arc.c revision 329490
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 2017 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_no_grow_shift = 0; 362int zfs_arc_p_min_shift = 0; 363uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */ 364u_int zfs_arc_free_target = 0; 365 366/* Absolute min for arc min / max is 16MB. */ 367static uint64_t arc_abs_min = 16 << 20; 368 369boolean_t zfs_compressed_arc_enabled = B_TRUE; 370 371static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS); 372static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS); 373static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS); 374static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS); 375static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS); 376 377#if defined(__FreeBSD__) && defined(_KERNEL) 378static void 379arc_free_target_init(void *unused __unused) 380{ 381 382 zfs_arc_free_target = vm_pageout_wakeup_thresh; 383} 384SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY, 385 arc_free_target_init, NULL); 386 387TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit); 388TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min); 389TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift); 390TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry); 391TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift); 392SYSCTL_DECL(_vfs_zfs); 393SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN, 394 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size"); 395SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN, 396 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size"); 397SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN, 398 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U", 399 "log2(fraction of ARC which must be free to allow growing)"); 400SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN, 401 &zfs_arc_average_blocksize, 0, 402 "ARC average blocksize"); 403SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW, 404 &arc_shrink_shift, 0, 405 "log2(fraction of arc to reclaim)"); 406SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW, 407 &arc_grow_retry, 0, 408 "Wait in seconds before considering growing ARC"); 409SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN, 410 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC"); 411 412/* 413 * We don't have a tunable for arc_free_target due to the dependency on 414 * pagedaemon initialisation. 415 */ 416SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target, 417 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int), 418 sysctl_vfs_zfs_arc_free_target, "IU", 419 "Desired number of free pages below which ARC triggers reclaim"); 420 421static int 422sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS) 423{ 424 u_int val; 425 int err; 426 427 val = zfs_arc_free_target; 428 err = sysctl_handle_int(oidp, &val, 0, req); 429 if (err != 0 || req->newptr == NULL) 430 return (err); 431 432 if (val < minfree) 433 return (EINVAL); 434 if (val > vm_cnt.v_page_count) 435 return (EINVAL); 436 437 zfs_arc_free_target = val; 438 439 return (0); 440} 441 442/* 443 * Must be declared here, before the definition of corresponding kstat 444 * macro which uses the same names will confuse the compiler. 445 */ 446SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit, 447 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t), 448 sysctl_vfs_zfs_arc_meta_limit, "QU", 449 "ARC metadata limit"); 450#endif 451 452/* 453 * Note that buffers can be in one of 6 states: 454 * ARC_anon - anonymous (discussed below) 455 * ARC_mru - recently used, currently cached 456 * ARC_mru_ghost - recentely used, no longer in cache 457 * ARC_mfu - frequently used, currently cached 458 * ARC_mfu_ghost - frequently used, no longer in cache 459 * ARC_l2c_only - exists in L2ARC but not other states 460 * When there are no active references to the buffer, they are 461 * are linked onto a list in one of these arc states. These are 462 * the only buffers that can be evicted or deleted. Within each 463 * state there are multiple lists, one for meta-data and one for 464 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes, 465 * etc.) is tracked separately so that it can be managed more 466 * explicitly: favored over data, limited explicitly. 467 * 468 * Anonymous buffers are buffers that are not associated with 469 * a DVA. These are buffers that hold dirty block copies 470 * before they are written to stable storage. By definition, 471 * they are "ref'd" and are considered part of arc_mru 472 * that cannot be freed. Generally, they will aquire a DVA 473 * as they are written and migrate onto the arc_mru list. 474 * 475 * The ARC_l2c_only state is for buffers that are in the second 476 * level ARC but no longer in any of the ARC_m* lists. The second 477 * level ARC itself may also contain buffers that are in any of 478 * the ARC_m* states - meaning that a buffer can exist in two 479 * places. The reason for the ARC_l2c_only state is to keep the 480 * buffer header in the hash table, so that reads that hit the 481 * second level ARC benefit from these fast lookups. 482 */ 483 484typedef struct arc_state { 485 /* 486 * list of evictable buffers 487 */ 488 multilist_t *arcs_list[ARC_BUFC_NUMTYPES]; 489 /* 490 * total amount of evictable data in this state 491 */ 492 refcount_t arcs_esize[ARC_BUFC_NUMTYPES]; 493 /* 494 * total amount of data in this state; this includes: evictable, 495 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA. 496 */ 497 refcount_t arcs_size; 498} arc_state_t; 499 500/* The 6 states: */ 501static arc_state_t ARC_anon; 502static arc_state_t ARC_mru; 503static arc_state_t ARC_mru_ghost; 504static arc_state_t ARC_mfu; 505static arc_state_t ARC_mfu_ghost; 506static arc_state_t ARC_l2c_only; 507 508typedef struct arc_stats { 509 kstat_named_t arcstat_hits; 510 kstat_named_t arcstat_misses; 511 kstat_named_t arcstat_demand_data_hits; 512 kstat_named_t arcstat_demand_data_misses; 513 kstat_named_t arcstat_demand_metadata_hits; 514 kstat_named_t arcstat_demand_metadata_misses; 515 kstat_named_t arcstat_prefetch_data_hits; 516 kstat_named_t arcstat_prefetch_data_misses; 517 kstat_named_t arcstat_prefetch_metadata_hits; 518 kstat_named_t arcstat_prefetch_metadata_misses; 519 kstat_named_t arcstat_mru_hits; 520 kstat_named_t arcstat_mru_ghost_hits; 521 kstat_named_t arcstat_mfu_hits; 522 kstat_named_t arcstat_mfu_ghost_hits; 523 kstat_named_t arcstat_allocated; 524 kstat_named_t arcstat_deleted; 525 /* 526 * Number of buffers that could not be evicted because the hash lock 527 * was held by another thread. The lock may not necessarily be held 528 * by something using the same buffer, since hash locks are shared 529 * by multiple buffers. 530 */ 531 kstat_named_t arcstat_mutex_miss; 532 /* 533 * Number of buffers skipped because they have I/O in progress, are 534 * indrect prefetch buffers that have not lived long enough, or are 535 * not from the spa we're trying to evict from. 536 */ 537 kstat_named_t arcstat_evict_skip; 538 /* 539 * Number of times arc_evict_state() was unable to evict enough 540 * buffers to reach it's target amount. 541 */ 542 kstat_named_t arcstat_evict_not_enough; 543 kstat_named_t arcstat_evict_l2_cached; 544 kstat_named_t arcstat_evict_l2_eligible; 545 kstat_named_t arcstat_evict_l2_ineligible; 546 kstat_named_t arcstat_evict_l2_skip; 547 kstat_named_t arcstat_hash_elements; 548 kstat_named_t arcstat_hash_elements_max; 549 kstat_named_t arcstat_hash_collisions; 550 kstat_named_t arcstat_hash_chains; 551 kstat_named_t arcstat_hash_chain_max; 552 kstat_named_t arcstat_p; 553 kstat_named_t arcstat_c; 554 kstat_named_t arcstat_c_min; 555 kstat_named_t arcstat_c_max; 556 kstat_named_t arcstat_size; 557 /* 558 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd. 559 * Note that the compressed bytes may match the uncompressed bytes 560 * if the block is either not compressed or compressed arc is disabled. 561 */ 562 kstat_named_t arcstat_compressed_size; 563 /* 564 * Uncompressed size of the data stored in b_pabd. If compressed 565 * arc is disabled then this value will be identical to the stat 566 * above. 567 */ 568 kstat_named_t arcstat_uncompressed_size; 569 /* 570 * Number of bytes stored in all the arc_buf_t's. This is classified 571 * as "overhead" since this data is typically short-lived and will 572 * be evicted from the arc when it becomes unreferenced unless the 573 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level 574 * values have been set (see comment in dbuf.c for more information). 575 */ 576 kstat_named_t arcstat_overhead_size; 577 /* 578 * Number of bytes consumed by internal ARC structures necessary 579 * for tracking purposes; these structures are not actually 580 * backed by ARC buffers. This includes arc_buf_hdr_t structures 581 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only 582 * caches), and arc_buf_t structures (allocated via arc_buf_t 583 * cache). 584 */ 585 kstat_named_t arcstat_hdr_size; 586 /* 587 * Number of bytes consumed by ARC buffers of type equal to 588 * ARC_BUFC_DATA. This is generally consumed by buffers backing 589 * on disk user data (e.g. plain file contents). 590 */ 591 kstat_named_t arcstat_data_size; 592 /* 593 * Number of bytes consumed by ARC buffers of type equal to 594 * ARC_BUFC_METADATA. This is generally consumed by buffers 595 * backing on disk data that is used for internal ZFS 596 * structures (e.g. ZAP, dnode, indirect blocks, etc). 597 */ 598 kstat_named_t arcstat_metadata_size; 599 /* 600 * Number of bytes consumed by various buffers and structures 601 * not actually backed with ARC buffers. This includes bonus 602 * buffers (allocated directly via zio_buf_* functions), 603 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t 604 * cache), and dnode_t structures (allocated via dnode_t cache). 605 */ 606 kstat_named_t arcstat_other_size; 607 /* 608 * Total number of bytes consumed by ARC buffers residing in the 609 * arc_anon state. This includes *all* buffers in the arc_anon 610 * state; e.g. data, metadata, evictable, and unevictable buffers 611 * are all included in this value. 612 */ 613 kstat_named_t arcstat_anon_size; 614 /* 615 * Number of bytes consumed by ARC buffers that meet the 616 * following criteria: backing buffers of type ARC_BUFC_DATA, 617 * residing in the arc_anon state, and are eligible for eviction 618 * (e.g. have no outstanding holds on the buffer). 619 */ 620 kstat_named_t arcstat_anon_evictable_data; 621 /* 622 * Number of bytes consumed by ARC buffers that meet the 623 * following criteria: backing buffers of type ARC_BUFC_METADATA, 624 * residing in the arc_anon state, and are eligible for eviction 625 * (e.g. have no outstanding holds on the buffer). 626 */ 627 kstat_named_t arcstat_anon_evictable_metadata; 628 /* 629 * Total number of bytes consumed by ARC buffers residing in the 630 * arc_mru state. This includes *all* buffers in the arc_mru 631 * state; e.g. data, metadata, evictable, and unevictable buffers 632 * are all included in this value. 633 */ 634 kstat_named_t arcstat_mru_size; 635 /* 636 * Number of bytes consumed by ARC buffers that meet the 637 * following criteria: backing buffers of type ARC_BUFC_DATA, 638 * residing in the arc_mru state, and are eligible for eviction 639 * (e.g. have no outstanding holds on the buffer). 640 */ 641 kstat_named_t arcstat_mru_evictable_data; 642 /* 643 * Number of bytes consumed by ARC buffers that meet the 644 * following criteria: backing buffers of type ARC_BUFC_METADATA, 645 * residing in the arc_mru state, and are eligible for eviction 646 * (e.g. have no outstanding holds on the buffer). 647 */ 648 kstat_named_t arcstat_mru_evictable_metadata; 649 /* 650 * Total number of bytes that *would have been* consumed by ARC 651 * buffers in the arc_mru_ghost state. The key thing to note 652 * here, is the fact that this size doesn't actually indicate 653 * RAM consumption. The ghost lists only consist of headers and 654 * don't actually have ARC buffers linked off of these headers. 655 * Thus, *if* the headers had associated ARC buffers, these 656 * buffers *would have* consumed this number of bytes. 657 */ 658 kstat_named_t arcstat_mru_ghost_size; 659 /* 660 * Number of bytes that *would have been* consumed by ARC 661 * buffers that are eligible for eviction, of type 662 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state. 663 */ 664 kstat_named_t arcstat_mru_ghost_evictable_data; 665 /* 666 * Number of bytes that *would have been* consumed by ARC 667 * buffers that are eligible for eviction, of type 668 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 669 */ 670 kstat_named_t arcstat_mru_ghost_evictable_metadata; 671 /* 672 * Total number of bytes consumed by ARC buffers residing in the 673 * arc_mfu state. This includes *all* buffers in the arc_mfu 674 * state; e.g. data, metadata, evictable, and unevictable buffers 675 * are all included in this value. 676 */ 677 kstat_named_t arcstat_mfu_size; 678 /* 679 * Number of bytes consumed by ARC buffers that are eligible for 680 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu 681 * state. 682 */ 683 kstat_named_t arcstat_mfu_evictable_data; 684 /* 685 * Number of bytes consumed by ARC buffers that are eligible for 686 * eviction, of type ARC_BUFC_METADATA, and reside in the 687 * arc_mfu state. 688 */ 689 kstat_named_t arcstat_mfu_evictable_metadata; 690 /* 691 * Total number of bytes that *would have been* consumed by ARC 692 * buffers in the arc_mfu_ghost state. See the comment above 693 * arcstat_mru_ghost_size for more details. 694 */ 695 kstat_named_t arcstat_mfu_ghost_size; 696 /* 697 * Number of bytes that *would have been* consumed by ARC 698 * buffers that are eligible for eviction, of type 699 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state. 700 */ 701 kstat_named_t arcstat_mfu_ghost_evictable_data; 702 /* 703 * Number of bytes that *would have been* consumed by ARC 704 * buffers that are eligible for eviction, of type 705 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state. 706 */ 707 kstat_named_t arcstat_mfu_ghost_evictable_metadata; 708 kstat_named_t arcstat_l2_hits; 709 kstat_named_t arcstat_l2_misses; 710 kstat_named_t arcstat_l2_feeds; 711 kstat_named_t arcstat_l2_rw_clash; 712 kstat_named_t arcstat_l2_read_bytes; 713 kstat_named_t arcstat_l2_write_bytes; 714 kstat_named_t arcstat_l2_writes_sent; 715 kstat_named_t arcstat_l2_writes_done; 716 kstat_named_t arcstat_l2_writes_error; 717 kstat_named_t arcstat_l2_writes_lock_retry; 718 kstat_named_t arcstat_l2_evict_lock_retry; 719 kstat_named_t arcstat_l2_evict_reading; 720 kstat_named_t arcstat_l2_evict_l1cached; 721 kstat_named_t arcstat_l2_free_on_write; 722 kstat_named_t arcstat_l2_abort_lowmem; 723 kstat_named_t arcstat_l2_cksum_bad; 724 kstat_named_t arcstat_l2_io_error; 725 kstat_named_t arcstat_l2_lsize; 726 kstat_named_t arcstat_l2_psize; 727 kstat_named_t arcstat_l2_hdr_size; 728 kstat_named_t arcstat_l2_write_trylock_fail; 729 kstat_named_t arcstat_l2_write_passed_headroom; 730 kstat_named_t arcstat_l2_write_spa_mismatch; 731 kstat_named_t arcstat_l2_write_in_l2; 732 kstat_named_t arcstat_l2_write_hdr_io_in_progress; 733 kstat_named_t arcstat_l2_write_not_cacheable; 734 kstat_named_t arcstat_l2_write_full; 735 kstat_named_t arcstat_l2_write_buffer_iter; 736 kstat_named_t arcstat_l2_write_pios; 737 kstat_named_t arcstat_l2_write_buffer_bytes_scanned; 738 kstat_named_t arcstat_l2_write_buffer_list_iter; 739 kstat_named_t arcstat_l2_write_buffer_list_null_iter; 740 kstat_named_t arcstat_memory_throttle_count; 741 kstat_named_t arcstat_meta_used; 742 kstat_named_t arcstat_meta_limit; 743 kstat_named_t arcstat_meta_max; 744 kstat_named_t arcstat_meta_min; 745 kstat_named_t arcstat_sync_wait_for_async; 746 kstat_named_t arcstat_demand_hit_predictive_prefetch; 747} arc_stats_t; 748 749static arc_stats_t arc_stats = { 750 { "hits", KSTAT_DATA_UINT64 }, 751 { "misses", KSTAT_DATA_UINT64 }, 752 { "demand_data_hits", KSTAT_DATA_UINT64 }, 753 { "demand_data_misses", KSTAT_DATA_UINT64 }, 754 { "demand_metadata_hits", KSTAT_DATA_UINT64 }, 755 { "demand_metadata_misses", KSTAT_DATA_UINT64 }, 756 { "prefetch_data_hits", KSTAT_DATA_UINT64 }, 757 { "prefetch_data_misses", KSTAT_DATA_UINT64 }, 758 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 }, 759 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 }, 760 { "mru_hits", KSTAT_DATA_UINT64 }, 761 { "mru_ghost_hits", KSTAT_DATA_UINT64 }, 762 { "mfu_hits", KSTAT_DATA_UINT64 }, 763 { "mfu_ghost_hits", KSTAT_DATA_UINT64 }, 764 { "allocated", KSTAT_DATA_UINT64 }, 765 { "deleted", KSTAT_DATA_UINT64 }, 766 { "mutex_miss", KSTAT_DATA_UINT64 }, 767 { "evict_skip", KSTAT_DATA_UINT64 }, 768 { "evict_not_enough", KSTAT_DATA_UINT64 }, 769 { "evict_l2_cached", KSTAT_DATA_UINT64 }, 770 { "evict_l2_eligible", KSTAT_DATA_UINT64 }, 771 { "evict_l2_ineligible", KSTAT_DATA_UINT64 }, 772 { "evict_l2_skip", KSTAT_DATA_UINT64 }, 773 { "hash_elements", KSTAT_DATA_UINT64 }, 774 { "hash_elements_max", KSTAT_DATA_UINT64 }, 775 { "hash_collisions", KSTAT_DATA_UINT64 }, 776 { "hash_chains", KSTAT_DATA_UINT64 }, 777 { "hash_chain_max", KSTAT_DATA_UINT64 }, 778 { "p", KSTAT_DATA_UINT64 }, 779 { "c", KSTAT_DATA_UINT64 }, 780 { "c_min", KSTAT_DATA_UINT64 }, 781 { "c_max", KSTAT_DATA_UINT64 }, 782 { "size", KSTAT_DATA_UINT64 }, 783 { "compressed_size", KSTAT_DATA_UINT64 }, 784 { "uncompressed_size", KSTAT_DATA_UINT64 }, 785 { "overhead_size", KSTAT_DATA_UINT64 }, 786 { "hdr_size", KSTAT_DATA_UINT64 }, 787 { "data_size", KSTAT_DATA_UINT64 }, 788 { "metadata_size", KSTAT_DATA_UINT64 }, 789 { "other_size", KSTAT_DATA_UINT64 }, 790 { "anon_size", KSTAT_DATA_UINT64 }, 791 { "anon_evictable_data", KSTAT_DATA_UINT64 }, 792 { "anon_evictable_metadata", KSTAT_DATA_UINT64 }, 793 { "mru_size", KSTAT_DATA_UINT64 }, 794 { "mru_evictable_data", KSTAT_DATA_UINT64 }, 795 { "mru_evictable_metadata", KSTAT_DATA_UINT64 }, 796 { "mru_ghost_size", KSTAT_DATA_UINT64 }, 797 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 }, 798 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 799 { "mfu_size", KSTAT_DATA_UINT64 }, 800 { "mfu_evictable_data", KSTAT_DATA_UINT64 }, 801 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 }, 802 { "mfu_ghost_size", KSTAT_DATA_UINT64 }, 803 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 }, 804 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 }, 805 { "l2_hits", KSTAT_DATA_UINT64 }, 806 { "l2_misses", KSTAT_DATA_UINT64 }, 807 { "l2_feeds", KSTAT_DATA_UINT64 }, 808 { "l2_rw_clash", KSTAT_DATA_UINT64 }, 809 { "l2_read_bytes", KSTAT_DATA_UINT64 }, 810 { "l2_write_bytes", KSTAT_DATA_UINT64 }, 811 { "l2_writes_sent", KSTAT_DATA_UINT64 }, 812 { "l2_writes_done", KSTAT_DATA_UINT64 }, 813 { "l2_writes_error", KSTAT_DATA_UINT64 }, 814 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 }, 815 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, 816 { "l2_evict_reading", KSTAT_DATA_UINT64 }, 817 { "l2_evict_l1cached", KSTAT_DATA_UINT64 }, 818 { "l2_free_on_write", KSTAT_DATA_UINT64 }, 819 { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, 820 { "l2_cksum_bad", KSTAT_DATA_UINT64 }, 821 { "l2_io_error", KSTAT_DATA_UINT64 }, 822 { "l2_size", KSTAT_DATA_UINT64 }, 823 { "l2_asize", KSTAT_DATA_UINT64 }, 824 { "l2_hdr_size", KSTAT_DATA_UINT64 }, 825 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 }, 826 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 }, 827 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 }, 828 { "l2_write_in_l2", KSTAT_DATA_UINT64 }, 829 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 }, 830 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 }, 831 { "l2_write_full", KSTAT_DATA_UINT64 }, 832 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 }, 833 { "l2_write_pios", KSTAT_DATA_UINT64 }, 834 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 }, 835 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 }, 836 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }, 837 { "memory_throttle_count", KSTAT_DATA_UINT64 }, 838 { "arc_meta_used", KSTAT_DATA_UINT64 }, 839 { "arc_meta_limit", KSTAT_DATA_UINT64 }, 840 { "arc_meta_max", KSTAT_DATA_UINT64 }, 841 { "arc_meta_min", KSTAT_DATA_UINT64 }, 842 { "sync_wait_for_async", KSTAT_DATA_UINT64 }, 843 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 }, 844}; 845 846#define ARCSTAT(stat) (arc_stats.stat.value.ui64) 847 848#define ARCSTAT_INCR(stat, val) \ 849 atomic_add_64(&arc_stats.stat.value.ui64, (val)) 850 851#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1) 852#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1) 853 854#define ARCSTAT_MAX(stat, val) { \ 855 uint64_t m; \ 856 while ((val) > (m = arc_stats.stat.value.ui64) && \ 857 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \ 858 continue; \ 859} 860 861#define ARCSTAT_MAXSTAT(stat) \ 862 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64) 863 864/* 865 * We define a macro to allow ARC hits/misses to be easily broken down by 866 * two separate conditions, giving a total of four different subtypes for 867 * each of hits and misses (so eight statistics total). 868 */ 869#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \ 870 if (cond1) { \ 871 if (cond2) { \ 872 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \ 873 } else { \ 874 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \ 875 } \ 876 } else { \ 877 if (cond2) { \ 878 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \ 879 } else { \ 880 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\ 881 } \ 882 } 883 884kstat_t *arc_ksp; 885static arc_state_t *arc_anon; 886static arc_state_t *arc_mru; 887static arc_state_t *arc_mru_ghost; 888static arc_state_t *arc_mfu; 889static arc_state_t *arc_mfu_ghost; 890static arc_state_t *arc_l2c_only; 891 892/* 893 * There are several ARC variables that are critical to export as kstats -- 894 * but we don't want to have to grovel around in the kstat whenever we wish to 895 * manipulate them. For these variables, we therefore define them to be in 896 * terms of the statistic variable. This assures that we are not introducing 897 * the possibility of inconsistency by having shadow copies of the variables, 898 * while still allowing the code to be readable. 899 */ 900#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */ 901#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */ 902#define arc_c ARCSTAT(arcstat_c) /* target size of cache */ 903#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */ 904#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */ 905#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */ 906#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */ 907#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */ 908#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */ 909 910/* compressed size of entire arc */ 911#define arc_compressed_size ARCSTAT(arcstat_compressed_size) 912/* uncompressed size of entire arc */ 913#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size) 914/* number of bytes in the arc from arc_buf_t's */ 915#define arc_overhead_size ARCSTAT(arcstat_overhead_size) 916 917static int arc_no_grow; /* Don't try to grow cache size */ 918static uint64_t arc_tempreserve; 919static uint64_t arc_loaned_bytes; 920 921typedef struct arc_callback arc_callback_t; 922 923struct arc_callback { 924 void *acb_private; 925 arc_done_func_t *acb_done; 926 arc_buf_t *acb_buf; 927 boolean_t acb_compressed; 928 zio_t *acb_zio_dummy; 929 arc_callback_t *acb_next; 930}; 931 932typedef struct arc_write_callback arc_write_callback_t; 933 934struct arc_write_callback { 935 void *awcb_private; 936 arc_done_func_t *awcb_ready; 937 arc_done_func_t *awcb_children_ready; 938 arc_done_func_t *awcb_physdone; 939 arc_done_func_t *awcb_done; 940 arc_buf_t *awcb_buf; 941}; 942 943/* 944 * ARC buffers are separated into multiple structs as a memory saving measure: 945 * - Common fields struct, always defined, and embedded within it: 946 * - L2-only fields, always allocated but undefined when not in L2ARC 947 * - L1-only fields, only allocated when in L1ARC 948 * 949 * Buffer in L1 Buffer only in L2 950 * +------------------------+ +------------------------+ 951 * | arc_buf_hdr_t | | arc_buf_hdr_t | 952 * | | | | 953 * | | | | 954 * | | | | 955 * +------------------------+ +------------------------+ 956 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t | 957 * | (undefined if L1-only) | | | 958 * +------------------------+ +------------------------+ 959 * | l1arc_buf_hdr_t | 960 * | | 961 * | | 962 * | | 963 * | | 964 * +------------------------+ 965 * 966 * Because it's possible for the L2ARC to become extremely large, we can wind 967 * up eating a lot of memory in L2ARC buffer headers, so the size of a header 968 * is minimized by only allocating the fields necessary for an L1-cached buffer 969 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and 970 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple 971 * words in pointers. arc_hdr_realloc() is used to switch a header between 972 * these two allocation states. 973 */ 974typedef struct l1arc_buf_hdr { 975 kmutex_t b_freeze_lock; 976 zio_cksum_t *b_freeze_cksum; 977#ifdef ZFS_DEBUG 978 /* 979 * Used for debugging with kmem_flags - by allocating and freeing 980 * b_thawed when the buffer is thawed, we get a record of the stack 981 * trace that thawed it. 982 */ 983 void *b_thawed; 984#endif 985 986 arc_buf_t *b_buf; 987 uint32_t b_bufcnt; 988 /* for waiting on writes to complete */ 989 kcondvar_t b_cv; 990 uint8_t b_byteswap; 991 992 /* protected by arc state mutex */ 993 arc_state_t *b_state; 994 multilist_node_t b_arc_node; 995 996 /* updated atomically */ 997 clock_t b_arc_access; 998 999 /* self protecting */ 1000 refcount_t b_refcnt; 1001 1002 arc_callback_t *b_acb; 1003 abd_t *b_pabd; 1004} l1arc_buf_hdr_t; 1005 1006typedef struct l2arc_dev l2arc_dev_t; 1007 1008typedef struct l2arc_buf_hdr { 1009 /* protected by arc_buf_hdr mutex */ 1010 l2arc_dev_t *b_dev; /* L2ARC device */ 1011 uint64_t b_daddr; /* disk address, offset byte */ 1012 1013 list_node_t b_l2node; 1014} l2arc_buf_hdr_t; 1015 1016struct arc_buf_hdr { 1017 /* protected by hash lock */ 1018 dva_t b_dva; 1019 uint64_t b_birth; 1020 1021 arc_buf_contents_t b_type; 1022 arc_buf_hdr_t *b_hash_next; 1023 arc_flags_t b_flags; 1024 1025 /* 1026 * This field stores the size of the data buffer after 1027 * compression, and is set in the arc's zio completion handlers. 1028 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes). 1029 * 1030 * While the block pointers can store up to 32MB in their psize 1031 * field, we can only store up to 32MB minus 512B. This is due 1032 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e. 1033 * a field of zeros represents 512B in the bp). We can't use a 1034 * bias of 1 since we need to reserve a psize of zero, here, to 1035 * represent holes and embedded blocks. 1036 * 1037 * This isn't a problem in practice, since the maximum size of a 1038 * buffer is limited to 16MB, so we never need to store 32MB in 1039 * this field. Even in the upstream illumos code base, the 1040 * maximum size of a buffer is limited to 16MB. 1041 */ 1042 uint16_t b_psize; 1043 1044 /* 1045 * This field stores the size of the data buffer before 1046 * compression, and cannot change once set. It is in units 1047 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes) 1048 */ 1049 uint16_t b_lsize; /* immutable */ 1050 uint64_t b_spa; /* immutable */ 1051 1052 /* L2ARC fields. Undefined when not in L2ARC. */ 1053 l2arc_buf_hdr_t b_l2hdr; 1054 /* L1ARC fields. Undefined when in l2arc_only state */ 1055 l1arc_buf_hdr_t b_l1hdr; 1056}; 1057 1058#if defined(__FreeBSD__) && defined(_KERNEL) 1059static int 1060sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS) 1061{ 1062 uint64_t val; 1063 int err; 1064 1065 val = arc_meta_limit; 1066 err = sysctl_handle_64(oidp, &val, 0, req); 1067 if (err != 0 || req->newptr == NULL) 1068 return (err); 1069 1070 if (val <= 0 || val > arc_c_max) 1071 return (EINVAL); 1072 1073 arc_meta_limit = val; 1074 return (0); 1075} 1076 1077static int 1078sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS) 1079{ 1080 uint32_t val; 1081 int err; 1082 1083 val = arc_no_grow_shift; 1084 err = sysctl_handle_32(oidp, &val, 0, req); 1085 if (err != 0 || req->newptr == NULL) 1086 return (err); 1087 1088 if (val >= arc_shrink_shift) 1089 return (EINVAL); 1090 1091 arc_no_grow_shift = val; 1092 return (0); 1093} 1094 1095static int 1096sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS) 1097{ 1098 uint64_t val; 1099 int err; 1100 1101 val = zfs_arc_max; 1102 err = sysctl_handle_64(oidp, &val, 0, req); 1103 if (err != 0 || req->newptr == NULL) 1104 return (err); 1105 1106 if (zfs_arc_max == 0) { 1107 /* Loader tunable so blindly set */ 1108 zfs_arc_max = val; 1109 return (0); 1110 } 1111 1112 if (val < arc_abs_min || val > kmem_size()) 1113 return (EINVAL); 1114 if (val < arc_c_min) 1115 return (EINVAL); 1116 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit) 1117 return (EINVAL); 1118 1119 arc_c_max = val; 1120 1121 arc_c = arc_c_max; 1122 arc_p = (arc_c >> 1); 1123 1124 if (zfs_arc_meta_limit == 0) { 1125 /* limit meta-data to 1/4 of the arc capacity */ 1126 arc_meta_limit = arc_c_max / 4; 1127 } 1128 1129 /* if kmem_flags are set, lets try to use less memory */ 1130 if (kmem_debugging()) 1131 arc_c = arc_c / 2; 1132 1133 zfs_arc_max = arc_c; 1134 1135 return (0); 1136} 1137 1138static int 1139sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS) 1140{ 1141 uint64_t val; 1142 int err; 1143 1144 val = zfs_arc_min; 1145 err = sysctl_handle_64(oidp, &val, 0, req); 1146 if (err != 0 || req->newptr == NULL) 1147 return (err); 1148 1149 if (zfs_arc_min == 0) { 1150 /* Loader tunable so blindly set */ 1151 zfs_arc_min = val; 1152 return (0); 1153 } 1154 1155 if (val < arc_abs_min || val > arc_c_max) 1156 return (EINVAL); 1157 1158 arc_c_min = val; 1159 1160 if (zfs_arc_meta_min == 0) 1161 arc_meta_min = arc_c_min / 2; 1162 1163 if (arc_c < arc_c_min) 1164 arc_c = arc_c_min; 1165 1166 zfs_arc_min = arc_c_min; 1167 1168 return (0); 1169} 1170#endif 1171 1172#define GHOST_STATE(state) \ 1173 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \ 1174 (state) == arc_l2c_only) 1175 1176#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE) 1177#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) 1178#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR) 1179#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH) 1180#define HDR_COMPRESSION_ENABLED(hdr) \ 1181 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC) 1182 1183#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE) 1184#define HDR_L2_READING(hdr) \ 1185 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \ 1186 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)) 1187#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING) 1188#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED) 1189#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD) 1190#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA) 1191 1192#define HDR_ISTYPE_METADATA(hdr) \ 1193 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA) 1194#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr)) 1195 1196#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR) 1197#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR) 1198 1199/* For storing compression mode in b_flags */ 1200#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1) 1201 1202#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \ 1203 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS)) 1204#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \ 1205 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp)); 1206 1207#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL) 1208#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED) 1209#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED) 1210 1211/* 1212 * Other sizes 1213 */ 1214 1215#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t)) 1216#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr)) 1217 1218/* 1219 * Hash table routines 1220 */ 1221 1222#define HT_LOCK_PAD CACHE_LINE_SIZE 1223 1224struct ht_lock { 1225 kmutex_t ht_lock; 1226#ifdef _KERNEL 1227 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))]; 1228#endif 1229}; 1230 1231#define BUF_LOCKS 256 1232typedef struct buf_hash_table { 1233 uint64_t ht_mask; 1234 arc_buf_hdr_t **ht_table; 1235 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE); 1236} buf_hash_table_t; 1237 1238static buf_hash_table_t buf_hash_table; 1239 1240#define BUF_HASH_INDEX(spa, dva, birth) \ 1241 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask) 1242#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)]) 1243#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock)) 1244#define HDR_LOCK(hdr) \ 1245 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth))) 1246 1247uint64_t zfs_crc64_table[256]; 1248 1249/* 1250 * Level 2 ARC 1251 */ 1252 1253#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */ 1254#define L2ARC_HEADROOM 2 /* num of writes */ 1255/* 1256 * If we discover during ARC scan any buffers to be compressed, we boost 1257 * our headroom for the next scanning cycle by this percentage multiple. 1258 */ 1259#define L2ARC_HEADROOM_BOOST 200 1260#define L2ARC_FEED_SECS 1 /* caching interval secs */ 1261#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */ 1262 1263#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent) 1264#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done) 1265 1266/* L2ARC Performance Tunables */ 1267uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */ 1268uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */ 1269uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */ 1270uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST; 1271uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */ 1272uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */ 1273boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */ 1274boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */ 1275boolean_t l2arc_norw = B_TRUE; /* no reads during writes */ 1276 1277SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW, 1278 &l2arc_write_max, 0, "max write size"); 1279SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW, 1280 &l2arc_write_boost, 0, "extra write during warmup"); 1281SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW, 1282 &l2arc_headroom, 0, "number of dev writes"); 1283SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW, 1284 &l2arc_feed_secs, 0, "interval seconds"); 1285SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW, 1286 &l2arc_feed_min_ms, 0, "min interval milliseconds"); 1287 1288SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW, 1289 &l2arc_noprefetch, 0, "don't cache prefetch bufs"); 1290SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW, 1291 &l2arc_feed_again, 0, "turbo warmup"); 1292SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW, 1293 &l2arc_norw, 0, "no reads during writes"); 1294 1295SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD, 1296 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state"); 1297SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD, 1298 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1299 "size of anonymous state"); 1300SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD, 1301 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1302 "size of anonymous state"); 1303 1304SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD, 1305 &ARC_mru.arcs_size.rc_count, 0, "size of mru state"); 1306SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD, 1307 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1308 "size of metadata in mru state"); 1309SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD, 1310 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1311 "size of data in mru state"); 1312 1313SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD, 1314 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state"); 1315SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD, 1316 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1317 "size of metadata in mru ghost state"); 1318SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD, 1319 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1320 "size of data in mru ghost state"); 1321 1322SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD, 1323 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state"); 1324SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD, 1325 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1326 "size of metadata in mfu state"); 1327SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD, 1328 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1329 "size of data in mfu state"); 1330 1331SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD, 1332 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state"); 1333SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD, 1334 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0, 1335 "size of metadata in mfu ghost state"); 1336SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD, 1337 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0, 1338 "size of data in mfu ghost state"); 1339 1340SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD, 1341 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state"); 1342 1343/* 1344 * L2ARC Internals 1345 */ 1346struct l2arc_dev { 1347 vdev_t *l2ad_vdev; /* vdev */ 1348 spa_t *l2ad_spa; /* spa */ 1349 uint64_t l2ad_hand; /* next write location */ 1350 uint64_t l2ad_start; /* first addr on device */ 1351 uint64_t l2ad_end; /* last addr on device */ 1352 boolean_t l2ad_first; /* first sweep through */ 1353 boolean_t l2ad_writing; /* currently writing */ 1354 kmutex_t l2ad_mtx; /* lock for buffer list */ 1355 list_t l2ad_buflist; /* buffer list */ 1356 list_node_t l2ad_node; /* device list node */ 1357 refcount_t l2ad_alloc; /* allocated bytes */ 1358}; 1359 1360static list_t L2ARC_dev_list; /* device list */ 1361static list_t *l2arc_dev_list; /* device list pointer */ 1362static kmutex_t l2arc_dev_mtx; /* device list mutex */ 1363static l2arc_dev_t *l2arc_dev_last; /* last device used */ 1364static list_t L2ARC_free_on_write; /* free after write buf list */ 1365static list_t *l2arc_free_on_write; /* free after write list ptr */ 1366static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */ 1367static uint64_t l2arc_ndev; /* number of devices */ 1368 1369typedef struct l2arc_read_callback { 1370 arc_buf_hdr_t *l2rcb_hdr; /* read header */ 1371 blkptr_t l2rcb_bp; /* original blkptr */ 1372 zbookmark_phys_t l2rcb_zb; /* original bookmark */ 1373 int l2rcb_flags; /* original flags */ 1374 abd_t *l2rcb_abd; /* temporary buffer */ 1375} l2arc_read_callback_t; 1376 1377typedef struct l2arc_write_callback { 1378 l2arc_dev_t *l2wcb_dev; /* device info */ 1379 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */ 1380} l2arc_write_callback_t; 1381 1382typedef struct l2arc_data_free { 1383 /* protected by l2arc_free_on_write_mtx */ 1384 abd_t *l2df_abd; 1385 size_t l2df_size; 1386 arc_buf_contents_t l2df_type; 1387 list_node_t l2df_list_node; 1388} l2arc_data_free_t; 1389 1390static kmutex_t l2arc_feed_thr_lock; 1391static kcondvar_t l2arc_feed_thr_cv; 1392static uint8_t l2arc_thread_exit; 1393 1394static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *); 1395static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *); 1396static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *); 1397static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *); 1398static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *); 1399static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag); 1400static void arc_hdr_free_pabd(arc_buf_hdr_t *); 1401static void arc_hdr_alloc_pabd(arc_buf_hdr_t *); 1402static void arc_access(arc_buf_hdr_t *, kmutex_t *); 1403static boolean_t arc_is_overflowing(); 1404static void arc_buf_watch(arc_buf_t *); 1405 1406static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *); 1407static uint32_t arc_bufc_to_flags(arc_buf_contents_t); 1408static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1409static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags); 1410 1411static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *); 1412static void l2arc_read_done(zio_t *); 1413 1414static void 1415l2arc_trim(const arc_buf_hdr_t *hdr) 1416{ 1417 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 1418 1419 ASSERT(HDR_HAS_L2HDR(hdr)); 1420 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 1421 1422 if (HDR_GET_PSIZE(hdr) != 0) { 1423 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr, 1424 HDR_GET_PSIZE(hdr), 0); 1425 } 1426} 1427 1428static uint64_t 1429buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth) 1430{ 1431 uint8_t *vdva = (uint8_t *)dva; 1432 uint64_t crc = -1ULL; 1433 int i; 1434 1435 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY); 1436 1437 for (i = 0; i < sizeof (dva_t); i++) 1438 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF]; 1439 1440 crc ^= (spa>>8) ^ birth; 1441 1442 return (crc); 1443} 1444 1445#define HDR_EMPTY(hdr) \ 1446 ((hdr)->b_dva.dva_word[0] == 0 && \ 1447 (hdr)->b_dva.dva_word[1] == 0) 1448 1449#define HDR_EQUAL(spa, dva, birth, hdr) \ 1450 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \ 1451 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \ 1452 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa) 1453 1454static void 1455buf_discard_identity(arc_buf_hdr_t *hdr) 1456{ 1457 hdr->b_dva.dva_word[0] = 0; 1458 hdr->b_dva.dva_word[1] = 0; 1459 hdr->b_birth = 0; 1460} 1461 1462static arc_buf_hdr_t * 1463buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp) 1464{ 1465 const dva_t *dva = BP_IDENTITY(bp); 1466 uint64_t birth = BP_PHYSICAL_BIRTH(bp); 1467 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth); 1468 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1469 arc_buf_hdr_t *hdr; 1470 1471 mutex_enter(hash_lock); 1472 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL; 1473 hdr = hdr->b_hash_next) { 1474 if (HDR_EQUAL(spa, dva, birth, hdr)) { 1475 *lockp = hash_lock; 1476 return (hdr); 1477 } 1478 } 1479 mutex_exit(hash_lock); 1480 *lockp = NULL; 1481 return (NULL); 1482} 1483 1484/* 1485 * Insert an entry into the hash table. If there is already an element 1486 * equal to elem in the hash table, then the already existing element 1487 * will be returned and the new element will not be inserted. 1488 * Otherwise returns NULL. 1489 * If lockp == NULL, the caller is assumed to already hold the hash lock. 1490 */ 1491static arc_buf_hdr_t * 1492buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp) 1493{ 1494 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1495 kmutex_t *hash_lock = BUF_HASH_LOCK(idx); 1496 arc_buf_hdr_t *fhdr; 1497 uint32_t i; 1498 1499 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva)); 1500 ASSERT(hdr->b_birth != 0); 1501 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 1502 1503 if (lockp != NULL) { 1504 *lockp = hash_lock; 1505 mutex_enter(hash_lock); 1506 } else { 1507 ASSERT(MUTEX_HELD(hash_lock)); 1508 } 1509 1510 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL; 1511 fhdr = fhdr->b_hash_next, i++) { 1512 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr)) 1513 return (fhdr); 1514 } 1515 1516 hdr->b_hash_next = buf_hash_table.ht_table[idx]; 1517 buf_hash_table.ht_table[idx] = hdr; 1518 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1519 1520 /* collect some hash table performance data */ 1521 if (i > 0) { 1522 ARCSTAT_BUMP(arcstat_hash_collisions); 1523 if (i == 1) 1524 ARCSTAT_BUMP(arcstat_hash_chains); 1525 1526 ARCSTAT_MAX(arcstat_hash_chain_max, i); 1527 } 1528 1529 ARCSTAT_BUMP(arcstat_hash_elements); 1530 ARCSTAT_MAXSTAT(arcstat_hash_elements); 1531 1532 return (NULL); 1533} 1534 1535static void 1536buf_hash_remove(arc_buf_hdr_t *hdr) 1537{ 1538 arc_buf_hdr_t *fhdr, **hdrp; 1539 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth); 1540 1541 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx))); 1542 ASSERT(HDR_IN_HASH_TABLE(hdr)); 1543 1544 hdrp = &buf_hash_table.ht_table[idx]; 1545 while ((fhdr = *hdrp) != hdr) { 1546 ASSERT3P(fhdr, !=, NULL); 1547 hdrp = &fhdr->b_hash_next; 1548 } 1549 *hdrp = hdr->b_hash_next; 1550 hdr->b_hash_next = NULL; 1551 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 1552 1553 /* collect some hash table performance data */ 1554 ARCSTAT_BUMPDOWN(arcstat_hash_elements); 1555 1556 if (buf_hash_table.ht_table[idx] && 1557 buf_hash_table.ht_table[idx]->b_hash_next == NULL) 1558 ARCSTAT_BUMPDOWN(arcstat_hash_chains); 1559} 1560 1561/* 1562 * Global data structures and functions for the buf kmem cache. 1563 */ 1564static kmem_cache_t *hdr_full_cache; 1565static kmem_cache_t *hdr_l2only_cache; 1566static kmem_cache_t *buf_cache; 1567 1568static void 1569buf_fini(void) 1570{ 1571 int i; 1572 1573 kmem_free(buf_hash_table.ht_table, 1574 (buf_hash_table.ht_mask + 1) * sizeof (void *)); 1575 for (i = 0; i < BUF_LOCKS; i++) 1576 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock); 1577 kmem_cache_destroy(hdr_full_cache); 1578 kmem_cache_destroy(hdr_l2only_cache); 1579 kmem_cache_destroy(buf_cache); 1580} 1581 1582/* 1583 * Constructor callback - called when the cache is empty 1584 * and a new buf is requested. 1585 */ 1586/* ARGSUSED */ 1587static int 1588hdr_full_cons(void *vbuf, void *unused, int kmflag) 1589{ 1590 arc_buf_hdr_t *hdr = vbuf; 1591 1592 bzero(hdr, HDR_FULL_SIZE); 1593 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL); 1594 refcount_create(&hdr->b_l1hdr.b_refcnt); 1595 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL); 1596 multilist_link_init(&hdr->b_l1hdr.b_arc_node); 1597 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1598 1599 return (0); 1600} 1601 1602/* ARGSUSED */ 1603static int 1604hdr_l2only_cons(void *vbuf, void *unused, int kmflag) 1605{ 1606 arc_buf_hdr_t *hdr = vbuf; 1607 1608 bzero(hdr, HDR_L2ONLY_SIZE); 1609 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1610 1611 return (0); 1612} 1613 1614/* ARGSUSED */ 1615static int 1616buf_cons(void *vbuf, void *unused, int kmflag) 1617{ 1618 arc_buf_t *buf = vbuf; 1619 1620 bzero(buf, sizeof (arc_buf_t)); 1621 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL); 1622 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1623 1624 return (0); 1625} 1626 1627/* 1628 * Destructor callback - called when a cached buf is 1629 * no longer required. 1630 */ 1631/* ARGSUSED */ 1632static void 1633hdr_full_dest(void *vbuf, void *unused) 1634{ 1635 arc_buf_hdr_t *hdr = vbuf; 1636 1637 ASSERT(HDR_EMPTY(hdr)); 1638 cv_destroy(&hdr->b_l1hdr.b_cv); 1639 refcount_destroy(&hdr->b_l1hdr.b_refcnt); 1640 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock); 1641 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 1642 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS); 1643} 1644 1645/* ARGSUSED */ 1646static void 1647hdr_l2only_dest(void *vbuf, void *unused) 1648{ 1649 arc_buf_hdr_t *hdr = vbuf; 1650 1651 ASSERT(HDR_EMPTY(hdr)); 1652 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS); 1653} 1654 1655/* ARGSUSED */ 1656static void 1657buf_dest(void *vbuf, void *unused) 1658{ 1659 arc_buf_t *buf = vbuf; 1660 1661 mutex_destroy(&buf->b_evict_lock); 1662 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS); 1663} 1664 1665/* 1666 * Reclaim callback -- invoked when memory is low. 1667 */ 1668/* ARGSUSED */ 1669static void 1670hdr_recl(void *unused) 1671{ 1672 dprintf("hdr_recl called\n"); 1673 /* 1674 * umem calls the reclaim func when we destroy the buf cache, 1675 * which is after we do arc_fini(). 1676 */ 1677 if (!arc_dead) 1678 cv_signal(&arc_reclaim_thread_cv); 1679} 1680 1681static void 1682buf_init(void) 1683{ 1684 uint64_t *ct; 1685 uint64_t hsize = 1ULL << 12; 1686 int i, j; 1687 1688 /* 1689 * The hash table is big enough to fill all of physical memory 1690 * with an average block size of zfs_arc_average_blocksize (default 8K). 1691 * By default, the table will take up 1692 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers). 1693 */ 1694 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE) 1695 hsize <<= 1; 1696retry: 1697 buf_hash_table.ht_mask = hsize - 1; 1698 buf_hash_table.ht_table = 1699 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP); 1700 if (buf_hash_table.ht_table == NULL) { 1701 ASSERT(hsize > (1ULL << 8)); 1702 hsize >>= 1; 1703 goto retry; 1704 } 1705 1706 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE, 1707 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0); 1708 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only", 1709 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl, 1710 NULL, NULL, 0); 1711 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t), 1712 0, buf_cons, buf_dest, NULL, NULL, NULL, 0); 1713 1714 for (i = 0; i < 256; i++) 1715 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--) 1716 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY); 1717 1718 for (i = 0; i < BUF_LOCKS; i++) { 1719 mutex_init(&buf_hash_table.ht_locks[i].ht_lock, 1720 NULL, MUTEX_DEFAULT, NULL); 1721 } 1722} 1723 1724/* 1725 * This is the size that the buf occupies in memory. If the buf is compressed, 1726 * it will correspond to the compressed size. You should use this method of 1727 * getting the buf size unless you explicitly need the logical size. 1728 */ 1729int32_t 1730arc_buf_size(arc_buf_t *buf) 1731{ 1732 return (ARC_BUF_COMPRESSED(buf) ? 1733 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr)); 1734} 1735 1736int32_t 1737arc_buf_lsize(arc_buf_t *buf) 1738{ 1739 return (HDR_GET_LSIZE(buf->b_hdr)); 1740} 1741 1742enum zio_compress 1743arc_get_compression(arc_buf_t *buf) 1744{ 1745 return (ARC_BUF_COMPRESSED(buf) ? 1746 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF); 1747} 1748 1749#define ARC_MINTIME (hz>>4) /* 62 ms */ 1750 1751static inline boolean_t 1752arc_buf_is_shared(arc_buf_t *buf) 1753{ 1754 boolean_t shared = (buf->b_data != NULL && 1755 buf->b_hdr->b_l1hdr.b_pabd != NULL && 1756 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) && 1757 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd)); 1758 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr)); 1759 IMPLY(shared, ARC_BUF_SHARED(buf)); 1760 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf)); 1761 1762 /* 1763 * It would be nice to assert arc_can_share() too, but the "hdr isn't 1764 * already being shared" requirement prevents us from doing that. 1765 */ 1766 1767 return (shared); 1768} 1769 1770/* 1771 * Free the checksum associated with this header. If there is no checksum, this 1772 * is a no-op. 1773 */ 1774static inline void 1775arc_cksum_free(arc_buf_hdr_t *hdr) 1776{ 1777 ASSERT(HDR_HAS_L1HDR(hdr)); 1778 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1779 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1780 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t)); 1781 hdr->b_l1hdr.b_freeze_cksum = NULL; 1782 } 1783 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1784} 1785 1786/* 1787 * Return true iff at least one of the bufs on hdr is not compressed. 1788 */ 1789static boolean_t 1790arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr) 1791{ 1792 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) { 1793 if (!ARC_BUF_COMPRESSED(b)) { 1794 return (B_TRUE); 1795 } 1796 } 1797 return (B_FALSE); 1798} 1799 1800/* 1801 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data 1802 * matches the checksum that is stored in the hdr. If there is no checksum, 1803 * or if the buf is compressed, this is a no-op. 1804 */ 1805static void 1806arc_cksum_verify(arc_buf_t *buf) 1807{ 1808 arc_buf_hdr_t *hdr = buf->b_hdr; 1809 zio_cksum_t zc; 1810 1811 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1812 return; 1813 1814 if (ARC_BUF_COMPRESSED(buf)) { 1815 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 1816 arc_hdr_has_uncompressed_buf(hdr)); 1817 return; 1818 } 1819 1820 ASSERT(HDR_HAS_L1HDR(hdr)); 1821 1822 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 1823 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) { 1824 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1825 return; 1826 } 1827 1828 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc); 1829 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc)) 1830 panic("buffer modified while frozen!"); 1831 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1832} 1833 1834static boolean_t 1835arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio) 1836{ 1837 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp); 1838 boolean_t valid_cksum; 1839 1840 ASSERT(!BP_IS_EMBEDDED(zio->io_bp)); 1841 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr)); 1842 1843 /* 1844 * We rely on the blkptr's checksum to determine if the block 1845 * is valid or not. When compressed arc is enabled, the l2arc 1846 * writes the block to the l2arc just as it appears in the pool. 1847 * This allows us to use the blkptr's checksum to validate the 1848 * data that we just read off of the l2arc without having to store 1849 * a separate checksum in the arc_buf_hdr_t. However, if compressed 1850 * arc is disabled, then the data written to the l2arc is always 1851 * uncompressed and won't match the block as it exists in the main 1852 * pool. When this is the case, we must first compress it if it is 1853 * compressed on the main pool before we can validate the checksum. 1854 */ 1855 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) { 1856 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 1857 uint64_t lsize = HDR_GET_LSIZE(hdr); 1858 uint64_t csize; 1859 1860 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE); 1861 csize = zio_compress_data(compress, zio->io_abd, 1862 abd_to_buf(cdata), lsize); 1863 1864 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr)); 1865 if (csize < HDR_GET_PSIZE(hdr)) { 1866 /* 1867 * Compressed blocks are always a multiple of the 1868 * smallest ashift in the pool. Ideally, we would 1869 * like to round up the csize to the next 1870 * spa_min_ashift but that value may have changed 1871 * since the block was last written. Instead, 1872 * we rely on the fact that the hdr's psize 1873 * was set to the psize of the block when it was 1874 * last written. We set the csize to that value 1875 * and zero out any part that should not contain 1876 * data. 1877 */ 1878 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize); 1879 csize = HDR_GET_PSIZE(hdr); 1880 } 1881 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL); 1882 } 1883 1884 /* 1885 * Block pointers always store the checksum for the logical data. 1886 * If the block pointer has the gang bit set, then the checksum 1887 * it represents is for the reconstituted data and not for an 1888 * individual gang member. The zio pipeline, however, must be able to 1889 * determine the checksum of each of the gang constituents so it 1890 * treats the checksum comparison differently than what we need 1891 * for l2arc blocks. This prevents us from using the 1892 * zio_checksum_error() interface directly. Instead we must call the 1893 * zio_checksum_error_impl() so that we can ensure the checksum is 1894 * generated using the correct checksum algorithm and accounts for the 1895 * logical I/O size and not just a gang fragment. 1896 */ 1897 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp, 1898 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size, 1899 zio->io_offset, NULL) == 0); 1900 zio_pop_transforms(zio); 1901 return (valid_cksum); 1902} 1903 1904/* 1905 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a 1906 * checksum and attaches it to the buf's hdr so that we can ensure that the buf 1907 * isn't modified later on. If buf is compressed or there is already a checksum 1908 * on the hdr, this is a no-op (we only checksum uncompressed bufs). 1909 */ 1910static void 1911arc_cksum_compute(arc_buf_t *buf) 1912{ 1913 arc_buf_hdr_t *hdr = buf->b_hdr; 1914 1915 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 1916 return; 1917 1918 ASSERT(HDR_HAS_L1HDR(hdr)); 1919 1920 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock); 1921 if (hdr->b_l1hdr.b_freeze_cksum != NULL) { 1922 ASSERT(arc_hdr_has_uncompressed_buf(hdr)); 1923 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1924 return; 1925 } else if (ARC_BUF_COMPRESSED(buf)) { 1926 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1927 return; 1928 } 1929 1930 ASSERT(!ARC_BUF_COMPRESSED(buf)); 1931 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), 1932 KM_SLEEP); 1933 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, 1934 hdr->b_l1hdr.b_freeze_cksum); 1935 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 1936#ifdef illumos 1937 arc_buf_watch(buf); 1938#endif 1939} 1940 1941#ifdef illumos 1942#ifndef _KERNEL 1943typedef struct procctl { 1944 long cmd; 1945 prwatch_t prwatch; 1946} procctl_t; 1947#endif 1948 1949/* ARGSUSED */ 1950static void 1951arc_buf_unwatch(arc_buf_t *buf) 1952{ 1953#ifndef _KERNEL 1954 if (arc_watch) { 1955 int result; 1956 procctl_t ctl; 1957 ctl.cmd = PCWATCH; 1958 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1959 ctl.prwatch.pr_size = 0; 1960 ctl.prwatch.pr_wflags = 0; 1961 result = write(arc_procfd, &ctl, sizeof (ctl)); 1962 ASSERT3U(result, ==, sizeof (ctl)); 1963 } 1964#endif 1965} 1966 1967/* ARGSUSED */ 1968static void 1969arc_buf_watch(arc_buf_t *buf) 1970{ 1971#ifndef _KERNEL 1972 if (arc_watch) { 1973 int result; 1974 procctl_t ctl; 1975 ctl.cmd = PCWATCH; 1976 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data; 1977 ctl.prwatch.pr_size = arc_buf_size(buf); 1978 ctl.prwatch.pr_wflags = WA_WRITE; 1979 result = write(arc_procfd, &ctl, sizeof (ctl)); 1980 ASSERT3U(result, ==, sizeof (ctl)); 1981 } 1982#endif 1983} 1984#endif /* illumos */ 1985 1986static arc_buf_contents_t 1987arc_buf_type(arc_buf_hdr_t *hdr) 1988{ 1989 arc_buf_contents_t type; 1990 if (HDR_ISTYPE_METADATA(hdr)) { 1991 type = ARC_BUFC_METADATA; 1992 } else { 1993 type = ARC_BUFC_DATA; 1994 } 1995 VERIFY3U(hdr->b_type, ==, type); 1996 return (type); 1997} 1998 1999boolean_t 2000arc_is_metadata(arc_buf_t *buf) 2001{ 2002 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0); 2003} 2004 2005static uint32_t 2006arc_bufc_to_flags(arc_buf_contents_t type) 2007{ 2008 switch (type) { 2009 case ARC_BUFC_DATA: 2010 /* metadata field is 0 if buffer contains normal data */ 2011 return (0); 2012 case ARC_BUFC_METADATA: 2013 return (ARC_FLAG_BUFC_METADATA); 2014 default: 2015 break; 2016 } 2017 panic("undefined ARC buffer type!"); 2018 return ((uint32_t)-1); 2019} 2020 2021void 2022arc_buf_thaw(arc_buf_t *buf) 2023{ 2024 arc_buf_hdr_t *hdr = buf->b_hdr; 2025 2026 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 2027 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 2028 2029 arc_cksum_verify(buf); 2030 2031 /* 2032 * Compressed buffers do not manipulate the b_freeze_cksum or 2033 * allocate b_thawed. 2034 */ 2035 if (ARC_BUF_COMPRESSED(buf)) { 2036 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2037 arc_hdr_has_uncompressed_buf(hdr)); 2038 return; 2039 } 2040 2041 ASSERT(HDR_HAS_L1HDR(hdr)); 2042 arc_cksum_free(hdr); 2043 2044 mutex_enter(&hdr->b_l1hdr.b_freeze_lock); 2045#ifdef ZFS_DEBUG 2046 if (zfs_flags & ZFS_DEBUG_MODIFY) { 2047 if (hdr->b_l1hdr.b_thawed != NULL) 2048 kmem_free(hdr->b_l1hdr.b_thawed, 1); 2049 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP); 2050 } 2051#endif 2052 2053 mutex_exit(&hdr->b_l1hdr.b_freeze_lock); 2054 2055#ifdef illumos 2056 arc_buf_unwatch(buf); 2057#endif 2058} 2059 2060void 2061arc_buf_freeze(arc_buf_t *buf) 2062{ 2063 arc_buf_hdr_t *hdr = buf->b_hdr; 2064 kmutex_t *hash_lock; 2065 2066 if (!(zfs_flags & ZFS_DEBUG_MODIFY)) 2067 return; 2068 2069 if (ARC_BUF_COMPRESSED(buf)) { 2070 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL || 2071 arc_hdr_has_uncompressed_buf(hdr)); 2072 return; 2073 } 2074 2075 hash_lock = HDR_LOCK(hdr); 2076 mutex_enter(hash_lock); 2077 2078 ASSERT(HDR_HAS_L1HDR(hdr)); 2079 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL || 2080 hdr->b_l1hdr.b_state == arc_anon); 2081 arc_cksum_compute(buf); 2082 mutex_exit(hash_lock); 2083} 2084 2085/* 2086 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead, 2087 * the following functions should be used to ensure that the flags are 2088 * updated in a thread-safe way. When manipulating the flags either 2089 * the hash_lock must be held or the hdr must be undiscoverable. This 2090 * ensures that we're not racing with any other threads when updating 2091 * the flags. 2092 */ 2093static inline void 2094arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2095{ 2096 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2097 hdr->b_flags |= flags; 2098} 2099 2100static inline void 2101arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags) 2102{ 2103 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2104 hdr->b_flags &= ~flags; 2105} 2106 2107/* 2108 * Setting the compression bits in the arc_buf_hdr_t's b_flags is 2109 * done in a special way since we have to clear and set bits 2110 * at the same time. Consumers that wish to set the compression bits 2111 * must use this function to ensure that the flags are updated in 2112 * thread-safe manner. 2113 */ 2114static void 2115arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp) 2116{ 2117 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2118 2119 /* 2120 * Holes and embedded blocks will always have a psize = 0 so 2121 * we ignore the compression of the blkptr and set the 2122 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF. 2123 * Holes and embedded blocks remain anonymous so we don't 2124 * want to uncompress them. Mark them as uncompressed. 2125 */ 2126 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) { 2127 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2128 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF); 2129 ASSERT(!HDR_COMPRESSION_ENABLED(hdr)); 2130 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 2131 } else { 2132 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC); 2133 HDR_SET_COMPRESS(hdr, cmp); 2134 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp); 2135 ASSERT(HDR_COMPRESSION_ENABLED(hdr)); 2136 } 2137} 2138 2139/* 2140 * Looks for another buf on the same hdr which has the data decompressed, copies 2141 * from it, and returns true. If no such buf exists, returns false. 2142 */ 2143static boolean_t 2144arc_buf_try_copy_decompressed_data(arc_buf_t *buf) 2145{ 2146 arc_buf_hdr_t *hdr = buf->b_hdr; 2147 boolean_t copied = B_FALSE; 2148 2149 ASSERT(HDR_HAS_L1HDR(hdr)); 2150 ASSERT3P(buf->b_data, !=, NULL); 2151 ASSERT(!ARC_BUF_COMPRESSED(buf)); 2152 2153 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL; 2154 from = from->b_next) { 2155 /* can't use our own data buffer */ 2156 if (from == buf) { 2157 continue; 2158 } 2159 2160 if (!ARC_BUF_COMPRESSED(from)) { 2161 bcopy(from->b_data, buf->b_data, arc_buf_size(buf)); 2162 copied = B_TRUE; 2163 break; 2164 } 2165 } 2166 2167 /* 2168 * There were no decompressed bufs, so there should not be a 2169 * checksum on the hdr either. 2170 */ 2171 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL); 2172 2173 return (copied); 2174} 2175 2176/* 2177 * Given a buf that has a data buffer attached to it, this function will 2178 * efficiently fill the buf with data of the specified compression setting from 2179 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr 2180 * are already sharing a data buf, no copy is performed. 2181 * 2182 * If the buf is marked as compressed but uncompressed data was requested, this 2183 * will allocate a new data buffer for the buf, remove that flag, and fill the 2184 * buf with uncompressed data. You can't request a compressed buf on a hdr with 2185 * uncompressed data, and (since we haven't added support for it yet) if you 2186 * want compressed data your buf must already be marked as compressed and have 2187 * the correct-sized data buffer. 2188 */ 2189static int 2190arc_buf_fill(arc_buf_t *buf, boolean_t compressed) 2191{ 2192 arc_buf_hdr_t *hdr = buf->b_hdr; 2193 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 2194 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap; 2195 2196 ASSERT3P(buf->b_data, !=, NULL); 2197 IMPLY(compressed, hdr_compressed); 2198 IMPLY(compressed, ARC_BUF_COMPRESSED(buf)); 2199 2200 if (hdr_compressed == compressed) { 2201 if (!arc_buf_is_shared(buf)) { 2202 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd, 2203 arc_buf_size(buf)); 2204 } 2205 } else { 2206 ASSERT(hdr_compressed); 2207 ASSERT(!compressed); 2208 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr)); 2209 2210 /* 2211 * If the buf is sharing its data with the hdr, unlink it and 2212 * allocate a new data buffer for the buf. 2213 */ 2214 if (arc_buf_is_shared(buf)) { 2215 ASSERT(ARC_BUF_COMPRESSED(buf)); 2216 2217 /* We need to give the buf it's own b_data */ 2218 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2219 buf->b_data = 2220 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2221 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2222 2223 /* Previously overhead was 0; just add new overhead */ 2224 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr)); 2225 } else if (ARC_BUF_COMPRESSED(buf)) { 2226 /* We need to reallocate the buf's b_data */ 2227 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr), 2228 buf); 2229 buf->b_data = 2230 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf); 2231 2232 /* We increased the size of b_data; update overhead */ 2233 ARCSTAT_INCR(arcstat_overhead_size, 2234 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr)); 2235 } 2236 2237 /* 2238 * Regardless of the buf's previous compression settings, it 2239 * should not be compressed at the end of this function. 2240 */ 2241 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED; 2242 2243 /* 2244 * Try copying the data from another buf which already has a 2245 * decompressed version. If that's not possible, it's time to 2246 * bite the bullet and decompress the data from the hdr. 2247 */ 2248 if (arc_buf_try_copy_decompressed_data(buf)) { 2249 /* Skip byteswapping and checksumming (already done) */ 2250 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL); 2251 return (0); 2252 } else { 2253 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr), 2254 hdr->b_l1hdr.b_pabd, buf->b_data, 2255 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2256 2257 /* 2258 * Absent hardware errors or software bugs, this should 2259 * be impossible, but log it anyway so we can debug it. 2260 */ 2261 if (error != 0) { 2262 zfs_dbgmsg( 2263 "hdr %p, compress %d, psize %d, lsize %d", 2264 hdr, HDR_GET_COMPRESS(hdr), 2265 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr)); 2266 return (SET_ERROR(EIO)); 2267 } 2268 } 2269 } 2270 2271 /* Byteswap the buf's data if necessary */ 2272 if (bswap != DMU_BSWAP_NUMFUNCS) { 2273 ASSERT(!HDR_SHARED_DATA(hdr)); 2274 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS); 2275 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr)); 2276 } 2277 2278 /* Compute the hdr's checksum if necessary */ 2279 arc_cksum_compute(buf); 2280 2281 return (0); 2282} 2283 2284int 2285arc_decompress(arc_buf_t *buf) 2286{ 2287 return (arc_buf_fill(buf, B_FALSE)); 2288} 2289 2290/* 2291 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t. 2292 */ 2293static uint64_t 2294arc_hdr_size(arc_buf_hdr_t *hdr) 2295{ 2296 uint64_t size; 2297 2298 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF && 2299 HDR_GET_PSIZE(hdr) > 0) { 2300 size = HDR_GET_PSIZE(hdr); 2301 } else { 2302 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0); 2303 size = HDR_GET_LSIZE(hdr); 2304 } 2305 return (size); 2306} 2307 2308/* 2309 * Increment the amount of evictable space in the arc_state_t's refcount. 2310 * We account for the space used by the hdr and the arc buf individually 2311 * so that we can add and remove them from the refcount individually. 2312 */ 2313static void 2314arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state) 2315{ 2316 arc_buf_contents_t type = arc_buf_type(hdr); 2317 2318 ASSERT(HDR_HAS_L1HDR(hdr)); 2319 2320 if (GHOST_STATE(state)) { 2321 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2322 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2323 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2324 (void) refcount_add_many(&state->arcs_esize[type], 2325 HDR_GET_LSIZE(hdr), hdr); 2326 return; 2327 } 2328 2329 ASSERT(!GHOST_STATE(state)); 2330 if (hdr->b_l1hdr.b_pabd != NULL) { 2331 (void) refcount_add_many(&state->arcs_esize[type], 2332 arc_hdr_size(hdr), hdr); 2333 } 2334 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2335 buf = buf->b_next) { 2336 if (arc_buf_is_shared(buf)) 2337 continue; 2338 (void) refcount_add_many(&state->arcs_esize[type], 2339 arc_buf_size(buf), buf); 2340 } 2341} 2342 2343/* 2344 * Decrement the amount of evictable space in the arc_state_t's refcount. 2345 * We account for the space used by the hdr and the arc buf individually 2346 * so that we can add and remove them from the refcount individually. 2347 */ 2348static void 2349arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state) 2350{ 2351 arc_buf_contents_t type = arc_buf_type(hdr); 2352 2353 ASSERT(HDR_HAS_L1HDR(hdr)); 2354 2355 if (GHOST_STATE(state)) { 2356 ASSERT0(hdr->b_l1hdr.b_bufcnt); 2357 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2358 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2359 (void) refcount_remove_many(&state->arcs_esize[type], 2360 HDR_GET_LSIZE(hdr), hdr); 2361 return; 2362 } 2363 2364 ASSERT(!GHOST_STATE(state)); 2365 if (hdr->b_l1hdr.b_pabd != NULL) { 2366 (void) refcount_remove_many(&state->arcs_esize[type], 2367 arc_hdr_size(hdr), hdr); 2368 } 2369 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2370 buf = buf->b_next) { 2371 if (arc_buf_is_shared(buf)) 2372 continue; 2373 (void) refcount_remove_many(&state->arcs_esize[type], 2374 arc_buf_size(buf), buf); 2375 } 2376} 2377 2378/* 2379 * Add a reference to this hdr indicating that someone is actively 2380 * referencing that memory. When the refcount transitions from 0 to 1, 2381 * we remove it from the respective arc_state_t list to indicate that 2382 * it is not evictable. 2383 */ 2384static void 2385add_reference(arc_buf_hdr_t *hdr, void *tag) 2386{ 2387 ASSERT(HDR_HAS_L1HDR(hdr)); 2388 if (!MUTEX_HELD(HDR_LOCK(hdr))) { 2389 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 2390 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2391 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2392 } 2393 2394 arc_state_t *state = hdr->b_l1hdr.b_state; 2395 2396 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) && 2397 (state != arc_anon)) { 2398 /* We don't use the L2-only state list. */ 2399 if (state != arc_l2c_only) { 2400 multilist_remove(state->arcs_list[arc_buf_type(hdr)], 2401 hdr); 2402 arc_evictable_space_decrement(hdr, state); 2403 } 2404 /* remove the prefetch flag if we get a reference */ 2405 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 2406 } 2407} 2408 2409/* 2410 * Remove a reference from this hdr. When the reference transitions from 2411 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's 2412 * list making it eligible for eviction. 2413 */ 2414static int 2415remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag) 2416{ 2417 int cnt; 2418 arc_state_t *state = hdr->b_l1hdr.b_state; 2419 2420 ASSERT(HDR_HAS_L1HDR(hdr)); 2421 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock)); 2422 ASSERT(!GHOST_STATE(state)); 2423 2424 /* 2425 * arc_l2c_only counts as a ghost state so we don't need to explicitly 2426 * check to prevent usage of the arc_l2c_only list. 2427 */ 2428 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) && 2429 (state != arc_anon)) { 2430 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr); 2431 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 2432 arc_evictable_space_increment(hdr, state); 2433 } 2434 return (cnt); 2435} 2436 2437/* 2438 * Move the supplied buffer to the indicated state. The hash lock 2439 * for the buffer must be held by the caller. 2440 */ 2441static void 2442arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr, 2443 kmutex_t *hash_lock) 2444{ 2445 arc_state_t *old_state; 2446 int64_t refcnt; 2447 uint32_t bufcnt; 2448 boolean_t update_old, update_new; 2449 arc_buf_contents_t buftype = arc_buf_type(hdr); 2450 2451 /* 2452 * We almost always have an L1 hdr here, since we call arc_hdr_realloc() 2453 * in arc_read() when bringing a buffer out of the L2ARC. However, the 2454 * L1 hdr doesn't always exist when we change state to arc_anon before 2455 * destroying a header, in which case reallocating to add the L1 hdr is 2456 * pointless. 2457 */ 2458 if (HDR_HAS_L1HDR(hdr)) { 2459 old_state = hdr->b_l1hdr.b_state; 2460 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt); 2461 bufcnt = hdr->b_l1hdr.b_bufcnt; 2462 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL); 2463 } else { 2464 old_state = arc_l2c_only; 2465 refcnt = 0; 2466 bufcnt = 0; 2467 update_old = B_FALSE; 2468 } 2469 update_new = update_old; 2470 2471 ASSERT(MUTEX_HELD(hash_lock)); 2472 ASSERT3P(new_state, !=, old_state); 2473 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0); 2474 ASSERT(old_state != arc_anon || bufcnt <= 1); 2475 2476 /* 2477 * If this buffer is evictable, transfer it from the 2478 * old state list to the new state list. 2479 */ 2480 if (refcnt == 0) { 2481 if (old_state != arc_anon && old_state != arc_l2c_only) { 2482 ASSERT(HDR_HAS_L1HDR(hdr)); 2483 multilist_remove(old_state->arcs_list[buftype], hdr); 2484 2485 if (GHOST_STATE(old_state)) { 2486 ASSERT0(bufcnt); 2487 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2488 update_old = B_TRUE; 2489 } 2490 arc_evictable_space_decrement(hdr, old_state); 2491 } 2492 if (new_state != arc_anon && new_state != arc_l2c_only) { 2493 2494 /* 2495 * An L1 header always exists here, since if we're 2496 * moving to some L1-cached state (i.e. not l2c_only or 2497 * anonymous), we realloc the header to add an L1hdr 2498 * beforehand. 2499 */ 2500 ASSERT(HDR_HAS_L1HDR(hdr)); 2501 multilist_insert(new_state->arcs_list[buftype], hdr); 2502 2503 if (GHOST_STATE(new_state)) { 2504 ASSERT0(bufcnt); 2505 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 2506 update_new = B_TRUE; 2507 } 2508 arc_evictable_space_increment(hdr, new_state); 2509 } 2510 } 2511 2512 ASSERT(!HDR_EMPTY(hdr)); 2513 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr)) 2514 buf_hash_remove(hdr); 2515 2516 /* adjust state sizes (ignore arc_l2c_only) */ 2517 2518 if (update_new && new_state != arc_l2c_only) { 2519 ASSERT(HDR_HAS_L1HDR(hdr)); 2520 if (GHOST_STATE(new_state)) { 2521 ASSERT0(bufcnt); 2522 2523 /* 2524 * When moving a header to a ghost state, we first 2525 * remove all arc buffers. Thus, we'll have a 2526 * bufcnt of zero, and no arc buffer to use for 2527 * the reference. As a result, we use the arc 2528 * header pointer for the reference. 2529 */ 2530 (void) refcount_add_many(&new_state->arcs_size, 2531 HDR_GET_LSIZE(hdr), hdr); 2532 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2533 } else { 2534 uint32_t buffers = 0; 2535 2536 /* 2537 * Each individual buffer holds a unique reference, 2538 * thus we must remove each of these references one 2539 * at a time. 2540 */ 2541 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2542 buf = buf->b_next) { 2543 ASSERT3U(bufcnt, !=, 0); 2544 buffers++; 2545 2546 /* 2547 * When the arc_buf_t is sharing the data 2548 * block with the hdr, the owner of the 2549 * reference belongs to the hdr. Only 2550 * add to the refcount if the arc_buf_t is 2551 * not shared. 2552 */ 2553 if (arc_buf_is_shared(buf)) 2554 continue; 2555 2556 (void) refcount_add_many(&new_state->arcs_size, 2557 arc_buf_size(buf), buf); 2558 } 2559 ASSERT3U(bufcnt, ==, buffers); 2560 2561 if (hdr->b_l1hdr.b_pabd != NULL) { 2562 (void) refcount_add_many(&new_state->arcs_size, 2563 arc_hdr_size(hdr), hdr); 2564 } else { 2565 ASSERT(GHOST_STATE(old_state)); 2566 } 2567 } 2568 } 2569 2570 if (update_old && old_state != arc_l2c_only) { 2571 ASSERT(HDR_HAS_L1HDR(hdr)); 2572 if (GHOST_STATE(old_state)) { 2573 ASSERT0(bufcnt); 2574 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2575 2576 /* 2577 * When moving a header off of a ghost state, 2578 * the header will not contain any arc buffers. 2579 * We use the arc header pointer for the reference 2580 * which is exactly what we did when we put the 2581 * header on the ghost state. 2582 */ 2583 2584 (void) refcount_remove_many(&old_state->arcs_size, 2585 HDR_GET_LSIZE(hdr), hdr); 2586 } else { 2587 uint32_t buffers = 0; 2588 2589 /* 2590 * Each individual buffer holds a unique reference, 2591 * thus we must remove each of these references one 2592 * at a time. 2593 */ 2594 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL; 2595 buf = buf->b_next) { 2596 ASSERT3U(bufcnt, !=, 0); 2597 buffers++; 2598 2599 /* 2600 * When the arc_buf_t is sharing the data 2601 * block with the hdr, the owner of the 2602 * reference belongs to the hdr. Only 2603 * add to the refcount if the arc_buf_t is 2604 * not shared. 2605 */ 2606 if (arc_buf_is_shared(buf)) 2607 continue; 2608 2609 (void) refcount_remove_many( 2610 &old_state->arcs_size, arc_buf_size(buf), 2611 buf); 2612 } 2613 ASSERT3U(bufcnt, ==, buffers); 2614 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2615 (void) refcount_remove_many( 2616 &old_state->arcs_size, arc_hdr_size(hdr), hdr); 2617 } 2618 } 2619 2620 if (HDR_HAS_L1HDR(hdr)) 2621 hdr->b_l1hdr.b_state = new_state; 2622 2623 /* 2624 * L2 headers should never be on the L2 state list since they don't 2625 * have L1 headers allocated. 2626 */ 2627 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) && 2628 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA])); 2629} 2630 2631void 2632arc_space_consume(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 ARCSTAT_INCR(arcstat_meta_used, space); 2656 2657 atomic_add_64(&arc_size, space); 2658} 2659 2660void 2661arc_space_return(uint64_t space, arc_space_type_t type) 2662{ 2663 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES); 2664 2665 switch (type) { 2666 case ARC_SPACE_DATA: 2667 ARCSTAT_INCR(arcstat_data_size, -space); 2668 break; 2669 case ARC_SPACE_META: 2670 ARCSTAT_INCR(arcstat_metadata_size, -space); 2671 break; 2672 case ARC_SPACE_OTHER: 2673 ARCSTAT_INCR(arcstat_other_size, -space); 2674 break; 2675 case ARC_SPACE_HDRS: 2676 ARCSTAT_INCR(arcstat_hdr_size, -space); 2677 break; 2678 case ARC_SPACE_L2HDRS: 2679 ARCSTAT_INCR(arcstat_l2_hdr_size, -space); 2680 break; 2681 } 2682 2683 if (type != ARC_SPACE_DATA) { 2684 ASSERT(arc_meta_used >= space); 2685 if (arc_meta_max < arc_meta_used) 2686 arc_meta_max = arc_meta_used; 2687 ARCSTAT_INCR(arcstat_meta_used, -space); 2688 } 2689 2690 ASSERT(arc_size >= space); 2691 atomic_add_64(&arc_size, -space); 2692} 2693 2694/* 2695 * Given a hdr and a buf, returns whether that buf can share its b_data buffer 2696 * with the hdr's b_pabd. 2697 */ 2698static boolean_t 2699arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2700{ 2701 /* 2702 * The criteria for sharing a hdr's data are: 2703 * 1. the hdr's compression matches the buf's compression 2704 * 2. the hdr doesn't need to be byteswapped 2705 * 3. the hdr isn't already being shared 2706 * 4. the buf is either compressed or it is the last buf in the hdr list 2707 * 2708 * Criterion #4 maintains the invariant that shared uncompressed 2709 * bufs must be the final buf in the hdr's b_buf list. Reading this, you 2710 * might ask, "if a compressed buf is allocated first, won't that be the 2711 * last thing in the list?", but in that case it's impossible to create 2712 * a shared uncompressed buf anyway (because the hdr must be compressed 2713 * to have the compressed buf). You might also think that #3 is 2714 * sufficient to make this guarantee, however it's possible 2715 * (specifically in the rare L2ARC write race mentioned in 2716 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that 2717 * is sharable, but wasn't at the time of its allocation. Rather than 2718 * allow a new shared uncompressed buf to be created and then shuffle 2719 * the list around to make it the last element, this simply disallows 2720 * sharing if the new buf isn't the first to be added. 2721 */ 2722 ASSERT3P(buf->b_hdr, ==, hdr); 2723 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF; 2724 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0; 2725 return (buf_compressed == hdr_compressed && 2726 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS && 2727 !HDR_SHARED_DATA(hdr) && 2728 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf))); 2729} 2730 2731/* 2732 * Allocate a buf for this hdr. If you care about the data that's in the hdr, 2733 * or if you want a compressed buffer, pass those flags in. Returns 0 if the 2734 * copy was made successfully, or an error code otherwise. 2735 */ 2736static int 2737arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed, 2738 boolean_t fill, arc_buf_t **ret) 2739{ 2740 arc_buf_t *buf; 2741 2742 ASSERT(HDR_HAS_L1HDR(hdr)); 2743 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 2744 VERIFY(hdr->b_type == ARC_BUFC_DATA || 2745 hdr->b_type == ARC_BUFC_METADATA); 2746 ASSERT3P(ret, !=, NULL); 2747 ASSERT3P(*ret, ==, NULL); 2748 2749 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE); 2750 buf->b_hdr = hdr; 2751 buf->b_data = NULL; 2752 buf->b_next = hdr->b_l1hdr.b_buf; 2753 buf->b_flags = 0; 2754 2755 add_reference(hdr, tag); 2756 2757 /* 2758 * We're about to change the hdr's b_flags. We must either 2759 * hold the hash_lock or be undiscoverable. 2760 */ 2761 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2762 2763 /* 2764 * Only honor requests for compressed bufs if the hdr is actually 2765 * compressed. 2766 */ 2767 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) 2768 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED; 2769 2770 /* 2771 * If the hdr's data can be shared then we share the data buffer and 2772 * set the appropriate bit in the hdr's b_flags to indicate the hdr is 2773 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new 2774 * buffer to store the buf's data. 2775 * 2776 * There are two additional restrictions here because we're sharing 2777 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be 2778 * actively involved in an L2ARC write, because if this buf is used by 2779 * an arc_write() then the hdr's data buffer will be released when the 2780 * write completes, even though the L2ARC write might still be using it. 2781 * Second, the hdr's ABD must be linear so that the buf's user doesn't 2782 * need to be ABD-aware. 2783 */ 2784 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) && 2785 abd_is_linear(hdr->b_l1hdr.b_pabd); 2786 2787 /* Set up b_data and sharing */ 2788 if (can_share) { 2789 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd); 2790 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2791 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2792 } else { 2793 buf->b_data = 2794 arc_get_data_buf(hdr, arc_buf_size(buf), buf); 2795 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2796 } 2797 VERIFY3P(buf->b_data, !=, NULL); 2798 2799 hdr->b_l1hdr.b_buf = buf; 2800 hdr->b_l1hdr.b_bufcnt += 1; 2801 2802 /* 2803 * If the user wants the data from the hdr, we need to either copy or 2804 * decompress the data. 2805 */ 2806 if (fill) { 2807 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0)); 2808 } 2809 2810 return (0); 2811} 2812 2813static char *arc_onloan_tag = "onloan"; 2814 2815static inline void 2816arc_loaned_bytes_update(int64_t delta) 2817{ 2818 atomic_add_64(&arc_loaned_bytes, delta); 2819 2820 /* assert that it did not wrap around */ 2821 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 2822} 2823 2824/* 2825 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in 2826 * flight data by arc_tempreserve_space() until they are "returned". Loaned 2827 * buffers must be returned to the arc before they can be used by the DMU or 2828 * freed. 2829 */ 2830arc_buf_t * 2831arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size) 2832{ 2833 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag, 2834 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size); 2835 2836 arc_loaned_bytes_update(size); 2837 2838 return (buf); 2839} 2840 2841arc_buf_t * 2842arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize, 2843 enum zio_compress compression_type) 2844{ 2845 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag, 2846 psize, lsize, compression_type); 2847 2848 arc_loaned_bytes_update(psize); 2849 2850 return (buf); 2851} 2852 2853 2854/* 2855 * Return a loaned arc buffer to the arc. 2856 */ 2857void 2858arc_return_buf(arc_buf_t *buf, void *tag) 2859{ 2860 arc_buf_hdr_t *hdr = buf->b_hdr; 2861 2862 ASSERT3P(buf->b_data, !=, NULL); 2863 ASSERT(HDR_HAS_L1HDR(hdr)); 2864 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag); 2865 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2866 2867 arc_loaned_bytes_update(-arc_buf_size(buf)); 2868} 2869 2870/* Detach an arc_buf from a dbuf (tag) */ 2871void 2872arc_loan_inuse_buf(arc_buf_t *buf, void *tag) 2873{ 2874 arc_buf_hdr_t *hdr = buf->b_hdr; 2875 2876 ASSERT3P(buf->b_data, !=, NULL); 2877 ASSERT(HDR_HAS_L1HDR(hdr)); 2878 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag); 2879 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag); 2880 2881 arc_loaned_bytes_update(arc_buf_size(buf)); 2882} 2883 2884static void 2885l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type) 2886{ 2887 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP); 2888 2889 df->l2df_abd = abd; 2890 df->l2df_size = size; 2891 df->l2df_type = type; 2892 mutex_enter(&l2arc_free_on_write_mtx); 2893 list_insert_head(l2arc_free_on_write, df); 2894 mutex_exit(&l2arc_free_on_write_mtx); 2895} 2896 2897static void 2898arc_hdr_free_on_write(arc_buf_hdr_t *hdr) 2899{ 2900 arc_state_t *state = hdr->b_l1hdr.b_state; 2901 arc_buf_contents_t type = arc_buf_type(hdr); 2902 uint64_t size = arc_hdr_size(hdr); 2903 2904 /* protected by hash lock, if in the hash table */ 2905 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 2906 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 2907 ASSERT(state != arc_anon && state != arc_l2c_only); 2908 2909 (void) refcount_remove_many(&state->arcs_esize[type], 2910 size, hdr); 2911 } 2912 (void) refcount_remove_many(&state->arcs_size, size, hdr); 2913 if (type == ARC_BUFC_METADATA) { 2914 arc_space_return(size, ARC_SPACE_META); 2915 } else { 2916 ASSERT(type == ARC_BUFC_DATA); 2917 arc_space_return(size, ARC_SPACE_DATA); 2918 } 2919 2920 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type); 2921} 2922 2923/* 2924 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the 2925 * data buffer, we transfer the refcount ownership to the hdr and update 2926 * the appropriate kstats. 2927 */ 2928static void 2929arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2930{ 2931 arc_state_t *state = hdr->b_l1hdr.b_state; 2932 2933 ASSERT(arc_can_share(hdr, buf)); 2934 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 2935 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2936 2937 /* 2938 * Start sharing the data buffer. We transfer the 2939 * refcount ownership to the hdr since it always owns 2940 * the refcount whenever an arc_buf_t is shared. 2941 */ 2942 refcount_transfer_ownership(&state->arcs_size, buf, hdr); 2943 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); 2944 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, 2945 HDR_ISTYPE_METADATA(hdr)); 2946 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA); 2947 buf->b_flags |= ARC_BUF_FLAG_SHARED; 2948 2949 /* 2950 * Since we've transferred ownership to the hdr we need 2951 * to increment its compressed and uncompressed kstats and 2952 * decrement the overhead size. 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 2959static void 2960arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2961{ 2962 arc_state_t *state = hdr->b_l1hdr.b_state; 2963 2964 ASSERT(arc_buf_is_shared(buf)); 2965 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 2966 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2967 2968 /* 2969 * We are no longer sharing this buffer so we need 2970 * to transfer its ownership to the rightful owner. 2971 */ 2972 refcount_transfer_ownership(&state->arcs_size, hdr, buf); 2973 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 2974 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); 2975 abd_put(hdr->b_l1hdr.b_pabd); 2976 hdr->b_l1hdr.b_pabd = NULL; 2977 buf->b_flags &= ~ARC_BUF_FLAG_SHARED; 2978 2979 /* 2980 * Since the buffer is no longer shared between 2981 * the arc buf and the hdr, count it as overhead. 2982 */ 2983 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 2984 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 2985 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf)); 2986} 2987 2988/* 2989 * Remove an arc_buf_t from the hdr's buf list and return the last 2990 * arc_buf_t on the list. If no buffers remain on the list then return 2991 * NULL. 2992 */ 2993static arc_buf_t * 2994arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf) 2995{ 2996 ASSERT(HDR_HAS_L1HDR(hdr)); 2997 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 2998 2999 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf; 3000 arc_buf_t *lastbuf = NULL; 3001 3002 /* 3003 * Remove the buf from the hdr list and locate the last 3004 * remaining buffer on the list. 3005 */ 3006 while (*bufp != NULL) { 3007 if (*bufp == buf) 3008 *bufp = buf->b_next; 3009 3010 /* 3011 * If we've removed a buffer in the middle of 3012 * the list then update the lastbuf and update 3013 * bufp. 3014 */ 3015 if (*bufp != NULL) { 3016 lastbuf = *bufp; 3017 bufp = &(*bufp)->b_next; 3018 } 3019 } 3020 buf->b_next = NULL; 3021 ASSERT3P(lastbuf, !=, buf); 3022 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL); 3023 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL); 3024 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf)); 3025 3026 return (lastbuf); 3027} 3028 3029/* 3030 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's 3031 * list and free it. 3032 */ 3033static void 3034arc_buf_destroy_impl(arc_buf_t *buf) 3035{ 3036 arc_buf_hdr_t *hdr = buf->b_hdr; 3037 3038 /* 3039 * Free up the data associated with the buf but only if we're not 3040 * sharing this with the hdr. If we are sharing it with the hdr, the 3041 * hdr is responsible for doing the free. 3042 */ 3043 if (buf->b_data != NULL) { 3044 /* 3045 * We're about to change the hdr's b_flags. We must either 3046 * hold the hash_lock or be undiscoverable. 3047 */ 3048 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr)); 3049 3050 arc_cksum_verify(buf); 3051#ifdef illumos 3052 arc_buf_unwatch(buf); 3053#endif 3054 3055 if (arc_buf_is_shared(buf)) { 3056 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); 3057 } else { 3058 uint64_t size = arc_buf_size(buf); 3059 arc_free_data_buf(hdr, buf->b_data, size, buf); 3060 ARCSTAT_INCR(arcstat_overhead_size, -size); 3061 } 3062 buf->b_data = NULL; 3063 3064 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3065 hdr->b_l1hdr.b_bufcnt -= 1; 3066 } 3067 3068 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 3069 3070 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) { 3071 /* 3072 * If the current arc_buf_t is sharing its data buffer with the 3073 * hdr, then reassign the hdr's b_pabd to share it with the new 3074 * buffer at the end of the list. The shared buffer is always 3075 * the last one on the hdr's buffer list. 3076 * 3077 * There is an equivalent case for compressed bufs, but since 3078 * they aren't guaranteed to be the last buf in the list and 3079 * that is an exceedingly rare case, we just allow that space be 3080 * wasted temporarily. 3081 */ 3082 if (lastbuf != NULL) { 3083 /* Only one buf can be shared at once */ 3084 VERIFY(!arc_buf_is_shared(lastbuf)); 3085 /* hdr is uncompressed so can't have compressed buf */ 3086 VERIFY(!ARC_BUF_COMPRESSED(lastbuf)); 3087 3088 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3089 arc_hdr_free_pabd(hdr); 3090 3091 /* 3092 * We must setup a new shared block between the 3093 * last buffer and the hdr. The data would have 3094 * been allocated by the arc buf so we need to transfer 3095 * ownership to the hdr since it's now being shared. 3096 */ 3097 arc_share_buf(hdr, lastbuf); 3098 } 3099 } else if (HDR_SHARED_DATA(hdr)) { 3100 /* 3101 * Uncompressed shared buffers are always at the end 3102 * of the list. Compressed buffers don't have the 3103 * same requirements. This makes it hard to 3104 * simply assert that the lastbuf is shared so 3105 * we rely on the hdr's compression flags to determine 3106 * if we have a compressed, shared buffer. 3107 */ 3108 ASSERT3P(lastbuf, !=, NULL); 3109 ASSERT(arc_buf_is_shared(lastbuf) || 3110 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 3111 } 3112 3113 /* 3114 * Free the checksum if we're removing the last uncompressed buf from 3115 * this hdr. 3116 */ 3117 if (!arc_hdr_has_uncompressed_buf(hdr)) { 3118 arc_cksum_free(hdr); 3119 } 3120 3121 /* clean up the buf */ 3122 buf->b_hdr = NULL; 3123 kmem_cache_free(buf_cache, buf); 3124} 3125 3126static void 3127arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr) 3128{ 3129 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0); 3130 ASSERT(HDR_HAS_L1HDR(hdr)); 3131 ASSERT(!HDR_SHARED_DATA(hdr)); 3132 3133 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3134 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr); 3135 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3136 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3137 3138 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr)); 3139 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr)); 3140} 3141 3142static void 3143arc_hdr_free_pabd(arc_buf_hdr_t *hdr) 3144{ 3145 ASSERT(HDR_HAS_L1HDR(hdr)); 3146 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 3147 3148 /* 3149 * If the hdr is currently being written to the l2arc then 3150 * we defer freeing the data by adding it to the l2arc_free_on_write 3151 * list. The l2arc will free the data once it's finished 3152 * writing it to the l2arc device. 3153 */ 3154 if (HDR_L2_WRITING(hdr)) { 3155 arc_hdr_free_on_write(hdr); 3156 ARCSTAT_BUMP(arcstat_l2_free_on_write); 3157 } else { 3158 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, 3159 arc_hdr_size(hdr), hdr); 3160 } 3161 hdr->b_l1hdr.b_pabd = NULL; 3162 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 3163 3164 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr)); 3165 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr)); 3166} 3167 3168static arc_buf_hdr_t * 3169arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize, 3170 enum zio_compress compression_type, arc_buf_contents_t type) 3171{ 3172 arc_buf_hdr_t *hdr; 3173 3174 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA); 3175 3176 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE); 3177 ASSERT(HDR_EMPTY(hdr)); 3178 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3179 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL); 3180 HDR_SET_PSIZE(hdr, psize); 3181 HDR_SET_LSIZE(hdr, lsize); 3182 hdr->b_spa = spa; 3183 hdr->b_type = type; 3184 hdr->b_flags = 0; 3185 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR); 3186 arc_hdr_set_compress(hdr, compression_type); 3187 3188 hdr->b_l1hdr.b_state = arc_anon; 3189 hdr->b_l1hdr.b_arc_access = 0; 3190 hdr->b_l1hdr.b_bufcnt = 0; 3191 hdr->b_l1hdr.b_buf = NULL; 3192 3193 /* 3194 * Allocate the hdr's buffer. This will contain either 3195 * the compressed or uncompressed data depending on the block 3196 * it references and compressed arc enablement. 3197 */ 3198 arc_hdr_alloc_pabd(hdr); 3199 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3200 3201 return (hdr); 3202} 3203 3204/* 3205 * Transition between the two allocation states for the arc_buf_hdr struct. 3206 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without 3207 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller 3208 * version is used when a cache buffer is only in the L2ARC in order to reduce 3209 * memory usage. 3210 */ 3211static arc_buf_hdr_t * 3212arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new) 3213{ 3214 ASSERT(HDR_HAS_L2HDR(hdr)); 3215 3216 arc_buf_hdr_t *nhdr; 3217 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3218 3219 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) || 3220 (old == hdr_l2only_cache && new == hdr_full_cache)); 3221 3222 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE); 3223 3224 ASSERT(MUTEX_HELD(HDR_LOCK(hdr))); 3225 buf_hash_remove(hdr); 3226 3227 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE); 3228 3229 if (new == hdr_full_cache) { 3230 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3231 /* 3232 * arc_access and arc_change_state need to be aware that a 3233 * header has just come out of L2ARC, so we set its state to 3234 * l2c_only even though it's about to change. 3235 */ 3236 nhdr->b_l1hdr.b_state = arc_l2c_only; 3237 3238 /* Verify previous threads set to NULL before freeing */ 3239 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL); 3240 } else { 3241 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3242 ASSERT0(hdr->b_l1hdr.b_bufcnt); 3243 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3244 3245 /* 3246 * If we've reached here, We must have been called from 3247 * arc_evict_hdr(), as such we should have already been 3248 * removed from any ghost list we were previously on 3249 * (which protects us from racing with arc_evict_state), 3250 * thus no locking is needed during this check. 3251 */ 3252 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3253 3254 /* 3255 * A buffer must not be moved into the arc_l2c_only 3256 * state if it's not finished being written out to the 3257 * l2arc device. Otherwise, the b_l1hdr.b_pabd field 3258 * might try to be accessed, even though it was removed. 3259 */ 3260 VERIFY(!HDR_L2_WRITING(hdr)); 3261 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3262 3263#ifdef ZFS_DEBUG 3264 if (hdr->b_l1hdr.b_thawed != NULL) { 3265 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3266 hdr->b_l1hdr.b_thawed = NULL; 3267 } 3268#endif 3269 3270 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR); 3271 } 3272 /* 3273 * The header has been reallocated so we need to re-insert it into any 3274 * lists it was on. 3275 */ 3276 (void) buf_hash_insert(nhdr, NULL); 3277 3278 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node)); 3279 3280 mutex_enter(&dev->l2ad_mtx); 3281 3282 /* 3283 * We must place the realloc'ed header back into the list at 3284 * the same spot. Otherwise, if it's placed earlier in the list, 3285 * l2arc_write_buffers() could find it during the function's 3286 * write phase, and try to write it out to the l2arc. 3287 */ 3288 list_insert_after(&dev->l2ad_buflist, hdr, nhdr); 3289 list_remove(&dev->l2ad_buflist, hdr); 3290 3291 mutex_exit(&dev->l2ad_mtx); 3292 3293 /* 3294 * Since we're using the pointer address as the tag when 3295 * incrementing and decrementing the l2ad_alloc refcount, we 3296 * must remove the old pointer (that we're about to destroy) and 3297 * add the new pointer to the refcount. Otherwise we'd remove 3298 * the wrong pointer address when calling arc_hdr_destroy() later. 3299 */ 3300 3301 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr); 3302 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr); 3303 3304 buf_discard_identity(hdr); 3305 kmem_cache_free(old, hdr); 3306 3307 return (nhdr); 3308} 3309 3310/* 3311 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller. 3312 * The buf is returned thawed since we expect the consumer to modify it. 3313 */ 3314arc_buf_t * 3315arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size) 3316{ 3317 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size, 3318 ZIO_COMPRESS_OFF, type); 3319 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3320 3321 arc_buf_t *buf = NULL; 3322 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf)); 3323 arc_buf_thaw(buf); 3324 3325 return (buf); 3326} 3327 3328/* 3329 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this 3330 * for bufs containing metadata. 3331 */ 3332arc_buf_t * 3333arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize, 3334 enum zio_compress compression_type) 3335{ 3336 ASSERT3U(lsize, >, 0); 3337 ASSERT3U(lsize, >=, psize); 3338 ASSERT(compression_type > ZIO_COMPRESS_OFF); 3339 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS); 3340 3341 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 3342 compression_type, ARC_BUFC_DATA); 3343 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr))); 3344 3345 arc_buf_t *buf = NULL; 3346 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf)); 3347 arc_buf_thaw(buf); 3348 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 3349 3350 if (!arc_buf_is_shared(buf)) { 3351 /* 3352 * To ensure that the hdr has the correct data in it if we call 3353 * arc_decompress() on this buf before it's been written to 3354 * disk, it's easiest if we just set up sharing between the 3355 * buf and the hdr. 3356 */ 3357 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd)); 3358 arc_hdr_free_pabd(hdr); 3359 arc_share_buf(hdr, buf); 3360 } 3361 3362 return (buf); 3363} 3364 3365static void 3366arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr) 3367{ 3368 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr; 3369 l2arc_dev_t *dev = l2hdr->b_dev; 3370 uint64_t psize = arc_hdr_size(hdr); 3371 3372 ASSERT(MUTEX_HELD(&dev->l2ad_mtx)); 3373 ASSERT(HDR_HAS_L2HDR(hdr)); 3374 3375 list_remove(&dev->l2ad_buflist, hdr); 3376 3377 ARCSTAT_INCR(arcstat_l2_psize, -psize); 3378 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 3379 3380 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0); 3381 3382 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr); 3383 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 3384} 3385 3386static void 3387arc_hdr_destroy(arc_buf_hdr_t *hdr) 3388{ 3389 if (HDR_HAS_L1HDR(hdr)) { 3390 ASSERT(hdr->b_l1hdr.b_buf == NULL || 3391 hdr->b_l1hdr.b_bufcnt > 0); 3392 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 3393 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 3394 } 3395 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3396 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 3397 3398 if (!HDR_EMPTY(hdr)) 3399 buf_discard_identity(hdr); 3400 3401 if (HDR_HAS_L2HDR(hdr)) { 3402 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev; 3403 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx); 3404 3405 if (!buflist_held) 3406 mutex_enter(&dev->l2ad_mtx); 3407 3408 /* 3409 * Even though we checked this conditional above, we 3410 * need to check this again now that we have the 3411 * l2ad_mtx. This is because we could be racing with 3412 * another thread calling l2arc_evict() which might have 3413 * destroyed this header's L2 portion as we were waiting 3414 * to acquire the l2ad_mtx. If that happens, we don't 3415 * want to re-destroy the header's L2 portion. 3416 */ 3417 if (HDR_HAS_L2HDR(hdr)) { 3418 l2arc_trim(hdr); 3419 arc_hdr_l2hdr_destroy(hdr); 3420 } 3421 3422 if (!buflist_held) 3423 mutex_exit(&dev->l2ad_mtx); 3424 } 3425 3426 if (HDR_HAS_L1HDR(hdr)) { 3427 arc_cksum_free(hdr); 3428 3429 while (hdr->b_l1hdr.b_buf != NULL) 3430 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf); 3431 3432#ifdef ZFS_DEBUG 3433 if (hdr->b_l1hdr.b_thawed != NULL) { 3434 kmem_free(hdr->b_l1hdr.b_thawed, 1); 3435 hdr->b_l1hdr.b_thawed = NULL; 3436 } 3437#endif 3438 3439 if (hdr->b_l1hdr.b_pabd != NULL) { 3440 arc_hdr_free_pabd(hdr); 3441 } 3442 } 3443 3444 ASSERT3P(hdr->b_hash_next, ==, NULL); 3445 if (HDR_HAS_L1HDR(hdr)) { 3446 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 3447 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 3448 kmem_cache_free(hdr_full_cache, hdr); 3449 } else { 3450 kmem_cache_free(hdr_l2only_cache, hdr); 3451 } 3452} 3453 3454void 3455arc_buf_destroy(arc_buf_t *buf, void* tag) 3456{ 3457 arc_buf_hdr_t *hdr = buf->b_hdr; 3458 kmutex_t *hash_lock = HDR_LOCK(hdr); 3459 3460 if (hdr->b_l1hdr.b_state == arc_anon) { 3461 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 3462 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3463 VERIFY0(remove_reference(hdr, NULL, tag)); 3464 arc_hdr_destroy(hdr); 3465 return; 3466 } 3467 3468 mutex_enter(hash_lock); 3469 ASSERT3P(hdr, ==, buf->b_hdr); 3470 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 3471 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 3472 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon); 3473 ASSERT3P(buf->b_data, !=, NULL); 3474 3475 (void) remove_reference(hdr, hash_lock, tag); 3476 arc_buf_destroy_impl(buf); 3477 mutex_exit(hash_lock); 3478} 3479 3480/* 3481 * Evict the arc_buf_hdr that is provided as a parameter. The resultant 3482 * state of the header is dependent on it's state prior to entering this 3483 * function. The following transitions are possible: 3484 * 3485 * - arc_mru -> arc_mru_ghost 3486 * - arc_mfu -> arc_mfu_ghost 3487 * - arc_mru_ghost -> arc_l2c_only 3488 * - arc_mru_ghost -> deleted 3489 * - arc_mfu_ghost -> arc_l2c_only 3490 * - arc_mfu_ghost -> deleted 3491 */ 3492static int64_t 3493arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 3494{ 3495 arc_state_t *evicted_state, *state; 3496 int64_t bytes_evicted = 0; 3497 3498 ASSERT(MUTEX_HELD(hash_lock)); 3499 ASSERT(HDR_HAS_L1HDR(hdr)); 3500 3501 state = hdr->b_l1hdr.b_state; 3502 if (GHOST_STATE(state)) { 3503 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 3504 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 3505 3506 /* 3507 * l2arc_write_buffers() relies on a header's L1 portion 3508 * (i.e. its b_pabd field) during it's write phase. 3509 * Thus, we cannot push a header onto the arc_l2c_only 3510 * state (removing it's L1 piece) until the header is 3511 * done being written to the l2arc. 3512 */ 3513 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) { 3514 ARCSTAT_BUMP(arcstat_evict_l2_skip); 3515 return (bytes_evicted); 3516 } 3517 3518 ARCSTAT_BUMP(arcstat_deleted); 3519 bytes_evicted += HDR_GET_LSIZE(hdr); 3520 3521 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr); 3522 3523 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 3524 if (HDR_HAS_L2HDR(hdr)) { 3525 /* 3526 * This buffer is cached on the 2nd Level ARC; 3527 * don't destroy the header. 3528 */ 3529 arc_change_state(arc_l2c_only, hdr, hash_lock); 3530 /* 3531 * dropping from L1+L2 cached to L2-only, 3532 * realloc to remove the L1 header. 3533 */ 3534 hdr = arc_hdr_realloc(hdr, hdr_full_cache, 3535 hdr_l2only_cache); 3536 } else { 3537 arc_change_state(arc_anon, hdr, hash_lock); 3538 arc_hdr_destroy(hdr); 3539 } 3540 return (bytes_evicted); 3541 } 3542 3543 ASSERT(state == arc_mru || state == arc_mfu); 3544 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost; 3545 3546 /* prefetch buffers have a minimum lifespan */ 3547 if (HDR_IO_IN_PROGRESS(hdr) || 3548 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) && 3549 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < 3550 arc_min_prefetch_lifespan)) { 3551 ARCSTAT_BUMP(arcstat_evict_skip); 3552 return (bytes_evicted); 3553 } 3554 3555 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 3556 while (hdr->b_l1hdr.b_buf) { 3557 arc_buf_t *buf = hdr->b_l1hdr.b_buf; 3558 if (!mutex_tryenter(&buf->b_evict_lock)) { 3559 ARCSTAT_BUMP(arcstat_mutex_miss); 3560 break; 3561 } 3562 if (buf->b_data != NULL) 3563 bytes_evicted += HDR_GET_LSIZE(hdr); 3564 mutex_exit(&buf->b_evict_lock); 3565 arc_buf_destroy_impl(buf); 3566 } 3567 3568 if (HDR_HAS_L2HDR(hdr)) { 3569 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr)); 3570 } else { 3571 if (l2arc_write_eligible(hdr->b_spa, hdr)) { 3572 ARCSTAT_INCR(arcstat_evict_l2_eligible, 3573 HDR_GET_LSIZE(hdr)); 3574 } else { 3575 ARCSTAT_INCR(arcstat_evict_l2_ineligible, 3576 HDR_GET_LSIZE(hdr)); 3577 } 3578 } 3579 3580 if (hdr->b_l1hdr.b_bufcnt == 0) { 3581 arc_cksum_free(hdr); 3582 3583 bytes_evicted += arc_hdr_size(hdr); 3584 3585 /* 3586 * If this hdr is being evicted and has a compressed 3587 * buffer then we discard it here before we change states. 3588 * This ensures that the accounting is updated correctly 3589 * in arc_free_data_impl(). 3590 */ 3591 arc_hdr_free_pabd(hdr); 3592 3593 arc_change_state(evicted_state, hdr, hash_lock); 3594 ASSERT(HDR_IN_HASH_TABLE(hdr)); 3595 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE); 3596 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr); 3597 } 3598 3599 return (bytes_evicted); 3600} 3601 3602static uint64_t 3603arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker, 3604 uint64_t spa, int64_t bytes) 3605{ 3606 multilist_sublist_t *mls; 3607 uint64_t bytes_evicted = 0; 3608 arc_buf_hdr_t *hdr; 3609 kmutex_t *hash_lock; 3610 int evict_count = 0; 3611 3612 ASSERT3P(marker, !=, NULL); 3613 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3614 3615 mls = multilist_sublist_lock(ml, idx); 3616 3617 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL; 3618 hdr = multilist_sublist_prev(mls, marker)) { 3619 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) || 3620 (evict_count >= zfs_arc_evict_batch_limit)) 3621 break; 3622 3623 /* 3624 * To keep our iteration location, move the marker 3625 * forward. Since we're not holding hdr's hash lock, we 3626 * must be very careful and not remove 'hdr' from the 3627 * sublist. Otherwise, other consumers might mistake the 3628 * 'hdr' as not being on a sublist when they call the 3629 * multilist_link_active() function (they all rely on 3630 * the hash lock protecting concurrent insertions and 3631 * removals). multilist_sublist_move_forward() was 3632 * specifically implemented to ensure this is the case 3633 * (only 'marker' will be removed and re-inserted). 3634 */ 3635 multilist_sublist_move_forward(mls, marker); 3636 3637 /* 3638 * The only case where the b_spa field should ever be 3639 * zero, is the marker headers inserted by 3640 * arc_evict_state(). It's possible for multiple threads 3641 * to be calling arc_evict_state() concurrently (e.g. 3642 * dsl_pool_close() and zio_inject_fault()), so we must 3643 * skip any markers we see from these other threads. 3644 */ 3645 if (hdr->b_spa == 0) 3646 continue; 3647 3648 /* we're only interested in evicting buffers of a certain spa */ 3649 if (spa != 0 && hdr->b_spa != spa) { 3650 ARCSTAT_BUMP(arcstat_evict_skip); 3651 continue; 3652 } 3653 3654 hash_lock = HDR_LOCK(hdr); 3655 3656 /* 3657 * We aren't calling this function from any code path 3658 * that would already be holding a hash lock, so we're 3659 * asserting on this assumption to be defensive in case 3660 * this ever changes. Without this check, it would be 3661 * possible to incorrectly increment arcstat_mutex_miss 3662 * below (e.g. if the code changed such that we called 3663 * this function with a hash lock held). 3664 */ 3665 ASSERT(!MUTEX_HELD(hash_lock)); 3666 3667 if (mutex_tryenter(hash_lock)) { 3668 uint64_t evicted = arc_evict_hdr(hdr, hash_lock); 3669 mutex_exit(hash_lock); 3670 3671 bytes_evicted += evicted; 3672 3673 /* 3674 * If evicted is zero, arc_evict_hdr() must have 3675 * decided to skip this header, don't increment 3676 * evict_count in this case. 3677 */ 3678 if (evicted != 0) 3679 evict_count++; 3680 3681 /* 3682 * If arc_size isn't overflowing, signal any 3683 * threads that might happen to be waiting. 3684 * 3685 * For each header evicted, we wake up a single 3686 * thread. If we used cv_broadcast, we could 3687 * wake up "too many" threads causing arc_size 3688 * to significantly overflow arc_c; since 3689 * arc_get_data_impl() doesn't check for overflow 3690 * when it's woken up (it doesn't because it's 3691 * possible for the ARC to be overflowing while 3692 * full of un-evictable buffers, and the 3693 * function should proceed in this case). 3694 * 3695 * If threads are left sleeping, due to not 3696 * using cv_broadcast, they will be woken up 3697 * just before arc_reclaim_thread() sleeps. 3698 */ 3699 mutex_enter(&arc_reclaim_lock); 3700 if (!arc_is_overflowing()) 3701 cv_signal(&arc_reclaim_waiters_cv); 3702 mutex_exit(&arc_reclaim_lock); 3703 } else { 3704 ARCSTAT_BUMP(arcstat_mutex_miss); 3705 } 3706 } 3707 3708 multilist_sublist_unlock(mls); 3709 3710 return (bytes_evicted); 3711} 3712 3713/* 3714 * Evict buffers from the given arc state, until we've removed the 3715 * specified number of bytes. Move the removed buffers to the 3716 * appropriate evict state. 3717 * 3718 * This function makes a "best effort". It skips over any buffers 3719 * it can't get a hash_lock on, and so, may not catch all candidates. 3720 * It may also return without evicting as much space as requested. 3721 * 3722 * If bytes is specified using the special value ARC_EVICT_ALL, this 3723 * will evict all available (i.e. unlocked and evictable) buffers from 3724 * the given arc state; which is used by arc_flush(). 3725 */ 3726static uint64_t 3727arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes, 3728 arc_buf_contents_t type) 3729{ 3730 uint64_t total_evicted = 0; 3731 multilist_t *ml = state->arcs_list[type]; 3732 int num_sublists; 3733 arc_buf_hdr_t **markers; 3734 3735 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL); 3736 3737 num_sublists = multilist_get_num_sublists(ml); 3738 3739 /* 3740 * If we've tried to evict from each sublist, made some 3741 * progress, but still have not hit the target number of bytes 3742 * to evict, we want to keep trying. The markers allow us to 3743 * pick up where we left off for each individual sublist, rather 3744 * than starting from the tail each time. 3745 */ 3746 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP); 3747 for (int i = 0; i < num_sublists; i++) { 3748 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP); 3749 3750 /* 3751 * A b_spa of 0 is used to indicate that this header is 3752 * a marker. This fact is used in arc_adjust_type() and 3753 * arc_evict_state_impl(). 3754 */ 3755 markers[i]->b_spa = 0; 3756 3757 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3758 multilist_sublist_insert_tail(mls, markers[i]); 3759 multilist_sublist_unlock(mls); 3760 } 3761 3762 /* 3763 * While we haven't hit our target number of bytes to evict, or 3764 * we're evicting all available buffers. 3765 */ 3766 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) { 3767 /* 3768 * Start eviction using a randomly selected sublist, 3769 * this is to try and evenly balance eviction across all 3770 * sublists. Always starting at the same sublist 3771 * (e.g. index 0) would cause evictions to favor certain 3772 * sublists over others. 3773 */ 3774 int sublist_idx = multilist_get_random_index(ml); 3775 uint64_t scan_evicted = 0; 3776 3777 for (int i = 0; i < num_sublists; i++) { 3778 uint64_t bytes_remaining; 3779 uint64_t bytes_evicted; 3780 3781 if (bytes == ARC_EVICT_ALL) 3782 bytes_remaining = ARC_EVICT_ALL; 3783 else if (total_evicted < bytes) 3784 bytes_remaining = bytes - total_evicted; 3785 else 3786 break; 3787 3788 bytes_evicted = arc_evict_state_impl(ml, sublist_idx, 3789 markers[sublist_idx], spa, bytes_remaining); 3790 3791 scan_evicted += bytes_evicted; 3792 total_evicted += bytes_evicted; 3793 3794 /* we've reached the end, wrap to the beginning */ 3795 if (++sublist_idx >= num_sublists) 3796 sublist_idx = 0; 3797 } 3798 3799 /* 3800 * If we didn't evict anything during this scan, we have 3801 * no reason to believe we'll evict more during another 3802 * scan, so break the loop. 3803 */ 3804 if (scan_evicted == 0) { 3805 /* This isn't possible, let's make that obvious */ 3806 ASSERT3S(bytes, !=, 0); 3807 3808 /* 3809 * When bytes is ARC_EVICT_ALL, the only way to 3810 * break the loop is when scan_evicted is zero. 3811 * In that case, we actually have evicted enough, 3812 * so we don't want to increment the kstat. 3813 */ 3814 if (bytes != ARC_EVICT_ALL) { 3815 ASSERT3S(total_evicted, <, bytes); 3816 ARCSTAT_BUMP(arcstat_evict_not_enough); 3817 } 3818 3819 break; 3820 } 3821 } 3822 3823 for (int i = 0; i < num_sublists; i++) { 3824 multilist_sublist_t *mls = multilist_sublist_lock(ml, i); 3825 multilist_sublist_remove(mls, markers[i]); 3826 multilist_sublist_unlock(mls); 3827 3828 kmem_cache_free(hdr_full_cache, markers[i]); 3829 } 3830 kmem_free(markers, sizeof (*markers) * num_sublists); 3831 3832 return (total_evicted); 3833} 3834 3835/* 3836 * Flush all "evictable" data of the given type from the arc state 3837 * specified. This will not evict any "active" buffers (i.e. referenced). 3838 * 3839 * When 'retry' is set to B_FALSE, the function will make a single pass 3840 * over the state and evict any buffers that it can. Since it doesn't 3841 * continually retry the eviction, it might end up leaving some buffers 3842 * in the ARC due to lock misses. 3843 * 3844 * When 'retry' is set to B_TRUE, the function will continually retry the 3845 * eviction until *all* evictable buffers have been removed from the 3846 * state. As a result, if concurrent insertions into the state are 3847 * allowed (e.g. if the ARC isn't shutting down), this function might 3848 * wind up in an infinite loop, continually trying to evict buffers. 3849 */ 3850static uint64_t 3851arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type, 3852 boolean_t retry) 3853{ 3854 uint64_t evicted = 0; 3855 3856 while (refcount_count(&state->arcs_esize[type]) != 0) { 3857 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type); 3858 3859 if (!retry) 3860 break; 3861 } 3862 3863 return (evicted); 3864} 3865 3866/* 3867 * Evict the specified number of bytes from the state specified, 3868 * restricting eviction to the spa and type given. This function 3869 * prevents us from trying to evict more from a state's list than 3870 * is "evictable", and to skip evicting altogether when passed a 3871 * negative value for "bytes". In contrast, arc_evict_state() will 3872 * evict everything it can, when passed a negative value for "bytes". 3873 */ 3874static uint64_t 3875arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes, 3876 arc_buf_contents_t type) 3877{ 3878 int64_t delta; 3879 3880 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) { 3881 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes); 3882 return (arc_evict_state(state, spa, delta, type)); 3883 } 3884 3885 return (0); 3886} 3887 3888/* 3889 * Evict metadata buffers from the cache, such that arc_meta_used is 3890 * capped by the arc_meta_limit tunable. 3891 */ 3892static uint64_t 3893arc_adjust_meta(void) 3894{ 3895 uint64_t total_evicted = 0; 3896 int64_t target; 3897 3898 /* 3899 * If we're over the meta limit, we want to evict enough 3900 * metadata to get back under the meta limit. We don't want to 3901 * evict so much that we drop the MRU below arc_p, though. If 3902 * we're over the meta limit more than we're over arc_p, we 3903 * evict some from the MRU here, and some from the MFU below. 3904 */ 3905 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3906 (int64_t)(refcount_count(&arc_anon->arcs_size) + 3907 refcount_count(&arc_mru->arcs_size) - arc_p)); 3908 3909 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 3910 3911 /* 3912 * Similar to the above, we want to evict enough bytes to get us 3913 * below the meta limit, but not so much as to drop us below the 3914 * space allotted to the MFU (which is defined as arc_c - arc_p). 3915 */ 3916 target = MIN((int64_t)(arc_meta_used - arc_meta_limit), 3917 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p))); 3918 3919 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 3920 3921 return (total_evicted); 3922} 3923 3924/* 3925 * Return the type of the oldest buffer in the given arc state 3926 * 3927 * This function will select a random sublist of type ARC_BUFC_DATA and 3928 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist 3929 * is compared, and the type which contains the "older" buffer will be 3930 * returned. 3931 */ 3932static arc_buf_contents_t 3933arc_adjust_type(arc_state_t *state) 3934{ 3935 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA]; 3936 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA]; 3937 int data_idx = multilist_get_random_index(data_ml); 3938 int meta_idx = multilist_get_random_index(meta_ml); 3939 multilist_sublist_t *data_mls; 3940 multilist_sublist_t *meta_mls; 3941 arc_buf_contents_t type; 3942 arc_buf_hdr_t *data_hdr; 3943 arc_buf_hdr_t *meta_hdr; 3944 3945 /* 3946 * We keep the sublist lock until we're finished, to prevent 3947 * the headers from being destroyed via arc_evict_state(). 3948 */ 3949 data_mls = multilist_sublist_lock(data_ml, data_idx); 3950 meta_mls = multilist_sublist_lock(meta_ml, meta_idx); 3951 3952 /* 3953 * These two loops are to ensure we skip any markers that 3954 * might be at the tail of the lists due to arc_evict_state(). 3955 */ 3956 3957 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL; 3958 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) { 3959 if (data_hdr->b_spa != 0) 3960 break; 3961 } 3962 3963 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL; 3964 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) { 3965 if (meta_hdr->b_spa != 0) 3966 break; 3967 } 3968 3969 if (data_hdr == NULL && meta_hdr == NULL) { 3970 type = ARC_BUFC_DATA; 3971 } else if (data_hdr == NULL) { 3972 ASSERT3P(meta_hdr, !=, NULL); 3973 type = ARC_BUFC_METADATA; 3974 } else if (meta_hdr == NULL) { 3975 ASSERT3P(data_hdr, !=, NULL); 3976 type = ARC_BUFC_DATA; 3977 } else { 3978 ASSERT3P(data_hdr, !=, NULL); 3979 ASSERT3P(meta_hdr, !=, NULL); 3980 3981 /* The headers can't be on the sublist without an L1 header */ 3982 ASSERT(HDR_HAS_L1HDR(data_hdr)); 3983 ASSERT(HDR_HAS_L1HDR(meta_hdr)); 3984 3985 if (data_hdr->b_l1hdr.b_arc_access < 3986 meta_hdr->b_l1hdr.b_arc_access) { 3987 type = ARC_BUFC_DATA; 3988 } else { 3989 type = ARC_BUFC_METADATA; 3990 } 3991 } 3992 3993 multilist_sublist_unlock(meta_mls); 3994 multilist_sublist_unlock(data_mls); 3995 3996 return (type); 3997} 3998 3999/* 4000 * Evict buffers from the cache, such that arc_size is capped by arc_c. 4001 */ 4002static uint64_t 4003arc_adjust(void) 4004{ 4005 uint64_t total_evicted = 0; 4006 uint64_t bytes; 4007 int64_t target; 4008 4009 /* 4010 * If we're over arc_meta_limit, we want to correct that before 4011 * potentially evicting data buffers below. 4012 */ 4013 total_evicted += arc_adjust_meta(); 4014 4015 /* 4016 * Adjust MRU size 4017 * 4018 * If we're over the target cache size, we want to evict enough 4019 * from the list to get back to our target size. We don't want 4020 * to evict too much from the MRU, such that it drops below 4021 * arc_p. So, if we're over our target cache size more than 4022 * the MRU is over arc_p, we'll evict enough to get back to 4023 * arc_p here, and then evict more from the MFU below. 4024 */ 4025 target = MIN((int64_t)(arc_size - arc_c), 4026 (int64_t)(refcount_count(&arc_anon->arcs_size) + 4027 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p)); 4028 4029 /* 4030 * If we're below arc_meta_min, always prefer to evict data. 4031 * Otherwise, try to satisfy the requested number of bytes to 4032 * evict from the type which contains older buffers; in an 4033 * effort to keep newer buffers in the cache regardless of their 4034 * type. If we cannot satisfy the number of bytes from this 4035 * type, spill over into the next type. 4036 */ 4037 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA && 4038 arc_meta_used > arc_meta_min) { 4039 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4040 total_evicted += bytes; 4041 4042 /* 4043 * If we couldn't evict our target number of bytes from 4044 * metadata, we try to get the rest from data. 4045 */ 4046 target -= bytes; 4047 4048 total_evicted += 4049 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4050 } else { 4051 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA); 4052 total_evicted += bytes; 4053 4054 /* 4055 * If we couldn't evict our target number of bytes from 4056 * data, we try to get the rest from metadata. 4057 */ 4058 target -= bytes; 4059 4060 total_evicted += 4061 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA); 4062 } 4063 4064 /* 4065 * Adjust MFU size 4066 * 4067 * Now that we've tried to evict enough from the MRU to get its 4068 * size back to arc_p, if we're still above the target cache 4069 * size, we evict the rest from the MFU. 4070 */ 4071 target = arc_size - arc_c; 4072 4073 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA && 4074 arc_meta_used > arc_meta_min) { 4075 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4076 total_evicted += bytes; 4077 4078 /* 4079 * If we couldn't evict our target number of bytes from 4080 * metadata, we try to get the rest from data. 4081 */ 4082 target -= bytes; 4083 4084 total_evicted += 4085 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4086 } else { 4087 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA); 4088 total_evicted += bytes; 4089 4090 /* 4091 * If we couldn't evict our target number of bytes from 4092 * data, we try to get the rest from data. 4093 */ 4094 target -= bytes; 4095 4096 total_evicted += 4097 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA); 4098 } 4099 4100 /* 4101 * Adjust ghost lists 4102 * 4103 * In addition to the above, the ARC also defines target values 4104 * for the ghost lists. The sum of the mru list and mru ghost 4105 * list should never exceed the target size of the cache, and 4106 * the sum of the mru list, mfu list, mru ghost list, and mfu 4107 * ghost list should never exceed twice the target size of the 4108 * cache. The following logic enforces these limits on the ghost 4109 * caches, and evicts from them as needed. 4110 */ 4111 target = refcount_count(&arc_mru->arcs_size) + 4112 refcount_count(&arc_mru_ghost->arcs_size) - arc_c; 4113 4114 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA); 4115 total_evicted += bytes; 4116 4117 target -= bytes; 4118 4119 total_evicted += 4120 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA); 4121 4122 /* 4123 * We assume the sum of the mru list and mfu list is less than 4124 * or equal to arc_c (we enforced this above), which means we 4125 * can use the simpler of the two equations below: 4126 * 4127 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c 4128 * mru ghost + mfu ghost <= arc_c 4129 */ 4130 target = refcount_count(&arc_mru_ghost->arcs_size) + 4131 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c; 4132 4133 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA); 4134 total_evicted += bytes; 4135 4136 target -= bytes; 4137 4138 total_evicted += 4139 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA); 4140 4141 return (total_evicted); 4142} 4143 4144void 4145arc_flush(spa_t *spa, boolean_t retry) 4146{ 4147 uint64_t guid = 0; 4148 4149 /* 4150 * If retry is B_TRUE, a spa must not be specified since we have 4151 * no good way to determine if all of a spa's buffers have been 4152 * evicted from an arc state. 4153 */ 4154 ASSERT(!retry || spa == 0); 4155 4156 if (spa != NULL) 4157 guid = spa_load_guid(spa); 4158 4159 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry); 4160 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry); 4161 4162 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry); 4163 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry); 4164 4165 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry); 4166 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry); 4167 4168 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry); 4169 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry); 4170} 4171 4172void 4173arc_shrink(int64_t to_free) 4174{ 4175 if (arc_c > arc_c_min) { 4176 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t, 4177 arc_c_min, uint64_t, arc_p, uint64_t, to_free); 4178 if (arc_c > arc_c_min + to_free) 4179 atomic_add_64(&arc_c, -to_free); 4180 else 4181 arc_c = arc_c_min; 4182 4183 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift)); 4184 if (arc_c > arc_size) 4185 arc_c = MAX(arc_size, arc_c_min); 4186 if (arc_p > arc_c) 4187 arc_p = (arc_c >> 1); 4188 4189 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t, 4190 arc_p); 4191 4192 ASSERT(arc_c >= arc_c_min); 4193 ASSERT((int64_t)arc_p >= 0); 4194 } 4195 4196 if (arc_size > arc_c) { 4197 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size, 4198 uint64_t, arc_c); 4199 (void) arc_adjust(); 4200 } 4201} 4202 4203typedef enum free_memory_reason_t { 4204 FMR_UNKNOWN, 4205 FMR_NEEDFREE, 4206 FMR_LOTSFREE, 4207 FMR_SWAPFS_MINFREE, 4208 FMR_PAGES_PP_MAXIMUM, 4209 FMR_HEAP_ARENA, 4210 FMR_ZIO_ARENA, 4211 FMR_ZIO_FRAG, 4212} free_memory_reason_t; 4213 4214int64_t last_free_memory; 4215free_memory_reason_t last_free_reason; 4216 4217/* 4218 * Additional reserve of pages for pp_reserve. 4219 */ 4220int64_t arc_pages_pp_reserve = 64; 4221 4222/* 4223 * Additional reserve of pages for swapfs. 4224 */ 4225int64_t arc_swapfs_reserve = 64; 4226 4227/* 4228 * Return the amount of memory that can be consumed before reclaim will be 4229 * needed. Positive if there is sufficient free memory, negative indicates 4230 * the amount of memory that needs to be freed up. 4231 */ 4232static int64_t 4233arc_available_memory(void) 4234{ 4235 int64_t lowest = INT64_MAX; 4236 int64_t n; 4237 free_memory_reason_t r = FMR_UNKNOWN; 4238 4239#ifdef _KERNEL 4240 /* 4241 * Cooperate with pagedaemon when it's time for it to scan 4242 * and reclaim some pages. 4243 */ 4244 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target); 4245 if (n < lowest) { 4246 lowest = n; 4247 r = FMR_LOTSFREE; 4248 } 4249 4250#ifdef illumos 4251 /* 4252 * check that we're out of range of the pageout scanner. It starts to 4253 * schedule paging if freemem is less than lotsfree and needfree. 4254 * lotsfree is the high-water mark for pageout, and needfree is the 4255 * number of needed free pages. We add extra pages here to make sure 4256 * the scanner doesn't start up while we're freeing memory. 4257 */ 4258 n = PAGESIZE * (freemem - lotsfree - needfree - desfree); 4259 if (n < lowest) { 4260 lowest = n; 4261 r = FMR_LOTSFREE; 4262 } 4263 4264 /* 4265 * check to make sure that swapfs has enough space so that anon 4266 * reservations can still succeed. anon_resvmem() checks that the 4267 * availrmem is greater than swapfs_minfree, and the number of reserved 4268 * swap pages. We also add a bit of extra here just to prevent 4269 * circumstances from getting really dire. 4270 */ 4271 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve - 4272 desfree - arc_swapfs_reserve); 4273 if (n < lowest) { 4274 lowest = n; 4275 r = FMR_SWAPFS_MINFREE; 4276 } 4277 4278 4279 /* 4280 * Check that we have enough availrmem that memory locking (e.g., via 4281 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum 4282 * stores the number of pages that cannot be locked; when availrmem 4283 * drops below pages_pp_maximum, page locking mechanisms such as 4284 * page_pp_lock() will fail.) 4285 */ 4286 n = PAGESIZE * (availrmem - pages_pp_maximum - 4287 arc_pages_pp_reserve); 4288 if (n < lowest) { 4289 lowest = n; 4290 r = FMR_PAGES_PP_MAXIMUM; 4291 } 4292 4293#endif /* illumos */ 4294#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 4295 /* 4296 * If we're on an i386 platform, it's possible that we'll exhaust the 4297 * kernel heap space before we ever run out of available physical 4298 * memory. Most checks of the size of the heap_area compare against 4299 * tune.t_minarmem, which is the minimum available real memory that we 4300 * can have in the system. However, this is generally fixed at 25 pages 4301 * which is so low that it's useless. In this comparison, we seek to 4302 * calculate the total heap-size, and reclaim if more than 3/4ths of the 4303 * heap is allocated. (Or, in the calculation, if less than 1/4th is 4304 * free) 4305 */ 4306 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) - 4307 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2); 4308 if (n < lowest) { 4309 lowest = n; 4310 r = FMR_HEAP_ARENA; 4311 } 4312#define zio_arena NULL 4313#else 4314#define zio_arena heap_arena 4315#endif 4316 4317 /* 4318 * If zio data pages are being allocated out of a separate heap segment, 4319 * then enforce that the size of available vmem for this arena remains 4320 * above about 1/16th free. 4321 * 4322 * Note: The 1/16th arena free requirement was put in place 4323 * to aggressively evict memory from the arc in order to avoid 4324 * memory fragmentation issues. 4325 */ 4326 if (zio_arena != NULL) { 4327 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) - 4328 (vmem_size(zio_arena, VMEM_ALLOC) >> 4); 4329 if (n < lowest) { 4330 lowest = n; 4331 r = FMR_ZIO_ARENA; 4332 } 4333 } 4334 4335 /* 4336 * Above limits know nothing about real level of KVA fragmentation. 4337 * Start aggressive reclamation if too little sequential KVA left. 4338 */ 4339 if (lowest > 0) { 4340 n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ? 4341 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) : 4342 INT64_MAX; 4343 if (n < lowest) { 4344 lowest = n; 4345 r = FMR_ZIO_FRAG; 4346 } 4347 } 4348 4349#else /* _KERNEL */ 4350 /* Every 100 calls, free a small amount */ 4351 if (spa_get_random(100) == 0) 4352 lowest = -1024; 4353#endif /* _KERNEL */ 4354 4355 last_free_memory = lowest; 4356 last_free_reason = r; 4357 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r); 4358 return (lowest); 4359} 4360 4361 4362/* 4363 * Determine if the system is under memory pressure and is asking 4364 * to reclaim memory. A return value of B_TRUE indicates that the system 4365 * is under memory pressure and that the arc should adjust accordingly. 4366 */ 4367static boolean_t 4368arc_reclaim_needed(void) 4369{ 4370 return (arc_available_memory() < 0); 4371} 4372 4373extern kmem_cache_t *zio_buf_cache[]; 4374extern kmem_cache_t *zio_data_buf_cache[]; 4375extern kmem_cache_t *range_seg_cache; 4376extern kmem_cache_t *abd_chunk_cache; 4377 4378static __noinline void 4379arc_kmem_reap_now(void) 4380{ 4381 size_t i; 4382 kmem_cache_t *prev_cache = NULL; 4383 kmem_cache_t *prev_data_cache = NULL; 4384 4385 DTRACE_PROBE(arc__kmem_reap_start); 4386#ifdef _KERNEL 4387 if (arc_meta_used >= arc_meta_limit) { 4388 /* 4389 * We are exceeding our meta-data cache limit. 4390 * Purge some DNLC entries to release holds on meta-data. 4391 */ 4392 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent); 4393 } 4394#if defined(__i386) 4395 /* 4396 * Reclaim unused memory from all kmem caches. 4397 */ 4398 kmem_reap(); 4399#endif 4400#endif 4401 4402 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) { 4403 if (zio_buf_cache[i] != prev_cache) { 4404 prev_cache = zio_buf_cache[i]; 4405 kmem_cache_reap_now(zio_buf_cache[i]); 4406 } 4407 if (zio_data_buf_cache[i] != prev_data_cache) { 4408 prev_data_cache = zio_data_buf_cache[i]; 4409 kmem_cache_reap_now(zio_data_buf_cache[i]); 4410 } 4411 } 4412 kmem_cache_reap_now(abd_chunk_cache); 4413 kmem_cache_reap_now(buf_cache); 4414 kmem_cache_reap_now(hdr_full_cache); 4415 kmem_cache_reap_now(hdr_l2only_cache); 4416 kmem_cache_reap_now(range_seg_cache); 4417 4418#ifdef illumos 4419 if (zio_arena != NULL) { 4420 /* 4421 * Ask the vmem arena to reclaim unused memory from its 4422 * quantum caches. 4423 */ 4424 vmem_qcache_reap(zio_arena); 4425 } 4426#endif 4427 DTRACE_PROBE(arc__kmem_reap_end); 4428} 4429 4430/* 4431 * Threads can block in arc_get_data_impl() waiting for this thread to evict 4432 * enough data and signal them to proceed. When this happens, the threads in 4433 * arc_get_data_impl() are sleeping while holding the hash lock for their 4434 * particular arc header. Thus, we must be careful to never sleep on a 4435 * hash lock in this thread. This is to prevent the following deadlock: 4436 * 4437 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L", 4438 * waiting for the reclaim thread to signal it. 4439 * 4440 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter, 4441 * fails, and goes to sleep forever. 4442 * 4443 * This possible deadlock is avoided by always acquiring a hash lock 4444 * using mutex_tryenter() from arc_reclaim_thread(). 4445 */ 4446static void 4447arc_reclaim_thread(void *dummy __unused) 4448{ 4449 hrtime_t growtime = 0; 4450 callb_cpr_t cpr; 4451 4452 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG); 4453 4454 mutex_enter(&arc_reclaim_lock); 4455 while (!arc_reclaim_thread_exit) { 4456 uint64_t evicted = 0; 4457 4458 /* 4459 * This is necessary in order for the mdb ::arc dcmd to 4460 * show up to date information. Since the ::arc command 4461 * does not call the kstat's update function, without 4462 * this call, the command may show stale stats for the 4463 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even 4464 * with this change, the data might be up to 1 second 4465 * out of date; but that should suffice. The arc_state_t 4466 * structures can be queried directly if more accurate 4467 * information is needed. 4468 */ 4469 if (arc_ksp != NULL) 4470 arc_ksp->ks_update(arc_ksp, KSTAT_READ); 4471 4472 mutex_exit(&arc_reclaim_lock); 4473 4474 /* 4475 * We call arc_adjust() before (possibly) calling 4476 * arc_kmem_reap_now(), so that we can wake up 4477 * arc_get_data_impl() sooner. 4478 */ 4479 evicted = arc_adjust(); 4480 4481 int64_t free_memory = arc_available_memory(); 4482 if (free_memory < 0) { 4483 4484 arc_no_grow = B_TRUE; 4485 arc_warm = B_TRUE; 4486 4487 /* 4488 * Wait at least zfs_grow_retry (default 60) seconds 4489 * before considering growing. 4490 */ 4491 growtime = gethrtime() + SEC2NSEC(arc_grow_retry); 4492 4493 arc_kmem_reap_now(); 4494 4495 /* 4496 * If we are still low on memory, shrink the ARC 4497 * so that we have arc_shrink_min free space. 4498 */ 4499 free_memory = arc_available_memory(); 4500 4501 int64_t to_free = 4502 (arc_c >> arc_shrink_shift) - free_memory; 4503 if (to_free > 0) { 4504 arc_shrink(to_free); 4505 } 4506 } else if (free_memory < arc_c >> arc_no_grow_shift) { 4507 arc_no_grow = B_TRUE; 4508 } else if (gethrtime() >= growtime) { 4509 arc_no_grow = B_FALSE; 4510 } 4511 4512 mutex_enter(&arc_reclaim_lock); 4513 4514 /* 4515 * If evicted is zero, we couldn't evict anything via 4516 * arc_adjust(). This could be due to hash lock 4517 * collisions, but more likely due to the majority of 4518 * arc buffers being unevictable. Therefore, even if 4519 * arc_size is above arc_c, another pass is unlikely to 4520 * be helpful and could potentially cause us to enter an 4521 * infinite loop. 4522 */ 4523 if (arc_size <= arc_c || evicted == 0) { 4524 /* 4525 * We're either no longer overflowing, or we 4526 * can't evict anything more, so we should wake 4527 * up any threads before we go to sleep. 4528 */ 4529 cv_broadcast(&arc_reclaim_waiters_cv); 4530 4531 /* 4532 * Block until signaled, or after one second (we 4533 * might need to perform arc_kmem_reap_now() 4534 * even if we aren't being signalled) 4535 */ 4536 CALLB_CPR_SAFE_BEGIN(&cpr); 4537 (void) cv_timedwait_hires(&arc_reclaim_thread_cv, 4538 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0); 4539 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock); 4540 } 4541 } 4542 4543 arc_reclaim_thread_exit = B_FALSE; 4544 cv_broadcast(&arc_reclaim_thread_cv); 4545 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */ 4546 thread_exit(); 4547} 4548 4549static u_int arc_dnlc_evicts_arg; 4550extern struct vfsops zfs_vfsops; 4551 4552static void 4553arc_dnlc_evicts_thread(void *dummy __unused) 4554{ 4555 callb_cpr_t cpr; 4556 u_int percent; 4557 4558 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG); 4559 4560 mutex_enter(&arc_dnlc_evicts_lock); 4561 while (!arc_dnlc_evicts_thread_exit) { 4562 CALLB_CPR_SAFE_BEGIN(&cpr); 4563 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 4564 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock); 4565 if (arc_dnlc_evicts_arg != 0) { 4566 percent = arc_dnlc_evicts_arg; 4567 mutex_exit(&arc_dnlc_evicts_lock); 4568#ifdef _KERNEL 4569 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops); 4570#endif 4571 mutex_enter(&arc_dnlc_evicts_lock); 4572 /* 4573 * Clear our token only after vnlru_free() 4574 * pass is done, to avoid false queueing of 4575 * the requests. 4576 */ 4577 arc_dnlc_evicts_arg = 0; 4578 } 4579 } 4580 arc_dnlc_evicts_thread_exit = FALSE; 4581 cv_broadcast(&arc_dnlc_evicts_cv); 4582 CALLB_CPR_EXIT(&cpr); 4583 thread_exit(); 4584} 4585 4586void 4587dnlc_reduce_cache(void *arg) 4588{ 4589 u_int percent; 4590 4591 percent = (u_int)(uintptr_t)arg; 4592 mutex_enter(&arc_dnlc_evicts_lock); 4593 if (arc_dnlc_evicts_arg == 0) { 4594 arc_dnlc_evicts_arg = percent; 4595 cv_broadcast(&arc_dnlc_evicts_cv); 4596 } 4597 mutex_exit(&arc_dnlc_evicts_lock); 4598} 4599 4600/* 4601 * Adapt arc info given the number of bytes we are trying to add and 4602 * the state that we are comming from. This function is only called 4603 * when we are adding new content to the cache. 4604 */ 4605static void 4606arc_adapt(int bytes, arc_state_t *state) 4607{ 4608 int mult; 4609 uint64_t arc_p_min = (arc_c >> arc_p_min_shift); 4610 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size); 4611 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size); 4612 4613 if (state == arc_l2c_only) 4614 return; 4615 4616 ASSERT(bytes > 0); 4617 /* 4618 * Adapt the target size of the MRU list: 4619 * - if we just hit in the MRU ghost list, then increase 4620 * the target size of the MRU list. 4621 * - if we just hit in the MFU ghost list, then increase 4622 * the target size of the MFU list by decreasing the 4623 * target size of the MRU list. 4624 */ 4625 if (state == arc_mru_ghost) { 4626 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size); 4627 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */ 4628 4629 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult); 4630 } else if (state == arc_mfu_ghost) { 4631 uint64_t delta; 4632 4633 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size); 4634 mult = MIN(mult, 10); 4635 4636 delta = MIN(bytes * mult, arc_p); 4637 arc_p = MAX(arc_p_min, arc_p - delta); 4638 } 4639 ASSERT((int64_t)arc_p >= 0); 4640 4641 if (arc_reclaim_needed()) { 4642 cv_signal(&arc_reclaim_thread_cv); 4643 return; 4644 } 4645 4646 if (arc_no_grow) 4647 return; 4648 4649 if (arc_c >= arc_c_max) 4650 return; 4651 4652 /* 4653 * If we're within (2 * maxblocksize) bytes of the target 4654 * cache size, increment the target cache size 4655 */ 4656 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) { 4657 DTRACE_PROBE1(arc__inc_adapt, int, bytes); 4658 atomic_add_64(&arc_c, (int64_t)bytes); 4659 if (arc_c > arc_c_max) 4660 arc_c = arc_c_max; 4661 else if (state == arc_anon) 4662 atomic_add_64(&arc_p, (int64_t)bytes); 4663 if (arc_p > arc_c) 4664 arc_p = arc_c; 4665 } 4666 ASSERT((int64_t)arc_p >= 0); 4667} 4668 4669/* 4670 * Check if arc_size has grown past our upper threshold, determined by 4671 * zfs_arc_overflow_shift. 4672 */ 4673static boolean_t 4674arc_is_overflowing(void) 4675{ 4676 /* Always allow at least one block of overflow */ 4677 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE, 4678 arc_c >> zfs_arc_overflow_shift); 4679 4680 return (arc_size >= arc_c + overflow); 4681} 4682 4683static abd_t * 4684arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4685{ 4686 arc_buf_contents_t type = arc_buf_type(hdr); 4687 4688 arc_get_data_impl(hdr, size, tag); 4689 if (type == ARC_BUFC_METADATA) { 4690 return (abd_alloc(size, B_TRUE)); 4691 } else { 4692 ASSERT(type == ARC_BUFC_DATA); 4693 return (abd_alloc(size, B_FALSE)); 4694 } 4695} 4696 4697static void * 4698arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4699{ 4700 arc_buf_contents_t type = arc_buf_type(hdr); 4701 4702 arc_get_data_impl(hdr, size, tag); 4703 if (type == ARC_BUFC_METADATA) { 4704 return (zio_buf_alloc(size)); 4705 } else { 4706 ASSERT(type == ARC_BUFC_DATA); 4707 return (zio_data_buf_alloc(size)); 4708 } 4709} 4710 4711/* 4712 * Allocate a block and return it to the caller. If we are hitting the 4713 * hard limit for the cache size, we must sleep, waiting for the eviction 4714 * thread to catch up. If we're past the target size but below the hard 4715 * limit, we'll only signal the reclaim thread and continue on. 4716 */ 4717static void 4718arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4719{ 4720 arc_state_t *state = hdr->b_l1hdr.b_state; 4721 arc_buf_contents_t type = arc_buf_type(hdr); 4722 4723 arc_adapt(size, state); 4724 4725 /* 4726 * If arc_size is currently overflowing, and has grown past our 4727 * upper limit, we must be adding data faster than the evict 4728 * thread can evict. Thus, to ensure we don't compound the 4729 * problem by adding more data and forcing arc_size to grow even 4730 * further past it's target size, we halt and wait for the 4731 * eviction thread to catch up. 4732 * 4733 * It's also possible that the reclaim thread is unable to evict 4734 * enough buffers to get arc_size below the overflow limit (e.g. 4735 * due to buffers being un-evictable, or hash lock collisions). 4736 * In this case, we want to proceed regardless if we're 4737 * overflowing; thus we don't use a while loop here. 4738 */ 4739 if (arc_is_overflowing()) { 4740 mutex_enter(&arc_reclaim_lock); 4741 4742 /* 4743 * Now that we've acquired the lock, we may no longer be 4744 * over the overflow limit, lets check. 4745 * 4746 * We're ignoring the case of spurious wake ups. If that 4747 * were to happen, it'd let this thread consume an ARC 4748 * buffer before it should have (i.e. before we're under 4749 * the overflow limit and were signalled by the reclaim 4750 * thread). As long as that is a rare occurrence, it 4751 * shouldn't cause any harm. 4752 */ 4753 if (arc_is_overflowing()) { 4754 cv_signal(&arc_reclaim_thread_cv); 4755 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 4756 } 4757 4758 mutex_exit(&arc_reclaim_lock); 4759 } 4760 4761 VERIFY3U(hdr->b_type, ==, type); 4762 if (type == ARC_BUFC_METADATA) { 4763 arc_space_consume(size, ARC_SPACE_META); 4764 } else { 4765 arc_space_consume(size, ARC_SPACE_DATA); 4766 } 4767 4768 /* 4769 * Update the state size. Note that ghost states have a 4770 * "ghost size" and so don't need to be updated. 4771 */ 4772 if (!GHOST_STATE(state)) { 4773 4774 (void) refcount_add_many(&state->arcs_size, size, tag); 4775 4776 /* 4777 * If this is reached via arc_read, the link is 4778 * protected by the hash lock. If reached via 4779 * arc_buf_alloc, the header should not be accessed by 4780 * any other thread. And, if reached via arc_read_done, 4781 * the hash lock will protect it if it's found in the 4782 * hash table; otherwise no other thread should be 4783 * trying to [add|remove]_reference it. 4784 */ 4785 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4786 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4787 (void) refcount_add_many(&state->arcs_esize[type], 4788 size, tag); 4789 } 4790 4791 /* 4792 * If we are growing the cache, and we are adding anonymous 4793 * data, and we have outgrown arc_p, update arc_p 4794 */ 4795 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon && 4796 (refcount_count(&arc_anon->arcs_size) + 4797 refcount_count(&arc_mru->arcs_size) > arc_p)) 4798 arc_p = MIN(arc_c, arc_p + size); 4799 } 4800 ARCSTAT_BUMP(arcstat_allocated); 4801} 4802 4803static void 4804arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag) 4805{ 4806 arc_free_data_impl(hdr, size, tag); 4807 abd_free(abd); 4808} 4809 4810static void 4811arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag) 4812{ 4813 arc_buf_contents_t type = arc_buf_type(hdr); 4814 4815 arc_free_data_impl(hdr, size, tag); 4816 if (type == ARC_BUFC_METADATA) { 4817 zio_buf_free(buf, size); 4818 } else { 4819 ASSERT(type == ARC_BUFC_DATA); 4820 zio_data_buf_free(buf, size); 4821 } 4822} 4823 4824/* 4825 * Free the arc data buffer. 4826 */ 4827static void 4828arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag) 4829{ 4830 arc_state_t *state = hdr->b_l1hdr.b_state; 4831 arc_buf_contents_t type = arc_buf_type(hdr); 4832 4833 /* protected by hash lock, if in the hash table */ 4834 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) { 4835 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4836 ASSERT(state != arc_anon && state != arc_l2c_only); 4837 4838 (void) refcount_remove_many(&state->arcs_esize[type], 4839 size, tag); 4840 } 4841 (void) refcount_remove_many(&state->arcs_size, size, tag); 4842 4843 VERIFY3U(hdr->b_type, ==, type); 4844 if (type == ARC_BUFC_METADATA) { 4845 arc_space_return(size, ARC_SPACE_META); 4846 } else { 4847 ASSERT(type == ARC_BUFC_DATA); 4848 arc_space_return(size, ARC_SPACE_DATA); 4849 } 4850} 4851 4852/* 4853 * This routine is called whenever a buffer is accessed. 4854 * NOTE: the hash lock is dropped in this function. 4855 */ 4856static void 4857arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) 4858{ 4859 clock_t now; 4860 4861 ASSERT(MUTEX_HELD(hash_lock)); 4862 ASSERT(HDR_HAS_L1HDR(hdr)); 4863 4864 if (hdr->b_l1hdr.b_state == arc_anon) { 4865 /* 4866 * This buffer is not in the cache, and does not 4867 * appear in our "ghost" list. Add the new buffer 4868 * to the MRU state. 4869 */ 4870 4871 ASSERT0(hdr->b_l1hdr.b_arc_access); 4872 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4873 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4874 arc_change_state(arc_mru, hdr, hash_lock); 4875 4876 } else if (hdr->b_l1hdr.b_state == arc_mru) { 4877 now = ddi_get_lbolt(); 4878 4879 /* 4880 * If this buffer is here because of a prefetch, then either: 4881 * - clear the flag if this is a "referencing" read 4882 * (any subsequent access will bump this into the MFU state). 4883 * or 4884 * - move the buffer to the head of the list if this is 4885 * another prefetch (to make it less likely to be evicted). 4886 */ 4887 if (HDR_PREFETCH(hdr)) { 4888 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 4889 /* link protected by hash lock */ 4890 ASSERT(multilist_link_active( 4891 &hdr->b_l1hdr.b_arc_node)); 4892 } else { 4893 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4894 ARCSTAT_BUMP(arcstat_mru_hits); 4895 } 4896 hdr->b_l1hdr.b_arc_access = now; 4897 return; 4898 } 4899 4900 /* 4901 * This buffer has been "accessed" only once so far, 4902 * but it is still in the cache. Move it to the MFU 4903 * state. 4904 */ 4905 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) { 4906 /* 4907 * More than 125ms have passed since we 4908 * instantiated this buffer. Move it to the 4909 * most frequently used state. 4910 */ 4911 hdr->b_l1hdr.b_arc_access = now; 4912 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4913 arc_change_state(arc_mfu, hdr, hash_lock); 4914 } 4915 ARCSTAT_BUMP(arcstat_mru_hits); 4916 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) { 4917 arc_state_t *new_state; 4918 /* 4919 * This buffer has been "accessed" recently, but 4920 * was evicted from the cache. Move it to the 4921 * MFU state. 4922 */ 4923 4924 if (HDR_PREFETCH(hdr)) { 4925 new_state = arc_mru; 4926 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) 4927 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH); 4928 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr); 4929 } else { 4930 new_state = arc_mfu; 4931 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4932 } 4933 4934 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4935 arc_change_state(new_state, hdr, hash_lock); 4936 4937 ARCSTAT_BUMP(arcstat_mru_ghost_hits); 4938 } else if (hdr->b_l1hdr.b_state == arc_mfu) { 4939 /* 4940 * This buffer has been accessed more than once and is 4941 * still in the cache. Keep it in the MFU state. 4942 * 4943 * NOTE: an add_reference() that occurred when we did 4944 * the arc_read() will have kicked this off the list. 4945 * If it was a prefetch, we will explicitly move it to 4946 * the head of the list now. 4947 */ 4948 if ((HDR_PREFETCH(hdr)) != 0) { 4949 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 4950 /* link protected by hash_lock */ 4951 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 4952 } 4953 ARCSTAT_BUMP(arcstat_mfu_hits); 4954 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4955 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) { 4956 arc_state_t *new_state = arc_mfu; 4957 /* 4958 * This buffer has been accessed more than once but has 4959 * been evicted from the cache. Move it back to the 4960 * MFU state. 4961 */ 4962 4963 if (HDR_PREFETCH(hdr)) { 4964 /* 4965 * This is a prefetch access... 4966 * move this block back to the MRU state. 4967 */ 4968 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt)); 4969 new_state = arc_mru; 4970 } 4971 4972 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4973 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4974 arc_change_state(new_state, hdr, hash_lock); 4975 4976 ARCSTAT_BUMP(arcstat_mfu_ghost_hits); 4977 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) { 4978 /* 4979 * This buffer is on the 2nd Level ARC. 4980 */ 4981 4982 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt(); 4983 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr); 4984 arc_change_state(arc_mfu, hdr, hash_lock); 4985 } else { 4986 ASSERT(!"invalid arc state"); 4987 } 4988} 4989 4990/* a generic arc_done_func_t which you can use */ 4991/* ARGSUSED */ 4992void 4993arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg) 4994{ 4995 if (zio == NULL || zio->io_error == 0) 4996 bcopy(buf->b_data, arg, arc_buf_size(buf)); 4997 arc_buf_destroy(buf, arg); 4998} 4999 5000/* a generic arc_done_func_t */ 5001void 5002arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg) 5003{ 5004 arc_buf_t **bufp = arg; 5005 if (zio && zio->io_error) { 5006 arc_buf_destroy(buf, arg); 5007 *bufp = NULL; 5008 } else { 5009 *bufp = buf; 5010 ASSERT(buf->b_data); 5011 } 5012} 5013 5014static void 5015arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp) 5016{ 5017 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) { 5018 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0); 5019 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF); 5020 } else { 5021 if (HDR_COMPRESSION_ENABLED(hdr)) { 5022 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, 5023 BP_GET_COMPRESS(bp)); 5024 } 5025 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp)); 5026 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp)); 5027 } 5028} 5029 5030static void 5031arc_read_done(zio_t *zio) 5032{ 5033 arc_buf_hdr_t *hdr = zio->io_private; 5034 kmutex_t *hash_lock = NULL; 5035 arc_callback_t *callback_list; 5036 arc_callback_t *acb; 5037 boolean_t freeable = B_FALSE; 5038 boolean_t no_zio_error = (zio->io_error == 0); 5039 5040 /* 5041 * The hdr was inserted into hash-table and removed from lists 5042 * prior to starting I/O. We should find this header, since 5043 * it's in the hash table, and it should be legit since it's 5044 * not possible to evict it during the I/O. The only possible 5045 * reason for it not to be found is if we were freed during the 5046 * read. 5047 */ 5048 if (HDR_IN_HASH_TABLE(hdr)) { 5049 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp)); 5050 ASSERT3U(hdr->b_dva.dva_word[0], ==, 5051 BP_IDENTITY(zio->io_bp)->dva_word[0]); 5052 ASSERT3U(hdr->b_dva.dva_word[1], ==, 5053 BP_IDENTITY(zio->io_bp)->dva_word[1]); 5054 5055 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp, 5056 &hash_lock); 5057 5058 ASSERT((found == hdr && 5059 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) || 5060 (found == hdr && HDR_L2_READING(hdr))); 5061 ASSERT3P(hash_lock, !=, NULL); 5062 } 5063 5064 if (no_zio_error) { 5065 /* byteswap if necessary */ 5066 if (BP_SHOULD_BYTESWAP(zio->io_bp)) { 5067 if (BP_GET_LEVEL(zio->io_bp) > 0) { 5068 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64; 5069 } else { 5070 hdr->b_l1hdr.b_byteswap = 5071 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp)); 5072 } 5073 } else { 5074 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS; 5075 } 5076 } 5077 5078 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED); 5079 if (l2arc_noprefetch && HDR_PREFETCH(hdr)) 5080 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE); 5081 5082 callback_list = hdr->b_l1hdr.b_acb; 5083 ASSERT3P(callback_list, !=, NULL); 5084 5085 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) { 5086 /* 5087 * Only call arc_access on anonymous buffers. This is because 5088 * if we've issued an I/O for an evicted buffer, we've already 5089 * called arc_access (to prevent any simultaneous readers from 5090 * getting confused). 5091 */ 5092 arc_access(hdr, hash_lock); 5093 } 5094 5095 /* 5096 * If a read request has a callback (i.e. acb_done is not NULL), then we 5097 * make a buf containing the data according to the parameters which were 5098 * passed in. The implementation of arc_buf_alloc_impl() ensures that we 5099 * aren't needlessly decompressing the data multiple times. 5100 */ 5101 int callback_cnt = 0; 5102 for (acb = callback_list; acb != NULL; acb = acb->acb_next) { 5103 if (!acb->acb_done) 5104 continue; 5105 5106 /* This is a demand read since prefetches don't use callbacks */ 5107 callback_cnt++; 5108 5109 int error = arc_buf_alloc_impl(hdr, acb->acb_private, 5110 acb->acb_compressed, no_zio_error, &acb->acb_buf); 5111 if (no_zio_error) { 5112 zio->io_error = error; 5113 } 5114 } 5115 hdr->b_l1hdr.b_acb = NULL; 5116 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5117 if (callback_cnt == 0) { 5118 ASSERT(HDR_PREFETCH(hdr)); 5119 ASSERT0(hdr->b_l1hdr.b_bufcnt); 5120 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5121 } 5122 5123 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) || 5124 callback_list != NULL); 5125 5126 if (no_zio_error) { 5127 arc_hdr_verify(hdr, zio->io_bp); 5128 } else { 5129 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR); 5130 if (hdr->b_l1hdr.b_state != arc_anon) 5131 arc_change_state(arc_anon, hdr, hash_lock); 5132 if (HDR_IN_HASH_TABLE(hdr)) 5133 buf_hash_remove(hdr); 5134 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5135 } 5136 5137 /* 5138 * Broadcast before we drop the hash_lock to avoid the possibility 5139 * that the hdr (and hence the cv) might be freed before we get to 5140 * the cv_broadcast(). 5141 */ 5142 cv_broadcast(&hdr->b_l1hdr.b_cv); 5143 5144 if (hash_lock != NULL) { 5145 mutex_exit(hash_lock); 5146 } else { 5147 /* 5148 * This block was freed while we waited for the read to 5149 * complete. It has been removed from the hash table and 5150 * moved to the anonymous state (so that it won't show up 5151 * in the cache). 5152 */ 5153 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon); 5154 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt); 5155 } 5156 5157 /* execute each callback and free its structure */ 5158 while ((acb = callback_list) != NULL) { 5159 if (acb->acb_done) 5160 acb->acb_done(zio, acb->acb_buf, acb->acb_private); 5161 5162 if (acb->acb_zio_dummy != NULL) { 5163 acb->acb_zio_dummy->io_error = zio->io_error; 5164 zio_nowait(acb->acb_zio_dummy); 5165 } 5166 5167 callback_list = acb->acb_next; 5168 kmem_free(acb, sizeof (arc_callback_t)); 5169 } 5170 5171 if (freeable) 5172 arc_hdr_destroy(hdr); 5173} 5174 5175/* 5176 * "Read" the block at the specified DVA (in bp) via the 5177 * cache. If the block is found in the cache, invoke the provided 5178 * callback immediately and return. Note that the `zio' parameter 5179 * in the callback will be NULL in this case, since no IO was 5180 * required. If the block is not in the cache pass the read request 5181 * on to the spa with a substitute callback function, so that the 5182 * requested block will be added to the cache. 5183 * 5184 * If a read request arrives for a block that has a read in-progress, 5185 * either wait for the in-progress read to complete (and return the 5186 * results); or, if this is a read with a "done" func, add a record 5187 * to the read to invoke the "done" func when the read completes, 5188 * and return; or just return. 5189 * 5190 * arc_read_done() will invoke all the requested "done" functions 5191 * for readers of this block. 5192 */ 5193int 5194arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done, 5195 void *private, zio_priority_t priority, int zio_flags, 5196 arc_flags_t *arc_flags, const zbookmark_phys_t *zb) 5197{ 5198 arc_buf_hdr_t *hdr = NULL; 5199 kmutex_t *hash_lock = NULL; 5200 zio_t *rzio; 5201 uint64_t guid = spa_load_guid(spa); 5202 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0; 5203 5204 ASSERT(!BP_IS_EMBEDDED(bp) || 5205 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA); 5206 5207top: 5208 if (!BP_IS_EMBEDDED(bp)) { 5209 /* 5210 * Embedded BP's have no DVA and require no I/O to "read". 5211 * Create an anonymous arc buf to back it. 5212 */ 5213 hdr = buf_hash_find(guid, bp, &hash_lock); 5214 } 5215 5216 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) { 5217 arc_buf_t *buf = NULL; 5218 *arc_flags |= ARC_FLAG_CACHED; 5219 5220 if (HDR_IO_IN_PROGRESS(hdr)) { 5221 5222 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) && 5223 priority == ZIO_PRIORITY_SYNC_READ) { 5224 /* 5225 * This sync read must wait for an 5226 * in-progress async read (e.g. a predictive 5227 * prefetch). Async reads are queued 5228 * separately at the vdev_queue layer, so 5229 * this is a form of priority inversion. 5230 * Ideally, we would "inherit" the demand 5231 * i/o's priority by moving the i/o from 5232 * the async queue to the synchronous queue, 5233 * but there is currently no mechanism to do 5234 * so. Track this so that we can evaluate 5235 * the magnitude of this potential performance 5236 * problem. 5237 * 5238 * Note that if the prefetch i/o is already 5239 * active (has been issued to the device), 5240 * the prefetch improved performance, because 5241 * we issued it sooner than we would have 5242 * without the prefetch. 5243 */ 5244 DTRACE_PROBE1(arc__sync__wait__for__async, 5245 arc_buf_hdr_t *, hdr); 5246 ARCSTAT_BUMP(arcstat_sync_wait_for_async); 5247 } 5248 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5249 arc_hdr_clear_flags(hdr, 5250 ARC_FLAG_PREDICTIVE_PREFETCH); 5251 } 5252 5253 if (*arc_flags & ARC_FLAG_WAIT) { 5254 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock); 5255 mutex_exit(hash_lock); 5256 goto top; 5257 } 5258 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5259 5260 if (done) { 5261 arc_callback_t *acb = NULL; 5262 5263 acb = kmem_zalloc(sizeof (arc_callback_t), 5264 KM_SLEEP); 5265 acb->acb_done = done; 5266 acb->acb_private = private; 5267 acb->acb_compressed = compressed_read; 5268 if (pio != NULL) 5269 acb->acb_zio_dummy = zio_null(pio, 5270 spa, NULL, NULL, NULL, zio_flags); 5271 5272 ASSERT3P(acb->acb_done, !=, NULL); 5273 acb->acb_next = hdr->b_l1hdr.b_acb; 5274 hdr->b_l1hdr.b_acb = acb; 5275 mutex_exit(hash_lock); 5276 return (0); 5277 } 5278 mutex_exit(hash_lock); 5279 return (0); 5280 } 5281 5282 ASSERT(hdr->b_l1hdr.b_state == arc_mru || 5283 hdr->b_l1hdr.b_state == arc_mfu); 5284 5285 if (done) { 5286 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) { 5287 /* 5288 * This is a demand read which does not have to 5289 * wait for i/o because we did a predictive 5290 * prefetch i/o for it, which has completed. 5291 */ 5292 DTRACE_PROBE1( 5293 arc__demand__hit__predictive__prefetch, 5294 arc_buf_hdr_t *, hdr); 5295 ARCSTAT_BUMP( 5296 arcstat_demand_hit_predictive_prefetch); 5297 arc_hdr_clear_flags(hdr, 5298 ARC_FLAG_PREDICTIVE_PREFETCH); 5299 } 5300 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp)); 5301 5302 /* Get a buf with the desired data in it. */ 5303 VERIFY0(arc_buf_alloc_impl(hdr, private, 5304 compressed_read, B_TRUE, &buf)); 5305 } else if (*arc_flags & ARC_FLAG_PREFETCH && 5306 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) { 5307 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5308 } 5309 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); 5310 arc_access(hdr, hash_lock); 5311 if (*arc_flags & ARC_FLAG_L2CACHE) 5312 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5313 mutex_exit(hash_lock); 5314 ARCSTAT_BUMP(arcstat_hits); 5315 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5316 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5317 data, metadata, hits); 5318 5319 if (done) 5320 done(NULL, buf, private); 5321 } else { 5322 uint64_t lsize = BP_GET_LSIZE(bp); 5323 uint64_t psize = BP_GET_PSIZE(bp); 5324 arc_callback_t *acb; 5325 vdev_t *vd = NULL; 5326 uint64_t addr = 0; 5327 boolean_t devw = B_FALSE; 5328 uint64_t size; 5329 5330 if (hdr == NULL) { 5331 /* this block is not in the cache */ 5332 arc_buf_hdr_t *exists = NULL; 5333 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp); 5334 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, 5335 BP_GET_COMPRESS(bp), type); 5336 5337 if (!BP_IS_EMBEDDED(bp)) { 5338 hdr->b_dva = *BP_IDENTITY(bp); 5339 hdr->b_birth = BP_PHYSICAL_BIRTH(bp); 5340 exists = buf_hash_insert(hdr, &hash_lock); 5341 } 5342 if (exists != NULL) { 5343 /* somebody beat us to the hash insert */ 5344 mutex_exit(hash_lock); 5345 buf_discard_identity(hdr); 5346 arc_hdr_destroy(hdr); 5347 goto top; /* restart the IO request */ 5348 } 5349 } else { 5350 /* 5351 * This block is in the ghost cache. If it was L2-only 5352 * (and thus didn't have an L1 hdr), we realloc the 5353 * header to add an L1 hdr. 5354 */ 5355 if (!HDR_HAS_L1HDR(hdr)) { 5356 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache, 5357 hdr_full_cache); 5358 } 5359 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5360 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state)); 5361 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5362 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 5363 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL); 5364 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL); 5365 5366 /* 5367 * This is a delicate dance that we play here. 5368 * This hdr is in the ghost list so we access it 5369 * to move it out of the ghost list before we 5370 * initiate the read. If it's a prefetch then 5371 * it won't have a callback so we'll remove the 5372 * reference that arc_buf_alloc_impl() created. We 5373 * do this after we've called arc_access() to 5374 * avoid hitting an assert in remove_reference(). 5375 */ 5376 arc_access(hdr, hash_lock); 5377 arc_hdr_alloc_pabd(hdr); 5378 } 5379 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5380 size = arc_hdr_size(hdr); 5381 5382 /* 5383 * If compression is enabled on the hdr, then will do 5384 * RAW I/O and will store the compressed data in the hdr's 5385 * data block. Otherwise, the hdr's data block will contain 5386 * the uncompressed data. 5387 */ 5388 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5389 zio_flags |= ZIO_FLAG_RAW; 5390 } 5391 5392 if (*arc_flags & ARC_FLAG_PREFETCH) 5393 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH); 5394 if (*arc_flags & ARC_FLAG_L2CACHE) 5395 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 5396 if (BP_GET_LEVEL(bp) > 0) 5397 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT); 5398 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH) 5399 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH); 5400 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state)); 5401 5402 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP); 5403 acb->acb_done = done; 5404 acb->acb_private = private; 5405 acb->acb_compressed = compressed_read; 5406 5407 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5408 hdr->b_l1hdr.b_acb = acb; 5409 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5410 5411 if (HDR_HAS_L2HDR(hdr) && 5412 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) { 5413 devw = hdr->b_l2hdr.b_dev->l2ad_writing; 5414 addr = hdr->b_l2hdr.b_daddr; 5415 /* 5416 * Lock out device removal. 5417 */ 5418 if (vdev_is_dead(vd) || 5419 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER)) 5420 vd = NULL; 5421 } 5422 5423 if (priority == ZIO_PRIORITY_ASYNC_READ) 5424 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5425 else 5426 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ); 5427 5428 if (hash_lock != NULL) 5429 mutex_exit(hash_lock); 5430 5431 /* 5432 * At this point, we have a level 1 cache miss. Try again in 5433 * L2ARC if possible. 5434 */ 5435 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize); 5436 5437 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp, 5438 uint64_t, lsize, zbookmark_phys_t *, zb); 5439 ARCSTAT_BUMP(arcstat_misses); 5440 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), 5441 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), 5442 data, metadata, misses); 5443#ifdef _KERNEL 5444#ifdef RACCT 5445 if (racct_enable) { 5446 PROC_LOCK(curproc); 5447 racct_add_force(curproc, RACCT_READBPS, size); 5448 racct_add_force(curproc, RACCT_READIOPS, 1); 5449 PROC_UNLOCK(curproc); 5450 } 5451#endif /* RACCT */ 5452 curthread->td_ru.ru_inblock++; 5453#endif 5454 5455 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) { 5456 /* 5457 * Read from the L2ARC if the following are true: 5458 * 1. The L2ARC vdev was previously cached. 5459 * 2. This buffer still has L2ARC metadata. 5460 * 3. This buffer isn't currently writing to the L2ARC. 5461 * 4. The L2ARC entry wasn't evicted, which may 5462 * also have invalidated the vdev. 5463 * 5. This isn't prefetch and l2arc_noprefetch is set. 5464 */ 5465 if (HDR_HAS_L2HDR(hdr) && 5466 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) && 5467 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) { 5468 l2arc_read_callback_t *cb; 5469 abd_t *abd; 5470 uint64_t asize; 5471 5472 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr); 5473 ARCSTAT_BUMP(arcstat_l2_hits); 5474 5475 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), 5476 KM_SLEEP); 5477 cb->l2rcb_hdr = hdr; 5478 cb->l2rcb_bp = *bp; 5479 cb->l2rcb_zb = *zb; 5480 cb->l2rcb_flags = zio_flags; 5481 5482 asize = vdev_psize_to_asize(vd, size); 5483 if (asize != size) { 5484 abd = abd_alloc_for_io(asize, 5485 HDR_ISTYPE_METADATA(hdr)); 5486 cb->l2rcb_abd = abd; 5487 } else { 5488 abd = hdr->b_l1hdr.b_pabd; 5489 } 5490 5491 ASSERT(addr >= VDEV_LABEL_START_SIZE && 5492 addr + asize <= vd->vdev_psize - 5493 VDEV_LABEL_END_SIZE); 5494 5495 /* 5496 * l2arc read. The SCL_L2ARC lock will be 5497 * released by l2arc_read_done(). 5498 * Issue a null zio if the underlying buffer 5499 * was squashed to zero size by compression. 5500 */ 5501 ASSERT3U(HDR_GET_COMPRESS(hdr), !=, 5502 ZIO_COMPRESS_EMPTY); 5503 rzio = zio_read_phys(pio, vd, addr, 5504 asize, abd, 5505 ZIO_CHECKSUM_OFF, 5506 l2arc_read_done, cb, priority, 5507 zio_flags | ZIO_FLAG_DONT_CACHE | 5508 ZIO_FLAG_CANFAIL | 5509 ZIO_FLAG_DONT_PROPAGATE | 5510 ZIO_FLAG_DONT_RETRY, B_FALSE); 5511 DTRACE_PROBE2(l2arc__read, vdev_t *, vd, 5512 zio_t *, rzio); 5513 ARCSTAT_INCR(arcstat_l2_read_bytes, size); 5514 5515 if (*arc_flags & ARC_FLAG_NOWAIT) { 5516 zio_nowait(rzio); 5517 return (0); 5518 } 5519 5520 ASSERT(*arc_flags & ARC_FLAG_WAIT); 5521 if (zio_wait(rzio) == 0) 5522 return (0); 5523 5524 /* l2arc read error; goto zio_read() */ 5525 } else { 5526 DTRACE_PROBE1(l2arc__miss, 5527 arc_buf_hdr_t *, hdr); 5528 ARCSTAT_BUMP(arcstat_l2_misses); 5529 if (HDR_L2_WRITING(hdr)) 5530 ARCSTAT_BUMP(arcstat_l2_rw_clash); 5531 spa_config_exit(spa, SCL_L2ARC, vd); 5532 } 5533 } else { 5534 if (vd != NULL) 5535 spa_config_exit(spa, SCL_L2ARC, vd); 5536 if (l2arc_ndev != 0) { 5537 DTRACE_PROBE1(l2arc__miss, 5538 arc_buf_hdr_t *, hdr); 5539 ARCSTAT_BUMP(arcstat_l2_misses); 5540 } 5541 } 5542 5543 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size, 5544 arc_read_done, hdr, priority, zio_flags, zb); 5545 5546 if (*arc_flags & ARC_FLAG_WAIT) 5547 return (zio_wait(rzio)); 5548 5549 ASSERT(*arc_flags & ARC_FLAG_NOWAIT); 5550 zio_nowait(rzio); 5551 } 5552 return (0); 5553} 5554 5555/* 5556 * Notify the arc that a block was freed, and thus will never be used again. 5557 */ 5558void 5559arc_freed(spa_t *spa, const blkptr_t *bp) 5560{ 5561 arc_buf_hdr_t *hdr; 5562 kmutex_t *hash_lock; 5563 uint64_t guid = spa_load_guid(spa); 5564 5565 ASSERT(!BP_IS_EMBEDDED(bp)); 5566 5567 hdr = buf_hash_find(guid, bp, &hash_lock); 5568 if (hdr == NULL) 5569 return; 5570 5571 /* 5572 * We might be trying to free a block that is still doing I/O 5573 * (i.e. prefetch) or has a reference (i.e. a dedup-ed, 5574 * dmu_sync-ed block). If this block is being prefetched, then it 5575 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr 5576 * until the I/O completes. A block may also have a reference if it is 5577 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would 5578 * have written the new block to its final resting place on disk but 5579 * without the dedup flag set. This would have left the hdr in the MRU 5580 * state and discoverable. When the txg finally syncs it detects that 5581 * the block was overridden in open context and issues an override I/O. 5582 * Since this is a dedup block, the override I/O will determine if the 5583 * block is already in the DDT. If so, then it will replace the io_bp 5584 * with the bp from the DDT and allow the I/O to finish. When the I/O 5585 * reaches the done callback, dbuf_write_override_done, it will 5586 * check to see if the io_bp and io_bp_override are identical. 5587 * If they are not, then it indicates that the bp was replaced with 5588 * the bp in the DDT and the override bp is freed. This allows 5589 * us to arrive here with a reference on a block that is being 5590 * freed. So if we have an I/O in progress, or a reference to 5591 * this hdr, then we don't destroy the hdr. 5592 */ 5593 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) && 5594 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) { 5595 arc_change_state(arc_anon, hdr, hash_lock); 5596 arc_hdr_destroy(hdr); 5597 mutex_exit(hash_lock); 5598 } else { 5599 mutex_exit(hash_lock); 5600 } 5601 5602} 5603 5604/* 5605 * Release this buffer from the cache, making it an anonymous buffer. This 5606 * must be done after a read and prior to modifying the buffer contents. 5607 * If the buffer has more than one reference, we must make 5608 * a new hdr for the buffer. 5609 */ 5610void 5611arc_release(arc_buf_t *buf, void *tag) 5612{ 5613 arc_buf_hdr_t *hdr = buf->b_hdr; 5614 5615 /* 5616 * It would be nice to assert that if it's DMU metadata (level > 5617 * 0 || it's the dnode file), then it must be syncing context. 5618 * But we don't know that information at this level. 5619 */ 5620 5621 mutex_enter(&buf->b_evict_lock); 5622 5623 ASSERT(HDR_HAS_L1HDR(hdr)); 5624 5625 /* 5626 * We don't grab the hash lock prior to this check, because if 5627 * the buffer's header is in the arc_anon state, it won't be 5628 * linked into the hash table. 5629 */ 5630 if (hdr->b_l1hdr.b_state == arc_anon) { 5631 mutex_exit(&buf->b_evict_lock); 5632 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5633 ASSERT(!HDR_IN_HASH_TABLE(hdr)); 5634 ASSERT(!HDR_HAS_L2HDR(hdr)); 5635 ASSERT(HDR_EMPTY(hdr)); 5636 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5637 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1); 5638 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node)); 5639 5640 hdr->b_l1hdr.b_arc_access = 0; 5641 5642 /* 5643 * If the buf is being overridden then it may already 5644 * have a hdr that is not empty. 5645 */ 5646 buf_discard_identity(hdr); 5647 arc_buf_thaw(buf); 5648 5649 return; 5650 } 5651 5652 kmutex_t *hash_lock = HDR_LOCK(hdr); 5653 mutex_enter(hash_lock); 5654 5655 /* 5656 * This assignment is only valid as long as the hash_lock is 5657 * held, we must be careful not to reference state or the 5658 * b_state field after dropping the lock. 5659 */ 5660 arc_state_t *state = hdr->b_l1hdr.b_state; 5661 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 5662 ASSERT3P(state, !=, arc_anon); 5663 5664 /* this buffer is not on any list */ 5665 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0); 5666 5667 if (HDR_HAS_L2HDR(hdr)) { 5668 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5669 5670 /* 5671 * We have to recheck this conditional again now that 5672 * we're holding the l2ad_mtx to prevent a race with 5673 * another thread which might be concurrently calling 5674 * l2arc_evict(). In that case, l2arc_evict() might have 5675 * destroyed the header's L2 portion as we were waiting 5676 * to acquire the l2ad_mtx. 5677 */ 5678 if (HDR_HAS_L2HDR(hdr)) { 5679 l2arc_trim(hdr); 5680 arc_hdr_l2hdr_destroy(hdr); 5681 } 5682 5683 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx); 5684 } 5685 5686 /* 5687 * Do we have more than one buf? 5688 */ 5689 if (hdr->b_l1hdr.b_bufcnt > 1) { 5690 arc_buf_hdr_t *nhdr; 5691 uint64_t spa = hdr->b_spa; 5692 uint64_t psize = HDR_GET_PSIZE(hdr); 5693 uint64_t lsize = HDR_GET_LSIZE(hdr); 5694 enum zio_compress compress = HDR_GET_COMPRESS(hdr); 5695 arc_buf_contents_t type = arc_buf_type(hdr); 5696 VERIFY3U(hdr->b_type, ==, type); 5697 5698 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL); 5699 (void) remove_reference(hdr, hash_lock, tag); 5700 5701 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) { 5702 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf); 5703 ASSERT(ARC_BUF_LAST(buf)); 5704 } 5705 5706 /* 5707 * Pull the data off of this hdr and attach it to 5708 * a new anonymous hdr. Also find the last buffer 5709 * in the hdr's buffer list. 5710 */ 5711 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf); 5712 ASSERT3P(lastbuf, !=, NULL); 5713 5714 /* 5715 * If the current arc_buf_t and the hdr are sharing their data 5716 * buffer, then we must stop sharing that block. 5717 */ 5718 if (arc_buf_is_shared(buf)) { 5719 VERIFY(!arc_buf_is_shared(lastbuf)); 5720 5721 /* 5722 * First, sever the block sharing relationship between 5723 * buf and the arc_buf_hdr_t. 5724 */ 5725 arc_unshare_buf(hdr, buf); 5726 5727 /* 5728 * Now we need to recreate the hdr's b_pabd. Since we 5729 * have lastbuf handy, we try to share with it, but if 5730 * we can't then we allocate a new b_pabd and copy the 5731 * data from buf into it. 5732 */ 5733 if (arc_can_share(hdr, lastbuf)) { 5734 arc_share_buf(hdr, lastbuf); 5735 } else { 5736 arc_hdr_alloc_pabd(hdr); 5737 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, 5738 buf->b_data, psize); 5739 } 5740 VERIFY3P(lastbuf->b_data, !=, NULL); 5741 } else if (HDR_SHARED_DATA(hdr)) { 5742 /* 5743 * Uncompressed shared buffers are always at the end 5744 * of the list. Compressed buffers don't have the 5745 * same requirements. This makes it hard to 5746 * simply assert that the lastbuf is shared so 5747 * we rely on the hdr's compression flags to determine 5748 * if we have a compressed, shared buffer. 5749 */ 5750 ASSERT(arc_buf_is_shared(lastbuf) || 5751 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF); 5752 ASSERT(!ARC_BUF_SHARED(buf)); 5753 } 5754 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 5755 ASSERT3P(state, !=, arc_l2c_only); 5756 5757 (void) refcount_remove_many(&state->arcs_size, 5758 arc_buf_size(buf), buf); 5759 5760 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) { 5761 ASSERT3P(state, !=, arc_l2c_only); 5762 (void) refcount_remove_many(&state->arcs_esize[type], 5763 arc_buf_size(buf), buf); 5764 } 5765 5766 hdr->b_l1hdr.b_bufcnt -= 1; 5767 arc_cksum_verify(buf); 5768#ifdef illumos 5769 arc_buf_unwatch(buf); 5770#endif 5771 5772 mutex_exit(hash_lock); 5773 5774 /* 5775 * Allocate a new hdr. The new hdr will contain a b_pabd 5776 * buffer which will be freed in arc_write(). 5777 */ 5778 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type); 5779 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL); 5780 ASSERT0(nhdr->b_l1hdr.b_bufcnt); 5781 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt)); 5782 VERIFY3U(nhdr->b_type, ==, type); 5783 ASSERT(!HDR_SHARED_DATA(nhdr)); 5784 5785 nhdr->b_l1hdr.b_buf = buf; 5786 nhdr->b_l1hdr.b_bufcnt = 1; 5787 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag); 5788 buf->b_hdr = nhdr; 5789 5790 mutex_exit(&buf->b_evict_lock); 5791 (void) refcount_add_many(&arc_anon->arcs_size, 5792 arc_buf_size(buf), buf); 5793 } else { 5794 mutex_exit(&buf->b_evict_lock); 5795 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1); 5796 /* protected by hash lock, or hdr is on arc_anon */ 5797 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node)); 5798 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 5799 arc_change_state(arc_anon, hdr, hash_lock); 5800 hdr->b_l1hdr.b_arc_access = 0; 5801 mutex_exit(hash_lock); 5802 5803 buf_discard_identity(hdr); 5804 arc_buf_thaw(buf); 5805 } 5806} 5807 5808int 5809arc_released(arc_buf_t *buf) 5810{ 5811 int released; 5812 5813 mutex_enter(&buf->b_evict_lock); 5814 released = (buf->b_data != NULL && 5815 buf->b_hdr->b_l1hdr.b_state == arc_anon); 5816 mutex_exit(&buf->b_evict_lock); 5817 return (released); 5818} 5819 5820#ifdef ZFS_DEBUG 5821int 5822arc_referenced(arc_buf_t *buf) 5823{ 5824 int referenced; 5825 5826 mutex_enter(&buf->b_evict_lock); 5827 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt)); 5828 mutex_exit(&buf->b_evict_lock); 5829 return (referenced); 5830} 5831#endif 5832 5833static void 5834arc_write_ready(zio_t *zio) 5835{ 5836 arc_write_callback_t *callback = zio->io_private; 5837 arc_buf_t *buf = callback->awcb_buf; 5838 arc_buf_hdr_t *hdr = buf->b_hdr; 5839 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp); 5840 5841 ASSERT(HDR_HAS_L1HDR(hdr)); 5842 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt)); 5843 ASSERT(hdr->b_l1hdr.b_bufcnt > 0); 5844 5845 /* 5846 * If we're reexecuting this zio because the pool suspended, then 5847 * cleanup any state that was previously set the first time the 5848 * callback was invoked. 5849 */ 5850 if (zio->io_flags & ZIO_FLAG_REEXECUTED) { 5851 arc_cksum_free(hdr); 5852#ifdef illumos 5853 arc_buf_unwatch(buf); 5854#endif 5855 if (hdr->b_l1hdr.b_pabd != NULL) { 5856 if (arc_buf_is_shared(buf)) { 5857 arc_unshare_buf(hdr, buf); 5858 } else { 5859 arc_hdr_free_pabd(hdr); 5860 } 5861 } 5862 } 5863 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 5864 ASSERT(!HDR_SHARED_DATA(hdr)); 5865 ASSERT(!arc_buf_is_shared(buf)); 5866 5867 callback->awcb_ready(zio, buf, callback->awcb_private); 5868 5869 if (HDR_IO_IN_PROGRESS(hdr)) 5870 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED); 5871 5872 arc_cksum_compute(buf); 5873 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 5874 5875 enum zio_compress compress; 5876 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5877 compress = ZIO_COMPRESS_OFF; 5878 } else { 5879 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp)); 5880 compress = BP_GET_COMPRESS(zio->io_bp); 5881 } 5882 HDR_SET_PSIZE(hdr, psize); 5883 arc_hdr_set_compress(hdr, compress); 5884 5885 5886 /* 5887 * Fill the hdr with data. If the hdr is compressed, the data we want 5888 * is available from the zio, otherwise we can take it from the buf. 5889 * 5890 * We might be able to share the buf's data with the hdr here. However, 5891 * doing so would cause the ARC to be full of linear ABDs if we write a 5892 * lot of shareable data. As a compromise, we check whether scattered 5893 * ABDs are allowed, and assume that if they are then the user wants 5894 * the ARC to be primarily filled with them regardless of the data being 5895 * written. Therefore, if they're allowed then we allocate one and copy 5896 * the data into it; otherwise, we share the data directly if we can. 5897 */ 5898 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) { 5899 arc_hdr_alloc_pabd(hdr); 5900 5901 /* 5902 * Ideally, we would always copy the io_abd into b_pabd, but the 5903 * user may have disabled compressed ARC, thus we must check the 5904 * hdr's compression setting rather than the io_bp's. 5905 */ 5906 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) { 5907 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, 5908 ZIO_COMPRESS_OFF); 5909 ASSERT3U(psize, >, 0); 5910 5911 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize); 5912 } else { 5913 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr)); 5914 5915 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data, 5916 arc_buf_size(buf)); 5917 } 5918 } else { 5919 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd)); 5920 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf)); 5921 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1); 5922 5923 arc_share_buf(hdr, buf); 5924 } 5925 5926 arc_hdr_verify(hdr, zio->io_bp); 5927} 5928 5929static void 5930arc_write_children_ready(zio_t *zio) 5931{ 5932 arc_write_callback_t *callback = zio->io_private; 5933 arc_buf_t *buf = callback->awcb_buf; 5934 5935 callback->awcb_children_ready(zio, buf, callback->awcb_private); 5936} 5937 5938/* 5939 * The SPA calls this callback for each physical write that happens on behalf 5940 * of a logical write. See the comment in dbuf_write_physdone() for details. 5941 */ 5942static void 5943arc_write_physdone(zio_t *zio) 5944{ 5945 arc_write_callback_t *cb = zio->io_private; 5946 if (cb->awcb_physdone != NULL) 5947 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private); 5948} 5949 5950static void 5951arc_write_done(zio_t *zio) 5952{ 5953 arc_write_callback_t *callback = zio->io_private; 5954 arc_buf_t *buf = callback->awcb_buf; 5955 arc_buf_hdr_t *hdr = buf->b_hdr; 5956 5957 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 5958 5959 if (zio->io_error == 0) { 5960 arc_hdr_verify(hdr, zio->io_bp); 5961 5962 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) { 5963 buf_discard_identity(hdr); 5964 } else { 5965 hdr->b_dva = *BP_IDENTITY(zio->io_bp); 5966 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp); 5967 } 5968 } else { 5969 ASSERT(HDR_EMPTY(hdr)); 5970 } 5971 5972 /* 5973 * If the block to be written was all-zero or compressed enough to be 5974 * embedded in the BP, no write was performed so there will be no 5975 * dva/birth/checksum. The buffer must therefore remain anonymous 5976 * (and uncached). 5977 */ 5978 if (!HDR_EMPTY(hdr)) { 5979 arc_buf_hdr_t *exists; 5980 kmutex_t *hash_lock; 5981 5982 ASSERT3U(zio->io_error, ==, 0); 5983 5984 arc_cksum_verify(buf); 5985 5986 exists = buf_hash_insert(hdr, &hash_lock); 5987 if (exists != NULL) { 5988 /* 5989 * This can only happen if we overwrite for 5990 * sync-to-convergence, because we remove 5991 * buffers from the hash table when we arc_free(). 5992 */ 5993 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) { 5994 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 5995 panic("bad overwrite, hdr=%p exists=%p", 5996 (void *)hdr, (void *)exists); 5997 ASSERT(refcount_is_zero( 5998 &exists->b_l1hdr.b_refcnt)); 5999 arc_change_state(arc_anon, exists, hash_lock); 6000 mutex_exit(hash_lock); 6001 arc_hdr_destroy(exists); 6002 exists = buf_hash_insert(hdr, &hash_lock); 6003 ASSERT3P(exists, ==, NULL); 6004 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) { 6005 /* nopwrite */ 6006 ASSERT(zio->io_prop.zp_nopwrite); 6007 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp)) 6008 panic("bad nopwrite, hdr=%p exists=%p", 6009 (void *)hdr, (void *)exists); 6010 } else { 6011 /* Dedup */ 6012 ASSERT(hdr->b_l1hdr.b_bufcnt == 1); 6013 ASSERT(hdr->b_l1hdr.b_state == arc_anon); 6014 ASSERT(BP_GET_DEDUP(zio->io_bp)); 6015 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0); 6016 } 6017 } 6018 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6019 /* if it's not anon, we are doing a scrub */ 6020 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon) 6021 arc_access(hdr, hash_lock); 6022 mutex_exit(hash_lock); 6023 } else { 6024 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS); 6025 } 6026 6027 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt)); 6028 callback->awcb_done(zio, buf, callback->awcb_private); 6029 6030 abd_put(zio->io_abd); 6031 kmem_free(callback, sizeof (arc_write_callback_t)); 6032} 6033 6034zio_t * 6035arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf, 6036 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready, 6037 arc_done_func_t *children_ready, arc_done_func_t *physdone, 6038 arc_done_func_t *done, void *private, zio_priority_t priority, 6039 int zio_flags, const zbookmark_phys_t *zb) 6040{ 6041 arc_buf_hdr_t *hdr = buf->b_hdr; 6042 arc_write_callback_t *callback; 6043 zio_t *zio; 6044 zio_prop_t localprop = *zp; 6045 6046 ASSERT3P(ready, !=, NULL); 6047 ASSERT3P(done, !=, NULL); 6048 ASSERT(!HDR_IO_ERROR(hdr)); 6049 ASSERT(!HDR_IO_IN_PROGRESS(hdr)); 6050 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL); 6051 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0); 6052 if (l2arc) 6053 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE); 6054 if (ARC_BUF_COMPRESSED(buf)) { 6055 /* 6056 * We're writing a pre-compressed buffer. Make the 6057 * compression algorithm requested by the zio_prop_t match 6058 * the pre-compressed buffer's compression algorithm. 6059 */ 6060 localprop.zp_compress = HDR_GET_COMPRESS(hdr); 6061 6062 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf)); 6063 zio_flags |= ZIO_FLAG_RAW; 6064 } 6065 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP); 6066 callback->awcb_ready = ready; 6067 callback->awcb_children_ready = children_ready; 6068 callback->awcb_physdone = physdone; 6069 callback->awcb_done = done; 6070 callback->awcb_private = private; 6071 callback->awcb_buf = buf; 6072 6073 /* 6074 * The hdr's b_pabd is now stale, free it now. A new data block 6075 * will be allocated when the zio pipeline calls arc_write_ready(). 6076 */ 6077 if (hdr->b_l1hdr.b_pabd != NULL) { 6078 /* 6079 * If the buf is currently sharing the data block with 6080 * the hdr then we need to break that relationship here. 6081 * The hdr will remain with a NULL data pointer and the 6082 * buf will take sole ownership of the block. 6083 */ 6084 if (arc_buf_is_shared(buf)) { 6085 arc_unshare_buf(hdr, buf); 6086 } else { 6087 arc_hdr_free_pabd(hdr); 6088 } 6089 VERIFY3P(buf->b_data, !=, NULL); 6090 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF); 6091 } 6092 ASSERT(!arc_buf_is_shared(buf)); 6093 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL); 6094 6095 zio = zio_write(pio, spa, txg, bp, 6096 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)), 6097 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready, 6098 (children_ready != NULL) ? arc_write_children_ready : NULL, 6099 arc_write_physdone, arc_write_done, callback, 6100 priority, zio_flags, zb); 6101 6102 return (zio); 6103} 6104 6105static int 6106arc_memory_throttle(uint64_t reserve, uint64_t txg) 6107{ 6108#ifdef _KERNEL 6109 uint64_t available_memory = ptob(freemem); 6110 static uint64_t page_load = 0; 6111 static uint64_t last_txg = 0; 6112 6113#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC) 6114 available_memory = 6115 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE))); 6116#endif 6117 6118 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100) 6119 return (0); 6120 6121 if (txg > last_txg) { 6122 last_txg = txg; 6123 page_load = 0; 6124 } 6125 /* 6126 * If we are in pageout, we know that memory is already tight, 6127 * the arc is already going to be evicting, so we just want to 6128 * continue to let page writes occur as quickly as possible. 6129 */ 6130 if (curproc == pageproc) { 6131 if (page_load > MAX(ptob(minfree), available_memory) / 4) 6132 return (SET_ERROR(ERESTART)); 6133 /* Note: reserve is inflated, so we deflate */ 6134 page_load += reserve / 8; 6135 return (0); 6136 } else if (page_load > 0 && arc_reclaim_needed()) { 6137 /* memory is low, delay before restarting */ 6138 ARCSTAT_INCR(arcstat_memory_throttle_count, 1); 6139 return (SET_ERROR(EAGAIN)); 6140 } 6141 page_load = 0; 6142#endif 6143 return (0); 6144} 6145 6146void 6147arc_tempreserve_clear(uint64_t reserve) 6148{ 6149 atomic_add_64(&arc_tempreserve, -reserve); 6150 ASSERT((int64_t)arc_tempreserve >= 0); 6151} 6152 6153int 6154arc_tempreserve_space(uint64_t reserve, uint64_t txg) 6155{ 6156 int error; 6157 uint64_t anon_size; 6158 6159 if (reserve > arc_c/4 && !arc_no_grow) { 6160 arc_c = MIN(arc_c_max, reserve * 4); 6161 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c); 6162 } 6163 if (reserve > arc_c) 6164 return (SET_ERROR(ENOMEM)); 6165 6166 /* 6167 * Don't count loaned bufs as in flight dirty data to prevent long 6168 * network delays from blocking transactions that are ready to be 6169 * assigned to a txg. 6170 */ 6171 6172 /* assert that it has not wrapped around */ 6173 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0); 6174 6175 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) - 6176 arc_loaned_bytes), 0); 6177 6178 /* 6179 * Writes will, almost always, require additional memory allocations 6180 * in order to compress/encrypt/etc the data. We therefore need to 6181 * make sure that there is sufficient available memory for this. 6182 */ 6183 error = arc_memory_throttle(reserve, txg); 6184 if (error != 0) 6185 return (error); 6186 6187 /* 6188 * Throttle writes when the amount of dirty data in the cache 6189 * gets too large. We try to keep the cache less than half full 6190 * of dirty blocks so that our sync times don't grow too large. 6191 * Note: if two requests come in concurrently, we might let them 6192 * both succeed, when one of them should fail. Not a huge deal. 6193 */ 6194 6195 if (reserve + arc_tempreserve + anon_size > arc_c / 2 && 6196 anon_size > arc_c / 4) { 6197 uint64_t meta_esize = 6198 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6199 uint64_t data_esize = 6200 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6201 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK " 6202 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n", 6203 arc_tempreserve >> 10, meta_esize >> 10, 6204 data_esize >> 10, reserve >> 10, arc_c >> 10); 6205 return (SET_ERROR(ERESTART)); 6206 } 6207 atomic_add_64(&arc_tempreserve, reserve); 6208 return (0); 6209} 6210 6211static void 6212arc_kstat_update_state(arc_state_t *state, kstat_named_t *size, 6213 kstat_named_t *evict_data, kstat_named_t *evict_metadata) 6214{ 6215 size->value.ui64 = refcount_count(&state->arcs_size); 6216 evict_data->value.ui64 = 6217 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]); 6218 evict_metadata->value.ui64 = 6219 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]); 6220} 6221 6222static int 6223arc_kstat_update(kstat_t *ksp, int rw) 6224{ 6225 arc_stats_t *as = ksp->ks_data; 6226 6227 if (rw == KSTAT_WRITE) { 6228 return (EACCES); 6229 } else { 6230 arc_kstat_update_state(arc_anon, 6231 &as->arcstat_anon_size, 6232 &as->arcstat_anon_evictable_data, 6233 &as->arcstat_anon_evictable_metadata); 6234 arc_kstat_update_state(arc_mru, 6235 &as->arcstat_mru_size, 6236 &as->arcstat_mru_evictable_data, 6237 &as->arcstat_mru_evictable_metadata); 6238 arc_kstat_update_state(arc_mru_ghost, 6239 &as->arcstat_mru_ghost_size, 6240 &as->arcstat_mru_ghost_evictable_data, 6241 &as->arcstat_mru_ghost_evictable_metadata); 6242 arc_kstat_update_state(arc_mfu, 6243 &as->arcstat_mfu_size, 6244 &as->arcstat_mfu_evictable_data, 6245 &as->arcstat_mfu_evictable_metadata); 6246 arc_kstat_update_state(arc_mfu_ghost, 6247 &as->arcstat_mfu_ghost_size, 6248 &as->arcstat_mfu_ghost_evictable_data, 6249 &as->arcstat_mfu_ghost_evictable_metadata); 6250 } 6251 6252 return (0); 6253} 6254 6255/* 6256 * This function *must* return indices evenly distributed between all 6257 * sublists of the multilist. This is needed due to how the ARC eviction 6258 * code is laid out; arc_evict_state() assumes ARC buffers are evenly 6259 * distributed between all sublists and uses this assumption when 6260 * deciding which sublist to evict from and how much to evict from it. 6261 */ 6262unsigned int 6263arc_state_multilist_index_func(multilist_t *ml, void *obj) 6264{ 6265 arc_buf_hdr_t *hdr = obj; 6266 6267 /* 6268 * We rely on b_dva to generate evenly distributed index 6269 * numbers using buf_hash below. So, as an added precaution, 6270 * let's make sure we never add empty buffers to the arc lists. 6271 */ 6272 ASSERT(!HDR_EMPTY(hdr)); 6273 6274 /* 6275 * The assumption here, is the hash value for a given 6276 * arc_buf_hdr_t will remain constant throughout it's lifetime 6277 * (i.e. it's b_spa, b_dva, and b_birth fields don't change). 6278 * Thus, we don't need to store the header's sublist index 6279 * on insertion, as this index can be recalculated on removal. 6280 * 6281 * Also, the low order bits of the hash value are thought to be 6282 * distributed evenly. Otherwise, in the case that the multilist 6283 * has a power of two number of sublists, each sublists' usage 6284 * would not be evenly distributed. 6285 */ 6286 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) % 6287 multilist_get_num_sublists(ml)); 6288} 6289 6290#ifdef _KERNEL 6291static eventhandler_tag arc_event_lowmem = NULL; 6292 6293static void 6294arc_lowmem(void *arg __unused, int howto __unused) 6295{ 6296 6297 mutex_enter(&arc_reclaim_lock); 6298 DTRACE_PROBE1(arc__needfree, int64_t, ((int64_t)freemem - zfs_arc_free_target) * PAGESIZE); 6299 cv_signal(&arc_reclaim_thread_cv); 6300 6301 /* 6302 * It is unsafe to block here in arbitrary threads, because we can come 6303 * here from ARC itself and may hold ARC locks and thus risk a deadlock 6304 * with ARC reclaim thread. 6305 */ 6306 if (curproc == pageproc) 6307 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock); 6308 mutex_exit(&arc_reclaim_lock); 6309} 6310#endif 6311 6312static void 6313arc_state_init(void) 6314{ 6315 arc_anon = &ARC_anon; 6316 arc_mru = &ARC_mru; 6317 arc_mru_ghost = &ARC_mru_ghost; 6318 arc_mfu = &ARC_mfu; 6319 arc_mfu_ghost = &ARC_mfu_ghost; 6320 arc_l2c_only = &ARC_l2c_only; 6321 6322 arc_mru->arcs_list[ARC_BUFC_METADATA] = 6323 multilist_create(sizeof (arc_buf_hdr_t), 6324 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6325 arc_state_multilist_index_func); 6326 arc_mru->arcs_list[ARC_BUFC_DATA] = 6327 multilist_create(sizeof (arc_buf_hdr_t), 6328 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6329 arc_state_multilist_index_func); 6330 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] = 6331 multilist_create(sizeof (arc_buf_hdr_t), 6332 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6333 arc_state_multilist_index_func); 6334 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] = 6335 multilist_create(sizeof (arc_buf_hdr_t), 6336 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6337 arc_state_multilist_index_func); 6338 arc_mfu->arcs_list[ARC_BUFC_METADATA] = 6339 multilist_create(sizeof (arc_buf_hdr_t), 6340 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6341 arc_state_multilist_index_func); 6342 arc_mfu->arcs_list[ARC_BUFC_DATA] = 6343 multilist_create(sizeof (arc_buf_hdr_t), 6344 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6345 arc_state_multilist_index_func); 6346 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] = 6347 multilist_create(sizeof (arc_buf_hdr_t), 6348 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6349 arc_state_multilist_index_func); 6350 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] = 6351 multilist_create(sizeof (arc_buf_hdr_t), 6352 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6353 arc_state_multilist_index_func); 6354 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] = 6355 multilist_create(sizeof (arc_buf_hdr_t), 6356 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6357 arc_state_multilist_index_func); 6358 arc_l2c_only->arcs_list[ARC_BUFC_DATA] = 6359 multilist_create(sizeof (arc_buf_hdr_t), 6360 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node), 6361 arc_state_multilist_index_func); 6362 6363 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6364 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6365 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6366 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6367 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6368 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6369 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6370 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6371 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6372 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6373 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6374 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6375 6376 refcount_create(&arc_anon->arcs_size); 6377 refcount_create(&arc_mru->arcs_size); 6378 refcount_create(&arc_mru_ghost->arcs_size); 6379 refcount_create(&arc_mfu->arcs_size); 6380 refcount_create(&arc_mfu_ghost->arcs_size); 6381 refcount_create(&arc_l2c_only->arcs_size); 6382} 6383 6384static void 6385arc_state_fini(void) 6386{ 6387 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]); 6388 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]); 6389 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]); 6390 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]); 6391 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]); 6392 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]); 6393 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]); 6394 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]); 6395 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]); 6396 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]); 6397 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]); 6398 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]); 6399 6400 refcount_destroy(&arc_anon->arcs_size); 6401 refcount_destroy(&arc_mru->arcs_size); 6402 refcount_destroy(&arc_mru_ghost->arcs_size); 6403 refcount_destroy(&arc_mfu->arcs_size); 6404 refcount_destroy(&arc_mfu_ghost->arcs_size); 6405 refcount_destroy(&arc_l2c_only->arcs_size); 6406 6407 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]); 6408 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]); 6409 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]); 6410 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]); 6411 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]); 6412 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]); 6413 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]); 6414 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]); 6415} 6416 6417uint64_t 6418arc_max_bytes(void) 6419{ 6420 return (arc_c_max); 6421} 6422 6423void 6424arc_init(void) 6425{ 6426 int i, prefetch_tunable_set = 0; 6427 6428 /* 6429 * allmem is "all memory that we could possibly use". 6430 */ 6431#ifdef illumos 6432#ifdef _KERNEL 6433 uint64_t allmem = ptob(physmem - swapfs_minfree); 6434#else 6435 uint64_t allmem = (physmem * PAGESIZE) / 2; 6436#endif 6437#else 6438 uint64_t allmem = kmem_size(); 6439#endif 6440 6441 6442 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL); 6443 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL); 6444 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL); 6445 6446 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL); 6447 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL); 6448 6449 /* Convert seconds to clock ticks */ 6450 arc_min_prefetch_lifespan = 1 * hz; 6451 6452 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */ 6453 arc_c_min = MAX(allmem / 32, arc_abs_min); 6454 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */ 6455 if (allmem >= 1 << 30) 6456 arc_c_max = allmem - (1 << 30); 6457 else 6458 arc_c_max = arc_c_min; 6459 arc_c_max = MAX(allmem * 5 / 8, arc_c_max); 6460 6461 /* 6462 * In userland, there's only the memory pressure that we artificially 6463 * create (see arc_available_memory()). Don't let arc_c get too 6464 * small, because it can cause transactions to be larger than 6465 * arc_c, causing arc_tempreserve_space() to fail. 6466 */ 6467#ifndef _KERNEL 6468 arc_c_min = arc_c_max / 2; 6469#endif 6470 6471#ifdef _KERNEL 6472 /* 6473 * Allow the tunables to override our calculations if they are 6474 * reasonable. 6475 */ 6476 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) { 6477 arc_c_max = zfs_arc_max; 6478 arc_c_min = MIN(arc_c_min, arc_c_max); 6479 } 6480 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max) 6481 arc_c_min = zfs_arc_min; 6482#endif 6483 6484 arc_c = arc_c_max; 6485 arc_p = (arc_c >> 1); 6486 arc_size = 0; 6487 6488 /* limit meta-data to 1/4 of the arc capacity */ 6489 arc_meta_limit = arc_c_max / 4; 6490 6491#ifdef _KERNEL 6492 /* 6493 * Metadata is stored in the kernel's heap. Don't let us 6494 * use more than half the heap for the ARC. 6495 */ 6496 arc_meta_limit = MIN(arc_meta_limit, 6497 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2); 6498#endif 6499 6500 /* Allow the tunable to override if it is reasonable */ 6501 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max) 6502 arc_meta_limit = zfs_arc_meta_limit; 6503 6504 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0) 6505 arc_c_min = arc_meta_limit / 2; 6506 6507 if (zfs_arc_meta_min > 0) { 6508 arc_meta_min = zfs_arc_meta_min; 6509 } else { 6510 arc_meta_min = arc_c_min / 2; 6511 } 6512 6513 if (zfs_arc_grow_retry > 0) 6514 arc_grow_retry = zfs_arc_grow_retry; 6515 6516 if (zfs_arc_shrink_shift > 0) 6517 arc_shrink_shift = zfs_arc_shrink_shift; 6518 6519 if (zfs_arc_no_grow_shift > 0) 6520 arc_no_grow_shift = zfs_arc_no_grow_shift; 6521 /* 6522 * Ensure that arc_no_grow_shift is less than arc_shrink_shift. 6523 */ 6524 if (arc_no_grow_shift >= arc_shrink_shift) 6525 arc_no_grow_shift = arc_shrink_shift - 1; 6526 6527 if (zfs_arc_p_min_shift > 0) 6528 arc_p_min_shift = zfs_arc_p_min_shift; 6529 6530 /* if kmem_flags are set, lets try to use less memory */ 6531 if (kmem_debugging()) 6532 arc_c = arc_c / 2; 6533 if (arc_c < arc_c_min) 6534 arc_c = arc_c_min; 6535 6536 zfs_arc_min = arc_c_min; 6537 zfs_arc_max = arc_c_max; 6538 6539 arc_state_init(); 6540 buf_init(); 6541 6542 arc_reclaim_thread_exit = B_FALSE; 6543 arc_dnlc_evicts_thread_exit = FALSE; 6544 6545 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED, 6546 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); 6547 6548 if (arc_ksp != NULL) { 6549 arc_ksp->ks_data = &arc_stats; 6550 arc_ksp->ks_update = arc_kstat_update; 6551 kstat_install(arc_ksp); 6552 } 6553 6554 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0, 6555 TS_RUN, minclsyspri); 6556 6557#ifdef _KERNEL 6558 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL, 6559 EVENTHANDLER_PRI_FIRST); 6560#endif 6561 6562 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0, 6563 TS_RUN, minclsyspri); 6564 6565 arc_dead = B_FALSE; 6566 arc_warm = B_FALSE; 6567 6568 /* 6569 * Calculate maximum amount of dirty data per pool. 6570 * 6571 * If it has been set by /etc/system, take that. 6572 * Otherwise, use a percentage of physical memory defined by 6573 * zfs_dirty_data_max_percent (default 10%) with a cap at 6574 * zfs_dirty_data_max_max (default 4GB). 6575 */ 6576 if (zfs_dirty_data_max == 0) { 6577 zfs_dirty_data_max = ptob(physmem) * 6578 zfs_dirty_data_max_percent / 100; 6579 zfs_dirty_data_max = MIN(zfs_dirty_data_max, 6580 zfs_dirty_data_max_max); 6581 } 6582 6583#ifdef _KERNEL 6584 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable)) 6585 prefetch_tunable_set = 1; 6586 6587#ifdef __i386__ 6588 if (prefetch_tunable_set == 0) { 6589 printf("ZFS NOTICE: Prefetch is disabled by default on i386 " 6590 "-- to enable,\n"); 6591 printf(" add \"vfs.zfs.prefetch_disable=0\" " 6592 "to /boot/loader.conf.\n"); 6593 zfs_prefetch_disable = 1; 6594 } 6595#else 6596 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) && 6597 prefetch_tunable_set == 0) { 6598 printf("ZFS NOTICE: Prefetch is disabled by default if less " 6599 "than 4GB of RAM is present;\n" 6600 " to enable, add \"vfs.zfs.prefetch_disable=0\" " 6601 "to /boot/loader.conf.\n"); 6602 zfs_prefetch_disable = 1; 6603 } 6604#endif 6605 /* Warn about ZFS memory and address space requirements. */ 6606 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) { 6607 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; " 6608 "expect unstable behavior.\n"); 6609 } 6610 if (allmem < 512 * (1 << 20)) { 6611 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; " 6612 "expect unstable behavior.\n"); 6613 printf(" Consider tuning vm.kmem_size and " 6614 "vm.kmem_size_max\n"); 6615 printf(" in /boot/loader.conf.\n"); 6616 } 6617#endif 6618} 6619 6620void 6621arc_fini(void) 6622{ 6623#ifdef _KERNEL 6624 if (arc_event_lowmem != NULL) 6625 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem); 6626#endif 6627 6628 mutex_enter(&arc_reclaim_lock); 6629 arc_reclaim_thread_exit = B_TRUE; 6630 /* 6631 * The reclaim thread will set arc_reclaim_thread_exit back to 6632 * B_FALSE when it is finished exiting; we're waiting for that. 6633 */ 6634 while (arc_reclaim_thread_exit) { 6635 cv_signal(&arc_reclaim_thread_cv); 6636 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock); 6637 } 6638 mutex_exit(&arc_reclaim_lock); 6639 6640 /* Use B_TRUE to ensure *all* buffers are evicted */ 6641 arc_flush(NULL, B_TRUE); 6642 6643 mutex_enter(&arc_dnlc_evicts_lock); 6644 arc_dnlc_evicts_thread_exit = TRUE; 6645 /* 6646 * The user evicts thread will set arc_user_evicts_thread_exit 6647 * to FALSE when it is finished exiting; we're waiting for that. 6648 */ 6649 while (arc_dnlc_evicts_thread_exit) { 6650 cv_signal(&arc_dnlc_evicts_cv); 6651 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock); 6652 } 6653 mutex_exit(&arc_dnlc_evicts_lock); 6654 6655 arc_dead = B_TRUE; 6656 6657 if (arc_ksp != NULL) { 6658 kstat_delete(arc_ksp); 6659 arc_ksp = NULL; 6660 } 6661 6662 mutex_destroy(&arc_reclaim_lock); 6663 cv_destroy(&arc_reclaim_thread_cv); 6664 cv_destroy(&arc_reclaim_waiters_cv); 6665 6666 mutex_destroy(&arc_dnlc_evicts_lock); 6667 cv_destroy(&arc_dnlc_evicts_cv); 6668 6669 arc_state_fini(); 6670 buf_fini(); 6671 6672 ASSERT0(arc_loaned_bytes); 6673} 6674 6675/* 6676 * Level 2 ARC 6677 * 6678 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk. 6679 * It uses dedicated storage devices to hold cached data, which are populated 6680 * using large infrequent writes. The main role of this cache is to boost 6681 * the performance of random read workloads. The intended L2ARC devices 6682 * include short-stroked disks, solid state disks, and other media with 6683 * substantially faster read latency than disk. 6684 * 6685 * +-----------------------+ 6686 * | ARC | 6687 * +-----------------------+ 6688 * | ^ ^ 6689 * | | | 6690 * l2arc_feed_thread() arc_read() 6691 * | | | 6692 * | l2arc read | 6693 * V | | 6694 * +---------------+ | 6695 * | L2ARC | | 6696 * +---------------+ | 6697 * | ^ | 6698 * l2arc_write() | | 6699 * | | | 6700 * V | | 6701 * +-------+ +-------+ 6702 * | vdev | | vdev | 6703 * | cache | | cache | 6704 * +-------+ +-------+ 6705 * +=========+ .-----. 6706 * : L2ARC : |-_____-| 6707 * : devices : | Disks | 6708 * +=========+ `-_____-' 6709 * 6710 * Read requests are satisfied from the following sources, in order: 6711 * 6712 * 1) ARC 6713 * 2) vdev cache of L2ARC devices 6714 * 3) L2ARC devices 6715 * 4) vdev cache of disks 6716 * 5) disks 6717 * 6718 * Some L2ARC device types exhibit extremely slow write performance. 6719 * To accommodate for this there are some significant differences between 6720 * the L2ARC and traditional cache design: 6721 * 6722 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from 6723 * the ARC behave as usual, freeing buffers and placing headers on ghost 6724 * lists. The ARC does not send buffers to the L2ARC during eviction as 6725 * this would add inflated write latencies for all ARC memory pressure. 6726 * 6727 * 2. The L2ARC attempts to cache data from the ARC before it is evicted. 6728 * It does this by periodically scanning buffers from the eviction-end of 6729 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are 6730 * not already there. It scans until a headroom of buffers is satisfied, 6731 * which itself is a buffer for ARC eviction. If a compressible buffer is 6732 * found during scanning and selected for writing to an L2ARC device, we 6733 * temporarily boost scanning headroom during the next scan cycle to make 6734 * sure we adapt to compression effects (which might significantly reduce 6735 * the data volume we write to L2ARC). The thread that does this is 6736 * l2arc_feed_thread(), illustrated below; example sizes are included to 6737 * provide a better sense of ratio than this diagram: 6738 * 6739 * head --> tail 6740 * +---------------------+----------+ 6741 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC 6742 * +---------------------+----------+ | o L2ARC eligible 6743 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer 6744 * +---------------------+----------+ | 6745 * 15.9 Gbytes ^ 32 Mbytes | 6746 * headroom | 6747 * l2arc_feed_thread() 6748 * | 6749 * l2arc write hand <--[oooo]--' 6750 * | 8 Mbyte 6751 * | write max 6752 * V 6753 * +==============================+ 6754 * L2ARC dev |####|#|###|###| |####| ... | 6755 * +==============================+ 6756 * 32 Gbytes 6757 * 6758 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of 6759 * evicted, then the L2ARC has cached a buffer much sooner than it probably 6760 * needed to, potentially wasting L2ARC device bandwidth and storage. It is 6761 * safe to say that this is an uncommon case, since buffers at the end of 6762 * the ARC lists have moved there due to inactivity. 6763 * 6764 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom, 6765 * then the L2ARC simply misses copying some buffers. This serves as a 6766 * pressure valve to prevent heavy read workloads from both stalling the ARC 6767 * with waits and clogging the L2ARC with writes. This also helps prevent 6768 * the potential for the L2ARC to churn if it attempts to cache content too 6769 * quickly, such as during backups of the entire pool. 6770 * 6771 * 5. After system boot and before the ARC has filled main memory, there are 6772 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru 6773 * lists can remain mostly static. Instead of searching from tail of these 6774 * lists as pictured, the l2arc_feed_thread() will search from the list heads 6775 * for eligible buffers, greatly increasing its chance of finding them. 6776 * 6777 * The L2ARC device write speed is also boosted during this time so that 6778 * the L2ARC warms up faster. Since there have been no ARC evictions yet, 6779 * there are no L2ARC reads, and no fear of degrading read performance 6780 * through increased writes. 6781 * 6782 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that 6783 * the vdev queue can aggregate them into larger and fewer writes. Each 6784 * device is written to in a rotor fashion, sweeping writes through 6785 * available space then repeating. 6786 * 6787 * 7. The L2ARC does not store dirty content. It never needs to flush 6788 * write buffers back to disk based storage. 6789 * 6790 * 8. If an ARC buffer is written (and dirtied) which also exists in the 6791 * L2ARC, the now stale L2ARC buffer is immediately dropped. 6792 * 6793 * The performance of the L2ARC can be tweaked by a number of tunables, which 6794 * may be necessary for different workloads: 6795 * 6796 * l2arc_write_max max write bytes per interval 6797 * l2arc_write_boost extra write bytes during device warmup 6798 * l2arc_noprefetch skip caching prefetched buffers 6799 * l2arc_headroom number of max device writes to precache 6800 * l2arc_headroom_boost when we find compressed buffers during ARC 6801 * scanning, we multiply headroom by this 6802 * percentage factor for the next scan cycle, 6803 * since more compressed buffers are likely to 6804 * be present 6805 * l2arc_feed_secs seconds between L2ARC writing 6806 * 6807 * Tunables may be removed or added as future performance improvements are 6808 * integrated, and also may become zpool properties. 6809 * 6810 * There are three key functions that control how the L2ARC warms up: 6811 * 6812 * l2arc_write_eligible() check if a buffer is eligible to cache 6813 * l2arc_write_size() calculate how much to write 6814 * l2arc_write_interval() calculate sleep delay between writes 6815 * 6816 * These three functions determine what to write, how much, and how quickly 6817 * to send writes. 6818 */ 6819 6820static boolean_t 6821l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr) 6822{ 6823 /* 6824 * A buffer is *not* eligible for the L2ARC if it: 6825 * 1. belongs to a different spa. 6826 * 2. is already cached on the L2ARC. 6827 * 3. has an I/O in progress (it may be an incomplete read). 6828 * 4. is flagged not eligible (zfs property). 6829 */ 6830 if (hdr->b_spa != spa_guid) { 6831 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch); 6832 return (B_FALSE); 6833 } 6834 if (HDR_HAS_L2HDR(hdr)) { 6835 ARCSTAT_BUMP(arcstat_l2_write_in_l2); 6836 return (B_FALSE); 6837 } 6838 if (HDR_IO_IN_PROGRESS(hdr)) { 6839 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress); 6840 return (B_FALSE); 6841 } 6842 if (!HDR_L2CACHE(hdr)) { 6843 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable); 6844 return (B_FALSE); 6845 } 6846 6847 return (B_TRUE); 6848} 6849 6850static uint64_t 6851l2arc_write_size(void) 6852{ 6853 uint64_t size; 6854 6855 /* 6856 * Make sure our globals have meaningful values in case the user 6857 * altered them. 6858 */ 6859 size = l2arc_write_max; 6860 if (size == 0) { 6861 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must " 6862 "be greater than zero, resetting it to the default (%d)", 6863 L2ARC_WRITE_SIZE); 6864 size = l2arc_write_max = L2ARC_WRITE_SIZE; 6865 } 6866 6867 if (arc_warm == B_FALSE) 6868 size += l2arc_write_boost; 6869 6870 return (size); 6871 6872} 6873 6874static clock_t 6875l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote) 6876{ 6877 clock_t interval, next, now; 6878 6879 /* 6880 * If the ARC lists are busy, increase our write rate; if the 6881 * lists are stale, idle back. This is achieved by checking 6882 * how much we previously wrote - if it was more than half of 6883 * what we wanted, schedule the next write much sooner. 6884 */ 6885 if (l2arc_feed_again && wrote > (wanted / 2)) 6886 interval = (hz * l2arc_feed_min_ms) / 1000; 6887 else 6888 interval = hz * l2arc_feed_secs; 6889 6890 now = ddi_get_lbolt(); 6891 next = MAX(now, MIN(now + interval, began + interval)); 6892 6893 return (next); 6894} 6895 6896/* 6897 * Cycle through L2ARC devices. This is how L2ARC load balances. 6898 * If a device is returned, this also returns holding the spa config lock. 6899 */ 6900static l2arc_dev_t * 6901l2arc_dev_get_next(void) 6902{ 6903 l2arc_dev_t *first, *next = NULL; 6904 6905 /* 6906 * Lock out the removal of spas (spa_namespace_lock), then removal 6907 * of cache devices (l2arc_dev_mtx). Once a device has been selected, 6908 * both locks will be dropped and a spa config lock held instead. 6909 */ 6910 mutex_enter(&spa_namespace_lock); 6911 mutex_enter(&l2arc_dev_mtx); 6912 6913 /* if there are no vdevs, there is nothing to do */ 6914 if (l2arc_ndev == 0) 6915 goto out; 6916 6917 first = NULL; 6918 next = l2arc_dev_last; 6919 do { 6920 /* loop around the list looking for a non-faulted vdev */ 6921 if (next == NULL) { 6922 next = list_head(l2arc_dev_list); 6923 } else { 6924 next = list_next(l2arc_dev_list, next); 6925 if (next == NULL) 6926 next = list_head(l2arc_dev_list); 6927 } 6928 6929 /* if we have come back to the start, bail out */ 6930 if (first == NULL) 6931 first = next; 6932 else if (next == first) 6933 break; 6934 6935 } while (vdev_is_dead(next->l2ad_vdev)); 6936 6937 /* if we were unable to find any usable vdevs, return NULL */ 6938 if (vdev_is_dead(next->l2ad_vdev)) 6939 next = NULL; 6940 6941 l2arc_dev_last = next; 6942 6943out: 6944 mutex_exit(&l2arc_dev_mtx); 6945 6946 /* 6947 * Grab the config lock to prevent the 'next' device from being 6948 * removed while we are writing to it. 6949 */ 6950 if (next != NULL) 6951 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER); 6952 mutex_exit(&spa_namespace_lock); 6953 6954 return (next); 6955} 6956 6957/* 6958 * Free buffers that were tagged for destruction. 6959 */ 6960static void 6961l2arc_do_free_on_write() 6962{ 6963 list_t *buflist; 6964 l2arc_data_free_t *df, *df_prev; 6965 6966 mutex_enter(&l2arc_free_on_write_mtx); 6967 buflist = l2arc_free_on_write; 6968 6969 for (df = list_tail(buflist); df; df = df_prev) { 6970 df_prev = list_prev(buflist, df); 6971 ASSERT3P(df->l2df_abd, !=, NULL); 6972 abd_free(df->l2df_abd); 6973 list_remove(buflist, df); 6974 kmem_free(df, sizeof (l2arc_data_free_t)); 6975 } 6976 6977 mutex_exit(&l2arc_free_on_write_mtx); 6978} 6979 6980/* 6981 * A write to a cache device has completed. Update all headers to allow 6982 * reads from these buffers to begin. 6983 */ 6984static void 6985l2arc_write_done(zio_t *zio) 6986{ 6987 l2arc_write_callback_t *cb; 6988 l2arc_dev_t *dev; 6989 list_t *buflist; 6990 arc_buf_hdr_t *head, *hdr, *hdr_prev; 6991 kmutex_t *hash_lock; 6992 int64_t bytes_dropped = 0; 6993 6994 cb = zio->io_private; 6995 ASSERT3P(cb, !=, NULL); 6996 dev = cb->l2wcb_dev; 6997 ASSERT3P(dev, !=, NULL); 6998 head = cb->l2wcb_head; 6999 ASSERT3P(head, !=, NULL); 7000 buflist = &dev->l2ad_buflist; 7001 ASSERT3P(buflist, !=, NULL); 7002 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio, 7003 l2arc_write_callback_t *, cb); 7004 7005 if (zio->io_error != 0) 7006 ARCSTAT_BUMP(arcstat_l2_writes_error); 7007 7008 /* 7009 * All writes completed, or an error was hit. 7010 */ 7011top: 7012 mutex_enter(&dev->l2ad_mtx); 7013 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) { 7014 hdr_prev = list_prev(buflist, hdr); 7015 7016 hash_lock = HDR_LOCK(hdr); 7017 7018 /* 7019 * We cannot use mutex_enter or else we can deadlock 7020 * with l2arc_write_buffers (due to swapping the order 7021 * the hash lock and l2ad_mtx are taken). 7022 */ 7023 if (!mutex_tryenter(hash_lock)) { 7024 /* 7025 * Missed the hash lock. We must retry so we 7026 * don't leave the ARC_FLAG_L2_WRITING bit set. 7027 */ 7028 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry); 7029 7030 /* 7031 * We don't want to rescan the headers we've 7032 * already marked as having been written out, so 7033 * we reinsert the head node so we can pick up 7034 * where we left off. 7035 */ 7036 list_remove(buflist, head); 7037 list_insert_after(buflist, hdr, head); 7038 7039 mutex_exit(&dev->l2ad_mtx); 7040 7041 /* 7042 * We wait for the hash lock to become available 7043 * to try and prevent busy waiting, and increase 7044 * the chance we'll be able to acquire the lock 7045 * the next time around. 7046 */ 7047 mutex_enter(hash_lock); 7048 mutex_exit(hash_lock); 7049 goto top; 7050 } 7051 7052 /* 7053 * We could not have been moved into the arc_l2c_only 7054 * state while in-flight due to our ARC_FLAG_L2_WRITING 7055 * bit being set. Let's just ensure that's being enforced. 7056 */ 7057 ASSERT(HDR_HAS_L1HDR(hdr)); 7058 7059 if (zio->io_error != 0) { 7060 /* 7061 * Error - drop L2ARC entry. 7062 */ 7063 list_remove(buflist, hdr); 7064 l2arc_trim(hdr); 7065 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR); 7066 7067 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr)); 7068 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr)); 7069 7070 bytes_dropped += arc_hdr_size(hdr); 7071 (void) refcount_remove_many(&dev->l2ad_alloc, 7072 arc_hdr_size(hdr), hdr); 7073 } 7074 7075 /* 7076 * Allow ARC to begin reads and ghost list evictions to 7077 * this L2ARC entry. 7078 */ 7079 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING); 7080 7081 mutex_exit(hash_lock); 7082 } 7083 7084 atomic_inc_64(&l2arc_writes_done); 7085 list_remove(buflist, head); 7086 ASSERT(!HDR_HAS_L1HDR(head)); 7087 kmem_cache_free(hdr_l2only_cache, head); 7088 mutex_exit(&dev->l2ad_mtx); 7089 7090 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0); 7091 7092 l2arc_do_free_on_write(); 7093 7094 kmem_free(cb, sizeof (l2arc_write_callback_t)); 7095} 7096 7097/* 7098 * A read to a cache device completed. Validate buffer contents before 7099 * handing over to the regular ARC routines. 7100 */ 7101static void 7102l2arc_read_done(zio_t *zio) 7103{ 7104 l2arc_read_callback_t *cb; 7105 arc_buf_hdr_t *hdr; 7106 kmutex_t *hash_lock; 7107 boolean_t valid_cksum; 7108 7109 ASSERT3P(zio->io_vd, !=, NULL); 7110 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE); 7111 7112 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd); 7113 7114 cb = zio->io_private; 7115 ASSERT3P(cb, !=, NULL); 7116 hdr = cb->l2rcb_hdr; 7117 ASSERT3P(hdr, !=, NULL); 7118 7119 hash_lock = HDR_LOCK(hdr); 7120 mutex_enter(hash_lock); 7121 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr)); 7122 7123 /* 7124 * If the data was read into a temporary buffer, 7125 * move it and free the buffer. 7126 */ 7127 if (cb->l2rcb_abd != NULL) { 7128 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size); 7129 if (zio->io_error == 0) { 7130 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd, 7131 arc_hdr_size(hdr)); 7132 } 7133 7134 /* 7135 * The following must be done regardless of whether 7136 * there was an error: 7137 * - free the temporary buffer 7138 * - point zio to the real ARC buffer 7139 * - set zio size accordingly 7140 * These are required because zio is either re-used for 7141 * an I/O of the block in the case of the error 7142 * or the zio is passed to arc_read_done() and it 7143 * needs real data. 7144 */ 7145 abd_free(cb->l2rcb_abd); 7146 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr); 7147 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd; 7148 } 7149 7150 ASSERT3P(zio->io_abd, !=, NULL); 7151 7152 /* 7153 * Check this survived the L2ARC journey. 7154 */ 7155 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd); 7156 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */ 7157 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */ 7158 7159 valid_cksum = arc_cksum_is_equal(hdr, zio); 7160 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) { 7161 mutex_exit(hash_lock); 7162 zio->io_private = hdr; 7163 arc_read_done(zio); 7164 } else { 7165 mutex_exit(hash_lock); 7166 /* 7167 * Buffer didn't survive caching. Increment stats and 7168 * reissue to the original storage device. 7169 */ 7170 if (zio->io_error != 0) { 7171 ARCSTAT_BUMP(arcstat_l2_io_error); 7172 } else { 7173 zio->io_error = SET_ERROR(EIO); 7174 } 7175 if (!valid_cksum) 7176 ARCSTAT_BUMP(arcstat_l2_cksum_bad); 7177 7178 /* 7179 * If there's no waiter, issue an async i/o to the primary 7180 * storage now. If there *is* a waiter, the caller must 7181 * issue the i/o in a context where it's OK to block. 7182 */ 7183 if (zio->io_waiter == NULL) { 7184 zio_t *pio = zio_unique_parent(zio); 7185 7186 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL); 7187 7188 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp, 7189 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done, 7190 hdr, zio->io_priority, cb->l2rcb_flags, 7191 &cb->l2rcb_zb)); 7192 } 7193 } 7194 7195 kmem_free(cb, sizeof (l2arc_read_callback_t)); 7196} 7197 7198/* 7199 * This is the list priority from which the L2ARC will search for pages to 7200 * cache. This is used within loops (0..3) to cycle through lists in the 7201 * desired order. This order can have a significant effect on cache 7202 * performance. 7203 * 7204 * Currently the metadata lists are hit first, MFU then MRU, followed by 7205 * the data lists. This function returns a locked list, and also returns 7206 * the lock pointer. 7207 */ 7208static multilist_sublist_t * 7209l2arc_sublist_lock(int list_num) 7210{ 7211 multilist_t *ml = NULL; 7212 unsigned int idx; 7213 7214 ASSERT(list_num >= 0 && list_num <= 3); 7215 7216 switch (list_num) { 7217 case 0: 7218 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA]; 7219 break; 7220 case 1: 7221 ml = arc_mru->arcs_list[ARC_BUFC_METADATA]; 7222 break; 7223 case 2: 7224 ml = arc_mfu->arcs_list[ARC_BUFC_DATA]; 7225 break; 7226 case 3: 7227 ml = arc_mru->arcs_list[ARC_BUFC_DATA]; 7228 break; 7229 } 7230 7231 /* 7232 * Return a randomly-selected sublist. This is acceptable 7233 * because the caller feeds only a little bit of data for each 7234 * call (8MB). Subsequent calls will result in different 7235 * sublists being selected. 7236 */ 7237 idx = multilist_get_random_index(ml); 7238 return (multilist_sublist_lock(ml, idx)); 7239} 7240 7241/* 7242 * Evict buffers from the device write hand to the distance specified in 7243 * bytes. This distance may span populated buffers, it may span nothing. 7244 * This is clearing a region on the L2ARC device ready for writing. 7245 * If the 'all' boolean is set, every buffer is evicted. 7246 */ 7247static void 7248l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all) 7249{ 7250 list_t *buflist; 7251 arc_buf_hdr_t *hdr, *hdr_prev; 7252 kmutex_t *hash_lock; 7253 uint64_t taddr; 7254 7255 buflist = &dev->l2ad_buflist; 7256 7257 if (!all && dev->l2ad_first) { 7258 /* 7259 * This is the first sweep through the device. There is 7260 * nothing to evict. 7261 */ 7262 return; 7263 } 7264 7265 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) { 7266 /* 7267 * When nearing the end of the device, evict to the end 7268 * before the device write hand jumps to the start. 7269 */ 7270 taddr = dev->l2ad_end; 7271 } else { 7272 taddr = dev->l2ad_hand + distance; 7273 } 7274 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist, 7275 uint64_t, taddr, boolean_t, all); 7276 7277top: 7278 mutex_enter(&dev->l2ad_mtx); 7279 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) { 7280 hdr_prev = list_prev(buflist, hdr); 7281 7282 hash_lock = HDR_LOCK(hdr); 7283 7284 /* 7285 * We cannot use mutex_enter or else we can deadlock 7286 * with l2arc_write_buffers (due to swapping the order 7287 * the hash lock and l2ad_mtx are taken). 7288 */ 7289 if (!mutex_tryenter(hash_lock)) { 7290 /* 7291 * Missed the hash lock. Retry. 7292 */ 7293 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry); 7294 mutex_exit(&dev->l2ad_mtx); 7295 mutex_enter(hash_lock); 7296 mutex_exit(hash_lock); 7297 goto top; 7298 } 7299 7300 /* 7301 * A header can't be on this list if it doesn't have L2 header. 7302 */ 7303 ASSERT(HDR_HAS_L2HDR(hdr)); 7304 7305 /* Ensure this header has finished being written. */ 7306 ASSERT(!HDR_L2_WRITING(hdr)); 7307 ASSERT(!HDR_L2_WRITE_HEAD(hdr)); 7308 7309 if (!all && (hdr->b_l2hdr.b_daddr >= taddr || 7310 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) { 7311 /* 7312 * We've evicted to the target address, 7313 * or the end of the device. 7314 */ 7315 mutex_exit(hash_lock); 7316 break; 7317 } 7318 7319 if (!HDR_HAS_L1HDR(hdr)) { 7320 ASSERT(!HDR_L2_READING(hdr)); 7321 /* 7322 * This doesn't exist in the ARC. Destroy. 7323 * arc_hdr_destroy() will call list_remove() 7324 * and decrement arcstat_l2_lsize. 7325 */ 7326 arc_change_state(arc_anon, hdr, hash_lock); 7327 arc_hdr_destroy(hdr); 7328 } else { 7329 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only); 7330 ARCSTAT_BUMP(arcstat_l2_evict_l1cached); 7331 /* 7332 * Invalidate issued or about to be issued 7333 * reads, since we may be about to write 7334 * over this location. 7335 */ 7336 if (HDR_L2_READING(hdr)) { 7337 ARCSTAT_BUMP(arcstat_l2_evict_reading); 7338 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED); 7339 } 7340 7341 arc_hdr_l2hdr_destroy(hdr); 7342 } 7343 mutex_exit(hash_lock); 7344 } 7345 mutex_exit(&dev->l2ad_mtx); 7346} 7347 7348/* 7349 * Find and write ARC buffers to the L2ARC device. 7350 * 7351 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid 7352 * for reading until they have completed writing. 7353 * The headroom_boost is an in-out parameter used to maintain headroom boost 7354 * state between calls to this function. 7355 * 7356 * Returns the number of bytes actually written (which may be smaller than 7357 * the delta by which the device hand has changed due to alignment). 7358 */ 7359static uint64_t 7360l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz) 7361{ 7362 arc_buf_hdr_t *hdr, *hdr_prev, *head; 7363 uint64_t write_asize, write_psize, write_lsize, headroom; 7364 boolean_t full; 7365 l2arc_write_callback_t *cb; 7366 zio_t *pio, *wzio; 7367 uint64_t guid = spa_load_guid(spa); 7368 int try; 7369 7370 ASSERT3P(dev->l2ad_vdev, !=, NULL); 7371 7372 pio = NULL; 7373 write_lsize = write_asize = write_psize = 0; 7374 full = B_FALSE; 7375 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE); 7376 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR); 7377 7378 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter); 7379 /* 7380 * Copy buffers for L2ARC writing. 7381 */ 7382 for (try = 0; try <= 3; try++) { 7383 multilist_sublist_t *mls = l2arc_sublist_lock(try); 7384 uint64_t passed_sz = 0; 7385 7386 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter); 7387 7388 /* 7389 * L2ARC fast warmup. 7390 * 7391 * Until the ARC is warm and starts to evict, read from the 7392 * head of the ARC lists rather than the tail. 7393 */ 7394 if (arc_warm == B_FALSE) 7395 hdr = multilist_sublist_head(mls); 7396 else 7397 hdr = multilist_sublist_tail(mls); 7398 if (hdr == NULL) 7399 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter); 7400 7401 headroom = target_sz * l2arc_headroom; 7402 if (zfs_compressed_arc_enabled) 7403 headroom = (headroom * l2arc_headroom_boost) / 100; 7404 7405 for (; hdr; hdr = hdr_prev) { 7406 kmutex_t *hash_lock; 7407 7408 if (arc_warm == B_FALSE) 7409 hdr_prev = multilist_sublist_next(mls, hdr); 7410 else 7411 hdr_prev = multilist_sublist_prev(mls, hdr); 7412 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, 7413 HDR_GET_LSIZE(hdr)); 7414 7415 hash_lock = HDR_LOCK(hdr); 7416 if (!mutex_tryenter(hash_lock)) { 7417 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail); 7418 /* 7419 * Skip this buffer rather than waiting. 7420 */ 7421 continue; 7422 } 7423 7424 passed_sz += HDR_GET_LSIZE(hdr); 7425 if (passed_sz > headroom) { 7426 /* 7427 * Searched too far. 7428 */ 7429 mutex_exit(hash_lock); 7430 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom); 7431 break; 7432 } 7433 7434 if (!l2arc_write_eligible(guid, hdr)) { 7435 mutex_exit(hash_lock); 7436 continue; 7437 } 7438 7439 /* 7440 * We rely on the L1 portion of the header below, so 7441 * it's invalid for this header to have been evicted out 7442 * of the ghost cache, prior to being written out. The 7443 * ARC_FLAG_L2_WRITING bit ensures this won't happen. 7444 */ 7445 ASSERT(HDR_HAS_L1HDR(hdr)); 7446 7447 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0); 7448 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL); 7449 ASSERT3U(arc_hdr_size(hdr), >, 0); 7450 uint64_t psize = arc_hdr_size(hdr); 7451 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, 7452 psize); 7453 7454 if ((write_asize + asize) > target_sz) { 7455 full = B_TRUE; 7456 mutex_exit(hash_lock); 7457 ARCSTAT_BUMP(arcstat_l2_write_full); 7458 break; 7459 } 7460 7461 if (pio == NULL) { 7462 /* 7463 * Insert a dummy header on the buflist so 7464 * l2arc_write_done() can find where the 7465 * write buffers begin without searching. 7466 */ 7467 mutex_enter(&dev->l2ad_mtx); 7468 list_insert_head(&dev->l2ad_buflist, head); 7469 mutex_exit(&dev->l2ad_mtx); 7470 7471 cb = kmem_alloc( 7472 sizeof (l2arc_write_callback_t), KM_SLEEP); 7473 cb->l2wcb_dev = dev; 7474 cb->l2wcb_head = head; 7475 pio = zio_root(spa, l2arc_write_done, cb, 7476 ZIO_FLAG_CANFAIL); 7477 ARCSTAT_BUMP(arcstat_l2_write_pios); 7478 } 7479 7480 hdr->b_l2hdr.b_dev = dev; 7481 hdr->b_l2hdr.b_daddr = dev->l2ad_hand; 7482 arc_hdr_set_flags(hdr, 7483 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR); 7484 7485 mutex_enter(&dev->l2ad_mtx); 7486 list_insert_head(&dev->l2ad_buflist, hdr); 7487 mutex_exit(&dev->l2ad_mtx); 7488 7489 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr); 7490 7491 /* 7492 * Normally the L2ARC can use the hdr's data, but if 7493 * we're sharing data between the hdr and one of its 7494 * bufs, L2ARC needs its own copy of the data so that 7495 * the ZIO below can't race with the buf consumer. 7496 * Another case where we need to create a copy of the 7497 * data is when the buffer size is not device-aligned 7498 * and we need to pad the block to make it such. 7499 * That also keeps the clock hand suitably aligned. 7500 * 7501 * To ensure that the copy will be available for the 7502 * lifetime of the ZIO and be cleaned up afterwards, we 7503 * add it to the l2arc_free_on_write queue. 7504 */ 7505 abd_t *to_write; 7506 if (!HDR_SHARED_DATA(hdr) && psize == asize) { 7507 to_write = hdr->b_l1hdr.b_pabd; 7508 } else { 7509 to_write = abd_alloc_for_io(asize, 7510 HDR_ISTYPE_METADATA(hdr)); 7511 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize); 7512 if (asize != psize) { 7513 abd_zero_off(to_write, psize, 7514 asize - psize); 7515 } 7516 l2arc_free_abd_on_write(to_write, asize, 7517 arc_buf_type(hdr)); 7518 } 7519 wzio = zio_write_phys(pio, dev->l2ad_vdev, 7520 hdr->b_l2hdr.b_daddr, asize, to_write, 7521 ZIO_CHECKSUM_OFF, NULL, hdr, 7522 ZIO_PRIORITY_ASYNC_WRITE, 7523 ZIO_FLAG_CANFAIL, B_FALSE); 7524 7525 write_lsize += HDR_GET_LSIZE(hdr); 7526 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, 7527 zio_t *, wzio); 7528 7529 write_psize += psize; 7530 write_asize += asize; 7531 dev->l2ad_hand += asize; 7532 7533 mutex_exit(hash_lock); 7534 7535 (void) zio_nowait(wzio); 7536 } 7537 7538 multilist_sublist_unlock(mls); 7539 7540 if (full == B_TRUE) 7541 break; 7542 } 7543 7544 /* No buffers selected for writing? */ 7545 if (pio == NULL) { 7546 ASSERT0(write_lsize); 7547 ASSERT(!HDR_HAS_L1HDR(head)); 7548 kmem_cache_free(hdr_l2only_cache, head); 7549 return (0); 7550 } 7551 7552 ASSERT3U(write_psize, <=, target_sz); 7553 ARCSTAT_BUMP(arcstat_l2_writes_sent); 7554 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize); 7555 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize); 7556 ARCSTAT_INCR(arcstat_l2_psize, write_psize); 7557 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0); 7558 7559 /* 7560 * Bump device hand to the device start if it is approaching the end. 7561 * l2arc_evict() will already have evicted ahead for this case. 7562 */ 7563 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) { 7564 dev->l2ad_hand = dev->l2ad_start; 7565 dev->l2ad_first = B_FALSE; 7566 } 7567 7568 dev->l2ad_writing = B_TRUE; 7569 (void) zio_wait(pio); 7570 dev->l2ad_writing = B_FALSE; 7571 7572 return (write_asize); 7573} 7574 7575/* 7576 * This thread feeds the L2ARC at regular intervals. This is the beating 7577 * heart of the L2ARC. 7578 */ 7579static void 7580l2arc_feed_thread(void *dummy __unused) 7581{ 7582 callb_cpr_t cpr; 7583 l2arc_dev_t *dev; 7584 spa_t *spa; 7585 uint64_t size, wrote; 7586 clock_t begin, next = ddi_get_lbolt(); 7587 7588 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG); 7589 7590 mutex_enter(&l2arc_feed_thr_lock); 7591 7592 while (l2arc_thread_exit == 0) { 7593 CALLB_CPR_SAFE_BEGIN(&cpr); 7594 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock, 7595 next - ddi_get_lbolt()); 7596 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock); 7597 next = ddi_get_lbolt() + hz; 7598 7599 /* 7600 * Quick check for L2ARC devices. 7601 */ 7602 mutex_enter(&l2arc_dev_mtx); 7603 if (l2arc_ndev == 0) { 7604 mutex_exit(&l2arc_dev_mtx); 7605 continue; 7606 } 7607 mutex_exit(&l2arc_dev_mtx); 7608 begin = ddi_get_lbolt(); 7609 7610 /* 7611 * This selects the next l2arc device to write to, and in 7612 * doing so the next spa to feed from: dev->l2ad_spa. This 7613 * will return NULL if there are now no l2arc devices or if 7614 * they are all faulted. 7615 * 7616 * If a device is returned, its spa's config lock is also 7617 * held to prevent device removal. l2arc_dev_get_next() 7618 * will grab and release l2arc_dev_mtx. 7619 */ 7620 if ((dev = l2arc_dev_get_next()) == NULL) 7621 continue; 7622 7623 spa = dev->l2ad_spa; 7624 ASSERT3P(spa, !=, NULL); 7625 7626 /* 7627 * If the pool is read-only then force the feed thread to 7628 * sleep a little longer. 7629 */ 7630 if (!spa_writeable(spa)) { 7631 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz; 7632 spa_config_exit(spa, SCL_L2ARC, dev); 7633 continue; 7634 } 7635 7636 /* 7637 * Avoid contributing to memory pressure. 7638 */ 7639 if (arc_reclaim_needed()) { 7640 ARCSTAT_BUMP(arcstat_l2_abort_lowmem); 7641 spa_config_exit(spa, SCL_L2ARC, dev); 7642 continue; 7643 } 7644 7645 ARCSTAT_BUMP(arcstat_l2_feeds); 7646 7647 size = l2arc_write_size(); 7648 7649 /* 7650 * Evict L2ARC buffers that will be overwritten. 7651 */ 7652 l2arc_evict(dev, size, B_FALSE); 7653 7654 /* 7655 * Write ARC buffers. 7656 */ 7657 wrote = l2arc_write_buffers(spa, dev, size); 7658 7659 /* 7660 * Calculate interval between writes. 7661 */ 7662 next = l2arc_write_interval(begin, size, wrote); 7663 spa_config_exit(spa, SCL_L2ARC, dev); 7664 } 7665 7666 l2arc_thread_exit = 0; 7667 cv_broadcast(&l2arc_feed_thr_cv); 7668 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */ 7669 thread_exit(); 7670} 7671 7672boolean_t 7673l2arc_vdev_present(vdev_t *vd) 7674{ 7675 l2arc_dev_t *dev; 7676 7677 mutex_enter(&l2arc_dev_mtx); 7678 for (dev = list_head(l2arc_dev_list); dev != NULL; 7679 dev = list_next(l2arc_dev_list, dev)) { 7680 if (dev->l2ad_vdev == vd) 7681 break; 7682 } 7683 mutex_exit(&l2arc_dev_mtx); 7684 7685 return (dev != NULL); 7686} 7687 7688/* 7689 * Add a vdev for use by the L2ARC. By this point the spa has already 7690 * validated the vdev and opened it. 7691 */ 7692void 7693l2arc_add_vdev(spa_t *spa, vdev_t *vd) 7694{ 7695 l2arc_dev_t *adddev; 7696 7697 ASSERT(!l2arc_vdev_present(vd)); 7698 7699 vdev_ashift_optimize(vd); 7700 7701 /* 7702 * Create a new l2arc device entry. 7703 */ 7704 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP); 7705 adddev->l2ad_spa = spa; 7706 adddev->l2ad_vdev = vd; 7707 adddev->l2ad_start = VDEV_LABEL_START_SIZE; 7708 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd); 7709 adddev->l2ad_hand = adddev->l2ad_start; 7710 adddev->l2ad_first = B_TRUE; 7711 adddev->l2ad_writing = B_FALSE; 7712 7713 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL); 7714 /* 7715 * This is a list of all ARC buffers that are still valid on the 7716 * device. 7717 */ 7718 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t), 7719 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node)); 7720 7721 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand); 7722 refcount_create(&adddev->l2ad_alloc); 7723 7724 /* 7725 * Add device to global list 7726 */ 7727 mutex_enter(&l2arc_dev_mtx); 7728 list_insert_head(l2arc_dev_list, adddev); 7729 atomic_inc_64(&l2arc_ndev); 7730 mutex_exit(&l2arc_dev_mtx); 7731} 7732 7733/* 7734 * Remove a vdev from the L2ARC. 7735 */ 7736void 7737l2arc_remove_vdev(vdev_t *vd) 7738{ 7739 l2arc_dev_t *dev, *nextdev, *remdev = NULL; 7740 7741 /* 7742 * Find the device by vdev 7743 */ 7744 mutex_enter(&l2arc_dev_mtx); 7745 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) { 7746 nextdev = list_next(l2arc_dev_list, dev); 7747 if (vd == dev->l2ad_vdev) { 7748 remdev = dev; 7749 break; 7750 } 7751 } 7752 ASSERT3P(remdev, !=, NULL); 7753 7754 /* 7755 * Remove device from global list 7756 */ 7757 list_remove(l2arc_dev_list, remdev); 7758 l2arc_dev_last = NULL; /* may have been invalidated */ 7759 atomic_dec_64(&l2arc_ndev); 7760 mutex_exit(&l2arc_dev_mtx); 7761 7762 /* 7763 * Clear all buflists and ARC references. L2ARC device flush. 7764 */ 7765 l2arc_evict(remdev, 0, B_TRUE); 7766 list_destroy(&remdev->l2ad_buflist); 7767 mutex_destroy(&remdev->l2ad_mtx); 7768 refcount_destroy(&remdev->l2ad_alloc); 7769 kmem_free(remdev, sizeof (l2arc_dev_t)); 7770} 7771 7772void 7773l2arc_init(void) 7774{ 7775 l2arc_thread_exit = 0; 7776 l2arc_ndev = 0; 7777 l2arc_writes_sent = 0; 7778 l2arc_writes_done = 0; 7779 7780 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL); 7781 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL); 7782 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL); 7783 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL); 7784 7785 l2arc_dev_list = &L2ARC_dev_list; 7786 l2arc_free_on_write = &L2ARC_free_on_write; 7787 list_create(l2arc_dev_list, sizeof (l2arc_dev_t), 7788 offsetof(l2arc_dev_t, l2ad_node)); 7789 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t), 7790 offsetof(l2arc_data_free_t, l2df_list_node)); 7791} 7792 7793void 7794l2arc_fini(void) 7795{ 7796 /* 7797 * This is called from dmu_fini(), which is called from spa_fini(); 7798 * Because of this, we can assume that all l2arc devices have 7799 * already been removed when the pools themselves were removed. 7800 */ 7801 7802 l2arc_do_free_on_write(); 7803 7804 mutex_destroy(&l2arc_feed_thr_lock); 7805 cv_destroy(&l2arc_feed_thr_cv); 7806 mutex_destroy(&l2arc_dev_mtx); 7807 mutex_destroy(&l2arc_free_on_write_mtx); 7808 7809 list_destroy(l2arc_dev_list); 7810 list_destroy(l2arc_free_on_write); 7811} 7812 7813void 7814l2arc_start(void) 7815{ 7816 if (!(spa_mode_global & FWRITE)) 7817 return; 7818 7819 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0, 7820 TS_RUN, minclsyspri); 7821} 7822 7823void 7824l2arc_stop(void) 7825{ 7826 if (!(spa_mode_global & FWRITE)) 7827 return; 7828 7829 mutex_enter(&l2arc_feed_thr_lock); 7830 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */ 7831 l2arc_thread_exit = 1; 7832 while (l2arc_thread_exit != 0) 7833 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock); 7834 mutex_exit(&l2arc_feed_thr_lock); 7835} 7836