4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 * Copyright (c) 2012 by Delphix. All rights reserved.
28 * DVA-based Adjustable Replacement Cache
30 * While much of the theory of operation used here is
31 * based on the self-tuning, low overhead replacement cache
32 * presented by Megiddo and Modha at FAST 2003, there are some
33 * significant differences:
35 * 1. The Megiddo and Modha model assumes any page is evictable.
36 * Pages in its cache cannot be "locked" into memory. This makes
37 * the eviction algorithm simple: evict the last page in the list.
38 * This also make the performance characteristics easy to reason
39 * about. Our cache is not so simple. At any given moment, some
40 * subset of the blocks in the cache are un-evictable because we
41 * have handed out a reference to them. Blocks are only evictable
42 * when there are no external references active. This makes
43 * eviction far more problematic: we choose to evict the evictable
44 * blocks that are the "lowest" in the list.
46 * There are times when it is not possible to evict the requested
47 * space. In these circumstances we are unable to adjust the cache
48 * size. To prevent the cache growing unbounded at these times we
49 * implement a "cache throttle" that slows the flow of new data
50 * into the cache until we can make space available.
52 * 2. The Megiddo and Modha model assumes a fixed cache size.
53 * Pages are evicted when the cache is full and there is a cache
54 * miss. Our model has a variable sized cache. It grows with
55 * high use, but also tries to react to memory pressure from the
56 * operating system: decreasing its size when system memory is
59 * 3. The Megiddo and Modha model assumes a fixed page size. All
60 * elements of the cache are therefor exactly the same size. So
61 * when adjusting the cache size following a cache miss, its simply
62 * a matter of choosing a single page to evict. In our model, we
63 * have variable sized cache blocks (rangeing from 512 bytes to
64 * 128K bytes). We therefor choose a set of blocks to evict to make
65 * space for a cache miss that approximates as closely as possible
66 * the space used by the new block.
68 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
69 * by N. Megiddo & D. Modha, FAST 2003
75 * A new reference to a cache buffer can be obtained in two
76 * ways: 1) via a hash table lookup using the DVA as a key,
77 * or 2) via one of the ARC lists. The arc_read() interface
78 * uses method 1, while the internal arc algorithms for
79 * adjusting the cache use method 2. We therefor provide two
80 * types of locks: 1) the hash table lock array, and 2) the
83 * Buffers do not have their own mutexes, rather they rely on the
84 * hash table mutexes for the bulk of their protection (i.e. most
85 * fields in the arc_buf_hdr_t are protected by these mutexes).
87 * buf_hash_find() returns the appropriate mutex (held) when it
88 * locates the requested buffer in the hash table. It returns
89 * NULL for the mutex if the buffer was not in the table.
91 * buf_hash_remove() expects the appropriate hash mutex to be
92 * already held before it is invoked.
94 * Each arc state also has a mutex which is used to protect the
95 * buffer list associated with the state. When attempting to
96 * obtain a hash table lock while holding an arc list lock you
97 * must use: mutex_tryenter() to avoid deadlock. Also note that
98 * the active state mutex must be held before the ghost state mutex.
100 * Arc buffers may have an associated eviction callback function.
101 * This function will be invoked prior to removing the buffer (e.g.
102 * in arc_do_user_evicts()). Note however that the data associated
103 * with the buffer may be evicted prior to the callback. The callback
104 * must be made with *no locks held* (to prevent deadlock). Additionally,
105 * the users of callbacks must ensure that their private data is
106 * protected from simultaneous callbacks from arc_buf_evict()
107 * and arc_do_user_evicts().
109 * Note that the majority of the performance stats are manipulated
110 * with atomic operations.
112 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
114 * - L2ARC buflist creation
115 * - L2ARC buflist eviction
116 * - L2ARC write completion, which walks L2ARC buflists
117 * - ARC header destruction, as it removes from L2ARC buflists
118 * - ARC header release, as it removes from L2ARC buflists
123 #include <sys/zfs_context.h>
125 #include <sys/refcount.h>
126 #include <sys/vdev.h>
127 #include <sys/vdev_impl.h>
129 #include <sys/vmsystm.h>
131 #include <sys/fs/swapnode.h>
132 #include <sys/dnlc.h>
134 #include <sys/callb.h>
135 #include <sys/kstat.h>
136 #include <zfs_fletcher.h>
139 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
140 boolean_t arc_watch
= B_FALSE
;
144 static kmutex_t arc_reclaim_thr_lock
;
145 static kcondvar_t arc_reclaim_thr_cv
; /* used to signal reclaim thr */
146 static uint8_t arc_thread_exit
;
148 extern int zfs_write_limit_shift
;
149 extern uint64_t zfs_write_limit_max
;
150 extern kmutex_t zfs_write_limit_lock
;
152 #define ARC_REDUCE_DNLC_PERCENT 3
153 uint_t arc_reduce_dnlc_percent
= ARC_REDUCE_DNLC_PERCENT
;
155 typedef enum arc_reclaim_strategy
{
156 ARC_RECLAIM_AGGR
, /* Aggressive reclaim strategy */
157 ARC_RECLAIM_CONS
/* Conservative reclaim strategy */
158 } arc_reclaim_strategy_t
;
160 /* number of seconds before growing cache again */
161 static int arc_grow_retry
= 60;
163 /* shift of arc_c for calculating both min and max arc_p */
164 static int arc_p_min_shift
= 4;
166 /* log2(fraction of arc to reclaim) */
167 static int arc_shrink_shift
= 5;
170 * minimum lifespan of a prefetch block in clock ticks
171 * (initialized in arc_init())
173 static int arc_min_prefetch_lifespan
;
178 * The arc has filled available memory and has now warmed up.
180 static boolean_t arc_warm
;
183 * These tunables are for performance analysis.
185 uint64_t zfs_arc_max
;
186 uint64_t zfs_arc_min
;
187 uint64_t zfs_arc_meta_limit
= 0;
188 int zfs_arc_grow_retry
= 0;
189 int zfs_arc_shrink_shift
= 0;
190 int zfs_arc_p_min_shift
= 0;
191 int zfs_disable_dup_eviction
= 0;
194 * Note that buffers can be in one of 6 states:
195 * ARC_anon - anonymous (discussed below)
196 * ARC_mru - recently used, currently cached
197 * ARC_mru_ghost - recentely used, no longer in cache
198 * ARC_mfu - frequently used, currently cached
199 * ARC_mfu_ghost - frequently used, no longer in cache
200 * ARC_l2c_only - exists in L2ARC but not other states
201 * When there are no active references to the buffer, they are
202 * are linked onto a list in one of these arc states. These are
203 * the only buffers that can be evicted or deleted. Within each
204 * state there are multiple lists, one for meta-data and one for
205 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
206 * etc.) is tracked separately so that it can be managed more
207 * explicitly: favored over data, limited explicitly.
209 * Anonymous buffers are buffers that are not associated with
210 * a DVA. These are buffers that hold dirty block copies
211 * before they are written to stable storage. By definition,
212 * they are "ref'd" and are considered part of arc_mru
213 * that cannot be freed. Generally, they will aquire a DVA
214 * as they are written and migrate onto the arc_mru list.
216 * The ARC_l2c_only state is for buffers that are in the second
217 * level ARC but no longer in any of the ARC_m* lists. The second
218 * level ARC itself may also contain buffers that are in any of
219 * the ARC_m* states - meaning that a buffer can exist in two
220 * places. The reason for the ARC_l2c_only state is to keep the
221 * buffer header in the hash table, so that reads that hit the
222 * second level ARC benefit from these fast lookups.
225 typedef struct arc_state
{
226 list_t arcs_list
[ARC_BUFC_NUMTYPES
]; /* list of evictable buffers */
227 uint64_t arcs_lsize
[ARC_BUFC_NUMTYPES
]; /* amount of evictable data */
228 uint64_t arcs_size
; /* total amount of data in this state */
233 static arc_state_t ARC_anon
;
234 static arc_state_t ARC_mru
;
235 static arc_state_t ARC_mru_ghost
;
236 static arc_state_t ARC_mfu
;
237 static arc_state_t ARC_mfu_ghost
;
238 static arc_state_t ARC_l2c_only
;
240 typedef struct arc_stats
{
241 kstat_named_t arcstat_hits
;
242 kstat_named_t arcstat_misses
;
243 kstat_named_t arcstat_demand_data_hits
;
244 kstat_named_t arcstat_demand_data_misses
;
245 kstat_named_t arcstat_demand_metadata_hits
;
246 kstat_named_t arcstat_demand_metadata_misses
;
247 kstat_named_t arcstat_prefetch_data_hits
;
248 kstat_named_t arcstat_prefetch_data_misses
;
249 kstat_named_t arcstat_prefetch_metadata_hits
;
250 kstat_named_t arcstat_prefetch_metadata_misses
;
251 kstat_named_t arcstat_mru_hits
;
252 kstat_named_t arcstat_mru_ghost_hits
;
253 kstat_named_t arcstat_mfu_hits
;
254 kstat_named_t arcstat_mfu_ghost_hits
;
255 kstat_named_t arcstat_deleted
;
256 kstat_named_t arcstat_recycle_miss
;
257 kstat_named_t arcstat_mutex_miss
;
258 kstat_named_t arcstat_evict_skip
;
259 kstat_named_t arcstat_evict_l2_cached
;
260 kstat_named_t arcstat_evict_l2_eligible
;
261 kstat_named_t arcstat_evict_l2_ineligible
;
262 kstat_named_t arcstat_hash_elements
;
263 kstat_named_t arcstat_hash_elements_max
;
264 kstat_named_t arcstat_hash_collisions
;
265 kstat_named_t arcstat_hash_chains
;
266 kstat_named_t arcstat_hash_chain_max
;
267 kstat_named_t arcstat_p
;
268 kstat_named_t arcstat_c
;
269 kstat_named_t arcstat_c_min
;
270 kstat_named_t arcstat_c_max
;
271 kstat_named_t arcstat_size
;
272 kstat_named_t arcstat_hdr_size
;
273 kstat_named_t arcstat_data_size
;
274 kstat_named_t arcstat_other_size
;
275 kstat_named_t arcstat_l2_hits
;
276 kstat_named_t arcstat_l2_misses
;
277 kstat_named_t arcstat_l2_feeds
;
278 kstat_named_t arcstat_l2_rw_clash
;
279 kstat_named_t arcstat_l2_read_bytes
;
280 kstat_named_t arcstat_l2_write_bytes
;
281 kstat_named_t arcstat_l2_writes_sent
;
282 kstat_named_t arcstat_l2_writes_done
;
283 kstat_named_t arcstat_l2_writes_error
;
284 kstat_named_t arcstat_l2_writes_hdr_miss
;
285 kstat_named_t arcstat_l2_evict_lock_retry
;
286 kstat_named_t arcstat_l2_evict_reading
;
287 kstat_named_t arcstat_l2_free_on_write
;
288 kstat_named_t arcstat_l2_abort_lowmem
;
289 kstat_named_t arcstat_l2_cksum_bad
;
290 kstat_named_t arcstat_l2_io_error
;
291 kstat_named_t arcstat_l2_size
;
292 kstat_named_t arcstat_l2_hdr_size
;
293 kstat_named_t arcstat_memory_throttle_count
;
294 kstat_named_t arcstat_duplicate_buffers
;
295 kstat_named_t arcstat_duplicate_buffers_size
;
296 kstat_named_t arcstat_duplicate_reads
;
299 static arc_stats_t arc_stats
= {
300 { "hits", KSTAT_DATA_UINT64
},
301 { "misses", KSTAT_DATA_UINT64
},
302 { "demand_data_hits", KSTAT_DATA_UINT64
},
303 { "demand_data_misses", KSTAT_DATA_UINT64
},
304 { "demand_metadata_hits", KSTAT_DATA_UINT64
},
305 { "demand_metadata_misses", KSTAT_DATA_UINT64
},
306 { "prefetch_data_hits", KSTAT_DATA_UINT64
},
307 { "prefetch_data_misses", KSTAT_DATA_UINT64
},
308 { "prefetch_metadata_hits", KSTAT_DATA_UINT64
},
309 { "prefetch_metadata_misses", KSTAT_DATA_UINT64
},
310 { "mru_hits", KSTAT_DATA_UINT64
},
311 { "mru_ghost_hits", KSTAT_DATA_UINT64
},
312 { "mfu_hits", KSTAT_DATA_UINT64
},
313 { "mfu_ghost_hits", KSTAT_DATA_UINT64
},
314 { "deleted", KSTAT_DATA_UINT64
},
315 { "recycle_miss", KSTAT_DATA_UINT64
},
316 { "mutex_miss", KSTAT_DATA_UINT64
},
317 { "evict_skip", KSTAT_DATA_UINT64
},
318 { "evict_l2_cached", KSTAT_DATA_UINT64
},
319 { "evict_l2_eligible", KSTAT_DATA_UINT64
},
320 { "evict_l2_ineligible", KSTAT_DATA_UINT64
},
321 { "hash_elements", KSTAT_DATA_UINT64
},
322 { "hash_elements_max", KSTAT_DATA_UINT64
},
323 { "hash_collisions", KSTAT_DATA_UINT64
},
324 { "hash_chains", KSTAT_DATA_UINT64
},
325 { "hash_chain_max", KSTAT_DATA_UINT64
},
326 { "p", KSTAT_DATA_UINT64
},
327 { "c", KSTAT_DATA_UINT64
},
328 { "c_min", KSTAT_DATA_UINT64
},
329 { "c_max", KSTAT_DATA_UINT64
},
330 { "size", KSTAT_DATA_UINT64
},
331 { "hdr_size", KSTAT_DATA_UINT64
},
332 { "data_size", KSTAT_DATA_UINT64
},
333 { "other_size", KSTAT_DATA_UINT64
},
334 { "l2_hits", KSTAT_DATA_UINT64
},
335 { "l2_misses", KSTAT_DATA_UINT64
},
336 { "l2_feeds", KSTAT_DATA_UINT64
},
337 { "l2_rw_clash", KSTAT_DATA_UINT64
},
338 { "l2_read_bytes", KSTAT_DATA_UINT64
},
339 { "l2_write_bytes", KSTAT_DATA_UINT64
},
340 { "l2_writes_sent", KSTAT_DATA_UINT64
},
341 { "l2_writes_done", KSTAT_DATA_UINT64
},
342 { "l2_writes_error", KSTAT_DATA_UINT64
},
343 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64
},
344 { "l2_evict_lock_retry", KSTAT_DATA_UINT64
},
345 { "l2_evict_reading", KSTAT_DATA_UINT64
},
346 { "l2_free_on_write", KSTAT_DATA_UINT64
},
347 { "l2_abort_lowmem", KSTAT_DATA_UINT64
},
348 { "l2_cksum_bad", KSTAT_DATA_UINT64
},
349 { "l2_io_error", KSTAT_DATA_UINT64
},
350 { "l2_size", KSTAT_DATA_UINT64
},
351 { "l2_hdr_size", KSTAT_DATA_UINT64
},
352 { "memory_throttle_count", KSTAT_DATA_UINT64
},
353 { "duplicate_buffers", KSTAT_DATA_UINT64
},
354 { "duplicate_buffers_size", KSTAT_DATA_UINT64
},
355 { "duplicate_reads", KSTAT_DATA_UINT64
}
358 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
360 #define ARCSTAT_INCR(stat, val) \
361 atomic_add_64(&arc_stats.stat.value.ui64, (val));
363 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
364 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
366 #define ARCSTAT_MAX(stat, val) { \
368 while ((val) > (m = arc_stats.stat.value.ui64) && \
369 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
373 #define ARCSTAT_MAXSTAT(stat) \
374 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
377 * We define a macro to allow ARC hits/misses to be easily broken down by
378 * two separate conditions, giving a total of four different subtypes for
379 * each of hits and misses (so eight statistics total).
381 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
384 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
386 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
390 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
392 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
397 static arc_state_t
*arc_anon
;
398 static arc_state_t
*arc_mru
;
399 static arc_state_t
*arc_mru_ghost
;
400 static arc_state_t
*arc_mfu
;
401 static arc_state_t
*arc_mfu_ghost
;
402 static arc_state_t
*arc_l2c_only
;
405 * There are several ARC variables that are critical to export as kstats --
406 * but we don't want to have to grovel around in the kstat whenever we wish to
407 * manipulate them. For these variables, we therefore define them to be in
408 * terms of the statistic variable. This assures that we are not introducing
409 * the possibility of inconsistency by having shadow copies of the variables,
410 * while still allowing the code to be readable.
412 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
413 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
414 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
415 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
416 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
418 static int arc_no_grow
; /* Don't try to grow cache size */
419 static uint64_t arc_tempreserve
;
420 static uint64_t arc_loaned_bytes
;
421 static uint64_t arc_meta_used
;
422 static uint64_t arc_meta_limit
;
423 static uint64_t arc_meta_max
= 0;
425 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t
;
427 typedef struct arc_callback arc_callback_t
;
429 struct arc_callback
{
431 arc_done_func_t
*acb_done
;
433 zio_t
*acb_zio_dummy
;
434 arc_callback_t
*acb_next
;
437 typedef struct arc_write_callback arc_write_callback_t
;
439 struct arc_write_callback
{
441 arc_done_func_t
*awcb_ready
;
442 arc_done_func_t
*awcb_done
;
447 /* protected by hash lock */
452 kmutex_t b_freeze_lock
;
453 zio_cksum_t
*b_freeze_cksum
;
456 arc_buf_hdr_t
*b_hash_next
;
461 arc_callback_t
*b_acb
;
465 arc_buf_contents_t b_type
;
469 /* protected by arc state mutex */
470 arc_state_t
*b_state
;
471 list_node_t b_arc_node
;
473 /* updated atomically */
474 clock_t b_arc_access
;
476 /* self protecting */
479 l2arc_buf_hdr_t
*b_l2hdr
;
480 list_node_t b_l2node
;
483 static arc_buf_t
*arc_eviction_list
;
484 static kmutex_t arc_eviction_mtx
;
485 static arc_buf_hdr_t arc_eviction_hdr
;
486 static void arc_get_data_buf(arc_buf_t
*buf
);
487 static void arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
);
488 static int arc_evict_needed(arc_buf_contents_t type
);
489 static void arc_evict_ghost(arc_state_t
*state
, uint64_t spa
, int64_t bytes
);
490 static void arc_buf_watch(arc_buf_t
*buf
);
492 static boolean_t
l2arc_write_eligible(uint64_t spa_guid
, arc_buf_hdr_t
*ab
);
494 #define GHOST_STATE(state) \
495 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
496 (state) == arc_l2c_only)
499 * Private ARC flags. These flags are private ARC only flags that will show up
500 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
501 * be passed in as arc_flags in things like arc_read. However, these flags
502 * should never be passed and should only be set by ARC code. When adding new
503 * public flags, make sure not to smash the private ones.
506 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
507 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
508 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
509 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
510 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
511 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
512 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
513 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
514 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
515 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
517 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
518 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
519 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
520 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
521 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
522 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
523 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
524 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
525 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
526 (hdr)->b_l2hdr != NULL)
527 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
528 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
529 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
535 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
536 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
539 * Hash table routines
542 #define HT_LOCK_PAD 64
547 unsigned char pad
[(HT_LOCK_PAD
- sizeof (kmutex_t
))];
551 #define BUF_LOCKS 256
552 typedef struct buf_hash_table
{
554 arc_buf_hdr_t
**ht_table
;
555 struct ht_lock ht_locks
[BUF_LOCKS
];
558 static buf_hash_table_t buf_hash_table
;
560 #define BUF_HASH_INDEX(spa, dva, birth) \
561 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
562 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
563 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
564 #define HDR_LOCK(hdr) \
565 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
567 uint64_t zfs_crc64_table
[256];
573 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
574 #define L2ARC_HEADROOM 2 /* num of writes */
575 #define L2ARC_FEED_SECS 1 /* caching interval secs */
576 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
578 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
579 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
582 * L2ARC Performance Tunables
584 uint64_t l2arc_write_max
= L2ARC_WRITE_SIZE
; /* default max write size */
585 uint64_t l2arc_write_boost
= L2ARC_WRITE_SIZE
; /* extra write during warmup */
586 uint64_t l2arc_headroom
= L2ARC_HEADROOM
; /* number of dev writes */
587 uint64_t l2arc_feed_secs
= L2ARC_FEED_SECS
; /* interval seconds */
588 uint64_t l2arc_feed_min_ms
= L2ARC_FEED_MIN_MS
; /* min interval milliseconds */
589 boolean_t l2arc_noprefetch
= B_TRUE
; /* don't cache prefetch bufs */
590 boolean_t l2arc_feed_again
= B_TRUE
; /* turbo warmup */
591 boolean_t l2arc_norw
= B_TRUE
; /* no reads during writes */
596 typedef struct l2arc_dev
{
597 vdev_t
*l2ad_vdev
; /* vdev */
598 spa_t
*l2ad_spa
; /* spa */
599 uint64_t l2ad_hand
; /* next write location */
600 uint64_t l2ad_write
; /* desired write size, bytes */
601 uint64_t l2ad_boost
; /* warmup write boost, bytes */
602 uint64_t l2ad_start
; /* first addr on device */
603 uint64_t l2ad_end
; /* last addr on device */
604 uint64_t l2ad_evict
; /* last addr eviction reached */
605 boolean_t l2ad_first
; /* first sweep through */
606 boolean_t l2ad_writing
; /* currently writing */
607 list_t
*l2ad_buflist
; /* buffer list */
608 list_node_t l2ad_node
; /* device list node */
611 static list_t L2ARC_dev_list
; /* device list */
612 static list_t
*l2arc_dev_list
; /* device list pointer */
613 static kmutex_t l2arc_dev_mtx
; /* device list mutex */
614 static l2arc_dev_t
*l2arc_dev_last
; /* last device used */
615 static kmutex_t l2arc_buflist_mtx
; /* mutex for all buflists */
616 static list_t L2ARC_free_on_write
; /* free after write buf list */
617 static list_t
*l2arc_free_on_write
; /* free after write list ptr */
618 static kmutex_t l2arc_free_on_write_mtx
; /* mutex for list */
619 static uint64_t l2arc_ndev
; /* number of devices */
621 typedef struct l2arc_read_callback
{
622 arc_buf_t
*l2rcb_buf
; /* read buffer */
623 spa_t
*l2rcb_spa
; /* spa */
624 blkptr_t l2rcb_bp
; /* original blkptr */
625 zbookmark_t l2rcb_zb
; /* original bookmark */
626 int l2rcb_flags
; /* original flags */
627 } l2arc_read_callback_t
;
629 typedef struct l2arc_write_callback
{
630 l2arc_dev_t
*l2wcb_dev
; /* device info */
631 arc_buf_hdr_t
*l2wcb_head
; /* head of write buflist */
632 } l2arc_write_callback_t
;
634 struct l2arc_buf_hdr
{
635 /* protected by arc_buf_hdr mutex */
636 l2arc_dev_t
*b_dev
; /* L2ARC device */
637 uint64_t b_daddr
; /* disk address, offset byte */
640 typedef struct l2arc_data_free
{
641 /* protected by l2arc_free_on_write_mtx */
644 void (*l2df_func
)(void *, size_t);
645 list_node_t l2df_list_node
;
648 static kmutex_t l2arc_feed_thr_lock
;
649 static kcondvar_t l2arc_feed_thr_cv
;
650 static uint8_t l2arc_thread_exit
;
652 static void l2arc_read_done(zio_t
*zio
);
653 static void l2arc_hdr_stat_add(void);
654 static void l2arc_hdr_stat_remove(void);
657 buf_hash(uint64_t spa
, const dva_t
*dva
, uint64_t birth
)
659 uint8_t *vdva
= (uint8_t *)dva
;
660 uint64_t crc
= -1ULL;
663 ASSERT(zfs_crc64_table
[128] == ZFS_CRC64_POLY
);
665 for (i
= 0; i
< sizeof (dva_t
); i
++)
666 crc
= (crc
>> 8) ^ zfs_crc64_table
[(crc
^ vdva
[i
]) & 0xFF];
668 crc
^= (spa
>>8) ^ birth
;
673 #define BUF_EMPTY(buf) \
674 ((buf)->b_dva.dva_word[0] == 0 && \
675 (buf)->b_dva.dva_word[1] == 0 && \
678 #define BUF_EQUAL(spa, dva, birth, buf) \
679 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
680 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
681 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
684 buf_discard_identity(arc_buf_hdr_t
*hdr
)
686 hdr
->b_dva
.dva_word
[0] = 0;
687 hdr
->b_dva
.dva_word
[1] = 0;
692 static arc_buf_hdr_t
*
693 buf_hash_find(uint64_t spa
, const dva_t
*dva
, uint64_t birth
, kmutex_t
**lockp
)
695 uint64_t idx
= BUF_HASH_INDEX(spa
, dva
, birth
);
696 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
699 mutex_enter(hash_lock
);
700 for (buf
= buf_hash_table
.ht_table
[idx
]; buf
!= NULL
;
701 buf
= buf
->b_hash_next
) {
702 if (BUF_EQUAL(spa
, dva
, birth
, buf
)) {
707 mutex_exit(hash_lock
);
713 * Insert an entry into the hash table. If there is already an element
714 * equal to elem in the hash table, then the already existing element
715 * will be returned and the new element will not be inserted.
716 * Otherwise returns NULL.
718 static arc_buf_hdr_t
*
719 buf_hash_insert(arc_buf_hdr_t
*buf
, kmutex_t
**lockp
)
721 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
722 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
726 ASSERT(!HDR_IN_HASH_TABLE(buf
));
728 mutex_enter(hash_lock
);
729 for (fbuf
= buf_hash_table
.ht_table
[idx
], i
= 0; fbuf
!= NULL
;
730 fbuf
= fbuf
->b_hash_next
, i
++) {
731 if (BUF_EQUAL(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
, fbuf
))
735 buf
->b_hash_next
= buf_hash_table
.ht_table
[idx
];
736 buf_hash_table
.ht_table
[idx
] = buf
;
737 buf
->b_flags
|= ARC_IN_HASH_TABLE
;
739 /* collect some hash table performance data */
741 ARCSTAT_BUMP(arcstat_hash_collisions
);
743 ARCSTAT_BUMP(arcstat_hash_chains
);
745 ARCSTAT_MAX(arcstat_hash_chain_max
, i
);
748 ARCSTAT_BUMP(arcstat_hash_elements
);
749 ARCSTAT_MAXSTAT(arcstat_hash_elements
);
755 buf_hash_remove(arc_buf_hdr_t
*buf
)
757 arc_buf_hdr_t
*fbuf
, **bufp
;
758 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
760 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx
)));
761 ASSERT(HDR_IN_HASH_TABLE(buf
));
763 bufp
= &buf_hash_table
.ht_table
[idx
];
764 while ((fbuf
= *bufp
) != buf
) {
765 ASSERT(fbuf
!= NULL
);
766 bufp
= &fbuf
->b_hash_next
;
768 *bufp
= buf
->b_hash_next
;
769 buf
->b_hash_next
= NULL
;
770 buf
->b_flags
&= ~ARC_IN_HASH_TABLE
;
772 /* collect some hash table performance data */
773 ARCSTAT_BUMPDOWN(arcstat_hash_elements
);
775 if (buf_hash_table
.ht_table
[idx
] &&
776 buf_hash_table
.ht_table
[idx
]->b_hash_next
== NULL
)
777 ARCSTAT_BUMPDOWN(arcstat_hash_chains
);
781 * Global data structures and functions for the buf kmem cache.
783 static kmem_cache_t
*hdr_cache
;
784 static kmem_cache_t
*buf_cache
;
791 kmem_free(buf_hash_table
.ht_table
,
792 (buf_hash_table
.ht_mask
+ 1) * sizeof (void *));
793 for (i
= 0; i
< BUF_LOCKS
; i
++)
794 mutex_destroy(&buf_hash_table
.ht_locks
[i
].ht_lock
);
795 kmem_cache_destroy(hdr_cache
);
796 kmem_cache_destroy(buf_cache
);
800 * Constructor callback - called when the cache is empty
801 * and a new buf is requested.
805 hdr_cons(void *vbuf
, void *unused
, int kmflag
)
807 arc_buf_hdr_t
*buf
= vbuf
;
809 bzero(buf
, sizeof (arc_buf_hdr_t
));
810 refcount_create(&buf
->b_refcnt
);
811 cv_init(&buf
->b_cv
, NULL
, CV_DEFAULT
, NULL
);
812 mutex_init(&buf
->b_freeze_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
813 arc_space_consume(sizeof (arc_buf_hdr_t
), ARC_SPACE_HDRS
);
820 buf_cons(void *vbuf
, void *unused
, int kmflag
)
822 arc_buf_t
*buf
= vbuf
;
824 bzero(buf
, sizeof (arc_buf_t
));
825 mutex_init(&buf
->b_evict_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
826 rw_init(&buf
->b_data_lock
, NULL
, RW_DEFAULT
, NULL
);
827 arc_space_consume(sizeof (arc_buf_t
), ARC_SPACE_HDRS
);
833 * Destructor callback - called when a cached buf is
834 * no longer required.
838 hdr_dest(void *vbuf
, void *unused
)
840 arc_buf_hdr_t
*buf
= vbuf
;
842 ASSERT(BUF_EMPTY(buf
));
843 refcount_destroy(&buf
->b_refcnt
);
844 cv_destroy(&buf
->b_cv
);
845 mutex_destroy(&buf
->b_freeze_lock
);
846 arc_space_return(sizeof (arc_buf_hdr_t
), ARC_SPACE_HDRS
);
851 buf_dest(void *vbuf
, void *unused
)
853 arc_buf_t
*buf
= vbuf
;
855 mutex_destroy(&buf
->b_evict_lock
);
856 rw_destroy(&buf
->b_data_lock
);
857 arc_space_return(sizeof (arc_buf_t
), ARC_SPACE_HDRS
);
861 * Reclaim callback -- invoked when memory is low.
865 hdr_recl(void *unused
)
867 dprintf("hdr_recl called\n");
869 * umem calls the reclaim func when we destroy the buf cache,
870 * which is after we do arc_fini().
873 cv_signal(&arc_reclaim_thr_cv
);
880 uint64_t hsize
= 1ULL << 12;
884 * The hash table is big enough to fill all of physical memory
885 * with an average 64K block size. The table will take up
886 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
888 while (hsize
* 65536 < physmem
* PAGESIZE
)
891 buf_hash_table
.ht_mask
= hsize
- 1;
892 buf_hash_table
.ht_table
=
893 kmem_zalloc(hsize
* sizeof (void*), KM_NOSLEEP
);
894 if (buf_hash_table
.ht_table
== NULL
) {
895 ASSERT(hsize
> (1ULL << 8));
900 hdr_cache
= kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t
),
901 0, hdr_cons
, hdr_dest
, hdr_recl
, NULL
, NULL
, 0);
902 buf_cache
= kmem_cache_create("arc_buf_t", sizeof (arc_buf_t
),
903 0, buf_cons
, buf_dest
, NULL
, NULL
, NULL
, 0);
905 for (i
= 0; i
< 256; i
++)
906 for (ct
= zfs_crc64_table
+ i
, *ct
= i
, j
= 8; j
> 0; j
--)
907 *ct
= (*ct
>> 1) ^ (-(*ct
& 1) & ZFS_CRC64_POLY
);
909 for (i
= 0; i
< BUF_LOCKS
; i
++) {
910 mutex_init(&buf_hash_table
.ht_locks
[i
].ht_lock
,
911 NULL
, MUTEX_DEFAULT
, NULL
);
915 #define ARC_MINTIME (hz>>4) /* 62 ms */
918 arc_cksum_verify(arc_buf_t
*buf
)
922 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
925 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
926 if (buf
->b_hdr
->b_freeze_cksum
== NULL
||
927 (buf
->b_hdr
->b_flags
& ARC_IO_ERROR
)) {
928 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
931 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
932 if (!ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
))
933 panic("buffer modified while frozen!");
934 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
938 arc_cksum_equal(arc_buf_t
*buf
)
943 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
944 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
945 equal
= ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
);
946 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
952 arc_cksum_compute(arc_buf_t
*buf
, boolean_t force
)
954 if (!force
&& !(zfs_flags
& ZFS_DEBUG_MODIFY
))
957 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
958 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
959 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
962 buf
->b_hdr
->b_freeze_cksum
= kmem_alloc(sizeof (zio_cksum_t
), KM_SLEEP
);
963 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
,
964 buf
->b_hdr
->b_freeze_cksum
);
965 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
970 typedef struct procctl
{
978 arc_buf_unwatch(arc_buf_t
*buf
)
985 ctl
.prwatch
.pr_vaddr
= (uintptr_t)buf
->b_data
;
986 ctl
.prwatch
.pr_size
= 0;
987 ctl
.prwatch
.pr_wflags
= 0;
988 result
= write(arc_procfd
, &ctl
, sizeof (ctl
));
989 ASSERT3U(result
, ==, sizeof (ctl
));
996 arc_buf_watch(arc_buf_t
*buf
)
1003 ctl
.prwatch
.pr_vaddr
= (uintptr_t)buf
->b_data
;
1004 ctl
.prwatch
.pr_size
= buf
->b_hdr
->b_size
;
1005 ctl
.prwatch
.pr_wflags
= WA_WRITE
;
1006 result
= write(arc_procfd
, &ctl
, sizeof (ctl
));
1007 ASSERT3U(result
, ==, sizeof (ctl
));
1013 arc_buf_thaw(arc_buf_t
*buf
)
1015 if (zfs_flags
& ZFS_DEBUG_MODIFY
) {
1016 if (buf
->b_hdr
->b_state
!= arc_anon
)
1017 panic("modifying non-anon buffer!");
1018 if (buf
->b_hdr
->b_flags
& ARC_IO_IN_PROGRESS
)
1019 panic("modifying buffer while i/o in progress!");
1020 arc_cksum_verify(buf
);
1023 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
1024 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
1025 kmem_free(buf
->b_hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
1026 buf
->b_hdr
->b_freeze_cksum
= NULL
;
1029 if (zfs_flags
& ZFS_DEBUG_MODIFY
) {
1030 if (buf
->b_hdr
->b_thawed
)
1031 kmem_free(buf
->b_hdr
->b_thawed
, 1);
1032 buf
->b_hdr
->b_thawed
= kmem_alloc(1, KM_SLEEP
);
1035 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1037 arc_buf_unwatch(buf
);
1041 arc_buf_freeze(arc_buf_t
*buf
)
1043 kmutex_t
*hash_lock
;
1045 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
1048 hash_lock
= HDR_LOCK(buf
->b_hdr
);
1049 mutex_enter(hash_lock
);
1051 ASSERT(buf
->b_hdr
->b_freeze_cksum
!= NULL
||
1052 buf
->b_hdr
->b_state
== arc_anon
);
1053 arc_cksum_compute(buf
, B_FALSE
);
1054 mutex_exit(hash_lock
);
1059 add_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
1061 ASSERT(MUTEX_HELD(hash_lock
));
1063 if ((refcount_add(&ab
->b_refcnt
, tag
) == 1) &&
1064 (ab
->b_state
!= arc_anon
)) {
1065 uint64_t delta
= ab
->b_size
* ab
->b_datacnt
;
1066 list_t
*list
= &ab
->b_state
->arcs_list
[ab
->b_type
];
1067 uint64_t *size
= &ab
->b_state
->arcs_lsize
[ab
->b_type
];
1069 ASSERT(!MUTEX_HELD(&ab
->b_state
->arcs_mtx
));
1070 mutex_enter(&ab
->b_state
->arcs_mtx
);
1071 ASSERT(list_link_active(&ab
->b_arc_node
));
1072 list_remove(list
, ab
);
1073 if (GHOST_STATE(ab
->b_state
)) {
1074 ASSERT0(ab
->b_datacnt
);
1075 ASSERT3P(ab
->b_buf
, ==, NULL
);
1079 ASSERT3U(*size
, >=, delta
);
1080 atomic_add_64(size
, -delta
);
1081 mutex_exit(&ab
->b_state
->arcs_mtx
);
1082 /* remove the prefetch flag if we get a reference */
1083 if (ab
->b_flags
& ARC_PREFETCH
)
1084 ab
->b_flags
&= ~ARC_PREFETCH
;
1089 remove_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
1092 arc_state_t
*state
= ab
->b_state
;
1094 ASSERT(state
== arc_anon
|| MUTEX_HELD(hash_lock
));
1095 ASSERT(!GHOST_STATE(state
));
1097 if (((cnt
= refcount_remove(&ab
->b_refcnt
, tag
)) == 0) &&
1098 (state
!= arc_anon
)) {
1099 uint64_t *size
= &state
->arcs_lsize
[ab
->b_type
];
1101 ASSERT(!MUTEX_HELD(&state
->arcs_mtx
));
1102 mutex_enter(&state
->arcs_mtx
);
1103 ASSERT(!list_link_active(&ab
->b_arc_node
));
1104 list_insert_head(&state
->arcs_list
[ab
->b_type
], ab
);
1105 ASSERT(ab
->b_datacnt
> 0);
1106 atomic_add_64(size
, ab
->b_size
* ab
->b_datacnt
);
1107 mutex_exit(&state
->arcs_mtx
);
1113 * Move the supplied buffer to the indicated state. The mutex
1114 * for the buffer must be held by the caller.
1117 arc_change_state(arc_state_t
*new_state
, arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
)
1119 arc_state_t
*old_state
= ab
->b_state
;
1120 int64_t refcnt
= refcount_count(&ab
->b_refcnt
);
1121 uint64_t from_delta
, to_delta
;
1123 ASSERT(MUTEX_HELD(hash_lock
));
1124 ASSERT(new_state
!= old_state
);
1125 ASSERT(refcnt
== 0 || ab
->b_datacnt
> 0);
1126 ASSERT(ab
->b_datacnt
== 0 || !GHOST_STATE(new_state
));
1127 ASSERT(ab
->b_datacnt
<= 1 || old_state
!= arc_anon
);
1129 from_delta
= to_delta
= ab
->b_datacnt
* ab
->b_size
;
1132 * If this buffer is evictable, transfer it from the
1133 * old state list to the new state list.
1136 if (old_state
!= arc_anon
) {
1137 int use_mutex
= !MUTEX_HELD(&old_state
->arcs_mtx
);
1138 uint64_t *size
= &old_state
->arcs_lsize
[ab
->b_type
];
1141 mutex_enter(&old_state
->arcs_mtx
);
1143 ASSERT(list_link_active(&ab
->b_arc_node
));
1144 list_remove(&old_state
->arcs_list
[ab
->b_type
], ab
);
1147 * If prefetching out of the ghost cache,
1148 * we will have a non-zero datacnt.
1150 if (GHOST_STATE(old_state
) && ab
->b_datacnt
== 0) {
1151 /* ghost elements have a ghost size */
1152 ASSERT(ab
->b_buf
== NULL
);
1153 from_delta
= ab
->b_size
;
1155 ASSERT3U(*size
, >=, from_delta
);
1156 atomic_add_64(size
, -from_delta
);
1159 mutex_exit(&old_state
->arcs_mtx
);
1161 if (new_state
!= arc_anon
) {
1162 int use_mutex
= !MUTEX_HELD(&new_state
->arcs_mtx
);
1163 uint64_t *size
= &new_state
->arcs_lsize
[ab
->b_type
];
1166 mutex_enter(&new_state
->arcs_mtx
);
1168 list_insert_head(&new_state
->arcs_list
[ab
->b_type
], ab
);
1170 /* ghost elements have a ghost size */
1171 if (GHOST_STATE(new_state
)) {
1172 ASSERT(ab
->b_datacnt
== 0);
1173 ASSERT(ab
->b_buf
== NULL
);
1174 to_delta
= ab
->b_size
;
1176 atomic_add_64(size
, to_delta
);
1179 mutex_exit(&new_state
->arcs_mtx
);
1183 ASSERT(!BUF_EMPTY(ab
));
1184 if (new_state
== arc_anon
&& HDR_IN_HASH_TABLE(ab
))
1185 buf_hash_remove(ab
);
1187 /* adjust state sizes */
1189 atomic_add_64(&new_state
->arcs_size
, to_delta
);
1191 ASSERT3U(old_state
->arcs_size
, >=, from_delta
);
1192 atomic_add_64(&old_state
->arcs_size
, -from_delta
);
1194 ab
->b_state
= new_state
;
1196 /* adjust l2arc hdr stats */
1197 if (new_state
== arc_l2c_only
)
1198 l2arc_hdr_stat_add();
1199 else if (old_state
== arc_l2c_only
)
1200 l2arc_hdr_stat_remove();
1204 arc_space_consume(uint64_t space
, arc_space_type_t type
)
1206 ASSERT(type
>= 0 && type
< ARC_SPACE_NUMTYPES
);
1209 case ARC_SPACE_DATA
:
1210 ARCSTAT_INCR(arcstat_data_size
, space
);
1212 case ARC_SPACE_OTHER
:
1213 ARCSTAT_INCR(arcstat_other_size
, space
);
1215 case ARC_SPACE_HDRS
:
1216 ARCSTAT_INCR(arcstat_hdr_size
, space
);
1218 case ARC_SPACE_L2HDRS
:
1219 ARCSTAT_INCR(arcstat_l2_hdr_size
, space
);
1223 atomic_add_64(&arc_meta_used
, space
);
1224 atomic_add_64(&arc_size
, space
);
1228 arc_space_return(uint64_t space
, arc_space_type_t type
)
1230 ASSERT(type
>= 0 && type
< ARC_SPACE_NUMTYPES
);
1233 case ARC_SPACE_DATA
:
1234 ARCSTAT_INCR(arcstat_data_size
, -space
);
1236 case ARC_SPACE_OTHER
:
1237 ARCSTAT_INCR(arcstat_other_size
, -space
);
1239 case ARC_SPACE_HDRS
:
1240 ARCSTAT_INCR(arcstat_hdr_size
, -space
);
1242 case ARC_SPACE_L2HDRS
:
1243 ARCSTAT_INCR(arcstat_l2_hdr_size
, -space
);
1247 ASSERT(arc_meta_used
>= space
);
1248 if (arc_meta_max
< arc_meta_used
)
1249 arc_meta_max
= arc_meta_used
;
1250 atomic_add_64(&arc_meta_used
, -space
);
1251 ASSERT(arc_size
>= space
);
1252 atomic_add_64(&arc_size
, -space
);
1256 arc_data_buf_alloc(uint64_t size
)
1258 if (arc_evict_needed(ARC_BUFC_DATA
))
1259 cv_signal(&arc_reclaim_thr_cv
);
1260 atomic_add_64(&arc_size
, size
);
1261 return (zio_data_buf_alloc(size
));
1265 arc_data_buf_free(void *buf
, uint64_t size
)
1267 zio_data_buf_free(buf
, size
);
1268 ASSERT(arc_size
>= size
);
1269 atomic_add_64(&arc_size
, -size
);
1273 arc_buf_alloc(spa_t
*spa
, int size
, void *tag
, arc_buf_contents_t type
)
1278 ASSERT3U(size
, >, 0);
1279 hdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
1280 ASSERT(BUF_EMPTY(hdr
));
1283 hdr
->b_spa
= spa_load_guid(spa
);
1284 hdr
->b_state
= arc_anon
;
1285 hdr
->b_arc_access
= 0;
1286 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1289 buf
->b_efunc
= NULL
;
1290 buf
->b_private
= NULL
;
1293 arc_get_data_buf(buf
);
1296 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1297 (void) refcount_add(&hdr
->b_refcnt
, tag
);
1302 static char *arc_onloan_tag
= "onloan";
1305 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1306 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1307 * buffers must be returned to the arc before they can be used by the DMU or
1311 arc_loan_buf(spa_t
*spa
, int size
)
1315 buf
= arc_buf_alloc(spa
, size
, arc_onloan_tag
, ARC_BUFC_DATA
);
1317 atomic_add_64(&arc_loaned_bytes
, size
);
1322 * Return a loaned arc buffer to the arc.
1325 arc_return_buf(arc_buf_t
*buf
, void *tag
)
1327 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1329 ASSERT(buf
->b_data
!= NULL
);
1330 (void) refcount_add(&hdr
->b_refcnt
, tag
);
1331 (void) refcount_remove(&hdr
->b_refcnt
, arc_onloan_tag
);
1333 atomic_add_64(&arc_loaned_bytes
, -hdr
->b_size
);
1336 /* Detach an arc_buf from a dbuf (tag) */
1338 arc_loan_inuse_buf(arc_buf_t
*buf
, void *tag
)
1342 ASSERT(buf
->b_data
!= NULL
);
1344 (void) refcount_add(&hdr
->b_refcnt
, arc_onloan_tag
);
1345 (void) refcount_remove(&hdr
->b_refcnt
, tag
);
1346 buf
->b_efunc
= NULL
;
1347 buf
->b_private
= NULL
;
1349 atomic_add_64(&arc_loaned_bytes
, hdr
->b_size
);
1353 arc_buf_clone(arc_buf_t
*from
)
1356 arc_buf_hdr_t
*hdr
= from
->b_hdr
;
1357 uint64_t size
= hdr
->b_size
;
1359 ASSERT(hdr
->b_state
!= arc_anon
);
1361 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1364 buf
->b_efunc
= NULL
;
1365 buf
->b_private
= NULL
;
1366 buf
->b_next
= hdr
->b_buf
;
1368 arc_get_data_buf(buf
);
1369 bcopy(from
->b_data
, buf
->b_data
, size
);
1372 * This buffer already exists in the arc so create a duplicate
1373 * copy for the caller. If the buffer is associated with user data
1374 * then track the size and number of duplicates. These stats will be
1375 * updated as duplicate buffers are created and destroyed.
1377 if (hdr
->b_type
== ARC_BUFC_DATA
) {
1378 ARCSTAT_BUMP(arcstat_duplicate_buffers
);
1379 ARCSTAT_INCR(arcstat_duplicate_buffers_size
, size
);
1381 hdr
->b_datacnt
+= 1;
1386 arc_buf_add_ref(arc_buf_t
*buf
, void* tag
)
1389 kmutex_t
*hash_lock
;
1392 * Check to see if this buffer is evicted. Callers
1393 * must verify b_data != NULL to know if the add_ref
1396 mutex_enter(&buf
->b_evict_lock
);
1397 if (buf
->b_data
== NULL
) {
1398 mutex_exit(&buf
->b_evict_lock
);
1401 hash_lock
= HDR_LOCK(buf
->b_hdr
);
1402 mutex_enter(hash_lock
);
1404 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1405 mutex_exit(&buf
->b_evict_lock
);
1407 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
1408 add_reference(hdr
, hash_lock
, tag
);
1409 DTRACE_PROBE1(arc__hit
, arc_buf_hdr_t
*, hdr
);
1410 arc_access(hdr
, hash_lock
);
1411 mutex_exit(hash_lock
);
1412 ARCSTAT_BUMP(arcstat_hits
);
1413 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
1414 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
1415 data
, metadata
, hits
);
1419 * Free the arc data buffer. If it is an l2arc write in progress,
1420 * the buffer is placed on l2arc_free_on_write to be freed later.
1423 arc_buf_data_free(arc_buf_t
*buf
, void (*free_func
)(void *, size_t))
1425 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1427 if (HDR_L2_WRITING(hdr
)) {
1428 l2arc_data_free_t
*df
;
1429 df
= kmem_alloc(sizeof (l2arc_data_free_t
), KM_SLEEP
);
1430 df
->l2df_data
= buf
->b_data
;
1431 df
->l2df_size
= hdr
->b_size
;
1432 df
->l2df_func
= free_func
;
1433 mutex_enter(&l2arc_free_on_write_mtx
);
1434 list_insert_head(l2arc_free_on_write
, df
);
1435 mutex_exit(&l2arc_free_on_write_mtx
);
1436 ARCSTAT_BUMP(arcstat_l2_free_on_write
);
1438 free_func(buf
->b_data
, hdr
->b_size
);
1443 arc_buf_destroy(arc_buf_t
*buf
, boolean_t recycle
, boolean_t all
)
1447 /* free up data associated with the buf */
1449 arc_state_t
*state
= buf
->b_hdr
->b_state
;
1450 uint64_t size
= buf
->b_hdr
->b_size
;
1451 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
1453 arc_cksum_verify(buf
);
1454 arc_buf_unwatch(buf
);
1457 if (type
== ARC_BUFC_METADATA
) {
1458 arc_buf_data_free(buf
, zio_buf_free
);
1459 arc_space_return(size
, ARC_SPACE_DATA
);
1461 ASSERT(type
== ARC_BUFC_DATA
);
1462 arc_buf_data_free(buf
, zio_data_buf_free
);
1463 ARCSTAT_INCR(arcstat_data_size
, -size
);
1464 atomic_add_64(&arc_size
, -size
);
1467 if (list_link_active(&buf
->b_hdr
->b_arc_node
)) {
1468 uint64_t *cnt
= &state
->arcs_lsize
[type
];
1470 ASSERT(refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
1471 ASSERT(state
!= arc_anon
);
1473 ASSERT3U(*cnt
, >=, size
);
1474 atomic_add_64(cnt
, -size
);
1476 ASSERT3U(state
->arcs_size
, >=, size
);
1477 atomic_add_64(&state
->arcs_size
, -size
);
1481 * If we're destroying a duplicate buffer make sure
1482 * that the appropriate statistics are updated.
1484 if (buf
->b_hdr
->b_datacnt
> 1 &&
1485 buf
->b_hdr
->b_type
== ARC_BUFC_DATA
) {
1486 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers
);
1487 ARCSTAT_INCR(arcstat_duplicate_buffers_size
, -size
);
1489 ASSERT(buf
->b_hdr
->b_datacnt
> 0);
1490 buf
->b_hdr
->b_datacnt
-= 1;
1493 /* only remove the buf if requested */
1497 /* remove the buf from the hdr list */
1498 for (bufp
= &buf
->b_hdr
->b_buf
; *bufp
!= buf
; bufp
= &(*bufp
)->b_next
)
1500 *bufp
= buf
->b_next
;
1503 ASSERT(buf
->b_efunc
== NULL
);
1505 /* clean up the buf */
1507 kmem_cache_free(buf_cache
, buf
);
1511 arc_hdr_destroy(arc_buf_hdr_t
*hdr
)
1513 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1514 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
1515 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
1516 l2arc_buf_hdr_t
*l2hdr
= hdr
->b_l2hdr
;
1518 if (l2hdr
!= NULL
) {
1519 boolean_t buflist_held
= MUTEX_HELD(&l2arc_buflist_mtx
);
1521 * To prevent arc_free() and l2arc_evict() from
1522 * attempting to free the same buffer at the same time,
1523 * a FREE_IN_PROGRESS flag is given to arc_free() to
1524 * give it priority. l2arc_evict() can't destroy this
1525 * header while we are waiting on l2arc_buflist_mtx.
1527 * The hdr may be removed from l2ad_buflist before we
1528 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1530 if (!buflist_held
) {
1531 mutex_enter(&l2arc_buflist_mtx
);
1532 l2hdr
= hdr
->b_l2hdr
;
1535 if (l2hdr
!= NULL
) {
1536 list_remove(l2hdr
->b_dev
->l2ad_buflist
, hdr
);
1537 ARCSTAT_INCR(arcstat_l2_size
, -hdr
->b_size
);
1538 kmem_free(l2hdr
, sizeof (l2arc_buf_hdr_t
));
1539 if (hdr
->b_state
== arc_l2c_only
)
1540 l2arc_hdr_stat_remove();
1541 hdr
->b_l2hdr
= NULL
;
1545 mutex_exit(&l2arc_buflist_mtx
);
1548 if (!BUF_EMPTY(hdr
)) {
1549 ASSERT(!HDR_IN_HASH_TABLE(hdr
));
1550 buf_discard_identity(hdr
);
1552 while (hdr
->b_buf
) {
1553 arc_buf_t
*buf
= hdr
->b_buf
;
1556 mutex_enter(&arc_eviction_mtx
);
1557 mutex_enter(&buf
->b_evict_lock
);
1558 ASSERT(buf
->b_hdr
!= NULL
);
1559 arc_buf_destroy(hdr
->b_buf
, FALSE
, FALSE
);
1560 hdr
->b_buf
= buf
->b_next
;
1561 buf
->b_hdr
= &arc_eviction_hdr
;
1562 buf
->b_next
= arc_eviction_list
;
1563 arc_eviction_list
= buf
;
1564 mutex_exit(&buf
->b_evict_lock
);
1565 mutex_exit(&arc_eviction_mtx
);
1567 arc_buf_destroy(hdr
->b_buf
, FALSE
, TRUE
);
1570 if (hdr
->b_freeze_cksum
!= NULL
) {
1571 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
1572 hdr
->b_freeze_cksum
= NULL
;
1574 if (hdr
->b_thawed
) {
1575 kmem_free(hdr
->b_thawed
, 1);
1576 hdr
->b_thawed
= NULL
;
1579 ASSERT(!list_link_active(&hdr
->b_arc_node
));
1580 ASSERT3P(hdr
->b_hash_next
, ==, NULL
);
1581 ASSERT3P(hdr
->b_acb
, ==, NULL
);
1582 kmem_cache_free(hdr_cache
, hdr
);
1586 arc_buf_free(arc_buf_t
*buf
, void *tag
)
1588 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1589 int hashed
= hdr
->b_state
!= arc_anon
;
1591 ASSERT(buf
->b_efunc
== NULL
);
1592 ASSERT(buf
->b_data
!= NULL
);
1595 kmutex_t
*hash_lock
= HDR_LOCK(hdr
);
1597 mutex_enter(hash_lock
);
1599 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1601 (void) remove_reference(hdr
, hash_lock
, tag
);
1602 if (hdr
->b_datacnt
> 1) {
1603 arc_buf_destroy(buf
, FALSE
, TRUE
);
1605 ASSERT(buf
== hdr
->b_buf
);
1606 ASSERT(buf
->b_efunc
== NULL
);
1607 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1609 mutex_exit(hash_lock
);
1610 } else if (HDR_IO_IN_PROGRESS(hdr
)) {
1613 * We are in the middle of an async write. Don't destroy
1614 * this buffer unless the write completes before we finish
1615 * decrementing the reference count.
1617 mutex_enter(&arc_eviction_mtx
);
1618 (void) remove_reference(hdr
, NULL
, tag
);
1619 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1620 destroy_hdr
= !HDR_IO_IN_PROGRESS(hdr
);
1621 mutex_exit(&arc_eviction_mtx
);
1623 arc_hdr_destroy(hdr
);
1625 if (remove_reference(hdr
, NULL
, tag
) > 0)
1626 arc_buf_destroy(buf
, FALSE
, TRUE
);
1628 arc_hdr_destroy(hdr
);
1633 arc_buf_remove_ref(arc_buf_t
*buf
, void* tag
)
1635 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1636 kmutex_t
*hash_lock
= HDR_LOCK(hdr
);
1637 int no_callback
= (buf
->b_efunc
== NULL
);
1639 if (hdr
->b_state
== arc_anon
) {
1640 ASSERT(hdr
->b_datacnt
== 1);
1641 arc_buf_free(buf
, tag
);
1642 return (no_callback
);
1645 mutex_enter(hash_lock
);
1647 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1648 ASSERT(hdr
->b_state
!= arc_anon
);
1649 ASSERT(buf
->b_data
!= NULL
);
1651 (void) remove_reference(hdr
, hash_lock
, tag
);
1652 if (hdr
->b_datacnt
> 1) {
1654 arc_buf_destroy(buf
, FALSE
, TRUE
);
1655 } else if (no_callback
) {
1656 ASSERT(hdr
->b_buf
== buf
&& buf
->b_next
== NULL
);
1657 ASSERT(buf
->b_efunc
== NULL
);
1658 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1660 ASSERT(no_callback
|| hdr
->b_datacnt
> 1 ||
1661 refcount_is_zero(&hdr
->b_refcnt
));
1662 mutex_exit(hash_lock
);
1663 return (no_callback
);
1667 arc_buf_size(arc_buf_t
*buf
)
1669 return (buf
->b_hdr
->b_size
);
1673 * Called from the DMU to determine if the current buffer should be
1674 * evicted. In order to ensure proper locking, the eviction must be initiated
1675 * from the DMU. Return true if the buffer is associated with user data and
1676 * duplicate buffers still exist.
1679 arc_buf_eviction_needed(arc_buf_t
*buf
)
1682 boolean_t evict_needed
= B_FALSE
;
1684 if (zfs_disable_dup_eviction
)
1687 mutex_enter(&buf
->b_evict_lock
);
1691 * We are in arc_do_user_evicts(); let that function
1692 * perform the eviction.
1694 ASSERT(buf
->b_data
== NULL
);
1695 mutex_exit(&buf
->b_evict_lock
);
1697 } else if (buf
->b_data
== NULL
) {
1699 * We have already been added to the arc eviction list;
1700 * recommend eviction.
1702 ASSERT3P(hdr
, ==, &arc_eviction_hdr
);
1703 mutex_exit(&buf
->b_evict_lock
);
1707 if (hdr
->b_datacnt
> 1 && hdr
->b_type
== ARC_BUFC_DATA
)
1708 evict_needed
= B_TRUE
;
1710 mutex_exit(&buf
->b_evict_lock
);
1711 return (evict_needed
);
1715 * Evict buffers from list until we've removed the specified number of
1716 * bytes. Move the removed buffers to the appropriate evict state.
1717 * If the recycle flag is set, then attempt to "recycle" a buffer:
1718 * - look for a buffer to evict that is `bytes' long.
1719 * - return the data block from this buffer rather than freeing it.
1720 * This flag is used by callers that are trying to make space for a
1721 * new buffer in a full arc cache.
1723 * This function makes a "best effort". It skips over any buffers
1724 * it can't get a hash_lock on, and so may not catch all candidates.
1725 * It may also return without evicting as much space as requested.
1728 arc_evict(arc_state_t
*state
, uint64_t spa
, int64_t bytes
, boolean_t recycle
,
1729 arc_buf_contents_t type
)
1731 arc_state_t
*evicted_state
;
1732 uint64_t bytes_evicted
= 0, skipped
= 0, missed
= 0;
1733 arc_buf_hdr_t
*ab
, *ab_prev
= NULL
;
1734 list_t
*list
= &state
->arcs_list
[type
];
1735 kmutex_t
*hash_lock
;
1736 boolean_t have_lock
;
1737 void *stolen
= NULL
;
1739 ASSERT(state
== arc_mru
|| state
== arc_mfu
);
1741 evicted_state
= (state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
1743 mutex_enter(&state
->arcs_mtx
);
1744 mutex_enter(&evicted_state
->arcs_mtx
);
1746 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1747 ab_prev
= list_prev(list
, ab
);
1748 /* prefetch buffers have a minimum lifespan */
1749 if (HDR_IO_IN_PROGRESS(ab
) ||
1750 (spa
&& ab
->b_spa
!= spa
) ||
1751 (ab
->b_flags
& (ARC_PREFETCH
|ARC_INDIRECT
) &&
1752 ddi_get_lbolt() - ab
->b_arc_access
<
1753 arc_min_prefetch_lifespan
)) {
1757 /* "lookahead" for better eviction candidate */
1758 if (recycle
&& ab
->b_size
!= bytes
&&
1759 ab_prev
&& ab_prev
->b_size
== bytes
)
1761 hash_lock
= HDR_LOCK(ab
);
1762 have_lock
= MUTEX_HELD(hash_lock
);
1763 if (have_lock
|| mutex_tryenter(hash_lock
)) {
1764 ASSERT0(refcount_count(&ab
->b_refcnt
));
1765 ASSERT(ab
->b_datacnt
> 0);
1767 arc_buf_t
*buf
= ab
->b_buf
;
1768 if (!mutex_tryenter(&buf
->b_evict_lock
)) {
1773 bytes_evicted
+= ab
->b_size
;
1774 if (recycle
&& ab
->b_type
== type
&&
1775 ab
->b_size
== bytes
&&
1776 !HDR_L2_WRITING(ab
)) {
1777 stolen
= buf
->b_data
;
1782 mutex_enter(&arc_eviction_mtx
);
1783 arc_buf_destroy(buf
,
1784 buf
->b_data
== stolen
, FALSE
);
1785 ab
->b_buf
= buf
->b_next
;
1786 buf
->b_hdr
= &arc_eviction_hdr
;
1787 buf
->b_next
= arc_eviction_list
;
1788 arc_eviction_list
= buf
;
1789 mutex_exit(&arc_eviction_mtx
);
1790 mutex_exit(&buf
->b_evict_lock
);
1792 mutex_exit(&buf
->b_evict_lock
);
1793 arc_buf_destroy(buf
,
1794 buf
->b_data
== stolen
, TRUE
);
1799 ARCSTAT_INCR(arcstat_evict_l2_cached
,
1802 if (l2arc_write_eligible(ab
->b_spa
, ab
)) {
1803 ARCSTAT_INCR(arcstat_evict_l2_eligible
,
1807 arcstat_evict_l2_ineligible
,
1812 if (ab
->b_datacnt
== 0) {
1813 arc_change_state(evicted_state
, ab
, hash_lock
);
1814 ASSERT(HDR_IN_HASH_TABLE(ab
));
1815 ab
->b_flags
|= ARC_IN_HASH_TABLE
;
1816 ab
->b_flags
&= ~ARC_BUF_AVAILABLE
;
1817 DTRACE_PROBE1(arc__evict
, arc_buf_hdr_t
*, ab
);
1820 mutex_exit(hash_lock
);
1821 if (bytes
>= 0 && bytes_evicted
>= bytes
)
1828 mutex_exit(&evicted_state
->arcs_mtx
);
1829 mutex_exit(&state
->arcs_mtx
);
1831 if (bytes_evicted
< bytes
)
1832 dprintf("only evicted %lld bytes from %x",
1833 (longlong_t
)bytes_evicted
, state
);
1836 ARCSTAT_INCR(arcstat_evict_skip
, skipped
);
1839 ARCSTAT_INCR(arcstat_mutex_miss
, missed
);
1842 * We have just evicted some date into the ghost state, make
1843 * sure we also adjust the ghost state size if necessary.
1846 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
> arc_c
) {
1847 int64_t mru_over
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
+
1848 arc_mru_ghost
->arcs_size
- arc_c
;
1850 if (mru_over
> 0 && arc_mru_ghost
->arcs_lsize
[type
] > 0) {
1852 MIN(arc_mru_ghost
->arcs_lsize
[type
], mru_over
);
1853 arc_evict_ghost(arc_mru_ghost
, NULL
, todelete
);
1854 } else if (arc_mfu_ghost
->arcs_lsize
[type
] > 0) {
1855 int64_t todelete
= MIN(arc_mfu_ghost
->arcs_lsize
[type
],
1856 arc_mru_ghost
->arcs_size
+
1857 arc_mfu_ghost
->arcs_size
- arc_c
);
1858 arc_evict_ghost(arc_mfu_ghost
, NULL
, todelete
);
1866 * Remove buffers from list until we've removed the specified number of
1867 * bytes. Destroy the buffers that are removed.
1870 arc_evict_ghost(arc_state_t
*state
, uint64_t spa
, int64_t bytes
)
1872 arc_buf_hdr_t
*ab
, *ab_prev
;
1873 arc_buf_hdr_t marker
= { 0 };
1874 list_t
*list
= &state
->arcs_list
[ARC_BUFC_DATA
];
1875 kmutex_t
*hash_lock
;
1876 uint64_t bytes_deleted
= 0;
1877 uint64_t bufs_skipped
= 0;
1879 ASSERT(GHOST_STATE(state
));
1881 mutex_enter(&state
->arcs_mtx
);
1882 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1883 ab_prev
= list_prev(list
, ab
);
1884 if (spa
&& ab
->b_spa
!= spa
)
1887 /* ignore markers */
1891 hash_lock
= HDR_LOCK(ab
);
1892 /* caller may be trying to modify this buffer, skip it */
1893 if (MUTEX_HELD(hash_lock
))
1895 if (mutex_tryenter(hash_lock
)) {
1896 ASSERT(!HDR_IO_IN_PROGRESS(ab
));
1897 ASSERT(ab
->b_buf
== NULL
);
1898 ARCSTAT_BUMP(arcstat_deleted
);
1899 bytes_deleted
+= ab
->b_size
;
1901 if (ab
->b_l2hdr
!= NULL
) {
1903 * This buffer is cached on the 2nd Level ARC;
1904 * don't destroy the header.
1906 arc_change_state(arc_l2c_only
, ab
, hash_lock
);
1907 mutex_exit(hash_lock
);
1909 arc_change_state(arc_anon
, ab
, hash_lock
);
1910 mutex_exit(hash_lock
);
1911 arc_hdr_destroy(ab
);
1914 DTRACE_PROBE1(arc__delete
, arc_buf_hdr_t
*, ab
);
1915 if (bytes
>= 0 && bytes_deleted
>= bytes
)
1917 } else if (bytes
< 0) {
1919 * Insert a list marker and then wait for the
1920 * hash lock to become available. Once its
1921 * available, restart from where we left off.
1923 list_insert_after(list
, ab
, &marker
);
1924 mutex_exit(&state
->arcs_mtx
);
1925 mutex_enter(hash_lock
);
1926 mutex_exit(hash_lock
);
1927 mutex_enter(&state
->arcs_mtx
);
1928 ab_prev
= list_prev(list
, &marker
);
1929 list_remove(list
, &marker
);
1933 mutex_exit(&state
->arcs_mtx
);
1935 if (list
== &state
->arcs_list
[ARC_BUFC_DATA
] &&
1936 (bytes
< 0 || bytes_deleted
< bytes
)) {
1937 list
= &state
->arcs_list
[ARC_BUFC_METADATA
];
1942 ARCSTAT_INCR(arcstat_mutex_miss
, bufs_skipped
);
1946 if (bytes_deleted
< bytes
)
1947 dprintf("only deleted %lld bytes from %p",
1948 (longlong_t
)bytes_deleted
, state
);
1954 int64_t adjustment
, delta
;
1960 adjustment
= MIN((int64_t)(arc_size
- arc_c
),
1961 (int64_t)(arc_anon
->arcs_size
+ arc_mru
->arcs_size
+ arc_meta_used
-
1964 if (adjustment
> 0 && arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
1965 delta
= MIN(arc_mru
->arcs_lsize
[ARC_BUFC_DATA
], adjustment
);
1966 (void) arc_evict(arc_mru
, NULL
, delta
, FALSE
, ARC_BUFC_DATA
);
1967 adjustment
-= delta
;
1970 if (adjustment
> 0 && arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
1971 delta
= MIN(arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
], adjustment
);
1972 (void) arc_evict(arc_mru
, NULL
, delta
, FALSE
,
1980 adjustment
= arc_size
- arc_c
;
1982 if (adjustment
> 0 && arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
1983 delta
= MIN(adjustment
, arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
]);
1984 (void) arc_evict(arc_mfu
, NULL
, delta
, FALSE
, ARC_BUFC_DATA
);
1985 adjustment
-= delta
;
1988 if (adjustment
> 0 && arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
1989 int64_t delta
= MIN(adjustment
,
1990 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
]);
1991 (void) arc_evict(arc_mfu
, NULL
, delta
, FALSE
,
1996 * Adjust ghost lists
1999 adjustment
= arc_mru
->arcs_size
+ arc_mru_ghost
->arcs_size
- arc_c
;
2001 if (adjustment
> 0 && arc_mru_ghost
->arcs_size
> 0) {
2002 delta
= MIN(arc_mru_ghost
->arcs_size
, adjustment
);
2003 arc_evict_ghost(arc_mru_ghost
, NULL
, delta
);
2007 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
- arc_c
;
2009 if (adjustment
> 0 && arc_mfu_ghost
->arcs_size
> 0) {
2010 delta
= MIN(arc_mfu_ghost
->arcs_size
, adjustment
);
2011 arc_evict_ghost(arc_mfu_ghost
, NULL
, delta
);
2016 arc_do_user_evicts(void)
2018 mutex_enter(&arc_eviction_mtx
);
2019 while (arc_eviction_list
!= NULL
) {
2020 arc_buf_t
*buf
= arc_eviction_list
;
2021 arc_eviction_list
= buf
->b_next
;
2022 mutex_enter(&buf
->b_evict_lock
);
2024 mutex_exit(&buf
->b_evict_lock
);
2025 mutex_exit(&arc_eviction_mtx
);
2027 if (buf
->b_efunc
!= NULL
)
2028 VERIFY(buf
->b_efunc(buf
) == 0);
2030 buf
->b_efunc
= NULL
;
2031 buf
->b_private
= NULL
;
2032 kmem_cache_free(buf_cache
, buf
);
2033 mutex_enter(&arc_eviction_mtx
);
2035 mutex_exit(&arc_eviction_mtx
);
2039 * Flush all *evictable* data from the cache for the given spa.
2040 * NOTE: this will not touch "active" (i.e. referenced) data.
2043 arc_flush(spa_t
*spa
)
2048 guid
= spa_load_guid(spa
);
2050 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_DATA
])) {
2051 (void) arc_evict(arc_mru
, guid
, -1, FALSE
, ARC_BUFC_DATA
);
2055 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
])) {
2056 (void) arc_evict(arc_mru
, guid
, -1, FALSE
, ARC_BUFC_METADATA
);
2060 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
])) {
2061 (void) arc_evict(arc_mfu
, guid
, -1, FALSE
, ARC_BUFC_DATA
);
2065 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
])) {
2066 (void) arc_evict(arc_mfu
, guid
, -1, FALSE
, ARC_BUFC_METADATA
);
2071 arc_evict_ghost(arc_mru_ghost
, guid
, -1);
2072 arc_evict_ghost(arc_mfu_ghost
, guid
, -1);
2074 mutex_enter(&arc_reclaim_thr_lock
);
2075 arc_do_user_evicts();
2076 mutex_exit(&arc_reclaim_thr_lock
);
2077 ASSERT(spa
|| arc_eviction_list
== NULL
);
2083 if (arc_c
> arc_c_min
) {
2087 to_free
= MAX(arc_c
>> arc_shrink_shift
, ptob(needfree
));
2089 to_free
= arc_c
>> arc_shrink_shift
;
2091 if (arc_c
> arc_c_min
+ to_free
)
2092 atomic_add_64(&arc_c
, -to_free
);
2096 atomic_add_64(&arc_p
, -(arc_p
>> arc_shrink_shift
));
2097 if (arc_c
> arc_size
)
2098 arc_c
= MAX(arc_size
, arc_c_min
);
2100 arc_p
= (arc_c
>> 1);
2101 ASSERT(arc_c
>= arc_c_min
);
2102 ASSERT((int64_t)arc_p
>= 0);
2105 if (arc_size
> arc_c
)
2110 * Determine if the system is under memory pressure and is asking
2111 * to reclaim memory. A return value of 1 indicates that the system
2112 * is under memory pressure and that the arc should adjust accordingly.
2115 arc_reclaim_needed(void)
2125 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2130 * check that we're out of range of the pageout scanner. It starts to
2131 * schedule paging if freemem is less than lotsfree and needfree.
2132 * lotsfree is the high-water mark for pageout, and needfree is the
2133 * number of needed free pages. We add extra pages here to make sure
2134 * the scanner doesn't start up while we're freeing memory.
2136 if (freemem
< lotsfree
+ needfree
+ extra
)
2140 * check to make sure that swapfs has enough space so that anon
2141 * reservations can still succeed. anon_resvmem() checks that the
2142 * availrmem is greater than swapfs_minfree, and the number of reserved
2143 * swap pages. We also add a bit of extra here just to prevent
2144 * circumstances from getting really dire.
2146 if (availrmem
< swapfs_minfree
+ swapfs_reserve
+ extra
)
2151 * If we're on an i386 platform, it's possible that we'll exhaust the
2152 * kernel heap space before we ever run out of available physical
2153 * memory. Most checks of the size of the heap_area compare against
2154 * tune.t_minarmem, which is the minimum available real memory that we
2155 * can have in the system. However, this is generally fixed at 25 pages
2156 * which is so low that it's useless. In this comparison, we seek to
2157 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2158 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2161 if (vmem_size(heap_arena
, VMEM_FREE
) <
2162 (vmem_size(heap_arena
, VMEM_FREE
| VMEM_ALLOC
) >> 2))
2167 * If zio data pages are being allocated out of a separate heap segment,
2168 * then enforce that the size of available vmem for this arena remains
2169 * above about 1/16th free.
2171 * Note: The 1/16th arena free requirement was put in place
2172 * to aggressively evict memory from the arc in order to avoid
2173 * memory fragmentation issues.
2175 if (zio_arena
!= NULL
&&
2176 vmem_size(zio_arena
, VMEM_FREE
) <
2177 (vmem_size(zio_arena
, VMEM_ALLOC
) >> 4))
2180 if (spa_get_random(100) == 0)
2187 arc_kmem_reap_now(arc_reclaim_strategy_t strat
)
2190 kmem_cache_t
*prev_cache
= NULL
;
2191 kmem_cache_t
*prev_data_cache
= NULL
;
2192 extern kmem_cache_t
*zio_buf_cache
[];
2193 extern kmem_cache_t
*zio_data_buf_cache
[];
2196 if (arc_meta_used
>= arc_meta_limit
) {
2198 * We are exceeding our meta-data cache limit.
2199 * Purge some DNLC entries to release holds on meta-data.
2201 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent
);
2205 * Reclaim unused memory from all kmem caches.
2212 * An aggressive reclamation will shrink the cache size as well as
2213 * reap free buffers from the arc kmem caches.
2215 if (strat
== ARC_RECLAIM_AGGR
)
2218 for (i
= 0; i
< SPA_MAXBLOCKSIZE
>> SPA_MINBLOCKSHIFT
; i
++) {
2219 if (zio_buf_cache
[i
] != prev_cache
) {
2220 prev_cache
= zio_buf_cache
[i
];
2221 kmem_cache_reap_now(zio_buf_cache
[i
]);
2223 if (zio_data_buf_cache
[i
] != prev_data_cache
) {
2224 prev_data_cache
= zio_data_buf_cache
[i
];
2225 kmem_cache_reap_now(zio_data_buf_cache
[i
]);
2228 kmem_cache_reap_now(buf_cache
);
2229 kmem_cache_reap_now(hdr_cache
);
2232 * Ask the vmem areana to reclaim unused memory from its
2235 if (zio_arena
!= NULL
&& strat
== ARC_RECLAIM_AGGR
)
2236 vmem_qcache_reap(zio_arena
);
2240 arc_reclaim_thread(void)
2242 clock_t growtime
= 0;
2243 arc_reclaim_strategy_t last_reclaim
= ARC_RECLAIM_CONS
;
2246 CALLB_CPR_INIT(&cpr
, &arc_reclaim_thr_lock
, callb_generic_cpr
, FTAG
);
2248 mutex_enter(&arc_reclaim_thr_lock
);
2249 while (arc_thread_exit
== 0) {
2250 if (arc_reclaim_needed()) {
2253 if (last_reclaim
== ARC_RECLAIM_CONS
) {
2254 last_reclaim
= ARC_RECLAIM_AGGR
;
2256 last_reclaim
= ARC_RECLAIM_CONS
;
2260 last_reclaim
= ARC_RECLAIM_AGGR
;
2264 /* reset the growth delay for every reclaim */
2265 growtime
= ddi_get_lbolt() + (arc_grow_retry
* hz
);
2267 arc_kmem_reap_now(last_reclaim
);
2270 } else if (arc_no_grow
&& ddi_get_lbolt() >= growtime
) {
2271 arc_no_grow
= FALSE
;
2276 if (arc_eviction_list
!= NULL
)
2277 arc_do_user_evicts();
2279 /* block until needed, or one second, whichever is shorter */
2280 CALLB_CPR_SAFE_BEGIN(&cpr
);
2281 (void) cv_timedwait(&arc_reclaim_thr_cv
,
2282 &arc_reclaim_thr_lock
, (ddi_get_lbolt() + hz
));
2283 CALLB_CPR_SAFE_END(&cpr
, &arc_reclaim_thr_lock
);
2286 arc_thread_exit
= 0;
2287 cv_broadcast(&arc_reclaim_thr_cv
);
2288 CALLB_CPR_EXIT(&cpr
); /* drops arc_reclaim_thr_lock */
2293 * Adapt arc info given the number of bytes we are trying to add and
2294 * the state that we are comming from. This function is only called
2295 * when we are adding new content to the cache.
2298 arc_adapt(int bytes
, arc_state_t
*state
)
2301 uint64_t arc_p_min
= (arc_c
>> arc_p_min_shift
);
2303 if (state
== arc_l2c_only
)
2308 * Adapt the target size of the MRU list:
2309 * - if we just hit in the MRU ghost list, then increase
2310 * the target size of the MRU list.
2311 * - if we just hit in the MFU ghost list, then increase
2312 * the target size of the MFU list by decreasing the
2313 * target size of the MRU list.
2315 if (state
== arc_mru_ghost
) {
2316 mult
= ((arc_mru_ghost
->arcs_size
>= arc_mfu_ghost
->arcs_size
) ?
2317 1 : (arc_mfu_ghost
->arcs_size
/arc_mru_ghost
->arcs_size
));
2318 mult
= MIN(mult
, 10); /* avoid wild arc_p adjustment */
2320 arc_p
= MIN(arc_c
- arc_p_min
, arc_p
+ bytes
* mult
);
2321 } else if (state
== arc_mfu_ghost
) {
2324 mult
= ((arc_mfu_ghost
->arcs_size
>= arc_mru_ghost
->arcs_size
) ?
2325 1 : (arc_mru_ghost
->arcs_size
/arc_mfu_ghost
->arcs_size
));
2326 mult
= MIN(mult
, 10);
2328 delta
= MIN(bytes
* mult
, arc_p
);
2329 arc_p
= MAX(arc_p_min
, arc_p
- delta
);
2331 ASSERT((int64_t)arc_p
>= 0);
2333 if (arc_reclaim_needed()) {
2334 cv_signal(&arc_reclaim_thr_cv
);
2341 if (arc_c
>= arc_c_max
)
2345 * If we're within (2 * maxblocksize) bytes of the target
2346 * cache size, increment the target cache size
2348 if (arc_size
> arc_c
- (2ULL << SPA_MAXBLOCKSHIFT
)) {
2349 atomic_add_64(&arc_c
, (int64_t)bytes
);
2350 if (arc_c
> arc_c_max
)
2352 else if (state
== arc_anon
)
2353 atomic_add_64(&arc_p
, (int64_t)bytes
);
2357 ASSERT((int64_t)arc_p
>= 0);
2361 * Check if the cache has reached its limits and eviction is required
2365 arc_evict_needed(arc_buf_contents_t type
)
2367 if (type
== ARC_BUFC_METADATA
&& arc_meta_used
>= arc_meta_limit
)
2370 if (arc_reclaim_needed())
2373 return (arc_size
> arc_c
);
2377 * The buffer, supplied as the first argument, needs a data block.
2378 * So, if we are at cache max, determine which cache should be victimized.
2379 * We have the following cases:
2381 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2382 * In this situation if we're out of space, but the resident size of the MFU is
2383 * under the limit, victimize the MFU cache to satisfy this insertion request.
2385 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2386 * Here, we've used up all of the available space for the MRU, so we need to
2387 * evict from our own cache instead. Evict from the set of resident MRU
2390 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2391 * c minus p represents the MFU space in the cache, since p is the size of the
2392 * cache that is dedicated to the MRU. In this situation there's still space on
2393 * the MFU side, so the MRU side needs to be victimized.
2395 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2396 * MFU's resident set is consuming more space than it has been allotted. In
2397 * this situation, we must victimize our own cache, the MFU, for this insertion.
2400 arc_get_data_buf(arc_buf_t
*buf
)
2402 arc_state_t
*state
= buf
->b_hdr
->b_state
;
2403 uint64_t size
= buf
->b_hdr
->b_size
;
2404 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
2406 arc_adapt(size
, state
);
2409 * We have not yet reached cache maximum size,
2410 * just allocate a new buffer.
2412 if (!arc_evict_needed(type
)) {
2413 if (type
== ARC_BUFC_METADATA
) {
2414 buf
->b_data
= zio_buf_alloc(size
);
2415 arc_space_consume(size
, ARC_SPACE_DATA
);
2417 ASSERT(type
== ARC_BUFC_DATA
);
2418 buf
->b_data
= zio_data_buf_alloc(size
);
2419 ARCSTAT_INCR(arcstat_data_size
, size
);
2420 atomic_add_64(&arc_size
, size
);
2426 * If we are prefetching from the mfu ghost list, this buffer
2427 * will end up on the mru list; so steal space from there.
2429 if (state
== arc_mfu_ghost
)
2430 state
= buf
->b_hdr
->b_flags
& ARC_PREFETCH
? arc_mru
: arc_mfu
;
2431 else if (state
== arc_mru_ghost
)
2434 if (state
== arc_mru
|| state
== arc_anon
) {
2435 uint64_t mru_used
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
;
2436 state
= (arc_mfu
->arcs_lsize
[type
] >= size
&&
2437 arc_p
> mru_used
) ? arc_mfu
: arc_mru
;
2440 uint64_t mfu_space
= arc_c
- arc_p
;
2441 state
= (arc_mru
->arcs_lsize
[type
] >= size
&&
2442 mfu_space
> arc_mfu
->arcs_size
) ? arc_mru
: arc_mfu
;
2444 if ((buf
->b_data
= arc_evict(state
, NULL
, size
, TRUE
, type
)) == NULL
) {
2445 if (type
== ARC_BUFC_METADATA
) {
2446 buf
->b_data
= zio_buf_alloc(size
);
2447 arc_space_consume(size
, ARC_SPACE_DATA
);
2449 ASSERT(type
== ARC_BUFC_DATA
);
2450 buf
->b_data
= zio_data_buf_alloc(size
);
2451 ARCSTAT_INCR(arcstat_data_size
, size
);
2452 atomic_add_64(&arc_size
, size
);
2454 ARCSTAT_BUMP(arcstat_recycle_miss
);
2456 ASSERT(buf
->b_data
!= NULL
);
2459 * Update the state size. Note that ghost states have a
2460 * "ghost size" and so don't need to be updated.
2462 if (!GHOST_STATE(buf
->b_hdr
->b_state
)) {
2463 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
2465 atomic_add_64(&hdr
->b_state
->arcs_size
, size
);
2466 if (list_link_active(&hdr
->b_arc_node
)) {
2467 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
2468 atomic_add_64(&hdr
->b_state
->arcs_lsize
[type
], size
);
2471 * If we are growing the cache, and we are adding anonymous
2472 * data, and we have outgrown arc_p, update arc_p
2474 if (arc_size
< arc_c
&& hdr
->b_state
== arc_anon
&&
2475 arc_anon
->arcs_size
+ arc_mru
->arcs_size
> arc_p
)
2476 arc_p
= MIN(arc_c
, arc_p
+ size
);
2481 * This routine is called whenever a buffer is accessed.
2482 * NOTE: the hash lock is dropped in this function.
2485 arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
)
2489 ASSERT(MUTEX_HELD(hash_lock
));
2491 if (buf
->b_state
== arc_anon
) {
2493 * This buffer is not in the cache, and does not
2494 * appear in our "ghost" list. Add the new buffer
2498 ASSERT(buf
->b_arc_access
== 0);
2499 buf
->b_arc_access
= ddi_get_lbolt();
2500 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2501 arc_change_state(arc_mru
, buf
, hash_lock
);
2503 } else if (buf
->b_state
== arc_mru
) {
2504 now
= ddi_get_lbolt();
2507 * If this buffer is here because of a prefetch, then either:
2508 * - clear the flag if this is a "referencing" read
2509 * (any subsequent access will bump this into the MFU state).
2511 * - move the buffer to the head of the list if this is
2512 * another prefetch (to make it less likely to be evicted).
2514 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2515 if (refcount_count(&buf
->b_refcnt
) == 0) {
2516 ASSERT(list_link_active(&buf
->b_arc_node
));
2518 buf
->b_flags
&= ~ARC_PREFETCH
;
2519 ARCSTAT_BUMP(arcstat_mru_hits
);
2521 buf
->b_arc_access
= now
;
2526 * This buffer has been "accessed" only once so far,
2527 * but it is still in the cache. Move it to the MFU
2530 if (now
> buf
->b_arc_access
+ ARC_MINTIME
) {
2532 * More than 125ms have passed since we
2533 * instantiated this buffer. Move it to the
2534 * most frequently used state.
2536 buf
->b_arc_access
= now
;
2537 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2538 arc_change_state(arc_mfu
, buf
, hash_lock
);
2540 ARCSTAT_BUMP(arcstat_mru_hits
);
2541 } else if (buf
->b_state
== arc_mru_ghost
) {
2542 arc_state_t
*new_state
;
2544 * This buffer has been "accessed" recently, but
2545 * was evicted from the cache. Move it to the
2549 if (buf
->b_flags
& ARC_PREFETCH
) {
2550 new_state
= arc_mru
;
2551 if (refcount_count(&buf
->b_refcnt
) > 0)
2552 buf
->b_flags
&= ~ARC_PREFETCH
;
2553 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2555 new_state
= arc_mfu
;
2556 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2559 buf
->b_arc_access
= ddi_get_lbolt();
2560 arc_change_state(new_state
, buf
, hash_lock
);
2562 ARCSTAT_BUMP(arcstat_mru_ghost_hits
);
2563 } else if (buf
->b_state
== arc_mfu
) {
2565 * This buffer has been accessed more than once and is
2566 * still in the cache. Keep it in the MFU state.
2568 * NOTE: an add_reference() that occurred when we did
2569 * the arc_read() will have kicked this off the list.
2570 * If it was a prefetch, we will explicitly move it to
2571 * the head of the list now.
2573 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2574 ASSERT(refcount_count(&buf
->b_refcnt
) == 0);
2575 ASSERT(list_link_active(&buf
->b_arc_node
));
2577 ARCSTAT_BUMP(arcstat_mfu_hits
);
2578 buf
->b_arc_access
= ddi_get_lbolt();
2579 } else if (buf
->b_state
== arc_mfu_ghost
) {
2580 arc_state_t
*new_state
= arc_mfu
;
2582 * This buffer has been accessed more than once but has
2583 * been evicted from the cache. Move it back to the
2587 if (buf
->b_flags
& ARC_PREFETCH
) {
2589 * This is a prefetch access...
2590 * move this block back to the MRU state.
2592 ASSERT0(refcount_count(&buf
->b_refcnt
));
2593 new_state
= arc_mru
;
2596 buf
->b_arc_access
= ddi_get_lbolt();
2597 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2598 arc_change_state(new_state
, buf
, hash_lock
);
2600 ARCSTAT_BUMP(arcstat_mfu_ghost_hits
);
2601 } else if (buf
->b_state
== arc_l2c_only
) {
2603 * This buffer is on the 2nd Level ARC.
2606 buf
->b_arc_access
= ddi_get_lbolt();
2607 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2608 arc_change_state(arc_mfu
, buf
, hash_lock
);
2610 ASSERT(!"invalid arc state");
2614 /* a generic arc_done_func_t which you can use */
2617 arc_bcopy_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2619 if (zio
== NULL
|| zio
->io_error
== 0)
2620 bcopy(buf
->b_data
, arg
, buf
->b_hdr
->b_size
);
2621 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2624 /* a generic arc_done_func_t */
2626 arc_getbuf_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2628 arc_buf_t
**bufp
= arg
;
2629 if (zio
&& zio
->io_error
) {
2630 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2634 ASSERT(buf
->b_data
);
2639 arc_read_done(zio_t
*zio
)
2641 arc_buf_hdr_t
*hdr
, *found
;
2643 arc_buf_t
*abuf
; /* buffer we're assigning to callback */
2644 kmutex_t
*hash_lock
;
2645 arc_callback_t
*callback_list
, *acb
;
2646 int freeable
= FALSE
;
2648 buf
= zio
->io_private
;
2652 * The hdr was inserted into hash-table and removed from lists
2653 * prior to starting I/O. We should find this header, since
2654 * it's in the hash table, and it should be legit since it's
2655 * not possible to evict it during the I/O. The only possible
2656 * reason for it not to be found is if we were freed during the
2659 found
= buf_hash_find(hdr
->b_spa
, &hdr
->b_dva
, hdr
->b_birth
,
2662 ASSERT((found
== NULL
&& HDR_FREED_IN_READ(hdr
) && hash_lock
== NULL
) ||
2663 (found
== hdr
&& DVA_EQUAL(&hdr
->b_dva
, BP_IDENTITY(zio
->io_bp
))) ||
2664 (found
== hdr
&& HDR_L2_READING(hdr
)));
2666 hdr
->b_flags
&= ~ARC_L2_EVICTED
;
2667 if (l2arc_noprefetch
&& (hdr
->b_flags
& ARC_PREFETCH
))
2668 hdr
->b_flags
&= ~ARC_L2CACHE
;
2670 /* byteswap if necessary */
2671 callback_list
= hdr
->b_acb
;
2672 ASSERT(callback_list
!= NULL
);
2673 if (BP_SHOULD_BYTESWAP(zio
->io_bp
) && zio
->io_error
== 0) {
2674 dmu_object_byteswap_t bswap
=
2675 DMU_OT_BYTESWAP(BP_GET_TYPE(zio
->io_bp
));
2676 arc_byteswap_func_t
*func
= BP_GET_LEVEL(zio
->io_bp
) > 0 ?
2677 byteswap_uint64_array
:
2678 dmu_ot_byteswap
[bswap
].ob_func
;
2679 func(buf
->b_data
, hdr
->b_size
);
2682 arc_cksum_compute(buf
, B_FALSE
);
2685 if (hash_lock
&& zio
->io_error
== 0 && hdr
->b_state
== arc_anon
) {
2687 * Only call arc_access on anonymous buffers. This is because
2688 * if we've issued an I/O for an evicted buffer, we've already
2689 * called arc_access (to prevent any simultaneous readers from
2690 * getting confused).
2692 arc_access(hdr
, hash_lock
);
2695 /* create copies of the data buffer for the callers */
2697 for (acb
= callback_list
; acb
; acb
= acb
->acb_next
) {
2698 if (acb
->acb_done
) {
2700 ARCSTAT_BUMP(arcstat_duplicate_reads
);
2701 abuf
= arc_buf_clone(buf
);
2703 acb
->acb_buf
= abuf
;
2708 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
2709 ASSERT(!HDR_BUF_AVAILABLE(hdr
));
2711 ASSERT(buf
->b_efunc
== NULL
);
2712 ASSERT(hdr
->b_datacnt
== 1);
2713 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
2716 ASSERT(refcount_is_zero(&hdr
->b_refcnt
) || callback_list
!= NULL
);
2718 if (zio
->io_error
!= 0) {
2719 hdr
->b_flags
|= ARC_IO_ERROR
;
2720 if (hdr
->b_state
!= arc_anon
)
2721 arc_change_state(arc_anon
, hdr
, hash_lock
);
2722 if (HDR_IN_HASH_TABLE(hdr
))
2723 buf_hash_remove(hdr
);
2724 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2728 * Broadcast before we drop the hash_lock to avoid the possibility
2729 * that the hdr (and hence the cv) might be freed before we get to
2730 * the cv_broadcast().
2732 cv_broadcast(&hdr
->b_cv
);
2735 mutex_exit(hash_lock
);
2738 * This block was freed while we waited for the read to
2739 * complete. It has been removed from the hash table and
2740 * moved to the anonymous state (so that it won't show up
2743 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
2744 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2747 /* execute each callback and free its structure */
2748 while ((acb
= callback_list
) != NULL
) {
2750 acb
->acb_done(zio
, acb
->acb_buf
, acb
->acb_private
);
2752 if (acb
->acb_zio_dummy
!= NULL
) {
2753 acb
->acb_zio_dummy
->io_error
= zio
->io_error
;
2754 zio_nowait(acb
->acb_zio_dummy
);
2757 callback_list
= acb
->acb_next
;
2758 kmem_free(acb
, sizeof (arc_callback_t
));
2762 arc_hdr_destroy(hdr
);
2766 * "Read" the block at the specified DVA (in bp) via the
2767 * cache. If the block is found in the cache, invoke the provided
2768 * callback immediately and return. Note that the `zio' parameter
2769 * in the callback will be NULL in this case, since no IO was
2770 * required. If the block is not in the cache pass the read request
2771 * on to the spa with a substitute callback function, so that the
2772 * requested block will be added to the cache.
2774 * If a read request arrives for a block that has a read in-progress,
2775 * either wait for the in-progress read to complete (and return the
2776 * results); or, if this is a read with a "done" func, add a record
2777 * to the read to invoke the "done" func when the read completes,
2778 * and return; or just return.
2780 * arc_read_done() will invoke all the requested "done" functions
2781 * for readers of this block.
2783 * Normal callers should use arc_read and pass the arc buffer and offset
2784 * for the bp. But if you know you don't need locking, you can use
2788 arc_read(zio_t
*pio
, spa_t
*spa
, const blkptr_t
*bp
, arc_buf_t
*pbuf
,
2789 arc_done_func_t
*done
, void *private, int priority
, int zio_flags
,
2790 uint32_t *arc_flags
, const zbookmark_t
*zb
)
2796 * XXX This happens from traverse callback funcs, for
2797 * the objset_phys_t block.
2799 return (arc_read_nolock(pio
, spa
, bp
, done
, private, priority
,
2800 zio_flags
, arc_flags
, zb
));
2803 ASSERT(!refcount_is_zero(&pbuf
->b_hdr
->b_refcnt
));
2804 ASSERT3U((char *)bp
- (char *)pbuf
->b_data
, <, pbuf
->b_hdr
->b_size
);
2805 rw_enter(&pbuf
->b_data_lock
, RW_READER
);
2807 err
= arc_read_nolock(pio
, spa
, bp
, done
, private, priority
,
2808 zio_flags
, arc_flags
, zb
);
2809 rw_exit(&pbuf
->b_data_lock
);
2815 arc_read_nolock(zio_t
*pio
, spa_t
*spa
, const blkptr_t
*bp
,
2816 arc_done_func_t
*done
, void *private, int priority
, int zio_flags
,
2817 uint32_t *arc_flags
, const zbookmark_t
*zb
)
2821 kmutex_t
*hash_lock
;
2823 uint64_t guid
= spa_load_guid(spa
);
2826 hdr
= buf_hash_find(guid
, BP_IDENTITY(bp
), BP_PHYSICAL_BIRTH(bp
),
2828 if (hdr
&& hdr
->b_datacnt
> 0) {
2830 *arc_flags
|= ARC_CACHED
;
2832 if (HDR_IO_IN_PROGRESS(hdr
)) {
2834 if (*arc_flags
& ARC_WAIT
) {
2835 cv_wait(&hdr
->b_cv
, hash_lock
);
2836 mutex_exit(hash_lock
);
2839 ASSERT(*arc_flags
& ARC_NOWAIT
);
2842 arc_callback_t
*acb
= NULL
;
2844 acb
= kmem_zalloc(sizeof (arc_callback_t
),
2846 acb
->acb_done
= done
;
2847 acb
->acb_private
= private;
2849 acb
->acb_zio_dummy
= zio_null(pio
,
2850 spa
, NULL
, NULL
, NULL
, zio_flags
);
2852 ASSERT(acb
->acb_done
!= NULL
);
2853 acb
->acb_next
= hdr
->b_acb
;
2855 add_reference(hdr
, hash_lock
, private);
2856 mutex_exit(hash_lock
);
2859 mutex_exit(hash_lock
);
2863 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
2866 add_reference(hdr
, hash_lock
, private);
2868 * If this block is already in use, create a new
2869 * copy of the data so that we will be guaranteed
2870 * that arc_release() will always succeed.
2874 ASSERT(buf
->b_data
);
2875 if (HDR_BUF_AVAILABLE(hdr
)) {
2876 ASSERT(buf
->b_efunc
== NULL
);
2877 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
2879 buf
= arc_buf_clone(buf
);
2882 } else if (*arc_flags
& ARC_PREFETCH
&&
2883 refcount_count(&hdr
->b_refcnt
) == 0) {
2884 hdr
->b_flags
|= ARC_PREFETCH
;
2886 DTRACE_PROBE1(arc__hit
, arc_buf_hdr_t
*, hdr
);
2887 arc_access(hdr
, hash_lock
);
2888 if (*arc_flags
& ARC_L2CACHE
)
2889 hdr
->b_flags
|= ARC_L2CACHE
;
2890 mutex_exit(hash_lock
);
2891 ARCSTAT_BUMP(arcstat_hits
);
2892 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
2893 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
2894 data
, metadata
, hits
);
2897 done(NULL
, buf
, private);
2899 uint64_t size
= BP_GET_LSIZE(bp
);
2900 arc_callback_t
*acb
;
2903 boolean_t devw
= B_FALSE
;
2906 /* this block is not in the cache */
2907 arc_buf_hdr_t
*exists
;
2908 arc_buf_contents_t type
= BP_GET_BUFC_TYPE(bp
);
2909 buf
= arc_buf_alloc(spa
, size
, private, type
);
2911 hdr
->b_dva
= *BP_IDENTITY(bp
);
2912 hdr
->b_birth
= BP_PHYSICAL_BIRTH(bp
);
2913 hdr
->b_cksum0
= bp
->blk_cksum
.zc_word
[0];
2914 exists
= buf_hash_insert(hdr
, &hash_lock
);
2916 /* somebody beat us to the hash insert */
2917 mutex_exit(hash_lock
);
2918 buf_discard_identity(hdr
);
2919 (void) arc_buf_remove_ref(buf
, private);
2920 goto top
; /* restart the IO request */
2922 /* if this is a prefetch, we don't have a reference */
2923 if (*arc_flags
& ARC_PREFETCH
) {
2924 (void) remove_reference(hdr
, hash_lock
,
2926 hdr
->b_flags
|= ARC_PREFETCH
;
2928 if (*arc_flags
& ARC_L2CACHE
)
2929 hdr
->b_flags
|= ARC_L2CACHE
;
2930 if (BP_GET_LEVEL(bp
) > 0)
2931 hdr
->b_flags
|= ARC_INDIRECT
;
2933 /* this block is in the ghost cache */
2934 ASSERT(GHOST_STATE(hdr
->b_state
));
2935 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
2936 ASSERT0(refcount_count(&hdr
->b_refcnt
));
2937 ASSERT(hdr
->b_buf
== NULL
);
2939 /* if this is a prefetch, we don't have a reference */
2940 if (*arc_flags
& ARC_PREFETCH
)
2941 hdr
->b_flags
|= ARC_PREFETCH
;
2943 add_reference(hdr
, hash_lock
, private);
2944 if (*arc_flags
& ARC_L2CACHE
)
2945 hdr
->b_flags
|= ARC_L2CACHE
;
2946 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
2949 buf
->b_efunc
= NULL
;
2950 buf
->b_private
= NULL
;
2953 ASSERT(hdr
->b_datacnt
== 0);
2955 arc_get_data_buf(buf
);
2956 arc_access(hdr
, hash_lock
);
2959 ASSERT(!GHOST_STATE(hdr
->b_state
));
2961 acb
= kmem_zalloc(sizeof (arc_callback_t
), KM_SLEEP
);
2962 acb
->acb_done
= done
;
2963 acb
->acb_private
= private;
2965 ASSERT(hdr
->b_acb
== NULL
);
2967 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
2969 if (HDR_L2CACHE(hdr
) && hdr
->b_l2hdr
!= NULL
&&
2970 (vd
= hdr
->b_l2hdr
->b_dev
->l2ad_vdev
) != NULL
) {
2971 devw
= hdr
->b_l2hdr
->b_dev
->l2ad_writing
;
2972 addr
= hdr
->b_l2hdr
->b_daddr
;
2974 * Lock out device removal.
2976 if (vdev_is_dead(vd
) ||
2977 !spa_config_tryenter(spa
, SCL_L2ARC
, vd
, RW_READER
))
2981 mutex_exit(hash_lock
);
2983 ASSERT3U(hdr
->b_size
, ==, size
);
2984 DTRACE_PROBE4(arc__miss
, arc_buf_hdr_t
*, hdr
, blkptr_t
*, bp
,
2985 uint64_t, size
, zbookmark_t
*, zb
);
2986 ARCSTAT_BUMP(arcstat_misses
);
2987 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
2988 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
2989 data
, metadata
, misses
);
2991 if (vd
!= NULL
&& l2arc_ndev
!= 0 && !(l2arc_norw
&& devw
)) {
2993 * Read from the L2ARC if the following are true:
2994 * 1. The L2ARC vdev was previously cached.
2995 * 2. This buffer still has L2ARC metadata.
2996 * 3. This buffer isn't currently writing to the L2ARC.
2997 * 4. The L2ARC entry wasn't evicted, which may
2998 * also have invalidated the vdev.
2999 * 5. This isn't prefetch and l2arc_noprefetch is set.
3001 if (hdr
->b_l2hdr
!= NULL
&&
3002 !HDR_L2_WRITING(hdr
) && !HDR_L2_EVICTED(hdr
) &&
3003 !(l2arc_noprefetch
&& HDR_PREFETCH(hdr
))) {
3004 l2arc_read_callback_t
*cb
;
3006 DTRACE_PROBE1(l2arc__hit
, arc_buf_hdr_t
*, hdr
);
3007 ARCSTAT_BUMP(arcstat_l2_hits
);
3009 cb
= kmem_zalloc(sizeof (l2arc_read_callback_t
),
3011 cb
->l2rcb_buf
= buf
;
3012 cb
->l2rcb_spa
= spa
;
3015 cb
->l2rcb_flags
= zio_flags
;
3018 * l2arc read. The SCL_L2ARC lock will be
3019 * released by l2arc_read_done().
3021 rzio
= zio_read_phys(pio
, vd
, addr
, size
,
3022 buf
->b_data
, ZIO_CHECKSUM_OFF
,
3023 l2arc_read_done
, cb
, priority
, zio_flags
|
3024 ZIO_FLAG_DONT_CACHE
| ZIO_FLAG_CANFAIL
|
3025 ZIO_FLAG_DONT_PROPAGATE
|
3026 ZIO_FLAG_DONT_RETRY
, B_FALSE
);
3027 DTRACE_PROBE2(l2arc__read
, vdev_t
*, vd
,
3029 ARCSTAT_INCR(arcstat_l2_read_bytes
, size
);
3031 if (*arc_flags
& ARC_NOWAIT
) {
3036 ASSERT(*arc_flags
& ARC_WAIT
);
3037 if (zio_wait(rzio
) == 0)
3040 /* l2arc read error; goto zio_read() */
3042 DTRACE_PROBE1(l2arc__miss
,
3043 arc_buf_hdr_t
*, hdr
);
3044 ARCSTAT_BUMP(arcstat_l2_misses
);
3045 if (HDR_L2_WRITING(hdr
))
3046 ARCSTAT_BUMP(arcstat_l2_rw_clash
);
3047 spa_config_exit(spa
, SCL_L2ARC
, vd
);
3051 spa_config_exit(spa
, SCL_L2ARC
, vd
);
3052 if (l2arc_ndev
!= 0) {
3053 DTRACE_PROBE1(l2arc__miss
,
3054 arc_buf_hdr_t
*, hdr
);
3055 ARCSTAT_BUMP(arcstat_l2_misses
);
3059 rzio
= zio_read(pio
, spa
, bp
, buf
->b_data
, size
,
3060 arc_read_done
, buf
, priority
, zio_flags
, zb
);
3062 if (*arc_flags
& ARC_WAIT
)
3063 return (zio_wait(rzio
));
3065 ASSERT(*arc_flags
& ARC_NOWAIT
);
3072 arc_set_callback(arc_buf_t
*buf
, arc_evict_func_t
*func
, void *private)
3074 ASSERT(buf
->b_hdr
!= NULL
);
3075 ASSERT(buf
->b_hdr
->b_state
!= arc_anon
);
3076 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
) || func
== NULL
);
3077 ASSERT(buf
->b_efunc
== NULL
);
3078 ASSERT(!HDR_BUF_AVAILABLE(buf
->b_hdr
));
3080 buf
->b_efunc
= func
;
3081 buf
->b_private
= private;
3085 * This is used by the DMU to let the ARC know that a buffer is
3086 * being evicted, so the ARC should clean up. If this arc buf
3087 * is not yet in the evicted state, it will be put there.
3090 arc_buf_evict(arc_buf_t
*buf
)
3093 kmutex_t
*hash_lock
;
3096 mutex_enter(&buf
->b_evict_lock
);
3100 * We are in arc_do_user_evicts().
3102 ASSERT(buf
->b_data
== NULL
);
3103 mutex_exit(&buf
->b_evict_lock
);
3105 } else if (buf
->b_data
== NULL
) {
3106 arc_buf_t copy
= *buf
; /* structure assignment */
3108 * We are on the eviction list; process this buffer now
3109 * but let arc_do_user_evicts() do the reaping.
3111 buf
->b_efunc
= NULL
;
3112 mutex_exit(&buf
->b_evict_lock
);
3113 VERIFY(copy
.b_efunc(©
) == 0);
3116 hash_lock
= HDR_LOCK(hdr
);
3117 mutex_enter(hash_lock
);
3119 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
3121 ASSERT3U(refcount_count(&hdr
->b_refcnt
), <, hdr
->b_datacnt
);
3122 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
3125 * Pull this buffer off of the hdr
3128 while (*bufp
!= buf
)
3129 bufp
= &(*bufp
)->b_next
;
3130 *bufp
= buf
->b_next
;
3132 ASSERT(buf
->b_data
!= NULL
);
3133 arc_buf_destroy(buf
, FALSE
, FALSE
);
3135 if (hdr
->b_datacnt
== 0) {
3136 arc_state_t
*old_state
= hdr
->b_state
;
3137 arc_state_t
*evicted_state
;
3139 ASSERT(hdr
->b_buf
== NULL
);
3140 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
3143 (old_state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
3145 mutex_enter(&old_state
->arcs_mtx
);
3146 mutex_enter(&evicted_state
->arcs_mtx
);
3148 arc_change_state(evicted_state
, hdr
, hash_lock
);
3149 ASSERT(HDR_IN_HASH_TABLE(hdr
));
3150 hdr
->b_flags
|= ARC_IN_HASH_TABLE
;
3151 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
3153 mutex_exit(&evicted_state
->arcs_mtx
);
3154 mutex_exit(&old_state
->arcs_mtx
);
3156 mutex_exit(hash_lock
);
3157 mutex_exit(&buf
->b_evict_lock
);
3159 VERIFY(buf
->b_efunc(buf
) == 0);
3160 buf
->b_efunc
= NULL
;
3161 buf
->b_private
= NULL
;
3164 kmem_cache_free(buf_cache
, buf
);
3169 * Release this buffer from the cache. This must be done
3170 * after a read and prior to modifying the buffer contents.
3171 * If the buffer has more than one reference, we must make
3172 * a new hdr for the buffer.
3175 arc_release(arc_buf_t
*buf
, void *tag
)
3178 kmutex_t
*hash_lock
= NULL
;
3179 l2arc_buf_hdr_t
*l2hdr
;
3183 * It would be nice to assert that if it's DMU metadata (level >
3184 * 0 || it's the dnode file), then it must be syncing context.
3185 * But we don't know that information at this level.
3188 mutex_enter(&buf
->b_evict_lock
);
3191 /* this buffer is not on any list */
3192 ASSERT(refcount_count(&hdr
->b_refcnt
) > 0);
3194 if (hdr
->b_state
== arc_anon
) {
3195 /* this buffer is already released */
3196 ASSERT(buf
->b_efunc
== NULL
);
3198 hash_lock
= HDR_LOCK(hdr
);
3199 mutex_enter(hash_lock
);
3201 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
3204 l2hdr
= hdr
->b_l2hdr
;
3206 mutex_enter(&l2arc_buflist_mtx
);
3207 hdr
->b_l2hdr
= NULL
;
3208 buf_size
= hdr
->b_size
;
3212 * Do we have more than one buf?
3214 if (hdr
->b_datacnt
> 1) {
3215 arc_buf_hdr_t
*nhdr
;
3217 uint64_t blksz
= hdr
->b_size
;
3218 uint64_t spa
= hdr
->b_spa
;
3219 arc_buf_contents_t type
= hdr
->b_type
;
3220 uint32_t flags
= hdr
->b_flags
;
3222 ASSERT(hdr
->b_buf
!= buf
|| buf
->b_next
!= NULL
);
3224 * Pull the data off of this hdr and attach it to
3225 * a new anonymous hdr.
3227 (void) remove_reference(hdr
, hash_lock
, tag
);
3229 while (*bufp
!= buf
)
3230 bufp
= &(*bufp
)->b_next
;
3231 *bufp
= buf
->b_next
;
3234 ASSERT3U(hdr
->b_state
->arcs_size
, >=, hdr
->b_size
);
3235 atomic_add_64(&hdr
->b_state
->arcs_size
, -hdr
->b_size
);
3236 if (refcount_is_zero(&hdr
->b_refcnt
)) {
3237 uint64_t *size
= &hdr
->b_state
->arcs_lsize
[hdr
->b_type
];
3238 ASSERT3U(*size
, >=, hdr
->b_size
);
3239 atomic_add_64(size
, -hdr
->b_size
);
3243 * We're releasing a duplicate user data buffer, update
3244 * our statistics accordingly.
3246 if (hdr
->b_type
== ARC_BUFC_DATA
) {
3247 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers
);
3248 ARCSTAT_INCR(arcstat_duplicate_buffers_size
,
3251 hdr
->b_datacnt
-= 1;
3252 arc_cksum_verify(buf
);
3253 arc_buf_unwatch(buf
);
3255 mutex_exit(hash_lock
);
3257 nhdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
3258 nhdr
->b_size
= blksz
;
3260 nhdr
->b_type
= type
;
3262 nhdr
->b_state
= arc_anon
;
3263 nhdr
->b_arc_access
= 0;
3264 nhdr
->b_flags
= flags
& ARC_L2_WRITING
;
3265 nhdr
->b_l2hdr
= NULL
;
3266 nhdr
->b_datacnt
= 1;
3267 nhdr
->b_freeze_cksum
= NULL
;
3268 (void) refcount_add(&nhdr
->b_refcnt
, tag
);
3270 mutex_exit(&buf
->b_evict_lock
);
3271 atomic_add_64(&arc_anon
->arcs_size
, blksz
);
3273 mutex_exit(&buf
->b_evict_lock
);
3274 ASSERT(refcount_count(&hdr
->b_refcnt
) == 1);
3275 ASSERT(!list_link_active(&hdr
->b_arc_node
));
3276 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
3277 if (hdr
->b_state
!= arc_anon
)
3278 arc_change_state(arc_anon
, hdr
, hash_lock
);
3279 hdr
->b_arc_access
= 0;
3281 mutex_exit(hash_lock
);
3283 buf_discard_identity(hdr
);
3286 buf
->b_efunc
= NULL
;
3287 buf
->b_private
= NULL
;
3290 list_remove(l2hdr
->b_dev
->l2ad_buflist
, hdr
);
3291 kmem_free(l2hdr
, sizeof (l2arc_buf_hdr_t
));
3292 ARCSTAT_INCR(arcstat_l2_size
, -buf_size
);
3293 mutex_exit(&l2arc_buflist_mtx
);
3298 * Release this buffer. If it does not match the provided BP, fill it
3299 * with that block's contents.
3303 arc_release_bp(arc_buf_t
*buf
, void *tag
, blkptr_t
*bp
, spa_t
*spa
,
3306 arc_release(buf
, tag
);
3311 arc_released(arc_buf_t
*buf
)
3315 mutex_enter(&buf
->b_evict_lock
);
3316 released
= (buf
->b_data
!= NULL
&& buf
->b_hdr
->b_state
== arc_anon
);
3317 mutex_exit(&buf
->b_evict_lock
);
3322 arc_has_callback(arc_buf_t
*buf
)
3326 mutex_enter(&buf
->b_evict_lock
);
3327 callback
= (buf
->b_efunc
!= NULL
);
3328 mutex_exit(&buf
->b_evict_lock
);
3334 arc_referenced(arc_buf_t
*buf
)
3338 mutex_enter(&buf
->b_evict_lock
);
3339 referenced
= (refcount_count(&buf
->b_hdr
->b_refcnt
));
3340 mutex_exit(&buf
->b_evict_lock
);
3341 return (referenced
);
3346 arc_write_ready(zio_t
*zio
)
3348 arc_write_callback_t
*callback
= zio
->io_private
;
3349 arc_buf_t
*buf
= callback
->awcb_buf
;
3350 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3352 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
3353 callback
->awcb_ready(zio
, buf
, callback
->awcb_private
);
3356 * If the IO is already in progress, then this is a re-write
3357 * attempt, so we need to thaw and re-compute the cksum.
3358 * It is the responsibility of the callback to handle the
3359 * accounting for any re-write attempt.
3361 if (HDR_IO_IN_PROGRESS(hdr
)) {
3362 mutex_enter(&hdr
->b_freeze_lock
);
3363 if (hdr
->b_freeze_cksum
!= NULL
) {
3364 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
3365 hdr
->b_freeze_cksum
= NULL
;
3367 mutex_exit(&hdr
->b_freeze_lock
);
3369 arc_cksum_compute(buf
, B_FALSE
);
3370 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
3374 arc_write_done(zio_t
*zio
)
3376 arc_write_callback_t
*callback
= zio
->io_private
;
3377 arc_buf_t
*buf
= callback
->awcb_buf
;
3378 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3380 ASSERT(hdr
->b_acb
== NULL
);
3382 if (zio
->io_error
== 0) {
3383 hdr
->b_dva
= *BP_IDENTITY(zio
->io_bp
);
3384 hdr
->b_birth
= BP_PHYSICAL_BIRTH(zio
->io_bp
);
3385 hdr
->b_cksum0
= zio
->io_bp
->blk_cksum
.zc_word
[0];
3387 ASSERT(BUF_EMPTY(hdr
));
3391 * If the block to be written was all-zero, we may have
3392 * compressed it away. In this case no write was performed
3393 * so there will be no dva/birth/checksum. The buffer must
3394 * therefore remain anonymous (and uncached).
3396 if (!BUF_EMPTY(hdr
)) {
3397 arc_buf_hdr_t
*exists
;
3398 kmutex_t
*hash_lock
;
3400 ASSERT(zio
->io_error
== 0);
3402 arc_cksum_verify(buf
);
3404 exists
= buf_hash_insert(hdr
, &hash_lock
);
3407 * This can only happen if we overwrite for
3408 * sync-to-convergence, because we remove
3409 * buffers from the hash table when we arc_free().
3411 if (zio
->io_flags
& ZIO_FLAG_IO_REWRITE
) {
3412 if (!BP_EQUAL(&zio
->io_bp_orig
, zio
->io_bp
))
3413 panic("bad overwrite, hdr=%p exists=%p",
3414 (void *)hdr
, (void *)exists
);
3415 ASSERT(refcount_is_zero(&exists
->b_refcnt
));
3416 arc_change_state(arc_anon
, exists
, hash_lock
);
3417 mutex_exit(hash_lock
);
3418 arc_hdr_destroy(exists
);
3419 exists
= buf_hash_insert(hdr
, &hash_lock
);
3420 ASSERT3P(exists
, ==, NULL
);
3421 } else if (zio
->io_flags
& ZIO_FLAG_NOPWRITE
) {
3423 ASSERT(zio
->io_prop
.zp_nopwrite
);
3424 if (!BP_EQUAL(&zio
->io_bp_orig
, zio
->io_bp
))
3425 panic("bad nopwrite, hdr=%p exists=%p",
3426 (void *)hdr
, (void *)exists
);
3429 ASSERT(hdr
->b_datacnt
== 1);
3430 ASSERT(hdr
->b_state
== arc_anon
);
3431 ASSERT(BP_GET_DEDUP(zio
->io_bp
));
3432 ASSERT(BP_GET_LEVEL(zio
->io_bp
) == 0);
3435 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3436 /* if it's not anon, we are doing a scrub */
3437 if (!exists
&& hdr
->b_state
== arc_anon
)
3438 arc_access(hdr
, hash_lock
);
3439 mutex_exit(hash_lock
);
3441 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3444 ASSERT(!refcount_is_zero(&hdr
->b_refcnt
));
3445 callback
->awcb_done(zio
, buf
, callback
->awcb_private
);
3447 kmem_free(callback
, sizeof (arc_write_callback_t
));
3451 arc_write(zio_t
*pio
, spa_t
*spa
, uint64_t txg
,
3452 blkptr_t
*bp
, arc_buf_t
*buf
, boolean_t l2arc
, const zio_prop_t
*zp
,
3453 arc_done_func_t
*ready
, arc_done_func_t
*done
, void *private,
3454 int priority
, int zio_flags
, const zbookmark_t
*zb
)
3456 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3457 arc_write_callback_t
*callback
;
3460 ASSERT(ready
!= NULL
);
3461 ASSERT(done
!= NULL
);
3462 ASSERT(!HDR_IO_ERROR(hdr
));
3463 ASSERT((hdr
->b_flags
& ARC_IO_IN_PROGRESS
) == 0);
3464 ASSERT(hdr
->b_acb
== NULL
);
3466 hdr
->b_flags
|= ARC_L2CACHE
;
3467 callback
= kmem_zalloc(sizeof (arc_write_callback_t
), KM_SLEEP
);
3468 callback
->awcb_ready
= ready
;
3469 callback
->awcb_done
= done
;
3470 callback
->awcb_private
= private;
3471 callback
->awcb_buf
= buf
;
3473 zio
= zio_write(pio
, spa
, txg
, bp
, buf
->b_data
, hdr
->b_size
, zp
,
3474 arc_write_ready
, arc_write_done
, callback
, priority
, zio_flags
, zb
);
3480 arc_memory_throttle(uint64_t reserve
, uint64_t inflight_data
, uint64_t txg
)
3483 uint64_t available_memory
= ptob(freemem
);
3484 static uint64_t page_load
= 0;
3485 static uint64_t last_txg
= 0;
3489 MIN(available_memory
, vmem_size(heap_arena
, VMEM_FREE
));
3491 if (available_memory
>= zfs_write_limit_max
)
3494 if (txg
> last_txg
) {
3499 * If we are in pageout, we know that memory is already tight,
3500 * the arc is already going to be evicting, so we just want to
3501 * continue to let page writes occur as quickly as possible.
3503 if (curproc
== proc_pageout
) {
3504 if (page_load
> MAX(ptob(minfree
), available_memory
) / 4)
3506 /* Note: reserve is inflated, so we deflate */
3507 page_load
+= reserve
/ 8;
3509 } else if (page_load
> 0 && arc_reclaim_needed()) {
3510 /* memory is low, delay before restarting */
3511 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3516 if (arc_size
> arc_c_min
) {
3517 uint64_t evictable_memory
=
3518 arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] +
3519 arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] +
3520 arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] +
3521 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
];
3522 available_memory
+= MIN(evictable_memory
, arc_size
- arc_c_min
);
3525 if (inflight_data
> available_memory
/ 4) {
3526 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3534 arc_tempreserve_clear(uint64_t reserve
)
3536 atomic_add_64(&arc_tempreserve
, -reserve
);
3537 ASSERT((int64_t)arc_tempreserve
>= 0);
3541 arc_tempreserve_space(uint64_t reserve
, uint64_t txg
)
3548 * Once in a while, fail for no reason. Everything should cope.
3550 if (spa_get_random(10000) == 0) {
3551 dprintf("forcing random failure\n");
3555 if (reserve
> arc_c
/4 && !arc_no_grow
)
3556 arc_c
= MIN(arc_c_max
, reserve
* 4);
3557 if (reserve
> arc_c
)
3561 * Don't count loaned bufs as in flight dirty data to prevent long
3562 * network delays from blocking transactions that are ready to be
3563 * assigned to a txg.
3565 anon_size
= MAX((int64_t)(arc_anon
->arcs_size
- arc_loaned_bytes
), 0);
3568 * Writes will, almost always, require additional memory allocations
3569 * in order to compress/encrypt/etc the data. We therefor need to
3570 * make sure that there is sufficient available memory for this.
3572 if (error
= arc_memory_throttle(reserve
, anon_size
, txg
))
3576 * Throttle writes when the amount of dirty data in the cache
3577 * gets too large. We try to keep the cache less than half full
3578 * of dirty blocks so that our sync times don't grow too large.
3579 * Note: if two requests come in concurrently, we might let them
3580 * both succeed, when one of them should fail. Not a huge deal.
3583 if (reserve
+ arc_tempreserve
+ anon_size
> arc_c
/ 2 &&
3584 anon_size
> arc_c
/ 4) {
3585 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3586 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3587 arc_tempreserve
>>10,
3588 arc_anon
->arcs_lsize
[ARC_BUFC_METADATA
]>>10,
3589 arc_anon
->arcs_lsize
[ARC_BUFC_DATA
]>>10,
3590 reserve
>>10, arc_c
>>10);
3593 atomic_add_64(&arc_tempreserve
, reserve
);
3600 mutex_init(&arc_reclaim_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3601 cv_init(&arc_reclaim_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
3603 /* Convert seconds to clock ticks */
3604 arc_min_prefetch_lifespan
= 1 * hz
;
3606 /* Start out with 1/8 of all memory */
3607 arc_c
= physmem
* PAGESIZE
/ 8;
3611 * On architectures where the physical memory can be larger
3612 * than the addressable space (intel in 32-bit mode), we may
3613 * need to limit the cache to 1/8 of VM size.
3615 arc_c
= MIN(arc_c
, vmem_size(heap_arena
, VMEM_ALLOC
| VMEM_FREE
) / 8);
3618 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3619 arc_c_min
= MAX(arc_c
/ 4, 64<<20);
3620 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3621 if (arc_c
* 8 >= 1<<30)
3622 arc_c_max
= (arc_c
* 8) - (1<<30);
3624 arc_c_max
= arc_c_min
;
3625 arc_c_max
= MAX(arc_c
* 6, arc_c_max
);
3628 * Allow the tunables to override our calculations if they are
3629 * reasonable (ie. over 64MB)
3631 if (zfs_arc_max
> 64<<20 && zfs_arc_max
< physmem
* PAGESIZE
)
3632 arc_c_max
= zfs_arc_max
;
3633 if (zfs_arc_min
> 64<<20 && zfs_arc_min
<= arc_c_max
)
3634 arc_c_min
= zfs_arc_min
;
3637 arc_p
= (arc_c
>> 1);
3639 /* limit meta-data to 1/4 of the arc capacity */
3640 arc_meta_limit
= arc_c_max
/ 4;
3642 /* Allow the tunable to override if it is reasonable */
3643 if (zfs_arc_meta_limit
> 0 && zfs_arc_meta_limit
<= arc_c_max
)
3644 arc_meta_limit
= zfs_arc_meta_limit
;
3646 if (arc_c_min
< arc_meta_limit
/ 2 && zfs_arc_min
== 0)
3647 arc_c_min
= arc_meta_limit
/ 2;
3649 if (zfs_arc_grow_retry
> 0)
3650 arc_grow_retry
= zfs_arc_grow_retry
;
3652 if (zfs_arc_shrink_shift
> 0)
3653 arc_shrink_shift
= zfs_arc_shrink_shift
;
3655 if (zfs_arc_p_min_shift
> 0)
3656 arc_p_min_shift
= zfs_arc_p_min_shift
;
3658 /* if kmem_flags are set, lets try to use less memory */
3659 if (kmem_debugging())
3661 if (arc_c
< arc_c_min
)
3664 arc_anon
= &ARC_anon
;
3666 arc_mru_ghost
= &ARC_mru_ghost
;
3668 arc_mfu_ghost
= &ARC_mfu_ghost
;
3669 arc_l2c_only
= &ARC_l2c_only
;
3672 mutex_init(&arc_anon
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3673 mutex_init(&arc_mru
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3674 mutex_init(&arc_mru_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3675 mutex_init(&arc_mfu
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3676 mutex_init(&arc_mfu_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3677 mutex_init(&arc_l2c_only
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3679 list_create(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
],
3680 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3681 list_create(&arc_mru
->arcs_list
[ARC_BUFC_DATA
],
3682 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3683 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3684 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3685 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
],
3686 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3687 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
],
3688 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3689 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
],
3690 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3691 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3692 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3693 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
],
3694 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3695 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_METADATA
],
3696 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3697 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_DATA
],
3698 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3702 arc_thread_exit
= 0;
3703 arc_eviction_list
= NULL
;
3704 mutex_init(&arc_eviction_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3705 bzero(&arc_eviction_hdr
, sizeof (arc_buf_hdr_t
));
3707 arc_ksp
= kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED
,
3708 sizeof (arc_stats
) / sizeof (kstat_named_t
), KSTAT_FLAG_VIRTUAL
);
3710 if (arc_ksp
!= NULL
) {
3711 arc_ksp
->ks_data
= &arc_stats
;
3712 kstat_install(arc_ksp
);
3715 (void) thread_create(NULL
, 0, arc_reclaim_thread
, NULL
, 0, &p0
,
3716 TS_RUN
, minclsyspri
);
3721 if (zfs_write_limit_max
== 0)
3722 zfs_write_limit_max
= ptob(physmem
) >> zfs_write_limit_shift
;
3724 zfs_write_limit_shift
= 0;
3725 mutex_init(&zfs_write_limit_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3731 mutex_enter(&arc_reclaim_thr_lock
);
3732 arc_thread_exit
= 1;
3733 while (arc_thread_exit
!= 0)
3734 cv_wait(&arc_reclaim_thr_cv
, &arc_reclaim_thr_lock
);
3735 mutex_exit(&arc_reclaim_thr_lock
);
3741 if (arc_ksp
!= NULL
) {
3742 kstat_delete(arc_ksp
);
3746 mutex_destroy(&arc_eviction_mtx
);
3747 mutex_destroy(&arc_reclaim_thr_lock
);
3748 cv_destroy(&arc_reclaim_thr_cv
);
3750 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
]);
3751 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3752 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
]);
3753 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3754 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_DATA
]);
3755 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3756 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
]);
3757 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3759 mutex_destroy(&arc_anon
->arcs_mtx
);
3760 mutex_destroy(&arc_mru
->arcs_mtx
);
3761 mutex_destroy(&arc_mru_ghost
->arcs_mtx
);
3762 mutex_destroy(&arc_mfu
->arcs_mtx
);
3763 mutex_destroy(&arc_mfu_ghost
->arcs_mtx
);
3764 mutex_destroy(&arc_l2c_only
->arcs_mtx
);
3766 mutex_destroy(&zfs_write_limit_lock
);
3770 ASSERT(arc_loaned_bytes
== 0);
3776 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3777 * It uses dedicated storage devices to hold cached data, which are populated
3778 * using large infrequent writes. The main role of this cache is to boost
3779 * the performance of random read workloads. The intended L2ARC devices
3780 * include short-stroked disks, solid state disks, and other media with
3781 * substantially faster read latency than disk.
3783 * +-----------------------+
3785 * +-----------------------+
3788 * l2arc_feed_thread() arc_read()
3792 * +---------------+ |
3794 * +---------------+ |
3799 * +-------+ +-------+
3801 * | cache | | cache |
3802 * +-------+ +-------+
3803 * +=========+ .-----.
3804 * : L2ARC : |-_____-|
3805 * : devices : | Disks |
3806 * +=========+ `-_____-'
3808 * Read requests are satisfied from the following sources, in order:
3811 * 2) vdev cache of L2ARC devices
3813 * 4) vdev cache of disks
3816 * Some L2ARC device types exhibit extremely slow write performance.
3817 * To accommodate for this there are some significant differences between
3818 * the L2ARC and traditional cache design:
3820 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3821 * the ARC behave as usual, freeing buffers and placing headers on ghost
3822 * lists. The ARC does not send buffers to the L2ARC during eviction as
3823 * this would add inflated write latencies for all ARC memory pressure.
3825 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3826 * It does this by periodically scanning buffers from the eviction-end of
3827 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3828 * not already there. It scans until a headroom of buffers is satisfied,
3829 * which itself is a buffer for ARC eviction. The thread that does this is
3830 * l2arc_feed_thread(), illustrated below; example sizes are included to
3831 * provide a better sense of ratio than this diagram:
3834 * +---------------------+----------+
3835 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3836 * +---------------------+----------+ | o L2ARC eligible
3837 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3838 * +---------------------+----------+ |
3839 * 15.9 Gbytes ^ 32 Mbytes |
3841 * l2arc_feed_thread()
3843 * l2arc write hand <--[oooo]--'
3847 * +==============================+
3848 * L2ARC dev |####|#|###|###| |####| ... |
3849 * +==============================+
3852 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3853 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3854 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3855 * safe to say that this is an uncommon case, since buffers at the end of
3856 * the ARC lists have moved there due to inactivity.
3858 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3859 * then the L2ARC simply misses copying some buffers. This serves as a
3860 * pressure valve to prevent heavy read workloads from both stalling the ARC
3861 * with waits and clogging the L2ARC with writes. This also helps prevent
3862 * the potential for the L2ARC to churn if it attempts to cache content too
3863 * quickly, such as during backups of the entire pool.
3865 * 5. After system boot and before the ARC has filled main memory, there are
3866 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3867 * lists can remain mostly static. Instead of searching from tail of these
3868 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3869 * for eligible buffers, greatly increasing its chance of finding them.
3871 * The L2ARC device write speed is also boosted during this time so that
3872 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
3873 * there are no L2ARC reads, and no fear of degrading read performance
3874 * through increased writes.
3876 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
3877 * the vdev queue can aggregate them into larger and fewer writes. Each
3878 * device is written to in a rotor fashion, sweeping writes through
3879 * available space then repeating.
3881 * 7. The L2ARC does not store dirty content. It never needs to flush
3882 * write buffers back to disk based storage.
3884 * 8. If an ARC buffer is written (and dirtied) which also exists in the
3885 * L2ARC, the now stale L2ARC buffer is immediately dropped.
3887 * The performance of the L2ARC can be tweaked by a number of tunables, which
3888 * may be necessary for different workloads:
3890 * l2arc_write_max max write bytes per interval
3891 * l2arc_write_boost extra write bytes during device warmup
3892 * l2arc_noprefetch skip caching prefetched buffers
3893 * l2arc_headroom number of max device writes to precache
3894 * l2arc_feed_secs seconds between L2ARC writing
3896 * Tunables may be removed or added as future performance improvements are
3897 * integrated, and also may become zpool properties.
3899 * There are three key functions that control how the L2ARC warms up:
3901 * l2arc_write_eligible() check if a buffer is eligible to cache
3902 * l2arc_write_size() calculate how much to write
3903 * l2arc_write_interval() calculate sleep delay between writes
3905 * These three functions determine what to write, how much, and how quickly
3910 l2arc_write_eligible(uint64_t spa_guid
, arc_buf_hdr_t
*ab
)
3913 * A buffer is *not* eligible for the L2ARC if it:
3914 * 1. belongs to a different spa.
3915 * 2. is already cached on the L2ARC.
3916 * 3. has an I/O in progress (it may be an incomplete read).
3917 * 4. is flagged not eligible (zfs property).
3919 if (ab
->b_spa
!= spa_guid
|| ab
->b_l2hdr
!= NULL
||
3920 HDR_IO_IN_PROGRESS(ab
) || !HDR_L2CACHE(ab
))
3927 l2arc_write_size(l2arc_dev_t
*dev
)
3931 size
= dev
->l2ad_write
;
3933 if (arc_warm
== B_FALSE
)
3934 size
+= dev
->l2ad_boost
;
3941 l2arc_write_interval(clock_t began
, uint64_t wanted
, uint64_t wrote
)
3943 clock_t interval
, next
, now
;
3946 * If the ARC lists are busy, increase our write rate; if the
3947 * lists are stale, idle back. This is achieved by checking
3948 * how much we previously wrote - if it was more than half of
3949 * what we wanted, schedule the next write much sooner.
3951 if (l2arc_feed_again
&& wrote
> (wanted
/ 2))
3952 interval
= (hz
* l2arc_feed_min_ms
) / 1000;
3954 interval
= hz
* l2arc_feed_secs
;
3956 now
= ddi_get_lbolt();
3957 next
= MAX(now
, MIN(now
+ interval
, began
+ interval
));
3963 l2arc_hdr_stat_add(void)
3965 ARCSTAT_INCR(arcstat_l2_hdr_size
, HDR_SIZE
+ L2HDR_SIZE
);
3966 ARCSTAT_INCR(arcstat_hdr_size
, -HDR_SIZE
);
3970 l2arc_hdr_stat_remove(void)
3972 ARCSTAT_INCR(arcstat_l2_hdr_size
, -(HDR_SIZE
+ L2HDR_SIZE
));
3973 ARCSTAT_INCR(arcstat_hdr_size
, HDR_SIZE
);
3977 * Cycle through L2ARC devices. This is how L2ARC load balances.
3978 * If a device is returned, this also returns holding the spa config lock.
3980 static l2arc_dev_t
*
3981 l2arc_dev_get_next(void)
3983 l2arc_dev_t
*first
, *next
= NULL
;
3986 * Lock out the removal of spas (spa_namespace_lock), then removal
3987 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
3988 * both locks will be dropped and a spa config lock held instead.
3990 mutex_enter(&spa_namespace_lock
);
3991 mutex_enter(&l2arc_dev_mtx
);
3993 /* if there are no vdevs, there is nothing to do */
3994 if (l2arc_ndev
== 0)
3998 next
= l2arc_dev_last
;
4000 /* loop around the list looking for a non-faulted vdev */
4002 next
= list_head(l2arc_dev_list
);
4004 next
= list_next(l2arc_dev_list
, next
);
4006 next
= list_head(l2arc_dev_list
);
4009 /* if we have come back to the start, bail out */
4012 else if (next
== first
)
4015 } while (vdev_is_dead(next
->l2ad_vdev
));
4017 /* if we were unable to find any usable vdevs, return NULL */
4018 if (vdev_is_dead(next
->l2ad_vdev
))
4021 l2arc_dev_last
= next
;
4024 mutex_exit(&l2arc_dev_mtx
);
4027 * Grab the config lock to prevent the 'next' device from being
4028 * removed while we are writing to it.
4031 spa_config_enter(next
->l2ad_spa
, SCL_L2ARC
, next
, RW_READER
);
4032 mutex_exit(&spa_namespace_lock
);
4038 * Free buffers that were tagged for destruction.
4041 l2arc_do_free_on_write()
4044 l2arc_data_free_t
*df
, *df_prev
;
4046 mutex_enter(&l2arc_free_on_write_mtx
);
4047 buflist
= l2arc_free_on_write
;
4049 for (df
= list_tail(buflist
); df
; df
= df_prev
) {
4050 df_prev
= list_prev(buflist
, df
);
4051 ASSERT(df
->l2df_data
!= NULL
);
4052 ASSERT(df
->l2df_func
!= NULL
);
4053 df
->l2df_func(df
->l2df_data
, df
->l2df_size
);
4054 list_remove(buflist
, df
);
4055 kmem_free(df
, sizeof (l2arc_data_free_t
));
4058 mutex_exit(&l2arc_free_on_write_mtx
);
4062 * A write to a cache device has completed. Update all headers to allow
4063 * reads from these buffers to begin.
4066 l2arc_write_done(zio_t
*zio
)
4068 l2arc_write_callback_t
*cb
;
4071 arc_buf_hdr_t
*head
, *ab
, *ab_prev
;
4072 l2arc_buf_hdr_t
*abl2
;
4073 kmutex_t
*hash_lock
;
4075 cb
= zio
->io_private
;
4077 dev
= cb
->l2wcb_dev
;
4078 ASSERT(dev
!= NULL
);
4079 head
= cb
->l2wcb_head
;
4080 ASSERT(head
!= NULL
);
4081 buflist
= dev
->l2ad_buflist
;
4082 ASSERT(buflist
!= NULL
);
4083 DTRACE_PROBE2(l2arc__iodone
, zio_t
*, zio
,
4084 l2arc_write_callback_t
*, cb
);
4086 if (zio
->io_error
!= 0)
4087 ARCSTAT_BUMP(arcstat_l2_writes_error
);
4089 mutex_enter(&l2arc_buflist_mtx
);
4092 * All writes completed, or an error was hit.
4094 for (ab
= list_prev(buflist
, head
); ab
; ab
= ab_prev
) {
4095 ab_prev
= list_prev(buflist
, ab
);
4097 hash_lock
= HDR_LOCK(ab
);
4098 if (!mutex_tryenter(hash_lock
)) {
4100 * This buffer misses out. It may be in a stage
4101 * of eviction. Its ARC_L2_WRITING flag will be
4102 * left set, denying reads to this buffer.
4104 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss
);
4108 if (zio
->io_error
!= 0) {
4110 * Error - drop L2ARC entry.
4112 list_remove(buflist
, ab
);
4115 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
4116 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
4120 * Allow ARC to begin reads to this L2ARC entry.
4122 ab
->b_flags
&= ~ARC_L2_WRITING
;
4124 mutex_exit(hash_lock
);
4127 atomic_inc_64(&l2arc_writes_done
);
4128 list_remove(buflist
, head
);
4129 kmem_cache_free(hdr_cache
, head
);
4130 mutex_exit(&l2arc_buflist_mtx
);
4132 l2arc_do_free_on_write();
4134 kmem_free(cb
, sizeof (l2arc_write_callback_t
));
4138 * A read to a cache device completed. Validate buffer contents before
4139 * handing over to the regular ARC routines.
4142 l2arc_read_done(zio_t
*zio
)
4144 l2arc_read_callback_t
*cb
;
4147 kmutex_t
*hash_lock
;
4150 ASSERT(zio
->io_vd
!= NULL
);
4151 ASSERT(zio
->io_flags
& ZIO_FLAG_DONT_PROPAGATE
);
4153 spa_config_exit(zio
->io_spa
, SCL_L2ARC
, zio
->io_vd
);
4155 cb
= zio
->io_private
;
4157 buf
= cb
->l2rcb_buf
;
4158 ASSERT(buf
!= NULL
);
4160 hash_lock
= HDR_LOCK(buf
->b_hdr
);
4161 mutex_enter(hash_lock
);
4163 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
4166 * Check this survived the L2ARC journey.
4168 equal
= arc_cksum_equal(buf
);
4169 if (equal
&& zio
->io_error
== 0 && !HDR_L2_EVICTED(hdr
)) {
4170 mutex_exit(hash_lock
);
4171 zio
->io_private
= buf
;
4172 zio
->io_bp_copy
= cb
->l2rcb_bp
; /* XXX fix in L2ARC 2.0 */
4173 zio
->io_bp
= &zio
->io_bp_copy
; /* XXX fix in L2ARC 2.0 */
4176 mutex_exit(hash_lock
);
4178 * Buffer didn't survive caching. Increment stats and
4179 * reissue to the original storage device.
4181 if (zio
->io_error
!= 0) {
4182 ARCSTAT_BUMP(arcstat_l2_io_error
);
4184 zio
->io_error
= EIO
;
4187 ARCSTAT_BUMP(arcstat_l2_cksum_bad
);
4190 * If there's no waiter, issue an async i/o to the primary
4191 * storage now. If there *is* a waiter, the caller must
4192 * issue the i/o in a context where it's OK to block.
4194 if (zio
->io_waiter
== NULL
) {
4195 zio_t
*pio
= zio_unique_parent(zio
);
4197 ASSERT(!pio
|| pio
->io_child_type
== ZIO_CHILD_LOGICAL
);
4199 zio_nowait(zio_read(pio
, cb
->l2rcb_spa
, &cb
->l2rcb_bp
,
4200 buf
->b_data
, zio
->io_size
, arc_read_done
, buf
,
4201 zio
->io_priority
, cb
->l2rcb_flags
, &cb
->l2rcb_zb
));
4205 kmem_free(cb
, sizeof (l2arc_read_callback_t
));
4209 * This is the list priority from which the L2ARC will search for pages to
4210 * cache. This is used within loops (0..3) to cycle through lists in the
4211 * desired order. This order can have a significant effect on cache
4214 * Currently the metadata lists are hit first, MFU then MRU, followed by
4215 * the data lists. This function returns a locked list, and also returns
4219 l2arc_list_locked(int list_num
, kmutex_t
**lock
)
4223 ASSERT(list_num
>= 0 && list_num
<= 3);
4227 list
= &arc_mfu
->arcs_list
[ARC_BUFC_METADATA
];
4228 *lock
= &arc_mfu
->arcs_mtx
;
4231 list
= &arc_mru
->arcs_list
[ARC_BUFC_METADATA
];
4232 *lock
= &arc_mru
->arcs_mtx
;
4235 list
= &arc_mfu
->arcs_list
[ARC_BUFC_DATA
];
4236 *lock
= &arc_mfu
->arcs_mtx
;
4239 list
= &arc_mru
->arcs_list
[ARC_BUFC_DATA
];
4240 *lock
= &arc_mru
->arcs_mtx
;
4244 ASSERT(!(MUTEX_HELD(*lock
)));
4250 * Evict buffers from the device write hand to the distance specified in
4251 * bytes. This distance may span populated buffers, it may span nothing.
4252 * This is clearing a region on the L2ARC device ready for writing.
4253 * If the 'all' boolean is set, every buffer is evicted.
4256 l2arc_evict(l2arc_dev_t
*dev
, uint64_t distance
, boolean_t all
)
4259 l2arc_buf_hdr_t
*abl2
;
4260 arc_buf_hdr_t
*ab
, *ab_prev
;
4261 kmutex_t
*hash_lock
;
4264 buflist
= dev
->l2ad_buflist
;
4266 if (buflist
== NULL
)
4269 if (!all
&& dev
->l2ad_first
) {
4271 * This is the first sweep through the device. There is
4277 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- (2 * distance
))) {
4279 * When nearing the end of the device, evict to the end
4280 * before the device write hand jumps to the start.
4282 taddr
= dev
->l2ad_end
;
4284 taddr
= dev
->l2ad_hand
+ distance
;
4286 DTRACE_PROBE4(l2arc__evict
, l2arc_dev_t
*, dev
, list_t
*, buflist
,
4287 uint64_t, taddr
, boolean_t
, all
);
4290 mutex_enter(&l2arc_buflist_mtx
);
4291 for (ab
= list_tail(buflist
); ab
; ab
= ab_prev
) {
4292 ab_prev
= list_prev(buflist
, ab
);
4294 hash_lock
= HDR_LOCK(ab
);
4295 if (!mutex_tryenter(hash_lock
)) {
4297 * Missed the hash lock. Retry.
4299 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry
);
4300 mutex_exit(&l2arc_buflist_mtx
);
4301 mutex_enter(hash_lock
);
4302 mutex_exit(hash_lock
);
4306 if (HDR_L2_WRITE_HEAD(ab
)) {
4308 * We hit a write head node. Leave it for
4309 * l2arc_write_done().
4311 list_remove(buflist
, ab
);
4312 mutex_exit(hash_lock
);
4316 if (!all
&& ab
->b_l2hdr
!= NULL
&&
4317 (ab
->b_l2hdr
->b_daddr
> taddr
||
4318 ab
->b_l2hdr
->b_daddr
< dev
->l2ad_hand
)) {
4320 * We've evicted to the target address,
4321 * or the end of the device.
4323 mutex_exit(hash_lock
);
4327 if (HDR_FREE_IN_PROGRESS(ab
)) {
4329 * Already on the path to destruction.
4331 mutex_exit(hash_lock
);
4335 if (ab
->b_state
== arc_l2c_only
) {
4336 ASSERT(!HDR_L2_READING(ab
));
4338 * This doesn't exist in the ARC. Destroy.
4339 * arc_hdr_destroy() will call list_remove()
4340 * and decrement arcstat_l2_size.
4342 arc_change_state(arc_anon
, ab
, hash_lock
);
4343 arc_hdr_destroy(ab
);
4346 * Invalidate issued or about to be issued
4347 * reads, since we may be about to write
4348 * over this location.
4350 if (HDR_L2_READING(ab
)) {
4351 ARCSTAT_BUMP(arcstat_l2_evict_reading
);
4352 ab
->b_flags
|= ARC_L2_EVICTED
;
4356 * Tell ARC this no longer exists in L2ARC.
4358 if (ab
->b_l2hdr
!= NULL
) {
4361 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
4362 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
4364 list_remove(buflist
, ab
);
4367 * This may have been leftover after a
4370 ab
->b_flags
&= ~ARC_L2_WRITING
;
4372 mutex_exit(hash_lock
);
4374 mutex_exit(&l2arc_buflist_mtx
);
4376 vdev_space_update(dev
->l2ad_vdev
, -(taddr
- dev
->l2ad_evict
), 0, 0);
4377 dev
->l2ad_evict
= taddr
;
4381 * Find and write ARC buffers to the L2ARC device.
4383 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4384 * for reading until they have completed writing.
4387 l2arc_write_buffers(spa_t
*spa
, l2arc_dev_t
*dev
, uint64_t target_sz
)
4389 arc_buf_hdr_t
*ab
, *ab_prev
, *head
;
4390 l2arc_buf_hdr_t
*hdrl2
;
4392 uint64_t passed_sz
, write_sz
, buf_sz
, headroom
;
4394 kmutex_t
*hash_lock
, *list_lock
;
4395 boolean_t have_lock
, full
;
4396 l2arc_write_callback_t
*cb
;
4398 uint64_t guid
= spa_load_guid(spa
);
4400 ASSERT(dev
->l2ad_vdev
!= NULL
);
4405 head
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
4406 head
->b_flags
|= ARC_L2_WRITE_HEAD
;
4409 * Copy buffers for L2ARC writing.
4411 mutex_enter(&l2arc_buflist_mtx
);
4412 for (int try = 0; try <= 3; try++) {
4413 list
= l2arc_list_locked(try, &list_lock
);
4417 * L2ARC fast warmup.
4419 * Until the ARC is warm and starts to evict, read from the
4420 * head of the ARC lists rather than the tail.
4422 headroom
= target_sz
* l2arc_headroom
;
4423 if (arc_warm
== B_FALSE
)
4424 ab
= list_head(list
);
4426 ab
= list_tail(list
);
4428 for (; ab
; ab
= ab_prev
) {
4429 if (arc_warm
== B_FALSE
)
4430 ab_prev
= list_next(list
, ab
);
4432 ab_prev
= list_prev(list
, ab
);
4434 hash_lock
= HDR_LOCK(ab
);
4435 have_lock
= MUTEX_HELD(hash_lock
);
4436 if (!have_lock
&& !mutex_tryenter(hash_lock
)) {
4438 * Skip this buffer rather than waiting.
4443 passed_sz
+= ab
->b_size
;
4444 if (passed_sz
> headroom
) {
4448 mutex_exit(hash_lock
);
4452 if (!l2arc_write_eligible(guid
, ab
)) {
4453 mutex_exit(hash_lock
);
4457 if ((write_sz
+ ab
->b_size
) > target_sz
) {
4459 mutex_exit(hash_lock
);
4465 * Insert a dummy header on the buflist so
4466 * l2arc_write_done() can find where the
4467 * write buffers begin without searching.
4469 list_insert_head(dev
->l2ad_buflist
, head
);
4472 sizeof (l2arc_write_callback_t
), KM_SLEEP
);
4473 cb
->l2wcb_dev
= dev
;
4474 cb
->l2wcb_head
= head
;
4475 pio
= zio_root(spa
, l2arc_write_done
, cb
,
4480 * Create and add a new L2ARC header.
4482 hdrl2
= kmem_zalloc(sizeof (l2arc_buf_hdr_t
), KM_SLEEP
);
4484 hdrl2
->b_daddr
= dev
->l2ad_hand
;
4486 ab
->b_flags
|= ARC_L2_WRITING
;
4487 ab
->b_l2hdr
= hdrl2
;
4488 list_insert_head(dev
->l2ad_buflist
, ab
);
4489 buf_data
= ab
->b_buf
->b_data
;
4490 buf_sz
= ab
->b_size
;
4493 * Compute and store the buffer cksum before
4494 * writing. On debug the cksum is verified first.
4496 arc_cksum_verify(ab
->b_buf
);
4497 arc_cksum_compute(ab
->b_buf
, B_TRUE
);
4499 mutex_exit(hash_lock
);
4501 wzio
= zio_write_phys(pio
, dev
->l2ad_vdev
,
4502 dev
->l2ad_hand
, buf_sz
, buf_data
, ZIO_CHECKSUM_OFF
,
4503 NULL
, NULL
, ZIO_PRIORITY_ASYNC_WRITE
,
4504 ZIO_FLAG_CANFAIL
, B_FALSE
);
4506 DTRACE_PROBE2(l2arc__write
, vdev_t
*, dev
->l2ad_vdev
,
4508 (void) zio_nowait(wzio
);
4511 * Keep the clock hand suitably device-aligned.
4513 buf_sz
= vdev_psize_to_asize(dev
->l2ad_vdev
, buf_sz
);
4516 dev
->l2ad_hand
+= buf_sz
;
4519 mutex_exit(list_lock
);
4524 mutex_exit(&l2arc_buflist_mtx
);
4528 kmem_cache_free(hdr_cache
, head
);
4532 ASSERT3U(write_sz
, <=, target_sz
);
4533 ARCSTAT_BUMP(arcstat_l2_writes_sent
);
4534 ARCSTAT_INCR(arcstat_l2_write_bytes
, write_sz
);
4535 ARCSTAT_INCR(arcstat_l2_size
, write_sz
);
4536 vdev_space_update(dev
->l2ad_vdev
, write_sz
, 0, 0);
4539 * Bump device hand to the device start if it is approaching the end.
4540 * l2arc_evict() will already have evicted ahead for this case.
4542 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- target_sz
)) {
4543 vdev_space_update(dev
->l2ad_vdev
,
4544 dev
->l2ad_end
- dev
->l2ad_hand
, 0, 0);
4545 dev
->l2ad_hand
= dev
->l2ad_start
;
4546 dev
->l2ad_evict
= dev
->l2ad_start
;
4547 dev
->l2ad_first
= B_FALSE
;
4550 dev
->l2ad_writing
= B_TRUE
;
4551 (void) zio_wait(pio
);
4552 dev
->l2ad_writing
= B_FALSE
;
4558 * This thread feeds the L2ARC at regular intervals. This is the beating
4559 * heart of the L2ARC.
4562 l2arc_feed_thread(void)
4567 uint64_t size
, wrote
;
4568 clock_t begin
, next
= ddi_get_lbolt();
4570 CALLB_CPR_INIT(&cpr
, &l2arc_feed_thr_lock
, callb_generic_cpr
, FTAG
);
4572 mutex_enter(&l2arc_feed_thr_lock
);
4574 while (l2arc_thread_exit
== 0) {
4575 CALLB_CPR_SAFE_BEGIN(&cpr
);
4576 (void) cv_timedwait(&l2arc_feed_thr_cv
, &l2arc_feed_thr_lock
,
4578 CALLB_CPR_SAFE_END(&cpr
, &l2arc_feed_thr_lock
);
4579 next
= ddi_get_lbolt() + hz
;
4582 * Quick check for L2ARC devices.
4584 mutex_enter(&l2arc_dev_mtx
);
4585 if (l2arc_ndev
== 0) {
4586 mutex_exit(&l2arc_dev_mtx
);
4589 mutex_exit(&l2arc_dev_mtx
);
4590 begin
= ddi_get_lbolt();
4593 * This selects the next l2arc device to write to, and in
4594 * doing so the next spa to feed from: dev->l2ad_spa. This
4595 * will return NULL if there are now no l2arc devices or if
4596 * they are all faulted.
4598 * If a device is returned, its spa's config lock is also
4599 * held to prevent device removal. l2arc_dev_get_next()
4600 * will grab and release l2arc_dev_mtx.
4602 if ((dev
= l2arc_dev_get_next()) == NULL
)
4605 spa
= dev
->l2ad_spa
;
4606 ASSERT(spa
!= NULL
);
4609 * If the pool is read-only then force the feed thread to
4610 * sleep a little longer.
4612 if (!spa_writeable(spa
)) {
4613 next
= ddi_get_lbolt() + 5 * l2arc_feed_secs
* hz
;
4614 spa_config_exit(spa
, SCL_L2ARC
, dev
);
4619 * Avoid contributing to memory pressure.
4621 if (arc_reclaim_needed()) {
4622 ARCSTAT_BUMP(arcstat_l2_abort_lowmem
);
4623 spa_config_exit(spa
, SCL_L2ARC
, dev
);
4627 ARCSTAT_BUMP(arcstat_l2_feeds
);
4629 size
= l2arc_write_size(dev
);
4632 * Evict L2ARC buffers that will be overwritten.
4634 l2arc_evict(dev
, size
, B_FALSE
);
4637 * Write ARC buffers.
4639 wrote
= l2arc_write_buffers(spa
, dev
, size
);
4642 * Calculate interval between writes.
4644 next
= l2arc_write_interval(begin
, size
, wrote
);
4645 spa_config_exit(spa
, SCL_L2ARC
, dev
);
4648 l2arc_thread_exit
= 0;
4649 cv_broadcast(&l2arc_feed_thr_cv
);
4650 CALLB_CPR_EXIT(&cpr
); /* drops l2arc_feed_thr_lock */
4655 l2arc_vdev_present(vdev_t
*vd
)
4659 mutex_enter(&l2arc_dev_mtx
);
4660 for (dev
= list_head(l2arc_dev_list
); dev
!= NULL
;
4661 dev
= list_next(l2arc_dev_list
, dev
)) {
4662 if (dev
->l2ad_vdev
== vd
)
4665 mutex_exit(&l2arc_dev_mtx
);
4667 return (dev
!= NULL
);
4671 * Add a vdev for use by the L2ARC. By this point the spa has already
4672 * validated the vdev and opened it.
4675 l2arc_add_vdev(spa_t
*spa
, vdev_t
*vd
)
4677 l2arc_dev_t
*adddev
;
4679 ASSERT(!l2arc_vdev_present(vd
));
4682 * Create a new l2arc device entry.
4684 adddev
= kmem_zalloc(sizeof (l2arc_dev_t
), KM_SLEEP
);
4685 adddev
->l2ad_spa
= spa
;
4686 adddev
->l2ad_vdev
= vd
;
4687 adddev
->l2ad_write
= l2arc_write_max
;
4688 adddev
->l2ad_boost
= l2arc_write_boost
;
4689 adddev
->l2ad_start
= VDEV_LABEL_START_SIZE
;
4690 adddev
->l2ad_end
= VDEV_LABEL_START_SIZE
+ vdev_get_min_asize(vd
);
4691 adddev
->l2ad_hand
= adddev
->l2ad_start
;
4692 adddev
->l2ad_evict
= adddev
->l2ad_start
;
4693 adddev
->l2ad_first
= B_TRUE
;
4694 adddev
->l2ad_writing
= B_FALSE
;
4695 ASSERT3U(adddev
->l2ad_write
, >, 0);
4698 * This is a list of all ARC buffers that are still valid on the
4701 adddev
->l2ad_buflist
= kmem_zalloc(sizeof (list_t
), KM_SLEEP
);
4702 list_create(adddev
->l2ad_buflist
, sizeof (arc_buf_hdr_t
),
4703 offsetof(arc_buf_hdr_t
, b_l2node
));
4705 vdev_space_update(vd
, 0, 0, adddev
->l2ad_end
- adddev
->l2ad_hand
);
4708 * Add device to global list
4710 mutex_enter(&l2arc_dev_mtx
);
4711 list_insert_head(l2arc_dev_list
, adddev
);
4712 atomic_inc_64(&l2arc_ndev
);
4713 mutex_exit(&l2arc_dev_mtx
);
4717 * Remove a vdev from the L2ARC.
4720 l2arc_remove_vdev(vdev_t
*vd
)
4722 l2arc_dev_t
*dev
, *nextdev
, *remdev
= NULL
;
4725 * Find the device by vdev
4727 mutex_enter(&l2arc_dev_mtx
);
4728 for (dev
= list_head(l2arc_dev_list
); dev
; dev
= nextdev
) {
4729 nextdev
= list_next(l2arc_dev_list
, dev
);
4730 if (vd
== dev
->l2ad_vdev
) {
4735 ASSERT(remdev
!= NULL
);
4738 * Remove device from global list
4740 list_remove(l2arc_dev_list
, remdev
);
4741 l2arc_dev_last
= NULL
; /* may have been invalidated */
4742 atomic_dec_64(&l2arc_ndev
);
4743 mutex_exit(&l2arc_dev_mtx
);
4746 * Clear all buflists and ARC references. L2ARC device flush.
4748 l2arc_evict(remdev
, 0, B_TRUE
);
4749 list_destroy(remdev
->l2ad_buflist
);
4750 kmem_free(remdev
->l2ad_buflist
, sizeof (list_t
));
4751 kmem_free(remdev
, sizeof (l2arc_dev_t
));
4757 l2arc_thread_exit
= 0;
4759 l2arc_writes_sent
= 0;
4760 l2arc_writes_done
= 0;
4762 mutex_init(&l2arc_feed_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
4763 cv_init(&l2arc_feed_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
4764 mutex_init(&l2arc_dev_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4765 mutex_init(&l2arc_buflist_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4766 mutex_init(&l2arc_free_on_write_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
4768 l2arc_dev_list
= &L2ARC_dev_list
;
4769 l2arc_free_on_write
= &L2ARC_free_on_write
;
4770 list_create(l2arc_dev_list
, sizeof (l2arc_dev_t
),
4771 offsetof(l2arc_dev_t
, l2ad_node
));
4772 list_create(l2arc_free_on_write
, sizeof (l2arc_data_free_t
),
4773 offsetof(l2arc_data_free_t
, l2df_list_node
));
4780 * This is called from dmu_fini(), which is called from spa_fini();
4781 * Because of this, we can assume that all l2arc devices have
4782 * already been removed when the pools themselves were removed.
4785 l2arc_do_free_on_write();
4787 mutex_destroy(&l2arc_feed_thr_lock
);
4788 cv_destroy(&l2arc_feed_thr_cv
);
4789 mutex_destroy(&l2arc_dev_mtx
);
4790 mutex_destroy(&l2arc_buflist_mtx
);
4791 mutex_destroy(&l2arc_free_on_write_mtx
);
4793 list_destroy(l2arc_dev_list
);
4794 list_destroy(l2arc_free_on_write
);
4800 if (!(spa_mode_global
& FWRITE
))
4803 (void) thread_create(NULL
, 0, l2arc_feed_thread
, NULL
, 0, &p0
,
4804 TS_RUN
, minclsyspri
);
4810 if (!(spa_mode_global
& FWRITE
))
4813 mutex_enter(&l2arc_feed_thr_lock
);
4814 cv_signal(&l2arc_feed_thr_cv
); /* kick thread out of startup */
4815 l2arc_thread_exit
= 1;
4816 while (l2arc_thread_exit
!= 0)
4817 cv_wait(&l2arc_feed_thr_cv
, &l2arc_feed_thr_lock
);
4818 mutex_exit(&l2arc_feed_thr_lock
);