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);
211 arc_free_target_init(void *unused __unused)
214 zfs_arc_free_target = vm_pageout_wakeup_thresh;
216 SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
217 arc_free_target_init, NULL);
219 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
220 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
221 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
222 TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize);
223 TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
224 SYSCTL_DECL(_vfs_zfs);
225 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
227 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
229 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
230 &zfs_arc_average_blocksize, 0,
231 "ARC average blocksize");
232 SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
233 &arc_shrink_shift, 0,
234 "log2(fraction of arc to reclaim)");
237 * We don't have a tunable for arc_free_target due to the dependency on
238 * pagedaemon initialisation.
240 SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
241 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
242 sysctl_vfs_zfs_arc_free_target, "IU",
243 "Desired number of free pages below which ARC triggers reclaim");
246 sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
251 val = zfs_arc_free_target;
252 err = sysctl_handle_int(oidp, &val, 0, req);
253 if (err != 0 || req->newptr == NULL)
258 if (val > cnt.v_page_count)
261 zfs_arc_free_target = val;
268 * Note that buffers can be in one of 6 states:
269 * ARC_anon - anonymous (discussed below)
270 * ARC_mru - recently used, currently cached
271 * ARC_mru_ghost - recentely used, no longer in cache
272 * ARC_mfu - frequently used, currently cached
273 * ARC_mfu_ghost - frequently used, no longer in cache
274 * ARC_l2c_only - exists in L2ARC but not other states
275 * When there are no active references to the buffer, they are
276 * are linked onto a list in one of these arc states. These are
277 * the only buffers that can be evicted or deleted. Within each
278 * state there are multiple lists, one for meta-data and one for
279 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
280 * etc.) is tracked separately so that it can be managed more
281 * explicitly: favored over data, limited explicitly.
283 * Anonymous buffers are buffers that are not associated with
284 * a DVA. These are buffers that hold dirty block copies
285 * before they are written to stable storage. By definition,
286 * they are "ref'd" and are considered part of arc_mru
287 * that cannot be freed. Generally, they will aquire a DVA
288 * as they are written and migrate onto the arc_mru list.
290 * The ARC_l2c_only state is for buffers that are in the second
291 * level ARC but no longer in any of the ARC_m* lists. The second
292 * level ARC itself may also contain buffers that are in any of
293 * the ARC_m* states - meaning that a buffer can exist in two
294 * places. The reason for the ARC_l2c_only state is to keep the
295 * buffer header in the hash table, so that reads that hit the
296 * second level ARC benefit from these fast lookups.
299 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
303 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
308 * must be power of two for mask use to work
311 #define ARC_BUFC_NUMDATALISTS 16
312 #define ARC_BUFC_NUMMETADATALISTS 16
313 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
315 typedef struct arc_state {
316 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
317 uint64_t arcs_size; /* total amount of data in this state */
318 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
319 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
322 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
325 static arc_state_t ARC_anon;
326 static arc_state_t ARC_mru;
327 static arc_state_t ARC_mru_ghost;
328 static arc_state_t ARC_mfu;
329 static arc_state_t ARC_mfu_ghost;
330 static arc_state_t ARC_l2c_only;
332 typedef struct arc_stats {
333 kstat_named_t arcstat_hits;
334 kstat_named_t arcstat_misses;
335 kstat_named_t arcstat_demand_data_hits;
336 kstat_named_t arcstat_demand_data_misses;
337 kstat_named_t arcstat_demand_metadata_hits;
338 kstat_named_t arcstat_demand_metadata_misses;
339 kstat_named_t arcstat_prefetch_data_hits;
340 kstat_named_t arcstat_prefetch_data_misses;
341 kstat_named_t arcstat_prefetch_metadata_hits;
342 kstat_named_t arcstat_prefetch_metadata_misses;
343 kstat_named_t arcstat_mru_hits;
344 kstat_named_t arcstat_mru_ghost_hits;
345 kstat_named_t arcstat_mfu_hits;
346 kstat_named_t arcstat_mfu_ghost_hits;
347 kstat_named_t arcstat_allocated;
348 kstat_named_t arcstat_deleted;
349 kstat_named_t arcstat_stolen;
350 kstat_named_t arcstat_recycle_miss;
352 * Number of buffers that could not be evicted because the hash lock
353 * was held by another thread. The lock may not necessarily be held
354 * by something using the same buffer, since hash locks are shared
355 * by multiple buffers.
357 kstat_named_t arcstat_mutex_miss;
359 * Number of buffers skipped because they have I/O in progress, are
360 * indrect prefetch buffers that have not lived long enough, or are
361 * not from the spa we're trying to evict from.
363 kstat_named_t arcstat_evict_skip;
364 kstat_named_t arcstat_evict_l2_cached;
365 kstat_named_t arcstat_evict_l2_eligible;
366 kstat_named_t arcstat_evict_l2_ineligible;
367 kstat_named_t arcstat_hash_elements;
368 kstat_named_t arcstat_hash_elements_max;
369 kstat_named_t arcstat_hash_collisions;
370 kstat_named_t arcstat_hash_chains;
371 kstat_named_t arcstat_hash_chain_max;
372 kstat_named_t arcstat_p;
373 kstat_named_t arcstat_c;
374 kstat_named_t arcstat_c_min;
375 kstat_named_t arcstat_c_max;
376 kstat_named_t arcstat_size;
377 kstat_named_t arcstat_hdr_size;
378 kstat_named_t arcstat_data_size;
379 kstat_named_t arcstat_other_size;
380 kstat_named_t arcstat_l2_hits;
381 kstat_named_t arcstat_l2_misses;
382 kstat_named_t arcstat_l2_feeds;
383 kstat_named_t arcstat_l2_rw_clash;
384 kstat_named_t arcstat_l2_read_bytes;
385 kstat_named_t arcstat_l2_write_bytes;
386 kstat_named_t arcstat_l2_writes_sent;
387 kstat_named_t arcstat_l2_writes_done;
388 kstat_named_t arcstat_l2_writes_error;
389 kstat_named_t arcstat_l2_writes_hdr_miss;
390 kstat_named_t arcstat_l2_evict_lock_retry;
391 kstat_named_t arcstat_l2_evict_reading;
392 kstat_named_t arcstat_l2_free_on_write;
393 kstat_named_t arcstat_l2_abort_lowmem;
394 kstat_named_t arcstat_l2_cksum_bad;
395 kstat_named_t arcstat_l2_io_error;
396 kstat_named_t arcstat_l2_size;
397 kstat_named_t arcstat_l2_asize;
398 kstat_named_t arcstat_l2_hdr_size;
399 kstat_named_t arcstat_l2_compress_successes;
400 kstat_named_t arcstat_l2_compress_zeros;
401 kstat_named_t arcstat_l2_compress_failures;
402 kstat_named_t arcstat_l2_write_trylock_fail;
403 kstat_named_t arcstat_l2_write_passed_headroom;
404 kstat_named_t arcstat_l2_write_spa_mismatch;
405 kstat_named_t arcstat_l2_write_in_l2;
406 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
407 kstat_named_t arcstat_l2_write_not_cacheable;
408 kstat_named_t arcstat_l2_write_full;
409 kstat_named_t arcstat_l2_write_buffer_iter;
410 kstat_named_t arcstat_l2_write_pios;
411 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
412 kstat_named_t arcstat_l2_write_buffer_list_iter;
413 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
414 kstat_named_t arcstat_memory_throttle_count;
415 kstat_named_t arcstat_duplicate_buffers;
416 kstat_named_t arcstat_duplicate_buffers_size;
417 kstat_named_t arcstat_duplicate_reads;
420 static arc_stats_t arc_stats = {
421 { "hits", KSTAT_DATA_UINT64 },
422 { "misses", KSTAT_DATA_UINT64 },
423 { "demand_data_hits", KSTAT_DATA_UINT64 },
424 { "demand_data_misses", KSTAT_DATA_UINT64 },
425 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
426 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
427 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
428 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
429 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
430 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
431 { "mru_hits", KSTAT_DATA_UINT64 },
432 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
433 { "mfu_hits", KSTAT_DATA_UINT64 },
434 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
435 { "allocated", KSTAT_DATA_UINT64 },
436 { "deleted", KSTAT_DATA_UINT64 },
437 { "stolen", KSTAT_DATA_UINT64 },
438 { "recycle_miss", KSTAT_DATA_UINT64 },
439 { "mutex_miss", KSTAT_DATA_UINT64 },
440 { "evict_skip", KSTAT_DATA_UINT64 },
441 { "evict_l2_cached", KSTAT_DATA_UINT64 },
442 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
443 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
444 { "hash_elements", KSTAT_DATA_UINT64 },
445 { "hash_elements_max", KSTAT_DATA_UINT64 },
446 { "hash_collisions", KSTAT_DATA_UINT64 },
447 { "hash_chains", KSTAT_DATA_UINT64 },
448 { "hash_chain_max", KSTAT_DATA_UINT64 },
449 { "p", KSTAT_DATA_UINT64 },
450 { "c", KSTAT_DATA_UINT64 },
451 { "c_min", KSTAT_DATA_UINT64 },
452 { "c_max", KSTAT_DATA_UINT64 },
453 { "size", KSTAT_DATA_UINT64 },
454 { "hdr_size", KSTAT_DATA_UINT64 },
455 { "data_size", KSTAT_DATA_UINT64 },
456 { "other_size", KSTAT_DATA_UINT64 },
457 { "l2_hits", KSTAT_DATA_UINT64 },
458 { "l2_misses", KSTAT_DATA_UINT64 },
459 { "l2_feeds", KSTAT_DATA_UINT64 },
460 { "l2_rw_clash", KSTAT_DATA_UINT64 },
461 { "l2_read_bytes", KSTAT_DATA_UINT64 },
462 { "l2_write_bytes", KSTAT_DATA_UINT64 },
463 { "l2_writes_sent", KSTAT_DATA_UINT64 },
464 { "l2_writes_done", KSTAT_DATA_UINT64 },
465 { "l2_writes_error", KSTAT_DATA_UINT64 },
466 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
467 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
468 { "l2_evict_reading", KSTAT_DATA_UINT64 },
469 { "l2_free_on_write", KSTAT_DATA_UINT64 },
470 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
471 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
472 { "l2_io_error", KSTAT_DATA_UINT64 },
473 { "l2_size", KSTAT_DATA_UINT64 },
474 { "l2_asize", KSTAT_DATA_UINT64 },
475 { "l2_hdr_size", KSTAT_DATA_UINT64 },
476 { "l2_compress_successes", KSTAT_DATA_UINT64 },
477 { "l2_compress_zeros", KSTAT_DATA_UINT64 },
478 { "l2_compress_failures", KSTAT_DATA_UINT64 },
479 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
480 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
481 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
482 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
483 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
484 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
485 { "l2_write_full", KSTAT_DATA_UINT64 },
486 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
487 { "l2_write_pios", KSTAT_DATA_UINT64 },
488 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
489 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
490 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
491 { "memory_throttle_count", KSTAT_DATA_UINT64 },
492 { "duplicate_buffers", KSTAT_DATA_UINT64 },
493 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
494 { "duplicate_reads", KSTAT_DATA_UINT64 }
497 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
499 #define ARCSTAT_INCR(stat, val) \
500 atomic_add_64(&arc_stats.stat.value.ui64, (val))
502 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
503 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
505 #define ARCSTAT_MAX(stat, val) { \
507 while ((val) > (m = arc_stats.stat.value.ui64) && \
508 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
512 #define ARCSTAT_MAXSTAT(stat) \
513 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
516 * We define a macro to allow ARC hits/misses to be easily broken down by
517 * two separate conditions, giving a total of four different subtypes for
518 * each of hits and misses (so eight statistics total).
520 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
523 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
525 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
529 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
531 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
536 static arc_state_t *arc_anon;
537 static arc_state_t *arc_mru;
538 static arc_state_t *arc_mru_ghost;
539 static arc_state_t *arc_mfu;
540 static arc_state_t *arc_mfu_ghost;
541 static arc_state_t *arc_l2c_only;
544 * There are several ARC variables that are critical to export as kstats --
545 * but we don't want to have to grovel around in the kstat whenever we wish to
546 * manipulate them. For these variables, we therefore define them to be in
547 * terms of the statistic variable. This assures that we are not introducing
548 * the possibility of inconsistency by having shadow copies of the variables,
549 * while still allowing the code to be readable.
551 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
552 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
553 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
554 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
555 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
557 #define L2ARC_IS_VALID_COMPRESS(_c_) \
558 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
560 static int arc_no_grow; /* Don't try to grow cache size */
561 static uint64_t arc_tempreserve;
562 static uint64_t arc_loaned_bytes;
563 static uint64_t arc_meta_used;
564 static uint64_t arc_meta_limit;
565 static uint64_t arc_meta_max = 0;
566 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RD, &arc_meta_used, 0,
567 "ARC metadata used");
568 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RW, &arc_meta_limit, 0,
569 "ARC metadata limit");
571 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
573 typedef struct arc_callback arc_callback_t;
575 struct arc_callback {
577 arc_done_func_t *acb_done;
579 zio_t *acb_zio_dummy;
580 arc_callback_t *acb_next;
583 typedef struct arc_write_callback arc_write_callback_t;
585 struct arc_write_callback {
587 arc_done_func_t *awcb_ready;
588 arc_done_func_t *awcb_physdone;
589 arc_done_func_t *awcb_done;
594 /* protected by hash lock */
599 kmutex_t b_freeze_lock;
600 zio_cksum_t *b_freeze_cksum;
603 arc_buf_hdr_t *b_hash_next;
608 arc_callback_t *b_acb;
612 arc_buf_contents_t b_type;
616 /* protected by arc state mutex */
617 arc_state_t *b_state;
618 list_node_t b_arc_node;
620 /* updated atomically */
621 clock_t b_arc_access;
623 /* self protecting */
626 l2arc_buf_hdr_t *b_l2hdr;
627 list_node_t b_l2node;
630 static arc_buf_t *arc_eviction_list;
631 static kmutex_t arc_eviction_mtx;
632 static arc_buf_hdr_t arc_eviction_hdr;
633 static void arc_get_data_buf(arc_buf_t *buf);
634 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
635 static int arc_evict_needed(arc_buf_contents_t type);
636 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
638 static void arc_buf_watch(arc_buf_t *buf);
641 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
643 #define GHOST_STATE(state) \
644 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
645 (state) == arc_l2c_only)
648 * Private ARC flags. These flags are private ARC only flags that will show up
649 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
650 * be passed in as arc_flags in things like arc_read. However, these flags
651 * should never be passed and should only be set by ARC code. When adding new
652 * public flags, make sure not to smash the private ones.
655 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
656 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
657 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
658 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
659 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
660 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
661 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
662 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
663 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
664 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
666 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
667 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
668 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
669 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
670 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
671 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
672 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
673 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
674 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
675 (hdr)->b_l2hdr != NULL)
676 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
677 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
678 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
684 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
685 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
688 * Hash table routines
691 #define HT_LOCK_PAD CACHE_LINE_SIZE
696 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
700 #define BUF_LOCKS 256
701 typedef struct buf_hash_table {
703 arc_buf_hdr_t **ht_table;
704 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
707 static buf_hash_table_t buf_hash_table;
709 #define BUF_HASH_INDEX(spa, dva, birth) \
710 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
711 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
712 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
713 #define HDR_LOCK(hdr) \
714 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
716 uint64_t zfs_crc64_table[256];
722 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
723 #define L2ARC_HEADROOM 2 /* num of writes */
725 * If we discover during ARC scan any buffers to be compressed, we boost
726 * our headroom for the next scanning cycle by this percentage multiple.
728 #define L2ARC_HEADROOM_BOOST 200
729 #define L2ARC_FEED_SECS 1 /* caching interval secs */
730 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
732 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
733 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
735 /* L2ARC Performance Tunables */
736 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
737 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
738 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
739 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
740 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
741 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
742 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
743 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
744 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
746 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
747 &l2arc_write_max, 0, "max write size");
748 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
749 &l2arc_write_boost, 0, "extra write during warmup");
750 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
751 &l2arc_headroom, 0, "number of dev writes");
752 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
753 &l2arc_feed_secs, 0, "interval seconds");
754 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
755 &l2arc_feed_min_ms, 0, "min interval milliseconds");
757 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
758 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
759 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
760 &l2arc_feed_again, 0, "turbo warmup");
761 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
762 &l2arc_norw, 0, "no reads during writes");
764 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
765 &ARC_anon.arcs_size, 0, "size of anonymous state");
766 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
767 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
768 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
769 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
771 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
772 &ARC_mru.arcs_size, 0, "size of mru state");
773 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
774 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
775 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
776 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
778 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
779 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
780 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
781 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
782 "size of metadata in mru ghost state");
783 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
784 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
785 "size of data in mru ghost state");
787 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
788 &ARC_mfu.arcs_size, 0, "size of mfu state");
789 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
790 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
791 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
792 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
794 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
795 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
796 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
797 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
798 "size of metadata in mfu ghost state");
799 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
800 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
801 "size of data in mfu ghost state");
803 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
804 &ARC_l2c_only.arcs_size, 0, "size of mru state");
809 typedef struct l2arc_dev {
810 vdev_t *l2ad_vdev; /* vdev */
811 spa_t *l2ad_spa; /* spa */
812 uint64_t l2ad_hand; /* next write location */
813 uint64_t l2ad_start; /* first addr on device */
814 uint64_t l2ad_end; /* last addr on device */
815 uint64_t l2ad_evict; /* last addr eviction reached */
816 boolean_t l2ad_first; /* first sweep through */
817 boolean_t l2ad_writing; /* currently writing */
818 list_t *l2ad_buflist; /* buffer list */
819 list_node_t l2ad_node; /* device list node */
822 static list_t L2ARC_dev_list; /* device list */
823 static list_t *l2arc_dev_list; /* device list pointer */
824 static kmutex_t l2arc_dev_mtx; /* device list mutex */
825 static l2arc_dev_t *l2arc_dev_last; /* last device used */
826 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
827 static list_t L2ARC_free_on_write; /* free after write buf list */
828 static list_t *l2arc_free_on_write; /* free after write list ptr */
829 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
830 static uint64_t l2arc_ndev; /* number of devices */
832 typedef struct l2arc_read_callback {
833 arc_buf_t *l2rcb_buf; /* read buffer */
834 spa_t *l2rcb_spa; /* spa */
835 blkptr_t l2rcb_bp; /* original blkptr */
836 zbookmark_phys_t l2rcb_zb; /* original bookmark */
837 int l2rcb_flags; /* original flags */
838 enum zio_compress l2rcb_compress; /* applied compress */
839 } l2arc_read_callback_t;
841 typedef struct l2arc_write_callback {
842 l2arc_dev_t *l2wcb_dev; /* device info */
843 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
844 } l2arc_write_callback_t;
846 struct l2arc_buf_hdr {
847 /* protected by arc_buf_hdr mutex */
848 l2arc_dev_t *b_dev; /* L2ARC device */
849 uint64_t b_daddr; /* disk address, offset byte */
850 /* compression applied to buffer data */
851 enum zio_compress b_compress;
852 /* real alloc'd buffer size depending on b_compress applied */
854 /* temporary buffer holder for in-flight compressed data */
858 typedef struct l2arc_data_free {
859 /* protected by l2arc_free_on_write_mtx */
862 void (*l2df_func)(void *, size_t);
863 list_node_t l2df_list_node;
866 static kmutex_t l2arc_feed_thr_lock;
867 static kcondvar_t l2arc_feed_thr_cv;
868 static uint8_t l2arc_thread_exit;
870 static void l2arc_read_done(zio_t *zio);
871 static void l2arc_hdr_stat_add(void);
872 static void l2arc_hdr_stat_remove(void);
874 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
875 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
876 enum zio_compress c);
877 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
880 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
882 uint8_t *vdva = (uint8_t *)dva;
883 uint64_t crc = -1ULL;
886 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
888 for (i = 0; i < sizeof (dva_t); i++)
889 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
891 crc ^= (spa>>8) ^ birth;
896 #define BUF_EMPTY(buf) \
897 ((buf)->b_dva.dva_word[0] == 0 && \
898 (buf)->b_dva.dva_word[1] == 0 && \
899 (buf)->b_cksum0 == 0)
901 #define BUF_EQUAL(spa, dva, birth, buf) \
902 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
903 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
904 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
907 buf_discard_identity(arc_buf_hdr_t *hdr)
909 hdr->b_dva.dva_word[0] = 0;
910 hdr->b_dva.dva_word[1] = 0;
915 static arc_buf_hdr_t *
916 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
918 const dva_t *dva = BP_IDENTITY(bp);
919 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
920 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
921 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
924 mutex_enter(hash_lock);
925 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
926 buf = buf->b_hash_next) {
927 if (BUF_EQUAL(spa, dva, birth, buf)) {
932 mutex_exit(hash_lock);
938 * Insert an entry into the hash table. If there is already an element
939 * equal to elem in the hash table, then the already existing element
940 * will be returned and the new element will not be inserted.
941 * Otherwise returns NULL.
943 static arc_buf_hdr_t *
944 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
946 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
947 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
951 ASSERT(!DVA_IS_EMPTY(&buf->b_dva));
952 ASSERT(buf->b_birth != 0);
953 ASSERT(!HDR_IN_HASH_TABLE(buf));
955 mutex_enter(hash_lock);
956 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
957 fbuf = fbuf->b_hash_next, i++) {
958 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
962 buf->b_hash_next = buf_hash_table.ht_table[idx];
963 buf_hash_table.ht_table[idx] = buf;
964 buf->b_flags |= ARC_IN_HASH_TABLE;
966 /* collect some hash table performance data */
968 ARCSTAT_BUMP(arcstat_hash_collisions);
970 ARCSTAT_BUMP(arcstat_hash_chains);
972 ARCSTAT_MAX(arcstat_hash_chain_max, i);
975 ARCSTAT_BUMP(arcstat_hash_elements);
976 ARCSTAT_MAXSTAT(arcstat_hash_elements);
982 buf_hash_remove(arc_buf_hdr_t *buf)
984 arc_buf_hdr_t *fbuf, **bufp;
985 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
987 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
988 ASSERT(HDR_IN_HASH_TABLE(buf));
990 bufp = &buf_hash_table.ht_table[idx];
991 while ((fbuf = *bufp) != buf) {
992 ASSERT(fbuf != NULL);
993 bufp = &fbuf->b_hash_next;
995 *bufp = buf->b_hash_next;
996 buf->b_hash_next = NULL;
997 buf->b_flags &= ~ARC_IN_HASH_TABLE;
999 /* collect some hash table performance data */
1000 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1002 if (buf_hash_table.ht_table[idx] &&
1003 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1004 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1008 * Global data structures and functions for the buf kmem cache.
1010 static kmem_cache_t *hdr_cache;
1011 static kmem_cache_t *buf_cache;
1018 kmem_free(buf_hash_table.ht_table,
1019 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1020 for (i = 0; i < BUF_LOCKS; i++)
1021 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1022 kmem_cache_destroy(hdr_cache);
1023 kmem_cache_destroy(buf_cache);
1027 * Constructor callback - called when the cache is empty
1028 * and a new buf is requested.
1032 hdr_cons(void *vbuf, void *unused, int kmflag)
1034 arc_buf_hdr_t *buf = vbuf;
1036 bzero(buf, sizeof (arc_buf_hdr_t));
1037 refcount_create(&buf->b_refcnt);
1038 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
1039 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1040 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1047 buf_cons(void *vbuf, void *unused, int kmflag)
1049 arc_buf_t *buf = vbuf;
1051 bzero(buf, sizeof (arc_buf_t));
1052 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1053 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1059 * Destructor callback - called when a cached buf is
1060 * no longer required.
1064 hdr_dest(void *vbuf, void *unused)
1066 arc_buf_hdr_t *buf = vbuf;
1068 ASSERT(BUF_EMPTY(buf));
1069 refcount_destroy(&buf->b_refcnt);
1070 cv_destroy(&buf->b_cv);
1071 mutex_destroy(&buf->b_freeze_lock);
1072 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1077 buf_dest(void *vbuf, void *unused)
1079 arc_buf_t *buf = vbuf;
1081 mutex_destroy(&buf->b_evict_lock);
1082 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1086 * Reclaim callback -- invoked when memory is low.
1090 hdr_recl(void *unused)
1092 dprintf("hdr_recl called\n");
1094 * umem calls the reclaim func when we destroy the buf cache,
1095 * which is after we do arc_fini().
1098 cv_signal(&arc_reclaim_thr_cv);
1105 uint64_t hsize = 1ULL << 12;
1109 * The hash table is big enough to fill all of physical memory
1110 * with an average block size of zfs_arc_average_blocksize (default 8K).
1111 * By default, the table will take up
1112 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1114 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1117 buf_hash_table.ht_mask = hsize - 1;
1118 buf_hash_table.ht_table =
1119 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1120 if (buf_hash_table.ht_table == NULL) {
1121 ASSERT(hsize > (1ULL << 8));
1126 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
1127 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
1128 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1129 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1131 for (i = 0; i < 256; i++)
1132 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1133 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1135 for (i = 0; i < BUF_LOCKS; i++) {
1136 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1137 NULL, MUTEX_DEFAULT, NULL);
1141 #define ARC_MINTIME (hz>>4) /* 62 ms */
1144 arc_cksum_verify(arc_buf_t *buf)
1148 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1151 mutex_enter(&buf->b_hdr->b_freeze_lock);
1152 if (buf->b_hdr->b_freeze_cksum == NULL ||
1153 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1154 mutex_exit(&buf->b_hdr->b_freeze_lock);
1157 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1158 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1159 panic("buffer modified while frozen!");
1160 mutex_exit(&buf->b_hdr->b_freeze_lock);
1164 arc_cksum_equal(arc_buf_t *buf)
1169 mutex_enter(&buf->b_hdr->b_freeze_lock);
1170 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1171 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1172 mutex_exit(&buf->b_hdr->b_freeze_lock);
1178 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1180 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1183 mutex_enter(&buf->b_hdr->b_freeze_lock);
1184 if (buf->b_hdr->b_freeze_cksum != NULL) {
1185 mutex_exit(&buf->b_hdr->b_freeze_lock);
1188 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1189 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1190 buf->b_hdr->b_freeze_cksum);
1191 mutex_exit(&buf->b_hdr->b_freeze_lock);
1194 #endif /* illumos */
1199 typedef struct procctl {
1207 arc_buf_unwatch(arc_buf_t *buf)
1214 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1215 ctl.prwatch.pr_size = 0;
1216 ctl.prwatch.pr_wflags = 0;
1217 result = write(arc_procfd, &ctl, sizeof (ctl));
1218 ASSERT3U(result, ==, sizeof (ctl));
1225 arc_buf_watch(arc_buf_t *buf)
1232 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1233 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1234 ctl.prwatch.pr_wflags = WA_WRITE;
1235 result = write(arc_procfd, &ctl, sizeof (ctl));
1236 ASSERT3U(result, ==, sizeof (ctl));
1240 #endif /* illumos */
1243 arc_buf_thaw(arc_buf_t *buf)
1245 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1246 if (buf->b_hdr->b_state != arc_anon)
1247 panic("modifying non-anon buffer!");
1248 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1249 panic("modifying buffer while i/o in progress!");
1250 arc_cksum_verify(buf);
1253 mutex_enter(&buf->b_hdr->b_freeze_lock);
1254 if (buf->b_hdr->b_freeze_cksum != NULL) {
1255 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1256 buf->b_hdr->b_freeze_cksum = NULL;
1259 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1260 if (buf->b_hdr->b_thawed)
1261 kmem_free(buf->b_hdr->b_thawed, 1);
1262 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1265 mutex_exit(&buf->b_hdr->b_freeze_lock);
1268 arc_buf_unwatch(buf);
1269 #endif /* illumos */
1273 arc_buf_freeze(arc_buf_t *buf)
1275 kmutex_t *hash_lock;
1277 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1280 hash_lock = HDR_LOCK(buf->b_hdr);
1281 mutex_enter(hash_lock);
1283 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1284 buf->b_hdr->b_state == arc_anon);
1285 arc_cksum_compute(buf, B_FALSE);
1286 mutex_exit(hash_lock);
1291 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1293 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1295 if (ab->b_type == ARC_BUFC_METADATA)
1296 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1298 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1299 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1302 *list = &state->arcs_lists[buf_hashid];
1303 *lock = ARCS_LOCK(state, buf_hashid);
1308 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1310 ASSERT(MUTEX_HELD(hash_lock));
1312 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1313 (ab->b_state != arc_anon)) {
1314 uint64_t delta = ab->b_size * ab->b_datacnt;
1315 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1319 get_buf_info(ab, ab->b_state, &list, &lock);
1320 ASSERT(!MUTEX_HELD(lock));
1322 ASSERT(list_link_active(&ab->b_arc_node));
1323 list_remove(list, ab);
1324 if (GHOST_STATE(ab->b_state)) {
1325 ASSERT0(ab->b_datacnt);
1326 ASSERT3P(ab->b_buf, ==, NULL);
1330 ASSERT3U(*size, >=, delta);
1331 atomic_add_64(size, -delta);
1333 /* remove the prefetch flag if we get a reference */
1334 if (ab->b_flags & ARC_PREFETCH)
1335 ab->b_flags &= ~ARC_PREFETCH;
1340 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1343 arc_state_t *state = ab->b_state;
1345 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1346 ASSERT(!GHOST_STATE(state));
1348 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1349 (state != arc_anon)) {
1350 uint64_t *size = &state->arcs_lsize[ab->b_type];
1354 get_buf_info(ab, state, &list, &lock);
1355 ASSERT(!MUTEX_HELD(lock));
1357 ASSERT(!list_link_active(&ab->b_arc_node));
1358 list_insert_head(list, ab);
1359 ASSERT(ab->b_datacnt > 0);
1360 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1367 * Move the supplied buffer to the indicated state. The mutex
1368 * for the buffer must be held by the caller.
1371 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1373 arc_state_t *old_state = ab->b_state;
1374 int64_t refcnt = refcount_count(&ab->b_refcnt);
1375 uint64_t from_delta, to_delta;
1379 ASSERT(MUTEX_HELD(hash_lock));
1380 ASSERT3P(new_state, !=, old_state);
1381 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1382 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1383 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1385 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1388 * If this buffer is evictable, transfer it from the
1389 * old state list to the new state list.
1392 if (old_state != arc_anon) {
1394 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1396 get_buf_info(ab, old_state, &list, &lock);
1397 use_mutex = !MUTEX_HELD(lock);
1401 ASSERT(list_link_active(&ab->b_arc_node));
1402 list_remove(list, ab);
1405 * If prefetching out of the ghost cache,
1406 * we will have a non-zero datacnt.
1408 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1409 /* ghost elements have a ghost size */
1410 ASSERT(ab->b_buf == NULL);
1411 from_delta = ab->b_size;
1413 ASSERT3U(*size, >=, from_delta);
1414 atomic_add_64(size, -from_delta);
1419 if (new_state != arc_anon) {
1421 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1423 get_buf_info(ab, new_state, &list, &lock);
1424 use_mutex = !MUTEX_HELD(lock);
1428 list_insert_head(list, ab);
1430 /* ghost elements have a ghost size */
1431 if (GHOST_STATE(new_state)) {
1432 ASSERT(ab->b_datacnt == 0);
1433 ASSERT(ab->b_buf == NULL);
1434 to_delta = ab->b_size;
1436 atomic_add_64(size, to_delta);
1443 ASSERT(!BUF_EMPTY(ab));
1444 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1445 buf_hash_remove(ab);
1447 /* adjust state sizes */
1449 atomic_add_64(&new_state->arcs_size, to_delta);
1451 ASSERT3U(old_state->arcs_size, >=, from_delta);
1452 atomic_add_64(&old_state->arcs_size, -from_delta);
1454 ab->b_state = new_state;
1456 /* adjust l2arc hdr stats */
1457 if (new_state == arc_l2c_only)
1458 l2arc_hdr_stat_add();
1459 else if (old_state == arc_l2c_only)
1460 l2arc_hdr_stat_remove();
1464 arc_space_consume(uint64_t space, arc_space_type_t type)
1466 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1469 case ARC_SPACE_DATA:
1470 ARCSTAT_INCR(arcstat_data_size, space);
1472 case ARC_SPACE_OTHER:
1473 ARCSTAT_INCR(arcstat_other_size, space);
1475 case ARC_SPACE_HDRS:
1476 ARCSTAT_INCR(arcstat_hdr_size, space);
1478 case ARC_SPACE_L2HDRS:
1479 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1483 atomic_add_64(&arc_meta_used, space);
1484 atomic_add_64(&arc_size, space);
1488 arc_space_return(uint64_t space, arc_space_type_t type)
1490 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1493 case ARC_SPACE_DATA:
1494 ARCSTAT_INCR(arcstat_data_size, -space);
1496 case ARC_SPACE_OTHER:
1497 ARCSTAT_INCR(arcstat_other_size, -space);
1499 case ARC_SPACE_HDRS:
1500 ARCSTAT_INCR(arcstat_hdr_size, -space);
1502 case ARC_SPACE_L2HDRS:
1503 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1507 ASSERT(arc_meta_used >= space);
1508 if (arc_meta_max < arc_meta_used)
1509 arc_meta_max = arc_meta_used;
1510 atomic_add_64(&arc_meta_used, -space);
1511 ASSERT(arc_size >= space);
1512 atomic_add_64(&arc_size, -space);
1516 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1521 ASSERT3U(size, >, 0);
1522 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1523 ASSERT(BUF_EMPTY(hdr));
1526 hdr->b_spa = spa_load_guid(spa);
1527 hdr->b_state = arc_anon;
1528 hdr->b_arc_access = 0;
1529 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1532 buf->b_efunc = NULL;
1533 buf->b_private = NULL;
1536 arc_get_data_buf(buf);
1539 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1540 (void) refcount_add(&hdr->b_refcnt, tag);
1545 static char *arc_onloan_tag = "onloan";
1548 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1549 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1550 * buffers must be returned to the arc before they can be used by the DMU or
1554 arc_loan_buf(spa_t *spa, int size)
1558 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1560 atomic_add_64(&arc_loaned_bytes, size);
1565 * Return a loaned arc buffer to the arc.
1568 arc_return_buf(arc_buf_t *buf, void *tag)
1570 arc_buf_hdr_t *hdr = buf->b_hdr;
1572 ASSERT(buf->b_data != NULL);
1573 (void) refcount_add(&hdr->b_refcnt, tag);
1574 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1576 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1579 /* Detach an arc_buf from a dbuf (tag) */
1581 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1585 ASSERT(buf->b_data != NULL);
1587 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1588 (void) refcount_remove(&hdr->b_refcnt, tag);
1589 buf->b_efunc = NULL;
1590 buf->b_private = NULL;
1592 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1596 arc_buf_clone(arc_buf_t *from)
1599 arc_buf_hdr_t *hdr = from->b_hdr;
1600 uint64_t size = hdr->b_size;
1602 ASSERT(hdr->b_state != arc_anon);
1604 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1607 buf->b_efunc = NULL;
1608 buf->b_private = NULL;
1609 buf->b_next = hdr->b_buf;
1611 arc_get_data_buf(buf);
1612 bcopy(from->b_data, buf->b_data, size);
1615 * This buffer already exists in the arc so create a duplicate
1616 * copy for the caller. If the buffer is associated with user data
1617 * then track the size and number of duplicates. These stats will be
1618 * updated as duplicate buffers are created and destroyed.
1620 if (hdr->b_type == ARC_BUFC_DATA) {
1621 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1622 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1624 hdr->b_datacnt += 1;
1629 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1632 kmutex_t *hash_lock;
1635 * Check to see if this buffer is evicted. Callers
1636 * must verify b_data != NULL to know if the add_ref
1639 mutex_enter(&buf->b_evict_lock);
1640 if (buf->b_data == NULL) {
1641 mutex_exit(&buf->b_evict_lock);
1644 hash_lock = HDR_LOCK(buf->b_hdr);
1645 mutex_enter(hash_lock);
1647 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1648 mutex_exit(&buf->b_evict_lock);
1650 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1651 add_reference(hdr, hash_lock, tag);
1652 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1653 arc_access(hdr, hash_lock);
1654 mutex_exit(hash_lock);
1655 ARCSTAT_BUMP(arcstat_hits);
1656 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1657 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1658 data, metadata, hits);
1662 * Free the arc data buffer. If it is an l2arc write in progress,
1663 * the buffer is placed on l2arc_free_on_write to be freed later.
1666 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1668 arc_buf_hdr_t *hdr = buf->b_hdr;
1670 if (HDR_L2_WRITING(hdr)) {
1671 l2arc_data_free_t *df;
1672 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1673 df->l2df_data = buf->b_data;
1674 df->l2df_size = hdr->b_size;
1675 df->l2df_func = free_func;
1676 mutex_enter(&l2arc_free_on_write_mtx);
1677 list_insert_head(l2arc_free_on_write, df);
1678 mutex_exit(&l2arc_free_on_write_mtx);
1679 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1681 free_func(buf->b_data, hdr->b_size);
1686 * Free up buf->b_data and if 'remove' is set, then pull the
1687 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
1690 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
1694 /* free up data associated with the buf */
1696 arc_state_t *state = buf->b_hdr->b_state;
1697 uint64_t size = buf->b_hdr->b_size;
1698 arc_buf_contents_t type = buf->b_hdr->b_type;
1700 arc_cksum_verify(buf);
1702 arc_buf_unwatch(buf);
1703 #endif /* illumos */
1706 if (type == ARC_BUFC_METADATA) {
1707 arc_buf_data_free(buf, zio_buf_free);
1708 arc_space_return(size, ARC_SPACE_DATA);
1710 ASSERT(type == ARC_BUFC_DATA);
1711 arc_buf_data_free(buf, zio_data_buf_free);
1712 ARCSTAT_INCR(arcstat_data_size, -size);
1713 atomic_add_64(&arc_size, -size);
1716 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1717 uint64_t *cnt = &state->arcs_lsize[type];
1719 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1720 ASSERT(state != arc_anon);
1722 ASSERT3U(*cnt, >=, size);
1723 atomic_add_64(cnt, -size);
1725 ASSERT3U(state->arcs_size, >=, size);
1726 atomic_add_64(&state->arcs_size, -size);
1730 * If we're destroying a duplicate buffer make sure
1731 * that the appropriate statistics are updated.
1733 if (buf->b_hdr->b_datacnt > 1 &&
1734 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1735 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1736 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1738 ASSERT(buf->b_hdr->b_datacnt > 0);
1739 buf->b_hdr->b_datacnt -= 1;
1742 /* only remove the buf if requested */
1746 /* remove the buf from the hdr list */
1747 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1749 *bufp = buf->b_next;
1752 ASSERT(buf->b_efunc == NULL);
1754 /* clean up the buf */
1756 kmem_cache_free(buf_cache, buf);
1760 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1762 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1763 ASSERT3P(hdr->b_state, ==, arc_anon);
1764 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1765 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1767 if (l2hdr != NULL) {
1768 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1770 * To prevent arc_free() and l2arc_evict() from
1771 * attempting to free the same buffer at the same time,
1772 * a FREE_IN_PROGRESS flag is given to arc_free() to
1773 * give it priority. l2arc_evict() can't destroy this
1774 * header while we are waiting on l2arc_buflist_mtx.
1776 * The hdr may be removed from l2ad_buflist before we
1777 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1779 if (!buflist_held) {
1780 mutex_enter(&l2arc_buflist_mtx);
1781 l2hdr = hdr->b_l2hdr;
1784 if (l2hdr != NULL) {
1785 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
1787 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1788 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1789 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
1790 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
1791 -l2hdr->b_asize, 0, 0);
1792 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1793 if (hdr->b_state == arc_l2c_only)
1794 l2arc_hdr_stat_remove();
1795 hdr->b_l2hdr = NULL;
1799 mutex_exit(&l2arc_buflist_mtx);
1802 if (!BUF_EMPTY(hdr)) {
1803 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1804 buf_discard_identity(hdr);
1806 while (hdr->b_buf) {
1807 arc_buf_t *buf = hdr->b_buf;
1810 mutex_enter(&arc_eviction_mtx);
1811 mutex_enter(&buf->b_evict_lock);
1812 ASSERT(buf->b_hdr != NULL);
1813 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1814 hdr->b_buf = buf->b_next;
1815 buf->b_hdr = &arc_eviction_hdr;
1816 buf->b_next = arc_eviction_list;
1817 arc_eviction_list = buf;
1818 mutex_exit(&buf->b_evict_lock);
1819 mutex_exit(&arc_eviction_mtx);
1821 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1824 if (hdr->b_freeze_cksum != NULL) {
1825 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1826 hdr->b_freeze_cksum = NULL;
1828 if (hdr->b_thawed) {
1829 kmem_free(hdr->b_thawed, 1);
1830 hdr->b_thawed = NULL;
1833 ASSERT(!list_link_active(&hdr->b_arc_node));
1834 ASSERT3P(hdr->b_hash_next, ==, NULL);
1835 ASSERT3P(hdr->b_acb, ==, NULL);
1836 kmem_cache_free(hdr_cache, hdr);
1840 arc_buf_free(arc_buf_t *buf, void *tag)
1842 arc_buf_hdr_t *hdr = buf->b_hdr;
1843 int hashed = hdr->b_state != arc_anon;
1845 ASSERT(buf->b_efunc == NULL);
1846 ASSERT(buf->b_data != NULL);
1849 kmutex_t *hash_lock = HDR_LOCK(hdr);
1851 mutex_enter(hash_lock);
1853 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1855 (void) remove_reference(hdr, hash_lock, tag);
1856 if (hdr->b_datacnt > 1) {
1857 arc_buf_destroy(buf, FALSE, TRUE);
1859 ASSERT(buf == hdr->b_buf);
1860 ASSERT(buf->b_efunc == NULL);
1861 hdr->b_flags |= ARC_BUF_AVAILABLE;
1863 mutex_exit(hash_lock);
1864 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1867 * We are in the middle of an async write. Don't destroy
1868 * this buffer unless the write completes before we finish
1869 * decrementing the reference count.
1871 mutex_enter(&arc_eviction_mtx);
1872 (void) remove_reference(hdr, NULL, tag);
1873 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1874 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1875 mutex_exit(&arc_eviction_mtx);
1877 arc_hdr_destroy(hdr);
1879 if (remove_reference(hdr, NULL, tag) > 0)
1880 arc_buf_destroy(buf, FALSE, TRUE);
1882 arc_hdr_destroy(hdr);
1887 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1889 arc_buf_hdr_t *hdr = buf->b_hdr;
1890 kmutex_t *hash_lock = HDR_LOCK(hdr);
1891 boolean_t no_callback = (buf->b_efunc == NULL);
1893 if (hdr->b_state == arc_anon) {
1894 ASSERT(hdr->b_datacnt == 1);
1895 arc_buf_free(buf, tag);
1896 return (no_callback);
1899 mutex_enter(hash_lock);
1901 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1902 ASSERT(hdr->b_state != arc_anon);
1903 ASSERT(buf->b_data != NULL);
1905 (void) remove_reference(hdr, hash_lock, tag);
1906 if (hdr->b_datacnt > 1) {
1908 arc_buf_destroy(buf, FALSE, TRUE);
1909 } else if (no_callback) {
1910 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1911 ASSERT(buf->b_efunc == NULL);
1912 hdr->b_flags |= ARC_BUF_AVAILABLE;
1914 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1915 refcount_is_zero(&hdr->b_refcnt));
1916 mutex_exit(hash_lock);
1917 return (no_callback);
1921 arc_buf_size(arc_buf_t *buf)
1923 return (buf->b_hdr->b_size);
1927 * Called from the DMU to determine if the current buffer should be
1928 * evicted. In order to ensure proper locking, the eviction must be initiated
1929 * from the DMU. Return true if the buffer is associated with user data and
1930 * duplicate buffers still exist.
1933 arc_buf_eviction_needed(arc_buf_t *buf)
1936 boolean_t evict_needed = B_FALSE;
1938 if (zfs_disable_dup_eviction)
1941 mutex_enter(&buf->b_evict_lock);
1945 * We are in arc_do_user_evicts(); let that function
1946 * perform the eviction.
1948 ASSERT(buf->b_data == NULL);
1949 mutex_exit(&buf->b_evict_lock);
1951 } else if (buf->b_data == NULL) {
1953 * We have already been added to the arc eviction list;
1954 * recommend eviction.
1956 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1957 mutex_exit(&buf->b_evict_lock);
1961 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1962 evict_needed = B_TRUE;
1964 mutex_exit(&buf->b_evict_lock);
1965 return (evict_needed);
1969 * Evict buffers from list until we've removed the specified number of
1970 * bytes. Move the removed buffers to the appropriate evict state.
1971 * If the recycle flag is set, then attempt to "recycle" a buffer:
1972 * - look for a buffer to evict that is `bytes' long.
1973 * - return the data block from this buffer rather than freeing it.
1974 * This flag is used by callers that are trying to make space for a
1975 * new buffer in a full arc cache.
1977 * This function makes a "best effort". It skips over any buffers
1978 * it can't get a hash_lock on, and so may not catch all candidates.
1979 * It may also return without evicting as much space as requested.
1982 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1983 arc_buf_contents_t type)
1985 arc_state_t *evicted_state;
1986 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1987 int64_t bytes_remaining;
1988 arc_buf_hdr_t *ab, *ab_prev = NULL;
1989 list_t *evicted_list, *list, *evicted_list_start, *list_start;
1990 kmutex_t *lock, *evicted_lock;
1991 kmutex_t *hash_lock;
1992 boolean_t have_lock;
1993 void *stolen = NULL;
1994 arc_buf_hdr_t marker = { 0 };
1996 static int evict_metadata_offset, evict_data_offset;
1997 int i, idx, offset, list_count, lists;
1999 ASSERT(state == arc_mru || state == arc_mfu);
2001 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2003 if (type == ARC_BUFC_METADATA) {
2005 list_count = ARC_BUFC_NUMMETADATALISTS;
2006 list_start = &state->arcs_lists[0];
2007 evicted_list_start = &evicted_state->arcs_lists[0];
2008 idx = evict_metadata_offset;
2010 offset = ARC_BUFC_NUMMETADATALISTS;
2011 list_start = &state->arcs_lists[offset];
2012 evicted_list_start = &evicted_state->arcs_lists[offset];
2013 list_count = ARC_BUFC_NUMDATALISTS;
2014 idx = evict_data_offset;
2016 bytes_remaining = evicted_state->arcs_lsize[type];
2020 list = &list_start[idx];
2021 evicted_list = &evicted_list_start[idx];
2022 lock = ARCS_LOCK(state, (offset + idx));
2023 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
2026 mutex_enter(evicted_lock);
2028 for (ab = list_tail(list); ab; ab = ab_prev) {
2029 ab_prev = list_prev(list, ab);
2030 bytes_remaining -= (ab->b_size * ab->b_datacnt);
2031 /* prefetch buffers have a minimum lifespan */
2032 if (HDR_IO_IN_PROGRESS(ab) ||
2033 (spa && ab->b_spa != spa) ||
2034 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
2035 ddi_get_lbolt() - ab->b_arc_access <
2036 arc_min_prefetch_lifespan)) {
2040 /* "lookahead" for better eviction candidate */
2041 if (recycle && ab->b_size != bytes &&
2042 ab_prev && ab_prev->b_size == bytes)
2045 /* ignore markers */
2050 * It may take a long time to evict all the bufs requested.
2051 * To avoid blocking all arc activity, periodically drop
2052 * the arcs_mtx and give other threads a chance to run
2053 * before reacquiring the lock.
2055 * If we are looking for a buffer to recycle, we are in
2056 * the hot code path, so don't sleep.
2058 if (!recycle && count++ > arc_evict_iterations) {
2059 list_insert_after(list, ab, &marker);
2060 mutex_exit(evicted_lock);
2062 kpreempt(KPREEMPT_SYNC);
2064 mutex_enter(evicted_lock);
2065 ab_prev = list_prev(list, &marker);
2066 list_remove(list, &marker);
2071 hash_lock = HDR_LOCK(ab);
2072 have_lock = MUTEX_HELD(hash_lock);
2073 if (have_lock || mutex_tryenter(hash_lock)) {
2074 ASSERT0(refcount_count(&ab->b_refcnt));
2075 ASSERT(ab->b_datacnt > 0);
2077 arc_buf_t *buf = ab->b_buf;
2078 if (!mutex_tryenter(&buf->b_evict_lock)) {
2083 bytes_evicted += ab->b_size;
2084 if (recycle && ab->b_type == type &&
2085 ab->b_size == bytes &&
2086 !HDR_L2_WRITING(ab)) {
2087 stolen = buf->b_data;
2092 mutex_enter(&arc_eviction_mtx);
2093 arc_buf_destroy(buf,
2094 buf->b_data == stolen, FALSE);
2095 ab->b_buf = buf->b_next;
2096 buf->b_hdr = &arc_eviction_hdr;
2097 buf->b_next = arc_eviction_list;
2098 arc_eviction_list = buf;
2099 mutex_exit(&arc_eviction_mtx);
2100 mutex_exit(&buf->b_evict_lock);
2102 mutex_exit(&buf->b_evict_lock);
2103 arc_buf_destroy(buf,
2104 buf->b_data == stolen, TRUE);
2109 ARCSTAT_INCR(arcstat_evict_l2_cached,
2112 if (l2arc_write_eligible(ab->b_spa, ab)) {
2113 ARCSTAT_INCR(arcstat_evict_l2_eligible,
2117 arcstat_evict_l2_ineligible,
2122 if (ab->b_datacnt == 0) {
2123 arc_change_state(evicted_state, ab, hash_lock);
2124 ASSERT(HDR_IN_HASH_TABLE(ab));
2125 ab->b_flags |= ARC_IN_HASH_TABLE;
2126 ab->b_flags &= ~ARC_BUF_AVAILABLE;
2127 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
2130 mutex_exit(hash_lock);
2131 if (bytes >= 0 && bytes_evicted >= bytes)
2133 if (bytes_remaining > 0) {
2134 mutex_exit(evicted_lock);
2136 idx = ((idx + 1) & (list_count - 1));
2145 mutex_exit(evicted_lock);
2148 idx = ((idx + 1) & (list_count - 1));
2151 if (bytes_evicted < bytes) {
2152 if (lists < list_count)
2155 dprintf("only evicted %lld bytes from %x",
2156 (longlong_t)bytes_evicted, state);
2158 if (type == ARC_BUFC_METADATA)
2159 evict_metadata_offset = idx;
2161 evict_data_offset = idx;
2164 ARCSTAT_INCR(arcstat_evict_skip, skipped);
2167 ARCSTAT_INCR(arcstat_mutex_miss, missed);
2170 * Note: we have just evicted some data into the ghost state,
2171 * potentially putting the ghost size over the desired size. Rather
2172 * that evicting from the ghost list in this hot code path, leave
2173 * this chore to the arc_reclaim_thread().
2177 ARCSTAT_BUMP(arcstat_stolen);
2182 * Remove buffers from list until we've removed the specified number of
2183 * bytes. Destroy the buffers that are removed.
2186 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
2188 arc_buf_hdr_t *ab, *ab_prev;
2189 arc_buf_hdr_t marker = { 0 };
2190 list_t *list, *list_start;
2191 kmutex_t *hash_lock, *lock;
2192 uint64_t bytes_deleted = 0;
2193 uint64_t bufs_skipped = 0;
2195 static int evict_offset;
2196 int list_count, idx = evict_offset;
2197 int offset, lists = 0;
2199 ASSERT(GHOST_STATE(state));
2202 * data lists come after metadata lists
2204 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
2205 list_count = ARC_BUFC_NUMDATALISTS;
2206 offset = ARC_BUFC_NUMMETADATALISTS;
2209 list = &list_start[idx];
2210 lock = ARCS_LOCK(state, idx + offset);
2213 for (ab = list_tail(list); ab; ab = ab_prev) {
2214 ab_prev = list_prev(list, ab);
2215 if (ab->b_type > ARC_BUFC_NUMTYPES)
2216 panic("invalid ab=%p", (void *)ab);
2217 if (spa && ab->b_spa != spa)
2220 /* ignore markers */
2224 hash_lock = HDR_LOCK(ab);
2225 /* caller may be trying to modify this buffer, skip it */
2226 if (MUTEX_HELD(hash_lock))
2230 * It may take a long time to evict all the bufs requested.
2231 * To avoid blocking all arc activity, periodically drop
2232 * the arcs_mtx and give other threads a chance to run
2233 * before reacquiring the lock.
2235 if (count++ > arc_evict_iterations) {
2236 list_insert_after(list, ab, &marker);
2238 kpreempt(KPREEMPT_SYNC);
2240 ab_prev = list_prev(list, &marker);
2241 list_remove(list, &marker);
2245 if (mutex_tryenter(hash_lock)) {
2246 ASSERT(!HDR_IO_IN_PROGRESS(ab));
2247 ASSERT(ab->b_buf == NULL);
2248 ARCSTAT_BUMP(arcstat_deleted);
2249 bytes_deleted += ab->b_size;
2251 if (ab->b_l2hdr != NULL) {
2253 * This buffer is cached on the 2nd Level ARC;
2254 * don't destroy the header.
2256 arc_change_state(arc_l2c_only, ab, hash_lock);
2257 mutex_exit(hash_lock);
2259 arc_change_state(arc_anon, ab, hash_lock);
2260 mutex_exit(hash_lock);
2261 arc_hdr_destroy(ab);
2264 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
2265 if (bytes >= 0 && bytes_deleted >= bytes)
2267 } else if (bytes < 0) {
2269 * Insert a list marker and then wait for the
2270 * hash lock to become available. Once its
2271 * available, restart from where we left off.
2273 list_insert_after(list, ab, &marker);
2275 mutex_enter(hash_lock);
2276 mutex_exit(hash_lock);
2278 ab_prev = list_prev(list, &marker);
2279 list_remove(list, &marker);
2286 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
2289 if (lists < list_count)
2293 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
2294 (bytes < 0 || bytes_deleted < bytes)) {
2295 list_start = &state->arcs_lists[0];
2296 list_count = ARC_BUFC_NUMMETADATALISTS;
2302 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2306 if (bytes_deleted < bytes)
2307 dprintf("only deleted %lld bytes from %p",
2308 (longlong_t)bytes_deleted, state);
2314 int64_t adjustment, delta;
2320 adjustment = MIN((int64_t)(arc_size - arc_c),
2321 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2324 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2325 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2326 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
2327 adjustment -= delta;
2330 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2331 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2332 (void) arc_evict(arc_mru, 0, delta, FALSE,
2340 adjustment = arc_size - arc_c;
2342 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2343 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2344 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
2345 adjustment -= delta;
2348 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2349 int64_t delta = MIN(adjustment,
2350 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2351 (void) arc_evict(arc_mfu, 0, delta, FALSE,
2356 * Adjust ghost lists
2359 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2361 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2362 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2363 arc_evict_ghost(arc_mru_ghost, 0, delta);
2367 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2369 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2370 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2371 arc_evict_ghost(arc_mfu_ghost, 0, delta);
2376 arc_do_user_evicts(void)
2378 static arc_buf_t *tmp_arc_eviction_list;
2381 * Move list over to avoid LOR
2384 mutex_enter(&arc_eviction_mtx);
2385 tmp_arc_eviction_list = arc_eviction_list;
2386 arc_eviction_list = NULL;
2387 mutex_exit(&arc_eviction_mtx);
2389 while (tmp_arc_eviction_list != NULL) {
2390 arc_buf_t *buf = tmp_arc_eviction_list;
2391 tmp_arc_eviction_list = buf->b_next;
2392 mutex_enter(&buf->b_evict_lock);
2394 mutex_exit(&buf->b_evict_lock);
2396 if (buf->b_efunc != NULL)
2397 VERIFY0(buf->b_efunc(buf->b_private));
2399 buf->b_efunc = NULL;
2400 buf->b_private = NULL;
2401 kmem_cache_free(buf_cache, buf);
2404 if (arc_eviction_list != NULL)
2409 * Flush all *evictable* data from the cache for the given spa.
2410 * NOTE: this will not touch "active" (i.e. referenced) data.
2413 arc_flush(spa_t *spa)
2418 guid = spa_load_guid(spa);
2420 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2421 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2425 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2426 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2430 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2431 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2435 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2436 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2441 arc_evict_ghost(arc_mru_ghost, guid, -1);
2442 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2444 mutex_enter(&arc_reclaim_thr_lock);
2445 arc_do_user_evicts();
2446 mutex_exit(&arc_reclaim_thr_lock);
2447 ASSERT(spa || arc_eviction_list == NULL);
2454 if (arc_c > arc_c_min) {
2457 DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
2458 arc_c_min, uint64_t, arc_p, uint64_t, to_free);
2460 to_free = arc_c >> arc_shrink_shift;
2462 to_free = arc_c >> arc_shrink_shift;
2464 if (arc_c > arc_c_min + to_free)
2465 atomic_add_64(&arc_c, -to_free);
2469 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2470 if (arc_c > arc_size)
2471 arc_c = MAX(arc_size, arc_c_min);
2473 arc_p = (arc_c >> 1);
2475 DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
2478 ASSERT(arc_c >= arc_c_min);
2479 ASSERT((int64_t)arc_p >= 0);
2482 if (arc_size > arc_c) {
2483 DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size,
2489 static int needfree = 0;
2492 arc_reclaim_needed(void)
2498 DTRACE_PROBE(arc__reclaim_needfree);
2503 * Cooperate with pagedaemon when it's time for it to scan
2504 * and reclaim some pages.
2506 if (freemem < zfs_arc_free_target) {
2507 DTRACE_PROBE2(arc__reclaim_freemem, uint64_t,
2508 freemem, uint64_t, zfs_arc_free_target);
2514 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2519 * check that we're out of range of the pageout scanner. It starts to
2520 * schedule paging if freemem is less than lotsfree and needfree.
2521 * lotsfree is the high-water mark for pageout, and needfree is the
2522 * number of needed free pages. We add extra pages here to make sure
2523 * the scanner doesn't start up while we're freeing memory.
2525 if (freemem < lotsfree + needfree + extra)
2529 * check to make sure that swapfs has enough space so that anon
2530 * reservations can still succeed. anon_resvmem() checks that the
2531 * availrmem is greater than swapfs_minfree, and the number of reserved
2532 * swap pages. We also add a bit of extra here just to prevent
2533 * circumstances from getting really dire.
2535 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2539 * Check that we have enough availrmem that memory locking (e.g., via
2540 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
2541 * stores the number of pages that cannot be locked; when availrmem
2542 * drops below pages_pp_maximum, page locking mechanisms such as
2543 * page_pp_lock() will fail.)
2545 if (availrmem <= pages_pp_maximum)
2549 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
2551 * If we're on an i386 platform, it's possible that we'll exhaust the
2552 * kernel heap space before we ever run out of available physical
2553 * memory. Most checks of the size of the heap_area compare against
2554 * tune.t_minarmem, which is the minimum available real memory that we
2555 * can have in the system. However, this is generally fixed at 25 pages
2556 * which is so low that it's useless. In this comparison, we seek to
2557 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2558 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2561 if (vmem_size(heap_arena, VMEM_FREE) <
2562 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2)) {
2563 DTRACE_PROBE2(arc__reclaim_used, uint64_t,
2564 vmem_size(heap_arena, VMEM_FREE), uint64_t,
2565 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2);
2571 * If zio data pages are being allocated out of a separate heap segment,
2572 * then enforce that the size of available vmem for this arena remains
2573 * above about 1/16th free.
2575 * Note: The 1/16th arena free requirement was put in place
2576 * to aggressively evict memory from the arc in order to avoid
2577 * memory fragmentation issues.
2579 if (zio_arena != NULL &&
2580 vmem_size(zio_arena, VMEM_FREE) <
2581 (vmem_size(zio_arena, VMEM_ALLOC) >> 4))
2585 if (spa_get_random(100) == 0)
2587 #endif /* _KERNEL */
2588 DTRACE_PROBE(arc__reclaim_no);
2593 extern kmem_cache_t *zio_buf_cache[];
2594 extern kmem_cache_t *zio_data_buf_cache[];
2595 extern kmem_cache_t *range_seg_cache;
2597 static void __noinline
2598 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2601 kmem_cache_t *prev_cache = NULL;
2602 kmem_cache_t *prev_data_cache = NULL;
2604 DTRACE_PROBE(arc__kmem_reap_start);
2606 if (arc_meta_used >= arc_meta_limit) {
2608 * We are exceeding our meta-data cache limit.
2609 * Purge some DNLC entries to release holds on meta-data.
2611 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2615 * Reclaim unused memory from all kmem caches.
2622 * An aggressive reclamation will shrink the cache size as well as
2623 * reap free buffers from the arc kmem caches.
2625 if (strat == ARC_RECLAIM_AGGR)
2628 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2629 if (zio_buf_cache[i] != prev_cache) {
2630 prev_cache = zio_buf_cache[i];
2631 kmem_cache_reap_now(zio_buf_cache[i]);
2633 if (zio_data_buf_cache[i] != prev_data_cache) {
2634 prev_data_cache = zio_data_buf_cache[i];
2635 kmem_cache_reap_now(zio_data_buf_cache[i]);
2638 kmem_cache_reap_now(buf_cache);
2639 kmem_cache_reap_now(hdr_cache);
2640 kmem_cache_reap_now(range_seg_cache);
2644 * Ask the vmem arena to reclaim unused memory from its
2647 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
2648 vmem_qcache_reap(zio_arena);
2650 DTRACE_PROBE(arc__kmem_reap_end);
2654 arc_reclaim_thread(void *dummy __unused)
2656 clock_t growtime = 0;
2657 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2660 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2662 mutex_enter(&arc_reclaim_thr_lock);
2663 while (arc_thread_exit == 0) {
2664 if (arc_reclaim_needed()) {
2667 if (last_reclaim == ARC_RECLAIM_CONS) {
2668 DTRACE_PROBE(arc__reclaim_aggr_no_grow);
2669 last_reclaim = ARC_RECLAIM_AGGR;
2671 last_reclaim = ARC_RECLAIM_CONS;
2675 last_reclaim = ARC_RECLAIM_AGGR;
2676 DTRACE_PROBE(arc__reclaim_aggr);
2680 /* reset the growth delay for every reclaim */
2681 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2683 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2685 * If needfree is TRUE our vm_lowmem hook
2686 * was called and in that case we must free some
2687 * memory, so switch to aggressive mode.
2690 last_reclaim = ARC_RECLAIM_AGGR;
2692 arc_kmem_reap_now(last_reclaim);
2695 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2696 arc_no_grow = FALSE;
2701 if (arc_eviction_list != NULL)
2702 arc_do_user_evicts();
2711 /* block until needed, or one second, whichever is shorter */
2712 CALLB_CPR_SAFE_BEGIN(&cpr);
2713 (void) cv_timedwait(&arc_reclaim_thr_cv,
2714 &arc_reclaim_thr_lock, hz);
2715 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2718 arc_thread_exit = 0;
2719 cv_broadcast(&arc_reclaim_thr_cv);
2720 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2725 * Adapt arc info given the number of bytes we are trying to add and
2726 * the state that we are comming from. This function is only called
2727 * when we are adding new content to the cache.
2730 arc_adapt(int bytes, arc_state_t *state)
2733 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2735 if (state == arc_l2c_only)
2740 * Adapt the target size of the MRU list:
2741 * - if we just hit in the MRU ghost list, then increase
2742 * the target size of the MRU list.
2743 * - if we just hit in the MFU ghost list, then increase
2744 * the target size of the MFU list by decreasing the
2745 * target size of the MRU list.
2747 if (state == arc_mru_ghost) {
2748 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2749 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2750 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2752 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2753 } else if (state == arc_mfu_ghost) {
2756 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2757 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2758 mult = MIN(mult, 10);
2760 delta = MIN(bytes * mult, arc_p);
2761 arc_p = MAX(arc_p_min, arc_p - delta);
2763 ASSERT((int64_t)arc_p >= 0);
2765 if (arc_reclaim_needed()) {
2766 cv_signal(&arc_reclaim_thr_cv);
2773 if (arc_c >= arc_c_max)
2777 * If we're within (2 * maxblocksize) bytes of the target
2778 * cache size, increment the target cache size
2780 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2781 DTRACE_PROBE1(arc__inc_adapt, int, bytes);
2782 atomic_add_64(&arc_c, (int64_t)bytes);
2783 if (arc_c > arc_c_max)
2785 else if (state == arc_anon)
2786 atomic_add_64(&arc_p, (int64_t)bytes);
2790 ASSERT((int64_t)arc_p >= 0);
2794 * Check if the cache has reached its limits and eviction is required
2798 arc_evict_needed(arc_buf_contents_t type)
2800 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2803 if (arc_reclaim_needed())
2806 return (arc_size > arc_c);
2810 * The buffer, supplied as the first argument, needs a data block.
2811 * So, if we are at cache max, determine which cache should be victimized.
2812 * We have the following cases:
2814 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2815 * In this situation if we're out of space, but the resident size of the MFU is
2816 * under the limit, victimize the MFU cache to satisfy this insertion request.
2818 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2819 * Here, we've used up all of the available space for the MRU, so we need to
2820 * evict from our own cache instead. Evict from the set of resident MRU
2823 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2824 * c minus p represents the MFU space in the cache, since p is the size of the
2825 * cache that is dedicated to the MRU. In this situation there's still space on
2826 * the MFU side, so the MRU side needs to be victimized.
2828 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2829 * MFU's resident set is consuming more space than it has been allotted. In
2830 * this situation, we must victimize our own cache, the MFU, for this insertion.
2833 arc_get_data_buf(arc_buf_t *buf)
2835 arc_state_t *state = buf->b_hdr->b_state;
2836 uint64_t size = buf->b_hdr->b_size;
2837 arc_buf_contents_t type = buf->b_hdr->b_type;
2839 arc_adapt(size, state);
2842 * We have not yet reached cache maximum size,
2843 * just allocate a new buffer.
2845 if (!arc_evict_needed(type)) {
2846 if (type == ARC_BUFC_METADATA) {
2847 buf->b_data = zio_buf_alloc(size);
2848 arc_space_consume(size, ARC_SPACE_DATA);
2850 ASSERT(type == ARC_BUFC_DATA);
2851 buf->b_data = zio_data_buf_alloc(size);
2852 ARCSTAT_INCR(arcstat_data_size, size);
2853 atomic_add_64(&arc_size, size);
2859 * If we are prefetching from the mfu ghost list, this buffer
2860 * will end up on the mru list; so steal space from there.
2862 if (state == arc_mfu_ghost)
2863 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2864 else if (state == arc_mru_ghost)
2867 if (state == arc_mru || state == arc_anon) {
2868 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2869 state = (arc_mfu->arcs_lsize[type] >= size &&
2870 arc_p > mru_used) ? arc_mfu : arc_mru;
2873 uint64_t mfu_space = arc_c - arc_p;
2874 state = (arc_mru->arcs_lsize[type] >= size &&
2875 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2877 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2878 if (type == ARC_BUFC_METADATA) {
2879 buf->b_data = zio_buf_alloc(size);
2880 arc_space_consume(size, ARC_SPACE_DATA);
2882 ASSERT(type == ARC_BUFC_DATA);
2883 buf->b_data = zio_data_buf_alloc(size);
2884 ARCSTAT_INCR(arcstat_data_size, size);
2885 atomic_add_64(&arc_size, size);
2887 ARCSTAT_BUMP(arcstat_recycle_miss);
2889 ASSERT(buf->b_data != NULL);
2892 * Update the state size. Note that ghost states have a
2893 * "ghost size" and so don't need to be updated.
2895 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2896 arc_buf_hdr_t *hdr = buf->b_hdr;
2898 atomic_add_64(&hdr->b_state->arcs_size, size);
2899 if (list_link_active(&hdr->b_arc_node)) {
2900 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2901 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2904 * If we are growing the cache, and we are adding anonymous
2905 * data, and we have outgrown arc_p, update arc_p
2907 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2908 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2909 arc_p = MIN(arc_c, arc_p + size);
2911 ARCSTAT_BUMP(arcstat_allocated);
2915 * This routine is called whenever a buffer is accessed.
2916 * NOTE: the hash lock is dropped in this function.
2919 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2923 ASSERT(MUTEX_HELD(hash_lock));
2925 if (buf->b_state == arc_anon) {
2927 * This buffer is not in the cache, and does not
2928 * appear in our "ghost" list. Add the new buffer
2932 ASSERT(buf->b_arc_access == 0);
2933 buf->b_arc_access = ddi_get_lbolt();
2934 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2935 arc_change_state(arc_mru, buf, hash_lock);
2937 } else if (buf->b_state == arc_mru) {
2938 now = ddi_get_lbolt();
2941 * If this buffer is here because of a prefetch, then either:
2942 * - clear the flag if this is a "referencing" read
2943 * (any subsequent access will bump this into the MFU state).
2945 * - move the buffer to the head of the list if this is
2946 * another prefetch (to make it less likely to be evicted).
2948 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2949 if (refcount_count(&buf->b_refcnt) == 0) {
2950 ASSERT(list_link_active(&buf->b_arc_node));
2952 buf->b_flags &= ~ARC_PREFETCH;
2953 ARCSTAT_BUMP(arcstat_mru_hits);
2955 buf->b_arc_access = now;
2960 * This buffer has been "accessed" only once so far,
2961 * but it is still in the cache. Move it to the MFU
2964 if (now > buf->b_arc_access + ARC_MINTIME) {
2966 * More than 125ms have passed since we
2967 * instantiated this buffer. Move it to the
2968 * most frequently used state.
2970 buf->b_arc_access = now;
2971 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2972 arc_change_state(arc_mfu, buf, hash_lock);
2974 ARCSTAT_BUMP(arcstat_mru_hits);
2975 } else if (buf->b_state == arc_mru_ghost) {
2976 arc_state_t *new_state;
2978 * This buffer has been "accessed" recently, but
2979 * was evicted from the cache. Move it to the
2983 if (buf->b_flags & ARC_PREFETCH) {
2984 new_state = arc_mru;
2985 if (refcount_count(&buf->b_refcnt) > 0)
2986 buf->b_flags &= ~ARC_PREFETCH;
2987 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2989 new_state = arc_mfu;
2990 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2993 buf->b_arc_access = ddi_get_lbolt();
2994 arc_change_state(new_state, buf, hash_lock);
2996 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2997 } else if (buf->b_state == arc_mfu) {
2999 * This buffer has been accessed more than once and is
3000 * still in the cache. Keep it in the MFU state.
3002 * NOTE: an add_reference() that occurred when we did
3003 * the arc_read() will have kicked this off the list.
3004 * If it was a prefetch, we will explicitly move it to
3005 * the head of the list now.
3007 if ((buf->b_flags & ARC_PREFETCH) != 0) {
3008 ASSERT(refcount_count(&buf->b_refcnt) == 0);
3009 ASSERT(list_link_active(&buf->b_arc_node));
3011 ARCSTAT_BUMP(arcstat_mfu_hits);
3012 buf->b_arc_access = ddi_get_lbolt();
3013 } else if (buf->b_state == arc_mfu_ghost) {
3014 arc_state_t *new_state = arc_mfu;
3016 * This buffer has been accessed more than once but has
3017 * been evicted from the cache. Move it back to the
3021 if (buf->b_flags & ARC_PREFETCH) {
3023 * This is a prefetch access...
3024 * move this block back to the MRU state.
3026 ASSERT0(refcount_count(&buf->b_refcnt));
3027 new_state = arc_mru;
3030 buf->b_arc_access = ddi_get_lbolt();
3031 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3032 arc_change_state(new_state, buf, hash_lock);
3034 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
3035 } else if (buf->b_state == arc_l2c_only) {
3037 * This buffer is on the 2nd Level ARC.
3040 buf->b_arc_access = ddi_get_lbolt();
3041 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
3042 arc_change_state(arc_mfu, buf, hash_lock);
3044 ASSERT(!"invalid arc state");
3048 /* a generic arc_done_func_t which you can use */
3051 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
3053 if (zio == NULL || zio->io_error == 0)
3054 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
3055 VERIFY(arc_buf_remove_ref(buf, arg));
3058 /* a generic arc_done_func_t */
3060 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
3062 arc_buf_t **bufp = arg;
3063 if (zio && zio->io_error) {
3064 VERIFY(arc_buf_remove_ref(buf, arg));
3068 ASSERT(buf->b_data);
3073 arc_read_done(zio_t *zio)
3077 arc_buf_t *abuf; /* buffer we're assigning to callback */
3078 kmutex_t *hash_lock = NULL;
3079 arc_callback_t *callback_list, *acb;
3080 int freeable = FALSE;
3082 buf = zio->io_private;
3086 * The hdr was inserted into hash-table and removed from lists
3087 * prior to starting I/O. We should find this header, since
3088 * it's in the hash table, and it should be legit since it's
3089 * not possible to evict it during the I/O. The only possible
3090 * reason for it not to be found is if we were freed during the
3093 if (HDR_IN_HASH_TABLE(hdr)) {
3094 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
3095 ASSERT3U(hdr->b_dva.dva_word[0], ==,
3096 BP_IDENTITY(zio->io_bp)->dva_word[0]);
3097 ASSERT3U(hdr->b_dva.dva_word[1], ==,
3098 BP_IDENTITY(zio->io_bp)->dva_word[1]);
3100 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
3103 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
3104 hash_lock == NULL) ||
3106 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
3107 (found == hdr && HDR_L2_READING(hdr)));
3110 hdr->b_flags &= ~ARC_L2_EVICTED;
3111 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
3112 hdr->b_flags &= ~ARC_L2CACHE;
3114 /* byteswap if necessary */
3115 callback_list = hdr->b_acb;
3116 ASSERT(callback_list != NULL);
3117 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3118 dmu_object_byteswap_t bswap =
3119 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3120 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3121 byteswap_uint64_array :
3122 dmu_ot_byteswap[bswap].ob_func;
3123 func(buf->b_data, hdr->b_size);
3126 arc_cksum_compute(buf, B_FALSE);
3129 #endif /* illumos */
3131 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
3133 * Only call arc_access on anonymous buffers. This is because
3134 * if we've issued an I/O for an evicted buffer, we've already
3135 * called arc_access (to prevent any simultaneous readers from
3136 * getting confused).
3138 arc_access(hdr, hash_lock);
3141 /* create copies of the data buffer for the callers */
3143 for (acb = callback_list; acb; acb = acb->acb_next) {
3144 if (acb->acb_done) {
3146 ARCSTAT_BUMP(arcstat_duplicate_reads);
3147 abuf = arc_buf_clone(buf);
3149 acb->acb_buf = abuf;
3154 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3155 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3157 ASSERT(buf->b_efunc == NULL);
3158 ASSERT(hdr->b_datacnt == 1);
3159 hdr->b_flags |= ARC_BUF_AVAILABLE;
3162 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
3164 if (zio->io_error != 0) {
3165 hdr->b_flags |= ARC_IO_ERROR;
3166 if (hdr->b_state != arc_anon)
3167 arc_change_state(arc_anon, hdr, hash_lock);
3168 if (HDR_IN_HASH_TABLE(hdr))
3169 buf_hash_remove(hdr);
3170 freeable = refcount_is_zero(&hdr->b_refcnt);
3174 * Broadcast before we drop the hash_lock to avoid the possibility
3175 * that the hdr (and hence the cv) might be freed before we get to
3176 * the cv_broadcast().
3178 cv_broadcast(&hdr->b_cv);
3181 mutex_exit(hash_lock);
3184 * This block was freed while we waited for the read to
3185 * complete. It has been removed from the hash table and
3186 * moved to the anonymous state (so that it won't show up
3189 ASSERT3P(hdr->b_state, ==, arc_anon);
3190 freeable = refcount_is_zero(&hdr->b_refcnt);
3193 /* execute each callback and free its structure */
3194 while ((acb = callback_list) != NULL) {
3196 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3198 if (acb->acb_zio_dummy != NULL) {
3199 acb->acb_zio_dummy->io_error = zio->io_error;
3200 zio_nowait(acb->acb_zio_dummy);
3203 callback_list = acb->acb_next;
3204 kmem_free(acb, sizeof (arc_callback_t));
3208 arc_hdr_destroy(hdr);
3212 * "Read" the block block at the specified DVA (in bp) via the
3213 * cache. If the block is found in the cache, invoke the provided
3214 * callback immediately and return. Note that the `zio' parameter
3215 * in the callback will be NULL in this case, since no IO was
3216 * required. If the block is not in the cache pass the read request
3217 * on to the spa with a substitute callback function, so that the
3218 * requested block will be added to the cache.
3220 * If a read request arrives for a block that has a read in-progress,
3221 * either wait for the in-progress read to complete (and return the
3222 * results); or, if this is a read with a "done" func, add a record
3223 * to the read to invoke the "done" func when the read completes,
3224 * and return; or just return.
3226 * arc_read_done() will invoke all the requested "done" functions
3227 * for readers of this block.
3230 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3231 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
3232 const zbookmark_phys_t *zb)
3234 arc_buf_hdr_t *hdr = NULL;
3235 arc_buf_t *buf = NULL;
3236 kmutex_t *hash_lock = NULL;
3238 uint64_t guid = spa_load_guid(spa);
3240 ASSERT(!BP_IS_EMBEDDED(bp) ||
3241 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3244 if (!BP_IS_EMBEDDED(bp)) {
3246 * Embedded BP's have no DVA and require no I/O to "read".
3247 * Create an anonymous arc buf to back it.
3249 hdr = buf_hash_find(guid, bp, &hash_lock);
3252 if (hdr != NULL && hdr->b_datacnt > 0) {
3254 *arc_flags |= ARC_CACHED;
3256 if (HDR_IO_IN_PROGRESS(hdr)) {
3258 if (*arc_flags & ARC_WAIT) {
3259 cv_wait(&hdr->b_cv, hash_lock);
3260 mutex_exit(hash_lock);
3263 ASSERT(*arc_flags & ARC_NOWAIT);
3266 arc_callback_t *acb = NULL;
3268 acb = kmem_zalloc(sizeof (arc_callback_t),
3270 acb->acb_done = done;
3271 acb->acb_private = private;
3273 acb->acb_zio_dummy = zio_null(pio,
3274 spa, NULL, NULL, NULL, zio_flags);
3276 ASSERT(acb->acb_done != NULL);
3277 acb->acb_next = hdr->b_acb;
3279 add_reference(hdr, hash_lock, private);
3280 mutex_exit(hash_lock);
3283 mutex_exit(hash_lock);
3287 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3290 add_reference(hdr, hash_lock, private);
3292 * If this block is already in use, create a new
3293 * copy of the data so that we will be guaranteed
3294 * that arc_release() will always succeed.
3298 ASSERT(buf->b_data);
3299 if (HDR_BUF_AVAILABLE(hdr)) {
3300 ASSERT(buf->b_efunc == NULL);
3301 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3303 buf = arc_buf_clone(buf);
3306 } else if (*arc_flags & ARC_PREFETCH &&
3307 refcount_count(&hdr->b_refcnt) == 0) {
3308 hdr->b_flags |= ARC_PREFETCH;
3310 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3311 arc_access(hdr, hash_lock);
3312 if (*arc_flags & ARC_L2CACHE)
3313 hdr->b_flags |= ARC_L2CACHE;
3314 if (*arc_flags & ARC_L2COMPRESS)
3315 hdr->b_flags |= ARC_L2COMPRESS;
3316 mutex_exit(hash_lock);
3317 ARCSTAT_BUMP(arcstat_hits);
3318 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3319 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3320 data, metadata, hits);
3323 done(NULL, buf, private);
3325 uint64_t size = BP_GET_LSIZE(bp);
3326 arc_callback_t *acb;
3329 boolean_t devw = B_FALSE;
3330 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
3331 uint64_t b_asize = 0;
3334 /* this block is not in the cache */
3335 arc_buf_hdr_t *exists = NULL;
3336 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3337 buf = arc_buf_alloc(spa, size, private, type);
3339 if (!BP_IS_EMBEDDED(bp)) {
3340 hdr->b_dva = *BP_IDENTITY(bp);
3341 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3342 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3343 exists = buf_hash_insert(hdr, &hash_lock);
3345 if (exists != NULL) {
3346 /* somebody beat us to the hash insert */
3347 mutex_exit(hash_lock);
3348 buf_discard_identity(hdr);
3349 (void) arc_buf_remove_ref(buf, private);
3350 goto top; /* restart the IO request */
3352 /* if this is a prefetch, we don't have a reference */
3353 if (*arc_flags & ARC_PREFETCH) {
3354 (void) remove_reference(hdr, hash_lock,
3356 hdr->b_flags |= ARC_PREFETCH;
3358 if (*arc_flags & ARC_L2CACHE)
3359 hdr->b_flags |= ARC_L2CACHE;
3360 if (*arc_flags & ARC_L2COMPRESS)
3361 hdr->b_flags |= ARC_L2COMPRESS;
3362 if (BP_GET_LEVEL(bp) > 0)
3363 hdr->b_flags |= ARC_INDIRECT;
3365 /* this block is in the ghost cache */
3366 ASSERT(GHOST_STATE(hdr->b_state));
3367 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3368 ASSERT0(refcount_count(&hdr->b_refcnt));
3369 ASSERT(hdr->b_buf == NULL);
3371 /* if this is a prefetch, we don't have a reference */
3372 if (*arc_flags & ARC_PREFETCH)
3373 hdr->b_flags |= ARC_PREFETCH;
3375 add_reference(hdr, hash_lock, private);
3376 if (*arc_flags & ARC_L2CACHE)
3377 hdr->b_flags |= ARC_L2CACHE;
3378 if (*arc_flags & ARC_L2COMPRESS)
3379 hdr->b_flags |= ARC_L2COMPRESS;
3380 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3383 buf->b_efunc = NULL;
3384 buf->b_private = NULL;
3387 ASSERT(hdr->b_datacnt == 0);
3389 arc_get_data_buf(buf);
3390 arc_access(hdr, hash_lock);
3393 ASSERT(!GHOST_STATE(hdr->b_state));
3395 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3396 acb->acb_done = done;
3397 acb->acb_private = private;
3399 ASSERT(hdr->b_acb == NULL);
3401 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3403 if (hdr->b_l2hdr != NULL &&
3404 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3405 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3406 addr = hdr->b_l2hdr->b_daddr;
3407 b_compress = hdr->b_l2hdr->b_compress;
3408 b_asize = hdr->b_l2hdr->b_asize;
3410 * Lock out device removal.
3412 if (vdev_is_dead(vd) ||
3413 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3417 if (hash_lock != NULL)
3418 mutex_exit(hash_lock);
3421 * At this point, we have a level 1 cache miss. Try again in
3422 * L2ARC if possible.
3424 ASSERT3U(hdr->b_size, ==, size);
3425 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3426 uint64_t, size, zbookmark_phys_t *, zb);
3427 ARCSTAT_BUMP(arcstat_misses);
3428 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3429 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3430 data, metadata, misses);
3432 curthread->td_ru.ru_inblock++;
3435 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3437 * Read from the L2ARC if the following are true:
3438 * 1. The L2ARC vdev was previously cached.
3439 * 2. This buffer still has L2ARC metadata.
3440 * 3. This buffer isn't currently writing to the L2ARC.
3441 * 4. The L2ARC entry wasn't evicted, which may
3442 * also have invalidated the vdev.
3443 * 5. This isn't prefetch and l2arc_noprefetch is set.
3445 if (hdr->b_l2hdr != NULL &&
3446 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3447 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3448 l2arc_read_callback_t *cb;
3450 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3451 ARCSTAT_BUMP(arcstat_l2_hits);
3453 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3455 cb->l2rcb_buf = buf;
3456 cb->l2rcb_spa = spa;
3459 cb->l2rcb_flags = zio_flags;
3460 cb->l2rcb_compress = b_compress;
3462 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3463 addr + size < vd->vdev_psize -
3464 VDEV_LABEL_END_SIZE);
3467 * l2arc read. The SCL_L2ARC lock will be
3468 * released by l2arc_read_done().
3469 * Issue a null zio if the underlying buffer
3470 * was squashed to zero size by compression.
3472 if (b_compress == ZIO_COMPRESS_EMPTY) {
3473 rzio = zio_null(pio, spa, vd,
3474 l2arc_read_done, cb,
3475 zio_flags | ZIO_FLAG_DONT_CACHE |
3477 ZIO_FLAG_DONT_PROPAGATE |
3478 ZIO_FLAG_DONT_RETRY);
3480 rzio = zio_read_phys(pio, vd, addr,
3481 b_asize, buf->b_data,
3483 l2arc_read_done, cb, priority,
3484 zio_flags | ZIO_FLAG_DONT_CACHE |
3486 ZIO_FLAG_DONT_PROPAGATE |
3487 ZIO_FLAG_DONT_RETRY, B_FALSE);
3489 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3491 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
3493 if (*arc_flags & ARC_NOWAIT) {
3498 ASSERT(*arc_flags & ARC_WAIT);
3499 if (zio_wait(rzio) == 0)
3502 /* l2arc read error; goto zio_read() */
3504 DTRACE_PROBE1(l2arc__miss,
3505 arc_buf_hdr_t *, hdr);
3506 ARCSTAT_BUMP(arcstat_l2_misses);
3507 if (HDR_L2_WRITING(hdr))
3508 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3509 spa_config_exit(spa, SCL_L2ARC, vd);
3513 spa_config_exit(spa, SCL_L2ARC, vd);
3514 if (l2arc_ndev != 0) {
3515 DTRACE_PROBE1(l2arc__miss,
3516 arc_buf_hdr_t *, hdr);
3517 ARCSTAT_BUMP(arcstat_l2_misses);
3521 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3522 arc_read_done, buf, priority, zio_flags, zb);
3524 if (*arc_flags & ARC_WAIT)
3525 return (zio_wait(rzio));
3527 ASSERT(*arc_flags & ARC_NOWAIT);
3534 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3536 ASSERT(buf->b_hdr != NULL);
3537 ASSERT(buf->b_hdr->b_state != arc_anon);
3538 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3539 ASSERT(buf->b_efunc == NULL);
3540 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3542 buf->b_efunc = func;
3543 buf->b_private = private;
3547 * Notify the arc that a block was freed, and thus will never be used again.
3550 arc_freed(spa_t *spa, const blkptr_t *bp)
3553 kmutex_t *hash_lock;
3554 uint64_t guid = spa_load_guid(spa);
3556 ASSERT(!BP_IS_EMBEDDED(bp));
3558 hdr = buf_hash_find(guid, bp, &hash_lock);
3561 if (HDR_BUF_AVAILABLE(hdr)) {
3562 arc_buf_t *buf = hdr->b_buf;
3563 add_reference(hdr, hash_lock, FTAG);
3564 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3565 mutex_exit(hash_lock);
3567 arc_release(buf, FTAG);
3568 (void) arc_buf_remove_ref(buf, FTAG);
3570 mutex_exit(hash_lock);
3576 * Clear the user eviction callback set by arc_set_callback(), first calling
3577 * it if it exists. Because the presence of a callback keeps an arc_buf cached
3578 * clearing the callback may result in the arc_buf being destroyed. However,
3579 * it will not result in the *last* arc_buf being destroyed, hence the data
3580 * will remain cached in the ARC. We make a copy of the arc buffer here so
3581 * that we can process the callback without holding any locks.
3583 * It's possible that the callback is already in the process of being cleared
3584 * by another thread. In this case we can not clear the callback.
3586 * Returns B_TRUE if the callback was successfully called and cleared.
3589 arc_clear_callback(arc_buf_t *buf)
3592 kmutex_t *hash_lock;
3593 arc_evict_func_t *efunc = buf->b_efunc;
3594 void *private = buf->b_private;
3595 list_t *list, *evicted_list;
3596 kmutex_t *lock, *evicted_lock;
3598 mutex_enter(&buf->b_evict_lock);
3602 * We are in arc_do_user_evicts().
3604 ASSERT(buf->b_data == NULL);
3605 mutex_exit(&buf->b_evict_lock);
3607 } else if (buf->b_data == NULL) {
3609 * We are on the eviction list; process this buffer now
3610 * but let arc_do_user_evicts() do the reaping.
3612 buf->b_efunc = NULL;
3613 mutex_exit(&buf->b_evict_lock);
3614 VERIFY0(efunc(private));
3617 hash_lock = HDR_LOCK(hdr);
3618 mutex_enter(hash_lock);
3620 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3622 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3623 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3625 buf->b_efunc = NULL;
3626 buf->b_private = NULL;
3628 if (hdr->b_datacnt > 1) {
3629 mutex_exit(&buf->b_evict_lock);
3630 arc_buf_destroy(buf, FALSE, TRUE);
3632 ASSERT(buf == hdr->b_buf);
3633 hdr->b_flags |= ARC_BUF_AVAILABLE;
3634 mutex_exit(&buf->b_evict_lock);
3637 mutex_exit(hash_lock);
3638 VERIFY0(efunc(private));
3643 * Release this buffer from the cache, making it an anonymous buffer. This
3644 * must be done after a read and prior to modifying the buffer contents.
3645 * If the buffer has more than one reference, we must make
3646 * a new hdr for the buffer.
3649 arc_release(arc_buf_t *buf, void *tag)
3652 kmutex_t *hash_lock = NULL;
3653 l2arc_buf_hdr_t *l2hdr;
3657 * It would be nice to assert that if it's DMU metadata (level >
3658 * 0 || it's the dnode file), then it must be syncing context.
3659 * But we don't know that information at this level.
3662 mutex_enter(&buf->b_evict_lock);
3665 /* this buffer is not on any list */
3666 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3668 if (hdr->b_state == arc_anon) {
3669 /* this buffer is already released */
3670 ASSERT(buf->b_efunc == NULL);
3672 hash_lock = HDR_LOCK(hdr);
3673 mutex_enter(hash_lock);
3675 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3678 l2hdr = hdr->b_l2hdr;
3680 mutex_enter(&l2arc_buflist_mtx);
3681 hdr->b_l2hdr = NULL;
3682 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3684 buf_size = hdr->b_size;
3687 * Do we have more than one buf?
3689 if (hdr->b_datacnt > 1) {
3690 arc_buf_hdr_t *nhdr;
3692 uint64_t blksz = hdr->b_size;
3693 uint64_t spa = hdr->b_spa;
3694 arc_buf_contents_t type = hdr->b_type;
3695 uint32_t flags = hdr->b_flags;
3697 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3699 * Pull the data off of this hdr and attach it to
3700 * a new anonymous hdr.
3702 (void) remove_reference(hdr, hash_lock, tag);
3704 while (*bufp != buf)
3705 bufp = &(*bufp)->b_next;
3706 *bufp = buf->b_next;
3709 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3710 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3711 if (refcount_is_zero(&hdr->b_refcnt)) {
3712 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3713 ASSERT3U(*size, >=, hdr->b_size);
3714 atomic_add_64(size, -hdr->b_size);
3718 * We're releasing a duplicate user data buffer, update
3719 * our statistics accordingly.
3721 if (hdr->b_type == ARC_BUFC_DATA) {
3722 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3723 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3726 hdr->b_datacnt -= 1;
3727 arc_cksum_verify(buf);
3729 arc_buf_unwatch(buf);
3730 #endif /* illumos */
3732 mutex_exit(hash_lock);
3734 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3735 nhdr->b_size = blksz;
3737 nhdr->b_type = type;
3739 nhdr->b_state = arc_anon;
3740 nhdr->b_arc_access = 0;
3741 nhdr->b_flags = flags & ARC_L2_WRITING;
3742 nhdr->b_l2hdr = NULL;
3743 nhdr->b_datacnt = 1;
3744 nhdr->b_freeze_cksum = NULL;
3745 (void) refcount_add(&nhdr->b_refcnt, tag);
3747 mutex_exit(&buf->b_evict_lock);
3748 atomic_add_64(&arc_anon->arcs_size, blksz);
3750 mutex_exit(&buf->b_evict_lock);
3751 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3752 ASSERT(!list_link_active(&hdr->b_arc_node));
3753 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3754 if (hdr->b_state != arc_anon)
3755 arc_change_state(arc_anon, hdr, hash_lock);
3756 hdr->b_arc_access = 0;
3758 mutex_exit(hash_lock);
3760 buf_discard_identity(hdr);
3763 buf->b_efunc = NULL;
3764 buf->b_private = NULL;
3767 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
3768 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
3769 -l2hdr->b_asize, 0, 0);
3770 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
3772 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3773 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3774 mutex_exit(&l2arc_buflist_mtx);
3779 arc_released(arc_buf_t *buf)
3783 mutex_enter(&buf->b_evict_lock);
3784 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3785 mutex_exit(&buf->b_evict_lock);
3791 arc_referenced(arc_buf_t *buf)
3795 mutex_enter(&buf->b_evict_lock);
3796 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3797 mutex_exit(&buf->b_evict_lock);
3798 return (referenced);
3803 arc_write_ready(zio_t *zio)
3805 arc_write_callback_t *callback = zio->io_private;
3806 arc_buf_t *buf = callback->awcb_buf;
3807 arc_buf_hdr_t *hdr = buf->b_hdr;
3809 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3810 callback->awcb_ready(zio, buf, callback->awcb_private);
3813 * If the IO is already in progress, then this is a re-write
3814 * attempt, so we need to thaw and re-compute the cksum.
3815 * It is the responsibility of the callback to handle the
3816 * accounting for any re-write attempt.
3818 if (HDR_IO_IN_PROGRESS(hdr)) {
3819 mutex_enter(&hdr->b_freeze_lock);
3820 if (hdr->b_freeze_cksum != NULL) {
3821 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3822 hdr->b_freeze_cksum = NULL;
3824 mutex_exit(&hdr->b_freeze_lock);
3826 arc_cksum_compute(buf, B_FALSE);
3827 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3831 * The SPA calls this callback for each physical write that happens on behalf
3832 * of a logical write. See the comment in dbuf_write_physdone() for details.
3835 arc_write_physdone(zio_t *zio)
3837 arc_write_callback_t *cb = zio->io_private;
3838 if (cb->awcb_physdone != NULL)
3839 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
3843 arc_write_done(zio_t *zio)
3845 arc_write_callback_t *callback = zio->io_private;
3846 arc_buf_t *buf = callback->awcb_buf;
3847 arc_buf_hdr_t *hdr = buf->b_hdr;
3849 ASSERT(hdr->b_acb == NULL);
3851 if (zio->io_error == 0) {
3852 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
3853 buf_discard_identity(hdr);
3855 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3856 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3857 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3860 ASSERT(BUF_EMPTY(hdr));
3864 * If the block to be written was all-zero or compressed enough to be
3865 * embedded in the BP, no write was performed so there will be no
3866 * dva/birth/checksum. The buffer must therefore remain anonymous
3869 if (!BUF_EMPTY(hdr)) {
3870 arc_buf_hdr_t *exists;
3871 kmutex_t *hash_lock;
3873 ASSERT(zio->io_error == 0);
3875 arc_cksum_verify(buf);
3877 exists = buf_hash_insert(hdr, &hash_lock);
3880 * This can only happen if we overwrite for
3881 * sync-to-convergence, because we remove
3882 * buffers from the hash table when we arc_free().
3884 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3885 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3886 panic("bad overwrite, hdr=%p exists=%p",
3887 (void *)hdr, (void *)exists);
3888 ASSERT(refcount_is_zero(&exists->b_refcnt));
3889 arc_change_state(arc_anon, exists, hash_lock);
3890 mutex_exit(hash_lock);
3891 arc_hdr_destroy(exists);
3892 exists = buf_hash_insert(hdr, &hash_lock);
3893 ASSERT3P(exists, ==, NULL);
3894 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3896 ASSERT(zio->io_prop.zp_nopwrite);
3897 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3898 panic("bad nopwrite, hdr=%p exists=%p",
3899 (void *)hdr, (void *)exists);
3902 ASSERT(hdr->b_datacnt == 1);
3903 ASSERT(hdr->b_state == arc_anon);
3904 ASSERT(BP_GET_DEDUP(zio->io_bp));
3905 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3908 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3909 /* if it's not anon, we are doing a scrub */
3910 if (!exists && hdr->b_state == arc_anon)
3911 arc_access(hdr, hash_lock);
3912 mutex_exit(hash_lock);
3914 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3917 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3918 callback->awcb_done(zio, buf, callback->awcb_private);
3920 kmem_free(callback, sizeof (arc_write_callback_t));
3924 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3925 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
3926 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
3927 arc_done_func_t *done, void *private, zio_priority_t priority,
3928 int zio_flags, const zbookmark_phys_t *zb)
3930 arc_buf_hdr_t *hdr = buf->b_hdr;
3931 arc_write_callback_t *callback;
3934 ASSERT(ready != NULL);
3935 ASSERT(done != NULL);
3936 ASSERT(!HDR_IO_ERROR(hdr));
3937 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3938 ASSERT(hdr->b_acb == NULL);
3940 hdr->b_flags |= ARC_L2CACHE;
3942 hdr->b_flags |= ARC_L2COMPRESS;
3943 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3944 callback->awcb_ready = ready;
3945 callback->awcb_physdone = physdone;
3946 callback->awcb_done = done;
3947 callback->awcb_private = private;
3948 callback->awcb_buf = buf;
3950 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3951 arc_write_ready, arc_write_physdone, arc_write_done, callback,
3952 priority, zio_flags, zb);
3958 arc_memory_throttle(uint64_t reserve, uint64_t txg)
3961 uint64_t available_memory = ptob(freemem);
3962 static uint64_t page_load = 0;
3963 static uint64_t last_txg = 0;
3965 #if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
3967 MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE)));
3970 if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
3973 if (txg > last_txg) {
3978 * If we are in pageout, we know that memory is already tight,
3979 * the arc is already going to be evicting, so we just want to
3980 * continue to let page writes occur as quickly as possible.
3982 if (curproc == pageproc) {
3983 if (page_load > MAX(ptob(minfree), available_memory) / 4)
3984 return (SET_ERROR(ERESTART));
3985 /* Note: reserve is inflated, so we deflate */
3986 page_load += reserve / 8;
3988 } else if (page_load > 0 && arc_reclaim_needed()) {
3989 /* memory is low, delay before restarting */
3990 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3991 return (SET_ERROR(EAGAIN));
3999 arc_tempreserve_clear(uint64_t reserve)
4001 atomic_add_64(&arc_tempreserve, -reserve);
4002 ASSERT((int64_t)arc_tempreserve >= 0);
4006 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
4011 if (reserve > arc_c/4 && !arc_no_grow) {
4012 arc_c = MIN(arc_c_max, reserve * 4);
4013 DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
4015 if (reserve > arc_c)
4016 return (SET_ERROR(ENOMEM));
4019 * Don't count loaned bufs as in flight dirty data to prevent long
4020 * network delays from blocking transactions that are ready to be
4021 * assigned to a txg.
4023 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
4026 * Writes will, almost always, require additional memory allocations
4027 * in order to compress/encrypt/etc the data. We therefore need to
4028 * make sure that there is sufficient available memory for this.
4030 error = arc_memory_throttle(reserve, txg);
4035 * Throttle writes when the amount of dirty data in the cache
4036 * gets too large. We try to keep the cache less than half full
4037 * of dirty blocks so that our sync times don't grow too large.
4038 * Note: if two requests come in concurrently, we might let them
4039 * both succeed, when one of them should fail. Not a huge deal.
4042 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
4043 anon_size > arc_c / 4) {
4044 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
4045 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
4046 arc_tempreserve>>10,
4047 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
4048 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
4049 reserve>>10, arc_c>>10);
4050 return (SET_ERROR(ERESTART));
4052 atomic_add_64(&arc_tempreserve, reserve);
4056 static kmutex_t arc_lowmem_lock;
4058 static eventhandler_tag arc_event_lowmem = NULL;
4061 arc_lowmem(void *arg __unused, int howto __unused)
4064 /* Serialize access via arc_lowmem_lock. */
4065 mutex_enter(&arc_lowmem_lock);
4066 mutex_enter(&arc_reclaim_thr_lock);
4068 DTRACE_PROBE(arc__needfree);
4069 cv_signal(&arc_reclaim_thr_cv);
4072 * It is unsafe to block here in arbitrary threads, because we can come
4073 * here from ARC itself and may hold ARC locks and thus risk a deadlock
4074 * with ARC reclaim thread.
4076 if (curproc == pageproc) {
4078 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
4080 mutex_exit(&arc_reclaim_thr_lock);
4081 mutex_exit(&arc_lowmem_lock);
4088 int i, prefetch_tunable_set = 0;
4090 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4091 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
4092 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
4094 /* Convert seconds to clock ticks */
4095 arc_min_prefetch_lifespan = 1 * hz;
4097 /* Start out with 1/8 of all memory */
4098 arc_c = kmem_size() / 8;
4103 * On architectures where the physical memory can be larger
4104 * than the addressable space (intel in 32-bit mode), we may
4105 * need to limit the cache to 1/8 of VM size.
4107 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
4110 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
4111 arc_c_min = MAX(arc_c / 4, 64<<18);
4112 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
4113 if (arc_c * 8 >= 1<<30)
4114 arc_c_max = (arc_c * 8) - (1<<30);
4116 arc_c_max = arc_c_min;
4117 arc_c_max = MAX(arc_c * 5, arc_c_max);
4121 * Allow the tunables to override our calculations if they are
4122 * reasonable (ie. over 16MB)
4124 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size())
4125 arc_c_max = zfs_arc_max;
4126 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max)
4127 arc_c_min = zfs_arc_min;
4131 arc_p = (arc_c >> 1);
4133 /* limit meta-data to 1/4 of the arc capacity */
4134 arc_meta_limit = arc_c_max / 4;
4136 /* Allow the tunable to override if it is reasonable */
4137 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
4138 arc_meta_limit = zfs_arc_meta_limit;
4140 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
4141 arc_c_min = arc_meta_limit / 2;
4143 if (zfs_arc_grow_retry > 0)
4144 arc_grow_retry = zfs_arc_grow_retry;
4146 if (zfs_arc_shrink_shift > 0)
4147 arc_shrink_shift = zfs_arc_shrink_shift;
4149 if (zfs_arc_p_min_shift > 0)
4150 arc_p_min_shift = zfs_arc_p_min_shift;
4152 /* if kmem_flags are set, lets try to use less memory */
4153 if (kmem_debugging())
4155 if (arc_c < arc_c_min)
4158 zfs_arc_min = arc_c_min;
4159 zfs_arc_max = arc_c_max;
4161 arc_anon = &ARC_anon;
4163 arc_mru_ghost = &ARC_mru_ghost;
4165 arc_mfu_ghost = &ARC_mfu_ghost;
4166 arc_l2c_only = &ARC_l2c_only;
4169 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4170 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
4171 NULL, MUTEX_DEFAULT, NULL);
4172 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
4173 NULL, MUTEX_DEFAULT, NULL);
4174 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
4175 NULL, MUTEX_DEFAULT, NULL);
4176 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
4177 NULL, MUTEX_DEFAULT, NULL);
4178 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
4179 NULL, MUTEX_DEFAULT, NULL);
4180 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
4181 NULL, MUTEX_DEFAULT, NULL);
4183 list_create(&arc_mru->arcs_lists[i],
4184 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4185 list_create(&arc_mru_ghost->arcs_lists[i],
4186 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4187 list_create(&arc_mfu->arcs_lists[i],
4188 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4189 list_create(&arc_mfu_ghost->arcs_lists[i],
4190 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4191 list_create(&arc_mfu_ghost->arcs_lists[i],
4192 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4193 list_create(&arc_l2c_only->arcs_lists[i],
4194 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4199 arc_thread_exit = 0;
4200 arc_eviction_list = NULL;
4201 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
4202 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
4204 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
4205 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
4207 if (arc_ksp != NULL) {
4208 arc_ksp->ks_data = &arc_stats;
4209 kstat_install(arc_ksp);
4212 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
4213 TS_RUN, minclsyspri);
4216 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
4217 EVENTHANDLER_PRI_FIRST);
4224 * Calculate maximum amount of dirty data per pool.
4226 * If it has been set by /etc/system, take that.
4227 * Otherwise, use a percentage of physical memory defined by
4228 * zfs_dirty_data_max_percent (default 10%) with a cap at
4229 * zfs_dirty_data_max_max (default 4GB).
4231 if (zfs_dirty_data_max == 0) {
4232 zfs_dirty_data_max = ptob(physmem) *
4233 zfs_dirty_data_max_percent / 100;
4234 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
4235 zfs_dirty_data_max_max);
4239 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
4240 prefetch_tunable_set = 1;
4243 if (prefetch_tunable_set == 0) {
4244 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
4246 printf(" add \"vfs.zfs.prefetch_disable=0\" "
4247 "to /boot/loader.conf.\n");
4248 zfs_prefetch_disable = 1;
4251 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
4252 prefetch_tunable_set == 0) {
4253 printf("ZFS NOTICE: Prefetch is disabled by default if less "
4254 "than 4GB of RAM is present;\n"
4255 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
4256 "to /boot/loader.conf.\n");
4257 zfs_prefetch_disable = 1;
4260 /* Warn about ZFS memory and address space requirements. */
4261 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
4262 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
4263 "expect unstable behavior.\n");
4265 if (kmem_size() < 512 * (1 << 20)) {
4266 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
4267 "expect unstable behavior.\n");
4268 printf(" Consider tuning vm.kmem_size and "
4269 "vm.kmem_size_max\n");
4270 printf(" in /boot/loader.conf.\n");
4280 mutex_enter(&arc_reclaim_thr_lock);
4281 arc_thread_exit = 1;
4282 cv_signal(&arc_reclaim_thr_cv);
4283 while (arc_thread_exit != 0)
4284 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
4285 mutex_exit(&arc_reclaim_thr_lock);
4291 if (arc_ksp != NULL) {
4292 kstat_delete(arc_ksp);
4296 mutex_destroy(&arc_eviction_mtx);
4297 mutex_destroy(&arc_reclaim_thr_lock);
4298 cv_destroy(&arc_reclaim_thr_cv);
4300 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4301 list_destroy(&arc_mru->arcs_lists[i]);
4302 list_destroy(&arc_mru_ghost->arcs_lists[i]);
4303 list_destroy(&arc_mfu->arcs_lists[i]);
4304 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
4305 list_destroy(&arc_l2c_only->arcs_lists[i]);
4307 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
4308 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
4309 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
4310 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
4311 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
4312 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
4317 ASSERT(arc_loaned_bytes == 0);
4319 mutex_destroy(&arc_lowmem_lock);
4321 if (arc_event_lowmem != NULL)
4322 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
4329 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
4330 * It uses dedicated storage devices to hold cached data, which are populated
4331 * using large infrequent writes. The main role of this cache is to boost
4332 * the performance of random read workloads. The intended L2ARC devices
4333 * include short-stroked disks, solid state disks, and other media with
4334 * substantially faster read latency than disk.
4336 * +-----------------------+
4338 * +-----------------------+
4341 * l2arc_feed_thread() arc_read()
4345 * +---------------+ |
4347 * +---------------+ |
4352 * +-------+ +-------+
4354 * | cache | | cache |
4355 * +-------+ +-------+
4356 * +=========+ .-----.
4357 * : L2ARC : |-_____-|
4358 * : devices : | Disks |
4359 * +=========+ `-_____-'
4361 * Read requests are satisfied from the following sources, in order:
4364 * 2) vdev cache of L2ARC devices
4366 * 4) vdev cache of disks
4369 * Some L2ARC device types exhibit extremely slow write performance.
4370 * To accommodate for this there are some significant differences between
4371 * the L2ARC and traditional cache design:
4373 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4374 * the ARC behave as usual, freeing buffers and placing headers on ghost
4375 * lists. The ARC does not send buffers to the L2ARC during eviction as
4376 * this would add inflated write latencies for all ARC memory pressure.
4378 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4379 * It does this by periodically scanning buffers from the eviction-end of
4380 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4381 * not already there. It scans until a headroom of buffers is satisfied,
4382 * which itself is a buffer for ARC eviction. If a compressible buffer is
4383 * found during scanning and selected for writing to an L2ARC device, we
4384 * temporarily boost scanning headroom during the next scan cycle to make
4385 * sure we adapt to compression effects (which might significantly reduce
4386 * the data volume we write to L2ARC). The thread that does this is
4387 * l2arc_feed_thread(), illustrated below; example sizes are included to
4388 * provide a better sense of ratio than this diagram:
4391 * +---------------------+----------+
4392 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4393 * +---------------------+----------+ | o L2ARC eligible
4394 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4395 * +---------------------+----------+ |
4396 * 15.9 Gbytes ^ 32 Mbytes |
4398 * l2arc_feed_thread()
4400 * l2arc write hand <--[oooo]--'
4404 * +==============================+
4405 * L2ARC dev |####|#|###|###| |####| ... |
4406 * +==============================+
4409 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4410 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4411 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4412 * safe to say that this is an uncommon case, since buffers at the end of
4413 * the ARC lists have moved there due to inactivity.
4415 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4416 * then the L2ARC simply misses copying some buffers. This serves as a
4417 * pressure valve to prevent heavy read workloads from both stalling the ARC
4418 * with waits and clogging the L2ARC with writes. This also helps prevent
4419 * the potential for the L2ARC to churn if it attempts to cache content too
4420 * quickly, such as during backups of the entire pool.
4422 * 5. After system boot and before the ARC has filled main memory, there are
4423 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4424 * lists can remain mostly static. Instead of searching from tail of these
4425 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4426 * for eligible buffers, greatly increasing its chance of finding them.
4428 * The L2ARC device write speed is also boosted during this time so that
4429 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4430 * there are no L2ARC reads, and no fear of degrading read performance
4431 * through increased writes.
4433 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4434 * the vdev queue can aggregate them into larger and fewer writes. Each
4435 * device is written to in a rotor fashion, sweeping writes through
4436 * available space then repeating.
4438 * 7. The L2ARC does not store dirty content. It never needs to flush
4439 * write buffers back to disk based storage.
4441 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4442 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4444 * The performance of the L2ARC can be tweaked by a number of tunables, which
4445 * may be necessary for different workloads:
4447 * l2arc_write_max max write bytes per interval
4448 * l2arc_write_boost extra write bytes during device warmup
4449 * l2arc_noprefetch skip caching prefetched buffers
4450 * l2arc_headroom number of max device writes to precache
4451 * l2arc_headroom_boost when we find compressed buffers during ARC
4452 * scanning, we multiply headroom by this
4453 * percentage factor for the next scan cycle,
4454 * since more compressed buffers are likely to
4456 * l2arc_feed_secs seconds between L2ARC writing
4458 * Tunables may be removed or added as future performance improvements are
4459 * integrated, and also may become zpool properties.
4461 * There are three key functions that control how the L2ARC warms up:
4463 * l2arc_write_eligible() check if a buffer is eligible to cache
4464 * l2arc_write_size() calculate how much to write
4465 * l2arc_write_interval() calculate sleep delay between writes
4467 * These three functions determine what to write, how much, and how quickly
4472 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4475 * A buffer is *not* eligible for the L2ARC if it:
4476 * 1. belongs to a different spa.
4477 * 2. is already cached on the L2ARC.
4478 * 3. has an I/O in progress (it may be an incomplete read).
4479 * 4. is flagged not eligible (zfs property).
4481 if (ab->b_spa != spa_guid) {
4482 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4485 if (ab->b_l2hdr != NULL) {
4486 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4489 if (HDR_IO_IN_PROGRESS(ab)) {
4490 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4493 if (!HDR_L2CACHE(ab)) {
4494 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4502 l2arc_write_size(void)
4507 * Make sure our globals have meaningful values in case the user
4510 size = l2arc_write_max;
4512 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
4513 "be greater than zero, resetting it to the default (%d)",
4515 size = l2arc_write_max = L2ARC_WRITE_SIZE;
4518 if (arc_warm == B_FALSE)
4519 size += l2arc_write_boost;
4526 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4528 clock_t interval, next, now;
4531 * If the ARC lists are busy, increase our write rate; if the
4532 * lists are stale, idle back. This is achieved by checking
4533 * how much we previously wrote - if it was more than half of
4534 * what we wanted, schedule the next write much sooner.
4536 if (l2arc_feed_again && wrote > (wanted / 2))
4537 interval = (hz * l2arc_feed_min_ms) / 1000;
4539 interval = hz * l2arc_feed_secs;
4541 now = ddi_get_lbolt();
4542 next = MAX(now, MIN(now + interval, began + interval));
4548 l2arc_hdr_stat_add(void)
4550 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4551 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4555 l2arc_hdr_stat_remove(void)
4557 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4558 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4562 * Cycle through L2ARC devices. This is how L2ARC load balances.
4563 * If a device is returned, this also returns holding the spa config lock.
4565 static l2arc_dev_t *
4566 l2arc_dev_get_next(void)
4568 l2arc_dev_t *first, *next = NULL;
4571 * Lock out the removal of spas (spa_namespace_lock), then removal
4572 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4573 * both locks will be dropped and a spa config lock held instead.
4575 mutex_enter(&spa_namespace_lock);
4576 mutex_enter(&l2arc_dev_mtx);
4578 /* if there are no vdevs, there is nothing to do */
4579 if (l2arc_ndev == 0)
4583 next = l2arc_dev_last;
4585 /* loop around the list looking for a non-faulted vdev */
4587 next = list_head(l2arc_dev_list);
4589 next = list_next(l2arc_dev_list, next);
4591 next = list_head(l2arc_dev_list);
4594 /* if we have come back to the start, bail out */
4597 else if (next == first)
4600 } while (vdev_is_dead(next->l2ad_vdev));
4602 /* if we were unable to find any usable vdevs, return NULL */
4603 if (vdev_is_dead(next->l2ad_vdev))
4606 l2arc_dev_last = next;
4609 mutex_exit(&l2arc_dev_mtx);
4612 * Grab the config lock to prevent the 'next' device from being
4613 * removed while we are writing to it.
4616 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4617 mutex_exit(&spa_namespace_lock);
4623 * Free buffers that were tagged for destruction.
4626 l2arc_do_free_on_write()
4629 l2arc_data_free_t *df, *df_prev;
4631 mutex_enter(&l2arc_free_on_write_mtx);
4632 buflist = l2arc_free_on_write;
4634 for (df = list_tail(buflist); df; df = df_prev) {
4635 df_prev = list_prev(buflist, df);
4636 ASSERT(df->l2df_data != NULL);
4637 ASSERT(df->l2df_func != NULL);
4638 df->l2df_func(df->l2df_data, df->l2df_size);
4639 list_remove(buflist, df);
4640 kmem_free(df, sizeof (l2arc_data_free_t));
4643 mutex_exit(&l2arc_free_on_write_mtx);
4647 * A write to a cache device has completed. Update all headers to allow
4648 * reads from these buffers to begin.
4651 l2arc_write_done(zio_t *zio)
4653 l2arc_write_callback_t *cb;
4656 arc_buf_hdr_t *head, *ab, *ab_prev;
4657 l2arc_buf_hdr_t *abl2;
4658 kmutex_t *hash_lock;
4659 int64_t bytes_dropped = 0;
4661 cb = zio->io_private;
4663 dev = cb->l2wcb_dev;
4664 ASSERT(dev != NULL);
4665 head = cb->l2wcb_head;
4666 ASSERT(head != NULL);
4667 buflist = dev->l2ad_buflist;
4668 ASSERT(buflist != NULL);
4669 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4670 l2arc_write_callback_t *, cb);
4672 if (zio->io_error != 0)
4673 ARCSTAT_BUMP(arcstat_l2_writes_error);
4675 mutex_enter(&l2arc_buflist_mtx);
4678 * All writes completed, or an error was hit.
4680 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4681 ab_prev = list_prev(buflist, ab);
4685 * Release the temporary compressed buffer as soon as possible.
4687 if (abl2->b_compress != ZIO_COMPRESS_OFF)
4688 l2arc_release_cdata_buf(ab);
4690 hash_lock = HDR_LOCK(ab);
4691 if (!mutex_tryenter(hash_lock)) {
4693 * This buffer misses out. It may be in a stage
4694 * of eviction. Its ARC_L2_WRITING flag will be
4695 * left set, denying reads to this buffer.
4697 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4701 if (zio->io_error != 0) {
4703 * Error - drop L2ARC entry.
4705 list_remove(buflist, ab);
4706 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4707 bytes_dropped += abl2->b_asize;
4709 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr,
4711 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4712 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4716 * Allow ARC to begin reads to this L2ARC entry.
4718 ab->b_flags &= ~ARC_L2_WRITING;
4720 mutex_exit(hash_lock);
4723 atomic_inc_64(&l2arc_writes_done);
4724 list_remove(buflist, head);
4725 kmem_cache_free(hdr_cache, head);
4726 mutex_exit(&l2arc_buflist_mtx);
4728 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
4730 l2arc_do_free_on_write();
4732 kmem_free(cb, sizeof (l2arc_write_callback_t));
4736 * A read to a cache device completed. Validate buffer contents before
4737 * handing over to the regular ARC routines.
4740 l2arc_read_done(zio_t *zio)
4742 l2arc_read_callback_t *cb;
4745 kmutex_t *hash_lock;
4748 ASSERT(zio->io_vd != NULL);
4749 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4751 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4753 cb = zio->io_private;
4755 buf = cb->l2rcb_buf;
4756 ASSERT(buf != NULL);
4758 hash_lock = HDR_LOCK(buf->b_hdr);
4759 mutex_enter(hash_lock);
4761 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4764 * If the buffer was compressed, decompress it first.
4766 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
4767 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
4768 ASSERT(zio->io_data != NULL);
4771 * Check this survived the L2ARC journey.
4773 equal = arc_cksum_equal(buf);
4774 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4775 mutex_exit(hash_lock);
4776 zio->io_private = buf;
4777 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4778 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4781 mutex_exit(hash_lock);
4783 * Buffer didn't survive caching. Increment stats and
4784 * reissue to the original storage device.
4786 if (zio->io_error != 0) {
4787 ARCSTAT_BUMP(arcstat_l2_io_error);
4789 zio->io_error = SET_ERROR(EIO);
4792 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4795 * If there's no waiter, issue an async i/o to the primary
4796 * storage now. If there *is* a waiter, the caller must
4797 * issue the i/o in a context where it's OK to block.
4799 if (zio->io_waiter == NULL) {
4800 zio_t *pio = zio_unique_parent(zio);
4802 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4804 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4805 buf->b_data, zio->io_size, arc_read_done, buf,
4806 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4810 kmem_free(cb, sizeof (l2arc_read_callback_t));
4814 * This is the list priority from which the L2ARC will search for pages to
4815 * cache. This is used within loops (0..3) to cycle through lists in the
4816 * desired order. This order can have a significant effect on cache
4819 * Currently the metadata lists are hit first, MFU then MRU, followed by
4820 * the data lists. This function returns a locked list, and also returns
4824 l2arc_list_locked(int list_num, kmutex_t **lock)
4826 list_t *list = NULL;
4829 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4831 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4833 list = &arc_mfu->arcs_lists[idx];
4834 *lock = ARCS_LOCK(arc_mfu, idx);
4835 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4836 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4837 list = &arc_mru->arcs_lists[idx];
4838 *lock = ARCS_LOCK(arc_mru, idx);
4839 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4840 ARC_BUFC_NUMDATALISTS)) {
4841 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4842 list = &arc_mfu->arcs_lists[idx];
4843 *lock = ARCS_LOCK(arc_mfu, idx);
4845 idx = list_num - ARC_BUFC_NUMLISTS;
4846 list = &arc_mru->arcs_lists[idx];
4847 *lock = ARCS_LOCK(arc_mru, idx);
4850 ASSERT(!(MUTEX_HELD(*lock)));
4856 * Evict buffers from the device write hand to the distance specified in
4857 * bytes. This distance may span populated buffers, it may span nothing.
4858 * This is clearing a region on the L2ARC device ready for writing.
4859 * If the 'all' boolean is set, every buffer is evicted.
4862 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4865 l2arc_buf_hdr_t *abl2;
4866 arc_buf_hdr_t *ab, *ab_prev;
4867 kmutex_t *hash_lock;
4869 int64_t bytes_evicted = 0;
4871 buflist = dev->l2ad_buflist;
4873 if (buflist == NULL)
4876 if (!all && dev->l2ad_first) {
4878 * This is the first sweep through the device. There is
4884 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4886 * When nearing the end of the device, evict to the end
4887 * before the device write hand jumps to the start.
4889 taddr = dev->l2ad_end;
4891 taddr = dev->l2ad_hand + distance;
4893 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4894 uint64_t, taddr, boolean_t, all);
4897 mutex_enter(&l2arc_buflist_mtx);
4898 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4899 ab_prev = list_prev(buflist, ab);
4901 hash_lock = HDR_LOCK(ab);
4902 if (!mutex_tryenter(hash_lock)) {
4904 * Missed the hash lock. Retry.
4906 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4907 mutex_exit(&l2arc_buflist_mtx);
4908 mutex_enter(hash_lock);
4909 mutex_exit(hash_lock);
4913 if (HDR_L2_WRITE_HEAD(ab)) {
4915 * We hit a write head node. Leave it for
4916 * l2arc_write_done().
4918 list_remove(buflist, ab);
4919 mutex_exit(hash_lock);
4923 if (!all && ab->b_l2hdr != NULL &&
4924 (ab->b_l2hdr->b_daddr > taddr ||
4925 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4927 * We've evicted to the target address,
4928 * or the end of the device.
4930 mutex_exit(hash_lock);
4934 if (HDR_FREE_IN_PROGRESS(ab)) {
4936 * Already on the path to destruction.
4938 mutex_exit(hash_lock);
4942 if (ab->b_state == arc_l2c_only) {
4943 ASSERT(!HDR_L2_READING(ab));
4945 * This doesn't exist in the ARC. Destroy.
4946 * arc_hdr_destroy() will call list_remove()
4947 * and decrement arcstat_l2_size.
4949 arc_change_state(arc_anon, ab, hash_lock);
4950 arc_hdr_destroy(ab);
4953 * Invalidate issued or about to be issued
4954 * reads, since we may be about to write
4955 * over this location.
4957 if (HDR_L2_READING(ab)) {
4958 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4959 ab->b_flags |= ARC_L2_EVICTED;
4963 * Tell ARC this no longer exists in L2ARC.
4965 if (ab->b_l2hdr != NULL) {
4967 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4968 bytes_evicted += abl2->b_asize;
4970 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4971 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4973 list_remove(buflist, ab);
4976 * This may have been leftover after a
4979 ab->b_flags &= ~ARC_L2_WRITING;
4981 mutex_exit(hash_lock);
4983 mutex_exit(&l2arc_buflist_mtx);
4985 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0);
4986 dev->l2ad_evict = taddr;
4990 * Find and write ARC buffers to the L2ARC device.
4992 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4993 * for reading until they have completed writing.
4994 * The headroom_boost is an in-out parameter used to maintain headroom boost
4995 * state between calls to this function.
4997 * Returns the number of bytes actually written (which may be smaller than
4998 * the delta by which the device hand has changed due to alignment).
5001 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
5002 boolean_t *headroom_boost)
5004 arc_buf_hdr_t *ab, *ab_prev, *head;
5006 uint64_t write_asize, write_psize, write_sz, headroom,
5009 kmutex_t *list_lock;
5011 l2arc_write_callback_t *cb;
5013 uint64_t guid = spa_load_guid(spa);
5014 const boolean_t do_headroom_boost = *headroom_boost;
5017 ASSERT(dev->l2ad_vdev != NULL);
5019 /* Lower the flag now, we might want to raise it again later. */
5020 *headroom_boost = B_FALSE;
5023 write_sz = write_asize = write_psize = 0;
5025 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
5026 head->b_flags |= ARC_L2_WRITE_HEAD;
5028 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
5030 * We will want to try to compress buffers that are at least 2x the
5031 * device sector size.
5033 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
5036 * Copy buffers for L2ARC writing.
5038 mutex_enter(&l2arc_buflist_mtx);
5039 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
5040 uint64_t passed_sz = 0;
5042 list = l2arc_list_locked(try, &list_lock);
5043 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
5046 * L2ARC fast warmup.
5048 * Until the ARC is warm and starts to evict, read from the
5049 * head of the ARC lists rather than the tail.
5051 if (arc_warm == B_FALSE)
5052 ab = list_head(list);
5054 ab = list_tail(list);
5056 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
5058 headroom = target_sz * l2arc_headroom;
5059 if (do_headroom_boost)
5060 headroom = (headroom * l2arc_headroom_boost) / 100;
5062 for (; ab; ab = ab_prev) {
5063 l2arc_buf_hdr_t *l2hdr;
5064 kmutex_t *hash_lock;
5067 if (arc_warm == B_FALSE)
5068 ab_prev = list_next(list, ab);
5070 ab_prev = list_prev(list, ab);
5071 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
5073 hash_lock = HDR_LOCK(ab);
5074 if (!mutex_tryenter(hash_lock)) {
5075 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
5077 * Skip this buffer rather than waiting.
5082 passed_sz += ab->b_size;
5083 if (passed_sz > headroom) {
5087 mutex_exit(hash_lock);
5088 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
5092 if (!l2arc_write_eligible(guid, ab)) {
5093 mutex_exit(hash_lock);
5097 if ((write_sz + ab->b_size) > target_sz) {
5099 mutex_exit(hash_lock);
5100 ARCSTAT_BUMP(arcstat_l2_write_full);
5106 * Insert a dummy header on the buflist so
5107 * l2arc_write_done() can find where the
5108 * write buffers begin without searching.
5110 list_insert_head(dev->l2ad_buflist, head);
5113 sizeof (l2arc_write_callback_t), KM_SLEEP);
5114 cb->l2wcb_dev = dev;
5115 cb->l2wcb_head = head;
5116 pio = zio_root(spa, l2arc_write_done, cb,
5118 ARCSTAT_BUMP(arcstat_l2_write_pios);
5122 * Create and add a new L2ARC header.
5124 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
5126 ab->b_flags |= ARC_L2_WRITING;
5129 * Temporarily stash the data buffer in b_tmp_cdata.
5130 * The subsequent write step will pick it up from
5131 * there. This is because can't access ab->b_buf
5132 * without holding the hash_lock, which we in turn
5133 * can't access without holding the ARC list locks
5134 * (which we want to avoid during compression/writing).
5136 l2hdr->b_compress = ZIO_COMPRESS_OFF;
5137 l2hdr->b_asize = ab->b_size;
5138 l2hdr->b_tmp_cdata = ab->b_buf->b_data;
5140 buf_sz = ab->b_size;
5141 ab->b_l2hdr = l2hdr;
5143 list_insert_head(dev->l2ad_buflist, ab);
5146 * Compute and store the buffer cksum before
5147 * writing. On debug the cksum is verified first.
5149 arc_cksum_verify(ab->b_buf);
5150 arc_cksum_compute(ab->b_buf, B_TRUE);
5152 mutex_exit(hash_lock);
5157 mutex_exit(list_lock);
5163 /* No buffers selected for writing? */
5166 mutex_exit(&l2arc_buflist_mtx);
5167 kmem_cache_free(hdr_cache, head);
5172 * Now start writing the buffers. We're starting at the write head
5173 * and work backwards, retracing the course of the buffer selector
5176 for (ab = list_prev(dev->l2ad_buflist, head); ab;
5177 ab = list_prev(dev->l2ad_buflist, ab)) {
5178 l2arc_buf_hdr_t *l2hdr;
5182 * We shouldn't need to lock the buffer here, since we flagged
5183 * it as ARC_L2_WRITING in the previous step, but we must take
5184 * care to only access its L2 cache parameters. In particular,
5185 * ab->b_buf may be invalid by now due to ARC eviction.
5187 l2hdr = ab->b_l2hdr;
5188 l2hdr->b_daddr = dev->l2ad_hand;
5190 if ((ab->b_flags & ARC_L2COMPRESS) &&
5191 l2hdr->b_asize >= buf_compress_minsz) {
5192 if (l2arc_compress_buf(l2hdr)) {
5194 * If compression succeeded, enable headroom
5195 * boost on the next scan cycle.
5197 *headroom_boost = B_TRUE;
5202 * Pick up the buffer data we had previously stashed away
5203 * (and now potentially also compressed).
5205 buf_data = l2hdr->b_tmp_cdata;
5206 buf_sz = l2hdr->b_asize;
5208 /* Compression may have squashed the buffer to zero length. */
5212 wzio = zio_write_phys(pio, dev->l2ad_vdev,
5213 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
5214 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
5215 ZIO_FLAG_CANFAIL, B_FALSE);
5217 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
5219 (void) zio_nowait(wzio);
5221 write_asize += buf_sz;
5223 * Keep the clock hand suitably device-aligned.
5225 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
5226 write_psize += buf_p_sz;
5227 dev->l2ad_hand += buf_p_sz;
5231 mutex_exit(&l2arc_buflist_mtx);
5233 ASSERT3U(write_asize, <=, target_sz);
5234 ARCSTAT_BUMP(arcstat_l2_writes_sent);
5235 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
5236 ARCSTAT_INCR(arcstat_l2_size, write_sz);
5237 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
5238 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
5241 * Bump device hand to the device start if it is approaching the end.
5242 * l2arc_evict() will already have evicted ahead for this case.
5244 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
5245 dev->l2ad_hand = dev->l2ad_start;
5246 dev->l2ad_evict = dev->l2ad_start;
5247 dev->l2ad_first = B_FALSE;
5250 dev->l2ad_writing = B_TRUE;
5251 (void) zio_wait(pio);
5252 dev->l2ad_writing = B_FALSE;
5254 return (write_asize);
5258 * Compresses an L2ARC buffer.
5259 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
5260 * size in l2hdr->b_asize. This routine tries to compress the data and
5261 * depending on the compression result there are three possible outcomes:
5262 * *) The buffer was incompressible. The original l2hdr contents were left
5263 * untouched and are ready for writing to an L2 device.
5264 * *) The buffer was all-zeros, so there is no need to write it to an L2
5265 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
5266 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
5267 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
5268 * data buffer which holds the compressed data to be written, and b_asize
5269 * tells us how much data there is. b_compress is set to the appropriate
5270 * compression algorithm. Once writing is done, invoke
5271 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
5273 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
5274 * buffer was incompressible).
5277 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
5280 size_t csize, len, rounded;
5282 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
5283 ASSERT(l2hdr->b_tmp_cdata != NULL);
5285 len = l2hdr->b_asize;
5286 cdata = zio_data_buf_alloc(len);
5287 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
5288 cdata, l2hdr->b_asize);
5290 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
5291 if (rounded > csize) {
5292 bzero((char *)cdata + csize, rounded - csize);
5297 /* zero block, indicate that there's nothing to write */
5298 zio_data_buf_free(cdata, len);
5299 l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
5301 l2hdr->b_tmp_cdata = NULL;
5302 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
5304 } else if (csize > 0 && csize < len) {
5306 * Compression succeeded, we'll keep the cdata around for
5307 * writing and release it afterwards.
5309 l2hdr->b_compress = ZIO_COMPRESS_LZ4;
5310 l2hdr->b_asize = csize;
5311 l2hdr->b_tmp_cdata = cdata;
5312 ARCSTAT_BUMP(arcstat_l2_compress_successes);
5316 * Compression failed, release the compressed buffer.
5317 * l2hdr will be left unmodified.
5319 zio_data_buf_free(cdata, len);
5320 ARCSTAT_BUMP(arcstat_l2_compress_failures);
5326 * Decompresses a zio read back from an l2arc device. On success, the
5327 * underlying zio's io_data buffer is overwritten by the uncompressed
5328 * version. On decompression error (corrupt compressed stream), the
5329 * zio->io_error value is set to signal an I/O error.
5331 * Please note that the compressed data stream is not checksummed, so
5332 * if the underlying device is experiencing data corruption, we may feed
5333 * corrupt data to the decompressor, so the decompressor needs to be
5334 * able to handle this situation (LZ4 does).
5337 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
5339 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
5341 if (zio->io_error != 0) {
5343 * An io error has occured, just restore the original io
5344 * size in preparation for a main pool read.
5346 zio->io_orig_size = zio->io_size = hdr->b_size;
5350 if (c == ZIO_COMPRESS_EMPTY) {
5352 * An empty buffer results in a null zio, which means we
5353 * need to fill its io_data after we're done restoring the
5354 * buffer's contents.
5356 ASSERT(hdr->b_buf != NULL);
5357 bzero(hdr->b_buf->b_data, hdr->b_size);
5358 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data;
5360 ASSERT(zio->io_data != NULL);
5362 * We copy the compressed data from the start of the arc buffer
5363 * (the zio_read will have pulled in only what we need, the
5364 * rest is garbage which we will overwrite at decompression)
5365 * and then decompress back to the ARC data buffer. This way we
5366 * can minimize copying by simply decompressing back over the
5367 * original compressed data (rather than decompressing to an
5368 * aux buffer and then copying back the uncompressed buffer,
5369 * which is likely to be much larger).
5374 csize = zio->io_size;
5375 cdata = zio_data_buf_alloc(csize);
5376 bcopy(zio->io_data, cdata, csize);
5377 if (zio_decompress_data(c, cdata, zio->io_data, csize,
5379 zio->io_error = EIO;
5380 zio_data_buf_free(cdata, csize);
5383 /* Restore the expected uncompressed IO size. */
5384 zio->io_orig_size = zio->io_size = hdr->b_size;
5388 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
5389 * This buffer serves as a temporary holder of compressed data while
5390 * the buffer entry is being written to an l2arc device. Once that is
5391 * done, we can dispose of it.
5394 l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
5396 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
5398 if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) {
5400 * If the data was compressed, then we've allocated a
5401 * temporary buffer for it, so now we need to release it.
5403 ASSERT(l2hdr->b_tmp_cdata != NULL);
5404 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
5406 l2hdr->b_tmp_cdata = NULL;
5410 * This thread feeds the L2ARC at regular intervals. This is the beating
5411 * heart of the L2ARC.
5414 l2arc_feed_thread(void *dummy __unused)
5419 uint64_t size, wrote;
5420 clock_t begin, next = ddi_get_lbolt();
5421 boolean_t headroom_boost = B_FALSE;
5423 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
5425 mutex_enter(&l2arc_feed_thr_lock);
5427 while (l2arc_thread_exit == 0) {
5428 CALLB_CPR_SAFE_BEGIN(&cpr);
5429 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
5430 next - ddi_get_lbolt());
5431 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
5432 next = ddi_get_lbolt() + hz;
5435 * Quick check for L2ARC devices.
5437 mutex_enter(&l2arc_dev_mtx);
5438 if (l2arc_ndev == 0) {
5439 mutex_exit(&l2arc_dev_mtx);
5442 mutex_exit(&l2arc_dev_mtx);
5443 begin = ddi_get_lbolt();
5446 * This selects the next l2arc device to write to, and in
5447 * doing so the next spa to feed from: dev->l2ad_spa. This
5448 * will return NULL if there are now no l2arc devices or if
5449 * they are all faulted.
5451 * If a device is returned, its spa's config lock is also
5452 * held to prevent device removal. l2arc_dev_get_next()
5453 * will grab and release l2arc_dev_mtx.
5455 if ((dev = l2arc_dev_get_next()) == NULL)
5458 spa = dev->l2ad_spa;
5459 ASSERT(spa != NULL);
5462 * If the pool is read-only then force the feed thread to
5463 * sleep a little longer.
5465 if (!spa_writeable(spa)) {
5466 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
5467 spa_config_exit(spa, SCL_L2ARC, dev);
5472 * Avoid contributing to memory pressure.
5474 if (arc_reclaim_needed()) {
5475 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
5476 spa_config_exit(spa, SCL_L2ARC, dev);
5480 ARCSTAT_BUMP(arcstat_l2_feeds);
5482 size = l2arc_write_size();
5485 * Evict L2ARC buffers that will be overwritten.
5487 l2arc_evict(dev, size, B_FALSE);
5490 * Write ARC buffers.
5492 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
5495 * Calculate interval between writes.
5497 next = l2arc_write_interval(begin, size, wrote);
5498 spa_config_exit(spa, SCL_L2ARC, dev);
5501 l2arc_thread_exit = 0;
5502 cv_broadcast(&l2arc_feed_thr_cv);
5503 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
5508 l2arc_vdev_present(vdev_t *vd)
5512 mutex_enter(&l2arc_dev_mtx);
5513 for (dev = list_head(l2arc_dev_list); dev != NULL;
5514 dev = list_next(l2arc_dev_list, dev)) {
5515 if (dev->l2ad_vdev == vd)
5518 mutex_exit(&l2arc_dev_mtx);
5520 return (dev != NULL);
5524 * Add a vdev for use by the L2ARC. By this point the spa has already
5525 * validated the vdev and opened it.
5528 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
5530 l2arc_dev_t *adddev;
5532 ASSERT(!l2arc_vdev_present(vd));
5534 vdev_ashift_optimize(vd);
5537 * Create a new l2arc device entry.
5539 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
5540 adddev->l2ad_spa = spa;
5541 adddev->l2ad_vdev = vd;
5542 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
5543 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
5544 adddev->l2ad_hand = adddev->l2ad_start;
5545 adddev->l2ad_evict = adddev->l2ad_start;
5546 adddev->l2ad_first = B_TRUE;
5547 adddev->l2ad_writing = B_FALSE;
5550 * This is a list of all ARC buffers that are still valid on the
5553 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
5554 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
5555 offsetof(arc_buf_hdr_t, b_l2node));
5557 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
5560 * Add device to global list
5562 mutex_enter(&l2arc_dev_mtx);
5563 list_insert_head(l2arc_dev_list, adddev);
5564 atomic_inc_64(&l2arc_ndev);
5565 mutex_exit(&l2arc_dev_mtx);
5569 * Remove a vdev from the L2ARC.
5572 l2arc_remove_vdev(vdev_t *vd)
5574 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
5577 * Find the device by vdev
5579 mutex_enter(&l2arc_dev_mtx);
5580 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
5581 nextdev = list_next(l2arc_dev_list, dev);
5582 if (vd == dev->l2ad_vdev) {
5587 ASSERT(remdev != NULL);
5590 * Remove device from global list
5592 list_remove(l2arc_dev_list, remdev);
5593 l2arc_dev_last = NULL; /* may have been invalidated */
5594 atomic_dec_64(&l2arc_ndev);
5595 mutex_exit(&l2arc_dev_mtx);
5598 * Clear all buflists and ARC references. L2ARC device flush.
5600 l2arc_evict(remdev, 0, B_TRUE);
5601 list_destroy(remdev->l2ad_buflist);
5602 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
5603 kmem_free(remdev, sizeof (l2arc_dev_t));
5609 l2arc_thread_exit = 0;
5611 l2arc_writes_sent = 0;
5612 l2arc_writes_done = 0;
5614 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
5615 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
5616 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
5617 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
5618 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
5620 l2arc_dev_list = &L2ARC_dev_list;
5621 l2arc_free_on_write = &L2ARC_free_on_write;
5622 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
5623 offsetof(l2arc_dev_t, l2ad_node));
5624 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
5625 offsetof(l2arc_data_free_t, l2df_list_node));
5632 * This is called from dmu_fini(), which is called from spa_fini();
5633 * Because of this, we can assume that all l2arc devices have
5634 * already been removed when the pools themselves were removed.
5637 l2arc_do_free_on_write();
5639 mutex_destroy(&l2arc_feed_thr_lock);
5640 cv_destroy(&l2arc_feed_thr_cv);
5641 mutex_destroy(&l2arc_dev_mtx);
5642 mutex_destroy(&l2arc_buflist_mtx);
5643 mutex_destroy(&l2arc_free_on_write_mtx);
5645 list_destroy(l2arc_dev_list);
5646 list_destroy(l2arc_free_on_write);
5652 if (!(spa_mode_global & FWRITE))
5655 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5656 TS_RUN, minclsyspri);
5662 if (!(spa_mode_global & FWRITE))
5665 mutex_enter(&l2arc_feed_thr_lock);
5666 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5667 l2arc_thread_exit = 1;
5668 while (l2arc_thread_exit != 0)
5669 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5670 mutex_exit(&l2arc_feed_thr_lock);