4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
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) 2011, 2014 by Delphix. All rights reserved.
24 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
25 * Copyright 2014 Nexenta Systems, Inc. All rights reserved.
29 * DVA-based Adjustable Replacement Cache
31 * While much of the theory of operation used here is
32 * based on the self-tuning, low overhead replacement cache
33 * presented by Megiddo and Modha at FAST 2003, there are some
34 * significant differences:
36 * 1. The Megiddo and Modha model assumes any page is evictable.
37 * Pages in its cache cannot be "locked" into memory. This makes
38 * the eviction algorithm simple: evict the last page in the list.
39 * This also make the performance characteristics easy to reason
40 * about. Our cache is not so simple. At any given moment, some
41 * subset of the blocks in the cache are un-evictable because we
42 * have handed out a reference to them. Blocks are only evictable
43 * when there are no external references active. This makes
44 * eviction far more problematic: we choose to evict the evictable
45 * blocks that are the "lowest" in the list.
47 * There are times when it is not possible to evict the requested
48 * space. In these circumstances we are unable to adjust the cache
49 * size. To prevent the cache growing unbounded at these times we
50 * implement a "cache throttle" that slows the flow of new data
51 * into the cache until we can make space available.
53 * 2. The Megiddo and Modha model assumes a fixed cache size.
54 * Pages are evicted when the cache is full and there is a cache
55 * miss. Our model has a variable sized cache. It grows with
56 * high use, but also tries to react to memory pressure from the
57 * operating system: decreasing its size when system memory is
60 * 3. The Megiddo and Modha model assumes a fixed page size. All
61 * elements of the cache are therefore exactly the same size. So
62 * when adjusting the cache size following a cache miss, its simply
63 * a matter of choosing a single page to evict. In our model, we
64 * have variable sized cache blocks (rangeing from 512 bytes to
65 * 128K bytes). We therefore choose a set of blocks to evict to make
66 * space for a cache miss that approximates as closely as possible
67 * the space used by the new block.
69 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
70 * by N. Megiddo & D. Modha, FAST 2003
76 * A new reference to a cache buffer can be obtained in two
77 * ways: 1) via a hash table lookup using the DVA as a key,
78 * or 2) via one of the ARC lists. The arc_read() interface
79 * uses method 1, while the internal arc algorithms for
80 * adjusting the cache use method 2. We therefore provide two
81 * types of locks: 1) the hash table lock array, and 2) the
84 * Buffers do not have their own mutexs, rather they rely on the
85 * hash table mutexs for the bulk of their protection (i.e. most
86 * fields in the arc_buf_hdr_t are protected by these mutexs).
88 * buf_hash_find() returns the appropriate mutex (held) when it
89 * locates the requested buffer in the hash table. It returns
90 * NULL for the mutex if the buffer was not in the table.
92 * buf_hash_remove() expects the appropriate hash mutex to be
93 * already held before it is invoked.
95 * Each arc state also has a mutex which is used to protect the
96 * buffer list associated with the state. When attempting to
97 * obtain a hash table lock while holding an arc list lock you
98 * must use: mutex_tryenter() to avoid deadlock. Also note that
99 * the active state mutex must be held before the ghost state mutex.
101 * Arc buffers may have an associated eviction callback function.
102 * This function will be invoked prior to removing the buffer (e.g.
103 * in arc_do_user_evicts()). Note however that the data associated
104 * with the buffer may be evicted prior to the callback. The callback
105 * must be made with *no locks held* (to prevent deadlock). Additionally,
106 * the users of callbacks must ensure that their private data is
107 * protected from simultaneous callbacks from arc_clear_callback()
108 * and arc_do_user_evicts().
110 * Note that the majority of the performance stats are manipulated
111 * with atomic operations.
113 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
115 * - L2ARC buflist creation
116 * - L2ARC buflist eviction
117 * - L2ARC write completion, which walks L2ARC buflists
118 * - ARC header destruction, as it removes from L2ARC buflists
119 * - ARC header release, as it removes from L2ARC buflists
124 #include <sys/zio_compress.h>
125 #include <sys/zfs_context.h>
127 #include <sys/refcount.h>
128 #include <sys/vdev.h>
129 #include <sys/vdev_impl.h>
130 #include <sys/dsl_pool.h>
132 #include <sys/dnlc.h>
134 #include <sys/callb.h>
135 #include <sys/kstat.h>
136 #include <sys/trim_map.h>
137 #include <zfs_fletcher.h>
140 #include <vm/vm_pageout.h>
141 #include <machine/vmparam.h>
145 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
146 boolean_t arc_watch = B_FALSE;
151 static kmutex_t arc_reclaim_thr_lock;
152 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
153 static uint8_t arc_thread_exit;
155 #define ARC_REDUCE_DNLC_PERCENT 3
156 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
158 typedef enum arc_reclaim_strategy {
159 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
160 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
161 } arc_reclaim_strategy_t;
164 * The number of iterations through arc_evict_*() before we
165 * drop & reacquire the lock.
167 int arc_evict_iterations = 100;
169 /* number of seconds before growing cache again */
170 static int arc_grow_retry = 60;
172 /* shift of arc_c for calculating both min and max arc_p */
173 static int arc_p_min_shift = 4;
175 /* log2(fraction of arc to reclaim) */
176 static int arc_shrink_shift = 5;
179 * minimum lifespan of a prefetch block in clock ticks
180 * (initialized in arc_init())
182 static int arc_min_prefetch_lifespan;
185 * If this percent of memory is free, don't throttle.
187 int arc_lotsfree_percent = 10;
190 extern int zfs_prefetch_disable;
193 * The arc has filled available memory and has now warmed up.
195 static boolean_t arc_warm;
197 uint64_t zfs_arc_max;
198 uint64_t zfs_arc_min;
199 uint64_t zfs_arc_meta_limit = 0;
200 int zfs_arc_grow_retry = 0;
201 int zfs_arc_shrink_shift = 0;
202 int zfs_arc_p_min_shift = 0;
203 int zfs_disable_dup_eviction = 0;
204 uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
205 u_int zfs_arc_free_target = 0;
207 static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS);
208 static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS);
212 arc_free_target_init(void *unused __unused)
215 zfs_arc_free_target = vm_pageout_wakeup_thresh;
217 SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
218 arc_free_target_init, NULL);
220 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
221 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
222 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
223 TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize);
224 TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
225 SYSCTL_DECL(_vfs_zfs);
226 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
228 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
230 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
231 &zfs_arc_average_blocksize, 0,
232 "ARC average blocksize");
233 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
234 &arc_shrink_shift, 0,
235 "log2(fraction of arc to reclaim)");
238 * We don't have a tunable for arc_free_target due to the dependency on
239 * pagedaemon initialisation.
241 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
242 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
243 sysctl_vfs_zfs_arc_free_target, "IU",
244 "Desired number of free pages below which ARC triggers reclaim");
247 sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
252 val = zfs_arc_free_target;
253 err = sysctl_handle_int(oidp, &val, 0, req);
254 if (err != 0 || req->newptr == NULL)
259 if (val > cnt.v_page_count)
262 zfs_arc_free_target = val;
268 * Must be declared here, before the definition of corresponding kstat
269 * macro which uses the same names will confuse the compiler.
271 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit,
272 CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t),
273 sysctl_vfs_zfs_arc_meta_limit, "QU",
274 "ARC metadata limit");
278 * Note that buffers can be in one of 6 states:
279 * ARC_anon - anonymous (discussed below)
280 * ARC_mru - recently used, currently cached
281 * ARC_mru_ghost - recentely used, no longer in cache
282 * ARC_mfu - frequently used, currently cached
283 * ARC_mfu_ghost - frequently used, no longer in cache
284 * ARC_l2c_only - exists in L2ARC but not other states
285 * When there are no active references to the buffer, they are
286 * are linked onto a list in one of these arc states. These are
287 * the only buffers that can be evicted or deleted. Within each
288 * state there are multiple lists, one for meta-data and one for
289 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
290 * etc.) is tracked separately so that it can be managed more
291 * explicitly: favored over data, limited explicitly.
293 * Anonymous buffers are buffers that are not associated with
294 * a DVA. These are buffers that hold dirty block copies
295 * before they are written to stable storage. By definition,
296 * they are "ref'd" and are considered part of arc_mru
297 * that cannot be freed. Generally, they will aquire a DVA
298 * as they are written and migrate onto the arc_mru list.
300 * The ARC_l2c_only state is for buffers that are in the second
301 * level ARC but no longer in any of the ARC_m* lists. The second
302 * level ARC itself may also contain buffers that are in any of
303 * the ARC_m* states - meaning that a buffer can exist in two
304 * places. The reason for the ARC_l2c_only state is to keep the
305 * buffer header in the hash table, so that reads that hit the
306 * second level ARC benefit from these fast lookups.
309 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
313 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
318 * must be power of two for mask use to work
321 #define ARC_BUFC_NUMDATALISTS 16
322 #define ARC_BUFC_NUMMETADATALISTS 16
323 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
325 typedef struct arc_state {
326 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
327 uint64_t arcs_size; /* total amount of data in this state */
328 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
329 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
332 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
335 static arc_state_t ARC_anon;
336 static arc_state_t ARC_mru;
337 static arc_state_t ARC_mru_ghost;
338 static arc_state_t ARC_mfu;
339 static arc_state_t ARC_mfu_ghost;
340 static arc_state_t ARC_l2c_only;
342 typedef struct arc_stats {
343 kstat_named_t arcstat_hits;
344 kstat_named_t arcstat_misses;
345 kstat_named_t arcstat_demand_data_hits;
346 kstat_named_t arcstat_demand_data_misses;
347 kstat_named_t arcstat_demand_metadata_hits;
348 kstat_named_t arcstat_demand_metadata_misses;
349 kstat_named_t arcstat_prefetch_data_hits;
350 kstat_named_t arcstat_prefetch_data_misses;
351 kstat_named_t arcstat_prefetch_metadata_hits;
352 kstat_named_t arcstat_prefetch_metadata_misses;
353 kstat_named_t arcstat_mru_hits;
354 kstat_named_t arcstat_mru_ghost_hits;
355 kstat_named_t arcstat_mfu_hits;
356 kstat_named_t arcstat_mfu_ghost_hits;
357 kstat_named_t arcstat_allocated;
358 kstat_named_t arcstat_deleted;
359 kstat_named_t arcstat_stolen;
360 kstat_named_t arcstat_recycle_miss;
362 * Number of buffers that could not be evicted because the hash lock
363 * was held by another thread. The lock may not necessarily be held
364 * by something using the same buffer, since hash locks are shared
365 * by multiple buffers.
367 kstat_named_t arcstat_mutex_miss;
369 * Number of buffers skipped because they have I/O in progress, are
370 * indrect prefetch buffers that have not lived long enough, or are
371 * not from the spa we're trying to evict from.
373 kstat_named_t arcstat_evict_skip;
374 kstat_named_t arcstat_evict_l2_cached;
375 kstat_named_t arcstat_evict_l2_eligible;
376 kstat_named_t arcstat_evict_l2_ineligible;
377 kstat_named_t arcstat_hash_elements;
378 kstat_named_t arcstat_hash_elements_max;
379 kstat_named_t arcstat_hash_collisions;
380 kstat_named_t arcstat_hash_chains;
381 kstat_named_t arcstat_hash_chain_max;
382 kstat_named_t arcstat_p;
383 kstat_named_t arcstat_c;
384 kstat_named_t arcstat_c_min;
385 kstat_named_t arcstat_c_max;
386 kstat_named_t arcstat_size;
387 kstat_named_t arcstat_hdr_size;
388 kstat_named_t arcstat_data_size;
389 kstat_named_t arcstat_other_size;
390 kstat_named_t arcstat_l2_hits;
391 kstat_named_t arcstat_l2_misses;
392 kstat_named_t arcstat_l2_feeds;
393 kstat_named_t arcstat_l2_rw_clash;
394 kstat_named_t arcstat_l2_read_bytes;
395 kstat_named_t arcstat_l2_write_bytes;
396 kstat_named_t arcstat_l2_writes_sent;
397 kstat_named_t arcstat_l2_writes_done;
398 kstat_named_t arcstat_l2_writes_error;
399 kstat_named_t arcstat_l2_writes_hdr_miss;
400 kstat_named_t arcstat_l2_evict_lock_retry;
401 kstat_named_t arcstat_l2_evict_reading;
402 kstat_named_t arcstat_l2_free_on_write;
403 kstat_named_t arcstat_l2_cdata_free_on_write;
404 kstat_named_t arcstat_l2_abort_lowmem;
405 kstat_named_t arcstat_l2_cksum_bad;
406 kstat_named_t arcstat_l2_io_error;
407 kstat_named_t arcstat_l2_size;
408 kstat_named_t arcstat_l2_asize;
409 kstat_named_t arcstat_l2_hdr_size;
410 kstat_named_t arcstat_l2_compress_successes;
411 kstat_named_t arcstat_l2_compress_zeros;
412 kstat_named_t arcstat_l2_compress_failures;
413 kstat_named_t arcstat_l2_write_trylock_fail;
414 kstat_named_t arcstat_l2_write_passed_headroom;
415 kstat_named_t arcstat_l2_write_spa_mismatch;
416 kstat_named_t arcstat_l2_write_in_l2;
417 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
418 kstat_named_t arcstat_l2_write_not_cacheable;
419 kstat_named_t arcstat_l2_write_full;
420 kstat_named_t arcstat_l2_write_buffer_iter;
421 kstat_named_t arcstat_l2_write_pios;
422 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
423 kstat_named_t arcstat_l2_write_buffer_list_iter;
424 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
425 kstat_named_t arcstat_memory_throttle_count;
426 kstat_named_t arcstat_duplicate_buffers;
427 kstat_named_t arcstat_duplicate_buffers_size;
428 kstat_named_t arcstat_duplicate_reads;
429 kstat_named_t arcstat_meta_used;
430 kstat_named_t arcstat_meta_limit;
431 kstat_named_t arcstat_meta_max;
434 static arc_stats_t arc_stats = {
435 { "hits", KSTAT_DATA_UINT64 },
436 { "misses", KSTAT_DATA_UINT64 },
437 { "demand_data_hits", KSTAT_DATA_UINT64 },
438 { "demand_data_misses", KSTAT_DATA_UINT64 },
439 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
440 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
441 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
442 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
443 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
444 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
445 { "mru_hits", KSTAT_DATA_UINT64 },
446 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
447 { "mfu_hits", KSTAT_DATA_UINT64 },
448 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
449 { "allocated", KSTAT_DATA_UINT64 },
450 { "deleted", KSTAT_DATA_UINT64 },
451 { "stolen", KSTAT_DATA_UINT64 },
452 { "recycle_miss", KSTAT_DATA_UINT64 },
453 { "mutex_miss", KSTAT_DATA_UINT64 },
454 { "evict_skip", KSTAT_DATA_UINT64 },
455 { "evict_l2_cached", KSTAT_DATA_UINT64 },
456 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
457 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
458 { "hash_elements", KSTAT_DATA_UINT64 },
459 { "hash_elements_max", KSTAT_DATA_UINT64 },
460 { "hash_collisions", KSTAT_DATA_UINT64 },
461 { "hash_chains", KSTAT_DATA_UINT64 },
462 { "hash_chain_max", KSTAT_DATA_UINT64 },
463 { "p", KSTAT_DATA_UINT64 },
464 { "c", KSTAT_DATA_UINT64 },
465 { "c_min", KSTAT_DATA_UINT64 },
466 { "c_max", KSTAT_DATA_UINT64 },
467 { "size", KSTAT_DATA_UINT64 },
468 { "hdr_size", KSTAT_DATA_UINT64 },
469 { "data_size", KSTAT_DATA_UINT64 },
470 { "other_size", KSTAT_DATA_UINT64 },
471 { "l2_hits", KSTAT_DATA_UINT64 },
472 { "l2_misses", KSTAT_DATA_UINT64 },
473 { "l2_feeds", KSTAT_DATA_UINT64 },
474 { "l2_rw_clash", KSTAT_DATA_UINT64 },
475 { "l2_read_bytes", KSTAT_DATA_UINT64 },
476 { "l2_write_bytes", KSTAT_DATA_UINT64 },
477 { "l2_writes_sent", KSTAT_DATA_UINT64 },
478 { "l2_writes_done", KSTAT_DATA_UINT64 },
479 { "l2_writes_error", KSTAT_DATA_UINT64 },
480 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
481 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
482 { "l2_evict_reading", KSTAT_DATA_UINT64 },
483 { "l2_free_on_write", KSTAT_DATA_UINT64 },
484 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 },
485 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
486 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
487 { "l2_io_error", KSTAT_DATA_UINT64 },
488 { "l2_size", KSTAT_DATA_UINT64 },
489 { "l2_asize", KSTAT_DATA_UINT64 },
490 { "l2_hdr_size", KSTAT_DATA_UINT64 },
491 { "l2_compress_successes", KSTAT_DATA_UINT64 },
492 { "l2_compress_zeros", KSTAT_DATA_UINT64 },
493 { "l2_compress_failures", KSTAT_DATA_UINT64 },
494 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
495 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
496 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
497 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
498 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
499 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
500 { "l2_write_full", KSTAT_DATA_UINT64 },
501 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
502 { "l2_write_pios", KSTAT_DATA_UINT64 },
503 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
504 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
505 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
506 { "memory_throttle_count", KSTAT_DATA_UINT64 },
507 { "duplicate_buffers", KSTAT_DATA_UINT64 },
508 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
509 { "duplicate_reads", KSTAT_DATA_UINT64 },
510 { "arc_meta_used", KSTAT_DATA_UINT64 },
511 { "arc_meta_limit", KSTAT_DATA_UINT64 },
512 { "arc_meta_max", KSTAT_DATA_UINT64 }
515 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
517 #define ARCSTAT_INCR(stat, val) \
518 atomic_add_64(&arc_stats.stat.value.ui64, (val))
520 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
521 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
523 #define ARCSTAT_MAX(stat, val) { \
525 while ((val) > (m = arc_stats.stat.value.ui64) && \
526 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
530 #define ARCSTAT_MAXSTAT(stat) \
531 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
534 * We define a macro to allow ARC hits/misses to be easily broken down by
535 * two separate conditions, giving a total of four different subtypes for
536 * each of hits and misses (so eight statistics total).
538 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
541 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
543 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
547 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
549 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
554 static arc_state_t *arc_anon;
555 static arc_state_t *arc_mru;
556 static arc_state_t *arc_mru_ghost;
557 static arc_state_t *arc_mfu;
558 static arc_state_t *arc_mfu_ghost;
559 static arc_state_t *arc_l2c_only;
562 * There are several ARC variables that are critical to export as kstats --
563 * but we don't want to have to grovel around in the kstat whenever we wish to
564 * manipulate them. For these variables, we therefore define them to be in
565 * terms of the statistic variable. This assures that we are not introducing
566 * the possibility of inconsistency by having shadow copies of the variables,
567 * while still allowing the code to be readable.
569 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
570 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
571 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
572 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
573 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
574 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
575 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
576 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
578 #define L2ARC_IS_VALID_COMPRESS(_c_) \
579 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
581 static int arc_no_grow; /* Don't try to grow cache size */
582 static uint64_t arc_tempreserve;
583 static uint64_t arc_loaned_bytes;
585 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
587 typedef struct arc_callback arc_callback_t;
589 struct arc_callback {
591 arc_done_func_t *acb_done;
593 zio_t *acb_zio_dummy;
594 arc_callback_t *acb_next;
597 typedef struct arc_write_callback arc_write_callback_t;
599 struct arc_write_callback {
601 arc_done_func_t *awcb_ready;
602 arc_done_func_t *awcb_physdone;
603 arc_done_func_t *awcb_done;
608 /* protected by hash lock */
613 kmutex_t b_freeze_lock;
614 zio_cksum_t *b_freeze_cksum;
617 arc_buf_hdr_t *b_hash_next;
622 arc_callback_t *b_acb;
626 arc_buf_contents_t b_type;
630 /* protected by arc state mutex */
631 arc_state_t *b_state;
632 list_node_t b_arc_node;
634 /* updated atomically */
635 clock_t b_arc_access;
637 /* self protecting */
640 l2arc_buf_hdr_t *b_l2hdr;
641 list_node_t b_l2node;
646 sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS)
651 val = arc_meta_limit;
652 err = sysctl_handle_64(oidp, &val, 0, req);
653 if (err != 0 || req->newptr == NULL)
656 if (val <= 0 || val > arc_c_max)
659 arc_meta_limit = val;
664 static arc_buf_t *arc_eviction_list;
665 static kmutex_t arc_eviction_mtx;
666 static arc_buf_hdr_t arc_eviction_hdr;
667 static void arc_get_data_buf(arc_buf_t *buf);
668 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
669 static int arc_evict_needed(arc_buf_contents_t type);
670 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
672 static void arc_buf_watch(arc_buf_t *buf);
675 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
677 #define GHOST_STATE(state) \
678 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
679 (state) == arc_l2c_only)
682 * Private ARC flags. These flags are private ARC only flags that will show up
683 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
684 * be passed in as arc_flags in things like arc_read. However, these flags
685 * should never be passed and should only be set by ARC code. When adding new
686 * public flags, make sure not to smash the private ones.
689 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
690 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
691 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
692 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
693 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
694 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
695 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
696 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
697 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
698 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
700 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
701 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
702 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
703 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
704 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
705 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
706 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
707 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
708 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
709 (hdr)->b_l2hdr != NULL)
710 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
711 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
712 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
718 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
719 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
722 * Hash table routines
725 #define HT_LOCK_PAD CACHE_LINE_SIZE
730 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
734 #define BUF_LOCKS 256
735 typedef struct buf_hash_table {
737 arc_buf_hdr_t **ht_table;
738 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
741 static buf_hash_table_t buf_hash_table;
743 #define BUF_HASH_INDEX(spa, dva, birth) \
744 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
745 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
746 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
747 #define HDR_LOCK(hdr) \
748 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
750 uint64_t zfs_crc64_table[256];
756 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
757 #define L2ARC_HEADROOM 2 /* num of writes */
759 * If we discover during ARC scan any buffers to be compressed, we boost
760 * our headroom for the next scanning cycle by this percentage multiple.
762 #define L2ARC_HEADROOM_BOOST 200
763 #define L2ARC_FEED_SECS 1 /* caching interval secs */
764 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
766 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
767 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
769 /* L2ARC Performance Tunables */
770 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
771 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
772 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
773 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
774 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
775 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
776 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
777 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
778 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
780 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
781 &l2arc_write_max, 0, "max write size");
782 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
783 &l2arc_write_boost, 0, "extra write during warmup");
784 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
785 &l2arc_headroom, 0, "number of dev writes");
786 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
787 &l2arc_feed_secs, 0, "interval seconds");
788 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
789 &l2arc_feed_min_ms, 0, "min interval milliseconds");
791 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
792 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
793 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
794 &l2arc_feed_again, 0, "turbo warmup");
795 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
796 &l2arc_norw, 0, "no reads during writes");
798 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
799 &ARC_anon.arcs_size, 0, "size of anonymous state");
800 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
801 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
802 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
803 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
805 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
806 &ARC_mru.arcs_size, 0, "size of mru state");
807 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
808 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
809 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
810 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
812 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
813 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
814 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
815 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
816 "size of metadata in mru ghost state");
817 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
818 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
819 "size of data in mru ghost state");
821 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
822 &ARC_mfu.arcs_size, 0, "size of mfu state");
823 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
824 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
825 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
826 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
828 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
829 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
830 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
831 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
832 "size of metadata in mfu ghost state");
833 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
834 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
835 "size of data in mfu ghost state");
837 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
838 &ARC_l2c_only.arcs_size, 0, "size of mru state");
843 typedef struct l2arc_dev {
844 vdev_t *l2ad_vdev; /* vdev */
845 spa_t *l2ad_spa; /* spa */
846 uint64_t l2ad_hand; /* next write location */
847 uint64_t l2ad_start; /* first addr on device */
848 uint64_t l2ad_end; /* last addr on device */
849 uint64_t l2ad_evict; /* last addr eviction reached */
850 boolean_t l2ad_first; /* first sweep through */
851 boolean_t l2ad_writing; /* currently writing */
852 list_t *l2ad_buflist; /* buffer list */
853 list_node_t l2ad_node; /* device list node */
856 static list_t L2ARC_dev_list; /* device list */
857 static list_t *l2arc_dev_list; /* device list pointer */
858 static kmutex_t l2arc_dev_mtx; /* device list mutex */
859 static l2arc_dev_t *l2arc_dev_last; /* last device used */
860 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
861 static list_t L2ARC_free_on_write; /* free after write buf list */
862 static list_t *l2arc_free_on_write; /* free after write list ptr */
863 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
864 static uint64_t l2arc_ndev; /* number of devices */
866 typedef struct l2arc_read_callback {
867 arc_buf_t *l2rcb_buf; /* read buffer */
868 spa_t *l2rcb_spa; /* spa */
869 blkptr_t l2rcb_bp; /* original blkptr */
870 zbookmark_phys_t l2rcb_zb; /* original bookmark */
871 int l2rcb_flags; /* original flags */
872 enum zio_compress l2rcb_compress; /* applied compress */
873 } l2arc_read_callback_t;
875 typedef struct l2arc_write_callback {
876 l2arc_dev_t *l2wcb_dev; /* device info */
877 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
878 } l2arc_write_callback_t;
880 struct l2arc_buf_hdr {
881 /* protected by arc_buf_hdr mutex */
882 l2arc_dev_t *b_dev; /* L2ARC device */
883 uint64_t b_daddr; /* disk address, offset byte */
884 /* compression applied to buffer data */
885 enum zio_compress b_compress;
886 /* real alloc'd buffer size depending on b_compress applied */
888 /* temporary buffer holder for in-flight compressed data */
892 typedef struct l2arc_data_free {
893 /* protected by l2arc_free_on_write_mtx */
896 void (*l2df_func)(void *, size_t);
897 list_node_t l2df_list_node;
900 static kmutex_t l2arc_feed_thr_lock;
901 static kcondvar_t l2arc_feed_thr_cv;
902 static uint8_t l2arc_thread_exit;
904 static void l2arc_read_done(zio_t *zio);
905 static void l2arc_hdr_stat_add(void);
906 static void l2arc_hdr_stat_remove(void);
908 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
909 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
910 enum zio_compress c);
911 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
914 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
916 uint8_t *vdva = (uint8_t *)dva;
917 uint64_t crc = -1ULL;
920 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
922 for (i = 0; i < sizeof (dva_t); i++)
923 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
925 crc ^= (spa>>8) ^ birth;
930 #define BUF_EMPTY(buf) \
931 ((buf)->b_dva.dva_word[0] == 0 && \
932 (buf)->b_dva.dva_word[1] == 0 && \
933 (buf)->b_cksum0 == 0)
935 #define BUF_EQUAL(spa, dva, birth, buf) \
936 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
937 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
938 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
941 buf_discard_identity(arc_buf_hdr_t *hdr)
943 hdr->b_dva.dva_word[0] = 0;
944 hdr->b_dva.dva_word[1] = 0;
949 static arc_buf_hdr_t *
950 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
952 const dva_t *dva = BP_IDENTITY(bp);
953 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
954 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
955 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
958 mutex_enter(hash_lock);
959 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
960 buf = buf->b_hash_next) {
961 if (BUF_EQUAL(spa, dva, birth, buf)) {
966 mutex_exit(hash_lock);
972 * Insert an entry into the hash table. If there is already an element
973 * equal to elem in the hash table, then the already existing element
974 * will be returned and the new element will not be inserted.
975 * Otherwise returns NULL.
977 static arc_buf_hdr_t *
978 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
980 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
981 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
985 ASSERT(!DVA_IS_EMPTY(&buf->b_dva));
986 ASSERT(buf->b_birth != 0);
987 ASSERT(!HDR_IN_HASH_TABLE(buf));
989 mutex_enter(hash_lock);
990 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
991 fbuf = fbuf->b_hash_next, i++) {
992 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
996 buf->b_hash_next = buf_hash_table.ht_table[idx];
997 buf_hash_table.ht_table[idx] = buf;
998 buf->b_flags |= ARC_IN_HASH_TABLE;
1000 /* collect some hash table performance data */
1002 ARCSTAT_BUMP(arcstat_hash_collisions);
1004 ARCSTAT_BUMP(arcstat_hash_chains);
1006 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1009 ARCSTAT_BUMP(arcstat_hash_elements);
1010 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1016 buf_hash_remove(arc_buf_hdr_t *buf)
1018 arc_buf_hdr_t *fbuf, **bufp;
1019 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
1021 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1022 ASSERT(HDR_IN_HASH_TABLE(buf));
1024 bufp = &buf_hash_table.ht_table[idx];
1025 while ((fbuf = *bufp) != buf) {
1026 ASSERT(fbuf != NULL);
1027 bufp = &fbuf->b_hash_next;
1029 *bufp = buf->b_hash_next;
1030 buf->b_hash_next = NULL;
1031 buf->b_flags &= ~ARC_IN_HASH_TABLE;
1033 /* collect some hash table performance data */
1034 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1036 if (buf_hash_table.ht_table[idx] &&
1037 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1038 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1042 * Global data structures and functions for the buf kmem cache.
1044 static kmem_cache_t *hdr_cache;
1045 static kmem_cache_t *buf_cache;
1052 kmem_free(buf_hash_table.ht_table,
1053 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1054 for (i = 0; i < BUF_LOCKS; i++)
1055 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1056 kmem_cache_destroy(hdr_cache);
1057 kmem_cache_destroy(buf_cache);
1061 * Constructor callback - called when the cache is empty
1062 * and a new buf is requested.
1066 hdr_cons(void *vbuf, void *unused, int kmflag)
1068 arc_buf_hdr_t *buf = vbuf;
1070 bzero(buf, sizeof (arc_buf_hdr_t));
1071 refcount_create(&buf->b_refcnt);
1072 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
1073 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1074 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1081 buf_cons(void *vbuf, void *unused, int kmflag)
1083 arc_buf_t *buf = vbuf;
1085 bzero(buf, sizeof (arc_buf_t));
1086 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1087 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1093 * Destructor callback - called when a cached buf is
1094 * no longer required.
1098 hdr_dest(void *vbuf, void *unused)
1100 arc_buf_hdr_t *buf = vbuf;
1102 ASSERT(BUF_EMPTY(buf));
1103 refcount_destroy(&buf->b_refcnt);
1104 cv_destroy(&buf->b_cv);
1105 mutex_destroy(&buf->b_freeze_lock);
1106 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1111 buf_dest(void *vbuf, void *unused)
1113 arc_buf_t *buf = vbuf;
1115 mutex_destroy(&buf->b_evict_lock);
1116 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1120 * Reclaim callback -- invoked when memory is low.
1124 hdr_recl(void *unused)
1126 dprintf("hdr_recl called\n");
1128 * umem calls the reclaim func when we destroy the buf cache,
1129 * which is after we do arc_fini().
1132 cv_signal(&arc_reclaim_thr_cv);
1139 uint64_t hsize = 1ULL << 12;
1143 * The hash table is big enough to fill all of physical memory
1144 * with an average block size of zfs_arc_average_blocksize (default 8K).
1145 * By default, the table will take up
1146 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1148 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1151 buf_hash_table.ht_mask = hsize - 1;
1152 buf_hash_table.ht_table =
1153 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1154 if (buf_hash_table.ht_table == NULL) {
1155 ASSERT(hsize > (1ULL << 8));
1160 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
1161 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
1162 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1163 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1165 for (i = 0; i < 256; i++)
1166 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1167 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1169 for (i = 0; i < BUF_LOCKS; i++) {
1170 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1171 NULL, MUTEX_DEFAULT, NULL);
1175 #define ARC_MINTIME (hz>>4) /* 62 ms */
1178 arc_cksum_verify(arc_buf_t *buf)
1182 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1185 mutex_enter(&buf->b_hdr->b_freeze_lock);
1186 if (buf->b_hdr->b_freeze_cksum == NULL ||
1187 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1188 mutex_exit(&buf->b_hdr->b_freeze_lock);
1191 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1192 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1193 panic("buffer modified while frozen!");
1194 mutex_exit(&buf->b_hdr->b_freeze_lock);
1198 arc_cksum_equal(arc_buf_t *buf)
1203 mutex_enter(&buf->b_hdr->b_freeze_lock);
1204 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1205 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1206 mutex_exit(&buf->b_hdr->b_freeze_lock);
1212 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1214 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1217 mutex_enter(&buf->b_hdr->b_freeze_lock);
1218 if (buf->b_hdr->b_freeze_cksum != NULL) {
1219 mutex_exit(&buf->b_hdr->b_freeze_lock);
1222 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1223 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1224 buf->b_hdr->b_freeze_cksum);
1225 mutex_exit(&buf->b_hdr->b_freeze_lock);
1228 #endif /* illumos */
1233 typedef struct procctl {
1241 arc_buf_unwatch(arc_buf_t *buf)
1248 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1249 ctl.prwatch.pr_size = 0;
1250 ctl.prwatch.pr_wflags = 0;
1251 result = write(arc_procfd, &ctl, sizeof (ctl));
1252 ASSERT3U(result, ==, sizeof (ctl));
1259 arc_buf_watch(arc_buf_t *buf)
1266 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1267 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1268 ctl.prwatch.pr_wflags = WA_WRITE;
1269 result = write(arc_procfd, &ctl, sizeof (ctl));
1270 ASSERT3U(result, ==, sizeof (ctl));
1274 #endif /* illumos */
1277 arc_buf_thaw(arc_buf_t *buf)
1279 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1280 if (buf->b_hdr->b_state != arc_anon)
1281 panic("modifying non-anon buffer!");
1282 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1283 panic("modifying buffer while i/o in progress!");
1284 arc_cksum_verify(buf);
1287 mutex_enter(&buf->b_hdr->b_freeze_lock);
1288 if (buf->b_hdr->b_freeze_cksum != NULL) {
1289 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1290 buf->b_hdr->b_freeze_cksum = NULL;
1293 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1294 if (buf->b_hdr->b_thawed)
1295 kmem_free(buf->b_hdr->b_thawed, 1);
1296 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1299 mutex_exit(&buf->b_hdr->b_freeze_lock);
1302 arc_buf_unwatch(buf);
1303 #endif /* illumos */
1307 arc_buf_freeze(arc_buf_t *buf)
1309 kmutex_t *hash_lock;
1311 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1314 hash_lock = HDR_LOCK(buf->b_hdr);
1315 mutex_enter(hash_lock);
1317 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1318 buf->b_hdr->b_state == arc_anon);
1319 arc_cksum_compute(buf, B_FALSE);
1320 mutex_exit(hash_lock);
1325 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1327 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1329 if (ab->b_type == ARC_BUFC_METADATA)
1330 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1332 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1333 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1336 *list = &state->arcs_lists[buf_hashid];
1337 *lock = ARCS_LOCK(state, buf_hashid);
1342 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1344 ASSERT(MUTEX_HELD(hash_lock));
1346 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1347 (ab->b_state != arc_anon)) {
1348 uint64_t delta = ab->b_size * ab->b_datacnt;
1349 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1353 get_buf_info(ab, ab->b_state, &list, &lock);
1354 ASSERT(!MUTEX_HELD(lock));
1356 ASSERT(list_link_active(&ab->b_arc_node));
1357 list_remove(list, ab);
1358 if (GHOST_STATE(ab->b_state)) {
1359 ASSERT0(ab->b_datacnt);
1360 ASSERT3P(ab->b_buf, ==, NULL);
1364 ASSERT3U(*size, >=, delta);
1365 atomic_add_64(size, -delta);
1367 /* remove the prefetch flag if we get a reference */
1368 if (ab->b_flags & ARC_PREFETCH)
1369 ab->b_flags &= ~ARC_PREFETCH;
1374 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1377 arc_state_t *state = ab->b_state;
1379 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1380 ASSERT(!GHOST_STATE(state));
1382 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1383 (state != arc_anon)) {
1384 uint64_t *size = &state->arcs_lsize[ab->b_type];
1388 get_buf_info(ab, state, &list, &lock);
1389 ASSERT(!MUTEX_HELD(lock));
1391 ASSERT(!list_link_active(&ab->b_arc_node));
1392 list_insert_head(list, ab);
1393 ASSERT(ab->b_datacnt > 0);
1394 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1401 * Move the supplied buffer to the indicated state. The mutex
1402 * for the buffer must be held by the caller.
1405 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1407 arc_state_t *old_state = ab->b_state;
1408 int64_t refcnt = refcount_count(&ab->b_refcnt);
1409 uint64_t from_delta, to_delta;
1413 ASSERT(MUTEX_HELD(hash_lock));
1414 ASSERT3P(new_state, !=, old_state);
1415 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1416 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1417 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1419 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1422 * If this buffer is evictable, transfer it from the
1423 * old state list to the new state list.
1426 if (old_state != arc_anon) {
1428 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1430 get_buf_info(ab, old_state, &list, &lock);
1431 use_mutex = !MUTEX_HELD(lock);
1435 ASSERT(list_link_active(&ab->b_arc_node));
1436 list_remove(list, ab);
1439 * If prefetching out of the ghost cache,
1440 * we will have a non-zero datacnt.
1442 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1443 /* ghost elements have a ghost size */
1444 ASSERT(ab->b_buf == NULL);
1445 from_delta = ab->b_size;
1447 ASSERT3U(*size, >=, from_delta);
1448 atomic_add_64(size, -from_delta);
1453 if (new_state != arc_anon) {
1455 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1457 get_buf_info(ab, new_state, &list, &lock);
1458 use_mutex = !MUTEX_HELD(lock);
1462 list_insert_head(list, ab);
1464 /* ghost elements have a ghost size */
1465 if (GHOST_STATE(new_state)) {
1466 ASSERT(ab->b_datacnt == 0);
1467 ASSERT(ab->b_buf == NULL);
1468 to_delta = ab->b_size;
1470 atomic_add_64(size, to_delta);
1477 ASSERT(!BUF_EMPTY(ab));
1478 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1479 buf_hash_remove(ab);
1481 /* adjust state sizes */
1483 atomic_add_64(&new_state->arcs_size, to_delta);
1485 ASSERT3U(old_state->arcs_size, >=, from_delta);
1486 atomic_add_64(&old_state->arcs_size, -from_delta);
1488 ab->b_state = new_state;
1490 /* adjust l2arc hdr stats */
1491 if (new_state == arc_l2c_only)
1492 l2arc_hdr_stat_add();
1493 else if (old_state == arc_l2c_only)
1494 l2arc_hdr_stat_remove();
1498 arc_space_consume(uint64_t space, arc_space_type_t type)
1500 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1503 case ARC_SPACE_DATA:
1504 ARCSTAT_INCR(arcstat_data_size, space);
1506 case ARC_SPACE_OTHER:
1507 ARCSTAT_INCR(arcstat_other_size, space);
1509 case ARC_SPACE_HDRS:
1510 ARCSTAT_INCR(arcstat_hdr_size, space);
1512 case ARC_SPACE_L2HDRS:
1513 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1517 ARCSTAT_INCR(arcstat_meta_used, space);
1518 atomic_add_64(&arc_size, space);
1522 arc_space_return(uint64_t space, arc_space_type_t type)
1524 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1527 case ARC_SPACE_DATA:
1528 ARCSTAT_INCR(arcstat_data_size, -space);
1530 case ARC_SPACE_OTHER:
1531 ARCSTAT_INCR(arcstat_other_size, -space);
1533 case ARC_SPACE_HDRS:
1534 ARCSTAT_INCR(arcstat_hdr_size, -space);
1536 case ARC_SPACE_L2HDRS:
1537 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1541 ASSERT(arc_meta_used >= space);
1542 if (arc_meta_max < arc_meta_used)
1543 arc_meta_max = arc_meta_used;
1544 ARCSTAT_INCR(arcstat_meta_used, -space);
1545 ASSERT(arc_size >= space);
1546 atomic_add_64(&arc_size, -space);
1550 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1555 ASSERT3U(size, >, 0);
1556 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1557 ASSERT(BUF_EMPTY(hdr));
1560 hdr->b_spa = spa_load_guid(spa);
1561 hdr->b_state = arc_anon;
1562 hdr->b_arc_access = 0;
1563 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1566 buf->b_efunc = NULL;
1567 buf->b_private = NULL;
1570 arc_get_data_buf(buf);
1573 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1574 (void) refcount_add(&hdr->b_refcnt, tag);
1579 static char *arc_onloan_tag = "onloan";
1582 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1583 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1584 * buffers must be returned to the arc before they can be used by the DMU or
1588 arc_loan_buf(spa_t *spa, int size)
1592 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1594 atomic_add_64(&arc_loaned_bytes, size);
1599 * Return a loaned arc buffer to the arc.
1602 arc_return_buf(arc_buf_t *buf, void *tag)
1604 arc_buf_hdr_t *hdr = buf->b_hdr;
1606 ASSERT(buf->b_data != NULL);
1607 (void) refcount_add(&hdr->b_refcnt, tag);
1608 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1610 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1613 /* Detach an arc_buf from a dbuf (tag) */
1615 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1619 ASSERT(buf->b_data != NULL);
1621 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1622 (void) refcount_remove(&hdr->b_refcnt, tag);
1623 buf->b_efunc = NULL;
1624 buf->b_private = NULL;
1626 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1630 arc_buf_clone(arc_buf_t *from)
1633 arc_buf_hdr_t *hdr = from->b_hdr;
1634 uint64_t size = hdr->b_size;
1636 ASSERT(hdr->b_state != arc_anon);
1638 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1641 buf->b_efunc = NULL;
1642 buf->b_private = NULL;
1643 buf->b_next = hdr->b_buf;
1645 arc_get_data_buf(buf);
1646 bcopy(from->b_data, buf->b_data, size);
1649 * This buffer already exists in the arc so create a duplicate
1650 * copy for the caller. If the buffer is associated with user data
1651 * then track the size and number of duplicates. These stats will be
1652 * updated as duplicate buffers are created and destroyed.
1654 if (hdr->b_type == ARC_BUFC_DATA) {
1655 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1656 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1658 hdr->b_datacnt += 1;
1663 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1666 kmutex_t *hash_lock;
1669 * Check to see if this buffer is evicted. Callers
1670 * must verify b_data != NULL to know if the add_ref
1673 mutex_enter(&buf->b_evict_lock);
1674 if (buf->b_data == NULL) {
1675 mutex_exit(&buf->b_evict_lock);
1678 hash_lock = HDR_LOCK(buf->b_hdr);
1679 mutex_enter(hash_lock);
1681 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1682 mutex_exit(&buf->b_evict_lock);
1684 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1685 add_reference(hdr, hash_lock, tag);
1686 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1687 arc_access(hdr, hash_lock);
1688 mutex_exit(hash_lock);
1689 ARCSTAT_BUMP(arcstat_hits);
1690 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1691 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1692 data, metadata, hits);
1696 arc_buf_free_on_write(void *data, size_t size,
1697 void (*free_func)(void *, size_t))
1699 l2arc_data_free_t *df;
1701 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1702 df->l2df_data = data;
1703 df->l2df_size = size;
1704 df->l2df_func = free_func;
1705 mutex_enter(&l2arc_free_on_write_mtx);
1706 list_insert_head(l2arc_free_on_write, df);
1707 mutex_exit(&l2arc_free_on_write_mtx);
1711 * Free the arc data buffer. If it is an l2arc write in progress,
1712 * the buffer is placed on l2arc_free_on_write to be freed later.
1715 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1717 arc_buf_hdr_t *hdr = buf->b_hdr;
1719 if (HDR_L2_WRITING(hdr)) {
1720 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
1721 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1723 free_func(buf->b_data, hdr->b_size);
1728 * Free up buf->b_data and if 'remove' is set, then pull the
1729 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
1732 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
1734 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1736 ASSERT(MUTEX_HELD(&l2arc_buflist_mtx));
1738 if (l2hdr->b_tmp_cdata == NULL)
1741 ASSERT(HDR_L2_WRITING(hdr));
1742 arc_buf_free_on_write(l2hdr->b_tmp_cdata, hdr->b_size,
1744 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
1745 l2hdr->b_tmp_cdata = NULL;
1749 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
1753 /* free up data associated with the buf */
1755 arc_state_t *state = buf->b_hdr->b_state;
1756 uint64_t size = buf->b_hdr->b_size;
1757 arc_buf_contents_t type = buf->b_hdr->b_type;
1759 arc_cksum_verify(buf);
1761 arc_buf_unwatch(buf);
1762 #endif /* illumos */
1765 if (type == ARC_BUFC_METADATA) {
1766 arc_buf_data_free(buf, zio_buf_free);
1767 arc_space_return(size, ARC_SPACE_DATA);
1769 ASSERT(type == ARC_BUFC_DATA);
1770 arc_buf_data_free(buf, zio_data_buf_free);
1771 ARCSTAT_INCR(arcstat_data_size, -size);
1772 atomic_add_64(&arc_size, -size);
1775 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1776 uint64_t *cnt = &state->arcs_lsize[type];
1778 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1779 ASSERT(state != arc_anon);
1781 ASSERT3U(*cnt, >=, size);
1782 atomic_add_64(cnt, -size);
1784 ASSERT3U(state->arcs_size, >=, size);
1785 atomic_add_64(&state->arcs_size, -size);
1789 * If we're destroying a duplicate buffer make sure
1790 * that the appropriate statistics are updated.
1792 if (buf->b_hdr->b_datacnt > 1 &&
1793 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1794 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1795 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1797 ASSERT(buf->b_hdr->b_datacnt > 0);
1798 buf->b_hdr->b_datacnt -= 1;
1801 /* only remove the buf if requested */
1805 /* remove the buf from the hdr list */
1806 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1808 *bufp = buf->b_next;
1811 ASSERT(buf->b_efunc == NULL);
1813 /* clean up the buf */
1815 kmem_cache_free(buf_cache, buf);
1819 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1821 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1822 ASSERT3P(hdr->b_state, ==, arc_anon);
1823 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1824 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1826 if (l2hdr != NULL) {
1827 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1829 * To prevent arc_free() and l2arc_evict() from
1830 * attempting to free the same buffer at the same time,
1831 * a FREE_IN_PROGRESS flag is given to arc_free() to
1832 * give it priority. l2arc_evict() can't destroy this
1833 * header while we are waiting on l2arc_buflist_mtx.
1835 * The hdr may be removed from l2ad_buflist before we
1836 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1838 if (!buflist_held) {
1839 mutex_enter(&l2arc_buflist_mtx);
1840 l2hdr = hdr->b_l2hdr;
1843 if (l2hdr != NULL) {
1844 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
1846 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1847 arc_buf_l2_cdata_free(hdr);
1848 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1849 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
1850 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
1851 -l2hdr->b_asize, 0, 0);
1852 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1853 if (hdr->b_state == arc_l2c_only)
1854 l2arc_hdr_stat_remove();
1855 hdr->b_l2hdr = NULL;
1859 mutex_exit(&l2arc_buflist_mtx);
1862 if (!BUF_EMPTY(hdr)) {
1863 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1864 buf_discard_identity(hdr);
1866 while (hdr->b_buf) {
1867 arc_buf_t *buf = hdr->b_buf;
1870 mutex_enter(&arc_eviction_mtx);
1871 mutex_enter(&buf->b_evict_lock);
1872 ASSERT(buf->b_hdr != NULL);
1873 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1874 hdr->b_buf = buf->b_next;
1875 buf->b_hdr = &arc_eviction_hdr;
1876 buf->b_next = arc_eviction_list;
1877 arc_eviction_list = buf;
1878 mutex_exit(&buf->b_evict_lock);
1879 mutex_exit(&arc_eviction_mtx);
1881 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1884 if (hdr->b_freeze_cksum != NULL) {
1885 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1886 hdr->b_freeze_cksum = NULL;
1888 if (hdr->b_thawed) {
1889 kmem_free(hdr->b_thawed, 1);
1890 hdr->b_thawed = NULL;
1893 ASSERT(!list_link_active(&hdr->b_arc_node));
1894 ASSERT3P(hdr->b_hash_next, ==, NULL);
1895 ASSERT3P(hdr->b_acb, ==, NULL);
1896 kmem_cache_free(hdr_cache, hdr);
1900 arc_buf_free(arc_buf_t *buf, void *tag)
1902 arc_buf_hdr_t *hdr = buf->b_hdr;
1903 int hashed = hdr->b_state != arc_anon;
1905 ASSERT(buf->b_efunc == NULL);
1906 ASSERT(buf->b_data != NULL);
1909 kmutex_t *hash_lock = HDR_LOCK(hdr);
1911 mutex_enter(hash_lock);
1913 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1915 (void) remove_reference(hdr, hash_lock, tag);
1916 if (hdr->b_datacnt > 1) {
1917 arc_buf_destroy(buf, FALSE, TRUE);
1919 ASSERT(buf == hdr->b_buf);
1920 ASSERT(buf->b_efunc == NULL);
1921 hdr->b_flags |= ARC_BUF_AVAILABLE;
1923 mutex_exit(hash_lock);
1924 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1927 * We are in the middle of an async write. Don't destroy
1928 * this buffer unless the write completes before we finish
1929 * decrementing the reference count.
1931 mutex_enter(&arc_eviction_mtx);
1932 (void) remove_reference(hdr, NULL, tag);
1933 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1934 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1935 mutex_exit(&arc_eviction_mtx);
1937 arc_hdr_destroy(hdr);
1939 if (remove_reference(hdr, NULL, tag) > 0)
1940 arc_buf_destroy(buf, FALSE, TRUE);
1942 arc_hdr_destroy(hdr);
1947 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1949 arc_buf_hdr_t *hdr = buf->b_hdr;
1950 kmutex_t *hash_lock = HDR_LOCK(hdr);
1951 boolean_t no_callback = (buf->b_efunc == NULL);
1953 if (hdr->b_state == arc_anon) {
1954 ASSERT(hdr->b_datacnt == 1);
1955 arc_buf_free(buf, tag);
1956 return (no_callback);
1959 mutex_enter(hash_lock);
1961 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1962 ASSERT(hdr->b_state != arc_anon);
1963 ASSERT(buf->b_data != NULL);
1965 (void) remove_reference(hdr, hash_lock, tag);
1966 if (hdr->b_datacnt > 1) {
1968 arc_buf_destroy(buf, FALSE, TRUE);
1969 } else if (no_callback) {
1970 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1971 ASSERT(buf->b_efunc == NULL);
1972 hdr->b_flags |= ARC_BUF_AVAILABLE;
1974 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1975 refcount_is_zero(&hdr->b_refcnt));
1976 mutex_exit(hash_lock);
1977 return (no_callback);
1981 arc_buf_size(arc_buf_t *buf)
1983 return (buf->b_hdr->b_size);
1987 * Called from the DMU to determine if the current buffer should be
1988 * evicted. In order to ensure proper locking, the eviction must be initiated
1989 * from the DMU. Return true if the buffer is associated with user data and
1990 * duplicate buffers still exist.
1993 arc_buf_eviction_needed(arc_buf_t *buf)
1996 boolean_t evict_needed = B_FALSE;
1998 if (zfs_disable_dup_eviction)
2001 mutex_enter(&buf->b_evict_lock);
2005 * We are in arc_do_user_evicts(); let that function
2006 * perform the eviction.
2008 ASSERT(buf->b_data == NULL);
2009 mutex_exit(&buf->b_evict_lock);
2011 } else if (buf->b_data == NULL) {
2013 * We have already been added to the arc eviction list;
2014 * recommend eviction.
2016 ASSERT3P(hdr, ==, &arc_eviction_hdr);
2017 mutex_exit(&buf->b_evict_lock);
2021 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
2022 evict_needed = B_TRUE;
2024 mutex_exit(&buf->b_evict_lock);
2025 return (evict_needed);
2029 * Evict buffers from list until we've removed the specified number of
2030 * bytes. Move the removed buffers to the appropriate evict state.
2031 * If the recycle flag is set, then attempt to "recycle" a buffer:
2032 * - look for a buffer to evict that is `bytes' long.
2033 * - return the data block from this buffer rather than freeing it.
2034 * This flag is used by callers that are trying to make space for a
2035 * new buffer in a full arc cache.
2037 * This function makes a "best effort". It skips over any buffers
2038 * it can't get a hash_lock on, and so may not catch all candidates.
2039 * It may also return without evicting as much space as requested.
2042 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
2043 arc_buf_contents_t type)
2045 arc_state_t *evicted_state;
2046 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
2047 int64_t bytes_remaining;
2048 arc_buf_hdr_t *ab, *ab_prev = NULL;
2049 list_t *evicted_list, *list, *evicted_list_start, *list_start;
2050 kmutex_t *lock, *evicted_lock;
2051 kmutex_t *hash_lock;
2052 boolean_t have_lock;
2053 void *stolen = NULL;
2054 arc_buf_hdr_t marker = { 0 };
2056 static int evict_metadata_offset, evict_data_offset;
2057 int i, idx, offset, list_count, lists;
2059 ASSERT(state == arc_mru || state == arc_mfu);
2061 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2063 if (type == ARC_BUFC_METADATA) {
2065 list_count = ARC_BUFC_NUMMETADATALISTS;
2066 list_start = &state->arcs_lists[0];
2067 evicted_list_start = &evicted_state->arcs_lists[0];
2068 idx = evict_metadata_offset;
2070 offset = ARC_BUFC_NUMMETADATALISTS;
2071 list_start = &state->arcs_lists[offset];
2072 evicted_list_start = &evicted_state->arcs_lists[offset];
2073 list_count = ARC_BUFC_NUMDATALISTS;
2074 idx = evict_data_offset;
2076 bytes_remaining = evicted_state->arcs_lsize[type];
2080 list = &list_start[idx];
2081 evicted_list = &evicted_list_start[idx];
2082 lock = ARCS_LOCK(state, (offset + idx));
2083 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
2086 mutex_enter(evicted_lock);
2088 for (ab = list_tail(list); ab; ab = ab_prev) {
2089 ab_prev = list_prev(list, ab);
2090 bytes_remaining -= (ab->b_size * ab->b_datacnt);
2091 /* prefetch buffers have a minimum lifespan */
2092 if (HDR_IO_IN_PROGRESS(ab) ||
2093 (spa && ab->b_spa != spa) ||
2094 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
2095 ddi_get_lbolt() - ab->b_arc_access <
2096 arc_min_prefetch_lifespan)) {
2100 /* "lookahead" for better eviction candidate */
2101 if (recycle && ab->b_size != bytes &&
2102 ab_prev && ab_prev->b_size == bytes)
2105 /* ignore markers */
2110 * It may take a long time to evict all the bufs requested.
2111 * To avoid blocking all arc activity, periodically drop
2112 * the arcs_mtx and give other threads a chance to run
2113 * before reacquiring the lock.
2115 * If we are looking for a buffer to recycle, we are in
2116 * the hot code path, so don't sleep.
2118 if (!recycle && count++ > arc_evict_iterations) {
2119 list_insert_after(list, ab, &marker);
2120 mutex_exit(evicted_lock);
2122 kpreempt(KPREEMPT_SYNC);
2124 mutex_enter(evicted_lock);
2125 ab_prev = list_prev(list, &marker);
2126 list_remove(list, &marker);
2131 hash_lock = HDR_LOCK(ab);
2132 have_lock = MUTEX_HELD(hash_lock);
2133 if (have_lock || mutex_tryenter(hash_lock)) {
2134 ASSERT0(refcount_count(&ab->b_refcnt));
2135 ASSERT(ab->b_datacnt > 0);
2137 arc_buf_t *buf = ab->b_buf;
2138 if (!mutex_tryenter(&buf->b_evict_lock)) {
2143 bytes_evicted += ab->b_size;
2144 if (recycle && ab->b_type == type &&
2145 ab->b_size == bytes &&
2146 !HDR_L2_WRITING(ab)) {
2147 stolen = buf->b_data;
2152 mutex_enter(&arc_eviction_mtx);
2153 arc_buf_destroy(buf,
2154 buf->b_data == stolen, FALSE);
2155 ab->b_buf = buf->b_next;
2156 buf->b_hdr = &arc_eviction_hdr;
2157 buf->b_next = arc_eviction_list;
2158 arc_eviction_list = buf;
2159 mutex_exit(&arc_eviction_mtx);
2160 mutex_exit(&buf->b_evict_lock);
2162 mutex_exit(&buf->b_evict_lock);
2163 arc_buf_destroy(buf,
2164 buf->b_data == stolen, TRUE);
2169 ARCSTAT_INCR(arcstat_evict_l2_cached,
2172 if (l2arc_write_eligible(ab->b_spa, ab)) {
2173 ARCSTAT_INCR(arcstat_evict_l2_eligible,
2177 arcstat_evict_l2_ineligible,
2182 if (ab->b_datacnt == 0) {
2183 arc_change_state(evicted_state, ab, hash_lock);
2184 ASSERT(HDR_IN_HASH_TABLE(ab));
2185 ab->b_flags |= ARC_IN_HASH_TABLE;
2186 ab->b_flags &= ~ARC_BUF_AVAILABLE;
2187 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
2190 mutex_exit(hash_lock);
2191 if (bytes >= 0 && bytes_evicted >= bytes)
2193 if (bytes_remaining > 0) {
2194 mutex_exit(evicted_lock);
2196 idx = ((idx + 1) & (list_count - 1));
2205 mutex_exit(evicted_lock);
2208 idx = ((idx + 1) & (list_count - 1));
2211 if (bytes_evicted < bytes) {
2212 if (lists < list_count)
2215 dprintf("only evicted %lld bytes from %x",
2216 (longlong_t)bytes_evicted, state);
2218 if (type == ARC_BUFC_METADATA)
2219 evict_metadata_offset = idx;
2221 evict_data_offset = idx;
2224 ARCSTAT_INCR(arcstat_evict_skip, skipped);
2227 ARCSTAT_INCR(arcstat_mutex_miss, missed);
2230 * Note: we have just evicted some data into the ghost state,
2231 * potentially putting the ghost size over the desired size. Rather
2232 * that evicting from the ghost list in this hot code path, leave
2233 * this chore to the arc_reclaim_thread().
2237 ARCSTAT_BUMP(arcstat_stolen);
2242 * Remove buffers from list until we've removed the specified number of
2243 * bytes. Destroy the buffers that are removed.
2246 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
2248 arc_buf_hdr_t *ab, *ab_prev;
2249 arc_buf_hdr_t marker = { 0 };
2250 list_t *list, *list_start;
2251 kmutex_t *hash_lock, *lock;
2252 uint64_t bytes_deleted = 0;
2253 uint64_t bufs_skipped = 0;
2255 static int evict_offset;
2256 int list_count, idx = evict_offset;
2257 int offset, lists = 0;
2259 ASSERT(GHOST_STATE(state));
2262 * data lists come after metadata lists
2264 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
2265 list_count = ARC_BUFC_NUMDATALISTS;
2266 offset = ARC_BUFC_NUMMETADATALISTS;
2269 list = &list_start[idx];
2270 lock = ARCS_LOCK(state, idx + offset);
2273 for (ab = list_tail(list); ab; ab = ab_prev) {
2274 ab_prev = list_prev(list, ab);
2275 if (ab->b_type > ARC_BUFC_NUMTYPES)
2276 panic("invalid ab=%p", (void *)ab);
2277 if (spa && ab->b_spa != spa)
2280 /* ignore markers */
2284 hash_lock = HDR_LOCK(ab);
2285 /* caller may be trying to modify this buffer, skip it */
2286 if (MUTEX_HELD(hash_lock))
2290 * It may take a long time to evict all the bufs requested.
2291 * To avoid blocking all arc activity, periodically drop
2292 * the arcs_mtx and give other threads a chance to run
2293 * before reacquiring the lock.
2295 if (count++ > arc_evict_iterations) {
2296 list_insert_after(list, ab, &marker);
2298 kpreempt(KPREEMPT_SYNC);
2300 ab_prev = list_prev(list, &marker);
2301 list_remove(list, &marker);
2305 if (mutex_tryenter(hash_lock)) {
2306 ASSERT(!HDR_IO_IN_PROGRESS(ab));
2307 ASSERT(ab->b_buf == NULL);
2308 ARCSTAT_BUMP(arcstat_deleted);
2309 bytes_deleted += ab->b_size;
2311 if (ab->b_l2hdr != NULL) {
2313 * This buffer is cached on the 2nd Level ARC;
2314 * don't destroy the header.
2316 arc_change_state(arc_l2c_only, ab, hash_lock);
2317 mutex_exit(hash_lock);
2319 arc_change_state(arc_anon, ab, hash_lock);
2320 mutex_exit(hash_lock);
2321 arc_hdr_destroy(ab);
2324 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
2325 if (bytes >= 0 && bytes_deleted >= bytes)
2327 } else if (bytes < 0) {
2329 * Insert a list marker and then wait for the
2330 * hash lock to become available. Once its
2331 * available, restart from where we left off.
2333 list_insert_after(list, ab, &marker);
2335 mutex_enter(hash_lock);
2336 mutex_exit(hash_lock);
2338 ab_prev = list_prev(list, &marker);
2339 list_remove(list, &marker);
2346 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
2349 if (lists < list_count)
2353 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
2354 (bytes < 0 || bytes_deleted < bytes)) {
2355 list_start = &state->arcs_lists[0];
2356 list_count = ARC_BUFC_NUMMETADATALISTS;
2362 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2366 if (bytes_deleted < bytes)
2367 dprintf("only deleted %lld bytes from %p",
2368 (longlong_t)bytes_deleted, state);
2374 int64_t adjustment, delta;
2380 adjustment = MIN((int64_t)(arc_size - arc_c),
2381 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2384 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2385 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2386 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
2387 adjustment -= delta;
2390 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2391 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2392 (void) arc_evict(arc_mru, 0, delta, FALSE,
2400 adjustment = arc_size - arc_c;
2402 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2403 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2404 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
2405 adjustment -= delta;
2408 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2409 int64_t delta = MIN(adjustment,
2410 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2411 (void) arc_evict(arc_mfu, 0, delta, FALSE,
2416 * Adjust ghost lists
2419 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2421 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2422 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2423 arc_evict_ghost(arc_mru_ghost, 0, delta);
2427 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2429 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2430 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2431 arc_evict_ghost(arc_mfu_ghost, 0, delta);
2436 arc_do_user_evicts(void)
2438 static arc_buf_t *tmp_arc_eviction_list;
2441 * Move list over to avoid LOR
2444 mutex_enter(&arc_eviction_mtx);
2445 tmp_arc_eviction_list = arc_eviction_list;
2446 arc_eviction_list = NULL;
2447 mutex_exit(&arc_eviction_mtx);
2449 while (tmp_arc_eviction_list != NULL) {
2450 arc_buf_t *buf = tmp_arc_eviction_list;
2451 tmp_arc_eviction_list = buf->b_next;
2452 mutex_enter(&buf->b_evict_lock);
2454 mutex_exit(&buf->b_evict_lock);
2456 if (buf->b_efunc != NULL)
2457 VERIFY0(buf->b_efunc(buf->b_private));
2459 buf->b_efunc = NULL;
2460 buf->b_private = NULL;
2461 kmem_cache_free(buf_cache, buf);
2464 if (arc_eviction_list != NULL)
2469 * Flush all *evictable* data from the cache for the given spa.
2470 * NOTE: this will not touch "active" (i.e. referenced) data.
2473 arc_flush(spa_t *spa)
2478 guid = spa_load_guid(spa);
2480 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2481 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2485 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2486 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2490 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2491 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2495 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2496 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2501 arc_evict_ghost(arc_mru_ghost, guid, -1);
2502 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2504 mutex_enter(&arc_reclaim_thr_lock);
2505 arc_do_user_evicts();
2506 mutex_exit(&arc_reclaim_thr_lock);
2507 ASSERT(spa || arc_eviction_list == NULL);
2514 if (arc_c > arc_c_min) {
2517 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
2518 arc_c_min, uint64_t, arc_p, uint64_t, to_free);
2520 to_free = arc_c >> arc_shrink_shift;
2522 to_free = arc_c >> arc_shrink_shift;
2524 if (arc_c > arc_c_min + to_free)
2525 atomic_add_64(&arc_c, -to_free);
2529 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2530 if (arc_c > arc_size)
2531 arc_c = MAX(arc_size, arc_c_min);
2533 arc_p = (arc_c >> 1);
2535 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
2538 ASSERT(arc_c >= arc_c_min);
2539 ASSERT((int64_t)arc_p >= 0);
2542 if (arc_size > arc_c) {
2543 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size,
2549 static int needfree = 0;
2552 arc_reclaim_needed(void)
2558 DTRACE_PROBE(arc__reclaim_needfree);
2563 * Cooperate with pagedaemon when it's time for it to scan
2564 * and reclaim some pages.
2566 if (freemem < zfs_arc_free_target) {
2567 DTRACE_PROBE2(arc__reclaim_freemem, uint64_t,
2568 freemem, uint64_t, zfs_arc_free_target);
2574 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2579 * check that we're out of range of the pageout scanner. It starts to
2580 * schedule paging if freemem is less than lotsfree and needfree.
2581 * lotsfree is the high-water mark for pageout, and needfree is the
2582 * number of needed free pages. We add extra pages here to make sure
2583 * the scanner doesn't start up while we're freeing memory.
2585 if (freemem < lotsfree + needfree + extra)
2589 * check to make sure that swapfs has enough space so that anon
2590 * reservations can still succeed. anon_resvmem() checks that the
2591 * availrmem is greater than swapfs_minfree, and the number of reserved
2592 * swap pages. We also add a bit of extra here just to prevent
2593 * circumstances from getting really dire.
2595 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2599 * Check that we have enough availrmem that memory locking (e.g., via
2600 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
2601 * stores the number of pages that cannot be locked; when availrmem
2602 * drops below pages_pp_maximum, page locking mechanisms such as
2603 * page_pp_lock() will fail.)
2605 if (availrmem <= pages_pp_maximum)
2609 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
2611 * If we're on an i386 platform, it's possible that we'll exhaust the
2612 * kernel heap space before we ever run out of available physical
2613 * memory. Most checks of the size of the heap_area compare against
2614 * tune.t_minarmem, which is the minimum available real memory that we
2615 * can have in the system. However, this is generally fixed at 25 pages
2616 * which is so low that it's useless. In this comparison, we seek to
2617 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2618 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2621 if (vmem_size(heap_arena, VMEM_FREE) <
2622 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) {
2623 DTRACE_PROBE2(arc__reclaim_used, uint64_t,
2624 vmem_size(heap_arena, VMEM_FREE), uint64_t,
2625 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2);
2631 * If zio data pages are being allocated out of a separate heap segment,
2632 * then enforce that the size of available vmem for this arena remains
2633 * above about 1/16th free.
2635 * Note: The 1/16th arena free requirement was put in place
2636 * to aggressively evict memory from the arc in order to avoid
2637 * memory fragmentation issues.
2639 if (zio_arena != NULL &&
2640 vmem_size(zio_arena, VMEM_FREE) <
2641 (vmem_size(zio_arena, VMEM_ALLOC) >> 4))
2645 if (spa_get_random(100) == 0)
2647 #endif /* _KERNEL */
2648 DTRACE_PROBE(arc__reclaim_no);
2653 extern kmem_cache_t *zio_buf_cache[];
2654 extern kmem_cache_t *zio_data_buf_cache[];
2655 extern kmem_cache_t *range_seg_cache;
2657 static void __noinline
2658 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2661 kmem_cache_t *prev_cache = NULL;
2662 kmem_cache_t *prev_data_cache = NULL;
2664 DTRACE_PROBE(arc__kmem_reap_start);
2666 if (arc_meta_used >= arc_meta_limit) {
2668 * We are exceeding our meta-data cache limit.
2669 * Purge some DNLC entries to release holds on meta-data.
2671 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2675 * Reclaim unused memory from all kmem caches.
2682 * An aggressive reclamation will shrink the cache size as well as
2683 * reap free buffers from the arc kmem caches.
2685 if (strat == ARC_RECLAIM_AGGR)
2688 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2689 if (zio_buf_cache[i] != prev_cache) {
2690 prev_cache = zio_buf_cache[i];
2691 kmem_cache_reap_now(zio_buf_cache[i]);
2693 if (zio_data_buf_cache[i] != prev_data_cache) {
2694 prev_data_cache = zio_data_buf_cache[i];
2695 kmem_cache_reap_now(zio_data_buf_cache[i]);
2698 kmem_cache_reap_now(buf_cache);
2699 kmem_cache_reap_now(hdr_cache);
2700 kmem_cache_reap_now(range_seg_cache);
2704 * Ask the vmem arena to reclaim unused memory from its
2707 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
2708 vmem_qcache_reap(zio_arena);
2710 DTRACE_PROBE(arc__kmem_reap_end);
2714 arc_reclaim_thread(void *dummy __unused)
2716 clock_t growtime = 0;
2717 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2720 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2722 mutex_enter(&arc_reclaim_thr_lock);
2723 while (arc_thread_exit == 0) {
2724 if (arc_reclaim_needed()) {
2727 if (last_reclaim == ARC_RECLAIM_CONS) {
2728 DTRACE_PROBE(arc__reclaim_aggr_no_grow);
2729 last_reclaim = ARC_RECLAIM_AGGR;
2731 last_reclaim = ARC_RECLAIM_CONS;
2735 last_reclaim = ARC_RECLAIM_AGGR;
2736 DTRACE_PROBE(arc__reclaim_aggr);
2740 /* reset the growth delay for every reclaim */
2741 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2743 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2745 * If needfree is TRUE our vm_lowmem hook
2746 * was called and in that case we must free some
2747 * memory, so switch to aggressive mode.
2750 last_reclaim = ARC_RECLAIM_AGGR;
2752 arc_kmem_reap_now(last_reclaim);
2755 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2756 arc_no_grow = FALSE;
2761 if (arc_eviction_list != NULL)
2762 arc_do_user_evicts();
2771 /* block until needed, or one second, whichever is shorter */
2772 CALLB_CPR_SAFE_BEGIN(&cpr);
2773 (void) cv_timedwait(&arc_reclaim_thr_cv,
2774 &arc_reclaim_thr_lock, hz);
2775 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2778 arc_thread_exit = 0;
2779 cv_broadcast(&arc_reclaim_thr_cv);
2780 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2785 * Adapt arc info given the number of bytes we are trying to add and
2786 * the state that we are comming from. This function is only called
2787 * when we are adding new content to the cache.
2790 arc_adapt(int bytes, arc_state_t *state)
2793 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2795 if (state == arc_l2c_only)
2800 * Adapt the target size of the MRU list:
2801 * - if we just hit in the MRU ghost list, then increase
2802 * the target size of the MRU list.
2803 * - if we just hit in the MFU ghost list, then increase
2804 * the target size of the MFU list by decreasing the
2805 * target size of the MRU list.
2807 if (state == arc_mru_ghost) {
2808 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2809 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2810 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2812 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2813 } else if (state == arc_mfu_ghost) {
2816 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2817 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2818 mult = MIN(mult, 10);
2820 delta = MIN(bytes * mult, arc_p);
2821 arc_p = MAX(arc_p_min, arc_p - delta);
2823 ASSERT((int64_t)arc_p >= 0);
2825 if (arc_reclaim_needed()) {
2826 cv_signal(&arc_reclaim_thr_cv);
2833 if (arc_c >= arc_c_max)
2837 * If we're within (2 * maxblocksize) bytes of the target
2838 * cache size, increment the target cache size
2840 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2841 DTRACE_PROBE1(arc__inc_adapt, int, bytes);
2842 atomic_add_64(&arc_c, (int64_t)bytes);
2843 if (arc_c > arc_c_max)
2845 else if (state == arc_anon)
2846 atomic_add_64(&arc_p, (int64_t)bytes);
2850 ASSERT((int64_t)arc_p >= 0);
2854 * Check if the cache has reached its limits and eviction is required
2858 arc_evict_needed(arc_buf_contents_t type)
2860 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2863 if (arc_reclaim_needed())
2866 return (arc_size > arc_c);
2870 * The buffer, supplied as the first argument, needs a data block.
2871 * So, if we are at cache max, determine which cache should be victimized.
2872 * We have the following cases:
2874 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2875 * In this situation if we're out of space, but the resident size of the MFU is
2876 * under the limit, victimize the MFU cache to satisfy this insertion request.
2878 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2879 * Here, we've used up all of the available space for the MRU, so we need to
2880 * evict from our own cache instead. Evict from the set of resident MRU
2883 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2884 * c minus p represents the MFU space in the cache, since p is the size of the
2885 * cache that is dedicated to the MRU. In this situation there's still space on
2886 * the MFU side, so the MRU side needs to be victimized.
2888 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2889 * MFU's resident set is consuming more space than it has been allotted. In
2890 * this situation, we must victimize our own cache, the MFU, for this insertion.
2893 arc_get_data_buf(arc_buf_t *buf)
2895 arc_state_t *state = buf->b_hdr->b_state;
2896 uint64_t size = buf->b_hdr->b_size;
2897 arc_buf_contents_t type = buf->b_hdr->b_type;
2899 arc_adapt(size, state);
2902 * We have not yet reached cache maximum size,
2903 * just allocate a new buffer.
2905 if (!arc_evict_needed(type)) {
2906 if (type == ARC_BUFC_METADATA) {
2907 buf->b_data = zio_buf_alloc(size);
2908 arc_space_consume(size, ARC_SPACE_DATA);
2910 ASSERT(type == ARC_BUFC_DATA);
2911 buf->b_data = zio_data_buf_alloc(size);
2912 ARCSTAT_INCR(arcstat_data_size, size);
2913 atomic_add_64(&arc_size, size);
2919 * If we are prefetching from the mfu ghost list, this buffer
2920 * will end up on the mru list; so steal space from there.
2922 if (state == arc_mfu_ghost)
2923 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2924 else if (state == arc_mru_ghost)
2927 if (state == arc_mru || state == arc_anon) {
2928 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2929 state = (arc_mfu->arcs_lsize[type] >= size &&
2930 arc_p > mru_used) ? arc_mfu : arc_mru;
2933 uint64_t mfu_space = arc_c - arc_p;
2934 state = (arc_mru->arcs_lsize[type] >= size &&
2935 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2937 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2938 if (type == ARC_BUFC_METADATA) {
2939 buf->b_data = zio_buf_alloc(size);
2940 arc_space_consume(size, ARC_SPACE_DATA);
2942 ASSERT(type == ARC_BUFC_DATA);
2943 buf->b_data = zio_data_buf_alloc(size);
2944 ARCSTAT_INCR(arcstat_data_size, size);
2945 atomic_add_64(&arc_size, size);
2947 ARCSTAT_BUMP(arcstat_recycle_miss);
2949 ASSERT(buf->b_data != NULL);
2952 * Update the state size. Note that ghost states have a
2953 * "ghost size" and so don't need to be updated.
2955 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2956 arc_buf_hdr_t *hdr = buf->b_hdr;
2958 atomic_add_64(&hdr->b_state->arcs_size, size);
2959 if (list_link_active(&hdr->b_arc_node)) {
2960 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2961 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2964 * If we are growing the cache, and we are adding anonymous
2965 * data, and we have outgrown arc_p, update arc_p
2967 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2968 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2969 arc_p = MIN(arc_c, arc_p + size);
2971 ARCSTAT_BUMP(arcstat_allocated);
2975 * This routine is called whenever a buffer is accessed.
2976 * NOTE: the hash lock is dropped in this function.
2979 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2983 ASSERT(MUTEX_HELD(hash_lock));
2985 if (buf->b_state == arc_anon) {
2987 * This buffer is not in the cache, and does not
2988 * appear in our "ghost" list. Add the new buffer
2992 ASSERT(buf->b_arc_access == 0);
2993 buf->b_arc_access = ddi_get_lbolt();
2994 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2995 arc_change_state(arc_mru, buf, hash_lock);
2997 } else if (buf->b_state == arc_mru) {
2998 now = ddi_get_lbolt();
3001 * If this buffer is here because of a prefetch, then either:
3002 * - clear the flag if this is a "referencing" read
3003 * (any subsequent access will bump this into the MFU state).
3005 * - move the buffer to the head of the list if this is
3006 * another prefetch (to make it less likely to be evicted).
3008 if ((buf->b_flags & ARC_PREFETCH) != 0) {
3009 if (refcount_count(&buf->b_refcnt) == 0) {
3010 ASSERT(list_link_active(&buf->b_arc_node));
3012 buf->b_flags &= ~ARC_PREFETCH;
3013 ARCSTAT_BUMP(arcstat_mru_hits);
3015 buf->b_arc_access = now;
3020 * This buffer has been "accessed" only once so far,
3021 * but it is still in the cache. Move it to the MFU
3024 if (now > buf->b_arc_access + ARC_MINTIME) {
3026 * More than 125ms have passed since we
3027 * instantiated this buffer. Move it to the
3028 * most frequently used state.
3030 buf->b_arc_access = now;
3031 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3032 arc_change_state(arc_mfu, buf, hash_lock);
3034 ARCSTAT_BUMP(arcstat_mru_hits);
3035 } else if (buf->b_state == arc_mru_ghost) {
3036 arc_state_t *new_state;
3038 * This buffer has been "accessed" recently, but
3039 * was evicted from the cache. Move it to the
3043 if (buf->b_flags & ARC_PREFETCH) {
3044 new_state = arc_mru;
3045 if (refcount_count(&buf->b_refcnt) > 0)
3046 buf->b_flags &= ~ARC_PREFETCH;
3047 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
3049 new_state = arc_mfu;
3050 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3053 buf->b_arc_access = ddi_get_lbolt();
3054 arc_change_state(new_state, buf, hash_lock);
3056 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
3057 } else if (buf->b_state == arc_mfu) {
3059 * This buffer has been accessed more than once and is
3060 * still in the cache. Keep it in the MFU state.
3062 * NOTE: an add_reference() that occurred when we did
3063 * the arc_read() will have kicked this off the list.
3064 * If it was a prefetch, we will explicitly move it to
3065 * the head of the list now.
3067 if ((buf->b_flags & ARC_PREFETCH) != 0) {
3068 ASSERT(refcount_count(&buf->b_refcnt) == 0);
3069 ASSERT(list_link_active(&buf->b_arc_node));
3071 ARCSTAT_BUMP(arcstat_mfu_hits);
3072 buf->b_arc_access = ddi_get_lbolt();
3073 } else if (buf->b_state == arc_mfu_ghost) {
3074 arc_state_t *new_state = arc_mfu;
3076 * This buffer has been accessed more than once but has
3077 * been evicted from the cache. Move it back to the
3081 if (buf->b_flags & ARC_PREFETCH) {
3083 * This is a prefetch access...
3084 * move this block back to the MRU state.
3086 ASSERT0(refcount_count(&buf->b_refcnt));
3087 new_state = arc_mru;
3090 buf->b_arc_access = ddi_get_lbolt();
3091 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3092 arc_change_state(new_state, buf, hash_lock);
3094 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
3095 } else if (buf->b_state == arc_l2c_only) {
3097 * This buffer is on the 2nd Level ARC.
3100 buf->b_arc_access = ddi_get_lbolt();
3101 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3102 arc_change_state(arc_mfu, buf, hash_lock);
3104 ASSERT(!"invalid arc state");
3108 /* a generic arc_done_func_t which you can use */
3111 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
3113 if (zio == NULL || zio->io_error == 0)
3114 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
3115 VERIFY(arc_buf_remove_ref(buf, arg));
3118 /* a generic arc_done_func_t */
3120 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
3122 arc_buf_t **bufp = arg;
3123 if (zio && zio->io_error) {
3124 VERIFY(arc_buf_remove_ref(buf, arg));
3128 ASSERT(buf->b_data);
3133 arc_read_done(zio_t *zio)
3137 arc_buf_t *abuf; /* buffer we're assigning to callback */
3138 kmutex_t *hash_lock = NULL;
3139 arc_callback_t *callback_list, *acb;
3140 int freeable = FALSE;
3142 buf = zio->io_private;
3146 * The hdr was inserted into hash-table and removed from lists
3147 * prior to starting I/O. We should find this header, since
3148 * it's in the hash table, and it should be legit since it's
3149 * not possible to evict it during the I/O. The only possible
3150 * reason for it not to be found is if we were freed during the
3153 if (HDR_IN_HASH_TABLE(hdr)) {
3154 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
3155 ASSERT3U(hdr->b_dva.dva_word[0], ==,
3156 BP_IDENTITY(zio->io_bp)->dva_word[0]);
3157 ASSERT3U(hdr->b_dva.dva_word[1], ==,
3158 BP_IDENTITY(zio->io_bp)->dva_word[1]);
3160 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
3163 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
3164 hash_lock == NULL) ||
3166 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
3167 (found == hdr && HDR_L2_READING(hdr)));
3170 hdr->b_flags &= ~ARC_L2_EVICTED;
3171 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
3172 hdr->b_flags &= ~ARC_L2CACHE;
3174 /* byteswap if necessary */
3175 callback_list = hdr->b_acb;
3176 ASSERT(callback_list != NULL);
3177 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3178 dmu_object_byteswap_t bswap =
3179 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3180 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3181 byteswap_uint64_array :
3182 dmu_ot_byteswap[bswap].ob_func;
3183 func(buf->b_data, hdr->b_size);
3186 arc_cksum_compute(buf, B_FALSE);
3189 #endif /* illumos */
3191 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
3193 * Only call arc_access on anonymous buffers. This is because
3194 * if we've issued an I/O for an evicted buffer, we've already
3195 * called arc_access (to prevent any simultaneous readers from
3196 * getting confused).
3198 arc_access(hdr, hash_lock);
3201 /* create copies of the data buffer for the callers */
3203 for (acb = callback_list; acb; acb = acb->acb_next) {
3204 if (acb->acb_done) {
3206 ARCSTAT_BUMP(arcstat_duplicate_reads);
3207 abuf = arc_buf_clone(buf);
3209 acb->acb_buf = abuf;
3214 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3215 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3217 ASSERT(buf->b_efunc == NULL);
3218 ASSERT(hdr->b_datacnt == 1);
3219 hdr->b_flags |= ARC_BUF_AVAILABLE;
3222 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
3224 if (zio->io_error != 0) {
3225 hdr->b_flags |= ARC_IO_ERROR;
3226 if (hdr->b_state != arc_anon)
3227 arc_change_state(arc_anon, hdr, hash_lock);
3228 if (HDR_IN_HASH_TABLE(hdr))
3229 buf_hash_remove(hdr);
3230 freeable = refcount_is_zero(&hdr->b_refcnt);
3234 * Broadcast before we drop the hash_lock to avoid the possibility
3235 * that the hdr (and hence the cv) might be freed before we get to
3236 * the cv_broadcast().
3238 cv_broadcast(&hdr->b_cv);
3241 mutex_exit(hash_lock);
3244 * This block was freed while we waited for the read to
3245 * complete. It has been removed from the hash table and
3246 * moved to the anonymous state (so that it won't show up
3249 ASSERT3P(hdr->b_state, ==, arc_anon);
3250 freeable = refcount_is_zero(&hdr->b_refcnt);
3253 /* execute each callback and free its structure */
3254 while ((acb = callback_list) != NULL) {
3256 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3258 if (acb->acb_zio_dummy != NULL) {
3259 acb->acb_zio_dummy->io_error = zio->io_error;
3260 zio_nowait(acb->acb_zio_dummy);
3263 callback_list = acb->acb_next;
3264 kmem_free(acb, sizeof (arc_callback_t));
3268 arc_hdr_destroy(hdr);
3272 * "Read" the block block at the specified DVA (in bp) via the
3273 * cache. If the block is found in the cache, invoke the provided
3274 * callback immediately and return. Note that the `zio' parameter
3275 * in the callback will be NULL in this case, since no IO was
3276 * required. If the block is not in the cache pass the read request
3277 * on to the spa with a substitute callback function, so that the
3278 * requested block will be added to the cache.
3280 * If a read request arrives for a block that has a read in-progress,
3281 * either wait for the in-progress read to complete (and return the
3282 * results); or, if this is a read with a "done" func, add a record
3283 * to the read to invoke the "done" func when the read completes,
3284 * and return; or just return.
3286 * arc_read_done() will invoke all the requested "done" functions
3287 * for readers of this block.
3290 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3291 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
3292 const zbookmark_phys_t *zb)
3294 arc_buf_hdr_t *hdr = NULL;
3295 arc_buf_t *buf = NULL;
3296 kmutex_t *hash_lock = NULL;
3298 uint64_t guid = spa_load_guid(spa);
3300 ASSERT(!BP_IS_EMBEDDED(bp) ||
3301 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3304 if (!BP_IS_EMBEDDED(bp)) {
3306 * Embedded BP's have no DVA and require no I/O to "read".
3307 * Create an anonymous arc buf to back it.
3309 hdr = buf_hash_find(guid, bp, &hash_lock);
3312 if (hdr != NULL && hdr->b_datacnt > 0) {
3314 *arc_flags |= ARC_CACHED;
3316 if (HDR_IO_IN_PROGRESS(hdr)) {
3318 if (*arc_flags & ARC_WAIT) {
3319 cv_wait(&hdr->b_cv, hash_lock);
3320 mutex_exit(hash_lock);
3323 ASSERT(*arc_flags & ARC_NOWAIT);
3326 arc_callback_t *acb = NULL;
3328 acb = kmem_zalloc(sizeof (arc_callback_t),
3330 acb->acb_done = done;
3331 acb->acb_private = private;
3333 acb->acb_zio_dummy = zio_null(pio,
3334 spa, NULL, NULL, NULL, zio_flags);
3336 ASSERT(acb->acb_done != NULL);
3337 acb->acb_next = hdr->b_acb;
3339 add_reference(hdr, hash_lock, private);
3340 mutex_exit(hash_lock);
3343 mutex_exit(hash_lock);
3347 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3350 add_reference(hdr, hash_lock, private);
3352 * If this block is already in use, create a new
3353 * copy of the data so that we will be guaranteed
3354 * that arc_release() will always succeed.
3358 ASSERT(buf->b_data);
3359 if (HDR_BUF_AVAILABLE(hdr)) {
3360 ASSERT(buf->b_efunc == NULL);
3361 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3363 buf = arc_buf_clone(buf);
3366 } else if (*arc_flags & ARC_PREFETCH &&
3367 refcount_count(&hdr->b_refcnt) == 0) {
3368 hdr->b_flags |= ARC_PREFETCH;
3370 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3371 arc_access(hdr, hash_lock);
3372 if (*arc_flags & ARC_L2CACHE)
3373 hdr->b_flags |= ARC_L2CACHE;
3374 if (*arc_flags & ARC_L2COMPRESS)
3375 hdr->b_flags |= ARC_L2COMPRESS;
3376 mutex_exit(hash_lock);
3377 ARCSTAT_BUMP(arcstat_hits);
3378 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3379 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3380 data, metadata, hits);
3383 done(NULL, buf, private);
3385 uint64_t size = BP_GET_LSIZE(bp);
3386 arc_callback_t *acb;
3389 boolean_t devw = B_FALSE;
3390 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
3391 uint64_t b_asize = 0;
3394 /* this block is not in the cache */
3395 arc_buf_hdr_t *exists = NULL;
3396 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3397 buf = arc_buf_alloc(spa, size, private, type);
3399 if (!BP_IS_EMBEDDED(bp)) {
3400 hdr->b_dva = *BP_IDENTITY(bp);
3401 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3402 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3403 exists = buf_hash_insert(hdr, &hash_lock);
3405 if (exists != NULL) {
3406 /* somebody beat us to the hash insert */
3407 mutex_exit(hash_lock);
3408 buf_discard_identity(hdr);
3409 (void) arc_buf_remove_ref(buf, private);
3410 goto top; /* restart the IO request */
3412 /* if this is a prefetch, we don't have a reference */
3413 if (*arc_flags & ARC_PREFETCH) {
3414 (void) remove_reference(hdr, hash_lock,
3416 hdr->b_flags |= ARC_PREFETCH;
3418 if (*arc_flags & ARC_L2CACHE)
3419 hdr->b_flags |= ARC_L2CACHE;
3420 if (*arc_flags & ARC_L2COMPRESS)
3421 hdr->b_flags |= ARC_L2COMPRESS;
3422 if (BP_GET_LEVEL(bp) > 0)
3423 hdr->b_flags |= ARC_INDIRECT;
3425 /* this block is in the ghost cache */
3426 ASSERT(GHOST_STATE(hdr->b_state));
3427 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3428 ASSERT0(refcount_count(&hdr->b_refcnt));
3429 ASSERT(hdr->b_buf == NULL);
3431 /* if this is a prefetch, we don't have a reference */
3432 if (*arc_flags & ARC_PREFETCH)
3433 hdr->b_flags |= ARC_PREFETCH;
3435 add_reference(hdr, hash_lock, private);
3436 if (*arc_flags & ARC_L2CACHE)
3437 hdr->b_flags |= ARC_L2CACHE;
3438 if (*arc_flags & ARC_L2COMPRESS)
3439 hdr->b_flags |= ARC_L2COMPRESS;
3440 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3443 buf->b_efunc = NULL;
3444 buf->b_private = NULL;
3447 ASSERT(hdr->b_datacnt == 0);
3449 arc_get_data_buf(buf);
3450 arc_access(hdr, hash_lock);
3453 ASSERT(!GHOST_STATE(hdr->b_state));
3455 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3456 acb->acb_done = done;
3457 acb->acb_private = private;
3459 ASSERT(hdr->b_acb == NULL);
3461 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3463 if (hdr->b_l2hdr != NULL &&
3464 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3465 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3466 addr = hdr->b_l2hdr->b_daddr;
3467 b_compress = hdr->b_l2hdr->b_compress;
3468 b_asize = hdr->b_l2hdr->b_asize;
3470 * Lock out device removal.
3472 if (vdev_is_dead(vd) ||
3473 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3477 if (hash_lock != NULL)
3478 mutex_exit(hash_lock);
3481 * At this point, we have a level 1 cache miss. Try again in
3482 * L2ARC if possible.
3484 ASSERT3U(hdr->b_size, ==, size);
3485 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3486 uint64_t, size, zbookmark_phys_t *, zb);
3487 ARCSTAT_BUMP(arcstat_misses);
3488 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3489 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3490 data, metadata, misses);
3492 curthread->td_ru.ru_inblock++;
3495 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3497 * Read from the L2ARC if the following are true:
3498 * 1. The L2ARC vdev was previously cached.
3499 * 2. This buffer still has L2ARC metadata.
3500 * 3. This buffer isn't currently writing to the L2ARC.
3501 * 4. The L2ARC entry wasn't evicted, which may
3502 * also have invalidated the vdev.
3503 * 5. This isn't prefetch and l2arc_noprefetch is set.
3505 if (hdr->b_l2hdr != NULL &&
3506 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3507 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3508 l2arc_read_callback_t *cb;
3510 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3511 ARCSTAT_BUMP(arcstat_l2_hits);
3513 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3515 cb->l2rcb_buf = buf;
3516 cb->l2rcb_spa = spa;
3519 cb->l2rcb_flags = zio_flags;
3520 cb->l2rcb_compress = b_compress;
3522 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3523 addr + size < vd->vdev_psize -
3524 VDEV_LABEL_END_SIZE);
3527 * l2arc read. The SCL_L2ARC lock will be
3528 * released by l2arc_read_done().
3529 * Issue a null zio if the underlying buffer
3530 * was squashed to zero size by compression.
3532 if (b_compress == ZIO_COMPRESS_EMPTY) {
3533 rzio = zio_null(pio, spa, vd,
3534 l2arc_read_done, cb,
3535 zio_flags | ZIO_FLAG_DONT_CACHE |
3537 ZIO_FLAG_DONT_PROPAGATE |
3538 ZIO_FLAG_DONT_RETRY);
3540 rzio = zio_read_phys(pio, vd, addr,
3541 b_asize, buf->b_data,
3543 l2arc_read_done, cb, priority,
3544 zio_flags | ZIO_FLAG_DONT_CACHE |
3546 ZIO_FLAG_DONT_PROPAGATE |
3547 ZIO_FLAG_DONT_RETRY, B_FALSE);
3549 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3551 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
3553 if (*arc_flags & ARC_NOWAIT) {
3558 ASSERT(*arc_flags & ARC_WAIT);
3559 if (zio_wait(rzio) == 0)
3562 /* l2arc read error; goto zio_read() */
3564 DTRACE_PROBE1(l2arc__miss,
3565 arc_buf_hdr_t *, hdr);
3566 ARCSTAT_BUMP(arcstat_l2_misses);
3567 if (HDR_L2_WRITING(hdr))
3568 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3569 spa_config_exit(spa, SCL_L2ARC, vd);
3573 spa_config_exit(spa, SCL_L2ARC, vd);
3574 if (l2arc_ndev != 0) {
3575 DTRACE_PROBE1(l2arc__miss,
3576 arc_buf_hdr_t *, hdr);
3577 ARCSTAT_BUMP(arcstat_l2_misses);
3581 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3582 arc_read_done, buf, priority, zio_flags, zb);
3584 if (*arc_flags & ARC_WAIT)
3585 return (zio_wait(rzio));
3587 ASSERT(*arc_flags & ARC_NOWAIT);
3594 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3596 ASSERT(buf->b_hdr != NULL);
3597 ASSERT(buf->b_hdr->b_state != arc_anon);
3598 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3599 ASSERT(buf->b_efunc == NULL);
3600 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3602 buf->b_efunc = func;
3603 buf->b_private = private;
3607 * Notify the arc that a block was freed, and thus will never be used again.
3610 arc_freed(spa_t *spa, const blkptr_t *bp)
3613 kmutex_t *hash_lock;
3614 uint64_t guid = spa_load_guid(spa);
3616 ASSERT(!BP_IS_EMBEDDED(bp));
3618 hdr = buf_hash_find(guid, bp, &hash_lock);
3621 if (HDR_BUF_AVAILABLE(hdr)) {
3622 arc_buf_t *buf = hdr->b_buf;
3623 add_reference(hdr, hash_lock, FTAG);
3624 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3625 mutex_exit(hash_lock);
3627 arc_release(buf, FTAG);
3628 (void) arc_buf_remove_ref(buf, FTAG);
3630 mutex_exit(hash_lock);
3636 * Clear the user eviction callback set by arc_set_callback(), first calling
3637 * it if it exists. Because the presence of a callback keeps an arc_buf cached
3638 * clearing the callback may result in the arc_buf being destroyed. However,
3639 * it will not result in the *last* arc_buf being destroyed, hence the data
3640 * will remain cached in the ARC. We make a copy of the arc buffer here so
3641 * that we can process the callback without holding any locks.
3643 * It's possible that the callback is already in the process of being cleared
3644 * by another thread. In this case we can not clear the callback.
3646 * Returns B_TRUE if the callback was successfully called and cleared.
3649 arc_clear_callback(arc_buf_t *buf)
3652 kmutex_t *hash_lock;
3653 arc_evict_func_t *efunc = buf->b_efunc;
3654 void *private = buf->b_private;
3655 list_t *list, *evicted_list;
3656 kmutex_t *lock, *evicted_lock;
3658 mutex_enter(&buf->b_evict_lock);
3662 * We are in arc_do_user_evicts().
3664 ASSERT(buf->b_data == NULL);
3665 mutex_exit(&buf->b_evict_lock);
3667 } else if (buf->b_data == NULL) {
3669 * We are on the eviction list; process this buffer now
3670 * but let arc_do_user_evicts() do the reaping.
3672 buf->b_efunc = NULL;
3673 mutex_exit(&buf->b_evict_lock);
3674 VERIFY0(efunc(private));
3677 hash_lock = HDR_LOCK(hdr);
3678 mutex_enter(hash_lock);
3680 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3682 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3683 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3685 buf->b_efunc = NULL;
3686 buf->b_private = NULL;
3688 if (hdr->b_datacnt > 1) {
3689 mutex_exit(&buf->b_evict_lock);
3690 arc_buf_destroy(buf, FALSE, TRUE);
3692 ASSERT(buf == hdr->b_buf);
3693 hdr->b_flags |= ARC_BUF_AVAILABLE;
3694 mutex_exit(&buf->b_evict_lock);
3697 mutex_exit(hash_lock);
3698 VERIFY0(efunc(private));
3703 * Release this buffer from the cache, making it an anonymous buffer. This
3704 * must be done after a read and prior to modifying the buffer contents.
3705 * If the buffer has more than one reference, we must make
3706 * a new hdr for the buffer.
3709 arc_release(arc_buf_t *buf, void *tag)
3712 kmutex_t *hash_lock = NULL;
3713 l2arc_buf_hdr_t *l2hdr;
3717 * It would be nice to assert that if it's DMU metadata (level >
3718 * 0 || it's the dnode file), then it must be syncing context.
3719 * But we don't know that information at this level.
3722 mutex_enter(&buf->b_evict_lock);
3725 /* this buffer is not on any list */
3726 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3728 if (hdr->b_state == arc_anon) {
3729 /* this buffer is already released */
3730 ASSERT(buf->b_efunc == NULL);
3732 hash_lock = HDR_LOCK(hdr);
3733 mutex_enter(hash_lock);
3735 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3738 l2hdr = hdr->b_l2hdr;
3740 mutex_enter(&l2arc_buflist_mtx);
3741 arc_buf_l2_cdata_free(hdr);
3742 hdr->b_l2hdr = NULL;
3743 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3745 buf_size = hdr->b_size;
3748 * Do we have more than one buf?
3750 if (hdr->b_datacnt > 1) {
3751 arc_buf_hdr_t *nhdr;
3753 uint64_t blksz = hdr->b_size;
3754 uint64_t spa = hdr->b_spa;
3755 arc_buf_contents_t type = hdr->b_type;
3756 uint32_t flags = hdr->b_flags;
3758 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3760 * Pull the data off of this hdr and attach it to
3761 * a new anonymous hdr.
3763 (void) remove_reference(hdr, hash_lock, tag);
3765 while (*bufp != buf)
3766 bufp = &(*bufp)->b_next;
3767 *bufp = buf->b_next;
3770 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3771 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3772 if (refcount_is_zero(&hdr->b_refcnt)) {
3773 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3774 ASSERT3U(*size, >=, hdr->b_size);
3775 atomic_add_64(size, -hdr->b_size);
3779 * We're releasing a duplicate user data buffer, update
3780 * our statistics accordingly.
3782 if (hdr->b_type == ARC_BUFC_DATA) {
3783 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3784 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3787 hdr->b_datacnt -= 1;
3788 arc_cksum_verify(buf);
3790 arc_buf_unwatch(buf);
3791 #endif /* illumos */
3793 mutex_exit(hash_lock);
3795 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3796 nhdr->b_size = blksz;
3798 nhdr->b_type = type;
3800 nhdr->b_state = arc_anon;
3801 nhdr->b_arc_access = 0;
3802 nhdr->b_flags = flags & ARC_L2_WRITING;
3803 nhdr->b_l2hdr = NULL;
3804 nhdr->b_datacnt = 1;
3805 nhdr->b_freeze_cksum = NULL;
3806 (void) refcount_add(&nhdr->b_refcnt, tag);
3808 mutex_exit(&buf->b_evict_lock);
3809 atomic_add_64(&arc_anon->arcs_size, blksz);
3811 mutex_exit(&buf->b_evict_lock);
3812 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3813 ASSERT(!list_link_active(&hdr->b_arc_node));
3814 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3815 if (hdr->b_state != arc_anon)
3816 arc_change_state(arc_anon, hdr, hash_lock);
3817 hdr->b_arc_access = 0;
3819 mutex_exit(hash_lock);
3821 buf_discard_identity(hdr);
3824 buf->b_efunc = NULL;
3825 buf->b_private = NULL;
3828 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
3829 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
3830 -l2hdr->b_asize, 0, 0);
3831 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
3833 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3834 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3835 mutex_exit(&l2arc_buflist_mtx);
3840 arc_released(arc_buf_t *buf)
3844 mutex_enter(&buf->b_evict_lock);
3845 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3846 mutex_exit(&buf->b_evict_lock);
3852 arc_referenced(arc_buf_t *buf)
3856 mutex_enter(&buf->b_evict_lock);
3857 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3858 mutex_exit(&buf->b_evict_lock);
3859 return (referenced);
3864 arc_write_ready(zio_t *zio)
3866 arc_write_callback_t *callback = zio->io_private;
3867 arc_buf_t *buf = callback->awcb_buf;
3868 arc_buf_hdr_t *hdr = buf->b_hdr;
3870 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3871 callback->awcb_ready(zio, buf, callback->awcb_private);
3874 * If the IO is already in progress, then this is a re-write
3875 * attempt, so we need to thaw and re-compute the cksum.
3876 * It is the responsibility of the callback to handle the
3877 * accounting for any re-write attempt.
3879 if (HDR_IO_IN_PROGRESS(hdr)) {
3880 mutex_enter(&hdr->b_freeze_lock);
3881 if (hdr->b_freeze_cksum != NULL) {
3882 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3883 hdr->b_freeze_cksum = NULL;
3885 mutex_exit(&hdr->b_freeze_lock);
3887 arc_cksum_compute(buf, B_FALSE);
3888 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3892 * The SPA calls this callback for each physical write that happens on behalf
3893 * of a logical write. See the comment in dbuf_write_physdone() for details.
3896 arc_write_physdone(zio_t *zio)
3898 arc_write_callback_t *cb = zio->io_private;
3899 if (cb->awcb_physdone != NULL)
3900 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
3904 arc_write_done(zio_t *zio)
3906 arc_write_callback_t *callback = zio->io_private;
3907 arc_buf_t *buf = callback->awcb_buf;
3908 arc_buf_hdr_t *hdr = buf->b_hdr;
3910 ASSERT(hdr->b_acb == NULL);
3912 if (zio->io_error == 0) {
3913 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
3914 buf_discard_identity(hdr);
3916 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3917 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3918 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3921 ASSERT(BUF_EMPTY(hdr));
3925 * If the block to be written was all-zero or compressed enough to be
3926 * embedded in the BP, no write was performed so there will be no
3927 * dva/birth/checksum. The buffer must therefore remain anonymous
3930 if (!BUF_EMPTY(hdr)) {
3931 arc_buf_hdr_t *exists;
3932 kmutex_t *hash_lock;
3934 ASSERT(zio->io_error == 0);
3936 arc_cksum_verify(buf);
3938 exists = buf_hash_insert(hdr, &hash_lock);
3941 * This can only happen if we overwrite for
3942 * sync-to-convergence, because we remove
3943 * buffers from the hash table when we arc_free().
3945 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3946 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3947 panic("bad overwrite, hdr=%p exists=%p",
3948 (void *)hdr, (void *)exists);
3949 ASSERT(refcount_is_zero(&exists->b_refcnt));
3950 arc_change_state(arc_anon, exists, hash_lock);
3951 mutex_exit(hash_lock);
3952 arc_hdr_destroy(exists);
3953 exists = buf_hash_insert(hdr, &hash_lock);
3954 ASSERT3P(exists, ==, NULL);
3955 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3957 ASSERT(zio->io_prop.zp_nopwrite);
3958 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3959 panic("bad nopwrite, hdr=%p exists=%p",
3960 (void *)hdr, (void *)exists);
3963 ASSERT(hdr->b_datacnt == 1);
3964 ASSERT(hdr->b_state == arc_anon);
3965 ASSERT(BP_GET_DEDUP(zio->io_bp));
3966 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3969 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3970 /* if it's not anon, we are doing a scrub */
3971 if (!exists && hdr->b_state == arc_anon)
3972 arc_access(hdr, hash_lock);
3973 mutex_exit(hash_lock);
3975 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3978 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3979 callback->awcb_done(zio, buf, callback->awcb_private);
3981 kmem_free(callback, sizeof (arc_write_callback_t));
3985 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3986 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
3987 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
3988 arc_done_func_t *done, void *private, zio_priority_t priority,
3989 int zio_flags, const zbookmark_phys_t *zb)
3991 arc_buf_hdr_t *hdr = buf->b_hdr;
3992 arc_write_callback_t *callback;
3995 ASSERT(ready != NULL);
3996 ASSERT(done != NULL);
3997 ASSERT(!HDR_IO_ERROR(hdr));
3998 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3999 ASSERT(hdr->b_acb == NULL);
4001 hdr->b_flags |= ARC_L2CACHE;
4003 hdr->b_flags |= ARC_L2COMPRESS;
4004 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
4005 callback->awcb_ready = ready;
4006 callback->awcb_physdone = physdone;
4007 callback->awcb_done = done;
4008 callback->awcb_private = private;
4009 callback->awcb_buf = buf;
4011 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
4012 arc_write_ready, arc_write_physdone, arc_write_done, callback,
4013 priority, zio_flags, zb);
4019 arc_memory_throttle(uint64_t reserve, uint64_t txg)
4022 uint64_t available_memory = ptob(freemem);
4023 static uint64_t page_load = 0;
4024 static uint64_t last_txg = 0;
4026 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
4028 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE)));
4031 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
4034 if (txg > last_txg) {
4039 * If we are in pageout, we know that memory is already tight,
4040 * the arc is already going to be evicting, so we just want to
4041 * continue to let page writes occur as quickly as possible.
4043 if (curproc == pageproc) {
4044 if (page_load > MAX(ptob(minfree), available_memory) / 4)
4045 return (SET_ERROR(ERESTART));
4046 /* Note: reserve is inflated, so we deflate */
4047 page_load += reserve / 8;
4049 } else if (page_load > 0 && arc_reclaim_needed()) {
4050 /* memory is low, delay before restarting */
4051 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
4052 return (SET_ERROR(EAGAIN));
4060 arc_tempreserve_clear(uint64_t reserve)
4062 atomic_add_64(&arc_tempreserve, -reserve);
4063 ASSERT((int64_t)arc_tempreserve >= 0);
4067 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
4072 if (reserve > arc_c/4 && !arc_no_grow) {
4073 arc_c = MIN(arc_c_max, reserve * 4);
4074 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
4076 if (reserve > arc_c)
4077 return (SET_ERROR(ENOMEM));
4080 * Don't count loaned bufs as in flight dirty data to prevent long
4081 * network delays from blocking transactions that are ready to be
4082 * assigned to a txg.
4084 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
4087 * Writes will, almost always, require additional memory allocations
4088 * in order to compress/encrypt/etc the data. We therefore need to
4089 * make sure that there is sufficient available memory for this.
4091 error = arc_memory_throttle(reserve, txg);
4096 * Throttle writes when the amount of dirty data in the cache
4097 * gets too large. We try to keep the cache less than half full
4098 * of dirty blocks so that our sync times don't grow too large.
4099 * Note: if two requests come in concurrently, we might let them
4100 * both succeed, when one of them should fail. Not a huge deal.
4103 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
4104 anon_size > arc_c / 4) {
4105 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
4106 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
4107 arc_tempreserve>>10,
4108 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
4109 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
4110 reserve>>10, arc_c>>10);
4111 return (SET_ERROR(ERESTART));
4113 atomic_add_64(&arc_tempreserve, reserve);
4117 static kmutex_t arc_lowmem_lock;
4119 static eventhandler_tag arc_event_lowmem = NULL;
4122 arc_lowmem(void *arg __unused, int howto __unused)
4125 /* Serialize access via arc_lowmem_lock. */
4126 mutex_enter(&arc_lowmem_lock);
4127 mutex_enter(&arc_reclaim_thr_lock);
4129 DTRACE_PROBE(arc__needfree);
4130 cv_signal(&arc_reclaim_thr_cv);
4133 * It is unsafe to block here in arbitrary threads, because we can come
4134 * here from ARC itself and may hold ARC locks and thus risk a deadlock
4135 * with ARC reclaim thread.
4137 if (curproc == pageproc) {
4139 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
4141 mutex_exit(&arc_reclaim_thr_lock);
4142 mutex_exit(&arc_lowmem_lock);
4149 int i, prefetch_tunable_set = 0;
4151 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4152 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
4153 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
4155 /* Convert seconds to clock ticks */
4156 arc_min_prefetch_lifespan = 1 * hz;
4158 /* Start out with 1/8 of all memory */
4159 arc_c = kmem_size() / 8;
4164 * On architectures where the physical memory can be larger
4165 * than the addressable space (intel in 32-bit mode), we may
4166 * need to limit the cache to 1/8 of VM size.
4168 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
4171 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
4172 arc_c_min = MAX(arc_c / 4, 64<<18);
4173 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
4174 if (arc_c * 8 >= 1<<30)
4175 arc_c_max = (arc_c * 8) - (1<<30);
4177 arc_c_max = arc_c_min;
4178 arc_c_max = MAX(arc_c * 5, arc_c_max);
4182 * Allow the tunables to override our calculations if they are
4183 * reasonable (ie. over 16MB)
4185 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size())
4186 arc_c_max = zfs_arc_max;
4187 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max)
4188 arc_c_min = zfs_arc_min;
4192 arc_p = (arc_c >> 1);
4194 /* limit meta-data to 1/4 of the arc capacity */
4195 arc_meta_limit = arc_c_max / 4;
4197 /* Allow the tunable to override if it is reasonable */
4198 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
4199 arc_meta_limit = zfs_arc_meta_limit;
4201 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
4202 arc_c_min = arc_meta_limit / 2;
4204 if (zfs_arc_grow_retry > 0)
4205 arc_grow_retry = zfs_arc_grow_retry;
4207 if (zfs_arc_shrink_shift > 0)
4208 arc_shrink_shift = zfs_arc_shrink_shift;
4210 if (zfs_arc_p_min_shift > 0)
4211 arc_p_min_shift = zfs_arc_p_min_shift;
4213 /* if kmem_flags are set, lets try to use less memory */
4214 if (kmem_debugging())
4216 if (arc_c < arc_c_min)
4219 zfs_arc_min = arc_c_min;
4220 zfs_arc_max = arc_c_max;
4222 arc_anon = &ARC_anon;
4224 arc_mru_ghost = &ARC_mru_ghost;
4226 arc_mfu_ghost = &ARC_mfu_ghost;
4227 arc_l2c_only = &ARC_l2c_only;
4230 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4231 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
4232 NULL, MUTEX_DEFAULT, NULL);
4233 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
4234 NULL, MUTEX_DEFAULT, NULL);
4235 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
4236 NULL, MUTEX_DEFAULT, NULL);
4237 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
4238 NULL, MUTEX_DEFAULT, NULL);
4239 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
4240 NULL, MUTEX_DEFAULT, NULL);
4241 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
4242 NULL, MUTEX_DEFAULT, NULL);
4244 list_create(&arc_mru->arcs_lists[i],
4245 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4246 list_create(&arc_mru_ghost->arcs_lists[i],
4247 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4248 list_create(&arc_mfu->arcs_lists[i],
4249 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4250 list_create(&arc_mfu_ghost->arcs_lists[i],
4251 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4252 list_create(&arc_mfu_ghost->arcs_lists[i],
4253 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4254 list_create(&arc_l2c_only->arcs_lists[i],
4255 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4260 arc_thread_exit = 0;
4261 arc_eviction_list = NULL;
4262 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
4263 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
4265 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
4266 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
4268 if (arc_ksp != NULL) {
4269 arc_ksp->ks_data = &arc_stats;
4270 kstat_install(arc_ksp);
4273 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
4274 TS_RUN, minclsyspri);
4277 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
4278 EVENTHANDLER_PRI_FIRST);
4285 * Calculate maximum amount of dirty data per pool.
4287 * If it has been set by /etc/system, take that.
4288 * Otherwise, use a percentage of physical memory defined by
4289 * zfs_dirty_data_max_percent (default 10%) with a cap at
4290 * zfs_dirty_data_max_max (default 4GB).
4292 if (zfs_dirty_data_max == 0) {
4293 zfs_dirty_data_max = ptob(physmem) *
4294 zfs_dirty_data_max_percent / 100;
4295 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
4296 zfs_dirty_data_max_max);
4300 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
4301 prefetch_tunable_set = 1;
4304 if (prefetch_tunable_set == 0) {
4305 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
4307 printf(" add \"vfs.zfs.prefetch_disable=0\" "
4308 "to /boot/loader.conf.\n");
4309 zfs_prefetch_disable = 1;
4312 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
4313 prefetch_tunable_set == 0) {
4314 printf("ZFS NOTICE: Prefetch is disabled by default if less "
4315 "than 4GB of RAM is present;\n"
4316 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
4317 "to /boot/loader.conf.\n");
4318 zfs_prefetch_disable = 1;
4321 /* Warn about ZFS memory and address space requirements. */
4322 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
4323 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
4324 "expect unstable behavior.\n");
4326 if (kmem_size() < 512 * (1 << 20)) {
4327 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
4328 "expect unstable behavior.\n");
4329 printf(" Consider tuning vm.kmem_size and "
4330 "vm.kmem_size_max\n");
4331 printf(" in /boot/loader.conf.\n");
4341 mutex_enter(&arc_reclaim_thr_lock);
4342 arc_thread_exit = 1;
4343 cv_signal(&arc_reclaim_thr_cv);
4344 while (arc_thread_exit != 0)
4345 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
4346 mutex_exit(&arc_reclaim_thr_lock);
4352 if (arc_ksp != NULL) {
4353 kstat_delete(arc_ksp);
4357 mutex_destroy(&arc_eviction_mtx);
4358 mutex_destroy(&arc_reclaim_thr_lock);
4359 cv_destroy(&arc_reclaim_thr_cv);
4361 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4362 list_destroy(&arc_mru->arcs_lists[i]);
4363 list_destroy(&arc_mru_ghost->arcs_lists[i]);
4364 list_destroy(&arc_mfu->arcs_lists[i]);
4365 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
4366 list_destroy(&arc_l2c_only->arcs_lists[i]);
4368 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
4369 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
4370 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
4371 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
4372 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
4373 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
4378 ASSERT(arc_loaned_bytes == 0);
4380 mutex_destroy(&arc_lowmem_lock);
4382 if (arc_event_lowmem != NULL)
4383 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
4390 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
4391 * It uses dedicated storage devices to hold cached data, which are populated
4392 * using large infrequent writes. The main role of this cache is to boost
4393 * the performance of random read workloads. The intended L2ARC devices
4394 * include short-stroked disks, solid state disks, and other media with
4395 * substantially faster read latency than disk.
4397 * +-----------------------+
4399 * +-----------------------+
4402 * l2arc_feed_thread() arc_read()
4406 * +---------------+ |
4408 * +---------------+ |
4413 * +-------+ +-------+
4415 * | cache | | cache |
4416 * +-------+ +-------+
4417 * +=========+ .-----.
4418 * : L2ARC : |-_____-|
4419 * : devices : | Disks |
4420 * +=========+ `-_____-'
4422 * Read requests are satisfied from the following sources, in order:
4425 * 2) vdev cache of L2ARC devices
4427 * 4) vdev cache of disks
4430 * Some L2ARC device types exhibit extremely slow write performance.
4431 * To accommodate for this there are some significant differences between
4432 * the L2ARC and traditional cache design:
4434 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4435 * the ARC behave as usual, freeing buffers and placing headers on ghost
4436 * lists. The ARC does not send buffers to the L2ARC during eviction as
4437 * this would add inflated write latencies for all ARC memory pressure.
4439 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4440 * It does this by periodically scanning buffers from the eviction-end of
4441 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4442 * not already there. It scans until a headroom of buffers is satisfied,
4443 * which itself is a buffer for ARC eviction. If a compressible buffer is
4444 * found during scanning and selected for writing to an L2ARC device, we
4445 * temporarily boost scanning headroom during the next scan cycle to make
4446 * sure we adapt to compression effects (which might significantly reduce
4447 * the data volume we write to L2ARC). The thread that does this is
4448 * l2arc_feed_thread(), illustrated below; example sizes are included to
4449 * provide a better sense of ratio than this diagram:
4452 * +---------------------+----------+
4453 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4454 * +---------------------+----------+ | o L2ARC eligible
4455 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4456 * +---------------------+----------+ |
4457 * 15.9 Gbytes ^ 32 Mbytes |
4459 * l2arc_feed_thread()
4461 * l2arc write hand <--[oooo]--'
4465 * +==============================+
4466 * L2ARC dev |####|#|###|###| |####| ... |
4467 * +==============================+
4470 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4471 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4472 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4473 * safe to say that this is an uncommon case, since buffers at the end of
4474 * the ARC lists have moved there due to inactivity.
4476 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4477 * then the L2ARC simply misses copying some buffers. This serves as a
4478 * pressure valve to prevent heavy read workloads from both stalling the ARC
4479 * with waits and clogging the L2ARC with writes. This also helps prevent
4480 * the potential for the L2ARC to churn if it attempts to cache content too
4481 * quickly, such as during backups of the entire pool.
4483 * 5. After system boot and before the ARC has filled main memory, there are
4484 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4485 * lists can remain mostly static. Instead of searching from tail of these
4486 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4487 * for eligible buffers, greatly increasing its chance of finding them.
4489 * The L2ARC device write speed is also boosted during this time so that
4490 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4491 * there are no L2ARC reads, and no fear of degrading read performance
4492 * through increased writes.
4494 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4495 * the vdev queue can aggregate them into larger and fewer writes. Each
4496 * device is written to in a rotor fashion, sweeping writes through
4497 * available space then repeating.
4499 * 7. The L2ARC does not store dirty content. It never needs to flush
4500 * write buffers back to disk based storage.
4502 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4503 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4505 * The performance of the L2ARC can be tweaked by a number of tunables, which
4506 * may be necessary for different workloads:
4508 * l2arc_write_max max write bytes per interval
4509 * l2arc_write_boost extra write bytes during device warmup
4510 * l2arc_noprefetch skip caching prefetched buffers
4511 * l2arc_headroom number of max device writes to precache
4512 * l2arc_headroom_boost when we find compressed buffers during ARC
4513 * scanning, we multiply headroom by this
4514 * percentage factor for the next scan cycle,
4515 * since more compressed buffers are likely to
4517 * l2arc_feed_secs seconds between L2ARC writing
4519 * Tunables may be removed or added as future performance improvements are
4520 * integrated, and also may become zpool properties.
4522 * There are three key functions that control how the L2ARC warms up:
4524 * l2arc_write_eligible() check if a buffer is eligible to cache
4525 * l2arc_write_size() calculate how much to write
4526 * l2arc_write_interval() calculate sleep delay between writes
4528 * These three functions determine what to write, how much, and how quickly
4533 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4536 * A buffer is *not* eligible for the L2ARC if it:
4537 * 1. belongs to a different spa.
4538 * 2. is already cached on the L2ARC.
4539 * 3. has an I/O in progress (it may be an incomplete read).
4540 * 4. is flagged not eligible (zfs property).
4542 if (ab->b_spa != spa_guid) {
4543 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4546 if (ab->b_l2hdr != NULL) {
4547 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4550 if (HDR_IO_IN_PROGRESS(ab)) {
4551 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4554 if (!HDR_L2CACHE(ab)) {
4555 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4563 l2arc_write_size(void)
4568 * Make sure our globals have meaningful values in case the user
4571 size = l2arc_write_max;
4573 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
4574 "be greater than zero, resetting it to the default (%d)",
4576 size = l2arc_write_max = L2ARC_WRITE_SIZE;
4579 if (arc_warm == B_FALSE)
4580 size += l2arc_write_boost;
4587 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4589 clock_t interval, next, now;
4592 * If the ARC lists are busy, increase our write rate; if the
4593 * lists are stale, idle back. This is achieved by checking
4594 * how much we previously wrote - if it was more than half of
4595 * what we wanted, schedule the next write much sooner.
4597 if (l2arc_feed_again && wrote > (wanted / 2))
4598 interval = (hz * l2arc_feed_min_ms) / 1000;
4600 interval = hz * l2arc_feed_secs;
4602 now = ddi_get_lbolt();
4603 next = MAX(now, MIN(now + interval, began + interval));
4609 l2arc_hdr_stat_add(void)
4611 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4612 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4616 l2arc_hdr_stat_remove(void)
4618 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4619 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4623 * Cycle through L2ARC devices. This is how L2ARC load balances.
4624 * If a device is returned, this also returns holding the spa config lock.
4626 static l2arc_dev_t *
4627 l2arc_dev_get_next(void)
4629 l2arc_dev_t *first, *next = NULL;
4632 * Lock out the removal of spas (spa_namespace_lock), then removal
4633 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4634 * both locks will be dropped and a spa config lock held instead.
4636 mutex_enter(&spa_namespace_lock);
4637 mutex_enter(&l2arc_dev_mtx);
4639 /* if there are no vdevs, there is nothing to do */
4640 if (l2arc_ndev == 0)
4644 next = l2arc_dev_last;
4646 /* loop around the list looking for a non-faulted vdev */
4648 next = list_head(l2arc_dev_list);
4650 next = list_next(l2arc_dev_list, next);
4652 next = list_head(l2arc_dev_list);
4655 /* if we have come back to the start, bail out */
4658 else if (next == first)
4661 } while (vdev_is_dead(next->l2ad_vdev));
4663 /* if we were unable to find any usable vdevs, return NULL */
4664 if (vdev_is_dead(next->l2ad_vdev))
4667 l2arc_dev_last = next;
4670 mutex_exit(&l2arc_dev_mtx);
4673 * Grab the config lock to prevent the 'next' device from being
4674 * removed while we are writing to it.
4677 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4678 mutex_exit(&spa_namespace_lock);
4684 * Free buffers that were tagged for destruction.
4687 l2arc_do_free_on_write()
4690 l2arc_data_free_t *df, *df_prev;
4692 mutex_enter(&l2arc_free_on_write_mtx);
4693 buflist = l2arc_free_on_write;
4695 for (df = list_tail(buflist); df; df = df_prev) {
4696 df_prev = list_prev(buflist, df);
4697 ASSERT(df->l2df_data != NULL);
4698 ASSERT(df->l2df_func != NULL);
4699 df->l2df_func(df->l2df_data, df->l2df_size);
4700 list_remove(buflist, df);
4701 kmem_free(df, sizeof (l2arc_data_free_t));
4704 mutex_exit(&l2arc_free_on_write_mtx);
4708 * A write to a cache device has completed. Update all headers to allow
4709 * reads from these buffers to begin.
4712 l2arc_write_done(zio_t *zio)
4714 l2arc_write_callback_t *cb;
4717 arc_buf_hdr_t *head, *ab, *ab_prev;
4718 l2arc_buf_hdr_t *abl2;
4719 kmutex_t *hash_lock;
4720 int64_t bytes_dropped = 0;
4722 cb = zio->io_private;
4724 dev = cb->l2wcb_dev;
4725 ASSERT(dev != NULL);
4726 head = cb->l2wcb_head;
4727 ASSERT(head != NULL);
4728 buflist = dev->l2ad_buflist;
4729 ASSERT(buflist != NULL);
4730 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4731 l2arc_write_callback_t *, cb);
4733 if (zio->io_error != 0)
4734 ARCSTAT_BUMP(arcstat_l2_writes_error);
4736 mutex_enter(&l2arc_buflist_mtx);
4739 * All writes completed, or an error was hit.
4741 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4742 ab_prev = list_prev(buflist, ab);
4746 * Release the temporary compressed buffer as soon as possible.
4748 if (abl2->b_compress != ZIO_COMPRESS_OFF)
4749 l2arc_release_cdata_buf(ab);
4751 hash_lock = HDR_LOCK(ab);
4752 if (!mutex_tryenter(hash_lock)) {
4754 * This buffer misses out. It may be in a stage
4755 * of eviction. Its ARC_L2_WRITING flag will be
4756 * left set, denying reads to this buffer.
4758 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4762 if (zio->io_error != 0) {
4764 * Error - drop L2ARC entry.
4766 list_remove(buflist, ab);
4767 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4768 bytes_dropped += abl2->b_asize;
4770 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr,
4772 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4773 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4777 * Allow ARC to begin reads to this L2ARC entry.
4779 ab->b_flags &= ~ARC_L2_WRITING;
4781 mutex_exit(hash_lock);
4784 atomic_inc_64(&l2arc_writes_done);
4785 list_remove(buflist, head);
4786 kmem_cache_free(hdr_cache, head);
4787 mutex_exit(&l2arc_buflist_mtx);
4789 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
4791 l2arc_do_free_on_write();
4793 kmem_free(cb, sizeof (l2arc_write_callback_t));
4797 * A read to a cache device completed. Validate buffer contents before
4798 * handing over to the regular ARC routines.
4801 l2arc_read_done(zio_t *zio)
4803 l2arc_read_callback_t *cb;
4806 kmutex_t *hash_lock;
4809 ASSERT(zio->io_vd != NULL);
4810 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4812 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4814 cb = zio->io_private;
4816 buf = cb->l2rcb_buf;
4817 ASSERT(buf != NULL);
4819 hash_lock = HDR_LOCK(buf->b_hdr);
4820 mutex_enter(hash_lock);
4822 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4825 * If the buffer was compressed, decompress it first.
4827 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
4828 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
4829 ASSERT(zio->io_data != NULL);
4832 * Check this survived the L2ARC journey.
4834 equal = arc_cksum_equal(buf);
4835 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4836 mutex_exit(hash_lock);
4837 zio->io_private = buf;
4838 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4839 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4842 mutex_exit(hash_lock);
4844 * Buffer didn't survive caching. Increment stats and
4845 * reissue to the original storage device.
4847 if (zio->io_error != 0) {
4848 ARCSTAT_BUMP(arcstat_l2_io_error);
4850 zio->io_error = SET_ERROR(EIO);
4853 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4856 * If there's no waiter, issue an async i/o to the primary
4857 * storage now. If there *is* a waiter, the caller must
4858 * issue the i/o in a context where it's OK to block.
4860 if (zio->io_waiter == NULL) {
4861 zio_t *pio = zio_unique_parent(zio);
4863 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4865 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4866 buf->b_data, zio->io_size, arc_read_done, buf,
4867 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4871 kmem_free(cb, sizeof (l2arc_read_callback_t));
4875 * This is the list priority from which the L2ARC will search for pages to
4876 * cache. This is used within loops (0..3) to cycle through lists in the
4877 * desired order. This order can have a significant effect on cache
4880 * Currently the metadata lists are hit first, MFU then MRU, followed by
4881 * the data lists. This function returns a locked list, and also returns
4885 l2arc_list_locked(int list_num, kmutex_t **lock)
4887 list_t *list = NULL;
4890 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4892 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4894 list = &arc_mfu->arcs_lists[idx];
4895 *lock = ARCS_LOCK(arc_mfu, idx);
4896 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4897 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4898 list = &arc_mru->arcs_lists[idx];
4899 *lock = ARCS_LOCK(arc_mru, idx);
4900 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4901 ARC_BUFC_NUMDATALISTS)) {
4902 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4903 list = &arc_mfu->arcs_lists[idx];
4904 *lock = ARCS_LOCK(arc_mfu, idx);
4906 idx = list_num - ARC_BUFC_NUMLISTS;
4907 list = &arc_mru->arcs_lists[idx];
4908 *lock = ARCS_LOCK(arc_mru, idx);
4911 ASSERT(!(MUTEX_HELD(*lock)));
4917 * Evict buffers from the device write hand to the distance specified in
4918 * bytes. This distance may span populated buffers, it may span nothing.
4919 * This is clearing a region on the L2ARC device ready for writing.
4920 * If the 'all' boolean is set, every buffer is evicted.
4923 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4926 l2arc_buf_hdr_t *abl2;
4927 arc_buf_hdr_t *ab, *ab_prev;
4928 kmutex_t *hash_lock;
4930 int64_t bytes_evicted = 0;
4932 buflist = dev->l2ad_buflist;
4934 if (buflist == NULL)
4937 if (!all && dev->l2ad_first) {
4939 * This is the first sweep through the device. There is
4945 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4947 * When nearing the end of the device, evict to the end
4948 * before the device write hand jumps to the start.
4950 taddr = dev->l2ad_end;
4952 taddr = dev->l2ad_hand + distance;
4954 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4955 uint64_t, taddr, boolean_t, all);
4958 mutex_enter(&l2arc_buflist_mtx);
4959 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4960 ab_prev = list_prev(buflist, ab);
4962 hash_lock = HDR_LOCK(ab);
4963 if (!mutex_tryenter(hash_lock)) {
4965 * Missed the hash lock. Retry.
4967 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4968 mutex_exit(&l2arc_buflist_mtx);
4969 mutex_enter(hash_lock);
4970 mutex_exit(hash_lock);
4974 if (HDR_L2_WRITE_HEAD(ab)) {
4976 * We hit a write head node. Leave it for
4977 * l2arc_write_done().
4979 list_remove(buflist, ab);
4980 mutex_exit(hash_lock);
4984 if (!all && ab->b_l2hdr != NULL &&
4985 (ab->b_l2hdr->b_daddr > taddr ||
4986 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4988 * We've evicted to the target address,
4989 * or the end of the device.
4991 mutex_exit(hash_lock);
4995 if (HDR_FREE_IN_PROGRESS(ab)) {
4997 * Already on the path to destruction.
4999 mutex_exit(hash_lock);
5003 if (ab->b_state == arc_l2c_only) {
5004 ASSERT(!HDR_L2_READING(ab));
5006 * This doesn't exist in the ARC. Destroy.
5007 * arc_hdr_destroy() will call list_remove()
5008 * and decrement arcstat_l2_size.
5010 arc_change_state(arc_anon, ab, hash_lock);
5011 arc_hdr_destroy(ab);
5014 * Invalidate issued or about to be issued
5015 * reads, since we may be about to write
5016 * over this location.
5018 if (HDR_L2_READING(ab)) {
5019 ARCSTAT_BUMP(arcstat_l2_evict_reading);
5020 ab->b_flags |= ARC_L2_EVICTED;
5024 * Tell ARC this no longer exists in L2ARC.
5026 if (ab->b_l2hdr != NULL) {
5028 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
5029 bytes_evicted += abl2->b_asize;
5032 * We are destroying l2hdr, so ensure that
5033 * its compressed buffer, if any, is not leaked.
5035 ASSERT(abl2->b_tmp_cdata == NULL);
5036 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
5037 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
5039 list_remove(buflist, ab);
5042 * This may have been leftover after a
5045 ab->b_flags &= ~ARC_L2_WRITING;
5047 mutex_exit(hash_lock);
5049 mutex_exit(&l2arc_buflist_mtx);
5051 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0);
5052 dev->l2ad_evict = taddr;
5056 * Find and write ARC buffers to the L2ARC device.
5058 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
5059 * for reading until they have completed writing.
5060 * The headroom_boost is an in-out parameter used to maintain headroom boost
5061 * state between calls to this function.
5063 * Returns the number of bytes actually written (which may be smaller than
5064 * the delta by which the device hand has changed due to alignment).
5067 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
5068 boolean_t *headroom_boost)
5070 arc_buf_hdr_t *ab, *ab_prev, *head;
5072 uint64_t write_asize, write_psize, write_sz, headroom,
5075 kmutex_t *list_lock;
5077 l2arc_write_callback_t *cb;
5079 uint64_t guid = spa_load_guid(spa);
5080 const boolean_t do_headroom_boost = *headroom_boost;
5083 ASSERT(dev->l2ad_vdev != NULL);
5085 /* Lower the flag now, we might want to raise it again later. */
5086 *headroom_boost = B_FALSE;
5089 write_sz = write_asize = write_psize = 0;
5091 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
5092 head->b_flags |= ARC_L2_WRITE_HEAD;
5094 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
5096 * We will want to try to compress buffers that are at least 2x the
5097 * device sector size.
5099 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
5102 * Copy buffers for L2ARC writing.
5104 mutex_enter(&l2arc_buflist_mtx);
5105 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
5106 uint64_t passed_sz = 0;
5108 list = l2arc_list_locked(try, &list_lock);
5109 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
5112 * L2ARC fast warmup.
5114 * Until the ARC is warm and starts to evict, read from the
5115 * head of the ARC lists rather than the tail.
5117 if (arc_warm == B_FALSE)
5118 ab = list_head(list);
5120 ab = list_tail(list);
5122 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
5124 headroom = target_sz * l2arc_headroom * 2 / ARC_BUFC_NUMLISTS;
5125 if (do_headroom_boost)
5126 headroom = (headroom * l2arc_headroom_boost) / 100;
5128 for (; ab; ab = ab_prev) {
5129 l2arc_buf_hdr_t *l2hdr;
5130 kmutex_t *hash_lock;
5133 if (arc_warm == B_FALSE)
5134 ab_prev = list_next(list, ab);
5136 ab_prev = list_prev(list, ab);
5137 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
5139 hash_lock = HDR_LOCK(ab);
5140 if (!mutex_tryenter(hash_lock)) {
5141 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
5143 * Skip this buffer rather than waiting.
5148 passed_sz += ab->b_size;
5149 if (passed_sz > headroom) {
5153 mutex_exit(hash_lock);
5154 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
5158 if (!l2arc_write_eligible(guid, ab)) {
5159 mutex_exit(hash_lock);
5163 if ((write_sz + ab->b_size) > target_sz) {
5165 mutex_exit(hash_lock);
5166 ARCSTAT_BUMP(arcstat_l2_write_full);
5172 * Insert a dummy header on the buflist so
5173 * l2arc_write_done() can find where the
5174 * write buffers begin without searching.
5176 list_insert_head(dev->l2ad_buflist, head);
5179 sizeof (l2arc_write_callback_t), KM_SLEEP);
5180 cb->l2wcb_dev = dev;
5181 cb->l2wcb_head = head;
5182 pio = zio_root(spa, l2arc_write_done, cb,
5184 ARCSTAT_BUMP(arcstat_l2_write_pios);
5188 * Create and add a new L2ARC header.
5190 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
5192 ab->b_flags |= ARC_L2_WRITING;
5195 * Temporarily stash the data buffer in b_tmp_cdata.
5196 * The subsequent write step will pick it up from
5197 * there. This is because can't access ab->b_buf
5198 * without holding the hash_lock, which we in turn
5199 * can't access without holding the ARC list locks
5200 * (which we want to avoid during compression/writing).
5202 l2hdr->b_compress = ZIO_COMPRESS_OFF;
5203 l2hdr->b_asize = ab->b_size;
5204 l2hdr->b_tmp_cdata = ab->b_buf->b_data;
5206 buf_sz = ab->b_size;
5207 ab->b_l2hdr = l2hdr;
5209 list_insert_head(dev->l2ad_buflist, ab);
5212 * Compute and store the buffer cksum before
5213 * writing. On debug the cksum is verified first.
5215 arc_cksum_verify(ab->b_buf);
5216 arc_cksum_compute(ab->b_buf, B_TRUE);
5218 mutex_exit(hash_lock);
5223 mutex_exit(list_lock);
5229 /* No buffers selected for writing? */
5232 mutex_exit(&l2arc_buflist_mtx);
5233 kmem_cache_free(hdr_cache, head);
5238 * Now start writing the buffers. We're starting at the write head
5239 * and work backwards, retracing the course of the buffer selector
5242 for (ab = list_prev(dev->l2ad_buflist, head); ab;
5243 ab = list_prev(dev->l2ad_buflist, ab)) {
5244 l2arc_buf_hdr_t *l2hdr;
5248 * We shouldn't need to lock the buffer here, since we flagged
5249 * it as ARC_L2_WRITING in the previous step, but we must take
5250 * care to only access its L2 cache parameters. In particular,
5251 * ab->b_buf may be invalid by now due to ARC eviction.
5253 l2hdr = ab->b_l2hdr;
5254 l2hdr->b_daddr = dev->l2ad_hand;
5256 if ((ab->b_flags & ARC_L2COMPRESS) &&
5257 l2hdr->b_asize >= buf_compress_minsz) {
5258 if (l2arc_compress_buf(l2hdr)) {
5260 * If compression succeeded, enable headroom
5261 * boost on the next scan cycle.
5263 *headroom_boost = B_TRUE;
5268 * Pick up the buffer data we had previously stashed away
5269 * (and now potentially also compressed).
5271 buf_data = l2hdr->b_tmp_cdata;
5272 buf_sz = l2hdr->b_asize;
5275 * If the data has not been compressed, then clear b_tmp_cdata
5276 * to make sure that it points only to a temporary compression
5279 if (!L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress))
5280 l2hdr->b_tmp_cdata = NULL;
5282 /* Compression may have squashed the buffer to zero length. */
5286 wzio = zio_write_phys(pio, dev->l2ad_vdev,
5287 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
5288 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
5289 ZIO_FLAG_CANFAIL, B_FALSE);
5291 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
5293 (void) zio_nowait(wzio);
5295 write_asize += buf_sz;
5297 * Keep the clock hand suitably device-aligned.
5299 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
5300 write_psize += buf_p_sz;
5301 dev->l2ad_hand += buf_p_sz;
5305 mutex_exit(&l2arc_buflist_mtx);
5307 ASSERT3U(write_asize, <=, target_sz);
5308 ARCSTAT_BUMP(arcstat_l2_writes_sent);
5309 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
5310 ARCSTAT_INCR(arcstat_l2_size, write_sz);
5311 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
5312 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
5315 * Bump device hand to the device start if it is approaching the end.
5316 * l2arc_evict() will already have evicted ahead for this case.
5318 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
5319 dev->l2ad_hand = dev->l2ad_start;
5320 dev->l2ad_evict = dev->l2ad_start;
5321 dev->l2ad_first = B_FALSE;
5324 dev->l2ad_writing = B_TRUE;
5325 (void) zio_wait(pio);
5326 dev->l2ad_writing = B_FALSE;
5328 return (write_asize);
5332 * Compresses an L2ARC buffer.
5333 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
5334 * size in l2hdr->b_asize. This routine tries to compress the data and
5335 * depending on the compression result there are three possible outcomes:
5336 * *) The buffer was incompressible. The original l2hdr contents were left
5337 * untouched and are ready for writing to an L2 device.
5338 * *) The buffer was all-zeros, so there is no need to write it to an L2
5339 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
5340 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
5341 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
5342 * data buffer which holds the compressed data to be written, and b_asize
5343 * tells us how much data there is. b_compress is set to the appropriate
5344 * compression algorithm. Once writing is done, invoke
5345 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
5347 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
5348 * buffer was incompressible).
5351 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
5354 size_t csize, len, rounded;
5356 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
5357 ASSERT(l2hdr->b_tmp_cdata != NULL);
5359 len = l2hdr->b_asize;
5360 cdata = zio_data_buf_alloc(len);
5361 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
5362 cdata, l2hdr->b_asize);
5365 /* zero block, indicate that there's nothing to write */
5366 zio_data_buf_free(cdata, len);
5367 l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
5369 l2hdr->b_tmp_cdata = NULL;
5370 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
5374 rounded = P2ROUNDUP(csize,
5375 (size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift);
5376 if (rounded < len) {
5378 * Compression succeeded, we'll keep the cdata around for
5379 * writing and release it afterwards.
5381 if (rounded > csize) {
5382 bzero((char *)cdata + csize, rounded - csize);
5385 l2hdr->b_compress = ZIO_COMPRESS_LZ4;
5386 l2hdr->b_asize = csize;
5387 l2hdr->b_tmp_cdata = cdata;
5388 ARCSTAT_BUMP(arcstat_l2_compress_successes);
5392 * Compression failed, release the compressed buffer.
5393 * l2hdr will be left unmodified.
5395 zio_data_buf_free(cdata, len);
5396 ARCSTAT_BUMP(arcstat_l2_compress_failures);
5402 * Decompresses a zio read back from an l2arc device. On success, the
5403 * underlying zio's io_data buffer is overwritten by the uncompressed
5404 * version. On decompression error (corrupt compressed stream), the
5405 * zio->io_error value is set to signal an I/O error.
5407 * Please note that the compressed data stream is not checksummed, so
5408 * if the underlying device is experiencing data corruption, we may feed
5409 * corrupt data to the decompressor, so the decompressor needs to be
5410 * able to handle this situation (LZ4 does).
5413 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
5415 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
5417 if (zio->io_error != 0) {
5419 * An io error has occured, just restore the original io
5420 * size in preparation for a main pool read.
5422 zio->io_orig_size = zio->io_size = hdr->b_size;
5426 if (c == ZIO_COMPRESS_EMPTY) {
5428 * An empty buffer results in a null zio, which means we
5429 * need to fill its io_data after we're done restoring the
5430 * buffer's contents.
5432 ASSERT(hdr->b_buf != NULL);
5433 bzero(hdr->b_buf->b_data, hdr->b_size);
5434 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data;
5436 ASSERT(zio->io_data != NULL);
5438 * We copy the compressed data from the start of the arc buffer
5439 * (the zio_read will have pulled in only what we need, the
5440 * rest is garbage which we will overwrite at decompression)
5441 * and then decompress back to the ARC data buffer. This way we
5442 * can minimize copying by simply decompressing back over the
5443 * original compressed data (rather than decompressing to an
5444 * aux buffer and then copying back the uncompressed buffer,
5445 * which is likely to be much larger).
5450 csize = zio->io_size;
5451 cdata = zio_data_buf_alloc(csize);
5452 bcopy(zio->io_data, cdata, csize);
5453 if (zio_decompress_data(c, cdata, zio->io_data, csize,
5455 zio->io_error = EIO;
5456 zio_data_buf_free(cdata, csize);
5459 /* Restore the expected uncompressed IO size. */
5460 zio->io_orig_size = zio->io_size = hdr->b_size;
5464 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
5465 * This buffer serves as a temporary holder of compressed data while
5466 * the buffer entry is being written to an l2arc device. Once that is
5467 * done, we can dispose of it.
5470 l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
5472 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
5474 ASSERT(L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress));
5475 if (l2hdr->b_compress != ZIO_COMPRESS_EMPTY) {
5477 * If the data was compressed, then we've allocated a
5478 * temporary buffer for it, so now we need to release it.
5480 ASSERT(l2hdr->b_tmp_cdata != NULL);
5481 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
5482 l2hdr->b_tmp_cdata = NULL;
5484 ASSERT(l2hdr->b_tmp_cdata == NULL);
5489 * This thread feeds the L2ARC at regular intervals. This is the beating
5490 * heart of the L2ARC.
5493 l2arc_feed_thread(void *dummy __unused)
5498 uint64_t size, wrote;
5499 clock_t begin, next = ddi_get_lbolt();
5500 boolean_t headroom_boost = B_FALSE;
5502 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
5504 mutex_enter(&l2arc_feed_thr_lock);
5506 while (l2arc_thread_exit == 0) {
5507 CALLB_CPR_SAFE_BEGIN(&cpr);
5508 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
5509 next - ddi_get_lbolt());
5510 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
5511 next = ddi_get_lbolt() + hz;
5514 * Quick check for L2ARC devices.
5516 mutex_enter(&l2arc_dev_mtx);
5517 if (l2arc_ndev == 0) {
5518 mutex_exit(&l2arc_dev_mtx);
5521 mutex_exit(&l2arc_dev_mtx);
5522 begin = ddi_get_lbolt();
5525 * This selects the next l2arc device to write to, and in
5526 * doing so the next spa to feed from: dev->l2ad_spa. This
5527 * will return NULL if there are now no l2arc devices or if
5528 * they are all faulted.
5530 * If a device is returned, its spa's config lock is also
5531 * held to prevent device removal. l2arc_dev_get_next()
5532 * will grab and release l2arc_dev_mtx.
5534 if ((dev = l2arc_dev_get_next()) == NULL)
5537 spa = dev->l2ad_spa;
5538 ASSERT(spa != NULL);
5541 * If the pool is read-only then force the feed thread to
5542 * sleep a little longer.
5544 if (!spa_writeable(spa)) {
5545 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
5546 spa_config_exit(spa, SCL_L2ARC, dev);
5551 * Avoid contributing to memory pressure.
5553 if (arc_reclaim_needed()) {
5554 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
5555 spa_config_exit(spa, SCL_L2ARC, dev);
5559 ARCSTAT_BUMP(arcstat_l2_feeds);
5561 size = l2arc_write_size();
5564 * Evict L2ARC buffers that will be overwritten.
5566 l2arc_evict(dev, size, B_FALSE);
5569 * Write ARC buffers.
5571 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
5574 * Calculate interval between writes.
5576 next = l2arc_write_interval(begin, size, wrote);
5577 spa_config_exit(spa, SCL_L2ARC, dev);
5580 l2arc_thread_exit = 0;
5581 cv_broadcast(&l2arc_feed_thr_cv);
5582 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
5587 l2arc_vdev_present(vdev_t *vd)
5591 mutex_enter(&l2arc_dev_mtx);
5592 for (dev = list_head(l2arc_dev_list); dev != NULL;
5593 dev = list_next(l2arc_dev_list, dev)) {
5594 if (dev->l2ad_vdev == vd)
5597 mutex_exit(&l2arc_dev_mtx);
5599 return (dev != NULL);
5603 * Add a vdev for use by the L2ARC. By this point the spa has already
5604 * validated the vdev and opened it.
5607 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
5609 l2arc_dev_t *adddev;
5611 ASSERT(!l2arc_vdev_present(vd));
5613 vdev_ashift_optimize(vd);
5616 * Create a new l2arc device entry.
5618 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
5619 adddev->l2ad_spa = spa;
5620 adddev->l2ad_vdev = vd;
5621 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
5622 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
5623 adddev->l2ad_hand = adddev->l2ad_start;
5624 adddev->l2ad_evict = adddev->l2ad_start;
5625 adddev->l2ad_first = B_TRUE;
5626 adddev->l2ad_writing = B_FALSE;
5629 * This is a list of all ARC buffers that are still valid on the
5632 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
5633 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
5634 offsetof(arc_buf_hdr_t, b_l2node));
5636 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
5639 * Add device to global list
5641 mutex_enter(&l2arc_dev_mtx);
5642 list_insert_head(l2arc_dev_list, adddev);
5643 atomic_inc_64(&l2arc_ndev);
5644 mutex_exit(&l2arc_dev_mtx);
5648 * Remove a vdev from the L2ARC.
5651 l2arc_remove_vdev(vdev_t *vd)
5653 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
5656 * Find the device by vdev
5658 mutex_enter(&l2arc_dev_mtx);
5659 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
5660 nextdev = list_next(l2arc_dev_list, dev);
5661 if (vd == dev->l2ad_vdev) {
5666 ASSERT(remdev != NULL);
5669 * Remove device from global list
5671 list_remove(l2arc_dev_list, remdev);
5672 l2arc_dev_last = NULL; /* may have been invalidated */
5673 atomic_dec_64(&l2arc_ndev);
5674 mutex_exit(&l2arc_dev_mtx);
5677 * Clear all buflists and ARC references. L2ARC device flush.
5679 l2arc_evict(remdev, 0, B_TRUE);
5680 list_destroy(remdev->l2ad_buflist);
5681 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
5682 kmem_free(remdev, sizeof (l2arc_dev_t));
5688 l2arc_thread_exit = 0;
5690 l2arc_writes_sent = 0;
5691 l2arc_writes_done = 0;
5693 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
5694 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
5695 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
5696 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
5697 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
5699 l2arc_dev_list = &L2ARC_dev_list;
5700 l2arc_free_on_write = &L2ARC_free_on_write;
5701 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
5702 offsetof(l2arc_dev_t, l2ad_node));
5703 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
5704 offsetof(l2arc_data_free_t, l2df_list_node));
5711 * This is called from dmu_fini(), which is called from spa_fini();
5712 * Because of this, we can assume that all l2arc devices have
5713 * already been removed when the pools themselves were removed.
5716 l2arc_do_free_on_write();
5718 mutex_destroy(&l2arc_feed_thr_lock);
5719 cv_destroy(&l2arc_feed_thr_cv);
5720 mutex_destroy(&l2arc_dev_mtx);
5721 mutex_destroy(&l2arc_buflist_mtx);
5722 mutex_destroy(&l2arc_free_on_write_mtx);
5724 list_destroy(l2arc_dev_list);
5725 list_destroy(l2arc_free_on_write);
5731 if (!(spa_mode_global & FWRITE))
5734 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5735 TS_RUN, minclsyspri);
5741 if (!(spa_mode_global & FWRITE))
5744 mutex_enter(&l2arc_feed_thr_lock);
5745 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5746 l2arc_thread_exit = 1;
5747 while (l2arc_thread_exit != 0)
5748 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5749 mutex_exit(&l2arc_feed_thr_lock);