arc.c revision 307297
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#include <sys/racct.h> 261#endif 262#include <sys/callb.h> 263#include <sys/kstat.h> 264#include <sys/trim_map.h> 265#include <zfs_fletcher.h> 266#include <sys/sdt.h> 267 268#include <machine/vmparam.h> 269 270#ifdef illumos 271#ifndef _KERNEL 272/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 273boolean_t arc_watch = B_FALSE; 274int arc_procfd; 275#endif 276#endif /* illumos */ 277 278static kmutex_t arc_reclaim_lock; 279static kcondvar_t arc_reclaim_thread_cv; 280static boolean_t arc_reclaim_thread_exit; 281static kcondvar_t arc_reclaim_waiters_cv; 282 283static kmutex_t arc_dnlc_evicts_lock; 284static kcondvar_t arc_dnlc_evicts_cv; 285static boolean_t arc_dnlc_evicts_thread_exit; 286 287uint_t arc_reduce_dnlc_percent = 3; 288 289/* 290 * The number of headers to evict in arc_evict_state_impl() before 291 * dropping the sublist lock and evicting from another sublist. A lower 292 * value means we're more likely to evict the "correct" header (i.e. the 293 * oldest header in the arc state), but comes with higher overhead 294 * (i.e. more invocations of arc_evict_state_impl()). 295 */ 296int zfs_arc_evict_batch_limit = 10; 297 298/* 299 * The number of sublists used for each of the arc state lists. If this 300 * is not set to a suitable value by the user, it will be configured to 301 * the number of CPUs on the system in arc_init(). 302 */ 303int zfs_arc_num_sublists_per_state = 0; 304 305/* number of seconds before growing cache again */ 306static int arc_grow_retry = 60; 307 308/* shift of arc_c for calculating overflow limit in arc_get_data_buf */ 309int zfs_arc_overflow_shift = 8; 310 311/* shift of arc_c for calculating both min and max arc_p */ 312static int arc_p_min_shift = 4; 313 314/* log2(fraction of arc to reclaim) */ 315static int arc_shrink_shift = 7; 316 317/* 318 * log2(fraction of ARC which must be free to allow growing). 319 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 320 * when reading a new block into the ARC, we will evict an equal-sized block 321 * from the ARC. 322 * 323 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 324 * we will still not allow it to grow. 325 */ 326int arc_no_grow_shift = 5; 327 328 329/* 330 * minimum lifespan of a prefetch block in clock ticks 331 * (initialized in arc_init()) 332 */ 333static int arc_min_prefetch_lifespan; 334 335/* 336 * If this percent of memory is free, don't throttle. 337 */ 338int arc_lotsfree_percent = 10; 339 340static int arc_dead; 341extern boolean_t zfs_prefetch_disable; 342 343/* 344 * The arc has filled available memory and has now warmed up. 345 */ 346static boolean_t arc_warm; 347 348/* 349 * These tunables are for performance analysis. 350 */ 351uint64_t zfs_arc_max; 352uint64_t zfs_arc_min; 353uint64_t zfs_arc_meta_limit = 0; 354uint64_t zfs_arc_meta_min = 0; 355int zfs_arc_grow_retry = 0; 356int zfs_arc_shrink_shift = 0; 357int zfs_arc_p_min_shift = 0; 358uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 359u_int zfs_arc_free_target = 0; 360 361/* Absolute min for arc min / max is 16MB. */ 362static uint64_t arc_abs_min = 16 << 20; 363 364boolean_t zfs_compressed_arc_enabled = B_TRUE; 365 366static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 367static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 368static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 369static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 370 371#if defined(__FreeBSD__) && defined(_KERNEL) 372static void 373arc_free_target_init(void *unused __unused) 374{ 375 376 zfs_arc_free_target = vm_pageout_wakeup_thresh; 377} 378SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 379 arc_free_target_init, NULL); 380 381TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 382TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 383TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 384SYSCTL_DECL(_vfs_zfs); 385SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 386 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 387SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 388 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 389SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 390 &zfs_arc_average_blocksize, 0, 391 "ARC average blocksize"); 392SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 393 &arc_shrink_shift, 0, 394 "log2(fraction of arc to reclaim)"); 395SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 396 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC"); 397 398/* 399 * We don't have a tunable for arc_free_target due to the dependency on 400 * pagedaemon initialisation. 401 */ 402SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 403 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 404 sysctl_vfs_zfs_arc_free_target, "IU", 405 "Desired number of free pages below which ARC triggers reclaim"); 406 407static int 408sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 409{ 410 u_int val; 411 int err; 412 413 val = zfs_arc_free_target; 414 err = sysctl_handle_int(oidp, &val, 0, req); 415 if (err != 0 || req->newptr == NULL) 416 return (err); 417 418 if (val < minfree) 419 return (EINVAL); 420 if (val > vm_cnt.v_page_count) 421 return (EINVAL); 422 423 zfs_arc_free_target = val; 424 425 return (0); 426} 427 428/* 429 * Must be declared here, before the definition of corresponding kstat 430 * macro which uses the same names will confuse the compiler. 431 */ 432SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 433 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 434 sysctl_vfs_zfs_arc_meta_limit, "QU", 435 "ARC metadata limit"); 436#endif 437 438/* 439 * Note that buffers can be in one of 6 states: 440 * ARC_anon - anonymous (discussed below) 441 * ARC_mru - recently used, currently cached 442 * ARC_mru_ghost - recentely used, no longer in cache 443 * ARC_mfu - frequently used, currently cached 444 * ARC_mfu_ghost - frequently used, no longer in cache 445 * ARC_l2c_only - exists in L2ARC but not other states 446 * When there are no active references to the buffer, they are 447 * are linked onto a list in one of these arc states. These are 448 * the only buffers that can be evicted or deleted. Within each 449 * state there are multiple lists, one for meta-data and one for 450 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 451 * etc.) is tracked separately so that it can be managed more 452 * explicitly: favored over data, limited explicitly. 453 * 454 * Anonymous buffers are buffers that are not associated with 455 * a DVA. These are buffers that hold dirty block copies 456 * before they are written to stable storage. By definition, 457 * they are "ref'd" and are considered part of arc_mru 458 * that cannot be freed. Generally, they will aquire a DVA 459 * as they are written and migrate onto the arc_mru list. 460 * 461 * The ARC_l2c_only state is for buffers that are in the second 462 * level ARC but no longer in any of the ARC_m* lists. The second 463 * level ARC itself may also contain buffers that are in any of 464 * the ARC_m* states - meaning that a buffer can exist in two 465 * places. The reason for the ARC_l2c_only state is to keep the 466 * buffer header in the hash table, so that reads that hit the 467 * second level ARC benefit from these fast lookups. 468 */ 469 470typedef struct arc_state { 471 /* 472 * list of evictable buffers 473 */ 474 multilist_t arcs_list[ARC_BUFC_NUMTYPES]; 475 /* 476 * total amount of evictable data in this state 477 */ 478 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 479 /* 480 * total amount of data in this state; this includes: evictable, 481 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 482 */ 483 refcount_t arcs_size; 484} arc_state_t; 485 486/* The 6 states: */ 487static arc_state_t ARC_anon; 488static arc_state_t ARC_mru; 489static arc_state_t ARC_mru_ghost; 490static arc_state_t ARC_mfu; 491static arc_state_t ARC_mfu_ghost; 492static arc_state_t ARC_l2c_only; 493 494typedef struct arc_stats { 495 kstat_named_t arcstat_hits; 496 kstat_named_t arcstat_misses; 497 kstat_named_t arcstat_demand_data_hits; 498 kstat_named_t arcstat_demand_data_misses; 499 kstat_named_t arcstat_demand_metadata_hits; 500 kstat_named_t arcstat_demand_metadata_misses; 501 kstat_named_t arcstat_prefetch_data_hits; 502 kstat_named_t arcstat_prefetch_data_misses; 503 kstat_named_t arcstat_prefetch_metadata_hits; 504 kstat_named_t arcstat_prefetch_metadata_misses; 505 kstat_named_t arcstat_mru_hits; 506 kstat_named_t arcstat_mru_ghost_hits; 507 kstat_named_t arcstat_mfu_hits; 508 kstat_named_t arcstat_mfu_ghost_hits; 509 kstat_named_t arcstat_allocated; 510 kstat_named_t arcstat_deleted; 511 /* 512 * Number of buffers that could not be evicted because the hash lock 513 * was held by another thread. The lock may not necessarily be held 514 * by something using the same buffer, since hash locks are shared 515 * by multiple buffers. 516 */ 517 kstat_named_t arcstat_mutex_miss; 518 /* 519 * Number of buffers skipped because they have I/O in progress, are 520 * indrect prefetch buffers that have not lived long enough, or are 521 * not from the spa we're trying to evict from. 522 */ 523 kstat_named_t arcstat_evict_skip; 524 /* 525 * Number of times arc_evict_state() was unable to evict enough 526 * buffers to reach it's target amount. 527 */ 528 kstat_named_t arcstat_evict_not_enough; 529 kstat_named_t arcstat_evict_l2_cached; 530 kstat_named_t arcstat_evict_l2_eligible; 531 kstat_named_t arcstat_evict_l2_ineligible; 532 kstat_named_t arcstat_evict_l2_skip; 533 kstat_named_t arcstat_hash_elements; 534 kstat_named_t arcstat_hash_elements_max; 535 kstat_named_t arcstat_hash_collisions; 536 kstat_named_t arcstat_hash_chains; 537 kstat_named_t arcstat_hash_chain_max; 538 kstat_named_t arcstat_p; 539 kstat_named_t arcstat_c; 540 kstat_named_t arcstat_c_min; 541 kstat_named_t arcstat_c_max; 542 kstat_named_t arcstat_size; 543 /* 544 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pdata. 545 * Note that the compressed bytes may match the uncompressed bytes 546 * if the block is either not compressed or compressed arc is disabled. 547 */ 548 kstat_named_t arcstat_compressed_size; 549 /* 550 * Uncompressed size of the data stored in b_pdata. If compressed 551 * arc is disabled then this value will be identical to the stat 552 * above. 553 */ 554 kstat_named_t arcstat_uncompressed_size; 555 /* 556 * Number of bytes stored in all the arc_buf_t's. This is classified 557 * as "overhead" since this data is typically short-lived and will 558 * be evicted from the arc when it becomes unreferenced unless the 559 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 560 * values have been set (see comment in dbuf.c for more information). 561 */ 562 kstat_named_t arcstat_overhead_size; 563 /* 564 * Number of bytes consumed by internal ARC structures necessary 565 * for tracking purposes; these structures are not actually 566 * backed by ARC buffers. This includes arc_buf_hdr_t structures 567 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 568 * caches), and arc_buf_t structures (allocated via arc_buf_t 569 * cache). 570 */ 571 kstat_named_t arcstat_hdr_size; 572 /* 573 * Number of bytes consumed by ARC buffers of type equal to 574 * ARC_BUFC_DATA. This is generally consumed by buffers backing 575 * on disk user data (e.g. plain file contents). 576 */ 577 kstat_named_t arcstat_data_size; 578 /* 579 * Number of bytes consumed by ARC buffers of type equal to 580 * ARC_BUFC_METADATA. This is generally consumed by buffers 581 * backing on disk data that is used for internal ZFS 582 * structures (e.g. ZAP, dnode, indirect blocks, etc). 583 */ 584 kstat_named_t arcstat_metadata_size; 585 /* 586 * Number of bytes consumed by various buffers and structures 587 * not actually backed with ARC buffers. This includes bonus 588 * buffers (allocated directly via zio_buf_* functions), 589 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 590 * cache), and dnode_t structures (allocated via dnode_t cache). 591 */ 592 kstat_named_t arcstat_other_size; 593 /* 594 * Total number of bytes consumed by ARC buffers residing in the 595 * arc_anon state. This includes *all* buffers in the arc_anon 596 * state; e.g. data, metadata, evictable, and unevictable buffers 597 * are all included in this value. 598 */ 599 kstat_named_t arcstat_anon_size; 600 /* 601 * Number of bytes consumed by ARC buffers that meet the 602 * following criteria: backing buffers of type ARC_BUFC_DATA, 603 * residing in the arc_anon state, and are eligible for eviction 604 * (e.g. have no outstanding holds on the buffer). 605 */ 606 kstat_named_t arcstat_anon_evictable_data; 607 /* 608 * Number of bytes consumed by ARC buffers that meet the 609 * following criteria: backing buffers of type ARC_BUFC_METADATA, 610 * residing in the arc_anon state, and are eligible for eviction 611 * (e.g. have no outstanding holds on the buffer). 612 */ 613 kstat_named_t arcstat_anon_evictable_metadata; 614 /* 615 * Total number of bytes consumed by ARC buffers residing in the 616 * arc_mru state. This includes *all* buffers in the arc_mru 617 * state; e.g. data, metadata, evictable, and unevictable buffers 618 * are all included in this value. 619 */ 620 kstat_named_t arcstat_mru_size; 621 /* 622 * Number of bytes consumed by ARC buffers that meet the 623 * following criteria: backing buffers of type ARC_BUFC_DATA, 624 * residing in the arc_mru state, and are eligible for eviction 625 * (e.g. have no outstanding holds on the buffer). 626 */ 627 kstat_named_t arcstat_mru_evictable_data; 628 /* 629 * Number of bytes consumed by ARC buffers that meet the 630 * following criteria: backing buffers of type ARC_BUFC_METADATA, 631 * residing in the arc_mru state, and are eligible for eviction 632 * (e.g. have no outstanding holds on the buffer). 633 */ 634 kstat_named_t arcstat_mru_evictable_metadata; 635 /* 636 * Total number of bytes that *would have been* consumed by ARC 637 * buffers in the arc_mru_ghost state. The key thing to note 638 * here, is the fact that this size doesn't actually indicate 639 * RAM consumption. The ghost lists only consist of headers and 640 * don't actually have ARC buffers linked off of these headers. 641 * Thus, *if* the headers had associated ARC buffers, these 642 * buffers *would have* consumed this number of bytes. 643 */ 644 kstat_named_t arcstat_mru_ghost_size; 645 /* 646 * Number of bytes that *would have been* consumed by ARC 647 * buffers that are eligible for eviction, of type 648 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 649 */ 650 kstat_named_t arcstat_mru_ghost_evictable_data; 651 /* 652 * Number of bytes that *would have been* consumed by ARC 653 * buffers that are eligible for eviction, of type 654 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 655 */ 656 kstat_named_t arcstat_mru_ghost_evictable_metadata; 657 /* 658 * Total number of bytes consumed by ARC buffers residing in the 659 * arc_mfu state. This includes *all* buffers in the arc_mfu 660 * state; e.g. data, metadata, evictable, and unevictable buffers 661 * are all included in this value. 662 */ 663 kstat_named_t arcstat_mfu_size; 664 /* 665 * Number of bytes consumed by ARC buffers that are eligible for 666 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 667 * state. 668 */ 669 kstat_named_t arcstat_mfu_evictable_data; 670 /* 671 * Number of bytes consumed by ARC buffers that are eligible for 672 * eviction, of type ARC_BUFC_METADATA, and reside in the 673 * arc_mfu state. 674 */ 675 kstat_named_t arcstat_mfu_evictable_metadata; 676 /* 677 * Total number of bytes that *would have been* consumed by ARC 678 * buffers in the arc_mfu_ghost state. See the comment above 679 * arcstat_mru_ghost_size for more details. 680 */ 681 kstat_named_t arcstat_mfu_ghost_size; 682 /* 683 * Number of bytes that *would have been* consumed by ARC 684 * buffers that are eligible for eviction, of type 685 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 686 */ 687 kstat_named_t arcstat_mfu_ghost_evictable_data; 688 /* 689 * Number of bytes that *would have been* consumed by ARC 690 * buffers that are eligible for eviction, of type 691 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 692 */ 693 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 694 kstat_named_t arcstat_l2_hits; 695 kstat_named_t arcstat_l2_misses; 696 kstat_named_t arcstat_l2_feeds; 697 kstat_named_t arcstat_l2_rw_clash; 698 kstat_named_t arcstat_l2_read_bytes; 699 kstat_named_t arcstat_l2_write_bytes; 700 kstat_named_t arcstat_l2_writes_sent; 701 kstat_named_t arcstat_l2_writes_done; 702 kstat_named_t arcstat_l2_writes_error; 703 kstat_named_t arcstat_l2_writes_lock_retry; 704 kstat_named_t arcstat_l2_evict_lock_retry; 705 kstat_named_t arcstat_l2_evict_reading; 706 kstat_named_t arcstat_l2_evict_l1cached; 707 kstat_named_t arcstat_l2_free_on_write; 708 kstat_named_t arcstat_l2_abort_lowmem; 709 kstat_named_t arcstat_l2_cksum_bad; 710 kstat_named_t arcstat_l2_io_error; 711 kstat_named_t arcstat_l2_size; 712 kstat_named_t arcstat_l2_asize; 713 kstat_named_t arcstat_l2_hdr_size; 714 kstat_named_t arcstat_l2_padding_needed; 715 kstat_named_t arcstat_l2_write_trylock_fail; 716 kstat_named_t arcstat_l2_write_passed_headroom; 717 kstat_named_t arcstat_l2_write_spa_mismatch; 718 kstat_named_t arcstat_l2_write_in_l2; 719 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 720 kstat_named_t arcstat_l2_write_not_cacheable; 721 kstat_named_t arcstat_l2_write_full; 722 kstat_named_t arcstat_l2_write_buffer_iter; 723 kstat_named_t arcstat_l2_write_pios; 724 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 725 kstat_named_t arcstat_l2_write_buffer_list_iter; 726 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 727 kstat_named_t arcstat_memory_throttle_count; 728 kstat_named_t arcstat_meta_used; 729 kstat_named_t arcstat_meta_limit; 730 kstat_named_t arcstat_meta_max; 731 kstat_named_t arcstat_meta_min; 732 kstat_named_t arcstat_sync_wait_for_async; 733 kstat_named_t arcstat_demand_hit_predictive_prefetch; 734} arc_stats_t; 735 736static arc_stats_t arc_stats = { 737 { "hits", KSTAT_DATA_UINT64 }, 738 { "misses", KSTAT_DATA_UINT64 }, 739 { "demand_data_hits", KSTAT_DATA_UINT64 }, 740 { "demand_data_misses", KSTAT_DATA_UINT64 }, 741 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 742 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 743 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 744 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 745 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 746 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 747 { "mru_hits", KSTAT_DATA_UINT64 }, 748 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 749 { "mfu_hits", KSTAT_DATA_UINT64 }, 750 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 751 { "allocated", KSTAT_DATA_UINT64 }, 752 { "deleted", KSTAT_DATA_UINT64 }, 753 { "mutex_miss", KSTAT_DATA_UINT64 }, 754 { "evict_skip", KSTAT_DATA_UINT64 }, 755 { "evict_not_enough", KSTAT_DATA_UINT64 }, 756 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 757 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 758 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 759 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 760 { "hash_elements", KSTAT_DATA_UINT64 }, 761 { "hash_elements_max", KSTAT_DATA_UINT64 }, 762 { "hash_collisions", KSTAT_DATA_UINT64 }, 763 { "hash_chains", KSTAT_DATA_UINT64 }, 764 { "hash_chain_max", KSTAT_DATA_UINT64 }, 765 { "p", KSTAT_DATA_UINT64 }, 766 { "c", KSTAT_DATA_UINT64 }, 767 { "c_min", KSTAT_DATA_UINT64 }, 768 { "c_max", KSTAT_DATA_UINT64 }, 769 { "size", KSTAT_DATA_UINT64 }, 770 { "compressed_size", KSTAT_DATA_UINT64 }, 771 { "uncompressed_size", KSTAT_DATA_UINT64 }, 772 { "overhead_size", KSTAT_DATA_UINT64 }, 773 { "hdr_size", KSTAT_DATA_UINT64 }, 774 { "data_size", KSTAT_DATA_UINT64 }, 775 { "metadata_size", KSTAT_DATA_UINT64 }, 776 { "other_size", KSTAT_DATA_UINT64 }, 777 { "anon_size", KSTAT_DATA_UINT64 }, 778 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 779 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 780 { "mru_size", KSTAT_DATA_UINT64 }, 781 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 782 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 783 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 784 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 785 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 786 { "mfu_size", KSTAT_DATA_UINT64 }, 787 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 788 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 789 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 790 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 791 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 792 { "l2_hits", KSTAT_DATA_UINT64 }, 793 { "l2_misses", KSTAT_DATA_UINT64 }, 794 { "l2_feeds", KSTAT_DATA_UINT64 }, 795 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 796 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 797 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 798 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 799 { "l2_writes_done", KSTAT_DATA_UINT64 }, 800 { "l2_writes_error", KSTAT_DATA_UINT64 }, 801 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 802 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 803 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 804 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 805 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 806 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 807 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 808 { "l2_io_error", KSTAT_DATA_UINT64 }, 809 { "l2_size", KSTAT_DATA_UINT64 }, 810 { "l2_asize", KSTAT_DATA_UINT64 }, 811 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 812 { "l2_padding_needed", KSTAT_DATA_UINT64 }, 813 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 814 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 815 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 816 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 817 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 818 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 819 { "l2_write_full", KSTAT_DATA_UINT64 }, 820 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 821 { "l2_write_pios", KSTAT_DATA_UINT64 }, 822 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 823 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 824 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 825 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 826 { "arc_meta_used", KSTAT_DATA_UINT64 }, 827 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 828 { "arc_meta_max", KSTAT_DATA_UINT64 }, 829 { "arc_meta_min", KSTAT_DATA_UINT64 }, 830 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 831 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 832}; 833 834#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 835 836#define ARCSTAT_INCR(stat, val) \ 837 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 838 839#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 840#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 841 842#define ARCSTAT_MAX(stat, val) { \ 843 uint64_t m; \ 844 while ((val) > (m = arc_stats.stat.value.ui64) && \ 845 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 846 continue; \ 847} 848 849#define ARCSTAT_MAXSTAT(stat) \ 850 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 851 852/* 853 * We define a macro to allow ARC hits/misses to be easily broken down by 854 * two separate conditions, giving a total of four different subtypes for 855 * each of hits and misses (so eight statistics total). 856 */ 857#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 858 if (cond1) { \ 859 if (cond2) { \ 860 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 861 } else { \ 862 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 863 } \ 864 } else { \ 865 if (cond2) { \ 866 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 867 } else { \ 868 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 869 } \ 870 } 871 872kstat_t *arc_ksp; 873static arc_state_t *arc_anon; 874static arc_state_t *arc_mru; 875static arc_state_t *arc_mru_ghost; 876static arc_state_t *arc_mfu; 877static arc_state_t *arc_mfu_ghost; 878static arc_state_t *arc_l2c_only; 879 880/* 881 * There are several ARC variables that are critical to export as kstats -- 882 * but we don't want to have to grovel around in the kstat whenever we wish to 883 * manipulate them. For these variables, we therefore define them to be in 884 * terms of the statistic variable. This assures that we are not introducing 885 * the possibility of inconsistency by having shadow copies of the variables, 886 * while still allowing the code to be readable. 887 */ 888#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 889#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 890#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 891#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 892#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 893#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 894#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 895#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 896#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 897 898/* compressed size of entire arc */ 899#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 900/* uncompressed size of entire arc */ 901#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 902/* number of bytes in the arc from arc_buf_t's */ 903#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 904 905static int arc_no_grow; /* Don't try to grow cache size */ 906static uint64_t arc_tempreserve; 907static uint64_t arc_loaned_bytes; 908 909typedef struct arc_callback arc_callback_t; 910 911struct arc_callback { 912 void *acb_private; 913 arc_done_func_t *acb_done; 914 arc_buf_t *acb_buf; 915 zio_t *acb_zio_dummy; 916 arc_callback_t *acb_next; 917}; 918 919typedef struct arc_write_callback arc_write_callback_t; 920 921struct arc_write_callback { 922 void *awcb_private; 923 arc_done_func_t *awcb_ready; 924 arc_done_func_t *awcb_children_ready; 925 arc_done_func_t *awcb_physdone; 926 arc_done_func_t *awcb_done; 927 arc_buf_t *awcb_buf; 928}; 929 930/* 931 * ARC buffers are separated into multiple structs as a memory saving measure: 932 * - Common fields struct, always defined, and embedded within it: 933 * - L2-only fields, always allocated but undefined when not in L2ARC 934 * - L1-only fields, only allocated when in L1ARC 935 * 936 * Buffer in L1 Buffer only in L2 937 * +------------------------+ +------------------------+ 938 * | arc_buf_hdr_t | | arc_buf_hdr_t | 939 * | | | | 940 * | | | | 941 * | | | | 942 * +------------------------+ +------------------------+ 943 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 944 * | (undefined if L1-only) | | | 945 * +------------------------+ +------------------------+ 946 * | l1arc_buf_hdr_t | 947 * | | 948 * | | 949 * | | 950 * | | 951 * +------------------------+ 952 * 953 * Because it's possible for the L2ARC to become extremely large, we can wind 954 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 955 * is minimized by only allocating the fields necessary for an L1-cached buffer 956 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 957 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 958 * words in pointers. arc_hdr_realloc() is used to switch a header between 959 * these two allocation states. 960 */ 961typedef struct l1arc_buf_hdr { 962 kmutex_t b_freeze_lock; 963 zio_cksum_t *b_freeze_cksum; 964#ifdef ZFS_DEBUG 965 /* 966 * used for debugging wtih kmem_flags - by allocating and freeing 967 * b_thawed when the buffer is thawed, we get a record of the stack 968 * trace that thawed it. 969 */ 970 void *b_thawed; 971#endif 972 973 arc_buf_t *b_buf; 974 uint32_t b_bufcnt; 975 /* for waiting on writes to complete */ 976 kcondvar_t b_cv; 977 uint8_t b_byteswap; 978 979 /* protected by arc state mutex */ 980 arc_state_t *b_state; 981 multilist_node_t b_arc_node; 982 983 /* updated atomically */ 984 clock_t b_arc_access; 985 986 /* self protecting */ 987 refcount_t b_refcnt; 988 989 arc_callback_t *b_acb; 990 void *b_pdata; 991} l1arc_buf_hdr_t; 992 993typedef struct l2arc_dev l2arc_dev_t; 994 995typedef struct l2arc_buf_hdr { 996 /* protected by arc_buf_hdr mutex */ 997 l2arc_dev_t *b_dev; /* L2ARC device */ 998 uint64_t b_daddr; /* disk address, offset byte */ 999 1000 list_node_t b_l2node; 1001} l2arc_buf_hdr_t; 1002 1003struct arc_buf_hdr { 1004 /* protected by hash lock */ 1005 dva_t b_dva; 1006 uint64_t b_birth; 1007 1008 arc_buf_contents_t b_type; 1009 arc_buf_hdr_t *b_hash_next; 1010 arc_flags_t b_flags; 1011 1012 /* 1013 * This field stores the size of the data buffer after 1014 * compression, and is set in the arc's zio completion handlers. 1015 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1016 * 1017 * While the block pointers can store up to 32MB in their psize 1018 * field, we can only store up to 32MB minus 512B. This is due 1019 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1020 * a field of zeros represents 512B in the bp). We can't use a 1021 * bias of 1 since we need to reserve a psize of zero, here, to 1022 * represent holes and embedded blocks. 1023 * 1024 * This isn't a problem in practice, since the maximum size of a 1025 * buffer is limited to 16MB, so we never need to store 32MB in 1026 * this field. Even in the upstream illumos code base, the 1027 * maximum size of a buffer is limited to 16MB. 1028 */ 1029 uint16_t b_psize; 1030 1031 /* 1032 * This field stores the size of the data buffer before 1033 * compression, and cannot change once set. It is in units 1034 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1035 */ 1036 uint16_t b_lsize; /* immutable */ 1037 uint64_t b_spa; /* immutable */ 1038 1039 /* L2ARC fields. Undefined when not in L2ARC. */ 1040 l2arc_buf_hdr_t b_l2hdr; 1041 /* L1ARC fields. Undefined when in l2arc_only state */ 1042 l1arc_buf_hdr_t b_l1hdr; 1043}; 1044 1045#if defined(__FreeBSD__) && defined(_KERNEL) 1046static int 1047sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1048{ 1049 uint64_t val; 1050 int err; 1051 1052 val = arc_meta_limit; 1053 err = sysctl_handle_64(oidp, &val, 0, req); 1054 if (err != 0 || req->newptr == NULL) 1055 return (err); 1056 1057 if (val <= 0 || val > arc_c_max) 1058 return (EINVAL); 1059 1060 arc_meta_limit = val; 1061 return (0); 1062} 1063 1064static int 1065sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1066{ 1067 uint64_t val; 1068 int err; 1069 1070 val = zfs_arc_max; 1071 err = sysctl_handle_64(oidp, &val, 0, req); 1072 if (err != 0 || req->newptr == NULL) 1073 return (err); 1074 1075 if (zfs_arc_max == 0) { 1076 /* Loader tunable so blindly set */ 1077 zfs_arc_max = val; 1078 return (0); 1079 } 1080 1081 if (val < arc_abs_min || val > kmem_size()) 1082 return (EINVAL); 1083 if (val < arc_c_min) 1084 return (EINVAL); 1085 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1086 return (EINVAL); 1087 1088 arc_c_max = val; 1089 1090 arc_c = arc_c_max; 1091 arc_p = (arc_c >> 1); 1092 1093 if (zfs_arc_meta_limit == 0) { 1094 /* limit meta-data to 1/4 of the arc capacity */ 1095 arc_meta_limit = arc_c_max / 4; 1096 } 1097 1098 /* if kmem_flags are set, lets try to use less memory */ 1099 if (kmem_debugging()) 1100 arc_c = arc_c / 2; 1101 1102 zfs_arc_max = arc_c; 1103 1104 return (0); 1105} 1106 1107static int 1108sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1109{ 1110 uint64_t val; 1111 int err; 1112 1113 val = zfs_arc_min; 1114 err = sysctl_handle_64(oidp, &val, 0, req); 1115 if (err != 0 || req->newptr == NULL) 1116 return (err); 1117 1118 if (zfs_arc_min == 0) { 1119 /* Loader tunable so blindly set */ 1120 zfs_arc_min = val; 1121 return (0); 1122 } 1123 1124 if (val < arc_abs_min || val > arc_c_max) 1125 return (EINVAL); 1126 1127 arc_c_min = val; 1128 1129 if (zfs_arc_meta_min == 0) 1130 arc_meta_min = arc_c_min / 2; 1131 1132 if (arc_c < arc_c_min) 1133 arc_c = arc_c_min; 1134 1135 zfs_arc_min = arc_c_min; 1136 1137 return (0); 1138} 1139#endif 1140 1141#define GHOST_STATE(state) \ 1142 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1143 (state) == arc_l2c_only) 1144 1145#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1146#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1147#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1148#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1149#define HDR_COMPRESSION_ENABLED(hdr) \ 1150 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1151 1152#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1153#define HDR_L2_READING(hdr) \ 1154 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1155 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1156#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1157#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1158#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1159#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1160 1161#define HDR_ISTYPE_METADATA(hdr) \ 1162 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1163#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1164 1165#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1166#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1167 1168/* For storing compression mode in b_flags */ 1169#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1170 1171#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1172 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1173#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1174 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1175 1176#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1177 1178/* 1179 * Other sizes 1180 */ 1181 1182#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1183#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1184 1185/* 1186 * Hash table routines 1187 */ 1188 1189#define HT_LOCK_PAD CACHE_LINE_SIZE 1190 1191struct ht_lock { 1192 kmutex_t ht_lock; 1193#ifdef _KERNEL 1194 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1195#endif 1196}; 1197 1198#define BUF_LOCKS 256 1199typedef struct buf_hash_table { 1200 uint64_t ht_mask; 1201 arc_buf_hdr_t **ht_table; 1202 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1203} buf_hash_table_t; 1204 1205static buf_hash_table_t buf_hash_table; 1206 1207#define BUF_HASH_INDEX(spa, dva, birth) \ 1208 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1209#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1210#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1211#define HDR_LOCK(hdr) \ 1212 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1213 1214uint64_t zfs_crc64_table[256]; 1215 1216/* 1217 * Level 2 ARC 1218 */ 1219 1220#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1221#define L2ARC_HEADROOM 2 /* num of writes */ 1222/* 1223 * If we discover during ARC scan any buffers to be compressed, we boost 1224 * our headroom for the next scanning cycle by this percentage multiple. 1225 */ 1226#define L2ARC_HEADROOM_BOOST 200 1227#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1228#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1229 1230#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1231#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1232 1233/* L2ARC Performance Tunables */ 1234uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1235uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1236uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1237uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1238uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1239uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1240boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1241boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1242boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1243 1244SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1245 &l2arc_write_max, 0, "max write size"); 1246SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1247 &l2arc_write_boost, 0, "extra write during warmup"); 1248SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1249 &l2arc_headroom, 0, "number of dev writes"); 1250SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1251 &l2arc_feed_secs, 0, "interval seconds"); 1252SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1253 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1254 1255SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1256 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1257SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1258 &l2arc_feed_again, 0, "turbo warmup"); 1259SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1260 &l2arc_norw, 0, "no reads during writes"); 1261 1262SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1263 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1264SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1265 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1266 "size of anonymous state"); 1267SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1268 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1269 "size of anonymous state"); 1270 1271SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1272 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1273SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1274 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1275 "size of metadata in mru state"); 1276SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1277 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1278 "size of data in mru state"); 1279 1280SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1281 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1282SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1283 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1284 "size of metadata in mru ghost state"); 1285SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1286 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1287 "size of data in mru ghost state"); 1288 1289SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1290 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1291SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1292 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1293 "size of metadata in mfu state"); 1294SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1295 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1296 "size of data in mfu state"); 1297 1298SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1299 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1300SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1301 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1302 "size of metadata in mfu ghost state"); 1303SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1304 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1305 "size of data in mfu ghost state"); 1306 1307SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1308 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1309 1310/* 1311 * L2ARC Internals 1312 */ 1313struct l2arc_dev { 1314 vdev_t *l2ad_vdev; /* vdev */ 1315 spa_t *l2ad_spa; /* spa */ 1316 uint64_t l2ad_hand; /* next write location */ 1317 uint64_t l2ad_start; /* first addr on device */ 1318 uint64_t l2ad_end; /* last addr on device */ 1319 boolean_t l2ad_first; /* first sweep through */ 1320 boolean_t l2ad_writing; /* currently writing */ 1321 kmutex_t l2ad_mtx; /* lock for buffer list */ 1322 list_t l2ad_buflist; /* buffer list */ 1323 list_node_t l2ad_node; /* device list node */ 1324 refcount_t l2ad_alloc; /* allocated bytes */ 1325}; 1326 1327static list_t L2ARC_dev_list; /* device list */ 1328static list_t *l2arc_dev_list; /* device list pointer */ 1329static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1330static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1331static list_t L2ARC_free_on_write; /* free after write buf list */ 1332static list_t *l2arc_free_on_write; /* free after write list ptr */ 1333static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1334static uint64_t l2arc_ndev; /* number of devices */ 1335 1336typedef struct l2arc_read_callback { 1337 arc_buf_hdr_t *l2rcb_hdr; /* read buffer */ 1338 blkptr_t l2rcb_bp; /* original blkptr */ 1339 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1340 int l2rcb_flags; /* original flags */ 1341 void *l2rcb_data; /* temporary buffer */ 1342} l2arc_read_callback_t; 1343 1344typedef struct l2arc_write_callback { 1345 l2arc_dev_t *l2wcb_dev; /* device info */ 1346 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1347} l2arc_write_callback_t; 1348 1349typedef struct l2arc_data_free { 1350 /* protected by l2arc_free_on_write_mtx */ 1351 void *l2df_data; 1352 size_t l2df_size; 1353 arc_buf_contents_t l2df_type; 1354 list_node_t l2df_list_node; 1355} l2arc_data_free_t; 1356 1357static kmutex_t l2arc_feed_thr_lock; 1358static kcondvar_t l2arc_feed_thr_cv; 1359static uint8_t l2arc_thread_exit; 1360 1361static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1362static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1363static void arc_hdr_free_pdata(arc_buf_hdr_t *hdr); 1364static void arc_hdr_alloc_pdata(arc_buf_hdr_t *); 1365static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1366static boolean_t arc_is_overflowing(); 1367static void arc_buf_watch(arc_buf_t *); 1368 1369static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1370static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1371static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1372static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1373 1374static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1375static void l2arc_read_done(zio_t *); 1376 1377static void 1378l2arc_trim(const arc_buf_hdr_t *hdr) 1379{ 1380 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1381 1382 ASSERT(HDR_HAS_L2HDR(hdr)); 1383 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1384 1385 if (HDR_GET_PSIZE(hdr) != 0) { 1386 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1387 HDR_GET_PSIZE(hdr), 0); 1388 } 1389} 1390 1391static uint64_t 1392buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1393{ 1394 uint8_t *vdva = (uint8_t *)dva; 1395 uint64_t crc = -1ULL; 1396 int i; 1397 1398 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1399 1400 for (i = 0; i < sizeof (dva_t); i++) 1401 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1402 1403 crc ^= (spa>>8) ^ birth; 1404 1405 return (crc); 1406} 1407 1408#define HDR_EMPTY(hdr) \ 1409 ((hdr)->b_dva.dva_word[0] == 0 && \ 1410 (hdr)->b_dva.dva_word[1] == 0) 1411 1412#define HDR_EQUAL(spa, dva, birth, hdr) \ 1413 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1414 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1415 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1416 1417static void 1418buf_discard_identity(arc_buf_hdr_t *hdr) 1419{ 1420 hdr->b_dva.dva_word[0] = 0; 1421 hdr->b_dva.dva_word[1] = 0; 1422 hdr->b_birth = 0; 1423} 1424 1425static arc_buf_hdr_t * 1426buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1427{ 1428 const dva_t *dva = BP_IDENTITY(bp); 1429 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1430 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1431 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1432 arc_buf_hdr_t *hdr; 1433 1434 mutex_enter(hash_lock); 1435 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1436 hdr = hdr->b_hash_next) { 1437 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1438 *lockp = hash_lock; 1439 return (hdr); 1440 } 1441 } 1442 mutex_exit(hash_lock); 1443 *lockp = NULL; 1444 return (NULL); 1445} 1446 1447/* 1448 * Insert an entry into the hash table. If there is already an element 1449 * equal to elem in the hash table, then the already existing element 1450 * will be returned and the new element will not be inserted. 1451 * Otherwise returns NULL. 1452 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1453 */ 1454static arc_buf_hdr_t * 1455buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1456{ 1457 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1458 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1459 arc_buf_hdr_t *fhdr; 1460 uint32_t i; 1461 1462 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1463 ASSERT(hdr->b_birth != 0); 1464 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1465 1466 if (lockp != NULL) { 1467 *lockp = hash_lock; 1468 mutex_enter(hash_lock); 1469 } else { 1470 ASSERT(MUTEX_HELD(hash_lock)); 1471 } 1472 1473 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1474 fhdr = fhdr->b_hash_next, i++) { 1475 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1476 return (fhdr); 1477 } 1478 1479 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1480 buf_hash_table.ht_table[idx] = hdr; 1481 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1482 1483 /* collect some hash table performance data */ 1484 if (i > 0) { 1485 ARCSTAT_BUMP(arcstat_hash_collisions); 1486 if (i == 1) 1487 ARCSTAT_BUMP(arcstat_hash_chains); 1488 1489 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1490 } 1491 1492 ARCSTAT_BUMP(arcstat_hash_elements); 1493 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1494 1495 return (NULL); 1496} 1497 1498static void 1499buf_hash_remove(arc_buf_hdr_t *hdr) 1500{ 1501 arc_buf_hdr_t *fhdr, **hdrp; 1502 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1503 1504 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1505 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1506 1507 hdrp = &buf_hash_table.ht_table[idx]; 1508 while ((fhdr = *hdrp) != hdr) { 1509 ASSERT3P(fhdr, !=, NULL); 1510 hdrp = &fhdr->b_hash_next; 1511 } 1512 *hdrp = hdr->b_hash_next; 1513 hdr->b_hash_next = NULL; 1514 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1515 1516 /* collect some hash table performance data */ 1517 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1518 1519 if (buf_hash_table.ht_table[idx] && 1520 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1521 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1522} 1523 1524/* 1525 * Global data structures and functions for the buf kmem cache. 1526 */ 1527static kmem_cache_t *hdr_full_cache; 1528static kmem_cache_t *hdr_l2only_cache; 1529static kmem_cache_t *buf_cache; 1530 1531static void 1532buf_fini(void) 1533{ 1534 int i; 1535 1536 kmem_free(buf_hash_table.ht_table, 1537 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1538 for (i = 0; i < BUF_LOCKS; i++) 1539 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1540 kmem_cache_destroy(hdr_full_cache); 1541 kmem_cache_destroy(hdr_l2only_cache); 1542 kmem_cache_destroy(buf_cache); 1543} 1544 1545/* 1546 * Constructor callback - called when the cache is empty 1547 * and a new buf is requested. 1548 */ 1549/* ARGSUSED */ 1550static int 1551hdr_full_cons(void *vbuf, void *unused, int kmflag) 1552{ 1553 arc_buf_hdr_t *hdr = vbuf; 1554 1555 bzero(hdr, HDR_FULL_SIZE); 1556 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1557 refcount_create(&hdr->b_l1hdr.b_refcnt); 1558 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1559 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1560 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1561 1562 return (0); 1563} 1564 1565/* ARGSUSED */ 1566static int 1567hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1568{ 1569 arc_buf_hdr_t *hdr = vbuf; 1570 1571 bzero(hdr, HDR_L2ONLY_SIZE); 1572 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1573 1574 return (0); 1575} 1576 1577/* ARGSUSED */ 1578static int 1579buf_cons(void *vbuf, void *unused, int kmflag) 1580{ 1581 arc_buf_t *buf = vbuf; 1582 1583 bzero(buf, sizeof (arc_buf_t)); 1584 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1585 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1586 1587 return (0); 1588} 1589 1590/* 1591 * Destructor callback - called when a cached buf is 1592 * no longer required. 1593 */ 1594/* ARGSUSED */ 1595static void 1596hdr_full_dest(void *vbuf, void *unused) 1597{ 1598 arc_buf_hdr_t *hdr = vbuf; 1599 1600 ASSERT(HDR_EMPTY(hdr)); 1601 cv_destroy(&hdr->b_l1hdr.b_cv); 1602 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1603 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1604 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1605 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1606} 1607 1608/* ARGSUSED */ 1609static void 1610hdr_l2only_dest(void *vbuf, void *unused) 1611{ 1612 arc_buf_hdr_t *hdr = vbuf; 1613 1614 ASSERT(HDR_EMPTY(hdr)); 1615 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1616} 1617 1618/* ARGSUSED */ 1619static void 1620buf_dest(void *vbuf, void *unused) 1621{ 1622 arc_buf_t *buf = vbuf; 1623 1624 mutex_destroy(&buf->b_evict_lock); 1625 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1626} 1627 1628/* 1629 * Reclaim callback -- invoked when memory is low. 1630 */ 1631/* ARGSUSED */ 1632static void 1633hdr_recl(void *unused) 1634{ 1635 dprintf("hdr_recl called\n"); 1636 /* 1637 * umem calls the reclaim func when we destroy the buf cache, 1638 * which is after we do arc_fini(). 1639 */ 1640 if (!arc_dead) 1641 cv_signal(&arc_reclaim_thread_cv); 1642} 1643 1644static void 1645buf_init(void) 1646{ 1647 uint64_t *ct; 1648 uint64_t hsize = 1ULL << 12; 1649 int i, j; 1650 1651 /* 1652 * The hash table is big enough to fill all of physical memory 1653 * with an average block size of zfs_arc_average_blocksize (default 8K). 1654 * By default, the table will take up 1655 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1656 */ 1657 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1658 hsize <<= 1; 1659retry: 1660 buf_hash_table.ht_mask = hsize - 1; 1661 buf_hash_table.ht_table = 1662 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1663 if (buf_hash_table.ht_table == NULL) { 1664 ASSERT(hsize > (1ULL << 8)); 1665 hsize >>= 1; 1666 goto retry; 1667 } 1668 1669 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1670 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1671 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1672 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1673 NULL, NULL, 0); 1674 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1675 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1676 1677 for (i = 0; i < 256; i++) 1678 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1679 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1680 1681 for (i = 0; i < BUF_LOCKS; i++) { 1682 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1683 NULL, MUTEX_DEFAULT, NULL); 1684 } 1685} 1686 1687#define ARC_MINTIME (hz>>4) /* 62 ms */ 1688 1689static inline boolean_t 1690arc_buf_is_shared(arc_buf_t *buf) 1691{ 1692 boolean_t shared = (buf->b_data != NULL && 1693 buf->b_data == buf->b_hdr->b_l1hdr.b_pdata); 1694 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1695 return (shared); 1696} 1697 1698static inline void 1699arc_cksum_free(arc_buf_hdr_t *hdr) 1700{ 1701 ASSERT(HDR_HAS_L1HDR(hdr)); 1702 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1703 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1704 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1705 hdr->b_l1hdr.b_freeze_cksum = NULL; 1706 } 1707 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1708} 1709 1710static void 1711arc_cksum_verify(arc_buf_t *buf) 1712{ 1713 arc_buf_hdr_t *hdr = buf->b_hdr; 1714 zio_cksum_t zc; 1715 1716 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1717 return; 1718 1719 ASSERT(HDR_HAS_L1HDR(hdr)); 1720 1721 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1722 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1723 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1724 return; 1725 } 1726 fletcher_2_native(buf->b_data, HDR_GET_LSIZE(hdr), NULL, &zc); 1727 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1728 panic("buffer modified while frozen!"); 1729 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1730} 1731 1732static boolean_t 1733arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1734{ 1735 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1736 boolean_t valid_cksum; 1737 1738 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1739 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1740 1741 /* 1742 * We rely on the blkptr's checksum to determine if the block 1743 * is valid or not. When compressed arc is enabled, the l2arc 1744 * writes the block to the l2arc just as it appears in the pool. 1745 * This allows us to use the blkptr's checksum to validate the 1746 * data that we just read off of the l2arc without having to store 1747 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1748 * arc is disabled, then the data written to the l2arc is always 1749 * uncompressed and won't match the block as it exists in the main 1750 * pool. When this is the case, we must first compress it if it is 1751 * compressed on the main pool before we can validate the checksum. 1752 */ 1753 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1754 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1755 uint64_t lsize = HDR_GET_LSIZE(hdr); 1756 uint64_t csize; 1757 1758 void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr)); 1759 csize = zio_compress_data(compress, zio->io_data, cbuf, lsize); 1760 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1761 if (csize < HDR_GET_PSIZE(hdr)) { 1762 /* 1763 * Compressed blocks are always a multiple of the 1764 * smallest ashift in the pool. Ideally, we would 1765 * like to round up the csize to the next 1766 * spa_min_ashift but that value may have changed 1767 * since the block was last written. Instead, 1768 * we rely on the fact that the hdr's psize 1769 * was set to the psize of the block when it was 1770 * last written. We set the csize to that value 1771 * and zero out any part that should not contain 1772 * data. 1773 */ 1774 bzero((char *)cbuf + csize, HDR_GET_PSIZE(hdr) - csize); 1775 csize = HDR_GET_PSIZE(hdr); 1776 } 1777 zio_push_transform(zio, cbuf, csize, HDR_GET_PSIZE(hdr), NULL); 1778 } 1779 1780 /* 1781 * Block pointers always store the checksum for the logical data. 1782 * If the block pointer has the gang bit set, then the checksum 1783 * it represents is for the reconstituted data and not for an 1784 * individual gang member. The zio pipeline, however, must be able to 1785 * determine the checksum of each of the gang constituents so it 1786 * treats the checksum comparison differently than what we need 1787 * for l2arc blocks. This prevents us from using the 1788 * zio_checksum_error() interface directly. Instead we must call the 1789 * zio_checksum_error_impl() so that we can ensure the checksum is 1790 * generated using the correct checksum algorithm and accounts for the 1791 * logical I/O size and not just a gang fragment. 1792 */ 1793 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1794 BP_GET_CHECKSUM(zio->io_bp), zio->io_data, zio->io_size, 1795 zio->io_offset, NULL) == 0); 1796 zio_pop_transforms(zio); 1797 return (valid_cksum); 1798} 1799 1800static void 1801arc_cksum_compute(arc_buf_t *buf) 1802{ 1803 arc_buf_hdr_t *hdr = buf->b_hdr; 1804 1805 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1806 return; 1807 1808 ASSERT(HDR_HAS_L1HDR(hdr)); 1809 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1810 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1811 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1812 return; 1813 } 1814 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1815 KM_SLEEP); 1816 fletcher_2_native(buf->b_data, HDR_GET_LSIZE(hdr), NULL, 1817 hdr->b_l1hdr.b_freeze_cksum); 1818 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1819#ifdef illumos 1820 arc_buf_watch(buf); 1821#endif 1822} 1823 1824#ifdef illumos 1825#ifndef _KERNEL 1826typedef struct procctl { 1827 long cmd; 1828 prwatch_t prwatch; 1829} procctl_t; 1830#endif 1831 1832/* ARGSUSED */ 1833static void 1834arc_buf_unwatch(arc_buf_t *buf) 1835{ 1836#ifndef _KERNEL 1837 if (arc_watch) { 1838 int result; 1839 procctl_t ctl; 1840 ctl.cmd = PCWATCH; 1841 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1842 ctl.prwatch.pr_size = 0; 1843 ctl.prwatch.pr_wflags = 0; 1844 result = write(arc_procfd, &ctl, sizeof (ctl)); 1845 ASSERT3U(result, ==, sizeof (ctl)); 1846 } 1847#endif 1848} 1849 1850/* ARGSUSED */ 1851static void 1852arc_buf_watch(arc_buf_t *buf) 1853{ 1854#ifndef _KERNEL 1855 if (arc_watch) { 1856 int result; 1857 procctl_t ctl; 1858 ctl.cmd = PCWATCH; 1859 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1860 ctl.prwatch.pr_size = HDR_GET_LSIZE(buf->b_hdr); 1861 ctl.prwatch.pr_wflags = WA_WRITE; 1862 result = write(arc_procfd, &ctl, sizeof (ctl)); 1863 ASSERT3U(result, ==, sizeof (ctl)); 1864 } 1865#endif 1866} 1867#endif /* illumos */ 1868 1869static arc_buf_contents_t 1870arc_buf_type(arc_buf_hdr_t *hdr) 1871{ 1872 arc_buf_contents_t type; 1873 if (HDR_ISTYPE_METADATA(hdr)) { 1874 type = ARC_BUFC_METADATA; 1875 } else { 1876 type = ARC_BUFC_DATA; 1877 } 1878 VERIFY3U(hdr->b_type, ==, type); 1879 return (type); 1880} 1881 1882static uint32_t 1883arc_bufc_to_flags(arc_buf_contents_t type) 1884{ 1885 switch (type) { 1886 case ARC_BUFC_DATA: 1887 /* metadata field is 0 if buffer contains normal data */ 1888 return (0); 1889 case ARC_BUFC_METADATA: 1890 return (ARC_FLAG_BUFC_METADATA); 1891 default: 1892 break; 1893 } 1894 panic("undefined ARC buffer type!"); 1895 return ((uint32_t)-1); 1896} 1897 1898void 1899arc_buf_thaw(arc_buf_t *buf) 1900{ 1901 arc_buf_hdr_t *hdr = buf->b_hdr; 1902 1903 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1904 if (hdr->b_l1hdr.b_state != arc_anon) 1905 panic("modifying non-anon buffer!"); 1906 if (HDR_IO_IN_PROGRESS(hdr)) 1907 panic("modifying buffer while i/o in progress!"); 1908 arc_cksum_verify(buf); 1909 } 1910 1911 ASSERT(HDR_HAS_L1HDR(hdr)); 1912 arc_cksum_free(hdr); 1913 1914 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1915#ifdef ZFS_DEBUG 1916 if (zfs_flags & ZFS_DEBUG_MODIFY) { 1917 if (hdr->b_l1hdr.b_thawed != NULL) 1918 kmem_free(hdr->b_l1hdr.b_thawed, 1); 1919 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 1920 } 1921#endif 1922 1923 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1924 1925#ifdef illumos 1926 arc_buf_unwatch(buf); 1927#endif 1928} 1929 1930void 1931arc_buf_freeze(arc_buf_t *buf) 1932{ 1933 arc_buf_hdr_t *hdr = buf->b_hdr; 1934 kmutex_t *hash_lock; 1935 1936 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1937 return; 1938 1939 hash_lock = HDR_LOCK(hdr); 1940 mutex_enter(hash_lock); 1941 1942 ASSERT(HDR_HAS_L1HDR(hdr)); 1943 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 1944 hdr->b_l1hdr.b_state == arc_anon); 1945 arc_cksum_compute(buf); 1946 mutex_exit(hash_lock); 1947 1948} 1949 1950/* 1951 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 1952 * the following functions should be used to ensure that the flags are 1953 * updated in a thread-safe way. When manipulating the flags either 1954 * the hash_lock must be held or the hdr must be undiscoverable. This 1955 * ensures that we're not racing with any other threads when updating 1956 * the flags. 1957 */ 1958static inline void 1959arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 1960{ 1961 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1962 hdr->b_flags |= flags; 1963} 1964 1965static inline void 1966arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 1967{ 1968 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1969 hdr->b_flags &= ~flags; 1970} 1971 1972/* 1973 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 1974 * done in a special way since we have to clear and set bits 1975 * at the same time. Consumers that wish to set the compression bits 1976 * must use this function to ensure that the flags are updated in 1977 * thread-safe manner. 1978 */ 1979static void 1980arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 1981{ 1982 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 1983 1984 /* 1985 * Holes and embedded blocks will always have a psize = 0 so 1986 * we ignore the compression of the blkptr and set the 1987 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 1988 * Holes and embedded blocks remain anonymous so we don't 1989 * want to uncompress them. Mark them as uncompressed. 1990 */ 1991 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 1992 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 1993 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 1994 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 1995 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1996 } else { 1997 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 1998 HDR_SET_COMPRESS(hdr, cmp); 1999 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2000 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2001 } 2002} 2003 2004static int 2005arc_decompress(arc_buf_t *buf) 2006{ 2007 arc_buf_hdr_t *hdr = buf->b_hdr; 2008 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2009 int error; 2010 2011 if (arc_buf_is_shared(buf)) { 2012 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2013 } else if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) { 2014 /* 2015 * The arc_buf_hdr_t is either not compressed or is 2016 * associated with an embedded block or a hole in which 2017 * case they remain anonymous. 2018 */ 2019 IMPLY(HDR_COMPRESSION_ENABLED(hdr), HDR_GET_PSIZE(hdr) == 0 || 2020 HDR_GET_PSIZE(hdr) == HDR_GET_LSIZE(hdr)); 2021 ASSERT(!HDR_SHARED_DATA(hdr)); 2022 bcopy(hdr->b_l1hdr.b_pdata, buf->b_data, HDR_GET_LSIZE(hdr)); 2023 } else { 2024 ASSERT(!HDR_SHARED_DATA(hdr)); 2025 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2026 error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2027 hdr->b_l1hdr.b_pdata, buf->b_data, HDR_GET_PSIZE(hdr), 2028 HDR_GET_LSIZE(hdr)); 2029 if (error != 0) { 2030 zfs_dbgmsg("hdr %p, compress %d, psize %d, lsize %d", 2031 hdr, HDR_GET_COMPRESS(hdr), HDR_GET_PSIZE(hdr), 2032 HDR_GET_LSIZE(hdr)); 2033 return (SET_ERROR(EIO)); 2034 } 2035 } 2036 if (bswap != DMU_BSWAP_NUMFUNCS) { 2037 ASSERT(!HDR_SHARED_DATA(hdr)); 2038 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2039 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2040 } 2041 arc_cksum_compute(buf); 2042 return (0); 2043} 2044 2045/* 2046 * Return the size of the block, b_pdata, that is stored in the arc_buf_hdr_t. 2047 */ 2048static uint64_t 2049arc_hdr_size(arc_buf_hdr_t *hdr) 2050{ 2051 uint64_t size; 2052 2053 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2054 HDR_GET_PSIZE(hdr) > 0) { 2055 size = HDR_GET_PSIZE(hdr); 2056 } else { 2057 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2058 size = HDR_GET_LSIZE(hdr); 2059 } 2060 return (size); 2061} 2062 2063/* 2064 * Increment the amount of evictable space in the arc_state_t's refcount. 2065 * We account for the space used by the hdr and the arc buf individually 2066 * so that we can add and remove them from the refcount individually. 2067 */ 2068static void 2069arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2070{ 2071 arc_buf_contents_t type = arc_buf_type(hdr); 2072 uint64_t lsize = HDR_GET_LSIZE(hdr); 2073 2074 ASSERT(HDR_HAS_L1HDR(hdr)); 2075 2076 if (GHOST_STATE(state)) { 2077 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2078 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2079 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2080 (void) refcount_add_many(&state->arcs_esize[type], lsize, hdr); 2081 return; 2082 } 2083 2084 ASSERT(!GHOST_STATE(state)); 2085 if (hdr->b_l1hdr.b_pdata != NULL) { 2086 (void) refcount_add_many(&state->arcs_esize[type], 2087 arc_hdr_size(hdr), hdr); 2088 } 2089 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2090 buf = buf->b_next) { 2091 if (arc_buf_is_shared(buf)) { 2092 ASSERT(ARC_BUF_LAST(buf)); 2093 continue; 2094 } 2095 (void) refcount_add_many(&state->arcs_esize[type], lsize, buf); 2096 } 2097} 2098 2099/* 2100 * Decrement the amount of evictable space in the arc_state_t's refcount. 2101 * We account for the space used by the hdr and the arc buf individually 2102 * so that we can add and remove them from the refcount individually. 2103 */ 2104static void 2105arc_evitable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2106{ 2107 arc_buf_contents_t type = arc_buf_type(hdr); 2108 uint64_t lsize = HDR_GET_LSIZE(hdr); 2109 2110 ASSERT(HDR_HAS_L1HDR(hdr)); 2111 2112 if (GHOST_STATE(state)) { 2113 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2114 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2115 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2116 (void) refcount_remove_many(&state->arcs_esize[type], 2117 lsize, hdr); 2118 return; 2119 } 2120 2121 ASSERT(!GHOST_STATE(state)); 2122 if (hdr->b_l1hdr.b_pdata != NULL) { 2123 (void) refcount_remove_many(&state->arcs_esize[type], 2124 arc_hdr_size(hdr), hdr); 2125 } 2126 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2127 buf = buf->b_next) { 2128 if (arc_buf_is_shared(buf)) { 2129 ASSERT(ARC_BUF_LAST(buf)); 2130 continue; 2131 } 2132 (void) refcount_remove_many(&state->arcs_esize[type], 2133 lsize, buf); 2134 } 2135} 2136 2137/* 2138 * Add a reference to this hdr indicating that someone is actively 2139 * referencing that memory. When the refcount transitions from 0 to 1, 2140 * we remove it from the respective arc_state_t list to indicate that 2141 * it is not evictable. 2142 */ 2143static void 2144add_reference(arc_buf_hdr_t *hdr, void *tag) 2145{ 2146 ASSERT(HDR_HAS_L1HDR(hdr)); 2147 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2148 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2149 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2150 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2151 } 2152 2153 arc_state_t *state = hdr->b_l1hdr.b_state; 2154 2155 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2156 (state != arc_anon)) { 2157 /* We don't use the L2-only state list. */ 2158 if (state != arc_l2c_only) { 2159 multilist_remove(&state->arcs_list[arc_buf_type(hdr)], 2160 hdr); 2161 arc_evitable_space_decrement(hdr, state); 2162 } 2163 /* remove the prefetch flag if we get a reference */ 2164 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2165 } 2166} 2167 2168/* 2169 * Remove a reference from this hdr. When the reference transitions from 2170 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2171 * list making it eligible for eviction. 2172 */ 2173static int 2174remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2175{ 2176 int cnt; 2177 arc_state_t *state = hdr->b_l1hdr.b_state; 2178 2179 ASSERT(HDR_HAS_L1HDR(hdr)); 2180 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2181 ASSERT(!GHOST_STATE(state)); 2182 2183 /* 2184 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2185 * check to prevent usage of the arc_l2c_only list. 2186 */ 2187 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2188 (state != arc_anon)) { 2189 multilist_insert(&state->arcs_list[arc_buf_type(hdr)], hdr); 2190 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2191 arc_evictable_space_increment(hdr, state); 2192 } 2193 return (cnt); 2194} 2195 2196/* 2197 * Move the supplied buffer to the indicated state. The hash lock 2198 * for the buffer must be held by the caller. 2199 */ 2200static void 2201arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2202 kmutex_t *hash_lock) 2203{ 2204 arc_state_t *old_state; 2205 int64_t refcnt; 2206 uint32_t bufcnt; 2207 boolean_t update_old, update_new; 2208 arc_buf_contents_t buftype = arc_buf_type(hdr); 2209 2210 /* 2211 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2212 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2213 * L1 hdr doesn't always exist when we change state to arc_anon before 2214 * destroying a header, in which case reallocating to add the L1 hdr is 2215 * pointless. 2216 */ 2217 if (HDR_HAS_L1HDR(hdr)) { 2218 old_state = hdr->b_l1hdr.b_state; 2219 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2220 bufcnt = hdr->b_l1hdr.b_bufcnt; 2221 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pdata != NULL); 2222 } else { 2223 old_state = arc_l2c_only; 2224 refcnt = 0; 2225 bufcnt = 0; 2226 update_old = B_FALSE; 2227 } 2228 update_new = update_old; 2229 2230 ASSERT(MUTEX_HELD(hash_lock)); 2231 ASSERT3P(new_state, !=, old_state); 2232 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2233 ASSERT(old_state != arc_anon || bufcnt <= 1); 2234 2235 /* 2236 * If this buffer is evictable, transfer it from the 2237 * old state list to the new state list. 2238 */ 2239 if (refcnt == 0) { 2240 if (old_state != arc_anon && old_state != arc_l2c_only) { 2241 ASSERT(HDR_HAS_L1HDR(hdr)); 2242 multilist_remove(&old_state->arcs_list[buftype], hdr); 2243 2244 if (GHOST_STATE(old_state)) { 2245 ASSERT0(bufcnt); 2246 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2247 update_old = B_TRUE; 2248 } 2249 arc_evitable_space_decrement(hdr, old_state); 2250 } 2251 if (new_state != arc_anon && new_state != arc_l2c_only) { 2252 2253 /* 2254 * An L1 header always exists here, since if we're 2255 * moving to some L1-cached state (i.e. not l2c_only or 2256 * anonymous), we realloc the header to add an L1hdr 2257 * beforehand. 2258 */ 2259 ASSERT(HDR_HAS_L1HDR(hdr)); 2260 multilist_insert(&new_state->arcs_list[buftype], hdr); 2261 2262 if (GHOST_STATE(new_state)) { 2263 ASSERT0(bufcnt); 2264 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2265 update_new = B_TRUE; 2266 } 2267 arc_evictable_space_increment(hdr, new_state); 2268 } 2269 } 2270 2271 ASSERT(!HDR_EMPTY(hdr)); 2272 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2273 buf_hash_remove(hdr); 2274 2275 /* adjust state sizes (ignore arc_l2c_only) */ 2276 2277 if (update_new && new_state != arc_l2c_only) { 2278 ASSERT(HDR_HAS_L1HDR(hdr)); 2279 if (GHOST_STATE(new_state)) { 2280 ASSERT0(bufcnt); 2281 2282 /* 2283 * When moving a header to a ghost state, we first 2284 * remove all arc buffers. Thus, we'll have a 2285 * bufcnt of zero, and no arc buffer to use for 2286 * the reference. As a result, we use the arc 2287 * header pointer for the reference. 2288 */ 2289 (void) refcount_add_many(&new_state->arcs_size, 2290 HDR_GET_LSIZE(hdr), hdr); 2291 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2292 } else { 2293 uint32_t buffers = 0; 2294 2295 /* 2296 * Each individual buffer holds a unique reference, 2297 * thus we must remove each of these references one 2298 * at a time. 2299 */ 2300 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2301 buf = buf->b_next) { 2302 ASSERT3U(bufcnt, !=, 0); 2303 buffers++; 2304 2305 /* 2306 * When the arc_buf_t is sharing the data 2307 * block with the hdr, the owner of the 2308 * reference belongs to the hdr. Only 2309 * add to the refcount if the arc_buf_t is 2310 * not shared. 2311 */ 2312 if (arc_buf_is_shared(buf)) { 2313 ASSERT(ARC_BUF_LAST(buf)); 2314 continue; 2315 } 2316 2317 (void) refcount_add_many(&new_state->arcs_size, 2318 HDR_GET_LSIZE(hdr), buf); 2319 } 2320 ASSERT3U(bufcnt, ==, buffers); 2321 2322 if (hdr->b_l1hdr.b_pdata != NULL) { 2323 (void) refcount_add_many(&new_state->arcs_size, 2324 arc_hdr_size(hdr), hdr); 2325 } else { 2326 ASSERT(GHOST_STATE(old_state)); 2327 } 2328 } 2329 } 2330 2331 if (update_old && old_state != arc_l2c_only) { 2332 ASSERT(HDR_HAS_L1HDR(hdr)); 2333 if (GHOST_STATE(old_state)) { 2334 ASSERT0(bufcnt); 2335 2336 /* 2337 * When moving a header off of a ghost state, 2338 * the header will not contain any arc buffers. 2339 * We use the arc header pointer for the reference 2340 * which is exactly what we did when we put the 2341 * header on the ghost state. 2342 */ 2343 2344 (void) refcount_remove_many(&old_state->arcs_size, 2345 HDR_GET_LSIZE(hdr), hdr); 2346 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2347 } else { 2348 uint32_t buffers = 0; 2349 2350 /* 2351 * Each individual buffer holds a unique reference, 2352 * thus we must remove each of these references one 2353 * at a time. 2354 */ 2355 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2356 buf = buf->b_next) { 2357 ASSERT3P(bufcnt, !=, 0); 2358 buffers++; 2359 2360 /* 2361 * When the arc_buf_t is sharing the data 2362 * block with the hdr, the owner of the 2363 * reference belongs to the hdr. Only 2364 * add to the refcount if the arc_buf_t is 2365 * not shared. 2366 */ 2367 if (arc_buf_is_shared(buf)) { 2368 ASSERT(ARC_BUF_LAST(buf)); 2369 continue; 2370 } 2371 2372 (void) refcount_remove_many( 2373 &old_state->arcs_size, HDR_GET_LSIZE(hdr), 2374 buf); 2375 } 2376 ASSERT3U(bufcnt, ==, buffers); 2377 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2378 (void) refcount_remove_many( 2379 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2380 } 2381 } 2382 2383 if (HDR_HAS_L1HDR(hdr)) 2384 hdr->b_l1hdr.b_state = new_state; 2385 2386 /* 2387 * L2 headers should never be on the L2 state list since they don't 2388 * have L1 headers allocated. 2389 */ 2390 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2391 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2392} 2393 2394void 2395arc_space_consume(uint64_t space, arc_space_type_t type) 2396{ 2397 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2398 2399 switch (type) { 2400 case ARC_SPACE_DATA: 2401 ARCSTAT_INCR(arcstat_data_size, space); 2402 break; 2403 case ARC_SPACE_META: 2404 ARCSTAT_INCR(arcstat_metadata_size, space); 2405 break; 2406 case ARC_SPACE_OTHER: 2407 ARCSTAT_INCR(arcstat_other_size, space); 2408 break; 2409 case ARC_SPACE_HDRS: 2410 ARCSTAT_INCR(arcstat_hdr_size, space); 2411 break; 2412 case ARC_SPACE_L2HDRS: 2413 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2414 break; 2415 } 2416 2417 if (type != ARC_SPACE_DATA) 2418 ARCSTAT_INCR(arcstat_meta_used, space); 2419 2420 atomic_add_64(&arc_size, space); 2421} 2422 2423void 2424arc_space_return(uint64_t space, arc_space_type_t type) 2425{ 2426 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2427 2428 switch (type) { 2429 case ARC_SPACE_DATA: 2430 ARCSTAT_INCR(arcstat_data_size, -space); 2431 break; 2432 case ARC_SPACE_META: 2433 ARCSTAT_INCR(arcstat_metadata_size, -space); 2434 break; 2435 case ARC_SPACE_OTHER: 2436 ARCSTAT_INCR(arcstat_other_size, -space); 2437 break; 2438 case ARC_SPACE_HDRS: 2439 ARCSTAT_INCR(arcstat_hdr_size, -space); 2440 break; 2441 case ARC_SPACE_L2HDRS: 2442 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2443 break; 2444 } 2445 2446 if (type != ARC_SPACE_DATA) { 2447 ASSERT(arc_meta_used >= space); 2448 if (arc_meta_max < arc_meta_used) 2449 arc_meta_max = arc_meta_used; 2450 ARCSTAT_INCR(arcstat_meta_used, -space); 2451 } 2452 2453 ASSERT(arc_size >= space); 2454 atomic_add_64(&arc_size, -space); 2455} 2456 2457/* 2458 * Allocate an initial buffer for this hdr, subsequent buffers will 2459 * use arc_buf_clone(). 2460 */ 2461static arc_buf_t * 2462arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag) 2463{ 2464 arc_buf_t *buf; 2465 2466 ASSERT(HDR_HAS_L1HDR(hdr)); 2467 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2468 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2469 hdr->b_type == ARC_BUFC_METADATA); 2470 2471 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2472 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2473 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2474 2475 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2476 buf->b_hdr = hdr; 2477 buf->b_data = NULL; 2478 buf->b_next = NULL; 2479 2480 add_reference(hdr, tag); 2481 2482 /* 2483 * We're about to change the hdr's b_flags. We must either 2484 * hold the hash_lock or be undiscoverable. 2485 */ 2486 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2487 2488 /* 2489 * If the hdr's data can be shared (no byteswapping, hdr is 2490 * uncompressed, hdr's data is not currently being written to the 2491 * L2ARC write) then we share the data buffer and set the appropriate 2492 * bit in the hdr's b_flags to indicate the hdr is sharing it's 2493 * b_pdata with the arc_buf_t. Otherwise, we allocate a new buffer to 2494 * store the buf's data. 2495 */ 2496 if (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2497 HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF && !HDR_L2_WRITING(hdr)) { 2498 buf->b_data = hdr->b_l1hdr.b_pdata; 2499 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2500 } else { 2501 buf->b_data = arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2502 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2503 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2504 } 2505 VERIFY3P(buf->b_data, !=, NULL); 2506 2507 hdr->b_l1hdr.b_buf = buf; 2508 hdr->b_l1hdr.b_bufcnt += 1; 2509 2510 return (buf); 2511} 2512 2513/* 2514 * Used when allocating additional buffers. 2515 */ 2516static arc_buf_t * 2517arc_buf_clone(arc_buf_t *from) 2518{ 2519 arc_buf_t *buf; 2520 arc_buf_hdr_t *hdr = from->b_hdr; 2521 uint64_t size = HDR_GET_LSIZE(hdr); 2522 2523 ASSERT(HDR_HAS_L1HDR(hdr)); 2524 ASSERT(hdr->b_l1hdr.b_state != arc_anon); 2525 2526 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2527 buf->b_hdr = hdr; 2528 buf->b_data = NULL; 2529 buf->b_next = hdr->b_l1hdr.b_buf; 2530 hdr->b_l1hdr.b_buf = buf; 2531 buf->b_data = arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2532 bcopy(from->b_data, buf->b_data, size); 2533 hdr->b_l1hdr.b_bufcnt += 1; 2534 2535 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2536 return (buf); 2537} 2538 2539static char *arc_onloan_tag = "onloan"; 2540 2541/* 2542 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2543 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2544 * buffers must be returned to the arc before they can be used by the DMU or 2545 * freed. 2546 */ 2547arc_buf_t * 2548arc_loan_buf(spa_t *spa, int size) 2549{ 2550 arc_buf_t *buf; 2551 2552 buf = arc_alloc_buf(spa, size, arc_onloan_tag, ARC_BUFC_DATA); 2553 2554 atomic_add_64(&arc_loaned_bytes, size); 2555 return (buf); 2556} 2557 2558/* 2559 * Return a loaned arc buffer to the arc. 2560 */ 2561void 2562arc_return_buf(arc_buf_t *buf, void *tag) 2563{ 2564 arc_buf_hdr_t *hdr = buf->b_hdr; 2565 2566 ASSERT3P(buf->b_data, !=, NULL); 2567 ASSERT(HDR_HAS_L1HDR(hdr)); 2568 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2569 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2570 2571 atomic_add_64(&arc_loaned_bytes, -HDR_GET_LSIZE(hdr)); 2572} 2573 2574/* Detach an arc_buf from a dbuf (tag) */ 2575void 2576arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2577{ 2578 arc_buf_hdr_t *hdr = buf->b_hdr; 2579 2580 ASSERT3P(buf->b_data, !=, NULL); 2581 ASSERT(HDR_HAS_L1HDR(hdr)); 2582 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2583 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2584 2585 atomic_add_64(&arc_loaned_bytes, HDR_GET_LSIZE(hdr)); 2586} 2587 2588static void 2589l2arc_free_data_on_write(void *data, size_t size, arc_buf_contents_t type) 2590{ 2591 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2592 2593 df->l2df_data = data; 2594 df->l2df_size = size; 2595 df->l2df_type = type; 2596 mutex_enter(&l2arc_free_on_write_mtx); 2597 list_insert_head(l2arc_free_on_write, df); 2598 mutex_exit(&l2arc_free_on_write_mtx); 2599} 2600 2601static void 2602arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2603{ 2604 arc_state_t *state = hdr->b_l1hdr.b_state; 2605 arc_buf_contents_t type = arc_buf_type(hdr); 2606 uint64_t size = arc_hdr_size(hdr); 2607 2608 /* protected by hash lock, if in the hash table */ 2609 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2610 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2611 ASSERT(state != arc_anon && state != arc_l2c_only); 2612 2613 (void) refcount_remove_many(&state->arcs_esize[type], 2614 size, hdr); 2615 } 2616 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2617 2618 l2arc_free_data_on_write(hdr->b_l1hdr.b_pdata, size, type); 2619} 2620 2621/* 2622 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2623 * data buffer, we transfer the refcount ownership to the hdr and update 2624 * the appropriate kstats. 2625 */ 2626static void 2627arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2628{ 2629 arc_state_t *state = hdr->b_l1hdr.b_state; 2630 2631 ASSERT(!HDR_SHARED_DATA(hdr)); 2632 ASSERT(!arc_buf_is_shared(buf)); 2633 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2634 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2635 2636 /* 2637 * Start sharing the data buffer. We transfer the 2638 * refcount ownership to the hdr since it always owns 2639 * the refcount whenever an arc_buf_t is shared. 2640 */ 2641 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 2642 hdr->b_l1hdr.b_pdata = buf->b_data; 2643 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2644 2645 /* 2646 * Since we've transferred ownership to the hdr we need 2647 * to increment its compressed and uncompressed kstats and 2648 * decrement the overhead size. 2649 */ 2650 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2651 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 2652 ARCSTAT_INCR(arcstat_overhead_size, -HDR_GET_LSIZE(hdr)); 2653} 2654 2655static void 2656arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2657{ 2658 arc_state_t *state = hdr->b_l1hdr.b_state; 2659 2660 ASSERT(HDR_SHARED_DATA(hdr)); 2661 ASSERT(arc_buf_is_shared(buf)); 2662 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2663 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2664 2665 /* 2666 * We are no longer sharing this buffer so we need 2667 * to transfer its ownership to the rightful owner. 2668 */ 2669 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 2670 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2671 hdr->b_l1hdr.b_pdata = NULL; 2672 2673 /* 2674 * Since the buffer is no longer shared between 2675 * the arc buf and the hdr, count it as overhead. 2676 */ 2677 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2678 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2679 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2680} 2681 2682/* 2683 * Free up buf->b_data and if 'remove' is set, then pull the 2684 * arc_buf_t off of the the arc_buf_hdr_t's list and free it. 2685 */ 2686static void 2687arc_buf_destroy_impl(arc_buf_t *buf, boolean_t remove) 2688{ 2689 arc_buf_t **bufp; 2690 arc_buf_hdr_t *hdr = buf->b_hdr; 2691 uint64_t size = HDR_GET_LSIZE(hdr); 2692 boolean_t destroyed_buf_is_shared = arc_buf_is_shared(buf); 2693 2694 /* 2695 * Free up the data associated with the buf but only 2696 * if we're not sharing this with the hdr. If we are sharing 2697 * it with the hdr, then hdr will have performed the allocation 2698 * so allow it to do the free. 2699 */ 2700 if (buf->b_data != NULL) { 2701 /* 2702 * We're about to change the hdr's b_flags. We must either 2703 * hold the hash_lock or be undiscoverable. 2704 */ 2705 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2706 2707 arc_cksum_verify(buf); 2708#ifdef illumos 2709 arc_buf_unwatch(buf); 2710#endif 2711 2712 if (destroyed_buf_is_shared) { 2713 ASSERT(ARC_BUF_LAST(buf)); 2714 ASSERT(HDR_SHARED_DATA(hdr)); 2715 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2716 } else { 2717 arc_free_data_buf(hdr, buf->b_data, size, buf); 2718 ARCSTAT_INCR(arcstat_overhead_size, -size); 2719 } 2720 buf->b_data = NULL; 2721 2722 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 2723 hdr->b_l1hdr.b_bufcnt -= 1; 2724 } 2725 2726 /* only remove the buf if requested */ 2727 if (!remove) 2728 return; 2729 2730 /* remove the buf from the hdr list */ 2731 arc_buf_t *lastbuf = NULL; 2732 bufp = &hdr->b_l1hdr.b_buf; 2733 while (*bufp != NULL) { 2734 if (*bufp == buf) 2735 *bufp = buf->b_next; 2736 2737 /* 2738 * If we've removed a buffer in the middle of 2739 * the list then update the lastbuf and update 2740 * bufp. 2741 */ 2742 if (*bufp != NULL) { 2743 lastbuf = *bufp; 2744 bufp = &(*bufp)->b_next; 2745 } 2746 } 2747 buf->b_next = NULL; 2748 ASSERT3P(lastbuf, !=, buf); 2749 2750 /* 2751 * If the current arc_buf_t is sharing its data 2752 * buffer with the hdr, then reassign the hdr's 2753 * b_pdata to share it with the new buffer at the end 2754 * of the list. The shared buffer is always the last one 2755 * on the hdr's buffer list. 2756 */ 2757 if (destroyed_buf_is_shared && lastbuf != NULL) { 2758 ASSERT(ARC_BUF_LAST(buf)); 2759 ASSERT(ARC_BUF_LAST(lastbuf)); 2760 VERIFY(!arc_buf_is_shared(lastbuf)); 2761 2762 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2763 arc_hdr_free_pdata(hdr); 2764 2765 /* 2766 * We must setup a new shared block between the 2767 * last buffer and the hdr. The data would have 2768 * been allocated by the arc buf so we need to transfer 2769 * ownership to the hdr since it's now being shared. 2770 */ 2771 arc_share_buf(hdr, lastbuf); 2772 } else if (HDR_SHARED_DATA(hdr)) { 2773 ASSERT(arc_buf_is_shared(lastbuf)); 2774 } 2775 2776 if (hdr->b_l1hdr.b_bufcnt == 0) 2777 arc_cksum_free(hdr); 2778 2779 /* clean up the buf */ 2780 buf->b_hdr = NULL; 2781 kmem_cache_free(buf_cache, buf); 2782} 2783 2784static void 2785arc_hdr_alloc_pdata(arc_buf_hdr_t *hdr) 2786{ 2787 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2788 ASSERT(HDR_HAS_L1HDR(hdr)); 2789 ASSERT(!HDR_SHARED_DATA(hdr)); 2790 2791 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2792 hdr->b_l1hdr.b_pdata = arc_get_data_buf(hdr, arc_hdr_size(hdr), hdr); 2793 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 2794 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2795 2796 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2797 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 2798} 2799 2800static void 2801arc_hdr_free_pdata(arc_buf_hdr_t *hdr) 2802{ 2803 ASSERT(HDR_HAS_L1HDR(hdr)); 2804 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 2805 2806 /* 2807 * If the hdr is currently being written to the l2arc then 2808 * we defer freeing the data by adding it to the l2arc_free_on_write 2809 * list. The l2arc will free the data once it's finished 2810 * writing it to the l2arc device. 2811 */ 2812 if (HDR_L2_WRITING(hdr)) { 2813 arc_hdr_free_on_write(hdr); 2814 ARCSTAT_BUMP(arcstat_l2_free_on_write); 2815 } else { 2816 arc_free_data_buf(hdr, hdr->b_l1hdr.b_pdata, 2817 arc_hdr_size(hdr), hdr); 2818 } 2819 hdr->b_l1hdr.b_pdata = NULL; 2820 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 2821 2822 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2823 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2824} 2825 2826static arc_buf_hdr_t * 2827arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 2828 enum zio_compress compress, arc_buf_contents_t type) 2829{ 2830 arc_buf_hdr_t *hdr; 2831 2832 ASSERT3U(lsize, >, 0); 2833 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 2834 2835 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 2836 ASSERT(HDR_EMPTY(hdr)); 2837 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 2838 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 2839 HDR_SET_PSIZE(hdr, psize); 2840 HDR_SET_LSIZE(hdr, lsize); 2841 hdr->b_spa = spa; 2842 hdr->b_type = type; 2843 hdr->b_flags = 0; 2844 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 2845 arc_hdr_set_compress(hdr, compress); 2846 2847 hdr->b_l1hdr.b_state = arc_anon; 2848 hdr->b_l1hdr.b_arc_access = 0; 2849 hdr->b_l1hdr.b_bufcnt = 0; 2850 hdr->b_l1hdr.b_buf = NULL; 2851 2852 /* 2853 * Allocate the hdr's buffer. This will contain either 2854 * the compressed or uncompressed data depending on the block 2855 * it references and compressed arc enablement. 2856 */ 2857 arc_hdr_alloc_pdata(hdr); 2858 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2859 2860 return (hdr); 2861} 2862 2863/* 2864 * Transition between the two allocation states for the arc_buf_hdr struct. 2865 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 2866 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 2867 * version is used when a cache buffer is only in the L2ARC in order to reduce 2868 * memory usage. 2869 */ 2870static arc_buf_hdr_t * 2871arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 2872{ 2873 ASSERT(HDR_HAS_L2HDR(hdr)); 2874 2875 arc_buf_hdr_t *nhdr; 2876 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 2877 2878 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 2879 (old == hdr_l2only_cache && new == hdr_full_cache)); 2880 2881 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 2882 2883 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 2884 buf_hash_remove(hdr); 2885 2886 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 2887 2888 if (new == hdr_full_cache) { 2889 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 2890 /* 2891 * arc_access and arc_change_state need to be aware that a 2892 * header has just come out of L2ARC, so we set its state to 2893 * l2c_only even though it's about to change. 2894 */ 2895 nhdr->b_l1hdr.b_state = arc_l2c_only; 2896 2897 /* Verify previous threads set to NULL before freeing */ 2898 ASSERT3P(nhdr->b_l1hdr.b_pdata, ==, NULL); 2899 } else { 2900 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2901 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2902 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 2903 2904 /* 2905 * If we've reached here, We must have been called from 2906 * arc_evict_hdr(), as such we should have already been 2907 * removed from any ghost list we were previously on 2908 * (which protects us from racing with arc_evict_state), 2909 * thus no locking is needed during this check. 2910 */ 2911 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 2912 2913 /* 2914 * A buffer must not be moved into the arc_l2c_only 2915 * state if it's not finished being written out to the 2916 * l2arc device. Otherwise, the b_l1hdr.b_pdata field 2917 * might try to be accessed, even though it was removed. 2918 */ 2919 VERIFY(!HDR_L2_WRITING(hdr)); 2920 VERIFY3P(hdr->b_l1hdr.b_pdata, ==, NULL); 2921 2922#ifdef ZFS_DEBUG 2923 if (hdr->b_l1hdr.b_thawed != NULL) { 2924 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2925 hdr->b_l1hdr.b_thawed = NULL; 2926 } 2927#endif 2928 2929 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 2930 } 2931 /* 2932 * The header has been reallocated so we need to re-insert it into any 2933 * lists it was on. 2934 */ 2935 (void) buf_hash_insert(nhdr, NULL); 2936 2937 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 2938 2939 mutex_enter(&dev->l2ad_mtx); 2940 2941 /* 2942 * We must place the realloc'ed header back into the list at 2943 * the same spot. Otherwise, if it's placed earlier in the list, 2944 * l2arc_write_buffers() could find it during the function's 2945 * write phase, and try to write it out to the l2arc. 2946 */ 2947 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 2948 list_remove(&dev->l2ad_buflist, hdr); 2949 2950 mutex_exit(&dev->l2ad_mtx); 2951 2952 /* 2953 * Since we're using the pointer address as the tag when 2954 * incrementing and decrementing the l2ad_alloc refcount, we 2955 * must remove the old pointer (that we're about to destroy) and 2956 * add the new pointer to the refcount. Otherwise we'd remove 2957 * the wrong pointer address when calling arc_hdr_destroy() later. 2958 */ 2959 2960 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 2961 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 2962 2963 buf_discard_identity(hdr); 2964 kmem_cache_free(old, hdr); 2965 2966 return (nhdr); 2967} 2968 2969/* 2970 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 2971 * The buf is returned thawed since we expect the consumer to modify it. 2972 */ 2973arc_buf_t * 2974arc_alloc_buf(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type) 2975{ 2976 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 2977 ZIO_COMPRESS_OFF, type); 2978 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 2979 arc_buf_t *buf = arc_buf_alloc_impl(hdr, tag); 2980 arc_buf_thaw(buf); 2981 return (buf); 2982} 2983 2984static void 2985arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 2986{ 2987 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 2988 l2arc_dev_t *dev = l2hdr->b_dev; 2989 uint64_t asize = arc_hdr_size(hdr); 2990 2991 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 2992 ASSERT(HDR_HAS_L2HDR(hdr)); 2993 2994 list_remove(&dev->l2ad_buflist, hdr); 2995 2996 ARCSTAT_INCR(arcstat_l2_asize, -asize); 2997 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 2998 2999 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0); 3000 3001 (void) refcount_remove_many(&dev->l2ad_alloc, asize, hdr); 3002 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3003} 3004 3005static void 3006arc_hdr_destroy(arc_buf_hdr_t *hdr) 3007{ 3008 if (HDR_HAS_L1HDR(hdr)) { 3009 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3010 hdr->b_l1hdr.b_bufcnt > 0); 3011 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3012 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3013 } 3014 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3015 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3016 3017 if (!HDR_EMPTY(hdr)) 3018 buf_discard_identity(hdr); 3019 3020 if (HDR_HAS_L2HDR(hdr)) { 3021 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3022 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3023 3024 if (!buflist_held) 3025 mutex_enter(&dev->l2ad_mtx); 3026 3027 /* 3028 * Even though we checked this conditional above, we 3029 * need to check this again now that we have the 3030 * l2ad_mtx. This is because we could be racing with 3031 * another thread calling l2arc_evict() which might have 3032 * destroyed this header's L2 portion as we were waiting 3033 * to acquire the l2ad_mtx. If that happens, we don't 3034 * want to re-destroy the header's L2 portion. 3035 */ 3036 if (HDR_HAS_L2HDR(hdr)) { 3037 l2arc_trim(hdr); 3038 arc_hdr_l2hdr_destroy(hdr); 3039 } 3040 3041 if (!buflist_held) 3042 mutex_exit(&dev->l2ad_mtx); 3043 } 3044 3045 if (HDR_HAS_L1HDR(hdr)) { 3046 arc_cksum_free(hdr); 3047 3048 while (hdr->b_l1hdr.b_buf != NULL) 3049 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf, B_TRUE); 3050 3051#ifdef ZFS_DEBUG 3052 if (hdr->b_l1hdr.b_thawed != NULL) { 3053 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3054 hdr->b_l1hdr.b_thawed = NULL; 3055 } 3056#endif 3057 3058 if (hdr->b_l1hdr.b_pdata != NULL) { 3059 arc_hdr_free_pdata(hdr); 3060 } 3061 } 3062 3063 ASSERT3P(hdr->b_hash_next, ==, NULL); 3064 if (HDR_HAS_L1HDR(hdr)) { 3065 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3066 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3067 kmem_cache_free(hdr_full_cache, hdr); 3068 } else { 3069 kmem_cache_free(hdr_l2only_cache, hdr); 3070 } 3071} 3072 3073void 3074arc_buf_destroy(arc_buf_t *buf, void* tag) 3075{ 3076 arc_buf_hdr_t *hdr = buf->b_hdr; 3077 kmutex_t *hash_lock = HDR_LOCK(hdr); 3078 3079 if (hdr->b_l1hdr.b_state == arc_anon) { 3080 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3081 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3082 VERIFY0(remove_reference(hdr, NULL, tag)); 3083 arc_hdr_destroy(hdr); 3084 return; 3085 } 3086 3087 mutex_enter(hash_lock); 3088 ASSERT3P(hdr, ==, buf->b_hdr); 3089 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3090 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3091 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3092 ASSERT3P(buf->b_data, !=, NULL); 3093 3094 (void) remove_reference(hdr, hash_lock, tag); 3095 arc_buf_destroy_impl(buf, B_TRUE); 3096 mutex_exit(hash_lock); 3097} 3098 3099int32_t 3100arc_buf_size(arc_buf_t *buf) 3101{ 3102 return (HDR_GET_LSIZE(buf->b_hdr)); 3103} 3104 3105/* 3106 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3107 * state of the header is dependent on it's state prior to entering this 3108 * function. The following transitions are possible: 3109 * 3110 * - arc_mru -> arc_mru_ghost 3111 * - arc_mfu -> arc_mfu_ghost 3112 * - arc_mru_ghost -> arc_l2c_only 3113 * - arc_mru_ghost -> deleted 3114 * - arc_mfu_ghost -> arc_l2c_only 3115 * - arc_mfu_ghost -> deleted 3116 */ 3117static int64_t 3118arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3119{ 3120 arc_state_t *evicted_state, *state; 3121 int64_t bytes_evicted = 0; 3122 3123 ASSERT(MUTEX_HELD(hash_lock)); 3124 ASSERT(HDR_HAS_L1HDR(hdr)); 3125 3126 state = hdr->b_l1hdr.b_state; 3127 if (GHOST_STATE(state)) { 3128 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3129 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3130 3131 /* 3132 * l2arc_write_buffers() relies on a header's L1 portion 3133 * (i.e. its b_pdata field) during its write phase. 3134 * Thus, we cannot push a header onto the arc_l2c_only 3135 * state (removing it's L1 piece) until the header is 3136 * done being written to the l2arc. 3137 */ 3138 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3139 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3140 return (bytes_evicted); 3141 } 3142 3143 ARCSTAT_BUMP(arcstat_deleted); 3144 bytes_evicted += HDR_GET_LSIZE(hdr); 3145 3146 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3147 3148 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 3149 if (HDR_HAS_L2HDR(hdr)) { 3150 ASSERT(hdr->b_l1hdr.b_pdata == NULL); 3151 /* 3152 * This buffer is cached on the 2nd Level ARC; 3153 * don't destroy the header. 3154 */ 3155 arc_change_state(arc_l2c_only, hdr, hash_lock); 3156 /* 3157 * dropping from L1+L2 cached to L2-only, 3158 * realloc to remove the L1 header. 3159 */ 3160 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3161 hdr_l2only_cache); 3162 } else { 3163 ASSERT(hdr->b_l1hdr.b_pdata == NULL); 3164 arc_change_state(arc_anon, hdr, hash_lock); 3165 arc_hdr_destroy(hdr); 3166 } 3167 return (bytes_evicted); 3168 } 3169 3170 ASSERT(state == arc_mru || state == arc_mfu); 3171 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3172 3173 /* prefetch buffers have a minimum lifespan */ 3174 if (HDR_IO_IN_PROGRESS(hdr) || 3175 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3176 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 3177 arc_min_prefetch_lifespan)) { 3178 ARCSTAT_BUMP(arcstat_evict_skip); 3179 return (bytes_evicted); 3180 } 3181 3182 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3183 while (hdr->b_l1hdr.b_buf) { 3184 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3185 if (!mutex_tryenter(&buf->b_evict_lock)) { 3186 ARCSTAT_BUMP(arcstat_mutex_miss); 3187 break; 3188 } 3189 if (buf->b_data != NULL) 3190 bytes_evicted += HDR_GET_LSIZE(hdr); 3191 mutex_exit(&buf->b_evict_lock); 3192 arc_buf_destroy_impl(buf, B_TRUE); 3193 } 3194 3195 if (HDR_HAS_L2HDR(hdr)) { 3196 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3197 } else { 3198 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3199 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3200 HDR_GET_LSIZE(hdr)); 3201 } else { 3202 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3203 HDR_GET_LSIZE(hdr)); 3204 } 3205 } 3206 3207 if (hdr->b_l1hdr.b_bufcnt == 0) { 3208 arc_cksum_free(hdr); 3209 3210 bytes_evicted += arc_hdr_size(hdr); 3211 3212 /* 3213 * If this hdr is being evicted and has a compressed 3214 * buffer then we discard it here before we change states. 3215 * This ensures that the accounting is updated correctly 3216 * in arc_free_data_buf(). 3217 */ 3218 arc_hdr_free_pdata(hdr); 3219 3220 arc_change_state(evicted_state, hdr, hash_lock); 3221 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3222 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3223 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3224 } 3225 3226 return (bytes_evicted); 3227} 3228 3229static uint64_t 3230arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3231 uint64_t spa, int64_t bytes) 3232{ 3233 multilist_sublist_t *mls; 3234 uint64_t bytes_evicted = 0; 3235 arc_buf_hdr_t *hdr; 3236 kmutex_t *hash_lock; 3237 int evict_count = 0; 3238 3239 ASSERT3P(marker, !=, NULL); 3240 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3241 3242 mls = multilist_sublist_lock(ml, idx); 3243 3244 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3245 hdr = multilist_sublist_prev(mls, marker)) { 3246 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3247 (evict_count >= zfs_arc_evict_batch_limit)) 3248 break; 3249 3250 /* 3251 * To keep our iteration location, move the marker 3252 * forward. Since we're not holding hdr's hash lock, we 3253 * must be very careful and not remove 'hdr' from the 3254 * sublist. Otherwise, other consumers might mistake the 3255 * 'hdr' as not being on a sublist when they call the 3256 * multilist_link_active() function (they all rely on 3257 * the hash lock protecting concurrent insertions and 3258 * removals). multilist_sublist_move_forward() was 3259 * specifically implemented to ensure this is the case 3260 * (only 'marker' will be removed and re-inserted). 3261 */ 3262 multilist_sublist_move_forward(mls, marker); 3263 3264 /* 3265 * The only case where the b_spa field should ever be 3266 * zero, is the marker headers inserted by 3267 * arc_evict_state(). It's possible for multiple threads 3268 * to be calling arc_evict_state() concurrently (e.g. 3269 * dsl_pool_close() and zio_inject_fault()), so we must 3270 * skip any markers we see from these other threads. 3271 */ 3272 if (hdr->b_spa == 0) 3273 continue; 3274 3275 /* we're only interested in evicting buffers of a certain spa */ 3276 if (spa != 0 && hdr->b_spa != spa) { 3277 ARCSTAT_BUMP(arcstat_evict_skip); 3278 continue; 3279 } 3280 3281 hash_lock = HDR_LOCK(hdr); 3282 3283 /* 3284 * We aren't calling this function from any code path 3285 * that would already be holding a hash lock, so we're 3286 * asserting on this assumption to be defensive in case 3287 * this ever changes. Without this check, it would be 3288 * possible to incorrectly increment arcstat_mutex_miss 3289 * below (e.g. if the code changed such that we called 3290 * this function with a hash lock held). 3291 */ 3292 ASSERT(!MUTEX_HELD(hash_lock)); 3293 3294 if (mutex_tryenter(hash_lock)) { 3295 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3296 mutex_exit(hash_lock); 3297 3298 bytes_evicted += evicted; 3299 3300 /* 3301 * If evicted is zero, arc_evict_hdr() must have 3302 * decided to skip this header, don't increment 3303 * evict_count in this case. 3304 */ 3305 if (evicted != 0) 3306 evict_count++; 3307 3308 /* 3309 * If arc_size isn't overflowing, signal any 3310 * threads that might happen to be waiting. 3311 * 3312 * For each header evicted, we wake up a single 3313 * thread. If we used cv_broadcast, we could 3314 * wake up "too many" threads causing arc_size 3315 * to significantly overflow arc_c; since 3316 * arc_get_data_buf() doesn't check for overflow 3317 * when it's woken up (it doesn't because it's 3318 * possible for the ARC to be overflowing while 3319 * full of un-evictable buffers, and the 3320 * function should proceed in this case). 3321 * 3322 * If threads are left sleeping, due to not 3323 * using cv_broadcast, they will be woken up 3324 * just before arc_reclaim_thread() sleeps. 3325 */ 3326 mutex_enter(&arc_reclaim_lock); 3327 if (!arc_is_overflowing()) 3328 cv_signal(&arc_reclaim_waiters_cv); 3329 mutex_exit(&arc_reclaim_lock); 3330 } else { 3331 ARCSTAT_BUMP(arcstat_mutex_miss); 3332 } 3333 } 3334 3335 multilist_sublist_unlock(mls); 3336 3337 return (bytes_evicted); 3338} 3339 3340/* 3341 * Evict buffers from the given arc state, until we've removed the 3342 * specified number of bytes. Move the removed buffers to the 3343 * appropriate evict state. 3344 * 3345 * This function makes a "best effort". It skips over any buffers 3346 * it can't get a hash_lock on, and so, may not catch all candidates. 3347 * It may also return without evicting as much space as requested. 3348 * 3349 * If bytes is specified using the special value ARC_EVICT_ALL, this 3350 * will evict all available (i.e. unlocked and evictable) buffers from 3351 * the given arc state; which is used by arc_flush(). 3352 */ 3353static uint64_t 3354arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3355 arc_buf_contents_t type) 3356{ 3357 uint64_t total_evicted = 0; 3358 multilist_t *ml = &state->arcs_list[type]; 3359 int num_sublists; 3360 arc_buf_hdr_t **markers; 3361 3362 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3363 3364 num_sublists = multilist_get_num_sublists(ml); 3365 3366 /* 3367 * If we've tried to evict from each sublist, made some 3368 * progress, but still have not hit the target number of bytes 3369 * to evict, we want to keep trying. The markers allow us to 3370 * pick up where we left off for each individual sublist, rather 3371 * than starting from the tail each time. 3372 */ 3373 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3374 for (int i = 0; i < num_sublists; i++) { 3375 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3376 3377 /* 3378 * A b_spa of 0 is used to indicate that this header is 3379 * a marker. This fact is used in arc_adjust_type() and 3380 * arc_evict_state_impl(). 3381 */ 3382 markers[i]->b_spa = 0; 3383 3384 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3385 multilist_sublist_insert_tail(mls, markers[i]); 3386 multilist_sublist_unlock(mls); 3387 } 3388 3389 /* 3390 * While we haven't hit our target number of bytes to evict, or 3391 * we're evicting all available buffers. 3392 */ 3393 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3394 /* 3395 * Start eviction using a randomly selected sublist, 3396 * this is to try and evenly balance eviction across all 3397 * sublists. Always starting at the same sublist 3398 * (e.g. index 0) would cause evictions to favor certain 3399 * sublists over others. 3400 */ 3401 int sublist_idx = multilist_get_random_index(ml); 3402 uint64_t scan_evicted = 0; 3403 3404 for (int i = 0; i < num_sublists; i++) { 3405 uint64_t bytes_remaining; 3406 uint64_t bytes_evicted; 3407 3408 if (bytes == ARC_EVICT_ALL) 3409 bytes_remaining = ARC_EVICT_ALL; 3410 else if (total_evicted < bytes) 3411 bytes_remaining = bytes - total_evicted; 3412 else 3413 break; 3414 3415 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3416 markers[sublist_idx], spa, bytes_remaining); 3417 3418 scan_evicted += bytes_evicted; 3419 total_evicted += bytes_evicted; 3420 3421 /* we've reached the end, wrap to the beginning */ 3422 if (++sublist_idx >= num_sublists) 3423 sublist_idx = 0; 3424 } 3425 3426 /* 3427 * If we didn't evict anything during this scan, we have 3428 * no reason to believe we'll evict more during another 3429 * scan, so break the loop. 3430 */ 3431 if (scan_evicted == 0) { 3432 /* This isn't possible, let's make that obvious */ 3433 ASSERT3S(bytes, !=, 0); 3434 3435 /* 3436 * When bytes is ARC_EVICT_ALL, the only way to 3437 * break the loop is when scan_evicted is zero. 3438 * In that case, we actually have evicted enough, 3439 * so we don't want to increment the kstat. 3440 */ 3441 if (bytes != ARC_EVICT_ALL) { 3442 ASSERT3S(total_evicted, <, bytes); 3443 ARCSTAT_BUMP(arcstat_evict_not_enough); 3444 } 3445 3446 break; 3447 } 3448 } 3449 3450 for (int i = 0; i < num_sublists; i++) { 3451 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3452 multilist_sublist_remove(mls, markers[i]); 3453 multilist_sublist_unlock(mls); 3454 3455 kmem_cache_free(hdr_full_cache, markers[i]); 3456 } 3457 kmem_free(markers, sizeof (*markers) * num_sublists); 3458 3459 return (total_evicted); 3460} 3461 3462/* 3463 * Flush all "evictable" data of the given type from the arc state 3464 * specified. This will not evict any "active" buffers (i.e. referenced). 3465 * 3466 * When 'retry' is set to B_FALSE, the function will make a single pass 3467 * over the state and evict any buffers that it can. Since it doesn't 3468 * continually retry the eviction, it might end up leaving some buffers 3469 * in the ARC due to lock misses. 3470 * 3471 * When 'retry' is set to B_TRUE, the function will continually retry the 3472 * eviction until *all* evictable buffers have been removed from the 3473 * state. As a result, if concurrent insertions into the state are 3474 * allowed (e.g. if the ARC isn't shutting down), this function might 3475 * wind up in an infinite loop, continually trying to evict buffers. 3476 */ 3477static uint64_t 3478arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3479 boolean_t retry) 3480{ 3481 uint64_t evicted = 0; 3482 3483 while (refcount_count(&state->arcs_esize[type]) != 0) { 3484 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3485 3486 if (!retry) 3487 break; 3488 } 3489 3490 return (evicted); 3491} 3492 3493/* 3494 * Evict the specified number of bytes from the state specified, 3495 * restricting eviction to the spa and type given. This function 3496 * prevents us from trying to evict more from a state's list than 3497 * is "evictable", and to skip evicting altogether when passed a 3498 * negative value for "bytes". In contrast, arc_evict_state() will 3499 * evict everything it can, when passed a negative value for "bytes". 3500 */ 3501static uint64_t 3502arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3503 arc_buf_contents_t type) 3504{ 3505 int64_t delta; 3506 3507 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3508 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3509 return (arc_evict_state(state, spa, delta, type)); 3510 } 3511 3512 return (0); 3513} 3514 3515/* 3516 * Evict metadata buffers from the cache, such that arc_meta_used is 3517 * capped by the arc_meta_limit tunable. 3518 */ 3519static uint64_t 3520arc_adjust_meta(void) 3521{ 3522 uint64_t total_evicted = 0; 3523 int64_t target; 3524 3525 /* 3526 * If we're over the meta limit, we want to evict enough 3527 * metadata to get back under the meta limit. We don't want to 3528 * evict so much that we drop the MRU below arc_p, though. If 3529 * we're over the meta limit more than we're over arc_p, we 3530 * evict some from the MRU here, and some from the MFU below. 3531 */ 3532 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3533 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3534 refcount_count(&arc_mru->arcs_size) - arc_p)); 3535 3536 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3537 3538 /* 3539 * Similar to the above, we want to evict enough bytes to get us 3540 * below the meta limit, but not so much as to drop us below the 3541 * space alloted to the MFU (which is defined as arc_c - arc_p). 3542 */ 3543 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3544 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3545 3546 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3547 3548 return (total_evicted); 3549} 3550 3551/* 3552 * Return the type of the oldest buffer in the given arc state 3553 * 3554 * This function will select a random sublist of type ARC_BUFC_DATA and 3555 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3556 * is compared, and the type which contains the "older" buffer will be 3557 * returned. 3558 */ 3559static arc_buf_contents_t 3560arc_adjust_type(arc_state_t *state) 3561{ 3562 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA]; 3563 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA]; 3564 int data_idx = multilist_get_random_index(data_ml); 3565 int meta_idx = multilist_get_random_index(meta_ml); 3566 multilist_sublist_t *data_mls; 3567 multilist_sublist_t *meta_mls; 3568 arc_buf_contents_t type; 3569 arc_buf_hdr_t *data_hdr; 3570 arc_buf_hdr_t *meta_hdr; 3571 3572 /* 3573 * We keep the sublist lock until we're finished, to prevent 3574 * the headers from being destroyed via arc_evict_state(). 3575 */ 3576 data_mls = multilist_sublist_lock(data_ml, data_idx); 3577 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3578 3579 /* 3580 * These two loops are to ensure we skip any markers that 3581 * might be at the tail of the lists due to arc_evict_state(). 3582 */ 3583 3584 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3585 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3586 if (data_hdr->b_spa != 0) 3587 break; 3588 } 3589 3590 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3591 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3592 if (meta_hdr->b_spa != 0) 3593 break; 3594 } 3595 3596 if (data_hdr == NULL && meta_hdr == NULL) { 3597 type = ARC_BUFC_DATA; 3598 } else if (data_hdr == NULL) { 3599 ASSERT3P(meta_hdr, !=, NULL); 3600 type = ARC_BUFC_METADATA; 3601 } else if (meta_hdr == NULL) { 3602 ASSERT3P(data_hdr, !=, NULL); 3603 type = ARC_BUFC_DATA; 3604 } else { 3605 ASSERT3P(data_hdr, !=, NULL); 3606 ASSERT3P(meta_hdr, !=, NULL); 3607 3608 /* The headers can't be on the sublist without an L1 header */ 3609 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3610 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3611 3612 if (data_hdr->b_l1hdr.b_arc_access < 3613 meta_hdr->b_l1hdr.b_arc_access) { 3614 type = ARC_BUFC_DATA; 3615 } else { 3616 type = ARC_BUFC_METADATA; 3617 } 3618 } 3619 3620 multilist_sublist_unlock(meta_mls); 3621 multilist_sublist_unlock(data_mls); 3622 3623 return (type); 3624} 3625 3626/* 3627 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3628 */ 3629static uint64_t 3630arc_adjust(void) 3631{ 3632 uint64_t total_evicted = 0; 3633 uint64_t bytes; 3634 int64_t target; 3635 3636 /* 3637 * If we're over arc_meta_limit, we want to correct that before 3638 * potentially evicting data buffers below. 3639 */ 3640 total_evicted += arc_adjust_meta(); 3641 3642 /* 3643 * Adjust MRU size 3644 * 3645 * If we're over the target cache size, we want to evict enough 3646 * from the list to get back to our target size. We don't want 3647 * to evict too much from the MRU, such that it drops below 3648 * arc_p. So, if we're over our target cache size more than 3649 * the MRU is over arc_p, we'll evict enough to get back to 3650 * arc_p here, and then evict more from the MFU below. 3651 */ 3652 target = MIN((int64_t)(arc_size - arc_c), 3653 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3654 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3655 3656 /* 3657 * If we're below arc_meta_min, always prefer to evict data. 3658 * Otherwise, try to satisfy the requested number of bytes to 3659 * evict from the type which contains older buffers; in an 3660 * effort to keep newer buffers in the cache regardless of their 3661 * type. If we cannot satisfy the number of bytes from this 3662 * type, spill over into the next type. 3663 */ 3664 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 3665 arc_meta_used > arc_meta_min) { 3666 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3667 total_evicted += bytes; 3668 3669 /* 3670 * If we couldn't evict our target number of bytes from 3671 * metadata, we try to get the rest from data. 3672 */ 3673 target -= bytes; 3674 3675 total_evicted += 3676 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3677 } else { 3678 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 3679 total_evicted += bytes; 3680 3681 /* 3682 * If we couldn't evict our target number of bytes from 3683 * data, we try to get the rest from metadata. 3684 */ 3685 target -= bytes; 3686 3687 total_evicted += 3688 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3689 } 3690 3691 /* 3692 * Adjust MFU size 3693 * 3694 * Now that we've tried to evict enough from the MRU to get its 3695 * size back to arc_p, if we're still above the target cache 3696 * size, we evict the rest from the MFU. 3697 */ 3698 target = arc_size - arc_c; 3699 3700 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 3701 arc_meta_used > arc_meta_min) { 3702 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3703 total_evicted += bytes; 3704 3705 /* 3706 * If we couldn't evict our target number of bytes from 3707 * metadata, we try to get the rest from data. 3708 */ 3709 target -= bytes; 3710 3711 total_evicted += 3712 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3713 } else { 3714 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 3715 total_evicted += bytes; 3716 3717 /* 3718 * If we couldn't evict our target number of bytes from 3719 * data, we try to get the rest from data. 3720 */ 3721 target -= bytes; 3722 3723 total_evicted += 3724 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3725 } 3726 3727 /* 3728 * Adjust ghost lists 3729 * 3730 * In addition to the above, the ARC also defines target values 3731 * for the ghost lists. The sum of the mru list and mru ghost 3732 * list should never exceed the target size of the cache, and 3733 * the sum of the mru list, mfu list, mru ghost list, and mfu 3734 * ghost list should never exceed twice the target size of the 3735 * cache. The following logic enforces these limits on the ghost 3736 * caches, and evicts from them as needed. 3737 */ 3738 target = refcount_count(&arc_mru->arcs_size) + 3739 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 3740 3741 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 3742 total_evicted += bytes; 3743 3744 target -= bytes; 3745 3746 total_evicted += 3747 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 3748 3749 /* 3750 * We assume the sum of the mru list and mfu list is less than 3751 * or equal to arc_c (we enforced this above), which means we 3752 * can use the simpler of the two equations below: 3753 * 3754 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 3755 * mru ghost + mfu ghost <= arc_c 3756 */ 3757 target = refcount_count(&arc_mru_ghost->arcs_size) + 3758 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 3759 3760 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 3761 total_evicted += bytes; 3762 3763 target -= bytes; 3764 3765 total_evicted += 3766 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 3767 3768 return (total_evicted); 3769} 3770 3771void 3772arc_flush(spa_t *spa, boolean_t retry) 3773{ 3774 uint64_t guid = 0; 3775 3776 /* 3777 * If retry is B_TRUE, a spa must not be specified since we have 3778 * no good way to determine if all of a spa's buffers have been 3779 * evicted from an arc state. 3780 */ 3781 ASSERT(!retry || spa == 0); 3782 3783 if (spa != NULL) 3784 guid = spa_load_guid(spa); 3785 3786 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 3787 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 3788 3789 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 3790 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 3791 3792 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 3793 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 3794 3795 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 3796 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 3797} 3798 3799void 3800arc_shrink(int64_t to_free) 3801{ 3802 if (arc_c > arc_c_min) { 3803 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 3804 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 3805 if (arc_c > arc_c_min + to_free) 3806 atomic_add_64(&arc_c, -to_free); 3807 else 3808 arc_c = arc_c_min; 3809 3810 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 3811 if (arc_c > arc_size) 3812 arc_c = MAX(arc_size, arc_c_min); 3813 if (arc_p > arc_c) 3814 arc_p = (arc_c >> 1); 3815 3816 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 3817 arc_p); 3818 3819 ASSERT(arc_c >= arc_c_min); 3820 ASSERT((int64_t)arc_p >= 0); 3821 } 3822 3823 if (arc_size > arc_c) { 3824 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 3825 uint64_t, arc_c); 3826 (void) arc_adjust(); 3827 } 3828} 3829 3830static long needfree = 0; 3831 3832typedef enum free_memory_reason_t { 3833 FMR_UNKNOWN, 3834 FMR_NEEDFREE, 3835 FMR_LOTSFREE, 3836 FMR_SWAPFS_MINFREE, 3837 FMR_PAGES_PP_MAXIMUM, 3838 FMR_HEAP_ARENA, 3839 FMR_ZIO_ARENA, 3840 FMR_ZIO_FRAG, 3841} free_memory_reason_t; 3842 3843int64_t last_free_memory; 3844free_memory_reason_t last_free_reason; 3845 3846/* 3847 * Additional reserve of pages for pp_reserve. 3848 */ 3849int64_t arc_pages_pp_reserve = 64; 3850 3851/* 3852 * Additional reserve of pages for swapfs. 3853 */ 3854int64_t arc_swapfs_reserve = 64; 3855 3856/* 3857 * Return the amount of memory that can be consumed before reclaim will be 3858 * needed. Positive if there is sufficient free memory, negative indicates 3859 * the amount of memory that needs to be freed up. 3860 */ 3861static int64_t 3862arc_available_memory(void) 3863{ 3864 int64_t lowest = INT64_MAX; 3865 int64_t n; 3866 free_memory_reason_t r = FMR_UNKNOWN; 3867 3868#ifdef _KERNEL 3869 if (needfree > 0) { 3870 n = PAGESIZE * (-needfree); 3871 if (n < lowest) { 3872 lowest = n; 3873 r = FMR_NEEDFREE; 3874 } 3875 } 3876 3877 /* 3878 * Cooperate with pagedaemon when it's time for it to scan 3879 * and reclaim some pages. 3880 */ 3881 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 3882 if (n < lowest) { 3883 lowest = n; 3884 r = FMR_LOTSFREE; 3885 } 3886 3887#ifdef illumos 3888 /* 3889 * check that we're out of range of the pageout scanner. It starts to 3890 * schedule paging if freemem is less than lotsfree and needfree. 3891 * lotsfree is the high-water mark for pageout, and needfree is the 3892 * number of needed free pages. We add extra pages here to make sure 3893 * the scanner doesn't start up while we're freeing memory. 3894 */ 3895 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 3896 if (n < lowest) { 3897 lowest = n; 3898 r = FMR_LOTSFREE; 3899 } 3900 3901 /* 3902 * check to make sure that swapfs has enough space so that anon 3903 * reservations can still succeed. anon_resvmem() checks that the 3904 * availrmem is greater than swapfs_minfree, and the number of reserved 3905 * swap pages. We also add a bit of extra here just to prevent 3906 * circumstances from getting really dire. 3907 */ 3908 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 3909 desfree - arc_swapfs_reserve); 3910 if (n < lowest) { 3911 lowest = n; 3912 r = FMR_SWAPFS_MINFREE; 3913 } 3914 3915 3916 /* 3917 * Check that we have enough availrmem that memory locking (e.g., via 3918 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 3919 * stores the number of pages that cannot be locked; when availrmem 3920 * drops below pages_pp_maximum, page locking mechanisms such as 3921 * page_pp_lock() will fail.) 3922 */ 3923 n = PAGESIZE * (availrmem - pages_pp_maximum - 3924 arc_pages_pp_reserve); 3925 if (n < lowest) { 3926 lowest = n; 3927 r = FMR_PAGES_PP_MAXIMUM; 3928 } 3929 3930#endif /* illumos */ 3931#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 3932 /* 3933 * If we're on an i386 platform, it's possible that we'll exhaust the 3934 * kernel heap space before we ever run out of available physical 3935 * memory. Most checks of the size of the heap_area compare against 3936 * tune.t_minarmem, which is the minimum available real memory that we 3937 * can have in the system. However, this is generally fixed at 25 pages 3938 * which is so low that it's useless. In this comparison, we seek to 3939 * calculate the total heap-size, and reclaim if more than 3/4ths of the 3940 * heap is allocated. (Or, in the calculation, if less than 1/4th is 3941 * free) 3942 */ 3943 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 3944 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 3945 if (n < lowest) { 3946 lowest = n; 3947 r = FMR_HEAP_ARENA; 3948 } 3949#define zio_arena NULL 3950#else 3951#define zio_arena heap_arena 3952#endif 3953 3954 /* 3955 * If zio data pages are being allocated out of a separate heap segment, 3956 * then enforce that the size of available vmem for this arena remains 3957 * above about 1/16th free. 3958 * 3959 * Note: The 1/16th arena free requirement was put in place 3960 * to aggressively evict memory from the arc in order to avoid 3961 * memory fragmentation issues. 3962 */ 3963 if (zio_arena != NULL) { 3964 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 3965 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 3966 if (n < lowest) { 3967 lowest = n; 3968 r = FMR_ZIO_ARENA; 3969 } 3970 } 3971 3972 /* 3973 * Above limits know nothing about real level of KVA fragmentation. 3974 * Start aggressive reclamation if too little sequential KVA left. 3975 */ 3976 if (lowest > 0) { 3977 n = (vmem_size(heap_arena, VMEM_MAXFREE) < zfs_max_recordsize) ? 3978 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 3979 INT64_MAX; 3980 if (n < lowest) { 3981 lowest = n; 3982 r = FMR_ZIO_FRAG; 3983 } 3984 } 3985 3986#else /* _KERNEL */ 3987 /* Every 100 calls, free a small amount */ 3988 if (spa_get_random(100) == 0) 3989 lowest = -1024; 3990#endif /* _KERNEL */ 3991 3992 last_free_memory = lowest; 3993 last_free_reason = r; 3994 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 3995 return (lowest); 3996} 3997 3998 3999/* 4000 * Determine if the system is under memory pressure and is asking 4001 * to reclaim memory. A return value of B_TRUE indicates that the system 4002 * is under memory pressure and that the arc should adjust accordingly. 4003 */ 4004static boolean_t 4005arc_reclaim_needed(void) 4006{ 4007 return (arc_available_memory() < 0); 4008} 4009 4010extern kmem_cache_t *zio_buf_cache[]; 4011extern kmem_cache_t *zio_data_buf_cache[]; 4012extern kmem_cache_t *range_seg_cache; 4013 4014static __noinline void 4015arc_kmem_reap_now(void) 4016{ 4017 size_t i; 4018 kmem_cache_t *prev_cache = NULL; 4019 kmem_cache_t *prev_data_cache = NULL; 4020 4021 DTRACE_PROBE(arc__kmem_reap_start); 4022#ifdef _KERNEL 4023 if (arc_meta_used >= arc_meta_limit) { 4024 /* 4025 * We are exceeding our meta-data cache limit. 4026 * Purge some DNLC entries to release holds on meta-data. 4027 */ 4028 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4029 } 4030#if defined(__i386) 4031 /* 4032 * Reclaim unused memory from all kmem caches. 4033 */ 4034 kmem_reap(); 4035#endif 4036#endif 4037 4038 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4039 if (zio_buf_cache[i] != prev_cache) { 4040 prev_cache = zio_buf_cache[i]; 4041 kmem_cache_reap_now(zio_buf_cache[i]); 4042 } 4043 if (zio_data_buf_cache[i] != prev_data_cache) { 4044 prev_data_cache = zio_data_buf_cache[i]; 4045 kmem_cache_reap_now(zio_data_buf_cache[i]); 4046 } 4047 } 4048 kmem_cache_reap_now(buf_cache); 4049 kmem_cache_reap_now(hdr_full_cache); 4050 kmem_cache_reap_now(hdr_l2only_cache); 4051 kmem_cache_reap_now(range_seg_cache); 4052 4053#ifdef illumos 4054 if (zio_arena != NULL) { 4055 /* 4056 * Ask the vmem arena to reclaim unused memory from its 4057 * quantum caches. 4058 */ 4059 vmem_qcache_reap(zio_arena); 4060 } 4061#endif 4062 DTRACE_PROBE(arc__kmem_reap_end); 4063} 4064 4065/* 4066 * Threads can block in arc_get_data_buf() waiting for this thread to evict 4067 * enough data and signal them to proceed. When this happens, the threads in 4068 * arc_get_data_buf() are sleeping while holding the hash lock for their 4069 * particular arc header. Thus, we must be careful to never sleep on a 4070 * hash lock in this thread. This is to prevent the following deadlock: 4071 * 4072 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L", 4073 * waiting for the reclaim thread to signal it. 4074 * 4075 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4076 * fails, and goes to sleep forever. 4077 * 4078 * This possible deadlock is avoided by always acquiring a hash lock 4079 * using mutex_tryenter() from arc_reclaim_thread(). 4080 */ 4081static void 4082arc_reclaim_thread(void *dummy __unused) 4083{ 4084 hrtime_t growtime = 0; 4085 callb_cpr_t cpr; 4086 4087 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4088 4089 mutex_enter(&arc_reclaim_lock); 4090 while (!arc_reclaim_thread_exit) { 4091 int64_t free_memory = arc_available_memory(); 4092 uint64_t evicted = 0; 4093 4094 /* 4095 * This is necessary in order for the mdb ::arc dcmd to 4096 * show up to date information. Since the ::arc command 4097 * does not call the kstat's update function, without 4098 * this call, the command may show stale stats for the 4099 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4100 * with this change, the data might be up to 1 second 4101 * out of date; but that should suffice. The arc_state_t 4102 * structures can be queried directly if more accurate 4103 * information is needed. 4104 */ 4105 if (arc_ksp != NULL) 4106 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4107 4108 mutex_exit(&arc_reclaim_lock); 4109 4110 if (free_memory < 0) { 4111 4112 arc_no_grow = B_TRUE; 4113 arc_warm = B_TRUE; 4114 4115 /* 4116 * Wait at least zfs_grow_retry (default 60) seconds 4117 * before considering growing. 4118 */ 4119 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 4120 4121 arc_kmem_reap_now(); 4122 4123 /* 4124 * If we are still low on memory, shrink the ARC 4125 * so that we have arc_shrink_min free space. 4126 */ 4127 free_memory = arc_available_memory(); 4128 4129 int64_t to_free = 4130 (arc_c >> arc_shrink_shift) - free_memory; 4131 if (to_free > 0) { 4132#ifdef _KERNEL 4133 to_free = MAX(to_free, ptob(needfree)); 4134#endif 4135 arc_shrink(to_free); 4136 } 4137 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4138 arc_no_grow = B_TRUE; 4139 } else if (gethrtime() >= growtime) { 4140 arc_no_grow = B_FALSE; 4141 } 4142 4143 evicted = arc_adjust(); 4144 4145 mutex_enter(&arc_reclaim_lock); 4146 4147 /* 4148 * If evicted is zero, we couldn't evict anything via 4149 * arc_adjust(). This could be due to hash lock 4150 * collisions, but more likely due to the majority of 4151 * arc buffers being unevictable. Therefore, even if 4152 * arc_size is above arc_c, another pass is unlikely to 4153 * be helpful and could potentially cause us to enter an 4154 * infinite loop. 4155 */ 4156 if (arc_size <= arc_c || evicted == 0) { 4157#ifdef _KERNEL 4158 needfree = 0; 4159#endif 4160 /* 4161 * We're either no longer overflowing, or we 4162 * can't evict anything more, so we should wake 4163 * up any threads before we go to sleep. 4164 */ 4165 cv_broadcast(&arc_reclaim_waiters_cv); 4166 4167 /* 4168 * Block until signaled, or after one second (we 4169 * might need to perform arc_kmem_reap_now() 4170 * even if we aren't being signalled) 4171 */ 4172 CALLB_CPR_SAFE_BEGIN(&cpr); 4173 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4174 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4175 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4176 } 4177 } 4178 4179 arc_reclaim_thread_exit = B_FALSE; 4180 cv_broadcast(&arc_reclaim_thread_cv); 4181 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4182 thread_exit(); 4183} 4184 4185static u_int arc_dnlc_evicts_arg; 4186extern struct vfsops zfs_vfsops; 4187 4188static void 4189arc_dnlc_evicts_thread(void *dummy __unused) 4190{ 4191 callb_cpr_t cpr; 4192 u_int percent; 4193 4194 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 4195 4196 mutex_enter(&arc_dnlc_evicts_lock); 4197 while (!arc_dnlc_evicts_thread_exit) { 4198 CALLB_CPR_SAFE_BEGIN(&cpr); 4199 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 4200 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 4201 if (arc_dnlc_evicts_arg != 0) { 4202 percent = arc_dnlc_evicts_arg; 4203 mutex_exit(&arc_dnlc_evicts_lock); 4204#ifdef _KERNEL 4205 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 4206#endif 4207 mutex_enter(&arc_dnlc_evicts_lock); 4208 /* 4209 * Clear our token only after vnlru_free() 4210 * pass is done, to avoid false queueing of 4211 * the requests. 4212 */ 4213 arc_dnlc_evicts_arg = 0; 4214 } 4215 } 4216 arc_dnlc_evicts_thread_exit = FALSE; 4217 cv_broadcast(&arc_dnlc_evicts_cv); 4218 CALLB_CPR_EXIT(&cpr); 4219 thread_exit(); 4220} 4221 4222void 4223dnlc_reduce_cache(void *arg) 4224{ 4225 u_int percent; 4226 4227 percent = (u_int)(uintptr_t)arg; 4228 mutex_enter(&arc_dnlc_evicts_lock); 4229 if (arc_dnlc_evicts_arg == 0) { 4230 arc_dnlc_evicts_arg = percent; 4231 cv_broadcast(&arc_dnlc_evicts_cv); 4232 } 4233 mutex_exit(&arc_dnlc_evicts_lock); 4234} 4235 4236/* 4237 * Adapt arc info given the number of bytes we are trying to add and 4238 * the state that we are comming from. This function is only called 4239 * when we are adding new content to the cache. 4240 */ 4241static void 4242arc_adapt(int bytes, arc_state_t *state) 4243{ 4244 int mult; 4245 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4246 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4247 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4248 4249 if (state == arc_l2c_only) 4250 return; 4251 4252 ASSERT(bytes > 0); 4253 /* 4254 * Adapt the target size of the MRU list: 4255 * - if we just hit in the MRU ghost list, then increase 4256 * the target size of the MRU list. 4257 * - if we just hit in the MFU ghost list, then increase 4258 * the target size of the MFU list by decreasing the 4259 * target size of the MRU list. 4260 */ 4261 if (state == arc_mru_ghost) { 4262 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4263 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4264 4265 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4266 } else if (state == arc_mfu_ghost) { 4267 uint64_t delta; 4268 4269 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4270 mult = MIN(mult, 10); 4271 4272 delta = MIN(bytes * mult, arc_p); 4273 arc_p = MAX(arc_p_min, arc_p - delta); 4274 } 4275 ASSERT((int64_t)arc_p >= 0); 4276 4277 if (arc_reclaim_needed()) { 4278 cv_signal(&arc_reclaim_thread_cv); 4279 return; 4280 } 4281 4282 if (arc_no_grow) 4283 return; 4284 4285 if (arc_c >= arc_c_max) 4286 return; 4287 4288 /* 4289 * If we're within (2 * maxblocksize) bytes of the target 4290 * cache size, increment the target cache size 4291 */ 4292 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 4293 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4294 atomic_add_64(&arc_c, (int64_t)bytes); 4295 if (arc_c > arc_c_max) 4296 arc_c = arc_c_max; 4297 else if (state == arc_anon) 4298 atomic_add_64(&arc_p, (int64_t)bytes); 4299 if (arc_p > arc_c) 4300 arc_p = arc_c; 4301 } 4302 ASSERT((int64_t)arc_p >= 0); 4303} 4304 4305/* 4306 * Check if arc_size has grown past our upper threshold, determined by 4307 * zfs_arc_overflow_shift. 4308 */ 4309static boolean_t 4310arc_is_overflowing(void) 4311{ 4312 /* Always allow at least one block of overflow */ 4313 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4314 arc_c >> zfs_arc_overflow_shift); 4315 4316 return (arc_size >= arc_c + overflow); 4317} 4318 4319/* 4320 * Allocate a block and return it to the caller. If we are hitting the 4321 * hard limit for the cache size, we must sleep, waiting for the eviction 4322 * thread to catch up. If we're past the target size but below the hard 4323 * limit, we'll only signal the reclaim thread and continue on. 4324 */ 4325static void * 4326arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4327{ 4328 void *datap = NULL; 4329 arc_state_t *state = hdr->b_l1hdr.b_state; 4330 arc_buf_contents_t type = arc_buf_type(hdr); 4331 4332 arc_adapt(size, state); 4333 4334 /* 4335 * If arc_size is currently overflowing, and has grown past our 4336 * upper limit, we must be adding data faster than the evict 4337 * thread can evict. Thus, to ensure we don't compound the 4338 * problem by adding more data and forcing arc_size to grow even 4339 * further past it's target size, we halt and wait for the 4340 * eviction thread to catch up. 4341 * 4342 * It's also possible that the reclaim thread is unable to evict 4343 * enough buffers to get arc_size below the overflow limit (e.g. 4344 * due to buffers being un-evictable, or hash lock collisions). 4345 * In this case, we want to proceed regardless if we're 4346 * overflowing; thus we don't use a while loop here. 4347 */ 4348 if (arc_is_overflowing()) { 4349 mutex_enter(&arc_reclaim_lock); 4350 4351 /* 4352 * Now that we've acquired the lock, we may no longer be 4353 * over the overflow limit, lets check. 4354 * 4355 * We're ignoring the case of spurious wake ups. If that 4356 * were to happen, it'd let this thread consume an ARC 4357 * buffer before it should have (i.e. before we're under 4358 * the overflow limit and were signalled by the reclaim 4359 * thread). As long as that is a rare occurrence, it 4360 * shouldn't cause any harm. 4361 */ 4362 if (arc_is_overflowing()) { 4363 cv_signal(&arc_reclaim_thread_cv); 4364 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4365 } 4366 4367 mutex_exit(&arc_reclaim_lock); 4368 } 4369 4370 VERIFY3U(hdr->b_type, ==, type); 4371 if (type == ARC_BUFC_METADATA) { 4372 datap = zio_buf_alloc(size); 4373 arc_space_consume(size, ARC_SPACE_META); 4374 } else { 4375 ASSERT(type == ARC_BUFC_DATA); 4376 datap = zio_data_buf_alloc(size); 4377 arc_space_consume(size, ARC_SPACE_DATA); 4378 } 4379 4380 /* 4381 * Update the state size. Note that ghost states have a 4382 * "ghost size" and so don't need to be updated. 4383 */ 4384 if (!GHOST_STATE(state)) { 4385 4386 (void) refcount_add_many(&state->arcs_size, size, tag); 4387 4388 /* 4389 * If this is reached via arc_read, the link is 4390 * protected by the hash lock. If reached via 4391 * arc_buf_alloc, the header should not be accessed by 4392 * any other thread. And, if reached via arc_read_done, 4393 * the hash lock will protect it if it's found in the 4394 * hash table; otherwise no other thread should be 4395 * trying to [add|remove]_reference it. 4396 */ 4397 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4398 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4399 (void) refcount_add_many(&state->arcs_esize[type], 4400 size, tag); 4401 } 4402 4403 /* 4404 * If we are growing the cache, and we are adding anonymous 4405 * data, and we have outgrown arc_p, update arc_p 4406 */ 4407 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4408 (refcount_count(&arc_anon->arcs_size) + 4409 refcount_count(&arc_mru->arcs_size) > arc_p)) 4410 arc_p = MIN(arc_c, arc_p + size); 4411 } 4412 ARCSTAT_BUMP(arcstat_allocated); 4413 return (datap); 4414} 4415 4416/* 4417 * Free the arc data buffer. 4418 */ 4419static void 4420arc_free_data_buf(arc_buf_hdr_t *hdr, void *data, uint64_t size, void *tag) 4421{ 4422 arc_state_t *state = hdr->b_l1hdr.b_state; 4423 arc_buf_contents_t type = arc_buf_type(hdr); 4424 4425 /* protected by hash lock, if in the hash table */ 4426 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4427 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4428 ASSERT(state != arc_anon && state != arc_l2c_only); 4429 4430 (void) refcount_remove_many(&state->arcs_esize[type], 4431 size, tag); 4432 } 4433 (void) refcount_remove_many(&state->arcs_size, size, tag); 4434 4435 VERIFY3U(hdr->b_type, ==, type); 4436 if (type == ARC_BUFC_METADATA) { 4437 zio_buf_free(data, size); 4438 arc_space_return(size, ARC_SPACE_META); 4439 } else { 4440 ASSERT(type == ARC_BUFC_DATA); 4441 zio_data_buf_free(data, size); 4442 arc_space_return(size, ARC_SPACE_DATA); 4443 } 4444} 4445 4446/* 4447 * This routine is called whenever a buffer is accessed. 4448 * NOTE: the hash lock is dropped in this function. 4449 */ 4450static void 4451arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4452{ 4453 clock_t now; 4454 4455 ASSERT(MUTEX_HELD(hash_lock)); 4456 ASSERT(HDR_HAS_L1HDR(hdr)); 4457 4458 if (hdr->b_l1hdr.b_state == arc_anon) { 4459 /* 4460 * This buffer is not in the cache, and does not 4461 * appear in our "ghost" list. Add the new buffer 4462 * to the MRU state. 4463 */ 4464 4465 ASSERT0(hdr->b_l1hdr.b_arc_access); 4466 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4467 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4468 arc_change_state(arc_mru, hdr, hash_lock); 4469 4470 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4471 now = ddi_get_lbolt(); 4472 4473 /* 4474 * If this buffer is here because of a prefetch, then either: 4475 * - clear the flag if this is a "referencing" read 4476 * (any subsequent access will bump this into the MFU state). 4477 * or 4478 * - move the buffer to the head of the list if this is 4479 * another prefetch (to make it less likely to be evicted). 4480 */ 4481 if (HDR_PREFETCH(hdr)) { 4482 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4483 /* link protected by hash lock */ 4484 ASSERT(multilist_link_active( 4485 &hdr->b_l1hdr.b_arc_node)); 4486 } else { 4487 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4488 ARCSTAT_BUMP(arcstat_mru_hits); 4489 } 4490 hdr->b_l1hdr.b_arc_access = now; 4491 return; 4492 } 4493 4494 /* 4495 * This buffer has been "accessed" only once so far, 4496 * but it is still in the cache. Move it to the MFU 4497 * state. 4498 */ 4499 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4500 /* 4501 * More than 125ms have passed since we 4502 * instantiated this buffer. Move it to the 4503 * most frequently used state. 4504 */ 4505 hdr->b_l1hdr.b_arc_access = now; 4506 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4507 arc_change_state(arc_mfu, hdr, hash_lock); 4508 } 4509 ARCSTAT_BUMP(arcstat_mru_hits); 4510 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4511 arc_state_t *new_state; 4512 /* 4513 * This buffer has been "accessed" recently, but 4514 * was evicted from the cache. Move it to the 4515 * MFU state. 4516 */ 4517 4518 if (HDR_PREFETCH(hdr)) { 4519 new_state = arc_mru; 4520 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4521 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4522 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4523 } else { 4524 new_state = arc_mfu; 4525 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4526 } 4527 4528 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4529 arc_change_state(new_state, hdr, hash_lock); 4530 4531 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4532 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4533 /* 4534 * This buffer has been accessed more than once and is 4535 * still in the cache. Keep it in the MFU state. 4536 * 4537 * NOTE: an add_reference() that occurred when we did 4538 * the arc_read() will have kicked this off the list. 4539 * If it was a prefetch, we will explicitly move it to 4540 * the head of the list now. 4541 */ 4542 if ((HDR_PREFETCH(hdr)) != 0) { 4543 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4544 /* link protected by hash_lock */ 4545 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4546 } 4547 ARCSTAT_BUMP(arcstat_mfu_hits); 4548 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4549 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4550 arc_state_t *new_state = arc_mfu; 4551 /* 4552 * This buffer has been accessed more than once but has 4553 * been evicted from the cache. Move it back to the 4554 * MFU state. 4555 */ 4556 4557 if (HDR_PREFETCH(hdr)) { 4558 /* 4559 * This is a prefetch access... 4560 * move this block back to the MRU state. 4561 */ 4562 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4563 new_state = arc_mru; 4564 } 4565 4566 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4567 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4568 arc_change_state(new_state, hdr, hash_lock); 4569 4570 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4571 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4572 /* 4573 * This buffer is on the 2nd Level ARC. 4574 */ 4575 4576 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4577 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4578 arc_change_state(arc_mfu, hdr, hash_lock); 4579 } else { 4580 ASSERT(!"invalid arc state"); 4581 } 4582} 4583 4584/* a generic arc_done_func_t which you can use */ 4585/* ARGSUSED */ 4586void 4587arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4588{ 4589 if (zio == NULL || zio->io_error == 0) 4590 bcopy(buf->b_data, arg, HDR_GET_LSIZE(buf->b_hdr)); 4591 arc_buf_destroy(buf, arg); 4592} 4593 4594/* a generic arc_done_func_t */ 4595void 4596arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4597{ 4598 arc_buf_t **bufp = arg; 4599 if (zio && zio->io_error) { 4600 arc_buf_destroy(buf, arg); 4601 *bufp = NULL; 4602 } else { 4603 *bufp = buf; 4604 ASSERT(buf->b_data); 4605 } 4606} 4607 4608static void 4609arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 4610{ 4611 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 4612 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 4613 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 4614 } else { 4615 if (HDR_COMPRESSION_ENABLED(hdr)) { 4616 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 4617 BP_GET_COMPRESS(bp)); 4618 } 4619 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 4620 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 4621 } 4622} 4623 4624static void 4625arc_read_done(zio_t *zio) 4626{ 4627 arc_buf_hdr_t *hdr = zio->io_private; 4628 arc_buf_t *abuf = NULL; /* buffer we're assigning to callback */ 4629 kmutex_t *hash_lock = NULL; 4630 arc_callback_t *callback_list, *acb; 4631 int freeable = B_FALSE; 4632 4633 /* 4634 * The hdr was inserted into hash-table and removed from lists 4635 * prior to starting I/O. We should find this header, since 4636 * it's in the hash table, and it should be legit since it's 4637 * not possible to evict it during the I/O. The only possible 4638 * reason for it not to be found is if we were freed during the 4639 * read. 4640 */ 4641 if (HDR_IN_HASH_TABLE(hdr)) { 4642 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 4643 ASSERT3U(hdr->b_dva.dva_word[0], ==, 4644 BP_IDENTITY(zio->io_bp)->dva_word[0]); 4645 ASSERT3U(hdr->b_dva.dva_word[1], ==, 4646 BP_IDENTITY(zio->io_bp)->dva_word[1]); 4647 4648 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 4649 &hash_lock); 4650 4651 ASSERT((found == hdr && 4652 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 4653 (found == hdr && HDR_L2_READING(hdr))); 4654 ASSERT3P(hash_lock, !=, NULL); 4655 } 4656 4657 if (zio->io_error == 0) { 4658 /* byteswap if necessary */ 4659 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 4660 if (BP_GET_LEVEL(zio->io_bp) > 0) { 4661 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 4662 } else { 4663 hdr->b_l1hdr.b_byteswap = 4664 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 4665 } 4666 } else { 4667 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 4668 } 4669 } 4670 4671 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 4672 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 4673 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 4674 4675 callback_list = hdr->b_l1hdr.b_acb; 4676 ASSERT3P(callback_list, !=, NULL); 4677 4678 if (hash_lock && zio->io_error == 0 && 4679 hdr->b_l1hdr.b_state == arc_anon) { 4680 /* 4681 * Only call arc_access on anonymous buffers. This is because 4682 * if we've issued an I/O for an evicted buffer, we've already 4683 * called arc_access (to prevent any simultaneous readers from 4684 * getting confused). 4685 */ 4686 arc_access(hdr, hash_lock); 4687 } 4688 4689 /* create copies of the data buffer for the callers */ 4690 for (acb = callback_list; acb; acb = acb->acb_next) { 4691 if (acb->acb_done != NULL) { 4692 /* 4693 * If we're here, then this must be a demand read 4694 * since prefetch requests don't have callbacks. 4695 * If a read request has a callback (i.e. acb_done is 4696 * not NULL), then we decompress the data for the 4697 * first request and clone the rest. This avoids 4698 * having to waste cpu resources decompressing data 4699 * that nobody is explicitly waiting to read. 4700 */ 4701 if (abuf == NULL) { 4702 acb->acb_buf = arc_buf_alloc_impl(hdr, 4703 acb->acb_private); 4704 if (zio->io_error == 0) { 4705 zio->io_error = 4706 arc_decompress(acb->acb_buf); 4707 } 4708 abuf = acb->acb_buf; 4709 } else { 4710 add_reference(hdr, acb->acb_private); 4711 acb->acb_buf = arc_buf_clone(abuf); 4712 } 4713 } 4714 } 4715 hdr->b_l1hdr.b_acb = NULL; 4716 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 4717 if (abuf == NULL) { 4718 /* 4719 * This buffer didn't have a callback so it must 4720 * be a prefetch. 4721 */ 4722 ASSERT(HDR_PREFETCH(hdr)); 4723 ASSERT0(hdr->b_l1hdr.b_bufcnt); 4724 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 4725 } 4726 4727 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 4728 callback_list != NULL); 4729 4730 if (zio->io_error == 0) { 4731 arc_hdr_verify(hdr, zio->io_bp); 4732 } else { 4733 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 4734 if (hdr->b_l1hdr.b_state != arc_anon) 4735 arc_change_state(arc_anon, hdr, hash_lock); 4736 if (HDR_IN_HASH_TABLE(hdr)) 4737 buf_hash_remove(hdr); 4738 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4739 } 4740 4741 /* 4742 * Broadcast before we drop the hash_lock to avoid the possibility 4743 * that the hdr (and hence the cv) might be freed before we get to 4744 * the cv_broadcast(). 4745 */ 4746 cv_broadcast(&hdr->b_l1hdr.b_cv); 4747 4748 if (hash_lock != NULL) { 4749 mutex_exit(hash_lock); 4750 } else { 4751 /* 4752 * This block was freed while we waited for the read to 4753 * complete. It has been removed from the hash table and 4754 * moved to the anonymous state (so that it won't show up 4755 * in the cache). 4756 */ 4757 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 4758 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 4759 } 4760 4761 /* execute each callback and free its structure */ 4762 while ((acb = callback_list) != NULL) { 4763 if (acb->acb_done) 4764 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 4765 4766 if (acb->acb_zio_dummy != NULL) { 4767 acb->acb_zio_dummy->io_error = zio->io_error; 4768 zio_nowait(acb->acb_zio_dummy); 4769 } 4770 4771 callback_list = acb->acb_next; 4772 kmem_free(acb, sizeof (arc_callback_t)); 4773 } 4774 4775 if (freeable) 4776 arc_hdr_destroy(hdr); 4777} 4778 4779/* 4780 * "Read" the block at the specified DVA (in bp) via the 4781 * cache. If the block is found in the cache, invoke the provided 4782 * callback immediately and return. Note that the `zio' parameter 4783 * in the callback will be NULL in this case, since no IO was 4784 * required. If the block is not in the cache pass the read request 4785 * on to the spa with a substitute callback function, so that the 4786 * requested block will be added to the cache. 4787 * 4788 * If a read request arrives for a block that has a read in-progress, 4789 * either wait for the in-progress read to complete (and return the 4790 * results); or, if this is a read with a "done" func, add a record 4791 * to the read to invoke the "done" func when the read completes, 4792 * and return; or just return. 4793 * 4794 * arc_read_done() will invoke all the requested "done" functions 4795 * for readers of this block. 4796 */ 4797int 4798arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 4799 void *private, zio_priority_t priority, int zio_flags, 4800 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 4801{ 4802 arc_buf_hdr_t *hdr = NULL; 4803 kmutex_t *hash_lock = NULL; 4804 zio_t *rzio; 4805 uint64_t guid = spa_load_guid(spa); 4806 4807 ASSERT(!BP_IS_EMBEDDED(bp) || 4808 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 4809 4810top: 4811 if (!BP_IS_EMBEDDED(bp)) { 4812 /* 4813 * Embedded BP's have no DVA and require no I/O to "read". 4814 * Create an anonymous arc buf to back it. 4815 */ 4816 hdr = buf_hash_find(guid, bp, &hash_lock); 4817 } 4818 4819 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pdata != NULL) { 4820 arc_buf_t *buf = NULL; 4821 *arc_flags |= ARC_FLAG_CACHED; 4822 4823 if (HDR_IO_IN_PROGRESS(hdr)) { 4824 4825 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 4826 priority == ZIO_PRIORITY_SYNC_READ) { 4827 /* 4828 * This sync read must wait for an 4829 * in-progress async read (e.g. a predictive 4830 * prefetch). Async reads are queued 4831 * separately at the vdev_queue layer, so 4832 * this is a form of priority inversion. 4833 * Ideally, we would "inherit" the demand 4834 * i/o's priority by moving the i/o from 4835 * the async queue to the synchronous queue, 4836 * but there is currently no mechanism to do 4837 * so. Track this so that we can evaluate 4838 * the magnitude of this potential performance 4839 * problem. 4840 * 4841 * Note that if the prefetch i/o is already 4842 * active (has been issued to the device), 4843 * the prefetch improved performance, because 4844 * we issued it sooner than we would have 4845 * without the prefetch. 4846 */ 4847 DTRACE_PROBE1(arc__sync__wait__for__async, 4848 arc_buf_hdr_t *, hdr); 4849 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 4850 } 4851 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4852 arc_hdr_clear_flags(hdr, 4853 ARC_FLAG_PREDICTIVE_PREFETCH); 4854 } 4855 4856 if (*arc_flags & ARC_FLAG_WAIT) { 4857 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 4858 mutex_exit(hash_lock); 4859 goto top; 4860 } 4861 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 4862 4863 if (done) { 4864 arc_callback_t *acb = NULL; 4865 4866 acb = kmem_zalloc(sizeof (arc_callback_t), 4867 KM_SLEEP); 4868 acb->acb_done = done; 4869 acb->acb_private = private; 4870 if (pio != NULL) 4871 acb->acb_zio_dummy = zio_null(pio, 4872 spa, NULL, NULL, NULL, zio_flags); 4873 4874 ASSERT3P(acb->acb_done, !=, NULL); 4875 acb->acb_next = hdr->b_l1hdr.b_acb; 4876 hdr->b_l1hdr.b_acb = acb; 4877 mutex_exit(hash_lock); 4878 return (0); 4879 } 4880 mutex_exit(hash_lock); 4881 return (0); 4882 } 4883 4884 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 4885 hdr->b_l1hdr.b_state == arc_mfu); 4886 4887 if (done) { 4888 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 4889 /* 4890 * This is a demand read which does not have to 4891 * wait for i/o because we did a predictive 4892 * prefetch i/o for it, which has completed. 4893 */ 4894 DTRACE_PROBE1( 4895 arc__demand__hit__predictive__prefetch, 4896 arc_buf_hdr_t *, hdr); 4897 ARCSTAT_BUMP( 4898 arcstat_demand_hit_predictive_prefetch); 4899 arc_hdr_clear_flags(hdr, 4900 ARC_FLAG_PREDICTIVE_PREFETCH); 4901 } 4902 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 4903 4904 /* 4905 * If this block is already in use, create a new 4906 * copy of the data so that we will be guaranteed 4907 * that arc_release() will always succeed. 4908 */ 4909 buf = hdr->b_l1hdr.b_buf; 4910 if (buf == NULL) { 4911 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4912 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 4913 buf = arc_buf_alloc_impl(hdr, private); 4914 VERIFY0(arc_decompress(buf)); 4915 } else { 4916 add_reference(hdr, private); 4917 buf = arc_buf_clone(buf); 4918 } 4919 ASSERT3P(buf->b_data, !=, NULL); 4920 4921 } else if (*arc_flags & ARC_FLAG_PREFETCH && 4922 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4923 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 4924 } 4925 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 4926 arc_access(hdr, hash_lock); 4927 if (*arc_flags & ARC_FLAG_L2CACHE) 4928 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 4929 mutex_exit(hash_lock); 4930 ARCSTAT_BUMP(arcstat_hits); 4931 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 4932 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 4933 data, metadata, hits); 4934 4935 if (done) 4936 done(NULL, buf, private); 4937 } else { 4938 uint64_t lsize = BP_GET_LSIZE(bp); 4939 uint64_t psize = BP_GET_PSIZE(bp); 4940 arc_callback_t *acb; 4941 vdev_t *vd = NULL; 4942 uint64_t addr = 0; 4943 boolean_t devw = B_FALSE; 4944 uint64_t size; 4945 4946 if (hdr == NULL) { 4947 /* this block is not in the cache */ 4948 arc_buf_hdr_t *exists = NULL; 4949 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 4950 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 4951 BP_GET_COMPRESS(bp), type); 4952 4953 if (!BP_IS_EMBEDDED(bp)) { 4954 hdr->b_dva = *BP_IDENTITY(bp); 4955 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 4956 exists = buf_hash_insert(hdr, &hash_lock); 4957 } 4958 if (exists != NULL) { 4959 /* somebody beat us to the hash insert */ 4960 mutex_exit(hash_lock); 4961 buf_discard_identity(hdr); 4962 arc_hdr_destroy(hdr); 4963 goto top; /* restart the IO request */ 4964 } 4965 } else { 4966 /* 4967 * This block is in the ghost cache. If it was L2-only 4968 * (and thus didn't have an L1 hdr), we realloc the 4969 * header to add an L1 hdr. 4970 */ 4971 if (!HDR_HAS_L1HDR(hdr)) { 4972 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 4973 hdr_full_cache); 4974 } 4975 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 4976 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 4977 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 4978 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4979 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 4980 4981 /* 4982 * This is a delicate dance that we play here. 4983 * This hdr is in the ghost list so we access it 4984 * to move it out of the ghost list before we 4985 * initiate the read. If it's a prefetch then 4986 * it won't have a callback so we'll remove the 4987 * reference that arc_buf_alloc_impl() created. We 4988 * do this after we've called arc_access() to 4989 * avoid hitting an assert in remove_reference(). 4990 */ 4991 arc_access(hdr, hash_lock); 4992 arc_hdr_alloc_pdata(hdr); 4993 } 4994 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 4995 size = arc_hdr_size(hdr); 4996 4997 /* 4998 * If compression is enabled on the hdr, then will do 4999 * RAW I/O and will store the compressed data in the hdr's 5000 * data block. Otherwise, the hdr's data block will contain 5001 * the uncompressed data. 5002 */ 5003 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5004 zio_flags |= ZIO_FLAG_RAW; 5005 } 5006 5007 if (*arc_flags & ARC_FLAG_PREFETCH) 5008 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5009 if (*arc_flags & ARC_FLAG_L2CACHE) 5010 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5011 if (BP_GET_LEVEL(bp) > 0) 5012 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5013 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5014 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5015 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5016 5017 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5018 acb->acb_done = done; 5019 acb->acb_private = private; 5020 5021 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5022 hdr->b_l1hdr.b_acb = acb; 5023 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5024 5025 if (HDR_HAS_L2HDR(hdr) && 5026 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5027 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5028 addr = hdr->b_l2hdr.b_daddr; 5029 /* 5030 * Lock out device removal. 5031 */ 5032 if (vdev_is_dead(vd) || 5033 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 5034 vd = NULL; 5035 } 5036 5037 if (priority == ZIO_PRIORITY_ASYNC_READ) 5038 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5039 else 5040 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5041 5042 if (hash_lock != NULL) 5043 mutex_exit(hash_lock); 5044 5045 /* 5046 * At this point, we have a level 1 cache miss. Try again in 5047 * L2ARC if possible. 5048 */ 5049 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 5050 5051 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 5052 uint64_t, lsize, zbookmark_phys_t *, zb); 5053 ARCSTAT_BUMP(arcstat_misses); 5054 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5055 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5056 data, metadata, misses); 5057#ifdef _KERNEL 5058#ifdef RACCT 5059 if (racct_enable) { 5060 PROC_LOCK(curproc); 5061 racct_add_force(curproc, RACCT_READBPS, size); 5062 racct_add_force(curproc, RACCT_READIOPS, 1); 5063 PROC_UNLOCK(curproc); 5064 } 5065#endif /* RACCT */ 5066 curthread->td_ru.ru_inblock++; 5067#endif 5068 5069 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5070 /* 5071 * Read from the L2ARC if the following are true: 5072 * 1. The L2ARC vdev was previously cached. 5073 * 2. This buffer still has L2ARC metadata. 5074 * 3. This buffer isn't currently writing to the L2ARC. 5075 * 4. The L2ARC entry wasn't evicted, which may 5076 * also have invalidated the vdev. 5077 * 5. This isn't prefetch and l2arc_noprefetch is set. 5078 */ 5079 if (HDR_HAS_L2HDR(hdr) && 5080 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5081 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5082 l2arc_read_callback_t *cb; 5083 void* b_data; 5084 5085 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5086 ARCSTAT_BUMP(arcstat_l2_hits); 5087 5088 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5089 KM_SLEEP); 5090 cb->l2rcb_hdr = hdr; 5091 cb->l2rcb_bp = *bp; 5092 cb->l2rcb_zb = *zb; 5093 cb->l2rcb_flags = zio_flags; 5094 uint64_t asize = vdev_psize_to_asize(vd, size); 5095 if (asize != size) { 5096 b_data = zio_data_buf_alloc(asize); 5097 cb->l2rcb_data = b_data; 5098 } else { 5099 b_data = hdr->b_l1hdr.b_pdata; 5100 } 5101 5102 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5103 addr + asize < vd->vdev_psize - 5104 VDEV_LABEL_END_SIZE); 5105 5106 /* 5107 * l2arc read. The SCL_L2ARC lock will be 5108 * released by l2arc_read_done(). 5109 * Issue a null zio if the underlying buffer 5110 * was squashed to zero size by compression. 5111 */ 5112 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5113 ZIO_COMPRESS_EMPTY); 5114 rzio = zio_read_phys(pio, vd, addr, 5115 asize, b_data, 5116 ZIO_CHECKSUM_OFF, 5117 l2arc_read_done, cb, priority, 5118 zio_flags | ZIO_FLAG_DONT_CACHE | 5119 ZIO_FLAG_CANFAIL | 5120 ZIO_FLAG_DONT_PROPAGATE | 5121 ZIO_FLAG_DONT_RETRY, B_FALSE); 5122 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5123 zio_t *, rzio); 5124 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5125 5126 if (*arc_flags & ARC_FLAG_NOWAIT) { 5127 zio_nowait(rzio); 5128 return (0); 5129 } 5130 5131 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5132 if (zio_wait(rzio) == 0) 5133 return (0); 5134 5135 /* l2arc read error; goto zio_read() */ 5136 } else { 5137 DTRACE_PROBE1(l2arc__miss, 5138 arc_buf_hdr_t *, hdr); 5139 ARCSTAT_BUMP(arcstat_l2_misses); 5140 if (HDR_L2_WRITING(hdr)) 5141 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5142 spa_config_exit(spa, SCL_L2ARC, vd); 5143 } 5144 } else { 5145 if (vd != NULL) 5146 spa_config_exit(spa, SCL_L2ARC, vd); 5147 if (l2arc_ndev != 0) { 5148 DTRACE_PROBE1(l2arc__miss, 5149 arc_buf_hdr_t *, hdr); 5150 ARCSTAT_BUMP(arcstat_l2_misses); 5151 } 5152 } 5153 5154 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pdata, size, 5155 arc_read_done, hdr, priority, zio_flags, zb); 5156 5157 if (*arc_flags & ARC_FLAG_WAIT) 5158 return (zio_wait(rzio)); 5159 5160 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5161 zio_nowait(rzio); 5162 } 5163 return (0); 5164} 5165 5166/* 5167 * Notify the arc that a block was freed, and thus will never be used again. 5168 */ 5169void 5170arc_freed(spa_t *spa, const blkptr_t *bp) 5171{ 5172 arc_buf_hdr_t *hdr; 5173 kmutex_t *hash_lock; 5174 uint64_t guid = spa_load_guid(spa); 5175 5176 ASSERT(!BP_IS_EMBEDDED(bp)); 5177 5178 hdr = buf_hash_find(guid, bp, &hash_lock); 5179 if (hdr == NULL) 5180 return; 5181 5182 /* 5183 * We might be trying to free a block that is still doing I/O 5184 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5185 * dmu_sync-ed block). If this block is being prefetched, then it 5186 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5187 * until the I/O completes. A block may also have a reference if it is 5188 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5189 * have written the new block to its final resting place on disk but 5190 * without the dedup flag set. This would have left the hdr in the MRU 5191 * state and discoverable. When the txg finally syncs it detects that 5192 * the block was overridden in open context and issues an override I/O. 5193 * Since this is a dedup block, the override I/O will determine if the 5194 * block is already in the DDT. If so, then it will replace the io_bp 5195 * with the bp from the DDT and allow the I/O to finish. When the I/O 5196 * reaches the done callback, dbuf_write_override_done, it will 5197 * check to see if the io_bp and io_bp_override are identical. 5198 * If they are not, then it indicates that the bp was replaced with 5199 * the bp in the DDT and the override bp is freed. This allows 5200 * us to arrive here with a reference on a block that is being 5201 * freed. So if we have an I/O in progress, or a reference to 5202 * this hdr, then we don't destroy the hdr. 5203 */ 5204 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5205 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5206 arc_change_state(arc_anon, hdr, hash_lock); 5207 arc_hdr_destroy(hdr); 5208 mutex_exit(hash_lock); 5209 } else { 5210 mutex_exit(hash_lock); 5211 } 5212 5213} 5214 5215/* 5216 * Release this buffer from the cache, making it an anonymous buffer. This 5217 * must be done after a read and prior to modifying the buffer contents. 5218 * If the buffer has more than one reference, we must make 5219 * a new hdr for the buffer. 5220 */ 5221void 5222arc_release(arc_buf_t *buf, void *tag) 5223{ 5224 arc_buf_hdr_t *hdr = buf->b_hdr; 5225 5226 /* 5227 * It would be nice to assert that if it's DMU metadata (level > 5228 * 0 || it's the dnode file), then it must be syncing context. 5229 * But we don't know that information at this level. 5230 */ 5231 5232 mutex_enter(&buf->b_evict_lock); 5233 5234 ASSERT(HDR_HAS_L1HDR(hdr)); 5235 5236 /* 5237 * We don't grab the hash lock prior to this check, because if 5238 * the buffer's header is in the arc_anon state, it won't be 5239 * linked into the hash table. 5240 */ 5241 if (hdr->b_l1hdr.b_state == arc_anon) { 5242 mutex_exit(&buf->b_evict_lock); 5243 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5244 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5245 ASSERT(!HDR_HAS_L2HDR(hdr)); 5246 ASSERT(HDR_EMPTY(hdr)); 5247 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5248 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5249 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5250 5251 hdr->b_l1hdr.b_arc_access = 0; 5252 5253 /* 5254 * If the buf is being overridden then it may already 5255 * have a hdr that is not empty. 5256 */ 5257 buf_discard_identity(hdr); 5258 arc_buf_thaw(buf); 5259 5260 return; 5261 } 5262 5263 kmutex_t *hash_lock = HDR_LOCK(hdr); 5264 mutex_enter(hash_lock); 5265 5266 /* 5267 * This assignment is only valid as long as the hash_lock is 5268 * held, we must be careful not to reference state or the 5269 * b_state field after dropping the lock. 5270 */ 5271 arc_state_t *state = hdr->b_l1hdr.b_state; 5272 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5273 ASSERT3P(state, !=, arc_anon); 5274 5275 /* this buffer is not on any list */ 5276 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0); 5277 5278 if (HDR_HAS_L2HDR(hdr)) { 5279 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5280 5281 /* 5282 * We have to recheck this conditional again now that 5283 * we're holding the l2ad_mtx to prevent a race with 5284 * another thread which might be concurrently calling 5285 * l2arc_evict(). In that case, l2arc_evict() might have 5286 * destroyed the header's L2 portion as we were waiting 5287 * to acquire the l2ad_mtx. 5288 */ 5289 if (HDR_HAS_L2HDR(hdr)) { 5290 l2arc_trim(hdr); 5291 arc_hdr_l2hdr_destroy(hdr); 5292 } 5293 5294 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5295 } 5296 5297 /* 5298 * Do we have more than one buf? 5299 */ 5300 if (hdr->b_l1hdr.b_bufcnt > 1) { 5301 arc_buf_hdr_t *nhdr; 5302 arc_buf_t **bufp; 5303 uint64_t spa = hdr->b_spa; 5304 uint64_t psize = HDR_GET_PSIZE(hdr); 5305 uint64_t lsize = HDR_GET_LSIZE(hdr); 5306 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5307 arc_buf_contents_t type = arc_buf_type(hdr); 5308 VERIFY3U(hdr->b_type, ==, type); 5309 5310 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5311 (void) remove_reference(hdr, hash_lock, tag); 5312 5313 if (arc_buf_is_shared(buf)) { 5314 ASSERT(HDR_SHARED_DATA(hdr)); 5315 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5316 ASSERT(ARC_BUF_LAST(buf)); 5317 } 5318 5319 /* 5320 * Pull the data off of this hdr and attach it to 5321 * a new anonymous hdr. Also find the last buffer 5322 * in the hdr's buffer list. 5323 */ 5324 arc_buf_t *lastbuf = NULL; 5325 bufp = &hdr->b_l1hdr.b_buf; 5326 while (*bufp != NULL) { 5327 if (*bufp == buf) { 5328 *bufp = buf->b_next; 5329 } 5330 5331 /* 5332 * If we've removed a buffer in the middle of 5333 * the list then update the lastbuf and update 5334 * bufp. 5335 */ 5336 if (*bufp != NULL) { 5337 lastbuf = *bufp; 5338 bufp = &(*bufp)->b_next; 5339 } 5340 } 5341 buf->b_next = NULL; 5342 ASSERT3P(lastbuf, !=, buf); 5343 ASSERT3P(lastbuf, !=, NULL); 5344 5345 /* 5346 * If the current arc_buf_t and the hdr are sharing their data 5347 * buffer, then we must stop sharing that block, transfer 5348 * ownership and setup sharing with a new arc_buf_t at the end 5349 * of the hdr's b_buf list. 5350 */ 5351 if (arc_buf_is_shared(buf)) { 5352 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5353 ASSERT(ARC_BUF_LAST(lastbuf)); 5354 VERIFY(!arc_buf_is_shared(lastbuf)); 5355 5356 /* 5357 * First, sever the block sharing relationship between 5358 * buf and the arc_buf_hdr_t. Then, setup a new 5359 * block sharing relationship with the last buffer 5360 * on the arc_buf_t list. 5361 */ 5362 arc_unshare_buf(hdr, buf); 5363 arc_share_buf(hdr, lastbuf); 5364 VERIFY3P(lastbuf->b_data, !=, NULL); 5365 } else if (HDR_SHARED_DATA(hdr)) { 5366 ASSERT(arc_buf_is_shared(lastbuf)); 5367 } 5368 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 5369 ASSERT3P(state, !=, arc_l2c_only); 5370 5371 (void) refcount_remove_many(&state->arcs_size, 5372 HDR_GET_LSIZE(hdr), buf); 5373 5374 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5375 ASSERT3P(state, !=, arc_l2c_only); 5376 (void) refcount_remove_many(&state->arcs_esize[type], 5377 HDR_GET_LSIZE(hdr), buf); 5378 } 5379 5380 hdr->b_l1hdr.b_bufcnt -= 1; 5381 arc_cksum_verify(buf); 5382#ifdef illumos 5383 arc_buf_unwatch(buf); 5384#endif 5385 5386 mutex_exit(hash_lock); 5387 5388 /* 5389 * Allocate a new hdr. The new hdr will contain a b_pdata 5390 * buffer which will be freed in arc_write(). 5391 */ 5392 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 5393 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 5394 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 5395 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 5396 VERIFY3U(nhdr->b_type, ==, type); 5397 ASSERT(!HDR_SHARED_DATA(nhdr)); 5398 5399 nhdr->b_l1hdr.b_buf = buf; 5400 nhdr->b_l1hdr.b_bufcnt = 1; 5401 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 5402 buf->b_hdr = nhdr; 5403 5404 mutex_exit(&buf->b_evict_lock); 5405 (void) refcount_add_many(&arc_anon->arcs_size, 5406 HDR_GET_LSIZE(nhdr), buf); 5407 } else { 5408 mutex_exit(&buf->b_evict_lock); 5409 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 5410 /* protected by hash lock, or hdr is on arc_anon */ 5411 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5412 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5413 arc_change_state(arc_anon, hdr, hash_lock); 5414 hdr->b_l1hdr.b_arc_access = 0; 5415 mutex_exit(hash_lock); 5416 5417 buf_discard_identity(hdr); 5418 arc_buf_thaw(buf); 5419 } 5420} 5421 5422int 5423arc_released(arc_buf_t *buf) 5424{ 5425 int released; 5426 5427 mutex_enter(&buf->b_evict_lock); 5428 released = (buf->b_data != NULL && 5429 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5430 mutex_exit(&buf->b_evict_lock); 5431 return (released); 5432} 5433 5434#ifdef ZFS_DEBUG 5435int 5436arc_referenced(arc_buf_t *buf) 5437{ 5438 int referenced; 5439 5440 mutex_enter(&buf->b_evict_lock); 5441 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5442 mutex_exit(&buf->b_evict_lock); 5443 return (referenced); 5444} 5445#endif 5446 5447static void 5448arc_write_ready(zio_t *zio) 5449{ 5450 arc_write_callback_t *callback = zio->io_private; 5451 arc_buf_t *buf = callback->awcb_buf; 5452 arc_buf_hdr_t *hdr = buf->b_hdr; 5453 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 5454 5455 ASSERT(HDR_HAS_L1HDR(hdr)); 5456 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5457 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 5458 5459 /* 5460 * If we're reexecuting this zio because the pool suspended, then 5461 * cleanup any state that was previously set the first time the 5462 * callback as invoked. 5463 */ 5464 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 5465 arc_cksum_free(hdr); 5466#ifdef illumos 5467 arc_buf_unwatch(buf); 5468#endif 5469 if (hdr->b_l1hdr.b_pdata != NULL) { 5470 if (arc_buf_is_shared(buf)) { 5471 ASSERT(HDR_SHARED_DATA(hdr)); 5472 5473 arc_unshare_buf(hdr, buf); 5474 } else { 5475 arc_hdr_free_pdata(hdr); 5476 } 5477 } 5478 } 5479 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5480 ASSERT(!HDR_SHARED_DATA(hdr)); 5481 ASSERT(!arc_buf_is_shared(buf)); 5482 5483 callback->awcb_ready(zio, buf, callback->awcb_private); 5484 5485 if (HDR_IO_IN_PROGRESS(hdr)) 5486 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 5487 5488 arc_cksum_compute(buf); 5489 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5490 5491 enum zio_compress compress; 5492 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5493 compress = ZIO_COMPRESS_OFF; 5494 } else { 5495 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 5496 compress = BP_GET_COMPRESS(zio->io_bp); 5497 } 5498 HDR_SET_PSIZE(hdr, psize); 5499 arc_hdr_set_compress(hdr, compress); 5500 5501 /* 5502 * If the hdr is compressed, then copy the compressed 5503 * zio contents into arc_buf_hdr_t. Otherwise, copy the original 5504 * data buf into the hdr. Ideally, we would like to always copy the 5505 * io_data into b_pdata but the user may have disabled compressed 5506 * arc thus the on-disk block may or may not match what we maintain 5507 * in the hdr's b_pdata field. 5508 */ 5509 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5510 ASSERT(BP_GET_COMPRESS(zio->io_bp) != ZIO_COMPRESS_OFF); 5511 ASSERT3U(psize, >, 0); 5512 arc_hdr_alloc_pdata(hdr); 5513 bcopy(zio->io_data, hdr->b_l1hdr.b_pdata, psize); 5514 } else { 5515 ASSERT3P(buf->b_data, ==, zio->io_orig_data); 5516 ASSERT3U(zio->io_orig_size, ==, HDR_GET_LSIZE(hdr)); 5517 ASSERT3U(hdr->b_l1hdr.b_byteswap, ==, DMU_BSWAP_NUMFUNCS); 5518 ASSERT(!HDR_SHARED_DATA(hdr)); 5519 ASSERT(!arc_buf_is_shared(buf)); 5520 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5521 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5522 5523 /* 5524 * This hdr is not compressed so we're able to share 5525 * the arc_buf_t data buffer with the hdr. 5526 */ 5527 arc_share_buf(hdr, buf); 5528 VERIFY0(bcmp(zio->io_orig_data, hdr->b_l1hdr.b_pdata, 5529 HDR_GET_LSIZE(hdr))); 5530 } 5531 arc_hdr_verify(hdr, zio->io_bp); 5532} 5533 5534static void 5535arc_write_children_ready(zio_t *zio) 5536{ 5537 arc_write_callback_t *callback = zio->io_private; 5538 arc_buf_t *buf = callback->awcb_buf; 5539 5540 callback->awcb_children_ready(zio, buf, callback->awcb_private); 5541} 5542 5543/* 5544 * The SPA calls this callback for each physical write that happens on behalf 5545 * of a logical write. See the comment in dbuf_write_physdone() for details. 5546 */ 5547static void 5548arc_write_physdone(zio_t *zio) 5549{ 5550 arc_write_callback_t *cb = zio->io_private; 5551 if (cb->awcb_physdone != NULL) 5552 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5553} 5554 5555static void 5556arc_write_done(zio_t *zio) 5557{ 5558 arc_write_callback_t *callback = zio->io_private; 5559 arc_buf_t *buf = callback->awcb_buf; 5560 arc_buf_hdr_t *hdr = buf->b_hdr; 5561 5562 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5563 5564 if (zio->io_error == 0) { 5565 arc_hdr_verify(hdr, zio->io_bp); 5566 5567 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5568 buf_discard_identity(hdr); 5569 } else { 5570 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5571 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5572 } 5573 } else { 5574 ASSERT(HDR_EMPTY(hdr)); 5575 } 5576 5577 /* 5578 * If the block to be written was all-zero or compressed enough to be 5579 * embedded in the BP, no write was performed so there will be no 5580 * dva/birth/checksum. The buffer must therefore remain anonymous 5581 * (and uncached). 5582 */ 5583 if (!HDR_EMPTY(hdr)) { 5584 arc_buf_hdr_t *exists; 5585 kmutex_t *hash_lock; 5586 5587 ASSERT(zio->io_error == 0); 5588 5589 arc_cksum_verify(buf); 5590 5591 exists = buf_hash_insert(hdr, &hash_lock); 5592 if (exists != NULL) { 5593 /* 5594 * This can only happen if we overwrite for 5595 * sync-to-convergence, because we remove 5596 * buffers from the hash table when we arc_free(). 5597 */ 5598 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5599 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5600 panic("bad overwrite, hdr=%p exists=%p", 5601 (void *)hdr, (void *)exists); 5602 ASSERT(refcount_is_zero( 5603 &exists->b_l1hdr.b_refcnt)); 5604 arc_change_state(arc_anon, exists, hash_lock); 5605 mutex_exit(hash_lock); 5606 arc_hdr_destroy(exists); 5607 exists = buf_hash_insert(hdr, &hash_lock); 5608 ASSERT3P(exists, ==, NULL); 5609 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5610 /* nopwrite */ 5611 ASSERT(zio->io_prop.zp_nopwrite); 5612 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5613 panic("bad nopwrite, hdr=%p exists=%p", 5614 (void *)hdr, (void *)exists); 5615 } else { 5616 /* Dedup */ 5617 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 5618 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 5619 ASSERT(BP_GET_DEDUP(zio->io_bp)); 5620 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 5621 } 5622 } 5623 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5624 /* if it's not anon, we are doing a scrub */ 5625 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 5626 arc_access(hdr, hash_lock); 5627 mutex_exit(hash_lock); 5628 } else { 5629 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5630 } 5631 5632 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5633 callback->awcb_done(zio, buf, callback->awcb_private); 5634 5635 kmem_free(callback, sizeof (arc_write_callback_t)); 5636} 5637 5638zio_t * 5639arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 5640 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready, 5641 arc_done_func_t *children_ready, arc_done_func_t *physdone, 5642 arc_done_func_t *done, void *private, zio_priority_t priority, 5643 int zio_flags, const zbookmark_phys_t *zb) 5644{ 5645 arc_buf_hdr_t *hdr = buf->b_hdr; 5646 arc_write_callback_t *callback; 5647 zio_t *zio; 5648 5649 ASSERT3P(ready, !=, NULL); 5650 ASSERT3P(done, !=, NULL); 5651 ASSERT(!HDR_IO_ERROR(hdr)); 5652 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5653 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5654 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 5655 if (l2arc) 5656 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5657 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 5658 callback->awcb_ready = ready; 5659 callback->awcb_children_ready = children_ready; 5660 callback->awcb_physdone = physdone; 5661 callback->awcb_done = done; 5662 callback->awcb_private = private; 5663 callback->awcb_buf = buf; 5664 5665 /* 5666 * The hdr's b_pdata is now stale, free it now. A new data block 5667 * will be allocated when the zio pipeline calls arc_write_ready(). 5668 */ 5669 if (hdr->b_l1hdr.b_pdata != NULL) { 5670 /* 5671 * If the buf is currently sharing the data block with 5672 * the hdr then we need to break that relationship here. 5673 * The hdr will remain with a NULL data pointer and the 5674 * buf will take sole ownership of the block. 5675 */ 5676 if (arc_buf_is_shared(buf)) { 5677 ASSERT(ARC_BUF_LAST(buf)); 5678 arc_unshare_buf(hdr, buf); 5679 } else { 5680 arc_hdr_free_pdata(hdr); 5681 } 5682 VERIFY3P(buf->b_data, !=, NULL); 5683 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 5684 } 5685 ASSERT(!arc_buf_is_shared(buf)); 5686 ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL); 5687 5688 zio = zio_write(pio, spa, txg, bp, buf->b_data, HDR_GET_LSIZE(hdr), zp, 5689 arc_write_ready, 5690 (children_ready != NULL) ? arc_write_children_ready : NULL, 5691 arc_write_physdone, arc_write_done, callback, 5692 priority, zio_flags, zb); 5693 5694 return (zio); 5695} 5696 5697static int 5698arc_memory_throttle(uint64_t reserve, uint64_t txg) 5699{ 5700#ifdef _KERNEL 5701 uint64_t available_memory = ptob(freemem); 5702 static uint64_t page_load = 0; 5703 static uint64_t last_txg = 0; 5704 5705#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 5706 available_memory = 5707 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 5708#endif 5709 5710 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 5711 return (0); 5712 5713 if (txg > last_txg) { 5714 last_txg = txg; 5715 page_load = 0; 5716 } 5717 /* 5718 * If we are in pageout, we know that memory is already tight, 5719 * the arc is already going to be evicting, so we just want to 5720 * continue to let page writes occur as quickly as possible. 5721 */ 5722 if (curproc == pageproc) { 5723 if (page_load > MAX(ptob(minfree), available_memory) / 4) 5724 return (SET_ERROR(ERESTART)); 5725 /* Note: reserve is inflated, so we deflate */ 5726 page_load += reserve / 8; 5727 return (0); 5728 } else if (page_load > 0 && arc_reclaim_needed()) { 5729 /* memory is low, delay before restarting */ 5730 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 5731 return (SET_ERROR(EAGAIN)); 5732 } 5733 page_load = 0; 5734#endif 5735 return (0); 5736} 5737 5738void 5739arc_tempreserve_clear(uint64_t reserve) 5740{ 5741 atomic_add_64(&arc_tempreserve, -reserve); 5742 ASSERT((int64_t)arc_tempreserve >= 0); 5743} 5744 5745int 5746arc_tempreserve_space(uint64_t reserve, uint64_t txg) 5747{ 5748 int error; 5749 uint64_t anon_size; 5750 5751 if (reserve > arc_c/4 && !arc_no_grow) { 5752 arc_c = MIN(arc_c_max, reserve * 4); 5753 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 5754 } 5755 if (reserve > arc_c) 5756 return (SET_ERROR(ENOMEM)); 5757 5758 /* 5759 * Don't count loaned bufs as in flight dirty data to prevent long 5760 * network delays from blocking transactions that are ready to be 5761 * assigned to a txg. 5762 */ 5763 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 5764 arc_loaned_bytes), 0); 5765 5766 /* 5767 * Writes will, almost always, require additional memory allocations 5768 * in order to compress/encrypt/etc the data. We therefore need to 5769 * make sure that there is sufficient available memory for this. 5770 */ 5771 error = arc_memory_throttle(reserve, txg); 5772 if (error != 0) 5773 return (error); 5774 5775 /* 5776 * Throttle writes when the amount of dirty data in the cache 5777 * gets too large. We try to keep the cache less than half full 5778 * of dirty blocks so that our sync times don't grow too large. 5779 * Note: if two requests come in concurrently, we might let them 5780 * both succeed, when one of them should fail. Not a huge deal. 5781 */ 5782 5783 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 5784 anon_size > arc_c / 4) { 5785 uint64_t meta_esize = 5786 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5787 uint64_t data_esize = 5788 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5789 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 5790 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 5791 arc_tempreserve >> 10, meta_esize >> 10, 5792 data_esize >> 10, reserve >> 10, arc_c >> 10); 5793 return (SET_ERROR(ERESTART)); 5794 } 5795 atomic_add_64(&arc_tempreserve, reserve); 5796 return (0); 5797} 5798 5799static void 5800arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 5801 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 5802{ 5803 size->value.ui64 = refcount_count(&state->arcs_size); 5804 evict_data->value.ui64 = 5805 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 5806 evict_metadata->value.ui64 = 5807 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 5808} 5809 5810static int 5811arc_kstat_update(kstat_t *ksp, int rw) 5812{ 5813 arc_stats_t *as = ksp->ks_data; 5814 5815 if (rw == KSTAT_WRITE) { 5816 return (EACCES); 5817 } else { 5818 arc_kstat_update_state(arc_anon, 5819 &as->arcstat_anon_size, 5820 &as->arcstat_anon_evictable_data, 5821 &as->arcstat_anon_evictable_metadata); 5822 arc_kstat_update_state(arc_mru, 5823 &as->arcstat_mru_size, 5824 &as->arcstat_mru_evictable_data, 5825 &as->arcstat_mru_evictable_metadata); 5826 arc_kstat_update_state(arc_mru_ghost, 5827 &as->arcstat_mru_ghost_size, 5828 &as->arcstat_mru_ghost_evictable_data, 5829 &as->arcstat_mru_ghost_evictable_metadata); 5830 arc_kstat_update_state(arc_mfu, 5831 &as->arcstat_mfu_size, 5832 &as->arcstat_mfu_evictable_data, 5833 &as->arcstat_mfu_evictable_metadata); 5834 arc_kstat_update_state(arc_mfu_ghost, 5835 &as->arcstat_mfu_ghost_size, 5836 &as->arcstat_mfu_ghost_evictable_data, 5837 &as->arcstat_mfu_ghost_evictable_metadata); 5838 } 5839 5840 return (0); 5841} 5842 5843/* 5844 * This function *must* return indices evenly distributed between all 5845 * sublists of the multilist. This is needed due to how the ARC eviction 5846 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 5847 * distributed between all sublists and uses this assumption when 5848 * deciding which sublist to evict from and how much to evict from it. 5849 */ 5850unsigned int 5851arc_state_multilist_index_func(multilist_t *ml, void *obj) 5852{ 5853 arc_buf_hdr_t *hdr = obj; 5854 5855 /* 5856 * We rely on b_dva to generate evenly distributed index 5857 * numbers using buf_hash below. So, as an added precaution, 5858 * let's make sure we never add empty buffers to the arc lists. 5859 */ 5860 ASSERT(!HDR_EMPTY(hdr)); 5861 5862 /* 5863 * The assumption here, is the hash value for a given 5864 * arc_buf_hdr_t will remain constant throughout it's lifetime 5865 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 5866 * Thus, we don't need to store the header's sublist index 5867 * on insertion, as this index can be recalculated on removal. 5868 * 5869 * Also, the low order bits of the hash value are thought to be 5870 * distributed evenly. Otherwise, in the case that the multilist 5871 * has a power of two number of sublists, each sublists' usage 5872 * would not be evenly distributed. 5873 */ 5874 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 5875 multilist_get_num_sublists(ml)); 5876} 5877 5878#ifdef _KERNEL 5879static eventhandler_tag arc_event_lowmem = NULL; 5880 5881static void 5882arc_lowmem(void *arg __unused, int howto __unused) 5883{ 5884 5885 mutex_enter(&arc_reclaim_lock); 5886 /* XXX: Memory deficit should be passed as argument. */ 5887 needfree = btoc(arc_c >> arc_shrink_shift); 5888 DTRACE_PROBE(arc__needfree); 5889 cv_signal(&arc_reclaim_thread_cv); 5890 5891 /* 5892 * It is unsafe to block here in arbitrary threads, because we can come 5893 * here from ARC itself and may hold ARC locks and thus risk a deadlock 5894 * with ARC reclaim thread. 5895 */ 5896 if (curproc == pageproc) 5897 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 5898 mutex_exit(&arc_reclaim_lock); 5899} 5900#endif 5901 5902static void 5903arc_state_init(void) 5904{ 5905 arc_anon = &ARC_anon; 5906 arc_mru = &ARC_mru; 5907 arc_mru_ghost = &ARC_mru_ghost; 5908 arc_mfu = &ARC_mfu; 5909 arc_mfu_ghost = &ARC_mfu_ghost; 5910 arc_l2c_only = &ARC_l2c_only; 5911 5912 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA], 5913 sizeof (arc_buf_hdr_t), 5914 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5915 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5916 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA], 5917 sizeof (arc_buf_hdr_t), 5918 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5919 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5920 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA], 5921 sizeof (arc_buf_hdr_t), 5922 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5923 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5924 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA], 5925 sizeof (arc_buf_hdr_t), 5926 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5927 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5928 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA], 5929 sizeof (arc_buf_hdr_t), 5930 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5931 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5932 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA], 5933 sizeof (arc_buf_hdr_t), 5934 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5935 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5936 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA], 5937 sizeof (arc_buf_hdr_t), 5938 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5939 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5940 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA], 5941 sizeof (arc_buf_hdr_t), 5942 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5943 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5944 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA], 5945 sizeof (arc_buf_hdr_t), 5946 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5947 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5948 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA], 5949 sizeof (arc_buf_hdr_t), 5950 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 5951 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func); 5952 5953 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5954 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5955 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 5956 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 5957 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 5958 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 5959 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 5960 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 5961 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 5962 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 5963 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 5964 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 5965 5966 refcount_create(&arc_anon->arcs_size); 5967 refcount_create(&arc_mru->arcs_size); 5968 refcount_create(&arc_mru_ghost->arcs_size); 5969 refcount_create(&arc_mfu->arcs_size); 5970 refcount_create(&arc_mfu_ghost->arcs_size); 5971 refcount_create(&arc_l2c_only->arcs_size); 5972} 5973 5974static void 5975arc_state_fini(void) 5976{ 5977 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 5978 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 5979 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 5980 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 5981 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 5982 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 5983 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 5984 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 5985 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 5986 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 5987 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 5988 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 5989 5990 refcount_destroy(&arc_anon->arcs_size); 5991 refcount_destroy(&arc_mru->arcs_size); 5992 refcount_destroy(&arc_mru_ghost->arcs_size); 5993 refcount_destroy(&arc_mfu->arcs_size); 5994 refcount_destroy(&arc_mfu_ghost->arcs_size); 5995 refcount_destroy(&arc_l2c_only->arcs_size); 5996 5997 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]); 5998 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 5999 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]); 6000 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 6001 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]); 6002 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 6003 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]); 6004 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 6005} 6006 6007uint64_t 6008arc_max_bytes(void) 6009{ 6010 return (arc_c_max); 6011} 6012 6013void 6014arc_init(void) 6015{ 6016 int i, prefetch_tunable_set = 0; 6017 6018 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 6019 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 6020 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 6021 6022 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 6023 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 6024 6025 /* Convert seconds to clock ticks */ 6026 arc_min_prefetch_lifespan = 1 * hz; 6027 6028 /* Start out with 1/8 of all memory */ 6029 arc_c = kmem_size() / 8; 6030 6031#ifdef illumos 6032#ifdef _KERNEL 6033 /* 6034 * On architectures where the physical memory can be larger 6035 * than the addressable space (intel in 32-bit mode), we may 6036 * need to limit the cache to 1/8 of VM size. 6037 */ 6038 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8); 6039#endif 6040#endif /* illumos */ 6041 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 6042 arc_c_min = MAX(arc_c / 4, arc_abs_min); 6043 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */ 6044 if (arc_c * 8 >= 1 << 30) 6045 arc_c_max = (arc_c * 8) - (1 << 30); 6046 else 6047 arc_c_max = arc_c_min; 6048 arc_c_max = MAX(arc_c * 5, arc_c_max); 6049 6050 /* 6051 * In userland, there's only the memory pressure that we artificially 6052 * create (see arc_available_memory()). Don't let arc_c get too 6053 * small, because it can cause transactions to be larger than 6054 * arc_c, causing arc_tempreserve_space() to fail. 6055 */ 6056#ifndef _KERNEL 6057 arc_c_min = arc_c_max / 2; 6058#endif 6059 6060#ifdef _KERNEL 6061 /* 6062 * Allow the tunables to override our calculations if they are 6063 * reasonable. 6064 */ 6065 if (zfs_arc_max > arc_abs_min && zfs_arc_max < kmem_size()) { 6066 arc_c_max = zfs_arc_max; 6067 arc_c_min = MIN(arc_c_min, arc_c_max); 6068 } 6069 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6070 arc_c_min = zfs_arc_min; 6071#endif 6072 6073 arc_c = arc_c_max; 6074 arc_p = (arc_c >> 1); 6075 arc_size = 0; 6076 6077 /* limit meta-data to 1/4 of the arc capacity */ 6078 arc_meta_limit = arc_c_max / 4; 6079 6080 /* Allow the tunable to override if it is reasonable */ 6081 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6082 arc_meta_limit = zfs_arc_meta_limit; 6083 6084 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6085 arc_c_min = arc_meta_limit / 2; 6086 6087 if (zfs_arc_meta_min > 0) { 6088 arc_meta_min = zfs_arc_meta_min; 6089 } else { 6090 arc_meta_min = arc_c_min / 2; 6091 } 6092 6093 if (zfs_arc_grow_retry > 0) 6094 arc_grow_retry = zfs_arc_grow_retry; 6095 6096 if (zfs_arc_shrink_shift > 0) 6097 arc_shrink_shift = zfs_arc_shrink_shift; 6098 6099 /* 6100 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6101 */ 6102 if (arc_no_grow_shift >= arc_shrink_shift) 6103 arc_no_grow_shift = arc_shrink_shift - 1; 6104 6105 if (zfs_arc_p_min_shift > 0) 6106 arc_p_min_shift = zfs_arc_p_min_shift; 6107 6108 if (zfs_arc_num_sublists_per_state < 1) 6109 zfs_arc_num_sublists_per_state = MAX(max_ncpus, 1); 6110 6111 /* if kmem_flags are set, lets try to use less memory */ 6112 if (kmem_debugging()) 6113 arc_c = arc_c / 2; 6114 if (arc_c < arc_c_min) 6115 arc_c = arc_c_min; 6116 6117 zfs_arc_min = arc_c_min; 6118 zfs_arc_max = arc_c_max; 6119 6120 arc_state_init(); 6121 buf_init(); 6122 6123 arc_reclaim_thread_exit = B_FALSE; 6124 arc_dnlc_evicts_thread_exit = FALSE; 6125 6126 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6127 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6128 6129 if (arc_ksp != NULL) { 6130 arc_ksp->ks_data = &arc_stats; 6131 arc_ksp->ks_update = arc_kstat_update; 6132 kstat_install(arc_ksp); 6133 } 6134 6135 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6136 TS_RUN, minclsyspri); 6137 6138#ifdef _KERNEL 6139 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6140 EVENTHANDLER_PRI_FIRST); 6141#endif 6142 6143 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 6144 TS_RUN, minclsyspri); 6145 6146 arc_dead = B_FALSE; 6147 arc_warm = B_FALSE; 6148 6149 /* 6150 * Calculate maximum amount of dirty data per pool. 6151 * 6152 * If it has been set by /etc/system, take that. 6153 * Otherwise, use a percentage of physical memory defined by 6154 * zfs_dirty_data_max_percent (default 10%) with a cap at 6155 * zfs_dirty_data_max_max (default 4GB). 6156 */ 6157 if (zfs_dirty_data_max == 0) { 6158 zfs_dirty_data_max = ptob(physmem) * 6159 zfs_dirty_data_max_percent / 100; 6160 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6161 zfs_dirty_data_max_max); 6162 } 6163 6164#ifdef _KERNEL 6165 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6166 prefetch_tunable_set = 1; 6167 6168#ifdef __i386__ 6169 if (prefetch_tunable_set == 0) { 6170 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6171 "-- to enable,\n"); 6172 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6173 "to /boot/loader.conf.\n"); 6174 zfs_prefetch_disable = 1; 6175 } 6176#else 6177 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6178 prefetch_tunable_set == 0) { 6179 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6180 "than 4GB of RAM is present;\n" 6181 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6182 "to /boot/loader.conf.\n"); 6183 zfs_prefetch_disable = 1; 6184 } 6185#endif 6186 /* Warn about ZFS memory and address space requirements. */ 6187 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6188 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6189 "expect unstable behavior.\n"); 6190 } 6191 if (kmem_size() < 512 * (1 << 20)) { 6192 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6193 "expect unstable behavior.\n"); 6194 printf(" Consider tuning vm.kmem_size and " 6195 "vm.kmem_size_max\n"); 6196 printf(" in /boot/loader.conf.\n"); 6197 } 6198#endif 6199} 6200 6201void 6202arc_fini(void) 6203{ 6204 mutex_enter(&arc_reclaim_lock); 6205 arc_reclaim_thread_exit = B_TRUE; 6206 /* 6207 * The reclaim thread will set arc_reclaim_thread_exit back to 6208 * B_FALSE when it is finished exiting; we're waiting for that. 6209 */ 6210 while (arc_reclaim_thread_exit) { 6211 cv_signal(&arc_reclaim_thread_cv); 6212 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6213 } 6214 mutex_exit(&arc_reclaim_lock); 6215 6216 /* Use B_TRUE to ensure *all* buffers are evicted */ 6217 arc_flush(NULL, B_TRUE); 6218 6219 mutex_enter(&arc_dnlc_evicts_lock); 6220 arc_dnlc_evicts_thread_exit = TRUE; 6221 /* 6222 * The user evicts thread will set arc_user_evicts_thread_exit 6223 * to FALSE when it is finished exiting; we're waiting for that. 6224 */ 6225 while (arc_dnlc_evicts_thread_exit) { 6226 cv_signal(&arc_dnlc_evicts_cv); 6227 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 6228 } 6229 mutex_exit(&arc_dnlc_evicts_lock); 6230 6231 arc_dead = B_TRUE; 6232 6233 if (arc_ksp != NULL) { 6234 kstat_delete(arc_ksp); 6235 arc_ksp = NULL; 6236 } 6237 6238 mutex_destroy(&arc_reclaim_lock); 6239 cv_destroy(&arc_reclaim_thread_cv); 6240 cv_destroy(&arc_reclaim_waiters_cv); 6241 6242 mutex_destroy(&arc_dnlc_evicts_lock); 6243 cv_destroy(&arc_dnlc_evicts_cv); 6244 6245 arc_state_fini(); 6246 buf_fini(); 6247 6248 ASSERT0(arc_loaned_bytes); 6249 6250#ifdef _KERNEL 6251 if (arc_event_lowmem != NULL) 6252 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6253#endif 6254} 6255 6256/* 6257 * Level 2 ARC 6258 * 6259 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6260 * It uses dedicated storage devices to hold cached data, which are populated 6261 * using large infrequent writes. The main role of this cache is to boost 6262 * the performance of random read workloads. The intended L2ARC devices 6263 * include short-stroked disks, solid state disks, and other media with 6264 * substantially faster read latency than disk. 6265 * 6266 * +-----------------------+ 6267 * | ARC | 6268 * +-----------------------+ 6269 * | ^ ^ 6270 * | | | 6271 * l2arc_feed_thread() arc_read() 6272 * | | | 6273 * | l2arc read | 6274 * V | | 6275 * +---------------+ | 6276 * | L2ARC | | 6277 * +---------------+ | 6278 * | ^ | 6279 * l2arc_write() | | 6280 * | | | 6281 * V | | 6282 * +-------+ +-------+ 6283 * | vdev | | vdev | 6284 * | cache | | cache | 6285 * +-------+ +-------+ 6286 * +=========+ .-----. 6287 * : L2ARC : |-_____-| 6288 * : devices : | Disks | 6289 * +=========+ `-_____-' 6290 * 6291 * Read requests are satisfied from the following sources, in order: 6292 * 6293 * 1) ARC 6294 * 2) vdev cache of L2ARC devices 6295 * 3) L2ARC devices 6296 * 4) vdev cache of disks 6297 * 5) disks 6298 * 6299 * Some L2ARC device types exhibit extremely slow write performance. 6300 * To accommodate for this there are some significant differences between 6301 * the L2ARC and traditional cache design: 6302 * 6303 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6304 * the ARC behave as usual, freeing buffers and placing headers on ghost 6305 * lists. The ARC does not send buffers to the L2ARC during eviction as 6306 * this would add inflated write latencies for all ARC memory pressure. 6307 * 6308 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6309 * It does this by periodically scanning buffers from the eviction-end of 6310 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6311 * not already there. It scans until a headroom of buffers is satisfied, 6312 * which itself is a buffer for ARC eviction. If a compressible buffer is 6313 * found during scanning and selected for writing to an L2ARC device, we 6314 * temporarily boost scanning headroom during the next scan cycle to make 6315 * sure we adapt to compression effects (which might significantly reduce 6316 * the data volume we write to L2ARC). The thread that does this is 6317 * l2arc_feed_thread(), illustrated below; example sizes are included to 6318 * provide a better sense of ratio than this diagram: 6319 * 6320 * head --> tail 6321 * +---------------------+----------+ 6322 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6323 * +---------------------+----------+ | o L2ARC eligible 6324 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6325 * +---------------------+----------+ | 6326 * 15.9 Gbytes ^ 32 Mbytes | 6327 * headroom | 6328 * l2arc_feed_thread() 6329 * | 6330 * l2arc write hand <--[oooo]--' 6331 * | 8 Mbyte 6332 * | write max 6333 * V 6334 * +==============================+ 6335 * L2ARC dev |####|#|###|###| |####| ... | 6336 * +==============================+ 6337 * 32 Gbytes 6338 * 6339 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 6340 * evicted, then the L2ARC has cached a buffer much sooner than it probably 6341 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 6342 * safe to say that this is an uncommon case, since buffers at the end of 6343 * the ARC lists have moved there due to inactivity. 6344 * 6345 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 6346 * then the L2ARC simply misses copying some buffers. This serves as a 6347 * pressure valve to prevent heavy read workloads from both stalling the ARC 6348 * with waits and clogging the L2ARC with writes. This also helps prevent 6349 * the potential for the L2ARC to churn if it attempts to cache content too 6350 * quickly, such as during backups of the entire pool. 6351 * 6352 * 5. After system boot and before the ARC has filled main memory, there are 6353 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 6354 * lists can remain mostly static. Instead of searching from tail of these 6355 * lists as pictured, the l2arc_feed_thread() will search from the list heads 6356 * for eligible buffers, greatly increasing its chance of finding them. 6357 * 6358 * The L2ARC device write speed is also boosted during this time so that 6359 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 6360 * there are no L2ARC reads, and no fear of degrading read performance 6361 * through increased writes. 6362 * 6363 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 6364 * the vdev queue can aggregate them into larger and fewer writes. Each 6365 * device is written to in a rotor fashion, sweeping writes through 6366 * available space then repeating. 6367 * 6368 * 7. The L2ARC does not store dirty content. It never needs to flush 6369 * write buffers back to disk based storage. 6370 * 6371 * 8. If an ARC buffer is written (and dirtied) which also exists in the 6372 * L2ARC, the now stale L2ARC buffer is immediately dropped. 6373 * 6374 * The performance of the L2ARC can be tweaked by a number of tunables, which 6375 * may be necessary for different workloads: 6376 * 6377 * l2arc_write_max max write bytes per interval 6378 * l2arc_write_boost extra write bytes during device warmup 6379 * l2arc_noprefetch skip caching prefetched buffers 6380 * l2arc_headroom number of max device writes to precache 6381 * l2arc_headroom_boost when we find compressed buffers during ARC 6382 * scanning, we multiply headroom by this 6383 * percentage factor for the next scan cycle, 6384 * since more compressed buffers are likely to 6385 * be present 6386 * l2arc_feed_secs seconds between L2ARC writing 6387 * 6388 * Tunables may be removed or added as future performance improvements are 6389 * integrated, and also may become zpool properties. 6390 * 6391 * There are three key functions that control how the L2ARC warms up: 6392 * 6393 * l2arc_write_eligible() check if a buffer is eligible to cache 6394 * l2arc_write_size() calculate how much to write 6395 * l2arc_write_interval() calculate sleep delay between writes 6396 * 6397 * These three functions determine what to write, how much, and how quickly 6398 * to send writes. 6399 */ 6400 6401static boolean_t 6402l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 6403{ 6404 /* 6405 * A buffer is *not* eligible for the L2ARC if it: 6406 * 1. belongs to a different spa. 6407 * 2. is already cached on the L2ARC. 6408 * 3. has an I/O in progress (it may be an incomplete read). 6409 * 4. is flagged not eligible (zfs property). 6410 */ 6411 if (hdr->b_spa != spa_guid) { 6412 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 6413 return (B_FALSE); 6414 } 6415 if (HDR_HAS_L2HDR(hdr)) { 6416 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 6417 return (B_FALSE); 6418 } 6419 if (HDR_IO_IN_PROGRESS(hdr)) { 6420 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 6421 return (B_FALSE); 6422 } 6423 if (!HDR_L2CACHE(hdr)) { 6424 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 6425 return (B_FALSE); 6426 } 6427 6428 return (B_TRUE); 6429} 6430 6431static uint64_t 6432l2arc_write_size(void) 6433{ 6434 uint64_t size; 6435 6436 /* 6437 * Make sure our globals have meaningful values in case the user 6438 * altered them. 6439 */ 6440 size = l2arc_write_max; 6441 if (size == 0) { 6442 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 6443 "be greater than zero, resetting it to the default (%d)", 6444 L2ARC_WRITE_SIZE); 6445 size = l2arc_write_max = L2ARC_WRITE_SIZE; 6446 } 6447 6448 if (arc_warm == B_FALSE) 6449 size += l2arc_write_boost; 6450 6451 return (size); 6452 6453} 6454 6455static clock_t 6456l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 6457{ 6458 clock_t interval, next, now; 6459 6460 /* 6461 * If the ARC lists are busy, increase our write rate; if the 6462 * lists are stale, idle back. This is achieved by checking 6463 * how much we previously wrote - if it was more than half of 6464 * what we wanted, schedule the next write much sooner. 6465 */ 6466 if (l2arc_feed_again && wrote > (wanted / 2)) 6467 interval = (hz * l2arc_feed_min_ms) / 1000; 6468 else 6469 interval = hz * l2arc_feed_secs; 6470 6471 now = ddi_get_lbolt(); 6472 next = MAX(now, MIN(now + interval, began + interval)); 6473 6474 return (next); 6475} 6476 6477/* 6478 * Cycle through L2ARC devices. This is how L2ARC load balances. 6479 * If a device is returned, this also returns holding the spa config lock. 6480 */ 6481static l2arc_dev_t * 6482l2arc_dev_get_next(void) 6483{ 6484 l2arc_dev_t *first, *next = NULL; 6485 6486 /* 6487 * Lock out the removal of spas (spa_namespace_lock), then removal 6488 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 6489 * both locks will be dropped and a spa config lock held instead. 6490 */ 6491 mutex_enter(&spa_namespace_lock); 6492 mutex_enter(&l2arc_dev_mtx); 6493 6494 /* if there are no vdevs, there is nothing to do */ 6495 if (l2arc_ndev == 0) 6496 goto out; 6497 6498 first = NULL; 6499 next = l2arc_dev_last; 6500 do { 6501 /* loop around the list looking for a non-faulted vdev */ 6502 if (next == NULL) { 6503 next = list_head(l2arc_dev_list); 6504 } else { 6505 next = list_next(l2arc_dev_list, next); 6506 if (next == NULL) 6507 next = list_head(l2arc_dev_list); 6508 } 6509 6510 /* if we have come back to the start, bail out */ 6511 if (first == NULL) 6512 first = next; 6513 else if (next == first) 6514 break; 6515 6516 } while (vdev_is_dead(next->l2ad_vdev)); 6517 6518 /* if we were unable to find any usable vdevs, return NULL */ 6519 if (vdev_is_dead(next->l2ad_vdev)) 6520 next = NULL; 6521 6522 l2arc_dev_last = next; 6523 6524out: 6525 mutex_exit(&l2arc_dev_mtx); 6526 6527 /* 6528 * Grab the config lock to prevent the 'next' device from being 6529 * removed while we are writing to it. 6530 */ 6531 if (next != NULL) 6532 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 6533 mutex_exit(&spa_namespace_lock); 6534 6535 return (next); 6536} 6537 6538/* 6539 * Free buffers that were tagged for destruction. 6540 */ 6541static void 6542l2arc_do_free_on_write() 6543{ 6544 list_t *buflist; 6545 l2arc_data_free_t *df, *df_prev; 6546 6547 mutex_enter(&l2arc_free_on_write_mtx); 6548 buflist = l2arc_free_on_write; 6549 6550 for (df = list_tail(buflist); df; df = df_prev) { 6551 df_prev = list_prev(buflist, df); 6552 ASSERT3P(df->l2df_data, !=, NULL); 6553 if (df->l2df_type == ARC_BUFC_METADATA) { 6554 zio_buf_free(df->l2df_data, df->l2df_size); 6555 } else { 6556 ASSERT(df->l2df_type == ARC_BUFC_DATA); 6557 zio_data_buf_free(df->l2df_data, df->l2df_size); 6558 } 6559 list_remove(buflist, df); 6560 kmem_free(df, sizeof (l2arc_data_free_t)); 6561 } 6562 6563 mutex_exit(&l2arc_free_on_write_mtx); 6564} 6565 6566/* 6567 * A write to a cache device has completed. Update all headers to allow 6568 * reads from these buffers to begin. 6569 */ 6570static void 6571l2arc_write_done(zio_t *zio) 6572{ 6573 l2arc_write_callback_t *cb; 6574 l2arc_dev_t *dev; 6575 list_t *buflist; 6576 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6577 kmutex_t *hash_lock; 6578 int64_t bytes_dropped = 0; 6579 6580 cb = zio->io_private; 6581 ASSERT3P(cb, !=, NULL); 6582 dev = cb->l2wcb_dev; 6583 ASSERT3P(dev, !=, NULL); 6584 head = cb->l2wcb_head; 6585 ASSERT3P(head, !=, NULL); 6586 buflist = &dev->l2ad_buflist; 6587 ASSERT3P(buflist, !=, NULL); 6588 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6589 l2arc_write_callback_t *, cb); 6590 6591 if (zio->io_error != 0) 6592 ARCSTAT_BUMP(arcstat_l2_writes_error); 6593 6594 /* 6595 * All writes completed, or an error was hit. 6596 */ 6597top: 6598 mutex_enter(&dev->l2ad_mtx); 6599 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 6600 hdr_prev = list_prev(buflist, hdr); 6601 6602 hash_lock = HDR_LOCK(hdr); 6603 6604 /* 6605 * We cannot use mutex_enter or else we can deadlock 6606 * with l2arc_write_buffers (due to swapping the order 6607 * the hash lock and l2ad_mtx are taken). 6608 */ 6609 if (!mutex_tryenter(hash_lock)) { 6610 /* 6611 * Missed the hash lock. We must retry so we 6612 * don't leave the ARC_FLAG_L2_WRITING bit set. 6613 */ 6614 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 6615 6616 /* 6617 * We don't want to rescan the headers we've 6618 * already marked as having been written out, so 6619 * we reinsert the head node so we can pick up 6620 * where we left off. 6621 */ 6622 list_remove(buflist, head); 6623 list_insert_after(buflist, hdr, head); 6624 6625 mutex_exit(&dev->l2ad_mtx); 6626 6627 /* 6628 * We wait for the hash lock to become available 6629 * to try and prevent busy waiting, and increase 6630 * the chance we'll be able to acquire the lock 6631 * the next time around. 6632 */ 6633 mutex_enter(hash_lock); 6634 mutex_exit(hash_lock); 6635 goto top; 6636 } 6637 6638 /* 6639 * We could not have been moved into the arc_l2c_only 6640 * state while in-flight due to our ARC_FLAG_L2_WRITING 6641 * bit being set. Let's just ensure that's being enforced. 6642 */ 6643 ASSERT(HDR_HAS_L1HDR(hdr)); 6644 6645 if (zio->io_error != 0) { 6646 /* 6647 * Error - drop L2ARC entry. 6648 */ 6649 list_remove(buflist, hdr); 6650 l2arc_trim(hdr); 6651 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 6652 6653 ARCSTAT_INCR(arcstat_l2_asize, -arc_hdr_size(hdr)); 6654 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 6655 6656 bytes_dropped += arc_hdr_size(hdr); 6657 (void) refcount_remove_many(&dev->l2ad_alloc, 6658 arc_hdr_size(hdr), hdr); 6659 } 6660 6661 /* 6662 * Allow ARC to begin reads and ghost list evictions to 6663 * this L2ARC entry. 6664 */ 6665 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 6666 6667 mutex_exit(hash_lock); 6668 } 6669 6670 atomic_inc_64(&l2arc_writes_done); 6671 list_remove(buflist, head); 6672 ASSERT(!HDR_HAS_L1HDR(head)); 6673 kmem_cache_free(hdr_l2only_cache, head); 6674 mutex_exit(&dev->l2ad_mtx); 6675 6676 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 6677 6678 l2arc_do_free_on_write(); 6679 6680 kmem_free(cb, sizeof (l2arc_write_callback_t)); 6681} 6682 6683/* 6684 * A read to a cache device completed. Validate buffer contents before 6685 * handing over to the regular ARC routines. 6686 */ 6687static void 6688l2arc_read_done(zio_t *zio) 6689{ 6690 l2arc_read_callback_t *cb; 6691 arc_buf_hdr_t *hdr; 6692 kmutex_t *hash_lock; 6693 boolean_t valid_cksum; 6694 6695 ASSERT3P(zio->io_vd, !=, NULL); 6696 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 6697 6698 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 6699 6700 cb = zio->io_private; 6701 ASSERT3P(cb, !=, NULL); 6702 hdr = cb->l2rcb_hdr; 6703 ASSERT3P(hdr, !=, NULL); 6704 6705 hash_lock = HDR_LOCK(hdr); 6706 mutex_enter(hash_lock); 6707 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 6708 6709 /* 6710 * If the data was read into a temporary buffer, 6711 * move it and free the buffer. 6712 */ 6713 if (cb->l2rcb_data != NULL) { 6714 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 6715 if (zio->io_error == 0) { 6716 bcopy(cb->l2rcb_data, hdr->b_l1hdr.b_pdata, 6717 arc_hdr_size(hdr)); 6718 } 6719 6720 /* 6721 * The following must be done regardless of whether 6722 * there was an error: 6723 * - free the temporary buffer 6724 * - point zio to the real ARC buffer 6725 * - set zio size accordingly 6726 * These are required because zio is either re-used for 6727 * an I/O of the block in the case of the error 6728 * or the zio is passed to arc_read_done() and it 6729 * needs real data. 6730 */ 6731 zio_data_buf_free(cb->l2rcb_data, zio->io_size); 6732 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 6733 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_pdata; 6734 } 6735 6736 ASSERT3P(zio->io_data, !=, NULL); 6737 6738 /* 6739 * Check this survived the L2ARC journey. 6740 */ 6741 ASSERT3P(zio->io_data, ==, hdr->b_l1hdr.b_pdata); 6742 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 6743 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 6744 6745 valid_cksum = arc_cksum_is_equal(hdr, zio); 6746 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 6747 mutex_exit(hash_lock); 6748 zio->io_private = hdr; 6749 arc_read_done(zio); 6750 } else { 6751 mutex_exit(hash_lock); 6752 /* 6753 * Buffer didn't survive caching. Increment stats and 6754 * reissue to the original storage device. 6755 */ 6756 if (zio->io_error != 0) { 6757 ARCSTAT_BUMP(arcstat_l2_io_error); 6758 } else { 6759 zio->io_error = SET_ERROR(EIO); 6760 } 6761 if (!valid_cksum) 6762 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 6763 6764 /* 6765 * If there's no waiter, issue an async i/o to the primary 6766 * storage now. If there *is* a waiter, the caller must 6767 * issue the i/o in a context where it's OK to block. 6768 */ 6769 if (zio->io_waiter == NULL) { 6770 zio_t *pio = zio_unique_parent(zio); 6771 6772 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 6773 6774 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 6775 hdr->b_l1hdr.b_pdata, zio->io_size, arc_read_done, 6776 hdr, zio->io_priority, cb->l2rcb_flags, 6777 &cb->l2rcb_zb)); 6778 } 6779 } 6780 6781 kmem_free(cb, sizeof (l2arc_read_callback_t)); 6782} 6783 6784/* 6785 * This is the list priority from which the L2ARC will search for pages to 6786 * cache. This is used within loops (0..3) to cycle through lists in the 6787 * desired order. This order can have a significant effect on cache 6788 * performance. 6789 * 6790 * Currently the metadata lists are hit first, MFU then MRU, followed by 6791 * the data lists. This function returns a locked list, and also returns 6792 * the lock pointer. 6793 */ 6794static multilist_sublist_t * 6795l2arc_sublist_lock(int list_num) 6796{ 6797 multilist_t *ml = NULL; 6798 unsigned int idx; 6799 6800 ASSERT(list_num >= 0 && list_num <= 3); 6801 6802 switch (list_num) { 6803 case 0: 6804 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA]; 6805 break; 6806 case 1: 6807 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA]; 6808 break; 6809 case 2: 6810 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA]; 6811 break; 6812 case 3: 6813 ml = &arc_mru->arcs_list[ARC_BUFC_DATA]; 6814 break; 6815 } 6816 6817 /* 6818 * Return a randomly-selected sublist. This is acceptable 6819 * because the caller feeds only a little bit of data for each 6820 * call (8MB). Subsequent calls will result in different 6821 * sublists being selected. 6822 */ 6823 idx = multilist_get_random_index(ml); 6824 return (multilist_sublist_lock(ml, idx)); 6825} 6826 6827/* 6828 * Evict buffers from the device write hand to the distance specified in 6829 * bytes. This distance may span populated buffers, it may span nothing. 6830 * This is clearing a region on the L2ARC device ready for writing. 6831 * If the 'all' boolean is set, every buffer is evicted. 6832 */ 6833static void 6834l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 6835{ 6836 list_t *buflist; 6837 arc_buf_hdr_t *hdr, *hdr_prev; 6838 kmutex_t *hash_lock; 6839 uint64_t taddr; 6840 6841 buflist = &dev->l2ad_buflist; 6842 6843 if (!all && dev->l2ad_first) { 6844 /* 6845 * This is the first sweep through the device. There is 6846 * nothing to evict. 6847 */ 6848 return; 6849 } 6850 6851 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 6852 /* 6853 * When nearing the end of the device, evict to the end 6854 * before the device write hand jumps to the start. 6855 */ 6856 taddr = dev->l2ad_end; 6857 } else { 6858 taddr = dev->l2ad_hand + distance; 6859 } 6860 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 6861 uint64_t, taddr, boolean_t, all); 6862 6863top: 6864 mutex_enter(&dev->l2ad_mtx); 6865 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 6866 hdr_prev = list_prev(buflist, hdr); 6867 6868 hash_lock = HDR_LOCK(hdr); 6869 6870 /* 6871 * We cannot use mutex_enter or else we can deadlock 6872 * with l2arc_write_buffers (due to swapping the order 6873 * the hash lock and l2ad_mtx are taken). 6874 */ 6875 if (!mutex_tryenter(hash_lock)) { 6876 /* 6877 * Missed the hash lock. Retry. 6878 */ 6879 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 6880 mutex_exit(&dev->l2ad_mtx); 6881 mutex_enter(hash_lock); 6882 mutex_exit(hash_lock); 6883 goto top; 6884 } 6885 6886 if (HDR_L2_WRITE_HEAD(hdr)) { 6887 /* 6888 * We hit a write head node. Leave it for 6889 * l2arc_write_done(). 6890 */ 6891 list_remove(buflist, hdr); 6892 mutex_exit(hash_lock); 6893 continue; 6894 } 6895 6896 if (!all && HDR_HAS_L2HDR(hdr) && 6897 (hdr->b_l2hdr.b_daddr > taddr || 6898 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 6899 /* 6900 * We've evicted to the target address, 6901 * or the end of the device. 6902 */ 6903 mutex_exit(hash_lock); 6904 break; 6905 } 6906 6907 ASSERT(HDR_HAS_L2HDR(hdr)); 6908 if (!HDR_HAS_L1HDR(hdr)) { 6909 ASSERT(!HDR_L2_READING(hdr)); 6910 /* 6911 * This doesn't exist in the ARC. Destroy. 6912 * arc_hdr_destroy() will call list_remove() 6913 * and decrement arcstat_l2_size. 6914 */ 6915 arc_change_state(arc_anon, hdr, hash_lock); 6916 arc_hdr_destroy(hdr); 6917 } else { 6918 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 6919 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 6920 /* 6921 * Invalidate issued or about to be issued 6922 * reads, since we may be about to write 6923 * over this location. 6924 */ 6925 if (HDR_L2_READING(hdr)) { 6926 ARCSTAT_BUMP(arcstat_l2_evict_reading); 6927 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 6928 } 6929 6930 /* Ensure this header has finished being written */ 6931 ASSERT(!HDR_L2_WRITING(hdr)); 6932 6933 arc_hdr_l2hdr_destroy(hdr); 6934 } 6935 mutex_exit(hash_lock); 6936 } 6937 mutex_exit(&dev->l2ad_mtx); 6938} 6939 6940/* 6941 * Find and write ARC buffers to the L2ARC device. 6942 * 6943 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 6944 * for reading until they have completed writing. 6945 * The headroom_boost is an in-out parameter used to maintain headroom boost 6946 * state between calls to this function. 6947 * 6948 * Returns the number of bytes actually written (which may be smaller than 6949 * the delta by which the device hand has changed due to alignment). 6950 */ 6951static uint64_t 6952l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 6953{ 6954 arc_buf_hdr_t *hdr, *hdr_prev, *head; 6955 uint64_t write_asize, write_psize, write_sz, headroom; 6956 boolean_t full; 6957 l2arc_write_callback_t *cb; 6958 zio_t *pio, *wzio; 6959 uint64_t guid = spa_load_guid(spa); 6960 int try; 6961 6962 ASSERT3P(dev->l2ad_vdev, !=, NULL); 6963 6964 pio = NULL; 6965 write_sz = write_asize = write_psize = 0; 6966 full = B_FALSE; 6967 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 6968 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 6969 6970 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 6971 /* 6972 * Copy buffers for L2ARC writing. 6973 */ 6974 for (try = 0; try <= 3; try++) { 6975 multilist_sublist_t *mls = l2arc_sublist_lock(try); 6976 uint64_t passed_sz = 0; 6977 6978 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 6979 6980 /* 6981 * L2ARC fast warmup. 6982 * 6983 * Until the ARC is warm and starts to evict, read from the 6984 * head of the ARC lists rather than the tail. 6985 */ 6986 if (arc_warm == B_FALSE) 6987 hdr = multilist_sublist_head(mls); 6988 else 6989 hdr = multilist_sublist_tail(mls); 6990 if (hdr == NULL) 6991 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 6992 6993 headroom = target_sz * l2arc_headroom; 6994 if (zfs_compressed_arc_enabled) 6995 headroom = (headroom * l2arc_headroom_boost) / 100; 6996 6997 for (; hdr; hdr = hdr_prev) { 6998 kmutex_t *hash_lock; 6999 7000 if (arc_warm == B_FALSE) 7001 hdr_prev = multilist_sublist_next(mls, hdr); 7002 else 7003 hdr_prev = multilist_sublist_prev(mls, hdr); 7004 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 7005 HDR_GET_LSIZE(hdr)); 7006 7007 hash_lock = HDR_LOCK(hdr); 7008 if (!mutex_tryenter(hash_lock)) { 7009 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 7010 /* 7011 * Skip this buffer rather than waiting. 7012 */ 7013 continue; 7014 } 7015 7016 passed_sz += HDR_GET_LSIZE(hdr); 7017 if (passed_sz > headroom) { 7018 /* 7019 * Searched too far. 7020 */ 7021 mutex_exit(hash_lock); 7022 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 7023 break; 7024 } 7025 7026 if (!l2arc_write_eligible(guid, hdr)) { 7027 mutex_exit(hash_lock); 7028 continue; 7029 } 7030 7031 if ((write_asize + HDR_GET_LSIZE(hdr)) > target_sz) { 7032 full = B_TRUE; 7033 mutex_exit(hash_lock); 7034 ARCSTAT_BUMP(arcstat_l2_write_full); 7035 break; 7036 } 7037 7038 if (pio == NULL) { 7039 /* 7040 * Insert a dummy header on the buflist so 7041 * l2arc_write_done() can find where the 7042 * write buffers begin without searching. 7043 */ 7044 mutex_enter(&dev->l2ad_mtx); 7045 list_insert_head(&dev->l2ad_buflist, head); 7046 mutex_exit(&dev->l2ad_mtx); 7047 7048 cb = kmem_alloc( 7049 sizeof (l2arc_write_callback_t), KM_SLEEP); 7050 cb->l2wcb_dev = dev; 7051 cb->l2wcb_head = head; 7052 pio = zio_root(spa, l2arc_write_done, cb, 7053 ZIO_FLAG_CANFAIL); 7054 ARCSTAT_BUMP(arcstat_l2_write_pios); 7055 } 7056 7057 hdr->b_l2hdr.b_dev = dev; 7058 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 7059 arc_hdr_set_flags(hdr, 7060 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 7061 7062 mutex_enter(&dev->l2ad_mtx); 7063 list_insert_head(&dev->l2ad_buflist, hdr); 7064 mutex_exit(&dev->l2ad_mtx); 7065 7066 /* 7067 * We rely on the L1 portion of the header below, so 7068 * it's invalid for this header to have been evicted out 7069 * of the ghost cache, prior to being written out. The 7070 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 7071 */ 7072 ASSERT(HDR_HAS_L1HDR(hdr)); 7073 7074 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 7075 ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL); 7076 ASSERT3U(arc_hdr_size(hdr), >, 0); 7077 uint64_t size = arc_hdr_size(hdr); 7078 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 7079 size); 7080 7081 (void) refcount_add_many(&dev->l2ad_alloc, size, hdr); 7082 7083 /* 7084 * Normally the L2ARC can use the hdr's data, but if 7085 * we're sharing data between the hdr and one of its 7086 * bufs, L2ARC needs its own copy of the data so that 7087 * the ZIO below can't race with the buf consumer. To 7088 * ensure that this copy will be available for the 7089 * lifetime of the ZIO and be cleaned up afterwards, we 7090 * add it to the l2arc_free_on_write queue. 7091 */ 7092 void *to_write; 7093 if (!HDR_SHARED_DATA(hdr) && size == asize) { 7094 to_write = hdr->b_l1hdr.b_pdata; 7095 } else { 7096 arc_buf_contents_t type = arc_buf_type(hdr); 7097 if (type == ARC_BUFC_METADATA) { 7098 to_write = zio_buf_alloc(asize); 7099 } else { 7100 ASSERT3U(type, ==, ARC_BUFC_DATA); 7101 to_write = zio_data_buf_alloc(asize); 7102 } 7103 7104 bcopy(hdr->b_l1hdr.b_pdata, to_write, size); 7105 if (asize != size) 7106 bzero(to_write + size, asize - size); 7107 l2arc_free_data_on_write(to_write, asize, type); 7108 } 7109 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7110 hdr->b_l2hdr.b_daddr, asize, to_write, 7111 ZIO_CHECKSUM_OFF, NULL, hdr, 7112 ZIO_PRIORITY_ASYNC_WRITE, 7113 ZIO_FLAG_CANFAIL, B_FALSE); 7114 7115 write_sz += HDR_GET_LSIZE(hdr); 7116 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7117 zio_t *, wzio); 7118 7119 write_asize += size; 7120 write_psize += asize; 7121 dev->l2ad_hand += asize; 7122 7123 mutex_exit(hash_lock); 7124 7125 (void) zio_nowait(wzio); 7126 } 7127 7128 multilist_sublist_unlock(mls); 7129 7130 if (full == B_TRUE) 7131 break; 7132 } 7133 7134 /* No buffers selected for writing? */ 7135 if (pio == NULL) { 7136 ASSERT0(write_sz); 7137 ASSERT(!HDR_HAS_L1HDR(head)); 7138 kmem_cache_free(hdr_l2only_cache, head); 7139 return (0); 7140 } 7141 7142 ASSERT3U(write_asize, <=, target_sz); 7143 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7144 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 7145 ARCSTAT_INCR(arcstat_l2_size, write_sz); 7146 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 7147 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 7148 7149 /* 7150 * Bump device hand to the device start if it is approaching the end. 7151 * l2arc_evict() will already have evicted ahead for this case. 7152 */ 7153 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7154 dev->l2ad_hand = dev->l2ad_start; 7155 dev->l2ad_first = B_FALSE; 7156 } 7157 7158 dev->l2ad_writing = B_TRUE; 7159 (void) zio_wait(pio); 7160 dev->l2ad_writing = B_FALSE; 7161 7162 return (write_asize); 7163} 7164 7165/* 7166 * This thread feeds the L2ARC at regular intervals. This is the beating 7167 * heart of the L2ARC. 7168 */ 7169static void 7170l2arc_feed_thread(void *dummy __unused) 7171{ 7172 callb_cpr_t cpr; 7173 l2arc_dev_t *dev; 7174 spa_t *spa; 7175 uint64_t size, wrote; 7176 clock_t begin, next = ddi_get_lbolt(); 7177 7178 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7179 7180 mutex_enter(&l2arc_feed_thr_lock); 7181 7182 while (l2arc_thread_exit == 0) { 7183 CALLB_CPR_SAFE_BEGIN(&cpr); 7184 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7185 next - ddi_get_lbolt()); 7186 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7187 next = ddi_get_lbolt() + hz; 7188 7189 /* 7190 * Quick check for L2ARC devices. 7191 */ 7192 mutex_enter(&l2arc_dev_mtx); 7193 if (l2arc_ndev == 0) { 7194 mutex_exit(&l2arc_dev_mtx); 7195 continue; 7196 } 7197 mutex_exit(&l2arc_dev_mtx); 7198 begin = ddi_get_lbolt(); 7199 7200 /* 7201 * This selects the next l2arc device to write to, and in 7202 * doing so the next spa to feed from: dev->l2ad_spa. This 7203 * will return NULL if there are now no l2arc devices or if 7204 * they are all faulted. 7205 * 7206 * If a device is returned, its spa's config lock is also 7207 * held to prevent device removal. l2arc_dev_get_next() 7208 * will grab and release l2arc_dev_mtx. 7209 */ 7210 if ((dev = l2arc_dev_get_next()) == NULL) 7211 continue; 7212 7213 spa = dev->l2ad_spa; 7214 ASSERT3P(spa, !=, NULL); 7215 7216 /* 7217 * If the pool is read-only then force the feed thread to 7218 * sleep a little longer. 7219 */ 7220 if (!spa_writeable(spa)) { 7221 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7222 spa_config_exit(spa, SCL_L2ARC, dev); 7223 continue; 7224 } 7225 7226 /* 7227 * Avoid contributing to memory pressure. 7228 */ 7229 if (arc_reclaim_needed()) { 7230 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7231 spa_config_exit(spa, SCL_L2ARC, dev); 7232 continue; 7233 } 7234 7235 ARCSTAT_BUMP(arcstat_l2_feeds); 7236 7237 size = l2arc_write_size(); 7238 7239 /* 7240 * Evict L2ARC buffers that will be overwritten. 7241 */ 7242 l2arc_evict(dev, size, B_FALSE); 7243 7244 /* 7245 * Write ARC buffers. 7246 */ 7247 wrote = l2arc_write_buffers(spa, dev, size); 7248 7249 /* 7250 * Calculate interval between writes. 7251 */ 7252 next = l2arc_write_interval(begin, size, wrote); 7253 spa_config_exit(spa, SCL_L2ARC, dev); 7254 } 7255 7256 l2arc_thread_exit = 0; 7257 cv_broadcast(&l2arc_feed_thr_cv); 7258 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7259 thread_exit(); 7260} 7261 7262boolean_t 7263l2arc_vdev_present(vdev_t *vd) 7264{ 7265 l2arc_dev_t *dev; 7266 7267 mutex_enter(&l2arc_dev_mtx); 7268 for (dev = list_head(l2arc_dev_list); dev != NULL; 7269 dev = list_next(l2arc_dev_list, dev)) { 7270 if (dev->l2ad_vdev == vd) 7271 break; 7272 } 7273 mutex_exit(&l2arc_dev_mtx); 7274 7275 return (dev != NULL); 7276} 7277 7278/* 7279 * Add a vdev for use by the L2ARC. By this point the spa has already 7280 * validated the vdev and opened it. 7281 */ 7282void 7283l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7284{ 7285 l2arc_dev_t *adddev; 7286 7287 ASSERT(!l2arc_vdev_present(vd)); 7288 7289 vdev_ashift_optimize(vd); 7290 7291 /* 7292 * Create a new l2arc device entry. 7293 */ 7294 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7295 adddev->l2ad_spa = spa; 7296 adddev->l2ad_vdev = vd; 7297 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7298 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7299 adddev->l2ad_hand = adddev->l2ad_start; 7300 adddev->l2ad_first = B_TRUE; 7301 adddev->l2ad_writing = B_FALSE; 7302 7303 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7304 /* 7305 * This is a list of all ARC buffers that are still valid on the 7306 * device. 7307 */ 7308 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7309 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7310 7311 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7312 refcount_create(&adddev->l2ad_alloc); 7313 7314 /* 7315 * Add device to global list 7316 */ 7317 mutex_enter(&l2arc_dev_mtx); 7318 list_insert_head(l2arc_dev_list, adddev); 7319 atomic_inc_64(&l2arc_ndev); 7320 mutex_exit(&l2arc_dev_mtx); 7321} 7322 7323/* 7324 * Remove a vdev from the L2ARC. 7325 */ 7326void 7327l2arc_remove_vdev(vdev_t *vd) 7328{ 7329 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7330 7331 /* 7332 * Find the device by vdev 7333 */ 7334 mutex_enter(&l2arc_dev_mtx); 7335 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7336 nextdev = list_next(l2arc_dev_list, dev); 7337 if (vd == dev->l2ad_vdev) { 7338 remdev = dev; 7339 break; 7340 } 7341 } 7342 ASSERT3P(remdev, !=, NULL); 7343 7344 /* 7345 * Remove device from global list 7346 */ 7347 list_remove(l2arc_dev_list, remdev); 7348 l2arc_dev_last = NULL; /* may have been invalidated */ 7349 atomic_dec_64(&l2arc_ndev); 7350 mutex_exit(&l2arc_dev_mtx); 7351 7352 /* 7353 * Clear all buflists and ARC references. L2ARC device flush. 7354 */ 7355 l2arc_evict(remdev, 0, B_TRUE); 7356 list_destroy(&remdev->l2ad_buflist); 7357 mutex_destroy(&remdev->l2ad_mtx); 7358 refcount_destroy(&remdev->l2ad_alloc); 7359 kmem_free(remdev, sizeof (l2arc_dev_t)); 7360} 7361 7362void 7363l2arc_init(void) 7364{ 7365 l2arc_thread_exit = 0; 7366 l2arc_ndev = 0; 7367 l2arc_writes_sent = 0; 7368 l2arc_writes_done = 0; 7369 7370 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7371 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7372 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7373 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7374 7375 l2arc_dev_list = &L2ARC_dev_list; 7376 l2arc_free_on_write = &L2ARC_free_on_write; 7377 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7378 offsetof(l2arc_dev_t, l2ad_node)); 7379 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7380 offsetof(l2arc_data_free_t, l2df_list_node)); 7381} 7382 7383void 7384l2arc_fini(void) 7385{ 7386 /* 7387 * This is called from dmu_fini(), which is called from spa_fini(); 7388 * Because of this, we can assume that all l2arc devices have 7389 * already been removed when the pools themselves were removed. 7390 */ 7391 7392 l2arc_do_free_on_write(); 7393 7394 mutex_destroy(&l2arc_feed_thr_lock); 7395 cv_destroy(&l2arc_feed_thr_cv); 7396 mutex_destroy(&l2arc_dev_mtx); 7397 mutex_destroy(&l2arc_free_on_write_mtx); 7398 7399 list_destroy(l2arc_dev_list); 7400 list_destroy(l2arc_free_on_write); 7401} 7402 7403void 7404l2arc_start(void) 7405{ 7406 if (!(spa_mode_global & FWRITE)) 7407 return; 7408 7409 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7410 TS_RUN, minclsyspri); 7411} 7412 7413void 7414l2arc_stop(void) 7415{ 7416 if (!(spa_mode_global & FWRITE)) 7417 return; 7418 7419 mutex_enter(&l2arc_feed_thr_lock); 7420 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7421 l2arc_thread_exit = 1; 7422 while (l2arc_thread_exit != 0) 7423 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7424 mutex_exit(&l2arc_feed_thr_lock); 7425} 7426