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>
144 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
145 boolean_t arc_watch = B_FALSE;
150 static kmutex_t arc_reclaim_thr_lock;
151 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
152 static uint8_t arc_thread_exit;
154 #define ARC_REDUCE_DNLC_PERCENT 3
155 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
157 typedef enum arc_reclaim_strategy {
158 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
159 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
160 } arc_reclaim_strategy_t;
163 * The number of iterations through arc_evict_*() before we
164 * drop & reacquire the lock.
166 int arc_evict_iterations = 100;
168 /* number of seconds before growing cache again */
169 static int arc_grow_retry = 60;
171 /* shift of arc_c for calculating both min and max arc_p */
172 static int arc_p_min_shift = 4;
174 /* log2(fraction of arc to reclaim) */
175 static int arc_shrink_shift = 5;
178 * minimum lifespan of a prefetch block in clock ticks
179 * (initialized in arc_init())
181 static int arc_min_prefetch_lifespan;
184 * If this percent of memory is free, don't throttle.
186 int arc_lotsfree_percent = 10;
189 extern int zfs_prefetch_disable;
192 * The arc has filled available memory and has now warmed up.
194 static boolean_t arc_warm;
197 * These tunables are for performance analysis.
199 uint64_t zfs_arc_max;
200 uint64_t zfs_arc_min;
201 uint64_t zfs_arc_meta_limit = 0;
202 int zfs_arc_grow_retry = 0;
203 int zfs_arc_shrink_shift = 0;
204 int zfs_arc_p_min_shift = 0;
205 int zfs_disable_dup_eviction = 0;
206 uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
208 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
209 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
210 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
211 TUNABLE_QUAD("vfs.zfs.arc_average_blocksize", &zfs_arc_average_blocksize);
212 SYSCTL_DECL(_vfs_zfs);
213 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
215 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
217 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
218 &zfs_arc_average_blocksize, 0,
219 "ARC average blocksize");
222 * Note that buffers can be in one of 6 states:
223 * ARC_anon - anonymous (discussed below)
224 * ARC_mru - recently used, currently cached
225 * ARC_mru_ghost - recentely used, no longer in cache
226 * ARC_mfu - frequently used, currently cached
227 * ARC_mfu_ghost - frequently used, no longer in cache
228 * ARC_l2c_only - exists in L2ARC but not other states
229 * When there are no active references to the buffer, they are
230 * are linked onto a list in one of these arc states. These are
231 * the only buffers that can be evicted or deleted. Within each
232 * state there are multiple lists, one for meta-data and one for
233 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
234 * etc.) is tracked separately so that it can be managed more
235 * explicitly: favored over data, limited explicitly.
237 * Anonymous buffers are buffers that are not associated with
238 * a DVA. These are buffers that hold dirty block copies
239 * before they are written to stable storage. By definition,
240 * they are "ref'd" and are considered part of arc_mru
241 * that cannot be freed. Generally, they will aquire a DVA
242 * as they are written and migrate onto the arc_mru list.
244 * The ARC_l2c_only state is for buffers that are in the second
245 * level ARC but no longer in any of the ARC_m* lists. The second
246 * level ARC itself may also contain buffers that are in any of
247 * the ARC_m* states - meaning that a buffer can exist in two
248 * places. The reason for the ARC_l2c_only state is to keep the
249 * buffer header in the hash table, so that reads that hit the
250 * second level ARC benefit from these fast lookups.
253 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
257 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
262 * must be power of two for mask use to work
265 #define ARC_BUFC_NUMDATALISTS 16
266 #define ARC_BUFC_NUMMETADATALISTS 16
267 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
269 typedef struct arc_state {
270 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
271 uint64_t arcs_size; /* total amount of data in this state */
272 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
273 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
276 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
279 static arc_state_t ARC_anon;
280 static arc_state_t ARC_mru;
281 static arc_state_t ARC_mru_ghost;
282 static arc_state_t ARC_mfu;
283 static arc_state_t ARC_mfu_ghost;
284 static arc_state_t ARC_l2c_only;
286 typedef struct arc_stats {
287 kstat_named_t arcstat_hits;
288 kstat_named_t arcstat_misses;
289 kstat_named_t arcstat_demand_data_hits;
290 kstat_named_t arcstat_demand_data_misses;
291 kstat_named_t arcstat_demand_metadata_hits;
292 kstat_named_t arcstat_demand_metadata_misses;
293 kstat_named_t arcstat_prefetch_data_hits;
294 kstat_named_t arcstat_prefetch_data_misses;
295 kstat_named_t arcstat_prefetch_metadata_hits;
296 kstat_named_t arcstat_prefetch_metadata_misses;
297 kstat_named_t arcstat_mru_hits;
298 kstat_named_t arcstat_mru_ghost_hits;
299 kstat_named_t arcstat_mfu_hits;
300 kstat_named_t arcstat_mfu_ghost_hits;
301 kstat_named_t arcstat_allocated;
302 kstat_named_t arcstat_deleted;
303 kstat_named_t arcstat_stolen;
304 kstat_named_t arcstat_recycle_miss;
306 * Number of buffers that could not be evicted because the hash lock
307 * was held by another thread. The lock may not necessarily be held
308 * by something using the same buffer, since hash locks are shared
309 * by multiple buffers.
311 kstat_named_t arcstat_mutex_miss;
313 * Number of buffers skipped because they have I/O in progress, are
314 * indrect prefetch buffers that have not lived long enough, or are
315 * not from the spa we're trying to evict from.
317 kstat_named_t arcstat_evict_skip;
318 kstat_named_t arcstat_evict_l2_cached;
319 kstat_named_t arcstat_evict_l2_eligible;
320 kstat_named_t arcstat_evict_l2_ineligible;
321 kstat_named_t arcstat_hash_elements;
322 kstat_named_t arcstat_hash_elements_max;
323 kstat_named_t arcstat_hash_collisions;
324 kstat_named_t arcstat_hash_chains;
325 kstat_named_t arcstat_hash_chain_max;
326 kstat_named_t arcstat_p;
327 kstat_named_t arcstat_c;
328 kstat_named_t arcstat_c_min;
329 kstat_named_t arcstat_c_max;
330 kstat_named_t arcstat_size;
331 kstat_named_t arcstat_hdr_size;
332 kstat_named_t arcstat_data_size;
333 kstat_named_t arcstat_other_size;
334 kstat_named_t arcstat_l2_hits;
335 kstat_named_t arcstat_l2_misses;
336 kstat_named_t arcstat_l2_feeds;
337 kstat_named_t arcstat_l2_rw_clash;
338 kstat_named_t arcstat_l2_read_bytes;
339 kstat_named_t arcstat_l2_write_bytes;
340 kstat_named_t arcstat_l2_writes_sent;
341 kstat_named_t arcstat_l2_writes_done;
342 kstat_named_t arcstat_l2_writes_error;
343 kstat_named_t arcstat_l2_writes_hdr_miss;
344 kstat_named_t arcstat_l2_evict_lock_retry;
345 kstat_named_t arcstat_l2_evict_reading;
346 kstat_named_t arcstat_l2_free_on_write;
347 kstat_named_t arcstat_l2_cdata_free_on_write;
348 kstat_named_t arcstat_l2_abort_lowmem;
349 kstat_named_t arcstat_l2_cksum_bad;
350 kstat_named_t arcstat_l2_io_error;
351 kstat_named_t arcstat_l2_size;
352 kstat_named_t arcstat_l2_asize;
353 kstat_named_t arcstat_l2_hdr_size;
354 kstat_named_t arcstat_l2_compress_successes;
355 kstat_named_t arcstat_l2_compress_zeros;
356 kstat_named_t arcstat_l2_compress_failures;
357 kstat_named_t arcstat_l2_write_trylock_fail;
358 kstat_named_t arcstat_l2_write_passed_headroom;
359 kstat_named_t arcstat_l2_write_spa_mismatch;
360 kstat_named_t arcstat_l2_write_in_l2;
361 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
362 kstat_named_t arcstat_l2_write_not_cacheable;
363 kstat_named_t arcstat_l2_write_full;
364 kstat_named_t arcstat_l2_write_buffer_iter;
365 kstat_named_t arcstat_l2_write_pios;
366 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
367 kstat_named_t arcstat_l2_write_buffer_list_iter;
368 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
369 kstat_named_t arcstat_memory_throttle_count;
370 kstat_named_t arcstat_duplicate_buffers;
371 kstat_named_t arcstat_duplicate_buffers_size;
372 kstat_named_t arcstat_duplicate_reads;
375 static arc_stats_t arc_stats = {
376 { "hits", KSTAT_DATA_UINT64 },
377 { "misses", KSTAT_DATA_UINT64 },
378 { "demand_data_hits", KSTAT_DATA_UINT64 },
379 { "demand_data_misses", KSTAT_DATA_UINT64 },
380 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
381 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
382 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
383 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
384 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
385 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
386 { "mru_hits", KSTAT_DATA_UINT64 },
387 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
388 { "mfu_hits", KSTAT_DATA_UINT64 },
389 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
390 { "allocated", KSTAT_DATA_UINT64 },
391 { "deleted", KSTAT_DATA_UINT64 },
392 { "stolen", KSTAT_DATA_UINT64 },
393 { "recycle_miss", KSTAT_DATA_UINT64 },
394 { "mutex_miss", KSTAT_DATA_UINT64 },
395 { "evict_skip", KSTAT_DATA_UINT64 },
396 { "evict_l2_cached", KSTAT_DATA_UINT64 },
397 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
398 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
399 { "hash_elements", KSTAT_DATA_UINT64 },
400 { "hash_elements_max", KSTAT_DATA_UINT64 },
401 { "hash_collisions", KSTAT_DATA_UINT64 },
402 { "hash_chains", KSTAT_DATA_UINT64 },
403 { "hash_chain_max", KSTAT_DATA_UINT64 },
404 { "p", KSTAT_DATA_UINT64 },
405 { "c", KSTAT_DATA_UINT64 },
406 { "c_min", KSTAT_DATA_UINT64 },
407 { "c_max", KSTAT_DATA_UINT64 },
408 { "size", KSTAT_DATA_UINT64 },
409 { "hdr_size", KSTAT_DATA_UINT64 },
410 { "data_size", KSTAT_DATA_UINT64 },
411 { "other_size", KSTAT_DATA_UINT64 },
412 { "l2_hits", KSTAT_DATA_UINT64 },
413 { "l2_misses", KSTAT_DATA_UINT64 },
414 { "l2_feeds", KSTAT_DATA_UINT64 },
415 { "l2_rw_clash", KSTAT_DATA_UINT64 },
416 { "l2_read_bytes", KSTAT_DATA_UINT64 },
417 { "l2_write_bytes", KSTAT_DATA_UINT64 },
418 { "l2_writes_sent", KSTAT_DATA_UINT64 },
419 { "l2_writes_done", KSTAT_DATA_UINT64 },
420 { "l2_writes_error", KSTAT_DATA_UINT64 },
421 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
422 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
423 { "l2_evict_reading", KSTAT_DATA_UINT64 },
424 { "l2_free_on_write", KSTAT_DATA_UINT64 },
425 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 },
426 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
427 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
428 { "l2_io_error", KSTAT_DATA_UINT64 },
429 { "l2_size", KSTAT_DATA_UINT64 },
430 { "l2_asize", KSTAT_DATA_UINT64 },
431 { "l2_hdr_size", KSTAT_DATA_UINT64 },
432 { "l2_compress_successes", KSTAT_DATA_UINT64 },
433 { "l2_compress_zeros", KSTAT_DATA_UINT64 },
434 { "l2_compress_failures", KSTAT_DATA_UINT64 },
435 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
436 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
437 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
438 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
439 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
440 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
441 { "l2_write_full", KSTAT_DATA_UINT64 },
442 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
443 { "l2_write_pios", KSTAT_DATA_UINT64 },
444 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
445 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
446 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
447 { "memory_throttle_count", KSTAT_DATA_UINT64 },
448 { "duplicate_buffers", KSTAT_DATA_UINT64 },
449 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
450 { "duplicate_reads", KSTAT_DATA_UINT64 }
453 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
455 #define ARCSTAT_INCR(stat, val) \
456 atomic_add_64(&arc_stats.stat.value.ui64, (val))
458 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
459 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
461 #define ARCSTAT_MAX(stat, val) { \
463 while ((val) > (m = arc_stats.stat.value.ui64) && \
464 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
468 #define ARCSTAT_MAXSTAT(stat) \
469 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
472 * We define a macro to allow ARC hits/misses to be easily broken down by
473 * two separate conditions, giving a total of four different subtypes for
474 * each of hits and misses (so eight statistics total).
476 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
479 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
481 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
485 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
487 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
492 static arc_state_t *arc_anon;
493 static arc_state_t *arc_mru;
494 static arc_state_t *arc_mru_ghost;
495 static arc_state_t *arc_mfu;
496 static arc_state_t *arc_mfu_ghost;
497 static arc_state_t *arc_l2c_only;
500 * There are several ARC variables that are critical to export as kstats --
501 * but we don't want to have to grovel around in the kstat whenever we wish to
502 * manipulate them. For these variables, we therefore define them to be in
503 * terms of the statistic variable. This assures that we are not introducing
504 * the possibility of inconsistency by having shadow copies of the variables,
505 * while still allowing the code to be readable.
507 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
508 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
509 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
510 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
511 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
513 #define L2ARC_IS_VALID_COMPRESS(_c_) \
514 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
516 static int arc_no_grow; /* Don't try to grow cache size */
517 static uint64_t arc_tempreserve;
518 static uint64_t arc_loaned_bytes;
519 static uint64_t arc_meta_used;
520 static uint64_t arc_meta_limit;
521 static uint64_t arc_meta_max = 0;
522 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RD, &arc_meta_used, 0,
523 "ARC metadata used");
524 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RW, &arc_meta_limit, 0,
525 "ARC metadata limit");
527 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
529 typedef struct arc_callback arc_callback_t;
531 struct arc_callback {
533 arc_done_func_t *acb_done;
535 zio_t *acb_zio_dummy;
536 arc_callback_t *acb_next;
539 typedef struct arc_write_callback arc_write_callback_t;
541 struct arc_write_callback {
543 arc_done_func_t *awcb_ready;
544 arc_done_func_t *awcb_physdone;
545 arc_done_func_t *awcb_done;
550 /* protected by hash lock */
555 kmutex_t b_freeze_lock;
556 zio_cksum_t *b_freeze_cksum;
559 arc_buf_hdr_t *b_hash_next;
564 arc_callback_t *b_acb;
568 arc_buf_contents_t b_type;
572 /* protected by arc state mutex */
573 arc_state_t *b_state;
574 list_node_t b_arc_node;
576 /* updated atomically */
577 clock_t b_arc_access;
579 /* self protecting */
582 l2arc_buf_hdr_t *b_l2hdr;
583 list_node_t b_l2node;
586 static arc_buf_t *arc_eviction_list;
587 static kmutex_t arc_eviction_mtx;
588 static arc_buf_hdr_t arc_eviction_hdr;
589 static void arc_get_data_buf(arc_buf_t *buf);
590 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
591 static int arc_evict_needed(arc_buf_contents_t type);
592 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
594 static void arc_buf_watch(arc_buf_t *buf);
597 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
599 #define GHOST_STATE(state) \
600 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
601 (state) == arc_l2c_only)
604 * Private ARC flags. These flags are private ARC only flags that will show up
605 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
606 * be passed in as arc_flags in things like arc_read. However, these flags
607 * should never be passed and should only be set by ARC code. When adding new
608 * public flags, make sure not to smash the private ones.
611 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
612 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
613 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
614 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
615 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
616 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
617 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
618 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
619 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
620 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
622 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
623 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
624 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
625 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
626 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
627 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
628 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
629 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
630 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
631 (hdr)->b_l2hdr != NULL)
632 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
633 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
634 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
640 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
641 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
644 * Hash table routines
647 #define HT_LOCK_PAD CACHE_LINE_SIZE
652 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
656 #define BUF_LOCKS 256
657 typedef struct buf_hash_table {
659 arc_buf_hdr_t **ht_table;
660 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
663 static buf_hash_table_t buf_hash_table;
665 #define BUF_HASH_INDEX(spa, dva, birth) \
666 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
667 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
668 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
669 #define HDR_LOCK(hdr) \
670 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
672 uint64_t zfs_crc64_table[256];
678 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
679 #define L2ARC_HEADROOM 2 /* num of writes */
681 * If we discover during ARC scan any buffers to be compressed, we boost
682 * our headroom for the next scanning cycle by this percentage multiple.
684 #define L2ARC_HEADROOM_BOOST 200
685 #define L2ARC_FEED_SECS 1 /* caching interval secs */
686 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
688 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
689 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
691 /* L2ARC Performance Tunables */
692 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
693 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
694 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
695 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
696 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
697 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
698 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
699 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
700 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
702 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
703 &l2arc_write_max, 0, "max write size");
704 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
705 &l2arc_write_boost, 0, "extra write during warmup");
706 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
707 &l2arc_headroom, 0, "number of dev writes");
708 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
709 &l2arc_feed_secs, 0, "interval seconds");
710 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
711 &l2arc_feed_min_ms, 0, "min interval milliseconds");
713 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
714 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
715 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
716 &l2arc_feed_again, 0, "turbo warmup");
717 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
718 &l2arc_norw, 0, "no reads during writes");
720 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
721 &ARC_anon.arcs_size, 0, "size of anonymous state");
722 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
723 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
724 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
725 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
727 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
728 &ARC_mru.arcs_size, 0, "size of mru state");
729 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
730 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
731 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
732 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
734 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
735 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
736 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
737 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
738 "size of metadata in mru ghost state");
739 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
740 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
741 "size of data in mru ghost state");
743 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
744 &ARC_mfu.arcs_size, 0, "size of mfu state");
745 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
746 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
747 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
748 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
750 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
751 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
752 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
753 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
754 "size of metadata in mfu ghost state");
755 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
756 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
757 "size of data in mfu ghost state");
759 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
760 &ARC_l2c_only.arcs_size, 0, "size of mru state");
765 typedef struct l2arc_dev {
766 vdev_t *l2ad_vdev; /* vdev */
767 spa_t *l2ad_spa; /* spa */
768 uint64_t l2ad_hand; /* next write location */
769 uint64_t l2ad_start; /* first addr on device */
770 uint64_t l2ad_end; /* last addr on device */
771 uint64_t l2ad_evict; /* last addr eviction reached */
772 boolean_t l2ad_first; /* first sweep through */
773 boolean_t l2ad_writing; /* currently writing */
774 list_t *l2ad_buflist; /* buffer list */
775 list_node_t l2ad_node; /* device list node */
778 static list_t L2ARC_dev_list; /* device list */
779 static list_t *l2arc_dev_list; /* device list pointer */
780 static kmutex_t l2arc_dev_mtx; /* device list mutex */
781 static l2arc_dev_t *l2arc_dev_last; /* last device used */
782 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
783 static list_t L2ARC_free_on_write; /* free after write buf list */
784 static list_t *l2arc_free_on_write; /* free after write list ptr */
785 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
786 static uint64_t l2arc_ndev; /* number of devices */
788 typedef struct l2arc_read_callback {
789 arc_buf_t *l2rcb_buf; /* read buffer */
790 spa_t *l2rcb_spa; /* spa */
791 blkptr_t l2rcb_bp; /* original blkptr */
792 zbookmark_phys_t l2rcb_zb; /* original bookmark */
793 int l2rcb_flags; /* original flags */
794 enum zio_compress l2rcb_compress; /* applied compress */
795 } l2arc_read_callback_t;
797 typedef struct l2arc_write_callback {
798 l2arc_dev_t *l2wcb_dev; /* device info */
799 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
800 } l2arc_write_callback_t;
802 struct l2arc_buf_hdr {
803 /* protected by arc_buf_hdr mutex */
804 l2arc_dev_t *b_dev; /* L2ARC device */
805 uint64_t b_daddr; /* disk address, offset byte */
806 /* compression applied to buffer data */
807 enum zio_compress b_compress;
808 /* real alloc'd buffer size depending on b_compress applied */
810 /* temporary buffer holder for in-flight compressed data */
814 typedef struct l2arc_data_free {
815 /* protected by l2arc_free_on_write_mtx */
818 void (*l2df_func)(void *, size_t);
819 list_node_t l2df_list_node;
822 static kmutex_t l2arc_feed_thr_lock;
823 static kcondvar_t l2arc_feed_thr_cv;
824 static uint8_t l2arc_thread_exit;
826 static void l2arc_read_done(zio_t *zio);
827 static void l2arc_hdr_stat_add(void);
828 static void l2arc_hdr_stat_remove(void);
830 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
831 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
832 enum zio_compress c);
833 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
836 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
838 uint8_t *vdva = (uint8_t *)dva;
839 uint64_t crc = -1ULL;
842 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
844 for (i = 0; i < sizeof (dva_t); i++)
845 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
847 crc ^= (spa>>8) ^ birth;
852 #define BUF_EMPTY(buf) \
853 ((buf)->b_dva.dva_word[0] == 0 && \
854 (buf)->b_dva.dva_word[1] == 0 && \
855 (buf)->b_cksum0 == 0)
857 #define BUF_EQUAL(spa, dva, birth, buf) \
858 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
859 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
860 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
863 buf_discard_identity(arc_buf_hdr_t *hdr)
865 hdr->b_dva.dva_word[0] = 0;
866 hdr->b_dva.dva_word[1] = 0;
871 static arc_buf_hdr_t *
872 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
874 const dva_t *dva = BP_IDENTITY(bp);
875 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
876 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
877 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
880 mutex_enter(hash_lock);
881 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
882 buf = buf->b_hash_next) {
883 if (BUF_EQUAL(spa, dva, birth, buf)) {
888 mutex_exit(hash_lock);
894 * Insert an entry into the hash table. If there is already an element
895 * equal to elem in the hash table, then the already existing element
896 * will be returned and the new element will not be inserted.
897 * Otherwise returns NULL.
899 static arc_buf_hdr_t *
900 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
902 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
903 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
907 ASSERT(!DVA_IS_EMPTY(&buf->b_dva));
908 ASSERT(buf->b_birth != 0);
909 ASSERT(!HDR_IN_HASH_TABLE(buf));
911 mutex_enter(hash_lock);
912 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
913 fbuf = fbuf->b_hash_next, i++) {
914 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
918 buf->b_hash_next = buf_hash_table.ht_table[idx];
919 buf_hash_table.ht_table[idx] = buf;
920 buf->b_flags |= ARC_IN_HASH_TABLE;
922 /* collect some hash table performance data */
924 ARCSTAT_BUMP(arcstat_hash_collisions);
926 ARCSTAT_BUMP(arcstat_hash_chains);
928 ARCSTAT_MAX(arcstat_hash_chain_max, i);
931 ARCSTAT_BUMP(arcstat_hash_elements);
932 ARCSTAT_MAXSTAT(arcstat_hash_elements);
938 buf_hash_remove(arc_buf_hdr_t *buf)
940 arc_buf_hdr_t *fbuf, **bufp;
941 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
943 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
944 ASSERT(HDR_IN_HASH_TABLE(buf));
946 bufp = &buf_hash_table.ht_table[idx];
947 while ((fbuf = *bufp) != buf) {
948 ASSERT(fbuf != NULL);
949 bufp = &fbuf->b_hash_next;
951 *bufp = buf->b_hash_next;
952 buf->b_hash_next = NULL;
953 buf->b_flags &= ~ARC_IN_HASH_TABLE;
955 /* collect some hash table performance data */
956 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
958 if (buf_hash_table.ht_table[idx] &&
959 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
960 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
964 * Global data structures and functions for the buf kmem cache.
966 static kmem_cache_t *hdr_cache;
967 static kmem_cache_t *buf_cache;
974 kmem_free(buf_hash_table.ht_table,
975 (buf_hash_table.ht_mask + 1) * sizeof (void *));
976 for (i = 0; i < BUF_LOCKS; i++)
977 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
978 kmem_cache_destroy(hdr_cache);
979 kmem_cache_destroy(buf_cache);
983 * Constructor callback - called when the cache is empty
984 * and a new buf is requested.
988 hdr_cons(void *vbuf, void *unused, int kmflag)
990 arc_buf_hdr_t *buf = vbuf;
992 bzero(buf, sizeof (arc_buf_hdr_t));
993 refcount_create(&buf->b_refcnt);
994 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
995 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
996 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1003 buf_cons(void *vbuf, void *unused, int kmflag)
1005 arc_buf_t *buf = vbuf;
1007 bzero(buf, sizeof (arc_buf_t));
1008 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1009 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1015 * Destructor callback - called when a cached buf is
1016 * no longer required.
1020 hdr_dest(void *vbuf, void *unused)
1022 arc_buf_hdr_t *buf = vbuf;
1024 ASSERT(BUF_EMPTY(buf));
1025 refcount_destroy(&buf->b_refcnt);
1026 cv_destroy(&buf->b_cv);
1027 mutex_destroy(&buf->b_freeze_lock);
1028 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
1033 buf_dest(void *vbuf, void *unused)
1035 arc_buf_t *buf = vbuf;
1037 mutex_destroy(&buf->b_evict_lock);
1038 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1042 * Reclaim callback -- invoked when memory is low.
1046 hdr_recl(void *unused)
1048 dprintf("hdr_recl called\n");
1050 * umem calls the reclaim func when we destroy the buf cache,
1051 * which is after we do arc_fini().
1054 cv_signal(&arc_reclaim_thr_cv);
1061 uint64_t hsize = 1ULL << 12;
1065 * The hash table is big enough to fill all of physical memory
1066 * with an average block size of zfs_arc_average_blocksize (default 8K).
1067 * By default, the table will take up
1068 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1070 while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
1073 buf_hash_table.ht_mask = hsize - 1;
1074 buf_hash_table.ht_table =
1075 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1076 if (buf_hash_table.ht_table == NULL) {
1077 ASSERT(hsize > (1ULL << 8));
1082 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
1083 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
1084 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1085 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1087 for (i = 0; i < 256; i++)
1088 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1089 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1091 for (i = 0; i < BUF_LOCKS; i++) {
1092 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1093 NULL, MUTEX_DEFAULT, NULL);
1097 #define ARC_MINTIME (hz>>4) /* 62 ms */
1100 arc_cksum_verify(arc_buf_t *buf)
1104 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1107 mutex_enter(&buf->b_hdr->b_freeze_lock);
1108 if (buf->b_hdr->b_freeze_cksum == NULL ||
1109 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1110 mutex_exit(&buf->b_hdr->b_freeze_lock);
1113 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1114 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1115 panic("buffer modified while frozen!");
1116 mutex_exit(&buf->b_hdr->b_freeze_lock);
1120 arc_cksum_equal(arc_buf_t *buf)
1125 mutex_enter(&buf->b_hdr->b_freeze_lock);
1126 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1127 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1128 mutex_exit(&buf->b_hdr->b_freeze_lock);
1134 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1136 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1139 mutex_enter(&buf->b_hdr->b_freeze_lock);
1140 if (buf->b_hdr->b_freeze_cksum != NULL) {
1141 mutex_exit(&buf->b_hdr->b_freeze_lock);
1144 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1145 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1146 buf->b_hdr->b_freeze_cksum);
1147 mutex_exit(&buf->b_hdr->b_freeze_lock);
1150 #endif /* illumos */
1155 typedef struct procctl {
1163 arc_buf_unwatch(arc_buf_t *buf)
1170 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1171 ctl.prwatch.pr_size = 0;
1172 ctl.prwatch.pr_wflags = 0;
1173 result = write(arc_procfd, &ctl, sizeof (ctl));
1174 ASSERT3U(result, ==, sizeof (ctl));
1181 arc_buf_watch(arc_buf_t *buf)
1188 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1189 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1190 ctl.prwatch.pr_wflags = WA_WRITE;
1191 result = write(arc_procfd, &ctl, sizeof (ctl));
1192 ASSERT3U(result, ==, sizeof (ctl));
1196 #endif /* illumos */
1199 arc_buf_thaw(arc_buf_t *buf)
1201 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1202 if (buf->b_hdr->b_state != arc_anon)
1203 panic("modifying non-anon buffer!");
1204 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1205 panic("modifying buffer while i/o in progress!");
1206 arc_cksum_verify(buf);
1209 mutex_enter(&buf->b_hdr->b_freeze_lock);
1210 if (buf->b_hdr->b_freeze_cksum != NULL) {
1211 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1212 buf->b_hdr->b_freeze_cksum = NULL;
1215 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1216 if (buf->b_hdr->b_thawed)
1217 kmem_free(buf->b_hdr->b_thawed, 1);
1218 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1221 mutex_exit(&buf->b_hdr->b_freeze_lock);
1224 arc_buf_unwatch(buf);
1225 #endif /* illumos */
1229 arc_buf_freeze(arc_buf_t *buf)
1231 kmutex_t *hash_lock;
1233 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1236 hash_lock = HDR_LOCK(buf->b_hdr);
1237 mutex_enter(hash_lock);
1239 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1240 buf->b_hdr->b_state == arc_anon);
1241 arc_cksum_compute(buf, B_FALSE);
1242 mutex_exit(hash_lock);
1247 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1249 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1251 if (ab->b_type == ARC_BUFC_METADATA)
1252 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1254 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1255 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1258 *list = &state->arcs_lists[buf_hashid];
1259 *lock = ARCS_LOCK(state, buf_hashid);
1264 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1266 ASSERT(MUTEX_HELD(hash_lock));
1268 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1269 (ab->b_state != arc_anon)) {
1270 uint64_t delta = ab->b_size * ab->b_datacnt;
1271 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1275 get_buf_info(ab, ab->b_state, &list, &lock);
1276 ASSERT(!MUTEX_HELD(lock));
1278 ASSERT(list_link_active(&ab->b_arc_node));
1279 list_remove(list, ab);
1280 if (GHOST_STATE(ab->b_state)) {
1281 ASSERT0(ab->b_datacnt);
1282 ASSERT3P(ab->b_buf, ==, NULL);
1286 ASSERT3U(*size, >=, delta);
1287 atomic_add_64(size, -delta);
1289 /* remove the prefetch flag if we get a reference */
1290 if (ab->b_flags & ARC_PREFETCH)
1291 ab->b_flags &= ~ARC_PREFETCH;
1296 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1299 arc_state_t *state = ab->b_state;
1301 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1302 ASSERT(!GHOST_STATE(state));
1304 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1305 (state != arc_anon)) {
1306 uint64_t *size = &state->arcs_lsize[ab->b_type];
1310 get_buf_info(ab, state, &list, &lock);
1311 ASSERT(!MUTEX_HELD(lock));
1313 ASSERT(!list_link_active(&ab->b_arc_node));
1314 list_insert_head(list, ab);
1315 ASSERT(ab->b_datacnt > 0);
1316 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1323 * Move the supplied buffer to the indicated state. The mutex
1324 * for the buffer must be held by the caller.
1327 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1329 arc_state_t *old_state = ab->b_state;
1330 int64_t refcnt = refcount_count(&ab->b_refcnt);
1331 uint64_t from_delta, to_delta;
1335 ASSERT(MUTEX_HELD(hash_lock));
1336 ASSERT3P(new_state, !=, old_state);
1337 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1338 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1339 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1341 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1344 * If this buffer is evictable, transfer it from the
1345 * old state list to the new state list.
1348 if (old_state != arc_anon) {
1350 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1352 get_buf_info(ab, old_state, &list, &lock);
1353 use_mutex = !MUTEX_HELD(lock);
1357 ASSERT(list_link_active(&ab->b_arc_node));
1358 list_remove(list, ab);
1361 * If prefetching out of the ghost cache,
1362 * we will have a non-zero datacnt.
1364 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1365 /* ghost elements have a ghost size */
1366 ASSERT(ab->b_buf == NULL);
1367 from_delta = ab->b_size;
1369 ASSERT3U(*size, >=, from_delta);
1370 atomic_add_64(size, -from_delta);
1375 if (new_state != arc_anon) {
1377 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1379 get_buf_info(ab, new_state, &list, &lock);
1380 use_mutex = !MUTEX_HELD(lock);
1384 list_insert_head(list, ab);
1386 /* ghost elements have a ghost size */
1387 if (GHOST_STATE(new_state)) {
1388 ASSERT(ab->b_datacnt == 0);
1389 ASSERT(ab->b_buf == NULL);
1390 to_delta = ab->b_size;
1392 atomic_add_64(size, to_delta);
1399 ASSERT(!BUF_EMPTY(ab));
1400 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1401 buf_hash_remove(ab);
1403 /* adjust state sizes */
1405 atomic_add_64(&new_state->arcs_size, to_delta);
1407 ASSERT3U(old_state->arcs_size, >=, from_delta);
1408 atomic_add_64(&old_state->arcs_size, -from_delta);
1410 ab->b_state = new_state;
1412 /* adjust l2arc hdr stats */
1413 if (new_state == arc_l2c_only)
1414 l2arc_hdr_stat_add();
1415 else if (old_state == arc_l2c_only)
1416 l2arc_hdr_stat_remove();
1420 arc_space_consume(uint64_t space, arc_space_type_t type)
1422 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1425 case ARC_SPACE_DATA:
1426 ARCSTAT_INCR(arcstat_data_size, space);
1428 case ARC_SPACE_OTHER:
1429 ARCSTAT_INCR(arcstat_other_size, space);
1431 case ARC_SPACE_HDRS:
1432 ARCSTAT_INCR(arcstat_hdr_size, space);
1434 case ARC_SPACE_L2HDRS:
1435 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1439 atomic_add_64(&arc_meta_used, space);
1440 atomic_add_64(&arc_size, space);
1444 arc_space_return(uint64_t space, arc_space_type_t type)
1446 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1449 case ARC_SPACE_DATA:
1450 ARCSTAT_INCR(arcstat_data_size, -space);
1452 case ARC_SPACE_OTHER:
1453 ARCSTAT_INCR(arcstat_other_size, -space);
1455 case ARC_SPACE_HDRS:
1456 ARCSTAT_INCR(arcstat_hdr_size, -space);
1458 case ARC_SPACE_L2HDRS:
1459 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1463 ASSERT(arc_meta_used >= space);
1464 if (arc_meta_max < arc_meta_used)
1465 arc_meta_max = arc_meta_used;
1466 atomic_add_64(&arc_meta_used, -space);
1467 ASSERT(arc_size >= space);
1468 atomic_add_64(&arc_size, -space);
1472 arc_data_buf_alloc(uint64_t size)
1474 if (arc_evict_needed(ARC_BUFC_DATA))
1475 cv_signal(&arc_reclaim_thr_cv);
1476 atomic_add_64(&arc_size, size);
1477 return (zio_data_buf_alloc(size));
1481 arc_data_buf_free(void *buf, uint64_t size)
1483 zio_data_buf_free(buf, size);
1484 ASSERT(arc_size >= size);
1485 atomic_add_64(&arc_size, -size);
1489 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1494 ASSERT3U(size, >, 0);
1495 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1496 ASSERT(BUF_EMPTY(hdr));
1499 hdr->b_spa = spa_load_guid(spa);
1500 hdr->b_state = arc_anon;
1501 hdr->b_arc_access = 0;
1502 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1505 buf->b_efunc = NULL;
1506 buf->b_private = NULL;
1509 arc_get_data_buf(buf);
1512 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1513 (void) refcount_add(&hdr->b_refcnt, tag);
1518 static char *arc_onloan_tag = "onloan";
1521 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1522 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1523 * buffers must be returned to the arc before they can be used by the DMU or
1527 arc_loan_buf(spa_t *spa, int size)
1531 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1533 atomic_add_64(&arc_loaned_bytes, size);
1538 * Return a loaned arc buffer to the arc.
1541 arc_return_buf(arc_buf_t *buf, void *tag)
1543 arc_buf_hdr_t *hdr = buf->b_hdr;
1545 ASSERT(buf->b_data != NULL);
1546 (void) refcount_add(&hdr->b_refcnt, tag);
1547 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1549 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1552 /* Detach an arc_buf from a dbuf (tag) */
1554 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1558 ASSERT(buf->b_data != NULL);
1560 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1561 (void) refcount_remove(&hdr->b_refcnt, tag);
1562 buf->b_efunc = NULL;
1563 buf->b_private = NULL;
1565 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1569 arc_buf_clone(arc_buf_t *from)
1572 arc_buf_hdr_t *hdr = from->b_hdr;
1573 uint64_t size = hdr->b_size;
1575 ASSERT(hdr->b_state != arc_anon);
1577 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1580 buf->b_efunc = NULL;
1581 buf->b_private = NULL;
1582 buf->b_next = hdr->b_buf;
1584 arc_get_data_buf(buf);
1585 bcopy(from->b_data, buf->b_data, size);
1588 * This buffer already exists in the arc so create a duplicate
1589 * copy for the caller. If the buffer is associated with user data
1590 * then track the size and number of duplicates. These stats will be
1591 * updated as duplicate buffers are created and destroyed.
1593 if (hdr->b_type == ARC_BUFC_DATA) {
1594 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1595 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1597 hdr->b_datacnt += 1;
1602 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1605 kmutex_t *hash_lock;
1608 * Check to see if this buffer is evicted. Callers
1609 * must verify b_data != NULL to know if the add_ref
1612 mutex_enter(&buf->b_evict_lock);
1613 if (buf->b_data == NULL) {
1614 mutex_exit(&buf->b_evict_lock);
1617 hash_lock = HDR_LOCK(buf->b_hdr);
1618 mutex_enter(hash_lock);
1620 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1621 mutex_exit(&buf->b_evict_lock);
1623 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1624 add_reference(hdr, hash_lock, tag);
1625 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1626 arc_access(hdr, hash_lock);
1627 mutex_exit(hash_lock);
1628 ARCSTAT_BUMP(arcstat_hits);
1629 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1630 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1631 data, metadata, hits);
1635 arc_buf_free_on_write(void *data, size_t size,
1636 void (*free_func)(void *, size_t))
1638 l2arc_data_free_t *df;
1640 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1641 df->l2df_data = data;
1642 df->l2df_size = size;
1643 df->l2df_func = free_func;
1644 mutex_enter(&l2arc_free_on_write_mtx);
1645 list_insert_head(l2arc_free_on_write, df);
1646 mutex_exit(&l2arc_free_on_write_mtx);
1650 * Free the arc data buffer. If it is an l2arc write in progress,
1651 * the buffer is placed on l2arc_free_on_write to be freed later.
1654 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1656 arc_buf_hdr_t *hdr = buf->b_hdr;
1658 if (HDR_L2_WRITING(hdr)) {
1659 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
1660 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1662 free_func(buf->b_data, hdr->b_size);
1667 * Free up buf->b_data and if 'remove' is set, then pull the
1668 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
1671 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
1673 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1675 ASSERT(MUTEX_HELD(&l2arc_buflist_mtx));
1677 if (l2hdr->b_tmp_cdata == NULL)
1680 ASSERT(HDR_L2_WRITING(hdr));
1681 arc_buf_free_on_write(l2hdr->b_tmp_cdata, hdr->b_size,
1683 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
1684 l2hdr->b_tmp_cdata = NULL;
1688 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
1692 /* free up data associated with the buf */
1694 arc_state_t *state = buf->b_hdr->b_state;
1695 uint64_t size = buf->b_hdr->b_size;
1696 arc_buf_contents_t type = buf->b_hdr->b_type;
1698 arc_cksum_verify(buf);
1700 arc_buf_unwatch(buf);
1701 #endif /* illumos */
1704 if (type == ARC_BUFC_METADATA) {
1705 arc_buf_data_free(buf, zio_buf_free);
1706 arc_space_return(size, ARC_SPACE_DATA);
1708 ASSERT(type == ARC_BUFC_DATA);
1709 arc_buf_data_free(buf, zio_data_buf_free);
1710 ARCSTAT_INCR(arcstat_data_size, -size);
1711 atomic_add_64(&arc_size, -size);
1714 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1715 uint64_t *cnt = &state->arcs_lsize[type];
1717 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1718 ASSERT(state != arc_anon);
1720 ASSERT3U(*cnt, >=, size);
1721 atomic_add_64(cnt, -size);
1723 ASSERT3U(state->arcs_size, >=, size);
1724 atomic_add_64(&state->arcs_size, -size);
1728 * If we're destroying a duplicate buffer make sure
1729 * that the appropriate statistics are updated.
1731 if (buf->b_hdr->b_datacnt > 1 &&
1732 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1733 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1734 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1736 ASSERT(buf->b_hdr->b_datacnt > 0);
1737 buf->b_hdr->b_datacnt -= 1;
1740 /* only remove the buf if requested */
1744 /* remove the buf from the hdr list */
1745 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1747 *bufp = buf->b_next;
1750 ASSERT(buf->b_efunc == NULL);
1752 /* clean up the buf */
1754 kmem_cache_free(buf_cache, buf);
1758 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1760 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1761 ASSERT3P(hdr->b_state, ==, arc_anon);
1762 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1763 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1765 if (l2hdr != NULL) {
1766 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1768 * To prevent arc_free() and l2arc_evict() from
1769 * attempting to free the same buffer at the same time,
1770 * a FREE_IN_PROGRESS flag is given to arc_free() to
1771 * give it priority. l2arc_evict() can't destroy this
1772 * header while we are waiting on l2arc_buflist_mtx.
1774 * The hdr may be removed from l2ad_buflist before we
1775 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1777 if (!buflist_held) {
1778 mutex_enter(&l2arc_buflist_mtx);
1779 l2hdr = hdr->b_l2hdr;
1782 if (l2hdr != NULL) {
1783 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
1785 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1786 arc_buf_l2_cdata_free(hdr);
1787 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1788 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
1789 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
1790 -l2hdr->b_asize, 0, 0);
1791 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1792 if (hdr->b_state == arc_l2c_only)
1793 l2arc_hdr_stat_remove();
1794 hdr->b_l2hdr = NULL;
1798 mutex_exit(&l2arc_buflist_mtx);
1801 if (!BUF_EMPTY(hdr)) {
1802 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1803 buf_discard_identity(hdr);
1805 while (hdr->b_buf) {
1806 arc_buf_t *buf = hdr->b_buf;
1809 mutex_enter(&arc_eviction_mtx);
1810 mutex_enter(&buf->b_evict_lock);
1811 ASSERT(buf->b_hdr != NULL);
1812 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1813 hdr->b_buf = buf->b_next;
1814 buf->b_hdr = &arc_eviction_hdr;
1815 buf->b_next = arc_eviction_list;
1816 arc_eviction_list = buf;
1817 mutex_exit(&buf->b_evict_lock);
1818 mutex_exit(&arc_eviction_mtx);
1820 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1823 if (hdr->b_freeze_cksum != NULL) {
1824 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1825 hdr->b_freeze_cksum = NULL;
1827 if (hdr->b_thawed) {
1828 kmem_free(hdr->b_thawed, 1);
1829 hdr->b_thawed = NULL;
1832 ASSERT(!list_link_active(&hdr->b_arc_node));
1833 ASSERT3P(hdr->b_hash_next, ==, NULL);
1834 ASSERT3P(hdr->b_acb, ==, NULL);
1835 kmem_cache_free(hdr_cache, hdr);
1839 arc_buf_free(arc_buf_t *buf, void *tag)
1841 arc_buf_hdr_t *hdr = buf->b_hdr;
1842 int hashed = hdr->b_state != arc_anon;
1844 ASSERT(buf->b_efunc == NULL);
1845 ASSERT(buf->b_data != NULL);
1848 kmutex_t *hash_lock = HDR_LOCK(hdr);
1850 mutex_enter(hash_lock);
1852 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1854 (void) remove_reference(hdr, hash_lock, tag);
1855 if (hdr->b_datacnt > 1) {
1856 arc_buf_destroy(buf, FALSE, TRUE);
1858 ASSERT(buf == hdr->b_buf);
1859 ASSERT(buf->b_efunc == NULL);
1860 hdr->b_flags |= ARC_BUF_AVAILABLE;
1862 mutex_exit(hash_lock);
1863 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1866 * We are in the middle of an async write. Don't destroy
1867 * this buffer unless the write completes before we finish
1868 * decrementing the reference count.
1870 mutex_enter(&arc_eviction_mtx);
1871 (void) remove_reference(hdr, NULL, tag);
1872 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1873 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1874 mutex_exit(&arc_eviction_mtx);
1876 arc_hdr_destroy(hdr);
1878 if (remove_reference(hdr, NULL, tag) > 0)
1879 arc_buf_destroy(buf, FALSE, TRUE);
1881 arc_hdr_destroy(hdr);
1886 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1888 arc_buf_hdr_t *hdr = buf->b_hdr;
1889 kmutex_t *hash_lock = HDR_LOCK(hdr);
1890 boolean_t no_callback = (buf->b_efunc == NULL);
1892 if (hdr->b_state == arc_anon) {
1893 ASSERT(hdr->b_datacnt == 1);
1894 arc_buf_free(buf, tag);
1895 return (no_callback);
1898 mutex_enter(hash_lock);
1900 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1901 ASSERT(hdr->b_state != arc_anon);
1902 ASSERT(buf->b_data != NULL);
1904 (void) remove_reference(hdr, hash_lock, tag);
1905 if (hdr->b_datacnt > 1) {
1907 arc_buf_destroy(buf, FALSE, TRUE);
1908 } else if (no_callback) {
1909 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1910 ASSERT(buf->b_efunc == NULL);
1911 hdr->b_flags |= ARC_BUF_AVAILABLE;
1913 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1914 refcount_is_zero(&hdr->b_refcnt));
1915 mutex_exit(hash_lock);
1916 return (no_callback);
1920 arc_buf_size(arc_buf_t *buf)
1922 return (buf->b_hdr->b_size);
1926 * Called from the DMU to determine if the current buffer should be
1927 * evicted. In order to ensure proper locking, the eviction must be initiated
1928 * from the DMU. Return true if the buffer is associated with user data and
1929 * duplicate buffers still exist.
1932 arc_buf_eviction_needed(arc_buf_t *buf)
1935 boolean_t evict_needed = B_FALSE;
1937 if (zfs_disable_dup_eviction)
1940 mutex_enter(&buf->b_evict_lock);
1944 * We are in arc_do_user_evicts(); let that function
1945 * perform the eviction.
1947 ASSERT(buf->b_data == NULL);
1948 mutex_exit(&buf->b_evict_lock);
1950 } else if (buf->b_data == NULL) {
1952 * We have already been added to the arc eviction list;
1953 * recommend eviction.
1955 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1956 mutex_exit(&buf->b_evict_lock);
1960 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1961 evict_needed = B_TRUE;
1963 mutex_exit(&buf->b_evict_lock);
1964 return (evict_needed);
1968 * Evict buffers from list until we've removed the specified number of
1969 * bytes. Move the removed buffers to the appropriate evict state.
1970 * If the recycle flag is set, then attempt to "recycle" a buffer:
1971 * - look for a buffer to evict that is `bytes' long.
1972 * - return the data block from this buffer rather than freeing it.
1973 * This flag is used by callers that are trying to make space for a
1974 * new buffer in a full arc cache.
1976 * This function makes a "best effort". It skips over any buffers
1977 * it can't get a hash_lock on, and so may not catch all candidates.
1978 * It may also return without evicting as much space as requested.
1981 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1982 arc_buf_contents_t type)
1984 arc_state_t *evicted_state;
1985 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1986 int64_t bytes_remaining;
1987 arc_buf_hdr_t *ab, *ab_prev = NULL;
1988 list_t *evicted_list, *list, *evicted_list_start, *list_start;
1989 kmutex_t *lock, *evicted_lock;
1990 kmutex_t *hash_lock;
1991 boolean_t have_lock;
1992 void *stolen = NULL;
1993 arc_buf_hdr_t marker = { 0 };
1995 static int evict_metadata_offset, evict_data_offset;
1996 int i, idx, offset, list_count, lists;
1998 ASSERT(state == arc_mru || state == arc_mfu);
2000 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2002 if (type == ARC_BUFC_METADATA) {
2004 list_count = ARC_BUFC_NUMMETADATALISTS;
2005 list_start = &state->arcs_lists[0];
2006 evicted_list_start = &evicted_state->arcs_lists[0];
2007 idx = evict_metadata_offset;
2009 offset = ARC_BUFC_NUMMETADATALISTS;
2010 list_start = &state->arcs_lists[offset];
2011 evicted_list_start = &evicted_state->arcs_lists[offset];
2012 list_count = ARC_BUFC_NUMDATALISTS;
2013 idx = evict_data_offset;
2015 bytes_remaining = evicted_state->arcs_lsize[type];
2019 list = &list_start[idx];
2020 evicted_list = &evicted_list_start[idx];
2021 lock = ARCS_LOCK(state, (offset + idx));
2022 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
2025 mutex_enter(evicted_lock);
2027 for (ab = list_tail(list); ab; ab = ab_prev) {
2028 ab_prev = list_prev(list, ab);
2029 bytes_remaining -= (ab->b_size * ab->b_datacnt);
2030 /* prefetch buffers have a minimum lifespan */
2031 if (HDR_IO_IN_PROGRESS(ab) ||
2032 (spa && ab->b_spa != spa) ||
2033 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
2034 ddi_get_lbolt() - ab->b_arc_access <
2035 arc_min_prefetch_lifespan)) {
2039 /* "lookahead" for better eviction candidate */
2040 if (recycle && ab->b_size != bytes &&
2041 ab_prev && ab_prev->b_size == bytes)
2044 /* ignore markers */
2049 * It may take a long time to evict all the bufs requested.
2050 * To avoid blocking all arc activity, periodically drop
2051 * the arcs_mtx and give other threads a chance to run
2052 * before reacquiring the lock.
2054 * If we are looking for a buffer to recycle, we are in
2055 * the hot code path, so don't sleep.
2057 if (!recycle && count++ > arc_evict_iterations) {
2058 list_insert_after(list, ab, &marker);
2059 mutex_exit(evicted_lock);
2061 kpreempt(KPREEMPT_SYNC);
2063 mutex_enter(evicted_lock);
2064 ab_prev = list_prev(list, &marker);
2065 list_remove(list, &marker);
2070 hash_lock = HDR_LOCK(ab);
2071 have_lock = MUTEX_HELD(hash_lock);
2072 if (have_lock || mutex_tryenter(hash_lock)) {
2073 ASSERT0(refcount_count(&ab->b_refcnt));
2074 ASSERT(ab->b_datacnt > 0);
2076 arc_buf_t *buf = ab->b_buf;
2077 if (!mutex_tryenter(&buf->b_evict_lock)) {
2082 bytes_evicted += ab->b_size;
2083 if (recycle && ab->b_type == type &&
2084 ab->b_size == bytes &&
2085 !HDR_L2_WRITING(ab)) {
2086 stolen = buf->b_data;
2091 mutex_enter(&arc_eviction_mtx);
2092 arc_buf_destroy(buf,
2093 buf->b_data == stolen, FALSE);
2094 ab->b_buf = buf->b_next;
2095 buf->b_hdr = &arc_eviction_hdr;
2096 buf->b_next = arc_eviction_list;
2097 arc_eviction_list = buf;
2098 mutex_exit(&arc_eviction_mtx);
2099 mutex_exit(&buf->b_evict_lock);
2101 mutex_exit(&buf->b_evict_lock);
2102 arc_buf_destroy(buf,
2103 buf->b_data == stolen, TRUE);
2108 ARCSTAT_INCR(arcstat_evict_l2_cached,
2111 if (l2arc_write_eligible(ab->b_spa, ab)) {
2112 ARCSTAT_INCR(arcstat_evict_l2_eligible,
2116 arcstat_evict_l2_ineligible,
2121 if (ab->b_datacnt == 0) {
2122 arc_change_state(evicted_state, ab, hash_lock);
2123 ASSERT(HDR_IN_HASH_TABLE(ab));
2124 ab->b_flags |= ARC_IN_HASH_TABLE;
2125 ab->b_flags &= ~ARC_BUF_AVAILABLE;
2126 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
2129 mutex_exit(hash_lock);
2130 if (bytes >= 0 && bytes_evicted >= bytes)
2132 if (bytes_remaining > 0) {
2133 mutex_exit(evicted_lock);
2135 idx = ((idx + 1) & (list_count - 1));
2144 mutex_exit(evicted_lock);
2147 idx = ((idx + 1) & (list_count - 1));
2150 if (bytes_evicted < bytes) {
2151 if (lists < list_count)
2154 dprintf("only evicted %lld bytes from %x",
2155 (longlong_t)bytes_evicted, state);
2157 if (type == ARC_BUFC_METADATA)
2158 evict_metadata_offset = idx;
2160 evict_data_offset = idx;
2163 ARCSTAT_INCR(arcstat_evict_skip, skipped);
2166 ARCSTAT_INCR(arcstat_mutex_miss, missed);
2169 * Note: we have just evicted some data into the ghost state,
2170 * potentially putting the ghost size over the desired size. Rather
2171 * that evicting from the ghost list in this hot code path, leave
2172 * this chore to the arc_reclaim_thread().
2176 ARCSTAT_BUMP(arcstat_stolen);
2181 * Remove buffers from list until we've removed the specified number of
2182 * bytes. Destroy the buffers that are removed.
2185 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
2187 arc_buf_hdr_t *ab, *ab_prev;
2188 arc_buf_hdr_t marker = { 0 };
2189 list_t *list, *list_start;
2190 kmutex_t *hash_lock, *lock;
2191 uint64_t bytes_deleted = 0;
2192 uint64_t bufs_skipped = 0;
2194 static int evict_offset;
2195 int list_count, idx = evict_offset;
2196 int offset, lists = 0;
2198 ASSERT(GHOST_STATE(state));
2201 * data lists come after metadata lists
2203 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
2204 list_count = ARC_BUFC_NUMDATALISTS;
2205 offset = ARC_BUFC_NUMMETADATALISTS;
2208 list = &list_start[idx];
2209 lock = ARCS_LOCK(state, idx + offset);
2212 for (ab = list_tail(list); ab; ab = ab_prev) {
2213 ab_prev = list_prev(list, ab);
2214 if (ab->b_type > ARC_BUFC_NUMTYPES)
2215 panic("invalid ab=%p", (void *)ab);
2216 if (spa && ab->b_spa != spa)
2219 /* ignore markers */
2223 hash_lock = HDR_LOCK(ab);
2224 /* caller may be trying to modify this buffer, skip it */
2225 if (MUTEX_HELD(hash_lock))
2229 * It may take a long time to evict all the bufs requested.
2230 * To avoid blocking all arc activity, periodically drop
2231 * the arcs_mtx and give other threads a chance to run
2232 * before reacquiring the lock.
2234 if (count++ > arc_evict_iterations) {
2235 list_insert_after(list, ab, &marker);
2237 kpreempt(KPREEMPT_SYNC);
2239 ab_prev = list_prev(list, &marker);
2240 list_remove(list, &marker);
2244 if (mutex_tryenter(hash_lock)) {
2245 ASSERT(!HDR_IO_IN_PROGRESS(ab));
2246 ASSERT(ab->b_buf == NULL);
2247 ARCSTAT_BUMP(arcstat_deleted);
2248 bytes_deleted += ab->b_size;
2250 if (ab->b_l2hdr != NULL) {
2252 * This buffer is cached on the 2nd Level ARC;
2253 * don't destroy the header.
2255 arc_change_state(arc_l2c_only, ab, hash_lock);
2256 mutex_exit(hash_lock);
2258 arc_change_state(arc_anon, ab, hash_lock);
2259 mutex_exit(hash_lock);
2260 arc_hdr_destroy(ab);
2263 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
2264 if (bytes >= 0 && bytes_deleted >= bytes)
2266 } else if (bytes < 0) {
2268 * Insert a list marker and then wait for the
2269 * hash lock to become available. Once its
2270 * available, restart from where we left off.
2272 list_insert_after(list, ab, &marker);
2274 mutex_enter(hash_lock);
2275 mutex_exit(hash_lock);
2277 ab_prev = list_prev(list, &marker);
2278 list_remove(list, &marker);
2285 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
2288 if (lists < list_count)
2292 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
2293 (bytes < 0 || bytes_deleted < bytes)) {
2294 list_start = &state->arcs_lists[0];
2295 list_count = ARC_BUFC_NUMMETADATALISTS;
2301 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2305 if (bytes_deleted < bytes)
2306 dprintf("only deleted %lld bytes from %p",
2307 (longlong_t)bytes_deleted, state);
2313 int64_t adjustment, delta;
2319 adjustment = MIN((int64_t)(arc_size - arc_c),
2320 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2323 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2324 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2325 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
2326 adjustment -= delta;
2329 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2330 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2331 (void) arc_evict(arc_mru, 0, delta, FALSE,
2339 adjustment = arc_size - arc_c;
2341 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2342 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2343 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
2344 adjustment -= delta;
2347 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2348 int64_t delta = MIN(adjustment,
2349 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2350 (void) arc_evict(arc_mfu, 0, delta, FALSE,
2355 * Adjust ghost lists
2358 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2360 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2361 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2362 arc_evict_ghost(arc_mru_ghost, 0, delta);
2366 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2368 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2369 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2370 arc_evict_ghost(arc_mfu_ghost, 0, delta);
2375 arc_do_user_evicts(void)
2377 static arc_buf_t *tmp_arc_eviction_list;
2380 * Move list over to avoid LOR
2383 mutex_enter(&arc_eviction_mtx);
2384 tmp_arc_eviction_list = arc_eviction_list;
2385 arc_eviction_list = NULL;
2386 mutex_exit(&arc_eviction_mtx);
2388 while (tmp_arc_eviction_list != NULL) {
2389 arc_buf_t *buf = tmp_arc_eviction_list;
2390 tmp_arc_eviction_list = buf->b_next;
2391 mutex_enter(&buf->b_evict_lock);
2393 mutex_exit(&buf->b_evict_lock);
2395 if (buf->b_efunc != NULL)
2396 VERIFY0(buf->b_efunc(buf->b_private));
2398 buf->b_efunc = NULL;
2399 buf->b_private = NULL;
2400 kmem_cache_free(buf_cache, buf);
2403 if (arc_eviction_list != NULL)
2408 * Flush all *evictable* data from the cache for the given spa.
2409 * NOTE: this will not touch "active" (i.e. referenced) data.
2412 arc_flush(spa_t *spa)
2417 guid = spa_load_guid(spa);
2419 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2420 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2424 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2425 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2429 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2430 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2434 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2435 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2440 arc_evict_ghost(arc_mru_ghost, guid, -1);
2441 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2443 mutex_enter(&arc_reclaim_thr_lock);
2444 arc_do_user_evicts();
2445 mutex_exit(&arc_reclaim_thr_lock);
2446 ASSERT(spa || arc_eviction_list == NULL);
2452 if (arc_c > arc_c_min) {
2456 to_free = arc_c >> arc_shrink_shift;
2458 to_free = arc_c >> arc_shrink_shift;
2460 if (arc_c > arc_c_min + to_free)
2461 atomic_add_64(&arc_c, -to_free);
2465 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2466 if (arc_c > arc_size)
2467 arc_c = MAX(arc_size, arc_c_min);
2469 arc_p = (arc_c >> 1);
2470 ASSERT(arc_c >= arc_c_min);
2471 ASSERT((int64_t)arc_p >= 0);
2474 if (arc_size > arc_c)
2478 static int needfree = 0;
2481 arc_reclaim_needed(void)
2490 * Cooperate with pagedaemon when it's time for it to scan
2491 * and reclaim some pages.
2493 if (vm_paging_needed())
2498 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2503 * check that we're out of range of the pageout scanner. It starts to
2504 * schedule paging if freemem is less than lotsfree and needfree.
2505 * lotsfree is the high-water mark for pageout, and needfree is the
2506 * number of needed free pages. We add extra pages here to make sure
2507 * the scanner doesn't start up while we're freeing memory.
2509 if (freemem < lotsfree + needfree + extra)
2513 * check to make sure that swapfs has enough space so that anon
2514 * reservations can still succeed. anon_resvmem() checks that the
2515 * availrmem is greater than swapfs_minfree, and the number of reserved
2516 * swap pages. We also add a bit of extra here just to prevent
2517 * circumstances from getting really dire.
2519 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2524 * If we're on an i386 platform, it's possible that we'll exhaust the
2525 * kernel heap space before we ever run out of available physical
2526 * memory. Most checks of the size of the heap_area compare against
2527 * tune.t_minarmem, which is the minimum available real memory that we
2528 * can have in the system. However, this is generally fixed at 25 pages
2529 * which is so low that it's useless. In this comparison, we seek to
2530 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2531 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2534 if (btop(vmem_size(heap_arena, VMEM_FREE)) <
2535 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
2539 if (kmem_used() > (kmem_size() * 3) / 4)
2544 if (spa_get_random(100) == 0)
2550 extern kmem_cache_t *zio_buf_cache[];
2551 extern kmem_cache_t *zio_data_buf_cache[];
2554 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2557 kmem_cache_t *prev_cache = NULL;
2558 kmem_cache_t *prev_data_cache = NULL;
2561 if (arc_meta_used >= arc_meta_limit) {
2563 * We are exceeding our meta-data cache limit.
2564 * Purge some DNLC entries to release holds on meta-data.
2566 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2570 * Reclaim unused memory from all kmem caches.
2577 * An aggressive reclamation will shrink the cache size as well as
2578 * reap free buffers from the arc kmem caches.
2580 if (strat == ARC_RECLAIM_AGGR)
2583 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2584 if (zio_buf_cache[i] != prev_cache) {
2585 prev_cache = zio_buf_cache[i];
2586 kmem_cache_reap_now(zio_buf_cache[i]);
2588 if (zio_data_buf_cache[i] != prev_data_cache) {
2589 prev_data_cache = zio_data_buf_cache[i];
2590 kmem_cache_reap_now(zio_data_buf_cache[i]);
2593 kmem_cache_reap_now(buf_cache);
2594 kmem_cache_reap_now(hdr_cache);
2598 arc_reclaim_thread(void *dummy __unused)
2600 clock_t growtime = 0;
2601 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2604 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2606 mutex_enter(&arc_reclaim_thr_lock);
2607 while (arc_thread_exit == 0) {
2608 if (arc_reclaim_needed()) {
2611 if (last_reclaim == ARC_RECLAIM_CONS) {
2612 last_reclaim = ARC_RECLAIM_AGGR;
2614 last_reclaim = ARC_RECLAIM_CONS;
2618 last_reclaim = ARC_RECLAIM_AGGR;
2622 /* reset the growth delay for every reclaim */
2623 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2625 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2627 * If needfree is TRUE our vm_lowmem hook
2628 * was called and in that case we must free some
2629 * memory, so switch to aggressive mode.
2632 last_reclaim = ARC_RECLAIM_AGGR;
2634 arc_kmem_reap_now(last_reclaim);
2637 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2638 arc_no_grow = FALSE;
2643 if (arc_eviction_list != NULL)
2644 arc_do_user_evicts();
2653 /* block until needed, or one second, whichever is shorter */
2654 CALLB_CPR_SAFE_BEGIN(&cpr);
2655 (void) cv_timedwait(&arc_reclaim_thr_cv,
2656 &arc_reclaim_thr_lock, hz);
2657 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2660 arc_thread_exit = 0;
2661 cv_broadcast(&arc_reclaim_thr_cv);
2662 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2667 * Adapt arc info given the number of bytes we are trying to add and
2668 * the state that we are comming from. This function is only called
2669 * when we are adding new content to the cache.
2672 arc_adapt(int bytes, arc_state_t *state)
2675 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2677 if (state == arc_l2c_only)
2682 * Adapt the target size of the MRU list:
2683 * - if we just hit in the MRU ghost list, then increase
2684 * the target size of the MRU list.
2685 * - if we just hit in the MFU ghost list, then increase
2686 * the target size of the MFU list by decreasing the
2687 * target size of the MRU list.
2689 if (state == arc_mru_ghost) {
2690 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2691 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2692 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2694 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2695 } else if (state == arc_mfu_ghost) {
2698 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2699 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2700 mult = MIN(mult, 10);
2702 delta = MIN(bytes * mult, arc_p);
2703 arc_p = MAX(arc_p_min, arc_p - delta);
2705 ASSERT((int64_t)arc_p >= 0);
2707 if (arc_reclaim_needed()) {
2708 cv_signal(&arc_reclaim_thr_cv);
2715 if (arc_c >= arc_c_max)
2719 * If we're within (2 * maxblocksize) bytes of the target
2720 * cache size, increment the target cache size
2722 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2723 atomic_add_64(&arc_c, (int64_t)bytes);
2724 if (arc_c > arc_c_max)
2726 else if (state == arc_anon)
2727 atomic_add_64(&arc_p, (int64_t)bytes);
2731 ASSERT((int64_t)arc_p >= 0);
2735 * Check if the cache has reached its limits and eviction is required
2739 arc_evict_needed(arc_buf_contents_t type)
2741 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2747 * If zio data pages are being allocated out of a separate heap segment,
2748 * then enforce that the size of available vmem for this area remains
2749 * above about 1/32nd free.
2751 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2752 vmem_size(zio_arena, VMEM_FREE) <
2753 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2758 if (arc_reclaim_needed())
2761 return (arc_size > arc_c);
2765 * The buffer, supplied as the first argument, needs a data block.
2766 * So, if we are at cache max, determine which cache should be victimized.
2767 * We have the following cases:
2769 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2770 * In this situation if we're out of space, but the resident size of the MFU is
2771 * under the limit, victimize the MFU cache to satisfy this insertion request.
2773 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2774 * Here, we've used up all of the available space for the MRU, so we need to
2775 * evict from our own cache instead. Evict from the set of resident MRU
2778 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2779 * c minus p represents the MFU space in the cache, since p is the size of the
2780 * cache that is dedicated to the MRU. In this situation there's still space on
2781 * the MFU side, so the MRU side needs to be victimized.
2783 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2784 * MFU's resident set is consuming more space than it has been allotted. In
2785 * this situation, we must victimize our own cache, the MFU, for this insertion.
2788 arc_get_data_buf(arc_buf_t *buf)
2790 arc_state_t *state = buf->b_hdr->b_state;
2791 uint64_t size = buf->b_hdr->b_size;
2792 arc_buf_contents_t type = buf->b_hdr->b_type;
2794 arc_adapt(size, state);
2797 * We have not yet reached cache maximum size,
2798 * just allocate a new buffer.
2800 if (!arc_evict_needed(type)) {
2801 if (type == ARC_BUFC_METADATA) {
2802 buf->b_data = zio_buf_alloc(size);
2803 arc_space_consume(size, ARC_SPACE_DATA);
2805 ASSERT(type == ARC_BUFC_DATA);
2806 buf->b_data = zio_data_buf_alloc(size);
2807 ARCSTAT_INCR(arcstat_data_size, size);
2808 atomic_add_64(&arc_size, size);
2814 * If we are prefetching from the mfu ghost list, this buffer
2815 * will end up on the mru list; so steal space from there.
2817 if (state == arc_mfu_ghost)
2818 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2819 else if (state == arc_mru_ghost)
2822 if (state == arc_mru || state == arc_anon) {
2823 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2824 state = (arc_mfu->arcs_lsize[type] >= size &&
2825 arc_p > mru_used) ? arc_mfu : arc_mru;
2828 uint64_t mfu_space = arc_c - arc_p;
2829 state = (arc_mru->arcs_lsize[type] >= size &&
2830 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2832 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2833 if (type == ARC_BUFC_METADATA) {
2834 buf->b_data = zio_buf_alloc(size);
2835 arc_space_consume(size, ARC_SPACE_DATA);
2837 ASSERT(type == ARC_BUFC_DATA);
2838 buf->b_data = zio_data_buf_alloc(size);
2839 ARCSTAT_INCR(arcstat_data_size, size);
2840 atomic_add_64(&arc_size, size);
2842 ARCSTAT_BUMP(arcstat_recycle_miss);
2844 ASSERT(buf->b_data != NULL);
2847 * Update the state size. Note that ghost states have a
2848 * "ghost size" and so don't need to be updated.
2850 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2851 arc_buf_hdr_t *hdr = buf->b_hdr;
2853 atomic_add_64(&hdr->b_state->arcs_size, size);
2854 if (list_link_active(&hdr->b_arc_node)) {
2855 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2856 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2859 * If we are growing the cache, and we are adding anonymous
2860 * data, and we have outgrown arc_p, update arc_p
2862 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2863 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2864 arc_p = MIN(arc_c, arc_p + size);
2866 ARCSTAT_BUMP(arcstat_allocated);
2870 * This routine is called whenever a buffer is accessed.
2871 * NOTE: the hash lock is dropped in this function.
2874 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2878 ASSERT(MUTEX_HELD(hash_lock));
2880 if (buf->b_state == arc_anon) {
2882 * This buffer is not in the cache, and does not
2883 * appear in our "ghost" list. Add the new buffer
2887 ASSERT(buf->b_arc_access == 0);
2888 buf->b_arc_access = ddi_get_lbolt();
2889 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2890 arc_change_state(arc_mru, buf, hash_lock);
2892 } else if (buf->b_state == arc_mru) {
2893 now = ddi_get_lbolt();
2896 * If this buffer is here because of a prefetch, then either:
2897 * - clear the flag if this is a "referencing" read
2898 * (any subsequent access will bump this into the MFU state).
2900 * - move the buffer to the head of the list if this is
2901 * another prefetch (to make it less likely to be evicted).
2903 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2904 if (refcount_count(&buf->b_refcnt) == 0) {
2905 ASSERT(list_link_active(&buf->b_arc_node));
2907 buf->b_flags &= ~ARC_PREFETCH;
2908 ARCSTAT_BUMP(arcstat_mru_hits);
2910 buf->b_arc_access = now;
2915 * This buffer has been "accessed" only once so far,
2916 * but it is still in the cache. Move it to the MFU
2919 if (now > buf->b_arc_access + ARC_MINTIME) {
2921 * More than 125ms have passed since we
2922 * instantiated this buffer. Move it to the
2923 * most frequently used state.
2925 buf->b_arc_access = now;
2926 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2927 arc_change_state(arc_mfu, buf, hash_lock);
2929 ARCSTAT_BUMP(arcstat_mru_hits);
2930 } else if (buf->b_state == arc_mru_ghost) {
2931 arc_state_t *new_state;
2933 * This buffer has been "accessed" recently, but
2934 * was evicted from the cache. Move it to the
2938 if (buf->b_flags & ARC_PREFETCH) {
2939 new_state = arc_mru;
2940 if (refcount_count(&buf->b_refcnt) > 0)
2941 buf->b_flags &= ~ARC_PREFETCH;
2942 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2944 new_state = arc_mfu;
2945 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2948 buf->b_arc_access = ddi_get_lbolt();
2949 arc_change_state(new_state, buf, hash_lock);
2951 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2952 } else if (buf->b_state == arc_mfu) {
2954 * This buffer has been accessed more than once and is
2955 * still in the cache. Keep it in the MFU state.
2957 * NOTE: an add_reference() that occurred when we did
2958 * the arc_read() will have kicked this off the list.
2959 * If it was a prefetch, we will explicitly move it to
2960 * the head of the list now.
2962 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2963 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2964 ASSERT(list_link_active(&buf->b_arc_node));
2966 ARCSTAT_BUMP(arcstat_mfu_hits);
2967 buf->b_arc_access = ddi_get_lbolt();
2968 } else if (buf->b_state == arc_mfu_ghost) {
2969 arc_state_t *new_state = arc_mfu;
2971 * This buffer has been accessed more than once but has
2972 * been evicted from the cache. Move it back to the
2976 if (buf->b_flags & ARC_PREFETCH) {
2978 * This is a prefetch access...
2979 * move this block back to the MRU state.
2981 ASSERT0(refcount_count(&buf->b_refcnt));
2982 new_state = arc_mru;
2985 buf->b_arc_access = ddi_get_lbolt();
2986 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2987 arc_change_state(new_state, buf, hash_lock);
2989 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2990 } else if (buf->b_state == arc_l2c_only) {
2992 * This buffer is on the 2nd Level ARC.
2995 buf->b_arc_access = ddi_get_lbolt();
2996 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2997 arc_change_state(arc_mfu, buf, hash_lock);
2999 ASSERT(!"invalid arc state");
3003 /* a generic arc_done_func_t which you can use */
3006 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
3008 if (zio == NULL || zio->io_error == 0)
3009 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
3010 VERIFY(arc_buf_remove_ref(buf, arg));
3013 /* a generic arc_done_func_t */
3015 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
3017 arc_buf_t **bufp = arg;
3018 if (zio && zio->io_error) {
3019 VERIFY(arc_buf_remove_ref(buf, arg));
3023 ASSERT(buf->b_data);
3028 arc_read_done(zio_t *zio)
3032 arc_buf_t *abuf; /* buffer we're assigning to callback */
3033 kmutex_t *hash_lock = NULL;
3034 arc_callback_t *callback_list, *acb;
3035 int freeable = FALSE;
3037 buf = zio->io_private;
3041 * The hdr was inserted into hash-table and removed from lists
3042 * prior to starting I/O. We should find this header, since
3043 * it's in the hash table, and it should be legit since it's
3044 * not possible to evict it during the I/O. The only possible
3045 * reason for it not to be found is if we were freed during the
3048 if (HDR_IN_HASH_TABLE(hdr)) {
3049 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
3050 ASSERT3U(hdr->b_dva.dva_word[0], ==,
3051 BP_IDENTITY(zio->io_bp)->dva_word[0]);
3052 ASSERT3U(hdr->b_dva.dva_word[1], ==,
3053 BP_IDENTITY(zio->io_bp)->dva_word[1]);
3055 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
3058 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
3059 hash_lock == NULL) ||
3061 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
3062 (found == hdr && HDR_L2_READING(hdr)));
3065 hdr->b_flags &= ~ARC_L2_EVICTED;
3066 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
3067 hdr->b_flags &= ~ARC_L2CACHE;
3069 /* byteswap if necessary */
3070 callback_list = hdr->b_acb;
3071 ASSERT(callback_list != NULL);
3072 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3073 dmu_object_byteswap_t bswap =
3074 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3075 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3076 byteswap_uint64_array :
3077 dmu_ot_byteswap[bswap].ob_func;
3078 func(buf->b_data, hdr->b_size);
3081 arc_cksum_compute(buf, B_FALSE);
3084 #endif /* illumos */
3086 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
3088 * Only call arc_access on anonymous buffers. This is because
3089 * if we've issued an I/O for an evicted buffer, we've already
3090 * called arc_access (to prevent any simultaneous readers from
3091 * getting confused).
3093 arc_access(hdr, hash_lock);
3096 /* create copies of the data buffer for the callers */
3098 for (acb = callback_list; acb; acb = acb->acb_next) {
3099 if (acb->acb_done) {
3101 ARCSTAT_BUMP(arcstat_duplicate_reads);
3102 abuf = arc_buf_clone(buf);
3104 acb->acb_buf = abuf;
3109 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3110 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3112 ASSERT(buf->b_efunc == NULL);
3113 ASSERT(hdr->b_datacnt == 1);
3114 hdr->b_flags |= ARC_BUF_AVAILABLE;
3117 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
3119 if (zio->io_error != 0) {
3120 hdr->b_flags |= ARC_IO_ERROR;
3121 if (hdr->b_state != arc_anon)
3122 arc_change_state(arc_anon, hdr, hash_lock);
3123 if (HDR_IN_HASH_TABLE(hdr))
3124 buf_hash_remove(hdr);
3125 freeable = refcount_is_zero(&hdr->b_refcnt);
3129 * Broadcast before we drop the hash_lock to avoid the possibility
3130 * that the hdr (and hence the cv) might be freed before we get to
3131 * the cv_broadcast().
3133 cv_broadcast(&hdr->b_cv);
3136 mutex_exit(hash_lock);
3139 * This block was freed while we waited for the read to
3140 * complete. It has been removed from the hash table and
3141 * moved to the anonymous state (so that it won't show up
3144 ASSERT3P(hdr->b_state, ==, arc_anon);
3145 freeable = refcount_is_zero(&hdr->b_refcnt);
3148 /* execute each callback and free its structure */
3149 while ((acb = callback_list) != NULL) {
3151 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3153 if (acb->acb_zio_dummy != NULL) {
3154 acb->acb_zio_dummy->io_error = zio->io_error;
3155 zio_nowait(acb->acb_zio_dummy);
3158 callback_list = acb->acb_next;
3159 kmem_free(acb, sizeof (arc_callback_t));
3163 arc_hdr_destroy(hdr);
3167 * "Read" the block block at the specified DVA (in bp) via the
3168 * cache. If the block is found in the cache, invoke the provided
3169 * callback immediately and return. Note that the `zio' parameter
3170 * in the callback will be NULL in this case, since no IO was
3171 * required. If the block is not in the cache pass the read request
3172 * on to the spa with a substitute callback function, so that the
3173 * requested block will be added to the cache.
3175 * If a read request arrives for a block that has a read in-progress,
3176 * either wait for the in-progress read to complete (and return the
3177 * results); or, if this is a read with a "done" func, add a record
3178 * to the read to invoke the "done" func when the read completes,
3179 * and return; or just return.
3181 * arc_read_done() will invoke all the requested "done" functions
3182 * for readers of this block.
3185 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3186 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
3187 const zbookmark_phys_t *zb)
3189 arc_buf_hdr_t *hdr = NULL;
3190 arc_buf_t *buf = NULL;
3191 kmutex_t *hash_lock = NULL;
3193 uint64_t guid = spa_load_guid(spa);
3195 ASSERT(!BP_IS_EMBEDDED(bp) ||
3196 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3199 if (!BP_IS_EMBEDDED(bp)) {
3201 * Embedded BP's have no DVA and require no I/O to "read".
3202 * Create an anonymous arc buf to back it.
3204 hdr = buf_hash_find(guid, bp, &hash_lock);
3207 if (hdr != NULL && hdr->b_datacnt > 0) {
3209 *arc_flags |= ARC_CACHED;
3211 if (HDR_IO_IN_PROGRESS(hdr)) {
3213 if (*arc_flags & ARC_WAIT) {
3214 cv_wait(&hdr->b_cv, hash_lock);
3215 mutex_exit(hash_lock);
3218 ASSERT(*arc_flags & ARC_NOWAIT);
3221 arc_callback_t *acb = NULL;
3223 acb = kmem_zalloc(sizeof (arc_callback_t),
3225 acb->acb_done = done;
3226 acb->acb_private = private;
3228 acb->acb_zio_dummy = zio_null(pio,
3229 spa, NULL, NULL, NULL, zio_flags);
3231 ASSERT(acb->acb_done != NULL);
3232 acb->acb_next = hdr->b_acb;
3234 add_reference(hdr, hash_lock, private);
3235 mutex_exit(hash_lock);
3238 mutex_exit(hash_lock);
3242 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3245 add_reference(hdr, hash_lock, private);
3247 * If this block is already in use, create a new
3248 * copy of the data so that we will be guaranteed
3249 * that arc_release() will always succeed.
3253 ASSERT(buf->b_data);
3254 if (HDR_BUF_AVAILABLE(hdr)) {
3255 ASSERT(buf->b_efunc == NULL);
3256 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3258 buf = arc_buf_clone(buf);
3261 } else if (*arc_flags & ARC_PREFETCH &&
3262 refcount_count(&hdr->b_refcnt) == 0) {
3263 hdr->b_flags |= ARC_PREFETCH;
3265 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3266 arc_access(hdr, hash_lock);
3267 if (*arc_flags & ARC_L2CACHE)
3268 hdr->b_flags |= ARC_L2CACHE;
3269 if (*arc_flags & ARC_L2COMPRESS)
3270 hdr->b_flags |= ARC_L2COMPRESS;
3271 mutex_exit(hash_lock);
3272 ARCSTAT_BUMP(arcstat_hits);
3273 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3274 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3275 data, metadata, hits);
3278 done(NULL, buf, private);
3280 uint64_t size = BP_GET_LSIZE(bp);
3281 arc_callback_t *acb;
3284 boolean_t devw = B_FALSE;
3285 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
3286 uint64_t b_asize = 0;
3289 /* this block is not in the cache */
3290 arc_buf_hdr_t *exists = NULL;
3291 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3292 buf = arc_buf_alloc(spa, size, private, type);
3294 if (!BP_IS_EMBEDDED(bp)) {
3295 hdr->b_dva = *BP_IDENTITY(bp);
3296 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3297 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3298 exists = buf_hash_insert(hdr, &hash_lock);
3300 if (exists != NULL) {
3301 /* somebody beat us to the hash insert */
3302 mutex_exit(hash_lock);
3303 buf_discard_identity(hdr);
3304 (void) arc_buf_remove_ref(buf, private);
3305 goto top; /* restart the IO request */
3307 /* if this is a prefetch, we don't have a reference */
3308 if (*arc_flags & ARC_PREFETCH) {
3309 (void) remove_reference(hdr, hash_lock,
3311 hdr->b_flags |= ARC_PREFETCH;
3313 if (*arc_flags & ARC_L2CACHE)
3314 hdr->b_flags |= ARC_L2CACHE;
3315 if (*arc_flags & ARC_L2COMPRESS)
3316 hdr->b_flags |= ARC_L2COMPRESS;
3317 if (BP_GET_LEVEL(bp) > 0)
3318 hdr->b_flags |= ARC_INDIRECT;
3320 /* this block is in the ghost cache */
3321 ASSERT(GHOST_STATE(hdr->b_state));
3322 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3323 ASSERT0(refcount_count(&hdr->b_refcnt));
3324 ASSERT(hdr->b_buf == NULL);
3326 /* if this is a prefetch, we don't have a reference */
3327 if (*arc_flags & ARC_PREFETCH)
3328 hdr->b_flags |= ARC_PREFETCH;
3330 add_reference(hdr, hash_lock, private);
3331 if (*arc_flags & ARC_L2CACHE)
3332 hdr->b_flags |= ARC_L2CACHE;
3333 if (*arc_flags & ARC_L2COMPRESS)
3334 hdr->b_flags |= ARC_L2COMPRESS;
3335 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3338 buf->b_efunc = NULL;
3339 buf->b_private = NULL;
3342 ASSERT(hdr->b_datacnt == 0);
3344 arc_get_data_buf(buf);
3345 arc_access(hdr, hash_lock);
3348 ASSERT(!GHOST_STATE(hdr->b_state));
3350 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3351 acb->acb_done = done;
3352 acb->acb_private = private;
3354 ASSERT(hdr->b_acb == NULL);
3356 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3358 if (hdr->b_l2hdr != NULL &&
3359 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3360 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3361 addr = hdr->b_l2hdr->b_daddr;
3362 b_compress = hdr->b_l2hdr->b_compress;
3363 b_asize = hdr->b_l2hdr->b_asize;
3365 * Lock out device removal.
3367 if (vdev_is_dead(vd) ||
3368 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3372 if (hash_lock != NULL)
3373 mutex_exit(hash_lock);
3376 * At this point, we have a level 1 cache miss. Try again in
3377 * L2ARC if possible.
3379 ASSERT3U(hdr->b_size, ==, size);
3380 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3381 uint64_t, size, zbookmark_phys_t *, zb);
3382 ARCSTAT_BUMP(arcstat_misses);
3383 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3384 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3385 data, metadata, misses);
3387 curthread->td_ru.ru_inblock++;
3390 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3392 * Read from the L2ARC if the following are true:
3393 * 1. The L2ARC vdev was previously cached.
3394 * 2. This buffer still has L2ARC metadata.
3395 * 3. This buffer isn't currently writing to the L2ARC.
3396 * 4. The L2ARC entry wasn't evicted, which may
3397 * also have invalidated the vdev.
3398 * 5. This isn't prefetch and l2arc_noprefetch is set.
3400 if (hdr->b_l2hdr != NULL &&
3401 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3402 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3403 l2arc_read_callback_t *cb;
3405 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3406 ARCSTAT_BUMP(arcstat_l2_hits);
3408 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3410 cb->l2rcb_buf = buf;
3411 cb->l2rcb_spa = spa;
3414 cb->l2rcb_flags = zio_flags;
3415 cb->l2rcb_compress = b_compress;
3417 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3418 addr + size < vd->vdev_psize -
3419 VDEV_LABEL_END_SIZE);
3422 * l2arc read. The SCL_L2ARC lock will be
3423 * released by l2arc_read_done().
3424 * Issue a null zio if the underlying buffer
3425 * was squashed to zero size by compression.
3427 if (b_compress == ZIO_COMPRESS_EMPTY) {
3428 rzio = zio_null(pio, spa, vd,
3429 l2arc_read_done, cb,
3430 zio_flags | ZIO_FLAG_DONT_CACHE |
3432 ZIO_FLAG_DONT_PROPAGATE |
3433 ZIO_FLAG_DONT_RETRY);
3435 rzio = zio_read_phys(pio, vd, addr,
3436 b_asize, buf->b_data,
3438 l2arc_read_done, cb, priority,
3439 zio_flags | ZIO_FLAG_DONT_CACHE |
3441 ZIO_FLAG_DONT_PROPAGATE |
3442 ZIO_FLAG_DONT_RETRY, B_FALSE);
3444 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3446 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
3448 if (*arc_flags & ARC_NOWAIT) {
3453 ASSERT(*arc_flags & ARC_WAIT);
3454 if (zio_wait(rzio) == 0)
3457 /* l2arc read error; goto zio_read() */
3459 DTRACE_PROBE1(l2arc__miss,
3460 arc_buf_hdr_t *, hdr);
3461 ARCSTAT_BUMP(arcstat_l2_misses);
3462 if (HDR_L2_WRITING(hdr))
3463 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3464 spa_config_exit(spa, SCL_L2ARC, vd);
3468 spa_config_exit(spa, SCL_L2ARC, vd);
3469 if (l2arc_ndev != 0) {
3470 DTRACE_PROBE1(l2arc__miss,
3471 arc_buf_hdr_t *, hdr);
3472 ARCSTAT_BUMP(arcstat_l2_misses);
3476 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3477 arc_read_done, buf, priority, zio_flags, zb);
3479 if (*arc_flags & ARC_WAIT)
3480 return (zio_wait(rzio));
3482 ASSERT(*arc_flags & ARC_NOWAIT);
3489 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3491 ASSERT(buf->b_hdr != NULL);
3492 ASSERT(buf->b_hdr->b_state != arc_anon);
3493 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3494 ASSERT(buf->b_efunc == NULL);
3495 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3497 buf->b_efunc = func;
3498 buf->b_private = private;
3502 * Notify the arc that a block was freed, and thus will never be used again.
3505 arc_freed(spa_t *spa, const blkptr_t *bp)
3508 kmutex_t *hash_lock;
3509 uint64_t guid = spa_load_guid(spa);
3511 ASSERT(!BP_IS_EMBEDDED(bp));
3513 hdr = buf_hash_find(guid, bp, &hash_lock);
3516 if (HDR_BUF_AVAILABLE(hdr)) {
3517 arc_buf_t *buf = hdr->b_buf;
3518 add_reference(hdr, hash_lock, FTAG);
3519 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3520 mutex_exit(hash_lock);
3522 arc_release(buf, FTAG);
3523 (void) arc_buf_remove_ref(buf, FTAG);
3525 mutex_exit(hash_lock);
3531 * Clear the user eviction callback set by arc_set_callback(), first calling
3532 * it if it exists. Because the presence of a callback keeps an arc_buf cached
3533 * clearing the callback may result in the arc_buf being destroyed. However,
3534 * it will not result in the *last* arc_buf being destroyed, hence the data
3535 * will remain cached in the ARC. We make a copy of the arc buffer here so
3536 * that we can process the callback without holding any locks.
3538 * It's possible that the callback is already in the process of being cleared
3539 * by another thread. In this case we can not clear the callback.
3541 * Returns B_TRUE if the callback was successfully called and cleared.
3544 arc_clear_callback(arc_buf_t *buf)
3547 kmutex_t *hash_lock;
3548 arc_evict_func_t *efunc = buf->b_efunc;
3549 void *private = buf->b_private;
3550 list_t *list, *evicted_list;
3551 kmutex_t *lock, *evicted_lock;
3553 mutex_enter(&buf->b_evict_lock);
3557 * We are in arc_do_user_evicts().
3559 ASSERT(buf->b_data == NULL);
3560 mutex_exit(&buf->b_evict_lock);
3562 } else if (buf->b_data == NULL) {
3564 * We are on the eviction list; process this buffer now
3565 * but let arc_do_user_evicts() do the reaping.
3567 buf->b_efunc = NULL;
3568 mutex_exit(&buf->b_evict_lock);
3569 VERIFY0(efunc(private));
3572 hash_lock = HDR_LOCK(hdr);
3573 mutex_enter(hash_lock);
3575 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3577 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3578 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3580 buf->b_efunc = NULL;
3581 buf->b_private = NULL;
3583 if (hdr->b_datacnt > 1) {
3584 mutex_exit(&buf->b_evict_lock);
3585 arc_buf_destroy(buf, FALSE, TRUE);
3587 ASSERT(buf == hdr->b_buf);
3588 hdr->b_flags |= ARC_BUF_AVAILABLE;
3589 mutex_exit(&buf->b_evict_lock);
3592 mutex_exit(hash_lock);
3593 VERIFY0(efunc(private));
3598 * Release this buffer from the cache, making it an anonymous buffer. This
3599 * must be done after a read and prior to modifying the buffer contents.
3600 * If the buffer has more than one reference, we must make
3601 * a new hdr for the buffer.
3604 arc_release(arc_buf_t *buf, void *tag)
3607 kmutex_t *hash_lock = NULL;
3608 l2arc_buf_hdr_t *l2hdr;
3612 * It would be nice to assert that if it's DMU metadata (level >
3613 * 0 || it's the dnode file), then it must be syncing context.
3614 * But we don't know that information at this level.
3617 mutex_enter(&buf->b_evict_lock);
3620 /* this buffer is not on any list */
3621 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3623 if (hdr->b_state == arc_anon) {
3624 /* this buffer is already released */
3625 ASSERT(buf->b_efunc == NULL);
3627 hash_lock = HDR_LOCK(hdr);
3628 mutex_enter(hash_lock);
3630 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3633 l2hdr = hdr->b_l2hdr;
3635 mutex_enter(&l2arc_buflist_mtx);
3636 arc_buf_l2_cdata_free(hdr);
3637 hdr->b_l2hdr = NULL;
3638 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3640 buf_size = hdr->b_size;
3643 * Do we have more than one buf?
3645 if (hdr->b_datacnt > 1) {
3646 arc_buf_hdr_t *nhdr;
3648 uint64_t blksz = hdr->b_size;
3649 uint64_t spa = hdr->b_spa;
3650 arc_buf_contents_t type = hdr->b_type;
3651 uint32_t flags = hdr->b_flags;
3653 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3655 * Pull the data off of this hdr and attach it to
3656 * a new anonymous hdr.
3658 (void) remove_reference(hdr, hash_lock, tag);
3660 while (*bufp != buf)
3661 bufp = &(*bufp)->b_next;
3662 *bufp = buf->b_next;
3665 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3666 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3667 if (refcount_is_zero(&hdr->b_refcnt)) {
3668 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3669 ASSERT3U(*size, >=, hdr->b_size);
3670 atomic_add_64(size, -hdr->b_size);
3674 * We're releasing a duplicate user data buffer, update
3675 * our statistics accordingly.
3677 if (hdr->b_type == ARC_BUFC_DATA) {
3678 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3679 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3682 hdr->b_datacnt -= 1;
3683 arc_cksum_verify(buf);
3685 arc_buf_unwatch(buf);
3686 #endif /* illumos */
3688 mutex_exit(hash_lock);
3690 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3691 nhdr->b_size = blksz;
3693 nhdr->b_type = type;
3695 nhdr->b_state = arc_anon;
3696 nhdr->b_arc_access = 0;
3697 nhdr->b_flags = flags & ARC_L2_WRITING;
3698 nhdr->b_l2hdr = NULL;
3699 nhdr->b_datacnt = 1;
3700 nhdr->b_freeze_cksum = NULL;
3701 (void) refcount_add(&nhdr->b_refcnt, tag);
3703 mutex_exit(&buf->b_evict_lock);
3704 atomic_add_64(&arc_anon->arcs_size, blksz);
3706 mutex_exit(&buf->b_evict_lock);
3707 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3708 ASSERT(!list_link_active(&hdr->b_arc_node));
3709 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3710 if (hdr->b_state != arc_anon)
3711 arc_change_state(arc_anon, hdr, hash_lock);
3712 hdr->b_arc_access = 0;
3714 mutex_exit(hash_lock);
3716 buf_discard_identity(hdr);
3719 buf->b_efunc = NULL;
3720 buf->b_private = NULL;
3723 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
3724 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
3725 -l2hdr->b_asize, 0, 0);
3726 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
3728 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3729 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3730 mutex_exit(&l2arc_buflist_mtx);
3735 arc_released(arc_buf_t *buf)
3739 mutex_enter(&buf->b_evict_lock);
3740 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3741 mutex_exit(&buf->b_evict_lock);
3747 arc_referenced(arc_buf_t *buf)
3751 mutex_enter(&buf->b_evict_lock);
3752 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3753 mutex_exit(&buf->b_evict_lock);
3754 return (referenced);
3759 arc_write_ready(zio_t *zio)
3761 arc_write_callback_t *callback = zio->io_private;
3762 arc_buf_t *buf = callback->awcb_buf;
3763 arc_buf_hdr_t *hdr = buf->b_hdr;
3765 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3766 callback->awcb_ready(zio, buf, callback->awcb_private);
3769 * If the IO is already in progress, then this is a re-write
3770 * attempt, so we need to thaw and re-compute the cksum.
3771 * It is the responsibility of the callback to handle the
3772 * accounting for any re-write attempt.
3774 if (HDR_IO_IN_PROGRESS(hdr)) {
3775 mutex_enter(&hdr->b_freeze_lock);
3776 if (hdr->b_freeze_cksum != NULL) {
3777 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3778 hdr->b_freeze_cksum = NULL;
3780 mutex_exit(&hdr->b_freeze_lock);
3782 arc_cksum_compute(buf, B_FALSE);
3783 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3787 * The SPA calls this callback for each physical write that happens on behalf
3788 * of a logical write. See the comment in dbuf_write_physdone() for details.
3791 arc_write_physdone(zio_t *zio)
3793 arc_write_callback_t *cb = zio->io_private;
3794 if (cb->awcb_physdone != NULL)
3795 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
3799 arc_write_done(zio_t *zio)
3801 arc_write_callback_t *callback = zio->io_private;
3802 arc_buf_t *buf = callback->awcb_buf;
3803 arc_buf_hdr_t *hdr = buf->b_hdr;
3805 ASSERT(hdr->b_acb == NULL);
3807 if (zio->io_error == 0) {
3808 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
3809 buf_discard_identity(hdr);
3811 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3812 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3813 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3816 ASSERT(BUF_EMPTY(hdr));
3820 * If the block to be written was all-zero or compressed enough to be
3821 * embedded in the BP, no write was performed so there will be no
3822 * dva/birth/checksum. The buffer must therefore remain anonymous
3825 if (!BUF_EMPTY(hdr)) {
3826 arc_buf_hdr_t *exists;
3827 kmutex_t *hash_lock;
3829 ASSERT(zio->io_error == 0);
3831 arc_cksum_verify(buf);
3833 exists = buf_hash_insert(hdr, &hash_lock);
3836 * This can only happen if we overwrite for
3837 * sync-to-convergence, because we remove
3838 * buffers from the hash table when we arc_free().
3840 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3841 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3842 panic("bad overwrite, hdr=%p exists=%p",
3843 (void *)hdr, (void *)exists);
3844 ASSERT(refcount_is_zero(&exists->b_refcnt));
3845 arc_change_state(arc_anon, exists, hash_lock);
3846 mutex_exit(hash_lock);
3847 arc_hdr_destroy(exists);
3848 exists = buf_hash_insert(hdr, &hash_lock);
3849 ASSERT3P(exists, ==, NULL);
3850 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3852 ASSERT(zio->io_prop.zp_nopwrite);
3853 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3854 panic("bad nopwrite, hdr=%p exists=%p",
3855 (void *)hdr, (void *)exists);
3858 ASSERT(hdr->b_datacnt == 1);
3859 ASSERT(hdr->b_state == arc_anon);
3860 ASSERT(BP_GET_DEDUP(zio->io_bp));
3861 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3864 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3865 /* if it's not anon, we are doing a scrub */
3866 if (!exists && hdr->b_state == arc_anon)
3867 arc_access(hdr, hash_lock);
3868 mutex_exit(hash_lock);
3870 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3873 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3874 callback->awcb_done(zio, buf, callback->awcb_private);
3876 kmem_free(callback, sizeof (arc_write_callback_t));
3880 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3881 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
3882 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
3883 arc_done_func_t *done, void *private, zio_priority_t priority,
3884 int zio_flags, const zbookmark_phys_t *zb)
3886 arc_buf_hdr_t *hdr = buf->b_hdr;
3887 arc_write_callback_t *callback;
3890 ASSERT(ready != NULL);
3891 ASSERT(done != NULL);
3892 ASSERT(!HDR_IO_ERROR(hdr));
3893 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3894 ASSERT(hdr->b_acb == NULL);
3896 hdr->b_flags |= ARC_L2CACHE;
3898 hdr->b_flags |= ARC_L2COMPRESS;
3899 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3900 callback->awcb_ready = ready;
3901 callback->awcb_physdone = physdone;
3902 callback->awcb_done = done;
3903 callback->awcb_private = private;
3904 callback->awcb_buf = buf;
3906 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3907 arc_write_ready, arc_write_physdone, arc_write_done, callback,
3908 priority, zio_flags, zb);
3914 arc_memory_throttle(uint64_t reserve, uint64_t txg)
3917 uint64_t available_memory =
3918 ptoa((uintmax_t)cnt.v_free_count + cnt.v_cache_count);
3919 static uint64_t page_load = 0;
3920 static uint64_t last_txg = 0;
3925 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3929 if (cnt.v_free_count + cnt.v_cache_count >
3930 (uint64_t)physmem * arc_lotsfree_percent / 100)
3933 if (txg > last_txg) {
3938 * If we are in pageout, we know that memory is already tight,
3939 * the arc is already going to be evicting, so we just want to
3940 * continue to let page writes occur as quickly as possible.
3942 if (curproc == pageproc) {
3943 if (page_load > available_memory / 4)
3944 return (SET_ERROR(ERESTART));
3945 /* Note: reserve is inflated, so we deflate */
3946 page_load += reserve / 8;
3948 } else if (page_load > 0 && arc_reclaim_needed()) {
3949 /* memory is low, delay before restarting */
3950 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3951 return (SET_ERROR(EAGAIN));
3959 arc_tempreserve_clear(uint64_t reserve)
3961 atomic_add_64(&arc_tempreserve, -reserve);
3962 ASSERT((int64_t)arc_tempreserve >= 0);
3966 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3971 if (reserve > arc_c/4 && !arc_no_grow)
3972 arc_c = MIN(arc_c_max, reserve * 4);
3973 if (reserve > arc_c)
3974 return (SET_ERROR(ENOMEM));
3977 * Don't count loaned bufs as in flight dirty data to prevent long
3978 * network delays from blocking transactions that are ready to be
3979 * assigned to a txg.
3981 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3984 * Writes will, almost always, require additional memory allocations
3985 * in order to compress/encrypt/etc the data. We therefore need to
3986 * make sure that there is sufficient available memory for this.
3988 error = arc_memory_throttle(reserve, txg);
3993 * Throttle writes when the amount of dirty data in the cache
3994 * gets too large. We try to keep the cache less than half full
3995 * of dirty blocks so that our sync times don't grow too large.
3996 * Note: if two requests come in concurrently, we might let them
3997 * both succeed, when one of them should fail. Not a huge deal.
4000 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
4001 anon_size > arc_c / 4) {
4002 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
4003 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
4004 arc_tempreserve>>10,
4005 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
4006 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
4007 reserve>>10, arc_c>>10);
4008 return (SET_ERROR(ERESTART));
4010 atomic_add_64(&arc_tempreserve, reserve);
4014 static kmutex_t arc_lowmem_lock;
4016 static eventhandler_tag arc_event_lowmem = NULL;
4019 arc_lowmem(void *arg __unused, int howto __unused)
4022 /* Serialize access via arc_lowmem_lock. */
4023 mutex_enter(&arc_lowmem_lock);
4024 mutex_enter(&arc_reclaim_thr_lock);
4026 cv_signal(&arc_reclaim_thr_cv);
4029 * It is unsafe to block here in arbitrary threads, because we can come
4030 * here from ARC itself and may hold ARC locks and thus risk a deadlock
4031 * with ARC reclaim thread.
4033 if (curproc == pageproc) {
4035 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
4037 mutex_exit(&arc_reclaim_thr_lock);
4038 mutex_exit(&arc_lowmem_lock);
4045 int i, prefetch_tunable_set = 0;
4047 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4048 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
4049 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
4051 /* Convert seconds to clock ticks */
4052 arc_min_prefetch_lifespan = 1 * hz;
4054 /* Start out with 1/8 of all memory */
4055 arc_c = kmem_size() / 8;
4060 * On architectures where the physical memory can be larger
4061 * than the addressable space (intel in 32-bit mode), we may
4062 * need to limit the cache to 1/8 of VM size.
4064 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
4067 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
4068 arc_c_min = MAX(arc_c / 4, 64<<18);
4069 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
4070 if (arc_c * 8 >= 1<<30)
4071 arc_c_max = (arc_c * 8) - (1<<30);
4073 arc_c_max = arc_c_min;
4074 arc_c_max = MAX(arc_c * 5, arc_c_max);
4078 * Allow the tunables to override our calculations if they are
4079 * reasonable (ie. over 16MB)
4081 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size())
4082 arc_c_max = zfs_arc_max;
4083 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max)
4084 arc_c_min = zfs_arc_min;
4088 arc_p = (arc_c >> 1);
4090 /* limit meta-data to 1/4 of the arc capacity */
4091 arc_meta_limit = arc_c_max / 4;
4093 /* Allow the tunable to override if it is reasonable */
4094 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
4095 arc_meta_limit = zfs_arc_meta_limit;
4097 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
4098 arc_c_min = arc_meta_limit / 2;
4100 if (zfs_arc_grow_retry > 0)
4101 arc_grow_retry = zfs_arc_grow_retry;
4103 if (zfs_arc_shrink_shift > 0)
4104 arc_shrink_shift = zfs_arc_shrink_shift;
4106 if (zfs_arc_p_min_shift > 0)
4107 arc_p_min_shift = zfs_arc_p_min_shift;
4109 /* if kmem_flags are set, lets try to use less memory */
4110 if (kmem_debugging())
4112 if (arc_c < arc_c_min)
4115 zfs_arc_min = arc_c_min;
4116 zfs_arc_max = arc_c_max;
4118 arc_anon = &ARC_anon;
4120 arc_mru_ghost = &ARC_mru_ghost;
4122 arc_mfu_ghost = &ARC_mfu_ghost;
4123 arc_l2c_only = &ARC_l2c_only;
4126 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4127 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
4128 NULL, MUTEX_DEFAULT, NULL);
4129 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
4130 NULL, MUTEX_DEFAULT, NULL);
4131 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
4132 NULL, MUTEX_DEFAULT, NULL);
4133 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
4134 NULL, MUTEX_DEFAULT, NULL);
4135 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
4136 NULL, MUTEX_DEFAULT, NULL);
4137 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
4138 NULL, MUTEX_DEFAULT, NULL);
4140 list_create(&arc_mru->arcs_lists[i],
4141 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4142 list_create(&arc_mru_ghost->arcs_lists[i],
4143 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4144 list_create(&arc_mfu->arcs_lists[i],
4145 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4146 list_create(&arc_mfu_ghost->arcs_lists[i],
4147 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4148 list_create(&arc_mfu_ghost->arcs_lists[i],
4149 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4150 list_create(&arc_l2c_only->arcs_lists[i],
4151 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4156 arc_thread_exit = 0;
4157 arc_eviction_list = NULL;
4158 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
4159 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
4161 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
4162 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
4164 if (arc_ksp != NULL) {
4165 arc_ksp->ks_data = &arc_stats;
4166 kstat_install(arc_ksp);
4169 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
4170 TS_RUN, minclsyspri);
4173 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
4174 EVENTHANDLER_PRI_FIRST);
4181 * Calculate maximum amount of dirty data per pool.
4183 * If it has been set by /etc/system, take that.
4184 * Otherwise, use a percentage of physical memory defined by
4185 * zfs_dirty_data_max_percent (default 10%) with a cap at
4186 * zfs_dirty_data_max_max (default 4GB).
4188 if (zfs_dirty_data_max == 0) {
4189 zfs_dirty_data_max = ptob(physmem) *
4190 zfs_dirty_data_max_percent / 100;
4191 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
4192 zfs_dirty_data_max_max);
4196 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
4197 prefetch_tunable_set = 1;
4200 if (prefetch_tunable_set == 0) {
4201 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
4203 printf(" add \"vfs.zfs.prefetch_disable=0\" "
4204 "to /boot/loader.conf.\n");
4205 zfs_prefetch_disable = 1;
4208 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
4209 prefetch_tunable_set == 0) {
4210 printf("ZFS NOTICE: Prefetch is disabled by default if less "
4211 "than 4GB of RAM is present;\n"
4212 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
4213 "to /boot/loader.conf.\n");
4214 zfs_prefetch_disable = 1;
4217 /* Warn about ZFS memory and address space requirements. */
4218 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
4219 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
4220 "expect unstable behavior.\n");
4222 if (kmem_size() < 512 * (1 << 20)) {
4223 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
4224 "expect unstable behavior.\n");
4225 printf(" Consider tuning vm.kmem_size and "
4226 "vm.kmem_size_max\n");
4227 printf(" in /boot/loader.conf.\n");
4237 mutex_enter(&arc_reclaim_thr_lock);
4238 arc_thread_exit = 1;
4239 cv_signal(&arc_reclaim_thr_cv);
4240 while (arc_thread_exit != 0)
4241 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
4242 mutex_exit(&arc_reclaim_thr_lock);
4248 if (arc_ksp != NULL) {
4249 kstat_delete(arc_ksp);
4253 mutex_destroy(&arc_eviction_mtx);
4254 mutex_destroy(&arc_reclaim_thr_lock);
4255 cv_destroy(&arc_reclaim_thr_cv);
4257 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4258 list_destroy(&arc_mru->arcs_lists[i]);
4259 list_destroy(&arc_mru_ghost->arcs_lists[i]);
4260 list_destroy(&arc_mfu->arcs_lists[i]);
4261 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
4262 list_destroy(&arc_l2c_only->arcs_lists[i]);
4264 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
4265 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
4266 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
4267 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
4268 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
4269 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
4274 ASSERT(arc_loaned_bytes == 0);
4276 mutex_destroy(&arc_lowmem_lock);
4278 if (arc_event_lowmem != NULL)
4279 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
4286 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
4287 * It uses dedicated storage devices to hold cached data, which are populated
4288 * using large infrequent writes. The main role of this cache is to boost
4289 * the performance of random read workloads. The intended L2ARC devices
4290 * include short-stroked disks, solid state disks, and other media with
4291 * substantially faster read latency than disk.
4293 * +-----------------------+
4295 * +-----------------------+
4298 * l2arc_feed_thread() arc_read()
4302 * +---------------+ |
4304 * +---------------+ |
4309 * +-------+ +-------+
4311 * | cache | | cache |
4312 * +-------+ +-------+
4313 * +=========+ .-----.
4314 * : L2ARC : |-_____-|
4315 * : devices : | Disks |
4316 * +=========+ `-_____-'
4318 * Read requests are satisfied from the following sources, in order:
4321 * 2) vdev cache of L2ARC devices
4323 * 4) vdev cache of disks
4326 * Some L2ARC device types exhibit extremely slow write performance.
4327 * To accommodate for this there are some significant differences between
4328 * the L2ARC and traditional cache design:
4330 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4331 * the ARC behave as usual, freeing buffers and placing headers on ghost
4332 * lists. The ARC does not send buffers to the L2ARC during eviction as
4333 * this would add inflated write latencies for all ARC memory pressure.
4335 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4336 * It does this by periodically scanning buffers from the eviction-end of
4337 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4338 * not already there. It scans until a headroom of buffers is satisfied,
4339 * which itself is a buffer for ARC eviction. If a compressible buffer is
4340 * found during scanning and selected for writing to an L2ARC device, we
4341 * temporarily boost scanning headroom during the next scan cycle to make
4342 * sure we adapt to compression effects (which might significantly reduce
4343 * the data volume we write to L2ARC). The thread that does this is
4344 * l2arc_feed_thread(), illustrated below; example sizes are included to
4345 * provide a better sense of ratio than this diagram:
4348 * +---------------------+----------+
4349 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4350 * +---------------------+----------+ | o L2ARC eligible
4351 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4352 * +---------------------+----------+ |
4353 * 15.9 Gbytes ^ 32 Mbytes |
4355 * l2arc_feed_thread()
4357 * l2arc write hand <--[oooo]--'
4361 * +==============================+
4362 * L2ARC dev |####|#|###|###| |####| ... |
4363 * +==============================+
4366 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4367 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4368 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4369 * safe to say that this is an uncommon case, since buffers at the end of
4370 * the ARC lists have moved there due to inactivity.
4372 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4373 * then the L2ARC simply misses copying some buffers. This serves as a
4374 * pressure valve to prevent heavy read workloads from both stalling the ARC
4375 * with waits and clogging the L2ARC with writes. This also helps prevent
4376 * the potential for the L2ARC to churn if it attempts to cache content too
4377 * quickly, such as during backups of the entire pool.
4379 * 5. After system boot and before the ARC has filled main memory, there are
4380 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4381 * lists can remain mostly static. Instead of searching from tail of these
4382 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4383 * for eligible buffers, greatly increasing its chance of finding them.
4385 * The L2ARC device write speed is also boosted during this time so that
4386 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4387 * there are no L2ARC reads, and no fear of degrading read performance
4388 * through increased writes.
4390 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4391 * the vdev queue can aggregate them into larger and fewer writes. Each
4392 * device is written to in a rotor fashion, sweeping writes through
4393 * available space then repeating.
4395 * 7. The L2ARC does not store dirty content. It never needs to flush
4396 * write buffers back to disk based storage.
4398 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4399 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4401 * The performance of the L2ARC can be tweaked by a number of tunables, which
4402 * may be necessary for different workloads:
4404 * l2arc_write_max max write bytes per interval
4405 * l2arc_write_boost extra write bytes during device warmup
4406 * l2arc_noprefetch skip caching prefetched buffers
4407 * l2arc_headroom number of max device writes to precache
4408 * l2arc_headroom_boost when we find compressed buffers during ARC
4409 * scanning, we multiply headroom by this
4410 * percentage factor for the next scan cycle,
4411 * since more compressed buffers are likely to
4413 * l2arc_feed_secs seconds between L2ARC writing
4415 * Tunables may be removed or added as future performance improvements are
4416 * integrated, and also may become zpool properties.
4418 * There are three key functions that control how the L2ARC warms up:
4420 * l2arc_write_eligible() check if a buffer is eligible to cache
4421 * l2arc_write_size() calculate how much to write
4422 * l2arc_write_interval() calculate sleep delay between writes
4424 * These three functions determine what to write, how much, and how quickly
4429 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4432 * A buffer is *not* eligible for the L2ARC if it:
4433 * 1. belongs to a different spa.
4434 * 2. is already cached on the L2ARC.
4435 * 3. has an I/O in progress (it may be an incomplete read).
4436 * 4. is flagged not eligible (zfs property).
4438 if (ab->b_spa != spa_guid) {
4439 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4442 if (ab->b_l2hdr != NULL) {
4443 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4446 if (HDR_IO_IN_PROGRESS(ab)) {
4447 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4450 if (!HDR_L2CACHE(ab)) {
4451 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4459 l2arc_write_size(void)
4464 * Make sure our globals have meaningful values in case the user
4467 size = l2arc_write_max;
4469 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
4470 "be greater than zero, resetting it to the default (%d)",
4472 size = l2arc_write_max = L2ARC_WRITE_SIZE;
4475 if (arc_warm == B_FALSE)
4476 size += l2arc_write_boost;
4483 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4485 clock_t interval, next, now;
4488 * If the ARC lists are busy, increase our write rate; if the
4489 * lists are stale, idle back. This is achieved by checking
4490 * how much we previously wrote - if it was more than half of
4491 * what we wanted, schedule the next write much sooner.
4493 if (l2arc_feed_again && wrote > (wanted / 2))
4494 interval = (hz * l2arc_feed_min_ms) / 1000;
4496 interval = hz * l2arc_feed_secs;
4498 now = ddi_get_lbolt();
4499 next = MAX(now, MIN(now + interval, began + interval));
4505 l2arc_hdr_stat_add(void)
4507 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4508 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4512 l2arc_hdr_stat_remove(void)
4514 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4515 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4519 * Cycle through L2ARC devices. This is how L2ARC load balances.
4520 * If a device is returned, this also returns holding the spa config lock.
4522 static l2arc_dev_t *
4523 l2arc_dev_get_next(void)
4525 l2arc_dev_t *first, *next = NULL;
4528 * Lock out the removal of spas (spa_namespace_lock), then removal
4529 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4530 * both locks will be dropped and a spa config lock held instead.
4532 mutex_enter(&spa_namespace_lock);
4533 mutex_enter(&l2arc_dev_mtx);
4535 /* if there are no vdevs, there is nothing to do */
4536 if (l2arc_ndev == 0)
4540 next = l2arc_dev_last;
4542 /* loop around the list looking for a non-faulted vdev */
4544 next = list_head(l2arc_dev_list);
4546 next = list_next(l2arc_dev_list, next);
4548 next = list_head(l2arc_dev_list);
4551 /* if we have come back to the start, bail out */
4554 else if (next == first)
4557 } while (vdev_is_dead(next->l2ad_vdev));
4559 /* if we were unable to find any usable vdevs, return NULL */
4560 if (vdev_is_dead(next->l2ad_vdev))
4563 l2arc_dev_last = next;
4566 mutex_exit(&l2arc_dev_mtx);
4569 * Grab the config lock to prevent the 'next' device from being
4570 * removed while we are writing to it.
4573 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4574 mutex_exit(&spa_namespace_lock);
4580 * Free buffers that were tagged for destruction.
4583 l2arc_do_free_on_write()
4586 l2arc_data_free_t *df, *df_prev;
4588 mutex_enter(&l2arc_free_on_write_mtx);
4589 buflist = l2arc_free_on_write;
4591 for (df = list_tail(buflist); df; df = df_prev) {
4592 df_prev = list_prev(buflist, df);
4593 ASSERT(df->l2df_data != NULL);
4594 ASSERT(df->l2df_func != NULL);
4595 df->l2df_func(df->l2df_data, df->l2df_size);
4596 list_remove(buflist, df);
4597 kmem_free(df, sizeof (l2arc_data_free_t));
4600 mutex_exit(&l2arc_free_on_write_mtx);
4604 * A write to a cache device has completed. Update all headers to allow
4605 * reads from these buffers to begin.
4608 l2arc_write_done(zio_t *zio)
4610 l2arc_write_callback_t *cb;
4613 arc_buf_hdr_t *head, *ab, *ab_prev;
4614 l2arc_buf_hdr_t *abl2;
4615 kmutex_t *hash_lock;
4616 int64_t bytes_dropped = 0;
4618 cb = zio->io_private;
4620 dev = cb->l2wcb_dev;
4621 ASSERT(dev != NULL);
4622 head = cb->l2wcb_head;
4623 ASSERT(head != NULL);
4624 buflist = dev->l2ad_buflist;
4625 ASSERT(buflist != NULL);
4626 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4627 l2arc_write_callback_t *, cb);
4629 if (zio->io_error != 0)
4630 ARCSTAT_BUMP(arcstat_l2_writes_error);
4632 mutex_enter(&l2arc_buflist_mtx);
4635 * All writes completed, or an error was hit.
4637 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4638 ab_prev = list_prev(buflist, ab);
4642 * Release the temporary compressed buffer as soon as possible.
4644 if (abl2->b_compress != ZIO_COMPRESS_OFF)
4645 l2arc_release_cdata_buf(ab);
4647 hash_lock = HDR_LOCK(ab);
4648 if (!mutex_tryenter(hash_lock)) {
4650 * This buffer misses out. It may be in a stage
4651 * of eviction. Its ARC_L2_WRITING flag will be
4652 * left set, denying reads to this buffer.
4654 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4658 if (zio->io_error != 0) {
4660 * Error - drop L2ARC entry.
4662 list_remove(buflist, ab);
4663 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4664 bytes_dropped += abl2->b_asize;
4666 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr,
4668 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4669 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4673 * Allow ARC to begin reads to this L2ARC entry.
4675 ab->b_flags &= ~ARC_L2_WRITING;
4677 mutex_exit(hash_lock);
4680 atomic_inc_64(&l2arc_writes_done);
4681 list_remove(buflist, head);
4682 kmem_cache_free(hdr_cache, head);
4683 mutex_exit(&l2arc_buflist_mtx);
4685 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
4687 l2arc_do_free_on_write();
4689 kmem_free(cb, sizeof (l2arc_write_callback_t));
4693 * A read to a cache device completed. Validate buffer contents before
4694 * handing over to the regular ARC routines.
4697 l2arc_read_done(zio_t *zio)
4699 l2arc_read_callback_t *cb;
4702 kmutex_t *hash_lock;
4705 ASSERT(zio->io_vd != NULL);
4706 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4708 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4710 cb = zio->io_private;
4712 buf = cb->l2rcb_buf;
4713 ASSERT(buf != NULL);
4715 hash_lock = HDR_LOCK(buf->b_hdr);
4716 mutex_enter(hash_lock);
4718 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4721 * If the buffer was compressed, decompress it first.
4723 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
4724 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
4725 ASSERT(zio->io_data != NULL);
4728 * Check this survived the L2ARC journey.
4730 equal = arc_cksum_equal(buf);
4731 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4732 mutex_exit(hash_lock);
4733 zio->io_private = buf;
4734 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4735 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4738 mutex_exit(hash_lock);
4740 * Buffer didn't survive caching. Increment stats and
4741 * reissue to the original storage device.
4743 if (zio->io_error != 0) {
4744 ARCSTAT_BUMP(arcstat_l2_io_error);
4746 zio->io_error = SET_ERROR(EIO);
4749 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4752 * If there's no waiter, issue an async i/o to the primary
4753 * storage now. If there *is* a waiter, the caller must
4754 * issue the i/o in a context where it's OK to block.
4756 if (zio->io_waiter == NULL) {
4757 zio_t *pio = zio_unique_parent(zio);
4759 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4761 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4762 buf->b_data, zio->io_size, arc_read_done, buf,
4763 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4767 kmem_free(cb, sizeof (l2arc_read_callback_t));
4771 * This is the list priority from which the L2ARC will search for pages to
4772 * cache. This is used within loops (0..3) to cycle through lists in the
4773 * desired order. This order can have a significant effect on cache
4776 * Currently the metadata lists are hit first, MFU then MRU, followed by
4777 * the data lists. This function returns a locked list, and also returns
4781 l2arc_list_locked(int list_num, kmutex_t **lock)
4783 list_t *list = NULL;
4786 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4788 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4790 list = &arc_mfu->arcs_lists[idx];
4791 *lock = ARCS_LOCK(arc_mfu, idx);
4792 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4793 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4794 list = &arc_mru->arcs_lists[idx];
4795 *lock = ARCS_LOCK(arc_mru, idx);
4796 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4797 ARC_BUFC_NUMDATALISTS)) {
4798 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4799 list = &arc_mfu->arcs_lists[idx];
4800 *lock = ARCS_LOCK(arc_mfu, idx);
4802 idx = list_num - ARC_BUFC_NUMLISTS;
4803 list = &arc_mru->arcs_lists[idx];
4804 *lock = ARCS_LOCK(arc_mru, idx);
4807 ASSERT(!(MUTEX_HELD(*lock)));
4813 * Evict buffers from the device write hand to the distance specified in
4814 * bytes. This distance may span populated buffers, it may span nothing.
4815 * This is clearing a region on the L2ARC device ready for writing.
4816 * If the 'all' boolean is set, every buffer is evicted.
4819 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4822 l2arc_buf_hdr_t *abl2;
4823 arc_buf_hdr_t *ab, *ab_prev;
4824 kmutex_t *hash_lock;
4826 int64_t bytes_evicted = 0;
4828 buflist = dev->l2ad_buflist;
4830 if (buflist == NULL)
4833 if (!all && dev->l2ad_first) {
4835 * This is the first sweep through the device. There is
4841 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4843 * When nearing the end of the device, evict to the end
4844 * before the device write hand jumps to the start.
4846 taddr = dev->l2ad_end;
4848 taddr = dev->l2ad_hand + distance;
4850 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4851 uint64_t, taddr, boolean_t, all);
4854 mutex_enter(&l2arc_buflist_mtx);
4855 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4856 ab_prev = list_prev(buflist, ab);
4858 hash_lock = HDR_LOCK(ab);
4859 if (!mutex_tryenter(hash_lock)) {
4861 * Missed the hash lock. Retry.
4863 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4864 mutex_exit(&l2arc_buflist_mtx);
4865 mutex_enter(hash_lock);
4866 mutex_exit(hash_lock);
4870 if (HDR_L2_WRITE_HEAD(ab)) {
4872 * We hit a write head node. Leave it for
4873 * l2arc_write_done().
4875 list_remove(buflist, ab);
4876 mutex_exit(hash_lock);
4880 if (!all && ab->b_l2hdr != NULL &&
4881 (ab->b_l2hdr->b_daddr > taddr ||
4882 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4884 * We've evicted to the target address,
4885 * or the end of the device.
4887 mutex_exit(hash_lock);
4891 if (HDR_FREE_IN_PROGRESS(ab)) {
4893 * Already on the path to destruction.
4895 mutex_exit(hash_lock);
4899 if (ab->b_state == arc_l2c_only) {
4900 ASSERT(!HDR_L2_READING(ab));
4902 * This doesn't exist in the ARC. Destroy.
4903 * arc_hdr_destroy() will call list_remove()
4904 * and decrement arcstat_l2_size.
4906 arc_change_state(arc_anon, ab, hash_lock);
4907 arc_hdr_destroy(ab);
4910 * Invalidate issued or about to be issued
4911 * reads, since we may be about to write
4912 * over this location.
4914 if (HDR_L2_READING(ab)) {
4915 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4916 ab->b_flags |= ARC_L2_EVICTED;
4920 * Tell ARC this no longer exists in L2ARC.
4922 if (ab->b_l2hdr != NULL) {
4924 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4925 bytes_evicted += abl2->b_asize;
4928 * We are destroying l2hdr, so ensure that
4929 * its compressed buffer, if any, is not leaked.
4931 ASSERT(abl2->b_tmp_cdata == NULL);
4932 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4933 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4935 list_remove(buflist, ab);
4938 * This may have been leftover after a
4941 ab->b_flags &= ~ARC_L2_WRITING;
4943 mutex_exit(hash_lock);
4945 mutex_exit(&l2arc_buflist_mtx);
4947 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0);
4948 dev->l2ad_evict = taddr;
4952 * Find and write ARC buffers to the L2ARC device.
4954 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4955 * for reading until they have completed writing.
4956 * The headroom_boost is an in-out parameter used to maintain headroom boost
4957 * state between calls to this function.
4959 * Returns the number of bytes actually written (which may be smaller than
4960 * the delta by which the device hand has changed due to alignment).
4963 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
4964 boolean_t *headroom_boost)
4966 arc_buf_hdr_t *ab, *ab_prev, *head;
4968 uint64_t write_asize, write_psize, write_sz, headroom,
4971 kmutex_t *list_lock;
4973 l2arc_write_callback_t *cb;
4975 uint64_t guid = spa_load_guid(spa);
4976 const boolean_t do_headroom_boost = *headroom_boost;
4979 ASSERT(dev->l2ad_vdev != NULL);
4981 /* Lower the flag now, we might want to raise it again later. */
4982 *headroom_boost = B_FALSE;
4985 write_sz = write_asize = write_psize = 0;
4987 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4988 head->b_flags |= ARC_L2_WRITE_HEAD;
4990 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
4992 * We will want to try to compress buffers that are at least 2x the
4993 * device sector size.
4995 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
4998 * Copy buffers for L2ARC writing.
5000 mutex_enter(&l2arc_buflist_mtx);
5001 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
5002 uint64_t passed_sz = 0;
5004 list = l2arc_list_locked(try, &list_lock);
5005 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
5008 * L2ARC fast warmup.
5010 * Until the ARC is warm and starts to evict, read from the
5011 * head of the ARC lists rather than the tail.
5013 if (arc_warm == B_FALSE)
5014 ab = list_head(list);
5016 ab = list_tail(list);
5018 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
5020 headroom = target_sz * l2arc_headroom;
5021 if (do_headroom_boost)
5022 headroom = (headroom * l2arc_headroom_boost) / 100;
5024 for (; ab; ab = ab_prev) {
5025 l2arc_buf_hdr_t *l2hdr;
5026 kmutex_t *hash_lock;
5029 if (arc_warm == B_FALSE)
5030 ab_prev = list_next(list, ab);
5032 ab_prev = list_prev(list, ab);
5033 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
5035 hash_lock = HDR_LOCK(ab);
5036 if (!mutex_tryenter(hash_lock)) {
5037 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
5039 * Skip this buffer rather than waiting.
5044 passed_sz += ab->b_size;
5045 if (passed_sz > headroom) {
5049 mutex_exit(hash_lock);
5050 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
5054 if (!l2arc_write_eligible(guid, ab)) {
5055 mutex_exit(hash_lock);
5059 if ((write_sz + ab->b_size) > target_sz) {
5061 mutex_exit(hash_lock);
5062 ARCSTAT_BUMP(arcstat_l2_write_full);
5068 * Insert a dummy header on the buflist so
5069 * l2arc_write_done() can find where the
5070 * write buffers begin without searching.
5072 list_insert_head(dev->l2ad_buflist, head);
5075 sizeof (l2arc_write_callback_t), KM_SLEEP);
5076 cb->l2wcb_dev = dev;
5077 cb->l2wcb_head = head;
5078 pio = zio_root(spa, l2arc_write_done, cb,
5080 ARCSTAT_BUMP(arcstat_l2_write_pios);
5084 * Create and add a new L2ARC header.
5086 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
5088 ab->b_flags |= ARC_L2_WRITING;
5091 * Temporarily stash the data buffer in b_tmp_cdata.
5092 * The subsequent write step will pick it up from
5093 * there. This is because can't access ab->b_buf
5094 * without holding the hash_lock, which we in turn
5095 * can't access without holding the ARC list locks
5096 * (which we want to avoid during compression/writing).
5098 l2hdr->b_compress = ZIO_COMPRESS_OFF;
5099 l2hdr->b_asize = ab->b_size;
5100 l2hdr->b_tmp_cdata = ab->b_buf->b_data;
5102 buf_sz = ab->b_size;
5103 ab->b_l2hdr = l2hdr;
5105 list_insert_head(dev->l2ad_buflist, ab);
5108 * Compute and store the buffer cksum before
5109 * writing. On debug the cksum is verified first.
5111 arc_cksum_verify(ab->b_buf);
5112 arc_cksum_compute(ab->b_buf, B_TRUE);
5114 mutex_exit(hash_lock);
5119 mutex_exit(list_lock);
5125 /* No buffers selected for writing? */
5128 mutex_exit(&l2arc_buflist_mtx);
5129 kmem_cache_free(hdr_cache, head);
5134 * Now start writing the buffers. We're starting at the write head
5135 * and work backwards, retracing the course of the buffer selector
5138 for (ab = list_prev(dev->l2ad_buflist, head); ab;
5139 ab = list_prev(dev->l2ad_buflist, ab)) {
5140 l2arc_buf_hdr_t *l2hdr;
5144 * We shouldn't need to lock the buffer here, since we flagged
5145 * it as ARC_L2_WRITING in the previous step, but we must take
5146 * care to only access its L2 cache parameters. In particular,
5147 * ab->b_buf may be invalid by now due to ARC eviction.
5149 l2hdr = ab->b_l2hdr;
5150 l2hdr->b_daddr = dev->l2ad_hand;
5152 if ((ab->b_flags & ARC_L2COMPRESS) &&
5153 l2hdr->b_asize >= buf_compress_minsz) {
5154 if (l2arc_compress_buf(l2hdr)) {
5156 * If compression succeeded, enable headroom
5157 * boost on the next scan cycle.
5159 *headroom_boost = B_TRUE;
5164 * Pick up the buffer data we had previously stashed away
5165 * (and now potentially also compressed).
5167 buf_data = l2hdr->b_tmp_cdata;
5168 buf_sz = l2hdr->b_asize;
5171 * If the data has not been compressed, then clear b_tmp_cdata
5172 * to make sure that it points only to a temporary compression
5175 if (!L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress))
5176 l2hdr->b_tmp_cdata = NULL;
5178 /* Compression may have squashed the buffer to zero length. */
5182 wzio = zio_write_phys(pio, dev->l2ad_vdev,
5183 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
5184 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
5185 ZIO_FLAG_CANFAIL, B_FALSE);
5187 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
5189 (void) zio_nowait(wzio);
5191 write_asize += buf_sz;
5193 * Keep the clock hand suitably device-aligned.
5195 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
5196 write_psize += buf_p_sz;
5197 dev->l2ad_hand += buf_p_sz;
5201 mutex_exit(&l2arc_buflist_mtx);
5203 ASSERT3U(write_asize, <=, target_sz);
5204 ARCSTAT_BUMP(arcstat_l2_writes_sent);
5205 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
5206 ARCSTAT_INCR(arcstat_l2_size, write_sz);
5207 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
5208 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
5211 * Bump device hand to the device start if it is approaching the end.
5212 * l2arc_evict() will already have evicted ahead for this case.
5214 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
5215 dev->l2ad_hand = dev->l2ad_start;
5216 dev->l2ad_evict = dev->l2ad_start;
5217 dev->l2ad_first = B_FALSE;
5220 dev->l2ad_writing = B_TRUE;
5221 (void) zio_wait(pio);
5222 dev->l2ad_writing = B_FALSE;
5224 return (write_asize);
5228 * Compresses an L2ARC buffer.
5229 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
5230 * size in l2hdr->b_asize. This routine tries to compress the data and
5231 * depending on the compression result there are three possible outcomes:
5232 * *) The buffer was incompressible. The original l2hdr contents were left
5233 * untouched and are ready for writing to an L2 device.
5234 * *) The buffer was all-zeros, so there is no need to write it to an L2
5235 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
5236 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
5237 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
5238 * data buffer which holds the compressed data to be written, and b_asize
5239 * tells us how much data there is. b_compress is set to the appropriate
5240 * compression algorithm. Once writing is done, invoke
5241 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
5243 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
5244 * buffer was incompressible).
5247 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
5250 size_t csize, len, rounded;
5252 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
5253 ASSERT(l2hdr->b_tmp_cdata != NULL);
5255 len = l2hdr->b_asize;
5256 cdata = zio_data_buf_alloc(len);
5257 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
5258 cdata, l2hdr->b_asize);
5260 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
5261 if (rounded > csize) {
5262 bzero((char *)cdata + csize, rounded - csize);
5267 /* zero block, indicate that there's nothing to write */
5268 zio_data_buf_free(cdata, len);
5269 l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
5271 l2hdr->b_tmp_cdata = NULL;
5272 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
5274 } else if (csize > 0 && csize < len) {
5276 * Compression succeeded, we'll keep the cdata around for
5277 * writing and release it afterwards.
5279 l2hdr->b_compress = ZIO_COMPRESS_LZ4;
5280 l2hdr->b_asize = csize;
5281 l2hdr->b_tmp_cdata = cdata;
5282 ARCSTAT_BUMP(arcstat_l2_compress_successes);
5286 * Compression failed, release the compressed buffer.
5287 * l2hdr will be left unmodified.
5289 zio_data_buf_free(cdata, len);
5290 ARCSTAT_BUMP(arcstat_l2_compress_failures);
5296 * Decompresses a zio read back from an l2arc device. On success, the
5297 * underlying zio's io_data buffer is overwritten by the uncompressed
5298 * version. On decompression error (corrupt compressed stream), the
5299 * zio->io_error value is set to signal an I/O error.
5301 * Please note that the compressed data stream is not checksummed, so
5302 * if the underlying device is experiencing data corruption, we may feed
5303 * corrupt data to the decompressor, so the decompressor needs to be
5304 * able to handle this situation (LZ4 does).
5307 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
5309 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
5311 if (zio->io_error != 0) {
5313 * An io error has occured, just restore the original io
5314 * size in preparation for a main pool read.
5316 zio->io_orig_size = zio->io_size = hdr->b_size;
5320 if (c == ZIO_COMPRESS_EMPTY) {
5322 * An empty buffer results in a null zio, which means we
5323 * need to fill its io_data after we're done restoring the
5324 * buffer's contents.
5326 ASSERT(hdr->b_buf != NULL);
5327 bzero(hdr->b_buf->b_data, hdr->b_size);
5328 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data;
5330 ASSERT(zio->io_data != NULL);
5332 * We copy the compressed data from the start of the arc buffer
5333 * (the zio_read will have pulled in only what we need, the
5334 * rest is garbage which we will overwrite at decompression)
5335 * and then decompress back to the ARC data buffer. This way we
5336 * can minimize copying by simply decompressing back over the
5337 * original compressed data (rather than decompressing to an
5338 * aux buffer and then copying back the uncompressed buffer,
5339 * which is likely to be much larger).
5344 csize = zio->io_size;
5345 cdata = zio_data_buf_alloc(csize);
5346 bcopy(zio->io_data, cdata, csize);
5347 if (zio_decompress_data(c, cdata, zio->io_data, csize,
5349 zio->io_error = EIO;
5350 zio_data_buf_free(cdata, csize);
5353 /* Restore the expected uncompressed IO size. */
5354 zio->io_orig_size = zio->io_size = hdr->b_size;
5358 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
5359 * This buffer serves as a temporary holder of compressed data while
5360 * the buffer entry is being written to an l2arc device. Once that is
5361 * done, we can dispose of it.
5364 l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
5366 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
5368 ASSERT(L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress));
5369 if (l2hdr->b_compress != ZIO_COMPRESS_EMPTY) {
5371 * If the data was compressed, then we've allocated a
5372 * temporary buffer for it, so now we need to release it.
5374 ASSERT(l2hdr->b_tmp_cdata != NULL);
5375 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
5376 l2hdr->b_tmp_cdata = NULL;
5378 ASSERT(l2hdr->b_tmp_cdata == NULL);
5383 * This thread feeds the L2ARC at regular intervals. This is the beating
5384 * heart of the L2ARC.
5387 l2arc_feed_thread(void *dummy __unused)
5392 uint64_t size, wrote;
5393 clock_t begin, next = ddi_get_lbolt();
5394 boolean_t headroom_boost = B_FALSE;
5396 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
5398 mutex_enter(&l2arc_feed_thr_lock);
5400 while (l2arc_thread_exit == 0) {
5401 CALLB_CPR_SAFE_BEGIN(&cpr);
5402 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
5403 next - ddi_get_lbolt());
5404 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
5405 next = ddi_get_lbolt() + hz;
5408 * Quick check for L2ARC devices.
5410 mutex_enter(&l2arc_dev_mtx);
5411 if (l2arc_ndev == 0) {
5412 mutex_exit(&l2arc_dev_mtx);
5415 mutex_exit(&l2arc_dev_mtx);
5416 begin = ddi_get_lbolt();
5419 * This selects the next l2arc device to write to, and in
5420 * doing so the next spa to feed from: dev->l2ad_spa. This
5421 * will return NULL if there are now no l2arc devices or if
5422 * they are all faulted.
5424 * If a device is returned, its spa's config lock is also
5425 * held to prevent device removal. l2arc_dev_get_next()
5426 * will grab and release l2arc_dev_mtx.
5428 if ((dev = l2arc_dev_get_next()) == NULL)
5431 spa = dev->l2ad_spa;
5432 ASSERT(spa != NULL);
5435 * If the pool is read-only then force the feed thread to
5436 * sleep a little longer.
5438 if (!spa_writeable(spa)) {
5439 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
5440 spa_config_exit(spa, SCL_L2ARC, dev);
5445 * Avoid contributing to memory pressure.
5447 if (arc_reclaim_needed()) {
5448 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
5449 spa_config_exit(spa, SCL_L2ARC, dev);
5453 ARCSTAT_BUMP(arcstat_l2_feeds);
5455 size = l2arc_write_size();
5458 * Evict L2ARC buffers that will be overwritten.
5460 l2arc_evict(dev, size, B_FALSE);
5463 * Write ARC buffers.
5465 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
5468 * Calculate interval between writes.
5470 next = l2arc_write_interval(begin, size, wrote);
5471 spa_config_exit(spa, SCL_L2ARC, dev);
5474 l2arc_thread_exit = 0;
5475 cv_broadcast(&l2arc_feed_thr_cv);
5476 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
5481 l2arc_vdev_present(vdev_t *vd)
5485 mutex_enter(&l2arc_dev_mtx);
5486 for (dev = list_head(l2arc_dev_list); dev != NULL;
5487 dev = list_next(l2arc_dev_list, dev)) {
5488 if (dev->l2ad_vdev == vd)
5491 mutex_exit(&l2arc_dev_mtx);
5493 return (dev != NULL);
5497 * Add a vdev for use by the L2ARC. By this point the spa has already
5498 * validated the vdev and opened it.
5501 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
5503 l2arc_dev_t *adddev;
5505 ASSERT(!l2arc_vdev_present(vd));
5507 vdev_ashift_optimize(vd);
5510 * Create a new l2arc device entry.
5512 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
5513 adddev->l2ad_spa = spa;
5514 adddev->l2ad_vdev = vd;
5515 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
5516 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
5517 adddev->l2ad_hand = adddev->l2ad_start;
5518 adddev->l2ad_evict = adddev->l2ad_start;
5519 adddev->l2ad_first = B_TRUE;
5520 adddev->l2ad_writing = B_FALSE;
5523 * This is a list of all ARC buffers that are still valid on the
5526 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
5527 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
5528 offsetof(arc_buf_hdr_t, b_l2node));
5530 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
5533 * Add device to global list
5535 mutex_enter(&l2arc_dev_mtx);
5536 list_insert_head(l2arc_dev_list, adddev);
5537 atomic_inc_64(&l2arc_ndev);
5538 mutex_exit(&l2arc_dev_mtx);
5542 * Remove a vdev from the L2ARC.
5545 l2arc_remove_vdev(vdev_t *vd)
5547 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
5550 * Find the device by vdev
5552 mutex_enter(&l2arc_dev_mtx);
5553 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
5554 nextdev = list_next(l2arc_dev_list, dev);
5555 if (vd == dev->l2ad_vdev) {
5560 ASSERT(remdev != NULL);
5563 * Remove device from global list
5565 list_remove(l2arc_dev_list, remdev);
5566 l2arc_dev_last = NULL; /* may have been invalidated */
5567 atomic_dec_64(&l2arc_ndev);
5568 mutex_exit(&l2arc_dev_mtx);
5571 * Clear all buflists and ARC references. L2ARC device flush.
5573 l2arc_evict(remdev, 0, B_TRUE);
5574 list_destroy(remdev->l2ad_buflist);
5575 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
5576 kmem_free(remdev, sizeof (l2arc_dev_t));
5582 l2arc_thread_exit = 0;
5584 l2arc_writes_sent = 0;
5585 l2arc_writes_done = 0;
5587 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
5588 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
5589 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
5590 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
5591 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
5593 l2arc_dev_list = &L2ARC_dev_list;
5594 l2arc_free_on_write = &L2ARC_free_on_write;
5595 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
5596 offsetof(l2arc_dev_t, l2ad_node));
5597 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
5598 offsetof(l2arc_data_free_t, l2df_list_node));
5605 * This is called from dmu_fini(), which is called from spa_fini();
5606 * Because of this, we can assume that all l2arc devices have
5607 * already been removed when the pools themselves were removed.
5610 l2arc_do_free_on_write();
5612 mutex_destroy(&l2arc_feed_thr_lock);
5613 cv_destroy(&l2arc_feed_thr_cv);
5614 mutex_destroy(&l2arc_dev_mtx);
5615 mutex_destroy(&l2arc_buflist_mtx);
5616 mutex_destroy(&l2arc_free_on_write_mtx);
5618 list_destroy(l2arc_dev_list);
5619 list_destroy(l2arc_free_on_write);
5625 if (!(spa_mode_global & FWRITE))
5628 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5629 TS_RUN, minclsyspri);
5635 if (!(spa_mode_global & FWRITE))
5638 mutex_enter(&l2arc_feed_thr_lock);
5639 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5640 l2arc_thread_exit = 1;
5641 while (l2arc_thread_exit != 0)
5642 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5643 mutex_exit(&l2arc_feed_thr_lock);