thus, we can't simply 6557 * change the b_flags field to denote that the 6558 * IO has been sent. We can change the b_daddr 6559 * field of the L2 portion, though, since we'll 6560 * be holding the l2ad_mtx; which is why we're 6561 * using it to denote the header's state change. 6562 */ 6563 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 6564 6565 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 6566 6567 mutex_enter(&dev->l2ad_mtx); 6568 list_insert_head(&dev->l2ad_buflist, hdr); 6569 mutex_exit(&dev->l2ad_mtx); 6570 6571 /* 6572 * Compute and store the buffer cksum before 6573 * writing. On debug the cksum is verified first. 6574 */ 6575 arc_cksum_verify(hdr->b_l1hdr.b_buf); 6576 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 6577 6578 mutex_exit(hash_lock); 6579 6580 write_sz += buf_sz; 6581 write_asize += buf_a_sz; 6582 } 6583 6584 multilist_sublist_unlock(mls); 6585 6586 if (full == B_TRUE) 6587 break; 6588 } 6589 6590 /* No buffers selected for writing? */ 6591 if (pio == NULL) { 6592 ASSERT0(write_sz); 6593 ASSERT(!HDR_HAS_L1HDR(head)); 6594 kmem_cache_free(hdr_l2only_cache, head); 6595 return (0); 6596 } 6597 6598 mutex_enter(&dev->l2ad_mtx); 6599 6600 /* 6601 * Now start writing the buffers. We're starting at the write head 6602 * and work backwards, retracing the course of the buffer selector 6603 * loop above. 6604 */ 6605 write_asize = 0; 6606 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 6607 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 6608 uint64_t buf_sz; 6609 boolean_t compress; 6610 6611 /* 6612 * We rely on the L1 portion of the header below, so 6613 * it's invalid for this header to have been evicted out 6614 * of the ghost cache, prior to being written out. The 6615 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6616 */ 6617 ASSERT(HDR_HAS_L1HDR(hdr)); 6618 6619 /* 6620 * We shouldn't need to lock the buffer here, since we flagged 6621 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 6622 * take care to only access its L2 cache parameters. In 6623 * particular, hdr->l1hdr.b_buf may be invalid by now due to 6624 * ARC eviction. 6625 */ 6626 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6627 6628 /* 6629 * Save a pointer to the original buffer data we had previously 6630 * stashed away. 6631 */ 6632 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6633 6634 compress = HDR_L2COMPRESS(hdr) && 6635 hdr->b_l2hdr.b_asize >= buf_compress_minsz; 6636 if (l2arc_transform_buf(hdr, compress)) { 6637 /* 6638 * If compression succeeded, enable headroom 6639 * boost on the next scan cycle. 6640 */ 6641 *headroom_boost = B_TRUE; 6642 } 6643 6644 /* 6645 * Get the new buffer size that accounts for compression 6646 * and padding. 6647 */ 6648 buf_sz = hdr->b_l2hdr.b_asize; 6649 6650 /* 6651 * We need to do this regardless if buf_sz is zero or 6652 * not, otherwise, when this l2hdr is evicted we'll 6653 * remove a reference that was never added. 6654 */ 6655 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6656 6657 /* Compression may have squashed the buffer to zero length. */ 6658 if (buf_sz != 0) { 6659 /* 6660 * If the data was padded or compressed, then it 6661 * it is in a new buffer. 6662 */ 6663 if (hdr->b_l1hdr.b_tmp_cdata != NULL) 6664 buf_data = hdr->b_l1hdr.b_tmp_cdata; 6665 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6666 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6667 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6668 ZIO_FLAG_CANFAIL, B_FALSE); 6669 6670 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6671 zio_t *, wzio); 6672 (void) zio_nowait(wzio); 6673 6674 write_asize += buf_sz; 6675 dev->l2ad_hand += buf_sz; 6676 } 6677 } 6678 6679 mutex_exit(&dev->l2ad_mtx); 6680 6681 ASSERT3U(write_asize, <=, target_sz); 6682 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6683 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6684 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6685 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6686 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6687 6688 /* 6689 * Bump device hand to the device start if it is approaching the end. 6690 * l2arc_evict() will already have evicted ahead for this case. 6691 */ 6692 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6693 dev->l2ad_hand = dev->l2ad_start; 6694 dev->l2ad_first = B_FALSE; 6695 } 6696 6697 dev->l2ad_writing = B_TRUE; 6698 (void) zio_wait(pio); 6699 dev->l2ad_writing = B_FALSE; 6700 6701 return (write_asize); 6702} 6703 6704/* 6705 * Transforms, possibly compresses and pads, an L2ARC buffer. 6706 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6707 * size in l2hdr->b_asize. This routine tries to compress the data and 6708 * depending on the compression result there are three possible outcomes: 6709 * *) The buffer was incompressible. The buffer size was already ashift aligned. 6710 * The original hdr contents were left untouched except for b_tmp_cdata, 6711 * which is reset to NULL. The caller must keep a pointer to the original 6712 * data. 6713 * *) The buffer was incompressible. The buffer size was not ashift aligned. 6714 * b_tmp_cdata was replaced with a temporary data buffer which holds a padded 6715 * (aligned) copy of the data. Once writing is done, invoke 6716 * l2arc_release_cdata_buf on this hdr to free the temporary buffer. 6717 * *) The buffer was all-zeros, so there is no need to write it to an L2 6718 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6719 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6720 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6721 * data buffer which holds the compressed data to be written, and b_asize 6722 * tells us how much data there is. b_compress is set to the appropriate 6723 * compression algorithm. Once writing is done, invoke 6724 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6725 * 6726 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6727 * buffer was incompressible). 6728 */ 6729static boolean_t 6730l2arc_transform_buf(arc_buf_hdr_t *hdr, boolean_t compress) 6731{ 6732 void *cdata; 6733 size_t align, asize, csize, len, rounded; 6734 6735 ASSERT(HDR_HAS_L2HDR(hdr)); 6736 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6737 6738 ASSERT(HDR_HAS_L1HDR(hdr)); 6739 ASSERT3S(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF); 6740 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6741 6742 len = l2hdr->b_asize; 6743 align = (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift; 6744 asize = P2ROUNDUP(len, align); 6745 cdata = zio_data_buf_alloc(asize); 6746 ASSERT3P(cdata, !=, NULL); 6747 if (compress) 6748 csize = zio_compress_data(ZIO_COMPRESS_LZ4, 6749 hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6750 else 6751 csize = len; 6752 6753 if (csize == 0) { 6754 /* zero block, indicate that there's nothing to write */ 6755 zio_data_buf_free(cdata, asize); 6756 l2hdr->b_compress = ZIO_COMPRESS_EMPTY; 6757 l2hdr->b_asize = 0; 6758 hdr->b_l1hdr.b_tmp_cdata = NULL; 6759 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6760 return (B_TRUE); 6761 } 6762 6763 rounded = P2ROUNDUP(csize, align); 6764 ASSERT3U(rounded, <=, asize); 6765 if (rounded < len) { 6766 /* 6767 * Compression succeeded, we'll keep the cdata around for 6768 * writing and release it afterwards. 6769 */ 6770 if (rounded > csize) { 6771 bzero((char *)cdata + csize, rounded - csize); 6772 csize = rounded; 6773 } 6774 l2hdr->b_compress = ZIO_COMPRESS_LZ4; 6775 l2hdr->b_asize = csize; 6776 hdr->b_l1hdr.b_tmp_cdata = cdata; 6777 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6778 return (B_TRUE); 6779 } else { 6780 /* 6781 * Compression did not save space. 6782 */ 6783 if (P2PHASE(len, align) != 0) { 6784 /* 6785 * Use compression buffer for a copy of data padded to 6786 * the proper size. Compression algorithm remains set 6787 * to ZIO_COMPRESS_OFF. 6788 */ 6789 ASSERT3U(len, <, asize); 6790 bcopy(hdr->b_l1hdr.b_tmp_cdata, cdata, len); 6791 bzero((char *)cdata + len, asize - len); 6792 l2hdr->b_asize = asize; 6793 hdr->b_l1hdr.b_tmp_cdata = cdata; 6794 ARCSTAT_BUMP(arcstat_l2_padding_needed); 6795 } else { 6796 ASSERT3U(len, ==, asize); 6797 /* 6798 * The original buffer is good as is, 6799 * release the compressed buffer. 6800 * l2hdr will be left unmodified except for b_tmp_cdata. 6801 */ 6802 zio_data_buf_free(cdata, asize); 6803 hdr->b_l1hdr.b_tmp_cdata = NULL; 6804 } 6805 if (compress) 6806 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6807 return (B_FALSE); 6808 } 6809} 6810 6811/* 6812 * Decompresses a zio read back from an l2arc device. On success, the 6813 * underlying zio's io_data buffer is overwritten by the uncompressed 6814 * version. On decompression error (corrupt compressed stream), the 6815 * zio->io_error value is set to signal an I/O error. 6816 * 6817 * Please note that the compressed data stream is not checksummed, so 6818 * if the underlying device is experiencing data corruption, we may feed 6819 * corrupt data to the decompressor, so the decompressor needs to be 6820 * able to handle this situation (LZ4 does). 6821 */ 6822static void 6823l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6824{ 6825 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6826 6827 if (zio->io_error != 0) { 6828 /* 6829 * An io error has occured, just restore the original io 6830 * size in preparation for a main pool read. 6831 */ 6832 zio->io_orig_size = zio->io_size = hdr->b_size; 6833 return; 6834 } 6835 6836 if (c == ZIO_COMPRESS_EMPTY) { 6837 /* 6838 * An empty buffer results in a null zio, which means we 6839 * need to fill its io_data after we're done restoring the 6840 * buffer's contents. 6841 */ 6842 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6843 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6844 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6845 } else { 6846 ASSERT(zio->io_data != NULL); 6847 /* 6848 * We copy the compressed data from the start of the arc buffer 6849 * (the zio_read will have pulled in only what we need, the 6850 * rest is garbage which we will overwrite at decompression) 6851 * and then decompress back to the ARC data buffer. This way we 6852 * can minimize copying by simply decompressing back over the 6853 * original compressed data (rather than decompressing to an 6854 * aux buffer and then copying back the uncompressed buffer, 6855 * which is likely to be much larger). 6856 */ 6857 uint64_t csize; 6858 void *cdata; 6859 6860 csize = zio->io_size; 6861 cdata = zio_data_buf_alloc(csize); 6862 bcopy(zio->io_data, cdata, csize); 6863 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6864 hdr->b_size) != 0) 6865 zio->io_error = EIO; 6866 zio_data_buf_free(cdata, csize); 6867 } 6868 6869 /* Restore the expected uncompressed IO size. */ 6870 zio->io_orig_size = zio->io_size = hdr->b_size; 6871} 6872 6873/* 6874 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6875 * This buffer serves as a temporary holder of compressed or padded data while 6876 * the buffer entry is being written to an l2arc device. Once that is 6877 * done, we can dispose of it. 6878 */ 6879static void 6880l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6881{ 6882 size_t align, asize, len; 6883 enum zio_compress comp = hdr->b_l2hdr.b_compress; 6884 6885 ASSERT(HDR_HAS_L2HDR(hdr)); 6886 ASSERT(HDR_HAS_L1HDR(hdr)); 6887 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp)); 6888 6889 if (hdr->b_l1hdr.b_tmp_cdata != NULL) { 6890 ASSERT(comp != ZIO_COMPRESS_EMPTY); 6891 len = hdr->b_size; 6892 align = (size_t)1 << hdr->b_l2hdr.b_dev->l2ad_vdev->vdev_ashift; 6893 asize = P2ROUNDUP(len, align); 6894 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, asize); 6895 hdr->b_l1hdr.b_tmp_cdata = NULL; 6896 } else { 6897 ASSERT(comp == ZIO_COMPRESS_OFF || comp == ZIO_COMPRESS_EMPTY); 6898 } 6899} 6900 6901/* 6902 * This thread feeds the L2ARC at regular intervals. This is the beating 6903 * heart of the L2ARC. 6904 */ 6905static void 6906l2arc_feed_thread(void *dummy __unused) 6907{ 6908 callb_cpr_t cpr; 6909 l2arc_dev_t *dev; 6910 spa_t *spa; 6911 uint64_t size, wrote; 6912 clock_t begin, next = ddi_get_lbolt(); 6913 boolean_t headroom_boost = B_FALSE; 6914 6915 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6916 6917 mutex_enter(&l2arc_feed_thr_lock); 6918 6919 while (l2arc_thread_exit == 0) { 6920 CALLB_CPR_SAFE_BEGIN(&cpr); 6921 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6922 next - ddi_get_lbolt()); 6923 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6924 next = ddi_get_lbolt() + hz; 6925 6926 /* 6927 * Quick check for L2ARC devices. 6928 */ 6929 mutex_enter(&l2arc_dev_mtx); 6930 if (l2arc_ndev == 0) { 6931 mutex_exit(&l2arc_dev_mtx); 6932 continue; 6933 } 6934 mutex_exit(&l2arc_dev_mtx); 6935 begin = ddi_get_lbolt(); 6936 6937 /* 6938 * This selects the next l2arc device to write to, and in 6939 * doing so the next spa to feed from: dev->l2ad_spa. This 6940 * will return NULL if there are now no l2arc devices or if 6941 * they are all faulted. 6942 * 6943 * If a device is returned, its spa's config lock is also 6944 * held to prevent device removal. l2arc_dev_get_next() 6945 * will grab and release l2arc_dev_mtx. 6946 */ 6947 if ((dev = l2arc_dev_get_next()) == NULL) 6948 continue; 6949 6950 spa = dev->l2ad_spa; 6951 ASSERT(spa != NULL); 6952 6953 /* 6954 * If the pool is read-only then force the feed thread to 6955 * sleep a little longer. 6956 */ 6957 if (!spa_writeable(spa)) { 6958 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6959 spa_config_exit(spa, SCL_L2ARC, dev); 6960 continue; 6961 } 6962 6963 /* 6964 * Avoid contributing to memory pressure. 6965 */ 6966 if (arc_reclaim_needed()) { 6967 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6968 spa_config_exit(spa, SCL_L2ARC, dev); 6969 continue; 6970 } 6971 6972 ARCSTAT_BUMP(arcstat_l2_feeds); 6973 6974 size = l2arc_write_size(); 6975 6976 /* 6977 * Evict L2ARC buffers that will be overwritten. 6978 */ 6979 l2arc_evict(dev, size, B_FALSE); 6980 6981 /* 6982 * Write ARC buffers. 6983 */ 6984 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6985 6986 /* 6987 * Calculate interval between writes. 6988 */ 6989 next = l2arc_write_interval(begin, size, wrote); 6990 spa_config_exit(spa, SCL_L2ARC, dev); 6991 } 6992 6993 l2arc_thread_exit = 0; 6994 cv_broadcast(&l2arc_feed_thr_cv); 6995 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6996 thread_exit(); 6997} 6998 6999boolean_t 7000l2arc_vdev_present(vdev_t *vd) 7001{ 7002 l2arc_dev_t *dev; 7003 7004 mutex_enter(&l2arc_dev_mtx); 7005 for (dev = list_head(l2arc_dev_list); dev != NULL; 7006 dev = list_next(l2arc_dev_list, dev)) { 7007 if (dev->l2ad_vdev == vd) 7008 break; 7009 } 7010 mutex_exit(&l2arc_dev_mtx); 7011 7012 return (dev != NULL); 7013} 7014 7015/* 7016 * Add a vdev for use by the L2ARC. By this point the spa has already 7017 * validated the vdev and opened it. 7018 */ 7019void 7020l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7021{ 7022 l2arc_dev_t *adddev; 7023 7024 ASSERT(!l2arc_vdev_present(vd)); 7025 7026 vdev_ashift_optimize(vd); 7027 7028 /* 7029 * Create a new l2arc device entry. 7030 */ 7031 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7032 adddev->l2ad_spa = spa; 7033 adddev->l2ad_vdev = vd; 7034 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7035 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7036 adddev->l2ad_hand = adddev->l2ad_start; 7037 adddev->l2ad_first = B_TRUE; 7038 adddev->l2ad_writing = B_FALSE; 7039 7040 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7041 /* 7042 * This is a list of all ARC buffers that are still valid on the 7043 * device. 7044 */ 7045 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7046 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7047 7048 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7049 refcount_create(&adddev->l2ad_alloc); 7050 7051 /* 7052 * Add device to global list 7053 */ 7054 mutex_enter(&l2arc_dev_mtx); 7055 list_insert_head(l2arc_dev_list, adddev); 7056 atomic_inc_64(&l2arc_ndev); 7057 mutex_exit(&l2arc_dev_mtx); 7058} 7059 7060/* 7061 * Remove a vdev from the L2ARC. 7062 */ 7063void 7064l2arc_remove_vdev(vdev_t *vd) 7065{ 7066 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7067 7068 /* 7069 * Find the device by vdev 7070 */ 7071 mutex_enter(&l2arc_dev_mtx); 7072 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7073 nextdev = list_next(l2arc_dev_list, dev); 7074 if (vd == dev->l2ad_vdev) { 7075 remdev = dev; 7076 break; 7077 } 7078 } 7079 ASSERT(remdev != NULL); 7080 7081 /* 7082 * Remove device from global list 7083 */ 7084 list_remove(l2arc_dev_list, remdev); 7085 l2arc_dev_last = NULL; /* may have been invalidated */ 7086 atomic_dec_64(&l2arc_ndev); 7087 mutex_exit(&l2arc_dev_mtx); 7088 7089 /* 7090 * Clear all buflists and ARC references. L2ARC device flush. 7091 */ 7092 l2arc_evict(remdev, 0, B_TRUE); 7093 list_destroy(&remdev->l2ad_buflist); 7094 mutex_destroy(&remdev->l2ad_mtx); 7095 refcount_destroy(&remdev->l2ad_alloc); 7096 kmem_free(remdev, sizeof (l2arc_dev_t)); 7097} 7098 7099void 7100l2arc_init(void) 7101{ 7102 l2arc_thread_exit = 0; 7103 l2arc_ndev = 0; 7104 l2arc_writes_sent = 0; 7105 l2arc_writes_done = 0; 7106 7107 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7108 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7109 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7110 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7111 7112 l2arc_dev_list = &L2ARC_dev_list; 7113 l2arc_free_on_write = &L2ARC_free_on_write; 7114 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7115 offsetof(l2arc_dev_t, l2ad_node)); 7116 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7117 offsetof(l2arc_data_free_t, l2df_list_node)); 7118} 7119 7120void 7121l2arc_fini(void) 7122{ 7123 /* 7124 * This is called from dmu_fini(), which is called from spa_fini(); 7125 * Because of this, we can assume that all l2arc devices have 7126 * already been removed when the pools themselves were removed. 7127 */ 7128 7129 l2arc_do_free_on_write(); 7130 7131 mutex_destroy(&l2arc_feed_thr_lock); 7132 cv_destroy(&l2arc_feed_thr_cv); 7133 mutex_destroy(&l2arc_dev_mtx); 7134 mutex_destroy(&l2arc_free_on_write_mtx); 7135 7136 list_destroy(l2arc_dev_list); 7137 list_destroy(l2arc_free_on_write); 7138} 7139 7140void 7141l2arc_start(void) 7142{ 7143 if (!(spa_mode_global & FWRITE)) 7144 return; 7145 7146 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7147 TS_RUN, minclsyspri); 7148} 7149 7150void 7151l2arc_stop(void) 7152{ 7153 if (!(spa_mode_global & FWRITE)) 7154 return; 7155 7156 mutex_enter(&l2arc_feed_thr_lock); 7157 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7158 l2arc_thread_exit = 1; 7159 while (l2arc_thread_exit != 0) 7160 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7161 mutex_exit(&l2arc_feed_thr_lock); 7162} 7163