arc.c revision 321613
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, 2017 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 * Note that the majority of the performance stats are manipulated 103 * with atomic operations. 104 * 105 * The L2ARC uses the l2ad_mtx on each vdev for the following: 106 * 107 * - L2ARC buflist creation 108 * - L2ARC buflist eviction 109 * - L2ARC write completion, which walks L2ARC buflists 110 * - ARC header destruction, as it removes from L2ARC buflists 111 * - ARC header release, as it removes from L2ARC buflists 112 */ 113 114/* 115 * ARC operation: 116 * 117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure. 118 * This structure can point either to a block that is still in the cache or to 119 * one that is only accessible in an L2 ARC device, or it can provide 120 * information about a block that was recently evicted. If a block is 121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough 122 * information to retrieve it from the L2ARC device. This information is 123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block 124 * that is in this state cannot access the data directly. 125 * 126 * Blocks that are actively being referenced or have not been evicted 127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within 128 * the arc_buf_hdr_t that will point to the data block in memory. A block can 129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC 130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and 131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd). 132 * 133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the 134 * ability to store the physical data (b_pabd) associated with the DVA of the 135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block, 136 * it will match its on-disk compression characteristics. This behavior can be 137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the 138 * compressed ARC functionality is disabled, the b_pabd will point to an 139 * uncompressed version of the on-disk data. 140 * 141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each 142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it. 143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC 144 * consumer. The ARC will provide references to this data and will keep it 145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical 146 * data block and will evict any arc_buf_t that is no longer referenced. The 147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the 148 * "overhead_size" kstat. 149 * 150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or 151 * compressed form. The typical case is that consumers will want uncompressed 152 * data, and when that happens a new data buffer is allocated where the data is 153 * decompressed for them to use. Currently the only consumer who wants 154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it 155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared 156 * with the arc_buf_hdr_t. 157 * 158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The 159 * first one is owned by a compressed send consumer (and therefore references 160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be 161 * used by any other consumer (and has its own uncompressed copy of the data 162 * buffer). 163 * 164 * arc_buf_hdr_t 165 * +-----------+ 166 * | fields | 167 * | common to | 168 * | L1- and | 169 * | L2ARC | 170 * +-----------+ 171 * | l2arc_buf_hdr_t 172 * | | 173 * +-----------+ 174 * | l1arc_buf_hdr_t 175 * | | arc_buf_t 176 * | b_buf +------------>+-----------+ arc_buf_t 177 * | b_pabd +-+ |b_next +---->+-----------+ 178 * +-----------+ | |-----------| |b_next +-->NULL 179 * | |b_comp = T | +-----------+ 180 * | |b_data +-+ |b_comp = F | 181 * | +-----------+ | |b_data +-+ 182 * +->+------+ | +-----------+ | 183 * compressed | | | | 184 * data | |<--------------+ | uncompressed 185 * +------+ compressed, | data 186 * shared +-->+------+ 187 * data | | 188 * | | 189 * +------+ 190 * 191 * When a consumer reads a block, the ARC must first look to see if the 192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new 193 * arc_buf_t and either copies uncompressed data into a new data buffer from an 194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a 195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the 196 * hdr is compressed and the desired compression characteristics of the 197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the 198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be 199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can 200 * be anywhere in the hdr's list. 201 * 202 * The diagram below shows an example of an uncompressed ARC hdr that is 203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is 204 * the last element in the buf list): 205 * 206 * arc_buf_hdr_t 207 * +-----------+ 208 * | | 209 * | | 210 * | | 211 * +-----------+ 212 * l2arc_buf_hdr_t| | 213 * | | 214 * +-----------+ 215 * l1arc_buf_hdr_t| | 216 * | | arc_buf_t (shared) 217 * | b_buf +------------>+---------+ arc_buf_t 218 * | | |b_next +---->+---------+ 219 * | b_pabd +-+ |---------| |b_next +-->NULL 220 * +-----------+ | | | +---------+ 221 * | |b_data +-+ | | 222 * | +---------+ | |b_data +-+ 223 * +->+------+ | +---------+ | 224 * | | | | 225 * uncompressed | | | | 226 * data +------+ | | 227 * ^ +->+------+ | 228 * | uncompressed | | | 229 * | data | | | 230 * | +------+ | 231 * +---------------------------------+ 232 * 233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd 234 * since the physical block is about to be rewritten. The new data contents 235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write, 236 * it may compress the data before writing it to disk. The ARC will be called 237 * with the transformed data and will bcopy the transformed on-disk block into 238 * a newly allocated b_pabd. Writes are always done into buffers which have 239 * either been loaned (and hence are new and don't have other readers) or 240 * buffers which have been released (and hence have their own hdr, if there 241 * were originally other readers of the buf's original hdr). This ensures that 242 * the ARC only needs to update a single buf and its hdr after a write occurs. 243 * 244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The 245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means 246 * that when compressed ARC is enabled that the L2ARC blocks are identical 247 * to the on-disk block in the main data pool. This provides a significant 248 * advantage since the ARC can leverage the bp's checksum when reading from the 249 * L2ARC to determine if the contents are valid. However, if the compressed 250 * ARC is disabled, then the L2ARC's block must be transformed to look 251 * like the physical block in the main data pool before comparing the 252 * checksum and determining its validity. 253 */ 254 255#include <sys/spa.h> 256#include <sys/zio.h> 257#include <sys/spa_impl.h> 258#include <sys/zio_compress.h> 259#include <sys/zio_checksum.h> 260#include <sys/zfs_context.h> 261#include <sys/arc.h> 262#include <sys/refcount.h> 263#include <sys/vdev.h> 264#include <sys/vdev_impl.h> 265#include <sys/dsl_pool.h> 266#include <sys/zio_checksum.h> 267#include <sys/multilist.h> 268#include <sys/abd.h> 269#ifdef _KERNEL 270#include <sys/dnlc.h> 271#include <sys/racct.h> 272#endif 273#include <sys/callb.h> 274#include <sys/kstat.h> 275#include <sys/trim_map.h> 276#include <zfs_fletcher.h> 277#include <sys/sdt.h> 278 279#include <machine/vmparam.h> 280 281#ifdef illumos 282#ifndef _KERNEL 283/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */ 284boolean_t arc_watch = B_FALSE; 285int arc_procfd; 286#endif 287#endif /* illumos */ 288 289static kmutex_t arc_reclaim_lock; 290static kcondvar_t arc_reclaim_thread_cv; 291static boolean_t arc_reclaim_thread_exit; 292static kcondvar_t arc_reclaim_waiters_cv; 293 294static kmutex_t arc_dnlc_evicts_lock; 295static kcondvar_t arc_dnlc_evicts_cv; 296static boolean_t arc_dnlc_evicts_thread_exit; 297 298uint_t arc_reduce_dnlc_percent = 3; 299 300/* 301 * The number of headers to evict in arc_evict_state_impl() before 302 * dropping the sublist lock and evicting from another sublist. A lower 303 * value means we're more likely to evict the "correct" header (i.e. the 304 * oldest header in the arc state), but comes with higher overhead 305 * (i.e. more invocations of arc_evict_state_impl()). 306 */ 307int zfs_arc_evict_batch_limit = 10; 308 309/* number of seconds before growing cache again */ 310static int arc_grow_retry = 60; 311 312/* shift of arc_c for calculating overflow limit in arc_get_data_impl */ 313int zfs_arc_overflow_shift = 8; 314 315/* shift of arc_c for calculating both min and max arc_p */ 316static int arc_p_min_shift = 4; 317 318/* log2(fraction of arc to reclaim) */ 319static int arc_shrink_shift = 7; 320 321/* 322 * log2(fraction of ARC which must be free to allow growing). 323 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory, 324 * when reading a new block into the ARC, we will evict an equal-sized block 325 * from the ARC. 326 * 327 * This must be less than arc_shrink_shift, so that when we shrink the ARC, 328 * we will still not allow it to grow. 329 */ 330int arc_no_grow_shift = 5; 331 332 333/* 334 * minimum lifespan of a prefetch block in clock ticks 335 * (initialized in arc_init()) 336 */ 337static int arc_min_prefetch_lifespan; 338 339/* 340 * If this percent of memory is free, don't throttle. 341 */ 342int arc_lotsfree_percent = 10; 343 344static int arc_dead; 345extern boolean_t zfs_prefetch_disable; 346 347/* 348 * The arc has filled available memory and has now warmed up. 349 */ 350static boolean_t arc_warm; 351 352/* 353 * These tunables are for performance analysis. 354 */ 355uint64_t zfs_arc_max; 356uint64_t zfs_arc_min; 357uint64_t zfs_arc_meta_limit = 0; 358uint64_t zfs_arc_meta_min = 0; 359int zfs_arc_grow_retry = 0; 360int zfs_arc_shrink_shift = 0; 361int zfs_arc_p_min_shift = 0; 362uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 363u_int zfs_arc_free_target = 0; 364 365/* Absolute min for arc min / max is 16MB. */ 366static uint64_t arc_abs_min = 16 << 20; 367 368boolean_t zfs_compressed_arc_enabled = B_TRUE; 369 370static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 371static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 372static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 373static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 374 375#if defined(__FreeBSD__) && defined(_KERNEL) 376static void 377arc_free_target_init(void *unused __unused) 378{ 379 380 zfs_arc_free_target = vm_pageout_wakeup_thresh; 381} 382SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 383 arc_free_target_init, NULL); 384 385TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 386TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 387TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 388SYSCTL_DECL(_vfs_zfs); 389SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 390 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 391SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 392 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 393SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 394 &zfs_arc_average_blocksize, 0, 395 "ARC average blocksize"); 396SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 397 &arc_shrink_shift, 0, 398 "log2(fraction of arc to reclaim)"); 399SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 400 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC"); 401 402/* 403 * We don't have a tunable for arc_free_target due to the dependency on 404 * pagedaemon initialisation. 405 */ 406SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 407 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 408 sysctl_vfs_zfs_arc_free_target, "IU", 409 "Desired number of free pages below which ARC triggers reclaim"); 410 411static int 412sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 413{ 414 u_int val; 415 int err; 416 417 val = zfs_arc_free_target; 418 err = sysctl_handle_int(oidp, &val, 0, req); 419 if (err != 0 || req->newptr == NULL) 420 return (err); 421 422 if (val < minfree) 423 return (EINVAL); 424 if (val > vm_cnt.v_page_count) 425 return (EINVAL); 426 427 zfs_arc_free_target = val; 428 429 return (0); 430} 431 432/* 433 * Must be declared here, before the definition of corresponding kstat 434 * macro which uses the same names will confuse the compiler. 435 */ 436SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 437 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 438 sysctl_vfs_zfs_arc_meta_limit, "QU", 439 "ARC metadata limit"); 440#endif 441 442/* 443 * Note that buffers can be in one of 6 states: 444 * ARC_anon - anonymous (discussed below) 445 * ARC_mru - recently used, currently cached 446 * ARC_mru_ghost - recentely used, no longer in cache 447 * ARC_mfu - frequently used, currently cached 448 * ARC_mfu_ghost - frequently used, no longer in cache 449 * ARC_l2c_only - exists in L2ARC but not other states 450 * When there are no active references to the buffer, they are 451 * are linked onto a list in one of these arc states. These are 452 * the only buffers that can be evicted or deleted. Within each 453 * state there are multiple lists, one for meta-data and one for 454 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 455 * etc.) is tracked separately so that it can be managed more 456 * explicitly: favored over data, limited explicitly. 457 * 458 * Anonymous buffers are buffers that are not associated with 459 * a DVA. These are buffers that hold dirty block copies 460 * before they are written to stable storage. By definition, 461 * they are "ref'd" and are considered part of arc_mru 462 * that cannot be freed. Generally, they will aquire a DVA 463 * as they are written and migrate onto the arc_mru list. 464 * 465 * The ARC_l2c_only state is for buffers that are in the second 466 * level ARC but no longer in any of the ARC_m* lists. The second 467 * level ARC itself may also contain buffers that are in any of 468 * the ARC_m* states - meaning that a buffer can exist in two 469 * places. The reason for the ARC_l2c_only state is to keep the 470 * buffer header in the hash table, so that reads that hit the 471 * second level ARC benefit from these fast lookups. 472 */ 473 474typedef struct arc_state { 475 /* 476 * list of evictable buffers 477 */ 478 multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; 479 /* 480 * total amount of evictable data in this state 481 */ 482 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 483 /* 484 * total amount of data in this state; this includes: evictable, 485 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 486 */ 487 refcount_t arcs_size; 488} arc_state_t; 489 490/* The 6 states: */ 491static arc_state_t ARC_anon; 492static arc_state_t ARC_mru; 493static arc_state_t ARC_mru_ghost; 494static arc_state_t ARC_mfu; 495static arc_state_t ARC_mfu_ghost; 496static arc_state_t ARC_l2c_only; 497 498typedef struct arc_stats { 499 kstat_named_t arcstat_hits; 500 kstat_named_t arcstat_misses; 501 kstat_named_t arcstat_demand_data_hits; 502 kstat_named_t arcstat_demand_data_misses; 503 kstat_named_t arcstat_demand_metadata_hits; 504 kstat_named_t arcstat_demand_metadata_misses; 505 kstat_named_t arcstat_prefetch_data_hits; 506 kstat_named_t arcstat_prefetch_data_misses; 507 kstat_named_t arcstat_prefetch_metadata_hits; 508 kstat_named_t arcstat_prefetch_metadata_misses; 509 kstat_named_t arcstat_mru_hits; 510 kstat_named_t arcstat_mru_ghost_hits; 511 kstat_named_t arcstat_mfu_hits; 512 kstat_named_t arcstat_mfu_ghost_hits; 513 kstat_named_t arcstat_allocated; 514 kstat_named_t arcstat_deleted; 515 /* 516 * Number of buffers that could not be evicted because the hash lock 517 * was held by another thread. The lock may not necessarily be held 518 * by something using the same buffer, since hash locks are shared 519 * by multiple buffers. 520 */ 521 kstat_named_t arcstat_mutex_miss; 522 /* 523 * Number of buffers skipped because they have I/O in progress, are 524 * indrect prefetch buffers that have not lived long enough, or are 525 * not from the spa we're trying to evict from. 526 */ 527 kstat_named_t arcstat_evict_skip; 528 /* 529 * Number of times arc_evict_state() was unable to evict enough 530 * buffers to reach it's target amount. 531 */ 532 kstat_named_t arcstat_evict_not_enough; 533 kstat_named_t arcstat_evict_l2_cached; 534 kstat_named_t arcstat_evict_l2_eligible; 535 kstat_named_t arcstat_evict_l2_ineligible; 536 kstat_named_t arcstat_evict_l2_skip; 537 kstat_named_t arcstat_hash_elements; 538 kstat_named_t arcstat_hash_elements_max; 539 kstat_named_t arcstat_hash_collisions; 540 kstat_named_t arcstat_hash_chains; 541 kstat_named_t arcstat_hash_chain_max; 542 kstat_named_t arcstat_p; 543 kstat_named_t arcstat_c; 544 kstat_named_t arcstat_c_min; 545 kstat_named_t arcstat_c_max; 546 kstat_named_t arcstat_size; 547 /* 548 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. 549 * Note that the compressed bytes may match the uncompressed bytes 550 * if the block is either not compressed or compressed arc is disabled. 551 */ 552 kstat_named_t arcstat_compressed_size; 553 /* 554 * Uncompressed size of the data stored in b_pabd. If compressed 555 * arc is disabled then this value will be identical to the stat 556 * above. 557 */ 558 kstat_named_t arcstat_uncompressed_size; 559 /* 560 * Number of bytes stored in all the arc_buf_t's. This is classified 561 * as "overhead" since this data is typically short-lived and will 562 * be evicted from the arc when it becomes unreferenced unless the 563 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 564 * values have been set (see comment in dbuf.c for more information). 565 */ 566 kstat_named_t arcstat_overhead_size; 567 /* 568 * Number of bytes consumed by internal ARC structures necessary 569 * for tracking purposes; these structures are not actually 570 * backed by ARC buffers. This includes arc_buf_hdr_t structures 571 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 572 * caches), and arc_buf_t structures (allocated via arc_buf_t 573 * cache). 574 */ 575 kstat_named_t arcstat_hdr_size; 576 /* 577 * Number of bytes consumed by ARC buffers of type equal to 578 * ARC_BUFC_DATA. This is generally consumed by buffers backing 579 * on disk user data (e.g. plain file contents). 580 */ 581 kstat_named_t arcstat_data_size; 582 /* 583 * Number of bytes consumed by ARC buffers of type equal to 584 * ARC_BUFC_METADATA. This is generally consumed by buffers 585 * backing on disk data that is used for internal ZFS 586 * structures (e.g. ZAP, dnode, indirect blocks, etc). 587 */ 588 kstat_named_t arcstat_metadata_size; 589 /* 590 * Number of bytes consumed by various buffers and structures 591 * not actually backed with ARC buffers. This includes bonus 592 * buffers (allocated directly via zio_buf_* functions), 593 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 594 * cache), and dnode_t structures (allocated via dnode_t cache). 595 */ 596 kstat_named_t arcstat_other_size; 597 /* 598 * Total number of bytes consumed by ARC buffers residing in the 599 * arc_anon state. This includes *all* buffers in the arc_anon 600 * state; e.g. data, metadata, evictable, and unevictable buffers 601 * are all included in this value. 602 */ 603 kstat_named_t arcstat_anon_size; 604 /* 605 * Number of bytes consumed by ARC buffers that meet the 606 * following criteria: backing buffers of type ARC_BUFC_DATA, 607 * residing in the arc_anon state, and are eligible for eviction 608 * (e.g. have no outstanding holds on the buffer). 609 */ 610 kstat_named_t arcstat_anon_evictable_data; 611 /* 612 * Number of bytes consumed by ARC buffers that meet the 613 * following criteria: backing buffers of type ARC_BUFC_METADATA, 614 * residing in the arc_anon state, and are eligible for eviction 615 * (e.g. have no outstanding holds on the buffer). 616 */ 617 kstat_named_t arcstat_anon_evictable_metadata; 618 /* 619 * Total number of bytes consumed by ARC buffers residing in the 620 * arc_mru state. This includes *all* buffers in the arc_mru 621 * state; e.g. data, metadata, evictable, and unevictable buffers 622 * are all included in this value. 623 */ 624 kstat_named_t arcstat_mru_size; 625 /* 626 * Number of bytes consumed by ARC buffers that meet the 627 * following criteria: backing buffers of type ARC_BUFC_DATA, 628 * residing in the arc_mru state, and are eligible for eviction 629 * (e.g. have no outstanding holds on the buffer). 630 */ 631 kstat_named_t arcstat_mru_evictable_data; 632 /* 633 * Number of bytes consumed by ARC buffers that meet the 634 * following criteria: backing buffers of type ARC_BUFC_METADATA, 635 * residing in the arc_mru state, and are eligible for eviction 636 * (e.g. have no outstanding holds on the buffer). 637 */ 638 kstat_named_t arcstat_mru_evictable_metadata; 639 /* 640 * Total number of bytes that *would have been* consumed by ARC 641 * buffers in the arc_mru_ghost state. The key thing to note 642 * here, is the fact that this size doesn't actually indicate 643 * RAM consumption. The ghost lists only consist of headers and 644 * don't actually have ARC buffers linked off of these headers. 645 * Thus, *if* the headers had associated ARC buffers, these 646 * buffers *would have* consumed this number of bytes. 647 */ 648 kstat_named_t arcstat_mru_ghost_size; 649 /* 650 * Number of bytes that *would have been* consumed by ARC 651 * buffers that are eligible for eviction, of type 652 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 653 */ 654 kstat_named_t arcstat_mru_ghost_evictable_data; 655 /* 656 * Number of bytes that *would have been* consumed by ARC 657 * buffers that are eligible for eviction, of type 658 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 659 */ 660 kstat_named_t arcstat_mru_ghost_evictable_metadata; 661 /* 662 * Total number of bytes consumed by ARC buffers residing in the 663 * arc_mfu state. This includes *all* buffers in the arc_mfu 664 * state; e.g. data, metadata, evictable, and unevictable buffers 665 * are all included in this value. 666 */ 667 kstat_named_t arcstat_mfu_size; 668 /* 669 * Number of bytes consumed by ARC buffers that are eligible for 670 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 671 * state. 672 */ 673 kstat_named_t arcstat_mfu_evictable_data; 674 /* 675 * Number of bytes consumed by ARC buffers that are eligible for 676 * eviction, of type ARC_BUFC_METADATA, and reside in the 677 * arc_mfu state. 678 */ 679 kstat_named_t arcstat_mfu_evictable_metadata; 680 /* 681 * Total number of bytes that *would have been* consumed by ARC 682 * buffers in the arc_mfu_ghost state. See the comment above 683 * arcstat_mru_ghost_size for more details. 684 */ 685 kstat_named_t arcstat_mfu_ghost_size; 686 /* 687 * Number of bytes that *would have been* consumed by ARC 688 * buffers that are eligible for eviction, of type 689 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 690 */ 691 kstat_named_t arcstat_mfu_ghost_evictable_data; 692 /* 693 * Number of bytes that *would have been* consumed by ARC 694 * buffers that are eligible for eviction, of type 695 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 696 */ 697 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 698 kstat_named_t arcstat_l2_hits; 699 kstat_named_t arcstat_l2_misses; 700 kstat_named_t arcstat_l2_feeds; 701 kstat_named_t arcstat_l2_rw_clash; 702 kstat_named_t arcstat_l2_read_bytes; 703 kstat_named_t arcstat_l2_write_bytes; 704 kstat_named_t arcstat_l2_writes_sent; 705 kstat_named_t arcstat_l2_writes_done; 706 kstat_named_t arcstat_l2_writes_error; 707 kstat_named_t arcstat_l2_writes_lock_retry; 708 kstat_named_t arcstat_l2_evict_lock_retry; 709 kstat_named_t arcstat_l2_evict_reading; 710 kstat_named_t arcstat_l2_evict_l1cached; 711 kstat_named_t arcstat_l2_free_on_write; 712 kstat_named_t arcstat_l2_abort_lowmem; 713 kstat_named_t arcstat_l2_cksum_bad; 714 kstat_named_t arcstat_l2_io_error; 715 kstat_named_t arcstat_l2_size; 716 kstat_named_t arcstat_l2_asize; 717 kstat_named_t arcstat_l2_hdr_size; 718 kstat_named_t arcstat_l2_write_trylock_fail; 719 kstat_named_t arcstat_l2_write_passed_headroom; 720 kstat_named_t arcstat_l2_write_spa_mismatch; 721 kstat_named_t arcstat_l2_write_in_l2; 722 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 723 kstat_named_t arcstat_l2_write_not_cacheable; 724 kstat_named_t arcstat_l2_write_full; 725 kstat_named_t arcstat_l2_write_buffer_iter; 726 kstat_named_t arcstat_l2_write_pios; 727 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 728 kstat_named_t arcstat_l2_write_buffer_list_iter; 729 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 730 kstat_named_t arcstat_memory_throttle_count; 731 kstat_named_t arcstat_meta_used; 732 kstat_named_t arcstat_meta_limit; 733 kstat_named_t arcstat_meta_max; 734 kstat_named_t arcstat_meta_min; 735 kstat_named_t arcstat_sync_wait_for_async; 736 kstat_named_t arcstat_demand_hit_predictive_prefetch; 737} arc_stats_t; 738 739static arc_stats_t arc_stats = { 740 { "hits", KSTAT_DATA_UINT64 }, 741 { "misses", KSTAT_DATA_UINT64 }, 742 { "demand_data_hits", KSTAT_DATA_UINT64 }, 743 { "demand_data_misses", KSTAT_DATA_UINT64 }, 744 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 745 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 746 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 747 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 748 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 749 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 750 { "mru_hits", KSTAT_DATA_UINT64 }, 751 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 752 { "mfu_hits", KSTAT_DATA_UINT64 }, 753 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 754 { "allocated", KSTAT_DATA_UINT64 }, 755 { "deleted", KSTAT_DATA_UINT64 }, 756 { "mutex_miss", KSTAT_DATA_UINT64 }, 757 { "evict_skip", KSTAT_DATA_UINT64 }, 758 { "evict_not_enough", KSTAT_DATA_UINT64 }, 759 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 760 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 761 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 762 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 763 { "hash_elements", KSTAT_DATA_UINT64 }, 764 { "hash_elements_max", KSTAT_DATA_UINT64 }, 765 { "hash_collisions", KSTAT_DATA_UINT64 }, 766 { "hash_chains", KSTAT_DATA_UINT64 }, 767 { "hash_chain_max", KSTAT_DATA_UINT64 }, 768 { "p", KSTAT_DATA_UINT64 }, 769 { "c", KSTAT_DATA_UINT64 }, 770 { "c_min", KSTAT_DATA_UINT64 }, 771 { "c_max", KSTAT_DATA_UINT64 }, 772 { "size", KSTAT_DATA_UINT64 }, 773 { "compressed_size", KSTAT_DATA_UINT64 }, 774 { "uncompressed_size", KSTAT_DATA_UINT64 }, 775 { "overhead_size", KSTAT_DATA_UINT64 }, 776 { "hdr_size", KSTAT_DATA_UINT64 }, 777 { "data_size", KSTAT_DATA_UINT64 }, 778 { "metadata_size", KSTAT_DATA_UINT64 }, 779 { "other_size", KSTAT_DATA_UINT64 }, 780 { "anon_size", KSTAT_DATA_UINT64 }, 781 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 782 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 783 { "mru_size", KSTAT_DATA_UINT64 }, 784 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 785 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 786 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 787 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 788 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 789 { "mfu_size", KSTAT_DATA_UINT64 }, 790 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 791 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 792 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 793 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 794 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 795 { "l2_hits", KSTAT_DATA_UINT64 }, 796 { "l2_misses", KSTAT_DATA_UINT64 }, 797 { "l2_feeds", KSTAT_DATA_UINT64 }, 798 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 799 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 800 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 801 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 802 { "l2_writes_done", KSTAT_DATA_UINT64 }, 803 { "l2_writes_error", KSTAT_DATA_UINT64 }, 804 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 805 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 806 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 807 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 808 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 809 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 810 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 811 { "l2_io_error", KSTAT_DATA_UINT64 }, 812 { "l2_size", KSTAT_DATA_UINT64 }, 813 { "l2_asize", KSTAT_DATA_UINT64 }, 814 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 815 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 816 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 817 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 818 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 819 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 820 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 821 { "l2_write_full", KSTAT_DATA_UINT64 }, 822 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 823 { "l2_write_pios", KSTAT_DATA_UINT64 }, 824 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 825 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 826 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 827 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 828 { "arc_meta_used", KSTAT_DATA_UINT64 }, 829 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 830 { "arc_meta_max", KSTAT_DATA_UINT64 }, 831 { "arc_meta_min", KSTAT_DATA_UINT64 }, 832 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 833 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 834}; 835 836#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 837 838#define ARCSTAT_INCR(stat, val) \ 839 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 840 841#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 842#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 843 844#define ARCSTAT_MAX(stat, val) { \ 845 uint64_t m; \ 846 while ((val) > (m = arc_stats.stat.value.ui64) && \ 847 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 848 continue; \ 849} 850 851#define ARCSTAT_MAXSTAT(stat) \ 852 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 853 854/* 855 * We define a macro to allow ARC hits/misses to be easily broken down by 856 * two separate conditions, giving a total of four different subtypes for 857 * each of hits and misses (so eight statistics total). 858 */ 859#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 860 if (cond1) { \ 861 if (cond2) { \ 862 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 863 } else { \ 864 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 865 } \ 866 } else { \ 867 if (cond2) { \ 868 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 869 } else { \ 870 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 871 } \ 872 } 873 874kstat_t *arc_ksp; 875static arc_state_t *arc_anon; 876static arc_state_t *arc_mru; 877static arc_state_t *arc_mru_ghost; 878static arc_state_t *arc_mfu; 879static arc_state_t *arc_mfu_ghost; 880static arc_state_t *arc_l2c_only; 881 882/* 883 * There are several ARC variables that are critical to export as kstats -- 884 * but we don't want to have to grovel around in the kstat whenever we wish to 885 * manipulate them. For these variables, we therefore define them to be in 886 * terms of the statistic variable. This assures that we are not introducing 887 * the possibility of inconsistency by having shadow copies of the variables, 888 * while still allowing the code to be readable. 889 */ 890#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 891#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 892#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 893#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 894#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 895#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 896#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 897#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 898#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 899 900/* compressed size of entire arc */ 901#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 902/* uncompressed size of entire arc */ 903#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 904/* number of bytes in the arc from arc_buf_t's */ 905#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 906 907static int arc_no_grow; /* Don't try to grow cache size */ 908static uint64_t arc_tempreserve; 909static uint64_t arc_loaned_bytes; 910 911typedef struct arc_callback arc_callback_t; 912 913struct arc_callback { 914 void *acb_private; 915 arc_done_func_t *acb_done; 916 arc_buf_t *acb_buf; 917 boolean_t acb_compressed; 918 zio_t *acb_zio_dummy; 919 arc_callback_t *acb_next; 920}; 921 922typedef struct arc_write_callback arc_write_callback_t; 923 924struct arc_write_callback { 925 void *awcb_private; 926 arc_done_func_t *awcb_ready; 927 arc_done_func_t *awcb_children_ready; 928 arc_done_func_t *awcb_physdone; 929 arc_done_func_t *awcb_done; 930 arc_buf_t *awcb_buf; 931}; 932 933/* 934 * ARC buffers are separated into multiple structs as a memory saving measure: 935 * - Common fields struct, always defined, and embedded within it: 936 * - L2-only fields, always allocated but undefined when not in L2ARC 937 * - L1-only fields, only allocated when in L1ARC 938 * 939 * Buffer in L1 Buffer only in L2 940 * +------------------------+ +------------------------+ 941 * | arc_buf_hdr_t | | arc_buf_hdr_t | 942 * | | | | 943 * | | | | 944 * | | | | 945 * +------------------------+ +------------------------+ 946 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 947 * | (undefined if L1-only) | | | 948 * +------------------------+ +------------------------+ 949 * | l1arc_buf_hdr_t | 950 * | | 951 * | | 952 * | | 953 * | | 954 * +------------------------+ 955 * 956 * Because it's possible for the L2ARC to become extremely large, we can wind 957 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 958 * is minimized by only allocating the fields necessary for an L1-cached buffer 959 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 960 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 961 * words in pointers. arc_hdr_realloc() is used to switch a header between 962 * these two allocation states. 963 */ 964typedef struct l1arc_buf_hdr { 965 kmutex_t b_freeze_lock; 966 zio_cksum_t *b_freeze_cksum; 967#ifdef ZFS_DEBUG 968 /* 969 * Used for debugging with kmem_flags - by allocating and freeing 970 * b_thawed when the buffer is thawed, we get a record of the stack 971 * trace that thawed it. 972 */ 973 void *b_thawed; 974#endif 975 976 arc_buf_t *b_buf; 977 uint32_t b_bufcnt; 978 /* for waiting on writes to complete */ 979 kcondvar_t b_cv; 980 uint8_t b_byteswap; 981 982 /* protected by arc state mutex */ 983 arc_state_t *b_state; 984 multilist_node_t b_arc_node; 985 986 /* updated atomically */ 987 clock_t b_arc_access; 988 989 /* self protecting */ 990 refcount_t b_refcnt; 991 992 arc_callback_t *b_acb; 993 abd_t *b_pabd; 994} l1arc_buf_hdr_t; 995 996typedef struct l2arc_dev l2arc_dev_t; 997 998typedef struct l2arc_buf_hdr { 999 /* protected by arc_buf_hdr mutex */ 1000 l2arc_dev_t *b_dev; /* L2ARC device */ 1001 uint64_t b_daddr; /* disk address, offset byte */ 1002 1003 list_node_t b_l2node; 1004} l2arc_buf_hdr_t; 1005 1006struct arc_buf_hdr { 1007 /* protected by hash lock */ 1008 dva_t b_dva; 1009 uint64_t b_birth; 1010 1011 arc_buf_contents_t b_type; 1012 arc_buf_hdr_t *b_hash_next; 1013 arc_flags_t b_flags; 1014 1015 /* 1016 * This field stores the size of the data buffer after 1017 * compression, and is set in the arc's zio completion handlers. 1018 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1019 * 1020 * While the block pointers can store up to 32MB in their psize 1021 * field, we can only store up to 32MB minus 512B. This is due 1022 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1023 * a field of zeros represents 512B in the bp). We can't use a 1024 * bias of 1 since we need to reserve a psize of zero, here, to 1025 * represent holes and embedded blocks. 1026 * 1027 * This isn't a problem in practice, since the maximum size of a 1028 * buffer is limited to 16MB, so we never need to store 32MB in 1029 * this field. Even in the upstream illumos code base, the 1030 * maximum size of a buffer is limited to 16MB. 1031 */ 1032 uint16_t b_psize; 1033 1034 /* 1035 * This field stores the size of the data buffer before 1036 * compression, and cannot change once set. It is in units 1037 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1038 */ 1039 uint16_t b_lsize; /* immutable */ 1040 uint64_t b_spa; /* immutable */ 1041 1042 /* L2ARC fields. Undefined when not in L2ARC. */ 1043 l2arc_buf_hdr_t b_l2hdr; 1044 /* L1ARC fields. Undefined when in l2arc_only state */ 1045 l1arc_buf_hdr_t b_l1hdr; 1046}; 1047 1048#if defined(__FreeBSD__) && defined(_KERNEL) 1049static int 1050sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1051{ 1052 uint64_t val; 1053 int err; 1054 1055 val = arc_meta_limit; 1056 err = sysctl_handle_64(oidp, &val, 0, req); 1057 if (err != 0 || req->newptr == NULL) 1058 return (err); 1059 1060 if (val <= 0 || val > arc_c_max) 1061 return (EINVAL); 1062 1063 arc_meta_limit = val; 1064 return (0); 1065} 1066 1067static int 1068sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1069{ 1070 uint64_t val; 1071 int err; 1072 1073 val = zfs_arc_max; 1074 err = sysctl_handle_64(oidp, &val, 0, req); 1075 if (err != 0 || req->newptr == NULL) 1076 return (err); 1077 1078 if (zfs_arc_max == 0) { 1079 /* Loader tunable so blindly set */ 1080 zfs_arc_max = val; 1081 return (0); 1082 } 1083 1084 if (val < arc_abs_min || val > kmem_size()) 1085 return (EINVAL); 1086 if (val < arc_c_min) 1087 return (EINVAL); 1088 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1089 return (EINVAL); 1090 1091 arc_c_max = val; 1092 1093 arc_c = arc_c_max; 1094 arc_p = (arc_c >> 1); 1095 1096 if (zfs_arc_meta_limit == 0) { 1097 /* limit meta-data to 1/4 of the arc capacity */ 1098 arc_meta_limit = arc_c_max / 4; 1099 } 1100 1101 /* if kmem_flags are set, lets try to use less memory */ 1102 if (kmem_debugging()) 1103 arc_c = arc_c / 2; 1104 1105 zfs_arc_max = arc_c; 1106 1107 return (0); 1108} 1109 1110static int 1111sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1112{ 1113 uint64_t val; 1114 int err; 1115 1116 val = zfs_arc_min; 1117 err = sysctl_handle_64(oidp, &val, 0, req); 1118 if (err != 0 || req->newptr == NULL) 1119 return (err); 1120 1121 if (zfs_arc_min == 0) { 1122 /* Loader tunable so blindly set */ 1123 zfs_arc_min = val; 1124 return (0); 1125 } 1126 1127 if (val < arc_abs_min || val > arc_c_max) 1128 return (EINVAL); 1129 1130 arc_c_min = val; 1131 1132 if (zfs_arc_meta_min == 0) 1133 arc_meta_min = arc_c_min / 2; 1134 1135 if (arc_c < arc_c_min) 1136 arc_c = arc_c_min; 1137 1138 zfs_arc_min = arc_c_min; 1139 1140 return (0); 1141} 1142#endif 1143 1144#define GHOST_STATE(state) \ 1145 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1146 (state) == arc_l2c_only) 1147 1148#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1149#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1150#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1151#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1152#define HDR_COMPRESSION_ENABLED(hdr) \ 1153 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1154 1155#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1156#define HDR_L2_READING(hdr) \ 1157 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1158 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1159#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1160#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1161#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1162#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1163 1164#define HDR_ISTYPE_METADATA(hdr) \ 1165 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1166#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1167 1168#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1169#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1170 1171/* For storing compression mode in b_flags */ 1172#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1173 1174#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1175 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1176#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1177 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1178 1179#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1180#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) 1181#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) 1182 1183/* 1184 * Other sizes 1185 */ 1186 1187#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1188#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1189 1190/* 1191 * Hash table routines 1192 */ 1193 1194#define HT_LOCK_PAD CACHE_LINE_SIZE 1195 1196struct ht_lock { 1197 kmutex_t ht_lock; 1198#ifdef _KERNEL 1199 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1200#endif 1201}; 1202 1203#define BUF_LOCKS 256 1204typedef struct buf_hash_table { 1205 uint64_t ht_mask; 1206 arc_buf_hdr_t **ht_table; 1207 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1208} buf_hash_table_t; 1209 1210static buf_hash_table_t buf_hash_table; 1211 1212#define BUF_HASH_INDEX(spa, dva, birth) \ 1213 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1214#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1215#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1216#define HDR_LOCK(hdr) \ 1217 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1218 1219uint64_t zfs_crc64_table[256]; 1220 1221/* 1222 * Level 2 ARC 1223 */ 1224 1225#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1226#define L2ARC_HEADROOM 2 /* num of writes */ 1227/* 1228 * If we discover during ARC scan any buffers to be compressed, we boost 1229 * our headroom for the next scanning cycle by this percentage multiple. 1230 */ 1231#define L2ARC_HEADROOM_BOOST 200 1232#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1233#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1234 1235#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1236#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1237 1238/* L2ARC Performance Tunables */ 1239uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1240uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1241uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1242uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1243uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1244uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1245boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1246boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1247boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1248 1249SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1250 &l2arc_write_max, 0, "max write size"); 1251SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1252 &l2arc_write_boost, 0, "extra write during warmup"); 1253SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1254 &l2arc_headroom, 0, "number of dev writes"); 1255SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1256 &l2arc_feed_secs, 0, "interval seconds"); 1257SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1258 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1259 1260SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1261 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1262SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1263 &l2arc_feed_again, 0, "turbo warmup"); 1264SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1265 &l2arc_norw, 0, "no reads during writes"); 1266 1267SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1268 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1269SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1270 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1271 "size of anonymous state"); 1272SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1273 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1274 "size of anonymous state"); 1275 1276SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1277 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1278SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1279 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1280 "size of metadata in mru state"); 1281SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1282 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1283 "size of data in mru state"); 1284 1285SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1286 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1287SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1288 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1289 "size of metadata in mru ghost state"); 1290SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1291 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1292 "size of data in mru ghost state"); 1293 1294SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1295 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1296SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1297 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1298 "size of metadata in mfu state"); 1299SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1300 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1301 "size of data in mfu state"); 1302 1303SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1304 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1305SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1306 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1307 "size of metadata in mfu ghost state"); 1308SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1309 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1310 "size of data in mfu ghost state"); 1311 1312SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1313 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1314 1315/* 1316 * L2ARC Internals 1317 */ 1318struct l2arc_dev { 1319 vdev_t *l2ad_vdev; /* vdev */ 1320 spa_t *l2ad_spa; /* spa */ 1321 uint64_t l2ad_hand; /* next write location */ 1322 uint64_t l2ad_start; /* first addr on device */ 1323 uint64_t l2ad_end; /* last addr on device */ 1324 boolean_t l2ad_first; /* first sweep through */ 1325 boolean_t l2ad_writing; /* currently writing */ 1326 kmutex_t l2ad_mtx; /* lock for buffer list */ 1327 list_t l2ad_buflist; /* buffer list */ 1328 list_node_t l2ad_node; /* device list node */ 1329 refcount_t l2ad_alloc; /* allocated bytes */ 1330}; 1331 1332static list_t L2ARC_dev_list; /* device list */ 1333static list_t *l2arc_dev_list; /* device list pointer */ 1334static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1335static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1336static list_t L2ARC_free_on_write; /* free after write buf list */ 1337static list_t *l2arc_free_on_write; /* free after write list ptr */ 1338static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1339static uint64_t l2arc_ndev; /* number of devices */ 1340 1341typedef struct l2arc_read_callback { 1342 arc_buf_hdr_t *l2rcb_hdr; /* read header */ 1343 blkptr_t l2rcb_bp; /* original blkptr */ 1344 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1345 int l2rcb_flags; /* original flags */ 1346 abd_t *l2rcb_abd; /* temporary buffer */ 1347} l2arc_read_callback_t; 1348 1349typedef struct l2arc_write_callback { 1350 l2arc_dev_t *l2wcb_dev; /* device info */ 1351 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1352} l2arc_write_callback_t; 1353 1354typedef struct l2arc_data_free { 1355 /* protected by l2arc_free_on_write_mtx */ 1356 abd_t *l2df_abd; 1357 size_t l2df_size; 1358 arc_buf_contents_t l2df_type; 1359 list_node_t l2df_list_node; 1360} l2arc_data_free_t; 1361 1362static kmutex_t l2arc_feed_thr_lock; 1363static kcondvar_t l2arc_feed_thr_cv; 1364static uint8_t l2arc_thread_exit; 1365 1366static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *); 1367static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1368static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *); 1369static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); 1370static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1371static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); 1372static void arc_hdr_free_pabd(arc_buf_hdr_t *); 1373static void arc_hdr_alloc_pabd(arc_buf_hdr_t *); 1374static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1375static boolean_t arc_is_overflowing(); 1376static void arc_buf_watch(arc_buf_t *); 1377 1378static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1379static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1380static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1381static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1382 1383static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1384static void l2arc_read_done(zio_t *); 1385 1386static void 1387l2arc_trim(const arc_buf_hdr_t *hdr) 1388{ 1389 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1390 1391 ASSERT(HDR_HAS_L2HDR(hdr)); 1392 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1393 1394 if (HDR_GET_PSIZE(hdr) != 0) { 1395 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1396 HDR_GET_PSIZE(hdr), 0); 1397 } 1398} 1399 1400static uint64_t 1401buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1402{ 1403 uint8_t *vdva = (uint8_t *)dva; 1404 uint64_t crc = -1ULL; 1405 int i; 1406 1407 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1408 1409 for (i = 0; i < sizeof (dva_t); i++) 1410 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1411 1412 crc ^= (spa>>8) ^ birth; 1413 1414 return (crc); 1415} 1416 1417#define HDR_EMPTY(hdr) \ 1418 ((hdr)->b_dva.dva_word[0] == 0 && \ 1419 (hdr)->b_dva.dva_word[1] == 0) 1420 1421#define HDR_EQUAL(spa, dva, birth, hdr) \ 1422 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1423 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1424 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1425 1426static void 1427buf_discard_identity(arc_buf_hdr_t *hdr) 1428{ 1429 hdr->b_dva.dva_word[0] = 0; 1430 hdr->b_dva.dva_word[1] = 0; 1431 hdr->b_birth = 0; 1432} 1433 1434static arc_buf_hdr_t * 1435buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1436{ 1437 const dva_t *dva = BP_IDENTITY(bp); 1438 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1439 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1440 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1441 arc_buf_hdr_t *hdr; 1442 1443 mutex_enter(hash_lock); 1444 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1445 hdr = hdr->b_hash_next) { 1446 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1447 *lockp = hash_lock; 1448 return (hdr); 1449 } 1450 } 1451 mutex_exit(hash_lock); 1452 *lockp = NULL; 1453 return (NULL); 1454} 1455 1456/* 1457 * Insert an entry into the hash table. If there is already an element 1458 * equal to elem in the hash table, then the already existing element 1459 * will be returned and the new element will not be inserted. 1460 * Otherwise returns NULL. 1461 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1462 */ 1463static arc_buf_hdr_t * 1464buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1465{ 1466 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1467 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1468 arc_buf_hdr_t *fhdr; 1469 uint32_t i; 1470 1471 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1472 ASSERT(hdr->b_birth != 0); 1473 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1474 1475 if (lockp != NULL) { 1476 *lockp = hash_lock; 1477 mutex_enter(hash_lock); 1478 } else { 1479 ASSERT(MUTEX_HELD(hash_lock)); 1480 } 1481 1482 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1483 fhdr = fhdr->b_hash_next, i++) { 1484 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1485 return (fhdr); 1486 } 1487 1488 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1489 buf_hash_table.ht_table[idx] = hdr; 1490 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1491 1492 /* collect some hash table performance data */ 1493 if (i > 0) { 1494 ARCSTAT_BUMP(arcstat_hash_collisions); 1495 if (i == 1) 1496 ARCSTAT_BUMP(arcstat_hash_chains); 1497 1498 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1499 } 1500 1501 ARCSTAT_BUMP(arcstat_hash_elements); 1502 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1503 1504 return (NULL); 1505} 1506 1507static void 1508buf_hash_remove(arc_buf_hdr_t *hdr) 1509{ 1510 arc_buf_hdr_t *fhdr, **hdrp; 1511 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1512 1513 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1514 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1515 1516 hdrp = &buf_hash_table.ht_table[idx]; 1517 while ((fhdr = *hdrp) != hdr) { 1518 ASSERT3P(fhdr, !=, NULL); 1519 hdrp = &fhdr->b_hash_next; 1520 } 1521 *hdrp = hdr->b_hash_next; 1522 hdr->b_hash_next = NULL; 1523 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1524 1525 /* collect some hash table performance data */ 1526 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1527 1528 if (buf_hash_table.ht_table[idx] && 1529 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1530 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1531} 1532 1533/* 1534 * Global data structures and functions for the buf kmem cache. 1535 */ 1536static kmem_cache_t *hdr_full_cache; 1537static kmem_cache_t *hdr_l2only_cache; 1538static kmem_cache_t *buf_cache; 1539 1540static void 1541buf_fini(void) 1542{ 1543 int i; 1544 1545 kmem_free(buf_hash_table.ht_table, 1546 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1547 for (i = 0; i < BUF_LOCKS; i++) 1548 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1549 kmem_cache_destroy(hdr_full_cache); 1550 kmem_cache_destroy(hdr_l2only_cache); 1551 kmem_cache_destroy(buf_cache); 1552} 1553 1554/* 1555 * Constructor callback - called when the cache is empty 1556 * and a new buf is requested. 1557 */ 1558/* ARGSUSED */ 1559static int 1560hdr_full_cons(void *vbuf, void *unused, int kmflag) 1561{ 1562 arc_buf_hdr_t *hdr = vbuf; 1563 1564 bzero(hdr, HDR_FULL_SIZE); 1565 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1566 refcount_create(&hdr->b_l1hdr.b_refcnt); 1567 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1568 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1569 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1570 1571 return (0); 1572} 1573 1574/* ARGSUSED */ 1575static int 1576hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1577{ 1578 arc_buf_hdr_t *hdr = vbuf; 1579 1580 bzero(hdr, HDR_L2ONLY_SIZE); 1581 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1582 1583 return (0); 1584} 1585 1586/* ARGSUSED */ 1587static int 1588buf_cons(void *vbuf, void *unused, int kmflag) 1589{ 1590 arc_buf_t *buf = vbuf; 1591 1592 bzero(buf, sizeof (arc_buf_t)); 1593 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1594 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1595 1596 return (0); 1597} 1598 1599/* 1600 * Destructor callback - called when a cached buf is 1601 * no longer required. 1602 */ 1603/* ARGSUSED */ 1604static void 1605hdr_full_dest(void *vbuf, void *unused) 1606{ 1607 arc_buf_hdr_t *hdr = vbuf; 1608 1609 ASSERT(HDR_EMPTY(hdr)); 1610 cv_destroy(&hdr->b_l1hdr.b_cv); 1611 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1612 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1613 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1614 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1615} 1616 1617/* ARGSUSED */ 1618static void 1619hdr_l2only_dest(void *vbuf, void *unused) 1620{ 1621 arc_buf_hdr_t *hdr = vbuf; 1622 1623 ASSERT(HDR_EMPTY(hdr)); 1624 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1625} 1626 1627/* ARGSUSED */ 1628static void 1629buf_dest(void *vbuf, void *unused) 1630{ 1631 arc_buf_t *buf = vbuf; 1632 1633 mutex_destroy(&buf->b_evict_lock); 1634 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1635} 1636 1637/* 1638 * Reclaim callback -- invoked when memory is low. 1639 */ 1640/* ARGSUSED */ 1641static void 1642hdr_recl(void *unused) 1643{ 1644 dprintf("hdr_recl called\n"); 1645 /* 1646 * umem calls the reclaim func when we destroy the buf cache, 1647 * which is after we do arc_fini(). 1648 */ 1649 if (!arc_dead) 1650 cv_signal(&arc_reclaim_thread_cv); 1651} 1652 1653static void 1654buf_init(void) 1655{ 1656 uint64_t *ct; 1657 uint64_t hsize = 1ULL << 12; 1658 int i, j; 1659 1660 /* 1661 * The hash table is big enough to fill all of physical memory 1662 * with an average block size of zfs_arc_average_blocksize (default 8K). 1663 * By default, the table will take up 1664 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1665 */ 1666 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1667 hsize <<= 1; 1668retry: 1669 buf_hash_table.ht_mask = hsize - 1; 1670 buf_hash_table.ht_table = 1671 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1672 if (buf_hash_table.ht_table == NULL) { 1673 ASSERT(hsize > (1ULL << 8)); 1674 hsize >>= 1; 1675 goto retry; 1676 } 1677 1678 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1679 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1680 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1681 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1682 NULL, NULL, 0); 1683 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1684 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1685 1686 for (i = 0; i < 256; i++) 1687 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1688 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1689 1690 for (i = 0; i < BUF_LOCKS; i++) { 1691 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1692 NULL, MUTEX_DEFAULT, NULL); 1693 } 1694} 1695 1696/* 1697 * This is the size that the buf occupies in memory. If the buf is compressed, 1698 * it will correspond to the compressed size. You should use this method of 1699 * getting the buf size unless you explicitly need the logical size. 1700 */ 1701int32_t 1702arc_buf_size(arc_buf_t *buf) 1703{ 1704 return (ARC_BUF_COMPRESSED(buf) ? 1705 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); 1706} 1707 1708int32_t 1709arc_buf_lsize(arc_buf_t *buf) 1710{ 1711 return (HDR_GET_LSIZE(buf->b_hdr)); 1712} 1713 1714enum zio_compress 1715arc_get_compression(arc_buf_t *buf) 1716{ 1717 return (ARC_BUF_COMPRESSED(buf) ? 1718 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); 1719} 1720 1721#define ARC_MINTIME (hz>>4) /* 62 ms */ 1722 1723static inline boolean_t 1724arc_buf_is_shared(arc_buf_t *buf) 1725{ 1726 boolean_t shared = (buf->b_data != NULL && 1727 buf->b_hdr->b_l1hdr.b_pabd != NULL && 1728 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && 1729 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); 1730 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1731 IMPLY(shared, ARC_BUF_SHARED(buf)); 1732 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); 1733 1734 /* 1735 * It would be nice to assert arc_can_share() too, but the "hdr isn't 1736 * already being shared" requirement prevents us from doing that. 1737 */ 1738 1739 return (shared); 1740} 1741 1742/* 1743 * Free the checksum associated with this header. If there is no checksum, this 1744 * is a no-op. 1745 */ 1746static inline void 1747arc_cksum_free(arc_buf_hdr_t *hdr) 1748{ 1749 ASSERT(HDR_HAS_L1HDR(hdr)); 1750 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1751 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1752 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1753 hdr->b_l1hdr.b_freeze_cksum = NULL; 1754 } 1755 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1756} 1757 1758/* 1759 * Return true iff at least one of the bufs on hdr is not compressed. 1760 */ 1761static boolean_t 1762arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) 1763{ 1764 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { 1765 if (!ARC_BUF_COMPRESSED(b)) { 1766 return (B_TRUE); 1767 } 1768 } 1769 return (B_FALSE); 1770} 1771 1772/* 1773 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data 1774 * matches the checksum that is stored in the hdr. If there is no checksum, 1775 * or if the buf is compressed, this is a no-op. 1776 */ 1777static void 1778arc_cksum_verify(arc_buf_t *buf) 1779{ 1780 arc_buf_hdr_t *hdr = buf->b_hdr; 1781 zio_cksum_t zc; 1782 1783 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1784 return; 1785 1786 if (ARC_BUF_COMPRESSED(buf)) { 1787 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 1788 arc_hdr_has_uncompressed_buf(hdr)); 1789 return; 1790 } 1791 1792 ASSERT(HDR_HAS_L1HDR(hdr)); 1793 1794 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1795 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1796 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1797 return; 1798 } 1799 1800 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); 1801 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1802 panic("buffer modified while frozen!"); 1803 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1804} 1805 1806static boolean_t 1807arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1808{ 1809 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1810 boolean_t valid_cksum; 1811 1812 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1813 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1814 1815 /* 1816 * We rely on the blkptr's checksum to determine if the block 1817 * is valid or not. When compressed arc is enabled, the l2arc 1818 * writes the block to the l2arc just as it appears in the pool. 1819 * This allows us to use the blkptr's checksum to validate the 1820 * data that we just read off of the l2arc without having to store 1821 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1822 * arc is disabled, then the data written to the l2arc is always 1823 * uncompressed and won't match the block as it exists in the main 1824 * pool. When this is the case, we must first compress it if it is 1825 * compressed on the main pool before we can validate the checksum. 1826 */ 1827 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1828 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1829 uint64_t lsize = HDR_GET_LSIZE(hdr); 1830 uint64_t csize; 1831 1832 void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr)); 1833 csize = zio_compress_data(compress, zio->io_abd, cbuf, lsize); 1834 1835 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1836 if (csize < HDR_GET_PSIZE(hdr)) { 1837 /* 1838 * Compressed blocks are always a multiple of the 1839 * smallest ashift in the pool. Ideally, we would 1840 * like to round up the csize to the next 1841 * spa_min_ashift but that value may have changed 1842 * since the block was last written. Instead, 1843 * we rely on the fact that the hdr's psize 1844 * was set to the psize of the block when it was 1845 * last written. We set the csize to that value 1846 * and zero out any part that should not contain 1847 * data. 1848 */ 1849 bzero((char *)cbuf + csize, HDR_GET_PSIZE(hdr) - csize); 1850 csize = HDR_GET_PSIZE(hdr); 1851 } 1852 zio_push_transform(zio, cbuf, csize, HDR_GET_PSIZE(hdr), NULL); 1853 } 1854 1855 /* 1856 * Block pointers always store the checksum for the logical data. 1857 * If the block pointer has the gang bit set, then the checksum 1858 * it represents is for the reconstituted data and not for an 1859 * individual gang member. The zio pipeline, however, must be able to 1860 * determine the checksum of each of the gang constituents so it 1861 * treats the checksum comparison differently than what we need 1862 * for l2arc blocks. This prevents us from using the 1863 * zio_checksum_error() interface directly. Instead we must call the 1864 * zio_checksum_error_impl() so that we can ensure the checksum is 1865 * generated using the correct checksum algorithm and accounts for the 1866 * logical I/O size and not just a gang fragment. 1867 */ 1868 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1869 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, 1870 zio->io_offset, NULL) == 0); 1871 zio_pop_transforms(zio); 1872 return (valid_cksum); 1873} 1874 1875/* 1876 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a 1877 * checksum and attaches it to the buf's hdr so that we can ensure that the buf 1878 * isn't modified later on. If buf is compressed or there is already a checksum 1879 * on the hdr, this is a no-op (we only checksum uncompressed bufs). 1880 */ 1881static void 1882arc_cksum_compute(arc_buf_t *buf) 1883{ 1884 arc_buf_hdr_t *hdr = buf->b_hdr; 1885 1886 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1887 return; 1888 1889 ASSERT(HDR_HAS_L1HDR(hdr)); 1890 1891 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1892 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1893 ASSERT(arc_hdr_has_uncompressed_buf(hdr)); 1894 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1895 return; 1896 } else if (ARC_BUF_COMPRESSED(buf)) { 1897 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1898 return; 1899 } 1900 1901 ASSERT(!ARC_BUF_COMPRESSED(buf)); 1902 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1903 KM_SLEEP); 1904 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, 1905 hdr->b_l1hdr.b_freeze_cksum); 1906 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1907#ifdef illumos 1908 arc_buf_watch(buf); 1909#endif 1910} 1911 1912#ifdef illumos 1913#ifndef _KERNEL 1914typedef struct procctl { 1915 long cmd; 1916 prwatch_t prwatch; 1917} procctl_t; 1918#endif 1919 1920/* ARGSUSED */ 1921static void 1922arc_buf_unwatch(arc_buf_t *buf) 1923{ 1924#ifndef _KERNEL 1925 if (arc_watch) { 1926 int result; 1927 procctl_t ctl; 1928 ctl.cmd = PCWATCH; 1929 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1930 ctl.prwatch.pr_size = 0; 1931 ctl.prwatch.pr_wflags = 0; 1932 result = write(arc_procfd, &ctl, sizeof (ctl)); 1933 ASSERT3U(result, ==, sizeof (ctl)); 1934 } 1935#endif 1936} 1937 1938/* ARGSUSED */ 1939static void 1940arc_buf_watch(arc_buf_t *buf) 1941{ 1942#ifndef _KERNEL 1943 if (arc_watch) { 1944 int result; 1945 procctl_t ctl; 1946 ctl.cmd = PCWATCH; 1947 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1948 ctl.prwatch.pr_size = arc_buf_size(buf); 1949 ctl.prwatch.pr_wflags = WA_WRITE; 1950 result = write(arc_procfd, &ctl, sizeof (ctl)); 1951 ASSERT3U(result, ==, sizeof (ctl)); 1952 } 1953#endif 1954} 1955#endif /* illumos */ 1956 1957static arc_buf_contents_t 1958arc_buf_type(arc_buf_hdr_t *hdr) 1959{ 1960 arc_buf_contents_t type; 1961 if (HDR_ISTYPE_METADATA(hdr)) { 1962 type = ARC_BUFC_METADATA; 1963 } else { 1964 type = ARC_BUFC_DATA; 1965 } 1966 VERIFY3U(hdr->b_type, ==, type); 1967 return (type); 1968} 1969 1970boolean_t 1971arc_is_metadata(arc_buf_t *buf) 1972{ 1973 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); 1974} 1975 1976static uint32_t 1977arc_bufc_to_flags(arc_buf_contents_t type) 1978{ 1979 switch (type) { 1980 case ARC_BUFC_DATA: 1981 /* metadata field is 0 if buffer contains normal data */ 1982 return (0); 1983 case ARC_BUFC_METADATA: 1984 return (ARC_FLAG_BUFC_METADATA); 1985 default: 1986 break; 1987 } 1988 panic("undefined ARC buffer type!"); 1989 return ((uint32_t)-1); 1990} 1991 1992void 1993arc_buf_thaw(arc_buf_t *buf) 1994{ 1995 arc_buf_hdr_t *hdr = buf->b_hdr; 1996 1997 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 1998 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 1999 2000 arc_cksum_verify(buf); 2001 2002 /* 2003 * Compressed buffers do not manipulate the b_freeze_cksum or 2004 * allocate b_thawed. 2005 */ 2006 if (ARC_BUF_COMPRESSED(buf)) { 2007 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2008 arc_hdr_has_uncompressed_buf(hdr)); 2009 return; 2010 } 2011 2012 ASSERT(HDR_HAS_L1HDR(hdr)); 2013 arc_cksum_free(hdr); 2014 2015 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 2016#ifdef ZFS_DEBUG 2017 if (zfs_flags & ZFS_DEBUG_MODIFY) { 2018 if (hdr->b_l1hdr.b_thawed != NULL) 2019 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2020 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 2021 } 2022#endif 2023 2024 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2025 2026#ifdef illumos 2027 arc_buf_unwatch(buf); 2028#endif 2029} 2030 2031void 2032arc_buf_freeze(arc_buf_t *buf) 2033{ 2034 arc_buf_hdr_t *hdr = buf->b_hdr; 2035 kmutex_t *hash_lock; 2036 2037 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2038 return; 2039 2040 if (ARC_BUF_COMPRESSED(buf)) { 2041 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2042 arc_hdr_has_uncompressed_buf(hdr)); 2043 return; 2044 } 2045 2046 hash_lock = HDR_LOCK(hdr); 2047 mutex_enter(hash_lock); 2048 2049 ASSERT(HDR_HAS_L1HDR(hdr)); 2050 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 2051 hdr->b_l1hdr.b_state == arc_anon); 2052 arc_cksum_compute(buf); 2053 mutex_exit(hash_lock); 2054} 2055 2056/* 2057 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 2058 * the following functions should be used to ensure that the flags are 2059 * updated in a thread-safe way. When manipulating the flags either 2060 * the hash_lock must be held or the hdr must be undiscoverable. This 2061 * ensures that we're not racing with any other threads when updating 2062 * the flags. 2063 */ 2064static inline void 2065arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2066{ 2067 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2068 hdr->b_flags |= flags; 2069} 2070 2071static inline void 2072arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2073{ 2074 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2075 hdr->b_flags &= ~flags; 2076} 2077 2078/* 2079 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 2080 * done in a special way since we have to clear and set bits 2081 * at the same time. Consumers that wish to set the compression bits 2082 * must use this function to ensure that the flags are updated in 2083 * thread-safe manner. 2084 */ 2085static void 2086arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 2087{ 2088 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2089 2090 /* 2091 * Holes and embedded blocks will always have a psize = 0 so 2092 * we ignore the compression of the blkptr and set the 2093 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 2094 * Holes and embedded blocks remain anonymous so we don't 2095 * want to uncompress them. Mark them as uncompressed. 2096 */ 2097 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 2098 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2099 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 2100 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 2101 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2102 } else { 2103 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2104 HDR_SET_COMPRESS(hdr, cmp); 2105 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2106 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2107 } 2108} 2109 2110/* 2111 * Looks for another buf on the same hdr which has the data decompressed, copies 2112 * from it, and returns true. If no such buf exists, returns false. 2113 */ 2114static boolean_t 2115arc_buf_try_copy_decompressed_data(arc_buf_t *buf) 2116{ 2117 arc_buf_hdr_t *hdr = buf->b_hdr; 2118 boolean_t copied = B_FALSE; 2119 2120 ASSERT(HDR_HAS_L1HDR(hdr)); 2121 ASSERT3P(buf->b_data, !=, NULL); 2122 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2123 2124 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; 2125 from = from->b_next) { 2126 /* can't use our own data buffer */ 2127 if (from == buf) { 2128 continue; 2129 } 2130 2131 if (!ARC_BUF_COMPRESSED(from)) { 2132 bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); 2133 copied = B_TRUE; 2134 break; 2135 } 2136 } 2137 2138 /* 2139 * There were no decompressed bufs, so there should not be a 2140 * checksum on the hdr either. 2141 */ 2142 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); 2143 2144 return (copied); 2145} 2146 2147/* 2148 * Given a buf that has a data buffer attached to it, this function will 2149 * efficiently fill the buf with data of the specified compression setting from 2150 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr 2151 * are already sharing a data buf, no copy is performed. 2152 * 2153 * If the buf is marked as compressed but uncompressed data was requested, this 2154 * will allocate a new data buffer for the buf, remove that flag, and fill the 2155 * buf with uncompressed data. You can't request a compressed buf on a hdr with 2156 * uncompressed data, and (since we haven't added support for it yet) if you 2157 * want compressed data your buf must already be marked as compressed and have 2158 * the correct-sized data buffer. 2159 */ 2160static int 2161arc_buf_fill(arc_buf_t *buf, boolean_t compressed) 2162{ 2163 arc_buf_hdr_t *hdr = buf->b_hdr; 2164 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 2165 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2166 2167 ASSERT3P(buf->b_data, !=, NULL); 2168 IMPLY(compressed, hdr_compressed); 2169 IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); 2170 2171 if (hdr_compressed == compressed) { 2172 if (!arc_buf_is_shared(buf)) { 2173 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, 2174 arc_buf_size(buf)); 2175 } 2176 } else { 2177 ASSERT(hdr_compressed); 2178 ASSERT(!compressed); 2179 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2180 2181 /* 2182 * If the buf is sharing its data with the hdr, unlink it and 2183 * allocate a new data buffer for the buf. 2184 */ 2185 if (arc_buf_is_shared(buf)) { 2186 ASSERT(ARC_BUF_COMPRESSED(buf)); 2187 2188 /* We need to give the buf it's own b_data */ 2189 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2190 buf->b_data = 2191 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2192 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2193 2194 /* Previously overhead was 0; just add new overhead */ 2195 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2196 } else if (ARC_BUF_COMPRESSED(buf)) { 2197 /* We need to reallocate the buf's b_data */ 2198 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), 2199 buf); 2200 buf->b_data = 2201 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2202 2203 /* We increased the size of b_data; update overhead */ 2204 ARCSTAT_INCR(arcstat_overhead_size, 2205 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); 2206 } 2207 2208 /* 2209 * Regardless of the buf's previous compression settings, it 2210 * should not be compressed at the end of this function. 2211 */ 2212 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; 2213 2214 /* 2215 * Try copying the data from another buf which already has a 2216 * decompressed version. If that's not possible, it's time to 2217 * bite the bullet and decompress the data from the hdr. 2218 */ 2219 if (arc_buf_try_copy_decompressed_data(buf)) { 2220 /* Skip byteswapping and checksumming (already done) */ 2221 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); 2222 return (0); 2223 } else { 2224 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2225 hdr->b_l1hdr.b_pabd, buf->b_data, 2226 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2227 2228 /* 2229 * Absent hardware errors or software bugs, this should 2230 * be impossible, but log it anyway so we can debug it. 2231 */ 2232 if (error != 0) { 2233 zfs_dbgmsg( 2234 "hdr %p, compress %d, psize %d, lsize %d", 2235 hdr, HDR_GET_COMPRESS(hdr), 2236 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2237 return (SET_ERROR(EIO)); 2238 } 2239 } 2240 } 2241 2242 /* Byteswap the buf's data if necessary */ 2243 if (bswap != DMU_BSWAP_NUMFUNCS) { 2244 ASSERT(!HDR_SHARED_DATA(hdr)); 2245 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2246 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2247 } 2248 2249 /* Compute the hdr's checksum if necessary */ 2250 arc_cksum_compute(buf); 2251 2252 return (0); 2253} 2254 2255int 2256arc_decompress(arc_buf_t *buf) 2257{ 2258 return (arc_buf_fill(buf, B_FALSE)); 2259} 2260 2261/* 2262 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. 2263 */ 2264static uint64_t 2265arc_hdr_size(arc_buf_hdr_t *hdr) 2266{ 2267 uint64_t size; 2268 2269 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2270 HDR_GET_PSIZE(hdr) > 0) { 2271 size = HDR_GET_PSIZE(hdr); 2272 } else { 2273 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2274 size = HDR_GET_LSIZE(hdr); 2275 } 2276 return (size); 2277} 2278 2279/* 2280 * Increment the amount of evictable space in the arc_state_t's refcount. 2281 * We account for the space used by the hdr and the arc buf individually 2282 * so that we can add and remove them from the refcount individually. 2283 */ 2284static void 2285arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2286{ 2287 arc_buf_contents_t type = arc_buf_type(hdr); 2288 2289 ASSERT(HDR_HAS_L1HDR(hdr)); 2290 2291 if (GHOST_STATE(state)) { 2292 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2293 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2294 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2295 (void) refcount_add_many(&state->arcs_esize[type], 2296 HDR_GET_LSIZE(hdr), hdr); 2297 return; 2298 } 2299 2300 ASSERT(!GHOST_STATE(state)); 2301 if (hdr->b_l1hdr.b_pabd != NULL) { 2302 (void) refcount_add_many(&state->arcs_esize[type], 2303 arc_hdr_size(hdr), hdr); 2304 } 2305 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2306 buf = buf->b_next) { 2307 if (arc_buf_is_shared(buf)) 2308 continue; 2309 (void) refcount_add_many(&state->arcs_esize[type], 2310 arc_buf_size(buf), buf); 2311 } 2312} 2313 2314/* 2315 * Decrement the amount of evictable space in the arc_state_t's refcount. 2316 * We account for the space used by the hdr and the arc buf individually 2317 * so that we can add and remove them from the refcount individually. 2318 */ 2319static void 2320arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2321{ 2322 arc_buf_contents_t type = arc_buf_type(hdr); 2323 2324 ASSERT(HDR_HAS_L1HDR(hdr)); 2325 2326 if (GHOST_STATE(state)) { 2327 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2328 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2329 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2330 (void) refcount_remove_many(&state->arcs_esize[type], 2331 HDR_GET_LSIZE(hdr), hdr); 2332 return; 2333 } 2334 2335 ASSERT(!GHOST_STATE(state)); 2336 if (hdr->b_l1hdr.b_pabd != NULL) { 2337 (void) refcount_remove_many(&state->arcs_esize[type], 2338 arc_hdr_size(hdr), hdr); 2339 } 2340 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2341 buf = buf->b_next) { 2342 if (arc_buf_is_shared(buf)) 2343 continue; 2344 (void) refcount_remove_many(&state->arcs_esize[type], 2345 arc_buf_size(buf), buf); 2346 } 2347} 2348 2349/* 2350 * Add a reference to this hdr indicating that someone is actively 2351 * referencing that memory. When the refcount transitions from 0 to 1, 2352 * we remove it from the respective arc_state_t list to indicate that 2353 * it is not evictable. 2354 */ 2355static void 2356add_reference(arc_buf_hdr_t *hdr, void *tag) 2357{ 2358 ASSERT(HDR_HAS_L1HDR(hdr)); 2359 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2360 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2361 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2362 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2363 } 2364 2365 arc_state_t *state = hdr->b_l1hdr.b_state; 2366 2367 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2368 (state != arc_anon)) { 2369 /* We don't use the L2-only state list. */ 2370 if (state != arc_l2c_only) { 2371 multilist_remove(state->arcs_list[arc_buf_type(hdr)], 2372 hdr); 2373 arc_evictable_space_decrement(hdr, state); 2374 } 2375 /* remove the prefetch flag if we get a reference */ 2376 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2377 } 2378} 2379 2380/* 2381 * Remove a reference from this hdr. When the reference transitions from 2382 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2383 * list making it eligible for eviction. 2384 */ 2385static int 2386remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2387{ 2388 int cnt; 2389 arc_state_t *state = hdr->b_l1hdr.b_state; 2390 2391 ASSERT(HDR_HAS_L1HDR(hdr)); 2392 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2393 ASSERT(!GHOST_STATE(state)); 2394 2395 /* 2396 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2397 * check to prevent usage of the arc_l2c_only list. 2398 */ 2399 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2400 (state != arc_anon)) { 2401 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); 2402 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2403 arc_evictable_space_increment(hdr, state); 2404 } 2405 return (cnt); 2406} 2407 2408/* 2409 * Move the supplied buffer to the indicated state. The hash lock 2410 * for the buffer must be held by the caller. 2411 */ 2412static void 2413arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2414 kmutex_t *hash_lock) 2415{ 2416 arc_state_t *old_state; 2417 int64_t refcnt; 2418 uint32_t bufcnt; 2419 boolean_t update_old, update_new; 2420 arc_buf_contents_t buftype = arc_buf_type(hdr); 2421 2422 /* 2423 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2424 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2425 * L1 hdr doesn't always exist when we change state to arc_anon before 2426 * destroying a header, in which case reallocating to add the L1 hdr is 2427 * pointless. 2428 */ 2429 if (HDR_HAS_L1HDR(hdr)) { 2430 old_state = hdr->b_l1hdr.b_state; 2431 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2432 bufcnt = hdr->b_l1hdr.b_bufcnt; 2433 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); 2434 } else { 2435 old_state = arc_l2c_only; 2436 refcnt = 0; 2437 bufcnt = 0; 2438 update_old = B_FALSE; 2439 } 2440 update_new = update_old; 2441 2442 ASSERT(MUTEX_HELD(hash_lock)); 2443 ASSERT3P(new_state, !=, old_state); 2444 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2445 ASSERT(old_state != arc_anon || bufcnt <= 1); 2446 2447 /* 2448 * If this buffer is evictable, transfer it from the 2449 * old state list to the new state list. 2450 */ 2451 if (refcnt == 0) { 2452 if (old_state != arc_anon && old_state != arc_l2c_only) { 2453 ASSERT(HDR_HAS_L1HDR(hdr)); 2454 multilist_remove(old_state->arcs_list[buftype], hdr); 2455 2456 if (GHOST_STATE(old_state)) { 2457 ASSERT0(bufcnt); 2458 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2459 update_old = B_TRUE; 2460 } 2461 arc_evictable_space_decrement(hdr, old_state); 2462 } 2463 if (new_state != arc_anon && new_state != arc_l2c_only) { 2464 2465 /* 2466 * An L1 header always exists here, since if we're 2467 * moving to some L1-cached state (i.e. not l2c_only or 2468 * anonymous), we realloc the header to add an L1hdr 2469 * beforehand. 2470 */ 2471 ASSERT(HDR_HAS_L1HDR(hdr)); 2472 multilist_insert(new_state->arcs_list[buftype], hdr); 2473 2474 if (GHOST_STATE(new_state)) { 2475 ASSERT0(bufcnt); 2476 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2477 update_new = B_TRUE; 2478 } 2479 arc_evictable_space_increment(hdr, new_state); 2480 } 2481 } 2482 2483 ASSERT(!HDR_EMPTY(hdr)); 2484 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2485 buf_hash_remove(hdr); 2486 2487 /* adjust state sizes (ignore arc_l2c_only) */ 2488 2489 if (update_new && new_state != arc_l2c_only) { 2490 ASSERT(HDR_HAS_L1HDR(hdr)); 2491 if (GHOST_STATE(new_state)) { 2492 ASSERT0(bufcnt); 2493 2494 /* 2495 * When moving a header to a ghost state, we first 2496 * remove all arc buffers. Thus, we'll have a 2497 * bufcnt of zero, and no arc buffer to use for 2498 * the reference. As a result, we use the arc 2499 * header pointer for the reference. 2500 */ 2501 (void) refcount_add_many(&new_state->arcs_size, 2502 HDR_GET_LSIZE(hdr), hdr); 2503 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2504 } else { 2505 uint32_t buffers = 0; 2506 2507 /* 2508 * Each individual buffer holds a unique reference, 2509 * thus we must remove each of these references one 2510 * at a time. 2511 */ 2512 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2513 buf = buf->b_next) { 2514 ASSERT3U(bufcnt, !=, 0); 2515 buffers++; 2516 2517 /* 2518 * When the arc_buf_t is sharing the data 2519 * block with the hdr, the owner of the 2520 * reference belongs to the hdr. Only 2521 * add to the refcount if the arc_buf_t is 2522 * not shared. 2523 */ 2524 if (arc_buf_is_shared(buf)) 2525 continue; 2526 2527 (void) refcount_add_many(&new_state->arcs_size, 2528 arc_buf_size(buf), buf); 2529 } 2530 ASSERT3U(bufcnt, ==, buffers); 2531 2532 if (hdr->b_l1hdr.b_pabd != NULL) { 2533 (void) refcount_add_many(&new_state->arcs_size, 2534 arc_hdr_size(hdr), hdr); 2535 } else { 2536 ASSERT(GHOST_STATE(old_state)); 2537 } 2538 } 2539 } 2540 2541 if (update_old && old_state != arc_l2c_only) { 2542 ASSERT(HDR_HAS_L1HDR(hdr)); 2543 if (GHOST_STATE(old_state)) { 2544 ASSERT0(bufcnt); 2545 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2546 2547 /* 2548 * When moving a header off of a ghost state, 2549 * the header will not contain any arc buffers. 2550 * We use the arc header pointer for the reference 2551 * which is exactly what we did when we put the 2552 * header on the ghost state. 2553 */ 2554 2555 (void) refcount_remove_many(&old_state->arcs_size, 2556 HDR_GET_LSIZE(hdr), hdr); 2557 } else { 2558 uint32_t buffers = 0; 2559 2560 /* 2561 * Each individual buffer holds a unique reference, 2562 * thus we must remove each of these references one 2563 * at a time. 2564 */ 2565 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2566 buf = buf->b_next) { 2567 ASSERT3U(bufcnt, !=, 0); 2568 buffers++; 2569 2570 /* 2571 * When the arc_buf_t is sharing the data 2572 * block with the hdr, the owner of the 2573 * reference belongs to the hdr. Only 2574 * add to the refcount if the arc_buf_t is 2575 * not shared. 2576 */ 2577 if (arc_buf_is_shared(buf)) 2578 continue; 2579 2580 (void) refcount_remove_many( 2581 &old_state->arcs_size, arc_buf_size(buf), 2582 buf); 2583 } 2584 ASSERT3U(bufcnt, ==, buffers); 2585 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2586 (void) refcount_remove_many( 2587 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2588 } 2589 } 2590 2591 if (HDR_HAS_L1HDR(hdr)) 2592 hdr->b_l1hdr.b_state = new_state; 2593 2594 /* 2595 * L2 headers should never be on the L2 state list since they don't 2596 * have L1 headers allocated. 2597 */ 2598 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2599 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2600} 2601 2602void 2603arc_space_consume(uint64_t space, arc_space_type_t type) 2604{ 2605 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2606 2607 switch (type) { 2608 case ARC_SPACE_DATA: 2609 ARCSTAT_INCR(arcstat_data_size, space); 2610 break; 2611 case ARC_SPACE_META: 2612 ARCSTAT_INCR(arcstat_metadata_size, space); 2613 break; 2614 case ARC_SPACE_OTHER: 2615 ARCSTAT_INCR(arcstat_other_size, space); 2616 break; 2617 case ARC_SPACE_HDRS: 2618 ARCSTAT_INCR(arcstat_hdr_size, space); 2619 break; 2620 case ARC_SPACE_L2HDRS: 2621 ARCSTAT_INCR(arcstat_l2_hdr_size, space); 2622 break; 2623 } 2624 2625 if (type != ARC_SPACE_DATA) 2626 ARCSTAT_INCR(arcstat_meta_used, space); 2627 2628 atomic_add_64(&arc_size, space); 2629} 2630 2631void 2632arc_space_return(uint64_t space, arc_space_type_t type) 2633{ 2634 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2635 2636 switch (type) { 2637 case ARC_SPACE_DATA: 2638 ARCSTAT_INCR(arcstat_data_size, -space); 2639 break; 2640 case ARC_SPACE_META: 2641 ARCSTAT_INCR(arcstat_metadata_size, -space); 2642 break; 2643 case ARC_SPACE_OTHER: 2644 ARCSTAT_INCR(arcstat_other_size, -space); 2645 break; 2646 case ARC_SPACE_HDRS: 2647 ARCSTAT_INCR(arcstat_hdr_size, -space); 2648 break; 2649 case ARC_SPACE_L2HDRS: 2650 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2651 break; 2652 } 2653 2654 if (type != ARC_SPACE_DATA) { 2655 ASSERT(arc_meta_used >= space); 2656 if (arc_meta_max < arc_meta_used) 2657 arc_meta_max = arc_meta_used; 2658 ARCSTAT_INCR(arcstat_meta_used, -space); 2659 } 2660 2661 ASSERT(arc_size >= space); 2662 atomic_add_64(&arc_size, -space); 2663} 2664 2665/* 2666 * Given a hdr and a buf, returns whether that buf can share its b_data buffer 2667 * with the hdr's b_pabd. 2668 */ 2669static boolean_t 2670arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2671{ 2672 /* 2673 * The criteria for sharing a hdr's data are: 2674 * 1. the hdr's compression matches the buf's compression 2675 * 2. the hdr doesn't need to be byteswapped 2676 * 3. the hdr isn't already being shared 2677 * 4. the buf is either compressed or it is the last buf in the hdr list 2678 * 2679 * Criterion #4 maintains the invariant that shared uncompressed 2680 * bufs must be the final buf in the hdr's b_buf list. Reading this, you 2681 * might ask, "if a compressed buf is allocated first, won't that be the 2682 * last thing in the list?", but in that case it's impossible to create 2683 * a shared uncompressed buf anyway (because the hdr must be compressed 2684 * to have the compressed buf). You might also think that #3 is 2685 * sufficient to make this guarantee, however it's possible 2686 * (specifically in the rare L2ARC write race mentioned in 2687 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that 2688 * is sharable, but wasn't at the time of its allocation. Rather than 2689 * allow a new shared uncompressed buf to be created and then shuffle 2690 * the list around to make it the last element, this simply disallows 2691 * sharing if the new buf isn't the first to be added. 2692 */ 2693 ASSERT3P(buf->b_hdr, ==, hdr); 2694 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; 2695 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; 2696 return (buf_compressed == hdr_compressed && 2697 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2698 !HDR_SHARED_DATA(hdr) && 2699 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); 2700} 2701 2702/* 2703 * Allocate a buf for this hdr. If you care about the data that's in the hdr, 2704 * or if you want a compressed buffer, pass those flags in. Returns 0 if the 2705 * copy was made successfully, or an error code otherwise. 2706 */ 2707static int 2708arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed, 2709 boolean_t fill, arc_buf_t **ret) 2710{ 2711 arc_buf_t *buf; 2712 2713 ASSERT(HDR_HAS_L1HDR(hdr)); 2714 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2715 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2716 hdr->b_type == ARC_BUFC_METADATA); 2717 ASSERT3P(ret, !=, NULL); 2718 ASSERT3P(*ret, ==, NULL); 2719 2720 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2721 buf->b_hdr = hdr; 2722 buf->b_data = NULL; 2723 buf->b_next = hdr->b_l1hdr.b_buf; 2724 buf->b_flags = 0; 2725 2726 add_reference(hdr, tag); 2727 2728 /* 2729 * We're about to change the hdr's b_flags. We must either 2730 * hold the hash_lock or be undiscoverable. 2731 */ 2732 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2733 2734 /* 2735 * Only honor requests for compressed bufs if the hdr is actually 2736 * compressed. 2737 */ 2738 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 2739 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; 2740 2741 /* 2742 * If the hdr's data can be shared then we share the data buffer and 2743 * set the appropriate bit in the hdr's b_flags to indicate the hdr is 2744 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new 2745 * buffer to store the buf's data. 2746 * 2747 * There are two additional restrictions here because we're sharing 2748 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be 2749 * actively involved in an L2ARC write, because if this buf is used by 2750 * an arc_write() then the hdr's data buffer will be released when the 2751 * write completes, even though the L2ARC write might still be using it. 2752 * Second, the hdr's ABD must be linear so that the buf's user doesn't 2753 * need to be ABD-aware. 2754 */ 2755 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && 2756 abd_is_linear(hdr->b_l1hdr.b_pabd); 2757 2758 /* Set up b_data and sharing */ 2759 if (can_share) { 2760 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); 2761 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2762 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2763 } else { 2764 buf->b_data = 2765 arc_get_data_buf(hdr, arc_buf_size(buf), buf); 2766 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2767 } 2768 VERIFY3P(buf->b_data, !=, NULL); 2769 2770 hdr->b_l1hdr.b_buf = buf; 2771 hdr->b_l1hdr.b_bufcnt += 1; 2772 2773 /* 2774 * If the user wants the data from the hdr, we need to either copy or 2775 * decompress the data. 2776 */ 2777 if (fill) { 2778 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); 2779 } 2780 2781 return (0); 2782} 2783 2784static char *arc_onloan_tag = "onloan"; 2785 2786static inline void 2787arc_loaned_bytes_update(int64_t delta) 2788{ 2789 atomic_add_64(&arc_loaned_bytes, delta); 2790 2791 /* assert that it did not wrap around */ 2792 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 2793} 2794 2795/* 2796 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2797 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2798 * buffers must be returned to the arc before they can be used by the DMU or 2799 * freed. 2800 */ 2801arc_buf_t * 2802arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) 2803{ 2804 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, 2805 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); 2806 2807 arc_loaned_bytes_update(size); 2808 2809 return (buf); 2810} 2811 2812arc_buf_t * 2813arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, 2814 enum zio_compress compression_type) 2815{ 2816 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, 2817 psize, lsize, compression_type); 2818 2819 arc_loaned_bytes_update(psize); 2820 2821 return (buf); 2822} 2823 2824 2825/* 2826 * Return a loaned arc buffer to the arc. 2827 */ 2828void 2829arc_return_buf(arc_buf_t *buf, void *tag) 2830{ 2831 arc_buf_hdr_t *hdr = buf->b_hdr; 2832 2833 ASSERT3P(buf->b_data, !=, NULL); 2834 ASSERT(HDR_HAS_L1HDR(hdr)); 2835 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2836 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2837 2838 arc_loaned_bytes_update(-arc_buf_size(buf)); 2839} 2840 2841/* Detach an arc_buf from a dbuf (tag) */ 2842void 2843arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2844{ 2845 arc_buf_hdr_t *hdr = buf->b_hdr; 2846 2847 ASSERT3P(buf->b_data, !=, NULL); 2848 ASSERT(HDR_HAS_L1HDR(hdr)); 2849 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2850 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2851 2852 arc_loaned_bytes_update(arc_buf_size(buf)); 2853} 2854 2855static void 2856l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) 2857{ 2858 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2859 2860 df->l2df_abd = abd; 2861 df->l2df_size = size; 2862 df->l2df_type = type; 2863 mutex_enter(&l2arc_free_on_write_mtx); 2864 list_insert_head(l2arc_free_on_write, df); 2865 mutex_exit(&l2arc_free_on_write_mtx); 2866} 2867 2868static void 2869arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2870{ 2871 arc_state_t *state = hdr->b_l1hdr.b_state; 2872 arc_buf_contents_t type = arc_buf_type(hdr); 2873 uint64_t size = arc_hdr_size(hdr); 2874 2875 /* protected by hash lock, if in the hash table */ 2876 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2877 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2878 ASSERT(state != arc_anon && state != arc_l2c_only); 2879 2880 (void) refcount_remove_many(&state->arcs_esize[type], 2881 size, hdr); 2882 } 2883 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2884 if (type == ARC_BUFC_METADATA) { 2885 arc_space_return(size, ARC_SPACE_META); 2886 } else { 2887 ASSERT(type == ARC_BUFC_DATA); 2888 arc_space_return(size, ARC_SPACE_DATA); 2889 } 2890 2891 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); 2892} 2893 2894/* 2895 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2896 * data buffer, we transfer the refcount ownership to the hdr and update 2897 * the appropriate kstats. 2898 */ 2899static void 2900arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2901{ 2902 arc_state_t *state = hdr->b_l1hdr.b_state; 2903 2904 ASSERT(arc_can_share(hdr, buf)); 2905 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2906 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2907 2908 /* 2909 * Start sharing the data buffer. We transfer the 2910 * refcount ownership to the hdr since it always owns 2911 * the refcount whenever an arc_buf_t is shared. 2912 */ 2913 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 2914 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); 2915 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, 2916 HDR_ISTYPE_METADATA(hdr)); 2917 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2918 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2919 2920 /* 2921 * Since we've transferred ownership to the hdr we need 2922 * to increment its compressed and uncompressed kstats and 2923 * decrement the overhead size. 2924 */ 2925 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 2926 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 2927 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf)); 2928} 2929 2930static void 2931arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2932{ 2933 arc_state_t *state = hdr->b_l1hdr.b_state; 2934 2935 ASSERT(arc_buf_is_shared(buf)); 2936 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2937 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2938 2939 /* 2940 * We are no longer sharing this buffer so we need 2941 * to transfer its ownership to the rightful owner. 2942 */ 2943 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 2944 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2945 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); 2946 abd_put(hdr->b_l1hdr.b_pabd); 2947 hdr->b_l1hdr.b_pabd = NULL; 2948 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2949 2950 /* 2951 * Since the buffer is no longer shared between 2952 * the arc buf and the hdr, count it as overhead. 2953 */ 2954 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2955 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2956 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2957} 2958 2959/* 2960 * Remove an arc_buf_t from the hdr's buf list and return the last 2961 * arc_buf_t on the list. If no buffers remain on the list then return 2962 * NULL. 2963 */ 2964static arc_buf_t * 2965arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2966{ 2967 ASSERT(HDR_HAS_L1HDR(hdr)); 2968 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2969 2970 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; 2971 arc_buf_t *lastbuf = NULL; 2972 2973 /* 2974 * Remove the buf from the hdr list and locate the last 2975 * remaining buffer on the list. 2976 */ 2977 while (*bufp != NULL) { 2978 if (*bufp == buf) 2979 *bufp = buf->b_next; 2980 2981 /* 2982 * If we've removed a buffer in the middle of 2983 * the list then update the lastbuf and update 2984 * bufp. 2985 */ 2986 if (*bufp != NULL) { 2987 lastbuf = *bufp; 2988 bufp = &(*bufp)->b_next; 2989 } 2990 } 2991 buf->b_next = NULL; 2992 ASSERT3P(lastbuf, !=, buf); 2993 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); 2994 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); 2995 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); 2996 2997 return (lastbuf); 2998} 2999 3000/* 3001 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's 3002 * list and free it. 3003 */ 3004static void 3005arc_buf_destroy_impl(arc_buf_t *buf) 3006{ 3007 arc_buf_hdr_t *hdr = buf->b_hdr; 3008 3009 /* 3010 * Free up the data associated with the buf but only if we're not 3011 * sharing this with the hdr. If we are sharing it with the hdr, the 3012 * hdr is responsible for doing the free. 3013 */ 3014 if (buf->b_data != NULL) { 3015 /* 3016 * We're about to change the hdr's b_flags. We must either 3017 * hold the hash_lock or be undiscoverable. 3018 */ 3019 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3020 3021 arc_cksum_verify(buf); 3022#ifdef illumos 3023 arc_buf_unwatch(buf); 3024#endif 3025 3026 if (arc_buf_is_shared(buf)) { 3027 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3028 } else { 3029 uint64_t size = arc_buf_size(buf); 3030 arc_free_data_buf(hdr, buf->b_data, size, buf); 3031 ARCSTAT_INCR(arcstat_overhead_size, -size); 3032 } 3033 buf->b_data = NULL; 3034 3035 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3036 hdr->b_l1hdr.b_bufcnt -= 1; 3037 } 3038 3039 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 3040 3041 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { 3042 /* 3043 * If the current arc_buf_t is sharing its data buffer with the 3044 * hdr, then reassign the hdr's b_pabd to share it with the new 3045 * buffer at the end of the list. The shared buffer is always 3046 * the last one on the hdr's buffer list. 3047 * 3048 * There is an equivalent case for compressed bufs, but since 3049 * they aren't guaranteed to be the last buf in the list and 3050 * that is an exceedingly rare case, we just allow that space be 3051 * wasted temporarily. 3052 */ 3053 if (lastbuf != NULL) { 3054 /* Only one buf can be shared at once */ 3055 VERIFY(!arc_buf_is_shared(lastbuf)); 3056 /* hdr is uncompressed so can't have compressed buf */ 3057 VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); 3058 3059 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3060 arc_hdr_free_pabd(hdr); 3061 3062 /* 3063 * We must setup a new shared block between the 3064 * last buffer and the hdr. The data would have 3065 * been allocated by the arc buf so we need to transfer 3066 * ownership to the hdr since it's now being shared. 3067 */ 3068 arc_share_buf(hdr, lastbuf); 3069 } 3070 } else if (HDR_SHARED_DATA(hdr)) { 3071 /* 3072 * Uncompressed shared buffers are always at the end 3073 * of the list. Compressed buffers don't have the 3074 * same requirements. This makes it hard to 3075 * simply assert that the lastbuf is shared so 3076 * we rely on the hdr's compression flags to determine 3077 * if we have a compressed, shared buffer. 3078 */ 3079 ASSERT3P(lastbuf, !=, NULL); 3080 ASSERT(arc_buf_is_shared(lastbuf) || 3081 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 3082 } 3083 3084 /* 3085 * Free the checksum if we're removing the last uncompressed buf from 3086 * this hdr. 3087 */ 3088 if (!arc_hdr_has_uncompressed_buf(hdr)) { 3089 arc_cksum_free(hdr); 3090 } 3091 3092 /* clean up the buf */ 3093 buf->b_hdr = NULL; 3094 kmem_cache_free(buf_cache, buf); 3095} 3096 3097static void 3098arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr) 3099{ 3100 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 3101 ASSERT(HDR_HAS_L1HDR(hdr)); 3102 ASSERT(!HDR_SHARED_DATA(hdr)); 3103 3104 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3105 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr); 3106 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3107 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3108 3109 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3110 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3111} 3112 3113static void 3114arc_hdr_free_pabd(arc_buf_hdr_t *hdr) 3115{ 3116 ASSERT(HDR_HAS_L1HDR(hdr)); 3117 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3118 3119 /* 3120 * If the hdr is currently being written to the l2arc then 3121 * we defer freeing the data by adding it to the l2arc_free_on_write 3122 * list. The l2arc will free the data once it's finished 3123 * writing it to the l2arc device. 3124 */ 3125 if (HDR_L2_WRITING(hdr)) { 3126 arc_hdr_free_on_write(hdr); 3127 ARCSTAT_BUMP(arcstat_l2_free_on_write); 3128 } else { 3129 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, 3130 arc_hdr_size(hdr), hdr); 3131 } 3132 hdr->b_l1hdr.b_pabd = NULL; 3133 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3134 3135 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3136 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3137} 3138 3139static arc_buf_hdr_t * 3140arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 3141 enum zio_compress compression_type, arc_buf_contents_t type) 3142{ 3143 arc_buf_hdr_t *hdr; 3144 3145 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 3146 3147 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3148 ASSERT(HDR_EMPTY(hdr)); 3149 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3150 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 3151 HDR_SET_PSIZE(hdr, psize); 3152 HDR_SET_LSIZE(hdr, lsize); 3153 hdr->b_spa = spa; 3154 hdr->b_type = type; 3155 hdr->b_flags = 0; 3156 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 3157 arc_hdr_set_compress(hdr, compression_type); 3158 3159 hdr->b_l1hdr.b_state = arc_anon; 3160 hdr->b_l1hdr.b_arc_access = 0; 3161 hdr->b_l1hdr.b_bufcnt = 0; 3162 hdr->b_l1hdr.b_buf = NULL; 3163 3164 /* 3165 * Allocate the hdr's buffer. This will contain either 3166 * the compressed or uncompressed data depending on the block 3167 * it references and compressed arc enablement. 3168 */ 3169 arc_hdr_alloc_pabd(hdr); 3170 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3171 3172 return (hdr); 3173} 3174 3175/* 3176 * Transition between the two allocation states for the arc_buf_hdr struct. 3177 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 3178 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 3179 * version is used when a cache buffer is only in the L2ARC in order to reduce 3180 * memory usage. 3181 */ 3182static arc_buf_hdr_t * 3183arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 3184{ 3185 ASSERT(HDR_HAS_L2HDR(hdr)); 3186 3187 arc_buf_hdr_t *nhdr; 3188 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3189 3190 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 3191 (old == hdr_l2only_cache && new == hdr_full_cache)); 3192 3193 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 3194 3195 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 3196 buf_hash_remove(hdr); 3197 3198 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 3199 3200 if (new == hdr_full_cache) { 3201 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3202 /* 3203 * arc_access and arc_change_state need to be aware that a 3204 * header has just come out of L2ARC, so we set its state to 3205 * l2c_only even though it's about to change. 3206 */ 3207 nhdr->b_l1hdr.b_state = arc_l2c_only; 3208 3209 /* Verify previous threads set to NULL before freeing */ 3210 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); 3211 } else { 3212 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3213 ASSERT0(hdr->b_l1hdr.b_bufcnt); 3214 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3215 3216 /* 3217 * If we've reached here, We must have been called from 3218 * arc_evict_hdr(), as such we should have already been 3219 * removed from any ghost list we were previously on 3220 * (which protects us from racing with arc_evict_state), 3221 * thus no locking is needed during this check. 3222 */ 3223 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3224 3225 /* 3226 * A buffer must not be moved into the arc_l2c_only 3227 * state if it's not finished being written out to the 3228 * l2arc device. Otherwise, the b_l1hdr.b_pabd field 3229 * might try to be accessed, even though it was removed. 3230 */ 3231 VERIFY(!HDR_L2_WRITING(hdr)); 3232 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3233 3234#ifdef ZFS_DEBUG 3235 if (hdr->b_l1hdr.b_thawed != NULL) { 3236 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3237 hdr->b_l1hdr.b_thawed = NULL; 3238 } 3239#endif 3240 3241 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3242 } 3243 /* 3244 * The header has been reallocated so we need to re-insert it into any 3245 * lists it was on. 3246 */ 3247 (void) buf_hash_insert(nhdr, NULL); 3248 3249 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 3250 3251 mutex_enter(&dev->l2ad_mtx); 3252 3253 /* 3254 * We must place the realloc'ed header back into the list at 3255 * the same spot. Otherwise, if it's placed earlier in the list, 3256 * l2arc_write_buffers() could find it during the function's 3257 * write phase, and try to write it out to the l2arc. 3258 */ 3259 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 3260 list_remove(&dev->l2ad_buflist, hdr); 3261 3262 mutex_exit(&dev->l2ad_mtx); 3263 3264 /* 3265 * Since we're using the pointer address as the tag when 3266 * incrementing and decrementing the l2ad_alloc refcount, we 3267 * must remove the old pointer (that we're about to destroy) and 3268 * add the new pointer to the refcount. Otherwise we'd remove 3269 * the wrong pointer address when calling arc_hdr_destroy() later. 3270 */ 3271 3272 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 3273 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 3274 3275 buf_discard_identity(hdr); 3276 kmem_cache_free(old, hdr); 3277 3278 return (nhdr); 3279} 3280 3281/* 3282 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 3283 * The buf is returned thawed since we expect the consumer to modify it. 3284 */ 3285arc_buf_t * 3286arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) 3287{ 3288 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 3289 ZIO_COMPRESS_OFF, type); 3290 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3291 3292 arc_buf_t *buf = NULL; 3293 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf)); 3294 arc_buf_thaw(buf); 3295 3296 return (buf); 3297} 3298 3299/* 3300 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this 3301 * for bufs containing metadata. 3302 */ 3303arc_buf_t * 3304arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, 3305 enum zio_compress compression_type) 3306{ 3307 ASSERT3U(lsize, >, 0); 3308 ASSERT3U(lsize, >=, psize); 3309 ASSERT(compression_type > ZIO_COMPRESS_OFF); 3310 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); 3311 3312 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 3313 compression_type, ARC_BUFC_DATA); 3314 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3315 3316 arc_buf_t *buf = NULL; 3317 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf)); 3318 arc_buf_thaw(buf); 3319 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3320 3321 if (!arc_buf_is_shared(buf)) { 3322 /* 3323 * To ensure that the hdr has the correct data in it if we call 3324 * arc_decompress() on this buf before it's been written to 3325 * disk, it's easiest if we just set up sharing between the 3326 * buf and the hdr. 3327 */ 3328 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); 3329 arc_hdr_free_pabd(hdr); 3330 arc_share_buf(hdr, buf); 3331 } 3332 3333 return (buf); 3334} 3335 3336static void 3337arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 3338{ 3339 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 3340 l2arc_dev_t *dev = l2hdr->b_dev; 3341 uint64_t asize = arc_hdr_size(hdr); 3342 3343 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 3344 ASSERT(HDR_HAS_L2HDR(hdr)); 3345 3346 list_remove(&dev->l2ad_buflist, hdr); 3347 3348 ARCSTAT_INCR(arcstat_l2_asize, -asize); 3349 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 3350 3351 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0); 3352 3353 (void) refcount_remove_many(&dev->l2ad_alloc, asize, hdr); 3354 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3355} 3356 3357static void 3358arc_hdr_destroy(arc_buf_hdr_t *hdr) 3359{ 3360 if (HDR_HAS_L1HDR(hdr)) { 3361 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3362 hdr->b_l1hdr.b_bufcnt > 0); 3363 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3364 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3365 } 3366 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3367 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3368 3369 if (!HDR_EMPTY(hdr)) 3370 buf_discard_identity(hdr); 3371 3372 if (HDR_HAS_L2HDR(hdr)) { 3373 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3374 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3375 3376 if (!buflist_held) 3377 mutex_enter(&dev->l2ad_mtx); 3378 3379 /* 3380 * Even though we checked this conditional above, we 3381 * need to check this again now that we have the 3382 * l2ad_mtx. This is because we could be racing with 3383 * another thread calling l2arc_evict() which might have 3384 * destroyed this header's L2 portion as we were waiting 3385 * to acquire the l2ad_mtx. If that happens, we don't 3386 * want to re-destroy the header's L2 portion. 3387 */ 3388 if (HDR_HAS_L2HDR(hdr)) { 3389 l2arc_trim(hdr); 3390 arc_hdr_l2hdr_destroy(hdr); 3391 } 3392 3393 if (!buflist_held) 3394 mutex_exit(&dev->l2ad_mtx); 3395 } 3396 3397 if (HDR_HAS_L1HDR(hdr)) { 3398 arc_cksum_free(hdr); 3399 3400 while (hdr->b_l1hdr.b_buf != NULL) 3401 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); 3402 3403#ifdef ZFS_DEBUG 3404 if (hdr->b_l1hdr.b_thawed != NULL) { 3405 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3406 hdr->b_l1hdr.b_thawed = NULL; 3407 } 3408#endif 3409 3410 if (hdr->b_l1hdr.b_pabd != NULL) { 3411 arc_hdr_free_pabd(hdr); 3412 } 3413 } 3414 3415 ASSERT3P(hdr->b_hash_next, ==, NULL); 3416 if (HDR_HAS_L1HDR(hdr)) { 3417 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3418 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3419 kmem_cache_free(hdr_full_cache, hdr); 3420 } else { 3421 kmem_cache_free(hdr_l2only_cache, hdr); 3422 } 3423} 3424 3425void 3426arc_buf_destroy(arc_buf_t *buf, void* tag) 3427{ 3428 arc_buf_hdr_t *hdr = buf->b_hdr; 3429 kmutex_t *hash_lock = HDR_LOCK(hdr); 3430 3431 if (hdr->b_l1hdr.b_state == arc_anon) { 3432 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3433 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3434 VERIFY0(remove_reference(hdr, NULL, tag)); 3435 arc_hdr_destroy(hdr); 3436 return; 3437 } 3438 3439 mutex_enter(hash_lock); 3440 ASSERT3P(hdr, ==, buf->b_hdr); 3441 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3442 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3443 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3444 ASSERT3P(buf->b_data, !=, NULL); 3445 3446 (void) remove_reference(hdr, hash_lock, tag); 3447 arc_buf_destroy_impl(buf); 3448 mutex_exit(hash_lock); 3449} 3450 3451/* 3452 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3453 * state of the header is dependent on it's state prior to entering this 3454 * function. The following transitions are possible: 3455 * 3456 * - arc_mru -> arc_mru_ghost 3457 * - arc_mfu -> arc_mfu_ghost 3458 * - arc_mru_ghost -> arc_l2c_only 3459 * - arc_mru_ghost -> deleted 3460 * - arc_mfu_ghost -> arc_l2c_only 3461 * - arc_mfu_ghost -> deleted 3462 */ 3463static int64_t 3464arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3465{ 3466 arc_state_t *evicted_state, *state; 3467 int64_t bytes_evicted = 0; 3468 3469 ASSERT(MUTEX_HELD(hash_lock)); 3470 ASSERT(HDR_HAS_L1HDR(hdr)); 3471 3472 state = hdr->b_l1hdr.b_state; 3473 if (GHOST_STATE(state)) { 3474 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3475 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3476 3477 /* 3478 * l2arc_write_buffers() relies on a header's L1 portion 3479 * (i.e. its b_pabd field) during it's write phase. 3480 * Thus, we cannot push a header onto the arc_l2c_only 3481 * state (removing it's L1 piece) until the header is 3482 * done being written to the l2arc. 3483 */ 3484 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3485 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3486 return (bytes_evicted); 3487 } 3488 3489 ARCSTAT_BUMP(arcstat_deleted); 3490 bytes_evicted += HDR_GET_LSIZE(hdr); 3491 3492 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3493 3494 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3495 if (HDR_HAS_L2HDR(hdr)) { 3496 /* 3497 * This buffer is cached on the 2nd Level ARC; 3498 * don't destroy the header. 3499 */ 3500 arc_change_state(arc_l2c_only, hdr, hash_lock); 3501 /* 3502 * dropping from L1+L2 cached to L2-only, 3503 * realloc to remove the L1 header. 3504 */ 3505 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3506 hdr_l2only_cache); 3507 } else { 3508 arc_change_state(arc_anon, hdr, hash_lock); 3509 arc_hdr_destroy(hdr); 3510 } 3511 return (bytes_evicted); 3512 } 3513 3514 ASSERT(state == arc_mru || state == arc_mfu); 3515 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3516 3517 /* prefetch buffers have a minimum lifespan */ 3518 if (HDR_IO_IN_PROGRESS(hdr) || 3519 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3520 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 3521 arc_min_prefetch_lifespan)) { 3522 ARCSTAT_BUMP(arcstat_evict_skip); 3523 return (bytes_evicted); 3524 } 3525 3526 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3527 while (hdr->b_l1hdr.b_buf) { 3528 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3529 if (!mutex_tryenter(&buf->b_evict_lock)) { 3530 ARCSTAT_BUMP(arcstat_mutex_miss); 3531 break; 3532 } 3533 if (buf->b_data != NULL) 3534 bytes_evicted += HDR_GET_LSIZE(hdr); 3535 mutex_exit(&buf->b_evict_lock); 3536 arc_buf_destroy_impl(buf); 3537 } 3538 3539 if (HDR_HAS_L2HDR(hdr)) { 3540 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3541 } else { 3542 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3543 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3544 HDR_GET_LSIZE(hdr)); 3545 } else { 3546 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3547 HDR_GET_LSIZE(hdr)); 3548 } 3549 } 3550 3551 if (hdr->b_l1hdr.b_bufcnt == 0) { 3552 arc_cksum_free(hdr); 3553 3554 bytes_evicted += arc_hdr_size(hdr); 3555 3556 /* 3557 * If this hdr is being evicted and has a compressed 3558 * buffer then we discard it here before we change states. 3559 * This ensures that the accounting is updated correctly 3560 * in arc_free_data_impl(). 3561 */ 3562 arc_hdr_free_pabd(hdr); 3563 3564 arc_change_state(evicted_state, hdr, hash_lock); 3565 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3566 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3567 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3568 } 3569 3570 return (bytes_evicted); 3571} 3572 3573static uint64_t 3574arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3575 uint64_t spa, int64_t bytes) 3576{ 3577 multilist_sublist_t *mls; 3578 uint64_t bytes_evicted = 0; 3579 arc_buf_hdr_t *hdr; 3580 kmutex_t *hash_lock; 3581 int evict_count = 0; 3582 3583 ASSERT3P(marker, !=, NULL); 3584 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3585 3586 mls = multilist_sublist_lock(ml, idx); 3587 3588 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3589 hdr = multilist_sublist_prev(mls, marker)) { 3590 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3591 (evict_count >= zfs_arc_evict_batch_limit)) 3592 break; 3593 3594 /* 3595 * To keep our iteration location, move the marker 3596 * forward. Since we're not holding hdr's hash lock, we 3597 * must be very careful and not remove 'hdr' from the 3598 * sublist. Otherwise, other consumers might mistake the 3599 * 'hdr' as not being on a sublist when they call the 3600 * multilist_link_active() function (they all rely on 3601 * the hash lock protecting concurrent insertions and 3602 * removals). multilist_sublist_move_forward() was 3603 * specifically implemented to ensure this is the case 3604 * (only 'marker' will be removed and re-inserted). 3605 */ 3606 multilist_sublist_move_forward(mls, marker); 3607 3608 /* 3609 * The only case where the b_spa field should ever be 3610 * zero, is the marker headers inserted by 3611 * arc_evict_state(). It's possible for multiple threads 3612 * to be calling arc_evict_state() concurrently (e.g. 3613 * dsl_pool_close() and zio_inject_fault()), so we must 3614 * skip any markers we see from these other threads. 3615 */ 3616 if (hdr->b_spa == 0) 3617 continue; 3618 3619 /* we're only interested in evicting buffers of a certain spa */ 3620 if (spa != 0 && hdr->b_spa != spa) { 3621 ARCSTAT_BUMP(arcstat_evict_skip); 3622 continue; 3623 } 3624 3625 hash_lock = HDR_LOCK(hdr); 3626 3627 /* 3628 * We aren't calling this function from any code path 3629 * that would already be holding a hash lock, so we're 3630 * asserting on this assumption to be defensive in case 3631 * this ever changes. Without this check, it would be 3632 * possible to incorrectly increment arcstat_mutex_miss 3633 * below (e.g. if the code changed such that we called 3634 * this function with a hash lock held). 3635 */ 3636 ASSERT(!MUTEX_HELD(hash_lock)); 3637 3638 if (mutex_tryenter(hash_lock)) { 3639 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3640 mutex_exit(hash_lock); 3641 3642 bytes_evicted += evicted; 3643 3644 /* 3645 * If evicted is zero, arc_evict_hdr() must have 3646 * decided to skip this header, don't increment 3647 * evict_count in this case. 3648 */ 3649 if (evicted != 0) 3650 evict_count++; 3651 3652 /* 3653 * If arc_size isn't overflowing, signal any 3654 * threads that might happen to be waiting. 3655 * 3656 * For each header evicted, we wake up a single 3657 * thread. If we used cv_broadcast, we could 3658 * wake up "too many" threads causing arc_size 3659 * to significantly overflow arc_c; since 3660 * arc_get_data_impl() doesn't check for overflow 3661 * when it's woken up (it doesn't because it's 3662 * possible for the ARC to be overflowing while 3663 * full of un-evictable buffers, and the 3664 * function should proceed in this case). 3665 * 3666 * If threads are left sleeping, due to not 3667 * using cv_broadcast, they will be woken up 3668 * just before arc_reclaim_thread() sleeps. 3669 */ 3670 mutex_enter(&arc_reclaim_lock); 3671 if (!arc_is_overflowing()) 3672 cv_signal(&arc_reclaim_waiters_cv); 3673 mutex_exit(&arc_reclaim_lock); 3674 } else { 3675 ARCSTAT_BUMP(arcstat_mutex_miss); 3676 } 3677 } 3678 3679 multilist_sublist_unlock(mls); 3680 3681 return (bytes_evicted); 3682} 3683 3684/* 3685 * Evict buffers from the given arc state, until we've removed the 3686 * specified number of bytes. Move the removed buffers to the 3687 * appropriate evict state. 3688 * 3689 * This function makes a "best effort". It skips over any buffers 3690 * it can't get a hash_lock on, and so, may not catch all candidates. 3691 * It may also return without evicting as much space as requested. 3692 * 3693 * If bytes is specified using the special value ARC_EVICT_ALL, this 3694 * will evict all available (i.e. unlocked and evictable) buffers from 3695 * the given arc state; which is used by arc_flush(). 3696 */ 3697static uint64_t 3698arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3699 arc_buf_contents_t type) 3700{ 3701 uint64_t total_evicted = 0; 3702 multilist_t *ml = state->arcs_list[type]; 3703 int num_sublists; 3704 arc_buf_hdr_t **markers; 3705 3706 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3707 3708 num_sublists = multilist_get_num_sublists(ml); 3709 3710 /* 3711 * If we've tried to evict from each sublist, made some 3712 * progress, but still have not hit the target number of bytes 3713 * to evict, we want to keep trying. The markers allow us to 3714 * pick up where we left off for each individual sublist, rather 3715 * than starting from the tail each time. 3716 */ 3717 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3718 for (int i = 0; i < num_sublists; i++) { 3719 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3720 3721 /* 3722 * A b_spa of 0 is used to indicate that this header is 3723 * a marker. This fact is used in arc_adjust_type() and 3724 * arc_evict_state_impl(). 3725 */ 3726 markers[i]->b_spa = 0; 3727 3728 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3729 multilist_sublist_insert_tail(mls, markers[i]); 3730 multilist_sublist_unlock(mls); 3731 } 3732 3733 /* 3734 * While we haven't hit our target number of bytes to evict, or 3735 * we're evicting all available buffers. 3736 */ 3737 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3738 /* 3739 * Start eviction using a randomly selected sublist, 3740 * this is to try and evenly balance eviction across all 3741 * sublists. Always starting at the same sublist 3742 * (e.g. index 0) would cause evictions to favor certain 3743 * sublists over others. 3744 */ 3745 int sublist_idx = multilist_get_random_index(ml); 3746 uint64_t scan_evicted = 0; 3747 3748 for (int i = 0; i < num_sublists; i++) { 3749 uint64_t bytes_remaining; 3750 uint64_t bytes_evicted; 3751 3752 if (bytes == ARC_EVICT_ALL) 3753 bytes_remaining = ARC_EVICT_ALL; 3754 else if (total_evicted < bytes) 3755 bytes_remaining = bytes - total_evicted; 3756 else 3757 break; 3758 3759 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3760 markers[sublist_idx], spa, bytes_remaining); 3761 3762 scan_evicted += bytes_evicted; 3763 total_evicted += bytes_evicted; 3764 3765 /* we've reached the end, wrap to the beginning */ 3766 if (++sublist_idx >= num_sublists) 3767 sublist_idx = 0; 3768 } 3769 3770 /* 3771 * If we didn't evict anything during this scan, we have 3772 * no reason to believe we'll evict more during another 3773 * scan, so break the loop. 3774 */ 3775 if (scan_evicted == 0) { 3776 /* This isn't possible, let's make that obvious */ 3777 ASSERT3S(bytes, !=, 0); 3778 3779 /* 3780 * When bytes is ARC_EVICT_ALL, the only way to 3781 * break the loop is when scan_evicted is zero. 3782 * In that case, we actually have evicted enough, 3783 * so we don't want to increment the kstat. 3784 */ 3785 if (bytes != ARC_EVICT_ALL) { 3786 ASSERT3S(total_evicted, <, bytes); 3787 ARCSTAT_BUMP(arcstat_evict_not_enough); 3788 } 3789 3790 break; 3791 } 3792 } 3793 3794 for (int i = 0; i < num_sublists; i++) { 3795 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3796 multilist_sublist_remove(mls, markers[i]); 3797 multilist_sublist_unlock(mls); 3798 3799 kmem_cache_free(hdr_full_cache, markers[i]); 3800 } 3801 kmem_free(markers, sizeof (*markers) * num_sublists); 3802 3803 return (total_evicted); 3804} 3805 3806/* 3807 * Flush all "evictable" data of the given type from the arc state 3808 * specified. This will not evict any "active" buffers (i.e. referenced). 3809 * 3810 * When 'retry' is set to B_FALSE, the function will make a single pass 3811 * over the state and evict any buffers that it can. Since it doesn't 3812 * continually retry the eviction, it might end up leaving some buffers 3813 * in the ARC due to lock misses. 3814 * 3815 * When 'retry' is set to B_TRUE, the function will continually retry the 3816 * eviction until *all* evictable buffers have been removed from the 3817 * state. As a result, if concurrent insertions into the state are 3818 * allowed (e.g. if the ARC isn't shutting down), this function might 3819 * wind up in an infinite loop, continually trying to evict buffers. 3820 */ 3821static uint64_t 3822arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3823 boolean_t retry) 3824{ 3825 uint64_t evicted = 0; 3826 3827 while (refcount_count(&state->arcs_esize[type]) != 0) { 3828 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3829 3830 if (!retry) 3831 break; 3832 } 3833 3834 return (evicted); 3835} 3836 3837/* 3838 * Evict the specified number of bytes from the state specified, 3839 * restricting eviction to the spa and type given. This function 3840 * prevents us from trying to evict more from a state's list than 3841 * is "evictable", and to skip evicting altogether when passed a 3842 * negative value for "bytes". In contrast, arc_evict_state() will 3843 * evict everything it can, when passed a negative value for "bytes". 3844 */ 3845static uint64_t 3846arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3847 arc_buf_contents_t type) 3848{ 3849 int64_t delta; 3850 3851 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3852 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3853 return (arc_evict_state(state, spa, delta, type)); 3854 } 3855 3856 return (0); 3857} 3858 3859/* 3860 * Evict metadata buffers from the cache, such that arc_meta_used is 3861 * capped by the arc_meta_limit tunable. 3862 */ 3863static uint64_t 3864arc_adjust_meta(void) 3865{ 3866 uint64_t total_evicted = 0; 3867 int64_t target; 3868 3869 /* 3870 * If we're over the meta limit, we want to evict enough 3871 * metadata to get back under the meta limit. We don't want to 3872 * evict so much that we drop the MRU below arc_p, though. If 3873 * we're over the meta limit more than we're over arc_p, we 3874 * evict some from the MRU here, and some from the MFU below. 3875 */ 3876 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3877 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3878 refcount_count(&arc_mru->arcs_size) - arc_p)); 3879 3880 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3881 3882 /* 3883 * Similar to the above, we want to evict enough bytes to get us 3884 * below the meta limit, but not so much as to drop us below the 3885 * space allotted to the MFU (which is defined as arc_c - arc_p). 3886 */ 3887 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3888 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3889 3890 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3891 3892 return (total_evicted); 3893} 3894 3895/* 3896 * Return the type of the oldest buffer in the given arc state 3897 * 3898 * This function will select a random sublist of type ARC_BUFC_DATA and 3899 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3900 * is compared, and the type which contains the "older" buffer will be 3901 * returned. 3902 */ 3903static arc_buf_contents_t 3904arc_adjust_type(arc_state_t *state) 3905{ 3906 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; 3907 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; 3908 int data_idx = multilist_get_random_index(data_ml); 3909 int meta_idx = multilist_get_random_index(meta_ml); 3910 multilist_sublist_t *data_mls; 3911 multilist_sublist_t *meta_mls; 3912 arc_buf_contents_t type; 3913 arc_buf_hdr_t *data_hdr; 3914 arc_buf_hdr_t *meta_hdr; 3915 3916 /* 3917 * We keep the sublist lock until we're finished, to prevent 3918 * the headers from being destroyed via arc_evict_state(). 3919 */ 3920 data_mls = multilist_sublist_lock(data_ml, data_idx); 3921 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3922 3923 /* 3924 * These two loops are to ensure we skip any markers that 3925 * might be at the tail of the lists due to arc_evict_state(). 3926 */ 3927 3928 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3929 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3930 if (data_hdr->b_spa != 0) 3931 break; 3932 } 3933 3934 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3935 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3936 if (meta_hdr->b_spa != 0) 3937 break; 3938 } 3939 3940 if (data_hdr == NULL && meta_hdr == NULL) { 3941 type = ARC_BUFC_DATA; 3942 } else if (data_hdr == NULL) { 3943 ASSERT3P(meta_hdr, !=, NULL); 3944 type = ARC_BUFC_METADATA; 3945 } else if (meta_hdr == NULL) { 3946 ASSERT3P(data_hdr, !=, NULL); 3947 type = ARC_BUFC_DATA; 3948 } else { 3949 ASSERT3P(data_hdr, !=, NULL); 3950 ASSERT3P(meta_hdr, !=, NULL); 3951 3952 /* The headers can't be on the sublist without an L1 header */ 3953 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3954 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3955 3956 if (data_hdr->b_l1hdr.b_arc_access < 3957 meta_hdr->b_l1hdr.b_arc_access) { 3958 type = ARC_BUFC_DATA; 3959 } else { 3960 type = ARC_BUFC_METADATA; 3961 } 3962 } 3963 3964 multilist_sublist_unlock(meta_mls); 3965 multilist_sublist_unlock(data_mls); 3966 3967 return (type); 3968} 3969 3970/* 3971 * Evict buffers from the cache, such that arc_size is capped by arc_c. 3972 */ 3973static uint64_t 3974arc_adjust(void) 3975{ 3976 uint64_t total_evicted = 0; 3977 uint64_t bytes; 3978 int64_t target; 3979 3980 /* 3981 * If we're over arc_meta_limit, we want to correct that before 3982 * potentially evicting data buffers below. 3983 */ 3984 total_evicted += arc_adjust_meta(); 3985 3986 /* 3987 * Adjust MRU size 3988 * 3989 * If we're over the target cache size, we want to evict enough 3990 * from the list to get back to our target size. We don't want 3991 * to evict too much from the MRU, such that it drops below 3992 * arc_p. So, if we're over our target cache size more than 3993 * the MRU is over arc_p, we'll evict enough to get back to 3994 * arc_p here, and then evict more from the MFU below. 3995 */ 3996 target = MIN((int64_t)(arc_size - arc_c), 3997 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3998 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 3999 4000 /* 4001 * If we're below arc_meta_min, always prefer to evict data. 4002 * Otherwise, try to satisfy the requested number of bytes to 4003 * evict from the type which contains older buffers; in an 4004 * effort to keep newer buffers in the cache regardless of their 4005 * type. If we cannot satisfy the number of bytes from this 4006 * type, spill over into the next type. 4007 */ 4008 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 4009 arc_meta_used > arc_meta_min) { 4010 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4011 total_evicted += bytes; 4012 4013 /* 4014 * If we couldn't evict our target number of bytes from 4015 * metadata, we try to get the rest from data. 4016 */ 4017 target -= bytes; 4018 4019 total_evicted += 4020 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4021 } else { 4022 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4023 total_evicted += bytes; 4024 4025 /* 4026 * If we couldn't evict our target number of bytes from 4027 * data, we try to get the rest from metadata. 4028 */ 4029 target -= bytes; 4030 4031 total_evicted += 4032 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4033 } 4034 4035 /* 4036 * Adjust MFU size 4037 * 4038 * Now that we've tried to evict enough from the MRU to get its 4039 * size back to arc_p, if we're still above the target cache 4040 * size, we evict the rest from the MFU. 4041 */ 4042 target = arc_size - arc_c; 4043 4044 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 4045 arc_meta_used > arc_meta_min) { 4046 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4047 total_evicted += bytes; 4048 4049 /* 4050 * If we couldn't evict our target number of bytes from 4051 * metadata, we try to get the rest from data. 4052 */ 4053 target -= bytes; 4054 4055 total_evicted += 4056 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4057 } else { 4058 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4059 total_evicted += bytes; 4060 4061 /* 4062 * If we couldn't evict our target number of bytes from 4063 * data, we try to get the rest from data. 4064 */ 4065 target -= bytes; 4066 4067 total_evicted += 4068 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4069 } 4070 4071 /* 4072 * Adjust ghost lists 4073 * 4074 * In addition to the above, the ARC also defines target values 4075 * for the ghost lists. The sum of the mru list and mru ghost 4076 * list should never exceed the target size of the cache, and 4077 * the sum of the mru list, mfu list, mru ghost list, and mfu 4078 * ghost list should never exceed twice the target size of the 4079 * cache. The following logic enforces these limits on the ghost 4080 * caches, and evicts from them as needed. 4081 */ 4082 target = refcount_count(&arc_mru->arcs_size) + 4083 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 4084 4085 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 4086 total_evicted += bytes; 4087 4088 target -= bytes; 4089 4090 total_evicted += 4091 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 4092 4093 /* 4094 * We assume the sum of the mru list and mfu list is less than 4095 * or equal to arc_c (we enforced this above), which means we 4096 * can use the simpler of the two equations below: 4097 * 4098 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 4099 * mru ghost + mfu ghost <= arc_c 4100 */ 4101 target = refcount_count(&arc_mru_ghost->arcs_size) + 4102 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 4103 4104 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 4105 total_evicted += bytes; 4106 4107 target -= bytes; 4108 4109 total_evicted += 4110 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 4111 4112 return (total_evicted); 4113} 4114 4115void 4116arc_flush(spa_t *spa, boolean_t retry) 4117{ 4118 uint64_t guid = 0; 4119 4120 /* 4121 * If retry is B_TRUE, a spa must not be specified since we have 4122 * no good way to determine if all of a spa's buffers have been 4123 * evicted from an arc state. 4124 */ 4125 ASSERT(!retry || spa == 0); 4126 4127 if (spa != NULL) 4128 guid = spa_load_guid(spa); 4129 4130 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 4131 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 4132 4133 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 4134 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 4135 4136 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 4137 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 4138 4139 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 4140 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 4141} 4142 4143void 4144arc_shrink(int64_t to_free) 4145{ 4146 if (arc_c > arc_c_min) { 4147 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 4148 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 4149 if (arc_c > arc_c_min + to_free) 4150 atomic_add_64(&arc_c, -to_free); 4151 else 4152 arc_c = arc_c_min; 4153 4154 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 4155 if (arc_c > arc_size) 4156 arc_c = MAX(arc_size, arc_c_min); 4157 if (arc_p > arc_c) 4158 arc_p = (arc_c >> 1); 4159 4160 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 4161 arc_p); 4162 4163 ASSERT(arc_c >= arc_c_min); 4164 ASSERT((int64_t)arc_p >= 0); 4165 } 4166 4167 if (arc_size > arc_c) { 4168 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 4169 uint64_t, arc_c); 4170 (void) arc_adjust(); 4171 } 4172} 4173 4174static long needfree = 0; 4175 4176typedef enum free_memory_reason_t { 4177 FMR_UNKNOWN, 4178 FMR_NEEDFREE, 4179 FMR_LOTSFREE, 4180 FMR_SWAPFS_MINFREE, 4181 FMR_PAGES_PP_MAXIMUM, 4182 FMR_HEAP_ARENA, 4183 FMR_ZIO_ARENA, 4184 FMR_ZIO_FRAG, 4185} free_memory_reason_t; 4186 4187int64_t last_free_memory; 4188free_memory_reason_t last_free_reason; 4189 4190/* 4191 * Additional reserve of pages for pp_reserve. 4192 */ 4193int64_t arc_pages_pp_reserve = 64; 4194 4195/* 4196 * Additional reserve of pages for swapfs. 4197 */ 4198int64_t arc_swapfs_reserve = 64; 4199 4200/* 4201 * Return the amount of memory that can be consumed before reclaim will be 4202 * needed. Positive if there is sufficient free memory, negative indicates 4203 * the amount of memory that needs to be freed up. 4204 */ 4205static int64_t 4206arc_available_memory(void) 4207{ 4208 int64_t lowest = INT64_MAX; 4209 int64_t n; 4210 free_memory_reason_t r = FMR_UNKNOWN; 4211 4212#ifdef _KERNEL 4213 if (needfree > 0) { 4214 n = PAGESIZE * (-needfree); 4215 if (n < lowest) { 4216 lowest = n; 4217 r = FMR_NEEDFREE; 4218 } 4219 } 4220 4221 /* 4222 * Cooperate with pagedaemon when it's time for it to scan 4223 * and reclaim some pages. 4224 */ 4225 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 4226 if (n < lowest) { 4227 lowest = n; 4228 r = FMR_LOTSFREE; 4229 } 4230 4231#ifdef illumos 4232 /* 4233 * check that we're out of range of the pageout scanner. It starts to 4234 * schedule paging if freemem is less than lotsfree and needfree. 4235 * lotsfree is the high-water mark for pageout, and needfree is the 4236 * number of needed free pages. We add extra pages here to make sure 4237 * the scanner doesn't start up while we're freeing memory. 4238 */ 4239 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 4240 if (n < lowest) { 4241 lowest = n; 4242 r = FMR_LOTSFREE; 4243 } 4244 4245 /* 4246 * check to make sure that swapfs has enough space so that anon 4247 * reservations can still succeed. anon_resvmem() checks that the 4248 * availrmem is greater than swapfs_minfree, and the number of reserved 4249 * swap pages. We also add a bit of extra here just to prevent 4250 * circumstances from getting really dire. 4251 */ 4252 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 4253 desfree - arc_swapfs_reserve); 4254 if (n < lowest) { 4255 lowest = n; 4256 r = FMR_SWAPFS_MINFREE; 4257 } 4258 4259 4260 /* 4261 * Check that we have enough availrmem that memory locking (e.g., via 4262 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 4263 * stores the number of pages that cannot be locked; when availrmem 4264 * drops below pages_pp_maximum, page locking mechanisms such as 4265 * page_pp_lock() will fail.) 4266 */ 4267 n = PAGESIZE * (availrmem - pages_pp_maximum - 4268 arc_pages_pp_reserve); 4269 if (n < lowest) { 4270 lowest = n; 4271 r = FMR_PAGES_PP_MAXIMUM; 4272 } 4273 4274#endif /* illumos */ 4275#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4276 /* 4277 * If we're on an i386 platform, it's possible that we'll exhaust the 4278 * kernel heap space before we ever run out of available physical 4279 * memory. Most checks of the size of the heap_area compare against 4280 * tune.t_minarmem, which is the minimum available real memory that we 4281 * can have in the system. However, this is generally fixed at 25 pages 4282 * which is so low that it's useless. In this comparison, we seek to 4283 * calculate the total heap-size, and reclaim if more than 3/4ths of the 4284 * heap is allocated. (Or, in the calculation, if less than 1/4th is 4285 * free) 4286 */ 4287 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 4288 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 4289 if (n < lowest) { 4290 lowest = n; 4291 r = FMR_HEAP_ARENA; 4292 } 4293#define zio_arena NULL 4294#else 4295#define zio_arena heap_arena 4296#endif 4297 4298 /* 4299 * If zio data pages are being allocated out of a separate heap segment, 4300 * then enforce that the size of available vmem for this arena remains 4301 * above about 1/16th free. 4302 * 4303 * Note: The 1/16th arena free requirement was put in place 4304 * to aggressively evict memory from the arc in order to avoid 4305 * memory fragmentation issues. 4306 */ 4307 if (zio_arena != NULL) { 4308 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 4309 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 4310 if (n < lowest) { 4311 lowest = n; 4312 r = FMR_ZIO_ARENA; 4313 } 4314 } 4315 4316 /* 4317 * Above limits know nothing about real level of KVA fragmentation. 4318 * Start aggressive reclamation if too little sequential KVA left. 4319 */ 4320 if (lowest > 0) { 4321 n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ? 4322 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 4323 INT64_MAX; 4324 if (n < lowest) { 4325 lowest = n; 4326 r = FMR_ZIO_FRAG; 4327 } 4328 } 4329 4330#else /* _KERNEL */ 4331 /* Every 100 calls, free a small amount */ 4332 if (spa_get_random(100) == 0) 4333 lowest = -1024; 4334#endif /* _KERNEL */ 4335 4336 last_free_memory = lowest; 4337 last_free_reason = r; 4338 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 4339 return (lowest); 4340} 4341 4342 4343/* 4344 * Determine if the system is under memory pressure and is asking 4345 * to reclaim memory. A return value of B_TRUE indicates that the system 4346 * is under memory pressure and that the arc should adjust accordingly. 4347 */ 4348static boolean_t 4349arc_reclaim_needed(void) 4350{ 4351 return (arc_available_memory() < 0); 4352} 4353 4354extern kmem_cache_t *zio_buf_cache[]; 4355extern kmem_cache_t *zio_data_buf_cache[]; 4356extern kmem_cache_t *range_seg_cache; 4357extern kmem_cache_t *abd_chunk_cache; 4358 4359static __noinline void 4360arc_kmem_reap_now(void) 4361{ 4362 size_t i; 4363 kmem_cache_t *prev_cache = NULL; 4364 kmem_cache_t *prev_data_cache = NULL; 4365 4366 DTRACE_PROBE(arc__kmem_reap_start); 4367#ifdef _KERNEL 4368 if (arc_meta_used >= arc_meta_limit) { 4369 /* 4370 * We are exceeding our meta-data cache limit. 4371 * Purge some DNLC entries to release holds on meta-data. 4372 */ 4373 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4374 } 4375#if defined(__i386) 4376 /* 4377 * Reclaim unused memory from all kmem caches. 4378 */ 4379 kmem_reap(); 4380#endif 4381#endif 4382 4383 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4384 if (zio_buf_cache[i] != prev_cache) { 4385 prev_cache = zio_buf_cache[i]; 4386 kmem_cache_reap_now(zio_buf_cache[i]); 4387 } 4388 if (zio_data_buf_cache[i] != prev_data_cache) { 4389 prev_data_cache = zio_data_buf_cache[i]; 4390 kmem_cache_reap_now(zio_data_buf_cache[i]); 4391 } 4392 } 4393 kmem_cache_reap_now(abd_chunk_cache); 4394 kmem_cache_reap_now(buf_cache); 4395 kmem_cache_reap_now(hdr_full_cache); 4396 kmem_cache_reap_now(hdr_l2only_cache); 4397 kmem_cache_reap_now(range_seg_cache); 4398 4399#ifdef illumos 4400 if (zio_arena != NULL) { 4401 /* 4402 * Ask the vmem arena to reclaim unused memory from its 4403 * quantum caches. 4404 */ 4405 vmem_qcache_reap(zio_arena); 4406 } 4407#endif 4408 DTRACE_PROBE(arc__kmem_reap_end); 4409} 4410 4411/* 4412 * Threads can block in arc_get_data_impl() waiting for this thread to evict 4413 * enough data and signal them to proceed. When this happens, the threads in 4414 * arc_get_data_impl() are sleeping while holding the hash lock for their 4415 * particular arc header. Thus, we must be careful to never sleep on a 4416 * hash lock in this thread. This is to prevent the following deadlock: 4417 * 4418 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L", 4419 * waiting for the reclaim thread to signal it. 4420 * 4421 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4422 * fails, and goes to sleep forever. 4423 * 4424 * This possible deadlock is avoided by always acquiring a hash lock 4425 * using mutex_tryenter() from arc_reclaim_thread(). 4426 */ 4427static void 4428arc_reclaim_thread(void *dummy __unused) 4429{ 4430 hrtime_t growtime = 0; 4431 callb_cpr_t cpr; 4432 4433 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4434 4435 mutex_enter(&arc_reclaim_lock); 4436 while (!arc_reclaim_thread_exit) { 4437 uint64_t evicted = 0; 4438 4439 /* 4440 * This is necessary in order for the mdb ::arc dcmd to 4441 * show up to date information. Since the ::arc command 4442 * does not call the kstat's update function, without 4443 * this call, the command may show stale stats for the 4444 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4445 * with this change, the data might be up to 1 second 4446 * out of date; but that should suffice. The arc_state_t 4447 * structures can be queried directly if more accurate 4448 * information is needed. 4449 */ 4450 if (arc_ksp != NULL) 4451 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4452 4453 mutex_exit(&arc_reclaim_lock); 4454 4455 /* 4456 * We call arc_adjust() before (possibly) calling 4457 * arc_kmem_reap_now(), so that we can wake up 4458 * arc_get_data_impl() sooner. 4459 */ 4460 evicted = arc_adjust(); 4461 4462 int64_t free_memory = arc_available_memory(); 4463 if (free_memory < 0) { 4464 4465 arc_no_grow = B_TRUE; 4466 arc_warm = B_TRUE; 4467 4468 /* 4469 * Wait at least zfs_grow_retry (default 60) seconds 4470 * before considering growing. 4471 */ 4472 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 4473 4474 arc_kmem_reap_now(); 4475 4476 /* 4477 * If we are still low on memory, shrink the ARC 4478 * so that we have arc_shrink_min free space. 4479 */ 4480 free_memory = arc_available_memory(); 4481 4482 int64_t to_free = 4483 (arc_c >> arc_shrink_shift) - free_memory; 4484 if (to_free > 0) { 4485#ifdef _KERNEL 4486 to_free = MAX(to_free, ptob(needfree)); 4487#endif 4488 arc_shrink(to_free); 4489 } 4490 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4491 arc_no_grow = B_TRUE; 4492 } else if (gethrtime() >= growtime) { 4493 arc_no_grow = B_FALSE; 4494 } 4495 4496 mutex_enter(&arc_reclaim_lock); 4497 4498 /* 4499 * If evicted is zero, we couldn't evict anything via 4500 * arc_adjust(). This could be due to hash lock 4501 * collisions, but more likely due to the majority of 4502 * arc buffers being unevictable. Therefore, even if 4503 * arc_size is above arc_c, another pass is unlikely to 4504 * be helpful and could potentially cause us to enter an 4505 * infinite loop. 4506 */ 4507 if (arc_size <= arc_c || evicted == 0) { 4508#ifdef _KERNEL 4509 needfree = 0; 4510#endif 4511 /* 4512 * We're either no longer overflowing, or we 4513 * can't evict anything more, so we should wake 4514 * up any threads before we go to sleep. 4515 */ 4516 cv_broadcast(&arc_reclaim_waiters_cv); 4517 4518 /* 4519 * Block until signaled, or after one second (we 4520 * might need to perform arc_kmem_reap_now() 4521 * even if we aren't being signalled) 4522 */ 4523 CALLB_CPR_SAFE_BEGIN(&cpr); 4524 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4525 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4526 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4527 } 4528 } 4529 4530 arc_reclaim_thread_exit = B_FALSE; 4531 cv_broadcast(&arc_reclaim_thread_cv); 4532 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4533 thread_exit(); 4534} 4535 4536static u_int arc_dnlc_evicts_arg; 4537extern struct vfsops zfs_vfsops; 4538 4539static void 4540arc_dnlc_evicts_thread(void *dummy __unused) 4541{ 4542 callb_cpr_t cpr; 4543 u_int percent; 4544 4545 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 4546 4547 mutex_enter(&arc_dnlc_evicts_lock); 4548 while (!arc_dnlc_evicts_thread_exit) { 4549 CALLB_CPR_SAFE_BEGIN(&cpr); 4550 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 4551 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 4552 if (arc_dnlc_evicts_arg != 0) { 4553 percent = arc_dnlc_evicts_arg; 4554 mutex_exit(&arc_dnlc_evicts_lock); 4555#ifdef _KERNEL 4556 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 4557#endif 4558 mutex_enter(&arc_dnlc_evicts_lock); 4559 /* 4560 * Clear our token only after vnlru_free() 4561 * pass is done, to avoid false queueing of 4562 * the requests. 4563 */ 4564 arc_dnlc_evicts_arg = 0; 4565 } 4566 } 4567 arc_dnlc_evicts_thread_exit = FALSE; 4568 cv_broadcast(&arc_dnlc_evicts_cv); 4569 CALLB_CPR_EXIT(&cpr); 4570 thread_exit(); 4571} 4572 4573void 4574dnlc_reduce_cache(void *arg) 4575{ 4576 u_int percent; 4577 4578 percent = (u_int)(uintptr_t)arg; 4579 mutex_enter(&arc_dnlc_evicts_lock); 4580 if (arc_dnlc_evicts_arg == 0) { 4581 arc_dnlc_evicts_arg = percent; 4582 cv_broadcast(&arc_dnlc_evicts_cv); 4583 } 4584 mutex_exit(&arc_dnlc_evicts_lock); 4585} 4586 4587/* 4588 * Adapt arc info given the number of bytes we are trying to add and 4589 * the state that we are comming from. This function is only called 4590 * when we are adding new content to the cache. 4591 */ 4592static void 4593arc_adapt(int bytes, arc_state_t *state) 4594{ 4595 int mult; 4596 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4597 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4598 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4599 4600 if (state == arc_l2c_only) 4601 return; 4602 4603 ASSERT(bytes > 0); 4604 /* 4605 * Adapt the target size of the MRU list: 4606 * - if we just hit in the MRU ghost list, then increase 4607 * the target size of the MRU list. 4608 * - if we just hit in the MFU ghost list, then increase 4609 * the target size of the MFU list by decreasing the 4610 * target size of the MRU list. 4611 */ 4612 if (state == arc_mru_ghost) { 4613 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4614 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4615 4616 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4617 } else if (state == arc_mfu_ghost) { 4618 uint64_t delta; 4619 4620 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4621 mult = MIN(mult, 10); 4622 4623 delta = MIN(bytes * mult, arc_p); 4624 arc_p = MAX(arc_p_min, arc_p - delta); 4625 } 4626 ASSERT((int64_t)arc_p >= 0); 4627 4628 if (arc_reclaim_needed()) { 4629 cv_signal(&arc_reclaim_thread_cv); 4630 return; 4631 } 4632 4633 if (arc_no_grow) 4634 return; 4635 4636 if (arc_c >= arc_c_max) 4637 return; 4638 4639 /* 4640 * If we're within (2 * maxblocksize) bytes of the target 4641 * cache size, increment the target cache size 4642 */ 4643 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 4644 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4645 atomic_add_64(&arc_c, (int64_t)bytes); 4646 if (arc_c > arc_c_max) 4647 arc_c = arc_c_max; 4648 else if (state == arc_anon) 4649 atomic_add_64(&arc_p, (int64_t)bytes); 4650 if (arc_p > arc_c) 4651 arc_p = arc_c; 4652 } 4653 ASSERT((int64_t)arc_p >= 0); 4654} 4655 4656/* 4657 * Check if arc_size has grown past our upper threshold, determined by 4658 * zfs_arc_overflow_shift. 4659 */ 4660static boolean_t 4661arc_is_overflowing(void) 4662{ 4663 /* Always allow at least one block of overflow */ 4664 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4665 arc_c >> zfs_arc_overflow_shift); 4666 4667 return (arc_size >= arc_c + overflow); 4668} 4669 4670static abd_t * 4671arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4672{ 4673 arc_buf_contents_t type = arc_buf_type(hdr); 4674 4675 arc_get_data_impl(hdr, size, tag); 4676 if (type == ARC_BUFC_METADATA) { 4677 return (abd_alloc(size, B_TRUE)); 4678 } else { 4679 ASSERT(type == ARC_BUFC_DATA); 4680 return (abd_alloc(size, B_FALSE)); 4681 } 4682} 4683 4684static void * 4685arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4686{ 4687 arc_buf_contents_t type = arc_buf_type(hdr); 4688 4689 arc_get_data_impl(hdr, size, tag); 4690 if (type == ARC_BUFC_METADATA) { 4691 return (zio_buf_alloc(size)); 4692 } else { 4693 ASSERT(type == ARC_BUFC_DATA); 4694 return (zio_data_buf_alloc(size)); 4695 } 4696} 4697 4698/* 4699 * Allocate a block and return it to the caller. If we are hitting the 4700 * hard limit for the cache size, we must sleep, waiting for the eviction 4701 * thread to catch up. If we're past the target size but below the hard 4702 * limit, we'll only signal the reclaim thread and continue on. 4703 */ 4704static void 4705arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4706{ 4707 arc_state_t *state = hdr->b_l1hdr.b_state; 4708 arc_buf_contents_t type = arc_buf_type(hdr); 4709 4710 arc_adapt(size, state); 4711 4712 /* 4713 * If arc_size is currently overflowing, and has grown past our 4714 * upper limit, we must be adding data faster than the evict 4715 * thread can evict. Thus, to ensure we don't compound the 4716 * problem by adding more data and forcing arc_size to grow even 4717 * further past it's target size, we halt and wait for the 4718 * eviction thread to catch up. 4719 * 4720 * It's also possible that the reclaim thread is unable to evict 4721 * enough buffers to get arc_size below the overflow limit (e.g. 4722 * due to buffers being un-evictable, or hash lock collisions). 4723 * In this case, we want to proceed regardless if we're 4724 * overflowing; thus we don't use a while loop here. 4725 */ 4726 if (arc_is_overflowing()) { 4727 mutex_enter(&arc_reclaim_lock); 4728 4729 /* 4730 * Now that we've acquired the lock, we may no longer be 4731 * over the overflow limit, lets check. 4732 * 4733 * We're ignoring the case of spurious wake ups. If that 4734 * were to happen, it'd let this thread consume an ARC 4735 * buffer before it should have (i.e. before we're under 4736 * the overflow limit and were signalled by the reclaim 4737 * thread). As long as that is a rare occurrence, it 4738 * shouldn't cause any harm. 4739 */ 4740 if (arc_is_overflowing()) { 4741 cv_signal(&arc_reclaim_thread_cv); 4742 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4743 } 4744 4745 mutex_exit(&arc_reclaim_lock); 4746 } 4747 4748 VERIFY3U(hdr->b_type, ==, type); 4749 if (type == ARC_BUFC_METADATA) { 4750 arc_space_consume(size, ARC_SPACE_META); 4751 } else { 4752 arc_space_consume(size, ARC_SPACE_DATA); 4753 } 4754 4755 /* 4756 * Update the state size. Note that ghost states have a 4757 * "ghost size" and so don't need to be updated. 4758 */ 4759 if (!GHOST_STATE(state)) { 4760 4761 (void) refcount_add_many(&state->arcs_size, size, tag); 4762 4763 /* 4764 * If this is reached via arc_read, the link is 4765 * protected by the hash lock. If reached via 4766 * arc_buf_alloc, the header should not be accessed by 4767 * any other thread. And, if reached via arc_read_done, 4768 * the hash lock will protect it if it's found in the 4769 * hash table; otherwise no other thread should be 4770 * trying to [add|remove]_reference it. 4771 */ 4772 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4773 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4774 (void) refcount_add_many(&state->arcs_esize[type], 4775 size, tag); 4776 } 4777 4778 /* 4779 * If we are growing the cache, and we are adding anonymous 4780 * data, and we have outgrown arc_p, update arc_p 4781 */ 4782 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4783 (refcount_count(&arc_anon->arcs_size) + 4784 refcount_count(&arc_mru->arcs_size) > arc_p)) 4785 arc_p = MIN(arc_c, arc_p + size); 4786 } 4787 ARCSTAT_BUMP(arcstat_allocated); 4788} 4789 4790static void 4791arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) 4792{ 4793 arc_free_data_impl(hdr, size, tag); 4794 abd_free(abd); 4795} 4796 4797static void 4798arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) 4799{ 4800 arc_buf_contents_t type = arc_buf_type(hdr); 4801 4802 arc_free_data_impl(hdr, size, tag); 4803 if (type == ARC_BUFC_METADATA) { 4804 zio_buf_free(buf, size); 4805 } else { 4806 ASSERT(type == ARC_BUFC_DATA); 4807 zio_data_buf_free(buf, size); 4808 } 4809} 4810 4811/* 4812 * Free the arc data buffer. 4813 */ 4814static void 4815arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4816{ 4817 arc_state_t *state = hdr->b_l1hdr.b_state; 4818 arc_buf_contents_t type = arc_buf_type(hdr); 4819 4820 /* protected by hash lock, if in the hash table */ 4821 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4822 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4823 ASSERT(state != arc_anon && state != arc_l2c_only); 4824 4825 (void) refcount_remove_many(&state->arcs_esize[type], 4826 size, tag); 4827 } 4828 (void) refcount_remove_many(&state->arcs_size, size, tag); 4829 4830 VERIFY3U(hdr->b_type, ==, type); 4831 if (type == ARC_BUFC_METADATA) { 4832 arc_space_return(size, ARC_SPACE_META); 4833 } else { 4834 ASSERT(type == ARC_BUFC_DATA); 4835 arc_space_return(size, ARC_SPACE_DATA); 4836 } 4837} 4838 4839/* 4840 * This routine is called whenever a buffer is accessed. 4841 * NOTE: the hash lock is dropped in this function. 4842 */ 4843static void 4844arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4845{ 4846 clock_t now; 4847 4848 ASSERT(MUTEX_HELD(hash_lock)); 4849 ASSERT(HDR_HAS_L1HDR(hdr)); 4850 4851 if (hdr->b_l1hdr.b_state == arc_anon) { 4852 /* 4853 * This buffer is not in the cache, and does not 4854 * appear in our "ghost" list. Add the new buffer 4855 * to the MRU state. 4856 */ 4857 4858 ASSERT0(hdr->b_l1hdr.b_arc_access); 4859 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4860 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4861 arc_change_state(arc_mru, hdr, hash_lock); 4862 4863 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4864 now = ddi_get_lbolt(); 4865 4866 /* 4867 * If this buffer is here because of a prefetch, then either: 4868 * - clear the flag if this is a "referencing" read 4869 * (any subsequent access will bump this into the MFU state). 4870 * or 4871 * - move the buffer to the head of the list if this is 4872 * another prefetch (to make it less likely to be evicted). 4873 */ 4874 if (HDR_PREFETCH(hdr)) { 4875 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4876 /* link protected by hash lock */ 4877 ASSERT(multilist_link_active( 4878 &hdr->b_l1hdr.b_arc_node)); 4879 } else { 4880 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4881 ARCSTAT_BUMP(arcstat_mru_hits); 4882 } 4883 hdr->b_l1hdr.b_arc_access = now; 4884 return; 4885 } 4886 4887 /* 4888 * This buffer has been "accessed" only once so far, 4889 * but it is still in the cache. Move it to the MFU 4890 * state. 4891 */ 4892 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4893 /* 4894 * More than 125ms have passed since we 4895 * instantiated this buffer. Move it to the 4896 * most frequently used state. 4897 */ 4898 hdr->b_l1hdr.b_arc_access = now; 4899 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4900 arc_change_state(arc_mfu, hdr, hash_lock); 4901 } 4902 ARCSTAT_BUMP(arcstat_mru_hits); 4903 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4904 arc_state_t *new_state; 4905 /* 4906 * This buffer has been "accessed" recently, but 4907 * was evicted from the cache. Move it to the 4908 * MFU state. 4909 */ 4910 4911 if (HDR_PREFETCH(hdr)) { 4912 new_state = arc_mru; 4913 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4914 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4915 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4916 } else { 4917 new_state = arc_mfu; 4918 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4919 } 4920 4921 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4922 arc_change_state(new_state, hdr, hash_lock); 4923 4924 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4925 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4926 /* 4927 * This buffer has been accessed more than once and is 4928 * still in the cache. Keep it in the MFU state. 4929 * 4930 * NOTE: an add_reference() that occurred when we did 4931 * the arc_read() will have kicked this off the list. 4932 * If it was a prefetch, we will explicitly move it to 4933 * the head of the list now. 4934 */ 4935 if ((HDR_PREFETCH(hdr)) != 0) { 4936 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4937 /* link protected by hash_lock */ 4938 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4939 } 4940 ARCSTAT_BUMP(arcstat_mfu_hits); 4941 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4942 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4943 arc_state_t *new_state = arc_mfu; 4944 /* 4945 * This buffer has been accessed more than once but has 4946 * been evicted from the cache. Move it back to the 4947 * MFU state. 4948 */ 4949 4950 if (HDR_PREFETCH(hdr)) { 4951 /* 4952 * This is a prefetch access... 4953 * move this block back to the MRU state. 4954 */ 4955 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4956 new_state = arc_mru; 4957 } 4958 4959 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4960 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4961 arc_change_state(new_state, hdr, hash_lock); 4962 4963 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4964 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4965 /* 4966 * This buffer is on the 2nd Level ARC. 4967 */ 4968 4969 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4970 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4971 arc_change_state(arc_mfu, hdr, hash_lock); 4972 } else { 4973 ASSERT(!"invalid arc state"); 4974 } 4975} 4976 4977/* a generic arc_done_func_t which you can use */ 4978/* ARGSUSED */ 4979void 4980arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4981{ 4982 if (zio == NULL || zio->io_error == 0) 4983 bcopy(buf->b_data, arg, arc_buf_size(buf)); 4984 arc_buf_destroy(buf, arg); 4985} 4986 4987/* a generic arc_done_func_t */ 4988void 4989arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 4990{ 4991 arc_buf_t **bufp = arg; 4992 if (zio && zio->io_error) { 4993 arc_buf_destroy(buf, arg); 4994 *bufp = NULL; 4995 } else { 4996 *bufp = buf; 4997 ASSERT(buf->b_data); 4998 } 4999} 5000 5001static void 5002arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 5003{ 5004 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 5005 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 5006 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 5007 } else { 5008 if (HDR_COMPRESSION_ENABLED(hdr)) { 5009 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 5010 BP_GET_COMPRESS(bp)); 5011 } 5012 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 5013 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 5014 } 5015} 5016 5017static void 5018arc_read_done(zio_t *zio) 5019{ 5020 arc_buf_hdr_t *hdr = zio->io_private; 5021 kmutex_t *hash_lock = NULL; 5022 arc_callback_t *callback_list; 5023 arc_callback_t *acb; 5024 boolean_t freeable = B_FALSE; 5025 boolean_t no_zio_error = (zio->io_error == 0); 5026 5027 /* 5028 * The hdr was inserted into hash-table and removed from lists 5029 * prior to starting I/O. We should find this header, since 5030 * it's in the hash table, and it should be legit since it's 5031 * not possible to evict it during the I/O. The only possible 5032 * reason for it not to be found is if we were freed during the 5033 * read. 5034 */ 5035 if (HDR_IN_HASH_TABLE(hdr)) { 5036 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 5037 ASSERT3U(hdr->b_dva.dva_word[0], ==, 5038 BP_IDENTITY(zio->io_bp)->dva_word[0]); 5039 ASSERT3U(hdr->b_dva.dva_word[1], ==, 5040 BP_IDENTITY(zio->io_bp)->dva_word[1]); 5041 5042 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 5043 &hash_lock); 5044 5045 ASSERT((found == hdr && 5046 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 5047 (found == hdr && HDR_L2_READING(hdr))); 5048 ASSERT3P(hash_lock, !=, NULL); 5049 } 5050 5051 if (no_zio_error) { 5052 /* byteswap if necessary */ 5053 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 5054 if (BP_GET_LEVEL(zio->io_bp) > 0) { 5055 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 5056 } else { 5057 hdr->b_l1hdr.b_byteswap = 5058 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 5059 } 5060 } else { 5061 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 5062 } 5063 } 5064 5065 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 5066 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 5067 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 5068 5069 callback_list = hdr->b_l1hdr.b_acb; 5070 ASSERT3P(callback_list, !=, NULL); 5071 5072 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) { 5073 /* 5074 * Only call arc_access on anonymous buffers. This is because 5075 * if we've issued an I/O for an evicted buffer, we've already 5076 * called arc_access (to prevent any simultaneous readers from 5077 * getting confused). 5078 */ 5079 arc_access(hdr, hash_lock); 5080 } 5081 5082 /* 5083 * If a read request has a callback (i.e. acb_done is not NULL), then we 5084 * make a buf containing the data according to the parameters which were 5085 * passed in. The implementation of arc_buf_alloc_impl() ensures that we 5086 * aren't needlessly decompressing the data multiple times. 5087 */ 5088 int callback_cnt = 0; 5089 for (acb = callback_list; acb != NULL; acb = acb->acb_next) { 5090 if (!acb->acb_done) 5091 continue; 5092 5093 /* This is a demand read since prefetches don't use callbacks */ 5094 callback_cnt++; 5095 5096 int error = arc_buf_alloc_impl(hdr, acb->acb_private, 5097 acb->acb_compressed, no_zio_error, &acb->acb_buf); 5098 if (no_zio_error) { 5099 zio->io_error = error; 5100 } 5101 } 5102 hdr->b_l1hdr.b_acb = NULL; 5103 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5104 if (callback_cnt == 0) { 5105 ASSERT(HDR_PREFETCH(hdr)); 5106 ASSERT0(hdr->b_l1hdr.b_bufcnt); 5107 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5108 } 5109 5110 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 5111 callback_list != NULL); 5112 5113 if (no_zio_error) { 5114 arc_hdr_verify(hdr, zio->io_bp); 5115 } else { 5116 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 5117 if (hdr->b_l1hdr.b_state != arc_anon) 5118 arc_change_state(arc_anon, hdr, hash_lock); 5119 if (HDR_IN_HASH_TABLE(hdr)) 5120 buf_hash_remove(hdr); 5121 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5122 } 5123 5124 /* 5125 * Broadcast before we drop the hash_lock to avoid the possibility 5126 * that the hdr (and hence the cv) might be freed before we get to 5127 * the cv_broadcast(). 5128 */ 5129 cv_broadcast(&hdr->b_l1hdr.b_cv); 5130 5131 if (hash_lock != NULL) { 5132 mutex_exit(hash_lock); 5133 } else { 5134 /* 5135 * This block was freed while we waited for the read to 5136 * complete. It has been removed from the hash table and 5137 * moved to the anonymous state (so that it won't show up 5138 * in the cache). 5139 */ 5140 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 5141 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5142 } 5143 5144 /* execute each callback and free its structure */ 5145 while ((acb = callback_list) != NULL) { 5146 if (acb->acb_done) 5147 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 5148 5149 if (acb->acb_zio_dummy != NULL) { 5150 acb->acb_zio_dummy->io_error = zio->io_error; 5151 zio_nowait(acb->acb_zio_dummy); 5152 } 5153 5154 callback_list = acb->acb_next; 5155 kmem_free(acb, sizeof (arc_callback_t)); 5156 } 5157 5158 if (freeable) 5159 arc_hdr_destroy(hdr); 5160} 5161 5162/* 5163 * "Read" the block at the specified DVA (in bp) via the 5164 * cache. If the block is found in the cache, invoke the provided 5165 * callback immediately and return. Note that the `zio' parameter 5166 * in the callback will be NULL in this case, since no IO was 5167 * required. If the block is not in the cache pass the read request 5168 * on to the spa with a substitute callback function, so that the 5169 * requested block will be added to the cache. 5170 * 5171 * If a read request arrives for a block that has a read in-progress, 5172 * either wait for the in-progress read to complete (and return the 5173 * results); or, if this is a read with a "done" func, add a record 5174 * to the read to invoke the "done" func when the read completes, 5175 * and return; or just return. 5176 * 5177 * arc_read_done() will invoke all the requested "done" functions 5178 * for readers of this block. 5179 */ 5180int 5181arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 5182 void *private, zio_priority_t priority, int zio_flags, 5183 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 5184{ 5185 arc_buf_hdr_t *hdr = NULL; 5186 kmutex_t *hash_lock = NULL; 5187 zio_t *rzio; 5188 uint64_t guid = spa_load_guid(spa); 5189 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0; 5190 5191 ASSERT(!BP_IS_EMBEDDED(bp) || 5192 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 5193 5194top: 5195 if (!BP_IS_EMBEDDED(bp)) { 5196 /* 5197 * Embedded BP's have no DVA and require no I/O to "read". 5198 * Create an anonymous arc buf to back it. 5199 */ 5200 hdr = buf_hash_find(guid, bp, &hash_lock); 5201 } 5202 5203 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { 5204 arc_buf_t *buf = NULL; 5205 *arc_flags |= ARC_FLAG_CACHED; 5206 5207 if (HDR_IO_IN_PROGRESS(hdr)) { 5208 5209 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 5210 priority == ZIO_PRIORITY_SYNC_READ) { 5211 /* 5212 * This sync read must wait for an 5213 * in-progress async read (e.g. a predictive 5214 * prefetch). Async reads are queued 5215 * separately at the vdev_queue layer, so 5216 * this is a form of priority inversion. 5217 * Ideally, we would "inherit" the demand 5218 * i/o's priority by moving the i/o from 5219 * the async queue to the synchronous queue, 5220 * but there is currently no mechanism to do 5221 * so. Track this so that we can evaluate 5222 * the magnitude of this potential performance 5223 * problem. 5224 * 5225 * Note that if the prefetch i/o is already 5226 * active (has been issued to the device), 5227 * the prefetch improved performance, because 5228 * we issued it sooner than we would have 5229 * without the prefetch. 5230 */ 5231 DTRACE_PROBE1(arc__sync__wait__for__async, 5232 arc_buf_hdr_t *, hdr); 5233 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 5234 } 5235 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5236 arc_hdr_clear_flags(hdr, 5237 ARC_FLAG_PREDICTIVE_PREFETCH); 5238 } 5239 5240 if (*arc_flags & ARC_FLAG_WAIT) { 5241 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 5242 mutex_exit(hash_lock); 5243 goto top; 5244 } 5245 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5246 5247 if (done) { 5248 arc_callback_t *acb = NULL; 5249 5250 acb = kmem_zalloc(sizeof (arc_callback_t), 5251 KM_SLEEP); 5252 acb->acb_done = done; 5253 acb->acb_private = private; 5254 acb->acb_compressed = compressed_read; 5255 if (pio != NULL) 5256 acb->acb_zio_dummy = zio_null(pio, 5257 spa, NULL, NULL, NULL, zio_flags); 5258 5259 ASSERT3P(acb->acb_done, !=, NULL); 5260 acb->acb_next = hdr->b_l1hdr.b_acb; 5261 hdr->b_l1hdr.b_acb = acb; 5262 mutex_exit(hash_lock); 5263 return (0); 5264 } 5265 mutex_exit(hash_lock); 5266 return (0); 5267 } 5268 5269 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5270 hdr->b_l1hdr.b_state == arc_mfu); 5271 5272 if (done) { 5273 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5274 /* 5275 * This is a demand read which does not have to 5276 * wait for i/o because we did a predictive 5277 * prefetch i/o for it, which has completed. 5278 */ 5279 DTRACE_PROBE1( 5280 arc__demand__hit__predictive__prefetch, 5281 arc_buf_hdr_t *, hdr); 5282 ARCSTAT_BUMP( 5283 arcstat_demand_hit_predictive_prefetch); 5284 arc_hdr_clear_flags(hdr, 5285 ARC_FLAG_PREDICTIVE_PREFETCH); 5286 } 5287 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 5288 5289 /* Get a buf with the desired data in it. */ 5290 VERIFY0(arc_buf_alloc_impl(hdr, private, 5291 compressed_read, B_TRUE, &buf)); 5292 } else if (*arc_flags & ARC_FLAG_PREFETCH && 5293 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5294 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5295 } 5296 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5297 arc_access(hdr, hash_lock); 5298 if (*arc_flags & ARC_FLAG_L2CACHE) 5299 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5300 mutex_exit(hash_lock); 5301 ARCSTAT_BUMP(arcstat_hits); 5302 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5303 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5304 data, metadata, hits); 5305 5306 if (done) 5307 done(NULL, buf, private); 5308 } else { 5309 uint64_t lsize = BP_GET_LSIZE(bp); 5310 uint64_t psize = BP_GET_PSIZE(bp); 5311 arc_callback_t *acb; 5312 vdev_t *vd = NULL; 5313 uint64_t addr = 0; 5314 boolean_t devw = B_FALSE; 5315 uint64_t size; 5316 5317 if (hdr == NULL) { 5318 /* this block is not in the cache */ 5319 arc_buf_hdr_t *exists = NULL; 5320 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 5321 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 5322 BP_GET_COMPRESS(bp), type); 5323 5324 if (!BP_IS_EMBEDDED(bp)) { 5325 hdr->b_dva = *BP_IDENTITY(bp); 5326 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 5327 exists = buf_hash_insert(hdr, &hash_lock); 5328 } 5329 if (exists != NULL) { 5330 /* somebody beat us to the hash insert */ 5331 mutex_exit(hash_lock); 5332 buf_discard_identity(hdr); 5333 arc_hdr_destroy(hdr); 5334 goto top; /* restart the IO request */ 5335 } 5336 } else { 5337 /* 5338 * This block is in the ghost cache. If it was L2-only 5339 * (and thus didn't have an L1 hdr), we realloc the 5340 * header to add an L1 hdr. 5341 */ 5342 if (!HDR_HAS_L1HDR(hdr)) { 5343 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 5344 hdr_full_cache); 5345 } 5346 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5347 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 5348 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5349 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5350 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 5351 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 5352 5353 /* 5354 * This is a delicate dance that we play here. 5355 * This hdr is in the ghost list so we access it 5356 * to move it out of the ghost list before we 5357 * initiate the read. If it's a prefetch then 5358 * it won't have a callback so we'll remove the 5359 * reference that arc_buf_alloc_impl() created. We 5360 * do this after we've called arc_access() to 5361 * avoid hitting an assert in remove_reference(). 5362 */ 5363 arc_access(hdr, hash_lock); 5364 arc_hdr_alloc_pabd(hdr); 5365 } 5366 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5367 size = arc_hdr_size(hdr); 5368 5369 /* 5370 * If compression is enabled on the hdr, then will do 5371 * RAW I/O and will store the compressed data in the hdr's 5372 * data block. Otherwise, the hdr's data block will contain 5373 * the uncompressed data. 5374 */ 5375 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5376 zio_flags |= ZIO_FLAG_RAW; 5377 } 5378 5379 if (*arc_flags & ARC_FLAG_PREFETCH) 5380 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5381 if (*arc_flags & ARC_FLAG_L2CACHE) 5382 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5383 if (BP_GET_LEVEL(bp) > 0) 5384 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5385 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5386 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5387 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5388 5389 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5390 acb->acb_done = done; 5391 acb->acb_private = private; 5392 acb->acb_compressed = compressed_read; 5393 5394 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5395 hdr->b_l1hdr.b_acb = acb; 5396 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5397 5398 if (HDR_HAS_L2HDR(hdr) && 5399 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5400 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5401 addr = hdr->b_l2hdr.b_daddr; 5402 /* 5403 * Lock out device removal. 5404 */ 5405 if (vdev_is_dead(vd) || 5406 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 5407 vd = NULL; 5408 } 5409 5410 if (priority == ZIO_PRIORITY_ASYNC_READ) 5411 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5412 else 5413 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5414 5415 if (hash_lock != NULL) 5416 mutex_exit(hash_lock); 5417 5418 /* 5419 * At this point, we have a level 1 cache miss. Try again in 5420 * L2ARC if possible. 5421 */ 5422 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 5423 5424 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 5425 uint64_t, lsize, zbookmark_phys_t *, zb); 5426 ARCSTAT_BUMP(arcstat_misses); 5427 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5428 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5429 data, metadata, misses); 5430#ifdef _KERNEL 5431#ifdef RACCT 5432 if (racct_enable) { 5433 PROC_LOCK(curproc); 5434 racct_add_force(curproc, RACCT_READBPS, size); 5435 racct_add_force(curproc, RACCT_READIOPS, 1); 5436 PROC_UNLOCK(curproc); 5437 } 5438#endif /* RACCT */ 5439 curthread->td_ru.ru_inblock++; 5440#endif 5441 5442 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5443 /* 5444 * Read from the L2ARC if the following are true: 5445 * 1. The L2ARC vdev was previously cached. 5446 * 2. This buffer still has L2ARC metadata. 5447 * 3. This buffer isn't currently writing to the L2ARC. 5448 * 4. The L2ARC entry wasn't evicted, which may 5449 * also have invalidated the vdev. 5450 * 5. This isn't prefetch and l2arc_noprefetch is set. 5451 */ 5452 if (HDR_HAS_L2HDR(hdr) && 5453 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5454 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5455 l2arc_read_callback_t *cb; 5456 abd_t *abd; 5457 uint64_t asize; 5458 5459 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5460 ARCSTAT_BUMP(arcstat_l2_hits); 5461 5462 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5463 KM_SLEEP); 5464 cb->l2rcb_hdr = hdr; 5465 cb->l2rcb_bp = *bp; 5466 cb->l2rcb_zb = *zb; 5467 cb->l2rcb_flags = zio_flags; 5468 5469 asize = vdev_psize_to_asize(vd, size); 5470 if (asize != size) { 5471 abd = abd_alloc_for_io(asize, 5472 HDR_ISTYPE_METADATA(hdr)); 5473 cb->l2rcb_abd = abd; 5474 } else { 5475 abd = hdr->b_l1hdr.b_pabd; 5476 } 5477 5478 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5479 addr + asize <= vd->vdev_psize - 5480 VDEV_LABEL_END_SIZE); 5481 5482 /* 5483 * l2arc read. The SCL_L2ARC lock will be 5484 * released by l2arc_read_done(). 5485 * Issue a null zio if the underlying buffer 5486 * was squashed to zero size by compression. 5487 */ 5488 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5489 ZIO_COMPRESS_EMPTY); 5490 rzio = zio_read_phys(pio, vd, addr, 5491 asize, abd, 5492 ZIO_CHECKSUM_OFF, 5493 l2arc_read_done, cb, priority, 5494 zio_flags | ZIO_FLAG_DONT_CACHE | 5495 ZIO_FLAG_CANFAIL | 5496 ZIO_FLAG_DONT_PROPAGATE | 5497 ZIO_FLAG_DONT_RETRY, B_FALSE); 5498 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5499 zio_t *, rzio); 5500 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5501 5502 if (*arc_flags & ARC_FLAG_NOWAIT) { 5503 zio_nowait(rzio); 5504 return (0); 5505 } 5506 5507 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5508 if (zio_wait(rzio) == 0) 5509 return (0); 5510 5511 /* l2arc read error; goto zio_read() */ 5512 } else { 5513 DTRACE_PROBE1(l2arc__miss, 5514 arc_buf_hdr_t *, hdr); 5515 ARCSTAT_BUMP(arcstat_l2_misses); 5516 if (HDR_L2_WRITING(hdr)) 5517 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5518 spa_config_exit(spa, SCL_L2ARC, vd); 5519 } 5520 } else { 5521 if (vd != NULL) 5522 spa_config_exit(spa, SCL_L2ARC, vd); 5523 if (l2arc_ndev != 0) { 5524 DTRACE_PROBE1(l2arc__miss, 5525 arc_buf_hdr_t *, hdr); 5526 ARCSTAT_BUMP(arcstat_l2_misses); 5527 } 5528 } 5529 5530 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size, 5531 arc_read_done, hdr, priority, zio_flags, zb); 5532 5533 if (*arc_flags & ARC_FLAG_WAIT) 5534 return (zio_wait(rzio)); 5535 5536 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5537 zio_nowait(rzio); 5538 } 5539 return (0); 5540} 5541 5542/* 5543 * Notify the arc that a block was freed, and thus will never be used again. 5544 */ 5545void 5546arc_freed(spa_t *spa, const blkptr_t *bp) 5547{ 5548 arc_buf_hdr_t *hdr; 5549 kmutex_t *hash_lock; 5550 uint64_t guid = spa_load_guid(spa); 5551 5552 ASSERT(!BP_IS_EMBEDDED(bp)); 5553 5554 hdr = buf_hash_find(guid, bp, &hash_lock); 5555 if (hdr == NULL) 5556 return; 5557 5558 /* 5559 * We might be trying to free a block that is still doing I/O 5560 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5561 * dmu_sync-ed block). If this block is being prefetched, then it 5562 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5563 * until the I/O completes. A block may also have a reference if it is 5564 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5565 * have written the new block to its final resting place on disk but 5566 * without the dedup flag set. This would have left the hdr in the MRU 5567 * state and discoverable. When the txg finally syncs it detects that 5568 * the block was overridden in open context and issues an override I/O. 5569 * Since this is a dedup block, the override I/O will determine if the 5570 * block is already in the DDT. If so, then it will replace the io_bp 5571 * with the bp from the DDT and allow the I/O to finish. When the I/O 5572 * reaches the done callback, dbuf_write_override_done, it will 5573 * check to see if the io_bp and io_bp_override are identical. 5574 * If they are not, then it indicates that the bp was replaced with 5575 * the bp in the DDT and the override bp is freed. This allows 5576 * us to arrive here with a reference on a block that is being 5577 * freed. So if we have an I/O in progress, or a reference to 5578 * this hdr, then we don't destroy the hdr. 5579 */ 5580 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5581 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5582 arc_change_state(arc_anon, hdr, hash_lock); 5583 arc_hdr_destroy(hdr); 5584 mutex_exit(hash_lock); 5585 } else { 5586 mutex_exit(hash_lock); 5587 } 5588 5589} 5590 5591/* 5592 * Release this buffer from the cache, making it an anonymous buffer. This 5593 * must be done after a read and prior to modifying the buffer contents. 5594 * If the buffer has more than one reference, we must make 5595 * a new hdr for the buffer. 5596 */ 5597void 5598arc_release(arc_buf_t *buf, void *tag) 5599{ 5600 arc_buf_hdr_t *hdr = buf->b_hdr; 5601 5602 /* 5603 * It would be nice to assert that if it's DMU metadata (level > 5604 * 0 || it's the dnode file), then it must be syncing context. 5605 * But we don't know that information at this level. 5606 */ 5607 5608 mutex_enter(&buf->b_evict_lock); 5609 5610 ASSERT(HDR_HAS_L1HDR(hdr)); 5611 5612 /* 5613 * We don't grab the hash lock prior to this check, because if 5614 * the buffer's header is in the arc_anon state, it won't be 5615 * linked into the hash table. 5616 */ 5617 if (hdr->b_l1hdr.b_state == arc_anon) { 5618 mutex_exit(&buf->b_evict_lock); 5619 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5620 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5621 ASSERT(!HDR_HAS_L2HDR(hdr)); 5622 ASSERT(HDR_EMPTY(hdr)); 5623 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5624 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5625 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5626 5627 hdr->b_l1hdr.b_arc_access = 0; 5628 5629 /* 5630 * If the buf is being overridden then it may already 5631 * have a hdr that is not empty. 5632 */ 5633 buf_discard_identity(hdr); 5634 arc_buf_thaw(buf); 5635 5636 return; 5637 } 5638 5639 kmutex_t *hash_lock = HDR_LOCK(hdr); 5640 mutex_enter(hash_lock); 5641 5642 /* 5643 * This assignment is only valid as long as the hash_lock is 5644 * held, we must be careful not to reference state or the 5645 * b_state field after dropping the lock. 5646 */ 5647 arc_state_t *state = hdr->b_l1hdr.b_state; 5648 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5649 ASSERT3P(state, !=, arc_anon); 5650 5651 /* this buffer is not on any list */ 5652 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); 5653 5654 if (HDR_HAS_L2HDR(hdr)) { 5655 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5656 5657 /* 5658 * We have to recheck this conditional again now that 5659 * we're holding the l2ad_mtx to prevent a race with 5660 * another thread which might be concurrently calling 5661 * l2arc_evict(). In that case, l2arc_evict() might have 5662 * destroyed the header's L2 portion as we were waiting 5663 * to acquire the l2ad_mtx. 5664 */ 5665 if (HDR_HAS_L2HDR(hdr)) { 5666 l2arc_trim(hdr); 5667 arc_hdr_l2hdr_destroy(hdr); 5668 } 5669 5670 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5671 } 5672 5673 /* 5674 * Do we have more than one buf? 5675 */ 5676 if (hdr->b_l1hdr.b_bufcnt > 1) { 5677 arc_buf_hdr_t *nhdr; 5678 uint64_t spa = hdr->b_spa; 5679 uint64_t psize = HDR_GET_PSIZE(hdr); 5680 uint64_t lsize = HDR_GET_LSIZE(hdr); 5681 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5682 arc_buf_contents_t type = arc_buf_type(hdr); 5683 VERIFY3U(hdr->b_type, ==, type); 5684 5685 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5686 (void) remove_reference(hdr, hash_lock, tag); 5687 5688 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { 5689 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5690 ASSERT(ARC_BUF_LAST(buf)); 5691 } 5692 5693 /* 5694 * Pull the data off of this hdr and attach it to 5695 * a new anonymous hdr. Also find the last buffer 5696 * in the hdr's buffer list. 5697 */ 5698 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 5699 ASSERT3P(lastbuf, !=, NULL); 5700 5701 /* 5702 * If the current arc_buf_t and the hdr are sharing their data 5703 * buffer, then we must stop sharing that block. 5704 */ 5705 if (arc_buf_is_shared(buf)) { 5706 VERIFY(!arc_buf_is_shared(lastbuf)); 5707 5708 /* 5709 * First, sever the block sharing relationship between 5710 * buf and the arc_buf_hdr_t. 5711 */ 5712 arc_unshare_buf(hdr, buf); 5713 5714 /* 5715 * Now we need to recreate the hdr's b_pabd. Since we 5716 * have lastbuf handy, we try to share with it, but if 5717 * we can't then we allocate a new b_pabd and copy the 5718 * data from buf into it. 5719 */ 5720 if (arc_can_share(hdr, lastbuf)) { 5721 arc_share_buf(hdr, lastbuf); 5722 } else { 5723 arc_hdr_alloc_pabd(hdr); 5724 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, 5725 buf->b_data, psize); 5726 } 5727 VERIFY3P(lastbuf->b_data, !=, NULL); 5728 } else if (HDR_SHARED_DATA(hdr)) { 5729 /* 5730 * Uncompressed shared buffers are always at the end 5731 * of the list. Compressed buffers don't have the 5732 * same requirements. This makes it hard to 5733 * simply assert that the lastbuf is shared so 5734 * we rely on the hdr's compression flags to determine 5735 * if we have a compressed, shared buffer. 5736 */ 5737 ASSERT(arc_buf_is_shared(lastbuf) || 5738 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 5739 ASSERT(!ARC_BUF_SHARED(buf)); 5740 } 5741 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5742 ASSERT3P(state, !=, arc_l2c_only); 5743 5744 (void) refcount_remove_many(&state->arcs_size, 5745 arc_buf_size(buf), buf); 5746 5747 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5748 ASSERT3P(state, !=, arc_l2c_only); 5749 (void) refcount_remove_many(&state->arcs_esize[type], 5750 arc_buf_size(buf), buf); 5751 } 5752 5753 hdr->b_l1hdr.b_bufcnt -= 1; 5754 arc_cksum_verify(buf); 5755#ifdef illumos 5756 arc_buf_unwatch(buf); 5757#endif 5758 5759 mutex_exit(hash_lock); 5760 5761 /* 5762 * Allocate a new hdr. The new hdr will contain a b_pabd 5763 * buffer which will be freed in arc_write(). 5764 */ 5765 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 5766 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 5767 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 5768 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 5769 VERIFY3U(nhdr->b_type, ==, type); 5770 ASSERT(!HDR_SHARED_DATA(nhdr)); 5771 5772 nhdr->b_l1hdr.b_buf = buf; 5773 nhdr->b_l1hdr.b_bufcnt = 1; 5774 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 5775 buf->b_hdr = nhdr; 5776 5777 mutex_exit(&buf->b_evict_lock); 5778 (void) refcount_add_many(&arc_anon->arcs_size, 5779 arc_buf_size(buf), buf); 5780 } else { 5781 mutex_exit(&buf->b_evict_lock); 5782 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 5783 /* protected by hash lock, or hdr is on arc_anon */ 5784 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5785 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5786 arc_change_state(arc_anon, hdr, hash_lock); 5787 hdr->b_l1hdr.b_arc_access = 0; 5788 mutex_exit(hash_lock); 5789 5790 buf_discard_identity(hdr); 5791 arc_buf_thaw(buf); 5792 } 5793} 5794 5795int 5796arc_released(arc_buf_t *buf) 5797{ 5798 int released; 5799 5800 mutex_enter(&buf->b_evict_lock); 5801 released = (buf->b_data != NULL && 5802 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5803 mutex_exit(&buf->b_evict_lock); 5804 return (released); 5805} 5806 5807#ifdef ZFS_DEBUG 5808int 5809arc_referenced(arc_buf_t *buf) 5810{ 5811 int referenced; 5812 5813 mutex_enter(&buf->b_evict_lock); 5814 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5815 mutex_exit(&buf->b_evict_lock); 5816 return (referenced); 5817} 5818#endif 5819 5820static void 5821arc_write_ready(zio_t *zio) 5822{ 5823 arc_write_callback_t *callback = zio->io_private; 5824 arc_buf_t *buf = callback->awcb_buf; 5825 arc_buf_hdr_t *hdr = buf->b_hdr; 5826 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 5827 5828 ASSERT(HDR_HAS_L1HDR(hdr)); 5829 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5830 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 5831 5832 /* 5833 * If we're reexecuting this zio because the pool suspended, then 5834 * cleanup any state that was previously set the first time the 5835 * callback was invoked. 5836 */ 5837 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 5838 arc_cksum_free(hdr); 5839#ifdef illumos 5840 arc_buf_unwatch(buf); 5841#endif 5842 if (hdr->b_l1hdr.b_pabd != NULL) { 5843 if (arc_buf_is_shared(buf)) { 5844 arc_unshare_buf(hdr, buf); 5845 } else { 5846 arc_hdr_free_pabd(hdr); 5847 } 5848 } 5849 } 5850 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5851 ASSERT(!HDR_SHARED_DATA(hdr)); 5852 ASSERT(!arc_buf_is_shared(buf)); 5853 5854 callback->awcb_ready(zio, buf, callback->awcb_private); 5855 5856 if (HDR_IO_IN_PROGRESS(hdr)) 5857 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 5858 5859 arc_cksum_compute(buf); 5860 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5861 5862 enum zio_compress compress; 5863 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5864 compress = ZIO_COMPRESS_OFF; 5865 } else { 5866 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 5867 compress = BP_GET_COMPRESS(zio->io_bp); 5868 } 5869 HDR_SET_PSIZE(hdr, psize); 5870 arc_hdr_set_compress(hdr, compress); 5871 5872 5873 /* 5874 * Fill the hdr with data. If the hdr is compressed, the data we want 5875 * is available from the zio, otherwise we can take it from the buf. 5876 * 5877 * We might be able to share the buf's data with the hdr here. However, 5878 * doing so would cause the ARC to be full of linear ABDs if we write a 5879 * lot of shareable data. As a compromise, we check whether scattered 5880 * ABDs are allowed, and assume that if they are then the user wants 5881 * the ARC to be primarily filled with them regardless of the data being 5882 * written. Therefore, if they're allowed then we allocate one and copy 5883 * the data into it; otherwise, we share the data directly if we can. 5884 */ 5885 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { 5886 arc_hdr_alloc_pabd(hdr); 5887 5888 /* 5889 * Ideally, we would always copy the io_abd into b_pabd, but the 5890 * user may have disabled compressed ARC, thus we must check the 5891 * hdr's compression setting rather than the io_bp's. 5892 */ 5893 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5894 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, 5895 ZIO_COMPRESS_OFF); 5896 ASSERT3U(psize, >, 0); 5897 5898 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); 5899 } else { 5900 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); 5901 5902 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, 5903 arc_buf_size(buf)); 5904 } 5905 } else { 5906 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); 5907 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); 5908 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5909 5910 arc_share_buf(hdr, buf); 5911 } 5912 5913 arc_hdr_verify(hdr, zio->io_bp); 5914} 5915 5916static void 5917arc_write_children_ready(zio_t *zio) 5918{ 5919 arc_write_callback_t *callback = zio->io_private; 5920 arc_buf_t *buf = callback->awcb_buf; 5921 5922 callback->awcb_children_ready(zio, buf, callback->awcb_private); 5923} 5924 5925/* 5926 * The SPA calls this callback for each physical write that happens on behalf 5927 * of a logical write. See the comment in dbuf_write_physdone() for details. 5928 */ 5929static void 5930arc_write_physdone(zio_t *zio) 5931{ 5932 arc_write_callback_t *cb = zio->io_private; 5933 if (cb->awcb_physdone != NULL) 5934 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5935} 5936 5937static void 5938arc_write_done(zio_t *zio) 5939{ 5940 arc_write_callback_t *callback = zio->io_private; 5941 arc_buf_t *buf = callback->awcb_buf; 5942 arc_buf_hdr_t *hdr = buf->b_hdr; 5943 5944 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5945 5946 if (zio->io_error == 0) { 5947 arc_hdr_verify(hdr, zio->io_bp); 5948 5949 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5950 buf_discard_identity(hdr); 5951 } else { 5952 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5953 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5954 } 5955 } else { 5956 ASSERT(HDR_EMPTY(hdr)); 5957 } 5958 5959 /* 5960 * If the block to be written was all-zero or compressed enough to be 5961 * embedded in the BP, no write was performed so there will be no 5962 * dva/birth/checksum. The buffer must therefore remain anonymous 5963 * (and uncached). 5964 */ 5965 if (!HDR_EMPTY(hdr)) { 5966 arc_buf_hdr_t *exists; 5967 kmutex_t *hash_lock; 5968 5969 ASSERT3U(zio->io_error, ==, 0); 5970 5971 arc_cksum_verify(buf); 5972 5973 exists = buf_hash_insert(hdr, &hash_lock); 5974 if (exists != NULL) { 5975 /* 5976 * This can only happen if we overwrite for 5977 * sync-to-convergence, because we remove 5978 * buffers from the hash table when we arc_free(). 5979 */ 5980 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5981 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5982 panic("bad overwrite, hdr=%p exists=%p", 5983 (void *)hdr, (void *)exists); 5984 ASSERT(refcount_is_zero( 5985 &exists->b_l1hdr.b_refcnt)); 5986 arc_change_state(arc_anon, exists, hash_lock); 5987 mutex_exit(hash_lock); 5988 arc_hdr_destroy(exists); 5989 exists = buf_hash_insert(hdr, &hash_lock); 5990 ASSERT3P(exists, ==, NULL); 5991 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 5992 /* nopwrite */ 5993 ASSERT(zio->io_prop.zp_nopwrite); 5994 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5995 panic("bad nopwrite, hdr=%p exists=%p", 5996 (void *)hdr, (void *)exists); 5997 } else { 5998 /* Dedup */ 5999 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 6000 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 6001 ASSERT(BP_GET_DEDUP(zio->io_bp)); 6002 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 6003 } 6004 } 6005 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6006 /* if it's not anon, we are doing a scrub */ 6007 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 6008 arc_access(hdr, hash_lock); 6009 mutex_exit(hash_lock); 6010 } else { 6011 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6012 } 6013 6014 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 6015 callback->awcb_done(zio, buf, callback->awcb_private); 6016 6017 abd_put(zio->io_abd); 6018 kmem_free(callback, sizeof (arc_write_callback_t)); 6019} 6020 6021zio_t * 6022arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 6023 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready, 6024 arc_done_func_t *children_ready, arc_done_func_t *physdone, 6025 arc_done_func_t *done, void *private, zio_priority_t priority, 6026 int zio_flags, const zbookmark_phys_t *zb) 6027{ 6028 arc_buf_hdr_t *hdr = buf->b_hdr; 6029 arc_write_callback_t *callback; 6030 zio_t *zio; 6031 zio_prop_t localprop = *zp; 6032 6033 ASSERT3P(ready, !=, NULL); 6034 ASSERT3P(done, !=, NULL); 6035 ASSERT(!HDR_IO_ERROR(hdr)); 6036 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6037 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6038 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 6039 if (l2arc) 6040 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 6041 if (ARC_BUF_COMPRESSED(buf)) { 6042 /* 6043 * We're writing a pre-compressed buffer. Make the 6044 * compression algorithm requested by the zio_prop_t match 6045 * the pre-compressed buffer's compression algorithm. 6046 */ 6047 localprop.zp_compress = HDR_GET_COMPRESS(hdr); 6048 6049 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); 6050 zio_flags |= ZIO_FLAG_RAW; 6051 } 6052 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 6053 callback->awcb_ready = ready; 6054 callback->awcb_children_ready = children_ready; 6055 callback->awcb_physdone = physdone; 6056 callback->awcb_done = done; 6057 callback->awcb_private = private; 6058 callback->awcb_buf = buf; 6059 6060 /* 6061 * The hdr's b_pabd is now stale, free it now. A new data block 6062 * will be allocated when the zio pipeline calls arc_write_ready(). 6063 */ 6064 if (hdr->b_l1hdr.b_pabd != NULL) { 6065 /* 6066 * If the buf is currently sharing the data block with 6067 * the hdr then we need to break that relationship here. 6068 * The hdr will remain with a NULL data pointer and the 6069 * buf will take sole ownership of the block. 6070 */ 6071 if (arc_buf_is_shared(buf)) { 6072 arc_unshare_buf(hdr, buf); 6073 } else { 6074 arc_hdr_free_pabd(hdr); 6075 } 6076 VERIFY3P(buf->b_data, !=, NULL); 6077 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 6078 } 6079 ASSERT(!arc_buf_is_shared(buf)); 6080 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6081 6082 zio = zio_write(pio, spa, txg, bp, 6083 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), 6084 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, 6085 (children_ready != NULL) ? arc_write_children_ready : NULL, 6086 arc_write_physdone, arc_write_done, callback, 6087 priority, zio_flags, zb); 6088 6089 return (zio); 6090} 6091 6092static int 6093arc_memory_throttle(uint64_t reserve, uint64_t txg) 6094{ 6095#ifdef _KERNEL 6096 uint64_t available_memory = ptob(freemem); 6097 static uint64_t page_load = 0; 6098 static uint64_t last_txg = 0; 6099 6100#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 6101 available_memory = 6102 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 6103#endif 6104 6105 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 6106 return (0); 6107 6108 if (txg > last_txg) { 6109 last_txg = txg; 6110 page_load = 0; 6111 } 6112 /* 6113 * If we are in pageout, we know that memory is already tight, 6114 * the arc is already going to be evicting, so we just want to 6115 * continue to let page writes occur as quickly as possible. 6116 */ 6117 if (curproc == pageproc) { 6118 if (page_load > MAX(ptob(minfree), available_memory) / 4) 6119 return (SET_ERROR(ERESTART)); 6120 /* Note: reserve is inflated, so we deflate */ 6121 page_load += reserve / 8; 6122 return (0); 6123 } else if (page_load > 0 && arc_reclaim_needed()) { 6124 /* memory is low, delay before restarting */ 6125 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 6126 return (SET_ERROR(EAGAIN)); 6127 } 6128 page_load = 0; 6129#endif 6130 return (0); 6131} 6132 6133void 6134arc_tempreserve_clear(uint64_t reserve) 6135{ 6136 atomic_add_64(&arc_tempreserve, -reserve); 6137 ASSERT((int64_t)arc_tempreserve >= 0); 6138} 6139 6140int 6141arc_tempreserve_space(uint64_t reserve, uint64_t txg) 6142{ 6143 int error; 6144 uint64_t anon_size; 6145 6146 if (reserve > arc_c/4 && !arc_no_grow) { 6147 arc_c = MIN(arc_c_max, reserve * 4); 6148 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 6149 } 6150 if (reserve > arc_c) 6151 return (SET_ERROR(ENOMEM)); 6152 6153 /* 6154 * Don't count loaned bufs as in flight dirty data to prevent long 6155 * network delays from blocking transactions that are ready to be 6156 * assigned to a txg. 6157 */ 6158 6159 /* assert that it has not wrapped around */ 6160 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 6161 6162 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 6163 arc_loaned_bytes), 0); 6164 6165 /* 6166 * Writes will, almost always, require additional memory allocations 6167 * in order to compress/encrypt/etc the data. We therefore need to 6168 * make sure that there is sufficient available memory for this. 6169 */ 6170 error = arc_memory_throttle(reserve, txg); 6171 if (error != 0) 6172 return (error); 6173 6174 /* 6175 * Throttle writes when the amount of dirty data in the cache 6176 * gets too large. We try to keep the cache less than half full 6177 * of dirty blocks so that our sync times don't grow too large. 6178 * Note: if two requests come in concurrently, we might let them 6179 * both succeed, when one of them should fail. Not a huge deal. 6180 */ 6181 6182 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 6183 anon_size > arc_c / 4) { 6184 uint64_t meta_esize = 6185 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6186 uint64_t data_esize = 6187 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6188 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 6189 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 6190 arc_tempreserve >> 10, meta_esize >> 10, 6191 data_esize >> 10, reserve >> 10, arc_c >> 10); 6192 return (SET_ERROR(ERESTART)); 6193 } 6194 atomic_add_64(&arc_tempreserve, reserve); 6195 return (0); 6196} 6197 6198static void 6199arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 6200 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 6201{ 6202 size->value.ui64 = refcount_count(&state->arcs_size); 6203 evict_data->value.ui64 = 6204 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 6205 evict_metadata->value.ui64 = 6206 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 6207} 6208 6209static int 6210arc_kstat_update(kstat_t *ksp, int rw) 6211{ 6212 arc_stats_t *as = ksp->ks_data; 6213 6214 if (rw == KSTAT_WRITE) { 6215 return (EACCES); 6216 } else { 6217 arc_kstat_update_state(arc_anon, 6218 &as->arcstat_anon_size, 6219 &as->arcstat_anon_evictable_data, 6220 &as->arcstat_anon_evictable_metadata); 6221 arc_kstat_update_state(arc_mru, 6222 &as->arcstat_mru_size, 6223 &as->arcstat_mru_evictable_data, 6224 &as->arcstat_mru_evictable_metadata); 6225 arc_kstat_update_state(arc_mru_ghost, 6226 &as->arcstat_mru_ghost_size, 6227 &as->arcstat_mru_ghost_evictable_data, 6228 &as->arcstat_mru_ghost_evictable_metadata); 6229 arc_kstat_update_state(arc_mfu, 6230 &as->arcstat_mfu_size, 6231 &as->arcstat_mfu_evictable_data, 6232 &as->arcstat_mfu_evictable_metadata); 6233 arc_kstat_update_state(arc_mfu_ghost, 6234 &as->arcstat_mfu_ghost_size, 6235 &as->arcstat_mfu_ghost_evictable_data, 6236 &as->arcstat_mfu_ghost_evictable_metadata); 6237 } 6238 6239 return (0); 6240} 6241 6242/* 6243 * This function *must* return indices evenly distributed between all 6244 * sublists of the multilist. This is needed due to how the ARC eviction 6245 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 6246 * distributed between all sublists and uses this assumption when 6247 * deciding which sublist to evict from and how much to evict from it. 6248 */ 6249unsigned int 6250arc_state_multilist_index_func(multilist_t *ml, void *obj) 6251{ 6252 arc_buf_hdr_t *hdr = obj; 6253 6254 /* 6255 * We rely on b_dva to generate evenly distributed index 6256 * numbers using buf_hash below. So, as an added precaution, 6257 * let's make sure we never add empty buffers to the arc lists. 6258 */ 6259 ASSERT(!HDR_EMPTY(hdr)); 6260 6261 /* 6262 * The assumption here, is the hash value for a given 6263 * arc_buf_hdr_t will remain constant throughout it's lifetime 6264 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 6265 * Thus, we don't need to store the header's sublist index 6266 * on insertion, as this index can be recalculated on removal. 6267 * 6268 * Also, the low order bits of the hash value are thought to be 6269 * distributed evenly. Otherwise, in the case that the multilist 6270 * has a power of two number of sublists, each sublists' usage 6271 * would not be evenly distributed. 6272 */ 6273 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 6274 multilist_get_num_sublists(ml)); 6275} 6276 6277#ifdef _KERNEL 6278static eventhandler_tag arc_event_lowmem = NULL; 6279 6280static void 6281arc_lowmem(void *arg __unused, int howto __unused) 6282{ 6283 6284 mutex_enter(&arc_reclaim_lock); 6285 /* XXX: Memory deficit should be passed as argument. */ 6286 needfree = btoc(arc_c >> arc_shrink_shift); 6287 DTRACE_PROBE(arc__needfree); 6288 cv_signal(&arc_reclaim_thread_cv); 6289 6290 /* 6291 * It is unsafe to block here in arbitrary threads, because we can come 6292 * here from ARC itself and may hold ARC locks and thus risk a deadlock 6293 * with ARC reclaim thread. 6294 */ 6295 if (curproc == pageproc) 6296 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 6297 mutex_exit(&arc_reclaim_lock); 6298} 6299#endif 6300 6301static void 6302arc_state_init(void) 6303{ 6304 arc_anon = &ARC_anon; 6305 arc_mru = &ARC_mru; 6306 arc_mru_ghost = &ARC_mru_ghost; 6307 arc_mfu = &ARC_mfu; 6308 arc_mfu_ghost = &ARC_mfu_ghost; 6309 arc_l2c_only = &ARC_l2c_only; 6310 6311 arc_mru->arcs_list[ARC_BUFC_METADATA] = 6312 multilist_create(sizeof (arc_buf_hdr_t), 6313 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6314 arc_state_multilist_index_func); 6315 arc_mru->arcs_list[ARC_BUFC_DATA] = 6316 multilist_create(sizeof (arc_buf_hdr_t), 6317 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6318 arc_state_multilist_index_func); 6319 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = 6320 multilist_create(sizeof (arc_buf_hdr_t), 6321 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6322 arc_state_multilist_index_func); 6323 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = 6324 multilist_create(sizeof (arc_buf_hdr_t), 6325 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6326 arc_state_multilist_index_func); 6327 arc_mfu->arcs_list[ARC_BUFC_METADATA] = 6328 multilist_create(sizeof (arc_buf_hdr_t), 6329 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6330 arc_state_multilist_index_func); 6331 arc_mfu->arcs_list[ARC_BUFC_DATA] = 6332 multilist_create(sizeof (arc_buf_hdr_t), 6333 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6334 arc_state_multilist_index_func); 6335 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = 6336 multilist_create(sizeof (arc_buf_hdr_t), 6337 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6338 arc_state_multilist_index_func); 6339 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = 6340 multilist_create(sizeof (arc_buf_hdr_t), 6341 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6342 arc_state_multilist_index_func); 6343 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = 6344 multilist_create(sizeof (arc_buf_hdr_t), 6345 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6346 arc_state_multilist_index_func); 6347 arc_l2c_only->arcs_list[ARC_BUFC_DATA] = 6348 multilist_create(sizeof (arc_buf_hdr_t), 6349 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6350 arc_state_multilist_index_func); 6351 6352 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6353 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6354 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6355 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6356 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6357 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6358 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6359 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6360 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6361 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6362 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6363 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6364 6365 refcount_create(&arc_anon->arcs_size); 6366 refcount_create(&arc_mru->arcs_size); 6367 refcount_create(&arc_mru_ghost->arcs_size); 6368 refcount_create(&arc_mfu->arcs_size); 6369 refcount_create(&arc_mfu_ghost->arcs_size); 6370 refcount_create(&arc_l2c_only->arcs_size); 6371} 6372 6373static void 6374arc_state_fini(void) 6375{ 6376 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6377 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6378 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6379 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6380 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6381 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6382 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6383 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6384 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6385 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6386 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6387 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6388 6389 refcount_destroy(&arc_anon->arcs_size); 6390 refcount_destroy(&arc_mru->arcs_size); 6391 refcount_destroy(&arc_mru_ghost->arcs_size); 6392 refcount_destroy(&arc_mfu->arcs_size); 6393 refcount_destroy(&arc_mfu_ghost->arcs_size); 6394 refcount_destroy(&arc_l2c_only->arcs_size); 6395 6396 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); 6397 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 6398 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); 6399 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 6400 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); 6401 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 6402 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); 6403 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 6404} 6405 6406uint64_t 6407arc_max_bytes(void) 6408{ 6409 return (arc_c_max); 6410} 6411 6412void 6413arc_init(void) 6414{ 6415 int i, prefetch_tunable_set = 0; 6416 6417 /* 6418 * allmem is "all memory that we could possibly use". 6419 */ 6420#ifdef illumos 6421#ifdef _KERNEL 6422 uint64_t allmem = ptob(physmem - swapfs_minfree); 6423#else 6424 uint64_t allmem = (physmem * PAGESIZE) / 2; 6425#endif 6426#else 6427 uint64_t allmem = kmem_size(); 6428#endif 6429 6430 6431 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 6432 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 6433 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 6434 6435 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 6436 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 6437 6438 /* Convert seconds to clock ticks */ 6439 arc_min_prefetch_lifespan = 1 * hz; 6440 6441 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 6442 arc_c_min = MAX(allmem / 32, arc_abs_min); 6443 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ 6444 if (allmem >= 1 << 30) 6445 arc_c_max = allmem - (1 << 30); 6446 else 6447 arc_c_max = arc_c_min; 6448 arc_c_max = MAX(allmem * 5 / 8, arc_c_max); 6449 6450 /* 6451 * In userland, there's only the memory pressure that we artificially 6452 * create (see arc_available_memory()). Don't let arc_c get too 6453 * small, because it can cause transactions to be larger than 6454 * arc_c, causing arc_tempreserve_space() to fail. 6455 */ 6456#ifndef _KERNEL 6457 arc_c_min = arc_c_max / 2; 6458#endif 6459 6460#ifdef _KERNEL 6461 /* 6462 * Allow the tunables to override our calculations if they are 6463 * reasonable. 6464 */ 6465 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { 6466 arc_c_max = zfs_arc_max; 6467 arc_c_min = MIN(arc_c_min, arc_c_max); 6468 } 6469 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6470 arc_c_min = zfs_arc_min; 6471#endif 6472 6473 arc_c = arc_c_max; 6474 arc_p = (arc_c >> 1); 6475 arc_size = 0; 6476 6477 /* limit meta-data to 1/4 of the arc capacity */ 6478 arc_meta_limit = arc_c_max / 4; 6479 6480#ifdef _KERNEL 6481 /* 6482 * Metadata is stored in the kernel's heap. Don't let us 6483 * use more than half the heap for the ARC. 6484 */ 6485 arc_meta_limit = MIN(arc_meta_limit, 6486 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 6487#endif 6488 6489 /* Allow the tunable to override if it is reasonable */ 6490 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6491 arc_meta_limit = zfs_arc_meta_limit; 6492 6493 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6494 arc_c_min = arc_meta_limit / 2; 6495 6496 if (zfs_arc_meta_min > 0) { 6497 arc_meta_min = zfs_arc_meta_min; 6498 } else { 6499 arc_meta_min = arc_c_min / 2; 6500 } 6501 6502 if (zfs_arc_grow_retry > 0) 6503 arc_grow_retry = zfs_arc_grow_retry; 6504 6505 if (zfs_arc_shrink_shift > 0) 6506 arc_shrink_shift = zfs_arc_shrink_shift; 6507 6508 /* 6509 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6510 */ 6511 if (arc_no_grow_shift >= arc_shrink_shift) 6512 arc_no_grow_shift = arc_shrink_shift - 1; 6513 6514 if (zfs_arc_p_min_shift > 0) 6515 arc_p_min_shift = zfs_arc_p_min_shift; 6516 6517 /* if kmem_flags are set, lets try to use less memory */ 6518 if (kmem_debugging()) 6519 arc_c = arc_c / 2; 6520 if (arc_c < arc_c_min) 6521 arc_c = arc_c_min; 6522 6523 zfs_arc_min = arc_c_min; 6524 zfs_arc_max = arc_c_max; 6525 6526 arc_state_init(); 6527 buf_init(); 6528 6529 arc_reclaim_thread_exit = B_FALSE; 6530 arc_dnlc_evicts_thread_exit = FALSE; 6531 6532 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6533 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6534 6535 if (arc_ksp != NULL) { 6536 arc_ksp->ks_data = &arc_stats; 6537 arc_ksp->ks_update = arc_kstat_update; 6538 kstat_install(arc_ksp); 6539 } 6540 6541 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6542 TS_RUN, minclsyspri); 6543 6544#ifdef _KERNEL 6545 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6546 EVENTHANDLER_PRI_FIRST); 6547#endif 6548 6549 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 6550 TS_RUN, minclsyspri); 6551 6552 arc_dead = B_FALSE; 6553 arc_warm = B_FALSE; 6554 6555 /* 6556 * Calculate maximum amount of dirty data per pool. 6557 * 6558 * If it has been set by /etc/system, take that. 6559 * Otherwise, use a percentage of physical memory defined by 6560 * zfs_dirty_data_max_percent (default 10%) with a cap at 6561 * zfs_dirty_data_max_max (default 4GB). 6562 */ 6563 if (zfs_dirty_data_max == 0) { 6564 zfs_dirty_data_max = ptob(physmem) * 6565 zfs_dirty_data_max_percent / 100; 6566 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6567 zfs_dirty_data_max_max); 6568 } 6569 6570#ifdef _KERNEL 6571 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6572 prefetch_tunable_set = 1; 6573 6574#ifdef __i386__ 6575 if (prefetch_tunable_set == 0) { 6576 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6577 "-- to enable,\n"); 6578 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6579 "to /boot/loader.conf.\n"); 6580 zfs_prefetch_disable = 1; 6581 } 6582#else 6583 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6584 prefetch_tunable_set == 0) { 6585 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6586 "than 4GB of RAM is present;\n" 6587 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6588 "to /boot/loader.conf.\n"); 6589 zfs_prefetch_disable = 1; 6590 } 6591#endif 6592 /* Warn about ZFS memory and address space requirements. */ 6593 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6594 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6595 "expect unstable behavior.\n"); 6596 } 6597 if (allmem < 512 * (1 << 20)) { 6598 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6599 "expect unstable behavior.\n"); 6600 printf(" Consider tuning vm.kmem_size and " 6601 "vm.kmem_size_max\n"); 6602 printf(" in /boot/loader.conf.\n"); 6603 } 6604#endif 6605} 6606 6607void 6608arc_fini(void) 6609{ 6610 mutex_enter(&arc_reclaim_lock); 6611 arc_reclaim_thread_exit = B_TRUE; 6612 /* 6613 * The reclaim thread will set arc_reclaim_thread_exit back to 6614 * B_FALSE when it is finished exiting; we're waiting for that. 6615 */ 6616 while (arc_reclaim_thread_exit) { 6617 cv_signal(&arc_reclaim_thread_cv); 6618 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6619 } 6620 mutex_exit(&arc_reclaim_lock); 6621 6622 /* Use B_TRUE to ensure *all* buffers are evicted */ 6623 arc_flush(NULL, B_TRUE); 6624 6625 mutex_enter(&arc_dnlc_evicts_lock); 6626 arc_dnlc_evicts_thread_exit = TRUE; 6627 /* 6628 * The user evicts thread will set arc_user_evicts_thread_exit 6629 * to FALSE when it is finished exiting; we're waiting for that. 6630 */ 6631 while (arc_dnlc_evicts_thread_exit) { 6632 cv_signal(&arc_dnlc_evicts_cv); 6633 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 6634 } 6635 mutex_exit(&arc_dnlc_evicts_lock); 6636 6637 arc_dead = B_TRUE; 6638 6639 if (arc_ksp != NULL) { 6640 kstat_delete(arc_ksp); 6641 arc_ksp = NULL; 6642 } 6643 6644 mutex_destroy(&arc_reclaim_lock); 6645 cv_destroy(&arc_reclaim_thread_cv); 6646 cv_destroy(&arc_reclaim_waiters_cv); 6647 6648 mutex_destroy(&arc_dnlc_evicts_lock); 6649 cv_destroy(&arc_dnlc_evicts_cv); 6650 6651 arc_state_fini(); 6652 buf_fini(); 6653 6654 ASSERT0(arc_loaned_bytes); 6655 6656#ifdef _KERNEL 6657 if (arc_event_lowmem != NULL) 6658 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6659#endif 6660} 6661 6662/* 6663 * Level 2 ARC 6664 * 6665 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6666 * It uses dedicated storage devices to hold cached data, which are populated 6667 * using large infrequent writes. The main role of this cache is to boost 6668 * the performance of random read workloads. The intended L2ARC devices 6669 * include short-stroked disks, solid state disks, and other media with 6670 * substantially faster read latency than disk. 6671 * 6672 * +-----------------------+ 6673 * | ARC | 6674 * +-----------------------+ 6675 * | ^ ^ 6676 * | | | 6677 * l2arc_feed_thread() arc_read() 6678 * | | | 6679 * | l2arc read | 6680 * V | | 6681 * +---------------+ | 6682 * | L2ARC | | 6683 * +---------------+ | 6684 * | ^ | 6685 * l2arc_write() | | 6686 * | | | 6687 * V | | 6688 * +-------+ +-------+ 6689 * | vdev | | vdev | 6690 * | cache | | cache | 6691 * +-------+ +-------+ 6692 * +=========+ .-----. 6693 * : L2ARC : |-_____-| 6694 * : devices : | Disks | 6695 * +=========+ `-_____-' 6696 * 6697 * Read requests are satisfied from the following sources, in order: 6698 * 6699 * 1) ARC 6700 * 2) vdev cache of L2ARC devices 6701 * 3) L2ARC devices 6702 * 4) vdev cache of disks 6703 * 5) disks 6704 * 6705 * Some L2ARC device types exhibit extremely slow write performance. 6706 * To accommodate for this there are some significant differences between 6707 * the L2ARC and traditional cache design: 6708 * 6709 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6710 * the ARC behave as usual, freeing buffers and placing headers on ghost 6711 * lists. The ARC does not send buffers to the L2ARC during eviction as 6712 * this would add inflated write latencies for all ARC memory pressure. 6713 * 6714 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6715 * It does this by periodically scanning buffers from the eviction-end of 6716 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6717 * not already there. It scans until a headroom of buffers is satisfied, 6718 * which itself is a buffer for ARC eviction. If a compressible buffer is 6719 * found during scanning and selected for writing to an L2ARC device, we 6720 * temporarily boost scanning headroom during the next scan cycle to make 6721 * sure we adapt to compression effects (which might significantly reduce 6722 * the data volume we write to L2ARC). The thread that does this is 6723 * l2arc_feed_thread(), illustrated below; example sizes are included to 6724 * provide a better sense of ratio than this diagram: 6725 * 6726 * head --> tail 6727 * +---------------------+----------+ 6728 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6729 * +---------------------+----------+ | o L2ARC eligible 6730 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6731 * +---------------------+----------+ | 6732 * 15.9 Gbytes ^ 32 Mbytes | 6733 * headroom | 6734 * l2arc_feed_thread() 6735 * | 6736 * l2arc write hand <--[oooo]--' 6737 * | 8 Mbyte 6738 * | write max 6739 * V 6740 * +==============================+ 6741 * L2ARC dev |####|#|###|###| |####| ... | 6742 * +==============================+ 6743 * 32 Gbytes 6744 * 6745 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 6746 * evicted, then the L2ARC has cached a buffer much sooner than it probably 6747 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 6748 * safe to say that this is an uncommon case, since buffers at the end of 6749 * the ARC lists have moved there due to inactivity. 6750 * 6751 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 6752 * then the L2ARC simply misses copying some buffers. This serves as a 6753 * pressure valve to prevent heavy read workloads from both stalling the ARC 6754 * with waits and clogging the L2ARC with writes. This also helps prevent 6755 * the potential for the L2ARC to churn if it attempts to cache content too 6756 * quickly, such as during backups of the entire pool. 6757 * 6758 * 5. After system boot and before the ARC has filled main memory, there are 6759 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 6760 * lists can remain mostly static. Instead of searching from tail of these 6761 * lists as pictured, the l2arc_feed_thread() will search from the list heads 6762 * for eligible buffers, greatly increasing its chance of finding them. 6763 * 6764 * The L2ARC device write speed is also boosted during this time so that 6765 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 6766 * there are no L2ARC reads, and no fear of degrading read performance 6767 * through increased writes. 6768 * 6769 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 6770 * the vdev queue can aggregate them into larger and fewer writes. Each 6771 * device is written to in a rotor fashion, sweeping writes through 6772 * available space then repeating. 6773 * 6774 * 7. The L2ARC does not store dirty content. It never needs to flush 6775 * write buffers back to disk based storage. 6776 * 6777 * 8. If an ARC buffer is written (and dirtied) which also exists in the 6778 * L2ARC, the now stale L2ARC buffer is immediately dropped. 6779 * 6780 * The performance of the L2ARC can be tweaked by a number of tunables, which 6781 * may be necessary for different workloads: 6782 * 6783 * l2arc_write_max max write bytes per interval 6784 * l2arc_write_boost extra write bytes during device warmup 6785 * l2arc_noprefetch skip caching prefetched buffers 6786 * l2arc_headroom number of max device writes to precache 6787 * l2arc_headroom_boost when we find compressed buffers during ARC 6788 * scanning, we multiply headroom by this 6789 * percentage factor for the next scan cycle, 6790 * since more compressed buffers are likely to 6791 * be present 6792 * l2arc_feed_secs seconds between L2ARC writing 6793 * 6794 * Tunables may be removed or added as future performance improvements are 6795 * integrated, and also may become zpool properties. 6796 * 6797 * There are three key functions that control how the L2ARC warms up: 6798 * 6799 * l2arc_write_eligible() check if a buffer is eligible to cache 6800 * l2arc_write_size() calculate how much to write 6801 * l2arc_write_interval() calculate sleep delay between writes 6802 * 6803 * These three functions determine what to write, how much, and how quickly 6804 * to send writes. 6805 */ 6806 6807static boolean_t 6808l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 6809{ 6810 /* 6811 * A buffer is *not* eligible for the L2ARC if it: 6812 * 1. belongs to a different spa. 6813 * 2. is already cached on the L2ARC. 6814 * 3. has an I/O in progress (it may be an incomplete read). 6815 * 4. is flagged not eligible (zfs property). 6816 */ 6817 if (hdr->b_spa != spa_guid) { 6818 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 6819 return (B_FALSE); 6820 } 6821 if (HDR_HAS_L2HDR(hdr)) { 6822 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 6823 return (B_FALSE); 6824 } 6825 if (HDR_IO_IN_PROGRESS(hdr)) { 6826 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 6827 return (B_FALSE); 6828 } 6829 if (!HDR_L2CACHE(hdr)) { 6830 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 6831 return (B_FALSE); 6832 } 6833 6834 return (B_TRUE); 6835} 6836 6837static uint64_t 6838l2arc_write_size(void) 6839{ 6840 uint64_t size; 6841 6842 /* 6843 * Make sure our globals have meaningful values in case the user 6844 * altered them. 6845 */ 6846 size = l2arc_write_max; 6847 if (size == 0) { 6848 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 6849 "be greater than zero, resetting it to the default (%d)", 6850 L2ARC_WRITE_SIZE); 6851 size = l2arc_write_max = L2ARC_WRITE_SIZE; 6852 } 6853 6854 if (arc_warm == B_FALSE) 6855 size += l2arc_write_boost; 6856 6857 return (size); 6858 6859} 6860 6861static clock_t 6862l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 6863{ 6864 clock_t interval, next, now; 6865 6866 /* 6867 * If the ARC lists are busy, increase our write rate; if the 6868 * lists are stale, idle back. This is achieved by checking 6869 * how much we previously wrote - if it was more than half of 6870 * what we wanted, schedule the next write much sooner. 6871 */ 6872 if (l2arc_feed_again && wrote > (wanted / 2)) 6873 interval = (hz * l2arc_feed_min_ms) / 1000; 6874 else 6875 interval = hz * l2arc_feed_secs; 6876 6877 now = ddi_get_lbolt(); 6878 next = MAX(now, MIN(now + interval, began + interval)); 6879 6880 return (next); 6881} 6882 6883/* 6884 * Cycle through L2ARC devices. This is how L2ARC load balances. 6885 * If a device is returned, this also returns holding the spa config lock. 6886 */ 6887static l2arc_dev_t * 6888l2arc_dev_get_next(void) 6889{ 6890 l2arc_dev_t *first, *next = NULL; 6891 6892 /* 6893 * Lock out the removal of spas (spa_namespace_lock), then removal 6894 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 6895 * both locks will be dropped and a spa config lock held instead. 6896 */ 6897 mutex_enter(&spa_namespace_lock); 6898 mutex_enter(&l2arc_dev_mtx); 6899 6900 /* if there are no vdevs, there is nothing to do */ 6901 if (l2arc_ndev == 0) 6902 goto out; 6903 6904 first = NULL; 6905 next = l2arc_dev_last; 6906 do { 6907 /* loop around the list looking for a non-faulted vdev */ 6908 if (next == NULL) { 6909 next = list_head(l2arc_dev_list); 6910 } else { 6911 next = list_next(l2arc_dev_list, next); 6912 if (next == NULL) 6913 next = list_head(l2arc_dev_list); 6914 } 6915 6916 /* if we have come back to the start, bail out */ 6917 if (first == NULL) 6918 first = next; 6919 else if (next == first) 6920 break; 6921 6922 } while (vdev_is_dead(next->l2ad_vdev)); 6923 6924 /* if we were unable to find any usable vdevs, return NULL */ 6925 if (vdev_is_dead(next->l2ad_vdev)) 6926 next = NULL; 6927 6928 l2arc_dev_last = next; 6929 6930out: 6931 mutex_exit(&l2arc_dev_mtx); 6932 6933 /* 6934 * Grab the config lock to prevent the 'next' device from being 6935 * removed while we are writing to it. 6936 */ 6937 if (next != NULL) 6938 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 6939 mutex_exit(&spa_namespace_lock); 6940 6941 return (next); 6942} 6943 6944/* 6945 * Free buffers that were tagged for destruction. 6946 */ 6947static void 6948l2arc_do_free_on_write() 6949{ 6950 list_t *buflist; 6951 l2arc_data_free_t *df, *df_prev; 6952 6953 mutex_enter(&l2arc_free_on_write_mtx); 6954 buflist = l2arc_free_on_write; 6955 6956 for (df = list_tail(buflist); df; df = df_prev) { 6957 df_prev = list_prev(buflist, df); 6958 ASSERT3P(df->l2df_abd, !=, NULL); 6959 abd_free(df->l2df_abd); 6960 list_remove(buflist, df); 6961 kmem_free(df, sizeof (l2arc_data_free_t)); 6962 } 6963 6964 mutex_exit(&l2arc_free_on_write_mtx); 6965} 6966 6967/* 6968 * A write to a cache device has completed. Update all headers to allow 6969 * reads from these buffers to begin. 6970 */ 6971static void 6972l2arc_write_done(zio_t *zio) 6973{ 6974 l2arc_write_callback_t *cb; 6975 l2arc_dev_t *dev; 6976 list_t *buflist; 6977 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6978 kmutex_t *hash_lock; 6979 int64_t bytes_dropped = 0; 6980 6981 cb = zio->io_private; 6982 ASSERT3P(cb, !=, NULL); 6983 dev = cb->l2wcb_dev; 6984 ASSERT3P(dev, !=, NULL); 6985 head = cb->l2wcb_head; 6986 ASSERT3P(head, !=, NULL); 6987 buflist = &dev->l2ad_buflist; 6988 ASSERT3P(buflist, !=, NULL); 6989 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 6990 l2arc_write_callback_t *, cb); 6991 6992 if (zio->io_error != 0) 6993 ARCSTAT_BUMP(arcstat_l2_writes_error); 6994 6995 /* 6996 * All writes completed, or an error was hit. 6997 */ 6998top: 6999 mutex_enter(&dev->l2ad_mtx); 7000 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 7001 hdr_prev = list_prev(buflist, hdr); 7002 7003 hash_lock = HDR_LOCK(hdr); 7004 7005 /* 7006 * We cannot use mutex_enter or else we can deadlock 7007 * with l2arc_write_buffers (due to swapping the order 7008 * the hash lock and l2ad_mtx are taken). 7009 */ 7010 if (!mutex_tryenter(hash_lock)) { 7011 /* 7012 * Missed the hash lock. We must retry so we 7013 * don't leave the ARC_FLAG_L2_WRITING bit set. 7014 */ 7015 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 7016 7017 /* 7018 * We don't want to rescan the headers we've 7019 * already marked as having been written out, so 7020 * we reinsert the head node so we can pick up 7021 * where we left off. 7022 */ 7023 list_remove(buflist, head); 7024 list_insert_after(buflist, hdr, head); 7025 7026 mutex_exit(&dev->l2ad_mtx); 7027 7028 /* 7029 * We wait for the hash lock to become available 7030 * to try and prevent busy waiting, and increase 7031 * the chance we'll be able to acquire the lock 7032 * the next time around. 7033 */ 7034 mutex_enter(hash_lock); 7035 mutex_exit(hash_lock); 7036 goto top; 7037 } 7038 7039 /* 7040 * We could not have been moved into the arc_l2c_only 7041 * state while in-flight due to our ARC_FLAG_L2_WRITING 7042 * bit being set. Let's just ensure that's being enforced. 7043 */ 7044 ASSERT(HDR_HAS_L1HDR(hdr)); 7045 7046 if (zio->io_error != 0) { 7047 /* 7048 * Error - drop L2ARC entry. 7049 */ 7050 list_remove(buflist, hdr); 7051 l2arc_trim(hdr); 7052 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 7053 7054 ARCSTAT_INCR(arcstat_l2_asize, -arc_hdr_size(hdr)); 7055 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr)); 7056 7057 bytes_dropped += arc_hdr_size(hdr); 7058 (void) refcount_remove_many(&dev->l2ad_alloc, 7059 arc_hdr_size(hdr), hdr); 7060 } 7061 7062 /* 7063 * Allow ARC to begin reads and ghost list evictions to 7064 * this L2ARC entry. 7065 */ 7066 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 7067 7068 mutex_exit(hash_lock); 7069 } 7070 7071 atomic_inc_64(&l2arc_writes_done); 7072 list_remove(buflist, head); 7073 ASSERT(!HDR_HAS_L1HDR(head)); 7074 kmem_cache_free(hdr_l2only_cache, head); 7075 mutex_exit(&dev->l2ad_mtx); 7076 7077 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 7078 7079 l2arc_do_free_on_write(); 7080 7081 kmem_free(cb, sizeof (l2arc_write_callback_t)); 7082} 7083 7084/* 7085 * A read to a cache device completed. Validate buffer contents before 7086 * handing over to the regular ARC routines. 7087 */ 7088static void 7089l2arc_read_done(zio_t *zio) 7090{ 7091 l2arc_read_callback_t *cb; 7092 arc_buf_hdr_t *hdr; 7093 kmutex_t *hash_lock; 7094 boolean_t valid_cksum; 7095 7096 ASSERT3P(zio->io_vd, !=, NULL); 7097 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 7098 7099 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 7100 7101 cb = zio->io_private; 7102 ASSERT3P(cb, !=, NULL); 7103 hdr = cb->l2rcb_hdr; 7104 ASSERT3P(hdr, !=, NULL); 7105 7106 hash_lock = HDR_LOCK(hdr); 7107 mutex_enter(hash_lock); 7108 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 7109 7110 /* 7111 * If the data was read into a temporary buffer, 7112 * move it and free the buffer. 7113 */ 7114 if (cb->l2rcb_abd != NULL) { 7115 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 7116 if (zio->io_error == 0) { 7117 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd, 7118 arc_hdr_size(hdr)); 7119 } 7120 7121 /* 7122 * The following must be done regardless of whether 7123 * there was an error: 7124 * - free the temporary buffer 7125 * - point zio to the real ARC buffer 7126 * - set zio size accordingly 7127 * These are required because zio is either re-used for 7128 * an I/O of the block in the case of the error 7129 * or the zio is passed to arc_read_done() and it 7130 * needs real data. 7131 */ 7132 abd_free(cb->l2rcb_abd); 7133 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 7134 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; 7135 } 7136 7137 ASSERT3P(zio->io_abd, !=, NULL); 7138 7139 /* 7140 * Check this survived the L2ARC journey. 7141 */ 7142 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); 7143 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 7144 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 7145 7146 valid_cksum = arc_cksum_is_equal(hdr, zio); 7147 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 7148 mutex_exit(hash_lock); 7149 zio->io_private = hdr; 7150 arc_read_done(zio); 7151 } else { 7152 mutex_exit(hash_lock); 7153 /* 7154 * Buffer didn't survive caching. Increment stats and 7155 * reissue to the original storage device. 7156 */ 7157 if (zio->io_error != 0) { 7158 ARCSTAT_BUMP(arcstat_l2_io_error); 7159 } else { 7160 zio->io_error = SET_ERROR(EIO); 7161 } 7162 if (!valid_cksum) 7163 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 7164 7165 /* 7166 * If there's no waiter, issue an async i/o to the primary 7167 * storage now. If there *is* a waiter, the caller must 7168 * issue the i/o in a context where it's OK to block. 7169 */ 7170 if (zio->io_waiter == NULL) { 7171 zio_t *pio = zio_unique_parent(zio); 7172 7173 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 7174 7175 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 7176 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, 7177 hdr, zio->io_priority, cb->l2rcb_flags, 7178 &cb->l2rcb_zb)); 7179 } 7180 } 7181 7182 kmem_free(cb, sizeof (l2arc_read_callback_t)); 7183} 7184 7185/* 7186 * This is the list priority from which the L2ARC will search for pages to 7187 * cache. This is used within loops (0..3) to cycle through lists in the 7188 * desired order. This order can have a significant effect on cache 7189 * performance. 7190 * 7191 * Currently the metadata lists are hit first, MFU then MRU, followed by 7192 * the data lists. This function returns a locked list, and also returns 7193 * the lock pointer. 7194 */ 7195static multilist_sublist_t * 7196l2arc_sublist_lock(int list_num) 7197{ 7198 multilist_t *ml = NULL; 7199 unsigned int idx; 7200 7201 ASSERT(list_num >= 0 && list_num <= 3); 7202 7203 switch (list_num) { 7204 case 0: 7205 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; 7206 break; 7207 case 1: 7208 ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; 7209 break; 7210 case 2: 7211 ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; 7212 break; 7213 case 3: 7214 ml = arc_mru->arcs_list[ARC_BUFC_DATA]; 7215 break; 7216 } 7217 7218 /* 7219 * Return a randomly-selected sublist. This is acceptable 7220 * because the caller feeds only a little bit of data for each 7221 * call (8MB). Subsequent calls will result in different 7222 * sublists being selected. 7223 */ 7224 idx = multilist_get_random_index(ml); 7225 return (multilist_sublist_lock(ml, idx)); 7226} 7227 7228/* 7229 * Evict buffers from the device write hand to the distance specified in 7230 * bytes. This distance may span populated buffers, it may span nothing. 7231 * This is clearing a region on the L2ARC device ready for writing. 7232 * If the 'all' boolean is set, every buffer is evicted. 7233 */ 7234static void 7235l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 7236{ 7237 list_t *buflist; 7238 arc_buf_hdr_t *hdr, *hdr_prev; 7239 kmutex_t *hash_lock; 7240 uint64_t taddr; 7241 7242 buflist = &dev->l2ad_buflist; 7243 7244 if (!all && dev->l2ad_first) { 7245 /* 7246 * This is the first sweep through the device. There is 7247 * nothing to evict. 7248 */ 7249 return; 7250 } 7251 7252 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 7253 /* 7254 * When nearing the end of the device, evict to the end 7255 * before the device write hand jumps to the start. 7256 */ 7257 taddr = dev->l2ad_end; 7258 } else { 7259 taddr = dev->l2ad_hand + distance; 7260 } 7261 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 7262 uint64_t, taddr, boolean_t, all); 7263 7264top: 7265 mutex_enter(&dev->l2ad_mtx); 7266 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 7267 hdr_prev = list_prev(buflist, hdr); 7268 7269 hash_lock = HDR_LOCK(hdr); 7270 7271 /* 7272 * We cannot use mutex_enter or else we can deadlock 7273 * with l2arc_write_buffers (due to swapping the order 7274 * the hash lock and l2ad_mtx are taken). 7275 */ 7276 if (!mutex_tryenter(hash_lock)) { 7277 /* 7278 * Missed the hash lock. Retry. 7279 */ 7280 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 7281 mutex_exit(&dev->l2ad_mtx); 7282 mutex_enter(hash_lock); 7283 mutex_exit(hash_lock); 7284 goto top; 7285 } 7286 7287 if (HDR_L2_WRITE_HEAD(hdr)) { 7288 /* 7289 * We hit a write head node. Leave it for 7290 * l2arc_write_done(). 7291 */ 7292 list_remove(buflist, hdr); 7293 mutex_exit(hash_lock); 7294 continue; 7295 } 7296 7297 if (!all && HDR_HAS_L2HDR(hdr) && 7298 (hdr->b_l2hdr.b_daddr >= taddr || 7299 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 7300 /* 7301 * We've evicted to the target address, 7302 * or the end of the device. 7303 */ 7304 mutex_exit(hash_lock); 7305 break; 7306 } 7307 7308 ASSERT(HDR_HAS_L2HDR(hdr)); 7309 if (!HDR_HAS_L1HDR(hdr)) { 7310 ASSERT(!HDR_L2_READING(hdr)); 7311 /* 7312 * This doesn't exist in the ARC. Destroy. 7313 * arc_hdr_destroy() will call list_remove() 7314 * and decrement arcstat_l2_size. 7315 */ 7316 arc_change_state(arc_anon, hdr, hash_lock); 7317 arc_hdr_destroy(hdr); 7318 } else { 7319 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 7320 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 7321 /* 7322 * Invalidate issued or about to be issued 7323 * reads, since we may be about to write 7324 * over this location. 7325 */ 7326 if (HDR_L2_READING(hdr)) { 7327 ARCSTAT_BUMP(arcstat_l2_evict_reading); 7328 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 7329 } 7330 7331 /* Ensure this header has finished being written */ 7332 ASSERT(!HDR_L2_WRITING(hdr)); 7333 7334 arc_hdr_l2hdr_destroy(hdr); 7335 } 7336 mutex_exit(hash_lock); 7337 } 7338 mutex_exit(&dev->l2ad_mtx); 7339} 7340 7341/* 7342 * Find and write ARC buffers to the L2ARC device. 7343 * 7344 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 7345 * for reading until they have completed writing. 7346 * The headroom_boost is an in-out parameter used to maintain headroom boost 7347 * state between calls to this function. 7348 * 7349 * Returns the number of bytes actually written (which may be smaller than 7350 * the delta by which the device hand has changed due to alignment). 7351 */ 7352static uint64_t 7353l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 7354{ 7355 arc_buf_hdr_t *hdr, *hdr_prev, *head; 7356 uint64_t write_asize, write_psize, write_sz, headroom; 7357 boolean_t full; 7358 l2arc_write_callback_t *cb; 7359 zio_t *pio, *wzio; 7360 uint64_t guid = spa_load_guid(spa); 7361 int try; 7362 7363 ASSERT3P(dev->l2ad_vdev, !=, NULL); 7364 7365 pio = NULL; 7366 write_sz = write_asize = write_psize = 0; 7367 full = B_FALSE; 7368 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 7369 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 7370 7371 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 7372 /* 7373 * Copy buffers for L2ARC writing. 7374 */ 7375 for (try = 0; try <= 3; try++) { 7376 multilist_sublist_t *mls = l2arc_sublist_lock(try); 7377 uint64_t passed_sz = 0; 7378 7379 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 7380 7381 /* 7382 * L2ARC fast warmup. 7383 * 7384 * Until the ARC is warm and starts to evict, read from the 7385 * head of the ARC lists rather than the tail. 7386 */ 7387 if (arc_warm == B_FALSE) 7388 hdr = multilist_sublist_head(mls); 7389 else 7390 hdr = multilist_sublist_tail(mls); 7391 if (hdr == NULL) 7392 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 7393 7394 headroom = target_sz * l2arc_headroom; 7395 if (zfs_compressed_arc_enabled) 7396 headroom = (headroom * l2arc_headroom_boost) / 100; 7397 7398 for (; hdr; hdr = hdr_prev) { 7399 kmutex_t *hash_lock; 7400 7401 if (arc_warm == B_FALSE) 7402 hdr_prev = multilist_sublist_next(mls, hdr); 7403 else 7404 hdr_prev = multilist_sublist_prev(mls, hdr); 7405 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 7406 HDR_GET_LSIZE(hdr)); 7407 7408 hash_lock = HDR_LOCK(hdr); 7409 if (!mutex_tryenter(hash_lock)) { 7410 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 7411 /* 7412 * Skip this buffer rather than waiting. 7413 */ 7414 continue; 7415 } 7416 7417 passed_sz += HDR_GET_LSIZE(hdr); 7418 if (passed_sz > headroom) { 7419 /* 7420 * Searched too far. 7421 */ 7422 mutex_exit(hash_lock); 7423 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 7424 break; 7425 } 7426 7427 if (!l2arc_write_eligible(guid, hdr)) { 7428 mutex_exit(hash_lock); 7429 continue; 7430 } 7431 7432 /* 7433 * We rely on the L1 portion of the header below, so 7434 * it's invalid for this header to have been evicted out 7435 * of the ghost cache, prior to being written out. The 7436 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 7437 */ 7438 ASSERT(HDR_HAS_L1HDR(hdr)); 7439 7440 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 7441 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 7442 ASSERT3U(arc_hdr_size(hdr), >, 0); 7443 uint64_t size = arc_hdr_size(hdr); 7444 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 7445 size); 7446 7447 if ((write_psize + asize) > target_sz) { 7448 full = B_TRUE; 7449 mutex_exit(hash_lock); 7450 ARCSTAT_BUMP(arcstat_l2_write_full); 7451 break; 7452 } 7453 7454 if (pio == NULL) { 7455 /* 7456 * Insert a dummy header on the buflist so 7457 * l2arc_write_done() can find where the 7458 * write buffers begin without searching. 7459 */ 7460 mutex_enter(&dev->l2ad_mtx); 7461 list_insert_head(&dev->l2ad_buflist, head); 7462 mutex_exit(&dev->l2ad_mtx); 7463 7464 cb = kmem_alloc( 7465 sizeof (l2arc_write_callback_t), KM_SLEEP); 7466 cb->l2wcb_dev = dev; 7467 cb->l2wcb_head = head; 7468 pio = zio_root(spa, l2arc_write_done, cb, 7469 ZIO_FLAG_CANFAIL); 7470 ARCSTAT_BUMP(arcstat_l2_write_pios); 7471 } 7472 7473 hdr->b_l2hdr.b_dev = dev; 7474 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 7475 arc_hdr_set_flags(hdr, 7476 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 7477 7478 mutex_enter(&dev->l2ad_mtx); 7479 list_insert_head(&dev->l2ad_buflist, hdr); 7480 mutex_exit(&dev->l2ad_mtx); 7481 7482 (void) refcount_add_many(&dev->l2ad_alloc, size, hdr); 7483 7484 /* 7485 * Normally the L2ARC can use the hdr's data, but if 7486 * we're sharing data between the hdr and one of its 7487 * bufs, L2ARC needs its own copy of the data so that 7488 * the ZIO below can't race with the buf consumer. 7489 * Another case where we need to create a copy of the 7490 * data is when the buffer size is not device-aligned 7491 * and we need to pad the block to make it such. 7492 * That also keeps the clock hand suitably aligned. 7493 * 7494 * To ensure that the copy will be available for the 7495 * lifetime of the ZIO and be cleaned up afterwards, we 7496 * add it to the l2arc_free_on_write queue. 7497 */ 7498 abd_t *to_write; 7499 if (!HDR_SHARED_DATA(hdr) && size == asize) { 7500 to_write = hdr->b_l1hdr.b_pabd; 7501 } else { 7502 to_write = abd_alloc_for_io(asize, 7503 HDR_ISTYPE_METADATA(hdr)); 7504 abd_copy(to_write, hdr->b_l1hdr.b_pabd, size); 7505 if (asize != size) { 7506 abd_zero_off(to_write, size, 7507 asize - size); 7508 } 7509 l2arc_free_abd_on_write(to_write, asize, 7510 arc_buf_type(hdr)); 7511 } 7512 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7513 hdr->b_l2hdr.b_daddr, asize, to_write, 7514 ZIO_CHECKSUM_OFF, NULL, hdr, 7515 ZIO_PRIORITY_ASYNC_WRITE, 7516 ZIO_FLAG_CANFAIL, B_FALSE); 7517 7518 write_sz += HDR_GET_LSIZE(hdr); 7519 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7520 zio_t *, wzio); 7521 7522 write_asize += size; 7523 write_psize += asize; 7524 dev->l2ad_hand += asize; 7525 7526 mutex_exit(hash_lock); 7527 7528 (void) zio_nowait(wzio); 7529 } 7530 7531 multilist_sublist_unlock(mls); 7532 7533 if (full == B_TRUE) 7534 break; 7535 } 7536 7537 /* No buffers selected for writing? */ 7538 if (pio == NULL) { 7539 ASSERT0(write_sz); 7540 ASSERT(!HDR_HAS_L1HDR(head)); 7541 kmem_cache_free(hdr_l2only_cache, head); 7542 return (0); 7543 } 7544 7545 ASSERT3U(write_psize, <=, target_sz); 7546 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7547 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize); 7548 ARCSTAT_INCR(arcstat_l2_size, write_sz); 7549 ARCSTAT_INCR(arcstat_l2_asize, write_asize); 7550 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0); 7551 7552 /* 7553 * Bump device hand to the device start if it is approaching the end. 7554 * l2arc_evict() will already have evicted ahead for this case. 7555 */ 7556 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7557 dev->l2ad_hand = dev->l2ad_start; 7558 dev->l2ad_first = B_FALSE; 7559 } 7560 7561 dev->l2ad_writing = B_TRUE; 7562 (void) zio_wait(pio); 7563 dev->l2ad_writing = B_FALSE; 7564 7565 return (write_asize); 7566} 7567 7568/* 7569 * This thread feeds the L2ARC at regular intervals. This is the beating 7570 * heart of the L2ARC. 7571 */ 7572static void 7573l2arc_feed_thread(void *dummy __unused) 7574{ 7575 callb_cpr_t cpr; 7576 l2arc_dev_t *dev; 7577 spa_t *spa; 7578 uint64_t size, wrote; 7579 clock_t begin, next = ddi_get_lbolt(); 7580 7581 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7582 7583 mutex_enter(&l2arc_feed_thr_lock); 7584 7585 while (l2arc_thread_exit == 0) { 7586 CALLB_CPR_SAFE_BEGIN(&cpr); 7587 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7588 next - ddi_get_lbolt()); 7589 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7590 next = ddi_get_lbolt() + hz; 7591 7592 /* 7593 * Quick check for L2ARC devices. 7594 */ 7595 mutex_enter(&l2arc_dev_mtx); 7596 if (l2arc_ndev == 0) { 7597 mutex_exit(&l2arc_dev_mtx); 7598 continue; 7599 } 7600 mutex_exit(&l2arc_dev_mtx); 7601 begin = ddi_get_lbolt(); 7602 7603 /* 7604 * This selects the next l2arc device to write to, and in 7605 * doing so the next spa to feed from: dev->l2ad_spa. This 7606 * will return NULL if there are now no l2arc devices or if 7607 * they are all faulted. 7608 * 7609 * If a device is returned, its spa's config lock is also 7610 * held to prevent device removal. l2arc_dev_get_next() 7611 * will grab and release l2arc_dev_mtx. 7612 */ 7613 if ((dev = l2arc_dev_get_next()) == NULL) 7614 continue; 7615 7616 spa = dev->l2ad_spa; 7617 ASSERT3P(spa, !=, NULL); 7618 7619 /* 7620 * If the pool is read-only then force the feed thread to 7621 * sleep a little longer. 7622 */ 7623 if (!spa_writeable(spa)) { 7624 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7625 spa_config_exit(spa, SCL_L2ARC, dev); 7626 continue; 7627 } 7628 7629 /* 7630 * Avoid contributing to memory pressure. 7631 */ 7632 if (arc_reclaim_needed()) { 7633 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7634 spa_config_exit(spa, SCL_L2ARC, dev); 7635 continue; 7636 } 7637 7638 ARCSTAT_BUMP(arcstat_l2_feeds); 7639 7640 size = l2arc_write_size(); 7641 7642 /* 7643 * Evict L2ARC buffers that will be overwritten. 7644 */ 7645 l2arc_evict(dev, size, B_FALSE); 7646 7647 /* 7648 * Write ARC buffers. 7649 */ 7650 wrote = l2arc_write_buffers(spa, dev, size); 7651 7652 /* 7653 * Calculate interval between writes. 7654 */ 7655 next = l2arc_write_interval(begin, size, wrote); 7656 spa_config_exit(spa, SCL_L2ARC, dev); 7657 } 7658 7659 l2arc_thread_exit = 0; 7660 cv_broadcast(&l2arc_feed_thr_cv); 7661 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7662 thread_exit(); 7663} 7664 7665boolean_t 7666l2arc_vdev_present(vdev_t *vd) 7667{ 7668 l2arc_dev_t *dev; 7669 7670 mutex_enter(&l2arc_dev_mtx); 7671 for (dev = list_head(l2arc_dev_list); dev != NULL; 7672 dev = list_next(l2arc_dev_list, dev)) { 7673 if (dev->l2ad_vdev == vd) 7674 break; 7675 } 7676 mutex_exit(&l2arc_dev_mtx); 7677 7678 return (dev != NULL); 7679} 7680 7681/* 7682 * Add a vdev for use by the L2ARC. By this point the spa has already 7683 * validated the vdev and opened it. 7684 */ 7685void 7686l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7687{ 7688 l2arc_dev_t *adddev; 7689 7690 ASSERT(!l2arc_vdev_present(vd)); 7691 7692 vdev_ashift_optimize(vd); 7693 7694 /* 7695 * Create a new l2arc device entry. 7696 */ 7697 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7698 adddev->l2ad_spa = spa; 7699 adddev->l2ad_vdev = vd; 7700 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7701 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7702 adddev->l2ad_hand = adddev->l2ad_start; 7703 adddev->l2ad_first = B_TRUE; 7704 adddev->l2ad_writing = B_FALSE; 7705 7706 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7707 /* 7708 * This is a list of all ARC buffers that are still valid on the 7709 * device. 7710 */ 7711 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7712 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7713 7714 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7715 refcount_create(&adddev->l2ad_alloc); 7716 7717 /* 7718 * Add device to global list 7719 */ 7720 mutex_enter(&l2arc_dev_mtx); 7721 list_insert_head(l2arc_dev_list, adddev); 7722 atomic_inc_64(&l2arc_ndev); 7723 mutex_exit(&l2arc_dev_mtx); 7724} 7725 7726/* 7727 * Remove a vdev from the L2ARC. 7728 */ 7729void 7730l2arc_remove_vdev(vdev_t *vd) 7731{ 7732 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7733 7734 /* 7735 * Find the device by vdev 7736 */ 7737 mutex_enter(&l2arc_dev_mtx); 7738 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7739 nextdev = list_next(l2arc_dev_list, dev); 7740 if (vd == dev->l2ad_vdev) { 7741 remdev = dev; 7742 break; 7743 } 7744 } 7745 ASSERT3P(remdev, !=, NULL); 7746 7747 /* 7748 * Remove device from global list 7749 */ 7750 list_remove(l2arc_dev_list, remdev); 7751 l2arc_dev_last = NULL; /* may have been invalidated */ 7752 atomic_dec_64(&l2arc_ndev); 7753 mutex_exit(&l2arc_dev_mtx); 7754 7755 /* 7756 * Clear all buflists and ARC references. L2ARC device flush. 7757 */ 7758 l2arc_evict(remdev, 0, B_TRUE); 7759 list_destroy(&remdev->l2ad_buflist); 7760 mutex_destroy(&remdev->l2ad_mtx); 7761 refcount_destroy(&remdev->l2ad_alloc); 7762 kmem_free(remdev, sizeof (l2arc_dev_t)); 7763} 7764 7765void 7766l2arc_init(void) 7767{ 7768 l2arc_thread_exit = 0; 7769 l2arc_ndev = 0; 7770 l2arc_writes_sent = 0; 7771 l2arc_writes_done = 0; 7772 7773 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7774 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7775 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7776 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7777 7778 l2arc_dev_list = &L2ARC_dev_list; 7779 l2arc_free_on_write = &L2ARC_free_on_write; 7780 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7781 offsetof(l2arc_dev_t, l2ad_node)); 7782 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7783 offsetof(l2arc_data_free_t, l2df_list_node)); 7784} 7785 7786void 7787l2arc_fini(void) 7788{ 7789 /* 7790 * This is called from dmu_fini(), which is called from spa_fini(); 7791 * Because of this, we can assume that all l2arc devices have 7792 * already been removed when the pools themselves were removed. 7793 */ 7794 7795 l2arc_do_free_on_write(); 7796 7797 mutex_destroy(&l2arc_feed_thr_lock); 7798 cv_destroy(&l2arc_feed_thr_cv); 7799 mutex_destroy(&l2arc_dev_mtx); 7800 mutex_destroy(&l2arc_free_on_write_mtx); 7801 7802 list_destroy(l2arc_dev_list); 7803 list_destroy(l2arc_free_on_write); 7804} 7805 7806void 7807l2arc_start(void) 7808{ 7809 if (!(spa_mode_global & FWRITE)) 7810 return; 7811 7812 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7813 TS_RUN, minclsyspri); 7814} 7815 7816void 7817l2arc_stop(void) 7818{ 7819 if (!(spa_mode_global & FWRITE)) 7820 return; 7821 7822 mutex_enter(&l2arc_feed_thr_lock); 7823 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7824 l2arc_thread_exit = 1; 7825 while (l2arc_thread_exit != 0) 7826 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7827 mutex_exit(&l2arc_feed_thr_lock); 7828} 7829