arc.c revision 307266
1/* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21/* 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 23 * Copyright (c) 2012, Joyent, Inc. All rights reserved. 24 * Copyright (c) 2011, 2016 by Delphix. All rights reserved. 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved. 26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved. 27 */ 28 29/* 30 * DVA-based Adjustable Replacement Cache 31 * 32 * While much of the theory of operation used here is 33 * based on the self-tuning, low overhead replacement cache 34 * presented by Megiddo and Modha at FAST 2003, there are some 35 * significant differences: 36 * 37 * 1. The Megiddo and Modha model assumes any page is evictable. 38 * Pages in its cache cannot be "locked" into memory. This makes 39 * the eviction algorithm simple: evict the last page in the list. 40 * This also make the performance characteristics easy to reason 41 * about. Our cache is not so simple. At any given moment, some 42 * subset of the blocks in the cache are un-evictable because we 43 * have handed out a reference to them. Blocks are only evictable 44 * when there are no external references active. This makes 45 * eviction far more problematic: we choose to evict the evictable 46 * blocks that are the "lowest" in the list. 47 * 48 * There are times when it is not possible to evict the requested 49 * space. In these circumstances we are unable to adjust the cache 50 * size. To prevent the cache growing unbounded at these times we 51 * implement a "cache throttle" that slows the flow of new data 52 * into the cache until we can make space available. 53 * 54 * 2. The Megiddo and Modha model assumes a fixed cache size. 55 * Pages are evicted when the cache is full and there is a cache 56 * miss. Our model has a variable sized cache. It grows with 57 * high use, but also tries to react to memory pressure from the 58 * operating system: decreasing its size when system memory is 59 * tight. 60 * 61 * 3. The Megiddo and Modha model assumes a fixed page size. All 62 * elements of the cache are therefore exactly the same size. So 63 * when adjusting the cache size following a cache miss, its simply 64 * a matter of choosing a single page to evict. In our model, we 65 * have variable sized cache blocks (rangeing from 512 bytes to 66 * 128K bytes). We therefore choose a set of blocks to evict to make 67 * space for a cache miss that approximates as closely as possible 68 * the space used by the new block. 69 * 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" 71 * by N. Megiddo & D. Modha, FAST 2003 72 */ 73 74/* 75 * The locking model: 76 * 77 * A new reference to a cache buffer can be obtained in two 78 * ways: 1) via a hash table lookup using the DVA as a key, 79 * or 2) via one of the ARC lists. The arc_read() interface 80 * uses method 1, while the internal arc algorithms for 81 * adjusting the cache use method 2. We therefore provide two 82 * types of locks: 1) the hash table lock array, and 2) the 83 * arc list locks. 84 * 85 * Buffers do not have their own mutexes, rather they rely on the 86 * hash table mutexes for the bulk of their protection (i.e. most 87 * fields in the arc_buf_hdr_t are protected by these mutexes). 88 * 89 * buf_hash_find() returns the appropriate mutex (held) when it 90 * locates the requested buffer in the hash table. It returns 91 * NULL for the mutex if the buffer was not in the table. 92 * 93 * buf_hash_remove() expects the appropriate hash mutex to be 94 * already held before it is invoked. 95 * 96 * Each arc state also has a mutex which is used to protect the 97 * buffer list associated with the state. When attempting to 98 * obtain a hash table lock while holding an arc list lock you 99 * must use: mutex_tryenter() to avoid deadlock. Also note that 100 * the active state mutex must be held before the ghost state mutex. 101 * 102 * Arc buffers may have an associated eviction callback function. 103 * This function will be invoked prior to removing the buffer (e.g. 104 * in arc_do_user_evicts()). Note however that the data associated 105 * with the buffer may be evicted prior to the callback. The callback 106 * must be made with *no locks held* (to prevent deadlock). Additionally, 107 * the users of callbacks must ensure that their private data is 108 * protected from simultaneous callbacks from arc_clear_callback() 109 * and arc_do_user_evicts(). 110 * 111 * Note that the majority of the performance stats are manipulated 112 * with atomic operations. 113 * 114 * The L2ARC uses the l2ad_mtx on each vdev for the following: 115 * 116 * - L2ARC buflist creation 117 * - L2ARC buflist eviction 118 * - L2ARC write completion, which walks L2ARC buflists 119 * - ARC header destruction, as it removes from L2ARC buflists 120 * - ARC header release, as it removes from L2ARC buflists 121 */ 122 123/* 124 * ARC operation: 125 * 126 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure. 127 * This structure can point either to a block that is still in the cache or to 128 * one that is only accessible in an L2 ARC device, or it can provide 129 * information about a block that was recently evicted. If a block is 130 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough 131 * information to retrieve it from the L2ARC device. This information is 132 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block 133 * that is in this state cannot access the data directly. 134 * 135 * Blocks that are actively being referenced or have not been evicted 136 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within 137 * the arc_buf_hdr_t that will point to the data block in memory. A block can 138 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC 139 * caches data in two ways -- in a list of arc buffers (arc_buf_t) and 140 * also in the arc_buf_hdr_t's private physical data block pointer (b_pdata). 141 * Each arc buffer (arc_buf_t) is being actively accessed by a specific ARC 142 * consumer, and always contains uncompressed data. The ARC will provide 143 * references to this data and will keep it cached until it is no longer in 144 * use. Typically, the arc will try to cache only the L1ARC's physical data 145 * block and will aggressively evict any arc_buf_t that is no longer referenced. 146 * The amount of memory consumed by the arc_buf_t's can be seen via the 147 * "overhead_size" kstat. 148 * 149 * 150 * arc_buf_hdr_t 151 * +-----------+ 152 * | | 153 * | | 154 * | | 155 * +-----------+ 156 * l2arc_buf_hdr_t| | 157 * | | 158 * +-----------+ 159 * l1arc_buf_hdr_t| | 160 * | | arc_buf_t 161 * | b_buf +------------>+---------+ arc_buf_t 162 * | | |b_next +---->+---------+ 163 * | b_pdata +-+ |---------| |b_next +-->NULL 164 * +-----------+ | | | +---------+ 165 * | |b_data +-+ | | 166 * | +---------+ | |b_data +-+ 167 * +->+------+ | +---------+ | 168 * (potentially) | | | | 169 * compressed | | | | 170 * data +------+ | v 171 * +->+------+ +------+ 172 * uncompressed | | | | 173 * data | | | | 174 * +------+ +------+ 175 * 176 * The L1ARC's data pointer, however, may or may not be uncompressed. The 177 * ARC has the ability to store the physical data (b_pdata) associated with 178 * the DVA of the arc_buf_hdr_t. Since the b_pdata is a copy of the on-disk 179 * physical block, it will match its on-disk compression characteristics. 180 * If the block on-disk is compressed, then the physical data block 181 * in the cache will also be compressed and vice-versa. This behavior 182 * can be disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the 183 * compressed ARC functionality is disabled, the b_pdata will point to an 184 * uncompressed version of the on-disk data. 185 * 186 * When a consumer reads a block, the ARC must first look to see if the 187 * arc_buf_hdr_t is cached. If the hdr is cached and already has an arc_buf_t, 188 * then an additional arc_buf_t is allocated and the uncompressed data is 189 * bcopied from the existing arc_buf_t. If the hdr is cached but does not 190 * have an arc_buf_t, then the ARC allocates a new arc_buf_t and decompresses 191 * the b_pdata contents into the arc_buf_t's b_data. If the arc_buf_hdr_t's 192 * b_pdata is not compressed, then the block is shared with the newly 193 * allocated arc_buf_t. This block sharing only occurs with one arc_buf_t 194 * in the arc buffer chain. Sharing the block reduces the memory overhead 195 * required when the hdr is caching uncompressed blocks or the compressed 196 * arc functionality has been disabled via 'zfs_compressed_arc_enabled'. 197 * 198 * The diagram below shows an example of an uncompressed ARC hdr that is 199 * sharing its data with an arc_buf_t: 200 * 201 * arc_buf_hdr_t 202 * +-----------+ 203 * | | 204 * | | 205 * | | 206 * +-----------+ 207 * l2arc_buf_hdr_t| | 208 * | | 209 * +-----------+ 210 * l1arc_buf_hdr_t| | 211 * | | arc_buf_t (shared) 212 * | b_buf +------------>+---------+ arc_buf_t 213 * | | |b_next +---->+---------+ 214 * | b_pdata +-+ |---------| |b_next +-->NULL 215 * +-----------+ | | | +---------+ 216 * | |b_data +-+ | | 217 * | +---------+ | |b_data +-+ 218 * +->+------+ | +---------+ | 219 * | | | | 220 * uncompressed | | | | 221 * data +------+ | | 222 * ^ +->+------+ | 223 * | uncompressed | | | 224 * | data | | | 225 * | +------+ | 226 * +---------------------------------+ 227 * 228 * Writing to the arc requires that the ARC first discard the b_pdata 229 * since the physical block is about to be rewritten. The new data contents 230 * will be contained in the arc_buf_t (uncompressed). As the I/O pipeline 231 * performs the write, it may compress the data before writing it to disk. 232 * The ARC will be called with the transformed data and will bcopy the 233 * transformed on-disk block into a newly allocated b_pdata. 234 * 235 * When the L2ARC is in use, it will also take advantage of the b_pdata. The 236 * L2ARC will always write the contents of b_pdata to the L2ARC. This means 237 * that when compressed arc is enabled that the L2ARC blocks are identical 238 * to the on-disk block in the main data pool. This provides a significant 239 * advantage since the ARC can leverage the bp's checksum when reading from the 240 * L2ARC to determine if the contents are valid. However, if the compressed 241 * arc is disabled, then the L2ARC's block must be transformed to look 242 * like the physical block in the main data pool before comparing the 243 * checksum and determining its validity. 244 */ 245 246#include <sys/spa.h> 247#include <sys/zio.h> 248#include <sys/spa_impl.h> 249#include <sys/zio_compress.h> 250#include <sys/zio_checksum.h> 251#include <sys/zfs_context.h> 252#include <sys/arc.h> 253#include <sys/refcount.h> 254#include <sys/vdev.h> 255#include <sys/vdev_impl.h> 256#include <sys/dsl_pool.h> 257#include <sys/multilist.h> 258#ifdef _KERNEL 259#include <sys/dnlc.h> 260#endif 261#include <sys/callb.h> 262#include <sys/kstat.h> 263#include <sys/trim_map.h> 264#include <zfs_fletcher.h> 265#include <sys/sdt.h> 266 267#include <machine/vmparam.h> 268 269#ifdef illumos 270#ifndef _KERNEL 271/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 272boolean_t arc_watch = B_FALSE; 273int arc_procfd; 274#endif 275#endif /* illumos */ 276 277static kmutex_t arc_reclaim_lock; 278static kcondvar_t arc_reclaim_thread_cv; 279static boolean_t arc_reclaim_thread_exit; 280static kcondvar_t arc_reclaim_waiters_cv; 281 282uint_t arc_reduce_dnlc_percent = 3; 283 284/* 285 * The number of headers to evict in arc_evict_state_impl() before 286 * dropping the sublist lock and evicting from another sublist. A lower 287 * value means we're more likely to evict the "correct" header (i.e. the 288 * oldest header in the arc state), but comes with higher overhead 289 * (i.e. more invocations of arc_evict_state_impl()). 290 */ 291int zfs_arc_evict_batch_limit = 10; 292 293/* 294 * The number of sublists used for each of the arc state lists. If this 295 * is not set to a suitable value by the user, it will be configured to 296 * the number of CPUs on the system in arc_init(). 297 */ 298int zfs_arc_num_sublists_per_state = 0; 299 300/* number of seconds before growing cache again */ 301static int arc_grow_retry = 60; 302 303/* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 304int zfs_arc_overflow_shift = 8; 305 306/* shift of arc_c for calculating both min and max arc_p */ 307static int arc_p_min_shift = 4; 308 309/* log2(fraction of arc to reclaim) */ 310static int arc_shrink_shift = 7; 311 312/* 313 * log2(fraction of ARC which must be free to allow growing). 314 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 315 * when reading a new block into the ARC, we will evict an equal-sized block 316 * from the ARC. 317 * 318 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 319 * we will still not allow it to grow. 320 */ 321int arc_no_grow_shift = 5; 322 323 324/* 325 * minimum lifespan of a prefetch block in clock ticks 326 * (initialized in arc_init()) 327 */ 328static int arc_min_prefetch_lifespan; 329 330/* 331 * If this percent of memory is free, don't throttle. 332 */ 333int arc_lotsfree_percent = 10; 334 335static int arc_dead; 336extern boolean_t zfs_prefetch_disable; 337 338/* 339 * The arc has filled available memory and has now warmed up. 340 */ 341static boolean_t arc_warm; 342 343/* 344 * These tunables are for performance analysis. 345 */ 346uint64_t zfs_arc_max; 347uint64_t zfs_arc_min; 348uint64_t zfs_arc_meta_limit = 0; 349uint64_t zfs_arc_meta_min = 0; 350int zfs_arc_grow_retry = 0; 351int zfs_arc_shrink_shift = 0; 352int zfs_arc_p_min_shift = 0; 353uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 354u_int zfs_arc_free_target = 0; 355 356/* Absolute min for arc min / max is 16MB. */ 357static uint64_t arc_abs_min = 16 << 20; 358 359boolean_t zfs_compressed_arc_enabled = B_TRUE; 360 361static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 362static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 363static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 364static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 365 366#if defined(__FreeBSD__) && defined(_KERNEL) 367static void 368arc_free_target_init(void *unused __unused) 369{ 370 371 zfs_arc_free_target = vm_pageout_wakeup_thresh; 372} 373SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 374 arc_free_target_init, NULL); 375 376TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max); 377TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min); 378TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 379TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 380TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize); 381TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 382SYSCTL_DECL(_vfs_zfs); 383SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 384 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 385SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 386 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 387SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 388 &zfs_arc_average_blocksize, 0, 389 "ARC average blocksize"); 390SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 391 &arc_shrink_shift, 0, 392 "log2(fraction of arc to reclaim)"); 393SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 394 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC"); 395 396/* 397 * We don't have a tunable for arc_free_target due to the dependency on 398 * pagedaemon initialisation. 399 */ 400SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 401 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 402 sysctl_vfs_zfs_arc_free_target, "IU", 403 "Desired number of free pages below which ARC triggers reclaim"); 404 405static int 406sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 407{ 408 u_int val; 409 int err; 410 411 val = zfs_arc_free_target; 412 err = sysctl_handle_int(oidp, &val, 0, req); 413 if (err != 0 || req->newptr == NULL) 414 return (err); 415 416 if (val < minfree) 417 return (EINVAL); 418 if (val > cnt.v_page_count) 419 return (EINVAL); 420 421 zfs_arc_free_target = val; 422 423 return (0); 424} 425 426/* 427 * Must be declared here, before the definition of corresponding kstat 428 * macro which uses the same names will confuse the compiler. 429 */ 430SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 431 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 432 sysctl_vfs_zfs_arc_meta_limit, "QU", 433 "ARC metadata limit"); 434#endif 435 436/* 437 * Note that buffers can be in one of 6 states: 438 * ARC_anon - anonymous (discussed below) 439 * ARC_mru - recently used, currently cached 440 * ARC_mru_ghost - recentely used, no longer in cache 441 * ARC_mfu - frequently used, currently cached 442 * ARC_mfu_ghost - frequently used, no longer in cache 443 * ARC_l2c_only - exists in L2ARC but not other states 444 * When there are no active references to the buffer, they are 445 * are linked onto a list in one of these arc states. These are 446 * the only buffers that can be evicted or deleted. Within each 447 * state there are multiple lists, one for meta-data and one for 448 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 449 * etc.) is tracked separately so that it can be managed more 450 * explicitly: favored over data, limited explicitly. 451 * 452 * Anonymous buffers are buffers that are not associated with 453 * a DVA. These are buffers that hold dirty block copies 454 * before they are written to stable storage. By definition, 455 * they are "ref'd" and are considered part of arc_mru 456 * that cannot be freed. Generally, they will aquire a DVA 457 * as they are written and migrate onto the arc_mru list. 458 * 459 * The ARC_l2c_only state is for buffers that are in the second 460 * level ARC but no longer in any of the ARC_m* lists. The second 461 * level ARC itself may also contain buffers that are in any of 462 * the ARC_m* states - meaning that a buffer can exist in two 463 * places. The reason for the ARC_l2c_only state is to keep the 464 * buffer header in the hash table, so that reads that hit the 465 * second level ARC benefit from these fast lookups. 466 */ 467 468typedef struct arc_state { 469 /* 470 * list of evictable buffers 471 */ 472 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 473 /* 474 * total amount of evictable data in this state 475 */ 476 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 477 /* 478 * total amount of data in this state; this includes: evictable, 479 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 480 */ 481 refcount_t arcs_size; 482} arc_state_t; 483 484/* The 6 states: */ 485static arc_state_t ARC_anon; 486static arc_state_t ARC_mru; 487static arc_state_t ARC_mru_ghost; 488static arc_state_t ARC_mfu; 489static arc_state_t ARC_mfu_ghost; 490static arc_state_t ARC_l2c_only; 491 492typedef struct arc_stats { 493 kstat_named_t arcstat_hits; 494 kstat_named_t arcstat_misses; 495 kstat_named_t arcstat_demand_data_hits; 496 kstat_named_t arcstat_demand_data_misses; 497 kstat_named_t arcstat_demand_metadata_hits; 498 kstat_named_t arcstat_demand_metadata_misses; 499 kstat_named_t arcstat_prefetch_data_hits; 500 kstat_named_t arcstat_prefetch_data_misses; 501 kstat_named_t arcstat_prefetch_metadata_hits; 502 kstat_named_t arcstat_prefetch_metadata_misses; 503 kstat_named_t arcstat_mru_hits; 504 kstat_named_t arcstat_mru_ghost_hits; 505 kstat_named_t arcstat_mfu_hits; 506 kstat_named_t arcstat_mfu_ghost_hits; 507 kstat_named_t arcstat_allocated; 508 kstat_named_t arcstat_deleted; 509 /* 510 * Number of buffers that could not be evicted because the hash lock 511 * was held by another thread. The lock may not necessarily be held 512 * by something using the same buffer, since hash locks are shared 513 * by multiple buffers. 514 */ 515 kstat_named_t arcstat_mutex_miss; 516 /* 517 * Number of buffers skipped because they have I/O in progress, are 518 * indrect prefetch buffers that have not lived long enough, or are 519 * not from the spa we're trying to evict from. 520 */ 521 kstat_named_t arcstat_evict_skip; 522 /* 523 * Number of times arc_evict_state() was unable to evict enough 524 * buffers to reach it's target amount. 525 */ 526 kstat_named_t arcstat_evict_not_enough; 527 kstat_named_t arcstat_evict_l2_cached; 528 kstat_named_t arcstat_evict_l2_eligible; 529 kstat_named_t arcstat_evict_l2_ineligible; 530 kstat_named_t arcstat_evict_l2_skip; 531 kstat_named_t arcstat_hash_elements; 532 kstat_named_t arcstat_hash_elements_max; 533 kstat_named_t arcstat_hash_collisions; 534 kstat_named_t arcstat_hash_chains; 535 kstat_named_t arcstat_hash_chain_max; 536 kstat_named_t arcstat_p; 537 kstat_named_t arcstat_c; 538 kstat_named_t arcstat_c_min; 539 kstat_named_t arcstat_c_max; 540 kstat_named_t arcstat_size; 541 /* 542 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pdata. 543 * Note that the compressed bytes may match the uncompressed bytes 544 * if the block is either not compressed or compressed arc is disabled. 545 */ 546 kstat_named_t arcstat_compressed_size; 547 /* 548 * Uncompressed size of the data stored in b_pdata. If compressed 549 * arc is disabled then this value will be identical to the stat 550 * above. 551 */ 552 kstat_named_t arcstat_uncompressed_size; 553 /* 554 * Number of bytes stored in all the arc_buf_t's. This is classified 555 * as "overhead" since this data is typically short-lived and will 556 * be evicted from the arc when it becomes unreferenced unless the 557 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 558 * values have been set (see comment in dbuf.c for more information). 559 */ 560 kstat_named_t arcstat_overhead_size; 561 /* 562 * Number of bytes consumed by internal ARC structures necessary 563 * for tracking purposes; these structures are not actually 564 * backed by ARC buffers. This includes arc_buf_hdr_t structures 565 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 566 * caches), and arc_buf_t structures (allocated via arc_buf_t 567 * cache). 568 */ 569 kstat_named_t arcstat_hdr_size; 570 /* 571 * Number of bytes consumed by ARC buffers of type equal to 572 * ARC_BUFC_DATA. This is generally consumed by buffers backing 573 * on disk user data (e.g. plain file contents). 574 */ 575 kstat_named_t arcstat_data_size; 576 /* 577 * Number of bytes consumed by ARC buffers of type equal to 578 * ARC_BUFC_METADATA. This is generally consumed by buffers 579 * backing on disk data that is used for internal ZFS 580 * structures (e.g. ZAP, dnode, indirect blocks, etc). 581 */ 582 kstat_named_t arcstat_metadata_size; 583 /* 584 * Number of bytes consumed by various buffers and structures 585 * not actually backed with ARC buffers. This includes bonus 586 * buffers (allocated directly via zio_buf_* functions), 587 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 588 * cache), and dnode_t structures (allocated via dnode_t cache). 589 */ 590 kstat_named_t arcstat_other_size; 591 /* 592 * Total number of bytes consumed by ARC buffers residing in the 593 * arc_anon state. This includes *all* buffers in the arc_anon 594 * state; e.g. data, metadata, evictable, and unevictable buffers 595 * are all included in this value. 596 */ 597 kstat_named_t arcstat_anon_size; 598 /* 599 * Number of bytes consumed by ARC buffers that meet the 600 * following criteria: backing buffers of type ARC_BUFC_DATA, 601 * residing in the arc_anon state, and are eligible for eviction 602 * (e.g. have no outstanding holds on the buffer). 603 */ 604 kstat_named_t arcstat_anon_evictable_data; 605 /* 606 * Number of bytes consumed by ARC buffers that meet the 607 * following criteria: backing buffers of type ARC_BUFC_METADATA, 608 * residing in the arc_anon state, and are eligible for eviction 609 * (e.g. have no outstanding holds on the buffer). 610 */ 611 kstat_named_t arcstat_anon_evictable_metadata; 612 /* 613 * Total number of bytes consumed by ARC buffers residing in the 614 * arc_mru state. This includes *all* buffers in the arc_mru 615 * state; e.g. data, metadata, evictable, and unevictable buffers 616 * are all included in this value. 617 */ 618 kstat_named_t arcstat_mru_size; 619 /* 620 * Number of bytes consumed by ARC buffers that meet the 621 * following criteria: backing buffers of type ARC_BUFC_DATA, 622 * residing in the arc_mru state, and are eligible for eviction 623 * (e.g. have no outstanding holds on the buffer). 624 */ 625 kstat_named_t arcstat_mru_evictable_data; 626 /* 627 * Number of bytes consumed by ARC buffers that meet the 628 * following criteria: backing buffers of type ARC_BUFC_METADATA, 629 * residing in the arc_mru state, and are eligible for eviction 630 * (e.g. have no outstanding holds on the buffer). 631 */ 632 kstat_named_t arcstat_mru_evictable_metadata; 633 /* 634 * Total number of bytes that *would have been* consumed by ARC 635 * buffers in the arc_mru_ghost state. The key thing to note 636 * here, is the fact that this size doesn't actually indicate 637 * RAM consumption. The ghost lists only consist of headers and 638 * don't actually have ARC buffers linked off of these headers. 639 * Thus, *if* the headers had associated ARC buffers, these 640 * buffers *would have* consumed this number of bytes. 641 */ 642 kstat_named_t arcstat_mru_ghost_size; 643 /* 644 * Number of bytes that *would have been* consumed by ARC 645 * buffers that are eligible for eviction, of type 646 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 647 */ 648 kstat_named_t arcstat_mru_ghost_evictable_data; 649 /* 650 * Number of bytes that *would have been* consumed by ARC 651 * buffers that are eligible for eviction, of type 652 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 653 */ 654 kstat_named_t arcstat_mru_ghost_evictable_metadata; 655 /* 656 * Total number of bytes consumed by ARC buffers residing in the 657 * arc_mfu state. This includes *all* buffers in the arc_mfu 658 * state; e.g. data, metadata, evictable, and unevictable buffers 659 * are all included in this value. 660 */ 661 kstat_named_t arcstat_mfu_size; 662 /* 663 * Number of bytes consumed by ARC buffers that are eligible for 664 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 665 * state. 666 */ 667 kstat_named_t arcstat_mfu_evictable_data; 668 /* 669 * Number of bytes consumed by ARC buffers that are eligible for 670 * eviction, of type ARC_BUFC_METADATA, and reside in the 671 * arc_mfu state. 672 */ 673 kstat_named_t arcstat_mfu_evictable_metadata; 674 /* 675 * Total number of bytes that *would have been* consumed by ARC 676 * buffers in the arc_mfu_ghost state. See the comment above 677 * arcstat_mru_ghost_size for more details. 678 */ 679 kstat_named_t arcstat_mfu_ghost_size; 680 /* 681 * Number of bytes that *would have been* consumed by ARC 682 * buffers that are eligible for eviction, of type 683 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 684 */ 685 kstat_named_t arcstat_mfu_ghost_evictable_data; 686 /* 687 * Number of bytes that *would have been* consumed by ARC 688 * buffers that are eligible for eviction, of type 689 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 690 */ 691 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 692 kstat_named_t arcstat_l2_hits; 693 kstat_named_t arcstat_l2_misses; 694 kstat_named_t arcstat_l2_feeds; 695 kstat_named_t arcstat_l2_rw_clash; 696 kstat_named_t arcstat_l2_read_bytes; 697 kstat_named_t arcstat_l2_write_bytes; 698 kstat_named_t arcstat_l2_writes_sent; 699 kstat_named_t arcstat_l2_writes_done; 700 kstat_named_t arcstat_l2_writes_error; 701 kstat_named_t arcstat_l2_writes_lock_retry; 702 kstat_named_t arcstat_l2_evict_lock_retry; 703 kstat_named_t arcstat_l2_evict_reading; 704 kstat_named_t arcstat_l2_evict_l1cached; 705 kstat_named_t arcstat_l2_free_on_write; 706 kstat_named_t arcstat_l2_abort_lowmem; 707 kstat_named_t arcstat_l2_cksum_bad; 708 kstat_named_t arcstat_l2_io_error; 709 kstat_named_t arcstat_l2_size; 710 kstat_named_t arcstat_l2_asize; 711 kstat_named_t arcstat_l2_hdr_size; 712 kstat_named_t arcstat_l2_padding_needed; 713 kstat_named_t arcstat_l2_write_trylock_fail; 714 kstat_named_t arcstat_l2_write_passed_headroom; 715 kstat_named_t arcstat_l2_write_spa_mismatch; 716 kstat_named_t arcstat_l2_write_in_l2; 717 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 718 kstat_named_t arcstat_l2_write_not_cacheable; 719 kstat_named_t arcstat_l2_write_full; 720 kstat_named_t arcstat_l2_write_buffer_iter; 721 kstat_named_t arcstat_l2_write_pios; 722 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 723 kstat_named_t arcstat_l2_write_buffer_list_iter; 724 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 725 kstat_named_t arcstat_memory_throttle_count; 726 kstat_named_t arcstat_meta_used; 727 kstat_named_t arcstat_meta_limit; 728 kstat_named_t arcstat_meta_max; 729 kstat_named_t arcstat_meta_min; 730 kstat_named_t arcstat_sync_wait_for_async; 731 kstat_named_t arcstat_demand_hit_predictive_prefetch; 732} arc_stats_t; 733 734static arc_stats_t arc_stats = { 735 { "hits", KSTAT_DATA_UINT64 }, 736 { "misses", KSTAT_DATA_UINT64 }, 737 { "demand_data_hits", KSTAT_DATA_UINT64 }, 738 { "demand_data_misses", KSTAT_DATA_UINT64 }, 739 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 740 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 741 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 742 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 743 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 744 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 745 { "mru_hits", KSTAT_DATA_UINT64 }, 746 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 747 { "mfu_hits", KSTAT_DATA_UINT64 }, 748 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 749 { "allocated", KSTAT_DATA_UINT64 }, 750 { "deleted", KSTAT_DATA_UINT64 }, 751 { "mutex_miss", KSTAT_DATA_UINT64 }, 752 { "evict_skip", KSTAT_DATA_UINT64 }, 753 { "evict_not_enough", KSTAT_DATA_UINT64 }, 754 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 755 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 756 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 757 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 758 { "hash_elements", KSTAT_DATA_UINT64 }, 759 { "hash_elements_max", KSTAT_DATA_UINT64 }, 760 { "hash_collisions", KSTAT_DATA_UINT64 }, 761 { "hash_chains", KSTAT_DATA_UINT64 }, 762 { "hash_chain_max", KSTAT_DATA_UINT64 }, 763 { "p", KSTAT_DATA_UINT64 }, 764 { "c", KSTAT_DATA_UINT64 }, 765 { "c_min", KSTAT_DATA_UINT64 }, 766 { "c_max", KSTAT_DATA_UINT64 }, 767 { "size", KSTAT_DATA_UINT64 }, 768 { "compressed_size", KSTAT_DATA_UINT64 }, 769 { "uncompressed_size", KSTAT_DATA_UINT64 }, 770 { "overhead_size", KSTAT_DATA_UINT64 }, 771 { "hdr_size", KSTAT_DATA_UINT64 }, 772 { "data_size", KSTAT_DATA_UINT64 }, 773 { "metadata_size", KSTAT_DATA_UINT64 }, 774 { "other_size", KSTAT_DATA_UINT64 }, 775 { "anon_size", KSTAT_DATA_UINT64 }, 776 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 777 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 778 { "mru_size", KSTAT_DATA_UINT64 }, 779 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 780 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 781 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 782 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 783 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 784 { "mfu_size", KSTAT_DATA_UINT64 }, 785 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 786 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 787 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 788 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 789 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 790 { "l2_hits", KSTAT_DATA_UINT64 }, 791 { "l2_misses", KSTAT_DATA_UINT64 }, 792 { "l2_feeds", KSTAT_DATA_UINT64 }, 793 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 794 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 795 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 796 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 797 { "l2_writes_done", KSTAT_DATA_UINT64 }, 798 { "l2_writes_error", KSTAT_DATA_UINT64 }, 799 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 800 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 801 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 802 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 803 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 804 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 805 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 806 { "l2_io_error", KSTAT_DATA_UINT64 }, 807 { "l2_size", KSTAT_DATA_UINT64 }, 808 { "l2_asize", KSTAT_DATA_UINT64 }, 809 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 810 { "l2_padding_needed", KSTAT_DATA_UINT64 }, 811 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 812 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 813 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 814 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 815 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 816 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 817 { "l2_write_full", KSTAT_DATA_UINT64 }, 818 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 819 { "l2_write_pios", KSTAT_DATA_UINT64 }, 820 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 821 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 822 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 823 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 824 { "arc_meta_used", KSTAT_DATA_UINT64 }, 825 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 826 { "arc_meta_max", KSTAT_DATA_UINT64 }, 827 { "arc_meta_min", KSTAT_DATA_UINT64 }, 828 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 829 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 830}; 831 832#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 833 834#define ARCSTAT_INCR(stat, val) \ 835 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 836 837#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 838#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 839 840#define ARCSTAT_MAX(stat, val) { \ 841 uint64_t m; \ 842 while ((val) > (m = arc_stats.stat.value.ui64) && \ 843 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 844 continue; \ 845} 846 847#define ARCSTAT_MAXSTAT(stat) \ 848 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 849 850/* 851 * We define a macro to allow ARC hits/misses to be easily broken down by 852 * two separate conditions, giving a total of four different subtypes for 853 * each of hits and misses (so eight statistics total). 854 */ 855#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 856 if (cond1) { \ 857 if (cond2) { \ 858 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 859 } else { \ 860 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 861 } \ 862 } else { \ 863 if (cond2) { \ 864 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 865 } else { \ 866 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 867 } \ 868 } 869 870kstat_t *arc_ksp; 871static arc_state_t *arc_anon; 872static arc_state_t *arc_mru; 873static arc_state_t *arc_mru_ghost; 874static arc_state_t *arc_mfu; 875static arc_state_t *arc_mfu_ghost; 876static arc_state_t *arc_l2c_only; 877 878/* 879 * There are several ARC variables that are critical to export as kstats -- 880 * but we don't want to have to grovel around in the kstat whenever we wish to 881 * manipulate them. For these variables, we therefore define them to be in 882 * terms of the statistic variable. This assures that we are not introducing 883 * the possibility of inconsistency by having shadow copies of the variables, 884 * while still allowing the code to be readable. 885 */ 886#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 887#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 888#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 889#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 890#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 891#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 892#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 893#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 894#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 895 896/* compressed size of entire arc */ 897#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 898/* uncompressed size of entire arc */ 899#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 900/* number of bytes in the arc from arc_buf_t's */ 901#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 902 903static int arc_no_grow; /* Don't try to grow cache size */ 904static uint64_t arc_tempreserve; 905static uint64_t arc_loaned_bytes; 906 907typedef struct arc_callback arc_callback_t; 908 909struct arc_callback { 910 void *acb_private; 911 arc_done_func_t *acb_done; 912 arc_buf_t *acb_buf; 913 zio_t *acb_zio_dummy; 914 arc_callback_t *acb_next; 915}; 916 917typedef struct arc_write_callback arc_write_callback_t; 918 919struct arc_write_callback { 920 void *awcb_private; 921 arc_done_func_t *awcb_ready; 922 arc_done_func_t *awcb_children_ready; 923 arc_done_func_t *awcb_physdone; 924 arc_done_func_t *awcb_done; 925 arc_buf_t *awcb_buf; 926}; 927 928/* 929 * ARC buffers are separated into multiple structs as a memory saving measure: 930 * - Common fields struct, always defined, and embedded within it: 931 * - L2-only fields, always allocated but undefined when not in L2ARC 932 * - L1-only fields, only allocated when in L1ARC 933 * 934 * Buffer in L1 Buffer only in L2 935 * +------------------------+ +------------------------+ 936 * | arc_buf_hdr_t | | arc_buf_hdr_t | 937 * | | | | 938 * | | | | 939 * | | | | 940 * +------------------------+ +------------------------+ 941 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 942 * | (undefined if L1-only) | | | 943 * +------------------------+ +------------------------+ 944 * | l1arc_buf_hdr_t | 945 * | | 946 * | | 947 * | | 948 * | | 949 * +------------------------+ 950 * 951 * Because it's possible for the L2ARC to become extremely large, we can wind 952 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 953 * is minimized by only allocating the fields necessary for an L1-cached buffer 954 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 955 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 956 * words in pointers. arc_hdr_realloc() is used to switch a header between 957 * these two allocation states. 958 */ 959typedef struct l1arc_buf_hdr { 960 kmutex_t b_freeze_lock; 961 zio_cksum_t *b_freeze_cksum; 962#ifdef ZFS_DEBUG 963 /* 964 * used for debugging wtih kmem_flags - by allocating and freeing 965 * b_thawed when the buffer is thawed, we get a record of the stack 966 * trace that thawed it. 967 */ 968 void *b_thawed; 969#endif 970 971 arc_buf_t *b_buf; 972 uint32_t b_bufcnt; 973 /* for waiting on writes to complete */ 974 kcondvar_t b_cv; 975 uint8_t b_byteswap; 976 977 /* protected by arc state mutex */ 978 arc_state_t *b_state; 979 multilist_node_t b_arc_node; 980 981 /* updated atomically */ 982 clock_t b_arc_access; 983 984 /* self protecting */ 985 refcount_t b_refcnt; 986 987 arc_callback_t *b_acb; 988 void *b_pdata; 989} l1arc_buf_hdr_t; 990 991typedef struct l2arc_dev l2arc_dev_t; 992 993typedef struct l2arc_buf_hdr { 994 /* protected by arc_buf_hdr mutex */ 995 l2arc_dev_t *b_dev; /* L2ARC device */ 996 uint64_t b_daddr; /* disk address, offset byte */ 997 998 list_node_t b_l2node; 999} l2arc_buf_hdr_t; 1000 1001struct arc_buf_hdr { 1002 /* protected by hash lock */ 1003 dva_t b_dva; 1004 uint64_t b_birth; 1005 1006 arc_buf_contents_t b_type; 1007 arc_buf_hdr_t *b_hash_next; 1008 arc_flags_t b_flags; 1009 1010 /* 1011 * This field stores the size of the data buffer after 1012 * compression, and is set in the arc's zio completion handlers. 1013 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1014 * 1015 * While the block pointers can store up to 32MB in their psize 1016 * field, we can only store up to 32MB minus 512B. This is due 1017 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1018 * a field of zeros represents 512B in the bp). We can't use a 1019 * bias of 1 since we need to reserve a psize of zero, here, to 1020 * represent holes and embedded blocks. 1021 * 1022 * This isn't a problem in practice, since the maximum size of a 1023 * buffer is limited to 16MB, so we never need to store 32MB in 1024 * this field. Even in the upstream illumos code base, the 1025 * maximum size of a buffer is limited to 16MB. 1026 */ 1027 uint16_t b_psize; 1028 1029 /* 1030 * This field stores the size of the data buffer before 1031 * compression, and cannot change once set. It is in units 1032 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1033 */ 1034 uint16_t b_lsize; /* immutable */ 1035 uint64_t b_spa; /* immutable */ 1036 1037 /* L2ARC fields. Undefined when not in L2ARC. */ 1038 l2arc_buf_hdr_t b_l2hdr; 1039 /* L1ARC fields. Undefined when in l2arc_only state */ 1040 l1arc_buf_hdr_t b_l1hdr; 1041}; 1042 1043#if defined(__FreeBSD__) && defined(_KERNEL) 1044static int 1045sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1046{ 1047 uint64_t val; 1048 int err; 1049 1050 val = arc_meta_limit; 1051 err = sysctl_handle_64(oidp, &val, 0, req); 1052 if (err != 0 || req->newptr == NULL) 1053 return (err); 1054 1055 if (val <= 0 || val > arc_c_max) 1056 return (EINVAL); 1057 1058 arc_meta_limit = val; 1059 return (0); 1060} 1061 1062static int 1063sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1064{ 1065 uint64_t val; 1066 int err; 1067 1068 val = zfs_arc_max; 1069 err = sysctl_handle_64(oidp, &val, 0, req); 1070 if (err != 0 || req->newptr == NULL) 1071 return (err); 1072 1073 if (zfs_arc_max == 0) { 1074 /* Loader tunable so blindly set */ 1075 zfs_arc_max = val; 1076 return (0); 1077 } 1078 1079 if (val < arc_abs_min || val > kmem_size()) 1080 return (EINVAL); 1081 if (val < arc_c_min) 1082 return (EINVAL); 1083 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1084 return (EINVAL); 1085 1086 arc_c_max = val; 1087 1088 arc_c = arc_c_max; 1089 arc_p = (arc_c >> 1); 1090 1091 if (zfs_arc_meta_limit == 0) { 1092 /* limit meta-data to 1/4 of the arc capacity */ 1093 arc_meta_limit = arc_c_max / 4; 1094 } 1095 1096 /* if kmem_flags are set, lets try to use less memory */ 1097 if (kmem_debugging()) 1098 arc_c = arc_c / 2; 1099 1100 zfs_arc_max = arc_c; 1101 1102 return (0); 1103} 1104 1105static int 1106sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1107{ 1108 uint64_t val; 1109 int err; 1110 1111 val = zfs_arc_min; 1112 err = sysctl_handle_64(oidp, &val, 0, req); 1113 if (err != 0 || req->newptr == NULL) 1114 return (err); 1115 1116 if (zfs_arc_min == 0) { 1117 /* Loader tunable so blindly set */ 1118 zfs_arc_min = val; 1119 return (0); 1120 } 1121 1122 if (val < arc_abs_min || val > arc_c_max) 1123 return (EINVAL); 1124 1125 arc_c_min = val; 1126 1127 if (zfs_arc_meta_min == 0) 1128 arc_meta_min = arc_c_min / 2; 1129 1130 if (arc_c < arc_c_min) 1131 arc_c = arc_c_min; 1132 1133 zfs_arc_min = arc_c_min; 1134 1135 return (0); 1136} 1137#endif 1138 1139#define GHOST_STATE(state) \ 1140 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1141 (state) == arc_l2c_only) 1142 1143#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1144#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1145#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1146#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1147#define HDR_COMPRESSION_ENABLED(hdr) \ 1148 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1149 1150#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1151#define HDR_L2_READING(hdr) \ 1152 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1153 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1154#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1155#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1156#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1157#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1158 1159#define HDR_ISTYPE_METADATA(hdr) \ 1160 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1161#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1162 1163#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1164#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1165 1166/* For storing compression mode in b_flags */ 1167#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1168 1169#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1170 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1171#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1172 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1173 1174#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1175 1176/* 1177 * Other sizes 1178 */ 1179 1180#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1181#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1182 1183/* 1184 * Hash table routines 1185 */ 1186 1187#define HT_LOCK_PAD CACHE_LINE_SIZE 1188 1189struct ht_lock { 1190 kmutex_t ht_lock; 1191#ifdef _KERNEL 1192 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1193#endif 1194}; 1195 1196#define BUF_LOCKS 256 1197typedef struct buf_hash_table { 1198 uint64_t ht_mask; 1199 arc_buf_hdr_t **ht_table; 1200 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1201} buf_hash_table_t; 1202 1203static buf_hash_table_t buf_hash_table; 1204 1205#define BUF_HASH_INDEX(spa, dva, birth) \ 1206 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1207#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1208#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1209#define HDR_LOCK(hdr) \ 1210 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1211 1212uint64_t zfs_crc64_table[256]; 1213 1214/* 1215 * Level 2 ARC 1216 */ 1217 1218#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1219#define L2ARC_HEADROOM 2 /* num of writes */ 1220/* 1221 * If we discover during ARC scan any buffers to be compressed, we boost 1222 * our headroom for the next scanning cycle by this percentage multiple. 1223 */ 1224#define L2ARC_HEADROOM_BOOST 200 1225#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1226#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1227 1228#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1229#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1230 1231/* L2ARC Performance Tunables */ 1232uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1233uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1234uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1235uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1236uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1237uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1238boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1239boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1240boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1241 1242SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1243 &l2arc_write_max, 0, "max write size"); 1244SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1245 &l2arc_write_boost, 0, "extra write during warmup"); 1246SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1247 &l2arc_headroom, 0, "number of dev writes"); 1248SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1249 &l2arc_feed_secs, 0, "interval seconds"); 1250SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1251 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1252 1253SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1254 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1255SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1256 &l2arc_feed_again, 0, "turbo warmup"); 1257SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1258 &l2arc_norw, 0, "no reads during writes"); 1259 1260SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1261 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1262SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1263 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1264 "size of anonymous state"); 1265SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1266 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1267 "size of anonymous state"); 1268 1269SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1270 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1271SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1272 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1273 "size of metadata in mru state"); 1274SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1275 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1276 "size of data in mru state"); 1277 1278SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1279 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1280SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1281 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1282 "size of metadata in mru ghost state"); 1283SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1284 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1285 "size of data in mru ghost state"); 1286 1287SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1288 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1289SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1290 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1291 "size of metadata in mfu state"); 1292SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1293 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1294 "size of data in mfu state"); 1295 1296SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1297 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1298SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1299 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1300 "size of metadata in mfu ghost state"); 1301SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1302 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1303 "size of data in mfu ghost state"); 1304 1305SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1306 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1307 1308/* 1309 * L2ARC Internals 1310 */ 1311struct l2arc_dev { 1312 vdev_t *l2ad_vdev; /* vdev */ 1313 spa_t *l2ad_spa; /* spa */ 1314 uint64_t l2ad_hand; /* next write location */ 1315 uint64_t l2ad_start; /* first addr on device */ 1316 uint64_t l2ad_end; /* last addr on device */ 1317 boolean_t l2ad_first; /* first sweep through */ 1318 boolean_t l2ad_writing; /* currently writing */ 1319 kmutex_t l2ad_mtx; /* lock for buffer list */ 1320 list_t l2ad_buflist; /* buffer list */ 1321 list_node_t l2ad_node; /* device list node */ 1322 refcount_t l2ad_alloc; /* allocated bytes */ 1323}; 1324 1325static list_t L2ARC_dev_list; /* device list */ 1326static list_t *l2arc_dev_list; /* device list pointer */ 1327static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1328static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1329static list_t L2ARC_free_on_write; /* free after write buf list */ 1330static list_t *l2arc_free_on_write; /* free after write list ptr */ 1331static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1332static uint64_t l2arc_ndev; /* number of devices */ 1333 1334typedef struct l2arc_read_callback { 1335 arc_buf_hdr_t *l2rcb_hdr; /* read buffer */ 1336 blkptr_t l2rcb_bp; /* original blkptr */ 1337 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1338 int l2rcb_flags; /* original flags */ 1339 void *l2rcb_data; /* temporary buffer */ 1340} l2arc_read_callback_t; 1341 1342typedef struct l2arc_write_callback { 1343 l2arc_dev_t *l2wcb_dev; /* device info */ 1344 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1345} l2arc_write_callback_t; 1346 1347typedef struct l2arc_data_free { 1348 /* protected by l2arc_free_on_write_mtx */ 1349 void *l2df_data; 1350 size_t l2df_size; 1351 arc_buf_contents_t l2df_type; 1352 list_node_t l2df_list_node; 1353} l2arc_data_free_t; 1354 1355static kmutex_t l2arc_feed_thr_lock; 1356static kcondvar_t l2arc_feed_thr_cv; 1357static uint8_t l2arc_thread_exit; 1358 1359static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1360static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1361static void arc_hdr_free_pdata(arc_buf_hdr_t *hdr); 1362static void arc_hdr_alloc_pdata(arc_buf_hdr_t *); 1363static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1364static boolean_t arc_is_overflowing(); 1365static void arc_buf_watch(arc_buf_t *); 1366 1367static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1368static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1369static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1370static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1371 1372static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1373static void l2arc_read_done(zio_t *); 1374 1375static void 1376l2arc_trim(const arc_buf_hdr_t *hdr) 1377{ 1378 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1379 1380 ASSERT(HDR_HAS_L2HDR(hdr)); 1381 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1382 1383 if (HDR_GET_PSIZE(hdr) != 0) { 1384 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1385 HDR_GET_PSIZE(hdr), 0); 1386 } 1387} 1388 1389static uint64_t 1390buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1391{ 1392 uint8_t *vdva = (uint8_t *)dva; 1393 uint64_t crc = -1ULL; 1394 int i; 1395 1396 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1397 1398 for (i = 0; i < sizeof (dva_t); i++) 1399 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1400 1401 crc ^= (spa>>8) ^ birth; 1402 1403 return (crc); 1404} 1405 1406#define HDR_EMPTY(hdr) \ 1407 ((hdr)->b_dva.dva_word[0] == 0 && \ 1408 (hdr)->b_dva.dva_word[1] == 0) 1409 1410#define HDR_EQUAL(spa, dva, birth, hdr) \ 1411 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1412 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1413 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1414 1415static void 1416buf_discard_identity(arc_buf_hdr_t *hdr) 1417{ 1418 hdr->b_dva.dva_word[0] = 0; 1419 hdr->b_dva.dva_word[1] = 0; 1420 hdr->b_birth = 0; 1421} 1422 1423static arc_buf_hdr_t * 1424buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1425{ 1426 const dva_t *dva = BP_IDENTITY(bp); 1427 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1428 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1429 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1430 arc_buf_hdr_t *hdr; 1431 1432 mutex_enter(hash_lock); 1433 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1434 hdr = hdr->b_hash_next) { 1435 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1436 *lockp = hash_lock; 1437 return (hdr); 1438 } 1439 } 1440 mutex_exit(hash_lock); 1441 *lockp = NULL; 1442 return (NULL); 1443} 1444 1445/* 1446 * Insert an entry into the hash table. If there is already an element 1447 * equal to elem in the hash table, then the already existing element 1448 * will be returned and the new element will not be inserted. 1449 * Otherwise returns NULL. 1450 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1451 */ 1452static arc_buf_hdr_t * 1453buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1454{ 1455 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1456 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1457 arc_buf_hdr_t *fhdr; 1458 uint32_t i; 1459 1460 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1461 ASSERT(hdr->b_birth != 0); 1462 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1463 1464 if (lockp != NULL) { 1465 *lockp = hash_lock; 1466 mutex_enter(hash_lock); 1467 } else { 1468 ASSERT(MUTEX_HELD(hash_lock)); 1469 } 1470 1471 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1472 fhdr = fhdr->b_hash_next, i++) { 1473 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1474 return (fhdr); 1475 } 1476 1477 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1478 buf_hash_table.ht_table[idx] = hdr; 1479 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1480 1481 /* collect some hash table performance data */ 1482 if (i > 0) { 1483 ARCSTAT_BUMP(arcstat_hash_collisions); 1484 if (i == 1) 1485 ARCSTAT_BUMP(arcstat_hash_chains); 1486 1487 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1488 } 1489 1490 ARCSTAT_BUMP(arcstat_hash_elements); 1491 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1492 1493 return (NULL); 1494} 1495 1496static void 1497buf_hash_remove(arc_buf_hdr_t *hdr) 1498{ 1499 arc_buf_hdr_t *fhdr, **hdrp; 1500 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1501 1502 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1503 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1504 1505 hdrp = &buf_hash_table.ht_table[idx]; 1506 while ((fhdr = *hdrp) != hdr) { 1507 ASSERT3P(fhdr, !=, NULL); 1508 hdrp = &fhdr->b_hash_next; 1509 } 1510 *hdrp = hdr->b_hash_next; 1511 hdr->b_hash_next = NULL; 1512 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1513 1514 /* collect some hash table performance data */ 1515 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1516 1517 if (buf_hash_table.ht_table[idx] && 1518 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1519 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1520} 1521 1522/* 1523 * Global data structures and functions for the buf kmem cache. 1524 */ 1525static kmem_cache_t *hdr_full_cache; 1526static kmem_cache_t *hdr_l2only_cache; 1527static kmem_cache_t *buf_cache; 1528 1529static void 1530buf_fini(void) 1531{ 1532 int i; 1533 1534 kmem_free(buf_hash_table.ht_table, 1535 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1536 for (i = 0; i < BUF_LOCKS; i++) 1537 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1538 kmem_cache_destroy(hdr_full_cache); 1539 kmem_cache_destroy(hdr_l2only_cache); 1540 kmem_cache_destroy(buf_cache); 1541} 1542 1543/* 1544 * Constructor callback - called when the cache is empty 1545 * and a new buf is requested. 1546 */ 1547/* ARGSUSED */ 1548static int 1549hdr_full_cons(void *vbuf, void *unused, int kmflag) 1550{ 1551 arc_buf_hdr_t *hdr = vbuf; 1552 1553 bzero(hdr, HDR_FULL_SIZE); 1554 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1555 refcount_create(&hdr->b_l1hdr.b_refcnt); 1556 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1557 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1558 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1559 1560 return (0); 1561} 1562 1563/* ARGSUSED */ 1564static int 1565hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1566{ 1567 arc_buf_hdr_t *hdr = vbuf; 1568 1569 bzero(hdr, HDR_L2ONLY_SIZE); 1570 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1571 1572 return (0); 1573} 1574 1575/* ARGSUSED */ 1576static int 1577buf_cons(void *vbuf, void *unused, int kmflag) 1578{ 1579 arc_buf_t *buf = vbuf; 1580 1581 bzero(buf, sizeof (arc_buf_t)); 1582 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1583 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1584 1585 return (0); 1586} 1587 1588/* 1589 * Destructor callback - called when a cached buf is 1590 * no longer required. 1591 */ 1592/* ARGSUSED */ 1593static void 1594hdr_full_dest(void *vbuf, void *unused) 1595{ 1596 arc_buf_hdr_t *hdr = vbuf; 1597 1598 ASSERT(HDR_EMPTY(hdr)); 1599 cv_destroy(&hdr->b_l1hdr.b_cv); 1600 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1601 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1602 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1603 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1604} 1605 1606/* ARGSUSED */ 1607static void 1608hdr_l2only_dest(void *vbuf, void *unused) 1609{ 1610 arc_buf_hdr_t *hdr = vbuf; 1611 1612 ASSERT(HDR_EMPTY(hdr)); 1613 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1614} 1615 1616/* ARGSUSED */ 1617static void 1618buf_dest(void *vbuf, void *unused) 1619{ 1620 arc_buf_t *buf = vbuf; 1621 1622 mutex_destroy(&buf->b_evict_lock); 1623 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1624} 1625 1626/* 1627 * Reclaim callback -- invoked when memory is low. 1628 */ 1629/* ARGSUSED */ 1630static void 1631hdr_recl(void *unused) 1632{ 1633 dprintf("hdr_recl called\n"); 1634 /* 1635 * umem calls the reclaim func when we destroy the buf cache, 1636 * which is after we do arc_fini(). 1637 */ 1638 if (!arc_dead) 1639 cv_signal(&arc_reclaim_thread_cv); 1640} 1641 1642static void 1643buf_init(void) 1644{ 1645 uint64_t *ct; 1646 uint64_t hsize = 1ULL << 12; 1647 int i, j; 1648 1649 /* 1650 * The hash table is big enough to fill all of physical memory 1651 * with an average block size of zfs_arc_average_blocksize (default 8K). 1652 * By default, the table will take up 1653 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1654 */ 1655 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1656 hsize <<= 1; 1657retry: 1658 buf_hash_table.ht_mask = hsize - 1; 1659 buf_hash_table.ht_table = 1660 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1661 if (buf_hash_table.ht_table == NULL) { 1662 ASSERT(hsize > (1ULL << 8)); 1663 hsize >>= 1; 1664 goto retry; 1665 } 1666 1667 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1668 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1669 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1670 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1671 NULL, NULL, 0); 1672 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1673 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1674 1675 for (i = 0; i < 256; i++) 1676 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1677 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1678 1679 for (i = 0; i < BUF_LOCKS; i++) { 1680 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1681 NULL, MUTEX_DEFAULT, NULL); 1682 } 1683} 1684 1685#define ARC_MINTIME (hz>>4) /* 62 ms */ 1686 1687static inline boolean_t 1688arc_buf_is_shared(arc_buf_t *buf) 1689{ 1690 boolean_t shared = (buf->b_data != NULL && 1691 buf->b_data == buf->b_hdr->b_l1hdr.b_pdata); 1692 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1693 return (shared); 1694} 1695 1696static inline void 1697arc_cksum_free(arc_buf_hdr_t *hdr) 1698{ 1699 ASSERT(HDR_HAS_L1HDR(hdr)); 1700 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1701 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1702 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1703 hdr->b_l1hdr.b_freeze_cksum = NULL; 1704 } 1705 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1706} 1707 1708static void 1709arc_cksum_verify(arc_buf_t *buf) 1710{ 1711 arc_buf_hdr_t *hdr = buf->b_hdr; 1712 zio_cksum_t zc; 1713 1714 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1715 return; 1716 1717 ASSERT(HDR_HAS_L1HDR(hdr)); 1718 1719 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1720 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1721 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1722 return; 1723 } 1724 fletcher_2_native(buf->b_data, HDR_GET_LSIZE(hdr), NULL, &zc); 1725 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1726 panic("buffer modified while frozen!"); 1727 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1728} 1729 1730static boolean_t 1731arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1732{ 1733 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1734 boolean_t valid_cksum; 1735 1736 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1737 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1738 1739 /* 1740 * We rely on the blkptr's checksum to determine if the block 1741 * is valid or not. When compressed arc is enabled, the l2arc 1742 * writes the block to the l2arc just as it appears in the pool. 1743 * This allows us to use the blkptr's checksum to validate the 1744 * data that we just read off of the l2arc without having to store 1745 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1746 * arc is disabled, then the data written to the l2arc is always 1747 * uncompressed and won't match the block as it exists in the main 1748 * pool. When this is the case, we must first compress it if it is 1749 * compressed on the main pool before we can validate the checksum. 1750 */ 1751 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1752 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1753 uint64_t lsize = HDR_GET_LSIZE(hdr); 1754 uint64_t csize; 1755 1756 void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr)); 1757 csize = zio_compress_data(compress, zio->io_data, cbuf, lsize); 1758 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1759 if (csize < HDR_GET_PSIZE(hdr)) { 1760 /* 1761 * Compressed blocks are always a multiple of the 1762 * smallest ashift in the pool. Ideally, we would 1763 * like to round up the csize to the next 1764 * spa_min_ashift but that value may have changed 1765 * since the block was last written. Instead, 1766 * we rely on the fact that the hdr's psize 1767 * was set to the psize of the block when it was 1768 * last written. We set the csize to that value 1769 * and zero out any part that should not contain 1770 * data. 1771 */ 1772 bzero((char *)cbuf + csize, HDR_GET_PSIZE(hdr) - csize); 1773 csize = HDR_GET_PSIZE(hdr); 1774 } 1775 zio_push_transform(zio, cbuf, csize, HDR_GET_PSIZE(hdr), NULL); 1776 } 1777 1778 /* 1779 * Block pointers always store the checksum for the logical data. 1780 * If the block pointer has the gang bit set, then the checksum 1781 * it represents is for the reconstituted data and not for an 1782 * individual gang member. The zio pipeline, however, must be able to 1783 * determine the checksum of each of the gang constituents so it 1784 * treats the checksum comparison differently than what we need 1785 * for l2arc blocks. This prevents us from using the 1786 * zio_checksum_error() interface directly. Instead we must call the 1787 * zio_checksum_error_impl() so that we can ensure the checksum is 1788 * generated using the correct checksum algorithm and accounts for the 1789 * logical I/O size and not just a gang fragment. 1790 */ 1791 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1792 BP_GET_CHECKSUM(zio->io_bp), zio->io_data, zio->io_size, 1793 zio->io_offset, NULL) == 0); 1794 zio_pop_transforms(zio); 1795 return (valid_cksum); 1796} 1797 1798static void 1799arc_cksum_compute(arc_buf_t *buf) 1800{ 1801 arc_buf_hdr_t *hdr = buf->b_hdr; 1802 1803 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1804 return; 1805 1806 ASSERT(HDR_HAS_L1HDR(hdr)); 1807 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1808 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1809 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1810 return; 1811 } 1812 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1813 KM_SLEEP); 1814 fletcher_2_native(buf->b_data, HDR_GET_LSIZE(hdr), NULL, 1815 hdr->b_l1hdr.b_freeze_cksum); 1816 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1817#ifdef illumos 1818 arc_buf_watch(buf); 1819#endif 1820} 1821 1822#ifdef illumos 1823#ifndef _KERNEL 1824typedef struct procctl { 1825 long cmd; 1826 prwatch_t prwatch; 1827} procctl_t; 1828#endif 1829 1830/* ARGSUSED */ 1831static void 1832arc_buf_unwatch(arc_buf_t *buf) 1833{ 1834#ifndef _KERNEL 1835 if (arc_watch) { 1836 int result; 1837 procctl_t ctl; 1838 ctl.cmd = PCWATCH; 1839 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1840 ctl.prwatch.pr_size = 0; 1841 ctl.prwatch.pr_wflags = 0; 1842 result = write(arc_procfd, &ctl, sizeof (ctl)); 1843 ASSERT3U(result, ==, sizeof (ctl)); 1844 } 1845#endif 1846} 1847 1848/* ARGSUSED */ 1849static void 1850arc_buf_watch(arc_buf_t *buf) 1851{ 1852#ifndef _KERNEL 1853 if (arc_watch) { 1854 int result; 1855 procctl_t ctl; 1856 ctl.cmd = PCWATCH; 1857 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1858 ctl.prwatch.pr_size = HDR_GET_LSIZE(buf->b_hdr); 1859 ctl.prwatch.pr_wflags = WA_WRITE; 1860 result = write(arc_procfd, &ctl, sizeof (ctl)); 1861 ASSERT3U(result, ==, sizeof (ctl)); 1862 } 1863#endif 1864} 1865#endif /* illumos */ 1866 1867static arc_buf_contents_t 1868arc_buf_type(arc_buf_hdr_t *hdr) 1869{ 1870 arc_buf_contents_t type; 1871 if (HDR_ISTYPE_METADATA(hdr)) { 1872 type = ARC_BUFC_METADATA; 1873 } else { 1874 type = ARC_BUFC_DATA; 1875 } 1876 VERIFY3U(hdr->b_type, ==, type); 1877 return (type); 1878} 1879 1880static uint32_t 1881arc_bufc_to_flags(arc_buf_contents_t type) 1882{ 1883 switch (type) { 1884 case ARC_BUFC_DATA: 1885 /* metadata field is 0 if buffer contains normal data */ 1886 return (0); 1887 case ARC_BUFC_METADATA: 1888 return (ARC_FLAG_BUFC_METADATA); 1889 default: 1890 break; 1891 } 1892 panic("undefined ARC buffer type!"); 1893 return ((uint32_t)-1); 1894} 1895 1896void 1897arc_buf_thaw(arc_buf_t *buf) 1898{ 1899 arc_buf_hdr_t *hdr = buf->b_hdr; 1900 1901 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1902 if (hdr->b_l1hdr.b_state != arc_anon) 1903 panic("modifying non-anon buffer!"); 1904 if (HDR_IO_IN_PROGRESS(hdr)) 1905 panic("modifying buffer while i/o in progress!"); 1906 arc_cksum_verify(buf); 1907 } 1908 1909 ASSERT(HDR_HAS_L1HDR(hdr)); 1910 arc_cksum_free(hdr); 1911 1912 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1913#ifdef ZFS_DEBUG 1914 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1915 if (hdr->b_l1hdr.b_thawed != NULL) 1916 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1917 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1918 } 1919#endif 1920 1921 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1922 1923#ifdef illumos 1924 arc_buf_unwatch(buf); 1925#endif 1926} 1927 1928void 1929arc_buf_freeze(arc_buf_t *buf) 1930{ 1931 arc_buf_hdr_t *hdr = buf->b_hdr; 1932 kmutex_t *hash_lock; 1933 1934 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1935 return; 1936 1937 hash_lock = HDR_LOCK(hdr); 1938 mutex_enter(hash_lock); 1939 1940 ASSERT(HDR_HAS_L1HDR(hdr)); 1941 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 1942 hdr->b_l1hdr.b_state == arc_anon); 1943 arc_cksum_compute(buf); 1944 mutex_exit(hash_lock); 1945 1946} 1947 1948/* 1949 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 1950 * the following functions should be used to ensure that the flags are 1951 * updated in a thread-safe way. When manipulating the flags either 1952 * the hash_lock must be held or the hdr must be undiscoverable. This 1953 * ensures that we're not racing with any other threads when updating 1954 * the flags. 1955 */ 1956static inline void 1957arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 1958{ 1959 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1960 hdr->b_flags |= flags; 1961} 1962 1963static inline void 1964arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 1965{ 1966 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1967 hdr->b_flags &= ~flags; 1968} 1969 1970/* 1971 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 1972 * done in a special way since we have to clear and set bits 1973 * at the same time. Consumers that wish to set the compression bits 1974 * must use this function to ensure that the flags are updated in 1975 * thread-safe manner. 1976 */ 1977static void 1978arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 1979{ 1980 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1981 1982 /* 1983 * Holes and embedded blocks will always have a psize = 0 so 1984 * we ignore the compression of the blkptr and set the 1985 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 1986 * Holes and embedded blocks remain anonymous so we don't 1987 * want to uncompress them. Mark them as uncompressed. 1988 */ 1989 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 1990 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 1991 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 1992 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 1993 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1994 } else { 1995 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 1996 HDR_SET_COMPRESS(hdr, cmp); 1997 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 1998 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 1999 } 2000} 2001 2002static int 2003arc_decompress(arc_buf_t *buf) 2004{ 2005 arc_buf_hdr_t *hdr = buf->b_hdr; 2006 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2007 int error; 2008 2009 if (arc_buf_is_shared(buf)) { 2010 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2011 } else if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 2012 /* 2013 * The arc_buf_hdr_t is either not compressed or is 2014 * associated with an embedded block or a hole in which 2015 * case they remain anonymous. 2016 */ 2017 IMPLY(HDR_COMPRESSION_ENABLED(hdr), HDR_GET_PSIZE(hdr) == 0 || 2018 HDR_GET_PSIZE(hdr) == HDR_GET_LSIZE(hdr)); 2019 ASSERT(!HDR_SHARED_DATA(hdr)); 2020 bcopy(hdr->b_l1hdr.b_pdata, buf->b_data, HDR_GET_LSIZE(hdr)); 2021 } else { 2022 ASSERT(!HDR_SHARED_DATA(hdr)); 2023 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2024 error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2025 hdr->b_l1hdr.b_pdata, buf->b_data, HDR_GET_PSIZE(hdr), 2026 HDR_GET_LSIZE(hdr)); 2027 if (error != 0) { 2028 zfs_dbgmsg("hdr %p, compress %d, psize %d, lsize %d", 2029 hdr, HDR_GET_COMPRESS(hdr), HDR_GET_PSIZE(hdr), 2030 HDR_GET_LSIZE(hdr)); 2031 return (SET_ERROR(EIO)); 2032 } 2033 } 2034 if (bswap != DMU_BSWAP_NUMFUNCS) { 2035 ASSERT(!HDR_SHARED_DATA(hdr)); 2036 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2037 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2038 } 2039 arc_cksum_compute(buf); 2040 return (0); 2041} 2042 2043/* 2044 * Return the size of the block, b_pdata, that is stored in the arc_buf_hdr_t. 2045 */ 2046static uint64_t 2047arc_hdr_size(arc_buf_hdr_t *hdr) 2048{ 2049 uint64_t size; 2050 2051 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2052 HDR_GET_PSIZE(hdr) > 0) { 2053 size = HDR_GET_PSIZE(hdr); 2054 } else { 2055 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2056 size = HDR_GET_LSIZE(hdr); 2057 } 2058 return (size); 2059} 2060 2061/* 2062 * Increment the amount of evictable space in the arc_state_t's refcount. 2063 * We account for the space used by the hdr and the arc buf individually 2064 * so that we can add and remove them from the refcount individually. 2065 */ 2066static void 2067arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2068{ 2069 arc_buf_contents_t type = arc_buf_type(hdr); 2070 uint64_t lsize = HDR_GET_LSIZE(hdr); 2071 2072 ASSERT(HDR_HAS_L1HDR(hdr)); 2073 2074 if (GHOST_STATE(state)) { 2075 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2076 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2077 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2078 (void) refcount_add_many(&state->arcs_esize[type], lsize, hdr); 2079 return; 2080 } 2081 2082 ASSERT(!GHOST_STATE(state)); 2083 if (hdr->b_l1hdr.b_pdata != NULL) { 2084 (void) refcount_add_many(&state->arcs_esize[type], 2085 arc_hdr_size(hdr), hdr); 2086 } 2087 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2088 buf = buf->b_next) { 2089 if (arc_buf_is_shared(buf)) { 2090 ASSERT(ARC_BUF_LAST(buf)); 2091 continue; 2092 } 2093 (void) refcount_add_many(&state->arcs_esize[type], lsize, buf); 2094 } 2095} 2096 2097/* 2098 * Decrement the amount of evictable space in the arc_state_t's refcount. 2099 * We account for the space used by the hdr and the arc buf individually 2100 * so that we can add and remove them from the refcount individually. 2101 */ 2102static void 2103arc_evitable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2104{ 2105 arc_buf_contents_t type = arc_buf_type(hdr); 2106 uint64_t lsize = HDR_GET_LSIZE(hdr); 2107 2108 ASSERT(HDR_HAS_L1HDR(hdr)); 2109 2110 if (GHOST_STATE(state)) { 2111 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2112 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2113 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2114 (void) refcount_remove_many(&state->arcs_esize[type], 2115 lsize, hdr); 2116 return; 2117 } 2118 2119 ASSERT(!GHOST_STATE(state)); 2120 if (hdr->b_l1hdr.b_pdata != NULL) { 2121 (void) refcount_remove_many(&state->arcs_esize[type], 2122 arc_hdr_size(hdr), hdr); 2123 } 2124 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2125 buf = buf->b_next) { 2126 if (arc_buf_is_shared(buf)) { 2127 ASSERT(ARC_BUF_LAST(buf)); 2128 continue; 2129 } 2130 (void) refcount_remove_many(&state->arcs_esize[type], 2131 lsize, buf); 2132 } 2133} 2134 2135/* 2136 * Add a reference to this hdr indicating that someone is actively 2137 * referencing that memory. When the refcount transitions from 0 to 1, 2138 * we remove it from the respective arc_state_t list to indicate that 2139 * it is not evictable. 2140 */ 2141static void 2142add_reference(arc_buf_hdr_t *hdr, void *tag) 2143{ 2144 ASSERT(HDR_HAS_L1HDR(hdr)); 2145 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2146 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2147 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2148 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2149 } 2150 2151 arc_state_t *state = hdr->b_l1hdr.b_state; 2152 2153 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2154 (state != arc_anon)) { 2155 /* We don't use the L2-only state list. */ 2156 if (state != arc_l2c_only) { 2157 multilist_remove(&state->arcs_list[arc_buf_type(hdr)], 2158 hdr); 2159 arc_evitable_space_decrement(hdr, state); 2160 } 2161 /* remove the prefetch flag if we get a reference */ 2162 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2163 } 2164} 2165 2166/* 2167 * Remove a reference from this hdr. When the reference transitions from 2168 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2169 * list making it eligible for eviction. 2170 */ 2171static int 2172remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2173{ 2174 int cnt; 2175 arc_state_t *state = hdr->b_l1hdr.b_state; 2176 2177 ASSERT(HDR_HAS_L1HDR(hdr)); 2178 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2179 ASSERT(!GHOST_STATE(state)); 2180 2181 /* 2182 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2183 * check to prevent usage of the arc_l2c_only list. 2184 */ 2185 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2186 (state != arc_anon)) { 2187 multilist_insert(&state->arcs_list[arc_buf_type(hdr)], hdr); 2188 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2189 arc_evictable_space_increment(hdr, state); 2190 } 2191 return (cnt); 2192} 2193 2194/* 2195 * Move the supplied buffer to the indicated state. The hash lock 2196 * for the buffer must be held by the caller. 2197 */ 2198static void 2199arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2200 kmutex_t *hash_lock) 2201{ 2202 arc_state_t *old_state; 2203 int64_t refcnt; 2204 uint32_t bufcnt; 2205 boolean_t update_old, update_new; 2206 arc_buf_contents_t buftype = arc_buf_type(hdr); 2207 2208 /* 2209 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2210 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2211 * L1 hdr doesn't always exist when we change state to arc_anon before 2212 * destroying a header, in which case reallocating to add the L1 hdr is 2213 * pointless. 2214 */ 2215 if (HDR_HAS_L1HDR(hdr)) { 2216 old_state = hdr->b_l1hdr.b_state; 2217 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2218 bufcnt = hdr->b_l1hdr.b_bufcnt; 2219 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pdata != NULL); 2220 } else { 2221 old_state = arc_l2c_only; 2222 refcnt = 0; 2223 bufcnt = 0; 2224 update_old = B_FALSE; 2225 } 2226 update_new = update_old; 2227 2228 ASSERT(MUTEX_HELD(hash_lock)); 2229 ASSERT3P(new_state, !=, old_state); 2230 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2231 ASSERT(old_state != arc_anon || bufcnt <= 1); 2232 2233 /* 2234 * If this buffer is evictable, transfer it from the 2235 * old state list to the new state list. 2236 */ 2237 if (refcnt == 0) { 2238 if (old_state != arc_anon && old_state != arc_l2c_only) { 2239 ASSERT(HDR_HAS_L1HDR(hdr)); 2240 multilist_remove(&old_state->arcs_list[buftype], hdr); 2241 2242 if (GHOST_STATE(old_state)) { 2243 ASSERT0(bufcnt); 2244 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2245 update_old = B_TRUE; 2246 } 2247 arc_evitable_space_decrement(hdr, old_state); 2248 } 2249 if (new_state != arc_anon && new_state != arc_l2c_only) { 2250 2251 /* 2252 * An L1 header always exists here, since if we're 2253 * moving to some L1-cached state (i.e. not l2c_only or 2254 * anonymous), we realloc the header to add an L1hdr 2255 * beforehand. 2256 */ 2257 ASSERT(HDR_HAS_L1HDR(hdr)); 2258 multilist_insert(&new_state->arcs_list[buftype], hdr); 2259 2260 if (GHOST_STATE(new_state)) { 2261 ASSERT0(bufcnt); 2262 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2263 update_new = B_TRUE; 2264 } 2265 arc_evictable_space_increment(hdr, new_state); 2266 } 2267 } 2268 2269 ASSERT(!HDR_EMPTY(hdr)); 2270 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2271 buf_hash_remove(hdr); 2272 2273 /* adjust state sizes (ignore arc_l2c_only) */ 2274 2275 if (update_new && new_state != arc_l2c_only) { 2276 ASSERT(HDR_HAS_L1HDR(hdr)); 2277 if (GHOST_STATE(new_state)) { 2278 ASSERT0(bufcnt); 2279 2280 /* 2281 * When moving a header to a ghost state, we first 2282 * remove all arc buffers. Thus, we'll have a 2283 * bufcnt of zero, and no arc buffer to use for 2284 * the reference. As a result, we use the arc 2285 * header pointer for the reference. 2286 */ 2287 (void) refcount_add_many(&new_state->arcs_size, 2288 HDR_GET_LSIZE(hdr), hdr); 2289 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2290 } else { 2291 uint32_t buffers = 0; 2292 2293 /* 2294 * Each individual buffer holds a unique reference, 2295 * thus we must remove each of these references one 2296 * at a time. 2297 */ 2298 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2299 buf = buf->b_next) { 2300 ASSERT3U(bufcnt, !=, 0); 2301 buffers++; 2302 2303 /* 2304 * When the arc_buf_t is sharing the data 2305 * block with the hdr, the owner of the 2306 * reference belongs to the hdr. Only 2307 * add to the refcount if the arc_buf_t is 2308 * not shared. 2309 */ 2310 if (arc_buf_is_shared(buf)) { 2311 ASSERT(ARC_BUF_LAST(buf)); 2312 continue; 2313 } 2314 2315 (void) refcount_add_many(&new_state->arcs_size, 2316 HDR_GET_LSIZE(hdr), buf); 2317 } 2318 ASSERT3U(bufcnt, ==, buffers); 2319 2320 if (hdr->b_l1hdr.b_pdata != NULL) { 2321 (void) refcount_add_many(&new_state->arcs_size, 2322 arc_hdr_size(hdr), hdr); 2323 } else { 2324 ASSERT(GHOST_STATE(old_state)); 2325 } 2326 } 2327 } 2328 2329 if (update_old && old_state != arc_l2c_only) { 2330 ASSERT(HDR_HAS_L1HDR(hdr)); 2331 if (GHOST_STATE(old_state)) { 2332 ASSERT0(bufcnt); 2333 2334 /* 2335 * When moving a header off of a ghost state, 2336 * the header will not contain any arc buffers. 2337 * We use the arc header pointer for the reference 2338 * which is exactly what we did when we put the 2339 * header on the ghost state. 2340 */ 2341 2342 (void) refcount_remove_many(&old_state->arcs_size, 2343 HDR_GET_LSIZE(hdr), hdr); 2344 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2345 } else { 2346 uint32_t buffers = 0; 2347 2348 /* 2349 * Each individual buffer holds a unique reference, 2350 * thus we must remove each of these references one 2351 * at a time. 2352 */ 2353 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2354 buf = buf->b_next) { 2355 ASSERT3P(bufcnt, !=, 0); 2356 buffers++; 2357 2358 /* 2359 * When the arc_buf_t is sharing the data 2360 * block with the hdr, the owner of the 2361 * reference belongs to the hdr. Only 2362 * add to the refcount if the arc_buf_t is 2363 * not shared. 2364 */ 2365 if (arc_buf_is_shared(buf)) { 2366 ASSERT(ARC_BUF_LAST(buf)); 2367 continue; 2368 } 2369 2370 (void) refcount_remove_many( 2371 &old_state->arcs_size, HDR_GET_LSIZE(hdr), 2372 buf); 2373 } 2374 ASSERT3U(bufcnt, ==, buffers); 2375 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2376 (void) refcount_remove_many( 2377 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2378 } 2379 } 2380 2381 if (HDR_HAS_L1HDR(hdr)) 2382 hdr->b_l1hdr.b_state = new_state; 2383 2384 /* 2385 * L2 headers should never be on the L2 state list since they don't 2386 * have L1 headers allocated. 2387 */ 2388 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2389 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2390} 2391 2392void 2393arc_space_consume(uint64_t space, arc_space_type_t type) 2394{ 2395 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2396 2397 switch (type) { 2398 case ARC_SPACE_DATA: 2399 ARCSTAT_INCR(arcstat_data_size, space); 2400 break; 2401 case ARC_SPACE_META: 2402 ARCSTAT_INCR(arcstat_metadata_size, space); 2403 break; 2404 case ARC_SPACE_OTHER: 2405 ARCSTAT_INCR(arcstat_other_size, space); 2406 break; 2407 case ARC_SPACE_HDRS: 2408 ARCSTAT_INCR(arcstat_hdr_size, space); 2409 break; 2410 case ARC_SPACE_L2HDRS: 2411 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2412 break; 2413 } 2414 2415 if (type != ARC_SPACE_DATA) 2416 ARCSTAT_INCR(arcstat_meta_used, space); 2417 2418 atomic_add_64(&arc_size, space); 2419} 2420 2421void 2422arc_space_return(uint64_t space, arc_space_type_t type) 2423{ 2424 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2425 2426 switch (type) { 2427 case ARC_SPACE_DATA: 2428 ARCSTAT_INCR(arcstat_data_size, -space); 2429 break; 2430 case ARC_SPACE_META: 2431 ARCSTAT_INCR(arcstat_metadata_size, -space); 2432 break; 2433 case ARC_SPACE_OTHER: 2434 ARCSTAT_INCR(arcstat_other_size, -space); 2435 break; 2436 case ARC_SPACE_HDRS: 2437 ARCSTAT_INCR(arcstat_hdr_size, -space); 2438 break; 2439 case ARC_SPACE_L2HDRS: 2440 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2441 break; 2442 } 2443 2444 if (type != ARC_SPACE_DATA) { 2445 ASSERT(arc_meta_used >= space); 2446 if (arc_meta_max < arc_meta_used) 2447 arc_meta_max = arc_meta_used; 2448 ARCSTAT_INCR(arcstat_meta_used, -space); 2449 } 2450 2451 ASSERT(arc_size >= space); 2452 atomic_add_64(&arc_size, -space); 2453} 2454 2455/* 2456 * Allocate an initial buffer for this hdr, subsequent buffers will 2457 * use arc_buf_clone(). 2458 */ 2459static arc_buf_t * 2460arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag) 2461{ 2462 arc_buf_t *buf; 2463 2464 ASSERT(HDR_HAS_L1HDR(hdr)); 2465 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2466 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2467 hdr->b_type == ARC_BUFC_METADATA); 2468 2469 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2470 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2471 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2472 2473 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2474 buf->b_hdr = hdr; 2475 buf->b_data = NULL; 2476 buf->b_next = NULL; 2477 2478 add_reference(hdr, tag); 2479 2480 /* 2481 * We're about to change the hdr's b_flags. We must either 2482 * hold the hash_lock or be undiscoverable. 2483 */ 2484 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2485 2486 /* 2487 * If the hdr's data can be shared (no byteswapping, hdr is 2488 * uncompressed, hdr's data is not currently being written to the 2489 * L2ARC write) then we share the data buffer and set the appropriate 2490 * bit in the hdr's b_flags to indicate the hdr is sharing it's 2491 * b_pdata with the arc_buf_t. Otherwise, we allocate a new buffer to 2492 * store the buf's data. 2493 */ 2494 if (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2495 HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF && !HDR_L2_WRITING(hdr)) { 2496 buf->b_data = hdr->b_l1hdr.b_pdata; 2497 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2498 } else { 2499 buf->b_data = arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2500 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2501 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2502 } 2503 VERIFY3P(buf->b_data, !=, NULL); 2504 2505 hdr->b_l1hdr.b_buf = buf; 2506 hdr->b_l1hdr.b_bufcnt += 1; 2507 2508 return (buf); 2509} 2510 2511/* 2512 * Used when allocating additional buffers. 2513 */ 2514static arc_buf_t * 2515arc_buf_clone(arc_buf_t *from) 2516{ 2517 arc_buf_t *buf; 2518 arc_buf_hdr_t *hdr = from->b_hdr; 2519 uint64_t size = HDR_GET_LSIZE(hdr); 2520 2521 ASSERT(HDR_HAS_L1HDR(hdr)); 2522 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2523 2524 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2525 buf->b_hdr = hdr; 2526 buf->b_data = NULL; 2527 buf->b_next = hdr->b_l1hdr.b_buf; 2528 hdr->b_l1hdr.b_buf = buf; 2529 buf->b_data = arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2530 bcopy(from->b_data, buf->b_data, size); 2531 hdr->b_l1hdr.b_bufcnt += 1; 2532 2533 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2534 return (buf); 2535} 2536 2537static char *arc_onloan_tag = "onloan"; 2538 2539/* 2540 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2541 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2542 * buffers must be returned to the arc before they can be used by the DMU or 2543 * freed. 2544 */ 2545arc_buf_t * 2546arc_loan_buf(spa_t *spa, int size) 2547{ 2548 arc_buf_t *buf; 2549 2550 buf = arc_alloc_buf(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2551 2552 atomic_add_64(&arc_loaned_bytes, size); 2553 return (buf); 2554} 2555 2556/* 2557 * Return a loaned arc buffer to the arc. 2558 */ 2559void 2560arc_return_buf(arc_buf_t *buf, void *tag) 2561{ 2562 arc_buf_hdr_t *hdr = buf->b_hdr; 2563 2564 ASSERT3P(buf->b_data, !=, NULL); 2565 ASSERT(HDR_HAS_L1HDR(hdr)); 2566 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2567 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2568 2569 atomic_add_64(&arc_loaned_bytes, -HDR_GET_LSIZE(hdr)); 2570} 2571 2572/* Detach an arc_buf from a dbuf (tag) */ 2573void 2574arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2575{ 2576 arc_buf_hdr_t *hdr = buf->b_hdr; 2577 2578 ASSERT3P(buf->b_data, !=, NULL); 2579 ASSERT(HDR_HAS_L1HDR(hdr)); 2580 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2581 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2582 2583 atomic_add_64(&arc_loaned_bytes, HDR_GET_LSIZE(hdr)); 2584} 2585 2586static void 2587l2arc_free_data_on_write(void *data, size_t size, arc_buf_contents_t type) 2588{ 2589 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2590 2591 df->l2df_data = data; 2592 df->l2df_size = size; 2593 df->l2df_type = type; 2594 mutex_enter(&l2arc_free_on_write_mtx); 2595 list_insert_head(l2arc_free_on_write, df); 2596 mutex_exit(&l2arc_free_on_write_mtx); 2597} 2598 2599static void 2600arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2601{ 2602 arc_state_t *state = hdr->b_l1hdr.b_state; 2603 arc_buf_contents_t type = arc_buf_type(hdr); 2604 uint64_t size = arc_hdr_size(hdr); 2605 2606 /* protected by hash lock, if in the hash table */ 2607 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2608 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2609 ASSERT(state != arc_anon && state != arc_l2c_only); 2610 2611 (void) refcount_remove_many(&state->arcs_esize[type], 2612 size, hdr); 2613 } 2614 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2615 2616 l2arc_free_data_on_write(hdr->b_l1hdr.b_pdata, size, type); 2617} 2618 2619/* 2620 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2621 * data buffer, we transfer the refcount ownership to the hdr and update 2622 * the appropriate kstats. 2623 */ 2624static void 2625arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2626{ 2627 arc_state_t *state = hdr->b_l1hdr.b_state; 2628 2629 ASSERT(!HDR_SHARED_DATA(hdr)); 2630 ASSERT(!arc_buf_is_shared(buf)); 2631 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2632 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2633 2634 /* 2635 * Start sharing the data buffer. We transfer the 2636 * refcount ownership to the hdr since it always owns 2637 * the refcount whenever an arc_buf_t is shared. 2638 */ 2639 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 2640 hdr->b_l1hdr.b_pdata = buf->b_data; 2641 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2642 2643 /* 2644 * Since we've transferred ownership to the hdr we need 2645 * to increment its compressed and uncompressed kstats and 2646 * decrement the overhead size. 2647 */ 2648 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2649 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 2650 ARCSTAT_INCR(arcstat_overhead_size, -HDR_GET_LSIZE(hdr)); 2651} 2652 2653static void 2654arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2655{ 2656 arc_state_t *state = hdr->b_l1hdr.b_state; 2657 2658 ASSERT(HDR_SHARED_DATA(hdr)); 2659 ASSERT(arc_buf_is_shared(buf)); 2660 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2661 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2662 2663 /* 2664 * We are no longer sharing this buffer so we need 2665 * to transfer its ownership to the rightful owner. 2666 */ 2667 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 2668 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2669 hdr->b_l1hdr.b_pdata = NULL; 2670 2671 /* 2672 * Since the buffer is no longer shared between 2673 * the arc buf and the hdr, count it as overhead. 2674 */ 2675 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2676 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2677 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2678} 2679 2680/* 2681 * Free up buf->b_data and if 'remove' is set, then pull the 2682 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2683 */ 2684static void 2685arc_buf_destroy_impl(arc_buf_t *buf, boolean_t remove) 2686{ 2687 arc_buf_t **bufp; 2688 arc_buf_hdr_t *hdr = buf->b_hdr; 2689 uint64_t size = HDR_GET_LSIZE(hdr); 2690 boolean_t destroyed_buf_is_shared = arc_buf_is_shared(buf); 2691 2692 /* 2693 * Free up the data associated with the buf but only 2694 * if we're not sharing this with the hdr. If we are sharing 2695 * it with the hdr, then hdr will have performed the allocation 2696 * so allow it to do the free. 2697 */ 2698 if (buf->b_data != NULL) { 2699 /* 2700 * We're about to change the hdr's b_flags. We must either 2701 * hold the hash_lock or be undiscoverable. 2702 */ 2703 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2704 2705 arc_cksum_verify(buf); 2706#ifdef illumos 2707 arc_buf_unwatch(buf); 2708#endif 2709 2710 if (destroyed_buf_is_shared) { 2711 ASSERT(ARC_BUF_LAST(buf)); 2712 ASSERT(HDR_SHARED_DATA(hdr)); 2713 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2714 } else { 2715 arc_free_data_buf(hdr, buf->b_data, size, buf); 2716 ARCSTAT_INCR(arcstat_overhead_size, -size); 2717 } 2718 buf->b_data = NULL; 2719 2720 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 2721 hdr->b_l1hdr.b_bufcnt -= 1; 2722 } 2723 2724 /* only remove the buf if requested */ 2725 if (!remove) 2726 return; 2727 2728 /* remove the buf from the hdr list */ 2729 arc_buf_t *lastbuf = NULL; 2730 bufp = &hdr->b_l1hdr.b_buf; 2731 while (*bufp != NULL) { 2732 if (*bufp == buf) 2733 *bufp = buf->b_next; 2734 2735 /* 2736 * If we've removed a buffer in the middle of 2737 * the list then update the lastbuf and update 2738 * bufp. 2739 */ 2740 if (*bufp != NULL) { 2741 lastbuf = *bufp; 2742 bufp = &(*bufp)->b_next; 2743 } 2744 } 2745 buf->b_next = NULL; 2746 ASSERT3P(lastbuf, !=, buf); 2747 2748 /* 2749 * If the current arc_buf_t is sharing its data 2750 * buffer with the hdr, then reassign the hdr's 2751 * b_pdata to share it with the new buffer at the end 2752 * of the list. The shared buffer is always the last one 2753 * on the hdr's buffer list. 2754 */ 2755 if (destroyed_buf_is_shared && lastbuf != NULL) { 2756 ASSERT(ARC_BUF_LAST(buf)); 2757 ASSERT(ARC_BUF_LAST(lastbuf)); 2758 VERIFY(!arc_buf_is_shared(lastbuf)); 2759 2760 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2761 arc_hdr_free_pdata(hdr); 2762 2763 /* 2764 * We must setup a new shared block between the 2765 * last buffer and the hdr. The data would have 2766 * been allocated by the arc buf so we need to transfer 2767 * ownership to the hdr since it's now being shared. 2768 */ 2769 arc_share_buf(hdr, lastbuf); 2770 } else if (HDR_SHARED_DATA(hdr)) { 2771 ASSERT(arc_buf_is_shared(lastbuf)); 2772 } 2773 2774 if (hdr->b_l1hdr.b_bufcnt == 0) 2775 arc_cksum_free(hdr); 2776 2777 /* clean up the buf */ 2778 buf->b_hdr = NULL; 2779 kmem_cache_free(buf_cache, buf); 2780} 2781 2782static void 2783arc_hdr_alloc_pdata(arc_buf_hdr_t *hdr) 2784{ 2785 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2786 ASSERT(HDR_HAS_L1HDR(hdr)); 2787 ASSERT(!HDR_SHARED_DATA(hdr)); 2788 2789 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2790 hdr->b_l1hdr.b_pdata = arc_get_data_buf(hdr, arc_hdr_size(hdr), hdr); 2791 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 2792 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2793 2794 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2795 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 2796} 2797 2798static void 2799arc_hdr_free_pdata(arc_buf_hdr_t *hdr) 2800{ 2801 ASSERT(HDR_HAS_L1HDR(hdr)); 2802 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2803 2804 /* 2805 * If the hdr is currently being written to the l2arc then 2806 * we defer freeing the data by adding it to the l2arc_free_on_write 2807 * list. The l2arc will free the data once it's finished 2808 * writing it to the l2arc device. 2809 */ 2810 if (HDR_L2_WRITING(hdr)) { 2811 arc_hdr_free_on_write(hdr); 2812 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2813 } else { 2814 arc_free_data_buf(hdr, hdr->b_l1hdr.b_pdata, 2815 arc_hdr_size(hdr), hdr); 2816 } 2817 hdr->b_l1hdr.b_pdata = NULL; 2818 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 2819 2820 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2821 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2822} 2823 2824static arc_buf_hdr_t * 2825arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 2826 enum zio_compress compress, arc_buf_contents_t type) 2827{ 2828 arc_buf_hdr_t *hdr; 2829 2830 ASSERT3U(lsize, >, 0); 2831 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 2832 2833 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2834 ASSERT(HDR_EMPTY(hdr)); 2835 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 2836 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 2837 HDR_SET_PSIZE(hdr, psize); 2838 HDR_SET_LSIZE(hdr, lsize); 2839 hdr->b_spa = spa; 2840 hdr->b_type = type; 2841 hdr->b_flags = 0; 2842 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 2843 arc_hdr_set_compress(hdr, compress); 2844 2845 hdr->b_l1hdr.b_state = arc_anon; 2846 hdr->b_l1hdr.b_arc_access = 0; 2847 hdr->b_l1hdr.b_bufcnt = 0; 2848 hdr->b_l1hdr.b_buf = NULL; 2849 2850 /* 2851 * Allocate the hdr's buffer. This will contain either 2852 * the compressed or uncompressed data depending on the block 2853 * it references and compressed arc enablement. 2854 */ 2855 arc_hdr_alloc_pdata(hdr); 2856 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2857 2858 return (hdr); 2859} 2860 2861/* 2862 * Transition between the two allocation states for the arc_buf_hdr struct. 2863 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 2864 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 2865 * version is used when a cache buffer is only in the L2ARC in order to reduce 2866 * memory usage. 2867 */ 2868static arc_buf_hdr_t * 2869arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 2870{ 2871 ASSERT(HDR_HAS_L2HDR(hdr)); 2872 2873 arc_buf_hdr_t *nhdr; 2874 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2875 2876 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 2877 (old == hdr_l2only_cache && new == hdr_full_cache)); 2878 2879 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 2880 2881 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 2882 buf_hash_remove(hdr); 2883 2884 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 2885 2886 if (new == hdr_full_cache) { 2887 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 2888 /* 2889 * arc_access and arc_change_state need to be aware that a 2890 * header has just come out of L2ARC, so we set its state to 2891 * l2c_only even though it's about to change. 2892 */ 2893 nhdr->b_l1hdr.b_state = arc_l2c_only; 2894 2895 /* Verify previous threads set to NULL before freeing */ 2896 ASSERT3P(nhdr->b_l1hdr.b_pdata, ==, NULL); 2897 } else { 2898 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2899 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2900 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 2901 2902 /* 2903 * If we've reached here, We must have been called from 2904 * arc_evict_hdr(), as such we should have already been 2905 * removed from any ghost list we were previously on 2906 * (which protects us from racing with arc_evict_state), 2907 * thus no locking is needed during this check. 2908 */ 2909 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2910 2911 /* 2912 * A buffer must not be moved into the arc_l2c_only 2913 * state if it's not finished being written out to the 2914 * l2arc device. Otherwise, the b_l1hdr.b_pdata field 2915 * might try to be accessed, even though it was removed. 2916 */ 2917 VERIFY(!HDR_L2_WRITING(hdr)); 2918 VERIFY3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2919 2920#ifdef ZFS_DEBUG 2921 if (hdr->b_l1hdr.b_thawed != NULL) { 2922 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2923 hdr->b_l1hdr.b_thawed = NULL; 2924 } 2925#endif 2926 2927 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 2928 } 2929 /* 2930 * The header has been reallocated so we need to re-insert it into any 2931 * lists it was on. 2932 */ 2933 (void) buf_hash_insert(nhdr, NULL); 2934 2935 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 2936 2937 mutex_enter(&dev->l2ad_mtx); 2938 2939 /* 2940 * We must place the realloc'ed header back into the list at 2941 * the same spot. Otherwise, if it's placed earlier in the list, 2942 * l2arc_write_buffers() could find it during the function's 2943 * write phase, and try to write it out to the l2arc. 2944 */ 2945 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 2946 list_remove(&dev->l2ad_buflist, hdr); 2947 2948 mutex_exit(&dev->l2ad_mtx); 2949 2950 /* 2951 * Since we're using the pointer address as the tag when 2952 * incrementing and decrementing the l2ad_alloc refcount, we 2953 * must remove the old pointer (that we're about to destroy) and 2954 * add the new pointer to the refcount. Otherwise we'd remove 2955 * the wrong pointer address when calling arc_hdr_destroy() later. 2956 */ 2957 2958 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 2959 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 2960 2961 buf_discard_identity(hdr); 2962 kmem_cache_free(old, hdr); 2963 2964 return (nhdr); 2965} 2966 2967/* 2968 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 2969 * The buf is returned thawed since we expect the consumer to modify it. 2970 */ 2971arc_buf_t * 2972arc_alloc_buf(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2973{ 2974 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 2975 ZIO_COMPRESS_OFF, type); 2976 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 2977 arc_buf_t *buf = arc_buf_alloc_impl(hdr, tag); 2978 arc_buf_thaw(buf); 2979 return (buf); 2980} 2981 2982static void 2983arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2984{ 2985 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2986 l2arc_dev_t *dev = l2hdr->b_dev; 2987 uint64_t asize = arc_hdr_size(hdr); 2988 2989 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2990 ASSERT(HDR_HAS_L2HDR(hdr)); 2991 2992 list_remove(&dev->l2ad_buflist, hdr); 2993 2994 ARCSTAT_INCR(arcstat_l2_asize, -asize); 2995 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 2996 2997 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0); 2998 2999 (void) refcount_remove_many(&dev->l2ad_alloc, asize, hdr); 3000 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3001} 3002 3003static void 3004arc_hdr_destroy(arc_buf_hdr_t *hdr) 3005{ 3006 if (HDR_HAS_L1HDR(hdr)) { 3007 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3008 hdr->b_l1hdr.b_bufcnt > 0); 3009 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3010 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3011 } 3012 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3013 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3014 3015 if (!HDR_EMPTY(hdr)) 3016 buf_discard_identity(hdr); 3017 3018 if (HDR_HAS_L2HDR(hdr)) { 3019 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3020 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3021 3022 if (!buflist_held) 3023 mutex_enter(&dev->l2ad_mtx); 3024 3025 /* 3026 * Even though we checked this conditional above, we 3027 * need to check this again now that we have the 3028 * l2ad_mtx. This is because we could be racing with 3029 * another thread calling l2arc_evict() which might have 3030 * destroyed this header's L2 portion as we were waiting 3031 * to acquire the l2ad_mtx. If that happens, we don't 3032 * want to re-destroy the header's L2 portion. 3033 */ 3034 if (HDR_HAS_L2HDR(hdr)) { 3035 l2arc_trim(hdr); 3036 arc_hdr_l2hdr_destroy(hdr); 3037 } 3038 3039 if (!buflist_held) 3040 mutex_exit(&dev->l2ad_mtx); 3041 } 3042 3043 if (HDR_HAS_L1HDR(hdr)) { 3044 arc_cksum_free(hdr); 3045 3046 while (hdr->b_l1hdr.b_buf != NULL) 3047 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf, B_TRUE); 3048 3049#ifdef ZFS_DEBUG 3050 if (hdr->b_l1hdr.b_thawed != NULL) { 3051 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3052 hdr->b_l1hdr.b_thawed = NULL; 3053 } 3054#endif 3055 3056 if (hdr->b_l1hdr.b_pdata != NULL) { 3057 arc_hdr_free_pdata(hdr); 3058 } 3059 } 3060 3061 ASSERT3P(hdr->b_hash_next, ==, NULL); 3062 if (HDR_HAS_L1HDR(hdr)) { 3063 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3064 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3065 kmem_cache_free(hdr_full_cache, hdr); 3066 } else { 3067 kmem_cache_free(hdr_l2only_cache, hdr); 3068 } 3069} 3070 3071void 3072arc_buf_destroy(arc_buf_t *buf, void* tag) 3073{ 3074 arc_buf_hdr_t *hdr = buf->b_hdr; 3075 kmutex_t *hash_lock = HDR_LOCK(hdr); 3076 3077 if (hdr->b_l1hdr.b_state == arc_anon) { 3078 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3079 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3080 VERIFY0(remove_reference(hdr, NULL, tag)); 3081 arc_hdr_destroy(hdr); 3082 return; 3083 } 3084 3085 mutex_enter(hash_lock); 3086 ASSERT3P(hdr, ==, buf->b_hdr); 3087 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3088 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3089 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3090 ASSERT3P(buf->b_data, !=, NULL); 3091 3092 (void) remove_reference(hdr, hash_lock, tag); 3093 arc_buf_destroy_impl(buf, B_TRUE); 3094 mutex_exit(hash_lock); 3095} 3096 3097int32_t 3098arc_buf_size(arc_buf_t *buf) 3099{ 3100 return (HDR_GET_LSIZE(buf->b_hdr)); 3101} 3102 3103/* 3104 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3105 * state of the header is dependent on it's state prior to entering this 3106 * function. The following transitions are possible: 3107 * 3108 * - arc_mru -> arc_mru_ghost 3109 * - arc_mfu -> arc_mfu_ghost 3110 * - arc_mru_ghost -> arc_l2c_only 3111 * - arc_mru_ghost -> deleted 3112 * - arc_mfu_ghost -> arc_l2c_only 3113 * - arc_mfu_ghost -> deleted 3114 */ 3115static int64_t 3116arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3117{ 3118 arc_state_t *evicted_state, *state; 3119 int64_t bytes_evicted = 0; 3120 3121 ASSERT(MUTEX_HELD(hash_lock)); 3122 ASSERT(HDR_HAS_L1HDR(hdr)); 3123 3124 state = hdr->b_l1hdr.b_state; 3125 if (GHOST_STATE(state)) { 3126 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3127 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3128 3129 /* 3130 * l2arc_write_buffers() relies on a header's L1 portion 3131 * (i.e. its b_pdata field) during its write phase. 3132 * Thus, we cannot push a header onto the arc_l2c_only 3133 * state (removing it's L1 piece) until the header is 3134 * done being written to the l2arc. 3135 */ 3136 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3137 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3138 return (bytes_evicted); 3139 } 3140 3141 ARCSTAT_BUMP(arcstat_deleted); 3142 bytes_evicted += HDR_GET_LSIZE(hdr); 3143 3144 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3145 3146 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 3147 if (HDR_HAS_L2HDR(hdr)) { 3148 ASSERT(hdr->b_l1hdr.b_pdata == NULL); 3149 /* 3150 * This buffer is cached on the 2nd Level ARC; 3151 * don't destroy the header. 3152 */ 3153 arc_change_state(arc_l2c_only, hdr, hash_lock); 3154 /* 3155 * dropping from L1+L2 cached to L2-only, 3156 * realloc to remove the L1 header. 3157 */ 3158 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3159 hdr_l2only_cache); 3160 } else { 3161 ASSERT(hdr->b_l1hdr.b_pdata == NULL); 3162 arc_change_state(arc_anon, hdr, hash_lock); 3163 arc_hdr_destroy(hdr); 3164 } 3165 return (bytes_evicted); 3166 } 3167 3168 ASSERT(state == arc_mru || state == arc_mfu); 3169 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3170 3171 /* prefetch buffers have a minimum lifespan */ 3172 if (HDR_IO_IN_PROGRESS(hdr) || 3173 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3174 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 3175 arc_min_prefetch_lifespan)) { 3176 ARCSTAT_BUMP(arcstat_evict_skip); 3177 return (bytes_evicted); 3178 } 3179 3180 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3181 while (hdr->b_l1hdr.b_buf) { 3182 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3183 if (!mutex_tryenter(&buf->b_evict_lock)) { 3184 ARCSTAT_BUMP(arcstat_mutex_miss); 3185 break; 3186 } 3187 if (buf->b_data != NULL) 3188 bytes_evicted += HDR_GET_LSIZE(hdr); 3189 mutex_exit(&buf->b_evict_lock); 3190 arc_buf_destroy_impl(buf, B_TRUE); 3191 } 3192 3193 if (HDR_HAS_L2HDR(hdr)) { 3194 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3195 } else { 3196 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3197 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3198 HDR_GET_LSIZE(hdr)); 3199 } else { 3200 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3201 HDR_GET_LSIZE(hdr)); 3202 } 3203 } 3204 3205 if (hdr->b_l1hdr.b_bufcnt == 0) { 3206 arc_cksum_free(hdr); 3207 3208 bytes_evicted += arc_hdr_size(hdr); 3209 3210 /* 3211 * If this hdr is being evicted and has a compressed 3212 * buffer then we discard it here before we change states. 3213 * This ensures that the accounting is updated correctly 3214 * in arc_free_data_buf(). 3215 */ 3216 arc_hdr_free_pdata(hdr); 3217 3218 arc_change_state(evicted_state, hdr, hash_lock); 3219 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3220 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3221 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3222 } 3223 3224 return (bytes_evicted); 3225} 3226 3227static uint64_t 3228arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3229 uint64_t spa, int64_t bytes) 3230{ 3231 multilist_sublist_t *mls; 3232 uint64_t bytes_evicted = 0; 3233 arc_buf_hdr_t *hdr; 3234 kmutex_t *hash_lock; 3235 int evict_count = 0; 3236 3237 ASSERT3P(marker, !=, NULL); 3238 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3239 3240 mls = multilist_sublist_lock(ml, idx); 3241 3242 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3243 hdr = multilist_sublist_prev(mls, marker)) { 3244 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3245 (evict_count >= zfs_arc_evict_batch_limit)) 3246 break; 3247 3248 /* 3249 * To keep our iteration location, move the marker 3250 * forward. Since we're not holding hdr's hash lock, we 3251 * must be very careful and not remove 'hdr' from the 3252 * sublist. Otherwise, other consumers might mistake the 3253 * 'hdr' as not being on a sublist when they call the 3254 * multilist_link_active() function (they all rely on 3255 * the hash lock protecting concurrent insertions and 3256 * removals). multilist_sublist_move_forward() was 3257 * specifically implemented to ensure this is the case 3258 * (only 'marker' will be removed and re-inserted). 3259 */ 3260 multilist_sublist_move_forward(mls, marker); 3261 3262 /* 3263 * The only case where the b_spa field should ever be 3264 * zero, is the marker headers inserted by 3265 * arc_evict_state(). It's possible for multiple threads 3266 * to be calling arc_evict_state() concurrently (e.g. 3267 * dsl_pool_close() and zio_inject_fault()), so we must 3268 * skip any markers we see from these other threads. 3269 */ 3270 if (hdr->b_spa == 0) 3271 continue; 3272 3273 /* we're only interested in evicting buffers of a certain spa */ 3274 if (spa != 0 && hdr->b_spa != spa) { 3275 ARCSTAT_BUMP(arcstat_evict_skip); 3276 continue; 3277 } 3278 3279 hash_lock = HDR_LOCK(hdr); 3280 3281 /* 3282 * We aren't calling this function from any code path 3283 * that would already be holding a hash lock, so we're 3284 * asserting on this assumption to be defensive in case 3285 * this ever changes. Without this check, it would be 3286 * possible to incorrectly increment arcstat_mutex_miss 3287 * below (e.g. if the code changed such that we called 3288 * this function with a hash lock held). 3289 */ 3290 ASSERT(!MUTEX_HELD(hash_lock)); 3291 3292 if (mutex_tryenter(hash_lock)) { 3293 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3294 mutex_exit(hash_lock); 3295 3296 bytes_evicted += evicted; 3297 3298 /* 3299 * If evicted is zero, arc_evict_hdr() must have 3300 * decided to skip this header, don't increment 3301 * evict_count in this case. 3302 */ 3303 if (evicted != 0) 3304 evict_count++; 3305 3306 /* 3307 * If arc_size isn't overflowing, signal any 3308 * threads that might happen to be waiting. 3309 * 3310 * For each header evicted, we wake up a single 3311 * thread. If we used cv_broadcast, we could 3312 * wake up "too many" threads causing arc_size 3313 * to significantly overflow arc_c; since 3314 * arc_get_data_buf() doesn't check for overflow 3315 * when it's woken up (it doesn't because it's 3316 * possible for the ARC to be overflowing while 3317 * full of un-evictable buffers, and the 3318 * function should proceed in this case). 3319 * 3320 * If threads are left sleeping, due to not 3321 * using cv_broadcast, they will be woken up 3322 * just before arc_reclaim_thread() sleeps. 3323 */ 3324 mutex_enter(&arc_reclaim_lock); 3325 if (!arc_is_overflowing()) 3326 cv_signal(&arc_reclaim_waiters_cv); 3327 mutex_exit(&arc_reclaim_lock); 3328 } else { 3329 ARCSTAT_BUMP(arcstat_mutex_miss); 3330 } 3331 } 3332 3333 multilist_sublist_unlock(mls); 3334 3335 return (bytes_evicted); 3336} 3337 3338/* 3339 * Evict buffers from the given arc state, until we've removed the 3340 * specified number of bytes. Move the removed buffers to the 3341 * appropriate evict state. 3342 * 3343 * This function makes a "best effort". It skips over any buffers 3344 * it can't get a hash_lock on, and so, may not catch all candidates. 3345 * It may also return without evicting as much space as requested. 3346 * 3347 * If bytes is specified using the special value ARC_EVICT_ALL, this 3348 * will evict all available (i.e. unlocked and evictable) buffers from 3349 * the given arc state; which is used by arc_flush(). 3350 */ 3351static uint64_t 3352arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3353 arc_buf_contents_t type) 3354{ 3355 uint64_t total_evicted = 0; 3356 multilist_t *ml = &state->arcs_list[type]; 3357 int num_sublists; 3358 arc_buf_hdr_t **markers; 3359 3360 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3361 3362 num_sublists = multilist_get_num_sublists(ml); 3363 3364 /* 3365 * If we've tried to evict from each sublist, made some 3366 * progress, but still have not hit the target number of bytes 3367 * to evict, we want to keep trying. The markers allow us to 3368 * pick up where we left off for each individual sublist, rather 3369 * than starting from the tail each time. 3370 */ 3371 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3372 for (int i = 0; i < num_sublists; i++) { 3373 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3374 3375 /* 3376 * A b_spa of 0 is used to indicate that this header is 3377 * a marker. This fact is used in arc_adjust_type() and 3378 * arc_evict_state_impl(). 3379 */ 3380 markers[i]->b_spa = 0; 3381 3382 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3383 multilist_sublist_insert_tail(mls, markers[i]); 3384 multilist_sublist_unlock(mls); 3385 } 3386 3387 /* 3388 * While we haven't hit our target number of bytes to evict, or 3389 * we're evicting all available buffers. 3390 */ 3391 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3392 /* 3393 * Start eviction using a randomly selected sublist, 3394 * this is to try and evenly balance eviction across all 3395 * sublists. Always starting at the same sublist 3396 * (e.g. index 0) would cause evictions to favor certain 3397 * sublists over others. 3398 */ 3399 int sublist_idx = multilist_get_random_index(ml); 3400 uint64_t scan_evicted = 0; 3401 3402 for (int i = 0; i < num_sublists; i++) { 3403 uint64_t bytes_remaining; 3404 uint64_t bytes_evicted; 3405 3406 if (bytes == ARC_EVICT_ALL) 3407 bytes_remaining = ARC_EVICT_ALL; 3408 else if (total_evicted < bytes) 3409 bytes_remaining = bytes - total_evicted; 3410 else 3411 break; 3412 3413 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3414 markers[sublist_idx], spa, bytes_remaining); 3415 3416 scan_evicted += bytes_evicted; 3417 total_evicted += bytes_evicted; 3418 3419 /* we've reached the end, wrap to the beginning */ 3420 if (++sublist_idx >= num_sublists) 3421 sublist_idx = 0; 3422 } 3423 3424 /* 3425 * If we didn't evict anything during this scan, we have 3426 * no reason to believe we'll evict more during another 3427 * scan, so break the loop. 3428 */ 3429 if (scan_evicted == 0) { 3430 /* This isn't possible, let's make that obvious */ 3431 ASSERT3S(bytes, !=, 0); 3432 3433 /* 3434 * When bytes is ARC_EVICT_ALL, the only way to 3435 * break the loop is when scan_evicted is zero. 3436 * In that case, we actually have evicted enough, 3437 * so we don't want to increment the kstat. 3438 */ 3439 if (bytes != ARC_EVICT_ALL) { 3440 ASSERT3S(total_evicted, <, bytes); 3441 ARCSTAT_BUMP(arcstat_evict_not_enough); 3442 } 3443 3444 break; 3445 } 3446 } 3447 3448 for (int i = 0; i < num_sublists; i++) { 3449 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3450 multilist_sublist_remove(mls, markers[i]); 3451 multilist_sublist_unlock(mls); 3452 3453 kmem_cache_free(hdr_full_cache, markers[i]); 3454 } 3455 kmem_free(markers, sizeof (*markers) * num_sublists); 3456 3457 return (total_evicted); 3458} 3459 3460/* 3461 * Flush all "evictable" data of the given type from the arc state 3462 * specified. This will not evict any "active" buffers (i.e. referenced). 3463 * 3464 * When 'retry' is set to B_FALSE, the function will make a single pass 3465 * over the state and evict any buffers that it can. Since it doesn't 3466 * continually retry the eviction, it might end up leaving some buffers 3467 * in the ARC due to lock misses. 3468 * 3469 * When 'retry' is set to B_TRUE, the function will continually retry the 3470 * eviction until *all* evictable buffers have been removed from the 3471 * state. As a result, if concurrent insertions into the state are 3472 * allowed (e.g. if the ARC isn't shutting down), this function might 3473 * wind up in an infinite loop, continually trying to evict buffers. 3474 */ 3475static uint64_t 3476arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3477 boolean_t retry) 3478{ 3479 uint64_t evicted = 0; 3480 3481 while (refcount_count(&state->arcs_esize[type]) != 0) { 3482 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3483 3484 if (!retry) 3485 break; 3486 } 3487 3488 return (evicted); 3489} 3490 3491/* 3492 * Evict the specified number of bytes from the state specified, 3493 * restricting eviction to the spa and type given. This function 3494 * prevents us from trying to evict more from a state's list than 3495 * is "evictable", and to skip evicting altogether when passed a 3496 * negative value for "bytes". In contrast, arc_evict_state() will 3497 * evict everything it can, when passed a negative value for "bytes". 3498 */ 3499static uint64_t 3500arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3501 arc_buf_contents_t type) 3502{ 3503 int64_t delta; 3504 3505 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3506 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3507 return (arc_evict_state(state, spa, delta, type)); 3508 } 3509 3510 return (0); 3511} 3512 3513/* 3514 * Evict metadata buffers from the cache, such that arc_meta_used is 3515 * capped by the arc_meta_limit tunable. 3516 */ 3517static uint64_t 3518arc_adjust_meta(void) 3519{ 3520 uint64_t total_evicted = 0; 3521 int64_t target; 3522 3523 /* 3524 * If we're over the meta limit, we want to evict enough 3525 * metadata to get back under the meta limit. We don't want to 3526 * evict so much that we drop the MRU below arc_p, though. If 3527 * we're over the meta limit more than we're over arc_p, we 3528 * evict some from the MRU here, and some from the MFU below. 3529 */ 3530 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3531 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3532 refcount_count(&arc_mru->arcs_size) - arc_p)); 3533 3534 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3535 3536 /* 3537 * Similar to the above, we want to evict enough bytes to get us 3538 * below the meta limit, but not so much as to drop us below the 3539 * space alloted to the MFU (which is defined as arc_c - arc_p). 3540 */ 3541 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3542 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3543 3544 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3545 3546 return (total_evicted); 3547} 3548 3549/* 3550 * Return the type of the oldest buffer in the given arc state 3551 * 3552 * This function will select a random sublist of type ARC_BUFC_DATA and 3553 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3554 * is compared, and the type which contains the "older" buffer will be 3555 * returned. 3556 */ 3557static arc_buf_contents_t 3558arc_adjust_type(arc_state_t *state) 3559{ 3560 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3561 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3562 int data_idx = multilist_get_random_index(data_ml); 3563 int meta_idx = multilist_get_random_index(meta_ml); 3564 multilist_sublist_t *data_mls; 3565 multilist_sublist_t *meta_mls; 3566 arc_buf_contents_t type; 3567 arc_buf_hdr_t *data_hdr; 3568 arc_buf_hdr_t *meta_hdr; 3569 3570 /* 3571 * We keep the sublist lock until we're finished, to prevent 3572 * the headers from being destroyed via arc_evict_state(). 3573 */ 3574 data_mls = multilist_sublist_lock(data_ml, data_idx); 3575 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3576 3577 /* 3578 * These two loops are to ensure we skip any markers that 3579 * might be at the tail of the lists due to arc_evict_state(). 3580 */ 3581 3582 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3583 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3584 if (data_hdr->b_spa != 0) 3585 break; 3586 } 3587 3588 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3589 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3590 if (meta_hdr->b_spa != 0) 3591 break; 3592 } 3593 3594 if (data_hdr == NULL && meta_hdr == NULL) { 3595 type = ARC_BUFC_DATA; 3596 } else if (data_hdr == NULL) { 3597 ASSERT3P(meta_hdr, !=, NULL); 3598 type = ARC_BUFC_METADATA; 3599 } else if (meta_hdr == NULL) { 3600 ASSERT3P(data_hdr, !=, NULL); 3601 type = ARC_BUFC_DATA; 3602 } else { 3603 ASSERT3P(data_hdr, !=, NULL); 3604 ASSERT3P(meta_hdr, !=, NULL); 3605 3606 /* The headers can't be on the sublist without an L1 header */ 3607 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3608 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3609 3610 if (data_hdr->b_l1hdr.b_arc_access < 3611 meta_hdr->b_l1hdr.b_arc_access) { 3612 type = ARC_BUFC_DATA; 3613 } else { 3614 type = ARC_BUFC_METADATA; 3615 } 3616 } 3617 3618 multilist_sublist_unlock(meta_mls); 3619 multilist_sublist_unlock(data_mls); 3620 3621 return (type); 3622} 3623 3624/* 3625 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3626 */ 3627static uint64_t 3628arc_adjust(void) 3629{ 3630 uint64_t total_evicted = 0; 3631 uint64_t bytes; 3632 int64_t target; 3633 3634 /* 3635 * If we're over arc_meta_limit, we want to correct that before 3636 * potentially evicting data buffers below. 3637 */ 3638 total_evicted += arc_adjust_meta(); 3639 3640 /* 3641 * Adjust MRU size 3642 * 3643 * If we're over the target cache size, we want to evict enough 3644 * from the list to get back to our target size. We don't want 3645 * to evict too much from the MRU, such that it drops below 3646 * arc_p. So, if we're over our target cache size more than 3647 * the MRU is over arc_p, we'll evict enough to get back to 3648 * arc_p here, and then evict more from the MFU below. 3649 */ 3650 target = MIN((int64_t)(arc_size - arc_c), 3651 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3652 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3653 3654 /* 3655 * If we're below arc_meta_min, always prefer to evict data. 3656 * Otherwise, try to satisfy the requested number of bytes to 3657 * evict from the type which contains older buffers; in an 3658 * effort to keep newer buffers in the cache regardless of their 3659 * type. If we cannot satisfy the number of bytes from this 3660 * type, spill over into the next type. 3661 */ 3662 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3663 arc_meta_used > arc_meta_min) { 3664 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3665 total_evicted += bytes; 3666 3667 /* 3668 * If we couldn't evict our target number of bytes from 3669 * metadata, we try to get the rest from data. 3670 */ 3671 target -= bytes; 3672 3673 total_evicted += 3674 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3675 } else { 3676 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3677 total_evicted += bytes; 3678 3679 /* 3680 * If we couldn't evict our target number of bytes from 3681 * data, we try to get the rest from metadata. 3682 */ 3683 target -= bytes; 3684 3685 total_evicted += 3686 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3687 } 3688 3689 /* 3690 * Adjust MFU size 3691 * 3692 * Now that we've tried to evict enough from the MRU to get its 3693 * size back to arc_p, if we're still above the target cache 3694 * size, we evict the rest from the MFU. 3695 */ 3696 target = arc_size - arc_c; 3697 3698 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3699 arc_meta_used > arc_meta_min) { 3700 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3701 total_evicted += bytes; 3702 3703 /* 3704 * If we couldn't evict our target number of bytes from 3705 * metadata, we try to get the rest from data. 3706 */ 3707 target -= bytes; 3708 3709 total_evicted += 3710 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3711 } else { 3712 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3713 total_evicted += bytes; 3714 3715 /* 3716 * If we couldn't evict our target number of bytes from 3717 * data, we try to get the rest from data. 3718 */ 3719 target -= bytes; 3720 3721 total_evicted += 3722 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3723 } 3724 3725 /* 3726 * Adjust ghost lists 3727 * 3728 * In addition to the above, the ARC also defines target values 3729 * for the ghost lists. The sum of the mru list and mru ghost 3730 * list should never exceed the target size of the cache, and 3731 * the sum of the mru list, mfu list, mru ghost list, and mfu 3732 * ghost list should never exceed twice the target size of the 3733 * cache. The following logic enforces these limits on the ghost 3734 * caches, and evicts from them as needed. 3735 */ 3736 target = refcount_count(&arc_mru->arcs_size) + 3737 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3738 3739 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3740 total_evicted += bytes; 3741 3742 target -= bytes; 3743 3744 total_evicted += 3745 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3746 3747 /* 3748 * We assume the sum of the mru list and mfu list is less than 3749 * or equal to arc_c (we enforced this above), which means we 3750 * can use the simpler of the two equations below: 3751 * 3752 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3753 * mru ghost + mfu ghost <= arc_c 3754 */ 3755 target = refcount_count(&arc_mru_ghost->arcs_size) + 3756 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3757 3758 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3759 total_evicted += bytes; 3760 3761 target -= bytes; 3762 3763 total_evicted += 3764 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3765 3766 return (total_evicted); 3767} 3768 3769void 3770arc_flush(spa_t *spa, boolean_t retry) 3771{ 3772 uint64_t guid = 0; 3773 3774 /* 3775 * If retry is B_TRUE, a spa must not be specified since we have 3776 * no good way to determine if all of a spa's buffers have been 3777 * evicted from an arc state. 3778 */ 3779 ASSERT(!retry || spa == 0); 3780 3781 if (spa != NULL) 3782 guid = spa_load_guid(spa); 3783 3784 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3785 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3786 3787 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3788 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3789 3790 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3791 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3792 3793 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3794 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3795} 3796 3797void 3798arc_shrink(int64_t to_free) 3799{ 3800 if (arc_c > arc_c_min) { 3801 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3802 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3803 if (arc_c > arc_c_min + to_free) 3804 atomic_add_64(&arc_c, -to_free); 3805 else 3806 arc_c = arc_c_min; 3807 3808 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3809 if (arc_c > arc_size) 3810 arc_c = MAX(arc_size, arc_c_min); 3811 if (arc_p > arc_c) 3812 arc_p = (arc_c >> 1); 3813 3814 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3815 arc_p); 3816 3817 ASSERT(arc_c >= arc_c_min); 3818 ASSERT((int64_t)arc_p >= 0); 3819 } 3820 3821 if (arc_size > arc_c) { 3822 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3823 uint64_t, arc_c); 3824 (void) arc_adjust(); 3825 } 3826} 3827 3828static long needfree = 0; 3829 3830typedef enum free_memory_reason_t { 3831 FMR_UNKNOWN, 3832 FMR_NEEDFREE, 3833 FMR_LOTSFREE, 3834 FMR_SWAPFS_MINFREE, 3835 FMR_PAGES_PP_MAXIMUM, 3836 FMR_HEAP_ARENA, 3837 FMR_ZIO_ARENA, 3838 FMR_ZIO_FRAG, 3839} free_memory_reason_t; 3840 3841int64_t last_free_memory; 3842free_memory_reason_t last_free_reason; 3843 3844/* 3845 * Additional reserve of pages for pp_reserve. 3846 */ 3847int64_t arc_pages_pp_reserve = 64; 3848 3849/* 3850 * Additional reserve of pages for swapfs. 3851 */ 3852int64_t arc_swapfs_reserve = 64; 3853 3854/* 3855 * Return the amount of memory that can be consumed before reclaim will be 3856 * needed. Positive if there is sufficient free memory, negative indicates 3857 * the amount of memory that needs to be freed up. 3858 */ 3859static int64_t 3860arc_available_memory(void) 3861{ 3862 int64_t lowest = INT64_MAX; 3863 int64_t n; 3864 free_memory_reason_t r = FMR_UNKNOWN; 3865 3866#ifdef _KERNEL 3867 if (needfree > 0) { 3868 n = PAGESIZE * (-needfree); 3869 if (n < lowest) { 3870 lowest = n; 3871 r = FMR_NEEDFREE; 3872 } 3873 } 3874 3875 /* 3876 * Cooperate with pagedaemon when it's time for it to scan 3877 * and reclaim some pages. 3878 */ 3879 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3880 if (n < lowest) { 3881 lowest = n; 3882 r = FMR_LOTSFREE; 3883 } 3884 3885#ifdef illumos 3886 /* 3887 * check that we're out of range of the pageout scanner. It starts to 3888 * schedule paging if freemem is less than lotsfree and needfree. 3889 * lotsfree is the high-water mark for pageout, and needfree is the 3890 * number of needed free pages. We add extra pages here to make sure 3891 * the scanner doesn't start up while we're freeing memory. 3892 */ 3893 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3894 if (n < lowest) { 3895 lowest = n; 3896 r = FMR_LOTSFREE; 3897 } 3898 3899 /* 3900 * check to make sure that swapfs has enough space so that anon 3901 * reservations can still succeed. anon_resvmem() checks that the 3902 * availrmem is greater than swapfs_minfree, and the number of reserved 3903 * swap pages. We also add a bit of extra here just to prevent 3904 * circumstances from getting really dire. 3905 */ 3906 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3907 desfree - arc_swapfs_reserve); 3908 if (n < lowest) { 3909 lowest = n; 3910 r = FMR_SWAPFS_MINFREE; 3911 } 3912 3913 3914 /* 3915 * Check that we have enough availrmem that memory locking (e.g., via 3916 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3917 * stores the number of pages that cannot be locked; when availrmem 3918 * drops below pages_pp_maximum, page locking mechanisms such as 3919 * page_pp_lock() will fail.) 3920 */ 3921 n = PAGESIZE * (availrmem - pages_pp_maximum - 3922 arc_pages_pp_reserve); 3923 if (n < lowest) { 3924 lowest = n; 3925 r = FMR_PAGES_PP_MAXIMUM; 3926 } 3927 3928#endif /* illumos */ 3929#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3930 /* 3931 * If we're on an i386 platform, it's possible that we'll exhaust the 3932 * kernel heap space before we ever run out of available physical 3933 * memory. Most checks of the size of the heap_area compare against 3934 * tune.t_minarmem, which is the minimum available real memory that we 3935 * can have in the system. However, this is generally fixed at 25 pages 3936 * which is so low that it's useless. In this comparison, we seek to 3937 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3938 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3939 * free) 3940 */ 3941 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3942 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3943 if (n < lowest) { 3944 lowest = n; 3945 r = FMR_HEAP_ARENA; 3946 } 3947#define zio_arena NULL 3948#else 3949#define zio_arena heap_arena 3950#endif 3951 3952 /* 3953 * If zio data pages are being allocated out of a separate heap segment, 3954 * then enforce that the size of available vmem for this arena remains 3955 * above about 1/16th free. 3956 * 3957 * Note: The 1/16th arena free requirement was put in place 3958 * to aggressively evict memory from the arc in order to avoid 3959 * memory fragmentation issues. 3960 */ 3961 if (zio_arena != NULL) { 3962 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3963 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3964 if (n < lowest) { 3965 lowest = n; 3966 r = FMR_ZIO_ARENA; 3967 } 3968 } 3969 3970 /* 3971 * Above limits know nothing about real level of KVA fragmentation. 3972 * Start aggressive reclamation if too little sequential KVA left. 3973 */ 3974 if (lowest > 0) { 3975 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3976 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3977 INT64_MAX; 3978 if (n < lowest) { 3979 lowest = n; 3980 r = FMR_ZIO_FRAG; 3981 } 3982 } 3983 3984#else /* _KERNEL */ 3985 /* Every 100 calls, free a small amount */ 3986 if (spa_get_random(100) == 0) 3987 lowest = -1024; 3988#endif /* _KERNEL */ 3989 3990 last_free_memory = lowest; 3991 last_free_reason = r; 3992 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3993 return (lowest); 3994} 3995 3996 3997/* 3998 * Determine if the system is under memory pressure and is asking 3999 * to reclaim memory. A return value of B_TRUE indicates that the system 4000 * is under memory pressure and that the arc should adjust accordingly. 4001 */ 4002static boolean_t 4003arc_reclaim_needed(void) 4004{ 4005 return (arc_available_memory() < 0); 4006} 4007 4008extern kmem_cache_t *zio_buf_cache[]; 4009extern kmem_cache_t *zio_data_buf_cache[]; 4010extern kmem_cache_t *range_seg_cache; 4011 4012static __noinline void 4013arc_kmem_reap_now(void) 4014{ 4015 size_t i; 4016 kmem_cache_t *prev_cache = NULL; 4017 kmem_cache_t *prev_data_cache = NULL; 4018 4019 DTRACE_PROBE(arc__kmem_reap_start); 4020#ifdef _KERNEL 4021 if (arc_meta_used >= arc_meta_limit) { 4022 /* 4023 * We are exceeding our meta-data cache limit. 4024 * Purge some DNLC entries to release holds on meta-data. 4025 */ 4026 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4027 } 4028#if defined(__i386) 4029 /* 4030 * Reclaim unused memory from all kmem caches. 4031 */ 4032 kmem_reap(); 4033#endif 4034#endif 4035 4036 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4037 if (zio_buf_cache[i] != prev_cache) { 4038 prev_cache = zio_buf_cache[i]; 4039 kmem_cache_reap_now(zio_buf_cache[i]); 4040 } 4041 if (zio_data_buf_cache[i] != prev_data_cache) { 4042 prev_data_cache = zio_data_buf_cache[i]; 4043 kmem_cache_reap_now(zio_data_buf_cache[i]); 4044 } 4045 } 4046 kmem_cache_reap_now(buf_cache); 4047 kmem_cache_reap_now(hdr_full_cache); 4048 kmem_cache_reap_now(hdr_l2only_cache); 4049 kmem_cache_reap_now(range_seg_cache); 4050 4051#ifdef illumos 4052 if (zio_arena != NULL) { 4053 /* 4054 * Ask the vmem arena to reclaim unused memory from its 4055 * quantum caches. 4056 */ 4057 vmem_qcache_reap(zio_arena); 4058 } 4059#endif 4060 DTRACE_PROBE(arc__kmem_reap_end); 4061} 4062 4063/* 4064 * Threads can block in arc_get_data_buf() waiting for this thread to evict 4065 * enough data and signal them to proceed. When this happens, the threads in 4066 * arc_get_data_buf() are sleeping while holding the hash lock for their 4067 * particular arc header. Thus, we must be careful to never sleep on a 4068 * hash lock in this thread. This is to prevent the following deadlock: 4069 * 4070 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 4071 * waiting for the reclaim thread to signal it. 4072 * 4073 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4074 * fails, and goes to sleep forever. 4075 * 4076 * This possible deadlock is avoided by always acquiring a hash lock 4077 * using mutex_tryenter() from arc_reclaim_thread(). 4078 */ 4079static void 4080arc_reclaim_thread(void *dummy __unused) 4081{ 4082 hrtime_t growtime = 0; 4083 callb_cpr_t cpr; 4084 4085 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4086 4087 mutex_enter(&arc_reclaim_lock); 4088 while (!arc_reclaim_thread_exit) { 4089 int64_t free_memory = arc_available_memory(); 4090 uint64_t evicted = 0; 4091 4092 /* 4093 * This is necessary in order for the mdb ::arc dcmd to 4094 * show up to date information. Since the ::arc command 4095 * does not call the kstat's update function, without 4096 * this call, the command may show stale stats for the 4097 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4098 * with this change, the data might be up to 1 second 4099 * out of date; but that should suffice. The arc_state_t 4100 * structures can be queried directly if more accurate 4101 * information is needed. 4102 */ 4103 if (arc_ksp != NULL) 4104 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4105 4106 mutex_exit(&arc_reclaim_lock); 4107 4108 if (free_memory < 0) { 4109 4110 arc_no_grow = B_TRUE; 4111 arc_warm = B_TRUE; 4112 4113 /* 4114 * Wait at least zfs_grow_retry (default 60) seconds 4115 * before considering growing. 4116 */ 4117 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 4118 4119 arc_kmem_reap_now(); 4120 4121 /* 4122 * If we are still low on memory, shrink the ARC 4123 * so that we have arc_shrink_min free space. 4124 */ 4125 free_memory = arc_available_memory(); 4126 4127 int64_t to_free = 4128 (arc_c >> arc_shrink_shift) - free_memory; 4129 if (to_free > 0) { 4130#ifdef _KERNEL 4131 to_free = MAX(to_free, ptob(needfree)); 4132#endif 4133 arc_shrink(to_free); 4134 } 4135 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4136 arc_no_grow = B_TRUE; 4137 } else if (gethrtime() >= growtime) { 4138 arc_no_grow = B_FALSE; 4139 } 4140 4141 evicted = arc_adjust(); 4142 4143 mutex_enter(&arc_reclaim_lock); 4144 4145 /* 4146 * If evicted is zero, we couldn't evict anything via 4147 * arc_adjust(). This could be due to hash lock 4148 * collisions, but more likely due to the majority of 4149 * arc buffers being unevictable. Therefore, even if 4150 * arc_size is above arc_c, another pass is unlikely to 4151 * be helpful and could potentially cause us to enter an 4152 * infinite loop. 4153 */ 4154 if (arc_size <= arc_c || evicted == 0) { 4155#ifdef _KERNEL 4156 needfree = 0; 4157#endif 4158 /* 4159 * We're either no longer overflowing, or we 4160 * can't evict anything more, so we should wake 4161 * up any threads before we go to sleep. 4162 */ 4163 cv_broadcast(&arc_reclaim_waiters_cv); 4164 4165 /* 4166 * Block until signaled, or after one second (we 4167 * might need to perform arc_kmem_reap_now() 4168 * even if we aren't being signalled) 4169 */ 4170 CALLB_CPR_SAFE_BEGIN(&cpr); 4171 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4172 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4173 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4174 } 4175 } 4176 4177 arc_reclaim_thread_exit = B_FALSE; 4178 cv_broadcast(&arc_reclaim_thread_cv); 4179 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4180 thread_exit(); 4181} 4182 4183/* 4184 * Adapt arc info given the number of bytes we are trying to add and 4185 * the state that we are comming from. This function is only called 4186 * when we are adding new content to the cache. 4187 */ 4188static void 4189arc_adapt(int bytes, arc_state_t *state) 4190{ 4191 int mult; 4192 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4193 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4194 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4195 4196 if (state == arc_l2c_only) 4197 return; 4198 4199 ASSERT(bytes > 0); 4200 /* 4201 * Adapt the target size of the MRU list: 4202 * - if we just hit in the MRU ghost list, then increase 4203 * the target size of the MRU list. 4204 * - if we just hit in the MFU ghost list, then increase 4205 * the target size of the MFU list by decreasing the 4206 * target size of the MRU list. 4207 */ 4208 if (state == arc_mru_ghost) { 4209 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4210 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4211 4212 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4213 } else if (state == arc_mfu_ghost) { 4214 uint64_t delta; 4215 4216 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4217 mult = MIN(mult, 10); 4218 4219 delta = MIN(bytes * mult, arc_p); 4220 arc_p = MAX(arc_p_min, arc_p - delta); 4221 } 4222 ASSERT((int64_t)arc_p >= 0); 4223 4224 if (arc_reclaim_needed()) { 4225 cv_signal(&arc_reclaim_thread_cv); 4226 return; 4227 } 4228 4229 if (arc_no_grow) 4230 return; 4231 4232 if (arc_c >= arc_c_max) 4233 return; 4234 4235 /* 4236 * If we're within (2 * maxblocksize) bytes of the target 4237 * cache size, increment the target cache size 4238 */ 4239 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 4240 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4241 atomic_add_64(&arc_c, (int64_t)bytes); 4242 if (arc_c > arc_c_max) 4243 arc_c = arc_c_max; 4244 else if (state == arc_anon) 4245 atomic_add_64(&arc_p, (int64_t)bytes); 4246 if (arc_p > arc_c) 4247 arc_p = arc_c; 4248 } 4249 ASSERT((int64_t)arc_p >= 0); 4250} 4251 4252/* 4253 * Check if arc_size has grown past our upper threshold, determined by 4254 * zfs_arc_overflow_shift. 4255 */ 4256static boolean_t 4257arc_is_overflowing(void) 4258{ 4259 /* Always allow at least one block of overflow */ 4260 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4261 arc_c >> zfs_arc_overflow_shift); 4262 4263 return (arc_size >= arc_c + overflow); 4264} 4265 4266/* 4267 * Allocate a block and return it to the caller. If we are hitting the 4268 * hard limit for the cache size, we must sleep, waiting for the eviction 4269 * thread to catch up. If we're past the target size but below the hard 4270 * limit, we'll only signal the reclaim thread and continue on. 4271 */ 4272static void * 4273arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4274{ 4275 void *datap = NULL; 4276 arc_state_t *state = hdr->b_l1hdr.b_state; 4277 arc_buf_contents_t type = arc_buf_type(hdr); 4278 4279 arc_adapt(size, state); 4280 4281 /* 4282 * If arc_size is currently overflowing, and has grown past our 4283 * upper limit, we must be adding data faster than the evict 4284 * thread can evict. Thus, to ensure we don't compound the 4285 * problem by adding more data and forcing arc_size to grow even 4286 * further past it's target size, we halt and wait for the 4287 * eviction thread to catch up. 4288 * 4289 * It's also possible that the reclaim thread is unable to evict 4290 * enough buffers to get arc_size below the overflow limit (e.g. 4291 * due to buffers being un-evictable, or hash lock collisions). 4292 * In this case, we want to proceed regardless if we're 4293 * overflowing; thus we don't use a while loop here. 4294 */ 4295 if (arc_is_overflowing()) { 4296 mutex_enter(&arc_reclaim_lock); 4297 4298 /* 4299 * Now that we've acquired the lock, we may no longer be 4300 * over the overflow limit, lets check. 4301 * 4302 * We're ignoring the case of spurious wake ups. If that 4303 * were to happen, it'd let this thread consume an ARC 4304 * buffer before it should have (i.e. before we're under 4305 * the overflow limit and were signalled by the reclaim 4306 * thread). As long as that is a rare occurrence, it 4307 * shouldn't cause any harm. 4308 */ 4309 if (arc_is_overflowing()) { 4310 cv_signal(&arc_reclaim_thread_cv); 4311 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4312 } 4313 4314 mutex_exit(&arc_reclaim_lock); 4315 } 4316 4317 VERIFY3U(hdr->b_type, ==, type); 4318 if (type == ARC_BUFC_METADATA) { 4319 datap = zio_buf_alloc(size); 4320 arc_space_consume(size, ARC_SPACE_META); 4321 } else { 4322 ASSERT(type == ARC_BUFC_DATA); 4323 datap = zio_data_buf_alloc(size); 4324 arc_space_consume(size, ARC_SPACE_DATA); 4325 } 4326 4327 /* 4328 * Update the state size. Note that ghost states have a 4329 * "ghost size" and so don't need to be updated. 4330 */ 4331 if (!GHOST_STATE(state)) { 4332 4333 (void) refcount_add_many(&state->arcs_size, size, tag); 4334 4335 /* 4336 * If this is reached via arc_read, the link is 4337 * protected by the hash lock. If reached via 4338 * arc_buf_alloc, the header should not be accessed by 4339 * any other thread. And, if reached via arc_read_done, 4340 * the hash lock will protect it if it's found in the 4341 * hash table; otherwise no other thread should be 4342 * trying to [add|remove]_reference it. 4343 */ 4344 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4345 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4346 (void) refcount_add_many(&state->arcs_esize[type], 4347 size, tag); 4348 } 4349 4350 /* 4351 * If we are growing the cache, and we are adding anonymous 4352 * data, and we have outgrown arc_p, update arc_p 4353 */ 4354 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4355 (refcount_count(&arc_anon->arcs_size) + 4356 refcount_count(&arc_mru->arcs_size) > arc_p)) 4357 arc_p = MIN(arc_c, arc_p + size); 4358 } 4359 ARCSTAT_BUMP(arcstat_allocated); 4360 return (datap); 4361} 4362 4363/* 4364 * Free the arc data buffer. 4365 */ 4366static void 4367arc_free_data_buf(arc_buf_hdr_t *hdr, void *data, uint64_t size, void *tag) 4368{ 4369 arc_state_t *state = hdr->b_l1hdr.b_state; 4370 arc_buf_contents_t type = arc_buf_type(hdr); 4371 4372 /* protected by hash lock, if in the hash table */ 4373 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4374 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4375 ASSERT(state != arc_anon && state != arc_l2c_only); 4376 4377 (void) refcount_remove_many(&state->arcs_esize[type], 4378 size, tag); 4379 } 4380 (void) refcount_remove_many(&state->arcs_size, size, tag); 4381 4382 VERIFY3U(hdr->b_type, ==, type); 4383 if (type == ARC_BUFC_METADATA) { 4384 zio_buf_free(data, size); 4385 arc_space_return(size, ARC_SPACE_META); 4386 } else { 4387 ASSERT(type == ARC_BUFC_DATA); 4388 zio_data_buf_free(data, size); 4389 arc_space_return(size, ARC_SPACE_DATA); 4390 } 4391} 4392 4393/* 4394 * This routine is called whenever a buffer is accessed. 4395 * NOTE: the hash lock is dropped in this function. 4396 */ 4397static void 4398arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4399{ 4400 clock_t now; 4401 4402 ASSERT(MUTEX_HELD(hash_lock)); 4403 ASSERT(HDR_HAS_L1HDR(hdr)); 4404 4405 if (hdr->b_l1hdr.b_state == arc_anon) { 4406 /* 4407 * This buffer is not in the cache, and does not 4408 * appear in our "ghost" list. Add the new buffer 4409 * to the MRU state. 4410 */ 4411 4412 ASSERT0(hdr->b_l1hdr.b_arc_access); 4413 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4414 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4415 arc_change_state(arc_mru, hdr, hash_lock); 4416 4417 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4418 now = ddi_get_lbolt(); 4419 4420 /* 4421 * If this buffer is here because of a prefetch, then either: 4422 * - clear the flag if this is a "referencing" read 4423 * (any subsequent access will bump this into the MFU state). 4424 * or 4425 * - move the buffer to the head of the list if this is 4426 * another prefetch (to make it less likely to be evicted). 4427 */ 4428 if (HDR_PREFETCH(hdr)) { 4429 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4430 /* link protected by hash lock */ 4431 ASSERT(multilist_link_active( 4432 &hdr->b_l1hdr.b_arc_node)); 4433 } else { 4434 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4435 ARCSTAT_BUMP(arcstat_mru_hits); 4436 } 4437 hdr->b_l1hdr.b_arc_access = now; 4438 return; 4439 } 4440 4441 /* 4442 * This buffer has been "accessed" only once so far, 4443 * but it is still in the cache. Move it to the MFU 4444 * state. 4445 */ 4446 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4447 /* 4448 * More than 125ms have passed since we 4449 * instantiated this buffer. Move it to the 4450 * most frequently used state. 4451 */ 4452 hdr->b_l1hdr.b_arc_access = now; 4453 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4454 arc_change_state(arc_mfu, hdr, hash_lock); 4455 } 4456 ARCSTAT_BUMP(arcstat_mru_hits); 4457 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4458 arc_state_t *new_state; 4459 /* 4460 * This buffer has been "accessed" recently, but 4461 * was evicted from the cache. Move it to the 4462 * MFU state. 4463 */ 4464 4465 if (HDR_PREFETCH(hdr)) { 4466 new_state = arc_mru; 4467 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4468 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4469 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4470 } else { 4471 new_state = arc_mfu; 4472 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4473 } 4474 4475 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4476 arc_change_state(new_state, hdr, hash_lock); 4477 4478 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4479 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4480 /* 4481 * This buffer has been accessed more than once and is 4482 * still in the cache. Keep it in the MFU state. 4483 * 4484 * NOTE: an add_reference() that occurred when we did 4485 * the arc_read() will have kicked this off the list. 4486 * If it was a prefetch, we will explicitly move it to 4487 * the head of the list now. 4488 */ 4489 if ((HDR_PREFETCH(hdr)) != 0) { 4490 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4491 /* link protected by hash_lock */ 4492 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4493 } 4494 ARCSTAT_BUMP(arcstat_mfu_hits); 4495 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4496 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4497 arc_state_t *new_state = arc_mfu; 4498 /* 4499 * This buffer has been accessed more than once but has 4500 * been evicted from the cache. Move it back to the 4501 * MFU state. 4502 */ 4503 4504 if (HDR_PREFETCH(hdr)) { 4505 /* 4506 * This is a prefetch access... 4507 * move this block back to the MRU state. 4508 */ 4509 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4510 new_state = arc_mru; 4511 } 4512 4513 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4514 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4515 arc_change_state(new_state, hdr, hash_lock); 4516 4517 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4518 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4519 /* 4520 * This buffer is on the 2nd Level ARC. 4521 */ 4522 4523 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4524 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4525 arc_change_state(arc_mfu, hdr, hash_lock); 4526 } else { 4527 ASSERT(!"invalid arc state"); 4528 } 4529} 4530 4531/* a generic arc_done_func_t which you can use */ 4532/* ARGSUSED */ 4533void 4534arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4535{ 4536 if (zio == NULL || zio->io_error == 0) 4537 bcopy(buf->b_data, arg, HDR_GET_LSIZE(buf->b_hdr)); 4538 arc_buf_destroy(buf, arg); 4539} 4540 4541/* a generic arc_done_func_t */ 4542void 4543arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4544{ 4545 arc_buf_t **bufp = arg; 4546 if (zio && zio->io_error) { 4547 arc_buf_destroy(buf, arg); 4548 *bufp = NULL; 4549 } else { 4550 *bufp = buf; 4551 ASSERT(buf->b_data); 4552 } 4553} 4554 4555static void 4556arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 4557{ 4558 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 4559 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 4560 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 4561 } else { 4562 if (HDR_COMPRESSION_ENABLED(hdr)) { 4563 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 4564 BP_GET_COMPRESS(bp)); 4565 } 4566 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 4567 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 4568 } 4569} 4570 4571static void 4572arc_read_done(zio_t *zio) 4573{ 4574 arc_buf_hdr_t *hdr = zio->io_private; 4575 arc_buf_t *abuf = NULL; /* buffer we're assigning to callback */ 4576 kmutex_t *hash_lock = NULL; 4577 arc_callback_t *callback_list, *acb; 4578 int freeable = B_FALSE; 4579 4580 /* 4581 * The hdr was inserted into hash-table and removed from lists 4582 * prior to starting I/O. We should find this header, since 4583 * it's in the hash table, and it should be legit since it's 4584 * not possible to evict it during the I/O. The only possible 4585 * reason for it not to be found is if we were freed during the 4586 * read. 4587 */ 4588 if (HDR_IN_HASH_TABLE(hdr)) { 4589 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4590 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4591 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4592 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4593 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4594 4595 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4596 &hash_lock); 4597 4598 ASSERT((found == hdr && 4599 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4600 (found == hdr && HDR_L2_READING(hdr))); 4601 ASSERT3P(hash_lock, !=, NULL); 4602 } 4603 4604 if (zio->io_error == 0) { 4605 /* byteswap if necessary */ 4606 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 4607 if (BP_GET_LEVEL(zio->io_bp) > 0) { 4608 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 4609 } else { 4610 hdr->b_l1hdr.b_byteswap = 4611 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4612 } 4613 } else { 4614 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 4615 } 4616 } 4617 4618 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 4619 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4620 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 4621 4622 callback_list = hdr->b_l1hdr.b_acb; 4623 ASSERT3P(callback_list, !=, NULL); 4624 4625 if (hash_lock && zio->io_error == 0 && 4626 hdr->b_l1hdr.b_state == arc_anon) { 4627 /* 4628 * Only call arc_access on anonymous buffers. This is because 4629 * if we've issued an I/O for an evicted buffer, we've already 4630 * called arc_access (to prevent any simultaneous readers from 4631 * getting confused). 4632 */ 4633 arc_access(hdr, hash_lock); 4634 } 4635 4636 /* create copies of the data buffer for the callers */ 4637 for (acb = callback_list; acb; acb = acb->acb_next) { 4638 if (acb->acb_done != NULL) { 4639 /* 4640 * If we're here, then this must be a demand read 4641 * since prefetch requests don't have callbacks. 4642 * If a read request has a callback (i.e. acb_done is 4643 * not NULL), then we decompress the data for the 4644 * first request and clone the rest. This avoids 4645 * having to waste cpu resources decompressing data 4646 * that nobody is explicitly waiting to read. 4647 */ 4648 if (abuf == NULL) { 4649 acb->acb_buf = arc_buf_alloc_impl(hdr, 4650 acb->acb_private); 4651 if (zio->io_error == 0) { 4652 zio->io_error = 4653 arc_decompress(acb->acb_buf); 4654 } 4655 abuf = acb->acb_buf; 4656 } else { 4657 add_reference(hdr, acb->acb_private); 4658 acb->acb_buf = arc_buf_clone(abuf); 4659 } 4660 } 4661 } 4662 hdr->b_l1hdr.b_acb = NULL; 4663 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 4664 if (abuf == NULL) { 4665 /* 4666 * This buffer didn't have a callback so it must 4667 * be a prefetch. 4668 */ 4669 ASSERT(HDR_PREFETCH(hdr)); 4670 ASSERT0(hdr->b_l1hdr.b_bufcnt); 4671 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 4672 } 4673 4674 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4675 callback_list != NULL); 4676 4677 if (zio->io_error == 0) { 4678 arc_hdr_verify(hdr, zio->io_bp); 4679 } else { 4680 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 4681 if (hdr->b_l1hdr.b_state != arc_anon) 4682 arc_change_state(arc_anon, hdr, hash_lock); 4683 if (HDR_IN_HASH_TABLE(hdr)) 4684 buf_hash_remove(hdr); 4685 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4686 } 4687 4688 /* 4689 * Broadcast before we drop the hash_lock to avoid the possibility 4690 * that the hdr (and hence the cv) might be freed before we get to 4691 * the cv_broadcast(). 4692 */ 4693 cv_broadcast(&hdr->b_l1hdr.b_cv); 4694 4695 if (hash_lock != NULL) { 4696 mutex_exit(hash_lock); 4697 } else { 4698 /* 4699 * This block was freed while we waited for the read to 4700 * complete. It has been removed from the hash table and 4701 * moved to the anonymous state (so that it won't show up 4702 * in the cache). 4703 */ 4704 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4705 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4706 } 4707 4708 /* execute each callback and free its structure */ 4709 while ((acb = callback_list) != NULL) { 4710 if (acb->acb_done) 4711 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4712 4713 if (acb->acb_zio_dummy != NULL) { 4714 acb->acb_zio_dummy->io_error = zio->io_error; 4715 zio_nowait(acb->acb_zio_dummy); 4716 } 4717 4718 callback_list = acb->acb_next; 4719 kmem_free(acb, sizeof (arc_callback_t)); 4720 } 4721 4722 if (freeable) 4723 arc_hdr_destroy(hdr); 4724} 4725 4726/* 4727 * "Read" the block at the specified DVA (in bp) via the 4728 * cache. If the block is found in the cache, invoke the provided 4729 * callback immediately and return. Note that the `zio' parameter 4730 * in the callback will be NULL in this case, since no IO was 4731 * required. If the block is not in the cache pass the read request 4732 * on to the spa with a substitute callback function, so that the 4733 * requested block will be added to the cache. 4734 * 4735 * If a read request arrives for a block that has a read in-progress, 4736 * either wait for the in-progress read to complete (and return the 4737 * results); or, if this is a read with a "done" func, add a record 4738 * to the read to invoke the "done" func when the read completes, 4739 * and return; or just return. 4740 * 4741 * arc_read_done() will invoke all the requested "done" functions 4742 * for readers of this block. 4743 */ 4744int 4745arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4746 void *private, zio_priority_t priority, int zio_flags, 4747 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4748{ 4749 arc_buf_hdr_t *hdr = NULL; 4750 kmutex_t *hash_lock = NULL; 4751 zio_t *rzio; 4752 uint64_t guid = spa_load_guid(spa); 4753 4754 ASSERT(!BP_IS_EMBEDDED(bp) || 4755 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4756 4757top: 4758 if (!BP_IS_EMBEDDED(bp)) { 4759 /* 4760 * Embedded BP's have no DVA and require no I/O to "read". 4761 * Create an anonymous arc buf to back it. 4762 */ 4763 hdr = buf_hash_find(guid, bp, &hash_lock); 4764 } 4765 4766 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pdata != NULL) { 4767 arc_buf_t *buf = NULL; 4768 *arc_flags |= ARC_FLAG_CACHED; 4769 4770 if (HDR_IO_IN_PROGRESS(hdr)) { 4771 4772 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4773 priority == ZIO_PRIORITY_SYNC_READ) { 4774 /* 4775 * This sync read must wait for an 4776 * in-progress async read (e.g. a predictive 4777 * prefetch). Async reads are queued 4778 * separately at the vdev_queue layer, so 4779 * this is a form of priority inversion. 4780 * Ideally, we would "inherit" the demand 4781 * i/o's priority by moving the i/o from 4782 * the async queue to the synchronous queue, 4783 * but there is currently no mechanism to do 4784 * so. Track this so that we can evaluate 4785 * the magnitude of this potential performance 4786 * problem. 4787 * 4788 * Note that if the prefetch i/o is already 4789 * active (has been issued to the device), 4790 * the prefetch improved performance, because 4791 * we issued it sooner than we would have 4792 * without the prefetch. 4793 */ 4794 DTRACE_PROBE1(arc__sync__wait__for__async, 4795 arc_buf_hdr_t *, hdr); 4796 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4797 } 4798 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4799 arc_hdr_clear_flags(hdr, 4800 ARC_FLAG_PREDICTIVE_PREFETCH); 4801 } 4802 4803 if (*arc_flags & ARC_FLAG_WAIT) { 4804 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4805 mutex_exit(hash_lock); 4806 goto top; 4807 } 4808 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4809 4810 if (done) { 4811 arc_callback_t *acb = NULL; 4812 4813 acb = kmem_zalloc(sizeof (arc_callback_t), 4814 KM_SLEEP); 4815 acb->acb_done = done; 4816 acb->acb_private = private; 4817 if (pio != NULL) 4818 acb->acb_zio_dummy = zio_null(pio, 4819 spa, NULL, NULL, NULL, zio_flags); 4820 4821 ASSERT3P(acb->acb_done, !=, NULL); 4822 acb->acb_next = hdr->b_l1hdr.b_acb; 4823 hdr->b_l1hdr.b_acb = acb; 4824 mutex_exit(hash_lock); 4825 return (0); 4826 } 4827 mutex_exit(hash_lock); 4828 return (0); 4829 } 4830 4831 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4832 hdr->b_l1hdr.b_state == arc_mfu); 4833 4834 if (done) { 4835 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4836 /* 4837 * This is a demand read which does not have to 4838 * wait for i/o because we did a predictive 4839 * prefetch i/o for it, which has completed. 4840 */ 4841 DTRACE_PROBE1( 4842 arc__demand__hit__predictive__prefetch, 4843 arc_buf_hdr_t *, hdr); 4844 ARCSTAT_BUMP( 4845 arcstat_demand_hit_predictive_prefetch); 4846 arc_hdr_clear_flags(hdr, 4847 ARC_FLAG_PREDICTIVE_PREFETCH); 4848 } 4849 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 4850 4851 /* 4852 * If this block is already in use, create a new 4853 * copy of the data so that we will be guaranteed 4854 * that arc_release() will always succeed. 4855 */ 4856 buf = hdr->b_l1hdr.b_buf; 4857 if (buf == NULL) { 4858 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4859 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 4860 buf = arc_buf_alloc_impl(hdr, private); 4861 VERIFY0(arc_decompress(buf)); 4862 } else { 4863 add_reference(hdr, private); 4864 buf = arc_buf_clone(buf); 4865 } 4866 ASSERT3P(buf->b_data, !=, NULL); 4867 4868 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4869 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4870 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 4871 } 4872 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4873 arc_access(hdr, hash_lock); 4874 if (*arc_flags & ARC_FLAG_L2CACHE) 4875 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 4876 mutex_exit(hash_lock); 4877 ARCSTAT_BUMP(arcstat_hits); 4878 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4879 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4880 data, metadata, hits); 4881 4882 if (done) 4883 done(NULL, buf, private); 4884 } else { 4885 uint64_t lsize = BP_GET_LSIZE(bp); 4886 uint64_t psize = BP_GET_PSIZE(bp); 4887 arc_callback_t *acb; 4888 vdev_t *vd = NULL; 4889 uint64_t addr = 0; 4890 boolean_t devw = B_FALSE; 4891 uint64_t size; 4892 4893 if (hdr == NULL) { 4894 /* this block is not in the cache */ 4895 arc_buf_hdr_t *exists = NULL; 4896 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4897 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 4898 BP_GET_COMPRESS(bp), type); 4899 4900 if (!BP_IS_EMBEDDED(bp)) { 4901 hdr->b_dva = *BP_IDENTITY(bp); 4902 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4903 exists = buf_hash_insert(hdr, &hash_lock); 4904 } 4905 if (exists != NULL) { 4906 /* somebody beat us to the hash insert */ 4907 mutex_exit(hash_lock); 4908 buf_discard_identity(hdr); 4909 arc_hdr_destroy(hdr); 4910 goto top; /* restart the IO request */ 4911 } 4912 } else { 4913 /* 4914 * This block is in the ghost cache. If it was L2-only 4915 * (and thus didn't have an L1 hdr), we realloc the 4916 * header to add an L1 hdr. 4917 */ 4918 if (!HDR_HAS_L1HDR(hdr)) { 4919 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4920 hdr_full_cache); 4921 } 4922 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 4923 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4924 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4925 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4926 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4927 4928 /* 4929 * This is a delicate dance that we play here. 4930 * This hdr is in the ghost list so we access it 4931 * to move it out of the ghost list before we 4932 * initiate the read. If it's a prefetch then 4933 * it won't have a callback so we'll remove the 4934 * reference that arc_buf_alloc_impl() created. We 4935 * do this after we've called arc_access() to 4936 * avoid hitting an assert in remove_reference(). 4937 */ 4938 arc_access(hdr, hash_lock); 4939 arc_hdr_alloc_pdata(hdr); 4940 } 4941 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 4942 size = arc_hdr_size(hdr); 4943 4944 /* 4945 * If compression is enabled on the hdr, then will do 4946 * RAW I/O and will store the compressed data in the hdr's 4947 * data block. Otherwise, the hdr's data block will contain 4948 * the uncompressed data. 4949 */ 4950 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 4951 zio_flags |= ZIO_FLAG_RAW; 4952 } 4953 4954 if (*arc_flags & ARC_FLAG_PREFETCH) 4955 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 4956 if (*arc_flags & ARC_FLAG_L2CACHE) 4957 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 4958 if (BP_GET_LEVEL(bp) > 0) 4959 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 4960 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 4961 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 4962 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 4963 4964 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 4965 acb->acb_done = done; 4966 acb->acb_private = private; 4967 4968 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 4969 hdr->b_l1hdr.b_acb = acb; 4970 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 4971 4972 if (HDR_HAS_L2HDR(hdr) && 4973 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 4974 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 4975 addr = hdr->b_l2hdr.b_daddr; 4976 /* 4977 * Lock out device removal. 4978 */ 4979 if (vdev_is_dead(vd) || 4980 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 4981 vd = NULL; 4982 } 4983 4984 if (priority == ZIO_PRIORITY_ASYNC_READ) 4985 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 4986 else 4987 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 4988 4989 if (hash_lock != NULL) 4990 mutex_exit(hash_lock); 4991 4992 /* 4993 * At this point, we have a level 1 cache miss. Try again in 4994 * L2ARC if possible. 4995 */ 4996 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 4997 4998 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 4999 uint64_t, lsize, zbookmark_phys_t *, zb); 5000 ARCSTAT_BUMP(arcstat_misses); 5001 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5002 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5003 data, metadata, misses); 5004#ifdef _KERNEL 5005 curthread->td_ru.ru_inblock++; 5006#endif 5007 5008 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5009 /* 5010 * Read from the L2ARC if the following are true: 5011 * 1. The L2ARC vdev was previously cached. 5012 * 2. This buffer still has L2ARC metadata. 5013 * 3. This buffer isn't currently writing to the L2ARC. 5014 * 4. The L2ARC entry wasn't evicted, which may 5015 * also have invalidated the vdev. 5016 * 5. This isn't prefetch and l2arc_noprefetch is set. 5017 */ 5018 if (HDR_HAS_L2HDR(hdr) && 5019 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5020 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5021 l2arc_read_callback_t *cb; 5022 void* b_data; 5023 5024 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5025 ARCSTAT_BUMP(arcstat_l2_hits); 5026 5027 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5028 KM_SLEEP); 5029 cb->l2rcb_hdr = hdr; 5030 cb->l2rcb_bp = *bp; 5031 cb->l2rcb_zb = *zb; 5032 cb->l2rcb_flags = zio_flags; 5033 uint64_t asize = vdev_psize_to_asize(vd, size); 5034 if (asize != size) { 5035 b_data = zio_data_buf_alloc(asize); 5036 cb->l2rcb_data = b_data; 5037 } else { 5038 b_data = hdr->b_l1hdr.b_pdata; 5039 } 5040 5041 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5042 addr + asize < vd->vdev_psize - 5043 VDEV_LABEL_END_SIZE); 5044 5045 /* 5046 * l2arc read. The SCL_L2ARC lock will be 5047 * released by l2arc_read_done(). 5048 * Issue a null zio if the underlying buffer 5049 * was squashed to zero size by compression. 5050 */ 5051 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5052 ZIO_COMPRESS_EMPTY); 5053 rzio = zio_read_phys(pio, vd, addr, 5054 asize, b_data, 5055 ZIO_CHECKSUM_OFF, 5056 l2arc_read_done, cb, priority, 5057 zio_flags | ZIO_FLAG_DONT_CACHE | 5058 ZIO_FLAG_CANFAIL | 5059 ZIO_FLAG_DONT_PROPAGATE | 5060 ZIO_FLAG_DONT_RETRY, B_FALSE); 5061 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5062 zio_t *, rzio); 5063 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5064 5065 if (*arc_flags & ARC_FLAG_NOWAIT) { 5066 zio_nowait(rzio); 5067 return (0); 5068 } 5069 5070 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5071 if (zio_wait(rzio) == 0) 5072 return (0); 5073 5074 /* l2arc read error; goto zio_read() */ 5075 } else { 5076 DTRACE_PROBE1(l2arc__miss, 5077 arc_buf_hdr_t *, hdr); 5078 ARCSTAT_BUMP(arcstat_l2_misses); 5079 if (HDR_L2_WRITING(hdr)) 5080 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5081 spa_config_exit(spa, SCL_L2ARC, vd); 5082 } 5083 } else { 5084 if (vd != NULL) 5085 spa_config_exit(spa, SCL_L2ARC, vd); 5086 if (l2arc_ndev != 0) { 5087 DTRACE_PROBE1(l2arc__miss, 5088 arc_buf_hdr_t *, hdr); 5089 ARCSTAT_BUMP(arcstat_l2_misses); 5090 } 5091 } 5092 5093 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pdata, size, 5094 arc_read_done, hdr, priority, zio_flags, zb); 5095 5096 if (*arc_flags & ARC_FLAG_WAIT) 5097 return (zio_wait(rzio)); 5098 5099 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5100 zio_nowait(rzio); 5101 } 5102 return (0); 5103} 5104 5105/* 5106 * Notify the arc that a block was freed, and thus will never be used again. 5107 */ 5108void 5109arc_freed(spa_t *spa, const blkptr_t *bp) 5110{ 5111 arc_buf_hdr_t *hdr; 5112 kmutex_t *hash_lock; 5113 uint64_t guid = spa_load_guid(spa); 5114 5115 ASSERT(!BP_IS_EMBEDDED(bp)); 5116 5117 hdr = buf_hash_find(guid, bp, &hash_lock); 5118 if (hdr == NULL) 5119 return; 5120 5121 /* 5122 * We might be trying to free a block that is still doing I/O 5123 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5124 * dmu_sync-ed block). If this block is being prefetched, then it 5125 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5126 * until the I/O completes. A block may also have a reference if it is 5127 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5128 * have written the new block to its final resting place on disk but 5129 * without the dedup flag set. This would have left the hdr in the MRU 5130 * state and discoverable. When the txg finally syncs it detects that 5131 * the block was overridden in open context and issues an override I/O. 5132 * Since this is a dedup block, the override I/O will determine if the 5133 * block is already in the DDT. If so, then it will replace the io_bp 5134 * with the bp from the DDT and allow the I/O to finish. When the I/O 5135 * reaches the done callback, dbuf_write_override_done, it will 5136 * check to see if the io_bp and io_bp_override are identical. 5137 * If they are not, then it indicates that the bp was replaced with 5138 * the bp in the DDT and the override bp is freed. This allows 5139 * us to arrive here with a reference on a block that is being 5140 * freed. So if we have an I/O in progress, or a reference to 5141 * this hdr, then we don't destroy the hdr. 5142 */ 5143 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5144 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5145 arc_change_state(arc_anon, hdr, hash_lock); 5146 arc_hdr_destroy(hdr); 5147 mutex_exit(hash_lock); 5148 } else { 5149 mutex_exit(hash_lock); 5150 } 5151 5152} 5153 5154/* 5155 * Release this buffer from the cache, making it an anonymous buffer. This 5156 * must be done after a read and prior to modifying the buffer contents. 5157 * If the buffer has more than one reference, we must make 5158 * a new hdr for the buffer. 5159 */ 5160void 5161arc_release(arc_buf_t *buf, void *tag) 5162{ 5163 arc_buf_hdr_t *hdr = buf->b_hdr; 5164 5165 /* 5166 * It would be nice to assert that if it's DMU metadata (level > 5167 * 0 || it's the dnode file), then it must be syncing context. 5168 * But we don't know that information at this level. 5169 */ 5170 5171 mutex_enter(&buf->b_evict_lock); 5172 5173 ASSERT(HDR_HAS_L1HDR(hdr)); 5174 5175 /* 5176 * We don't grab the hash lock prior to this check, because if 5177 * the buffer's header is in the arc_anon state, it won't be 5178 * linked into the hash table. 5179 */ 5180 if (hdr->b_l1hdr.b_state == arc_anon) { 5181 mutex_exit(&buf->b_evict_lock); 5182 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5183 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5184 ASSERT(!HDR_HAS_L2HDR(hdr)); 5185 ASSERT(HDR_EMPTY(hdr)); 5186 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5187 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5188 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5189 5190 hdr->b_l1hdr.b_arc_access = 0; 5191 5192 /* 5193 * If the buf is being overridden then it may already 5194 * have a hdr that is not empty. 5195 */ 5196 buf_discard_identity(hdr); 5197 arc_buf_thaw(buf); 5198 5199 return; 5200 } 5201 5202 kmutex_t *hash_lock = HDR_LOCK(hdr); 5203 mutex_enter(hash_lock); 5204 5205 /* 5206 * This assignment is only valid as long as the hash_lock is 5207 * held, we must be careful not to reference state or the 5208 * b_state field after dropping the lock. 5209 */ 5210 arc_state_t *state = hdr->b_l1hdr.b_state; 5211 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5212 ASSERT3P(state, !=, arc_anon); 5213 5214 /* this buffer is not on any list */ 5215 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 5216 5217 if (HDR_HAS_L2HDR(hdr)) { 5218 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5219 5220 /* 5221 * We have to recheck this conditional again now that 5222 * we're holding the l2ad_mtx to prevent a race with 5223 * another thread which might be concurrently calling 5224 * l2arc_evict(). In that case, l2arc_evict() might have 5225 * destroyed the header's L2 portion as we were waiting 5226 * to acquire the l2ad_mtx. 5227 */ 5228 if (HDR_HAS_L2HDR(hdr)) { 5229 l2arc_trim(hdr); 5230 arc_hdr_l2hdr_destroy(hdr); 5231 } 5232 5233 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5234 } 5235 5236 /* 5237 * Do we have more than one buf? 5238 */ 5239 if (hdr->b_l1hdr.b_bufcnt > 1) { 5240 arc_buf_hdr_t *nhdr; 5241 arc_buf_t **bufp; 5242 uint64_t spa = hdr->b_spa; 5243 uint64_t psize = HDR_GET_PSIZE(hdr); 5244 uint64_t lsize = HDR_GET_LSIZE(hdr); 5245 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5246 arc_buf_contents_t type = arc_buf_type(hdr); 5247 VERIFY3U(hdr->b_type, ==, type); 5248 5249 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5250 (void) remove_reference(hdr, hash_lock, tag); 5251 5252 if (arc_buf_is_shared(buf)) { 5253 ASSERT(HDR_SHARED_DATA(hdr)); 5254 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5255 ASSERT(ARC_BUF_LAST(buf)); 5256 } 5257 5258 /* 5259 * Pull the data off of this hdr and attach it to 5260 * a new anonymous hdr. Also find the last buffer 5261 * in the hdr's buffer list. 5262 */ 5263 arc_buf_t *lastbuf = NULL; 5264 bufp = &hdr->b_l1hdr.b_buf; 5265 while (*bufp != NULL) { 5266 if (*bufp == buf) { 5267 *bufp = buf->b_next; 5268 } 5269 5270 /* 5271 * If we've removed a buffer in the middle of 5272 * the list then update the lastbuf and update 5273 * bufp. 5274 */ 5275 if (*bufp != NULL) { 5276 lastbuf = *bufp; 5277 bufp = &(*bufp)->b_next; 5278 } 5279 } 5280 buf->b_next = NULL; 5281 ASSERT3P(lastbuf, !=, buf); 5282 ASSERT3P(lastbuf, !=, NULL); 5283 5284 /* 5285 * If the current arc_buf_t and the hdr are sharing their data 5286 * buffer, then we must stop sharing that block, transfer 5287 * ownership and setup sharing with a new arc_buf_t at the end 5288 * of the hdr's b_buf list. 5289 */ 5290 if (arc_buf_is_shared(buf)) { 5291 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5292 ASSERT(ARC_BUF_LAST(lastbuf)); 5293 VERIFY(!arc_buf_is_shared(lastbuf)); 5294 5295 /* 5296 * First, sever the block sharing relationship between 5297 * buf and the arc_buf_hdr_t. Then, setup a new 5298 * block sharing relationship with the last buffer 5299 * on the arc_buf_t list. 5300 */ 5301 arc_unshare_buf(hdr, buf); 5302 arc_share_buf(hdr, lastbuf); 5303 VERIFY3P(lastbuf->b_data, !=, NULL); 5304 } else if (HDR_SHARED_DATA(hdr)) { 5305 ASSERT(arc_buf_is_shared(lastbuf)); 5306 } 5307 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 5308 ASSERT3P(state, !=, arc_l2c_only); 5309 5310 (void) refcount_remove_many(&state->arcs_size, 5311 HDR_GET_LSIZE(hdr), buf); 5312 5313 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5314 ASSERT3P(state, !=, arc_l2c_only); 5315 (void) refcount_remove_many(&state->arcs_esize[type], 5316 HDR_GET_LSIZE(hdr), buf); 5317 } 5318 5319 hdr->b_l1hdr.b_bufcnt -= 1; 5320 arc_cksum_verify(buf); 5321#ifdef illumos 5322 arc_buf_unwatch(buf); 5323#endif 5324 5325 mutex_exit(hash_lock); 5326 5327 /* 5328 * Allocate a new hdr. The new hdr will contain a b_pdata 5329 * buffer which will be freed in arc_write(). 5330 */ 5331 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 5332 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 5333 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 5334 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 5335 VERIFY3U(nhdr->b_type, ==, type); 5336 ASSERT(!HDR_SHARED_DATA(nhdr)); 5337 5338 nhdr->b_l1hdr.b_buf = buf; 5339 nhdr->b_l1hdr.b_bufcnt = 1; 5340 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 5341 buf->b_hdr = nhdr; 5342 5343 mutex_exit(&buf->b_evict_lock); 5344 (void) refcount_add_many(&arc_anon->arcs_size, 5345 HDR_GET_LSIZE(nhdr), buf); 5346 } else { 5347 mutex_exit(&buf->b_evict_lock); 5348 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 5349 /* protected by hash lock, or hdr is on arc_anon */ 5350 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5351 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5352 arc_change_state(arc_anon, hdr, hash_lock); 5353 hdr->b_l1hdr.b_arc_access = 0; 5354 mutex_exit(hash_lock); 5355 5356 buf_discard_identity(hdr); 5357 arc_buf_thaw(buf); 5358 } 5359} 5360 5361int 5362arc_released(arc_buf_t *buf) 5363{ 5364 int released; 5365 5366 mutex_enter(&buf->b_evict_lock); 5367 released = (buf->b_data != NULL && 5368 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5369 mutex_exit(&buf->b_evict_lock); 5370 return (released); 5371} 5372 5373#ifdef ZFS_DEBUG 5374int 5375arc_referenced(arc_buf_t *buf) 5376{ 5377 int referenced; 5378 5379 mutex_enter(&buf->b_evict_lock); 5380 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5381 mutex_exit(&buf->b_evict_lock); 5382 return (referenced); 5383} 5384#endif 5385 5386static void 5387arc_write_ready(zio_t *zio) 5388{ 5389 arc_write_callback_t *callback = zio->io_private; 5390 arc_buf_t *buf = callback->awcb_buf; 5391 arc_buf_hdr_t *hdr = buf->b_hdr; 5392 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 5393 5394 ASSERT(HDR_HAS_L1HDR(hdr)); 5395 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5396 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 5397 5398 /* 5399 * If we're reexecuting this zio because the pool suspended, then 5400 * cleanup any state that was previously set the first time the 5401 * callback as invoked. 5402 */ 5403 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 5404 arc_cksum_free(hdr); 5405#ifdef illumos 5406 arc_buf_unwatch(buf); 5407#endif 5408 if (hdr->b_l1hdr.b_pdata != NULL) { 5409 if (arc_buf_is_shared(buf)) { 5410 ASSERT(HDR_SHARED_DATA(hdr)); 5411 5412 arc_unshare_buf(hdr, buf); 5413 } else { 5414 arc_hdr_free_pdata(hdr); 5415 } 5416 } 5417 } 5418 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5419 ASSERT(!HDR_SHARED_DATA(hdr)); 5420 ASSERT(!arc_buf_is_shared(buf)); 5421 5422 callback->awcb_ready(zio, buf, callback->awcb_private); 5423 5424 if (HDR_IO_IN_PROGRESS(hdr)) 5425 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 5426 5427 arc_cksum_compute(buf); 5428 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5429 5430 enum zio_compress compress; 5431 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5432 compress = ZIO_COMPRESS_OFF; 5433 } else { 5434 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 5435 compress = BP_GET_COMPRESS(zio->io_bp); 5436 } 5437 HDR_SET_PSIZE(hdr, psize); 5438 arc_hdr_set_compress(hdr, compress); 5439 5440 /* 5441 * If the hdr is compressed, then copy the compressed 5442 * zio contents into arc_buf_hdr_t. Otherwise, copy the original 5443 * data buf into the hdr. Ideally, we would like to always copy the 5444 * io_data into b_pdata but the user may have disabled compressed 5445 * arc thus the on-disk block may or may not match what we maintain 5446 * in the hdr's b_pdata field. 5447 */ 5448 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5449 ASSERT(BP_GET_COMPRESS(zio->io_bp) != ZIO_COMPRESS_OFF); 5450 ASSERT3U(psize, >, 0); 5451 arc_hdr_alloc_pdata(hdr); 5452 bcopy(zio->io_data, hdr->b_l1hdr.b_pdata, psize); 5453 } else { 5454 ASSERT3P(buf->b_data, ==, zio->io_orig_data); 5455 ASSERT3U(zio->io_orig_size, ==, HDR_GET_LSIZE(hdr)); 5456 ASSERT3U(hdr->b_l1hdr.b_byteswap, ==, DMU_BSWAP_NUMFUNCS); 5457 ASSERT(!HDR_SHARED_DATA(hdr)); 5458 ASSERT(!arc_buf_is_shared(buf)); 5459 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5460 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5461 5462 /* 5463 * This hdr is not compressed so we're able to share 5464 * the arc_buf_t data buffer with the hdr. 5465 */ 5466 arc_share_buf(hdr, buf); 5467 VERIFY0(bcmp(zio->io_orig_data, hdr->b_l1hdr.b_pdata, 5468 HDR_GET_LSIZE(hdr))); 5469 } 5470 arc_hdr_verify(hdr, zio->io_bp); 5471} 5472 5473static void 5474arc_write_children_ready(zio_t *zio) 5475{ 5476 arc_write_callback_t *callback = zio->io_private; 5477 arc_buf_t *buf = callback->awcb_buf; 5478 5479 callback->awcb_children_ready(zio, buf, callback->awcb_private); 5480} 5481 5482/* 5483 * The SPA calls this callback for each physical write that happens on behalf 5484 * of a logical write. See the comment in dbuf_write_physdone() for details. 5485 */ 5486static void 5487arc_write_physdone(zio_t *zio) 5488{ 5489 arc_write_callback_t *cb = zio->io_private; 5490 if (cb->awcb_physdone != NULL) 5491 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5492} 5493 5494static void 5495arc_write_done(zio_t *zio) 5496{ 5497 arc_write_callback_t *callback = zio->io_private; 5498 arc_buf_t *buf = callback->awcb_buf; 5499 arc_buf_hdr_t *hdr = buf->b_hdr; 5500 5501 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5502 5503 if (zio->io_error == 0) { 5504 arc_hdr_verify(hdr, zio->io_bp); 5505 5506 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5507 buf_discard_identity(hdr); 5508 } else { 5509 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5510 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5511 } 5512 } else { 5513 ASSERT(HDR_EMPTY(hdr)); 5514 } 5515 5516 /* 5517 * If the block to be written was all-zero or compressed enough to be 5518 * embedded in the BP, no write was performed so there will be no 5519 * dva/birth/checksum. The buffer must therefore remain anonymous 5520 * (and uncached). 5521 */ 5522 if (!HDR_EMPTY(hdr)) { 5523 arc_buf_hdr_t *exists; 5524 kmutex_t *hash_lock; 5525 5526 ASSERT(zio->io_error == 0); 5527 5528 arc_cksum_verify(buf); 5529 5530 exists = buf_hash_insert(hdr, &hash_lock); 5531 if (exists != NULL) { 5532 /* 5533 * This can only happen if we overwrite for 5534 * sync-to-convergence, because we remove 5535 * buffers from the hash table when we arc_free(). 5536 */ 5537 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5538 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5539 panic("bad overwrite, hdr=%p exists=%p", 5540 (void *)hdr, (void *)exists); 5541 ASSERT(refcount_is_zero( 5542 &exists->b_l1hdr.b_refcnt)); 5543 arc_change_state(arc_anon, exists, hash_lock); 5544 mutex_exit(hash_lock); 5545 arc_hdr_destroy(exists); 5546 exists = buf_hash_insert(hdr, &hash_lock); 5547 ASSERT3P(exists, ==, NULL); 5548 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5549 /* nopwrite */ 5550 ASSERT(zio->io_prop.zp_nopwrite); 5551 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5552 panic("bad nopwrite, hdr=%p exists=%p", 5553 (void *)hdr, (void *)exists); 5554 } else { 5555 /* Dedup */ 5556 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 5557 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5558 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5559 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5560 } 5561 } 5562 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5563 /* if it's not anon, we are doing a scrub */ 5564 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5565 arc_access(hdr, hash_lock); 5566 mutex_exit(hash_lock); 5567 } else { 5568 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5569 } 5570 5571 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5572 callback->awcb_done(zio, buf, callback->awcb_private); 5573 5574 kmem_free(callback, sizeof (arc_write_callback_t)); 5575} 5576 5577zio_t * 5578arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 5579 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready, 5580 arc_done_func_t *children_ready, arc_done_func_t *physdone, 5581 arc_done_func_t *done, void *private, zio_priority_t priority, 5582 int zio_flags, const zbookmark_phys_t *zb) 5583{ 5584 arc_buf_hdr_t *hdr = buf->b_hdr; 5585 arc_write_callback_t *callback; 5586 zio_t *zio; 5587 5588 ASSERT3P(ready, !=, NULL); 5589 ASSERT3P(done, !=, NULL); 5590 ASSERT(!HDR_IO_ERROR(hdr)); 5591 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5592 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5593 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 5594 if (l2arc) 5595 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5596 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5597 callback->awcb_ready = ready; 5598 callback->awcb_children_ready = children_ready; 5599 callback->awcb_physdone = physdone; 5600 callback->awcb_done = done; 5601 callback->awcb_private = private; 5602 callback->awcb_buf = buf; 5603 5604 /* 5605 * The hdr's b_pdata is now stale, free it now. A new data block 5606 * will be allocated when the zio pipeline calls arc_write_ready(). 5607 */ 5608 if (hdr->b_l1hdr.b_pdata != NULL) { 5609 /* 5610 * If the buf is currently sharing the data block with 5611 * the hdr then we need to break that relationship here. 5612 * The hdr will remain with a NULL data pointer and the 5613 * buf will take sole ownership of the block. 5614 */ 5615 if (arc_buf_is_shared(buf)) { 5616 ASSERT(ARC_BUF_LAST(buf)); 5617 arc_unshare_buf(hdr, buf); 5618 } else { 5619 arc_hdr_free_pdata(hdr); 5620 } 5621 VERIFY3P(buf->b_data, !=, NULL); 5622 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 5623 } 5624 ASSERT(!arc_buf_is_shared(buf)); 5625 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5626 5627 zio = zio_write(pio, spa, txg, bp, buf->b_data, HDR_GET_LSIZE(hdr), zp, 5628 arc_write_ready, 5629 (children_ready != NULL) ? arc_write_children_ready : NULL, 5630 arc_write_physdone, arc_write_done, callback, 5631 priority, zio_flags, zb); 5632 5633 return (zio); 5634} 5635 5636static int 5637arc_memory_throttle(uint64_t reserve, uint64_t txg) 5638{ 5639#ifdef _KERNEL 5640 uint64_t available_memory = ptob(freemem); 5641 static uint64_t page_load = 0; 5642 static uint64_t last_txg = 0; 5643 5644#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5645 available_memory = 5646 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5647#endif 5648 5649 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5650 return (0); 5651 5652 if (txg > last_txg) { 5653 last_txg = txg; 5654 page_load = 0; 5655 } 5656 /* 5657 * If we are in pageout, we know that memory is already tight, 5658 * the arc is already going to be evicting, so we just want to 5659 * continue to let page writes occur as quickly as possible. 5660 */ 5661 if (curproc == pageproc) { 5662 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5663 return (SET_ERROR(ERESTART)); 5664 /* Note: reserve is inflated, so we deflate */ 5665 page_load += reserve / 8; 5666 return (0); 5667 } else if (page_load > 0 && arc_reclaim_needed()) { 5668 /* memory is low, delay before restarting */ 5669 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5670 return (SET_ERROR(EAGAIN)); 5671 } 5672 page_load = 0; 5673#endif 5674 return (0); 5675} 5676 5677void 5678arc_tempreserve_clear(uint64_t reserve) 5679{ 5680 atomic_add_64(&arc_tempreserve, -reserve); 5681 ASSERT((int64_t)arc_tempreserve >= 0); 5682} 5683 5684int 5685arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5686{ 5687 int error; 5688 uint64_t anon_size; 5689 5690 if (reserve > arc_c/4 && !arc_no_grow) { 5691 arc_c = MIN(arc_c_max, reserve * 4); 5692 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5693 } 5694 if (reserve > arc_c) 5695 return (SET_ERROR(ENOMEM)); 5696 5697 /* 5698 * Don't count loaned bufs as in flight dirty data to prevent long 5699 * network delays from blocking transactions that are ready to be 5700 * assigned to a txg. 5701 */ 5702 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5703 arc_loaned_bytes), 0); 5704 5705 /* 5706 * Writes will, almost always, require additional memory allocations 5707 * in order to compress/encrypt/etc the data. We therefore need to 5708 * make sure that there is sufficient available memory for this. 5709 */ 5710 error = arc_memory_throttle(reserve, txg); 5711 if (error != 0) 5712 return (error); 5713 5714 /* 5715 * Throttle writes when the amount of dirty data in the cache 5716 * gets too large. We try to keep the cache less than half full 5717 * of dirty blocks so that our sync times don't grow too large. 5718 * Note: if two requests come in concurrently, we might let them 5719 * both succeed, when one of them should fail. Not a huge deal. 5720 */ 5721 5722 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5723 anon_size > arc_c / 4) { 5724 uint64_t meta_esize = 5725 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5726 uint64_t data_esize = 5727 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5728 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5729 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5730 arc_tempreserve >> 10, meta_esize >> 10, 5731 data_esize >> 10, reserve >> 10, arc_c >> 10); 5732 return (SET_ERROR(ERESTART)); 5733 } 5734 atomic_add_64(&arc_tempreserve, reserve); 5735 return (0); 5736} 5737 5738static void 5739arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5740 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5741{ 5742 size->value.ui64 = refcount_count(&state->arcs_size); 5743 evict_data->value.ui64 = 5744 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 5745 evict_metadata->value.ui64 = 5746 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 5747} 5748 5749static int 5750arc_kstat_update(kstat_t *ksp, int rw) 5751{ 5752 arc_stats_t *as = ksp->ks_data; 5753 5754 if (rw == KSTAT_WRITE) { 5755 return (EACCES); 5756 } else { 5757 arc_kstat_update_state(arc_anon, 5758 &as->arcstat_anon_size, 5759 &as->arcstat_anon_evictable_data, 5760 &as->arcstat_anon_evictable_metadata); 5761 arc_kstat_update_state(arc_mru, 5762 &as->arcstat_mru_size, 5763 &as->arcstat_mru_evictable_data, 5764 &as->arcstat_mru_evictable_metadata); 5765 arc_kstat_update_state(arc_mru_ghost, 5766 &as->arcstat_mru_ghost_size, 5767 &as->arcstat_mru_ghost_evictable_data, 5768 &as->arcstat_mru_ghost_evictable_metadata); 5769 arc_kstat_update_state(arc_mfu, 5770 &as->arcstat_mfu_size, 5771 &as->arcstat_mfu_evictable_data, 5772 &as->arcstat_mfu_evictable_metadata); 5773 arc_kstat_update_state(arc_mfu_ghost, 5774 &as->arcstat_mfu_ghost_size, 5775 &as->arcstat_mfu_ghost_evictable_data, 5776 &as->arcstat_mfu_ghost_evictable_metadata); 5777 } 5778 5779 return (0); 5780} 5781 5782/* 5783 * This function *must* return indices evenly distributed between all 5784 * sublists of the multilist. This is needed due to how the ARC eviction 5785 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5786 * distributed between all sublists and uses this assumption when 5787 * deciding which sublist to evict from and how much to evict from it. 5788 */ 5789unsigned int 5790arc_state_multilist_index_func(multilist_t *ml, void *obj) 5791{ 5792 arc_buf_hdr_t *hdr = obj; 5793 5794 /* 5795 * We rely on b_dva to generate evenly distributed index 5796 * numbers using buf_hash below. So, as an added precaution, 5797 * let's make sure we never add empty buffers to the arc lists. 5798 */ 5799 ASSERT(!HDR_EMPTY(hdr)); 5800 5801 /* 5802 * The assumption here, is the hash value for a given 5803 * arc_buf_hdr_t will remain constant throughout it's lifetime 5804 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5805 * Thus, we don't need to store the header's sublist index 5806 * on insertion, as this index can be recalculated on removal. 5807 * 5808 * Also, the low order bits of the hash value are thought to be 5809 * distributed evenly. Otherwise, in the case that the multilist 5810 * has a power of two number of sublists, each sublists' usage 5811 * would not be evenly distributed. 5812 */ 5813 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5814 multilist_get_num_sublists(ml)); 5815} 5816 5817#ifdef _KERNEL 5818static eventhandler_tag arc_event_lowmem = NULL; 5819 5820static void 5821arc_lowmem(void *arg __unused, int howto __unused) 5822{ 5823 5824 mutex_enter(&arc_reclaim_lock); 5825 /* XXX: Memory deficit should be passed as argument. */ 5826 needfree = btoc(arc_c >> arc_shrink_shift); 5827 DTRACE_PROBE(arc__needfree); 5828 cv_signal(&arc_reclaim_thread_cv); 5829 5830 /* 5831 * It is unsafe to block here in arbitrary threads, because we can come 5832 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5833 * with ARC reclaim thread. 5834 */ 5835 if (curproc == pageproc) 5836 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5837 mutex_exit(&arc_reclaim_lock); 5838} 5839#endif 5840 5841static void 5842arc_state_init(void) 5843{ 5844 arc_anon = &ARC_anon; 5845 arc_mru = &ARC_mru; 5846 arc_mru_ghost = &ARC_mru_ghost; 5847 arc_mfu = &ARC_mfu; 5848 arc_mfu_ghost = &ARC_mfu_ghost; 5849 arc_l2c_only = &ARC_l2c_only; 5850 5851 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5852 sizeof (arc_buf_hdr_t), 5853 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5854 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5855 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5856 sizeof (arc_buf_hdr_t), 5857 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5858 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5859 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5860 sizeof (arc_buf_hdr_t), 5861 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5862 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5863 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5864 sizeof (arc_buf_hdr_t), 5865 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5866 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5867 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5868 sizeof (arc_buf_hdr_t), 5869 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5870 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5871 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5872 sizeof (arc_buf_hdr_t), 5873 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5874 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5875 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5876 sizeof (arc_buf_hdr_t), 5877 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5878 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5879 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5880 sizeof (arc_buf_hdr_t), 5881 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5882 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5883 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5884 sizeof (arc_buf_hdr_t), 5885 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5886 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5887 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5888 sizeof (arc_buf_hdr_t), 5889 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5890 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5891 5892 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5893 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5894 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 5895 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 5896 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 5897 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 5898 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 5899 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 5900 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 5901 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 5902 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 5903 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 5904 5905 refcount_create(&arc_anon->arcs_size); 5906 refcount_create(&arc_mru->arcs_size); 5907 refcount_create(&arc_mru_ghost->arcs_size); 5908 refcount_create(&arc_mfu->arcs_size); 5909 refcount_create(&arc_mfu_ghost->arcs_size); 5910 refcount_create(&arc_l2c_only->arcs_size); 5911} 5912 5913static void 5914arc_state_fini(void) 5915{ 5916 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5917 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5918 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 5919 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 5920 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 5921 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 5922 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 5923 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 5924 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 5925 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 5926 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 5927 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 5928 5929 refcount_destroy(&arc_anon->arcs_size); 5930 refcount_destroy(&arc_mru->arcs_size); 5931 refcount_destroy(&arc_mru_ghost->arcs_size); 5932 refcount_destroy(&arc_mfu->arcs_size); 5933 refcount_destroy(&arc_mfu_ghost->arcs_size); 5934 refcount_destroy(&arc_l2c_only->arcs_size); 5935 5936 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5937 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5938 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 5939 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 5940 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 5941 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 5942 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 5943 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 5944} 5945 5946uint64_t 5947arc_max_bytes(void) 5948{ 5949 return (arc_c_max); 5950} 5951 5952void 5953arc_init(void) 5954{ 5955 int i, prefetch_tunable_set = 0; 5956 5957 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 5958 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 5959 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 5960 5961 /* Convert seconds to clock ticks */ 5962 arc_min_prefetch_lifespan = 1 * hz; 5963 5964 /* Start out with 1/8 of all memory */ 5965 arc_c = kmem_size() / 8; 5966 5967#ifdef illumos 5968#ifdef _KERNEL 5969 /* 5970 * On architectures where the physical memory can be larger 5971 * than the addressable space (intel in 32-bit mode), we may 5972 * need to limit the cache to 1/8 of VM size. 5973 */ 5974 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 5975#endif 5976#endif /* illumos */ 5977 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 5978 arc_c_min = MAX(arc_c / 4, arc_abs_min); 5979 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 5980 if (arc_c * 8 >= 1 << 30) 5981 arc_c_max = (arc_c * 8) - (1 << 30); 5982 else 5983 arc_c_max = arc_c_min; 5984 arc_c_max = MAX(arc_c * 5, arc_c_max); 5985 5986 /* 5987 * In userland, there's only the memory pressure that we artificially 5988 * create (see arc_available_memory()). Don't let arc_c get too 5989 * small, because it can cause transactions to be larger than 5990 * arc_c, causing arc_tempreserve_space() to fail. 5991 */ 5992#ifndef _KERNEL 5993 arc_c_min = arc_c_max / 2; 5994#endif 5995 5996#ifdef _KERNEL 5997 /* 5998 * Allow the tunables to override our calculations if they are 5999 * reasonable. 6000 */ 6001 if (zfs_arc_max > arc_abs_min && zfs_arc_max < kmem_size()) 6002 arc_c_max = zfs_arc_max; 6003 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6004 arc_c_min = zfs_arc_min; 6005#endif 6006 6007 arc_c = arc_c_max; 6008 arc_p = (arc_c >> 1); 6009 arc_size = 0; 6010 6011 /* limit meta-data to 1/4 of the arc capacity */ 6012 arc_meta_limit = arc_c_max / 4; 6013 6014 /* Allow the tunable to override if it is reasonable */ 6015 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6016 arc_meta_limit = zfs_arc_meta_limit; 6017 6018 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6019 arc_c_min = arc_meta_limit / 2; 6020 6021 if (zfs_arc_meta_min > 0) { 6022 arc_meta_min = zfs_arc_meta_min; 6023 } else { 6024 arc_meta_min = arc_c_min / 2; 6025 } 6026 6027 if (zfs_arc_grow_retry > 0) 6028 arc_grow_retry = zfs_arc_grow_retry; 6029 6030 if (zfs_arc_shrink_shift > 0) 6031 arc_shrink_shift = zfs_arc_shrink_shift; 6032 6033 /* 6034 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6035 */ 6036 if (arc_no_grow_shift >= arc_shrink_shift) 6037 arc_no_grow_shift = arc_shrink_shift - 1; 6038 6039 if (zfs_arc_p_min_shift > 0) 6040 arc_p_min_shift = zfs_arc_p_min_shift; 6041 6042 if (zfs_arc_num_sublists_per_state < 1) 6043 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 6044 6045 /* if kmem_flags are set, lets try to use less memory */ 6046 if (kmem_debugging()) 6047 arc_c = arc_c / 2; 6048 if (arc_c < arc_c_min) 6049 arc_c = arc_c_min; 6050 6051 zfs_arc_min = arc_c_min; 6052 zfs_arc_max = arc_c_max; 6053 6054 arc_state_init(); 6055 buf_init(); 6056 6057 arc_reclaim_thread_exit = B_FALSE; 6058 6059 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6060 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6061 6062 if (arc_ksp != NULL) { 6063 arc_ksp->ks_data = &arc_stats; 6064 arc_ksp->ks_update = arc_kstat_update; 6065 kstat_install(arc_ksp); 6066 } 6067 6068 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6069 TS_RUN, minclsyspri); 6070 6071#ifdef _KERNEL 6072 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6073 EVENTHANDLER_PRI_FIRST); 6074#endif 6075 6076 arc_dead = B_FALSE; 6077 arc_warm = B_FALSE; 6078 6079 /* 6080 * Calculate maximum amount of dirty data per pool. 6081 * 6082 * If it has been set by /etc/system, take that. 6083 * Otherwise, use a percentage of physical memory defined by 6084 * zfs_dirty_data_max_percent (default 10%) with a cap at 6085 * zfs_dirty_data_max_max (default 4GB). 6086 */ 6087 if (zfs_dirty_data_max == 0) { 6088 zfs_dirty_data_max = ptob(physmem) * 6089 zfs_dirty_data_max_percent / 100; 6090 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6091 zfs_dirty_data_max_max); 6092 } 6093 6094#ifdef _KERNEL 6095 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6096 prefetch_tunable_set = 1; 6097 6098#ifdef __i386__ 6099 if (prefetch_tunable_set == 0) { 6100 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6101 "-- to enable,\n"); 6102 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6103 "to /boot/loader.conf.\n"); 6104 zfs_prefetch_disable = 1; 6105 } 6106#else 6107 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6108 prefetch_tunable_set == 0) { 6109 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6110 "than 4GB of RAM is present;\n" 6111 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6112 "to /boot/loader.conf.\n"); 6113 zfs_prefetch_disable = 1; 6114 } 6115#endif 6116 /* Warn about ZFS memory and address space requirements. */ 6117 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6118 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6119 "expect unstable behavior.\n"); 6120 } 6121 if (kmem_size() < 512 * (1 << 20)) { 6122 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6123 "expect unstable behavior.\n"); 6124 printf(" Consider tuning vm.kmem_size and " 6125 "vm.kmem_size_max\n"); 6126 printf(" in /boot/loader.conf.\n"); 6127 } 6128#endif 6129} 6130 6131void 6132arc_fini(void) 6133{ 6134 mutex_enter(&arc_reclaim_lock); 6135 arc_reclaim_thread_exit = B_TRUE; 6136 /* 6137 * The reclaim thread will set arc_reclaim_thread_exit back to 6138 * B_FALSE when it is finished exiting; we're waiting for that. 6139 */ 6140 while (arc_reclaim_thread_exit) { 6141 cv_signal(&arc_reclaim_thread_cv); 6142 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6143 } 6144 mutex_exit(&arc_reclaim_lock); 6145 6146 /* Use B_TRUE to ensure *all* buffers are evicted */ 6147 arc_flush(NULL, B_TRUE); 6148 6149 arc_dead = B_TRUE; 6150 6151 if (arc_ksp != NULL) { 6152 kstat_delete(arc_ksp); 6153 arc_ksp = NULL; 6154 } 6155 6156 mutex_destroy(&arc_reclaim_lock); 6157 cv_destroy(&arc_reclaim_thread_cv); 6158 cv_destroy(&arc_reclaim_waiters_cv); 6159 6160 arc_state_fini(); 6161 buf_fini(); 6162 6163 ASSERT0(arc_loaned_bytes); 6164 6165#ifdef _KERNEL 6166 if (arc_event_lowmem != NULL) 6167 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6168#endif 6169} 6170 6171/* 6172 * Level 2 ARC 6173 * 6174 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6175 * It uses dedicated storage devices to hold cached data, which are populated 6176 * using large infrequent writes. The main role of this cache is to boost 6177 * the performance of random read workloads. The intended L2ARC devices 6178 * include short-stroked disks, solid state disks, and other media with 6179 * substantially faster read latency than disk. 6180 * 6181 * +-----------------------+ 6182 * | ARC | 6183 * +-----------------------+ 6184 * | ^ ^ 6185 * | | | 6186 * l2arc_feed_thread() arc_read() 6187 * | | | 6188 * | l2arc read | 6189 * V | | 6190 * +---------------+ | 6191 * | L2ARC | | 6192 * +---------------+ | 6193 * | ^ | 6194 * l2arc_write() | | 6195 * | | | 6196 * V | | 6197 * +-------+ +-------+ 6198 * | vdev | | vdev | 6199 * | cache | | cache | 6200 * +-------+ +-------+ 6201 * +=========+ .-----. 6202 * : L2ARC : |-_____-| 6203 * : devices : | Disks | 6204 * +=========+ `-_____-' 6205 * 6206 * Read requests are satisfied from the following sources, in order: 6207 * 6208 * 1) ARC 6209 * 2) vdev cache of L2ARC devices 6210 * 3) L2ARC devices 6211 * 4) vdev cache of disks 6212 * 5) disks 6213 * 6214 * Some L2ARC device types exhibit extremely slow write performance. 6215 * To accommodate for this there are some significant differences between 6216 * the L2ARC and traditional cache design: 6217 * 6218 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6219 * the ARC behave as usual, freeing buffers and placing headers on ghost 6220 * lists. The ARC does not send buffers to the L2ARC during eviction as 6221 * this would add inflated write latencies for all ARC memory pressure. 6222 * 6223 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6224 * It does this by periodically scanning buffers from the eviction-end of 6225 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6226 * not already there. It scans until a headroom of buffers is satisfied, 6227 * which itself is a buffer for ARC eviction. If a compressible buffer is 6228 * found during scanning and selected for writing to an L2ARC device, we 6229 * temporarily boost scanning headroom during the next scan cycle to make 6230 * sure we adapt to compression effects (which might significantly reduce 6231 * the data volume we write to L2ARC). The thread that does this is 6232 * l2arc_feed_thread(), illustrated below; example sizes are included to 6233 * provide a better sense of ratio than this diagram: 6234 * 6235 * head --> tail 6236 * +---------------------+----------+ 6237 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6238 * +---------------------+----------+ | o L2ARC eligible 6239 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6240 * +---------------------+----------+ | 6241 * 15.9 Gbytes ^ 32 Mbytes | 6242 * headroom | 6243 * l2arc_feed_thread() 6244 * | 6245 * l2arc write hand <--[oooo]--' 6246 * | 8 Mbyte 6247 * | write max 6248 * V 6249 * +==============================+ 6250 * L2ARC dev |####|#|###|###| |####| ... | 6251 * +==============================+ 6252 * 32 Gbytes 6253 * 6254 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 6255 * evicted, then the L2ARC has cached a buffer much sooner than it probably 6256 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 6257 * safe to say that this is an uncommon case, since buffers at the end of 6258 * the ARC lists have moved there due to inactivity. 6259 * 6260 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 6261 * then the L2ARC simply misses copying some buffers. This serves as a 6262 * pressure valve to prevent heavy read workloads from both stalling the ARC 6263 * with waits and clogging the L2ARC with writes. This also helps prevent 6264 * the potential for the L2ARC to churn if it attempts to cache content too 6265 * quickly, such as during backups of the entire pool. 6266 * 6267 * 5. After system boot and before the ARC has filled main memory, there are 6268 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 6269 * lists can remain mostly static. Instead of searching from tail of these 6270 * lists as pictured, the l2arc_feed_thread() will search from the list heads 6271 * for eligible buffers, greatly increasing its chance of finding them. 6272 * 6273 * The L2ARC device write speed is also boosted during this time so that 6274 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 6275 * there are no L2ARC reads, and no fear of degrading read performance 6276 * through increased writes. 6277 * 6278 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 6279 * the vdev queue can aggregate them into larger and fewer writes. Each 6280 * device is written to in a rotor fashion, sweeping writes through 6281 * available space then repeating. 6282 * 6283 * 7. The L2ARC does not store dirty content. It never needs to flush 6284 * write buffers back to disk based storage. 6285 * 6286 * 8. If an ARC buffer is written (and dirtied) which also exists in the 6287 * L2ARC, the now stale L2ARC buffer is immediately dropped. 6288 * 6289 * The performance of the L2ARC can be tweaked by a number of tunables, which 6290 * may be necessary for different workloads: 6291 * 6292 * l2arc_write_max max write bytes per interval 6293 * l2arc_write_boost extra write bytes during device warmup 6294 * l2arc_noprefetch skip caching prefetched buffers 6295 * l2arc_headroom number of max device writes to precache 6296 * l2arc_headroom_boost when we find compressed buffers during ARC 6297 * scanning, we multiply headroom by this 6298 * percentage factor for the next scan cycle, 6299 * since more compressed buffers are likely to 6300 * be present 6301 * l2arc_feed_secs seconds between L2ARC writing 6302 * 6303 * Tunables may be removed or added as future performance improvements are 6304 * integrated, and also may become zpool properties. 6305 * 6306 * There are three key functions that control how the L2ARC warms up: 6307 * 6308 * l2arc_write_eligible() check if a buffer is eligible to cache 6309 * l2arc_write_size() calculate how much to write 6310 * l2arc_write_interval() calculate sleep delay between writes 6311 * 6312 * These three functions determine what to write, how much, and how quickly 6313 * to send writes. 6314 */ 6315 6316static boolean_t 6317l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 6318{ 6319 /* 6320 * A buffer is *not* eligible for the L2ARC if it: 6321 * 1. belongs to a different spa. 6322 * 2. is already cached on the L2ARC. 6323 * 3. has an I/O in progress (it may be an incomplete read). 6324 * 4. is flagged not eligible (zfs property). 6325 */ 6326 if (hdr->b_spa != spa_guid) { 6327 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 6328 return (B_FALSE); 6329 } 6330 if (HDR_HAS_L2HDR(hdr)) { 6331 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 6332 return (B_FALSE); 6333 } 6334 if (HDR_IO_IN_PROGRESS(hdr)) { 6335 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 6336 return (B_FALSE); 6337 } 6338 if (!HDR_L2CACHE(hdr)) { 6339 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 6340 return (B_FALSE); 6341 } 6342 6343 return (B_TRUE); 6344} 6345 6346static uint64_t 6347l2arc_write_size(void) 6348{ 6349 uint64_t size; 6350 6351 /* 6352 * Make sure our globals have meaningful values in case the user 6353 * altered them. 6354 */ 6355 size = l2arc_write_max; 6356 if (size == 0) { 6357 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 6358 "be greater than zero, resetting it to the default (%d)", 6359 L2ARC_WRITE_SIZE); 6360 size = l2arc_write_max = L2ARC_WRITE_SIZE; 6361 } 6362 6363 if (arc_warm == B_FALSE) 6364 size += l2arc_write_boost; 6365 6366 return (size); 6367 6368} 6369 6370static clock_t 6371l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 6372{ 6373 clock_t interval, next, now; 6374 6375 /* 6376 * If the ARC lists are busy, increase our write rate; if the 6377 * lists are stale, idle back. This is achieved by checking 6378 * how much we previously wrote - if it was more than half of 6379 * what we wanted, schedule the next write much sooner. 6380 */ 6381 if (l2arc_feed_again && wrote > (wanted / 2)) 6382 interval = (hz * l2arc_feed_min_ms) / 1000; 6383 else 6384 interval = hz * l2arc_feed_secs; 6385 6386 now = ddi_get_lbolt(); 6387 next = MAX(now, MIN(now + interval, began + interval)); 6388 6389 return (next); 6390} 6391 6392/* 6393 * Cycle through L2ARC devices. This is how L2ARC load balances. 6394 * If a device is returned, this also returns holding the spa config lock. 6395 */ 6396static l2arc_dev_t * 6397l2arc_dev_get_next(void) 6398{ 6399 l2arc_dev_t *first, *next = NULL; 6400 6401 /* 6402 * Lock out the removal of spas (spa_namespace_lock), then removal 6403 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 6404 * both locks will be dropped and a spa config lock held instead. 6405 */ 6406 mutex_enter(&spa_namespace_lock); 6407 mutex_enter(&l2arc_dev_mtx); 6408 6409 /* if there are no vdevs, there is nothing to do */ 6410 if (l2arc_ndev == 0) 6411 goto out; 6412 6413 first = NULL; 6414 next = l2arc_dev_last; 6415 do { 6416 /* loop around the list looking for a non-faulted vdev */ 6417 if (next == NULL) { 6418 next = list_head(l2arc_dev_list); 6419 } else { 6420 next = list_next(l2arc_dev_list, next); 6421 if (next == NULL) 6422 next = list_head(l2arc_dev_list); 6423 } 6424 6425 /* if we have come back to the start, bail out */ 6426 if (first == NULL) 6427 first = next; 6428 else if (next == first) 6429 break; 6430 6431 } while (vdev_is_dead(next->l2ad_vdev)); 6432 6433 /* if we were unable to find any usable vdevs, return NULL */ 6434 if (vdev_is_dead(next->l2ad_vdev)) 6435 next = NULL; 6436 6437 l2arc_dev_last = next; 6438 6439out: 6440 mutex_exit(&l2arc_dev_mtx); 6441 6442 /* 6443 * Grab the config lock to prevent the 'next' device from being 6444 * removed while we are writing to it. 6445 */ 6446 if (next != NULL) 6447 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 6448 mutex_exit(&spa_namespace_lock); 6449 6450 return (next); 6451} 6452 6453/* 6454 * Free buffers that were tagged for destruction. 6455 */ 6456static void 6457l2arc_do_free_on_write() 6458{ 6459 list_t *buflist; 6460 l2arc_data_free_t *df, *df_prev; 6461 6462 mutex_enter(&l2arc_free_on_write_mtx); 6463 buflist = l2arc_free_on_write; 6464 6465 for (df = list_tail(buflist); df; df = df_prev) { 6466 df_prev = list_prev(buflist, df); 6467 ASSERT3P(df->l2df_data, !=, NULL); 6468 if (df->l2df_type == ARC_BUFC_METADATA) { 6469 zio_buf_free(df->l2df_data, df->l2df_size); 6470 } else { 6471 ASSERT(df->l2df_type == ARC_BUFC_DATA); 6472 zio_data_buf_free(df->l2df_data, df->l2df_size); 6473 } 6474 list_remove(buflist, df); 6475 kmem_free(df, sizeof (l2arc_data_free_t)); 6476 } 6477 6478 mutex_exit(&l2arc_free_on_write_mtx); 6479} 6480 6481/* 6482 * A write to a cache device has completed. Update all headers to allow 6483 * reads from these buffers to begin. 6484 */ 6485static void 6486l2arc_write_done(zio_t *zio) 6487{ 6488 l2arc_write_callback_t *cb; 6489 l2arc_dev_t *dev; 6490 list_t *buflist; 6491 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6492 kmutex_t *hash_lock; 6493 int64_t bytes_dropped = 0; 6494 6495 cb = zio->io_private; 6496 ASSERT3P(cb, !=, NULL); 6497 dev = cb->l2wcb_dev; 6498 ASSERT3P(dev, !=, NULL); 6499 head = cb->l2wcb_head; 6500 ASSERT3P(head, !=, NULL); 6501 buflist = &dev->l2ad_buflist; 6502 ASSERT3P(buflist, !=, NULL); 6503 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6504 l2arc_write_callback_t *, cb); 6505 6506 if (zio->io_error != 0) 6507 ARCSTAT_BUMP(arcstat_l2_writes_error); 6508 6509 /* 6510 * All writes completed, or an error was hit. 6511 */ 6512top: 6513 mutex_enter(&dev->l2ad_mtx); 6514 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 6515 hdr_prev = list_prev(buflist, hdr); 6516 6517 hash_lock = HDR_LOCK(hdr); 6518 6519 /* 6520 * We cannot use mutex_enter or else we can deadlock 6521 * with l2arc_write_buffers (due to swapping the order 6522 * the hash lock and l2ad_mtx are taken). 6523 */ 6524 if (!mutex_tryenter(hash_lock)) { 6525 /* 6526 * Missed the hash lock. We must retry so we 6527 * don't leave the ARC_FLAG_L2_WRITING bit set. 6528 */ 6529 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 6530 6531 /* 6532 * We don't want to rescan the headers we've 6533 * already marked as having been written out, so 6534 * we reinsert the head node so we can pick up 6535 * where we left off. 6536 */ 6537 list_remove(buflist, head); 6538 list_insert_after(buflist, hdr, head); 6539 6540 mutex_exit(&dev->l2ad_mtx); 6541 6542 /* 6543 * We wait for the hash lock to become available 6544 * to try and prevent busy waiting, and increase 6545 * the chance we'll be able to acquire the lock 6546 * the next time around. 6547 */ 6548 mutex_enter(hash_lock); 6549 mutex_exit(hash_lock); 6550 goto top; 6551 } 6552 6553 /* 6554 * We could not have been moved into the arc_l2c_only 6555 * state while in-flight due to our ARC_FLAG_L2_WRITING 6556 * bit being set. Let's just ensure that's being enforced. 6557 */ 6558 ASSERT(HDR_HAS_L1HDR(hdr)); 6559 6560 if (zio->io_error != 0) { 6561 /* 6562 * Error - drop L2ARC entry. 6563 */ 6564 list_remove(buflist, hdr); 6565 l2arc_trim(hdr); 6566 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 6567 6568 ARCSTAT_INCR(arcstat_l2_asize, -arc_hdr_size(hdr)); 6569 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 6570 6571 bytes_dropped += arc_hdr_size(hdr); 6572 (void) refcount_remove_many(&dev->l2ad_alloc, 6573 arc_hdr_size(hdr), hdr); 6574 } 6575 6576 /* 6577 * Allow ARC to begin reads and ghost list evictions to 6578 * this L2ARC entry. 6579 */ 6580 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 6581 6582 mutex_exit(hash_lock); 6583 } 6584 6585 atomic_inc_64(&l2arc_writes_done); 6586 list_remove(buflist, head); 6587 ASSERT(!HDR_HAS_L1HDR(head)); 6588 kmem_cache_free(hdr_l2only_cache, head); 6589 mutex_exit(&dev->l2ad_mtx); 6590 6591 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6592 6593 l2arc_do_free_on_write(); 6594 6595 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6596} 6597 6598/* 6599 * A read to a cache device completed. Validate buffer contents before 6600 * handing over to the regular ARC routines. 6601 */ 6602static void 6603l2arc_read_done(zio_t *zio) 6604{ 6605 l2arc_read_callback_t *cb; 6606 arc_buf_hdr_t *hdr; 6607 kmutex_t *hash_lock; 6608 boolean_t valid_cksum; 6609 6610 ASSERT3P(zio->io_vd, !=, NULL); 6611 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6612 6613 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6614 6615 cb = zio->io_private; 6616 ASSERT3P(cb, !=, NULL); 6617 hdr = cb->l2rcb_hdr; 6618 ASSERT3P(hdr, !=, NULL); 6619 6620 hash_lock = HDR_LOCK(hdr); 6621 mutex_enter(hash_lock); 6622 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6623 6624 /* 6625 * If the data was read into a temporary buffer, 6626 * move it and free the buffer. 6627 */ 6628 if (cb->l2rcb_data != NULL) { 6629 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 6630 if (zio->io_error == 0) { 6631 bcopy(cb->l2rcb_data, hdr->b_l1hdr.b_pdata, 6632 arc_hdr_size(hdr)); 6633 } 6634 6635 /* 6636 * The following must be done regardless of whether 6637 * there was an error: 6638 * - free the temporary buffer 6639 * - point zio to the real ARC buffer 6640 * - set zio size accordingly 6641 * These are required because zio is either re-used for 6642 * an I/O of the block in the case of the error 6643 * or the zio is passed to arc_read_done() and it 6644 * needs real data. 6645 */ 6646 zio_data_buf_free(cb->l2rcb_data, zio->io_size); 6647 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 6648 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_pdata; 6649 } 6650 6651 ASSERT3P(zio->io_data, !=, NULL); 6652 6653 /* 6654 * Check this survived the L2ARC journey. 6655 */ 6656 ASSERT3P(zio->io_data, ==, hdr->b_l1hdr.b_pdata); 6657 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6658 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6659 6660 valid_cksum = arc_cksum_is_equal(hdr, zio); 6661 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6662 mutex_exit(hash_lock); 6663 zio->io_private = hdr; 6664 arc_read_done(zio); 6665 } else { 6666 mutex_exit(hash_lock); 6667 /* 6668 * Buffer didn't survive caching. Increment stats and 6669 * reissue to the original storage device. 6670 */ 6671 if (zio->io_error != 0) { 6672 ARCSTAT_BUMP(arcstat_l2_io_error); 6673 } else { 6674 zio->io_error = SET_ERROR(EIO); 6675 } 6676 if (!valid_cksum) 6677 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6678 6679 /* 6680 * If there's no waiter, issue an async i/o to the primary 6681 * storage now. If there *is* a waiter, the caller must 6682 * issue the i/o in a context where it's OK to block. 6683 */ 6684 if (zio->io_waiter == NULL) { 6685 zio_t *pio = zio_unique_parent(zio); 6686 6687 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6688 6689 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 6690 hdr->b_l1hdr.b_pdata, zio->io_size, arc_read_done, 6691 hdr, zio->io_priority, cb->l2rcb_flags, 6692 &cb->l2rcb_zb)); 6693 } 6694 } 6695 6696 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6697} 6698 6699/* 6700 * This is the list priority from which the L2ARC will search for pages to 6701 * cache. This is used within loops (0..3) to cycle through lists in the 6702 * desired order. This order can have a significant effect on cache 6703 * performance. 6704 * 6705 * Currently the metadata lists are hit first, MFU then MRU, followed by 6706 * the data lists. This function returns a locked list, and also returns 6707 * the lock pointer. 6708 */ 6709static multilist_sublist_t * 6710l2arc_sublist_lock(int list_num) 6711{ 6712 multilist_t *ml = NULL; 6713 unsigned int idx; 6714 6715 ASSERT(list_num >= 0 && list_num <= 3); 6716 6717 switch (list_num) { 6718 case 0: 6719 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6720 break; 6721 case 1: 6722 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6723 break; 6724 case 2: 6725 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6726 break; 6727 case 3: 6728 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6729 break; 6730 } 6731 6732 /* 6733 * Return a randomly-selected sublist. This is acceptable 6734 * because the caller feeds only a little bit of data for each 6735 * call (8MB). Subsequent calls will result in different 6736 * sublists being selected. 6737 */ 6738 idx = multilist_get_random_index(ml); 6739 return (multilist_sublist_lock(ml, idx)); 6740} 6741 6742/* 6743 * Evict buffers from the device write hand to the distance specified in 6744 * bytes. This distance may span populated buffers, it may span nothing. 6745 * This is clearing a region on the L2ARC device ready for writing. 6746 * If the 'all' boolean is set, every buffer is evicted. 6747 */ 6748static void 6749l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6750{ 6751 list_t *buflist; 6752 arc_buf_hdr_t *hdr, *hdr_prev; 6753 kmutex_t *hash_lock; 6754 uint64_t taddr; 6755 6756 buflist = &dev->l2ad_buflist; 6757 6758 if (!all && dev->l2ad_first) { 6759 /* 6760 * This is the first sweep through the device. There is 6761 * nothing to evict. 6762 */ 6763 return; 6764 } 6765 6766 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6767 /* 6768 * When nearing the end of the device, evict to the end 6769 * before the device write hand jumps to the start. 6770 */ 6771 taddr = dev->l2ad_end; 6772 } else { 6773 taddr = dev->l2ad_hand + distance; 6774 } 6775 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6776 uint64_t, taddr, boolean_t, all); 6777 6778top: 6779 mutex_enter(&dev->l2ad_mtx); 6780 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6781 hdr_prev = list_prev(buflist, hdr); 6782 6783 hash_lock = HDR_LOCK(hdr); 6784 6785 /* 6786 * We cannot use mutex_enter or else we can deadlock 6787 * with l2arc_write_buffers (due to swapping the order 6788 * the hash lock and l2ad_mtx are taken). 6789 */ 6790 if (!mutex_tryenter(hash_lock)) { 6791 /* 6792 * Missed the hash lock. Retry. 6793 */ 6794 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6795 mutex_exit(&dev->l2ad_mtx); 6796 mutex_enter(hash_lock); 6797 mutex_exit(hash_lock); 6798 goto top; 6799 } 6800 6801 if (HDR_L2_WRITE_HEAD(hdr)) { 6802 /* 6803 * We hit a write head node. Leave it for 6804 * l2arc_write_done(). 6805 */ 6806 list_remove(buflist, hdr); 6807 mutex_exit(hash_lock); 6808 continue; 6809 } 6810 6811 if (!all && HDR_HAS_L2HDR(hdr) && 6812 (hdr->b_l2hdr.b_daddr > taddr || 6813 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6814 /* 6815 * We've evicted to the target address, 6816 * or the end of the device. 6817 */ 6818 mutex_exit(hash_lock); 6819 break; 6820 } 6821 6822 ASSERT(HDR_HAS_L2HDR(hdr)); 6823 if (!HDR_HAS_L1HDR(hdr)) { 6824 ASSERT(!HDR_L2_READING(hdr)); 6825 /* 6826 * This doesn't exist in the ARC. Destroy. 6827 * arc_hdr_destroy() will call list_remove() 6828 * and decrement arcstat_l2_size. 6829 */ 6830 arc_change_state(arc_anon, hdr, hash_lock); 6831 arc_hdr_destroy(hdr); 6832 } else { 6833 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6834 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6835 /* 6836 * Invalidate issued or about to be issued 6837 * reads, since we may be about to write 6838 * over this location. 6839 */ 6840 if (HDR_L2_READING(hdr)) { 6841 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6842 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 6843 } 6844 6845 /* Ensure this header has finished being written */ 6846 ASSERT(!HDR_L2_WRITING(hdr)); 6847 6848 arc_hdr_l2hdr_destroy(hdr); 6849 } 6850 mutex_exit(hash_lock); 6851 } 6852 mutex_exit(&dev->l2ad_mtx); 6853} 6854 6855/* 6856 * Find and write ARC buffers to the L2ARC device. 6857 * 6858 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6859 * for reading until they have completed writing. 6860 * The headroom_boost is an in-out parameter used to maintain headroom boost 6861 * state between calls to this function. 6862 * 6863 * Returns the number of bytes actually written (which may be smaller than 6864 * the delta by which the device hand has changed due to alignment). 6865 */ 6866static uint64_t 6867l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 6868{ 6869 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6870 uint64_t write_asize, write_psize, write_sz, headroom; 6871 boolean_t full; 6872 l2arc_write_callback_t *cb; 6873 zio_t *pio, *wzio; 6874 uint64_t guid = spa_load_guid(spa); 6875 int try; 6876 6877 ASSERT3P(dev->l2ad_vdev, !=, NULL); 6878 6879 pio = NULL; 6880 write_sz = write_asize = write_psize = 0; 6881 full = B_FALSE; 6882 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6883 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 6884 6885 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6886 /* 6887 * Copy buffers for L2ARC writing. 6888 */ 6889 for (try = 0; try <= 3; try++) { 6890 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6891 uint64_t passed_sz = 0; 6892 6893 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6894 6895 /* 6896 * L2ARC fast warmup. 6897 * 6898 * Until the ARC is warm and starts to evict, read from the 6899 * head of the ARC lists rather than the tail. 6900 */ 6901 if (arc_warm == B_FALSE) 6902 hdr = multilist_sublist_head(mls); 6903 else 6904 hdr = multilist_sublist_tail(mls); 6905 if (hdr == NULL) 6906 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6907 6908 headroom = target_sz * l2arc_headroom; 6909 if (zfs_compressed_arc_enabled) 6910 headroom = (headroom * l2arc_headroom_boost) / 100; 6911 6912 for (; hdr; hdr = hdr_prev) { 6913 kmutex_t *hash_lock; 6914 6915 if (arc_warm == B_FALSE) 6916 hdr_prev = multilist_sublist_next(mls, hdr); 6917 else 6918 hdr_prev = multilist_sublist_prev(mls, hdr); 6919 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 6920 HDR_GET_LSIZE(hdr)); 6921 6922 hash_lock = HDR_LOCK(hdr); 6923 if (!mutex_tryenter(hash_lock)) { 6924 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 6925 /* 6926 * Skip this buffer rather than waiting. 6927 */ 6928 continue; 6929 } 6930 6931 passed_sz += HDR_GET_LSIZE(hdr); 6932 if (passed_sz > headroom) { 6933 /* 6934 * Searched too far. 6935 */ 6936 mutex_exit(hash_lock); 6937 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 6938 break; 6939 } 6940 6941 if (!l2arc_write_eligible(guid, hdr)) { 6942 mutex_exit(hash_lock); 6943 continue; 6944 } 6945 6946 if ((write_asize + HDR_GET_LSIZE(hdr)) > target_sz) { 6947 full = B_TRUE; 6948 mutex_exit(hash_lock); 6949 ARCSTAT_BUMP(arcstat_l2_write_full); 6950 break; 6951 } 6952 6953 if (pio == NULL) { 6954 /* 6955 * Insert a dummy header on the buflist so 6956 * l2arc_write_done() can find where the 6957 * write buffers begin without searching. 6958 */ 6959 mutex_enter(&dev->l2ad_mtx); 6960 list_insert_head(&dev->l2ad_buflist, head); 6961 mutex_exit(&dev->l2ad_mtx); 6962 6963 cb = kmem_alloc( 6964 sizeof (l2arc_write_callback_t), KM_SLEEP); 6965 cb->l2wcb_dev = dev; 6966 cb->l2wcb_head = head; 6967 pio = zio_root(spa, l2arc_write_done, cb, 6968 ZIO_FLAG_CANFAIL); 6969 ARCSTAT_BUMP(arcstat_l2_write_pios); 6970 } 6971 6972 hdr->b_l2hdr.b_dev = dev; 6973 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 6974 arc_hdr_set_flags(hdr, 6975 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 6976 6977 mutex_enter(&dev->l2ad_mtx); 6978 list_insert_head(&dev->l2ad_buflist, hdr); 6979 mutex_exit(&dev->l2ad_mtx); 6980 6981 /* 6982 * We rely on the L1 portion of the header below, so 6983 * it's invalid for this header to have been evicted out 6984 * of the ghost cache, prior to being written out. The 6985 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 6986 */ 6987 ASSERT(HDR_HAS_L1HDR(hdr)); 6988 6989 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 6990 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 6991 ASSERT3U(arc_hdr_size(hdr), >, 0); 6992 uint64_t size = arc_hdr_size(hdr); 6993 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 6994 size); 6995 6996 (void) refcount_add_many(&dev->l2ad_alloc, size, hdr); 6997 6998 /* 6999 * Normally the L2ARC can use the hdr's data, but if 7000 * we're sharing data between the hdr and one of its 7001 * bufs, L2ARC needs its own copy of the data so that 7002 * the ZIO below can't race with the buf consumer. To 7003 * ensure that this copy will be available for the 7004 * lifetime of the ZIO and be cleaned up afterwards, we 7005 * add it to the l2arc_free_on_write queue. 7006 */ 7007 void *to_write; 7008 if (!HDR_SHARED_DATA(hdr) && size == asize) { 7009 to_write = hdr->b_l1hdr.b_pdata; 7010 } else { 7011 arc_buf_contents_t type = arc_buf_type(hdr); 7012 if (type == ARC_BUFC_METADATA) { 7013 to_write = zio_buf_alloc(asize); 7014 } else { 7015 ASSERT3U(type, ==, ARC_BUFC_DATA); 7016 to_write = zio_data_buf_alloc(asize); 7017 } 7018 7019 bcopy(hdr->b_l1hdr.b_pdata, to_write, size); 7020 if (asize != size) 7021 bzero(to_write + size, asize - size); 7022 l2arc_free_data_on_write(to_write, asize, type); 7023 } 7024 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7025 hdr->b_l2hdr.b_daddr, asize, to_write, 7026 ZIO_CHECKSUM_OFF, NULL, hdr, 7027 ZIO_PRIORITY_ASYNC_WRITE, 7028 ZIO_FLAG_CANFAIL, B_FALSE); 7029 7030 write_sz += HDR_GET_LSIZE(hdr); 7031 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7032 zio_t *, wzio); 7033 7034 write_asize += size; 7035 write_psize += asize; 7036 dev->l2ad_hand += asize; 7037 7038 mutex_exit(hash_lock); 7039 7040 (void) zio_nowait(wzio); 7041 } 7042 7043 multilist_sublist_unlock(mls); 7044 7045 if (full == B_TRUE) 7046 break; 7047 } 7048 7049 /* No buffers selected for writing? */ 7050 if (pio == NULL) { 7051 ASSERT0(write_sz); 7052 ASSERT(!HDR_HAS_L1HDR(head)); 7053 kmem_cache_free(hdr_l2only_cache, head); 7054 return (0); 7055 } 7056 7057 ASSERT3U(write_asize, <=, target_sz); 7058 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7059 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 7060 ARCSTAT_INCR(arcstat_l2_size, write_sz); 7061 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 7062 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 7063 7064 /* 7065 * Bump device hand to the device start if it is approaching the end. 7066 * l2arc_evict() will already have evicted ahead for this case. 7067 */ 7068 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7069 dev->l2ad_hand = dev->l2ad_start; 7070 dev->l2ad_first = B_FALSE; 7071 } 7072 7073 dev->l2ad_writing = B_TRUE; 7074 (void) zio_wait(pio); 7075 dev->l2ad_writing = B_FALSE; 7076 7077 return (write_asize); 7078} 7079 7080/* 7081 * This thread feeds the L2ARC at regular intervals. This is the beating 7082 * heart of the L2ARC. 7083 */ 7084static void 7085l2arc_feed_thread(void *dummy __unused) 7086{ 7087 callb_cpr_t cpr; 7088 l2arc_dev_t *dev; 7089 spa_t *spa; 7090 uint64_t size, wrote; 7091 clock_t begin, next = ddi_get_lbolt(); 7092 7093 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7094 7095 mutex_enter(&l2arc_feed_thr_lock); 7096 7097 while (l2arc_thread_exit == 0) { 7098 CALLB_CPR_SAFE_BEGIN(&cpr); 7099 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7100 next - ddi_get_lbolt()); 7101 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7102 next = ddi_get_lbolt() + hz; 7103 7104 /* 7105 * Quick check for L2ARC devices. 7106 */ 7107 mutex_enter(&l2arc_dev_mtx); 7108 if (l2arc_ndev == 0) { 7109 mutex_exit(&l2arc_dev_mtx); 7110 continue; 7111 } 7112 mutex_exit(&l2arc_dev_mtx); 7113 begin = ddi_get_lbolt(); 7114 7115 /* 7116 * This selects the next l2arc device to write to, and in 7117 * doing so the next spa to feed from: dev->l2ad_spa. This 7118 * will return NULL if there are now no l2arc devices or if 7119 * they are all faulted. 7120 * 7121 * If a device is returned, its spa's config lock is also 7122 * held to prevent device removal. l2arc_dev_get_next() 7123 * will grab and release l2arc_dev_mtx. 7124 */ 7125 if ((dev = l2arc_dev_get_next()) == NULL) 7126 continue; 7127 7128 spa = dev->l2ad_spa; 7129 ASSERT3P(spa, !=, NULL); 7130 7131 /* 7132 * If the pool is read-only then force the feed thread to 7133 * sleep a little longer. 7134 */ 7135 if (!spa_writeable(spa)) { 7136 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7137 spa_config_exit(spa, SCL_L2ARC, dev); 7138 continue; 7139 } 7140 7141 /* 7142 * Avoid contributing to memory pressure. 7143 */ 7144 if (arc_reclaim_needed()) { 7145 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7146 spa_config_exit(spa, SCL_L2ARC, dev); 7147 continue; 7148 } 7149 7150 ARCSTAT_BUMP(arcstat_l2_feeds); 7151 7152 size = l2arc_write_size(); 7153 7154 /* 7155 * Evict L2ARC buffers that will be overwritten. 7156 */ 7157 l2arc_evict(dev, size, B_FALSE); 7158 7159 /* 7160 * Write ARC buffers. 7161 */ 7162 wrote = l2arc_write_buffers(spa, dev, size); 7163 7164 /* 7165 * Calculate interval between writes. 7166 */ 7167 next = l2arc_write_interval(begin, size, wrote); 7168 spa_config_exit(spa, SCL_L2ARC, dev); 7169 } 7170 7171 l2arc_thread_exit = 0; 7172 cv_broadcast(&l2arc_feed_thr_cv); 7173 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7174 thread_exit(); 7175} 7176 7177boolean_t 7178l2arc_vdev_present(vdev_t *vd) 7179{ 7180 l2arc_dev_t *dev; 7181 7182 mutex_enter(&l2arc_dev_mtx); 7183 for (dev = list_head(l2arc_dev_list); dev != NULL; 7184 dev = list_next(l2arc_dev_list, dev)) { 7185 if (dev->l2ad_vdev == vd) 7186 break; 7187 } 7188 mutex_exit(&l2arc_dev_mtx); 7189 7190 return (dev != NULL); 7191} 7192 7193/* 7194 * Add a vdev for use by the L2ARC. By this point the spa has already 7195 * validated the vdev and opened it. 7196 */ 7197void 7198l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7199{ 7200 l2arc_dev_t *adddev; 7201 7202 ASSERT(!l2arc_vdev_present(vd)); 7203 7204 vdev_ashift_optimize(vd); 7205 7206 /* 7207 * Create a new l2arc device entry. 7208 */ 7209 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7210 adddev->l2ad_spa = spa; 7211 adddev->l2ad_vdev = vd; 7212 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7213 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7214 adddev->l2ad_hand = adddev->l2ad_start; 7215 adddev->l2ad_first = B_TRUE; 7216 adddev->l2ad_writing = B_FALSE; 7217 7218 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7219 /* 7220 * This is a list of all ARC buffers that are still valid on the 7221 * device. 7222 */ 7223 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7224 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7225 7226 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7227 refcount_create(&adddev->l2ad_alloc); 7228 7229 /* 7230 * Add device to global list 7231 */ 7232 mutex_enter(&l2arc_dev_mtx); 7233 list_insert_head(l2arc_dev_list, adddev); 7234 atomic_inc_64(&l2arc_ndev); 7235 mutex_exit(&l2arc_dev_mtx); 7236} 7237 7238/* 7239 * Remove a vdev from the L2ARC. 7240 */ 7241void 7242l2arc_remove_vdev(vdev_t *vd) 7243{ 7244 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7245 7246 /* 7247 * Find the device by vdev 7248 */ 7249 mutex_enter(&l2arc_dev_mtx); 7250 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7251 nextdev = list_next(l2arc_dev_list, dev); 7252 if (vd == dev->l2ad_vdev) { 7253 remdev = dev; 7254 break; 7255 } 7256 } 7257 ASSERT3P(remdev, !=, NULL); 7258 7259 /* 7260 * Remove device from global list 7261 */ 7262 list_remove(l2arc_dev_list, remdev); 7263 l2arc_dev_last = NULL; /* may have been invalidated */ 7264 atomic_dec_64(&l2arc_ndev); 7265 mutex_exit(&l2arc_dev_mtx); 7266 7267 /* 7268 * Clear all buflists and ARC references. L2ARC device flush. 7269 */ 7270 l2arc_evict(remdev, 0, B_TRUE); 7271 list_destroy(&remdev->l2ad_buflist); 7272 mutex_destroy(&remdev->l2ad_mtx); 7273 refcount_destroy(&remdev->l2ad_alloc); 7274 kmem_free(remdev, sizeof (l2arc_dev_t)); 7275} 7276 7277void 7278l2arc_init(void) 7279{ 7280 l2arc_thread_exit = 0; 7281 l2arc_ndev = 0; 7282 l2arc_writes_sent = 0; 7283 l2arc_writes_done = 0; 7284 7285 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7286 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7287 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7288 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7289 7290 l2arc_dev_list = &L2ARC_dev_list; 7291 l2arc_free_on_write = &L2ARC_free_on_write; 7292 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7293 offsetof(l2arc_dev_t, l2ad_node)); 7294 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7295 offsetof(l2arc_data_free_t, l2df_list_node)); 7296} 7297 7298void 7299l2arc_fini(void) 7300{ 7301 /* 7302 * This is called from dmu_fini(), which is called from spa_fini(); 7303 * Because of this, we can assume that all l2arc devices have 7304 * already been removed when the pools themselves were removed. 7305 */ 7306 7307 l2arc_do_free_on_write(); 7308 7309 mutex_destroy(&l2arc_feed_thr_lock); 7310 cv_destroy(&l2arc_feed_thr_cv); 7311 mutex_destroy(&l2arc_dev_mtx); 7312 mutex_destroy(&l2arc_free_on_write_mtx); 7313 7314 list_destroy(l2arc_dev_list); 7315 list_destroy(l2arc_free_on_write); 7316} 7317 7318void 7319l2arc_start(void) 7320{ 7321 if (!(spa_mode_global & FWRITE)) 7322 return; 7323 7324 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7325 TS_RUN, minclsyspri); 7326} 7327 7328void 7329l2arc_stop(void) 7330{ 7331 if (!(spa_mode_global & FWRITE)) 7332 return; 7333 7334 mutex_enter(&l2arc_feed_thr_lock); 7335 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7336 l2arc_thread_exit = 1; 7337 while (l2arc_thread_exit != 0) 7338 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7339 mutex_exit(&l2arc_feed_thr_lock); 7340} 7341