arc.c revision 288564
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, 2014 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2014 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 mutexs, rather they rely on the 86 * hash table mutexs for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexs). 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#ifdef _KERNEL 133#include <sys/dnlc.h> 134#endif 135#include <sys/callb.h> 136#include <sys/kstat.h> 137#include <sys/trim_map.h> 138#include <zfs_fletcher.h> 139#include <sys/sdt.h> 140 141#include <vm/vm_pageout.h> 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_thr_lock; 153static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */ 154static uint8_t arc_thread_exit; 155 156uint_t arc_reduce_dnlc_percent = 3; 157 158/* 159 * The number of iterations through arc_evict_*() before we 160 * drop & reacquire the lock. 161 */ 162int arc_evict_iterations = 100; 163 164/* number of seconds before growing cache again */ 165static int arc_grow_retry = 60; 166 167/* shift of arc_c for calculating both min and max arc_p */ 168static int arc_p_min_shift = 4; 169 170/* log2(fraction of arc to reclaim) */ 171static int arc_shrink_shift = 7; 172 173/* 174 * log2(fraction of ARC which must be free to allow growing). 175 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 176 * when reading a new block into the ARC, we will evict an equal-sized block 177 * from the ARC. 178 * 179 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 180 * we will still not allow it to grow. 181 */ 182int arc_no_grow_shift = 5; 183 184 185/* 186 * minimum lifespan of a prefetch block in clock ticks 187 * (initialized in arc_init()) 188 */ 189static int arc_min_prefetch_lifespan; 190 191/* 192 * If this percent of memory is free, don't throttle. 193 */ 194int arc_lotsfree_percent = 10; 195 196static int arc_dead; 197extern int zfs_prefetch_disable; 198 199/* 200 * The arc has filled available memory and has now warmed up. 201 */ 202static boolean_t arc_warm; 203 204uint64_t zfs_arc_max; 205uint64_t zfs_arc_min; 206uint64_t zfs_arc_meta_limit = 0; 207uint64_t zfs_arc_meta_min = 0; 208int zfs_arc_grow_retry = 0; 209int zfs_arc_shrink_shift = 0; 210int zfs_arc_p_min_shift = 0; 211int zfs_disable_dup_eviction = 0; 212uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 213u_int zfs_arc_free_target = 0; 214 215static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 216static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 217 218#ifdef _KERNEL 219static void 220arc_free_target_init(void *unused __unused) 221{ 222 223 zfs_arc_free_target = vm_pageout_wakeup_thresh; 224} 225SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 226 arc_free_target_init, NULL); 227 228TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max); 229TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min); 230TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 231TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 232TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize); 233TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 234SYSCTL_DECL(_vfs_zfs); 235SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 236 "Maximum ARC size"); 237SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 238 "Minimum ARC size"); 239SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 240 &zfs_arc_average_blocksize, 0, 241 "ARC average blocksize"); 242SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 243 &arc_shrink_shift, 0, 244 "log2(fraction of arc to reclaim)"); 245 246/* 247 * We don't have a tunable for arc_free_target due to the dependency on 248 * pagedaemon initialisation. 249 */ 250SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 251 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 252 sysctl_vfs_zfs_arc_free_target, "IU", 253 "Desired number of free pages below which ARC triggers reclaim"); 254 255static int 256sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 257{ 258 u_int val; 259 int err; 260 261 val = zfs_arc_free_target; 262 err = sysctl_handle_int(oidp, &val, 0, req); 263 if (err != 0 || req->newptr == NULL) 264 return (err); 265 266 if (val < minfree) 267 return (EINVAL); 268 if (val > cnt.v_page_count) 269 return (EINVAL); 270 271 zfs_arc_free_target = val; 272 273 return (0); 274} 275 276/* 277 * Must be declared here, before the definition of corresponding kstat 278 * macro which uses the same names will confuse the compiler. 279 */ 280SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 281 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 282 sysctl_vfs_zfs_arc_meta_limit, "QU", 283 "ARC metadata limit"); 284#endif 285 286/* 287 * Note that buffers can be in one of 6 states: 288 * ARC_anon - anonymous (discussed below) 289 * ARC_mru - recently used, currently cached 290 * ARC_mru_ghost - recentely used, no longer in cache 291 * ARC_mfu - frequently used, currently cached 292 * ARC_mfu_ghost - frequently used, no longer in cache 293 * ARC_l2c_only - exists in L2ARC but not other states 294 * When there are no active references to the buffer, they are 295 * are linked onto a list in one of these arc states. These are 296 * the only buffers that can be evicted or deleted. Within each 297 * state there are multiple lists, one for meta-data and one for 298 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 299 * etc.) is tracked separately so that it can be managed more 300 * explicitly: favored over data, limited explicitly. 301 * 302 * Anonymous buffers are buffers that are not associated with 303 * a DVA. These are buffers that hold dirty block copies 304 * before they are written to stable storage. By definition, 305 * they are "ref'd" and are considered part of arc_mru 306 * that cannot be freed. Generally, they will aquire a DVA 307 * as they are written and migrate onto the arc_mru list. 308 * 309 * The ARC_l2c_only state is for buffers that are in the second 310 * level ARC but no longer in any of the ARC_m* lists. The second 311 * level ARC itself may also contain buffers that are in any of 312 * the ARC_m* states - meaning that a buffer can exist in two 313 * places. The reason for the ARC_l2c_only state is to keep the 314 * buffer header in the hash table, so that reads that hit the 315 * second level ARC benefit from these fast lookups. 316 */ 317 318#define ARCS_LOCK_PAD CACHE_LINE_SIZE 319struct arcs_lock { 320 kmutex_t arcs_lock; 321#ifdef _KERNEL 322 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))]; 323#endif 324}; 325 326/* 327 * must be power of two for mask use to work 328 * 329 */ 330#define ARC_BUFC_NUMDATALISTS 16 331#define ARC_BUFC_NUMMETADATALISTS 16 332#define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS) 333 334typedef struct arc_state { 335 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 336 uint64_t arcs_size; /* total amount of data in this state */ 337 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */ 338 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE); 339} arc_state_t; 340 341#define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock)) 342 343/* The 6 states: */ 344static arc_state_t ARC_anon; 345static arc_state_t ARC_mru; 346static arc_state_t ARC_mru_ghost; 347static arc_state_t ARC_mfu; 348static arc_state_t ARC_mfu_ghost; 349static arc_state_t ARC_l2c_only; 350 351typedef struct arc_stats { 352 kstat_named_t arcstat_hits; 353 kstat_named_t arcstat_misses; 354 kstat_named_t arcstat_demand_data_hits; 355 kstat_named_t arcstat_demand_data_misses; 356 kstat_named_t arcstat_demand_metadata_hits; 357 kstat_named_t arcstat_demand_metadata_misses; 358 kstat_named_t arcstat_prefetch_data_hits; 359 kstat_named_t arcstat_prefetch_data_misses; 360 kstat_named_t arcstat_prefetch_metadata_hits; 361 kstat_named_t arcstat_prefetch_metadata_misses; 362 kstat_named_t arcstat_mru_hits; 363 kstat_named_t arcstat_mru_ghost_hits; 364 kstat_named_t arcstat_mfu_hits; 365 kstat_named_t arcstat_mfu_ghost_hits; 366 kstat_named_t arcstat_allocated; 367 kstat_named_t arcstat_deleted; 368 kstat_named_t arcstat_stolen; 369 kstat_named_t arcstat_recycle_miss; 370 /* 371 * Number of buffers that could not be evicted because the hash lock 372 * was held by another thread. The lock may not necessarily be held 373 * by something using the same buffer, since hash locks are shared 374 * by multiple buffers. 375 */ 376 kstat_named_t arcstat_mutex_miss; 377 /* 378 * Number of buffers skipped because they have I/O in progress, are 379 * indrect prefetch buffers that have not lived long enough, or are 380 * not from the spa we're trying to evict from. 381 */ 382 kstat_named_t arcstat_evict_skip; 383 kstat_named_t arcstat_evict_l2_cached; 384 kstat_named_t arcstat_evict_l2_eligible; 385 kstat_named_t arcstat_evict_l2_ineligible; 386 kstat_named_t arcstat_hash_elements; 387 kstat_named_t arcstat_hash_elements_max; 388 kstat_named_t arcstat_hash_collisions; 389 kstat_named_t arcstat_hash_chains; 390 kstat_named_t arcstat_hash_chain_max; 391 kstat_named_t arcstat_p; 392 kstat_named_t arcstat_c; 393 kstat_named_t arcstat_c_min; 394 kstat_named_t arcstat_c_max; 395 kstat_named_t arcstat_size; 396 /* 397 * Number of bytes consumed by internal ARC structures necessary 398 * for tracking purposes; these structures are not actually 399 * backed by ARC buffers. This includes arc_buf_hdr_t structures 400 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 401 * caches), and arc_buf_t structures (allocated via arc_buf_t 402 * cache). 403 */ 404 kstat_named_t arcstat_hdr_size; 405 /* 406 * Number of bytes consumed by ARC buffers of type equal to 407 * ARC_BUFC_DATA. This is generally consumed by buffers backing 408 * on disk user data (e.g. plain file contents). 409 */ 410 kstat_named_t arcstat_data_size; 411 /* 412 * Number of bytes consumed by ARC buffers of type equal to 413 * ARC_BUFC_METADATA. This is generally consumed by buffers 414 * backing on disk data that is used for internal ZFS 415 * structures (e.g. ZAP, dnode, indirect blocks, etc). 416 */ 417 kstat_named_t arcstat_metadata_size; 418 /* 419 * Number of bytes consumed by various buffers and structures 420 * not actually backed with ARC buffers. This includes bonus 421 * buffers (allocated directly via zio_buf_* functions), 422 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 423 * cache), and dnode_t structures (allocated via dnode_t cache). 424 */ 425 kstat_named_t arcstat_other_size; 426 /* 427 * Total number of bytes consumed by ARC buffers residing in the 428 * arc_anon state. This includes *all* buffers in the arc_anon 429 * state; e.g. data, metadata, evictable, and unevictable buffers 430 * are all included in this value. 431 */ 432 kstat_named_t arcstat_anon_size; 433 /* 434 * Number of bytes consumed by ARC buffers that meet the 435 * following criteria: backing buffers of type ARC_BUFC_DATA, 436 * residing in the arc_anon state, and are eligible for eviction 437 * (e.g. have no outstanding holds on the buffer). 438 */ 439 kstat_named_t arcstat_anon_evictable_data; 440 /* 441 * Number of bytes consumed by ARC buffers that meet the 442 * following criteria: backing buffers of type ARC_BUFC_METADATA, 443 * residing in the arc_anon state, and are eligible for eviction 444 * (e.g. have no outstanding holds on the buffer). 445 */ 446 kstat_named_t arcstat_anon_evictable_metadata; 447 /* 448 * Total number of bytes consumed by ARC buffers residing in the 449 * arc_mru state. This includes *all* buffers in the arc_mru 450 * state; e.g. data, metadata, evictable, and unevictable buffers 451 * are all included in this value. 452 */ 453 kstat_named_t arcstat_mru_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_mru state, and are eligible for eviction 458 * (e.g. have no outstanding holds on the buffer). 459 */ 460 kstat_named_t arcstat_mru_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_mru state, and are eligible for eviction 465 * (e.g. have no outstanding holds on the buffer). 466 */ 467 kstat_named_t arcstat_mru_evictable_metadata; 468 /* 469 * Total number of bytes that *would have been* consumed by ARC 470 * buffers in the arc_mru_ghost state. The key thing to note 471 * here, is the fact that this size doesn't actually indicate 472 * RAM consumption. The ghost lists only consist of headers and 473 * don't actually have ARC buffers linked off of these headers. 474 * Thus, *if* the headers had associated ARC buffers, these 475 * buffers *would have* consumed this number of bytes. 476 */ 477 kstat_named_t arcstat_mru_ghost_size; 478 /* 479 * Number of bytes that *would have been* consumed by ARC 480 * buffers that are eligible for eviction, of type 481 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 482 */ 483 kstat_named_t arcstat_mru_ghost_evictable_data; 484 /* 485 * Number of bytes that *would have been* consumed by ARC 486 * buffers that are eligible for eviction, of type 487 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 488 */ 489 kstat_named_t arcstat_mru_ghost_evictable_metadata; 490 /* 491 * Total number of bytes consumed by ARC buffers residing in the 492 * arc_mfu state. This includes *all* buffers in the arc_mfu 493 * state; e.g. data, metadata, evictable, and unevictable buffers 494 * are all included in this value. 495 */ 496 kstat_named_t arcstat_mfu_size; 497 /* 498 * Number of bytes consumed by ARC buffers that are eligible for 499 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 500 * state. 501 */ 502 kstat_named_t arcstat_mfu_evictable_data; 503 /* 504 * Number of bytes consumed by ARC buffers that are eligible for 505 * eviction, of type ARC_BUFC_METADATA, and reside in the 506 * arc_mfu state. 507 */ 508 kstat_named_t arcstat_mfu_evictable_metadata; 509 /* 510 * Total number of bytes that *would have been* consumed by ARC 511 * buffers in the arc_mfu_ghost state. See the comment above 512 * arcstat_mru_ghost_size for more details. 513 */ 514 kstat_named_t arcstat_mfu_ghost_size; 515 /* 516 * Number of bytes that *would have been* consumed by ARC 517 * buffers that are eligible for eviction, of type 518 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 519 */ 520 kstat_named_t arcstat_mfu_ghost_evictable_data; 521 /* 522 * Number of bytes that *would have been* consumed by ARC 523 * buffers that are eligible for eviction, of type 524 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 525 */ 526 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 527 kstat_named_t arcstat_l2_hits; 528 kstat_named_t arcstat_l2_misses; 529 kstat_named_t arcstat_l2_feeds; 530 kstat_named_t arcstat_l2_rw_clash; 531 kstat_named_t arcstat_l2_read_bytes; 532 kstat_named_t arcstat_l2_write_bytes; 533 kstat_named_t arcstat_l2_writes_sent; 534 kstat_named_t arcstat_l2_writes_done; 535 kstat_named_t arcstat_l2_writes_error; 536 kstat_named_t arcstat_l2_writes_hdr_miss; 537 kstat_named_t arcstat_l2_evict_lock_retry; 538 kstat_named_t arcstat_l2_evict_reading; 539 kstat_named_t arcstat_l2_evict_l1cached; 540 kstat_named_t arcstat_l2_free_on_write; 541 kstat_named_t arcstat_l2_cdata_free_on_write; 542 kstat_named_t arcstat_l2_abort_lowmem; 543 kstat_named_t arcstat_l2_cksum_bad; 544 kstat_named_t arcstat_l2_io_error; 545 kstat_named_t arcstat_l2_size; 546 kstat_named_t arcstat_l2_asize; 547 kstat_named_t arcstat_l2_hdr_size; 548 kstat_named_t arcstat_l2_compress_successes; 549 kstat_named_t arcstat_l2_compress_zeros; 550 kstat_named_t arcstat_l2_compress_failures; 551 kstat_named_t arcstat_l2_write_trylock_fail; 552 kstat_named_t arcstat_l2_write_passed_headroom; 553 kstat_named_t arcstat_l2_write_spa_mismatch; 554 kstat_named_t arcstat_l2_write_in_l2; 555 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 556 kstat_named_t arcstat_l2_write_not_cacheable; 557 kstat_named_t arcstat_l2_write_full; 558 kstat_named_t arcstat_l2_write_buffer_iter; 559 kstat_named_t arcstat_l2_write_pios; 560 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 561 kstat_named_t arcstat_l2_write_buffer_list_iter; 562 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 563 kstat_named_t arcstat_memory_throttle_count; 564 kstat_named_t arcstat_duplicate_buffers; 565 kstat_named_t arcstat_duplicate_buffers_size; 566 kstat_named_t arcstat_duplicate_reads; 567 kstat_named_t arcstat_meta_used; 568 kstat_named_t arcstat_meta_limit; 569 kstat_named_t arcstat_meta_max; 570 kstat_named_t arcstat_meta_min; 571} arc_stats_t; 572 573static arc_stats_t arc_stats = { 574 { "hits", KSTAT_DATA_UINT64 }, 575 { "misses", KSTAT_DATA_UINT64 }, 576 { "demand_data_hits", KSTAT_DATA_UINT64 }, 577 { "demand_data_misses", KSTAT_DATA_UINT64 }, 578 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 579 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 580 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 581 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 582 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 583 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 584 { "mru_hits", KSTAT_DATA_UINT64 }, 585 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 586 { "mfu_hits", KSTAT_DATA_UINT64 }, 587 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 588 { "allocated", KSTAT_DATA_UINT64 }, 589 { "deleted", KSTAT_DATA_UINT64 }, 590 { "stolen", KSTAT_DATA_UINT64 }, 591 { "recycle_miss", KSTAT_DATA_UINT64 }, 592 { "mutex_miss", KSTAT_DATA_UINT64 }, 593 { "evict_skip", KSTAT_DATA_UINT64 }, 594 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 595 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 596 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 597 { "hash_elements", KSTAT_DATA_UINT64 }, 598 { "hash_elements_max", KSTAT_DATA_UINT64 }, 599 { "hash_collisions", KSTAT_DATA_UINT64 }, 600 { "hash_chains", KSTAT_DATA_UINT64 }, 601 { "hash_chain_max", KSTAT_DATA_UINT64 }, 602 { "p", KSTAT_DATA_UINT64 }, 603 { "c", KSTAT_DATA_UINT64 }, 604 { "c_min", KSTAT_DATA_UINT64 }, 605 { "c_max", KSTAT_DATA_UINT64 }, 606 { "size", KSTAT_DATA_UINT64 }, 607 { "hdr_size", KSTAT_DATA_UINT64 }, 608 { "data_size", KSTAT_DATA_UINT64 }, 609 { "metadata_size", KSTAT_DATA_UINT64 }, 610 { "other_size", KSTAT_DATA_UINT64 }, 611 { "anon_size", KSTAT_DATA_UINT64 }, 612 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 613 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 614 { "mru_size", KSTAT_DATA_UINT64 }, 615 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 616 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 617 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 618 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 619 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 620 { "mfu_size", KSTAT_DATA_UINT64 }, 621 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 622 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 623 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 624 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 625 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 626 { "l2_hits", KSTAT_DATA_UINT64 }, 627 { "l2_misses", KSTAT_DATA_UINT64 }, 628 { "l2_feeds", KSTAT_DATA_UINT64 }, 629 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 630 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 631 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 632 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 633 { "l2_writes_done", KSTAT_DATA_UINT64 }, 634 { "l2_writes_error", KSTAT_DATA_UINT64 }, 635 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 636 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 637 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 638 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 639 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 640 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 641 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 642 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 643 { "l2_io_error", KSTAT_DATA_UINT64 }, 644 { "l2_size", KSTAT_DATA_UINT64 }, 645 { "l2_asize", KSTAT_DATA_UINT64 }, 646 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 647 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 648 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 649 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 650 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 651 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 652 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 653 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 654 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 655 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 656 { "l2_write_full", KSTAT_DATA_UINT64 }, 657 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 658 { "l2_write_pios", KSTAT_DATA_UINT64 }, 659 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 660 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 661 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 662 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 663 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 664 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 665 { "duplicate_reads", KSTAT_DATA_UINT64 }, 666 { "arc_meta_used", KSTAT_DATA_UINT64 }, 667 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 668 { "arc_meta_max", KSTAT_DATA_UINT64 }, 669 { "arc_meta_min", KSTAT_DATA_UINT64 } 670}; 671 672#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 673 674#define ARCSTAT_INCR(stat, val) \ 675 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 676 677#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 678#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 679 680#define ARCSTAT_MAX(stat, val) { \ 681 uint64_t m; \ 682 while ((val) > (m = arc_stats.stat.value.ui64) && \ 683 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 684 continue; \ 685} 686 687#define ARCSTAT_MAXSTAT(stat) \ 688 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 689 690/* 691 * We define a macro to allow ARC hits/misses to be easily broken down by 692 * two separate conditions, giving a total of four different subtypes for 693 * each of hits and misses (so eight statistics total). 694 */ 695#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 696 if (cond1) { \ 697 if (cond2) { \ 698 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 699 } else { \ 700 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 701 } \ 702 } else { \ 703 if (cond2) { \ 704 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 705 } else { \ 706 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 707 } \ 708 } 709 710kstat_t *arc_ksp; 711static arc_state_t *arc_anon; 712static arc_state_t *arc_mru; 713static arc_state_t *arc_mru_ghost; 714static arc_state_t *arc_mfu; 715static arc_state_t *arc_mfu_ghost; 716static arc_state_t *arc_l2c_only; 717 718/* 719 * There are several ARC variables that are critical to export as kstats -- 720 * but we don't want to have to grovel around in the kstat whenever we wish to 721 * manipulate them. For these variables, we therefore define them to be in 722 * terms of the statistic variable. This assures that we are not introducing 723 * the possibility of inconsistency by having shadow copies of the variables, 724 * while still allowing the code to be readable. 725 */ 726#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 727#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 728#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 729#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 730#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 731#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 732#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 733#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 734#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 735 736#define L2ARC_IS_VALID_COMPRESS(_c_) \ 737 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 738 739static int arc_no_grow; /* Don't try to grow cache size */ 740static uint64_t arc_tempreserve; 741static uint64_t arc_loaned_bytes; 742 743typedef struct arc_callback arc_callback_t; 744 745struct arc_callback { 746 void *acb_private; 747 arc_done_func_t *acb_done; 748 arc_buf_t *acb_buf; 749 zio_t *acb_zio_dummy; 750 arc_callback_t *acb_next; 751}; 752 753typedef struct arc_write_callback arc_write_callback_t; 754 755struct arc_write_callback { 756 void *awcb_private; 757 arc_done_func_t *awcb_ready; 758 arc_done_func_t *awcb_physdone; 759 arc_done_func_t *awcb_done; 760 arc_buf_t *awcb_buf; 761}; 762 763/* 764 * ARC buffers are separated into multiple structs as a memory saving measure: 765 * - Common fields struct, always defined, and embedded within it: 766 * - L2-only fields, always allocated but undefined when not in L2ARC 767 * - L1-only fields, only allocated when in L1ARC 768 * 769 * Buffer in L1 Buffer only in L2 770 * +------------------------+ +------------------------+ 771 * | arc_buf_hdr_t | | arc_buf_hdr_t | 772 * | | | | 773 * | | | | 774 * | | | | 775 * +------------------------+ +------------------------+ 776 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 777 * | (undefined if L1-only) | | | 778 * +------------------------+ +------------------------+ 779 * | l1arc_buf_hdr_t | 780 * | | 781 * | | 782 * | | 783 * | | 784 * +------------------------+ 785 * 786 * Because it's possible for the L2ARC to become extremely large, we can wind 787 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 788 * is minimized by only allocating the fields necessary for an L1-cached buffer 789 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 790 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 791 * words in pointers. arc_hdr_realloc() is used to switch a header between 792 * these two allocation states. 793 */ 794typedef struct l1arc_buf_hdr { 795 kmutex_t b_freeze_lock; 796#ifdef ZFS_DEBUG 797 /* 798 * used for debugging wtih kmem_flags - by allocating and freeing 799 * b_thawed when the buffer is thawed, we get a record of the stack 800 * trace that thawed it. 801 */ 802 void *b_thawed; 803#endif 804 805 arc_buf_t *b_buf; 806 uint32_t b_datacnt; 807 /* for waiting on writes to complete */ 808 kcondvar_t b_cv; 809 810 /* protected by arc state mutex */ 811 arc_state_t *b_state; 812 list_node_t b_arc_node; 813 814 /* updated atomically */ 815 clock_t b_arc_access; 816 817 /* self protecting */ 818 refcount_t b_refcnt; 819 820 arc_callback_t *b_acb; 821 /* temporary buffer holder for in-flight compressed data */ 822 void *b_tmp_cdata; 823} l1arc_buf_hdr_t; 824 825typedef struct l2arc_dev l2arc_dev_t; 826 827typedef struct l2arc_buf_hdr { 828 /* protected by arc_buf_hdr mutex */ 829 l2arc_dev_t *b_dev; /* L2ARC device */ 830 uint64_t b_daddr; /* disk address, offset byte */ 831 /* real alloc'd buffer size depending on b_compress applied */ 832 int32_t b_asize; 833 834 list_node_t b_l2node; 835} l2arc_buf_hdr_t; 836 837struct arc_buf_hdr { 838 /* protected by hash lock */ 839 dva_t b_dva; 840 uint64_t b_birth; 841 /* 842 * Even though this checksum is only set/verified when a buffer is in 843 * the L1 cache, it needs to be in the set of common fields because it 844 * must be preserved from the time before a buffer is written out to 845 * L2ARC until after it is read back in. 846 */ 847 zio_cksum_t *b_freeze_cksum; 848 849 arc_buf_hdr_t *b_hash_next; 850 arc_flags_t b_flags; 851 852 /* immutable */ 853 int32_t b_size; 854 uint64_t b_spa; 855 856 /* L2ARC fields. Undefined when not in L2ARC. */ 857 l2arc_buf_hdr_t b_l2hdr; 858 /* L1ARC fields. Undefined when in l2arc_only state */ 859 l1arc_buf_hdr_t b_l1hdr; 860}; 861 862#ifdef _KERNEL 863static int 864sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 865{ 866 uint64_t val; 867 int err; 868 869 val = arc_meta_limit; 870 err = sysctl_handle_64(oidp, &val, 0, req); 871 if (err != 0 || req->newptr == NULL) 872 return (err); 873 874 if (val <= 0 || val > arc_c_max) 875 return (EINVAL); 876 877 arc_meta_limit = val; 878 return (0); 879} 880#endif 881 882static arc_buf_t *arc_eviction_list; 883static kmutex_t arc_eviction_mtx; 884static arc_buf_hdr_t arc_eviction_hdr; 885 886#define GHOST_STATE(state) \ 887 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 888 (state) == arc_l2c_only) 889 890#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 891#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 892#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 893#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 894#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 895#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 896 897#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 898#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 899#define HDR_L2_READING(hdr) \ 900 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 901 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 902#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 903#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 904#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 905 906#define HDR_ISTYPE_METADATA(hdr) \ 907 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 908#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 909 910#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 911#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 912 913/* For storing compression mode in b_flags */ 914#define HDR_COMPRESS_OFFSET 24 915#define HDR_COMPRESS_NBITS 7 916 917#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 918 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 919#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 920 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 921 922/* 923 * Other sizes 924 */ 925 926#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 927#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 928 929/* 930 * Hash table routines 931 */ 932 933#define HT_LOCK_PAD CACHE_LINE_SIZE 934 935struct ht_lock { 936 kmutex_t ht_lock; 937#ifdef _KERNEL 938 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 939#endif 940}; 941 942#define BUF_LOCKS 256 943typedef struct buf_hash_table { 944 uint64_t ht_mask; 945 arc_buf_hdr_t **ht_table; 946 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 947} buf_hash_table_t; 948 949static buf_hash_table_t buf_hash_table; 950 951#define BUF_HASH_INDEX(spa, dva, birth) \ 952 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 953#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 954#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 955#define HDR_LOCK(hdr) \ 956 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 957 958uint64_t zfs_crc64_table[256]; 959 960/* 961 * Level 2 ARC 962 */ 963 964#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 965#define L2ARC_HEADROOM 2 /* num of writes */ 966/* 967 * If we discover during ARC scan any buffers to be compressed, we boost 968 * our headroom for the next scanning cycle by this percentage multiple. 969 */ 970#define L2ARC_HEADROOM_BOOST 200 971#define L2ARC_FEED_SECS 1 /* caching interval secs */ 972#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 973 974/* 975 * Used to distinguish headers that are being process by 976 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 977 * address. This can happen when the header is added to the l2arc's list 978 * of buffers to write in the first stage of l2arc_write_buffers(), but 979 * has not yet been written out which happens in the second stage of 980 * l2arc_write_buffers(). 981 */ 982#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 983 984#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 985#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 986 987/* L2ARC Performance Tunables */ 988uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 989uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 990uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 991uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 992uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 993uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 994boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 995boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 996boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 997 998SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 999 &l2arc_write_max, 0, "max write size"); 1000SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1001 &l2arc_write_boost, 0, "extra write during warmup"); 1002SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1003 &l2arc_headroom, 0, "number of dev writes"); 1004SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1005 &l2arc_feed_secs, 0, "interval seconds"); 1006SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1007 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1008 1009SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1010 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1011SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1012 &l2arc_feed_again, 0, "turbo warmup"); 1013SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1014 &l2arc_norw, 0, "no reads during writes"); 1015 1016SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1017 &ARC_anon.arcs_size, 0, "size of anonymous state"); 1018SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1019 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1020SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1021 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1022 1023SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1024 &ARC_mru.arcs_size, 0, "size of mru state"); 1025SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1026 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1027SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1028 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1029 1030SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1031 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state"); 1032SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1033 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1034 "size of metadata in mru ghost state"); 1035SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1036 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1037 "size of data in mru ghost state"); 1038 1039SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1040 &ARC_mfu.arcs_size, 0, "size of mfu state"); 1041SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1042 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1043SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1044 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1045 1046SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1047 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state"); 1048SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1049 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1050 "size of metadata in mfu ghost state"); 1051SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1052 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1053 "size of data in mfu ghost state"); 1054 1055SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1056 &ARC_l2c_only.arcs_size, 0, "size of mru state"); 1057 1058/* 1059 * L2ARC Internals 1060 */ 1061struct l2arc_dev { 1062 vdev_t *l2ad_vdev; /* vdev */ 1063 spa_t *l2ad_spa; /* spa */ 1064 uint64_t l2ad_hand; /* next write location */ 1065 uint64_t l2ad_start; /* first addr on device */ 1066 uint64_t l2ad_end; /* last addr on device */ 1067 boolean_t l2ad_first; /* first sweep through */ 1068 boolean_t l2ad_writing; /* currently writing */ 1069 kmutex_t l2ad_mtx; /* lock for buffer list */ 1070 list_t l2ad_buflist; /* buffer list */ 1071 list_node_t l2ad_node; /* device list node */ 1072 refcount_t l2ad_alloc; /* allocated bytes */ 1073}; 1074 1075static list_t L2ARC_dev_list; /* device list */ 1076static list_t *l2arc_dev_list; /* device list pointer */ 1077static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1078static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1079static list_t L2ARC_free_on_write; /* free after write buf list */ 1080static list_t *l2arc_free_on_write; /* free after write list ptr */ 1081static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1082static uint64_t l2arc_ndev; /* number of devices */ 1083 1084typedef struct l2arc_read_callback { 1085 arc_buf_t *l2rcb_buf; /* read buffer */ 1086 spa_t *l2rcb_spa; /* spa */ 1087 blkptr_t l2rcb_bp; /* original blkptr */ 1088 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1089 int l2rcb_flags; /* original flags */ 1090 enum zio_compress l2rcb_compress; /* applied compress */ 1091} l2arc_read_callback_t; 1092 1093typedef struct l2arc_write_callback { 1094 l2arc_dev_t *l2wcb_dev; /* device info */ 1095 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1096} l2arc_write_callback_t; 1097 1098typedef struct l2arc_data_free { 1099 /* protected by l2arc_free_on_write_mtx */ 1100 void *l2df_data; 1101 size_t l2df_size; 1102 void (*l2df_func)(void *, size_t); 1103 list_node_t l2df_list_node; 1104} l2arc_data_free_t; 1105 1106static kmutex_t l2arc_feed_thr_lock; 1107static kcondvar_t l2arc_feed_thr_cv; 1108static uint8_t l2arc_thread_exit; 1109 1110static void arc_get_data_buf(arc_buf_t *); 1111static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1112static int arc_evict_needed(arc_buf_contents_t); 1113static void arc_evict_ghost(arc_state_t *, uint64_t, int64_t); 1114static void arc_buf_watch(arc_buf_t *); 1115 1116static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1117static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1118 1119static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1120static void l2arc_read_done(zio_t *); 1121 1122static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 1123static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1124static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1125 1126static uint64_t 1127buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1128{ 1129 uint8_t *vdva = (uint8_t *)dva; 1130 uint64_t crc = -1ULL; 1131 int i; 1132 1133 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1134 1135 for (i = 0; i < sizeof (dva_t); i++) 1136 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1137 1138 crc ^= (spa>>8) ^ birth; 1139 1140 return (crc); 1141} 1142 1143#define BUF_EMPTY(buf) \ 1144 ((buf)->b_dva.dva_word[0] == 0 && \ 1145 (buf)->b_dva.dva_word[1] == 0) 1146 1147#define BUF_EQUAL(spa, dva, birth, buf) \ 1148 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1149 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1150 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1151 1152static void 1153buf_discard_identity(arc_buf_hdr_t *hdr) 1154{ 1155 hdr->b_dva.dva_word[0] = 0; 1156 hdr->b_dva.dva_word[1] = 0; 1157 hdr->b_birth = 0; 1158} 1159 1160static arc_buf_hdr_t * 1161buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1162{ 1163 const dva_t *dva = BP_IDENTITY(bp); 1164 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1165 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1166 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1167 arc_buf_hdr_t *hdr; 1168 1169 mutex_enter(hash_lock); 1170 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1171 hdr = hdr->b_hash_next) { 1172 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1173 *lockp = hash_lock; 1174 return (hdr); 1175 } 1176 } 1177 mutex_exit(hash_lock); 1178 *lockp = NULL; 1179 return (NULL); 1180} 1181 1182/* 1183 * Insert an entry into the hash table. If there is already an element 1184 * equal to elem in the hash table, then the already existing element 1185 * will be returned and the new element will not be inserted. 1186 * Otherwise returns NULL. 1187 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1188 */ 1189static arc_buf_hdr_t * 1190buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1191{ 1192 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1193 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1194 arc_buf_hdr_t *fhdr; 1195 uint32_t i; 1196 1197 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1198 ASSERT(hdr->b_birth != 0); 1199 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1200 1201 if (lockp != NULL) { 1202 *lockp = hash_lock; 1203 mutex_enter(hash_lock); 1204 } else { 1205 ASSERT(MUTEX_HELD(hash_lock)); 1206 } 1207 1208 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1209 fhdr = fhdr->b_hash_next, i++) { 1210 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1211 return (fhdr); 1212 } 1213 1214 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1215 buf_hash_table.ht_table[idx] = hdr; 1216 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1217 1218 /* collect some hash table performance data */ 1219 if (i > 0) { 1220 ARCSTAT_BUMP(arcstat_hash_collisions); 1221 if (i == 1) 1222 ARCSTAT_BUMP(arcstat_hash_chains); 1223 1224 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1225 } 1226 1227 ARCSTAT_BUMP(arcstat_hash_elements); 1228 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1229 1230 return (NULL); 1231} 1232 1233static void 1234buf_hash_remove(arc_buf_hdr_t *hdr) 1235{ 1236 arc_buf_hdr_t *fhdr, **hdrp; 1237 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1238 1239 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1240 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1241 1242 hdrp = &buf_hash_table.ht_table[idx]; 1243 while ((fhdr = *hdrp) != hdr) { 1244 ASSERT(fhdr != NULL); 1245 hdrp = &fhdr->b_hash_next; 1246 } 1247 *hdrp = hdr->b_hash_next; 1248 hdr->b_hash_next = NULL; 1249 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1250 1251 /* collect some hash table performance data */ 1252 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1253 1254 if (buf_hash_table.ht_table[idx] && 1255 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1256 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1257} 1258 1259/* 1260 * Global data structures and functions for the buf kmem cache. 1261 */ 1262static kmem_cache_t *hdr_full_cache; 1263static kmem_cache_t *hdr_l2only_cache; 1264static kmem_cache_t *buf_cache; 1265 1266static void 1267buf_fini(void) 1268{ 1269 int i; 1270 1271 kmem_free(buf_hash_table.ht_table, 1272 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1273 for (i = 0; i < BUF_LOCKS; i++) 1274 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1275 kmem_cache_destroy(hdr_full_cache); 1276 kmem_cache_destroy(hdr_l2only_cache); 1277 kmem_cache_destroy(buf_cache); 1278} 1279 1280/* 1281 * Constructor callback - called when the cache is empty 1282 * and a new buf is requested. 1283 */ 1284/* ARGSUSED */ 1285static int 1286hdr_full_cons(void *vbuf, void *unused, int kmflag) 1287{ 1288 arc_buf_hdr_t *hdr = vbuf; 1289 1290 bzero(hdr, HDR_FULL_SIZE); 1291 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1292 refcount_create(&hdr->b_l1hdr.b_refcnt); 1293 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1294 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1295 1296 return (0); 1297} 1298 1299/* ARGSUSED */ 1300static int 1301hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1302{ 1303 arc_buf_hdr_t *hdr = vbuf; 1304 1305 bzero(hdr, HDR_L2ONLY_SIZE); 1306 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1307 1308 return (0); 1309} 1310 1311/* ARGSUSED */ 1312static int 1313buf_cons(void *vbuf, void *unused, int kmflag) 1314{ 1315 arc_buf_t *buf = vbuf; 1316 1317 bzero(buf, sizeof (arc_buf_t)); 1318 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1319 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1320 1321 return (0); 1322} 1323 1324/* 1325 * Destructor callback - called when a cached buf is 1326 * no longer required. 1327 */ 1328/* ARGSUSED */ 1329static void 1330hdr_full_dest(void *vbuf, void *unused) 1331{ 1332 arc_buf_hdr_t *hdr = vbuf; 1333 1334 ASSERT(BUF_EMPTY(hdr)); 1335 cv_destroy(&hdr->b_l1hdr.b_cv); 1336 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1337 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1338 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1339} 1340 1341/* ARGSUSED */ 1342static void 1343hdr_l2only_dest(void *vbuf, void *unused) 1344{ 1345 arc_buf_hdr_t *hdr = vbuf; 1346 1347 ASSERT(BUF_EMPTY(hdr)); 1348 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1349} 1350 1351/* ARGSUSED */ 1352static void 1353buf_dest(void *vbuf, void *unused) 1354{ 1355 arc_buf_t *buf = vbuf; 1356 1357 mutex_destroy(&buf->b_evict_lock); 1358 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1359} 1360 1361/* 1362 * Reclaim callback -- invoked when memory is low. 1363 */ 1364/* ARGSUSED */ 1365static void 1366hdr_recl(void *unused) 1367{ 1368 dprintf("hdr_recl called\n"); 1369 /* 1370 * umem calls the reclaim func when we destroy the buf cache, 1371 * which is after we do arc_fini(). 1372 */ 1373 if (!arc_dead) 1374 cv_signal(&arc_reclaim_thr_cv); 1375} 1376 1377static void 1378buf_init(void) 1379{ 1380 uint64_t *ct; 1381 uint64_t hsize = 1ULL << 12; 1382 int i, j; 1383 1384 /* 1385 * The hash table is big enough to fill all of physical memory 1386 * with an average block size of zfs_arc_average_blocksize (default 8K). 1387 * By default, the table will take up 1388 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1389 */ 1390 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1391 hsize <<= 1; 1392retry: 1393 buf_hash_table.ht_mask = hsize - 1; 1394 buf_hash_table.ht_table = 1395 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1396 if (buf_hash_table.ht_table == NULL) { 1397 ASSERT(hsize > (1ULL << 8)); 1398 hsize >>= 1; 1399 goto retry; 1400 } 1401 1402 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1403 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1404 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1405 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1406 NULL, NULL, 0); 1407 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1408 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1409 1410 for (i = 0; i < 256; i++) 1411 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1412 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1413 1414 for (i = 0; i < BUF_LOCKS; i++) { 1415 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1416 NULL, MUTEX_DEFAULT, NULL); 1417 } 1418} 1419 1420/* 1421 * Transition between the two allocation states for the arc_buf_hdr struct. 1422 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1423 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1424 * version is used when a cache buffer is only in the L2ARC in order to reduce 1425 * memory usage. 1426 */ 1427static arc_buf_hdr_t * 1428arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1429{ 1430 ASSERT(HDR_HAS_L2HDR(hdr)); 1431 1432 arc_buf_hdr_t *nhdr; 1433 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1434 1435 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1436 (old == hdr_l2only_cache && new == hdr_full_cache)); 1437 1438 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1439 1440 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1441 buf_hash_remove(hdr); 1442 1443 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1444 1445 if (new == hdr_full_cache) { 1446 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1447 /* 1448 * arc_access and arc_change_state need to be aware that a 1449 * header has just come out of L2ARC, so we set its state to 1450 * l2c_only even though it's about to change. 1451 */ 1452 nhdr->b_l1hdr.b_state = arc_l2c_only; 1453 } else { 1454 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1455 ASSERT0(hdr->b_l1hdr.b_datacnt); 1456 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1457 /* 1458 * We might be removing the L1hdr of a buffer which was just 1459 * written out to L2ARC. If such a buffer is compressed then we 1460 * need to free its b_tmp_cdata before destroying the header. 1461 */ 1462 if (hdr->b_l1hdr.b_tmp_cdata != NULL && 1463 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 1464 l2arc_release_cdata_buf(hdr); 1465 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1466 } 1467 /* 1468 * The header has been reallocated so we need to re-insert it into any 1469 * lists it was on. 1470 */ 1471 (void) buf_hash_insert(nhdr, NULL); 1472 1473 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1474 1475 mutex_enter(&dev->l2ad_mtx); 1476 1477 /* 1478 * We must place the realloc'ed header back into the list at 1479 * the same spot. Otherwise, if it's placed earlier in the list, 1480 * l2arc_write_buffers() could find it during the function's 1481 * write phase, and try to write it out to the l2arc. 1482 */ 1483 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1484 list_remove(&dev->l2ad_buflist, hdr); 1485 1486 mutex_exit(&dev->l2ad_mtx); 1487 1488 /* 1489 * Since we're using the pointer address as the tag when 1490 * incrementing and decrementing the l2ad_alloc refcount, we 1491 * must remove the old pointer (that we're about to destroy) and 1492 * add the new pointer to the refcount. Otherwise we'd remove 1493 * the wrong pointer address when calling arc_hdr_destroy() later. 1494 */ 1495 1496 (void) refcount_remove_many(&dev->l2ad_alloc, 1497 hdr->b_l2hdr.b_asize, hdr); 1498 1499 (void) refcount_add_many(&dev->l2ad_alloc, 1500 nhdr->b_l2hdr.b_asize, nhdr); 1501 1502 buf_discard_identity(hdr); 1503 hdr->b_freeze_cksum = NULL; 1504 kmem_cache_free(old, hdr); 1505 1506 return (nhdr); 1507} 1508 1509 1510#define ARC_MINTIME (hz>>4) /* 62 ms */ 1511 1512static void 1513arc_cksum_verify(arc_buf_t *buf) 1514{ 1515 zio_cksum_t zc; 1516 1517 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1518 return; 1519 1520 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1521 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1522 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1523 return; 1524 } 1525 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1526 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1527 panic("buffer modified while frozen!"); 1528 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1529} 1530 1531static int 1532arc_cksum_equal(arc_buf_t *buf) 1533{ 1534 zio_cksum_t zc; 1535 int equal; 1536 1537 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1538 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1539 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1540 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1541 1542 return (equal); 1543} 1544 1545static void 1546arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1547{ 1548 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1549 return; 1550 1551 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1552 if (buf->b_hdr->b_freeze_cksum != NULL) { 1553 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1554 return; 1555 } 1556 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1557 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1558 buf->b_hdr->b_freeze_cksum); 1559 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1560#ifdef illumos 1561 arc_buf_watch(buf); 1562#endif /* illumos */ 1563} 1564 1565#ifdef illumos 1566#ifndef _KERNEL 1567typedef struct procctl { 1568 long cmd; 1569 prwatch_t prwatch; 1570} procctl_t; 1571#endif 1572 1573/* ARGSUSED */ 1574static void 1575arc_buf_unwatch(arc_buf_t *buf) 1576{ 1577#ifndef _KERNEL 1578 if (arc_watch) { 1579 int result; 1580 procctl_t ctl; 1581 ctl.cmd = PCWATCH; 1582 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1583 ctl.prwatch.pr_size = 0; 1584 ctl.prwatch.pr_wflags = 0; 1585 result = write(arc_procfd, &ctl, sizeof (ctl)); 1586 ASSERT3U(result, ==, sizeof (ctl)); 1587 } 1588#endif 1589} 1590 1591/* ARGSUSED */ 1592static void 1593arc_buf_watch(arc_buf_t *buf) 1594{ 1595#ifndef _KERNEL 1596 if (arc_watch) { 1597 int result; 1598 procctl_t ctl; 1599 ctl.cmd = PCWATCH; 1600 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1601 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1602 ctl.prwatch.pr_wflags = WA_WRITE; 1603 result = write(arc_procfd, &ctl, sizeof (ctl)); 1604 ASSERT3U(result, ==, sizeof (ctl)); 1605 } 1606#endif 1607} 1608#endif /* illumos */ 1609 1610static arc_buf_contents_t 1611arc_buf_type(arc_buf_hdr_t *hdr) 1612{ 1613 if (HDR_ISTYPE_METADATA(hdr)) { 1614 return (ARC_BUFC_METADATA); 1615 } else { 1616 return (ARC_BUFC_DATA); 1617 } 1618} 1619 1620static uint32_t 1621arc_bufc_to_flags(arc_buf_contents_t type) 1622{ 1623 switch (type) { 1624 case ARC_BUFC_DATA: 1625 /* metadata field is 0 if buffer contains normal data */ 1626 return (0); 1627 case ARC_BUFC_METADATA: 1628 return (ARC_FLAG_BUFC_METADATA); 1629 default: 1630 break; 1631 } 1632 panic("undefined ARC buffer type!"); 1633 return ((uint32_t)-1); 1634} 1635 1636void 1637arc_buf_thaw(arc_buf_t *buf) 1638{ 1639 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1640 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1641 panic("modifying non-anon buffer!"); 1642 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1643 panic("modifying buffer while i/o in progress!"); 1644 arc_cksum_verify(buf); 1645 } 1646 1647 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1648 if (buf->b_hdr->b_freeze_cksum != NULL) { 1649 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1650 buf->b_hdr->b_freeze_cksum = NULL; 1651 } 1652 1653#ifdef ZFS_DEBUG 1654 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1655 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1656 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1657 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1658 } 1659#endif 1660 1661 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1662 1663#ifdef illumos 1664 arc_buf_unwatch(buf); 1665#endif /* illumos */ 1666} 1667 1668void 1669arc_buf_freeze(arc_buf_t *buf) 1670{ 1671 kmutex_t *hash_lock; 1672 1673 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1674 return; 1675 1676 hash_lock = HDR_LOCK(buf->b_hdr); 1677 mutex_enter(hash_lock); 1678 1679 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1680 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1681 arc_cksum_compute(buf, B_FALSE); 1682 mutex_exit(hash_lock); 1683 1684} 1685 1686static void 1687get_buf_info(arc_buf_hdr_t *hdr, arc_state_t *state, list_t **list, kmutex_t **lock) 1688{ 1689 uint64_t buf_hashid = buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1690 1691 if (arc_buf_type(hdr) == ARC_BUFC_METADATA) 1692 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1); 1693 else { 1694 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1); 1695 buf_hashid += ARC_BUFC_NUMMETADATALISTS; 1696 } 1697 1698 *list = &state->arcs_lists[buf_hashid]; 1699 *lock = ARCS_LOCK(state, buf_hashid); 1700} 1701 1702 1703static void 1704add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1705{ 1706 ASSERT(HDR_HAS_L1HDR(hdr)); 1707 ASSERT(MUTEX_HELD(hash_lock)); 1708 arc_state_t *state = hdr->b_l1hdr.b_state; 1709 1710 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1711 (state != arc_anon)) { 1712 /* We don't use the L2-only state list. */ 1713 if (state != arc_l2c_only) { 1714 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1715 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1716 list_t *list; 1717 kmutex_t *lock; 1718 1719 get_buf_info(hdr, state, &list, &lock); 1720 ASSERT(!MUTEX_HELD(lock)); 1721 mutex_enter(lock); 1722 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1723 list_remove(list, hdr); 1724 if (GHOST_STATE(state)) { 1725 ASSERT0(hdr->b_l1hdr.b_datacnt); 1726 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1727 delta = hdr->b_size; 1728 } 1729 ASSERT(delta > 0); 1730 ASSERT3U(*size, >=, delta); 1731 atomic_add_64(size, -delta); 1732 mutex_exit(lock); 1733 } 1734 /* remove the prefetch flag if we get a reference */ 1735 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1736 } 1737} 1738 1739static int 1740remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1741{ 1742 int cnt; 1743 arc_state_t *state = hdr->b_l1hdr.b_state; 1744 1745 ASSERT(HDR_HAS_L1HDR(hdr)); 1746 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1747 ASSERT(!GHOST_STATE(state)); 1748 1749 /* 1750 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1751 * check to prevent usage of the arc_l2c_only list. 1752 */ 1753 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1754 (state != arc_anon)) { 1755 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1756 list_t *list; 1757 kmutex_t *lock; 1758 1759 get_buf_info(hdr, state, &list, &lock); 1760 ASSERT(!MUTEX_HELD(lock)); 1761 mutex_enter(lock); 1762 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1763 list_insert_head(list, hdr); 1764 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1765 atomic_add_64(size, hdr->b_size * 1766 hdr->b_l1hdr.b_datacnt); 1767 mutex_exit(lock); 1768 } 1769 return (cnt); 1770} 1771 1772/* 1773 * Move the supplied buffer to the indicated state. The mutex 1774 * for the buffer must be held by the caller. 1775 */ 1776static void 1777arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1778 kmutex_t *hash_lock) 1779{ 1780 arc_state_t *old_state; 1781 int64_t refcnt; 1782 uint32_t datacnt; 1783 uint64_t from_delta, to_delta; 1784 arc_buf_contents_t buftype = arc_buf_type(hdr); 1785 list_t *list; 1786 kmutex_t *lock; 1787 1788 /* 1789 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1790 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1791 * L1 hdr doesn't always exist when we change state to arc_anon before 1792 * destroying a header, in which case reallocating to add the L1 hdr is 1793 * pointless. 1794 */ 1795 if (HDR_HAS_L1HDR(hdr)) { 1796 old_state = hdr->b_l1hdr.b_state; 1797 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1798 datacnt = hdr->b_l1hdr.b_datacnt; 1799 } else { 1800 old_state = arc_l2c_only; 1801 refcnt = 0; 1802 datacnt = 0; 1803 } 1804 1805 ASSERT(MUTEX_HELD(hash_lock)); 1806 ASSERT3P(new_state, !=, old_state); 1807 ASSERT(refcnt == 0 || datacnt > 0); 1808 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1809 ASSERT(old_state != arc_anon || datacnt <= 1); 1810 1811 from_delta = to_delta = datacnt * hdr->b_size; 1812 1813 /* 1814 * If this buffer is evictable, transfer it from the 1815 * old state list to the new state list. 1816 */ 1817 if (refcnt == 0) { 1818 if (old_state != arc_anon && old_state != arc_l2c_only) { 1819 int use_mutex; 1820 uint64_t *size = &old_state->arcs_lsize[buftype]; 1821 1822 get_buf_info(hdr, old_state, &list, &lock); 1823 use_mutex = !MUTEX_HELD(lock); 1824 if (use_mutex) 1825 mutex_enter(lock); 1826 1827 ASSERT(HDR_HAS_L1HDR(hdr)); 1828 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1829 list_remove(list, hdr); 1830 1831 /* 1832 * If prefetching out of the ghost cache, 1833 * we will have a non-zero datacnt. 1834 */ 1835 if (GHOST_STATE(old_state) && datacnt == 0) { 1836 /* ghost elements have a ghost size */ 1837 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1838 from_delta = hdr->b_size; 1839 } 1840 ASSERT3U(*size, >=, from_delta); 1841 atomic_add_64(size, -from_delta); 1842 1843 if (use_mutex) 1844 mutex_exit(lock); 1845 } 1846 if (new_state != arc_anon && new_state != arc_l2c_only) { 1847 int use_mutex; 1848 uint64_t *size = &new_state->arcs_lsize[buftype]; 1849 1850 /* 1851 * An L1 header always exists here, since if we're 1852 * moving to some L1-cached state (i.e. not l2c_only or 1853 * anonymous), we realloc the header to add an L1hdr 1854 * beforehand. 1855 */ 1856 ASSERT(HDR_HAS_L1HDR(hdr)); 1857 get_buf_info(hdr, new_state, &list, &lock); 1858 use_mutex = !MUTEX_HELD(lock); 1859 if (use_mutex) 1860 mutex_enter(lock); 1861 1862 list_insert_head(list, hdr); 1863 1864 /* ghost elements have a ghost size */ 1865 if (GHOST_STATE(new_state)) { 1866 ASSERT(datacnt == 0); 1867 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1868 to_delta = hdr->b_size; 1869 } 1870 atomic_add_64(size, to_delta); 1871 1872 if (use_mutex) 1873 mutex_exit(lock); 1874 } 1875 } 1876 1877 ASSERT(!BUF_EMPTY(hdr)); 1878 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1879 buf_hash_remove(hdr); 1880 1881 /* adjust state sizes (ignore arc_l2c_only) */ 1882 if (to_delta && new_state != arc_l2c_only) 1883 atomic_add_64(&new_state->arcs_size, to_delta); 1884 if (from_delta && old_state != arc_l2c_only) { 1885 ASSERT3U(old_state->arcs_size, >=, from_delta); 1886 atomic_add_64(&old_state->arcs_size, -from_delta); 1887 } 1888 if (HDR_HAS_L1HDR(hdr)) 1889 hdr->b_l1hdr.b_state = new_state; 1890 1891 /* 1892 * L2 headers should never be on the L2 state list since they don't 1893 * have L1 headers allocated. 1894 */ 1895#ifdef illumos 1896 ASSERT(list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1897 list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1898#endif 1899} 1900 1901void 1902arc_space_consume(uint64_t space, arc_space_type_t type) 1903{ 1904 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1905 1906 switch (type) { 1907 case ARC_SPACE_DATA: 1908 ARCSTAT_INCR(arcstat_data_size, space); 1909 break; 1910 case ARC_SPACE_META: 1911 ARCSTAT_INCR(arcstat_metadata_size, space); 1912 break; 1913 case ARC_SPACE_OTHER: 1914 ARCSTAT_INCR(arcstat_other_size, space); 1915 break; 1916 case ARC_SPACE_HDRS: 1917 ARCSTAT_INCR(arcstat_hdr_size, space); 1918 break; 1919 case ARC_SPACE_L2HDRS: 1920 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1921 break; 1922 } 1923 1924 if (type != ARC_SPACE_DATA) 1925 ARCSTAT_INCR(arcstat_meta_used, space); 1926 1927 atomic_add_64(&arc_size, space); 1928} 1929 1930void 1931arc_space_return(uint64_t space, arc_space_type_t type) 1932{ 1933 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1934 1935 switch (type) { 1936 case ARC_SPACE_DATA: 1937 ARCSTAT_INCR(arcstat_data_size, -space); 1938 break; 1939 case ARC_SPACE_META: 1940 ARCSTAT_INCR(arcstat_metadata_size, -space); 1941 break; 1942 case ARC_SPACE_OTHER: 1943 ARCSTAT_INCR(arcstat_other_size, -space); 1944 break; 1945 case ARC_SPACE_HDRS: 1946 ARCSTAT_INCR(arcstat_hdr_size, -space); 1947 break; 1948 case ARC_SPACE_L2HDRS: 1949 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1950 break; 1951 } 1952 1953 if (type != ARC_SPACE_DATA) { 1954 ASSERT(arc_meta_used >= space); 1955 if (arc_meta_max < arc_meta_used) 1956 arc_meta_max = arc_meta_used; 1957 ARCSTAT_INCR(arcstat_meta_used, -space); 1958 } 1959 1960 ASSERT(arc_size >= space); 1961 atomic_add_64(&arc_size, -space); 1962} 1963 1964arc_buf_t * 1965arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1966{ 1967 arc_buf_hdr_t *hdr; 1968 arc_buf_t *buf; 1969 1970 ASSERT3U(size, >, 0); 1971 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1972 ASSERT(BUF_EMPTY(hdr)); 1973 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1974 hdr->b_size = size; 1975 hdr->b_spa = spa_load_guid(spa); 1976 1977 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1978 buf->b_hdr = hdr; 1979 buf->b_data = NULL; 1980 buf->b_efunc = NULL; 1981 buf->b_private = NULL; 1982 buf->b_next = NULL; 1983 1984 hdr->b_flags = arc_bufc_to_flags(type); 1985 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1986 1987 hdr->b_l1hdr.b_buf = buf; 1988 hdr->b_l1hdr.b_state = arc_anon; 1989 hdr->b_l1hdr.b_arc_access = 0; 1990 hdr->b_l1hdr.b_datacnt = 1; 1991 1992 arc_get_data_buf(buf); 1993 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1994 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1995 1996 return (buf); 1997} 1998 1999static char *arc_onloan_tag = "onloan"; 2000 2001/* 2002 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2003 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2004 * buffers must be returned to the arc before they can be used by the DMU or 2005 * freed. 2006 */ 2007arc_buf_t * 2008arc_loan_buf(spa_t *spa, int size) 2009{ 2010 arc_buf_t *buf; 2011 2012 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2013 2014 atomic_add_64(&arc_loaned_bytes, size); 2015 return (buf); 2016} 2017 2018/* 2019 * Return a loaned arc buffer to the arc. 2020 */ 2021void 2022arc_return_buf(arc_buf_t *buf, void *tag) 2023{ 2024 arc_buf_hdr_t *hdr = buf->b_hdr; 2025 2026 ASSERT(buf->b_data != NULL); 2027 ASSERT(HDR_HAS_L1HDR(hdr)); 2028 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2029 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2030 2031 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2032} 2033 2034/* Detach an arc_buf from a dbuf (tag) */ 2035void 2036arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2037{ 2038 arc_buf_hdr_t *hdr = buf->b_hdr; 2039 2040 ASSERT(buf->b_data != NULL); 2041 ASSERT(HDR_HAS_L1HDR(hdr)); 2042 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2043 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2044 buf->b_efunc = NULL; 2045 buf->b_private = NULL; 2046 2047 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2048} 2049 2050static arc_buf_t * 2051arc_buf_clone(arc_buf_t *from) 2052{ 2053 arc_buf_t *buf; 2054 arc_buf_hdr_t *hdr = from->b_hdr; 2055 uint64_t size = hdr->b_size; 2056 2057 ASSERT(HDR_HAS_L1HDR(hdr)); 2058 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2059 2060 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2061 buf->b_hdr = hdr; 2062 buf->b_data = NULL; 2063 buf->b_efunc = NULL; 2064 buf->b_private = NULL; 2065 buf->b_next = hdr->b_l1hdr.b_buf; 2066 hdr->b_l1hdr.b_buf = buf; 2067 arc_get_data_buf(buf); 2068 bcopy(from->b_data, buf->b_data, size); 2069 2070 /* 2071 * This buffer already exists in the arc so create a duplicate 2072 * copy for the caller. If the buffer is associated with user data 2073 * then track the size and number of duplicates. These stats will be 2074 * updated as duplicate buffers are created and destroyed. 2075 */ 2076 if (HDR_ISTYPE_DATA(hdr)) { 2077 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2078 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2079 } 2080 hdr->b_l1hdr.b_datacnt += 1; 2081 return (buf); 2082} 2083 2084void 2085arc_buf_add_ref(arc_buf_t *buf, void* tag) 2086{ 2087 arc_buf_hdr_t *hdr; 2088 kmutex_t *hash_lock; 2089 2090 /* 2091 * Check to see if this buffer is evicted. Callers 2092 * must verify b_data != NULL to know if the add_ref 2093 * was successful. 2094 */ 2095 mutex_enter(&buf->b_evict_lock); 2096 if (buf->b_data == NULL) { 2097 mutex_exit(&buf->b_evict_lock); 2098 return; 2099 } 2100 hash_lock = HDR_LOCK(buf->b_hdr); 2101 mutex_enter(hash_lock); 2102 hdr = buf->b_hdr; 2103 ASSERT(HDR_HAS_L1HDR(hdr)); 2104 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2105 mutex_exit(&buf->b_evict_lock); 2106 2107 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2108 hdr->b_l1hdr.b_state == arc_mfu); 2109 2110 add_reference(hdr, hash_lock, tag); 2111 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2112 arc_access(hdr, hash_lock); 2113 mutex_exit(hash_lock); 2114 ARCSTAT_BUMP(arcstat_hits); 2115 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2116 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2117 data, metadata, hits); 2118} 2119 2120static void 2121arc_buf_free_on_write(void *data, size_t size, 2122 void (*free_func)(void *, size_t)) 2123{ 2124 l2arc_data_free_t *df; 2125 2126 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 2127 df->l2df_data = data; 2128 df->l2df_size = size; 2129 df->l2df_func = free_func; 2130 mutex_enter(&l2arc_free_on_write_mtx); 2131 list_insert_head(l2arc_free_on_write, df); 2132 mutex_exit(&l2arc_free_on_write_mtx); 2133} 2134 2135/* 2136 * Free the arc data buffer. If it is an l2arc write in progress, 2137 * the buffer is placed on l2arc_free_on_write to be freed later. 2138 */ 2139static void 2140arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2141{ 2142 arc_buf_hdr_t *hdr = buf->b_hdr; 2143 2144 if (HDR_L2_WRITING(hdr)) { 2145 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2146 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2147 } else { 2148 free_func(buf->b_data, hdr->b_size); 2149 } 2150} 2151 2152/* 2153 * Free up buf->b_data and if 'remove' is set, then pull the 2154 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2155 */ 2156static void 2157arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2158{ 2159 ASSERT(HDR_HAS_L2HDR(hdr)); 2160 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2161 2162 /* 2163 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2164 * that doesn't exist, the header is in the arc_l2c_only state, 2165 * and there isn't anything to free (it's already been freed). 2166 */ 2167 if (!HDR_HAS_L1HDR(hdr)) 2168 return; 2169 2170 if (hdr->b_l1hdr.b_tmp_cdata == NULL) 2171 return; 2172 2173 ASSERT(HDR_L2_WRITING(hdr)); 2174 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, hdr->b_size, 2175 zio_data_buf_free); 2176 2177 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2178 hdr->b_l1hdr.b_tmp_cdata = NULL; 2179} 2180 2181static void 2182arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) 2183{ 2184 arc_buf_t **bufp; 2185 2186 /* free up data associated with the buf */ 2187 if (buf->b_data != NULL) { 2188 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2189 uint64_t size = buf->b_hdr->b_size; 2190 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2191 2192 arc_cksum_verify(buf); 2193#ifdef illumos 2194 arc_buf_unwatch(buf); 2195#endif /* illumos */ 2196 2197 if (!recycle) { 2198 if (type == ARC_BUFC_METADATA) { 2199 arc_buf_data_free(buf, zio_buf_free); 2200 arc_space_return(size, ARC_SPACE_META); 2201 } else { 2202 ASSERT(type == ARC_BUFC_DATA); 2203 arc_buf_data_free(buf, zio_data_buf_free); 2204 arc_space_return(size, ARC_SPACE_DATA); 2205 } 2206 } 2207 if (list_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2208 uint64_t *cnt = &state->arcs_lsize[type]; 2209 2210 ASSERT(refcount_is_zero( 2211 &buf->b_hdr->b_l1hdr.b_refcnt)); 2212 ASSERT(state != arc_anon && state != arc_l2c_only); 2213 2214 ASSERT3U(*cnt, >=, size); 2215 atomic_add_64(cnt, -size); 2216 } 2217 ASSERT3U(state->arcs_size, >=, size); 2218 atomic_add_64(&state->arcs_size, -size); 2219 buf->b_data = NULL; 2220 2221 /* 2222 * If we're destroying a duplicate buffer make sure 2223 * that the appropriate statistics are updated. 2224 */ 2225 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2226 HDR_ISTYPE_DATA(buf->b_hdr)) { 2227 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2228 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2229 } 2230 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2231 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2232 } 2233 2234 /* only remove the buf if requested */ 2235 if (!remove) 2236 return; 2237 2238 /* remove the buf from the hdr list */ 2239 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2240 bufp = &(*bufp)->b_next) 2241 continue; 2242 *bufp = buf->b_next; 2243 buf->b_next = NULL; 2244 2245 ASSERT(buf->b_efunc == NULL); 2246 2247 /* clean up the buf */ 2248 buf->b_hdr = NULL; 2249 kmem_cache_free(buf_cache, buf); 2250} 2251 2252static void 2253arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2254{ 2255 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2256 l2arc_dev_t *dev = l2hdr->b_dev; 2257 2258 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2259 ASSERT(HDR_HAS_L2HDR(hdr)); 2260 2261 list_remove(&dev->l2ad_buflist, hdr); 2262 2263 /* 2264 * We don't want to leak the b_tmp_cdata buffer that was 2265 * allocated in l2arc_write_buffers() 2266 */ 2267 arc_buf_l2_cdata_free(hdr); 2268 2269 /* 2270 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2271 * this header is being processed by l2arc_write_buffers() (i.e. 2272 * it's in the first stage of l2arc_write_buffers()). 2273 * Re-affirming that truth here, just to serve as a reminder. If 2274 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2275 * may not have its HDR_L2_WRITING flag set. (the write may have 2276 * completed, in which case HDR_L2_WRITING will be false and the 2277 * b_daddr field will point to the address of the buffer on disk). 2278 */ 2279 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2280 2281 /* 2282 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2283 * l2arc_write_buffers(). Since we've just removed this header 2284 * from the l2arc buffer list, this header will never reach the 2285 * second stage of l2arc_write_buffers(), which increments the 2286 * accounting stats for this header. Thus, we must be careful 2287 * not to decrement them for this header either. 2288 */ 2289 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2290 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2291 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2292 2293 vdev_space_update(dev->l2ad_vdev, 2294 -l2hdr->b_asize, 0, 0); 2295 2296 (void) refcount_remove_many(&dev->l2ad_alloc, 2297 l2hdr->b_asize, hdr); 2298 } 2299 2300 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2301} 2302 2303static void 2304arc_hdr_destroy(arc_buf_hdr_t *hdr) 2305{ 2306 if (HDR_HAS_L1HDR(hdr)) { 2307 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2308 hdr->b_l1hdr.b_datacnt > 0); 2309 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2310 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2311 } 2312 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2313 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2314 2315 if (HDR_HAS_L2HDR(hdr)) { 2316 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2317 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2318 2319 if (!buflist_held) 2320 mutex_enter(&dev->l2ad_mtx); 2321 2322 /* 2323 * Even though we checked this conditional above, we 2324 * need to check this again now that we have the 2325 * l2ad_mtx. This is because we could be racing with 2326 * another thread calling l2arc_evict() which might have 2327 * destroyed this header's L2 portion as we were waiting 2328 * to acquire the l2ad_mtx. If that happens, we don't 2329 * want to re-destroy the header's L2 portion. 2330 */ 2331 if (HDR_HAS_L2HDR(hdr)) { 2332 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 2333 hdr->b_l2hdr.b_asize, 0); 2334 arc_hdr_l2hdr_destroy(hdr); 2335 } 2336 2337 if (!buflist_held) 2338 mutex_exit(&dev->l2ad_mtx); 2339 } 2340 2341 if (!BUF_EMPTY(hdr)) 2342 buf_discard_identity(hdr); 2343 if (hdr->b_freeze_cksum != NULL) { 2344 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2345 hdr->b_freeze_cksum = NULL; 2346 } 2347 2348 if (HDR_HAS_L1HDR(hdr)) { 2349 while (hdr->b_l1hdr.b_buf) { 2350 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2351 2352 if (buf->b_efunc != NULL) { 2353 mutex_enter(&arc_eviction_mtx); 2354 mutex_enter(&buf->b_evict_lock); 2355 ASSERT(buf->b_hdr != NULL); 2356 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2357 FALSE); 2358 hdr->b_l1hdr.b_buf = buf->b_next; 2359 buf->b_hdr = &arc_eviction_hdr; 2360 buf->b_next = arc_eviction_list; 2361 arc_eviction_list = buf; 2362 mutex_exit(&buf->b_evict_lock); 2363 mutex_exit(&arc_eviction_mtx); 2364 } else { 2365 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2366 TRUE); 2367 } 2368 } 2369#ifdef ZFS_DEBUG 2370 if (hdr->b_l1hdr.b_thawed != NULL) { 2371 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2372 hdr->b_l1hdr.b_thawed = NULL; 2373 } 2374#endif 2375 } 2376 2377 ASSERT3P(hdr->b_hash_next, ==, NULL); 2378 if (HDR_HAS_L1HDR(hdr)) { 2379 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 2380 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2381 kmem_cache_free(hdr_full_cache, hdr); 2382 } else { 2383 kmem_cache_free(hdr_l2only_cache, hdr); 2384 } 2385} 2386 2387void 2388arc_buf_free(arc_buf_t *buf, void *tag) 2389{ 2390 arc_buf_hdr_t *hdr = buf->b_hdr; 2391 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2392 2393 ASSERT(buf->b_efunc == NULL); 2394 ASSERT(buf->b_data != NULL); 2395 2396 if (hashed) { 2397 kmutex_t *hash_lock = HDR_LOCK(hdr); 2398 2399 mutex_enter(hash_lock); 2400 hdr = buf->b_hdr; 2401 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2402 2403 (void) remove_reference(hdr, hash_lock, tag); 2404 if (hdr->b_l1hdr.b_datacnt > 1) { 2405 arc_buf_destroy(buf, FALSE, TRUE); 2406 } else { 2407 ASSERT(buf == hdr->b_l1hdr.b_buf); 2408 ASSERT(buf->b_efunc == NULL); 2409 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2410 } 2411 mutex_exit(hash_lock); 2412 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2413 int destroy_hdr; 2414 /* 2415 * We are in the middle of an async write. Don't destroy 2416 * this buffer unless the write completes before we finish 2417 * decrementing the reference count. 2418 */ 2419 mutex_enter(&arc_eviction_mtx); 2420 (void) remove_reference(hdr, NULL, tag); 2421 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2422 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2423 mutex_exit(&arc_eviction_mtx); 2424 if (destroy_hdr) 2425 arc_hdr_destroy(hdr); 2426 } else { 2427 if (remove_reference(hdr, NULL, tag) > 0) 2428 arc_buf_destroy(buf, FALSE, TRUE); 2429 else 2430 arc_hdr_destroy(hdr); 2431 } 2432} 2433 2434boolean_t 2435arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2436{ 2437 arc_buf_hdr_t *hdr = buf->b_hdr; 2438 kmutex_t *hash_lock = HDR_LOCK(hdr); 2439 boolean_t no_callback = (buf->b_efunc == NULL); 2440 2441 if (hdr->b_l1hdr.b_state == arc_anon) { 2442 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2443 arc_buf_free(buf, tag); 2444 return (no_callback); 2445 } 2446 2447 mutex_enter(hash_lock); 2448 hdr = buf->b_hdr; 2449 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2450 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2451 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2452 ASSERT(buf->b_data != NULL); 2453 2454 (void) remove_reference(hdr, hash_lock, tag); 2455 if (hdr->b_l1hdr.b_datacnt > 1) { 2456 if (no_callback) 2457 arc_buf_destroy(buf, FALSE, TRUE); 2458 } else if (no_callback) { 2459 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2460 ASSERT(buf->b_efunc == NULL); 2461 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2462 } 2463 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2464 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2465 mutex_exit(hash_lock); 2466 return (no_callback); 2467} 2468 2469int32_t 2470arc_buf_size(arc_buf_t *buf) 2471{ 2472 return (buf->b_hdr->b_size); 2473} 2474 2475/* 2476 * Called from the DMU to determine if the current buffer should be 2477 * evicted. In order to ensure proper locking, the eviction must be initiated 2478 * from the DMU. Return true if the buffer is associated with user data and 2479 * duplicate buffers still exist. 2480 */ 2481boolean_t 2482arc_buf_eviction_needed(arc_buf_t *buf) 2483{ 2484 arc_buf_hdr_t *hdr; 2485 boolean_t evict_needed = B_FALSE; 2486 2487 if (zfs_disable_dup_eviction) 2488 return (B_FALSE); 2489 2490 mutex_enter(&buf->b_evict_lock); 2491 hdr = buf->b_hdr; 2492 if (hdr == NULL) { 2493 /* 2494 * We are in arc_do_user_evicts(); let that function 2495 * perform the eviction. 2496 */ 2497 ASSERT(buf->b_data == NULL); 2498 mutex_exit(&buf->b_evict_lock); 2499 return (B_FALSE); 2500 } else if (buf->b_data == NULL) { 2501 /* 2502 * We have already been added to the arc eviction list; 2503 * recommend eviction. 2504 */ 2505 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2506 mutex_exit(&buf->b_evict_lock); 2507 return (B_TRUE); 2508 } 2509 2510 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2511 evict_needed = B_TRUE; 2512 2513 mutex_exit(&buf->b_evict_lock); 2514 return (evict_needed); 2515} 2516 2517/* 2518 * Evict buffers from list until we've removed the specified number of 2519 * bytes. Move the removed buffers to the appropriate evict state. 2520 * If the recycle flag is set, then attempt to "recycle" a buffer: 2521 * - look for a buffer to evict that is `bytes' long. 2522 * - return the data block from this buffer rather than freeing it. 2523 * This flag is used by callers that are trying to make space for a 2524 * new buffer in a full arc cache. 2525 * 2526 * This function makes a "best effort". It skips over any buffers 2527 * it can't get a hash_lock on, and so may not catch all candidates. 2528 * It may also return without evicting as much space as requested. 2529 */ 2530static void * 2531arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 2532 arc_buf_contents_t type) 2533{ 2534 arc_state_t *evicted_state; 2535 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 2536 int64_t bytes_remaining; 2537 arc_buf_hdr_t *hdr, *hdr_prev = NULL; 2538 list_t *evicted_list, *list, *evicted_list_start, *list_start; 2539 kmutex_t *lock, *evicted_lock; 2540 kmutex_t *hash_lock; 2541 boolean_t have_lock; 2542 void *stolen = NULL; 2543 arc_buf_hdr_t marker = { 0 }; 2544 int count = 0; 2545 static int evict_metadata_offset, evict_data_offset; 2546 int i, idx, offset, list_count, lists; 2547 2548 ASSERT(state == arc_mru || state == arc_mfu); 2549 2550 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2551 2552 /* 2553 * Decide which "type" (data vs metadata) to recycle from. 2554 * 2555 * If we are over the metadata limit, recycle from metadata. 2556 * If we are under the metadata minimum, recycle from data. 2557 * Otherwise, recycle from whichever type has the oldest (least 2558 * recently accessed) header. This is not yet implemented. 2559 */ 2560 if (recycle) { 2561 arc_buf_contents_t realtype; 2562 if (state->arcs_lsize[ARC_BUFC_DATA] == 0) { 2563 realtype = ARC_BUFC_METADATA; 2564 } else if (state->arcs_lsize[ARC_BUFC_METADATA] == 0) { 2565 realtype = ARC_BUFC_DATA; 2566 } else if (arc_meta_used >= arc_meta_limit) { 2567 realtype = ARC_BUFC_METADATA; 2568 } else if (arc_meta_used <= arc_meta_min) { 2569 realtype = ARC_BUFC_DATA; 2570#ifdef illumos 2571 } else if (HDR_HAS_L1HDR(data_hdr) && 2572 HDR_HAS_L1HDR(metadata_hdr) && 2573 data_hdr->b_l1hdr.b_arc_access < 2574 metadata_hdr->b_l1hdr.b_arc_access) { 2575 realtype = ARC_BUFC_DATA; 2576 } else { 2577 realtype = ARC_BUFC_METADATA; 2578#else 2579 } else { 2580 /* TODO */ 2581 realtype = type; 2582#endif 2583 } 2584 if (realtype != type) { 2585 /* 2586 * If we want to evict from a different list, 2587 * we can not recycle, because DATA vs METADATA 2588 * buffers are segregated into different kmem 2589 * caches (and vmem arenas). 2590 */ 2591 type = realtype; 2592 recycle = B_FALSE; 2593 } 2594 } 2595 2596 if (type == ARC_BUFC_METADATA) { 2597 offset = 0; 2598 list_count = ARC_BUFC_NUMMETADATALISTS; 2599 list_start = &state->arcs_lists[0]; 2600 evicted_list_start = &evicted_state->arcs_lists[0]; 2601 idx = evict_metadata_offset; 2602 } else { 2603 offset = ARC_BUFC_NUMMETADATALISTS; 2604 list_start = &state->arcs_lists[offset]; 2605 evicted_list_start = &evicted_state->arcs_lists[offset]; 2606 list_count = ARC_BUFC_NUMDATALISTS; 2607 idx = evict_data_offset; 2608 } 2609 bytes_remaining = evicted_state->arcs_lsize[type]; 2610 lists = 0; 2611 2612evict_start: 2613 list = &list_start[idx]; 2614 evicted_list = &evicted_list_start[idx]; 2615 lock = ARCS_LOCK(state, (offset + idx)); 2616 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx)); 2617 2618 /* 2619 * The ghost list lock must be acquired first in order to prevent 2620 * a 3 party deadlock: 2621 * 2622 * - arc_evict_ghost acquires arc_*_ghost->arcs_mtx, followed by 2623 * l2ad_mtx in arc_hdr_realloc 2624 * - l2arc_write_buffers acquires l2ad_mtx, followed by arc_*->arcs_mtx 2625 * - arc_evict acquires arc_*_ghost->arcs_mtx, followed by 2626 * arc_*_ghost->arcs_mtx and forms a deadlock cycle. 2627 * 2628 * This situation is avoided by acquiring the ghost list lock first. 2629 */ 2630 mutex_enter(evicted_lock); 2631 mutex_enter(lock); 2632 2633 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2634 hdr_prev = list_prev(list, hdr); 2635 if (HDR_HAS_L1HDR(hdr)) { 2636 bytes_remaining -= 2637 (hdr->b_size * hdr->b_l1hdr.b_datacnt); 2638 } 2639 /* prefetch buffers have a minimum lifespan */ 2640 if (HDR_IO_IN_PROGRESS(hdr) || 2641 (spa && hdr->b_spa != spa) || 2642 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2643 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2644 arc_min_prefetch_lifespan)) { 2645 skipped++; 2646 continue; 2647 } 2648 /* "lookahead" for better eviction candidate */ 2649 if (recycle && hdr->b_size != bytes && 2650 hdr_prev && hdr_prev->b_size == bytes) 2651 continue; 2652 2653 /* ignore markers */ 2654 if (hdr->b_spa == 0) 2655 continue; 2656 2657 /* 2658 * It may take a long time to evict all the bufs requested. 2659 * To avoid blocking all arc activity, periodically drop 2660 * the arcs_mtx and give other threads a chance to run 2661 * before reacquiring the lock. 2662 * 2663 * If we are looking for a buffer to recycle, we are in 2664 * the hot code path, so don't sleep. 2665 */ 2666 if (!recycle && count++ > arc_evict_iterations) { 2667 list_insert_after(list, hdr, &marker); 2668 mutex_exit(lock); 2669 mutex_exit(evicted_lock); 2670 kpreempt(KPREEMPT_SYNC); 2671 mutex_enter(evicted_lock); 2672 mutex_enter(lock); 2673 hdr_prev = list_prev(list, &marker); 2674 list_remove(list, &marker); 2675 count = 0; 2676 continue; 2677 } 2678 2679 hash_lock = HDR_LOCK(hdr); 2680 have_lock = MUTEX_HELD(hash_lock); 2681 if (have_lock || mutex_tryenter(hash_lock)) { 2682 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2683 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2684 while (hdr->b_l1hdr.b_buf) { 2685 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2686 if (!mutex_tryenter(&buf->b_evict_lock)) { 2687 missed += 1; 2688 break; 2689 } 2690 if (buf->b_data != NULL) { 2691 bytes_evicted += hdr->b_size; 2692 if (recycle && 2693 arc_buf_type(hdr) == type && 2694 hdr->b_size == bytes && 2695 !HDR_L2_WRITING(hdr)) { 2696 stolen = buf->b_data; 2697 recycle = FALSE; 2698 } 2699 } 2700 if (buf->b_efunc != NULL) { 2701 mutex_enter(&arc_eviction_mtx); 2702 arc_buf_destroy(buf, 2703 buf->b_data == stolen, FALSE); 2704 hdr->b_l1hdr.b_buf = buf->b_next; 2705 buf->b_hdr = &arc_eviction_hdr; 2706 buf->b_next = arc_eviction_list; 2707 arc_eviction_list = buf; 2708 mutex_exit(&arc_eviction_mtx); 2709 mutex_exit(&buf->b_evict_lock); 2710 } else { 2711 mutex_exit(&buf->b_evict_lock); 2712 arc_buf_destroy(buf, 2713 buf->b_data == stolen, TRUE); 2714 } 2715 } 2716 2717 if (HDR_HAS_L2HDR(hdr)) { 2718 ARCSTAT_INCR(arcstat_evict_l2_cached, 2719 hdr->b_size); 2720 } else { 2721 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 2722 ARCSTAT_INCR(arcstat_evict_l2_eligible, 2723 hdr->b_size); 2724 } else { 2725 ARCSTAT_INCR( 2726 arcstat_evict_l2_ineligible, 2727 hdr->b_size); 2728 } 2729 } 2730 2731 if (hdr->b_l1hdr.b_datacnt == 0) { 2732 arc_change_state(evicted_state, hdr, hash_lock); 2733 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2734 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2735 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2736 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2737 } 2738 if (!have_lock) 2739 mutex_exit(hash_lock); 2740 if (bytes >= 0 && bytes_evicted >= bytes) 2741 break; 2742 if (bytes_remaining > 0) { 2743 mutex_exit(evicted_lock); 2744 mutex_exit(lock); 2745 idx = ((idx + 1) & (list_count - 1)); 2746 lists++; 2747 goto evict_start; 2748 } 2749 } else { 2750 missed += 1; 2751 } 2752 } 2753 2754 mutex_exit(lock); 2755 mutex_exit(evicted_lock); 2756 2757 idx = ((idx + 1) & (list_count - 1)); 2758 lists++; 2759 2760 if (bytes_evicted < bytes) { 2761 if (lists < list_count) 2762 goto evict_start; 2763 else 2764 dprintf("only evicted %lld bytes from %x", 2765 (longlong_t)bytes_evicted, state); 2766 } 2767 if (type == ARC_BUFC_METADATA) 2768 evict_metadata_offset = idx; 2769 else 2770 evict_data_offset = idx; 2771 2772 if (skipped) 2773 ARCSTAT_INCR(arcstat_evict_skip, skipped); 2774 2775 if (missed) 2776 ARCSTAT_INCR(arcstat_mutex_miss, missed); 2777 2778 /* 2779 * Note: we have just evicted some data into the ghost state, 2780 * potentially putting the ghost size over the desired size. Rather 2781 * that evicting from the ghost list in this hot code path, leave 2782 * this chore to the arc_reclaim_thread(). 2783 */ 2784 2785 if (stolen) 2786 ARCSTAT_BUMP(arcstat_stolen); 2787 return (stolen); 2788} 2789 2790/* 2791 * Remove buffers from list until we've removed the specified number of 2792 * bytes. Destroy the buffers that are removed. 2793 */ 2794static void 2795arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 2796{ 2797 arc_buf_hdr_t *hdr, *hdr_prev; 2798 arc_buf_hdr_t marker = { 0 }; 2799 list_t *list, *list_start; 2800 kmutex_t *hash_lock, *lock; 2801 uint64_t bytes_deleted = 0; 2802 uint64_t bufs_skipped = 0; 2803 int count = 0; 2804 static int evict_offset; 2805 int list_count, idx = evict_offset; 2806 int offset, lists = 0; 2807 2808 ASSERT(GHOST_STATE(state)); 2809 2810 /* 2811 * data lists come after metadata lists 2812 */ 2813 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS]; 2814 list_count = ARC_BUFC_NUMDATALISTS; 2815 offset = ARC_BUFC_NUMMETADATALISTS; 2816 2817evict_start: 2818 list = &list_start[idx]; 2819 lock = ARCS_LOCK(state, idx + offset); 2820 2821 mutex_enter(lock); 2822 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2823 hdr_prev = list_prev(list, hdr); 2824 if (arc_buf_type(hdr) >= ARC_BUFC_NUMTYPES) 2825 panic("invalid hdr=%p", (void *)hdr); 2826 if (spa && hdr->b_spa != spa) 2827 continue; 2828 2829 /* ignore markers */ 2830 if (hdr->b_spa == 0) 2831 continue; 2832 2833 hash_lock = HDR_LOCK(hdr); 2834 /* caller may be trying to modify this buffer, skip it */ 2835 if (MUTEX_HELD(hash_lock)) 2836 continue; 2837 2838 /* 2839 * It may take a long time to evict all the bufs requested. 2840 * To avoid blocking all arc activity, periodically drop 2841 * the arcs_mtx and give other threads a chance to run 2842 * before reacquiring the lock. 2843 */ 2844 if (count++ > arc_evict_iterations) { 2845 list_insert_after(list, hdr, &marker); 2846 mutex_exit(lock); 2847 kpreempt(KPREEMPT_SYNC); 2848 mutex_enter(lock); 2849 hdr_prev = list_prev(list, &marker); 2850 list_remove(list, &marker); 2851 count = 0; 2852 continue; 2853 } 2854 if (mutex_tryenter(hash_lock)) { 2855 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2856 ASSERT(!HDR_HAS_L1HDR(hdr) || 2857 hdr->b_l1hdr.b_buf == NULL); 2858 ARCSTAT_BUMP(arcstat_deleted); 2859 bytes_deleted += hdr->b_size; 2860 2861 if (HDR_HAS_L2HDR(hdr)) { 2862 /* 2863 * This buffer is cached on the 2nd Level ARC; 2864 * don't destroy the header. 2865 */ 2866 arc_change_state(arc_l2c_only, hdr, hash_lock); 2867 /* 2868 * dropping from L1+L2 cached to L2-only, 2869 * realloc to remove the L1 header. 2870 */ 2871 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2872 hdr_l2only_cache); 2873 mutex_exit(hash_lock); 2874 } else { 2875 arc_change_state(arc_anon, hdr, hash_lock); 2876 mutex_exit(hash_lock); 2877 arc_hdr_destroy(hdr); 2878 } 2879 2880 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2881 if (bytes >= 0 && bytes_deleted >= bytes) 2882 break; 2883 } else if (bytes < 0) { 2884 /* 2885 * Insert a list marker and then wait for the 2886 * hash lock to become available. Once its 2887 * available, restart from where we left off. 2888 */ 2889 list_insert_after(list, hdr, &marker); 2890 mutex_exit(lock); 2891 mutex_enter(hash_lock); 2892 mutex_exit(hash_lock); 2893 mutex_enter(lock); 2894 hdr_prev = list_prev(list, &marker); 2895 list_remove(list, &marker); 2896 } else { 2897 bufs_skipped += 1; 2898 } 2899 2900 } 2901 mutex_exit(lock); 2902 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1)); 2903 lists++; 2904 2905 if (lists < list_count) 2906 goto evict_start; 2907 2908 evict_offset = idx; 2909 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] && 2910 (bytes < 0 || bytes_deleted < bytes)) { 2911 list_start = &state->arcs_lists[0]; 2912 list_count = ARC_BUFC_NUMMETADATALISTS; 2913 offset = lists = 0; 2914 goto evict_start; 2915 } 2916 2917 if (bufs_skipped) { 2918 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2919 ASSERT(bytes >= 0); 2920 } 2921 2922 if (bytes_deleted < bytes) 2923 dprintf("only deleted %lld bytes from %p", 2924 (longlong_t)bytes_deleted, state); 2925} 2926 2927static void 2928arc_adjust(void) 2929{ 2930 int64_t adjustment, delta; 2931 2932 /* 2933 * Adjust MRU size 2934 */ 2935 2936 adjustment = MIN((int64_t)(arc_size - arc_c), 2937 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2938 arc_p)); 2939 2940 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2941 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2942 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA); 2943 adjustment -= delta; 2944 } 2945 2946 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2947 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2948 (void) arc_evict(arc_mru, 0, delta, FALSE, 2949 ARC_BUFC_METADATA); 2950 } 2951 2952 /* 2953 * Adjust MFU size 2954 */ 2955 2956 adjustment = arc_size - arc_c; 2957 2958 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2959 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2960 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA); 2961 adjustment -= delta; 2962 } 2963 2964 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2965 int64_t delta = MIN(adjustment, 2966 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2967 (void) arc_evict(arc_mfu, 0, delta, FALSE, 2968 ARC_BUFC_METADATA); 2969 } 2970 2971 /* 2972 * Adjust ghost lists 2973 */ 2974 2975 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2976 2977 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2978 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2979 arc_evict_ghost(arc_mru_ghost, 0, delta); 2980 } 2981 2982 adjustment = 2983 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2984 2985 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2986 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2987 arc_evict_ghost(arc_mfu_ghost, 0, delta); 2988 } 2989} 2990 2991static void 2992arc_do_user_evicts(void) 2993{ 2994 static arc_buf_t *tmp_arc_eviction_list; 2995 2996 /* 2997 * Move list over to avoid LOR 2998 */ 2999restart: 3000 mutex_enter(&arc_eviction_mtx); 3001 tmp_arc_eviction_list = arc_eviction_list; 3002 arc_eviction_list = NULL; 3003 mutex_exit(&arc_eviction_mtx); 3004 3005 while (tmp_arc_eviction_list != NULL) { 3006 arc_buf_t *buf = tmp_arc_eviction_list; 3007 tmp_arc_eviction_list = buf->b_next; 3008 mutex_enter(&buf->b_evict_lock); 3009 buf->b_hdr = NULL; 3010 mutex_exit(&buf->b_evict_lock); 3011 3012 if (buf->b_efunc != NULL) 3013 VERIFY0(buf->b_efunc(buf->b_private)); 3014 3015 buf->b_efunc = NULL; 3016 buf->b_private = NULL; 3017 kmem_cache_free(buf_cache, buf); 3018 } 3019 3020 if (arc_eviction_list != NULL) 3021 goto restart; 3022} 3023 3024/* 3025 * Flush all *evictable* data from the cache for the given spa. 3026 * NOTE: this will not touch "active" (i.e. referenced) data. 3027 */ 3028void 3029arc_flush(spa_t *spa) 3030{ 3031 uint64_t guid = 0; 3032 3033 if (spa != NULL) 3034 guid = spa_load_guid(spa); 3035 3036 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) { 3037 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 3038 if (spa != NULL) 3039 break; 3040 } 3041 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) { 3042 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 3043 if (spa != NULL) 3044 break; 3045 } 3046 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) { 3047 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 3048 if (spa != NULL) 3049 break; 3050 } 3051 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) { 3052 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 3053 if (spa != NULL) 3054 break; 3055 } 3056 3057 arc_evict_ghost(arc_mru_ghost, guid, -1); 3058 arc_evict_ghost(arc_mfu_ghost, guid, -1); 3059 3060 mutex_enter(&arc_reclaim_thr_lock); 3061 arc_do_user_evicts(); 3062 mutex_exit(&arc_reclaim_thr_lock); 3063 ASSERT(spa || arc_eviction_list == NULL); 3064} 3065 3066void 3067arc_shrink(int64_t to_free) 3068{ 3069 3070 if (arc_c > arc_c_min) { 3071 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3072 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3073 if (arc_c > arc_c_min + to_free) 3074 atomic_add_64(&arc_c, -to_free); 3075 else 3076 arc_c = arc_c_min; 3077 3078 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3079 if (arc_c > arc_size) 3080 arc_c = MAX(arc_size, arc_c_min); 3081 if (arc_p > arc_c) 3082 arc_p = (arc_c >> 1); 3083 3084 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3085 arc_p); 3086 3087 ASSERT(arc_c >= arc_c_min); 3088 ASSERT((int64_t)arc_p >= 0); 3089 } 3090 3091 if (arc_size > arc_c) { 3092 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3093 uint64_t, arc_c); 3094 arc_adjust(); 3095 } 3096} 3097 3098static long needfree = 0; 3099 3100typedef enum free_memory_reason_t { 3101 FMR_UNKNOWN, 3102 FMR_NEEDFREE, 3103 FMR_LOTSFREE, 3104 FMR_SWAPFS_MINFREE, 3105 FMR_PAGES_PP_MAXIMUM, 3106 FMR_HEAP_ARENA, 3107 FMR_ZIO_ARENA, 3108 FMR_ZIO_FRAG, 3109} free_memory_reason_t; 3110 3111int64_t last_free_memory; 3112free_memory_reason_t last_free_reason; 3113 3114/* 3115 * Additional reserve of pages for pp_reserve. 3116 */ 3117int64_t arc_pages_pp_reserve = 64; 3118 3119/* 3120 * Additional reserve of pages for swapfs. 3121 */ 3122int64_t arc_swapfs_reserve = 64; 3123 3124/* 3125 * Return the amount of memory that can be consumed before reclaim will be 3126 * needed. Positive if there is sufficient free memory, negative indicates 3127 * the amount of memory that needs to be freed up. 3128 */ 3129static int64_t 3130arc_available_memory(void) 3131{ 3132 int64_t lowest = INT64_MAX; 3133 int64_t n; 3134 free_memory_reason_t r = FMR_UNKNOWN; 3135 3136#ifdef _KERNEL 3137 if (needfree > 0) { 3138 n = PAGESIZE * (-needfree); 3139 if (n < lowest) { 3140 lowest = n; 3141 r = FMR_NEEDFREE; 3142 } 3143 } 3144 3145 /* 3146 * Cooperate with pagedaemon when it's time for it to scan 3147 * and reclaim some pages. 3148 */ 3149 n = PAGESIZE * (int64_t)(freemem - zfs_arc_free_target); 3150 if (n < lowest) { 3151 lowest = n; 3152 r = FMR_LOTSFREE; 3153 } 3154 3155#ifdef sun 3156 /* 3157 * check that we're out of range of the pageout scanner. It starts to 3158 * schedule paging if freemem is less than lotsfree and needfree. 3159 * lotsfree is the high-water mark for pageout, and needfree is the 3160 * number of needed free pages. We add extra pages here to make sure 3161 * the scanner doesn't start up while we're freeing memory. 3162 */ 3163 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3164 if (n < lowest) { 3165 lowest = n; 3166 r = FMR_LOTSFREE; 3167 } 3168 3169 /* 3170 * check to make sure that swapfs has enough space so that anon 3171 * reservations can still succeed. anon_resvmem() checks that the 3172 * availrmem is greater than swapfs_minfree, and the number of reserved 3173 * swap pages. We also add a bit of extra here just to prevent 3174 * circumstances from getting really dire. 3175 */ 3176 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3177 desfree - arc_swapfs_reserve); 3178 if (n < lowest) { 3179 lowest = n; 3180 r = FMR_SWAPFS_MINFREE; 3181 } 3182 3183 3184 /* 3185 * Check that we have enough availrmem that memory locking (e.g., via 3186 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3187 * stores the number of pages that cannot be locked; when availrmem 3188 * drops below pages_pp_maximum, page locking mechanisms such as 3189 * page_pp_lock() will fail.) 3190 */ 3191 n = PAGESIZE * (availrmem - pages_pp_maximum - 3192 arc_pages_pp_reserve); 3193 if (n < lowest) { 3194 lowest = n; 3195 r = FMR_PAGES_PP_MAXIMUM; 3196 } 3197 3198#endif /* sun */ 3199#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3200 /* 3201 * If we're on an i386 platform, it's possible that we'll exhaust the 3202 * kernel heap space before we ever run out of available physical 3203 * memory. Most checks of the size of the heap_area compare against 3204 * tune.t_minarmem, which is the minimum available real memory that we 3205 * can have in the system. However, this is generally fixed at 25 pages 3206 * which is so low that it's useless. In this comparison, we seek to 3207 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3208 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3209 * free) 3210 */ 3211 n = vmem_size(heap_arena, VMEM_FREE) - 3212 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3213 if (n < lowest) { 3214 lowest = n; 3215 r = FMR_HEAP_ARENA; 3216 } 3217#define zio_arena NULL 3218#else 3219#define zio_arena heap_arena 3220#endif 3221 3222 /* 3223 * If zio data pages are being allocated out of a separate heap segment, 3224 * then enforce that the size of available vmem for this arena remains 3225 * above about 1/16th free. 3226 * 3227 * Note: The 1/16th arena free requirement was put in place 3228 * to aggressively evict memory from the arc in order to avoid 3229 * memory fragmentation issues. 3230 */ 3231 if (zio_arena != NULL) { 3232 n = vmem_size(zio_arena, VMEM_FREE) - 3233 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3234 if (n < lowest) { 3235 lowest = n; 3236 r = FMR_ZIO_ARENA; 3237 } 3238 } 3239 3240 /* 3241 * Above limits know nothing about real level of KVA fragmentation. 3242 * Start aggressive reclamation if too little sequential KVA left. 3243 */ 3244 if (lowest > 0) { 3245 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3246 -(vmem_size(heap_arena, VMEM_ALLOC) >> 4) : INT64_MAX; 3247 if (n < lowest) { 3248 lowest = n; 3249 r = FMR_ZIO_FRAG; 3250 } 3251 } 3252 3253#else /* _KERNEL */ 3254 /* Every 100 calls, free a small amount */ 3255 if (spa_get_random(100) == 0) 3256 lowest = -1024; 3257#endif /* _KERNEL */ 3258 3259 last_free_memory = lowest; 3260 last_free_reason = r; 3261 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3262 return (lowest); 3263} 3264 3265 3266/* 3267 * Determine if the system is under memory pressure and is asking 3268 * to reclaim memory. A return value of TRUE indicates that the system 3269 * is under memory pressure and that the arc should adjust accordingly. 3270 */ 3271static boolean_t 3272arc_reclaim_needed(void) 3273{ 3274 return (arc_available_memory() < 0); 3275} 3276 3277extern kmem_cache_t *zio_buf_cache[]; 3278extern kmem_cache_t *zio_data_buf_cache[]; 3279extern kmem_cache_t *range_seg_cache; 3280 3281static __noinline void 3282arc_kmem_reap_now(void) 3283{ 3284 size_t i; 3285 kmem_cache_t *prev_cache = NULL; 3286 kmem_cache_t *prev_data_cache = NULL; 3287 3288 DTRACE_PROBE(arc__kmem_reap_start); 3289#ifdef _KERNEL 3290 if (arc_meta_used >= arc_meta_limit) { 3291 /* 3292 * We are exceeding our meta-data cache limit. 3293 * Purge some DNLC entries to release holds on meta-data. 3294 */ 3295 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3296 } 3297#if defined(__i386) 3298 /* 3299 * Reclaim unused memory from all kmem caches. 3300 */ 3301 kmem_reap(); 3302#endif 3303#endif 3304 3305 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3306 if (zio_buf_cache[i] != prev_cache) { 3307 prev_cache = zio_buf_cache[i]; 3308 kmem_cache_reap_now(zio_buf_cache[i]); 3309 } 3310 if (zio_data_buf_cache[i] != prev_data_cache) { 3311 prev_data_cache = zio_data_buf_cache[i]; 3312 kmem_cache_reap_now(zio_data_buf_cache[i]); 3313 } 3314 } 3315 kmem_cache_reap_now(buf_cache); 3316 kmem_cache_reap_now(hdr_full_cache); 3317 kmem_cache_reap_now(hdr_l2only_cache); 3318 kmem_cache_reap_now(range_seg_cache); 3319 3320#ifdef sun 3321 if (zio_arena != NULL) { 3322 /* 3323 * Ask the vmem arena to reclaim unused memory from its 3324 * quantum caches. 3325 */ 3326 vmem_qcache_reap(zio_arena); 3327 } 3328#endif 3329 DTRACE_PROBE(arc__kmem_reap_end); 3330} 3331 3332static void 3333arc_reclaim_thread(void *dummy __unused) 3334{ 3335 clock_t growtime = 0; 3336 callb_cpr_t cpr; 3337 3338 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 3339 3340 mutex_enter(&arc_reclaim_thr_lock); 3341 while (arc_thread_exit == 0) { 3342 int64_t free_memory = arc_available_memory(); 3343 if (free_memory < 0) { 3344 3345 arc_no_grow = B_TRUE; 3346 arc_warm = B_TRUE; 3347 3348 /* 3349 * Wait at least zfs_grow_retry (default 60) seconds 3350 * before considering growing. 3351 */ 3352 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3353 3354 arc_kmem_reap_now(); 3355 3356 /* 3357 * If we are still low on memory, shrink the ARC 3358 * so that we have arc_shrink_min free space. 3359 */ 3360 free_memory = arc_available_memory(); 3361 3362 int64_t to_free = 3363 (arc_c >> arc_shrink_shift) - free_memory; 3364 if (to_free > 0) { 3365#ifdef _KERNEL 3366 to_free = MAX(to_free, ptob(needfree)); 3367#endif 3368 arc_shrink(to_free); 3369 } 3370 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3371 arc_no_grow = B_TRUE; 3372 } else if (ddi_get_lbolt() >= growtime) { 3373 arc_no_grow = B_FALSE; 3374 } 3375 3376 arc_adjust(); 3377 3378 if (arc_eviction_list != NULL) 3379 arc_do_user_evicts(); 3380 3381#ifdef _KERNEL 3382 if (needfree) { 3383 needfree = 0; 3384 wakeup(&needfree); 3385 } 3386#endif 3387 3388 /* 3389 * This is necessary in order for the mdb ::arc dcmd to 3390 * show up to date information. Since the ::arc command 3391 * does not call the kstat's update function, without 3392 * this call, the command may show stale stats for the 3393 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3394 * with this change, the data might be up to 1 second 3395 * out of date; but that should suffice. The arc_state_t 3396 * structures can be queried directly if more accurate 3397 * information is needed. 3398 */ 3399 if (arc_ksp != NULL) 3400 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3401 3402 /* block until needed, or one second, whichever is shorter */ 3403 CALLB_CPR_SAFE_BEGIN(&cpr); 3404 (void) cv_timedwait(&arc_reclaim_thr_cv, 3405 &arc_reclaim_thr_lock, hz); 3406 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 3407 } 3408 3409 arc_thread_exit = 0; 3410 cv_broadcast(&arc_reclaim_thr_cv); 3411 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 3412 thread_exit(); 3413} 3414 3415/* 3416 * Adapt arc info given the number of bytes we are trying to add and 3417 * the state that we are comming from. This function is only called 3418 * when we are adding new content to the cache. 3419 */ 3420static void 3421arc_adapt(int bytes, arc_state_t *state) 3422{ 3423 int mult; 3424 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3425 3426 if (state == arc_l2c_only) 3427 return; 3428 3429 ASSERT(bytes > 0); 3430 /* 3431 * Adapt the target size of the MRU list: 3432 * - if we just hit in the MRU ghost list, then increase 3433 * the target size of the MRU list. 3434 * - if we just hit in the MFU ghost list, then increase 3435 * the target size of the MFU list by decreasing the 3436 * target size of the MRU list. 3437 */ 3438 if (state == arc_mru_ghost) { 3439 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 3440 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 3441 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3442 3443 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3444 } else if (state == arc_mfu_ghost) { 3445 uint64_t delta; 3446 3447 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 3448 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 3449 mult = MIN(mult, 10); 3450 3451 delta = MIN(bytes * mult, arc_p); 3452 arc_p = MAX(arc_p_min, arc_p - delta); 3453 } 3454 ASSERT((int64_t)arc_p >= 0); 3455 3456 if (arc_reclaim_needed()) { 3457 cv_signal(&arc_reclaim_thr_cv); 3458 return; 3459 } 3460 3461 if (arc_no_grow) 3462 return; 3463 3464 if (arc_c >= arc_c_max) 3465 return; 3466 3467 /* 3468 * If we're within (2 * maxblocksize) bytes of the target 3469 * cache size, increment the target cache size 3470 */ 3471 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3472 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3473 atomic_add_64(&arc_c, (int64_t)bytes); 3474 if (arc_c > arc_c_max) 3475 arc_c = arc_c_max; 3476 else if (state == arc_anon) 3477 atomic_add_64(&arc_p, (int64_t)bytes); 3478 if (arc_p > arc_c) 3479 arc_p = arc_c; 3480 } 3481 ASSERT((int64_t)arc_p >= 0); 3482} 3483 3484/* 3485 * Check if the cache has reached its limits and eviction is required 3486 * prior to insert. 3487 */ 3488static int 3489arc_evict_needed(arc_buf_contents_t type) 3490{ 3491 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 3492 return (1); 3493 3494 if (arc_reclaim_needed()) 3495 return (1); 3496 3497 return (arc_size > arc_c); 3498} 3499 3500/* 3501 * The buffer, supplied as the first argument, needs a data block. 3502 * So, if we are at cache max, determine which cache should be victimized. 3503 * We have the following cases: 3504 * 3505 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 3506 * In this situation if we're out of space, but the resident size of the MFU is 3507 * under the limit, victimize the MFU cache to satisfy this insertion request. 3508 * 3509 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 3510 * Here, we've used up all of the available space for the MRU, so we need to 3511 * evict from our own cache instead. Evict from the set of resident MRU 3512 * entries. 3513 * 3514 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 3515 * c minus p represents the MFU space in the cache, since p is the size of the 3516 * cache that is dedicated to the MRU. In this situation there's still space on 3517 * the MFU side, so the MRU side needs to be victimized. 3518 * 3519 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 3520 * MFU's resident set is consuming more space than it has been allotted. In 3521 * this situation, we must victimize our own cache, the MFU, for this insertion. 3522 */ 3523static void 3524arc_get_data_buf(arc_buf_t *buf) 3525{ 3526 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3527 uint64_t size = buf->b_hdr->b_size; 3528 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3529 3530 arc_adapt(size, state); 3531 3532 /* 3533 * We have not yet reached cache maximum size, 3534 * just allocate a new buffer. 3535 */ 3536 if (!arc_evict_needed(type)) { 3537 if (type == ARC_BUFC_METADATA) { 3538 buf->b_data = zio_buf_alloc(size); 3539 arc_space_consume(size, ARC_SPACE_META); 3540 } else { 3541 ASSERT(type == ARC_BUFC_DATA); 3542 buf->b_data = zio_data_buf_alloc(size); 3543 arc_space_consume(size, ARC_SPACE_DATA); 3544 } 3545 goto out; 3546 } 3547 3548 /* 3549 * If we are prefetching from the mfu ghost list, this buffer 3550 * will end up on the mru list; so steal space from there. 3551 */ 3552 if (state == arc_mfu_ghost) 3553 state = HDR_PREFETCH(buf->b_hdr) ? arc_mru : arc_mfu; 3554 else if (state == arc_mru_ghost) 3555 state = arc_mru; 3556 3557 if (state == arc_mru || state == arc_anon) { 3558 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 3559 state = (arc_mfu->arcs_lsize[type] >= size && 3560 arc_p > mru_used) ? arc_mfu : arc_mru; 3561 } else { 3562 /* MFU cases */ 3563 uint64_t mfu_space = arc_c - arc_p; 3564 state = (arc_mru->arcs_lsize[type] >= size && 3565 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 3566 } 3567 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) { 3568 if (type == ARC_BUFC_METADATA) { 3569 buf->b_data = zio_buf_alloc(size); 3570 arc_space_consume(size, ARC_SPACE_META); 3571 } else { 3572 ASSERT(type == ARC_BUFC_DATA); 3573 buf->b_data = zio_data_buf_alloc(size); 3574 arc_space_consume(size, ARC_SPACE_DATA); 3575 } 3576 ARCSTAT_BUMP(arcstat_recycle_miss); 3577 } 3578 ASSERT(buf->b_data != NULL); 3579out: 3580 /* 3581 * Update the state size. Note that ghost states have a 3582 * "ghost size" and so don't need to be updated. 3583 */ 3584 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3585 arc_buf_hdr_t *hdr = buf->b_hdr; 3586 3587 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_size, size); 3588 if (list_link_active(&hdr->b_l1hdr.b_arc_node)) { 3589 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3590 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3591 size); 3592 } 3593 /* 3594 * If we are growing the cache, and we are adding anonymous 3595 * data, and we have outgrown arc_p, update arc_p 3596 */ 3597 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3598 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 3599 arc_p = MIN(arc_c, arc_p + size); 3600 } 3601 ARCSTAT_BUMP(arcstat_allocated); 3602} 3603 3604/* 3605 * This routine is called whenever a buffer is accessed. 3606 * NOTE: the hash lock is dropped in this function. 3607 */ 3608static void 3609arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3610{ 3611 clock_t now; 3612 3613 ASSERT(MUTEX_HELD(hash_lock)); 3614 ASSERT(HDR_HAS_L1HDR(hdr)); 3615 3616 if (hdr->b_l1hdr.b_state == arc_anon) { 3617 /* 3618 * This buffer is not in the cache, and does not 3619 * appear in our "ghost" list. Add the new buffer 3620 * to the MRU state. 3621 */ 3622 3623 ASSERT0(hdr->b_l1hdr.b_arc_access); 3624 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3625 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3626 arc_change_state(arc_mru, hdr, hash_lock); 3627 3628 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3629 now = ddi_get_lbolt(); 3630 3631 /* 3632 * If this buffer is here because of a prefetch, then either: 3633 * - clear the flag if this is a "referencing" read 3634 * (any subsequent access will bump this into the MFU state). 3635 * or 3636 * - move the buffer to the head of the list if this is 3637 * another prefetch (to make it less likely to be evicted). 3638 */ 3639 if (HDR_PREFETCH(hdr)) { 3640 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3641 ASSERT(list_link_active( 3642 &hdr->b_l1hdr.b_arc_node)); 3643 } else { 3644 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3645 ARCSTAT_BUMP(arcstat_mru_hits); 3646 } 3647 hdr->b_l1hdr.b_arc_access = now; 3648 return; 3649 } 3650 3651 /* 3652 * This buffer has been "accessed" only once so far, 3653 * but it is still in the cache. Move it to the MFU 3654 * state. 3655 */ 3656 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3657 /* 3658 * More than 125ms have passed since we 3659 * instantiated this buffer. Move it to the 3660 * most frequently used state. 3661 */ 3662 hdr->b_l1hdr.b_arc_access = now; 3663 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3664 arc_change_state(arc_mfu, hdr, hash_lock); 3665 } 3666 ARCSTAT_BUMP(arcstat_mru_hits); 3667 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3668 arc_state_t *new_state; 3669 /* 3670 * This buffer has been "accessed" recently, but 3671 * was evicted from the cache. Move it to the 3672 * MFU state. 3673 */ 3674 3675 if (HDR_PREFETCH(hdr)) { 3676 new_state = arc_mru; 3677 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3678 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3679 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3680 } else { 3681 new_state = arc_mfu; 3682 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3683 } 3684 3685 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3686 arc_change_state(new_state, hdr, hash_lock); 3687 3688 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3689 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3690 /* 3691 * This buffer has been accessed more than once and is 3692 * still in the cache. Keep it in the MFU state. 3693 * 3694 * NOTE: an add_reference() that occurred when we did 3695 * the arc_read() will have kicked this off the list. 3696 * If it was a prefetch, we will explicitly move it to 3697 * the head of the list now. 3698 */ 3699 if ((HDR_PREFETCH(hdr)) != 0) { 3700 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3701 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 3702 } 3703 ARCSTAT_BUMP(arcstat_mfu_hits); 3704 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3705 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3706 arc_state_t *new_state = arc_mfu; 3707 /* 3708 * This buffer has been accessed more than once but has 3709 * been evicted from the cache. Move it back to the 3710 * MFU state. 3711 */ 3712 3713 if (HDR_PREFETCH(hdr)) { 3714 /* 3715 * This is a prefetch access... 3716 * move this block back to the MRU state. 3717 */ 3718 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3719 new_state = arc_mru; 3720 } 3721 3722 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3723 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3724 arc_change_state(new_state, hdr, hash_lock); 3725 3726 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3727 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3728 /* 3729 * This buffer is on the 2nd Level ARC. 3730 */ 3731 3732 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3733 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3734 arc_change_state(arc_mfu, hdr, hash_lock); 3735 } else { 3736 ASSERT(!"invalid arc state"); 3737 } 3738} 3739 3740/* a generic arc_done_func_t which you can use */ 3741/* ARGSUSED */ 3742void 3743arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3744{ 3745 if (zio == NULL || zio->io_error == 0) 3746 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3747 VERIFY(arc_buf_remove_ref(buf, arg)); 3748} 3749 3750/* a generic arc_done_func_t */ 3751void 3752arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3753{ 3754 arc_buf_t **bufp = arg; 3755 if (zio && zio->io_error) { 3756 VERIFY(arc_buf_remove_ref(buf, arg)); 3757 *bufp = NULL; 3758 } else { 3759 *bufp = buf; 3760 ASSERT(buf->b_data); 3761 } 3762} 3763 3764static void 3765arc_read_done(zio_t *zio) 3766{ 3767 arc_buf_hdr_t *hdr; 3768 arc_buf_t *buf; 3769 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3770 kmutex_t *hash_lock = NULL; 3771 arc_callback_t *callback_list, *acb; 3772 int freeable = FALSE; 3773 3774 buf = zio->io_private; 3775 hdr = buf->b_hdr; 3776 3777 /* 3778 * The hdr was inserted into hash-table and removed from lists 3779 * prior to starting I/O. We should find this header, since 3780 * it's in the hash table, and it should be legit since it's 3781 * not possible to evict it during the I/O. The only possible 3782 * reason for it not to be found is if we were freed during the 3783 * read. 3784 */ 3785 if (HDR_IN_HASH_TABLE(hdr)) { 3786 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3787 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3788 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3789 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3790 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3791 3792 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3793 &hash_lock); 3794 3795 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3796 hash_lock == NULL) || 3797 (found == hdr && 3798 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3799 (found == hdr && HDR_L2_READING(hdr))); 3800 } 3801 3802 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3803 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3804 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3805 3806 /* byteswap if necessary */ 3807 callback_list = hdr->b_l1hdr.b_acb; 3808 ASSERT(callback_list != NULL); 3809 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3810 dmu_object_byteswap_t bswap = 3811 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3812 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3813 byteswap_uint64_array : 3814 dmu_ot_byteswap[bswap].ob_func; 3815 func(buf->b_data, hdr->b_size); 3816 } 3817 3818 arc_cksum_compute(buf, B_FALSE); 3819#ifdef illumos 3820 arc_buf_watch(buf); 3821#endif /* illumos */ 3822 3823 if (hash_lock && zio->io_error == 0 && 3824 hdr->b_l1hdr.b_state == arc_anon) { 3825 /* 3826 * Only call arc_access on anonymous buffers. This is because 3827 * if we've issued an I/O for an evicted buffer, we've already 3828 * called arc_access (to prevent any simultaneous readers from 3829 * getting confused). 3830 */ 3831 arc_access(hdr, hash_lock); 3832 } 3833 3834 /* create copies of the data buffer for the callers */ 3835 abuf = buf; 3836 for (acb = callback_list; acb; acb = acb->acb_next) { 3837 if (acb->acb_done) { 3838 if (abuf == NULL) { 3839 ARCSTAT_BUMP(arcstat_duplicate_reads); 3840 abuf = arc_buf_clone(buf); 3841 } 3842 acb->acb_buf = abuf; 3843 abuf = NULL; 3844 } 3845 } 3846 hdr->b_l1hdr.b_acb = NULL; 3847 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3848 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3849 if (abuf == buf) { 3850 ASSERT(buf->b_efunc == NULL); 3851 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3852 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3853 } 3854 3855 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3856 callback_list != NULL); 3857 3858 if (zio->io_error != 0) { 3859 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3860 if (hdr->b_l1hdr.b_state != arc_anon) 3861 arc_change_state(arc_anon, hdr, hash_lock); 3862 if (HDR_IN_HASH_TABLE(hdr)) 3863 buf_hash_remove(hdr); 3864 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3865 } 3866 3867 /* 3868 * Broadcast before we drop the hash_lock to avoid the possibility 3869 * that the hdr (and hence the cv) might be freed before we get to 3870 * the cv_broadcast(). 3871 */ 3872 cv_broadcast(&hdr->b_l1hdr.b_cv); 3873 3874 if (hash_lock != NULL) { 3875 mutex_exit(hash_lock); 3876 } else { 3877 /* 3878 * This block was freed while we waited for the read to 3879 * complete. It has been removed from the hash table and 3880 * moved to the anonymous state (so that it won't show up 3881 * in the cache). 3882 */ 3883 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3884 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3885 } 3886 3887 /* execute each callback and free its structure */ 3888 while ((acb = callback_list) != NULL) { 3889 if (acb->acb_done) 3890 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3891 3892 if (acb->acb_zio_dummy != NULL) { 3893 acb->acb_zio_dummy->io_error = zio->io_error; 3894 zio_nowait(acb->acb_zio_dummy); 3895 } 3896 3897 callback_list = acb->acb_next; 3898 kmem_free(acb, sizeof (arc_callback_t)); 3899 } 3900 3901 if (freeable) 3902 arc_hdr_destroy(hdr); 3903} 3904 3905/* 3906 * "Read" the block block at the specified DVA (in bp) via the 3907 * cache. If the block is found in the cache, invoke the provided 3908 * callback immediately and return. Note that the `zio' parameter 3909 * in the callback will be NULL in this case, since no IO was 3910 * required. If the block is not in the cache pass the read request 3911 * on to the spa with a substitute callback function, so that the 3912 * requested block will be added to the cache. 3913 * 3914 * If a read request arrives for a block that has a read in-progress, 3915 * either wait for the in-progress read to complete (and return the 3916 * results); or, if this is a read with a "done" func, add a record 3917 * to the read to invoke the "done" func when the read completes, 3918 * and return; or just return. 3919 * 3920 * arc_read_done() will invoke all the requested "done" functions 3921 * for readers of this block. 3922 */ 3923int 3924arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3925 void *private, zio_priority_t priority, int zio_flags, 3926 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3927{ 3928 arc_buf_hdr_t *hdr = NULL; 3929 arc_buf_t *buf = NULL; 3930 kmutex_t *hash_lock = NULL; 3931 zio_t *rzio; 3932 uint64_t guid = spa_load_guid(spa); 3933 3934 ASSERT(!BP_IS_EMBEDDED(bp) || 3935 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3936 3937top: 3938 if (!BP_IS_EMBEDDED(bp)) { 3939 /* 3940 * Embedded BP's have no DVA and require no I/O to "read". 3941 * Create an anonymous arc buf to back it. 3942 */ 3943 hdr = buf_hash_find(guid, bp, &hash_lock); 3944 } 3945 3946 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 3947 3948 *arc_flags |= ARC_FLAG_CACHED; 3949 3950 if (HDR_IO_IN_PROGRESS(hdr)) { 3951 3952 if (*arc_flags & ARC_FLAG_WAIT) { 3953 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 3954 mutex_exit(hash_lock); 3955 goto top; 3956 } 3957 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3958 3959 if (done) { 3960 arc_callback_t *acb = NULL; 3961 3962 acb = kmem_zalloc(sizeof (arc_callback_t), 3963 KM_SLEEP); 3964 acb->acb_done = done; 3965 acb->acb_private = private; 3966 if (pio != NULL) 3967 acb->acb_zio_dummy = zio_null(pio, 3968 spa, NULL, NULL, NULL, zio_flags); 3969 3970 ASSERT(acb->acb_done != NULL); 3971 acb->acb_next = hdr->b_l1hdr.b_acb; 3972 hdr->b_l1hdr.b_acb = acb; 3973 add_reference(hdr, hash_lock, private); 3974 mutex_exit(hash_lock); 3975 return (0); 3976 } 3977 mutex_exit(hash_lock); 3978 return (0); 3979 } 3980 3981 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3982 hdr->b_l1hdr.b_state == arc_mfu); 3983 3984 if (done) { 3985 add_reference(hdr, hash_lock, private); 3986 /* 3987 * If this block is already in use, create a new 3988 * copy of the data so that we will be guaranteed 3989 * that arc_release() will always succeed. 3990 */ 3991 buf = hdr->b_l1hdr.b_buf; 3992 ASSERT(buf); 3993 ASSERT(buf->b_data); 3994 if (HDR_BUF_AVAILABLE(hdr)) { 3995 ASSERT(buf->b_efunc == NULL); 3996 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3997 } else { 3998 buf = arc_buf_clone(buf); 3999 } 4000 4001 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4002 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4003 hdr->b_flags |= ARC_FLAG_PREFETCH; 4004 } 4005 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4006 arc_access(hdr, hash_lock); 4007 if (*arc_flags & ARC_FLAG_L2CACHE) 4008 hdr->b_flags |= ARC_FLAG_L2CACHE; 4009 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4010 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4011 mutex_exit(hash_lock); 4012 ARCSTAT_BUMP(arcstat_hits); 4013 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4014 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4015 data, metadata, hits); 4016 4017 if (done) 4018 done(NULL, buf, private); 4019 } else { 4020 uint64_t size = BP_GET_LSIZE(bp); 4021 arc_callback_t *acb; 4022 vdev_t *vd = NULL; 4023 uint64_t addr = 0; 4024 boolean_t devw = B_FALSE; 4025 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4026 int32_t b_asize = 0; 4027 4028 if (hdr == NULL) { 4029 /* this block is not in the cache */ 4030 arc_buf_hdr_t *exists = NULL; 4031 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4032 buf = arc_buf_alloc(spa, size, private, type); 4033 hdr = buf->b_hdr; 4034 if (!BP_IS_EMBEDDED(bp)) { 4035 hdr->b_dva = *BP_IDENTITY(bp); 4036 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4037 exists = buf_hash_insert(hdr, &hash_lock); 4038 } 4039 if (exists != NULL) { 4040 /* somebody beat us to the hash insert */ 4041 mutex_exit(hash_lock); 4042 buf_discard_identity(hdr); 4043 (void) arc_buf_remove_ref(buf, private); 4044 goto top; /* restart the IO request */ 4045 } 4046 4047 /* if this is a prefetch, we don't have a reference */ 4048 if (*arc_flags & ARC_FLAG_PREFETCH) { 4049 (void) remove_reference(hdr, hash_lock, 4050 private); 4051 hdr->b_flags |= ARC_FLAG_PREFETCH; 4052 } 4053 if (*arc_flags & ARC_FLAG_L2CACHE) 4054 hdr->b_flags |= ARC_FLAG_L2CACHE; 4055 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4056 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4057 if (BP_GET_LEVEL(bp) > 0) 4058 hdr->b_flags |= ARC_FLAG_INDIRECT; 4059 } else { 4060 /* 4061 * This block is in the ghost cache. If it was L2-only 4062 * (and thus didn't have an L1 hdr), we realloc the 4063 * header to add an L1 hdr. 4064 */ 4065 if (!HDR_HAS_L1HDR(hdr)) { 4066 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4067 hdr_full_cache); 4068 } 4069 4070 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4071 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4072 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4073 ASSERT(hdr->b_l1hdr.b_buf == NULL); 4074 4075 /* if this is a prefetch, we don't have a reference */ 4076 if (*arc_flags & ARC_FLAG_PREFETCH) 4077 hdr->b_flags |= ARC_FLAG_PREFETCH; 4078 else 4079 add_reference(hdr, hash_lock, private); 4080 if (*arc_flags & ARC_FLAG_L2CACHE) 4081 hdr->b_flags |= ARC_FLAG_L2CACHE; 4082 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4083 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4084 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4085 buf->b_hdr = hdr; 4086 buf->b_data = NULL; 4087 buf->b_efunc = NULL; 4088 buf->b_private = NULL; 4089 buf->b_next = NULL; 4090 hdr->b_l1hdr.b_buf = buf; 4091 ASSERT0(hdr->b_l1hdr.b_datacnt); 4092 hdr->b_l1hdr.b_datacnt = 1; 4093 arc_get_data_buf(buf); 4094 arc_access(hdr, hash_lock); 4095 } 4096 4097 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4098 4099 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4100 acb->acb_done = done; 4101 acb->acb_private = private; 4102 4103 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4104 hdr->b_l1hdr.b_acb = acb; 4105 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4106 4107 if (HDR_HAS_L2HDR(hdr) && 4108 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4109 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4110 addr = hdr->b_l2hdr.b_daddr; 4111 b_compress = HDR_GET_COMPRESS(hdr); 4112 b_asize = hdr->b_l2hdr.b_asize; 4113 /* 4114 * Lock out device removal. 4115 */ 4116 if (vdev_is_dead(vd) || 4117 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4118 vd = NULL; 4119 } 4120 4121 if (hash_lock != NULL) 4122 mutex_exit(hash_lock); 4123 4124 /* 4125 * At this point, we have a level 1 cache miss. Try again in 4126 * L2ARC if possible. 4127 */ 4128 ASSERT3U(hdr->b_size, ==, size); 4129 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4130 uint64_t, size, zbookmark_phys_t *, zb); 4131 ARCSTAT_BUMP(arcstat_misses); 4132 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4133 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4134 data, metadata, misses); 4135#ifdef _KERNEL 4136 curthread->td_ru.ru_inblock++; 4137#endif 4138 4139 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4140 /* 4141 * Read from the L2ARC if the following are true: 4142 * 1. The L2ARC vdev was previously cached. 4143 * 2. This buffer still has L2ARC metadata. 4144 * 3. This buffer isn't currently writing to the L2ARC. 4145 * 4. The L2ARC entry wasn't evicted, which may 4146 * also have invalidated the vdev. 4147 * 5. This isn't prefetch and l2arc_noprefetch is set. 4148 */ 4149 if (HDR_HAS_L2HDR(hdr) && 4150 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4151 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4152 l2arc_read_callback_t *cb; 4153 4154 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4155 ARCSTAT_BUMP(arcstat_l2_hits); 4156 4157 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4158 KM_SLEEP); 4159 cb->l2rcb_buf = buf; 4160 cb->l2rcb_spa = spa; 4161 cb->l2rcb_bp = *bp; 4162 cb->l2rcb_zb = *zb; 4163 cb->l2rcb_flags = zio_flags; 4164 cb->l2rcb_compress = b_compress; 4165 4166 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4167 addr + size < vd->vdev_psize - 4168 VDEV_LABEL_END_SIZE); 4169 4170 /* 4171 * l2arc read. The SCL_L2ARC lock will be 4172 * released by l2arc_read_done(). 4173 * Issue a null zio if the underlying buffer 4174 * was squashed to zero size by compression. 4175 */ 4176 if (b_compress == ZIO_COMPRESS_EMPTY) { 4177 rzio = zio_null(pio, spa, vd, 4178 l2arc_read_done, cb, 4179 zio_flags | ZIO_FLAG_DONT_CACHE | 4180 ZIO_FLAG_CANFAIL | 4181 ZIO_FLAG_DONT_PROPAGATE | 4182 ZIO_FLAG_DONT_RETRY); 4183 } else { 4184 rzio = zio_read_phys(pio, vd, addr, 4185 b_asize, buf->b_data, 4186 ZIO_CHECKSUM_OFF, 4187 l2arc_read_done, cb, priority, 4188 zio_flags | ZIO_FLAG_DONT_CACHE | 4189 ZIO_FLAG_CANFAIL | 4190 ZIO_FLAG_DONT_PROPAGATE | 4191 ZIO_FLAG_DONT_RETRY, B_FALSE); 4192 } 4193 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4194 zio_t *, rzio); 4195 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4196 4197 if (*arc_flags & ARC_FLAG_NOWAIT) { 4198 zio_nowait(rzio); 4199 return (0); 4200 } 4201 4202 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4203 if (zio_wait(rzio) == 0) 4204 return (0); 4205 4206 /* l2arc read error; goto zio_read() */ 4207 } else { 4208 DTRACE_PROBE1(l2arc__miss, 4209 arc_buf_hdr_t *, hdr); 4210 ARCSTAT_BUMP(arcstat_l2_misses); 4211 if (HDR_L2_WRITING(hdr)) 4212 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4213 spa_config_exit(spa, SCL_L2ARC, vd); 4214 } 4215 } else { 4216 if (vd != NULL) 4217 spa_config_exit(spa, SCL_L2ARC, vd); 4218 if (l2arc_ndev != 0) { 4219 DTRACE_PROBE1(l2arc__miss, 4220 arc_buf_hdr_t *, hdr); 4221 ARCSTAT_BUMP(arcstat_l2_misses); 4222 } 4223 } 4224 4225 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4226 arc_read_done, buf, priority, zio_flags, zb); 4227 4228 if (*arc_flags & ARC_FLAG_WAIT) 4229 return (zio_wait(rzio)); 4230 4231 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4232 zio_nowait(rzio); 4233 } 4234 return (0); 4235} 4236 4237void 4238arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4239{ 4240 ASSERT(buf->b_hdr != NULL); 4241 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4242 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4243 func == NULL); 4244 ASSERT(buf->b_efunc == NULL); 4245 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4246 4247 buf->b_efunc = func; 4248 buf->b_private = private; 4249} 4250 4251/* 4252 * Notify the arc that a block was freed, and thus will never be used again. 4253 */ 4254void 4255arc_freed(spa_t *spa, const blkptr_t *bp) 4256{ 4257 arc_buf_hdr_t *hdr; 4258 kmutex_t *hash_lock; 4259 uint64_t guid = spa_load_guid(spa); 4260 4261 ASSERT(!BP_IS_EMBEDDED(bp)); 4262 4263 hdr = buf_hash_find(guid, bp, &hash_lock); 4264 if (hdr == NULL) 4265 return; 4266 if (HDR_BUF_AVAILABLE(hdr)) { 4267 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4268 add_reference(hdr, hash_lock, FTAG); 4269 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4270 mutex_exit(hash_lock); 4271 4272 arc_release(buf, FTAG); 4273 (void) arc_buf_remove_ref(buf, FTAG); 4274 } else { 4275 mutex_exit(hash_lock); 4276 } 4277 4278} 4279 4280/* 4281 * Clear the user eviction callback set by arc_set_callback(), first calling 4282 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4283 * clearing the callback may result in the arc_buf being destroyed. However, 4284 * it will not result in the *last* arc_buf being destroyed, hence the data 4285 * will remain cached in the ARC. We make a copy of the arc buffer here so 4286 * that we can process the callback without holding any locks. 4287 * 4288 * It's possible that the callback is already in the process of being cleared 4289 * by another thread. In this case we can not clear the callback. 4290 * 4291 * Returns B_TRUE if the callback was successfully called and cleared. 4292 */ 4293boolean_t 4294arc_clear_callback(arc_buf_t *buf) 4295{ 4296 arc_buf_hdr_t *hdr; 4297 kmutex_t *hash_lock; 4298 arc_evict_func_t *efunc = buf->b_efunc; 4299 void *private = buf->b_private; 4300 list_t *list, *evicted_list; 4301 kmutex_t *lock, *evicted_lock; 4302 4303 mutex_enter(&buf->b_evict_lock); 4304 hdr = buf->b_hdr; 4305 if (hdr == NULL) { 4306 /* 4307 * We are in arc_do_user_evicts(). 4308 */ 4309 ASSERT(buf->b_data == NULL); 4310 mutex_exit(&buf->b_evict_lock); 4311 return (B_FALSE); 4312 } else if (buf->b_data == NULL) { 4313 /* 4314 * We are on the eviction list; process this buffer now 4315 * but let arc_do_user_evicts() do the reaping. 4316 */ 4317 buf->b_efunc = NULL; 4318 mutex_exit(&buf->b_evict_lock); 4319 VERIFY0(efunc(private)); 4320 return (B_TRUE); 4321 } 4322 hash_lock = HDR_LOCK(hdr); 4323 mutex_enter(hash_lock); 4324 hdr = buf->b_hdr; 4325 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4326 4327 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4328 hdr->b_l1hdr.b_datacnt); 4329 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4330 hdr->b_l1hdr.b_state == arc_mfu); 4331 4332 buf->b_efunc = NULL; 4333 buf->b_private = NULL; 4334 4335 if (hdr->b_l1hdr.b_datacnt > 1) { 4336 mutex_exit(&buf->b_evict_lock); 4337 arc_buf_destroy(buf, FALSE, TRUE); 4338 } else { 4339 ASSERT(buf == hdr->b_l1hdr.b_buf); 4340 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4341 mutex_exit(&buf->b_evict_lock); 4342 } 4343 4344 mutex_exit(hash_lock); 4345 VERIFY0(efunc(private)); 4346 return (B_TRUE); 4347} 4348 4349/* 4350 * Release this buffer from the cache, making it an anonymous buffer. This 4351 * must be done after a read and prior to modifying the buffer contents. 4352 * If the buffer has more than one reference, we must make 4353 * a new hdr for the buffer. 4354 */ 4355void 4356arc_release(arc_buf_t *buf, void *tag) 4357{ 4358 arc_buf_hdr_t *hdr = buf->b_hdr; 4359 4360 /* 4361 * It would be nice to assert that if it's DMU metadata (level > 4362 * 0 || it's the dnode file), then it must be syncing context. 4363 * But we don't know that information at this level. 4364 */ 4365 4366 mutex_enter(&buf->b_evict_lock); 4367 /* 4368 * We don't grab the hash lock prior to this check, because if 4369 * the buffer's header is in the arc_anon state, it won't be 4370 * linked into the hash table. 4371 */ 4372 if (hdr->b_l1hdr.b_state == arc_anon) { 4373 mutex_exit(&buf->b_evict_lock); 4374 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4375 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4376 ASSERT(!HDR_HAS_L2HDR(hdr)); 4377 ASSERT(BUF_EMPTY(hdr)); 4378 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4379 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4380 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4381 4382 ASSERT3P(buf->b_efunc, ==, NULL); 4383 ASSERT3P(buf->b_private, ==, NULL); 4384 4385 hdr->b_l1hdr.b_arc_access = 0; 4386 arc_buf_thaw(buf); 4387 4388 return; 4389 } 4390 4391 kmutex_t *hash_lock = HDR_LOCK(hdr); 4392 mutex_enter(hash_lock); 4393 4394 /* 4395 * This assignment is only valid as long as the hash_lock is 4396 * held, we must be careful not to reference state or the 4397 * b_state field after dropping the lock. 4398 */ 4399 arc_state_t *state = hdr->b_l1hdr.b_state; 4400 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4401 ASSERT3P(state, !=, arc_anon); 4402 4403 /* this buffer is not on any list */ 4404 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4405 4406 if (HDR_HAS_L2HDR(hdr)) { 4407 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4408 4409 /* 4410 * We have to recheck this conditional again now that 4411 * we're holding the l2ad_mtx to prevent a race with 4412 * another thread which might be concurrently calling 4413 * l2arc_evict(). In that case, l2arc_evict() might have 4414 * destroyed the header's L2 portion as we were waiting 4415 * to acquire the l2ad_mtx. 4416 */ 4417 if (HDR_HAS_L2HDR(hdr)) { 4418 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 4419 hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0); 4420 arc_hdr_l2hdr_destroy(hdr); 4421 } 4422 4423 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4424 } 4425 4426 /* 4427 * Do we have more than one buf? 4428 */ 4429 if (hdr->b_l1hdr.b_datacnt > 1) { 4430 arc_buf_hdr_t *nhdr; 4431 arc_buf_t **bufp; 4432 uint64_t blksz = hdr->b_size; 4433 uint64_t spa = hdr->b_spa; 4434 arc_buf_contents_t type = arc_buf_type(hdr); 4435 uint32_t flags = hdr->b_flags; 4436 4437 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4438 /* 4439 * Pull the data off of this hdr and attach it to 4440 * a new anonymous hdr. 4441 */ 4442 (void) remove_reference(hdr, hash_lock, tag); 4443 bufp = &hdr->b_l1hdr.b_buf; 4444 while (*bufp != buf) 4445 bufp = &(*bufp)->b_next; 4446 *bufp = buf->b_next; 4447 buf->b_next = NULL; 4448 4449 ASSERT3P(state, !=, arc_l2c_only); 4450 ASSERT3U(state->arcs_size, >=, hdr->b_size); 4451 atomic_add_64(&state->arcs_size, -hdr->b_size); 4452 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4453 ASSERT3P(state, !=, arc_l2c_only); 4454 uint64_t *size = &state->arcs_lsize[type]; 4455 ASSERT3U(*size, >=, hdr->b_size); 4456 atomic_add_64(size, -hdr->b_size); 4457 } 4458 4459 /* 4460 * We're releasing a duplicate user data buffer, update 4461 * our statistics accordingly. 4462 */ 4463 if (HDR_ISTYPE_DATA(hdr)) { 4464 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4465 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4466 -hdr->b_size); 4467 } 4468 hdr->b_l1hdr.b_datacnt -= 1; 4469 arc_cksum_verify(buf); 4470#ifdef illumos 4471 arc_buf_unwatch(buf); 4472#endif /* illumos */ 4473 4474 mutex_exit(hash_lock); 4475 4476 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4477 nhdr->b_size = blksz; 4478 nhdr->b_spa = spa; 4479 4480 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4481 nhdr->b_flags |= arc_bufc_to_flags(type); 4482 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4483 4484 nhdr->b_l1hdr.b_buf = buf; 4485 nhdr->b_l1hdr.b_datacnt = 1; 4486 nhdr->b_l1hdr.b_state = arc_anon; 4487 nhdr->b_l1hdr.b_arc_access = 0; 4488 nhdr->b_freeze_cksum = NULL; 4489 4490 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4491 buf->b_hdr = nhdr; 4492 mutex_exit(&buf->b_evict_lock); 4493 atomic_add_64(&arc_anon->arcs_size, blksz); 4494 } else { 4495 mutex_exit(&buf->b_evict_lock); 4496 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4497 /* protected by hash lock */ 4498 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4499 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4500 arc_change_state(arc_anon, hdr, hash_lock); 4501 hdr->b_l1hdr.b_arc_access = 0; 4502 mutex_exit(hash_lock); 4503 4504 buf_discard_identity(hdr); 4505 arc_buf_thaw(buf); 4506 } 4507 buf->b_efunc = NULL; 4508 buf->b_private = NULL; 4509} 4510 4511int 4512arc_released(arc_buf_t *buf) 4513{ 4514 int released; 4515 4516 mutex_enter(&buf->b_evict_lock); 4517 released = (buf->b_data != NULL && 4518 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4519 mutex_exit(&buf->b_evict_lock); 4520 return (released); 4521} 4522 4523#ifdef ZFS_DEBUG 4524int 4525arc_referenced(arc_buf_t *buf) 4526{ 4527 int referenced; 4528 4529 mutex_enter(&buf->b_evict_lock); 4530 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4531 mutex_exit(&buf->b_evict_lock); 4532 return (referenced); 4533} 4534#endif 4535 4536static void 4537arc_write_ready(zio_t *zio) 4538{ 4539 arc_write_callback_t *callback = zio->io_private; 4540 arc_buf_t *buf = callback->awcb_buf; 4541 arc_buf_hdr_t *hdr = buf->b_hdr; 4542 4543 ASSERT(HDR_HAS_L1HDR(hdr)); 4544 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4545 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4546 callback->awcb_ready(zio, buf, callback->awcb_private); 4547 4548 /* 4549 * If the IO is already in progress, then this is a re-write 4550 * attempt, so we need to thaw and re-compute the cksum. 4551 * It is the responsibility of the callback to handle the 4552 * accounting for any re-write attempt. 4553 */ 4554 if (HDR_IO_IN_PROGRESS(hdr)) { 4555 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4556 if (hdr->b_freeze_cksum != NULL) { 4557 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4558 hdr->b_freeze_cksum = NULL; 4559 } 4560 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4561 } 4562 arc_cksum_compute(buf, B_FALSE); 4563 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4564} 4565 4566/* 4567 * The SPA calls this callback for each physical write that happens on behalf 4568 * of a logical write. See the comment in dbuf_write_physdone() for details. 4569 */ 4570static void 4571arc_write_physdone(zio_t *zio) 4572{ 4573 arc_write_callback_t *cb = zio->io_private; 4574 if (cb->awcb_physdone != NULL) 4575 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4576} 4577 4578static void 4579arc_write_done(zio_t *zio) 4580{ 4581 arc_write_callback_t *callback = zio->io_private; 4582 arc_buf_t *buf = callback->awcb_buf; 4583 arc_buf_hdr_t *hdr = buf->b_hdr; 4584 4585 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4586 4587 if (zio->io_error == 0) { 4588 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4589 buf_discard_identity(hdr); 4590 } else { 4591 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4592 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4593 } 4594 } else { 4595 ASSERT(BUF_EMPTY(hdr)); 4596 } 4597 4598 /* 4599 * If the block to be written was all-zero or compressed enough to be 4600 * embedded in the BP, no write was performed so there will be no 4601 * dva/birth/checksum. The buffer must therefore remain anonymous 4602 * (and uncached). 4603 */ 4604 if (!BUF_EMPTY(hdr)) { 4605 arc_buf_hdr_t *exists; 4606 kmutex_t *hash_lock; 4607 4608 ASSERT(zio->io_error == 0); 4609 4610 arc_cksum_verify(buf); 4611 4612 exists = buf_hash_insert(hdr, &hash_lock); 4613 if (exists != NULL) { 4614 /* 4615 * This can only happen if we overwrite for 4616 * sync-to-convergence, because we remove 4617 * buffers from the hash table when we arc_free(). 4618 */ 4619 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4620 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4621 panic("bad overwrite, hdr=%p exists=%p", 4622 (void *)hdr, (void *)exists); 4623 ASSERT(refcount_is_zero( 4624 &exists->b_l1hdr.b_refcnt)); 4625 arc_change_state(arc_anon, exists, hash_lock); 4626 mutex_exit(hash_lock); 4627 arc_hdr_destroy(exists); 4628 exists = buf_hash_insert(hdr, &hash_lock); 4629 ASSERT3P(exists, ==, NULL); 4630 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4631 /* nopwrite */ 4632 ASSERT(zio->io_prop.zp_nopwrite); 4633 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4634 panic("bad nopwrite, hdr=%p exists=%p", 4635 (void *)hdr, (void *)exists); 4636 } else { 4637 /* Dedup */ 4638 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4639 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4640 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4641 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4642 } 4643 } 4644 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4645 /* if it's not anon, we are doing a scrub */ 4646 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4647 arc_access(hdr, hash_lock); 4648 mutex_exit(hash_lock); 4649 } else { 4650 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4651 } 4652 4653 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4654 callback->awcb_done(zio, buf, callback->awcb_private); 4655 4656 kmem_free(callback, sizeof (arc_write_callback_t)); 4657} 4658 4659zio_t * 4660arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4661 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4662 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4663 arc_done_func_t *done, void *private, zio_priority_t priority, 4664 int zio_flags, const zbookmark_phys_t *zb) 4665{ 4666 arc_buf_hdr_t *hdr = buf->b_hdr; 4667 arc_write_callback_t *callback; 4668 zio_t *zio; 4669 4670 ASSERT(ready != NULL); 4671 ASSERT(done != NULL); 4672 ASSERT(!HDR_IO_ERROR(hdr)); 4673 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4674 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4675 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4676 if (l2arc) 4677 hdr->b_flags |= ARC_FLAG_L2CACHE; 4678 if (l2arc_compress) 4679 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4680 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4681 callback->awcb_ready = ready; 4682 callback->awcb_physdone = physdone; 4683 callback->awcb_done = done; 4684 callback->awcb_private = private; 4685 callback->awcb_buf = buf; 4686 4687 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4688 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4689 priority, zio_flags, zb); 4690 4691 return (zio); 4692} 4693 4694static int 4695arc_memory_throttle(uint64_t reserve, uint64_t txg) 4696{ 4697#ifdef _KERNEL 4698 uint64_t available_memory = ptob(freemem); 4699 static uint64_t page_load = 0; 4700 static uint64_t last_txg = 0; 4701 4702#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4703 available_memory = 4704 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 4705#endif 4706 4707 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 4708 return (0); 4709 4710 if (txg > last_txg) { 4711 last_txg = txg; 4712 page_load = 0; 4713 } 4714 /* 4715 * If we are in pageout, we know that memory is already tight, 4716 * the arc is already going to be evicting, so we just want to 4717 * continue to let page writes occur as quickly as possible. 4718 */ 4719 if (curproc == pageproc) { 4720 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4721 return (SET_ERROR(ERESTART)); 4722 /* Note: reserve is inflated, so we deflate */ 4723 page_load += reserve / 8; 4724 return (0); 4725 } else if (page_load > 0 && arc_reclaim_needed()) { 4726 /* memory is low, delay before restarting */ 4727 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4728 return (SET_ERROR(EAGAIN)); 4729 } 4730 page_load = 0; 4731#endif 4732 return (0); 4733} 4734 4735void 4736arc_tempreserve_clear(uint64_t reserve) 4737{ 4738 atomic_add_64(&arc_tempreserve, -reserve); 4739 ASSERT((int64_t)arc_tempreserve >= 0); 4740} 4741 4742int 4743arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4744{ 4745 int error; 4746 uint64_t anon_size; 4747 4748 if (reserve > arc_c/4 && !arc_no_grow) { 4749 arc_c = MIN(arc_c_max, reserve * 4); 4750 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 4751 } 4752 if (reserve > arc_c) 4753 return (SET_ERROR(ENOMEM)); 4754 4755 /* 4756 * Don't count loaned bufs as in flight dirty data to prevent long 4757 * network delays from blocking transactions that are ready to be 4758 * assigned to a txg. 4759 */ 4760 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 4761 4762 /* 4763 * Writes will, almost always, require additional memory allocations 4764 * in order to compress/encrypt/etc the data. We therefore need to 4765 * make sure that there is sufficient available memory for this. 4766 */ 4767 error = arc_memory_throttle(reserve, txg); 4768 if (error != 0) 4769 return (error); 4770 4771 /* 4772 * Throttle writes when the amount of dirty data in the cache 4773 * gets too large. We try to keep the cache less than half full 4774 * of dirty blocks so that our sync times don't grow too large. 4775 * Note: if two requests come in concurrently, we might let them 4776 * both succeed, when one of them should fail. Not a huge deal. 4777 */ 4778 4779 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4780 anon_size > arc_c / 4) { 4781 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4782 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4783 arc_tempreserve>>10, 4784 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4785 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4786 reserve>>10, arc_c>>10); 4787 return (SET_ERROR(ERESTART)); 4788 } 4789 atomic_add_64(&arc_tempreserve, reserve); 4790 return (0); 4791} 4792 4793static void 4794arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4795 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4796{ 4797 size->value.ui64 = state->arcs_size; 4798 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4799 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4800} 4801 4802static int 4803arc_kstat_update(kstat_t *ksp, int rw) 4804{ 4805 arc_stats_t *as = ksp->ks_data; 4806 4807 if (rw == KSTAT_WRITE) { 4808 return (EACCES); 4809 } else { 4810 arc_kstat_update_state(arc_anon, 4811 &as->arcstat_anon_size, 4812 &as->arcstat_anon_evictable_data, 4813 &as->arcstat_anon_evictable_metadata); 4814 arc_kstat_update_state(arc_mru, 4815 &as->arcstat_mru_size, 4816 &as->arcstat_mru_evictable_data, 4817 &as->arcstat_mru_evictable_metadata); 4818 arc_kstat_update_state(arc_mru_ghost, 4819 &as->arcstat_mru_ghost_size, 4820 &as->arcstat_mru_ghost_evictable_data, 4821 &as->arcstat_mru_ghost_evictable_metadata); 4822 arc_kstat_update_state(arc_mfu, 4823 &as->arcstat_mfu_size, 4824 &as->arcstat_mfu_evictable_data, 4825 &as->arcstat_mfu_evictable_metadata); 4826 arc_kstat_update_state(arc_mfu_ghost, 4827 &as->arcstat_mfu_ghost_size, 4828 &as->arcstat_mfu_ghost_evictable_data, 4829 &as->arcstat_mfu_ghost_evictable_metadata); 4830 } 4831 4832 return (0); 4833} 4834 4835#ifdef _KERNEL 4836static eventhandler_tag arc_event_lowmem = NULL; 4837 4838static void 4839arc_lowmem(void *arg __unused, int howto __unused) 4840{ 4841 4842 mutex_enter(&arc_reclaim_thr_lock); 4843 /* XXX: Memory deficit should be passed as argument. */ 4844 needfree = btoc(arc_c >> arc_shrink_shift); 4845 DTRACE_PROBE(arc__needfree); 4846 cv_signal(&arc_reclaim_thr_cv); 4847 4848 /* 4849 * It is unsafe to block here in arbitrary threads, because we can come 4850 * here from ARC itself and may hold ARC locks and thus risk a deadlock 4851 * with ARC reclaim thread. 4852 */ 4853 if (curproc == pageproc) 4854 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0); 4855 mutex_exit(&arc_reclaim_thr_lock); 4856} 4857#endif 4858 4859void 4860arc_init(void) 4861{ 4862 int i, prefetch_tunable_set = 0; 4863 4864 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4865 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 4866 4867 /* Convert seconds to clock ticks */ 4868 arc_min_prefetch_lifespan = 1 * hz; 4869 4870 /* Start out with 1/8 of all memory */ 4871 arc_c = kmem_size() / 8; 4872 4873#ifdef sun 4874#ifdef _KERNEL 4875 /* 4876 * On architectures where the physical memory can be larger 4877 * than the addressable space (intel in 32-bit mode), we may 4878 * need to limit the cache to 1/8 of VM size. 4879 */ 4880 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4881#endif 4882#endif /* sun */ 4883 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 4884 arc_c_min = MAX(arc_c / 4, 16 << 20); 4885 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 4886 if (arc_c * 8 >= 1 << 30) 4887 arc_c_max = (arc_c * 8) - (1 << 30); 4888 else 4889 arc_c_max = arc_c_min; 4890 arc_c_max = MAX(arc_c * 5, arc_c_max); 4891 4892#ifdef _KERNEL 4893 /* 4894 * Allow the tunables to override our calculations if they are 4895 * reasonable (ie. over 16MB) 4896 */ 4897 if (zfs_arc_max > 16 << 20 && zfs_arc_max < kmem_size()) 4898 arc_c_max = zfs_arc_max; 4899 if (zfs_arc_min > 16 << 20 && zfs_arc_min <= arc_c_max) 4900 arc_c_min = zfs_arc_min; 4901#endif 4902 4903 arc_c = arc_c_max; 4904 arc_p = (arc_c >> 1); 4905 4906 /* limit meta-data to 1/4 of the arc capacity */ 4907 arc_meta_limit = arc_c_max / 4; 4908 4909 /* Allow the tunable to override if it is reasonable */ 4910 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4911 arc_meta_limit = zfs_arc_meta_limit; 4912 4913 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4914 arc_c_min = arc_meta_limit / 2; 4915 4916 if (zfs_arc_meta_min > 0) { 4917 arc_meta_min = zfs_arc_meta_min; 4918 } else { 4919 arc_meta_min = arc_c_min / 2; 4920 } 4921 4922 if (zfs_arc_grow_retry > 0) 4923 arc_grow_retry = zfs_arc_grow_retry; 4924 4925 if (zfs_arc_shrink_shift > 0) 4926 arc_shrink_shift = zfs_arc_shrink_shift; 4927 4928 /* 4929 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 4930 */ 4931 if (arc_no_grow_shift >= arc_shrink_shift) 4932 arc_no_grow_shift = arc_shrink_shift - 1; 4933 4934 if (zfs_arc_p_min_shift > 0) 4935 arc_p_min_shift = zfs_arc_p_min_shift; 4936 4937 /* if kmem_flags are set, lets try to use less memory */ 4938 if (kmem_debugging()) 4939 arc_c = arc_c / 2; 4940 if (arc_c < arc_c_min) 4941 arc_c = arc_c_min; 4942 4943 zfs_arc_min = arc_c_min; 4944 zfs_arc_max = arc_c_max; 4945 4946 arc_anon = &ARC_anon; 4947 arc_mru = &ARC_mru; 4948 arc_mru_ghost = &ARC_mru_ghost; 4949 arc_mfu = &ARC_mfu; 4950 arc_mfu_ghost = &ARC_mfu_ghost; 4951 arc_l2c_only = &ARC_l2c_only; 4952 arc_size = 0; 4953 4954 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4955 mutex_init(&arc_anon->arcs_locks[i].arcs_lock, 4956 NULL, MUTEX_DEFAULT, NULL); 4957 mutex_init(&arc_mru->arcs_locks[i].arcs_lock, 4958 NULL, MUTEX_DEFAULT, NULL); 4959 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock, 4960 NULL, MUTEX_DEFAULT, NULL); 4961 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock, 4962 NULL, MUTEX_DEFAULT, NULL); 4963 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock, 4964 NULL, MUTEX_DEFAULT, NULL); 4965 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock, 4966 NULL, MUTEX_DEFAULT, NULL); 4967 4968 list_create(&arc_mru->arcs_lists[i], 4969 sizeof (arc_buf_hdr_t), 4970 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4971 list_create(&arc_mru_ghost->arcs_lists[i], 4972 sizeof (arc_buf_hdr_t), 4973 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4974 list_create(&arc_mfu->arcs_lists[i], 4975 sizeof (arc_buf_hdr_t), 4976 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4977 list_create(&arc_mfu_ghost->arcs_lists[i], 4978 sizeof (arc_buf_hdr_t), 4979 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4980 list_create(&arc_mfu_ghost->arcs_lists[i], 4981 sizeof (arc_buf_hdr_t), 4982 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4983 list_create(&arc_l2c_only->arcs_lists[i], 4984 sizeof (arc_buf_hdr_t), 4985 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4986 } 4987 4988 buf_init(); 4989 4990 arc_thread_exit = 0; 4991 arc_eviction_list = NULL; 4992 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 4993 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4994 4995 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4996 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4997 4998 if (arc_ksp != NULL) { 4999 arc_ksp->ks_data = &arc_stats; 5000 arc_ksp->ks_update = arc_kstat_update; 5001 kstat_install(arc_ksp); 5002 } 5003 5004 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5005 TS_RUN, minclsyspri); 5006 5007#ifdef _KERNEL 5008 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5009 EVENTHANDLER_PRI_FIRST); 5010#endif 5011 5012 arc_dead = FALSE; 5013 arc_warm = B_FALSE; 5014 5015 /* 5016 * Calculate maximum amount of dirty data per pool. 5017 * 5018 * If it has been set by /etc/system, take that. 5019 * Otherwise, use a percentage of physical memory defined by 5020 * zfs_dirty_data_max_percent (default 10%) with a cap at 5021 * zfs_dirty_data_max_max (default 4GB). 5022 */ 5023 if (zfs_dirty_data_max == 0) { 5024 zfs_dirty_data_max = ptob(physmem) * 5025 zfs_dirty_data_max_percent / 100; 5026 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5027 zfs_dirty_data_max_max); 5028 } 5029 5030#ifdef _KERNEL 5031 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5032 prefetch_tunable_set = 1; 5033 5034#ifdef __i386__ 5035 if (prefetch_tunable_set == 0) { 5036 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5037 "-- to enable,\n"); 5038 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5039 "to /boot/loader.conf.\n"); 5040 zfs_prefetch_disable = 1; 5041 } 5042#else 5043 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5044 prefetch_tunable_set == 0) { 5045 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5046 "than 4GB of RAM is present;\n" 5047 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5048 "to /boot/loader.conf.\n"); 5049 zfs_prefetch_disable = 1; 5050 } 5051#endif 5052 /* Warn about ZFS memory and address space requirements. */ 5053 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5054 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5055 "expect unstable behavior.\n"); 5056 } 5057 if (kmem_size() < 512 * (1 << 20)) { 5058 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5059 "expect unstable behavior.\n"); 5060 printf(" Consider tuning vm.kmem_size and " 5061 "vm.kmem_size_max\n"); 5062 printf(" in /boot/loader.conf.\n"); 5063 } 5064#endif 5065} 5066 5067void 5068arc_fini(void) 5069{ 5070 int i; 5071 5072 mutex_enter(&arc_reclaim_thr_lock); 5073 arc_thread_exit = 1; 5074 cv_signal(&arc_reclaim_thr_cv); 5075 while (arc_thread_exit != 0) 5076 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 5077 mutex_exit(&arc_reclaim_thr_lock); 5078 5079 arc_flush(NULL); 5080 5081 arc_dead = TRUE; 5082 5083 if (arc_ksp != NULL) { 5084 kstat_delete(arc_ksp); 5085 arc_ksp = NULL; 5086 } 5087 5088 mutex_destroy(&arc_eviction_mtx); 5089 mutex_destroy(&arc_reclaim_thr_lock); 5090 cv_destroy(&arc_reclaim_thr_cv); 5091 5092 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 5093 list_destroy(&arc_mru->arcs_lists[i]); 5094 list_destroy(&arc_mru_ghost->arcs_lists[i]); 5095 list_destroy(&arc_mfu->arcs_lists[i]); 5096 list_destroy(&arc_mfu_ghost->arcs_lists[i]); 5097 list_destroy(&arc_l2c_only->arcs_lists[i]); 5098 5099 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock); 5100 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock); 5101 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock); 5102 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock); 5103 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock); 5104 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock); 5105 } 5106 5107 buf_fini(); 5108 5109 ASSERT0(arc_loaned_bytes); 5110 5111#ifdef _KERNEL 5112 if (arc_event_lowmem != NULL) 5113 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5114#endif 5115} 5116 5117/* 5118 * Level 2 ARC 5119 * 5120 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5121 * It uses dedicated storage devices to hold cached data, which are populated 5122 * using large infrequent writes. The main role of this cache is to boost 5123 * the performance of random read workloads. The intended L2ARC devices 5124 * include short-stroked disks, solid state disks, and other media with 5125 * substantially faster read latency than disk. 5126 * 5127 * +-----------------------+ 5128 * | ARC | 5129 * +-----------------------+ 5130 * | ^ ^ 5131 * | | | 5132 * l2arc_feed_thread() arc_read() 5133 * | | | 5134 * | l2arc read | 5135 * V | | 5136 * +---------------+ | 5137 * | L2ARC | | 5138 * +---------------+ | 5139 * | ^ | 5140 * l2arc_write() | | 5141 * | | | 5142 * V | | 5143 * +-------+ +-------+ 5144 * | vdev | | vdev | 5145 * | cache | | cache | 5146 * +-------+ +-------+ 5147 * +=========+ .-----. 5148 * : L2ARC : |-_____-| 5149 * : devices : | Disks | 5150 * +=========+ `-_____-' 5151 * 5152 * Read requests are satisfied from the following sources, in order: 5153 * 5154 * 1) ARC 5155 * 2) vdev cache of L2ARC devices 5156 * 3) L2ARC devices 5157 * 4) vdev cache of disks 5158 * 5) disks 5159 * 5160 * Some L2ARC device types exhibit extremely slow write performance. 5161 * To accommodate for this there are some significant differences between 5162 * the L2ARC and traditional cache design: 5163 * 5164 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5165 * the ARC behave as usual, freeing buffers and placing headers on ghost 5166 * lists. The ARC does not send buffers to the L2ARC during eviction as 5167 * this would add inflated write latencies for all ARC memory pressure. 5168 * 5169 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5170 * It does this by periodically scanning buffers from the eviction-end of 5171 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5172 * not already there. It scans until a headroom of buffers is satisfied, 5173 * which itself is a buffer for ARC eviction. If a compressible buffer is 5174 * found during scanning and selected for writing to an L2ARC device, we 5175 * temporarily boost scanning headroom during the next scan cycle to make 5176 * sure we adapt to compression effects (which might significantly reduce 5177 * the data volume we write to L2ARC). The thread that does this is 5178 * l2arc_feed_thread(), illustrated below; example sizes are included to 5179 * provide a better sense of ratio than this diagram: 5180 * 5181 * head --> tail 5182 * +---------------------+----------+ 5183 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5184 * +---------------------+----------+ | o L2ARC eligible 5185 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5186 * +---------------------+----------+ | 5187 * 15.9 Gbytes ^ 32 Mbytes | 5188 * headroom | 5189 * l2arc_feed_thread() 5190 * | 5191 * l2arc write hand <--[oooo]--' 5192 * | 8 Mbyte 5193 * | write max 5194 * V 5195 * +==============================+ 5196 * L2ARC dev |####|#|###|###| |####| ... | 5197 * +==============================+ 5198 * 32 Gbytes 5199 * 5200 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5201 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5202 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5203 * safe to say that this is an uncommon case, since buffers at the end of 5204 * the ARC lists have moved there due to inactivity. 5205 * 5206 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5207 * then the L2ARC simply misses copying some buffers. This serves as a 5208 * pressure valve to prevent heavy read workloads from both stalling the ARC 5209 * with waits and clogging the L2ARC with writes. This also helps prevent 5210 * the potential for the L2ARC to churn if it attempts to cache content too 5211 * quickly, such as during backups of the entire pool. 5212 * 5213 * 5. After system boot and before the ARC has filled main memory, there are 5214 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5215 * lists can remain mostly static. Instead of searching from tail of these 5216 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5217 * for eligible buffers, greatly increasing its chance of finding them. 5218 * 5219 * The L2ARC device write speed is also boosted during this time so that 5220 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5221 * there are no L2ARC reads, and no fear of degrading read performance 5222 * through increased writes. 5223 * 5224 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5225 * the vdev queue can aggregate them into larger and fewer writes. Each 5226 * device is written to in a rotor fashion, sweeping writes through 5227 * available space then repeating. 5228 * 5229 * 7. The L2ARC does not store dirty content. It never needs to flush 5230 * write buffers back to disk based storage. 5231 * 5232 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5233 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5234 * 5235 * The performance of the L2ARC can be tweaked by a number of tunables, which 5236 * may be necessary for different workloads: 5237 * 5238 * l2arc_write_max max write bytes per interval 5239 * l2arc_write_boost extra write bytes during device warmup 5240 * l2arc_noprefetch skip caching prefetched buffers 5241 * l2arc_headroom number of max device writes to precache 5242 * l2arc_headroom_boost when we find compressed buffers during ARC 5243 * scanning, we multiply headroom by this 5244 * percentage factor for the next scan cycle, 5245 * since more compressed buffers are likely to 5246 * be present 5247 * l2arc_feed_secs seconds between L2ARC writing 5248 * 5249 * Tunables may be removed or added as future performance improvements are 5250 * integrated, and also may become zpool properties. 5251 * 5252 * There are three key functions that control how the L2ARC warms up: 5253 * 5254 * l2arc_write_eligible() check if a buffer is eligible to cache 5255 * l2arc_write_size() calculate how much to write 5256 * l2arc_write_interval() calculate sleep delay between writes 5257 * 5258 * These three functions determine what to write, how much, and how quickly 5259 * to send writes. 5260 */ 5261 5262static boolean_t 5263l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5264{ 5265 /* 5266 * A buffer is *not* eligible for the L2ARC if it: 5267 * 1. belongs to a different spa. 5268 * 2. is already cached on the L2ARC. 5269 * 3. has an I/O in progress (it may be an incomplete read). 5270 * 4. is flagged not eligible (zfs property). 5271 */ 5272 if (hdr->b_spa != spa_guid) { 5273 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5274 return (B_FALSE); 5275 } 5276 if (HDR_HAS_L2HDR(hdr)) { 5277 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5278 return (B_FALSE); 5279 } 5280 if (HDR_IO_IN_PROGRESS(hdr)) { 5281 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5282 return (B_FALSE); 5283 } 5284 if (!HDR_L2CACHE(hdr)) { 5285 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5286 return (B_FALSE); 5287 } 5288 5289 return (B_TRUE); 5290} 5291 5292static uint64_t 5293l2arc_write_size(void) 5294{ 5295 uint64_t size; 5296 5297 /* 5298 * Make sure our globals have meaningful values in case the user 5299 * altered them. 5300 */ 5301 size = l2arc_write_max; 5302 if (size == 0) { 5303 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5304 "be greater than zero, resetting it to the default (%d)", 5305 L2ARC_WRITE_SIZE); 5306 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5307 } 5308 5309 if (arc_warm == B_FALSE) 5310 size += l2arc_write_boost; 5311 5312 return (size); 5313 5314} 5315 5316static clock_t 5317l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5318{ 5319 clock_t interval, next, now; 5320 5321 /* 5322 * If the ARC lists are busy, increase our write rate; if the 5323 * lists are stale, idle back. This is achieved by checking 5324 * how much we previously wrote - if it was more than half of 5325 * what we wanted, schedule the next write much sooner. 5326 */ 5327 if (l2arc_feed_again && wrote > (wanted / 2)) 5328 interval = (hz * l2arc_feed_min_ms) / 1000; 5329 else 5330 interval = hz * l2arc_feed_secs; 5331 5332 now = ddi_get_lbolt(); 5333 next = MAX(now, MIN(now + interval, began + interval)); 5334 5335 return (next); 5336} 5337 5338/* 5339 * Cycle through L2ARC devices. This is how L2ARC load balances. 5340 * If a device is returned, this also returns holding the spa config lock. 5341 */ 5342static l2arc_dev_t * 5343l2arc_dev_get_next(void) 5344{ 5345 l2arc_dev_t *first, *next = NULL; 5346 5347 /* 5348 * Lock out the removal of spas (spa_namespace_lock), then removal 5349 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5350 * both locks will be dropped and a spa config lock held instead. 5351 */ 5352 mutex_enter(&spa_namespace_lock); 5353 mutex_enter(&l2arc_dev_mtx); 5354 5355 /* if there are no vdevs, there is nothing to do */ 5356 if (l2arc_ndev == 0) 5357 goto out; 5358 5359 first = NULL; 5360 next = l2arc_dev_last; 5361 do { 5362 /* loop around the list looking for a non-faulted vdev */ 5363 if (next == NULL) { 5364 next = list_head(l2arc_dev_list); 5365 } else { 5366 next = list_next(l2arc_dev_list, next); 5367 if (next == NULL) 5368 next = list_head(l2arc_dev_list); 5369 } 5370 5371 /* if we have come back to the start, bail out */ 5372 if (first == NULL) 5373 first = next; 5374 else if (next == first) 5375 break; 5376 5377 } while (vdev_is_dead(next->l2ad_vdev)); 5378 5379 /* if we were unable to find any usable vdevs, return NULL */ 5380 if (vdev_is_dead(next->l2ad_vdev)) 5381 next = NULL; 5382 5383 l2arc_dev_last = next; 5384 5385out: 5386 mutex_exit(&l2arc_dev_mtx); 5387 5388 /* 5389 * Grab the config lock to prevent the 'next' device from being 5390 * removed while we are writing to it. 5391 */ 5392 if (next != NULL) 5393 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5394 mutex_exit(&spa_namespace_lock); 5395 5396 return (next); 5397} 5398 5399/* 5400 * Free buffers that were tagged for destruction. 5401 */ 5402static void 5403l2arc_do_free_on_write() 5404{ 5405 list_t *buflist; 5406 l2arc_data_free_t *df, *df_prev; 5407 5408 mutex_enter(&l2arc_free_on_write_mtx); 5409 buflist = l2arc_free_on_write; 5410 5411 for (df = list_tail(buflist); df; df = df_prev) { 5412 df_prev = list_prev(buflist, df); 5413 ASSERT(df->l2df_data != NULL); 5414 ASSERT(df->l2df_func != NULL); 5415 df->l2df_func(df->l2df_data, df->l2df_size); 5416 list_remove(buflist, df); 5417 kmem_free(df, sizeof (l2arc_data_free_t)); 5418 } 5419 5420 mutex_exit(&l2arc_free_on_write_mtx); 5421} 5422 5423/* 5424 * A write to a cache device has completed. Update all headers to allow 5425 * reads from these buffers to begin. 5426 */ 5427static void 5428l2arc_write_done(zio_t *zio) 5429{ 5430 l2arc_write_callback_t *cb; 5431 l2arc_dev_t *dev; 5432 list_t *buflist; 5433 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5434 kmutex_t *hash_lock; 5435 int64_t bytes_dropped = 0; 5436 5437 cb = zio->io_private; 5438 ASSERT(cb != NULL); 5439 dev = cb->l2wcb_dev; 5440 ASSERT(dev != NULL); 5441 head = cb->l2wcb_head; 5442 ASSERT(head != NULL); 5443 buflist = &dev->l2ad_buflist; 5444 ASSERT(buflist != NULL); 5445 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5446 l2arc_write_callback_t *, cb); 5447 5448 if (zio->io_error != 0) 5449 ARCSTAT_BUMP(arcstat_l2_writes_error); 5450 5451 mutex_enter(&dev->l2ad_mtx); 5452 5453 /* 5454 * All writes completed, or an error was hit. 5455 */ 5456 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5457 hdr_prev = list_prev(buflist, hdr); 5458 5459 hash_lock = HDR_LOCK(hdr); 5460 if (!mutex_tryenter(hash_lock)) { 5461 /* 5462 * This buffer misses out. It may be in a stage 5463 * of eviction. Its ARC_FLAG_L2_WRITING flag will be 5464 * left set, denying reads to this buffer. 5465 */ 5466 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 5467 continue; 5468 } 5469 5470 /* 5471 * It's possible that this buffer got evicted from the L1 cache 5472 * before we grabbed the vdev + hash locks, in which case 5473 * arc_hdr_realloc freed b_tmp_cdata for us if it was allocated. 5474 * Only free the buffer if we still have an L1 hdr. 5475 */ 5476 if (HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_tmp_cdata != NULL && 5477 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 5478 l2arc_release_cdata_buf(hdr); 5479 5480 if (zio->io_error != 0) { 5481 /* 5482 * Error - drop L2ARC entry. 5483 */ 5484 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 5485 hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0); 5486 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5487 5488 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5489 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5490 5491 bytes_dropped += hdr->b_l2hdr.b_asize; 5492 (void) refcount_remove_many(&dev->l2ad_alloc, 5493 hdr->b_l2hdr.b_asize, hdr); 5494 } 5495 5496 /* 5497 * Allow ARC to begin reads to this L2ARC entry. 5498 */ 5499 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5500 5501 mutex_exit(hash_lock); 5502 } 5503 5504 atomic_inc_64(&l2arc_writes_done); 5505 list_remove(buflist, head); 5506 ASSERT(!HDR_HAS_L1HDR(head)); 5507 kmem_cache_free(hdr_l2only_cache, head); 5508 mutex_exit(&dev->l2ad_mtx); 5509 5510 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5511 5512 l2arc_do_free_on_write(); 5513 5514 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5515} 5516 5517/* 5518 * A read to a cache device completed. Validate buffer contents before 5519 * handing over to the regular ARC routines. 5520 */ 5521static void 5522l2arc_read_done(zio_t *zio) 5523{ 5524 l2arc_read_callback_t *cb; 5525 arc_buf_hdr_t *hdr; 5526 arc_buf_t *buf; 5527 kmutex_t *hash_lock; 5528 int equal; 5529 5530 ASSERT(zio->io_vd != NULL); 5531 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5532 5533 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5534 5535 cb = zio->io_private; 5536 ASSERT(cb != NULL); 5537 buf = cb->l2rcb_buf; 5538 ASSERT(buf != NULL); 5539 5540 hash_lock = HDR_LOCK(buf->b_hdr); 5541 mutex_enter(hash_lock); 5542 hdr = buf->b_hdr; 5543 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5544 5545 /* 5546 * If the buffer was compressed, decompress it first. 5547 */ 5548 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5549 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5550 ASSERT(zio->io_data != NULL); 5551 5552 /* 5553 * Check this survived the L2ARC journey. 5554 */ 5555 equal = arc_cksum_equal(buf); 5556 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5557 mutex_exit(hash_lock); 5558 zio->io_private = buf; 5559 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5560 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5561 arc_read_done(zio); 5562 } else { 5563 mutex_exit(hash_lock); 5564 /* 5565 * Buffer didn't survive caching. Increment stats and 5566 * reissue to the original storage device. 5567 */ 5568 if (zio->io_error != 0) { 5569 ARCSTAT_BUMP(arcstat_l2_io_error); 5570 } else { 5571 zio->io_error = SET_ERROR(EIO); 5572 } 5573 if (!equal) 5574 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5575 5576 /* 5577 * If there's no waiter, issue an async i/o to the primary 5578 * storage now. If there *is* a waiter, the caller must 5579 * issue the i/o in a context where it's OK to block. 5580 */ 5581 if (zio->io_waiter == NULL) { 5582 zio_t *pio = zio_unique_parent(zio); 5583 5584 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5585 5586 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5587 buf->b_data, zio->io_size, arc_read_done, buf, 5588 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5589 } 5590 } 5591 5592 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5593} 5594 5595/* 5596 * This is the list priority from which the L2ARC will search for pages to 5597 * cache. This is used within loops (0..3) to cycle through lists in the 5598 * desired order. This order can have a significant effect on cache 5599 * performance. 5600 * 5601 * Currently the metadata lists are hit first, MFU then MRU, followed by 5602 * the data lists. This function returns a locked list, and also returns 5603 * the lock pointer. 5604 */ 5605static list_t * 5606l2arc_list_locked(int list_num, kmutex_t **lock) 5607{ 5608 list_t *list = NULL; 5609 int idx; 5610 5611 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS); 5612 5613 if (list_num < ARC_BUFC_NUMMETADATALISTS) { 5614 idx = list_num; 5615 list = &arc_mfu->arcs_lists[idx]; 5616 *lock = ARCS_LOCK(arc_mfu, idx); 5617 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) { 5618 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 5619 list = &arc_mru->arcs_lists[idx]; 5620 *lock = ARCS_LOCK(arc_mru, idx); 5621 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 + 5622 ARC_BUFC_NUMDATALISTS)) { 5623 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 5624 list = &arc_mfu->arcs_lists[idx]; 5625 *lock = ARCS_LOCK(arc_mfu, idx); 5626 } else { 5627 idx = list_num - ARC_BUFC_NUMLISTS; 5628 list = &arc_mru->arcs_lists[idx]; 5629 *lock = ARCS_LOCK(arc_mru, idx); 5630 } 5631 5632 ASSERT(!(MUTEX_HELD(*lock))); 5633 mutex_enter(*lock); 5634 return (list); 5635} 5636 5637/* 5638 * Evict buffers from the device write hand to the distance specified in 5639 * bytes. This distance may span populated buffers, it may span nothing. 5640 * This is clearing a region on the L2ARC device ready for writing. 5641 * If the 'all' boolean is set, every buffer is evicted. 5642 */ 5643static void 5644l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5645{ 5646 list_t *buflist; 5647 arc_buf_hdr_t *hdr, *hdr_prev; 5648 kmutex_t *hash_lock; 5649 uint64_t taddr; 5650 5651 buflist = &dev->l2ad_buflist; 5652 5653 if (!all && dev->l2ad_first) { 5654 /* 5655 * This is the first sweep through the device. There is 5656 * nothing to evict. 5657 */ 5658 return; 5659 } 5660 5661 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5662 /* 5663 * When nearing the end of the device, evict to the end 5664 * before the device write hand jumps to the start. 5665 */ 5666 taddr = dev->l2ad_end; 5667 } else { 5668 taddr = dev->l2ad_hand + distance; 5669 } 5670 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5671 uint64_t, taddr, boolean_t, all); 5672 5673top: 5674 mutex_enter(&dev->l2ad_mtx); 5675 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5676 hdr_prev = list_prev(buflist, hdr); 5677 5678 hash_lock = HDR_LOCK(hdr); 5679 if (!mutex_tryenter(hash_lock)) { 5680 /* 5681 * Missed the hash lock. Retry. 5682 */ 5683 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5684 mutex_exit(&dev->l2ad_mtx); 5685 mutex_enter(hash_lock); 5686 mutex_exit(hash_lock); 5687 goto top; 5688 } 5689 5690 if (HDR_L2_WRITE_HEAD(hdr)) { 5691 /* 5692 * We hit a write head node. Leave it for 5693 * l2arc_write_done(). 5694 */ 5695 list_remove(buflist, hdr); 5696 mutex_exit(hash_lock); 5697 continue; 5698 } 5699 5700 if (!all && HDR_HAS_L2HDR(hdr) && 5701 (hdr->b_l2hdr.b_daddr > taddr || 5702 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5703 /* 5704 * We've evicted to the target address, 5705 * or the end of the device. 5706 */ 5707 mutex_exit(hash_lock); 5708 break; 5709 } 5710 5711 ASSERT(HDR_HAS_L2HDR(hdr)); 5712 if (!HDR_HAS_L1HDR(hdr)) { 5713 ASSERT(!HDR_L2_READING(hdr)); 5714 /* 5715 * This doesn't exist in the ARC. Destroy. 5716 * arc_hdr_destroy() will call list_remove() 5717 * and decrement arcstat_l2_size. 5718 */ 5719 arc_change_state(arc_anon, hdr, hash_lock); 5720 arc_hdr_destroy(hdr); 5721 } else { 5722 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5723 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5724 /* 5725 * Invalidate issued or about to be issued 5726 * reads, since we may be about to write 5727 * over this location. 5728 */ 5729 if (HDR_L2_READING(hdr)) { 5730 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5731 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5732 } 5733 5734 arc_hdr_l2hdr_destroy(hdr); 5735 } 5736 mutex_exit(hash_lock); 5737 } 5738 mutex_exit(&dev->l2ad_mtx); 5739} 5740 5741/* 5742 * Find and write ARC buffers to the L2ARC device. 5743 * 5744 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5745 * for reading until they have completed writing. 5746 * The headroom_boost is an in-out parameter used to maintain headroom boost 5747 * state between calls to this function. 5748 * 5749 * Returns the number of bytes actually written (which may be smaller than 5750 * the delta by which the device hand has changed due to alignment). 5751 */ 5752static uint64_t 5753l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5754 boolean_t *headroom_boost) 5755{ 5756 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5757 list_t *list; 5758 uint64_t write_asize, write_sz, headroom, buf_compress_minsz; 5759 void *buf_data; 5760 kmutex_t *list_lock; 5761 boolean_t full; 5762 l2arc_write_callback_t *cb; 5763 zio_t *pio, *wzio; 5764 uint64_t guid = spa_load_guid(spa); 5765 const boolean_t do_headroom_boost = *headroom_boost; 5766 int try; 5767 5768 ASSERT(dev->l2ad_vdev != NULL); 5769 5770 /* Lower the flag now, we might want to raise it again later. */ 5771 *headroom_boost = B_FALSE; 5772 5773 pio = NULL; 5774 write_sz = write_asize = 0; 5775 full = B_FALSE; 5776 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5777 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5778 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5779 5780 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 5781 /* 5782 * We will want to try to compress buffers that are at least 2x the 5783 * device sector size. 5784 */ 5785 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5786 5787 /* 5788 * Copy buffers for L2ARC writing. 5789 */ 5790 mutex_enter(&dev->l2ad_mtx); 5791 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) { 5792 uint64_t passed_sz = 0; 5793 5794 list = l2arc_list_locked(try, &list_lock); 5795 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 5796 5797 /* 5798 * L2ARC fast warmup. 5799 * 5800 * Until the ARC is warm and starts to evict, read from the 5801 * head of the ARC lists rather than the tail. 5802 */ 5803 if (arc_warm == B_FALSE) 5804 hdr = list_head(list); 5805 else 5806 hdr = list_tail(list); 5807 if (hdr == NULL) 5808 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 5809 5810 headroom = target_sz * l2arc_headroom * 2 / ARC_BUFC_NUMLISTS; 5811 if (do_headroom_boost) 5812 headroom = (headroom * l2arc_headroom_boost) / 100; 5813 5814 for (; hdr; hdr = hdr_prev) { 5815 kmutex_t *hash_lock; 5816 uint64_t buf_sz; 5817 uint64_t buf_a_sz; 5818 5819 if (arc_warm == B_FALSE) 5820 hdr_prev = list_next(list, hdr); 5821 else 5822 hdr_prev = list_prev(list, hdr); 5823 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 5824 5825 hash_lock = HDR_LOCK(hdr); 5826 if (!mutex_tryenter(hash_lock)) { 5827 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 5828 /* 5829 * Skip this buffer rather than waiting. 5830 */ 5831 continue; 5832 } 5833 5834 passed_sz += hdr->b_size; 5835 if (passed_sz > headroom) { 5836 /* 5837 * Searched too far. 5838 */ 5839 mutex_exit(hash_lock); 5840 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 5841 break; 5842 } 5843 5844 if (!l2arc_write_eligible(guid, hdr)) { 5845 mutex_exit(hash_lock); 5846 continue; 5847 } 5848 5849 /* 5850 * Assume that the buffer is not going to be compressed 5851 * and could take more space on disk because of a larger 5852 * disk block size. 5853 */ 5854 buf_sz = hdr->b_size; 5855 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 5856 5857 if ((write_asize + buf_a_sz) > target_sz) { 5858 full = B_TRUE; 5859 mutex_exit(hash_lock); 5860 ARCSTAT_BUMP(arcstat_l2_write_full); 5861 break; 5862 } 5863 5864 if (pio == NULL) { 5865 /* 5866 * Insert a dummy header on the buflist so 5867 * l2arc_write_done() can find where the 5868 * write buffers begin without searching. 5869 */ 5870 list_insert_head(&dev->l2ad_buflist, head); 5871 5872 cb = kmem_alloc( 5873 sizeof (l2arc_write_callback_t), KM_SLEEP); 5874 cb->l2wcb_dev = dev; 5875 cb->l2wcb_head = head; 5876 pio = zio_root(spa, l2arc_write_done, cb, 5877 ZIO_FLAG_CANFAIL); 5878 ARCSTAT_BUMP(arcstat_l2_write_pios); 5879 } 5880 5881 /* 5882 * Create and add a new L2ARC header. 5883 */ 5884 hdr->b_l2hdr.b_dev = dev; 5885 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5886 /* 5887 * Temporarily stash the data buffer in b_tmp_cdata. 5888 * The subsequent write step will pick it up from 5889 * there. This is because can't access b_l1hdr.b_buf 5890 * without holding the hash_lock, which we in turn 5891 * can't access without holding the ARC list locks 5892 * (which we want to avoid during compression/writing). 5893 */ 5894 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5895 hdr->b_l2hdr.b_asize = hdr->b_size; 5896 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5897 5898 /* 5899 * Explicitly set the b_daddr field to a known 5900 * value which means "invalid address". This 5901 * enables us to differentiate which stage of 5902 * l2arc_write_buffers() the particular header 5903 * is in (e.g. this loop, or the one below). 5904 * ARC_FLAG_L2_WRITING is not enough to make 5905 * this distinction, and we need to know in 5906 * order to do proper l2arc vdev accounting in 5907 * arc_release() and arc_hdr_destroy(). 5908 * 5909 * Note, we can't use a new flag to distinguish 5910 * the two stages because we don't hold the 5911 * header's hash_lock below, in the second stage 5912 * of this function. Thus, we can't simply 5913 * change the b_flags field to denote that the 5914 * IO has been sent. We can change the b_daddr 5915 * field of the L2 portion, though, since we'll 5916 * be holding the l2ad_mtx; which is why we're 5917 * using it to denote the header's state change. 5918 */ 5919 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 5920 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5921 5922 list_insert_head(&dev->l2ad_buflist, hdr); 5923 5924 /* 5925 * Compute and store the buffer cksum before 5926 * writing. On debug the cksum is verified first. 5927 */ 5928 arc_cksum_verify(hdr->b_l1hdr.b_buf); 5929 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 5930 5931 mutex_exit(hash_lock); 5932 5933 write_sz += buf_sz; 5934 write_asize += buf_a_sz; 5935 } 5936 5937 mutex_exit(list_lock); 5938 5939 if (full == B_TRUE) 5940 break; 5941 } 5942 5943 /* No buffers selected for writing? */ 5944 if (pio == NULL) { 5945 ASSERT0(write_sz); 5946 mutex_exit(&dev->l2ad_mtx); 5947 ASSERT(!HDR_HAS_L1HDR(head)); 5948 kmem_cache_free(hdr_l2only_cache, head); 5949 return (0); 5950 } 5951 5952 /* 5953 * Note that elsewhere in this file arcstat_l2_asize 5954 * and the used space on l2ad_vdev are updated using b_asize, 5955 * which is not necessarily rounded up to the device block size. 5956 * Too keep accounting consistent we do the same here as well: 5957 * stats_size accumulates the sum of b_asize of the written buffers, 5958 * while write_asize accumulates the sum of b_asize rounded up 5959 * to the device block size. 5960 * The latter sum is used only to validate the corectness of the code. 5961 */ 5962 uint64_t stats_size = 0; 5963 write_asize = 0; 5964 5965 /* 5966 * Now start writing the buffers. We're starting at the write head 5967 * and work backwards, retracing the course of the buffer selector 5968 * loop above. 5969 */ 5970 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 5971 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 5972 uint64_t buf_sz; 5973 5974 /* 5975 * We shouldn't need to lock the buffer here, since we flagged 5976 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5977 * take care to only access its L2 cache parameters. In 5978 * particular, hdr->l1hdr.b_buf may be invalid by now due to 5979 * ARC eviction. 5980 */ 5981 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 5982 5983 if ((HDR_L2COMPRESS(hdr)) && 5984 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 5985 if (l2arc_compress_buf(hdr)) { 5986 /* 5987 * If compression succeeded, enable headroom 5988 * boost on the next scan cycle. 5989 */ 5990 *headroom_boost = B_TRUE; 5991 } 5992 } 5993 5994 /* 5995 * Pick up the buffer data we had previously stashed away 5996 * (and now potentially also compressed). 5997 */ 5998 buf_data = hdr->b_l1hdr.b_tmp_cdata; 5999 buf_sz = hdr->b_l2hdr.b_asize; 6000 6001 /* 6002 * If the data has not been compressed, then clear b_tmp_cdata 6003 * to make sure that it points only to a temporary compression 6004 * buffer. 6005 */ 6006 if (!L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))) 6007 hdr->b_l1hdr.b_tmp_cdata = NULL; 6008 6009 /* 6010 * We need to do this regardless if buf_sz is zero or 6011 * not, otherwise, when this l2hdr is evicted we'll 6012 * remove a reference that was never added. 6013 */ 6014 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 6015 6016 /* Compression may have squashed the buffer to zero length. */ 6017 if (buf_sz != 0) { 6018 uint64_t buf_a_sz; 6019 6020 wzio = zio_write_phys(pio, dev->l2ad_vdev, 6021 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 6022 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6023 ZIO_FLAG_CANFAIL, B_FALSE); 6024 6025 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6026 zio_t *, wzio); 6027 (void) zio_nowait(wzio); 6028 6029 stats_size += buf_sz; 6030 6031 /* 6032 * Keep the clock hand suitably device-aligned. 6033 */ 6034 buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6035 write_asize += buf_a_sz; 6036 dev->l2ad_hand += buf_a_sz; 6037 } 6038 } 6039 6040 mutex_exit(&dev->l2ad_mtx); 6041 6042 ASSERT3U(write_asize, <=, target_sz); 6043 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6044 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6045 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6046 ARCSTAT_INCR(arcstat_l2_asize, stats_size); 6047 vdev_space_update(dev->l2ad_vdev, stats_size, 0, 0); 6048 6049 /* 6050 * Bump device hand to the device start if it is approaching the end. 6051 * l2arc_evict() will already have evicted ahead for this case. 6052 */ 6053 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6054 dev->l2ad_hand = dev->l2ad_start; 6055 dev->l2ad_first = B_FALSE; 6056 } 6057 6058 dev->l2ad_writing = B_TRUE; 6059 (void) zio_wait(pio); 6060 dev->l2ad_writing = B_FALSE; 6061 6062 return (write_asize); 6063} 6064 6065/* 6066 * Compresses an L2ARC buffer. 6067 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6068 * size in l2hdr->b_asize. This routine tries to compress the data and 6069 * depending on the compression result there are three possible outcomes: 6070 * *) The buffer was incompressible. The original l2hdr contents were left 6071 * untouched and are ready for writing to an L2 device. 6072 * *) The buffer was all-zeros, so there is no need to write it to an L2 6073 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6074 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6075 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6076 * data buffer which holds the compressed data to be written, and b_asize 6077 * tells us how much data there is. b_compress is set to the appropriate 6078 * compression algorithm. Once writing is done, invoke 6079 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6080 * 6081 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6082 * buffer was incompressible). 6083 */ 6084static boolean_t 6085l2arc_compress_buf(arc_buf_hdr_t *hdr) 6086{ 6087 void *cdata; 6088 size_t csize, len, rounded; 6089 ASSERT(HDR_HAS_L2HDR(hdr)); 6090 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6091 6092 ASSERT(HDR_HAS_L1HDR(hdr)); 6093 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 6094 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6095 6096 len = l2hdr->b_asize; 6097 cdata = zio_data_buf_alloc(len); 6098 ASSERT3P(cdata, !=, NULL); 6099 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6100 cdata, l2hdr->b_asize); 6101 6102 if (csize == 0) { 6103 /* zero block, indicate that there's nothing to write */ 6104 zio_data_buf_free(cdata, len); 6105 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 6106 l2hdr->b_asize = 0; 6107 hdr->b_l1hdr.b_tmp_cdata = NULL; 6108 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6109 return (B_TRUE); 6110 } 6111 6112 rounded = P2ROUNDUP(csize, 6113 (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift); 6114 if (rounded < len) { 6115 /* 6116 * Compression succeeded, we'll keep the cdata around for 6117 * writing and release it afterwards. 6118 */ 6119 if (rounded > csize) { 6120 bzero((char *)cdata + csize, rounded - csize); 6121 csize = rounded; 6122 } 6123 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 6124 l2hdr->b_asize = csize; 6125 hdr->b_l1hdr.b_tmp_cdata = cdata; 6126 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6127 return (B_TRUE); 6128 } else { 6129 /* 6130 * Compression failed, release the compressed buffer. 6131 * l2hdr will be left unmodified. 6132 */ 6133 zio_data_buf_free(cdata, len); 6134 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6135 return (B_FALSE); 6136 } 6137} 6138 6139/* 6140 * Decompresses a zio read back from an l2arc device. On success, the 6141 * underlying zio's io_data buffer is overwritten by the uncompressed 6142 * version. On decompression error (corrupt compressed stream), the 6143 * zio->io_error value is set to signal an I/O error. 6144 * 6145 * Please note that the compressed data stream is not checksummed, so 6146 * if the underlying device is experiencing data corruption, we may feed 6147 * corrupt data to the decompressor, so the decompressor needs to be 6148 * able to handle this situation (LZ4 does). 6149 */ 6150static void 6151l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6152{ 6153 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6154 6155 if (zio->io_error != 0) { 6156 /* 6157 * An io error has occured, just restore the original io 6158 * size in preparation for a main pool read. 6159 */ 6160 zio->io_orig_size = zio->io_size = hdr->b_size; 6161 return; 6162 } 6163 6164 if (c == ZIO_COMPRESS_EMPTY) { 6165 /* 6166 * An empty buffer results in a null zio, which means we 6167 * need to fill its io_data after we're done restoring the 6168 * buffer's contents. 6169 */ 6170 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6171 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6172 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6173 } else { 6174 ASSERT(zio->io_data != NULL); 6175 /* 6176 * We copy the compressed data from the start of the arc buffer 6177 * (the zio_read will have pulled in only what we need, the 6178 * rest is garbage which we will overwrite at decompression) 6179 * and then decompress back to the ARC data buffer. This way we 6180 * can minimize copying by simply decompressing back over the 6181 * original compressed data (rather than decompressing to an 6182 * aux buffer and then copying back the uncompressed buffer, 6183 * which is likely to be much larger). 6184 */ 6185 uint64_t csize; 6186 void *cdata; 6187 6188 csize = zio->io_size; 6189 cdata = zio_data_buf_alloc(csize); 6190 bcopy(zio->io_data, cdata, csize); 6191 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6192 hdr->b_size) != 0) 6193 zio->io_error = EIO; 6194 zio_data_buf_free(cdata, csize); 6195 } 6196 6197 /* Restore the expected uncompressed IO size. */ 6198 zio->io_orig_size = zio->io_size = hdr->b_size; 6199} 6200 6201/* 6202 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6203 * This buffer serves as a temporary holder of compressed data while 6204 * the buffer entry is being written to an l2arc device. Once that is 6205 * done, we can dispose of it. 6206 */ 6207static void 6208l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6209{ 6210 ASSERT(HDR_HAS_L1HDR(hdr)); 6211 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_EMPTY) { 6212 /* 6213 * If the data was compressed, then we've allocated a 6214 * temporary buffer for it, so now we need to release it. 6215 */ 6216 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6217 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6218 hdr->b_size); 6219 hdr->b_l1hdr.b_tmp_cdata = NULL; 6220 } else { 6221 ASSERT(hdr->b_l1hdr.b_tmp_cdata == NULL); 6222 } 6223} 6224 6225/* 6226 * This thread feeds the L2ARC at regular intervals. This is the beating 6227 * heart of the L2ARC. 6228 */ 6229static void 6230l2arc_feed_thread(void *dummy __unused) 6231{ 6232 callb_cpr_t cpr; 6233 l2arc_dev_t *dev; 6234 spa_t *spa; 6235 uint64_t size, wrote; 6236 clock_t begin, next = ddi_get_lbolt(); 6237 boolean_t headroom_boost = B_FALSE; 6238 6239 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6240 6241 mutex_enter(&l2arc_feed_thr_lock); 6242 6243 while (l2arc_thread_exit == 0) { 6244 CALLB_CPR_SAFE_BEGIN(&cpr); 6245 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6246 next - ddi_get_lbolt()); 6247 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6248 next = ddi_get_lbolt() + hz; 6249 6250 /* 6251 * Quick check for L2ARC devices. 6252 */ 6253 mutex_enter(&l2arc_dev_mtx); 6254 if (l2arc_ndev == 0) { 6255 mutex_exit(&l2arc_dev_mtx); 6256 continue; 6257 } 6258 mutex_exit(&l2arc_dev_mtx); 6259 begin = ddi_get_lbolt(); 6260 6261 /* 6262 * This selects the next l2arc device to write to, and in 6263 * doing so the next spa to feed from: dev->l2ad_spa. This 6264 * will return NULL if there are now no l2arc devices or if 6265 * they are all faulted. 6266 * 6267 * If a device is returned, its spa's config lock is also 6268 * held to prevent device removal. l2arc_dev_get_next() 6269 * will grab and release l2arc_dev_mtx. 6270 */ 6271 if ((dev = l2arc_dev_get_next()) == NULL) 6272 continue; 6273 6274 spa = dev->l2ad_spa; 6275 ASSERT(spa != NULL); 6276 6277 /* 6278 * If the pool is read-only then force the feed thread to 6279 * sleep a little longer. 6280 */ 6281 if (!spa_writeable(spa)) { 6282 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6283 spa_config_exit(spa, SCL_L2ARC, dev); 6284 continue; 6285 } 6286 6287 /* 6288 * Avoid contributing to memory pressure. 6289 */ 6290 if (arc_reclaim_needed()) { 6291 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6292 spa_config_exit(spa, SCL_L2ARC, dev); 6293 continue; 6294 } 6295 6296 ARCSTAT_BUMP(arcstat_l2_feeds); 6297 6298 size = l2arc_write_size(); 6299 6300 /* 6301 * Evict L2ARC buffers that will be overwritten. 6302 */ 6303 l2arc_evict(dev, size, B_FALSE); 6304 6305 /* 6306 * Write ARC buffers. 6307 */ 6308 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6309 6310 /* 6311 * Calculate interval between writes. 6312 */ 6313 next = l2arc_write_interval(begin, size, wrote); 6314 spa_config_exit(spa, SCL_L2ARC, dev); 6315 } 6316 6317 l2arc_thread_exit = 0; 6318 cv_broadcast(&l2arc_feed_thr_cv); 6319 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6320 thread_exit(); 6321} 6322 6323boolean_t 6324l2arc_vdev_present(vdev_t *vd) 6325{ 6326 l2arc_dev_t *dev; 6327 6328 mutex_enter(&l2arc_dev_mtx); 6329 for (dev = list_head(l2arc_dev_list); dev != NULL; 6330 dev = list_next(l2arc_dev_list, dev)) { 6331 if (dev->l2ad_vdev == vd) 6332 break; 6333 } 6334 mutex_exit(&l2arc_dev_mtx); 6335 6336 return (dev != NULL); 6337} 6338 6339/* 6340 * Add a vdev for use by the L2ARC. By this point the spa has already 6341 * validated the vdev and opened it. 6342 */ 6343void 6344l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6345{ 6346 l2arc_dev_t *adddev; 6347 6348 ASSERT(!l2arc_vdev_present(vd)); 6349 6350 vdev_ashift_optimize(vd); 6351 6352 /* 6353 * Create a new l2arc device entry. 6354 */ 6355 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6356 adddev->l2ad_spa = spa; 6357 adddev->l2ad_vdev = vd; 6358 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6359 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6360 adddev->l2ad_hand = adddev->l2ad_start; 6361 adddev->l2ad_first = B_TRUE; 6362 adddev->l2ad_writing = B_FALSE; 6363 6364 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6365 /* 6366 * This is a list of all ARC buffers that are still valid on the 6367 * device. 6368 */ 6369 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6370 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6371 6372 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6373 refcount_create(&adddev->l2ad_alloc); 6374 6375 /* 6376 * Add device to global list 6377 */ 6378 mutex_enter(&l2arc_dev_mtx); 6379 list_insert_head(l2arc_dev_list, adddev); 6380 atomic_inc_64(&l2arc_ndev); 6381 mutex_exit(&l2arc_dev_mtx); 6382} 6383 6384/* 6385 * Remove a vdev from the L2ARC. 6386 */ 6387void 6388l2arc_remove_vdev(vdev_t *vd) 6389{ 6390 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6391 6392 /* 6393 * Find the device by vdev 6394 */ 6395 mutex_enter(&l2arc_dev_mtx); 6396 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6397 nextdev = list_next(l2arc_dev_list, dev); 6398 if (vd == dev->l2ad_vdev) { 6399 remdev = dev; 6400 break; 6401 } 6402 } 6403 ASSERT(remdev != NULL); 6404 6405 /* 6406 * Remove device from global list 6407 */ 6408 list_remove(l2arc_dev_list, remdev); 6409 l2arc_dev_last = NULL; /* may have been invalidated */ 6410 atomic_dec_64(&l2arc_ndev); 6411 mutex_exit(&l2arc_dev_mtx); 6412 6413 /* 6414 * Clear all buflists and ARC references. L2ARC device flush. 6415 */ 6416 l2arc_evict(remdev, 0, B_TRUE); 6417 list_destroy(&remdev->l2ad_buflist); 6418 mutex_destroy(&remdev->l2ad_mtx); 6419 refcount_destroy(&remdev->l2ad_alloc); 6420 kmem_free(remdev, sizeof (l2arc_dev_t)); 6421} 6422 6423void 6424l2arc_init(void) 6425{ 6426 l2arc_thread_exit = 0; 6427 l2arc_ndev = 0; 6428 l2arc_writes_sent = 0; 6429 l2arc_writes_done = 0; 6430 6431 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6432 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6433 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6434 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6435 6436 l2arc_dev_list = &L2ARC_dev_list; 6437 l2arc_free_on_write = &L2ARC_free_on_write; 6438 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6439 offsetof(l2arc_dev_t, l2ad_node)); 6440 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6441 offsetof(l2arc_data_free_t, l2df_list_node)); 6442} 6443 6444void 6445l2arc_fini(void) 6446{ 6447 /* 6448 * This is called from dmu_fini(), which is called from spa_fini(); 6449 * Because of this, we can assume that all l2arc devices have 6450 * already been removed when the pools themselves were removed. 6451 */ 6452 6453 l2arc_do_free_on_write(); 6454 6455 mutex_destroy(&l2arc_feed_thr_lock); 6456 cv_destroy(&l2arc_feed_thr_cv); 6457 mutex_destroy(&l2arc_dev_mtx); 6458 mutex_destroy(&l2arc_free_on_write_mtx); 6459 6460 list_destroy(l2arc_dev_list); 6461 list_destroy(l2arc_free_on_write); 6462} 6463 6464void 6465l2arc_start(void) 6466{ 6467 if (!(spa_mode_global & FWRITE)) 6468 return; 6469 6470 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6471 TS_RUN, minclsyspri); 6472} 6473 6474void 6475l2arc_stop(void) 6476{ 6477 if (!(spa_mode_global & FWRITE)) 6478 return; 6479 6480 mutex_enter(&l2arc_feed_thr_lock); 6481 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6482 l2arc_thread_exit = 1; 6483 while (l2arc_thread_exit != 0) 6484 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6485 mutex_exit(&l2arc_feed_thr_lock); 6486} 6487