4 * The contents of this file are subject to the terms of the
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9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
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>
278 #include <sys/aggsum.h>
279 #include <sys/cityhash.h>
281 #include <machine/vmparam.h>
285 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
286 boolean_t arc_watch = B_FALSE;
291 static kmutex_t arc_reclaim_lock;
292 static kcondvar_t arc_reclaim_thread_cv;
293 static boolean_t arc_reclaim_thread_exit;
294 static kcondvar_t arc_reclaim_waiters_cv;
296 static kmutex_t arc_dnlc_evicts_lock;
297 static kcondvar_t arc_dnlc_evicts_cv;
298 static boolean_t arc_dnlc_evicts_thread_exit;
300 uint_t arc_reduce_dnlc_percent = 3;
303 * The number of headers to evict in arc_evict_state_impl() before
304 * dropping the sublist lock and evicting from another sublist. A lower
305 * value means we're more likely to evict the "correct" header (i.e. the
306 * oldest header in the arc state), but comes with higher overhead
307 * (i.e. more invocations of arc_evict_state_impl()).
309 int zfs_arc_evict_batch_limit = 10;
311 /* number of seconds before growing cache again */
312 static int arc_grow_retry = 60;
314 /* number of milliseconds before attempting a kmem-cache-reap */
315 static int arc_kmem_cache_reap_retry_ms = 1000;
317 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
318 int zfs_arc_overflow_shift = 8;
320 /* shift of arc_c for calculating both min and max arc_p */
321 static int arc_p_min_shift = 4;
323 /* log2(fraction of arc to reclaim) */
324 static int arc_shrink_shift = 7;
327 * log2(fraction of ARC which must be free to allow growing).
328 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
329 * when reading a new block into the ARC, we will evict an equal-sized block
332 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
333 * we will still not allow it to grow.
335 int arc_no_grow_shift = 5;
339 * minimum lifespan of a prefetch block in clock ticks
340 * (initialized in arc_init())
342 static int zfs_arc_min_prefetch_ms = 1;
343 static int zfs_arc_min_prescient_prefetch_ms = 6;
346 * If this percent of memory is free, don't throttle.
348 int arc_lotsfree_percent = 10;
351 extern boolean_t zfs_prefetch_disable;
354 * The arc has filled available memory and has now warmed up.
356 static boolean_t arc_warm;
359 * log2 fraction of the zio arena to keep free.
361 int arc_zio_arena_free_shift = 2;
364 * These tunables are for performance analysis.
366 uint64_t zfs_arc_max;
367 uint64_t zfs_arc_min;
368 uint64_t zfs_arc_meta_limit = 0;
369 uint64_t zfs_arc_meta_min = 0;
370 int zfs_arc_grow_retry = 0;
371 int zfs_arc_shrink_shift = 0;
372 int zfs_arc_no_grow_shift = 0;
373 int zfs_arc_p_min_shift = 0;
374 uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
375 u_int zfs_arc_free_target = 0;
377 /* Absolute min for arc min / max is 16MB. */
378 static uint64_t arc_abs_min = 16 << 20;
380 boolean_t zfs_compressed_arc_enabled = B_TRUE;
382 static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS);
383 static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS);
384 static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS);
385 static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS);
386 static int sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS);
388 #if defined(__FreeBSD__) && defined(_KERNEL)
390 arc_free_target_init(void *unused __unused)
393 zfs_arc_free_target = vm_cnt.v_free_target;
395 SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
396 arc_free_target_init, NULL);
398 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
399 TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min);
400 TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
401 TUNABLE_INT("vfs.zfs.arc_grow_retry", &zfs_arc_grow_retry);
402 TUNABLE_INT("vfs.zfs.arc_no_grow_shift", &zfs_arc_no_grow_shift);
403 SYSCTL_DECL(_vfs_zfs);
404 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN,
405 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size");
406 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN,
407 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size");
408 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_no_grow_shift, CTLTYPE_U32 | CTLFLAG_RWTUN,
409 0, sizeof(uint32_t), sysctl_vfs_zfs_arc_no_grow_shift, "U",
410 "log2(fraction of ARC which must be free to allow growing)");
411 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
412 &zfs_arc_average_blocksize, 0,
413 "ARC average blocksize");
414 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
415 &arc_shrink_shift, 0,
416 "log2(fraction of arc to reclaim)");
417 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_grow_retry, CTLFLAG_RW,
419 "Wait in seconds before considering growing ARC");
420 SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN,
421 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC");
424 * We don't have a tunable for arc_free_target due to the dependency on
425 * pagedaemon initialisation.
427 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
428 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
429 sysctl_vfs_zfs_arc_free_target, "IU",
430 "Desired number of free pages below which ARC triggers reclaim");
433 sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
438 val = zfs_arc_free_target;
439 err = sysctl_handle_int(oidp, &val, 0, req);
440 if (err != 0 || req->newptr == NULL)
445 if (val > vm_cnt.v_page_count)
448 zfs_arc_free_target = val;
454 * Must be declared here, before the definition of corresponding kstat
455 * macro which uses the same names will confuse the compiler.
457 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit,
458 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t),
459 sysctl_vfs_zfs_arc_meta_limit, "QU",
460 "ARC metadata limit");
464 * Note that buffers can be in one of 6 states:
465 * ARC_anon - anonymous (discussed below)
466 * ARC_mru - recently used, currently cached
467 * ARC_mru_ghost - recentely used, no longer in cache
468 * ARC_mfu - frequently used, currently cached
469 * ARC_mfu_ghost - frequently used, no longer in cache
470 * ARC_l2c_only - exists in L2ARC but not other states
471 * When there are no active references to the buffer, they are
472 * are linked onto a list in one of these arc states. These are
473 * the only buffers that can be evicted or deleted. Within each
474 * state there are multiple lists, one for meta-data and one for
475 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
476 * etc.) is tracked separately so that it can be managed more
477 * explicitly: favored over data, limited explicitly.
479 * Anonymous buffers are buffers that are not associated with
480 * a DVA. These are buffers that hold dirty block copies
481 * before they are written to stable storage. By definition,
482 * they are "ref'd" and are considered part of arc_mru
483 * that cannot be freed. Generally, they will aquire a DVA
484 * as they are written and migrate onto the arc_mru list.
486 * The ARC_l2c_only state is for buffers that are in the second
487 * level ARC but no longer in any of the ARC_m* lists. The second
488 * level ARC itself may also contain buffers that are in any of
489 * the ARC_m* states - meaning that a buffer can exist in two
490 * places. The reason for the ARC_l2c_only state is to keep the
491 * buffer header in the hash table, so that reads that hit the
492 * second level ARC benefit from these fast lookups.
495 typedef struct arc_state {
497 * list of evictable buffers
499 multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
501 * total amount of evictable data in this state
503 refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
505 * total amount of data in this state; this includes: evictable,
506 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
508 refcount_t arcs_size;
512 static arc_state_t ARC_anon;
513 static arc_state_t ARC_mru;
514 static arc_state_t ARC_mru_ghost;
515 static arc_state_t ARC_mfu;
516 static arc_state_t ARC_mfu_ghost;
517 static arc_state_t ARC_l2c_only;
519 typedef struct arc_stats {
520 kstat_named_t arcstat_hits;
521 kstat_named_t arcstat_misses;
522 kstat_named_t arcstat_demand_data_hits;
523 kstat_named_t arcstat_demand_data_misses;
524 kstat_named_t arcstat_demand_metadata_hits;
525 kstat_named_t arcstat_demand_metadata_misses;
526 kstat_named_t arcstat_prefetch_data_hits;
527 kstat_named_t arcstat_prefetch_data_misses;
528 kstat_named_t arcstat_prefetch_metadata_hits;
529 kstat_named_t arcstat_prefetch_metadata_misses;
530 kstat_named_t arcstat_mru_hits;
531 kstat_named_t arcstat_mru_ghost_hits;
532 kstat_named_t arcstat_mfu_hits;
533 kstat_named_t arcstat_mfu_ghost_hits;
534 kstat_named_t arcstat_allocated;
535 kstat_named_t arcstat_deleted;
537 * Number of buffers that could not be evicted because the hash lock
538 * was held by another thread. The lock may not necessarily be held
539 * by something using the same buffer, since hash locks are shared
540 * by multiple buffers.
542 kstat_named_t arcstat_mutex_miss;
544 * Number of buffers skipped when updating the access state due to the
545 * header having already been released after acquiring the hash lock.
547 kstat_named_t arcstat_access_skip;
549 * Number of buffers skipped because they have I/O in progress, are
550 * indirect prefetch buffers that have not lived long enough, or are
551 * not from the spa we're trying to evict from.
553 kstat_named_t arcstat_evict_skip;
555 * Number of times arc_evict_state() was unable to evict enough
556 * buffers to reach it's target amount.
558 kstat_named_t arcstat_evict_not_enough;
559 kstat_named_t arcstat_evict_l2_cached;
560 kstat_named_t arcstat_evict_l2_eligible;
561 kstat_named_t arcstat_evict_l2_ineligible;
562 kstat_named_t arcstat_evict_l2_skip;
563 kstat_named_t arcstat_hash_elements;
564 kstat_named_t arcstat_hash_elements_max;
565 kstat_named_t arcstat_hash_collisions;
566 kstat_named_t arcstat_hash_chains;
567 kstat_named_t arcstat_hash_chain_max;
568 kstat_named_t arcstat_p;
569 kstat_named_t arcstat_c;
570 kstat_named_t arcstat_c_min;
571 kstat_named_t arcstat_c_max;
572 /* Not updated directly; only synced in arc_kstat_update. */
573 kstat_named_t arcstat_size;
575 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
576 * Note that the compressed bytes may match the uncompressed bytes
577 * if the block is either not compressed or compressed arc is disabled.
579 kstat_named_t arcstat_compressed_size;
581 * Uncompressed size of the data stored in b_pabd. If compressed
582 * arc is disabled then this value will be identical to the stat
585 kstat_named_t arcstat_uncompressed_size;
587 * Number of bytes stored in all the arc_buf_t's. This is classified
588 * as "overhead" since this data is typically short-lived and will
589 * be evicted from the arc when it becomes unreferenced unless the
590 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
591 * values have been set (see comment in dbuf.c for more information).
593 kstat_named_t arcstat_overhead_size;
595 * Number of bytes consumed by internal ARC structures necessary
596 * for tracking purposes; these structures are not actually
597 * backed by ARC buffers. This includes arc_buf_hdr_t structures
598 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
599 * caches), and arc_buf_t structures (allocated via arc_buf_t
601 * Not updated directly; only synced in arc_kstat_update.
603 kstat_named_t arcstat_hdr_size;
605 * Number of bytes consumed by ARC buffers of type equal to
606 * ARC_BUFC_DATA. This is generally consumed by buffers backing
607 * on disk user data (e.g. plain file contents).
608 * Not updated directly; only synced in arc_kstat_update.
610 kstat_named_t arcstat_data_size;
612 * Number of bytes consumed by ARC buffers of type equal to
613 * ARC_BUFC_METADATA. This is generally consumed by buffers
614 * backing on disk data that is used for internal ZFS
615 * structures (e.g. ZAP, dnode, indirect blocks, etc).
616 * Not updated directly; only synced in arc_kstat_update.
618 kstat_named_t arcstat_metadata_size;
620 * Number of bytes consumed by various buffers and structures
621 * not actually backed with ARC buffers. This includes bonus
622 * buffers (allocated directly via zio_buf_* functions),
623 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
624 * cache), and dnode_t structures (allocated via dnode_t cache).
625 * Not updated directly; only synced in arc_kstat_update.
627 kstat_named_t arcstat_other_size;
629 * Total number of bytes consumed by ARC buffers residing in the
630 * arc_anon state. This includes *all* buffers in the arc_anon
631 * state; e.g. data, metadata, evictable, and unevictable buffers
632 * are all included in this value.
633 * Not updated directly; only synced in arc_kstat_update.
635 kstat_named_t arcstat_anon_size;
637 * Number of bytes consumed by ARC buffers that meet the
638 * following criteria: backing buffers of type ARC_BUFC_DATA,
639 * residing in the arc_anon state, and are eligible for eviction
640 * (e.g. have no outstanding holds on the buffer).
641 * Not updated directly; only synced in arc_kstat_update.
643 kstat_named_t arcstat_anon_evictable_data;
645 * Number of bytes consumed by ARC buffers that meet the
646 * following criteria: backing buffers of type ARC_BUFC_METADATA,
647 * residing in the arc_anon state, and are eligible for eviction
648 * (e.g. have no outstanding holds on the buffer).
649 * Not updated directly; only synced in arc_kstat_update.
651 kstat_named_t arcstat_anon_evictable_metadata;
653 * Total number of bytes consumed by ARC buffers residing in the
654 * arc_mru state. This includes *all* buffers in the arc_mru
655 * state; e.g. data, metadata, evictable, and unevictable buffers
656 * are all included in this value.
657 * Not updated directly; only synced in arc_kstat_update.
659 kstat_named_t arcstat_mru_size;
661 * Number of bytes consumed by ARC buffers that meet the
662 * following criteria: backing buffers of type ARC_BUFC_DATA,
663 * residing in the arc_mru state, and are eligible for eviction
664 * (e.g. have no outstanding holds on the buffer).
665 * Not updated directly; only synced in arc_kstat_update.
667 kstat_named_t arcstat_mru_evictable_data;
669 * Number of bytes consumed by ARC buffers that meet the
670 * following criteria: backing buffers of type ARC_BUFC_METADATA,
671 * residing in the arc_mru state, and are eligible for eviction
672 * (e.g. have no outstanding holds on the buffer).
673 * Not updated directly; only synced in arc_kstat_update.
675 kstat_named_t arcstat_mru_evictable_metadata;
677 * Total number of bytes that *would have been* consumed by ARC
678 * buffers in the arc_mru_ghost state. The key thing to note
679 * here, is the fact that this size doesn't actually indicate
680 * RAM consumption. The ghost lists only consist of headers and
681 * don't actually have ARC buffers linked off of these headers.
682 * Thus, *if* the headers had associated ARC buffers, these
683 * buffers *would have* consumed this number of bytes.
684 * Not updated directly; only synced in arc_kstat_update.
686 kstat_named_t arcstat_mru_ghost_size;
688 * Number of bytes that *would have been* consumed by ARC
689 * buffers that are eligible for eviction, of type
690 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
691 * Not updated directly; only synced in arc_kstat_update.
693 kstat_named_t arcstat_mru_ghost_evictable_data;
695 * Number of bytes that *would have been* consumed by ARC
696 * buffers that are eligible for eviction, of type
697 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
698 * Not updated directly; only synced in arc_kstat_update.
700 kstat_named_t arcstat_mru_ghost_evictable_metadata;
702 * Total number of bytes consumed by ARC buffers residing in the
703 * arc_mfu state. This includes *all* buffers in the arc_mfu
704 * state; e.g. data, metadata, evictable, and unevictable buffers
705 * are all included in this value.
706 * Not updated directly; only synced in arc_kstat_update.
708 kstat_named_t arcstat_mfu_size;
710 * Number of bytes consumed by ARC buffers that are eligible for
711 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
713 * Not updated directly; only synced in arc_kstat_update.
715 kstat_named_t arcstat_mfu_evictable_data;
717 * Number of bytes consumed by ARC buffers that are eligible for
718 * eviction, of type ARC_BUFC_METADATA, and reside in the
720 * Not updated directly; only synced in arc_kstat_update.
722 kstat_named_t arcstat_mfu_evictable_metadata;
724 * Total number of bytes that *would have been* consumed by ARC
725 * buffers in the arc_mfu_ghost state. See the comment above
726 * arcstat_mru_ghost_size for more details.
727 * Not updated directly; only synced in arc_kstat_update.
729 kstat_named_t arcstat_mfu_ghost_size;
731 * Number of bytes that *would have been* consumed by ARC
732 * buffers that are eligible for eviction, of type
733 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
734 * Not updated directly; only synced in arc_kstat_update.
736 kstat_named_t arcstat_mfu_ghost_evictable_data;
738 * Number of bytes that *would have been* consumed by ARC
739 * buffers that are eligible for eviction, of type
740 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
741 * Not updated directly; only synced in arc_kstat_update.
743 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
744 kstat_named_t arcstat_l2_hits;
745 kstat_named_t arcstat_l2_misses;
746 kstat_named_t arcstat_l2_feeds;
747 kstat_named_t arcstat_l2_rw_clash;
748 kstat_named_t arcstat_l2_read_bytes;
749 kstat_named_t arcstat_l2_write_bytes;
750 kstat_named_t arcstat_l2_writes_sent;
751 kstat_named_t arcstat_l2_writes_done;
752 kstat_named_t arcstat_l2_writes_error;
753 kstat_named_t arcstat_l2_writes_lock_retry;
754 kstat_named_t arcstat_l2_evict_lock_retry;
755 kstat_named_t arcstat_l2_evict_reading;
756 kstat_named_t arcstat_l2_evict_l1cached;
757 kstat_named_t arcstat_l2_free_on_write;
758 kstat_named_t arcstat_l2_abort_lowmem;
759 kstat_named_t arcstat_l2_cksum_bad;
760 kstat_named_t arcstat_l2_io_error;
761 kstat_named_t arcstat_l2_lsize;
762 kstat_named_t arcstat_l2_psize;
763 /* Not updated directly; only synced in arc_kstat_update. */
764 kstat_named_t arcstat_l2_hdr_size;
765 kstat_named_t arcstat_l2_write_trylock_fail;
766 kstat_named_t arcstat_l2_write_passed_headroom;
767 kstat_named_t arcstat_l2_write_spa_mismatch;
768 kstat_named_t arcstat_l2_write_in_l2;
769 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
770 kstat_named_t arcstat_l2_write_not_cacheable;
771 kstat_named_t arcstat_l2_write_full;
772 kstat_named_t arcstat_l2_write_buffer_iter;
773 kstat_named_t arcstat_l2_write_pios;
774 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
775 kstat_named_t arcstat_l2_write_buffer_list_iter;
776 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
777 kstat_named_t arcstat_memory_throttle_count;
778 /* Not updated directly; only synced in arc_kstat_update. */
779 kstat_named_t arcstat_meta_used;
780 kstat_named_t arcstat_meta_limit;
781 kstat_named_t arcstat_meta_max;
782 kstat_named_t arcstat_meta_min;
783 kstat_named_t arcstat_async_upgrade_sync;
784 kstat_named_t arcstat_demand_hit_predictive_prefetch;
785 kstat_named_t arcstat_demand_hit_prescient_prefetch;
788 static arc_stats_t arc_stats = {
789 { "hits", KSTAT_DATA_UINT64 },
790 { "misses", KSTAT_DATA_UINT64 },
791 { "demand_data_hits", KSTAT_DATA_UINT64 },
792 { "demand_data_misses", KSTAT_DATA_UINT64 },
793 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
794 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
795 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
796 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
797 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
798 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
799 { "mru_hits", KSTAT_DATA_UINT64 },
800 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
801 { "mfu_hits", KSTAT_DATA_UINT64 },
802 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
803 { "allocated", KSTAT_DATA_UINT64 },
804 { "deleted", KSTAT_DATA_UINT64 },
805 { "mutex_miss", KSTAT_DATA_UINT64 },
806 { "access_skip", KSTAT_DATA_UINT64 },
807 { "evict_skip", KSTAT_DATA_UINT64 },
808 { "evict_not_enough", KSTAT_DATA_UINT64 },
809 { "evict_l2_cached", KSTAT_DATA_UINT64 },
810 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
811 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
812 { "evict_l2_skip", KSTAT_DATA_UINT64 },
813 { "hash_elements", KSTAT_DATA_UINT64 },
814 { "hash_elements_max", KSTAT_DATA_UINT64 },
815 { "hash_collisions", KSTAT_DATA_UINT64 },
816 { "hash_chains", KSTAT_DATA_UINT64 },
817 { "hash_chain_max", KSTAT_DATA_UINT64 },
818 { "p", KSTAT_DATA_UINT64 },
819 { "c", KSTAT_DATA_UINT64 },
820 { "c_min", KSTAT_DATA_UINT64 },
821 { "c_max", KSTAT_DATA_UINT64 },
822 { "size", KSTAT_DATA_UINT64 },
823 { "compressed_size", KSTAT_DATA_UINT64 },
824 { "uncompressed_size", KSTAT_DATA_UINT64 },
825 { "overhead_size", KSTAT_DATA_UINT64 },
826 { "hdr_size", KSTAT_DATA_UINT64 },
827 { "data_size", KSTAT_DATA_UINT64 },
828 { "metadata_size", KSTAT_DATA_UINT64 },
829 { "other_size", KSTAT_DATA_UINT64 },
830 { "anon_size", KSTAT_DATA_UINT64 },
831 { "anon_evictable_data", KSTAT_DATA_UINT64 },
832 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
833 { "mru_size", KSTAT_DATA_UINT64 },
834 { "mru_evictable_data", KSTAT_DATA_UINT64 },
835 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
836 { "mru_ghost_size", KSTAT_DATA_UINT64 },
837 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
838 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
839 { "mfu_size", KSTAT_DATA_UINT64 },
840 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
841 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
842 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
843 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
844 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
845 { "l2_hits", KSTAT_DATA_UINT64 },
846 { "l2_misses", KSTAT_DATA_UINT64 },
847 { "l2_feeds", KSTAT_DATA_UINT64 },
848 { "l2_rw_clash", KSTAT_DATA_UINT64 },
849 { "l2_read_bytes", KSTAT_DATA_UINT64 },
850 { "l2_write_bytes", KSTAT_DATA_UINT64 },
851 { "l2_writes_sent", KSTAT_DATA_UINT64 },
852 { "l2_writes_done", KSTAT_DATA_UINT64 },
853 { "l2_writes_error", KSTAT_DATA_UINT64 },
854 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
855 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
856 { "l2_evict_reading", KSTAT_DATA_UINT64 },
857 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
858 { "l2_free_on_write", KSTAT_DATA_UINT64 },
859 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
860 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
861 { "l2_io_error", KSTAT_DATA_UINT64 },
862 { "l2_size", KSTAT_DATA_UINT64 },
863 { "l2_asize", KSTAT_DATA_UINT64 },
864 { "l2_hdr_size", KSTAT_DATA_UINT64 },
865 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
866 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
867 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
868 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
869 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
870 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
871 { "l2_write_full", KSTAT_DATA_UINT64 },
872 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
873 { "l2_write_pios", KSTAT_DATA_UINT64 },
874 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
875 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
876 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
877 { "memory_throttle_count", KSTAT_DATA_UINT64 },
878 { "arc_meta_used", KSTAT_DATA_UINT64 },
879 { "arc_meta_limit", KSTAT_DATA_UINT64 },
880 { "arc_meta_max", KSTAT_DATA_UINT64 },
881 { "arc_meta_min", KSTAT_DATA_UINT64 },
882 { "async_upgrade_sync", KSTAT_DATA_UINT64 },
883 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
884 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
887 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
889 #define ARCSTAT_INCR(stat, val) \
890 atomic_add_64(&arc_stats.stat.value.ui64, (val))
892 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
893 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
895 #define ARCSTAT_MAX(stat, val) { \
897 while ((val) > (m = arc_stats.stat.value.ui64) && \
898 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
902 #define ARCSTAT_MAXSTAT(stat) \
903 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
906 * We define a macro to allow ARC hits/misses to be easily broken down by
907 * two separate conditions, giving a total of four different subtypes for
908 * each of hits and misses (so eight statistics total).
910 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
913 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
915 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
919 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
921 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
926 static arc_state_t *arc_anon;
927 static arc_state_t *arc_mru;
928 static arc_state_t *arc_mru_ghost;
929 static arc_state_t *arc_mfu;
930 static arc_state_t *arc_mfu_ghost;
931 static arc_state_t *arc_l2c_only;
934 * There are several ARC variables that are critical to export as kstats --
935 * but we don't want to have to grovel around in the kstat whenever we wish to
936 * manipulate them. For these variables, we therefore define them to be in
937 * terms of the statistic variable. This assures that we are not introducing
938 * the possibility of inconsistency by having shadow copies of the variables,
939 * while still allowing the code to be readable.
941 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
942 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
943 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
944 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
945 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
946 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
947 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
949 /* compressed size of entire arc */
950 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
951 /* uncompressed size of entire arc */
952 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
953 /* number of bytes in the arc from arc_buf_t's */
954 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
957 * There are also some ARC variables that we want to export, but that are
958 * updated so often that having the canonical representation be the statistic
959 * variable causes a performance bottleneck. We want to use aggsum_t's for these
960 * instead, but still be able to export the kstat in the same way as before.
961 * The solution is to always use the aggsum version, except in the kstat update
965 aggsum_t arc_meta_used;
966 aggsum_t astat_data_size;
967 aggsum_t astat_metadata_size;
968 aggsum_t astat_hdr_size;
969 aggsum_t astat_other_size;
970 aggsum_t astat_l2_hdr_size;
972 static int arc_no_grow; /* Don't try to grow cache size */
973 static uint64_t arc_tempreserve;
974 static uint64_t arc_loaned_bytes;
976 typedef struct arc_callback arc_callback_t;
978 struct arc_callback {
980 arc_read_done_func_t *acb_done;
982 boolean_t acb_compressed;
983 zio_t *acb_zio_dummy;
985 arc_callback_t *acb_next;
988 typedef struct arc_write_callback arc_write_callback_t;
990 struct arc_write_callback {
992 arc_write_done_func_t *awcb_ready;
993 arc_write_done_func_t *awcb_children_ready;
994 arc_write_done_func_t *awcb_physdone;
995 arc_write_done_func_t *awcb_done;
1000 * ARC buffers are separated into multiple structs as a memory saving measure:
1001 * - Common fields struct, always defined, and embedded within it:
1002 * - L2-only fields, always allocated but undefined when not in L2ARC
1003 * - L1-only fields, only allocated when in L1ARC
1005 * Buffer in L1 Buffer only in L2
1006 * +------------------------+ +------------------------+
1007 * | arc_buf_hdr_t | | arc_buf_hdr_t |
1011 * +------------------------+ +------------------------+
1012 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
1013 * | (undefined if L1-only) | | |
1014 * +------------------------+ +------------------------+
1015 * | l1arc_buf_hdr_t |
1020 * +------------------------+
1022 * Because it's possible for the L2ARC to become extremely large, we can wind
1023 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
1024 * is minimized by only allocating the fields necessary for an L1-cached buffer
1025 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
1026 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
1027 * words in pointers. arc_hdr_realloc() is used to switch a header between
1028 * these two allocation states.
1030 typedef struct l1arc_buf_hdr {
1031 kmutex_t b_freeze_lock;
1032 zio_cksum_t *b_freeze_cksum;
1035 * Used for debugging with kmem_flags - by allocating and freeing
1036 * b_thawed when the buffer is thawed, we get a record of the stack
1037 * trace that thawed it.
1044 /* for waiting on writes to complete */
1048 /* protected by arc state mutex */
1049 arc_state_t *b_state;
1050 multilist_node_t b_arc_node;
1052 /* updated atomically */
1053 clock_t b_arc_access;
1055 /* self protecting */
1056 refcount_t b_refcnt;
1058 arc_callback_t *b_acb;
1062 typedef struct l2arc_dev l2arc_dev_t;
1064 typedef struct l2arc_buf_hdr {
1065 /* protected by arc_buf_hdr mutex */
1066 l2arc_dev_t *b_dev; /* L2ARC device */
1067 uint64_t b_daddr; /* disk address, offset byte */
1069 list_node_t b_l2node;
1072 struct arc_buf_hdr {
1073 /* protected by hash lock */
1077 arc_buf_contents_t b_type;
1078 arc_buf_hdr_t *b_hash_next;
1079 arc_flags_t b_flags;
1082 * This field stores the size of the data buffer after
1083 * compression, and is set in the arc's zio completion handlers.
1084 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
1086 * While the block pointers can store up to 32MB in their psize
1087 * field, we can only store up to 32MB minus 512B. This is due
1088 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
1089 * a field of zeros represents 512B in the bp). We can't use a
1090 * bias of 1 since we need to reserve a psize of zero, here, to
1091 * represent holes and embedded blocks.
1093 * This isn't a problem in practice, since the maximum size of a
1094 * buffer is limited to 16MB, so we never need to store 32MB in
1095 * this field. Even in the upstream illumos code base, the
1096 * maximum size of a buffer is limited to 16MB.
1101 * This field stores the size of the data buffer before
1102 * compression, and cannot change once set. It is in units
1103 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
1105 uint16_t b_lsize; /* immutable */
1106 uint64_t b_spa; /* immutable */
1108 /* L2ARC fields. Undefined when not in L2ARC. */
1109 l2arc_buf_hdr_t b_l2hdr;
1110 /* L1ARC fields. Undefined when in l2arc_only state */
1111 l1arc_buf_hdr_t b_l1hdr;
1114 #if defined(__FreeBSD__) && defined(_KERNEL)
1116 sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS)
1121 val = arc_meta_limit;
1122 err = sysctl_handle_64(oidp, &val, 0, req);
1123 if (err != 0 || req->newptr == NULL)
1126 if (val <= 0 || val > arc_c_max)
1129 arc_meta_limit = val;
1134 sysctl_vfs_zfs_arc_no_grow_shift(SYSCTL_HANDLER_ARGS)
1139 val = arc_no_grow_shift;
1140 err = sysctl_handle_32(oidp, &val, 0, req);
1141 if (err != 0 || req->newptr == NULL)
1144 if (val >= arc_shrink_shift)
1147 arc_no_grow_shift = val;
1152 sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS)
1158 err = sysctl_handle_64(oidp, &val, 0, req);
1159 if (err != 0 || req->newptr == NULL)
1162 if (zfs_arc_max == 0) {
1163 /* Loader tunable so blindly set */
1168 if (val < arc_abs_min || val > kmem_size())
1170 if (val < arc_c_min)
1172 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit)
1178 arc_p = (arc_c >> 1);
1180 if (zfs_arc_meta_limit == 0) {
1181 /* limit meta-data to 1/4 of the arc capacity */
1182 arc_meta_limit = arc_c_max / 4;
1185 /* if kmem_flags are set, lets try to use less memory */
1186 if (kmem_debugging())
1189 zfs_arc_max = arc_c;
1195 sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS)
1201 err = sysctl_handle_64(oidp, &val, 0, req);
1202 if (err != 0 || req->newptr == NULL)
1205 if (zfs_arc_min == 0) {
1206 /* Loader tunable so blindly set */
1211 if (val < arc_abs_min || val > arc_c_max)
1216 if (zfs_arc_meta_min == 0)
1217 arc_meta_min = arc_c_min / 2;
1219 if (arc_c < arc_c_min)
1222 zfs_arc_min = arc_c_min;
1228 #define GHOST_STATE(state) \
1229 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
1230 (state) == arc_l2c_only)
1232 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
1233 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
1234 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
1235 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
1236 #define HDR_PRESCIENT_PREFETCH(hdr) \
1237 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH)
1238 #define HDR_COMPRESSION_ENABLED(hdr) \
1239 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
1241 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
1242 #define HDR_L2_READING(hdr) \
1243 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
1244 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
1245 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
1246 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
1247 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
1248 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
1250 #define HDR_ISTYPE_METADATA(hdr) \
1251 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
1252 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
1254 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
1255 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
1257 /* For storing compression mode in b_flags */
1258 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
1260 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
1261 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
1262 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
1263 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
1265 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
1266 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
1267 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
1273 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
1274 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
1277 * Hash table routines
1280 #define HT_LOCK_PAD CACHE_LINE_SIZE
1285 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
1289 #define BUF_LOCKS 256
1290 typedef struct buf_hash_table {
1292 arc_buf_hdr_t **ht_table;
1293 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
1296 static buf_hash_table_t buf_hash_table;
1298 #define BUF_HASH_INDEX(spa, dva, birth) \
1299 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1300 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
1301 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
1302 #define HDR_LOCK(hdr) \
1303 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1305 uint64_t zfs_crc64_table[256];
1311 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1312 #define L2ARC_HEADROOM 2 /* num of writes */
1314 * If we discover during ARC scan any buffers to be compressed, we boost
1315 * our headroom for the next scanning cycle by this percentage multiple.
1317 #define L2ARC_HEADROOM_BOOST 200
1318 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1319 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1321 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1322 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1324 /* L2ARC Performance Tunables */
1325 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
1326 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
1327 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
1328 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1329 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1330 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
1331 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1332 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
1333 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
1335 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
1336 &l2arc_write_max, 0, "max write size");
1337 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
1338 &l2arc_write_boost, 0, "extra write during warmup");
1339 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
1340 &l2arc_headroom, 0, "number of dev writes");
1341 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
1342 &l2arc_feed_secs, 0, "interval seconds");
1343 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
1344 &l2arc_feed_min_ms, 0, "min interval milliseconds");
1346 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
1347 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
1348 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
1349 &l2arc_feed_again, 0, "turbo warmup");
1350 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
1351 &l2arc_norw, 0, "no reads during writes");
1353 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
1354 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state");
1355 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD,
1356 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1357 "size of anonymous state");
1358 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD,
1359 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1360 "size of anonymous state");
1362 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
1363 &ARC_mru.arcs_size.rc_count, 0, "size of mru state");
1364 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD,
1365 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1366 "size of metadata in mru state");
1367 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD,
1368 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1369 "size of data in mru state");
1371 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
1372 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state");
1373 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD,
1374 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1375 "size of metadata in mru ghost state");
1376 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD,
1377 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1378 "size of data in mru ghost state");
1380 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
1381 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state");
1382 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD,
1383 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1384 "size of metadata in mfu state");
1385 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD,
1386 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1387 "size of data in mfu state");
1389 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
1390 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state");
1391 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD,
1392 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1393 "size of metadata in mfu ghost state");
1394 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD,
1395 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1396 "size of data in mfu ghost state");
1398 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
1399 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state");
1401 SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prefetch_ms, CTLFLAG_RW,
1402 &zfs_arc_min_prefetch_ms, 0, "Min life of prefetch block in ms");
1403 SYSCTL_UINT(_vfs_zfs, OID_AUTO, arc_min_prescient_prefetch_ms, CTLFLAG_RW,
1404 &zfs_arc_min_prescient_prefetch_ms, 0, "Min life of prescient prefetched block in ms");
1410 vdev_t *l2ad_vdev; /* vdev */
1411 spa_t *l2ad_spa; /* spa */
1412 uint64_t l2ad_hand; /* next write location */
1413 uint64_t l2ad_start; /* first addr on device */
1414 uint64_t l2ad_end; /* last addr on device */
1415 boolean_t l2ad_first; /* first sweep through */
1416 boolean_t l2ad_writing; /* currently writing */
1417 kmutex_t l2ad_mtx; /* lock for buffer list */
1418 list_t l2ad_buflist; /* buffer list */
1419 list_node_t l2ad_node; /* device list node */
1420 refcount_t l2ad_alloc; /* allocated bytes */
1423 static list_t L2ARC_dev_list; /* device list */
1424 static list_t *l2arc_dev_list; /* device list pointer */
1425 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1426 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1427 static list_t L2ARC_free_on_write; /* free after write buf list */
1428 static list_t *l2arc_free_on_write; /* free after write list ptr */
1429 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1430 static uint64_t l2arc_ndev; /* number of devices */
1432 typedef struct l2arc_read_callback {
1433 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1434 blkptr_t l2rcb_bp; /* original blkptr */
1435 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1436 int l2rcb_flags; /* original flags */
1437 abd_t *l2rcb_abd; /* temporary buffer */
1438 } l2arc_read_callback_t;
1440 typedef struct l2arc_write_callback {
1441 l2arc_dev_t *l2wcb_dev; /* device info */
1442 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
1443 } l2arc_write_callback_t;
1445 typedef struct l2arc_data_free {
1446 /* protected by l2arc_free_on_write_mtx */
1449 arc_buf_contents_t l2df_type;
1450 list_node_t l2df_list_node;
1451 } l2arc_data_free_t;
1453 static kmutex_t l2arc_feed_thr_lock;
1454 static kcondvar_t l2arc_feed_thr_cv;
1455 static uint8_t l2arc_thread_exit;
1457 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1458 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1459 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1460 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1461 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1462 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1463 static void arc_hdr_free_pabd(arc_buf_hdr_t *);
1464 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *);
1465 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1466 static boolean_t arc_is_overflowing();
1467 static void arc_buf_watch(arc_buf_t *);
1469 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1470 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1471 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1472 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1474 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1475 static void l2arc_read_done(zio_t *);
1478 l2arc_trim(const arc_buf_hdr_t *hdr)
1480 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
1482 ASSERT(HDR_HAS_L2HDR(hdr));
1483 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
1485 if (HDR_GET_PSIZE(hdr) != 0) {
1486 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr,
1487 HDR_GET_PSIZE(hdr), 0);
1492 * We use Cityhash for this. It's fast, and has good hash properties without
1493 * requiring any large static buffers.
1496 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1498 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth));
1501 #define HDR_EMPTY(hdr) \
1502 ((hdr)->b_dva.dva_word[0] == 0 && \
1503 (hdr)->b_dva.dva_word[1] == 0)
1505 #define HDR_EQUAL(spa, dva, birth, hdr) \
1506 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1507 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1508 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1511 buf_discard_identity(arc_buf_hdr_t *hdr)
1513 hdr->b_dva.dva_word[0] = 0;
1514 hdr->b_dva.dva_word[1] = 0;
1518 static arc_buf_hdr_t *
1519 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1521 const dva_t *dva = BP_IDENTITY(bp);
1522 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1523 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1524 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1527 mutex_enter(hash_lock);
1528 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1529 hdr = hdr->b_hash_next) {
1530 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1535 mutex_exit(hash_lock);
1541 * Insert an entry into the hash table. If there is already an element
1542 * equal to elem in the hash table, then the already existing element
1543 * will be returned and the new element will not be inserted.
1544 * Otherwise returns NULL.
1545 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1547 static arc_buf_hdr_t *
1548 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1550 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1551 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1552 arc_buf_hdr_t *fhdr;
1555 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1556 ASSERT(hdr->b_birth != 0);
1557 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1559 if (lockp != NULL) {
1561 mutex_enter(hash_lock);
1563 ASSERT(MUTEX_HELD(hash_lock));
1566 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1567 fhdr = fhdr->b_hash_next, i++) {
1568 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1572 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1573 buf_hash_table.ht_table[idx] = hdr;
1574 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1576 /* collect some hash table performance data */
1578 ARCSTAT_BUMP(arcstat_hash_collisions);
1580 ARCSTAT_BUMP(arcstat_hash_chains);
1582 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1585 ARCSTAT_BUMP(arcstat_hash_elements);
1586 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1592 buf_hash_remove(arc_buf_hdr_t *hdr)
1594 arc_buf_hdr_t *fhdr, **hdrp;
1595 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1597 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1598 ASSERT(HDR_IN_HASH_TABLE(hdr));
1600 hdrp = &buf_hash_table.ht_table[idx];
1601 while ((fhdr = *hdrp) != hdr) {
1602 ASSERT3P(fhdr, !=, NULL);
1603 hdrp = &fhdr->b_hash_next;
1605 *hdrp = hdr->b_hash_next;
1606 hdr->b_hash_next = NULL;
1607 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1609 /* collect some hash table performance data */
1610 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1612 if (buf_hash_table.ht_table[idx] &&
1613 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1614 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1618 * Global data structures and functions for the buf kmem cache.
1620 static kmem_cache_t *hdr_full_cache;
1621 static kmem_cache_t *hdr_l2only_cache;
1622 static kmem_cache_t *buf_cache;
1629 kmem_free(buf_hash_table.ht_table,
1630 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1631 for (i = 0; i < BUF_LOCKS; i++)
1632 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1633 kmem_cache_destroy(hdr_full_cache);
1634 kmem_cache_destroy(hdr_l2only_cache);
1635 kmem_cache_destroy(buf_cache);
1639 * Constructor callback - called when the cache is empty
1640 * and a new buf is requested.
1644 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1646 arc_buf_hdr_t *hdr = vbuf;
1648 bzero(hdr, HDR_FULL_SIZE);
1649 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1650 refcount_create(&hdr->b_l1hdr.b_refcnt);
1651 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1652 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1653 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1660 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1662 arc_buf_hdr_t *hdr = vbuf;
1664 bzero(hdr, HDR_L2ONLY_SIZE);
1665 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1672 buf_cons(void *vbuf, void *unused, int kmflag)
1674 arc_buf_t *buf = vbuf;
1676 bzero(buf, sizeof (arc_buf_t));
1677 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1678 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1684 * Destructor callback - called when a cached buf is
1685 * no longer required.
1689 hdr_full_dest(void *vbuf, void *unused)
1691 arc_buf_hdr_t *hdr = vbuf;
1693 ASSERT(HDR_EMPTY(hdr));
1694 cv_destroy(&hdr->b_l1hdr.b_cv);
1695 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1696 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1697 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1698 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1703 hdr_l2only_dest(void *vbuf, void *unused)
1705 arc_buf_hdr_t *hdr = vbuf;
1707 ASSERT(HDR_EMPTY(hdr));
1708 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1713 buf_dest(void *vbuf, void *unused)
1715 arc_buf_t *buf = vbuf;
1717 mutex_destroy(&buf->b_evict_lock);
1718 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1722 * Reclaim callback -- invoked when memory is low.
1726 hdr_recl(void *unused)
1728 dprintf("hdr_recl called\n");
1730 * umem calls the reclaim func when we destroy the buf cache,
1731 * which is after we do arc_fini().
1734 cv_signal(&arc_reclaim_thread_cv);
1741 uint64_t hsize = 1ULL << 12;
1745 * The hash table is big enough to fill all of physical memory
1746 * with an average block size of zfs_arc_average_blocksize (default 8K).
1747 * By default, the table will take up
1748 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1750 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1753 buf_hash_table.ht_mask = hsize - 1;
1754 buf_hash_table.ht_table =
1755 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1756 if (buf_hash_table.ht_table == NULL) {
1757 ASSERT(hsize > (1ULL << 8));
1762 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1763 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1764 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1765 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1767 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1768 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1770 for (i = 0; i < 256; i++)
1771 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1772 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1774 for (i = 0; i < BUF_LOCKS; i++) {
1775 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1776 NULL, MUTEX_DEFAULT, NULL);
1781 * This is the size that the buf occupies in memory. If the buf is compressed,
1782 * it will correspond to the compressed size. You should use this method of
1783 * getting the buf size unless you explicitly need the logical size.
1786 arc_buf_size(arc_buf_t *buf)
1788 return (ARC_BUF_COMPRESSED(buf) ?
1789 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1793 arc_buf_lsize(arc_buf_t *buf)
1795 return (HDR_GET_LSIZE(buf->b_hdr));
1799 arc_get_compression(arc_buf_t *buf)
1801 return (ARC_BUF_COMPRESSED(buf) ?
1802 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1805 #define ARC_MINTIME (hz>>4) /* 62 ms */
1807 static inline boolean_t
1808 arc_buf_is_shared(arc_buf_t *buf)
1810 boolean_t shared = (buf->b_data != NULL &&
1811 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1812 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1813 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1814 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1815 IMPLY(shared, ARC_BUF_SHARED(buf));
1816 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1819 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1820 * already being shared" requirement prevents us from doing that.
1827 * Free the checksum associated with this header. If there is no checksum, this
1831 arc_cksum_free(arc_buf_hdr_t *hdr)
1833 ASSERT(HDR_HAS_L1HDR(hdr));
1834 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1835 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1836 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1837 hdr->b_l1hdr.b_freeze_cksum = NULL;
1839 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1843 * Return true iff at least one of the bufs on hdr is not compressed.
1846 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1848 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1849 if (!ARC_BUF_COMPRESSED(b)) {
1857 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1858 * matches the checksum that is stored in the hdr. If there is no checksum,
1859 * or if the buf is compressed, this is a no-op.
1862 arc_cksum_verify(arc_buf_t *buf)
1864 arc_buf_hdr_t *hdr = buf->b_hdr;
1867 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1870 if (ARC_BUF_COMPRESSED(buf)) {
1871 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1872 arc_hdr_has_uncompressed_buf(hdr));
1876 ASSERT(HDR_HAS_L1HDR(hdr));
1878 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1879 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1880 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1884 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1885 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1886 panic("buffer modified while frozen!");
1887 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1891 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1893 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1894 boolean_t valid_cksum;
1896 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1897 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1900 * We rely on the blkptr's checksum to determine if the block
1901 * is valid or not. When compressed arc is enabled, the l2arc
1902 * writes the block to the l2arc just as it appears in the pool.
1903 * This allows us to use the blkptr's checksum to validate the
1904 * data that we just read off of the l2arc without having to store
1905 * a separate checksum in the arc_buf_hdr_t. However, if compressed
1906 * arc is disabled, then the data written to the l2arc is always
1907 * uncompressed and won't match the block as it exists in the main
1908 * pool. When this is the case, we must first compress it if it is
1909 * compressed on the main pool before we can validate the checksum.
1911 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
1912 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1913 uint64_t lsize = HDR_GET_LSIZE(hdr);
1916 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE);
1917 csize = zio_compress_data(compress, zio->io_abd,
1918 abd_to_buf(cdata), lsize);
1920 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
1921 if (csize < HDR_GET_PSIZE(hdr)) {
1923 * Compressed blocks are always a multiple of the
1924 * smallest ashift in the pool. Ideally, we would
1925 * like to round up the csize to the next
1926 * spa_min_ashift but that value may have changed
1927 * since the block was last written. Instead,
1928 * we rely on the fact that the hdr's psize
1929 * was set to the psize of the block when it was
1930 * last written. We set the csize to that value
1931 * and zero out any part that should not contain
1934 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize);
1935 csize = HDR_GET_PSIZE(hdr);
1937 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL);
1941 * Block pointers always store the checksum for the logical data.
1942 * If the block pointer has the gang bit set, then the checksum
1943 * it represents is for the reconstituted data and not for an
1944 * individual gang member. The zio pipeline, however, must be able to
1945 * determine the checksum of each of the gang constituents so it
1946 * treats the checksum comparison differently than what we need
1947 * for l2arc blocks. This prevents us from using the
1948 * zio_checksum_error() interface directly. Instead we must call the
1949 * zio_checksum_error_impl() so that we can ensure the checksum is
1950 * generated using the correct checksum algorithm and accounts for the
1951 * logical I/O size and not just a gang fragment.
1953 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1954 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1955 zio->io_offset, NULL) == 0);
1956 zio_pop_transforms(zio);
1957 return (valid_cksum);
1961 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1962 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1963 * isn't modified later on. If buf is compressed or there is already a checksum
1964 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1967 arc_cksum_compute(arc_buf_t *buf)
1969 arc_buf_hdr_t *hdr = buf->b_hdr;
1971 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1974 ASSERT(HDR_HAS_L1HDR(hdr));
1976 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1977 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1978 ASSERT(arc_hdr_has_uncompressed_buf(hdr));
1979 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1981 } else if (ARC_BUF_COMPRESSED(buf)) {
1982 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1986 ASSERT(!ARC_BUF_COMPRESSED(buf));
1987 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1989 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1990 hdr->b_l1hdr.b_freeze_cksum);
1991 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1999 typedef struct procctl {
2007 arc_buf_unwatch(arc_buf_t *buf)
2014 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
2015 ctl.prwatch.pr_size = 0;
2016 ctl.prwatch.pr_wflags = 0;
2017 result = write(arc_procfd, &ctl, sizeof (ctl));
2018 ASSERT3U(result, ==, sizeof (ctl));
2025 arc_buf_watch(arc_buf_t *buf)
2032 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
2033 ctl.prwatch.pr_size = arc_buf_size(buf);
2034 ctl.prwatch.pr_wflags = WA_WRITE;
2035 result = write(arc_procfd, &ctl, sizeof (ctl));
2036 ASSERT3U(result, ==, sizeof (ctl));
2040 #endif /* illumos */
2042 static arc_buf_contents_t
2043 arc_buf_type(arc_buf_hdr_t *hdr)
2045 arc_buf_contents_t type;
2046 if (HDR_ISTYPE_METADATA(hdr)) {
2047 type = ARC_BUFC_METADATA;
2049 type = ARC_BUFC_DATA;
2051 VERIFY3U(hdr->b_type, ==, type);
2056 arc_is_metadata(arc_buf_t *buf)
2058 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
2062 arc_bufc_to_flags(arc_buf_contents_t type)
2066 /* metadata field is 0 if buffer contains normal data */
2068 case ARC_BUFC_METADATA:
2069 return (ARC_FLAG_BUFC_METADATA);
2073 panic("undefined ARC buffer type!");
2074 return ((uint32_t)-1);
2078 arc_buf_thaw(arc_buf_t *buf)
2080 arc_buf_hdr_t *hdr = buf->b_hdr;
2082 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
2083 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2085 arc_cksum_verify(buf);
2088 * Compressed buffers do not manipulate the b_freeze_cksum or
2089 * allocate b_thawed.
2091 if (ARC_BUF_COMPRESSED(buf)) {
2092 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2093 arc_hdr_has_uncompressed_buf(hdr));
2097 ASSERT(HDR_HAS_L1HDR(hdr));
2098 arc_cksum_free(hdr);
2100 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
2102 if (zfs_flags & ZFS_DEBUG_MODIFY) {
2103 if (hdr->b_l1hdr.b_thawed != NULL)
2104 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2105 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
2109 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2112 arc_buf_unwatch(buf);
2117 arc_buf_freeze(arc_buf_t *buf)
2119 arc_buf_hdr_t *hdr = buf->b_hdr;
2120 kmutex_t *hash_lock;
2122 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
2125 if (ARC_BUF_COMPRESSED(buf)) {
2126 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2127 arc_hdr_has_uncompressed_buf(hdr));
2131 hash_lock = HDR_LOCK(hdr);
2132 mutex_enter(hash_lock);
2134 ASSERT(HDR_HAS_L1HDR(hdr));
2135 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL ||
2136 hdr->b_l1hdr.b_state == arc_anon);
2137 arc_cksum_compute(buf);
2138 mutex_exit(hash_lock);
2142 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
2143 * the following functions should be used to ensure that the flags are
2144 * updated in a thread-safe way. When manipulating the flags either
2145 * the hash_lock must be held or the hdr must be undiscoverable. This
2146 * ensures that we're not racing with any other threads when updating
2150 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2152 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2153 hdr->b_flags |= flags;
2157 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2159 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2160 hdr->b_flags &= ~flags;
2164 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
2165 * done in a special way since we have to clear and set bits
2166 * at the same time. Consumers that wish to set the compression bits
2167 * must use this function to ensure that the flags are updated in
2168 * thread-safe manner.
2171 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
2173 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2176 * Holes and embedded blocks will always have a psize = 0 so
2177 * we ignore the compression of the blkptr and set the
2178 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
2179 * Holes and embedded blocks remain anonymous so we don't
2180 * want to uncompress them. Mark them as uncompressed.
2182 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
2183 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2184 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
2185 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
2186 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
2188 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2189 HDR_SET_COMPRESS(hdr, cmp);
2190 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
2191 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
2196 * Looks for another buf on the same hdr which has the data decompressed, copies
2197 * from it, and returns true. If no such buf exists, returns false.
2200 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
2202 arc_buf_hdr_t *hdr = buf->b_hdr;
2203 boolean_t copied = B_FALSE;
2205 ASSERT(HDR_HAS_L1HDR(hdr));
2206 ASSERT3P(buf->b_data, !=, NULL);
2207 ASSERT(!ARC_BUF_COMPRESSED(buf));
2209 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
2210 from = from->b_next) {
2211 /* can't use our own data buffer */
2216 if (!ARC_BUF_COMPRESSED(from)) {
2217 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
2224 * There were no decompressed bufs, so there should not be a
2225 * checksum on the hdr either.
2227 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
2233 * Given a buf that has a data buffer attached to it, this function will
2234 * efficiently fill the buf with data of the specified compression setting from
2235 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
2236 * are already sharing a data buf, no copy is performed.
2238 * If the buf is marked as compressed but uncompressed data was requested, this
2239 * will allocate a new data buffer for the buf, remove that flag, and fill the
2240 * buf with uncompressed data. You can't request a compressed buf on a hdr with
2241 * uncompressed data, and (since we haven't added support for it yet) if you
2242 * want compressed data your buf must already be marked as compressed and have
2243 * the correct-sized data buffer.
2246 arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
2248 arc_buf_hdr_t *hdr = buf->b_hdr;
2249 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
2250 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
2252 ASSERT3P(buf->b_data, !=, NULL);
2253 IMPLY(compressed, hdr_compressed);
2254 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
2256 if (hdr_compressed == compressed) {
2257 if (!arc_buf_is_shared(buf)) {
2258 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
2262 ASSERT(hdr_compressed);
2263 ASSERT(!compressed);
2264 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
2267 * If the buf is sharing its data with the hdr, unlink it and
2268 * allocate a new data buffer for the buf.
2270 if (arc_buf_is_shared(buf)) {
2271 ASSERT(ARC_BUF_COMPRESSED(buf));
2273 /* We need to give the buf it's own b_data */
2274 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2276 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2277 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2279 /* Previously overhead was 0; just add new overhead */
2280 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2281 } else if (ARC_BUF_COMPRESSED(buf)) {
2282 /* We need to reallocate the buf's b_data */
2283 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2286 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2288 /* We increased the size of b_data; update overhead */
2289 ARCSTAT_INCR(arcstat_overhead_size,
2290 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2294 * Regardless of the buf's previous compression settings, it
2295 * should not be compressed at the end of this function.
2297 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2300 * Try copying the data from another buf which already has a
2301 * decompressed version. If that's not possible, it's time to
2302 * bite the bullet and decompress the data from the hdr.
2304 if (arc_buf_try_copy_decompressed_data(buf)) {
2305 /* Skip byteswapping and checksumming (already done) */
2306 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
2309 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2310 hdr->b_l1hdr.b_pabd, buf->b_data,
2311 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2314 * Absent hardware errors or software bugs, this should
2315 * be impossible, but log it anyway so we can debug it.
2319 "hdr %p, compress %d, psize %d, lsize %d",
2320 hdr, HDR_GET_COMPRESS(hdr),
2321 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2322 return (SET_ERROR(EIO));
2327 /* Byteswap the buf's data if necessary */
2328 if (bswap != DMU_BSWAP_NUMFUNCS) {
2329 ASSERT(!HDR_SHARED_DATA(hdr));
2330 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2331 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2334 /* Compute the hdr's checksum if necessary */
2335 arc_cksum_compute(buf);
2341 arc_decompress(arc_buf_t *buf)
2343 return (arc_buf_fill(buf, B_FALSE));
2347 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
2350 arc_hdr_size(arc_buf_hdr_t *hdr)
2354 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
2355 HDR_GET_PSIZE(hdr) > 0) {
2356 size = HDR_GET_PSIZE(hdr);
2358 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
2359 size = HDR_GET_LSIZE(hdr);
2365 * Increment the amount of evictable space in the arc_state_t's refcount.
2366 * We account for the space used by the hdr and the arc buf individually
2367 * so that we can add and remove them from the refcount individually.
2370 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2372 arc_buf_contents_t type = arc_buf_type(hdr);
2374 ASSERT(HDR_HAS_L1HDR(hdr));
2376 if (GHOST_STATE(state)) {
2377 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2378 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2379 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2380 (void) refcount_add_many(&state->arcs_esize[type],
2381 HDR_GET_LSIZE(hdr), hdr);
2385 ASSERT(!GHOST_STATE(state));
2386 if (hdr->b_l1hdr.b_pabd != NULL) {
2387 (void) refcount_add_many(&state->arcs_esize[type],
2388 arc_hdr_size(hdr), hdr);
2390 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2391 buf = buf->b_next) {
2392 if (arc_buf_is_shared(buf))
2394 (void) refcount_add_many(&state->arcs_esize[type],
2395 arc_buf_size(buf), buf);
2400 * Decrement the amount of evictable space in the arc_state_t's refcount.
2401 * We account for the space used by the hdr and the arc buf individually
2402 * so that we can add and remove them from the refcount individually.
2405 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2407 arc_buf_contents_t type = arc_buf_type(hdr);
2409 ASSERT(HDR_HAS_L1HDR(hdr));
2411 if (GHOST_STATE(state)) {
2412 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2413 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2414 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2415 (void) refcount_remove_many(&state->arcs_esize[type],
2416 HDR_GET_LSIZE(hdr), hdr);
2420 ASSERT(!GHOST_STATE(state));
2421 if (hdr->b_l1hdr.b_pabd != NULL) {
2422 (void) refcount_remove_many(&state->arcs_esize[type],
2423 arc_hdr_size(hdr), hdr);
2425 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2426 buf = buf->b_next) {
2427 if (arc_buf_is_shared(buf))
2429 (void) refcount_remove_many(&state->arcs_esize[type],
2430 arc_buf_size(buf), buf);
2435 * Add a reference to this hdr indicating that someone is actively
2436 * referencing that memory. When the refcount transitions from 0 to 1,
2437 * we remove it from the respective arc_state_t list to indicate that
2438 * it is not evictable.
2441 add_reference(arc_buf_hdr_t *hdr, void *tag)
2443 ASSERT(HDR_HAS_L1HDR(hdr));
2444 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2445 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2446 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2447 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2450 arc_state_t *state = hdr->b_l1hdr.b_state;
2452 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2453 (state != arc_anon)) {
2454 /* We don't use the L2-only state list. */
2455 if (state != arc_l2c_only) {
2456 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2458 arc_evictable_space_decrement(hdr, state);
2460 /* remove the prefetch flag if we get a reference */
2461 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2466 * Remove a reference from this hdr. When the reference transitions from
2467 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2468 * list making it eligible for eviction.
2471 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2474 arc_state_t *state = hdr->b_l1hdr.b_state;
2476 ASSERT(HDR_HAS_L1HDR(hdr));
2477 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2478 ASSERT(!GHOST_STATE(state));
2481 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2482 * check to prevent usage of the arc_l2c_only list.
2484 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2485 (state != arc_anon)) {
2486 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2487 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2488 arc_evictable_space_increment(hdr, state);
2494 * Move the supplied buffer to the indicated state. The hash lock
2495 * for the buffer must be held by the caller.
2498 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2499 kmutex_t *hash_lock)
2501 arc_state_t *old_state;
2504 boolean_t update_old, update_new;
2505 arc_buf_contents_t buftype = arc_buf_type(hdr);
2508 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2509 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2510 * L1 hdr doesn't always exist when we change state to arc_anon before
2511 * destroying a header, in which case reallocating to add the L1 hdr is
2514 if (HDR_HAS_L1HDR(hdr)) {
2515 old_state = hdr->b_l1hdr.b_state;
2516 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
2517 bufcnt = hdr->b_l1hdr.b_bufcnt;
2518 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL);
2520 old_state = arc_l2c_only;
2523 update_old = B_FALSE;
2525 update_new = update_old;
2527 ASSERT(MUTEX_HELD(hash_lock));
2528 ASSERT3P(new_state, !=, old_state);
2529 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2530 ASSERT(old_state != arc_anon || bufcnt <= 1);
2533 * If this buffer is evictable, transfer it from the
2534 * old state list to the new state list.
2537 if (old_state != arc_anon && old_state != arc_l2c_only) {
2538 ASSERT(HDR_HAS_L1HDR(hdr));
2539 multilist_remove(old_state->arcs_list[buftype], hdr);
2541 if (GHOST_STATE(old_state)) {
2543 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2544 update_old = B_TRUE;
2546 arc_evictable_space_decrement(hdr, old_state);
2548 if (new_state != arc_anon && new_state != arc_l2c_only) {
2551 * An L1 header always exists here, since if we're
2552 * moving to some L1-cached state (i.e. not l2c_only or
2553 * anonymous), we realloc the header to add an L1hdr
2556 ASSERT(HDR_HAS_L1HDR(hdr));
2557 multilist_insert(new_state->arcs_list[buftype], hdr);
2559 if (GHOST_STATE(new_state)) {
2561 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2562 update_new = B_TRUE;
2564 arc_evictable_space_increment(hdr, new_state);
2568 ASSERT(!HDR_EMPTY(hdr));
2569 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2570 buf_hash_remove(hdr);
2572 /* adjust state sizes (ignore arc_l2c_only) */
2574 if (update_new && new_state != arc_l2c_only) {
2575 ASSERT(HDR_HAS_L1HDR(hdr));
2576 if (GHOST_STATE(new_state)) {
2580 * When moving a header to a ghost state, we first
2581 * remove all arc buffers. Thus, we'll have a
2582 * bufcnt of zero, and no arc buffer to use for
2583 * the reference. As a result, we use the arc
2584 * header pointer for the reference.
2586 (void) refcount_add_many(&new_state->arcs_size,
2587 HDR_GET_LSIZE(hdr), hdr);
2588 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2590 uint32_t buffers = 0;
2593 * Each individual buffer holds a unique reference,
2594 * thus we must remove each of these references one
2597 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2598 buf = buf->b_next) {
2599 ASSERT3U(bufcnt, !=, 0);
2603 * When the arc_buf_t is sharing the data
2604 * block with the hdr, the owner of the
2605 * reference belongs to the hdr. Only
2606 * add to the refcount if the arc_buf_t is
2609 if (arc_buf_is_shared(buf))
2612 (void) refcount_add_many(&new_state->arcs_size,
2613 arc_buf_size(buf), buf);
2615 ASSERT3U(bufcnt, ==, buffers);
2617 if (hdr->b_l1hdr.b_pabd != NULL) {
2618 (void) refcount_add_many(&new_state->arcs_size,
2619 arc_hdr_size(hdr), hdr);
2621 ASSERT(GHOST_STATE(old_state));
2626 if (update_old && old_state != arc_l2c_only) {
2627 ASSERT(HDR_HAS_L1HDR(hdr));
2628 if (GHOST_STATE(old_state)) {
2630 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2633 * When moving a header off of a ghost state,
2634 * the header will not contain any arc buffers.
2635 * We use the arc header pointer for the reference
2636 * which is exactly what we did when we put the
2637 * header on the ghost state.
2640 (void) refcount_remove_many(&old_state->arcs_size,
2641 HDR_GET_LSIZE(hdr), hdr);
2643 uint32_t buffers = 0;
2646 * Each individual buffer holds a unique reference,
2647 * thus we must remove each of these references one
2650 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2651 buf = buf->b_next) {
2652 ASSERT3U(bufcnt, !=, 0);
2656 * When the arc_buf_t is sharing the data
2657 * block with the hdr, the owner of the
2658 * reference belongs to the hdr. Only
2659 * add to the refcount if the arc_buf_t is
2662 if (arc_buf_is_shared(buf))
2665 (void) refcount_remove_many(
2666 &old_state->arcs_size, arc_buf_size(buf),
2669 ASSERT3U(bufcnt, ==, buffers);
2670 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2671 (void) refcount_remove_many(
2672 &old_state->arcs_size, arc_hdr_size(hdr), hdr);
2676 if (HDR_HAS_L1HDR(hdr))
2677 hdr->b_l1hdr.b_state = new_state;
2680 * L2 headers should never be on the L2 state list since they don't
2681 * have L1 headers allocated.
2683 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2684 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2688 arc_space_consume(uint64_t space, arc_space_type_t type)
2690 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2693 case ARC_SPACE_DATA:
2694 aggsum_add(&astat_data_size, space);
2696 case ARC_SPACE_META:
2697 aggsum_add(&astat_metadata_size, space);
2699 case ARC_SPACE_OTHER:
2700 aggsum_add(&astat_other_size, space);
2702 case ARC_SPACE_HDRS:
2703 aggsum_add(&astat_hdr_size, space);
2705 case ARC_SPACE_L2HDRS:
2706 aggsum_add(&astat_l2_hdr_size, space);
2710 if (type != ARC_SPACE_DATA)
2711 aggsum_add(&arc_meta_used, space);
2713 aggsum_add(&arc_size, space);
2717 arc_space_return(uint64_t space, arc_space_type_t type)
2719 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2722 case ARC_SPACE_DATA:
2723 aggsum_add(&astat_data_size, -space);
2725 case ARC_SPACE_META:
2726 aggsum_add(&astat_metadata_size, -space);
2728 case ARC_SPACE_OTHER:
2729 aggsum_add(&astat_other_size, -space);
2731 case ARC_SPACE_HDRS:
2732 aggsum_add(&astat_hdr_size, -space);
2734 case ARC_SPACE_L2HDRS:
2735 aggsum_add(&astat_l2_hdr_size, -space);
2739 if (type != ARC_SPACE_DATA) {
2740 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0);
2742 * We use the upper bound here rather than the precise value
2743 * because the arc_meta_max value doesn't need to be
2744 * precise. It's only consumed by humans via arcstats.
2746 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used))
2747 arc_meta_max = aggsum_upper_bound(&arc_meta_used);
2748 aggsum_add(&arc_meta_used, -space);
2751 ASSERT(aggsum_compare(&arc_size, space) >= 0);
2752 aggsum_add(&arc_size, -space);
2756 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2757 * with the hdr's b_pabd.
2760 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2763 * The criteria for sharing a hdr's data are:
2764 * 1. the hdr's compression matches the buf's compression
2765 * 2. the hdr doesn't need to be byteswapped
2766 * 3. the hdr isn't already being shared
2767 * 4. the buf is either compressed or it is the last buf in the hdr list
2769 * Criterion #4 maintains the invariant that shared uncompressed
2770 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2771 * might ask, "if a compressed buf is allocated first, won't that be the
2772 * last thing in the list?", but in that case it's impossible to create
2773 * a shared uncompressed buf anyway (because the hdr must be compressed
2774 * to have the compressed buf). You might also think that #3 is
2775 * sufficient to make this guarantee, however it's possible
2776 * (specifically in the rare L2ARC write race mentioned in
2777 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2778 * is sharable, but wasn't at the time of its allocation. Rather than
2779 * allow a new shared uncompressed buf to be created and then shuffle
2780 * the list around to make it the last element, this simply disallows
2781 * sharing if the new buf isn't the first to be added.
2783 ASSERT3P(buf->b_hdr, ==, hdr);
2784 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
2785 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2786 return (buf_compressed == hdr_compressed &&
2787 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2788 !HDR_SHARED_DATA(hdr) &&
2789 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2793 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2794 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2795 * copy was made successfully, or an error code otherwise.
2798 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
2799 boolean_t fill, arc_buf_t **ret)
2803 ASSERT(HDR_HAS_L1HDR(hdr));
2804 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2805 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2806 hdr->b_type == ARC_BUFC_METADATA);
2807 ASSERT3P(ret, !=, NULL);
2808 ASSERT3P(*ret, ==, NULL);
2810 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2813 buf->b_next = hdr->b_l1hdr.b_buf;
2816 add_reference(hdr, tag);
2819 * We're about to change the hdr's b_flags. We must either
2820 * hold the hash_lock or be undiscoverable.
2822 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2825 * Only honor requests for compressed bufs if the hdr is actually
2828 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
2829 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2832 * If the hdr's data can be shared then we share the data buffer and
2833 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2834 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
2835 * buffer to store the buf's data.
2837 * There are two additional restrictions here because we're sharing
2838 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2839 * actively involved in an L2ARC write, because if this buf is used by
2840 * an arc_write() then the hdr's data buffer will be released when the
2841 * write completes, even though the L2ARC write might still be using it.
2842 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2843 * need to be ABD-aware.
2845 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2846 abd_is_linear(hdr->b_l1hdr.b_pabd);
2848 /* Set up b_data and sharing */
2850 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2851 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2852 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2855 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2856 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2858 VERIFY3P(buf->b_data, !=, NULL);
2860 hdr->b_l1hdr.b_buf = buf;
2861 hdr->b_l1hdr.b_bufcnt += 1;
2864 * If the user wants the data from the hdr, we need to either copy or
2865 * decompress the data.
2868 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
2874 static char *arc_onloan_tag = "onloan";
2877 arc_loaned_bytes_update(int64_t delta)
2879 atomic_add_64(&arc_loaned_bytes, delta);
2881 /* assert that it did not wrap around */
2882 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2886 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2887 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2888 * buffers must be returned to the arc before they can be used by the DMU or
2892 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2894 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2895 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2897 arc_loaned_bytes_update(arc_buf_size(buf));
2903 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2904 enum zio_compress compression_type)
2906 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2907 psize, lsize, compression_type);
2909 arc_loaned_bytes_update(arc_buf_size(buf));
2916 * Return a loaned arc buffer to the arc.
2919 arc_return_buf(arc_buf_t *buf, void *tag)
2921 arc_buf_hdr_t *hdr = buf->b_hdr;
2923 ASSERT3P(buf->b_data, !=, NULL);
2924 ASSERT(HDR_HAS_L1HDR(hdr));
2925 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2926 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2928 arc_loaned_bytes_update(-arc_buf_size(buf));
2931 /* Detach an arc_buf from a dbuf (tag) */
2933 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2935 arc_buf_hdr_t *hdr = buf->b_hdr;
2937 ASSERT3P(buf->b_data, !=, NULL);
2938 ASSERT(HDR_HAS_L1HDR(hdr));
2939 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2940 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2942 arc_loaned_bytes_update(arc_buf_size(buf));
2946 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2948 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2951 df->l2df_size = size;
2952 df->l2df_type = type;
2953 mutex_enter(&l2arc_free_on_write_mtx);
2954 list_insert_head(l2arc_free_on_write, df);
2955 mutex_exit(&l2arc_free_on_write_mtx);
2959 arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
2961 arc_state_t *state = hdr->b_l1hdr.b_state;
2962 arc_buf_contents_t type = arc_buf_type(hdr);
2963 uint64_t size = arc_hdr_size(hdr);
2965 /* protected by hash lock, if in the hash table */
2966 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2967 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2968 ASSERT(state != arc_anon && state != arc_l2c_only);
2970 (void) refcount_remove_many(&state->arcs_esize[type],
2973 (void) refcount_remove_many(&state->arcs_size, size, hdr);
2974 if (type == ARC_BUFC_METADATA) {
2975 arc_space_return(size, ARC_SPACE_META);
2977 ASSERT(type == ARC_BUFC_DATA);
2978 arc_space_return(size, ARC_SPACE_DATA);
2981 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2985 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2986 * data buffer, we transfer the refcount ownership to the hdr and update
2987 * the appropriate kstats.
2990 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2992 arc_state_t *state = hdr->b_l1hdr.b_state;
2994 ASSERT(arc_can_share(hdr, buf));
2995 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2996 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2999 * Start sharing the data buffer. We transfer the
3000 * refcount ownership to the hdr since it always owns
3001 * the refcount whenever an arc_buf_t is shared.
3003 refcount_transfer_ownership(&state->arcs_size, buf, hdr);
3004 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
3005 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
3006 HDR_ISTYPE_METADATA(hdr));
3007 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
3008 buf->b_flags |= ARC_BUF_FLAG_SHARED;
3011 * Since we've transferred ownership to the hdr we need
3012 * to increment its compressed and uncompressed kstats and
3013 * decrement the overhead size.
3015 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3016 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3017 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
3021 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3023 arc_state_t *state = hdr->b_l1hdr.b_state;
3025 ASSERT(arc_buf_is_shared(buf));
3026 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3027 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3030 * We are no longer sharing this buffer so we need
3031 * to transfer its ownership to the rightful owner.
3033 refcount_transfer_ownership(&state->arcs_size, hdr, buf);
3034 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3035 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
3036 abd_put(hdr->b_l1hdr.b_pabd);
3037 hdr->b_l1hdr.b_pabd = NULL;
3038 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
3041 * Since the buffer is no longer shared between
3042 * the arc buf and the hdr, count it as overhead.
3044 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3045 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3046 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
3050 * Remove an arc_buf_t from the hdr's buf list and return the last
3051 * arc_buf_t on the list. If no buffers remain on the list then return
3055 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
3057 ASSERT(HDR_HAS_L1HDR(hdr));
3058 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3060 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
3061 arc_buf_t *lastbuf = NULL;
3064 * Remove the buf from the hdr list and locate the last
3065 * remaining buffer on the list.
3067 while (*bufp != NULL) {
3069 *bufp = buf->b_next;
3072 * If we've removed a buffer in the middle of
3073 * the list then update the lastbuf and update
3076 if (*bufp != NULL) {
3078 bufp = &(*bufp)->b_next;
3082 ASSERT3P(lastbuf, !=, buf);
3083 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
3084 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
3085 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
3091 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
3095 arc_buf_destroy_impl(arc_buf_t *buf)
3097 arc_buf_hdr_t *hdr = buf->b_hdr;
3100 * Free up the data associated with the buf but only if we're not
3101 * sharing this with the hdr. If we are sharing it with the hdr, the
3102 * hdr is responsible for doing the free.
3104 if (buf->b_data != NULL) {
3106 * We're about to change the hdr's b_flags. We must either
3107 * hold the hash_lock or be undiscoverable.
3109 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3111 arc_cksum_verify(buf);
3113 arc_buf_unwatch(buf);
3116 if (arc_buf_is_shared(buf)) {
3117 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3119 uint64_t size = arc_buf_size(buf);
3120 arc_free_data_buf(hdr, buf->b_data, size, buf);
3121 ARCSTAT_INCR(arcstat_overhead_size, -size);
3125 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3126 hdr->b_l1hdr.b_bufcnt -= 1;
3129 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3131 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3133 * If the current arc_buf_t is sharing its data buffer with the
3134 * hdr, then reassign the hdr's b_pabd to share it with the new
3135 * buffer at the end of the list. The shared buffer is always
3136 * the last one on the hdr's buffer list.
3138 * There is an equivalent case for compressed bufs, but since
3139 * they aren't guaranteed to be the last buf in the list and
3140 * that is an exceedingly rare case, we just allow that space be
3141 * wasted temporarily.
3143 if (lastbuf != NULL) {
3144 /* Only one buf can be shared at once */
3145 VERIFY(!arc_buf_is_shared(lastbuf));
3146 /* hdr is uncompressed so can't have compressed buf */
3147 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3149 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3150 arc_hdr_free_pabd(hdr);
3153 * We must setup a new shared block between the
3154 * last buffer and the hdr. The data would have
3155 * been allocated by the arc buf so we need to transfer
3156 * ownership to the hdr since it's now being shared.
3158 arc_share_buf(hdr, lastbuf);
3160 } else if (HDR_SHARED_DATA(hdr)) {
3162 * Uncompressed shared buffers are always at the end
3163 * of the list. Compressed buffers don't have the
3164 * same requirements. This makes it hard to
3165 * simply assert that the lastbuf is shared so
3166 * we rely on the hdr's compression flags to determine
3167 * if we have a compressed, shared buffer.
3169 ASSERT3P(lastbuf, !=, NULL);
3170 ASSERT(arc_buf_is_shared(lastbuf) ||
3171 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
3175 * Free the checksum if we're removing the last uncompressed buf from
3178 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3179 arc_cksum_free(hdr);
3182 /* clean up the buf */
3184 kmem_cache_free(buf_cache, buf);
3188 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr)
3190 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3191 ASSERT(HDR_HAS_L1HDR(hdr));
3192 ASSERT(!HDR_SHARED_DATA(hdr));
3194 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3195 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
3196 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3197 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3199 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3200 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3204 arc_hdr_free_pabd(arc_buf_hdr_t *hdr)
3206 ASSERT(HDR_HAS_L1HDR(hdr));
3207 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3210 * If the hdr is currently being written to the l2arc then
3211 * we defer freeing the data by adding it to the l2arc_free_on_write
3212 * list. The l2arc will free the data once it's finished
3213 * writing it to the l2arc device.
3215 if (HDR_L2_WRITING(hdr)) {
3216 arc_hdr_free_on_write(hdr);
3217 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3219 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3220 arc_hdr_size(hdr), hdr);
3222 hdr->b_l1hdr.b_pabd = NULL;
3223 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3225 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3226 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3229 static arc_buf_hdr_t *
3230 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3231 enum zio_compress compression_type, arc_buf_contents_t type)
3235 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3237 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3238 ASSERT(HDR_EMPTY(hdr));
3239 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3240 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3241 HDR_SET_PSIZE(hdr, psize);
3242 HDR_SET_LSIZE(hdr, lsize);
3246 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3247 arc_hdr_set_compress(hdr, compression_type);
3249 hdr->b_l1hdr.b_state = arc_anon;
3250 hdr->b_l1hdr.b_arc_access = 0;
3251 hdr->b_l1hdr.b_bufcnt = 0;
3252 hdr->b_l1hdr.b_buf = NULL;
3255 * Allocate the hdr's buffer. This will contain either
3256 * the compressed or uncompressed data depending on the block
3257 * it references and compressed arc enablement.
3259 arc_hdr_alloc_pabd(hdr);
3260 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3266 * Transition between the two allocation states for the arc_buf_hdr struct.
3267 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3268 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3269 * version is used when a cache buffer is only in the L2ARC in order to reduce
3272 static arc_buf_hdr_t *
3273 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3275 ASSERT(HDR_HAS_L2HDR(hdr));
3277 arc_buf_hdr_t *nhdr;
3278 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3280 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3281 (old == hdr_l2only_cache && new == hdr_full_cache));
3283 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3285 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3286 buf_hash_remove(hdr);
3288 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3290 if (new == hdr_full_cache) {
3291 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3293 * arc_access and arc_change_state need to be aware that a
3294 * header has just come out of L2ARC, so we set its state to
3295 * l2c_only even though it's about to change.
3297 nhdr->b_l1hdr.b_state = arc_l2c_only;
3299 /* Verify previous threads set to NULL before freeing */
3300 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3302 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3303 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3304 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3307 * If we've reached here, We must have been called from
3308 * arc_evict_hdr(), as such we should have already been
3309 * removed from any ghost list we were previously on
3310 * (which protects us from racing with arc_evict_state),
3311 * thus no locking is needed during this check.
3313 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3316 * A buffer must not be moved into the arc_l2c_only
3317 * state if it's not finished being written out to the
3318 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3319 * might try to be accessed, even though it was removed.
3321 VERIFY(!HDR_L2_WRITING(hdr));
3322 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3325 if (hdr->b_l1hdr.b_thawed != NULL) {
3326 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3327 hdr->b_l1hdr.b_thawed = NULL;
3331 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3334 * The header has been reallocated so we need to re-insert it into any
3337 (void) buf_hash_insert(nhdr, NULL);
3339 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3341 mutex_enter(&dev->l2ad_mtx);
3344 * We must place the realloc'ed header back into the list at
3345 * the same spot. Otherwise, if it's placed earlier in the list,
3346 * l2arc_write_buffers() could find it during the function's
3347 * write phase, and try to write it out to the l2arc.
3349 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3350 list_remove(&dev->l2ad_buflist, hdr);
3352 mutex_exit(&dev->l2ad_mtx);
3355 * Since we're using the pointer address as the tag when
3356 * incrementing and decrementing the l2ad_alloc refcount, we
3357 * must remove the old pointer (that we're about to destroy) and
3358 * add the new pointer to the refcount. Otherwise we'd remove
3359 * the wrong pointer address when calling arc_hdr_destroy() later.
3362 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
3363 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
3365 buf_discard_identity(hdr);
3366 kmem_cache_free(old, hdr);
3372 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3373 * The buf is returned thawed since we expect the consumer to modify it.
3376 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3378 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3379 ZIO_COMPRESS_OFF, type);
3380 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3382 arc_buf_t *buf = NULL;
3383 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
3390 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3391 * for bufs containing metadata.
3394 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3395 enum zio_compress compression_type)
3397 ASSERT3U(lsize, >, 0);
3398 ASSERT3U(lsize, >=, psize);
3399 ASSERT(compression_type > ZIO_COMPRESS_OFF);
3400 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
3402 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3403 compression_type, ARC_BUFC_DATA);
3404 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3406 arc_buf_t *buf = NULL;
3407 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
3409 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3411 if (!arc_buf_is_shared(buf)) {
3413 * To ensure that the hdr has the correct data in it if we call
3414 * arc_decompress() on this buf before it's been written to
3415 * disk, it's easiest if we just set up sharing between the
3418 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3419 arc_hdr_free_pabd(hdr);
3420 arc_share_buf(hdr, buf);
3427 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3429 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3430 l2arc_dev_t *dev = l2hdr->b_dev;
3431 uint64_t psize = arc_hdr_size(hdr);
3433 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3434 ASSERT(HDR_HAS_L2HDR(hdr));
3436 list_remove(&dev->l2ad_buflist, hdr);
3438 ARCSTAT_INCR(arcstat_l2_psize, -psize);
3439 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
3441 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0);
3443 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr);
3444 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3448 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3450 if (HDR_HAS_L1HDR(hdr)) {
3451 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3452 hdr->b_l1hdr.b_bufcnt > 0);
3453 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3454 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3456 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3457 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3459 if (!HDR_EMPTY(hdr))
3460 buf_discard_identity(hdr);
3462 if (HDR_HAS_L2HDR(hdr)) {
3463 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3464 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3467 mutex_enter(&dev->l2ad_mtx);
3470 * Even though we checked this conditional above, we
3471 * need to check this again now that we have the
3472 * l2ad_mtx. This is because we could be racing with
3473 * another thread calling l2arc_evict() which might have
3474 * destroyed this header's L2 portion as we were waiting
3475 * to acquire the l2ad_mtx. If that happens, we don't
3476 * want to re-destroy the header's L2 portion.
3478 if (HDR_HAS_L2HDR(hdr)) {
3480 arc_hdr_l2hdr_destroy(hdr);
3484 mutex_exit(&dev->l2ad_mtx);
3487 if (HDR_HAS_L1HDR(hdr)) {
3488 arc_cksum_free(hdr);
3490 while (hdr->b_l1hdr.b_buf != NULL)
3491 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3494 if (hdr->b_l1hdr.b_thawed != NULL) {
3495 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3496 hdr->b_l1hdr.b_thawed = NULL;
3500 if (hdr->b_l1hdr.b_pabd != NULL) {
3501 arc_hdr_free_pabd(hdr);
3505 ASSERT3P(hdr->b_hash_next, ==, NULL);
3506 if (HDR_HAS_L1HDR(hdr)) {
3507 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3508 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3509 kmem_cache_free(hdr_full_cache, hdr);
3511 kmem_cache_free(hdr_l2only_cache, hdr);
3516 arc_buf_destroy(arc_buf_t *buf, void* tag)
3518 arc_buf_hdr_t *hdr = buf->b_hdr;
3519 kmutex_t *hash_lock = HDR_LOCK(hdr);
3521 if (hdr->b_l1hdr.b_state == arc_anon) {
3522 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3523 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3524 VERIFY0(remove_reference(hdr, NULL, tag));
3525 arc_hdr_destroy(hdr);
3529 mutex_enter(hash_lock);
3530 ASSERT3P(hdr, ==, buf->b_hdr);
3531 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3532 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3533 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3534 ASSERT3P(buf->b_data, !=, NULL);
3536 (void) remove_reference(hdr, hash_lock, tag);
3537 arc_buf_destroy_impl(buf);
3538 mutex_exit(hash_lock);
3542 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3543 * state of the header is dependent on its state prior to entering this
3544 * function. The following transitions are possible:
3546 * - arc_mru -> arc_mru_ghost
3547 * - arc_mfu -> arc_mfu_ghost
3548 * - arc_mru_ghost -> arc_l2c_only
3549 * - arc_mru_ghost -> deleted
3550 * - arc_mfu_ghost -> arc_l2c_only
3551 * - arc_mfu_ghost -> deleted
3554 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3556 arc_state_t *evicted_state, *state;
3557 int64_t bytes_evicted = 0;
3558 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ?
3559 zfs_arc_min_prescient_prefetch_ms : zfs_arc_min_prefetch_ms;
3561 ASSERT(MUTEX_HELD(hash_lock));
3562 ASSERT(HDR_HAS_L1HDR(hdr));
3564 state = hdr->b_l1hdr.b_state;
3565 if (GHOST_STATE(state)) {
3566 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3567 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3570 * l2arc_write_buffers() relies on a header's L1 portion
3571 * (i.e. its b_pabd field) during it's write phase.
3572 * Thus, we cannot push a header onto the arc_l2c_only
3573 * state (removing it's L1 piece) until the header is
3574 * done being written to the l2arc.
3576 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3577 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3578 return (bytes_evicted);
3581 ARCSTAT_BUMP(arcstat_deleted);
3582 bytes_evicted += HDR_GET_LSIZE(hdr);
3584 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3586 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3587 if (HDR_HAS_L2HDR(hdr)) {
3589 * This buffer is cached on the 2nd Level ARC;
3590 * don't destroy the header.
3592 arc_change_state(arc_l2c_only, hdr, hash_lock);
3594 * dropping from L1+L2 cached to L2-only,
3595 * realloc to remove the L1 header.
3597 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3600 arc_change_state(arc_anon, hdr, hash_lock);
3601 arc_hdr_destroy(hdr);
3603 return (bytes_evicted);
3606 ASSERT(state == arc_mru || state == arc_mfu);
3607 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3609 /* prefetch buffers have a minimum lifespan */
3610 if (HDR_IO_IN_PROGRESS(hdr) ||
3611 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3612 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < min_lifetime * hz)) {
3613 ARCSTAT_BUMP(arcstat_evict_skip);
3614 return (bytes_evicted);
3617 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3618 while (hdr->b_l1hdr.b_buf) {
3619 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3620 if (!mutex_tryenter(&buf->b_evict_lock)) {
3621 ARCSTAT_BUMP(arcstat_mutex_miss);
3624 if (buf->b_data != NULL)
3625 bytes_evicted += HDR_GET_LSIZE(hdr);
3626 mutex_exit(&buf->b_evict_lock);
3627 arc_buf_destroy_impl(buf);
3630 if (HDR_HAS_L2HDR(hdr)) {
3631 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3633 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3634 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3635 HDR_GET_LSIZE(hdr));
3637 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3638 HDR_GET_LSIZE(hdr));
3642 if (hdr->b_l1hdr.b_bufcnt == 0) {
3643 arc_cksum_free(hdr);
3645 bytes_evicted += arc_hdr_size(hdr);
3648 * If this hdr is being evicted and has a compressed
3649 * buffer then we discard it here before we change states.
3650 * This ensures that the accounting is updated correctly
3651 * in arc_free_data_impl().
3653 arc_hdr_free_pabd(hdr);
3655 arc_change_state(evicted_state, hdr, hash_lock);
3656 ASSERT(HDR_IN_HASH_TABLE(hdr));
3657 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3658 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3661 return (bytes_evicted);
3665 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3666 uint64_t spa, int64_t bytes)
3668 multilist_sublist_t *mls;
3669 uint64_t bytes_evicted = 0;
3671 kmutex_t *hash_lock;
3672 int evict_count = 0;
3674 ASSERT3P(marker, !=, NULL);
3675 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3677 mls = multilist_sublist_lock(ml, idx);
3679 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3680 hdr = multilist_sublist_prev(mls, marker)) {
3681 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3682 (evict_count >= zfs_arc_evict_batch_limit))
3686 * To keep our iteration location, move the marker
3687 * forward. Since we're not holding hdr's hash lock, we
3688 * must be very careful and not remove 'hdr' from the
3689 * sublist. Otherwise, other consumers might mistake the
3690 * 'hdr' as not being on a sublist when they call the
3691 * multilist_link_active() function (they all rely on
3692 * the hash lock protecting concurrent insertions and
3693 * removals). multilist_sublist_move_forward() was
3694 * specifically implemented to ensure this is the case
3695 * (only 'marker' will be removed and re-inserted).
3697 multilist_sublist_move_forward(mls, marker);
3700 * The only case where the b_spa field should ever be
3701 * zero, is the marker headers inserted by
3702 * arc_evict_state(). It's possible for multiple threads
3703 * to be calling arc_evict_state() concurrently (e.g.
3704 * dsl_pool_close() and zio_inject_fault()), so we must
3705 * skip any markers we see from these other threads.
3707 if (hdr->b_spa == 0)
3710 /* we're only interested in evicting buffers of a certain spa */
3711 if (spa != 0 && hdr->b_spa != spa) {
3712 ARCSTAT_BUMP(arcstat_evict_skip);
3716 hash_lock = HDR_LOCK(hdr);
3719 * We aren't calling this function from any code path
3720 * that would already be holding a hash lock, so we're
3721 * asserting on this assumption to be defensive in case
3722 * this ever changes. Without this check, it would be
3723 * possible to incorrectly increment arcstat_mutex_miss
3724 * below (e.g. if the code changed such that we called
3725 * this function with a hash lock held).
3727 ASSERT(!MUTEX_HELD(hash_lock));
3729 if (mutex_tryenter(hash_lock)) {
3730 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3731 mutex_exit(hash_lock);
3733 bytes_evicted += evicted;
3736 * If evicted is zero, arc_evict_hdr() must have
3737 * decided to skip this header, don't increment
3738 * evict_count in this case.
3744 * If arc_size isn't overflowing, signal any
3745 * threads that might happen to be waiting.
3747 * For each header evicted, we wake up a single
3748 * thread. If we used cv_broadcast, we could
3749 * wake up "too many" threads causing arc_size
3750 * to significantly overflow arc_c; since
3751 * arc_get_data_impl() doesn't check for overflow
3752 * when it's woken up (it doesn't because it's
3753 * possible for the ARC to be overflowing while
3754 * full of un-evictable buffers, and the
3755 * function should proceed in this case).
3757 * If threads are left sleeping, due to not
3758 * using cv_broadcast, they will be woken up
3759 * just before arc_reclaim_thread() sleeps.
3761 mutex_enter(&arc_reclaim_lock);
3762 if (!arc_is_overflowing())
3763 cv_signal(&arc_reclaim_waiters_cv);
3764 mutex_exit(&arc_reclaim_lock);
3766 ARCSTAT_BUMP(arcstat_mutex_miss);
3770 multilist_sublist_unlock(mls);
3772 return (bytes_evicted);
3776 * Evict buffers from the given arc state, until we've removed the
3777 * specified number of bytes. Move the removed buffers to the
3778 * appropriate evict state.
3780 * This function makes a "best effort". It skips over any buffers
3781 * it can't get a hash_lock on, and so, may not catch all candidates.
3782 * It may also return without evicting as much space as requested.
3784 * If bytes is specified using the special value ARC_EVICT_ALL, this
3785 * will evict all available (i.e. unlocked and evictable) buffers from
3786 * the given arc state; which is used by arc_flush().
3789 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
3790 arc_buf_contents_t type)
3792 uint64_t total_evicted = 0;
3793 multilist_t *ml = state->arcs_list[type];
3795 arc_buf_hdr_t **markers;
3797 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3799 num_sublists = multilist_get_num_sublists(ml);
3802 * If we've tried to evict from each sublist, made some
3803 * progress, but still have not hit the target number of bytes
3804 * to evict, we want to keep trying. The markers allow us to
3805 * pick up where we left off for each individual sublist, rather
3806 * than starting from the tail each time.
3808 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
3809 for (int i = 0; i < num_sublists; i++) {
3810 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
3813 * A b_spa of 0 is used to indicate that this header is
3814 * a marker. This fact is used in arc_adjust_type() and
3815 * arc_evict_state_impl().
3817 markers[i]->b_spa = 0;
3819 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3820 multilist_sublist_insert_tail(mls, markers[i]);
3821 multilist_sublist_unlock(mls);
3825 * While we haven't hit our target number of bytes to evict, or
3826 * we're evicting all available buffers.
3828 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
3830 * Start eviction using a randomly selected sublist,
3831 * this is to try and evenly balance eviction across all
3832 * sublists. Always starting at the same sublist
3833 * (e.g. index 0) would cause evictions to favor certain
3834 * sublists over others.
3836 int sublist_idx = multilist_get_random_index(ml);
3837 uint64_t scan_evicted = 0;
3839 for (int i = 0; i < num_sublists; i++) {
3840 uint64_t bytes_remaining;
3841 uint64_t bytes_evicted;
3843 if (bytes == ARC_EVICT_ALL)
3844 bytes_remaining = ARC_EVICT_ALL;
3845 else if (total_evicted < bytes)
3846 bytes_remaining = bytes - total_evicted;
3850 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
3851 markers[sublist_idx], spa, bytes_remaining);
3853 scan_evicted += bytes_evicted;
3854 total_evicted += bytes_evicted;
3856 /* we've reached the end, wrap to the beginning */
3857 if (++sublist_idx >= num_sublists)
3862 * If we didn't evict anything during this scan, we have
3863 * no reason to believe we'll evict more during another
3864 * scan, so break the loop.
3866 if (scan_evicted == 0) {
3867 /* This isn't possible, let's make that obvious */
3868 ASSERT3S(bytes, !=, 0);
3871 * When bytes is ARC_EVICT_ALL, the only way to
3872 * break the loop is when scan_evicted is zero.
3873 * In that case, we actually have evicted enough,
3874 * so we don't want to increment the kstat.
3876 if (bytes != ARC_EVICT_ALL) {
3877 ASSERT3S(total_evicted, <, bytes);
3878 ARCSTAT_BUMP(arcstat_evict_not_enough);
3885 for (int i = 0; i < num_sublists; i++) {
3886 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3887 multilist_sublist_remove(mls, markers[i]);
3888 multilist_sublist_unlock(mls);
3890 kmem_cache_free(hdr_full_cache, markers[i]);
3892 kmem_free(markers, sizeof (*markers) * num_sublists);
3894 return (total_evicted);
3898 * Flush all "evictable" data of the given type from the arc state
3899 * specified. This will not evict any "active" buffers (i.e. referenced).
3901 * When 'retry' is set to B_FALSE, the function will make a single pass
3902 * over the state and evict any buffers that it can. Since it doesn't
3903 * continually retry the eviction, it might end up leaving some buffers
3904 * in the ARC due to lock misses.
3906 * When 'retry' is set to B_TRUE, the function will continually retry the
3907 * eviction until *all* evictable buffers have been removed from the
3908 * state. As a result, if concurrent insertions into the state are
3909 * allowed (e.g. if the ARC isn't shutting down), this function might
3910 * wind up in an infinite loop, continually trying to evict buffers.
3913 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
3916 uint64_t evicted = 0;
3918 while (refcount_count(&state->arcs_esize[type]) != 0) {
3919 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
3929 * Evict the specified number of bytes from the state specified,
3930 * restricting eviction to the spa and type given. This function
3931 * prevents us from trying to evict more from a state's list than
3932 * is "evictable", and to skip evicting altogether when passed a
3933 * negative value for "bytes". In contrast, arc_evict_state() will
3934 * evict everything it can, when passed a negative value for "bytes".
3937 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
3938 arc_buf_contents_t type)
3942 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
3943 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
3944 return (arc_evict_state(state, spa, delta, type));
3951 * Evict metadata buffers from the cache, such that arc_meta_used is
3952 * capped by the arc_meta_limit tunable.
3955 arc_adjust_meta(uint64_t meta_used)
3957 uint64_t total_evicted = 0;
3961 * If we're over the meta limit, we want to evict enough
3962 * metadata to get back under the meta limit. We don't want to
3963 * evict so much that we drop the MRU below arc_p, though. If
3964 * we're over the meta limit more than we're over arc_p, we
3965 * evict some from the MRU here, and some from the MFU below.
3967 target = MIN((int64_t)(meta_used - arc_meta_limit),
3968 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3969 refcount_count(&arc_mru->arcs_size) - arc_p));
3971 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3974 * Similar to the above, we want to evict enough bytes to get us
3975 * below the meta limit, but not so much as to drop us below the
3976 * space allotted to the MFU (which is defined as arc_c - arc_p).
3978 target = MIN((int64_t)(meta_used - arc_meta_limit),
3979 (int64_t)(refcount_count(&arc_mfu->arcs_size) -
3982 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3984 return (total_evicted);
3988 * Return the type of the oldest buffer in the given arc state
3990 * This function will select a random sublist of type ARC_BUFC_DATA and
3991 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
3992 * is compared, and the type which contains the "older" buffer will be
3995 static arc_buf_contents_t
3996 arc_adjust_type(arc_state_t *state)
3998 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
3999 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
4000 int data_idx = multilist_get_random_index(data_ml);
4001 int meta_idx = multilist_get_random_index(meta_ml);
4002 multilist_sublist_t *data_mls;
4003 multilist_sublist_t *meta_mls;
4004 arc_buf_contents_t type;
4005 arc_buf_hdr_t *data_hdr;
4006 arc_buf_hdr_t *meta_hdr;
4009 * We keep the sublist lock until we're finished, to prevent
4010 * the headers from being destroyed via arc_evict_state().
4012 data_mls = multilist_sublist_lock(data_ml, data_idx);
4013 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
4016 * These two loops are to ensure we skip any markers that
4017 * might be at the tail of the lists due to arc_evict_state().
4020 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
4021 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
4022 if (data_hdr->b_spa != 0)
4026 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
4027 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
4028 if (meta_hdr->b_spa != 0)
4032 if (data_hdr == NULL && meta_hdr == NULL) {
4033 type = ARC_BUFC_DATA;
4034 } else if (data_hdr == NULL) {
4035 ASSERT3P(meta_hdr, !=, NULL);
4036 type = ARC_BUFC_METADATA;
4037 } else if (meta_hdr == NULL) {
4038 ASSERT3P(data_hdr, !=, NULL);
4039 type = ARC_BUFC_DATA;
4041 ASSERT3P(data_hdr, !=, NULL);
4042 ASSERT3P(meta_hdr, !=, NULL);
4044 /* The headers can't be on the sublist without an L1 header */
4045 ASSERT(HDR_HAS_L1HDR(data_hdr));
4046 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4048 if (data_hdr->b_l1hdr.b_arc_access <
4049 meta_hdr->b_l1hdr.b_arc_access) {
4050 type = ARC_BUFC_DATA;
4052 type = ARC_BUFC_METADATA;
4056 multilist_sublist_unlock(meta_mls);
4057 multilist_sublist_unlock(data_mls);
4063 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4068 uint64_t total_evicted = 0;
4071 uint64_t asize = aggsum_value(&arc_size);
4072 uint64_t ameta = aggsum_value(&arc_meta_used);
4075 * If we're over arc_meta_limit, we want to correct that before
4076 * potentially evicting data buffers below.
4078 total_evicted += arc_adjust_meta(ameta);
4083 * If we're over the target cache size, we want to evict enough
4084 * from the list to get back to our target size. We don't want
4085 * to evict too much from the MRU, such that it drops below
4086 * arc_p. So, if we're over our target cache size more than
4087 * the MRU is over arc_p, we'll evict enough to get back to
4088 * arc_p here, and then evict more from the MFU below.
4090 target = MIN((int64_t)(asize - arc_c),
4091 (int64_t)(refcount_count(&arc_anon->arcs_size) +
4092 refcount_count(&arc_mru->arcs_size) + ameta - arc_p));
4095 * If we're below arc_meta_min, always prefer to evict data.
4096 * Otherwise, try to satisfy the requested number of bytes to
4097 * evict from the type which contains older buffers; in an
4098 * effort to keep newer buffers in the cache regardless of their
4099 * type. If we cannot satisfy the number of bytes from this
4100 * type, spill over into the next type.
4102 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4103 ameta > arc_meta_min) {
4104 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4105 total_evicted += bytes;
4108 * If we couldn't evict our target number of bytes from
4109 * metadata, we try to get the rest from data.
4114 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4116 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4117 total_evicted += bytes;
4120 * If we couldn't evict our target number of bytes from
4121 * data, we try to get the rest from metadata.
4126 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4132 * Now that we've tried to evict enough from the MRU to get its
4133 * size back to arc_p, if we're still above the target cache
4134 * size, we evict the rest from the MFU.
4136 target = asize - arc_c;
4138 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4139 ameta > arc_meta_min) {
4140 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4141 total_evicted += bytes;
4144 * If we couldn't evict our target number of bytes from
4145 * metadata, we try to get the rest from data.
4150 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4152 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4153 total_evicted += bytes;
4156 * If we couldn't evict our target number of bytes from
4157 * data, we try to get the rest from data.
4162 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4166 * Adjust ghost lists
4168 * In addition to the above, the ARC also defines target values
4169 * for the ghost lists. The sum of the mru list and mru ghost
4170 * list should never exceed the target size of the cache, and
4171 * the sum of the mru list, mfu list, mru ghost list, and mfu
4172 * ghost list should never exceed twice the target size of the
4173 * cache. The following logic enforces these limits on the ghost
4174 * caches, and evicts from them as needed.
4176 target = refcount_count(&arc_mru->arcs_size) +
4177 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4179 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4180 total_evicted += bytes;
4185 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4188 * We assume the sum of the mru list and mfu list is less than
4189 * or equal to arc_c (we enforced this above), which means we
4190 * can use the simpler of the two equations below:
4192 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4193 * mru ghost + mfu ghost <= arc_c
4195 target = refcount_count(&arc_mru_ghost->arcs_size) +
4196 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4198 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4199 total_evicted += bytes;
4204 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4206 return (total_evicted);
4210 arc_flush(spa_t *spa, boolean_t retry)
4215 * If retry is B_TRUE, a spa must not be specified since we have
4216 * no good way to determine if all of a spa's buffers have been
4217 * evicted from an arc state.
4219 ASSERT(!retry || spa == 0);
4222 guid = spa_load_guid(spa);
4224 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4225 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4227 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4228 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4230 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4231 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4233 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4234 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4238 arc_shrink(int64_t to_free)
4240 uint64_t asize = aggsum_value(&arc_size);
4241 if (arc_c > arc_c_min) {
4242 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
4243 arc_c_min, uint64_t, arc_p, uint64_t, to_free);
4244 if (arc_c > arc_c_min + to_free)
4245 atomic_add_64(&arc_c, -to_free);
4249 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4251 arc_c = MAX(asize, arc_c_min);
4253 arc_p = (arc_c >> 1);
4255 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
4258 ASSERT(arc_c >= arc_c_min);
4259 ASSERT((int64_t)arc_p >= 0);
4262 if (asize > arc_c) {
4263 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, asize,
4265 (void) arc_adjust();
4269 typedef enum free_memory_reason_t {
4274 FMR_PAGES_PP_MAXIMUM,
4277 } free_memory_reason_t;
4279 int64_t last_free_memory;
4280 free_memory_reason_t last_free_reason;
4283 * Additional reserve of pages for pp_reserve.
4285 int64_t arc_pages_pp_reserve = 64;
4288 * Additional reserve of pages for swapfs.
4290 int64_t arc_swapfs_reserve = 64;
4293 * Return the amount of memory that can be consumed before reclaim will be
4294 * needed. Positive if there is sufficient free memory, negative indicates
4295 * the amount of memory that needs to be freed up.
4298 arc_available_memory(void)
4300 int64_t lowest = INT64_MAX;
4302 free_memory_reason_t r = FMR_UNKNOWN;
4307 * Cooperate with pagedaemon when it's time for it to scan
4308 * and reclaim some pages.
4310 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target);
4318 n = PAGESIZE * (-needfree);
4326 * check that we're out of range of the pageout scanner. It starts to
4327 * schedule paging if freemem is less than lotsfree and needfree.
4328 * lotsfree is the high-water mark for pageout, and needfree is the
4329 * number of needed free pages. We add extra pages here to make sure
4330 * the scanner doesn't start up while we're freeing memory.
4332 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4339 * check to make sure that swapfs has enough space so that anon
4340 * reservations can still succeed. anon_resvmem() checks that the
4341 * availrmem is greater than swapfs_minfree, and the number of reserved
4342 * swap pages. We also add a bit of extra here just to prevent
4343 * circumstances from getting really dire.
4345 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4346 desfree - arc_swapfs_reserve);
4349 r = FMR_SWAPFS_MINFREE;
4354 * Check that we have enough availrmem that memory locking (e.g., via
4355 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4356 * stores the number of pages that cannot be locked; when availrmem
4357 * drops below pages_pp_maximum, page locking mechanisms such as
4358 * page_pp_lock() will fail.)
4360 n = PAGESIZE * (availrmem - pages_pp_maximum -
4361 arc_pages_pp_reserve);
4364 r = FMR_PAGES_PP_MAXIMUM;
4367 #endif /* __FreeBSD__ */
4368 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
4370 * If we're on an i386 platform, it's possible that we'll exhaust the
4371 * kernel heap space before we ever run out of available physical
4372 * memory. Most checks of the size of the heap_area compare against
4373 * tune.t_minarmem, which is the minimum available real memory that we
4374 * can have in the system. However, this is generally fixed at 25 pages
4375 * which is so low that it's useless. In this comparison, we seek to
4376 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4377 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4380 n = uma_avail() - (long)(uma_limit() / 4);
4388 * If zio data pages are being allocated out of a separate heap segment,
4389 * then enforce that the size of available vmem for this arena remains
4390 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4392 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4393 * memory (in the zio_arena) free, which can avoid memory
4394 * fragmentation issues.
4396 if (zio_arena != NULL) {
4397 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4398 (vmem_size(zio_arena, VMEM_ALLOC) >>
4399 arc_zio_arena_free_shift);
4407 /* Every 100 calls, free a small amount */
4408 if (spa_get_random(100) == 0)
4410 #endif /* _KERNEL */
4412 last_free_memory = lowest;
4413 last_free_reason = r;
4414 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r);
4420 * Determine if the system is under memory pressure and is asking
4421 * to reclaim memory. A return value of B_TRUE indicates that the system
4422 * is under memory pressure and that the arc should adjust accordingly.
4425 arc_reclaim_needed(void)
4427 return (arc_available_memory() < 0);
4430 extern kmem_cache_t *zio_buf_cache[];
4431 extern kmem_cache_t *zio_data_buf_cache[];
4432 extern kmem_cache_t *range_seg_cache;
4433 extern kmem_cache_t *abd_chunk_cache;
4435 static __noinline void
4436 arc_kmem_reap_now(void)
4439 kmem_cache_t *prev_cache = NULL;
4440 kmem_cache_t *prev_data_cache = NULL;
4442 DTRACE_PROBE(arc__kmem_reap_start);
4444 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) {
4446 * We are exceeding our meta-data cache limit.
4447 * Purge some DNLC entries to release holds on meta-data.
4449 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4453 * Reclaim unused memory from all kmem caches.
4460 * If a kmem reap is already active, don't schedule more. We must
4461 * check for this because kmem_cache_reap_soon() won't actually
4462 * block on the cache being reaped (this is to prevent callers from
4463 * becoming implicitly blocked by a system-wide kmem reap -- which,
4464 * on a system with many, many full magazines, can take minutes).
4466 if (kmem_cache_reap_active())
4469 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4470 if (zio_buf_cache[i] != prev_cache) {
4471 prev_cache = zio_buf_cache[i];
4472 kmem_cache_reap_soon(zio_buf_cache[i]);
4474 if (zio_data_buf_cache[i] != prev_data_cache) {
4475 prev_data_cache = zio_data_buf_cache[i];
4476 kmem_cache_reap_soon(zio_data_buf_cache[i]);
4479 kmem_cache_reap_soon(abd_chunk_cache);
4480 kmem_cache_reap_soon(buf_cache);
4481 kmem_cache_reap_soon(hdr_full_cache);
4482 kmem_cache_reap_soon(hdr_l2only_cache);
4483 kmem_cache_reap_soon(range_seg_cache);
4486 if (zio_arena != NULL) {
4488 * Ask the vmem arena to reclaim unused memory from its
4491 vmem_qcache_reap(zio_arena);
4494 DTRACE_PROBE(arc__kmem_reap_end);
4498 * Threads can block in arc_get_data_impl() waiting for this thread to evict
4499 * enough data and signal them to proceed. When this happens, the threads in
4500 * arc_get_data_impl() are sleeping while holding the hash lock for their
4501 * particular arc header. Thus, we must be careful to never sleep on a
4502 * hash lock in this thread. This is to prevent the following deadlock:
4504 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
4505 * waiting for the reclaim thread to signal it.
4507 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
4508 * fails, and goes to sleep forever.
4510 * This possible deadlock is avoided by always acquiring a hash lock
4511 * using mutex_tryenter() from arc_reclaim_thread().
4515 arc_reclaim_thread(void *unused __unused)
4517 hrtime_t growtime = 0;
4518 hrtime_t kmem_reap_time = 0;
4521 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
4523 mutex_enter(&arc_reclaim_lock);
4524 while (!arc_reclaim_thread_exit) {
4525 uint64_t evicted = 0;
4528 * This is necessary in order for the mdb ::arc dcmd to
4529 * show up to date information. Since the ::arc command
4530 * does not call the kstat's update function, without
4531 * this call, the command may show stale stats for the
4532 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4533 * with this change, the data might be up to 1 second
4534 * out of date; but that should suffice. The arc_state_t
4535 * structures can be queried directly if more accurate
4536 * information is needed.
4538 if (arc_ksp != NULL)
4539 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4541 mutex_exit(&arc_reclaim_lock);
4544 * We call arc_adjust() before (possibly) calling
4545 * arc_kmem_reap_now(), so that we can wake up
4546 * arc_get_data_impl() sooner.
4548 evicted = arc_adjust();
4550 int64_t free_memory = arc_available_memory();
4551 if (free_memory < 0) {
4552 hrtime_t curtime = gethrtime();
4553 arc_no_grow = B_TRUE;
4557 * Wait at least zfs_grow_retry (default 60) seconds
4558 * before considering growing.
4560 growtime = curtime + SEC2NSEC(arc_grow_retry);
4563 * Wait at least arc_kmem_cache_reap_retry_ms
4564 * between arc_kmem_reap_now() calls. Without
4565 * this check it is possible to end up in a
4566 * situation where we spend lots of time
4567 * reaping caches, while we're near arc_c_min.
4569 if (curtime >= kmem_reap_time) {
4570 arc_kmem_reap_now();
4571 kmem_reap_time = gethrtime() +
4572 MSEC2NSEC(arc_kmem_cache_reap_retry_ms);
4576 * If we are still low on memory, shrink the ARC
4577 * so that we have arc_shrink_min free space.
4579 free_memory = arc_available_memory();
4582 (arc_c >> arc_shrink_shift) - free_memory;
4586 to_free = MAX(to_free, ptob(needfree));
4589 arc_shrink(to_free);
4591 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4592 arc_no_grow = B_TRUE;
4593 } else if (gethrtime() >= growtime) {
4594 arc_no_grow = B_FALSE;
4597 mutex_enter(&arc_reclaim_lock);
4600 * If evicted is zero, we couldn't evict anything via
4601 * arc_adjust(). This could be due to hash lock
4602 * collisions, but more likely due to the majority of
4603 * arc buffers being unevictable. Therefore, even if
4604 * arc_size is above arc_c, another pass is unlikely to
4605 * be helpful and could potentially cause us to enter an
4608 if (aggsum_compare(&arc_size, arc_c) <= 0|| evicted == 0) {
4610 * We're either no longer overflowing, or we
4611 * can't evict anything more, so we should wake
4612 * up any threads before we go to sleep.
4614 cv_broadcast(&arc_reclaim_waiters_cv);
4617 * Block until signaled, or after one second (we
4618 * might need to perform arc_kmem_reap_now()
4619 * even if we aren't being signalled)
4621 CALLB_CPR_SAFE_BEGIN(&cpr);
4622 (void) cv_timedwait_hires(&arc_reclaim_thread_cv,
4623 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
4624 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
4628 arc_reclaim_thread_exit = B_FALSE;
4629 cv_broadcast(&arc_reclaim_thread_cv);
4630 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
4634 static u_int arc_dnlc_evicts_arg;
4635 extern struct vfsops zfs_vfsops;
4638 arc_dnlc_evicts_thread(void *dummy __unused)
4643 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG);
4645 mutex_enter(&arc_dnlc_evicts_lock);
4646 while (!arc_dnlc_evicts_thread_exit) {
4647 CALLB_CPR_SAFE_BEGIN(&cpr);
4648 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
4649 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock);
4650 if (arc_dnlc_evicts_arg != 0) {
4651 percent = arc_dnlc_evicts_arg;
4652 mutex_exit(&arc_dnlc_evicts_lock);
4654 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops);
4656 mutex_enter(&arc_dnlc_evicts_lock);
4658 * Clear our token only after vnlru_free()
4659 * pass is done, to avoid false queueing of
4662 arc_dnlc_evicts_arg = 0;
4665 arc_dnlc_evicts_thread_exit = FALSE;
4666 cv_broadcast(&arc_dnlc_evicts_cv);
4667 CALLB_CPR_EXIT(&cpr);
4672 dnlc_reduce_cache(void *arg)
4676 percent = (u_int)(uintptr_t)arg;
4677 mutex_enter(&arc_dnlc_evicts_lock);
4678 if (arc_dnlc_evicts_arg == 0) {
4679 arc_dnlc_evicts_arg = percent;
4680 cv_broadcast(&arc_dnlc_evicts_cv);
4682 mutex_exit(&arc_dnlc_evicts_lock);
4686 * Adapt arc info given the number of bytes we are trying to add and
4687 * the state that we are comming from. This function is only called
4688 * when we are adding new content to the cache.
4691 arc_adapt(int bytes, arc_state_t *state)
4694 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4695 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
4696 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
4698 if (state == arc_l2c_only)
4703 * Adapt the target size of the MRU list:
4704 * - if we just hit in the MRU ghost list, then increase
4705 * the target size of the MRU list.
4706 * - if we just hit in the MFU ghost list, then increase
4707 * the target size of the MFU list by decreasing the
4708 * target size of the MRU list.
4710 if (state == arc_mru_ghost) {
4711 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4712 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4714 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4715 } else if (state == arc_mfu_ghost) {
4718 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4719 mult = MIN(mult, 10);
4721 delta = MIN(bytes * mult, arc_p);
4722 arc_p = MAX(arc_p_min, arc_p - delta);
4724 ASSERT((int64_t)arc_p >= 0);
4726 if (arc_reclaim_needed()) {
4727 cv_signal(&arc_reclaim_thread_cv);
4734 if (arc_c >= arc_c_max)
4738 * If we're within (2 * maxblocksize) bytes of the target
4739 * cache size, increment the target cache size
4741 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) >
4743 DTRACE_PROBE1(arc__inc_adapt, int, bytes);
4744 atomic_add_64(&arc_c, (int64_t)bytes);
4745 if (arc_c > arc_c_max)
4747 else if (state == arc_anon)
4748 atomic_add_64(&arc_p, (int64_t)bytes);
4752 ASSERT((int64_t)arc_p >= 0);
4756 * Check if arc_size has grown past our upper threshold, determined by
4757 * zfs_arc_overflow_shift.
4760 arc_is_overflowing(void)
4762 /* Always allow at least one block of overflow */
4763 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4764 arc_c >> zfs_arc_overflow_shift);
4767 * We just compare the lower bound here for performance reasons. Our
4768 * primary goals are to make sure that the arc never grows without
4769 * bound, and that it can reach its maximum size. This check
4770 * accomplishes both goals. The maximum amount we could run over by is
4771 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block
4772 * in the ARC. In practice, that's in the tens of MB, which is low
4773 * enough to be safe.
4775 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow);
4779 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4781 arc_buf_contents_t type = arc_buf_type(hdr);
4783 arc_get_data_impl(hdr, size, tag);
4784 if (type == ARC_BUFC_METADATA) {
4785 return (abd_alloc(size, B_TRUE));
4787 ASSERT(type == ARC_BUFC_DATA);
4788 return (abd_alloc(size, B_FALSE));
4793 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4795 arc_buf_contents_t type = arc_buf_type(hdr);
4797 arc_get_data_impl(hdr, size, tag);
4798 if (type == ARC_BUFC_METADATA) {
4799 return (zio_buf_alloc(size));
4801 ASSERT(type == ARC_BUFC_DATA);
4802 return (zio_data_buf_alloc(size));
4807 * Allocate a block and return it to the caller. If we are hitting the
4808 * hard limit for the cache size, we must sleep, waiting for the eviction
4809 * thread to catch up. If we're past the target size but below the hard
4810 * limit, we'll only signal the reclaim thread and continue on.
4813 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4815 arc_state_t *state = hdr->b_l1hdr.b_state;
4816 arc_buf_contents_t type = arc_buf_type(hdr);
4818 arc_adapt(size, state);
4821 * If arc_size is currently overflowing, and has grown past our
4822 * upper limit, we must be adding data faster than the evict
4823 * thread can evict. Thus, to ensure we don't compound the
4824 * problem by adding more data and forcing arc_size to grow even
4825 * further past it's target size, we halt and wait for the
4826 * eviction thread to catch up.
4828 * It's also possible that the reclaim thread is unable to evict
4829 * enough buffers to get arc_size below the overflow limit (e.g.
4830 * due to buffers being un-evictable, or hash lock collisions).
4831 * In this case, we want to proceed regardless if we're
4832 * overflowing; thus we don't use a while loop here.
4834 if (arc_is_overflowing()) {
4835 mutex_enter(&arc_reclaim_lock);
4838 * Now that we've acquired the lock, we may no longer be
4839 * over the overflow limit, lets check.
4841 * We're ignoring the case of spurious wake ups. If that
4842 * were to happen, it'd let this thread consume an ARC
4843 * buffer before it should have (i.e. before we're under
4844 * the overflow limit and were signalled by the reclaim
4845 * thread). As long as that is a rare occurrence, it
4846 * shouldn't cause any harm.
4848 if (arc_is_overflowing()) {
4849 cv_signal(&arc_reclaim_thread_cv);
4850 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
4853 mutex_exit(&arc_reclaim_lock);
4856 VERIFY3U(hdr->b_type, ==, type);
4857 if (type == ARC_BUFC_METADATA) {
4858 arc_space_consume(size, ARC_SPACE_META);
4860 arc_space_consume(size, ARC_SPACE_DATA);
4864 * Update the state size. Note that ghost states have a
4865 * "ghost size" and so don't need to be updated.
4867 if (!GHOST_STATE(state)) {
4869 (void) refcount_add_many(&state->arcs_size, size, tag);
4872 * If this is reached via arc_read, the link is
4873 * protected by the hash lock. If reached via
4874 * arc_buf_alloc, the header should not be accessed by
4875 * any other thread. And, if reached via arc_read_done,
4876 * the hash lock will protect it if it's found in the
4877 * hash table; otherwise no other thread should be
4878 * trying to [add|remove]_reference it.
4880 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4881 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4882 (void) refcount_add_many(&state->arcs_esize[type],
4887 * If we are growing the cache, and we are adding anonymous
4888 * data, and we have outgrown arc_p, update arc_p
4890 if (aggsum_compare(&arc_size, arc_c) < 0 &&
4891 hdr->b_l1hdr.b_state == arc_anon &&
4892 (refcount_count(&arc_anon->arcs_size) +
4893 refcount_count(&arc_mru->arcs_size) > arc_p))
4894 arc_p = MIN(arc_c, arc_p + size);
4896 ARCSTAT_BUMP(arcstat_allocated);
4900 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
4902 arc_free_data_impl(hdr, size, tag);
4907 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
4909 arc_buf_contents_t type = arc_buf_type(hdr);
4911 arc_free_data_impl(hdr, size, tag);
4912 if (type == ARC_BUFC_METADATA) {
4913 zio_buf_free(buf, size);
4915 ASSERT(type == ARC_BUFC_DATA);
4916 zio_data_buf_free(buf, size);
4921 * Free the arc data buffer.
4924 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4926 arc_state_t *state = hdr->b_l1hdr.b_state;
4927 arc_buf_contents_t type = arc_buf_type(hdr);
4929 /* protected by hash lock, if in the hash table */
4930 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4931 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4932 ASSERT(state != arc_anon && state != arc_l2c_only);
4934 (void) refcount_remove_many(&state->arcs_esize[type],
4937 (void) refcount_remove_many(&state->arcs_size, size, tag);
4939 VERIFY3U(hdr->b_type, ==, type);
4940 if (type == ARC_BUFC_METADATA) {
4941 arc_space_return(size, ARC_SPACE_META);
4943 ASSERT(type == ARC_BUFC_DATA);
4944 arc_space_return(size, ARC_SPACE_DATA);
4949 * This routine is called whenever a buffer is accessed.
4950 * NOTE: the hash lock is dropped in this function.
4953 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
4957 ASSERT(MUTEX_HELD(hash_lock));
4958 ASSERT(HDR_HAS_L1HDR(hdr));
4960 if (hdr->b_l1hdr.b_state == arc_anon) {
4962 * This buffer is not in the cache, and does not
4963 * appear in our "ghost" list. Add the new buffer
4967 ASSERT0(hdr->b_l1hdr.b_arc_access);
4968 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4969 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4970 arc_change_state(arc_mru, hdr, hash_lock);
4972 } else if (hdr->b_l1hdr.b_state == arc_mru) {
4973 now = ddi_get_lbolt();
4976 * If this buffer is here because of a prefetch, then either:
4977 * - clear the flag if this is a "referencing" read
4978 * (any subsequent access will bump this into the MFU state).
4980 * - move the buffer to the head of the list if this is
4981 * another prefetch (to make it less likely to be evicted).
4983 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
4984 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4985 /* link protected by hash lock */
4986 ASSERT(multilist_link_active(
4987 &hdr->b_l1hdr.b_arc_node));
4989 arc_hdr_clear_flags(hdr,
4991 ARC_FLAG_PRESCIENT_PREFETCH);
4992 ARCSTAT_BUMP(arcstat_mru_hits);
4994 hdr->b_l1hdr.b_arc_access = now;
4999 * This buffer has been "accessed" only once so far,
5000 * but it is still in the cache. Move it to the MFU
5003 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
5005 * More than 125ms have passed since we
5006 * instantiated this buffer. Move it to the
5007 * most frequently used state.
5009 hdr->b_l1hdr.b_arc_access = now;
5010 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5011 arc_change_state(arc_mfu, hdr, hash_lock);
5013 ARCSTAT_BUMP(arcstat_mru_hits);
5014 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
5015 arc_state_t *new_state;
5017 * This buffer has been "accessed" recently, but
5018 * was evicted from the cache. Move it to the
5022 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5023 new_state = arc_mru;
5024 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) {
5025 arc_hdr_clear_flags(hdr,
5027 ARC_FLAG_PRESCIENT_PREFETCH);
5029 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5031 new_state = arc_mfu;
5032 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5035 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5036 arc_change_state(new_state, hdr, hash_lock);
5038 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
5039 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
5041 * This buffer has been accessed more than once and is
5042 * still in the cache. Keep it in the MFU state.
5044 * NOTE: an add_reference() that occurred when we did
5045 * the arc_read() will have kicked this off the list.
5046 * If it was a prefetch, we will explicitly move it to
5047 * the head of the list now.
5050 ARCSTAT_BUMP(arcstat_mfu_hits);
5051 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5052 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
5053 arc_state_t *new_state = arc_mfu;
5055 * This buffer has been accessed more than once but has
5056 * been evicted from the cache. Move it back to the
5060 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5062 * This is a prefetch access...
5063 * move this block back to the MRU state.
5065 new_state = arc_mru;
5068 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5069 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5070 arc_change_state(new_state, hdr, hash_lock);
5072 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5073 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5075 * This buffer is on the 2nd Level ARC.
5078 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5079 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5080 arc_change_state(arc_mfu, hdr, hash_lock);
5082 ASSERT(!"invalid arc state");
5087 * This routine is called by dbuf_hold() to update the arc_access() state
5088 * which otherwise would be skipped for entries in the dbuf cache.
5091 arc_buf_access(arc_buf_t *buf)
5093 mutex_enter(&buf->b_evict_lock);
5094 arc_buf_hdr_t *hdr = buf->b_hdr;
5097 * Avoid taking the hash_lock when possible as an optimization.
5098 * The header must be checked again under the hash_lock in order
5099 * to handle the case where it is concurrently being released.
5101 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5102 mutex_exit(&buf->b_evict_lock);
5103 ARCSTAT_BUMP(arcstat_access_skip);
5107 kmutex_t *hash_lock = HDR_LOCK(hdr);
5108 mutex_enter(hash_lock);
5110 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5111 mutex_exit(hash_lock);
5112 mutex_exit(&buf->b_evict_lock);
5113 ARCSTAT_BUMP(arcstat_access_skip);
5117 mutex_exit(&buf->b_evict_lock);
5119 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5120 hdr->b_l1hdr.b_state == arc_mfu);
5122 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5123 arc_access(hdr, hash_lock);
5124 mutex_exit(hash_lock);
5126 ARCSTAT_BUMP(arcstat_hits);
5127 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5128 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits);
5131 /* a generic arc_read_done_func_t which you can use */
5134 arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5135 arc_buf_t *buf, void *arg)
5140 bcopy(buf->b_data, arg, arc_buf_size(buf));
5141 arc_buf_destroy(buf, arg);
5144 /* a generic arc_read_done_func_t */
5147 arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5148 arc_buf_t *buf, void *arg)
5150 arc_buf_t **bufp = arg;
5156 ASSERT(buf->b_data);
5161 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
5163 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5164 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5165 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
5167 if (HDR_COMPRESSION_ENABLED(hdr)) {
5168 ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
5169 BP_GET_COMPRESS(bp));
5171 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5172 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5177 arc_read_done(zio_t *zio)
5179 arc_buf_hdr_t *hdr = zio->io_private;
5180 kmutex_t *hash_lock = NULL;
5181 arc_callback_t *callback_list;
5182 arc_callback_t *acb;
5183 boolean_t freeable = B_FALSE;
5186 * The hdr was inserted into hash-table and removed from lists
5187 * prior to starting I/O. We should find this header, since
5188 * it's in the hash table, and it should be legit since it's
5189 * not possible to evict it during the I/O. The only possible
5190 * reason for it not to be found is if we were freed during the
5193 if (HDR_IN_HASH_TABLE(hdr)) {
5194 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5195 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5196 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5197 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5198 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5200 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5203 ASSERT((found == hdr &&
5204 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5205 (found == hdr && HDR_L2_READING(hdr)));
5206 ASSERT3P(hash_lock, !=, NULL);
5209 if (zio->io_error == 0) {
5210 /* byteswap if necessary */
5211 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5212 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5213 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5215 hdr->b_l1hdr.b_byteswap =
5216 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5219 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5223 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5224 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
5225 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
5227 callback_list = hdr->b_l1hdr.b_acb;
5228 ASSERT3P(callback_list, !=, NULL);
5230 if (hash_lock && zio->io_error == 0 &&
5231 hdr->b_l1hdr.b_state == arc_anon) {
5233 * Only call arc_access on anonymous buffers. This is because
5234 * if we've issued an I/O for an evicted buffer, we've already
5235 * called arc_access (to prevent any simultaneous readers from
5236 * getting confused).
5238 arc_access(hdr, hash_lock);
5242 * If a read request has a callback (i.e. acb_done is not NULL), then we
5243 * make a buf containing the data according to the parameters which were
5244 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5245 * aren't needlessly decompressing the data multiple times.
5247 int callback_cnt = 0;
5248 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5254 if (zio->io_error != 0)
5257 int error = arc_buf_alloc_impl(hdr, acb->acb_private,
5258 acb->acb_compressed,
5259 B_TRUE, &acb->acb_buf);
5261 arc_buf_destroy(acb->acb_buf, acb->acb_private);
5262 acb->acb_buf = NULL;
5265 if (zio->io_error == 0)
5266 zio->io_error = error;
5268 hdr->b_l1hdr.b_acb = NULL;
5269 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5270 if (callback_cnt == 0) {
5271 ASSERT(HDR_PREFETCH(hdr));
5272 ASSERT0(hdr->b_l1hdr.b_bufcnt);
5273 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5276 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5277 callback_list != NULL);
5279 if (zio->io_error == 0) {
5280 arc_hdr_verify(hdr, zio->io_bp);
5282 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5283 if (hdr->b_l1hdr.b_state != arc_anon)
5284 arc_change_state(arc_anon, hdr, hash_lock);
5285 if (HDR_IN_HASH_TABLE(hdr))
5286 buf_hash_remove(hdr);
5287 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5291 * Broadcast before we drop the hash_lock to avoid the possibility
5292 * that the hdr (and hence the cv) might be freed before we get to
5293 * the cv_broadcast().
5295 cv_broadcast(&hdr->b_l1hdr.b_cv);
5297 if (hash_lock != NULL) {
5298 mutex_exit(hash_lock);
5301 * This block was freed while we waited for the read to
5302 * complete. It has been removed from the hash table and
5303 * moved to the anonymous state (so that it won't show up
5306 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5307 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5310 /* execute each callback and free its structure */
5311 while ((acb = callback_list) != NULL) {
5312 if (acb->acb_done) {
5313 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp,
5314 acb->acb_buf, acb->acb_private);
5317 if (acb->acb_zio_dummy != NULL) {
5318 acb->acb_zio_dummy->io_error = zio->io_error;
5319 zio_nowait(acb->acb_zio_dummy);
5322 callback_list = acb->acb_next;
5323 kmem_free(acb, sizeof (arc_callback_t));
5327 arc_hdr_destroy(hdr);
5331 * "Read" the block at the specified DVA (in bp) via the
5332 * cache. If the block is found in the cache, invoke the provided
5333 * callback immediately and return. Note that the `zio' parameter
5334 * in the callback will be NULL in this case, since no IO was
5335 * required. If the block is not in the cache pass the read request
5336 * on to the spa with a substitute callback function, so that the
5337 * requested block will be added to the cache.
5339 * If a read request arrives for a block that has a read in-progress,
5340 * either wait for the in-progress read to complete (and return the
5341 * results); or, if this is a read with a "done" func, add a record
5342 * to the read to invoke the "done" func when the read completes,
5343 * and return; or just return.
5345 * arc_read_done() will invoke all the requested "done" functions
5346 * for readers of this block.
5349 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_read_done_func_t *done,
5350 void *private, zio_priority_t priority, int zio_flags,
5351 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5353 arc_buf_hdr_t *hdr = NULL;
5354 kmutex_t *hash_lock = NULL;
5356 uint64_t guid = spa_load_guid(spa);
5357 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
5360 ASSERT(!BP_IS_EMBEDDED(bp) ||
5361 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5364 if (!BP_IS_EMBEDDED(bp)) {
5366 * Embedded BP's have no DVA and require no I/O to "read".
5367 * Create an anonymous arc buf to back it.
5369 hdr = buf_hash_find(guid, bp, &hash_lock);
5372 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) {
5373 arc_buf_t *buf = NULL;
5374 *arc_flags |= ARC_FLAG_CACHED;
5376 if (HDR_IO_IN_PROGRESS(hdr)) {
5377 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;
5379 ASSERT3P(head_zio, !=, NULL);
5380 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5381 priority == ZIO_PRIORITY_SYNC_READ) {
5383 * This is a sync read that needs to wait for
5384 * an in-flight async read. Request that the
5385 * zio have its priority upgraded.
5387 zio_change_priority(head_zio, priority);
5388 DTRACE_PROBE1(arc__async__upgrade__sync,
5389 arc_buf_hdr_t *, hdr);
5390 ARCSTAT_BUMP(arcstat_async_upgrade_sync);
5392 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5393 arc_hdr_clear_flags(hdr,
5394 ARC_FLAG_PREDICTIVE_PREFETCH);
5397 if (*arc_flags & ARC_FLAG_WAIT) {
5398 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5399 mutex_exit(hash_lock);
5402 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5405 arc_callback_t *acb = NULL;
5407 acb = kmem_zalloc(sizeof (arc_callback_t),
5409 acb->acb_done = done;
5410 acb->acb_private = private;
5411 acb->acb_compressed = compressed_read;
5413 acb->acb_zio_dummy = zio_null(pio,
5414 spa, NULL, NULL, NULL, zio_flags);
5416 ASSERT3P(acb->acb_done, !=, NULL);
5417 acb->acb_zio_head = head_zio;
5418 acb->acb_next = hdr->b_l1hdr.b_acb;
5419 hdr->b_l1hdr.b_acb = acb;
5420 mutex_exit(hash_lock);
5423 mutex_exit(hash_lock);
5427 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5428 hdr->b_l1hdr.b_state == arc_mfu);
5431 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5433 * This is a demand read which does not have to
5434 * wait for i/o because we did a predictive
5435 * prefetch i/o for it, which has completed.
5438 arc__demand__hit__predictive__prefetch,
5439 arc_buf_hdr_t *, hdr);
5441 arcstat_demand_hit_predictive_prefetch);
5442 arc_hdr_clear_flags(hdr,
5443 ARC_FLAG_PREDICTIVE_PREFETCH);
5446 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) {
5448 arcstat_demand_hit_prescient_prefetch);
5449 arc_hdr_clear_flags(hdr,
5450 ARC_FLAG_PRESCIENT_PREFETCH);
5453 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5454 /* Get a buf with the desired data in it. */
5455 rc = arc_buf_alloc_impl(hdr, private,
5456 compressed_read, B_TRUE, &buf);
5458 arc_buf_destroy(buf, private);
5461 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) ||
5462 rc == 0 || rc != ENOENT);
5463 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5464 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5465 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5467 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5468 arc_access(hdr, hash_lock);
5469 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5470 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5471 if (*arc_flags & ARC_FLAG_L2CACHE)
5472 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5473 mutex_exit(hash_lock);
5474 ARCSTAT_BUMP(arcstat_hits);
5475 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5476 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5477 data, metadata, hits);
5480 done(NULL, zb, bp, buf, private);
5482 uint64_t lsize = BP_GET_LSIZE(bp);
5483 uint64_t psize = BP_GET_PSIZE(bp);
5484 arc_callback_t *acb;
5487 boolean_t devw = B_FALSE;
5491 /* this block is not in the cache */
5492 arc_buf_hdr_t *exists = NULL;
5493 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5494 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5495 BP_GET_COMPRESS(bp), type);
5497 if (!BP_IS_EMBEDDED(bp)) {
5498 hdr->b_dva = *BP_IDENTITY(bp);
5499 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5500 exists = buf_hash_insert(hdr, &hash_lock);
5502 if (exists != NULL) {
5503 /* somebody beat us to the hash insert */
5504 mutex_exit(hash_lock);
5505 buf_discard_identity(hdr);
5506 arc_hdr_destroy(hdr);
5507 goto top; /* restart the IO request */
5511 * This block is in the ghost cache. If it was L2-only
5512 * (and thus didn't have an L1 hdr), we realloc the
5513 * header to add an L1 hdr.
5515 if (!HDR_HAS_L1HDR(hdr)) {
5516 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5519 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5520 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
5521 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5522 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5523 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5524 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
5527 * This is a delicate dance that we play here.
5528 * This hdr is in the ghost list so we access it
5529 * to move it out of the ghost list before we
5530 * initiate the read. If it's a prefetch then
5531 * it won't have a callback so we'll remove the
5532 * reference that arc_buf_alloc_impl() created. We
5533 * do this after we've called arc_access() to
5534 * avoid hitting an assert in remove_reference().
5536 arc_access(hdr, hash_lock);
5537 arc_hdr_alloc_pabd(hdr);
5539 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5540 size = arc_hdr_size(hdr);
5543 * If compression is enabled on the hdr, then will do
5544 * RAW I/O and will store the compressed data in the hdr's
5545 * data block. Otherwise, the hdr's data block will contain
5546 * the uncompressed data.
5548 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5549 zio_flags |= ZIO_FLAG_RAW;
5552 if (*arc_flags & ARC_FLAG_PREFETCH)
5553 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5554 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5555 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5557 if (*arc_flags & ARC_FLAG_L2CACHE)
5558 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5559 if (BP_GET_LEVEL(bp) > 0)
5560 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5561 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5562 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5563 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5565 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5566 acb->acb_done = done;
5567 acb->acb_private = private;
5568 acb->acb_compressed = compressed_read;
5570 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5571 hdr->b_l1hdr.b_acb = acb;
5572 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5574 if (HDR_HAS_L2HDR(hdr) &&
5575 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5576 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5577 addr = hdr->b_l2hdr.b_daddr;
5579 * Lock out L2ARC device removal.
5581 if (vdev_is_dead(vd) ||
5582 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5587 * We count both async reads and scrub IOs as asynchronous so
5588 * that both can be upgraded in the event of a cache hit while
5589 * the read IO is still in-flight.
5591 if (priority == ZIO_PRIORITY_ASYNC_READ ||
5592 priority == ZIO_PRIORITY_SCRUB)
5593 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5595 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5598 * At this point, we have a level 1 cache miss. Try again in
5599 * L2ARC if possible.
5601 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5603 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5604 uint64_t, lsize, zbookmark_phys_t *, zb);
5605 ARCSTAT_BUMP(arcstat_misses);
5606 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5607 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5608 data, metadata, misses);
5613 racct_add_force(curproc, RACCT_READBPS, size);
5614 racct_add_force(curproc, RACCT_READIOPS, 1);
5615 PROC_UNLOCK(curproc);
5618 curthread->td_ru.ru_inblock++;
5621 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5623 * Read from the L2ARC if the following are true:
5624 * 1. The L2ARC vdev was previously cached.
5625 * 2. This buffer still has L2ARC metadata.
5626 * 3. This buffer isn't currently writing to the L2ARC.
5627 * 4. The L2ARC entry wasn't evicted, which may
5628 * also have invalidated the vdev.
5629 * 5. This isn't prefetch and l2arc_noprefetch is set.
5631 if (HDR_HAS_L2HDR(hdr) &&
5632 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5633 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5634 l2arc_read_callback_t *cb;
5638 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5639 ARCSTAT_BUMP(arcstat_l2_hits);
5641 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5643 cb->l2rcb_hdr = hdr;
5646 cb->l2rcb_flags = zio_flags;
5648 asize = vdev_psize_to_asize(vd, size);
5649 if (asize != size) {
5650 abd = abd_alloc_for_io(asize,
5651 HDR_ISTYPE_METADATA(hdr));
5652 cb->l2rcb_abd = abd;
5654 abd = hdr->b_l1hdr.b_pabd;
5657 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
5658 addr + asize <= vd->vdev_psize -
5659 VDEV_LABEL_END_SIZE);
5662 * l2arc read. The SCL_L2ARC lock will be
5663 * released by l2arc_read_done().
5664 * Issue a null zio if the underlying buffer
5665 * was squashed to zero size by compression.
5667 ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
5668 ZIO_COMPRESS_EMPTY);
5669 rzio = zio_read_phys(pio, vd, addr,
5672 l2arc_read_done, cb, priority,
5673 zio_flags | ZIO_FLAG_DONT_CACHE |
5675 ZIO_FLAG_DONT_PROPAGATE |
5676 ZIO_FLAG_DONT_RETRY, B_FALSE);
5677 acb->acb_zio_head = rzio;
5679 if (hash_lock != NULL)
5680 mutex_exit(hash_lock);
5682 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
5684 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
5686 if (*arc_flags & ARC_FLAG_NOWAIT) {
5691 ASSERT(*arc_flags & ARC_FLAG_WAIT);
5692 if (zio_wait(rzio) == 0)
5695 /* l2arc read error; goto zio_read() */
5696 if (hash_lock != NULL)
5697 mutex_enter(hash_lock);
5699 DTRACE_PROBE1(l2arc__miss,
5700 arc_buf_hdr_t *, hdr);
5701 ARCSTAT_BUMP(arcstat_l2_misses);
5702 if (HDR_L2_WRITING(hdr))
5703 ARCSTAT_BUMP(arcstat_l2_rw_clash);
5704 spa_config_exit(spa, SCL_L2ARC, vd);
5708 spa_config_exit(spa, SCL_L2ARC, vd);
5709 if (l2arc_ndev != 0) {
5710 DTRACE_PROBE1(l2arc__miss,
5711 arc_buf_hdr_t *, hdr);
5712 ARCSTAT_BUMP(arcstat_l2_misses);
5716 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size,
5717 arc_read_done, hdr, priority, zio_flags, zb);
5718 acb->acb_zio_head = rzio;
5720 if (hash_lock != NULL)
5721 mutex_exit(hash_lock);
5723 if (*arc_flags & ARC_FLAG_WAIT)
5724 return (zio_wait(rzio));
5726 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5733 * Notify the arc that a block was freed, and thus will never be used again.
5736 arc_freed(spa_t *spa, const blkptr_t *bp)
5739 kmutex_t *hash_lock;
5740 uint64_t guid = spa_load_guid(spa);
5742 ASSERT(!BP_IS_EMBEDDED(bp));
5744 hdr = buf_hash_find(guid, bp, &hash_lock);
5749 * We might be trying to free a block that is still doing I/O
5750 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
5751 * dmu_sync-ed block). If this block is being prefetched, then it
5752 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
5753 * until the I/O completes. A block may also have a reference if it is
5754 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
5755 * have written the new block to its final resting place on disk but
5756 * without the dedup flag set. This would have left the hdr in the MRU
5757 * state and discoverable. When the txg finally syncs it detects that
5758 * the block was overridden in open context and issues an override I/O.
5759 * Since this is a dedup block, the override I/O will determine if the
5760 * block is already in the DDT. If so, then it will replace the io_bp
5761 * with the bp from the DDT and allow the I/O to finish. When the I/O
5762 * reaches the done callback, dbuf_write_override_done, it will
5763 * check to see if the io_bp and io_bp_override are identical.
5764 * If they are not, then it indicates that the bp was replaced with
5765 * the bp in the DDT and the override bp is freed. This allows
5766 * us to arrive here with a reference on a block that is being
5767 * freed. So if we have an I/O in progress, or a reference to
5768 * this hdr, then we don't destroy the hdr.
5770 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
5771 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
5772 arc_change_state(arc_anon, hdr, hash_lock);
5773 arc_hdr_destroy(hdr);
5774 mutex_exit(hash_lock);
5776 mutex_exit(hash_lock);
5782 * Release this buffer from the cache, making it an anonymous buffer. This
5783 * must be done after a read and prior to modifying the buffer contents.
5784 * If the buffer has more than one reference, we must make
5785 * a new hdr for the buffer.
5788 arc_release(arc_buf_t *buf, void *tag)
5790 arc_buf_hdr_t *hdr = buf->b_hdr;
5793 * It would be nice to assert that if it's DMU metadata (level >
5794 * 0 || it's the dnode file), then it must be syncing context.
5795 * But we don't know that information at this level.
5798 mutex_enter(&buf->b_evict_lock);
5800 ASSERT(HDR_HAS_L1HDR(hdr));
5803 * We don't grab the hash lock prior to this check, because if
5804 * the buffer's header is in the arc_anon state, it won't be
5805 * linked into the hash table.
5807 if (hdr->b_l1hdr.b_state == arc_anon) {
5808 mutex_exit(&buf->b_evict_lock);
5809 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5810 ASSERT(!HDR_IN_HASH_TABLE(hdr));
5811 ASSERT(!HDR_HAS_L2HDR(hdr));
5812 ASSERT(HDR_EMPTY(hdr));
5813 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5814 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
5815 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
5817 hdr->b_l1hdr.b_arc_access = 0;
5820 * If the buf is being overridden then it may already
5821 * have a hdr that is not empty.
5823 buf_discard_identity(hdr);
5829 kmutex_t *hash_lock = HDR_LOCK(hdr);
5830 mutex_enter(hash_lock);
5833 * This assignment is only valid as long as the hash_lock is
5834 * held, we must be careful not to reference state or the
5835 * b_state field after dropping the lock.
5837 arc_state_t *state = hdr->b_l1hdr.b_state;
5838 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5839 ASSERT3P(state, !=, arc_anon);
5841 /* this buffer is not on any list */
5842 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
5844 if (HDR_HAS_L2HDR(hdr)) {
5845 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5848 * We have to recheck this conditional again now that
5849 * we're holding the l2ad_mtx to prevent a race with
5850 * another thread which might be concurrently calling
5851 * l2arc_evict(). In that case, l2arc_evict() might have
5852 * destroyed the header's L2 portion as we were waiting
5853 * to acquire the l2ad_mtx.
5855 if (HDR_HAS_L2HDR(hdr)) {
5857 arc_hdr_l2hdr_destroy(hdr);
5860 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5864 * Do we have more than one buf?
5866 if (hdr->b_l1hdr.b_bufcnt > 1) {
5867 arc_buf_hdr_t *nhdr;
5868 uint64_t spa = hdr->b_spa;
5869 uint64_t psize = HDR_GET_PSIZE(hdr);
5870 uint64_t lsize = HDR_GET_LSIZE(hdr);
5871 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
5872 arc_buf_contents_t type = arc_buf_type(hdr);
5873 VERIFY3U(hdr->b_type, ==, type);
5875 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
5876 (void) remove_reference(hdr, hash_lock, tag);
5878 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
5879 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
5880 ASSERT(ARC_BUF_LAST(buf));
5884 * Pull the data off of this hdr and attach it to
5885 * a new anonymous hdr. Also find the last buffer
5886 * in the hdr's buffer list.
5888 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
5889 ASSERT3P(lastbuf, !=, NULL);
5892 * If the current arc_buf_t and the hdr are sharing their data
5893 * buffer, then we must stop sharing that block.
5895 if (arc_buf_is_shared(buf)) {
5896 VERIFY(!arc_buf_is_shared(lastbuf));
5899 * First, sever the block sharing relationship between
5900 * buf and the arc_buf_hdr_t.
5902 arc_unshare_buf(hdr, buf);
5905 * Now we need to recreate the hdr's b_pabd. Since we
5906 * have lastbuf handy, we try to share with it, but if
5907 * we can't then we allocate a new b_pabd and copy the
5908 * data from buf into it.
5910 if (arc_can_share(hdr, lastbuf)) {
5911 arc_share_buf(hdr, lastbuf);
5913 arc_hdr_alloc_pabd(hdr);
5914 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
5915 buf->b_data, psize);
5917 VERIFY3P(lastbuf->b_data, !=, NULL);
5918 } else if (HDR_SHARED_DATA(hdr)) {
5920 * Uncompressed shared buffers are always at the end
5921 * of the list. Compressed buffers don't have the
5922 * same requirements. This makes it hard to
5923 * simply assert that the lastbuf is shared so
5924 * we rely on the hdr's compression flags to determine
5925 * if we have a compressed, shared buffer.
5927 ASSERT(arc_buf_is_shared(lastbuf) ||
5928 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
5929 ASSERT(!ARC_BUF_SHARED(buf));
5931 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5932 ASSERT3P(state, !=, arc_l2c_only);
5934 (void) refcount_remove_many(&state->arcs_size,
5935 arc_buf_size(buf), buf);
5937 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5938 ASSERT3P(state, !=, arc_l2c_only);
5939 (void) refcount_remove_many(&state->arcs_esize[type],
5940 arc_buf_size(buf), buf);
5943 hdr->b_l1hdr.b_bufcnt -= 1;
5944 arc_cksum_verify(buf);
5946 arc_buf_unwatch(buf);
5949 mutex_exit(hash_lock);
5952 * Allocate a new hdr. The new hdr will contain a b_pabd
5953 * buffer which will be freed in arc_write().
5955 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
5956 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
5957 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
5958 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
5959 VERIFY3U(nhdr->b_type, ==, type);
5960 ASSERT(!HDR_SHARED_DATA(nhdr));
5962 nhdr->b_l1hdr.b_buf = buf;
5963 nhdr->b_l1hdr.b_bufcnt = 1;
5964 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
5967 mutex_exit(&buf->b_evict_lock);
5968 (void) refcount_add_many(&arc_anon->arcs_size,
5969 arc_buf_size(buf), buf);
5971 mutex_exit(&buf->b_evict_lock);
5972 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
5973 /* protected by hash lock, or hdr is on arc_anon */
5974 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
5975 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5976 arc_change_state(arc_anon, hdr, hash_lock);
5977 hdr->b_l1hdr.b_arc_access = 0;
5978 mutex_exit(hash_lock);
5980 buf_discard_identity(hdr);
5986 arc_released(arc_buf_t *buf)
5990 mutex_enter(&buf->b_evict_lock);
5991 released = (buf->b_data != NULL &&
5992 buf->b_hdr->b_l1hdr.b_state == arc_anon);
5993 mutex_exit(&buf->b_evict_lock);
5999 arc_referenced(arc_buf_t *buf)
6003 mutex_enter(&buf->b_evict_lock);
6004 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
6005 mutex_exit(&buf->b_evict_lock);
6006 return (referenced);
6011 arc_write_ready(zio_t *zio)
6013 arc_write_callback_t *callback = zio->io_private;
6014 arc_buf_t *buf = callback->awcb_buf;
6015 arc_buf_hdr_t *hdr = buf->b_hdr;
6016 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
6018 ASSERT(HDR_HAS_L1HDR(hdr));
6019 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
6020 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
6023 * If we're reexecuting this zio because the pool suspended, then
6024 * cleanup any state that was previously set the first time the
6025 * callback was invoked.
6027 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
6028 arc_cksum_free(hdr);
6030 arc_buf_unwatch(buf);
6032 if (hdr->b_l1hdr.b_pabd != NULL) {
6033 if (arc_buf_is_shared(buf)) {
6034 arc_unshare_buf(hdr, buf);
6036 arc_hdr_free_pabd(hdr);
6040 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6041 ASSERT(!HDR_SHARED_DATA(hdr));
6042 ASSERT(!arc_buf_is_shared(buf));
6044 callback->awcb_ready(zio, buf, callback->awcb_private);
6046 if (HDR_IO_IN_PROGRESS(hdr))
6047 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
6049 arc_cksum_compute(buf);
6050 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6052 enum zio_compress compress;
6053 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6054 compress = ZIO_COMPRESS_OFF;
6056 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
6057 compress = BP_GET_COMPRESS(zio->io_bp);
6059 HDR_SET_PSIZE(hdr, psize);
6060 arc_hdr_set_compress(hdr, compress);
6064 * Fill the hdr with data. If the hdr is compressed, the data we want
6065 * is available from the zio, otherwise we can take it from the buf.
6067 * We might be able to share the buf's data with the hdr here. However,
6068 * doing so would cause the ARC to be full of linear ABDs if we write a
6069 * lot of shareable data. As a compromise, we check whether scattered
6070 * ABDs are allowed, and assume that if they are then the user wants
6071 * the ARC to be primarily filled with them regardless of the data being
6072 * written. Therefore, if they're allowed then we allocate one and copy
6073 * the data into it; otherwise, we share the data directly if we can.
6075 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
6076 arc_hdr_alloc_pabd(hdr);
6079 * Ideally, we would always copy the io_abd into b_pabd, but the
6080 * user may have disabled compressed ARC, thus we must check the
6081 * hdr's compression setting rather than the io_bp's.
6083 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
6084 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=,
6086 ASSERT3U(psize, >, 0);
6088 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
6090 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
6092 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
6096 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
6097 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
6098 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6100 arc_share_buf(hdr, buf);
6103 arc_hdr_verify(hdr, zio->io_bp);
6107 arc_write_children_ready(zio_t *zio)
6109 arc_write_callback_t *callback = zio->io_private;
6110 arc_buf_t *buf = callback->awcb_buf;
6112 callback->awcb_children_ready(zio, buf, callback->awcb_private);
6116 * The SPA calls this callback for each physical write that happens on behalf
6117 * of a logical write. See the comment in dbuf_write_physdone() for details.
6120 arc_write_physdone(zio_t *zio)
6122 arc_write_callback_t *cb = zio->io_private;
6123 if (cb->awcb_physdone != NULL)
6124 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
6128 arc_write_done(zio_t *zio)
6130 arc_write_callback_t *callback = zio->io_private;
6131 arc_buf_t *buf = callback->awcb_buf;
6132 arc_buf_hdr_t *hdr = buf->b_hdr;
6134 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6136 if (zio->io_error == 0) {
6137 arc_hdr_verify(hdr, zio->io_bp);
6139 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6140 buf_discard_identity(hdr);
6142 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
6143 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
6146 ASSERT(HDR_EMPTY(hdr));
6150 * If the block to be written was all-zero or compressed enough to be
6151 * embedded in the BP, no write was performed so there will be no
6152 * dva/birth/checksum. The buffer must therefore remain anonymous
6155 if (!HDR_EMPTY(hdr)) {
6156 arc_buf_hdr_t *exists;
6157 kmutex_t *hash_lock;
6159 ASSERT3U(zio->io_error, ==, 0);
6161 arc_cksum_verify(buf);
6163 exists = buf_hash_insert(hdr, &hash_lock);
6164 if (exists != NULL) {
6166 * This can only happen if we overwrite for
6167 * sync-to-convergence, because we remove
6168 * buffers from the hash table when we arc_free().
6170 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
6171 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6172 panic("bad overwrite, hdr=%p exists=%p",
6173 (void *)hdr, (void *)exists);
6174 ASSERT(refcount_is_zero(
6175 &exists->b_l1hdr.b_refcnt));
6176 arc_change_state(arc_anon, exists, hash_lock);
6177 mutex_exit(hash_lock);
6178 arc_hdr_destroy(exists);
6179 exists = buf_hash_insert(hdr, &hash_lock);
6180 ASSERT3P(exists, ==, NULL);
6181 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
6183 ASSERT(zio->io_prop.zp_nopwrite);
6184 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6185 panic("bad nopwrite, hdr=%p exists=%p",
6186 (void *)hdr, (void *)exists);
6189 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6190 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6191 ASSERT(BP_GET_DEDUP(zio->io_bp));
6192 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6195 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6196 /* if it's not anon, we are doing a scrub */
6197 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6198 arc_access(hdr, hash_lock);
6199 mutex_exit(hash_lock);
6201 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6204 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6205 callback->awcb_done(zio, buf, callback->awcb_private);
6207 abd_put(zio->io_abd);
6208 kmem_free(callback, sizeof (arc_write_callback_t));
6212 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6213 boolean_t l2arc, const zio_prop_t *zp, arc_write_done_func_t *ready,
6214 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone,
6215 arc_write_done_func_t *done, void *private, zio_priority_t priority,
6216 int zio_flags, const zbookmark_phys_t *zb)
6218 arc_buf_hdr_t *hdr = buf->b_hdr;
6219 arc_write_callback_t *callback;
6221 zio_prop_t localprop = *zp;
6223 ASSERT3P(ready, !=, NULL);
6224 ASSERT3P(done, !=, NULL);
6225 ASSERT(!HDR_IO_ERROR(hdr));
6226 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6227 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6228 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6230 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6231 if (ARC_BUF_COMPRESSED(buf)) {
6233 * We're writing a pre-compressed buffer. Make the
6234 * compression algorithm requested by the zio_prop_t match
6235 * the pre-compressed buffer's compression algorithm.
6237 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6239 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6240 zio_flags |= ZIO_FLAG_RAW;
6242 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6243 callback->awcb_ready = ready;
6244 callback->awcb_children_ready = children_ready;
6245 callback->awcb_physdone = physdone;
6246 callback->awcb_done = done;
6247 callback->awcb_private = private;
6248 callback->awcb_buf = buf;
6251 * The hdr's b_pabd is now stale, free it now. A new data block
6252 * will be allocated when the zio pipeline calls arc_write_ready().
6254 if (hdr->b_l1hdr.b_pabd != NULL) {
6256 * If the buf is currently sharing the data block with
6257 * the hdr then we need to break that relationship here.
6258 * The hdr will remain with a NULL data pointer and the
6259 * buf will take sole ownership of the block.
6261 if (arc_buf_is_shared(buf)) {
6262 arc_unshare_buf(hdr, buf);
6264 arc_hdr_free_pabd(hdr);
6266 VERIFY3P(buf->b_data, !=, NULL);
6267 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6269 ASSERT(!arc_buf_is_shared(buf));
6270 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6272 zio = zio_write(pio, spa, txg, bp,
6273 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6274 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6275 (children_ready != NULL) ? arc_write_children_ready : NULL,
6276 arc_write_physdone, arc_write_done, callback,
6277 priority, zio_flags, zb);
6283 arc_memory_throttle(uint64_t reserve, uint64_t txg)
6286 uint64_t available_memory = ptob(freemem);
6287 static uint64_t page_load = 0;
6288 static uint64_t last_txg = 0;
6290 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
6291 available_memory = MIN(available_memory, uma_avail());
6294 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
6297 if (txg > last_txg) {
6302 * If we are in pageout, we know that memory is already tight,
6303 * the arc is already going to be evicting, so we just want to
6304 * continue to let page writes occur as quickly as possible.
6306 if (curproc == pageproc) {
6307 if (page_load > MAX(ptob(minfree), available_memory) / 4)
6308 return (SET_ERROR(ERESTART));
6309 /* Note: reserve is inflated, so we deflate */
6310 page_load += reserve / 8;
6312 } else if (page_load > 0 && arc_reclaim_needed()) {
6313 /* memory is low, delay before restarting */
6314 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6315 return (SET_ERROR(EAGAIN));
6323 arc_tempreserve_clear(uint64_t reserve)
6325 atomic_add_64(&arc_tempreserve, -reserve);
6326 ASSERT((int64_t)arc_tempreserve >= 0);
6330 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
6335 if (reserve > arc_c/4 && !arc_no_grow) {
6336 arc_c = MIN(arc_c_max, reserve * 4);
6337 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
6339 if (reserve > arc_c)
6340 return (SET_ERROR(ENOMEM));
6343 * Don't count loaned bufs as in flight dirty data to prevent long
6344 * network delays from blocking transactions that are ready to be
6345 * assigned to a txg.
6348 /* assert that it has not wrapped around */
6349 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6351 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
6352 arc_loaned_bytes), 0);
6355 * Writes will, almost always, require additional memory allocations
6356 * in order to compress/encrypt/etc the data. We therefore need to
6357 * make sure that there is sufficient available memory for this.
6359 error = arc_memory_throttle(reserve, txg);
6364 * Throttle writes when the amount of dirty data in the cache
6365 * gets too large. We try to keep the cache less than half full
6366 * of dirty blocks so that our sync times don't grow too large.
6367 * Note: if two requests come in concurrently, we might let them
6368 * both succeed, when one of them should fail. Not a huge deal.
6371 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
6372 anon_size > arc_c / 4) {
6373 uint64_t meta_esize =
6374 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6375 uint64_t data_esize =
6376 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6377 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6378 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6379 arc_tempreserve >> 10, meta_esize >> 10,
6380 data_esize >> 10, reserve >> 10, arc_c >> 10);
6381 return (SET_ERROR(ERESTART));
6383 atomic_add_64(&arc_tempreserve, reserve);
6388 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6389 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
6391 size->value.ui64 = refcount_count(&state->arcs_size);
6392 evict_data->value.ui64 =
6393 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6394 evict_metadata->value.ui64 =
6395 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6399 arc_kstat_update(kstat_t *ksp, int rw)
6401 arc_stats_t *as = ksp->ks_data;
6403 if (rw == KSTAT_WRITE) {
6406 arc_kstat_update_state(arc_anon,
6407 &as->arcstat_anon_size,
6408 &as->arcstat_anon_evictable_data,
6409 &as->arcstat_anon_evictable_metadata);
6410 arc_kstat_update_state(arc_mru,
6411 &as->arcstat_mru_size,
6412 &as->arcstat_mru_evictable_data,
6413 &as->arcstat_mru_evictable_metadata);
6414 arc_kstat_update_state(arc_mru_ghost,
6415 &as->arcstat_mru_ghost_size,
6416 &as->arcstat_mru_ghost_evictable_data,
6417 &as->arcstat_mru_ghost_evictable_metadata);
6418 arc_kstat_update_state(arc_mfu,
6419 &as->arcstat_mfu_size,
6420 &as->arcstat_mfu_evictable_data,
6421 &as->arcstat_mfu_evictable_metadata);
6422 arc_kstat_update_state(arc_mfu_ghost,
6423 &as->arcstat_mfu_ghost_size,
6424 &as->arcstat_mfu_ghost_evictable_data,
6425 &as->arcstat_mfu_ghost_evictable_metadata);
6427 ARCSTAT(arcstat_size) = aggsum_value(&arc_size);
6428 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used);
6429 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size);
6430 ARCSTAT(arcstat_metadata_size) =
6431 aggsum_value(&astat_metadata_size);
6432 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size);
6433 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_other_size);
6434 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size);
6441 * This function *must* return indices evenly distributed between all
6442 * sublists of the multilist. This is needed due to how the ARC eviction
6443 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6444 * distributed between all sublists and uses this assumption when
6445 * deciding which sublist to evict from and how much to evict from it.
6448 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6450 arc_buf_hdr_t *hdr = obj;
6453 * We rely on b_dva to generate evenly distributed index
6454 * numbers using buf_hash below. So, as an added precaution,
6455 * let's make sure we never add empty buffers to the arc lists.
6457 ASSERT(!HDR_EMPTY(hdr));
6460 * The assumption here, is the hash value for a given
6461 * arc_buf_hdr_t will remain constant throughout it's lifetime
6462 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
6463 * Thus, we don't need to store the header's sublist index
6464 * on insertion, as this index can be recalculated on removal.
6466 * Also, the low order bits of the hash value are thought to be
6467 * distributed evenly. Otherwise, in the case that the multilist
6468 * has a power of two number of sublists, each sublists' usage
6469 * would not be evenly distributed.
6471 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
6472 multilist_get_num_sublists(ml));
6476 static eventhandler_tag arc_event_lowmem = NULL;
6479 arc_lowmem(void *arg __unused, int howto __unused)
6482 mutex_enter(&arc_reclaim_lock);
6483 DTRACE_PROBE1(arc__needfree, int64_t, ((int64_t)freemem - zfs_arc_free_target) * PAGESIZE);
6484 cv_signal(&arc_reclaim_thread_cv);
6487 * It is unsafe to block here in arbitrary threads, because we can come
6488 * here from ARC itself and may hold ARC locks and thus risk a deadlock
6489 * with ARC reclaim thread.
6491 if (curproc == pageproc)
6492 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
6493 mutex_exit(&arc_reclaim_lock);
6498 arc_state_init(void)
6500 arc_anon = &ARC_anon;
6502 arc_mru_ghost = &ARC_mru_ghost;
6504 arc_mfu_ghost = &ARC_mfu_ghost;
6505 arc_l2c_only = &ARC_l2c_only;
6507 arc_mru->arcs_list[ARC_BUFC_METADATA] =
6508 multilist_create(sizeof (arc_buf_hdr_t),
6509 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6510 arc_state_multilist_index_func);
6511 arc_mru->arcs_list[ARC_BUFC_DATA] =
6512 multilist_create(sizeof (arc_buf_hdr_t),
6513 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6514 arc_state_multilist_index_func);
6515 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
6516 multilist_create(sizeof (arc_buf_hdr_t),
6517 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6518 arc_state_multilist_index_func);
6519 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
6520 multilist_create(sizeof (arc_buf_hdr_t),
6521 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6522 arc_state_multilist_index_func);
6523 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
6524 multilist_create(sizeof (arc_buf_hdr_t),
6525 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6526 arc_state_multilist_index_func);
6527 arc_mfu->arcs_list[ARC_BUFC_DATA] =
6528 multilist_create(sizeof (arc_buf_hdr_t),
6529 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6530 arc_state_multilist_index_func);
6531 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
6532 multilist_create(sizeof (arc_buf_hdr_t),
6533 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6534 arc_state_multilist_index_func);
6535 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
6536 multilist_create(sizeof (arc_buf_hdr_t),
6537 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6538 arc_state_multilist_index_func);
6539 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
6540 multilist_create(sizeof (arc_buf_hdr_t),
6541 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6542 arc_state_multilist_index_func);
6543 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
6544 multilist_create(sizeof (arc_buf_hdr_t),
6545 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6546 arc_state_multilist_index_func);
6548 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6549 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6550 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6551 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6552 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6553 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6554 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6555 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6556 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6557 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6558 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6559 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6561 refcount_create(&arc_anon->arcs_size);
6562 refcount_create(&arc_mru->arcs_size);
6563 refcount_create(&arc_mru_ghost->arcs_size);
6564 refcount_create(&arc_mfu->arcs_size);
6565 refcount_create(&arc_mfu_ghost->arcs_size);
6566 refcount_create(&arc_l2c_only->arcs_size);
6568 aggsum_init(&arc_meta_used, 0);
6569 aggsum_init(&arc_size, 0);
6570 aggsum_init(&astat_data_size, 0);
6571 aggsum_init(&astat_metadata_size, 0);
6572 aggsum_init(&astat_hdr_size, 0);
6573 aggsum_init(&astat_other_size, 0);
6574 aggsum_init(&astat_l2_hdr_size, 0);
6578 arc_state_fini(void)
6580 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6581 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6582 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6583 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6584 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6585 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6586 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6587 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6588 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6589 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6590 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6591 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6593 refcount_destroy(&arc_anon->arcs_size);
6594 refcount_destroy(&arc_mru->arcs_size);
6595 refcount_destroy(&arc_mru_ghost->arcs_size);
6596 refcount_destroy(&arc_mfu->arcs_size);
6597 refcount_destroy(&arc_mfu_ghost->arcs_size);
6598 refcount_destroy(&arc_l2c_only->arcs_size);
6600 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
6601 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
6602 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
6603 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
6604 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
6605 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
6606 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
6607 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
6619 int i, prefetch_tunable_set = 0;
6622 * allmem is "all memory that we could possibly use".
6626 uint64_t allmem = ptob(physmem - swapfs_minfree);
6628 uint64_t allmem = (physmem * PAGESIZE) / 2;
6631 uint64_t allmem = kmem_size();
6635 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
6636 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
6637 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
6639 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
6640 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL);
6642 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */
6643 arc_c_min = MAX(allmem / 32, arc_abs_min);
6644 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */
6645 if (allmem >= 1 << 30)
6646 arc_c_max = allmem - (1 << 30);
6648 arc_c_max = arc_c_min;
6649 arc_c_max = MAX(allmem * 5 / 8, arc_c_max);
6652 * In userland, there's only the memory pressure that we artificially
6653 * create (see arc_available_memory()). Don't let arc_c get too
6654 * small, because it can cause transactions to be larger than
6655 * arc_c, causing arc_tempreserve_space() to fail.
6658 arc_c_min = arc_c_max / 2;
6663 * Allow the tunables to override our calculations if they are
6666 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) {
6667 arc_c_max = zfs_arc_max;
6668 arc_c_min = MIN(arc_c_min, arc_c_max);
6670 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max)
6671 arc_c_min = zfs_arc_min;
6675 arc_p = (arc_c >> 1);
6677 /* limit meta-data to 1/4 of the arc capacity */
6678 arc_meta_limit = arc_c_max / 4;
6682 * Metadata is stored in the kernel's heap. Don't let us
6683 * use more than half the heap for the ARC.
6686 arc_meta_limit = MIN(arc_meta_limit, uma_limit() / 2);
6688 arc_meta_limit = MIN(arc_meta_limit,
6689 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
6693 /* Allow the tunable to override if it is reasonable */
6694 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
6695 arc_meta_limit = zfs_arc_meta_limit;
6697 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
6698 arc_c_min = arc_meta_limit / 2;
6700 if (zfs_arc_meta_min > 0) {
6701 arc_meta_min = zfs_arc_meta_min;
6703 arc_meta_min = arc_c_min / 2;
6706 if (zfs_arc_grow_retry > 0)
6707 arc_grow_retry = zfs_arc_grow_retry;
6709 if (zfs_arc_shrink_shift > 0)
6710 arc_shrink_shift = zfs_arc_shrink_shift;
6712 if (zfs_arc_no_grow_shift > 0)
6713 arc_no_grow_shift = zfs_arc_no_grow_shift;
6715 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
6717 if (arc_no_grow_shift >= arc_shrink_shift)
6718 arc_no_grow_shift = arc_shrink_shift - 1;
6720 if (zfs_arc_p_min_shift > 0)
6721 arc_p_min_shift = zfs_arc_p_min_shift;
6723 /* if kmem_flags are set, lets try to use less memory */
6724 if (kmem_debugging())
6726 if (arc_c < arc_c_min)
6729 zfs_arc_min = arc_c_min;
6730 zfs_arc_max = arc_c_max;
6735 arc_reclaim_thread_exit = B_FALSE;
6736 arc_dnlc_evicts_thread_exit = FALSE;
6738 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
6739 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
6741 if (arc_ksp != NULL) {
6742 arc_ksp->ks_data = &arc_stats;
6743 arc_ksp->ks_update = arc_kstat_update;
6744 kstat_install(arc_ksp);
6747 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
6748 TS_RUN, minclsyspri);
6751 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
6752 EVENTHANDLER_PRI_FIRST);
6755 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0,
6756 TS_RUN, minclsyspri);
6762 * Calculate maximum amount of dirty data per pool.
6764 * If it has been set by /etc/system, take that.
6765 * Otherwise, use a percentage of physical memory defined by
6766 * zfs_dirty_data_max_percent (default 10%) with a cap at
6767 * zfs_dirty_data_max_max (default 4GB).
6769 if (zfs_dirty_data_max == 0) {
6770 zfs_dirty_data_max = ptob(physmem) *
6771 zfs_dirty_data_max_percent / 100;
6772 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
6773 zfs_dirty_data_max_max);
6777 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
6778 prefetch_tunable_set = 1;
6781 if (prefetch_tunable_set == 0) {
6782 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
6784 printf(" add \"vfs.zfs.prefetch_disable=0\" "
6785 "to /boot/loader.conf.\n");
6786 zfs_prefetch_disable = 1;
6789 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
6790 prefetch_tunable_set == 0) {
6791 printf("ZFS NOTICE: Prefetch is disabled by default if less "
6792 "than 4GB of RAM is present;\n"
6793 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
6794 "to /boot/loader.conf.\n");
6795 zfs_prefetch_disable = 1;
6798 /* Warn about ZFS memory and address space requirements. */
6799 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
6800 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
6801 "expect unstable behavior.\n");
6803 if (allmem < 512 * (1 << 20)) {
6804 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
6805 "expect unstable behavior.\n");
6806 printf(" Consider tuning vm.kmem_size and "
6807 "vm.kmem_size_max\n");
6808 printf(" in /boot/loader.conf.\n");
6817 if (arc_event_lowmem != NULL)
6818 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
6821 mutex_enter(&arc_reclaim_lock);
6822 arc_reclaim_thread_exit = B_TRUE;
6824 * The reclaim thread will set arc_reclaim_thread_exit back to
6825 * B_FALSE when it is finished exiting; we're waiting for that.
6827 while (arc_reclaim_thread_exit) {
6828 cv_signal(&arc_reclaim_thread_cv);
6829 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
6831 mutex_exit(&arc_reclaim_lock);
6833 /* Use B_TRUE to ensure *all* buffers are evicted */
6834 arc_flush(NULL, B_TRUE);
6836 mutex_enter(&arc_dnlc_evicts_lock);
6837 arc_dnlc_evicts_thread_exit = TRUE;
6839 * The user evicts thread will set arc_user_evicts_thread_exit
6840 * to FALSE when it is finished exiting; we're waiting for that.
6842 while (arc_dnlc_evicts_thread_exit) {
6843 cv_signal(&arc_dnlc_evicts_cv);
6844 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
6846 mutex_exit(&arc_dnlc_evicts_lock);
6850 if (arc_ksp != NULL) {
6851 kstat_delete(arc_ksp);
6855 mutex_destroy(&arc_reclaim_lock);
6856 cv_destroy(&arc_reclaim_thread_cv);
6857 cv_destroy(&arc_reclaim_waiters_cv);
6859 mutex_destroy(&arc_dnlc_evicts_lock);
6860 cv_destroy(&arc_dnlc_evicts_cv);
6865 ASSERT0(arc_loaned_bytes);
6871 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
6872 * It uses dedicated storage devices to hold cached data, which are populated
6873 * using large infrequent writes. The main role of this cache is to boost
6874 * the performance of random read workloads. The intended L2ARC devices
6875 * include short-stroked disks, solid state disks, and other media with
6876 * substantially faster read latency than disk.
6878 * +-----------------------+
6880 * +-----------------------+
6883 * l2arc_feed_thread() arc_read()
6887 * +---------------+ |
6889 * +---------------+ |
6894 * +-------+ +-------+
6896 * | cache | | cache |
6897 * +-------+ +-------+
6898 * +=========+ .-----.
6899 * : L2ARC : |-_____-|
6900 * : devices : | Disks |
6901 * +=========+ `-_____-'
6903 * Read requests are satisfied from the following sources, in order:
6906 * 2) vdev cache of L2ARC devices
6908 * 4) vdev cache of disks
6911 * Some L2ARC device types exhibit extremely slow write performance.
6912 * To accommodate for this there are some significant differences between
6913 * the L2ARC and traditional cache design:
6915 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
6916 * the ARC behave as usual, freeing buffers and placing headers on ghost
6917 * lists. The ARC does not send buffers to the L2ARC during eviction as
6918 * this would add inflated write latencies for all ARC memory pressure.
6920 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
6921 * It does this by periodically scanning buffers from the eviction-end of
6922 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
6923 * not already there. It scans until a headroom of buffers is satisfied,
6924 * which itself is a buffer for ARC eviction. If a compressible buffer is
6925 * found during scanning and selected for writing to an L2ARC device, we
6926 * temporarily boost scanning headroom during the next scan cycle to make
6927 * sure we adapt to compression effects (which might significantly reduce
6928 * the data volume we write to L2ARC). The thread that does this is
6929 * l2arc_feed_thread(), illustrated below; example sizes are included to
6930 * provide a better sense of ratio than this diagram:
6933 * +---------------------+----------+
6934 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
6935 * +---------------------+----------+ | o L2ARC eligible
6936 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
6937 * +---------------------+----------+ |
6938 * 15.9 Gbytes ^ 32 Mbytes |
6940 * l2arc_feed_thread()
6942 * l2arc write hand <--[oooo]--'
6946 * +==============================+
6947 * L2ARC dev |####|#|###|###| |####| ... |
6948 * +==============================+
6951 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
6952 * evicted, then the L2ARC has cached a buffer much sooner than it probably
6953 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
6954 * safe to say that this is an uncommon case, since buffers at the end of
6955 * the ARC lists have moved there due to inactivity.
6957 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
6958 * then the L2ARC simply misses copying some buffers. This serves as a
6959 * pressure valve to prevent heavy read workloads from both stalling the ARC
6960 * with waits and clogging the L2ARC with writes. This also helps prevent
6961 * the potential for the L2ARC to churn if it attempts to cache content too
6962 * quickly, such as during backups of the entire pool.
6964 * 5. After system boot and before the ARC has filled main memory, there are
6965 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
6966 * lists can remain mostly static. Instead of searching from tail of these
6967 * lists as pictured, the l2arc_feed_thread() will search from the list heads
6968 * for eligible buffers, greatly increasing its chance of finding them.
6970 * The L2ARC device write speed is also boosted during this time so that
6971 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
6972 * there are no L2ARC reads, and no fear of degrading read performance
6973 * through increased writes.
6975 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
6976 * the vdev queue can aggregate them into larger and fewer writes. Each
6977 * device is written to in a rotor fashion, sweeping writes through
6978 * available space then repeating.
6980 * 7. The L2ARC does not store dirty content. It never needs to flush
6981 * write buffers back to disk based storage.
6983 * 8. If an ARC buffer is written (and dirtied) which also exists in the
6984 * L2ARC, the now stale L2ARC buffer is immediately dropped.
6986 * The performance of the L2ARC can be tweaked by a number of tunables, which
6987 * may be necessary for different workloads:
6989 * l2arc_write_max max write bytes per interval
6990 * l2arc_write_boost extra write bytes during device warmup
6991 * l2arc_noprefetch skip caching prefetched buffers
6992 * l2arc_headroom number of max device writes to precache
6993 * l2arc_headroom_boost when we find compressed buffers during ARC
6994 * scanning, we multiply headroom by this
6995 * percentage factor for the next scan cycle,
6996 * since more compressed buffers are likely to
6998 * l2arc_feed_secs seconds between L2ARC writing
7000 * Tunables may be removed or added as future performance improvements are
7001 * integrated, and also may become zpool properties.
7003 * There are three key functions that control how the L2ARC warms up:
7005 * l2arc_write_eligible() check if a buffer is eligible to cache
7006 * l2arc_write_size() calculate how much to write
7007 * l2arc_write_interval() calculate sleep delay between writes
7009 * These three functions determine what to write, how much, and how quickly
7014 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
7017 * A buffer is *not* eligible for the L2ARC if it:
7018 * 1. belongs to a different spa.
7019 * 2. is already cached on the L2ARC.
7020 * 3. has an I/O in progress (it may be an incomplete read).
7021 * 4. is flagged not eligible (zfs property).
7023 if (hdr->b_spa != spa_guid) {
7024 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
7027 if (HDR_HAS_L2HDR(hdr)) {
7028 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
7031 if (HDR_IO_IN_PROGRESS(hdr)) {
7032 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
7035 if (!HDR_L2CACHE(hdr)) {
7036 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
7044 l2arc_write_size(void)
7049 * Make sure our globals have meaningful values in case the user
7052 size = l2arc_write_max;
7054 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
7055 "be greater than zero, resetting it to the default (%d)",
7057 size = l2arc_write_max = L2ARC_WRITE_SIZE;
7060 if (arc_warm == B_FALSE)
7061 size += l2arc_write_boost;
7068 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
7070 clock_t interval, next, now;
7073 * If the ARC lists are busy, increase our write rate; if the
7074 * lists are stale, idle back. This is achieved by checking
7075 * how much we previously wrote - if it was more than half of
7076 * what we wanted, schedule the next write much sooner.
7078 if (l2arc_feed_again && wrote > (wanted / 2))
7079 interval = (hz * l2arc_feed_min_ms) / 1000;
7081 interval = hz * l2arc_feed_secs;
7083 now = ddi_get_lbolt();
7084 next = MAX(now, MIN(now + interval, began + interval));
7090 * Cycle through L2ARC devices. This is how L2ARC load balances.
7091 * If a device is returned, this also returns holding the spa config lock.
7093 static l2arc_dev_t *
7094 l2arc_dev_get_next(void)
7096 l2arc_dev_t *first, *next = NULL;
7099 * Lock out the removal of spas (spa_namespace_lock), then removal
7100 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
7101 * both locks will be dropped and a spa config lock held instead.
7103 mutex_enter(&spa_namespace_lock);
7104 mutex_enter(&l2arc_dev_mtx);
7106 /* if there are no vdevs, there is nothing to do */
7107 if (l2arc_ndev == 0)
7111 next = l2arc_dev_last;
7113 /* loop around the list looking for a non-faulted vdev */
7115 next = list_head(l2arc_dev_list);
7117 next = list_next(l2arc_dev_list, next);
7119 next = list_head(l2arc_dev_list);
7122 /* if we have come back to the start, bail out */
7125 else if (next == first)
7128 } while (vdev_is_dead(next->l2ad_vdev));
7130 /* if we were unable to find any usable vdevs, return NULL */
7131 if (vdev_is_dead(next->l2ad_vdev))
7134 l2arc_dev_last = next;
7137 mutex_exit(&l2arc_dev_mtx);
7140 * Grab the config lock to prevent the 'next' device from being
7141 * removed while we are writing to it.
7144 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
7145 mutex_exit(&spa_namespace_lock);
7151 * Free buffers that were tagged for destruction.
7154 l2arc_do_free_on_write()
7157 l2arc_data_free_t *df, *df_prev;
7159 mutex_enter(&l2arc_free_on_write_mtx);
7160 buflist = l2arc_free_on_write;
7162 for (df = list_tail(buflist); df; df = df_prev) {
7163 df_prev = list_prev(buflist, df);
7164 ASSERT3P(df->l2df_abd, !=, NULL);
7165 abd_free(df->l2df_abd);
7166 list_remove(buflist, df);
7167 kmem_free(df, sizeof (l2arc_data_free_t));
7170 mutex_exit(&l2arc_free_on_write_mtx);
7174 * A write to a cache device has completed. Update all headers to allow
7175 * reads from these buffers to begin.
7178 l2arc_write_done(zio_t *zio)
7180 l2arc_write_callback_t *cb;
7183 arc_buf_hdr_t *head, *hdr, *hdr_prev;
7184 kmutex_t *hash_lock;
7185 int64_t bytes_dropped = 0;
7187 cb = zio->io_private;
7188 ASSERT3P(cb, !=, NULL);
7189 dev = cb->l2wcb_dev;
7190 ASSERT3P(dev, !=, NULL);
7191 head = cb->l2wcb_head;
7192 ASSERT3P(head, !=, NULL);
7193 buflist = &dev->l2ad_buflist;
7194 ASSERT3P(buflist, !=, NULL);
7195 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
7196 l2arc_write_callback_t *, cb);
7198 if (zio->io_error != 0)
7199 ARCSTAT_BUMP(arcstat_l2_writes_error);
7202 * All writes completed, or an error was hit.
7205 mutex_enter(&dev->l2ad_mtx);
7206 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7207 hdr_prev = list_prev(buflist, hdr);
7209 hash_lock = HDR_LOCK(hdr);
7212 * We cannot use mutex_enter or else we can deadlock
7213 * with l2arc_write_buffers (due to swapping the order
7214 * the hash lock and l2ad_mtx are taken).
7216 if (!mutex_tryenter(hash_lock)) {
7218 * Missed the hash lock. We must retry so we
7219 * don't leave the ARC_FLAG_L2_WRITING bit set.
7221 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7224 * We don't want to rescan the headers we've
7225 * already marked as having been written out, so
7226 * we reinsert the head node so we can pick up
7227 * where we left off.
7229 list_remove(buflist, head);
7230 list_insert_after(buflist, hdr, head);
7232 mutex_exit(&dev->l2ad_mtx);
7235 * We wait for the hash lock to become available
7236 * to try and prevent busy waiting, and increase
7237 * the chance we'll be able to acquire the lock
7238 * the next time around.
7240 mutex_enter(hash_lock);
7241 mutex_exit(hash_lock);
7246 * We could not have been moved into the arc_l2c_only
7247 * state while in-flight due to our ARC_FLAG_L2_WRITING
7248 * bit being set. Let's just ensure that's being enforced.
7250 ASSERT(HDR_HAS_L1HDR(hdr));
7252 if (zio->io_error != 0) {
7254 * Error - drop L2ARC entry.
7256 list_remove(buflist, hdr);
7258 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7260 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr));
7261 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
7263 bytes_dropped += arc_hdr_size(hdr);
7264 (void) refcount_remove_many(&dev->l2ad_alloc,
7265 arc_hdr_size(hdr), hdr);
7269 * Allow ARC to begin reads and ghost list evictions to
7272 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7274 mutex_exit(hash_lock);
7277 atomic_inc_64(&l2arc_writes_done);
7278 list_remove(buflist, head);
7279 ASSERT(!HDR_HAS_L1HDR(head));
7280 kmem_cache_free(hdr_l2only_cache, head);
7281 mutex_exit(&dev->l2ad_mtx);
7283 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7285 l2arc_do_free_on_write();
7287 kmem_free(cb, sizeof (l2arc_write_callback_t));
7291 * A read to a cache device completed. Validate buffer contents before
7292 * handing over to the regular ARC routines.
7295 l2arc_read_done(zio_t *zio)
7297 l2arc_read_callback_t *cb;
7299 kmutex_t *hash_lock;
7300 boolean_t valid_cksum;
7302 ASSERT3P(zio->io_vd, !=, NULL);
7303 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
7305 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
7307 cb = zio->io_private;
7308 ASSERT3P(cb, !=, NULL);
7309 hdr = cb->l2rcb_hdr;
7310 ASSERT3P(hdr, !=, NULL);
7312 hash_lock = HDR_LOCK(hdr);
7313 mutex_enter(hash_lock);
7314 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
7317 * If the data was read into a temporary buffer,
7318 * move it and free the buffer.
7320 if (cb->l2rcb_abd != NULL) {
7321 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
7322 if (zio->io_error == 0) {
7323 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd,
7328 * The following must be done regardless of whether
7329 * there was an error:
7330 * - free the temporary buffer
7331 * - point zio to the real ARC buffer
7332 * - set zio size accordingly
7333 * These are required because zio is either re-used for
7334 * an I/O of the block in the case of the error
7335 * or the zio is passed to arc_read_done() and it
7338 abd_free(cb->l2rcb_abd);
7339 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
7340 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
7343 ASSERT3P(zio->io_abd, !=, NULL);
7346 * Check this survived the L2ARC journey.
7348 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd);
7349 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
7350 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
7352 valid_cksum = arc_cksum_is_equal(hdr, zio);
7353 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
7354 mutex_exit(hash_lock);
7355 zio->io_private = hdr;
7358 mutex_exit(hash_lock);
7360 * Buffer didn't survive caching. Increment stats and
7361 * reissue to the original storage device.
7363 if (zio->io_error != 0) {
7364 ARCSTAT_BUMP(arcstat_l2_io_error);
7366 zio->io_error = SET_ERROR(EIO);
7369 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
7372 * If there's no waiter, issue an async i/o to the primary
7373 * storage now. If there *is* a waiter, the caller must
7374 * issue the i/o in a context where it's OK to block.
7376 if (zio->io_waiter == NULL) {
7377 zio_t *pio = zio_unique_parent(zio);
7379 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
7381 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
7382 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done,
7383 hdr, zio->io_priority, cb->l2rcb_flags,
7388 kmem_free(cb, sizeof (l2arc_read_callback_t));
7392 * This is the list priority from which the L2ARC will search for pages to
7393 * cache. This is used within loops (0..3) to cycle through lists in the
7394 * desired order. This order can have a significant effect on cache
7397 * Currently the metadata lists are hit first, MFU then MRU, followed by
7398 * the data lists. This function returns a locked list, and also returns
7401 static multilist_sublist_t *
7402 l2arc_sublist_lock(int list_num)
7404 multilist_t *ml = NULL;
7407 ASSERT(list_num >= 0 && list_num <= 3);
7411 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
7414 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
7417 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
7420 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
7425 * Return a randomly-selected sublist. This is acceptable
7426 * because the caller feeds only a little bit of data for each
7427 * call (8MB). Subsequent calls will result in different
7428 * sublists being selected.
7430 idx = multilist_get_random_index(ml);
7431 return (multilist_sublist_lock(ml, idx));
7435 * Evict buffers from the device write hand to the distance specified in
7436 * bytes. This distance may span populated buffers, it may span nothing.
7437 * This is clearing a region on the L2ARC device ready for writing.
7438 * If the 'all' boolean is set, every buffer is evicted.
7441 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
7444 arc_buf_hdr_t *hdr, *hdr_prev;
7445 kmutex_t *hash_lock;
7448 buflist = &dev->l2ad_buflist;
7450 if (!all && dev->l2ad_first) {
7452 * This is the first sweep through the device. There is
7458 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
7460 * When nearing the end of the device, evict to the end
7461 * before the device write hand jumps to the start.
7463 taddr = dev->l2ad_end;
7465 taddr = dev->l2ad_hand + distance;
7467 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
7468 uint64_t, taddr, boolean_t, all);
7471 mutex_enter(&dev->l2ad_mtx);
7472 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
7473 hdr_prev = list_prev(buflist, hdr);
7475 hash_lock = HDR_LOCK(hdr);
7478 * We cannot use mutex_enter or else we can deadlock
7479 * with l2arc_write_buffers (due to swapping the order
7480 * the hash lock and l2ad_mtx are taken).
7482 if (!mutex_tryenter(hash_lock)) {
7484 * Missed the hash lock. Retry.
7486 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
7487 mutex_exit(&dev->l2ad_mtx);
7488 mutex_enter(hash_lock);
7489 mutex_exit(hash_lock);
7494 * A header can't be on this list if it doesn't have L2 header.
7496 ASSERT(HDR_HAS_L2HDR(hdr));
7498 /* Ensure this header has finished being written. */
7499 ASSERT(!HDR_L2_WRITING(hdr));
7500 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
7502 if (!all && (hdr->b_l2hdr.b_daddr >= taddr ||
7503 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
7505 * We've evicted to the target address,
7506 * or the end of the device.
7508 mutex_exit(hash_lock);
7512 if (!HDR_HAS_L1HDR(hdr)) {
7513 ASSERT(!HDR_L2_READING(hdr));
7515 * This doesn't exist in the ARC. Destroy.
7516 * arc_hdr_destroy() will call list_remove()
7517 * and decrement arcstat_l2_lsize.
7519 arc_change_state(arc_anon, hdr, hash_lock);
7520 arc_hdr_destroy(hdr);
7522 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
7523 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
7525 * Invalidate issued or about to be issued
7526 * reads, since we may be about to write
7527 * over this location.
7529 if (HDR_L2_READING(hdr)) {
7530 ARCSTAT_BUMP(arcstat_l2_evict_reading);
7531 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
7534 arc_hdr_l2hdr_destroy(hdr);
7536 mutex_exit(hash_lock);
7538 mutex_exit(&dev->l2ad_mtx);
7542 * Find and write ARC buffers to the L2ARC device.
7544 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
7545 * for reading until they have completed writing.
7546 * The headroom_boost is an in-out parameter used to maintain headroom boost
7547 * state between calls to this function.
7549 * Returns the number of bytes actually written (which may be smaller than
7550 * the delta by which the device hand has changed due to alignment).
7553 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
7555 arc_buf_hdr_t *hdr, *hdr_prev, *head;
7556 uint64_t write_asize, write_psize, write_lsize, headroom;
7558 l2arc_write_callback_t *cb;
7560 uint64_t guid = spa_load_guid(spa);
7563 ASSERT3P(dev->l2ad_vdev, !=, NULL);
7566 write_lsize = write_asize = write_psize = 0;
7568 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
7569 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
7571 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
7573 * Copy buffers for L2ARC writing.
7575 for (try = 0; try <= 3; try++) {
7576 multilist_sublist_t *mls = l2arc_sublist_lock(try);
7577 uint64_t passed_sz = 0;
7579 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
7582 * L2ARC fast warmup.
7584 * Until the ARC is warm and starts to evict, read from the
7585 * head of the ARC lists rather than the tail.
7587 if (arc_warm == B_FALSE)
7588 hdr = multilist_sublist_head(mls);
7590 hdr = multilist_sublist_tail(mls);
7592 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
7594 headroom = target_sz * l2arc_headroom;
7595 if (zfs_compressed_arc_enabled)
7596 headroom = (headroom * l2arc_headroom_boost) / 100;
7598 for (; hdr; hdr = hdr_prev) {
7599 kmutex_t *hash_lock;
7601 if (arc_warm == B_FALSE)
7602 hdr_prev = multilist_sublist_next(mls, hdr);
7604 hdr_prev = multilist_sublist_prev(mls, hdr);
7605 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned,
7606 HDR_GET_LSIZE(hdr));
7608 hash_lock = HDR_LOCK(hdr);
7609 if (!mutex_tryenter(hash_lock)) {
7610 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
7612 * Skip this buffer rather than waiting.
7617 passed_sz += HDR_GET_LSIZE(hdr);
7618 if (passed_sz > headroom) {
7622 mutex_exit(hash_lock);
7623 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
7627 if (!l2arc_write_eligible(guid, hdr)) {
7628 mutex_exit(hash_lock);
7633 * We rely on the L1 portion of the header below, so
7634 * it's invalid for this header to have been evicted out
7635 * of the ghost cache, prior to being written out. The
7636 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
7638 ASSERT(HDR_HAS_L1HDR(hdr));
7640 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
7641 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7642 ASSERT3U(arc_hdr_size(hdr), >, 0);
7643 uint64_t psize = arc_hdr_size(hdr);
7644 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
7647 if ((write_asize + asize) > target_sz) {
7649 mutex_exit(hash_lock);
7650 ARCSTAT_BUMP(arcstat_l2_write_full);
7656 * Insert a dummy header on the buflist so
7657 * l2arc_write_done() can find where the
7658 * write buffers begin without searching.
7660 mutex_enter(&dev->l2ad_mtx);
7661 list_insert_head(&dev->l2ad_buflist, head);
7662 mutex_exit(&dev->l2ad_mtx);
7665 sizeof (l2arc_write_callback_t), KM_SLEEP);
7666 cb->l2wcb_dev = dev;
7667 cb->l2wcb_head = head;
7668 pio = zio_root(spa, l2arc_write_done, cb,
7670 ARCSTAT_BUMP(arcstat_l2_write_pios);
7673 hdr->b_l2hdr.b_dev = dev;
7674 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
7675 arc_hdr_set_flags(hdr,
7676 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
7678 mutex_enter(&dev->l2ad_mtx);
7679 list_insert_head(&dev->l2ad_buflist, hdr);
7680 mutex_exit(&dev->l2ad_mtx);
7682 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr);
7685 * Normally the L2ARC can use the hdr's data, but if
7686 * we're sharing data between the hdr and one of its
7687 * bufs, L2ARC needs its own copy of the data so that
7688 * the ZIO below can't race with the buf consumer.
7689 * Another case where we need to create a copy of the
7690 * data is when the buffer size is not device-aligned
7691 * and we need to pad the block to make it such.
7692 * That also keeps the clock hand suitably aligned.
7694 * To ensure that the copy will be available for the
7695 * lifetime of the ZIO and be cleaned up afterwards, we
7696 * add it to the l2arc_free_on_write queue.
7699 if (!HDR_SHARED_DATA(hdr) && psize == asize) {
7700 to_write = hdr->b_l1hdr.b_pabd;
7702 to_write = abd_alloc_for_io(asize,
7703 HDR_ISTYPE_METADATA(hdr));
7704 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize);
7705 if (asize != psize) {
7706 abd_zero_off(to_write, psize,
7709 l2arc_free_abd_on_write(to_write, asize,
7712 wzio = zio_write_phys(pio, dev->l2ad_vdev,
7713 hdr->b_l2hdr.b_daddr, asize, to_write,
7714 ZIO_CHECKSUM_OFF, NULL, hdr,
7715 ZIO_PRIORITY_ASYNC_WRITE,
7716 ZIO_FLAG_CANFAIL, B_FALSE);
7718 write_lsize += HDR_GET_LSIZE(hdr);
7719 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
7722 write_psize += psize;
7723 write_asize += asize;
7724 dev->l2ad_hand += asize;
7726 mutex_exit(hash_lock);
7728 (void) zio_nowait(wzio);
7731 multilist_sublist_unlock(mls);
7737 /* No buffers selected for writing? */
7739 ASSERT0(write_lsize);
7740 ASSERT(!HDR_HAS_L1HDR(head));
7741 kmem_cache_free(hdr_l2only_cache, head);
7745 ASSERT3U(write_psize, <=, target_sz);
7746 ARCSTAT_BUMP(arcstat_l2_writes_sent);
7747 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
7748 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
7749 ARCSTAT_INCR(arcstat_l2_psize, write_psize);
7750 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
7753 * Bump device hand to the device start if it is approaching the end.
7754 * l2arc_evict() will already have evicted ahead for this case.
7756 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
7757 dev->l2ad_hand = dev->l2ad_start;
7758 dev->l2ad_first = B_FALSE;
7761 dev->l2ad_writing = B_TRUE;
7762 (void) zio_wait(pio);
7763 dev->l2ad_writing = B_FALSE;
7765 return (write_asize);
7769 * This thread feeds the L2ARC at regular intervals. This is the beating
7770 * heart of the L2ARC.
7774 l2arc_feed_thread(void *unused __unused)
7779 uint64_t size, wrote;
7780 clock_t begin, next = ddi_get_lbolt();
7782 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
7784 mutex_enter(&l2arc_feed_thr_lock);
7786 while (l2arc_thread_exit == 0) {
7787 CALLB_CPR_SAFE_BEGIN(&cpr);
7788 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
7789 next - ddi_get_lbolt());
7790 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
7791 next = ddi_get_lbolt() + hz;
7794 * Quick check for L2ARC devices.
7796 mutex_enter(&l2arc_dev_mtx);
7797 if (l2arc_ndev == 0) {
7798 mutex_exit(&l2arc_dev_mtx);
7801 mutex_exit(&l2arc_dev_mtx);
7802 begin = ddi_get_lbolt();
7805 * This selects the next l2arc device to write to, and in
7806 * doing so the next spa to feed from: dev->l2ad_spa. This
7807 * will return NULL if there are now no l2arc devices or if
7808 * they are all faulted.
7810 * If a device is returned, its spa's config lock is also
7811 * held to prevent device removal. l2arc_dev_get_next()
7812 * will grab and release l2arc_dev_mtx.
7814 if ((dev = l2arc_dev_get_next()) == NULL)
7817 spa = dev->l2ad_spa;
7818 ASSERT3P(spa, !=, NULL);
7821 * If the pool is read-only then force the feed thread to
7822 * sleep a little longer.
7824 if (!spa_writeable(spa)) {
7825 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
7826 spa_config_exit(spa, SCL_L2ARC, dev);
7831 * Avoid contributing to memory pressure.
7833 if (arc_reclaim_needed()) {
7834 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
7835 spa_config_exit(spa, SCL_L2ARC, dev);
7839 ARCSTAT_BUMP(arcstat_l2_feeds);
7841 size = l2arc_write_size();
7844 * Evict L2ARC buffers that will be overwritten.
7846 l2arc_evict(dev, size, B_FALSE);
7849 * Write ARC buffers.
7851 wrote = l2arc_write_buffers(spa, dev, size);
7854 * Calculate interval between writes.
7856 next = l2arc_write_interval(begin, size, wrote);
7857 spa_config_exit(spa, SCL_L2ARC, dev);
7860 l2arc_thread_exit = 0;
7861 cv_broadcast(&l2arc_feed_thr_cv);
7862 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
7867 l2arc_vdev_present(vdev_t *vd)
7871 mutex_enter(&l2arc_dev_mtx);
7872 for (dev = list_head(l2arc_dev_list); dev != NULL;
7873 dev = list_next(l2arc_dev_list, dev)) {
7874 if (dev->l2ad_vdev == vd)
7877 mutex_exit(&l2arc_dev_mtx);
7879 return (dev != NULL);
7883 * Add a vdev for use by the L2ARC. By this point the spa has already
7884 * validated the vdev and opened it.
7887 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
7889 l2arc_dev_t *adddev;
7891 ASSERT(!l2arc_vdev_present(vd));
7893 vdev_ashift_optimize(vd);
7896 * Create a new l2arc device entry.
7898 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
7899 adddev->l2ad_spa = spa;
7900 adddev->l2ad_vdev = vd;
7901 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
7902 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
7903 adddev->l2ad_hand = adddev->l2ad_start;
7904 adddev->l2ad_first = B_TRUE;
7905 adddev->l2ad_writing = B_FALSE;
7907 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
7909 * This is a list of all ARC buffers that are still valid on the
7912 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
7913 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
7915 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
7916 refcount_create(&adddev->l2ad_alloc);
7919 * Add device to global list
7921 mutex_enter(&l2arc_dev_mtx);
7922 list_insert_head(l2arc_dev_list, adddev);
7923 atomic_inc_64(&l2arc_ndev);
7924 mutex_exit(&l2arc_dev_mtx);
7928 * Remove a vdev from the L2ARC.
7931 l2arc_remove_vdev(vdev_t *vd)
7933 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
7936 * Find the device by vdev
7938 mutex_enter(&l2arc_dev_mtx);
7939 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
7940 nextdev = list_next(l2arc_dev_list, dev);
7941 if (vd == dev->l2ad_vdev) {
7946 ASSERT3P(remdev, !=, NULL);
7949 * Remove device from global list
7951 list_remove(l2arc_dev_list, remdev);
7952 l2arc_dev_last = NULL; /* may have been invalidated */
7953 atomic_dec_64(&l2arc_ndev);
7954 mutex_exit(&l2arc_dev_mtx);
7957 * Clear all buflists and ARC references. L2ARC device flush.
7959 l2arc_evict(remdev, 0, B_TRUE);
7960 list_destroy(&remdev->l2ad_buflist);
7961 mutex_destroy(&remdev->l2ad_mtx);
7962 refcount_destroy(&remdev->l2ad_alloc);
7963 kmem_free(remdev, sizeof (l2arc_dev_t));
7969 l2arc_thread_exit = 0;
7971 l2arc_writes_sent = 0;
7972 l2arc_writes_done = 0;
7974 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
7975 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
7976 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
7977 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
7979 l2arc_dev_list = &L2ARC_dev_list;
7980 l2arc_free_on_write = &L2ARC_free_on_write;
7981 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
7982 offsetof(l2arc_dev_t, l2ad_node));
7983 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
7984 offsetof(l2arc_data_free_t, l2df_list_node));
7991 * This is called from dmu_fini(), which is called from spa_fini();
7992 * Because of this, we can assume that all l2arc devices have
7993 * already been removed when the pools themselves were removed.
7996 l2arc_do_free_on_write();
7998 mutex_destroy(&l2arc_feed_thr_lock);
7999 cv_destroy(&l2arc_feed_thr_cv);
8000 mutex_destroy(&l2arc_dev_mtx);
8001 mutex_destroy(&l2arc_free_on_write_mtx);
8003 list_destroy(l2arc_dev_list);
8004 list_destroy(l2arc_free_on_write);
8010 if (!(spa_mode_global & FWRITE))
8013 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
8014 TS_RUN, minclsyspri);
8020 if (!(spa_mode_global & FWRITE))
8023 mutex_enter(&l2arc_feed_thr_lock);
8024 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
8025 l2arc_thread_exit = 1;
8026 while (l2arc_thread_exit != 0)
8027 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
8028 mutex_exit(&l2arc_feed_thr_lock);
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