arc.c revision 286628
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_meta_limit", &zfs_arc_meta_limit); 229TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 230TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 231SYSCTL_DECL(_vfs_zfs); 232SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0, 233 "Maximum ARC size"); 234SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0, 235 "Minimum ARC size"); 236SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 237 &zfs_arc_average_blocksize, 0, 238 "ARC average blocksize"); 239SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 240 &arc_shrink_shift, 0, 241 "log2(fraction of arc to reclaim)"); 242 243/* 244 * We don't have a tunable for arc_free_target due to the dependency on 245 * pagedaemon initialisation. 246 */ 247SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 248 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 249 sysctl_vfs_zfs_arc_free_target, "IU", 250 "Desired number of free pages below which ARC triggers reclaim"); 251 252static int 253sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 254{ 255 u_int val; 256 int err; 257 258 val = zfs_arc_free_target; 259 err = sysctl_handle_int(oidp, &val, 0, req); 260 if (err != 0 || req->newptr == NULL) 261 return (err); 262 263 if (val < minfree) 264 return (EINVAL); 265 if (val > vm_cnt.v_page_count) 266 return (EINVAL); 267 268 zfs_arc_free_target = val; 269 270 return (0); 271} 272 273/* 274 * Must be declared here, before the definition of corresponding kstat 275 * macro which uses the same names will confuse the compiler. 276 */ 277SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 278 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 279 sysctl_vfs_zfs_arc_meta_limit, "QU", 280 "ARC metadata limit"); 281#endif 282 283/* 284 * Note that buffers can be in one of 6 states: 285 * ARC_anon - anonymous (discussed below) 286 * ARC_mru - recently used, currently cached 287 * ARC_mru_ghost - recentely used, no longer in cache 288 * ARC_mfu - frequently used, currently cached 289 * ARC_mfu_ghost - frequently used, no longer in cache 290 * ARC_l2c_only - exists in L2ARC but not other states 291 * When there are no active references to the buffer, they are 292 * are linked onto a list in one of these arc states. These are 293 * the only buffers that can be evicted or deleted. Within each 294 * state there are multiple lists, one for meta-data and one for 295 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 296 * etc.) is tracked separately so that it can be managed more 297 * explicitly: favored over data, limited explicitly. 298 * 299 * Anonymous buffers are buffers that are not associated with 300 * a DVA. These are buffers that hold dirty block copies 301 * before they are written to stable storage. By definition, 302 * they are "ref'd" and are considered part of arc_mru 303 * that cannot be freed. Generally, they will aquire a DVA 304 * as they are written and migrate onto the arc_mru list. 305 * 306 * The ARC_l2c_only state is for buffers that are in the second 307 * level ARC but no longer in any of the ARC_m* lists. The second 308 * level ARC itself may also contain buffers that are in any of 309 * the ARC_m* states - meaning that a buffer can exist in two 310 * places. The reason for the ARC_l2c_only state is to keep the 311 * buffer header in the hash table, so that reads that hit the 312 * second level ARC benefit from these fast lookups. 313 */ 314 315#define ARCS_LOCK_PAD CACHE_LINE_SIZE 316struct arcs_lock { 317 kmutex_t arcs_lock; 318#ifdef _KERNEL 319 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))]; 320#endif 321}; 322 323/* 324 * must be power of two for mask use to work 325 * 326 */ 327#define ARC_BUFC_NUMDATALISTS 16 328#define ARC_BUFC_NUMMETADATALISTS 16 329#define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS) 330 331typedef struct arc_state { 332 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */ 333 uint64_t arcs_size; /* total amount of data in this state */ 334 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */ 335 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE); 336} arc_state_t; 337 338#define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock)) 339 340/* The 6 states: */ 341static arc_state_t ARC_anon; 342static arc_state_t ARC_mru; 343static arc_state_t ARC_mru_ghost; 344static arc_state_t ARC_mfu; 345static arc_state_t ARC_mfu_ghost; 346static arc_state_t ARC_l2c_only; 347 348typedef struct arc_stats { 349 kstat_named_t arcstat_hits; 350 kstat_named_t arcstat_misses; 351 kstat_named_t arcstat_demand_data_hits; 352 kstat_named_t arcstat_demand_data_misses; 353 kstat_named_t arcstat_demand_metadata_hits; 354 kstat_named_t arcstat_demand_metadata_misses; 355 kstat_named_t arcstat_prefetch_data_hits; 356 kstat_named_t arcstat_prefetch_data_misses; 357 kstat_named_t arcstat_prefetch_metadata_hits; 358 kstat_named_t arcstat_prefetch_metadata_misses; 359 kstat_named_t arcstat_mru_hits; 360 kstat_named_t arcstat_mru_ghost_hits; 361 kstat_named_t arcstat_mfu_hits; 362 kstat_named_t arcstat_mfu_ghost_hits; 363 kstat_named_t arcstat_allocated; 364 kstat_named_t arcstat_deleted; 365 kstat_named_t arcstat_stolen; 366 kstat_named_t arcstat_recycle_miss; 367 /* 368 * Number of buffers that could not be evicted because the hash lock 369 * was held by another thread. The lock may not necessarily be held 370 * by something using the same buffer, since hash locks are shared 371 * by multiple buffers. 372 */ 373 kstat_named_t arcstat_mutex_miss; 374 /* 375 * Number of buffers skipped because they have I/O in progress, are 376 * indrect prefetch buffers that have not lived long enough, or are 377 * not from the spa we're trying to evict from. 378 */ 379 kstat_named_t arcstat_evict_skip; 380 kstat_named_t arcstat_evict_l2_cached; 381 kstat_named_t arcstat_evict_l2_eligible; 382 kstat_named_t arcstat_evict_l2_ineligible; 383 kstat_named_t arcstat_hash_elements; 384 kstat_named_t arcstat_hash_elements_max; 385 kstat_named_t arcstat_hash_collisions; 386 kstat_named_t arcstat_hash_chains; 387 kstat_named_t arcstat_hash_chain_max; 388 kstat_named_t arcstat_p; 389 kstat_named_t arcstat_c; 390 kstat_named_t arcstat_c_min; 391 kstat_named_t arcstat_c_max; 392 kstat_named_t arcstat_size; 393 /* 394 * Number of bytes consumed by internal ARC structures necessary 395 * for tracking purposes; these structures are not actually 396 * backed by ARC buffers. This includes arc_buf_hdr_t structures 397 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 398 * caches), and arc_buf_t structures (allocated via arc_buf_t 399 * cache). 400 */ 401 kstat_named_t arcstat_hdr_size; 402 /* 403 * Number of bytes consumed by ARC buffers of type equal to 404 * ARC_BUFC_DATA. This is generally consumed by buffers backing 405 * on disk user data (e.g. plain file contents). 406 */ 407 kstat_named_t arcstat_data_size; 408 /* 409 * Number of bytes consumed by ARC buffers of type equal to 410 * ARC_BUFC_METADATA. This is generally consumed by buffers 411 * backing on disk data that is used for internal ZFS 412 * structures (e.g. ZAP, dnode, indirect blocks, etc). 413 */ 414 kstat_named_t arcstat_metadata_size; 415 /* 416 * Number of bytes consumed by various buffers and structures 417 * not actually backed with ARC buffers. This includes bonus 418 * buffers (allocated directly via zio_buf_* functions), 419 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 420 * cache), and dnode_t structures (allocated via dnode_t cache). 421 */ 422 kstat_named_t arcstat_other_size; 423 /* 424 * Total number of bytes consumed by ARC buffers residing in the 425 * arc_anon state. This includes *all* buffers in the arc_anon 426 * state; e.g. data, metadata, evictable, and unevictable buffers 427 * are all included in this value. 428 */ 429 kstat_named_t arcstat_anon_size; 430 /* 431 * Number of bytes consumed by ARC buffers that meet the 432 * following criteria: backing buffers of type ARC_BUFC_DATA, 433 * residing in the arc_anon state, and are eligible for eviction 434 * (e.g. have no outstanding holds on the buffer). 435 */ 436 kstat_named_t arcstat_anon_evictable_data; 437 /* 438 * Number of bytes consumed by ARC buffers that meet the 439 * following criteria: backing buffers of type ARC_BUFC_METADATA, 440 * residing in the arc_anon state, and are eligible for eviction 441 * (e.g. have no outstanding holds on the buffer). 442 */ 443 kstat_named_t arcstat_anon_evictable_metadata; 444 /* 445 * Total number of bytes consumed by ARC buffers residing in the 446 * arc_mru state. This includes *all* buffers in the arc_mru 447 * state; e.g. data, metadata, evictable, and unevictable buffers 448 * are all included in this value. 449 */ 450 kstat_named_t arcstat_mru_size; 451 /* 452 * Number of bytes consumed by ARC buffers that meet the 453 * following criteria: backing buffers of type ARC_BUFC_DATA, 454 * residing in the arc_mru state, and are eligible for eviction 455 * (e.g. have no outstanding holds on the buffer). 456 */ 457 kstat_named_t arcstat_mru_evictable_data; 458 /* 459 * Number of bytes consumed by ARC buffers that meet the 460 * following criteria: backing buffers of type ARC_BUFC_METADATA, 461 * residing in the arc_mru state, and are eligible for eviction 462 * (e.g. have no outstanding holds on the buffer). 463 */ 464 kstat_named_t arcstat_mru_evictable_metadata; 465 /* 466 * Total number of bytes that *would have been* consumed by ARC 467 * buffers in the arc_mru_ghost state. The key thing to note 468 * here, is the fact that this size doesn't actually indicate 469 * RAM consumption. The ghost lists only consist of headers and 470 * don't actually have ARC buffers linked off of these headers. 471 * Thus, *if* the headers had associated ARC buffers, these 472 * buffers *would have* consumed this number of bytes. 473 */ 474 kstat_named_t arcstat_mru_ghost_size; 475 /* 476 * Number of bytes that *would have been* consumed by ARC 477 * buffers that are eligible for eviction, of type 478 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 479 */ 480 kstat_named_t arcstat_mru_ghost_evictable_data; 481 /* 482 * Number of bytes that *would have been* consumed by ARC 483 * buffers that are eligible for eviction, of type 484 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 485 */ 486 kstat_named_t arcstat_mru_ghost_evictable_metadata; 487 /* 488 * Total number of bytes consumed by ARC buffers residing in the 489 * arc_mfu state. This includes *all* buffers in the arc_mfu 490 * state; e.g. data, metadata, evictable, and unevictable buffers 491 * are all included in this value. 492 */ 493 kstat_named_t arcstat_mfu_size; 494 /* 495 * Number of bytes consumed by ARC buffers that are eligible for 496 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 497 * state. 498 */ 499 kstat_named_t arcstat_mfu_evictable_data; 500 /* 501 * Number of bytes consumed by ARC buffers that are eligible for 502 * eviction, of type ARC_BUFC_METADATA, and reside in the 503 * arc_mfu state. 504 */ 505 kstat_named_t arcstat_mfu_evictable_metadata; 506 /* 507 * Total number of bytes that *would have been* consumed by ARC 508 * buffers in the arc_mfu_ghost state. See the comment above 509 * arcstat_mru_ghost_size for more details. 510 */ 511 kstat_named_t arcstat_mfu_ghost_size; 512 /* 513 * Number of bytes that *would have been* consumed by ARC 514 * buffers that are eligible for eviction, of type 515 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 516 */ 517 kstat_named_t arcstat_mfu_ghost_evictable_data; 518 /* 519 * Number of bytes that *would have been* consumed by ARC 520 * buffers that are eligible for eviction, of type 521 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 522 */ 523 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 524 kstat_named_t arcstat_l2_hits; 525 kstat_named_t arcstat_l2_misses; 526 kstat_named_t arcstat_l2_feeds; 527 kstat_named_t arcstat_l2_rw_clash; 528 kstat_named_t arcstat_l2_read_bytes; 529 kstat_named_t arcstat_l2_write_bytes; 530 kstat_named_t arcstat_l2_writes_sent; 531 kstat_named_t arcstat_l2_writes_done; 532 kstat_named_t arcstat_l2_writes_error; 533 kstat_named_t arcstat_l2_writes_hdr_miss; 534 kstat_named_t arcstat_l2_evict_lock_retry; 535 kstat_named_t arcstat_l2_evict_reading; 536 kstat_named_t arcstat_l2_evict_l1cached; 537 kstat_named_t arcstat_l2_free_on_write; 538 kstat_named_t arcstat_l2_cdata_free_on_write; 539 kstat_named_t arcstat_l2_abort_lowmem; 540 kstat_named_t arcstat_l2_cksum_bad; 541 kstat_named_t arcstat_l2_io_error; 542 kstat_named_t arcstat_l2_size; 543 kstat_named_t arcstat_l2_asize; 544 kstat_named_t arcstat_l2_hdr_size; 545 kstat_named_t arcstat_l2_compress_successes; 546 kstat_named_t arcstat_l2_compress_zeros; 547 kstat_named_t arcstat_l2_compress_failures; 548 kstat_named_t arcstat_l2_write_trylock_fail; 549 kstat_named_t arcstat_l2_write_passed_headroom; 550 kstat_named_t arcstat_l2_write_spa_mismatch; 551 kstat_named_t arcstat_l2_write_in_l2; 552 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 553 kstat_named_t arcstat_l2_write_not_cacheable; 554 kstat_named_t arcstat_l2_write_full; 555 kstat_named_t arcstat_l2_write_buffer_iter; 556 kstat_named_t arcstat_l2_write_pios; 557 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 558 kstat_named_t arcstat_l2_write_buffer_list_iter; 559 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 560 kstat_named_t arcstat_memory_throttle_count; 561 kstat_named_t arcstat_duplicate_buffers; 562 kstat_named_t arcstat_duplicate_buffers_size; 563 kstat_named_t arcstat_duplicate_reads; 564 kstat_named_t arcstat_meta_used; 565 kstat_named_t arcstat_meta_limit; 566 kstat_named_t arcstat_meta_max; 567 kstat_named_t arcstat_meta_min; 568} arc_stats_t; 569 570static arc_stats_t arc_stats = { 571 { "hits", KSTAT_DATA_UINT64 }, 572 { "misses", KSTAT_DATA_UINT64 }, 573 { "demand_data_hits", KSTAT_DATA_UINT64 }, 574 { "demand_data_misses", KSTAT_DATA_UINT64 }, 575 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 576 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 577 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 578 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 579 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 580 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 581 { "mru_hits", KSTAT_DATA_UINT64 }, 582 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 583 { "mfu_hits", KSTAT_DATA_UINT64 }, 584 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 585 { "allocated", KSTAT_DATA_UINT64 }, 586 { "deleted", KSTAT_DATA_UINT64 }, 587 { "stolen", KSTAT_DATA_UINT64 }, 588 { "recycle_miss", KSTAT_DATA_UINT64 }, 589 { "mutex_miss", KSTAT_DATA_UINT64 }, 590 { "evict_skip", KSTAT_DATA_UINT64 }, 591 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 592 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 593 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 594 { "hash_elements", KSTAT_DATA_UINT64 }, 595 { "hash_elements_max", KSTAT_DATA_UINT64 }, 596 { "hash_collisions", KSTAT_DATA_UINT64 }, 597 { "hash_chains", KSTAT_DATA_UINT64 }, 598 { "hash_chain_max", KSTAT_DATA_UINT64 }, 599 { "p", KSTAT_DATA_UINT64 }, 600 { "c", KSTAT_DATA_UINT64 }, 601 { "c_min", KSTAT_DATA_UINT64 }, 602 { "c_max", KSTAT_DATA_UINT64 }, 603 { "size", KSTAT_DATA_UINT64 }, 604 { "hdr_size", KSTAT_DATA_UINT64 }, 605 { "data_size", KSTAT_DATA_UINT64 }, 606 { "metadata_size", KSTAT_DATA_UINT64 }, 607 { "other_size", KSTAT_DATA_UINT64 }, 608 { "anon_size", KSTAT_DATA_UINT64 }, 609 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 610 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 611 { "mru_size", KSTAT_DATA_UINT64 }, 612 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 613 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 614 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 615 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 616 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 617 { "mfu_size", KSTAT_DATA_UINT64 }, 618 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 619 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 620 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 621 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 622 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 623 { "l2_hits", KSTAT_DATA_UINT64 }, 624 { "l2_misses", KSTAT_DATA_UINT64 }, 625 { "l2_feeds", KSTAT_DATA_UINT64 }, 626 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 627 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 628 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 629 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 630 { "l2_writes_done", KSTAT_DATA_UINT64 }, 631 { "l2_writes_error", KSTAT_DATA_UINT64 }, 632 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 }, 633 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 634 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 635 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 636 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 637 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, 638 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 639 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 640 { "l2_io_error", KSTAT_DATA_UINT64 }, 641 { "l2_size", KSTAT_DATA_UINT64 }, 642 { "l2_asize", KSTAT_DATA_UINT64 }, 643 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 644 { "l2_compress_successes", KSTAT_DATA_UINT64 }, 645 { "l2_compress_zeros", KSTAT_DATA_UINT64 }, 646 { "l2_compress_failures", KSTAT_DATA_UINT64 }, 647 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 648 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 649 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 650 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 651 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 652 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 653 { "l2_write_full", KSTAT_DATA_UINT64 }, 654 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 655 { "l2_write_pios", KSTAT_DATA_UINT64 }, 656 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 657 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 658 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 659 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 660 { "duplicate_buffers", KSTAT_DATA_UINT64 }, 661 { "duplicate_buffers_size", KSTAT_DATA_UINT64 }, 662 { "duplicate_reads", KSTAT_DATA_UINT64 }, 663 { "arc_meta_used", KSTAT_DATA_UINT64 }, 664 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 665 { "arc_meta_max", KSTAT_DATA_UINT64 }, 666 { "arc_meta_min", KSTAT_DATA_UINT64 } 667}; 668 669#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 670 671#define ARCSTAT_INCR(stat, val) \ 672 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 673 674#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 675#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 676 677#define ARCSTAT_MAX(stat, val) { \ 678 uint64_t m; \ 679 while ((val) > (m = arc_stats.stat.value.ui64) && \ 680 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 681 continue; \ 682} 683 684#define ARCSTAT_MAXSTAT(stat) \ 685 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 686 687/* 688 * We define a macro to allow ARC hits/misses to be easily broken down by 689 * two separate conditions, giving a total of four different subtypes for 690 * each of hits and misses (so eight statistics total). 691 */ 692#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 693 if (cond1) { \ 694 if (cond2) { \ 695 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 696 } else { \ 697 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 698 } \ 699 } else { \ 700 if (cond2) { \ 701 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 702 } else { \ 703 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 704 } \ 705 } 706 707kstat_t *arc_ksp; 708static arc_state_t *arc_anon; 709static arc_state_t *arc_mru; 710static arc_state_t *arc_mru_ghost; 711static arc_state_t *arc_mfu; 712static arc_state_t *arc_mfu_ghost; 713static arc_state_t *arc_l2c_only; 714 715/* 716 * There are several ARC variables that are critical to export as kstats -- 717 * but we don't want to have to grovel around in the kstat whenever we wish to 718 * manipulate them. For these variables, we therefore define them to be in 719 * terms of the statistic variable. This assures that we are not introducing 720 * the possibility of inconsistency by having shadow copies of the variables, 721 * while still allowing the code to be readable. 722 */ 723#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 724#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 725#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 726#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 727#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 728#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 729#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 730#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 731#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 732 733#define L2ARC_IS_VALID_COMPRESS(_c_) \ 734 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY) 735 736static int arc_no_grow; /* Don't try to grow cache size */ 737static uint64_t arc_tempreserve; 738static uint64_t arc_loaned_bytes; 739 740typedef struct arc_callback arc_callback_t; 741 742struct arc_callback { 743 void *acb_private; 744 arc_done_func_t *acb_done; 745 arc_buf_t *acb_buf; 746 zio_t *acb_zio_dummy; 747 arc_callback_t *acb_next; 748}; 749 750typedef struct arc_write_callback arc_write_callback_t; 751 752struct arc_write_callback { 753 void *awcb_private; 754 arc_done_func_t *awcb_ready; 755 arc_done_func_t *awcb_physdone; 756 arc_done_func_t *awcb_done; 757 arc_buf_t *awcb_buf; 758}; 759 760/* 761 * ARC buffers are separated into multiple structs as a memory saving measure: 762 * - Common fields struct, always defined, and embedded within it: 763 * - L2-only fields, always allocated but undefined when not in L2ARC 764 * - L1-only fields, only allocated when in L1ARC 765 * 766 * Buffer in L1 Buffer only in L2 767 * +------------------------+ +------------------------+ 768 * | arc_buf_hdr_t | | arc_buf_hdr_t | 769 * | | | | 770 * | | | | 771 * | | | | 772 * +------------------------+ +------------------------+ 773 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 774 * | (undefined if L1-only) | | | 775 * +------------------------+ +------------------------+ 776 * | l1arc_buf_hdr_t | 777 * | | 778 * | | 779 * | | 780 * | | 781 * +------------------------+ 782 * 783 * Because it's possible for the L2ARC to become extremely large, we can wind 784 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 785 * is minimized by only allocating the fields necessary for an L1-cached buffer 786 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 787 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 788 * words in pointers. arc_hdr_realloc() is used to switch a header between 789 * these two allocation states. 790 */ 791typedef struct l1arc_buf_hdr { 792 kmutex_t b_freeze_lock; 793#ifdef ZFS_DEBUG 794 /* 795 * used for debugging wtih kmem_flags - by allocating and freeing 796 * b_thawed when the buffer is thawed, we get a record of the stack 797 * trace that thawed it. 798 */ 799 void *b_thawed; 800#endif 801 802 arc_buf_t *b_buf; 803 uint32_t b_datacnt; 804 /* for waiting on writes to complete */ 805 kcondvar_t b_cv; 806 807 /* protected by arc state mutex */ 808 arc_state_t *b_state; 809 list_node_t b_arc_node; 810 811 /* updated atomically */ 812 clock_t b_arc_access; 813 814 /* self protecting */ 815 refcount_t b_refcnt; 816 817 arc_callback_t *b_acb; 818 /* temporary buffer holder for in-flight compressed data */ 819 void *b_tmp_cdata; 820} l1arc_buf_hdr_t; 821 822typedef struct l2arc_dev l2arc_dev_t; 823 824typedef struct l2arc_buf_hdr { 825 /* protected by arc_buf_hdr mutex */ 826 l2arc_dev_t *b_dev; /* L2ARC device */ 827 uint64_t b_daddr; /* disk address, offset byte */ 828 /* real alloc'd buffer size depending on b_compress applied */ 829 int32_t b_asize; 830 831 list_node_t b_l2node; 832} l2arc_buf_hdr_t; 833 834struct arc_buf_hdr { 835 /* protected by hash lock */ 836 dva_t b_dva; 837 uint64_t b_birth; 838 /* 839 * Even though this checksum is only set/verified when a buffer is in 840 * the L1 cache, it needs to be in the set of common fields because it 841 * must be preserved from the time before a buffer is written out to 842 * L2ARC until after it is read back in. 843 */ 844 zio_cksum_t *b_freeze_cksum; 845 846 arc_buf_hdr_t *b_hash_next; 847 arc_flags_t b_flags; 848 849 /* immutable */ 850 int32_t b_size; 851 uint64_t b_spa; 852 853 /* L2ARC fields. Undefined when not in L2ARC. */ 854 l2arc_buf_hdr_t b_l2hdr; 855 /* L1ARC fields. Undefined when in l2arc_only state */ 856 l1arc_buf_hdr_t b_l1hdr; 857}; 858 859#ifdef _KERNEL 860static int 861sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 862{ 863 uint64_t val; 864 int err; 865 866 val = arc_meta_limit; 867 err = sysctl_handle_64(oidp, &val, 0, req); 868 if (err != 0 || req->newptr == NULL) 869 return (err); 870 871 if (val <= 0 || val > arc_c_max) 872 return (EINVAL); 873 874 arc_meta_limit = val; 875 return (0); 876} 877#endif 878 879static arc_buf_t *arc_eviction_list; 880static kmutex_t arc_eviction_mtx; 881static arc_buf_hdr_t arc_eviction_hdr; 882 883#define GHOST_STATE(state) \ 884 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 885 (state) == arc_l2c_only) 886 887#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 888#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 889#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 890#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 891#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ) 892#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE) 893 894#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 895#define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS) 896#define HDR_L2_READING(hdr) \ 897 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 898 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 899#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 900#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 901#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 902 903#define HDR_ISTYPE_METADATA(hdr) \ 904 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 905#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 906 907#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 908#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 909 910/* For storing compression mode in b_flags */ 911#define HDR_COMPRESS_OFFSET 24 912#define HDR_COMPRESS_NBITS 7 913 914#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \ 915 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS)) 916#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \ 917 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp)) 918 919/* 920 * Other sizes 921 */ 922 923#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 924#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 925 926/* 927 * Hash table routines 928 */ 929 930#define HT_LOCK_PAD CACHE_LINE_SIZE 931 932struct ht_lock { 933 kmutex_t ht_lock; 934#ifdef _KERNEL 935 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 936#endif 937}; 938 939#define BUF_LOCKS 256 940typedef struct buf_hash_table { 941 uint64_t ht_mask; 942 arc_buf_hdr_t **ht_table; 943 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 944} buf_hash_table_t; 945 946static buf_hash_table_t buf_hash_table; 947 948#define BUF_HASH_INDEX(spa, dva, birth) \ 949 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 950#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 951#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 952#define HDR_LOCK(hdr) \ 953 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 954 955uint64_t zfs_crc64_table[256]; 956 957/* 958 * Level 2 ARC 959 */ 960 961#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 962#define L2ARC_HEADROOM 2 /* num of writes */ 963/* 964 * If we discover during ARC scan any buffers to be compressed, we boost 965 * our headroom for the next scanning cycle by this percentage multiple. 966 */ 967#define L2ARC_HEADROOM_BOOST 200 968#define L2ARC_FEED_SECS 1 /* caching interval secs */ 969#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 970 971/* 972 * Used to distinguish headers that are being process by 973 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk 974 * address. This can happen when the header is added to the l2arc's list 975 * of buffers to write in the first stage of l2arc_write_buffers(), but 976 * has not yet been written out which happens in the second stage of 977 * l2arc_write_buffers(). 978 */ 979#define L2ARC_ADDR_UNSET ((uint64_t)(-1)) 980 981#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 982#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 983 984/* L2ARC Performance Tunables */ 985uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 986uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 987uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 988uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 989uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 990uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 991boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 992boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 993boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 994 995SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 996 &l2arc_write_max, 0, "max write size"); 997SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 998 &l2arc_write_boost, 0, "extra write during warmup"); 999SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1000 &l2arc_headroom, 0, "number of dev writes"); 1001SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1002 &l2arc_feed_secs, 0, "interval seconds"); 1003SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1004 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1005 1006SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1007 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1008SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1009 &l2arc_feed_again, 0, "turbo warmup"); 1010SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1011 &l2arc_norw, 0, "no reads during writes"); 1012 1013SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1014 &ARC_anon.arcs_size, 0, "size of anonymous state"); 1015SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD, 1016 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state"); 1017SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD, 1018 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state"); 1019 1020SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1021 &ARC_mru.arcs_size, 0, "size of mru state"); 1022SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD, 1023 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state"); 1024SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD, 1025 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state"); 1026 1027SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1028 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state"); 1029SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD, 1030 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1031 "size of metadata in mru ghost state"); 1032SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD, 1033 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1034 "size of data in mru ghost state"); 1035 1036SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1037 &ARC_mfu.arcs_size, 0, "size of mfu state"); 1038SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD, 1039 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state"); 1040SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD, 1041 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state"); 1042 1043SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1044 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state"); 1045SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD, 1046 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0, 1047 "size of metadata in mfu ghost state"); 1048SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD, 1049 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0, 1050 "size of data in mfu ghost state"); 1051 1052SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1053 &ARC_l2c_only.arcs_size, 0, "size of mru state"); 1054 1055/* 1056 * L2ARC Internals 1057 */ 1058struct l2arc_dev { 1059 vdev_t *l2ad_vdev; /* vdev */ 1060 spa_t *l2ad_spa; /* spa */ 1061 uint64_t l2ad_hand; /* next write location */ 1062 uint64_t l2ad_start; /* first addr on device */ 1063 uint64_t l2ad_end; /* last addr on device */ 1064 boolean_t l2ad_first; /* first sweep through */ 1065 boolean_t l2ad_writing; /* currently writing */ 1066 kmutex_t l2ad_mtx; /* lock for buffer list */ 1067 list_t l2ad_buflist; /* buffer list */ 1068 list_node_t l2ad_node; /* device list node */ 1069 refcount_t l2ad_alloc; /* allocated bytes */ 1070}; 1071 1072static list_t L2ARC_dev_list; /* device list */ 1073static list_t *l2arc_dev_list; /* device list pointer */ 1074static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1075static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1076static list_t L2ARC_free_on_write; /* free after write buf list */ 1077static list_t *l2arc_free_on_write; /* free after write list ptr */ 1078static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1079static uint64_t l2arc_ndev; /* number of devices */ 1080 1081typedef struct l2arc_read_callback { 1082 arc_buf_t *l2rcb_buf; /* read buffer */ 1083 spa_t *l2rcb_spa; /* spa */ 1084 blkptr_t l2rcb_bp; /* original blkptr */ 1085 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1086 int l2rcb_flags; /* original flags */ 1087 enum zio_compress l2rcb_compress; /* applied compress */ 1088} l2arc_read_callback_t; 1089 1090typedef struct l2arc_write_callback { 1091 l2arc_dev_t *l2wcb_dev; /* device info */ 1092 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1093} l2arc_write_callback_t; 1094 1095typedef struct l2arc_data_free { 1096 /* protected by l2arc_free_on_write_mtx */ 1097 void *l2df_data; 1098 size_t l2df_size; 1099 void (*l2df_func)(void *, size_t); 1100 list_node_t l2df_list_node; 1101} l2arc_data_free_t; 1102 1103static kmutex_t l2arc_feed_thr_lock; 1104static kcondvar_t l2arc_feed_thr_cv; 1105static uint8_t l2arc_thread_exit; 1106 1107static void arc_get_data_buf(arc_buf_t *); 1108static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1109static int arc_evict_needed(arc_buf_contents_t); 1110static void arc_evict_ghost(arc_state_t *, uint64_t, int64_t); 1111static void arc_buf_watch(arc_buf_t *); 1112 1113static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1114static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1115 1116static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1117static void l2arc_read_done(zio_t *); 1118 1119static boolean_t l2arc_compress_buf(arc_buf_hdr_t *); 1120static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress); 1121static void l2arc_release_cdata_buf(arc_buf_hdr_t *); 1122 1123static uint64_t 1124buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1125{ 1126 uint8_t *vdva = (uint8_t *)dva; 1127 uint64_t crc = -1ULL; 1128 int i; 1129 1130 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1131 1132 for (i = 0; i < sizeof (dva_t); i++) 1133 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1134 1135 crc ^= (spa>>8) ^ birth; 1136 1137 return (crc); 1138} 1139 1140#define BUF_EMPTY(buf) \ 1141 ((buf)->b_dva.dva_word[0] == 0 && \ 1142 (buf)->b_dva.dva_word[1] == 0) 1143 1144#define BUF_EQUAL(spa, dva, birth, buf) \ 1145 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1146 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1147 ((buf)->b_birth == birth) && ((buf)->b_spa == spa) 1148 1149static void 1150buf_discard_identity(arc_buf_hdr_t *hdr) 1151{ 1152 hdr->b_dva.dva_word[0] = 0; 1153 hdr->b_dva.dva_word[1] = 0; 1154 hdr->b_birth = 0; 1155} 1156 1157static arc_buf_hdr_t * 1158buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1159{ 1160 const dva_t *dva = BP_IDENTITY(bp); 1161 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1162 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1163 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1164 arc_buf_hdr_t *hdr; 1165 1166 mutex_enter(hash_lock); 1167 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1168 hdr = hdr->b_hash_next) { 1169 if (BUF_EQUAL(spa, dva, birth, hdr)) { 1170 *lockp = hash_lock; 1171 return (hdr); 1172 } 1173 } 1174 mutex_exit(hash_lock); 1175 *lockp = NULL; 1176 return (NULL); 1177} 1178 1179/* 1180 * Insert an entry into the hash table. If there is already an element 1181 * equal to elem in the hash table, then the already existing element 1182 * will be returned and the new element will not be inserted. 1183 * Otherwise returns NULL. 1184 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1185 */ 1186static arc_buf_hdr_t * 1187buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1188{ 1189 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1190 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1191 arc_buf_hdr_t *fhdr; 1192 uint32_t i; 1193 1194 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1195 ASSERT(hdr->b_birth != 0); 1196 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1197 1198 if (lockp != NULL) { 1199 *lockp = hash_lock; 1200 mutex_enter(hash_lock); 1201 } else { 1202 ASSERT(MUTEX_HELD(hash_lock)); 1203 } 1204 1205 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1206 fhdr = fhdr->b_hash_next, i++) { 1207 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1208 return (fhdr); 1209 } 1210 1211 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1212 buf_hash_table.ht_table[idx] = hdr; 1213 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 1214 1215 /* collect some hash table performance data */ 1216 if (i > 0) { 1217 ARCSTAT_BUMP(arcstat_hash_collisions); 1218 if (i == 1) 1219 ARCSTAT_BUMP(arcstat_hash_chains); 1220 1221 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1222 } 1223 1224 ARCSTAT_BUMP(arcstat_hash_elements); 1225 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1226 1227 return (NULL); 1228} 1229 1230static void 1231buf_hash_remove(arc_buf_hdr_t *hdr) 1232{ 1233 arc_buf_hdr_t *fhdr, **hdrp; 1234 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1235 1236 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1237 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1238 1239 hdrp = &buf_hash_table.ht_table[idx]; 1240 while ((fhdr = *hdrp) != hdr) { 1241 ASSERT(fhdr != NULL); 1242 hdrp = &fhdr->b_hash_next; 1243 } 1244 *hdrp = hdr->b_hash_next; 1245 hdr->b_hash_next = NULL; 1246 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE; 1247 1248 /* collect some hash table performance data */ 1249 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1250 1251 if (buf_hash_table.ht_table[idx] && 1252 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1253 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1254} 1255 1256/* 1257 * Global data structures and functions for the buf kmem cache. 1258 */ 1259static kmem_cache_t *hdr_full_cache; 1260static kmem_cache_t *hdr_l2only_cache; 1261static kmem_cache_t *buf_cache; 1262 1263static void 1264buf_fini(void) 1265{ 1266 int i; 1267 1268 kmem_free(buf_hash_table.ht_table, 1269 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1270 for (i = 0; i < BUF_LOCKS; i++) 1271 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1272 kmem_cache_destroy(hdr_full_cache); 1273 kmem_cache_destroy(hdr_l2only_cache); 1274 kmem_cache_destroy(buf_cache); 1275} 1276 1277/* 1278 * Constructor callback - called when the cache is empty 1279 * and a new buf is requested. 1280 */ 1281/* ARGSUSED */ 1282static int 1283hdr_full_cons(void *vbuf, void *unused, int kmflag) 1284{ 1285 arc_buf_hdr_t *hdr = vbuf; 1286 1287 bzero(hdr, HDR_FULL_SIZE); 1288 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1289 refcount_create(&hdr->b_l1hdr.b_refcnt); 1290 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1291 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1292 1293 return (0); 1294} 1295 1296/* ARGSUSED */ 1297static int 1298hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1299{ 1300 arc_buf_hdr_t *hdr = vbuf; 1301 1302 bzero(hdr, HDR_L2ONLY_SIZE); 1303 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1304 1305 return (0); 1306} 1307 1308/* ARGSUSED */ 1309static int 1310buf_cons(void *vbuf, void *unused, int kmflag) 1311{ 1312 arc_buf_t *buf = vbuf; 1313 1314 bzero(buf, sizeof (arc_buf_t)); 1315 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1316 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1317 1318 return (0); 1319} 1320 1321/* 1322 * Destructor callback - called when a cached buf is 1323 * no longer required. 1324 */ 1325/* ARGSUSED */ 1326static void 1327hdr_full_dest(void *vbuf, void *unused) 1328{ 1329 arc_buf_hdr_t *hdr = vbuf; 1330 1331 ASSERT(BUF_EMPTY(hdr)); 1332 cv_destroy(&hdr->b_l1hdr.b_cv); 1333 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1334 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1335 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1336} 1337 1338/* ARGSUSED */ 1339static void 1340hdr_l2only_dest(void *vbuf, void *unused) 1341{ 1342 arc_buf_hdr_t *hdr = vbuf; 1343 1344 ASSERT(BUF_EMPTY(hdr)); 1345 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1346} 1347 1348/* ARGSUSED */ 1349static void 1350buf_dest(void *vbuf, void *unused) 1351{ 1352 arc_buf_t *buf = vbuf; 1353 1354 mutex_destroy(&buf->b_evict_lock); 1355 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1356} 1357 1358/* 1359 * Reclaim callback -- invoked when memory is low. 1360 */ 1361/* ARGSUSED */ 1362static void 1363hdr_recl(void *unused) 1364{ 1365 dprintf("hdr_recl called\n"); 1366 /* 1367 * umem calls the reclaim func when we destroy the buf cache, 1368 * which is after we do arc_fini(). 1369 */ 1370 if (!arc_dead) 1371 cv_signal(&arc_reclaim_thr_cv); 1372} 1373 1374static void 1375buf_init(void) 1376{ 1377 uint64_t *ct; 1378 uint64_t hsize = 1ULL << 12; 1379 int i, j; 1380 1381 /* 1382 * The hash table is big enough to fill all of physical memory 1383 * with an average block size of zfs_arc_average_blocksize (default 8K). 1384 * By default, the table will take up 1385 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1386 */ 1387 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1388 hsize <<= 1; 1389retry: 1390 buf_hash_table.ht_mask = hsize - 1; 1391 buf_hash_table.ht_table = 1392 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1393 if (buf_hash_table.ht_table == NULL) { 1394 ASSERT(hsize > (1ULL << 8)); 1395 hsize >>= 1; 1396 goto retry; 1397 } 1398 1399 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1400 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1401 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1402 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1403 NULL, NULL, 0); 1404 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1405 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1406 1407 for (i = 0; i < 256; i++) 1408 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1409 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1410 1411 for (i = 0; i < BUF_LOCKS; i++) { 1412 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1413 NULL, MUTEX_DEFAULT, NULL); 1414 } 1415} 1416 1417/* 1418 * Transition between the two allocation states for the arc_buf_hdr struct. 1419 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 1420 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 1421 * version is used when a cache buffer is only in the L2ARC in order to reduce 1422 * memory usage. 1423 */ 1424static arc_buf_hdr_t * 1425arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 1426{ 1427 ASSERT(HDR_HAS_L2HDR(hdr)); 1428 1429 arc_buf_hdr_t *nhdr; 1430 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1431 1432 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 1433 (old == hdr_l2only_cache && new == hdr_full_cache)); 1434 1435 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 1436 1437 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 1438 buf_hash_remove(hdr); 1439 1440 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 1441 1442 if (new == hdr_full_cache) { 1443 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1444 /* 1445 * arc_access and arc_change_state need to be aware that a 1446 * header has just come out of L2ARC, so we set its state to 1447 * l2c_only even though it's about to change. 1448 */ 1449 nhdr->b_l1hdr.b_state = arc_l2c_only; 1450 } else { 1451 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1452 ASSERT0(hdr->b_l1hdr.b_datacnt); 1453 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1454 /* 1455 * We might be removing the L1hdr of a buffer which was just 1456 * written out to L2ARC. If such a buffer is compressed then we 1457 * need to free its b_tmp_cdata before destroying the header. 1458 */ 1459 if (hdr->b_l1hdr.b_tmp_cdata != NULL && 1460 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 1461 l2arc_release_cdata_buf(hdr); 1462 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR; 1463 } 1464 /* 1465 * The header has been reallocated so we need to re-insert it into any 1466 * lists it was on. 1467 */ 1468 (void) buf_hash_insert(nhdr, NULL); 1469 1470 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 1471 1472 mutex_enter(&dev->l2ad_mtx); 1473 1474 /* 1475 * We must place the realloc'ed header back into the list at 1476 * the same spot. Otherwise, if it's placed earlier in the list, 1477 * l2arc_write_buffers() could find it during the function's 1478 * write phase, and try to write it out to the l2arc. 1479 */ 1480 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 1481 list_remove(&dev->l2ad_buflist, hdr); 1482 1483 mutex_exit(&dev->l2ad_mtx); 1484 1485 /* 1486 * Since we're using the pointer address as the tag when 1487 * incrementing and decrementing the l2ad_alloc refcount, we 1488 * must remove the old pointer (that we're about to destroy) and 1489 * add the new pointer to the refcount. Otherwise we'd remove 1490 * the wrong pointer address when calling arc_hdr_destroy() later. 1491 */ 1492 1493 (void) refcount_remove_many(&dev->l2ad_alloc, 1494 hdr->b_l2hdr.b_asize, hdr); 1495 1496 (void) refcount_add_many(&dev->l2ad_alloc, 1497 nhdr->b_l2hdr.b_asize, nhdr); 1498 1499 buf_discard_identity(hdr); 1500 hdr->b_freeze_cksum = NULL; 1501 kmem_cache_free(old, hdr); 1502 1503 return (nhdr); 1504} 1505 1506 1507#define ARC_MINTIME (hz>>4) /* 62 ms */ 1508 1509static void 1510arc_cksum_verify(arc_buf_t *buf) 1511{ 1512 zio_cksum_t zc; 1513 1514 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1515 return; 1516 1517 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1518 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) { 1519 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1520 return; 1521 } 1522 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1523 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc)) 1524 panic("buffer modified while frozen!"); 1525 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1526} 1527 1528static int 1529arc_cksum_equal(arc_buf_t *buf) 1530{ 1531 zio_cksum_t zc; 1532 int equal; 1533 1534 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1535 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc); 1536 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc); 1537 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1538 1539 return (equal); 1540} 1541 1542static void 1543arc_cksum_compute(arc_buf_t *buf, boolean_t force) 1544{ 1545 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY)) 1546 return; 1547 1548 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1549 if (buf->b_hdr->b_freeze_cksum != NULL) { 1550 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1551 return; 1552 } 1553 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP); 1554 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, 1555 buf->b_hdr->b_freeze_cksum); 1556 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1557#ifdef illumos 1558 arc_buf_watch(buf); 1559#endif 1560} 1561 1562#ifdef illumos 1563#ifndef _KERNEL 1564typedef struct procctl { 1565 long cmd; 1566 prwatch_t prwatch; 1567} procctl_t; 1568#endif 1569 1570/* ARGSUSED */ 1571static void 1572arc_buf_unwatch(arc_buf_t *buf) 1573{ 1574#ifndef _KERNEL 1575 if (arc_watch) { 1576 int result; 1577 procctl_t ctl; 1578 ctl.cmd = PCWATCH; 1579 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1580 ctl.prwatch.pr_size = 0; 1581 ctl.prwatch.pr_wflags = 0; 1582 result = write(arc_procfd, &ctl, sizeof (ctl)); 1583 ASSERT3U(result, ==, sizeof (ctl)); 1584 } 1585#endif 1586} 1587 1588/* ARGSUSED */ 1589static void 1590arc_buf_watch(arc_buf_t *buf) 1591{ 1592#ifndef _KERNEL 1593 if (arc_watch) { 1594 int result; 1595 procctl_t ctl; 1596 ctl.cmd = PCWATCH; 1597 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1598 ctl.prwatch.pr_size = buf->b_hdr->b_size; 1599 ctl.prwatch.pr_wflags = WA_WRITE; 1600 result = write(arc_procfd, &ctl, sizeof (ctl)); 1601 ASSERT3U(result, ==, sizeof (ctl)); 1602 } 1603#endif 1604} 1605#endif /* illumos */ 1606 1607static arc_buf_contents_t 1608arc_buf_type(arc_buf_hdr_t *hdr) 1609{ 1610 if (HDR_ISTYPE_METADATA(hdr)) { 1611 return (ARC_BUFC_METADATA); 1612 } else { 1613 return (ARC_BUFC_DATA); 1614 } 1615} 1616 1617static uint32_t 1618arc_bufc_to_flags(arc_buf_contents_t type) 1619{ 1620 switch (type) { 1621 case ARC_BUFC_DATA: 1622 /* metadata field is 0 if buffer contains normal data */ 1623 return (0); 1624 case ARC_BUFC_METADATA: 1625 return (ARC_FLAG_BUFC_METADATA); 1626 default: 1627 break; 1628 } 1629 panic("undefined ARC buffer type!"); 1630 return ((uint32_t)-1); 1631} 1632 1633void 1634arc_buf_thaw(arc_buf_t *buf) 1635{ 1636 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1637 if (buf->b_hdr->b_l1hdr.b_state != arc_anon) 1638 panic("modifying non-anon buffer!"); 1639 if (HDR_IO_IN_PROGRESS(buf->b_hdr)) 1640 panic("modifying buffer while i/o in progress!"); 1641 arc_cksum_verify(buf); 1642 } 1643 1644 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1645 if (buf->b_hdr->b_freeze_cksum != NULL) { 1646 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 1647 buf->b_hdr->b_freeze_cksum = NULL; 1648 } 1649 1650#ifdef ZFS_DEBUG 1651 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1652 if (buf->b_hdr->b_l1hdr.b_thawed != NULL) 1653 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1); 1654 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1655 } 1656#endif 1657 1658 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1659 1660#ifdef illumos 1661 arc_buf_unwatch(buf); 1662#endif 1663} 1664 1665void 1666arc_buf_freeze(arc_buf_t *buf) 1667{ 1668 kmutex_t *hash_lock; 1669 1670 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1671 return; 1672 1673 hash_lock = HDR_LOCK(buf->b_hdr); 1674 mutex_enter(hash_lock); 1675 1676 ASSERT(buf->b_hdr->b_freeze_cksum != NULL || 1677 buf->b_hdr->b_l1hdr.b_state == arc_anon); 1678 arc_cksum_compute(buf, B_FALSE); 1679 mutex_exit(hash_lock); 1680 1681} 1682 1683static void 1684get_buf_info(arc_buf_hdr_t *hdr, arc_state_t *state, list_t **list, kmutex_t **lock) 1685{ 1686 uint64_t buf_hashid = buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1687 1688 if (arc_buf_type(hdr) == ARC_BUFC_METADATA) 1689 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1); 1690 else { 1691 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1); 1692 buf_hashid += ARC_BUFC_NUMMETADATALISTS; 1693 } 1694 1695 *list = &state->arcs_lists[buf_hashid]; 1696 *lock = ARCS_LOCK(state, buf_hashid); 1697} 1698 1699 1700static void 1701add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1702{ 1703 ASSERT(HDR_HAS_L1HDR(hdr)); 1704 ASSERT(MUTEX_HELD(hash_lock)); 1705 arc_state_t *state = hdr->b_l1hdr.b_state; 1706 1707 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 1708 (state != arc_anon)) { 1709 /* We don't use the L2-only state list. */ 1710 if (state != arc_l2c_only) { 1711 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt; 1712 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1713 list_t *list; 1714 kmutex_t *lock; 1715 1716 get_buf_info(hdr, state, &list, &lock); 1717 ASSERT(!MUTEX_HELD(lock)); 1718 mutex_enter(lock); 1719 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1720 list_remove(list, hdr); 1721 if (GHOST_STATE(state)) { 1722 ASSERT0(hdr->b_l1hdr.b_datacnt); 1723 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 1724 delta = hdr->b_size; 1725 } 1726 ASSERT(delta > 0); 1727 ASSERT3U(*size, >=, delta); 1728 atomic_add_64(size, -delta); 1729 mutex_exit(lock); 1730 } 1731 /* remove the prefetch flag if we get a reference */ 1732 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 1733 } 1734} 1735 1736static int 1737remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 1738{ 1739 int cnt; 1740 arc_state_t *state = hdr->b_l1hdr.b_state; 1741 1742 ASSERT(HDR_HAS_L1HDR(hdr)); 1743 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 1744 ASSERT(!GHOST_STATE(state)); 1745 1746 /* 1747 * arc_l2c_only counts as a ghost state so we don't need to explicitly 1748 * check to prevent usage of the arc_l2c_only list. 1749 */ 1750 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 1751 (state != arc_anon)) { 1752 uint64_t *size = &state->arcs_lsize[arc_buf_type(hdr)]; 1753 list_t *list; 1754 kmutex_t *lock; 1755 1756 get_buf_info(hdr, state, &list, &lock); 1757 ASSERT(!MUTEX_HELD(lock)); 1758 mutex_enter(lock); 1759 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 1760 list_insert_head(list, hdr); 1761 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 1762 atomic_add_64(size, hdr->b_size * 1763 hdr->b_l1hdr.b_datacnt); 1764 mutex_exit(lock); 1765 } 1766 return (cnt); 1767} 1768 1769/* 1770 * Move the supplied buffer to the indicated state. The mutex 1771 * for the buffer must be held by the caller. 1772 */ 1773static void 1774arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 1775 kmutex_t *hash_lock) 1776{ 1777 arc_state_t *old_state; 1778 int64_t refcnt; 1779 uint32_t datacnt; 1780 uint64_t from_delta, to_delta; 1781 arc_buf_contents_t buftype = arc_buf_type(hdr); 1782 list_t *list; 1783 kmutex_t *lock; 1784 1785 /* 1786 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 1787 * in arc_read() when bringing a buffer out of the L2ARC. However, the 1788 * L1 hdr doesn't always exist when we change state to arc_anon before 1789 * destroying a header, in which case reallocating to add the L1 hdr is 1790 * pointless. 1791 */ 1792 if (HDR_HAS_L1HDR(hdr)) { 1793 old_state = hdr->b_l1hdr.b_state; 1794 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 1795 datacnt = hdr->b_l1hdr.b_datacnt; 1796 } else { 1797 old_state = arc_l2c_only; 1798 refcnt = 0; 1799 datacnt = 0; 1800 } 1801 1802 ASSERT(MUTEX_HELD(hash_lock)); 1803 ASSERT3P(new_state, !=, old_state); 1804 ASSERT(refcnt == 0 || datacnt > 0); 1805 ASSERT(!GHOST_STATE(new_state) || datacnt == 0); 1806 ASSERT(old_state != arc_anon || datacnt <= 1); 1807 1808 from_delta = to_delta = datacnt * hdr->b_size; 1809 1810 /* 1811 * If this buffer is evictable, transfer it from the 1812 * old state list to the new state list. 1813 */ 1814 if (refcnt == 0) { 1815 if (old_state != arc_anon && old_state != arc_l2c_only) { 1816 int use_mutex; 1817 uint64_t *size = &old_state->arcs_lsize[buftype]; 1818 1819 get_buf_info(hdr, old_state, &list, &lock); 1820 use_mutex = !MUTEX_HELD(lock); 1821 if (use_mutex) 1822 mutex_enter(lock); 1823 1824 ASSERT(HDR_HAS_L1HDR(hdr)); 1825 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 1826 list_remove(list, hdr); 1827 1828 /* 1829 * If prefetching out of the ghost cache, 1830 * we will have a non-zero datacnt. 1831 */ 1832 if (GHOST_STATE(old_state) && datacnt == 0) { 1833 /* ghost elements have a ghost size */ 1834 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1835 from_delta = hdr->b_size; 1836 } 1837 ASSERT3U(*size, >=, from_delta); 1838 atomic_add_64(size, -from_delta); 1839 1840 if (use_mutex) 1841 mutex_exit(lock); 1842 } 1843 if (new_state != arc_anon && new_state != arc_l2c_only) { 1844 int use_mutex; 1845 uint64_t *size = &new_state->arcs_lsize[buftype]; 1846 1847 /* 1848 * An L1 header always exists here, since if we're 1849 * moving to some L1-cached state (i.e. not l2c_only or 1850 * anonymous), we realloc the header to add an L1hdr 1851 * beforehand. 1852 */ 1853 ASSERT(HDR_HAS_L1HDR(hdr)); 1854 get_buf_info(hdr, new_state, &list, &lock); 1855 use_mutex = !MUTEX_HELD(lock); 1856 if (use_mutex) 1857 mutex_enter(lock); 1858 1859 list_insert_head(list, hdr); 1860 1861 /* ghost elements have a ghost size */ 1862 if (GHOST_STATE(new_state)) { 1863 ASSERT(datacnt == 0); 1864 ASSERT(hdr->b_l1hdr.b_buf == NULL); 1865 to_delta = hdr->b_size; 1866 } 1867 atomic_add_64(size, to_delta); 1868 1869 if (use_mutex) 1870 mutex_exit(lock); 1871 } 1872 } 1873 1874 ASSERT(!BUF_EMPTY(hdr)); 1875 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 1876 buf_hash_remove(hdr); 1877 1878 /* adjust state sizes (ignore arc_l2c_only) */ 1879 if (to_delta && new_state != arc_l2c_only) 1880 atomic_add_64(&new_state->arcs_size, to_delta); 1881 if (from_delta && old_state != arc_l2c_only) { 1882 ASSERT3U(old_state->arcs_size, >=, from_delta); 1883 atomic_add_64(&old_state->arcs_size, -from_delta); 1884 } 1885 if (HDR_HAS_L1HDR(hdr)) 1886 hdr->b_l1hdr.b_state = new_state; 1887 1888 /* 1889 * L2 headers should never be on the L2 state list since they don't 1890 * have L1 headers allocated. 1891 */ 1892#ifdef illumos 1893 ASSERT(list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 1894 list_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 1895#endif 1896} 1897 1898void 1899arc_space_consume(uint64_t space, arc_space_type_t type) 1900{ 1901 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1902 1903 switch (type) { 1904 case ARC_SPACE_DATA: 1905 ARCSTAT_INCR(arcstat_data_size, space); 1906 break; 1907 case ARC_SPACE_META: 1908 ARCSTAT_INCR(arcstat_metadata_size, space); 1909 break; 1910 case ARC_SPACE_OTHER: 1911 ARCSTAT_INCR(arcstat_other_size, space); 1912 break; 1913 case ARC_SPACE_HDRS: 1914 ARCSTAT_INCR(arcstat_hdr_size, space); 1915 break; 1916 case ARC_SPACE_L2HDRS: 1917 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 1918 break; 1919 } 1920 1921 if (type != ARC_SPACE_DATA) 1922 ARCSTAT_INCR(arcstat_meta_used, space); 1923 1924 atomic_add_64(&arc_size, space); 1925} 1926 1927void 1928arc_space_return(uint64_t space, arc_space_type_t type) 1929{ 1930 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 1931 1932 switch (type) { 1933 case ARC_SPACE_DATA: 1934 ARCSTAT_INCR(arcstat_data_size, -space); 1935 break; 1936 case ARC_SPACE_META: 1937 ARCSTAT_INCR(arcstat_metadata_size, -space); 1938 break; 1939 case ARC_SPACE_OTHER: 1940 ARCSTAT_INCR(arcstat_other_size, -space); 1941 break; 1942 case ARC_SPACE_HDRS: 1943 ARCSTAT_INCR(arcstat_hdr_size, -space); 1944 break; 1945 case ARC_SPACE_L2HDRS: 1946 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 1947 break; 1948 } 1949 1950 if (type != ARC_SPACE_DATA) { 1951 ASSERT(arc_meta_used >= space); 1952 if (arc_meta_max < arc_meta_used) 1953 arc_meta_max = arc_meta_used; 1954 ARCSTAT_INCR(arcstat_meta_used, -space); 1955 } 1956 1957 ASSERT(arc_size >= space); 1958 atomic_add_64(&arc_size, -space); 1959} 1960 1961arc_buf_t * 1962arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 1963{ 1964 arc_buf_hdr_t *hdr; 1965 arc_buf_t *buf; 1966 1967 ASSERT3U(size, >, 0); 1968 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 1969 ASSERT(BUF_EMPTY(hdr)); 1970 ASSERT3P(hdr->b_freeze_cksum, ==, NULL); 1971 hdr->b_size = size; 1972 hdr->b_spa = spa_load_guid(spa); 1973 1974 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 1975 buf->b_hdr = hdr; 1976 buf->b_data = NULL; 1977 buf->b_efunc = NULL; 1978 buf->b_private = NULL; 1979 buf->b_next = NULL; 1980 1981 hdr->b_flags = arc_bufc_to_flags(type); 1982 hdr->b_flags |= ARC_FLAG_HAS_L1HDR; 1983 1984 hdr->b_l1hdr.b_buf = buf; 1985 hdr->b_l1hdr.b_state = arc_anon; 1986 hdr->b_l1hdr.b_arc_access = 0; 1987 hdr->b_l1hdr.b_datacnt = 1; 1988 1989 arc_get_data_buf(buf); 1990 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 1991 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 1992 1993 return (buf); 1994} 1995 1996static char *arc_onloan_tag = "onloan"; 1997 1998/* 1999 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2000 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2001 * buffers must be returned to the arc before they can be used by the DMU or 2002 * freed. 2003 */ 2004arc_buf_t * 2005arc_loan_buf(spa_t *spa, int size) 2006{ 2007 arc_buf_t *buf; 2008 2009 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2010 2011 atomic_add_64(&arc_loaned_bytes, size); 2012 return (buf); 2013} 2014 2015/* 2016 * Return a loaned arc buffer to the arc. 2017 */ 2018void 2019arc_return_buf(arc_buf_t *buf, void *tag) 2020{ 2021 arc_buf_hdr_t *hdr = buf->b_hdr; 2022 2023 ASSERT(buf->b_data != NULL); 2024 ASSERT(HDR_HAS_L1HDR(hdr)); 2025 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2026 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2027 2028 atomic_add_64(&arc_loaned_bytes, -hdr->b_size); 2029} 2030 2031/* Detach an arc_buf from a dbuf (tag) */ 2032void 2033arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2034{ 2035 arc_buf_hdr_t *hdr = buf->b_hdr; 2036 2037 ASSERT(buf->b_data != NULL); 2038 ASSERT(HDR_HAS_L1HDR(hdr)); 2039 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2040 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2041 buf->b_efunc = NULL; 2042 buf->b_private = NULL; 2043 2044 atomic_add_64(&arc_loaned_bytes, hdr->b_size); 2045} 2046 2047static arc_buf_t * 2048arc_buf_clone(arc_buf_t *from) 2049{ 2050 arc_buf_t *buf; 2051 arc_buf_hdr_t *hdr = from->b_hdr; 2052 uint64_t size = hdr->b_size; 2053 2054 ASSERT(HDR_HAS_L1HDR(hdr)); 2055 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2056 2057 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2058 buf->b_hdr = hdr; 2059 buf->b_data = NULL; 2060 buf->b_efunc = NULL; 2061 buf->b_private = NULL; 2062 buf->b_next = hdr->b_l1hdr.b_buf; 2063 hdr->b_l1hdr.b_buf = buf; 2064 arc_get_data_buf(buf); 2065 bcopy(from->b_data, buf->b_data, size); 2066 2067 /* 2068 * This buffer already exists in the arc so create a duplicate 2069 * copy for the caller. If the buffer is associated with user data 2070 * then track the size and number of duplicates. These stats will be 2071 * updated as duplicate buffers are created and destroyed. 2072 */ 2073 if (HDR_ISTYPE_DATA(hdr)) { 2074 ARCSTAT_BUMP(arcstat_duplicate_buffers); 2075 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size); 2076 } 2077 hdr->b_l1hdr.b_datacnt += 1; 2078 return (buf); 2079} 2080 2081void 2082arc_buf_add_ref(arc_buf_t *buf, void* tag) 2083{ 2084 arc_buf_hdr_t *hdr; 2085 kmutex_t *hash_lock; 2086 2087 /* 2088 * Check to see if this buffer is evicted. Callers 2089 * must verify b_data != NULL to know if the add_ref 2090 * was successful. 2091 */ 2092 mutex_enter(&buf->b_evict_lock); 2093 if (buf->b_data == NULL) { 2094 mutex_exit(&buf->b_evict_lock); 2095 return; 2096 } 2097 hash_lock = HDR_LOCK(buf->b_hdr); 2098 mutex_enter(hash_lock); 2099 hdr = buf->b_hdr; 2100 ASSERT(HDR_HAS_L1HDR(hdr)); 2101 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2102 mutex_exit(&buf->b_evict_lock); 2103 2104 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 2105 hdr->b_l1hdr.b_state == arc_mfu); 2106 2107 add_reference(hdr, hash_lock, tag); 2108 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 2109 arc_access(hdr, hash_lock); 2110 mutex_exit(hash_lock); 2111 ARCSTAT_BUMP(arcstat_hits); 2112 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 2113 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 2114 data, metadata, hits); 2115} 2116 2117static void 2118arc_buf_free_on_write(void *data, size_t size, 2119 void (*free_func)(void *, size_t)) 2120{ 2121 l2arc_data_free_t *df; 2122 2123 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); 2124 df->l2df_data = data; 2125 df->l2df_size = size; 2126 df->l2df_func = free_func; 2127 mutex_enter(&l2arc_free_on_write_mtx); 2128 list_insert_head(l2arc_free_on_write, df); 2129 mutex_exit(&l2arc_free_on_write_mtx); 2130} 2131 2132/* 2133 * Free the arc data buffer. If it is an l2arc write in progress, 2134 * the buffer is placed on l2arc_free_on_write to be freed later. 2135 */ 2136static void 2137arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t)) 2138{ 2139 arc_buf_hdr_t *hdr = buf->b_hdr; 2140 2141 if (HDR_L2_WRITING(hdr)) { 2142 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); 2143 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2144 } else { 2145 free_func(buf->b_data, hdr->b_size); 2146 } 2147} 2148 2149/* 2150 * Free up buf->b_data and if 'remove' is set, then pull the 2151 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2152 */ 2153static void 2154arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) 2155{ 2156 ASSERT(HDR_HAS_L2HDR(hdr)); 2157 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx)); 2158 2159 /* 2160 * The b_tmp_cdata field is linked off of the b_l1hdr, so if 2161 * that doesn't exist, the header is in the arc_l2c_only state, 2162 * and there isn't anything to free (it's already been freed). 2163 */ 2164 if (!HDR_HAS_L1HDR(hdr)) 2165 return; 2166 2167 if (hdr->b_l1hdr.b_tmp_cdata == NULL) 2168 return; 2169 2170 ASSERT(HDR_L2_WRITING(hdr)); 2171 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata, hdr->b_size, 2172 zio_data_buf_free); 2173 2174 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); 2175 hdr->b_l1hdr.b_tmp_cdata = NULL; 2176} 2177 2178static void 2179arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) 2180{ 2181 arc_buf_t **bufp; 2182 2183 /* free up data associated with the buf */ 2184 if (buf->b_data != NULL) { 2185 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 2186 uint64_t size = buf->b_hdr->b_size; 2187 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 2188 2189 arc_cksum_verify(buf); 2190#ifdef illumos 2191 arc_buf_unwatch(buf); 2192#endif 2193 2194 if (!recycle) { 2195 if (type == ARC_BUFC_METADATA) { 2196 arc_buf_data_free(buf, zio_buf_free); 2197 arc_space_return(size, ARC_SPACE_META); 2198 } else { 2199 ASSERT(type == ARC_BUFC_DATA); 2200 arc_buf_data_free(buf, zio_data_buf_free); 2201 arc_space_return(size, ARC_SPACE_DATA); 2202 } 2203 } 2204 if (list_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) { 2205 uint64_t *cnt = &state->arcs_lsize[type]; 2206 2207 ASSERT(refcount_is_zero( 2208 &buf->b_hdr->b_l1hdr.b_refcnt)); 2209 ASSERT(state != arc_anon && state != arc_l2c_only); 2210 2211 ASSERT3U(*cnt, >=, size); 2212 atomic_add_64(cnt, -size); 2213 } 2214 ASSERT3U(state->arcs_size, >=, size); 2215 atomic_add_64(&state->arcs_size, -size); 2216 buf->b_data = NULL; 2217 2218 /* 2219 * If we're destroying a duplicate buffer make sure 2220 * that the appropriate statistics are updated. 2221 */ 2222 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 && 2223 HDR_ISTYPE_DATA(buf->b_hdr)) { 2224 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 2225 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size); 2226 } 2227 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0); 2228 buf->b_hdr->b_l1hdr.b_datacnt -= 1; 2229 } 2230 2231 /* only remove the buf if requested */ 2232 if (!remove) 2233 return; 2234 2235 /* remove the buf from the hdr list */ 2236 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf; 2237 bufp = &(*bufp)->b_next) 2238 continue; 2239 *bufp = buf->b_next; 2240 buf->b_next = NULL; 2241 2242 ASSERT(buf->b_efunc == NULL); 2243 2244 /* clean up the buf */ 2245 buf->b_hdr = NULL; 2246 kmem_cache_free(buf_cache, buf); 2247} 2248 2249static void 2250arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2251{ 2252 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2253 l2arc_dev_t *dev = l2hdr->b_dev; 2254 2255 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2256 ASSERT(HDR_HAS_L2HDR(hdr)); 2257 2258 list_remove(&dev->l2ad_buflist, hdr); 2259 2260 /* 2261 * We don't want to leak the b_tmp_cdata buffer that was 2262 * allocated in l2arc_write_buffers() 2263 */ 2264 arc_buf_l2_cdata_free(hdr); 2265 2266 /* 2267 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then 2268 * this header is being processed by l2arc_write_buffers() (i.e. 2269 * it's in the first stage of l2arc_write_buffers()). 2270 * Re-affirming that truth here, just to serve as a reminder. If 2271 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or 2272 * may not have its HDR_L2_WRITING flag set. (the write may have 2273 * completed, in which case HDR_L2_WRITING will be false and the 2274 * b_daddr field will point to the address of the buffer on disk). 2275 */ 2276 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr)); 2277 2278 /* 2279 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with 2280 * l2arc_write_buffers(). Since we've just removed this header 2281 * from the l2arc buffer list, this header will never reach the 2282 * second stage of l2arc_write_buffers(), which increments the 2283 * accounting stats for this header. Thus, we must be careful 2284 * not to decrement them for this header either. 2285 */ 2286 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) { 2287 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); 2288 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 2289 2290 vdev_space_update(dev->l2ad_vdev, 2291 -l2hdr->b_asize, 0, 0); 2292 2293 (void) refcount_remove_many(&dev->l2ad_alloc, 2294 l2hdr->b_asize, hdr); 2295 } 2296 2297 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 2298} 2299 2300static void 2301arc_hdr_destroy(arc_buf_hdr_t *hdr) 2302{ 2303 if (HDR_HAS_L1HDR(hdr)) { 2304 ASSERT(hdr->b_l1hdr.b_buf == NULL || 2305 hdr->b_l1hdr.b_datacnt > 0); 2306 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2307 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2308 } 2309 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2310 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 2311 2312 if (HDR_HAS_L2HDR(hdr)) { 2313 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2314 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 2315 2316 if (!buflist_held) 2317 mutex_enter(&dev->l2ad_mtx); 2318 2319 /* 2320 * Even though we checked this conditional above, we 2321 * need to check this again now that we have the 2322 * l2ad_mtx. This is because we could be racing with 2323 * another thread calling l2arc_evict() which might have 2324 * destroyed this header's L2 portion as we were waiting 2325 * to acquire the l2ad_mtx. If that happens, we don't 2326 * want to re-destroy the header's L2 portion. 2327 */ 2328 if (HDR_HAS_L2HDR(hdr)) { 2329 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 2330 hdr->b_l2hdr.b_asize, 0); 2331 arc_hdr_l2hdr_destroy(hdr); 2332 } 2333 2334 if (!buflist_held) 2335 mutex_exit(&dev->l2ad_mtx); 2336 } 2337 2338 if (!BUF_EMPTY(hdr)) 2339 buf_discard_identity(hdr); 2340 if (hdr->b_freeze_cksum != NULL) { 2341 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 2342 hdr->b_freeze_cksum = NULL; 2343 } 2344 2345 if (HDR_HAS_L1HDR(hdr)) { 2346 while (hdr->b_l1hdr.b_buf) { 2347 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2348 2349 if (buf->b_efunc != NULL) { 2350 mutex_enter(&arc_eviction_mtx); 2351 mutex_enter(&buf->b_evict_lock); 2352 ASSERT(buf->b_hdr != NULL); 2353 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2354 FALSE); 2355 hdr->b_l1hdr.b_buf = buf->b_next; 2356 buf->b_hdr = &arc_eviction_hdr; 2357 buf->b_next = arc_eviction_list; 2358 arc_eviction_list = buf; 2359 mutex_exit(&buf->b_evict_lock); 2360 mutex_exit(&arc_eviction_mtx); 2361 } else { 2362 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE, 2363 TRUE); 2364 } 2365 } 2366#ifdef ZFS_DEBUG 2367 if (hdr->b_l1hdr.b_thawed != NULL) { 2368 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2369 hdr->b_l1hdr.b_thawed = NULL; 2370 } 2371#endif 2372 } 2373 2374 ASSERT3P(hdr->b_hash_next, ==, NULL); 2375 if (HDR_HAS_L1HDR(hdr)) { 2376 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 2377 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 2378 kmem_cache_free(hdr_full_cache, hdr); 2379 } else { 2380 kmem_cache_free(hdr_l2only_cache, hdr); 2381 } 2382} 2383 2384void 2385arc_buf_free(arc_buf_t *buf, void *tag) 2386{ 2387 arc_buf_hdr_t *hdr = buf->b_hdr; 2388 int hashed = hdr->b_l1hdr.b_state != arc_anon; 2389 2390 ASSERT(buf->b_efunc == NULL); 2391 ASSERT(buf->b_data != NULL); 2392 2393 if (hashed) { 2394 kmutex_t *hash_lock = HDR_LOCK(hdr); 2395 2396 mutex_enter(hash_lock); 2397 hdr = buf->b_hdr; 2398 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2399 2400 (void) remove_reference(hdr, hash_lock, tag); 2401 if (hdr->b_l1hdr.b_datacnt > 1) { 2402 arc_buf_destroy(buf, FALSE, TRUE); 2403 } else { 2404 ASSERT(buf == hdr->b_l1hdr.b_buf); 2405 ASSERT(buf->b_efunc == NULL); 2406 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2407 } 2408 mutex_exit(hash_lock); 2409 } else if (HDR_IO_IN_PROGRESS(hdr)) { 2410 int destroy_hdr; 2411 /* 2412 * We are in the middle of an async write. Don't destroy 2413 * this buffer unless the write completes before we finish 2414 * decrementing the reference count. 2415 */ 2416 mutex_enter(&arc_eviction_mtx); 2417 (void) remove_reference(hdr, NULL, tag); 2418 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2419 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr); 2420 mutex_exit(&arc_eviction_mtx); 2421 if (destroy_hdr) 2422 arc_hdr_destroy(hdr); 2423 } else { 2424 if (remove_reference(hdr, NULL, tag) > 0) 2425 arc_buf_destroy(buf, FALSE, TRUE); 2426 else 2427 arc_hdr_destroy(hdr); 2428 } 2429} 2430 2431boolean_t 2432arc_buf_remove_ref(arc_buf_t *buf, void* tag) 2433{ 2434 arc_buf_hdr_t *hdr = buf->b_hdr; 2435 kmutex_t *hash_lock = HDR_LOCK(hdr); 2436 boolean_t no_callback = (buf->b_efunc == NULL); 2437 2438 if (hdr->b_l1hdr.b_state == arc_anon) { 2439 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 2440 arc_buf_free(buf, tag); 2441 return (no_callback); 2442 } 2443 2444 mutex_enter(hash_lock); 2445 hdr = buf->b_hdr; 2446 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 2447 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 2448 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2449 ASSERT(buf->b_data != NULL); 2450 2451 (void) remove_reference(hdr, hash_lock, tag); 2452 if (hdr->b_l1hdr.b_datacnt > 1) { 2453 if (no_callback) 2454 arc_buf_destroy(buf, FALSE, TRUE); 2455 } else if (no_callback) { 2456 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL); 2457 ASSERT(buf->b_efunc == NULL); 2458 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 2459 } 2460 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 || 2461 refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2462 mutex_exit(hash_lock); 2463 return (no_callback); 2464} 2465 2466int32_t 2467arc_buf_size(arc_buf_t *buf) 2468{ 2469 return (buf->b_hdr->b_size); 2470} 2471 2472/* 2473 * Called from the DMU to determine if the current buffer should be 2474 * evicted. In order to ensure proper locking, the eviction must be initiated 2475 * from the DMU. Return true if the buffer is associated with user data and 2476 * duplicate buffers still exist. 2477 */ 2478boolean_t 2479arc_buf_eviction_needed(arc_buf_t *buf) 2480{ 2481 arc_buf_hdr_t *hdr; 2482 boolean_t evict_needed = B_FALSE; 2483 2484 if (zfs_disable_dup_eviction) 2485 return (B_FALSE); 2486 2487 mutex_enter(&buf->b_evict_lock); 2488 hdr = buf->b_hdr; 2489 if (hdr == NULL) { 2490 /* 2491 * We are in arc_do_user_evicts(); let that function 2492 * perform the eviction. 2493 */ 2494 ASSERT(buf->b_data == NULL); 2495 mutex_exit(&buf->b_evict_lock); 2496 return (B_FALSE); 2497 } else if (buf->b_data == NULL) { 2498 /* 2499 * We have already been added to the arc eviction list; 2500 * recommend eviction. 2501 */ 2502 ASSERT3P(hdr, ==, &arc_eviction_hdr); 2503 mutex_exit(&buf->b_evict_lock); 2504 return (B_TRUE); 2505 } 2506 2507 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr)) 2508 evict_needed = B_TRUE; 2509 2510 mutex_exit(&buf->b_evict_lock); 2511 return (evict_needed); 2512} 2513 2514/* 2515 * Evict buffers from list until we've removed the specified number of 2516 * bytes. Move the removed buffers to the appropriate evict state. 2517 * If the recycle flag is set, then attempt to "recycle" a buffer: 2518 * - look for a buffer to evict that is `bytes' long. 2519 * - return the data block from this buffer rather than freeing it. 2520 * This flag is used by callers that are trying to make space for a 2521 * new buffer in a full arc cache. 2522 * 2523 * This function makes a "best effort". It skips over any buffers 2524 * it can't get a hash_lock on, and so may not catch all candidates. 2525 * It may also return without evicting as much space as requested. 2526 */ 2527static void * 2528arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle, 2529 arc_buf_contents_t type) 2530{ 2531 arc_state_t *evicted_state; 2532 uint64_t bytes_evicted = 0, skipped = 0, missed = 0; 2533 int64_t bytes_remaining; 2534 arc_buf_hdr_t *hdr, *hdr_prev = NULL; 2535 list_t *evicted_list, *list, *evicted_list_start, *list_start; 2536 kmutex_t *lock, *evicted_lock; 2537 kmutex_t *hash_lock; 2538 boolean_t have_lock; 2539 void *stolen = NULL; 2540 arc_buf_hdr_t marker = { 0 }; 2541 int count = 0; 2542 static int evict_metadata_offset, evict_data_offset; 2543 int i, idx, offset, list_count, lists; 2544 2545 ASSERT(state == arc_mru || state == arc_mfu); 2546 2547 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 2548 2549 /* 2550 * Decide which "type" (data vs metadata) to recycle from. 2551 * 2552 * If we are over the metadata limit, recycle from metadata. 2553 * If we are under the metadata minimum, recycle from data. 2554 * Otherwise, recycle from whichever type has the oldest (least 2555 * recently accessed) header. This is not yet implemented. 2556 */ 2557 if (recycle) { 2558 arc_buf_contents_t realtype; 2559 if (state->arcs_lsize[ARC_BUFC_DATA] == 0) { 2560 realtype = ARC_BUFC_METADATA; 2561 } else if (state->arcs_lsize[ARC_BUFC_METADATA] == 0) { 2562 realtype = ARC_BUFC_DATA; 2563 } else if (arc_meta_used >= arc_meta_limit) { 2564 realtype = ARC_BUFC_METADATA; 2565 } else if (arc_meta_used <= arc_meta_min) { 2566 realtype = ARC_BUFC_DATA; 2567#ifdef illumos 2568 } else if (HDR_HAS_L1HDR(data_hdr) && 2569 HDR_HAS_L1HDR(metadata_hdr) && 2570 data_hdr->b_l1hdr.b_arc_access < 2571 metadata_hdr->b_l1hdr.b_arc_access) { 2572 realtype = ARC_BUFC_DATA; 2573 } else { 2574 realtype = ARC_BUFC_METADATA; 2575#else 2576 } else { 2577 /* TODO */ 2578 realtype = type; 2579#endif 2580 } 2581 if (realtype != type) { 2582 /* 2583 * If we want to evict from a different list, 2584 * we can not recycle, because DATA vs METADATA 2585 * buffers are segregated into different kmem 2586 * caches (and vmem arenas). 2587 */ 2588 type = realtype; 2589 recycle = B_FALSE; 2590 } 2591 } 2592 2593 if (type == ARC_BUFC_METADATA) { 2594 offset = 0; 2595 list_count = ARC_BUFC_NUMMETADATALISTS; 2596 list_start = &state->arcs_lists[0]; 2597 evicted_list_start = &evicted_state->arcs_lists[0]; 2598 idx = evict_metadata_offset; 2599 } else { 2600 offset = ARC_BUFC_NUMMETADATALISTS; 2601 list_start = &state->arcs_lists[offset]; 2602 evicted_list_start = &evicted_state->arcs_lists[offset]; 2603 list_count = ARC_BUFC_NUMDATALISTS; 2604 idx = evict_data_offset; 2605 } 2606 bytes_remaining = evicted_state->arcs_lsize[type]; 2607 lists = 0; 2608 2609evict_start: 2610 list = &list_start[idx]; 2611 evicted_list = &evicted_list_start[idx]; 2612 lock = ARCS_LOCK(state, (offset + idx)); 2613 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx)); 2614 2615 /* 2616 * The ghost list lock must be acquired first in order to prevent 2617 * a 3 party deadlock: 2618 * 2619 * - arc_evict_ghost acquires arc_*_ghost->arcs_mtx, followed by 2620 * l2ad_mtx in arc_hdr_realloc 2621 * - l2arc_write_buffers acquires l2ad_mtx, followed by arc_*->arcs_mtx 2622 * - arc_evict acquires arc_*_ghost->arcs_mtx, followed by 2623 * arc_*_ghost->arcs_mtx and forms a deadlock cycle. 2624 * 2625 * This situation is avoided by acquiring the ghost list lock first. 2626 */ 2627 mutex_enter(evicted_lock); 2628 mutex_enter(lock); 2629 2630 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2631 hdr_prev = list_prev(list, hdr); 2632 if (HDR_HAS_L1HDR(hdr)) { 2633 bytes_remaining -= 2634 (hdr->b_size * hdr->b_l1hdr.b_datacnt); 2635 } 2636 /* prefetch buffers have a minimum lifespan */ 2637 if (HDR_IO_IN_PROGRESS(hdr) || 2638 (spa && hdr->b_spa != spa) || 2639 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 2640 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 2641 arc_min_prefetch_lifespan)) { 2642 skipped++; 2643 continue; 2644 } 2645 /* "lookahead" for better eviction candidate */ 2646 if (recycle && hdr->b_size != bytes && 2647 hdr_prev && hdr_prev->b_size == bytes) 2648 continue; 2649 2650 /* ignore markers */ 2651 if (hdr->b_spa == 0) 2652 continue; 2653 2654 /* 2655 * It may take a long time to evict all the bufs requested. 2656 * To avoid blocking all arc activity, periodically drop 2657 * the arcs_mtx and give other threads a chance to run 2658 * before reacquiring the lock. 2659 * 2660 * If we are looking for a buffer to recycle, we are in 2661 * the hot code path, so don't sleep. 2662 */ 2663 if (!recycle && count++ > arc_evict_iterations) { 2664 list_insert_after(list, hdr, &marker); 2665 mutex_exit(lock); 2666 mutex_exit(evicted_lock); 2667 kpreempt(KPREEMPT_SYNC); 2668 mutex_enter(evicted_lock); 2669 mutex_enter(lock); 2670 hdr_prev = list_prev(list, &marker); 2671 list_remove(list, &marker); 2672 count = 0; 2673 continue; 2674 } 2675 2676 hash_lock = HDR_LOCK(hdr); 2677 have_lock = MUTEX_HELD(hash_lock); 2678 if (have_lock || mutex_tryenter(hash_lock)) { 2679 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 2680 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0); 2681 while (hdr->b_l1hdr.b_buf) { 2682 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 2683 if (!mutex_tryenter(&buf->b_evict_lock)) { 2684 missed += 1; 2685 break; 2686 } 2687 if (buf->b_data != NULL) { 2688 bytes_evicted += hdr->b_size; 2689 if (recycle && 2690 arc_buf_type(hdr) == type && 2691 hdr->b_size == bytes && 2692 !HDR_L2_WRITING(hdr)) { 2693 stolen = buf->b_data; 2694 recycle = FALSE; 2695 } 2696 } 2697 if (buf->b_efunc != NULL) { 2698 mutex_enter(&arc_eviction_mtx); 2699 arc_buf_destroy(buf, 2700 buf->b_data == stolen, FALSE); 2701 hdr->b_l1hdr.b_buf = buf->b_next; 2702 buf->b_hdr = &arc_eviction_hdr; 2703 buf->b_next = arc_eviction_list; 2704 arc_eviction_list = buf; 2705 mutex_exit(&arc_eviction_mtx); 2706 mutex_exit(&buf->b_evict_lock); 2707 } else { 2708 mutex_exit(&buf->b_evict_lock); 2709 arc_buf_destroy(buf, 2710 buf->b_data == stolen, TRUE); 2711 } 2712 } 2713 2714 if (HDR_HAS_L2HDR(hdr)) { 2715 ARCSTAT_INCR(arcstat_evict_l2_cached, 2716 hdr->b_size); 2717 } else { 2718 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 2719 ARCSTAT_INCR(arcstat_evict_l2_eligible, 2720 hdr->b_size); 2721 } else { 2722 ARCSTAT_INCR( 2723 arcstat_evict_l2_ineligible, 2724 hdr->b_size); 2725 } 2726 } 2727 2728 if (hdr->b_l1hdr.b_datacnt == 0) { 2729 arc_change_state(evicted_state, hdr, hash_lock); 2730 ASSERT(HDR_IN_HASH_TABLE(hdr)); 2731 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE; 2732 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 2733 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 2734 } 2735 if (!have_lock) 2736 mutex_exit(hash_lock); 2737 if (bytes >= 0 && bytes_evicted >= bytes) 2738 break; 2739 if (bytes_remaining > 0) { 2740 mutex_exit(evicted_lock); 2741 mutex_exit(lock); 2742 idx = ((idx + 1) & (list_count - 1)); 2743 lists++; 2744 goto evict_start; 2745 } 2746 } else { 2747 missed += 1; 2748 } 2749 } 2750 2751 mutex_exit(lock); 2752 mutex_exit(evicted_lock); 2753 2754 idx = ((idx + 1) & (list_count - 1)); 2755 lists++; 2756 2757 if (bytes_evicted < bytes) { 2758 if (lists < list_count) 2759 goto evict_start; 2760 else 2761 dprintf("only evicted %lld bytes from %x", 2762 (longlong_t)bytes_evicted, state); 2763 } 2764 if (type == ARC_BUFC_METADATA) 2765 evict_metadata_offset = idx; 2766 else 2767 evict_data_offset = idx; 2768 2769 if (skipped) 2770 ARCSTAT_INCR(arcstat_evict_skip, skipped); 2771 2772 if (missed) 2773 ARCSTAT_INCR(arcstat_mutex_miss, missed); 2774 2775 /* 2776 * Note: we have just evicted some data into the ghost state, 2777 * potentially putting the ghost size over the desired size. Rather 2778 * that evicting from the ghost list in this hot code path, leave 2779 * this chore to the arc_reclaim_thread(). 2780 */ 2781 2782 if (stolen) 2783 ARCSTAT_BUMP(arcstat_stolen); 2784 return (stolen); 2785} 2786 2787/* 2788 * Remove buffers from list until we've removed the specified number of 2789 * bytes. Destroy the buffers that are removed. 2790 */ 2791static void 2792arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes) 2793{ 2794 arc_buf_hdr_t *hdr, *hdr_prev; 2795 arc_buf_hdr_t marker = { 0 }; 2796 list_t *list, *list_start; 2797 kmutex_t *hash_lock, *lock; 2798 uint64_t bytes_deleted = 0; 2799 uint64_t bufs_skipped = 0; 2800 int count = 0; 2801 static int evict_offset; 2802 int list_count, idx = evict_offset; 2803 int offset, lists = 0; 2804 2805 ASSERT(GHOST_STATE(state)); 2806 2807 /* 2808 * data lists come after metadata lists 2809 */ 2810 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS]; 2811 list_count = ARC_BUFC_NUMDATALISTS; 2812 offset = ARC_BUFC_NUMMETADATALISTS; 2813 2814evict_start: 2815 list = &list_start[idx]; 2816 lock = ARCS_LOCK(state, idx + offset); 2817 2818 mutex_enter(lock); 2819 for (hdr = list_tail(list); hdr; hdr = hdr_prev) { 2820 hdr_prev = list_prev(list, hdr); 2821 if (arc_buf_type(hdr) >= ARC_BUFC_NUMTYPES) 2822 panic("invalid hdr=%p", (void *)hdr); 2823 if (spa && hdr->b_spa != spa) 2824 continue; 2825 2826 /* ignore markers */ 2827 if (hdr->b_spa == 0) 2828 continue; 2829 2830 hash_lock = HDR_LOCK(hdr); 2831 /* caller may be trying to modify this buffer, skip it */ 2832 if (MUTEX_HELD(hash_lock)) 2833 continue; 2834 2835 /* 2836 * It may take a long time to evict all the bufs requested. 2837 * To avoid blocking all arc activity, periodically drop 2838 * the arcs_mtx and give other threads a chance to run 2839 * before reacquiring the lock. 2840 */ 2841 if (count++ > arc_evict_iterations) { 2842 list_insert_after(list, hdr, &marker); 2843 mutex_exit(lock); 2844 kpreempt(KPREEMPT_SYNC); 2845 mutex_enter(lock); 2846 hdr_prev = list_prev(list, &marker); 2847 list_remove(list, &marker); 2848 count = 0; 2849 continue; 2850 } 2851 if (mutex_tryenter(hash_lock)) { 2852 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2853 ASSERT(!HDR_HAS_L1HDR(hdr) || 2854 hdr->b_l1hdr.b_buf == NULL); 2855 ARCSTAT_BUMP(arcstat_deleted); 2856 bytes_deleted += hdr->b_size; 2857 2858 if (HDR_HAS_L2HDR(hdr)) { 2859 /* 2860 * This buffer is cached on the 2nd Level ARC; 2861 * don't destroy the header. 2862 */ 2863 arc_change_state(arc_l2c_only, hdr, hash_lock); 2864 /* 2865 * dropping from L1+L2 cached to L2-only, 2866 * realloc to remove the L1 header. 2867 */ 2868 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 2869 hdr_l2only_cache); 2870 mutex_exit(hash_lock); 2871 } else { 2872 arc_change_state(arc_anon, hdr, hash_lock); 2873 mutex_exit(hash_lock); 2874 arc_hdr_destroy(hdr); 2875 } 2876 2877 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 2878 if (bytes >= 0 && bytes_deleted >= bytes) 2879 break; 2880 } else if (bytes < 0) { 2881 /* 2882 * Insert a list marker and then wait for the 2883 * hash lock to become available. Once its 2884 * available, restart from where we left off. 2885 */ 2886 list_insert_after(list, hdr, &marker); 2887 mutex_exit(lock); 2888 mutex_enter(hash_lock); 2889 mutex_exit(hash_lock); 2890 mutex_enter(lock); 2891 hdr_prev = list_prev(list, &marker); 2892 list_remove(list, &marker); 2893 } else { 2894 bufs_skipped += 1; 2895 } 2896 2897 } 2898 mutex_exit(lock); 2899 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1)); 2900 lists++; 2901 2902 if (lists < list_count) 2903 goto evict_start; 2904 2905 evict_offset = idx; 2906 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] && 2907 (bytes < 0 || bytes_deleted < bytes)) { 2908 list_start = &state->arcs_lists[0]; 2909 list_count = ARC_BUFC_NUMMETADATALISTS; 2910 offset = lists = 0; 2911 goto evict_start; 2912 } 2913 2914 if (bufs_skipped) { 2915 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped); 2916 ASSERT(bytes >= 0); 2917 } 2918 2919 if (bytes_deleted < bytes) 2920 dprintf("only deleted %lld bytes from %p", 2921 (longlong_t)bytes_deleted, state); 2922} 2923 2924static void 2925arc_adjust(void) 2926{ 2927 int64_t adjustment, delta; 2928 2929 /* 2930 * Adjust MRU size 2931 */ 2932 2933 adjustment = MIN((int64_t)(arc_size - arc_c), 2934 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - 2935 arc_p)); 2936 2937 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) { 2938 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment); 2939 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA); 2940 adjustment -= delta; 2941 } 2942 2943 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2944 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment); 2945 (void) arc_evict(arc_mru, 0, delta, FALSE, 2946 ARC_BUFC_METADATA); 2947 } 2948 2949 /* 2950 * Adjust MFU size 2951 */ 2952 2953 adjustment = arc_size - arc_c; 2954 2955 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) { 2956 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]); 2957 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA); 2958 adjustment -= delta; 2959 } 2960 2961 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) { 2962 int64_t delta = MIN(adjustment, 2963 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]); 2964 (void) arc_evict(arc_mfu, 0, delta, FALSE, 2965 ARC_BUFC_METADATA); 2966 } 2967 2968 /* 2969 * Adjust ghost lists 2970 */ 2971 2972 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c; 2973 2974 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) { 2975 delta = MIN(arc_mru_ghost->arcs_size, adjustment); 2976 arc_evict_ghost(arc_mru_ghost, 0, delta); 2977 } 2978 2979 adjustment = 2980 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c; 2981 2982 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) { 2983 delta = MIN(arc_mfu_ghost->arcs_size, adjustment); 2984 arc_evict_ghost(arc_mfu_ghost, 0, delta); 2985 } 2986} 2987 2988static void 2989arc_do_user_evicts(void) 2990{ 2991 static arc_buf_t *tmp_arc_eviction_list; 2992 2993 /* 2994 * Move list over to avoid LOR 2995 */ 2996restart: 2997 mutex_enter(&arc_eviction_mtx); 2998 tmp_arc_eviction_list = arc_eviction_list; 2999 arc_eviction_list = NULL; 3000 mutex_exit(&arc_eviction_mtx); 3001 3002 while (tmp_arc_eviction_list != NULL) { 3003 arc_buf_t *buf = tmp_arc_eviction_list; 3004 tmp_arc_eviction_list = buf->b_next; 3005 mutex_enter(&buf->b_evict_lock); 3006 buf->b_hdr = NULL; 3007 mutex_exit(&buf->b_evict_lock); 3008 3009 if (buf->b_efunc != NULL) 3010 VERIFY0(buf->b_efunc(buf->b_private)); 3011 3012 buf->b_efunc = NULL; 3013 buf->b_private = NULL; 3014 kmem_cache_free(buf_cache, buf); 3015 } 3016 3017 if (arc_eviction_list != NULL) 3018 goto restart; 3019} 3020 3021/* 3022 * Flush all *evictable* data from the cache for the given spa. 3023 * NOTE: this will not touch "active" (i.e. referenced) data. 3024 */ 3025void 3026arc_flush(spa_t *spa) 3027{ 3028 uint64_t guid = 0; 3029 3030 if (spa != NULL) 3031 guid = spa_load_guid(spa); 3032 3033 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) { 3034 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA); 3035 if (spa != NULL) 3036 break; 3037 } 3038 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) { 3039 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA); 3040 if (spa != NULL) 3041 break; 3042 } 3043 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) { 3044 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA); 3045 if (spa != NULL) 3046 break; 3047 } 3048 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) { 3049 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA); 3050 if (spa != NULL) 3051 break; 3052 } 3053 3054 arc_evict_ghost(arc_mru_ghost, guid, -1); 3055 arc_evict_ghost(arc_mfu_ghost, guid, -1); 3056 3057 mutex_enter(&arc_reclaim_thr_lock); 3058 arc_do_user_evicts(); 3059 mutex_exit(&arc_reclaim_thr_lock); 3060 ASSERT(spa || arc_eviction_list == NULL); 3061} 3062 3063void 3064arc_shrink(int64_t to_free) 3065{ 3066 3067 if (arc_c > arc_c_min) { 3068 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3069 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3070 if (arc_c > arc_c_min + to_free) 3071 atomic_add_64(&arc_c, -to_free); 3072 else 3073 arc_c = arc_c_min; 3074 3075 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3076 if (arc_c > arc_size) 3077 arc_c = MAX(arc_size, arc_c_min); 3078 if (arc_p > arc_c) 3079 arc_p = (arc_c >> 1); 3080 3081 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3082 arc_p); 3083 3084 ASSERT(arc_c >= arc_c_min); 3085 ASSERT((int64_t)arc_p >= 0); 3086 } 3087 3088 if (arc_size > arc_c) { 3089 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3090 uint64_t, arc_c); 3091 arc_adjust(); 3092 } 3093} 3094 3095static long needfree = 0; 3096 3097typedef enum free_memory_reason_t { 3098 FMR_UNKNOWN, 3099 FMR_NEEDFREE, 3100 FMR_LOTSFREE, 3101 FMR_SWAPFS_MINFREE, 3102 FMR_PAGES_PP_MAXIMUM, 3103 FMR_HEAP_ARENA, 3104 FMR_ZIO_ARENA, 3105 FMR_ZIO_FRAG, 3106} free_memory_reason_t; 3107 3108int64_t last_free_memory; 3109free_memory_reason_t last_free_reason; 3110 3111/* 3112 * Additional reserve of pages for pp_reserve. 3113 */ 3114int64_t arc_pages_pp_reserve = 64; 3115 3116/* 3117 * Additional reserve of pages for swapfs. 3118 */ 3119int64_t arc_swapfs_reserve = 64; 3120 3121/* 3122 * Return the amount of memory that can be consumed before reclaim will be 3123 * needed. Positive if there is sufficient free memory, negative indicates 3124 * the amount of memory that needs to be freed up. 3125 */ 3126static int64_t 3127arc_available_memory(void) 3128{ 3129 int64_t lowest = INT64_MAX; 3130 int64_t n; 3131 free_memory_reason_t r = FMR_UNKNOWN; 3132 3133#ifdef _KERNEL 3134 if (needfree > 0) { 3135 n = PAGESIZE * (-needfree); 3136 if (n < lowest) { 3137 lowest = n; 3138 r = FMR_NEEDFREE; 3139 } 3140 } 3141 3142 /* 3143 * Cooperate with pagedaemon when it's time for it to scan 3144 * and reclaim some pages. 3145 */ 3146 n = PAGESIZE * (int64_t)(freemem - zfs_arc_free_target); 3147 if (n < lowest) { 3148 lowest = n; 3149 r = FMR_LOTSFREE; 3150 } 3151 3152#ifdef illumos 3153 /* 3154 * check that we're out of range of the pageout scanner. It starts to 3155 * schedule paging if freemem is less than lotsfree and needfree. 3156 * lotsfree is the high-water mark for pageout, and needfree is the 3157 * number of needed free pages. We add extra pages here to make sure 3158 * the scanner doesn't start up while we're freeing memory. 3159 */ 3160 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3161 if (n < lowest) { 3162 lowest = n; 3163 r = FMR_LOTSFREE; 3164 } 3165 3166 /* 3167 * check to make sure that swapfs has enough space so that anon 3168 * reservations can still succeed. anon_resvmem() checks that the 3169 * availrmem is greater than swapfs_minfree, and the number of reserved 3170 * swap pages. We also add a bit of extra here just to prevent 3171 * circumstances from getting really dire. 3172 */ 3173 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3174 desfree - arc_swapfs_reserve); 3175 if (n < lowest) { 3176 lowest = n; 3177 r = FMR_SWAPFS_MINFREE; 3178 } 3179 3180 3181 /* 3182 * Check that we have enough availrmem that memory locking (e.g., via 3183 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3184 * stores the number of pages that cannot be locked; when availrmem 3185 * drops below pages_pp_maximum, page locking mechanisms such as 3186 * page_pp_lock() will fail.) 3187 */ 3188 n = PAGESIZE * (availrmem - pages_pp_maximum - 3189 arc_pages_pp_reserve); 3190 if (n < lowest) { 3191 lowest = n; 3192 r = FMR_PAGES_PP_MAXIMUM; 3193 } 3194 3195#endif /* illumos */ 3196#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3197 /* 3198 * If we're on an i386 platform, it's possible that we'll exhaust the 3199 * kernel heap space before we ever run out of available physical 3200 * memory. Most checks of the size of the heap_area compare against 3201 * tune.t_minarmem, which is the minimum available real memory that we 3202 * can have in the system. However, this is generally fixed at 25 pages 3203 * which is so low that it's useless. In this comparison, we seek to 3204 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3205 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3206 * free) 3207 */ 3208 n = vmem_size(heap_arena, VMEM_FREE) - 3209 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3210 if (n < lowest) { 3211 lowest = n; 3212 r = FMR_HEAP_ARENA; 3213 } 3214#define zio_arena NULL 3215#else 3216#define zio_arena heap_arena 3217#endif 3218 3219 /* 3220 * If zio data pages are being allocated out of a separate heap segment, 3221 * then enforce that the size of available vmem for this arena remains 3222 * above about 1/16th free. 3223 * 3224 * Note: The 1/16th arena free requirement was put in place 3225 * to aggressively evict memory from the arc in order to avoid 3226 * memory fragmentation issues. 3227 */ 3228 if (zio_arena != NULL) { 3229 n = vmem_size(zio_arena, VMEM_FREE) - 3230 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3231 if (n < lowest) { 3232 lowest = n; 3233 r = FMR_ZIO_ARENA; 3234 } 3235 } 3236 3237 /* 3238 * Above limits know nothing about real level of KVA fragmentation. 3239 * Start aggressive reclamation if too little sequential KVA left. 3240 */ 3241 if (lowest > 0) { 3242 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3243 -(vmem_size(heap_arena, VMEM_ALLOC) >> 4) : INT64_MAX; 3244 if (n < lowest) { 3245 lowest = n; 3246 r = FMR_ZIO_FRAG; 3247 } 3248 } 3249 3250#else /* _KERNEL */ 3251 /* Every 100 calls, free a small amount */ 3252 if (spa_get_random(100) == 0) 3253 lowest = -1024; 3254#endif /* _KERNEL */ 3255 3256 last_free_memory = lowest; 3257 last_free_reason = r; 3258 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3259 return (lowest); 3260} 3261 3262 3263/* 3264 * Determine if the system is under memory pressure and is asking 3265 * to reclaim memory. A return value of TRUE indicates that the system 3266 * is under memory pressure and that the arc should adjust accordingly. 3267 */ 3268static boolean_t 3269arc_reclaim_needed(void) 3270{ 3271 return (arc_available_memory() < 0); 3272} 3273 3274extern kmem_cache_t *zio_buf_cache[]; 3275extern kmem_cache_t *zio_data_buf_cache[]; 3276extern kmem_cache_t *range_seg_cache; 3277 3278static __noinline void 3279arc_kmem_reap_now(void) 3280{ 3281 size_t i; 3282 kmem_cache_t *prev_cache = NULL; 3283 kmem_cache_t *prev_data_cache = NULL; 3284 3285 DTRACE_PROBE(arc__kmem_reap_start); 3286#ifdef _KERNEL 3287 if (arc_meta_used >= arc_meta_limit) { 3288 /* 3289 * We are exceeding our meta-data cache limit. 3290 * Purge some DNLC entries to release holds on meta-data. 3291 */ 3292 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 3293 } 3294#if defined(__i386) 3295 /* 3296 * Reclaim unused memory from all kmem caches. 3297 */ 3298 kmem_reap(); 3299#endif 3300#endif 3301 3302 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 3303 if (zio_buf_cache[i] != prev_cache) { 3304 prev_cache = zio_buf_cache[i]; 3305 kmem_cache_reap_now(zio_buf_cache[i]); 3306 } 3307 if (zio_data_buf_cache[i] != prev_data_cache) { 3308 prev_data_cache = zio_data_buf_cache[i]; 3309 kmem_cache_reap_now(zio_data_buf_cache[i]); 3310 } 3311 } 3312 kmem_cache_reap_now(buf_cache); 3313 kmem_cache_reap_now(hdr_full_cache); 3314 kmem_cache_reap_now(hdr_l2only_cache); 3315 kmem_cache_reap_now(range_seg_cache); 3316 3317#ifdef illumos 3318 if (zio_arena != NULL) { 3319 /* 3320 * Ask the vmem arena to reclaim unused memory from its 3321 * quantum caches. 3322 */ 3323 vmem_qcache_reap(zio_arena); 3324 } 3325#endif 3326 DTRACE_PROBE(arc__kmem_reap_end); 3327} 3328 3329static void 3330arc_reclaim_thread(void *dummy __unused) 3331{ 3332 clock_t growtime = 0; 3333 callb_cpr_t cpr; 3334 3335 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG); 3336 3337 mutex_enter(&arc_reclaim_thr_lock); 3338 while (arc_thread_exit == 0) { 3339 int64_t free_memory = arc_available_memory(); 3340 if (free_memory < 0) { 3341 3342 arc_no_grow = B_TRUE; 3343 arc_warm = B_TRUE; 3344 3345 /* 3346 * Wait at least zfs_grow_retry (default 60) seconds 3347 * before considering growing. 3348 */ 3349 growtime = ddi_get_lbolt() + (arc_grow_retry * hz); 3350 3351 arc_kmem_reap_now(); 3352 3353 /* 3354 * If we are still low on memory, shrink the ARC 3355 * so that we have arc_shrink_min free space. 3356 */ 3357 free_memory = arc_available_memory(); 3358 3359 int64_t to_free = 3360 (arc_c >> arc_shrink_shift) - free_memory; 3361 if (to_free > 0) { 3362#ifdef _KERNEL 3363 to_free = MAX(to_free, ptob(needfree)); 3364#endif 3365 arc_shrink(to_free); 3366 } 3367 } else if (free_memory < arc_c >> arc_no_grow_shift) { 3368 arc_no_grow = B_TRUE; 3369 } else if (ddi_get_lbolt() >= growtime) { 3370 arc_no_grow = B_FALSE; 3371 } 3372 3373 arc_adjust(); 3374 3375 if (arc_eviction_list != NULL) 3376 arc_do_user_evicts(); 3377 3378#ifdef _KERNEL 3379 if (needfree) { 3380 needfree = 0; 3381 wakeup(&needfree); 3382 } 3383#endif 3384 3385 /* 3386 * This is necessary in order for the mdb ::arc dcmd to 3387 * show up to date information. Since the ::arc command 3388 * does not call the kstat's update function, without 3389 * this call, the command may show stale stats for the 3390 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 3391 * with this change, the data might be up to 1 second 3392 * out of date; but that should suffice. The arc_state_t 3393 * structures can be queried directly if more accurate 3394 * information is needed. 3395 */ 3396 if (arc_ksp != NULL) 3397 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 3398 3399 /* block until needed, or one second, whichever is shorter */ 3400 CALLB_CPR_SAFE_BEGIN(&cpr); 3401 (void) cv_timedwait(&arc_reclaim_thr_cv, 3402 &arc_reclaim_thr_lock, hz); 3403 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock); 3404 } 3405 3406 arc_thread_exit = 0; 3407 cv_broadcast(&arc_reclaim_thr_cv); 3408 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */ 3409 thread_exit(); 3410} 3411 3412/* 3413 * Adapt arc info given the number of bytes we are trying to add and 3414 * the state that we are comming from. This function is only called 3415 * when we are adding new content to the cache. 3416 */ 3417static void 3418arc_adapt(int bytes, arc_state_t *state) 3419{ 3420 int mult; 3421 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 3422 3423 if (state == arc_l2c_only) 3424 return; 3425 3426 ASSERT(bytes > 0); 3427 /* 3428 * Adapt the target size of the MRU list: 3429 * - if we just hit in the MRU ghost list, then increase 3430 * the target size of the MRU list. 3431 * - if we just hit in the MFU ghost list, then increase 3432 * the target size of the MFU list by decreasing the 3433 * target size of the MRU list. 3434 */ 3435 if (state == arc_mru_ghost) { 3436 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ? 3437 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size)); 3438 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 3439 3440 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 3441 } else if (state == arc_mfu_ghost) { 3442 uint64_t delta; 3443 3444 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ? 3445 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size)); 3446 mult = MIN(mult, 10); 3447 3448 delta = MIN(bytes * mult, arc_p); 3449 arc_p = MAX(arc_p_min, arc_p - delta); 3450 } 3451 ASSERT((int64_t)arc_p >= 0); 3452 3453 if (arc_reclaim_needed()) { 3454 cv_signal(&arc_reclaim_thr_cv); 3455 return; 3456 } 3457 3458 if (arc_no_grow) 3459 return; 3460 3461 if (arc_c >= arc_c_max) 3462 return; 3463 3464 /* 3465 * If we're within (2 * maxblocksize) bytes of the target 3466 * cache size, increment the target cache size 3467 */ 3468 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 3469 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 3470 atomic_add_64(&arc_c, (int64_t)bytes); 3471 if (arc_c > arc_c_max) 3472 arc_c = arc_c_max; 3473 else if (state == arc_anon) 3474 atomic_add_64(&arc_p, (int64_t)bytes); 3475 if (arc_p > arc_c) 3476 arc_p = arc_c; 3477 } 3478 ASSERT((int64_t)arc_p >= 0); 3479} 3480 3481/* 3482 * Check if the cache has reached its limits and eviction is required 3483 * prior to insert. 3484 */ 3485static int 3486arc_evict_needed(arc_buf_contents_t type) 3487{ 3488 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit) 3489 return (1); 3490 3491 if (arc_reclaim_needed()) 3492 return (1); 3493 3494 return (arc_size > arc_c); 3495} 3496 3497/* 3498 * The buffer, supplied as the first argument, needs a data block. 3499 * So, if we are at cache max, determine which cache should be victimized. 3500 * We have the following cases: 3501 * 3502 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) -> 3503 * In this situation if we're out of space, but the resident size of the MFU is 3504 * under the limit, victimize the MFU cache to satisfy this insertion request. 3505 * 3506 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) -> 3507 * Here, we've used up all of the available space for the MRU, so we need to 3508 * evict from our own cache instead. Evict from the set of resident MRU 3509 * entries. 3510 * 3511 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) -> 3512 * c minus p represents the MFU space in the cache, since p is the size of the 3513 * cache that is dedicated to the MRU. In this situation there's still space on 3514 * the MFU side, so the MRU side needs to be victimized. 3515 * 3516 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) -> 3517 * MFU's resident set is consuming more space than it has been allotted. In 3518 * this situation, we must victimize our own cache, the MFU, for this insertion. 3519 */ 3520static void 3521arc_get_data_buf(arc_buf_t *buf) 3522{ 3523 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state; 3524 uint64_t size = buf->b_hdr->b_size; 3525 arc_buf_contents_t type = arc_buf_type(buf->b_hdr); 3526 3527 arc_adapt(size, state); 3528 3529 /* 3530 * We have not yet reached cache maximum size, 3531 * just allocate a new buffer. 3532 */ 3533 if (!arc_evict_needed(type)) { 3534 if (type == ARC_BUFC_METADATA) { 3535 buf->b_data = zio_buf_alloc(size); 3536 arc_space_consume(size, ARC_SPACE_META); 3537 } else { 3538 ASSERT(type == ARC_BUFC_DATA); 3539 buf->b_data = zio_data_buf_alloc(size); 3540 arc_space_consume(size, ARC_SPACE_DATA); 3541 } 3542 goto out; 3543 } 3544 3545 /* 3546 * If we are prefetching from the mfu ghost list, this buffer 3547 * will end up on the mru list; so steal space from there. 3548 */ 3549 if (state == arc_mfu_ghost) 3550 state = HDR_PREFETCH(buf->b_hdr) ? arc_mru : arc_mfu; 3551 else if (state == arc_mru_ghost) 3552 state = arc_mru; 3553 3554 if (state == arc_mru || state == arc_anon) { 3555 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size; 3556 state = (arc_mfu->arcs_lsize[type] >= size && 3557 arc_p > mru_used) ? arc_mfu : arc_mru; 3558 } else { 3559 /* MFU cases */ 3560 uint64_t mfu_space = arc_c - arc_p; 3561 state = (arc_mru->arcs_lsize[type] >= size && 3562 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu; 3563 } 3564 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) { 3565 if (type == ARC_BUFC_METADATA) { 3566 buf->b_data = zio_buf_alloc(size); 3567 arc_space_consume(size, ARC_SPACE_META); 3568 } else { 3569 ASSERT(type == ARC_BUFC_DATA); 3570 buf->b_data = zio_data_buf_alloc(size); 3571 arc_space_consume(size, ARC_SPACE_DATA); 3572 } 3573 ARCSTAT_BUMP(arcstat_recycle_miss); 3574 } 3575 ASSERT(buf->b_data != NULL); 3576out: 3577 /* 3578 * Update the state size. Note that ghost states have a 3579 * "ghost size" and so don't need to be updated. 3580 */ 3581 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) { 3582 arc_buf_hdr_t *hdr = buf->b_hdr; 3583 3584 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_size, size); 3585 if (list_link_active(&hdr->b_l1hdr.b_arc_node)) { 3586 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3587 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type], 3588 size); 3589 } 3590 /* 3591 * If we are growing the cache, and we are adding anonymous 3592 * data, and we have outgrown arc_p, update arc_p 3593 */ 3594 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 3595 arc_anon->arcs_size + arc_mru->arcs_size > arc_p) 3596 arc_p = MIN(arc_c, arc_p + size); 3597 } 3598 ARCSTAT_BUMP(arcstat_allocated); 3599} 3600 3601/* 3602 * This routine is called whenever a buffer is accessed. 3603 * NOTE: the hash lock is dropped in this function. 3604 */ 3605static void 3606arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3607{ 3608 clock_t now; 3609 3610 ASSERT(MUTEX_HELD(hash_lock)); 3611 ASSERT(HDR_HAS_L1HDR(hdr)); 3612 3613 if (hdr->b_l1hdr.b_state == arc_anon) { 3614 /* 3615 * This buffer is not in the cache, and does not 3616 * appear in our "ghost" list. Add the new buffer 3617 * to the MRU state. 3618 */ 3619 3620 ASSERT0(hdr->b_l1hdr.b_arc_access); 3621 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3622 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3623 arc_change_state(arc_mru, hdr, hash_lock); 3624 3625 } else if (hdr->b_l1hdr.b_state == arc_mru) { 3626 now = ddi_get_lbolt(); 3627 3628 /* 3629 * If this buffer is here because of a prefetch, then either: 3630 * - clear the flag if this is a "referencing" read 3631 * (any subsequent access will bump this into the MFU state). 3632 * or 3633 * - move the buffer to the head of the list if this is 3634 * another prefetch (to make it less likely to be evicted). 3635 */ 3636 if (HDR_PREFETCH(hdr)) { 3637 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 3638 ASSERT(list_link_active( 3639 &hdr->b_l1hdr.b_arc_node)); 3640 } else { 3641 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3642 ARCSTAT_BUMP(arcstat_mru_hits); 3643 } 3644 hdr->b_l1hdr.b_arc_access = now; 3645 return; 3646 } 3647 3648 /* 3649 * This buffer has been "accessed" only once so far, 3650 * but it is still in the cache. Move it to the MFU 3651 * state. 3652 */ 3653 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 3654 /* 3655 * More than 125ms have passed since we 3656 * instantiated this buffer. Move it to the 3657 * most frequently used state. 3658 */ 3659 hdr->b_l1hdr.b_arc_access = now; 3660 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3661 arc_change_state(arc_mfu, hdr, hash_lock); 3662 } 3663 ARCSTAT_BUMP(arcstat_mru_hits); 3664 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 3665 arc_state_t *new_state; 3666 /* 3667 * This buffer has been "accessed" recently, but 3668 * was evicted from the cache. Move it to the 3669 * MFU state. 3670 */ 3671 3672 if (HDR_PREFETCH(hdr)) { 3673 new_state = arc_mru; 3674 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 3675 hdr->b_flags &= ~ARC_FLAG_PREFETCH; 3676 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 3677 } else { 3678 new_state = arc_mfu; 3679 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3680 } 3681 3682 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3683 arc_change_state(new_state, hdr, hash_lock); 3684 3685 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 3686 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 3687 /* 3688 * This buffer has been accessed more than once and is 3689 * still in the cache. Keep it in the MFU state. 3690 * 3691 * NOTE: an add_reference() that occurred when we did 3692 * the arc_read() will have kicked this off the list. 3693 * If it was a prefetch, we will explicitly move it to 3694 * the head of the list now. 3695 */ 3696 if ((HDR_PREFETCH(hdr)) != 0) { 3697 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3698 ASSERT(list_link_active(&hdr->b_l1hdr.b_arc_node)); 3699 } 3700 ARCSTAT_BUMP(arcstat_mfu_hits); 3701 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3702 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 3703 arc_state_t *new_state = arc_mfu; 3704 /* 3705 * This buffer has been accessed more than once but has 3706 * been evicted from the cache. Move it back to the 3707 * MFU state. 3708 */ 3709 3710 if (HDR_PREFETCH(hdr)) { 3711 /* 3712 * This is a prefetch access... 3713 * move this block back to the MRU state. 3714 */ 3715 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3716 new_state = arc_mru; 3717 } 3718 3719 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3720 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3721 arc_change_state(new_state, hdr, hash_lock); 3722 3723 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 3724 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 3725 /* 3726 * This buffer is on the 2nd Level ARC. 3727 */ 3728 3729 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 3730 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 3731 arc_change_state(arc_mfu, hdr, hash_lock); 3732 } else { 3733 ASSERT(!"invalid arc state"); 3734 } 3735} 3736 3737/* a generic arc_done_func_t which you can use */ 3738/* ARGSUSED */ 3739void 3740arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 3741{ 3742 if (zio == NULL || zio->io_error == 0) 3743 bcopy(buf->b_data, arg, buf->b_hdr->b_size); 3744 VERIFY(arc_buf_remove_ref(buf, arg)); 3745} 3746 3747/* a generic arc_done_func_t */ 3748void 3749arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 3750{ 3751 arc_buf_t **bufp = arg; 3752 if (zio && zio->io_error) { 3753 VERIFY(arc_buf_remove_ref(buf, arg)); 3754 *bufp = NULL; 3755 } else { 3756 *bufp = buf; 3757 ASSERT(buf->b_data); 3758 } 3759} 3760 3761static void 3762arc_read_done(zio_t *zio) 3763{ 3764 arc_buf_hdr_t *hdr; 3765 arc_buf_t *buf; 3766 arc_buf_t *abuf; /* buffer we're assigning to callback */ 3767 kmutex_t *hash_lock = NULL; 3768 arc_callback_t *callback_list, *acb; 3769 int freeable = FALSE; 3770 3771 buf = zio->io_private; 3772 hdr = buf->b_hdr; 3773 3774 /* 3775 * The hdr was inserted into hash-table and removed from lists 3776 * prior to starting I/O. We should find this header, since 3777 * it's in the hash table, and it should be legit since it's 3778 * not possible to evict it during the I/O. The only possible 3779 * reason for it not to be found is if we were freed during the 3780 * read. 3781 */ 3782 if (HDR_IN_HASH_TABLE(hdr)) { 3783 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 3784 ASSERT3U(hdr->b_dva.dva_word[0], ==, 3785 BP_IDENTITY(zio->io_bp)->dva_word[0]); 3786 ASSERT3U(hdr->b_dva.dva_word[1], ==, 3787 BP_IDENTITY(zio->io_bp)->dva_word[1]); 3788 3789 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 3790 &hash_lock); 3791 3792 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && 3793 hash_lock == NULL) || 3794 (found == hdr && 3795 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 3796 (found == hdr && HDR_L2_READING(hdr))); 3797 } 3798 3799 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED; 3800 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 3801 hdr->b_flags &= ~ARC_FLAG_L2CACHE; 3802 3803 /* byteswap if necessary */ 3804 callback_list = hdr->b_l1hdr.b_acb; 3805 ASSERT(callback_list != NULL); 3806 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) { 3807 dmu_object_byteswap_t bswap = 3808 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 3809 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ? 3810 byteswap_uint64_array : 3811 dmu_ot_byteswap[bswap].ob_func; 3812 func(buf->b_data, hdr->b_size); 3813 } 3814 3815 arc_cksum_compute(buf, B_FALSE); 3816#ifdef illumos 3817 arc_buf_watch(buf); 3818#endif 3819 3820 if (hash_lock && zio->io_error == 0 && 3821 hdr->b_l1hdr.b_state == arc_anon) { 3822 /* 3823 * Only call arc_access on anonymous buffers. This is because 3824 * if we've issued an I/O for an evicted buffer, we've already 3825 * called arc_access (to prevent any simultaneous readers from 3826 * getting confused). 3827 */ 3828 arc_access(hdr, hash_lock); 3829 } 3830 3831 /* create copies of the data buffer for the callers */ 3832 abuf = buf; 3833 for (acb = callback_list; acb; acb = acb->acb_next) { 3834 if (acb->acb_done) { 3835 if (abuf == NULL) { 3836 ARCSTAT_BUMP(arcstat_duplicate_reads); 3837 abuf = arc_buf_clone(buf); 3838 } 3839 acb->acb_buf = abuf; 3840 abuf = NULL; 3841 } 3842 } 3843 hdr->b_l1hdr.b_acb = NULL; 3844 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 3845 ASSERT(!HDR_BUF_AVAILABLE(hdr)); 3846 if (abuf == buf) { 3847 ASSERT(buf->b_efunc == NULL); 3848 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 3849 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 3850 } 3851 3852 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 3853 callback_list != NULL); 3854 3855 if (zio->io_error != 0) { 3856 hdr->b_flags |= ARC_FLAG_IO_ERROR; 3857 if (hdr->b_l1hdr.b_state != arc_anon) 3858 arc_change_state(arc_anon, hdr, hash_lock); 3859 if (HDR_IN_HASH_TABLE(hdr)) 3860 buf_hash_remove(hdr); 3861 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3862 } 3863 3864 /* 3865 * Broadcast before we drop the hash_lock to avoid the possibility 3866 * that the hdr (and hence the cv) might be freed before we get to 3867 * the cv_broadcast(). 3868 */ 3869 cv_broadcast(&hdr->b_l1hdr.b_cv); 3870 3871 if (hash_lock != NULL) { 3872 mutex_exit(hash_lock); 3873 } else { 3874 /* 3875 * This block was freed while we waited for the read to 3876 * complete. It has been removed from the hash table and 3877 * moved to the anonymous state (so that it won't show up 3878 * in the cache). 3879 */ 3880 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3881 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 3882 } 3883 3884 /* execute each callback and free its structure */ 3885 while ((acb = callback_list) != NULL) { 3886 if (acb->acb_done) 3887 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 3888 3889 if (acb->acb_zio_dummy != NULL) { 3890 acb->acb_zio_dummy->io_error = zio->io_error; 3891 zio_nowait(acb->acb_zio_dummy); 3892 } 3893 3894 callback_list = acb->acb_next; 3895 kmem_free(acb, sizeof (arc_callback_t)); 3896 } 3897 3898 if (freeable) 3899 arc_hdr_destroy(hdr); 3900} 3901 3902/* 3903 * "Read" the block block at the specified DVA (in bp) via the 3904 * cache. If the block is found in the cache, invoke the provided 3905 * callback immediately and return. Note that the `zio' parameter 3906 * in the callback will be NULL in this case, since no IO was 3907 * required. If the block is not in the cache pass the read request 3908 * on to the spa with a substitute callback function, so that the 3909 * requested block will be added to the cache. 3910 * 3911 * If a read request arrives for a block that has a read in-progress, 3912 * either wait for the in-progress read to complete (and return the 3913 * results); or, if this is a read with a "done" func, add a record 3914 * to the read to invoke the "done" func when the read completes, 3915 * and return; or just return. 3916 * 3917 * arc_read_done() will invoke all the requested "done" functions 3918 * for readers of this block. 3919 */ 3920int 3921arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 3922 void *private, zio_priority_t priority, int zio_flags, 3923 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 3924{ 3925 arc_buf_hdr_t *hdr = NULL; 3926 arc_buf_t *buf = NULL; 3927 kmutex_t *hash_lock = NULL; 3928 zio_t *rzio; 3929 uint64_t guid = spa_load_guid(spa); 3930 3931 ASSERT(!BP_IS_EMBEDDED(bp) || 3932 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 3933 3934top: 3935 if (!BP_IS_EMBEDDED(bp)) { 3936 /* 3937 * Embedded BP's have no DVA and require no I/O to "read". 3938 * Create an anonymous arc buf to back it. 3939 */ 3940 hdr = buf_hash_find(guid, bp, &hash_lock); 3941 } 3942 3943 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) { 3944 3945 *arc_flags |= ARC_FLAG_CACHED; 3946 3947 if (HDR_IO_IN_PROGRESS(hdr)) { 3948 3949 if (*arc_flags & ARC_FLAG_WAIT) { 3950 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 3951 mutex_exit(hash_lock); 3952 goto top; 3953 } 3954 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 3955 3956 if (done) { 3957 arc_callback_t *acb = NULL; 3958 3959 acb = kmem_zalloc(sizeof (arc_callback_t), 3960 KM_SLEEP); 3961 acb->acb_done = done; 3962 acb->acb_private = private; 3963 if (pio != NULL) 3964 acb->acb_zio_dummy = zio_null(pio, 3965 spa, NULL, NULL, NULL, zio_flags); 3966 3967 ASSERT(acb->acb_done != NULL); 3968 acb->acb_next = hdr->b_l1hdr.b_acb; 3969 hdr->b_l1hdr.b_acb = acb; 3970 add_reference(hdr, hash_lock, private); 3971 mutex_exit(hash_lock); 3972 return (0); 3973 } 3974 mutex_exit(hash_lock); 3975 return (0); 3976 } 3977 3978 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 3979 hdr->b_l1hdr.b_state == arc_mfu); 3980 3981 if (done) { 3982 add_reference(hdr, hash_lock, private); 3983 /* 3984 * If this block is already in use, create a new 3985 * copy of the data so that we will be guaranteed 3986 * that arc_release() will always succeed. 3987 */ 3988 buf = hdr->b_l1hdr.b_buf; 3989 ASSERT(buf); 3990 ASSERT(buf->b_data); 3991 if (HDR_BUF_AVAILABLE(hdr)) { 3992 ASSERT(buf->b_efunc == NULL); 3993 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 3994 } else { 3995 buf = arc_buf_clone(buf); 3996 } 3997 3998 } else if (*arc_flags & ARC_FLAG_PREFETCH && 3999 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4000 hdr->b_flags |= ARC_FLAG_PREFETCH; 4001 } 4002 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4003 arc_access(hdr, hash_lock); 4004 if (*arc_flags & ARC_FLAG_L2CACHE) 4005 hdr->b_flags |= ARC_FLAG_L2CACHE; 4006 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4007 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4008 mutex_exit(hash_lock); 4009 ARCSTAT_BUMP(arcstat_hits); 4010 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4011 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4012 data, metadata, hits); 4013 4014 if (done) 4015 done(NULL, buf, private); 4016 } else { 4017 uint64_t size = BP_GET_LSIZE(bp); 4018 arc_callback_t *acb; 4019 vdev_t *vd = NULL; 4020 uint64_t addr = 0; 4021 boolean_t devw = B_FALSE; 4022 enum zio_compress b_compress = ZIO_COMPRESS_OFF; 4023 int32_t b_asize = 0; 4024 4025 if (hdr == NULL) { 4026 /* this block is not in the cache */ 4027 arc_buf_hdr_t *exists = NULL; 4028 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4029 buf = arc_buf_alloc(spa, size, private, type); 4030 hdr = buf->b_hdr; 4031 if (!BP_IS_EMBEDDED(bp)) { 4032 hdr->b_dva = *BP_IDENTITY(bp); 4033 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4034 exists = buf_hash_insert(hdr, &hash_lock); 4035 } 4036 if (exists != NULL) { 4037 /* somebody beat us to the hash insert */ 4038 mutex_exit(hash_lock); 4039 buf_discard_identity(hdr); 4040 (void) arc_buf_remove_ref(buf, private); 4041 goto top; /* restart the IO request */ 4042 } 4043 4044 /* if this is a prefetch, we don't have a reference */ 4045 if (*arc_flags & ARC_FLAG_PREFETCH) { 4046 (void) remove_reference(hdr, hash_lock, 4047 private); 4048 hdr->b_flags |= ARC_FLAG_PREFETCH; 4049 } 4050 if (*arc_flags & ARC_FLAG_L2CACHE) 4051 hdr->b_flags |= ARC_FLAG_L2CACHE; 4052 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4053 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4054 if (BP_GET_LEVEL(bp) > 0) 4055 hdr->b_flags |= ARC_FLAG_INDIRECT; 4056 } else { 4057 /* 4058 * This block is in the ghost cache. If it was L2-only 4059 * (and thus didn't have an L1 hdr), we realloc the 4060 * header to add an L1 hdr. 4061 */ 4062 if (!HDR_HAS_L1HDR(hdr)) { 4063 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4064 hdr_full_cache); 4065 } 4066 4067 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4068 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4069 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4070 ASSERT(hdr->b_l1hdr.b_buf == NULL); 4071 4072 /* if this is a prefetch, we don't have a reference */ 4073 if (*arc_flags & ARC_FLAG_PREFETCH) 4074 hdr->b_flags |= ARC_FLAG_PREFETCH; 4075 else 4076 add_reference(hdr, hash_lock, private); 4077 if (*arc_flags & ARC_FLAG_L2CACHE) 4078 hdr->b_flags |= ARC_FLAG_L2CACHE; 4079 if (*arc_flags & ARC_FLAG_L2COMPRESS) 4080 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4081 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 4082 buf->b_hdr = hdr; 4083 buf->b_data = NULL; 4084 buf->b_efunc = NULL; 4085 buf->b_private = NULL; 4086 buf->b_next = NULL; 4087 hdr->b_l1hdr.b_buf = buf; 4088 ASSERT0(hdr->b_l1hdr.b_datacnt); 4089 hdr->b_l1hdr.b_datacnt = 1; 4090 arc_get_data_buf(buf); 4091 arc_access(hdr, hash_lock); 4092 } 4093 4094 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4095 4096 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4097 acb->acb_done = done; 4098 acb->acb_private = private; 4099 4100 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4101 hdr->b_l1hdr.b_acb = acb; 4102 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4103 4104 if (HDR_HAS_L2HDR(hdr) && 4105 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4106 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4107 addr = hdr->b_l2hdr.b_daddr; 4108 b_compress = HDR_GET_COMPRESS(hdr); 4109 b_asize = hdr->b_l2hdr.b_asize; 4110 /* 4111 * Lock out device removal. 4112 */ 4113 if (vdev_is_dead(vd) || 4114 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4115 vd = NULL; 4116 } 4117 4118 if (hash_lock != NULL) 4119 mutex_exit(hash_lock); 4120 4121 /* 4122 * At this point, we have a level 1 cache miss. Try again in 4123 * L2ARC if possible. 4124 */ 4125 ASSERT3U(hdr->b_size, ==, size); 4126 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4127 uint64_t, size, zbookmark_phys_t *, zb); 4128 ARCSTAT_BUMP(arcstat_misses); 4129 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4130 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4131 data, metadata, misses); 4132#ifdef _KERNEL 4133 curthread->td_ru.ru_inblock++; 4134#endif 4135 4136 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 4137 /* 4138 * Read from the L2ARC if the following are true: 4139 * 1. The L2ARC vdev was previously cached. 4140 * 2. This buffer still has L2ARC metadata. 4141 * 3. This buffer isn't currently writing to the L2ARC. 4142 * 4. The L2ARC entry wasn't evicted, which may 4143 * also have invalidated the vdev. 4144 * 5. This isn't prefetch and l2arc_noprefetch is set. 4145 */ 4146 if (HDR_HAS_L2HDR(hdr) && 4147 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 4148 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 4149 l2arc_read_callback_t *cb; 4150 4151 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 4152 ARCSTAT_BUMP(arcstat_l2_hits); 4153 4154 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 4155 KM_SLEEP); 4156 cb->l2rcb_buf = buf; 4157 cb->l2rcb_spa = spa; 4158 cb->l2rcb_bp = *bp; 4159 cb->l2rcb_zb = *zb; 4160 cb->l2rcb_flags = zio_flags; 4161 cb->l2rcb_compress = b_compress; 4162 4163 ASSERT(addr >= VDEV_LABEL_START_SIZE && 4164 addr + size < vd->vdev_psize - 4165 VDEV_LABEL_END_SIZE); 4166 4167 /* 4168 * l2arc read. The SCL_L2ARC lock will be 4169 * released by l2arc_read_done(). 4170 * Issue a null zio if the underlying buffer 4171 * was squashed to zero size by compression. 4172 */ 4173 if (b_compress == ZIO_COMPRESS_EMPTY) { 4174 rzio = zio_null(pio, spa, vd, 4175 l2arc_read_done, cb, 4176 zio_flags | ZIO_FLAG_DONT_CACHE | 4177 ZIO_FLAG_CANFAIL | 4178 ZIO_FLAG_DONT_PROPAGATE | 4179 ZIO_FLAG_DONT_RETRY); 4180 } else { 4181 rzio = zio_read_phys(pio, vd, addr, 4182 b_asize, buf->b_data, 4183 ZIO_CHECKSUM_OFF, 4184 l2arc_read_done, cb, priority, 4185 zio_flags | ZIO_FLAG_DONT_CACHE | 4186 ZIO_FLAG_CANFAIL | 4187 ZIO_FLAG_DONT_PROPAGATE | 4188 ZIO_FLAG_DONT_RETRY, B_FALSE); 4189 } 4190 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 4191 zio_t *, rzio); 4192 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize); 4193 4194 if (*arc_flags & ARC_FLAG_NOWAIT) { 4195 zio_nowait(rzio); 4196 return (0); 4197 } 4198 4199 ASSERT(*arc_flags & ARC_FLAG_WAIT); 4200 if (zio_wait(rzio) == 0) 4201 return (0); 4202 4203 /* l2arc read error; goto zio_read() */ 4204 } else { 4205 DTRACE_PROBE1(l2arc__miss, 4206 arc_buf_hdr_t *, hdr); 4207 ARCSTAT_BUMP(arcstat_l2_misses); 4208 if (HDR_L2_WRITING(hdr)) 4209 ARCSTAT_BUMP(arcstat_l2_rw_clash); 4210 spa_config_exit(spa, SCL_L2ARC, vd); 4211 } 4212 } else { 4213 if (vd != NULL) 4214 spa_config_exit(spa, SCL_L2ARC, vd); 4215 if (l2arc_ndev != 0) { 4216 DTRACE_PROBE1(l2arc__miss, 4217 arc_buf_hdr_t *, hdr); 4218 ARCSTAT_BUMP(arcstat_l2_misses); 4219 } 4220 } 4221 4222 rzio = zio_read(pio, spa, bp, buf->b_data, size, 4223 arc_read_done, buf, priority, zio_flags, zb); 4224 4225 if (*arc_flags & ARC_FLAG_WAIT) 4226 return (zio_wait(rzio)); 4227 4228 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4229 zio_nowait(rzio); 4230 } 4231 return (0); 4232} 4233 4234void 4235arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private) 4236{ 4237 ASSERT(buf->b_hdr != NULL); 4238 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon); 4239 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) || 4240 func == NULL); 4241 ASSERT(buf->b_efunc == NULL); 4242 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr)); 4243 4244 buf->b_efunc = func; 4245 buf->b_private = private; 4246} 4247 4248/* 4249 * Notify the arc that a block was freed, and thus will never be used again. 4250 */ 4251void 4252arc_freed(spa_t *spa, const blkptr_t *bp) 4253{ 4254 arc_buf_hdr_t *hdr; 4255 kmutex_t *hash_lock; 4256 uint64_t guid = spa_load_guid(spa); 4257 4258 ASSERT(!BP_IS_EMBEDDED(bp)); 4259 4260 hdr = buf_hash_find(guid, bp, &hash_lock); 4261 if (hdr == NULL) 4262 return; 4263 if (HDR_BUF_AVAILABLE(hdr)) { 4264 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 4265 add_reference(hdr, hash_lock, FTAG); 4266 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE; 4267 mutex_exit(hash_lock); 4268 4269 arc_release(buf, FTAG); 4270 (void) arc_buf_remove_ref(buf, FTAG); 4271 } else { 4272 mutex_exit(hash_lock); 4273 } 4274 4275} 4276 4277/* 4278 * Clear the user eviction callback set by arc_set_callback(), first calling 4279 * it if it exists. Because the presence of a callback keeps an arc_buf cached 4280 * clearing the callback may result in the arc_buf being destroyed. However, 4281 * it will not result in the *last* arc_buf being destroyed, hence the data 4282 * will remain cached in the ARC. We make a copy of the arc buffer here so 4283 * that we can process the callback without holding any locks. 4284 * 4285 * It's possible that the callback is already in the process of being cleared 4286 * by another thread. In this case we can not clear the callback. 4287 * 4288 * Returns B_TRUE if the callback was successfully called and cleared. 4289 */ 4290boolean_t 4291arc_clear_callback(arc_buf_t *buf) 4292{ 4293 arc_buf_hdr_t *hdr; 4294 kmutex_t *hash_lock; 4295 arc_evict_func_t *efunc = buf->b_efunc; 4296 void *private = buf->b_private; 4297 list_t *list, *evicted_list; 4298 kmutex_t *lock, *evicted_lock; 4299 4300 mutex_enter(&buf->b_evict_lock); 4301 hdr = buf->b_hdr; 4302 if (hdr == NULL) { 4303 /* 4304 * We are in arc_do_user_evicts(). 4305 */ 4306 ASSERT(buf->b_data == NULL); 4307 mutex_exit(&buf->b_evict_lock); 4308 return (B_FALSE); 4309 } else if (buf->b_data == NULL) { 4310 /* 4311 * We are on the eviction list; process this buffer now 4312 * but let arc_do_user_evicts() do the reaping. 4313 */ 4314 buf->b_efunc = NULL; 4315 mutex_exit(&buf->b_evict_lock); 4316 VERIFY0(efunc(private)); 4317 return (B_TRUE); 4318 } 4319 hash_lock = HDR_LOCK(hdr); 4320 mutex_enter(hash_lock); 4321 hdr = buf->b_hdr; 4322 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4323 4324 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <, 4325 hdr->b_l1hdr.b_datacnt); 4326 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4327 hdr->b_l1hdr.b_state == arc_mfu); 4328 4329 buf->b_efunc = NULL; 4330 buf->b_private = NULL; 4331 4332 if (hdr->b_l1hdr.b_datacnt > 1) { 4333 mutex_exit(&buf->b_evict_lock); 4334 arc_buf_destroy(buf, FALSE, TRUE); 4335 } else { 4336 ASSERT(buf == hdr->b_l1hdr.b_buf); 4337 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE; 4338 mutex_exit(&buf->b_evict_lock); 4339 } 4340 4341 mutex_exit(hash_lock); 4342 VERIFY0(efunc(private)); 4343 return (B_TRUE); 4344} 4345 4346/* 4347 * Release this buffer from the cache, making it an anonymous buffer. This 4348 * must be done after a read and prior to modifying the buffer contents. 4349 * If the buffer has more than one reference, we must make 4350 * a new hdr for the buffer. 4351 */ 4352void 4353arc_release(arc_buf_t *buf, void *tag) 4354{ 4355 arc_buf_hdr_t *hdr = buf->b_hdr; 4356 4357 /* 4358 * It would be nice to assert that if it's DMU metadata (level > 4359 * 0 || it's the dnode file), then it must be syncing context. 4360 * But we don't know that information at this level. 4361 */ 4362 4363 mutex_enter(&buf->b_evict_lock); 4364 /* 4365 * We don't grab the hash lock prior to this check, because if 4366 * the buffer's header is in the arc_anon state, it won't be 4367 * linked into the hash table. 4368 */ 4369 if (hdr->b_l1hdr.b_state == arc_anon) { 4370 mutex_exit(&buf->b_evict_lock); 4371 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4372 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 4373 ASSERT(!HDR_HAS_L2HDR(hdr)); 4374 ASSERT(BUF_EMPTY(hdr)); 4375 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1); 4376 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 4377 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4378 4379 ASSERT3P(buf->b_efunc, ==, NULL); 4380 ASSERT3P(buf->b_private, ==, NULL); 4381 4382 hdr->b_l1hdr.b_arc_access = 0; 4383 arc_buf_thaw(buf); 4384 4385 return; 4386 } 4387 4388 kmutex_t *hash_lock = HDR_LOCK(hdr); 4389 mutex_enter(hash_lock); 4390 4391 /* 4392 * This assignment is only valid as long as the hash_lock is 4393 * held, we must be careful not to reference state or the 4394 * b_state field after dropping the lock. 4395 */ 4396 arc_state_t *state = hdr->b_l1hdr.b_state; 4397 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 4398 ASSERT3P(state, !=, arc_anon); 4399 4400 /* this buffer is not on any list */ 4401 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 4402 4403 if (HDR_HAS_L2HDR(hdr)) { 4404 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4405 4406 /* 4407 * We have to recheck this conditional again now that 4408 * we're holding the l2ad_mtx to prevent a race with 4409 * another thread which might be concurrently calling 4410 * l2arc_evict(). In that case, l2arc_evict() might have 4411 * destroyed the header's L2 portion as we were waiting 4412 * to acquire the l2ad_mtx. 4413 */ 4414 if (HDR_HAS_L2HDR(hdr)) { 4415 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 4416 hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0); 4417 arc_hdr_l2hdr_destroy(hdr); 4418 } 4419 4420 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 4421 } 4422 4423 /* 4424 * Do we have more than one buf? 4425 */ 4426 if (hdr->b_l1hdr.b_datacnt > 1) { 4427 arc_buf_hdr_t *nhdr; 4428 arc_buf_t **bufp; 4429 uint64_t blksz = hdr->b_size; 4430 uint64_t spa = hdr->b_spa; 4431 arc_buf_contents_t type = arc_buf_type(hdr); 4432 uint32_t flags = hdr->b_flags; 4433 4434 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 4435 /* 4436 * Pull the data off of this hdr and attach it to 4437 * a new anonymous hdr. 4438 */ 4439 (void) remove_reference(hdr, hash_lock, tag); 4440 bufp = &hdr->b_l1hdr.b_buf; 4441 while (*bufp != buf) 4442 bufp = &(*bufp)->b_next; 4443 *bufp = buf->b_next; 4444 buf->b_next = NULL; 4445 4446 ASSERT3P(state, !=, arc_l2c_only); 4447 ASSERT3U(state->arcs_size, >=, hdr->b_size); 4448 atomic_add_64(&state->arcs_size, -hdr->b_size); 4449 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 4450 ASSERT3P(state, !=, arc_l2c_only); 4451 uint64_t *size = &state->arcs_lsize[type]; 4452 ASSERT3U(*size, >=, hdr->b_size); 4453 atomic_add_64(size, -hdr->b_size); 4454 } 4455 4456 /* 4457 * We're releasing a duplicate user data buffer, update 4458 * our statistics accordingly. 4459 */ 4460 if (HDR_ISTYPE_DATA(hdr)) { 4461 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers); 4462 ARCSTAT_INCR(arcstat_duplicate_buffers_size, 4463 -hdr->b_size); 4464 } 4465 hdr->b_l1hdr.b_datacnt -= 1; 4466 arc_cksum_verify(buf); 4467#ifdef illumos 4468 arc_buf_unwatch(buf); 4469#endif 4470 4471 mutex_exit(hash_lock); 4472 4473 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 4474 nhdr->b_size = blksz; 4475 nhdr->b_spa = spa; 4476 4477 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING; 4478 nhdr->b_flags |= arc_bufc_to_flags(type); 4479 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR; 4480 4481 nhdr->b_l1hdr.b_buf = buf; 4482 nhdr->b_l1hdr.b_datacnt = 1; 4483 nhdr->b_l1hdr.b_state = arc_anon; 4484 nhdr->b_l1hdr.b_arc_access = 0; 4485 nhdr->b_freeze_cksum = NULL; 4486 4487 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 4488 buf->b_hdr = nhdr; 4489 mutex_exit(&buf->b_evict_lock); 4490 atomic_add_64(&arc_anon->arcs_size, blksz); 4491 } else { 4492 mutex_exit(&buf->b_evict_lock); 4493 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 4494 /* protected by hash lock */ 4495 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 4496 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4497 arc_change_state(arc_anon, hdr, hash_lock); 4498 hdr->b_l1hdr.b_arc_access = 0; 4499 mutex_exit(hash_lock); 4500 4501 buf_discard_identity(hdr); 4502 arc_buf_thaw(buf); 4503 } 4504 buf->b_efunc = NULL; 4505 buf->b_private = NULL; 4506} 4507 4508int 4509arc_released(arc_buf_t *buf) 4510{ 4511 int released; 4512 4513 mutex_enter(&buf->b_evict_lock); 4514 released = (buf->b_data != NULL && 4515 buf->b_hdr->b_l1hdr.b_state == arc_anon); 4516 mutex_exit(&buf->b_evict_lock); 4517 return (released); 4518} 4519 4520#ifdef ZFS_DEBUG 4521int 4522arc_referenced(arc_buf_t *buf) 4523{ 4524 int referenced; 4525 4526 mutex_enter(&buf->b_evict_lock); 4527 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 4528 mutex_exit(&buf->b_evict_lock); 4529 return (referenced); 4530} 4531#endif 4532 4533static void 4534arc_write_ready(zio_t *zio) 4535{ 4536 arc_write_callback_t *callback = zio->io_private; 4537 arc_buf_t *buf = callback->awcb_buf; 4538 arc_buf_hdr_t *hdr = buf->b_hdr; 4539 4540 ASSERT(HDR_HAS_L1HDR(hdr)); 4541 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 4542 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4543 callback->awcb_ready(zio, buf, callback->awcb_private); 4544 4545 /* 4546 * If the IO is already in progress, then this is a re-write 4547 * attempt, so we need to thaw and re-compute the cksum. 4548 * It is the responsibility of the callback to handle the 4549 * accounting for any re-write attempt. 4550 */ 4551 if (HDR_IO_IN_PROGRESS(hdr)) { 4552 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 4553 if (hdr->b_freeze_cksum != NULL) { 4554 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t)); 4555 hdr->b_freeze_cksum = NULL; 4556 } 4557 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 4558 } 4559 arc_cksum_compute(buf, B_FALSE); 4560 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS; 4561} 4562 4563/* 4564 * The SPA calls this callback for each physical write that happens on behalf 4565 * of a logical write. See the comment in dbuf_write_physdone() for details. 4566 */ 4567static void 4568arc_write_physdone(zio_t *zio) 4569{ 4570 arc_write_callback_t *cb = zio->io_private; 4571 if (cb->awcb_physdone != NULL) 4572 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 4573} 4574 4575static void 4576arc_write_done(zio_t *zio) 4577{ 4578 arc_write_callback_t *callback = zio->io_private; 4579 arc_buf_t *buf = callback->awcb_buf; 4580 arc_buf_hdr_t *hdr = buf->b_hdr; 4581 4582 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4583 4584 if (zio->io_error == 0) { 4585 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 4586 buf_discard_identity(hdr); 4587 } else { 4588 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 4589 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 4590 } 4591 } else { 4592 ASSERT(BUF_EMPTY(hdr)); 4593 } 4594 4595 /* 4596 * If the block to be written was all-zero or compressed enough to be 4597 * embedded in the BP, no write was performed so there will be no 4598 * dva/birth/checksum. The buffer must therefore remain anonymous 4599 * (and uncached). 4600 */ 4601 if (!BUF_EMPTY(hdr)) { 4602 arc_buf_hdr_t *exists; 4603 kmutex_t *hash_lock; 4604 4605 ASSERT(zio->io_error == 0); 4606 4607 arc_cksum_verify(buf); 4608 4609 exists = buf_hash_insert(hdr, &hash_lock); 4610 if (exists != NULL) { 4611 /* 4612 * This can only happen if we overwrite for 4613 * sync-to-convergence, because we remove 4614 * buffers from the hash table when we arc_free(). 4615 */ 4616 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 4617 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4618 panic("bad overwrite, hdr=%p exists=%p", 4619 (void *)hdr, (void *)exists); 4620 ASSERT(refcount_is_zero( 4621 &exists->b_l1hdr.b_refcnt)); 4622 arc_change_state(arc_anon, exists, hash_lock); 4623 mutex_exit(hash_lock); 4624 arc_hdr_destroy(exists); 4625 exists = buf_hash_insert(hdr, &hash_lock); 4626 ASSERT3P(exists, ==, NULL); 4627 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 4628 /* nopwrite */ 4629 ASSERT(zio->io_prop.zp_nopwrite); 4630 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 4631 panic("bad nopwrite, hdr=%p exists=%p", 4632 (void *)hdr, (void *)exists); 4633 } else { 4634 /* Dedup */ 4635 ASSERT(hdr->b_l1hdr.b_datacnt == 1); 4636 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 4637 ASSERT(BP_GET_DEDUP(zio->io_bp)); 4638 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 4639 } 4640 } 4641 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4642 /* if it's not anon, we are doing a scrub */ 4643 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 4644 arc_access(hdr, hash_lock); 4645 mutex_exit(hash_lock); 4646 } else { 4647 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS; 4648 } 4649 4650 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4651 callback->awcb_done(zio, buf, callback->awcb_private); 4652 4653 kmem_free(callback, sizeof (arc_write_callback_t)); 4654} 4655 4656zio_t * 4657arc_write(zio_t *pio, spa_t *spa, uint64_t txg, 4658 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress, 4659 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone, 4660 arc_done_func_t *done, void *private, zio_priority_t priority, 4661 int zio_flags, const zbookmark_phys_t *zb) 4662{ 4663 arc_buf_hdr_t *hdr = buf->b_hdr; 4664 arc_write_callback_t *callback; 4665 zio_t *zio; 4666 4667 ASSERT(ready != NULL); 4668 ASSERT(done != NULL); 4669 ASSERT(!HDR_IO_ERROR(hdr)); 4670 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4671 ASSERT(hdr->b_l1hdr.b_acb == NULL); 4672 ASSERT(hdr->b_l1hdr.b_datacnt > 0); 4673 if (l2arc) 4674 hdr->b_flags |= ARC_FLAG_L2CACHE; 4675 if (l2arc_compress) 4676 hdr->b_flags |= ARC_FLAG_L2COMPRESS; 4677 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 4678 callback->awcb_ready = ready; 4679 callback->awcb_physdone = physdone; 4680 callback->awcb_done = done; 4681 callback->awcb_private = private; 4682 callback->awcb_buf = buf; 4683 4684 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp, 4685 arc_write_ready, arc_write_physdone, arc_write_done, callback, 4686 priority, zio_flags, zb); 4687 4688 return (zio); 4689} 4690 4691static int 4692arc_memory_throttle(uint64_t reserve, uint64_t txg) 4693{ 4694#ifdef _KERNEL 4695 uint64_t available_memory = ptob(freemem); 4696 static uint64_t page_load = 0; 4697 static uint64_t last_txg = 0; 4698 4699#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4700 available_memory = 4701 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 4702#endif 4703 4704 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 4705 return (0); 4706 4707 if (txg > last_txg) { 4708 last_txg = txg; 4709 page_load = 0; 4710 } 4711 /* 4712 * If we are in pageout, we know that memory is already tight, 4713 * the arc is already going to be evicting, so we just want to 4714 * continue to let page writes occur as quickly as possible. 4715 */ 4716 if (curproc == pageproc) { 4717 if (page_load > MAX(ptob(minfree), available_memory) / 4) 4718 return (SET_ERROR(ERESTART)); 4719 /* Note: reserve is inflated, so we deflate */ 4720 page_load += reserve / 8; 4721 return (0); 4722 } else if (page_load > 0 && arc_reclaim_needed()) { 4723 /* memory is low, delay before restarting */ 4724 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 4725 return (SET_ERROR(EAGAIN)); 4726 } 4727 page_load = 0; 4728#endif 4729 return (0); 4730} 4731 4732void 4733arc_tempreserve_clear(uint64_t reserve) 4734{ 4735 atomic_add_64(&arc_tempreserve, -reserve); 4736 ASSERT((int64_t)arc_tempreserve >= 0); 4737} 4738 4739int 4740arc_tempreserve_space(uint64_t reserve, uint64_t txg) 4741{ 4742 int error; 4743 uint64_t anon_size; 4744 4745 if (reserve > arc_c/4 && !arc_no_grow) { 4746 arc_c = MIN(arc_c_max, reserve * 4); 4747 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 4748 } 4749 if (reserve > arc_c) 4750 return (SET_ERROR(ENOMEM)); 4751 4752 /* 4753 * Don't count loaned bufs as in flight dirty data to prevent long 4754 * network delays from blocking transactions that are ready to be 4755 * assigned to a txg. 4756 */ 4757 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0); 4758 4759 /* 4760 * Writes will, almost always, require additional memory allocations 4761 * in order to compress/encrypt/etc the data. We therefore need to 4762 * make sure that there is sufficient available memory for this. 4763 */ 4764 error = arc_memory_throttle(reserve, txg); 4765 if (error != 0) 4766 return (error); 4767 4768 /* 4769 * Throttle writes when the amount of dirty data in the cache 4770 * gets too large. We try to keep the cache less than half full 4771 * of dirty blocks so that our sync times don't grow too large. 4772 * Note: if two requests come in concurrently, we might let them 4773 * both succeed, when one of them should fail. Not a huge deal. 4774 */ 4775 4776 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 4777 anon_size > arc_c / 4) { 4778 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 4779 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 4780 arc_tempreserve>>10, 4781 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10, 4782 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10, 4783 reserve>>10, arc_c>>10); 4784 return (SET_ERROR(ERESTART)); 4785 } 4786 atomic_add_64(&arc_tempreserve, reserve); 4787 return (0); 4788} 4789 4790static void 4791arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 4792 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 4793{ 4794 size->value.ui64 = state->arcs_size; 4795 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA]; 4796 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA]; 4797} 4798 4799static int 4800arc_kstat_update(kstat_t *ksp, int rw) 4801{ 4802 arc_stats_t *as = ksp->ks_data; 4803 4804 if (rw == KSTAT_WRITE) { 4805 return (EACCES); 4806 } else { 4807 arc_kstat_update_state(arc_anon, 4808 &as->arcstat_anon_size, 4809 &as->arcstat_anon_evictable_data, 4810 &as->arcstat_anon_evictable_metadata); 4811 arc_kstat_update_state(arc_mru, 4812 &as->arcstat_mru_size, 4813 &as->arcstat_mru_evictable_data, 4814 &as->arcstat_mru_evictable_metadata); 4815 arc_kstat_update_state(arc_mru_ghost, 4816 &as->arcstat_mru_ghost_size, 4817 &as->arcstat_mru_ghost_evictable_data, 4818 &as->arcstat_mru_ghost_evictable_metadata); 4819 arc_kstat_update_state(arc_mfu, 4820 &as->arcstat_mfu_size, 4821 &as->arcstat_mfu_evictable_data, 4822 &as->arcstat_mfu_evictable_metadata); 4823 arc_kstat_update_state(arc_mfu_ghost, 4824 &as->arcstat_mfu_ghost_size, 4825 &as->arcstat_mfu_ghost_evictable_data, 4826 &as->arcstat_mfu_ghost_evictable_metadata); 4827 } 4828 4829 return (0); 4830} 4831 4832#ifdef _KERNEL 4833static eventhandler_tag arc_event_lowmem = NULL; 4834 4835static void 4836arc_lowmem(void *arg __unused, int howto __unused) 4837{ 4838 4839 mutex_enter(&arc_reclaim_thr_lock); 4840 /* XXX: Memory deficit should be passed as argument. */ 4841 needfree = btoc(arc_c >> arc_shrink_shift); 4842 DTRACE_PROBE(arc__needfree); 4843 cv_signal(&arc_reclaim_thr_cv); 4844 4845 /* 4846 * It is unsafe to block here in arbitrary threads, because we can come 4847 * here from ARC itself and may hold ARC locks and thus risk a deadlock 4848 * with ARC reclaim thread. 4849 */ 4850 if (curproc == pageproc) 4851 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0); 4852 mutex_exit(&arc_reclaim_thr_lock); 4853} 4854#endif 4855 4856void 4857arc_init(void) 4858{ 4859 int i, prefetch_tunable_set = 0; 4860 4861 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL); 4862 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL); 4863 4864 /* Convert seconds to clock ticks */ 4865 arc_min_prefetch_lifespan = 1 * hz; 4866 4867 /* Start out with 1/8 of all memory */ 4868 arc_c = kmem_size() / 8; 4869 4870#ifdef illumos 4871#ifdef _KERNEL 4872 /* 4873 * On architectures where the physical memory can be larger 4874 * than the addressable space (intel in 32-bit mode), we may 4875 * need to limit the cache to 1/8 of VM size. 4876 */ 4877 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 4878#endif 4879#endif /* illumos */ 4880 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ 4881 arc_c_min = MAX(arc_c / 4, 16 << 20); 4882 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 4883 if (arc_c * 8 >= 1 << 30) 4884 arc_c_max = (arc_c * 8) - (1 << 30); 4885 else 4886 arc_c_max = arc_c_min; 4887 arc_c_max = MAX(arc_c * 5, arc_c_max); 4888 4889#ifdef _KERNEL 4890 /* 4891 * Allow the tunables to override our calculations if they are 4892 * reasonable (ie. over 16MB) 4893 */ 4894 if (zfs_arc_max > 16 << 20 && zfs_arc_max < kmem_size()) 4895 arc_c_max = zfs_arc_max; 4896 if (zfs_arc_min > 16 << 20 && zfs_arc_min <= arc_c_max) 4897 arc_c_min = zfs_arc_min; 4898#endif 4899 4900 arc_c = arc_c_max; 4901 arc_p = (arc_c >> 1); 4902 4903 /* limit meta-data to 1/4 of the arc capacity */ 4904 arc_meta_limit = arc_c_max / 4; 4905 4906 /* Allow the tunable to override if it is reasonable */ 4907 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 4908 arc_meta_limit = zfs_arc_meta_limit; 4909 4910 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 4911 arc_c_min = arc_meta_limit / 2; 4912 4913 if (zfs_arc_meta_min > 0) { 4914 arc_meta_min = zfs_arc_meta_min; 4915 } else { 4916 arc_meta_min = arc_c_min / 2; 4917 } 4918 4919 if (zfs_arc_grow_retry > 0) 4920 arc_grow_retry = zfs_arc_grow_retry; 4921 4922 if (zfs_arc_shrink_shift > 0) 4923 arc_shrink_shift = zfs_arc_shrink_shift; 4924 4925 /* 4926 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 4927 */ 4928 if (arc_no_grow_shift >= arc_shrink_shift) 4929 arc_no_grow_shift = arc_shrink_shift - 1; 4930 4931 if (zfs_arc_p_min_shift > 0) 4932 arc_p_min_shift = zfs_arc_p_min_shift; 4933 4934 /* if kmem_flags are set, lets try to use less memory */ 4935 if (kmem_debugging()) 4936 arc_c = arc_c / 2; 4937 if (arc_c < arc_c_min) 4938 arc_c = arc_c_min; 4939 4940 zfs_arc_min = arc_c_min; 4941 zfs_arc_max = arc_c_max; 4942 4943 arc_anon = &ARC_anon; 4944 arc_mru = &ARC_mru; 4945 arc_mru_ghost = &ARC_mru_ghost; 4946 arc_mfu = &ARC_mfu; 4947 arc_mfu_ghost = &ARC_mfu_ghost; 4948 arc_l2c_only = &ARC_l2c_only; 4949 arc_size = 0; 4950 4951 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 4952 mutex_init(&arc_anon->arcs_locks[i].arcs_lock, 4953 NULL, MUTEX_DEFAULT, NULL); 4954 mutex_init(&arc_mru->arcs_locks[i].arcs_lock, 4955 NULL, MUTEX_DEFAULT, NULL); 4956 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock, 4957 NULL, MUTEX_DEFAULT, NULL); 4958 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock, 4959 NULL, MUTEX_DEFAULT, NULL); 4960 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock, 4961 NULL, MUTEX_DEFAULT, NULL); 4962 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock, 4963 NULL, MUTEX_DEFAULT, NULL); 4964 4965 list_create(&arc_mru->arcs_lists[i], 4966 sizeof (arc_buf_hdr_t), 4967 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4968 list_create(&arc_mru_ghost->arcs_lists[i], 4969 sizeof (arc_buf_hdr_t), 4970 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4971 list_create(&arc_mfu->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_ghost->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_l2c_only->arcs_lists[i], 4981 sizeof (arc_buf_hdr_t), 4982 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node)); 4983 } 4984 4985 buf_init(); 4986 4987 arc_thread_exit = 0; 4988 arc_eviction_list = NULL; 4989 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL); 4990 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t)); 4991 4992 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 4993 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 4994 4995 if (arc_ksp != NULL) { 4996 arc_ksp->ks_data = &arc_stats; 4997 arc_ksp->ks_update = arc_kstat_update; 4998 kstat_install(arc_ksp); 4999 } 5000 5001 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 5002 TS_RUN, minclsyspri); 5003 5004#ifdef _KERNEL 5005 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 5006 EVENTHANDLER_PRI_FIRST); 5007#endif 5008 5009 arc_dead = FALSE; 5010 arc_warm = B_FALSE; 5011 5012 /* 5013 * Calculate maximum amount of dirty data per pool. 5014 * 5015 * If it has been set by /etc/system, take that. 5016 * Otherwise, use a percentage of physical memory defined by 5017 * zfs_dirty_data_max_percent (default 10%) with a cap at 5018 * zfs_dirty_data_max_max (default 4GB). 5019 */ 5020 if (zfs_dirty_data_max == 0) { 5021 zfs_dirty_data_max = ptob(physmem) * 5022 zfs_dirty_data_max_percent / 100; 5023 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 5024 zfs_dirty_data_max_max); 5025 } 5026 5027#ifdef _KERNEL 5028 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 5029 prefetch_tunable_set = 1; 5030 5031#ifdef __i386__ 5032 if (prefetch_tunable_set == 0) { 5033 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 5034 "-- to enable,\n"); 5035 printf(" add \"vfs.zfs.prefetch_disable=0\" " 5036 "to /boot/loader.conf.\n"); 5037 zfs_prefetch_disable = 1; 5038 } 5039#else 5040 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 5041 prefetch_tunable_set == 0) { 5042 printf("ZFS NOTICE: Prefetch is disabled by default if less " 5043 "than 4GB of RAM is present;\n" 5044 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 5045 "to /boot/loader.conf.\n"); 5046 zfs_prefetch_disable = 1; 5047 } 5048#endif 5049 /* Warn about ZFS memory and address space requirements. */ 5050 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 5051 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 5052 "expect unstable behavior.\n"); 5053 } 5054 if (kmem_size() < 512 * (1 << 20)) { 5055 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 5056 "expect unstable behavior.\n"); 5057 printf(" Consider tuning vm.kmem_size and " 5058 "vm.kmem_size_max\n"); 5059 printf(" in /boot/loader.conf.\n"); 5060 } 5061#endif 5062} 5063 5064void 5065arc_fini(void) 5066{ 5067 int i; 5068 5069 mutex_enter(&arc_reclaim_thr_lock); 5070 arc_thread_exit = 1; 5071 cv_signal(&arc_reclaim_thr_cv); 5072 while (arc_thread_exit != 0) 5073 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock); 5074 mutex_exit(&arc_reclaim_thr_lock); 5075 5076 arc_flush(NULL); 5077 5078 arc_dead = TRUE; 5079 5080 if (arc_ksp != NULL) { 5081 kstat_delete(arc_ksp); 5082 arc_ksp = NULL; 5083 } 5084 5085 mutex_destroy(&arc_eviction_mtx); 5086 mutex_destroy(&arc_reclaim_thr_lock); 5087 cv_destroy(&arc_reclaim_thr_cv); 5088 5089 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) { 5090 list_destroy(&arc_mru->arcs_lists[i]); 5091 list_destroy(&arc_mru_ghost->arcs_lists[i]); 5092 list_destroy(&arc_mfu->arcs_lists[i]); 5093 list_destroy(&arc_mfu_ghost->arcs_lists[i]); 5094 list_destroy(&arc_l2c_only->arcs_lists[i]); 5095 5096 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock); 5097 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock); 5098 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock); 5099 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock); 5100 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock); 5101 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock); 5102 } 5103 5104 buf_fini(); 5105 5106 ASSERT0(arc_loaned_bytes); 5107 5108#ifdef _KERNEL 5109 if (arc_event_lowmem != NULL) 5110 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 5111#endif 5112} 5113 5114/* 5115 * Level 2 ARC 5116 * 5117 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 5118 * It uses dedicated storage devices to hold cached data, which are populated 5119 * using large infrequent writes. The main role of this cache is to boost 5120 * the performance of random read workloads. The intended L2ARC devices 5121 * include short-stroked disks, solid state disks, and other media with 5122 * substantially faster read latency than disk. 5123 * 5124 * +-----------------------+ 5125 * | ARC | 5126 * +-----------------------+ 5127 * | ^ ^ 5128 * | | | 5129 * l2arc_feed_thread() arc_read() 5130 * | | | 5131 * | l2arc read | 5132 * V | | 5133 * +---------------+ | 5134 * | L2ARC | | 5135 * +---------------+ | 5136 * | ^ | 5137 * l2arc_write() | | 5138 * | | | 5139 * V | | 5140 * +-------+ +-------+ 5141 * | vdev | | vdev | 5142 * | cache | | cache | 5143 * +-------+ +-------+ 5144 * +=========+ .-----. 5145 * : L2ARC : |-_____-| 5146 * : devices : | Disks | 5147 * +=========+ `-_____-' 5148 * 5149 * Read requests are satisfied from the following sources, in order: 5150 * 5151 * 1) ARC 5152 * 2) vdev cache of L2ARC devices 5153 * 3) L2ARC devices 5154 * 4) vdev cache of disks 5155 * 5) disks 5156 * 5157 * Some L2ARC device types exhibit extremely slow write performance. 5158 * To accommodate for this there are some significant differences between 5159 * the L2ARC and traditional cache design: 5160 * 5161 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 5162 * the ARC behave as usual, freeing buffers and placing headers on ghost 5163 * lists. The ARC does not send buffers to the L2ARC during eviction as 5164 * this would add inflated write latencies for all ARC memory pressure. 5165 * 5166 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 5167 * It does this by periodically scanning buffers from the eviction-end of 5168 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 5169 * not already there. It scans until a headroom of buffers is satisfied, 5170 * which itself is a buffer for ARC eviction. If a compressible buffer is 5171 * found during scanning and selected for writing to an L2ARC device, we 5172 * temporarily boost scanning headroom during the next scan cycle to make 5173 * sure we adapt to compression effects (which might significantly reduce 5174 * the data volume we write to L2ARC). The thread that does this is 5175 * l2arc_feed_thread(), illustrated below; example sizes are included to 5176 * provide a better sense of ratio than this diagram: 5177 * 5178 * head --> tail 5179 * +---------------------+----------+ 5180 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 5181 * +---------------------+----------+ | o L2ARC eligible 5182 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 5183 * +---------------------+----------+ | 5184 * 15.9 Gbytes ^ 32 Mbytes | 5185 * headroom | 5186 * l2arc_feed_thread() 5187 * | 5188 * l2arc write hand <--[oooo]--' 5189 * | 8 Mbyte 5190 * | write max 5191 * V 5192 * +==============================+ 5193 * L2ARC dev |####|#|###|###| |####| ... | 5194 * +==============================+ 5195 * 32 Gbytes 5196 * 5197 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 5198 * evicted, then the L2ARC has cached a buffer much sooner than it probably 5199 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 5200 * safe to say that this is an uncommon case, since buffers at the end of 5201 * the ARC lists have moved there due to inactivity. 5202 * 5203 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 5204 * then the L2ARC simply misses copying some buffers. This serves as a 5205 * pressure valve to prevent heavy read workloads from both stalling the ARC 5206 * with waits and clogging the L2ARC with writes. This also helps prevent 5207 * the potential for the L2ARC to churn if it attempts to cache content too 5208 * quickly, such as during backups of the entire pool. 5209 * 5210 * 5. After system boot and before the ARC has filled main memory, there are 5211 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 5212 * lists can remain mostly static. Instead of searching from tail of these 5213 * lists as pictured, the l2arc_feed_thread() will search from the list heads 5214 * for eligible buffers, greatly increasing its chance of finding them. 5215 * 5216 * The L2ARC device write speed is also boosted during this time so that 5217 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 5218 * there are no L2ARC reads, and no fear of degrading read performance 5219 * through increased writes. 5220 * 5221 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 5222 * the vdev queue can aggregate them into larger and fewer writes. Each 5223 * device is written to in a rotor fashion, sweeping writes through 5224 * available space then repeating. 5225 * 5226 * 7. The L2ARC does not store dirty content. It never needs to flush 5227 * write buffers back to disk based storage. 5228 * 5229 * 8. If an ARC buffer is written (and dirtied) which also exists in the 5230 * L2ARC, the now stale L2ARC buffer is immediately dropped. 5231 * 5232 * The performance of the L2ARC can be tweaked by a number of tunables, which 5233 * may be necessary for different workloads: 5234 * 5235 * l2arc_write_max max write bytes per interval 5236 * l2arc_write_boost extra write bytes during device warmup 5237 * l2arc_noprefetch skip caching prefetched buffers 5238 * l2arc_headroom number of max device writes to precache 5239 * l2arc_headroom_boost when we find compressed buffers during ARC 5240 * scanning, we multiply headroom by this 5241 * percentage factor for the next scan cycle, 5242 * since more compressed buffers are likely to 5243 * be present 5244 * l2arc_feed_secs seconds between L2ARC writing 5245 * 5246 * Tunables may be removed or added as future performance improvements are 5247 * integrated, and also may become zpool properties. 5248 * 5249 * There are three key functions that control how the L2ARC warms up: 5250 * 5251 * l2arc_write_eligible() check if a buffer is eligible to cache 5252 * l2arc_write_size() calculate how much to write 5253 * l2arc_write_interval() calculate sleep delay between writes 5254 * 5255 * These three functions determine what to write, how much, and how quickly 5256 * to send writes. 5257 */ 5258 5259static boolean_t 5260l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 5261{ 5262 /* 5263 * A buffer is *not* eligible for the L2ARC if it: 5264 * 1. belongs to a different spa. 5265 * 2. is already cached on the L2ARC. 5266 * 3. has an I/O in progress (it may be an incomplete read). 5267 * 4. is flagged not eligible (zfs property). 5268 */ 5269 if (hdr->b_spa != spa_guid) { 5270 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 5271 return (B_FALSE); 5272 } 5273 if (HDR_HAS_L2HDR(hdr)) { 5274 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 5275 return (B_FALSE); 5276 } 5277 if (HDR_IO_IN_PROGRESS(hdr)) { 5278 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 5279 return (B_FALSE); 5280 } 5281 if (!HDR_L2CACHE(hdr)) { 5282 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 5283 return (B_FALSE); 5284 } 5285 5286 return (B_TRUE); 5287} 5288 5289static uint64_t 5290l2arc_write_size(void) 5291{ 5292 uint64_t size; 5293 5294 /* 5295 * Make sure our globals have meaningful values in case the user 5296 * altered them. 5297 */ 5298 size = l2arc_write_max; 5299 if (size == 0) { 5300 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 5301 "be greater than zero, resetting it to the default (%d)", 5302 L2ARC_WRITE_SIZE); 5303 size = l2arc_write_max = L2ARC_WRITE_SIZE; 5304 } 5305 5306 if (arc_warm == B_FALSE) 5307 size += l2arc_write_boost; 5308 5309 return (size); 5310 5311} 5312 5313static clock_t 5314l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 5315{ 5316 clock_t interval, next, now; 5317 5318 /* 5319 * If the ARC lists are busy, increase our write rate; if the 5320 * lists are stale, idle back. This is achieved by checking 5321 * how much we previously wrote - if it was more than half of 5322 * what we wanted, schedule the next write much sooner. 5323 */ 5324 if (l2arc_feed_again && wrote > (wanted / 2)) 5325 interval = (hz * l2arc_feed_min_ms) / 1000; 5326 else 5327 interval = hz * l2arc_feed_secs; 5328 5329 now = ddi_get_lbolt(); 5330 next = MAX(now, MIN(now + interval, began + interval)); 5331 5332 return (next); 5333} 5334 5335/* 5336 * Cycle through L2ARC devices. This is how L2ARC load balances. 5337 * If a device is returned, this also returns holding the spa config lock. 5338 */ 5339static l2arc_dev_t * 5340l2arc_dev_get_next(void) 5341{ 5342 l2arc_dev_t *first, *next = NULL; 5343 5344 /* 5345 * Lock out the removal of spas (spa_namespace_lock), then removal 5346 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 5347 * both locks will be dropped and a spa config lock held instead. 5348 */ 5349 mutex_enter(&spa_namespace_lock); 5350 mutex_enter(&l2arc_dev_mtx); 5351 5352 /* if there are no vdevs, there is nothing to do */ 5353 if (l2arc_ndev == 0) 5354 goto out; 5355 5356 first = NULL; 5357 next = l2arc_dev_last; 5358 do { 5359 /* loop around the list looking for a non-faulted vdev */ 5360 if (next == NULL) { 5361 next = list_head(l2arc_dev_list); 5362 } else { 5363 next = list_next(l2arc_dev_list, next); 5364 if (next == NULL) 5365 next = list_head(l2arc_dev_list); 5366 } 5367 5368 /* if we have come back to the start, bail out */ 5369 if (first == NULL) 5370 first = next; 5371 else if (next == first) 5372 break; 5373 5374 } while (vdev_is_dead(next->l2ad_vdev)); 5375 5376 /* if we were unable to find any usable vdevs, return NULL */ 5377 if (vdev_is_dead(next->l2ad_vdev)) 5378 next = NULL; 5379 5380 l2arc_dev_last = next; 5381 5382out: 5383 mutex_exit(&l2arc_dev_mtx); 5384 5385 /* 5386 * Grab the config lock to prevent the 'next' device from being 5387 * removed while we are writing to it. 5388 */ 5389 if (next != NULL) 5390 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 5391 mutex_exit(&spa_namespace_lock); 5392 5393 return (next); 5394} 5395 5396/* 5397 * Free buffers that were tagged for destruction. 5398 */ 5399static void 5400l2arc_do_free_on_write() 5401{ 5402 list_t *buflist; 5403 l2arc_data_free_t *df, *df_prev; 5404 5405 mutex_enter(&l2arc_free_on_write_mtx); 5406 buflist = l2arc_free_on_write; 5407 5408 for (df = list_tail(buflist); df; df = df_prev) { 5409 df_prev = list_prev(buflist, df); 5410 ASSERT(df->l2df_data != NULL); 5411 ASSERT(df->l2df_func != NULL); 5412 df->l2df_func(df->l2df_data, df->l2df_size); 5413 list_remove(buflist, df); 5414 kmem_free(df, sizeof (l2arc_data_free_t)); 5415 } 5416 5417 mutex_exit(&l2arc_free_on_write_mtx); 5418} 5419 5420/* 5421 * A write to a cache device has completed. Update all headers to allow 5422 * reads from these buffers to begin. 5423 */ 5424static void 5425l2arc_write_done(zio_t *zio) 5426{ 5427 l2arc_write_callback_t *cb; 5428 l2arc_dev_t *dev; 5429 list_t *buflist; 5430 arc_buf_hdr_t *head, *hdr, *hdr_prev; 5431 kmutex_t *hash_lock; 5432 int64_t bytes_dropped = 0; 5433 5434 cb = zio->io_private; 5435 ASSERT(cb != NULL); 5436 dev = cb->l2wcb_dev; 5437 ASSERT(dev != NULL); 5438 head = cb->l2wcb_head; 5439 ASSERT(head != NULL); 5440 buflist = &dev->l2ad_buflist; 5441 ASSERT(buflist != NULL); 5442 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 5443 l2arc_write_callback_t *, cb); 5444 5445 if (zio->io_error != 0) 5446 ARCSTAT_BUMP(arcstat_l2_writes_error); 5447 5448 mutex_enter(&dev->l2ad_mtx); 5449 5450 /* 5451 * All writes completed, or an error was hit. 5452 */ 5453 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 5454 hdr_prev = list_prev(buflist, hdr); 5455 5456 hash_lock = HDR_LOCK(hdr); 5457 if (!mutex_tryenter(hash_lock)) { 5458 /* 5459 * This buffer misses out. It may be in a stage 5460 * of eviction. Its ARC_FLAG_L2_WRITING flag will be 5461 * left set, denying reads to this buffer. 5462 */ 5463 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss); 5464 continue; 5465 } 5466 5467 /* 5468 * It's possible that this buffer got evicted from the L1 cache 5469 * before we grabbed the vdev + hash locks, in which case 5470 * arc_hdr_realloc freed b_tmp_cdata for us if it was allocated. 5471 * Only free the buffer if we still have an L1 hdr. 5472 */ 5473 if (HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_tmp_cdata != NULL && 5474 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 5475 l2arc_release_cdata_buf(hdr); 5476 5477 if (zio->io_error != 0) { 5478 /* 5479 * Error - drop L2ARC entry. 5480 */ 5481 trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev, 5482 hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0); 5483 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR; 5484 5485 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize); 5486 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); 5487 5488 bytes_dropped += hdr->b_l2hdr.b_asize; 5489 (void) refcount_remove_many(&dev->l2ad_alloc, 5490 hdr->b_l2hdr.b_asize, hdr); 5491 } 5492 5493 /* 5494 * Allow ARC to begin reads to this L2ARC entry. 5495 */ 5496 hdr->b_flags &= ~ARC_FLAG_L2_WRITING; 5497 5498 mutex_exit(hash_lock); 5499 } 5500 5501 atomic_inc_64(&l2arc_writes_done); 5502 list_remove(buflist, head); 5503 ASSERT(!HDR_HAS_L1HDR(head)); 5504 kmem_cache_free(hdr_l2only_cache, head); 5505 mutex_exit(&dev->l2ad_mtx); 5506 5507 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 5508 5509 l2arc_do_free_on_write(); 5510 5511 kmem_free(cb, sizeof (l2arc_write_callback_t)); 5512} 5513 5514/* 5515 * A read to a cache device completed. Validate buffer contents before 5516 * handing over to the regular ARC routines. 5517 */ 5518static void 5519l2arc_read_done(zio_t *zio) 5520{ 5521 l2arc_read_callback_t *cb; 5522 arc_buf_hdr_t *hdr; 5523 arc_buf_t *buf; 5524 kmutex_t *hash_lock; 5525 int equal; 5526 5527 ASSERT(zio->io_vd != NULL); 5528 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 5529 5530 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 5531 5532 cb = zio->io_private; 5533 ASSERT(cb != NULL); 5534 buf = cb->l2rcb_buf; 5535 ASSERT(buf != NULL); 5536 5537 hash_lock = HDR_LOCK(buf->b_hdr); 5538 mutex_enter(hash_lock); 5539 hdr = buf->b_hdr; 5540 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5541 5542 /* 5543 * If the buffer was compressed, decompress it first. 5544 */ 5545 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF) 5546 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress); 5547 ASSERT(zio->io_data != NULL); 5548 5549 /* 5550 * Check this survived the L2ARC journey. 5551 */ 5552 equal = arc_cksum_equal(buf); 5553 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 5554 mutex_exit(hash_lock); 5555 zio->io_private = buf; 5556 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 5557 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 5558 arc_read_done(zio); 5559 } else { 5560 mutex_exit(hash_lock); 5561 /* 5562 * Buffer didn't survive caching. Increment stats and 5563 * reissue to the original storage device. 5564 */ 5565 if (zio->io_error != 0) { 5566 ARCSTAT_BUMP(arcstat_l2_io_error); 5567 } else { 5568 zio->io_error = SET_ERROR(EIO); 5569 } 5570 if (!equal) 5571 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 5572 5573 /* 5574 * If there's no waiter, issue an async i/o to the primary 5575 * storage now. If there *is* a waiter, the caller must 5576 * issue the i/o in a context where it's OK to block. 5577 */ 5578 if (zio->io_waiter == NULL) { 5579 zio_t *pio = zio_unique_parent(zio); 5580 5581 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 5582 5583 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp, 5584 buf->b_data, zio->io_size, arc_read_done, buf, 5585 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb)); 5586 } 5587 } 5588 5589 kmem_free(cb, sizeof (l2arc_read_callback_t)); 5590} 5591 5592/* 5593 * This is the list priority from which the L2ARC will search for pages to 5594 * cache. This is used within loops (0..3) to cycle through lists in the 5595 * desired order. This order can have a significant effect on cache 5596 * performance. 5597 * 5598 * Currently the metadata lists are hit first, MFU then MRU, followed by 5599 * the data lists. This function returns a locked list, and also returns 5600 * the lock pointer. 5601 */ 5602static list_t * 5603l2arc_list_locked(int list_num, kmutex_t **lock) 5604{ 5605 list_t *list = NULL; 5606 int idx; 5607 5608 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS); 5609 5610 if (list_num < ARC_BUFC_NUMMETADATALISTS) { 5611 idx = list_num; 5612 list = &arc_mfu->arcs_lists[idx]; 5613 *lock = ARCS_LOCK(arc_mfu, idx); 5614 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) { 5615 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 5616 list = &arc_mru->arcs_lists[idx]; 5617 *lock = ARCS_LOCK(arc_mru, idx); 5618 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 + 5619 ARC_BUFC_NUMDATALISTS)) { 5620 idx = list_num - ARC_BUFC_NUMMETADATALISTS; 5621 list = &arc_mfu->arcs_lists[idx]; 5622 *lock = ARCS_LOCK(arc_mfu, idx); 5623 } else { 5624 idx = list_num - ARC_BUFC_NUMLISTS; 5625 list = &arc_mru->arcs_lists[idx]; 5626 *lock = ARCS_LOCK(arc_mru, idx); 5627 } 5628 5629 ASSERT(!(MUTEX_HELD(*lock))); 5630 mutex_enter(*lock); 5631 return (list); 5632} 5633 5634/* 5635 * Evict buffers from the device write hand to the distance specified in 5636 * bytes. This distance may span populated buffers, it may span nothing. 5637 * This is clearing a region on the L2ARC device ready for writing. 5638 * If the 'all' boolean is set, every buffer is evicted. 5639 */ 5640static void 5641l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 5642{ 5643 list_t *buflist; 5644 arc_buf_hdr_t *hdr, *hdr_prev; 5645 kmutex_t *hash_lock; 5646 uint64_t taddr; 5647 5648 buflist = &dev->l2ad_buflist; 5649 5650 if (!all && dev->l2ad_first) { 5651 /* 5652 * This is the first sweep through the device. There is 5653 * nothing to evict. 5654 */ 5655 return; 5656 } 5657 5658 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 5659 /* 5660 * When nearing the end of the device, evict to the end 5661 * before the device write hand jumps to the start. 5662 */ 5663 taddr = dev->l2ad_end; 5664 } else { 5665 taddr = dev->l2ad_hand + distance; 5666 } 5667 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 5668 uint64_t, taddr, boolean_t, all); 5669 5670top: 5671 mutex_enter(&dev->l2ad_mtx); 5672 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 5673 hdr_prev = list_prev(buflist, hdr); 5674 5675 hash_lock = HDR_LOCK(hdr); 5676 if (!mutex_tryenter(hash_lock)) { 5677 /* 5678 * Missed the hash lock. Retry. 5679 */ 5680 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 5681 mutex_exit(&dev->l2ad_mtx); 5682 mutex_enter(hash_lock); 5683 mutex_exit(hash_lock); 5684 goto top; 5685 } 5686 5687 if (HDR_L2_WRITE_HEAD(hdr)) { 5688 /* 5689 * We hit a write head node. Leave it for 5690 * l2arc_write_done(). 5691 */ 5692 list_remove(buflist, hdr); 5693 mutex_exit(hash_lock); 5694 continue; 5695 } 5696 5697 if (!all && HDR_HAS_L2HDR(hdr) && 5698 (hdr->b_l2hdr.b_daddr > taddr || 5699 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 5700 /* 5701 * We've evicted to the target address, 5702 * or the end of the device. 5703 */ 5704 mutex_exit(hash_lock); 5705 break; 5706 } 5707 5708 ASSERT(HDR_HAS_L2HDR(hdr)); 5709 if (!HDR_HAS_L1HDR(hdr)) { 5710 ASSERT(!HDR_L2_READING(hdr)); 5711 /* 5712 * This doesn't exist in the ARC. Destroy. 5713 * arc_hdr_destroy() will call list_remove() 5714 * and decrement arcstat_l2_size. 5715 */ 5716 arc_change_state(arc_anon, hdr, hash_lock); 5717 arc_hdr_destroy(hdr); 5718 } else { 5719 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 5720 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 5721 /* 5722 * Invalidate issued or about to be issued 5723 * reads, since we may be about to write 5724 * over this location. 5725 */ 5726 if (HDR_L2_READING(hdr)) { 5727 ARCSTAT_BUMP(arcstat_l2_evict_reading); 5728 hdr->b_flags |= ARC_FLAG_L2_EVICTED; 5729 } 5730 5731 arc_hdr_l2hdr_destroy(hdr); 5732 } 5733 mutex_exit(hash_lock); 5734 } 5735 mutex_exit(&dev->l2ad_mtx); 5736} 5737 5738/* 5739 * Find and write ARC buffers to the L2ARC device. 5740 * 5741 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 5742 * for reading until they have completed writing. 5743 * The headroom_boost is an in-out parameter used to maintain headroom boost 5744 * state between calls to this function. 5745 * 5746 * Returns the number of bytes actually written (which may be smaller than 5747 * the delta by which the device hand has changed due to alignment). 5748 */ 5749static uint64_t 5750l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz, 5751 boolean_t *headroom_boost) 5752{ 5753 arc_buf_hdr_t *hdr, *hdr_prev, *head; 5754 list_t *list; 5755 uint64_t write_asize, write_psize, write_sz, headroom, 5756 buf_compress_minsz; 5757 void *buf_data; 5758 kmutex_t *list_lock; 5759 boolean_t full; 5760 l2arc_write_callback_t *cb; 5761 zio_t *pio, *wzio; 5762 uint64_t guid = spa_load_guid(spa); 5763 const boolean_t do_headroom_boost = *headroom_boost; 5764 int try; 5765 5766 ASSERT(dev->l2ad_vdev != NULL); 5767 5768 /* Lower the flag now, we might want to raise it again later. */ 5769 *headroom_boost = B_FALSE; 5770 5771 pio = NULL; 5772 write_sz = write_asize = write_psize = 0; 5773 full = B_FALSE; 5774 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 5775 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD; 5776 head->b_flags |= ARC_FLAG_HAS_L2HDR; 5777 5778 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 5779 /* 5780 * We will want to try to compress buffers that are at least 2x the 5781 * device sector size. 5782 */ 5783 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift; 5784 5785 /* 5786 * Copy buffers for L2ARC writing. 5787 */ 5788 mutex_enter(&dev->l2ad_mtx); 5789 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) { 5790 uint64_t passed_sz = 0; 5791 5792 list = l2arc_list_locked(try, &list_lock); 5793 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 5794 5795 /* 5796 * L2ARC fast warmup. 5797 * 5798 * Until the ARC is warm and starts to evict, read from the 5799 * head of the ARC lists rather than the tail. 5800 */ 5801 if (arc_warm == B_FALSE) 5802 hdr = list_head(list); 5803 else 5804 hdr = list_tail(list); 5805 if (hdr == NULL) 5806 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 5807 5808 headroom = target_sz * l2arc_headroom * 2 / ARC_BUFC_NUMLISTS; 5809 if (do_headroom_boost) 5810 headroom = (headroom * l2arc_headroom_boost) / 100; 5811 5812 for (; hdr; hdr = hdr_prev) { 5813 kmutex_t *hash_lock; 5814 uint64_t buf_sz; 5815 5816 if (arc_warm == B_FALSE) 5817 hdr_prev = list_next(list, hdr); 5818 else 5819 hdr_prev = list_prev(list, hdr); 5820 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, hdr->b_size); 5821 5822 hash_lock = HDR_LOCK(hdr); 5823 if (!mutex_tryenter(hash_lock)) { 5824 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 5825 /* 5826 * Skip this buffer rather than waiting. 5827 */ 5828 continue; 5829 } 5830 5831 passed_sz += hdr->b_size; 5832 if (passed_sz > headroom) { 5833 /* 5834 * Searched too far. 5835 */ 5836 mutex_exit(hash_lock); 5837 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 5838 break; 5839 } 5840 5841 if (!l2arc_write_eligible(guid, hdr)) { 5842 mutex_exit(hash_lock); 5843 continue; 5844 } 5845 5846 if ((write_sz + hdr->b_size) > target_sz) { 5847 full = B_TRUE; 5848 mutex_exit(hash_lock); 5849 ARCSTAT_BUMP(arcstat_l2_write_full); 5850 break; 5851 } 5852 5853 if (pio == NULL) { 5854 /* 5855 * Insert a dummy header on the buflist so 5856 * l2arc_write_done() can find where the 5857 * write buffers begin without searching. 5858 */ 5859 list_insert_head(&dev->l2ad_buflist, head); 5860 5861 cb = kmem_alloc( 5862 sizeof (l2arc_write_callback_t), KM_SLEEP); 5863 cb->l2wcb_dev = dev; 5864 cb->l2wcb_head = head; 5865 pio = zio_root(spa, l2arc_write_done, cb, 5866 ZIO_FLAG_CANFAIL); 5867 ARCSTAT_BUMP(arcstat_l2_write_pios); 5868 } 5869 5870 /* 5871 * Create and add a new L2ARC header. 5872 */ 5873 hdr->b_l2hdr.b_dev = dev; 5874 hdr->b_flags |= ARC_FLAG_L2_WRITING; 5875 /* 5876 * Temporarily stash the data buffer in b_tmp_cdata. 5877 * The subsequent write step will pick it up from 5878 * there. This is because can't access b_l1hdr.b_buf 5879 * without holding the hash_lock, which we in turn 5880 * can't access without holding the ARC list locks 5881 * (which we want to avoid during compression/writing). 5882 */ 5883 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 5884 hdr->b_l2hdr.b_asize = hdr->b_size; 5885 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data; 5886 5887 /* 5888 * Explicitly set the b_daddr field to a known 5889 * value which means "invalid address". This 5890 * enables us to differentiate which stage of 5891 * l2arc_write_buffers() the particular header 5892 * is in (e.g. this loop, or the one below). 5893 * ARC_FLAG_L2_WRITING is not enough to make 5894 * this distinction, and we need to know in 5895 * order to do proper l2arc vdev accounting in 5896 * arc_release() and arc_hdr_destroy(). 5897 * 5898 * Note, we can't use a new flag to distinguish 5899 * the two stages because we don't hold the 5900 * header's hash_lock below, in the second stage 5901 * of this function. Thus, we can't simply 5902 * change the b_flags field to denote that the 5903 * IO has been sent. We can change the b_daddr 5904 * field of the L2 portion, though, since we'll 5905 * be holding the l2ad_mtx; which is why we're 5906 * using it to denote the header's state change. 5907 */ 5908 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET; 5909 5910 buf_sz = hdr->b_size; 5911 hdr->b_flags |= ARC_FLAG_HAS_L2HDR; 5912 5913 list_insert_head(&dev->l2ad_buflist, hdr); 5914 5915 /* 5916 * Compute and store the buffer cksum before 5917 * writing. On debug the cksum is verified first. 5918 */ 5919 arc_cksum_verify(hdr->b_l1hdr.b_buf); 5920 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE); 5921 5922 mutex_exit(hash_lock); 5923 5924 write_sz += buf_sz; 5925 } 5926 5927 mutex_exit(list_lock); 5928 5929 if (full == B_TRUE) 5930 break; 5931 } 5932 5933 /* No buffers selected for writing? */ 5934 if (pio == NULL) { 5935 ASSERT0(write_sz); 5936 mutex_exit(&dev->l2ad_mtx); 5937 ASSERT(!HDR_HAS_L1HDR(head)); 5938 kmem_cache_free(hdr_l2only_cache, head); 5939 return (0); 5940 } 5941 5942 /* 5943 * Now start writing the buffers. We're starting at the write head 5944 * and work backwards, retracing the course of the buffer selector 5945 * loop above. 5946 */ 5947 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr; 5948 hdr = list_prev(&dev->l2ad_buflist, hdr)) { 5949 uint64_t buf_sz; 5950 5951 /* 5952 * We shouldn't need to lock the buffer here, since we flagged 5953 * it as ARC_FLAG_L2_WRITING in the previous step, but we must 5954 * take care to only access its L2 cache parameters. In 5955 * particular, hdr->l1hdr.b_buf may be invalid by now due to 5956 * ARC eviction. 5957 */ 5958 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 5959 5960 if ((HDR_L2COMPRESS(hdr)) && 5961 hdr->b_l2hdr.b_asize >= buf_compress_minsz) { 5962 if (l2arc_compress_buf(hdr)) { 5963 /* 5964 * If compression succeeded, enable headroom 5965 * boost on the next scan cycle. 5966 */ 5967 *headroom_boost = B_TRUE; 5968 } 5969 } 5970 5971 /* 5972 * Pick up the buffer data we had previously stashed away 5973 * (and now potentially also compressed). 5974 */ 5975 buf_data = hdr->b_l1hdr.b_tmp_cdata; 5976 buf_sz = hdr->b_l2hdr.b_asize; 5977 5978 /* 5979 * If the data has not been compressed, then clear b_tmp_cdata 5980 * to make sure that it points only to a temporary compression 5981 * buffer. 5982 */ 5983 if (!L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr))) 5984 hdr->b_l1hdr.b_tmp_cdata = NULL; 5985 5986 /* 5987 * We need to do this regardless if buf_sz is zero or 5988 * not, otherwise, when this l2hdr is evicted we'll 5989 * remove a reference that was never added. 5990 */ 5991 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr); 5992 5993 /* Compression may have squashed the buffer to zero length. */ 5994 if (buf_sz != 0) { 5995 uint64_t buf_p_sz; 5996 5997 wzio = zio_write_phys(pio, dev->l2ad_vdev, 5998 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF, 5999 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE, 6000 ZIO_FLAG_CANFAIL, B_FALSE); 6001 6002 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 6003 zio_t *, wzio); 6004 (void) zio_nowait(wzio); 6005 6006 write_asize += buf_sz; 6007 6008 /* 6009 * Keep the clock hand suitably device-aligned. 6010 */ 6011 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz); 6012 write_psize += buf_p_sz; 6013 dev->l2ad_hand += buf_p_sz; 6014 } 6015 } 6016 6017 mutex_exit(&dev->l2ad_mtx); 6018 6019 ASSERT3U(write_asize, <=, target_sz); 6020 ARCSTAT_BUMP(arcstat_l2_writes_sent); 6021 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 6022 ARCSTAT_INCR(arcstat_l2_size, write_sz); 6023 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 6024 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 6025 6026 /* 6027 * Bump device hand to the device start if it is approaching the end. 6028 * l2arc_evict() will already have evicted ahead for this case. 6029 */ 6030 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 6031 dev->l2ad_hand = dev->l2ad_start; 6032 dev->l2ad_first = B_FALSE; 6033 } 6034 6035 dev->l2ad_writing = B_TRUE; 6036 (void) zio_wait(pio); 6037 dev->l2ad_writing = B_FALSE; 6038 6039 return (write_asize); 6040} 6041 6042/* 6043 * Compresses an L2ARC buffer. 6044 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its 6045 * size in l2hdr->b_asize. This routine tries to compress the data and 6046 * depending on the compression result there are three possible outcomes: 6047 * *) The buffer was incompressible. The original l2hdr contents were left 6048 * untouched and are ready for writing to an L2 device. 6049 * *) The buffer was all-zeros, so there is no need to write it to an L2 6050 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is 6051 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY. 6052 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary 6053 * data buffer which holds the compressed data to be written, and b_asize 6054 * tells us how much data there is. b_compress is set to the appropriate 6055 * compression algorithm. Once writing is done, invoke 6056 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer. 6057 * 6058 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the 6059 * buffer was incompressible). 6060 */ 6061static boolean_t 6062l2arc_compress_buf(arc_buf_hdr_t *hdr) 6063{ 6064 void *cdata; 6065 size_t csize, len, rounded; 6066 ASSERT(HDR_HAS_L2HDR(hdr)); 6067 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 6068 6069 ASSERT(HDR_HAS_L1HDR(hdr)); 6070 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF); 6071 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6072 6073 len = l2hdr->b_asize; 6074 cdata = zio_data_buf_alloc(len); 6075 ASSERT3P(cdata, !=, NULL); 6076 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata, 6077 cdata, l2hdr->b_asize); 6078 6079 if (csize == 0) { 6080 /* zero block, indicate that there's nothing to write */ 6081 zio_data_buf_free(cdata, len); 6082 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY); 6083 l2hdr->b_asize = 0; 6084 hdr->b_l1hdr.b_tmp_cdata = NULL; 6085 ARCSTAT_BUMP(arcstat_l2_compress_zeros); 6086 return (B_TRUE); 6087 } 6088 6089 rounded = P2ROUNDUP(csize, 6090 (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift); 6091 if (rounded < len) { 6092 /* 6093 * Compression succeeded, we'll keep the cdata around for 6094 * writing and release it afterwards. 6095 */ 6096 if (rounded > csize) { 6097 bzero((char *)cdata + csize, rounded - csize); 6098 csize = rounded; 6099 } 6100 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4); 6101 l2hdr->b_asize = csize; 6102 hdr->b_l1hdr.b_tmp_cdata = cdata; 6103 ARCSTAT_BUMP(arcstat_l2_compress_successes); 6104 return (B_TRUE); 6105 } else { 6106 /* 6107 * Compression failed, release the compressed buffer. 6108 * l2hdr will be left unmodified. 6109 */ 6110 zio_data_buf_free(cdata, len); 6111 ARCSTAT_BUMP(arcstat_l2_compress_failures); 6112 return (B_FALSE); 6113 } 6114} 6115 6116/* 6117 * Decompresses a zio read back from an l2arc device. On success, the 6118 * underlying zio's io_data buffer is overwritten by the uncompressed 6119 * version. On decompression error (corrupt compressed stream), the 6120 * zio->io_error value is set to signal an I/O error. 6121 * 6122 * Please note that the compressed data stream is not checksummed, so 6123 * if the underlying device is experiencing data corruption, we may feed 6124 * corrupt data to the decompressor, so the decompressor needs to be 6125 * able to handle this situation (LZ4 does). 6126 */ 6127static void 6128l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c) 6129{ 6130 ASSERT(L2ARC_IS_VALID_COMPRESS(c)); 6131 6132 if (zio->io_error != 0) { 6133 /* 6134 * An io error has occured, just restore the original io 6135 * size in preparation for a main pool read. 6136 */ 6137 zio->io_orig_size = zio->io_size = hdr->b_size; 6138 return; 6139 } 6140 6141 if (c == ZIO_COMPRESS_EMPTY) { 6142 /* 6143 * An empty buffer results in a null zio, which means we 6144 * need to fill its io_data after we're done restoring the 6145 * buffer's contents. 6146 */ 6147 ASSERT(hdr->b_l1hdr.b_buf != NULL); 6148 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size); 6149 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data; 6150 } else { 6151 ASSERT(zio->io_data != NULL); 6152 /* 6153 * We copy the compressed data from the start of the arc buffer 6154 * (the zio_read will have pulled in only what we need, the 6155 * rest is garbage which we will overwrite at decompression) 6156 * and then decompress back to the ARC data buffer. This way we 6157 * can minimize copying by simply decompressing back over the 6158 * original compressed data (rather than decompressing to an 6159 * aux buffer and then copying back the uncompressed buffer, 6160 * which is likely to be much larger). 6161 */ 6162 uint64_t csize; 6163 void *cdata; 6164 6165 csize = zio->io_size; 6166 cdata = zio_data_buf_alloc(csize); 6167 bcopy(zio->io_data, cdata, csize); 6168 if (zio_decompress_data(c, cdata, zio->io_data, csize, 6169 hdr->b_size) != 0) 6170 zio->io_error = EIO; 6171 zio_data_buf_free(cdata, csize); 6172 } 6173 6174 /* Restore the expected uncompressed IO size. */ 6175 zio->io_orig_size = zio->io_size = hdr->b_size; 6176} 6177 6178/* 6179 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure. 6180 * This buffer serves as a temporary holder of compressed data while 6181 * the buffer entry is being written to an l2arc device. Once that is 6182 * done, we can dispose of it. 6183 */ 6184static void 6185l2arc_release_cdata_buf(arc_buf_hdr_t *hdr) 6186{ 6187 ASSERT(HDR_HAS_L1HDR(hdr)); 6188 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_EMPTY) { 6189 /* 6190 * If the data was compressed, then we've allocated a 6191 * temporary buffer for it, so now we need to release it. 6192 */ 6193 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL); 6194 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata, 6195 hdr->b_size); 6196 hdr->b_l1hdr.b_tmp_cdata = NULL; 6197 } else { 6198 ASSERT(hdr->b_l1hdr.b_tmp_cdata == NULL); 6199 } 6200} 6201 6202/* 6203 * This thread feeds the L2ARC at regular intervals. This is the beating 6204 * heart of the L2ARC. 6205 */ 6206static void 6207l2arc_feed_thread(void *dummy __unused) 6208{ 6209 callb_cpr_t cpr; 6210 l2arc_dev_t *dev; 6211 spa_t *spa; 6212 uint64_t size, wrote; 6213 clock_t begin, next = ddi_get_lbolt(); 6214 boolean_t headroom_boost = B_FALSE; 6215 6216 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 6217 6218 mutex_enter(&l2arc_feed_thr_lock); 6219 6220 while (l2arc_thread_exit == 0) { 6221 CALLB_CPR_SAFE_BEGIN(&cpr); 6222 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 6223 next - ddi_get_lbolt()); 6224 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 6225 next = ddi_get_lbolt() + hz; 6226 6227 /* 6228 * Quick check for L2ARC devices. 6229 */ 6230 mutex_enter(&l2arc_dev_mtx); 6231 if (l2arc_ndev == 0) { 6232 mutex_exit(&l2arc_dev_mtx); 6233 continue; 6234 } 6235 mutex_exit(&l2arc_dev_mtx); 6236 begin = ddi_get_lbolt(); 6237 6238 /* 6239 * This selects the next l2arc device to write to, and in 6240 * doing so the next spa to feed from: dev->l2ad_spa. This 6241 * will return NULL if there are now no l2arc devices or if 6242 * they are all faulted. 6243 * 6244 * If a device is returned, its spa's config lock is also 6245 * held to prevent device removal. l2arc_dev_get_next() 6246 * will grab and release l2arc_dev_mtx. 6247 */ 6248 if ((dev = l2arc_dev_get_next()) == NULL) 6249 continue; 6250 6251 spa = dev->l2ad_spa; 6252 ASSERT(spa != NULL); 6253 6254 /* 6255 * If the pool is read-only then force the feed thread to 6256 * sleep a little longer. 6257 */ 6258 if (!spa_writeable(spa)) { 6259 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 6260 spa_config_exit(spa, SCL_L2ARC, dev); 6261 continue; 6262 } 6263 6264 /* 6265 * Avoid contributing to memory pressure. 6266 */ 6267 if (arc_reclaim_needed()) { 6268 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 6269 spa_config_exit(spa, SCL_L2ARC, dev); 6270 continue; 6271 } 6272 6273 ARCSTAT_BUMP(arcstat_l2_feeds); 6274 6275 size = l2arc_write_size(); 6276 6277 /* 6278 * Evict L2ARC buffers that will be overwritten. 6279 */ 6280 l2arc_evict(dev, size, B_FALSE); 6281 6282 /* 6283 * Write ARC buffers. 6284 */ 6285 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost); 6286 6287 /* 6288 * Calculate interval between writes. 6289 */ 6290 next = l2arc_write_interval(begin, size, wrote); 6291 spa_config_exit(spa, SCL_L2ARC, dev); 6292 } 6293 6294 l2arc_thread_exit = 0; 6295 cv_broadcast(&l2arc_feed_thr_cv); 6296 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 6297 thread_exit(); 6298} 6299 6300boolean_t 6301l2arc_vdev_present(vdev_t *vd) 6302{ 6303 l2arc_dev_t *dev; 6304 6305 mutex_enter(&l2arc_dev_mtx); 6306 for (dev = list_head(l2arc_dev_list); dev != NULL; 6307 dev = list_next(l2arc_dev_list, dev)) { 6308 if (dev->l2ad_vdev == vd) 6309 break; 6310 } 6311 mutex_exit(&l2arc_dev_mtx); 6312 6313 return (dev != NULL); 6314} 6315 6316/* 6317 * Add a vdev for use by the L2ARC. By this point the spa has already 6318 * validated the vdev and opened it. 6319 */ 6320void 6321l2arc_add_vdev(spa_t *spa, vdev_t *vd) 6322{ 6323 l2arc_dev_t *adddev; 6324 6325 ASSERT(!l2arc_vdev_present(vd)); 6326 6327 vdev_ashift_optimize(vd); 6328 6329 /* 6330 * Create a new l2arc device entry. 6331 */ 6332 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 6333 adddev->l2ad_spa = spa; 6334 adddev->l2ad_vdev = vd; 6335 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 6336 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 6337 adddev->l2ad_hand = adddev->l2ad_start; 6338 adddev->l2ad_first = B_TRUE; 6339 adddev->l2ad_writing = B_FALSE; 6340 6341 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 6342 /* 6343 * This is a list of all ARC buffers that are still valid on the 6344 * device. 6345 */ 6346 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 6347 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 6348 6349 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 6350 refcount_create(&adddev->l2ad_alloc); 6351 6352 /* 6353 * Add device to global list 6354 */ 6355 mutex_enter(&l2arc_dev_mtx); 6356 list_insert_head(l2arc_dev_list, adddev); 6357 atomic_inc_64(&l2arc_ndev); 6358 mutex_exit(&l2arc_dev_mtx); 6359} 6360 6361/* 6362 * Remove a vdev from the L2ARC. 6363 */ 6364void 6365l2arc_remove_vdev(vdev_t *vd) 6366{ 6367 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 6368 6369 /* 6370 * Find the device by vdev 6371 */ 6372 mutex_enter(&l2arc_dev_mtx); 6373 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 6374 nextdev = list_next(l2arc_dev_list, dev); 6375 if (vd == dev->l2ad_vdev) { 6376 remdev = dev; 6377 break; 6378 } 6379 } 6380 ASSERT(remdev != NULL); 6381 6382 /* 6383 * Remove device from global list 6384 */ 6385 list_remove(l2arc_dev_list, remdev); 6386 l2arc_dev_last = NULL; /* may have been invalidated */ 6387 atomic_dec_64(&l2arc_ndev); 6388 mutex_exit(&l2arc_dev_mtx); 6389 6390 /* 6391 * Clear all buflists and ARC references. L2ARC device flush. 6392 */ 6393 l2arc_evict(remdev, 0, B_TRUE); 6394 list_destroy(&remdev->l2ad_buflist); 6395 mutex_destroy(&remdev->l2ad_mtx); 6396 refcount_destroy(&remdev->l2ad_alloc); 6397 kmem_free(remdev, sizeof (l2arc_dev_t)); 6398} 6399 6400void 6401l2arc_init(void) 6402{ 6403 l2arc_thread_exit = 0; 6404 l2arc_ndev = 0; 6405 l2arc_writes_sent = 0; 6406 l2arc_writes_done = 0; 6407 6408 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 6409 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 6410 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 6411 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 6412 6413 l2arc_dev_list = &L2ARC_dev_list; 6414 l2arc_free_on_write = &L2ARC_free_on_write; 6415 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 6416 offsetof(l2arc_dev_t, l2ad_node)); 6417 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 6418 offsetof(l2arc_data_free_t, l2df_list_node)); 6419} 6420 6421void 6422l2arc_fini(void) 6423{ 6424 /* 6425 * This is called from dmu_fini(), which is called from spa_fini(); 6426 * Because of this, we can assume that all l2arc devices have 6427 * already been removed when the pools themselves were removed. 6428 */ 6429 6430 l2arc_do_free_on_write(); 6431 6432 mutex_destroy(&l2arc_feed_thr_lock); 6433 cv_destroy(&l2arc_feed_thr_cv); 6434 mutex_destroy(&l2arc_dev_mtx); 6435 mutex_destroy(&l2arc_free_on_write_mtx); 6436 6437 list_destroy(l2arc_dev_list); 6438 list_destroy(l2arc_free_on_write); 6439} 6440 6441void 6442l2arc_start(void) 6443{ 6444 if (!(spa_mode_global & FWRITE)) 6445 return; 6446 6447 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 6448 TS_RUN, minclsyspri); 6449} 6450 6451void 6452l2arc_stop(void) 6453{ 6454 if (!(spa_mode_global & FWRITE)) 6455 return; 6456 6457 mutex_enter(&l2arc_feed_thr_lock); 6458 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 6459 l2arc_thread_exit = 1; 6460 while (l2arc_thread_exit != 0) 6461 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 6462 mutex_exit(&l2arc_feed_thr_lock); 6463} 6464