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) 2011 by Delphix. All rights reserved.
25 * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
29 * DVA-based Adjustable Replacement Cache
31 * While much of the theory of operation used here is
32 * based on the self-tuning, low overhead replacement cache
33 * presented by Megiddo and Modha at FAST 2003, there are some
34 * significant differences:
36 * 1. The Megiddo and Modha model assumes any page is evictable.
37 * Pages in its cache cannot be "locked" into memory. This makes
38 * the eviction algorithm simple: evict the last page in the list.
39 * This also make the performance characteristics easy to reason
40 * about. Our cache is not so simple. At any given moment, some
41 * subset of the blocks in the cache are un-evictable because we
42 * have handed out a reference to them. Blocks are only evictable
43 * when there are no external references active. This makes
44 * eviction far more problematic: we choose to evict the evictable
45 * blocks that are the "lowest" in the list.
47 * There are times when it is not possible to evict the requested
48 * space. In these circumstances we are unable to adjust the cache
49 * size. To prevent the cache growing unbounded at these times we
50 * implement a "cache throttle" that slows the flow of new data
51 * into the cache until we can make space available.
53 * 2. The Megiddo and Modha model assumes a fixed cache size.
54 * Pages are evicted when the cache is full and there is a cache
55 * miss. Our model has a variable sized cache. It grows with
56 * high use, but also tries to react to memory pressure from the
57 * operating system: decreasing its size when system memory is
60 * 3. The Megiddo and Modha model assumes a fixed page size. All
61 * elements of the cache are therefor exactly the same size. So
62 * when adjusting the cache size following a cache miss, its simply
63 * a matter of choosing a single page to evict. In our model, we
64 * have variable sized cache blocks (rangeing from 512 bytes to
65 * 128K bytes). We therefor choose a set of blocks to evict to make
66 * space for a cache miss that approximates as closely as possible
67 * the space used by the new block.
69 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
70 * by N. Megiddo & D. Modha, FAST 2003
76 * A new reference to a cache buffer can be obtained in two
77 * ways: 1) via a hash table lookup using the DVA as a key,
78 * or 2) via one of the ARC lists. The arc_read() interface
79 * uses method 1, while the internal arc algorithms for
80 * adjusting the cache use method 2. We therefor provide two
81 * types of locks: 1) the hash table lock array, and 2) the
84 * Buffers do not have their own mutexes, rather they rely on the
85 * hash table mutexes for the bulk of their protection (i.e. most
86 * fields in the arc_buf_hdr_t are protected by these mutexes).
88 * buf_hash_find() returns the appropriate mutex (held) when it
89 * locates the requested buffer in the hash table. It returns
90 * NULL for the mutex if the buffer was not in the table.
92 * buf_hash_remove() expects the appropriate hash mutex to be
93 * already held before it is invoked.
95 * Each arc state also has a mutex which is used to protect the
96 * buffer list associated with the state. When attempting to
97 * obtain a hash table lock while holding an arc list lock you
98 * must use: mutex_tryenter() to avoid deadlock. Also note that
99 * the active state mutex must be held before the ghost state mutex.
101 * Arc buffers may have an associated eviction callback function.
102 * This function will be invoked prior to removing the buffer (e.g.
103 * in arc_do_user_evicts()). Note however that the data associated
104 * with the buffer may be evicted prior to the callback. The callback
105 * must be made with *no locks held* (to prevent deadlock). Additionally,
106 * the users of callbacks must ensure that their private data is
107 * protected from simultaneous callbacks from arc_buf_evict()
108 * and arc_do_user_evicts().
110 * It as also possible to register a callback which is run when the
111 * arc_meta_limit is reached and no buffers can be safely evicted. In
112 * this case the arc user should drop a reference on some arc buffers so
113 * they can be reclaimed and the arc_meta_limit honored. For example,
114 * when using the ZPL each dentry holds a references on a znode. These
115 * dentries must be pruned before the arc buffer holding the znode can
118 * Note that the majority of the performance stats are manipulated
119 * with atomic operations.
121 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
123 * - L2ARC buflist creation
124 * - L2ARC buflist eviction
125 * - L2ARC write completion, which walks L2ARC buflists
126 * - ARC header destruction, as it removes from L2ARC buflists
127 * - ARC header release, as it removes from L2ARC buflists
132 #include <sys/zio_compress.h>
133 #include <sys/zfs_context.h>
135 #include <sys/vdev.h>
136 #include <sys/vdev_impl.h>
138 #include <sys/vmsystm.h>
140 #include <sys/fs/swapnode.h>
143 #include <sys/callb.h>
144 #include <sys/kstat.h>
145 #include <sys/dmu_tx.h>
146 #include <zfs_fletcher.h>
148 static kmutex_t arc_reclaim_thr_lock
;
149 static kcondvar_t arc_reclaim_thr_cv
; /* used to signal reclaim thr */
150 static uint8_t arc_thread_exit
;
152 /* number of bytes to prune from caches when at arc_meta_limit is reached */
153 int zfs_arc_meta_prune
= 1048576;
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 int zfs_arc_grow_retry
= 5;
163 /* shift of arc_c for calculating both min and max arc_p */
164 int zfs_arc_p_min_shift
= 4;
166 /* log2(fraction of arc to reclaim) */
167 int zfs_arc_shrink_shift
= 5;
170 * minimum lifespan of a prefetch block in clock ticks
171 * (initialized in arc_init())
173 int zfs_arc_min_prefetch_lifespan
= HZ
;
175 /* disable arc proactive arc throttle due to low memory */
176 int zfs_arc_memory_throttle_disable
= 1;
178 /* disable duplicate buffer eviction */
179 int zfs_disable_dup_eviction
= 0;
183 /* expiration time for arc_no_grow */
184 static clock_t arc_grow_time
= 0;
187 * The arc has filled available memory and has now warmed up.
189 static boolean_t arc_warm
;
192 * These tunables are for performance analysis.
194 unsigned long zfs_arc_max
= 0;
195 unsigned long zfs_arc_min
= 0;
196 unsigned long zfs_arc_meta_limit
= 0;
199 * Note that buffers can be in one of 6 states:
200 * ARC_anon - anonymous (discussed below)
201 * ARC_mru - recently used, currently cached
202 * ARC_mru_ghost - recentely used, no longer in cache
203 * ARC_mfu - frequently used, currently cached
204 * ARC_mfu_ghost - frequently used, no longer in cache
205 * ARC_l2c_only - exists in L2ARC but not other states
206 * When there are no active references to the buffer, they are
207 * are linked onto a list in one of these arc states. These are
208 * the only buffers that can be evicted or deleted. Within each
209 * state there are multiple lists, one for meta-data and one for
210 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
211 * etc.) is tracked separately so that it can be managed more
212 * explicitly: favored over data, limited explicitly.
214 * Anonymous buffers are buffers that are not associated with
215 * a DVA. These are buffers that hold dirty block copies
216 * before they are written to stable storage. By definition,
217 * they are "ref'd" and are considered part of arc_mru
218 * that cannot be freed. Generally, they will aquire a DVA
219 * as they are written and migrate onto the arc_mru list.
221 * The ARC_l2c_only state is for buffers that are in the second
222 * level ARC but no longer in any of the ARC_m* lists. The second
223 * level ARC itself may also contain buffers that are in any of
224 * the ARC_m* states - meaning that a buffer can exist in two
225 * places. The reason for the ARC_l2c_only state is to keep the
226 * buffer header in the hash table, so that reads that hit the
227 * second level ARC benefit from these fast lookups.
230 typedef struct arc_state
{
231 list_t arcs_list
[ARC_BUFC_NUMTYPES
]; /* list of evictable buffers */
232 uint64_t arcs_lsize
[ARC_BUFC_NUMTYPES
]; /* amount of evictable data */
233 uint64_t arcs_size
; /* total amount of data in this state */
238 static arc_state_t ARC_anon
;
239 static arc_state_t ARC_mru
;
240 static arc_state_t ARC_mru_ghost
;
241 static arc_state_t ARC_mfu
;
242 static arc_state_t ARC_mfu_ghost
;
243 static arc_state_t ARC_l2c_only
;
245 typedef struct arc_stats
{
246 kstat_named_t arcstat_hits
;
247 kstat_named_t arcstat_misses
;
248 kstat_named_t arcstat_demand_data_hits
;
249 kstat_named_t arcstat_demand_data_misses
;
250 kstat_named_t arcstat_demand_metadata_hits
;
251 kstat_named_t arcstat_demand_metadata_misses
;
252 kstat_named_t arcstat_prefetch_data_hits
;
253 kstat_named_t arcstat_prefetch_data_misses
;
254 kstat_named_t arcstat_prefetch_metadata_hits
;
255 kstat_named_t arcstat_prefetch_metadata_misses
;
256 kstat_named_t arcstat_mru_hits
;
257 kstat_named_t arcstat_mru_ghost_hits
;
258 kstat_named_t arcstat_mfu_hits
;
259 kstat_named_t arcstat_mfu_ghost_hits
;
260 kstat_named_t arcstat_deleted
;
261 kstat_named_t arcstat_recycle_miss
;
262 kstat_named_t arcstat_mutex_miss
;
263 kstat_named_t arcstat_evict_skip
;
264 kstat_named_t arcstat_evict_l2_cached
;
265 kstat_named_t arcstat_evict_l2_eligible
;
266 kstat_named_t arcstat_evict_l2_ineligible
;
267 kstat_named_t arcstat_hash_elements
;
268 kstat_named_t arcstat_hash_elements_max
;
269 kstat_named_t arcstat_hash_collisions
;
270 kstat_named_t arcstat_hash_chains
;
271 kstat_named_t arcstat_hash_chain_max
;
272 kstat_named_t arcstat_p
;
273 kstat_named_t arcstat_c
;
274 kstat_named_t arcstat_c_min
;
275 kstat_named_t arcstat_c_max
;
276 kstat_named_t arcstat_size
;
277 kstat_named_t arcstat_hdr_size
;
278 kstat_named_t arcstat_data_size
;
279 kstat_named_t arcstat_other_size
;
280 kstat_named_t arcstat_anon_size
;
281 kstat_named_t arcstat_anon_evict_data
;
282 kstat_named_t arcstat_anon_evict_metadata
;
283 kstat_named_t arcstat_mru_size
;
284 kstat_named_t arcstat_mru_evict_data
;
285 kstat_named_t arcstat_mru_evict_metadata
;
286 kstat_named_t arcstat_mru_ghost_size
;
287 kstat_named_t arcstat_mru_ghost_evict_data
;
288 kstat_named_t arcstat_mru_ghost_evict_metadata
;
289 kstat_named_t arcstat_mfu_size
;
290 kstat_named_t arcstat_mfu_evict_data
;
291 kstat_named_t arcstat_mfu_evict_metadata
;
292 kstat_named_t arcstat_mfu_ghost_size
;
293 kstat_named_t arcstat_mfu_ghost_evict_data
;
294 kstat_named_t arcstat_mfu_ghost_evict_metadata
;
295 kstat_named_t arcstat_l2_hits
;
296 kstat_named_t arcstat_l2_misses
;
297 kstat_named_t arcstat_l2_feeds
;
298 kstat_named_t arcstat_l2_rw_clash
;
299 kstat_named_t arcstat_l2_read_bytes
;
300 kstat_named_t arcstat_l2_write_bytes
;
301 kstat_named_t arcstat_l2_writes_sent
;
302 kstat_named_t arcstat_l2_writes_done
;
303 kstat_named_t arcstat_l2_writes_error
;
304 kstat_named_t arcstat_l2_writes_hdr_miss
;
305 kstat_named_t arcstat_l2_evict_lock_retry
;
306 kstat_named_t arcstat_l2_evict_reading
;
307 kstat_named_t arcstat_l2_free_on_write
;
308 kstat_named_t arcstat_l2_abort_lowmem
;
309 kstat_named_t arcstat_l2_cksum_bad
;
310 kstat_named_t arcstat_l2_io_error
;
311 kstat_named_t arcstat_l2_size
;
312 kstat_named_t arcstat_l2_asize
;
313 kstat_named_t arcstat_l2_hdr_size
;
314 kstat_named_t arcstat_l2_compress_successes
;
315 kstat_named_t arcstat_l2_compress_zeros
;
316 kstat_named_t arcstat_l2_compress_failures
;
317 kstat_named_t arcstat_memory_throttle_count
;
318 kstat_named_t arcstat_duplicate_buffers
;
319 kstat_named_t arcstat_duplicate_buffers_size
;
320 kstat_named_t arcstat_duplicate_reads
;
321 kstat_named_t arcstat_memory_direct_count
;
322 kstat_named_t arcstat_memory_indirect_count
;
323 kstat_named_t arcstat_no_grow
;
324 kstat_named_t arcstat_tempreserve
;
325 kstat_named_t arcstat_loaned_bytes
;
326 kstat_named_t arcstat_prune
;
327 kstat_named_t arcstat_meta_used
;
328 kstat_named_t arcstat_meta_limit
;
329 kstat_named_t arcstat_meta_max
;
332 static arc_stats_t arc_stats
= {
333 { "hits", KSTAT_DATA_UINT64
},
334 { "misses", KSTAT_DATA_UINT64
},
335 { "demand_data_hits", KSTAT_DATA_UINT64
},
336 { "demand_data_misses", KSTAT_DATA_UINT64
},
337 { "demand_metadata_hits", KSTAT_DATA_UINT64
},
338 { "demand_metadata_misses", KSTAT_DATA_UINT64
},
339 { "prefetch_data_hits", KSTAT_DATA_UINT64
},
340 { "prefetch_data_misses", KSTAT_DATA_UINT64
},
341 { "prefetch_metadata_hits", KSTAT_DATA_UINT64
},
342 { "prefetch_metadata_misses", KSTAT_DATA_UINT64
},
343 { "mru_hits", KSTAT_DATA_UINT64
},
344 { "mru_ghost_hits", KSTAT_DATA_UINT64
},
345 { "mfu_hits", KSTAT_DATA_UINT64
},
346 { "mfu_ghost_hits", KSTAT_DATA_UINT64
},
347 { "deleted", KSTAT_DATA_UINT64
},
348 { "recycle_miss", KSTAT_DATA_UINT64
},
349 { "mutex_miss", KSTAT_DATA_UINT64
},
350 { "evict_skip", KSTAT_DATA_UINT64
},
351 { "evict_l2_cached", KSTAT_DATA_UINT64
},
352 { "evict_l2_eligible", KSTAT_DATA_UINT64
},
353 { "evict_l2_ineligible", KSTAT_DATA_UINT64
},
354 { "hash_elements", KSTAT_DATA_UINT64
},
355 { "hash_elements_max", KSTAT_DATA_UINT64
},
356 { "hash_collisions", KSTAT_DATA_UINT64
},
357 { "hash_chains", KSTAT_DATA_UINT64
},
358 { "hash_chain_max", KSTAT_DATA_UINT64
},
359 { "p", KSTAT_DATA_UINT64
},
360 { "c", KSTAT_DATA_UINT64
},
361 { "c_min", KSTAT_DATA_UINT64
},
362 { "c_max", KSTAT_DATA_UINT64
},
363 { "size", KSTAT_DATA_UINT64
},
364 { "hdr_size", KSTAT_DATA_UINT64
},
365 { "data_size", KSTAT_DATA_UINT64
},
366 { "other_size", KSTAT_DATA_UINT64
},
367 { "anon_size", KSTAT_DATA_UINT64
},
368 { "anon_evict_data", KSTAT_DATA_UINT64
},
369 { "anon_evict_metadata", KSTAT_DATA_UINT64
},
370 { "mru_size", KSTAT_DATA_UINT64
},
371 { "mru_evict_data", KSTAT_DATA_UINT64
},
372 { "mru_evict_metadata", KSTAT_DATA_UINT64
},
373 { "mru_ghost_size", KSTAT_DATA_UINT64
},
374 { "mru_ghost_evict_data", KSTAT_DATA_UINT64
},
375 { "mru_ghost_evict_metadata", KSTAT_DATA_UINT64
},
376 { "mfu_size", KSTAT_DATA_UINT64
},
377 { "mfu_evict_data", KSTAT_DATA_UINT64
},
378 { "mfu_evict_metadata", KSTAT_DATA_UINT64
},
379 { "mfu_ghost_size", KSTAT_DATA_UINT64
},
380 { "mfu_ghost_evict_data", KSTAT_DATA_UINT64
},
381 { "mfu_ghost_evict_metadata", KSTAT_DATA_UINT64
},
382 { "l2_hits", KSTAT_DATA_UINT64
},
383 { "l2_misses", KSTAT_DATA_UINT64
},
384 { "l2_feeds", KSTAT_DATA_UINT64
},
385 { "l2_rw_clash", KSTAT_DATA_UINT64
},
386 { "l2_read_bytes", KSTAT_DATA_UINT64
},
387 { "l2_write_bytes", KSTAT_DATA_UINT64
},
388 { "l2_writes_sent", KSTAT_DATA_UINT64
},
389 { "l2_writes_done", KSTAT_DATA_UINT64
},
390 { "l2_writes_error", KSTAT_DATA_UINT64
},
391 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64
},
392 { "l2_evict_lock_retry", KSTAT_DATA_UINT64
},
393 { "l2_evict_reading", KSTAT_DATA_UINT64
},
394 { "l2_free_on_write", KSTAT_DATA_UINT64
},
395 { "l2_abort_lowmem", KSTAT_DATA_UINT64
},
396 { "l2_cksum_bad", KSTAT_DATA_UINT64
},
397 { "l2_io_error", KSTAT_DATA_UINT64
},
398 { "l2_size", KSTAT_DATA_UINT64
},
399 { "l2_asize", KSTAT_DATA_UINT64
},
400 { "l2_hdr_size", KSTAT_DATA_UINT64
},
401 { "l2_compress_successes", KSTAT_DATA_UINT64
},
402 { "l2_compress_zeros", KSTAT_DATA_UINT64
},
403 { "l2_compress_failures", KSTAT_DATA_UINT64
},
404 { "memory_throttle_count", KSTAT_DATA_UINT64
},
405 { "duplicate_buffers", KSTAT_DATA_UINT64
},
406 { "duplicate_buffers_size", KSTAT_DATA_UINT64
},
407 { "duplicate_reads", KSTAT_DATA_UINT64
},
408 { "memory_direct_count", KSTAT_DATA_UINT64
},
409 { "memory_indirect_count", KSTAT_DATA_UINT64
},
410 { "arc_no_grow", KSTAT_DATA_UINT64
},
411 { "arc_tempreserve", KSTAT_DATA_UINT64
},
412 { "arc_loaned_bytes", KSTAT_DATA_UINT64
},
413 { "arc_prune", KSTAT_DATA_UINT64
},
414 { "arc_meta_used", KSTAT_DATA_UINT64
},
415 { "arc_meta_limit", KSTAT_DATA_UINT64
},
416 { "arc_meta_max", KSTAT_DATA_UINT64
},
419 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
421 #define ARCSTAT_INCR(stat, val) \
422 atomic_add_64(&arc_stats.stat.value.ui64, (val));
424 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
425 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
427 #define ARCSTAT_MAX(stat, val) { \
429 while ((val) > (m = arc_stats.stat.value.ui64) && \
430 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
434 #define ARCSTAT_MAXSTAT(stat) \
435 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
438 * We define a macro to allow ARC hits/misses to be easily broken down by
439 * two separate conditions, giving a total of four different subtypes for
440 * each of hits and misses (so eight statistics total).
442 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
445 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
447 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
451 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
453 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
458 static arc_state_t
*arc_anon
;
459 static arc_state_t
*arc_mru
;
460 static arc_state_t
*arc_mru_ghost
;
461 static arc_state_t
*arc_mfu
;
462 static arc_state_t
*arc_mfu_ghost
;
463 static arc_state_t
*arc_l2c_only
;
466 * There are several ARC variables that are critical to export as kstats --
467 * but we don't want to have to grovel around in the kstat whenever we wish to
468 * manipulate them. For these variables, we therefore define them to be in
469 * terms of the statistic variable. This assures that we are not introducing
470 * the possibility of inconsistency by having shadow copies of the variables,
471 * while still allowing the code to be readable.
473 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
474 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
475 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
476 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
477 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
478 #define arc_no_grow ARCSTAT(arcstat_no_grow)
479 #define arc_tempreserve ARCSTAT(arcstat_tempreserve)
480 #define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
481 #define arc_meta_used ARCSTAT(arcstat_meta_used)
482 #define arc_meta_limit ARCSTAT(arcstat_meta_limit)
483 #define arc_meta_max ARCSTAT(arcstat_meta_max)
485 #define L2ARC_IS_VALID_COMPRESS(_c_) \
486 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
488 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t
;
490 typedef struct arc_callback arc_callback_t
;
492 struct arc_callback
{
494 arc_done_func_t
*acb_done
;
496 zio_t
*acb_zio_dummy
;
497 arc_callback_t
*acb_next
;
500 typedef struct arc_write_callback arc_write_callback_t
;
502 struct arc_write_callback
{
504 arc_done_func_t
*awcb_ready
;
505 arc_done_func_t
*awcb_done
;
510 /* protected by hash lock */
515 kmutex_t b_freeze_lock
;
516 zio_cksum_t
*b_freeze_cksum
;
518 arc_buf_hdr_t
*b_hash_next
;
523 arc_callback_t
*b_acb
;
527 arc_buf_contents_t b_type
;
531 /* protected by arc state mutex */
532 arc_state_t
*b_state
;
533 list_node_t b_arc_node
;
535 /* updated atomically */
536 clock_t b_arc_access
;
538 /* self protecting */
541 l2arc_buf_hdr_t
*b_l2hdr
;
542 list_node_t b_l2node
;
545 static list_t arc_prune_list
;
546 static kmutex_t arc_prune_mtx
;
547 static arc_buf_t
*arc_eviction_list
;
548 static kmutex_t arc_eviction_mtx
;
549 static arc_buf_hdr_t arc_eviction_hdr
;
550 static void arc_get_data_buf(arc_buf_t
*buf
);
551 static void arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
);
552 static int arc_evict_needed(arc_buf_contents_t type
);
553 static void arc_evict_ghost(arc_state_t
*state
, uint64_t spa
, int64_t bytes
,
554 arc_buf_contents_t type
);
556 static boolean_t
l2arc_write_eligible(uint64_t spa_guid
, arc_buf_hdr_t
*ab
);
558 #define GHOST_STATE(state) \
559 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
560 (state) == arc_l2c_only)
563 * Private ARC flags. These flags are private ARC only flags that will show up
564 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
565 * be passed in as arc_flags in things like arc_read. However, these flags
566 * should never be passed and should only be set by ARC code. When adding new
567 * public flags, make sure not to smash the private ones.
570 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
571 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
572 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
573 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
574 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
575 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
576 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
577 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
578 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
579 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
581 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
582 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
583 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
584 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
585 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
586 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
587 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
588 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
589 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
590 (hdr)->b_l2hdr != NULL)
591 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
592 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
593 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
599 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
600 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
603 * Hash table routines
606 #define HT_LOCK_ALIGN 64
607 #define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
612 unsigned char pad
[HT_LOCK_PAD
];
616 #define BUF_LOCKS 256
617 typedef struct buf_hash_table
{
619 arc_buf_hdr_t
**ht_table
;
620 struct ht_lock ht_locks
[BUF_LOCKS
];
623 static buf_hash_table_t buf_hash_table
;
625 #define BUF_HASH_INDEX(spa, dva, birth) \
626 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
627 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
628 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
629 #define HDR_LOCK(hdr) \
630 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
632 uint64_t zfs_crc64_table
[256];
638 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
639 #define L2ARC_HEADROOM 2 /* num of writes */
641 * If we discover during ARC scan any buffers to be compressed, we boost
642 * our headroom for the next scanning cycle by this percentage multiple.
644 #define L2ARC_HEADROOM_BOOST 200
645 #define L2ARC_FEED_SECS 1 /* caching interval secs */
646 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
648 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
649 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
652 * L2ARC Performance Tunables
654 unsigned long l2arc_write_max
= L2ARC_WRITE_SIZE
; /* def max write size */
655 unsigned long l2arc_write_boost
= L2ARC_WRITE_SIZE
; /* extra warmup write */
656 unsigned long l2arc_headroom
= L2ARC_HEADROOM
; /* # of dev writes */
657 unsigned long l2arc_headroom_boost
= L2ARC_HEADROOM_BOOST
;
658 unsigned long l2arc_feed_secs
= L2ARC_FEED_SECS
; /* interval seconds */
659 unsigned long l2arc_feed_min_ms
= L2ARC_FEED_MIN_MS
; /* min interval msecs */
660 int l2arc_noprefetch
= B_TRUE
; /* don't cache prefetch bufs */
661 int l2arc_nocompress
= B_FALSE
; /* don't compress bufs */
662 int l2arc_feed_again
= B_TRUE
; /* turbo warmup */
663 int l2arc_norw
= B_FALSE
; /* no reads during writes */
668 typedef struct l2arc_dev
{
669 vdev_t
*l2ad_vdev
; /* vdev */
670 spa_t
*l2ad_spa
; /* spa */
671 uint64_t l2ad_hand
; /* next write location */
672 uint64_t l2ad_start
; /* first addr on device */
673 uint64_t l2ad_end
; /* last addr on device */
674 uint64_t l2ad_evict
; /* last addr eviction reached */
675 boolean_t l2ad_first
; /* first sweep through */
676 boolean_t l2ad_writing
; /* currently writing */
677 list_t
*l2ad_buflist
; /* buffer list */
678 list_node_t l2ad_node
; /* device list node */
681 static list_t L2ARC_dev_list
; /* device list */
682 static list_t
*l2arc_dev_list
; /* device list pointer */
683 static kmutex_t l2arc_dev_mtx
; /* device list mutex */
684 static l2arc_dev_t
*l2arc_dev_last
; /* last device used */
685 static kmutex_t l2arc_buflist_mtx
; /* mutex for all buflists */
686 static list_t L2ARC_free_on_write
; /* free after write buf list */
687 static list_t
*l2arc_free_on_write
; /* free after write list ptr */
688 static kmutex_t l2arc_free_on_write_mtx
; /* mutex for list */
689 static uint64_t l2arc_ndev
; /* number of devices */
691 typedef struct l2arc_read_callback
{
692 arc_buf_t
*l2rcb_buf
; /* read buffer */
693 spa_t
*l2rcb_spa
; /* spa */
694 blkptr_t l2rcb_bp
; /* original blkptr */
695 zbookmark_t l2rcb_zb
; /* original bookmark */
696 int l2rcb_flags
; /* original flags */
697 enum zio_compress l2rcb_compress
; /* applied compress */
698 } l2arc_read_callback_t
;
700 typedef struct l2arc_write_callback
{
701 l2arc_dev_t
*l2wcb_dev
; /* device info */
702 arc_buf_hdr_t
*l2wcb_head
; /* head of write buflist */
703 } l2arc_write_callback_t
;
705 struct l2arc_buf_hdr
{
706 /* protected by arc_buf_hdr mutex */
707 l2arc_dev_t
*b_dev
; /* L2ARC device */
708 uint64_t b_daddr
; /* disk address, offset byte */
709 /* compression applied to buffer data */
710 enum zio_compress b_compress
;
711 /* real alloc'd buffer size depending on b_compress applied */
713 /* temporary buffer holder for in-flight compressed data */
717 typedef struct l2arc_data_free
{
718 /* protected by l2arc_free_on_write_mtx */
721 void (*l2df_func
)(void *, size_t);
722 list_node_t l2df_list_node
;
725 static kmutex_t l2arc_feed_thr_lock
;
726 static kcondvar_t l2arc_feed_thr_cv
;
727 static uint8_t l2arc_thread_exit
;
729 static void l2arc_read_done(zio_t
*zio
);
730 static void l2arc_hdr_stat_add(void);
731 static void l2arc_hdr_stat_remove(void);
733 static boolean_t
l2arc_compress_buf(l2arc_buf_hdr_t
*l2hdr
);
734 static void l2arc_decompress_zio(zio_t
*zio
, arc_buf_hdr_t
*hdr
,
735 enum zio_compress c
);
736 static void l2arc_release_cdata_buf(arc_buf_hdr_t
*ab
);
739 buf_hash(uint64_t spa
, const dva_t
*dva
, uint64_t birth
)
741 uint8_t *vdva
= (uint8_t *)dva
;
742 uint64_t crc
= -1ULL;
745 ASSERT(zfs_crc64_table
[128] == ZFS_CRC64_POLY
);
747 for (i
= 0; i
< sizeof (dva_t
); i
++)
748 crc
= (crc
>> 8) ^ zfs_crc64_table
[(crc
^ vdva
[i
]) & 0xFF];
750 crc
^= (spa
>>8) ^ birth
;
755 #define BUF_EMPTY(buf) \
756 ((buf)->b_dva.dva_word[0] == 0 && \
757 (buf)->b_dva.dva_word[1] == 0 && \
760 #define BUF_EQUAL(spa, dva, birth, buf) \
761 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
762 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
763 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
766 buf_discard_identity(arc_buf_hdr_t
*hdr
)
768 hdr
->b_dva
.dva_word
[0] = 0;
769 hdr
->b_dva
.dva_word
[1] = 0;
774 static arc_buf_hdr_t
*
775 buf_hash_find(uint64_t spa
, const dva_t
*dva
, uint64_t birth
, kmutex_t
**lockp
)
777 uint64_t idx
= BUF_HASH_INDEX(spa
, dva
, birth
);
778 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
781 mutex_enter(hash_lock
);
782 for (buf
= buf_hash_table
.ht_table
[idx
]; buf
!= NULL
;
783 buf
= buf
->b_hash_next
) {
784 if (BUF_EQUAL(spa
, dva
, birth
, buf
)) {
789 mutex_exit(hash_lock
);
795 * Insert an entry into the hash table. If there is already an element
796 * equal to elem in the hash table, then the already existing element
797 * will be returned and the new element will not be inserted.
798 * Otherwise returns NULL.
800 static arc_buf_hdr_t
*
801 buf_hash_insert(arc_buf_hdr_t
*buf
, kmutex_t
**lockp
)
803 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
804 kmutex_t
*hash_lock
= BUF_HASH_LOCK(idx
);
808 ASSERT(!HDR_IN_HASH_TABLE(buf
));
810 mutex_enter(hash_lock
);
811 for (fbuf
= buf_hash_table
.ht_table
[idx
], i
= 0; fbuf
!= NULL
;
812 fbuf
= fbuf
->b_hash_next
, i
++) {
813 if (BUF_EQUAL(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
, fbuf
))
817 buf
->b_hash_next
= buf_hash_table
.ht_table
[idx
];
818 buf_hash_table
.ht_table
[idx
] = buf
;
819 buf
->b_flags
|= ARC_IN_HASH_TABLE
;
821 /* collect some hash table performance data */
823 ARCSTAT_BUMP(arcstat_hash_collisions
);
825 ARCSTAT_BUMP(arcstat_hash_chains
);
827 ARCSTAT_MAX(arcstat_hash_chain_max
, i
);
830 ARCSTAT_BUMP(arcstat_hash_elements
);
831 ARCSTAT_MAXSTAT(arcstat_hash_elements
);
837 buf_hash_remove(arc_buf_hdr_t
*buf
)
839 arc_buf_hdr_t
*fbuf
, **bufp
;
840 uint64_t idx
= BUF_HASH_INDEX(buf
->b_spa
, &buf
->b_dva
, buf
->b_birth
);
842 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx
)));
843 ASSERT(HDR_IN_HASH_TABLE(buf
));
845 bufp
= &buf_hash_table
.ht_table
[idx
];
846 while ((fbuf
= *bufp
) != buf
) {
847 ASSERT(fbuf
!= NULL
);
848 bufp
= &fbuf
->b_hash_next
;
850 *bufp
= buf
->b_hash_next
;
851 buf
->b_hash_next
= NULL
;
852 buf
->b_flags
&= ~ARC_IN_HASH_TABLE
;
854 /* collect some hash table performance data */
855 ARCSTAT_BUMPDOWN(arcstat_hash_elements
);
857 if (buf_hash_table
.ht_table
[idx
] &&
858 buf_hash_table
.ht_table
[idx
]->b_hash_next
== NULL
)
859 ARCSTAT_BUMPDOWN(arcstat_hash_chains
);
863 * Global data structures and functions for the buf kmem cache.
865 static kmem_cache_t
*hdr_cache
;
866 static kmem_cache_t
*buf_cache
;
873 #if defined(_KERNEL) && defined(HAVE_SPL)
874 /* Large allocations which do not require contiguous pages
875 * should be using vmem_free() in the linux kernel */
876 vmem_free(buf_hash_table
.ht_table
,
877 (buf_hash_table
.ht_mask
+ 1) * sizeof (void *));
879 kmem_free(buf_hash_table
.ht_table
,
880 (buf_hash_table
.ht_mask
+ 1) * sizeof (void *));
882 for (i
= 0; i
< BUF_LOCKS
; i
++)
883 mutex_destroy(&buf_hash_table
.ht_locks
[i
].ht_lock
);
884 kmem_cache_destroy(hdr_cache
);
885 kmem_cache_destroy(buf_cache
);
889 * Constructor callback - called when the cache is empty
890 * and a new buf is requested.
894 hdr_cons(void *vbuf
, void *unused
, int kmflag
)
896 arc_buf_hdr_t
*buf
= vbuf
;
898 bzero(buf
, sizeof (arc_buf_hdr_t
));
899 refcount_create(&buf
->b_refcnt
);
900 cv_init(&buf
->b_cv
, NULL
, CV_DEFAULT
, NULL
);
901 mutex_init(&buf
->b_freeze_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
902 list_link_init(&buf
->b_arc_node
);
903 list_link_init(&buf
->b_l2node
);
904 arc_space_consume(sizeof (arc_buf_hdr_t
), ARC_SPACE_HDRS
);
911 buf_cons(void *vbuf
, void *unused
, int kmflag
)
913 arc_buf_t
*buf
= vbuf
;
915 bzero(buf
, sizeof (arc_buf_t
));
916 mutex_init(&buf
->b_evict_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
917 arc_space_consume(sizeof (arc_buf_t
), ARC_SPACE_HDRS
);
923 * Destructor callback - called when a cached buf is
924 * no longer required.
928 hdr_dest(void *vbuf
, void *unused
)
930 arc_buf_hdr_t
*buf
= vbuf
;
932 ASSERT(BUF_EMPTY(buf
));
933 refcount_destroy(&buf
->b_refcnt
);
934 cv_destroy(&buf
->b_cv
);
935 mutex_destroy(&buf
->b_freeze_lock
);
936 arc_space_return(sizeof (arc_buf_hdr_t
), ARC_SPACE_HDRS
);
941 buf_dest(void *vbuf
, void *unused
)
943 arc_buf_t
*buf
= vbuf
;
945 mutex_destroy(&buf
->b_evict_lock
);
946 arc_space_return(sizeof (arc_buf_t
), ARC_SPACE_HDRS
);
953 uint64_t hsize
= 1ULL << 12;
957 * The hash table is big enough to fill all of physical memory
958 * with an average 64K block size. The table will take up
959 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
961 while (hsize
* 65536 < physmem
* PAGESIZE
)
964 buf_hash_table
.ht_mask
= hsize
- 1;
965 #if defined(_KERNEL) && defined(HAVE_SPL)
966 /* Large allocations which do not require contiguous pages
967 * should be using vmem_alloc() in the linux kernel */
968 buf_hash_table
.ht_table
=
969 vmem_zalloc(hsize
* sizeof (void*), KM_SLEEP
);
971 buf_hash_table
.ht_table
=
972 kmem_zalloc(hsize
* sizeof (void*), KM_NOSLEEP
);
974 if (buf_hash_table
.ht_table
== NULL
) {
975 ASSERT(hsize
> (1ULL << 8));
980 hdr_cache
= kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t
),
981 0, hdr_cons
, hdr_dest
, NULL
, NULL
, NULL
, 0);
982 buf_cache
= kmem_cache_create("arc_buf_t", sizeof (arc_buf_t
),
983 0, buf_cons
, buf_dest
, NULL
, NULL
, NULL
, 0);
985 for (i
= 0; i
< 256; i
++)
986 for (ct
= zfs_crc64_table
+ i
, *ct
= i
, j
= 8; j
> 0; j
--)
987 *ct
= (*ct
>> 1) ^ (-(*ct
& 1) & ZFS_CRC64_POLY
);
989 for (i
= 0; i
< BUF_LOCKS
; i
++) {
990 mutex_init(&buf_hash_table
.ht_locks
[i
].ht_lock
,
991 NULL
, MUTEX_DEFAULT
, NULL
);
995 #define ARC_MINTIME (hz>>4) /* 62 ms */
998 arc_cksum_verify(arc_buf_t
*buf
)
1002 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
1005 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
1006 if (buf
->b_hdr
->b_freeze_cksum
== NULL
||
1007 (buf
->b_hdr
->b_flags
& ARC_IO_ERROR
)) {
1008 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1011 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
1012 if (!ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
))
1013 panic("buffer modified while frozen!");
1014 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1018 arc_cksum_equal(arc_buf_t
*buf
)
1023 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
1024 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
, &zc
);
1025 equal
= ZIO_CHECKSUM_EQUAL(*buf
->b_hdr
->b_freeze_cksum
, zc
);
1026 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1032 arc_cksum_compute(arc_buf_t
*buf
, boolean_t force
)
1034 if (!force
&& !(zfs_flags
& ZFS_DEBUG_MODIFY
))
1037 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
1038 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
1039 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1042 buf
->b_hdr
->b_freeze_cksum
= kmem_alloc(sizeof (zio_cksum_t
),
1044 fletcher_2_native(buf
->b_data
, buf
->b_hdr
->b_size
,
1045 buf
->b_hdr
->b_freeze_cksum
);
1046 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1050 arc_buf_thaw(arc_buf_t
*buf
)
1052 if (zfs_flags
& ZFS_DEBUG_MODIFY
) {
1053 if (buf
->b_hdr
->b_state
!= arc_anon
)
1054 panic("modifying non-anon buffer!");
1055 if (buf
->b_hdr
->b_flags
& ARC_IO_IN_PROGRESS
)
1056 panic("modifying buffer while i/o in progress!");
1057 arc_cksum_verify(buf
);
1060 mutex_enter(&buf
->b_hdr
->b_freeze_lock
);
1061 if (buf
->b_hdr
->b_freeze_cksum
!= NULL
) {
1062 kmem_free(buf
->b_hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
1063 buf
->b_hdr
->b_freeze_cksum
= NULL
;
1066 mutex_exit(&buf
->b_hdr
->b_freeze_lock
);
1070 arc_buf_freeze(arc_buf_t
*buf
)
1072 kmutex_t
*hash_lock
;
1074 if (!(zfs_flags
& ZFS_DEBUG_MODIFY
))
1077 hash_lock
= HDR_LOCK(buf
->b_hdr
);
1078 mutex_enter(hash_lock
);
1080 ASSERT(buf
->b_hdr
->b_freeze_cksum
!= NULL
||
1081 buf
->b_hdr
->b_state
== arc_anon
);
1082 arc_cksum_compute(buf
, B_FALSE
);
1083 mutex_exit(hash_lock
);
1087 add_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
1089 ASSERT(MUTEX_HELD(hash_lock
));
1091 if ((refcount_add(&ab
->b_refcnt
, tag
) == 1) &&
1092 (ab
->b_state
!= arc_anon
)) {
1093 uint64_t delta
= ab
->b_size
* ab
->b_datacnt
;
1094 list_t
*list
= &ab
->b_state
->arcs_list
[ab
->b_type
];
1095 uint64_t *size
= &ab
->b_state
->arcs_lsize
[ab
->b_type
];
1097 ASSERT(!MUTEX_HELD(&ab
->b_state
->arcs_mtx
));
1098 mutex_enter(&ab
->b_state
->arcs_mtx
);
1099 ASSERT(list_link_active(&ab
->b_arc_node
));
1100 list_remove(list
, ab
);
1101 if (GHOST_STATE(ab
->b_state
)) {
1102 ASSERT0(ab
->b_datacnt
);
1103 ASSERT3P(ab
->b_buf
, ==, NULL
);
1107 ASSERT3U(*size
, >=, delta
);
1108 atomic_add_64(size
, -delta
);
1109 mutex_exit(&ab
->b_state
->arcs_mtx
);
1110 /* remove the prefetch flag if we get a reference */
1111 if (ab
->b_flags
& ARC_PREFETCH
)
1112 ab
->b_flags
&= ~ARC_PREFETCH
;
1117 remove_reference(arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
, void *tag
)
1120 arc_state_t
*state
= ab
->b_state
;
1122 ASSERT(state
== arc_anon
|| MUTEX_HELD(hash_lock
));
1123 ASSERT(!GHOST_STATE(state
));
1125 if (((cnt
= refcount_remove(&ab
->b_refcnt
, tag
)) == 0) &&
1126 (state
!= arc_anon
)) {
1127 uint64_t *size
= &state
->arcs_lsize
[ab
->b_type
];
1129 ASSERT(!MUTEX_HELD(&state
->arcs_mtx
));
1130 mutex_enter(&state
->arcs_mtx
);
1131 ASSERT(!list_link_active(&ab
->b_arc_node
));
1132 list_insert_head(&state
->arcs_list
[ab
->b_type
], ab
);
1133 ASSERT(ab
->b_datacnt
> 0);
1134 atomic_add_64(size
, ab
->b_size
* ab
->b_datacnt
);
1135 mutex_exit(&state
->arcs_mtx
);
1141 * Move the supplied buffer to the indicated state. The mutex
1142 * for the buffer must be held by the caller.
1145 arc_change_state(arc_state_t
*new_state
, arc_buf_hdr_t
*ab
, kmutex_t
*hash_lock
)
1147 arc_state_t
*old_state
= ab
->b_state
;
1148 int64_t refcnt
= refcount_count(&ab
->b_refcnt
);
1149 uint64_t from_delta
, to_delta
;
1151 ASSERT(MUTEX_HELD(hash_lock
));
1152 ASSERT(new_state
!= old_state
);
1153 ASSERT(refcnt
== 0 || ab
->b_datacnt
> 0);
1154 ASSERT(ab
->b_datacnt
== 0 || !GHOST_STATE(new_state
));
1155 ASSERT(ab
->b_datacnt
<= 1 || old_state
!= arc_anon
);
1157 from_delta
= to_delta
= ab
->b_datacnt
* ab
->b_size
;
1160 * If this buffer is evictable, transfer it from the
1161 * old state list to the new state list.
1164 if (old_state
!= arc_anon
) {
1165 int use_mutex
= !MUTEX_HELD(&old_state
->arcs_mtx
);
1166 uint64_t *size
= &old_state
->arcs_lsize
[ab
->b_type
];
1169 mutex_enter(&old_state
->arcs_mtx
);
1171 ASSERT(list_link_active(&ab
->b_arc_node
));
1172 list_remove(&old_state
->arcs_list
[ab
->b_type
], ab
);
1175 * If prefetching out of the ghost cache,
1176 * we will have a non-zero datacnt.
1178 if (GHOST_STATE(old_state
) && ab
->b_datacnt
== 0) {
1179 /* ghost elements have a ghost size */
1180 ASSERT(ab
->b_buf
== NULL
);
1181 from_delta
= ab
->b_size
;
1183 ASSERT3U(*size
, >=, from_delta
);
1184 atomic_add_64(size
, -from_delta
);
1187 mutex_exit(&old_state
->arcs_mtx
);
1189 if (new_state
!= arc_anon
) {
1190 int use_mutex
= !MUTEX_HELD(&new_state
->arcs_mtx
);
1191 uint64_t *size
= &new_state
->arcs_lsize
[ab
->b_type
];
1194 mutex_enter(&new_state
->arcs_mtx
);
1196 list_insert_head(&new_state
->arcs_list
[ab
->b_type
], ab
);
1198 /* ghost elements have a ghost size */
1199 if (GHOST_STATE(new_state
)) {
1200 ASSERT(ab
->b_datacnt
== 0);
1201 ASSERT(ab
->b_buf
== NULL
);
1202 to_delta
= ab
->b_size
;
1204 atomic_add_64(size
, to_delta
);
1207 mutex_exit(&new_state
->arcs_mtx
);
1211 ASSERT(!BUF_EMPTY(ab
));
1212 if (new_state
== arc_anon
&& HDR_IN_HASH_TABLE(ab
))
1213 buf_hash_remove(ab
);
1215 /* adjust state sizes */
1217 atomic_add_64(&new_state
->arcs_size
, to_delta
);
1219 ASSERT3U(old_state
->arcs_size
, >=, from_delta
);
1220 atomic_add_64(&old_state
->arcs_size
, -from_delta
);
1222 ab
->b_state
= new_state
;
1224 /* adjust l2arc hdr stats */
1225 if (new_state
== arc_l2c_only
)
1226 l2arc_hdr_stat_add();
1227 else if (old_state
== arc_l2c_only
)
1228 l2arc_hdr_stat_remove();
1232 arc_space_consume(uint64_t space
, arc_space_type_t type
)
1234 ASSERT(type
>= 0 && type
< ARC_SPACE_NUMTYPES
);
1239 case ARC_SPACE_DATA
:
1240 ARCSTAT_INCR(arcstat_data_size
, space
);
1242 case ARC_SPACE_OTHER
:
1243 ARCSTAT_INCR(arcstat_other_size
, space
);
1245 case ARC_SPACE_HDRS
:
1246 ARCSTAT_INCR(arcstat_hdr_size
, space
);
1248 case ARC_SPACE_L2HDRS
:
1249 ARCSTAT_INCR(arcstat_l2_hdr_size
, space
);
1253 atomic_add_64(&arc_meta_used
, space
);
1254 atomic_add_64(&arc_size
, space
);
1258 arc_space_return(uint64_t space
, arc_space_type_t type
)
1260 ASSERT(type
>= 0 && type
< ARC_SPACE_NUMTYPES
);
1265 case ARC_SPACE_DATA
:
1266 ARCSTAT_INCR(arcstat_data_size
, -space
);
1268 case ARC_SPACE_OTHER
:
1269 ARCSTAT_INCR(arcstat_other_size
, -space
);
1271 case ARC_SPACE_HDRS
:
1272 ARCSTAT_INCR(arcstat_hdr_size
, -space
);
1274 case ARC_SPACE_L2HDRS
:
1275 ARCSTAT_INCR(arcstat_l2_hdr_size
, -space
);
1279 ASSERT(arc_meta_used
>= space
);
1280 if (arc_meta_max
< arc_meta_used
)
1281 arc_meta_max
= arc_meta_used
;
1282 atomic_add_64(&arc_meta_used
, -space
);
1283 ASSERT(arc_size
>= space
);
1284 atomic_add_64(&arc_size
, -space
);
1288 arc_buf_alloc(spa_t
*spa
, int size
, void *tag
, arc_buf_contents_t type
)
1293 ASSERT3U(size
, >, 0);
1294 hdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
1295 ASSERT(BUF_EMPTY(hdr
));
1298 hdr
->b_spa
= spa_load_guid(spa
);
1299 hdr
->b_state
= arc_anon
;
1300 hdr
->b_arc_access
= 0;
1301 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1304 buf
->b_efunc
= NULL
;
1305 buf
->b_private
= NULL
;
1308 arc_get_data_buf(buf
);
1311 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1312 (void) refcount_add(&hdr
->b_refcnt
, tag
);
1317 static char *arc_onloan_tag
= "onloan";
1320 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1321 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1322 * buffers must be returned to the arc before they can be used by the DMU or
1326 arc_loan_buf(spa_t
*spa
, int size
)
1330 buf
= arc_buf_alloc(spa
, size
, arc_onloan_tag
, ARC_BUFC_DATA
);
1332 atomic_add_64(&arc_loaned_bytes
, size
);
1337 * Return a loaned arc buffer to the arc.
1340 arc_return_buf(arc_buf_t
*buf
, void *tag
)
1342 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1344 ASSERT(buf
->b_data
!= NULL
);
1345 (void) refcount_add(&hdr
->b_refcnt
, tag
);
1346 (void) refcount_remove(&hdr
->b_refcnt
, arc_onloan_tag
);
1348 atomic_add_64(&arc_loaned_bytes
, -hdr
->b_size
);
1351 /* Detach an arc_buf from a dbuf (tag) */
1353 arc_loan_inuse_buf(arc_buf_t
*buf
, void *tag
)
1357 ASSERT(buf
->b_data
!= NULL
);
1359 (void) refcount_add(&hdr
->b_refcnt
, arc_onloan_tag
);
1360 (void) refcount_remove(&hdr
->b_refcnt
, tag
);
1361 buf
->b_efunc
= NULL
;
1362 buf
->b_private
= NULL
;
1364 atomic_add_64(&arc_loaned_bytes
, hdr
->b_size
);
1368 arc_buf_clone(arc_buf_t
*from
)
1371 arc_buf_hdr_t
*hdr
= from
->b_hdr
;
1372 uint64_t size
= hdr
->b_size
;
1374 ASSERT(hdr
->b_state
!= arc_anon
);
1376 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
1379 buf
->b_efunc
= NULL
;
1380 buf
->b_private
= NULL
;
1381 buf
->b_next
= hdr
->b_buf
;
1383 arc_get_data_buf(buf
);
1384 bcopy(from
->b_data
, buf
->b_data
, size
);
1387 * This buffer already exists in the arc so create a duplicate
1388 * copy for the caller. If the buffer is associated with user data
1389 * then track the size and number of duplicates. These stats will be
1390 * updated as duplicate buffers are created and destroyed.
1392 if (hdr
->b_type
== ARC_BUFC_DATA
) {
1393 ARCSTAT_BUMP(arcstat_duplicate_buffers
);
1394 ARCSTAT_INCR(arcstat_duplicate_buffers_size
, size
);
1396 hdr
->b_datacnt
+= 1;
1401 arc_buf_add_ref(arc_buf_t
*buf
, void* tag
)
1404 kmutex_t
*hash_lock
;
1407 * Check to see if this buffer is evicted. Callers
1408 * must verify b_data != NULL to know if the add_ref
1411 mutex_enter(&buf
->b_evict_lock
);
1412 if (buf
->b_data
== NULL
) {
1413 mutex_exit(&buf
->b_evict_lock
);
1416 hash_lock
= HDR_LOCK(buf
->b_hdr
);
1417 mutex_enter(hash_lock
);
1419 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1420 mutex_exit(&buf
->b_evict_lock
);
1422 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
1423 add_reference(hdr
, hash_lock
, tag
);
1424 DTRACE_PROBE1(arc__hit
, arc_buf_hdr_t
*, hdr
);
1425 arc_access(hdr
, hash_lock
);
1426 mutex_exit(hash_lock
);
1427 ARCSTAT_BUMP(arcstat_hits
);
1428 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
1429 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
1430 data
, metadata
, hits
);
1434 * Free the arc data buffer. If it is an l2arc write in progress,
1435 * the buffer is placed on l2arc_free_on_write to be freed later.
1438 arc_buf_data_free(arc_buf_hdr_t
*hdr
, void (*free_func
)(void *, size_t),
1439 void *data
, size_t size
)
1441 if (HDR_L2_WRITING(hdr
)) {
1442 l2arc_data_free_t
*df
;
1443 df
= kmem_alloc(sizeof (l2arc_data_free_t
), KM_PUSHPAGE
);
1444 df
->l2df_data
= data
;
1445 df
->l2df_size
= size
;
1446 df
->l2df_func
= free_func
;
1447 mutex_enter(&l2arc_free_on_write_mtx
);
1448 list_insert_head(l2arc_free_on_write
, df
);
1449 mutex_exit(&l2arc_free_on_write_mtx
);
1450 ARCSTAT_BUMP(arcstat_l2_free_on_write
);
1452 free_func(data
, size
);
1457 arc_buf_destroy(arc_buf_t
*buf
, boolean_t recycle
, boolean_t all
)
1461 /* free up data associated with the buf */
1463 arc_state_t
*state
= buf
->b_hdr
->b_state
;
1464 uint64_t size
= buf
->b_hdr
->b_size
;
1465 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
1467 arc_cksum_verify(buf
);
1470 if (type
== ARC_BUFC_METADATA
) {
1471 arc_buf_data_free(buf
->b_hdr
, zio_buf_free
,
1473 arc_space_return(size
, ARC_SPACE_DATA
);
1475 ASSERT(type
== ARC_BUFC_DATA
);
1476 arc_buf_data_free(buf
->b_hdr
,
1477 zio_data_buf_free
, buf
->b_data
, size
);
1478 ARCSTAT_INCR(arcstat_data_size
, -size
);
1479 atomic_add_64(&arc_size
, -size
);
1482 if (list_link_active(&buf
->b_hdr
->b_arc_node
)) {
1483 uint64_t *cnt
= &state
->arcs_lsize
[type
];
1485 ASSERT(refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
1486 ASSERT(state
!= arc_anon
);
1488 ASSERT3U(*cnt
, >=, size
);
1489 atomic_add_64(cnt
, -size
);
1491 ASSERT3U(state
->arcs_size
, >=, size
);
1492 atomic_add_64(&state
->arcs_size
, -size
);
1496 * If we're destroying a duplicate buffer make sure
1497 * that the appropriate statistics are updated.
1499 if (buf
->b_hdr
->b_datacnt
> 1 &&
1500 buf
->b_hdr
->b_type
== ARC_BUFC_DATA
) {
1501 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers
);
1502 ARCSTAT_INCR(arcstat_duplicate_buffers_size
, -size
);
1504 ASSERT(buf
->b_hdr
->b_datacnt
> 0);
1505 buf
->b_hdr
->b_datacnt
-= 1;
1508 /* only remove the buf if requested */
1512 /* remove the buf from the hdr list */
1513 for (bufp
= &buf
->b_hdr
->b_buf
; *bufp
!= buf
; bufp
= &(*bufp
)->b_next
)
1515 *bufp
= buf
->b_next
;
1518 ASSERT(buf
->b_efunc
== NULL
);
1520 /* clean up the buf */
1522 kmem_cache_free(buf_cache
, buf
);
1526 arc_hdr_destroy(arc_buf_hdr_t
*hdr
)
1528 l2arc_buf_hdr_t
*l2hdr
= hdr
->b_l2hdr
;
1530 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1531 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
1532 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
1534 if (l2hdr
!= NULL
) {
1535 boolean_t buflist_held
= MUTEX_HELD(&l2arc_buflist_mtx
);
1537 * To prevent arc_free() and l2arc_evict() from
1538 * attempting to free the same buffer at the same time,
1539 * a FREE_IN_PROGRESS flag is given to arc_free() to
1540 * give it priority. l2arc_evict() can't destroy this
1541 * header while we are waiting on l2arc_buflist_mtx.
1543 * The hdr may be removed from l2ad_buflist before we
1544 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1546 if (!buflist_held
) {
1547 mutex_enter(&l2arc_buflist_mtx
);
1548 l2hdr
= hdr
->b_l2hdr
;
1551 if (l2hdr
!= NULL
) {
1552 list_remove(l2hdr
->b_dev
->l2ad_buflist
, hdr
);
1553 ARCSTAT_INCR(arcstat_l2_size
, -hdr
->b_size
);
1554 ARCSTAT_INCR(arcstat_l2_asize
, -l2hdr
->b_asize
);
1555 kmem_free(l2hdr
, sizeof (l2arc_buf_hdr_t
));
1556 arc_space_return(L2HDR_SIZE
, ARC_SPACE_L2HDRS
);
1557 if (hdr
->b_state
== arc_l2c_only
)
1558 l2arc_hdr_stat_remove();
1559 hdr
->b_l2hdr
= NULL
;
1563 mutex_exit(&l2arc_buflist_mtx
);
1566 if (!BUF_EMPTY(hdr
)) {
1567 ASSERT(!HDR_IN_HASH_TABLE(hdr
));
1568 buf_discard_identity(hdr
);
1570 while (hdr
->b_buf
) {
1571 arc_buf_t
*buf
= hdr
->b_buf
;
1574 mutex_enter(&arc_eviction_mtx
);
1575 mutex_enter(&buf
->b_evict_lock
);
1576 ASSERT(buf
->b_hdr
!= NULL
);
1577 arc_buf_destroy(hdr
->b_buf
, FALSE
, FALSE
);
1578 hdr
->b_buf
= buf
->b_next
;
1579 buf
->b_hdr
= &arc_eviction_hdr
;
1580 buf
->b_next
= arc_eviction_list
;
1581 arc_eviction_list
= buf
;
1582 mutex_exit(&buf
->b_evict_lock
);
1583 mutex_exit(&arc_eviction_mtx
);
1585 arc_buf_destroy(hdr
->b_buf
, FALSE
, TRUE
);
1588 if (hdr
->b_freeze_cksum
!= NULL
) {
1589 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
1590 hdr
->b_freeze_cksum
= NULL
;
1593 ASSERT(!list_link_active(&hdr
->b_arc_node
));
1594 ASSERT3P(hdr
->b_hash_next
, ==, NULL
);
1595 ASSERT3P(hdr
->b_acb
, ==, NULL
);
1596 kmem_cache_free(hdr_cache
, hdr
);
1600 arc_buf_free(arc_buf_t
*buf
, void *tag
)
1602 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1603 int hashed
= hdr
->b_state
!= arc_anon
;
1605 ASSERT(buf
->b_efunc
== NULL
);
1606 ASSERT(buf
->b_data
!= NULL
);
1609 kmutex_t
*hash_lock
= HDR_LOCK(hdr
);
1611 mutex_enter(hash_lock
);
1613 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1615 (void) remove_reference(hdr
, hash_lock
, tag
);
1616 if (hdr
->b_datacnt
> 1) {
1617 arc_buf_destroy(buf
, FALSE
, TRUE
);
1619 ASSERT(buf
== hdr
->b_buf
);
1620 ASSERT(buf
->b_efunc
== NULL
);
1621 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1623 mutex_exit(hash_lock
);
1624 } else if (HDR_IO_IN_PROGRESS(hdr
)) {
1627 * We are in the middle of an async write. Don't destroy
1628 * this buffer unless the write completes before we finish
1629 * decrementing the reference count.
1631 mutex_enter(&arc_eviction_mtx
);
1632 (void) remove_reference(hdr
, NULL
, tag
);
1633 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
1634 destroy_hdr
= !HDR_IO_IN_PROGRESS(hdr
);
1635 mutex_exit(&arc_eviction_mtx
);
1637 arc_hdr_destroy(hdr
);
1639 if (remove_reference(hdr
, NULL
, tag
) > 0)
1640 arc_buf_destroy(buf
, FALSE
, TRUE
);
1642 arc_hdr_destroy(hdr
);
1647 arc_buf_remove_ref(arc_buf_t
*buf
, void* tag
)
1649 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
1650 kmutex_t
*hash_lock
= NULL
;
1651 int no_callback
= (buf
->b_efunc
== NULL
);
1653 if (hdr
->b_state
== arc_anon
) {
1654 ASSERT(hdr
->b_datacnt
== 1);
1655 arc_buf_free(buf
, tag
);
1656 return (no_callback
);
1659 hash_lock
= HDR_LOCK(hdr
);
1660 mutex_enter(hash_lock
);
1662 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
1663 ASSERT(hdr
->b_state
!= arc_anon
);
1664 ASSERT(buf
->b_data
!= NULL
);
1666 (void) remove_reference(hdr
, hash_lock
, tag
);
1667 if (hdr
->b_datacnt
> 1) {
1669 arc_buf_destroy(buf
, FALSE
, TRUE
);
1670 } else if (no_callback
) {
1671 ASSERT(hdr
->b_buf
== buf
&& buf
->b_next
== NULL
);
1672 ASSERT(buf
->b_efunc
== NULL
);
1673 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
1675 ASSERT(no_callback
|| hdr
->b_datacnt
> 1 ||
1676 refcount_is_zero(&hdr
->b_refcnt
));
1677 mutex_exit(hash_lock
);
1678 return (no_callback
);
1682 arc_buf_size(arc_buf_t
*buf
)
1684 return (buf
->b_hdr
->b_size
);
1688 * Called from the DMU to determine if the current buffer should be
1689 * evicted. In order to ensure proper locking, the eviction must be initiated
1690 * from the DMU. Return true if the buffer is associated with user data and
1691 * duplicate buffers still exist.
1694 arc_buf_eviction_needed(arc_buf_t
*buf
)
1697 boolean_t evict_needed
= B_FALSE
;
1699 if (zfs_disable_dup_eviction
)
1702 mutex_enter(&buf
->b_evict_lock
);
1706 * We are in arc_do_user_evicts(); let that function
1707 * perform the eviction.
1709 ASSERT(buf
->b_data
== NULL
);
1710 mutex_exit(&buf
->b_evict_lock
);
1712 } else if (buf
->b_data
== NULL
) {
1714 * We have already been added to the arc eviction list;
1715 * recommend eviction.
1717 ASSERT3P(hdr
, ==, &arc_eviction_hdr
);
1718 mutex_exit(&buf
->b_evict_lock
);
1722 if (hdr
->b_datacnt
> 1 && hdr
->b_type
== ARC_BUFC_DATA
)
1723 evict_needed
= B_TRUE
;
1725 mutex_exit(&buf
->b_evict_lock
);
1726 return (evict_needed
);
1730 * Evict buffers from list until we've removed the specified number of
1731 * bytes. Move the removed buffers to the appropriate evict state.
1732 * If the recycle flag is set, then attempt to "recycle" a buffer:
1733 * - look for a buffer to evict that is `bytes' long.
1734 * - return the data block from this buffer rather than freeing it.
1735 * This flag is used by callers that are trying to make space for a
1736 * new buffer in a full arc cache.
1738 * This function makes a "best effort". It skips over any buffers
1739 * it can't get a hash_lock on, and so may not catch all candidates.
1740 * It may also return without evicting as much space as requested.
1743 arc_evict(arc_state_t
*state
, uint64_t spa
, int64_t bytes
, boolean_t recycle
,
1744 arc_buf_contents_t type
)
1746 arc_state_t
*evicted_state
;
1747 uint64_t bytes_evicted
= 0, skipped
= 0, missed
= 0;
1748 arc_buf_hdr_t
*ab
, *ab_prev
= NULL
;
1749 list_t
*list
= &state
->arcs_list
[type
];
1750 kmutex_t
*hash_lock
;
1751 boolean_t have_lock
;
1752 void *stolen
= NULL
;
1754 ASSERT(state
== arc_mru
|| state
== arc_mfu
);
1756 evicted_state
= (state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
1758 mutex_enter(&state
->arcs_mtx
);
1759 mutex_enter(&evicted_state
->arcs_mtx
);
1761 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1762 ab_prev
= list_prev(list
, ab
);
1763 /* prefetch buffers have a minimum lifespan */
1764 if (HDR_IO_IN_PROGRESS(ab
) ||
1765 (spa
&& ab
->b_spa
!= spa
) ||
1766 (ab
->b_flags
& (ARC_PREFETCH
|ARC_INDIRECT
) &&
1767 ddi_get_lbolt() - ab
->b_arc_access
<
1768 zfs_arc_min_prefetch_lifespan
)) {
1772 /* "lookahead" for better eviction candidate */
1773 if (recycle
&& ab
->b_size
!= bytes
&&
1774 ab_prev
&& ab_prev
->b_size
== bytes
)
1776 hash_lock
= HDR_LOCK(ab
);
1777 have_lock
= MUTEX_HELD(hash_lock
);
1778 if (have_lock
|| mutex_tryenter(hash_lock
)) {
1779 ASSERT0(refcount_count(&ab
->b_refcnt
));
1780 ASSERT(ab
->b_datacnt
> 0);
1782 arc_buf_t
*buf
= ab
->b_buf
;
1783 if (!mutex_tryenter(&buf
->b_evict_lock
)) {
1788 bytes_evicted
+= ab
->b_size
;
1789 if (recycle
&& ab
->b_type
== type
&&
1790 ab
->b_size
== bytes
&&
1791 !HDR_L2_WRITING(ab
)) {
1792 stolen
= buf
->b_data
;
1797 mutex_enter(&arc_eviction_mtx
);
1798 arc_buf_destroy(buf
,
1799 buf
->b_data
== stolen
, FALSE
);
1800 ab
->b_buf
= buf
->b_next
;
1801 buf
->b_hdr
= &arc_eviction_hdr
;
1802 buf
->b_next
= arc_eviction_list
;
1803 arc_eviction_list
= buf
;
1804 mutex_exit(&arc_eviction_mtx
);
1805 mutex_exit(&buf
->b_evict_lock
);
1807 mutex_exit(&buf
->b_evict_lock
);
1808 arc_buf_destroy(buf
,
1809 buf
->b_data
== stolen
, TRUE
);
1814 ARCSTAT_INCR(arcstat_evict_l2_cached
,
1817 if (l2arc_write_eligible(ab
->b_spa
, ab
)) {
1818 ARCSTAT_INCR(arcstat_evict_l2_eligible
,
1822 arcstat_evict_l2_ineligible
,
1827 if (ab
->b_datacnt
== 0) {
1828 arc_change_state(evicted_state
, ab
, hash_lock
);
1829 ASSERT(HDR_IN_HASH_TABLE(ab
));
1830 ab
->b_flags
|= ARC_IN_HASH_TABLE
;
1831 ab
->b_flags
&= ~ARC_BUF_AVAILABLE
;
1832 DTRACE_PROBE1(arc__evict
, arc_buf_hdr_t
*, ab
);
1835 mutex_exit(hash_lock
);
1836 if (bytes
>= 0 && bytes_evicted
>= bytes
)
1843 mutex_exit(&evicted_state
->arcs_mtx
);
1844 mutex_exit(&state
->arcs_mtx
);
1846 if (bytes_evicted
< bytes
)
1847 dprintf("only evicted %lld bytes from %x\n",
1848 (longlong_t
)bytes_evicted
, state
);
1851 ARCSTAT_INCR(arcstat_evict_skip
, skipped
);
1854 ARCSTAT_INCR(arcstat_mutex_miss
, missed
);
1857 * We have just evicted some date into the ghost state, make
1858 * sure we also adjust the ghost state size if necessary.
1861 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
> arc_c
) {
1862 int64_t mru_over
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
+
1863 arc_mru_ghost
->arcs_size
- arc_c
;
1865 if (mru_over
> 0 && arc_mru_ghost
->arcs_lsize
[type
] > 0) {
1867 MIN(arc_mru_ghost
->arcs_lsize
[type
], mru_over
);
1868 arc_evict_ghost(arc_mru_ghost
, 0, todelete
,
1870 } else if (arc_mfu_ghost
->arcs_lsize
[type
] > 0) {
1871 int64_t todelete
= MIN(arc_mfu_ghost
->arcs_lsize
[type
],
1872 arc_mru_ghost
->arcs_size
+
1873 arc_mfu_ghost
->arcs_size
- arc_c
);
1874 arc_evict_ghost(arc_mfu_ghost
, 0, todelete
,
1883 * Remove buffers from list until we've removed the specified number of
1884 * bytes. Destroy the buffers that are removed.
1887 arc_evict_ghost(arc_state_t
*state
, uint64_t spa
, int64_t bytes
,
1888 arc_buf_contents_t type
)
1890 arc_buf_hdr_t
*ab
, *ab_prev
;
1891 arc_buf_hdr_t marker
;
1892 list_t
*list
= &state
->arcs_list
[type
];
1893 kmutex_t
*hash_lock
;
1894 uint64_t bytes_deleted
= 0;
1895 uint64_t bufs_skipped
= 0;
1897 ASSERT(GHOST_STATE(state
));
1898 bzero(&marker
, sizeof(marker
));
1900 mutex_enter(&state
->arcs_mtx
);
1901 for (ab
= list_tail(list
); ab
; ab
= ab_prev
) {
1902 ab_prev
= list_prev(list
, ab
);
1903 if (spa
&& ab
->b_spa
!= spa
)
1906 /* ignore markers */
1910 hash_lock
= HDR_LOCK(ab
);
1911 /* caller may be trying to modify this buffer, skip it */
1912 if (MUTEX_HELD(hash_lock
))
1914 if (mutex_tryenter(hash_lock
)) {
1915 ASSERT(!HDR_IO_IN_PROGRESS(ab
));
1916 ASSERT(ab
->b_buf
== NULL
);
1917 ARCSTAT_BUMP(arcstat_deleted
);
1918 bytes_deleted
+= ab
->b_size
;
1920 if (ab
->b_l2hdr
!= NULL
) {
1922 * This buffer is cached on the 2nd Level ARC;
1923 * don't destroy the header.
1925 arc_change_state(arc_l2c_only
, ab
, hash_lock
);
1926 mutex_exit(hash_lock
);
1928 arc_change_state(arc_anon
, ab
, hash_lock
);
1929 mutex_exit(hash_lock
);
1930 arc_hdr_destroy(ab
);
1933 DTRACE_PROBE1(arc__delete
, arc_buf_hdr_t
*, ab
);
1934 if (bytes
>= 0 && bytes_deleted
>= bytes
)
1936 } else if (bytes
< 0) {
1938 * Insert a list marker and then wait for the
1939 * hash lock to become available. Once its
1940 * available, restart from where we left off.
1942 list_insert_after(list
, ab
, &marker
);
1943 mutex_exit(&state
->arcs_mtx
);
1944 mutex_enter(hash_lock
);
1945 mutex_exit(hash_lock
);
1946 mutex_enter(&state
->arcs_mtx
);
1947 ab_prev
= list_prev(list
, &marker
);
1948 list_remove(list
, &marker
);
1952 mutex_exit(&state
->arcs_mtx
);
1954 if (list
== &state
->arcs_list
[ARC_BUFC_DATA
] &&
1955 (bytes
< 0 || bytes_deleted
< bytes
)) {
1956 list
= &state
->arcs_list
[ARC_BUFC_METADATA
];
1961 ARCSTAT_INCR(arcstat_mutex_miss
, bufs_skipped
);
1965 if (bytes_deleted
< bytes
)
1966 dprintf("only deleted %lld bytes from %p\n",
1967 (longlong_t
)bytes_deleted
, state
);
1973 int64_t adjustment
, delta
;
1979 adjustment
= MIN((int64_t)(arc_size
- arc_c
),
1980 (int64_t)(arc_anon
->arcs_size
+ arc_mru
->arcs_size
+ arc_meta_used
-
1983 if (adjustment
> 0 && arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
1984 delta
= MIN(arc_mru
->arcs_lsize
[ARC_BUFC_DATA
], adjustment
);
1985 (void) arc_evict(arc_mru
, 0, delta
, FALSE
, ARC_BUFC_DATA
);
1986 adjustment
-= delta
;
1989 if (adjustment
> 0 && arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
1990 delta
= MIN(arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
], adjustment
);
1991 (void) arc_evict(arc_mru
, 0, delta
, FALSE
,
1999 adjustment
= arc_size
- arc_c
;
2001 if (adjustment
> 0 && arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] > 0) {
2002 delta
= MIN(adjustment
, arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
]);
2003 (void) arc_evict(arc_mfu
, 0, delta
, FALSE
, ARC_BUFC_DATA
);
2004 adjustment
-= delta
;
2007 if (adjustment
> 0 && arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
2008 int64_t delta
= MIN(adjustment
,
2009 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
]);
2010 (void) arc_evict(arc_mfu
, 0, delta
, FALSE
,
2015 * Adjust ghost lists
2018 adjustment
= arc_mru
->arcs_size
+ arc_mru_ghost
->arcs_size
- arc_c
;
2020 if (adjustment
> 0 && arc_mru_ghost
->arcs_size
> 0) {
2021 delta
= MIN(arc_mru_ghost
->arcs_size
, adjustment
);
2022 arc_evict_ghost(arc_mru_ghost
, 0, delta
, ARC_BUFC_DATA
);
2026 arc_mru_ghost
->arcs_size
+ arc_mfu_ghost
->arcs_size
- arc_c
;
2028 if (adjustment
> 0 && arc_mfu_ghost
->arcs_size
> 0) {
2029 delta
= MIN(arc_mfu_ghost
->arcs_size
, adjustment
);
2030 arc_evict_ghost(arc_mfu_ghost
, 0, delta
, ARC_BUFC_DATA
);
2035 * Request that arc user drop references so that N bytes can be released
2036 * from the cache. This provides a mechanism to ensure the arc can honor
2037 * the arc_meta_limit and reclaim buffers which are pinned in the cache
2038 * by higher layers. (i.e. the zpl)
2041 arc_do_user_prune(int64_t adjustment
)
2043 arc_prune_func_t
*func
;
2045 arc_prune_t
*cp
, *np
;
2047 mutex_enter(&arc_prune_mtx
);
2049 cp
= list_head(&arc_prune_list
);
2050 while (cp
!= NULL
) {
2052 private = cp
->p_private
;
2053 np
= list_next(&arc_prune_list
, cp
);
2054 refcount_add(&cp
->p_refcnt
, func
);
2055 mutex_exit(&arc_prune_mtx
);
2058 func(adjustment
, private);
2060 mutex_enter(&arc_prune_mtx
);
2062 /* User removed prune callback concurrently with execution */
2063 if (refcount_remove(&cp
->p_refcnt
, func
) == 0) {
2064 ASSERT(!list_link_active(&cp
->p_node
));
2065 refcount_destroy(&cp
->p_refcnt
);
2066 kmem_free(cp
, sizeof (*cp
));
2072 ARCSTAT_BUMP(arcstat_prune
);
2073 mutex_exit(&arc_prune_mtx
);
2077 arc_do_user_evicts(void)
2079 mutex_enter(&arc_eviction_mtx
);
2080 while (arc_eviction_list
!= NULL
) {
2081 arc_buf_t
*buf
= arc_eviction_list
;
2082 arc_eviction_list
= buf
->b_next
;
2083 mutex_enter(&buf
->b_evict_lock
);
2085 mutex_exit(&buf
->b_evict_lock
);
2086 mutex_exit(&arc_eviction_mtx
);
2088 if (buf
->b_efunc
!= NULL
)
2089 VERIFY(buf
->b_efunc(buf
) == 0);
2091 buf
->b_efunc
= NULL
;
2092 buf
->b_private
= NULL
;
2093 kmem_cache_free(buf_cache
, buf
);
2094 mutex_enter(&arc_eviction_mtx
);
2096 mutex_exit(&arc_eviction_mtx
);
2100 * Evict only meta data objects from the cache leaving the data objects.
2101 * This is only used to enforce the tunable arc_meta_limit, if we are
2102 * unable to evict enough buffers notify the user via the prune callback.
2105 arc_adjust_meta(int64_t adjustment
, boolean_t may_prune
)
2109 if (adjustment
> 0 && arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
2110 delta
= MIN(arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
], adjustment
);
2111 arc_evict(arc_mru
, 0, delta
, FALSE
, ARC_BUFC_METADATA
);
2112 adjustment
-= delta
;
2115 if (adjustment
> 0 && arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
] > 0) {
2116 delta
= MIN(arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
], adjustment
);
2117 arc_evict(arc_mfu
, 0, delta
, FALSE
, ARC_BUFC_METADATA
);
2118 adjustment
-= delta
;
2121 if (may_prune
&& (adjustment
> 0) && (arc_meta_used
> arc_meta_limit
))
2122 arc_do_user_prune(zfs_arc_meta_prune
);
2126 * Flush all *evictable* data from the cache for the given spa.
2127 * NOTE: this will not touch "active" (i.e. referenced) data.
2130 arc_flush(spa_t
*spa
)
2135 guid
= spa_load_guid(spa
);
2137 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_DATA
])) {
2138 (void) arc_evict(arc_mru
, guid
, -1, FALSE
, ARC_BUFC_DATA
);
2142 while (list_head(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
])) {
2143 (void) arc_evict(arc_mru
, guid
, -1, FALSE
, ARC_BUFC_METADATA
);
2147 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
])) {
2148 (void) arc_evict(arc_mfu
, guid
, -1, FALSE
, ARC_BUFC_DATA
);
2152 while (list_head(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
])) {
2153 (void) arc_evict(arc_mfu
, guid
, -1, FALSE
, ARC_BUFC_METADATA
);
2158 arc_evict_ghost(arc_mru_ghost
, guid
, -1, ARC_BUFC_DATA
);
2159 arc_evict_ghost(arc_mfu_ghost
, guid
, -1, ARC_BUFC_DATA
);
2161 mutex_enter(&arc_reclaim_thr_lock
);
2162 arc_do_user_evicts();
2163 mutex_exit(&arc_reclaim_thr_lock
);
2164 ASSERT(spa
|| arc_eviction_list
== NULL
);
2168 arc_shrink(uint64_t bytes
)
2170 if (arc_c
> arc_c_min
) {
2173 to_free
= bytes
? bytes
: arc_c
>> zfs_arc_shrink_shift
;
2175 if (arc_c
> arc_c_min
+ to_free
)
2176 atomic_add_64(&arc_c
, -to_free
);
2180 atomic_add_64(&arc_p
, -(arc_p
>> zfs_arc_shrink_shift
));
2181 if (arc_c
> arc_size
)
2182 arc_c
= MAX(arc_size
, arc_c_min
);
2184 arc_p
= (arc_c
>> 1);
2185 ASSERT(arc_c
>= arc_c_min
);
2186 ASSERT((int64_t)arc_p
>= 0);
2189 if (arc_size
> arc_c
)
2194 arc_kmem_reap_now(arc_reclaim_strategy_t strat
, uint64_t bytes
)
2197 kmem_cache_t
*prev_cache
= NULL
;
2198 kmem_cache_t
*prev_data_cache
= NULL
;
2199 extern kmem_cache_t
*zio_buf_cache
[];
2200 extern kmem_cache_t
*zio_data_buf_cache
[];
2203 * An aggressive reclamation will shrink the cache size as well as
2204 * reap free buffers from the arc kmem caches.
2206 if (strat
== ARC_RECLAIM_AGGR
)
2209 for (i
= 0; i
< SPA_MAXBLOCKSIZE
>> SPA_MINBLOCKSHIFT
; i
++) {
2210 if (zio_buf_cache
[i
] != prev_cache
) {
2211 prev_cache
= zio_buf_cache
[i
];
2212 kmem_cache_reap_now(zio_buf_cache
[i
]);
2214 if (zio_data_buf_cache
[i
] != prev_data_cache
) {
2215 prev_data_cache
= zio_data_buf_cache
[i
];
2216 kmem_cache_reap_now(zio_data_buf_cache
[i
]);
2220 kmem_cache_reap_now(buf_cache
);
2221 kmem_cache_reap_now(hdr_cache
);
2225 * Unlike other ZFS implementations this thread is only responsible for
2226 * adapting the target ARC size on Linux. The responsibility for memory
2227 * reclamation has been entirely delegated to the arc_shrinker_func()
2228 * which is registered with the VM. To reflect this change in behavior
2229 * the arc_reclaim thread has been renamed to arc_adapt.
2232 arc_adapt_thread(void)
2237 CALLB_CPR_INIT(&cpr
, &arc_reclaim_thr_lock
, callb_generic_cpr
, FTAG
);
2239 mutex_enter(&arc_reclaim_thr_lock
);
2240 while (arc_thread_exit
== 0) {
2242 arc_reclaim_strategy_t last_reclaim
= ARC_RECLAIM_CONS
;
2244 if (spa_get_random(100) == 0) {
2247 if (last_reclaim
== ARC_RECLAIM_CONS
) {
2248 last_reclaim
= ARC_RECLAIM_AGGR
;
2250 last_reclaim
= ARC_RECLAIM_CONS
;
2254 last_reclaim
= ARC_RECLAIM_AGGR
;
2258 /* reset the growth delay for every reclaim */
2259 arc_grow_time
= ddi_get_lbolt()+(zfs_arc_grow_retry
* hz
);
2261 arc_kmem_reap_now(last_reclaim
, 0);
2264 #endif /* !_KERNEL */
2266 /* No recent memory pressure allow the ARC to grow. */
2267 if (arc_no_grow
&& ddi_get_lbolt() >= arc_grow_time
)
2268 arc_no_grow
= FALSE
;
2271 * Keep meta data usage within limits, arc_shrink() is not
2272 * used to avoid collapsing the arc_c value when only the
2273 * arc_meta_limit is being exceeded.
2275 prune
= (int64_t)arc_meta_used
- (int64_t)arc_meta_limit
;
2277 arc_adjust_meta(prune
, B_TRUE
);
2281 if (arc_eviction_list
!= NULL
)
2282 arc_do_user_evicts();
2284 /* block until needed, or one second, whichever is shorter */
2285 CALLB_CPR_SAFE_BEGIN(&cpr
);
2286 (void) cv_timedwait_interruptible(&arc_reclaim_thr_cv
,
2287 &arc_reclaim_thr_lock
, (ddi_get_lbolt() + hz
));
2288 CALLB_CPR_SAFE_END(&cpr
, &arc_reclaim_thr_lock
);
2291 /* Allow the module options to be changed */
2292 if (zfs_arc_max
> 64 << 20 &&
2293 zfs_arc_max
< physmem
* PAGESIZE
&&
2294 zfs_arc_max
!= arc_c_max
)
2295 arc_c_max
= zfs_arc_max
;
2297 if (zfs_arc_min
> 0 &&
2298 zfs_arc_min
< arc_c_max
&&
2299 zfs_arc_min
!= arc_c_min
)
2300 arc_c_min
= zfs_arc_min
;
2302 if (zfs_arc_meta_limit
> 0 &&
2303 zfs_arc_meta_limit
<= arc_c_max
&&
2304 zfs_arc_meta_limit
!= arc_meta_limit
)
2305 arc_meta_limit
= zfs_arc_meta_limit
;
2311 arc_thread_exit
= 0;
2312 cv_broadcast(&arc_reclaim_thr_cv
);
2313 CALLB_CPR_EXIT(&cpr
); /* drops arc_reclaim_thr_lock */
2319 * Determine the amount of memory eligible for eviction contained in the
2320 * ARC. All clean data reported by the ghost lists can always be safely
2321 * evicted. Due to arc_c_min, the same does not hold for all clean data
2322 * contained by the regular mru and mfu lists.
2324 * In the case of the regular mru and mfu lists, we need to report as
2325 * much clean data as possible, such that evicting that same reported
2326 * data will not bring arc_size below arc_c_min. Thus, in certain
2327 * circumstances, the total amount of clean data in the mru and mfu
2328 * lists might not actually be evictable.
2330 * The following two distinct cases are accounted for:
2332 * 1. The sum of the amount of dirty data contained by both the mru and
2333 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
2334 * is greater than or equal to arc_c_min.
2335 * (i.e. amount of dirty data >= arc_c_min)
2337 * This is the easy case; all clean data contained by the mru and mfu
2338 * lists is evictable. Evicting all clean data can only drop arc_size
2339 * to the amount of dirty data, which is greater than arc_c_min.
2341 * 2. The sum of the amount of dirty data contained by both the mru and
2342 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
2343 * is less than arc_c_min.
2344 * (i.e. arc_c_min > amount of dirty data)
2346 * 2.1. arc_size is greater than or equal arc_c_min.
2347 * (i.e. arc_size >= arc_c_min > amount of dirty data)
2349 * In this case, not all clean data from the regular mru and mfu
2350 * lists is actually evictable; we must leave enough clean data
2351 * to keep arc_size above arc_c_min. Thus, the maximum amount of
2352 * evictable data from the two lists combined, is exactly the
2353 * difference between arc_size and arc_c_min.
2355 * 2.2. arc_size is less than arc_c_min
2356 * (i.e. arc_c_min > arc_size > amount of dirty data)
2358 * In this case, none of the data contained in the mru and mfu
2359 * lists is evictable, even if it's clean. Since arc_size is
2360 * already below arc_c_min, evicting any more would only
2361 * increase this negative difference.
2364 arc_evictable_memory(void) {
2365 uint64_t arc_clean
=
2366 arc_mru
->arcs_lsize
[ARC_BUFC_DATA
] +
2367 arc_mru
->arcs_lsize
[ARC_BUFC_METADATA
] +
2368 arc_mfu
->arcs_lsize
[ARC_BUFC_DATA
] +
2369 arc_mfu
->arcs_lsize
[ARC_BUFC_METADATA
];
2370 uint64_t ghost_clean
=
2371 arc_mru_ghost
->arcs_lsize
[ARC_BUFC_DATA
] +
2372 arc_mru_ghost
->arcs_lsize
[ARC_BUFC_METADATA
] +
2373 arc_mfu_ghost
->arcs_lsize
[ARC_BUFC_DATA
] +
2374 arc_mfu_ghost
->arcs_lsize
[ARC_BUFC_METADATA
];
2375 uint64_t arc_dirty
= MAX((int64_t)arc_size
- (int64_t)arc_clean
, 0);
2377 if (arc_dirty
>= arc_c_min
)
2378 return (ghost_clean
+ arc_clean
);
2380 return (ghost_clean
+ MAX((int64_t)arc_size
- (int64_t)arc_c_min
, 0));
2384 __arc_shrinker_func(struct shrinker
*shrink
, struct shrink_control
*sc
)
2388 /* The arc is considered warm once reclaim has occurred */
2389 if (unlikely(arc_warm
== B_FALSE
))
2392 /* Return the potential number of reclaimable pages */
2393 pages
= btop(arc_evictable_memory());
2394 if (sc
->nr_to_scan
== 0)
2397 /* Not allowed to perform filesystem reclaim */
2398 if (!(sc
->gfp_mask
& __GFP_FS
))
2401 /* Reclaim in progress */
2402 if (mutex_tryenter(&arc_reclaim_thr_lock
) == 0)
2406 * Evict the requested number of pages by shrinking arc_c the
2407 * requested amount. If there is nothing left to evict just
2408 * reap whatever we can from the various arc slabs.
2411 arc_kmem_reap_now(ARC_RECLAIM_AGGR
, ptob(sc
->nr_to_scan
));
2413 arc_kmem_reap_now(ARC_RECLAIM_CONS
, ptob(sc
->nr_to_scan
));
2417 * When direct reclaim is observed it usually indicates a rapid
2418 * increase in memory pressure. This occurs because the kswapd
2419 * threads were unable to asynchronously keep enough free memory
2420 * available. In this case set arc_no_grow to briefly pause arc
2421 * growth to avoid compounding the memory pressure.
2423 if (current_is_kswapd()) {
2424 ARCSTAT_BUMP(arcstat_memory_indirect_count
);
2426 arc_no_grow
= B_TRUE
;
2427 arc_grow_time
= ddi_get_lbolt() + (zfs_arc_grow_retry
* hz
);
2428 ARCSTAT_BUMP(arcstat_memory_direct_count
);
2431 mutex_exit(&arc_reclaim_thr_lock
);
2435 SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func
);
2437 SPL_SHRINKER_DECLARE(arc_shrinker
, arc_shrinker_func
, DEFAULT_SEEKS
);
2438 #endif /* _KERNEL */
2441 * Adapt arc info given the number of bytes we are trying to add and
2442 * the state that we are comming from. This function is only called
2443 * when we are adding new content to the cache.
2446 arc_adapt(int bytes
, arc_state_t
*state
)
2449 uint64_t arc_p_min
= (arc_c
>> zfs_arc_p_min_shift
);
2451 if (state
== arc_l2c_only
)
2456 * Adapt the target size of the MRU list:
2457 * - if we just hit in the MRU ghost list, then increase
2458 * the target size of the MRU list.
2459 * - if we just hit in the MFU ghost list, then increase
2460 * the target size of the MFU list by decreasing the
2461 * target size of the MRU list.
2463 if (state
== arc_mru_ghost
) {
2464 mult
= ((arc_mru_ghost
->arcs_size
>= arc_mfu_ghost
->arcs_size
) ?
2465 1 : (arc_mfu_ghost
->arcs_size
/arc_mru_ghost
->arcs_size
));
2466 mult
= MIN(mult
, 10); /* avoid wild arc_p adjustment */
2468 arc_p
= MIN(arc_c
- arc_p_min
, arc_p
+ bytes
* mult
);
2469 } else if (state
== arc_mfu_ghost
) {
2472 mult
= ((arc_mfu_ghost
->arcs_size
>= arc_mru_ghost
->arcs_size
) ?
2473 1 : (arc_mru_ghost
->arcs_size
/arc_mfu_ghost
->arcs_size
));
2474 mult
= MIN(mult
, 10);
2476 delta
= MIN(bytes
* mult
, arc_p
);
2477 arc_p
= MAX(arc_p_min
, arc_p
- delta
);
2479 ASSERT((int64_t)arc_p
>= 0);
2484 if (arc_c
>= arc_c_max
)
2488 * If we're within (2 * maxblocksize) bytes of the target
2489 * cache size, increment the target cache size
2491 if (arc_size
> arc_c
- (2ULL << SPA_MAXBLOCKSHIFT
)) {
2492 atomic_add_64(&arc_c
, (int64_t)bytes
);
2493 if (arc_c
> arc_c_max
)
2495 else if (state
== arc_anon
)
2496 atomic_add_64(&arc_p
, (int64_t)bytes
);
2500 ASSERT((int64_t)arc_p
>= 0);
2504 * Check if the cache has reached its limits and eviction is required
2508 arc_evict_needed(arc_buf_contents_t type
)
2510 if (type
== ARC_BUFC_METADATA
&& arc_meta_used
>= arc_meta_limit
)
2516 return (arc_size
> arc_c
);
2520 * The buffer, supplied as the first argument, needs a data block.
2521 * So, if we are at cache max, determine which cache should be victimized.
2522 * We have the following cases:
2524 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2525 * In this situation if we're out of space, but the resident size of the MFU is
2526 * under the limit, victimize the MFU cache to satisfy this insertion request.
2528 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2529 * Here, we've used up all of the available space for the MRU, so we need to
2530 * evict from our own cache instead. Evict from the set of resident MRU
2533 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2534 * c minus p represents the MFU space in the cache, since p is the size of the
2535 * cache that is dedicated to the MRU. In this situation there's still space on
2536 * the MFU side, so the MRU side needs to be victimized.
2538 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2539 * MFU's resident set is consuming more space than it has been allotted. In
2540 * this situation, we must victimize our own cache, the MFU, for this insertion.
2543 arc_get_data_buf(arc_buf_t
*buf
)
2545 arc_state_t
*state
= buf
->b_hdr
->b_state
;
2546 uint64_t size
= buf
->b_hdr
->b_size
;
2547 arc_buf_contents_t type
= buf
->b_hdr
->b_type
;
2549 arc_adapt(size
, state
);
2552 * We have not yet reached cache maximum size,
2553 * just allocate a new buffer.
2555 if (!arc_evict_needed(type
)) {
2556 if (type
== ARC_BUFC_METADATA
) {
2557 buf
->b_data
= zio_buf_alloc(size
);
2558 arc_space_consume(size
, ARC_SPACE_DATA
);
2560 ASSERT(type
== ARC_BUFC_DATA
);
2561 buf
->b_data
= zio_data_buf_alloc(size
);
2562 ARCSTAT_INCR(arcstat_data_size
, size
);
2563 atomic_add_64(&arc_size
, size
);
2569 * If we are prefetching from the mfu ghost list, this buffer
2570 * will end up on the mru list; so steal space from there.
2572 if (state
== arc_mfu_ghost
)
2573 state
= buf
->b_hdr
->b_flags
& ARC_PREFETCH
? arc_mru
: arc_mfu
;
2574 else if (state
== arc_mru_ghost
)
2577 if (state
== arc_mru
|| state
== arc_anon
) {
2578 uint64_t mru_used
= arc_anon
->arcs_size
+ arc_mru
->arcs_size
;
2579 state
= (arc_mfu
->arcs_lsize
[type
] >= size
&&
2580 arc_p
> mru_used
) ? arc_mfu
: arc_mru
;
2583 uint64_t mfu_space
= arc_c
- arc_p
;
2584 state
= (arc_mru
->arcs_lsize
[type
] >= size
&&
2585 mfu_space
> arc_mfu
->arcs_size
) ? arc_mru
: arc_mfu
;
2588 if ((buf
->b_data
= arc_evict(state
, 0, size
, TRUE
, type
)) == NULL
) {
2589 if (type
== ARC_BUFC_METADATA
) {
2590 buf
->b_data
= zio_buf_alloc(size
);
2591 arc_space_consume(size
, ARC_SPACE_DATA
);
2594 * If we are unable to recycle an existing meta buffer
2595 * signal the reclaim thread. It will notify users
2596 * via the prune callback to drop references. The
2597 * prune callback in run in the context of the reclaim
2598 * thread to avoid deadlocking on the hash_lock.
2600 cv_signal(&arc_reclaim_thr_cv
);
2602 ASSERT(type
== ARC_BUFC_DATA
);
2603 buf
->b_data
= zio_data_buf_alloc(size
);
2604 ARCSTAT_INCR(arcstat_data_size
, size
);
2605 atomic_add_64(&arc_size
, size
);
2608 ARCSTAT_BUMP(arcstat_recycle_miss
);
2610 ASSERT(buf
->b_data
!= NULL
);
2613 * Update the state size. Note that ghost states have a
2614 * "ghost size" and so don't need to be updated.
2616 if (!GHOST_STATE(buf
->b_hdr
->b_state
)) {
2617 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
2619 atomic_add_64(&hdr
->b_state
->arcs_size
, size
);
2620 if (list_link_active(&hdr
->b_arc_node
)) {
2621 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
2622 atomic_add_64(&hdr
->b_state
->arcs_lsize
[type
], size
);
2625 * If we are growing the cache, and we are adding anonymous
2626 * data, and we have outgrown arc_p, update arc_p
2628 if (arc_size
< arc_c
&& hdr
->b_state
== arc_anon
&&
2629 arc_anon
->arcs_size
+ arc_mru
->arcs_size
> arc_p
)
2630 arc_p
= MIN(arc_c
, arc_p
+ size
);
2635 * This routine is called whenever a buffer is accessed.
2636 * NOTE: the hash lock is dropped in this function.
2639 arc_access(arc_buf_hdr_t
*buf
, kmutex_t
*hash_lock
)
2643 ASSERT(MUTEX_HELD(hash_lock
));
2645 if (buf
->b_state
== arc_anon
) {
2647 * This buffer is not in the cache, and does not
2648 * appear in our "ghost" list. Add the new buffer
2652 ASSERT(buf
->b_arc_access
== 0);
2653 buf
->b_arc_access
= ddi_get_lbolt();
2654 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2655 arc_change_state(arc_mru
, buf
, hash_lock
);
2657 } else if (buf
->b_state
== arc_mru
) {
2658 now
= ddi_get_lbolt();
2661 * If this buffer is here because of a prefetch, then either:
2662 * - clear the flag if this is a "referencing" read
2663 * (any subsequent access will bump this into the MFU state).
2665 * - move the buffer to the head of the list if this is
2666 * another prefetch (to make it less likely to be evicted).
2668 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2669 if (refcount_count(&buf
->b_refcnt
) == 0) {
2670 ASSERT(list_link_active(&buf
->b_arc_node
));
2672 buf
->b_flags
&= ~ARC_PREFETCH
;
2673 ARCSTAT_BUMP(arcstat_mru_hits
);
2675 buf
->b_arc_access
= now
;
2680 * This buffer has been "accessed" only once so far,
2681 * but it is still in the cache. Move it to the MFU
2684 if (now
> buf
->b_arc_access
+ ARC_MINTIME
) {
2686 * More than 125ms have passed since we
2687 * instantiated this buffer. Move it to the
2688 * most frequently used state.
2690 buf
->b_arc_access
= now
;
2691 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2692 arc_change_state(arc_mfu
, buf
, hash_lock
);
2694 ARCSTAT_BUMP(arcstat_mru_hits
);
2695 } else if (buf
->b_state
== arc_mru_ghost
) {
2696 arc_state_t
*new_state
;
2698 * This buffer has been "accessed" recently, but
2699 * was evicted from the cache. Move it to the
2703 if (buf
->b_flags
& ARC_PREFETCH
) {
2704 new_state
= arc_mru
;
2705 if (refcount_count(&buf
->b_refcnt
) > 0)
2706 buf
->b_flags
&= ~ARC_PREFETCH
;
2707 DTRACE_PROBE1(new_state__mru
, arc_buf_hdr_t
*, buf
);
2709 new_state
= arc_mfu
;
2710 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2713 buf
->b_arc_access
= ddi_get_lbolt();
2714 arc_change_state(new_state
, buf
, hash_lock
);
2716 ARCSTAT_BUMP(arcstat_mru_ghost_hits
);
2717 } else if (buf
->b_state
== arc_mfu
) {
2719 * This buffer has been accessed more than once and is
2720 * still in the cache. Keep it in the MFU state.
2722 * NOTE: an add_reference() that occurred when we did
2723 * the arc_read() will have kicked this off the list.
2724 * If it was a prefetch, we will explicitly move it to
2725 * the head of the list now.
2727 if ((buf
->b_flags
& ARC_PREFETCH
) != 0) {
2728 ASSERT(refcount_count(&buf
->b_refcnt
) == 0);
2729 ASSERT(list_link_active(&buf
->b_arc_node
));
2731 ARCSTAT_BUMP(arcstat_mfu_hits
);
2732 buf
->b_arc_access
= ddi_get_lbolt();
2733 } else if (buf
->b_state
== arc_mfu_ghost
) {
2734 arc_state_t
*new_state
= arc_mfu
;
2736 * This buffer has been accessed more than once but has
2737 * been evicted from the cache. Move it back to the
2741 if (buf
->b_flags
& ARC_PREFETCH
) {
2743 * This is a prefetch access...
2744 * move this block back to the MRU state.
2746 ASSERT0(refcount_count(&buf
->b_refcnt
));
2747 new_state
= arc_mru
;
2750 buf
->b_arc_access
= ddi_get_lbolt();
2751 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2752 arc_change_state(new_state
, buf
, hash_lock
);
2754 ARCSTAT_BUMP(arcstat_mfu_ghost_hits
);
2755 } else if (buf
->b_state
== arc_l2c_only
) {
2757 * This buffer is on the 2nd Level ARC.
2760 buf
->b_arc_access
= ddi_get_lbolt();
2761 DTRACE_PROBE1(new_state__mfu
, arc_buf_hdr_t
*, buf
);
2762 arc_change_state(arc_mfu
, buf
, hash_lock
);
2764 ASSERT(!"invalid arc state");
2768 /* a generic arc_done_func_t which you can use */
2771 arc_bcopy_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2773 if (zio
== NULL
|| zio
->io_error
== 0)
2774 bcopy(buf
->b_data
, arg
, buf
->b_hdr
->b_size
);
2775 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2778 /* a generic arc_done_func_t */
2780 arc_getbuf_func(zio_t
*zio
, arc_buf_t
*buf
, void *arg
)
2782 arc_buf_t
**bufp
= arg
;
2783 if (zio
&& zio
->io_error
) {
2784 VERIFY(arc_buf_remove_ref(buf
, arg
) == 1);
2788 ASSERT(buf
->b_data
);
2793 arc_read_done(zio_t
*zio
)
2795 arc_buf_hdr_t
*hdr
, *found
;
2797 arc_buf_t
*abuf
; /* buffer we're assigning to callback */
2798 kmutex_t
*hash_lock
;
2799 arc_callback_t
*callback_list
, *acb
;
2800 int freeable
= FALSE
;
2802 buf
= zio
->io_private
;
2806 * The hdr was inserted into hash-table and removed from lists
2807 * prior to starting I/O. We should find this header, since
2808 * it's in the hash table, and it should be legit since it's
2809 * not possible to evict it during the I/O. The only possible
2810 * reason for it not to be found is if we were freed during the
2813 found
= buf_hash_find(hdr
->b_spa
, &hdr
->b_dva
, hdr
->b_birth
,
2816 ASSERT((found
== NULL
&& HDR_FREED_IN_READ(hdr
) && hash_lock
== NULL
) ||
2817 (found
== hdr
&& DVA_EQUAL(&hdr
->b_dva
, BP_IDENTITY(zio
->io_bp
))) ||
2818 (found
== hdr
&& HDR_L2_READING(hdr
)));
2820 hdr
->b_flags
&= ~ARC_L2_EVICTED
;
2821 if (l2arc_noprefetch
&& (hdr
->b_flags
& ARC_PREFETCH
))
2822 hdr
->b_flags
&= ~ARC_L2CACHE
;
2824 /* byteswap if necessary */
2825 callback_list
= hdr
->b_acb
;
2826 ASSERT(callback_list
!= NULL
);
2827 if (BP_SHOULD_BYTESWAP(zio
->io_bp
) && zio
->io_error
== 0) {
2828 dmu_object_byteswap_t bswap
=
2829 DMU_OT_BYTESWAP(BP_GET_TYPE(zio
->io_bp
));
2830 if (BP_GET_LEVEL(zio
->io_bp
) > 0)
2831 byteswap_uint64_array(buf
->b_data
, hdr
->b_size
);
2833 dmu_ot_byteswap
[bswap
].ob_func(buf
->b_data
, hdr
->b_size
);
2836 arc_cksum_compute(buf
, B_FALSE
);
2838 if (hash_lock
&& zio
->io_error
== 0 && hdr
->b_state
== arc_anon
) {
2840 * Only call arc_access on anonymous buffers. This is because
2841 * if we've issued an I/O for an evicted buffer, we've already
2842 * called arc_access (to prevent any simultaneous readers from
2843 * getting confused).
2845 arc_access(hdr
, hash_lock
);
2848 /* create copies of the data buffer for the callers */
2850 for (acb
= callback_list
; acb
; acb
= acb
->acb_next
) {
2851 if (acb
->acb_done
) {
2853 ARCSTAT_BUMP(arcstat_duplicate_reads
);
2854 abuf
= arc_buf_clone(buf
);
2856 acb
->acb_buf
= abuf
;
2861 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
2862 ASSERT(!HDR_BUF_AVAILABLE(hdr
));
2864 ASSERT(buf
->b_efunc
== NULL
);
2865 ASSERT(hdr
->b_datacnt
== 1);
2866 hdr
->b_flags
|= ARC_BUF_AVAILABLE
;
2869 ASSERT(refcount_is_zero(&hdr
->b_refcnt
) || callback_list
!= NULL
);
2871 if (zio
->io_error
!= 0) {
2872 hdr
->b_flags
|= ARC_IO_ERROR
;
2873 if (hdr
->b_state
!= arc_anon
)
2874 arc_change_state(arc_anon
, hdr
, hash_lock
);
2875 if (HDR_IN_HASH_TABLE(hdr
))
2876 buf_hash_remove(hdr
);
2877 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2881 * Broadcast before we drop the hash_lock to avoid the possibility
2882 * that the hdr (and hence the cv) might be freed before we get to
2883 * the cv_broadcast().
2885 cv_broadcast(&hdr
->b_cv
);
2888 mutex_exit(hash_lock
);
2891 * This block was freed while we waited for the read to
2892 * complete. It has been removed from the hash table and
2893 * moved to the anonymous state (so that it won't show up
2896 ASSERT3P(hdr
->b_state
, ==, arc_anon
);
2897 freeable
= refcount_is_zero(&hdr
->b_refcnt
);
2900 /* execute each callback and free its structure */
2901 while ((acb
= callback_list
) != NULL
) {
2903 acb
->acb_done(zio
, acb
->acb_buf
, acb
->acb_private
);
2905 if (acb
->acb_zio_dummy
!= NULL
) {
2906 acb
->acb_zio_dummy
->io_error
= zio
->io_error
;
2907 zio_nowait(acb
->acb_zio_dummy
);
2910 callback_list
= acb
->acb_next
;
2911 kmem_free(acb
, sizeof (arc_callback_t
));
2915 arc_hdr_destroy(hdr
);
2919 * "Read" the block at the specified DVA (in bp) via the
2920 * cache. If the block is found in the cache, invoke the provided
2921 * callback immediately and return. Note that the `zio' parameter
2922 * in the callback will be NULL in this case, since no IO was
2923 * required. If the block is not in the cache pass the read request
2924 * on to the spa with a substitute callback function, so that the
2925 * requested block will be added to the cache.
2927 * If a read request arrives for a block that has a read in-progress,
2928 * either wait for the in-progress read to complete (and return the
2929 * results); or, if this is a read with a "done" func, add a record
2930 * to the read to invoke the "done" func when the read completes,
2931 * and return; or just return.
2933 * arc_read_done() will invoke all the requested "done" functions
2934 * for readers of this block.
2937 arc_read(zio_t
*pio
, spa_t
*spa
, const blkptr_t
*bp
, arc_done_func_t
*done
,
2938 void *private, int priority
, int zio_flags
, uint32_t *arc_flags
,
2939 const zbookmark_t
*zb
)
2942 arc_buf_t
*buf
= NULL
;
2943 kmutex_t
*hash_lock
;
2945 uint64_t guid
= spa_load_guid(spa
);
2948 hdr
= buf_hash_find(guid
, BP_IDENTITY(bp
), BP_PHYSICAL_BIRTH(bp
),
2950 if (hdr
&& hdr
->b_datacnt
> 0) {
2952 *arc_flags
|= ARC_CACHED
;
2954 if (HDR_IO_IN_PROGRESS(hdr
)) {
2956 if (*arc_flags
& ARC_WAIT
) {
2957 cv_wait(&hdr
->b_cv
, hash_lock
);
2958 mutex_exit(hash_lock
);
2961 ASSERT(*arc_flags
& ARC_NOWAIT
);
2964 arc_callback_t
*acb
= NULL
;
2966 acb
= kmem_zalloc(sizeof (arc_callback_t
),
2968 acb
->acb_done
= done
;
2969 acb
->acb_private
= private;
2971 acb
->acb_zio_dummy
= zio_null(pio
,
2972 spa
, NULL
, NULL
, NULL
, zio_flags
);
2974 ASSERT(acb
->acb_done
!= NULL
);
2975 acb
->acb_next
= hdr
->b_acb
;
2977 add_reference(hdr
, hash_lock
, private);
2978 mutex_exit(hash_lock
);
2981 mutex_exit(hash_lock
);
2985 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
2988 add_reference(hdr
, hash_lock
, private);
2990 * If this block is already in use, create a new
2991 * copy of the data so that we will be guaranteed
2992 * that arc_release() will always succeed.
2996 ASSERT(buf
->b_data
);
2997 if (HDR_BUF_AVAILABLE(hdr
)) {
2998 ASSERT(buf
->b_efunc
== NULL
);
2999 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
3001 buf
= arc_buf_clone(buf
);
3004 } else if (*arc_flags
& ARC_PREFETCH
&&
3005 refcount_count(&hdr
->b_refcnt
) == 0) {
3006 hdr
->b_flags
|= ARC_PREFETCH
;
3008 DTRACE_PROBE1(arc__hit
, arc_buf_hdr_t
*, hdr
);
3009 arc_access(hdr
, hash_lock
);
3010 if (*arc_flags
& ARC_L2CACHE
)
3011 hdr
->b_flags
|= ARC_L2CACHE
;
3012 if (*arc_flags
& ARC_L2COMPRESS
)
3013 hdr
->b_flags
|= ARC_L2COMPRESS
;
3014 mutex_exit(hash_lock
);
3015 ARCSTAT_BUMP(arcstat_hits
);
3016 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
3017 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
3018 data
, metadata
, hits
);
3021 done(NULL
, buf
, private);
3023 uint64_t size
= BP_GET_LSIZE(bp
);
3024 arc_callback_t
*acb
;
3027 boolean_t devw
= B_FALSE
;
3030 /* this block is not in the cache */
3031 arc_buf_hdr_t
*exists
;
3032 arc_buf_contents_t type
= BP_GET_BUFC_TYPE(bp
);
3033 buf
= arc_buf_alloc(spa
, size
, private, type
);
3035 hdr
->b_dva
= *BP_IDENTITY(bp
);
3036 hdr
->b_birth
= BP_PHYSICAL_BIRTH(bp
);
3037 hdr
->b_cksum0
= bp
->blk_cksum
.zc_word
[0];
3038 exists
= buf_hash_insert(hdr
, &hash_lock
);
3040 /* somebody beat us to the hash insert */
3041 mutex_exit(hash_lock
);
3042 buf_discard_identity(hdr
);
3043 (void) arc_buf_remove_ref(buf
, private);
3044 goto top
; /* restart the IO request */
3046 /* if this is a prefetch, we don't have a reference */
3047 if (*arc_flags
& ARC_PREFETCH
) {
3048 (void) remove_reference(hdr
, hash_lock
,
3050 hdr
->b_flags
|= ARC_PREFETCH
;
3052 if (*arc_flags
& ARC_L2CACHE
)
3053 hdr
->b_flags
|= ARC_L2CACHE
;
3054 if (*arc_flags
& ARC_L2COMPRESS
)
3055 hdr
->b_flags
|= ARC_L2COMPRESS
;
3056 if (BP_GET_LEVEL(bp
) > 0)
3057 hdr
->b_flags
|= ARC_INDIRECT
;
3059 /* this block is in the ghost cache */
3060 ASSERT(GHOST_STATE(hdr
->b_state
));
3061 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
3062 ASSERT0(refcount_count(&hdr
->b_refcnt
));
3063 ASSERT(hdr
->b_buf
== NULL
);
3065 /* if this is a prefetch, we don't have a reference */
3066 if (*arc_flags
& ARC_PREFETCH
)
3067 hdr
->b_flags
|= ARC_PREFETCH
;
3069 add_reference(hdr
, hash_lock
, private);
3070 if (*arc_flags
& ARC_L2CACHE
)
3071 hdr
->b_flags
|= ARC_L2CACHE
;
3072 if (*arc_flags
& ARC_L2COMPRESS
)
3073 hdr
->b_flags
|= ARC_L2COMPRESS
;
3074 buf
= kmem_cache_alloc(buf_cache
, KM_PUSHPAGE
);
3077 buf
->b_efunc
= NULL
;
3078 buf
->b_private
= NULL
;
3081 ASSERT(hdr
->b_datacnt
== 0);
3083 arc_get_data_buf(buf
);
3084 arc_access(hdr
, hash_lock
);
3087 ASSERT(!GHOST_STATE(hdr
->b_state
));
3089 acb
= kmem_zalloc(sizeof (arc_callback_t
), KM_PUSHPAGE
);
3090 acb
->acb_done
= done
;
3091 acb
->acb_private
= private;
3093 ASSERT(hdr
->b_acb
== NULL
);
3095 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
3097 if (HDR_L2CACHE(hdr
) && hdr
->b_l2hdr
!= NULL
&&
3098 (vd
= hdr
->b_l2hdr
->b_dev
->l2ad_vdev
) != NULL
) {
3099 devw
= hdr
->b_l2hdr
->b_dev
->l2ad_writing
;
3100 addr
= hdr
->b_l2hdr
->b_daddr
;
3102 * Lock out device removal.
3104 if (vdev_is_dead(vd
) ||
3105 !spa_config_tryenter(spa
, SCL_L2ARC
, vd
, RW_READER
))
3109 mutex_exit(hash_lock
);
3111 ASSERT3U(hdr
->b_size
, ==, size
);
3112 DTRACE_PROBE4(arc__miss
, arc_buf_hdr_t
*, hdr
, blkptr_t
*, bp
,
3113 uint64_t, size
, zbookmark_t
*, zb
);
3114 ARCSTAT_BUMP(arcstat_misses
);
3115 ARCSTAT_CONDSTAT(!(hdr
->b_flags
& ARC_PREFETCH
),
3116 demand
, prefetch
, hdr
->b_type
!= ARC_BUFC_METADATA
,
3117 data
, metadata
, misses
);
3119 if (vd
!= NULL
&& l2arc_ndev
!= 0 && !(l2arc_norw
&& devw
)) {
3121 * Read from the L2ARC if the following are true:
3122 * 1. The L2ARC vdev was previously cached.
3123 * 2. This buffer still has L2ARC metadata.
3124 * 3. This buffer isn't currently writing to the L2ARC.
3125 * 4. The L2ARC entry wasn't evicted, which may
3126 * also have invalidated the vdev.
3127 * 5. This isn't prefetch and l2arc_noprefetch is set.
3129 if (hdr
->b_l2hdr
!= NULL
&&
3130 !HDR_L2_WRITING(hdr
) && !HDR_L2_EVICTED(hdr
) &&
3131 !(l2arc_noprefetch
&& HDR_PREFETCH(hdr
))) {
3132 l2arc_read_callback_t
*cb
;
3134 DTRACE_PROBE1(l2arc__hit
, arc_buf_hdr_t
*, hdr
);
3135 ARCSTAT_BUMP(arcstat_l2_hits
);
3137 cb
= kmem_zalloc(sizeof (l2arc_read_callback_t
),
3139 cb
->l2rcb_buf
= buf
;
3140 cb
->l2rcb_spa
= spa
;
3143 cb
->l2rcb_flags
= zio_flags
;
3144 cb
->l2rcb_compress
= hdr
->b_l2hdr
->b_compress
;
3147 * l2arc read. The SCL_L2ARC lock will be
3148 * released by l2arc_read_done().
3149 * Issue a null zio if the underlying buffer
3150 * was squashed to zero size by compression.
3152 if (hdr
->b_l2hdr
->b_compress
==
3153 ZIO_COMPRESS_EMPTY
) {
3154 rzio
= zio_null(pio
, spa
, vd
,
3155 l2arc_read_done
, cb
,
3156 zio_flags
| ZIO_FLAG_DONT_CACHE
|
3158 ZIO_FLAG_DONT_PROPAGATE
|
3159 ZIO_FLAG_DONT_RETRY
);
3161 rzio
= zio_read_phys(pio
, vd
, addr
,
3162 hdr
->b_l2hdr
->b_asize
,
3163 buf
->b_data
, ZIO_CHECKSUM_OFF
,
3164 l2arc_read_done
, cb
, priority
,
3165 zio_flags
| ZIO_FLAG_DONT_CACHE
|
3167 ZIO_FLAG_DONT_PROPAGATE
|
3168 ZIO_FLAG_DONT_RETRY
, B_FALSE
);
3170 DTRACE_PROBE2(l2arc__read
, vdev_t
*, vd
,
3172 ARCSTAT_INCR(arcstat_l2_read_bytes
,
3173 hdr
->b_l2hdr
->b_asize
);
3175 if (*arc_flags
& ARC_NOWAIT
) {
3180 ASSERT(*arc_flags
& ARC_WAIT
);
3181 if (zio_wait(rzio
) == 0)
3184 /* l2arc read error; goto zio_read() */
3186 DTRACE_PROBE1(l2arc__miss
,
3187 arc_buf_hdr_t
*, hdr
);
3188 ARCSTAT_BUMP(arcstat_l2_misses
);
3189 if (HDR_L2_WRITING(hdr
))
3190 ARCSTAT_BUMP(arcstat_l2_rw_clash
);
3191 spa_config_exit(spa
, SCL_L2ARC
, vd
);
3195 spa_config_exit(spa
, SCL_L2ARC
, vd
);
3196 if (l2arc_ndev
!= 0) {
3197 DTRACE_PROBE1(l2arc__miss
,
3198 arc_buf_hdr_t
*, hdr
);
3199 ARCSTAT_BUMP(arcstat_l2_misses
);
3203 rzio
= zio_read(pio
, spa
, bp
, buf
->b_data
, size
,
3204 arc_read_done
, buf
, priority
, zio_flags
, zb
);
3206 if (*arc_flags
& ARC_WAIT
)
3207 return (zio_wait(rzio
));
3209 ASSERT(*arc_flags
& ARC_NOWAIT
);
3216 arc_add_prune_callback(arc_prune_func_t
*func
, void *private)
3220 p
= kmem_alloc(sizeof(*p
), KM_SLEEP
);
3222 p
->p_private
= private;
3223 list_link_init(&p
->p_node
);
3224 refcount_create(&p
->p_refcnt
);
3226 mutex_enter(&arc_prune_mtx
);
3227 refcount_add(&p
->p_refcnt
, &arc_prune_list
);
3228 list_insert_head(&arc_prune_list
, p
);
3229 mutex_exit(&arc_prune_mtx
);
3235 arc_remove_prune_callback(arc_prune_t
*p
)
3237 mutex_enter(&arc_prune_mtx
);
3238 list_remove(&arc_prune_list
, p
);
3239 if (refcount_remove(&p
->p_refcnt
, &arc_prune_list
) == 0) {
3240 refcount_destroy(&p
->p_refcnt
);
3241 kmem_free(p
, sizeof (*p
));
3243 mutex_exit(&arc_prune_mtx
);
3247 arc_set_callback(arc_buf_t
*buf
, arc_evict_func_t
*func
, void *private)
3249 ASSERT(buf
->b_hdr
!= NULL
);
3250 ASSERT(buf
->b_hdr
->b_state
!= arc_anon
);
3251 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
) || func
== NULL
);
3252 ASSERT(buf
->b_efunc
== NULL
);
3253 ASSERT(!HDR_BUF_AVAILABLE(buf
->b_hdr
));
3255 buf
->b_efunc
= func
;
3256 buf
->b_private
= private;
3260 * Notify the arc that a block was freed, and thus will never be used again.
3263 arc_freed(spa_t
*spa
, const blkptr_t
*bp
)
3266 kmutex_t
*hash_lock
;
3267 uint64_t guid
= spa_load_guid(spa
);
3269 hdr
= buf_hash_find(guid
, BP_IDENTITY(bp
), BP_PHYSICAL_BIRTH(bp
),
3273 if (HDR_BUF_AVAILABLE(hdr
)) {
3274 arc_buf_t
*buf
= hdr
->b_buf
;
3275 add_reference(hdr
, hash_lock
, FTAG
);
3276 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
3277 mutex_exit(hash_lock
);
3279 arc_release(buf
, FTAG
);
3280 (void) arc_buf_remove_ref(buf
, FTAG
);
3282 mutex_exit(hash_lock
);
3288 * This is used by the DMU to let the ARC know that a buffer is
3289 * being evicted, so the ARC should clean up. If this arc buf
3290 * is not yet in the evicted state, it will be put there.
3293 arc_buf_evict(arc_buf_t
*buf
)
3296 kmutex_t
*hash_lock
;
3299 mutex_enter(&buf
->b_evict_lock
);
3303 * We are in arc_do_user_evicts().
3305 ASSERT(buf
->b_data
== NULL
);
3306 mutex_exit(&buf
->b_evict_lock
);
3308 } else if (buf
->b_data
== NULL
) {
3309 arc_buf_t copy
= *buf
; /* structure assignment */
3311 * We are on the eviction list; process this buffer now
3312 * but let arc_do_user_evicts() do the reaping.
3314 buf
->b_efunc
= NULL
;
3315 mutex_exit(&buf
->b_evict_lock
);
3316 VERIFY(copy
.b_efunc(©
) == 0);
3319 hash_lock
= HDR_LOCK(hdr
);
3320 mutex_enter(hash_lock
);
3322 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
3324 ASSERT3U(refcount_count(&hdr
->b_refcnt
), <, hdr
->b_datacnt
);
3325 ASSERT(hdr
->b_state
== arc_mru
|| hdr
->b_state
== arc_mfu
);
3328 * Pull this buffer off of the hdr
3331 while (*bufp
!= buf
)
3332 bufp
= &(*bufp
)->b_next
;
3333 *bufp
= buf
->b_next
;
3335 ASSERT(buf
->b_data
!= NULL
);
3336 arc_buf_destroy(buf
, FALSE
, FALSE
);
3338 if (hdr
->b_datacnt
== 0) {
3339 arc_state_t
*old_state
= hdr
->b_state
;
3340 arc_state_t
*evicted_state
;
3342 ASSERT(hdr
->b_buf
== NULL
);
3343 ASSERT(refcount_is_zero(&hdr
->b_refcnt
));
3346 (old_state
== arc_mru
) ? arc_mru_ghost
: arc_mfu_ghost
;
3348 mutex_enter(&old_state
->arcs_mtx
);
3349 mutex_enter(&evicted_state
->arcs_mtx
);
3351 arc_change_state(evicted_state
, hdr
, hash_lock
);
3352 ASSERT(HDR_IN_HASH_TABLE(hdr
));
3353 hdr
->b_flags
|= ARC_IN_HASH_TABLE
;
3354 hdr
->b_flags
&= ~ARC_BUF_AVAILABLE
;
3356 mutex_exit(&evicted_state
->arcs_mtx
);
3357 mutex_exit(&old_state
->arcs_mtx
);
3359 mutex_exit(hash_lock
);
3360 mutex_exit(&buf
->b_evict_lock
);
3362 VERIFY(buf
->b_efunc(buf
) == 0);
3363 buf
->b_efunc
= NULL
;
3364 buf
->b_private
= NULL
;
3367 kmem_cache_free(buf_cache
, buf
);
3372 * Release this buffer from the cache. This must be done
3373 * after a read and prior to modifying the buffer contents.
3374 * If the buffer has more than one reference, we must make
3375 * a new hdr for the buffer.
3378 arc_release(arc_buf_t
*buf
, void *tag
)
3381 kmutex_t
*hash_lock
= NULL
;
3382 l2arc_buf_hdr_t
*l2hdr
;
3383 uint64_t buf_size
= 0;
3386 * It would be nice to assert that if it's DMU metadata (level >
3387 * 0 || it's the dnode file), then it must be syncing context.
3388 * But we don't know that information at this level.
3391 mutex_enter(&buf
->b_evict_lock
);
3394 /* this buffer is not on any list */
3395 ASSERT(refcount_count(&hdr
->b_refcnt
) > 0);
3397 if (hdr
->b_state
== arc_anon
) {
3398 /* this buffer is already released */
3399 ASSERT(buf
->b_efunc
== NULL
);
3401 hash_lock
= HDR_LOCK(hdr
);
3402 mutex_enter(hash_lock
);
3404 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
3407 l2hdr
= hdr
->b_l2hdr
;
3409 mutex_enter(&l2arc_buflist_mtx
);
3410 hdr
->b_l2hdr
= NULL
;
3411 buf_size
= hdr
->b_size
;
3415 * Do we have more than one buf?
3417 if (hdr
->b_datacnt
> 1) {
3418 arc_buf_hdr_t
*nhdr
;
3420 uint64_t blksz
= hdr
->b_size
;
3421 uint64_t spa
= hdr
->b_spa
;
3422 arc_buf_contents_t type
= hdr
->b_type
;
3423 uint32_t flags
= hdr
->b_flags
;
3425 ASSERT(hdr
->b_buf
!= buf
|| buf
->b_next
!= NULL
);
3427 * Pull the data off of this hdr and attach it to
3428 * a new anonymous hdr.
3430 (void) remove_reference(hdr
, hash_lock
, tag
);
3432 while (*bufp
!= buf
)
3433 bufp
= &(*bufp
)->b_next
;
3434 *bufp
= buf
->b_next
;
3437 ASSERT3U(hdr
->b_state
->arcs_size
, >=, hdr
->b_size
);
3438 atomic_add_64(&hdr
->b_state
->arcs_size
, -hdr
->b_size
);
3439 if (refcount_is_zero(&hdr
->b_refcnt
)) {
3440 uint64_t *size
= &hdr
->b_state
->arcs_lsize
[hdr
->b_type
];
3441 ASSERT3U(*size
, >=, hdr
->b_size
);
3442 atomic_add_64(size
, -hdr
->b_size
);
3446 * We're releasing a duplicate user data buffer, update
3447 * our statistics accordingly.
3449 if (hdr
->b_type
== ARC_BUFC_DATA
) {
3450 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers
);
3451 ARCSTAT_INCR(arcstat_duplicate_buffers_size
,
3454 hdr
->b_datacnt
-= 1;
3455 arc_cksum_verify(buf
);
3457 mutex_exit(hash_lock
);
3459 nhdr
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
3460 nhdr
->b_size
= blksz
;
3462 nhdr
->b_type
= type
;
3464 nhdr
->b_state
= arc_anon
;
3465 nhdr
->b_arc_access
= 0;
3466 nhdr
->b_flags
= flags
& ARC_L2_WRITING
;
3467 nhdr
->b_l2hdr
= NULL
;
3468 nhdr
->b_datacnt
= 1;
3469 nhdr
->b_freeze_cksum
= NULL
;
3470 (void) refcount_add(&nhdr
->b_refcnt
, tag
);
3472 mutex_exit(&buf
->b_evict_lock
);
3473 atomic_add_64(&arc_anon
->arcs_size
, blksz
);
3475 mutex_exit(&buf
->b_evict_lock
);
3476 ASSERT(refcount_count(&hdr
->b_refcnt
) == 1);
3477 ASSERT(!list_link_active(&hdr
->b_arc_node
));
3478 ASSERT(!HDR_IO_IN_PROGRESS(hdr
));
3479 if (hdr
->b_state
!= arc_anon
)
3480 arc_change_state(arc_anon
, hdr
, hash_lock
);
3481 hdr
->b_arc_access
= 0;
3483 mutex_exit(hash_lock
);
3485 buf_discard_identity(hdr
);
3488 buf
->b_efunc
= NULL
;
3489 buf
->b_private
= NULL
;
3492 ARCSTAT_INCR(arcstat_l2_asize
, -l2hdr
->b_asize
);
3493 list_remove(l2hdr
->b_dev
->l2ad_buflist
, hdr
);
3494 kmem_free(l2hdr
, sizeof (l2arc_buf_hdr_t
));
3495 arc_space_return(L2HDR_SIZE
, ARC_SPACE_L2HDRS
);
3496 ARCSTAT_INCR(arcstat_l2_size
, -buf_size
);
3497 mutex_exit(&l2arc_buflist_mtx
);
3502 arc_released(arc_buf_t
*buf
)
3506 mutex_enter(&buf
->b_evict_lock
);
3507 released
= (buf
->b_data
!= NULL
&& buf
->b_hdr
->b_state
== arc_anon
);
3508 mutex_exit(&buf
->b_evict_lock
);
3513 arc_has_callback(arc_buf_t
*buf
)
3517 mutex_enter(&buf
->b_evict_lock
);
3518 callback
= (buf
->b_efunc
!= NULL
);
3519 mutex_exit(&buf
->b_evict_lock
);
3525 arc_referenced(arc_buf_t
*buf
)
3529 mutex_enter(&buf
->b_evict_lock
);
3530 referenced
= (refcount_count(&buf
->b_hdr
->b_refcnt
));
3531 mutex_exit(&buf
->b_evict_lock
);
3532 return (referenced
);
3537 arc_write_ready(zio_t
*zio
)
3539 arc_write_callback_t
*callback
= zio
->io_private
;
3540 arc_buf_t
*buf
= callback
->awcb_buf
;
3541 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3543 ASSERT(!refcount_is_zero(&buf
->b_hdr
->b_refcnt
));
3544 callback
->awcb_ready(zio
, buf
, callback
->awcb_private
);
3547 * If the IO is already in progress, then this is a re-write
3548 * attempt, so we need to thaw and re-compute the cksum.
3549 * It is the responsibility of the callback to handle the
3550 * accounting for any re-write attempt.
3552 if (HDR_IO_IN_PROGRESS(hdr
)) {
3553 mutex_enter(&hdr
->b_freeze_lock
);
3554 if (hdr
->b_freeze_cksum
!= NULL
) {
3555 kmem_free(hdr
->b_freeze_cksum
, sizeof (zio_cksum_t
));
3556 hdr
->b_freeze_cksum
= NULL
;
3558 mutex_exit(&hdr
->b_freeze_lock
);
3560 arc_cksum_compute(buf
, B_FALSE
);
3561 hdr
->b_flags
|= ARC_IO_IN_PROGRESS
;
3565 arc_write_done(zio_t
*zio
)
3567 arc_write_callback_t
*callback
= zio
->io_private
;
3568 arc_buf_t
*buf
= callback
->awcb_buf
;
3569 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3571 ASSERT(hdr
->b_acb
== NULL
);
3573 if (zio
->io_error
== 0) {
3574 hdr
->b_dva
= *BP_IDENTITY(zio
->io_bp
);
3575 hdr
->b_birth
= BP_PHYSICAL_BIRTH(zio
->io_bp
);
3576 hdr
->b_cksum0
= zio
->io_bp
->blk_cksum
.zc_word
[0];
3578 ASSERT(BUF_EMPTY(hdr
));
3582 * If the block to be written was all-zero, we may have
3583 * compressed it away. In this case no write was performed
3584 * so there will be no dva/birth/checksum. The buffer must
3585 * therefore remain anonymous (and uncached).
3587 if (!BUF_EMPTY(hdr
)) {
3588 arc_buf_hdr_t
*exists
;
3589 kmutex_t
*hash_lock
;
3591 ASSERT(zio
->io_error
== 0);
3593 arc_cksum_verify(buf
);
3595 exists
= buf_hash_insert(hdr
, &hash_lock
);
3598 * This can only happen if we overwrite for
3599 * sync-to-convergence, because we remove
3600 * buffers from the hash table when we arc_free().
3602 if (zio
->io_flags
& ZIO_FLAG_IO_REWRITE
) {
3603 if (!BP_EQUAL(&zio
->io_bp_orig
, zio
->io_bp
))
3604 panic("bad overwrite, hdr=%p exists=%p",
3605 (void *)hdr
, (void *)exists
);
3606 ASSERT(refcount_is_zero(&exists
->b_refcnt
));
3607 arc_change_state(arc_anon
, exists
, hash_lock
);
3608 mutex_exit(hash_lock
);
3609 arc_hdr_destroy(exists
);
3610 exists
= buf_hash_insert(hdr
, &hash_lock
);
3611 ASSERT3P(exists
, ==, NULL
);
3614 ASSERT(hdr
->b_datacnt
== 1);
3615 ASSERT(hdr
->b_state
== arc_anon
);
3616 ASSERT(BP_GET_DEDUP(zio
->io_bp
));
3617 ASSERT(BP_GET_LEVEL(zio
->io_bp
) == 0);
3620 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3621 /* if it's not anon, we are doing a scrub */
3622 if (!exists
&& hdr
->b_state
== arc_anon
)
3623 arc_access(hdr
, hash_lock
);
3624 mutex_exit(hash_lock
);
3626 hdr
->b_flags
&= ~ARC_IO_IN_PROGRESS
;
3629 ASSERT(!refcount_is_zero(&hdr
->b_refcnt
));
3630 callback
->awcb_done(zio
, buf
, callback
->awcb_private
);
3632 kmem_free(callback
, sizeof (arc_write_callback_t
));
3636 arc_write(zio_t
*pio
, spa_t
*spa
, uint64_t txg
,
3637 blkptr_t
*bp
, arc_buf_t
*buf
, boolean_t l2arc
, boolean_t l2arc_compress
,
3638 const zio_prop_t
*zp
, arc_done_func_t
*ready
, arc_done_func_t
*done
,
3639 void *private, int priority
, int zio_flags
, const zbookmark_t
*zb
)
3641 arc_buf_hdr_t
*hdr
= buf
->b_hdr
;
3642 arc_write_callback_t
*callback
;
3645 ASSERT(ready
!= NULL
);
3646 ASSERT(done
!= NULL
);
3647 ASSERT(!HDR_IO_ERROR(hdr
));
3648 ASSERT((hdr
->b_flags
& ARC_IO_IN_PROGRESS
) == 0);
3649 ASSERT(hdr
->b_acb
== NULL
);
3651 hdr
->b_flags
|= ARC_L2CACHE
;
3653 hdr
->b_flags
|= ARC_L2COMPRESS
;
3654 callback
= kmem_zalloc(sizeof (arc_write_callback_t
), KM_PUSHPAGE
);
3655 callback
->awcb_ready
= ready
;
3656 callback
->awcb_done
= done
;
3657 callback
->awcb_private
= private;
3658 callback
->awcb_buf
= buf
;
3660 zio
= zio_write(pio
, spa
, txg
, bp
, buf
->b_data
, hdr
->b_size
, zp
,
3661 arc_write_ready
, arc_write_done
, callback
, priority
, zio_flags
, zb
);
3667 arc_memory_throttle(uint64_t reserve
, uint64_t inflight_data
, uint64_t txg
)
3670 uint64_t available_memory
;
3672 if (zfs_arc_memory_throttle_disable
)
3675 /* Easily reclaimable memory (free + inactive + arc-evictable) */
3676 available_memory
= ptob(spl_kmem_availrmem()) + arc_evictable_memory();
3678 if (available_memory
<= zfs_write_limit_max
) {
3679 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3680 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim
);
3684 if (inflight_data
> available_memory
/ 4) {
3685 ARCSTAT_INCR(arcstat_memory_throttle_count
, 1);
3686 DMU_TX_STAT_BUMP(dmu_tx_memory_inflight
);
3694 arc_tempreserve_clear(uint64_t reserve
)
3696 atomic_add_64(&arc_tempreserve
, -reserve
);
3697 ASSERT((int64_t)arc_tempreserve
>= 0);
3701 arc_tempreserve_space(uint64_t reserve
, uint64_t txg
)
3708 * Once in a while, fail for no reason. Everything should cope.
3710 if (spa_get_random(10000) == 0) {
3711 dprintf("forcing random failure\n");
3715 if (reserve
> arc_c
/4 && !arc_no_grow
)
3716 arc_c
= MIN(arc_c_max
, reserve
* 4);
3717 if (reserve
> arc_c
) {
3718 DMU_TX_STAT_BUMP(dmu_tx_memory_reserve
);
3723 * Don't count loaned bufs as in flight dirty data to prevent long
3724 * network delays from blocking transactions that are ready to be
3725 * assigned to a txg.
3727 anon_size
= MAX((int64_t)(arc_anon
->arcs_size
- arc_loaned_bytes
), 0);
3730 * Writes will, almost always, require additional memory allocations
3731 * in order to compress/encrypt/etc the data. We therefor need to
3732 * make sure that there is sufficient available memory for this.
3734 if ((error
= arc_memory_throttle(reserve
, anon_size
, txg
)))
3738 * Throttle writes when the amount of dirty data in the cache
3739 * gets too large. We try to keep the cache less than half full
3740 * of dirty blocks so that our sync times don't grow too large.
3741 * Note: if two requests come in concurrently, we might let them
3742 * both succeed, when one of them should fail. Not a huge deal.
3745 if (reserve
+ arc_tempreserve
+ anon_size
> arc_c
/ 2 &&
3746 anon_size
> arc_c
/ 4) {
3747 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3748 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3749 arc_tempreserve
>>10,
3750 arc_anon
->arcs_lsize
[ARC_BUFC_METADATA
]>>10,
3751 arc_anon
->arcs_lsize
[ARC_BUFC_DATA
]>>10,
3752 reserve
>>10, arc_c
>>10);
3753 DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle
);
3756 atomic_add_64(&arc_tempreserve
, reserve
);
3761 arc_kstat_update_state(arc_state_t
*state
, kstat_named_t
*size
,
3762 kstat_named_t
*evict_data
, kstat_named_t
*evict_metadata
)
3764 size
->value
.ui64
= state
->arcs_size
;
3765 evict_data
->value
.ui64
= state
->arcs_lsize
[ARC_BUFC_DATA
];
3766 evict_metadata
->value
.ui64
= state
->arcs_lsize
[ARC_BUFC_METADATA
];
3770 arc_kstat_update(kstat_t
*ksp
, int rw
)
3772 arc_stats_t
*as
= ksp
->ks_data
;
3774 if (rw
== KSTAT_WRITE
) {
3777 arc_kstat_update_state(arc_anon
,
3778 &as
->arcstat_anon_size
,
3779 &as
->arcstat_anon_evict_data
,
3780 &as
->arcstat_anon_evict_metadata
);
3781 arc_kstat_update_state(arc_mru
,
3782 &as
->arcstat_mru_size
,
3783 &as
->arcstat_mru_evict_data
,
3784 &as
->arcstat_mru_evict_metadata
);
3785 arc_kstat_update_state(arc_mru_ghost
,
3786 &as
->arcstat_mru_ghost_size
,
3787 &as
->arcstat_mru_ghost_evict_data
,
3788 &as
->arcstat_mru_ghost_evict_metadata
);
3789 arc_kstat_update_state(arc_mfu
,
3790 &as
->arcstat_mfu_size
,
3791 &as
->arcstat_mfu_evict_data
,
3792 &as
->arcstat_mfu_evict_metadata
);
3793 arc_kstat_update_state(arc_mfu_ghost
,
3794 &as
->arcstat_mfu_ghost_size
,
3795 &as
->arcstat_mfu_ghost_evict_data
,
3796 &as
->arcstat_mfu_ghost_evict_metadata
);
3805 mutex_init(&arc_reclaim_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3806 cv_init(&arc_reclaim_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
3808 /* Convert seconds to clock ticks */
3809 zfs_arc_min_prefetch_lifespan
= 1 * hz
;
3811 /* Start out with 1/8 of all memory */
3812 arc_c
= physmem
* PAGESIZE
/ 8;
3816 * On architectures where the physical memory can be larger
3817 * than the addressable space (intel in 32-bit mode), we may
3818 * need to limit the cache to 1/8 of VM size.
3820 arc_c
= MIN(arc_c
, vmem_size(heap_arena
, VMEM_ALLOC
| VMEM_FREE
) / 8);
3822 * Register a shrinker to support synchronous (direct) memory
3823 * reclaim from the arc. This is done to prevent kswapd from
3824 * swapping out pages when it is preferable to shrink the arc.
3826 spl_register_shrinker(&arc_shrinker
);
3829 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3830 arc_c_min
= MAX(arc_c
/ 4, 64<<20);
3831 /* set max to 1/2 of all memory */
3832 arc_c_max
= MAX(arc_c
* 4, arc_c_max
);
3835 * Allow the tunables to override our calculations if they are
3836 * reasonable (ie. over 64MB)
3838 if (zfs_arc_max
> 64<<20 && zfs_arc_max
< physmem
* PAGESIZE
)
3839 arc_c_max
= zfs_arc_max
;
3840 if (zfs_arc_min
> 64<<20 && zfs_arc_min
<= arc_c_max
)
3841 arc_c_min
= zfs_arc_min
;
3844 arc_p
= (arc_c
>> 1);
3846 /* limit meta-data to 1/4 of the arc capacity */
3847 arc_meta_limit
= arc_c_max
/ 4;
3850 /* Allow the tunable to override if it is reasonable */
3851 if (zfs_arc_meta_limit
> 0 && zfs_arc_meta_limit
<= arc_c_max
)
3852 arc_meta_limit
= zfs_arc_meta_limit
;
3854 if (arc_c_min
< arc_meta_limit
/ 2 && zfs_arc_min
== 0)
3855 arc_c_min
= arc_meta_limit
/ 2;
3857 /* if kmem_flags are set, lets try to use less memory */
3858 if (kmem_debugging())
3860 if (arc_c
< arc_c_min
)
3863 arc_anon
= &ARC_anon
;
3865 arc_mru_ghost
= &ARC_mru_ghost
;
3867 arc_mfu_ghost
= &ARC_mfu_ghost
;
3868 arc_l2c_only
= &ARC_l2c_only
;
3871 mutex_init(&arc_anon
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3872 mutex_init(&arc_mru
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3873 mutex_init(&arc_mru_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3874 mutex_init(&arc_mfu
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3875 mutex_init(&arc_mfu_ghost
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3876 mutex_init(&arc_l2c_only
->arcs_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3878 list_create(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
],
3879 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3880 list_create(&arc_mru
->arcs_list
[ARC_BUFC_DATA
],
3881 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3882 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3883 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3884 list_create(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
],
3885 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3886 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
],
3887 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3888 list_create(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
],
3889 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3890 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
],
3891 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3892 list_create(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
],
3893 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3894 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_METADATA
],
3895 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3896 list_create(&arc_l2c_only
->arcs_list
[ARC_BUFC_DATA
],
3897 sizeof (arc_buf_hdr_t
), offsetof(arc_buf_hdr_t
, b_arc_node
));
3901 arc_thread_exit
= 0;
3902 list_create(&arc_prune_list
, sizeof (arc_prune_t
),
3903 offsetof(arc_prune_t
, p_node
));
3904 arc_eviction_list
= NULL
;
3905 mutex_init(&arc_prune_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3906 mutex_init(&arc_eviction_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
3907 bzero(&arc_eviction_hdr
, sizeof (arc_buf_hdr_t
));
3909 arc_ksp
= kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED
,
3910 sizeof (arc_stats
) / sizeof (kstat_named_t
), KSTAT_FLAG_VIRTUAL
);
3912 if (arc_ksp
!= NULL
) {
3913 arc_ksp
->ks_data
= &arc_stats
;
3914 arc_ksp
->ks_update
= arc_kstat_update
;
3915 kstat_install(arc_ksp
);
3918 (void) thread_create(NULL
, 0, arc_adapt_thread
, NULL
, 0, &p0
,
3919 TS_RUN
, minclsyspri
);
3924 if (zfs_write_limit_max
== 0)
3925 zfs_write_limit_max
= ptob(physmem
) >> zfs_write_limit_shift
;
3927 zfs_write_limit_shift
= 0;
3928 mutex_init(&zfs_write_limit_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
3936 mutex_enter(&arc_reclaim_thr_lock
);
3938 spl_unregister_shrinker(&arc_shrinker
);
3939 #endif /* _KERNEL */
3941 arc_thread_exit
= 1;
3942 while (arc_thread_exit
!= 0)
3943 cv_wait(&arc_reclaim_thr_cv
, &arc_reclaim_thr_lock
);
3944 mutex_exit(&arc_reclaim_thr_lock
);
3950 if (arc_ksp
!= NULL
) {
3951 kstat_delete(arc_ksp
);
3955 mutex_enter(&arc_prune_mtx
);
3956 while ((p
= list_head(&arc_prune_list
)) != NULL
) {
3957 list_remove(&arc_prune_list
, p
);
3958 refcount_remove(&p
->p_refcnt
, &arc_prune_list
);
3959 refcount_destroy(&p
->p_refcnt
);
3960 kmem_free(p
, sizeof (*p
));
3962 mutex_exit(&arc_prune_mtx
);
3964 list_destroy(&arc_prune_list
);
3965 mutex_destroy(&arc_prune_mtx
);
3966 mutex_destroy(&arc_eviction_mtx
);
3967 mutex_destroy(&arc_reclaim_thr_lock
);
3968 cv_destroy(&arc_reclaim_thr_cv
);
3970 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_METADATA
]);
3971 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3972 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_METADATA
]);
3973 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_METADATA
]);
3974 list_destroy(&arc_mru
->arcs_list
[ARC_BUFC_DATA
]);
3975 list_destroy(&arc_mru_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3976 list_destroy(&arc_mfu
->arcs_list
[ARC_BUFC_DATA
]);
3977 list_destroy(&arc_mfu_ghost
->arcs_list
[ARC_BUFC_DATA
]);
3979 mutex_destroy(&arc_anon
->arcs_mtx
);
3980 mutex_destroy(&arc_mru
->arcs_mtx
);
3981 mutex_destroy(&arc_mru_ghost
->arcs_mtx
);
3982 mutex_destroy(&arc_mfu
->arcs_mtx
);
3983 mutex_destroy(&arc_mfu_ghost
->arcs_mtx
);
3984 mutex_destroy(&arc_l2c_only
->arcs_mtx
);
3986 mutex_destroy(&zfs_write_limit_lock
);
3990 ASSERT(arc_loaned_bytes
== 0);
3996 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3997 * It uses dedicated storage devices to hold cached data, which are populated
3998 * using large infrequent writes. The main role of this cache is to boost
3999 * the performance of random read workloads. The intended L2ARC devices
4000 * include short-stroked disks, solid state disks, and other media with
4001 * substantially faster read latency than disk.
4003 * +-----------------------+
4005 * +-----------------------+
4008 * l2arc_feed_thread() arc_read()
4012 * +---------------+ |
4014 * +---------------+ |
4019 * +-------+ +-------+
4021 * | cache | | cache |
4022 * +-------+ +-------+
4023 * +=========+ .-----.
4024 * : L2ARC : |-_____-|
4025 * : devices : | Disks |
4026 * +=========+ `-_____-'
4028 * Read requests are satisfied from the following sources, in order:
4031 * 2) vdev cache of L2ARC devices
4033 * 4) vdev cache of disks
4036 * Some L2ARC device types exhibit extremely slow write performance.
4037 * To accommodate for this there are some significant differences between
4038 * the L2ARC and traditional cache design:
4040 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4041 * the ARC behave as usual, freeing buffers and placing headers on ghost
4042 * lists. The ARC does not send buffers to the L2ARC during eviction as
4043 * this would add inflated write latencies for all ARC memory pressure.
4045 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4046 * It does this by periodically scanning buffers from the eviction-end of
4047 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4048 * not already there. It scans until a headroom of buffers is satisfied,
4049 * which itself is a buffer for ARC eviction. If a compressible buffer is
4050 * found during scanning and selected for writing to an L2ARC device, we
4051 * temporarily boost scanning headroom during the next scan cycle to make
4052 * sure we adapt to compression effects (which might significantly reduce
4053 * the data volume we write to L2ARC). The thread that does this is
4054 * l2arc_feed_thread(), illustrated below; example sizes are included to
4055 * provide a better sense of ratio than this diagram:
4058 * +---------------------+----------+
4059 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4060 * +---------------------+----------+ | o L2ARC eligible
4061 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4062 * +---------------------+----------+ |
4063 * 15.9 Gbytes ^ 32 Mbytes |
4065 * l2arc_feed_thread()
4067 * l2arc write hand <--[oooo]--'
4071 * +==============================+
4072 * L2ARC dev |####|#|###|###| |####| ... |
4073 * +==============================+
4076 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4077 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4078 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4079 * safe to say that this is an uncommon case, since buffers at the end of
4080 * the ARC lists have moved there due to inactivity.
4082 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4083 * then the L2ARC simply misses copying some buffers. This serves as a
4084 * pressure valve to prevent heavy read workloads from both stalling the ARC
4085 * with waits and clogging the L2ARC with writes. This also helps prevent
4086 * the potential for the L2ARC to churn if it attempts to cache content too
4087 * quickly, such as during backups of the entire pool.
4089 * 5. After system boot and before the ARC has filled main memory, there are
4090 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4091 * lists can remain mostly static. Instead of searching from tail of these
4092 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4093 * for eligible buffers, greatly increasing its chance of finding them.
4095 * The L2ARC device write speed is also boosted during this time so that
4096 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4097 * there are no L2ARC reads, and no fear of degrading read performance
4098 * through increased writes.
4100 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4101 * the vdev queue can aggregate them into larger and fewer writes. Each
4102 * device is written to in a rotor fashion, sweeping writes through
4103 * available space then repeating.
4105 * 7. The L2ARC does not store dirty content. It never needs to flush
4106 * write buffers back to disk based storage.
4108 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4109 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4111 * The performance of the L2ARC can be tweaked by a number of tunables, which
4112 * may be necessary for different workloads:
4114 * l2arc_write_max max write bytes per interval
4115 * l2arc_write_boost extra write bytes during device warmup
4116 * l2arc_noprefetch skip caching prefetched buffers
4117 * l2arc_nocompress skip compressing buffers
4118 * l2arc_headroom number of max device writes to precache
4119 * l2arc_headroom_boost when we find compressed buffers during ARC
4120 * scanning, we multiply headroom by this
4121 * percentage factor for the next scan cycle,
4122 * since more compressed buffers are likely to
4124 * l2arc_feed_secs seconds between L2ARC writing
4126 * Tunables may be removed or added as future performance improvements are
4127 * integrated, and also may become zpool properties.
4129 * There are three key functions that control how the L2ARC warms up:
4131 * l2arc_write_eligible() check if a buffer is eligible to cache
4132 * l2arc_write_size() calculate how much to write
4133 * l2arc_write_interval() calculate sleep delay between writes
4135 * These three functions determine what to write, how much, and how quickly
4140 l2arc_write_eligible(uint64_t spa_guid
, arc_buf_hdr_t
*ab
)
4143 * A buffer is *not* eligible for the L2ARC if it:
4144 * 1. belongs to a different spa.
4145 * 2. is already cached on the L2ARC.
4146 * 3. has an I/O in progress (it may be an incomplete read).
4147 * 4. is flagged not eligible (zfs property).
4149 if (ab
->b_spa
!= spa_guid
|| ab
->b_l2hdr
!= NULL
||
4150 HDR_IO_IN_PROGRESS(ab
) || !HDR_L2CACHE(ab
))
4157 l2arc_write_size(void)
4162 * Make sure our globals have meaningful values in case the user
4165 size
= l2arc_write_max
;
4167 cmn_err(CE_NOTE
, "Bad value for l2arc_write_max, value must "
4168 "be greater than zero, resetting it to the default (%d)",
4170 size
= l2arc_write_max
= L2ARC_WRITE_SIZE
;
4173 if (arc_warm
== B_FALSE
)
4174 size
+= l2arc_write_boost
;
4181 l2arc_write_interval(clock_t began
, uint64_t wanted
, uint64_t wrote
)
4183 clock_t interval
, next
, now
;
4186 * If the ARC lists are busy, increase our write rate; if the
4187 * lists are stale, idle back. This is achieved by checking
4188 * how much we previously wrote - if it was more than half of
4189 * what we wanted, schedule the next write much sooner.
4191 if (l2arc_feed_again
&& wrote
> (wanted
/ 2))
4192 interval
= (hz
* l2arc_feed_min_ms
) / 1000;
4194 interval
= hz
* l2arc_feed_secs
;
4196 now
= ddi_get_lbolt();
4197 next
= MAX(now
, MIN(now
+ interval
, began
+ interval
));
4203 l2arc_hdr_stat_add(void)
4205 ARCSTAT_INCR(arcstat_l2_hdr_size
, HDR_SIZE
);
4206 ARCSTAT_INCR(arcstat_hdr_size
, -HDR_SIZE
);
4210 l2arc_hdr_stat_remove(void)
4212 ARCSTAT_INCR(arcstat_l2_hdr_size
, -HDR_SIZE
);
4213 ARCSTAT_INCR(arcstat_hdr_size
, HDR_SIZE
);
4217 * Cycle through L2ARC devices. This is how L2ARC load balances.
4218 * If a device is returned, this also returns holding the spa config lock.
4220 static l2arc_dev_t
*
4221 l2arc_dev_get_next(void)
4223 l2arc_dev_t
*first
, *next
= NULL
;
4226 * Lock out the removal of spas (spa_namespace_lock), then removal
4227 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4228 * both locks will be dropped and a spa config lock held instead.
4230 mutex_enter(&spa_namespace_lock
);
4231 mutex_enter(&l2arc_dev_mtx
);
4233 /* if there are no vdevs, there is nothing to do */
4234 if (l2arc_ndev
== 0)
4238 next
= l2arc_dev_last
;
4240 /* loop around the list looking for a non-faulted vdev */
4242 next
= list_head(l2arc_dev_list
);
4244 next
= list_next(l2arc_dev_list
, next
);
4246 next
= list_head(l2arc_dev_list
);
4249 /* if we have come back to the start, bail out */
4252 else if (next
== first
)
4255 } while (vdev_is_dead(next
->l2ad_vdev
));
4257 /* if we were unable to find any usable vdevs, return NULL */
4258 if (vdev_is_dead(next
->l2ad_vdev
))
4261 l2arc_dev_last
= next
;
4264 mutex_exit(&l2arc_dev_mtx
);
4267 * Grab the config lock to prevent the 'next' device from being
4268 * removed while we are writing to it.
4271 spa_config_enter(next
->l2ad_spa
, SCL_L2ARC
, next
, RW_READER
);
4272 mutex_exit(&spa_namespace_lock
);
4278 * Free buffers that were tagged for destruction.
4281 l2arc_do_free_on_write(void)
4284 l2arc_data_free_t
*df
, *df_prev
;
4286 mutex_enter(&l2arc_free_on_write_mtx
);
4287 buflist
= l2arc_free_on_write
;
4289 for (df
= list_tail(buflist
); df
; df
= df_prev
) {
4290 df_prev
= list_prev(buflist
, df
);
4291 ASSERT(df
->l2df_data
!= NULL
);
4292 ASSERT(df
->l2df_func
!= NULL
);
4293 df
->l2df_func(df
->l2df_data
, df
->l2df_size
);
4294 list_remove(buflist
, df
);
4295 kmem_free(df
, sizeof (l2arc_data_free_t
));
4298 mutex_exit(&l2arc_free_on_write_mtx
);
4302 * A write to a cache device has completed. Update all headers to allow
4303 * reads from these buffers to begin.
4306 l2arc_write_done(zio_t
*zio
)
4308 l2arc_write_callback_t
*cb
;
4311 arc_buf_hdr_t
*head
, *ab
, *ab_prev
;
4312 l2arc_buf_hdr_t
*abl2
;
4313 kmutex_t
*hash_lock
;
4315 cb
= zio
->io_private
;
4317 dev
= cb
->l2wcb_dev
;
4318 ASSERT(dev
!= NULL
);
4319 head
= cb
->l2wcb_head
;
4320 ASSERT(head
!= NULL
);
4321 buflist
= dev
->l2ad_buflist
;
4322 ASSERT(buflist
!= NULL
);
4323 DTRACE_PROBE2(l2arc__iodone
, zio_t
*, zio
,
4324 l2arc_write_callback_t
*, cb
);
4326 if (zio
->io_error
!= 0)
4327 ARCSTAT_BUMP(arcstat_l2_writes_error
);
4329 mutex_enter(&l2arc_buflist_mtx
);
4332 * All writes completed, or an error was hit.
4334 for (ab
= list_prev(buflist
, head
); ab
; ab
= ab_prev
) {
4335 ab_prev
= list_prev(buflist
, ab
);
4337 hash_lock
= HDR_LOCK(ab
);
4338 if (!mutex_tryenter(hash_lock
)) {
4340 * This buffer misses out. It may be in a stage
4341 * of eviction. Its ARC_L2_WRITING flag will be
4342 * left set, denying reads to this buffer.
4344 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss
);
4351 * Release the temporary compressed buffer as soon as possible.
4353 if (abl2
->b_compress
!= ZIO_COMPRESS_OFF
)
4354 l2arc_release_cdata_buf(ab
);
4356 if (zio
->io_error
!= 0) {
4358 * Error - drop L2ARC entry.
4360 list_remove(buflist
, ab
);
4361 ARCSTAT_INCR(arcstat_l2_asize
, -abl2
->b_asize
);
4363 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
4364 arc_space_return(L2HDR_SIZE
, ARC_SPACE_L2HDRS
);
4365 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
4369 * Allow ARC to begin reads to this L2ARC entry.
4371 ab
->b_flags
&= ~ARC_L2_WRITING
;
4373 mutex_exit(hash_lock
);
4376 atomic_inc_64(&l2arc_writes_done
);
4377 list_remove(buflist
, head
);
4378 kmem_cache_free(hdr_cache
, head
);
4379 mutex_exit(&l2arc_buflist_mtx
);
4381 l2arc_do_free_on_write();
4383 kmem_free(cb
, sizeof (l2arc_write_callback_t
));
4387 * A read to a cache device completed. Validate buffer contents before
4388 * handing over to the regular ARC routines.
4391 l2arc_read_done(zio_t
*zio
)
4393 l2arc_read_callback_t
*cb
;
4396 kmutex_t
*hash_lock
;
4399 ASSERT(zio
->io_vd
!= NULL
);
4400 ASSERT(zio
->io_flags
& ZIO_FLAG_DONT_PROPAGATE
);
4402 spa_config_exit(zio
->io_spa
, SCL_L2ARC
, zio
->io_vd
);
4404 cb
= zio
->io_private
;
4406 buf
= cb
->l2rcb_buf
;
4407 ASSERT(buf
!= NULL
);
4409 hash_lock
= HDR_LOCK(buf
->b_hdr
);
4410 mutex_enter(hash_lock
);
4412 ASSERT3P(hash_lock
, ==, HDR_LOCK(hdr
));
4415 * If the buffer was compressed, decompress it first.
4417 if (cb
->l2rcb_compress
!= ZIO_COMPRESS_OFF
)
4418 l2arc_decompress_zio(zio
, hdr
, cb
->l2rcb_compress
);
4419 ASSERT(zio
->io_data
!= NULL
);
4422 * Check this survived the L2ARC journey.
4424 equal
= arc_cksum_equal(buf
);
4425 if (equal
&& zio
->io_error
== 0 && !HDR_L2_EVICTED(hdr
)) {
4426 mutex_exit(hash_lock
);
4427 zio
->io_private
= buf
;
4428 zio
->io_bp_copy
= cb
->l2rcb_bp
; /* XXX fix in L2ARC 2.0 */
4429 zio
->io_bp
= &zio
->io_bp_copy
; /* XXX fix in L2ARC 2.0 */
4432 mutex_exit(hash_lock
);
4434 * Buffer didn't survive caching. Increment stats and
4435 * reissue to the original storage device.
4437 if (zio
->io_error
!= 0) {
4438 ARCSTAT_BUMP(arcstat_l2_io_error
);
4440 zio
->io_error
= EIO
;
4443 ARCSTAT_BUMP(arcstat_l2_cksum_bad
);
4446 * If there's no waiter, issue an async i/o to the primary
4447 * storage now. If there *is* a waiter, the caller must
4448 * issue the i/o in a context where it's OK to block.
4450 if (zio
->io_waiter
== NULL
) {
4451 zio_t
*pio
= zio_unique_parent(zio
);
4453 ASSERT(!pio
|| pio
->io_child_type
== ZIO_CHILD_LOGICAL
);
4455 zio_nowait(zio_read(pio
, cb
->l2rcb_spa
, &cb
->l2rcb_bp
,
4456 buf
->b_data
, zio
->io_size
, arc_read_done
, buf
,
4457 zio
->io_priority
, cb
->l2rcb_flags
, &cb
->l2rcb_zb
));
4461 kmem_free(cb
, sizeof (l2arc_read_callback_t
));
4465 * This is the list priority from which the L2ARC will search for pages to
4466 * cache. This is used within loops (0..3) to cycle through lists in the
4467 * desired order. This order can have a significant effect on cache
4470 * Currently the metadata lists are hit first, MFU then MRU, followed by
4471 * the data lists. This function returns a locked list, and also returns
4475 l2arc_list_locked(int list_num
, kmutex_t
**lock
)
4477 list_t
*list
= NULL
;
4479 ASSERT(list_num
>= 0 && list_num
<= 3);
4483 list
= &arc_mfu
->arcs_list
[ARC_BUFC_METADATA
];
4484 *lock
= &arc_mfu
->arcs_mtx
;
4487 list
= &arc_mru
->arcs_list
[ARC_BUFC_METADATA
];
4488 *lock
= &arc_mru
->arcs_mtx
;
4491 list
= &arc_mfu
->arcs_list
[ARC_BUFC_DATA
];
4492 *lock
= &arc_mfu
->arcs_mtx
;
4495 list
= &arc_mru
->arcs_list
[ARC_BUFC_DATA
];
4496 *lock
= &arc_mru
->arcs_mtx
;
4500 ASSERT(!(MUTEX_HELD(*lock
)));
4506 * Evict buffers from the device write hand to the distance specified in
4507 * bytes. This distance may span populated buffers, it may span nothing.
4508 * This is clearing a region on the L2ARC device ready for writing.
4509 * If the 'all' boolean is set, every buffer is evicted.
4512 l2arc_evict(l2arc_dev_t
*dev
, uint64_t distance
, boolean_t all
)
4515 l2arc_buf_hdr_t
*abl2
;
4516 arc_buf_hdr_t
*ab
, *ab_prev
;
4517 kmutex_t
*hash_lock
;
4520 buflist
= dev
->l2ad_buflist
;
4522 if (buflist
== NULL
)
4525 if (!all
&& dev
->l2ad_first
) {
4527 * This is the first sweep through the device. There is
4533 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- (2 * distance
))) {
4535 * When nearing the end of the device, evict to the end
4536 * before the device write hand jumps to the start.
4538 taddr
= dev
->l2ad_end
;
4540 taddr
= dev
->l2ad_hand
+ distance
;
4542 DTRACE_PROBE4(l2arc__evict
, l2arc_dev_t
*, dev
, list_t
*, buflist
,
4543 uint64_t, taddr
, boolean_t
, all
);
4546 mutex_enter(&l2arc_buflist_mtx
);
4547 for (ab
= list_tail(buflist
); ab
; ab
= ab_prev
) {
4548 ab_prev
= list_prev(buflist
, ab
);
4550 hash_lock
= HDR_LOCK(ab
);
4551 if (!mutex_tryenter(hash_lock
)) {
4553 * Missed the hash lock. Retry.
4555 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry
);
4556 mutex_exit(&l2arc_buflist_mtx
);
4557 mutex_enter(hash_lock
);
4558 mutex_exit(hash_lock
);
4562 if (HDR_L2_WRITE_HEAD(ab
)) {
4564 * We hit a write head node. Leave it for
4565 * l2arc_write_done().
4567 list_remove(buflist
, ab
);
4568 mutex_exit(hash_lock
);
4572 if (!all
&& ab
->b_l2hdr
!= NULL
&&
4573 (ab
->b_l2hdr
->b_daddr
> taddr
||
4574 ab
->b_l2hdr
->b_daddr
< dev
->l2ad_hand
)) {
4576 * We've evicted to the target address,
4577 * or the end of the device.
4579 mutex_exit(hash_lock
);
4583 if (HDR_FREE_IN_PROGRESS(ab
)) {
4585 * Already on the path to destruction.
4587 mutex_exit(hash_lock
);
4591 if (ab
->b_state
== arc_l2c_only
) {
4592 ASSERT(!HDR_L2_READING(ab
));
4594 * This doesn't exist in the ARC. Destroy.
4595 * arc_hdr_destroy() will call list_remove()
4596 * and decrement arcstat_l2_size.
4598 arc_change_state(arc_anon
, ab
, hash_lock
);
4599 arc_hdr_destroy(ab
);
4602 * Invalidate issued or about to be issued
4603 * reads, since we may be about to write
4604 * over this location.
4606 if (HDR_L2_READING(ab
)) {
4607 ARCSTAT_BUMP(arcstat_l2_evict_reading
);
4608 ab
->b_flags
|= ARC_L2_EVICTED
;
4612 * Tell ARC this no longer exists in L2ARC.
4614 if (ab
->b_l2hdr
!= NULL
) {
4616 ARCSTAT_INCR(arcstat_l2_asize
, -abl2
->b_asize
);
4618 kmem_free(abl2
, sizeof (l2arc_buf_hdr_t
));
4619 arc_space_return(L2HDR_SIZE
, ARC_SPACE_L2HDRS
);
4620 ARCSTAT_INCR(arcstat_l2_size
, -ab
->b_size
);
4622 list_remove(buflist
, ab
);
4625 * This may have been leftover after a
4628 ab
->b_flags
&= ~ARC_L2_WRITING
;
4630 mutex_exit(hash_lock
);
4632 mutex_exit(&l2arc_buflist_mtx
);
4634 vdev_space_update(dev
->l2ad_vdev
, -(taddr
- dev
->l2ad_evict
), 0, 0);
4635 dev
->l2ad_evict
= taddr
;
4639 * Find and write ARC buffers to the L2ARC device.
4641 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4642 * for reading until they have completed writing.
4643 * The headroom_boost is an in-out parameter used to maintain headroom boost
4644 * state between calls to this function.
4646 * Returns the number of bytes actually written (which may be smaller than
4647 * the delta by which the device hand has changed due to alignment).
4650 l2arc_write_buffers(spa_t
*spa
, l2arc_dev_t
*dev
, uint64_t target_sz
,
4651 boolean_t
*headroom_boost
)
4653 arc_buf_hdr_t
*ab
, *ab_prev
, *head
;
4655 uint64_t write_asize
, write_psize
, write_sz
, headroom
,
4658 kmutex_t
*list_lock
= NULL
;
4660 l2arc_write_callback_t
*cb
;
4662 uint64_t guid
= spa_load_guid(spa
);
4664 const boolean_t do_headroom_boost
= *headroom_boost
;
4666 ASSERT(dev
->l2ad_vdev
!= NULL
);
4668 /* Lower the flag now, we might want to raise it again later. */
4669 *headroom_boost
= B_FALSE
;
4672 write_sz
= write_asize
= write_psize
= 0;
4674 head
= kmem_cache_alloc(hdr_cache
, KM_PUSHPAGE
);
4675 head
->b_flags
|= ARC_L2_WRITE_HEAD
;
4678 * We will want to try to compress buffers that are at least 2x the
4679 * device sector size.
4681 buf_compress_minsz
= 2 << dev
->l2ad_vdev
->vdev_ashift
;
4684 * Copy buffers for L2ARC writing.
4686 mutex_enter(&l2arc_buflist_mtx
);
4687 for (try = 0; try <= 3; try++) {
4688 uint64_t passed_sz
= 0;
4690 list
= l2arc_list_locked(try, &list_lock
);
4693 * L2ARC fast warmup.
4695 * Until the ARC is warm and starts to evict, read from the
4696 * head of the ARC lists rather than the tail.
4698 if (arc_warm
== B_FALSE
)
4699 ab
= list_head(list
);
4701 ab
= list_tail(list
);
4703 headroom
= target_sz
* l2arc_headroom
;
4704 if (do_headroom_boost
)
4705 headroom
= (headroom
* l2arc_headroom_boost
) / 100;
4707 for (; ab
; ab
= ab_prev
) {
4708 l2arc_buf_hdr_t
*l2hdr
;
4709 kmutex_t
*hash_lock
;
4712 if (arc_warm
== B_FALSE
)
4713 ab_prev
= list_next(list
, ab
);
4715 ab_prev
= list_prev(list
, ab
);
4717 hash_lock
= HDR_LOCK(ab
);
4718 if (!mutex_tryenter(hash_lock
)) {
4720 * Skip this buffer rather than waiting.
4725 passed_sz
+= ab
->b_size
;
4726 if (passed_sz
> headroom
) {
4730 mutex_exit(hash_lock
);
4734 if (!l2arc_write_eligible(guid
, ab
)) {
4735 mutex_exit(hash_lock
);
4739 if ((write_sz
+ ab
->b_size
) > target_sz
) {
4741 mutex_exit(hash_lock
);
4747 * Insert a dummy header on the buflist so
4748 * l2arc_write_done() can find where the
4749 * write buffers begin without searching.
4751 list_insert_head(dev
->l2ad_buflist
, head
);
4753 cb
= kmem_alloc(sizeof (l2arc_write_callback_t
),
4755 cb
->l2wcb_dev
= dev
;
4756 cb
->l2wcb_head
= head
;
4757 pio
= zio_root(spa
, l2arc_write_done
, cb
,
4762 * Create and add a new L2ARC header.
4764 l2hdr
= kmem_zalloc(sizeof (l2arc_buf_hdr_t
),
4767 arc_space_consume(L2HDR_SIZE
, ARC_SPACE_L2HDRS
);
4769 ab
->b_flags
|= ARC_L2_WRITING
;
4772 * Temporarily stash the data buffer in b_tmp_cdata.
4773 * The subsequent write step will pick it up from
4774 * there. This is because can't access ab->b_buf
4775 * without holding the hash_lock, which we in turn
4776 * can't access without holding the ARC list locks
4777 * (which we want to avoid during compression/writing)
4779 l2hdr
->b_compress
= ZIO_COMPRESS_OFF
;
4780 l2hdr
->b_asize
= ab
->b_size
;
4781 l2hdr
->b_tmp_cdata
= ab
->b_buf
->b_data
;
4783 buf_sz
= ab
->b_size
;
4784 ab
->b_l2hdr
= l2hdr
;
4786 list_insert_head(dev
->l2ad_buflist
, ab
);
4789 * Compute and store the buffer cksum before
4790 * writing. On debug the cksum is verified first.
4792 arc_cksum_verify(ab
->b_buf
);
4793 arc_cksum_compute(ab
->b_buf
, B_TRUE
);
4795 mutex_exit(hash_lock
);
4800 mutex_exit(list_lock
);
4806 /* No buffers selected for writing? */
4809 mutex_exit(&l2arc_buflist_mtx
);
4810 kmem_cache_free(hdr_cache
, head
);
4815 * Now start writing the buffers. We're starting at the write head
4816 * and work backwards, retracing the course of the buffer selector
4819 for (ab
= list_prev(dev
->l2ad_buflist
, head
); ab
;
4820 ab
= list_prev(dev
->l2ad_buflist
, ab
)) {
4821 l2arc_buf_hdr_t
*l2hdr
;
4825 * We shouldn't need to lock the buffer here, since we flagged
4826 * it as ARC_L2_WRITING in the previous step, but we must take
4827 * care to only access its L2 cache parameters. In particular,
4828 * ab->b_buf may be invalid by now due to ARC eviction.
4830 l2hdr
= ab
->b_l2hdr
;
4831 l2hdr
->b_daddr
= dev
->l2ad_hand
;
4833 if (!l2arc_nocompress
&& (ab
->b_flags
& ARC_L2COMPRESS
) &&
4834 l2hdr
->b_asize
>= buf_compress_minsz
) {
4835 if (l2arc_compress_buf(l2hdr
)) {
4837 * If compression succeeded, enable headroom
4838 * boost on the next scan cycle.
4840 *headroom_boost
= B_TRUE
;
4845 * Pick up the buffer data we had previously stashed away
4846 * (and now potentially also compressed).
4848 buf_data
= l2hdr
->b_tmp_cdata
;
4849 buf_sz
= l2hdr
->b_asize
;
4851 /* Compression may have squashed the buffer to zero length. */
4855 wzio
= zio_write_phys(pio
, dev
->l2ad_vdev
,
4856 dev
->l2ad_hand
, buf_sz
, buf_data
, ZIO_CHECKSUM_OFF
,
4857 NULL
, NULL
, ZIO_PRIORITY_ASYNC_WRITE
,
4858 ZIO_FLAG_CANFAIL
, B_FALSE
);
4860 DTRACE_PROBE2(l2arc__write
, vdev_t
*, dev
->l2ad_vdev
,
4862 (void) zio_nowait(wzio
);
4864 write_asize
+= buf_sz
;
4866 * Keep the clock hand suitably device-aligned.
4868 buf_p_sz
= vdev_psize_to_asize(dev
->l2ad_vdev
, buf_sz
);
4869 write_psize
+= buf_p_sz
;
4870 dev
->l2ad_hand
+= buf_p_sz
;
4874 mutex_exit(&l2arc_buflist_mtx
);
4876 ASSERT3U(write_asize
, <=, target_sz
);
4877 ARCSTAT_BUMP(arcstat_l2_writes_sent
);
4878 ARCSTAT_INCR(arcstat_l2_write_bytes
, write_asize
);
4879 ARCSTAT_INCR(arcstat_l2_size
, write_sz
);
4880 ARCSTAT_INCR(arcstat_l2_asize
, write_asize
);
4881 vdev_space_update(dev
->l2ad_vdev
, write_psize
, 0, 0);
4884 * Bump device hand to the device start if it is approaching the end.
4885 * l2arc_evict() will already have evicted ahead for this case.
4887 if (dev
->l2ad_hand
>= (dev
->l2ad_end
- target_sz
)) {
4888 vdev_space_update(dev
->l2ad_vdev
,
4889 dev
->l2ad_end
- dev
->l2ad_hand
, 0, 0);
4890 dev
->l2ad_hand
= dev
->l2ad_start
;
4891 dev
->l2ad_evict
= dev
->l2ad_start
;
4892 dev
->l2ad_first
= B_FALSE
;
4895 dev
->l2ad_writing
= B_TRUE
;
4896 (void) zio_wait(pio
);
4897 dev
->l2ad_writing
= B_FALSE
;
4899 return (write_asize
);
4903 * Compresses an L2ARC buffer.
4904 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
4905 * size in l2hdr->b_asize. This routine tries to compress the data and
4906 * depending on the compression result there are three possible outcomes:
4907 * *) The buffer was incompressible. The original l2hdr contents were left
4908 * untouched and are ready for writing to an L2 device.
4909 * *) The buffer was all-zeros, so there is no need to write it to an L2
4910 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
4911 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
4912 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
4913 * data buffer which holds the compressed data to be written, and b_asize
4914 * tells us how much data there is. b_compress is set to the appropriate
4915 * compression algorithm. Once writing is done, invoke
4916 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
4918 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
4919 * buffer was incompressible).
4922 l2arc_compress_buf(l2arc_buf_hdr_t
*l2hdr
)
4927 ASSERT(l2hdr
->b_compress
== ZIO_COMPRESS_OFF
);
4928 ASSERT(l2hdr
->b_tmp_cdata
!= NULL
);
4930 len
= l2hdr
->b_asize
;
4931 cdata
= zio_data_buf_alloc(len
);
4932 csize
= zio_compress_data(ZIO_COMPRESS_LZ4
, l2hdr
->b_tmp_cdata
,
4933 cdata
, l2hdr
->b_asize
);
4936 /* zero block, indicate that there's nothing to write */
4937 zio_data_buf_free(cdata
, len
);
4938 l2hdr
->b_compress
= ZIO_COMPRESS_EMPTY
;
4940 l2hdr
->b_tmp_cdata
= NULL
;
4941 ARCSTAT_BUMP(arcstat_l2_compress_zeros
);
4943 } else if (csize
> 0 && csize
< len
) {
4945 * Compression succeeded, we'll keep the cdata around for
4946 * writing and release it afterwards.
4948 l2hdr
->b_compress
= ZIO_COMPRESS_LZ4
;
4949 l2hdr
->b_asize
= csize
;
4950 l2hdr
->b_tmp_cdata
= cdata
;
4951 ARCSTAT_BUMP(arcstat_l2_compress_successes
);
4955 * Compression failed, release the compressed buffer.
4956 * l2hdr will be left unmodified.
4958 zio_data_buf_free(cdata
, len
);
4959 ARCSTAT_BUMP(arcstat_l2_compress_failures
);
4965 * Decompresses a zio read back from an l2arc device. On success, the
4966 * underlying zio's io_data buffer is overwritten by the uncompressed
4967 * version. On decompression error (corrupt compressed stream), the
4968 * zio->io_error value is set to signal an I/O error.
4970 * Please note that the compressed data stream is not checksummed, so
4971 * if the underlying device is experiencing data corruption, we may feed
4972 * corrupt data to the decompressor, so the decompressor needs to be
4973 * able to handle this situation (LZ4 does).
4976 l2arc_decompress_zio(zio_t
*zio
, arc_buf_hdr_t
*hdr
, enum zio_compress c
)
4981 ASSERT(L2ARC_IS_VALID_COMPRESS(c
));
4983 if (zio
->io_error
!= 0) {
4985 * An io error has occured, just restore the original io
4986 * size in preparation for a main pool read.
4988 zio
->io_orig_size
= zio
->io_size
= hdr
->b_size
;
4992 if (c
== ZIO_COMPRESS_EMPTY
) {
4994 * An empty buffer results in a null zio, which means we
4995 * need to fill its io_data after we're done restoring the
4996 * buffer's contents.
4998 ASSERT(hdr
->b_buf
!= NULL
);
4999 bzero(hdr
->b_buf
->b_data
, hdr
->b_size
);
5000 zio
->io_data
= zio
->io_orig_data
= hdr
->b_buf
->b_data
;
5002 ASSERT(zio
->io_data
!= NULL
);
5004 * We copy the compressed data from the start of the arc buffer
5005 * (the zio_read will have pulled in only what we need, the
5006 * rest is garbage which we will overwrite at decompression)
5007 * and then decompress back to the ARC data buffer. This way we
5008 * can minimize copying by simply decompressing back over the
5009 * original compressed data (rather than decompressing to an
5010 * aux buffer and then copying back the uncompressed buffer,
5011 * which is likely to be much larger).
5013 csize
= zio
->io_size
;
5014 cdata
= zio_data_buf_alloc(csize
);
5015 bcopy(zio
->io_data
, cdata
, csize
);
5016 if (zio_decompress_data(c
, cdata
, zio
->io_data
, csize
,
5018 zio
->io_error
= EIO
;
5019 zio_data_buf_free(cdata
, csize
);
5022 /* Restore the expected uncompressed IO size. */
5023 zio
->io_orig_size
= zio
->io_size
= hdr
->b_size
;
5027 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
5028 * This buffer serves as a temporary holder of compressed data while
5029 * the buffer entry is being written to an l2arc device. Once that is
5030 * done, we can dispose of it.
5033 l2arc_release_cdata_buf(arc_buf_hdr_t
*ab
)
5035 l2arc_buf_hdr_t
*l2hdr
= ab
->b_l2hdr
;
5037 if (l2hdr
->b_compress
== ZIO_COMPRESS_LZ4
) {
5039 * If the data was compressed, then we've allocated a
5040 * temporary buffer for it, so now we need to release it.
5042 ASSERT(l2hdr
->b_tmp_cdata
!= NULL
);
5043 zio_data_buf_free(l2hdr
->b_tmp_cdata
, ab
->b_size
);
5045 l2hdr
->b_tmp_cdata
= NULL
;
5049 * This thread feeds the L2ARC at regular intervals. This is the beating
5050 * heart of the L2ARC.
5053 l2arc_feed_thread(void)
5058 uint64_t size
, wrote
;
5059 clock_t begin
, next
= ddi_get_lbolt();
5060 boolean_t headroom_boost
= B_FALSE
;
5062 CALLB_CPR_INIT(&cpr
, &l2arc_feed_thr_lock
, callb_generic_cpr
, FTAG
);
5064 mutex_enter(&l2arc_feed_thr_lock
);
5066 while (l2arc_thread_exit
== 0) {
5067 CALLB_CPR_SAFE_BEGIN(&cpr
);
5068 (void) cv_timedwait_interruptible(&l2arc_feed_thr_cv
,
5069 &l2arc_feed_thr_lock
, next
);
5070 CALLB_CPR_SAFE_END(&cpr
, &l2arc_feed_thr_lock
);
5071 next
= ddi_get_lbolt() + hz
;
5074 * Quick check for L2ARC devices.
5076 mutex_enter(&l2arc_dev_mtx
);
5077 if (l2arc_ndev
== 0) {
5078 mutex_exit(&l2arc_dev_mtx
);
5081 mutex_exit(&l2arc_dev_mtx
);
5082 begin
= ddi_get_lbolt();
5085 * This selects the next l2arc device to write to, and in
5086 * doing so the next spa to feed from: dev->l2ad_spa. This
5087 * will return NULL if there are now no l2arc devices or if
5088 * they are all faulted.
5090 * If a device is returned, its spa's config lock is also
5091 * held to prevent device removal. l2arc_dev_get_next()
5092 * will grab and release l2arc_dev_mtx.
5094 if ((dev
= l2arc_dev_get_next()) == NULL
)
5097 spa
= dev
->l2ad_spa
;
5098 ASSERT(spa
!= NULL
);
5101 * If the pool is read-only then force the feed thread to
5102 * sleep a little longer.
5104 if (!spa_writeable(spa
)) {
5105 next
= ddi_get_lbolt() + 5 * l2arc_feed_secs
* hz
;
5106 spa_config_exit(spa
, SCL_L2ARC
, dev
);
5111 * Avoid contributing to memory pressure.
5114 ARCSTAT_BUMP(arcstat_l2_abort_lowmem
);
5115 spa_config_exit(spa
, SCL_L2ARC
, dev
);
5119 ARCSTAT_BUMP(arcstat_l2_feeds
);
5121 size
= l2arc_write_size();
5124 * Evict L2ARC buffers that will be overwritten.
5126 l2arc_evict(dev
, size
, B_FALSE
);
5129 * Write ARC buffers.
5131 wrote
= l2arc_write_buffers(spa
, dev
, size
, &headroom_boost
);
5134 * Calculate interval between writes.
5136 next
= l2arc_write_interval(begin
, size
, wrote
);
5137 spa_config_exit(spa
, SCL_L2ARC
, dev
);
5140 l2arc_thread_exit
= 0;
5141 cv_broadcast(&l2arc_feed_thr_cv
);
5142 CALLB_CPR_EXIT(&cpr
); /* drops l2arc_feed_thr_lock */
5147 l2arc_vdev_present(vdev_t
*vd
)
5151 mutex_enter(&l2arc_dev_mtx
);
5152 for (dev
= list_head(l2arc_dev_list
); dev
!= NULL
;
5153 dev
= list_next(l2arc_dev_list
, dev
)) {
5154 if (dev
->l2ad_vdev
== vd
)
5157 mutex_exit(&l2arc_dev_mtx
);
5159 return (dev
!= NULL
);
5163 * Add a vdev for use by the L2ARC. By this point the spa has already
5164 * validated the vdev and opened it.
5167 l2arc_add_vdev(spa_t
*spa
, vdev_t
*vd
)
5169 l2arc_dev_t
*adddev
;
5171 ASSERT(!l2arc_vdev_present(vd
));
5174 * Create a new l2arc device entry.
5176 adddev
= kmem_zalloc(sizeof (l2arc_dev_t
), KM_SLEEP
);
5177 adddev
->l2ad_spa
= spa
;
5178 adddev
->l2ad_vdev
= vd
;
5179 adddev
->l2ad_start
= VDEV_LABEL_START_SIZE
;
5180 adddev
->l2ad_end
= VDEV_LABEL_START_SIZE
+ vdev_get_min_asize(vd
);
5181 adddev
->l2ad_hand
= adddev
->l2ad_start
;
5182 adddev
->l2ad_evict
= adddev
->l2ad_start
;
5183 adddev
->l2ad_first
= B_TRUE
;
5184 adddev
->l2ad_writing
= B_FALSE
;
5185 list_link_init(&adddev
->l2ad_node
);
5188 * This is a list of all ARC buffers that are still valid on the
5191 adddev
->l2ad_buflist
= kmem_zalloc(sizeof (list_t
), KM_SLEEP
);
5192 list_create(adddev
->l2ad_buflist
, sizeof (arc_buf_hdr_t
),
5193 offsetof(arc_buf_hdr_t
, b_l2node
));
5195 vdev_space_update(vd
, 0, 0, adddev
->l2ad_end
- adddev
->l2ad_hand
);
5198 * Add device to global list
5200 mutex_enter(&l2arc_dev_mtx
);
5201 list_insert_head(l2arc_dev_list
, adddev
);
5202 atomic_inc_64(&l2arc_ndev
);
5203 mutex_exit(&l2arc_dev_mtx
);
5207 * Remove a vdev from the L2ARC.
5210 l2arc_remove_vdev(vdev_t
*vd
)
5212 l2arc_dev_t
*dev
, *nextdev
, *remdev
= NULL
;
5215 * Find the device by vdev
5217 mutex_enter(&l2arc_dev_mtx
);
5218 for (dev
= list_head(l2arc_dev_list
); dev
; dev
= nextdev
) {
5219 nextdev
= list_next(l2arc_dev_list
, dev
);
5220 if (vd
== dev
->l2ad_vdev
) {
5225 ASSERT(remdev
!= NULL
);
5228 * Remove device from global list
5230 list_remove(l2arc_dev_list
, remdev
);
5231 l2arc_dev_last
= NULL
; /* may have been invalidated */
5232 atomic_dec_64(&l2arc_ndev
);
5233 mutex_exit(&l2arc_dev_mtx
);
5236 * Clear all buflists and ARC references. L2ARC device flush.
5238 l2arc_evict(remdev
, 0, B_TRUE
);
5239 list_destroy(remdev
->l2ad_buflist
);
5240 kmem_free(remdev
->l2ad_buflist
, sizeof (list_t
));
5241 kmem_free(remdev
, sizeof (l2arc_dev_t
));
5247 l2arc_thread_exit
= 0;
5249 l2arc_writes_sent
= 0;
5250 l2arc_writes_done
= 0;
5252 mutex_init(&l2arc_feed_thr_lock
, NULL
, MUTEX_DEFAULT
, NULL
);
5253 cv_init(&l2arc_feed_thr_cv
, NULL
, CV_DEFAULT
, NULL
);
5254 mutex_init(&l2arc_dev_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
5255 mutex_init(&l2arc_buflist_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
5256 mutex_init(&l2arc_free_on_write_mtx
, NULL
, MUTEX_DEFAULT
, NULL
);
5258 l2arc_dev_list
= &L2ARC_dev_list
;
5259 l2arc_free_on_write
= &L2ARC_free_on_write
;
5260 list_create(l2arc_dev_list
, sizeof (l2arc_dev_t
),
5261 offsetof(l2arc_dev_t
, l2ad_node
));
5262 list_create(l2arc_free_on_write
, sizeof (l2arc_data_free_t
),
5263 offsetof(l2arc_data_free_t
, l2df_list_node
));
5270 * This is called from dmu_fini(), which is called from spa_fini();
5271 * Because of this, we can assume that all l2arc devices have
5272 * already been removed when the pools themselves were removed.
5275 l2arc_do_free_on_write();
5277 mutex_destroy(&l2arc_feed_thr_lock
);
5278 cv_destroy(&l2arc_feed_thr_cv
);
5279 mutex_destroy(&l2arc_dev_mtx
);
5280 mutex_destroy(&l2arc_buflist_mtx
);
5281 mutex_destroy(&l2arc_free_on_write_mtx
);
5283 list_destroy(l2arc_dev_list
);
5284 list_destroy(l2arc_free_on_write
);
5290 if (!(spa_mode_global
& FWRITE
))
5293 (void) thread_create(NULL
, 0, l2arc_feed_thread
, NULL
, 0, &p0
,
5294 TS_RUN
, minclsyspri
);
5300 if (!(spa_mode_global
& FWRITE
))
5303 mutex_enter(&l2arc_feed_thr_lock
);
5304 cv_signal(&l2arc_feed_thr_cv
); /* kick thread out of startup */
5305 l2arc_thread_exit
= 1;
5306 while (l2arc_thread_exit
!= 0)
5307 cv_wait(&l2arc_feed_thr_cv
, &l2arc_feed_thr_lock
);
5308 mutex_exit(&l2arc_feed_thr_lock
);
5311 #if defined(_KERNEL) && defined(HAVE_SPL)
5312 EXPORT_SYMBOL(arc_read
);
5313 EXPORT_SYMBOL(arc_buf_remove_ref
);
5314 EXPORT_SYMBOL(arc_getbuf_func
);
5315 EXPORT_SYMBOL(arc_add_prune_callback
);
5316 EXPORT_SYMBOL(arc_remove_prune_callback
);
5318 module_param(zfs_arc_min
, ulong
, 0644);
5319 MODULE_PARM_DESC(zfs_arc_min
, "Min arc size");
5321 module_param(zfs_arc_max
, ulong
, 0644);
5322 MODULE_PARM_DESC(zfs_arc_max
, "Max arc size");
5324 module_param(zfs_arc_meta_limit
, ulong
, 0644);
5325 MODULE_PARM_DESC(zfs_arc_meta_limit
, "Meta limit for arc size");
5327 module_param(zfs_arc_meta_prune
, int, 0644);
5328 MODULE_PARM_DESC(zfs_arc_meta_prune
, "Bytes of meta data to prune");
5330 module_param(zfs_arc_grow_retry
, int, 0644);
5331 MODULE_PARM_DESC(zfs_arc_grow_retry
, "Seconds before growing arc size");
5333 module_param(zfs_arc_shrink_shift
, int, 0644);
5334 MODULE_PARM_DESC(zfs_arc_shrink_shift
, "log2(fraction of arc to reclaim)");
5336 module_param(zfs_arc_p_min_shift
, int, 0644);
5337 MODULE_PARM_DESC(zfs_arc_p_min_shift
, "arc_c shift to calc min/max arc_p");
5339 module_param(zfs_disable_dup_eviction
, int, 0644);
5340 MODULE_PARM_DESC(zfs_disable_dup_eviction
, "disable duplicate buffer eviction");
5342 module_param(zfs_arc_memory_throttle_disable
, int, 0644);
5343 MODULE_PARM_DESC(zfs_arc_memory_throttle_disable
, "disable memory throttle");
5345 module_param(zfs_arc_min_prefetch_lifespan
, int, 0644);
5346 MODULE_PARM_DESC(zfs_arc_min_prefetch_lifespan
, "Min life of prefetch block");
5348 module_param(l2arc_write_max
, ulong
, 0644);
5349 MODULE_PARM_DESC(l2arc_write_max
, "Max write bytes per interval");
5351 module_param(l2arc_write_boost
, ulong
, 0644);
5352 MODULE_PARM_DESC(l2arc_write_boost
, "Extra write bytes during device warmup");
5354 module_param(l2arc_headroom
, ulong
, 0644);
5355 MODULE_PARM_DESC(l2arc_headroom
, "Number of max device writes to precache");
5357 module_param(l2arc_headroom_boost
, ulong
, 0644);
5358 MODULE_PARM_DESC(l2arc_headroom_boost
, "Compressed l2arc_headroom multiplier");
5360 module_param(l2arc_feed_secs
, ulong
, 0644);
5361 MODULE_PARM_DESC(l2arc_feed_secs
, "Seconds between L2ARC writing");
5363 module_param(l2arc_feed_min_ms
, ulong
, 0644);
5364 MODULE_PARM_DESC(l2arc_feed_min_ms
, "Min feed interval in milliseconds");
5366 module_param(l2arc_noprefetch
, int, 0644);
5367 MODULE_PARM_DESC(l2arc_noprefetch
, "Skip caching prefetched buffers");
5369 module_param(l2arc_nocompress
, int, 0644);
5370 MODULE_PARM_DESC(l2arc_nocompress
, "Skip compressing L2ARC buffers");
5372 module_param(l2arc_feed_again
, int, 0644);
5373 MODULE_PARM_DESC(l2arc_feed_again
, "Turbo L2ARC warmup");
5375 module_param(l2arc_norw
, int, 0644);
5376 MODULE_PARM_DESC(l2arc_norw
, "No reads during writes");