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10 * See the License for the specific language governing permissions
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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]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2018, Joyent, Inc.
24 * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved.
30 * DVA-based Adjustable Replacement Cache
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:
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.
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.
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
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.
70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 * by N. Megiddo & D. Modha, FAST 2003
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
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).
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.
93 * buf_hash_remove() expects the appropriate hash mutex to be
94 * already held before it is invoked.
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.
102 * It as also possible to register a callback which is run when the
103 * arc_meta_limit is reached and no buffers can be safely evicted. In
104 * this case the arc user should drop a reference on some arc buffers so
105 * they can be reclaimed and the arc_meta_limit honored. For example,
106 * when using the ZPL each dentry holds a references on a znode. These
107 * dentries must be pruned before the arc buffer holding the znode can
110 * Note that the majority of the performance stats are manipulated
111 * with atomic operations.
113 * The L2ARC uses the l2ad_mtx on each vdev for the following:
115 * - L2ARC buflist creation
116 * - L2ARC buflist eviction
117 * - L2ARC write completion, which walks L2ARC buflists
118 * - ARC header destruction, as it removes from L2ARC buflists
119 * - ARC header release, as it removes from L2ARC buflists
125 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
126 * This structure can point either to a block that is still in the cache or to
127 * one that is only accessible in an L2 ARC device, or it can provide
128 * information about a block that was recently evicted. If a block is
129 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
130 * information to retrieve it from the L2ARC device. This information is
131 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
132 * that is in this state cannot access the data directly.
134 * Blocks that are actively being referenced or have not been evicted
135 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
136 * the arc_buf_hdr_t that will point to the data block in memory. A block can
137 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
138 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
139 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
141 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
142 * ability to store the physical data (b_pabd) associated with the DVA of the
143 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
144 * it will match its on-disk compression characteristics. This behavior can be
145 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
146 * compressed ARC functionality is disabled, the b_pabd will point to an
147 * uncompressed version of the on-disk data.
149 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
150 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
151 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
152 * consumer. The ARC will provide references to this data and will keep it
153 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
154 * data block and will evict any arc_buf_t that is no longer referenced. The
155 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
156 * "overhead_size" kstat.
158 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
159 * compressed form. The typical case is that consumers will want uncompressed
160 * data, and when that happens a new data buffer is allocated where the data is
161 * decompressed for them to use. Currently the only consumer who wants
162 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
163 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
164 * with the arc_buf_hdr_t.
166 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
167 * first one is owned by a compressed send consumer (and therefore references
168 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
169 * used by any other consumer (and has its own uncompressed copy of the data
184 * | b_buf +------------>+-----------+ arc_buf_t
185 * | b_pabd +-+ |b_next +---->+-----------+
186 * +-----------+ | |-----------| |b_next +-->NULL
187 * | |b_comp = T | +-----------+
188 * | |b_data +-+ |b_comp = F |
189 * | +-----------+ | |b_data +-+
190 * +->+------+ | +-----------+ |
192 * data | |<--------------+ | uncompressed
193 * +------+ compressed, | data
194 * shared +-->+------+
199 * When a consumer reads a block, the ARC must first look to see if the
200 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
201 * arc_buf_t and either copies uncompressed data into a new data buffer from an
202 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
203 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
204 * hdr is compressed and the desired compression characteristics of the
205 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
206 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
207 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
208 * be anywhere in the hdr's list.
210 * The diagram below shows an example of an uncompressed ARC hdr that is
211 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
212 * the last element in the buf list):
224 * | | arc_buf_t (shared)
225 * | b_buf +------------>+---------+ arc_buf_t
226 * | | |b_next +---->+---------+
227 * | b_pabd +-+ |---------| |b_next +-->NULL
228 * +-----------+ | | | +---------+
230 * | +---------+ | |b_data +-+
231 * +->+------+ | +---------+ |
233 * uncompressed | | | |
236 * | uncompressed | | |
239 * +---------------------------------+
241 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
242 * since the physical block is about to be rewritten. The new data contents
243 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
244 * it may compress the data before writing it to disk. The ARC will be called
245 * with the transformed data and will bcopy the transformed on-disk block into
246 * a newly allocated b_pabd. Writes are always done into buffers which have
247 * either been loaned (and hence are new and don't have other readers) or
248 * buffers which have been released (and hence have their own hdr, if there
249 * were originally other readers of the buf's original hdr). This ensures that
250 * the ARC only needs to update a single buf and its hdr after a write occurs.
252 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
253 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
254 * that when compressed ARC is enabled that the L2ARC blocks are identical
255 * to the on-disk block in the main data pool. This provides a significant
256 * advantage since the ARC can leverage the bp's checksum when reading from the
257 * L2ARC to determine if the contents are valid. However, if the compressed
258 * ARC is disabled, then the L2ARC's block must be transformed to look
259 * like the physical block in the main data pool before comparing the
260 * checksum and determining its validity.
262 * The L1ARC has a slightly different system for storing encrypted data.
263 * Raw (encrypted + possibly compressed) data has a few subtle differences from
264 * data that is just compressed. The biggest difference is that it is not
265 * possible to decrypt encrypted data (or visa versa) if the keys aren't loaded.
266 * The other difference is that encryption cannot be treated as a suggestion.
267 * If a caller would prefer compressed data, but they actually wind up with
268 * uncompressed data the worst thing that could happen is there might be a
269 * performance hit. If the caller requests encrypted data, however, we must be
270 * sure they actually get it or else secret information could be leaked. Raw
271 * data is stored in hdr->b_crypt_hdr.b_rabd. An encrypted header, therefore,
272 * may have both an encrypted version and a decrypted version of its data at
273 * once. When a caller needs a raw arc_buf_t, it is allocated and the data is
274 * copied out of this header. To avoid complications with b_pabd, raw buffers
280 #include <sys/spa_impl.h>
281 #include <sys/zio_compress.h>
282 #include <sys/zio_checksum.h>
283 #include <sys/zfs_context.h>
285 #include <sys/refcount.h>
286 #include <sys/vdev.h>
287 #include <sys/vdev_impl.h>
288 #include <sys/dsl_pool.h>
289 #include <sys/zio_checksum.h>
290 #include <sys/multilist.h>
293 #include <sys/fm/fs/zfs.h>
295 #include <sys/shrinker.h>
296 #include <sys/vmsystm.h>
298 #include <linux/page_compat.h>
300 #include <sys/callb.h>
301 #include <sys/kstat.h>
302 #include <sys/zthr.h>
303 #include <zfs_fletcher.h>
304 #include <sys/arc_impl.h>
305 #include <sys/trace_arc.h>
306 #include <sys/aggsum.h>
307 #include <sys/cityhash.h>
310 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
311 boolean_t arc_watch = B_FALSE;
315 * This thread's job is to keep enough free memory in the system, by
316 * calling arc_kmem_reap_soon() plus arc_reduce_target_size(), which improves
317 * arc_available_memory().
319 static zthr_t *arc_reap_zthr;
322 * This thread's job is to keep arc_size under arc_c, by calling
323 * arc_adjust(), which improves arc_is_overflowing().
325 static zthr_t *arc_adjust_zthr;
327 static kmutex_t arc_adjust_lock;
328 static kcondvar_t arc_adjust_waiters_cv;
329 static boolean_t arc_adjust_needed = B_FALSE;
332 * The number of headers to evict in arc_evict_state_impl() before
333 * dropping the sublist lock and evicting from another sublist. A lower
334 * value means we're more likely to evict the "correct" header (i.e. the
335 * oldest header in the arc state), but comes with higher overhead
336 * (i.e. more invocations of arc_evict_state_impl()).
338 int zfs_arc_evict_batch_limit = 10;
340 /* number of seconds before growing cache again */
341 static int arc_grow_retry = 5;
344 * Minimum time between calls to arc_kmem_reap_soon().
346 int arc_kmem_cache_reap_retry_ms = 1000;
348 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
349 int zfs_arc_overflow_shift = 8;
351 /* shift of arc_c for calculating both min and max arc_p */
352 int arc_p_min_shift = 4;
354 /* log2(fraction of arc to reclaim) */
355 static int arc_shrink_shift = 7;
357 /* percent of pagecache to reclaim arc to */
359 static uint_t zfs_arc_pc_percent = 0;
363 * log2(fraction of ARC which must be free to allow growing).
364 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
365 * when reading a new block into the ARC, we will evict an equal-sized block
368 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
369 * we will still not allow it to grow.
371 int arc_no_grow_shift = 5;
375 * minimum lifespan of a prefetch block in clock ticks
376 * (initialized in arc_init())
378 static int arc_min_prefetch_ms;
379 static int arc_min_prescient_prefetch_ms;
382 * If this percent of memory is free, don't throttle.
384 int arc_lotsfree_percent = 10;
387 * hdr_recl() uses this to determine if the arc is up and running.
389 static boolean_t arc_initialized;
392 * The arc has filled available memory and has now warmed up.
394 static boolean_t arc_warm;
397 * log2 fraction of the zio arena to keep free.
399 int arc_zio_arena_free_shift = 2;
402 * These tunables are for performance analysis.
404 unsigned long zfs_arc_max = 0;
405 unsigned long zfs_arc_min = 0;
406 unsigned long zfs_arc_meta_limit = 0;
407 unsigned long zfs_arc_meta_min = 0;
408 unsigned long zfs_arc_dnode_limit = 0;
409 unsigned long zfs_arc_dnode_reduce_percent = 10;
410 int zfs_arc_grow_retry = 0;
411 int zfs_arc_shrink_shift = 0;
412 int zfs_arc_p_min_shift = 0;
413 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
416 * ARC dirty data constraints for arc_tempreserve_space() throttle.
418 unsigned long zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */
419 unsigned long zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */
420 unsigned long zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */
423 * Enable or disable compressed arc buffers.
425 int zfs_compressed_arc_enabled = B_TRUE;
428 * ARC will evict meta buffers that exceed arc_meta_limit. This
429 * tunable make arc_meta_limit adjustable for different workloads.
431 unsigned long zfs_arc_meta_limit_percent = 75;
434 * Percentage that can be consumed by dnodes of ARC meta buffers.
436 unsigned long zfs_arc_dnode_limit_percent = 10;
439 * These tunables are Linux specific
441 unsigned long zfs_arc_sys_free = 0;
442 int zfs_arc_min_prefetch_ms = 0;
443 int zfs_arc_min_prescient_prefetch_ms = 0;
444 int zfs_arc_p_dampener_disable = 1;
445 int zfs_arc_meta_prune = 10000;
446 int zfs_arc_meta_strategy = ARC_STRATEGY_META_BALANCED;
447 int zfs_arc_meta_adjust_restarts = 4096;
448 int zfs_arc_lotsfree_percent = 10;
451 static arc_state_t ARC_anon;
452 static arc_state_t ARC_mru;
453 static arc_state_t ARC_mru_ghost;
454 static arc_state_t ARC_mfu;
455 static arc_state_t ARC_mfu_ghost;
456 static arc_state_t ARC_l2c_only;
458 typedef struct arc_stats {
459 kstat_named_t arcstat_hits;
460 kstat_named_t arcstat_misses;
461 kstat_named_t arcstat_demand_data_hits;
462 kstat_named_t arcstat_demand_data_misses;
463 kstat_named_t arcstat_demand_metadata_hits;
464 kstat_named_t arcstat_demand_metadata_misses;
465 kstat_named_t arcstat_prefetch_data_hits;
466 kstat_named_t arcstat_prefetch_data_misses;
467 kstat_named_t arcstat_prefetch_metadata_hits;
468 kstat_named_t arcstat_prefetch_metadata_misses;
469 kstat_named_t arcstat_mru_hits;
470 kstat_named_t arcstat_mru_ghost_hits;
471 kstat_named_t arcstat_mfu_hits;
472 kstat_named_t arcstat_mfu_ghost_hits;
473 kstat_named_t arcstat_deleted;
475 * Number of buffers that could not be evicted because the hash lock
476 * was held by another thread. The lock may not necessarily be held
477 * by something using the same buffer, since hash locks are shared
478 * by multiple buffers.
480 kstat_named_t arcstat_mutex_miss;
482 * Number of buffers skipped when updating the access state due to the
483 * header having already been released after acquiring the hash lock.
485 kstat_named_t arcstat_access_skip;
487 * Number of buffers skipped because they have I/O in progress, are
488 * indirect prefetch buffers that have not lived long enough, or are
489 * not from the spa we're trying to evict from.
491 kstat_named_t arcstat_evict_skip;
493 * Number of times arc_evict_state() was unable to evict enough
494 * buffers to reach its target amount.
496 kstat_named_t arcstat_evict_not_enough;
497 kstat_named_t arcstat_evict_l2_cached;
498 kstat_named_t arcstat_evict_l2_eligible;
499 kstat_named_t arcstat_evict_l2_ineligible;
500 kstat_named_t arcstat_evict_l2_skip;
501 kstat_named_t arcstat_hash_elements;
502 kstat_named_t arcstat_hash_elements_max;
503 kstat_named_t arcstat_hash_collisions;
504 kstat_named_t arcstat_hash_chains;
505 kstat_named_t arcstat_hash_chain_max;
506 kstat_named_t arcstat_p;
507 kstat_named_t arcstat_c;
508 kstat_named_t arcstat_c_min;
509 kstat_named_t arcstat_c_max;
510 /* Not updated directly; only synced in arc_kstat_update. */
511 kstat_named_t arcstat_size;
513 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
514 * Note that the compressed bytes may match the uncompressed bytes
515 * if the block is either not compressed or compressed arc is disabled.
517 kstat_named_t arcstat_compressed_size;
519 * Uncompressed size of the data stored in b_pabd. If compressed
520 * arc is disabled then this value will be identical to the stat
523 kstat_named_t arcstat_uncompressed_size;
525 * Number of bytes stored in all the arc_buf_t's. This is classified
526 * as "overhead" since this data is typically short-lived and will
527 * be evicted from the arc when it becomes unreferenced unless the
528 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
529 * values have been set (see comment in dbuf.c for more information).
531 kstat_named_t arcstat_overhead_size;
533 * Number of bytes consumed by internal ARC structures necessary
534 * for tracking purposes; these structures are not actually
535 * backed by ARC buffers. This includes arc_buf_hdr_t structures
536 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
537 * caches), and arc_buf_t structures (allocated via arc_buf_t
539 * Not updated directly; only synced in arc_kstat_update.
541 kstat_named_t arcstat_hdr_size;
543 * Number of bytes consumed by ARC buffers of type equal to
544 * ARC_BUFC_DATA. This is generally consumed by buffers backing
545 * on disk user data (e.g. plain file contents).
546 * Not updated directly; only synced in arc_kstat_update.
548 kstat_named_t arcstat_data_size;
550 * Number of bytes consumed by ARC buffers of type equal to
551 * ARC_BUFC_METADATA. This is generally consumed by buffers
552 * backing on disk data that is used for internal ZFS
553 * structures (e.g. ZAP, dnode, indirect blocks, etc).
554 * Not updated directly; only synced in arc_kstat_update.
556 kstat_named_t arcstat_metadata_size;
558 * Number of bytes consumed by dmu_buf_impl_t objects.
559 * Not updated directly; only synced in arc_kstat_update.
561 kstat_named_t arcstat_dbuf_size;
563 * Number of bytes consumed by dnode_t objects.
564 * Not updated directly; only synced in arc_kstat_update.
566 kstat_named_t arcstat_dnode_size;
568 * Number of bytes consumed by bonus buffers.
569 * Not updated directly; only synced in arc_kstat_update.
571 kstat_named_t arcstat_bonus_size;
573 * Total number of bytes consumed by ARC buffers residing in the
574 * arc_anon state. This includes *all* buffers in the arc_anon
575 * state; e.g. data, metadata, evictable, and unevictable buffers
576 * are all included in this value.
577 * Not updated directly; only synced in arc_kstat_update.
579 kstat_named_t arcstat_anon_size;
581 * Number of bytes consumed by ARC buffers that meet the
582 * following criteria: backing buffers of type ARC_BUFC_DATA,
583 * residing in the arc_anon state, and are eligible for eviction
584 * (e.g. have no outstanding holds on the buffer).
585 * Not updated directly; only synced in arc_kstat_update.
587 kstat_named_t arcstat_anon_evictable_data;
589 * Number of bytes consumed by ARC buffers that meet the
590 * following criteria: backing buffers of type ARC_BUFC_METADATA,
591 * residing in the arc_anon state, and are eligible for eviction
592 * (e.g. have no outstanding holds on the buffer).
593 * Not updated directly; only synced in arc_kstat_update.
595 kstat_named_t arcstat_anon_evictable_metadata;
597 * Total number of bytes consumed by ARC buffers residing in the
598 * arc_mru state. This includes *all* buffers in the arc_mru
599 * state; e.g. data, metadata, evictable, and unevictable buffers
600 * are all included in this value.
601 * Not updated directly; only synced in arc_kstat_update.
603 kstat_named_t arcstat_mru_size;
605 * Number of bytes consumed by ARC buffers that meet the
606 * following criteria: backing buffers of type ARC_BUFC_DATA,
607 * residing in the arc_mru state, and are eligible for eviction
608 * (e.g. have no outstanding holds on the buffer).
609 * Not updated directly; only synced in arc_kstat_update.
611 kstat_named_t arcstat_mru_evictable_data;
613 * Number of bytes consumed by ARC buffers that meet the
614 * following criteria: backing buffers of type ARC_BUFC_METADATA,
615 * residing in the arc_mru state, and are eligible for eviction
616 * (e.g. have no outstanding holds on the buffer).
617 * Not updated directly; only synced in arc_kstat_update.
619 kstat_named_t arcstat_mru_evictable_metadata;
621 * Total number of bytes that *would have been* consumed by ARC
622 * buffers in the arc_mru_ghost state. The key thing to note
623 * here, is the fact that this size doesn't actually indicate
624 * RAM consumption. The ghost lists only consist of headers and
625 * don't actually have ARC buffers linked off of these headers.
626 * Thus, *if* the headers had associated ARC buffers, these
627 * buffers *would have* consumed this number of bytes.
628 * Not updated directly; only synced in arc_kstat_update.
630 kstat_named_t arcstat_mru_ghost_size;
632 * Number of bytes that *would have been* consumed by ARC
633 * buffers that are eligible for eviction, of type
634 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
635 * Not updated directly; only synced in arc_kstat_update.
637 kstat_named_t arcstat_mru_ghost_evictable_data;
639 * Number of bytes that *would have been* consumed by ARC
640 * buffers that are eligible for eviction, of type
641 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
642 * Not updated directly; only synced in arc_kstat_update.
644 kstat_named_t arcstat_mru_ghost_evictable_metadata;
646 * Total number of bytes consumed by ARC buffers residing in the
647 * arc_mfu state. This includes *all* buffers in the arc_mfu
648 * state; e.g. data, metadata, evictable, and unevictable buffers
649 * are all included in this value.
650 * Not updated directly; only synced in arc_kstat_update.
652 kstat_named_t arcstat_mfu_size;
654 * Number of bytes consumed by ARC buffers that are eligible for
655 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
657 * Not updated directly; only synced in arc_kstat_update.
659 kstat_named_t arcstat_mfu_evictable_data;
661 * Number of bytes consumed by ARC buffers that are eligible for
662 * eviction, of type ARC_BUFC_METADATA, and reside in the
664 * Not updated directly; only synced in arc_kstat_update.
666 kstat_named_t arcstat_mfu_evictable_metadata;
668 * Total number of bytes that *would have been* consumed by ARC
669 * buffers in the arc_mfu_ghost state. See the comment above
670 * arcstat_mru_ghost_size for more details.
671 * Not updated directly; only synced in arc_kstat_update.
673 kstat_named_t arcstat_mfu_ghost_size;
675 * Number of bytes that *would have been* consumed by ARC
676 * buffers that are eligible for eviction, of type
677 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
678 * Not updated directly; only synced in arc_kstat_update.
680 kstat_named_t arcstat_mfu_ghost_evictable_data;
682 * Number of bytes that *would have been* consumed by ARC
683 * buffers that are eligible for eviction, of type
684 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
685 * Not updated directly; only synced in arc_kstat_update.
687 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
688 kstat_named_t arcstat_l2_hits;
689 kstat_named_t arcstat_l2_misses;
690 kstat_named_t arcstat_l2_feeds;
691 kstat_named_t arcstat_l2_rw_clash;
692 kstat_named_t arcstat_l2_read_bytes;
693 kstat_named_t arcstat_l2_write_bytes;
694 kstat_named_t arcstat_l2_writes_sent;
695 kstat_named_t arcstat_l2_writes_done;
696 kstat_named_t arcstat_l2_writes_error;
697 kstat_named_t arcstat_l2_writes_lock_retry;
698 kstat_named_t arcstat_l2_evict_lock_retry;
699 kstat_named_t arcstat_l2_evict_reading;
700 kstat_named_t arcstat_l2_evict_l1cached;
701 kstat_named_t arcstat_l2_free_on_write;
702 kstat_named_t arcstat_l2_abort_lowmem;
703 kstat_named_t arcstat_l2_cksum_bad;
704 kstat_named_t arcstat_l2_io_error;
705 kstat_named_t arcstat_l2_lsize;
706 kstat_named_t arcstat_l2_psize;
707 /* Not updated directly; only synced in arc_kstat_update. */
708 kstat_named_t arcstat_l2_hdr_size;
709 kstat_named_t arcstat_memory_throttle_count;
710 kstat_named_t arcstat_memory_direct_count;
711 kstat_named_t arcstat_memory_indirect_count;
712 kstat_named_t arcstat_memory_all_bytes;
713 kstat_named_t arcstat_memory_free_bytes;
714 kstat_named_t arcstat_memory_available_bytes;
715 kstat_named_t arcstat_no_grow;
716 kstat_named_t arcstat_tempreserve;
717 kstat_named_t arcstat_loaned_bytes;
718 kstat_named_t arcstat_prune;
719 /* Not updated directly; only synced in arc_kstat_update. */
720 kstat_named_t arcstat_meta_used;
721 kstat_named_t arcstat_meta_limit;
722 kstat_named_t arcstat_dnode_limit;
723 kstat_named_t arcstat_meta_max;
724 kstat_named_t arcstat_meta_min;
725 kstat_named_t arcstat_async_upgrade_sync;
726 kstat_named_t arcstat_demand_hit_predictive_prefetch;
727 kstat_named_t arcstat_demand_hit_prescient_prefetch;
728 kstat_named_t arcstat_need_free;
729 kstat_named_t arcstat_sys_free;
730 kstat_named_t arcstat_raw_size;
733 static arc_stats_t arc_stats = {
734 { "hits", KSTAT_DATA_UINT64 },
735 { "misses", KSTAT_DATA_UINT64 },
736 { "demand_data_hits", KSTAT_DATA_UINT64 },
737 { "demand_data_misses", KSTAT_DATA_UINT64 },
738 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
739 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
740 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
741 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
742 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
743 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
744 { "mru_hits", KSTAT_DATA_UINT64 },
745 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
746 { "mfu_hits", KSTAT_DATA_UINT64 },
747 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
748 { "deleted", KSTAT_DATA_UINT64 },
749 { "mutex_miss", KSTAT_DATA_UINT64 },
750 { "access_skip", KSTAT_DATA_UINT64 },
751 { "evict_skip", KSTAT_DATA_UINT64 },
752 { "evict_not_enough", KSTAT_DATA_UINT64 },
753 { "evict_l2_cached", KSTAT_DATA_UINT64 },
754 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
755 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
756 { "evict_l2_skip", KSTAT_DATA_UINT64 },
757 { "hash_elements", KSTAT_DATA_UINT64 },
758 { "hash_elements_max", KSTAT_DATA_UINT64 },
759 { "hash_collisions", KSTAT_DATA_UINT64 },
760 { "hash_chains", KSTAT_DATA_UINT64 },
761 { "hash_chain_max", KSTAT_DATA_UINT64 },
762 { "p", KSTAT_DATA_UINT64 },
763 { "c", KSTAT_DATA_UINT64 },
764 { "c_min", KSTAT_DATA_UINT64 },
765 { "c_max", KSTAT_DATA_UINT64 },
766 { "size", KSTAT_DATA_UINT64 },
767 { "compressed_size", KSTAT_DATA_UINT64 },
768 { "uncompressed_size", KSTAT_DATA_UINT64 },
769 { "overhead_size", KSTAT_DATA_UINT64 },
770 { "hdr_size", KSTAT_DATA_UINT64 },
771 { "data_size", KSTAT_DATA_UINT64 },
772 { "metadata_size", KSTAT_DATA_UINT64 },
773 { "dbuf_size", KSTAT_DATA_UINT64 },
774 { "dnode_size", KSTAT_DATA_UINT64 },
775 { "bonus_size", KSTAT_DATA_UINT64 },
776 { "anon_size", KSTAT_DATA_UINT64 },
777 { "anon_evictable_data", KSTAT_DATA_UINT64 },
778 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
779 { "mru_size", KSTAT_DATA_UINT64 },
780 { "mru_evictable_data", KSTAT_DATA_UINT64 },
781 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
782 { "mru_ghost_size", KSTAT_DATA_UINT64 },
783 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
784 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
785 { "mfu_size", KSTAT_DATA_UINT64 },
786 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
787 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
788 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
789 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
790 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
791 { "l2_hits", KSTAT_DATA_UINT64 },
792 { "l2_misses", KSTAT_DATA_UINT64 },
793 { "l2_feeds", KSTAT_DATA_UINT64 },
794 { "l2_rw_clash", KSTAT_DATA_UINT64 },
795 { "l2_read_bytes", KSTAT_DATA_UINT64 },
796 { "l2_write_bytes", KSTAT_DATA_UINT64 },
797 { "l2_writes_sent", KSTAT_DATA_UINT64 },
798 { "l2_writes_done", KSTAT_DATA_UINT64 },
799 { "l2_writes_error", KSTAT_DATA_UINT64 },
800 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
801 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
802 { "l2_evict_reading", KSTAT_DATA_UINT64 },
803 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
804 { "l2_free_on_write", KSTAT_DATA_UINT64 },
805 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
806 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
807 { "l2_io_error", KSTAT_DATA_UINT64 },
808 { "l2_size", KSTAT_DATA_UINT64 },
809 { "l2_asize", KSTAT_DATA_UINT64 },
810 { "l2_hdr_size", KSTAT_DATA_UINT64 },
811 { "memory_throttle_count", KSTAT_DATA_UINT64 },
812 { "memory_direct_count", KSTAT_DATA_UINT64 },
813 { "memory_indirect_count", KSTAT_DATA_UINT64 },
814 { "memory_all_bytes", KSTAT_DATA_UINT64 },
815 { "memory_free_bytes", KSTAT_DATA_UINT64 },
816 { "memory_available_bytes", KSTAT_DATA_INT64 },
817 { "arc_no_grow", KSTAT_DATA_UINT64 },
818 { "arc_tempreserve", KSTAT_DATA_UINT64 },
819 { "arc_loaned_bytes", KSTAT_DATA_UINT64 },
820 { "arc_prune", KSTAT_DATA_UINT64 },
821 { "arc_meta_used", KSTAT_DATA_UINT64 },
822 { "arc_meta_limit", KSTAT_DATA_UINT64 },
823 { "arc_dnode_limit", KSTAT_DATA_UINT64 },
824 { "arc_meta_max", KSTAT_DATA_UINT64 },
825 { "arc_meta_min", KSTAT_DATA_UINT64 },
826 { "async_upgrade_sync", KSTAT_DATA_UINT64 },
827 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
828 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
829 { "arc_need_free", KSTAT_DATA_UINT64 },
830 { "arc_sys_free", KSTAT_DATA_UINT64 },
831 { "arc_raw_size", KSTAT_DATA_UINT64 }
834 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
836 #define ARCSTAT_INCR(stat, val) \
837 atomic_add_64(&arc_stats.stat.value.ui64, (val))
839 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
840 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
842 #define ARCSTAT_MAX(stat, val) { \
844 while ((val) > (m = arc_stats.stat.value.ui64) && \
845 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
849 #define ARCSTAT_MAXSTAT(stat) \
850 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
853 * We define a macro to allow ARC hits/misses to be easily broken down by
854 * two separate conditions, giving a total of four different subtypes for
855 * each of hits and misses (so eight statistics total).
857 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
860 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
862 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
866 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
868 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
873 static arc_state_t *arc_anon;
874 static arc_state_t *arc_mru;
875 static arc_state_t *arc_mru_ghost;
876 static arc_state_t *arc_mfu;
877 static arc_state_t *arc_mfu_ghost;
878 static arc_state_t *arc_l2c_only;
881 * There are several ARC variables that are critical to export as kstats --
882 * but we don't want to have to grovel around in the kstat whenever we wish to
883 * manipulate them. For these variables, we therefore define them to be in
884 * terms of the statistic variable. This assures that we are not introducing
885 * the possibility of inconsistency by having shadow copies of the variables,
886 * while still allowing the code to be readable.
888 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
889 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
890 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
891 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
892 #define arc_no_grow ARCSTAT(arcstat_no_grow) /* do not grow cache size */
893 #define arc_tempreserve ARCSTAT(arcstat_tempreserve)
894 #define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
895 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
896 #define arc_dnode_limit ARCSTAT(arcstat_dnode_limit) /* max size for dnodes */
897 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
898 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
899 #define arc_need_free ARCSTAT(arcstat_need_free) /* bytes to be freed */
900 #define arc_sys_free ARCSTAT(arcstat_sys_free) /* target system free bytes */
902 /* size of all b_rabd's in entire arc */
903 #define arc_raw_size ARCSTAT(arcstat_raw_size)
904 /* compressed size of entire arc */
905 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
906 /* uncompressed size of entire arc */
907 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
908 /* number of bytes in the arc from arc_buf_t's */
909 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
912 * There are also some ARC variables that we want to export, but that are
913 * updated so often that having the canonical representation be the statistic
914 * variable causes a performance bottleneck. We want to use aggsum_t's for these
915 * instead, but still be able to export the kstat in the same way as before.
916 * The solution is to always use the aggsum version, except in the kstat update
920 aggsum_t arc_meta_used;
921 aggsum_t astat_data_size;
922 aggsum_t astat_metadata_size;
923 aggsum_t astat_dbuf_size;
924 aggsum_t astat_dnode_size;
925 aggsum_t astat_bonus_size;
926 aggsum_t astat_hdr_size;
927 aggsum_t astat_l2_hdr_size;
929 static hrtime_t arc_growtime;
930 static list_t arc_prune_list;
931 static kmutex_t arc_prune_mtx;
932 static taskq_t *arc_prune_taskq;
934 #define GHOST_STATE(state) \
935 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
936 (state) == arc_l2c_only)
938 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
939 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
940 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
941 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
942 #define HDR_PRESCIENT_PREFETCH(hdr) \
943 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH)
944 #define HDR_COMPRESSION_ENABLED(hdr) \
945 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
947 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
948 #define HDR_L2_READING(hdr) \
949 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
950 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
951 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
952 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
953 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
954 #define HDR_PROTECTED(hdr) ((hdr)->b_flags & ARC_FLAG_PROTECTED)
955 #define HDR_NOAUTH(hdr) ((hdr)->b_flags & ARC_FLAG_NOAUTH)
956 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
958 #define HDR_ISTYPE_METADATA(hdr) \
959 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
960 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
962 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
963 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
964 #define HDR_HAS_RABD(hdr) \
965 (HDR_HAS_L1HDR(hdr) && HDR_PROTECTED(hdr) && \
966 (hdr)->b_crypt_hdr.b_rabd != NULL)
967 #define HDR_ENCRYPTED(hdr) \
968 (HDR_PROTECTED(hdr) && DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
969 #define HDR_AUTHENTICATED(hdr) \
970 (HDR_PROTECTED(hdr) && !DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
972 /* For storing compression mode in b_flags */
973 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
975 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
976 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
977 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
978 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
980 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
981 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
982 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
983 #define ARC_BUF_ENCRYPTED(buf) ((buf)->b_flags & ARC_BUF_FLAG_ENCRYPTED)
989 #define HDR_FULL_CRYPT_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
990 #define HDR_FULL_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_crypt_hdr))
991 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
994 * Hash table routines
997 #define HT_LOCK_ALIGN 64
998 #define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
1003 unsigned char pad[HT_LOCK_PAD];
1007 #define BUF_LOCKS 8192
1008 typedef struct buf_hash_table {
1010 arc_buf_hdr_t **ht_table;
1011 struct ht_lock ht_locks[BUF_LOCKS];
1014 static buf_hash_table_t buf_hash_table;
1016 #define BUF_HASH_INDEX(spa, dva, birth) \
1017 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1018 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
1019 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
1020 #define HDR_LOCK(hdr) \
1021 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1023 uint64_t zfs_crc64_table[256];
1029 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1030 #define L2ARC_HEADROOM 2 /* num of writes */
1033 * If we discover during ARC scan any buffers to be compressed, we boost
1034 * our headroom for the next scanning cycle by this percentage multiple.
1036 #define L2ARC_HEADROOM_BOOST 200
1037 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1038 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1041 * We can feed L2ARC from two states of ARC buffers, mru and mfu,
1042 * and each of the state has two types: data and metadata.
1044 #define L2ARC_FEED_TYPES 4
1046 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1047 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1049 /* L2ARC Performance Tunables */
1050 unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
1051 unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
1052 unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
1053 unsigned long l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1054 unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1055 unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
1056 int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1057 int l2arc_feed_again = B_TRUE; /* turbo warmup */
1058 int l2arc_norw = B_FALSE; /* no reads during writes */
1063 static list_t L2ARC_dev_list; /* device list */
1064 static list_t *l2arc_dev_list; /* device list pointer */
1065 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1066 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1067 static list_t L2ARC_free_on_write; /* free after write buf list */
1068 static list_t *l2arc_free_on_write; /* free after write list ptr */
1069 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1070 static uint64_t l2arc_ndev; /* number of devices */
1072 typedef struct l2arc_read_callback {
1073 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1074 blkptr_t l2rcb_bp; /* original blkptr */
1075 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1076 int l2rcb_flags; /* original flags */
1077 abd_t *l2rcb_abd; /* temporary buffer */
1078 } l2arc_read_callback_t;
1080 typedef struct l2arc_data_free {
1081 /* protected by l2arc_free_on_write_mtx */
1084 arc_buf_contents_t l2df_type;
1085 list_node_t l2df_list_node;
1086 } l2arc_data_free_t;
1088 typedef enum arc_fill_flags {
1089 ARC_FILL_LOCKED = 1 << 0, /* hdr lock is held */
1090 ARC_FILL_COMPRESSED = 1 << 1, /* fill with compressed data */
1091 ARC_FILL_ENCRYPTED = 1 << 2, /* fill with encrypted data */
1092 ARC_FILL_NOAUTH = 1 << 3, /* don't attempt to authenticate */
1093 ARC_FILL_IN_PLACE = 1 << 4 /* fill in place (special case) */
1096 static kmutex_t l2arc_feed_thr_lock;
1097 static kcondvar_t l2arc_feed_thr_cv;
1098 static uint8_t l2arc_thread_exit;
1100 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1101 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1102 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1103 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1104 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1105 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1106 static void arc_hdr_free_abd(arc_buf_hdr_t *, boolean_t);
1107 static void arc_hdr_alloc_abd(arc_buf_hdr_t *, boolean_t);
1108 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1109 static boolean_t arc_is_overflowing(void);
1110 static void arc_buf_watch(arc_buf_t *);
1111 static void arc_tuning_update(void);
1112 static void arc_prune_async(int64_t);
1113 static uint64_t arc_all_memory(void);
1115 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1116 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1117 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1118 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1120 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1121 static void l2arc_read_done(zio_t *);
1125 * We use Cityhash for this. It's fast, and has good hash properties without
1126 * requiring any large static buffers.
1129 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1131 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth));
1134 #define HDR_EMPTY(hdr) \
1135 ((hdr)->b_dva.dva_word[0] == 0 && \
1136 (hdr)->b_dva.dva_word[1] == 0)
1138 #define HDR_EQUAL(spa, dva, birth, hdr) \
1139 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1140 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1141 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1144 buf_discard_identity(arc_buf_hdr_t *hdr)
1146 hdr->b_dva.dva_word[0] = 0;
1147 hdr->b_dva.dva_word[1] = 0;
1151 static arc_buf_hdr_t *
1152 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1154 const dva_t *dva = BP_IDENTITY(bp);
1155 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1156 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1157 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1160 mutex_enter(hash_lock);
1161 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1162 hdr = hdr->b_hash_next) {
1163 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1168 mutex_exit(hash_lock);
1174 * Insert an entry into the hash table. If there is already an element
1175 * equal to elem in the hash table, then the already existing element
1176 * will be returned and the new element will not be inserted.
1177 * Otherwise returns NULL.
1178 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1180 static arc_buf_hdr_t *
1181 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1183 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1184 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1185 arc_buf_hdr_t *fhdr;
1188 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1189 ASSERT(hdr->b_birth != 0);
1190 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1192 if (lockp != NULL) {
1194 mutex_enter(hash_lock);
1196 ASSERT(MUTEX_HELD(hash_lock));
1199 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1200 fhdr = fhdr->b_hash_next, i++) {
1201 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1205 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1206 buf_hash_table.ht_table[idx] = hdr;
1207 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1209 /* collect some hash table performance data */
1211 ARCSTAT_BUMP(arcstat_hash_collisions);
1213 ARCSTAT_BUMP(arcstat_hash_chains);
1215 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1218 ARCSTAT_BUMP(arcstat_hash_elements);
1219 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1225 buf_hash_remove(arc_buf_hdr_t *hdr)
1227 arc_buf_hdr_t *fhdr, **hdrp;
1228 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1230 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1231 ASSERT(HDR_IN_HASH_TABLE(hdr));
1233 hdrp = &buf_hash_table.ht_table[idx];
1234 while ((fhdr = *hdrp) != hdr) {
1235 ASSERT3P(fhdr, !=, NULL);
1236 hdrp = &fhdr->b_hash_next;
1238 *hdrp = hdr->b_hash_next;
1239 hdr->b_hash_next = NULL;
1240 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1242 /* collect some hash table performance data */
1243 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1245 if (buf_hash_table.ht_table[idx] &&
1246 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1247 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1251 * Global data structures and functions for the buf kmem cache.
1254 static kmem_cache_t *hdr_full_cache;
1255 static kmem_cache_t *hdr_full_crypt_cache;
1256 static kmem_cache_t *hdr_l2only_cache;
1257 static kmem_cache_t *buf_cache;
1264 #if defined(_KERNEL)
1266 * Large allocations which do not require contiguous pages
1267 * should be using vmem_free() in the linux kernel\
1269 vmem_free(buf_hash_table.ht_table,
1270 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1272 kmem_free(buf_hash_table.ht_table,
1273 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1275 for (i = 0; i < BUF_LOCKS; i++)
1276 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1277 kmem_cache_destroy(hdr_full_cache);
1278 kmem_cache_destroy(hdr_full_crypt_cache);
1279 kmem_cache_destroy(hdr_l2only_cache);
1280 kmem_cache_destroy(buf_cache);
1284 * Constructor callback - called when the cache is empty
1285 * and a new buf is requested.
1289 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1291 arc_buf_hdr_t *hdr = vbuf;
1293 bzero(hdr, HDR_FULL_SIZE);
1294 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
1295 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1296 zfs_refcount_create(&hdr->b_l1hdr.b_refcnt);
1297 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1298 list_link_init(&hdr->b_l1hdr.b_arc_node);
1299 list_link_init(&hdr->b_l2hdr.b_l2node);
1300 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1301 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1308 hdr_full_crypt_cons(void *vbuf, void *unused, int kmflag)
1310 arc_buf_hdr_t *hdr = vbuf;
1312 hdr_full_cons(vbuf, unused, kmflag);
1313 bzero(&hdr->b_crypt_hdr, sizeof (hdr->b_crypt_hdr));
1314 arc_space_consume(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1321 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1323 arc_buf_hdr_t *hdr = vbuf;
1325 bzero(hdr, HDR_L2ONLY_SIZE);
1326 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1333 buf_cons(void *vbuf, void *unused, int kmflag)
1335 arc_buf_t *buf = vbuf;
1337 bzero(buf, sizeof (arc_buf_t));
1338 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1339 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1345 * Destructor callback - called when a cached buf is
1346 * no longer required.
1350 hdr_full_dest(void *vbuf, void *unused)
1352 arc_buf_hdr_t *hdr = vbuf;
1354 ASSERT(HDR_EMPTY(hdr));
1355 cv_destroy(&hdr->b_l1hdr.b_cv);
1356 zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1357 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1358 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1359 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1364 hdr_full_crypt_dest(void *vbuf, void *unused)
1366 arc_buf_hdr_t *hdr = vbuf;
1368 hdr_full_dest(vbuf, unused);
1369 arc_space_return(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1374 hdr_l2only_dest(void *vbuf, void *unused)
1376 ASSERTV(arc_buf_hdr_t *hdr = vbuf);
1378 ASSERT(HDR_EMPTY(hdr));
1379 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1384 buf_dest(void *vbuf, void *unused)
1386 arc_buf_t *buf = vbuf;
1388 mutex_destroy(&buf->b_evict_lock);
1389 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1393 * Reclaim callback -- invoked when memory is low.
1397 hdr_recl(void *unused)
1399 dprintf("hdr_recl called\n");
1401 * umem calls the reclaim func when we destroy the buf cache,
1402 * which is after we do arc_fini().
1404 if (arc_initialized)
1405 zthr_wakeup(arc_reap_zthr);
1411 uint64_t *ct = NULL;
1412 uint64_t hsize = 1ULL << 12;
1416 * The hash table is big enough to fill all of physical memory
1417 * with an average block size of zfs_arc_average_blocksize (default 8K).
1418 * By default, the table will take up
1419 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1421 while (hsize * zfs_arc_average_blocksize < arc_all_memory())
1424 buf_hash_table.ht_mask = hsize - 1;
1425 #if defined(_KERNEL)
1427 * Large allocations which do not require contiguous pages
1428 * should be using vmem_alloc() in the linux kernel
1430 buf_hash_table.ht_table =
1431 vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
1433 buf_hash_table.ht_table =
1434 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1436 if (buf_hash_table.ht_table == NULL) {
1437 ASSERT(hsize > (1ULL << 8));
1442 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1443 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1444 hdr_full_crypt_cache = kmem_cache_create("arc_buf_hdr_t_full_crypt",
1445 HDR_FULL_CRYPT_SIZE, 0, hdr_full_crypt_cons, hdr_full_crypt_dest,
1446 hdr_recl, NULL, NULL, 0);
1447 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1448 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1450 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1451 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1453 for (i = 0; i < 256; i++)
1454 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1455 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1457 for (i = 0; i < BUF_LOCKS; i++) {
1458 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1459 NULL, MUTEX_DEFAULT, NULL);
1463 #define ARC_MINTIME (hz>>4) /* 62 ms */
1466 * This is the size that the buf occupies in memory. If the buf is compressed,
1467 * it will correspond to the compressed size. You should use this method of
1468 * getting the buf size unless you explicitly need the logical size.
1471 arc_buf_size(arc_buf_t *buf)
1473 return (ARC_BUF_COMPRESSED(buf) ?
1474 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1478 arc_buf_lsize(arc_buf_t *buf)
1480 return (HDR_GET_LSIZE(buf->b_hdr));
1484 * This function will return B_TRUE if the buffer is encrypted in memory.
1485 * This buffer can be decrypted by calling arc_untransform().
1488 arc_is_encrypted(arc_buf_t *buf)
1490 return (ARC_BUF_ENCRYPTED(buf) != 0);
1494 * Returns B_TRUE if the buffer represents data that has not had its MAC
1498 arc_is_unauthenticated(arc_buf_t *buf)
1500 return (HDR_NOAUTH(buf->b_hdr) != 0);
1504 arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt,
1505 uint8_t *iv, uint8_t *mac)
1507 arc_buf_hdr_t *hdr = buf->b_hdr;
1509 ASSERT(HDR_PROTECTED(hdr));
1511 bcopy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN);
1512 bcopy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN);
1513 bcopy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN);
1514 *byteorder = (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
1515 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
1519 * Indicates how this buffer is compressed in memory. If it is not compressed
1520 * the value will be ZIO_COMPRESS_OFF. It can be made normally readable with
1521 * arc_untransform() as long as it is also unencrypted.
1524 arc_get_compression(arc_buf_t *buf)
1526 return (ARC_BUF_COMPRESSED(buf) ?
1527 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1531 * Return the compression algorithm used to store this data in the ARC. If ARC
1532 * compression is enabled or this is an encrypted block, this will be the same
1533 * as what's used to store it on-disk. Otherwise, this will be ZIO_COMPRESS_OFF.
1535 static inline enum zio_compress
1536 arc_hdr_get_compress(arc_buf_hdr_t *hdr)
1538 return (HDR_COMPRESSION_ENABLED(hdr) ?
1539 HDR_GET_COMPRESS(hdr) : ZIO_COMPRESS_OFF);
1542 static inline boolean_t
1543 arc_buf_is_shared(arc_buf_t *buf)
1545 boolean_t shared = (buf->b_data != NULL &&
1546 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1547 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1548 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1549 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1550 IMPLY(shared, ARC_BUF_SHARED(buf));
1551 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1554 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1555 * already being shared" requirement prevents us from doing that.
1562 * Free the checksum associated with this header. If there is no checksum, this
1566 arc_cksum_free(arc_buf_hdr_t *hdr)
1568 ASSERT(HDR_HAS_L1HDR(hdr));
1570 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1571 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1572 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1573 hdr->b_l1hdr.b_freeze_cksum = NULL;
1575 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1579 * Return true iff at least one of the bufs on hdr is not compressed.
1580 * Encrypted buffers count as compressed.
1583 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1585 ASSERT(hdr->b_l1hdr.b_state == arc_anon ||
1586 MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1588 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1589 if (!ARC_BUF_COMPRESSED(b)) {
1598 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1599 * matches the checksum that is stored in the hdr. If there is no checksum,
1600 * or if the buf is compressed, this is a no-op.
1603 arc_cksum_verify(arc_buf_t *buf)
1605 arc_buf_hdr_t *hdr = buf->b_hdr;
1608 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1611 if (ARC_BUF_COMPRESSED(buf))
1614 ASSERT(HDR_HAS_L1HDR(hdr));
1616 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1618 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1619 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1623 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1624 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1625 panic("buffer modified while frozen!");
1626 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1630 * This function makes the assumption that data stored in the L2ARC
1631 * will be transformed exactly as it is in the main pool. Because of
1632 * this we can verify the checksum against the reading process's bp.
1635 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1637 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1638 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1641 * Block pointers always store the checksum for the logical data.
1642 * If the block pointer has the gang bit set, then the checksum
1643 * it represents is for the reconstituted data and not for an
1644 * individual gang member. The zio pipeline, however, must be able to
1645 * determine the checksum of each of the gang constituents so it
1646 * treats the checksum comparison differently than what we need
1647 * for l2arc blocks. This prevents us from using the
1648 * zio_checksum_error() interface directly. Instead we must call the
1649 * zio_checksum_error_impl() so that we can ensure the checksum is
1650 * generated using the correct checksum algorithm and accounts for the
1651 * logical I/O size and not just a gang fragment.
1653 return (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1654 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1655 zio->io_offset, NULL) == 0);
1659 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1660 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1661 * isn't modified later on. If buf is compressed or there is already a checksum
1662 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1665 arc_cksum_compute(arc_buf_t *buf)
1667 arc_buf_hdr_t *hdr = buf->b_hdr;
1669 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1672 ASSERT(HDR_HAS_L1HDR(hdr));
1674 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1675 if (hdr->b_l1hdr.b_freeze_cksum != NULL || ARC_BUF_COMPRESSED(buf)) {
1676 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1680 ASSERT(!ARC_BUF_ENCRYPTED(buf));
1681 ASSERT(!ARC_BUF_COMPRESSED(buf));
1682 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1684 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1685 hdr->b_l1hdr.b_freeze_cksum);
1686 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1692 arc_buf_sigsegv(int sig, siginfo_t *si, void *unused)
1694 panic("Got SIGSEGV at address: 0x%lx\n", (long)si->si_addr);
1700 arc_buf_unwatch(arc_buf_t *buf)
1704 ASSERT0(mprotect(buf->b_data, arc_buf_size(buf),
1705 PROT_READ | PROT_WRITE));
1712 arc_buf_watch(arc_buf_t *buf)
1716 ASSERT0(mprotect(buf->b_data, arc_buf_size(buf),
1721 static arc_buf_contents_t
1722 arc_buf_type(arc_buf_hdr_t *hdr)
1724 arc_buf_contents_t type;
1725 if (HDR_ISTYPE_METADATA(hdr)) {
1726 type = ARC_BUFC_METADATA;
1728 type = ARC_BUFC_DATA;
1730 VERIFY3U(hdr->b_type, ==, type);
1735 arc_is_metadata(arc_buf_t *buf)
1737 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
1741 arc_bufc_to_flags(arc_buf_contents_t type)
1745 /* metadata field is 0 if buffer contains normal data */
1747 case ARC_BUFC_METADATA:
1748 return (ARC_FLAG_BUFC_METADATA);
1752 panic("undefined ARC buffer type!");
1753 return ((uint32_t)-1);
1757 arc_buf_thaw(arc_buf_t *buf)
1759 arc_buf_hdr_t *hdr = buf->b_hdr;
1761 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
1762 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1764 arc_cksum_verify(buf);
1767 * Compressed buffers do not manipulate the b_freeze_cksum.
1769 if (ARC_BUF_COMPRESSED(buf))
1772 ASSERT(HDR_HAS_L1HDR(hdr));
1773 arc_cksum_free(hdr);
1774 arc_buf_unwatch(buf);
1778 arc_buf_freeze(arc_buf_t *buf)
1780 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1783 if (ARC_BUF_COMPRESSED(buf))
1786 ASSERT(HDR_HAS_L1HDR(buf->b_hdr));
1787 arc_cksum_compute(buf);
1791 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
1792 * the following functions should be used to ensure that the flags are
1793 * updated in a thread-safe way. When manipulating the flags either
1794 * the hash_lock must be held or the hdr must be undiscoverable. This
1795 * ensures that we're not racing with any other threads when updating
1799 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1801 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1802 hdr->b_flags |= flags;
1806 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1808 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1809 hdr->b_flags &= ~flags;
1813 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
1814 * done in a special way since we have to clear and set bits
1815 * at the same time. Consumers that wish to set the compression bits
1816 * must use this function to ensure that the flags are updated in
1817 * thread-safe manner.
1820 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
1822 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1825 * Holes and embedded blocks will always have a psize = 0 so
1826 * we ignore the compression of the blkptr and set the
1827 * want to uncompress them. Mark them as uncompressed.
1829 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
1830 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1831 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
1833 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1834 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
1837 HDR_SET_COMPRESS(hdr, cmp);
1838 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
1842 * Looks for another buf on the same hdr which has the data decompressed, copies
1843 * from it, and returns true. If no such buf exists, returns false.
1846 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
1848 arc_buf_hdr_t *hdr = buf->b_hdr;
1849 boolean_t copied = B_FALSE;
1851 ASSERT(HDR_HAS_L1HDR(hdr));
1852 ASSERT3P(buf->b_data, !=, NULL);
1853 ASSERT(!ARC_BUF_COMPRESSED(buf));
1855 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
1856 from = from->b_next) {
1857 /* can't use our own data buffer */
1862 if (!ARC_BUF_COMPRESSED(from)) {
1863 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
1870 * There were no decompressed bufs, so there should not be a
1871 * checksum on the hdr either.
1873 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
1879 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
1882 arc_hdr_size(arc_buf_hdr_t *hdr)
1886 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
1887 HDR_GET_PSIZE(hdr) > 0) {
1888 size = HDR_GET_PSIZE(hdr);
1890 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
1891 size = HDR_GET_LSIZE(hdr);
1897 arc_hdr_authenticate(arc_buf_hdr_t *hdr, spa_t *spa, uint64_t dsobj)
1901 uint64_t lsize = HDR_GET_LSIZE(hdr);
1902 uint64_t psize = HDR_GET_PSIZE(hdr);
1903 void *tmpbuf = NULL;
1904 abd_t *abd = hdr->b_l1hdr.b_pabd;
1906 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1907 ASSERT(HDR_AUTHENTICATED(hdr));
1908 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1911 * The MAC is calculated on the compressed data that is stored on disk.
1912 * However, if compressed arc is disabled we will only have the
1913 * decompressed data available to us now. Compress it into a temporary
1914 * abd so we can verify the MAC. The performance overhead of this will
1915 * be relatively low, since most objects in an encrypted objset will
1916 * be encrypted (instead of authenticated) anyway.
1918 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1919 !HDR_COMPRESSION_ENABLED(hdr)) {
1920 tmpbuf = zio_buf_alloc(lsize);
1921 abd = abd_get_from_buf(tmpbuf, lsize);
1922 abd_take_ownership_of_buf(abd, B_TRUE);
1924 csize = zio_compress_data(HDR_GET_COMPRESS(hdr),
1925 hdr->b_l1hdr.b_pabd, tmpbuf, lsize);
1926 ASSERT3U(csize, <=, psize);
1927 abd_zero_off(abd, csize, psize - csize);
1931 * Authentication is best effort. We authenticate whenever the key is
1932 * available. If we succeed we clear ARC_FLAG_NOAUTH.
1934 if (hdr->b_crypt_hdr.b_ot == DMU_OT_OBJSET) {
1935 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1936 ASSERT3U(lsize, ==, psize);
1937 ret = spa_do_crypt_objset_mac_abd(B_FALSE, spa, dsobj, abd,
1938 psize, hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1940 ret = spa_do_crypt_mac_abd(B_FALSE, spa, dsobj, abd, psize,
1941 hdr->b_crypt_hdr.b_mac);
1945 arc_hdr_clear_flags(hdr, ARC_FLAG_NOAUTH);
1946 else if (ret != ENOENT)
1962 * This function will take a header that only has raw encrypted data in
1963 * b_crypt_hdr.b_rabd and decrypt it into a new buffer which is stored in
1964 * b_l1hdr.b_pabd. If designated in the header flags, this function will
1965 * also decompress the data.
1968 arc_hdr_decrypt(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb)
1973 boolean_t no_crypt = B_FALSE;
1974 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1976 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1977 ASSERT(HDR_ENCRYPTED(hdr));
1979 arc_hdr_alloc_abd(hdr, B_FALSE);
1981 ret = spa_do_crypt_abd(B_FALSE, spa, zb, hdr->b_crypt_hdr.b_ot,
1982 B_FALSE, bswap, hdr->b_crypt_hdr.b_salt, hdr->b_crypt_hdr.b_iv,
1983 hdr->b_crypt_hdr.b_mac, HDR_GET_PSIZE(hdr), hdr->b_l1hdr.b_pabd,
1984 hdr->b_crypt_hdr.b_rabd, &no_crypt);
1989 abd_copy(hdr->b_l1hdr.b_pabd, hdr->b_crypt_hdr.b_rabd,
1990 HDR_GET_PSIZE(hdr));
1994 * If this header has disabled arc compression but the b_pabd is
1995 * compressed after decrypting it, we need to decompress the newly
1998 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1999 !HDR_COMPRESSION_ENABLED(hdr)) {
2001 * We want to make sure that we are correctly honoring the
2002 * zfs_abd_scatter_enabled setting, so we allocate an abd here
2003 * and then loan a buffer from it, rather than allocating a
2004 * linear buffer and wrapping it in an abd later.
2006 cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
2007 tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
2009 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2010 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
2011 HDR_GET_LSIZE(hdr));
2013 abd_return_buf(cabd, tmp, arc_hdr_size(hdr));
2017 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
2018 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
2019 arc_hdr_size(hdr), hdr);
2020 hdr->b_l1hdr.b_pabd = cabd;
2026 arc_hdr_free_abd(hdr, B_FALSE);
2028 arc_free_data_buf(hdr, cabd, arc_hdr_size(hdr), hdr);
2034 * This function is called during arc_buf_fill() to prepare the header's
2035 * abd plaintext pointer for use. This involves authenticated protected
2036 * data and decrypting encrypted data into the plaintext abd.
2039 arc_fill_hdr_crypt(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, spa_t *spa,
2040 const zbookmark_phys_t *zb, boolean_t noauth)
2044 ASSERT(HDR_PROTECTED(hdr));
2046 if (hash_lock != NULL)
2047 mutex_enter(hash_lock);
2049 if (HDR_NOAUTH(hdr) && !noauth) {
2051 * The caller requested authenticated data but our data has
2052 * not been authenticated yet. Verify the MAC now if we can.
2054 ret = arc_hdr_authenticate(hdr, spa, zb->zb_objset);
2057 } else if (HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd == NULL) {
2059 * If we only have the encrypted version of the data, but the
2060 * unencrypted version was requested we take this opportunity
2061 * to store the decrypted version in the header for future use.
2063 ret = arc_hdr_decrypt(hdr, spa, zb);
2068 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2070 if (hash_lock != NULL)
2071 mutex_exit(hash_lock);
2076 if (hash_lock != NULL)
2077 mutex_exit(hash_lock);
2083 * This function is used by the dbuf code to decrypt bonus buffers in place.
2084 * The dbuf code itself doesn't have any locking for decrypting a shared dnode
2085 * block, so we use the hash lock here to protect against concurrent calls to
2089 arc_buf_untransform_in_place(arc_buf_t *buf, kmutex_t *hash_lock)
2091 arc_buf_hdr_t *hdr = buf->b_hdr;
2093 ASSERT(HDR_ENCRYPTED(hdr));
2094 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
2095 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2096 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2098 zio_crypt_copy_dnode_bonus(hdr->b_l1hdr.b_pabd, buf->b_data,
2100 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
2101 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2102 hdr->b_crypt_hdr.b_ebufcnt -= 1;
2106 * Given a buf that has a data buffer attached to it, this function will
2107 * efficiently fill the buf with data of the specified compression setting from
2108 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
2109 * are already sharing a data buf, no copy is performed.
2111 * If the buf is marked as compressed but uncompressed data was requested, this
2112 * will allocate a new data buffer for the buf, remove that flag, and fill the
2113 * buf with uncompressed data. You can't request a compressed buf on a hdr with
2114 * uncompressed data, and (since we haven't added support for it yet) if you
2115 * want compressed data your buf must already be marked as compressed and have
2116 * the correct-sized data buffer.
2119 arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
2120 arc_fill_flags_t flags)
2123 arc_buf_hdr_t *hdr = buf->b_hdr;
2124 boolean_t hdr_compressed =
2125 (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
2126 boolean_t compressed = (flags & ARC_FILL_COMPRESSED) != 0;
2127 boolean_t encrypted = (flags & ARC_FILL_ENCRYPTED) != 0;
2128 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
2129 kmutex_t *hash_lock = (flags & ARC_FILL_LOCKED) ? NULL : HDR_LOCK(hdr);
2131 ASSERT3P(buf->b_data, !=, NULL);
2132 IMPLY(compressed, hdr_compressed || ARC_BUF_ENCRYPTED(buf));
2133 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
2134 IMPLY(encrypted, HDR_ENCRYPTED(hdr));
2135 IMPLY(encrypted, ARC_BUF_ENCRYPTED(buf));
2136 IMPLY(encrypted, ARC_BUF_COMPRESSED(buf));
2137 IMPLY(encrypted, !ARC_BUF_SHARED(buf));
2140 * If the caller wanted encrypted data we just need to copy it from
2141 * b_rabd and potentially byteswap it. We won't be able to do any
2142 * further transforms on it.
2145 ASSERT(HDR_HAS_RABD(hdr));
2146 abd_copy_to_buf(buf->b_data, hdr->b_crypt_hdr.b_rabd,
2147 HDR_GET_PSIZE(hdr));
2152 * Adjust encrypted and authenticated headers to accomodate
2153 * the request if needed. Dnode blocks (ARC_FILL_IN_PLACE) are
2154 * allowed to fail decryption due to keys not being loaded
2155 * without being marked as an IO error.
2157 if (HDR_PROTECTED(hdr)) {
2158 error = arc_fill_hdr_crypt(hdr, hash_lock, spa,
2159 zb, !!(flags & ARC_FILL_NOAUTH));
2160 if (error == EACCES && (flags & ARC_FILL_IN_PLACE) != 0) {
2162 } else if (error != 0) {
2163 if (hash_lock != NULL)
2164 mutex_enter(hash_lock);
2165 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
2166 if (hash_lock != NULL)
2167 mutex_exit(hash_lock);
2173 * There is a special case here for dnode blocks which are
2174 * decrypting their bonus buffers. These blocks may request to
2175 * be decrypted in-place. This is necessary because there may
2176 * be many dnodes pointing into this buffer and there is
2177 * currently no method to synchronize replacing the backing
2178 * b_data buffer and updating all of the pointers. Here we use
2179 * the hash lock to ensure there are no races. If the need
2180 * arises for other types to be decrypted in-place, they must
2181 * add handling here as well.
2183 if ((flags & ARC_FILL_IN_PLACE) != 0) {
2184 ASSERT(!hdr_compressed);
2185 ASSERT(!compressed);
2188 if (HDR_ENCRYPTED(hdr) && ARC_BUF_ENCRYPTED(buf)) {
2189 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
2191 if (hash_lock != NULL)
2192 mutex_enter(hash_lock);
2193 arc_buf_untransform_in_place(buf, hash_lock);
2194 if (hash_lock != NULL)
2195 mutex_exit(hash_lock);
2197 /* Compute the hdr's checksum if necessary */
2198 arc_cksum_compute(buf);
2204 if (hdr_compressed == compressed) {
2205 if (!arc_buf_is_shared(buf)) {
2206 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
2210 ASSERT(hdr_compressed);
2211 ASSERT(!compressed);
2212 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
2215 * If the buf is sharing its data with the hdr, unlink it and
2216 * allocate a new data buffer for the buf.
2218 if (arc_buf_is_shared(buf)) {
2219 ASSERT(ARC_BUF_COMPRESSED(buf));
2221 /* We need to give the buf it's own b_data */
2222 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2224 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2225 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2227 /* Previously overhead was 0; just add new overhead */
2228 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2229 } else if (ARC_BUF_COMPRESSED(buf)) {
2230 /* We need to reallocate the buf's b_data */
2231 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2234 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2236 /* We increased the size of b_data; update overhead */
2237 ARCSTAT_INCR(arcstat_overhead_size,
2238 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2242 * Regardless of the buf's previous compression settings, it
2243 * should not be compressed at the end of this function.
2245 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2248 * Try copying the data from another buf which already has a
2249 * decompressed version. If that's not possible, it's time to
2250 * bite the bullet and decompress the data from the hdr.
2252 if (arc_buf_try_copy_decompressed_data(buf)) {
2253 /* Skip byteswapping and checksumming (already done) */
2254 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
2257 error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2258 hdr->b_l1hdr.b_pabd, buf->b_data,
2259 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2262 * Absent hardware errors or software bugs, this should
2263 * be impossible, but log it anyway so we can debug it.
2267 "hdr %p, compress %d, psize %d, lsize %d",
2268 hdr, arc_hdr_get_compress(hdr),
2269 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2270 if (hash_lock != NULL)
2271 mutex_enter(hash_lock);
2272 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
2273 if (hash_lock != NULL)
2274 mutex_exit(hash_lock);
2275 return (SET_ERROR(EIO));
2281 /* Byteswap the buf's data if necessary */
2282 if (bswap != DMU_BSWAP_NUMFUNCS) {
2283 ASSERT(!HDR_SHARED_DATA(hdr));
2284 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2285 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2288 /* Compute the hdr's checksum if necessary */
2289 arc_cksum_compute(buf);
2295 * If this function is being called to decrypt an encrypted buffer or verify an
2296 * authenticated one, the key must be loaded and a mapping must be made
2297 * available in the keystore via spa_keystore_create_mapping() or one of its
2301 arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
2305 arc_fill_flags_t flags = 0;
2308 flags |= ARC_FILL_IN_PLACE;
2310 ret = arc_buf_fill(buf, spa, zb, flags);
2311 if (ret == ECKSUM) {
2313 * Convert authentication and decryption errors to EIO
2314 * (and generate an ereport) before leaving the ARC.
2316 ret = SET_ERROR(EIO);
2317 spa_log_error(spa, zb);
2318 zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION,
2319 spa, NULL, zb, NULL, 0, 0);
2326 * Increment the amount of evictable space in the arc_state_t's refcount.
2327 * We account for the space used by the hdr and the arc buf individually
2328 * so that we can add and remove them from the refcount individually.
2331 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2333 arc_buf_contents_t type = arc_buf_type(hdr);
2335 ASSERT(HDR_HAS_L1HDR(hdr));
2337 if (GHOST_STATE(state)) {
2338 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2339 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2340 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2341 ASSERT(!HDR_HAS_RABD(hdr));
2342 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2343 HDR_GET_LSIZE(hdr), hdr);
2347 ASSERT(!GHOST_STATE(state));
2348 if (hdr->b_l1hdr.b_pabd != NULL) {
2349 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2350 arc_hdr_size(hdr), hdr);
2352 if (HDR_HAS_RABD(hdr)) {
2353 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2354 HDR_GET_PSIZE(hdr), hdr);
2357 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2358 buf = buf->b_next) {
2359 if (arc_buf_is_shared(buf))
2361 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2362 arc_buf_size(buf), buf);
2367 * Decrement the amount of evictable space in the arc_state_t's refcount.
2368 * We account for the space used by the hdr and the arc buf individually
2369 * so that we can add and remove them from the refcount individually.
2372 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2374 arc_buf_contents_t type = arc_buf_type(hdr);
2376 ASSERT(HDR_HAS_L1HDR(hdr));
2378 if (GHOST_STATE(state)) {
2379 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2380 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2381 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2382 ASSERT(!HDR_HAS_RABD(hdr));
2383 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2384 HDR_GET_LSIZE(hdr), hdr);
2388 ASSERT(!GHOST_STATE(state));
2389 if (hdr->b_l1hdr.b_pabd != NULL) {
2390 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2391 arc_hdr_size(hdr), hdr);
2393 if (HDR_HAS_RABD(hdr)) {
2394 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2395 HDR_GET_PSIZE(hdr), hdr);
2398 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2399 buf = buf->b_next) {
2400 if (arc_buf_is_shared(buf))
2402 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2403 arc_buf_size(buf), buf);
2408 * Add a reference to this hdr indicating that someone is actively
2409 * referencing that memory. When the refcount transitions from 0 to 1,
2410 * we remove it from the respective arc_state_t list to indicate that
2411 * it is not evictable.
2414 add_reference(arc_buf_hdr_t *hdr, void *tag)
2418 ASSERT(HDR_HAS_L1HDR(hdr));
2419 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2420 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2421 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2422 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2425 state = hdr->b_l1hdr.b_state;
2427 if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2428 (state != arc_anon)) {
2429 /* We don't use the L2-only state list. */
2430 if (state != arc_l2c_only) {
2431 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2433 arc_evictable_space_decrement(hdr, state);
2435 /* remove the prefetch flag if we get a reference */
2436 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2441 * Remove a reference from this hdr. When the reference transitions from
2442 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2443 * list making it eligible for eviction.
2446 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2449 arc_state_t *state = hdr->b_l1hdr.b_state;
2451 ASSERT(HDR_HAS_L1HDR(hdr));
2452 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2453 ASSERT(!GHOST_STATE(state));
2456 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2457 * check to prevent usage of the arc_l2c_only list.
2459 if (((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2460 (state != arc_anon)) {
2461 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2462 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2463 arc_evictable_space_increment(hdr, state);
2469 * Returns detailed information about a specific arc buffer. When the
2470 * state_index argument is set the function will calculate the arc header
2471 * list position for its arc state. Since this requires a linear traversal
2472 * callers are strongly encourage not to do this. However, it can be helpful
2473 * for targeted analysis so the functionality is provided.
2476 arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
2478 arc_buf_hdr_t *hdr = ab->b_hdr;
2479 l1arc_buf_hdr_t *l1hdr = NULL;
2480 l2arc_buf_hdr_t *l2hdr = NULL;
2481 arc_state_t *state = NULL;
2483 memset(abi, 0, sizeof (arc_buf_info_t));
2488 abi->abi_flags = hdr->b_flags;
2490 if (HDR_HAS_L1HDR(hdr)) {
2491 l1hdr = &hdr->b_l1hdr;
2492 state = l1hdr->b_state;
2494 if (HDR_HAS_L2HDR(hdr))
2495 l2hdr = &hdr->b_l2hdr;
2498 abi->abi_bufcnt = l1hdr->b_bufcnt;
2499 abi->abi_access = l1hdr->b_arc_access;
2500 abi->abi_mru_hits = l1hdr->b_mru_hits;
2501 abi->abi_mru_ghost_hits = l1hdr->b_mru_ghost_hits;
2502 abi->abi_mfu_hits = l1hdr->b_mfu_hits;
2503 abi->abi_mfu_ghost_hits = l1hdr->b_mfu_ghost_hits;
2504 abi->abi_holds = zfs_refcount_count(&l1hdr->b_refcnt);
2508 abi->abi_l2arc_dattr = l2hdr->b_daddr;
2509 abi->abi_l2arc_hits = l2hdr->b_hits;
2512 abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON;
2513 abi->abi_state_contents = arc_buf_type(hdr);
2514 abi->abi_size = arc_hdr_size(hdr);
2518 * Move the supplied buffer to the indicated state. The hash lock
2519 * for the buffer must be held by the caller.
2522 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2523 kmutex_t *hash_lock)
2525 arc_state_t *old_state;
2528 boolean_t update_old, update_new;
2529 arc_buf_contents_t buftype = arc_buf_type(hdr);
2532 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2533 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2534 * L1 hdr doesn't always exist when we change state to arc_anon before
2535 * destroying a header, in which case reallocating to add the L1 hdr is
2538 if (HDR_HAS_L1HDR(hdr)) {
2539 old_state = hdr->b_l1hdr.b_state;
2540 refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt);
2541 bufcnt = hdr->b_l1hdr.b_bufcnt;
2542 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL ||
2545 old_state = arc_l2c_only;
2548 update_old = B_FALSE;
2550 update_new = update_old;
2552 ASSERT(MUTEX_HELD(hash_lock));
2553 ASSERT3P(new_state, !=, old_state);
2554 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2555 ASSERT(old_state != arc_anon || bufcnt <= 1);
2558 * If this buffer is evictable, transfer it from the
2559 * old state list to the new state list.
2562 if (old_state != arc_anon && old_state != arc_l2c_only) {
2563 ASSERT(HDR_HAS_L1HDR(hdr));
2564 multilist_remove(old_state->arcs_list[buftype], hdr);
2566 if (GHOST_STATE(old_state)) {
2568 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2569 update_old = B_TRUE;
2571 arc_evictable_space_decrement(hdr, old_state);
2573 if (new_state != arc_anon && new_state != arc_l2c_only) {
2575 * An L1 header always exists here, since if we're
2576 * moving to some L1-cached state (i.e. not l2c_only or
2577 * anonymous), we realloc the header to add an L1hdr
2580 ASSERT(HDR_HAS_L1HDR(hdr));
2581 multilist_insert(new_state->arcs_list[buftype], hdr);
2583 if (GHOST_STATE(new_state)) {
2585 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2586 update_new = B_TRUE;
2588 arc_evictable_space_increment(hdr, new_state);
2592 ASSERT(!HDR_EMPTY(hdr));
2593 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2594 buf_hash_remove(hdr);
2596 /* adjust state sizes (ignore arc_l2c_only) */
2598 if (update_new && new_state != arc_l2c_only) {
2599 ASSERT(HDR_HAS_L1HDR(hdr));
2600 if (GHOST_STATE(new_state)) {
2604 * When moving a header to a ghost state, we first
2605 * remove all arc buffers. Thus, we'll have a
2606 * bufcnt of zero, and no arc buffer to use for
2607 * the reference. As a result, we use the arc
2608 * header pointer for the reference.
2610 (void) zfs_refcount_add_many(&new_state->arcs_size,
2611 HDR_GET_LSIZE(hdr), hdr);
2612 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2613 ASSERT(!HDR_HAS_RABD(hdr));
2615 uint32_t buffers = 0;
2618 * Each individual buffer holds a unique reference,
2619 * thus we must remove each of these references one
2622 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2623 buf = buf->b_next) {
2624 ASSERT3U(bufcnt, !=, 0);
2628 * When the arc_buf_t is sharing the data
2629 * block with the hdr, the owner of the
2630 * reference belongs to the hdr. Only
2631 * add to the refcount if the arc_buf_t is
2634 if (arc_buf_is_shared(buf))
2637 (void) zfs_refcount_add_many(
2638 &new_state->arcs_size,
2639 arc_buf_size(buf), buf);
2641 ASSERT3U(bufcnt, ==, buffers);
2643 if (hdr->b_l1hdr.b_pabd != NULL) {
2644 (void) zfs_refcount_add_many(
2645 &new_state->arcs_size,
2646 arc_hdr_size(hdr), hdr);
2649 if (HDR_HAS_RABD(hdr)) {
2650 (void) zfs_refcount_add_many(
2651 &new_state->arcs_size,
2652 HDR_GET_PSIZE(hdr), hdr);
2657 if (update_old && old_state != arc_l2c_only) {
2658 ASSERT(HDR_HAS_L1HDR(hdr));
2659 if (GHOST_STATE(old_state)) {
2661 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2662 ASSERT(!HDR_HAS_RABD(hdr));
2665 * When moving a header off of a ghost state,
2666 * the header will not contain any arc buffers.
2667 * We use the arc header pointer for the reference
2668 * which is exactly what we did when we put the
2669 * header on the ghost state.
2672 (void) zfs_refcount_remove_many(&old_state->arcs_size,
2673 HDR_GET_LSIZE(hdr), hdr);
2675 uint32_t buffers = 0;
2678 * Each individual buffer holds a unique reference,
2679 * thus we must remove each of these references one
2682 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2683 buf = buf->b_next) {
2684 ASSERT3U(bufcnt, !=, 0);
2688 * When the arc_buf_t is sharing the data
2689 * block with the hdr, the owner of the
2690 * reference belongs to the hdr. Only
2691 * add to the refcount if the arc_buf_t is
2694 if (arc_buf_is_shared(buf))
2697 (void) zfs_refcount_remove_many(
2698 &old_state->arcs_size, arc_buf_size(buf),
2701 ASSERT3U(bufcnt, ==, buffers);
2702 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
2705 if (hdr->b_l1hdr.b_pabd != NULL) {
2706 (void) zfs_refcount_remove_many(
2707 &old_state->arcs_size, arc_hdr_size(hdr),
2711 if (HDR_HAS_RABD(hdr)) {
2712 (void) zfs_refcount_remove_many(
2713 &old_state->arcs_size, HDR_GET_PSIZE(hdr),
2719 if (HDR_HAS_L1HDR(hdr))
2720 hdr->b_l1hdr.b_state = new_state;
2723 * L2 headers should never be on the L2 state list since they don't
2724 * have L1 headers allocated.
2726 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2727 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2731 arc_space_consume(uint64_t space, arc_space_type_t type)
2733 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2738 case ARC_SPACE_DATA:
2739 aggsum_add(&astat_data_size, space);
2741 case ARC_SPACE_META:
2742 aggsum_add(&astat_metadata_size, space);
2744 case ARC_SPACE_BONUS:
2745 aggsum_add(&astat_bonus_size, space);
2747 case ARC_SPACE_DNODE:
2748 aggsum_add(&astat_dnode_size, space);
2750 case ARC_SPACE_DBUF:
2751 aggsum_add(&astat_dbuf_size, space);
2753 case ARC_SPACE_HDRS:
2754 aggsum_add(&astat_hdr_size, space);
2756 case ARC_SPACE_L2HDRS:
2757 aggsum_add(&astat_l2_hdr_size, space);
2761 if (type != ARC_SPACE_DATA)
2762 aggsum_add(&arc_meta_used, space);
2764 aggsum_add(&arc_size, space);
2768 arc_space_return(uint64_t space, arc_space_type_t type)
2770 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2775 case ARC_SPACE_DATA:
2776 aggsum_add(&astat_data_size, -space);
2778 case ARC_SPACE_META:
2779 aggsum_add(&astat_metadata_size, -space);
2781 case ARC_SPACE_BONUS:
2782 aggsum_add(&astat_bonus_size, -space);
2784 case ARC_SPACE_DNODE:
2785 aggsum_add(&astat_dnode_size, -space);
2787 case ARC_SPACE_DBUF:
2788 aggsum_add(&astat_dbuf_size, -space);
2790 case ARC_SPACE_HDRS:
2791 aggsum_add(&astat_hdr_size, -space);
2793 case ARC_SPACE_L2HDRS:
2794 aggsum_add(&astat_l2_hdr_size, -space);
2798 if (type != ARC_SPACE_DATA) {
2799 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0);
2801 * We use the upper bound here rather than the precise value
2802 * because the arc_meta_max value doesn't need to be
2803 * precise. It's only consumed by humans via arcstats.
2805 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used))
2806 arc_meta_max = aggsum_upper_bound(&arc_meta_used);
2807 aggsum_add(&arc_meta_used, -space);
2810 ASSERT(aggsum_compare(&arc_size, space) >= 0);
2811 aggsum_add(&arc_size, -space);
2815 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2816 * with the hdr's b_pabd.
2819 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2822 * The criteria for sharing a hdr's data are:
2823 * 1. the buffer is not encrypted
2824 * 2. the hdr's compression matches the buf's compression
2825 * 3. the hdr doesn't need to be byteswapped
2826 * 4. the hdr isn't already being shared
2827 * 5. the buf is either compressed or it is the last buf in the hdr list
2829 * Criterion #5 maintains the invariant that shared uncompressed
2830 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2831 * might ask, "if a compressed buf is allocated first, won't that be the
2832 * last thing in the list?", but in that case it's impossible to create
2833 * a shared uncompressed buf anyway (because the hdr must be compressed
2834 * to have the compressed buf). You might also think that #3 is
2835 * sufficient to make this guarantee, however it's possible
2836 * (specifically in the rare L2ARC write race mentioned in
2837 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2838 * is sharable, but wasn't at the time of its allocation. Rather than
2839 * allow a new shared uncompressed buf to be created and then shuffle
2840 * the list around to make it the last element, this simply disallows
2841 * sharing if the new buf isn't the first to be added.
2843 ASSERT3P(buf->b_hdr, ==, hdr);
2844 boolean_t hdr_compressed =
2845 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF;
2846 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2847 return (!ARC_BUF_ENCRYPTED(buf) &&
2848 buf_compressed == hdr_compressed &&
2849 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2850 !HDR_SHARED_DATA(hdr) &&
2851 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2855 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2856 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2857 * copy was made successfully, or an error code otherwise.
2860 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb,
2861 void *tag, boolean_t encrypted, boolean_t compressed, boolean_t noauth,
2862 boolean_t fill, arc_buf_t **ret)
2865 arc_fill_flags_t flags = ARC_FILL_LOCKED;
2867 ASSERT(HDR_HAS_L1HDR(hdr));
2868 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2869 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2870 hdr->b_type == ARC_BUFC_METADATA);
2871 ASSERT3P(ret, !=, NULL);
2872 ASSERT3P(*ret, ==, NULL);
2873 IMPLY(encrypted, compressed);
2875 hdr->b_l1hdr.b_mru_hits = 0;
2876 hdr->b_l1hdr.b_mru_ghost_hits = 0;
2877 hdr->b_l1hdr.b_mfu_hits = 0;
2878 hdr->b_l1hdr.b_mfu_ghost_hits = 0;
2879 hdr->b_l1hdr.b_l2_hits = 0;
2881 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2884 buf->b_next = hdr->b_l1hdr.b_buf;
2887 add_reference(hdr, tag);
2890 * We're about to change the hdr's b_flags. We must either
2891 * hold the hash_lock or be undiscoverable.
2893 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2896 * Only honor requests for compressed bufs if the hdr is actually
2897 * compressed. This must be overriden if the buffer is encrypted since
2898 * encrypted buffers cannot be decompressed.
2901 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2902 buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED;
2903 flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED;
2904 } else if (compressed &&
2905 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
2906 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2907 flags |= ARC_FILL_COMPRESSED;
2912 flags |= ARC_FILL_NOAUTH;
2916 * If the hdr's data can be shared then we share the data buffer and
2917 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2918 * allocate a new buffer to store the buf's data.
2920 * There are two additional restrictions here because we're sharing
2921 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2922 * actively involved in an L2ARC write, because if this buf is used by
2923 * an arc_write() then the hdr's data buffer will be released when the
2924 * write completes, even though the L2ARC write might still be using it.
2925 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2926 * need to be ABD-aware.
2928 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2929 hdr->b_l1hdr.b_pabd != NULL && abd_is_linear(hdr->b_l1hdr.b_pabd);
2931 /* Set up b_data and sharing */
2933 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2934 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2935 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2938 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2939 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2941 VERIFY3P(buf->b_data, !=, NULL);
2943 hdr->b_l1hdr.b_buf = buf;
2944 hdr->b_l1hdr.b_bufcnt += 1;
2946 hdr->b_crypt_hdr.b_ebufcnt += 1;
2949 * If the user wants the data from the hdr, we need to either copy or
2950 * decompress the data.
2953 ASSERT3P(zb, !=, NULL);
2954 return (arc_buf_fill(buf, spa, zb, flags));
2960 static char *arc_onloan_tag = "onloan";
2963 arc_loaned_bytes_update(int64_t delta)
2965 atomic_add_64(&arc_loaned_bytes, delta);
2967 /* assert that it did not wrap around */
2968 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2972 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2973 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2974 * buffers must be returned to the arc before they can be used by the DMU or
2978 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2980 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2981 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2983 arc_loaned_bytes_update(arc_buf_size(buf));
2989 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2990 enum zio_compress compression_type)
2992 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2993 psize, lsize, compression_type);
2995 arc_loaned_bytes_update(arc_buf_size(buf));
3001 arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder,
3002 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
3003 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
3004 enum zio_compress compression_type)
3006 arc_buf_t *buf = arc_alloc_raw_buf(spa, arc_onloan_tag, dsobj,
3007 byteorder, salt, iv, mac, ot, psize, lsize, compression_type);
3009 atomic_add_64(&arc_loaned_bytes, psize);
3015 * Return a loaned arc buffer to the arc.
3018 arc_return_buf(arc_buf_t *buf, void *tag)
3020 arc_buf_hdr_t *hdr = buf->b_hdr;
3022 ASSERT3P(buf->b_data, !=, NULL);
3023 ASSERT(HDR_HAS_L1HDR(hdr));
3024 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
3025 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
3027 arc_loaned_bytes_update(-arc_buf_size(buf));
3030 /* Detach an arc_buf from a dbuf (tag) */
3032 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
3034 arc_buf_hdr_t *hdr = buf->b_hdr;
3036 ASSERT3P(buf->b_data, !=, NULL);
3037 ASSERT(HDR_HAS_L1HDR(hdr));
3038 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
3039 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
3041 arc_loaned_bytes_update(arc_buf_size(buf));
3045 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
3047 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
3050 df->l2df_size = size;
3051 df->l2df_type = type;
3052 mutex_enter(&l2arc_free_on_write_mtx);
3053 list_insert_head(l2arc_free_on_write, df);
3054 mutex_exit(&l2arc_free_on_write_mtx);
3058 arc_hdr_free_on_write(arc_buf_hdr_t *hdr, boolean_t free_rdata)
3060 arc_state_t *state = hdr->b_l1hdr.b_state;
3061 arc_buf_contents_t type = arc_buf_type(hdr);
3062 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
3064 /* protected by hash lock, if in the hash table */
3065 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
3066 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3067 ASSERT(state != arc_anon && state != arc_l2c_only);
3069 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
3072 (void) zfs_refcount_remove_many(&state->arcs_size, size, hdr);
3073 if (type == ARC_BUFC_METADATA) {
3074 arc_space_return(size, ARC_SPACE_META);
3076 ASSERT(type == ARC_BUFC_DATA);
3077 arc_space_return(size, ARC_SPACE_DATA);
3081 l2arc_free_abd_on_write(hdr->b_crypt_hdr.b_rabd, size, type);
3083 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
3088 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
3089 * data buffer, we transfer the refcount ownership to the hdr and update
3090 * the appropriate kstats.
3093 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3095 ASSERT(arc_can_share(hdr, buf));
3096 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3097 ASSERT(!ARC_BUF_ENCRYPTED(buf));
3098 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3101 * Start sharing the data buffer. We transfer the
3102 * refcount ownership to the hdr since it always owns
3103 * the refcount whenever an arc_buf_t is shared.
3105 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
3106 arc_hdr_size(hdr), buf, hdr);
3107 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
3108 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
3109 HDR_ISTYPE_METADATA(hdr));
3110 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
3111 buf->b_flags |= ARC_BUF_FLAG_SHARED;
3114 * Since we've transferred ownership to the hdr we need
3115 * to increment its compressed and uncompressed kstats and
3116 * decrement the overhead size.
3118 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3119 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3120 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
3124 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3126 ASSERT(arc_buf_is_shared(buf));
3127 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3128 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3131 * We are no longer sharing this buffer so we need
3132 * to transfer its ownership to the rightful owner.
3134 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
3135 arc_hdr_size(hdr), hdr, buf);
3136 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3137 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
3138 abd_put(hdr->b_l1hdr.b_pabd);
3139 hdr->b_l1hdr.b_pabd = NULL;
3140 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
3143 * Since the buffer is no longer shared between
3144 * the arc buf and the hdr, count it as overhead.
3146 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3147 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3148 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
3152 * Remove an arc_buf_t from the hdr's buf list and return the last
3153 * arc_buf_t on the list. If no buffers remain on the list then return
3157 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3159 ASSERT(HDR_HAS_L1HDR(hdr));
3160 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3162 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
3163 arc_buf_t *lastbuf = NULL;
3166 * Remove the buf from the hdr list and locate the last
3167 * remaining buffer on the list.
3169 while (*bufp != NULL) {
3171 *bufp = buf->b_next;
3174 * If we've removed a buffer in the middle of
3175 * the list then update the lastbuf and update
3178 if (*bufp != NULL) {
3180 bufp = &(*bufp)->b_next;
3184 ASSERT3P(lastbuf, !=, buf);
3185 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
3186 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
3187 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
3193 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
3197 arc_buf_destroy_impl(arc_buf_t *buf)
3199 arc_buf_hdr_t *hdr = buf->b_hdr;
3202 * Free up the data associated with the buf but only if we're not
3203 * sharing this with the hdr. If we are sharing it with the hdr, the
3204 * hdr is responsible for doing the free.
3206 if (buf->b_data != NULL) {
3208 * We're about to change the hdr's b_flags. We must either
3209 * hold the hash_lock or be undiscoverable.
3211 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3213 arc_cksum_verify(buf);
3214 arc_buf_unwatch(buf);
3216 if (arc_buf_is_shared(buf)) {
3217 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3219 uint64_t size = arc_buf_size(buf);
3220 arc_free_data_buf(hdr, buf->b_data, size, buf);
3221 ARCSTAT_INCR(arcstat_overhead_size, -size);
3225 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3226 hdr->b_l1hdr.b_bufcnt -= 1;
3228 if (ARC_BUF_ENCRYPTED(buf)) {
3229 hdr->b_crypt_hdr.b_ebufcnt -= 1;
3232 * If we have no more encrypted buffers and we've
3233 * already gotten a copy of the decrypted data we can
3234 * free b_rabd to save some space.
3236 if (hdr->b_crypt_hdr.b_ebufcnt == 0 &&
3237 HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd != NULL &&
3238 !HDR_IO_IN_PROGRESS(hdr)) {
3239 arc_hdr_free_abd(hdr, B_TRUE);
3244 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3246 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3248 * If the current arc_buf_t is sharing its data buffer with the
3249 * hdr, then reassign the hdr's b_pabd to share it with the new
3250 * buffer at the end of the list. The shared buffer is always
3251 * the last one on the hdr's buffer list.
3253 * There is an equivalent case for compressed bufs, but since
3254 * they aren't guaranteed to be the last buf in the list and
3255 * that is an exceedingly rare case, we just allow that space be
3256 * wasted temporarily. We must also be careful not to share
3257 * encrypted buffers, since they cannot be shared.
3259 if (lastbuf != NULL && !ARC_BUF_ENCRYPTED(lastbuf)) {
3260 /* Only one buf can be shared at once */
3261 VERIFY(!arc_buf_is_shared(lastbuf));
3262 /* hdr is uncompressed so can't have compressed buf */
3263 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3265 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3266 arc_hdr_free_abd(hdr, B_FALSE);
3269 * We must setup a new shared block between the
3270 * last buffer and the hdr. The data would have
3271 * been allocated by the arc buf so we need to transfer
3272 * ownership to the hdr since it's now being shared.
3274 arc_share_buf(hdr, lastbuf);
3276 } else if (HDR_SHARED_DATA(hdr)) {
3278 * Uncompressed shared buffers are always at the end
3279 * of the list. Compressed buffers don't have the
3280 * same requirements. This makes it hard to
3281 * simply assert that the lastbuf is shared so
3282 * we rely on the hdr's compression flags to determine
3283 * if we have a compressed, shared buffer.
3285 ASSERT3P(lastbuf, !=, NULL);
3286 ASSERT(arc_buf_is_shared(lastbuf) ||
3287 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
3291 * Free the checksum if we're removing the last uncompressed buf from
3294 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3295 arc_cksum_free(hdr);
3298 /* clean up the buf */
3300 kmem_cache_free(buf_cache, buf);
3304 arc_hdr_alloc_abd(arc_buf_hdr_t *hdr, boolean_t alloc_rdata)
3308 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3309 ASSERT(HDR_HAS_L1HDR(hdr));
3310 ASSERT(!HDR_SHARED_DATA(hdr) || alloc_rdata);
3311 IMPLY(alloc_rdata, HDR_PROTECTED(hdr));
3314 size = HDR_GET_PSIZE(hdr);
3315 ASSERT3P(hdr->b_crypt_hdr.b_rabd, ==, NULL);
3316 hdr->b_crypt_hdr.b_rabd = arc_get_data_abd(hdr, size, hdr);
3317 ASSERT3P(hdr->b_crypt_hdr.b_rabd, !=, NULL);
3318 ARCSTAT_INCR(arcstat_raw_size, size);
3320 size = arc_hdr_size(hdr);
3321 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3322 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, size, hdr);
3323 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3326 ARCSTAT_INCR(arcstat_compressed_size, size);
3327 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3331 arc_hdr_free_abd(arc_buf_hdr_t *hdr, boolean_t free_rdata)
3333 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
3335 ASSERT(HDR_HAS_L1HDR(hdr));
3336 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
3337 IMPLY(free_rdata, HDR_HAS_RABD(hdr));
3340 * If the hdr is currently being written to the l2arc then
3341 * we defer freeing the data by adding it to the l2arc_free_on_write
3342 * list. The l2arc will free the data once it's finished
3343 * writing it to the l2arc device.
3345 if (HDR_L2_WRITING(hdr)) {
3346 arc_hdr_free_on_write(hdr, free_rdata);
3347 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3348 } else if (free_rdata) {
3349 arc_free_data_abd(hdr, hdr->b_crypt_hdr.b_rabd, size, hdr);
3351 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd, size, hdr);
3355 hdr->b_crypt_hdr.b_rabd = NULL;
3356 ARCSTAT_INCR(arcstat_raw_size, -size);
3358 hdr->b_l1hdr.b_pabd = NULL;
3361 if (hdr->b_l1hdr.b_pabd == NULL && !HDR_HAS_RABD(hdr))
3362 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3364 ARCSTAT_INCR(arcstat_compressed_size, -size);
3365 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3368 static arc_buf_hdr_t *
3369 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3370 boolean_t protected, enum zio_compress compression_type,
3371 arc_buf_contents_t type, boolean_t alloc_rdata)
3375 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3377 hdr = kmem_cache_alloc(hdr_full_crypt_cache, KM_PUSHPAGE);
3379 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3382 ASSERT(HDR_EMPTY(hdr));
3383 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3384 HDR_SET_PSIZE(hdr, psize);
3385 HDR_SET_LSIZE(hdr, lsize);
3389 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3390 arc_hdr_set_compress(hdr, compression_type);
3392 arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
3394 hdr->b_l1hdr.b_state = arc_anon;
3395 hdr->b_l1hdr.b_arc_access = 0;
3396 hdr->b_l1hdr.b_bufcnt = 0;
3397 hdr->b_l1hdr.b_buf = NULL;
3400 * Allocate the hdr's buffer. This will contain either
3401 * the compressed or uncompressed data depending on the block
3402 * it references and compressed arc enablement.
3404 arc_hdr_alloc_abd(hdr, alloc_rdata);
3405 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3411 * Transition between the two allocation states for the arc_buf_hdr struct.
3412 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3413 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3414 * version is used when a cache buffer is only in the L2ARC in order to reduce
3417 static arc_buf_hdr_t *
3418 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3420 ASSERT(HDR_HAS_L2HDR(hdr));
3422 arc_buf_hdr_t *nhdr;
3423 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3425 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3426 (old == hdr_l2only_cache && new == hdr_full_cache));
3429 * if the caller wanted a new full header and the header is to be
3430 * encrypted we will actually allocate the header from the full crypt
3431 * cache instead. The same applies to freeing from the old cache.
3433 if (HDR_PROTECTED(hdr) && new == hdr_full_cache)
3434 new = hdr_full_crypt_cache;
3435 if (HDR_PROTECTED(hdr) && old == hdr_full_cache)
3436 old = hdr_full_crypt_cache;
3438 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3440 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3441 buf_hash_remove(hdr);
3443 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3445 if (new == hdr_full_cache || new == hdr_full_crypt_cache) {
3446 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3448 * arc_access and arc_change_state need to be aware that a
3449 * header has just come out of L2ARC, so we set its state to
3450 * l2c_only even though it's about to change.
3452 nhdr->b_l1hdr.b_state = arc_l2c_only;
3454 /* Verify previous threads set to NULL before freeing */
3455 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3456 ASSERT(!HDR_HAS_RABD(hdr));
3458 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3459 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3460 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3463 * If we've reached here, We must have been called from
3464 * arc_evict_hdr(), as such we should have already been
3465 * removed from any ghost list we were previously on
3466 * (which protects us from racing with arc_evict_state),
3467 * thus no locking is needed during this check.
3469 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3472 * A buffer must not be moved into the arc_l2c_only
3473 * state if it's not finished being written out to the
3474 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3475 * might try to be accessed, even though it was removed.
3477 VERIFY(!HDR_L2_WRITING(hdr));
3478 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3479 ASSERT(!HDR_HAS_RABD(hdr));
3481 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3484 * The header has been reallocated so we need to re-insert it into any
3487 (void) buf_hash_insert(nhdr, NULL);
3489 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3491 mutex_enter(&dev->l2ad_mtx);
3494 * We must place the realloc'ed header back into the list at
3495 * the same spot. Otherwise, if it's placed earlier in the list,
3496 * l2arc_write_buffers() could find it during the function's
3497 * write phase, and try to write it out to the l2arc.
3499 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3500 list_remove(&dev->l2ad_buflist, hdr);
3502 mutex_exit(&dev->l2ad_mtx);
3505 * Since we're using the pointer address as the tag when
3506 * incrementing and decrementing the l2ad_alloc refcount, we
3507 * must remove the old pointer (that we're about to destroy) and
3508 * add the new pointer to the refcount. Otherwise we'd remove
3509 * the wrong pointer address when calling arc_hdr_destroy() later.
3512 (void) zfs_refcount_remove_many(&dev->l2ad_alloc,
3513 arc_hdr_size(hdr), hdr);
3514 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
3515 arc_hdr_size(nhdr), nhdr);
3517 buf_discard_identity(hdr);
3518 kmem_cache_free(old, hdr);
3524 * This function allows an L1 header to be reallocated as a crypt
3525 * header and vice versa. If we are going to a crypt header, the
3526 * new fields will be zeroed out.
3528 static arc_buf_hdr_t *
3529 arc_hdr_realloc_crypt(arc_buf_hdr_t *hdr, boolean_t need_crypt)
3531 arc_buf_hdr_t *nhdr;
3533 kmem_cache_t *ncache, *ocache;
3534 unsigned nsize, osize;
3537 * This function requires that hdr is in the arc_anon state.
3538 * Therefore it won't have any L2ARC data for us to worry
3541 ASSERT(HDR_HAS_L1HDR(hdr));
3542 ASSERT(!HDR_HAS_L2HDR(hdr));
3543 ASSERT3U(!!HDR_PROTECTED(hdr), !=, need_crypt);
3544 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3545 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3546 ASSERT(!list_link_active(&hdr->b_l2hdr.b_l2node));
3547 ASSERT3P(hdr->b_hash_next, ==, NULL);
3550 ncache = hdr_full_crypt_cache;
3551 nsize = sizeof (hdr->b_crypt_hdr);
3552 ocache = hdr_full_cache;
3553 osize = HDR_FULL_SIZE;
3555 ncache = hdr_full_cache;
3556 nsize = HDR_FULL_SIZE;
3557 ocache = hdr_full_crypt_cache;
3558 osize = sizeof (hdr->b_crypt_hdr);
3561 nhdr = kmem_cache_alloc(ncache, KM_PUSHPAGE);
3564 * Copy all members that aren't locks or condvars to the new header.
3565 * No lists are pointing to us (as we asserted above), so we don't
3566 * need to worry about the list nodes.
3568 nhdr->b_dva = hdr->b_dva;
3569 nhdr->b_birth = hdr->b_birth;
3570 nhdr->b_type = hdr->b_type;
3571 nhdr->b_flags = hdr->b_flags;
3572 nhdr->b_psize = hdr->b_psize;
3573 nhdr->b_lsize = hdr->b_lsize;
3574 nhdr->b_spa = hdr->b_spa;
3575 nhdr->b_l1hdr.b_freeze_cksum = hdr->b_l1hdr.b_freeze_cksum;
3576 nhdr->b_l1hdr.b_bufcnt = hdr->b_l1hdr.b_bufcnt;
3577 nhdr->b_l1hdr.b_byteswap = hdr->b_l1hdr.b_byteswap;
3578 nhdr->b_l1hdr.b_state = hdr->b_l1hdr.b_state;
3579 nhdr->b_l1hdr.b_arc_access = hdr->b_l1hdr.b_arc_access;
3580 nhdr->b_l1hdr.b_mru_hits = hdr->b_l1hdr.b_mru_hits;
3581 nhdr->b_l1hdr.b_mru_ghost_hits = hdr->b_l1hdr.b_mru_ghost_hits;
3582 nhdr->b_l1hdr.b_mfu_hits = hdr->b_l1hdr.b_mfu_hits;
3583 nhdr->b_l1hdr.b_mfu_ghost_hits = hdr->b_l1hdr.b_mfu_ghost_hits;
3584 nhdr->b_l1hdr.b_l2_hits = hdr->b_l1hdr.b_l2_hits;
3585 nhdr->b_l1hdr.b_acb = hdr->b_l1hdr.b_acb;
3586 nhdr->b_l1hdr.b_pabd = hdr->b_l1hdr.b_pabd;
3589 * This zfs_refcount_add() exists only to ensure that the individual
3590 * arc buffers always point to a header that is referenced, avoiding
3591 * a small race condition that could trigger ASSERTs.
3593 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, FTAG);
3594 nhdr->b_l1hdr.b_buf = hdr->b_l1hdr.b_buf;
3595 for (buf = nhdr->b_l1hdr.b_buf; buf != NULL; buf = buf->b_next) {
3596 mutex_enter(&buf->b_evict_lock);
3598 mutex_exit(&buf->b_evict_lock);
3601 zfs_refcount_transfer(&nhdr->b_l1hdr.b_refcnt, &hdr->b_l1hdr.b_refcnt);
3602 (void) zfs_refcount_remove(&nhdr->b_l1hdr.b_refcnt, FTAG);
3603 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3606 arc_hdr_set_flags(nhdr, ARC_FLAG_PROTECTED);
3608 arc_hdr_clear_flags(nhdr, ARC_FLAG_PROTECTED);
3611 /* unset all members of the original hdr */
3612 bzero(&hdr->b_dva, sizeof (dva_t));
3614 hdr->b_type = ARC_BUFC_INVALID;
3619 hdr->b_l1hdr.b_freeze_cksum = NULL;
3620 hdr->b_l1hdr.b_buf = NULL;
3621 hdr->b_l1hdr.b_bufcnt = 0;
3622 hdr->b_l1hdr.b_byteswap = 0;
3623 hdr->b_l1hdr.b_state = NULL;
3624 hdr->b_l1hdr.b_arc_access = 0;
3625 hdr->b_l1hdr.b_mru_hits = 0;
3626 hdr->b_l1hdr.b_mru_ghost_hits = 0;
3627 hdr->b_l1hdr.b_mfu_hits = 0;
3628 hdr->b_l1hdr.b_mfu_ghost_hits = 0;
3629 hdr->b_l1hdr.b_l2_hits = 0;
3630 hdr->b_l1hdr.b_acb = NULL;
3631 hdr->b_l1hdr.b_pabd = NULL;
3633 if (ocache == hdr_full_crypt_cache) {
3634 ASSERT(!HDR_HAS_RABD(hdr));
3635 hdr->b_crypt_hdr.b_ot = DMU_OT_NONE;
3636 hdr->b_crypt_hdr.b_ebufcnt = 0;
3637 hdr->b_crypt_hdr.b_dsobj = 0;
3638 bzero(hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3639 bzero(hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3640 bzero(hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3643 buf_discard_identity(hdr);
3644 kmem_cache_free(ocache, hdr);
3650 * This function is used by the send / receive code to convert a newly
3651 * allocated arc_buf_t to one that is suitable for a raw encrypted write. It
3652 * is also used to allow the root objset block to be uupdated without altering
3653 * its embedded MACs. Both block types will always be uncompressed so we do not
3654 * have to worry about compression type or psize.
3657 arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder,
3658 dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv,
3661 arc_buf_hdr_t *hdr = buf->b_hdr;
3663 ASSERT(ot == DMU_OT_DNODE || ot == DMU_OT_OBJSET);
3664 ASSERT(HDR_HAS_L1HDR(hdr));
3665 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3667 buf->b_flags |= (ARC_BUF_FLAG_COMPRESSED | ARC_BUF_FLAG_ENCRYPTED);
3668 if (!HDR_PROTECTED(hdr))
3669 hdr = arc_hdr_realloc_crypt(hdr, B_TRUE);
3670 hdr->b_crypt_hdr.b_dsobj = dsobj;
3671 hdr->b_crypt_hdr.b_ot = ot;
3672 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3673 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3674 if (!arc_hdr_has_uncompressed_buf(hdr))
3675 arc_cksum_free(hdr);
3678 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3680 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3682 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3686 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3687 * The buf is returned thawed since we expect the consumer to modify it.
3690 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3692 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3693 B_FALSE, ZIO_COMPRESS_OFF, type, B_FALSE);
3694 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3696 arc_buf_t *buf = NULL;
3697 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, B_FALSE,
3698 B_FALSE, B_FALSE, &buf));
3705 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3706 * for bufs containing metadata.
3709 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3710 enum zio_compress compression_type)
3712 ASSERT3U(lsize, >, 0);
3713 ASSERT3U(lsize, >=, psize);
3714 ASSERT3U(compression_type, >, ZIO_COMPRESS_OFF);
3715 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3717 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3718 B_FALSE, compression_type, ARC_BUFC_DATA, B_FALSE);
3719 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3721 arc_buf_t *buf = NULL;
3722 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE,
3723 B_TRUE, B_FALSE, B_FALSE, &buf));
3725 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3727 if (!arc_buf_is_shared(buf)) {
3729 * To ensure that the hdr has the correct data in it if we call
3730 * arc_untransform() on this buf before it's been written to
3731 * disk, it's easiest if we just set up sharing between the
3734 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3735 arc_hdr_free_abd(hdr, B_FALSE);
3736 arc_share_buf(hdr, buf);
3743 arc_alloc_raw_buf(spa_t *spa, void *tag, uint64_t dsobj, boolean_t byteorder,
3744 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
3745 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
3746 enum zio_compress compression_type)
3750 arc_buf_contents_t type = DMU_OT_IS_METADATA(ot) ?
3751 ARC_BUFC_METADATA : ARC_BUFC_DATA;
3753 ASSERT3U(lsize, >, 0);
3754 ASSERT3U(lsize, >=, psize);
3755 ASSERT3U(compression_type, >=, ZIO_COMPRESS_OFF);
3756 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3758 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, B_TRUE,
3759 compression_type, type, B_TRUE);
3760 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3762 hdr->b_crypt_hdr.b_dsobj = dsobj;
3763 hdr->b_crypt_hdr.b_ot = ot;
3764 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3765 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3766 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3767 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3768 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3771 * This buffer will be considered encrypted even if the ot is not an
3772 * encrypted type. It will become authenticated instead in
3773 * arc_write_ready().
3776 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_TRUE, B_TRUE,
3777 B_FALSE, B_FALSE, &buf));
3779 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3785 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3787 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3788 l2arc_dev_t *dev = l2hdr->b_dev;
3789 uint64_t psize = arc_hdr_size(hdr);
3791 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3792 ASSERT(HDR_HAS_L2HDR(hdr));
3794 list_remove(&dev->l2ad_buflist, hdr);
3796 ARCSTAT_INCR(arcstat_l2_psize, -psize);
3797 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
3799 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0);
3801 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, psize, hdr);
3802 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3806 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3808 if (HDR_HAS_L1HDR(hdr)) {
3809 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3810 hdr->b_l1hdr.b_bufcnt > 0);
3811 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3812 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3814 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3815 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3817 if (!HDR_EMPTY(hdr))
3818 buf_discard_identity(hdr);
3820 if (HDR_HAS_L2HDR(hdr)) {
3821 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3822 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3825 mutex_enter(&dev->l2ad_mtx);
3828 * Even though we checked this conditional above, we
3829 * need to check this again now that we have the
3830 * l2ad_mtx. This is because we could be racing with
3831 * another thread calling l2arc_evict() which might have
3832 * destroyed this header's L2 portion as we were waiting
3833 * to acquire the l2ad_mtx. If that happens, we don't
3834 * want to re-destroy the header's L2 portion.
3836 if (HDR_HAS_L2HDR(hdr))
3837 arc_hdr_l2hdr_destroy(hdr);
3840 mutex_exit(&dev->l2ad_mtx);
3843 if (HDR_HAS_L1HDR(hdr)) {
3844 arc_cksum_free(hdr);
3846 while (hdr->b_l1hdr.b_buf != NULL)
3847 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3849 if (hdr->b_l1hdr.b_pabd != NULL) {
3850 arc_hdr_free_abd(hdr, B_FALSE);
3853 if (HDR_HAS_RABD(hdr))
3854 arc_hdr_free_abd(hdr, B_TRUE);
3857 ASSERT3P(hdr->b_hash_next, ==, NULL);
3858 if (HDR_HAS_L1HDR(hdr)) {
3859 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3860 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3862 if (!HDR_PROTECTED(hdr)) {
3863 kmem_cache_free(hdr_full_cache, hdr);
3865 kmem_cache_free(hdr_full_crypt_cache, hdr);
3868 kmem_cache_free(hdr_l2only_cache, hdr);
3873 arc_buf_destroy(arc_buf_t *buf, void* tag)
3875 arc_buf_hdr_t *hdr = buf->b_hdr;
3876 kmutex_t *hash_lock = HDR_LOCK(hdr);
3878 if (hdr->b_l1hdr.b_state == arc_anon) {
3879 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3880 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3881 VERIFY0(remove_reference(hdr, NULL, tag));
3882 arc_hdr_destroy(hdr);
3886 mutex_enter(hash_lock);
3887 ASSERT3P(hdr, ==, buf->b_hdr);
3888 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3889 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3890 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3891 ASSERT3P(buf->b_data, !=, NULL);
3893 (void) remove_reference(hdr, hash_lock, tag);
3894 arc_buf_destroy_impl(buf);
3895 mutex_exit(hash_lock);
3899 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3900 * state of the header is dependent on its state prior to entering this
3901 * function. The following transitions are possible:
3903 * - arc_mru -> arc_mru_ghost
3904 * - arc_mfu -> arc_mfu_ghost
3905 * - arc_mru_ghost -> arc_l2c_only
3906 * - arc_mru_ghost -> deleted
3907 * - arc_mfu_ghost -> arc_l2c_only
3908 * - arc_mfu_ghost -> deleted
3911 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3913 arc_state_t *evicted_state, *state;
3914 int64_t bytes_evicted = 0;
3915 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ?
3916 arc_min_prescient_prefetch_ms : arc_min_prefetch_ms;
3918 ASSERT(MUTEX_HELD(hash_lock));
3919 ASSERT(HDR_HAS_L1HDR(hdr));
3921 state = hdr->b_l1hdr.b_state;
3922 if (GHOST_STATE(state)) {
3923 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3924 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3927 * l2arc_write_buffers() relies on a header's L1 portion
3928 * (i.e. its b_pabd field) during it's write phase.
3929 * Thus, we cannot push a header onto the arc_l2c_only
3930 * state (removing its L1 piece) until the header is
3931 * done being written to the l2arc.
3933 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3934 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3935 return (bytes_evicted);
3938 ARCSTAT_BUMP(arcstat_deleted);
3939 bytes_evicted += HDR_GET_LSIZE(hdr);
3941 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3943 if (HDR_HAS_L2HDR(hdr)) {
3944 ASSERT(hdr->b_l1hdr.b_pabd == NULL);
3945 ASSERT(!HDR_HAS_RABD(hdr));
3947 * This buffer is cached on the 2nd Level ARC;
3948 * don't destroy the header.
3950 arc_change_state(arc_l2c_only, hdr, hash_lock);
3952 * dropping from L1+L2 cached to L2-only,
3953 * realloc to remove the L1 header.
3955 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3958 arc_change_state(arc_anon, hdr, hash_lock);
3959 arc_hdr_destroy(hdr);
3961 return (bytes_evicted);
3964 ASSERT(state == arc_mru || state == arc_mfu);
3965 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3967 /* prefetch buffers have a minimum lifespan */
3968 if (HDR_IO_IN_PROGRESS(hdr) ||
3969 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3970 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
3971 MSEC_TO_TICK(min_lifetime))) {
3972 ARCSTAT_BUMP(arcstat_evict_skip);
3973 return (bytes_evicted);
3976 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3977 while (hdr->b_l1hdr.b_buf) {
3978 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3979 if (!mutex_tryenter(&buf->b_evict_lock)) {
3980 ARCSTAT_BUMP(arcstat_mutex_miss);
3983 if (buf->b_data != NULL)
3984 bytes_evicted += HDR_GET_LSIZE(hdr);
3985 mutex_exit(&buf->b_evict_lock);
3986 arc_buf_destroy_impl(buf);
3989 if (HDR_HAS_L2HDR(hdr)) {
3990 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3992 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3993 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3994 HDR_GET_LSIZE(hdr));
3996 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3997 HDR_GET_LSIZE(hdr));
4001 if (hdr->b_l1hdr.b_bufcnt == 0) {
4002 arc_cksum_free(hdr);
4004 bytes_evicted += arc_hdr_size(hdr);
4007 * If this hdr is being evicted and has a compressed
4008 * buffer then we discard it here before we change states.
4009 * This ensures that the accounting is updated correctly
4010 * in arc_free_data_impl().
4012 if (hdr->b_l1hdr.b_pabd != NULL)
4013 arc_hdr_free_abd(hdr, B_FALSE);
4015 if (HDR_HAS_RABD(hdr))
4016 arc_hdr_free_abd(hdr, B_TRUE);
4018 arc_change_state(evicted_state, hdr, hash_lock);
4019 ASSERT(HDR_IN_HASH_TABLE(hdr));
4020 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
4021 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
4024 return (bytes_evicted);
4028 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
4029 uint64_t spa, int64_t bytes)
4031 multilist_sublist_t *mls;
4032 uint64_t bytes_evicted = 0;
4034 kmutex_t *hash_lock;
4035 int evict_count = 0;
4037 ASSERT3P(marker, !=, NULL);
4038 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
4040 mls = multilist_sublist_lock(ml, idx);
4042 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
4043 hdr = multilist_sublist_prev(mls, marker)) {
4044 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
4045 (evict_count >= zfs_arc_evict_batch_limit))
4049 * To keep our iteration location, move the marker
4050 * forward. Since we're not holding hdr's hash lock, we
4051 * must be very careful and not remove 'hdr' from the
4052 * sublist. Otherwise, other consumers might mistake the
4053 * 'hdr' as not being on a sublist when they call the
4054 * multilist_link_active() function (they all rely on
4055 * the hash lock protecting concurrent insertions and
4056 * removals). multilist_sublist_move_forward() was
4057 * specifically implemented to ensure this is the case
4058 * (only 'marker' will be removed and re-inserted).
4060 multilist_sublist_move_forward(mls, marker);
4063 * The only case where the b_spa field should ever be
4064 * zero, is the marker headers inserted by
4065 * arc_evict_state(). It's possible for multiple threads
4066 * to be calling arc_evict_state() concurrently (e.g.
4067 * dsl_pool_close() and zio_inject_fault()), so we must
4068 * skip any markers we see from these other threads.
4070 if (hdr->b_spa == 0)
4073 /* we're only interested in evicting buffers of a certain spa */
4074 if (spa != 0 && hdr->b_spa != spa) {
4075 ARCSTAT_BUMP(arcstat_evict_skip);
4079 hash_lock = HDR_LOCK(hdr);
4082 * We aren't calling this function from any code path
4083 * that would already be holding a hash lock, so we're
4084 * asserting on this assumption to be defensive in case
4085 * this ever changes. Without this check, it would be
4086 * possible to incorrectly increment arcstat_mutex_miss
4087 * below (e.g. if the code changed such that we called
4088 * this function with a hash lock held).
4090 ASSERT(!MUTEX_HELD(hash_lock));
4092 if (mutex_tryenter(hash_lock)) {
4093 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
4094 mutex_exit(hash_lock);
4096 bytes_evicted += evicted;
4099 * If evicted is zero, arc_evict_hdr() must have
4100 * decided to skip this header, don't increment
4101 * evict_count in this case.
4107 * If arc_size isn't overflowing, signal any
4108 * threads that might happen to be waiting.
4110 * For each header evicted, we wake up a single
4111 * thread. If we used cv_broadcast, we could
4112 * wake up "too many" threads causing arc_size
4113 * to significantly overflow arc_c; since
4114 * arc_get_data_impl() doesn't check for overflow
4115 * when it's woken up (it doesn't because it's
4116 * possible for the ARC to be overflowing while
4117 * full of un-evictable buffers, and the
4118 * function should proceed in this case).
4120 * If threads are left sleeping, due to not
4121 * using cv_broadcast here, they will be woken
4122 * up via cv_broadcast in arc_adjust_cb() just
4123 * before arc_adjust_zthr sleeps.
4125 mutex_enter(&arc_adjust_lock);
4126 if (!arc_is_overflowing())
4127 cv_signal(&arc_adjust_waiters_cv);
4128 mutex_exit(&arc_adjust_lock);
4130 ARCSTAT_BUMP(arcstat_mutex_miss);
4134 multilist_sublist_unlock(mls);
4136 return (bytes_evicted);
4140 * Evict buffers from the given arc state, until we've removed the
4141 * specified number of bytes. Move the removed buffers to the
4142 * appropriate evict state.
4144 * This function makes a "best effort". It skips over any buffers
4145 * it can't get a hash_lock on, and so, may not catch all candidates.
4146 * It may also return without evicting as much space as requested.
4148 * If bytes is specified using the special value ARC_EVICT_ALL, this
4149 * will evict all available (i.e. unlocked and evictable) buffers from
4150 * the given arc state; which is used by arc_flush().
4153 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
4154 arc_buf_contents_t type)
4156 uint64_t total_evicted = 0;
4157 multilist_t *ml = state->arcs_list[type];
4159 arc_buf_hdr_t **markers;
4161 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
4163 num_sublists = multilist_get_num_sublists(ml);
4166 * If we've tried to evict from each sublist, made some
4167 * progress, but still have not hit the target number of bytes
4168 * to evict, we want to keep trying. The markers allow us to
4169 * pick up where we left off for each individual sublist, rather
4170 * than starting from the tail each time.
4172 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
4173 for (int i = 0; i < num_sublists; i++) {
4174 multilist_sublist_t *mls;
4176 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
4179 * A b_spa of 0 is used to indicate that this header is
4180 * a marker. This fact is used in arc_adjust_type() and
4181 * arc_evict_state_impl().
4183 markers[i]->b_spa = 0;
4185 mls = multilist_sublist_lock(ml, i);
4186 multilist_sublist_insert_tail(mls, markers[i]);
4187 multilist_sublist_unlock(mls);
4191 * While we haven't hit our target number of bytes to evict, or
4192 * we're evicting all available buffers.
4194 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
4195 int sublist_idx = multilist_get_random_index(ml);
4196 uint64_t scan_evicted = 0;
4199 * Try to reduce pinned dnodes with a floor of arc_dnode_limit.
4200 * Request that 10% of the LRUs be scanned by the superblock
4203 if (type == ARC_BUFC_DATA && aggsum_compare(&astat_dnode_size,
4204 arc_dnode_limit) > 0) {
4205 arc_prune_async((aggsum_upper_bound(&astat_dnode_size) -
4206 arc_dnode_limit) / sizeof (dnode_t) /
4207 zfs_arc_dnode_reduce_percent);
4211 * Start eviction using a randomly selected sublist,
4212 * this is to try and evenly balance eviction across all
4213 * sublists. Always starting at the same sublist
4214 * (e.g. index 0) would cause evictions to favor certain
4215 * sublists over others.
4217 for (int i = 0; i < num_sublists; i++) {
4218 uint64_t bytes_remaining;
4219 uint64_t bytes_evicted;
4221 if (bytes == ARC_EVICT_ALL)
4222 bytes_remaining = ARC_EVICT_ALL;
4223 else if (total_evicted < bytes)
4224 bytes_remaining = bytes - total_evicted;
4228 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
4229 markers[sublist_idx], spa, bytes_remaining);
4231 scan_evicted += bytes_evicted;
4232 total_evicted += bytes_evicted;
4234 /* we've reached the end, wrap to the beginning */
4235 if (++sublist_idx >= num_sublists)
4240 * If we didn't evict anything during this scan, we have
4241 * no reason to believe we'll evict more during another
4242 * scan, so break the loop.
4244 if (scan_evicted == 0) {
4245 /* This isn't possible, let's make that obvious */
4246 ASSERT3S(bytes, !=, 0);
4249 * When bytes is ARC_EVICT_ALL, the only way to
4250 * break the loop is when scan_evicted is zero.
4251 * In that case, we actually have evicted enough,
4252 * so we don't want to increment the kstat.
4254 if (bytes != ARC_EVICT_ALL) {
4255 ASSERT3S(total_evicted, <, bytes);
4256 ARCSTAT_BUMP(arcstat_evict_not_enough);
4263 for (int i = 0; i < num_sublists; i++) {
4264 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4265 multilist_sublist_remove(mls, markers[i]);
4266 multilist_sublist_unlock(mls);
4268 kmem_cache_free(hdr_full_cache, markers[i]);
4270 kmem_free(markers, sizeof (*markers) * num_sublists);
4272 return (total_evicted);
4276 * Flush all "evictable" data of the given type from the arc state
4277 * specified. This will not evict any "active" buffers (i.e. referenced).
4279 * When 'retry' is set to B_FALSE, the function will make a single pass
4280 * over the state and evict any buffers that it can. Since it doesn't
4281 * continually retry the eviction, it might end up leaving some buffers
4282 * in the ARC due to lock misses.
4284 * When 'retry' is set to B_TRUE, the function will continually retry the
4285 * eviction until *all* evictable buffers have been removed from the
4286 * state. As a result, if concurrent insertions into the state are
4287 * allowed (e.g. if the ARC isn't shutting down), this function might
4288 * wind up in an infinite loop, continually trying to evict buffers.
4291 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
4294 uint64_t evicted = 0;
4296 while (zfs_refcount_count(&state->arcs_esize[type]) != 0) {
4297 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
4307 * Helper function for arc_prune_async() it is responsible for safely
4308 * handling the execution of a registered arc_prune_func_t.
4311 arc_prune_task(void *ptr)
4313 arc_prune_t *ap = (arc_prune_t *)ptr;
4314 arc_prune_func_t *func = ap->p_pfunc;
4317 func(ap->p_adjust, ap->p_private);
4319 zfs_refcount_remove(&ap->p_refcnt, func);
4323 * Notify registered consumers they must drop holds on a portion of the ARC
4324 * buffered they reference. This provides a mechanism to ensure the ARC can
4325 * honor the arc_meta_limit and reclaim otherwise pinned ARC buffers. This
4326 * is analogous to dnlc_reduce_cache() but more generic.
4328 * This operation is performed asynchronously so it may be safely called
4329 * in the context of the arc_reclaim_thread(). A reference is taken here
4330 * for each registered arc_prune_t and the arc_prune_task() is responsible
4331 * for releasing it once the registered arc_prune_func_t has completed.
4334 arc_prune_async(int64_t adjust)
4338 mutex_enter(&arc_prune_mtx);
4339 for (ap = list_head(&arc_prune_list); ap != NULL;
4340 ap = list_next(&arc_prune_list, ap)) {
4342 if (zfs_refcount_count(&ap->p_refcnt) >= 2)
4345 zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc);
4346 ap->p_adjust = adjust;
4347 if (taskq_dispatch(arc_prune_taskq, arc_prune_task,
4348 ap, TQ_SLEEP) == TASKQID_INVALID) {
4349 zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc);
4352 ARCSTAT_BUMP(arcstat_prune);
4354 mutex_exit(&arc_prune_mtx);
4358 * Evict the specified number of bytes from the state specified,
4359 * restricting eviction to the spa and type given. This function
4360 * prevents us from trying to evict more from a state's list than
4361 * is "evictable", and to skip evicting altogether when passed a
4362 * negative value for "bytes". In contrast, arc_evict_state() will
4363 * evict everything it can, when passed a negative value for "bytes".
4366 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
4367 arc_buf_contents_t type)
4371 if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) {
4372 delta = MIN(zfs_refcount_count(&state->arcs_esize[type]),
4374 return (arc_evict_state(state, spa, delta, type));
4381 * The goal of this function is to evict enough meta data buffers from the
4382 * ARC in order to enforce the arc_meta_limit. Achieving this is slightly
4383 * more complicated than it appears because it is common for data buffers
4384 * to have holds on meta data buffers. In addition, dnode meta data buffers
4385 * will be held by the dnodes in the block preventing them from being freed.
4386 * This means we can't simply traverse the ARC and expect to always find
4387 * enough unheld meta data buffer to release.
4389 * Therefore, this function has been updated to make alternating passes
4390 * over the ARC releasing data buffers and then newly unheld meta data
4391 * buffers. This ensures forward progress is maintained and meta_used
4392 * will decrease. Normally this is sufficient, but if required the ARC
4393 * will call the registered prune callbacks causing dentry and inodes to
4394 * be dropped from the VFS cache. This will make dnode meta data buffers
4395 * available for reclaim.
4398 arc_adjust_meta_balanced(uint64_t meta_used)
4400 int64_t delta, prune = 0, adjustmnt;
4401 uint64_t total_evicted = 0;
4402 arc_buf_contents_t type = ARC_BUFC_DATA;
4403 int restarts = MAX(zfs_arc_meta_adjust_restarts, 0);
4407 * This slightly differs than the way we evict from the mru in
4408 * arc_adjust because we don't have a "target" value (i.e. no
4409 * "meta" arc_p). As a result, I think we can completely
4410 * cannibalize the metadata in the MRU before we evict the
4411 * metadata from the MFU. I think we probably need to implement a
4412 * "metadata arc_p" value to do this properly.
4414 adjustmnt = meta_used - arc_meta_limit;
4416 if (adjustmnt > 0 &&
4417 zfs_refcount_count(&arc_mru->arcs_esize[type]) > 0) {
4418 delta = MIN(zfs_refcount_count(&arc_mru->arcs_esize[type]),
4420 total_evicted += arc_adjust_impl(arc_mru, 0, delta, type);
4425 * We can't afford to recalculate adjustmnt here. If we do,
4426 * new metadata buffers can sneak into the MRU or ANON lists,
4427 * thus penalize the MFU metadata. Although the fudge factor is
4428 * small, it has been empirically shown to be significant for
4429 * certain workloads (e.g. creating many empty directories). As
4430 * such, we use the original calculation for adjustmnt, and
4431 * simply decrement the amount of data evicted from the MRU.
4434 if (adjustmnt > 0 &&
4435 zfs_refcount_count(&arc_mfu->arcs_esize[type]) > 0) {
4436 delta = MIN(zfs_refcount_count(&arc_mfu->arcs_esize[type]),
4438 total_evicted += arc_adjust_impl(arc_mfu, 0, delta, type);
4441 adjustmnt = meta_used - arc_meta_limit;
4443 if (adjustmnt > 0 &&
4444 zfs_refcount_count(&arc_mru_ghost->arcs_esize[type]) > 0) {
4445 delta = MIN(adjustmnt,
4446 zfs_refcount_count(&arc_mru_ghost->arcs_esize[type]));
4447 total_evicted += arc_adjust_impl(arc_mru_ghost, 0, delta, type);
4451 if (adjustmnt > 0 &&
4452 zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type]) > 0) {
4453 delta = MIN(adjustmnt,
4454 zfs_refcount_count(&arc_mfu_ghost->arcs_esize[type]));
4455 total_evicted += arc_adjust_impl(arc_mfu_ghost, 0, delta, type);
4459 * If after attempting to make the requested adjustment to the ARC
4460 * the meta limit is still being exceeded then request that the
4461 * higher layers drop some cached objects which have holds on ARC
4462 * meta buffers. Requests to the upper layers will be made with
4463 * increasingly large scan sizes until the ARC is below the limit.
4465 if (meta_used > arc_meta_limit) {
4466 if (type == ARC_BUFC_DATA) {
4467 type = ARC_BUFC_METADATA;
4469 type = ARC_BUFC_DATA;
4471 if (zfs_arc_meta_prune) {
4472 prune += zfs_arc_meta_prune;
4473 arc_prune_async(prune);
4482 return (total_evicted);
4486 * Evict metadata buffers from the cache, such that arc_meta_used is
4487 * capped by the arc_meta_limit tunable.
4490 arc_adjust_meta_only(uint64_t meta_used)
4492 uint64_t total_evicted = 0;
4496 * If we're over the meta limit, we want to evict enough
4497 * metadata to get back under the meta limit. We don't want to
4498 * evict so much that we drop the MRU below arc_p, though. If
4499 * we're over the meta limit more than we're over arc_p, we
4500 * evict some from the MRU here, and some from the MFU below.
4502 target = MIN((int64_t)(meta_used - arc_meta_limit),
4503 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4504 zfs_refcount_count(&arc_mru->arcs_size) - arc_p));
4506 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4509 * Similar to the above, we want to evict enough bytes to get us
4510 * below the meta limit, but not so much as to drop us below the
4511 * space allotted to the MFU (which is defined as arc_c - arc_p).
4513 target = MIN((int64_t)(meta_used - arc_meta_limit),
4514 (int64_t)(zfs_refcount_count(&arc_mfu->arcs_size) -
4517 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4519 return (total_evicted);
4523 arc_adjust_meta(uint64_t meta_used)
4525 if (zfs_arc_meta_strategy == ARC_STRATEGY_META_ONLY)
4526 return (arc_adjust_meta_only(meta_used));
4528 return (arc_adjust_meta_balanced(meta_used));
4532 * Return the type of the oldest buffer in the given arc state
4534 * This function will select a random sublist of type ARC_BUFC_DATA and
4535 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
4536 * is compared, and the type which contains the "older" buffer will be
4539 static arc_buf_contents_t
4540 arc_adjust_type(arc_state_t *state)
4542 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
4543 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
4544 int data_idx = multilist_get_random_index(data_ml);
4545 int meta_idx = multilist_get_random_index(meta_ml);
4546 multilist_sublist_t *data_mls;
4547 multilist_sublist_t *meta_mls;
4548 arc_buf_contents_t type;
4549 arc_buf_hdr_t *data_hdr;
4550 arc_buf_hdr_t *meta_hdr;
4553 * We keep the sublist lock until we're finished, to prevent
4554 * the headers from being destroyed via arc_evict_state().
4556 data_mls = multilist_sublist_lock(data_ml, data_idx);
4557 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
4560 * These two loops are to ensure we skip any markers that
4561 * might be at the tail of the lists due to arc_evict_state().
4564 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
4565 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
4566 if (data_hdr->b_spa != 0)
4570 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
4571 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
4572 if (meta_hdr->b_spa != 0)
4576 if (data_hdr == NULL && meta_hdr == NULL) {
4577 type = ARC_BUFC_DATA;
4578 } else if (data_hdr == NULL) {
4579 ASSERT3P(meta_hdr, !=, NULL);
4580 type = ARC_BUFC_METADATA;
4581 } else if (meta_hdr == NULL) {
4582 ASSERT3P(data_hdr, !=, NULL);
4583 type = ARC_BUFC_DATA;
4585 ASSERT3P(data_hdr, !=, NULL);
4586 ASSERT3P(meta_hdr, !=, NULL);
4588 /* The headers can't be on the sublist without an L1 header */
4589 ASSERT(HDR_HAS_L1HDR(data_hdr));
4590 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4592 if (data_hdr->b_l1hdr.b_arc_access <
4593 meta_hdr->b_l1hdr.b_arc_access) {
4594 type = ARC_BUFC_DATA;
4596 type = ARC_BUFC_METADATA;
4600 multilist_sublist_unlock(meta_mls);
4601 multilist_sublist_unlock(data_mls);
4607 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4612 uint64_t total_evicted = 0;
4615 uint64_t asize = aggsum_value(&arc_size);
4616 uint64_t ameta = aggsum_value(&arc_meta_used);
4619 * If we're over arc_meta_limit, we want to correct that before
4620 * potentially evicting data buffers below.
4622 total_evicted += arc_adjust_meta(ameta);
4627 * If we're over the target cache size, we want to evict enough
4628 * from the list to get back to our target size. We don't want
4629 * to evict too much from the MRU, such that it drops below
4630 * arc_p. So, if we're over our target cache size more than
4631 * the MRU is over arc_p, we'll evict enough to get back to
4632 * arc_p here, and then evict more from the MFU below.
4634 target = MIN((int64_t)(asize - arc_c),
4635 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4636 zfs_refcount_count(&arc_mru->arcs_size) + ameta - arc_p));
4639 * If we're below arc_meta_min, always prefer to evict data.
4640 * Otherwise, try to satisfy the requested number of bytes to
4641 * evict from the type which contains older buffers; in an
4642 * effort to keep newer buffers in the cache regardless of their
4643 * type. If we cannot satisfy the number of bytes from this
4644 * type, spill over into the next type.
4646 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4647 ameta > arc_meta_min) {
4648 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4649 total_evicted += bytes;
4652 * If we couldn't evict our target number of bytes from
4653 * metadata, we try to get the rest from data.
4658 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4660 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4661 total_evicted += bytes;
4664 * If we couldn't evict our target number of bytes from
4665 * data, we try to get the rest from metadata.
4670 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4674 * Re-sum ARC stats after the first round of evictions.
4676 asize = aggsum_value(&arc_size);
4677 ameta = aggsum_value(&arc_meta_used);
4683 * Now that we've tried to evict enough from the MRU to get its
4684 * size back to arc_p, if we're still above the target cache
4685 * size, we evict the rest from the MFU.
4687 target = asize - arc_c;
4689 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4690 ameta > arc_meta_min) {
4691 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4692 total_evicted += bytes;
4695 * If we couldn't evict our target number of bytes from
4696 * metadata, we try to get the rest from data.
4701 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4703 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4704 total_evicted += bytes;
4707 * If we couldn't evict our target number of bytes from
4708 * data, we try to get the rest from data.
4713 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4717 * Adjust ghost lists
4719 * In addition to the above, the ARC also defines target values
4720 * for the ghost lists. The sum of the mru list and mru ghost
4721 * list should never exceed the target size of the cache, and
4722 * the sum of the mru list, mfu list, mru ghost list, and mfu
4723 * ghost list should never exceed twice the target size of the
4724 * cache. The following logic enforces these limits on the ghost
4725 * caches, and evicts from them as needed.
4727 target = zfs_refcount_count(&arc_mru->arcs_size) +
4728 zfs_refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4730 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4731 total_evicted += bytes;
4736 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4739 * We assume the sum of the mru list and mfu list is less than
4740 * or equal to arc_c (we enforced this above), which means we
4741 * can use the simpler of the two equations below:
4743 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4744 * mru ghost + mfu ghost <= arc_c
4746 target = zfs_refcount_count(&arc_mru_ghost->arcs_size) +
4747 zfs_refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4749 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4750 total_evicted += bytes;
4755 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4757 return (total_evicted);
4761 arc_flush(spa_t *spa, boolean_t retry)
4766 * If retry is B_TRUE, a spa must not be specified since we have
4767 * no good way to determine if all of a spa's buffers have been
4768 * evicted from an arc state.
4770 ASSERT(!retry || spa == 0);
4773 guid = spa_load_guid(spa);
4775 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4776 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4778 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4779 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4781 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4782 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4784 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4785 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4789 arc_reduce_target_size(int64_t to_free)
4791 uint64_t asize = aggsum_value(&arc_size);
4794 if (c > to_free && c - to_free > arc_c_min) {
4795 arc_c = c - to_free;
4796 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4798 arc_c = MAX(asize, arc_c_min);
4800 arc_p = (arc_c >> 1);
4801 ASSERT(arc_c >= arc_c_min);
4802 ASSERT((int64_t)arc_p >= 0);
4807 if (asize > arc_c) {
4808 /* See comment in arc_adjust_cb_check() on why lock+flag */
4809 mutex_enter(&arc_adjust_lock);
4810 arc_adjust_needed = B_TRUE;
4811 mutex_exit(&arc_adjust_lock);
4812 zthr_wakeup(arc_adjust_zthr);
4816 * Return maximum amount of memory that we could possibly use. Reduced
4817 * to half of all memory in user space which is primarily used for testing.
4820 arc_all_memory(void)
4823 #ifdef CONFIG_HIGHMEM
4824 return (ptob(totalram_pages - totalhigh_pages));
4826 return (ptob(totalram_pages));
4827 #endif /* CONFIG_HIGHMEM */
4829 return (ptob(physmem) / 2);
4830 #endif /* _KERNEL */
4834 * Return the amount of memory that is considered free. In user space
4835 * which is primarily used for testing we pretend that free memory ranges
4836 * from 0-20% of all memory.
4839 arc_free_memory(void)
4842 #ifdef CONFIG_HIGHMEM
4845 return (ptob(si.freeram - si.freehigh));
4847 return (ptob(nr_free_pages() +
4848 nr_inactive_file_pages() +
4849 nr_inactive_anon_pages() +
4850 nr_slab_reclaimable_pages()));
4852 #endif /* CONFIG_HIGHMEM */
4854 return (spa_get_random(arc_all_memory() * 20 / 100));
4855 #endif /* _KERNEL */
4858 typedef enum free_memory_reason_t {
4863 FMR_PAGES_PP_MAXIMUM,
4866 } free_memory_reason_t;
4868 int64_t last_free_memory;
4869 free_memory_reason_t last_free_reason;
4873 * Additional reserve of pages for pp_reserve.
4875 int64_t arc_pages_pp_reserve = 64;
4878 * Additional reserve of pages for swapfs.
4880 int64_t arc_swapfs_reserve = 64;
4881 #endif /* _KERNEL */
4884 * Return the amount of memory that can be consumed before reclaim will be
4885 * needed. Positive if there is sufficient free memory, negative indicates
4886 * the amount of memory that needs to be freed up.
4889 arc_available_memory(void)
4891 int64_t lowest = INT64_MAX;
4892 free_memory_reason_t r = FMR_UNKNOWN;
4899 pgcnt_t needfree = btop(arc_need_free);
4900 pgcnt_t lotsfree = btop(arc_sys_free);
4901 pgcnt_t desfree = 0;
4902 pgcnt_t freemem = btop(arc_free_memory());
4906 n = PAGESIZE * (-needfree);
4914 * check that we're out of range of the pageout scanner. It starts to
4915 * schedule paging if freemem is less than lotsfree and needfree.
4916 * lotsfree is the high-water mark for pageout, and needfree is the
4917 * number of needed free pages. We add extra pages here to make sure
4918 * the scanner doesn't start up while we're freeing memory.
4920 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4928 * check to make sure that swapfs has enough space so that anon
4929 * reservations can still succeed. anon_resvmem() checks that the
4930 * availrmem is greater than swapfs_minfree, and the number of reserved
4931 * swap pages. We also add a bit of extra here just to prevent
4932 * circumstances from getting really dire.
4934 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4935 desfree - arc_swapfs_reserve);
4938 r = FMR_SWAPFS_MINFREE;
4942 * Check that we have enough availrmem that memory locking (e.g., via
4943 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4944 * stores the number of pages that cannot be locked; when availrmem
4945 * drops below pages_pp_maximum, page locking mechanisms such as
4946 * page_pp_lock() will fail.)
4948 n = PAGESIZE * (availrmem - pages_pp_maximum -
4949 arc_pages_pp_reserve);
4952 r = FMR_PAGES_PP_MAXIMUM;
4958 * If we're on a 32-bit platform, it's possible that we'll exhaust the
4959 * kernel heap space before we ever run out of available physical
4960 * memory. Most checks of the size of the heap_area compare against
4961 * tune.t_minarmem, which is the minimum available real memory that we
4962 * can have in the system. However, this is generally fixed at 25 pages
4963 * which is so low that it's useless. In this comparison, we seek to
4964 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4965 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4968 n = vmem_size(heap_arena, VMEM_FREE) -
4969 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
4977 * If zio data pages are being allocated out of a separate heap segment,
4978 * then enforce that the size of available vmem for this arena remains
4979 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4981 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4982 * memory (in the zio_arena) free, which can avoid memory
4983 * fragmentation issues.
4985 if (zio_arena != NULL) {
4986 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4987 (vmem_size(zio_arena, VMEM_ALLOC) >>
4988 arc_zio_arena_free_shift);
4995 /* Every 100 calls, free a small amount */
4996 if (spa_get_random(100) == 0)
4998 #endif /* _KERNEL */
5000 last_free_memory = lowest;
5001 last_free_reason = r;
5007 * Determine if the system is under memory pressure and is asking
5008 * to reclaim memory. A return value of B_TRUE indicates that the system
5009 * is under memory pressure and that the arc should adjust accordingly.
5012 arc_reclaim_needed(void)
5014 return (arc_available_memory() < 0);
5018 arc_kmem_reap_soon(void)
5021 kmem_cache_t *prev_cache = NULL;
5022 kmem_cache_t *prev_data_cache = NULL;
5023 extern kmem_cache_t *zio_buf_cache[];
5024 extern kmem_cache_t *zio_data_buf_cache[];
5025 extern kmem_cache_t *range_seg_cache;
5028 if ((aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) &&
5029 zfs_arc_meta_prune) {
5031 * We are exceeding our meta-data cache limit.
5032 * Prune some entries to release holds on meta-data.
5034 arc_prune_async(zfs_arc_meta_prune);
5038 * Reclaim unused memory from all kmem caches.
5044 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
5046 /* reach upper limit of cache size on 32-bit */
5047 if (zio_buf_cache[i] == NULL)
5050 if (zio_buf_cache[i] != prev_cache) {
5051 prev_cache = zio_buf_cache[i];
5052 kmem_cache_reap_now(zio_buf_cache[i]);
5054 if (zio_data_buf_cache[i] != prev_data_cache) {
5055 prev_data_cache = zio_data_buf_cache[i];
5056 kmem_cache_reap_now(zio_data_buf_cache[i]);
5059 kmem_cache_reap_now(buf_cache);
5060 kmem_cache_reap_now(hdr_full_cache);
5061 kmem_cache_reap_now(hdr_l2only_cache);
5062 kmem_cache_reap_now(range_seg_cache);
5064 if (zio_arena != NULL) {
5066 * Ask the vmem arena to reclaim unused memory from its
5069 vmem_qcache_reap(zio_arena);
5075 arc_adjust_cb_check(void *arg, zthr_t *zthr)
5078 * This is necessary in order to keep the kstat information
5079 * up to date for tools that display kstat data such as the
5080 * mdb ::arc dcmd and the Linux crash utility. These tools
5081 * typically do not call kstat's update function, but simply
5082 * dump out stats from the most recent update. Without
5083 * this call, these commands may show stale stats for the
5084 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
5085 * with this change, the data might be up to 1 second
5086 * out of date(the arc_adjust_zthr has a maximum sleep
5087 * time of 1 second); but that should suffice. The
5088 * arc_state_t structures can be queried directly if more
5089 * accurate information is needed.
5091 if (arc_ksp != NULL)
5092 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
5095 * We have to rely on arc_get_data_impl() to tell us when to adjust,
5096 * rather than checking if we are overflowing here, so that we are
5097 * sure to not leave arc_get_data_impl() waiting on
5098 * arc_adjust_waiters_cv. If we have become "not overflowing" since
5099 * arc_get_data_impl() checked, we need to wake it up. We could
5100 * broadcast the CV here, but arc_get_data_impl() may have not yet
5101 * gone to sleep. We would need to use a mutex to ensure that this
5102 * function doesn't broadcast until arc_get_data_impl() has gone to
5103 * sleep (e.g. the arc_adjust_lock). However, the lock ordering of
5104 * such a lock would necessarily be incorrect with respect to the
5105 * zthr_lock, which is held before this function is called, and is
5106 * held by arc_get_data_impl() when it calls zthr_wakeup().
5108 return (arc_adjust_needed);
5112 * Keep arc_size under arc_c by running arc_adjust which evicts data
5117 arc_adjust_cb(void *arg, zthr_t *zthr)
5119 uint64_t evicted = 0;
5120 fstrans_cookie_t cookie = spl_fstrans_mark();
5122 /* Evict from cache */
5123 evicted = arc_adjust();
5126 * If evicted is zero, we couldn't evict anything
5127 * via arc_adjust(). This could be due to hash lock
5128 * collisions, but more likely due to the majority of
5129 * arc buffers being unevictable. Therefore, even if
5130 * arc_size is above arc_c, another pass is unlikely to
5131 * be helpful and could potentially cause us to enter an
5132 * infinite loop. Additionally, zthr_iscancelled() is
5133 * checked here so that if the arc is shutting down, the
5134 * broadcast will wake any remaining arc adjust waiters.
5136 mutex_enter(&arc_adjust_lock);
5137 arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) &&
5138 evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0;
5139 if (!arc_adjust_needed) {
5141 * We're either no longer overflowing, or we
5142 * can't evict anything more, so we should wake
5143 * arc_get_data_impl() sooner.
5145 cv_broadcast(&arc_adjust_waiters_cv);
5148 mutex_exit(&arc_adjust_lock);
5149 spl_fstrans_unmark(cookie);
5156 arc_reap_cb_check(void *arg, zthr_t *zthr)
5158 int64_t free_memory = arc_available_memory();
5161 * If a kmem reap is already active, don't schedule more. We must
5162 * check for this because kmem_cache_reap_soon() won't actually
5163 * block on the cache being reaped (this is to prevent callers from
5164 * becoming implicitly blocked by a system-wide kmem reap -- which,
5165 * on a system with many, many full magazines, can take minutes).
5167 if (!kmem_cache_reap_active() && free_memory < 0) {
5169 arc_no_grow = B_TRUE;
5172 * Wait at least zfs_grow_retry (default 5) seconds
5173 * before considering growing.
5175 arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
5177 } else if (free_memory < arc_c >> arc_no_grow_shift) {
5178 arc_no_grow = B_TRUE;
5179 } else if (gethrtime() >= arc_growtime) {
5180 arc_no_grow = B_FALSE;
5187 * Keep enough free memory in the system by reaping the ARC's kmem
5188 * caches. To cause more slabs to be reapable, we may reduce the
5189 * target size of the cache (arc_c), causing the arc_adjust_cb()
5190 * to free more buffers.
5194 arc_reap_cb(void *arg, zthr_t *zthr)
5196 int64_t free_memory;
5197 fstrans_cookie_t cookie = spl_fstrans_mark();
5200 * Kick off asynchronous kmem_reap()'s of all our caches.
5202 arc_kmem_reap_soon();
5205 * Wait at least arc_kmem_cache_reap_retry_ms between
5206 * arc_kmem_reap_soon() calls. Without this check it is possible to
5207 * end up in a situation where we spend lots of time reaping
5208 * caches, while we're near arc_c_min. Waiting here also gives the
5209 * subsequent free memory check a chance of finding that the
5210 * asynchronous reap has already freed enough memory, and we don't
5211 * need to call arc_reduce_target_size().
5213 delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000);
5216 * Reduce the target size as needed to maintain the amount of free
5217 * memory in the system at a fraction of the arc_size (1/128th by
5218 * default). If oversubscribed (free_memory < 0) then reduce the
5219 * target arc_size by the deficit amount plus the fractional
5220 * amount. If free memory is positive but less then the fractional
5221 * amount, reduce by what is needed to hit the fractional amount.
5223 free_memory = arc_available_memory();
5226 (arc_c >> arc_shrink_shift) - free_memory;
5229 to_free = MAX(to_free, arc_need_free);
5231 arc_reduce_target_size(to_free);
5233 spl_fstrans_unmark(cookie);
5240 * Determine the amount of memory eligible for eviction contained in the
5241 * ARC. All clean data reported by the ghost lists can always be safely
5242 * evicted. Due to arc_c_min, the same does not hold for all clean data
5243 * contained by the regular mru and mfu lists.
5245 * In the case of the regular mru and mfu lists, we need to report as
5246 * much clean data as possible, such that evicting that same reported
5247 * data will not bring arc_size below arc_c_min. Thus, in certain
5248 * circumstances, the total amount of clean data in the mru and mfu
5249 * lists might not actually be evictable.
5251 * The following two distinct cases are accounted for:
5253 * 1. The sum of the amount of dirty data contained by both the mru and
5254 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
5255 * is greater than or equal to arc_c_min.
5256 * (i.e. amount of dirty data >= arc_c_min)
5258 * This is the easy case; all clean data contained by the mru and mfu
5259 * lists is evictable. Evicting all clean data can only drop arc_size
5260 * to the amount of dirty data, which is greater than arc_c_min.
5262 * 2. The sum of the amount of dirty data contained by both the mru and
5263 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
5264 * is less than arc_c_min.
5265 * (i.e. arc_c_min > amount of dirty data)
5267 * 2.1. arc_size is greater than or equal arc_c_min.
5268 * (i.e. arc_size >= arc_c_min > amount of dirty data)
5270 * In this case, not all clean data from the regular mru and mfu
5271 * lists is actually evictable; we must leave enough clean data
5272 * to keep arc_size above arc_c_min. Thus, the maximum amount of
5273 * evictable data from the two lists combined, is exactly the
5274 * difference between arc_size and arc_c_min.
5276 * 2.2. arc_size is less than arc_c_min
5277 * (i.e. arc_c_min > arc_size > amount of dirty data)
5279 * In this case, none of the data contained in the mru and mfu
5280 * lists is evictable, even if it's clean. Since arc_size is
5281 * already below arc_c_min, evicting any more would only
5282 * increase this negative difference.
5285 arc_evictable_memory(void)
5287 int64_t asize = aggsum_value(&arc_size);
5288 uint64_t arc_clean =
5289 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_DATA]) +
5290 zfs_refcount_count(&arc_mru->arcs_esize[ARC_BUFC_METADATA]) +
5291 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_DATA]) +
5292 zfs_refcount_count(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
5293 uint64_t arc_dirty = MAX((int64_t)asize - (int64_t)arc_clean, 0);
5296 * Scale reported evictable memory in proportion to page cache, cap
5297 * at specified min/max.
5299 uint64_t min = (ptob(nr_file_pages()) / 100) * zfs_arc_pc_percent;
5300 min = MAX(arc_c_min, MIN(arc_c_max, min));
5302 if (arc_dirty >= min)
5305 return (MAX((int64_t)asize - (int64_t)min, 0));
5309 * If sc->nr_to_scan is zero, the caller is requesting a query of the
5310 * number of objects which can potentially be freed. If it is nonzero,
5311 * the request is to free that many objects.
5313 * Linux kernels >= 3.12 have the count_objects and scan_objects callbacks
5314 * in struct shrinker and also require the shrinker to return the number
5317 * Older kernels require the shrinker to return the number of freeable
5318 * objects following the freeing of nr_to_free.
5320 static spl_shrinker_t
5321 __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
5325 /* The arc is considered warm once reclaim has occurred */
5326 if (unlikely(arc_warm == B_FALSE))
5329 /* Return the potential number of reclaimable pages */
5330 pages = btop((int64_t)arc_evictable_memory());
5331 if (sc->nr_to_scan == 0)
5334 /* Not allowed to perform filesystem reclaim */
5335 if (!(sc->gfp_mask & __GFP_FS))
5336 return (SHRINK_STOP);
5338 /* Reclaim in progress */
5339 if (mutex_tryenter(&arc_adjust_lock) == 0) {
5340 ARCSTAT_INCR(arcstat_need_free, ptob(sc->nr_to_scan));
5344 mutex_exit(&arc_adjust_lock);
5347 * Evict the requested number of pages by shrinking arc_c the
5351 arc_reduce_target_size(ptob(sc->nr_to_scan));
5352 if (current_is_kswapd())
5353 arc_kmem_reap_soon();
5354 #ifdef HAVE_SPLIT_SHRINKER_CALLBACK
5355 pages = MAX((int64_t)pages -
5356 (int64_t)btop(arc_evictable_memory()), 0);
5358 pages = btop(arc_evictable_memory());
5361 * We've shrunk what we can, wake up threads.
5363 cv_broadcast(&arc_adjust_waiters_cv);
5365 pages = SHRINK_STOP;
5368 * When direct reclaim is observed it usually indicates a rapid
5369 * increase in memory pressure. This occurs because the kswapd
5370 * threads were unable to asynchronously keep enough free memory
5371 * available. In this case set arc_no_grow to briefly pause arc
5372 * growth to avoid compounding the memory pressure.
5374 if (current_is_kswapd()) {
5375 ARCSTAT_BUMP(arcstat_memory_indirect_count);
5377 arc_no_grow = B_TRUE;
5378 arc_kmem_reap_soon();
5379 ARCSTAT_BUMP(arcstat_memory_direct_count);
5384 SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
5386 SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
5387 #endif /* _KERNEL */
5390 * Adapt arc info given the number of bytes we are trying to add and
5391 * the state that we are coming from. This function is only called
5392 * when we are adding new content to the cache.
5395 arc_adapt(int bytes, arc_state_t *state)
5398 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
5399 int64_t mrug_size = zfs_refcount_count(&arc_mru_ghost->arcs_size);
5400 int64_t mfug_size = zfs_refcount_count(&arc_mfu_ghost->arcs_size);
5402 if (state == arc_l2c_only)
5407 * Adapt the target size of the MRU list:
5408 * - if we just hit in the MRU ghost list, then increase
5409 * the target size of the MRU list.
5410 * - if we just hit in the MFU ghost list, then increase
5411 * the target size of the MFU list by decreasing the
5412 * target size of the MRU list.
5414 if (state == arc_mru_ghost) {
5415 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
5416 if (!zfs_arc_p_dampener_disable)
5417 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
5419 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
5420 } else if (state == arc_mfu_ghost) {
5423 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
5424 if (!zfs_arc_p_dampener_disable)
5425 mult = MIN(mult, 10);
5427 delta = MIN(bytes * mult, arc_p);
5428 arc_p = MAX(arc_p_min, arc_p - delta);
5430 ASSERT((int64_t)arc_p >= 0);
5433 * Wake reap thread if we do not have any available memory
5435 if (arc_reclaim_needed()) {
5436 zthr_wakeup(arc_reap_zthr);
5443 if (arc_c >= arc_c_max)
5447 * If we're within (2 * maxblocksize) bytes of the target
5448 * cache size, increment the target cache size
5450 ASSERT3U(arc_c, >=, 2ULL << SPA_MAXBLOCKSHIFT);
5451 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) >=
5453 atomic_add_64(&arc_c, (int64_t)bytes);
5454 if (arc_c > arc_c_max)
5456 else if (state == arc_anon)
5457 atomic_add_64(&arc_p, (int64_t)bytes);
5461 ASSERT((int64_t)arc_p >= 0);
5465 * Check if arc_size has grown past our upper threshold, determined by
5466 * zfs_arc_overflow_shift.
5469 arc_is_overflowing(void)
5471 /* Always allow at least one block of overflow */
5472 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
5473 arc_c >> zfs_arc_overflow_shift);
5476 * We just compare the lower bound here for performance reasons. Our
5477 * primary goals are to make sure that the arc never grows without
5478 * bound, and that it can reach its maximum size. This check
5479 * accomplishes both goals. The maximum amount we could run over by is
5480 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block
5481 * in the ARC. In practice, that's in the tens of MB, which is low
5482 * enough to be safe.
5484 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow);
5488 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5490 arc_buf_contents_t type = arc_buf_type(hdr);
5492 arc_get_data_impl(hdr, size, tag);
5493 if (type == ARC_BUFC_METADATA) {
5494 return (abd_alloc(size, B_TRUE));
5496 ASSERT(type == ARC_BUFC_DATA);
5497 return (abd_alloc(size, B_FALSE));
5502 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5504 arc_buf_contents_t type = arc_buf_type(hdr);
5506 arc_get_data_impl(hdr, size, tag);
5507 if (type == ARC_BUFC_METADATA) {
5508 return (zio_buf_alloc(size));
5510 ASSERT(type == ARC_BUFC_DATA);
5511 return (zio_data_buf_alloc(size));
5516 * Allocate a block and return it to the caller. If we are hitting the
5517 * hard limit for the cache size, we must sleep, waiting for the eviction
5518 * thread to catch up. If we're past the target size but below the hard
5519 * limit, we'll only signal the reclaim thread and continue on.
5522 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5524 arc_state_t *state = hdr->b_l1hdr.b_state;
5525 arc_buf_contents_t type = arc_buf_type(hdr);
5527 arc_adapt(size, state);
5530 * If arc_size is currently overflowing, and has grown past our
5531 * upper limit, we must be adding data faster than the evict
5532 * thread can evict. Thus, to ensure we don't compound the
5533 * problem by adding more data and forcing arc_size to grow even
5534 * further past it's target size, we halt and wait for the
5535 * eviction thread to catch up.
5537 * It's also possible that the reclaim thread is unable to evict
5538 * enough buffers to get arc_size below the overflow limit (e.g.
5539 * due to buffers being un-evictable, or hash lock collisions).
5540 * In this case, we want to proceed regardless if we're
5541 * overflowing; thus we don't use a while loop here.
5543 if (arc_is_overflowing()) {
5544 mutex_enter(&arc_adjust_lock);
5547 * Now that we've acquired the lock, we may no longer be
5548 * over the overflow limit, lets check.
5550 * We're ignoring the case of spurious wake ups. If that
5551 * were to happen, it'd let this thread consume an ARC
5552 * buffer before it should have (i.e. before we're under
5553 * the overflow limit and were signalled by the reclaim
5554 * thread). As long as that is a rare occurrence, it
5555 * shouldn't cause any harm.
5557 if (arc_is_overflowing()) {
5558 arc_adjust_needed = B_TRUE;
5559 zthr_wakeup(arc_adjust_zthr);
5560 (void) cv_wait(&arc_adjust_waiters_cv,
5563 mutex_exit(&arc_adjust_lock);
5566 VERIFY3U(hdr->b_type, ==, type);
5567 if (type == ARC_BUFC_METADATA) {
5568 arc_space_consume(size, ARC_SPACE_META);
5570 arc_space_consume(size, ARC_SPACE_DATA);
5574 * Update the state size. Note that ghost states have a
5575 * "ghost size" and so don't need to be updated.
5577 if (!GHOST_STATE(state)) {
5579 (void) zfs_refcount_add_many(&state->arcs_size, size, tag);
5582 * If this is reached via arc_read, the link is
5583 * protected by the hash lock. If reached via
5584 * arc_buf_alloc, the header should not be accessed by
5585 * any other thread. And, if reached via arc_read_done,
5586 * the hash lock will protect it if it's found in the
5587 * hash table; otherwise no other thread should be
5588 * trying to [add|remove]_reference it.
5590 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5591 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5592 (void) zfs_refcount_add_many(&state->arcs_esize[type],
5597 * If we are growing the cache, and we are adding anonymous
5598 * data, and we have outgrown arc_p, update arc_p
5600 if (aggsum_compare(&arc_size, arc_c) < 0 &&
5601 hdr->b_l1hdr.b_state == arc_anon &&
5602 (zfs_refcount_count(&arc_anon->arcs_size) +
5603 zfs_refcount_count(&arc_mru->arcs_size) > arc_p))
5604 arc_p = MIN(arc_c, arc_p + size);
5609 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
5611 arc_free_data_impl(hdr, size, tag);
5616 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
5618 arc_buf_contents_t type = arc_buf_type(hdr);
5620 arc_free_data_impl(hdr, size, tag);
5621 if (type == ARC_BUFC_METADATA) {
5622 zio_buf_free(buf, size);
5624 ASSERT(type == ARC_BUFC_DATA);
5625 zio_data_buf_free(buf, size);
5630 * Free the arc data buffer.
5633 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5635 arc_state_t *state = hdr->b_l1hdr.b_state;
5636 arc_buf_contents_t type = arc_buf_type(hdr);
5638 /* protected by hash lock, if in the hash table */
5639 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5640 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5641 ASSERT(state != arc_anon && state != arc_l2c_only);
5643 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
5646 (void) zfs_refcount_remove_many(&state->arcs_size, size, tag);
5648 VERIFY3U(hdr->b_type, ==, type);
5649 if (type == ARC_BUFC_METADATA) {
5650 arc_space_return(size, ARC_SPACE_META);
5652 ASSERT(type == ARC_BUFC_DATA);
5653 arc_space_return(size, ARC_SPACE_DATA);
5658 * This routine is called whenever a buffer is accessed.
5659 * NOTE: the hash lock is dropped in this function.
5662 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
5666 ASSERT(MUTEX_HELD(hash_lock));
5667 ASSERT(HDR_HAS_L1HDR(hdr));
5669 if (hdr->b_l1hdr.b_state == arc_anon) {
5671 * This buffer is not in the cache, and does not
5672 * appear in our "ghost" list. Add the new buffer
5676 ASSERT0(hdr->b_l1hdr.b_arc_access);
5677 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5678 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5679 arc_change_state(arc_mru, hdr, hash_lock);
5681 } else if (hdr->b_l1hdr.b_state == arc_mru) {
5682 now = ddi_get_lbolt();
5685 * If this buffer is here because of a prefetch, then either:
5686 * - clear the flag if this is a "referencing" read
5687 * (any subsequent access will bump this into the MFU state).
5689 * - move the buffer to the head of the list if this is
5690 * another prefetch (to make it less likely to be evicted).
5692 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5693 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5694 /* link protected by hash lock */
5695 ASSERT(multilist_link_active(
5696 &hdr->b_l1hdr.b_arc_node));
5698 arc_hdr_clear_flags(hdr,
5700 ARC_FLAG_PRESCIENT_PREFETCH);
5701 atomic_inc_32(&hdr->b_l1hdr.b_mru_hits);
5702 ARCSTAT_BUMP(arcstat_mru_hits);
5704 hdr->b_l1hdr.b_arc_access = now;
5709 * This buffer has been "accessed" only once so far,
5710 * but it is still in the cache. Move it to the MFU
5713 if (ddi_time_after(now, hdr->b_l1hdr.b_arc_access +
5716 * More than 125ms have passed since we
5717 * instantiated this buffer. Move it to the
5718 * most frequently used state.
5720 hdr->b_l1hdr.b_arc_access = now;
5721 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5722 arc_change_state(arc_mfu, hdr, hash_lock);
5724 atomic_inc_32(&hdr->b_l1hdr.b_mru_hits);
5725 ARCSTAT_BUMP(arcstat_mru_hits);
5726 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
5727 arc_state_t *new_state;
5729 * This buffer has been "accessed" recently, but
5730 * was evicted from the cache. Move it to the
5734 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5735 new_state = arc_mru;
5736 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) {
5737 arc_hdr_clear_flags(hdr,
5739 ARC_FLAG_PRESCIENT_PREFETCH);
5741 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5743 new_state = arc_mfu;
5744 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5747 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5748 arc_change_state(new_state, hdr, hash_lock);
5750 atomic_inc_32(&hdr->b_l1hdr.b_mru_ghost_hits);
5751 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
5752 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
5754 * This buffer has been accessed more than once and is
5755 * still in the cache. Keep it in the MFU state.
5757 * NOTE: an add_reference() that occurred when we did
5758 * the arc_read() will have kicked this off the list.
5759 * If it was a prefetch, we will explicitly move it to
5760 * the head of the list now.
5763 atomic_inc_32(&hdr->b_l1hdr.b_mfu_hits);
5764 ARCSTAT_BUMP(arcstat_mfu_hits);
5765 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5766 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
5767 arc_state_t *new_state = arc_mfu;
5769 * This buffer has been accessed more than once but has
5770 * been evicted from the cache. Move it back to the
5774 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5776 * This is a prefetch access...
5777 * move this block back to the MRU state.
5779 new_state = arc_mru;
5782 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5783 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5784 arc_change_state(new_state, hdr, hash_lock);
5786 atomic_inc_32(&hdr->b_l1hdr.b_mfu_ghost_hits);
5787 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5788 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5790 * This buffer is on the 2nd Level ARC.
5793 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5794 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5795 arc_change_state(arc_mfu, hdr, hash_lock);
5797 cmn_err(CE_PANIC, "invalid arc state 0x%p",
5798 hdr->b_l1hdr.b_state);
5803 * This routine is called by dbuf_hold() to update the arc_access() state
5804 * which otherwise would be skipped for entries in the dbuf cache.
5807 arc_buf_access(arc_buf_t *buf)
5809 mutex_enter(&buf->b_evict_lock);
5810 arc_buf_hdr_t *hdr = buf->b_hdr;
5813 * Avoid taking the hash_lock when possible as an optimization.
5814 * The header must be checked again under the hash_lock in order
5815 * to handle the case where it is concurrently being released.
5817 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5818 mutex_exit(&buf->b_evict_lock);
5822 kmutex_t *hash_lock = HDR_LOCK(hdr);
5823 mutex_enter(hash_lock);
5825 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5826 mutex_exit(hash_lock);
5827 mutex_exit(&buf->b_evict_lock);
5828 ARCSTAT_BUMP(arcstat_access_skip);
5832 mutex_exit(&buf->b_evict_lock);
5834 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5835 hdr->b_l1hdr.b_state == arc_mfu);
5837 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5838 arc_access(hdr, hash_lock);
5839 mutex_exit(hash_lock);
5841 ARCSTAT_BUMP(arcstat_hits);
5842 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr) && !HDR_PRESCIENT_PREFETCH(hdr),
5843 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits);
5846 /* a generic arc_read_done_func_t which you can use */
5849 arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5850 arc_buf_t *buf, void *arg)
5855 bcopy(buf->b_data, arg, arc_buf_size(buf));
5856 arc_buf_destroy(buf, arg);
5859 /* a generic arc_read_done_func_t */
5862 arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5863 arc_buf_t *buf, void *arg)
5865 arc_buf_t **bufp = arg;
5868 ASSERT(zio == NULL || zio->io_error != 0);
5871 ASSERT(zio == NULL || zio->io_error == 0);
5873 ASSERT(buf->b_data != NULL);
5878 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
5880 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5881 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5882 ASSERT3U(arc_hdr_get_compress(hdr), ==, ZIO_COMPRESS_OFF);
5884 if (HDR_COMPRESSION_ENABLED(hdr)) {
5885 ASSERT3U(arc_hdr_get_compress(hdr), ==,
5886 BP_GET_COMPRESS(bp));
5888 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5889 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5890 ASSERT3U(!!HDR_PROTECTED(hdr), ==, BP_IS_PROTECTED(bp));
5895 arc_read_done(zio_t *zio)
5897 blkptr_t *bp = zio->io_bp;
5898 arc_buf_hdr_t *hdr = zio->io_private;
5899 kmutex_t *hash_lock = NULL;
5900 arc_callback_t *callback_list;
5901 arc_callback_t *acb;
5902 boolean_t freeable = B_FALSE;
5905 * The hdr was inserted into hash-table and removed from lists
5906 * prior to starting I/O. We should find this header, since
5907 * it's in the hash table, and it should be legit since it's
5908 * not possible to evict it during the I/O. The only possible
5909 * reason for it not to be found is if we were freed during the
5912 if (HDR_IN_HASH_TABLE(hdr)) {
5913 arc_buf_hdr_t *found;
5915 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5916 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5917 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5918 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5919 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5921 found = buf_hash_find(hdr->b_spa, zio->io_bp, &hash_lock);
5923 ASSERT((found == hdr &&
5924 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5925 (found == hdr && HDR_L2_READING(hdr)));
5926 ASSERT3P(hash_lock, !=, NULL);
5929 if (BP_IS_PROTECTED(bp)) {
5930 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
5931 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
5932 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
5933 hdr->b_crypt_hdr.b_iv);
5935 if (BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG) {
5938 tmpbuf = abd_borrow_buf_copy(zio->io_abd,
5939 sizeof (zil_chain_t));
5940 zio_crypt_decode_mac_zil(tmpbuf,
5941 hdr->b_crypt_hdr.b_mac);
5942 abd_return_buf(zio->io_abd, tmpbuf,
5943 sizeof (zil_chain_t));
5945 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
5949 if (zio->io_error == 0) {
5950 /* byteswap if necessary */
5951 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5952 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5953 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5955 hdr->b_l1hdr.b_byteswap =
5956 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5959 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5963 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5964 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
5965 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
5967 callback_list = hdr->b_l1hdr.b_acb;
5968 ASSERT3P(callback_list, !=, NULL);
5970 if (hash_lock && zio->io_error == 0 &&
5971 hdr->b_l1hdr.b_state == arc_anon) {
5973 * Only call arc_access on anonymous buffers. This is because
5974 * if we've issued an I/O for an evicted buffer, we've already
5975 * called arc_access (to prevent any simultaneous readers from
5976 * getting confused).
5978 arc_access(hdr, hash_lock);
5982 * If a read request has a callback (i.e. acb_done is not NULL), then we
5983 * make a buf containing the data according to the parameters which were
5984 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5985 * aren't needlessly decompressing the data multiple times.
5987 int callback_cnt = 0;
5988 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5994 if (zio->io_error != 0)
5997 int error = arc_buf_alloc_impl(hdr, zio->io_spa,
5998 &acb->acb_zb, acb->acb_private, acb->acb_encrypted,
5999 acb->acb_compressed, acb->acb_noauth, B_TRUE,
6003 * Assert non-speculative zios didn't fail because an
6004 * encryption key wasn't loaded
6006 ASSERT((zio->io_flags & ZIO_FLAG_SPECULATIVE) ||
6010 * If we failed to decrypt, report an error now (as the zio
6011 * layer would have done if it had done the transforms).
6013 if (error == ECKSUM) {
6014 ASSERT(BP_IS_PROTECTED(bp));
6015 error = SET_ERROR(EIO);
6016 if ((zio->io_flags & ZIO_FLAG_SPECULATIVE) == 0) {
6017 spa_log_error(zio->io_spa, &acb->acb_zb);
6018 zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION,
6019 zio->io_spa, NULL, &acb->acb_zb, zio, 0, 0);
6025 * Decompression or decryption failed. Set
6026 * io_error so that when we call acb_done
6027 * (below), we will indicate that the read
6028 * failed. Note that in the unusual case
6029 * where one callback is compressed and another
6030 * uncompressed, we will mark all of them
6031 * as failed, even though the uncompressed
6032 * one can't actually fail. In this case,
6033 * the hdr will not be anonymous, because
6034 * if there are multiple callbacks, it's
6035 * because multiple threads found the same
6036 * arc buf in the hash table.
6038 zio->io_error = error;
6043 * If there are multiple callbacks, we must have the hash lock,
6044 * because the only way for multiple threads to find this hdr is
6045 * in the hash table. This ensures that if there are multiple
6046 * callbacks, the hdr is not anonymous. If it were anonymous,
6047 * we couldn't use arc_buf_destroy() in the error case below.
6049 ASSERT(callback_cnt < 2 || hash_lock != NULL);
6051 hdr->b_l1hdr.b_acb = NULL;
6052 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6053 if (callback_cnt == 0)
6054 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
6056 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
6057 callback_list != NULL);
6059 if (zio->io_error == 0) {
6060 arc_hdr_verify(hdr, zio->io_bp);
6062 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
6063 if (hdr->b_l1hdr.b_state != arc_anon)
6064 arc_change_state(arc_anon, hdr, hash_lock);
6065 if (HDR_IN_HASH_TABLE(hdr))
6066 buf_hash_remove(hdr);
6067 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
6071 * Broadcast before we drop the hash_lock to avoid the possibility
6072 * that the hdr (and hence the cv) might be freed before we get to
6073 * the cv_broadcast().
6075 cv_broadcast(&hdr->b_l1hdr.b_cv);
6077 if (hash_lock != NULL) {
6078 mutex_exit(hash_lock);
6081 * This block was freed while we waited for the read to
6082 * complete. It has been removed from the hash table and
6083 * moved to the anonymous state (so that it won't show up
6086 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
6087 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
6090 /* execute each callback and free its structure */
6091 while ((acb = callback_list) != NULL) {
6092 if (acb->acb_done != NULL) {
6093 if (zio->io_error != 0 && acb->acb_buf != NULL) {
6095 * If arc_buf_alloc_impl() fails during
6096 * decompression, the buf will still be
6097 * allocated, and needs to be freed here.
6099 arc_buf_destroy(acb->acb_buf,
6101 acb->acb_buf = NULL;
6103 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp,
6104 acb->acb_buf, acb->acb_private);
6107 if (acb->acb_zio_dummy != NULL) {
6108 acb->acb_zio_dummy->io_error = zio->io_error;
6109 zio_nowait(acb->acb_zio_dummy);
6112 callback_list = acb->acb_next;
6113 kmem_free(acb, sizeof (arc_callback_t));
6117 arc_hdr_destroy(hdr);
6121 * "Read" the block at the specified DVA (in bp) via the
6122 * cache. If the block is found in the cache, invoke the provided
6123 * callback immediately and return. Note that the `zio' parameter
6124 * in the callback will be NULL in this case, since no IO was
6125 * required. If the block is not in the cache pass the read request
6126 * on to the spa with a substitute callback function, so that the
6127 * requested block will be added to the cache.
6129 * If a read request arrives for a block that has a read in-progress,
6130 * either wait for the in-progress read to complete (and return the
6131 * results); or, if this is a read with a "done" func, add a record
6132 * to the read to invoke the "done" func when the read completes,
6133 * and return; or just return.
6135 * arc_read_done() will invoke all the requested "done" functions
6136 * for readers of this block.
6139 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
6140 arc_read_done_func_t *done, void *private, zio_priority_t priority,
6141 int zio_flags, arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
6143 arc_buf_hdr_t *hdr = NULL;
6144 kmutex_t *hash_lock = NULL;
6146 uint64_t guid = spa_load_guid(spa);
6147 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW_COMPRESS) != 0;
6148 boolean_t encrypted_read = BP_IS_ENCRYPTED(bp) &&
6149 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
6150 boolean_t noauth_read = BP_IS_AUTHENTICATED(bp) &&
6151 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
6154 ASSERT(!BP_IS_EMBEDDED(bp) ||
6155 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
6158 if (!BP_IS_EMBEDDED(bp)) {
6160 * Embedded BP's have no DVA and require no I/O to "read".
6161 * Create an anonymous arc buf to back it.
6163 hdr = buf_hash_find(guid, bp, &hash_lock);
6167 * Determine if we have an L1 cache hit or a cache miss. For simplicity
6168 * we maintain encrypted data seperately from compressed / uncompressed
6169 * data. If the user is requesting raw encrypted data and we don't have
6170 * that in the header we will read from disk to guarantee that we can
6171 * get it even if the encryption keys aren't loaded.
6173 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && (HDR_HAS_RABD(hdr) ||
6174 (hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) {
6175 arc_buf_t *buf = NULL;
6176 *arc_flags |= ARC_FLAG_CACHED;
6178 if (HDR_IO_IN_PROGRESS(hdr)) {
6179 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;
6181 ASSERT3P(head_zio, !=, NULL);
6182 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
6183 priority == ZIO_PRIORITY_SYNC_READ) {
6185 * This is a sync read that needs to wait for
6186 * an in-flight async read. Request that the
6187 * zio have its priority upgraded.
6189 zio_change_priority(head_zio, priority);
6190 DTRACE_PROBE1(arc__async__upgrade__sync,
6191 arc_buf_hdr_t *, hdr);
6192 ARCSTAT_BUMP(arcstat_async_upgrade_sync);
6194 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
6195 arc_hdr_clear_flags(hdr,
6196 ARC_FLAG_PREDICTIVE_PREFETCH);
6199 if (*arc_flags & ARC_FLAG_WAIT) {
6200 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
6201 mutex_exit(hash_lock);
6204 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
6207 arc_callback_t *acb = NULL;
6209 acb = kmem_zalloc(sizeof (arc_callback_t),
6211 acb->acb_done = done;
6212 acb->acb_private = private;
6213 acb->acb_compressed = compressed_read;
6214 acb->acb_encrypted = encrypted_read;
6215 acb->acb_noauth = noauth_read;
6218 acb->acb_zio_dummy = zio_null(pio,
6219 spa, NULL, NULL, NULL, zio_flags);
6221 ASSERT3P(acb->acb_done, !=, NULL);
6222 acb->acb_zio_head = head_zio;
6223 acb->acb_next = hdr->b_l1hdr.b_acb;
6224 hdr->b_l1hdr.b_acb = acb;
6225 mutex_exit(hash_lock);
6228 mutex_exit(hash_lock);
6232 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
6233 hdr->b_l1hdr.b_state == arc_mfu);
6236 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
6238 * This is a demand read which does not have to
6239 * wait for i/o because we did a predictive
6240 * prefetch i/o for it, which has completed.
6243 arc__demand__hit__predictive__prefetch,
6244 arc_buf_hdr_t *, hdr);
6246 arcstat_demand_hit_predictive_prefetch);
6247 arc_hdr_clear_flags(hdr,
6248 ARC_FLAG_PREDICTIVE_PREFETCH);
6251 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) {
6253 arcstat_demand_hit_prescient_prefetch);
6254 arc_hdr_clear_flags(hdr,
6255 ARC_FLAG_PRESCIENT_PREFETCH);
6258 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
6260 /* Get a buf with the desired data in it. */
6261 rc = arc_buf_alloc_impl(hdr, spa, zb, private,
6262 encrypted_read, compressed_read, noauth_read,
6266 * Convert authentication and decryption errors
6267 * to EIO (and generate an ereport if needed)
6268 * before leaving the ARC.
6270 rc = SET_ERROR(EIO);
6271 if ((zio_flags & ZIO_FLAG_SPECULATIVE) == 0) {
6272 spa_log_error(spa, zb);
6274 FM_EREPORT_ZFS_AUTHENTICATION,
6275 spa, NULL, zb, NULL, 0, 0);
6279 (void) remove_reference(hdr, hash_lock,
6281 arc_buf_destroy_impl(buf);
6285 /* assert any errors weren't due to unloaded keys */
6286 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) ||
6288 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
6289 zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
6290 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
6292 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
6293 arc_access(hdr, hash_lock);
6294 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
6295 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
6296 if (*arc_flags & ARC_FLAG_L2CACHE)
6297 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6298 mutex_exit(hash_lock);
6299 ARCSTAT_BUMP(arcstat_hits);
6300 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
6301 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
6302 data, metadata, hits);
6305 done(NULL, zb, bp, buf, private);
6307 uint64_t lsize = BP_GET_LSIZE(bp);
6308 uint64_t psize = BP_GET_PSIZE(bp);
6309 arc_callback_t *acb;
6312 boolean_t devw = B_FALSE;
6317 * Gracefully handle a damaged logical block size as a
6320 if (lsize > spa_maxblocksize(spa)) {
6321 rc = SET_ERROR(ECKSUM);
6326 /* this block is not in the cache */
6327 arc_buf_hdr_t *exists = NULL;
6328 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
6329 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
6330 BP_IS_PROTECTED(bp), BP_GET_COMPRESS(bp), type,
6333 if (!BP_IS_EMBEDDED(bp)) {
6334 hdr->b_dva = *BP_IDENTITY(bp);
6335 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
6336 exists = buf_hash_insert(hdr, &hash_lock);
6338 if (exists != NULL) {
6339 /* somebody beat us to the hash insert */
6340 mutex_exit(hash_lock);
6341 buf_discard_identity(hdr);
6342 arc_hdr_destroy(hdr);
6343 goto top; /* restart the IO request */
6347 * This block is in the ghost cache or encrypted data
6348 * was requested and we didn't have it. If it was
6349 * L2-only (and thus didn't have an L1 hdr),
6350 * we realloc the header to add an L1 hdr.
6352 if (!HDR_HAS_L1HDR(hdr)) {
6353 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
6357 if (GHOST_STATE(hdr->b_l1hdr.b_state)) {
6358 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6359 ASSERT(!HDR_HAS_RABD(hdr));
6360 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6361 ASSERT0(zfs_refcount_count(
6362 &hdr->b_l1hdr.b_refcnt));
6363 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
6364 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
6365 } else if (HDR_IO_IN_PROGRESS(hdr)) {
6367 * If this header already had an IO in progress
6368 * and we are performing another IO to fetch
6369 * encrypted data we must wait until the first
6370 * IO completes so as not to confuse
6371 * arc_read_done(). This should be very rare
6372 * and so the performance impact shouldn't
6375 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
6376 mutex_exit(hash_lock);
6381 * This is a delicate dance that we play here.
6382 * This hdr might be in the ghost list so we access
6383 * it to move it out of the ghost list before we
6384 * initiate the read. If it's a prefetch then
6385 * it won't have a callback so we'll remove the
6386 * reference that arc_buf_alloc_impl() created. We
6387 * do this after we've called arc_access() to
6388 * avoid hitting an assert in remove_reference().
6390 arc_access(hdr, hash_lock);
6391 arc_hdr_alloc_abd(hdr, encrypted_read);
6394 if (encrypted_read) {
6395 ASSERT(HDR_HAS_RABD(hdr));
6396 size = HDR_GET_PSIZE(hdr);
6397 hdr_abd = hdr->b_crypt_hdr.b_rabd;
6398 zio_flags |= ZIO_FLAG_RAW;
6400 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
6401 size = arc_hdr_size(hdr);
6402 hdr_abd = hdr->b_l1hdr.b_pabd;
6404 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
6405 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
6409 * For authenticated bp's, we do not ask the ZIO layer
6410 * to authenticate them since this will cause the entire
6411 * IO to fail if the key isn't loaded. Instead, we
6412 * defer authentication until arc_buf_fill(), which will
6413 * verify the data when the key is available.
6415 if (BP_IS_AUTHENTICATED(bp))
6416 zio_flags |= ZIO_FLAG_RAW_ENCRYPT;
6419 if (*arc_flags & ARC_FLAG_PREFETCH &&
6420 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))
6421 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
6422 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
6423 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
6424 if (*arc_flags & ARC_FLAG_L2CACHE)
6425 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6426 if (BP_IS_AUTHENTICATED(bp))
6427 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
6428 if (BP_GET_LEVEL(bp) > 0)
6429 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
6430 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
6431 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
6432 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
6434 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
6435 acb->acb_done = done;
6436 acb->acb_private = private;
6437 acb->acb_compressed = compressed_read;
6438 acb->acb_encrypted = encrypted_read;
6439 acb->acb_noauth = noauth_read;
6442 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6443 hdr->b_l1hdr.b_acb = acb;
6444 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6446 if (HDR_HAS_L2HDR(hdr) &&
6447 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
6448 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
6449 addr = hdr->b_l2hdr.b_daddr;
6451 * Lock out L2ARC device removal.
6453 if (vdev_is_dead(vd) ||
6454 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
6459 * We count both async reads and scrub IOs as asynchronous so
6460 * that both can be upgraded in the event of a cache hit while
6461 * the read IO is still in-flight.
6463 if (priority == ZIO_PRIORITY_ASYNC_READ ||
6464 priority == ZIO_PRIORITY_SCRUB)
6465 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
6467 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
6470 * At this point, we have a level 1 cache miss. Try again in
6471 * L2ARC if possible.
6473 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
6475 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
6476 uint64_t, lsize, zbookmark_phys_t *, zb);
6477 ARCSTAT_BUMP(arcstat_misses);
6478 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
6479 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
6480 data, metadata, misses);
6482 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
6484 * Read from the L2ARC if the following are true:
6485 * 1. The L2ARC vdev was previously cached.
6486 * 2. This buffer still has L2ARC metadata.
6487 * 3. This buffer isn't currently writing to the L2ARC.
6488 * 4. The L2ARC entry wasn't evicted, which may
6489 * also have invalidated the vdev.
6490 * 5. This isn't prefetch and l2arc_noprefetch is set.
6492 if (HDR_HAS_L2HDR(hdr) &&
6493 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
6494 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
6495 l2arc_read_callback_t *cb;
6499 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
6500 ARCSTAT_BUMP(arcstat_l2_hits);
6501 atomic_inc_32(&hdr->b_l2hdr.b_hits);
6503 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
6505 cb->l2rcb_hdr = hdr;
6508 cb->l2rcb_flags = zio_flags;
6510 asize = vdev_psize_to_asize(vd, size);
6511 if (asize != size) {
6512 abd = abd_alloc_for_io(asize,
6513 HDR_ISTYPE_METADATA(hdr));
6514 cb->l2rcb_abd = abd;
6519 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
6520 addr + asize <= vd->vdev_psize -
6521 VDEV_LABEL_END_SIZE);
6524 * l2arc read. The SCL_L2ARC lock will be
6525 * released by l2arc_read_done().
6526 * Issue a null zio if the underlying buffer
6527 * was squashed to zero size by compression.
6529 ASSERT3U(arc_hdr_get_compress(hdr), !=,
6530 ZIO_COMPRESS_EMPTY);
6531 rzio = zio_read_phys(pio, vd, addr,
6534 l2arc_read_done, cb, priority,
6535 zio_flags | ZIO_FLAG_DONT_CACHE |
6537 ZIO_FLAG_DONT_PROPAGATE |
6538 ZIO_FLAG_DONT_RETRY, B_FALSE);
6539 acb->acb_zio_head = rzio;
6541 if (hash_lock != NULL)
6542 mutex_exit(hash_lock);
6544 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
6546 ARCSTAT_INCR(arcstat_l2_read_bytes,
6547 HDR_GET_PSIZE(hdr));
6549 if (*arc_flags & ARC_FLAG_NOWAIT) {
6554 ASSERT(*arc_flags & ARC_FLAG_WAIT);
6555 if (zio_wait(rzio) == 0)
6558 /* l2arc read error; goto zio_read() */
6559 if (hash_lock != NULL)
6560 mutex_enter(hash_lock);
6562 DTRACE_PROBE1(l2arc__miss,
6563 arc_buf_hdr_t *, hdr);
6564 ARCSTAT_BUMP(arcstat_l2_misses);
6565 if (HDR_L2_WRITING(hdr))
6566 ARCSTAT_BUMP(arcstat_l2_rw_clash);
6567 spa_config_exit(spa, SCL_L2ARC, vd);
6571 spa_config_exit(spa, SCL_L2ARC, vd);
6572 if (l2arc_ndev != 0) {
6573 DTRACE_PROBE1(l2arc__miss,
6574 arc_buf_hdr_t *, hdr);
6575 ARCSTAT_BUMP(arcstat_l2_misses);
6579 rzio = zio_read(pio, spa, bp, hdr_abd, size,
6580 arc_read_done, hdr, priority, zio_flags, zb);
6581 acb->acb_zio_head = rzio;
6583 if (hash_lock != NULL)
6584 mutex_exit(hash_lock);
6586 if (*arc_flags & ARC_FLAG_WAIT) {
6587 rc = zio_wait(rzio);
6591 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
6596 /* embedded bps don't actually go to disk */
6597 if (!BP_IS_EMBEDDED(bp))
6598 spa_read_history_add(spa, zb, *arc_flags);
6603 arc_add_prune_callback(arc_prune_func_t *func, void *private)
6607 p = kmem_alloc(sizeof (*p), KM_SLEEP);
6609 p->p_private = private;
6610 list_link_init(&p->p_node);
6611 zfs_refcount_create(&p->p_refcnt);
6613 mutex_enter(&arc_prune_mtx);
6614 zfs_refcount_add(&p->p_refcnt, &arc_prune_list);
6615 list_insert_head(&arc_prune_list, p);
6616 mutex_exit(&arc_prune_mtx);
6622 arc_remove_prune_callback(arc_prune_t *p)
6624 boolean_t wait = B_FALSE;
6625 mutex_enter(&arc_prune_mtx);
6626 list_remove(&arc_prune_list, p);
6627 if (zfs_refcount_remove(&p->p_refcnt, &arc_prune_list) > 0)
6629 mutex_exit(&arc_prune_mtx);
6631 /* wait for arc_prune_task to finish */
6633 taskq_wait_outstanding(arc_prune_taskq, 0);
6634 ASSERT0(zfs_refcount_count(&p->p_refcnt));
6635 zfs_refcount_destroy(&p->p_refcnt);
6636 kmem_free(p, sizeof (*p));
6640 * Notify the arc that a block was freed, and thus will never be used again.
6643 arc_freed(spa_t *spa, const blkptr_t *bp)
6646 kmutex_t *hash_lock;
6647 uint64_t guid = spa_load_guid(spa);
6649 ASSERT(!BP_IS_EMBEDDED(bp));
6651 hdr = buf_hash_find(guid, bp, &hash_lock);
6656 * We might be trying to free a block that is still doing I/O
6657 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
6658 * dmu_sync-ed block). If this block is being prefetched, then it
6659 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
6660 * until the I/O completes. A block may also have a reference if it is
6661 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
6662 * have written the new block to its final resting place on disk but
6663 * without the dedup flag set. This would have left the hdr in the MRU
6664 * state and discoverable. When the txg finally syncs it detects that
6665 * the block was overridden in open context and issues an override I/O.
6666 * Since this is a dedup block, the override I/O will determine if the
6667 * block is already in the DDT. If so, then it will replace the io_bp
6668 * with the bp from the DDT and allow the I/O to finish. When the I/O
6669 * reaches the done callback, dbuf_write_override_done, it will
6670 * check to see if the io_bp and io_bp_override are identical.
6671 * If they are not, then it indicates that the bp was replaced with
6672 * the bp in the DDT and the override bp is freed. This allows
6673 * us to arrive here with a reference on a block that is being
6674 * freed. So if we have an I/O in progress, or a reference to
6675 * this hdr, then we don't destroy the hdr.
6677 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
6678 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
6679 arc_change_state(arc_anon, hdr, hash_lock);
6680 arc_hdr_destroy(hdr);
6681 mutex_exit(hash_lock);
6683 mutex_exit(hash_lock);
6689 * Release this buffer from the cache, making it an anonymous buffer. This
6690 * must be done after a read and prior to modifying the buffer contents.
6691 * If the buffer has more than one reference, we must make
6692 * a new hdr for the buffer.
6695 arc_release(arc_buf_t *buf, void *tag)
6697 arc_buf_hdr_t *hdr = buf->b_hdr;
6700 * It would be nice to assert that if its DMU metadata (level >
6701 * 0 || it's the dnode file), then it must be syncing context.
6702 * But we don't know that information at this level.
6705 mutex_enter(&buf->b_evict_lock);
6707 ASSERT(HDR_HAS_L1HDR(hdr));
6710 * We don't grab the hash lock prior to this check, because if
6711 * the buffer's header is in the arc_anon state, it won't be
6712 * linked into the hash table.
6714 if (hdr->b_l1hdr.b_state == arc_anon) {
6715 mutex_exit(&buf->b_evict_lock);
6716 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6717 ASSERT(!HDR_IN_HASH_TABLE(hdr));
6718 ASSERT(!HDR_HAS_L2HDR(hdr));
6719 ASSERT(HDR_EMPTY(hdr));
6721 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6722 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
6723 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
6725 hdr->b_l1hdr.b_arc_access = 0;
6728 * If the buf is being overridden then it may already
6729 * have a hdr that is not empty.
6731 buf_discard_identity(hdr);
6737 kmutex_t *hash_lock = HDR_LOCK(hdr);
6738 mutex_enter(hash_lock);
6741 * This assignment is only valid as long as the hash_lock is
6742 * held, we must be careful not to reference state or the
6743 * b_state field after dropping the lock.
6745 arc_state_t *state = hdr->b_l1hdr.b_state;
6746 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
6747 ASSERT3P(state, !=, arc_anon);
6749 /* this buffer is not on any list */
6750 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
6752 if (HDR_HAS_L2HDR(hdr)) {
6753 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6756 * We have to recheck this conditional again now that
6757 * we're holding the l2ad_mtx to prevent a race with
6758 * another thread which might be concurrently calling
6759 * l2arc_evict(). In that case, l2arc_evict() might have
6760 * destroyed the header's L2 portion as we were waiting
6761 * to acquire the l2ad_mtx.
6763 if (HDR_HAS_L2HDR(hdr))
6764 arc_hdr_l2hdr_destroy(hdr);
6766 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6770 * Do we have more than one buf?
6772 if (hdr->b_l1hdr.b_bufcnt > 1) {
6773 arc_buf_hdr_t *nhdr;
6774 uint64_t spa = hdr->b_spa;
6775 uint64_t psize = HDR_GET_PSIZE(hdr);
6776 uint64_t lsize = HDR_GET_LSIZE(hdr);
6777 boolean_t protected = HDR_PROTECTED(hdr);
6778 enum zio_compress compress = arc_hdr_get_compress(hdr);
6779 arc_buf_contents_t type = arc_buf_type(hdr);
6780 VERIFY3U(hdr->b_type, ==, type);
6782 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
6783 (void) remove_reference(hdr, hash_lock, tag);
6785 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
6786 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6787 ASSERT(ARC_BUF_LAST(buf));
6791 * Pull the data off of this hdr and attach it to
6792 * a new anonymous hdr. Also find the last buffer
6793 * in the hdr's buffer list.
6795 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
6796 ASSERT3P(lastbuf, !=, NULL);
6799 * If the current arc_buf_t and the hdr are sharing their data
6800 * buffer, then we must stop sharing that block.
6802 if (arc_buf_is_shared(buf)) {
6803 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6804 VERIFY(!arc_buf_is_shared(lastbuf));
6807 * First, sever the block sharing relationship between
6808 * buf and the arc_buf_hdr_t.
6810 arc_unshare_buf(hdr, buf);
6813 * Now we need to recreate the hdr's b_pabd. Since we
6814 * have lastbuf handy, we try to share with it, but if
6815 * we can't then we allocate a new b_pabd and copy the
6816 * data from buf into it.
6818 if (arc_can_share(hdr, lastbuf)) {
6819 arc_share_buf(hdr, lastbuf);
6821 arc_hdr_alloc_abd(hdr, B_FALSE);
6822 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
6823 buf->b_data, psize);
6825 VERIFY3P(lastbuf->b_data, !=, NULL);
6826 } else if (HDR_SHARED_DATA(hdr)) {
6828 * Uncompressed shared buffers are always at the end
6829 * of the list. Compressed buffers don't have the
6830 * same requirements. This makes it hard to
6831 * simply assert that the lastbuf is shared so
6832 * we rely on the hdr's compression flags to determine
6833 * if we have a compressed, shared buffer.
6835 ASSERT(arc_buf_is_shared(lastbuf) ||
6836 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
6837 ASSERT(!ARC_BUF_SHARED(buf));
6840 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
6841 ASSERT3P(state, !=, arc_l2c_only);
6843 (void) zfs_refcount_remove_many(&state->arcs_size,
6844 arc_buf_size(buf), buf);
6846 if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
6847 ASSERT3P(state, !=, arc_l2c_only);
6848 (void) zfs_refcount_remove_many(
6849 &state->arcs_esize[type],
6850 arc_buf_size(buf), buf);
6853 hdr->b_l1hdr.b_bufcnt -= 1;
6854 if (ARC_BUF_ENCRYPTED(buf))
6855 hdr->b_crypt_hdr.b_ebufcnt -= 1;
6857 arc_cksum_verify(buf);
6858 arc_buf_unwatch(buf);
6860 /* if this is the last uncompressed buf free the checksum */
6861 if (!arc_hdr_has_uncompressed_buf(hdr))
6862 arc_cksum_free(hdr);
6864 mutex_exit(hash_lock);
6867 * Allocate a new hdr. The new hdr will contain a b_pabd
6868 * buffer which will be freed in arc_write().
6870 nhdr = arc_hdr_alloc(spa, psize, lsize, protected,
6871 compress, type, HDR_HAS_RABD(hdr));
6872 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
6873 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
6874 ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt));
6875 VERIFY3U(nhdr->b_type, ==, type);
6876 ASSERT(!HDR_SHARED_DATA(nhdr));
6878 nhdr->b_l1hdr.b_buf = buf;
6879 nhdr->b_l1hdr.b_bufcnt = 1;
6880 if (ARC_BUF_ENCRYPTED(buf))
6881 nhdr->b_crypt_hdr.b_ebufcnt = 1;
6882 nhdr->b_l1hdr.b_mru_hits = 0;
6883 nhdr->b_l1hdr.b_mru_ghost_hits = 0;
6884 nhdr->b_l1hdr.b_mfu_hits = 0;
6885 nhdr->b_l1hdr.b_mfu_ghost_hits = 0;
6886 nhdr->b_l1hdr.b_l2_hits = 0;
6887 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
6890 mutex_exit(&buf->b_evict_lock);
6891 (void) zfs_refcount_add_many(&arc_anon->arcs_size,
6892 arc_buf_size(buf), buf);
6894 mutex_exit(&buf->b_evict_lock);
6895 ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
6896 /* protected by hash lock, or hdr is on arc_anon */
6897 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
6898 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6899 hdr->b_l1hdr.b_mru_hits = 0;
6900 hdr->b_l1hdr.b_mru_ghost_hits = 0;
6901 hdr->b_l1hdr.b_mfu_hits = 0;
6902 hdr->b_l1hdr.b_mfu_ghost_hits = 0;
6903 hdr->b_l1hdr.b_l2_hits = 0;
6904 arc_change_state(arc_anon, hdr, hash_lock);
6905 hdr->b_l1hdr.b_arc_access = 0;
6907 mutex_exit(hash_lock);
6908 buf_discard_identity(hdr);
6914 arc_released(arc_buf_t *buf)
6918 mutex_enter(&buf->b_evict_lock);
6919 released = (buf->b_data != NULL &&
6920 buf->b_hdr->b_l1hdr.b_state == arc_anon);
6921 mutex_exit(&buf->b_evict_lock);
6927 arc_referenced(arc_buf_t *buf)
6931 mutex_enter(&buf->b_evict_lock);
6932 referenced = (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
6933 mutex_exit(&buf->b_evict_lock);
6934 return (referenced);
6939 arc_write_ready(zio_t *zio)
6941 arc_write_callback_t *callback = zio->io_private;
6942 arc_buf_t *buf = callback->awcb_buf;
6943 arc_buf_hdr_t *hdr = buf->b_hdr;
6944 blkptr_t *bp = zio->io_bp;
6945 uint64_t psize = BP_IS_HOLE(bp) ? 0 : BP_GET_PSIZE(bp);
6946 fstrans_cookie_t cookie = spl_fstrans_mark();
6948 ASSERT(HDR_HAS_L1HDR(hdr));
6949 ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
6950 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
6953 * If we're reexecuting this zio because the pool suspended, then
6954 * cleanup any state that was previously set the first time the
6955 * callback was invoked.
6957 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
6958 arc_cksum_free(hdr);
6959 arc_buf_unwatch(buf);
6960 if (hdr->b_l1hdr.b_pabd != NULL) {
6961 if (arc_buf_is_shared(buf)) {
6962 arc_unshare_buf(hdr, buf);
6964 arc_hdr_free_abd(hdr, B_FALSE);
6968 if (HDR_HAS_RABD(hdr))
6969 arc_hdr_free_abd(hdr, B_TRUE);
6971 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6972 ASSERT(!HDR_HAS_RABD(hdr));
6973 ASSERT(!HDR_SHARED_DATA(hdr));
6974 ASSERT(!arc_buf_is_shared(buf));
6976 callback->awcb_ready(zio, buf, callback->awcb_private);
6978 if (HDR_IO_IN_PROGRESS(hdr))
6979 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
6981 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6983 if (BP_IS_PROTECTED(bp) != !!HDR_PROTECTED(hdr))
6984 hdr = arc_hdr_realloc_crypt(hdr, BP_IS_PROTECTED(bp));
6986 if (BP_IS_PROTECTED(bp)) {
6987 /* ZIL blocks are written through zio_rewrite */
6988 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
6989 ASSERT(HDR_PROTECTED(hdr));
6991 if (BP_SHOULD_BYTESWAP(bp)) {
6992 if (BP_GET_LEVEL(bp) > 0) {
6993 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
6995 hdr->b_l1hdr.b_byteswap =
6996 DMU_OT_BYTESWAP(BP_GET_TYPE(bp));
6999 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
7002 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
7003 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
7004 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
7005 hdr->b_crypt_hdr.b_iv);
7006 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
7010 * If this block was written for raw encryption but the zio layer
7011 * ended up only authenticating it, adjust the buffer flags now.
7013 if (BP_IS_AUTHENTICATED(bp) && ARC_BUF_ENCRYPTED(buf)) {
7014 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
7015 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
7016 if (BP_GET_COMPRESS(bp) == ZIO_COMPRESS_OFF)
7017 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
7018 } else if (BP_IS_HOLE(bp) && ARC_BUF_ENCRYPTED(buf)) {
7019 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
7020 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
7023 /* this must be done after the buffer flags are adjusted */
7024 arc_cksum_compute(buf);
7026 enum zio_compress compress;
7027 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
7028 compress = ZIO_COMPRESS_OFF;
7030 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
7031 compress = BP_GET_COMPRESS(bp);
7033 HDR_SET_PSIZE(hdr, psize);
7034 arc_hdr_set_compress(hdr, compress);
7036 if (zio->io_error != 0 || psize == 0)
7040 * Fill the hdr with data. If the buffer is encrypted we have no choice
7041 * but to copy the data into b_radb. If the hdr is compressed, the data
7042 * we want is available from the zio, otherwise we can take it from
7045 * We might be able to share the buf's data with the hdr here. However,
7046 * doing so would cause the ARC to be full of linear ABDs if we write a
7047 * lot of shareable data. As a compromise, we check whether scattered
7048 * ABDs are allowed, and assume that if they are then the user wants
7049 * the ARC to be primarily filled with them regardless of the data being
7050 * written. Therefore, if they're allowed then we allocate one and copy
7051 * the data into it; otherwise, we share the data directly if we can.
7053 if (ARC_BUF_ENCRYPTED(buf)) {
7054 ASSERT3U(psize, >, 0);
7055 ASSERT(ARC_BUF_COMPRESSED(buf));
7056 arc_hdr_alloc_abd(hdr, B_TRUE);
7057 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
7058 } else if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
7060 * Ideally, we would always copy the io_abd into b_pabd, but the
7061 * user may have disabled compressed ARC, thus we must check the
7062 * hdr's compression setting rather than the io_bp's.
7064 if (BP_IS_ENCRYPTED(bp)) {
7065 ASSERT3U(psize, >, 0);
7066 arc_hdr_alloc_abd(hdr, B_TRUE);
7067 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
7068 } else if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
7069 !ARC_BUF_COMPRESSED(buf)) {
7070 ASSERT3U(psize, >, 0);
7071 arc_hdr_alloc_abd(hdr, B_FALSE);
7072 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
7074 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
7075 arc_hdr_alloc_abd(hdr, B_FALSE);
7076 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
7080 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
7081 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
7082 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
7084 arc_share_buf(hdr, buf);
7088 arc_hdr_verify(hdr, bp);
7089 spl_fstrans_unmark(cookie);
7093 arc_write_children_ready(zio_t *zio)
7095 arc_write_callback_t *callback = zio->io_private;
7096 arc_buf_t *buf = callback->awcb_buf;
7098 callback->awcb_children_ready(zio, buf, callback->awcb_private);
7102 * The SPA calls this callback for each physical write that happens on behalf
7103 * of a logical write. See the comment in dbuf_write_physdone() for details.
7106 arc_write_physdone(zio_t *zio)
7108 arc_write_callback_t *cb = zio->io_private;
7109 if (cb->awcb_physdone != NULL)
7110 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
7114 arc_write_done(zio_t *zio)
7116 arc_write_callback_t *callback = zio->io_private;
7117 arc_buf_t *buf = callback->awcb_buf;
7118 arc_buf_hdr_t *hdr = buf->b_hdr;
7120 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
7122 if (zio->io_error == 0) {
7123 arc_hdr_verify(hdr, zio->io_bp);
7125 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
7126 buf_discard_identity(hdr);
7128 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
7129 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
7132 ASSERT(HDR_EMPTY(hdr));
7136 * If the block to be written was all-zero or compressed enough to be
7137 * embedded in the BP, no write was performed so there will be no
7138 * dva/birth/checksum. The buffer must therefore remain anonymous
7141 if (!HDR_EMPTY(hdr)) {
7142 arc_buf_hdr_t *exists;
7143 kmutex_t *hash_lock;
7145 ASSERT3U(zio->io_error, ==, 0);
7147 arc_cksum_verify(buf);
7149 exists = buf_hash_insert(hdr, &hash_lock);
7150 if (exists != NULL) {
7152 * This can only happen if we overwrite for
7153 * sync-to-convergence, because we remove
7154 * buffers from the hash table when we arc_free().
7156 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
7157 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
7158 panic("bad overwrite, hdr=%p exists=%p",
7159 (void *)hdr, (void *)exists);
7160 ASSERT(zfs_refcount_is_zero(
7161 &exists->b_l1hdr.b_refcnt));
7162 arc_change_state(arc_anon, exists, hash_lock);
7163 mutex_exit(hash_lock);
7164 arc_hdr_destroy(exists);
7165 exists = buf_hash_insert(hdr, &hash_lock);
7166 ASSERT3P(exists, ==, NULL);
7167 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
7169 ASSERT(zio->io_prop.zp_nopwrite);
7170 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
7171 panic("bad nopwrite, hdr=%p exists=%p",
7172 (void *)hdr, (void *)exists);
7175 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
7176 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
7177 ASSERT(BP_GET_DEDUP(zio->io_bp));
7178 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
7181 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
7182 /* if it's not anon, we are doing a scrub */
7183 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
7184 arc_access(hdr, hash_lock);
7185 mutex_exit(hash_lock);
7187 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
7190 ASSERT(!zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
7191 callback->awcb_done(zio, buf, callback->awcb_private);
7193 abd_put(zio->io_abd);
7194 kmem_free(callback, sizeof (arc_write_callback_t));
7198 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
7199 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc,
7200 const zio_prop_t *zp, arc_write_done_func_t *ready,
7201 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone,
7202 arc_write_done_func_t *done, void *private, zio_priority_t priority,
7203 int zio_flags, const zbookmark_phys_t *zb)
7205 arc_buf_hdr_t *hdr = buf->b_hdr;
7206 arc_write_callback_t *callback;
7208 zio_prop_t localprop = *zp;
7210 ASSERT3P(ready, !=, NULL);
7211 ASSERT3P(done, !=, NULL);
7212 ASSERT(!HDR_IO_ERROR(hdr));
7213 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
7214 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
7215 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
7217 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
7219 if (ARC_BUF_ENCRYPTED(buf)) {
7220 ASSERT(ARC_BUF_COMPRESSED(buf));
7221 localprop.zp_encrypt = B_TRUE;
7222 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
7223 localprop.zp_byteorder =
7224 (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
7225 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
7226 bcopy(hdr->b_crypt_hdr.b_salt, localprop.zp_salt,
7228 bcopy(hdr->b_crypt_hdr.b_iv, localprop.zp_iv,
7230 bcopy(hdr->b_crypt_hdr.b_mac, localprop.zp_mac,
7232 if (DMU_OT_IS_ENCRYPTED(localprop.zp_type)) {
7233 localprop.zp_nopwrite = B_FALSE;
7234 localprop.zp_copies =
7235 MIN(localprop.zp_copies, SPA_DVAS_PER_BP - 1);
7237 zio_flags |= ZIO_FLAG_RAW;
7238 } else if (ARC_BUF_COMPRESSED(buf)) {
7239 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
7240 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
7241 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
7243 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
7244 callback->awcb_ready = ready;
7245 callback->awcb_children_ready = children_ready;
7246 callback->awcb_physdone = physdone;
7247 callback->awcb_done = done;
7248 callback->awcb_private = private;
7249 callback->awcb_buf = buf;
7252 * The hdr's b_pabd is now stale, free it now. A new data block
7253 * will be allocated when the zio pipeline calls arc_write_ready().
7255 if (hdr->b_l1hdr.b_pabd != NULL) {
7257 * If the buf is currently sharing the data block with
7258 * the hdr then we need to break that relationship here.
7259 * The hdr will remain with a NULL data pointer and the
7260 * buf will take sole ownership of the block.
7262 if (arc_buf_is_shared(buf)) {
7263 arc_unshare_buf(hdr, buf);
7265 arc_hdr_free_abd(hdr, B_FALSE);
7267 VERIFY3P(buf->b_data, !=, NULL);
7270 if (HDR_HAS_RABD(hdr))
7271 arc_hdr_free_abd(hdr, B_TRUE);
7273 if (!(zio_flags & ZIO_FLAG_RAW))
7274 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
7276 ASSERT(!arc_buf_is_shared(buf));
7277 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
7279 zio = zio_write(pio, spa, txg, bp,
7280 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
7281 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
7282 (children_ready != NULL) ? arc_write_children_ready : NULL,
7283 arc_write_physdone, arc_write_done, callback,
7284 priority, zio_flags, zb);
7290 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
7293 uint64_t available_memory = arc_free_memory();
7297 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
7300 if (available_memory > arc_all_memory() * arc_lotsfree_percent / 100)
7303 if (txg > spa->spa_lowmem_last_txg) {
7304 spa->spa_lowmem_last_txg = txg;
7305 spa->spa_lowmem_page_load = 0;
7308 * If we are in pageout, we know that memory is already tight,
7309 * the arc is already going to be evicting, so we just want to
7310 * continue to let page writes occur as quickly as possible.
7312 if (current_is_kswapd()) {
7313 if (spa->spa_lowmem_page_load >
7314 MAX(arc_sys_free / 4, available_memory) / 4) {
7315 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
7316 return (SET_ERROR(ERESTART));
7318 /* Note: reserve is inflated, so we deflate */
7319 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8);
7321 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) {
7322 /* memory is low, delay before restarting */
7323 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
7324 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
7325 return (SET_ERROR(EAGAIN));
7327 spa->spa_lowmem_page_load = 0;
7328 #endif /* _KERNEL */
7333 arc_tempreserve_clear(uint64_t reserve)
7335 atomic_add_64(&arc_tempreserve, -reserve);
7336 ASSERT((int64_t)arc_tempreserve >= 0);
7340 arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
7346 reserve > arc_c/4 &&
7347 reserve * 4 > (2ULL << SPA_MAXBLOCKSHIFT))
7348 arc_c = MIN(arc_c_max, reserve * 4);
7351 * Throttle when the calculated memory footprint for the TXG
7352 * exceeds the target ARC size.
7354 if (reserve > arc_c) {
7355 DMU_TX_STAT_BUMP(dmu_tx_memory_reserve);
7356 return (SET_ERROR(ERESTART));
7360 * Don't count loaned bufs as in flight dirty data to prevent long
7361 * network delays from blocking transactions that are ready to be
7362 * assigned to a txg.
7365 /* assert that it has not wrapped around */
7366 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
7368 anon_size = MAX((int64_t)(zfs_refcount_count(&arc_anon->arcs_size) -
7369 arc_loaned_bytes), 0);
7372 * Writes will, almost always, require additional memory allocations
7373 * in order to compress/encrypt/etc the data. We therefore need to
7374 * make sure that there is sufficient available memory for this.
7376 error = arc_memory_throttle(spa, reserve, txg);
7381 * Throttle writes when the amount of dirty data in the cache
7382 * gets too large. We try to keep the cache less than half full
7383 * of dirty blocks so that our sync times don't grow too large.
7385 * In the case of one pool being built on another pool, we want
7386 * to make sure we don't end up throttling the lower (backing)
7387 * pool when the upper pool is the majority contributor to dirty
7388 * data. To insure we make forward progress during throttling, we
7389 * also check the current pool's net dirty data and only throttle
7390 * if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty
7391 * data in the cache.
7393 * Note: if two requests come in concurrently, we might let them
7394 * both succeed, when one of them should fail. Not a huge deal.
7396 uint64_t total_dirty = reserve + arc_tempreserve + anon_size;
7397 uint64_t spa_dirty_anon = spa_dirty_data(spa);
7399 if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 &&
7400 anon_size > arc_c * zfs_arc_anon_limit_percent / 100 &&
7401 spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) {
7403 uint64_t meta_esize = zfs_refcount_count(
7404 &arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7405 uint64_t data_esize =
7406 zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7407 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
7408 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
7409 arc_tempreserve >> 10, meta_esize >> 10,
7410 data_esize >> 10, reserve >> 10, arc_c >> 10);
7412 DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
7413 return (SET_ERROR(ERESTART));
7415 atomic_add_64(&arc_tempreserve, reserve);
7420 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
7421 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
7423 size->value.ui64 = zfs_refcount_count(&state->arcs_size);
7424 evict_data->value.ui64 =
7425 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
7426 evict_metadata->value.ui64 =
7427 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
7431 arc_kstat_update(kstat_t *ksp, int rw)
7433 arc_stats_t *as = ksp->ks_data;
7435 if (rw == KSTAT_WRITE) {
7436 return (SET_ERROR(EACCES));
7438 arc_kstat_update_state(arc_anon,
7439 &as->arcstat_anon_size,
7440 &as->arcstat_anon_evictable_data,
7441 &as->arcstat_anon_evictable_metadata);
7442 arc_kstat_update_state(arc_mru,
7443 &as->arcstat_mru_size,
7444 &as->arcstat_mru_evictable_data,
7445 &as->arcstat_mru_evictable_metadata);
7446 arc_kstat_update_state(arc_mru_ghost,
7447 &as->arcstat_mru_ghost_size,
7448 &as->arcstat_mru_ghost_evictable_data,
7449 &as->arcstat_mru_ghost_evictable_metadata);
7450 arc_kstat_update_state(arc_mfu,
7451 &as->arcstat_mfu_size,
7452 &as->arcstat_mfu_evictable_data,
7453 &as->arcstat_mfu_evictable_metadata);
7454 arc_kstat_update_state(arc_mfu_ghost,
7455 &as->arcstat_mfu_ghost_size,
7456 &as->arcstat_mfu_ghost_evictable_data,
7457 &as->arcstat_mfu_ghost_evictable_metadata);
7459 ARCSTAT(arcstat_size) = aggsum_value(&arc_size);
7460 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used);
7461 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size);
7462 ARCSTAT(arcstat_metadata_size) =
7463 aggsum_value(&astat_metadata_size);
7464 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size);
7465 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size);
7466 ARCSTAT(arcstat_dbuf_size) = aggsum_value(&astat_dbuf_size);
7467 ARCSTAT(arcstat_dnode_size) = aggsum_value(&astat_dnode_size);
7468 ARCSTAT(arcstat_bonus_size) = aggsum_value(&astat_bonus_size);
7470 as->arcstat_memory_all_bytes.value.ui64 =
7472 as->arcstat_memory_free_bytes.value.ui64 =
7474 as->arcstat_memory_available_bytes.value.i64 =
7475 arc_available_memory();
7482 * This function *must* return indices evenly distributed between all
7483 * sublists of the multilist. This is needed due to how the ARC eviction
7484 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
7485 * distributed between all sublists and uses this assumption when
7486 * deciding which sublist to evict from and how much to evict from it.
7489 arc_state_multilist_index_func(multilist_t *ml, void *obj)
7491 arc_buf_hdr_t *hdr = obj;
7494 * We rely on b_dva to generate evenly distributed index
7495 * numbers using buf_hash below. So, as an added precaution,
7496 * let's make sure we never add empty buffers to the arc lists.
7498 ASSERT(!HDR_EMPTY(hdr));
7501 * The assumption here, is the hash value for a given
7502 * arc_buf_hdr_t will remain constant throughout its lifetime
7503 * (i.e. its b_spa, b_dva, and b_birth fields don't change).
7504 * Thus, we don't need to store the header's sublist index
7505 * on insertion, as this index can be recalculated on removal.
7507 * Also, the low order bits of the hash value are thought to be
7508 * distributed evenly. Otherwise, in the case that the multilist
7509 * has a power of two number of sublists, each sublists' usage
7510 * would not be evenly distributed.
7512 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
7513 multilist_get_num_sublists(ml));
7517 * Called during module initialization and periodically thereafter to
7518 * apply reasonable changes to the exposed performance tunings. Non-zero
7519 * zfs_* values which differ from the currently set values will be applied.
7522 arc_tuning_update(void)
7524 uint64_t allmem = arc_all_memory();
7525 unsigned long limit;
7527 /* Valid range: 64M - <all physical memory> */
7528 if ((zfs_arc_max) && (zfs_arc_max != arc_c_max) &&
7529 (zfs_arc_max >= 64 << 20) && (zfs_arc_max < allmem) &&
7530 (zfs_arc_max > arc_c_min)) {
7531 arc_c_max = zfs_arc_max;
7533 arc_p = (arc_c >> 1);
7534 if (arc_meta_limit > arc_c_max)
7535 arc_meta_limit = arc_c_max;
7536 if (arc_dnode_limit > arc_meta_limit)
7537 arc_dnode_limit = arc_meta_limit;
7540 /* Valid range: 32M - <arc_c_max> */
7541 if ((zfs_arc_min) && (zfs_arc_min != arc_c_min) &&
7542 (zfs_arc_min >= 2ULL << SPA_MAXBLOCKSHIFT) &&
7543 (zfs_arc_min <= arc_c_max)) {
7544 arc_c_min = zfs_arc_min;
7545 arc_c = MAX(arc_c, arc_c_min);
7548 /* Valid range: 16M - <arc_c_max> */
7549 if ((zfs_arc_meta_min) && (zfs_arc_meta_min != arc_meta_min) &&
7550 (zfs_arc_meta_min >= 1ULL << SPA_MAXBLOCKSHIFT) &&
7551 (zfs_arc_meta_min <= arc_c_max)) {
7552 arc_meta_min = zfs_arc_meta_min;
7553 if (arc_meta_limit < arc_meta_min)
7554 arc_meta_limit = arc_meta_min;
7555 if (arc_dnode_limit < arc_meta_min)
7556 arc_dnode_limit = arc_meta_min;
7559 /* Valid range: <arc_meta_min> - <arc_c_max> */
7560 limit = zfs_arc_meta_limit ? zfs_arc_meta_limit :
7561 MIN(zfs_arc_meta_limit_percent, 100) * arc_c_max / 100;
7562 if ((limit != arc_meta_limit) &&
7563 (limit >= arc_meta_min) &&
7564 (limit <= arc_c_max))
7565 arc_meta_limit = limit;
7567 /* Valid range: <arc_meta_min> - <arc_meta_limit> */
7568 limit = zfs_arc_dnode_limit ? zfs_arc_dnode_limit :
7569 MIN(zfs_arc_dnode_limit_percent, 100) * arc_meta_limit / 100;
7570 if ((limit != arc_dnode_limit) &&
7571 (limit >= arc_meta_min) &&
7572 (limit <= arc_meta_limit))
7573 arc_dnode_limit = limit;
7575 /* Valid range: 1 - N */
7576 if (zfs_arc_grow_retry)
7577 arc_grow_retry = zfs_arc_grow_retry;
7579 /* Valid range: 1 - N */
7580 if (zfs_arc_shrink_shift) {
7581 arc_shrink_shift = zfs_arc_shrink_shift;
7582 arc_no_grow_shift = MIN(arc_no_grow_shift, arc_shrink_shift -1);
7585 /* Valid range: 1 - N */
7586 if (zfs_arc_p_min_shift)
7587 arc_p_min_shift = zfs_arc_p_min_shift;
7589 /* Valid range: 1 - N ms */
7590 if (zfs_arc_min_prefetch_ms)
7591 arc_min_prefetch_ms = zfs_arc_min_prefetch_ms;
7593 /* Valid range: 1 - N ms */
7594 if (zfs_arc_min_prescient_prefetch_ms) {
7595 arc_min_prescient_prefetch_ms =
7596 zfs_arc_min_prescient_prefetch_ms;
7599 /* Valid range: 0 - 100 */
7600 if ((zfs_arc_lotsfree_percent >= 0) &&
7601 (zfs_arc_lotsfree_percent <= 100))
7602 arc_lotsfree_percent = zfs_arc_lotsfree_percent;
7604 /* Valid range: 0 - <all physical memory> */
7605 if ((zfs_arc_sys_free) && (zfs_arc_sys_free != arc_sys_free))
7606 arc_sys_free = MIN(MAX(zfs_arc_sys_free, 0), allmem);
7611 arc_state_init(void)
7613 arc_anon = &ARC_anon;
7615 arc_mru_ghost = &ARC_mru_ghost;
7617 arc_mfu_ghost = &ARC_mfu_ghost;
7618 arc_l2c_only = &ARC_l2c_only;
7620 arc_mru->arcs_list[ARC_BUFC_METADATA] =
7621 multilist_create(sizeof (arc_buf_hdr_t),
7622 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7623 arc_state_multilist_index_func);
7624 arc_mru->arcs_list[ARC_BUFC_DATA] =
7625 multilist_create(sizeof (arc_buf_hdr_t),
7626 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7627 arc_state_multilist_index_func);
7628 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
7629 multilist_create(sizeof (arc_buf_hdr_t),
7630 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7631 arc_state_multilist_index_func);
7632 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
7633 multilist_create(sizeof (arc_buf_hdr_t),
7634 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7635 arc_state_multilist_index_func);
7636 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
7637 multilist_create(sizeof (arc_buf_hdr_t),
7638 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7639 arc_state_multilist_index_func);
7640 arc_mfu->arcs_list[ARC_BUFC_DATA] =
7641 multilist_create(sizeof (arc_buf_hdr_t),
7642 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7643 arc_state_multilist_index_func);
7644 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
7645 multilist_create(sizeof (arc_buf_hdr_t),
7646 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7647 arc_state_multilist_index_func);
7648 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
7649 multilist_create(sizeof (arc_buf_hdr_t),
7650 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7651 arc_state_multilist_index_func);
7652 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
7653 multilist_create(sizeof (arc_buf_hdr_t),
7654 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7655 arc_state_multilist_index_func);
7656 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
7657 multilist_create(sizeof (arc_buf_hdr_t),
7658 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
7659 arc_state_multilist_index_func);
7661 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7662 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7663 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7664 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7665 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7666 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7667 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7668 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7669 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7670 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7671 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7672 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7674 zfs_refcount_create(&arc_anon->arcs_size);
7675 zfs_refcount_create(&arc_mru->arcs_size);
7676 zfs_refcount_create(&arc_mru_ghost->arcs_size);
7677 zfs_refcount_create(&arc_mfu->arcs_size);
7678 zfs_refcount_create(&arc_mfu_ghost->arcs_size);
7679 zfs_refcount_create(&arc_l2c_only->arcs_size);
7681 aggsum_init(&arc_meta_used, 0);
7682 aggsum_init(&arc_size, 0);
7683 aggsum_init(&astat_data_size, 0);
7684 aggsum_init(&astat_metadata_size, 0);
7685 aggsum_init(&astat_hdr_size, 0);
7686 aggsum_init(&astat_l2_hdr_size, 0);
7687 aggsum_init(&astat_bonus_size, 0);
7688 aggsum_init(&astat_dnode_size, 0);
7689 aggsum_init(&astat_dbuf_size, 0);
7691 arc_anon->arcs_state = ARC_STATE_ANON;
7692 arc_mru->arcs_state = ARC_STATE_MRU;
7693 arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
7694 arc_mfu->arcs_state = ARC_STATE_MFU;
7695 arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
7696 arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
7700 arc_state_fini(void)
7702 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7703 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7704 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7705 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7706 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7707 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7708 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7709 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7710 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7711 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7712 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7713 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7715 zfs_refcount_destroy(&arc_anon->arcs_size);
7716 zfs_refcount_destroy(&arc_mru->arcs_size);
7717 zfs_refcount_destroy(&arc_mru_ghost->arcs_size);
7718 zfs_refcount_destroy(&arc_mfu->arcs_size);
7719 zfs_refcount_destroy(&arc_mfu_ghost->arcs_size);
7720 zfs_refcount_destroy(&arc_l2c_only->arcs_size);
7722 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
7723 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
7724 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
7725 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
7726 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
7727 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
7728 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
7729 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
7730 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]);
7731 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_DATA]);
7733 aggsum_fini(&arc_meta_used);
7734 aggsum_fini(&arc_size);
7735 aggsum_fini(&astat_data_size);
7736 aggsum_fini(&astat_metadata_size);
7737 aggsum_fini(&astat_hdr_size);
7738 aggsum_fini(&astat_l2_hdr_size);
7739 aggsum_fini(&astat_bonus_size);
7740 aggsum_fini(&astat_dnode_size);
7741 aggsum_fini(&astat_dbuf_size);
7745 arc_target_bytes(void)
7753 uint64_t percent, allmem = arc_all_memory();
7754 mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL);
7755 cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL);
7757 arc_min_prefetch_ms = 1000;
7758 arc_min_prescient_prefetch_ms = 6000;
7762 * Register a shrinker to support synchronous (direct) memory
7763 * reclaim from the arc. This is done to prevent kswapd from
7764 * swapping out pages when it is preferable to shrink the arc.
7766 spl_register_shrinker(&arc_shrinker);
7768 /* Set to 1/64 of all memory or a minimum of 512K */
7769 arc_sys_free = MAX(allmem / 64, (512 * 1024));
7773 /* Set max to 1/2 of all memory */
7774 arc_c_max = allmem / 2;
7777 /* Set min cache to 1/32 of all memory, or 32MB, whichever is more */
7778 arc_c_min = MAX(allmem / 32, 2ULL << SPA_MAXBLOCKSHIFT);
7781 * In userland, there's only the memory pressure that we artificially
7782 * create (see arc_available_memory()). Don't let arc_c get too
7783 * small, because it can cause transactions to be larger than
7784 * arc_c, causing arc_tempreserve_space() to fail.
7786 arc_c_min = MAX(arc_c_max / 2, 2ULL << SPA_MAXBLOCKSHIFT);
7790 arc_p = (arc_c >> 1);
7792 /* Set min to 1/2 of arc_c_min */
7793 arc_meta_min = 1ULL << SPA_MAXBLOCKSHIFT;
7794 /* Initialize maximum observed usage to zero */
7797 * Set arc_meta_limit to a percent of arc_c_max with a floor of
7798 * arc_meta_min, and a ceiling of arc_c_max.
7800 percent = MIN(zfs_arc_meta_limit_percent, 100);
7801 arc_meta_limit = MAX(arc_meta_min, (percent * arc_c_max) / 100);
7802 percent = MIN(zfs_arc_dnode_limit_percent, 100);
7803 arc_dnode_limit = (percent * arc_meta_limit) / 100;
7805 /* Apply user specified tunings */
7806 arc_tuning_update();
7808 /* if kmem_flags are set, lets try to use less memory */
7809 if (kmem_debugging())
7811 if (arc_c < arc_c_min)
7817 * The arc must be "uninitialized", so that hdr_recl() (which is
7818 * registered by buf_init()) will not access arc_reap_zthr before
7821 ASSERT(!arc_initialized);
7824 list_create(&arc_prune_list, sizeof (arc_prune_t),
7825 offsetof(arc_prune_t, p_node));
7826 mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
7828 arc_prune_taskq = taskq_create("arc_prune", max_ncpus, defclsyspri,
7829 max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
7831 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
7832 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
7834 if (arc_ksp != NULL) {
7835 arc_ksp->ks_data = &arc_stats;
7836 arc_ksp->ks_update = arc_kstat_update;
7837 kstat_install(arc_ksp);
7840 arc_adjust_zthr = zthr_create(arc_adjust_cb_check,
7841 arc_adjust_cb, NULL);
7842 arc_reap_zthr = zthr_create_timer(arc_reap_cb_check,
7843 arc_reap_cb, NULL, SEC2NSEC(1));
7845 arc_initialized = B_TRUE;
7849 * Calculate maximum amount of dirty data per pool.
7851 * If it has been set by a module parameter, take that.
7852 * Otherwise, use a percentage of physical memory defined by
7853 * zfs_dirty_data_max_percent (default 10%) with a cap at
7854 * zfs_dirty_data_max_max (default 4G or 25% of physical memory).
7856 if (zfs_dirty_data_max_max == 0)
7857 zfs_dirty_data_max_max = MIN(4ULL * 1024 * 1024 * 1024,
7858 allmem * zfs_dirty_data_max_max_percent / 100);
7860 if (zfs_dirty_data_max == 0) {
7861 zfs_dirty_data_max = allmem *
7862 zfs_dirty_data_max_percent / 100;
7863 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
7864 zfs_dirty_data_max_max);
7874 spl_unregister_shrinker(&arc_shrinker);
7875 #endif /* _KERNEL */
7877 /* Use B_TRUE to ensure *all* buffers are evicted */
7878 arc_flush(NULL, B_TRUE);
7880 arc_initialized = B_FALSE;
7882 if (arc_ksp != NULL) {
7883 kstat_delete(arc_ksp);
7887 taskq_wait(arc_prune_taskq);
7888 taskq_destroy(arc_prune_taskq);
7890 mutex_enter(&arc_prune_mtx);
7891 while ((p = list_head(&arc_prune_list)) != NULL) {
7892 list_remove(&arc_prune_list, p);
7893 zfs_refcount_remove(&p->p_refcnt, &arc_prune_list);
7894 zfs_refcount_destroy(&p->p_refcnt);
7895 kmem_free(p, sizeof (*p));
7897 mutex_exit(&arc_prune_mtx);
7899 list_destroy(&arc_prune_list);
7900 mutex_destroy(&arc_prune_mtx);
7901 (void) zthr_cancel(arc_adjust_zthr);
7902 zthr_destroy(arc_adjust_zthr);
7904 (void) zthr_cancel(arc_reap_zthr);
7905 zthr_destroy(arc_reap_zthr);
7907 mutex_destroy(&arc_adjust_lock);
7908 cv_destroy(&arc_adjust_waiters_cv);
7911 * buf_fini() must proceed arc_state_fini() because buf_fin() may
7912 * trigger the release of kmem magazines, which can callback to
7913 * arc_space_return() which accesses aggsums freed in act_state_fini().
7918 ASSERT0(arc_loaned_bytes);
7924 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
7925 * It uses dedicated storage devices to hold cached data, which are populated
7926 * using large infrequent writes. The main role of this cache is to boost
7927 * the performance of random read workloads. The intended L2ARC devices
7928 * include short-stroked disks, solid state disks, and other media with
7929 * substantially faster read latency than disk.
7931 * +-----------------------+
7933 * +-----------------------+
7936 * l2arc_feed_thread() arc_read()
7940 * +---------------+ |
7942 * +---------------+ |
7947 * +-------+ +-------+
7949 * | cache | | cache |
7950 * +-------+ +-------+
7951 * +=========+ .-----.
7952 * : L2ARC : |-_____-|
7953 * : devices : | Disks |
7954 * +=========+ `-_____-'
7956 * Read requests are satisfied from the following sources, in order:
7959 * 2) vdev cache of L2ARC devices
7961 * 4) vdev cache of disks
7964 * Some L2ARC device types exhibit extremely slow write performance.
7965 * To accommodate for this there are some significant differences between
7966 * the L2ARC and traditional cache design:
7968 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
7969 * the ARC behave as usual, freeing buffers and placing headers on ghost
7970 * lists. The ARC does not send buffers to the L2ARC during eviction as
7971 * this would add inflated write latencies for all ARC memory pressure.
7973 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
7974 * It does this by periodically scanning buffers from the eviction-end of
7975 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
7976 * not already there. It scans until a headroom of buffers is satisfied,
7977 * which itself is a buffer for ARC eviction. If a compressible buffer is
7978 * found during scanning and selected for writing to an L2ARC device, we
7979 * temporarily boost scanning headroom during the next scan cycle to make
7980 * sure we adapt to compression effects (which might significantly reduce
7981 * the data volume we write to L2ARC). The thread that does this is
7982 * l2arc_feed_thread(), illustrated below; example sizes are included to
7983 * provide a better sense of ratio than this diagram:
7986 * +---------------------+----------+
7987 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
7988 * +---------------------+----------+ | o L2ARC eligible
7989 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
7990 * +---------------------+----------+ |
7991 * 15.9 Gbytes ^ 32 Mbytes |
7993 * l2arc_feed_thread()
7995 * l2arc write hand <--[oooo]--'
7999 * +==============================+
8000 * L2ARC dev |####|#|###|###| |####| ... |
8001 * +==============================+
8004 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
8005 * evicted, then the L2ARC has cached a buffer much sooner than it probably
8006 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
8007 * safe to say that this is an uncommon case, since buffers at the end of
8008 * the ARC lists have moved there due to inactivity.
8010 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
8011 * then the L2ARC simply misses copying some buffers. This serves as a
8012 * pressure valve to prevent heavy read workloads from both stalling the ARC
8013 * with waits and clogging the L2ARC with writes. This also helps prevent
8014 * the potential for the L2ARC to churn if it attempts to cache content too
8015 * quickly, such as during backups of the entire pool.
8017 * 5. After system boot and before the ARC has filled main memory, there are
8018 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
8019 * lists can remain mostly static. Instead of searching from tail of these
8020 * lists as pictured, the l2arc_feed_thread() will search from the list heads
8021 * for eligible buffers, greatly increasing its chance of finding them.
8023 * The L2ARC device write speed is also boosted during this time so that
8024 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
8025 * there are no L2ARC reads, and no fear of degrading read performance
8026 * through increased writes.
8028 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
8029 * the vdev queue can aggregate them into larger and fewer writes. Each
8030 * device is written to in a rotor fashion, sweeping writes through
8031 * available space then repeating.
8033 * 7. The L2ARC does not store dirty content. It never needs to flush
8034 * write buffers back to disk based storage.
8036 * 8. If an ARC buffer is written (and dirtied) which also exists in the
8037 * L2ARC, the now stale L2ARC buffer is immediately dropped.
8039 * The performance of the L2ARC can be tweaked by a number of tunables, which
8040 * may be necessary for different workloads:
8042 * l2arc_write_max max write bytes per interval
8043 * l2arc_write_boost extra write bytes during device warmup
8044 * l2arc_noprefetch skip caching prefetched buffers
8045 * l2arc_headroom number of max device writes to precache
8046 * l2arc_headroom_boost when we find compressed buffers during ARC
8047 * scanning, we multiply headroom by this
8048 * percentage factor for the next scan cycle,
8049 * since more compressed buffers are likely to
8051 * l2arc_feed_secs seconds between L2ARC writing
8053 * Tunables may be removed or added as future performance improvements are
8054 * integrated, and also may become zpool properties.
8056 * There are three key functions that control how the L2ARC warms up:
8058 * l2arc_write_eligible() check if a buffer is eligible to cache
8059 * l2arc_write_size() calculate how much to write
8060 * l2arc_write_interval() calculate sleep delay between writes
8062 * These three functions determine what to write, how much, and how quickly
8067 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
8070 * A buffer is *not* eligible for the L2ARC if it:
8071 * 1. belongs to a different spa.
8072 * 2. is already cached on the L2ARC.
8073 * 3. has an I/O in progress (it may be an incomplete read).
8074 * 4. is flagged not eligible (zfs property).
8076 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
8077 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
8084 l2arc_write_size(void)
8089 * Make sure our globals have meaningful values in case the user
8092 size = l2arc_write_max;
8094 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
8095 "be greater than zero, resetting it to the default (%d)",
8097 size = l2arc_write_max = L2ARC_WRITE_SIZE;
8100 if (arc_warm == B_FALSE)
8101 size += l2arc_write_boost;
8108 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
8110 clock_t interval, next, now;
8113 * If the ARC lists are busy, increase our write rate; if the
8114 * lists are stale, idle back. This is achieved by checking
8115 * how much we previously wrote - if it was more than half of
8116 * what we wanted, schedule the next write much sooner.
8118 if (l2arc_feed_again && wrote > (wanted / 2))
8119 interval = (hz * l2arc_feed_min_ms) / 1000;
8121 interval = hz * l2arc_feed_secs;
8123 now = ddi_get_lbolt();
8124 next = MAX(now, MIN(now + interval, began + interval));
8130 * Cycle through L2ARC devices. This is how L2ARC load balances.
8131 * If a device is returned, this also returns holding the spa config lock.
8133 static l2arc_dev_t *
8134 l2arc_dev_get_next(void)
8136 l2arc_dev_t *first, *next = NULL;
8139 * Lock out the removal of spas (spa_namespace_lock), then removal
8140 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
8141 * both locks will be dropped and a spa config lock held instead.
8143 mutex_enter(&spa_namespace_lock);
8144 mutex_enter(&l2arc_dev_mtx);
8146 /* if there are no vdevs, there is nothing to do */
8147 if (l2arc_ndev == 0)
8151 next = l2arc_dev_last;
8153 /* loop around the list looking for a non-faulted vdev */
8155 next = list_head(l2arc_dev_list);
8157 next = list_next(l2arc_dev_list, next);
8159 next = list_head(l2arc_dev_list);
8162 /* if we have come back to the start, bail out */
8165 else if (next == first)
8168 } while (vdev_is_dead(next->l2ad_vdev));
8170 /* if we were unable to find any usable vdevs, return NULL */
8171 if (vdev_is_dead(next->l2ad_vdev))
8174 l2arc_dev_last = next;
8177 mutex_exit(&l2arc_dev_mtx);
8180 * Grab the config lock to prevent the 'next' device from being
8181 * removed while we are writing to it.
8184 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
8185 mutex_exit(&spa_namespace_lock);
8191 * Free buffers that were tagged for destruction.
8194 l2arc_do_free_on_write(void)
8197 l2arc_data_free_t *df, *df_prev;
8199 mutex_enter(&l2arc_free_on_write_mtx);
8200 buflist = l2arc_free_on_write;
8202 for (df = list_tail(buflist); df; df = df_prev) {
8203 df_prev = list_prev(buflist, df);
8204 ASSERT3P(df->l2df_abd, !=, NULL);
8205 abd_free(df->l2df_abd);
8206 list_remove(buflist, df);
8207 kmem_free(df, sizeof (l2arc_data_free_t));
8210 mutex_exit(&l2arc_free_on_write_mtx);
8214 * A write to a cache device has completed. Update all headers to allow
8215 * reads from these buffers to begin.
8218 l2arc_write_done(zio_t *zio)
8220 l2arc_write_callback_t *cb;
8223 arc_buf_hdr_t *head, *hdr, *hdr_prev;
8224 kmutex_t *hash_lock;
8225 int64_t bytes_dropped = 0;
8227 cb = zio->io_private;
8228 ASSERT3P(cb, !=, NULL);
8229 dev = cb->l2wcb_dev;
8230 ASSERT3P(dev, !=, NULL);
8231 head = cb->l2wcb_head;
8232 ASSERT3P(head, !=, NULL);
8233 buflist = &dev->l2ad_buflist;
8234 ASSERT3P(buflist, !=, NULL);
8235 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
8236 l2arc_write_callback_t *, cb);
8238 if (zio->io_error != 0)
8239 ARCSTAT_BUMP(arcstat_l2_writes_error);
8242 * All writes completed, or an error was hit.
8245 mutex_enter(&dev->l2ad_mtx);
8246 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
8247 hdr_prev = list_prev(buflist, hdr);
8249 hash_lock = HDR_LOCK(hdr);
8252 * We cannot use mutex_enter or else we can deadlock
8253 * with l2arc_write_buffers (due to swapping the order
8254 * the hash lock and l2ad_mtx are taken).
8256 if (!mutex_tryenter(hash_lock)) {
8258 * Missed the hash lock. We must retry so we
8259 * don't leave the ARC_FLAG_L2_WRITING bit set.
8261 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
8264 * We don't want to rescan the headers we've
8265 * already marked as having been written out, so
8266 * we reinsert the head node so we can pick up
8267 * where we left off.
8269 list_remove(buflist, head);
8270 list_insert_after(buflist, hdr, head);
8272 mutex_exit(&dev->l2ad_mtx);
8275 * We wait for the hash lock to become available
8276 * to try and prevent busy waiting, and increase
8277 * the chance we'll be able to acquire the lock
8278 * the next time around.
8280 mutex_enter(hash_lock);
8281 mutex_exit(hash_lock);
8286 * We could not have been moved into the arc_l2c_only
8287 * state while in-flight due to our ARC_FLAG_L2_WRITING
8288 * bit being set. Let's just ensure that's being enforced.
8290 ASSERT(HDR_HAS_L1HDR(hdr));
8293 * Skipped - drop L2ARC entry and mark the header as no
8294 * longer L2 eligibile.
8296 if (zio->io_error != 0) {
8298 * Error - drop L2ARC entry.
8300 list_remove(buflist, hdr);
8301 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
8303 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr));
8304 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
8306 bytes_dropped += arc_hdr_size(hdr);
8307 (void) zfs_refcount_remove_many(&dev->l2ad_alloc,
8308 arc_hdr_size(hdr), hdr);
8312 * Allow ARC to begin reads and ghost list evictions to
8315 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
8317 mutex_exit(hash_lock);
8320 atomic_inc_64(&l2arc_writes_done);
8321 list_remove(buflist, head);
8322 ASSERT(!HDR_HAS_L1HDR(head));
8323 kmem_cache_free(hdr_l2only_cache, head);
8324 mutex_exit(&dev->l2ad_mtx);
8326 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
8328 l2arc_do_free_on_write();
8330 kmem_free(cb, sizeof (l2arc_write_callback_t));
8334 l2arc_untransform(zio_t *zio, l2arc_read_callback_t *cb)
8337 spa_t *spa = zio->io_spa;
8338 arc_buf_hdr_t *hdr = cb->l2rcb_hdr;
8339 blkptr_t *bp = zio->io_bp;
8340 uint8_t salt[ZIO_DATA_SALT_LEN];
8341 uint8_t iv[ZIO_DATA_IV_LEN];
8342 uint8_t mac[ZIO_DATA_MAC_LEN];
8343 boolean_t no_crypt = B_FALSE;
8346 * ZIL data is never be written to the L2ARC, so we don't need
8347 * special handling for its unique MAC storage.
8349 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
8350 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
8351 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
8354 * If the data was encrypted, decrypt it now. Note that
8355 * we must check the bp here and not the hdr, since the
8356 * hdr does not have its encryption parameters updated
8357 * until arc_read_done().
8359 if (BP_IS_ENCRYPTED(bp)) {
8360 abd_t *eabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
8362 zio_crypt_decode_params_bp(bp, salt, iv);
8363 zio_crypt_decode_mac_bp(bp, mac);
8365 ret = spa_do_crypt_abd(B_FALSE, spa, &cb->l2rcb_zb,
8366 BP_GET_TYPE(bp), BP_GET_DEDUP(bp), BP_SHOULD_BYTESWAP(bp),
8367 salt, iv, mac, HDR_GET_PSIZE(hdr), eabd,
8368 hdr->b_l1hdr.b_pabd, &no_crypt);
8370 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
8375 * If we actually performed decryption, replace b_pabd
8376 * with the decrypted data. Otherwise we can just throw
8377 * our decryption buffer away.
8380 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
8381 arc_hdr_size(hdr), hdr);
8382 hdr->b_l1hdr.b_pabd = eabd;
8385 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
8390 * If the L2ARC block was compressed, but ARC compression
8391 * is disabled we decompress the data into a new buffer and
8392 * replace the existing data.
8394 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
8395 !HDR_COMPRESSION_ENABLED(hdr)) {
8396 abd_t *cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
8397 void *tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
8399 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
8400 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
8401 HDR_GET_LSIZE(hdr));
8403 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
8404 arc_free_data_abd(hdr, cabd, arc_hdr_size(hdr), hdr);
8408 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
8409 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
8410 arc_hdr_size(hdr), hdr);
8411 hdr->b_l1hdr.b_pabd = cabd;
8413 zio->io_size = HDR_GET_LSIZE(hdr);
8424 * A read to a cache device completed. Validate buffer contents before
8425 * handing over to the regular ARC routines.
8428 l2arc_read_done(zio_t *zio)
8431 l2arc_read_callback_t *cb = zio->io_private;
8433 kmutex_t *hash_lock;
8434 boolean_t valid_cksum;
8435 boolean_t using_rdata = (BP_IS_ENCRYPTED(&cb->l2rcb_bp) &&
8436 (cb->l2rcb_flags & ZIO_FLAG_RAW_ENCRYPT));
8438 ASSERT3P(zio->io_vd, !=, NULL);
8439 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
8441 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
8443 ASSERT3P(cb, !=, NULL);
8444 hdr = cb->l2rcb_hdr;
8445 ASSERT3P(hdr, !=, NULL);
8447 hash_lock = HDR_LOCK(hdr);
8448 mutex_enter(hash_lock);
8449 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
8452 * If the data was read into a temporary buffer,
8453 * move it and free the buffer.
8455 if (cb->l2rcb_abd != NULL) {
8456 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
8457 if (zio->io_error == 0) {
8459 abd_copy(hdr->b_crypt_hdr.b_rabd,
8460 cb->l2rcb_abd, arc_hdr_size(hdr));
8462 abd_copy(hdr->b_l1hdr.b_pabd,
8463 cb->l2rcb_abd, arc_hdr_size(hdr));
8468 * The following must be done regardless of whether
8469 * there was an error:
8470 * - free the temporary buffer
8471 * - point zio to the real ARC buffer
8472 * - set zio size accordingly
8473 * These are required because zio is either re-used for
8474 * an I/O of the block in the case of the error
8475 * or the zio is passed to arc_read_done() and it
8478 abd_free(cb->l2rcb_abd);
8479 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
8482 ASSERT(HDR_HAS_RABD(hdr));
8483 zio->io_abd = zio->io_orig_abd =
8484 hdr->b_crypt_hdr.b_rabd;
8486 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
8487 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
8491 ASSERT3P(zio->io_abd, !=, NULL);
8494 * Check this survived the L2ARC journey.
8496 ASSERT(zio->io_abd == hdr->b_l1hdr.b_pabd ||
8497 (HDR_HAS_RABD(hdr) && zio->io_abd == hdr->b_crypt_hdr.b_rabd));
8498 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
8499 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
8501 valid_cksum = arc_cksum_is_equal(hdr, zio);
8504 * b_rabd will always match the data as it exists on disk if it is
8505 * being used. Therefore if we are reading into b_rabd we do not
8506 * attempt to untransform the data.
8508 if (valid_cksum && !using_rdata)
8509 tfm_error = l2arc_untransform(zio, cb);
8511 if (valid_cksum && tfm_error == 0 && zio->io_error == 0 &&
8512 !HDR_L2_EVICTED(hdr)) {
8513 mutex_exit(hash_lock);
8514 zio->io_private = hdr;
8517 mutex_exit(hash_lock);
8519 * Buffer didn't survive caching. Increment stats and
8520 * reissue to the original storage device.
8522 if (zio->io_error != 0) {
8523 ARCSTAT_BUMP(arcstat_l2_io_error);
8525 zio->io_error = SET_ERROR(EIO);
8527 if (!valid_cksum || tfm_error != 0)
8528 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
8531 * If there's no waiter, issue an async i/o to the primary
8532 * storage now. If there *is* a waiter, the caller must
8533 * issue the i/o in a context where it's OK to block.
8535 if (zio->io_waiter == NULL) {
8536 zio_t *pio = zio_unique_parent(zio);
8537 void *abd = (using_rdata) ?
8538 hdr->b_crypt_hdr.b_rabd : hdr->b_l1hdr.b_pabd;
8540 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
8542 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
8543 abd, zio->io_size, arc_read_done,
8544 hdr, zio->io_priority, cb->l2rcb_flags,
8549 kmem_free(cb, sizeof (l2arc_read_callback_t));
8553 * This is the list priority from which the L2ARC will search for pages to
8554 * cache. This is used within loops (0..3) to cycle through lists in the
8555 * desired order. This order can have a significant effect on cache
8558 * Currently the metadata lists are hit first, MFU then MRU, followed by
8559 * the data lists. This function returns a locked list, and also returns
8562 static multilist_sublist_t *
8563 l2arc_sublist_lock(int list_num)
8565 multilist_t *ml = NULL;
8568 ASSERT(list_num >= 0 && list_num < L2ARC_FEED_TYPES);
8572 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
8575 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
8578 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
8581 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
8588 * Return a randomly-selected sublist. This is acceptable
8589 * because the caller feeds only a little bit of data for each
8590 * call (8MB). Subsequent calls will result in different
8591 * sublists being selected.
8593 idx = multilist_get_random_index(ml);
8594 return (multilist_sublist_lock(ml, idx));
8598 * Evict buffers from the device write hand to the distance specified in
8599 * bytes. This distance may span populated buffers, it may span nothing.
8600 * This is clearing a region on the L2ARC device ready for writing.
8601 * If the 'all' boolean is set, every buffer is evicted.
8604 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
8607 arc_buf_hdr_t *hdr, *hdr_prev;
8608 kmutex_t *hash_lock;
8611 buflist = &dev->l2ad_buflist;
8613 if (!all && dev->l2ad_first) {
8615 * This is the first sweep through the device. There is
8621 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
8623 * When nearing the end of the device, evict to the end
8624 * before the device write hand jumps to the start.
8626 taddr = dev->l2ad_end;
8628 taddr = dev->l2ad_hand + distance;
8630 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
8631 uint64_t, taddr, boolean_t, all);
8634 mutex_enter(&dev->l2ad_mtx);
8635 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
8636 hdr_prev = list_prev(buflist, hdr);
8638 hash_lock = HDR_LOCK(hdr);
8641 * We cannot use mutex_enter or else we can deadlock
8642 * with l2arc_write_buffers (due to swapping the order
8643 * the hash lock and l2ad_mtx are taken).
8645 if (!mutex_tryenter(hash_lock)) {
8647 * Missed the hash lock. Retry.
8649 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
8650 mutex_exit(&dev->l2ad_mtx);
8651 mutex_enter(hash_lock);
8652 mutex_exit(hash_lock);
8657 * A header can't be on this list if it doesn't have L2 header.
8659 ASSERT(HDR_HAS_L2HDR(hdr));
8661 /* Ensure this header has finished being written. */
8662 ASSERT(!HDR_L2_WRITING(hdr));
8663 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
8665 if (!all && (hdr->b_l2hdr.b_daddr >= taddr ||
8666 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
8668 * We've evicted to the target address,
8669 * or the end of the device.
8671 mutex_exit(hash_lock);
8675 if (!HDR_HAS_L1HDR(hdr)) {
8676 ASSERT(!HDR_L2_READING(hdr));
8678 * This doesn't exist in the ARC. Destroy.
8679 * arc_hdr_destroy() will call list_remove()
8680 * and decrement arcstat_l2_lsize.
8682 arc_change_state(arc_anon, hdr, hash_lock);
8683 arc_hdr_destroy(hdr);
8685 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
8686 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
8688 * Invalidate issued or about to be issued
8689 * reads, since we may be about to write
8690 * over this location.
8692 if (HDR_L2_READING(hdr)) {
8693 ARCSTAT_BUMP(arcstat_l2_evict_reading);
8694 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
8697 arc_hdr_l2hdr_destroy(hdr);
8699 mutex_exit(hash_lock);
8701 mutex_exit(&dev->l2ad_mtx);
8705 * Handle any abd transforms that might be required for writing to the L2ARC.
8706 * If successful, this function will always return an abd with the data
8707 * transformed as it is on disk in a new abd of asize bytes.
8710 l2arc_apply_transforms(spa_t *spa, arc_buf_hdr_t *hdr, uint64_t asize,
8715 abd_t *cabd = NULL, *eabd = NULL, *to_write = hdr->b_l1hdr.b_pabd;
8716 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
8717 uint64_t psize = HDR_GET_PSIZE(hdr);
8718 uint64_t size = arc_hdr_size(hdr);
8719 boolean_t ismd = HDR_ISTYPE_METADATA(hdr);
8720 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
8721 dsl_crypto_key_t *dck = NULL;
8722 uint8_t mac[ZIO_DATA_MAC_LEN] = { 0 };
8723 boolean_t no_crypt = B_FALSE;
8725 ASSERT((HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
8726 !HDR_COMPRESSION_ENABLED(hdr)) ||
8727 HDR_ENCRYPTED(hdr) || HDR_SHARED_DATA(hdr) || psize != asize);
8728 ASSERT3U(psize, <=, asize);
8731 * If this data simply needs its own buffer, we simply allocate it
8732 * and copy the data. This may be done to elimiate a depedency on a
8733 * shared buffer or to reallocate the buffer to match asize.
8735 if (HDR_HAS_RABD(hdr) && asize != psize) {
8736 ASSERT3U(asize, >=, psize);
8737 to_write = abd_alloc_for_io(asize, ismd);
8738 abd_copy(to_write, hdr->b_crypt_hdr.b_rabd, psize);
8740 abd_zero_off(to_write, psize, asize - psize);
8744 if ((compress == ZIO_COMPRESS_OFF || HDR_COMPRESSION_ENABLED(hdr)) &&
8745 !HDR_ENCRYPTED(hdr)) {
8746 ASSERT3U(size, ==, psize);
8747 to_write = abd_alloc_for_io(asize, ismd);
8748 abd_copy(to_write, hdr->b_l1hdr.b_pabd, size);
8750 abd_zero_off(to_write, size, asize - size);
8754 if (compress != ZIO_COMPRESS_OFF && !HDR_COMPRESSION_ENABLED(hdr)) {
8755 cabd = abd_alloc_for_io(asize, ismd);
8756 tmp = abd_borrow_buf(cabd, asize);
8758 psize = zio_compress_data(compress, to_write, tmp, size);
8759 ASSERT3U(psize, <=, HDR_GET_PSIZE(hdr));
8761 bzero((char *)tmp + psize, asize - psize);
8762 psize = HDR_GET_PSIZE(hdr);
8763 abd_return_buf_copy(cabd, tmp, asize);
8767 if (HDR_ENCRYPTED(hdr)) {
8768 eabd = abd_alloc_for_io(asize, ismd);
8771 * If the dataset was disowned before the buffer
8772 * made it to this point, the key to re-encrypt
8773 * it won't be available. In this case we simply
8774 * won't write the buffer to the L2ARC.
8776 ret = spa_keystore_lookup_key(spa, hdr->b_crypt_hdr.b_dsobj,
8781 ret = zio_do_crypt_abd(B_TRUE, &dck->dck_key,
8782 hdr->b_crypt_hdr.b_ot, bswap, hdr->b_crypt_hdr.b_salt,
8783 hdr->b_crypt_hdr.b_iv, mac, psize, to_write, eabd,
8789 abd_copy(eabd, to_write, psize);
8792 abd_zero_off(eabd, psize, asize - psize);
8794 /* assert that the MAC we got here matches the one we saved */
8795 ASSERT0(bcmp(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN));
8796 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8798 if (to_write == cabd)
8805 ASSERT3P(to_write, !=, hdr->b_l1hdr.b_pabd);
8806 *abd_out = to_write;
8811 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8822 * Find and write ARC buffers to the L2ARC device.
8824 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
8825 * for reading until they have completed writing.
8826 * The headroom_boost is an in-out parameter used to maintain headroom boost
8827 * state between calls to this function.
8829 * Returns the number of bytes actually written (which may be smaller than
8830 * the delta by which the device hand has changed due to alignment).
8833 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
8835 arc_buf_hdr_t *hdr, *hdr_prev, *head;
8836 uint64_t write_asize, write_psize, write_lsize, headroom;
8838 l2arc_write_callback_t *cb;
8840 uint64_t guid = spa_load_guid(spa);
8842 ASSERT3P(dev->l2ad_vdev, !=, NULL);
8845 write_lsize = write_asize = write_psize = 0;
8847 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
8848 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
8851 * Copy buffers for L2ARC writing.
8853 for (int try = 0; try < L2ARC_FEED_TYPES; try++) {
8854 multilist_sublist_t *mls = l2arc_sublist_lock(try);
8855 uint64_t passed_sz = 0;
8857 VERIFY3P(mls, !=, NULL);
8860 * L2ARC fast warmup.
8862 * Until the ARC is warm and starts to evict, read from the
8863 * head of the ARC lists rather than the tail.
8865 if (arc_warm == B_FALSE)
8866 hdr = multilist_sublist_head(mls);
8868 hdr = multilist_sublist_tail(mls);
8870 headroom = target_sz * l2arc_headroom;
8871 if (zfs_compressed_arc_enabled)
8872 headroom = (headroom * l2arc_headroom_boost) / 100;
8874 for (; hdr; hdr = hdr_prev) {
8875 kmutex_t *hash_lock;
8876 abd_t *to_write = NULL;
8878 if (arc_warm == B_FALSE)
8879 hdr_prev = multilist_sublist_next(mls, hdr);
8881 hdr_prev = multilist_sublist_prev(mls, hdr);
8883 hash_lock = HDR_LOCK(hdr);
8884 if (!mutex_tryenter(hash_lock)) {
8886 * Skip this buffer rather than waiting.
8891 passed_sz += HDR_GET_LSIZE(hdr);
8892 if (passed_sz > headroom) {
8896 mutex_exit(hash_lock);
8900 if (!l2arc_write_eligible(guid, hdr)) {
8901 mutex_exit(hash_lock);
8906 * We rely on the L1 portion of the header below, so
8907 * it's invalid for this header to have been evicted out
8908 * of the ghost cache, prior to being written out. The
8909 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
8911 ASSERT(HDR_HAS_L1HDR(hdr));
8913 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
8914 ASSERT3U(arc_hdr_size(hdr), >, 0);
8915 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
8917 uint64_t psize = HDR_GET_PSIZE(hdr);
8918 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
8921 if ((write_asize + asize) > target_sz) {
8923 mutex_exit(hash_lock);
8928 * We rely on the L1 portion of the header below, so
8929 * it's invalid for this header to have been evicted out
8930 * of the ghost cache, prior to being written out. The
8931 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
8933 arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING);
8934 ASSERT(HDR_HAS_L1HDR(hdr));
8936 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
8937 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
8939 ASSERT3U(arc_hdr_size(hdr), >, 0);
8942 * If this header has b_rabd, we can use this since it
8943 * must always match the data exactly as it exists on
8944 * disk. Otherwise, the L2ARC can normally use the
8945 * hdr's data, but if we're sharing data between the
8946 * hdr and one of its bufs, L2ARC needs its own copy of
8947 * the data so that the ZIO below can't race with the
8948 * buf consumer. To ensure that this copy will be
8949 * available for the lifetime of the ZIO and be cleaned
8950 * up afterwards, we add it to the l2arc_free_on_write
8951 * queue. If we need to apply any transforms to the
8952 * data (compression, encryption) we will also need the
8955 if (HDR_HAS_RABD(hdr) && psize == asize) {
8956 to_write = hdr->b_crypt_hdr.b_rabd;
8957 } else if ((HDR_COMPRESSION_ENABLED(hdr) ||
8958 HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) &&
8959 !HDR_ENCRYPTED(hdr) && !HDR_SHARED_DATA(hdr) &&
8961 to_write = hdr->b_l1hdr.b_pabd;
8964 arc_buf_contents_t type = arc_buf_type(hdr);
8966 ret = l2arc_apply_transforms(spa, hdr, asize,
8969 arc_hdr_clear_flags(hdr,
8970 ARC_FLAG_L2_WRITING);
8971 mutex_exit(hash_lock);
8975 l2arc_free_abd_on_write(to_write, asize, type);
8980 * Insert a dummy header on the buflist so
8981 * l2arc_write_done() can find where the
8982 * write buffers begin without searching.
8984 mutex_enter(&dev->l2ad_mtx);
8985 list_insert_head(&dev->l2ad_buflist, head);
8986 mutex_exit(&dev->l2ad_mtx);
8989 sizeof (l2arc_write_callback_t), KM_SLEEP);
8990 cb->l2wcb_dev = dev;
8991 cb->l2wcb_head = head;
8992 pio = zio_root(spa, l2arc_write_done, cb,
8996 hdr->b_l2hdr.b_dev = dev;
8997 hdr->b_l2hdr.b_hits = 0;
8999 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
9000 arc_hdr_set_flags(hdr, ARC_FLAG_HAS_L2HDR);
9002 mutex_enter(&dev->l2ad_mtx);
9003 list_insert_head(&dev->l2ad_buflist, hdr);
9004 mutex_exit(&dev->l2ad_mtx);
9006 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
9007 arc_hdr_size(hdr), hdr);
9009 wzio = zio_write_phys(pio, dev->l2ad_vdev,
9010 hdr->b_l2hdr.b_daddr, asize, to_write,
9011 ZIO_CHECKSUM_OFF, NULL, hdr,
9012 ZIO_PRIORITY_ASYNC_WRITE,
9013 ZIO_FLAG_CANFAIL, B_FALSE);
9015 write_lsize += HDR_GET_LSIZE(hdr);
9016 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
9019 write_psize += psize;
9020 write_asize += asize;
9021 dev->l2ad_hand += asize;
9023 mutex_exit(hash_lock);
9025 (void) zio_nowait(wzio);
9028 multilist_sublist_unlock(mls);
9034 /* No buffers selected for writing? */
9036 ASSERT0(write_lsize);
9037 ASSERT(!HDR_HAS_L1HDR(head));
9038 kmem_cache_free(hdr_l2only_cache, head);
9042 ASSERT3U(write_asize, <=, target_sz);
9043 ARCSTAT_BUMP(arcstat_l2_writes_sent);
9044 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
9045 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
9046 ARCSTAT_INCR(arcstat_l2_psize, write_psize);
9047 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
9050 * Bump device hand to the device start if it is approaching the end.
9051 * l2arc_evict() will already have evicted ahead for this case.
9053 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
9054 dev->l2ad_hand = dev->l2ad_start;
9055 dev->l2ad_first = B_FALSE;
9058 dev->l2ad_writing = B_TRUE;
9059 (void) zio_wait(pio);
9060 dev->l2ad_writing = B_FALSE;
9062 return (write_asize);
9066 * This thread feeds the L2ARC at regular intervals. This is the beating
9067 * heart of the L2ARC.
9071 l2arc_feed_thread(void *unused)
9076 uint64_t size, wrote;
9077 clock_t begin, next = ddi_get_lbolt();
9078 fstrans_cookie_t cookie;
9080 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
9082 mutex_enter(&l2arc_feed_thr_lock);
9084 cookie = spl_fstrans_mark();
9085 while (l2arc_thread_exit == 0) {
9086 CALLB_CPR_SAFE_BEGIN(&cpr);
9087 (void) cv_timedwait_sig(&l2arc_feed_thr_cv,
9088 &l2arc_feed_thr_lock, next);
9089 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
9090 next = ddi_get_lbolt() + hz;
9093 * Quick check for L2ARC devices.
9095 mutex_enter(&l2arc_dev_mtx);
9096 if (l2arc_ndev == 0) {
9097 mutex_exit(&l2arc_dev_mtx);
9100 mutex_exit(&l2arc_dev_mtx);
9101 begin = ddi_get_lbolt();
9104 * This selects the next l2arc device to write to, and in
9105 * doing so the next spa to feed from: dev->l2ad_spa. This
9106 * will return NULL if there are now no l2arc devices or if
9107 * they are all faulted.
9109 * If a device is returned, its spa's config lock is also
9110 * held to prevent device removal. l2arc_dev_get_next()
9111 * will grab and release l2arc_dev_mtx.
9113 if ((dev = l2arc_dev_get_next()) == NULL)
9116 spa = dev->l2ad_spa;
9117 ASSERT3P(spa, !=, NULL);
9120 * If the pool is read-only then force the feed thread to
9121 * sleep a little longer.
9123 if (!spa_writeable(spa)) {
9124 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
9125 spa_config_exit(spa, SCL_L2ARC, dev);
9130 * Avoid contributing to memory pressure.
9132 if (arc_reclaim_needed()) {
9133 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
9134 spa_config_exit(spa, SCL_L2ARC, dev);
9138 ARCSTAT_BUMP(arcstat_l2_feeds);
9140 size = l2arc_write_size();
9143 * Evict L2ARC buffers that will be overwritten.
9145 l2arc_evict(dev, size, B_FALSE);
9148 * Write ARC buffers.
9150 wrote = l2arc_write_buffers(spa, dev, size);
9153 * Calculate interval between writes.
9155 next = l2arc_write_interval(begin, size, wrote);
9156 spa_config_exit(spa, SCL_L2ARC, dev);
9158 spl_fstrans_unmark(cookie);
9160 l2arc_thread_exit = 0;
9161 cv_broadcast(&l2arc_feed_thr_cv);
9162 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
9167 l2arc_vdev_present(vdev_t *vd)
9171 mutex_enter(&l2arc_dev_mtx);
9172 for (dev = list_head(l2arc_dev_list); dev != NULL;
9173 dev = list_next(l2arc_dev_list, dev)) {
9174 if (dev->l2ad_vdev == vd)
9177 mutex_exit(&l2arc_dev_mtx);
9179 return (dev != NULL);
9183 * Add a vdev for use by the L2ARC. By this point the spa has already
9184 * validated the vdev and opened it.
9187 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
9189 l2arc_dev_t *adddev;
9191 ASSERT(!l2arc_vdev_present(vd));
9194 * Create a new l2arc device entry.
9196 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
9197 adddev->l2ad_spa = spa;
9198 adddev->l2ad_vdev = vd;
9199 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
9200 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
9201 adddev->l2ad_hand = adddev->l2ad_start;
9202 adddev->l2ad_first = B_TRUE;
9203 adddev->l2ad_writing = B_FALSE;
9204 list_link_init(&adddev->l2ad_node);
9206 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
9208 * This is a list of all ARC buffers that are still valid on the
9211 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
9212 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
9214 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
9215 zfs_refcount_create(&adddev->l2ad_alloc);
9218 * Add device to global list
9220 mutex_enter(&l2arc_dev_mtx);
9221 list_insert_head(l2arc_dev_list, adddev);
9222 atomic_inc_64(&l2arc_ndev);
9223 mutex_exit(&l2arc_dev_mtx);
9227 * Remove a vdev from the L2ARC.
9230 l2arc_remove_vdev(vdev_t *vd)
9232 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
9235 * Find the device by vdev
9237 mutex_enter(&l2arc_dev_mtx);
9238 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
9239 nextdev = list_next(l2arc_dev_list, dev);
9240 if (vd == dev->l2ad_vdev) {
9245 ASSERT3P(remdev, !=, NULL);
9248 * Remove device from global list
9250 list_remove(l2arc_dev_list, remdev);
9251 l2arc_dev_last = NULL; /* may have been invalidated */
9252 atomic_dec_64(&l2arc_ndev);
9253 mutex_exit(&l2arc_dev_mtx);
9256 * Clear all buflists and ARC references. L2ARC device flush.
9258 l2arc_evict(remdev, 0, B_TRUE);
9259 list_destroy(&remdev->l2ad_buflist);
9260 mutex_destroy(&remdev->l2ad_mtx);
9261 zfs_refcount_destroy(&remdev->l2ad_alloc);
9262 kmem_free(remdev, sizeof (l2arc_dev_t));
9268 l2arc_thread_exit = 0;
9270 l2arc_writes_sent = 0;
9271 l2arc_writes_done = 0;
9273 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
9274 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
9275 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
9276 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
9278 l2arc_dev_list = &L2ARC_dev_list;
9279 l2arc_free_on_write = &L2ARC_free_on_write;
9280 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
9281 offsetof(l2arc_dev_t, l2ad_node));
9282 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
9283 offsetof(l2arc_data_free_t, l2df_list_node));
9290 * This is called from dmu_fini(), which is called from spa_fini();
9291 * Because of this, we can assume that all l2arc devices have
9292 * already been removed when the pools themselves were removed.
9295 l2arc_do_free_on_write();
9297 mutex_destroy(&l2arc_feed_thr_lock);
9298 cv_destroy(&l2arc_feed_thr_cv);
9299 mutex_destroy(&l2arc_dev_mtx);
9300 mutex_destroy(&l2arc_free_on_write_mtx);
9302 list_destroy(l2arc_dev_list);
9303 list_destroy(l2arc_free_on_write);
9309 if (!(spa_mode_global & FWRITE))
9312 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
9313 TS_RUN, defclsyspri);
9319 if (!(spa_mode_global & FWRITE))
9322 mutex_enter(&l2arc_feed_thr_lock);
9323 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
9324 l2arc_thread_exit = 1;
9325 while (l2arc_thread_exit != 0)
9326 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
9327 mutex_exit(&l2arc_feed_thr_lock);
9330 #if defined(_KERNEL)
9331 EXPORT_SYMBOL(arc_buf_size);
9332 EXPORT_SYMBOL(arc_write);
9333 EXPORT_SYMBOL(arc_read);
9334 EXPORT_SYMBOL(arc_buf_info);
9335 EXPORT_SYMBOL(arc_getbuf_func);
9336 EXPORT_SYMBOL(arc_add_prune_callback);
9337 EXPORT_SYMBOL(arc_remove_prune_callback);
9340 module_param(zfs_arc_min, ulong, 0644);
9341 MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
9343 module_param(zfs_arc_max, ulong, 0644);
9344 MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
9346 module_param(zfs_arc_meta_limit, ulong, 0644);
9347 MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
9349 module_param(zfs_arc_meta_limit_percent, ulong, 0644);
9350 MODULE_PARM_DESC(zfs_arc_meta_limit_percent,
9351 "Percent of arc size for arc meta limit");
9353 module_param(zfs_arc_meta_min, ulong, 0644);
9354 MODULE_PARM_DESC(zfs_arc_meta_min, "Min arc metadata");
9356 module_param(zfs_arc_meta_prune, int, 0644);
9357 MODULE_PARM_DESC(zfs_arc_meta_prune, "Meta objects to scan for prune");
9359 module_param(zfs_arc_meta_adjust_restarts, int, 0644);
9360 MODULE_PARM_DESC(zfs_arc_meta_adjust_restarts,
9361 "Limit number of restarts in arc_adjust_meta");
9363 module_param(zfs_arc_meta_strategy, int, 0644);
9364 MODULE_PARM_DESC(zfs_arc_meta_strategy, "Meta reclaim strategy");
9366 module_param(zfs_arc_grow_retry, int, 0644);
9367 MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
9369 module_param(zfs_arc_p_dampener_disable, int, 0644);
9370 MODULE_PARM_DESC(zfs_arc_p_dampener_disable, "disable arc_p adapt dampener");
9372 module_param(zfs_arc_shrink_shift, int, 0644);
9373 MODULE_PARM_DESC(zfs_arc_shrink_shift, "log2(fraction of arc to reclaim)");
9375 module_param(zfs_arc_pc_percent, uint, 0644);
9376 MODULE_PARM_DESC(zfs_arc_pc_percent,
9377 "Percent of pagecache to reclaim arc to");
9379 module_param(zfs_arc_p_min_shift, int, 0644);
9380 MODULE_PARM_DESC(zfs_arc_p_min_shift, "arc_c shift to calc min/max arc_p");
9382 module_param(zfs_arc_average_blocksize, int, 0444);
9383 MODULE_PARM_DESC(zfs_arc_average_blocksize, "Target average block size");
9385 module_param(zfs_compressed_arc_enabled, int, 0644);
9386 MODULE_PARM_DESC(zfs_compressed_arc_enabled, "Disable compressed arc buffers");
9388 module_param(zfs_arc_min_prefetch_ms, int, 0644);
9389 MODULE_PARM_DESC(zfs_arc_min_prefetch_ms, "Min life of prefetch block in ms");
9391 module_param(zfs_arc_min_prescient_prefetch_ms, int, 0644);
9392 MODULE_PARM_DESC(zfs_arc_min_prescient_prefetch_ms,
9393 "Min life of prescient prefetched block in ms");
9395 module_param(l2arc_write_max, ulong, 0644);
9396 MODULE_PARM_DESC(l2arc_write_max, "Max write bytes per interval");
9398 module_param(l2arc_write_boost, ulong, 0644);
9399 MODULE_PARM_DESC(l2arc_write_boost, "Extra write bytes during device warmup");
9401 module_param(l2arc_headroom, ulong, 0644);
9402 MODULE_PARM_DESC(l2arc_headroom, "Number of max device writes to precache");
9404 module_param(l2arc_headroom_boost, ulong, 0644);
9405 MODULE_PARM_DESC(l2arc_headroom_boost, "Compressed l2arc_headroom multiplier");
9407 module_param(l2arc_feed_secs, ulong, 0644);
9408 MODULE_PARM_DESC(l2arc_feed_secs, "Seconds between L2ARC writing");
9410 module_param(l2arc_feed_min_ms, ulong, 0644);
9411 MODULE_PARM_DESC(l2arc_feed_min_ms, "Min feed interval in milliseconds");
9413 module_param(l2arc_noprefetch, int, 0644);
9414 MODULE_PARM_DESC(l2arc_noprefetch, "Skip caching prefetched buffers");
9416 module_param(l2arc_feed_again, int, 0644);
9417 MODULE_PARM_DESC(l2arc_feed_again, "Turbo L2ARC warmup");
9419 module_param(l2arc_norw, int, 0644);
9420 MODULE_PARM_DESC(l2arc_norw, "No reads during writes");
9422 module_param(zfs_arc_lotsfree_percent, int, 0644);
9423 MODULE_PARM_DESC(zfs_arc_lotsfree_percent,
9424 "System free memory I/O throttle in bytes");
9426 module_param(zfs_arc_sys_free, ulong, 0644);
9427 MODULE_PARM_DESC(zfs_arc_sys_free, "System free memory target size in bytes");
9429 module_param(zfs_arc_dnode_limit, ulong, 0644);
9430 MODULE_PARM_DESC(zfs_arc_dnode_limit, "Minimum bytes of dnodes in arc");
9432 module_param(zfs_arc_dnode_limit_percent, ulong, 0644);
9433 MODULE_PARM_DESC(zfs_arc_dnode_limit_percent,
9434 "Percent of ARC meta buffers for dnodes");
9436 module_param(zfs_arc_dnode_reduce_percent, ulong, 0644);
9437 MODULE_PARM_DESC(zfs_arc_dnode_reduce_percent,
9438 "Percentage of excess dnodes to try to unpin");
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