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 2008 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
27 * DVA-based Adjustable Replacement Cache
29 * While much of the theory of operation used here is
30 * based on the self-tuning, low overhead replacement cache
31 * presented by Megiddo and Modha at FAST 2003, there are some
32 * significant differences:
34 * 1. The Megiddo and Modha model assumes any page is evictable.
35 * Pages in its cache cannot be "locked" into memory. This makes
36 * the eviction algorithm simple: evict the last page in the list.
37 * This also make the performance characteristics easy to reason
38 * about. Our cache is not so simple. At any given moment, some
39 * subset of the blocks in the cache are un-evictable because we
40 * have handed out a reference to them. Blocks are only evictable
41 * when there are no external references active. This makes
42 * eviction far more problematic: we choose to evict the evictable
43 * blocks that are the "lowest" in the list.
45 * There are times when it is not possible to evict the requested
46 * space. In these circumstances we are unable to adjust the cache
47 * size. To prevent the cache growing unbounded at these times we
48 * implement a "cache throttle" that slows the flow of new data
49 * into the cache until we can make space available.
51 * 2. The Megiddo and Modha model assumes a fixed cache size.
52 * Pages are evicted when the cache is full and there is a cache
53 * miss. Our model has a variable sized cache. It grows with
54 * high use, but also tries to react to memory pressure from the
55 * operating system: decreasing its size when system memory is
58 * 3. The Megiddo and Modha model assumes a fixed page size. All
59 * elements of the cache are therefor exactly the same size. So
60 * when adjusting the cache size following a cache miss, its simply
61 * a matter of choosing a single page to evict. In our model, we
62 * have variable sized cache blocks (rangeing from 512 bytes to
63 * 128K bytes). We therefor choose a set of blocks to evict to make
64 * space for a cache miss that approximates as closely as possible
65 * the space used by the new block.
67 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
68 * by N. Megiddo & D. Modha, FAST 2003
74 * A new reference to a cache buffer can be obtained in two
75 * ways: 1) via a hash table lookup using the DVA as a key,
76 * or 2) via one of the ARC lists. The arc_read() interface
77 * uses method 1, while the internal arc algorithms for
78 * adjusting the cache use method 2. We therefor provide two
79 * types of locks: 1) the hash table lock array, and 2) the
82 * Buffers do not have their own mutexs, rather they rely on the
83 * hash table mutexs for the bulk of their protection (i.e. most
84 * fields in the arc_buf_hdr_t are protected by these mutexs).
86 * buf_hash_find() returns the appropriate mutex (held) when it
87 * locates the requested buffer in the hash table. It returns
88 * NULL for the mutex if the buffer was not in the table.
90 * buf_hash_remove() expects the appropriate hash mutex to be
91 * already held before it is invoked.
93 * Each arc state also has a mutex which is used to protect the
94 * buffer list associated with the state. When attempting to
95 * obtain a hash table lock while holding an arc list lock you
96 * must use: mutex_tryenter() to avoid deadlock. Also note that
97 * the active state mutex must be held before the ghost state mutex.
99 * Arc buffers may have an associated eviction callback function.
100 * This function will be invoked prior to removing the buffer (e.g.
101 * in arc_do_user_evicts()). Note however that the data associated
102 * with the buffer may be evicted prior to the callback. The callback
103 * must be made with *no locks held* (to prevent deadlock). Additionally,
104 * the users of callbacks must ensure that their private data is
105 * protected from simultaneous callbacks from arc_buf_evict()
106 * and arc_do_user_evicts().
108 * Note that the majority of the performance stats are manipulated
109 * with atomic operations.
111 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
113 * - L2ARC buflist creation
114 * - L2ARC buflist eviction
115 * - L2ARC write completion, which walks L2ARC buflists
116 * - ARC header destruction, as it removes from L2ARC buflists
117 * - ARC header release, as it removes from L2ARC buflists
122 #include <sys/zio_checksum.h>
123 #include <sys/zfs_context.h>
125 #include <sys/refcount.h>
126 #include <sys/vdev.h>
128 #include <sys/vmsystm.h>
130 #include <sys/fs/swapnode.h>
131 #include <sys/dnlc.h>
133 #include <sys/callb.h>
134 #include <sys/kstat.h>
136 static kmutex_t arc_reclaim_thr_lock
;
137 static kcondvar_t arc_reclaim_thr_cv
; /* used to signal reclaim thr */
138 static uint8_t arc_thread_exit
;
140 extern int zfs_write_limit_shift
;
141 extern uint64_t zfs_write_limit_max
;
142 extern kmutex_t zfs_write_limit_lock
;
144 #define ARC_REDUCE_DNLC_PERCENT 3
145 uint_t arc_reduce_dnlc_percent
= ARC_REDUCE_DNLC_PERCENT
;
147 typedef enum arc_reclaim_strategy
{
148 ARC_RECLAIM_AGGR
, /* Aggressive reclaim strategy */
149 ARC_RECLAIM_CONS
/* Conservative reclaim strategy */
150 } arc_reclaim_strategy_t
;
152 /* number of seconds before growing cache again */
153 static int arc_grow_retry
= 60;
156 * minimum lifespan of a prefetch block in clock ticks
157 * (initialized in arc_init())
159 static int arc_min_prefetch_lifespan
;
164 * The arc has filled available memory and has now warmed up.
166 static boolean_t arc_warm
;
169 * These tunables are for performance analysis.
171 uint64_t zfs_arc_max
;
172 uint64_t zfs_arc_min
;
173 uint64_t zfs_arc_meta_limit
= 0;
174 int zfs_mdcomp_disable
= 0;
177 * Note that buffers can be in one of 6 states:
178 * ARC_anon - anonymous (discussed below)
179 * ARC_mru - recently used, currently cached
180 * ARC_mru_ghost - recentely used, no longer in cache
181 * ARC_mfu - frequently used, currently cached
182 * ARC_mfu_ghost - frequently used, no longer in cache
183 * ARC_l2c_only - exists in L2ARC but not other states
184 * When there are no active references to the buffer, they are
185 * are linked onto a list in one of these arc states. These are
186 * the only buffers that can be evicted or deleted. Within each
187 * state there are multiple lists, one for meta-data and one for
188 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
189 * etc.) is tracked separately so that it can be managed more
190 * explicitly: favored over data, limited explicitly.
192 * Anonymous buffers are buffers that are not associated with
193 * a DVA. These are buffers that hold dirty block copies
194 * before they are written to stable storage. By definition,
195 * they are "ref'd" and are considered part of arc_mru
196 * that cannot be freed. Generally, they will aquire a DVA
197 * as they are written and migrate onto the arc_mru list.
199 * The ARC_l2c_only state is for buffers that are in the second
200 * level ARC but no longer in any of the ARC_m* lists. The second
201 * level ARC itself may also contain buffers that are in any of
202 * the ARC_m* states - meaning that a buffer can exist in two
203 * places. The reason for the ARC_l2c_only state is to keep the
204 * buffer header in the hash table, so that reads that hit the
205 * second level ARC benefit from these fast lookups.
208 typedef struct arc_state
{
209 list_t arcs_list
[ARC_BUFC_NUMTYPES
]; /* list of evictable buffers */
210 uint64_t arcs_lsize
[ARC_BUFC_NUMTYPES
]; /* amount of evictable data */
211 uint64_t arcs_size
; /* total amount of data in this state */
216 static arc_state_t ARC_anon
;
217 static arc_state_t ARC_mru
;
218 static arc_state_t ARC_mru_ghost
;
219 static arc_state_t ARC_mfu
;
220 static arc_state_t ARC_mfu_ghost
;
221 static arc_state_t ARC_l2c_only
;
223 typedef struct arc_stats
{
224 kstat_named_t arcstat_hits
;
225 kstat_named_t arcstat_misses
;
226 kstat_named_t arcstat_demand_data_hits
;
227 kstat_named_t arcstat_demand_data_misses
;
228 kstat_named_t arcstat_demand_metadata_hits
;
229 kstat_named_t arcstat_demand_metadata_misses
;
230 kstat_named_t arcstat_prefetch_data_hits
;
231 kstat_named_t arcstat_prefetch_data_misses
;
232 kstat_named_t arcstat_prefetch_metadata_hits
;
233 kstat_named_t arcstat_prefetch_metadata_misses
;
234 kstat_named_t arcstat_mru_hits
;
235 kstat_named_t arcstat_mru_ghost_hits
;
236 kstat_named_t arcstat_mfu_hits
;
237 kstat_named_t arcstat_mfu_ghost_hits
;
238 kstat_named_t arcstat_deleted
;
239 kstat_named_t arcstat_recycle_miss
;
240 kstat_named_t arcstat_mutex_miss
;
241 kstat_named_t arcstat_evict_skip
;
242 kstat_named_t arcstat_hash_elements
;
243 kstat_named_t arcstat_hash_elements_max
;
244 kstat_named_t arcstat_hash_collisions
;
245 kstat_named_t arcstat_hash_chains
;
246 kstat_named_t arcstat_hash_chain_max
;
247 kstat_named_t arcstat_p
;
248 kstat_named_t arcstat_c
;
249 kstat_named_t arcstat_c_min
;
250 kstat_named_t arcstat_c_max
;
251 kstat_named_t arcstat_size
;
252 kstat_named_t arcstat_hdr_size
;
253 kstat_named_t arcstat_l2_hits
;
254 kstat_named_t arcstat_l2_misses
;
255 kstat_named_t arcstat_l2_feeds
;
256 kstat_named_t arcstat_l2_rw_clash
;
257 kstat_named_t arcstat_l2_writes_sent
;
258 kstat_named_t arcstat_l2_writes_done
;
259 kstat_named_t arcstat_l2_writes_error
;
260 kstat_named_t arcstat_l2_writes_hdr_miss
;
261 kstat_named_t arcstat_l2_evict_lock_retry
;
262 kstat_named_t arcstat_l2_evict_reading
;
263 kstat_named_t arcstat_l2_free_on_write
;
264 kstat_named_t arcstat_l2_abort_lowmem
;
265 kstat_named_t arcstat_l2_cksum_bad
;
266 kstat_named_t arcstat_l2_io_error
;
267 kstat_named_t arcstat_l2_size
;
268 kstat_named_t arcstat_l2_hdr_size
;
269 kstat_named_t arcstat_memory_throttle_count
;
272 static arc_stats_t arc_stats
= {
273 { "hits", KSTAT_DATA_UINT64
},
274 { "misses", KSTAT_DATA_UINT64
},
275 { "demand_data_hits", KSTAT_DATA_UINT64
},
276 { "demand_data_misses", KSTAT_DATA_UINT64
},
277 { "demand_metadata_hits", KSTAT_DATA_UINT64
},
278 { "demand_metadata_misses", KSTAT_DATA_UINT64
},
279 { "prefetch_data_hits", KSTAT_DATA_UINT64
},
280 { "prefetch_data_misses", KSTAT_DATA_UINT64
},
281 { "prefetch_metadata_hits", KSTAT_DATA_UINT64
},
282 { "prefetch_metadata_misses", KSTAT_DATA_UINT64
},
283 { "mru_hits", KSTAT_DATA_UINT64
},
284 { "mru_ghost_hits", KSTAT_DATA_UINT64
},
285 { "mfu_hits", KSTAT_DATA_UINT64
},
286 { "mfu_ghost_hits", KSTAT_DATA_UINT64
},
287 { "deleted", KSTAT_DATA_UINT64
},
288 { "recycle_miss", KSTAT_DATA_UINT64
},
289 { "mutex_miss", KSTAT_DATA_UINT64
},
290 { "evict_skip", KSTAT_DATA_UINT64
},
291 { "hash_elements", KSTAT_DATA_UINT64
},
292 { "hash_elements_max", KSTAT_DATA_UINT64
},
293 { "hash_collisions", KSTAT_DATA_UINT64
},
294 { "hash_chains", KSTAT_DATA_UINT64
},
295 { "hash_chain_max", KSTAT_DATA_UINT64
},
296 { "p", KSTAT_DATA_UINT64
},
297 { "c", KSTAT_DATA_UINT64
},
298 { "c_min", KSTAT_DATA_UINT64
},
299 { "c_max", KSTAT_DATA_UINT64
},
300 { "size", KSTAT_DATA_UINT64
},
301 { "hdr_size", KSTAT_DATA_UINT64
},
302 { "l2_hits", KSTAT_DATA_UINT64
},
303 { "l2_misses", KSTAT_DATA_UINT64
},
304 { "l2_feeds", KSTAT_DATA_UINT64
},
305 { "l2_rw_clash", KSTAT_DATA_UINT64
},
306 { "l2_writes_sent", KSTAT_DATA_UINT64
},
307 { "l2_writes_done", KSTAT_DATA_UINT64
},
308 { "l2_writes_error", KSTAT_DATA_UINT64
},
309 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64
},
310 { "l2_evict_lock_retry", KSTAT_DATA_UINT64
},
311 { "l2_evict_reading", KSTAT_DATA_UINT64
},
312 { "l2_free_on_write", KSTAT_DATA_UINT64
},
313 { "l2_abort_lowmem", KSTAT_DATA_UINT64
},
314 { "l2_cksum_bad", KSTAT_DATA_UINT64
},
315 { "l2_io_error", KSTAT_DATA_UINT64
},
316 { "l2_size", KSTAT_DATA_UINT64
},
317 { "l2_hdr_size", KSTAT_DATA_UINT64
},
318 { "memory_throttle_count", KSTAT_DATA_UINT64
}
321 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
323 #define ARCSTAT_INCR(stat, val) \
324 atomic_add_64(&arc_stats.stat.value.ui64, (val));
326 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
327 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
329 #define ARCSTAT_MAX(stat, val) { \
331 while ((val) > (m = arc_stats.stat.value.ui64) && \
332 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
336 #define ARCSTAT_MAXSTAT(stat) \
337 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
340 * We define a macro to allow ARC hits/misses to be easily broken down by
341 * two separate conditions, giving a total of four different subtypes for
342 * each of hits and misses (so eight statistics total).
344 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
347 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
349 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
353 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
355 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
360 static arc_state_t
*arc_anon
;
361 static arc_state_t
*arc_mru
;
362 static arc_state_t
*arc_mru_ghost
;
363 static arc_state_t
*arc_mfu
;
364 static arc_state_t
*arc_mfu_ghost
;
365 static arc_state_t
*arc_l2c_only
;
368 * There are several ARC variables that are critical to export as kstats --
369 * but we don't want to have to grovel around in the kstat whenever we wish to
370 * manipulate them. For these variables, we therefore define them to be in
371 * terms of the statistic variable. This assures that we are not introducing
372 * the possibility of inconsistency by having shadow copies of the variables,
373 * while still allowing the code to be readable.
375 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
376 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
377 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
378 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
379 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
381 static int arc_no_grow
; /* Don't try to grow cache size */
382 static uint64_t arc_tempreserve
;
383 static uint64_t arc_meta_used
;
384 static uint64_t arc_meta_limit
;
385 static uint64_t arc_meta_max
= 0;
387 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t
;
389 typedef struct arc_callback arc_callback_t
;
391 struct arc_callback
{
393 arc_done_func_t
*acb_done
;
395 zio_t
*acb_zio_dummy
;
396 arc_callback_t
*acb_next
;
399 typedef struct arc_write_callback arc_write_callback_t
;
401 struct arc_write_callback
{
403 arc_done_func_t
*awcb_ready
;
404 arc_done_func_t
*awcb_done
;
409 /* protected by hash lock */
414 kmutex_t b_freeze_lock
;
415 zio_cksum_t
*b_freeze_cksum
;
417 arc_buf_hdr_t
*b_hash_next
;
422 arc_callback_t
*b_acb
;
426 arc_buf_contents_t b_type
;
430 /* protected by arc state mutex */
431 arc_state_t
*b_state
;
432 list_node_t b_arc_node
;
434 /* updated atomically */
435 clock_t b_arc_access
;
437 /* self protecting */
440 l2arc_buf_hdr_t
*b_l2hdr
;
441 list_node_t b_l2node
;
444 static arc_buf_t
*arc_eviction_list
;
445 static kmutex_t arc_eviction_mtx
;
446 static arc_buf_hdr_t arc_eviction_hdr
;
447 static void arc_get_data_buf(arc_buf_t
*buf
);
448 static void arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
);
449 static int arc_evict_needed(arc_buf_contents_t type
);
450 static void arc_evict_ghost(arc_state_t
*state
, spa_t
*spa
, int64_t bytes
);
452 #define GHOST_STATE(state) \
453 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
454 (state) == arc_l2c_only)
457 * Private ARC flags. These flags are private ARC only flags that will show up
458 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
459 * be passed in as arc_flags in things like arc_read. However, these flags
460 * should never be passed and should only be set by ARC code. When adding new
461 * public flags, make sure not to smash the private ones.
464 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
465 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
466 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
467 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
468 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
469 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
470 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
471 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
472 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
473 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
474 #define ARC_STORED (1 << 19) /* has been store()d to */
476 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
477 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
478 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
479 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
480 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
481 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
482 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
483 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
484 (hdr)->b_l2hdr != NULL)
485 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
486 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
487 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
493 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
494 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
497 * Hash table routines
500 #define HT_LOCK_PAD 64
505 unsigned char pad
[(HT_LOCK_PAD
- sizeof (kmutex_t
))];
509 #define BUF_LOCKS 256
510 typedef struct buf_hash_table
{
512 arc_buf_hdr_t
**ht_table
;
513 struct ht_lock ht_locks
[BUF_LOCKS
];
516 static buf_hash_table_t buf_hash_table
;
518 #define BUF_HASH_INDEX(spa, dva, birth) \
519 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
520 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
521 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
522 #define HDR_LOCK(buf) \
523 (BUF_HASH_LOCK(BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth)))
525 uint64_t zfs_crc64_table
[256];
531 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
532 #define L2ARC_HEADROOM 4 /* num of writes */
533 #define L2ARC_FEED_SECS 1 /* caching interval */
535 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
536 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
539 * L2ARC Performance Tunables
541 uint64_t l2arc_write_max
= L2ARC_WRITE_SIZE
; /* default max write size */
542 uint64_t l2arc_write_boost
= L2ARC_WRITE_SIZE
; /* extra write during warmup */
543 uint64_t l2arc_headroom
= L2ARC_HEADROOM
; /* number of dev writes */
544 uint64_t l2arc_feed_secs
= L2ARC_FEED_SECS
; /* interval seconds */
545 boolean_t l2arc_noprefetch
= B_TRUE
; /* don't cache prefetch bufs */
550 typedef struct l2arc_dev
{
551 vdev_t
*l2ad_vdev
; /* vdev */
552 spa_t
*l2ad_spa
; /* spa */
553 uint64_t l2ad_hand
; /* next write location */
554 uint64_t l2ad_write
; /* desired write size, bytes */
555 uint64_t l2ad_boost
; /* warmup write boost, bytes */
556 uint64_t l2ad_start
; /* first addr on device */
557 uint64_t l2ad_end
; /* last addr on device */
558 uint64_t l2ad_evict
; /* last addr eviction reached */
559 boolean_t l2ad_first
; /* first sweep through */
560 list_t
*l2ad_buflist
; /* buffer list */
561 list_node_t l2ad_node
; /* device list node */
564 static list_t L2ARC_dev_list
; /* device list */
565 static list_t
*l2arc_dev_list
; /* device list pointer */
566 static kmutex_t l2arc_dev_mtx
; /* device list mutex */
567 static l2arc_dev_t
*l2arc_dev_last
; /* last device used */
568 static kmutex_t l2arc_buflist_mtx
; /* mutex for all buflists */
569 static list_t L2ARC_free_on_write
; /* free after write buf list */
570 static list_t
*l2arc_free_on_write
; /* free after write list ptr */
571 static kmutex_t l2arc_free_on_write_mtx
; /* mutex for list */
572 static uint64_t l2arc_ndev
; /* number of devices */
574 typedef struct l2arc_read_callback
{
575 arc_buf_t
*l2rcb_buf
; /* read buffer */
576 spa_t
*l2rcb_spa
; /* spa */
577 blkptr_t l2rcb_bp
; /* original blkptr */
578 zbookmark_t l2rcb_zb
; /* original bookmark */
579 int l2rcb_flags
; /* original flags */
580 } l2arc_read_callback_t
;
582 typedef struct l2arc_write_callback
{
583 l2arc_dev_t
*l2wcb_dev
; /* device info */
584 arc_buf_hdr_t
*l2wcb_head
; /* head of write buflist */
585 } l2arc_write_callback_t
;
587 struct l2arc_buf_hdr
{
588 /* protected by arc_buf_hdr mutex */
589 l2arc_dev_t
*b_dev
; /* L2ARC device */
590 daddr_t b_daddr
; /* disk address, offset byte */
593 typedef struct l2arc_data_free
{
594 /* protected by l2arc_free_on_write_mtx */
597 void (*l2df_func
)(void *, size_t);
598 list_node_t l2df_list_node
;
601 static kmutex_t l2arc_feed_thr_lock
;
602 static kcondvar_t l2arc_feed_thr_cv
;
603 static uint8_t l2arc_thread_exit
;
605 static void l2arc_read_done(zio_t
*zio
);
606 static void l2arc_hdr_stat_add(void);
607 static void l2arc_hdr_stat_remove(void);
610 buf_hash(spa_t
*spa
, const dva_t
*dva
, uint64_t birth
)
612 uintptr_t spav
= (uintptr_t)spa
;
613 uint8_t *vdva
= (uint8_t *)dva
;
614 uint64_t crc
= -1ULL;
617 ASSERT(zfs_crc64_table
[128] == ZFS_CRC64_POLY
);
619 for (i
= 0; i
< sizeof (dva_t
); i
++)
620 crc
= (crc
>> 8) ^ zfs_crc64_table
[(crc
^ vdva
[i
]) & 0xFF];
622 crc
^= (spav
>>8) ^ birth
;
627 #define BUF_EMPTY(buf) \
628 ((buf)->b_dva.dva_word[0] == 0 && \
629 (buf)->b_dva.dva_word[1] == 0 && \
632 #define BUF_EQUAL(spa, dva, birth, buf) \
633 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
634 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
635 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
637 static arc_buf_hdr_t
*
638 buf_hash_find(spa_t
*spa
, const dva_t
*dva
, uint64_t birth
, kmutex_t
**lockp
)
640 uint64_t idx
= BUF_HASH_INDEX(spa
, dva
, birth
);
641 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
644 mutex_enter(hash_lock
);
645 for (buf
= buf_hash_table
.ht_table
[idx
]; buf
!= NULL
;
646 buf
= buf
->b_hash_next
) {
647 if (BUF_EQUAL(spa
, dva
, birth
, buf
)) {
652 mutex_exit(hash_lock
);
658 * Insert an entry into the hash table. If there is already an element
659 * equal to elem in the hash table, then the already existing element
660 * will be returned and the new element will not be inserted.
661 * Otherwise returns NULL.
663 static arc_buf_hdr_t
*
664 buf_hash_insert(arc_buf_hdr_t
*buf
, kmutex_t
**lockp
)
666 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
667 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
671 ASSERT(!HDR_IN_HASH_TABLE(buf
));
673 mutex_enter(hash_lock
);
674 for (fbuf
= buf_hash_table
.ht_table
[idx
], i
= 0; fbuf
!= NULL
;
675 fbuf
= fbuf
->b_hash_next
, i
++) {
676 if (BUF_EQUAL(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
, fbuf
))
680 buf
->b_hash_next
= buf_hash_table
.ht_table
[idx
];
681 buf_hash_table
.ht_table
[idx
] = buf
;
682 buf
->b_flags
|= ARC_IN_HASH_TABLE
;
684 /* collect some hash table performance data */
686 ARCSTAT_BUMP(arcstat_hash_collisions
);
688 ARCSTAT_BUMP(arcstat_hash_chains
);
690 ARCSTAT_MAX(arcstat_hash_chain_max
, i
);
693 ARCSTAT_BUMP(arcstat_hash_elements
);
694 ARCSTAT_MAXSTAT(arcstat_hash_elements
);
700 buf_hash_remove(arc_buf_hdr_t
*buf
)
702 arc_buf_hdr_t
*fbuf
, **bufp
;
703 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
705 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx
)));
706 ASSERT(HDR_IN_HASH_TABLE(buf
));
708 bufp
= &buf_hash_table
.ht_table
[idx
];
709 while ((fbuf
= *bufp
) != buf
) {
710 ASSERT(fbuf
!= NULL
);
711 bufp
= &fbuf
->b_hash_next
;
713 *bufp
= buf
->b_hash_next
;
714 buf
->b_hash_next
= NULL
;
715 buf
->b_flags
&= ~ARC_IN_HASH_TABLE
;
717 /* collect some hash table performance data */
718 ARCSTAT_BUMPDOWN(arcstat_hash_elements
);
720 if (buf_hash_table
.ht_table
[idx
] &&
721 buf_hash_table
.ht_table
[idx
]->b_hash_next
== NULL
)
722 ARCSTAT_BUMPDOWN(arcstat_hash_chains
);
726 * Global data structures and functions for the buf kmem cache.
728 static kmem_cache_t
*hdr_cache
;
729 static kmem_cache_t
*buf_cache
;
736 kmem_free(buf_hash_table
.ht_table
,
737 (buf_hash_table
.ht_mask
+ 1) * sizeof (void *));
738 for (i
= 0; i
< BUF_LOCKS
; i
++)
739 mutex_destroy(&buf_hash_table
.ht_locks
[i
].ht_lock
);
740 kmem_cache_destroy(hdr_cache
);
741 kmem_cache_destroy(buf_cache
);
745 * Constructor callback - called when the cache is empty
746 * and a new buf is requested.
750 hdr_cons(void *vbuf
, void *unused
, int kmflag
)
752 arc_buf_hdr_t
*buf
= vbuf
;
754 bzero(buf
, sizeof (arc_buf_hdr_t
));
755 refcount_create(&buf
->b_refcnt
);
756 cv_init(&buf
->b_cv
, NULL
, CV_DEFAULT
, NULL
);
757 mutex_init(&buf
->b_freeze_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
759 ARCSTAT_INCR(arcstat_hdr_size
, HDR_SIZE
);
765 buf_cons(void *vbuf
, void *unused
, int kmflag
)
767 arc_buf_t
*buf
= vbuf
;
769 bzero(buf
, sizeof (arc_buf_t
));
770 rw_init(&buf
->b_lock
, NULL
, RW_DEFAULT
, NULL
);
775 * Destructor callback - called when a cached buf is
776 * no longer required.
780 hdr_dest(void *vbuf
, void *unused
)
782 arc_buf_hdr_t
*buf
= vbuf
;
784 refcount_destroy(&buf
->b_refcnt
);
785 cv_destroy(&buf
->b_cv
);
786 mutex_destroy(&buf
->b_freeze_lock
);
788 ARCSTAT_INCR(arcstat_hdr_size
, -HDR_SIZE
);
793 buf_dest(void *vbuf
, void *unused
)
795 arc_buf_t
*buf
= vbuf
;
797 rw_destroy(&buf
->b_lock
);
801 * Reclaim callback -- invoked when memory is low.
805 hdr_recl(void *unused
)
807 dprintf("hdr_recl called\n");
809 * umem calls the reclaim func when we destroy the buf cache,
810 * which is after we do arc_fini().
813 cv_signal(&arc_reclaim_thr_cv
);
820 uint64_t hsize
= 1ULL << 12;
824 * The hash table is big enough to fill all of physical memory
825 * with an average 64K block size. The table will take up
826 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
828 while (hsize
* 65536 < physmem
* PAGESIZE
)
831 buf_hash_table
.ht_mask
= hsize
- 1;
832 buf_hash_table
.ht_table
=
833 kmem_zalloc(hsize
* sizeof (void*), KM_NOSLEEP
);
834 if (buf_hash_table
.ht_table
== NULL
) {
835 ASSERT(hsize
> (1ULL << 8));
840 hdr_cache
= kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t
),
841 0, hdr_cons
, hdr_dest
, hdr_recl
, NULL
, NULL
, 0);
842 buf_cache
= kmem_cache_create("arc_buf_t", sizeof (arc_buf_t
),
843 0, buf_cons
, buf_dest
, NULL
, NULL
, NULL
, 0);
845 for (i
= 0; i
< 256; i
++)
846 for (ct
= zfs_crc64_table
+ i
, *ct
= i
, j
= 8; j
> 0; j
--)
847 *ct
= (*ct
>> 1) ^ (-(*ct
& 1) & ZFS_CRC64_POLY
);
849 for (i
= 0; i
< BUF_LOCKS
; i
++) {
850 mutex_init(&buf_hash_table
.ht_locks
[i
].ht_lock
,
851 NULL
, MUTEX_DEFAULT
, NULL
);
855 #define ARC_MINTIME (hz>>4) /* 62 ms */
858 arc_cksum_verify(arc_buf_t
*buf
)
862 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
865 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
866 if (buf
->b_hdr
->b_freeze_cksum
== NULL
||
867 (buf
->b_hdr
->b_flags
& ARC_IO_ERROR
)) {
868 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
871 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
872 if (!ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
))
873 panic("buffer modified while frozen!");
874 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
878 arc_cksum_equal(arc_buf_t
*buf
)
883 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
884 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
885 equal
= ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
);
886 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
892 arc_cksum_compute(arc_buf_t
*buf
, boolean_t force
)
894 if (!force
&& !(zfs_flags
& ZFS_DEBUG_MODIFY
))
897 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
898 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
899 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
902 buf
->b_hdr
->b_freeze_cksum
= kmem_alloc(sizeof (zio_cksum_t
), KM_SLEEP
);
903 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
,
904 buf
->b_hdr
->b_freeze_cksum
);
905 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
909 arc_buf_thaw(arc_buf_t
*buf
)
911 if (zfs_flags
& ZFS_DEBUG_MODIFY
) {
912 if (buf
->b_hdr
->b_state
!= arc_anon
)
913 panic("modifying non-anon buffer!");
914 if (buf
->b_hdr
->b_flags
& ARC_IO_IN_PROGRESS
)
915 panic("modifying buffer while i/o in progress!");
916 arc_cksum_verify(buf
);
919 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
920 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
921 kmem_free(buf
->b_hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
922 buf
->b_hdr
->b_freeze_cksum
= NULL
;
924 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
928 arc_buf_freeze(arc_buf_t
*buf
)
930 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
933 ASSERT(buf
->b_hdr
->b_freeze_cksum
!= NULL
||
934 buf
->b_hdr
->b_state
== arc_anon
);
935 arc_cksum_compute(buf
, B_FALSE
);
939 add_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
941 ASSERT(MUTEX_HELD(hash_lock
));
943 if ((refcount_add(&ab
->b_refcnt
, tag
) == 1) &&
944 (ab
->b_state
!= arc_anon
)) {
945 uint64_t delta
= ab
->b_size
* ab
->b_datacnt
;
946 list_t
*list
= &ab
->b_state
->arcs_list
[ab
->b_type
];
947 uint64_t *size
= &ab
->b_state
->arcs_lsize
[ab
->b_type
];
949 ASSERT(!MUTEX_HELD(&ab
->b_state
->arcs_mtx
));
950 mutex_enter(&ab
->b_state
->arcs_mtx
);
951 ASSERT(list_link_active(&ab
->b_arc_node
));
952 list_remove(list
, ab
);
953 if (GHOST_STATE(ab
->b_state
)) {
954 ASSERT3U(ab
->b_datacnt
, ==, 0);
955 ASSERT3P(ab
->b_buf
, ==, NULL
);
959 ASSERT3U(*size
, >=, delta
);
960 atomic_add_64(size
, -delta
);
961 mutex_exit(&ab
->b_state
->arcs_mtx
);
962 /* remove the prefetch flag if we get a reference */
963 if (ab
->b_flags
& ARC_PREFETCH
)
964 ab
->b_flags
&= ~ARC_PREFETCH
;
969 remove_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
972 arc_state_t
*state
= ab
->b_state
;
974 ASSERT(state
== arc_anon
|| MUTEX_HELD(hash_lock
));
975 ASSERT(!GHOST_STATE(state
));
977 if (((cnt
= refcount_remove(&ab
->b_refcnt
, tag
)) == 0) &&
978 (state
!= arc_anon
)) {
979 uint64_t *size
= &state
->arcs_lsize
[ab
->b_type
];
981 ASSERT(!MUTEX_HELD(&state
->arcs_mtx
));
982 mutex_enter(&state
->arcs_mtx
);
983 ASSERT(!list_link_active(&ab
->b_arc_node
));
984 list_insert_head(&state
->arcs_list
[ab
->b_type
], ab
);
985 ASSERT(ab
->b_datacnt
> 0);
986 atomic_add_64(size
, ab
->b_size
* ab
->b_datacnt
);
987 mutex_exit(&state
->arcs_mtx
);
993 * Move the supplied buffer to the indicated state. The mutex
994 * for the buffer must be held by the caller.
997 arc_change_state(arc_state_t
*new_state
, arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
)
999 arc_state_t
*old_state
= ab
->b_state
;
1000 int64_t refcnt
= refcount_count(&ab
->b_refcnt
);
1001 uint64_t from_delta
, to_delta
;
1003 ASSERT(MUTEX_HELD(hash_lock
));
1004 ASSERT(new_state
!= old_state
);
1005 ASSERT(refcnt
== 0 || ab
->b_datacnt
> 0);
1006 ASSERT(ab
->b_datacnt
== 0 || !GHOST_STATE(new_state
));
1008 from_delta
= to_delta
= ab
->b_datacnt
* ab
->b_size
;
1011 * If this buffer is evictable, transfer it from the
1012 * old state list to the new state list.
1015 if (old_state
!= arc_anon
) {
1016 int use_mutex
= !MUTEX_HELD(&old_state
->arcs_mtx
);
1017 uint64_t *size
= &old_state
->arcs_lsize
[ab
->b_type
];
1020 mutex_enter(&old_state
->arcs_mtx
);
1022 ASSERT(list_link_active(&ab
->b_arc_node
));
1023 list_remove(&old_state
->arcs_list
[ab
->b_type
], ab
);
1026 * If prefetching out of the ghost cache,
1027 * we will have a non-null datacnt.
1029 if (GHOST_STATE(old_state
) && ab
->b_datacnt
== 0) {
1030 /* ghost elements have a ghost size */
1031 ASSERT(ab
->b_buf
== NULL
);
1032 from_delta
= ab
->b_size
;
1034 ASSERT3U(*size
, >=, from_delta
);
1035 atomic_add_64(size
, -from_delta
);
1038 mutex_exit(&old_state
->arcs_mtx
);
1040 if (new_state
!= arc_anon
) {
1041 int use_mutex
= !MUTEX_HELD(&new_state
->arcs_mtx
);
1042 uint64_t *size
= &new_state
->arcs_lsize
[ab
->b_type
];
1045 mutex_enter(&new_state
->arcs_mtx
);
1047 list_insert_head(&new_state
->arcs_list
[ab
->b_type
], ab
);
1049 /* ghost elements have a ghost size */
1050 if (GHOST_STATE(new_state
)) {
1051 ASSERT(ab
->b_datacnt
== 0);
1052 ASSERT(ab
->b_buf
== NULL
);
1053 to_delta
= ab
->b_size
;
1055 atomic_add_64(size
, to_delta
);
1058 mutex_exit(&new_state
->arcs_mtx
);
1062 ASSERT(!BUF_EMPTY(ab
));
1063 if (new_state
== arc_anon
) {
1064 buf_hash_remove(ab
);
1067 /* adjust state sizes */
1069 atomic_add_64(&new_state
->arcs_size
, to_delta
);
1071 ASSERT3U(old_state
->arcs_size
, >=, from_delta
);
1072 atomic_add_64(&old_state
->arcs_size
, -from_delta
);
1074 ab
->b_state
= new_state
;
1076 /* adjust l2arc hdr stats */
1077 if (new_state
== arc_l2c_only
)
1078 l2arc_hdr_stat_add();
1079 else if (old_state
== arc_l2c_only
)
1080 l2arc_hdr_stat_remove();
1084 arc_space_consume(uint64_t space
)
1086 atomic_add_64(&arc_meta_used
, space
);
1087 atomic_add_64(&arc_size
, space
);
1091 arc_space_return(uint64_t space
)
1093 ASSERT(arc_meta_used
>= space
);
1094 if (arc_meta_max
< arc_meta_used
)
1095 arc_meta_max
= arc_meta_used
;
1096 atomic_add_64(&arc_meta_used
, -space
);
1097 ASSERT(arc_size
>= space
);
1098 atomic_add_64(&arc_size
, -space
);
1102 arc_data_buf_alloc(uint64_t size
)
1104 if (arc_evict_needed(ARC_BUFC_DATA
))
1105 cv_signal(&arc_reclaim_thr_cv
);
1106 atomic_add_64(&arc_size
, size
);
1107 return (zio_data_buf_alloc(size
));
1111 arc_data_buf_free(void *buf
, uint64_t size
)
1113 zio_data_buf_free(buf
, size
);
1114 ASSERT(arc_size
>= size
);
1115 atomic_add_64(&arc_size
, -size
);
1119 arc_buf_alloc(spa_t
*spa
, int size
, void *tag
, arc_buf_contents_t type
)
1124 ASSERT3U(size
, >, 0);
1125 hdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
1126 ASSERT(BUF_EMPTY(hdr
));
1130 hdr
->b_state
= arc_anon
;
1131 hdr
->b_arc_access
= 0;
1132 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1135 buf
->b_efunc
= NULL
;
1136 buf
->b_private
= NULL
;
1139 arc_get_data_buf(buf
);
1142 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1143 (void) refcount_add(&hdr
->b_refcnt
, tag
);
1149 arc_buf_clone(arc_buf_t
*from
)
1152 arc_buf_hdr_t
*hdr
= from
->b_hdr
;
1153 uint64_t size
= hdr
->b_size
;
1155 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1158 buf
->b_efunc
= NULL
;
1159 buf
->b_private
= NULL
;
1160 buf
->b_next
= hdr
->b_buf
;
1162 arc_get_data_buf(buf
);
1163 bcopy(from
->b_data
, buf
->b_data
, size
);
1164 hdr
->b_datacnt
+= 1;
1169 arc_buf_add_ref(arc_buf_t
*buf
, void* tag
)
1172 kmutex_t
*hash_lock
;
1175 * Check to see if this buffer is evicted. Callers
1176 * must verify b_data != NULL to know if the add_ref
1179 rw_enter(&buf
->b_lock
, RW_READER
);
1180 if (buf
->b_data
== NULL
) {
1181 rw_exit(&buf
->b_lock
);
1185 ASSERT(hdr
!= NULL
);
1186 hash_lock
= HDR_LOCK(hdr
);
1187 mutex_enter(hash_lock
);
1188 rw_exit(&buf
->b_lock
);
1190 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
1191 add_reference(hdr
, hash_lock
, tag
);
1192 arc_access(hdr
, hash_lock
);
1193 mutex_exit(hash_lock
);
1194 ARCSTAT_BUMP(arcstat_hits
);
1195 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
1196 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
1197 data
, metadata
, hits
);
1201 * Free the arc data buffer. If it is an l2arc write in progress,
1202 * the buffer is placed on l2arc_free_on_write to be freed later.
1205 arc_buf_data_free(arc_buf_hdr_t
*hdr
, void (*free_func
)(void *, size_t),
1206 void *data
, size_t size
)
1208 if (HDR_L2_WRITING(hdr
)) {
1209 l2arc_data_free_t
*df
;
1210 df
= kmem_alloc(sizeof (l2arc_data_free_t
), KM_SLEEP
);
1211 df
->l2df_data
= data
;
1212 df
->l2df_size
= size
;
1213 df
->l2df_func
= free_func
;
1214 mutex_enter(&l2arc_free_on_write_mtx
);
1215 list_insert_head(l2arc_free_on_write
, df
);
1216 mutex_exit(&l2arc_free_on_write_mtx
);
1217 ARCSTAT_BUMP(arcstat_l2_free_on_write
);
1219 free_func(data
, size
);
1224 arc_buf_destroy(arc_buf_t
*buf
, boolean_t recycle
, boolean_t all
)
1228 /* free up data associated with the buf */
1230 arc_state_t
*state
= buf
->b_hdr
->b_state
;
1231 uint64_t size
= buf
->b_hdr
->b_size
;
1232 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
1234 arc_cksum_verify(buf
);
1236 if (type
== ARC_BUFC_METADATA
) {
1237 arc_buf_data_free(buf
->b_hdr
, zio_buf_free
,
1239 arc_space_return(size
);
1241 ASSERT(type
== ARC_BUFC_DATA
);
1242 arc_buf_data_free(buf
->b_hdr
,
1243 zio_data_buf_free
, buf
->b_data
, size
);
1244 atomic_add_64(&arc_size
, -size
);
1247 if (list_link_active(&buf
->b_hdr
->b_arc_node
)) {
1248 uint64_t *cnt
= &state
->arcs_lsize
[type
];
1250 ASSERT(refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
1251 ASSERT(state
!= arc_anon
);
1253 ASSERT3U(*cnt
, >=, size
);
1254 atomic_add_64(cnt
, -size
);
1256 ASSERT3U(state
->arcs_size
, >=, size
);
1257 atomic_add_64(&state
->arcs_size
, -size
);
1259 ASSERT(buf
->b_hdr
->b_datacnt
> 0);
1260 buf
->b_hdr
->b_datacnt
-= 1;
1263 /* only remove the buf if requested */
1267 /* remove the buf from the hdr list */
1268 for (bufp
= &buf
->b_hdr
->b_buf
; *bufp
!= buf
; bufp
= &(*bufp
)->b_next
)
1270 *bufp
= buf
->b_next
;
1272 ASSERT(buf
->b_efunc
== NULL
);
1274 /* clean up the buf */
1276 kmem_cache_free(buf_cache
, buf
);
1280 arc_hdr_destroy(arc_buf_hdr_t
*hdr
)
1282 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1283 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
1284 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
1285 ASSERT(!(hdr
->b_flags
& ARC_STORED
));
1287 if (hdr
->b_l2hdr
!= NULL
) {
1288 if (!MUTEX_HELD(&l2arc_buflist_mtx
)) {
1290 * To prevent arc_free() and l2arc_evict() from
1291 * attempting to free the same buffer at the same time,
1292 * a FREE_IN_PROGRESS flag is given to arc_free() to
1293 * give it priority. l2arc_evict() can't destroy this
1294 * header while we are waiting on l2arc_buflist_mtx.
1296 * The hdr may be removed from l2ad_buflist before we
1297 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1299 mutex_enter(&l2arc_buflist_mtx
);
1300 if (hdr
->b_l2hdr
!= NULL
) {
1301 list_remove(hdr
->b_l2hdr
->b_dev
->l2ad_buflist
,
1304 mutex_exit(&l2arc_buflist_mtx
);
1306 list_remove(hdr
->b_l2hdr
->b_dev
->l2ad_buflist
, hdr
);
1308 ARCSTAT_INCR(arcstat_l2_size
, -hdr
->b_size
);
1309 kmem_free(hdr
->b_l2hdr
, sizeof (l2arc_buf_hdr_t
));
1310 if (hdr
->b_state
== arc_l2c_only
)
1311 l2arc_hdr_stat_remove();
1312 hdr
->b_l2hdr
= NULL
;
1315 if (!BUF_EMPTY(hdr
)) {
1316 ASSERT(!HDR_IN_HASH_TABLE(hdr
));
1317 bzero(&hdr
->b_dva
, sizeof (dva_t
));
1321 while (hdr
->b_buf
) {
1322 arc_buf_t
*buf
= hdr
->b_buf
;
1325 mutex_enter(&arc_eviction_mtx
);
1326 rw_enter(&buf
->b_lock
, RW_WRITER
);
1327 ASSERT(buf
->b_hdr
!= NULL
);
1328 arc_buf_destroy(hdr
->b_buf
, FALSE
, FALSE
);
1329 hdr
->b_buf
= buf
->b_next
;
1330 buf
->b_hdr
= &arc_eviction_hdr
;
1331 buf
->b_next
= arc_eviction_list
;
1332 arc_eviction_list
= buf
;
1333 rw_exit(&buf
->b_lock
);
1334 mutex_exit(&arc_eviction_mtx
);
1336 arc_buf_destroy(hdr
->b_buf
, FALSE
, TRUE
);
1339 if (hdr
->b_freeze_cksum
!= NULL
) {
1340 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
1341 hdr
->b_freeze_cksum
= NULL
;
1344 ASSERT(!list_link_active(&hdr
->b_arc_node
));
1345 ASSERT3P(hdr
->b_hash_next
, ==, NULL
);
1346 ASSERT3P(hdr
->b_acb
, ==, NULL
);
1347 kmem_cache_free(hdr_cache
, hdr
);
1351 arc_buf_free(arc_buf_t
*buf
, void *tag
)
1353 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1354 int hashed
= hdr
->b_state
!= arc_anon
;
1356 ASSERT(buf
->b_efunc
== NULL
);
1357 ASSERT(buf
->b_data
!= NULL
);
1360 kmutex_t
*hash_lock
= HDR_LOCK(hdr
);
1362 mutex_enter(hash_lock
);
1363 (void) remove_reference(hdr
, hash_lock
, tag
);
1364 if (hdr
->b_datacnt
> 1)
1365 arc_buf_destroy(buf
, FALSE
, TRUE
);
1367 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1368 mutex_exit(hash_lock
);
1369 } else if (HDR_IO_IN_PROGRESS(hdr
)) {
1372 * We are in the middle of an async write. Don't destroy
1373 * this buffer unless the write completes before we finish
1374 * decrementing the reference count.
1376 mutex_enter(&arc_eviction_mtx
);
1377 (void) remove_reference(hdr
, NULL
, tag
);
1378 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1379 destroy_hdr
= !HDR_IO_IN_PROGRESS(hdr
);
1380 mutex_exit(&arc_eviction_mtx
);
1382 arc_hdr_destroy(hdr
);
1384 if (remove_reference(hdr
, NULL
, tag
) > 0) {
1385 ASSERT(HDR_IO_ERROR(hdr
));
1386 arc_buf_destroy(buf
, FALSE
, TRUE
);
1388 arc_hdr_destroy(hdr
);
1394 arc_buf_remove_ref(arc_buf_t
*buf
, void* tag
)
1396 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1397 kmutex_t
*hash_lock
= HDR_LOCK(hdr
);
1398 int no_callback
= (buf
->b_efunc
== NULL
);
1400 if (hdr
->b_state
== arc_anon
) {
1401 arc_buf_free(buf
, tag
);
1402 return (no_callback
);
1405 mutex_enter(hash_lock
);
1406 ASSERT(hdr
->b_state
!= arc_anon
);
1407 ASSERT(buf
->b_data
!= NULL
);
1409 (void) remove_reference(hdr
, hash_lock
, tag
);
1410 if (hdr
->b_datacnt
> 1) {
1412 arc_buf_destroy(buf
, FALSE
, TRUE
);
1413 } else if (no_callback
) {
1414 ASSERT(hdr
->b_buf
== buf
&& buf
->b_next
== NULL
);
1415 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1417 ASSERT(no_callback
|| hdr
->b_datacnt
> 1 ||
1418 refcount_is_zero(&hdr
->b_refcnt
));
1419 mutex_exit(hash_lock
);
1420 return (no_callback
);
1424 arc_buf_size(arc_buf_t
*buf
)
1426 return (buf
->b_hdr
->b_size
);
1430 * Evict buffers from list until we've removed the specified number of
1431 * bytes. Move the removed buffers to the appropriate evict state.
1432 * If the recycle flag is set, then attempt to "recycle" a buffer:
1433 * - look for a buffer to evict that is `bytes' long.
1434 * - return the data block from this buffer rather than freeing it.
1435 * This flag is used by callers that are trying to make space for a
1436 * new buffer in a full arc cache.
1438 * This function makes a "best effort". It skips over any buffers
1439 * it can't get a hash_lock on, and so may not catch all candidates.
1440 * It may also return without evicting as much space as requested.
1443 arc_evict(arc_state_t
*state
, spa_t
*spa
, int64_t bytes
, boolean_t recycle
,
1444 arc_buf_contents_t type
)
1446 arc_state_t
*evicted_state
;
1447 uint64_t bytes_evicted
= 0, skipped
= 0, missed
= 0;
1448 arc_buf_hdr_t
*ab
, *ab_prev
= NULL
;
1449 list_t
*list
= &state
->arcs_list
[type
];
1450 kmutex_t
*hash_lock
;
1451 boolean_t have_lock
;
1452 void *stolen
= NULL
;
1454 ASSERT(state
== arc_mru
|| state
== arc_mfu
);
1456 evicted_state
= (state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
1458 mutex_enter(&state
->arcs_mtx
);
1459 mutex_enter(&evicted_state
->arcs_mtx
);
1461 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1462 ab_prev
= list_prev(list
, ab
);
1463 /* prefetch buffers have a minimum lifespan */
1464 if (HDR_IO_IN_PROGRESS(ab
) ||
1465 (spa
&& ab
->b_spa
!= spa
) ||
1466 (ab
->b_flags
& (ARC_PREFETCH
|ARC_INDIRECT
) &&
1467 lbolt
- ab
->b_arc_access
< arc_min_prefetch_lifespan
)) {
1471 /* "lookahead" for better eviction candidate */
1472 if (recycle
&& ab
->b_size
!= bytes
&&
1473 ab_prev
&& ab_prev
->b_size
== bytes
)
1475 hash_lock
= HDR_LOCK(ab
);
1476 have_lock
= MUTEX_HELD(hash_lock
);
1477 if (have_lock
|| mutex_tryenter(hash_lock
)) {
1478 ASSERT3U(refcount_count(&ab
->b_refcnt
), ==, 0);
1479 ASSERT(ab
->b_datacnt
> 0);
1481 arc_buf_t
*buf
= ab
->b_buf
;
1482 if (!rw_tryenter(&buf
->b_lock
, RW_WRITER
)) {
1487 bytes_evicted
+= ab
->b_size
;
1488 if (recycle
&& ab
->b_type
== type
&&
1489 ab
->b_size
== bytes
&&
1490 !HDR_L2_WRITING(ab
)) {
1491 stolen
= buf
->b_data
;
1496 mutex_enter(&arc_eviction_mtx
);
1497 arc_buf_destroy(buf
,
1498 buf
->b_data
== stolen
, FALSE
);
1499 ab
->b_buf
= buf
->b_next
;
1500 buf
->b_hdr
= &arc_eviction_hdr
;
1501 buf
->b_next
= arc_eviction_list
;
1502 arc_eviction_list
= buf
;
1503 mutex_exit(&arc_eviction_mtx
);
1504 rw_exit(&buf
->b_lock
);
1506 rw_exit(&buf
->b_lock
);
1507 arc_buf_destroy(buf
,
1508 buf
->b_data
== stolen
, TRUE
);
1511 if (ab
->b_datacnt
== 0) {
1512 arc_change_state(evicted_state
, ab
, hash_lock
);
1513 ASSERT(HDR_IN_HASH_TABLE(ab
));
1514 ab
->b_flags
|= ARC_IN_HASH_TABLE
;
1515 ab
->b_flags
&= ~ARC_BUF_AVAILABLE
;
1516 DTRACE_PROBE1(arc__evict
, arc_buf_hdr_t
*, ab
);
1519 mutex_exit(hash_lock
);
1520 if (bytes
>= 0 && bytes_evicted
>= bytes
)
1527 mutex_exit(&evicted_state
->arcs_mtx
);
1528 mutex_exit(&state
->arcs_mtx
);
1530 if (bytes_evicted
< bytes
)
1531 dprintf("only evicted %lld bytes from %x",
1532 (longlong_t
)bytes_evicted
, state
);
1535 ARCSTAT_INCR(arcstat_evict_skip
, skipped
);
1538 ARCSTAT_INCR(arcstat_mutex_miss
, missed
);
1541 * We have just evicted some date into the ghost state, make
1542 * sure we also adjust the ghost state size if necessary.
1545 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
> arc_c
) {
1546 int64_t mru_over
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
+
1547 arc_mru_ghost
->arcs_size
- arc_c
;
1549 if (mru_over
> 0 && arc_mru_ghost
->arcs_lsize
[type
] > 0) {
1551 MIN(arc_mru_ghost
->arcs_lsize
[type
], mru_over
);
1552 arc_evict_ghost(arc_mru_ghost
, NULL
, todelete
);
1553 } else if (arc_mfu_ghost
->arcs_lsize
[type
] > 0) {
1554 int64_t todelete
= MIN(arc_mfu_ghost
->arcs_lsize
[type
],
1555 arc_mru_ghost
->arcs_size
+
1556 arc_mfu_ghost
->arcs_size
- arc_c
);
1557 arc_evict_ghost(arc_mfu_ghost
, NULL
, todelete
);
1565 * Remove buffers from list until we've removed the specified number of
1566 * bytes. Destroy the buffers that are removed.
1569 arc_evict_ghost(arc_state_t
*state
, spa_t
*spa
, int64_t bytes
)
1571 arc_buf_hdr_t
*ab
, *ab_prev
;
1572 list_t
*list
= &state
->arcs_list
[ARC_BUFC_DATA
];
1573 kmutex_t
*hash_lock
;
1574 uint64_t bytes_deleted
= 0;
1575 uint64_t bufs_skipped
= 0;
1577 ASSERT(GHOST_STATE(state
));
1579 mutex_enter(&state
->arcs_mtx
);
1580 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1581 ab_prev
= list_prev(list
, ab
);
1582 if (spa
&& ab
->b_spa
!= spa
)
1584 hash_lock
= HDR_LOCK(ab
);
1585 if (mutex_tryenter(hash_lock
)) {
1586 ASSERT(!HDR_IO_IN_PROGRESS(ab
));
1587 ASSERT(ab
->b_buf
== NULL
);
1588 ARCSTAT_BUMP(arcstat_deleted
);
1589 bytes_deleted
+= ab
->b_size
;
1591 if (ab
->b_l2hdr
!= NULL
) {
1593 * This buffer is cached on the 2nd Level ARC;
1594 * don't destroy the header.
1596 arc_change_state(arc_l2c_only
, ab
, hash_lock
);
1597 mutex_exit(hash_lock
);
1599 arc_change_state(arc_anon
, ab
, hash_lock
);
1600 mutex_exit(hash_lock
);
1601 arc_hdr_destroy(ab
);
1604 DTRACE_PROBE1(arc__delete
, arc_buf_hdr_t
*, ab
);
1605 if (bytes
>= 0 && bytes_deleted
>= bytes
)
1609 mutex_exit(&state
->arcs_mtx
);
1610 mutex_enter(hash_lock
);
1611 mutex_exit(hash_lock
);
1617 mutex_exit(&state
->arcs_mtx
);
1619 if (list
== &state
->arcs_list
[ARC_BUFC_DATA
] &&
1620 (bytes
< 0 || bytes_deleted
< bytes
)) {
1621 list
= &state
->arcs_list
[ARC_BUFC_METADATA
];
1626 ARCSTAT_INCR(arcstat_mutex_miss
, bufs_skipped
);
1630 if (bytes_deleted
< bytes
)
1631 dprintf("only deleted %lld bytes from %p",
1632 (longlong_t
)bytes_deleted
, state
);
1638 int64_t top_sz
, mru_over
, arc_over
, todelete
;
1640 top_sz
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
+ arc_meta_used
;
1642 if (top_sz
> arc_p
&& arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
1644 MIN(arc_mru
->arcs_lsize
[ARC_BUFC_DATA
], top_sz
- arc_p
);
1645 (void) arc_evict(arc_mru
, NULL
, toevict
, FALSE
, ARC_BUFC_DATA
);
1646 top_sz
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
;
1649 if (top_sz
> arc_p
&& arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
1651 MIN(arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
], top_sz
- arc_p
);
1652 (void) arc_evict(arc_mru
, NULL
, toevict
, FALSE
,
1654 top_sz
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
;
1657 mru_over
= top_sz
+ arc_mru_ghost
->arcs_size
- arc_c
;
1660 if (arc_mru_ghost
->arcs_size
> 0) {
1661 todelete
= MIN(arc_mru_ghost
->arcs_size
, mru_over
);
1662 arc_evict_ghost(arc_mru_ghost
, NULL
, todelete
);
1666 if ((arc_over
= arc_size
- arc_c
) > 0) {
1669 if (arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
1671 MIN(arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
], arc_over
);
1672 (void) arc_evict(arc_mfu
, NULL
, toevict
, FALSE
,
1674 arc_over
= arc_size
- arc_c
;
1678 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
1680 MIN(arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
],
1682 (void) arc_evict(arc_mfu
, NULL
, toevict
, FALSE
,
1686 tbl_over
= arc_size
+ arc_mru_ghost
->arcs_size
+
1687 arc_mfu_ghost
->arcs_size
- arc_c
* 2;
1689 if (tbl_over
> 0 && arc_mfu_ghost
->arcs_size
> 0) {
1690 todelete
= MIN(arc_mfu_ghost
->arcs_size
, tbl_over
);
1691 arc_evict_ghost(arc_mfu_ghost
, NULL
, todelete
);
1697 arc_do_user_evicts(void)
1699 mutex_enter(&arc_eviction_mtx
);
1700 while (arc_eviction_list
!= NULL
) {
1701 arc_buf_t
*buf
= arc_eviction_list
;
1702 arc_eviction_list
= buf
->b_next
;
1703 rw_enter(&buf
->b_lock
, RW_WRITER
);
1705 rw_exit(&buf
->b_lock
);
1706 mutex_exit(&arc_eviction_mtx
);
1708 if (buf
->b_efunc
!= NULL
)
1709 VERIFY(buf
->b_efunc(buf
) == 0);
1711 buf
->b_efunc
= NULL
;
1712 buf
->b_private
= NULL
;
1713 kmem_cache_free(buf_cache
, buf
);
1714 mutex_enter(&arc_eviction_mtx
);
1716 mutex_exit(&arc_eviction_mtx
);
1720 * Flush all *evictable* data from the cache for the given spa.
1721 * NOTE: this will not touch "active" (i.e. referenced) data.
1724 arc_flush(spa_t
*spa
)
1726 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_DATA
])) {
1727 (void) arc_evict(arc_mru
, spa
, -1, FALSE
, ARC_BUFC_DATA
);
1731 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
])) {
1732 (void) arc_evict(arc_mru
, spa
, -1, FALSE
, ARC_BUFC_METADATA
);
1736 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
])) {
1737 (void) arc_evict(arc_mfu
, spa
, -1, FALSE
, ARC_BUFC_DATA
);
1741 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
])) {
1742 (void) arc_evict(arc_mfu
, spa
, -1, FALSE
, ARC_BUFC_METADATA
);
1747 arc_evict_ghost(arc_mru_ghost
, spa
, -1);
1748 arc_evict_ghost(arc_mfu_ghost
, spa
, -1);
1750 mutex_enter(&arc_reclaim_thr_lock
);
1751 arc_do_user_evicts();
1752 mutex_exit(&arc_reclaim_thr_lock
);
1753 ASSERT(spa
|| arc_eviction_list
== NULL
);
1756 int arc_shrink_shift
= 5; /* log2(fraction of arc to reclaim) */
1761 if (arc_c
> arc_c_min
) {
1765 to_free
= MAX(arc_c
>> arc_shrink_shift
, ptob(needfree
));
1767 to_free
= arc_c
>> arc_shrink_shift
;
1769 if (arc_c
> arc_c_min
+ to_free
)
1770 atomic_add_64(&arc_c
, -to_free
);
1774 atomic_add_64(&arc_p
, -(arc_p
>> arc_shrink_shift
));
1775 if (arc_c
> arc_size
)
1776 arc_c
= MAX(arc_size
, arc_c_min
);
1778 arc_p
= (arc_c
>> 1);
1779 ASSERT(arc_c
>= arc_c_min
);
1780 ASSERT((int64_t)arc_p
>= 0);
1783 if (arc_size
> arc_c
)
1788 arc_reclaim_needed(void)
1798 * take 'desfree' extra pages, so we reclaim sooner, rather than later
1803 * check that we're out of range of the pageout scanner. It starts to
1804 * schedule paging if freemem is less than lotsfree and needfree.
1805 * lotsfree is the high-water mark for pageout, and needfree is the
1806 * number of needed free pages. We add extra pages here to make sure
1807 * the scanner doesn't start up while we're freeing memory.
1809 if (freemem
< lotsfree
+ needfree
+ extra
)
1813 * check to make sure that swapfs has enough space so that anon
1814 * reservations can still succeed. anon_resvmem() checks that the
1815 * availrmem is greater than swapfs_minfree, and the number of reserved
1816 * swap pages. We also add a bit of extra here just to prevent
1817 * circumstances from getting really dire.
1819 if (availrmem
< swapfs_minfree
+ swapfs_reserve
+ extra
)
1824 * If we're on an i386 platform, it's possible that we'll exhaust the
1825 * kernel heap space before we ever run out of available physical
1826 * memory. Most checks of the size of the heap_area compare against
1827 * tune.t_minarmem, which is the minimum available real memory that we
1828 * can have in the system. However, this is generally fixed at 25 pages
1829 * which is so low that it's useless. In this comparison, we seek to
1830 * calculate the total heap-size, and reclaim if more than 3/4ths of the
1831 * heap is allocated. (Or, in the calculation, if less than 1/4th is
1834 if (btop(vmem_size(heap_arena
, VMEM_FREE
)) <
1835 (btop(vmem_size(heap_arena
, VMEM_FREE
| VMEM_ALLOC
)) >> 2))
1840 if (spa_get_random(100) == 0)
1847 arc_kmem_reap_now(arc_reclaim_strategy_t strat
)
1850 kmem_cache_t
*prev_cache
= NULL
;
1851 kmem_cache_t
*prev_data_cache
= NULL
;
1852 extern kmem_cache_t
*zio_buf_cache
[];
1853 extern kmem_cache_t
*zio_data_buf_cache
[];
1856 if (arc_meta_used
>= arc_meta_limit
) {
1858 * We are exceeding our meta-data cache limit.
1859 * Purge some DNLC entries to release holds on meta-data.
1861 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent
);
1865 * Reclaim unused memory from all kmem caches.
1872 * An aggressive reclamation will shrink the cache size as well as
1873 * reap free buffers from the arc kmem caches.
1875 if (strat
== ARC_RECLAIM_AGGR
)
1878 for (i
= 0; i
< SPA_MAXBLOCKSIZE
>> SPA_MINBLOCKSHIFT
; i
++) {
1879 if (zio_buf_cache
[i
] != prev_cache
) {
1880 prev_cache
= zio_buf_cache
[i
];
1881 kmem_cache_reap_now(zio_buf_cache
[i
]);
1883 if (zio_data_buf_cache
[i
] != prev_data_cache
) {
1884 prev_data_cache
= zio_data_buf_cache
[i
];
1885 kmem_cache_reap_now(zio_data_buf_cache
[i
]);
1888 kmem_cache_reap_now(buf_cache
);
1889 kmem_cache_reap_now(hdr_cache
);
1893 arc_reclaim_thread(void)
1895 clock_t growtime
= 0;
1896 arc_reclaim_strategy_t last_reclaim
= ARC_RECLAIM_CONS
;
1899 CALLB_CPR_INIT(&cpr
, &arc_reclaim_thr_lock
, callb_generic_cpr
, FTAG
);
1901 mutex_enter(&arc_reclaim_thr_lock
);
1902 while (arc_thread_exit
== 0) {
1903 if (arc_reclaim_needed()) {
1906 if (last_reclaim
== ARC_RECLAIM_CONS
) {
1907 last_reclaim
= ARC_RECLAIM_AGGR
;
1909 last_reclaim
= ARC_RECLAIM_CONS
;
1913 last_reclaim
= ARC_RECLAIM_AGGR
;
1917 /* reset the growth delay for every reclaim */
1918 growtime
= lbolt
+ (arc_grow_retry
* hz
);
1920 arc_kmem_reap_now(last_reclaim
);
1923 } else if (arc_no_grow
&& lbolt
>= growtime
) {
1924 arc_no_grow
= FALSE
;
1927 if (2 * arc_c
< arc_size
+
1928 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
)
1931 if (arc_eviction_list
!= NULL
)
1932 arc_do_user_evicts();
1934 /* block until needed, or one second, whichever is shorter */
1935 CALLB_CPR_SAFE_BEGIN(&cpr
);
1936 (void) cv_timedwait(&arc_reclaim_thr_cv
,
1937 &arc_reclaim_thr_lock
, (lbolt
+ hz
));
1938 CALLB_CPR_SAFE_END(&cpr
, &arc_reclaim_thr_lock
);
1941 arc_thread_exit
= 0;
1942 cv_broadcast(&arc_reclaim_thr_cv
);
1943 CALLB_CPR_EXIT(&cpr
); /* drops arc_reclaim_thr_lock */
1948 * Adapt arc info given the number of bytes we are trying to add and
1949 * the state that we are comming from. This function is only called
1950 * when we are adding new content to the cache.
1953 arc_adapt(int bytes
, arc_state_t
*state
)
1957 if (state
== arc_l2c_only
)
1962 * Adapt the target size of the MRU list:
1963 * - if we just hit in the MRU ghost list, then increase
1964 * the target size of the MRU list.
1965 * - if we just hit in the MFU ghost list, then increase
1966 * the target size of the MFU list by decreasing the
1967 * target size of the MRU list.
1969 if (state
== arc_mru_ghost
) {
1970 mult
= ((arc_mru_ghost
->arcs_size
>= arc_mfu_ghost
->arcs_size
) ?
1971 1 : (arc_mfu_ghost
->arcs_size
/arc_mru_ghost
->arcs_size
));
1973 arc_p
= MIN(arc_c
, arc_p
+ bytes
* mult
);
1974 } else if (state
== arc_mfu_ghost
) {
1975 mult
= ((arc_mfu_ghost
->arcs_size
>= arc_mru_ghost
->arcs_size
) ?
1976 1 : (arc_mru_ghost
->arcs_size
/arc_mfu_ghost
->arcs_size
));
1978 arc_p
= MAX(0, (int64_t)arc_p
- bytes
* mult
);
1980 ASSERT((int64_t)arc_p
>= 0);
1982 if (arc_reclaim_needed()) {
1983 cv_signal(&arc_reclaim_thr_cv
);
1990 if (arc_c
>= arc_c_max
)
1994 * If we're within (2 * maxblocksize) bytes of the target
1995 * cache size, increment the target cache size
1997 if (arc_size
> arc_c
- (2ULL << SPA_MAXBLOCKSHIFT
)) {
1998 atomic_add_64(&arc_c
, (int64_t)bytes
);
1999 if (arc_c
> arc_c_max
)
2001 else if (state
== arc_anon
)
2002 atomic_add_64(&arc_p
, (int64_t)bytes
);
2006 ASSERT((int64_t)arc_p
>= 0);
2010 * Check if the cache has reached its limits and eviction is required
2014 arc_evict_needed(arc_buf_contents_t type
)
2016 if (type
== ARC_BUFC_METADATA
&& arc_meta_used
>= arc_meta_limit
)
2021 * If zio data pages are being allocated out of a separate heap segment,
2022 * then enforce that the size of available vmem for this area remains
2023 * above about 1/32nd free.
2025 if (type
== ARC_BUFC_DATA
&& zio_arena
!= NULL
&&
2026 vmem_size(zio_arena
, VMEM_FREE
) <
2027 (vmem_size(zio_arena
, VMEM_ALLOC
) >> 5))
2031 if (arc_reclaim_needed())
2034 return (arc_size
> arc_c
);
2038 * The buffer, supplied as the first argument, needs a data block.
2039 * So, if we are at cache max, determine which cache should be victimized.
2040 * We have the following cases:
2042 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2043 * In this situation if we're out of space, but the resident size of the MFU is
2044 * under the limit, victimize the MFU cache to satisfy this insertion request.
2046 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2047 * Here, we've used up all of the available space for the MRU, so we need to
2048 * evict from our own cache instead. Evict from the set of resident MRU
2051 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2052 * c minus p represents the MFU space in the cache, since p is the size of the
2053 * cache that is dedicated to the MRU. In this situation there's still space on
2054 * the MFU side, so the MRU side needs to be victimized.
2056 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2057 * MFU's resident set is consuming more space than it has been allotted. In
2058 * this situation, we must victimize our own cache, the MFU, for this insertion.
2061 arc_get_data_buf(arc_buf_t
*buf
)
2063 arc_state_t
*state
= buf
->b_hdr
->b_state
;
2064 uint64_t size
= buf
->b_hdr
->b_size
;
2065 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
2067 arc_adapt(size
, state
);
2070 * We have not yet reached cache maximum size,
2071 * just allocate a new buffer.
2073 if (!arc_evict_needed(type
)) {
2074 if (type
== ARC_BUFC_METADATA
) {
2075 buf
->b_data
= zio_buf_alloc(size
);
2076 arc_space_consume(size
);
2078 ASSERT(type
== ARC_BUFC_DATA
);
2079 buf
->b_data
= zio_data_buf_alloc(size
);
2080 atomic_add_64(&arc_size
, size
);
2086 * If we are prefetching from the mfu ghost list, this buffer
2087 * will end up on the mru list; so steal space from there.
2089 if (state
== arc_mfu_ghost
)
2090 state
= buf
->b_hdr
->b_flags
& ARC_PREFETCH
? arc_mru
: arc_mfu
;
2091 else if (state
== arc_mru_ghost
)
2094 if (state
== arc_mru
|| state
== arc_anon
) {
2095 uint64_t mru_used
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
;
2096 state
= (arc_mfu
->arcs_lsize
[type
] > 0 &&
2097 arc_p
> mru_used
) ? arc_mfu
: arc_mru
;
2100 uint64_t mfu_space
= arc_c
- arc_p
;
2101 state
= (arc_mru
->arcs_lsize
[type
] > 0 &&
2102 mfu_space
> arc_mfu
->arcs_size
) ? arc_mru
: arc_mfu
;
2104 if ((buf
->b_data
= arc_evict(state
, NULL
, size
, TRUE
, type
)) == NULL
) {
2105 if (type
== ARC_BUFC_METADATA
) {
2106 buf
->b_data
= zio_buf_alloc(size
);
2107 arc_space_consume(size
);
2109 ASSERT(type
== ARC_BUFC_DATA
);
2110 buf
->b_data
= zio_data_buf_alloc(size
);
2111 atomic_add_64(&arc_size
, size
);
2113 ARCSTAT_BUMP(arcstat_recycle_miss
);
2115 ASSERT(buf
->b_data
!= NULL
);
2118 * Update the state size. Note that ghost states have a
2119 * "ghost size" and so don't need to be updated.
2121 if (!GHOST_STATE(buf
->b_hdr
->b_state
)) {
2122 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
2124 atomic_add_64(&hdr
->b_state
->arcs_size
, size
);
2125 if (list_link_active(&hdr
->b_arc_node
)) {
2126 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
2127 atomic_add_64(&hdr
->b_state
->arcs_lsize
[type
], size
);
2130 * If we are growing the cache, and we are adding anonymous
2131 * data, and we have outgrown arc_p, update arc_p
2133 if (arc_size
< arc_c
&& hdr
->b_state
== arc_anon
&&
2134 arc_anon
->arcs_size
+ arc_mru
->arcs_size
> arc_p
)
2135 arc_p
= MIN(arc_c
, arc_p
+ size
);
2140 * This routine is called whenever a buffer is accessed.
2141 * NOTE: the hash lock is dropped in this function.
2144 arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
)
2146 ASSERT(MUTEX_HELD(hash_lock
));
2148 if (buf
->b_state
== arc_anon
) {
2150 * This buffer is not in the cache, and does not
2151 * appear in our "ghost" list. Add the new buffer
2155 ASSERT(buf
->b_arc_access
== 0);
2156 buf
->b_arc_access
= lbolt
;
2157 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2158 arc_change_state(arc_mru
, buf
, hash_lock
);
2160 } else if (buf
->b_state
== arc_mru
) {
2162 * If this buffer is here because of a prefetch, then either:
2163 * - clear the flag if this is a "referencing" read
2164 * (any subsequent access will bump this into the MFU state).
2166 * - move the buffer to the head of the list if this is
2167 * another prefetch (to make it less likely to be evicted).
2169 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2170 if (refcount_count(&buf
->b_refcnt
) == 0) {
2171 ASSERT(list_link_active(&buf
->b_arc_node
));
2173 buf
->b_flags
&= ~ARC_PREFETCH
;
2174 ARCSTAT_BUMP(arcstat_mru_hits
);
2176 buf
->b_arc_access
= lbolt
;
2181 * This buffer has been "accessed" only once so far,
2182 * but it is still in the cache. Move it to the MFU
2185 if (lbolt
> buf
->b_arc_access
+ ARC_MINTIME
) {
2187 * More than 125ms have passed since we
2188 * instantiated this buffer. Move it to the
2189 * most frequently used state.
2191 buf
->b_arc_access
= lbolt
;
2192 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2193 arc_change_state(arc_mfu
, buf
, hash_lock
);
2195 ARCSTAT_BUMP(arcstat_mru_hits
);
2196 } else if (buf
->b_state
== arc_mru_ghost
) {
2197 arc_state_t
*new_state
;
2199 * This buffer has been "accessed" recently, but
2200 * was evicted from the cache. Move it to the
2204 if (buf
->b_flags
& ARC_PREFETCH
) {
2205 new_state
= arc_mru
;
2206 if (refcount_count(&buf
->b_refcnt
) > 0)
2207 buf
->b_flags
&= ~ARC_PREFETCH
;
2208 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2210 new_state
= arc_mfu
;
2211 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2214 buf
->b_arc_access
= lbolt
;
2215 arc_change_state(new_state
, buf
, hash_lock
);
2217 ARCSTAT_BUMP(arcstat_mru_ghost_hits
);
2218 } else if (buf
->b_state
== arc_mfu
) {
2220 * This buffer has been accessed more than once and is
2221 * still in the cache. Keep it in the MFU state.
2223 * NOTE: an add_reference() that occurred when we did
2224 * the arc_read() will have kicked this off the list.
2225 * If it was a prefetch, we will explicitly move it to
2226 * the head of the list now.
2228 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2229 ASSERT(refcount_count(&buf
->b_refcnt
) == 0);
2230 ASSERT(list_link_active(&buf
->b_arc_node
));
2232 ARCSTAT_BUMP(arcstat_mfu_hits
);
2233 buf
->b_arc_access
= lbolt
;
2234 } else if (buf
->b_state
== arc_mfu_ghost
) {
2235 arc_state_t
*new_state
= arc_mfu
;
2237 * This buffer has been accessed more than once but has
2238 * been evicted from the cache. Move it back to the
2242 if (buf
->b_flags
& ARC_PREFETCH
) {
2244 * This is a prefetch access...
2245 * move this block back to the MRU state.
2247 ASSERT3U(refcount_count(&buf
->b_refcnt
), ==, 0);
2248 new_state
= arc_mru
;
2251 buf
->b_arc_access
= lbolt
;
2252 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2253 arc_change_state(new_state
, buf
, hash_lock
);
2255 ARCSTAT_BUMP(arcstat_mfu_ghost_hits
);
2256 } else if (buf
->b_state
== arc_l2c_only
) {
2258 * This buffer is on the 2nd Level ARC.
2261 buf
->b_arc_access
= lbolt
;
2262 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2263 arc_change_state(arc_mfu
, buf
, hash_lock
);
2265 ASSERT(!"invalid arc state");
2269 /* a generic arc_done_func_t which you can use */
2272 arc_bcopy_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2274 bcopy(buf
->b_data
, arg
, buf
->b_hdr
->b_size
);
2275 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2278 /* a generic arc_done_func_t */
2280 arc_getbuf_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2282 arc_buf_t
**bufp
= arg
;
2283 if (zio
&& zio
->io_error
) {
2284 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2292 arc_read_done(zio_t
*zio
)
2294 arc_buf_hdr_t
*hdr
, *found
;
2296 arc_buf_t
*abuf
; /* buffer we're assigning to callback */
2297 kmutex_t
*hash_lock
;
2298 arc_callback_t
*callback_list
, *acb
;
2299 int freeable
= FALSE
;
2301 buf
= zio
->io_private
;
2305 * The hdr was inserted into hash-table and removed from lists
2306 * prior to starting I/O. We should find this header, since
2307 * it's in the hash table, and it should be legit since it's
2308 * not possible to evict it during the I/O. The only possible
2309 * reason for it not to be found is if we were freed during the
2312 found
= buf_hash_find(zio
->io_spa
, &hdr
->b_dva
, hdr
->b_birth
,
2315 ASSERT((found
== NULL
&& HDR_FREED_IN_READ(hdr
) && hash_lock
== NULL
) ||
2316 (found
== hdr
&& DVA_EQUAL(&hdr
->b_dva
, BP_IDENTITY(zio
->io_bp
))) ||
2317 (found
== hdr
&& HDR_L2_READING(hdr
)));
2319 hdr
->b_flags
&= ~ARC_L2_EVICTED
;
2320 if (l2arc_noprefetch
&& (hdr
->b_flags
& ARC_PREFETCH
))
2321 hdr
->b_flags
&= ~ARC_L2CACHE
;
2323 /* byteswap if necessary */
2324 callback_list
= hdr
->b_acb
;
2325 ASSERT(callback_list
!= NULL
);
2326 if (BP_SHOULD_BYTESWAP(zio
->io_bp
)) {
2327 arc_byteswap_func_t
*func
= BP_GET_LEVEL(zio
->io_bp
) > 0 ?
2328 byteswap_uint64_array
:
2329 dmu_ot
[BP_GET_TYPE(zio
->io_bp
)].ot_byteswap
;
2330 func(buf
->b_data
, hdr
->b_size
);
2333 arc_cksum_compute(buf
, B_FALSE
);
2335 /* create copies of the data buffer for the callers */
2337 for (acb
= callback_list
; acb
; acb
= acb
->acb_next
) {
2338 if (acb
->acb_done
) {
2340 abuf
= arc_buf_clone(buf
);
2341 acb
->acb_buf
= abuf
;
2346 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
2347 ASSERT(!HDR_BUF_AVAILABLE(hdr
));
2349 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
2351 ASSERT(refcount_is_zero(&hdr
->b_refcnt
) || callback_list
!= NULL
);
2353 if (zio
->io_error
!= 0) {
2354 hdr
->b_flags
|= ARC_IO_ERROR
;
2355 if (hdr
->b_state
!= arc_anon
)
2356 arc_change_state(arc_anon
, hdr
, hash_lock
);
2357 if (HDR_IN_HASH_TABLE(hdr
))
2358 buf_hash_remove(hdr
);
2359 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2363 * Broadcast before we drop the hash_lock to avoid the possibility
2364 * that the hdr (and hence the cv) might be freed before we get to
2365 * the cv_broadcast().
2367 cv_broadcast(&hdr
->b_cv
);
2371 * Only call arc_access on anonymous buffers. This is because
2372 * if we've issued an I/O for an evicted buffer, we've already
2373 * called arc_access (to prevent any simultaneous readers from
2374 * getting confused).
2376 if (zio
->io_error
== 0 && hdr
->b_state
== arc_anon
)
2377 arc_access(hdr
, hash_lock
);
2378 mutex_exit(hash_lock
);
2381 * This block was freed while we waited for the read to
2382 * complete. It has been removed from the hash table and
2383 * moved to the anonymous state (so that it won't show up
2386 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
2387 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2390 /* execute each callback and free its structure */
2391 while ((acb
= callback_list
) != NULL
) {
2393 acb
->acb_done(zio
, acb
->acb_buf
, acb
->acb_private
);
2395 if (acb
->acb_zio_dummy
!= NULL
) {
2396 acb
->acb_zio_dummy
->io_error
= zio
->io_error
;
2397 zio_nowait(acb
->acb_zio_dummy
);
2400 callback_list
= acb
->acb_next
;
2401 kmem_free(acb
, sizeof (arc_callback_t
));
2405 arc_hdr_destroy(hdr
);
2409 * "Read" the block block at the specified DVA (in bp) via the
2410 * cache. If the block is found in the cache, invoke the provided
2411 * callback immediately and return. Note that the `zio' parameter
2412 * in the callback will be NULL in this case, since no IO was
2413 * required. If the block is not in the cache pass the read request
2414 * on to the spa with a substitute callback function, so that the
2415 * requested block will be added to the cache.
2417 * If a read request arrives for a block that has a read in-progress,
2418 * either wait for the in-progress read to complete (and return the
2419 * results); or, if this is a read with a "done" func, add a record
2420 * to the read to invoke the "done" func when the read completes,
2421 * and return; or just return.
2423 * arc_read_done() will invoke all the requested "done" functions
2424 * for readers of this block.
2426 * Normal callers should use arc_read and pass the arc buffer and offset
2427 * for the bp. But if you know you don't need locking, you can use
2431 arc_read(zio_t
*pio
, spa_t
*spa
, blkptr_t
*bp
, arc_buf_t
*pbuf
,
2432 arc_done_func_t
*done
, void *private, int priority
, int zio_flags
,
2433 uint32_t *arc_flags
, const zbookmark_t
*zb
)
2436 arc_buf_hdr_t
*hdr
= pbuf
->b_hdr
;
2438 ASSERT(!refcount_is_zero(&pbuf
->b_hdr
->b_refcnt
));
2439 ASSERT3U((char *)bp
- (char *)pbuf
->b_data
, <, pbuf
->b_hdr
->b_size
);
2440 rw_enter(&pbuf
->b_lock
, RW_READER
);
2442 err
= arc_read_nolock(pio
, spa
, bp
, done
, private, priority
,
2443 zio_flags
, arc_flags
, zb
);
2445 ASSERT3P(hdr
, ==, pbuf
->b_hdr
);
2446 rw_exit(&pbuf
->b_lock
);
2451 arc_read_nolock(zio_t
*pio
, spa_t
*spa
, blkptr_t
*bp
,
2452 arc_done_func_t
*done
, void *private, int priority
, int zio_flags
,
2453 uint32_t *arc_flags
, const zbookmark_t
*zb
)
2457 kmutex_t
*hash_lock
;
2461 hdr
= buf_hash_find(spa
, BP_IDENTITY(bp
), bp
->blk_birth
, &hash_lock
);
2462 if (hdr
&& hdr
->b_datacnt
> 0) {
2464 *arc_flags
|= ARC_CACHED
;
2466 if (HDR_IO_IN_PROGRESS(hdr
)) {
2468 if (*arc_flags
& ARC_WAIT
) {
2469 cv_wait(&hdr
->b_cv
, hash_lock
);
2470 mutex_exit(hash_lock
);
2473 ASSERT(*arc_flags
& ARC_NOWAIT
);
2476 arc_callback_t
*acb
= NULL
;
2478 acb
= kmem_zalloc(sizeof (arc_callback_t
),
2480 acb
->acb_done
= done
;
2481 acb
->acb_private
= private;
2483 acb
->acb_zio_dummy
= zio_null(pio
,
2484 spa
, NULL
, NULL
, zio_flags
);
2486 ASSERT(acb
->acb_done
!= NULL
);
2487 acb
->acb_next
= hdr
->b_acb
;
2489 add_reference(hdr
, hash_lock
, private);
2490 mutex_exit(hash_lock
);
2493 mutex_exit(hash_lock
);
2497 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
2500 add_reference(hdr
, hash_lock
, private);
2502 * If this block is already in use, create a new
2503 * copy of the data so that we will be guaranteed
2504 * that arc_release() will always succeed.
2508 ASSERT(buf
->b_data
);
2509 if (HDR_BUF_AVAILABLE(hdr
)) {
2510 ASSERT(buf
->b_efunc
== NULL
);
2511 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
2513 buf
= arc_buf_clone(buf
);
2515 } else if (*arc_flags
& ARC_PREFETCH
&&
2516 refcount_count(&hdr
->b_refcnt
) == 0) {
2517 hdr
->b_flags
|= ARC_PREFETCH
;
2519 DTRACE_PROBE1(arc__hit
, arc_buf_hdr_t
*, hdr
);
2520 arc_access(hdr
, hash_lock
);
2521 if (*arc_flags
& ARC_L2CACHE
)
2522 hdr
->b_flags
|= ARC_L2CACHE
;
2523 mutex_exit(hash_lock
);
2524 ARCSTAT_BUMP(arcstat_hits
);
2525 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
2526 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
2527 data
, metadata
, hits
);
2530 done(NULL
, buf
, private);
2532 uint64_t size
= BP_GET_LSIZE(bp
);
2533 arc_callback_t
*acb
;
2538 /* this block is not in the cache */
2539 arc_buf_hdr_t
*exists
;
2540 arc_buf_contents_t type
= BP_GET_BUFC_TYPE(bp
);
2541 buf
= arc_buf_alloc(spa
, size
, private, type
);
2543 hdr
->b_dva
= *BP_IDENTITY(bp
);
2544 hdr
->b_birth
= bp
->blk_birth
;
2545 hdr
->b_cksum0
= bp
->blk_cksum
.zc_word
[0];
2546 exists
= buf_hash_insert(hdr
, &hash_lock
);
2548 /* somebody beat us to the hash insert */
2549 mutex_exit(hash_lock
);
2550 bzero(&hdr
->b_dva
, sizeof (dva_t
));
2553 (void) arc_buf_remove_ref(buf
, private);
2554 goto top
; /* restart the IO request */
2556 /* if this is a prefetch, we don't have a reference */
2557 if (*arc_flags
& ARC_PREFETCH
) {
2558 (void) remove_reference(hdr
, hash_lock
,
2560 hdr
->b_flags
|= ARC_PREFETCH
;
2562 if (*arc_flags
& ARC_L2CACHE
)
2563 hdr
->b_flags
|= ARC_L2CACHE
;
2564 if (BP_GET_LEVEL(bp
) > 0)
2565 hdr
->b_flags
|= ARC_INDIRECT
;
2567 /* this block is in the ghost cache */
2568 ASSERT(GHOST_STATE(hdr
->b_state
));
2569 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
2570 ASSERT3U(refcount_count(&hdr
->b_refcnt
), ==, 0);
2571 ASSERT(hdr
->b_buf
== NULL
);
2573 /* if this is a prefetch, we don't have a reference */
2574 if (*arc_flags
& ARC_PREFETCH
)
2575 hdr
->b_flags
|= ARC_PREFETCH
;
2577 add_reference(hdr
, hash_lock
, private);
2578 if (*arc_flags
& ARC_L2CACHE
)
2579 hdr
->b_flags
|= ARC_L2CACHE
;
2580 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
2583 buf
->b_efunc
= NULL
;
2584 buf
->b_private
= NULL
;
2587 arc_get_data_buf(buf
);
2588 ASSERT(hdr
->b_datacnt
== 0);
2593 acb
= kmem_zalloc(sizeof (arc_callback_t
), KM_SLEEP
);
2594 acb
->acb_done
= done
;
2595 acb
->acb_private
= private;
2597 ASSERT(hdr
->b_acb
== NULL
);
2599 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
2602 * If the buffer has been evicted, migrate it to a present state
2603 * before issuing the I/O. Once we drop the hash-table lock,
2604 * the header will be marked as I/O in progress and have an
2605 * attached buffer. At this point, anybody who finds this
2606 * buffer ought to notice that it's legit but has a pending I/O.
2609 if (GHOST_STATE(hdr
->b_state
))
2610 arc_access(hdr
, hash_lock
);
2612 if (HDR_L2CACHE(hdr
) && hdr
->b_l2hdr
!= NULL
&&
2613 (vd
= hdr
->b_l2hdr
->b_dev
->l2ad_vdev
) != NULL
) {
2614 addr
= hdr
->b_l2hdr
->b_daddr
;
2616 * Lock out device removal.
2618 if (vdev_is_dead(vd
) ||
2619 !spa_config_tryenter(spa
, SCL_L2ARC
, vd
, RW_READER
))
2623 mutex_exit(hash_lock
);
2625 ASSERT3U(hdr
->b_size
, ==, size
);
2626 DTRACE_PROBE3(arc__miss
, blkptr_t
*, bp
, uint64_t, size
,
2628 ARCSTAT_BUMP(arcstat_misses
);
2629 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
2630 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
2631 data
, metadata
, misses
);
2635 * Read from the L2ARC if the following are true:
2636 * 1. The L2ARC vdev was previously cached.
2637 * 2. This buffer still has L2ARC metadata.
2638 * 3. This buffer isn't currently writing to the L2ARC.
2639 * 4. The L2ARC entry wasn't evicted, which may
2640 * also have invalidated the vdev.
2642 if (hdr
->b_l2hdr
!= NULL
&&
2643 !HDR_L2_WRITING(hdr
) && !HDR_L2_EVICTED(hdr
)) {
2644 l2arc_read_callback_t
*cb
;
2646 DTRACE_PROBE1(l2arc__hit
, arc_buf_hdr_t
*, hdr
);
2647 ARCSTAT_BUMP(arcstat_l2_hits
);
2649 cb
= kmem_zalloc(sizeof (l2arc_read_callback_t
),
2651 cb
->l2rcb_buf
= buf
;
2652 cb
->l2rcb_spa
= spa
;
2655 cb
->l2rcb_flags
= zio_flags
;
2658 * l2arc read. The SCL_L2ARC lock will be
2659 * released by l2arc_read_done().
2661 rzio
= zio_read_phys(pio
, vd
, addr
, size
,
2662 buf
->b_data
, ZIO_CHECKSUM_OFF
,
2663 l2arc_read_done
, cb
, priority
, zio_flags
|
2664 ZIO_FLAG_DONT_CACHE
| ZIO_FLAG_CANFAIL
|
2665 ZIO_FLAG_DONT_PROPAGATE
|
2666 ZIO_FLAG_DONT_RETRY
, B_FALSE
);
2667 DTRACE_PROBE2(l2arc__read
, vdev_t
*, vd
,
2670 if (*arc_flags
& ARC_NOWAIT
) {
2675 ASSERT(*arc_flags
& ARC_WAIT
);
2676 if (zio_wait(rzio
) == 0)
2679 /* l2arc read error; goto zio_read() */
2681 DTRACE_PROBE1(l2arc__miss
,
2682 arc_buf_hdr_t
*, hdr
);
2683 ARCSTAT_BUMP(arcstat_l2_misses
);
2684 if (HDR_L2_WRITING(hdr
))
2685 ARCSTAT_BUMP(arcstat_l2_rw_clash
);
2686 spa_config_exit(spa
, SCL_L2ARC
, vd
);
2690 rzio
= zio_read(pio
, spa
, bp
, buf
->b_data
, size
,
2691 arc_read_done
, buf
, priority
, zio_flags
, zb
);
2693 if (*arc_flags
& ARC_WAIT
)
2694 return (zio_wait(rzio
));
2696 ASSERT(*arc_flags
& ARC_NOWAIT
);
2703 * arc_read() variant to support pool traversal. If the block is already
2704 * in the ARC, make a copy of it; otherwise, the caller will do the I/O.
2705 * The idea is that we don't want pool traversal filling up memory, but
2706 * if the ARC already has the data anyway, we shouldn't pay for the I/O.
2709 arc_tryread(spa_t
*spa
, blkptr_t
*bp
, void *data
)
2715 hdr
= buf_hash_find(spa
, BP_IDENTITY(bp
), bp
->blk_birth
, &hash_mtx
);
2717 if (hdr
&& hdr
->b_datacnt
> 0 && !HDR_IO_IN_PROGRESS(hdr
)) {
2718 arc_buf_t
*buf
= hdr
->b_buf
;
2721 while (buf
->b_data
== NULL
) {
2725 bcopy(buf
->b_data
, data
, hdr
->b_size
);
2731 mutex_exit(hash_mtx
);
2737 arc_set_callback(arc_buf_t
*buf
, arc_evict_func_t
*func
, void *private)
2739 ASSERT(buf
->b_hdr
!= NULL
);
2740 ASSERT(buf
->b_hdr
->b_state
!= arc_anon
);
2741 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
) || func
== NULL
);
2742 buf
->b_efunc
= func
;
2743 buf
->b_private
= private;
2747 * This is used by the DMU to let the ARC know that a buffer is
2748 * being evicted, so the ARC should clean up. If this arc buf
2749 * is not yet in the evicted state, it will be put there.
2752 arc_buf_evict(arc_buf_t
*buf
)
2755 kmutex_t
*hash_lock
;
2758 rw_enter(&buf
->b_lock
, RW_WRITER
);
2762 * We are in arc_do_user_evicts().
2764 ASSERT(buf
->b_data
== NULL
);
2765 rw_exit(&buf
->b_lock
);
2767 } else if (buf
->b_data
== NULL
) {
2768 arc_buf_t copy
= *buf
; /* structure assignment */
2770 * We are on the eviction list; process this buffer now
2771 * but let arc_do_user_evicts() do the reaping.
2773 buf
->b_efunc
= NULL
;
2774 rw_exit(&buf
->b_lock
);
2775 VERIFY(copy
.b_efunc(©
) == 0);
2778 hash_lock
= HDR_LOCK(hdr
);
2779 mutex_enter(hash_lock
);
2781 ASSERT(buf
->b_hdr
== hdr
);
2782 ASSERT3U(refcount_count(&hdr
->b_refcnt
), <, hdr
->b_datacnt
);
2783 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
2786 * Pull this buffer off of the hdr
2789 while (*bufp
!= buf
)
2790 bufp
= &(*bufp
)->b_next
;
2791 *bufp
= buf
->b_next
;
2793 ASSERT(buf
->b_data
!= NULL
);
2794 arc_buf_destroy(buf
, FALSE
, FALSE
);
2796 if (hdr
->b_datacnt
== 0) {
2797 arc_state_t
*old_state
= hdr
->b_state
;
2798 arc_state_t
*evicted_state
;
2800 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
2803 (old_state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
2805 mutex_enter(&old_state
->arcs_mtx
);
2806 mutex_enter(&evicted_state
->arcs_mtx
);
2808 arc_change_state(evicted_state
, hdr
, hash_lock
);
2809 ASSERT(HDR_IN_HASH_TABLE(hdr
));
2810 hdr
->b_flags
|= ARC_IN_HASH_TABLE
;
2811 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
2813 mutex_exit(&evicted_state
->arcs_mtx
);
2814 mutex_exit(&old_state
->arcs_mtx
);
2816 mutex_exit(hash_lock
);
2817 rw_exit(&buf
->b_lock
);
2819 VERIFY(buf
->b_efunc(buf
) == 0);
2820 buf
->b_efunc
= NULL
;
2821 buf
->b_private
= NULL
;
2823 kmem_cache_free(buf_cache
, buf
);
2828 * Release this buffer from the cache. This must be done
2829 * after a read and prior to modifying the buffer contents.
2830 * If the buffer has more than one reference, we must make
2831 * a new hdr for the buffer.
2834 arc_release(arc_buf_t
*buf
, void *tag
)
2837 kmutex_t
*hash_lock
;
2838 l2arc_buf_hdr_t
*l2hdr
;
2841 rw_enter(&buf
->b_lock
, RW_WRITER
);
2844 /* this buffer is not on any list */
2845 ASSERT(refcount_count(&hdr
->b_refcnt
) > 0);
2846 ASSERT(!(hdr
->b_flags
& ARC_STORED
));
2848 if (hdr
->b_state
== arc_anon
) {
2849 /* this buffer is already released */
2850 ASSERT3U(refcount_count(&hdr
->b_refcnt
), ==, 1);
2851 ASSERT(BUF_EMPTY(hdr
));
2852 ASSERT(buf
->b_efunc
== NULL
);
2854 rw_exit(&buf
->b_lock
);
2858 hash_lock
= HDR_LOCK(hdr
);
2859 mutex_enter(hash_lock
);
2861 l2hdr
= hdr
->b_l2hdr
;
2863 mutex_enter(&l2arc_buflist_mtx
);
2864 hdr
->b_l2hdr
= NULL
;
2865 buf_size
= hdr
->b_size
;
2869 * Do we have more than one buf?
2871 if (hdr
->b_datacnt
> 1) {
2872 arc_buf_hdr_t
*nhdr
;
2874 uint64_t blksz
= hdr
->b_size
;
2875 spa_t
*spa
= hdr
->b_spa
;
2876 arc_buf_contents_t type
= hdr
->b_type
;
2877 uint32_t flags
= hdr
->b_flags
;
2879 ASSERT(hdr
->b_buf
!= buf
|| buf
->b_next
!= NULL
);
2881 * Pull the data off of this buf and attach it to
2882 * a new anonymous buf.
2884 (void) remove_reference(hdr
, hash_lock
, tag
);
2886 while (*bufp
!= buf
)
2887 bufp
= &(*bufp
)->b_next
;
2888 *bufp
= (*bufp
)->b_next
;
2891 ASSERT3U(hdr
->b_state
->arcs_size
, >=, hdr
->b_size
);
2892 atomic_add_64(&hdr
->b_state
->arcs_size
, -hdr
->b_size
);
2893 if (refcount_is_zero(&hdr
->b_refcnt
)) {
2894 uint64_t *size
= &hdr
->b_state
->arcs_lsize
[hdr
->b_type
];
2895 ASSERT3U(*size
, >=, hdr
->b_size
);
2896 atomic_add_64(size
, -hdr
->b_size
);
2898 hdr
->b_datacnt
-= 1;
2899 arc_cksum_verify(buf
);
2901 mutex_exit(hash_lock
);
2903 nhdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
2904 nhdr
->b_size
= blksz
;
2906 nhdr
->b_type
= type
;
2908 nhdr
->b_state
= arc_anon
;
2909 nhdr
->b_arc_access
= 0;
2910 nhdr
->b_flags
= flags
& ARC_L2_WRITING
;
2911 nhdr
->b_l2hdr
= NULL
;
2912 nhdr
->b_datacnt
= 1;
2913 nhdr
->b_freeze_cksum
= NULL
;
2914 (void) refcount_add(&nhdr
->b_refcnt
, tag
);
2916 rw_exit(&buf
->b_lock
);
2917 atomic_add_64(&arc_anon
->arcs_size
, blksz
);
2919 rw_exit(&buf
->b_lock
);
2920 ASSERT(refcount_count(&hdr
->b_refcnt
) == 1);
2921 ASSERT(!list_link_active(&hdr
->b_arc_node
));
2922 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
2923 arc_change_state(arc_anon
, hdr
, hash_lock
);
2924 hdr
->b_arc_access
= 0;
2925 mutex_exit(hash_lock
);
2927 bzero(&hdr
->b_dva
, sizeof (dva_t
));
2932 buf
->b_efunc
= NULL
;
2933 buf
->b_private
= NULL
;
2936 list_remove(l2hdr
->b_dev
->l2ad_buflist
, hdr
);
2937 kmem_free(l2hdr
, sizeof (l2arc_buf_hdr_t
));
2938 ARCSTAT_INCR(arcstat_l2_size
, -buf_size
);
2939 mutex_exit(&l2arc_buflist_mtx
);
2944 arc_released(arc_buf_t
*buf
)
2948 rw_enter(&buf
->b_lock
, RW_READER
);
2949 released
= (buf
->b_data
!= NULL
&& buf
->b_hdr
->b_state
== arc_anon
);
2950 rw_exit(&buf
->b_lock
);
2955 arc_has_callback(arc_buf_t
*buf
)
2959 rw_enter(&buf
->b_lock
, RW_READER
);
2960 callback
= (buf
->b_efunc
!= NULL
);
2961 rw_exit(&buf
->b_lock
);
2967 arc_referenced(arc_buf_t
*buf
)
2971 rw_enter(&buf
->b_lock
, RW_READER
);
2972 referenced
= (refcount_count(&buf
->b_hdr
->b_refcnt
));
2973 rw_exit(&buf
->b_lock
);
2974 return (referenced
);
2979 arc_write_ready(zio_t
*zio
)
2981 arc_write_callback_t
*callback
= zio
->io_private
;
2982 arc_buf_t
*buf
= callback
->awcb_buf
;
2983 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
2985 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
2986 callback
->awcb_ready(zio
, buf
, callback
->awcb_private
);
2989 * If the IO is already in progress, then this is a re-write
2990 * attempt, so we need to thaw and re-compute the cksum.
2991 * It is the responsibility of the callback to handle the
2992 * accounting for any re-write attempt.
2994 if (HDR_IO_IN_PROGRESS(hdr
)) {
2995 mutex_enter(&hdr
->b_freeze_lock
);
2996 if (hdr
->b_freeze_cksum
!= NULL
) {
2997 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
2998 hdr
->b_freeze_cksum
= NULL
;
3000 mutex_exit(&hdr
->b_freeze_lock
);
3002 arc_cksum_compute(buf
, B_FALSE
);
3003 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
3007 arc_write_done(zio_t
*zio
)
3009 arc_write_callback_t
*callback
= zio
->io_private
;
3010 arc_buf_t
*buf
= callback
->awcb_buf
;
3011 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3015 hdr
->b_dva
= *BP_IDENTITY(zio
->io_bp
);
3016 hdr
->b_birth
= zio
->io_bp
->blk_birth
;
3017 hdr
->b_cksum0
= zio
->io_bp
->blk_cksum
.zc_word
[0];
3019 * If the block to be written was all-zero, we may have
3020 * compressed it away. In this case no write was performed
3021 * so there will be no dva/birth-date/checksum. The buffer
3022 * must therefor remain anonymous (and uncached).
3024 if (!BUF_EMPTY(hdr
)) {
3025 arc_buf_hdr_t
*exists
;
3026 kmutex_t
*hash_lock
;
3028 arc_cksum_verify(buf
);
3030 exists
= buf_hash_insert(hdr
, &hash_lock
);
3033 * This can only happen if we overwrite for
3034 * sync-to-convergence, because we remove
3035 * buffers from the hash table when we arc_free().
3037 ASSERT(zio
->io_flags
& ZIO_FLAG_IO_REWRITE
);
3038 ASSERT(DVA_EQUAL(BP_IDENTITY(&zio
->io_bp_orig
),
3039 BP_IDENTITY(zio
->io_bp
)));
3040 ASSERT3U(zio
->io_bp_orig
.blk_birth
, ==,
3041 zio
->io_bp
->blk_birth
);
3043 ASSERT(refcount_is_zero(&exists
->b_refcnt
));
3044 arc_change_state(arc_anon
, exists
, hash_lock
);
3045 mutex_exit(hash_lock
);
3046 arc_hdr_destroy(exists
);
3047 exists
= buf_hash_insert(hdr
, &hash_lock
);
3048 ASSERT3P(exists
, ==, NULL
);
3050 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3051 /* if it's not anon, we are doing a scrub */
3052 if (hdr
->b_state
== arc_anon
)
3053 arc_access(hdr
, hash_lock
);
3054 mutex_exit(hash_lock
);
3055 } else if (callback
->awcb_done
== NULL
) {
3058 * This is an anonymous buffer with no user callback,
3059 * destroy it if there are no active references.
3061 mutex_enter(&arc_eviction_mtx
);
3062 destroy_hdr
= refcount_is_zero(&hdr
->b_refcnt
);
3063 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3064 mutex_exit(&arc_eviction_mtx
);
3066 arc_hdr_destroy(hdr
);
3068 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3070 hdr
->b_flags
&= ~ARC_STORED
;
3072 if (callback
->awcb_done
) {
3073 ASSERT(!refcount_is_zero(&hdr
->b_refcnt
));
3074 callback
->awcb_done(zio
, buf
, callback
->awcb_private
);
3077 kmem_free(callback
, sizeof (arc_write_callback_t
));
3081 write_policy(spa_t
*spa
, const writeprops_t
*wp
, zio_prop_t
*zp
)
3083 boolean_t ismd
= (wp
->wp_level
> 0 || dmu_ot
[wp
->wp_type
].ot_metadata
);
3085 /* Determine checksum setting */
3088 * Metadata always gets checksummed. If the data
3089 * checksum is multi-bit correctable, and it's not a
3090 * ZBT-style checksum, then it's suitable for metadata
3091 * as well. Otherwise, the metadata checksum defaults
3094 if (zio_checksum_table
[wp
->wp_oschecksum
].ci_correctable
&&
3095 !zio_checksum_table
[wp
->wp_oschecksum
].ci_zbt
)
3096 zp
->zp_checksum
= wp
->wp_oschecksum
;
3098 zp
->zp_checksum
= ZIO_CHECKSUM_FLETCHER_4
;
3100 zp
->zp_checksum
= zio_checksum_select(wp
->wp_dnchecksum
,
3104 /* Determine compression setting */
3107 * XXX -- we should design a compression algorithm
3108 * that specializes in arrays of bps.
3110 zp
->zp_compress
= zfs_mdcomp_disable
? ZIO_COMPRESS_EMPTY
:
3113 zp
->zp_compress
= zio_compress_select(wp
->wp_dncompress
,
3117 zp
->zp_type
= wp
->wp_type
;
3118 zp
->zp_level
= wp
->wp_level
;
3119 zp
->zp_ndvas
= MIN(wp
->wp_copies
+ ismd
, spa_max_replication(spa
));
3123 arc_write(zio_t
*pio
, spa_t
*spa
, const writeprops_t
*wp
,
3124 boolean_t l2arc
, uint64_t txg
, blkptr_t
*bp
, arc_buf_t
*buf
,
3125 arc_done_func_t
*ready
, arc_done_func_t
*done
, void *private, int priority
,
3126 int zio_flags
, const zbookmark_t
*zb
)
3128 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3129 arc_write_callback_t
*callback
;
3133 ASSERT(ready
!= NULL
);
3134 ASSERT(!HDR_IO_ERROR(hdr
));
3135 ASSERT((hdr
->b_flags
& ARC_IO_IN_PROGRESS
) == 0);
3136 ASSERT(hdr
->b_acb
== 0);
3138 hdr
->b_flags
|= ARC_L2CACHE
;
3139 callback
= kmem_zalloc(sizeof (arc_write_callback_t
), KM_SLEEP
);
3140 callback
->awcb_ready
= ready
;
3141 callback
->awcb_done
= done
;
3142 callback
->awcb_private
= private;
3143 callback
->awcb_buf
= buf
;
3145 write_policy(spa
, wp
, &zp
);
3146 zio
= zio_write(pio
, spa
, txg
, bp
, buf
->b_data
, hdr
->b_size
, &zp
,
3147 arc_write_ready
, arc_write_done
, callback
, priority
, zio_flags
, zb
);
3153 arc_free(zio_t
*pio
, spa_t
*spa
, uint64_t txg
, blkptr_t
*bp
,
3154 zio_done_func_t
*done
, void *private, uint32_t arc_flags
)
3157 kmutex_t
*hash_lock
;
3161 * If this buffer is in the cache, release it, so it
3164 ab
= buf_hash_find(spa
, BP_IDENTITY(bp
), bp
->blk_birth
, &hash_lock
);
3167 * The checksum of blocks to free is not always
3168 * preserved (eg. on the deadlist). However, if it is
3169 * nonzero, it should match what we have in the cache.
3171 ASSERT(bp
->blk_cksum
.zc_word
[0] == 0 ||
3172 bp
->blk_cksum
.zc_word
[0] == ab
->b_cksum0
||
3173 bp
->blk_fill
== BLK_FILL_ALREADY_FREED
);
3175 if (ab
->b_state
!= arc_anon
)
3176 arc_change_state(arc_anon
, ab
, hash_lock
);
3177 if (HDR_IO_IN_PROGRESS(ab
)) {
3179 * This should only happen when we prefetch.
3181 ASSERT(ab
->b_flags
& ARC_PREFETCH
);
3182 ASSERT3U(ab
->b_datacnt
, ==, 1);
3183 ab
->b_flags
|= ARC_FREED_IN_READ
;
3184 if (HDR_IN_HASH_TABLE(ab
))
3185 buf_hash_remove(ab
);
3186 ab
->b_arc_access
= 0;
3187 bzero(&ab
->b_dva
, sizeof (dva_t
));
3190 ab
->b_buf
->b_efunc
= NULL
;
3191 ab
->b_buf
->b_private
= NULL
;
3192 mutex_exit(hash_lock
);
3193 } else if (refcount_is_zero(&ab
->b_refcnt
)) {
3194 ab
->b_flags
|= ARC_FREE_IN_PROGRESS
;
3195 mutex_exit(hash_lock
);
3196 arc_hdr_destroy(ab
);
3197 ARCSTAT_BUMP(arcstat_deleted
);
3200 * We still have an active reference on this
3201 * buffer. This can happen, e.g., from
3202 * dbuf_unoverride().
3204 ASSERT(!HDR_IN_HASH_TABLE(ab
));
3205 ab
->b_arc_access
= 0;
3206 bzero(&ab
->b_dva
, sizeof (dva_t
));
3209 ab
->b_buf
->b_efunc
= NULL
;
3210 ab
->b_buf
->b_private
= NULL
;
3211 mutex_exit(hash_lock
);
3215 zio
= zio_free(pio
, spa
, txg
, bp
, done
, private, ZIO_FLAG_MUSTSUCCEED
);
3217 if (arc_flags
& ARC_WAIT
)
3218 return (zio_wait(zio
));
3220 ASSERT(arc_flags
& ARC_NOWAIT
);
3227 arc_memory_throttle(uint64_t reserve
, uint64_t txg
)
3230 uint64_t inflight_data
= arc_anon
->arcs_size
;
3231 uint64_t available_memory
= ptob(freemem
);
3232 static uint64_t page_load
= 0;
3233 static uint64_t last_txg
= 0;
3237 MIN(available_memory
, vmem_size(heap_arena
, VMEM_FREE
));
3239 if (available_memory
>= zfs_write_limit_max
)
3242 if (txg
> last_txg
) {
3247 * If we are in pageout, we know that memory is already tight,
3248 * the arc is already going to be evicting, so we just want to
3249 * continue to let page writes occur as quickly as possible.
3251 if (curproc
== proc_pageout
) {
3252 if (page_load
> MAX(ptob(minfree
), available_memory
) / 4)
3254 /* Note: reserve is inflated, so we deflate */
3255 page_load
+= reserve
/ 8;
3257 } else if (page_load
> 0 && arc_reclaim_needed()) {
3258 /* memory is low, delay before restarting */
3259 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3264 if (arc_size
> arc_c_min
) {
3265 uint64_t evictable_memory
=
3266 arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] +
3267 arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] +
3268 arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] +
3269 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
];
3270 available_memory
+= MIN(evictable_memory
, arc_size
- arc_c_min
);
3273 if (inflight_data
> available_memory
/ 4) {
3274 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3282 arc_tempreserve_clear(uint64_t reserve
)
3284 atomic_add_64(&arc_tempreserve
, -reserve
);
3285 ASSERT((int64_t)arc_tempreserve
>= 0);
3289 arc_tempreserve_space(uint64_t reserve
, uint64_t txg
)
3295 * Once in a while, fail for no reason. Everything should cope.
3297 if (spa_get_random(10000) == 0) {
3298 dprintf("forcing random failure\n");
3302 if (reserve
> arc_c
/4 && !arc_no_grow
)
3303 arc_c
= MIN(arc_c_max
, reserve
* 4);
3304 if (reserve
> arc_c
)
3308 * Writes will, almost always, require additional memory allocations
3309 * in order to compress/encrypt/etc the data. We therefor need to
3310 * make sure that there is sufficient available memory for this.
3312 if (error
= arc_memory_throttle(reserve
, txg
))
3316 * Throttle writes when the amount of dirty data in the cache
3317 * gets too large. We try to keep the cache less than half full
3318 * of dirty blocks so that our sync times don't grow too large.
3319 * Note: if two requests come in concurrently, we might let them
3320 * both succeed, when one of them should fail. Not a huge deal.
3322 if (reserve
+ arc_tempreserve
+ arc_anon
->arcs_size
> arc_c
/ 2 &&
3323 arc_anon
->arcs_size
> arc_c
/ 4) {
3324 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3325 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3326 arc_tempreserve
>>10,
3327 arc_anon
->arcs_lsize
[ARC_BUFC_METADATA
]>>10,
3328 arc_anon
->arcs_lsize
[ARC_BUFC_DATA
]>>10,
3329 reserve
>>10, arc_c
>>10);
3332 atomic_add_64(&arc_tempreserve
, reserve
);
3339 mutex_init(&arc_reclaim_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3340 cv_init(&arc_reclaim_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
3342 /* Convert seconds to clock ticks */
3343 arc_min_prefetch_lifespan
= 1 * hz
;
3345 /* Start out with 1/8 of all memory */
3346 arc_c
= physmem
* PAGESIZE
/ 8;
3350 * On architectures where the physical memory can be larger
3351 * than the addressable space (intel in 32-bit mode), we may
3352 * need to limit the cache to 1/8 of VM size.
3354 arc_c
= MIN(arc_c
, vmem_size(heap_arena
, VMEM_ALLOC
| VMEM_FREE
) / 8);
3357 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3358 arc_c_min
= MAX(arc_c
/ 4, 64<<20);
3359 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3360 if (arc_c
* 8 >= 1<<30)
3361 arc_c_max
= (arc_c
* 8) - (1<<30);
3363 arc_c_max
= arc_c_min
;
3364 arc_c_max
= MAX(arc_c
* 6, arc_c_max
);
3367 * Allow the tunables to override our calculations if they are
3368 * reasonable (ie. over 64MB)
3370 if (zfs_arc_max
> 64<<20 && zfs_arc_max
< physmem
* PAGESIZE
)
3371 arc_c_max
= zfs_arc_max
;
3372 if (zfs_arc_min
> 64<<20 && zfs_arc_min
<= arc_c_max
)
3373 arc_c_min
= zfs_arc_min
;
3376 arc_p
= (arc_c
>> 1);
3378 /* limit meta-data to 1/4 of the arc capacity */
3379 arc_meta_limit
= arc_c_max
/ 4;
3381 /* Allow the tunable to override if it is reasonable */
3382 if (zfs_arc_meta_limit
> 0 && zfs_arc_meta_limit
<= arc_c_max
)
3383 arc_meta_limit
= zfs_arc_meta_limit
;
3385 if (arc_c_min
< arc_meta_limit
/ 2 && zfs_arc_min
== 0)
3386 arc_c_min
= arc_meta_limit
/ 2;
3388 /* if kmem_flags are set, lets try to use less memory */
3389 if (kmem_debugging())
3391 if (arc_c
< arc_c_min
)
3394 arc_anon
= &ARC_anon
;
3396 arc_mru_ghost
= &ARC_mru_ghost
;
3398 arc_mfu_ghost
= &ARC_mfu_ghost
;
3399 arc_l2c_only
= &ARC_l2c_only
;
3402 mutex_init(&arc_anon
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3403 mutex_init(&arc_mru
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3404 mutex_init(&arc_mru_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3405 mutex_init(&arc_mfu
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3406 mutex_init(&arc_mfu_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3407 mutex_init(&arc_l2c_only
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3409 list_create(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
],
3410 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3411 list_create(&arc_mru
->arcs_list
[ARC_BUFC_DATA
],
3412 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3413 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3414 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3415 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
],
3416 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3417 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
],
3418 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3419 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
],
3420 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3421 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3422 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3423 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
],
3424 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3425 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_METADATA
],
3426 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3427 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_DATA
],
3428 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3432 arc_thread_exit
= 0;
3433 arc_eviction_list
= NULL
;
3434 mutex_init(&arc_eviction_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3435 bzero(&arc_eviction_hdr
, sizeof (arc_buf_hdr_t
));
3437 arc_ksp
= kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED
,
3438 sizeof (arc_stats
) / sizeof (kstat_named_t
), KSTAT_FLAG_VIRTUAL
);
3440 if (arc_ksp
!= NULL
) {
3441 arc_ksp
->ks_data
= &arc_stats
;
3442 kstat_install(arc_ksp
);
3445 (void) thread_create(NULL
, 0, arc_reclaim_thread
, NULL
, 0, &p0
,
3446 TS_RUN
, minclsyspri
);
3451 if (zfs_write_limit_max
== 0)
3452 zfs_write_limit_max
= ptob(physmem
) >> zfs_write_limit_shift
;
3454 zfs_write_limit_shift
= 0;
3455 mutex_init(&zfs_write_limit_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3461 mutex_enter(&arc_reclaim_thr_lock
);
3462 arc_thread_exit
= 1;
3463 while (arc_thread_exit
!= 0)
3464 cv_wait(&arc_reclaim_thr_cv
, &arc_reclaim_thr_lock
);
3465 mutex_exit(&arc_reclaim_thr_lock
);
3471 if (arc_ksp
!= NULL
) {
3472 kstat_delete(arc_ksp
);
3476 mutex_destroy(&arc_eviction_mtx
);
3477 mutex_destroy(&arc_reclaim_thr_lock
);
3478 cv_destroy(&arc_reclaim_thr_cv
);
3480 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
]);
3481 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3482 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
]);
3483 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3484 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_DATA
]);
3485 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3486 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
]);
3487 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3489 mutex_destroy(&arc_anon
->arcs_mtx
);
3490 mutex_destroy(&arc_mru
->arcs_mtx
);
3491 mutex_destroy(&arc_mru_ghost
->arcs_mtx
);
3492 mutex_destroy(&arc_mfu
->arcs_mtx
);
3493 mutex_destroy(&arc_mfu_ghost
->arcs_mtx
);
3494 mutex_destroy(&arc_l2c_only
->arcs_mtx
);
3496 mutex_destroy(&zfs_write_limit_lock
);
3504 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3505 * It uses dedicated storage devices to hold cached data, which are populated
3506 * using large infrequent writes. The main role of this cache is to boost
3507 * the performance of random read workloads. The intended L2ARC devices
3508 * include short-stroked disks, solid state disks, and other media with
3509 * substantially faster read latency than disk.
3511 * +-----------------------+
3513 * +-----------------------+
3516 * l2arc_feed_thread() arc_read()
3520 * +---------------+ |
3522 * +---------------+ |
3527 * +-------+ +-------+
3529 * | cache | | cache |
3530 * +-------+ +-------+
3531 * +=========+ .-----.
3532 * : L2ARC : |-_____-|
3533 * : devices : | Disks |
3534 * +=========+ `-_____-'
3536 * Read requests are satisfied from the following sources, in order:
3539 * 2) vdev cache of L2ARC devices
3541 * 4) vdev cache of disks
3544 * Some L2ARC device types exhibit extremely slow write performance.
3545 * To accommodate for this there are some significant differences between
3546 * the L2ARC and traditional cache design:
3548 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3549 * the ARC behave as usual, freeing buffers and placing headers on ghost
3550 * lists. The ARC does not send buffers to the L2ARC during eviction as
3551 * this would add inflated write latencies for all ARC memory pressure.
3553 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3554 * It does this by periodically scanning buffers from the eviction-end of
3555 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3556 * not already there. It scans until a headroom of buffers is satisfied,
3557 * which itself is a buffer for ARC eviction. The thread that does this is
3558 * l2arc_feed_thread(), illustrated below; example sizes are included to
3559 * provide a better sense of ratio than this diagram:
3562 * +---------------------+----------+
3563 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3564 * +---------------------+----------+ | o L2ARC eligible
3565 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3566 * +---------------------+----------+ |
3567 * 15.9 Gbytes ^ 32 Mbytes |
3569 * l2arc_feed_thread()
3571 * l2arc write hand <--[oooo]--'
3575 * +==============================+
3576 * L2ARC dev |####|#|###|###| |####| ... |
3577 * +==============================+
3580 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3581 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3582 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3583 * safe to say that this is an uncommon case, since buffers at the end of
3584 * the ARC lists have moved there due to inactivity.
3586 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3587 * then the L2ARC simply misses copying some buffers. This serves as a
3588 * pressure valve to prevent heavy read workloads from both stalling the ARC
3589 * with waits and clogging the L2ARC with writes. This also helps prevent
3590 * the potential for the L2ARC to churn if it attempts to cache content too
3591 * quickly, such as during backups of the entire pool.
3593 * 5. After system boot and before the ARC has filled main memory, there are
3594 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3595 * lists can remain mostly static. Instead of searching from tail of these
3596 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3597 * for eligible buffers, greatly increasing its chance of finding them.
3599 * The L2ARC device write speed is also boosted during this time so that
3600 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
3601 * there are no L2ARC reads, and no fear of degrading read performance
3602 * through increased writes.
3604 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
3605 * the vdev queue can aggregate them into larger and fewer writes. Each
3606 * device is written to in a rotor fashion, sweeping writes through
3607 * available space then repeating.
3609 * 7. The L2ARC does not store dirty content. It never needs to flush
3610 * write buffers back to disk based storage.
3612 * 8. If an ARC buffer is written (and dirtied) which also exists in the
3613 * L2ARC, the now stale L2ARC buffer is immediately dropped.
3615 * The performance of the L2ARC can be tweaked by a number of tunables, which
3616 * may be necessary for different workloads:
3618 * l2arc_write_max max write bytes per interval
3619 * l2arc_write_boost extra write bytes during device warmup
3620 * l2arc_noprefetch skip caching prefetched buffers
3621 * l2arc_headroom number of max device writes to precache
3622 * l2arc_feed_secs seconds between L2ARC writing
3624 * Tunables may be removed or added as future performance improvements are
3625 * integrated, and also may become zpool properties.
3629 l2arc_hdr_stat_add(void)
3631 ARCSTAT_INCR(arcstat_l2_hdr_size
, HDR_SIZE
+ L2HDR_SIZE
);
3632 ARCSTAT_INCR(arcstat_hdr_size
, -HDR_SIZE
);
3636 l2arc_hdr_stat_remove(void)
3638 ARCSTAT_INCR(arcstat_l2_hdr_size
, -(HDR_SIZE
+ L2HDR_SIZE
));
3639 ARCSTAT_INCR(arcstat_hdr_size
, HDR_SIZE
);
3643 * Cycle through L2ARC devices. This is how L2ARC load balances.
3644 * If a device is returned, this also returns holding the spa config lock.
3646 static l2arc_dev_t
*
3647 l2arc_dev_get_next(void)
3649 l2arc_dev_t
*first
, *next
= NULL
;
3652 * Lock out the removal of spas (spa_namespace_lock), then removal
3653 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
3654 * both locks will be dropped and a spa config lock held instead.
3656 mutex_enter(&spa_namespace_lock
);
3657 mutex_enter(&l2arc_dev_mtx
);
3659 /* if there are no vdevs, there is nothing to do */
3660 if (l2arc_ndev
== 0)
3664 next
= l2arc_dev_last
;
3666 /* loop around the list looking for a non-faulted vdev */
3668 next
= list_head(l2arc_dev_list
);
3670 next
= list_next(l2arc_dev_list
, next
);
3672 next
= list_head(l2arc_dev_list
);
3675 /* if we have come back to the start, bail out */
3678 else if (next
== first
)
3681 } while (vdev_is_dead(next
->l2ad_vdev
));
3683 /* if we were unable to find any usable vdevs, return NULL */
3684 if (vdev_is_dead(next
->l2ad_vdev
))
3687 l2arc_dev_last
= next
;
3690 mutex_exit(&l2arc_dev_mtx
);
3693 * Grab the config lock to prevent the 'next' device from being
3694 * removed while we are writing to it.
3697 spa_config_enter(next
->l2ad_spa
, SCL_L2ARC
, next
, RW_READER
);
3698 mutex_exit(&spa_namespace_lock
);
3704 * Free buffers that were tagged for destruction.
3707 l2arc_do_free_on_write()
3710 l2arc_data_free_t
*df
, *df_prev
;
3712 mutex_enter(&l2arc_free_on_write_mtx
);
3713 buflist
= l2arc_free_on_write
;
3715 for (df
= list_tail(buflist
); df
; df
= df_prev
) {
3716 df_prev
= list_prev(buflist
, df
);
3717 ASSERT(df
->l2df_data
!= NULL
);
3718 ASSERT(df
->l2df_func
!= NULL
);
3719 df
->l2df_func(df
->l2df_data
, df
->l2df_size
);
3720 list_remove(buflist
, df
);
3721 kmem_free(df
, sizeof (l2arc_data_free_t
));
3724 mutex_exit(&l2arc_free_on_write_mtx
);
3728 * A write to a cache device has completed. Update all headers to allow
3729 * reads from these buffers to begin.
3732 l2arc_write_done(zio_t
*zio
)
3734 l2arc_write_callback_t
*cb
;
3737 arc_buf_hdr_t
*head
, *ab
, *ab_prev
;
3738 l2arc_buf_hdr_t
*abl2
;
3739 kmutex_t
*hash_lock
;
3741 cb
= zio
->io_private
;
3743 dev
= cb
->l2wcb_dev
;
3744 ASSERT(dev
!= NULL
);
3745 head
= cb
->l2wcb_head
;
3746 ASSERT(head
!= NULL
);
3747 buflist
= dev
->l2ad_buflist
;
3748 ASSERT(buflist
!= NULL
);
3749 DTRACE_PROBE2(l2arc__iodone
, zio_t
*, zio
,
3750 l2arc_write_callback_t
*, cb
);
3752 if (zio
->io_error
!= 0)
3753 ARCSTAT_BUMP(arcstat_l2_writes_error
);
3755 mutex_enter(&l2arc_buflist_mtx
);
3758 * All writes completed, or an error was hit.
3760 for (ab
= list_prev(buflist
, head
); ab
; ab
= ab_prev
) {
3761 ab_prev
= list_prev(buflist
, ab
);
3763 hash_lock
= HDR_LOCK(ab
);
3764 if (!mutex_tryenter(hash_lock
)) {
3766 * This buffer misses out. It may be in a stage
3767 * of eviction. Its ARC_L2_WRITING flag will be
3768 * left set, denying reads to this buffer.
3770 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss
);
3774 if (zio
->io_error
!= 0) {
3776 * Error - drop L2ARC entry.
3778 list_remove(buflist
, ab
);
3781 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
3782 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
3786 * Allow ARC to begin reads to this L2ARC entry.
3788 ab
->b_flags
&= ~ARC_L2_WRITING
;
3790 mutex_exit(hash_lock
);
3793 atomic_inc_64(&l2arc_writes_done
);
3794 list_remove(buflist
, head
);
3795 kmem_cache_free(hdr_cache
, head
);
3796 mutex_exit(&l2arc_buflist_mtx
);
3798 l2arc_do_free_on_write();
3800 kmem_free(cb
, sizeof (l2arc_write_callback_t
));
3804 * A read to a cache device completed. Validate buffer contents before
3805 * handing over to the regular ARC routines.
3808 l2arc_read_done(zio_t
*zio
)
3810 l2arc_read_callback_t
*cb
;
3813 kmutex_t
*hash_lock
;
3816 ASSERT(zio
->io_vd
!= NULL
);
3817 ASSERT(zio
->io_flags
& ZIO_FLAG_DONT_PROPAGATE
);
3819 spa_config_exit(zio
->io_spa
, SCL_L2ARC
, zio
->io_vd
);
3821 cb
= zio
->io_private
;
3823 buf
= cb
->l2rcb_buf
;
3824 ASSERT(buf
!= NULL
);
3826 ASSERT(hdr
!= NULL
);
3828 hash_lock
= HDR_LOCK(hdr
);
3829 mutex_enter(hash_lock
);
3832 * Check this survived the L2ARC journey.
3834 equal
= arc_cksum_equal(buf
);
3835 if (equal
&& zio
->io_error
== 0 && !HDR_L2_EVICTED(hdr
)) {
3836 mutex_exit(hash_lock
);
3837 zio
->io_private
= buf
;
3838 zio
->io_bp_copy
= cb
->l2rcb_bp
; /* XXX fix in L2ARC 2.0 */
3839 zio
->io_bp
= &zio
->io_bp_copy
; /* XXX fix in L2ARC 2.0 */
3842 mutex_exit(hash_lock
);
3844 * Buffer didn't survive caching. Increment stats and
3845 * reissue to the original storage device.
3847 if (zio
->io_error
!= 0) {
3848 ARCSTAT_BUMP(arcstat_l2_io_error
);
3850 zio
->io_error
= EIO
;
3853 ARCSTAT_BUMP(arcstat_l2_cksum_bad
);
3856 * If there's no waiter, issue an async i/o to the primary
3857 * storage now. If there *is* a waiter, the caller must
3858 * issue the i/o in a context where it's OK to block.
3860 if (zio
->io_waiter
== NULL
)
3861 zio_nowait(zio_read(zio
->io_parent
,
3862 cb
->l2rcb_spa
, &cb
->l2rcb_bp
,
3863 buf
->b_data
, zio
->io_size
, arc_read_done
, buf
,
3864 zio
->io_priority
, cb
->l2rcb_flags
, &cb
->l2rcb_zb
));
3867 kmem_free(cb
, sizeof (l2arc_read_callback_t
));
3871 * This is the list priority from which the L2ARC will search for pages to
3872 * cache. This is used within loops (0..3) to cycle through lists in the
3873 * desired order. This order can have a significant effect on cache
3876 * Currently the metadata lists are hit first, MFU then MRU, followed by
3877 * the data lists. This function returns a locked list, and also returns
3881 l2arc_list_locked(int list_num
, kmutex_t
**lock
)
3885 ASSERT(list_num
>= 0 && list_num
<= 3);
3889 list
= &arc_mfu
->arcs_list
[ARC_BUFC_METADATA
];
3890 *lock
= &arc_mfu
->arcs_mtx
;
3893 list
= &arc_mru
->arcs_list
[ARC_BUFC_METADATA
];
3894 *lock
= &arc_mru
->arcs_mtx
;
3897 list
= &arc_mfu
->arcs_list
[ARC_BUFC_DATA
];
3898 *lock
= &arc_mfu
->arcs_mtx
;
3901 list
= &arc_mru
->arcs_list
[ARC_BUFC_DATA
];
3902 *lock
= &arc_mru
->arcs_mtx
;
3906 ASSERT(!(MUTEX_HELD(*lock
)));
3912 * Evict buffers from the device write hand to the distance specified in
3913 * bytes. This distance may span populated buffers, it may span nothing.
3914 * This is clearing a region on the L2ARC device ready for writing.
3915 * If the 'all' boolean is set, every buffer is evicted.
3918 l2arc_evict(l2arc_dev_t
*dev
, uint64_t distance
, boolean_t all
)
3921 l2arc_buf_hdr_t
*abl2
;
3922 arc_buf_hdr_t
*ab
, *ab_prev
;
3923 kmutex_t
*hash_lock
;
3926 buflist
= dev
->l2ad_buflist
;
3928 if (buflist
== NULL
)
3931 if (!all
&& dev
->l2ad_first
) {
3933 * This is the first sweep through the device. There is
3939 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- (2 * distance
))) {
3941 * When nearing the end of the device, evict to the end
3942 * before the device write hand jumps to the start.
3944 taddr
= dev
->l2ad_end
;
3946 taddr
= dev
->l2ad_hand
+ distance
;
3948 DTRACE_PROBE4(l2arc__evict
, l2arc_dev_t
*, dev
, list_t
*, buflist
,
3949 uint64_t, taddr
, boolean_t
, all
);
3952 mutex_enter(&l2arc_buflist_mtx
);
3953 for (ab
= list_tail(buflist
); ab
; ab
= ab_prev
) {
3954 ab_prev
= list_prev(buflist
, ab
);
3956 hash_lock
= HDR_LOCK(ab
);
3957 if (!mutex_tryenter(hash_lock
)) {
3959 * Missed the hash lock. Retry.
3961 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry
);
3962 mutex_exit(&l2arc_buflist_mtx
);
3963 mutex_enter(hash_lock
);
3964 mutex_exit(hash_lock
);
3968 if (HDR_L2_WRITE_HEAD(ab
)) {
3970 * We hit a write head node. Leave it for
3971 * l2arc_write_done().
3973 list_remove(buflist
, ab
);
3974 mutex_exit(hash_lock
);
3978 if (!all
&& ab
->b_l2hdr
!= NULL
&&
3979 (ab
->b_l2hdr
->b_daddr
> taddr
||
3980 ab
->b_l2hdr
->b_daddr
< dev
->l2ad_hand
)) {
3982 * We've evicted to the target address,
3983 * or the end of the device.
3985 mutex_exit(hash_lock
);
3989 if (HDR_FREE_IN_PROGRESS(ab
)) {
3991 * Already on the path to destruction.
3993 mutex_exit(hash_lock
);
3997 if (ab
->b_state
== arc_l2c_only
) {
3998 ASSERT(!HDR_L2_READING(ab
));
4000 * This doesn't exist in the ARC. Destroy.
4001 * arc_hdr_destroy() will call list_remove()
4002 * and decrement arcstat_l2_size.
4004 arc_change_state(arc_anon
, ab
, hash_lock
);
4005 arc_hdr_destroy(ab
);
4008 * Invalidate issued or about to be issued
4009 * reads, since we may be about to write
4010 * over this location.
4012 if (HDR_L2_READING(ab
)) {
4013 ARCSTAT_BUMP(arcstat_l2_evict_reading
);
4014 ab
->b_flags
|= ARC_L2_EVICTED
;
4018 * Tell ARC this no longer exists in L2ARC.
4020 if (ab
->b_l2hdr
!= NULL
) {
4023 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
4024 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
4026 list_remove(buflist
, ab
);
4029 * This may have been leftover after a
4032 ab
->b_flags
&= ~ARC_L2_WRITING
;
4034 mutex_exit(hash_lock
);
4036 mutex_exit(&l2arc_buflist_mtx
);
4038 spa_l2cache_space_update(dev
->l2ad_vdev
, 0, -(taddr
- dev
->l2ad_evict
));
4039 dev
->l2ad_evict
= taddr
;
4043 * Find and write ARC buffers to the L2ARC device.
4045 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4046 * for reading until they have completed writing.
4049 l2arc_write_buffers(spa_t
*spa
, l2arc_dev_t
*dev
, uint64_t target_sz
)
4051 arc_buf_hdr_t
*ab
, *ab_prev
, *head
;
4052 l2arc_buf_hdr_t
*hdrl2
;
4054 uint64_t passed_sz
, write_sz
, buf_sz
, headroom
;
4056 kmutex_t
*hash_lock
, *list_lock
;
4057 boolean_t have_lock
, full
;
4058 l2arc_write_callback_t
*cb
;
4061 ASSERT(dev
->l2ad_vdev
!= NULL
);
4066 head
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
4067 head
->b_flags
|= ARC_L2_WRITE_HEAD
;
4070 * Copy buffers for L2ARC writing.
4072 mutex_enter(&l2arc_buflist_mtx
);
4073 for (int try = 0; try <= 3; try++) {
4074 list
= l2arc_list_locked(try, &list_lock
);
4078 * L2ARC fast warmup.
4080 * Until the ARC is warm and starts to evict, read from the
4081 * head of the ARC lists rather than the tail.
4083 headroom
= target_sz
* l2arc_headroom
;
4084 if (arc_warm
== B_FALSE
)
4085 ab
= list_head(list
);
4087 ab
= list_tail(list
);
4089 for (; ab
; ab
= ab_prev
) {
4090 if (arc_warm
== B_FALSE
)
4091 ab_prev
= list_next(list
, ab
);
4093 ab_prev
= list_prev(list
, ab
);
4095 hash_lock
= HDR_LOCK(ab
);
4096 have_lock
= MUTEX_HELD(hash_lock
);
4097 if (!have_lock
&& !mutex_tryenter(hash_lock
)) {
4099 * Skip this buffer rather than waiting.
4104 passed_sz
+= ab
->b_size
;
4105 if (passed_sz
> headroom
) {
4109 mutex_exit(hash_lock
);
4113 if (ab
->b_spa
!= spa
) {
4114 mutex_exit(hash_lock
);
4118 if (ab
->b_l2hdr
!= NULL
) {
4122 mutex_exit(hash_lock
);
4126 if (HDR_IO_IN_PROGRESS(ab
) || !HDR_L2CACHE(ab
)) {
4127 mutex_exit(hash_lock
);
4131 if ((write_sz
+ ab
->b_size
) > target_sz
) {
4133 mutex_exit(hash_lock
);
4137 if (ab
->b_buf
== NULL
) {
4138 DTRACE_PROBE1(l2arc__buf__null
, void *, ab
);
4139 mutex_exit(hash_lock
);
4145 * Insert a dummy header on the buflist so
4146 * l2arc_write_done() can find where the
4147 * write buffers begin without searching.
4149 list_insert_head(dev
->l2ad_buflist
, head
);
4152 sizeof (l2arc_write_callback_t
), KM_SLEEP
);
4153 cb
->l2wcb_dev
= dev
;
4154 cb
->l2wcb_head
= head
;
4155 pio
= zio_root(spa
, l2arc_write_done
, cb
,
4160 * Create and add a new L2ARC header.
4162 hdrl2
= kmem_zalloc(sizeof (l2arc_buf_hdr_t
), KM_SLEEP
);
4164 hdrl2
->b_daddr
= dev
->l2ad_hand
;
4166 ab
->b_flags
|= ARC_L2_WRITING
;
4167 ab
->b_l2hdr
= hdrl2
;
4168 list_insert_head(dev
->l2ad_buflist
, ab
);
4169 buf_data
= ab
->b_buf
->b_data
;
4170 buf_sz
= ab
->b_size
;
4173 * Compute and store the buffer cksum before
4174 * writing. On debug the cksum is verified first.
4176 arc_cksum_verify(ab
->b_buf
);
4177 arc_cksum_compute(ab
->b_buf
, B_TRUE
);
4179 mutex_exit(hash_lock
);
4181 wzio
= zio_write_phys(pio
, dev
->l2ad_vdev
,
4182 dev
->l2ad_hand
, buf_sz
, buf_data
, ZIO_CHECKSUM_OFF
,
4183 NULL
, NULL
, ZIO_PRIORITY_ASYNC_WRITE
,
4184 ZIO_FLAG_CANFAIL
, B_FALSE
);
4186 DTRACE_PROBE2(l2arc__write
, vdev_t
*, dev
->l2ad_vdev
,
4188 (void) zio_nowait(wzio
);
4191 * Keep the clock hand suitably device-aligned.
4193 buf_sz
= vdev_psize_to_asize(dev
->l2ad_vdev
, buf_sz
);
4196 dev
->l2ad_hand
+= buf_sz
;
4199 mutex_exit(list_lock
);
4204 mutex_exit(&l2arc_buflist_mtx
);
4207 ASSERT3U(write_sz
, ==, 0);
4208 kmem_cache_free(hdr_cache
, head
);
4212 ASSERT3U(write_sz
, <=, target_sz
);
4213 ARCSTAT_BUMP(arcstat_l2_writes_sent
);
4214 ARCSTAT_INCR(arcstat_l2_size
, write_sz
);
4215 spa_l2cache_space_update(dev
->l2ad_vdev
, 0, write_sz
);
4218 * Bump device hand to the device start if it is approaching the end.
4219 * l2arc_evict() will already have evicted ahead for this case.
4221 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- target_sz
)) {
4222 spa_l2cache_space_update(dev
->l2ad_vdev
, 0,
4223 dev
->l2ad_end
- dev
->l2ad_hand
);
4224 dev
->l2ad_hand
= dev
->l2ad_start
;
4225 dev
->l2ad_evict
= dev
->l2ad_start
;
4226 dev
->l2ad_first
= B_FALSE
;
4229 (void) zio_wait(pio
);
4233 * This thread feeds the L2ARC at regular intervals. This is the beating
4234 * heart of the L2ARC.
4237 l2arc_feed_thread(void)
4244 CALLB_CPR_INIT(&cpr
, &l2arc_feed_thr_lock
, callb_generic_cpr
, FTAG
);
4246 mutex_enter(&l2arc_feed_thr_lock
);
4248 while (l2arc_thread_exit
== 0) {
4250 * Pause for l2arc_feed_secs seconds between writes.
4252 CALLB_CPR_SAFE_BEGIN(&cpr
);
4253 (void) cv_timedwait(&l2arc_feed_thr_cv
, &l2arc_feed_thr_lock
,
4254 lbolt
+ (hz
* l2arc_feed_secs
));
4255 CALLB_CPR_SAFE_END(&cpr
, &l2arc_feed_thr_lock
);
4258 * Quick check for L2ARC devices.
4260 mutex_enter(&l2arc_dev_mtx
);
4261 if (l2arc_ndev
== 0) {
4262 mutex_exit(&l2arc_dev_mtx
);
4265 mutex_exit(&l2arc_dev_mtx
);
4268 * This selects the next l2arc device to write to, and in
4269 * doing so the next spa to feed from: dev->l2ad_spa. This
4270 * will return NULL if there are now no l2arc devices or if
4271 * they are all faulted.
4273 * If a device is returned, its spa's config lock is also
4274 * held to prevent device removal. l2arc_dev_get_next()
4275 * will grab and release l2arc_dev_mtx.
4277 if ((dev
= l2arc_dev_get_next()) == NULL
)
4280 spa
= dev
->l2ad_spa
;
4281 ASSERT(spa
!= NULL
);
4284 * Avoid contributing to memory pressure.
4286 if (arc_reclaim_needed()) {
4287 ARCSTAT_BUMP(arcstat_l2_abort_lowmem
);
4288 spa_config_exit(spa
, SCL_L2ARC
, dev
);
4292 ARCSTAT_BUMP(arcstat_l2_feeds
);
4294 size
= dev
->l2ad_write
;
4295 if (arc_warm
== B_FALSE
)
4296 size
+= dev
->l2ad_boost
;
4299 * Evict L2ARC buffers that will be overwritten.
4301 l2arc_evict(dev
, size
, B_FALSE
);
4304 * Write ARC buffers.
4306 l2arc_write_buffers(spa
, dev
, size
);
4307 spa_config_exit(spa
, SCL_L2ARC
, dev
);
4310 l2arc_thread_exit
= 0;
4311 cv_broadcast(&l2arc_feed_thr_cv
);
4312 CALLB_CPR_EXIT(&cpr
); /* drops l2arc_feed_thr_lock */
4317 l2arc_vdev_present(vdev_t
*vd
)
4321 mutex_enter(&l2arc_dev_mtx
);
4322 for (dev
= list_head(l2arc_dev_list
); dev
!= NULL
;
4323 dev
= list_next(l2arc_dev_list
, dev
)) {
4324 if (dev
->l2ad_vdev
== vd
)
4327 mutex_exit(&l2arc_dev_mtx
);
4329 return (dev
!= NULL
);
4333 * Add a vdev for use by the L2ARC. By this point the spa has already
4334 * validated the vdev and opened it.
4337 l2arc_add_vdev(spa_t
*spa
, vdev_t
*vd
, uint64_t start
, uint64_t end
)
4339 l2arc_dev_t
*adddev
;
4341 ASSERT(!l2arc_vdev_present(vd
));
4344 * Create a new l2arc device entry.
4346 adddev
= kmem_zalloc(sizeof (l2arc_dev_t
), KM_SLEEP
);
4347 adddev
->l2ad_spa
= spa
;
4348 adddev
->l2ad_vdev
= vd
;
4349 adddev
->l2ad_write
= l2arc_write_max
;
4350 adddev
->l2ad_boost
= l2arc_write_boost
;
4351 adddev
->l2ad_start
= start
;
4352 adddev
->l2ad_end
= end
;
4353 adddev
->l2ad_hand
= adddev
->l2ad_start
;
4354 adddev
->l2ad_evict
= adddev
->l2ad_start
;
4355 adddev
->l2ad_first
= B_TRUE
;
4356 ASSERT3U(adddev
->l2ad_write
, >, 0);
4359 * This is a list of all ARC buffers that are still valid on the
4362 adddev
->l2ad_buflist
= kmem_zalloc(sizeof (list_t
), KM_SLEEP
);
4363 list_create(adddev
->l2ad_buflist
, sizeof (arc_buf_hdr_t
),
4364 offsetof(arc_buf_hdr_t
, b_l2node
));
4366 spa_l2cache_space_update(vd
, adddev
->l2ad_end
- adddev
->l2ad_hand
, 0);
4369 * Add device to global list
4371 mutex_enter(&l2arc_dev_mtx
);
4372 list_insert_head(l2arc_dev_list
, adddev
);
4373 atomic_inc_64(&l2arc_ndev
);
4374 mutex_exit(&l2arc_dev_mtx
);
4378 * Remove a vdev from the L2ARC.
4381 l2arc_remove_vdev(vdev_t
*vd
)
4383 l2arc_dev_t
*dev
, *nextdev
, *remdev
= NULL
;
4386 * Find the device by vdev
4388 mutex_enter(&l2arc_dev_mtx
);
4389 for (dev
= list_head(l2arc_dev_list
); dev
; dev
= nextdev
) {
4390 nextdev
= list_next(l2arc_dev_list
, dev
);
4391 if (vd
== dev
->l2ad_vdev
) {
4396 ASSERT(remdev
!= NULL
);
4399 * Remove device from global list
4401 list_remove(l2arc_dev_list
, remdev
);
4402 l2arc_dev_last
= NULL
; /* may have been invalidated */
4403 atomic_dec_64(&l2arc_ndev
);
4404 mutex_exit(&l2arc_dev_mtx
);
4407 * Clear all buflists and ARC references. L2ARC device flush.
4409 l2arc_evict(remdev
, 0, B_TRUE
);
4410 list_destroy(remdev
->l2ad_buflist
);
4411 kmem_free(remdev
->l2ad_buflist
, sizeof (list_t
));
4412 kmem_free(remdev
, sizeof (l2arc_dev_t
));
4418 l2arc_thread_exit
= 0;
4420 l2arc_writes_sent
= 0;
4421 l2arc_writes_done
= 0;
4423 mutex_init(&l2arc_feed_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
4424 cv_init(&l2arc_feed_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
4425 mutex_init(&l2arc_dev_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4426 mutex_init(&l2arc_buflist_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4427 mutex_init(&l2arc_free_on_write_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4429 l2arc_dev_list
= &L2ARC_dev_list
;
4430 l2arc_free_on_write
= &L2ARC_free_on_write
;
4431 list_create(l2arc_dev_list
, sizeof (l2arc_dev_t
),
4432 offsetof(l2arc_dev_t
, l2ad_node
));
4433 list_create(l2arc_free_on_write
, sizeof (l2arc_data_free_t
),
4434 offsetof(l2arc_data_free_t
, l2df_list_node
));
4441 * This is called from dmu_fini(), which is called from spa_fini();
4442 * Because of this, we can assume that all l2arc devices have
4443 * already been removed when the pools themselves were removed.
4446 l2arc_do_free_on_write();
4448 mutex_destroy(&l2arc_feed_thr_lock
);
4449 cv_destroy(&l2arc_feed_thr_cv
);
4450 mutex_destroy(&l2arc_dev_mtx
);
4451 mutex_destroy(&l2arc_buflist_mtx
);
4452 mutex_destroy(&l2arc_free_on_write_mtx
);
4454 list_destroy(l2arc_dev_list
);
4455 list_destroy(l2arc_free_on_write
);
4461 if (!(spa_mode_global
& FWRITE
))
4464 (void) thread_create(NULL
, 0, l2arc_feed_thread
, NULL
, 0, &p0
,
4465 TS_RUN
, minclsyspri
);
4471 if (!(spa_mode_global
& FWRITE
))
4474 mutex_enter(&l2arc_feed_thr_lock
);
4475 cv_signal(&l2arc_feed_thr_cv
); /* kick thread out of startup */
4476 l2arc_thread_exit
= 1;
4477 while (l2arc_thread_exit
!= 0)
4478 cv_wait(&l2arc_feed_thr_cv
, &l2arc_feed_thr_lock
);
4479 mutex_exit(&l2arc_feed_thr_lock
);