4 * The contents of this file are subject to the terms of the
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6 * You may not use this file except in compliance with the License.
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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) 2012, Joyent, Inc. All rights reserved.
24 * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
30 * DVA-based Adjustable Replacement Cache
32 * While much of the theory of operation used here is
33 * based on the self-tuning, low overhead replacement cache
34 * presented by Megiddo and Modha at FAST 2003, there are some
35 * significant differences:
37 * 1. The Megiddo and Modha model assumes any page is evictable.
38 * Pages in its cache cannot be "locked" into memory. This makes
39 * the eviction algorithm simple: evict the last page in the list.
40 * This also make the performance characteristics easy to reason
41 * about. Our cache is not so simple. At any given moment, some
42 * subset of the blocks in the cache are un-evictable because we
43 * have handed out a reference to them. Blocks are only evictable
44 * when there are no external references active. This makes
45 * eviction far more problematic: we choose to evict the evictable
46 * blocks that are the "lowest" in the list.
48 * There are times when it is not possible to evict the requested
49 * space. In these circumstances we are unable to adjust the cache
50 * size. To prevent the cache growing unbounded at these times we
51 * implement a "cache throttle" that slows the flow of new data
52 * into the cache until we can make space available.
54 * 2. The Megiddo and Modha model assumes a fixed cache size.
55 * Pages are evicted when the cache is full and there is a cache
56 * miss. Our model has a variable sized cache. It grows with
57 * high use, but also tries to react to memory pressure from the
58 * operating system: decreasing its size when system memory is
61 * 3. The Megiddo and Modha model assumes a fixed page size. All
62 * elements of the cache are therefore exactly the same size. So
63 * when adjusting the cache size following a cache miss, its simply
64 * a matter of choosing a single page to evict. In our model, we
65 * have variable sized cache blocks (rangeing from 512 bytes to
66 * 128K bytes). We therefore choose a set of blocks to evict to make
67 * space for a cache miss that approximates as closely as possible
68 * the space used by the new block.
70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 * by N. Megiddo & D. Modha, FAST 2003
77 * A new reference to a cache buffer can be obtained in two
78 * ways: 1) via a hash table lookup using the DVA as a key,
79 * or 2) via one of the ARC lists. The arc_read() interface
80 * uses method 1, while the internal ARC algorithms for
81 * adjusting the cache use method 2. We therefore provide two
82 * types of locks: 1) the hash table lock array, and 2) the
85 * Buffers do not have their own mutexes, rather they rely on the
86 * hash table mutexes for the bulk of their protection (i.e. most
87 * fields in the arc_buf_hdr_t are protected by these mutexes).
89 * buf_hash_find() returns the appropriate mutex (held) when it
90 * locates the requested buffer in the hash table. It returns
91 * NULL for the mutex if the buffer was not in the table.
93 * buf_hash_remove() expects the appropriate hash mutex to be
94 * already held before it is invoked.
96 * Each ARC state also has a mutex which is used to protect the
97 * buffer list associated with the state. When attempting to
98 * obtain a hash table lock while holding an ARC list lock you
99 * must use: mutex_tryenter() to avoid deadlock. Also note that
100 * the active state mutex must be held before the ghost state mutex.
102 * Note that the majority of the performance stats are manipulated
103 * with atomic operations.
105 * The L2ARC uses the l2ad_mtx on each vdev for the following:
107 * - L2ARC buflist creation
108 * - L2ARC buflist eviction
109 * - L2ARC write completion, which walks L2ARC buflists
110 * - ARC header destruction, as it removes from L2ARC buflists
111 * - ARC header release, as it removes from L2ARC buflists
117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
118 * This structure can point either to a block that is still in the cache or to
119 * one that is only accessible in an L2 ARC device, or it can provide
120 * information about a block that was recently evicted. If a block is
121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
122 * information to retrieve it from the L2ARC device. This information is
123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
124 * that is in this state cannot access the data directly.
126 * Blocks that are actively being referenced or have not been evicted
127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
128 * the arc_buf_hdr_t that will point to the data block in memory. A block can
129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
134 * ability to store the physical data (b_pabd) associated with the DVA of the
135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
136 * it will match its on-disk compression characteristics. This behavior can be
137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
138 * compressed ARC functionality is disabled, the b_pabd will point to an
139 * uncompressed version of the on-disk data.
141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
144 * consumer. The ARC will provide references to this data and will keep it
145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
146 * data block and will evict any arc_buf_t that is no longer referenced. The
147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
148 * "overhead_size" kstat.
150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
151 * compressed form. The typical case is that consumers will want uncompressed
152 * data, and when that happens a new data buffer is allocated where the data is
153 * decompressed for them to use. Currently the only consumer who wants
154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
156 * with the arc_buf_hdr_t.
158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
159 * first one is owned by a compressed send consumer (and therefore references
160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
161 * used by any other consumer (and has its own uncompressed copy of the data
176 * | b_buf +------------>+-----------+ arc_buf_t
177 * | b_pabd +-+ |b_next +---->+-----------+
178 * +-----------+ | |-----------| |b_next +-->NULL
179 * | |b_comp = T | +-----------+
180 * | |b_data +-+ |b_comp = F |
181 * | +-----------+ | |b_data +-+
182 * +->+------+ | +-----------+ |
184 * data | |<--------------+ | uncompressed
185 * +------+ compressed, | data
186 * shared +-->+------+
191 * When a consumer reads a block, the ARC must first look to see if the
192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
193 * arc_buf_t and either copies uncompressed data into a new data buffer from an
194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
196 * hdr is compressed and the desired compression characteristics of the
197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
200 * be anywhere in the hdr's list.
202 * The diagram below shows an example of an uncompressed ARC hdr that is
203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
204 * the last element in the buf list):
216 * | | arc_buf_t (shared)
217 * | b_buf +------------>+---------+ arc_buf_t
218 * | | |b_next +---->+---------+
219 * | b_pabd +-+ |---------| |b_next +-->NULL
220 * +-----------+ | | | +---------+
222 * | +---------+ | |b_data +-+
223 * +->+------+ | +---------+ |
225 * uncompressed | | | |
228 * | uncompressed | | |
231 * +---------------------------------+
233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
234 * since the physical block is about to be rewritten. The new data contents
235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
236 * it may compress the data before writing it to disk. The ARC will be called
237 * with the transformed data and will bcopy the transformed on-disk block into
238 * a newly allocated b_pabd. Writes are always done into buffers which have
239 * either been loaned (and hence are new and don't have other readers) or
240 * buffers which have been released (and hence have their own hdr, if there
241 * were originally other readers of the buf's original hdr). This ensures that
242 * the ARC only needs to update a single buf and its hdr after a write occurs.
244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
246 * that when compressed ARC is enabled that the L2ARC blocks are identical
247 * to the on-disk block in the main data pool. This provides a significant
248 * advantage since the ARC can leverage the bp's checksum when reading from the
249 * L2ARC to determine if the contents are valid. However, if the compressed
250 * ARC is disabled, then the L2ARC's block must be transformed to look
251 * like the physical block in the main data pool before comparing the
252 * checksum and determining its validity.
257 #include <sys/spa_impl.h>
258 #include <sys/zio_compress.h>
259 #include <sys/zio_checksum.h>
260 #include <sys/zfs_context.h>
262 #include <sys/refcount.h>
263 #include <sys/vdev.h>
264 #include <sys/vdev_impl.h>
265 #include <sys/dsl_pool.h>
266 #include <sys/zio_checksum.h>
267 #include <sys/multilist.h>
270 #include <sys/dnlc.h>
271 #include <sys/racct.h>
273 #include <sys/callb.h>
274 #include <sys/kstat.h>
275 #include <sys/trim_map.h>
276 #include <zfs_fletcher.h>
279 #include <machine/vmparam.h>
283 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
284 boolean_t arc_watch = B_FALSE;
289 static kmutex_t arc_reclaim_lock;
290 static kcondvar_t arc_reclaim_thread_cv;
291 static boolean_t arc_reclaim_thread_exit;
292 static kcondvar_t arc_reclaim_waiters_cv;
294 static kmutex_t arc_dnlc_evicts_lock;
295 static kcondvar_t arc_dnlc_evicts_cv;
296 static boolean_t arc_dnlc_evicts_thread_exit;
298 uint_t arc_reduce_dnlc_percent = 3;
301 * The number of headers to evict in arc_evict_state_impl() before
302 * dropping the sublist lock and evicting from another sublist. A lower
303 * value means we're more likely to evict the "correct" header (i.e. the
304 * oldest header in the arc state), but comes with higher overhead
305 * (i.e. more invocations of arc_evict_state_impl()).
307 int zfs_arc_evict_batch_limit = 10;
309 /* number of seconds before growing cache again */
310 static int arc_grow_retry = 60;
312 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
313 int zfs_arc_overflow_shift = 8;
315 /* shift of arc_c for calculating both min and max arc_p */
316 static int arc_p_min_shift = 4;
318 /* log2(fraction of arc to reclaim) */
319 static int arc_shrink_shift = 7;
322 * log2(fraction of ARC which must be free to allow growing).
323 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
324 * when reading a new block into the ARC, we will evict an equal-sized block
327 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
328 * we will still not allow it to grow.
330 int arc_no_grow_shift = 5;
334 * minimum lifespan of a prefetch block in clock ticks
335 * (initialized in arc_init())
337 static int arc_min_prefetch_lifespan;
340 * If this percent of memory is free, don't throttle.
342 int arc_lotsfree_percent = 10;
345 extern boolean_t zfs_prefetch_disable;
348 * The arc has filled available memory and has now warmed up.
350 static boolean_t arc_warm;
353 * These tunables are for performance analysis.
355 uint64_t zfs_arc_max;
356 uint64_t zfs_arc_min;
357 uint64_t zfs_arc_meta_limit = 0;
358 uint64_t zfs_arc_meta_min = 0;
359 int zfs_arc_grow_retry = 0;
360 int zfs_arc_shrink_shift = 0;
361 int zfs_arc_p_min_shift = 0;
362 uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
363 u_int zfs_arc_free_target = 0;
365 /* Absolute min for arc min / max is 16MB. */
366 static uint64_t arc_abs_min = 16 << 20;
368 boolean_t zfs_compressed_arc_enabled = B_TRUE;
370 static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS);
371 static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS);
372 static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS);
373 static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS);
375 #if defined(__FreeBSD__) && defined(_KERNEL)
377 arc_free_target_init(void *unused __unused)
380 zfs_arc_free_target = vm_pageout_wakeup_thresh;
382 SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
383 arc_free_target_init, NULL);
385 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
386 TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min);
387 TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
388 SYSCTL_DECL(_vfs_zfs);
389 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN,
390 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size");
391 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN,
392 0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size");
393 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
394 &zfs_arc_average_blocksize, 0,
395 "ARC average blocksize");
396 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
397 &arc_shrink_shift, 0,
398 "log2(fraction of arc to reclaim)");
399 SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN,
400 &zfs_compressed_arc_enabled, 0, "Enable compressed ARC");
403 * We don't have a tunable for arc_free_target due to the dependency on
404 * pagedaemon initialisation.
406 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
407 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
408 sysctl_vfs_zfs_arc_free_target, "IU",
409 "Desired number of free pages below which ARC triggers reclaim");
412 sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
417 val = zfs_arc_free_target;
418 err = sysctl_handle_int(oidp, &val, 0, req);
419 if (err != 0 || req->newptr == NULL)
424 if (val > vm_cnt.v_page_count)
427 zfs_arc_free_target = val;
433 * Must be declared here, before the definition of corresponding kstat
434 * macro which uses the same names will confuse the compiler.
436 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit,
437 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t),
438 sysctl_vfs_zfs_arc_meta_limit, "QU",
439 "ARC metadata limit");
443 * Note that buffers can be in one of 6 states:
444 * ARC_anon - anonymous (discussed below)
445 * ARC_mru - recently used, currently cached
446 * ARC_mru_ghost - recentely used, no longer in cache
447 * ARC_mfu - frequently used, currently cached
448 * ARC_mfu_ghost - frequently used, no longer in cache
449 * ARC_l2c_only - exists in L2ARC but not other states
450 * When there are no active references to the buffer, they are
451 * are linked onto a list in one of these arc states. These are
452 * the only buffers that can be evicted or deleted. Within each
453 * state there are multiple lists, one for meta-data and one for
454 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
455 * etc.) is tracked separately so that it can be managed more
456 * explicitly: favored over data, limited explicitly.
458 * Anonymous buffers are buffers that are not associated with
459 * a DVA. These are buffers that hold dirty block copies
460 * before they are written to stable storage. By definition,
461 * they are "ref'd" and are considered part of arc_mru
462 * that cannot be freed. Generally, they will aquire a DVA
463 * as they are written and migrate onto the arc_mru list.
465 * The ARC_l2c_only state is for buffers that are in the second
466 * level ARC but no longer in any of the ARC_m* lists. The second
467 * level ARC itself may also contain buffers that are in any of
468 * the ARC_m* states - meaning that a buffer can exist in two
469 * places. The reason for the ARC_l2c_only state is to keep the
470 * buffer header in the hash table, so that reads that hit the
471 * second level ARC benefit from these fast lookups.
474 typedef struct arc_state {
476 * list of evictable buffers
478 multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
480 * total amount of evictable data in this state
482 refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
484 * total amount of data in this state; this includes: evictable,
485 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
487 refcount_t arcs_size;
491 static arc_state_t ARC_anon;
492 static arc_state_t ARC_mru;
493 static arc_state_t ARC_mru_ghost;
494 static arc_state_t ARC_mfu;
495 static arc_state_t ARC_mfu_ghost;
496 static arc_state_t ARC_l2c_only;
498 typedef struct arc_stats {
499 kstat_named_t arcstat_hits;
500 kstat_named_t arcstat_misses;
501 kstat_named_t arcstat_demand_data_hits;
502 kstat_named_t arcstat_demand_data_misses;
503 kstat_named_t arcstat_demand_metadata_hits;
504 kstat_named_t arcstat_demand_metadata_misses;
505 kstat_named_t arcstat_prefetch_data_hits;
506 kstat_named_t arcstat_prefetch_data_misses;
507 kstat_named_t arcstat_prefetch_metadata_hits;
508 kstat_named_t arcstat_prefetch_metadata_misses;
509 kstat_named_t arcstat_mru_hits;
510 kstat_named_t arcstat_mru_ghost_hits;
511 kstat_named_t arcstat_mfu_hits;
512 kstat_named_t arcstat_mfu_ghost_hits;
513 kstat_named_t arcstat_allocated;
514 kstat_named_t arcstat_deleted;
516 * Number of buffers that could not be evicted because the hash lock
517 * was held by another thread. The lock may not necessarily be held
518 * by something using the same buffer, since hash locks are shared
519 * by multiple buffers.
521 kstat_named_t arcstat_mutex_miss;
523 * Number of buffers skipped because they have I/O in progress, are
524 * indrect prefetch buffers that have not lived long enough, or are
525 * not from the spa we're trying to evict from.
527 kstat_named_t arcstat_evict_skip;
529 * Number of times arc_evict_state() was unable to evict enough
530 * buffers to reach it's target amount.
532 kstat_named_t arcstat_evict_not_enough;
533 kstat_named_t arcstat_evict_l2_cached;
534 kstat_named_t arcstat_evict_l2_eligible;
535 kstat_named_t arcstat_evict_l2_ineligible;
536 kstat_named_t arcstat_evict_l2_skip;
537 kstat_named_t arcstat_hash_elements;
538 kstat_named_t arcstat_hash_elements_max;
539 kstat_named_t arcstat_hash_collisions;
540 kstat_named_t arcstat_hash_chains;
541 kstat_named_t arcstat_hash_chain_max;
542 kstat_named_t arcstat_p;
543 kstat_named_t arcstat_c;
544 kstat_named_t arcstat_c_min;
545 kstat_named_t arcstat_c_max;
546 kstat_named_t arcstat_size;
548 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
549 * Note that the compressed bytes may match the uncompressed bytes
550 * if the block is either not compressed or compressed arc is disabled.
552 kstat_named_t arcstat_compressed_size;
554 * Uncompressed size of the data stored in b_pabd. If compressed
555 * arc is disabled then this value will be identical to the stat
558 kstat_named_t arcstat_uncompressed_size;
560 * Number of bytes stored in all the arc_buf_t's. This is classified
561 * as "overhead" since this data is typically short-lived and will
562 * be evicted from the arc when it becomes unreferenced unless the
563 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
564 * values have been set (see comment in dbuf.c for more information).
566 kstat_named_t arcstat_overhead_size;
568 * Number of bytes consumed by internal ARC structures necessary
569 * for tracking purposes; these structures are not actually
570 * backed by ARC buffers. This includes arc_buf_hdr_t structures
571 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
572 * caches), and arc_buf_t structures (allocated via arc_buf_t
575 kstat_named_t arcstat_hdr_size;
577 * Number of bytes consumed by ARC buffers of type equal to
578 * ARC_BUFC_DATA. This is generally consumed by buffers backing
579 * on disk user data (e.g. plain file contents).
581 kstat_named_t arcstat_data_size;
583 * Number of bytes consumed by ARC buffers of type equal to
584 * ARC_BUFC_METADATA. This is generally consumed by buffers
585 * backing on disk data that is used for internal ZFS
586 * structures (e.g. ZAP, dnode, indirect blocks, etc).
588 kstat_named_t arcstat_metadata_size;
590 * Number of bytes consumed by various buffers and structures
591 * not actually backed with ARC buffers. This includes bonus
592 * buffers (allocated directly via zio_buf_* functions),
593 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
594 * cache), and dnode_t structures (allocated via dnode_t cache).
596 kstat_named_t arcstat_other_size;
598 * Total number of bytes consumed by ARC buffers residing in the
599 * arc_anon state. This includes *all* buffers in the arc_anon
600 * state; e.g. data, metadata, evictable, and unevictable buffers
601 * are all included in this value.
603 kstat_named_t arcstat_anon_size;
605 * Number of bytes consumed by ARC buffers that meet the
606 * following criteria: backing buffers of type ARC_BUFC_DATA,
607 * residing in the arc_anon state, and are eligible for eviction
608 * (e.g. have no outstanding holds on the buffer).
610 kstat_named_t arcstat_anon_evictable_data;
612 * Number of bytes consumed by ARC buffers that meet the
613 * following criteria: backing buffers of type ARC_BUFC_METADATA,
614 * residing in the arc_anon state, and are eligible for eviction
615 * (e.g. have no outstanding holds on the buffer).
617 kstat_named_t arcstat_anon_evictable_metadata;
619 * Total number of bytes consumed by ARC buffers residing in the
620 * arc_mru state. This includes *all* buffers in the arc_mru
621 * state; e.g. data, metadata, evictable, and unevictable buffers
622 * are all included in this value.
624 kstat_named_t arcstat_mru_size;
626 * Number of bytes consumed by ARC buffers that meet the
627 * following criteria: backing buffers of type ARC_BUFC_DATA,
628 * residing in the arc_mru state, and are eligible for eviction
629 * (e.g. have no outstanding holds on the buffer).
631 kstat_named_t arcstat_mru_evictable_data;
633 * Number of bytes consumed by ARC buffers that meet the
634 * following criteria: backing buffers of type ARC_BUFC_METADATA,
635 * residing in the arc_mru state, and are eligible for eviction
636 * (e.g. have no outstanding holds on the buffer).
638 kstat_named_t arcstat_mru_evictable_metadata;
640 * Total number of bytes that *would have been* consumed by ARC
641 * buffers in the arc_mru_ghost state. The key thing to note
642 * here, is the fact that this size doesn't actually indicate
643 * RAM consumption. The ghost lists only consist of headers and
644 * don't actually have ARC buffers linked off of these headers.
645 * Thus, *if* the headers had associated ARC buffers, these
646 * buffers *would have* consumed this number of bytes.
648 kstat_named_t arcstat_mru_ghost_size;
650 * Number of bytes that *would have been* consumed by ARC
651 * buffers that are eligible for eviction, of type
652 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
654 kstat_named_t arcstat_mru_ghost_evictable_data;
656 * Number of bytes that *would have been* consumed by ARC
657 * buffers that are eligible for eviction, of type
658 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
660 kstat_named_t arcstat_mru_ghost_evictable_metadata;
662 * Total number of bytes consumed by ARC buffers residing in the
663 * arc_mfu state. This includes *all* buffers in the arc_mfu
664 * state; e.g. data, metadata, evictable, and unevictable buffers
665 * are all included in this value.
667 kstat_named_t arcstat_mfu_size;
669 * Number of bytes consumed by ARC buffers that are eligible for
670 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
673 kstat_named_t arcstat_mfu_evictable_data;
675 * Number of bytes consumed by ARC buffers that are eligible for
676 * eviction, of type ARC_BUFC_METADATA, and reside in the
679 kstat_named_t arcstat_mfu_evictable_metadata;
681 * Total number of bytes that *would have been* consumed by ARC
682 * buffers in the arc_mfu_ghost state. See the comment above
683 * arcstat_mru_ghost_size for more details.
685 kstat_named_t arcstat_mfu_ghost_size;
687 * Number of bytes that *would have been* consumed by ARC
688 * buffers that are eligible for eviction, of type
689 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
691 kstat_named_t arcstat_mfu_ghost_evictable_data;
693 * Number of bytes that *would have been* consumed by ARC
694 * buffers that are eligible for eviction, of type
695 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
697 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
698 kstat_named_t arcstat_l2_hits;
699 kstat_named_t arcstat_l2_misses;
700 kstat_named_t arcstat_l2_feeds;
701 kstat_named_t arcstat_l2_rw_clash;
702 kstat_named_t arcstat_l2_read_bytes;
703 kstat_named_t arcstat_l2_write_bytes;
704 kstat_named_t arcstat_l2_writes_sent;
705 kstat_named_t arcstat_l2_writes_done;
706 kstat_named_t arcstat_l2_writes_error;
707 kstat_named_t arcstat_l2_writes_lock_retry;
708 kstat_named_t arcstat_l2_evict_lock_retry;
709 kstat_named_t arcstat_l2_evict_reading;
710 kstat_named_t arcstat_l2_evict_l1cached;
711 kstat_named_t arcstat_l2_free_on_write;
712 kstat_named_t arcstat_l2_abort_lowmem;
713 kstat_named_t arcstat_l2_cksum_bad;
714 kstat_named_t arcstat_l2_io_error;
715 kstat_named_t arcstat_l2_size;
716 kstat_named_t arcstat_l2_asize;
717 kstat_named_t arcstat_l2_hdr_size;
718 kstat_named_t arcstat_l2_write_trylock_fail;
719 kstat_named_t arcstat_l2_write_passed_headroom;
720 kstat_named_t arcstat_l2_write_spa_mismatch;
721 kstat_named_t arcstat_l2_write_in_l2;
722 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
723 kstat_named_t arcstat_l2_write_not_cacheable;
724 kstat_named_t arcstat_l2_write_full;
725 kstat_named_t arcstat_l2_write_buffer_iter;
726 kstat_named_t arcstat_l2_write_pios;
727 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
728 kstat_named_t arcstat_l2_write_buffer_list_iter;
729 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
730 kstat_named_t arcstat_memory_throttle_count;
731 kstat_named_t arcstat_meta_used;
732 kstat_named_t arcstat_meta_limit;
733 kstat_named_t arcstat_meta_max;
734 kstat_named_t arcstat_meta_min;
735 kstat_named_t arcstat_sync_wait_for_async;
736 kstat_named_t arcstat_demand_hit_predictive_prefetch;
739 static arc_stats_t arc_stats = {
740 { "hits", KSTAT_DATA_UINT64 },
741 { "misses", KSTAT_DATA_UINT64 },
742 { "demand_data_hits", KSTAT_DATA_UINT64 },
743 { "demand_data_misses", KSTAT_DATA_UINT64 },
744 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
745 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
746 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
747 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
748 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
749 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
750 { "mru_hits", KSTAT_DATA_UINT64 },
751 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
752 { "mfu_hits", KSTAT_DATA_UINT64 },
753 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
754 { "allocated", KSTAT_DATA_UINT64 },
755 { "deleted", KSTAT_DATA_UINT64 },
756 { "mutex_miss", KSTAT_DATA_UINT64 },
757 { "evict_skip", KSTAT_DATA_UINT64 },
758 { "evict_not_enough", KSTAT_DATA_UINT64 },
759 { "evict_l2_cached", KSTAT_DATA_UINT64 },
760 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
761 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
762 { "evict_l2_skip", KSTAT_DATA_UINT64 },
763 { "hash_elements", KSTAT_DATA_UINT64 },
764 { "hash_elements_max", KSTAT_DATA_UINT64 },
765 { "hash_collisions", KSTAT_DATA_UINT64 },
766 { "hash_chains", KSTAT_DATA_UINT64 },
767 { "hash_chain_max", KSTAT_DATA_UINT64 },
768 { "p", KSTAT_DATA_UINT64 },
769 { "c", KSTAT_DATA_UINT64 },
770 { "c_min", KSTAT_DATA_UINT64 },
771 { "c_max", KSTAT_DATA_UINT64 },
772 { "size", KSTAT_DATA_UINT64 },
773 { "compressed_size", KSTAT_DATA_UINT64 },
774 { "uncompressed_size", KSTAT_DATA_UINT64 },
775 { "overhead_size", KSTAT_DATA_UINT64 },
776 { "hdr_size", KSTAT_DATA_UINT64 },
777 { "data_size", KSTAT_DATA_UINT64 },
778 { "metadata_size", KSTAT_DATA_UINT64 },
779 { "other_size", KSTAT_DATA_UINT64 },
780 { "anon_size", KSTAT_DATA_UINT64 },
781 { "anon_evictable_data", KSTAT_DATA_UINT64 },
782 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
783 { "mru_size", KSTAT_DATA_UINT64 },
784 { "mru_evictable_data", KSTAT_DATA_UINT64 },
785 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
786 { "mru_ghost_size", KSTAT_DATA_UINT64 },
787 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
788 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
789 { "mfu_size", KSTAT_DATA_UINT64 },
790 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
791 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
792 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
793 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
794 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
795 { "l2_hits", KSTAT_DATA_UINT64 },
796 { "l2_misses", KSTAT_DATA_UINT64 },
797 { "l2_feeds", KSTAT_DATA_UINT64 },
798 { "l2_rw_clash", KSTAT_DATA_UINT64 },
799 { "l2_read_bytes", KSTAT_DATA_UINT64 },
800 { "l2_write_bytes", KSTAT_DATA_UINT64 },
801 { "l2_writes_sent", KSTAT_DATA_UINT64 },
802 { "l2_writes_done", KSTAT_DATA_UINT64 },
803 { "l2_writes_error", KSTAT_DATA_UINT64 },
804 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
805 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
806 { "l2_evict_reading", KSTAT_DATA_UINT64 },
807 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
808 { "l2_free_on_write", KSTAT_DATA_UINT64 },
809 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
810 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
811 { "l2_io_error", KSTAT_DATA_UINT64 },
812 { "l2_size", KSTAT_DATA_UINT64 },
813 { "l2_asize", KSTAT_DATA_UINT64 },
814 { "l2_hdr_size", KSTAT_DATA_UINT64 },
815 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
816 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
817 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
818 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
819 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
820 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
821 { "l2_write_full", KSTAT_DATA_UINT64 },
822 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
823 { "l2_write_pios", KSTAT_DATA_UINT64 },
824 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
825 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
826 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
827 { "memory_throttle_count", KSTAT_DATA_UINT64 },
828 { "arc_meta_used", KSTAT_DATA_UINT64 },
829 { "arc_meta_limit", KSTAT_DATA_UINT64 },
830 { "arc_meta_max", KSTAT_DATA_UINT64 },
831 { "arc_meta_min", KSTAT_DATA_UINT64 },
832 { "sync_wait_for_async", KSTAT_DATA_UINT64 },
833 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
836 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
838 #define ARCSTAT_INCR(stat, val) \
839 atomic_add_64(&arc_stats.stat.value.ui64, (val))
841 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
842 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
844 #define ARCSTAT_MAX(stat, val) { \
846 while ((val) > (m = arc_stats.stat.value.ui64) && \
847 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
851 #define ARCSTAT_MAXSTAT(stat) \
852 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
855 * We define a macro to allow ARC hits/misses to be easily broken down by
856 * two separate conditions, giving a total of four different subtypes for
857 * each of hits and misses (so eight statistics total).
859 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
862 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
864 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
868 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
870 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
875 static arc_state_t *arc_anon;
876 static arc_state_t *arc_mru;
877 static arc_state_t *arc_mru_ghost;
878 static arc_state_t *arc_mfu;
879 static arc_state_t *arc_mfu_ghost;
880 static arc_state_t *arc_l2c_only;
883 * There are several ARC variables that are critical to export as kstats --
884 * but we don't want to have to grovel around in the kstat whenever we wish to
885 * manipulate them. For these variables, we therefore define them to be in
886 * terms of the statistic variable. This assures that we are not introducing
887 * the possibility of inconsistency by having shadow copies of the variables,
888 * while still allowing the code to be readable.
890 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
891 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
892 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
893 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
894 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
895 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
896 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
897 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
898 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
900 /* compressed size of entire arc */
901 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
902 /* uncompressed size of entire arc */
903 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
904 /* number of bytes in the arc from arc_buf_t's */
905 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
907 static int arc_no_grow; /* Don't try to grow cache size */
908 static uint64_t arc_tempreserve;
909 static uint64_t arc_loaned_bytes;
911 typedef struct arc_callback arc_callback_t;
913 struct arc_callback {
915 arc_done_func_t *acb_done;
917 boolean_t acb_compressed;
918 zio_t *acb_zio_dummy;
919 arc_callback_t *acb_next;
922 typedef struct arc_write_callback arc_write_callback_t;
924 struct arc_write_callback {
926 arc_done_func_t *awcb_ready;
927 arc_done_func_t *awcb_children_ready;
928 arc_done_func_t *awcb_physdone;
929 arc_done_func_t *awcb_done;
934 * ARC buffers are separated into multiple structs as a memory saving measure:
935 * - Common fields struct, always defined, and embedded within it:
936 * - L2-only fields, always allocated but undefined when not in L2ARC
937 * - L1-only fields, only allocated when in L1ARC
939 * Buffer in L1 Buffer only in L2
940 * +------------------------+ +------------------------+
941 * | arc_buf_hdr_t | | arc_buf_hdr_t |
945 * +------------------------+ +------------------------+
946 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
947 * | (undefined if L1-only) | | |
948 * +------------------------+ +------------------------+
949 * | l1arc_buf_hdr_t |
954 * +------------------------+
956 * Because it's possible for the L2ARC to become extremely large, we can wind
957 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
958 * is minimized by only allocating the fields necessary for an L1-cached buffer
959 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
960 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
961 * words in pointers. arc_hdr_realloc() is used to switch a header between
962 * these two allocation states.
964 typedef struct l1arc_buf_hdr {
965 kmutex_t b_freeze_lock;
966 zio_cksum_t *b_freeze_cksum;
969 * Used for debugging with kmem_flags - by allocating and freeing
970 * b_thawed when the buffer is thawed, we get a record of the stack
971 * trace that thawed it.
978 /* for waiting on writes to complete */
982 /* protected by arc state mutex */
983 arc_state_t *b_state;
984 multilist_node_t b_arc_node;
986 /* updated atomically */
987 clock_t b_arc_access;
989 /* self protecting */
992 arc_callback_t *b_acb;
996 typedef struct l2arc_dev l2arc_dev_t;
998 typedef struct l2arc_buf_hdr {
999 /* protected by arc_buf_hdr mutex */
1000 l2arc_dev_t *b_dev; /* L2ARC device */
1001 uint64_t b_daddr; /* disk address, offset byte */
1003 list_node_t b_l2node;
1006 struct arc_buf_hdr {
1007 /* protected by hash lock */
1011 arc_buf_contents_t b_type;
1012 arc_buf_hdr_t *b_hash_next;
1013 arc_flags_t b_flags;
1016 * This field stores the size of the data buffer after
1017 * compression, and is set in the arc's zio completion handlers.
1018 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
1020 * While the block pointers can store up to 32MB in their psize
1021 * field, we can only store up to 32MB minus 512B. This is due
1022 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
1023 * a field of zeros represents 512B in the bp). We can't use a
1024 * bias of 1 since we need to reserve a psize of zero, here, to
1025 * represent holes and embedded blocks.
1027 * This isn't a problem in practice, since the maximum size of a
1028 * buffer is limited to 16MB, so we never need to store 32MB in
1029 * this field. Even in the upstream illumos code base, the
1030 * maximum size of a buffer is limited to 16MB.
1035 * This field stores the size of the data buffer before
1036 * compression, and cannot change once set. It is in units
1037 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
1039 uint16_t b_lsize; /* immutable */
1040 uint64_t b_spa; /* immutable */
1042 /* L2ARC fields. Undefined when not in L2ARC. */
1043 l2arc_buf_hdr_t b_l2hdr;
1044 /* L1ARC fields. Undefined when in l2arc_only state */
1045 l1arc_buf_hdr_t b_l1hdr;
1048 #if defined(__FreeBSD__) && defined(_KERNEL)
1050 sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS)
1055 val = arc_meta_limit;
1056 err = sysctl_handle_64(oidp, &val, 0, req);
1057 if (err != 0 || req->newptr == NULL)
1060 if (val <= 0 || val > arc_c_max)
1063 arc_meta_limit = val;
1068 sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS)
1074 err = sysctl_handle_64(oidp, &val, 0, req);
1075 if (err != 0 || req->newptr == NULL)
1078 if (zfs_arc_max == 0) {
1079 /* Loader tunable so blindly set */
1084 if (val < arc_abs_min || val > kmem_size())
1086 if (val < arc_c_min)
1088 if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit)
1094 arc_p = (arc_c >> 1);
1096 if (zfs_arc_meta_limit == 0) {
1097 /* limit meta-data to 1/4 of the arc capacity */
1098 arc_meta_limit = arc_c_max / 4;
1101 /* if kmem_flags are set, lets try to use less memory */
1102 if (kmem_debugging())
1105 zfs_arc_max = arc_c;
1111 sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS)
1117 err = sysctl_handle_64(oidp, &val, 0, req);
1118 if (err != 0 || req->newptr == NULL)
1121 if (zfs_arc_min == 0) {
1122 /* Loader tunable so blindly set */
1127 if (val < arc_abs_min || val > arc_c_max)
1132 if (zfs_arc_meta_min == 0)
1133 arc_meta_min = arc_c_min / 2;
1135 if (arc_c < arc_c_min)
1138 zfs_arc_min = arc_c_min;
1144 #define GHOST_STATE(state) \
1145 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
1146 (state) == arc_l2c_only)
1148 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
1149 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
1150 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
1151 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
1152 #define HDR_COMPRESSION_ENABLED(hdr) \
1153 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
1155 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
1156 #define HDR_L2_READING(hdr) \
1157 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
1158 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
1159 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
1160 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
1161 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
1162 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
1164 #define HDR_ISTYPE_METADATA(hdr) \
1165 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
1166 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
1168 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
1169 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
1171 /* For storing compression mode in b_flags */
1172 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
1174 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
1175 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
1176 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
1177 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
1179 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
1180 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
1181 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
1187 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
1188 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
1191 * Hash table routines
1194 #define HT_LOCK_PAD CACHE_LINE_SIZE
1199 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
1203 #define BUF_LOCKS 256
1204 typedef struct buf_hash_table {
1206 arc_buf_hdr_t **ht_table;
1207 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
1210 static buf_hash_table_t buf_hash_table;
1212 #define BUF_HASH_INDEX(spa, dva, birth) \
1213 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1214 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
1215 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
1216 #define HDR_LOCK(hdr) \
1217 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1219 uint64_t zfs_crc64_table[256];
1225 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1226 #define L2ARC_HEADROOM 2 /* num of writes */
1228 * If we discover during ARC scan any buffers to be compressed, we boost
1229 * our headroom for the next scanning cycle by this percentage multiple.
1231 #define L2ARC_HEADROOM_BOOST 200
1232 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1233 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1235 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1236 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1238 /* L2ARC Performance Tunables */
1239 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
1240 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
1241 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
1242 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1243 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1244 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
1245 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1246 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
1247 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
1249 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
1250 &l2arc_write_max, 0, "max write size");
1251 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
1252 &l2arc_write_boost, 0, "extra write during warmup");
1253 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
1254 &l2arc_headroom, 0, "number of dev writes");
1255 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
1256 &l2arc_feed_secs, 0, "interval seconds");
1257 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
1258 &l2arc_feed_min_ms, 0, "min interval milliseconds");
1260 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
1261 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
1262 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
1263 &l2arc_feed_again, 0, "turbo warmup");
1264 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
1265 &l2arc_norw, 0, "no reads during writes");
1267 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
1268 &ARC_anon.arcs_size.rc_count, 0, "size of anonymous state");
1269 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD,
1270 &ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1271 "size of anonymous state");
1272 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD,
1273 &ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1274 "size of anonymous state");
1276 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
1277 &ARC_mru.arcs_size.rc_count, 0, "size of mru state");
1278 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD,
1279 &ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1280 "size of metadata in mru state");
1281 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD,
1282 &ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1283 "size of data in mru state");
1285 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
1286 &ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state");
1287 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD,
1288 &ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1289 "size of metadata in mru ghost state");
1290 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD,
1291 &ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1292 "size of data in mru ghost state");
1294 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
1295 &ARC_mfu.arcs_size.rc_count, 0, "size of mfu state");
1296 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD,
1297 &ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1298 "size of metadata in mfu state");
1299 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD,
1300 &ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1301 "size of data in mfu state");
1303 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
1304 &ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state");
1305 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD,
1306 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
1307 "size of metadata in mfu ghost state");
1308 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD,
1309 &ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
1310 "size of data in mfu ghost state");
1312 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
1313 &ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state");
1319 vdev_t *l2ad_vdev; /* vdev */
1320 spa_t *l2ad_spa; /* spa */
1321 uint64_t l2ad_hand; /* next write location */
1322 uint64_t l2ad_start; /* first addr on device */
1323 uint64_t l2ad_end; /* last addr on device */
1324 boolean_t l2ad_first; /* first sweep through */
1325 boolean_t l2ad_writing; /* currently writing */
1326 kmutex_t l2ad_mtx; /* lock for buffer list */
1327 list_t l2ad_buflist; /* buffer list */
1328 list_node_t l2ad_node; /* device list node */
1329 refcount_t l2ad_alloc; /* allocated bytes */
1332 static list_t L2ARC_dev_list; /* device list */
1333 static list_t *l2arc_dev_list; /* device list pointer */
1334 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1335 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1336 static list_t L2ARC_free_on_write; /* free after write buf list */
1337 static list_t *l2arc_free_on_write; /* free after write list ptr */
1338 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1339 static uint64_t l2arc_ndev; /* number of devices */
1341 typedef struct l2arc_read_callback {
1342 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1343 blkptr_t l2rcb_bp; /* original blkptr */
1344 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1345 int l2rcb_flags; /* original flags */
1346 abd_t *l2rcb_abd; /* temporary buffer */
1347 } l2arc_read_callback_t;
1349 typedef struct l2arc_write_callback {
1350 l2arc_dev_t *l2wcb_dev; /* device info */
1351 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
1352 } l2arc_write_callback_t;
1354 typedef struct l2arc_data_free {
1355 /* protected by l2arc_free_on_write_mtx */
1358 arc_buf_contents_t l2df_type;
1359 list_node_t l2df_list_node;
1360 } l2arc_data_free_t;
1362 static kmutex_t l2arc_feed_thr_lock;
1363 static kcondvar_t l2arc_feed_thr_cv;
1364 static uint8_t l2arc_thread_exit;
1366 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1367 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1368 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1369 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1370 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1371 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1372 static void arc_hdr_free_pabd(arc_buf_hdr_t *);
1373 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *);
1374 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1375 static boolean_t arc_is_overflowing();
1376 static void arc_buf_watch(arc_buf_t *);
1378 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1379 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1380 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1381 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1383 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1384 static void l2arc_read_done(zio_t *);
1387 l2arc_trim(const arc_buf_hdr_t *hdr)
1389 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
1391 ASSERT(HDR_HAS_L2HDR(hdr));
1392 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
1394 if (HDR_GET_PSIZE(hdr) != 0) {
1395 trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr,
1396 HDR_GET_PSIZE(hdr), 0);
1401 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1403 uint8_t *vdva = (uint8_t *)dva;
1404 uint64_t crc = -1ULL;
1407 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
1409 for (i = 0; i < sizeof (dva_t); i++)
1410 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
1412 crc ^= (spa>>8) ^ birth;
1417 #define HDR_EMPTY(hdr) \
1418 ((hdr)->b_dva.dva_word[0] == 0 && \
1419 (hdr)->b_dva.dva_word[1] == 0)
1421 #define HDR_EQUAL(spa, dva, birth, hdr) \
1422 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1423 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1424 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1427 buf_discard_identity(arc_buf_hdr_t *hdr)
1429 hdr->b_dva.dva_word[0] = 0;
1430 hdr->b_dva.dva_word[1] = 0;
1434 static arc_buf_hdr_t *
1435 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1437 const dva_t *dva = BP_IDENTITY(bp);
1438 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1439 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1440 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1443 mutex_enter(hash_lock);
1444 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1445 hdr = hdr->b_hash_next) {
1446 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1451 mutex_exit(hash_lock);
1457 * Insert an entry into the hash table. If there is already an element
1458 * equal to elem in the hash table, then the already existing element
1459 * will be returned and the new element will not be inserted.
1460 * Otherwise returns NULL.
1461 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1463 static arc_buf_hdr_t *
1464 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1466 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1467 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1468 arc_buf_hdr_t *fhdr;
1471 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1472 ASSERT(hdr->b_birth != 0);
1473 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1475 if (lockp != NULL) {
1477 mutex_enter(hash_lock);
1479 ASSERT(MUTEX_HELD(hash_lock));
1482 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1483 fhdr = fhdr->b_hash_next, i++) {
1484 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1488 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1489 buf_hash_table.ht_table[idx] = hdr;
1490 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1492 /* collect some hash table performance data */
1494 ARCSTAT_BUMP(arcstat_hash_collisions);
1496 ARCSTAT_BUMP(arcstat_hash_chains);
1498 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1501 ARCSTAT_BUMP(arcstat_hash_elements);
1502 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1508 buf_hash_remove(arc_buf_hdr_t *hdr)
1510 arc_buf_hdr_t *fhdr, **hdrp;
1511 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1513 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1514 ASSERT(HDR_IN_HASH_TABLE(hdr));
1516 hdrp = &buf_hash_table.ht_table[idx];
1517 while ((fhdr = *hdrp) != hdr) {
1518 ASSERT3P(fhdr, !=, NULL);
1519 hdrp = &fhdr->b_hash_next;
1521 *hdrp = hdr->b_hash_next;
1522 hdr->b_hash_next = NULL;
1523 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1525 /* collect some hash table performance data */
1526 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1528 if (buf_hash_table.ht_table[idx] &&
1529 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1530 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1534 * Global data structures and functions for the buf kmem cache.
1536 static kmem_cache_t *hdr_full_cache;
1537 static kmem_cache_t *hdr_l2only_cache;
1538 static kmem_cache_t *buf_cache;
1545 kmem_free(buf_hash_table.ht_table,
1546 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1547 for (i = 0; i < BUF_LOCKS; i++)
1548 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1549 kmem_cache_destroy(hdr_full_cache);
1550 kmem_cache_destroy(hdr_l2only_cache);
1551 kmem_cache_destroy(buf_cache);
1555 * Constructor callback - called when the cache is empty
1556 * and a new buf is requested.
1560 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1562 arc_buf_hdr_t *hdr = vbuf;
1564 bzero(hdr, HDR_FULL_SIZE);
1565 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1566 refcount_create(&hdr->b_l1hdr.b_refcnt);
1567 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1568 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1569 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1576 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1578 arc_buf_hdr_t *hdr = vbuf;
1580 bzero(hdr, HDR_L2ONLY_SIZE);
1581 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1588 buf_cons(void *vbuf, void *unused, int kmflag)
1590 arc_buf_t *buf = vbuf;
1592 bzero(buf, sizeof (arc_buf_t));
1593 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1594 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1600 * Destructor callback - called when a cached buf is
1601 * no longer required.
1605 hdr_full_dest(void *vbuf, void *unused)
1607 arc_buf_hdr_t *hdr = vbuf;
1609 ASSERT(HDR_EMPTY(hdr));
1610 cv_destroy(&hdr->b_l1hdr.b_cv);
1611 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1612 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1613 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1614 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1619 hdr_l2only_dest(void *vbuf, void *unused)
1621 arc_buf_hdr_t *hdr = vbuf;
1623 ASSERT(HDR_EMPTY(hdr));
1624 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1629 buf_dest(void *vbuf, void *unused)
1631 arc_buf_t *buf = vbuf;
1633 mutex_destroy(&buf->b_evict_lock);
1634 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1638 * Reclaim callback -- invoked when memory is low.
1642 hdr_recl(void *unused)
1644 dprintf("hdr_recl called\n");
1646 * umem calls the reclaim func when we destroy the buf cache,
1647 * which is after we do arc_fini().
1650 cv_signal(&arc_reclaim_thread_cv);
1657 uint64_t hsize = 1ULL << 12;
1661 * The hash table is big enough to fill all of physical memory
1662 * with an average block size of zfs_arc_average_blocksize (default 8K).
1663 * By default, the table will take up
1664 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1666 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1669 buf_hash_table.ht_mask = hsize - 1;
1670 buf_hash_table.ht_table =
1671 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1672 if (buf_hash_table.ht_table == NULL) {
1673 ASSERT(hsize > (1ULL << 8));
1678 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1679 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1680 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1681 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1683 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1684 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1686 for (i = 0; i < 256; i++)
1687 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1688 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1690 for (i = 0; i < BUF_LOCKS; i++) {
1691 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1692 NULL, MUTEX_DEFAULT, NULL);
1697 * This is the size that the buf occupies in memory. If the buf is compressed,
1698 * it will correspond to the compressed size. You should use this method of
1699 * getting the buf size unless you explicitly need the logical size.
1702 arc_buf_size(arc_buf_t *buf)
1704 return (ARC_BUF_COMPRESSED(buf) ?
1705 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1709 arc_buf_lsize(arc_buf_t *buf)
1711 return (HDR_GET_LSIZE(buf->b_hdr));
1715 arc_get_compression(arc_buf_t *buf)
1717 return (ARC_BUF_COMPRESSED(buf) ?
1718 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1721 #define ARC_MINTIME (hz>>4) /* 62 ms */
1723 static inline boolean_t
1724 arc_buf_is_shared(arc_buf_t *buf)
1726 boolean_t shared = (buf->b_data != NULL &&
1727 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1728 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1729 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1730 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1731 IMPLY(shared, ARC_BUF_SHARED(buf));
1732 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1735 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1736 * already being shared" requirement prevents us from doing that.
1743 * Free the checksum associated with this header. If there is no checksum, this
1747 arc_cksum_free(arc_buf_hdr_t *hdr)
1749 ASSERT(HDR_HAS_L1HDR(hdr));
1750 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1751 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1752 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1753 hdr->b_l1hdr.b_freeze_cksum = NULL;
1755 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1759 * Return true iff at least one of the bufs on hdr is not compressed.
1762 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1764 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1765 if (!ARC_BUF_COMPRESSED(b)) {
1773 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1774 * matches the checksum that is stored in the hdr. If there is no checksum,
1775 * or if the buf is compressed, this is a no-op.
1778 arc_cksum_verify(arc_buf_t *buf)
1780 arc_buf_hdr_t *hdr = buf->b_hdr;
1783 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1786 if (ARC_BUF_COMPRESSED(buf)) {
1787 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1788 arc_hdr_has_uncompressed_buf(hdr));
1792 ASSERT(HDR_HAS_L1HDR(hdr));
1794 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1795 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1796 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1800 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1801 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1802 panic("buffer modified while frozen!");
1803 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1807 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1809 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1810 boolean_t valid_cksum;
1812 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1813 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1816 * We rely on the blkptr's checksum to determine if the block
1817 * is valid or not. When compressed arc is enabled, the l2arc
1818 * writes the block to the l2arc just as it appears in the pool.
1819 * This allows us to use the blkptr's checksum to validate the
1820 * data that we just read off of the l2arc without having to store
1821 * a separate checksum in the arc_buf_hdr_t. However, if compressed
1822 * arc is disabled, then the data written to the l2arc is always
1823 * uncompressed and won't match the block as it exists in the main
1824 * pool. When this is the case, we must first compress it if it is
1825 * compressed on the main pool before we can validate the checksum.
1827 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
1828 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1829 uint64_t lsize = HDR_GET_LSIZE(hdr);
1832 void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr));
1833 csize = zio_compress_data(compress, zio->io_abd, cbuf, lsize);
1835 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
1836 if (csize < HDR_GET_PSIZE(hdr)) {
1838 * Compressed blocks are always a multiple of the
1839 * smallest ashift in the pool. Ideally, we would
1840 * like to round up the csize to the next
1841 * spa_min_ashift but that value may have changed
1842 * since the block was last written. Instead,
1843 * we rely on the fact that the hdr's psize
1844 * was set to the psize of the block when it was
1845 * last written. We set the csize to that value
1846 * and zero out any part that should not contain
1849 bzero((char *)cbuf + csize, HDR_GET_PSIZE(hdr) - csize);
1850 csize = HDR_GET_PSIZE(hdr);
1852 zio_push_transform(zio, cbuf, csize, HDR_GET_PSIZE(hdr), NULL);
1856 * Block pointers always store the checksum for the logical data.
1857 * If the block pointer has the gang bit set, then the checksum
1858 * it represents is for the reconstituted data and not for an
1859 * individual gang member. The zio pipeline, however, must be able to
1860 * determine the checksum of each of the gang constituents so it
1861 * treats the checksum comparison differently than what we need
1862 * for l2arc blocks. This prevents us from using the
1863 * zio_checksum_error() interface directly. Instead we must call the
1864 * zio_checksum_error_impl() so that we can ensure the checksum is
1865 * generated using the correct checksum algorithm and accounts for the
1866 * logical I/O size and not just a gang fragment.
1868 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1869 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1870 zio->io_offset, NULL) == 0);
1871 zio_pop_transforms(zio);
1872 return (valid_cksum);
1876 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1877 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1878 * isn't modified later on. If buf is compressed or there is already a checksum
1879 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1882 arc_cksum_compute(arc_buf_t *buf)
1884 arc_buf_hdr_t *hdr = buf->b_hdr;
1886 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1889 ASSERT(HDR_HAS_L1HDR(hdr));
1891 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1892 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1893 ASSERT(arc_hdr_has_uncompressed_buf(hdr));
1894 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1896 } else if (ARC_BUF_COMPRESSED(buf)) {
1897 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1901 ASSERT(!ARC_BUF_COMPRESSED(buf));
1902 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1904 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1905 hdr->b_l1hdr.b_freeze_cksum);
1906 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1914 typedef struct procctl {
1922 arc_buf_unwatch(arc_buf_t *buf)
1929 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1930 ctl.prwatch.pr_size = 0;
1931 ctl.prwatch.pr_wflags = 0;
1932 result = write(arc_procfd, &ctl, sizeof (ctl));
1933 ASSERT3U(result, ==, sizeof (ctl));
1940 arc_buf_watch(arc_buf_t *buf)
1947 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1948 ctl.prwatch.pr_size = arc_buf_size(buf);
1949 ctl.prwatch.pr_wflags = WA_WRITE;
1950 result = write(arc_procfd, &ctl, sizeof (ctl));
1951 ASSERT3U(result, ==, sizeof (ctl));
1955 #endif /* illumos */
1957 static arc_buf_contents_t
1958 arc_buf_type(arc_buf_hdr_t *hdr)
1960 arc_buf_contents_t type;
1961 if (HDR_ISTYPE_METADATA(hdr)) {
1962 type = ARC_BUFC_METADATA;
1964 type = ARC_BUFC_DATA;
1966 VERIFY3U(hdr->b_type, ==, type);
1971 arc_is_metadata(arc_buf_t *buf)
1973 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
1977 arc_bufc_to_flags(arc_buf_contents_t type)
1981 /* metadata field is 0 if buffer contains normal data */
1983 case ARC_BUFC_METADATA:
1984 return (ARC_FLAG_BUFC_METADATA);
1988 panic("undefined ARC buffer type!");
1989 return ((uint32_t)-1);
1993 arc_buf_thaw(arc_buf_t *buf)
1995 arc_buf_hdr_t *hdr = buf->b_hdr;
1997 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
1998 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2000 arc_cksum_verify(buf);
2003 * Compressed buffers do not manipulate the b_freeze_cksum or
2004 * allocate b_thawed.
2006 if (ARC_BUF_COMPRESSED(buf)) {
2007 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2008 arc_hdr_has_uncompressed_buf(hdr));
2012 ASSERT(HDR_HAS_L1HDR(hdr));
2013 arc_cksum_free(hdr);
2015 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
2017 if (zfs_flags & ZFS_DEBUG_MODIFY) {
2018 if (hdr->b_l1hdr.b_thawed != NULL)
2019 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2020 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
2024 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
2027 arc_buf_unwatch(buf);
2032 arc_buf_freeze(arc_buf_t *buf)
2034 arc_buf_hdr_t *hdr = buf->b_hdr;
2035 kmutex_t *hash_lock;
2037 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
2040 if (ARC_BUF_COMPRESSED(buf)) {
2041 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
2042 arc_hdr_has_uncompressed_buf(hdr));
2046 hash_lock = HDR_LOCK(hdr);
2047 mutex_enter(hash_lock);
2049 ASSERT(HDR_HAS_L1HDR(hdr));
2050 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL ||
2051 hdr->b_l1hdr.b_state == arc_anon);
2052 arc_cksum_compute(buf);
2053 mutex_exit(hash_lock);
2057 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
2058 * the following functions should be used to ensure that the flags are
2059 * updated in a thread-safe way. When manipulating the flags either
2060 * the hash_lock must be held or the hdr must be undiscoverable. This
2061 * ensures that we're not racing with any other threads when updating
2065 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2067 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2068 hdr->b_flags |= flags;
2072 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
2074 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2075 hdr->b_flags &= ~flags;
2079 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
2080 * done in a special way since we have to clear and set bits
2081 * at the same time. Consumers that wish to set the compression bits
2082 * must use this function to ensure that the flags are updated in
2083 * thread-safe manner.
2086 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
2088 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2091 * Holes and embedded blocks will always have a psize = 0 so
2092 * we ignore the compression of the blkptr and set the
2093 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
2094 * Holes and embedded blocks remain anonymous so we don't
2095 * want to uncompress them. Mark them as uncompressed.
2097 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
2098 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2099 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
2100 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
2101 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
2103 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
2104 HDR_SET_COMPRESS(hdr, cmp);
2105 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
2106 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
2111 * Looks for another buf on the same hdr which has the data decompressed, copies
2112 * from it, and returns true. If no such buf exists, returns false.
2115 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
2117 arc_buf_hdr_t *hdr = buf->b_hdr;
2118 boolean_t copied = B_FALSE;
2120 ASSERT(HDR_HAS_L1HDR(hdr));
2121 ASSERT3P(buf->b_data, !=, NULL);
2122 ASSERT(!ARC_BUF_COMPRESSED(buf));
2124 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
2125 from = from->b_next) {
2126 /* can't use our own data buffer */
2131 if (!ARC_BUF_COMPRESSED(from)) {
2132 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
2139 * There were no decompressed bufs, so there should not be a
2140 * checksum on the hdr either.
2142 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
2148 * Given a buf that has a data buffer attached to it, this function will
2149 * efficiently fill the buf with data of the specified compression setting from
2150 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
2151 * are already sharing a data buf, no copy is performed.
2153 * If the buf is marked as compressed but uncompressed data was requested, this
2154 * will allocate a new data buffer for the buf, remove that flag, and fill the
2155 * buf with uncompressed data. You can't request a compressed buf on a hdr with
2156 * uncompressed data, and (since we haven't added support for it yet) if you
2157 * want compressed data your buf must already be marked as compressed and have
2158 * the correct-sized data buffer.
2161 arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
2163 arc_buf_hdr_t *hdr = buf->b_hdr;
2164 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
2165 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
2167 ASSERT3P(buf->b_data, !=, NULL);
2168 IMPLY(compressed, hdr_compressed);
2169 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
2171 if (hdr_compressed == compressed) {
2172 if (!arc_buf_is_shared(buf)) {
2173 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
2177 ASSERT(hdr_compressed);
2178 ASSERT(!compressed);
2179 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
2182 * If the buf is sharing its data with the hdr, unlink it and
2183 * allocate a new data buffer for the buf.
2185 if (arc_buf_is_shared(buf)) {
2186 ASSERT(ARC_BUF_COMPRESSED(buf));
2188 /* We need to give the buf it's own b_data */
2189 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2191 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2192 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2194 /* Previously overhead was 0; just add new overhead */
2195 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
2196 } else if (ARC_BUF_COMPRESSED(buf)) {
2197 /* We need to reallocate the buf's b_data */
2198 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
2201 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
2203 /* We increased the size of b_data; update overhead */
2204 ARCSTAT_INCR(arcstat_overhead_size,
2205 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
2209 * Regardless of the buf's previous compression settings, it
2210 * should not be compressed at the end of this function.
2212 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
2215 * Try copying the data from another buf which already has a
2216 * decompressed version. If that's not possible, it's time to
2217 * bite the bullet and decompress the data from the hdr.
2219 if (arc_buf_try_copy_decompressed_data(buf)) {
2220 /* Skip byteswapping and checksumming (already done) */
2221 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
2224 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
2225 hdr->b_l1hdr.b_pabd, buf->b_data,
2226 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2229 * Absent hardware errors or software bugs, this should
2230 * be impossible, but log it anyway so we can debug it.
2234 "hdr %p, compress %d, psize %d, lsize %d",
2235 hdr, HDR_GET_COMPRESS(hdr),
2236 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2237 return (SET_ERROR(EIO));
2242 /* Byteswap the buf's data if necessary */
2243 if (bswap != DMU_BSWAP_NUMFUNCS) {
2244 ASSERT(!HDR_SHARED_DATA(hdr));
2245 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2246 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2249 /* Compute the hdr's checksum if necessary */
2250 arc_cksum_compute(buf);
2256 arc_decompress(arc_buf_t *buf)
2258 return (arc_buf_fill(buf, B_FALSE));
2262 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
2265 arc_hdr_size(arc_buf_hdr_t *hdr)
2269 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
2270 HDR_GET_PSIZE(hdr) > 0) {
2271 size = HDR_GET_PSIZE(hdr);
2273 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
2274 size = HDR_GET_LSIZE(hdr);
2280 * Increment the amount of evictable space in the arc_state_t's refcount.
2281 * We account for the space used by the hdr and the arc buf individually
2282 * so that we can add and remove them from the refcount individually.
2285 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2287 arc_buf_contents_t type = arc_buf_type(hdr);
2289 ASSERT(HDR_HAS_L1HDR(hdr));
2291 if (GHOST_STATE(state)) {
2292 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2293 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2294 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2295 (void) refcount_add_many(&state->arcs_esize[type],
2296 HDR_GET_LSIZE(hdr), hdr);
2300 ASSERT(!GHOST_STATE(state));
2301 if (hdr->b_l1hdr.b_pabd != NULL) {
2302 (void) refcount_add_many(&state->arcs_esize[type],
2303 arc_hdr_size(hdr), hdr);
2305 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2306 buf = buf->b_next) {
2307 if (arc_buf_is_shared(buf))
2309 (void) refcount_add_many(&state->arcs_esize[type],
2310 arc_buf_size(buf), buf);
2315 * Decrement the amount of evictable space in the arc_state_t's refcount.
2316 * We account for the space used by the hdr and the arc buf individually
2317 * so that we can add and remove them from the refcount individually.
2320 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2322 arc_buf_contents_t type = arc_buf_type(hdr);
2324 ASSERT(HDR_HAS_L1HDR(hdr));
2326 if (GHOST_STATE(state)) {
2327 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2328 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2329 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2330 (void) refcount_remove_many(&state->arcs_esize[type],
2331 HDR_GET_LSIZE(hdr), hdr);
2335 ASSERT(!GHOST_STATE(state));
2336 if (hdr->b_l1hdr.b_pabd != NULL) {
2337 (void) refcount_remove_many(&state->arcs_esize[type],
2338 arc_hdr_size(hdr), hdr);
2340 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2341 buf = buf->b_next) {
2342 if (arc_buf_is_shared(buf))
2344 (void) refcount_remove_many(&state->arcs_esize[type],
2345 arc_buf_size(buf), buf);
2350 * Add a reference to this hdr indicating that someone is actively
2351 * referencing that memory. When the refcount transitions from 0 to 1,
2352 * we remove it from the respective arc_state_t list to indicate that
2353 * it is not evictable.
2356 add_reference(arc_buf_hdr_t *hdr, void *tag)
2358 ASSERT(HDR_HAS_L1HDR(hdr));
2359 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2360 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2361 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2362 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2365 arc_state_t *state = hdr->b_l1hdr.b_state;
2367 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2368 (state != arc_anon)) {
2369 /* We don't use the L2-only state list. */
2370 if (state != arc_l2c_only) {
2371 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2373 arc_evictable_space_decrement(hdr, state);
2375 /* remove the prefetch flag if we get a reference */
2376 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2381 * Remove a reference from this hdr. When the reference transitions from
2382 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2383 * list making it eligible for eviction.
2386 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2389 arc_state_t *state = hdr->b_l1hdr.b_state;
2391 ASSERT(HDR_HAS_L1HDR(hdr));
2392 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2393 ASSERT(!GHOST_STATE(state));
2396 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2397 * check to prevent usage of the arc_l2c_only list.
2399 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2400 (state != arc_anon)) {
2401 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2402 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2403 arc_evictable_space_increment(hdr, state);
2409 * Move the supplied buffer to the indicated state. The hash lock
2410 * for the buffer must be held by the caller.
2413 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2414 kmutex_t *hash_lock)
2416 arc_state_t *old_state;
2419 boolean_t update_old, update_new;
2420 arc_buf_contents_t buftype = arc_buf_type(hdr);
2423 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2424 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2425 * L1 hdr doesn't always exist when we change state to arc_anon before
2426 * destroying a header, in which case reallocating to add the L1 hdr is
2429 if (HDR_HAS_L1HDR(hdr)) {
2430 old_state = hdr->b_l1hdr.b_state;
2431 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
2432 bufcnt = hdr->b_l1hdr.b_bufcnt;
2433 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL);
2435 old_state = arc_l2c_only;
2438 update_old = B_FALSE;
2440 update_new = update_old;
2442 ASSERT(MUTEX_HELD(hash_lock));
2443 ASSERT3P(new_state, !=, old_state);
2444 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2445 ASSERT(old_state != arc_anon || bufcnt <= 1);
2448 * If this buffer is evictable, transfer it from the
2449 * old state list to the new state list.
2452 if (old_state != arc_anon && old_state != arc_l2c_only) {
2453 ASSERT(HDR_HAS_L1HDR(hdr));
2454 multilist_remove(old_state->arcs_list[buftype], hdr);
2456 if (GHOST_STATE(old_state)) {
2458 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2459 update_old = B_TRUE;
2461 arc_evictable_space_decrement(hdr, old_state);
2463 if (new_state != arc_anon && new_state != arc_l2c_only) {
2466 * An L1 header always exists here, since if we're
2467 * moving to some L1-cached state (i.e. not l2c_only or
2468 * anonymous), we realloc the header to add an L1hdr
2471 ASSERT(HDR_HAS_L1HDR(hdr));
2472 multilist_insert(new_state->arcs_list[buftype], hdr);
2474 if (GHOST_STATE(new_state)) {
2476 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2477 update_new = B_TRUE;
2479 arc_evictable_space_increment(hdr, new_state);
2483 ASSERT(!HDR_EMPTY(hdr));
2484 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2485 buf_hash_remove(hdr);
2487 /* adjust state sizes (ignore arc_l2c_only) */
2489 if (update_new && new_state != arc_l2c_only) {
2490 ASSERT(HDR_HAS_L1HDR(hdr));
2491 if (GHOST_STATE(new_state)) {
2495 * When moving a header to a ghost state, we first
2496 * remove all arc buffers. Thus, we'll have a
2497 * bufcnt of zero, and no arc buffer to use for
2498 * the reference. As a result, we use the arc
2499 * header pointer for the reference.
2501 (void) refcount_add_many(&new_state->arcs_size,
2502 HDR_GET_LSIZE(hdr), hdr);
2503 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2505 uint32_t buffers = 0;
2508 * Each individual buffer holds a unique reference,
2509 * thus we must remove each of these references one
2512 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2513 buf = buf->b_next) {
2514 ASSERT3U(bufcnt, !=, 0);
2518 * When the arc_buf_t is sharing the data
2519 * block with the hdr, the owner of the
2520 * reference belongs to the hdr. Only
2521 * add to the refcount if the arc_buf_t is
2524 if (arc_buf_is_shared(buf))
2527 (void) refcount_add_many(&new_state->arcs_size,
2528 arc_buf_size(buf), buf);
2530 ASSERT3U(bufcnt, ==, buffers);
2532 if (hdr->b_l1hdr.b_pabd != NULL) {
2533 (void) refcount_add_many(&new_state->arcs_size,
2534 arc_hdr_size(hdr), hdr);
2536 ASSERT(GHOST_STATE(old_state));
2541 if (update_old && old_state != arc_l2c_only) {
2542 ASSERT(HDR_HAS_L1HDR(hdr));
2543 if (GHOST_STATE(old_state)) {
2545 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2548 * When moving a header off of a ghost state,
2549 * the header will not contain any arc buffers.
2550 * We use the arc header pointer for the reference
2551 * which is exactly what we did when we put the
2552 * header on the ghost state.
2555 (void) refcount_remove_many(&old_state->arcs_size,
2556 HDR_GET_LSIZE(hdr), hdr);
2558 uint32_t buffers = 0;
2561 * Each individual buffer holds a unique reference,
2562 * thus we must remove each of these references one
2565 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2566 buf = buf->b_next) {
2567 ASSERT3U(bufcnt, !=, 0);
2571 * When the arc_buf_t is sharing the data
2572 * block with the hdr, the owner of the
2573 * reference belongs to the hdr. Only
2574 * add to the refcount if the arc_buf_t is
2577 if (arc_buf_is_shared(buf))
2580 (void) refcount_remove_many(
2581 &old_state->arcs_size, arc_buf_size(buf),
2584 ASSERT3U(bufcnt, ==, buffers);
2585 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2586 (void) refcount_remove_many(
2587 &old_state->arcs_size, arc_hdr_size(hdr), hdr);
2591 if (HDR_HAS_L1HDR(hdr))
2592 hdr->b_l1hdr.b_state = new_state;
2595 * L2 headers should never be on the L2 state list since they don't
2596 * have L1 headers allocated.
2598 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2599 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2603 arc_space_consume(uint64_t space, arc_space_type_t type)
2605 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2608 case ARC_SPACE_DATA:
2609 ARCSTAT_INCR(arcstat_data_size, space);
2611 case ARC_SPACE_META:
2612 ARCSTAT_INCR(arcstat_metadata_size, space);
2614 case ARC_SPACE_OTHER:
2615 ARCSTAT_INCR(arcstat_other_size, space);
2617 case ARC_SPACE_HDRS:
2618 ARCSTAT_INCR(arcstat_hdr_size, space);
2620 case ARC_SPACE_L2HDRS:
2621 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
2625 if (type != ARC_SPACE_DATA)
2626 ARCSTAT_INCR(arcstat_meta_used, space);
2628 atomic_add_64(&arc_size, space);
2632 arc_space_return(uint64_t space, arc_space_type_t type)
2634 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2637 case ARC_SPACE_DATA:
2638 ARCSTAT_INCR(arcstat_data_size, -space);
2640 case ARC_SPACE_META:
2641 ARCSTAT_INCR(arcstat_metadata_size, -space);
2643 case ARC_SPACE_OTHER:
2644 ARCSTAT_INCR(arcstat_other_size, -space);
2646 case ARC_SPACE_HDRS:
2647 ARCSTAT_INCR(arcstat_hdr_size, -space);
2649 case ARC_SPACE_L2HDRS:
2650 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
2654 if (type != ARC_SPACE_DATA) {
2655 ASSERT(arc_meta_used >= space);
2656 if (arc_meta_max < arc_meta_used)
2657 arc_meta_max = arc_meta_used;
2658 ARCSTAT_INCR(arcstat_meta_used, -space);
2661 ASSERT(arc_size >= space);
2662 atomic_add_64(&arc_size, -space);
2666 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2667 * with the hdr's b_pabd.
2670 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2673 * The criteria for sharing a hdr's data are:
2674 * 1. the hdr's compression matches the buf's compression
2675 * 2. the hdr doesn't need to be byteswapped
2676 * 3. the hdr isn't already being shared
2677 * 4. the buf is either compressed or it is the last buf in the hdr list
2679 * Criterion #4 maintains the invariant that shared uncompressed
2680 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2681 * might ask, "if a compressed buf is allocated first, won't that be the
2682 * last thing in the list?", but in that case it's impossible to create
2683 * a shared uncompressed buf anyway (because the hdr must be compressed
2684 * to have the compressed buf). You might also think that #3 is
2685 * sufficient to make this guarantee, however it's possible
2686 * (specifically in the rare L2ARC write race mentioned in
2687 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2688 * is sharable, but wasn't at the time of its allocation. Rather than
2689 * allow a new shared uncompressed buf to be created and then shuffle
2690 * the list around to make it the last element, this simply disallows
2691 * sharing if the new buf isn't the first to be added.
2693 ASSERT3P(buf->b_hdr, ==, hdr);
2694 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
2695 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2696 return (buf_compressed == hdr_compressed &&
2697 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2698 !HDR_SHARED_DATA(hdr) &&
2699 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2703 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2704 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2705 * copy was made successfully, or an error code otherwise.
2708 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
2709 boolean_t fill, arc_buf_t **ret)
2713 ASSERT(HDR_HAS_L1HDR(hdr));
2714 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2715 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2716 hdr->b_type == ARC_BUFC_METADATA);
2717 ASSERT3P(ret, !=, NULL);
2718 ASSERT3P(*ret, ==, NULL);
2720 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2723 buf->b_next = hdr->b_l1hdr.b_buf;
2726 add_reference(hdr, tag);
2729 * We're about to change the hdr's b_flags. We must either
2730 * hold the hash_lock or be undiscoverable.
2732 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2735 * Only honor requests for compressed bufs if the hdr is actually
2738 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
2739 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2742 * If the hdr's data can be shared then we share the data buffer and
2743 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2744 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
2745 * buffer to store the buf's data.
2747 * There are two additional restrictions here because we're sharing
2748 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2749 * actively involved in an L2ARC write, because if this buf is used by
2750 * an arc_write() then the hdr's data buffer will be released when the
2751 * write completes, even though the L2ARC write might still be using it.
2752 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2753 * need to be ABD-aware.
2755 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2756 abd_is_linear(hdr->b_l1hdr.b_pabd);
2758 /* Set up b_data and sharing */
2760 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2761 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2762 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2765 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2766 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2768 VERIFY3P(buf->b_data, !=, NULL);
2770 hdr->b_l1hdr.b_buf = buf;
2771 hdr->b_l1hdr.b_bufcnt += 1;
2774 * If the user wants the data from the hdr, we need to either copy or
2775 * decompress the data.
2778 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
2784 static char *arc_onloan_tag = "onloan";
2787 arc_loaned_bytes_update(int64_t delta)
2789 atomic_add_64(&arc_loaned_bytes, delta);
2791 /* assert that it did not wrap around */
2792 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2796 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2797 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2798 * buffers must be returned to the arc before they can be used by the DMU or
2802 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2804 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2805 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2807 arc_loaned_bytes_update(size);
2813 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2814 enum zio_compress compression_type)
2816 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2817 psize, lsize, compression_type);
2819 arc_loaned_bytes_update(psize);
2826 * Return a loaned arc buffer to the arc.
2829 arc_return_buf(arc_buf_t *buf, void *tag)
2831 arc_buf_hdr_t *hdr = buf->b_hdr;
2833 ASSERT3P(buf->b_data, !=, NULL);
2834 ASSERT(HDR_HAS_L1HDR(hdr));
2835 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2836 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2838 arc_loaned_bytes_update(-arc_buf_size(buf));
2841 /* Detach an arc_buf from a dbuf (tag) */
2843 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2845 arc_buf_hdr_t *hdr = buf->b_hdr;
2847 ASSERT3P(buf->b_data, !=, NULL);
2848 ASSERT(HDR_HAS_L1HDR(hdr));
2849 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2850 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2852 arc_loaned_bytes_update(arc_buf_size(buf));
2856 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2858 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2861 df->l2df_size = size;
2862 df->l2df_type = type;
2863 mutex_enter(&l2arc_free_on_write_mtx);
2864 list_insert_head(l2arc_free_on_write, df);
2865 mutex_exit(&l2arc_free_on_write_mtx);
2869 arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
2871 arc_state_t *state = hdr->b_l1hdr.b_state;
2872 arc_buf_contents_t type = arc_buf_type(hdr);
2873 uint64_t size = arc_hdr_size(hdr);
2875 /* protected by hash lock, if in the hash table */
2876 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2877 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2878 ASSERT(state != arc_anon && state != arc_l2c_only);
2880 (void) refcount_remove_many(&state->arcs_esize[type],
2883 (void) refcount_remove_many(&state->arcs_size, size, hdr);
2884 if (type == ARC_BUFC_METADATA) {
2885 arc_space_return(size, ARC_SPACE_META);
2887 ASSERT(type == ARC_BUFC_DATA);
2888 arc_space_return(size, ARC_SPACE_DATA);
2891 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2895 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2896 * data buffer, we transfer the refcount ownership to the hdr and update
2897 * the appropriate kstats.
2900 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2902 arc_state_t *state = hdr->b_l1hdr.b_state;
2904 ASSERT(arc_can_share(hdr, buf));
2905 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2906 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2909 * Start sharing the data buffer. We transfer the
2910 * refcount ownership to the hdr since it always owns
2911 * the refcount whenever an arc_buf_t is shared.
2913 refcount_transfer_ownership(&state->arcs_size, buf, hdr);
2914 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
2915 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
2916 HDR_ISTYPE_METADATA(hdr));
2917 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2918 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2921 * Since we've transferred ownership to the hdr we need
2922 * to increment its compressed and uncompressed kstats and
2923 * decrement the overhead size.
2925 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2926 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2927 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
2931 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2933 arc_state_t *state = hdr->b_l1hdr.b_state;
2935 ASSERT(arc_buf_is_shared(buf));
2936 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2937 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2940 * We are no longer sharing this buffer so we need
2941 * to transfer its ownership to the rightful owner.
2943 refcount_transfer_ownership(&state->arcs_size, hdr, buf);
2944 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2945 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
2946 abd_put(hdr->b_l1hdr.b_pabd);
2947 hdr->b_l1hdr.b_pabd = NULL;
2948 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2951 * Since the buffer is no longer shared between
2952 * the arc buf and the hdr, count it as overhead.
2954 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2955 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2956 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2960 * Remove an arc_buf_t from the hdr's buf list and return the last
2961 * arc_buf_t on the list. If no buffers remain on the list then return
2965 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2967 ASSERT(HDR_HAS_L1HDR(hdr));
2968 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2970 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
2971 arc_buf_t *lastbuf = NULL;
2974 * Remove the buf from the hdr list and locate the last
2975 * remaining buffer on the list.
2977 while (*bufp != NULL) {
2979 *bufp = buf->b_next;
2982 * If we've removed a buffer in the middle of
2983 * the list then update the lastbuf and update
2986 if (*bufp != NULL) {
2988 bufp = &(*bufp)->b_next;
2992 ASSERT3P(lastbuf, !=, buf);
2993 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
2994 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
2995 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
3001 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
3005 arc_buf_destroy_impl(arc_buf_t *buf)
3007 arc_buf_hdr_t *hdr = buf->b_hdr;
3010 * Free up the data associated with the buf but only if we're not
3011 * sharing this with the hdr. If we are sharing it with the hdr, the
3012 * hdr is responsible for doing the free.
3014 if (buf->b_data != NULL) {
3016 * We're about to change the hdr's b_flags. We must either
3017 * hold the hash_lock or be undiscoverable.
3019 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
3021 arc_cksum_verify(buf);
3023 arc_buf_unwatch(buf);
3026 if (arc_buf_is_shared(buf)) {
3027 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
3029 uint64_t size = arc_buf_size(buf);
3030 arc_free_data_buf(hdr, buf->b_data, size, buf);
3031 ARCSTAT_INCR(arcstat_overhead_size, -size);
3035 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3036 hdr->b_l1hdr.b_bufcnt -= 1;
3039 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
3041 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
3043 * If the current arc_buf_t is sharing its data buffer with the
3044 * hdr, then reassign the hdr's b_pabd to share it with the new
3045 * buffer at the end of the list. The shared buffer is always
3046 * the last one on the hdr's buffer list.
3048 * There is an equivalent case for compressed bufs, but since
3049 * they aren't guaranteed to be the last buf in the list and
3050 * that is an exceedingly rare case, we just allow that space be
3051 * wasted temporarily.
3053 if (lastbuf != NULL) {
3054 /* Only one buf can be shared at once */
3055 VERIFY(!arc_buf_is_shared(lastbuf));
3056 /* hdr is uncompressed so can't have compressed buf */
3057 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
3059 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3060 arc_hdr_free_pabd(hdr);
3063 * We must setup a new shared block between the
3064 * last buffer and the hdr. The data would have
3065 * been allocated by the arc buf so we need to transfer
3066 * ownership to the hdr since it's now being shared.
3068 arc_share_buf(hdr, lastbuf);
3070 } else if (HDR_SHARED_DATA(hdr)) {
3072 * Uncompressed shared buffers are always at the end
3073 * of the list. Compressed buffers don't have the
3074 * same requirements. This makes it hard to
3075 * simply assert that the lastbuf is shared so
3076 * we rely on the hdr's compression flags to determine
3077 * if we have a compressed, shared buffer.
3079 ASSERT3P(lastbuf, !=, NULL);
3080 ASSERT(arc_buf_is_shared(lastbuf) ||
3081 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
3085 * Free the checksum if we're removing the last uncompressed buf from
3088 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3089 arc_cksum_free(hdr);
3092 /* clean up the buf */
3094 kmem_cache_free(buf_cache, buf);
3098 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr)
3100 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3101 ASSERT(HDR_HAS_L1HDR(hdr));
3102 ASSERT(!HDR_SHARED_DATA(hdr));
3104 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3105 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
3106 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3107 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3109 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
3110 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3114 arc_hdr_free_pabd(arc_buf_hdr_t *hdr)
3116 ASSERT(HDR_HAS_L1HDR(hdr));
3117 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3120 * If the hdr is currently being written to the l2arc then
3121 * we defer freeing the data by adding it to the l2arc_free_on_write
3122 * list. The l2arc will free the data once it's finished
3123 * writing it to the l2arc device.
3125 if (HDR_L2_WRITING(hdr)) {
3126 arc_hdr_free_on_write(hdr);
3127 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3129 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3130 arc_hdr_size(hdr), hdr);
3132 hdr->b_l1hdr.b_pabd = NULL;
3133 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3135 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
3136 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3139 static arc_buf_hdr_t *
3140 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3141 enum zio_compress compression_type, arc_buf_contents_t type)
3145 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3147 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3148 ASSERT(HDR_EMPTY(hdr));
3149 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3150 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3151 HDR_SET_PSIZE(hdr, psize);
3152 HDR_SET_LSIZE(hdr, lsize);
3156 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3157 arc_hdr_set_compress(hdr, compression_type);
3159 hdr->b_l1hdr.b_state = arc_anon;
3160 hdr->b_l1hdr.b_arc_access = 0;
3161 hdr->b_l1hdr.b_bufcnt = 0;
3162 hdr->b_l1hdr.b_buf = NULL;
3165 * Allocate the hdr's buffer. This will contain either
3166 * the compressed or uncompressed data depending on the block
3167 * it references and compressed arc enablement.
3169 arc_hdr_alloc_pabd(hdr);
3170 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3176 * Transition between the two allocation states for the arc_buf_hdr struct.
3177 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3178 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3179 * version is used when a cache buffer is only in the L2ARC in order to reduce
3182 static arc_buf_hdr_t *
3183 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3185 ASSERT(HDR_HAS_L2HDR(hdr));
3187 arc_buf_hdr_t *nhdr;
3188 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3190 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3191 (old == hdr_l2only_cache && new == hdr_full_cache));
3193 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3195 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3196 buf_hash_remove(hdr);
3198 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3200 if (new == hdr_full_cache) {
3201 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3203 * arc_access and arc_change_state need to be aware that a
3204 * header has just come out of L2ARC, so we set its state to
3205 * l2c_only even though it's about to change.
3207 nhdr->b_l1hdr.b_state = arc_l2c_only;
3209 /* Verify previous threads set to NULL before freeing */
3210 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3212 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3213 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3214 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3217 * If we've reached here, We must have been called from
3218 * arc_evict_hdr(), as such we should have already been
3219 * removed from any ghost list we were previously on
3220 * (which protects us from racing with arc_evict_state),
3221 * thus no locking is needed during this check.
3223 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3226 * A buffer must not be moved into the arc_l2c_only
3227 * state if it's not finished being written out to the
3228 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3229 * might try to be accessed, even though it was removed.
3231 VERIFY(!HDR_L2_WRITING(hdr));
3232 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3235 if (hdr->b_l1hdr.b_thawed != NULL) {
3236 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3237 hdr->b_l1hdr.b_thawed = NULL;
3241 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3244 * The header has been reallocated so we need to re-insert it into any
3247 (void) buf_hash_insert(nhdr, NULL);
3249 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3251 mutex_enter(&dev->l2ad_mtx);
3254 * We must place the realloc'ed header back into the list at
3255 * the same spot. Otherwise, if it's placed earlier in the list,
3256 * l2arc_write_buffers() could find it during the function's
3257 * write phase, and try to write it out to the l2arc.
3259 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3260 list_remove(&dev->l2ad_buflist, hdr);
3262 mutex_exit(&dev->l2ad_mtx);
3265 * Since we're using the pointer address as the tag when
3266 * incrementing and decrementing the l2ad_alloc refcount, we
3267 * must remove the old pointer (that we're about to destroy) and
3268 * add the new pointer to the refcount. Otherwise we'd remove
3269 * the wrong pointer address when calling arc_hdr_destroy() later.
3272 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
3273 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
3275 buf_discard_identity(hdr);
3276 kmem_cache_free(old, hdr);
3282 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3283 * The buf is returned thawed since we expect the consumer to modify it.
3286 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3288 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3289 ZIO_COMPRESS_OFF, type);
3290 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3292 arc_buf_t *buf = NULL;
3293 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
3300 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3301 * for bufs containing metadata.
3304 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3305 enum zio_compress compression_type)
3307 ASSERT3U(lsize, >, 0);
3308 ASSERT3U(lsize, >=, psize);
3309 ASSERT(compression_type > ZIO_COMPRESS_OFF);
3310 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
3312 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3313 compression_type, ARC_BUFC_DATA);
3314 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3316 arc_buf_t *buf = NULL;
3317 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
3319 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3321 if (!arc_buf_is_shared(buf)) {
3323 * To ensure that the hdr has the correct data in it if we call
3324 * arc_decompress() on this buf before it's been written to
3325 * disk, it's easiest if we just set up sharing between the
3328 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3329 arc_hdr_free_pabd(hdr);
3330 arc_share_buf(hdr, buf);
3337 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3339 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3340 l2arc_dev_t *dev = l2hdr->b_dev;
3341 uint64_t asize = arc_hdr_size(hdr);
3343 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3344 ASSERT(HDR_HAS_L2HDR(hdr));
3346 list_remove(&dev->l2ad_buflist, hdr);
3348 ARCSTAT_INCR(arcstat_l2_asize, -asize);
3349 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr));
3351 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
3353 (void) refcount_remove_many(&dev->l2ad_alloc, asize, hdr);
3354 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3358 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3360 if (HDR_HAS_L1HDR(hdr)) {
3361 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3362 hdr->b_l1hdr.b_bufcnt > 0);
3363 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3364 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3366 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3367 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3369 if (!HDR_EMPTY(hdr))
3370 buf_discard_identity(hdr);
3372 if (HDR_HAS_L2HDR(hdr)) {
3373 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3374 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3377 mutex_enter(&dev->l2ad_mtx);
3380 * Even though we checked this conditional above, we
3381 * need to check this again now that we have the
3382 * l2ad_mtx. This is because we could be racing with
3383 * another thread calling l2arc_evict() which might have
3384 * destroyed this header's L2 portion as we were waiting
3385 * to acquire the l2ad_mtx. If that happens, we don't
3386 * want to re-destroy the header's L2 portion.
3388 if (HDR_HAS_L2HDR(hdr)) {
3390 arc_hdr_l2hdr_destroy(hdr);
3394 mutex_exit(&dev->l2ad_mtx);
3397 if (HDR_HAS_L1HDR(hdr)) {
3398 arc_cksum_free(hdr);
3400 while (hdr->b_l1hdr.b_buf != NULL)
3401 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3404 if (hdr->b_l1hdr.b_thawed != NULL) {
3405 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3406 hdr->b_l1hdr.b_thawed = NULL;
3410 if (hdr->b_l1hdr.b_pabd != NULL) {
3411 arc_hdr_free_pabd(hdr);
3415 ASSERT3P(hdr->b_hash_next, ==, NULL);
3416 if (HDR_HAS_L1HDR(hdr)) {
3417 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3418 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3419 kmem_cache_free(hdr_full_cache, hdr);
3421 kmem_cache_free(hdr_l2only_cache, hdr);
3426 arc_buf_destroy(arc_buf_t *buf, void* tag)
3428 arc_buf_hdr_t *hdr = buf->b_hdr;
3429 kmutex_t *hash_lock = HDR_LOCK(hdr);
3431 if (hdr->b_l1hdr.b_state == arc_anon) {
3432 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3433 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3434 VERIFY0(remove_reference(hdr, NULL, tag));
3435 arc_hdr_destroy(hdr);
3439 mutex_enter(hash_lock);
3440 ASSERT3P(hdr, ==, buf->b_hdr);
3441 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3442 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3443 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3444 ASSERT3P(buf->b_data, !=, NULL);
3446 (void) remove_reference(hdr, hash_lock, tag);
3447 arc_buf_destroy_impl(buf);
3448 mutex_exit(hash_lock);
3452 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3453 * state of the header is dependent on its state prior to entering this
3454 * function. The following transitions are possible:
3456 * - arc_mru -> arc_mru_ghost
3457 * - arc_mfu -> arc_mfu_ghost
3458 * - arc_mru_ghost -> arc_l2c_only
3459 * - arc_mru_ghost -> deleted
3460 * - arc_mfu_ghost -> arc_l2c_only
3461 * - arc_mfu_ghost -> deleted
3464 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3466 arc_state_t *evicted_state, *state;
3467 int64_t bytes_evicted = 0;
3469 ASSERT(MUTEX_HELD(hash_lock));
3470 ASSERT(HDR_HAS_L1HDR(hdr));
3472 state = hdr->b_l1hdr.b_state;
3473 if (GHOST_STATE(state)) {
3474 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3475 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3478 * l2arc_write_buffers() relies on a header's L1 portion
3479 * (i.e. its b_pabd field) during it's write phase.
3480 * Thus, we cannot push a header onto the arc_l2c_only
3481 * state (removing it's L1 piece) until the header is
3482 * done being written to the l2arc.
3484 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3485 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3486 return (bytes_evicted);
3489 ARCSTAT_BUMP(arcstat_deleted);
3490 bytes_evicted += HDR_GET_LSIZE(hdr);
3492 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3494 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3495 if (HDR_HAS_L2HDR(hdr)) {
3497 * This buffer is cached on the 2nd Level ARC;
3498 * don't destroy the header.
3500 arc_change_state(arc_l2c_only, hdr, hash_lock);
3502 * dropping from L1+L2 cached to L2-only,
3503 * realloc to remove the L1 header.
3505 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3508 arc_change_state(arc_anon, hdr, hash_lock);
3509 arc_hdr_destroy(hdr);
3511 return (bytes_evicted);
3514 ASSERT(state == arc_mru || state == arc_mfu);
3515 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3517 /* prefetch buffers have a minimum lifespan */
3518 if (HDR_IO_IN_PROGRESS(hdr) ||
3519 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3520 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
3521 arc_min_prefetch_lifespan)) {
3522 ARCSTAT_BUMP(arcstat_evict_skip);
3523 return (bytes_evicted);
3526 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3527 while (hdr->b_l1hdr.b_buf) {
3528 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3529 if (!mutex_tryenter(&buf->b_evict_lock)) {
3530 ARCSTAT_BUMP(arcstat_mutex_miss);
3533 if (buf->b_data != NULL)
3534 bytes_evicted += HDR_GET_LSIZE(hdr);
3535 mutex_exit(&buf->b_evict_lock);
3536 arc_buf_destroy_impl(buf);
3539 if (HDR_HAS_L2HDR(hdr)) {
3540 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3542 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3543 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3544 HDR_GET_LSIZE(hdr));
3546 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3547 HDR_GET_LSIZE(hdr));
3551 if (hdr->b_l1hdr.b_bufcnt == 0) {
3552 arc_cksum_free(hdr);
3554 bytes_evicted += arc_hdr_size(hdr);
3557 * If this hdr is being evicted and has a compressed
3558 * buffer then we discard it here before we change states.
3559 * This ensures that the accounting is updated correctly
3560 * in arc_free_data_impl().
3562 arc_hdr_free_pabd(hdr);
3564 arc_change_state(evicted_state, hdr, hash_lock);
3565 ASSERT(HDR_IN_HASH_TABLE(hdr));
3566 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3567 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3570 return (bytes_evicted);
3574 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3575 uint64_t spa, int64_t bytes)
3577 multilist_sublist_t *mls;
3578 uint64_t bytes_evicted = 0;
3580 kmutex_t *hash_lock;
3581 int evict_count = 0;
3583 ASSERT3P(marker, !=, NULL);
3584 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3586 mls = multilist_sublist_lock(ml, idx);
3588 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3589 hdr = multilist_sublist_prev(mls, marker)) {
3590 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3591 (evict_count >= zfs_arc_evict_batch_limit))
3595 * To keep our iteration location, move the marker
3596 * forward. Since we're not holding hdr's hash lock, we
3597 * must be very careful and not remove 'hdr' from the
3598 * sublist. Otherwise, other consumers might mistake the
3599 * 'hdr' as not being on a sublist when they call the
3600 * multilist_link_active() function (they all rely on
3601 * the hash lock protecting concurrent insertions and
3602 * removals). multilist_sublist_move_forward() was
3603 * specifically implemented to ensure this is the case
3604 * (only 'marker' will be removed and re-inserted).
3606 multilist_sublist_move_forward(mls, marker);
3609 * The only case where the b_spa field should ever be
3610 * zero, is the marker headers inserted by
3611 * arc_evict_state(). It's possible for multiple threads
3612 * to be calling arc_evict_state() concurrently (e.g.
3613 * dsl_pool_close() and zio_inject_fault()), so we must
3614 * skip any markers we see from these other threads.
3616 if (hdr->b_spa == 0)
3619 /* we're only interested in evicting buffers of a certain spa */
3620 if (spa != 0 && hdr->b_spa != spa) {
3621 ARCSTAT_BUMP(arcstat_evict_skip);
3625 hash_lock = HDR_LOCK(hdr);
3628 * We aren't calling this function from any code path
3629 * that would already be holding a hash lock, so we're
3630 * asserting on this assumption to be defensive in case
3631 * this ever changes. Without this check, it would be
3632 * possible to incorrectly increment arcstat_mutex_miss
3633 * below (e.g. if the code changed such that we called
3634 * this function with a hash lock held).
3636 ASSERT(!MUTEX_HELD(hash_lock));
3638 if (mutex_tryenter(hash_lock)) {
3639 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3640 mutex_exit(hash_lock);
3642 bytes_evicted += evicted;
3645 * If evicted is zero, arc_evict_hdr() must have
3646 * decided to skip this header, don't increment
3647 * evict_count in this case.
3653 * If arc_size isn't overflowing, signal any
3654 * threads that might happen to be waiting.
3656 * For each header evicted, we wake up a single
3657 * thread. If we used cv_broadcast, we could
3658 * wake up "too many" threads causing arc_size
3659 * to significantly overflow arc_c; since
3660 * arc_get_data_impl() doesn't check for overflow
3661 * when it's woken up (it doesn't because it's
3662 * possible for the ARC to be overflowing while
3663 * full of un-evictable buffers, and the
3664 * function should proceed in this case).
3666 * If threads are left sleeping, due to not
3667 * using cv_broadcast, they will be woken up
3668 * just before arc_reclaim_thread() sleeps.
3670 mutex_enter(&arc_reclaim_lock);
3671 if (!arc_is_overflowing())
3672 cv_signal(&arc_reclaim_waiters_cv);
3673 mutex_exit(&arc_reclaim_lock);
3675 ARCSTAT_BUMP(arcstat_mutex_miss);
3679 multilist_sublist_unlock(mls);
3681 return (bytes_evicted);
3685 * Evict buffers from the given arc state, until we've removed the
3686 * specified number of bytes. Move the removed buffers to the
3687 * appropriate evict state.
3689 * This function makes a "best effort". It skips over any buffers
3690 * it can't get a hash_lock on, and so, may not catch all candidates.
3691 * It may also return without evicting as much space as requested.
3693 * If bytes is specified using the special value ARC_EVICT_ALL, this
3694 * will evict all available (i.e. unlocked and evictable) buffers from
3695 * the given arc state; which is used by arc_flush().
3698 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
3699 arc_buf_contents_t type)
3701 uint64_t total_evicted = 0;
3702 multilist_t *ml = state->arcs_list[type];
3704 arc_buf_hdr_t **markers;
3706 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3708 num_sublists = multilist_get_num_sublists(ml);
3711 * If we've tried to evict from each sublist, made some
3712 * progress, but still have not hit the target number of bytes
3713 * to evict, we want to keep trying. The markers allow us to
3714 * pick up where we left off for each individual sublist, rather
3715 * than starting from the tail each time.
3717 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
3718 for (int i = 0; i < num_sublists; i++) {
3719 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
3722 * A b_spa of 0 is used to indicate that this header is
3723 * a marker. This fact is used in arc_adjust_type() and
3724 * arc_evict_state_impl().
3726 markers[i]->b_spa = 0;
3728 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3729 multilist_sublist_insert_tail(mls, markers[i]);
3730 multilist_sublist_unlock(mls);
3734 * While we haven't hit our target number of bytes to evict, or
3735 * we're evicting all available buffers.
3737 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
3739 * Start eviction using a randomly selected sublist,
3740 * this is to try and evenly balance eviction across all
3741 * sublists. Always starting at the same sublist
3742 * (e.g. index 0) would cause evictions to favor certain
3743 * sublists over others.
3745 int sublist_idx = multilist_get_random_index(ml);
3746 uint64_t scan_evicted = 0;
3748 for (int i = 0; i < num_sublists; i++) {
3749 uint64_t bytes_remaining;
3750 uint64_t bytes_evicted;
3752 if (bytes == ARC_EVICT_ALL)
3753 bytes_remaining = ARC_EVICT_ALL;
3754 else if (total_evicted < bytes)
3755 bytes_remaining = bytes - total_evicted;
3759 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
3760 markers[sublist_idx], spa, bytes_remaining);
3762 scan_evicted += bytes_evicted;
3763 total_evicted += bytes_evicted;
3765 /* we've reached the end, wrap to the beginning */
3766 if (++sublist_idx >= num_sublists)
3771 * If we didn't evict anything during this scan, we have
3772 * no reason to believe we'll evict more during another
3773 * scan, so break the loop.
3775 if (scan_evicted == 0) {
3776 /* This isn't possible, let's make that obvious */
3777 ASSERT3S(bytes, !=, 0);
3780 * When bytes is ARC_EVICT_ALL, the only way to
3781 * break the loop is when scan_evicted is zero.
3782 * In that case, we actually have evicted enough,
3783 * so we don't want to increment the kstat.
3785 if (bytes != ARC_EVICT_ALL) {
3786 ASSERT3S(total_evicted, <, bytes);
3787 ARCSTAT_BUMP(arcstat_evict_not_enough);
3794 for (int i = 0; i < num_sublists; i++) {
3795 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3796 multilist_sublist_remove(mls, markers[i]);
3797 multilist_sublist_unlock(mls);
3799 kmem_cache_free(hdr_full_cache, markers[i]);
3801 kmem_free(markers, sizeof (*markers) * num_sublists);
3803 return (total_evicted);
3807 * Flush all "evictable" data of the given type from the arc state
3808 * specified. This will not evict any "active" buffers (i.e. referenced).
3810 * When 'retry' is set to B_FALSE, the function will make a single pass
3811 * over the state and evict any buffers that it can. Since it doesn't
3812 * continually retry the eviction, it might end up leaving some buffers
3813 * in the ARC due to lock misses.
3815 * When 'retry' is set to B_TRUE, the function will continually retry the
3816 * eviction until *all* evictable buffers have been removed from the
3817 * state. As a result, if concurrent insertions into the state are
3818 * allowed (e.g. if the ARC isn't shutting down), this function might
3819 * wind up in an infinite loop, continually trying to evict buffers.
3822 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
3825 uint64_t evicted = 0;
3827 while (refcount_count(&state->arcs_esize[type]) != 0) {
3828 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
3838 * Evict the specified number of bytes from the state specified,
3839 * restricting eviction to the spa and type given. This function
3840 * prevents us from trying to evict more from a state's list than
3841 * is "evictable", and to skip evicting altogether when passed a
3842 * negative value for "bytes". In contrast, arc_evict_state() will
3843 * evict everything it can, when passed a negative value for "bytes".
3846 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
3847 arc_buf_contents_t type)
3851 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
3852 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
3853 return (arc_evict_state(state, spa, delta, type));
3860 * Evict metadata buffers from the cache, such that arc_meta_used is
3861 * capped by the arc_meta_limit tunable.
3864 arc_adjust_meta(void)
3866 uint64_t total_evicted = 0;
3870 * If we're over the meta limit, we want to evict enough
3871 * metadata to get back under the meta limit. We don't want to
3872 * evict so much that we drop the MRU below arc_p, though. If
3873 * we're over the meta limit more than we're over arc_p, we
3874 * evict some from the MRU here, and some from the MFU below.
3876 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3877 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3878 refcount_count(&arc_mru->arcs_size) - arc_p));
3880 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3883 * Similar to the above, we want to evict enough bytes to get us
3884 * below the meta limit, but not so much as to drop us below the
3885 * space allotted to the MFU (which is defined as arc_c - arc_p).
3887 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3888 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
3890 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3892 return (total_evicted);
3896 * Return the type of the oldest buffer in the given arc state
3898 * This function will select a random sublist of type ARC_BUFC_DATA and
3899 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
3900 * is compared, and the type which contains the "older" buffer will be
3903 static arc_buf_contents_t
3904 arc_adjust_type(arc_state_t *state)
3906 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
3907 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
3908 int data_idx = multilist_get_random_index(data_ml);
3909 int meta_idx = multilist_get_random_index(meta_ml);
3910 multilist_sublist_t *data_mls;
3911 multilist_sublist_t *meta_mls;
3912 arc_buf_contents_t type;
3913 arc_buf_hdr_t *data_hdr;
3914 arc_buf_hdr_t *meta_hdr;
3917 * We keep the sublist lock until we're finished, to prevent
3918 * the headers from being destroyed via arc_evict_state().
3920 data_mls = multilist_sublist_lock(data_ml, data_idx);
3921 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
3924 * These two loops are to ensure we skip any markers that
3925 * might be at the tail of the lists due to arc_evict_state().
3928 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
3929 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
3930 if (data_hdr->b_spa != 0)
3934 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
3935 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
3936 if (meta_hdr->b_spa != 0)
3940 if (data_hdr == NULL && meta_hdr == NULL) {
3941 type = ARC_BUFC_DATA;
3942 } else if (data_hdr == NULL) {
3943 ASSERT3P(meta_hdr, !=, NULL);
3944 type = ARC_BUFC_METADATA;
3945 } else if (meta_hdr == NULL) {
3946 ASSERT3P(data_hdr, !=, NULL);
3947 type = ARC_BUFC_DATA;
3949 ASSERT3P(data_hdr, !=, NULL);
3950 ASSERT3P(meta_hdr, !=, NULL);
3952 /* The headers can't be on the sublist without an L1 header */
3953 ASSERT(HDR_HAS_L1HDR(data_hdr));
3954 ASSERT(HDR_HAS_L1HDR(meta_hdr));
3956 if (data_hdr->b_l1hdr.b_arc_access <
3957 meta_hdr->b_l1hdr.b_arc_access) {
3958 type = ARC_BUFC_DATA;
3960 type = ARC_BUFC_METADATA;
3964 multilist_sublist_unlock(meta_mls);
3965 multilist_sublist_unlock(data_mls);
3971 * Evict buffers from the cache, such that arc_size is capped by arc_c.
3976 uint64_t total_evicted = 0;
3981 * If we're over arc_meta_limit, we want to correct that before
3982 * potentially evicting data buffers below.
3984 total_evicted += arc_adjust_meta();
3989 * If we're over the target cache size, we want to evict enough
3990 * from the list to get back to our target size. We don't want
3991 * to evict too much from the MRU, such that it drops below
3992 * arc_p. So, if we're over our target cache size more than
3993 * the MRU is over arc_p, we'll evict enough to get back to
3994 * arc_p here, and then evict more from the MFU below.
3996 target = MIN((int64_t)(arc_size - arc_c),
3997 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3998 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
4001 * If we're below arc_meta_min, always prefer to evict data.
4002 * Otherwise, try to satisfy the requested number of bytes to
4003 * evict from the type which contains older buffers; in an
4004 * effort to keep newer buffers in the cache regardless of their
4005 * type. If we cannot satisfy the number of bytes from this
4006 * type, spill over into the next type.
4008 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4009 arc_meta_used > arc_meta_min) {
4010 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4011 total_evicted += bytes;
4014 * If we couldn't evict our target number of bytes from
4015 * metadata, we try to get the rest from data.
4020 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4022 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4023 total_evicted += bytes;
4026 * If we couldn't evict our target number of bytes from
4027 * data, we try to get the rest from metadata.
4032 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4038 * Now that we've tried to evict enough from the MRU to get its
4039 * size back to arc_p, if we're still above the target cache
4040 * size, we evict the rest from the MFU.
4042 target = arc_size - arc_c;
4044 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4045 arc_meta_used > arc_meta_min) {
4046 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4047 total_evicted += bytes;
4050 * If we couldn't evict our target number of bytes from
4051 * metadata, we try to get the rest from data.
4056 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4058 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4059 total_evicted += bytes;
4062 * If we couldn't evict our target number of bytes from
4063 * data, we try to get the rest from data.
4068 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4072 * Adjust ghost lists
4074 * In addition to the above, the ARC also defines target values
4075 * for the ghost lists. The sum of the mru list and mru ghost
4076 * list should never exceed the target size of the cache, and
4077 * the sum of the mru list, mfu list, mru ghost list, and mfu
4078 * ghost list should never exceed twice the target size of the
4079 * cache. The following logic enforces these limits on the ghost
4080 * caches, and evicts from them as needed.
4082 target = refcount_count(&arc_mru->arcs_size) +
4083 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4085 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4086 total_evicted += bytes;
4091 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4094 * We assume the sum of the mru list and mfu list is less than
4095 * or equal to arc_c (we enforced this above), which means we
4096 * can use the simpler of the two equations below:
4098 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4099 * mru ghost + mfu ghost <= arc_c
4101 target = refcount_count(&arc_mru_ghost->arcs_size) +
4102 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4104 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4105 total_evicted += bytes;
4110 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4112 return (total_evicted);
4116 arc_flush(spa_t *spa, boolean_t retry)
4121 * If retry is B_TRUE, a spa must not be specified since we have
4122 * no good way to determine if all of a spa's buffers have been
4123 * evicted from an arc state.
4125 ASSERT(!retry || spa == 0);
4128 guid = spa_load_guid(spa);
4130 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4131 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4133 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4134 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4136 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4137 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4139 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4140 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4144 arc_shrink(int64_t to_free)
4146 if (arc_c > arc_c_min) {
4147 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
4148 arc_c_min, uint64_t, arc_p, uint64_t, to_free);
4149 if (arc_c > arc_c_min + to_free)
4150 atomic_add_64(&arc_c, -to_free);
4154 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4155 if (arc_c > arc_size)
4156 arc_c = MAX(arc_size, arc_c_min);
4158 arc_p = (arc_c >> 1);
4160 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
4163 ASSERT(arc_c >= arc_c_min);
4164 ASSERT((int64_t)arc_p >= 0);
4167 if (arc_size > arc_c) {
4168 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size,
4170 (void) arc_adjust();
4174 static long needfree = 0;
4176 typedef enum free_memory_reason_t {
4181 FMR_PAGES_PP_MAXIMUM,
4185 } free_memory_reason_t;
4187 int64_t last_free_memory;
4188 free_memory_reason_t last_free_reason;
4191 * Additional reserve of pages for pp_reserve.
4193 int64_t arc_pages_pp_reserve = 64;
4196 * Additional reserve of pages for swapfs.
4198 int64_t arc_swapfs_reserve = 64;
4201 * Return the amount of memory that can be consumed before reclaim will be
4202 * needed. Positive if there is sufficient free memory, negative indicates
4203 * the amount of memory that needs to be freed up.
4206 arc_available_memory(void)
4208 int64_t lowest = INT64_MAX;
4210 free_memory_reason_t r = FMR_UNKNOWN;
4214 n = PAGESIZE * (-needfree);
4222 * Cooperate with pagedaemon when it's time for it to scan
4223 * and reclaim some pages.
4225 n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target);
4233 * check that we're out of range of the pageout scanner. It starts to
4234 * schedule paging if freemem is less than lotsfree and needfree.
4235 * lotsfree is the high-water mark for pageout, and needfree is the
4236 * number of needed free pages. We add extra pages here to make sure
4237 * the scanner doesn't start up while we're freeing memory.
4239 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4246 * check to make sure that swapfs has enough space so that anon
4247 * reservations can still succeed. anon_resvmem() checks that the
4248 * availrmem is greater than swapfs_minfree, and the number of reserved
4249 * swap pages. We also add a bit of extra here just to prevent
4250 * circumstances from getting really dire.
4252 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4253 desfree - arc_swapfs_reserve);
4256 r = FMR_SWAPFS_MINFREE;
4261 * Check that we have enough availrmem that memory locking (e.g., via
4262 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4263 * stores the number of pages that cannot be locked; when availrmem
4264 * drops below pages_pp_maximum, page locking mechanisms such as
4265 * page_pp_lock() will fail.)
4267 n = PAGESIZE * (availrmem - pages_pp_maximum -
4268 arc_pages_pp_reserve);
4271 r = FMR_PAGES_PP_MAXIMUM;
4274 #endif /* illumos */
4275 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
4277 * If we're on an i386 platform, it's possible that we'll exhaust the
4278 * kernel heap space before we ever run out of available physical
4279 * memory. Most checks of the size of the heap_area compare against
4280 * tune.t_minarmem, which is the minimum available real memory that we
4281 * can have in the system. However, this is generally fixed at 25 pages
4282 * which is so low that it's useless. In this comparison, we seek to
4283 * calculate the total heap-size, and reclaim if more than 3/4ths of the
4284 * heap is allocated. (Or, in the calculation, if less than 1/4th is
4287 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) -
4288 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
4293 #define zio_arena NULL
4295 #define zio_arena heap_arena
4299 * If zio data pages are being allocated out of a separate heap segment,
4300 * then enforce that the size of available vmem for this arena remains
4301 * above about 1/16th free.
4303 * Note: The 1/16th arena free requirement was put in place
4304 * to aggressively evict memory from the arc in order to avoid
4305 * memory fragmentation issues.
4307 if (zio_arena != NULL) {
4308 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4309 (vmem_size(zio_arena, VMEM_ALLOC) >> 4);
4317 * Above limits know nothing about real level of KVA fragmentation.
4318 * Start aggressive reclamation if too little sequential KVA left.
4321 n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ?
4322 -((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) :
4331 /* Every 100 calls, free a small amount */
4332 if (spa_get_random(100) == 0)
4334 #endif /* _KERNEL */
4336 last_free_memory = lowest;
4337 last_free_reason = r;
4338 DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r);
4344 * Determine if the system is under memory pressure and is asking
4345 * to reclaim memory. A return value of B_TRUE indicates that the system
4346 * is under memory pressure and that the arc should adjust accordingly.
4349 arc_reclaim_needed(void)
4351 return (arc_available_memory() < 0);
4354 extern kmem_cache_t *zio_buf_cache[];
4355 extern kmem_cache_t *zio_data_buf_cache[];
4356 extern kmem_cache_t *range_seg_cache;
4357 extern kmem_cache_t *abd_chunk_cache;
4359 static __noinline void
4360 arc_kmem_reap_now(void)
4363 kmem_cache_t *prev_cache = NULL;
4364 kmem_cache_t *prev_data_cache = NULL;
4366 DTRACE_PROBE(arc__kmem_reap_start);
4368 if (arc_meta_used >= arc_meta_limit) {
4370 * We are exceeding our meta-data cache limit.
4371 * Purge some DNLC entries to release holds on meta-data.
4373 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4377 * Reclaim unused memory from all kmem caches.
4383 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4384 if (zio_buf_cache[i] != prev_cache) {
4385 prev_cache = zio_buf_cache[i];
4386 kmem_cache_reap_now(zio_buf_cache[i]);
4388 if (zio_data_buf_cache[i] != prev_data_cache) {
4389 prev_data_cache = zio_data_buf_cache[i];
4390 kmem_cache_reap_now(zio_data_buf_cache[i]);
4393 kmem_cache_reap_now(abd_chunk_cache);
4394 kmem_cache_reap_now(buf_cache);
4395 kmem_cache_reap_now(hdr_full_cache);
4396 kmem_cache_reap_now(hdr_l2only_cache);
4397 kmem_cache_reap_now(range_seg_cache);
4400 if (zio_arena != NULL) {
4402 * Ask the vmem arena to reclaim unused memory from its
4405 vmem_qcache_reap(zio_arena);
4408 DTRACE_PROBE(arc__kmem_reap_end);
4412 * Threads can block in arc_get_data_impl() waiting for this thread to evict
4413 * enough data and signal them to proceed. When this happens, the threads in
4414 * arc_get_data_impl() are sleeping while holding the hash lock for their
4415 * particular arc header. Thus, we must be careful to never sleep on a
4416 * hash lock in this thread. This is to prevent the following deadlock:
4418 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
4419 * waiting for the reclaim thread to signal it.
4421 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
4422 * fails, and goes to sleep forever.
4424 * This possible deadlock is avoided by always acquiring a hash lock
4425 * using mutex_tryenter() from arc_reclaim_thread().
4428 arc_reclaim_thread(void *dummy __unused)
4430 hrtime_t growtime = 0;
4433 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
4435 mutex_enter(&arc_reclaim_lock);
4436 while (!arc_reclaim_thread_exit) {
4437 uint64_t evicted = 0;
4440 * This is necessary in order for the mdb ::arc dcmd to
4441 * show up to date information. Since the ::arc command
4442 * does not call the kstat's update function, without
4443 * this call, the command may show stale stats for the
4444 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4445 * with this change, the data might be up to 1 second
4446 * out of date; but that should suffice. The arc_state_t
4447 * structures can be queried directly if more accurate
4448 * information is needed.
4450 if (arc_ksp != NULL)
4451 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4453 mutex_exit(&arc_reclaim_lock);
4456 * We call arc_adjust() before (possibly) calling
4457 * arc_kmem_reap_now(), so that we can wake up
4458 * arc_get_data_impl() sooner.
4460 evicted = arc_adjust();
4462 int64_t free_memory = arc_available_memory();
4463 if (free_memory < 0) {
4465 arc_no_grow = B_TRUE;
4469 * Wait at least zfs_grow_retry (default 60) seconds
4470 * before considering growing.
4472 growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
4474 arc_kmem_reap_now();
4477 * If we are still low on memory, shrink the ARC
4478 * so that we have arc_shrink_min free space.
4480 free_memory = arc_available_memory();
4483 (arc_c >> arc_shrink_shift) - free_memory;
4486 to_free = MAX(to_free, ptob(needfree));
4488 arc_shrink(to_free);
4490 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4491 arc_no_grow = B_TRUE;
4492 } else if (gethrtime() >= growtime) {
4493 arc_no_grow = B_FALSE;
4496 mutex_enter(&arc_reclaim_lock);
4499 * If evicted is zero, we couldn't evict anything via
4500 * arc_adjust(). This could be due to hash lock
4501 * collisions, but more likely due to the majority of
4502 * arc buffers being unevictable. Therefore, even if
4503 * arc_size is above arc_c, another pass is unlikely to
4504 * be helpful and could potentially cause us to enter an
4507 if (arc_size <= arc_c || evicted == 0) {
4512 * We're either no longer overflowing, or we
4513 * can't evict anything more, so we should wake
4514 * up any threads before we go to sleep.
4516 cv_broadcast(&arc_reclaim_waiters_cv);
4519 * Block until signaled, or after one second (we
4520 * might need to perform arc_kmem_reap_now()
4521 * even if we aren't being signalled)
4523 CALLB_CPR_SAFE_BEGIN(&cpr);
4524 (void) cv_timedwait_hires(&arc_reclaim_thread_cv,
4525 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
4526 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
4530 arc_reclaim_thread_exit = B_FALSE;
4531 cv_broadcast(&arc_reclaim_thread_cv);
4532 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
4536 static u_int arc_dnlc_evicts_arg;
4537 extern struct vfsops zfs_vfsops;
4540 arc_dnlc_evicts_thread(void *dummy __unused)
4545 CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG);
4547 mutex_enter(&arc_dnlc_evicts_lock);
4548 while (!arc_dnlc_evicts_thread_exit) {
4549 CALLB_CPR_SAFE_BEGIN(&cpr);
4550 (void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
4551 CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock);
4552 if (arc_dnlc_evicts_arg != 0) {
4553 percent = arc_dnlc_evicts_arg;
4554 mutex_exit(&arc_dnlc_evicts_lock);
4556 vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops);
4558 mutex_enter(&arc_dnlc_evicts_lock);
4560 * Clear our token only after vnlru_free()
4561 * pass is done, to avoid false queueing of
4564 arc_dnlc_evicts_arg = 0;
4567 arc_dnlc_evicts_thread_exit = FALSE;
4568 cv_broadcast(&arc_dnlc_evicts_cv);
4569 CALLB_CPR_EXIT(&cpr);
4574 dnlc_reduce_cache(void *arg)
4578 percent = (u_int)(uintptr_t)arg;
4579 mutex_enter(&arc_dnlc_evicts_lock);
4580 if (arc_dnlc_evicts_arg == 0) {
4581 arc_dnlc_evicts_arg = percent;
4582 cv_broadcast(&arc_dnlc_evicts_cv);
4584 mutex_exit(&arc_dnlc_evicts_lock);
4588 * Adapt arc info given the number of bytes we are trying to add and
4589 * the state that we are comming from. This function is only called
4590 * when we are adding new content to the cache.
4593 arc_adapt(int bytes, arc_state_t *state)
4596 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4597 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
4598 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
4600 if (state == arc_l2c_only)
4605 * Adapt the target size of the MRU list:
4606 * - if we just hit in the MRU ghost list, then increase
4607 * the target size of the MRU list.
4608 * - if we just hit in the MFU ghost list, then increase
4609 * the target size of the MFU list by decreasing the
4610 * target size of the MRU list.
4612 if (state == arc_mru_ghost) {
4613 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4614 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4616 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4617 } else if (state == arc_mfu_ghost) {
4620 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4621 mult = MIN(mult, 10);
4623 delta = MIN(bytes * mult, arc_p);
4624 arc_p = MAX(arc_p_min, arc_p - delta);
4626 ASSERT((int64_t)arc_p >= 0);
4628 if (arc_reclaim_needed()) {
4629 cv_signal(&arc_reclaim_thread_cv);
4636 if (arc_c >= arc_c_max)
4640 * If we're within (2 * maxblocksize) bytes of the target
4641 * cache size, increment the target cache size
4643 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
4644 DTRACE_PROBE1(arc__inc_adapt, int, bytes);
4645 atomic_add_64(&arc_c, (int64_t)bytes);
4646 if (arc_c > arc_c_max)
4648 else if (state == arc_anon)
4649 atomic_add_64(&arc_p, (int64_t)bytes);
4653 ASSERT((int64_t)arc_p >= 0);
4657 * Check if arc_size has grown past our upper threshold, determined by
4658 * zfs_arc_overflow_shift.
4661 arc_is_overflowing(void)
4663 /* Always allow at least one block of overflow */
4664 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4665 arc_c >> zfs_arc_overflow_shift);
4667 return (arc_size >= arc_c + overflow);
4671 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4673 arc_buf_contents_t type = arc_buf_type(hdr);
4675 arc_get_data_impl(hdr, size, tag);
4676 if (type == ARC_BUFC_METADATA) {
4677 return (abd_alloc(size, B_TRUE));
4679 ASSERT(type == ARC_BUFC_DATA);
4680 return (abd_alloc(size, B_FALSE));
4685 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4687 arc_buf_contents_t type = arc_buf_type(hdr);
4689 arc_get_data_impl(hdr, size, tag);
4690 if (type == ARC_BUFC_METADATA) {
4691 return (zio_buf_alloc(size));
4693 ASSERT(type == ARC_BUFC_DATA);
4694 return (zio_data_buf_alloc(size));
4699 * Allocate a block and return it to the caller. If we are hitting the
4700 * hard limit for the cache size, we must sleep, waiting for the eviction
4701 * thread to catch up. If we're past the target size but below the hard
4702 * limit, we'll only signal the reclaim thread and continue on.
4705 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4707 arc_state_t *state = hdr->b_l1hdr.b_state;
4708 arc_buf_contents_t type = arc_buf_type(hdr);
4710 arc_adapt(size, state);
4713 * If arc_size is currently overflowing, and has grown past our
4714 * upper limit, we must be adding data faster than the evict
4715 * thread can evict. Thus, to ensure we don't compound the
4716 * problem by adding more data and forcing arc_size to grow even
4717 * further past it's target size, we halt and wait for the
4718 * eviction thread to catch up.
4720 * It's also possible that the reclaim thread is unable to evict
4721 * enough buffers to get arc_size below the overflow limit (e.g.
4722 * due to buffers being un-evictable, or hash lock collisions).
4723 * In this case, we want to proceed regardless if we're
4724 * overflowing; thus we don't use a while loop here.
4726 if (arc_is_overflowing()) {
4727 mutex_enter(&arc_reclaim_lock);
4730 * Now that we've acquired the lock, we may no longer be
4731 * over the overflow limit, lets check.
4733 * We're ignoring the case of spurious wake ups. If that
4734 * were to happen, it'd let this thread consume an ARC
4735 * buffer before it should have (i.e. before we're under
4736 * the overflow limit and were signalled by the reclaim
4737 * thread). As long as that is a rare occurrence, it
4738 * shouldn't cause any harm.
4740 if (arc_is_overflowing()) {
4741 cv_signal(&arc_reclaim_thread_cv);
4742 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
4745 mutex_exit(&arc_reclaim_lock);
4748 VERIFY3U(hdr->b_type, ==, type);
4749 if (type == ARC_BUFC_METADATA) {
4750 arc_space_consume(size, ARC_SPACE_META);
4752 arc_space_consume(size, ARC_SPACE_DATA);
4756 * Update the state size. Note that ghost states have a
4757 * "ghost size" and so don't need to be updated.
4759 if (!GHOST_STATE(state)) {
4761 (void) refcount_add_many(&state->arcs_size, size, tag);
4764 * If this is reached via arc_read, the link is
4765 * protected by the hash lock. If reached via
4766 * arc_buf_alloc, the header should not be accessed by
4767 * any other thread. And, if reached via arc_read_done,
4768 * the hash lock will protect it if it's found in the
4769 * hash table; otherwise no other thread should be
4770 * trying to [add|remove]_reference it.
4772 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4773 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4774 (void) refcount_add_many(&state->arcs_esize[type],
4779 * If we are growing the cache, and we are adding anonymous
4780 * data, and we have outgrown arc_p, update arc_p
4782 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
4783 (refcount_count(&arc_anon->arcs_size) +
4784 refcount_count(&arc_mru->arcs_size) > arc_p))
4785 arc_p = MIN(arc_c, arc_p + size);
4787 ARCSTAT_BUMP(arcstat_allocated);
4791 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
4793 arc_free_data_impl(hdr, size, tag);
4798 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
4800 arc_buf_contents_t type = arc_buf_type(hdr);
4802 arc_free_data_impl(hdr, size, tag);
4803 if (type == ARC_BUFC_METADATA) {
4804 zio_buf_free(buf, size);
4806 ASSERT(type == ARC_BUFC_DATA);
4807 zio_data_buf_free(buf, size);
4812 * Free the arc data buffer.
4815 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4817 arc_state_t *state = hdr->b_l1hdr.b_state;
4818 arc_buf_contents_t type = arc_buf_type(hdr);
4820 /* protected by hash lock, if in the hash table */
4821 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4822 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4823 ASSERT(state != arc_anon && state != arc_l2c_only);
4825 (void) refcount_remove_many(&state->arcs_esize[type],
4828 (void) refcount_remove_many(&state->arcs_size, size, tag);
4830 VERIFY3U(hdr->b_type, ==, type);
4831 if (type == ARC_BUFC_METADATA) {
4832 arc_space_return(size, ARC_SPACE_META);
4834 ASSERT(type == ARC_BUFC_DATA);
4835 arc_space_return(size, ARC_SPACE_DATA);
4840 * This routine is called whenever a buffer is accessed.
4841 * NOTE: the hash lock is dropped in this function.
4844 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
4848 ASSERT(MUTEX_HELD(hash_lock));
4849 ASSERT(HDR_HAS_L1HDR(hdr));
4851 if (hdr->b_l1hdr.b_state == arc_anon) {
4853 * This buffer is not in the cache, and does not
4854 * appear in our "ghost" list. Add the new buffer
4858 ASSERT0(hdr->b_l1hdr.b_arc_access);
4859 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4860 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4861 arc_change_state(arc_mru, hdr, hash_lock);
4863 } else if (hdr->b_l1hdr.b_state == arc_mru) {
4864 now = ddi_get_lbolt();
4867 * If this buffer is here because of a prefetch, then either:
4868 * - clear the flag if this is a "referencing" read
4869 * (any subsequent access will bump this into the MFU state).
4871 * - move the buffer to the head of the list if this is
4872 * another prefetch (to make it less likely to be evicted).
4874 if (HDR_PREFETCH(hdr)) {
4875 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4876 /* link protected by hash lock */
4877 ASSERT(multilist_link_active(
4878 &hdr->b_l1hdr.b_arc_node));
4880 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4881 ARCSTAT_BUMP(arcstat_mru_hits);
4883 hdr->b_l1hdr.b_arc_access = now;
4888 * This buffer has been "accessed" only once so far,
4889 * but it is still in the cache. Move it to the MFU
4892 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
4894 * More than 125ms have passed since we
4895 * instantiated this buffer. Move it to the
4896 * most frequently used state.
4898 hdr->b_l1hdr.b_arc_access = now;
4899 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4900 arc_change_state(arc_mfu, hdr, hash_lock);
4902 ARCSTAT_BUMP(arcstat_mru_hits);
4903 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
4904 arc_state_t *new_state;
4906 * This buffer has been "accessed" recently, but
4907 * was evicted from the cache. Move it to the
4911 if (HDR_PREFETCH(hdr)) {
4912 new_state = arc_mru;
4913 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
4914 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4915 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4917 new_state = arc_mfu;
4918 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4921 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4922 arc_change_state(new_state, hdr, hash_lock);
4924 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
4925 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
4927 * This buffer has been accessed more than once and is
4928 * still in the cache. Keep it in the MFU state.
4930 * NOTE: an add_reference() that occurred when we did
4931 * the arc_read() will have kicked this off the list.
4932 * If it was a prefetch, we will explicitly move it to
4933 * the head of the list now.
4935 if ((HDR_PREFETCH(hdr)) != 0) {
4936 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4937 /* link protected by hash_lock */
4938 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
4940 ARCSTAT_BUMP(arcstat_mfu_hits);
4941 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4942 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
4943 arc_state_t *new_state = arc_mfu;
4945 * This buffer has been accessed more than once but has
4946 * been evicted from the cache. Move it back to the
4950 if (HDR_PREFETCH(hdr)) {
4952 * This is a prefetch access...
4953 * move this block back to the MRU state.
4955 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
4956 new_state = arc_mru;
4959 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4960 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4961 arc_change_state(new_state, hdr, hash_lock);
4963 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
4964 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
4966 * This buffer is on the 2nd Level ARC.
4969 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4970 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4971 arc_change_state(arc_mfu, hdr, hash_lock);
4973 ASSERT(!"invalid arc state");
4977 /* a generic arc_done_func_t which you can use */
4980 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
4982 if (zio == NULL || zio->io_error == 0)
4983 bcopy(buf->b_data, arg, arc_buf_size(buf));
4984 arc_buf_destroy(buf, arg);
4987 /* a generic arc_done_func_t */
4989 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
4991 arc_buf_t **bufp = arg;
4992 if (zio && zio->io_error) {
4993 arc_buf_destroy(buf, arg);
4997 ASSERT(buf->b_data);
5002 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
5004 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5005 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5006 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
5008 if (HDR_COMPRESSION_ENABLED(hdr)) {
5009 ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
5010 BP_GET_COMPRESS(bp));
5012 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5013 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5018 arc_read_done(zio_t *zio)
5020 arc_buf_hdr_t *hdr = zio->io_private;
5021 kmutex_t *hash_lock = NULL;
5022 arc_callback_t *callback_list;
5023 arc_callback_t *acb;
5024 boolean_t freeable = B_FALSE;
5025 boolean_t no_zio_error = (zio->io_error == 0);
5028 * The hdr was inserted into hash-table and removed from lists
5029 * prior to starting I/O. We should find this header, since
5030 * it's in the hash table, and it should be legit since it's
5031 * not possible to evict it during the I/O. The only possible
5032 * reason for it not to be found is if we were freed during the
5035 if (HDR_IN_HASH_TABLE(hdr)) {
5036 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5037 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5038 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5039 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5040 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5042 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5045 ASSERT((found == hdr &&
5046 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5047 (found == hdr && HDR_L2_READING(hdr)));
5048 ASSERT3P(hash_lock, !=, NULL);
5052 /* byteswap if necessary */
5053 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5054 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5055 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5057 hdr->b_l1hdr.b_byteswap =
5058 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5061 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5065 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5066 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
5067 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
5069 callback_list = hdr->b_l1hdr.b_acb;
5070 ASSERT3P(callback_list, !=, NULL);
5072 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) {
5074 * Only call arc_access on anonymous buffers. This is because
5075 * if we've issued an I/O for an evicted buffer, we've already
5076 * called arc_access (to prevent any simultaneous readers from
5077 * getting confused).
5079 arc_access(hdr, hash_lock);
5083 * If a read request has a callback (i.e. acb_done is not NULL), then we
5084 * make a buf containing the data according to the parameters which were
5085 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5086 * aren't needlessly decompressing the data multiple times.
5088 int callback_cnt = 0;
5089 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5093 /* This is a demand read since prefetches don't use callbacks */
5096 int error = arc_buf_alloc_impl(hdr, acb->acb_private,
5097 acb->acb_compressed, no_zio_error, &acb->acb_buf);
5099 zio->io_error = error;
5102 hdr->b_l1hdr.b_acb = NULL;
5103 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5104 if (callback_cnt == 0) {
5105 ASSERT(HDR_PREFETCH(hdr));
5106 ASSERT0(hdr->b_l1hdr.b_bufcnt);
5107 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5110 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5111 callback_list != NULL);
5114 arc_hdr_verify(hdr, zio->io_bp);
5116 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5117 if (hdr->b_l1hdr.b_state != arc_anon)
5118 arc_change_state(arc_anon, hdr, hash_lock);
5119 if (HDR_IN_HASH_TABLE(hdr))
5120 buf_hash_remove(hdr);
5121 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5125 * Broadcast before we drop the hash_lock to avoid the possibility
5126 * that the hdr (and hence the cv) might be freed before we get to
5127 * the cv_broadcast().
5129 cv_broadcast(&hdr->b_l1hdr.b_cv);
5131 if (hash_lock != NULL) {
5132 mutex_exit(hash_lock);
5135 * This block was freed while we waited for the read to
5136 * complete. It has been removed from the hash table and
5137 * moved to the anonymous state (so that it won't show up
5140 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5141 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5144 /* execute each callback and free its structure */
5145 while ((acb = callback_list) != NULL) {
5147 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
5149 if (acb->acb_zio_dummy != NULL) {
5150 acb->acb_zio_dummy->io_error = zio->io_error;
5151 zio_nowait(acb->acb_zio_dummy);
5154 callback_list = acb->acb_next;
5155 kmem_free(acb, sizeof (arc_callback_t));
5159 arc_hdr_destroy(hdr);
5163 * "Read" the block at the specified DVA (in bp) via the
5164 * cache. If the block is found in the cache, invoke the provided
5165 * callback immediately and return. Note that the `zio' parameter
5166 * in the callback will be NULL in this case, since no IO was
5167 * required. If the block is not in the cache pass the read request
5168 * on to the spa with a substitute callback function, so that the
5169 * requested block will be added to the cache.
5171 * If a read request arrives for a block that has a read in-progress,
5172 * either wait for the in-progress read to complete (and return the
5173 * results); or, if this is a read with a "done" func, add a record
5174 * to the read to invoke the "done" func when the read completes,
5175 * and return; or just return.
5177 * arc_read_done() will invoke all the requested "done" functions
5178 * for readers of this block.
5181 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
5182 void *private, zio_priority_t priority, int zio_flags,
5183 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5185 arc_buf_hdr_t *hdr = NULL;
5186 kmutex_t *hash_lock = NULL;
5188 uint64_t guid = spa_load_guid(spa);
5189 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
5191 ASSERT(!BP_IS_EMBEDDED(bp) ||
5192 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5195 if (!BP_IS_EMBEDDED(bp)) {
5197 * Embedded BP's have no DVA and require no I/O to "read".
5198 * Create an anonymous arc buf to back it.
5200 hdr = buf_hash_find(guid, bp, &hash_lock);
5203 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) {
5204 arc_buf_t *buf = NULL;
5205 *arc_flags |= ARC_FLAG_CACHED;
5207 if (HDR_IO_IN_PROGRESS(hdr)) {
5209 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5210 priority == ZIO_PRIORITY_SYNC_READ) {
5212 * This sync read must wait for an
5213 * in-progress async read (e.g. a predictive
5214 * prefetch). Async reads are queued
5215 * separately at the vdev_queue layer, so
5216 * this is a form of priority inversion.
5217 * Ideally, we would "inherit" the demand
5218 * i/o's priority by moving the i/o from
5219 * the async queue to the synchronous queue,
5220 * but there is currently no mechanism to do
5221 * so. Track this so that we can evaluate
5222 * the magnitude of this potential performance
5225 * Note that if the prefetch i/o is already
5226 * active (has been issued to the device),
5227 * the prefetch improved performance, because
5228 * we issued it sooner than we would have
5229 * without the prefetch.
5231 DTRACE_PROBE1(arc__sync__wait__for__async,
5232 arc_buf_hdr_t *, hdr);
5233 ARCSTAT_BUMP(arcstat_sync_wait_for_async);
5235 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5236 arc_hdr_clear_flags(hdr,
5237 ARC_FLAG_PREDICTIVE_PREFETCH);
5240 if (*arc_flags & ARC_FLAG_WAIT) {
5241 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5242 mutex_exit(hash_lock);
5245 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5248 arc_callback_t *acb = NULL;
5250 acb = kmem_zalloc(sizeof (arc_callback_t),
5252 acb->acb_done = done;
5253 acb->acb_private = private;
5254 acb->acb_compressed = compressed_read;
5256 acb->acb_zio_dummy = zio_null(pio,
5257 spa, NULL, NULL, NULL, zio_flags);
5259 ASSERT3P(acb->acb_done, !=, NULL);
5260 acb->acb_next = hdr->b_l1hdr.b_acb;
5261 hdr->b_l1hdr.b_acb = acb;
5262 mutex_exit(hash_lock);
5265 mutex_exit(hash_lock);
5269 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5270 hdr->b_l1hdr.b_state == arc_mfu);
5273 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5275 * This is a demand read which does not have to
5276 * wait for i/o because we did a predictive
5277 * prefetch i/o for it, which has completed.
5280 arc__demand__hit__predictive__prefetch,
5281 arc_buf_hdr_t *, hdr);
5283 arcstat_demand_hit_predictive_prefetch);
5284 arc_hdr_clear_flags(hdr,
5285 ARC_FLAG_PREDICTIVE_PREFETCH);
5287 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5289 /* Get a buf with the desired data in it. */
5290 VERIFY0(arc_buf_alloc_impl(hdr, private,
5291 compressed_read, B_TRUE, &buf));
5292 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5293 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5294 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5296 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5297 arc_access(hdr, hash_lock);
5298 if (*arc_flags & ARC_FLAG_L2CACHE)
5299 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5300 mutex_exit(hash_lock);
5301 ARCSTAT_BUMP(arcstat_hits);
5302 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5303 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5304 data, metadata, hits);
5307 done(NULL, buf, private);
5309 uint64_t lsize = BP_GET_LSIZE(bp);
5310 uint64_t psize = BP_GET_PSIZE(bp);
5311 arc_callback_t *acb;
5314 boolean_t devw = B_FALSE;
5318 /* this block is not in the cache */
5319 arc_buf_hdr_t *exists = NULL;
5320 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5321 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5322 BP_GET_COMPRESS(bp), type);
5324 if (!BP_IS_EMBEDDED(bp)) {
5325 hdr->b_dva = *BP_IDENTITY(bp);
5326 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5327 exists = buf_hash_insert(hdr, &hash_lock);
5329 if (exists != NULL) {
5330 /* somebody beat us to the hash insert */
5331 mutex_exit(hash_lock);
5332 buf_discard_identity(hdr);
5333 arc_hdr_destroy(hdr);
5334 goto top; /* restart the IO request */
5338 * This block is in the ghost cache. If it was L2-only
5339 * (and thus didn't have an L1 hdr), we realloc the
5340 * header to add an L1 hdr.
5342 if (!HDR_HAS_L1HDR(hdr)) {
5343 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5346 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5347 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
5348 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5349 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5350 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5351 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
5354 * This is a delicate dance that we play here.
5355 * This hdr is in the ghost list so we access it
5356 * to move it out of the ghost list before we
5357 * initiate the read. If it's a prefetch then
5358 * it won't have a callback so we'll remove the
5359 * reference that arc_buf_alloc_impl() created. We
5360 * do this after we've called arc_access() to
5361 * avoid hitting an assert in remove_reference().
5363 arc_access(hdr, hash_lock);
5364 arc_hdr_alloc_pabd(hdr);
5366 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5367 size = arc_hdr_size(hdr);
5370 * If compression is enabled on the hdr, then will do
5371 * RAW I/O and will store the compressed data in the hdr's
5372 * data block. Otherwise, the hdr's data block will contain
5373 * the uncompressed data.
5375 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5376 zio_flags |= ZIO_FLAG_RAW;
5379 if (*arc_flags & ARC_FLAG_PREFETCH)
5380 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5381 if (*arc_flags & ARC_FLAG_L2CACHE)
5382 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5383 if (BP_GET_LEVEL(bp) > 0)
5384 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5385 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5386 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5387 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5389 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5390 acb->acb_done = done;
5391 acb->acb_private = private;
5392 acb->acb_compressed = compressed_read;
5394 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5395 hdr->b_l1hdr.b_acb = acb;
5396 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5398 if (HDR_HAS_L2HDR(hdr) &&
5399 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5400 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5401 addr = hdr->b_l2hdr.b_daddr;
5403 * Lock out device removal.
5405 if (vdev_is_dead(vd) ||
5406 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5410 if (priority == ZIO_PRIORITY_ASYNC_READ)
5411 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5413 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5415 if (hash_lock != NULL)
5416 mutex_exit(hash_lock);
5419 * At this point, we have a level 1 cache miss. Try again in
5420 * L2ARC if possible.
5422 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5424 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5425 uint64_t, lsize, zbookmark_phys_t *, zb);
5426 ARCSTAT_BUMP(arcstat_misses);
5427 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5428 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5429 data, metadata, misses);
5434 racct_add_force(curproc, RACCT_READBPS, size);
5435 racct_add_force(curproc, RACCT_READIOPS, 1);
5436 PROC_UNLOCK(curproc);
5439 curthread->td_ru.ru_inblock++;
5442 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5444 * Read from the L2ARC if the following are true:
5445 * 1. The L2ARC vdev was previously cached.
5446 * 2. This buffer still has L2ARC metadata.
5447 * 3. This buffer isn't currently writing to the L2ARC.
5448 * 4. The L2ARC entry wasn't evicted, which may
5449 * also have invalidated the vdev.
5450 * 5. This isn't prefetch and l2arc_noprefetch is set.
5452 if (HDR_HAS_L2HDR(hdr) &&
5453 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5454 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5455 l2arc_read_callback_t *cb;
5459 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5460 ARCSTAT_BUMP(arcstat_l2_hits);
5462 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5464 cb->l2rcb_hdr = hdr;
5467 cb->l2rcb_flags = zio_flags;
5469 asize = vdev_psize_to_asize(vd, size);
5470 if (asize != size) {
5471 abd = abd_alloc_for_io(asize,
5472 HDR_ISTYPE_METADATA(hdr));
5473 cb->l2rcb_abd = abd;
5475 abd = hdr->b_l1hdr.b_pabd;
5478 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
5479 addr + asize <= vd->vdev_psize -
5480 VDEV_LABEL_END_SIZE);
5483 * l2arc read. The SCL_L2ARC lock will be
5484 * released by l2arc_read_done().
5485 * Issue a null zio if the underlying buffer
5486 * was squashed to zero size by compression.
5488 ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
5489 ZIO_COMPRESS_EMPTY);
5490 rzio = zio_read_phys(pio, vd, addr,
5493 l2arc_read_done, cb, priority,
5494 zio_flags | ZIO_FLAG_DONT_CACHE |
5496 ZIO_FLAG_DONT_PROPAGATE |
5497 ZIO_FLAG_DONT_RETRY, B_FALSE);
5498 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
5500 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
5502 if (*arc_flags & ARC_FLAG_NOWAIT) {
5507 ASSERT(*arc_flags & ARC_FLAG_WAIT);
5508 if (zio_wait(rzio) == 0)
5511 /* l2arc read error; goto zio_read() */
5513 DTRACE_PROBE1(l2arc__miss,
5514 arc_buf_hdr_t *, hdr);
5515 ARCSTAT_BUMP(arcstat_l2_misses);
5516 if (HDR_L2_WRITING(hdr))
5517 ARCSTAT_BUMP(arcstat_l2_rw_clash);
5518 spa_config_exit(spa, SCL_L2ARC, vd);
5522 spa_config_exit(spa, SCL_L2ARC, vd);
5523 if (l2arc_ndev != 0) {
5524 DTRACE_PROBE1(l2arc__miss,
5525 arc_buf_hdr_t *, hdr);
5526 ARCSTAT_BUMP(arcstat_l2_misses);
5530 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size,
5531 arc_read_done, hdr, priority, zio_flags, zb);
5533 if (*arc_flags & ARC_FLAG_WAIT)
5534 return (zio_wait(rzio));
5536 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5543 * Notify the arc that a block was freed, and thus will never be used again.
5546 arc_freed(spa_t *spa, const blkptr_t *bp)
5549 kmutex_t *hash_lock;
5550 uint64_t guid = spa_load_guid(spa);
5552 ASSERT(!BP_IS_EMBEDDED(bp));
5554 hdr = buf_hash_find(guid, bp, &hash_lock);
5559 * We might be trying to free a block that is still doing I/O
5560 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
5561 * dmu_sync-ed block). If this block is being prefetched, then it
5562 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
5563 * until the I/O completes. A block may also have a reference if it is
5564 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
5565 * have written the new block to its final resting place on disk but
5566 * without the dedup flag set. This would have left the hdr in the MRU
5567 * state and discoverable. When the txg finally syncs it detects that
5568 * the block was overridden in open context and issues an override I/O.
5569 * Since this is a dedup block, the override I/O will determine if the
5570 * block is already in the DDT. If so, then it will replace the io_bp
5571 * with the bp from the DDT and allow the I/O to finish. When the I/O
5572 * reaches the done callback, dbuf_write_override_done, it will
5573 * check to see if the io_bp and io_bp_override are identical.
5574 * If they are not, then it indicates that the bp was replaced with
5575 * the bp in the DDT and the override bp is freed. This allows
5576 * us to arrive here with a reference on a block that is being
5577 * freed. So if we have an I/O in progress, or a reference to
5578 * this hdr, then we don't destroy the hdr.
5580 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
5581 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
5582 arc_change_state(arc_anon, hdr, hash_lock);
5583 arc_hdr_destroy(hdr);
5584 mutex_exit(hash_lock);
5586 mutex_exit(hash_lock);
5592 * Release this buffer from the cache, making it an anonymous buffer. This
5593 * must be done after a read and prior to modifying the buffer contents.
5594 * If the buffer has more than one reference, we must make
5595 * a new hdr for the buffer.
5598 arc_release(arc_buf_t *buf, void *tag)
5600 arc_buf_hdr_t *hdr = buf->b_hdr;
5603 * It would be nice to assert that if it's DMU metadata (level >
5604 * 0 || it's the dnode file), then it must be syncing context.
5605 * But we don't know that information at this level.
5608 mutex_enter(&buf->b_evict_lock);
5610 ASSERT(HDR_HAS_L1HDR(hdr));
5613 * We don't grab the hash lock prior to this check, because if
5614 * the buffer's header is in the arc_anon state, it won't be
5615 * linked into the hash table.
5617 if (hdr->b_l1hdr.b_state == arc_anon) {
5618 mutex_exit(&buf->b_evict_lock);
5619 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5620 ASSERT(!HDR_IN_HASH_TABLE(hdr));
5621 ASSERT(!HDR_HAS_L2HDR(hdr));
5622 ASSERT(HDR_EMPTY(hdr));
5623 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5624 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
5625 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
5627 hdr->b_l1hdr.b_arc_access = 0;
5630 * If the buf is being overridden then it may already
5631 * have a hdr that is not empty.
5633 buf_discard_identity(hdr);
5639 kmutex_t *hash_lock = HDR_LOCK(hdr);
5640 mutex_enter(hash_lock);
5643 * This assignment is only valid as long as the hash_lock is
5644 * held, we must be careful not to reference state or the
5645 * b_state field after dropping the lock.
5647 arc_state_t *state = hdr->b_l1hdr.b_state;
5648 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5649 ASSERT3P(state, !=, arc_anon);
5651 /* this buffer is not on any list */
5652 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
5654 if (HDR_HAS_L2HDR(hdr)) {
5655 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5658 * We have to recheck this conditional again now that
5659 * we're holding the l2ad_mtx to prevent a race with
5660 * another thread which might be concurrently calling
5661 * l2arc_evict(). In that case, l2arc_evict() might have
5662 * destroyed the header's L2 portion as we were waiting
5663 * to acquire the l2ad_mtx.
5665 if (HDR_HAS_L2HDR(hdr)) {
5667 arc_hdr_l2hdr_destroy(hdr);
5670 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5674 * Do we have more than one buf?
5676 if (hdr->b_l1hdr.b_bufcnt > 1) {
5677 arc_buf_hdr_t *nhdr;
5678 uint64_t spa = hdr->b_spa;
5679 uint64_t psize = HDR_GET_PSIZE(hdr);
5680 uint64_t lsize = HDR_GET_LSIZE(hdr);
5681 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
5682 arc_buf_contents_t type = arc_buf_type(hdr);
5683 VERIFY3U(hdr->b_type, ==, type);
5685 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
5686 (void) remove_reference(hdr, hash_lock, tag);
5688 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
5689 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
5690 ASSERT(ARC_BUF_LAST(buf));
5694 * Pull the data off of this hdr and attach it to
5695 * a new anonymous hdr. Also find the last buffer
5696 * in the hdr's buffer list.
5698 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
5699 ASSERT3P(lastbuf, !=, NULL);
5702 * If the current arc_buf_t and the hdr are sharing their data
5703 * buffer, then we must stop sharing that block.
5705 if (arc_buf_is_shared(buf)) {
5706 VERIFY(!arc_buf_is_shared(lastbuf));
5709 * First, sever the block sharing relationship between
5710 * buf and the arc_buf_hdr_t.
5712 arc_unshare_buf(hdr, buf);
5715 * Now we need to recreate the hdr's b_pabd. Since we
5716 * have lastbuf handy, we try to share with it, but if
5717 * we can't then we allocate a new b_pabd and copy the
5718 * data from buf into it.
5720 if (arc_can_share(hdr, lastbuf)) {
5721 arc_share_buf(hdr, lastbuf);
5723 arc_hdr_alloc_pabd(hdr);
5724 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
5725 buf->b_data, psize);
5727 VERIFY3P(lastbuf->b_data, !=, NULL);
5728 } else if (HDR_SHARED_DATA(hdr)) {
5730 * Uncompressed shared buffers are always at the end
5731 * of the list. Compressed buffers don't have the
5732 * same requirements. This makes it hard to
5733 * simply assert that the lastbuf is shared so
5734 * we rely on the hdr's compression flags to determine
5735 * if we have a compressed, shared buffer.
5737 ASSERT(arc_buf_is_shared(lastbuf) ||
5738 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
5739 ASSERT(!ARC_BUF_SHARED(buf));
5741 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5742 ASSERT3P(state, !=, arc_l2c_only);
5744 (void) refcount_remove_many(&state->arcs_size,
5745 arc_buf_size(buf), buf);
5747 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5748 ASSERT3P(state, !=, arc_l2c_only);
5749 (void) refcount_remove_many(&state->arcs_esize[type],
5750 arc_buf_size(buf), buf);
5753 hdr->b_l1hdr.b_bufcnt -= 1;
5754 arc_cksum_verify(buf);
5756 arc_buf_unwatch(buf);
5759 mutex_exit(hash_lock);
5762 * Allocate a new hdr. The new hdr will contain a b_pabd
5763 * buffer which will be freed in arc_write().
5765 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
5766 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
5767 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
5768 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
5769 VERIFY3U(nhdr->b_type, ==, type);
5770 ASSERT(!HDR_SHARED_DATA(nhdr));
5772 nhdr->b_l1hdr.b_buf = buf;
5773 nhdr->b_l1hdr.b_bufcnt = 1;
5774 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
5777 mutex_exit(&buf->b_evict_lock);
5778 (void) refcount_add_many(&arc_anon->arcs_size,
5779 arc_buf_size(buf), buf);
5781 mutex_exit(&buf->b_evict_lock);
5782 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
5783 /* protected by hash lock, or hdr is on arc_anon */
5784 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
5785 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5786 arc_change_state(arc_anon, hdr, hash_lock);
5787 hdr->b_l1hdr.b_arc_access = 0;
5788 mutex_exit(hash_lock);
5790 buf_discard_identity(hdr);
5796 arc_released(arc_buf_t *buf)
5800 mutex_enter(&buf->b_evict_lock);
5801 released = (buf->b_data != NULL &&
5802 buf->b_hdr->b_l1hdr.b_state == arc_anon);
5803 mutex_exit(&buf->b_evict_lock);
5809 arc_referenced(arc_buf_t *buf)
5813 mutex_enter(&buf->b_evict_lock);
5814 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
5815 mutex_exit(&buf->b_evict_lock);
5816 return (referenced);
5821 arc_write_ready(zio_t *zio)
5823 arc_write_callback_t *callback = zio->io_private;
5824 arc_buf_t *buf = callback->awcb_buf;
5825 arc_buf_hdr_t *hdr = buf->b_hdr;
5826 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
5828 ASSERT(HDR_HAS_L1HDR(hdr));
5829 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
5830 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
5833 * If we're reexecuting this zio because the pool suspended, then
5834 * cleanup any state that was previously set the first time the
5835 * callback was invoked.
5837 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
5838 arc_cksum_free(hdr);
5840 arc_buf_unwatch(buf);
5842 if (hdr->b_l1hdr.b_pabd != NULL) {
5843 if (arc_buf_is_shared(buf)) {
5844 arc_unshare_buf(hdr, buf);
5846 arc_hdr_free_pabd(hdr);
5850 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5851 ASSERT(!HDR_SHARED_DATA(hdr));
5852 ASSERT(!arc_buf_is_shared(buf));
5854 callback->awcb_ready(zio, buf, callback->awcb_private);
5856 if (HDR_IO_IN_PROGRESS(hdr))
5857 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
5859 arc_cksum_compute(buf);
5860 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5862 enum zio_compress compress;
5863 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5864 compress = ZIO_COMPRESS_OFF;
5866 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
5867 compress = BP_GET_COMPRESS(zio->io_bp);
5869 HDR_SET_PSIZE(hdr, psize);
5870 arc_hdr_set_compress(hdr, compress);
5874 * Fill the hdr with data. If the hdr is compressed, the data we want
5875 * is available from the zio, otherwise we can take it from the buf.
5877 * We might be able to share the buf's data with the hdr here. However,
5878 * doing so would cause the ARC to be full of linear ABDs if we write a
5879 * lot of shareable data. As a compromise, we check whether scattered
5880 * ABDs are allowed, and assume that if they are then the user wants
5881 * the ARC to be primarily filled with them regardless of the data being
5882 * written. Therefore, if they're allowed then we allocate one and copy
5883 * the data into it; otherwise, we share the data directly if we can.
5885 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
5886 arc_hdr_alloc_pabd(hdr);
5889 * Ideally, we would always copy the io_abd into b_pabd, but the
5890 * user may have disabled compressed ARC, thus we must check the
5891 * hdr's compression setting rather than the io_bp's.
5893 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5894 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=,
5896 ASSERT3U(psize, >, 0);
5898 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
5900 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
5902 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
5906 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
5907 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
5908 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5910 arc_share_buf(hdr, buf);
5913 arc_hdr_verify(hdr, zio->io_bp);
5917 arc_write_children_ready(zio_t *zio)
5919 arc_write_callback_t *callback = zio->io_private;
5920 arc_buf_t *buf = callback->awcb_buf;
5922 callback->awcb_children_ready(zio, buf, callback->awcb_private);
5926 * The SPA calls this callback for each physical write that happens on behalf
5927 * of a logical write. See the comment in dbuf_write_physdone() for details.
5930 arc_write_physdone(zio_t *zio)
5932 arc_write_callback_t *cb = zio->io_private;
5933 if (cb->awcb_physdone != NULL)
5934 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
5938 arc_write_done(zio_t *zio)
5940 arc_write_callback_t *callback = zio->io_private;
5941 arc_buf_t *buf = callback->awcb_buf;
5942 arc_buf_hdr_t *hdr = buf->b_hdr;
5944 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5946 if (zio->io_error == 0) {
5947 arc_hdr_verify(hdr, zio->io_bp);
5949 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5950 buf_discard_identity(hdr);
5952 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
5953 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
5956 ASSERT(HDR_EMPTY(hdr));
5960 * If the block to be written was all-zero or compressed enough to be
5961 * embedded in the BP, no write was performed so there will be no
5962 * dva/birth/checksum. The buffer must therefore remain anonymous
5965 if (!HDR_EMPTY(hdr)) {
5966 arc_buf_hdr_t *exists;
5967 kmutex_t *hash_lock;
5969 ASSERT3U(zio->io_error, ==, 0);
5971 arc_cksum_verify(buf);
5973 exists = buf_hash_insert(hdr, &hash_lock);
5974 if (exists != NULL) {
5976 * This can only happen if we overwrite for
5977 * sync-to-convergence, because we remove
5978 * buffers from the hash table when we arc_free().
5980 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
5981 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
5982 panic("bad overwrite, hdr=%p exists=%p",
5983 (void *)hdr, (void *)exists);
5984 ASSERT(refcount_is_zero(
5985 &exists->b_l1hdr.b_refcnt));
5986 arc_change_state(arc_anon, exists, hash_lock);
5987 mutex_exit(hash_lock);
5988 arc_hdr_destroy(exists);
5989 exists = buf_hash_insert(hdr, &hash_lock);
5990 ASSERT3P(exists, ==, NULL);
5991 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
5993 ASSERT(zio->io_prop.zp_nopwrite);
5994 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
5995 panic("bad nopwrite, hdr=%p exists=%p",
5996 (void *)hdr, (void *)exists);
5999 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6000 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6001 ASSERT(BP_GET_DEDUP(zio->io_bp));
6002 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6005 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6006 /* if it's not anon, we are doing a scrub */
6007 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6008 arc_access(hdr, hash_lock);
6009 mutex_exit(hash_lock);
6011 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6014 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6015 callback->awcb_done(zio, buf, callback->awcb_private);
6017 abd_put(zio->io_abd);
6018 kmem_free(callback, sizeof (arc_write_callback_t));
6022 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6023 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready,
6024 arc_done_func_t *children_ready, arc_done_func_t *physdone,
6025 arc_done_func_t *done, void *private, zio_priority_t priority,
6026 int zio_flags, const zbookmark_phys_t *zb)
6028 arc_buf_hdr_t *hdr = buf->b_hdr;
6029 arc_write_callback_t *callback;
6031 zio_prop_t localprop = *zp;
6033 ASSERT3P(ready, !=, NULL);
6034 ASSERT3P(done, !=, NULL);
6035 ASSERT(!HDR_IO_ERROR(hdr));
6036 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6037 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6038 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6040 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6041 if (ARC_BUF_COMPRESSED(buf)) {
6043 * We're writing a pre-compressed buffer. Make the
6044 * compression algorithm requested by the zio_prop_t match
6045 * the pre-compressed buffer's compression algorithm.
6047 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6049 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6050 zio_flags |= ZIO_FLAG_RAW;
6052 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6053 callback->awcb_ready = ready;
6054 callback->awcb_children_ready = children_ready;
6055 callback->awcb_physdone = physdone;
6056 callback->awcb_done = done;
6057 callback->awcb_private = private;
6058 callback->awcb_buf = buf;
6061 * The hdr's b_pabd is now stale, free it now. A new data block
6062 * will be allocated when the zio pipeline calls arc_write_ready().
6064 if (hdr->b_l1hdr.b_pabd != NULL) {
6066 * If the buf is currently sharing the data block with
6067 * the hdr then we need to break that relationship here.
6068 * The hdr will remain with a NULL data pointer and the
6069 * buf will take sole ownership of the block.
6071 if (arc_buf_is_shared(buf)) {
6072 arc_unshare_buf(hdr, buf);
6074 arc_hdr_free_pabd(hdr);
6076 VERIFY3P(buf->b_data, !=, NULL);
6077 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6079 ASSERT(!arc_buf_is_shared(buf));
6080 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6082 zio = zio_write(pio, spa, txg, bp,
6083 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6084 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6085 (children_ready != NULL) ? arc_write_children_ready : NULL,
6086 arc_write_physdone, arc_write_done, callback,
6087 priority, zio_flags, zb);
6093 arc_memory_throttle(uint64_t reserve, uint64_t txg)
6096 uint64_t available_memory = ptob(freemem);
6097 static uint64_t page_load = 0;
6098 static uint64_t last_txg = 0;
6100 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
6102 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE)));
6105 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
6108 if (txg > last_txg) {
6113 * If we are in pageout, we know that memory is already tight,
6114 * the arc is already going to be evicting, so we just want to
6115 * continue to let page writes occur as quickly as possible.
6117 if (curproc == pageproc) {
6118 if (page_load > MAX(ptob(minfree), available_memory) / 4)
6119 return (SET_ERROR(ERESTART));
6120 /* Note: reserve is inflated, so we deflate */
6121 page_load += reserve / 8;
6123 } else if (page_load > 0 && arc_reclaim_needed()) {
6124 /* memory is low, delay before restarting */
6125 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6126 return (SET_ERROR(EAGAIN));
6134 arc_tempreserve_clear(uint64_t reserve)
6136 atomic_add_64(&arc_tempreserve, -reserve);
6137 ASSERT((int64_t)arc_tempreserve >= 0);
6141 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
6146 if (reserve > arc_c/4 && !arc_no_grow) {
6147 arc_c = MIN(arc_c_max, reserve * 4);
6148 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
6150 if (reserve > arc_c)
6151 return (SET_ERROR(ENOMEM));
6154 * Don't count loaned bufs as in flight dirty data to prevent long
6155 * network delays from blocking transactions that are ready to be
6156 * assigned to a txg.
6159 /* assert that it has not wrapped around */
6160 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6162 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
6163 arc_loaned_bytes), 0);
6166 * Writes will, almost always, require additional memory allocations
6167 * in order to compress/encrypt/etc the data. We therefore need to
6168 * make sure that there is sufficient available memory for this.
6170 error = arc_memory_throttle(reserve, txg);
6175 * Throttle writes when the amount of dirty data in the cache
6176 * gets too large. We try to keep the cache less than half full
6177 * of dirty blocks so that our sync times don't grow too large.
6178 * Note: if two requests come in concurrently, we might let them
6179 * both succeed, when one of them should fail. Not a huge deal.
6182 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
6183 anon_size > arc_c / 4) {
6184 uint64_t meta_esize =
6185 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6186 uint64_t data_esize =
6187 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6188 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6189 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6190 arc_tempreserve >> 10, meta_esize >> 10,
6191 data_esize >> 10, reserve >> 10, arc_c >> 10);
6192 return (SET_ERROR(ERESTART));
6194 atomic_add_64(&arc_tempreserve, reserve);
6199 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6200 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
6202 size->value.ui64 = refcount_count(&state->arcs_size);
6203 evict_data->value.ui64 =
6204 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6205 evict_metadata->value.ui64 =
6206 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6210 arc_kstat_update(kstat_t *ksp, int rw)
6212 arc_stats_t *as = ksp->ks_data;
6214 if (rw == KSTAT_WRITE) {
6217 arc_kstat_update_state(arc_anon,
6218 &as->arcstat_anon_size,
6219 &as->arcstat_anon_evictable_data,
6220 &as->arcstat_anon_evictable_metadata);
6221 arc_kstat_update_state(arc_mru,
6222 &as->arcstat_mru_size,
6223 &as->arcstat_mru_evictable_data,
6224 &as->arcstat_mru_evictable_metadata);
6225 arc_kstat_update_state(arc_mru_ghost,
6226 &as->arcstat_mru_ghost_size,
6227 &as->arcstat_mru_ghost_evictable_data,
6228 &as->arcstat_mru_ghost_evictable_metadata);
6229 arc_kstat_update_state(arc_mfu,
6230 &as->arcstat_mfu_size,
6231 &as->arcstat_mfu_evictable_data,
6232 &as->arcstat_mfu_evictable_metadata);
6233 arc_kstat_update_state(arc_mfu_ghost,
6234 &as->arcstat_mfu_ghost_size,
6235 &as->arcstat_mfu_ghost_evictable_data,
6236 &as->arcstat_mfu_ghost_evictable_metadata);
6243 * This function *must* return indices evenly distributed between all
6244 * sublists of the multilist. This is needed due to how the ARC eviction
6245 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6246 * distributed between all sublists and uses this assumption when
6247 * deciding which sublist to evict from and how much to evict from it.
6250 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6252 arc_buf_hdr_t *hdr = obj;
6255 * We rely on b_dva to generate evenly distributed index
6256 * numbers using buf_hash below. So, as an added precaution,
6257 * let's make sure we never add empty buffers to the arc lists.
6259 ASSERT(!HDR_EMPTY(hdr));
6262 * The assumption here, is the hash value for a given
6263 * arc_buf_hdr_t will remain constant throughout it's lifetime
6264 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
6265 * Thus, we don't need to store the header's sublist index
6266 * on insertion, as this index can be recalculated on removal.
6268 * Also, the low order bits of the hash value are thought to be
6269 * distributed evenly. Otherwise, in the case that the multilist
6270 * has a power of two number of sublists, each sublists' usage
6271 * would not be evenly distributed.
6273 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
6274 multilist_get_num_sublists(ml));
6278 static eventhandler_tag arc_event_lowmem = NULL;
6281 arc_lowmem(void *arg __unused, int howto __unused)
6284 mutex_enter(&arc_reclaim_lock);
6285 /* XXX: Memory deficit should be passed as argument. */
6286 needfree = btoc(arc_c >> arc_shrink_shift);
6287 DTRACE_PROBE(arc__needfree);
6288 cv_signal(&arc_reclaim_thread_cv);
6291 * It is unsafe to block here in arbitrary threads, because we can come
6292 * here from ARC itself and may hold ARC locks and thus risk a deadlock
6293 * with ARC reclaim thread.
6295 if (curproc == pageproc)
6296 (void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
6297 mutex_exit(&arc_reclaim_lock);
6302 arc_state_init(void)
6304 arc_anon = &ARC_anon;
6306 arc_mru_ghost = &ARC_mru_ghost;
6308 arc_mfu_ghost = &ARC_mfu_ghost;
6309 arc_l2c_only = &ARC_l2c_only;
6311 arc_mru->arcs_list[ARC_BUFC_METADATA] =
6312 multilist_create(sizeof (arc_buf_hdr_t),
6313 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6314 arc_state_multilist_index_func);
6315 arc_mru->arcs_list[ARC_BUFC_DATA] =
6316 multilist_create(sizeof (arc_buf_hdr_t),
6317 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6318 arc_state_multilist_index_func);
6319 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
6320 multilist_create(sizeof (arc_buf_hdr_t),
6321 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6322 arc_state_multilist_index_func);
6323 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
6324 multilist_create(sizeof (arc_buf_hdr_t),
6325 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6326 arc_state_multilist_index_func);
6327 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
6328 multilist_create(sizeof (arc_buf_hdr_t),
6329 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6330 arc_state_multilist_index_func);
6331 arc_mfu->arcs_list[ARC_BUFC_DATA] =
6332 multilist_create(sizeof (arc_buf_hdr_t),
6333 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6334 arc_state_multilist_index_func);
6335 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
6336 multilist_create(sizeof (arc_buf_hdr_t),
6337 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6338 arc_state_multilist_index_func);
6339 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
6340 multilist_create(sizeof (arc_buf_hdr_t),
6341 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6342 arc_state_multilist_index_func);
6343 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
6344 multilist_create(sizeof (arc_buf_hdr_t),
6345 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6346 arc_state_multilist_index_func);
6347 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
6348 multilist_create(sizeof (arc_buf_hdr_t),
6349 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6350 arc_state_multilist_index_func);
6352 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6353 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6354 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6355 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6356 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6357 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6358 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6359 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6360 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6361 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6362 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6363 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6365 refcount_create(&arc_anon->arcs_size);
6366 refcount_create(&arc_mru->arcs_size);
6367 refcount_create(&arc_mru_ghost->arcs_size);
6368 refcount_create(&arc_mfu->arcs_size);
6369 refcount_create(&arc_mfu_ghost->arcs_size);
6370 refcount_create(&arc_l2c_only->arcs_size);
6374 arc_state_fini(void)
6376 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6377 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6378 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
6379 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
6380 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
6381 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
6382 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
6383 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
6384 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
6385 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
6386 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
6387 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
6389 refcount_destroy(&arc_anon->arcs_size);
6390 refcount_destroy(&arc_mru->arcs_size);
6391 refcount_destroy(&arc_mru_ghost->arcs_size);
6392 refcount_destroy(&arc_mfu->arcs_size);
6393 refcount_destroy(&arc_mfu_ghost->arcs_size);
6394 refcount_destroy(&arc_l2c_only->arcs_size);
6396 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
6397 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
6398 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
6399 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
6400 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
6401 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
6402 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
6403 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
6415 int i, prefetch_tunable_set = 0;
6418 * allmem is "all memory that we could possibly use".
6422 uint64_t allmem = ptob(physmem - swapfs_minfree);
6424 uint64_t allmem = (physmem * PAGESIZE) / 2;
6427 uint64_t allmem = kmem_size();
6431 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
6432 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
6433 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
6435 mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
6436 cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL);
6438 /* Convert seconds to clock ticks */
6439 arc_min_prefetch_lifespan = 1 * hz;
6441 /* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */
6442 arc_c_min = MAX(allmem / 32, arc_abs_min);
6443 /* set max to 5/8 of all memory, or all but 1GB, whichever is more */
6444 if (allmem >= 1 << 30)
6445 arc_c_max = allmem - (1 << 30);
6447 arc_c_max = arc_c_min;
6448 arc_c_max = MAX(allmem * 5 / 8, arc_c_max);
6451 * In userland, there's only the memory pressure that we artificially
6452 * create (see arc_available_memory()). Don't let arc_c get too
6453 * small, because it can cause transactions to be larger than
6454 * arc_c, causing arc_tempreserve_space() to fail.
6457 arc_c_min = arc_c_max / 2;
6462 * Allow the tunables to override our calculations if they are
6465 if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) {
6466 arc_c_max = zfs_arc_max;
6467 arc_c_min = MIN(arc_c_min, arc_c_max);
6469 if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max)
6470 arc_c_min = zfs_arc_min;
6474 arc_p = (arc_c >> 1);
6477 /* limit meta-data to 1/4 of the arc capacity */
6478 arc_meta_limit = arc_c_max / 4;
6482 * Metadata is stored in the kernel's heap. Don't let us
6483 * use more than half the heap for the ARC.
6485 arc_meta_limit = MIN(arc_meta_limit,
6486 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
6489 /* Allow the tunable to override if it is reasonable */
6490 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
6491 arc_meta_limit = zfs_arc_meta_limit;
6493 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
6494 arc_c_min = arc_meta_limit / 2;
6496 if (zfs_arc_meta_min > 0) {
6497 arc_meta_min = zfs_arc_meta_min;
6499 arc_meta_min = arc_c_min / 2;
6502 if (zfs_arc_grow_retry > 0)
6503 arc_grow_retry = zfs_arc_grow_retry;
6505 if (zfs_arc_shrink_shift > 0)
6506 arc_shrink_shift = zfs_arc_shrink_shift;
6509 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
6511 if (arc_no_grow_shift >= arc_shrink_shift)
6512 arc_no_grow_shift = arc_shrink_shift - 1;
6514 if (zfs_arc_p_min_shift > 0)
6515 arc_p_min_shift = zfs_arc_p_min_shift;
6517 /* if kmem_flags are set, lets try to use less memory */
6518 if (kmem_debugging())
6520 if (arc_c < arc_c_min)
6523 zfs_arc_min = arc_c_min;
6524 zfs_arc_max = arc_c_max;
6529 arc_reclaim_thread_exit = B_FALSE;
6530 arc_dnlc_evicts_thread_exit = FALSE;
6532 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
6533 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
6535 if (arc_ksp != NULL) {
6536 arc_ksp->ks_data = &arc_stats;
6537 arc_ksp->ks_update = arc_kstat_update;
6538 kstat_install(arc_ksp);
6541 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
6542 TS_RUN, minclsyspri);
6545 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
6546 EVENTHANDLER_PRI_FIRST);
6549 (void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0,
6550 TS_RUN, minclsyspri);
6556 * Calculate maximum amount of dirty data per pool.
6558 * If it has been set by /etc/system, take that.
6559 * Otherwise, use a percentage of physical memory defined by
6560 * zfs_dirty_data_max_percent (default 10%) with a cap at
6561 * zfs_dirty_data_max_max (default 4GB).
6563 if (zfs_dirty_data_max == 0) {
6564 zfs_dirty_data_max = ptob(physmem) *
6565 zfs_dirty_data_max_percent / 100;
6566 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
6567 zfs_dirty_data_max_max);
6571 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
6572 prefetch_tunable_set = 1;
6575 if (prefetch_tunable_set == 0) {
6576 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
6578 printf(" add \"vfs.zfs.prefetch_disable=0\" "
6579 "to /boot/loader.conf.\n");
6580 zfs_prefetch_disable = 1;
6583 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
6584 prefetch_tunable_set == 0) {
6585 printf("ZFS NOTICE: Prefetch is disabled by default if less "
6586 "than 4GB of RAM is present;\n"
6587 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
6588 "to /boot/loader.conf.\n");
6589 zfs_prefetch_disable = 1;
6592 /* Warn about ZFS memory and address space requirements. */
6593 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
6594 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
6595 "expect unstable behavior.\n");
6597 if (allmem < 512 * (1 << 20)) {
6598 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
6599 "expect unstable behavior.\n");
6600 printf(" Consider tuning vm.kmem_size and "
6601 "vm.kmem_size_max\n");
6602 printf(" in /boot/loader.conf.\n");
6610 mutex_enter(&arc_reclaim_lock);
6611 arc_reclaim_thread_exit = B_TRUE;
6613 * The reclaim thread will set arc_reclaim_thread_exit back to
6614 * B_FALSE when it is finished exiting; we're waiting for that.
6616 while (arc_reclaim_thread_exit) {
6617 cv_signal(&arc_reclaim_thread_cv);
6618 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
6620 mutex_exit(&arc_reclaim_lock);
6622 /* Use B_TRUE to ensure *all* buffers are evicted */
6623 arc_flush(NULL, B_TRUE);
6625 mutex_enter(&arc_dnlc_evicts_lock);
6626 arc_dnlc_evicts_thread_exit = TRUE;
6628 * The user evicts thread will set arc_user_evicts_thread_exit
6629 * to FALSE when it is finished exiting; we're waiting for that.
6631 while (arc_dnlc_evicts_thread_exit) {
6632 cv_signal(&arc_dnlc_evicts_cv);
6633 cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
6635 mutex_exit(&arc_dnlc_evicts_lock);
6639 if (arc_ksp != NULL) {
6640 kstat_delete(arc_ksp);
6644 mutex_destroy(&arc_reclaim_lock);
6645 cv_destroy(&arc_reclaim_thread_cv);
6646 cv_destroy(&arc_reclaim_waiters_cv);
6648 mutex_destroy(&arc_dnlc_evicts_lock);
6649 cv_destroy(&arc_dnlc_evicts_cv);
6654 ASSERT0(arc_loaned_bytes);
6657 if (arc_event_lowmem != NULL)
6658 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
6665 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
6666 * It uses dedicated storage devices to hold cached data, which are populated
6667 * using large infrequent writes. The main role of this cache is to boost
6668 * the performance of random read workloads. The intended L2ARC devices
6669 * include short-stroked disks, solid state disks, and other media with
6670 * substantially faster read latency than disk.
6672 * +-----------------------+
6674 * +-----------------------+
6677 * l2arc_feed_thread() arc_read()
6681 * +---------------+ |
6683 * +---------------+ |
6688 * +-------+ +-------+
6690 * | cache | | cache |
6691 * +-------+ +-------+
6692 * +=========+ .-----.
6693 * : L2ARC : |-_____-|
6694 * : devices : | Disks |
6695 * +=========+ `-_____-'
6697 * Read requests are satisfied from the following sources, in order:
6700 * 2) vdev cache of L2ARC devices
6702 * 4) vdev cache of disks
6705 * Some L2ARC device types exhibit extremely slow write performance.
6706 * To accommodate for this there are some significant differences between
6707 * the L2ARC and traditional cache design:
6709 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
6710 * the ARC behave as usual, freeing buffers and placing headers on ghost
6711 * lists. The ARC does not send buffers to the L2ARC during eviction as
6712 * this would add inflated write latencies for all ARC memory pressure.
6714 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
6715 * It does this by periodically scanning buffers from the eviction-end of
6716 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
6717 * not already there. It scans until a headroom of buffers is satisfied,
6718 * which itself is a buffer for ARC eviction. If a compressible buffer is
6719 * found during scanning and selected for writing to an L2ARC device, we
6720 * temporarily boost scanning headroom during the next scan cycle to make
6721 * sure we adapt to compression effects (which might significantly reduce
6722 * the data volume we write to L2ARC). The thread that does this is
6723 * l2arc_feed_thread(), illustrated below; example sizes are included to
6724 * provide a better sense of ratio than this diagram:
6727 * +---------------------+----------+
6728 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
6729 * +---------------------+----------+ | o L2ARC eligible
6730 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
6731 * +---------------------+----------+ |
6732 * 15.9 Gbytes ^ 32 Mbytes |
6734 * l2arc_feed_thread()
6736 * l2arc write hand <--[oooo]--'
6740 * +==============================+
6741 * L2ARC dev |####|#|###|###| |####| ... |
6742 * +==============================+
6745 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
6746 * evicted, then the L2ARC has cached a buffer much sooner than it probably
6747 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
6748 * safe to say that this is an uncommon case, since buffers at the end of
6749 * the ARC lists have moved there due to inactivity.
6751 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
6752 * then the L2ARC simply misses copying some buffers. This serves as a
6753 * pressure valve to prevent heavy read workloads from both stalling the ARC
6754 * with waits and clogging the L2ARC with writes. This also helps prevent
6755 * the potential for the L2ARC to churn if it attempts to cache content too
6756 * quickly, such as during backups of the entire pool.
6758 * 5. After system boot and before the ARC has filled main memory, there are
6759 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
6760 * lists can remain mostly static. Instead of searching from tail of these
6761 * lists as pictured, the l2arc_feed_thread() will search from the list heads
6762 * for eligible buffers, greatly increasing its chance of finding them.
6764 * The L2ARC device write speed is also boosted during this time so that
6765 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
6766 * there are no L2ARC reads, and no fear of degrading read performance
6767 * through increased writes.
6769 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
6770 * the vdev queue can aggregate them into larger and fewer writes. Each
6771 * device is written to in a rotor fashion, sweeping writes through
6772 * available space then repeating.
6774 * 7. The L2ARC does not store dirty content. It never needs to flush
6775 * write buffers back to disk based storage.
6777 * 8. If an ARC buffer is written (and dirtied) which also exists in the
6778 * L2ARC, the now stale L2ARC buffer is immediately dropped.
6780 * The performance of the L2ARC can be tweaked by a number of tunables, which
6781 * may be necessary for different workloads:
6783 * l2arc_write_max max write bytes per interval
6784 * l2arc_write_boost extra write bytes during device warmup
6785 * l2arc_noprefetch skip caching prefetched buffers
6786 * l2arc_headroom number of max device writes to precache
6787 * l2arc_headroom_boost when we find compressed buffers during ARC
6788 * scanning, we multiply headroom by this
6789 * percentage factor for the next scan cycle,
6790 * since more compressed buffers are likely to
6792 * l2arc_feed_secs seconds between L2ARC writing
6794 * Tunables may be removed or added as future performance improvements are
6795 * integrated, and also may become zpool properties.
6797 * There are three key functions that control how the L2ARC warms up:
6799 * l2arc_write_eligible() check if a buffer is eligible to cache
6800 * l2arc_write_size() calculate how much to write
6801 * l2arc_write_interval() calculate sleep delay between writes
6803 * These three functions determine what to write, how much, and how quickly
6808 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
6811 * A buffer is *not* eligible for the L2ARC if it:
6812 * 1. belongs to a different spa.
6813 * 2. is already cached on the L2ARC.
6814 * 3. has an I/O in progress (it may be an incomplete read).
6815 * 4. is flagged not eligible (zfs property).
6817 if (hdr->b_spa != spa_guid) {
6818 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
6821 if (HDR_HAS_L2HDR(hdr)) {
6822 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
6825 if (HDR_IO_IN_PROGRESS(hdr)) {
6826 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
6829 if (!HDR_L2CACHE(hdr)) {
6830 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
6838 l2arc_write_size(void)
6843 * Make sure our globals have meaningful values in case the user
6846 size = l2arc_write_max;
6848 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
6849 "be greater than zero, resetting it to the default (%d)",
6851 size = l2arc_write_max = L2ARC_WRITE_SIZE;
6854 if (arc_warm == B_FALSE)
6855 size += l2arc_write_boost;
6862 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
6864 clock_t interval, next, now;
6867 * If the ARC lists are busy, increase our write rate; if the
6868 * lists are stale, idle back. This is achieved by checking
6869 * how much we previously wrote - if it was more than half of
6870 * what we wanted, schedule the next write much sooner.
6872 if (l2arc_feed_again && wrote > (wanted / 2))
6873 interval = (hz * l2arc_feed_min_ms) / 1000;
6875 interval = hz * l2arc_feed_secs;
6877 now = ddi_get_lbolt();
6878 next = MAX(now, MIN(now + interval, began + interval));
6884 * Cycle through L2ARC devices. This is how L2ARC load balances.
6885 * If a device is returned, this also returns holding the spa config lock.
6887 static l2arc_dev_t *
6888 l2arc_dev_get_next(void)
6890 l2arc_dev_t *first, *next = NULL;
6893 * Lock out the removal of spas (spa_namespace_lock), then removal
6894 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
6895 * both locks will be dropped and a spa config lock held instead.
6897 mutex_enter(&spa_namespace_lock);
6898 mutex_enter(&l2arc_dev_mtx);
6900 /* if there are no vdevs, there is nothing to do */
6901 if (l2arc_ndev == 0)
6905 next = l2arc_dev_last;
6907 /* loop around the list looking for a non-faulted vdev */
6909 next = list_head(l2arc_dev_list);
6911 next = list_next(l2arc_dev_list, next);
6913 next = list_head(l2arc_dev_list);
6916 /* if we have come back to the start, bail out */
6919 else if (next == first)
6922 } while (vdev_is_dead(next->l2ad_vdev));
6924 /* if we were unable to find any usable vdevs, return NULL */
6925 if (vdev_is_dead(next->l2ad_vdev))
6928 l2arc_dev_last = next;
6931 mutex_exit(&l2arc_dev_mtx);
6934 * Grab the config lock to prevent the 'next' device from being
6935 * removed while we are writing to it.
6938 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
6939 mutex_exit(&spa_namespace_lock);
6945 * Free buffers that were tagged for destruction.
6948 l2arc_do_free_on_write()
6951 l2arc_data_free_t *df, *df_prev;
6953 mutex_enter(&l2arc_free_on_write_mtx);
6954 buflist = l2arc_free_on_write;
6956 for (df = list_tail(buflist); df; df = df_prev) {
6957 df_prev = list_prev(buflist, df);
6958 ASSERT3P(df->l2df_abd, !=, NULL);
6959 abd_free(df->l2df_abd);
6960 list_remove(buflist, df);
6961 kmem_free(df, sizeof (l2arc_data_free_t));
6964 mutex_exit(&l2arc_free_on_write_mtx);
6968 * A write to a cache device has completed. Update all headers to allow
6969 * reads from these buffers to begin.
6972 l2arc_write_done(zio_t *zio)
6974 l2arc_write_callback_t *cb;
6977 arc_buf_hdr_t *head, *hdr, *hdr_prev;
6978 kmutex_t *hash_lock;
6979 int64_t bytes_dropped = 0;
6981 cb = zio->io_private;
6982 ASSERT3P(cb, !=, NULL);
6983 dev = cb->l2wcb_dev;
6984 ASSERT3P(dev, !=, NULL);
6985 head = cb->l2wcb_head;
6986 ASSERT3P(head, !=, NULL);
6987 buflist = &dev->l2ad_buflist;
6988 ASSERT3P(buflist, !=, NULL);
6989 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
6990 l2arc_write_callback_t *, cb);
6992 if (zio->io_error != 0)
6993 ARCSTAT_BUMP(arcstat_l2_writes_error);
6996 * All writes completed, or an error was hit.
6999 mutex_enter(&dev->l2ad_mtx);
7000 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7001 hdr_prev = list_prev(buflist, hdr);
7003 hash_lock = HDR_LOCK(hdr);
7006 * We cannot use mutex_enter or else we can deadlock
7007 * with l2arc_write_buffers (due to swapping the order
7008 * the hash lock and l2ad_mtx are taken).
7010 if (!mutex_tryenter(hash_lock)) {
7012 * Missed the hash lock. We must retry so we
7013 * don't leave the ARC_FLAG_L2_WRITING bit set.
7015 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7018 * We don't want to rescan the headers we've
7019 * already marked as having been written out, so
7020 * we reinsert the head node so we can pick up
7021 * where we left off.
7023 list_remove(buflist, head);
7024 list_insert_after(buflist, hdr, head);
7026 mutex_exit(&dev->l2ad_mtx);
7029 * We wait for the hash lock to become available
7030 * to try and prevent busy waiting, and increase
7031 * the chance we'll be able to acquire the lock
7032 * the next time around.
7034 mutex_enter(hash_lock);
7035 mutex_exit(hash_lock);
7040 * We could not have been moved into the arc_l2c_only
7041 * state while in-flight due to our ARC_FLAG_L2_WRITING
7042 * bit being set. Let's just ensure that's being enforced.
7044 ASSERT(HDR_HAS_L1HDR(hdr));
7046 if (zio->io_error != 0) {
7048 * Error - drop L2ARC entry.
7050 list_remove(buflist, hdr);
7052 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7054 ARCSTAT_INCR(arcstat_l2_asize, -arc_hdr_size(hdr));
7055 ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr));
7057 bytes_dropped += arc_hdr_size(hdr);
7058 (void) refcount_remove_many(&dev->l2ad_alloc,
7059 arc_hdr_size(hdr), hdr);
7063 * Allow ARC to begin reads and ghost list evictions to
7066 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7068 mutex_exit(hash_lock);
7071 atomic_inc_64(&l2arc_writes_done);
7072 list_remove(buflist, head);
7073 ASSERT(!HDR_HAS_L1HDR(head));
7074 kmem_cache_free(hdr_l2only_cache, head);
7075 mutex_exit(&dev->l2ad_mtx);
7077 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7079 l2arc_do_free_on_write();
7081 kmem_free(cb, sizeof (l2arc_write_callback_t));
7085 * A read to a cache device completed. Validate buffer contents before
7086 * handing over to the regular ARC routines.
7089 l2arc_read_done(zio_t *zio)
7091 l2arc_read_callback_t *cb;
7093 kmutex_t *hash_lock;
7094 boolean_t valid_cksum;
7096 ASSERT3P(zio->io_vd, !=, NULL);
7097 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
7099 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
7101 cb = zio->io_private;
7102 ASSERT3P(cb, !=, NULL);
7103 hdr = cb->l2rcb_hdr;
7104 ASSERT3P(hdr, !=, NULL);
7106 hash_lock = HDR_LOCK(hdr);
7107 mutex_enter(hash_lock);
7108 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
7111 * If the data was read into a temporary buffer,
7112 * move it and free the buffer.
7114 if (cb->l2rcb_abd != NULL) {
7115 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
7116 if (zio->io_error == 0) {
7117 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd,
7122 * The following must be done regardless of whether
7123 * there was an error:
7124 * - free the temporary buffer
7125 * - point zio to the real ARC buffer
7126 * - set zio size accordingly
7127 * These are required because zio is either re-used for
7128 * an I/O of the block in the case of the error
7129 * or the zio is passed to arc_read_done() and it
7132 abd_free(cb->l2rcb_abd);
7133 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
7134 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
7137 ASSERT3P(zio->io_abd, !=, NULL);
7140 * Check this survived the L2ARC journey.
7142 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd);
7143 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
7144 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
7146 valid_cksum = arc_cksum_is_equal(hdr, zio);
7147 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
7148 mutex_exit(hash_lock);
7149 zio->io_private = hdr;
7152 mutex_exit(hash_lock);
7154 * Buffer didn't survive caching. Increment stats and
7155 * reissue to the original storage device.
7157 if (zio->io_error != 0) {
7158 ARCSTAT_BUMP(arcstat_l2_io_error);
7160 zio->io_error = SET_ERROR(EIO);
7163 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
7166 * If there's no waiter, issue an async i/o to the primary
7167 * storage now. If there *is* a waiter, the caller must
7168 * issue the i/o in a context where it's OK to block.
7170 if (zio->io_waiter == NULL) {
7171 zio_t *pio = zio_unique_parent(zio);
7173 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
7175 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
7176 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done,
7177 hdr, zio->io_priority, cb->l2rcb_flags,
7182 kmem_free(cb, sizeof (l2arc_read_callback_t));
7186 * This is the list priority from which the L2ARC will search for pages to
7187 * cache. This is used within loops (0..3) to cycle through lists in the
7188 * desired order. This order can have a significant effect on cache
7191 * Currently the metadata lists are hit first, MFU then MRU, followed by
7192 * the data lists. This function returns a locked list, and also returns
7195 static multilist_sublist_t *
7196 l2arc_sublist_lock(int list_num)
7198 multilist_t *ml = NULL;
7201 ASSERT(list_num >= 0 && list_num <= 3);
7205 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
7208 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
7211 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
7214 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
7219 * Return a randomly-selected sublist. This is acceptable
7220 * because the caller feeds only a little bit of data for each
7221 * call (8MB). Subsequent calls will result in different
7222 * sublists being selected.
7224 idx = multilist_get_random_index(ml);
7225 return (multilist_sublist_lock(ml, idx));
7229 * Evict buffers from the device write hand to the distance specified in
7230 * bytes. This distance may span populated buffers, it may span nothing.
7231 * This is clearing a region on the L2ARC device ready for writing.
7232 * If the 'all' boolean is set, every buffer is evicted.
7235 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
7238 arc_buf_hdr_t *hdr, *hdr_prev;
7239 kmutex_t *hash_lock;
7242 buflist = &dev->l2ad_buflist;
7244 if (!all && dev->l2ad_first) {
7246 * This is the first sweep through the device. There is
7252 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
7254 * When nearing the end of the device, evict to the end
7255 * before the device write hand jumps to the start.
7257 taddr = dev->l2ad_end;
7259 taddr = dev->l2ad_hand + distance;
7261 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
7262 uint64_t, taddr, boolean_t, all);
7265 mutex_enter(&dev->l2ad_mtx);
7266 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
7267 hdr_prev = list_prev(buflist, hdr);
7269 hash_lock = HDR_LOCK(hdr);
7272 * We cannot use mutex_enter or else we can deadlock
7273 * with l2arc_write_buffers (due to swapping the order
7274 * the hash lock and l2ad_mtx are taken).
7276 if (!mutex_tryenter(hash_lock)) {
7278 * Missed the hash lock. Retry.
7280 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
7281 mutex_exit(&dev->l2ad_mtx);
7282 mutex_enter(hash_lock);
7283 mutex_exit(hash_lock);
7287 if (HDR_L2_WRITE_HEAD(hdr)) {
7289 * We hit a write head node. Leave it for
7290 * l2arc_write_done().
7292 list_remove(buflist, hdr);
7293 mutex_exit(hash_lock);
7297 if (!all && HDR_HAS_L2HDR(hdr) &&
7298 (hdr->b_l2hdr.b_daddr >= taddr ||
7299 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
7301 * We've evicted to the target address,
7302 * or the end of the device.
7304 mutex_exit(hash_lock);
7308 ASSERT(HDR_HAS_L2HDR(hdr));
7309 if (!HDR_HAS_L1HDR(hdr)) {
7310 ASSERT(!HDR_L2_READING(hdr));
7312 * This doesn't exist in the ARC. Destroy.
7313 * arc_hdr_destroy() will call list_remove()
7314 * and decrement arcstat_l2_size.
7316 arc_change_state(arc_anon, hdr, hash_lock);
7317 arc_hdr_destroy(hdr);
7319 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
7320 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
7322 * Invalidate issued or about to be issued
7323 * reads, since we may be about to write
7324 * over this location.
7326 if (HDR_L2_READING(hdr)) {
7327 ARCSTAT_BUMP(arcstat_l2_evict_reading);
7328 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
7331 /* Ensure this header has finished being written */
7332 ASSERT(!HDR_L2_WRITING(hdr));
7334 arc_hdr_l2hdr_destroy(hdr);
7336 mutex_exit(hash_lock);
7338 mutex_exit(&dev->l2ad_mtx);
7342 * Find and write ARC buffers to the L2ARC device.
7344 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
7345 * for reading until they have completed writing.
7346 * The headroom_boost is an in-out parameter used to maintain headroom boost
7347 * state between calls to this function.
7349 * Returns the number of bytes actually written (which may be smaller than
7350 * the delta by which the device hand has changed due to alignment).
7353 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
7355 arc_buf_hdr_t *hdr, *hdr_prev, *head;
7356 uint64_t write_asize, write_psize, write_sz, headroom;
7358 l2arc_write_callback_t *cb;
7360 uint64_t guid = spa_load_guid(spa);
7363 ASSERT3P(dev->l2ad_vdev, !=, NULL);
7366 write_sz = write_asize = write_psize = 0;
7368 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
7369 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
7371 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
7373 * Copy buffers for L2ARC writing.
7375 for (try = 0; try <= 3; try++) {
7376 multilist_sublist_t *mls = l2arc_sublist_lock(try);
7377 uint64_t passed_sz = 0;
7379 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
7382 * L2ARC fast warmup.
7384 * Until the ARC is warm and starts to evict, read from the
7385 * head of the ARC lists rather than the tail.
7387 if (arc_warm == B_FALSE)
7388 hdr = multilist_sublist_head(mls);
7390 hdr = multilist_sublist_tail(mls);
7392 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
7394 headroom = target_sz * l2arc_headroom;
7395 if (zfs_compressed_arc_enabled)
7396 headroom = (headroom * l2arc_headroom_boost) / 100;
7398 for (; hdr; hdr = hdr_prev) {
7399 kmutex_t *hash_lock;
7401 if (arc_warm == B_FALSE)
7402 hdr_prev = multilist_sublist_next(mls, hdr);
7404 hdr_prev = multilist_sublist_prev(mls, hdr);
7405 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned,
7406 HDR_GET_LSIZE(hdr));
7408 hash_lock = HDR_LOCK(hdr);
7409 if (!mutex_tryenter(hash_lock)) {
7410 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
7412 * Skip this buffer rather than waiting.
7417 passed_sz += HDR_GET_LSIZE(hdr);
7418 if (passed_sz > headroom) {
7422 mutex_exit(hash_lock);
7423 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
7427 if (!l2arc_write_eligible(guid, hdr)) {
7428 mutex_exit(hash_lock);
7433 * We rely on the L1 portion of the header below, so
7434 * it's invalid for this header to have been evicted out
7435 * of the ghost cache, prior to being written out. The
7436 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
7438 ASSERT(HDR_HAS_L1HDR(hdr));
7440 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
7441 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7442 ASSERT3U(arc_hdr_size(hdr), >, 0);
7443 uint64_t size = arc_hdr_size(hdr);
7444 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
7447 if ((write_psize + asize) > target_sz) {
7449 mutex_exit(hash_lock);
7450 ARCSTAT_BUMP(arcstat_l2_write_full);
7456 * Insert a dummy header on the buflist so
7457 * l2arc_write_done() can find where the
7458 * write buffers begin without searching.
7460 mutex_enter(&dev->l2ad_mtx);
7461 list_insert_head(&dev->l2ad_buflist, head);
7462 mutex_exit(&dev->l2ad_mtx);
7465 sizeof (l2arc_write_callback_t), KM_SLEEP);
7466 cb->l2wcb_dev = dev;
7467 cb->l2wcb_head = head;
7468 pio = zio_root(spa, l2arc_write_done, cb,
7470 ARCSTAT_BUMP(arcstat_l2_write_pios);
7473 hdr->b_l2hdr.b_dev = dev;
7474 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
7475 arc_hdr_set_flags(hdr,
7476 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
7478 mutex_enter(&dev->l2ad_mtx);
7479 list_insert_head(&dev->l2ad_buflist, hdr);
7480 mutex_exit(&dev->l2ad_mtx);
7482 (void) refcount_add_many(&dev->l2ad_alloc, size, hdr);
7485 * Normally the L2ARC can use the hdr's data, but if
7486 * we're sharing data between the hdr and one of its
7487 * bufs, L2ARC needs its own copy of the data so that
7488 * the ZIO below can't race with the buf consumer.
7489 * Another case where we need to create a copy of the
7490 * data is when the buffer size is not device-aligned
7491 * and we need to pad the block to make it such.
7492 * That also keeps the clock hand suitably aligned.
7494 * To ensure that the copy will be available for the
7495 * lifetime of the ZIO and be cleaned up afterwards, we
7496 * add it to the l2arc_free_on_write queue.
7499 if (!HDR_SHARED_DATA(hdr) && size == asize) {
7500 to_write = hdr->b_l1hdr.b_pabd;
7502 to_write = abd_alloc_for_io(asize,
7503 HDR_ISTYPE_METADATA(hdr));
7504 abd_copy(to_write, hdr->b_l1hdr.b_pabd, size);
7505 if (asize != size) {
7506 abd_zero_off(to_write, size,
7509 l2arc_free_abd_on_write(to_write, asize,
7512 wzio = zio_write_phys(pio, dev->l2ad_vdev,
7513 hdr->b_l2hdr.b_daddr, asize, to_write,
7514 ZIO_CHECKSUM_OFF, NULL, hdr,
7515 ZIO_PRIORITY_ASYNC_WRITE,
7516 ZIO_FLAG_CANFAIL, B_FALSE);
7518 write_sz += HDR_GET_LSIZE(hdr);
7519 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
7522 write_asize += size;
7523 write_psize += asize;
7524 dev->l2ad_hand += asize;
7526 mutex_exit(hash_lock);
7528 (void) zio_nowait(wzio);
7531 multilist_sublist_unlock(mls);
7537 /* No buffers selected for writing? */
7540 ASSERT(!HDR_HAS_L1HDR(head));
7541 kmem_cache_free(hdr_l2only_cache, head);
7545 ASSERT3U(write_psize, <=, target_sz);
7546 ARCSTAT_BUMP(arcstat_l2_writes_sent);
7547 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
7548 ARCSTAT_INCR(arcstat_l2_size, write_sz);
7549 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
7550 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0);
7553 * Bump device hand to the device start if it is approaching the end.
7554 * l2arc_evict() will already have evicted ahead for this case.
7556 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
7557 dev->l2ad_hand = dev->l2ad_start;
7558 dev->l2ad_first = B_FALSE;
7561 dev->l2ad_writing = B_TRUE;
7562 (void) zio_wait(pio);
7563 dev->l2ad_writing = B_FALSE;
7565 return (write_asize);
7569 * This thread feeds the L2ARC at regular intervals. This is the beating
7570 * heart of the L2ARC.
7573 l2arc_feed_thread(void *dummy __unused)
7578 uint64_t size, wrote;
7579 clock_t begin, next = ddi_get_lbolt();
7581 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
7583 mutex_enter(&l2arc_feed_thr_lock);
7585 while (l2arc_thread_exit == 0) {
7586 CALLB_CPR_SAFE_BEGIN(&cpr);
7587 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
7588 next - ddi_get_lbolt());
7589 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
7590 next = ddi_get_lbolt() + hz;
7593 * Quick check for L2ARC devices.
7595 mutex_enter(&l2arc_dev_mtx);
7596 if (l2arc_ndev == 0) {
7597 mutex_exit(&l2arc_dev_mtx);
7600 mutex_exit(&l2arc_dev_mtx);
7601 begin = ddi_get_lbolt();
7604 * This selects the next l2arc device to write to, and in
7605 * doing so the next spa to feed from: dev->l2ad_spa. This
7606 * will return NULL if there are now no l2arc devices or if
7607 * they are all faulted.
7609 * If a device is returned, its spa's config lock is also
7610 * held to prevent device removal. l2arc_dev_get_next()
7611 * will grab and release l2arc_dev_mtx.
7613 if ((dev = l2arc_dev_get_next()) == NULL)
7616 spa = dev->l2ad_spa;
7617 ASSERT3P(spa, !=, NULL);
7620 * If the pool is read-only then force the feed thread to
7621 * sleep a little longer.
7623 if (!spa_writeable(spa)) {
7624 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
7625 spa_config_exit(spa, SCL_L2ARC, dev);
7630 * Avoid contributing to memory pressure.
7632 if (arc_reclaim_needed()) {
7633 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
7634 spa_config_exit(spa, SCL_L2ARC, dev);
7638 ARCSTAT_BUMP(arcstat_l2_feeds);
7640 size = l2arc_write_size();
7643 * Evict L2ARC buffers that will be overwritten.
7645 l2arc_evict(dev, size, B_FALSE);
7648 * Write ARC buffers.
7650 wrote = l2arc_write_buffers(spa, dev, size);
7653 * Calculate interval between writes.
7655 next = l2arc_write_interval(begin, size, wrote);
7656 spa_config_exit(spa, SCL_L2ARC, dev);
7659 l2arc_thread_exit = 0;
7660 cv_broadcast(&l2arc_feed_thr_cv);
7661 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
7666 l2arc_vdev_present(vdev_t *vd)
7670 mutex_enter(&l2arc_dev_mtx);
7671 for (dev = list_head(l2arc_dev_list); dev != NULL;
7672 dev = list_next(l2arc_dev_list, dev)) {
7673 if (dev->l2ad_vdev == vd)
7676 mutex_exit(&l2arc_dev_mtx);
7678 return (dev != NULL);
7682 * Add a vdev for use by the L2ARC. By this point the spa has already
7683 * validated the vdev and opened it.
7686 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
7688 l2arc_dev_t *adddev;
7690 ASSERT(!l2arc_vdev_present(vd));
7692 vdev_ashift_optimize(vd);
7695 * Create a new l2arc device entry.
7697 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
7698 adddev->l2ad_spa = spa;
7699 adddev->l2ad_vdev = vd;
7700 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
7701 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
7702 adddev->l2ad_hand = adddev->l2ad_start;
7703 adddev->l2ad_first = B_TRUE;
7704 adddev->l2ad_writing = B_FALSE;
7706 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
7708 * This is a list of all ARC buffers that are still valid on the
7711 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
7712 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
7714 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
7715 refcount_create(&adddev->l2ad_alloc);
7718 * Add device to global list
7720 mutex_enter(&l2arc_dev_mtx);
7721 list_insert_head(l2arc_dev_list, adddev);
7722 atomic_inc_64(&l2arc_ndev);
7723 mutex_exit(&l2arc_dev_mtx);
7727 * Remove a vdev from the L2ARC.
7730 l2arc_remove_vdev(vdev_t *vd)
7732 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
7735 * Find the device by vdev
7737 mutex_enter(&l2arc_dev_mtx);
7738 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
7739 nextdev = list_next(l2arc_dev_list, dev);
7740 if (vd == dev->l2ad_vdev) {
7745 ASSERT3P(remdev, !=, NULL);
7748 * Remove device from global list
7750 list_remove(l2arc_dev_list, remdev);
7751 l2arc_dev_last = NULL; /* may have been invalidated */
7752 atomic_dec_64(&l2arc_ndev);
7753 mutex_exit(&l2arc_dev_mtx);
7756 * Clear all buflists and ARC references. L2ARC device flush.
7758 l2arc_evict(remdev, 0, B_TRUE);
7759 list_destroy(&remdev->l2ad_buflist);
7760 mutex_destroy(&remdev->l2ad_mtx);
7761 refcount_destroy(&remdev->l2ad_alloc);
7762 kmem_free(remdev, sizeof (l2arc_dev_t));
7768 l2arc_thread_exit = 0;
7770 l2arc_writes_sent = 0;
7771 l2arc_writes_done = 0;
7773 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
7774 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
7775 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
7776 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
7778 l2arc_dev_list = &L2ARC_dev_list;
7779 l2arc_free_on_write = &L2ARC_free_on_write;
7780 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
7781 offsetof(l2arc_dev_t, l2ad_node));
7782 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
7783 offsetof(l2arc_data_free_t, l2df_list_node));
7790 * This is called from dmu_fini(), which is called from spa_fini();
7791 * Because of this, we can assume that all l2arc devices have
7792 * already been removed when the pools themselves were removed.
7795 l2arc_do_free_on_write();
7797 mutex_destroy(&l2arc_feed_thr_lock);
7798 cv_destroy(&l2arc_feed_thr_cv);
7799 mutex_destroy(&l2arc_dev_mtx);
7800 mutex_destroy(&l2arc_free_on_write_mtx);
7802 list_destroy(l2arc_dev_list);
7803 list_destroy(l2arc_free_on_write);
7809 if (!(spa_mode_global & FWRITE))
7812 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
7813 TS_RUN, minclsyspri);
7819 if (!(spa_mode_global & FWRITE))
7822 mutex_enter(&l2arc_feed_thr_lock);
7823 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
7824 l2arc_thread_exit = 1;
7825 while (l2arc_thread_exit != 0)
7826 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
7827 mutex_exit(&l2arc_feed_thr_lock);
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