4 * The contents of this file are subject to the terms of the
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10 * See the License for the specific language governing permissions
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13 * When distributing Covered Code, include this CDDL HEADER in each
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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, 2017 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved.
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 * Note that the majority of the performance stats are manipulated
103 * with atomic operations.
105 * The L2ARC uses the l2ad_mtx on each vdev for the following:
107 * - L2ARC buflist creation
108 * - L2ARC buflist eviction
109 * - L2ARC write completion, which walks L2ARC buflists
110 * - ARC header destruction, as it removes from L2ARC buflists
111 * - ARC header release, as it removes from L2ARC buflists
117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
118 * This structure can point either to a block that is still in the cache or to
119 * one that is only accessible in an L2 ARC device, or it can provide
120 * information about a block that was recently evicted. If a block is
121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
122 * information to retrieve it from the L2ARC device. This information is
123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
124 * that is in this state cannot access the data directly.
126 * Blocks that are actively being referenced or have not been evicted
127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
128 * the arc_buf_hdr_t that will point to the data block in memory. A block can
129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
134 * ability to store the physical data (b_pabd) associated with the DVA of the
135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
136 * it will match its on-disk compression characteristics. This behavior can be
137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
138 * compressed ARC functionality is disabled, the b_pabd will point to an
139 * uncompressed version of the on-disk data.
141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
144 * consumer. The ARC will provide references to this data and will keep it
145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
146 * data block and will evict any arc_buf_t that is no longer referenced. The
147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
148 * "overhead_size" kstat.
150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
151 * compressed form. The typical case is that consumers will want uncompressed
152 * data, and when that happens a new data buffer is allocated where the data is
153 * decompressed for them to use. Currently the only consumer who wants
154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
156 * with the arc_buf_hdr_t.
158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
159 * first one is owned by a compressed send consumer (and therefore references
160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
161 * used by any other consumer (and has its own uncompressed copy of the data
176 * | b_buf +------------>+-----------+ arc_buf_t
177 * | b_pabd +-+ |b_next +---->+-----------+
178 * +-----------+ | |-----------| |b_next +-->NULL
179 * | |b_comp = T | +-----------+
180 * | |b_data +-+ |b_comp = F |
181 * | +-----------+ | |b_data +-+
182 * +->+------+ | +-----------+ |
184 * data | |<--------------+ | uncompressed
185 * +------+ compressed, | data
186 * shared +-->+------+
191 * When a consumer reads a block, the ARC must first look to see if the
192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
193 * arc_buf_t and either copies uncompressed data into a new data buffer from an
194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
196 * hdr is compressed and the desired compression characteristics of the
197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
200 * be anywhere in the hdr's list.
202 * The diagram below shows an example of an uncompressed ARC hdr that is
203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
204 * the last element in the buf list):
216 * | | arc_buf_t (shared)
217 * | b_buf +------------>+---------+ arc_buf_t
218 * | | |b_next +---->+---------+
219 * | b_pabd +-+ |---------| |b_next +-->NULL
220 * +-----------+ | | | +---------+
222 * | +---------+ | |b_data +-+
223 * +->+------+ | +---------+ |
225 * uncompressed | | | |
228 * | uncompressed | | |
231 * +---------------------------------+
233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
234 * since the physical block is about to be rewritten. The new data contents
235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
236 * it may compress the data before writing it to disk. The ARC will be called
237 * with the transformed data and will bcopy the transformed on-disk block into
238 * a newly allocated b_pabd. Writes are always done into buffers which have
239 * either been loaned (and hence are new and don't have other readers) or
240 * buffers which have been released (and hence have their own hdr, if there
241 * were originally other readers of the buf's original hdr). This ensures that
242 * the ARC only needs to update a single buf and its hdr after a write occurs.
244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
246 * that when compressed ARC is enabled that the L2ARC blocks are identical
247 * to the on-disk block in the main data pool. This provides a significant
248 * advantage since the ARC can leverage the bp's checksum when reading from the
249 * L2ARC to determine if the contents are valid. However, if the compressed
250 * ARC is disabled, then the L2ARC's block must be transformed to look
251 * like the physical block in the main data pool before comparing the
252 * checksum and determining its validity.
257 #include <sys/spa_impl.h>
258 #include <sys/zio_compress.h>
259 #include <sys/zio_checksum.h>
260 #include <sys/zfs_context.h>
262 #include <sys/refcount.h>
263 #include <sys/vdev.h>
264 #include <sys/vdev_impl.h>
265 #include <sys/dsl_pool.h>
266 #include <sys/zio_checksum.h>
267 #include <sys/multilist.h>
270 #include <sys/dnlc.h>
271 #include <sys/racct.h>
273 #include <sys/callb.h>
274 #include <sys/kstat.h>
275 #include <sys/trim_map.h>
276 #include <zfs_fletcher.h>
279 #include <machine/vmparam.h>
283 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
284 boolean_t arc_watch = B_FALSE;
289 static kmutex_t arc_reclaim_lock;
290 static kcondvar_t arc_reclaim_thread_cv;
291 static boolean_t arc_reclaim_thread_exit;
292 static kcondvar_t arc_reclaim_waiters_cv;
294 static kmutex_t arc_dnlc_evicts_lock;
295 static kcondvar_t arc_dnlc_evicts_cv;
296 static boolean_t arc_dnlc_evicts_thread_exit;
298 uint_t arc_reduce_dnlc_percent = 3;
301 * The number of headers to evict in arc_evict_state_impl() before
302 * dropping the sublist lock and evicting from another sublist. A lower
303 * value means we're more likely to evict the "correct" header (i.e. the
304 * oldest header in the arc state), but comes with higher overhead
305 * (i.e. more invocations of arc_evict_state_impl()).
307 int zfs_arc_evict_batch_limit = 10;
309 /* number of seconds before growing cache again */
310 static int arc_grow_retry = 60;
312 /* number of milliseconds before attempting a kmem-cache-reap */
313 static int arc_kmem_cache_reap_retry_ms = 1000;
315 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
316 int zfs_arc_overflow_shift = 8;
318 /* shift of arc_c for calculating both min and max arc_p */
319 static int arc_p_min_shift = 4;
321 /* log2(fraction of arc to reclaim) */
322 static int arc_shrink_shift = 7;
325 * log2(fraction of ARC which must be free to allow growing).
326 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
327 * when reading a new block into the ARC, we will evict an equal-sized block
330 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
331 * we will still not allow it to grow.
333 int arc_no_grow_shift = 5;
337 * minimum lifespan of a prefetch block in clock ticks
338 * (initialized in arc_init())
340 static int arc_min_prefetch_lifespan;
343 * If this percent of memory is free, don't throttle.
345 int arc_lotsfree_percent = 10;
348 extern boolean_t zfs_prefetch_disable;
351 * The arc has filled available memory and has now warmed up.
353 static boolean_t arc_warm;
356 * log2 fraction of the zio arena to keep free.
358 int arc_zio_arena_free_shift = 2;
361 * These tunables are for performance analysis.
363 uint64_t zfs_arc_max;
364 uint64_t zfs_arc_min;
365 uint64_t zfs_arc_meta_limit = 0;
366 uint64_t zfs_arc_meta_min = 0;
367 int zfs_arc_grow_retry = 0;
368 int zfs_arc_shrink_shift = 0;
369 int zfs_arc_no_grow_shift = 0;
370 int zfs_arc_p_min_shift = 0;
371 uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
372 u_int zfs_arc_free_target = 0;
374 /* Absolute min for arc min / max is 16MB. */
375 static uint64_t arc_abs_min = 16 << 20;
377 boolean_t zfs_compressed_arc_enabled = B_TRUE;
379 static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS);
380 static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS);
381 static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS);
382 static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS);
383 static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS);
385 #if defined(__FreeBSD__) && defined(_KERNEL)
387 arc_free_target_init(void *unused __unused)
390 zfs_arc_free_target = (vm_cnt.v_free_min / 10) * 11;
392 SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
393 arc_free_target_init, NULL);
395 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
396 TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min);
397 TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
398 TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry);
399 TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift);
400 SYSCTL_DECL(_vfs_zfs);
401 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN,
402 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size");
403 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN,
404 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size");
405 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN,
406 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U",
407 "log2(fraction of ARC which must be free to allow growing)");
408 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
409 &zfs_arc_average_blocksize, 0,
410 "ARC average blocksize");
411 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
412 &arc_shrink_shift, 0,
413 "log2(fraction of arc to reclaim)");
414 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW,
416 "Wait in seconds before considering growing ARC");
417 SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN,
418 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC");
421 * We don't have a tunable for arc_free_target due to the dependency on
422 * pagedaemon initialisation.
424 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
425 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
426 sysctl_vfs_zfs_arc_free_target, "IU",
427 "Desired number of free pages below which ARC triggers reclaim");
430 sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
435 val = zfs_arc_free_target;
436 err = sysctl_handle_int(oidp, &val, 0, req);
437 if (err != 0 || req->newptr == NULL)
442 if (val > vm_cnt.v_page_count)
445 zfs_arc_free_target = val;
451 * Must be declared here, before the definition of corresponding kstat
452 * macro which uses the same names will confuse the compiler.
454 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit,
455 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t),
456 sysctl_vfs_zfs_arc_meta_limit, "QU",
457 "ARC metadata limit");
461 * Note that buffers can be in one of 6 states:
462 * ARC_anon - anonymous (discussed below)
463 * ARC_mru - recently used, currently cached
464 * ARC_mru_ghost - recentely used, no longer in cache
465 * ARC_mfu - frequently used, currently cached
466 * ARC_mfu_ghost - frequently used, no longer in cache
467 * ARC_l2c_only - exists in L2ARC but not other states
468 * When there are no active references to the buffer, they are
469 * are linked onto a list in one of these arc states. These are
470 * the only buffers that can be evicted or deleted. Within each
471 * state there are multiple lists, one for meta-data and one for
472 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
473 * etc.) is tracked separately so that it can be managed more
474 * explicitly: favored over data, limited explicitly.
476 * Anonymous buffers are buffers that are not associated with
477 * a DVA. These are buffers that hold dirty block copies
478 * before they are written to stable storage. By definition,
479 * they are "ref'd" and are considered part of arc_mru
480 * that cannot be freed. Generally, they will aquire a DVA
481 * as they are written and migrate onto the arc_mru list.
483 * The ARC_l2c_only state is for buffers that are in the second
484 * level ARC but no longer in any of the ARC_m* lists. The second
485 * level ARC itself may also contain buffers that are in any of
486 * the ARC_m* states - meaning that a buffer can exist in two
487 * places. The reason for the ARC_l2c_only state is to keep the
488 * buffer header in the hash table, so that reads that hit the
489 * second level ARC benefit from these fast lookups.
492 typedef struct arc_state {
494 * list of evictable buffers
496 multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
498 * total amount of evictable data in this state
500 refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
502 * total amount of data in this state; this includes: evictable,
503 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
505 refcount_t arcs_size;
509 static arc_state_t ARC_anon;
510 static arc_state_t ARC_mru;
511 static arc_state_t ARC_mru_ghost;
512 static arc_state_t ARC_mfu;
513 static arc_state_t ARC_mfu_ghost;
514 static arc_state_t ARC_l2c_only;
516 typedef struct arc_stats {
517 kstat_named_t arcstat_hits;
518 kstat_named_t arcstat_misses;
519 kstat_named_t arcstat_demand_data_hits;
520 kstat_named_t arcstat_demand_data_misses;
521 kstat_named_t arcstat_demand_metadata_hits;
522 kstat_named_t arcstat_demand_metadata_misses;
523 kstat_named_t arcstat_prefetch_data_hits;
524 kstat_named_t arcstat_prefetch_data_misses;
525 kstat_named_t arcstat_prefetch_metadata_hits;
526 kstat_named_t arcstat_prefetch_metadata_misses;
527 kstat_named_t arcstat_mru_hits;
528 kstat_named_t arcstat_mru_ghost_hits;
529 kstat_named_t arcstat_mfu_hits;
530 kstat_named_t arcstat_mfu_ghost_hits;
531 kstat_named_t arcstat_allocated;
532 kstat_named_t arcstat_deleted;
534 * Number of buffers that could not be evicted because the hash lock
535 * was held by another thread. The lock may not necessarily be held
536 * by something using the same buffer, since hash locks are shared
537 * by multiple buffers.
539 kstat_named_t arcstat_mutex_miss;
541 * Number of buffers skipped because they have I/O in progress, are
542 * indrect prefetch buffers that have not lived long enough, or are
543 * not from the spa we're trying to evict from.
545 kstat_named_t arcstat_evict_skip;
547 * Number of times arc_evict_state() was unable to evict enough
548 * buffers to reach it's target amount.
550 kstat_named_t arcstat_evict_not_enough;
551 kstat_named_t arcstat_evict_l2_cached;
552 kstat_named_t arcstat_evict_l2_eligible;
553 kstat_named_t arcstat_evict_l2_ineligible;
554 kstat_named_t arcstat_evict_l2_skip;
555 kstat_named_t arcstat_hash_elements;
556 kstat_named_t arcstat_hash_elements_max;
557 kstat_named_t arcstat_hash_collisions;
558 kstat_named_t arcstat_hash_chains;
559 kstat_named_t arcstat_hash_chain_max;
560 kstat_named_t arcstat_p;
561 kstat_named_t arcstat_c;
562 kstat_named_t arcstat_c_min;
563 kstat_named_t arcstat_c_max;
564 kstat_named_t arcstat_size;
566 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
567 * Note that the compressed bytes may match the uncompressed bytes
568 * if the block is either not compressed or compressed arc is disabled.
570 kstat_named_t arcstat_compressed_size;
572 * Uncompressed size of the data stored in b_pabd. If compressed
573 * arc is disabled then this value will be identical to the stat
576 kstat_named_t arcstat_uncompressed_size;
578 * Number of bytes stored in all the arc_buf_t's. This is classified
579 * as "overhead" since this data is typically short-lived and will
580 * be evicted from the arc when it becomes unreferenced unless the
581 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
582 * values have been set (see comment in dbuf.c for more information).
584 kstat_named_t arcstat_overhead_size;
586 * Number of bytes consumed by internal ARC structures necessary
587 * for tracking purposes; these structures are not actually
588 * backed by ARC buffers. This includes arc_buf_hdr_t structures
589 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
590 * caches), and arc_buf_t structures (allocated via arc_buf_t
593 kstat_named_t arcstat_hdr_size;
595 * Number of bytes consumed by ARC buffers of type equal to
596 * ARC_BUFC_DATA. This is generally consumed by buffers backing
597 * on disk user data (e.g. plain file contents).
599 kstat_named_t arcstat_data_size;
601 * Number of bytes consumed by ARC buffers of type equal to
602 * ARC_BUFC_METADATA. This is generally consumed by buffers
603 * backing on disk data that is used for internal ZFS
604 * structures (e.g. ZAP, dnode, indirect blocks, etc).
606 kstat_named_t arcstat_metadata_size;
608 * Number of bytes consumed by various buffers and structures
609 * not actually backed with ARC buffers. This includes bonus
610 * buffers (allocated directly via zio_buf_* functions),
611 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
612 * cache), and dnode_t structures (allocated via dnode_t cache).
614 kstat_named_t arcstat_other_size;
616 * Total number of bytes consumed by ARC buffers residing in the
617 * arc_anon state. This includes *all* buffers in the arc_anon
618 * state; e.g. data, metadata, evictable, and unevictable buffers
619 * are all included in this value.
621 kstat_named_t arcstat_anon_size;
623 * Number of bytes consumed by ARC buffers that meet the
624 * following criteria: backing buffers of type ARC_BUFC_DATA,
625 * residing in the arc_anon state, and are eligible for eviction
626 * (e.g. have no outstanding holds on the buffer).
628 kstat_named_t arcstat_anon_evictable_data;
630 * Number of bytes consumed by ARC buffers that meet the
631 * following criteria: backing buffers of type ARC_BUFC_METADATA,
632 * residing in the arc_anon state, and are eligible for eviction
633 * (e.g. have no outstanding holds on the buffer).
635 kstat_named_t arcstat_anon_evictable_metadata;
637 * Total number of bytes consumed by ARC buffers residing in the
638 * arc_mru state. This includes *all* buffers in the arc_mru
639 * state; e.g. data, metadata, evictable, and unevictable buffers
640 * are all included in this value.
642 kstat_named_t arcstat_mru_size;
644 * Number of bytes consumed by ARC buffers that meet the
645 * following criteria: backing buffers of type ARC_BUFC_DATA,
646 * residing in the arc_mru state, and are eligible for eviction
647 * (e.g. have no outstanding holds on the buffer).
649 kstat_named_t arcstat_mru_evictable_data;
651 * Number of bytes consumed by ARC buffers that meet the
652 * following criteria: backing buffers of type ARC_BUFC_METADATA,
653 * residing in the arc_mru state, and are eligible for eviction
654 * (e.g. have no outstanding holds on the buffer).
656 kstat_named_t arcstat_mru_evictable_metadata;
658 * Total number of bytes that *would have been* consumed by ARC
659 * buffers in the arc_mru_ghost state. The key thing to note
660 * here, is the fact that this size doesn't actually indicate
661 * RAM consumption. The ghost lists only consist of headers and
662 * don't actually have ARC buffers linked off of these headers.
663 * Thus, *if* the headers had associated ARC buffers, these
664 * buffers *would have* consumed this number of bytes.
666 kstat_named_t arcstat_mru_ghost_size;
668 * Number of bytes that *would have been* consumed by ARC
669 * buffers that are eligible for eviction, of type
670 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
672 kstat_named_t arcstat_mru_ghost_evictable_data;
674 * Number of bytes that *would have been* consumed by ARC
675 * buffers that are eligible for eviction, of type
676 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
678 kstat_named_t arcstat_mru_ghost_evictable_metadata;
680 * Total number of bytes consumed by ARC buffers residing in the
681 * arc_mfu state. This includes *all* buffers in the arc_mfu
682 * state; e.g. data, metadata, evictable, and unevictable buffers
683 * are all included in this value.
685 kstat_named_t arcstat_mfu_size;
687 * Number of bytes consumed by ARC buffers that are eligible for
688 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
691 kstat_named_t arcstat_mfu_evictable_data;
693 * Number of bytes consumed by ARC buffers that are eligible for
694 * eviction, of type ARC_BUFC_METADATA, and reside in the
697 kstat_named_t arcstat_mfu_evictable_metadata;
699 * Total number of bytes that *would have been* consumed by ARC
700 * buffers in the arc_mfu_ghost state. See the comment above
701 * arcstat_mru_ghost_size for more details.
703 kstat_named_t arcstat_mfu_ghost_size;
705 * Number of bytes that *would have been* consumed by ARC
706 * buffers that are eligible for eviction, of type
707 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
709 kstat_named_t arcstat_mfu_ghost_evictable_data;
711 * Number of bytes that *would have been* consumed by ARC
712 * buffers that are eligible for eviction, of type
713 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
715 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
716 kstat_named_t arcstat_l2_hits;
717 kstat_named_t arcstat_l2_misses;
718 kstat_named_t arcstat_l2_feeds;
719 kstat_named_t arcstat_l2_rw_clash;
720 kstat_named_t arcstat_l2_read_bytes;
721 kstat_named_t arcstat_l2_write_bytes;
722 kstat_named_t arcstat_l2_writes_sent;
723 kstat_named_t arcstat_l2_writes_done;
724 kstat_named_t arcstat_l2_writes_error;
725 kstat_named_t arcstat_l2_writes_lock_retry;
726 kstat_named_t arcstat_l2_evict_lock_retry;
727 kstat_named_t arcstat_l2_evict_reading;
728 kstat_named_t arcstat_l2_evict_l1cached;
729 kstat_named_t arcstat_l2_free_on_write;
730 kstat_named_t arcstat_l2_abort_lowmem;
731 kstat_named_t arcstat_l2_cksum_bad;
732 kstat_named_t arcstat_l2_io_error;
733 kstat_named_t arcstat_l2_lsize;
734 kstat_named_t arcstat_l2_psize;
735 kstat_named_t arcstat_l2_hdr_size;
736 kstat_named_t arcstat_l2_write_trylock_fail;
737 kstat_named_t arcstat_l2_write_passed_headroom;
738 kstat_named_t arcstat_l2_write_spa_mismatch;
739 kstat_named_t arcstat_l2_write_in_l2;
740 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
741 kstat_named_t arcstat_l2_write_not_cacheable;
742 kstat_named_t arcstat_l2_write_full;
743 kstat_named_t arcstat_l2_write_buffer_iter;
744 kstat_named_t arcstat_l2_write_pios;
745 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
746 kstat_named_t arcstat_l2_write_buffer_list_iter;
747 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
748 kstat_named_t arcstat_memory_throttle_count;
749 kstat_named_t arcstat_meta_used;
750 kstat_named_t arcstat_meta_limit;
751 kstat_named_t arcstat_meta_max;
752 kstat_named_t arcstat_meta_min;
753 kstat_named_t arcstat_sync_wait_for_async;
754 kstat_named_t arcstat_demand_hit_predictive_prefetch;
757 static arc_stats_t arc_stats = {
758 { "hits", KSTAT_DATA_UINT64 },
759 { "misses", KSTAT_DATA_UINT64 },
760 { "demand_data_hits", KSTAT_DATA_UINT64 },
761 { "demand_data_misses", KSTAT_DATA_UINT64 },
762 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
763 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
764 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
765 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
766 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
767 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
768 { "mru_hits", KSTAT_DATA_UINT64 },
769 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
770 { "mfu_hits", KSTAT_DATA_UINT64 },
771 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
772 { "allocated", KSTAT_DATA_UINT64 },
773 { "deleted", KSTAT_DATA_UINT64 },
774 { "mutex_miss", KSTAT_DATA_UINT64 },
775 { "evict_skip", KSTAT_DATA_UINT64 },
776 { "evict_not_enough", KSTAT_DATA_UINT64 },
777 { "evict_l2_cached", KSTAT_DATA_UINT64 },
778 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
779 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
780 { "evict_l2_skip", KSTAT_DATA_UINT64 },
781 { "hash_elements", KSTAT_DATA_UINT64 },
782 { "hash_elements_max", KSTAT_DATA_UINT64 },
783 { "hash_collisions", KSTAT_DATA_UINT64 },
784 { "hash_chains", KSTAT_DATA_UINT64 },
785 { "hash_chain_max", KSTAT_DATA_UINT64 },
786 { "p", KSTAT_DATA_UINT64 },
787 { "c", KSTAT_DATA_UINT64 },
788 { "c_min", KSTAT_DATA_UINT64 },
789 { "c_max", KSTAT_DATA_UINT64 },
790 { "size", KSTAT_DATA_UINT64 },
791 { "compressed_size", KSTAT_DATA_UINT64 },
792 { "uncompressed_size", KSTAT_DATA_UINT64 },
793 { "overhead_size", KSTAT_DATA_UINT64 },
794 { "hdr_size", KSTAT_DATA_UINT64 },
795 { "data_size", KSTAT_DATA_UINT64 },
796 { "metadata_size", KSTAT_DATA_UINT64 },
797 { "other_size", KSTAT_DATA_UINT64 },
798 { "anon_size", KSTAT_DATA_UINT64 },
799 { "anon_evictable_data", KSTAT_DATA_UINT64 },
800 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
801 { "mru_size", KSTAT_DATA_UINT64 },
802 { "mru_evictable_data", KSTAT_DATA_UINT64 },
803 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
804 { "mru_ghost_size", KSTAT_DATA_UINT64 },
805 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
806 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
807 { "mfu_size", KSTAT_DATA_UINT64 },
808 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
809 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
810 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
811 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
812 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
813 { "l2_hits", KSTAT_DATA_UINT64 },
814 { "l2_misses", KSTAT_DATA_UINT64 },
815 { "l2_feeds", KSTAT_DATA_UINT64 },
816 { "l2_rw_clash", KSTAT_DATA_UINT64 },
817 { "l2_read_bytes", KSTAT_DATA_UINT64 },
818 { "l2_write_bytes", KSTAT_DATA_UINT64 },
819 { "l2_writes_sent", KSTAT_DATA_UINT64 },
820 { "l2_writes_done", KSTAT_DATA_UINT64 },
821 { "l2_writes_error", KSTAT_DATA_UINT64 },
822 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
823 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
824 { "l2_evict_reading", KSTAT_DATA_UINT64 },
825 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
826 { "l2_free_on_write", KSTAT_DATA_UINT64 },
827 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
828 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
829 { "l2_io_error", KSTAT_DATA_UINT64 },
830 { "l2_size", KSTAT_DATA_UINT64 },
831 { "l2_asize", KSTAT_DATA_UINT64 },
832 { "l2_hdr_size", KSTAT_DATA_UINT64 },
833 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
834 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
835 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
836 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
837 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
838 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
839 { "l2_write_full", KSTAT_DATA_UINT64 },
840 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
841 { "l2_write_pios", KSTAT_DATA_UINT64 },
842 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
843 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
844 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
845 { "memory_throttle_count", KSTAT_DATA_UINT64 },
846 { "arc_meta_used", KSTAT_DATA_UINT64 },
847 { "arc_meta_limit", KSTAT_DATA_UINT64 },
848 { "arc_meta_max", KSTAT_DATA_UINT64 },
849 { "arc_meta_min", KSTAT_DATA_UINT64 },
850 { "sync_wait_for_async", KSTAT_DATA_UINT64 },
851 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
854 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
856 #define ARCSTAT_INCR(stat, val) \
857 atomic_add_64(&arc_stats.stat.value.ui64, (val))
859 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
860 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
862 #define ARCSTAT_MAX(stat, val) { \
864 while ((val) > (m = arc_stats.stat.value.ui64) && \
865 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
869 #define ARCSTAT_MAXSTAT(stat) \
870 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
873 * We define a macro to allow ARC hits/misses to be easily broken down by
874 * two separate conditions, giving a total of four different subtypes for
875 * each of hits and misses (so eight statistics total).
877 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
880 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
882 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
886 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
888 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
893 static arc_state_t *arc_anon;
894 static arc_state_t *arc_mru;
895 static arc_state_t *arc_mru_ghost;
896 static arc_state_t *arc_mfu;
897 static arc_state_t *arc_mfu_ghost;
898 static arc_state_t *arc_l2c_only;
901 * There are several ARC variables that are critical to export as kstats --
902 * but we don't want to have to grovel around in the kstat whenever we wish to
903 * manipulate them. For these variables, we therefore define them to be in
904 * terms of the statistic variable. This assures that we are not introducing
905 * the possibility of inconsistency by having shadow copies of the variables,
906 * while still allowing the code to be readable.
908 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
909 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
910 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
911 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
912 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
913 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
914 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
915 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
916 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
918 /* compressed size of entire arc */
919 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
920 /* uncompressed size of entire arc */
921 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
922 /* number of bytes in the arc from arc_buf_t's */
923 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
925 static int arc_no_grow; /* Don't try to grow cache size */
926 static uint64_t arc_tempreserve;
927 static uint64_t arc_loaned_bytes;
929 typedef struct arc_callback arc_callback_t;
931 struct arc_callback {
933 arc_done_func_t *acb_done;
935 boolean_t acb_compressed;
936 zio_t *acb_zio_dummy;
937 arc_callback_t *acb_next;
940 typedef struct arc_write_callback arc_write_callback_t;
942 struct arc_write_callback {
944 arc_done_func_t *awcb_ready;
945 arc_done_func_t *awcb_children_ready;
946 arc_done_func_t *awcb_physdone;
947 arc_done_func_t *awcb_done;
952 * ARC buffers are separated into multiple structs as a memory saving measure:
953 * - Common fields struct, always defined, and embedded within it:
954 * - L2-only fields, always allocated but undefined when not in L2ARC
955 * - L1-only fields, only allocated when in L1ARC
957 * Buffer in L1 Buffer only in L2
958 * +------------------------+ +------------------------+
959 * | arc_buf_hdr_t | | arc_buf_hdr_t |
963 * +------------------------+ +------------------------+
964 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
965 * | (undefined if L1-only) | | |
966 * +------------------------+ +------------------------+
967 * | l1arc_buf_hdr_t |
972 * +------------------------+
974 * Because it's possible for the L2ARC to become extremely large, we can wind
975 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
976 * is minimized by only allocating the fields necessary for an L1-cached buffer
977 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
978 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
979 * words in pointers. arc_hdr_realloc() is used to switch a header between
980 * these two allocation states.
982 typedef struct l1arc_buf_hdr {
983 kmutex_t b_freeze_lock;
984 zio_cksum_t *b_freeze_cksum;
987 * Used for debugging with kmem_flags - by allocating and freeing
988 * b_thawed when the buffer is thawed, we get a record of the stack
989 * trace that thawed it.
996 /* for waiting on writes to complete */
1000 /* protected by arc state mutex */
1001 arc_state_t *b_state;
1002 multilist_node_t b_arc_node;
1004 /* updated atomically */
1005 clock_t b_arc_access;
1007 /* self protecting */
1008 refcount_t b_refcnt;
1010 arc_callback_t *b_acb;
1014 typedef struct l2arc_dev l2arc_dev_t;
1016 typedef struct l2arc_buf_hdr {
1017 /* protected by arc_buf_hdr mutex */
1018 l2arc_dev_t *b_dev; /* L2ARC device */
1019 uint64_t b_daddr; /* disk address, offset byte */
1021 list_node_t b_l2node;
1024 struct arc_buf_hdr {
1025 /* protected by hash lock */
1029 arc_buf_contents_t b_type;
1030 arc_buf_hdr_t *b_hash_next;
1031 arc_flags_t b_flags;
1034 * This field stores the size of the data buffer after
1035 * compression, and is set in the arc's zio completion handlers.
1036 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
1038 * While the block pointers can store up to 32MB in their psize
1039 * field, we can only store up to 32MB minus 512B. This is due
1040 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
1041 * a field of zeros represents 512B in the bp). We can't use a
1042 * bias of 1 since we need to reserve a psize of zero, here, to
1043 * represent holes and embedded blocks.
1045 * This isn't a problem in practice, since the maximum size of a
1046 * buffer is limited to 16MB, so we never need to store 32MB in
1047 * this field. Even in the upstream illumos code base, the
1048 * maximum size of a buffer is limited to 16MB.
1053 * This field stores the size of the data buffer before
1054 * compression, and cannot change once set. It is in units
1055 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
1057 uint16_t b_lsize; /* immutable */
1058 uint64_t b_spa; /* immutable */
1060 /* L2ARC fields. Undefined when not in L2ARC. */
1061 l2arc_buf_hdr_t b_l2hdr;
1062 /* L1ARC fields. Undefined when in l2arc_only state */
1063 l1arc_buf_hdr_t b_l1hdr;
1066 #if defined(__FreeBSD__) && defined(_KERNEL)
1068 sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS)
1073 val = arc_meta_limit;
1074 err = sysctl_handle_64(oidp, &val, 0, req);
1075 if (err != 0 || req->newptr == NULL)
1078 if (val <= 0 || val > arc_c_max)
1081 arc_meta_limit = val;
1086 sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS)
1091 val = arc_no_grow_shift;
1092 err = sysctl_handle_32(oidp, &val, 0, req);
1093 if (err != 0 || req->newptr == NULL)
1096 if (val >= arc_shrink_shift)
1099 arc_no_grow_shift = val;
1104 sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS)
1110 err = sysctl_handle_64(oidp, &val, 0, req);
1111 if (err != 0 || req->newptr == NULL)
1114 if (zfs_arc_max == 0) {
1115 /* Loader tunable so blindly set */
1120 if (val < arc_abs_min || val > kmem_size())
1122 if (val < arc_c_min)
1124 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit)
1130 arc_p = (arc_c >> 1);
1132 if (zfs_arc_meta_limit == 0) {
1133 /* limit meta-data to 1/4 of the arc capacity */
1134 arc_meta_limit = arc_c_max / 4;
1137 /* if kmem_flags are set, lets try to use less memory */
1138 if (kmem_debugging())
1141 zfs_arc_max = arc_c;
1147 sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS)
1153 err = sysctl_handle_64(oidp, &val, 0, req);
1154 if (err != 0 || req->newptr == NULL)
1157 if (zfs_arc_min == 0) {
1158 /* Loader tunable so blindly set */
1163 if (val < arc_abs_min || val > arc_c_max)
1168 if (zfs_arc_meta_min == 0)
1169 arc_meta_min = arc_c_min / 2;
1171 if (arc_c < arc_c_min)
1174 zfs_arc_min = arc_c_min;
1180 #define GHOST_STATE(state) \
1181 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
1182 (state) == arc_l2c_only)
1184 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
1185 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
1186 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
1187 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
1188 #define HDR_COMPRESSION_ENABLED(hdr) \
1189 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
1191 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
1192 #define HDR_L2_READING(hdr) \
1193 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
1194 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
1195 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
1196 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
1197 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
1198 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
1200 #define HDR_ISTYPE_METADATA(hdr) \
1201 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
1202 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
1204 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
1205 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
1207 /* For storing compression mode in b_flags */
1208 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
1210 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
1211 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
1212 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
1213 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
1215 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
1216 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
1217 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
1223 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
1224 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
1227 * Hash table routines
1230 #define HT_LOCK_PAD CACHE_LINE_SIZE
1235 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
1239 #define BUF_LOCKS 256
1240 typedef struct buf_hash_table {
1242 arc_buf_hdr_t **ht_table;
1243 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
1246 static buf_hash_table_t buf_hash_table;
1248 #define BUF_HASH_INDEX(spa, dva, birth) \
1249 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1250 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
1251 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
1252 #define HDR_LOCK(hdr) \
1253 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1255 uint64_t zfs_crc64_table[256];
1261 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1262 #define L2ARC_HEADROOM 2 /* num of writes */
1264 * If we discover during ARC scan any buffers to be compressed, we boost
1265 * our headroom for the next scanning cycle by this percentage multiple.
1267 #define L2ARC_HEADROOM_BOOST 200
1268 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1269 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1271 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1272 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1274 /* L2ARC Performance Tunables */
1275 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
1276 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
1277 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
1278 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1279 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1280 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
1281 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1282 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
1283 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
1285 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
1286 &l2arc_write_max, 0, "max write size");
1287 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
1288 &l2arc_write_boost, 0, "extra write during warmup");
1289 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
1290 &l2arc_headroom, 0, "number of dev writes");
1291 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
1292 &l2arc_feed_secs, 0, "interval seconds");
1293 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
1294 &l2arc_feed_min_ms, 0, "min interval milliseconds");
1296 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
1297 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
1298 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
1299 &l2arc_feed_again, 0, "turbo warmup");
1300 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
1301 &l2arc_norw, 0, "no reads during writes");
1303 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
1304 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state");
1305 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD,
1306 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1307 "size of anonymous state");
1308 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD,
1309 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1310 "size of anonymous state");
1312 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
1313 &ARC_mru.arcs_size.rc_count, 0, "size of mru state");
1314 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD,
1315 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1316 "size of metadata in mru state");
1317 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD,
1318 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1319 "size of data in mru state");
1321 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
1322 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state");
1323 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD,
1324 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1325 "size of metadata in mru ghost state");
1326 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD,
1327 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1328 "size of data in mru ghost state");
1330 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
1331 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state");
1332 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD,
1333 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1334 "size of metadata in mfu state");
1335 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD,
1336 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1337 "size of data in mfu state");
1339 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
1340 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state");
1341 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD,
1342 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1343 "size of metadata in mfu ghost state");
1344 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD,
1345 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1346 "size of data in mfu ghost state");
1348 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
1349 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state");
1355 vdev_t *l2ad_vdev; /* vdev */
1356 spa_t *l2ad_spa; /* spa */
1357 uint64_t l2ad_hand; /* next write location */
1358 uint64_t l2ad_start; /* first addr on device */
1359 uint64_t l2ad_end; /* last addr on device */
1360 boolean_t l2ad_first; /* first sweep through */
1361 boolean_t l2ad_writing; /* currently writing */
1362 kmutex_t l2ad_mtx; /* lock for buffer list */
1363 list_t l2ad_buflist; /* buffer list */
1364 list_node_t l2ad_node; /* device list node */
1365 refcount_t l2ad_alloc; /* allocated bytes */
1368 static list_t L2ARC_dev_list; /* device list */
1369 static list_t *l2arc_dev_list; /* device list pointer */
1370 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1371 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1372 static list_t L2ARC_free_on_write; /* free after write buf list */
1373 static list_t *l2arc_free_on_write; /* free after write list ptr */
1374 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1375 static uint64_t l2arc_ndev; /* number of devices */
1377 typedef struct l2arc_read_callback {
1378 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1379 blkptr_t l2rcb_bp; /* original blkptr */
1380 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1381 int l2rcb_flags; /* original flags */
1382 abd_t *l2rcb_abd; /* temporary buffer */
1383 } l2arc_read_callback_t;
1385 typedef struct l2arc_write_callback {
1386 l2arc_dev_t *l2wcb_dev; /* device info */
1387 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
1388 } l2arc_write_callback_t;
1390 typedef struct l2arc_data_free {
1391 /* protected by l2arc_free_on_write_mtx */
1394 arc_buf_contents_t l2df_type;
1395 list_node_t l2df_list_node;
1396 } l2arc_data_free_t;
1398 static kmutex_t l2arc_feed_thr_lock;
1399 static kcondvar_t l2arc_feed_thr_cv;
1400 static uint8_t l2arc_thread_exit;
1402 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1403 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1404 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1405 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1406 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1407 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1408 static void arc_hdr_free_pabd(arc_buf_hdr_t *);
1409 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *);
1410 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1411 static boolean_t arc_is_overflowing();
1412 static void arc_buf_watch(arc_buf_t *);
1414 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1415 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1416 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1417 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1419 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1420 static void l2arc_read_done(zio_t *);
1423 l2arc_trim(const arc_buf_hdr_t *hdr)
1425 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
1427 ASSERT(HDR_HAS_L2HDR(hdr));
1428 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
1430 if (HDR_GET_PSIZE(hdr) != 0) {
1431 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr,
1432 HDR_GET_PSIZE(hdr), 0);
1437 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1439 uint8_t *vdva = (uint8_t *)dva;
1440 uint64_t crc = -1ULL;
1443 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
1445 for (i = 0; i < sizeof (dva_t); i++)
1446 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
1448 crc ^= (spa>>8) ^ birth;
1453 #define HDR_EMPTY(hdr) \
1454 ((hdr)->b_dva.dva_word[0] == 0 && \
1455 (hdr)->b_dva.dva_word[1] == 0)
1457 #define HDR_EQUAL(spa, dva, birth, hdr) \
1458 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1459 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1460 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1463 buf_discard_identity(arc_buf_hdr_t *hdr)
1465 hdr->b_dva.dva_word[0] = 0;
1466 hdr->b_dva.dva_word[1] = 0;
1470 static arc_buf_hdr_t *
1471 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1473 const dva_t *dva = BP_IDENTITY(bp);
1474 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1475 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1476 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1479 mutex_enter(hash_lock);
1480 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1481 hdr = hdr->b_hash_next) {
1482 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1487 mutex_exit(hash_lock);
1493 * Insert an entry into the hash table. If there is already an element
1494 * equal to elem in the hash table, then the already existing element
1495 * will be returned and the new element will not be inserted.
1496 * Otherwise returns NULL.
1497 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1499 static arc_buf_hdr_t *
1500 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1502 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1503 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1504 arc_buf_hdr_t *fhdr;
1507 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1508 ASSERT(hdr->b_birth != 0);
1509 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1511 if (lockp != NULL) {
1513 mutex_enter(hash_lock);
1515 ASSERT(MUTEX_HELD(hash_lock));
1518 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1519 fhdr = fhdr->b_hash_next, i++) {
1520 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1524 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1525 buf_hash_table.ht_table[idx] = hdr;
1526 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1528 /* collect some hash table performance data */
1530 ARCSTAT_BUMP(arcstat_hash_collisions);
1532 ARCSTAT_BUMP(arcstat_hash_chains);
1534 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1537 ARCSTAT_BUMP(arcstat_hash_elements);
1538 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1544 buf_hash_remove(arc_buf_hdr_t *hdr)
1546 arc_buf_hdr_t *fhdr, **hdrp;
1547 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1549 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1550 ASSERT(HDR_IN_HASH_TABLE(hdr));
1552 hdrp = &buf_hash_table.ht_table[idx];
1553 while ((fhdr = *hdrp) != hdr) {
1554 ASSERT3P(fhdr, !=, NULL);
1555 hdrp = &fhdr->b_hash_next;
1557 *hdrp = hdr->b_hash_next;
1558 hdr->b_hash_next = NULL;
1559 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1561 /* collect some hash table performance data */
1562 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1564 if (buf_hash_table.ht_table[idx] &&
1565 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1566 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1570 * Global data structures and functions for the buf kmem cache.
1572 static kmem_cache_t *hdr_full_cache;
1573 static kmem_cache_t *hdr_l2only_cache;
1574 static kmem_cache_t *buf_cache;
1581 kmem_free(buf_hash_table.ht_table,
1582 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1583 for (i = 0; i < BUF_LOCKS; i++)
1584 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1585 kmem_cache_destroy(hdr_full_cache);
1586 kmem_cache_destroy(hdr_l2only_cache);
1587 kmem_cache_destroy(buf_cache);
1591 * Constructor callback - called when the cache is empty
1592 * and a new buf is requested.
1596 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1598 arc_buf_hdr_t *hdr = vbuf;
1600 bzero(hdr, HDR_FULL_SIZE);
1601 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1602 refcount_create(&hdr->b_l1hdr.b_refcnt);
1603 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1604 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1605 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1612 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1614 arc_buf_hdr_t *hdr = vbuf;
1616 bzero(hdr, HDR_L2ONLY_SIZE);
1617 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1624 buf_cons(void *vbuf, void *unused, int kmflag)
1626 arc_buf_t *buf = vbuf;
1628 bzero(buf, sizeof (arc_buf_t));
1629 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1630 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1636 * Destructor callback - called when a cached buf is
1637 * no longer required.
1641 hdr_full_dest(void *vbuf, void *unused)
1643 arc_buf_hdr_t *hdr = vbuf;
1645 ASSERT(HDR_EMPTY(hdr));
1646 cv_destroy(&hdr->b_l1hdr.b_cv);
1647 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1648 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1649 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1650 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1655 hdr_l2only_dest(void *vbuf, void *unused)
1657 arc_buf_hdr_t *hdr = vbuf;
1659 ASSERT(HDR_EMPTY(hdr));
1660 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1665 buf_dest(void *vbuf, void *unused)
1667 arc_buf_t *buf = vbuf;
1669 mutex_destroy(&buf->b_evict_lock);
1670 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1674 * Reclaim callback -- invoked when memory is low.
1678 hdr_recl(void *unused)
1680 dprintf("hdr_recl called\n");
1682 * umem calls the reclaim func when we destroy the buf cache,
1683 * which is after we do arc_fini().
1686 cv_signal(&arc_reclaim_thread_cv);
1693 uint64_t hsize = 1ULL << 12;
1697 * The hash table is big enough to fill all of physical memory
1698 * with an average block size of zfs_arc_average_blocksize (default 8K).
1699 * By default, the table will take up
1700 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1702 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1705 buf_hash_table.ht_mask = hsize - 1;
1706 buf_hash_table.ht_table =
1707 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1708 if (buf_hash_table.ht_table == NULL) {
1709 ASSERT(hsize > (1ULL << 8));
1714 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1715 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1716 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1717 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1719 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1720 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1722 for (i = 0; i < 256; i++)
1723 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1724 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1726 for (i = 0; i < BUF_LOCKS; i++) {
1727 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1728 NULL, MUTEX_DEFAULT, NULL);
1733 * This is the size that the buf occupies in memory. If the buf is compressed,
1734 * it will correspond to the compressed size. You should use this method of
1735 * getting the buf size unless you explicitly need the logical size.
1738 arc_buf_size(arc_buf_t *buf)
1740 return (ARC_BUF_COMPRESSED(buf) ?
1741 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1745 arc_buf_lsize(arc_buf_t *buf)
1747 return (HDR_GET_LSIZE(buf->b_hdr));
1751 arc_get_compression(arc_buf_t *buf)
1753 return (ARC_BUF_COMPRESSED(buf) ?
1754 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1757 #define ARC_MINTIME (hz>>4) /* 62 ms */
1759 static inline boolean_t
1760 arc_buf_is_shared(arc_buf_t *buf)
1762 boolean_t shared = (buf->b_data != NULL &&
1763 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1764 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1765 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1766 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1767 IMPLY(shared, ARC_BUF_SHARED(buf));
1768 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1771 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1772 * already being shared" requirement prevents us from doing that.
1779 * Free the checksum associated with this header. If there is no checksum, this
1783 arc_cksum_free(arc_buf_hdr_t *hdr)
1785 ASSERT(HDR_HAS_L1HDR(hdr));
1786 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1787 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1788 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1789 hdr->b_l1hdr.b_freeze_cksum = NULL;
1791 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1795 * Return true iff at least one of the bufs on hdr is not compressed.
1798 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1800 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1801 if (!ARC_BUF_COMPRESSED(b)) {
1809 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1810 * matches the checksum that is stored in the hdr. If there is no checksum,
1811 * or if the buf is compressed, this is a no-op.
1814 arc_cksum_verify(arc_buf_t *buf)
1816 arc_buf_hdr_t *hdr = buf->b_hdr;
1819 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1822 if (ARC_BUF_COMPRESSED(buf)) {
1823 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1824 arc_hdr_has_uncompressed_buf(hdr));
1828 ASSERT(HDR_HAS_L1HDR(hdr));
1830 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1831 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1832 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1836 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1837 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1838 panic("buffer modified while frozen!");
1839 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1843 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1845 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1846 boolean_t valid_cksum;
1848 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1849 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1852 * We rely on the blkptr's checksum to determine if the block
1853 * is valid or not. When compressed arc is enabled, the l2arc
1854 * writes the block to the l2arc just as it appears in the pool.
1855 * This allows us to use the blkptr's checksum to validate the
1856 * data that we just read off of the l2arc without having to store
1857 * a separate checksum in the arc_buf_hdr_t. However, if compressed
1858 * arc is disabled, then the data written to the l2arc is always
1859 * uncompressed and won't match the block as it exists in the main
1860 * pool. When this is the case, we must first compress it if it is
1861 * compressed on the main pool before we can validate the checksum.
1863 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
1864 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1865 uint64_t lsize = HDR_GET_LSIZE(hdr);
1868 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE);
1869 csize = zio_compress_data(compress, zio->io_abd,
1870 abd_to_buf(cdata), lsize);
1872 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
1873 if (csize < HDR_GET_PSIZE(hdr)) {
1875 * Compressed blocks are always a multiple of the
1876 * smallest ashift in the pool. Ideally, we would
1877 * like to round up the csize to the next
1878 * spa_min_ashift but that value may have changed
1879 * since the block was last written. Instead,
1880 * we rely on the fact that the hdr's psize
1881 * was set to the psize of the block when it was
1882 * last written. We set the csize to that value
1883 * and zero out any part that should not contain
1886 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize);
1887 csize = HDR_GET_PSIZE(hdr);
1889 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL);
1893 * Block pointers always store the checksum for the logical data.
1894 * If the block pointer has the gang bit set, then the checksum
1895 * it represents is for the reconstituted data and not for an
1896 * individual gang member. The zio pipeline, however, must be able to
1897 * determine the checksum of each of the gang constituents so it
1898 * treats the checksum comparison differently than what we need
1899 * for l2arc blocks. This prevents us from using the
1900 * zio_checksum_error() interface directly. Instead we must call the
1901 * zio_checksum_error_impl() so that we can ensure the checksum is
1902 * generated using the correct checksum algorithm and accounts for the
1903 * logical I/O size and not just a gang fragment.
1905 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1906 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1907 zio->io_offset, NULL) == 0);
1908 zio_pop_transforms(zio);
1909 return (valid_cksum);
1913 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1914 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1915 * isn't modified later on. If buf is compressed or there is already a checksum
1916 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1919 arc_cksum_compute(arc_buf_t *buf)
1921 arc_buf_hdr_t *hdr = buf->b_hdr;
1923 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1926 ASSERT(HDR_HAS_L1HDR(hdr));
1928 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1929 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1930 ASSERT(arc_hdr_has_uncompressed_buf(hdr));
1931 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1933 } else if (ARC_BUF_COMPRESSED(buf)) {
1934 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1938 ASSERT(!ARC_BUF_COMPRESSED(buf));
1939 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1941 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1942 hdr->b_l1hdr.b_freeze_cksum);
1943 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1951 typedef struct procctl {
1959 arc_buf_unwatch(arc_buf_t *buf)
1966 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1967 ctl.prwatch.pr_size = 0;
1968 ctl.prwatch.pr_wflags = 0;
1969 result = write(arc_procfd, &ctl, sizeof (ctl));
1970 ASSERT3U(result, ==, sizeof (ctl));
1977 arc_buf_watch(arc_buf_t *buf)
1984 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1985 ctl.prwatch.pr_size = arc_buf_size(buf);
1986 ctl.prwatch.pr_wflags = WA_WRITE;
1987 result = write(arc_procfd, &ctl, sizeof (ctl));
1988 ASSERT3U(result, ==, sizeof (ctl));
1992 #endif /* illumos */
1994 static arc_buf_contents_t
1995 arc_buf_type(arc_buf_hdr_t *hdr)
1997 arc_buf_contents_t type;
1998 if (HDR_ISTYPE_METADATA(hdr)) {
1999 type = ARC_BUFC_METADATA;
2001 type = ARC_BUFC_DATA;
2003 VERIFY3U(hdr->b_type, ==, type);
2008 arc_is_metadata(arc_buf_t *buf)
2010 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
2014 arc_bufc_to_flags(arc_buf_contents_t type)
2018 /* metadata field is 0 if buffer contains normal data */
2020 case ARC_BUFC_METADATA:
2021 return (ARC_FLAG_BUFC_METADATA);
2025 panic("undefined ARC buffer type!");
2026 return ((uint32_t)-1);
2030 arc_buf_thaw(arc_buf_t *buf)
2032 arc_buf_hdr_t *hdr = buf->b_hdr;
2034 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
2035 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2037 arc_cksum_verify(buf);
2040 * Compressed buffers do not manipulate the b_freeze_cksum or
2041 * allocate b_thawed.
2043 if (ARC_BUF_COMPRESSED(buf)) {
2044 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2045 arc_hdr_has_uncompressed_buf(hdr));
2049 ASSERT(HDR_HAS_L1HDR(hdr));
2050 arc_cksum_free(hdr);
2052 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
2054 if (zfs_flags & ZFS_DEBUG_MODIFY) {
2055 if (hdr->b_l1hdr.b_thawed != NULL)
2056 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2057 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
2061 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2064 arc_buf_unwatch(buf);
2069 arc_buf_freeze(arc_buf_t *buf)
2071 arc_buf_hdr_t *hdr = buf->b_hdr;
2072 kmutex_t *hash_lock;
2074 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
2077 if (ARC_BUF_COMPRESSED(buf)) {
2078 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2079 arc_hdr_has_uncompressed_buf(hdr));
2083 hash_lock = HDR_LOCK(hdr);
2084 mutex_enter(hash_lock);
2086 ASSERT(HDR_HAS_L1HDR(hdr));
2087 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL ||
2088 hdr->b_l1hdr.b_state == arc_anon);
2089 arc_cksum_compute(buf);
2090 mutex_exit(hash_lock);
2094 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
2095 * the following functions should be used to ensure that the flags are
2096 * updated in a thread-safe way. When manipulating the flags either
2097 * the hash_lock must be held or the hdr must be undiscoverable. This
2098 * ensures that we're not racing with any other threads when updating
2102 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2104 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2105 hdr->b_flags |= flags;
2109 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2111 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2112 hdr->b_flags &= ~flags;
2116 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
2117 * done in a special way since we have to clear and set bits
2118 * at the same time. Consumers that wish to set the compression bits
2119 * must use this function to ensure that the flags are updated in
2120 * thread-safe manner.
2123 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
2125 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2128 * Holes and embedded blocks will always have a psize = 0 so
2129 * we ignore the compression of the blkptr and set the
2130 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
2131 * Holes and embedded blocks remain anonymous so we don't
2132 * want to uncompress them. Mark them as uncompressed.
2134 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
2135 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2136 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
2137 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
2138 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
2140 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2141 HDR_SET_COMPRESS(hdr, cmp);
2142 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
2143 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
2148 * Looks for another buf on the same hdr which has the data decompressed, copies
2149 * from it, and returns true. If no such buf exists, returns false.
2152 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
2154 arc_buf_hdr_t *hdr = buf->b_hdr;
2155 boolean_t copied = B_FALSE;
2157 ASSERT(HDR_HAS_L1HDR(hdr));
2158 ASSERT3P(buf->b_data, !=, NULL);
2159 ASSERT(!ARC_BUF_COMPRESSED(buf));
2161 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
2162 from = from->b_next) {
2163 /* can't use our own data buffer */
2168 if (!ARC_BUF_COMPRESSED(from)) {
2169 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
2176 * There were no decompressed bufs, so there should not be a
2177 * checksum on the hdr either.
2179 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
2185 * Given a buf that has a data buffer attached to it, this function will
2186 * efficiently fill the buf with data of the specified compression setting from
2187 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
2188 * are already sharing a data buf, no copy is performed.
2190 * If the buf is marked as compressed but uncompressed data was requested, this
2191 * will allocate a new data buffer for the buf, remove that flag, and fill the
2192 * buf with uncompressed data. You can't request a compressed buf on a hdr with
2193 * uncompressed data, and (since we haven't added support for it yet) if you
2194 * want compressed data your buf must already be marked as compressed and have
2195 * the correct-sized data buffer.
2198 arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
2200 arc_buf_hdr_t *hdr = buf->b_hdr;
2201 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
2202 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
2204 ASSERT3P(buf->b_data, !=, NULL);
2205 IMPLY(compressed, hdr_compressed);
2206 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
2208 if (hdr_compressed == compressed) {
2209 if (!arc_buf_is_shared(buf)) {
2210 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
2214 ASSERT(hdr_compressed);
2215 ASSERT(!compressed);
2216 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
2219 * If the buf is sharing its data with the hdr, unlink it and
2220 * allocate a new data buffer for the buf.
2222 if (arc_buf_is_shared(buf)) {
2223 ASSERT(ARC_BUF_COMPRESSED(buf));
2225 /* We need to give the buf it's own b_data */
2226 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2228 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2229 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2231 /* Previously overhead was 0; just add new overhead */
2232 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2233 } else if (ARC_BUF_COMPRESSED(buf)) {
2234 /* We need to reallocate the buf's b_data */
2235 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2238 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2240 /* We increased the size of b_data; update overhead */
2241 ARCSTAT_INCR(arcstat_overhead_size,
2242 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2246 * Regardless of the buf's previous compression settings, it
2247 * should not be compressed at the end of this function.
2249 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2252 * Try copying the data from another buf which already has a
2253 * decompressed version. If that's not possible, it's time to
2254 * bite the bullet and decompress the data from the hdr.
2256 if (arc_buf_try_copy_decompressed_data(buf)) {
2257 /* Skip byteswapping and checksumming (already done) */
2258 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
2261 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2262 hdr->b_l1hdr.b_pabd, buf->b_data,
2263 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2266 * Absent hardware errors or software bugs, this should
2267 * be impossible, but log it anyway so we can debug it.
2271 "hdr %p, compress %d, psize %d, lsize %d",
2272 hdr, HDR_GET_COMPRESS(hdr),
2273 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2274 return (SET_ERROR(EIO));
2279 /* Byteswap the buf's data if necessary */
2280 if (bswap != DMU_BSWAP_NUMFUNCS) {
2281 ASSERT(!HDR_SHARED_DATA(hdr));
2282 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2283 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2286 /* Compute the hdr's checksum if necessary */
2287 arc_cksum_compute(buf);
2293 arc_decompress(arc_buf_t *buf)
2295 return (arc_buf_fill(buf, B_FALSE));
2299 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
2302 arc_hdr_size(arc_buf_hdr_t *hdr)
2306 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
2307 HDR_GET_PSIZE(hdr) > 0) {
2308 size = HDR_GET_PSIZE(hdr);
2310 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
2311 size = HDR_GET_LSIZE(hdr);
2317 * Increment the amount of evictable space in the arc_state_t's refcount.
2318 * We account for the space used by the hdr and the arc buf individually
2319 * so that we can add and remove them from the refcount individually.
2322 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2324 arc_buf_contents_t type = arc_buf_type(hdr);
2326 ASSERT(HDR_HAS_L1HDR(hdr));
2328 if (GHOST_STATE(state)) {
2329 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2330 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2331 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2332 (void) refcount_add_many(&state->arcs_esize[type],
2333 HDR_GET_LSIZE(hdr), hdr);
2337 ASSERT(!GHOST_STATE(state));
2338 if (hdr->b_l1hdr.b_pabd != NULL) {
2339 (void) refcount_add_many(&state->arcs_esize[type],
2340 arc_hdr_size(hdr), hdr);
2342 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2343 buf = buf->b_next) {
2344 if (arc_buf_is_shared(buf))
2346 (void) refcount_add_many(&state->arcs_esize[type],
2347 arc_buf_size(buf), buf);
2352 * Decrement the amount of evictable space in the arc_state_t's refcount.
2353 * We account for the space used by the hdr and the arc buf individually
2354 * so that we can add and remove them from the refcount individually.
2357 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2359 arc_buf_contents_t type = arc_buf_type(hdr);
2361 ASSERT(HDR_HAS_L1HDR(hdr));
2363 if (GHOST_STATE(state)) {
2364 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2365 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2366 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2367 (void) refcount_remove_many(&state->arcs_esize[type],
2368 HDR_GET_LSIZE(hdr), hdr);
2372 ASSERT(!GHOST_STATE(state));
2373 if (hdr->b_l1hdr.b_pabd != NULL) {
2374 (void) refcount_remove_many(&state->arcs_esize[type],
2375 arc_hdr_size(hdr), hdr);
2377 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2378 buf = buf->b_next) {
2379 if (arc_buf_is_shared(buf))
2381 (void) refcount_remove_many(&state->arcs_esize[type],
2382 arc_buf_size(buf), buf);
2387 * Add a reference to this hdr indicating that someone is actively
2388 * referencing that memory. When the refcount transitions from 0 to 1,
2389 * we remove it from the respective arc_state_t list to indicate that
2390 * it is not evictable.
2393 add_reference(arc_buf_hdr_t *hdr, void *tag)
2395 ASSERT(HDR_HAS_L1HDR(hdr));
2396 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2397 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2398 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2399 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2402 arc_state_t *state = hdr->b_l1hdr.b_state;
2404 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2405 (state != arc_anon)) {
2406 /* We don't use the L2-only state list. */
2407 if (state != arc_l2c_only) {
2408 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2410 arc_evictable_space_decrement(hdr, state);
2412 /* remove the prefetch flag if we get a reference */
2413 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2418 * Remove a reference from this hdr. When the reference transitions from
2419 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2420 * list making it eligible for eviction.
2423 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2426 arc_state_t *state = hdr->b_l1hdr.b_state;
2428 ASSERT(HDR_HAS_L1HDR(hdr));
2429 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2430 ASSERT(!GHOST_STATE(state));
2433 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2434 * check to prevent usage of the arc_l2c_only list.
2436 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2437 (state != arc_anon)) {
2438 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2439 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2440 arc_evictable_space_increment(hdr, state);
2446 * Move the supplied buffer to the indicated state. The hash lock
2447 * for the buffer must be held by the caller.
2450 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2451 kmutex_t *hash_lock)
2453 arc_state_t *old_state;
2456 boolean_t update_old, update_new;
2457 arc_buf_contents_t buftype = arc_buf_type(hdr);
2460 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2461 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2462 * L1 hdr doesn't always exist when we change state to arc_anon before
2463 * destroying a header, in which case reallocating to add the L1 hdr is
2466 if (HDR_HAS_L1HDR(hdr)) {
2467 old_state = hdr->b_l1hdr.b_state;
2468 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
2469 bufcnt = hdr->b_l1hdr.b_bufcnt;
2470 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL);
2472 old_state = arc_l2c_only;
2475 update_old = B_FALSE;
2477 update_new = update_old;
2479 ASSERT(MUTEX_HELD(hash_lock));
2480 ASSERT3P(new_state, !=, old_state);
2481 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2482 ASSERT(old_state != arc_anon || bufcnt <= 1);
2485 * If this buffer is evictable, transfer it from the
2486 * old state list to the new state list.
2489 if (old_state != arc_anon && old_state != arc_l2c_only) {
2490 ASSERT(HDR_HAS_L1HDR(hdr));
2491 multilist_remove(old_state->arcs_list[buftype], hdr);
2493 if (GHOST_STATE(old_state)) {
2495 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2496 update_old = B_TRUE;
2498 arc_evictable_space_decrement(hdr, old_state);
2500 if (new_state != arc_anon && new_state != arc_l2c_only) {
2503 * An L1 header always exists here, since if we're
2504 * moving to some L1-cached state (i.e. not l2c_only or
2505 * anonymous), we realloc the header to add an L1hdr
2508 ASSERT(HDR_HAS_L1HDR(hdr));
2509 multilist_insert(new_state->arcs_list[buftype], hdr);
2511 if (GHOST_STATE(new_state)) {
2513 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2514 update_new = B_TRUE;
2516 arc_evictable_space_increment(hdr, new_state);
2520 ASSERT(!HDR_EMPTY(hdr));
2521 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2522 buf_hash_remove(hdr);
2524 /* adjust state sizes (ignore arc_l2c_only) */
2526 if (update_new && new_state != arc_l2c_only) {
2527 ASSERT(HDR_HAS_L1HDR(hdr));
2528 if (GHOST_STATE(new_state)) {
2532 * When moving a header to a ghost state, we first
2533 * remove all arc buffers. Thus, we'll have a
2534 * bufcnt of zero, and no arc buffer to use for
2535 * the reference. As a result, we use the arc
2536 * header pointer for the reference.
2538 (void) refcount_add_many(&new_state->arcs_size,
2539 HDR_GET_LSIZE(hdr), hdr);
2540 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2542 uint32_t buffers = 0;
2545 * Each individual buffer holds a unique reference,
2546 * thus we must remove each of these references one
2549 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2550 buf = buf->b_next) {
2551 ASSERT3U(bufcnt, !=, 0);
2555 * When the arc_buf_t is sharing the data
2556 * block with the hdr, the owner of the
2557 * reference belongs to the hdr. Only
2558 * add to the refcount if the arc_buf_t is
2561 if (arc_buf_is_shared(buf))
2564 (void) refcount_add_many(&new_state->arcs_size,
2565 arc_buf_size(buf), buf);
2567 ASSERT3U(bufcnt, ==, buffers);
2569 if (hdr->b_l1hdr.b_pabd != NULL) {
2570 (void) refcount_add_many(&new_state->arcs_size,
2571 arc_hdr_size(hdr), hdr);
2573 ASSERT(GHOST_STATE(old_state));
2578 if (update_old && old_state != arc_l2c_only) {
2579 ASSERT(HDR_HAS_L1HDR(hdr));
2580 if (GHOST_STATE(old_state)) {
2582 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2585 * When moving a header off of a ghost state,
2586 * the header will not contain any arc buffers.
2587 * We use the arc header pointer for the reference
2588 * which is exactly what we did when we put the
2589 * header on the ghost state.
2592 (void) refcount_remove_many(&old_state->arcs_size,
2593 HDR_GET_LSIZE(hdr), hdr);
2595 uint32_t buffers = 0;
2598 * Each individual buffer holds a unique reference,
2599 * thus we must remove each of these references one
2602 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2603 buf = buf->b_next) {
2604 ASSERT3U(bufcnt, !=, 0);
2608 * When the arc_buf_t is sharing the data
2609 * block with the hdr, the owner of the
2610 * reference belongs to the hdr. Only
2611 * add to the refcount if the arc_buf_t is
2614 if (arc_buf_is_shared(buf))
2617 (void) refcount_remove_many(
2618 &old_state->arcs_size, arc_buf_size(buf),
2621 ASSERT3U(bufcnt, ==, buffers);
2622 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2623 (void) refcount_remove_many(
2624 &old_state->arcs_size, arc_hdr_size(hdr), hdr);
2628 if (HDR_HAS_L1HDR(hdr))
2629 hdr->b_l1hdr.b_state = new_state;
2632 * L2 headers should never be on the L2 state list since they don't
2633 * have L1 headers allocated.
2635 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2636 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2640 arc_space_consume(uint64_t space, arc_space_type_t type)
2642 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2645 case ARC_SPACE_DATA:
2646 ARCSTAT_INCR(arcstat_data_size, space);
2648 case ARC_SPACE_META:
2649 ARCSTAT_INCR(arcstat_metadata_size, space);
2651 case ARC_SPACE_OTHER:
2652 ARCSTAT_INCR(arcstat_other_size, space);
2654 case ARC_SPACE_HDRS:
2655 ARCSTAT_INCR(arcstat_hdr_size, space);
2657 case ARC_SPACE_L2HDRS:
2658 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
2662 if (type != ARC_SPACE_DATA)
2663 ARCSTAT_INCR(arcstat_meta_used, space);
2665 atomic_add_64(&arc_size, space);
2669 arc_space_return(uint64_t space, arc_space_type_t type)
2671 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2674 case ARC_SPACE_DATA:
2675 ARCSTAT_INCR(arcstat_data_size, -space);
2677 case ARC_SPACE_META:
2678 ARCSTAT_INCR(arcstat_metadata_size, -space);
2680 case ARC_SPACE_OTHER:
2681 ARCSTAT_INCR(arcstat_other_size, -space);
2683 case ARC_SPACE_HDRS:
2684 ARCSTAT_INCR(arcstat_hdr_size, -space);
2686 case ARC_SPACE_L2HDRS:
2687 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
2691 if (type != ARC_SPACE_DATA) {
2692 ASSERT(arc_meta_used >= space);
2693 if (arc_meta_max < arc_meta_used)
2694 arc_meta_max = arc_meta_used;
2695 ARCSTAT_INCR(arcstat_meta_used, -space);
2698 ASSERT(arc_size >= space);
2699 atomic_add_64(&arc_size, -space);
2703 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2704 * with the hdr's b_pabd.
2707 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2710 * The criteria for sharing a hdr's data are:
2711 * 1. the hdr's compression matches the buf's compression
2712 * 2. the hdr doesn't need to be byteswapped
2713 * 3. the hdr isn't already being shared
2714 * 4. the buf is either compressed or it is the last buf in the hdr list
2716 * Criterion #4 maintains the invariant that shared uncompressed
2717 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2718 * might ask, "if a compressed buf is allocated first, won't that be the
2719 * last thing in the list?", but in that case it's impossible to create
2720 * a shared uncompressed buf anyway (because the hdr must be compressed
2721 * to have the compressed buf). You might also think that #3 is
2722 * sufficient to make this guarantee, however it's possible
2723 * (specifically in the rare L2ARC write race mentioned in
2724 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2725 * is sharable, but wasn't at the time of its allocation. Rather than
2726 * allow a new shared uncompressed buf to be created and then shuffle
2727 * the list around to make it the last element, this simply disallows
2728 * sharing if the new buf isn't the first to be added.
2730 ASSERT3P(buf->b_hdr, ==, hdr);
2731 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
2732 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2733 return (buf_compressed == hdr_compressed &&
2734 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2735 !HDR_SHARED_DATA(hdr) &&
2736 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2740 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2741 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2742 * copy was made successfully, or an error code otherwise.
2745 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
2746 boolean_t fill, arc_buf_t **ret)
2750 ASSERT(HDR_HAS_L1HDR(hdr));
2751 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2752 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2753 hdr->b_type == ARC_BUFC_METADATA);
2754 ASSERT3P(ret, !=, NULL);
2755 ASSERT3P(*ret, ==, NULL);
2757 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2760 buf->b_next = hdr->b_l1hdr.b_buf;
2763 add_reference(hdr, tag);
2766 * We're about to change the hdr's b_flags. We must either
2767 * hold the hash_lock or be undiscoverable.
2769 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2772 * Only honor requests for compressed bufs if the hdr is actually
2775 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
2776 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2779 * If the hdr's data can be shared then we share the data buffer and
2780 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2781 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
2782 * buffer to store the buf's data.
2784 * There are two additional restrictions here because we're sharing
2785 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2786 * actively involved in an L2ARC write, because if this buf is used by
2787 * an arc_write() then the hdr's data buffer will be released when the
2788 * write completes, even though the L2ARC write might still be using it.
2789 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2790 * need to be ABD-aware.
2792 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2793 abd_is_linear(hdr->b_l1hdr.b_pabd);
2795 /* Set up b_data and sharing */
2797 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2798 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2799 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2802 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2803 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2805 VERIFY3P(buf->b_data, !=, NULL);
2807 hdr->b_l1hdr.b_buf = buf;
2808 hdr->b_l1hdr.b_bufcnt += 1;
2811 * If the user wants the data from the hdr, we need to either copy or
2812 * decompress the data.
2815 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
2821 static char *arc_onloan_tag = "onloan";
2824 arc_loaned_bytes_update(int64_t delta)
2826 atomic_add_64(&arc_loaned_bytes, delta);
2828 /* assert that it did not wrap around */
2829 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2833 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2834 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2835 * buffers must be returned to the arc before they can be used by the DMU or
2839 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2841 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2842 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2844 arc_loaned_bytes_update(size);
2850 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2851 enum zio_compress compression_type)
2853 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2854 psize, lsize, compression_type);
2856 arc_loaned_bytes_update(psize);
2863 * Return a loaned arc buffer to the arc.
2866 arc_return_buf(arc_buf_t *buf, void *tag)
2868 arc_buf_hdr_t *hdr = buf->b_hdr;
2870 ASSERT3P(buf->b_data, !=, NULL);
2871 ASSERT(HDR_HAS_L1HDR(hdr));
2872 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2873 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2875 arc_loaned_bytes_update(-arc_buf_size(buf));
2878 /* Detach an arc_buf from a dbuf (tag) */
2880 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2882 arc_buf_hdr_t *hdr = buf->b_hdr;
2884 ASSERT3P(buf->b_data, !=, NULL);
2885 ASSERT(HDR_HAS_L1HDR(hdr));
2886 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2887 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2889 arc_loaned_bytes_update(arc_buf_size(buf));
2893 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2895 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2898 df->l2df_size = size;
2899 df->l2df_type = type;
2900 mutex_enter(&l2arc_free_on_write_mtx);
2901 list_insert_head(l2arc_free_on_write, df);
2902 mutex_exit(&l2arc_free_on_write_mtx);
2906 arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
2908 arc_state_t *state = hdr->b_l1hdr.b_state;
2909 arc_buf_contents_t type = arc_buf_type(hdr);
2910 uint64_t size = arc_hdr_size(hdr);
2912 /* protected by hash lock, if in the hash table */
2913 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2914 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2915 ASSERT(state != arc_anon && state != arc_l2c_only);
2917 (void) refcount_remove_many(&state->arcs_esize[type],
2920 (void) refcount_remove_many(&state->arcs_size, size, hdr);
2921 if (type == ARC_BUFC_METADATA) {
2922 arc_space_return(size, ARC_SPACE_META);
2924 ASSERT(type == ARC_BUFC_DATA);
2925 arc_space_return(size, ARC_SPACE_DATA);
2928 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2932 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2933 * data buffer, we transfer the refcount ownership to the hdr and update
2934 * the appropriate kstats.
2937 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2939 arc_state_t *state = hdr->b_l1hdr.b_state;
2941 ASSERT(arc_can_share(hdr, buf));
2942 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2943 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2946 * Start sharing the data buffer. We transfer the
2947 * refcount ownership to the hdr since it always owns
2948 * the refcount whenever an arc_buf_t is shared.
2950 refcount_transfer_ownership(&state->arcs_size, buf, hdr);
2951 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
2952 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
2953 HDR_ISTYPE_METADATA(hdr));
2954 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2955 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2958 * Since we've transferred ownership to the hdr we need
2959 * to increment its compressed and uncompressed kstats and
2960 * decrement the overhead size.
2962 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2963 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2964 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
2968 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2970 arc_state_t *state = hdr->b_l1hdr.b_state;
2972 ASSERT(arc_buf_is_shared(buf));
2973 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2974 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2977 * We are no longer sharing this buffer so we need
2978 * to transfer its ownership to the rightful owner.
2980 refcount_transfer_ownership(&state->arcs_size, hdr, buf);
2981 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2982 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
2983 abd_put(hdr->b_l1hdr.b_pabd);
2984 hdr->b_l1hdr.b_pabd = NULL;
2985 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2988 * Since the buffer is no longer shared between
2989 * the arc buf and the hdr, count it as overhead.
2991 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2992 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2993 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2997 * Remove an arc_buf_t from the hdr's buf list and return the last
2998 * arc_buf_t on the list. If no buffers remain on the list then return
3002 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3004 ASSERT(HDR_HAS_L1HDR(hdr));
3005 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3007 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
3008 arc_buf_t *lastbuf = NULL;
3011 * Remove the buf from the hdr list and locate the last
3012 * remaining buffer on the list.
3014 while (*bufp != NULL) {
3016 *bufp = buf->b_next;
3019 * If we've removed a buffer in the middle of
3020 * the list then update the lastbuf and update
3023 if (*bufp != NULL) {
3025 bufp = &(*bufp)->b_next;
3029 ASSERT3P(lastbuf, !=, buf);
3030 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
3031 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
3032 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
3038 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
3042 arc_buf_destroy_impl(arc_buf_t *buf)
3044 arc_buf_hdr_t *hdr = buf->b_hdr;
3047 * Free up the data associated with the buf but only if we're not
3048 * sharing this with the hdr. If we are sharing it with the hdr, the
3049 * hdr is responsible for doing the free.
3051 if (buf->b_data != NULL) {
3053 * We're about to change the hdr's b_flags. We must either
3054 * hold the hash_lock or be undiscoverable.
3056 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3058 arc_cksum_verify(buf);
3060 arc_buf_unwatch(buf);
3063 if (arc_buf_is_shared(buf)) {
3064 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3066 uint64_t size = arc_buf_size(buf);
3067 arc_free_data_buf(hdr, buf->b_data, size, buf);
3068 ARCSTAT_INCR(arcstat_overhead_size, -size);
3072 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3073 hdr->b_l1hdr.b_bufcnt -= 1;
3076 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3078 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3080 * If the current arc_buf_t is sharing its data buffer with the
3081 * hdr, then reassign the hdr's b_pabd to share it with the new
3082 * buffer at the end of the list. The shared buffer is always
3083 * the last one on the hdr's buffer list.
3085 * There is an equivalent case for compressed bufs, but since
3086 * they aren't guaranteed to be the last buf in the list and
3087 * that is an exceedingly rare case, we just allow that space be
3088 * wasted temporarily.
3090 if (lastbuf != NULL) {
3091 /* Only one buf can be shared at once */
3092 VERIFY(!arc_buf_is_shared(lastbuf));
3093 /* hdr is uncompressed so can't have compressed buf */
3094 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3096 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3097 arc_hdr_free_pabd(hdr);
3100 * We must setup a new shared block between the
3101 * last buffer and the hdr. The data would have
3102 * been allocated by the arc buf so we need to transfer
3103 * ownership to the hdr since it's now being shared.
3105 arc_share_buf(hdr, lastbuf);
3107 } else if (HDR_SHARED_DATA(hdr)) {
3109 * Uncompressed shared buffers are always at the end
3110 * of the list. Compressed buffers don't have the
3111 * same requirements. This makes it hard to
3112 * simply assert that the lastbuf is shared so
3113 * we rely on the hdr's compression flags to determine
3114 * if we have a compressed, shared buffer.
3116 ASSERT3P(lastbuf, !=, NULL);
3117 ASSERT(arc_buf_is_shared(lastbuf) ||
3118 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
3122 * Free the checksum if we're removing the last uncompressed buf from
3125 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3126 arc_cksum_free(hdr);
3129 /* clean up the buf */
3131 kmem_cache_free(buf_cache, buf);
3135 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr)
3137 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3138 ASSERT(HDR_HAS_L1HDR(hdr));
3139 ASSERT(!HDR_SHARED_DATA(hdr));
3141 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3142 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
3143 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3144 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3146 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3147 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3151 arc_hdr_free_pabd(arc_buf_hdr_t *hdr)
3153 ASSERT(HDR_HAS_L1HDR(hdr));
3154 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3157 * If the hdr is currently being written to the l2arc then
3158 * we defer freeing the data by adding it to the l2arc_free_on_write
3159 * list. The l2arc will free the data once it's finished
3160 * writing it to the l2arc device.
3162 if (HDR_L2_WRITING(hdr)) {
3163 arc_hdr_free_on_write(hdr);
3164 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3166 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3167 arc_hdr_size(hdr), hdr);
3169 hdr->b_l1hdr.b_pabd = NULL;
3170 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3172 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3173 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3176 static arc_buf_hdr_t *
3177 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3178 enum zio_compress compression_type, arc_buf_contents_t type)
3182 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3184 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3185 ASSERT(HDR_EMPTY(hdr));
3186 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3187 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3188 HDR_SET_PSIZE(hdr, psize);
3189 HDR_SET_LSIZE(hdr, lsize);
3193 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3194 arc_hdr_set_compress(hdr, compression_type);
3196 hdr->b_l1hdr.b_state = arc_anon;
3197 hdr->b_l1hdr.b_arc_access = 0;
3198 hdr->b_l1hdr.b_bufcnt = 0;
3199 hdr->b_l1hdr.b_buf = NULL;
3202 * Allocate the hdr's buffer. This will contain either
3203 * the compressed or uncompressed data depending on the block
3204 * it references and compressed arc enablement.
3206 arc_hdr_alloc_pabd(hdr);
3207 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3213 * Transition between the two allocation states for the arc_buf_hdr struct.
3214 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3215 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3216 * version is used when a cache buffer is only in the L2ARC in order to reduce
3219 static arc_buf_hdr_t *
3220 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3222 ASSERT(HDR_HAS_L2HDR(hdr));
3224 arc_buf_hdr_t *nhdr;
3225 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3227 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3228 (old == hdr_l2only_cache && new == hdr_full_cache));
3230 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3232 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3233 buf_hash_remove(hdr);
3235 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3237 if (new == hdr_full_cache) {
3238 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3240 * arc_access and arc_change_state need to be aware that a
3241 * header has just come out of L2ARC, so we set its state to
3242 * l2c_only even though it's about to change.
3244 nhdr->b_l1hdr.b_state = arc_l2c_only;
3246 /* Verify previous threads set to NULL before freeing */
3247 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3249 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3250 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3251 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3254 * If we've reached here, We must have been called from
3255 * arc_evict_hdr(), as such we should have already been
3256 * removed from any ghost list we were previously on
3257 * (which protects us from racing with arc_evict_state),
3258 * thus no locking is needed during this check.
3260 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3263 * A buffer must not be moved into the arc_l2c_only
3264 * state if it's not finished being written out to the
3265 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3266 * might try to be accessed, even though it was removed.
3268 VERIFY(!HDR_L2_WRITING(hdr));
3269 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3272 if (hdr->b_l1hdr.b_thawed != NULL) {
3273 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3274 hdr->b_l1hdr.b_thawed = NULL;
3278 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3281 * The header has been reallocated so we need to re-insert it into any
3284 (void) buf_hash_insert(nhdr, NULL);
3286 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3288 mutex_enter(&dev->l2ad_mtx);
3291 * We must place the realloc'ed header back into the list at
3292 * the same spot. Otherwise, if it's placed earlier in the list,
3293 * l2arc_write_buffers() could find it during the function's
3294 * write phase, and try to write it out to the l2arc.
3296 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3297 list_remove(&dev->l2ad_buflist, hdr);
3299 mutex_exit(&dev->l2ad_mtx);
3302 * Since we're using the pointer address as the tag when
3303 * incrementing and decrementing the l2ad_alloc refcount, we
3304 * must remove the old pointer (that we're about to destroy) and
3305 * add the new pointer to the refcount. Otherwise we'd remove
3306 * the wrong pointer address when calling arc_hdr_destroy() later.
3309 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
3310 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
3312 buf_discard_identity(hdr);
3313 kmem_cache_free(old, hdr);
3319 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3320 * The buf is returned thawed since we expect the consumer to modify it.
3323 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3325 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3326 ZIO_COMPRESS_OFF, type);
3327 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3329 arc_buf_t *buf = NULL;
3330 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
3337 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3338 * for bufs containing metadata.
3341 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3342 enum zio_compress compression_type)
3344 ASSERT3U(lsize, >, 0);
3345 ASSERT3U(lsize, >=, psize);
3346 ASSERT(compression_type > ZIO_COMPRESS_OFF);
3347 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
3349 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3350 compression_type, ARC_BUFC_DATA);
3351 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3353 arc_buf_t *buf = NULL;
3354 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
3356 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3358 if (!arc_buf_is_shared(buf)) {
3360 * To ensure that the hdr has the correct data in it if we call
3361 * arc_decompress() on this buf before it's been written to
3362 * disk, it's easiest if we just set up sharing between the
3365 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3366 arc_hdr_free_pabd(hdr);
3367 arc_share_buf(hdr, buf);
3374 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3376 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3377 l2arc_dev_t *dev = l2hdr->b_dev;
3378 uint64_t psize = arc_hdr_size(hdr);
3380 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3381 ASSERT(HDR_HAS_L2HDR(hdr));
3383 list_remove(&dev->l2ad_buflist, hdr);
3385 ARCSTAT_INCR(arcstat_l2_psize, -psize);
3386 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
3388 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0);
3390 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr);
3391 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3395 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3397 if (HDR_HAS_L1HDR(hdr)) {
3398 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3399 hdr->b_l1hdr.b_bufcnt > 0);
3400 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3401 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3403 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3404 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3406 if (!HDR_EMPTY(hdr))
3407 buf_discard_identity(hdr);
3409 if (HDR_HAS_L2HDR(hdr)) {
3410 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3411 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3414 mutex_enter(&dev->l2ad_mtx);
3417 * Even though we checked this conditional above, we
3418 * need to check this again now that we have the
3419 * l2ad_mtx. This is because we could be racing with
3420 * another thread calling l2arc_evict() which might have
3421 * destroyed this header's L2 portion as we were waiting
3422 * to acquire the l2ad_mtx. If that happens, we don't
3423 * want to re-destroy the header's L2 portion.
3425 if (HDR_HAS_L2HDR(hdr)) {
3427 arc_hdr_l2hdr_destroy(hdr);
3431 mutex_exit(&dev->l2ad_mtx);
3434 if (HDR_HAS_L1HDR(hdr)) {
3435 arc_cksum_free(hdr);
3437 while (hdr->b_l1hdr.b_buf != NULL)
3438 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3441 if (hdr->b_l1hdr.b_thawed != NULL) {
3442 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3443 hdr->b_l1hdr.b_thawed = NULL;
3447 if (hdr->b_l1hdr.b_pabd != NULL) {
3448 arc_hdr_free_pabd(hdr);
3452 ASSERT3P(hdr->b_hash_next, ==, NULL);
3453 if (HDR_HAS_L1HDR(hdr)) {
3454 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3455 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3456 kmem_cache_free(hdr_full_cache, hdr);
3458 kmem_cache_free(hdr_l2only_cache, hdr);
3463 arc_buf_destroy(arc_buf_t *buf, void* tag)
3465 arc_buf_hdr_t *hdr = buf->b_hdr;
3466 kmutex_t *hash_lock = HDR_LOCK(hdr);
3468 if (hdr->b_l1hdr.b_state == arc_anon) {
3469 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3470 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3471 VERIFY0(remove_reference(hdr, NULL, tag));
3472 arc_hdr_destroy(hdr);
3476 mutex_enter(hash_lock);
3477 ASSERT3P(hdr, ==, buf->b_hdr);
3478 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3479 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3480 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3481 ASSERT3P(buf->b_data, !=, NULL);
3483 (void) remove_reference(hdr, hash_lock, tag);
3484 arc_buf_destroy_impl(buf);
3485 mutex_exit(hash_lock);
3489 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3490 * state of the header is dependent on its state prior to entering this
3491 * function. The following transitions are possible:
3493 * - arc_mru -> arc_mru_ghost
3494 * - arc_mfu -> arc_mfu_ghost
3495 * - arc_mru_ghost -> arc_l2c_only
3496 * - arc_mru_ghost -> deleted
3497 * - arc_mfu_ghost -> arc_l2c_only
3498 * - arc_mfu_ghost -> deleted
3501 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3503 arc_state_t *evicted_state, *state;
3504 int64_t bytes_evicted = 0;
3506 ASSERT(MUTEX_HELD(hash_lock));
3507 ASSERT(HDR_HAS_L1HDR(hdr));
3509 state = hdr->b_l1hdr.b_state;
3510 if (GHOST_STATE(state)) {
3511 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3512 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3515 * l2arc_write_buffers() relies on a header's L1 portion
3516 * (i.e. its b_pabd field) during it's write phase.
3517 * Thus, we cannot push a header onto the arc_l2c_only
3518 * state (removing it's L1 piece) until the header is
3519 * done being written to the l2arc.
3521 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3522 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3523 return (bytes_evicted);
3526 ARCSTAT_BUMP(arcstat_deleted);
3527 bytes_evicted += HDR_GET_LSIZE(hdr);
3529 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3531 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3532 if (HDR_HAS_L2HDR(hdr)) {
3534 * This buffer is cached on the 2nd Level ARC;
3535 * don't destroy the header.
3537 arc_change_state(arc_l2c_only, hdr, hash_lock);
3539 * dropping from L1+L2 cached to L2-only,
3540 * realloc to remove the L1 header.
3542 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3545 arc_change_state(arc_anon, hdr, hash_lock);
3546 arc_hdr_destroy(hdr);
3548 return (bytes_evicted);
3551 ASSERT(state == arc_mru || state == arc_mfu);
3552 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3554 /* prefetch buffers have a minimum lifespan */
3555 if (HDR_IO_IN_PROGRESS(hdr) ||
3556 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3557 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
3558 arc_min_prefetch_lifespan)) {
3559 ARCSTAT_BUMP(arcstat_evict_skip);
3560 return (bytes_evicted);
3563 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3564 while (hdr->b_l1hdr.b_buf) {
3565 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3566 if (!mutex_tryenter(&buf->b_evict_lock)) {
3567 ARCSTAT_BUMP(arcstat_mutex_miss);
3570 if (buf->b_data != NULL)
3571 bytes_evicted += HDR_GET_LSIZE(hdr);
3572 mutex_exit(&buf->b_evict_lock);
3573 arc_buf_destroy_impl(buf);
3576 if (HDR_HAS_L2HDR(hdr)) {
3577 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3579 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3580 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3581 HDR_GET_LSIZE(hdr));
3583 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3584 HDR_GET_LSIZE(hdr));
3588 if (hdr->b_l1hdr.b_bufcnt == 0) {
3589 arc_cksum_free(hdr);
3591 bytes_evicted += arc_hdr_size(hdr);
3594 * If this hdr is being evicted and has a compressed
3595 * buffer then we discard it here before we change states.
3596 * This ensures that the accounting is updated correctly
3597 * in arc_free_data_impl().
3599 arc_hdr_free_pabd(hdr);
3601 arc_change_state(evicted_state, hdr, hash_lock);
3602 ASSERT(HDR_IN_HASH_TABLE(hdr));
3603 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3604 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3607 return (bytes_evicted);
3611 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3612 uint64_t spa, int64_t bytes)
3614 multilist_sublist_t *mls;
3615 uint64_t bytes_evicted = 0;
3617 kmutex_t *hash_lock;
3618 int evict_count = 0;
3620 ASSERT3P(marker, !=, NULL);
3621 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3623 mls = multilist_sublist_lock(ml, idx);
3625 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3626 hdr = multilist_sublist_prev(mls, marker)) {
3627 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3628 (evict_count >= zfs_arc_evict_batch_limit))
3632 * To keep our iteration location, move the marker
3633 * forward. Since we're not holding hdr's hash lock, we
3634 * must be very careful and not remove 'hdr' from the
3635 * sublist. Otherwise, other consumers might mistake the
3636 * 'hdr' as not being on a sublist when they call the
3637 * multilist_link_active() function (they all rely on
3638 * the hash lock protecting concurrent insertions and
3639 * removals). multilist_sublist_move_forward() was
3640 * specifically implemented to ensure this is the case
3641 * (only 'marker' will be removed and re-inserted).
3643 multilist_sublist_move_forward(mls, marker);
3646 * The only case where the b_spa field should ever be
3647 * zero, is the marker headers inserted by
3648 * arc_evict_state(). It's possible for multiple threads
3649 * to be calling arc_evict_state() concurrently (e.g.
3650 * dsl_pool_close() and zio_inject_fault()), so we must
3651 * skip any markers we see from these other threads.
3653 if (hdr->b_spa == 0)
3656 /* we're only interested in evicting buffers of a certain spa */
3657 if (spa != 0 && hdr->b_spa != spa) {
3658 ARCSTAT_BUMP(arcstat_evict_skip);
3662 hash_lock = HDR_LOCK(hdr);
3665 * We aren't calling this function from any code path
3666 * that would already be holding a hash lock, so we're
3667 * asserting on this assumption to be defensive in case
3668 * this ever changes. Without this check, it would be
3669 * possible to incorrectly increment arcstat_mutex_miss
3670 * below (e.g. if the code changed such that we called
3671 * this function with a hash lock held).
3673 ASSERT(!MUTEX_HELD(hash_lock));
3675 if (mutex_tryenter(hash_lock)) {
3676 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3677 mutex_exit(hash_lock);
3679 bytes_evicted += evicted;
3682 * If evicted is zero, arc_evict_hdr() must have
3683 * decided to skip this header, don't increment
3684 * evict_count in this case.
3690 * If arc_size isn't overflowing, signal any
3691 * threads that might happen to be waiting.
3693 * For each header evicted, we wake up a single
3694 * thread. If we used cv_broadcast, we could
3695 * wake up "too many" threads causing arc_size
3696 * to significantly overflow arc_c; since
3697 * arc_get_data_impl() doesn't check for overflow
3698 * when it's woken up (it doesn't because it's
3699 * possible for the ARC to be overflowing while
3700 * full of un-evictable buffers, and the
3701 * function should proceed in this case).
3703 * If threads are left sleeping, due to not
3704 * using cv_broadcast, they will be woken up
3705 * just before arc_reclaim_thread() sleeps.
3707 mutex_enter(&arc_reclaim_lock);
3708 if (!arc_is_overflowing())
3709 cv_signal(&arc_reclaim_waiters_cv);
3710 mutex_exit(&arc_reclaim_lock);
3712 ARCSTAT_BUMP(arcstat_mutex_miss);
3716 multilist_sublist_unlock(mls);
3718 return (bytes_evicted);
3722 * Evict buffers from the given arc state, until we've removed the
3723 * specified number of bytes. Move the removed buffers to the
3724 * appropriate evict state.
3726 * This function makes a "best effort". It skips over any buffers
3727 * it can't get a hash_lock on, and so, may not catch all candidates.
3728 * It may also return without evicting as much space as requested.
3730 * If bytes is specified using the special value ARC_EVICT_ALL, this
3731 * will evict all available (i.e. unlocked and evictable) buffers from
3732 * the given arc state; which is used by arc_flush().
3735 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
3736 arc_buf_contents_t type)
3738 uint64_t total_evicted = 0;
3739 multilist_t *ml = state->arcs_list[type];
3741 arc_buf_hdr_t **markers;
3743 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3745 num_sublists = multilist_get_num_sublists(ml);
3748 * If we've tried to evict from each sublist, made some
3749 * progress, but still have not hit the target number of bytes
3750 * to evict, we want to keep trying. The markers allow us to
3751 * pick up where we left off for each individual sublist, rather
3752 * than starting from the tail each time.
3754 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
3755 for (int i = 0; i < num_sublists; i++) {
3756 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
3759 * A b_spa of 0 is used to indicate that this header is
3760 * a marker. This fact is used in arc_adjust_type() and
3761 * arc_evict_state_impl().
3763 markers[i]->b_spa = 0;
3765 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3766 multilist_sublist_insert_tail(mls, markers[i]);
3767 multilist_sublist_unlock(mls);
3771 * While we haven't hit our target number of bytes to evict, or
3772 * we're evicting all available buffers.
3774 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
3776 * Start eviction using a randomly selected sublist,
3777 * this is to try and evenly balance eviction across all
3778 * sublists. Always starting at the same sublist
3779 * (e.g. index 0) would cause evictions to favor certain
3780 * sublists over others.
3782 int sublist_idx = multilist_get_random_index(ml);
3783 uint64_t scan_evicted = 0;
3785 for (int i = 0; i < num_sublists; i++) {
3786 uint64_t bytes_remaining;
3787 uint64_t bytes_evicted;
3789 if (bytes == ARC_EVICT_ALL)
3790 bytes_remaining = ARC_EVICT_ALL;
3791 else if (total_evicted < bytes)
3792 bytes_remaining = bytes - total_evicted;
3796 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
3797 markers[sublist_idx], spa, bytes_remaining);
3799 scan_evicted += bytes_evicted;
3800 total_evicted += bytes_evicted;
3802 /* we've reached the end, wrap to the beginning */
3803 if (++sublist_idx >= num_sublists)
3808 * If we didn't evict anything during this scan, we have
3809 * no reason to believe we'll evict more during another
3810 * scan, so break the loop.
3812 if (scan_evicted == 0) {
3813 /* This isn't possible, let's make that obvious */
3814 ASSERT3S(bytes, !=, 0);
3817 * When bytes is ARC_EVICT_ALL, the only way to
3818 * break the loop is when scan_evicted is zero.
3819 * In that case, we actually have evicted enough,
3820 * so we don't want to increment the kstat.
3822 if (bytes != ARC_EVICT_ALL) {
3823 ASSERT3S(total_evicted, <, bytes);
3824 ARCSTAT_BUMP(arcstat_evict_not_enough);
3831 for (int i = 0; i < num_sublists; i++) {
3832 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3833 multilist_sublist_remove(mls, markers[i]);
3834 multilist_sublist_unlock(mls);
3836 kmem_cache_free(hdr_full_cache, markers[i]);
3838 kmem_free(markers, sizeof (*markers) * num_sublists);
3840 return (total_evicted);
3844 * Flush all "evictable" data of the given type from the arc state
3845 * specified. This will not evict any "active" buffers (i.e. referenced).
3847 * When 'retry' is set to B_FALSE, the function will make a single pass
3848 * over the state and evict any buffers that it can. Since it doesn't
3849 * continually retry the eviction, it might end up leaving some buffers
3850 * in the ARC due to lock misses.
3852 * When 'retry' is set to B_TRUE, the function will continually retry the
3853 * eviction until *all* evictable buffers have been removed from the
3854 * state. As a result, if concurrent insertions into the state are
3855 * allowed (e.g. if the ARC isn't shutting down), this function might
3856 * wind up in an infinite loop, continually trying to evict buffers.
3859 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
3862 uint64_t evicted = 0;
3864 while (refcount_count(&state->arcs_esize[type]) != 0) {
3865 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
3875 * Evict the specified number of bytes from the state specified,
3876 * restricting eviction to the spa and type given. This function
3877 * prevents us from trying to evict more from a state's list than
3878 * is "evictable", and to skip evicting altogether when passed a
3879 * negative value for "bytes". In contrast, arc_evict_state() will
3880 * evict everything it can, when passed a negative value for "bytes".
3883 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
3884 arc_buf_contents_t type)
3888 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
3889 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
3890 return (arc_evict_state(state, spa, delta, type));
3897 * Evict metadata buffers from the cache, such that arc_meta_used is
3898 * capped by the arc_meta_limit tunable.
3901 arc_adjust_meta(void)
3903 uint64_t total_evicted = 0;
3907 * If we're over the meta limit, we want to evict enough
3908 * metadata to get back under the meta limit. We don't want to
3909 * evict so much that we drop the MRU below arc_p, though. If
3910 * we're over the meta limit more than we're over arc_p, we
3911 * evict some from the MRU here, and some from the MFU below.
3913 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3914 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3915 refcount_count(&arc_mru->arcs_size) - arc_p));
3917 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3920 * Similar to the above, we want to evict enough bytes to get us
3921 * below the meta limit, but not so much as to drop us below the
3922 * space allotted to the MFU (which is defined as arc_c - arc_p).
3924 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3925 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
3927 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3929 return (total_evicted);
3933 * Return the type of the oldest buffer in the given arc state
3935 * This function will select a random sublist of type ARC_BUFC_DATA and
3936 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
3937 * is compared, and the type which contains the "older" buffer will be
3940 static arc_buf_contents_t
3941 arc_adjust_type(arc_state_t *state)
3943 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
3944 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
3945 int data_idx = multilist_get_random_index(data_ml);
3946 int meta_idx = multilist_get_random_index(meta_ml);
3947 multilist_sublist_t *data_mls;
3948 multilist_sublist_t *meta_mls;
3949 arc_buf_contents_t type;
3950 arc_buf_hdr_t *data_hdr;
3951 arc_buf_hdr_t *meta_hdr;
3954 * We keep the sublist lock until we're finished, to prevent
3955 * the headers from being destroyed via arc_evict_state().
3957 data_mls = multilist_sublist_lock(data_ml, data_idx);
3958 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
3961 * These two loops are to ensure we skip any markers that
3962 * might be at the tail of the lists due to arc_evict_state().
3965 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
3966 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
3967 if (data_hdr->b_spa != 0)
3971 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
3972 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
3973 if (meta_hdr->b_spa != 0)
3977 if (data_hdr == NULL && meta_hdr == NULL) {
3978 type = ARC_BUFC_DATA;
3979 } else if (data_hdr == NULL) {
3980 ASSERT3P(meta_hdr, !=, NULL);
3981 type = ARC_BUFC_METADATA;
3982 } else if (meta_hdr == NULL) {
3983 ASSERT3P(data_hdr, !=, NULL);
3984 type = ARC_BUFC_DATA;
3986 ASSERT3P(data_hdr, !=, NULL);
3987 ASSERT3P(meta_hdr, !=, NULL);
3989 /* The headers can't be on the sublist without an L1 header */
3990 ASSERT(HDR_HAS_L1HDR(data_hdr));
3991 ASSERT(HDR_HAS_L1HDR(meta_hdr));
3993 if (data_hdr->b_l1hdr.b_arc_access <
3994 meta_hdr->b_l1hdr.b_arc_access) {
3995 type = ARC_BUFC_DATA;
3997 type = ARC_BUFC_METADATA;
4001 multilist_sublist_unlock(meta_mls);
4002 multilist_sublist_unlock(data_mls);
4008 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4013 uint64_t total_evicted = 0;
4018 * If we're over arc_meta_limit, we want to correct that before
4019 * potentially evicting data buffers below.
4021 total_evicted += arc_adjust_meta();
4026 * If we're over the target cache size, we want to evict enough
4027 * from the list to get back to our target size. We don't want
4028 * to evict too much from the MRU, such that it drops below
4029 * arc_p. So, if we're over our target cache size more than
4030 * the MRU is over arc_p, we'll evict enough to get back to
4031 * arc_p here, and then evict more from the MFU below.
4033 target = MIN((int64_t)(arc_size - arc_c),
4034 (int64_t)(refcount_count(&arc_anon->arcs_size) +
4035 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
4038 * If we're below arc_meta_min, always prefer to evict data.
4039 * Otherwise, try to satisfy the requested number of bytes to
4040 * evict from the type which contains older buffers; in an
4041 * effort to keep newer buffers in the cache regardless of their
4042 * type. If we cannot satisfy the number of bytes from this
4043 * type, spill over into the next type.
4045 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4046 arc_meta_used > arc_meta_min) {
4047 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4048 total_evicted += bytes;
4051 * If we couldn't evict our target number of bytes from
4052 * metadata, we try to get the rest from data.
4057 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4059 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4060 total_evicted += bytes;
4063 * If we couldn't evict our target number of bytes from
4064 * data, we try to get the rest from metadata.
4069 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4075 * Now that we've tried to evict enough from the MRU to get its
4076 * size back to arc_p, if we're still above the target cache
4077 * size, we evict the rest from the MFU.
4079 target = arc_size - arc_c;
4081 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4082 arc_meta_used > arc_meta_min) {
4083 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4084 total_evicted += bytes;
4087 * If we couldn't evict our target number of bytes from
4088 * metadata, we try to get the rest from data.
4093 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4095 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4096 total_evicted += bytes;
4099 * If we couldn't evict our target number of bytes from
4100 * data, we try to get the rest from data.
4105 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4109 * Adjust ghost lists
4111 * In addition to the above, the ARC also defines target values
4112 * for the ghost lists. The sum of the mru list and mru ghost
4113 * list should never exceed the target size of the cache, and
4114 * the sum of the mru list, mfu list, mru ghost list, and mfu
4115 * ghost list should never exceed twice the target size of the
4116 * cache. The following logic enforces these limits on the ghost
4117 * caches, and evicts from them as needed.
4119 target = refcount_count(&arc_mru->arcs_size) +
4120 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4122 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4123 total_evicted += bytes;
4128 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4131 * We assume the sum of the mru list and mfu list is less than
4132 * or equal to arc_c (we enforced this above), which means we
4133 * can use the simpler of the two equations below:
4135 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4136 * mru ghost + mfu ghost <= arc_c
4138 target = refcount_count(&arc_mru_ghost->arcs_size) +
4139 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4141 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4142 total_evicted += bytes;
4147 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4149 return (total_evicted);
4153 arc_flush(spa_t *spa, boolean_t retry)
4158 * If retry is B_TRUE, a spa must not be specified since we have
4159 * no good way to determine if all of a spa's buffers have been
4160 * evicted from an arc state.
4162 ASSERT(!retry || spa == 0);
4165 guid = spa_load_guid(spa);
4167 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4168 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4170 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4171 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4173 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4174 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4176 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4177 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4181 arc_shrink(int64_t to_free)
4183 if (arc_c > arc_c_min) {
4184 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
4185 arc_c_min, uint64_t, arc_p, uint64_t, to_free);
4186 if (arc_c > arc_c_min + to_free)
4187 atomic_add_64(&arc_c, -to_free);
4191 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4192 if (arc_c > arc_size)
4193 arc_c = MAX(arc_size, arc_c_min);
4195 arc_p = (arc_c >> 1);
4197 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
4200 ASSERT(arc_c >= arc_c_min);
4201 ASSERT((int64_t)arc_p >= 0);
4204 if (arc_size > arc_c) {
4205 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size,
4207 (void) arc_adjust();
4211 typedef enum free_memory_reason_t {
4216 FMR_PAGES_PP_MAXIMUM,
4219 } free_memory_reason_t;
4221 int64_t last_free_memory;
4222 free_memory_reason_t last_free_reason;
4225 * Additional reserve of pages for pp_reserve.
4227 int64_t arc_pages_pp_reserve = 64;
4230 * Additional reserve of pages for swapfs.
4232 int64_t arc_swapfs_reserve = 64;
4235 * Return the amount of memory that can be consumed before reclaim will be
4236 * needed. Positive if there is sufficient free memory, negative indicates
4237 * the amount of memory that needs to be freed up.
4240 arc_available_memory(void)
4242 int64_t lowest = INT64_MAX;
4244 free_memory_reason_t r = FMR_UNKNOWN;
4249 * Cooperate with pagedaemon when it's time for it to scan
4250 * and reclaim some pages.
4252 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target);
4260 n = PAGESIZE * (-needfree);
4268 * check that we're out of range of the pageout scanner. It starts to
4269 * schedule paging if freemem is less than lotsfree and needfree.
4270 * lotsfree is the high-water mark for pageout, and needfree is the
4271 * number of needed free pages. We add extra pages here to make sure
4272 * the scanner doesn't start up while we're freeing memory.
4274 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4281 * check to make sure that swapfs has enough space so that anon
4282 * reservations can still succeed. anon_resvmem() checks that the
4283 * availrmem is greater than swapfs_minfree, and the number of reserved
4284 * swap pages. We also add a bit of extra here just to prevent
4285 * circumstances from getting really dire.
4287 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4288 desfree - arc_swapfs_reserve);
4291 r = FMR_SWAPFS_MINFREE;
4296 * Check that we have enough availrmem that memory locking (e.g., via
4297 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4298 * stores the number of pages that cannot be locked; when availrmem
4299 * drops below pages_pp_maximum, page locking mechanisms such as
4300 * page_pp_lock() will fail.)
4302 n = PAGESIZE * (availrmem - pages_pp_maximum -
4303 arc_pages_pp_reserve);
4306 r = FMR_PAGES_PP_MAXIMUM;
4309 #endif /* __FreeBSD__ */
4310 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
4312 * If we're on an i386 platform, it's possible that we'll exhaust the
4313 * kernel heap space before we ever run out of available physical
4314 * memory. Most checks of the size of the heap_area compare against
4315 * tune.t_minarmem, which is the minimum available real memory that we
4316 * can have in the system. However, this is generally fixed at 25 pages
4317 * which is so low that it's useless. In this comparison, we seek to
4318 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4319 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4322 n = uma_avail() - (long)(uma_limit() / 4);
4330 * If zio data pages are being allocated out of a separate heap segment,
4331 * then enforce that the size of available vmem for this arena remains
4332 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4334 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4335 * memory (in the zio_arena) free, which can avoid memory
4336 * fragmentation issues.
4338 if (zio_arena != NULL) {
4339 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4340 (vmem_size(zio_arena, VMEM_ALLOC) >>
4341 arc_zio_arena_free_shift);
4349 /* Every 100 calls, free a small amount */
4350 if (spa_get_random(100) == 0)
4352 #endif /* _KERNEL */
4354 last_free_memory = lowest;
4355 last_free_reason = r;
4356 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r);
4362 * Determine if the system is under memory pressure and is asking
4363 * to reclaim memory. A return value of B_TRUE indicates that the system
4364 * is under memory pressure and that the arc should adjust accordingly.
4367 arc_reclaim_needed(void)
4369 return (arc_available_memory() < 0);
4372 extern kmem_cache_t *zio_buf_cache[];
4373 extern kmem_cache_t *zio_data_buf_cache[];
4374 extern kmem_cache_t *range_seg_cache;
4375 extern kmem_cache_t *abd_chunk_cache;
4377 static __noinline void
4378 arc_kmem_reap_now(void)
4381 kmem_cache_t *prev_cache = NULL;
4382 kmem_cache_t *prev_data_cache = NULL;
4384 DTRACE_PROBE(arc__kmem_reap_start);
4386 if (arc_meta_used >= arc_meta_limit) {
4388 * We are exceeding our meta-data cache limit.
4389 * Purge some DNLC entries to release holds on meta-data.
4391 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4395 * Reclaim unused memory from all kmem caches.
4402 * If a kmem reap is already active, don't schedule more. We must
4403 * check for this because kmem_cache_reap_soon() won't actually
4404 * block on the cache being reaped (this is to prevent callers from
4405 * becoming implicitly blocked by a system-wide kmem reap -- which,
4406 * on a system with many, many full magazines, can take minutes).
4408 if (kmem_cache_reap_active())
4411 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4412 if (zio_buf_cache[i] != prev_cache) {
4413 prev_cache = zio_buf_cache[i];
4414 kmem_cache_reap_soon(zio_buf_cache[i]);
4416 if (zio_data_buf_cache[i] != prev_data_cache) {
4417 prev_data_cache = zio_data_buf_cache[i];
4418 kmem_cache_reap_soon(zio_data_buf_cache[i]);
4421 kmem_cache_reap_soon(abd_chunk_cache);
4422 kmem_cache_reap_soon(buf_cache);
4423 kmem_cache_reap_soon(hdr_full_cache);
4424 kmem_cache_reap_soon(hdr_l2only_cache);
4425 kmem_cache_reap_soon(range_seg_cache);
4428 if (zio_arena != NULL) {
4430 * Ask the vmem arena to reclaim unused memory from its
4433 vmem_qcache_reap(zio_arena);
4436 DTRACE_PROBE(arc__kmem_reap_end);
4440 * Threads can block in arc_get_data_impl() waiting for this thread to evict
4441 * enough data and signal them to proceed. When this happens, the threads in
4442 * arc_get_data_impl() are sleeping while holding the hash lock for their
4443 * particular arc header. Thus, we must be careful to never sleep on a
4444 * hash lock in this thread. This is to prevent the following deadlock:
4446 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
4447 * waiting for the reclaim thread to signal it.
4449 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
4450 * fails, and goes to sleep forever.
4452 * This possible deadlock is avoided by always acquiring a hash lock
4453 * using mutex_tryenter() from arc_reclaim_thread().
4457 arc_reclaim_thread(void *unused __unused)
4459 hrtime_t growtime = 0;
4460 hrtime_t kmem_reap_time = 0;
4463 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
4465 mutex_enter(&arc_reclaim_lock);
4466 while (!arc_reclaim_thread_exit) {
4467 uint64_t evicted = 0;
4470 * This is necessary in order for the mdb ::arc dcmd to
4471 * show up to date information. Since the ::arc command
4472 * does not call the kstat's update function, without
4473 * this call, the command may show stale stats for the
4474 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4475 * with this change, the data might be up to 1 second
4476 * out of date; but that should suffice. The arc_state_t
4477 * structures can be queried directly if more accurate
4478 * information is needed.
4480 if (arc_ksp != NULL)
4481 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4483 mutex_exit(&arc_reclaim_lock);
4486 * We call arc_adjust() before (possibly) calling
4487 * arc_kmem_reap_now(), so that we can wake up
4488 * arc_get_data_impl() sooner.
4490 evicted = arc_adjust();
4492 int64_t free_memory = arc_available_memory();
4493 if (free_memory < 0) {
4494 hrtime_t curtime = gethrtime();
4495 arc_no_grow = B_TRUE;
4499 * Wait at least zfs_grow_retry (default 60) seconds
4500 * before considering growing.
4502 growtime = curtime + SEC2NSEC(arc_grow_retry);
4505 * Wait at least arc_kmem_cache_reap_retry_ms
4506 * between arc_kmem_reap_now() calls. Without
4507 * this check it is possible to end up in a
4508 * situation where we spend lots of time
4509 * reaping caches, while we're near arc_c_min.
4511 if (curtime >= kmem_reap_time) {
4512 arc_kmem_reap_now();
4513 kmem_reap_time = gethrtime() +
4514 MSEC2NSEC(arc_kmem_cache_reap_retry_ms);
4518 * If we are still low on memory, shrink the ARC
4519 * so that we have arc_shrink_min free space.
4521 free_memory = arc_available_memory();
4524 (arc_c >> arc_shrink_shift) - free_memory;
4528 to_free = MAX(to_free, ptob(needfree));
4531 arc_shrink(to_free);
4533 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4534 arc_no_grow = B_TRUE;
4535 } else if (gethrtime() >= growtime) {
4536 arc_no_grow = B_FALSE;
4539 mutex_enter(&arc_reclaim_lock);
4542 * If evicted is zero, we couldn't evict anything via
4543 * arc_adjust(). This could be due to hash lock
4544 * collisions, but more likely due to the majority of
4545 * arc buffers being unevictable. Therefore, even if
4546 * arc_size is above arc_c, another pass is unlikely to
4547 * be helpful and could potentially cause us to enter an
4550 if (arc_size <= arc_c || evicted == 0) {
4552 * We're either no longer overflowing, or we
4553 * can't evict anything more, so we should wake
4554 * up any threads before we go to sleep.
4556 cv_broadcast(&arc_reclaim_waiters_cv);
4559 * Block until signaled, or after one second (we
4560 * might need to perform arc_kmem_reap_now()
4561 * even if we aren't being signalled)
4563 CALLB_CPR_SAFE_BEGIN(&cpr);
4564 (void) cv_timedwait_hires(&arc_reclaim_thread_cv,
4565 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
4566 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
4570 arc_reclaim_thread_exit = B_FALSE;
4571 cv_broadcast(&arc_reclaim_thread_cv);
4572 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
4576 static u_int arc_dnlc_evicts_arg;
4577 extern struct vfsops zfs_vfsops;
4580 arc_dnlc_evicts_thread(void *dummy __unused)
4585 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG);
4587 mutex_enter(&arc_dnlc_evicts_lock);
4588 while (!arc_dnlc_evicts_thread_exit) {
4589 CALLB_CPR_SAFE_BEGIN(&cpr);
4590 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
4591 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock);
4592 if (arc_dnlc_evicts_arg != 0) {
4593 percent = arc_dnlc_evicts_arg;
4594 mutex_exit(&arc_dnlc_evicts_lock);
4596 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops);
4598 mutex_enter(&arc_dnlc_evicts_lock);
4600 * Clear our token only after vnlru_free()
4601 * pass is done, to avoid false queueing of
4604 arc_dnlc_evicts_arg = 0;
4607 arc_dnlc_evicts_thread_exit = FALSE;
4608 cv_broadcast(&arc_dnlc_evicts_cv);
4609 CALLB_CPR_EXIT(&cpr);
4614 dnlc_reduce_cache(void *arg)
4618 percent = (u_int)(uintptr_t)arg;
4619 mutex_enter(&arc_dnlc_evicts_lock);
4620 if (arc_dnlc_evicts_arg == 0) {
4621 arc_dnlc_evicts_arg = percent;
4622 cv_broadcast(&arc_dnlc_evicts_cv);
4624 mutex_exit(&arc_dnlc_evicts_lock);
4628 * Adapt arc info given the number of bytes we are trying to add and
4629 * the state that we are comming from. This function is only called
4630 * when we are adding new content to the cache.
4633 arc_adapt(int bytes, arc_state_t *state)
4636 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4637 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
4638 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
4640 if (state == arc_l2c_only)
4645 * Adapt the target size of the MRU list:
4646 * - if we just hit in the MRU ghost list, then increase
4647 * the target size of the MRU list.
4648 * - if we just hit in the MFU ghost list, then increase
4649 * the target size of the MFU list by decreasing the
4650 * target size of the MRU list.
4652 if (state == arc_mru_ghost) {
4653 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4654 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4656 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4657 } else if (state == arc_mfu_ghost) {
4660 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4661 mult = MIN(mult, 10);
4663 delta = MIN(bytes * mult, arc_p);
4664 arc_p = MAX(arc_p_min, arc_p - delta);
4666 ASSERT((int64_t)arc_p >= 0);
4668 if (arc_reclaim_needed()) {
4669 cv_signal(&arc_reclaim_thread_cv);
4676 if (arc_c >= arc_c_max)
4680 * If we're within (2 * maxblocksize) bytes of the target
4681 * cache size, increment the target cache size
4683 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
4684 DTRACE_PROBE1(arc__inc_adapt, int, bytes);
4685 atomic_add_64(&arc_c, (int64_t)bytes);
4686 if (arc_c > arc_c_max)
4688 else if (state == arc_anon)
4689 atomic_add_64(&arc_p, (int64_t)bytes);
4693 ASSERT((int64_t)arc_p >= 0);
4697 * Check if arc_size has grown past our upper threshold, determined by
4698 * zfs_arc_overflow_shift.
4701 arc_is_overflowing(void)
4703 /* Always allow at least one block of overflow */
4704 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4705 arc_c >> zfs_arc_overflow_shift);
4707 return (arc_size >= arc_c + overflow);
4711 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4713 arc_buf_contents_t type = arc_buf_type(hdr);
4715 arc_get_data_impl(hdr, size, tag);
4716 if (type == ARC_BUFC_METADATA) {
4717 return (abd_alloc(size, B_TRUE));
4719 ASSERT(type == ARC_BUFC_DATA);
4720 return (abd_alloc(size, B_FALSE));
4725 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4727 arc_buf_contents_t type = arc_buf_type(hdr);
4729 arc_get_data_impl(hdr, size, tag);
4730 if (type == ARC_BUFC_METADATA) {
4731 return (zio_buf_alloc(size));
4733 ASSERT(type == ARC_BUFC_DATA);
4734 return (zio_data_buf_alloc(size));
4739 * Allocate a block and return it to the caller. If we are hitting the
4740 * hard limit for the cache size, we must sleep, waiting for the eviction
4741 * thread to catch up. If we're past the target size but below the hard
4742 * limit, we'll only signal the reclaim thread and continue on.
4745 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4747 arc_state_t *state = hdr->b_l1hdr.b_state;
4748 arc_buf_contents_t type = arc_buf_type(hdr);
4750 arc_adapt(size, state);
4753 * If arc_size is currently overflowing, and has grown past our
4754 * upper limit, we must be adding data faster than the evict
4755 * thread can evict. Thus, to ensure we don't compound the
4756 * problem by adding more data and forcing arc_size to grow even
4757 * further past it's target size, we halt and wait for the
4758 * eviction thread to catch up.
4760 * It's also possible that the reclaim thread is unable to evict
4761 * enough buffers to get arc_size below the overflow limit (e.g.
4762 * due to buffers being un-evictable, or hash lock collisions).
4763 * In this case, we want to proceed regardless if we're
4764 * overflowing; thus we don't use a while loop here.
4766 if (arc_is_overflowing()) {
4767 mutex_enter(&arc_reclaim_lock);
4770 * Now that we've acquired the lock, we may no longer be
4771 * over the overflow limit, lets check.
4773 * We're ignoring the case of spurious wake ups. If that
4774 * were to happen, it'd let this thread consume an ARC
4775 * buffer before it should have (i.e. before we're under
4776 * the overflow limit and were signalled by the reclaim
4777 * thread). As long as that is a rare occurrence, it
4778 * shouldn't cause any harm.
4780 if (arc_is_overflowing()) {
4781 cv_signal(&arc_reclaim_thread_cv);
4782 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
4785 mutex_exit(&arc_reclaim_lock);
4788 VERIFY3U(hdr->b_type, ==, type);
4789 if (type == ARC_BUFC_METADATA) {
4790 arc_space_consume(size, ARC_SPACE_META);
4792 arc_space_consume(size, ARC_SPACE_DATA);
4796 * Update the state size. Note that ghost states have a
4797 * "ghost size" and so don't need to be updated.
4799 if (!GHOST_STATE(state)) {
4801 (void) refcount_add_many(&state->arcs_size, size, tag);
4804 * If this is reached via arc_read, the link is
4805 * protected by the hash lock. If reached via
4806 * arc_buf_alloc, the header should not be accessed by
4807 * any other thread. And, if reached via arc_read_done,
4808 * the hash lock will protect it if it's found in the
4809 * hash table; otherwise no other thread should be
4810 * trying to [add|remove]_reference it.
4812 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4813 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4814 (void) refcount_add_many(&state->arcs_esize[type],
4819 * If we are growing the cache, and we are adding anonymous
4820 * data, and we have outgrown arc_p, update arc_p
4822 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
4823 (refcount_count(&arc_anon->arcs_size) +
4824 refcount_count(&arc_mru->arcs_size) > arc_p))
4825 arc_p = MIN(arc_c, arc_p + size);
4827 ARCSTAT_BUMP(arcstat_allocated);
4831 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
4833 arc_free_data_impl(hdr, size, tag);
4838 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
4840 arc_buf_contents_t type = arc_buf_type(hdr);
4842 arc_free_data_impl(hdr, size, tag);
4843 if (type == ARC_BUFC_METADATA) {
4844 zio_buf_free(buf, size);
4846 ASSERT(type == ARC_BUFC_DATA);
4847 zio_data_buf_free(buf, size);
4852 * Free the arc data buffer.
4855 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4857 arc_state_t *state = hdr->b_l1hdr.b_state;
4858 arc_buf_contents_t type = arc_buf_type(hdr);
4860 /* protected by hash lock, if in the hash table */
4861 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4862 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4863 ASSERT(state != arc_anon && state != arc_l2c_only);
4865 (void) refcount_remove_many(&state->arcs_esize[type],
4868 (void) refcount_remove_many(&state->arcs_size, size, tag);
4870 VERIFY3U(hdr->b_type, ==, type);
4871 if (type == ARC_BUFC_METADATA) {
4872 arc_space_return(size, ARC_SPACE_META);
4874 ASSERT(type == ARC_BUFC_DATA);
4875 arc_space_return(size, ARC_SPACE_DATA);
4880 * This routine is called whenever a buffer is accessed.
4881 * NOTE: the hash lock is dropped in this function.
4884 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
4888 ASSERT(MUTEX_HELD(hash_lock));
4889 ASSERT(HDR_HAS_L1HDR(hdr));
4891 if (hdr->b_l1hdr.b_state == arc_anon) {
4893 * This buffer is not in the cache, and does not
4894 * appear in our "ghost" list. Add the new buffer
4898 ASSERT0(hdr->b_l1hdr.b_arc_access);
4899 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4900 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4901 arc_change_state(arc_mru, hdr, hash_lock);
4903 } else if (hdr->b_l1hdr.b_state == arc_mru) {
4904 now = ddi_get_lbolt();
4907 * If this buffer is here because of a prefetch, then either:
4908 * - clear the flag if this is a "referencing" read
4909 * (any subsequent access will bump this into the MFU state).
4911 * - move the buffer to the head of the list if this is
4912 * another prefetch (to make it less likely to be evicted).
4914 if (HDR_PREFETCH(hdr)) {
4915 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4916 /* link protected by hash lock */
4917 ASSERT(multilist_link_active(
4918 &hdr->b_l1hdr.b_arc_node));
4920 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4921 ARCSTAT_BUMP(arcstat_mru_hits);
4923 hdr->b_l1hdr.b_arc_access = now;
4928 * This buffer has been "accessed" only once so far,
4929 * but it is still in the cache. Move it to the MFU
4932 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
4934 * More than 125ms have passed since we
4935 * instantiated this buffer. Move it to the
4936 * most frequently used state.
4938 hdr->b_l1hdr.b_arc_access = now;
4939 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4940 arc_change_state(arc_mfu, hdr, hash_lock);
4942 ARCSTAT_BUMP(arcstat_mru_hits);
4943 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
4944 arc_state_t *new_state;
4946 * This buffer has been "accessed" recently, but
4947 * was evicted from the cache. Move it to the
4951 if (HDR_PREFETCH(hdr)) {
4952 new_state = arc_mru;
4953 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
4954 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4955 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4957 new_state = arc_mfu;
4958 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4961 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4962 arc_change_state(new_state, hdr, hash_lock);
4964 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
4965 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
4967 * This buffer has been accessed more than once and is
4968 * still in the cache. Keep it in the MFU state.
4970 * NOTE: an add_reference() that occurred when we did
4971 * the arc_read() will have kicked this off the list.
4972 * If it was a prefetch, we will explicitly move it to
4973 * the head of the list now.
4975 if ((HDR_PREFETCH(hdr)) != 0) {
4976 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4977 /* link protected by hash_lock */
4978 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
4980 ARCSTAT_BUMP(arcstat_mfu_hits);
4981 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4982 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
4983 arc_state_t *new_state = arc_mfu;
4985 * This buffer has been accessed more than once but has
4986 * been evicted from the cache. Move it back to the
4990 if (HDR_PREFETCH(hdr)) {
4992 * This is a prefetch access...
4993 * move this block back to the MRU state.
4995 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
4996 new_state = arc_mru;
4999 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5000 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5001 arc_change_state(new_state, hdr, hash_lock);
5003 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5004 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5006 * This buffer is on the 2nd Level ARC.
5009 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5010 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5011 arc_change_state(arc_mfu, hdr, hash_lock);
5013 ASSERT(!"invalid arc state");
5017 /* a generic arc_done_func_t which you can use */
5020 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
5022 if (zio == NULL || zio->io_error == 0)
5023 bcopy(buf->b_data, arg, arc_buf_size(buf));
5024 arc_buf_destroy(buf, arg);
5027 /* a generic arc_done_func_t */
5029 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
5031 arc_buf_t **bufp = arg;
5032 if (zio && zio->io_error) {
5033 arc_buf_destroy(buf, arg);
5037 ASSERT(buf->b_data);
5042 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
5044 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5045 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5046 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
5048 if (HDR_COMPRESSION_ENABLED(hdr)) {
5049 ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
5050 BP_GET_COMPRESS(bp));
5052 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5053 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5058 arc_read_done(zio_t *zio)
5060 arc_buf_hdr_t *hdr = zio->io_private;
5061 kmutex_t *hash_lock = NULL;
5062 arc_callback_t *callback_list;
5063 arc_callback_t *acb;
5064 boolean_t freeable = B_FALSE;
5065 boolean_t no_zio_error = (zio->io_error == 0);
5068 * The hdr was inserted into hash-table and removed from lists
5069 * prior to starting I/O. We should find this header, since
5070 * it's in the hash table, and it should be legit since it's
5071 * not possible to evict it during the I/O. The only possible
5072 * reason for it not to be found is if we were freed during the
5075 if (HDR_IN_HASH_TABLE(hdr)) {
5076 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5077 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5078 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5079 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5080 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5082 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5085 ASSERT((found == hdr &&
5086 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5087 (found == hdr && HDR_L2_READING(hdr)));
5088 ASSERT3P(hash_lock, !=, NULL);
5092 /* byteswap if necessary */
5093 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5094 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5095 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5097 hdr->b_l1hdr.b_byteswap =
5098 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5101 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5105 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5106 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
5107 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
5109 callback_list = hdr->b_l1hdr.b_acb;
5110 ASSERT3P(callback_list, !=, NULL);
5112 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) {
5114 * Only call arc_access on anonymous buffers. This is because
5115 * if we've issued an I/O for an evicted buffer, we've already
5116 * called arc_access (to prevent any simultaneous readers from
5117 * getting confused).
5119 arc_access(hdr, hash_lock);
5123 * If a read request has a callback (i.e. acb_done is not NULL), then we
5124 * make a buf containing the data according to the parameters which were
5125 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5126 * aren't needlessly decompressing the data multiple times.
5128 int callback_cnt = 0;
5129 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5133 /* This is a demand read since prefetches don't use callbacks */
5136 int error = arc_buf_alloc_impl(hdr, acb->acb_private,
5137 acb->acb_compressed, no_zio_error, &acb->acb_buf);
5139 zio->io_error = error;
5142 hdr->b_l1hdr.b_acb = NULL;
5143 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5144 if (callback_cnt == 0) {
5145 ASSERT(HDR_PREFETCH(hdr));
5146 ASSERT0(hdr->b_l1hdr.b_bufcnt);
5147 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5150 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5151 callback_list != NULL);
5154 arc_hdr_verify(hdr, zio->io_bp);
5156 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5157 if (hdr->b_l1hdr.b_state != arc_anon)
5158 arc_change_state(arc_anon, hdr, hash_lock);
5159 if (HDR_IN_HASH_TABLE(hdr))
5160 buf_hash_remove(hdr);
5161 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5165 * Broadcast before we drop the hash_lock to avoid the possibility
5166 * that the hdr (and hence the cv) might be freed before we get to
5167 * the cv_broadcast().
5169 cv_broadcast(&hdr->b_l1hdr.b_cv);
5171 if (hash_lock != NULL) {
5172 mutex_exit(hash_lock);
5175 * This block was freed while we waited for the read to
5176 * complete. It has been removed from the hash table and
5177 * moved to the anonymous state (so that it won't show up
5180 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5181 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5184 /* execute each callback and free its structure */
5185 while ((acb = callback_list) != NULL) {
5187 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
5189 if (acb->acb_zio_dummy != NULL) {
5190 acb->acb_zio_dummy->io_error = zio->io_error;
5191 zio_nowait(acb->acb_zio_dummy);
5194 callback_list = acb->acb_next;
5195 kmem_free(acb, sizeof (arc_callback_t));
5199 arc_hdr_destroy(hdr);
5203 * "Read" the block at the specified DVA (in bp) via the
5204 * cache. If the block is found in the cache, invoke the provided
5205 * callback immediately and return. Note that the `zio' parameter
5206 * in the callback will be NULL in this case, since no IO was
5207 * required. If the block is not in the cache pass the read request
5208 * on to the spa with a substitute callback function, so that the
5209 * requested block will be added to the cache.
5211 * If a read request arrives for a block that has a read in-progress,
5212 * either wait for the in-progress read to complete (and return the
5213 * results); or, if this is a read with a "done" func, add a record
5214 * to the read to invoke the "done" func when the read completes,
5215 * and return; or just return.
5217 * arc_read_done() will invoke all the requested "done" functions
5218 * for readers of this block.
5221 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
5222 void *private, zio_priority_t priority, int zio_flags,
5223 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5225 arc_buf_hdr_t *hdr = NULL;
5226 kmutex_t *hash_lock = NULL;
5228 uint64_t guid = spa_load_guid(spa);
5229 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
5231 ASSERT(!BP_IS_EMBEDDED(bp) ||
5232 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5235 if (!BP_IS_EMBEDDED(bp)) {
5237 * Embedded BP's have no DVA and require no I/O to "read".
5238 * Create an anonymous arc buf to back it.
5240 hdr = buf_hash_find(guid, bp, &hash_lock);
5243 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) {
5244 arc_buf_t *buf = NULL;
5245 *arc_flags |= ARC_FLAG_CACHED;
5247 if (HDR_IO_IN_PROGRESS(hdr)) {
5249 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5250 priority == ZIO_PRIORITY_SYNC_READ) {
5252 * This sync read must wait for an
5253 * in-progress async read (e.g. a predictive
5254 * prefetch). Async reads are queued
5255 * separately at the vdev_queue layer, so
5256 * this is a form of priority inversion.
5257 * Ideally, we would "inherit" the demand
5258 * i/o's priority by moving the i/o from
5259 * the async queue to the synchronous queue,
5260 * but there is currently no mechanism to do
5261 * so. Track this so that we can evaluate
5262 * the magnitude of this potential performance
5265 * Note that if the prefetch i/o is already
5266 * active (has been issued to the device),
5267 * the prefetch improved performance, because
5268 * we issued it sooner than we would have
5269 * without the prefetch.
5271 DTRACE_PROBE1(arc__sync__wait__for__async,
5272 arc_buf_hdr_t *, hdr);
5273 ARCSTAT_BUMP(arcstat_sync_wait_for_async);
5275 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5276 arc_hdr_clear_flags(hdr,
5277 ARC_FLAG_PREDICTIVE_PREFETCH);
5280 if (*arc_flags & ARC_FLAG_WAIT) {
5281 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5282 mutex_exit(hash_lock);
5285 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5288 arc_callback_t *acb = NULL;
5290 acb = kmem_zalloc(sizeof (arc_callback_t),
5292 acb->acb_done = done;
5293 acb->acb_private = private;
5294 acb->acb_compressed = compressed_read;
5296 acb->acb_zio_dummy = zio_null(pio,
5297 spa, NULL, NULL, NULL, zio_flags);
5299 ASSERT3P(acb->acb_done, !=, NULL);
5300 acb->acb_next = hdr->b_l1hdr.b_acb;
5301 hdr->b_l1hdr.b_acb = acb;
5302 mutex_exit(hash_lock);
5305 mutex_exit(hash_lock);
5309 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5310 hdr->b_l1hdr.b_state == arc_mfu);
5313 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5315 * This is a demand read which does not have to
5316 * wait for i/o because we did a predictive
5317 * prefetch i/o for it, which has completed.
5320 arc__demand__hit__predictive__prefetch,
5321 arc_buf_hdr_t *, hdr);
5323 arcstat_demand_hit_predictive_prefetch);
5324 arc_hdr_clear_flags(hdr,
5325 ARC_FLAG_PREDICTIVE_PREFETCH);
5327 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5329 /* Get a buf with the desired data in it. */
5330 VERIFY0(arc_buf_alloc_impl(hdr, private,
5331 compressed_read, B_TRUE, &buf));
5332 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5333 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5334 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5336 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5337 arc_access(hdr, hash_lock);
5338 if (*arc_flags & ARC_FLAG_L2CACHE)
5339 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5340 mutex_exit(hash_lock);
5341 ARCSTAT_BUMP(arcstat_hits);
5342 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5343 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5344 data, metadata, hits);
5347 done(NULL, buf, private);
5349 uint64_t lsize = BP_GET_LSIZE(bp);
5350 uint64_t psize = BP_GET_PSIZE(bp);
5351 arc_callback_t *acb;
5354 boolean_t devw = B_FALSE;
5358 /* this block is not in the cache */
5359 arc_buf_hdr_t *exists = NULL;
5360 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5361 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5362 BP_GET_COMPRESS(bp), type);
5364 if (!BP_IS_EMBEDDED(bp)) {
5365 hdr->b_dva = *BP_IDENTITY(bp);
5366 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5367 exists = buf_hash_insert(hdr, &hash_lock);
5369 if (exists != NULL) {
5370 /* somebody beat us to the hash insert */
5371 mutex_exit(hash_lock);
5372 buf_discard_identity(hdr);
5373 arc_hdr_destroy(hdr);
5374 goto top; /* restart the IO request */
5378 * This block is in the ghost cache. If it was L2-only
5379 * (and thus didn't have an L1 hdr), we realloc the
5380 * header to add an L1 hdr.
5382 if (!HDR_HAS_L1HDR(hdr)) {
5383 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5386 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5387 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
5388 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5389 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5390 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5391 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
5394 * This is a delicate dance that we play here.
5395 * This hdr is in the ghost list so we access it
5396 * to move it out of the ghost list before we
5397 * initiate the read. If it's a prefetch then
5398 * it won't have a callback so we'll remove the
5399 * reference that arc_buf_alloc_impl() created. We
5400 * do this after we've called arc_access() to
5401 * avoid hitting an assert in remove_reference().
5403 arc_access(hdr, hash_lock);
5404 arc_hdr_alloc_pabd(hdr);
5406 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5407 size = arc_hdr_size(hdr);
5410 * If compression is enabled on the hdr, then will do
5411 * RAW I/O and will store the compressed data in the hdr's
5412 * data block. Otherwise, the hdr's data block will contain
5413 * the uncompressed data.
5415 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5416 zio_flags |= ZIO_FLAG_RAW;
5419 if (*arc_flags & ARC_FLAG_PREFETCH)
5420 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5421 if (*arc_flags & ARC_FLAG_L2CACHE)
5422 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5423 if (BP_GET_LEVEL(bp) > 0)
5424 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5425 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5426 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5427 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5429 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5430 acb->acb_done = done;
5431 acb->acb_private = private;
5432 acb->acb_compressed = compressed_read;
5434 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5435 hdr->b_l1hdr.b_acb = acb;
5436 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5438 if (HDR_HAS_L2HDR(hdr) &&
5439 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5440 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5441 addr = hdr->b_l2hdr.b_daddr;
5443 * Lock out L2ARC device removal.
5445 if (vdev_is_dead(vd) ||
5446 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5450 if (priority == ZIO_PRIORITY_ASYNC_READ)
5451 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5453 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5455 if (hash_lock != NULL)
5456 mutex_exit(hash_lock);
5459 * At this point, we have a level 1 cache miss. Try again in
5460 * L2ARC if possible.
5462 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5464 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5465 uint64_t, lsize, zbookmark_phys_t *, zb);
5466 ARCSTAT_BUMP(arcstat_misses);
5467 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5468 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5469 data, metadata, misses);
5474 racct_add_force(curproc, RACCT_READBPS, size);
5475 racct_add_force(curproc, RACCT_READIOPS, 1);
5476 PROC_UNLOCK(curproc);
5479 curthread->td_ru.ru_inblock++;
5482 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5484 * Read from the L2ARC if the following are true:
5485 * 1. The L2ARC vdev was previously cached.
5486 * 2. This buffer still has L2ARC metadata.
5487 * 3. This buffer isn't currently writing to the L2ARC.
5488 * 4. The L2ARC entry wasn't evicted, which may
5489 * also have invalidated the vdev.
5490 * 5. This isn't prefetch and l2arc_noprefetch is set.
5492 if (HDR_HAS_L2HDR(hdr) &&
5493 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5494 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5495 l2arc_read_callback_t *cb;
5499 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5500 ARCSTAT_BUMP(arcstat_l2_hits);
5502 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5504 cb->l2rcb_hdr = hdr;
5507 cb->l2rcb_flags = zio_flags;
5509 asize = vdev_psize_to_asize(vd, size);
5510 if (asize != size) {
5511 abd = abd_alloc_for_io(asize,
5512 HDR_ISTYPE_METADATA(hdr));
5513 cb->l2rcb_abd = abd;
5515 abd = hdr->b_l1hdr.b_pabd;
5518 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
5519 addr + asize <= vd->vdev_psize -
5520 VDEV_LABEL_END_SIZE);
5523 * l2arc read. The SCL_L2ARC lock will be
5524 * released by l2arc_read_done().
5525 * Issue a null zio if the underlying buffer
5526 * was squashed to zero size by compression.
5528 ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
5529 ZIO_COMPRESS_EMPTY);
5530 rzio = zio_read_phys(pio, vd, addr,
5533 l2arc_read_done, cb, priority,
5534 zio_flags | ZIO_FLAG_DONT_CACHE |
5536 ZIO_FLAG_DONT_PROPAGATE |
5537 ZIO_FLAG_DONT_RETRY, B_FALSE);
5538 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
5540 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
5542 if (*arc_flags & ARC_FLAG_NOWAIT) {
5547 ASSERT(*arc_flags & ARC_FLAG_WAIT);
5548 if (zio_wait(rzio) == 0)
5551 /* l2arc read error; goto zio_read() */
5553 DTRACE_PROBE1(l2arc__miss,
5554 arc_buf_hdr_t *, hdr);
5555 ARCSTAT_BUMP(arcstat_l2_misses);
5556 if (HDR_L2_WRITING(hdr))
5557 ARCSTAT_BUMP(arcstat_l2_rw_clash);
5558 spa_config_exit(spa, SCL_L2ARC, vd);
5562 spa_config_exit(spa, SCL_L2ARC, vd);
5563 if (l2arc_ndev != 0) {
5564 DTRACE_PROBE1(l2arc__miss,
5565 arc_buf_hdr_t *, hdr);
5566 ARCSTAT_BUMP(arcstat_l2_misses);
5570 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size,
5571 arc_read_done, hdr, priority, zio_flags, zb);
5573 if (*arc_flags & ARC_FLAG_WAIT)
5574 return (zio_wait(rzio));
5576 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5583 * Notify the arc that a block was freed, and thus will never be used again.
5586 arc_freed(spa_t *spa, const blkptr_t *bp)
5589 kmutex_t *hash_lock;
5590 uint64_t guid = spa_load_guid(spa);
5592 ASSERT(!BP_IS_EMBEDDED(bp));
5594 hdr = buf_hash_find(guid, bp, &hash_lock);
5599 * We might be trying to free a block that is still doing I/O
5600 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
5601 * dmu_sync-ed block). If this block is being prefetched, then it
5602 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
5603 * until the I/O completes. A block may also have a reference if it is
5604 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
5605 * have written the new block to its final resting place on disk but
5606 * without the dedup flag set. This would have left the hdr in the MRU
5607 * state and discoverable. When the txg finally syncs it detects that
5608 * the block was overridden in open context and issues an override I/O.
5609 * Since this is a dedup block, the override I/O will determine if the
5610 * block is already in the DDT. If so, then it will replace the io_bp
5611 * with the bp from the DDT and allow the I/O to finish. When the I/O
5612 * reaches the done callback, dbuf_write_override_done, it will
5613 * check to see if the io_bp and io_bp_override are identical.
5614 * If they are not, then it indicates that the bp was replaced with
5615 * the bp in the DDT and the override bp is freed. This allows
5616 * us to arrive here with a reference on a block that is being
5617 * freed. So if we have an I/O in progress, or a reference to
5618 * this hdr, then we don't destroy the hdr.
5620 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
5621 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
5622 arc_change_state(arc_anon, hdr, hash_lock);
5623 arc_hdr_destroy(hdr);
5624 mutex_exit(hash_lock);
5626 mutex_exit(hash_lock);
5632 * Release this buffer from the cache, making it an anonymous buffer. This
5633 * must be done after a read and prior to modifying the buffer contents.
5634 * If the buffer has more than one reference, we must make
5635 * a new hdr for the buffer.
5638 arc_release(arc_buf_t *buf, void *tag)
5640 arc_buf_hdr_t *hdr = buf->b_hdr;
5643 * It would be nice to assert that if it's DMU metadata (level >
5644 * 0 || it's the dnode file), then it must be syncing context.
5645 * But we don't know that information at this level.
5648 mutex_enter(&buf->b_evict_lock);
5650 ASSERT(HDR_HAS_L1HDR(hdr));
5653 * We don't grab the hash lock prior to this check, because if
5654 * the buffer's header is in the arc_anon state, it won't be
5655 * linked into the hash table.
5657 if (hdr->b_l1hdr.b_state == arc_anon) {
5658 mutex_exit(&buf->b_evict_lock);
5659 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5660 ASSERT(!HDR_IN_HASH_TABLE(hdr));
5661 ASSERT(!HDR_HAS_L2HDR(hdr));
5662 ASSERT(HDR_EMPTY(hdr));
5663 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5664 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
5665 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
5667 hdr->b_l1hdr.b_arc_access = 0;
5670 * If the buf is being overridden then it may already
5671 * have a hdr that is not empty.
5673 buf_discard_identity(hdr);
5679 kmutex_t *hash_lock = HDR_LOCK(hdr);
5680 mutex_enter(hash_lock);
5683 * This assignment is only valid as long as the hash_lock is
5684 * held, we must be careful not to reference state or the
5685 * b_state field after dropping the lock.
5687 arc_state_t *state = hdr->b_l1hdr.b_state;
5688 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5689 ASSERT3P(state, !=, arc_anon);
5691 /* this buffer is not on any list */
5692 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
5694 if (HDR_HAS_L2HDR(hdr)) {
5695 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5698 * We have to recheck this conditional again now that
5699 * we're holding the l2ad_mtx to prevent a race with
5700 * another thread which might be concurrently calling
5701 * l2arc_evict(). In that case, l2arc_evict() might have
5702 * destroyed the header's L2 portion as we were waiting
5703 * to acquire the l2ad_mtx.
5705 if (HDR_HAS_L2HDR(hdr)) {
5707 arc_hdr_l2hdr_destroy(hdr);
5710 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5714 * Do we have more than one buf?
5716 if (hdr->b_l1hdr.b_bufcnt > 1) {
5717 arc_buf_hdr_t *nhdr;
5718 uint64_t spa = hdr->b_spa;
5719 uint64_t psize = HDR_GET_PSIZE(hdr);
5720 uint64_t lsize = HDR_GET_LSIZE(hdr);
5721 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
5722 arc_buf_contents_t type = arc_buf_type(hdr);
5723 VERIFY3U(hdr->b_type, ==, type);
5725 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
5726 (void) remove_reference(hdr, hash_lock, tag);
5728 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
5729 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
5730 ASSERT(ARC_BUF_LAST(buf));
5734 * Pull the data off of this hdr and attach it to
5735 * a new anonymous hdr. Also find the last buffer
5736 * in the hdr's buffer list.
5738 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
5739 ASSERT3P(lastbuf, !=, NULL);
5742 * If the current arc_buf_t and the hdr are sharing their data
5743 * buffer, then we must stop sharing that block.
5745 if (arc_buf_is_shared(buf)) {
5746 VERIFY(!arc_buf_is_shared(lastbuf));
5749 * First, sever the block sharing relationship between
5750 * buf and the arc_buf_hdr_t.
5752 arc_unshare_buf(hdr, buf);
5755 * Now we need to recreate the hdr's b_pabd. Since we
5756 * have lastbuf handy, we try to share with it, but if
5757 * we can't then we allocate a new b_pabd and copy the
5758 * data from buf into it.
5760 if (arc_can_share(hdr, lastbuf)) {
5761 arc_share_buf(hdr, lastbuf);
5763 arc_hdr_alloc_pabd(hdr);
5764 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
5765 buf->b_data, psize);
5767 VERIFY3P(lastbuf->b_data, !=, NULL);
5768 } else if (HDR_SHARED_DATA(hdr)) {
5770 * Uncompressed shared buffers are always at the end
5771 * of the list. Compressed buffers don't have the
5772 * same requirements. This makes it hard to
5773 * simply assert that the lastbuf is shared so
5774 * we rely on the hdr's compression flags to determine
5775 * if we have a compressed, shared buffer.
5777 ASSERT(arc_buf_is_shared(lastbuf) ||
5778 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
5779 ASSERT(!ARC_BUF_SHARED(buf));
5781 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5782 ASSERT3P(state, !=, arc_l2c_only);
5784 (void) refcount_remove_many(&state->arcs_size,
5785 arc_buf_size(buf), buf);
5787 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5788 ASSERT3P(state, !=, arc_l2c_only);
5789 (void) refcount_remove_many(&state->arcs_esize[type],
5790 arc_buf_size(buf), buf);
5793 hdr->b_l1hdr.b_bufcnt -= 1;
5794 arc_cksum_verify(buf);
5796 arc_buf_unwatch(buf);
5799 mutex_exit(hash_lock);
5802 * Allocate a new hdr. The new hdr will contain a b_pabd
5803 * buffer which will be freed in arc_write().
5805 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
5806 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
5807 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
5808 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
5809 VERIFY3U(nhdr->b_type, ==, type);
5810 ASSERT(!HDR_SHARED_DATA(nhdr));
5812 nhdr->b_l1hdr.b_buf = buf;
5813 nhdr->b_l1hdr.b_bufcnt = 1;
5814 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
5817 mutex_exit(&buf->b_evict_lock);
5818 (void) refcount_add_many(&arc_anon->arcs_size,
5819 arc_buf_size(buf), buf);
5821 mutex_exit(&buf->b_evict_lock);
5822 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
5823 /* protected by hash lock, or hdr is on arc_anon */
5824 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
5825 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5826 arc_change_state(arc_anon, hdr, hash_lock);
5827 hdr->b_l1hdr.b_arc_access = 0;
5828 mutex_exit(hash_lock);
5830 buf_discard_identity(hdr);
5836 arc_released(arc_buf_t *buf)
5840 mutex_enter(&buf->b_evict_lock);
5841 released = (buf->b_data != NULL &&
5842 buf->b_hdr->b_l1hdr.b_state == arc_anon);
5843 mutex_exit(&buf->b_evict_lock);
5849 arc_referenced(arc_buf_t *buf)
5853 mutex_enter(&buf->b_evict_lock);
5854 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
5855 mutex_exit(&buf->b_evict_lock);
5856 return (referenced);
5861 arc_write_ready(zio_t *zio)
5863 arc_write_callback_t *callback = zio->io_private;
5864 arc_buf_t *buf = callback->awcb_buf;
5865 arc_buf_hdr_t *hdr = buf->b_hdr;
5866 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
5868 ASSERT(HDR_HAS_L1HDR(hdr));
5869 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
5870 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
5873 * If we're reexecuting this zio because the pool suspended, then
5874 * cleanup any state that was previously set the first time the
5875 * callback was invoked.
5877 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
5878 arc_cksum_free(hdr);
5880 arc_buf_unwatch(buf);
5882 if (hdr->b_l1hdr.b_pabd != NULL) {
5883 if (arc_buf_is_shared(buf)) {
5884 arc_unshare_buf(hdr, buf);
5886 arc_hdr_free_pabd(hdr);
5890 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5891 ASSERT(!HDR_SHARED_DATA(hdr));
5892 ASSERT(!arc_buf_is_shared(buf));
5894 callback->awcb_ready(zio, buf, callback->awcb_private);
5896 if (HDR_IO_IN_PROGRESS(hdr))
5897 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
5899 arc_cksum_compute(buf);
5900 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5902 enum zio_compress compress;
5903 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5904 compress = ZIO_COMPRESS_OFF;
5906 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
5907 compress = BP_GET_COMPRESS(zio->io_bp);
5909 HDR_SET_PSIZE(hdr, psize);
5910 arc_hdr_set_compress(hdr, compress);
5914 * Fill the hdr with data. If the hdr is compressed, the data we want
5915 * is available from the zio, otherwise we can take it from the buf.
5917 * We might be able to share the buf's data with the hdr here. However,
5918 * doing so would cause the ARC to be full of linear ABDs if we write a
5919 * lot of shareable data. As a compromise, we check whether scattered
5920 * ABDs are allowed, and assume that if they are then the user wants
5921 * the ARC to be primarily filled with them regardless of the data being
5922 * written. Therefore, if they're allowed then we allocate one and copy
5923 * the data into it; otherwise, we share the data directly if we can.
5925 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
5926 arc_hdr_alloc_pabd(hdr);
5929 * Ideally, we would always copy the io_abd into b_pabd, but the
5930 * user may have disabled compressed ARC, thus we must check the
5931 * hdr's compression setting rather than the io_bp's.
5933 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5934 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=,
5936 ASSERT3U(psize, >, 0);
5938 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
5940 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
5942 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
5946 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
5947 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
5948 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5950 arc_share_buf(hdr, buf);
5953 arc_hdr_verify(hdr, zio->io_bp);
5957 arc_write_children_ready(zio_t *zio)
5959 arc_write_callback_t *callback = zio->io_private;
5960 arc_buf_t *buf = callback->awcb_buf;
5962 callback->awcb_children_ready(zio, buf, callback->awcb_private);
5966 * The SPA calls this callback for each physical write that happens on behalf
5967 * of a logical write. See the comment in dbuf_write_physdone() for details.
5970 arc_write_physdone(zio_t *zio)
5972 arc_write_callback_t *cb = zio->io_private;
5973 if (cb->awcb_physdone != NULL)
5974 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
5978 arc_write_done(zio_t *zio)
5980 arc_write_callback_t *callback = zio->io_private;
5981 arc_buf_t *buf = callback->awcb_buf;
5982 arc_buf_hdr_t *hdr = buf->b_hdr;
5984 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5986 if (zio->io_error == 0) {
5987 arc_hdr_verify(hdr, zio->io_bp);
5989 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5990 buf_discard_identity(hdr);
5992 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
5993 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
5996 ASSERT(HDR_EMPTY(hdr));
6000 * If the block to be written was all-zero or compressed enough to be
6001 * embedded in the BP, no write was performed so there will be no
6002 * dva/birth/checksum. The buffer must therefore remain anonymous
6005 if (!HDR_EMPTY(hdr)) {
6006 arc_buf_hdr_t *exists;
6007 kmutex_t *hash_lock;
6009 ASSERT3U(zio->io_error, ==, 0);
6011 arc_cksum_verify(buf);
6013 exists = buf_hash_insert(hdr, &hash_lock);
6014 if (exists != NULL) {
6016 * This can only happen if we overwrite for
6017 * sync-to-convergence, because we remove
6018 * buffers from the hash table when we arc_free().
6020 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
6021 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6022 panic("bad overwrite, hdr=%p exists=%p",
6023 (void *)hdr, (void *)exists);
6024 ASSERT(refcount_is_zero(
6025 &exists->b_l1hdr.b_refcnt));
6026 arc_change_state(arc_anon, exists, hash_lock);
6027 mutex_exit(hash_lock);
6028 arc_hdr_destroy(exists);
6029 exists = buf_hash_insert(hdr, &hash_lock);
6030 ASSERT3P(exists, ==, NULL);
6031 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
6033 ASSERT(zio->io_prop.zp_nopwrite);
6034 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6035 panic("bad nopwrite, hdr=%p exists=%p",
6036 (void *)hdr, (void *)exists);
6039 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6040 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6041 ASSERT(BP_GET_DEDUP(zio->io_bp));
6042 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6045 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6046 /* if it's not anon, we are doing a scrub */
6047 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6048 arc_access(hdr, hash_lock);
6049 mutex_exit(hash_lock);
6051 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6054 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6055 callback->awcb_done(zio, buf, callback->awcb_private);
6057 abd_put(zio->io_abd);
6058 kmem_free(callback, sizeof (arc_write_callback_t));
6062 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6063 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready,
6064 arc_done_func_t *children_ready, arc_done_func_t *physdone,
6065 arc_done_func_t *done, void *private, zio_priority_t priority,
6066 int zio_flags, const zbookmark_phys_t *zb)
6068 arc_buf_hdr_t *hdr = buf->b_hdr;
6069 arc_write_callback_t *callback;
6071 zio_prop_t localprop = *zp;
6073 ASSERT3P(ready, !=, NULL);
6074 ASSERT3P(done, !=, NULL);
6075 ASSERT(!HDR_IO_ERROR(hdr));
6076 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6077 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6078 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6080 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6081 if (ARC_BUF_COMPRESSED(buf)) {
6083 * We're writing a pre-compressed buffer. Make the
6084 * compression algorithm requested by the zio_prop_t match
6085 * the pre-compressed buffer's compression algorithm.
6087 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6089 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6090 zio_flags |= ZIO_FLAG_RAW;
6092 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6093 callback->awcb_ready = ready;
6094 callback->awcb_children_ready = children_ready;
6095 callback->awcb_physdone = physdone;
6096 callback->awcb_done = done;
6097 callback->awcb_private = private;
6098 callback->awcb_buf = buf;
6101 * The hdr's b_pabd is now stale, free it now. A new data block
6102 * will be allocated when the zio pipeline calls arc_write_ready().
6104 if (hdr->b_l1hdr.b_pabd != NULL) {
6106 * If the buf is currently sharing the data block with
6107 * the hdr then we need to break that relationship here.
6108 * The hdr will remain with a NULL data pointer and the
6109 * buf will take sole ownership of the block.
6111 if (arc_buf_is_shared(buf)) {
6112 arc_unshare_buf(hdr, buf);
6114 arc_hdr_free_pabd(hdr);
6116 VERIFY3P(buf->b_data, !=, NULL);
6117 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6119 ASSERT(!arc_buf_is_shared(buf));
6120 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6122 zio = zio_write(pio, spa, txg, bp,
6123 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6124 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6125 (children_ready != NULL) ? arc_write_children_ready : NULL,
6126 arc_write_physdone, arc_write_done, callback,
6127 priority, zio_flags, zb);
6133 arc_memory_throttle(uint64_t reserve, uint64_t txg)
6136 uint64_t available_memory = ptob(freemem);
6137 static uint64_t page_load = 0;
6138 static uint64_t last_txg = 0;
6140 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
6141 available_memory = MIN(available_memory, uma_avail());
6144 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
6147 if (txg > last_txg) {
6152 * If we are in pageout, we know that memory is already tight,
6153 * the arc is already going to be evicting, so we just want to
6154 * continue to let page writes occur as quickly as possible.
6156 if (curproc == pageproc) {
6157 if (page_load > MAX(ptob(minfree), available_memory) / 4)
6158 return (SET_ERROR(ERESTART));
6159 /* Note: reserve is inflated, so we deflate */
6160 page_load += reserve / 8;
6162 } else if (page_load > 0 && arc_reclaim_needed()) {
6163 /* memory is low, delay before restarting */
6164 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6165 return (SET_ERROR(EAGAIN));
6173 arc_tempreserve_clear(uint64_t reserve)
6175 atomic_add_64(&arc_tempreserve, -reserve);
6176 ASSERT((int64_t)arc_tempreserve >= 0);
6180 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
6185 if (reserve > arc_c/4 && !arc_no_grow) {
6186 arc_c = MIN(arc_c_max, reserve * 4);
6187 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
6189 if (reserve > arc_c)
6190 return (SET_ERROR(ENOMEM));
6193 * Don't count loaned bufs as in flight dirty data to prevent long
6194 * network delays from blocking transactions that are ready to be
6195 * assigned to a txg.
6198 /* assert that it has not wrapped around */
6199 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6201 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
6202 arc_loaned_bytes), 0);
6205 * Writes will, almost always, require additional memory allocations
6206 * in order to compress/encrypt/etc the data. We therefore need to
6207 * make sure that there is sufficient available memory for this.
6209 error = arc_memory_throttle(reserve, txg);
6214 * Throttle writes when the amount of dirty data in the cache
6215 * gets too large. We try to keep the cache less than half full
6216 * of dirty blocks so that our sync times don't grow too large.
6217 * Note: if two requests come in concurrently, we might let them
6218 * both succeed, when one of them should fail. Not a huge deal.
6221 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
6222 anon_size > arc_c / 4) {
6223 uint64_t meta_esize =
6224 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6225 uint64_t data_esize =
6226 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6227 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6228 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6229 arc_tempreserve >> 10, meta_esize >> 10,
6230 data_esize >> 10, reserve >> 10, arc_c >> 10);
6231 return (SET_ERROR(ERESTART));
6233 atomic_add_64(&arc_tempreserve, reserve);
6238 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6239 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
6241 size->value.ui64 = refcount_count(&state->arcs_size);
6242 evict_data->value.ui64 =
6243 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6244 evict_metadata->value.ui64 =
6245 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6249 arc_kstat_update(kstat_t *ksp, int rw)
6251 arc_stats_t *as = ksp->ks_data;
6253 if (rw == KSTAT_WRITE) {
6256 arc_kstat_update_state(arc_anon,
6257 &as->arcstat_anon_size,
6258 &as->arcstat_anon_evictable_data,
6259 &as->arcstat_anon_evictable_metadata);
6260 arc_kstat_update_state(arc_mru,
6261 &as->arcstat_mru_size,
6262 &as->arcstat_mru_evictable_data,
6263 &as->arcstat_mru_evictable_metadata);
6264 arc_kstat_update_state(arc_mru_ghost,
6265 &as->arcstat_mru_ghost_size,
6266 &as->arcstat_mru_ghost_evictable_data,
6267 &as->arcstat_mru_ghost_evictable_metadata);
6268 arc_kstat_update_state(arc_mfu,
6269 &as->arcstat_mfu_size,
6270 &as->arcstat_mfu_evictable_data,
6271 &as->arcstat_mfu_evictable_metadata);
6272 arc_kstat_update_state(arc_mfu_ghost,
6273 &as->arcstat_mfu_ghost_size,
6274 &as->arcstat_mfu_ghost_evictable_data,
6275 &as->arcstat_mfu_ghost_evictable_metadata);
6282 * This function *must* return indices evenly distributed between all
6283 * sublists of the multilist. This is needed due to how the ARC eviction
6284 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6285 * distributed between all sublists and uses this assumption when
6286 * deciding which sublist to evict from and how much to evict from it.
6289 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6291 arc_buf_hdr_t *hdr = obj;
6294 * We rely on b_dva to generate evenly distributed index
6295 * numbers using buf_hash below. So, as an added precaution,
6296 * let's make sure we never add empty buffers to the arc lists.
6298 ASSERT(!HDR_EMPTY(hdr));
6301 * The assumption here, is the hash value for a given
6302 * arc_buf_hdr_t will remain constant throughout it's lifetime
6303 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
6304 * Thus, we don't need to store the header's sublist index
6305 * on insertion, as this index can be recalculated on removal.
6307 * Also, the low order bits of the hash value are thought to be
6308 * distributed evenly. Otherwise, in the case that the multilist
6309 * has a power of two number of sublists, each sublists' usage
6310 * would not be evenly distributed.
6312 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
6313 multilist_get_num_sublists(ml));
6317 static eventhandler_tag arc_event_lowmem = NULL;
6320 arc_lowmem(void *arg __unused, int howto __unused)
6323 mutex_enter(&arc_reclaim_lock);
6324 DTRACE_PROBE1(arc__needfree, int64_t, ((int64_t)freemem - zfs_arc_free_target) * PAGESIZE);
6325 cv_signal(&arc_reclaim_thread_cv);
6328 * It is unsafe to block here in arbitrary threads, because we can come
6329 * here from ARC itself and may hold ARC locks and thus risk a deadlock
6330 * with ARC reclaim thread.
6332 if (curproc == pageproc)
6333 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
6334 mutex_exit(&arc_reclaim_lock);
6339 arc_state_init(void)
6341 arc_anon = &ARC_anon;
6343 arc_mru_ghost = &ARC_mru_ghost;
6345 arc_mfu_ghost = &ARC_mfu_ghost;
6346 arc_l2c_only = &ARC_l2c_only;
6348 arc_mru->arcs_list[ARC_BUFC_METADATA] =
6349 multilist_create(sizeof (arc_buf_hdr_t),
6350 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6351 arc_state_multilist_index_func);
6352 arc_mru->arcs_list[ARC_BUFC_DATA] =
6353 multilist_create(sizeof (arc_buf_hdr_t),
6354 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6355 arc_state_multilist_index_func);
6356 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
6357 multilist_create(sizeof (arc_buf_hdr_t),
6358 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6359 arc_state_multilist_index_func);
6360 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
6361 multilist_create(sizeof (arc_buf_hdr_t),
6362 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6363 arc_state_multilist_index_func);
6364 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
6365 multilist_create(sizeof (arc_buf_hdr_t),
6366 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6367 arc_state_multilist_index_func);
6368 arc_mfu->arcs_list[ARC_BUFC_DATA] =
6369 multilist_create(sizeof (arc_buf_hdr_t),
6370 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6371 arc_state_multilist_index_func);
6372 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
6373 multilist_create(sizeof (arc_buf_hdr_t),
6374 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6375 arc_state_multilist_index_func);
6376 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
6377 multilist_create(sizeof (arc_buf_hdr_t),
6378 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6379 arc_state_multilist_index_func);
6380 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
6381 multilist_create(sizeof (arc_buf_hdr_t),
6382 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6383 arc_state_multilist_index_func);
6384 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
6385 multilist_create(sizeof (arc_buf_hdr_t),
6386 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6387 arc_state_multilist_index_func);
6389 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6390 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6391 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6392 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6393 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6394 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6395 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6396 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6397 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6398 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6399 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6400 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6402 refcount_create(&arc_anon->arcs_size);
6403 refcount_create(&arc_mru->arcs_size);
6404 refcount_create(&arc_mru_ghost->arcs_size);
6405 refcount_create(&arc_mfu->arcs_size);
6406 refcount_create(&arc_mfu_ghost->arcs_size);
6407 refcount_create(&arc_l2c_only->arcs_size);
6411 arc_state_fini(void)
6413 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6414 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6415 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6416 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6417 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6418 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6419 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6420 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6421 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6422 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6423 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6424 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6426 refcount_destroy(&arc_anon->arcs_size);
6427 refcount_destroy(&arc_mru->arcs_size);
6428 refcount_destroy(&arc_mru_ghost->arcs_size);
6429 refcount_destroy(&arc_mfu->arcs_size);
6430 refcount_destroy(&arc_mfu_ghost->arcs_size);
6431 refcount_destroy(&arc_l2c_only->arcs_size);
6433 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
6434 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
6435 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
6436 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
6437 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
6438 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
6439 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
6440 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
6452 int i, prefetch_tunable_set = 0;
6455 * allmem is "all memory that we could possibly use".
6459 uint64_t allmem = ptob(physmem - swapfs_minfree);
6461 uint64_t allmem = (physmem * PAGESIZE) / 2;
6464 uint64_t allmem = kmem_size();
6468 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
6469 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
6470 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
6472 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
6473 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL);
6475 /* Convert seconds to clock ticks */
6476 arc_min_prefetch_lifespan = 1 * hz;
6478 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */
6479 arc_c_min = MAX(allmem / 32, arc_abs_min);
6480 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */
6481 if (allmem >= 1 << 30)
6482 arc_c_max = allmem - (1 << 30);
6484 arc_c_max = arc_c_min;
6485 arc_c_max = MAX(allmem * 5 / 8, arc_c_max);
6488 * In userland, there's only the memory pressure that we artificially
6489 * create (see arc_available_memory()). Don't let arc_c get too
6490 * small, because it can cause transactions to be larger than
6491 * arc_c, causing arc_tempreserve_space() to fail.
6494 arc_c_min = arc_c_max / 2;
6499 * Allow the tunables to override our calculations if they are
6502 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) {
6503 arc_c_max = zfs_arc_max;
6504 arc_c_min = MIN(arc_c_min, arc_c_max);
6506 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max)
6507 arc_c_min = zfs_arc_min;
6511 arc_p = (arc_c >> 1);
6514 /* limit meta-data to 1/4 of the arc capacity */
6515 arc_meta_limit = arc_c_max / 4;
6519 * Metadata is stored in the kernel's heap. Don't let us
6520 * use more than half the heap for the ARC.
6523 arc_meta_limit = MIN(arc_meta_limit, uma_limit() / 2);
6525 arc_meta_limit = MIN(arc_meta_limit,
6526 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
6530 /* Allow the tunable to override if it is reasonable */
6531 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
6532 arc_meta_limit = zfs_arc_meta_limit;
6534 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
6535 arc_c_min = arc_meta_limit / 2;
6537 if (zfs_arc_meta_min > 0) {
6538 arc_meta_min = zfs_arc_meta_min;
6540 arc_meta_min = arc_c_min / 2;
6543 if (zfs_arc_grow_retry > 0)
6544 arc_grow_retry = zfs_arc_grow_retry;
6546 if (zfs_arc_shrink_shift > 0)
6547 arc_shrink_shift = zfs_arc_shrink_shift;
6549 if (zfs_arc_no_grow_shift > 0)
6550 arc_no_grow_shift = zfs_arc_no_grow_shift;
6552 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
6554 if (arc_no_grow_shift >= arc_shrink_shift)
6555 arc_no_grow_shift = arc_shrink_shift - 1;
6557 if (zfs_arc_p_min_shift > 0)
6558 arc_p_min_shift = zfs_arc_p_min_shift;
6560 /* if kmem_flags are set, lets try to use less memory */
6561 if (kmem_debugging())
6563 if (arc_c < arc_c_min)
6566 zfs_arc_min = arc_c_min;
6567 zfs_arc_max = arc_c_max;
6572 arc_reclaim_thread_exit = B_FALSE;
6573 arc_dnlc_evicts_thread_exit = FALSE;
6575 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
6576 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
6578 if (arc_ksp != NULL) {
6579 arc_ksp->ks_data = &arc_stats;
6580 arc_ksp->ks_update = arc_kstat_update;
6581 kstat_install(arc_ksp);
6584 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
6585 TS_RUN, minclsyspri);
6588 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
6589 EVENTHANDLER_PRI_FIRST);
6592 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0,
6593 TS_RUN, minclsyspri);
6599 * Calculate maximum amount of dirty data per pool.
6601 * If it has been set by /etc/system, take that.
6602 * Otherwise, use a percentage of physical memory defined by
6603 * zfs_dirty_data_max_percent (default 10%) with a cap at
6604 * zfs_dirty_data_max_max (default 4GB).
6606 if (zfs_dirty_data_max == 0) {
6607 zfs_dirty_data_max = ptob(physmem) *
6608 zfs_dirty_data_max_percent / 100;
6609 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
6610 zfs_dirty_data_max_max);
6614 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
6615 prefetch_tunable_set = 1;
6618 if (prefetch_tunable_set == 0) {
6619 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
6621 printf(" add \"vfs.zfs.prefetch_disable=0\" "
6622 "to /boot/loader.conf.\n");
6623 zfs_prefetch_disable = 1;
6626 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
6627 prefetch_tunable_set == 0) {
6628 printf("ZFS NOTICE: Prefetch is disabled by default if less "
6629 "than 4GB of RAM is present;\n"
6630 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
6631 "to /boot/loader.conf.\n");
6632 zfs_prefetch_disable = 1;
6635 /* Warn about ZFS memory and address space requirements. */
6636 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
6637 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
6638 "expect unstable behavior.\n");
6640 if (allmem < 512 * (1 << 20)) {
6641 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
6642 "expect unstable behavior.\n");
6643 printf(" Consider tuning vm.kmem_size and "
6644 "vm.kmem_size_max\n");
6645 printf(" in /boot/loader.conf.\n");
6654 if (arc_event_lowmem != NULL)
6655 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
6658 mutex_enter(&arc_reclaim_lock);
6659 arc_reclaim_thread_exit = B_TRUE;
6661 * The reclaim thread will set arc_reclaim_thread_exit back to
6662 * B_FALSE when it is finished exiting; we're waiting for that.
6664 while (arc_reclaim_thread_exit) {
6665 cv_signal(&arc_reclaim_thread_cv);
6666 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
6668 mutex_exit(&arc_reclaim_lock);
6670 /* Use B_TRUE to ensure *all* buffers are evicted */
6671 arc_flush(NULL, B_TRUE);
6673 mutex_enter(&arc_dnlc_evicts_lock);
6674 arc_dnlc_evicts_thread_exit = TRUE;
6676 * The user evicts thread will set arc_user_evicts_thread_exit
6677 * to FALSE when it is finished exiting; we're waiting for that.
6679 while (arc_dnlc_evicts_thread_exit) {
6680 cv_signal(&arc_dnlc_evicts_cv);
6681 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
6683 mutex_exit(&arc_dnlc_evicts_lock);
6687 if (arc_ksp != NULL) {
6688 kstat_delete(arc_ksp);
6692 mutex_destroy(&arc_reclaim_lock);
6693 cv_destroy(&arc_reclaim_thread_cv);
6694 cv_destroy(&arc_reclaim_waiters_cv);
6696 mutex_destroy(&arc_dnlc_evicts_lock);
6697 cv_destroy(&arc_dnlc_evicts_cv);
6702 ASSERT0(arc_loaned_bytes);
6708 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
6709 * It uses dedicated storage devices to hold cached data, which are populated
6710 * using large infrequent writes. The main role of this cache is to boost
6711 * the performance of random read workloads. The intended L2ARC devices
6712 * include short-stroked disks, solid state disks, and other media with
6713 * substantially faster read latency than disk.
6715 * +-----------------------+
6717 * +-----------------------+
6720 * l2arc_feed_thread() arc_read()
6724 * +---------------+ |
6726 * +---------------+ |
6731 * +-------+ +-------+
6733 * | cache | | cache |
6734 * +-------+ +-------+
6735 * +=========+ .-----.
6736 * : L2ARC : |-_____-|
6737 * : devices : | Disks |
6738 * +=========+ `-_____-'
6740 * Read requests are satisfied from the following sources, in order:
6743 * 2) vdev cache of L2ARC devices
6745 * 4) vdev cache of disks
6748 * Some L2ARC device types exhibit extremely slow write performance.
6749 * To accommodate for this there are some significant differences between
6750 * the L2ARC and traditional cache design:
6752 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
6753 * the ARC behave as usual, freeing buffers and placing headers on ghost
6754 * lists. The ARC does not send buffers to the L2ARC during eviction as
6755 * this would add inflated write latencies for all ARC memory pressure.
6757 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
6758 * It does this by periodically scanning buffers from the eviction-end of
6759 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
6760 * not already there. It scans until a headroom of buffers is satisfied,
6761 * which itself is a buffer for ARC eviction. If a compressible buffer is
6762 * found during scanning and selected for writing to an L2ARC device, we
6763 * temporarily boost scanning headroom during the next scan cycle to make
6764 * sure we adapt to compression effects (which might significantly reduce
6765 * the data volume we write to L2ARC). The thread that does this is
6766 * l2arc_feed_thread(), illustrated below; example sizes are included to
6767 * provide a better sense of ratio than this diagram:
6770 * +---------------------+----------+
6771 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
6772 * +---------------------+----------+ | o L2ARC eligible
6773 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
6774 * +---------------------+----------+ |
6775 * 15.9 Gbytes ^ 32 Mbytes |
6777 * l2arc_feed_thread()
6779 * l2arc write hand <--[oooo]--'
6783 * +==============================+
6784 * L2ARC dev |####|#|###|###| |####| ... |
6785 * +==============================+
6788 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
6789 * evicted, then the L2ARC has cached a buffer much sooner than it probably
6790 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
6791 * safe to say that this is an uncommon case, since buffers at the end of
6792 * the ARC lists have moved there due to inactivity.
6794 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
6795 * then the L2ARC simply misses copying some buffers. This serves as a
6796 * pressure valve to prevent heavy read workloads from both stalling the ARC
6797 * with waits and clogging the L2ARC with writes. This also helps prevent
6798 * the potential for the L2ARC to churn if it attempts to cache content too
6799 * quickly, such as during backups of the entire pool.
6801 * 5. After system boot and before the ARC has filled main memory, there are
6802 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
6803 * lists can remain mostly static. Instead of searching from tail of these
6804 * lists as pictured, the l2arc_feed_thread() will search from the list heads
6805 * for eligible buffers, greatly increasing its chance of finding them.
6807 * The L2ARC device write speed is also boosted during this time so that
6808 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
6809 * there are no L2ARC reads, and no fear of degrading read performance
6810 * through increased writes.
6812 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
6813 * the vdev queue can aggregate them into larger and fewer writes. Each
6814 * device is written to in a rotor fashion, sweeping writes through
6815 * available space then repeating.
6817 * 7. The L2ARC does not store dirty content. It never needs to flush
6818 * write buffers back to disk based storage.
6820 * 8. If an ARC buffer is written (and dirtied) which also exists in the
6821 * L2ARC, the now stale L2ARC buffer is immediately dropped.
6823 * The performance of the L2ARC can be tweaked by a number of tunables, which
6824 * may be necessary for different workloads:
6826 * l2arc_write_max max write bytes per interval
6827 * l2arc_write_boost extra write bytes during device warmup
6828 * l2arc_noprefetch skip caching prefetched buffers
6829 * l2arc_headroom number of max device writes to precache
6830 * l2arc_headroom_boost when we find compressed buffers during ARC
6831 * scanning, we multiply headroom by this
6832 * percentage factor for the next scan cycle,
6833 * since more compressed buffers are likely to
6835 * l2arc_feed_secs seconds between L2ARC writing
6837 * Tunables may be removed or added as future performance improvements are
6838 * integrated, and also may become zpool properties.
6840 * There are three key functions that control how the L2ARC warms up:
6842 * l2arc_write_eligible() check if a buffer is eligible to cache
6843 * l2arc_write_size() calculate how much to write
6844 * l2arc_write_interval() calculate sleep delay between writes
6846 * These three functions determine what to write, how much, and how quickly
6851 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
6854 * A buffer is *not* eligible for the L2ARC if it:
6855 * 1. belongs to a different spa.
6856 * 2. is already cached on the L2ARC.
6857 * 3. has an I/O in progress (it may be an incomplete read).
6858 * 4. is flagged not eligible (zfs property).
6860 if (hdr->b_spa != spa_guid) {
6861 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
6864 if (HDR_HAS_L2HDR(hdr)) {
6865 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
6868 if (HDR_IO_IN_PROGRESS(hdr)) {
6869 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
6872 if (!HDR_L2CACHE(hdr)) {
6873 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
6881 l2arc_write_size(void)
6886 * Make sure our globals have meaningful values in case the user
6889 size = l2arc_write_max;
6891 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
6892 "be greater than zero, resetting it to the default (%d)",
6894 size = l2arc_write_max = L2ARC_WRITE_SIZE;
6897 if (arc_warm == B_FALSE)
6898 size += l2arc_write_boost;
6905 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
6907 clock_t interval, next, now;
6910 * If the ARC lists are busy, increase our write rate; if the
6911 * lists are stale, idle back. This is achieved by checking
6912 * how much we previously wrote - if it was more than half of
6913 * what we wanted, schedule the next write much sooner.
6915 if (l2arc_feed_again && wrote > (wanted / 2))
6916 interval = (hz * l2arc_feed_min_ms) / 1000;
6918 interval = hz * l2arc_feed_secs;
6920 now = ddi_get_lbolt();
6921 next = MAX(now, MIN(now + interval, began + interval));
6927 * Cycle through L2ARC devices. This is how L2ARC load balances.
6928 * If a device is returned, this also returns holding the spa config lock.
6930 static l2arc_dev_t *
6931 l2arc_dev_get_next(void)
6933 l2arc_dev_t *first, *next = NULL;
6936 * Lock out the removal of spas (spa_namespace_lock), then removal
6937 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
6938 * both locks will be dropped and a spa config lock held instead.
6940 mutex_enter(&spa_namespace_lock);
6941 mutex_enter(&l2arc_dev_mtx);
6943 /* if there are no vdevs, there is nothing to do */
6944 if (l2arc_ndev == 0)
6948 next = l2arc_dev_last;
6950 /* loop around the list looking for a non-faulted vdev */
6952 next = list_head(l2arc_dev_list);
6954 next = list_next(l2arc_dev_list, next);
6956 next = list_head(l2arc_dev_list);
6959 /* if we have come back to the start, bail out */
6962 else if (next == first)
6965 } while (vdev_is_dead(next->l2ad_vdev));
6967 /* if we were unable to find any usable vdevs, return NULL */
6968 if (vdev_is_dead(next->l2ad_vdev))
6971 l2arc_dev_last = next;
6974 mutex_exit(&l2arc_dev_mtx);
6977 * Grab the config lock to prevent the 'next' device from being
6978 * removed while we are writing to it.
6981 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
6982 mutex_exit(&spa_namespace_lock);
6988 * Free buffers that were tagged for destruction.
6991 l2arc_do_free_on_write()
6994 l2arc_data_free_t *df, *df_prev;
6996 mutex_enter(&l2arc_free_on_write_mtx);
6997 buflist = l2arc_free_on_write;
6999 for (df = list_tail(buflist); df; df = df_prev) {
7000 df_prev = list_prev(buflist, df);
7001 ASSERT3P(df->l2df_abd, !=, NULL);
7002 abd_free(df->l2df_abd);
7003 list_remove(buflist, df);
7004 kmem_free(df, sizeof (l2arc_data_free_t));
7007 mutex_exit(&l2arc_free_on_write_mtx);
7011 * A write to a cache device has completed. Update all headers to allow
7012 * reads from these buffers to begin.
7015 l2arc_write_done(zio_t *zio)
7017 l2arc_write_callback_t *cb;
7020 arc_buf_hdr_t *head, *hdr, *hdr_prev;
7021 kmutex_t *hash_lock;
7022 int64_t bytes_dropped = 0;
7024 cb = zio->io_private;
7025 ASSERT3P(cb, !=, NULL);
7026 dev = cb->l2wcb_dev;
7027 ASSERT3P(dev, !=, NULL);
7028 head = cb->l2wcb_head;
7029 ASSERT3P(head, !=, NULL);
7030 buflist = &dev->l2ad_buflist;
7031 ASSERT3P(buflist, !=, NULL);
7032 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
7033 l2arc_write_callback_t *, cb);
7035 if (zio->io_error != 0)
7036 ARCSTAT_BUMP(arcstat_l2_writes_error);
7039 * All writes completed, or an error was hit.
7042 mutex_enter(&dev->l2ad_mtx);
7043 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7044 hdr_prev = list_prev(buflist, hdr);
7046 hash_lock = HDR_LOCK(hdr);
7049 * We cannot use mutex_enter or else we can deadlock
7050 * with l2arc_write_buffers (due to swapping the order
7051 * the hash lock and l2ad_mtx are taken).
7053 if (!mutex_tryenter(hash_lock)) {
7055 * Missed the hash lock. We must retry so we
7056 * don't leave the ARC_FLAG_L2_WRITING bit set.
7058 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7061 * We don't want to rescan the headers we've
7062 * already marked as having been written out, so
7063 * we reinsert the head node so we can pick up
7064 * where we left off.
7066 list_remove(buflist, head);
7067 list_insert_after(buflist, hdr, head);
7069 mutex_exit(&dev->l2ad_mtx);
7072 * We wait for the hash lock to become available
7073 * to try and prevent busy waiting, and increase
7074 * the chance we'll be able to acquire the lock
7075 * the next time around.
7077 mutex_enter(hash_lock);
7078 mutex_exit(hash_lock);
7083 * We could not have been moved into the arc_l2c_only
7084 * state while in-flight due to our ARC_FLAG_L2_WRITING
7085 * bit being set. Let's just ensure that's being enforced.
7087 ASSERT(HDR_HAS_L1HDR(hdr));
7089 if (zio->io_error != 0) {
7091 * Error - drop L2ARC entry.
7093 list_remove(buflist, hdr);
7095 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7097 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr));
7098 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
7100 bytes_dropped += arc_hdr_size(hdr);
7101 (void) refcount_remove_many(&dev->l2ad_alloc,
7102 arc_hdr_size(hdr), hdr);
7106 * Allow ARC to begin reads and ghost list evictions to
7109 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7111 mutex_exit(hash_lock);
7114 atomic_inc_64(&l2arc_writes_done);
7115 list_remove(buflist, head);
7116 ASSERT(!HDR_HAS_L1HDR(head));
7117 kmem_cache_free(hdr_l2only_cache, head);
7118 mutex_exit(&dev->l2ad_mtx);
7120 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7122 l2arc_do_free_on_write();
7124 kmem_free(cb, sizeof (l2arc_write_callback_t));
7128 * A read to a cache device completed. Validate buffer contents before
7129 * handing over to the regular ARC routines.
7132 l2arc_read_done(zio_t *zio)
7134 l2arc_read_callback_t *cb;
7136 kmutex_t *hash_lock;
7137 boolean_t valid_cksum;
7139 ASSERT3P(zio->io_vd, !=, NULL);
7140 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
7142 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
7144 cb = zio->io_private;
7145 ASSERT3P(cb, !=, NULL);
7146 hdr = cb->l2rcb_hdr;
7147 ASSERT3P(hdr, !=, NULL);
7149 hash_lock = HDR_LOCK(hdr);
7150 mutex_enter(hash_lock);
7151 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
7154 * If the data was read into a temporary buffer,
7155 * move it and free the buffer.
7157 if (cb->l2rcb_abd != NULL) {
7158 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
7159 if (zio->io_error == 0) {
7160 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd,
7165 * The following must be done regardless of whether
7166 * there was an error:
7167 * - free the temporary buffer
7168 * - point zio to the real ARC buffer
7169 * - set zio size accordingly
7170 * These are required because zio is either re-used for
7171 * an I/O of the block in the case of the error
7172 * or the zio is passed to arc_read_done() and it
7175 abd_free(cb->l2rcb_abd);
7176 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
7177 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
7180 ASSERT3P(zio->io_abd, !=, NULL);
7183 * Check this survived the L2ARC journey.
7185 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd);
7186 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
7187 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
7189 valid_cksum = arc_cksum_is_equal(hdr, zio);
7190 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
7191 mutex_exit(hash_lock);
7192 zio->io_private = hdr;
7195 mutex_exit(hash_lock);
7197 * Buffer didn't survive caching. Increment stats and
7198 * reissue to the original storage device.
7200 if (zio->io_error != 0) {
7201 ARCSTAT_BUMP(arcstat_l2_io_error);
7203 zio->io_error = SET_ERROR(EIO);
7206 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
7209 * If there's no waiter, issue an async i/o to the primary
7210 * storage now. If there *is* a waiter, the caller must
7211 * issue the i/o in a context where it's OK to block.
7213 if (zio->io_waiter == NULL) {
7214 zio_t *pio = zio_unique_parent(zio);
7216 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
7218 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
7219 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done,
7220 hdr, zio->io_priority, cb->l2rcb_flags,
7225 kmem_free(cb, sizeof (l2arc_read_callback_t));
7229 * This is the list priority from which the L2ARC will search for pages to
7230 * cache. This is used within loops (0..3) to cycle through lists in the
7231 * desired order. This order can have a significant effect on cache
7234 * Currently the metadata lists are hit first, MFU then MRU, followed by
7235 * the data lists. This function returns a locked list, and also returns
7238 static multilist_sublist_t *
7239 l2arc_sublist_lock(int list_num)
7241 multilist_t *ml = NULL;
7244 ASSERT(list_num >= 0 && list_num <= 3);
7248 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
7251 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
7254 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
7257 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
7262 * Return a randomly-selected sublist. This is acceptable
7263 * because the caller feeds only a little bit of data for each
7264 * call (8MB). Subsequent calls will result in different
7265 * sublists being selected.
7267 idx = multilist_get_random_index(ml);
7268 return (multilist_sublist_lock(ml, idx));
7272 * Evict buffers from the device write hand to the distance specified in
7273 * bytes. This distance may span populated buffers, it may span nothing.
7274 * This is clearing a region on the L2ARC device ready for writing.
7275 * If the 'all' boolean is set, every buffer is evicted.
7278 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
7281 arc_buf_hdr_t *hdr, *hdr_prev;
7282 kmutex_t *hash_lock;
7285 buflist = &dev->l2ad_buflist;
7287 if (!all && dev->l2ad_first) {
7289 * This is the first sweep through the device. There is
7295 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
7297 * When nearing the end of the device, evict to the end
7298 * before the device write hand jumps to the start.
7300 taddr = dev->l2ad_end;
7302 taddr = dev->l2ad_hand + distance;
7304 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
7305 uint64_t, taddr, boolean_t, all);
7308 mutex_enter(&dev->l2ad_mtx);
7309 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
7310 hdr_prev = list_prev(buflist, hdr);
7312 hash_lock = HDR_LOCK(hdr);
7315 * We cannot use mutex_enter or else we can deadlock
7316 * with l2arc_write_buffers (due to swapping the order
7317 * the hash lock and l2ad_mtx are taken).
7319 if (!mutex_tryenter(hash_lock)) {
7321 * Missed the hash lock. Retry.
7323 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
7324 mutex_exit(&dev->l2ad_mtx);
7325 mutex_enter(hash_lock);
7326 mutex_exit(hash_lock);
7331 * A header can't be on this list if it doesn't have L2 header.
7333 ASSERT(HDR_HAS_L2HDR(hdr));
7335 /* Ensure this header has finished being written. */
7336 ASSERT(!HDR_L2_WRITING(hdr));
7337 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
7339 if (!all && (hdr->b_l2hdr.b_daddr >= taddr ||
7340 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
7342 * We've evicted to the target address,
7343 * or the end of the device.
7345 mutex_exit(hash_lock);
7349 if (!HDR_HAS_L1HDR(hdr)) {
7350 ASSERT(!HDR_L2_READING(hdr));
7352 * This doesn't exist in the ARC. Destroy.
7353 * arc_hdr_destroy() will call list_remove()
7354 * and decrement arcstat_l2_lsize.
7356 arc_change_state(arc_anon, hdr, hash_lock);
7357 arc_hdr_destroy(hdr);
7359 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
7360 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
7362 * Invalidate issued or about to be issued
7363 * reads, since we may be about to write
7364 * over this location.
7366 if (HDR_L2_READING(hdr)) {
7367 ARCSTAT_BUMP(arcstat_l2_evict_reading);
7368 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
7371 arc_hdr_l2hdr_destroy(hdr);
7373 mutex_exit(hash_lock);
7375 mutex_exit(&dev->l2ad_mtx);
7379 * Find and write ARC buffers to the L2ARC device.
7381 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
7382 * for reading until they have completed writing.
7383 * The headroom_boost is an in-out parameter used to maintain headroom boost
7384 * state between calls to this function.
7386 * Returns the number of bytes actually written (which may be smaller than
7387 * the delta by which the device hand has changed due to alignment).
7390 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
7392 arc_buf_hdr_t *hdr, *hdr_prev, *head;
7393 uint64_t write_asize, write_psize, write_lsize, headroom;
7395 l2arc_write_callback_t *cb;
7397 uint64_t guid = spa_load_guid(spa);
7400 ASSERT3P(dev->l2ad_vdev, !=, NULL);
7403 write_lsize = write_asize = write_psize = 0;
7405 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
7406 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
7408 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
7410 * Copy buffers for L2ARC writing.
7412 for (try = 0; try <= 3; try++) {
7413 multilist_sublist_t *mls = l2arc_sublist_lock(try);
7414 uint64_t passed_sz = 0;
7416 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
7419 * L2ARC fast warmup.
7421 * Until the ARC is warm and starts to evict, read from the
7422 * head of the ARC lists rather than the tail.
7424 if (arc_warm == B_FALSE)
7425 hdr = multilist_sublist_head(mls);
7427 hdr = multilist_sublist_tail(mls);
7429 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
7431 headroom = target_sz * l2arc_headroom;
7432 if (zfs_compressed_arc_enabled)
7433 headroom = (headroom * l2arc_headroom_boost) / 100;
7435 for (; hdr; hdr = hdr_prev) {
7436 kmutex_t *hash_lock;
7438 if (arc_warm == B_FALSE)
7439 hdr_prev = multilist_sublist_next(mls, hdr);
7441 hdr_prev = multilist_sublist_prev(mls, hdr);
7442 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned,
7443 HDR_GET_LSIZE(hdr));
7445 hash_lock = HDR_LOCK(hdr);
7446 if (!mutex_tryenter(hash_lock)) {
7447 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
7449 * Skip this buffer rather than waiting.
7454 passed_sz += HDR_GET_LSIZE(hdr);
7455 if (passed_sz > headroom) {
7459 mutex_exit(hash_lock);
7460 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
7464 if (!l2arc_write_eligible(guid, hdr)) {
7465 mutex_exit(hash_lock);
7470 * We rely on the L1 portion of the header below, so
7471 * it's invalid for this header to have been evicted out
7472 * of the ghost cache, prior to being written out. The
7473 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
7475 ASSERT(HDR_HAS_L1HDR(hdr));
7477 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
7478 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7479 ASSERT3U(arc_hdr_size(hdr), >, 0);
7480 uint64_t psize = arc_hdr_size(hdr);
7481 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
7484 if ((write_asize + asize) > target_sz) {
7486 mutex_exit(hash_lock);
7487 ARCSTAT_BUMP(arcstat_l2_write_full);
7493 * Insert a dummy header on the buflist so
7494 * l2arc_write_done() can find where the
7495 * write buffers begin without searching.
7497 mutex_enter(&dev->l2ad_mtx);
7498 list_insert_head(&dev->l2ad_buflist, head);
7499 mutex_exit(&dev->l2ad_mtx);
7502 sizeof (l2arc_write_callback_t), KM_SLEEP);
7503 cb->l2wcb_dev = dev;
7504 cb->l2wcb_head = head;
7505 pio = zio_root(spa, l2arc_write_done, cb,
7507 ARCSTAT_BUMP(arcstat_l2_write_pios);
7510 hdr->b_l2hdr.b_dev = dev;
7511 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
7512 arc_hdr_set_flags(hdr,
7513 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
7515 mutex_enter(&dev->l2ad_mtx);
7516 list_insert_head(&dev->l2ad_buflist, hdr);
7517 mutex_exit(&dev->l2ad_mtx);
7519 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr);
7522 * Normally the L2ARC can use the hdr's data, but if
7523 * we're sharing data between the hdr and one of its
7524 * bufs, L2ARC needs its own copy of the data so that
7525 * the ZIO below can't race with the buf consumer.
7526 * Another case where we need to create a copy of the
7527 * data is when the buffer size is not device-aligned
7528 * and we need to pad the block to make it such.
7529 * That also keeps the clock hand suitably aligned.
7531 * To ensure that the copy will be available for the
7532 * lifetime of the ZIO and be cleaned up afterwards, we
7533 * add it to the l2arc_free_on_write queue.
7536 if (!HDR_SHARED_DATA(hdr) && psize == asize) {
7537 to_write = hdr->b_l1hdr.b_pabd;
7539 to_write = abd_alloc_for_io(asize,
7540 HDR_ISTYPE_METADATA(hdr));
7541 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize);
7542 if (asize != psize) {
7543 abd_zero_off(to_write, psize,
7546 l2arc_free_abd_on_write(to_write, asize,
7549 wzio = zio_write_phys(pio, dev->l2ad_vdev,
7550 hdr->b_l2hdr.b_daddr, asize, to_write,
7551 ZIO_CHECKSUM_OFF, NULL, hdr,
7552 ZIO_PRIORITY_ASYNC_WRITE,
7553 ZIO_FLAG_CANFAIL, B_FALSE);
7555 write_lsize += HDR_GET_LSIZE(hdr);
7556 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
7559 write_psize += psize;
7560 write_asize += asize;
7561 dev->l2ad_hand += asize;
7563 mutex_exit(hash_lock);
7565 (void) zio_nowait(wzio);
7568 multilist_sublist_unlock(mls);
7574 /* No buffers selected for writing? */
7576 ASSERT0(write_lsize);
7577 ASSERT(!HDR_HAS_L1HDR(head));
7578 kmem_cache_free(hdr_l2only_cache, head);
7582 ASSERT3U(write_psize, <=, target_sz);
7583 ARCSTAT_BUMP(arcstat_l2_writes_sent);
7584 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
7585 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
7586 ARCSTAT_INCR(arcstat_l2_psize, write_psize);
7587 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
7590 * Bump device hand to the device start if it is approaching the end.
7591 * l2arc_evict() will already have evicted ahead for this case.
7593 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
7594 dev->l2ad_hand = dev->l2ad_start;
7595 dev->l2ad_first = B_FALSE;
7598 dev->l2ad_writing = B_TRUE;
7599 (void) zio_wait(pio);
7600 dev->l2ad_writing = B_FALSE;
7602 return (write_asize);
7606 * This thread feeds the L2ARC at regular intervals. This is the beating
7607 * heart of the L2ARC.
7611 l2arc_feed_thread(void *unused __unused)
7616 uint64_t size, wrote;
7617 clock_t begin, next = ddi_get_lbolt();
7619 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
7621 mutex_enter(&l2arc_feed_thr_lock);
7623 while (l2arc_thread_exit == 0) {
7624 CALLB_CPR_SAFE_BEGIN(&cpr);
7625 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
7626 next - ddi_get_lbolt());
7627 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
7628 next = ddi_get_lbolt() + hz;
7631 * Quick check for L2ARC devices.
7633 mutex_enter(&l2arc_dev_mtx);
7634 if (l2arc_ndev == 0) {
7635 mutex_exit(&l2arc_dev_mtx);
7638 mutex_exit(&l2arc_dev_mtx);
7639 begin = ddi_get_lbolt();
7642 * This selects the next l2arc device to write to, and in
7643 * doing so the next spa to feed from: dev->l2ad_spa. This
7644 * will return NULL if there are now no l2arc devices or if
7645 * they are all faulted.
7647 * If a device is returned, its spa's config lock is also
7648 * held to prevent device removal. l2arc_dev_get_next()
7649 * will grab and release l2arc_dev_mtx.
7651 if ((dev = l2arc_dev_get_next()) == NULL)
7654 spa = dev->l2ad_spa;
7655 ASSERT3P(spa, !=, NULL);
7658 * If the pool is read-only then force the feed thread to
7659 * sleep a little longer.
7661 if (!spa_writeable(spa)) {
7662 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
7663 spa_config_exit(spa, SCL_L2ARC, dev);
7668 * Avoid contributing to memory pressure.
7670 if (arc_reclaim_needed()) {
7671 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
7672 spa_config_exit(spa, SCL_L2ARC, dev);
7676 ARCSTAT_BUMP(arcstat_l2_feeds);
7678 size = l2arc_write_size();
7681 * Evict L2ARC buffers that will be overwritten.
7683 l2arc_evict(dev, size, B_FALSE);
7686 * Write ARC buffers.
7688 wrote = l2arc_write_buffers(spa, dev, size);
7691 * Calculate interval between writes.
7693 next = l2arc_write_interval(begin, size, wrote);
7694 spa_config_exit(spa, SCL_L2ARC, dev);
7697 l2arc_thread_exit = 0;
7698 cv_broadcast(&l2arc_feed_thr_cv);
7699 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
7704 l2arc_vdev_present(vdev_t *vd)
7708 mutex_enter(&l2arc_dev_mtx);
7709 for (dev = list_head(l2arc_dev_list); dev != NULL;
7710 dev = list_next(l2arc_dev_list, dev)) {
7711 if (dev->l2ad_vdev == vd)
7714 mutex_exit(&l2arc_dev_mtx);
7716 return (dev != NULL);
7720 * Add a vdev for use by the L2ARC. By this point the spa has already
7721 * validated the vdev and opened it.
7724 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
7726 l2arc_dev_t *adddev;
7728 ASSERT(!l2arc_vdev_present(vd));
7730 vdev_ashift_optimize(vd);
7733 * Create a new l2arc device entry.
7735 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
7736 adddev->l2ad_spa = spa;
7737 adddev->l2ad_vdev = vd;
7738 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
7739 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
7740 adddev->l2ad_hand = adddev->l2ad_start;
7741 adddev->l2ad_first = B_TRUE;
7742 adddev->l2ad_writing = B_FALSE;
7744 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
7746 * This is a list of all ARC buffers that are still valid on the
7749 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
7750 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
7752 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
7753 refcount_create(&adddev->l2ad_alloc);
7756 * Add device to global list
7758 mutex_enter(&l2arc_dev_mtx);
7759 list_insert_head(l2arc_dev_list, adddev);
7760 atomic_inc_64(&l2arc_ndev);
7761 mutex_exit(&l2arc_dev_mtx);
7765 * Remove a vdev from the L2ARC.
7768 l2arc_remove_vdev(vdev_t *vd)
7770 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
7773 * Find the device by vdev
7775 mutex_enter(&l2arc_dev_mtx);
7776 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
7777 nextdev = list_next(l2arc_dev_list, dev);
7778 if (vd == dev->l2ad_vdev) {
7783 ASSERT3P(remdev, !=, NULL);
7786 * Remove device from global list
7788 list_remove(l2arc_dev_list, remdev);
7789 l2arc_dev_last = NULL; /* may have been invalidated */
7790 atomic_dec_64(&l2arc_ndev);
7791 mutex_exit(&l2arc_dev_mtx);
7794 * Clear all buflists and ARC references. L2ARC device flush.
7796 l2arc_evict(remdev, 0, B_TRUE);
7797 list_destroy(&remdev->l2ad_buflist);
7798 mutex_destroy(&remdev->l2ad_mtx);
7799 refcount_destroy(&remdev->l2ad_alloc);
7800 kmem_free(remdev, sizeof (l2arc_dev_t));
7806 l2arc_thread_exit = 0;
7808 l2arc_writes_sent = 0;
7809 l2arc_writes_done = 0;
7811 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
7812 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
7813 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
7814 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
7816 l2arc_dev_list = &L2ARC_dev_list;
7817 l2arc_free_on_write = &L2ARC_free_on_write;
7818 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
7819 offsetof(l2arc_dev_t, l2ad_node));
7820 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
7821 offsetof(l2arc_data_free_t, l2df_list_node));
7828 * This is called from dmu_fini(), which is called from spa_fini();
7829 * Because of this, we can assume that all l2arc devices have
7830 * already been removed when the pools themselves were removed.
7833 l2arc_do_free_on_write();
7835 mutex_destroy(&l2arc_feed_thr_lock);
7836 cv_destroy(&l2arc_feed_thr_cv);
7837 mutex_destroy(&l2arc_dev_mtx);
7838 mutex_destroy(&l2arc_free_on_write_mtx);
7840 list_destroy(l2arc_dev_list);
7841 list_destroy(l2arc_free_on_write);
7847 if (!(spa_mode_global & FWRITE))
7850 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
7851 TS_RUN, minclsyspri);
7857 if (!(spa_mode_global & FWRITE))
7860 mutex_enter(&l2arc_feed_thr_lock);
7861 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
7862 l2arc_thread_exit = 1;
7863 while (l2arc_thread_exit != 0)
7864 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
7865 mutex_exit(&l2arc_feed_thr_lock);
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