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.
26 * DVA-based Adjustable Replacement Cache
28 * While much of the theory of operation used here is
29 * based on the self-tuning, low overhead replacement cache
30 * presented by Megiddo and Modha at FAST 2003, there are some
31 * significant differences:
33 * 1. The Megiddo and Modha model assumes any page is evictable.
34 * Pages in its cache cannot be "locked" into memory. This makes
35 * the eviction algorithm simple: evict the last page in the list.
36 * This also make the performance characteristics easy to reason
37 * about. Our cache is not so simple. At any given moment, some
38 * subset of the blocks in the cache are un-evictable because we
39 * have handed out a reference to them. Blocks are only evictable
40 * when there are no external references active. This makes
41 * eviction far more problematic: we choose to evict the evictable
42 * blocks that are the "lowest" in the list.
44 * There are times when it is not possible to evict the requested
45 * space. In these circumstances we are unable to adjust the cache
46 * size. To prevent the cache growing unbounded at these times we
47 * implement a "cache throttle" that slows the flow of new data
48 * into the cache until we can make space available.
50 * 2. The Megiddo and Modha model assumes a fixed cache size.
51 * Pages are evicted when the cache is full and there is a cache
52 * miss. Our model has a variable sized cache. It grows with
53 * high use, but also tries to react to memory pressure from the
54 * operating system: decreasing its size when system memory is
57 * 3. The Megiddo and Modha model assumes a fixed page size. All
58 * elements of the cache are therefor exactly the same size. So
59 * when adjusting the cache size following a cache miss, its simply
60 * a matter of choosing a single page to evict. In our model, we
61 * have variable sized cache blocks (rangeing from 512 bytes to
62 * 128K bytes). We therefor choose a set of blocks to evict to make
63 * space for a cache miss that approximates as closely as possible
64 * the space used by the new block.
66 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
67 * by N. Megiddo & D. Modha, FAST 2003
73 * A new reference to a cache buffer can be obtained in two
74 * ways: 1) via a hash table lookup using the DVA as a key,
75 * or 2) via one of the ARC lists. The arc_read() interface
76 * uses method 1, while the internal arc algorithms for
77 * adjusting the cache use method 2. We therefor provide two
78 * types of locks: 1) the hash table lock array, and 2) the
81 * Buffers do not have their own mutexs, rather they rely on the
82 * hash table mutexs for the bulk of their protection (i.e. most
83 * fields in the arc_buf_hdr_t are protected by these mutexs).
85 * buf_hash_find() returns the appropriate mutex (held) when it
86 * locates the requested buffer in the hash table. It returns
87 * NULL for the mutex if the buffer was not in the table.
89 * buf_hash_remove() expects the appropriate hash mutex to be
90 * already held before it is invoked.
92 * Each arc state also has a mutex which is used to protect the
93 * buffer list associated with the state. When attempting to
94 * obtain a hash table lock while holding an arc list lock you
95 * must use: mutex_tryenter() to avoid deadlock. Also note that
96 * the active state mutex must be held before the ghost state mutex.
98 * Arc buffers may have an associated eviction callback function.
99 * This function will be invoked prior to removing the buffer (e.g.
100 * in arc_do_user_evicts()). Note however that the data associated
101 * with the buffer may be evicted prior to the callback. The callback
102 * must be made with *no locks held* (to prevent deadlock). Additionally,
103 * the users of callbacks must ensure that their private data is
104 * protected from simultaneous callbacks from arc_buf_evict()
105 * and arc_do_user_evicts().
107 * It as also possible to register a callback which is run when the
108 * arc_meta_limit is reached and no buffers can be safely evicted. In
109 * this case the arc user should drop a reference on some arc buffers so
110 * they can be reclaimed and the arc_meta_limit honored. For example,
111 * when using the ZPL each dentry holds a references on a znode. These
112 * dentries must be pruned before the arc buffer holding the znode can
115 * Note that the majority of the performance stats are manipulated
116 * with atomic operations.
118 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
120 * - L2ARC buflist creation
121 * - L2ARC buflist eviction
122 * - L2ARC write completion, which walks L2ARC buflists
123 * - ARC header destruction, as it removes from L2ARC buflists
124 * - ARC header release, as it removes from L2ARC buflists
129 #include <sys/zfs_context.h>
131 #include <sys/vdev.h>
132 #include <sys/vdev_impl.h>
134 #include <sys/vmsystm.h>
136 #include <sys/fs/swapnode.h>
139 #include <sys/callb.h>
140 #include <sys/kstat.h>
141 #include <sys/dmu_tx.h>
142 #include <zfs_fletcher.h>
144 static kmutex_t arc_reclaim_thr_lock;
145 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
146 static uint8_t arc_thread_exit;
148 extern int zfs_write_limit_shift;
149 extern uint64_t zfs_write_limit_max;
150 extern kmutex_t zfs_write_limit_lock;
152 /* number of bytes to prune from caches when at arc_meta_limit is reached */
153 uint_t 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 static int arc_grow_retry = 5;
163 /* expiration time for arc_no_grow */
164 static clock_t arc_grow_time = 0;
166 /* shift of arc_c for calculating both min and max arc_p */
167 static int arc_p_min_shift = 4;
169 /* log2(fraction of arc to reclaim) */
170 static int arc_shrink_shift = 5;
173 * minimum lifespan of a prefetch block in clock ticks
174 * (initialized in arc_init())
176 static int arc_min_prefetch_lifespan;
181 * The arc has filled available memory and has now warmed up.
183 static boolean_t arc_warm;
186 * These tunables are for performance analysis.
188 unsigned long zfs_arc_max = 0;
189 unsigned long zfs_arc_min = 0;
190 unsigned long zfs_arc_meta_limit = 0;
191 int zfs_arc_grow_retry = 0;
192 int zfs_arc_shrink_shift = 0;
193 int zfs_arc_p_min_shift = 0;
194 int zfs_arc_meta_prune = 0;
197 * Note that buffers can be in one of 6 states:
198 * ARC_anon - anonymous (discussed below)
199 * ARC_mru - recently used, currently cached
200 * ARC_mru_ghost - recentely used, no longer in cache
201 * ARC_mfu - frequently used, currently cached
202 * ARC_mfu_ghost - frequently used, no longer in cache
203 * ARC_l2c_only - exists in L2ARC but not other states
204 * When there are no active references to the buffer, they are
205 * are linked onto a list in one of these arc states. These are
206 * the only buffers that can be evicted or deleted. Within each
207 * state there are multiple lists, one for meta-data and one for
208 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
209 * etc.) is tracked separately so that it can be managed more
210 * explicitly: favored over data, limited explicitly.
212 * Anonymous buffers are buffers that are not associated with
213 * a DVA. These are buffers that hold dirty block copies
214 * before they are written to stable storage. By definition,
215 * they are "ref'd" and are considered part of arc_mru
216 * that cannot be freed. Generally, they will aquire a DVA
217 * as they are written and migrate onto the arc_mru list.
219 * The ARC_l2c_only state is for buffers that are in the second
220 * level ARC but no longer in any of the ARC_m* lists. The second
221 * level ARC itself may also contain buffers that are in any of
222 * the ARC_m* states - meaning that a buffer can exist in two
223 * places. The reason for the ARC_l2c_only state is to keep the
224 * buffer header in the hash table, so that reads that hit the
225 * second level ARC benefit from these fast lookups.
228 typedef struct arc_state {
229 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
230 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
231 uint64_t arcs_size; /* total amount of data in this state */
236 static arc_state_t ARC_anon;
237 static arc_state_t ARC_mru;
238 static arc_state_t ARC_mru_ghost;
239 static arc_state_t ARC_mfu;
240 static arc_state_t ARC_mfu_ghost;
241 static arc_state_t ARC_l2c_only;
243 typedef struct arc_stats {
244 kstat_named_t arcstat_hits;
245 kstat_named_t arcstat_misses;
246 kstat_named_t arcstat_demand_data_hits;
247 kstat_named_t arcstat_demand_data_misses;
248 kstat_named_t arcstat_demand_metadata_hits;
249 kstat_named_t arcstat_demand_metadata_misses;
250 kstat_named_t arcstat_prefetch_data_hits;
251 kstat_named_t arcstat_prefetch_data_misses;
252 kstat_named_t arcstat_prefetch_metadata_hits;
253 kstat_named_t arcstat_prefetch_metadata_misses;
254 kstat_named_t arcstat_mru_hits;
255 kstat_named_t arcstat_mru_ghost_hits;
256 kstat_named_t arcstat_mfu_hits;
257 kstat_named_t arcstat_mfu_ghost_hits;
258 kstat_named_t arcstat_deleted;
259 kstat_named_t arcstat_recycle_miss;
260 kstat_named_t arcstat_mutex_miss;
261 kstat_named_t arcstat_evict_skip;
262 kstat_named_t arcstat_evict_l2_cached;
263 kstat_named_t arcstat_evict_l2_eligible;
264 kstat_named_t arcstat_evict_l2_ineligible;
265 kstat_named_t arcstat_hash_elements;
266 kstat_named_t arcstat_hash_elements_max;
267 kstat_named_t arcstat_hash_collisions;
268 kstat_named_t arcstat_hash_chains;
269 kstat_named_t arcstat_hash_chain_max;
270 kstat_named_t arcstat_p;
271 kstat_named_t arcstat_c;
272 kstat_named_t arcstat_c_min;
273 kstat_named_t arcstat_c_max;
274 kstat_named_t arcstat_size;
275 kstat_named_t arcstat_hdr_size;
276 kstat_named_t arcstat_data_size;
277 kstat_named_t arcstat_other_size;
278 kstat_named_t arcstat_anon_size;
279 kstat_named_t arcstat_anon_evict_data;
280 kstat_named_t arcstat_anon_evict_metadata;
281 kstat_named_t arcstat_mru_size;
282 kstat_named_t arcstat_mru_evict_data;
283 kstat_named_t arcstat_mru_evict_metadata;
284 kstat_named_t arcstat_mru_ghost_size;
285 kstat_named_t arcstat_mru_ghost_evict_data;
286 kstat_named_t arcstat_mru_ghost_evict_metadata;
287 kstat_named_t arcstat_mfu_size;
288 kstat_named_t arcstat_mfu_evict_data;
289 kstat_named_t arcstat_mfu_evict_metadata;
290 kstat_named_t arcstat_mfu_ghost_size;
291 kstat_named_t arcstat_mfu_ghost_evict_data;
292 kstat_named_t arcstat_mfu_ghost_evict_metadata;
293 kstat_named_t arcstat_l2_hits;
294 kstat_named_t arcstat_l2_misses;
295 kstat_named_t arcstat_l2_feeds;
296 kstat_named_t arcstat_l2_rw_clash;
297 kstat_named_t arcstat_l2_read_bytes;
298 kstat_named_t arcstat_l2_write_bytes;
299 kstat_named_t arcstat_l2_writes_sent;
300 kstat_named_t arcstat_l2_writes_done;
301 kstat_named_t arcstat_l2_writes_error;
302 kstat_named_t arcstat_l2_writes_hdr_miss;
303 kstat_named_t arcstat_l2_evict_lock_retry;
304 kstat_named_t arcstat_l2_evict_reading;
305 kstat_named_t arcstat_l2_free_on_write;
306 kstat_named_t arcstat_l2_abort_lowmem;
307 kstat_named_t arcstat_l2_cksum_bad;
308 kstat_named_t arcstat_l2_io_error;
309 kstat_named_t arcstat_l2_size;
310 kstat_named_t arcstat_l2_hdr_size;
311 kstat_named_t arcstat_memory_throttle_count;
312 kstat_named_t arcstat_memory_direct_count;
313 kstat_named_t arcstat_memory_indirect_count;
314 kstat_named_t arcstat_no_grow;
315 kstat_named_t arcstat_tempreserve;
316 kstat_named_t arcstat_loaned_bytes;
317 kstat_named_t arcstat_prune;
318 kstat_named_t arcstat_meta_used;
319 kstat_named_t arcstat_meta_limit;
320 kstat_named_t arcstat_meta_max;
323 static arc_stats_t arc_stats = {
324 { "hits", KSTAT_DATA_UINT64 },
325 { "misses", KSTAT_DATA_UINT64 },
326 { "demand_data_hits", KSTAT_DATA_UINT64 },
327 { "demand_data_misses", KSTAT_DATA_UINT64 },
328 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
329 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
330 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
331 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
332 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
333 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
334 { "mru_hits", KSTAT_DATA_UINT64 },
335 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
336 { "mfu_hits", KSTAT_DATA_UINT64 },
337 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
338 { "deleted", KSTAT_DATA_UINT64 },
339 { "recycle_miss", KSTAT_DATA_UINT64 },
340 { "mutex_miss", KSTAT_DATA_UINT64 },
341 { "evict_skip", KSTAT_DATA_UINT64 },
342 { "evict_l2_cached", KSTAT_DATA_UINT64 },
343 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
344 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
345 { "hash_elements", KSTAT_DATA_UINT64 },
346 { "hash_elements_max", KSTAT_DATA_UINT64 },
347 { "hash_collisions", KSTAT_DATA_UINT64 },
348 { "hash_chains", KSTAT_DATA_UINT64 },
349 { "hash_chain_max", KSTAT_DATA_UINT64 },
350 { "p", KSTAT_DATA_UINT64 },
351 { "c", KSTAT_DATA_UINT64 },
352 { "c_min", KSTAT_DATA_UINT64 },
353 { "c_max", KSTAT_DATA_UINT64 },
354 { "size", KSTAT_DATA_UINT64 },
355 { "hdr_size", KSTAT_DATA_UINT64 },
356 { "data_size", KSTAT_DATA_UINT64 },
357 { "other_size", KSTAT_DATA_UINT64 },
358 { "anon_size", KSTAT_DATA_UINT64 },
359 { "anon_evict_data", KSTAT_DATA_UINT64 },
360 { "anon_evict_metadata", KSTAT_DATA_UINT64 },
361 { "mru_size", KSTAT_DATA_UINT64 },
362 { "mru_evict_data", KSTAT_DATA_UINT64 },
363 { "mru_evict_metadata", KSTAT_DATA_UINT64 },
364 { "mru_ghost_size", KSTAT_DATA_UINT64 },
365 { "mru_ghost_evict_data", KSTAT_DATA_UINT64 },
366 { "mru_ghost_evict_metadata", KSTAT_DATA_UINT64 },
367 { "mfu_size", KSTAT_DATA_UINT64 },
368 { "mfu_evict_data", KSTAT_DATA_UINT64 },
369 { "mfu_evict_metadata", KSTAT_DATA_UINT64 },
370 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
371 { "mfu_ghost_evict_data", KSTAT_DATA_UINT64 },
372 { "mfu_ghost_evict_metadata", KSTAT_DATA_UINT64 },
373 { "l2_hits", KSTAT_DATA_UINT64 },
374 { "l2_misses", KSTAT_DATA_UINT64 },
375 { "l2_feeds", KSTAT_DATA_UINT64 },
376 { "l2_rw_clash", KSTAT_DATA_UINT64 },
377 { "l2_read_bytes", KSTAT_DATA_UINT64 },
378 { "l2_write_bytes", KSTAT_DATA_UINT64 },
379 { "l2_writes_sent", KSTAT_DATA_UINT64 },
380 { "l2_writes_done", KSTAT_DATA_UINT64 },
381 { "l2_writes_error", KSTAT_DATA_UINT64 },
382 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
383 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
384 { "l2_evict_reading", KSTAT_DATA_UINT64 },
385 { "l2_free_on_write", KSTAT_DATA_UINT64 },
386 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
387 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
388 { "l2_io_error", KSTAT_DATA_UINT64 },
389 { "l2_size", KSTAT_DATA_UINT64 },
390 { "l2_hdr_size", KSTAT_DATA_UINT64 },
391 { "memory_throttle_count", KSTAT_DATA_UINT64 },
392 { "memory_direct_count", KSTAT_DATA_UINT64 },
393 { "memory_indirect_count", KSTAT_DATA_UINT64 },
394 { "arc_no_grow", KSTAT_DATA_UINT64 },
395 { "arc_tempreserve", KSTAT_DATA_UINT64 },
396 { "arc_loaned_bytes", KSTAT_DATA_UINT64 },
397 { "arc_prune", KSTAT_DATA_UINT64 },
398 { "arc_meta_used", KSTAT_DATA_UINT64 },
399 { "arc_meta_limit", KSTAT_DATA_UINT64 },
400 { "arc_meta_max", KSTAT_DATA_UINT64 },
403 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
405 #define ARCSTAT_INCR(stat, val) \
406 atomic_add_64(&arc_stats.stat.value.ui64, (val));
408 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
409 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
411 #define ARCSTAT_MAX(stat, val) { \
413 while ((val) > (m = arc_stats.stat.value.ui64) && \
414 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
418 #define ARCSTAT_MAXSTAT(stat) \
419 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
422 * We define a macro to allow ARC hits/misses to be easily broken down by
423 * two separate conditions, giving a total of four different subtypes for
424 * each of hits and misses (so eight statistics total).
426 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
429 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
431 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
435 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
437 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
442 static arc_state_t *arc_anon;
443 static arc_state_t *arc_mru;
444 static arc_state_t *arc_mru_ghost;
445 static arc_state_t *arc_mfu;
446 static arc_state_t *arc_mfu_ghost;
447 static arc_state_t *arc_l2c_only;
450 * There are several ARC variables that are critical to export as kstats --
451 * but we don't want to have to grovel around in the kstat whenever we wish to
452 * manipulate them. For these variables, we therefore define them to be in
453 * terms of the statistic variable. This assures that we are not introducing
454 * the possibility of inconsistency by having shadow copies of the variables,
455 * while still allowing the code to be readable.
457 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
458 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
459 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
460 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
461 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
462 #define arc_no_grow ARCSTAT(arcstat_no_grow)
463 #define arc_tempreserve ARCSTAT(arcstat_tempreserve)
464 #define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
465 #define arc_meta_used ARCSTAT(arcstat_meta_used)
466 #define arc_meta_limit ARCSTAT(arcstat_meta_limit)
467 #define arc_meta_max ARCSTAT(arcstat_meta_max)
469 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
471 typedef struct arc_callback arc_callback_t;
473 struct arc_callback {
475 arc_done_func_t *acb_done;
477 zio_t *acb_zio_dummy;
478 arc_callback_t *acb_next;
481 typedef struct arc_write_callback arc_write_callback_t;
483 struct arc_write_callback {
485 arc_done_func_t *awcb_ready;
486 arc_done_func_t *awcb_done;
491 /* protected by hash lock */
496 kmutex_t b_freeze_lock;
497 zio_cksum_t *b_freeze_cksum;
500 arc_buf_hdr_t *b_hash_next;
505 arc_callback_t *b_acb;
509 arc_buf_contents_t b_type;
513 /* protected by arc state mutex */
514 arc_state_t *b_state;
515 list_node_t b_arc_node;
517 /* updated atomically */
518 clock_t b_arc_access;
520 /* self protecting */
523 l2arc_buf_hdr_t *b_l2hdr;
524 list_node_t b_l2node;
527 static list_t arc_prune_list;
528 static kmutex_t arc_prune_mtx;
529 static arc_buf_t *arc_eviction_list;
530 static kmutex_t arc_eviction_mtx;
531 static arc_buf_hdr_t arc_eviction_hdr;
532 static void arc_get_data_buf(arc_buf_t *buf);
533 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
534 static int arc_evict_needed(arc_buf_contents_t type);
535 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
537 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
539 #define GHOST_STATE(state) \
540 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
541 (state) == arc_l2c_only)
544 * Private ARC flags. These flags are private ARC only flags that will show up
545 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
546 * be passed in as arc_flags in things like arc_read. However, these flags
547 * should never be passed and should only be set by ARC code. When adding new
548 * public flags, make sure not to smash the private ones.
551 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
552 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
553 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
554 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
555 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
556 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
557 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
558 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
559 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
560 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
562 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
563 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
564 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
565 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
566 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
567 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
568 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
569 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
570 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
571 (hdr)->b_l2hdr != NULL)
572 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
573 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
574 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
580 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
581 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
584 * Hash table routines
587 #define HT_LOCK_ALIGN 64
588 #define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
593 unsigned char pad[HT_LOCK_PAD];
597 #define BUF_LOCKS 256
598 typedef struct buf_hash_table {
600 arc_buf_hdr_t **ht_table;
601 struct ht_lock ht_locks[BUF_LOCKS];
604 static buf_hash_table_t buf_hash_table;
606 #define BUF_HASH_INDEX(spa, dva, birth) \
607 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
608 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
609 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
610 #define HDR_LOCK(hdr) \
611 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
613 uint64_t zfs_crc64_table[256];
619 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
620 #define L2ARC_HEADROOM 2 /* num of writes */
621 #define L2ARC_FEED_SECS 1 /* caching interval secs */
622 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
624 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
625 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
628 * L2ARC Performance Tunables
630 unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
631 unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
632 unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
633 unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
634 unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
635 int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
636 int l2arc_feed_again = B_TRUE; /* turbo warmup */
637 int l2arc_norw = B_TRUE; /* no reads during writes */
642 typedef struct l2arc_dev {
643 vdev_t *l2ad_vdev; /* vdev */
644 spa_t *l2ad_spa; /* spa */
645 uint64_t l2ad_hand; /* next write location */
646 uint64_t l2ad_write; /* desired write size, bytes */
647 uint64_t l2ad_boost; /* warmup write boost, bytes */
648 uint64_t l2ad_start; /* first addr on device */
649 uint64_t l2ad_end; /* last addr on device */
650 uint64_t l2ad_evict; /* last addr eviction reached */
651 boolean_t l2ad_first; /* first sweep through */
652 boolean_t l2ad_writing; /* currently writing */
653 list_t *l2ad_buflist; /* buffer list */
654 list_node_t l2ad_node; /* device list node */
657 static list_t L2ARC_dev_list; /* device list */
658 static list_t *l2arc_dev_list; /* device list pointer */
659 static kmutex_t l2arc_dev_mtx; /* device list mutex */
660 static l2arc_dev_t *l2arc_dev_last; /* last device used */
661 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
662 static list_t L2ARC_free_on_write; /* free after write buf list */
663 static list_t *l2arc_free_on_write; /* free after write list ptr */
664 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
665 static uint64_t l2arc_ndev; /* number of devices */
667 typedef struct l2arc_read_callback {
668 arc_buf_t *l2rcb_buf; /* read buffer */
669 spa_t *l2rcb_spa; /* spa */
670 blkptr_t l2rcb_bp; /* original blkptr */
671 zbookmark_t l2rcb_zb; /* original bookmark */
672 int l2rcb_flags; /* original flags */
673 } l2arc_read_callback_t;
675 typedef struct l2arc_write_callback {
676 l2arc_dev_t *l2wcb_dev; /* device info */
677 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
678 } l2arc_write_callback_t;
680 struct l2arc_buf_hdr {
681 /* protected by arc_buf_hdr mutex */
682 l2arc_dev_t *b_dev; /* L2ARC device */
683 uint64_t b_daddr; /* disk address, offset byte */
686 typedef struct l2arc_data_free {
687 /* protected by l2arc_free_on_write_mtx */
690 void (*l2df_func)(void *, size_t);
691 list_node_t l2df_list_node;
694 static kmutex_t l2arc_feed_thr_lock;
695 static kcondvar_t l2arc_feed_thr_cv;
696 static uint8_t l2arc_thread_exit;
698 static void l2arc_read_done(zio_t *zio);
699 static void l2arc_hdr_stat_add(void);
700 static void l2arc_hdr_stat_remove(void);
703 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
705 uint8_t *vdva = (uint8_t *)dva;
706 uint64_t crc = -1ULL;
709 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
711 for (i = 0; i < sizeof (dva_t); i++)
712 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
714 crc ^= (spa>>8) ^ birth;
719 #define BUF_EMPTY(buf) \
720 ((buf)->b_dva.dva_word[0] == 0 && \
721 (buf)->b_dva.dva_word[1] == 0 && \
724 #define BUF_EQUAL(spa, dva, birth, buf) \
725 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
726 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
727 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
730 buf_discard_identity(arc_buf_hdr_t *hdr)
732 hdr->b_dva.dva_word[0] = 0;
733 hdr->b_dva.dva_word[1] = 0;
738 static arc_buf_hdr_t *
739 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
741 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
742 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
745 mutex_enter(hash_lock);
746 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
747 buf = buf->b_hash_next) {
748 if (BUF_EQUAL(spa, dva, birth, buf)) {
753 mutex_exit(hash_lock);
759 * Insert an entry into the hash table. If there is already an element
760 * equal to elem in the hash table, then the already existing element
761 * will be returned and the new element will not be inserted.
762 * Otherwise returns NULL.
764 static arc_buf_hdr_t *
765 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
767 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
768 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
772 ASSERT(!HDR_IN_HASH_TABLE(buf));
774 mutex_enter(hash_lock);
775 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
776 fbuf = fbuf->b_hash_next, i++) {
777 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
781 buf->b_hash_next = buf_hash_table.ht_table[idx];
782 buf_hash_table.ht_table[idx] = buf;
783 buf->b_flags |= ARC_IN_HASH_TABLE;
785 /* collect some hash table performance data */
787 ARCSTAT_BUMP(arcstat_hash_collisions);
789 ARCSTAT_BUMP(arcstat_hash_chains);
791 ARCSTAT_MAX(arcstat_hash_chain_max, i);
794 ARCSTAT_BUMP(arcstat_hash_elements);
795 ARCSTAT_MAXSTAT(arcstat_hash_elements);
801 buf_hash_remove(arc_buf_hdr_t *buf)
803 arc_buf_hdr_t *fbuf, **bufp;
804 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
806 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
807 ASSERT(HDR_IN_HASH_TABLE(buf));
809 bufp = &buf_hash_table.ht_table[idx];
810 while ((fbuf = *bufp) != buf) {
811 ASSERT(fbuf != NULL);
812 bufp = &fbuf->b_hash_next;
814 *bufp = buf->b_hash_next;
815 buf->b_hash_next = NULL;
816 buf->b_flags &= ~ARC_IN_HASH_TABLE;
818 /* collect some hash table performance data */
819 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
821 if (buf_hash_table.ht_table[idx] &&
822 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
823 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
827 * Global data structures and functions for the buf kmem cache.
829 static kmem_cache_t *hdr_cache;
830 static kmem_cache_t *buf_cache;
837 #if defined(_KERNEL) && defined(HAVE_SPL)
838 /* Large allocations which do not require contiguous pages
839 * should be using vmem_free() in the linux kernel */
840 vmem_free(buf_hash_table.ht_table,
841 (buf_hash_table.ht_mask + 1) * sizeof (void *));
843 kmem_free(buf_hash_table.ht_table,
844 (buf_hash_table.ht_mask + 1) * sizeof (void *));
846 for (i = 0; i < BUF_LOCKS; i++)
847 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
848 kmem_cache_destroy(hdr_cache);
849 kmem_cache_destroy(buf_cache);
853 * Constructor callback - called when the cache is empty
854 * and a new buf is requested.
858 hdr_cons(void *vbuf, void *unused, int kmflag)
860 arc_buf_hdr_t *buf = vbuf;
862 bzero(buf, sizeof (arc_buf_hdr_t));
863 refcount_create(&buf->b_refcnt);
864 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
865 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
866 list_link_init(&buf->b_arc_node);
867 list_link_init(&buf->b_l2node);
868 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
875 buf_cons(void *vbuf, void *unused, int kmflag)
877 arc_buf_t *buf = vbuf;
879 bzero(buf, sizeof (arc_buf_t));
880 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
881 rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL);
882 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
888 * Destructor callback - called when a cached buf is
889 * no longer required.
893 hdr_dest(void *vbuf, void *unused)
895 arc_buf_hdr_t *buf = vbuf;
897 ASSERT(BUF_EMPTY(buf));
898 refcount_destroy(&buf->b_refcnt);
899 cv_destroy(&buf->b_cv);
900 mutex_destroy(&buf->b_freeze_lock);
901 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
906 buf_dest(void *vbuf, void *unused)
908 arc_buf_t *buf = vbuf;
910 mutex_destroy(&buf->b_evict_lock);
911 rw_destroy(&buf->b_data_lock);
912 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
919 uint64_t hsize = 1ULL << 12;
923 * The hash table is big enough to fill all of physical memory
924 * with an average 64K block size. The table will take up
925 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
927 while (hsize * 65536 < physmem * PAGESIZE)
930 buf_hash_table.ht_mask = hsize - 1;
931 #if defined(_KERNEL) && defined(HAVE_SPL)
932 /* Large allocations which do not require contiguous pages
933 * should be using vmem_alloc() in the linux kernel */
934 buf_hash_table.ht_table =
935 vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
937 buf_hash_table.ht_table =
938 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
940 if (buf_hash_table.ht_table == NULL) {
941 ASSERT(hsize > (1ULL << 8));
946 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
947 0, hdr_cons, hdr_dest, NULL, NULL, NULL, 0);
948 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
949 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
951 for (i = 0; i < 256; i++)
952 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
953 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
955 for (i = 0; i < BUF_LOCKS; i++) {
956 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
957 NULL, MUTEX_DEFAULT, NULL);
961 #define ARC_MINTIME (hz>>4) /* 62 ms */
964 arc_cksum_verify(arc_buf_t *buf)
968 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
971 mutex_enter(&buf->b_hdr->b_freeze_lock);
972 if (buf->b_hdr->b_freeze_cksum == NULL ||
973 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
974 mutex_exit(&buf->b_hdr->b_freeze_lock);
977 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
978 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
979 panic("buffer modified while frozen!");
980 mutex_exit(&buf->b_hdr->b_freeze_lock);
984 arc_cksum_equal(arc_buf_t *buf)
989 mutex_enter(&buf->b_hdr->b_freeze_lock);
990 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
991 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
992 mutex_exit(&buf->b_hdr->b_freeze_lock);
998 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1000 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1003 mutex_enter(&buf->b_hdr->b_freeze_lock);
1004 if (buf->b_hdr->b_freeze_cksum != NULL) {
1005 mutex_exit(&buf->b_hdr->b_freeze_lock);
1008 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1010 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1011 buf->b_hdr->b_freeze_cksum);
1012 mutex_exit(&buf->b_hdr->b_freeze_lock);
1016 arc_buf_thaw(arc_buf_t *buf)
1018 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1019 if (buf->b_hdr->b_state != arc_anon)
1020 panic("modifying non-anon buffer!");
1021 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1022 panic("modifying buffer while i/o in progress!");
1023 arc_cksum_verify(buf);
1026 mutex_enter(&buf->b_hdr->b_freeze_lock);
1027 if (buf->b_hdr->b_freeze_cksum != NULL) {
1028 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1029 buf->b_hdr->b_freeze_cksum = NULL;
1032 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1033 if (buf->b_hdr->b_thawed)
1034 kmem_free(buf->b_hdr->b_thawed, 1);
1035 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1038 mutex_exit(&buf->b_hdr->b_freeze_lock);
1042 arc_buf_freeze(arc_buf_t *buf)
1044 kmutex_t *hash_lock;
1046 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1049 hash_lock = HDR_LOCK(buf->b_hdr);
1050 mutex_enter(hash_lock);
1052 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1053 buf->b_hdr->b_state == arc_anon);
1054 arc_cksum_compute(buf, B_FALSE);
1055 mutex_exit(hash_lock);
1059 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1061 ASSERT(MUTEX_HELD(hash_lock));
1063 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1064 (ab->b_state != arc_anon)) {
1065 uint64_t delta = ab->b_size * ab->b_datacnt;
1066 list_t *list = &ab->b_state->arcs_list[ab->b_type];
1067 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1069 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
1070 mutex_enter(&ab->b_state->arcs_mtx);
1071 ASSERT(list_link_active(&ab->b_arc_node));
1072 list_remove(list, ab);
1073 if (GHOST_STATE(ab->b_state)) {
1074 ASSERT3U(ab->b_datacnt, ==, 0);
1075 ASSERT3P(ab->b_buf, ==, NULL);
1079 ASSERT3U(*size, >=, delta);
1080 atomic_add_64(size, -delta);
1081 mutex_exit(&ab->b_state->arcs_mtx);
1082 /* remove the prefetch flag if we get a reference */
1083 if (ab->b_flags & ARC_PREFETCH)
1084 ab->b_flags &= ~ARC_PREFETCH;
1089 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1092 arc_state_t *state = ab->b_state;
1094 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1095 ASSERT(!GHOST_STATE(state));
1097 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1098 (state != arc_anon)) {
1099 uint64_t *size = &state->arcs_lsize[ab->b_type];
1101 ASSERT(!MUTEX_HELD(&state->arcs_mtx));
1102 mutex_enter(&state->arcs_mtx);
1103 ASSERT(!list_link_active(&ab->b_arc_node));
1104 list_insert_head(&state->arcs_list[ab->b_type], ab);
1105 ASSERT(ab->b_datacnt > 0);
1106 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1107 mutex_exit(&state->arcs_mtx);
1113 * Move the supplied buffer to the indicated state. The mutex
1114 * for the buffer must be held by the caller.
1117 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1119 arc_state_t *old_state = ab->b_state;
1120 int64_t refcnt = refcount_count(&ab->b_refcnt);
1121 uint64_t from_delta, to_delta;
1123 ASSERT(MUTEX_HELD(hash_lock));
1124 ASSERT(new_state != old_state);
1125 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1126 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1127 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1129 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1132 * If this buffer is evictable, transfer it from the
1133 * old state list to the new state list.
1136 if (old_state != arc_anon) {
1137 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
1138 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1141 mutex_enter(&old_state->arcs_mtx);
1143 ASSERT(list_link_active(&ab->b_arc_node));
1144 list_remove(&old_state->arcs_list[ab->b_type], ab);
1147 * If prefetching out of the ghost cache,
1148 * we will have a non-zero datacnt.
1150 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1151 /* ghost elements have a ghost size */
1152 ASSERT(ab->b_buf == NULL);
1153 from_delta = ab->b_size;
1155 ASSERT3U(*size, >=, from_delta);
1156 atomic_add_64(size, -from_delta);
1159 mutex_exit(&old_state->arcs_mtx);
1161 if (new_state != arc_anon) {
1162 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
1163 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1166 mutex_enter(&new_state->arcs_mtx);
1168 list_insert_head(&new_state->arcs_list[ab->b_type], ab);
1170 /* ghost elements have a ghost size */
1171 if (GHOST_STATE(new_state)) {
1172 ASSERT(ab->b_datacnt == 0);
1173 ASSERT(ab->b_buf == NULL);
1174 to_delta = ab->b_size;
1176 atomic_add_64(size, to_delta);
1179 mutex_exit(&new_state->arcs_mtx);
1183 ASSERT(!BUF_EMPTY(ab));
1184 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1185 buf_hash_remove(ab);
1187 /* adjust state sizes */
1189 atomic_add_64(&new_state->arcs_size, to_delta);
1191 ASSERT3U(old_state->arcs_size, >=, from_delta);
1192 atomic_add_64(&old_state->arcs_size, -from_delta);
1194 ab->b_state = new_state;
1196 /* adjust l2arc hdr stats */
1197 if (new_state == arc_l2c_only)
1198 l2arc_hdr_stat_add();
1199 else if (old_state == arc_l2c_only)
1200 l2arc_hdr_stat_remove();
1204 arc_space_consume(uint64_t space, arc_space_type_t type)
1206 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1211 case ARC_SPACE_DATA:
1212 ARCSTAT_INCR(arcstat_data_size, space);
1214 case ARC_SPACE_OTHER:
1215 ARCSTAT_INCR(arcstat_other_size, space);
1217 case ARC_SPACE_HDRS:
1218 ARCSTAT_INCR(arcstat_hdr_size, space);
1220 case ARC_SPACE_L2HDRS:
1221 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1225 atomic_add_64(&arc_meta_used, space);
1226 atomic_add_64(&arc_size, space);
1230 arc_space_return(uint64_t space, arc_space_type_t type)
1232 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1237 case ARC_SPACE_DATA:
1238 ARCSTAT_INCR(arcstat_data_size, -space);
1240 case ARC_SPACE_OTHER:
1241 ARCSTAT_INCR(arcstat_other_size, -space);
1243 case ARC_SPACE_HDRS:
1244 ARCSTAT_INCR(arcstat_hdr_size, -space);
1246 case ARC_SPACE_L2HDRS:
1247 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1251 ASSERT(arc_meta_used >= space);
1252 if (arc_meta_max < arc_meta_used)
1253 arc_meta_max = arc_meta_used;
1254 atomic_add_64(&arc_meta_used, -space);
1255 ASSERT(arc_size >= space);
1256 atomic_add_64(&arc_size, -space);
1260 arc_data_buf_alloc(uint64_t size)
1262 if (arc_evict_needed(ARC_BUFC_DATA))
1263 cv_signal(&arc_reclaim_thr_cv);
1264 atomic_add_64(&arc_size, size);
1265 return (zio_data_buf_alloc(size));
1269 arc_data_buf_free(void *buf, uint64_t size)
1271 zio_data_buf_free(buf, size);
1272 ASSERT(arc_size >= size);
1273 atomic_add_64(&arc_size, -size);
1277 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1282 ASSERT3U(size, >, 0);
1283 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1284 ASSERT(BUF_EMPTY(hdr));
1287 hdr->b_spa = spa_guid(spa);
1288 hdr->b_state = arc_anon;
1289 hdr->b_arc_access = 0;
1290 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1293 buf->b_efunc = NULL;
1294 buf->b_private = NULL;
1297 arc_get_data_buf(buf);
1300 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1301 (void) refcount_add(&hdr->b_refcnt, tag);
1306 static char *arc_onloan_tag = "onloan";
1309 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1310 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1311 * buffers must be returned to the arc before they can be used by the DMU or
1315 arc_loan_buf(spa_t *spa, int size)
1319 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1321 atomic_add_64(&arc_loaned_bytes, size);
1326 * Return a loaned arc buffer to the arc.
1329 arc_return_buf(arc_buf_t *buf, void *tag)
1331 arc_buf_hdr_t *hdr = buf->b_hdr;
1333 ASSERT(buf->b_data != NULL);
1334 (void) refcount_add(&hdr->b_refcnt, tag);
1335 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1337 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1340 /* Detach an arc_buf from a dbuf (tag) */
1342 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1346 ASSERT(buf->b_data != NULL);
1348 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1349 (void) refcount_remove(&hdr->b_refcnt, tag);
1350 buf->b_efunc = NULL;
1351 buf->b_private = NULL;
1353 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1357 arc_buf_clone(arc_buf_t *from)
1360 arc_buf_hdr_t *hdr = from->b_hdr;
1361 uint64_t size = hdr->b_size;
1363 ASSERT(hdr->b_state != arc_anon);
1365 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1368 buf->b_efunc = NULL;
1369 buf->b_private = NULL;
1370 buf->b_next = hdr->b_buf;
1372 arc_get_data_buf(buf);
1373 bcopy(from->b_data, buf->b_data, size);
1374 hdr->b_datacnt += 1;
1379 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1382 kmutex_t *hash_lock;
1385 * Check to see if this buffer is evicted. Callers
1386 * must verify b_data != NULL to know if the add_ref
1389 mutex_enter(&buf->b_evict_lock);
1390 if (buf->b_data == NULL) {
1391 mutex_exit(&buf->b_evict_lock);
1394 hash_lock = HDR_LOCK(buf->b_hdr);
1395 mutex_enter(hash_lock);
1397 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1398 mutex_exit(&buf->b_evict_lock);
1400 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1401 add_reference(hdr, hash_lock, tag);
1402 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1403 arc_access(hdr, hash_lock);
1404 mutex_exit(hash_lock);
1405 ARCSTAT_BUMP(arcstat_hits);
1406 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1407 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1408 data, metadata, hits);
1412 * Free the arc data buffer. If it is an l2arc write in progress,
1413 * the buffer is placed on l2arc_free_on_write to be freed later.
1416 arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
1417 void *data, size_t size)
1419 if (HDR_L2_WRITING(hdr)) {
1420 l2arc_data_free_t *df;
1421 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1422 df->l2df_data = data;
1423 df->l2df_size = size;
1424 df->l2df_func = free_func;
1425 mutex_enter(&l2arc_free_on_write_mtx);
1426 list_insert_head(l2arc_free_on_write, df);
1427 mutex_exit(&l2arc_free_on_write_mtx);
1428 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1430 free_func(data, size);
1435 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1439 /* free up data associated with the buf */
1441 arc_state_t *state = buf->b_hdr->b_state;
1442 uint64_t size = buf->b_hdr->b_size;
1443 arc_buf_contents_t type = buf->b_hdr->b_type;
1445 arc_cksum_verify(buf);
1448 if (type == ARC_BUFC_METADATA) {
1449 arc_buf_data_free(buf->b_hdr, zio_buf_free,
1451 arc_space_return(size, ARC_SPACE_DATA);
1453 ASSERT(type == ARC_BUFC_DATA);
1454 arc_buf_data_free(buf->b_hdr,
1455 zio_data_buf_free, buf->b_data, size);
1456 ARCSTAT_INCR(arcstat_data_size, -size);
1457 atomic_add_64(&arc_size, -size);
1460 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1461 uint64_t *cnt = &state->arcs_lsize[type];
1463 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1464 ASSERT(state != arc_anon);
1466 ASSERT3U(*cnt, >=, size);
1467 atomic_add_64(cnt, -size);
1469 ASSERT3U(state->arcs_size, >=, size);
1470 atomic_add_64(&state->arcs_size, -size);
1472 ASSERT(buf->b_hdr->b_datacnt > 0);
1473 buf->b_hdr->b_datacnt -= 1;
1476 /* only remove the buf if requested */
1480 /* remove the buf from the hdr list */
1481 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1483 *bufp = buf->b_next;
1486 ASSERT(buf->b_efunc == NULL);
1488 /* clean up the buf */
1490 kmem_cache_free(buf_cache, buf);
1494 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1496 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1498 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1499 ASSERT3P(hdr->b_state, ==, arc_anon);
1500 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1502 if (l2hdr != NULL) {
1503 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1505 * To prevent arc_free() and l2arc_evict() from
1506 * attempting to free the same buffer at the same time,
1507 * a FREE_IN_PROGRESS flag is given to arc_free() to
1508 * give it priority. l2arc_evict() can't destroy this
1509 * header while we are waiting on l2arc_buflist_mtx.
1511 * The hdr may be removed from l2ad_buflist before we
1512 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1514 if (!buflist_held) {
1515 mutex_enter(&l2arc_buflist_mtx);
1516 l2hdr = hdr->b_l2hdr;
1519 if (l2hdr != NULL) {
1520 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1521 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1522 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1523 if (hdr->b_state == arc_l2c_only)
1524 l2arc_hdr_stat_remove();
1525 hdr->b_l2hdr = NULL;
1529 mutex_exit(&l2arc_buflist_mtx);
1532 if (!BUF_EMPTY(hdr)) {
1533 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1534 buf_discard_identity(hdr);
1536 while (hdr->b_buf) {
1537 arc_buf_t *buf = hdr->b_buf;
1540 mutex_enter(&arc_eviction_mtx);
1541 mutex_enter(&buf->b_evict_lock);
1542 ASSERT(buf->b_hdr != NULL);
1543 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1544 hdr->b_buf = buf->b_next;
1545 buf->b_hdr = &arc_eviction_hdr;
1546 buf->b_next = arc_eviction_list;
1547 arc_eviction_list = buf;
1548 mutex_exit(&buf->b_evict_lock);
1549 mutex_exit(&arc_eviction_mtx);
1551 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1554 if (hdr->b_freeze_cksum != NULL) {
1555 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1556 hdr->b_freeze_cksum = NULL;
1558 if (hdr->b_thawed) {
1559 kmem_free(hdr->b_thawed, 1);
1560 hdr->b_thawed = NULL;
1563 ASSERT(!list_link_active(&hdr->b_arc_node));
1564 ASSERT3P(hdr->b_hash_next, ==, NULL);
1565 ASSERT3P(hdr->b_acb, ==, NULL);
1566 kmem_cache_free(hdr_cache, hdr);
1570 arc_buf_free(arc_buf_t *buf, void *tag)
1572 arc_buf_hdr_t *hdr = buf->b_hdr;
1573 int hashed = hdr->b_state != arc_anon;
1575 ASSERT(buf->b_efunc == NULL);
1576 ASSERT(buf->b_data != NULL);
1579 kmutex_t *hash_lock = HDR_LOCK(hdr);
1581 mutex_enter(hash_lock);
1583 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1585 (void) remove_reference(hdr, hash_lock, tag);
1586 if (hdr->b_datacnt > 1) {
1587 arc_buf_destroy(buf, FALSE, TRUE);
1589 ASSERT(buf == hdr->b_buf);
1590 ASSERT(buf->b_efunc == NULL);
1591 hdr->b_flags |= ARC_BUF_AVAILABLE;
1593 mutex_exit(hash_lock);
1594 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1597 * We are in the middle of an async write. Don't destroy
1598 * this buffer unless the write completes before we finish
1599 * decrementing the reference count.
1601 mutex_enter(&arc_eviction_mtx);
1602 (void) remove_reference(hdr, NULL, tag);
1603 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1604 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1605 mutex_exit(&arc_eviction_mtx);
1607 arc_hdr_destroy(hdr);
1609 if (remove_reference(hdr, NULL, tag) > 0)
1610 arc_buf_destroy(buf, FALSE, TRUE);
1612 arc_hdr_destroy(hdr);
1617 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1619 arc_buf_hdr_t *hdr = buf->b_hdr;
1620 kmutex_t *hash_lock = HDR_LOCK(hdr);
1621 int no_callback = (buf->b_efunc == NULL);
1623 if (hdr->b_state == arc_anon) {
1624 ASSERT(hdr->b_datacnt == 1);
1625 arc_buf_free(buf, tag);
1626 return (no_callback);
1629 mutex_enter(hash_lock);
1631 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1632 ASSERT(hdr->b_state != arc_anon);
1633 ASSERT(buf->b_data != NULL);
1635 (void) remove_reference(hdr, hash_lock, tag);
1636 if (hdr->b_datacnt > 1) {
1638 arc_buf_destroy(buf, FALSE, TRUE);
1639 } else if (no_callback) {
1640 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1641 ASSERT(buf->b_efunc == NULL);
1642 hdr->b_flags |= ARC_BUF_AVAILABLE;
1644 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1645 refcount_is_zero(&hdr->b_refcnt));
1646 mutex_exit(hash_lock);
1647 return (no_callback);
1651 arc_buf_size(arc_buf_t *buf)
1653 return (buf->b_hdr->b_size);
1657 * Evict buffers from list until we've removed the specified number of
1658 * bytes. Move the removed buffers to the appropriate evict state.
1659 * If the recycle flag is set, then attempt to "recycle" a buffer:
1660 * - look for a buffer to evict that is `bytes' long.
1661 * - return the data block from this buffer rather than freeing it.
1662 * This flag is used by callers that are trying to make space for a
1663 * new buffer in a full arc cache.
1665 * This function makes a "best effort". It skips over any buffers
1666 * it can't get a hash_lock on, and so may not catch all candidates.
1667 * It may also return without evicting as much space as requested.
1670 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1671 arc_buf_contents_t type)
1673 arc_state_t *evicted_state;
1674 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1675 arc_buf_hdr_t *ab, *ab_prev = NULL;
1676 list_t *list = &state->arcs_list[type];
1677 kmutex_t *hash_lock;
1678 boolean_t have_lock;
1679 void *stolen = NULL;
1681 ASSERT(state == arc_mru || state == arc_mfu);
1683 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1685 mutex_enter(&state->arcs_mtx);
1686 mutex_enter(&evicted_state->arcs_mtx);
1688 for (ab = list_tail(list); ab; ab = ab_prev) {
1689 ab_prev = list_prev(list, ab);
1690 /* prefetch buffers have a minimum lifespan */
1691 if (HDR_IO_IN_PROGRESS(ab) ||
1692 (spa && ab->b_spa != spa) ||
1693 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1694 ddi_get_lbolt() - ab->b_arc_access <
1695 arc_min_prefetch_lifespan)) {
1699 /* "lookahead" for better eviction candidate */
1700 if (recycle && ab->b_size != bytes &&
1701 ab_prev && ab_prev->b_size == bytes)
1703 hash_lock = HDR_LOCK(ab);
1704 have_lock = MUTEX_HELD(hash_lock);
1705 if (have_lock || mutex_tryenter(hash_lock)) {
1706 ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
1707 ASSERT(ab->b_datacnt > 0);
1709 arc_buf_t *buf = ab->b_buf;
1710 if (!mutex_tryenter(&buf->b_evict_lock)) {
1715 bytes_evicted += ab->b_size;
1716 if (recycle && ab->b_type == type &&
1717 ab->b_size == bytes &&
1718 !HDR_L2_WRITING(ab)) {
1719 stolen = buf->b_data;
1724 mutex_enter(&arc_eviction_mtx);
1725 arc_buf_destroy(buf,
1726 buf->b_data == stolen, FALSE);
1727 ab->b_buf = buf->b_next;
1728 buf->b_hdr = &arc_eviction_hdr;
1729 buf->b_next = arc_eviction_list;
1730 arc_eviction_list = buf;
1731 mutex_exit(&arc_eviction_mtx);
1732 mutex_exit(&buf->b_evict_lock);
1734 mutex_exit(&buf->b_evict_lock);
1735 arc_buf_destroy(buf,
1736 buf->b_data == stolen, TRUE);
1741 ARCSTAT_INCR(arcstat_evict_l2_cached,
1744 if (l2arc_write_eligible(ab->b_spa, ab)) {
1745 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1749 arcstat_evict_l2_ineligible,
1754 if (ab->b_datacnt == 0) {
1755 arc_change_state(evicted_state, ab, hash_lock);
1756 ASSERT(HDR_IN_HASH_TABLE(ab));
1757 ab->b_flags |= ARC_IN_HASH_TABLE;
1758 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1759 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1762 mutex_exit(hash_lock);
1763 if (bytes >= 0 && bytes_evicted >= bytes)
1770 mutex_exit(&evicted_state->arcs_mtx);
1771 mutex_exit(&state->arcs_mtx);
1773 if (bytes_evicted < bytes)
1774 dprintf("only evicted %lld bytes from %x\n",
1775 (longlong_t)bytes_evicted, state);
1778 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1781 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1784 * We have just evicted some date into the ghost state, make
1785 * sure we also adjust the ghost state size if necessary.
1788 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1789 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1790 arc_mru_ghost->arcs_size - arc_c;
1792 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1794 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1795 arc_evict_ghost(arc_mru_ghost, 0, todelete);
1796 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1797 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1798 arc_mru_ghost->arcs_size +
1799 arc_mfu_ghost->arcs_size - arc_c);
1800 arc_evict_ghost(arc_mfu_ghost, 0, todelete);
1808 * Remove buffers from list until we've removed the specified number of
1809 * bytes. Destroy the buffers that are removed.
1812 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1814 arc_buf_hdr_t *ab, *ab_prev;
1815 arc_buf_hdr_t marker;
1816 list_t *list = &state->arcs_list[ARC_BUFC_DATA];
1817 kmutex_t *hash_lock;
1818 uint64_t bytes_deleted = 0;
1819 uint64_t bufs_skipped = 0;
1821 ASSERT(GHOST_STATE(state));
1822 bzero(&marker, sizeof(marker));
1824 mutex_enter(&state->arcs_mtx);
1825 for (ab = list_tail(list); ab; ab = ab_prev) {
1826 ab_prev = list_prev(list, ab);
1827 if (spa && ab->b_spa != spa)
1830 /* ignore markers */
1834 hash_lock = HDR_LOCK(ab);
1835 /* caller may be trying to modify this buffer, skip it */
1836 if (MUTEX_HELD(hash_lock))
1838 if (mutex_tryenter(hash_lock)) {
1839 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1840 ASSERT(ab->b_buf == NULL);
1841 ARCSTAT_BUMP(arcstat_deleted);
1842 bytes_deleted += ab->b_size;
1844 if (ab->b_l2hdr != NULL) {
1846 * This buffer is cached on the 2nd Level ARC;
1847 * don't destroy the header.
1849 arc_change_state(arc_l2c_only, ab, hash_lock);
1850 mutex_exit(hash_lock);
1852 arc_change_state(arc_anon, ab, hash_lock);
1853 mutex_exit(hash_lock);
1854 arc_hdr_destroy(ab);
1857 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1858 if (bytes >= 0 && bytes_deleted >= bytes)
1860 } else if (bytes < 0) {
1862 * Insert a list marker and then wait for the
1863 * hash lock to become available. Once its
1864 * available, restart from where we left off.
1866 list_insert_after(list, ab, &marker);
1867 mutex_exit(&state->arcs_mtx);
1868 mutex_enter(hash_lock);
1869 mutex_exit(hash_lock);
1870 mutex_enter(&state->arcs_mtx);
1871 ab_prev = list_prev(list, &marker);
1872 list_remove(list, &marker);
1876 mutex_exit(&state->arcs_mtx);
1878 if (list == &state->arcs_list[ARC_BUFC_DATA] &&
1879 (bytes < 0 || bytes_deleted < bytes)) {
1880 list = &state->arcs_list[ARC_BUFC_METADATA];
1885 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
1889 if (bytes_deleted < bytes)
1890 dprintf("only deleted %lld bytes from %p\n",
1891 (longlong_t)bytes_deleted, state);
1897 int64_t adjustment, delta;
1903 adjustment = MIN((int64_t)(arc_size - arc_c),
1904 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
1907 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
1908 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
1909 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
1910 adjustment -= delta;
1913 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1914 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
1915 (void) arc_evict(arc_mru, 0, delta, FALSE,
1923 adjustment = arc_size - arc_c;
1925 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
1926 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
1927 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
1928 adjustment -= delta;
1931 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1932 int64_t delta = MIN(adjustment,
1933 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
1934 (void) arc_evict(arc_mfu, 0, delta, FALSE,
1939 * Adjust ghost lists
1942 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
1944 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
1945 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
1946 arc_evict_ghost(arc_mru_ghost, 0, delta);
1950 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
1952 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
1953 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
1954 arc_evict_ghost(arc_mfu_ghost, 0, delta);
1959 * Request that arc user drop references so that N bytes can be released
1960 * from the cache. This provides a mechanism to ensure the arc can honor
1961 * the arc_meta_limit and reclaim buffers which are pinned in the cache
1962 * by higher layers. (i.e. the zpl)
1965 arc_do_user_prune(int64_t adjustment)
1967 arc_prune_func_t *func;
1969 arc_prune_t *cp, *np;
1971 mutex_enter(&arc_prune_mtx);
1973 cp = list_head(&arc_prune_list);
1974 while (cp != NULL) {
1976 private = cp->p_private;
1977 np = list_next(&arc_prune_list, cp);
1978 refcount_add(&cp->p_refcnt, func);
1979 mutex_exit(&arc_prune_mtx);
1982 func(adjustment, private);
1984 mutex_enter(&arc_prune_mtx);
1986 /* User removed prune callback concurrently with execution */
1987 if (refcount_remove(&cp->p_refcnt, func) == 0) {
1988 ASSERT(!list_link_active(&cp->p_node));
1989 refcount_destroy(&cp->p_refcnt);
1990 kmem_free(cp, sizeof (*cp));
1996 ARCSTAT_BUMP(arcstat_prune);
1997 mutex_exit(&arc_prune_mtx);
2001 arc_do_user_evicts(void)
2003 mutex_enter(&arc_eviction_mtx);
2004 while (arc_eviction_list != NULL) {
2005 arc_buf_t *buf = arc_eviction_list;
2006 arc_eviction_list = buf->b_next;
2007 mutex_enter(&buf->b_evict_lock);
2009 mutex_exit(&buf->b_evict_lock);
2010 mutex_exit(&arc_eviction_mtx);
2012 if (buf->b_efunc != NULL)
2013 VERIFY(buf->b_efunc(buf) == 0);
2015 buf->b_efunc = NULL;
2016 buf->b_private = NULL;
2017 kmem_cache_free(buf_cache, buf);
2018 mutex_enter(&arc_eviction_mtx);
2020 mutex_exit(&arc_eviction_mtx);
2024 * Evict only meta data objects from the cache leaving the data objects.
2025 * This is only used to enforce the tunable arc_meta_limit, if we are
2026 * unable to evict enough buffers notify the user via the prune callback.
2029 arc_adjust_meta(int64_t adjustment, boolean_t may_prune)
2033 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2034 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2035 arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_METADATA);
2036 adjustment -= delta;
2039 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2040 delta = MIN(arc_mfu->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2041 arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_METADATA);
2042 adjustment -= delta;
2045 if (may_prune && (adjustment > 0) && (arc_meta_used > arc_meta_limit))
2046 arc_do_user_prune(arc_meta_prune);
2050 * Flush all *evictable* data from the cache for the given spa.
2051 * NOTE: this will not touch "active" (i.e. referenced) data.
2054 arc_flush(spa_t *spa)
2059 guid = spa_guid(spa);
2061 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
2062 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2066 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
2067 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2071 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
2072 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2076 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
2077 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2082 arc_evict_ghost(arc_mru_ghost, guid, -1);
2083 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2085 mutex_enter(&arc_reclaim_thr_lock);
2086 arc_do_user_evicts();
2087 mutex_exit(&arc_reclaim_thr_lock);
2088 ASSERT(spa || arc_eviction_list == NULL);
2092 arc_shrink(uint64_t bytes)
2094 if (arc_c > arc_c_min) {
2097 to_free = bytes ? bytes : arc_c >> arc_shrink_shift;
2099 if (arc_c > arc_c_min + to_free)
2100 atomic_add_64(&arc_c, -to_free);
2104 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2105 if (arc_c > arc_size)
2106 arc_c = MAX(arc_size, arc_c_min);
2108 arc_p = (arc_c >> 1);
2109 ASSERT(arc_c >= arc_c_min);
2110 ASSERT((int64_t)arc_p >= 0);
2113 if (arc_size > arc_c)
2118 arc_kmem_reap_now(arc_reclaim_strategy_t strat, uint64_t bytes)
2121 kmem_cache_t *prev_cache = NULL;
2122 kmem_cache_t *prev_data_cache = NULL;
2123 extern kmem_cache_t *zio_buf_cache[];
2124 extern kmem_cache_t *zio_data_buf_cache[];
2127 * An aggressive reclamation will shrink the cache size as well as
2128 * reap free buffers from the arc kmem caches.
2130 if (strat == ARC_RECLAIM_AGGR)
2133 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2134 if (zio_buf_cache[i] != prev_cache) {
2135 prev_cache = zio_buf_cache[i];
2136 kmem_cache_reap_now(zio_buf_cache[i]);
2138 if (zio_data_buf_cache[i] != prev_data_cache) {
2139 prev_data_cache = zio_data_buf_cache[i];
2140 kmem_cache_reap_now(zio_data_buf_cache[i]);
2144 kmem_cache_reap_now(buf_cache);
2145 kmem_cache_reap_now(hdr_cache);
2149 * Unlike other ZFS implementations this thread is only responsible for
2150 * adapting the target ARC size on Linux. The responsibility for memory
2151 * reclamation has been entirely delegated to the arc_shrinker_func()
2152 * which is registered with the VM. To reflect this change in behavior
2153 * the arc_reclaim thread has been renamed to arc_adapt.
2156 arc_adapt_thread(void)
2161 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2163 mutex_enter(&arc_reclaim_thr_lock);
2164 while (arc_thread_exit == 0) {
2166 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2168 if (spa_get_random(100) == 0) {
2171 if (last_reclaim == ARC_RECLAIM_CONS) {
2172 last_reclaim = ARC_RECLAIM_AGGR;
2174 last_reclaim = ARC_RECLAIM_CONS;
2178 last_reclaim = ARC_RECLAIM_AGGR;
2182 /* reset the growth delay for every reclaim */
2183 arc_grow_time = ddi_get_lbolt()+(arc_grow_retry * hz);
2185 arc_kmem_reap_now(last_reclaim, 0);
2188 #endif /* !_KERNEL */
2190 /* No recent memory pressure allow the ARC to grow. */
2191 if (arc_no_grow && ddi_get_lbolt() >= arc_grow_time)
2192 arc_no_grow = FALSE;
2195 * Keep meta data usage within limits, arc_shrink() is not
2196 * used to avoid collapsing the arc_c value when only the
2197 * arc_meta_limit is being exceeded.
2199 prune = (int64_t)arc_meta_used - (int64_t)arc_meta_limit;
2201 arc_adjust_meta(prune, B_TRUE);
2205 if (arc_eviction_list != NULL)
2206 arc_do_user_evicts();
2208 /* block until needed, or one second, whichever is shorter */
2209 CALLB_CPR_SAFE_BEGIN(&cpr);
2210 (void) cv_timedwait_interruptible(&arc_reclaim_thr_cv,
2211 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
2212 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2215 arc_thread_exit = 0;
2216 cv_broadcast(&arc_reclaim_thr_cv);
2217 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2223 * Determine the amount of memory eligible for eviction contained in the
2224 * ARC. All clean data reported by the ghost lists can always be safely
2225 * evicted. Due to arc_c_min, the same does not hold for all clean data
2226 * contained by the regular mru and mfu lists.
2228 * In the case of the regular mru and mfu lists, we need to report as
2229 * much clean data as possible, such that evicting that same reported
2230 * data will not bring arc_size below arc_c_min. Thus, in certain
2231 * circumstances, the total amount of clean data in the mru and mfu
2232 * lists might not actually be evictable.
2234 * The following two distinct cases are accounted for:
2236 * 1. The sum of the amount of dirty data contained by both the mru and
2237 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
2238 * is greater than or equal to arc_c_min.
2239 * (i.e. amount of dirty data >= arc_c_min)
2241 * This is the easy case; all clean data contained by the mru and mfu
2242 * lists is evictable. Evicting all clean data can only drop arc_size
2243 * to the amount of dirty data, which is greater than arc_c_min.
2245 * 2. The sum of the amount of dirty data contained by both the mru and
2246 * mfu lists, plus the ARC's other accounting (e.g. the anon list),
2247 * is less than arc_c_min.
2248 * (i.e. arc_c_min > amount of dirty data)
2250 * 2.1. arc_size is greater than or equal arc_c_min.
2251 * (i.e. arc_size >= arc_c_min > amount of dirty data)
2253 * In this case, not all clean data from the regular mru and mfu
2254 * lists is actually evictable; we must leave enough clean data
2255 * to keep arc_size above arc_c_min. Thus, the maximum amount of
2256 * evictable data from the two lists combined, is exactly the
2257 * difference between arc_size and arc_c_min.
2259 * 2.2. arc_size is less than arc_c_min
2260 * (i.e. arc_c_min > arc_size > amount of dirty data)
2262 * In this case, none of the data contained in the mru and mfu
2263 * lists is evictable, even if it's clean. Since arc_size is
2264 * already below arc_c_min, evicting any more would only
2265 * increase this negative difference.
2268 arc_evictable_memory(void) {
2269 uint64_t arc_clean =
2270 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
2271 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
2272 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
2273 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
2274 uint64_t ghost_clean =
2275 arc_mru_ghost->arcs_lsize[ARC_BUFC_DATA] +
2276 arc_mru_ghost->arcs_lsize[ARC_BUFC_METADATA] +
2277 arc_mfu_ghost->arcs_lsize[ARC_BUFC_DATA] +
2278 arc_mfu_ghost->arcs_lsize[ARC_BUFC_METADATA];
2279 uint64_t arc_dirty = MAX((int64_t)arc_size - (int64_t)arc_clean, 0);
2281 if (arc_dirty >= arc_c_min)
2282 return (ghost_clean + arc_clean);
2284 return (ghost_clean + MAX((int64_t)arc_size - (int64_t)arc_c_min, 0));
2288 __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
2292 /* The arc is considered warm once reclaim has occurred */
2293 if (unlikely(arc_warm == B_FALSE))
2296 /* Return the potential number of reclaimable pages */
2297 pages = btop(arc_evictable_memory());
2298 if (sc->nr_to_scan == 0)
2301 /* Not allowed to perform filesystem reclaim */
2302 if (!(sc->gfp_mask & __GFP_FS))
2305 /* Reclaim in progress */
2306 if (mutex_tryenter(&arc_reclaim_thr_lock) == 0)
2310 * Evict the requested number of pages by shrinking arc_c the
2311 * requested amount. If there is nothing left to evict just
2312 * reap whatever we can from the various arc slabs.
2315 arc_kmem_reap_now(ARC_RECLAIM_AGGR, ptob(sc->nr_to_scan));
2316 pages = btop(arc_evictable_memory());
2318 arc_kmem_reap_now(ARC_RECLAIM_CONS, ptob(sc->nr_to_scan));
2323 * When direct reclaim is observed it usually indicates a rapid
2324 * increase in memory pressure. This occurs because the kswapd
2325 * threads were unable to asynchronously keep enough free memory
2326 * available. In this case set arc_no_grow to briefly pause arc
2327 * growth to avoid compounding the memory pressure.
2329 if (current_is_kswapd()) {
2330 ARCSTAT_BUMP(arcstat_memory_indirect_count);
2332 arc_no_grow = B_TRUE;
2333 arc_grow_time = ddi_get_lbolt() + (arc_grow_retry * hz);
2334 ARCSTAT_BUMP(arcstat_memory_direct_count);
2337 mutex_exit(&arc_reclaim_thr_lock);
2341 SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
2343 SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
2344 #endif /* _KERNEL */
2347 * Adapt arc info given the number of bytes we are trying to add and
2348 * the state that we are comming from. This function is only called
2349 * when we are adding new content to the cache.
2352 arc_adapt(int bytes, arc_state_t *state)
2355 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2357 if (state == arc_l2c_only)
2362 * Adapt the target size of the MRU list:
2363 * - if we just hit in the MRU ghost list, then increase
2364 * the target size of the MRU list.
2365 * - if we just hit in the MFU ghost list, then increase
2366 * the target size of the MFU list by decreasing the
2367 * target size of the MRU list.
2369 if (state == arc_mru_ghost) {
2370 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2371 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2372 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2374 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2375 } else if (state == arc_mfu_ghost) {
2378 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2379 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2380 mult = MIN(mult, 10);
2382 delta = MIN(bytes * mult, arc_p);
2383 arc_p = MAX(arc_p_min, arc_p - delta);
2385 ASSERT((int64_t)arc_p >= 0);
2390 if (arc_c >= arc_c_max)
2394 * If we're within (2 * maxblocksize) bytes of the target
2395 * cache size, increment the target cache size
2397 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2398 atomic_add_64(&arc_c, (int64_t)bytes);
2399 if (arc_c > arc_c_max)
2401 else if (state == arc_anon)
2402 atomic_add_64(&arc_p, (int64_t)bytes);
2406 ASSERT((int64_t)arc_p >= 0);
2410 * Check if the cache has reached its limits and eviction is required
2414 arc_evict_needed(arc_buf_contents_t type)
2416 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2421 * If zio data pages are being allocated out of a separate heap segment,
2422 * then enforce that the size of available vmem for this area remains
2423 * above about 1/32nd free.
2425 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2426 vmem_size(zio_arena, VMEM_FREE) <
2427 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2434 return (arc_size > arc_c);
2438 * The buffer, supplied as the first argument, needs a data block.
2439 * So, if we are at cache max, determine which cache should be victimized.
2440 * We have the following cases:
2442 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2443 * In this situation if we're out of space, but the resident size of the MFU is
2444 * under the limit, victimize the MFU cache to satisfy this insertion request.
2446 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2447 * Here, we've used up all of the available space for the MRU, so we need to
2448 * evict from our own cache instead. Evict from the set of resident MRU
2451 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2452 * c minus p represents the MFU space in the cache, since p is the size of the
2453 * cache that is dedicated to the MRU. In this situation there's still space on
2454 * the MFU side, so the MRU side needs to be victimized.
2456 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2457 * MFU's resident set is consuming more space than it has been allotted. In
2458 * this situation, we must victimize our own cache, the MFU, for this insertion.
2461 arc_get_data_buf(arc_buf_t *buf)
2463 arc_state_t *state = buf->b_hdr->b_state;
2464 uint64_t size = buf->b_hdr->b_size;
2465 arc_buf_contents_t type = buf->b_hdr->b_type;
2467 arc_adapt(size, state);
2470 * We have not yet reached cache maximum size,
2471 * just allocate a new buffer.
2473 if (!arc_evict_needed(type)) {
2474 if (type == ARC_BUFC_METADATA) {
2475 buf->b_data = zio_buf_alloc(size);
2476 arc_space_consume(size, ARC_SPACE_DATA);
2478 ASSERT(type == ARC_BUFC_DATA);
2479 buf->b_data = zio_data_buf_alloc(size);
2480 ARCSTAT_INCR(arcstat_data_size, size);
2481 atomic_add_64(&arc_size, size);
2487 * If we are prefetching from the mfu ghost list, this buffer
2488 * will end up on the mru list; so steal space from there.
2490 if (state == arc_mfu_ghost)
2491 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2492 else if (state == arc_mru_ghost)
2495 if (state == arc_mru || state == arc_anon) {
2496 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2497 state = (arc_mfu->arcs_lsize[type] >= size &&
2498 arc_p > mru_used) ? arc_mfu : arc_mru;
2501 uint64_t mfu_space = arc_c - arc_p;
2502 state = (arc_mru->arcs_lsize[type] >= size &&
2503 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2506 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2507 if (type == ARC_BUFC_METADATA) {
2508 buf->b_data = zio_buf_alloc(size);
2509 arc_space_consume(size, ARC_SPACE_DATA);
2512 * If we are unable to recycle an existing meta buffer
2513 * signal the reclaim thread. It will notify users
2514 * via the prune callback to drop references. The
2515 * prune callback in run in the context of the reclaim
2516 * thread to avoid deadlocking on the hash_lock.
2518 cv_signal(&arc_reclaim_thr_cv);
2520 ASSERT(type == ARC_BUFC_DATA);
2521 buf->b_data = zio_data_buf_alloc(size);
2522 ARCSTAT_INCR(arcstat_data_size, size);
2523 atomic_add_64(&arc_size, size);
2526 ARCSTAT_BUMP(arcstat_recycle_miss);
2528 ASSERT(buf->b_data != NULL);
2531 * Update the state size. Note that ghost states have a
2532 * "ghost size" and so don't need to be updated.
2534 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2535 arc_buf_hdr_t *hdr = buf->b_hdr;
2537 atomic_add_64(&hdr->b_state->arcs_size, size);
2538 if (list_link_active(&hdr->b_arc_node)) {
2539 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2540 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2543 * If we are growing the cache, and we are adding anonymous
2544 * data, and we have outgrown arc_p, update arc_p
2546 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2547 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2548 arc_p = MIN(arc_c, arc_p + size);
2553 * This routine is called whenever a buffer is accessed.
2554 * NOTE: the hash lock is dropped in this function.
2557 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2561 ASSERT(MUTEX_HELD(hash_lock));
2563 if (buf->b_state == arc_anon) {
2565 * This buffer is not in the cache, and does not
2566 * appear in our "ghost" list. Add the new buffer
2570 ASSERT(buf->b_arc_access == 0);
2571 buf->b_arc_access = ddi_get_lbolt();
2572 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2573 arc_change_state(arc_mru, buf, hash_lock);
2575 } else if (buf->b_state == arc_mru) {
2576 now = ddi_get_lbolt();
2579 * If this buffer is here because of a prefetch, then either:
2580 * - clear the flag if this is a "referencing" read
2581 * (any subsequent access will bump this into the MFU state).
2583 * - move the buffer to the head of the list if this is
2584 * another prefetch (to make it less likely to be evicted).
2586 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2587 if (refcount_count(&buf->b_refcnt) == 0) {
2588 ASSERT(list_link_active(&buf->b_arc_node));
2590 buf->b_flags &= ~ARC_PREFETCH;
2591 ARCSTAT_BUMP(arcstat_mru_hits);
2593 buf->b_arc_access = now;
2598 * This buffer has been "accessed" only once so far,
2599 * but it is still in the cache. Move it to the MFU
2602 if (now > buf->b_arc_access + ARC_MINTIME) {
2604 * More than 125ms have passed since we
2605 * instantiated this buffer. Move it to the
2606 * most frequently used state.
2608 buf->b_arc_access = now;
2609 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2610 arc_change_state(arc_mfu, buf, hash_lock);
2612 ARCSTAT_BUMP(arcstat_mru_hits);
2613 } else if (buf->b_state == arc_mru_ghost) {
2614 arc_state_t *new_state;
2616 * This buffer has been "accessed" recently, but
2617 * was evicted from the cache. Move it to the
2621 if (buf->b_flags & ARC_PREFETCH) {
2622 new_state = arc_mru;
2623 if (refcount_count(&buf->b_refcnt) > 0)
2624 buf->b_flags &= ~ARC_PREFETCH;
2625 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2627 new_state = arc_mfu;
2628 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2631 buf->b_arc_access = ddi_get_lbolt();
2632 arc_change_state(new_state, buf, hash_lock);
2634 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2635 } else if (buf->b_state == arc_mfu) {
2637 * This buffer has been accessed more than once and is
2638 * still in the cache. Keep it in the MFU state.
2640 * NOTE: an add_reference() that occurred when we did
2641 * the arc_read() will have kicked this off the list.
2642 * If it was a prefetch, we will explicitly move it to
2643 * the head of the list now.
2645 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2646 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2647 ASSERT(list_link_active(&buf->b_arc_node));
2649 ARCSTAT_BUMP(arcstat_mfu_hits);
2650 buf->b_arc_access = ddi_get_lbolt();
2651 } else if (buf->b_state == arc_mfu_ghost) {
2652 arc_state_t *new_state = arc_mfu;
2654 * This buffer has been accessed more than once but has
2655 * been evicted from the cache. Move it back to the
2659 if (buf->b_flags & ARC_PREFETCH) {
2661 * This is a prefetch access...
2662 * move this block back to the MRU state.
2664 ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
2665 new_state = arc_mru;
2668 buf->b_arc_access = ddi_get_lbolt();
2669 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2670 arc_change_state(new_state, buf, hash_lock);
2672 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2673 } else if (buf->b_state == arc_l2c_only) {
2675 * This buffer is on the 2nd Level ARC.
2678 buf->b_arc_access = ddi_get_lbolt();
2679 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2680 arc_change_state(arc_mfu, buf, hash_lock);
2682 ASSERT(!"invalid arc state");
2686 /* a generic arc_done_func_t which you can use */
2689 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2691 if (zio == NULL || zio->io_error == 0)
2692 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2693 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2696 /* a generic arc_done_func_t */
2698 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2700 arc_buf_t **bufp = arg;
2701 if (zio && zio->io_error) {
2702 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2706 ASSERT(buf->b_data);
2711 arc_read_done(zio_t *zio)
2713 arc_buf_hdr_t *hdr, *found;
2715 arc_buf_t *abuf; /* buffer we're assigning to callback */
2716 kmutex_t *hash_lock;
2717 arc_callback_t *callback_list, *acb;
2718 int freeable = FALSE;
2720 buf = zio->io_private;
2724 * The hdr was inserted into hash-table and removed from lists
2725 * prior to starting I/O. We should find this header, since
2726 * it's in the hash table, and it should be legit since it's
2727 * not possible to evict it during the I/O. The only possible
2728 * reason for it not to be found is if we were freed during the
2731 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2734 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2735 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2736 (found == hdr && HDR_L2_READING(hdr)));
2738 hdr->b_flags &= ~ARC_L2_EVICTED;
2739 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2740 hdr->b_flags &= ~ARC_L2CACHE;
2742 /* byteswap if necessary */
2743 callback_list = hdr->b_acb;
2744 ASSERT(callback_list != NULL);
2745 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
2746 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2747 byteswap_uint64_array :
2748 dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
2749 func(buf->b_data, hdr->b_size);
2752 arc_cksum_compute(buf, B_FALSE);
2754 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
2756 * Only call arc_access on anonymous buffers. This is because
2757 * if we've issued an I/O for an evicted buffer, we've already
2758 * called arc_access (to prevent any simultaneous readers from
2759 * getting confused).
2761 arc_access(hdr, hash_lock);
2764 /* create copies of the data buffer for the callers */
2766 for (acb = callback_list; acb; acb = acb->acb_next) {
2767 if (acb->acb_done) {
2769 abuf = arc_buf_clone(buf);
2770 acb->acb_buf = abuf;
2775 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2776 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2778 ASSERT(buf->b_efunc == NULL);
2779 ASSERT(hdr->b_datacnt == 1);
2780 hdr->b_flags |= ARC_BUF_AVAILABLE;
2783 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2785 if (zio->io_error != 0) {
2786 hdr->b_flags |= ARC_IO_ERROR;
2787 if (hdr->b_state != arc_anon)
2788 arc_change_state(arc_anon, hdr, hash_lock);
2789 if (HDR_IN_HASH_TABLE(hdr))
2790 buf_hash_remove(hdr);
2791 freeable = refcount_is_zero(&hdr->b_refcnt);
2795 * Broadcast before we drop the hash_lock to avoid the possibility
2796 * that the hdr (and hence the cv) might be freed before we get to
2797 * the cv_broadcast().
2799 cv_broadcast(&hdr->b_cv);
2802 mutex_exit(hash_lock);
2805 * This block was freed while we waited for the read to
2806 * complete. It has been removed from the hash table and
2807 * moved to the anonymous state (so that it won't show up
2810 ASSERT3P(hdr->b_state, ==, arc_anon);
2811 freeable = refcount_is_zero(&hdr->b_refcnt);
2814 /* execute each callback and free its structure */
2815 while ((acb = callback_list) != NULL) {
2817 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2819 if (acb->acb_zio_dummy != NULL) {
2820 acb->acb_zio_dummy->io_error = zio->io_error;
2821 zio_nowait(acb->acb_zio_dummy);
2824 callback_list = acb->acb_next;
2825 kmem_free(acb, sizeof (arc_callback_t));
2829 arc_hdr_destroy(hdr);
2833 * "Read" the block block at the specified DVA (in bp) via the
2834 * cache. If the block is found in the cache, invoke the provided
2835 * callback immediately and return. Note that the `zio' parameter
2836 * in the callback will be NULL in this case, since no IO was
2837 * required. If the block is not in the cache pass the read request
2838 * on to the spa with a substitute callback function, so that the
2839 * requested block will be added to the cache.
2841 * If a read request arrives for a block that has a read in-progress,
2842 * either wait for the in-progress read to complete (and return the
2843 * results); or, if this is a read with a "done" func, add a record
2844 * to the read to invoke the "done" func when the read completes,
2845 * and return; or just return.
2847 * arc_read_done() will invoke all the requested "done" functions
2848 * for readers of this block.
2850 * Normal callers should use arc_read and pass the arc buffer and offset
2851 * for the bp. But if you know you don't need locking, you can use
2855 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf,
2856 arc_done_func_t *done, void *private, int priority, int zio_flags,
2857 uint32_t *arc_flags, const zbookmark_t *zb)
2863 * XXX This happens from traverse callback funcs, for
2864 * the objset_phys_t block.
2866 return (arc_read_nolock(pio, spa, bp, done, private, priority,
2867 zio_flags, arc_flags, zb));
2870 ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
2871 ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
2872 rw_enter(&pbuf->b_data_lock, RW_READER);
2874 err = arc_read_nolock(pio, spa, bp, done, private, priority,
2875 zio_flags, arc_flags, zb);
2876 rw_exit(&pbuf->b_data_lock);
2882 arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
2883 arc_done_func_t *done, void *private, int priority, int zio_flags,
2884 uint32_t *arc_flags, const zbookmark_t *zb)
2887 arc_buf_t *buf = NULL;
2888 kmutex_t *hash_lock;
2890 uint64_t guid = spa_guid(spa);
2893 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
2895 if (hdr && hdr->b_datacnt > 0) {
2897 *arc_flags |= ARC_CACHED;
2899 if (HDR_IO_IN_PROGRESS(hdr)) {
2901 if (*arc_flags & ARC_WAIT) {
2902 cv_wait(&hdr->b_cv, hash_lock);
2903 mutex_exit(hash_lock);
2906 ASSERT(*arc_flags & ARC_NOWAIT);
2909 arc_callback_t *acb = NULL;
2911 acb = kmem_zalloc(sizeof (arc_callback_t),
2913 acb->acb_done = done;
2914 acb->acb_private = private;
2916 acb->acb_zio_dummy = zio_null(pio,
2917 spa, NULL, NULL, NULL, zio_flags);
2919 ASSERT(acb->acb_done != NULL);
2920 acb->acb_next = hdr->b_acb;
2922 add_reference(hdr, hash_lock, private);
2923 mutex_exit(hash_lock);
2926 mutex_exit(hash_lock);
2930 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2933 add_reference(hdr, hash_lock, private);
2935 * If this block is already in use, create a new
2936 * copy of the data so that we will be guaranteed
2937 * that arc_release() will always succeed.
2941 ASSERT(buf->b_data);
2942 if (HDR_BUF_AVAILABLE(hdr)) {
2943 ASSERT(buf->b_efunc == NULL);
2944 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2946 buf = arc_buf_clone(buf);
2949 } else if (*arc_flags & ARC_PREFETCH &&
2950 refcount_count(&hdr->b_refcnt) == 0) {
2951 hdr->b_flags |= ARC_PREFETCH;
2953 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
2954 arc_access(hdr, hash_lock);
2955 if (*arc_flags & ARC_L2CACHE)
2956 hdr->b_flags |= ARC_L2CACHE;
2957 mutex_exit(hash_lock);
2958 ARCSTAT_BUMP(arcstat_hits);
2959 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2960 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2961 data, metadata, hits);
2964 done(NULL, buf, private);
2966 uint64_t size = BP_GET_LSIZE(bp);
2967 arc_callback_t *acb;
2970 boolean_t devw = B_FALSE;
2973 /* this block is not in the cache */
2974 arc_buf_hdr_t *exists;
2975 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
2976 buf = arc_buf_alloc(spa, size, private, type);
2978 hdr->b_dva = *BP_IDENTITY(bp);
2979 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
2980 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
2981 exists = buf_hash_insert(hdr, &hash_lock);
2983 /* somebody beat us to the hash insert */
2984 mutex_exit(hash_lock);
2985 buf_discard_identity(hdr);
2986 (void) arc_buf_remove_ref(buf, private);
2987 goto top; /* restart the IO request */
2989 /* if this is a prefetch, we don't have a reference */
2990 if (*arc_flags & ARC_PREFETCH) {
2991 (void) remove_reference(hdr, hash_lock,
2993 hdr->b_flags |= ARC_PREFETCH;
2995 if (*arc_flags & ARC_L2CACHE)
2996 hdr->b_flags |= ARC_L2CACHE;
2997 if (BP_GET_LEVEL(bp) > 0)
2998 hdr->b_flags |= ARC_INDIRECT;
3000 /* this block is in the ghost cache */
3001 ASSERT(GHOST_STATE(hdr->b_state));
3002 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3003 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
3004 ASSERT(hdr->b_buf == NULL);
3006 /* if this is a prefetch, we don't have a reference */
3007 if (*arc_flags & ARC_PREFETCH)
3008 hdr->b_flags |= ARC_PREFETCH;
3010 add_reference(hdr, hash_lock, private);
3011 if (*arc_flags & ARC_L2CACHE)
3012 hdr->b_flags |= ARC_L2CACHE;
3013 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3016 buf->b_efunc = NULL;
3017 buf->b_private = NULL;
3020 ASSERT(hdr->b_datacnt == 0);
3022 arc_get_data_buf(buf);
3023 arc_access(hdr, hash_lock);
3026 ASSERT(!GHOST_STATE(hdr->b_state));
3028 acb = kmem_zalloc(sizeof (arc_callback_t), KM_PUSHPAGE);
3029 acb->acb_done = done;
3030 acb->acb_private = private;
3032 ASSERT(hdr->b_acb == NULL);
3034 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3036 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
3037 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3038 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3039 addr = hdr->b_l2hdr->b_daddr;
3041 * Lock out device removal.
3043 if (vdev_is_dead(vd) ||
3044 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3048 mutex_exit(hash_lock);
3050 ASSERT3U(hdr->b_size, ==, size);
3051 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3052 uint64_t, size, zbookmark_t *, zb);
3053 ARCSTAT_BUMP(arcstat_misses);
3054 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3055 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3056 data, metadata, misses);
3058 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3060 * Read from the L2ARC if the following are true:
3061 * 1. The L2ARC vdev was previously cached.
3062 * 2. This buffer still has L2ARC metadata.
3063 * 3. This buffer isn't currently writing to the L2ARC.
3064 * 4. The L2ARC entry wasn't evicted, which may
3065 * also have invalidated the vdev.
3066 * 5. This isn't prefetch and l2arc_noprefetch is set.
3068 if (hdr->b_l2hdr != NULL &&
3069 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3070 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3071 l2arc_read_callback_t *cb;
3073 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3074 ARCSTAT_BUMP(arcstat_l2_hits);
3076 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3078 cb->l2rcb_buf = buf;
3079 cb->l2rcb_spa = spa;
3082 cb->l2rcb_flags = zio_flags;
3085 * l2arc read. The SCL_L2ARC lock will be
3086 * released by l2arc_read_done().
3088 rzio = zio_read_phys(pio, vd, addr, size,
3089 buf->b_data, ZIO_CHECKSUM_OFF,
3090 l2arc_read_done, cb, priority, zio_flags |
3091 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3092 ZIO_FLAG_DONT_PROPAGATE |
3093 ZIO_FLAG_DONT_RETRY, B_FALSE);
3094 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3096 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3098 if (*arc_flags & ARC_NOWAIT) {
3103 ASSERT(*arc_flags & ARC_WAIT);
3104 if (zio_wait(rzio) == 0)
3107 /* l2arc read error; goto zio_read() */
3109 DTRACE_PROBE1(l2arc__miss,
3110 arc_buf_hdr_t *, hdr);
3111 ARCSTAT_BUMP(arcstat_l2_misses);
3112 if (HDR_L2_WRITING(hdr))
3113 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3114 spa_config_exit(spa, SCL_L2ARC, vd);
3118 spa_config_exit(spa, SCL_L2ARC, vd);
3119 if (l2arc_ndev != 0) {
3120 DTRACE_PROBE1(l2arc__miss,
3121 arc_buf_hdr_t *, hdr);
3122 ARCSTAT_BUMP(arcstat_l2_misses);
3126 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3127 arc_read_done, buf, priority, zio_flags, zb);
3129 if (*arc_flags & ARC_WAIT)
3130 return (zio_wait(rzio));
3132 ASSERT(*arc_flags & ARC_NOWAIT);
3139 arc_add_prune_callback(arc_prune_func_t *func, void *private)
3143 p = kmem_alloc(sizeof(*p), KM_SLEEP);
3145 p->p_private = private;
3146 list_link_init(&p->p_node);
3147 refcount_create(&p->p_refcnt);
3149 mutex_enter(&arc_prune_mtx);
3150 refcount_add(&p->p_refcnt, &arc_prune_list);
3151 list_insert_head(&arc_prune_list, p);
3152 mutex_exit(&arc_prune_mtx);
3158 arc_remove_prune_callback(arc_prune_t *p)
3160 mutex_enter(&arc_prune_mtx);
3161 list_remove(&arc_prune_list, p);
3162 if (refcount_remove(&p->p_refcnt, &arc_prune_list) == 0) {
3163 refcount_destroy(&p->p_refcnt);
3164 kmem_free(p, sizeof (*p));
3166 mutex_exit(&arc_prune_mtx);
3170 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3172 ASSERT(buf->b_hdr != NULL);
3173 ASSERT(buf->b_hdr->b_state != arc_anon);
3174 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3175 ASSERT(buf->b_efunc == NULL);
3176 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3178 buf->b_efunc = func;
3179 buf->b_private = private;
3183 * This is used by the DMU to let the ARC know that a buffer is
3184 * being evicted, so the ARC should clean up. If this arc buf
3185 * is not yet in the evicted state, it will be put there.
3188 arc_buf_evict(arc_buf_t *buf)
3191 kmutex_t *hash_lock;
3194 mutex_enter(&buf->b_evict_lock);
3198 * We are in arc_do_user_evicts().
3200 ASSERT(buf->b_data == NULL);
3201 mutex_exit(&buf->b_evict_lock);
3203 } else if (buf->b_data == NULL) {
3204 arc_buf_t copy = *buf; /* structure assignment */
3206 * We are on the eviction list; process this buffer now
3207 * but let arc_do_user_evicts() do the reaping.
3209 buf->b_efunc = NULL;
3210 mutex_exit(&buf->b_evict_lock);
3211 VERIFY(copy.b_efunc(©) == 0);
3214 hash_lock = HDR_LOCK(hdr);
3215 mutex_enter(hash_lock);
3217 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3219 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3220 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3223 * Pull this buffer off of the hdr
3226 while (*bufp != buf)
3227 bufp = &(*bufp)->b_next;
3228 *bufp = buf->b_next;
3230 ASSERT(buf->b_data != NULL);
3231 arc_buf_destroy(buf, FALSE, FALSE);
3233 if (hdr->b_datacnt == 0) {
3234 arc_state_t *old_state = hdr->b_state;
3235 arc_state_t *evicted_state;
3237 ASSERT(hdr->b_buf == NULL);
3238 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3241 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3243 mutex_enter(&old_state->arcs_mtx);
3244 mutex_enter(&evicted_state->arcs_mtx);
3246 arc_change_state(evicted_state, hdr, hash_lock);
3247 ASSERT(HDR_IN_HASH_TABLE(hdr));
3248 hdr->b_flags |= ARC_IN_HASH_TABLE;
3249 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3251 mutex_exit(&evicted_state->arcs_mtx);
3252 mutex_exit(&old_state->arcs_mtx);
3254 mutex_exit(hash_lock);
3255 mutex_exit(&buf->b_evict_lock);
3257 VERIFY(buf->b_efunc(buf) == 0);
3258 buf->b_efunc = NULL;
3259 buf->b_private = NULL;
3262 kmem_cache_free(buf_cache, buf);
3267 * Release this buffer from the cache. This must be done
3268 * after a read and prior to modifying the buffer contents.
3269 * If the buffer has more than one reference, we must make
3270 * a new hdr for the buffer.
3273 arc_release(arc_buf_t *buf, void *tag)
3276 kmutex_t *hash_lock = NULL;
3277 l2arc_buf_hdr_t *l2hdr;
3278 uint64_t buf_size = 0;
3281 * It would be nice to assert that if it's DMU metadata (level >
3282 * 0 || it's the dnode file), then it must be syncing context.
3283 * But we don't know that information at this level.
3286 mutex_enter(&buf->b_evict_lock);
3289 /* this buffer is not on any list */
3290 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3292 if (hdr->b_state == arc_anon) {
3293 /* this buffer is already released */
3294 ASSERT(buf->b_efunc == NULL);
3296 hash_lock = HDR_LOCK(hdr);
3297 mutex_enter(hash_lock);
3299 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3302 l2hdr = hdr->b_l2hdr;
3304 mutex_enter(&l2arc_buflist_mtx);
3305 hdr->b_l2hdr = NULL;
3306 buf_size = hdr->b_size;
3310 * Do we have more than one buf?
3312 if (hdr->b_datacnt > 1) {
3313 arc_buf_hdr_t *nhdr;
3315 uint64_t blksz = hdr->b_size;
3316 uint64_t spa = hdr->b_spa;
3317 arc_buf_contents_t type = hdr->b_type;
3318 uint32_t flags = hdr->b_flags;
3320 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3322 * Pull the data off of this hdr and attach it to
3323 * a new anonymous hdr.
3325 (void) remove_reference(hdr, hash_lock, tag);
3327 while (*bufp != buf)
3328 bufp = &(*bufp)->b_next;
3329 *bufp = buf->b_next;
3332 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3333 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3334 if (refcount_is_zero(&hdr->b_refcnt)) {
3335 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3336 ASSERT3U(*size, >=, hdr->b_size);
3337 atomic_add_64(size, -hdr->b_size);
3339 hdr->b_datacnt -= 1;
3340 arc_cksum_verify(buf);
3342 mutex_exit(hash_lock);
3344 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3345 nhdr->b_size = blksz;
3347 nhdr->b_type = type;
3349 nhdr->b_state = arc_anon;
3350 nhdr->b_arc_access = 0;
3351 nhdr->b_flags = flags & ARC_L2_WRITING;
3352 nhdr->b_l2hdr = NULL;
3353 nhdr->b_datacnt = 1;
3354 nhdr->b_freeze_cksum = NULL;
3355 (void) refcount_add(&nhdr->b_refcnt, tag);
3357 mutex_exit(&buf->b_evict_lock);
3358 atomic_add_64(&arc_anon->arcs_size, blksz);
3360 mutex_exit(&buf->b_evict_lock);
3361 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3362 ASSERT(!list_link_active(&hdr->b_arc_node));
3363 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3364 if (hdr->b_state != arc_anon)
3365 arc_change_state(arc_anon, hdr, hash_lock);
3366 hdr->b_arc_access = 0;
3368 mutex_exit(hash_lock);
3370 buf_discard_identity(hdr);
3373 buf->b_efunc = NULL;
3374 buf->b_private = NULL;
3377 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3378 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3379 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3380 mutex_exit(&l2arc_buflist_mtx);
3385 * Release this buffer. If it does not match the provided BP, fill it
3386 * with that block's contents.
3390 arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa,
3393 arc_release(buf, tag);
3398 arc_released(arc_buf_t *buf)
3402 mutex_enter(&buf->b_evict_lock);
3403 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3404 mutex_exit(&buf->b_evict_lock);
3409 arc_has_callback(arc_buf_t *buf)
3413 mutex_enter(&buf->b_evict_lock);
3414 callback = (buf->b_efunc != NULL);
3415 mutex_exit(&buf->b_evict_lock);
3421 arc_referenced(arc_buf_t *buf)
3425 mutex_enter(&buf->b_evict_lock);
3426 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3427 mutex_exit(&buf->b_evict_lock);
3428 return (referenced);
3433 arc_write_ready(zio_t *zio)
3435 arc_write_callback_t *callback = zio->io_private;
3436 arc_buf_t *buf = callback->awcb_buf;
3437 arc_buf_hdr_t *hdr = buf->b_hdr;
3439 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3440 callback->awcb_ready(zio, buf, callback->awcb_private);
3443 * If the IO is already in progress, then this is a re-write
3444 * attempt, so we need to thaw and re-compute the cksum.
3445 * It is the responsibility of the callback to handle the
3446 * accounting for any re-write attempt.
3448 if (HDR_IO_IN_PROGRESS(hdr)) {
3449 mutex_enter(&hdr->b_freeze_lock);
3450 if (hdr->b_freeze_cksum != NULL) {
3451 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3452 hdr->b_freeze_cksum = NULL;
3454 mutex_exit(&hdr->b_freeze_lock);
3456 arc_cksum_compute(buf, B_FALSE);
3457 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3461 arc_write_done(zio_t *zio)
3463 arc_write_callback_t *callback = zio->io_private;
3464 arc_buf_t *buf = callback->awcb_buf;
3465 arc_buf_hdr_t *hdr = buf->b_hdr;
3467 ASSERT(hdr->b_acb == NULL);
3469 if (zio->io_error == 0) {
3470 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3471 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3472 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3474 ASSERT(BUF_EMPTY(hdr));
3478 * If the block to be written was all-zero, we may have
3479 * compressed it away. In this case no write was performed
3480 * so there will be no dva/birth/checksum. The buffer must
3481 * therefore remain anonymous (and uncached).
3483 if (!BUF_EMPTY(hdr)) {
3484 arc_buf_hdr_t *exists;
3485 kmutex_t *hash_lock;
3487 ASSERT(zio->io_error == 0);
3489 arc_cksum_verify(buf);
3491 exists = buf_hash_insert(hdr, &hash_lock);
3494 * This can only happen if we overwrite for
3495 * sync-to-convergence, because we remove
3496 * buffers from the hash table when we arc_free().
3498 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3499 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3500 panic("bad overwrite, hdr=%p exists=%p",
3501 (void *)hdr, (void *)exists);
3502 ASSERT(refcount_is_zero(&exists->b_refcnt));
3503 arc_change_state(arc_anon, exists, hash_lock);
3504 mutex_exit(hash_lock);
3505 arc_hdr_destroy(exists);
3506 exists = buf_hash_insert(hdr, &hash_lock);
3507 ASSERT3P(exists, ==, NULL);
3510 ASSERT(hdr->b_datacnt == 1);
3511 ASSERT(hdr->b_state == arc_anon);
3512 ASSERT(BP_GET_DEDUP(zio->io_bp));
3513 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3516 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3517 /* if it's not anon, we are doing a scrub */
3518 if (!exists && hdr->b_state == arc_anon)
3519 arc_access(hdr, hash_lock);
3520 mutex_exit(hash_lock);
3522 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3525 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3526 callback->awcb_done(zio, buf, callback->awcb_private);
3528 kmem_free(callback, sizeof (arc_write_callback_t));
3532 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3533 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
3534 arc_done_func_t *ready, arc_done_func_t *done, void *private,
3535 int priority, int zio_flags, const zbookmark_t *zb)
3537 arc_buf_hdr_t *hdr = buf->b_hdr;
3538 arc_write_callback_t *callback;
3541 ASSERT(ready != NULL);
3542 ASSERT(done != NULL);
3543 ASSERT(!HDR_IO_ERROR(hdr));
3544 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3545 ASSERT(hdr->b_acb == NULL);
3547 hdr->b_flags |= ARC_L2CACHE;
3548 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3549 callback->awcb_ready = ready;
3550 callback->awcb_done = done;
3551 callback->awcb_private = private;
3552 callback->awcb_buf = buf;
3554 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3555 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3561 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3564 uint64_t available_memory;
3566 /* Easily reclaimable memory (free + inactive + arc-evictable) */
3567 available_memory = ptob(spl_kmem_availrmem()) + arc_evictable_memory();
3570 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3573 if (available_memory <= zfs_write_limit_max) {
3574 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3575 DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
3579 if (inflight_data > available_memory / 4) {
3580 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3581 DMU_TX_STAT_BUMP(dmu_tx_memory_inflight);
3589 arc_tempreserve_clear(uint64_t reserve)
3591 atomic_add_64(&arc_tempreserve, -reserve);
3592 ASSERT((int64_t)arc_tempreserve >= 0);
3596 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3603 * Once in a while, fail for no reason. Everything should cope.
3605 if (spa_get_random(10000) == 0) {
3606 dprintf("forcing random failure\n");
3610 if (reserve > arc_c/4 && !arc_no_grow)
3611 arc_c = MIN(arc_c_max, reserve * 4);
3612 if (reserve > arc_c) {
3613 DMU_TX_STAT_BUMP(dmu_tx_memory_reserve);
3618 * Don't count loaned bufs as in flight dirty data to prevent long
3619 * network delays from blocking transactions that are ready to be
3620 * assigned to a txg.
3622 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3625 * Writes will, almost always, require additional memory allocations
3626 * in order to compress/encrypt/etc the data. We therefor need to
3627 * make sure that there is sufficient available memory for this.
3629 if ((error = arc_memory_throttle(reserve, anon_size, txg)))
3633 * Throttle writes when the amount of dirty data in the cache
3634 * gets too large. We try to keep the cache less than half full
3635 * of dirty blocks so that our sync times don't grow too large.
3636 * Note: if two requests come in concurrently, we might let them
3637 * both succeed, when one of them should fail. Not a huge deal.
3640 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3641 anon_size > arc_c / 4) {
3642 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3643 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3644 arc_tempreserve>>10,
3645 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3646 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3647 reserve>>10, arc_c>>10);
3648 DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
3651 atomic_add_64(&arc_tempreserve, reserve);
3656 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
3657 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
3659 size->value.ui64 = state->arcs_size;
3660 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA];
3661 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA];
3665 arc_kstat_update(kstat_t *ksp, int rw)
3667 arc_stats_t *as = ksp->ks_data;
3669 if (rw == KSTAT_WRITE) {
3672 arc_kstat_update_state(arc_anon,
3673 &as->arcstat_anon_size,
3674 &as->arcstat_anon_evict_data,
3675 &as->arcstat_anon_evict_metadata);
3676 arc_kstat_update_state(arc_mru,
3677 &as->arcstat_mru_size,
3678 &as->arcstat_mru_evict_data,
3679 &as->arcstat_mru_evict_metadata);
3680 arc_kstat_update_state(arc_mru_ghost,
3681 &as->arcstat_mru_ghost_size,
3682 &as->arcstat_mru_ghost_evict_data,
3683 &as->arcstat_mru_ghost_evict_metadata);
3684 arc_kstat_update_state(arc_mfu,
3685 &as->arcstat_mfu_size,
3686 &as->arcstat_mfu_evict_data,
3687 &as->arcstat_mfu_evict_metadata);
3688 arc_kstat_update_state(arc_mfu_ghost,
3689 &as->arcstat_mfu_ghost_size,
3690 &as->arcstat_mfu_ghost_evict_data,
3691 &as->arcstat_mfu_ghost_evict_metadata);
3700 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3701 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3703 /* Convert seconds to clock ticks */
3704 arc_min_prefetch_lifespan = 1 * hz;
3706 /* Start out with 1/8 of all memory */
3707 arc_c = physmem * PAGESIZE / 8;
3711 * On architectures where the physical memory can be larger
3712 * than the addressable space (intel in 32-bit mode), we may
3713 * need to limit the cache to 1/8 of VM size.
3715 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3717 * Register a shrinker to support synchronous (direct) memory
3718 * reclaim from the arc. This is done to prevent kswapd from
3719 * swapping out pages when it is preferable to shrink the arc.
3721 spl_register_shrinker(&arc_shrinker);
3724 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3725 arc_c_min = MAX(arc_c / 4, 64<<20);
3726 /* set max to 1/2 of all memory */
3727 arc_c_max = MAX(arc_c * 4, arc_c_max);
3730 * Allow the tunables to override our calculations if they are
3731 * reasonable (ie. over 64MB)
3733 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
3734 arc_c_max = zfs_arc_max;
3735 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
3736 arc_c_min = zfs_arc_min;
3739 arc_p = (arc_c >> 1);
3741 /* limit meta-data to 1/4 of the arc capacity */
3742 arc_meta_limit = arc_c_max / 4;
3745 /* Allow the tunable to override if it is reasonable */
3746 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3747 arc_meta_limit = zfs_arc_meta_limit;
3749 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3750 arc_c_min = arc_meta_limit / 2;
3752 if (zfs_arc_grow_retry > 0)
3753 arc_grow_retry = zfs_arc_grow_retry;
3755 if (zfs_arc_shrink_shift > 0)
3756 arc_shrink_shift = zfs_arc_shrink_shift;
3758 if (zfs_arc_p_min_shift > 0)
3759 arc_p_min_shift = zfs_arc_p_min_shift;
3761 if (zfs_arc_meta_prune > 0)
3762 arc_meta_prune = zfs_arc_meta_prune;
3764 /* if kmem_flags are set, lets try to use less memory */
3765 if (kmem_debugging())
3767 if (arc_c < arc_c_min)
3770 arc_anon = &ARC_anon;
3772 arc_mru_ghost = &ARC_mru_ghost;
3774 arc_mfu_ghost = &ARC_mfu_ghost;
3775 arc_l2c_only = &ARC_l2c_only;
3778 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3779 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3780 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3781 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3782 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3783 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3785 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
3786 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3787 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
3788 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3789 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
3790 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3791 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
3792 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3793 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
3794 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3795 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
3796 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3797 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
3798 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3799 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
3800 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3801 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
3802 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3803 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
3804 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3808 arc_thread_exit = 0;
3809 list_create(&arc_prune_list, sizeof (arc_prune_t),
3810 offsetof(arc_prune_t, p_node));
3811 arc_eviction_list = NULL;
3812 mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
3813 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3814 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3816 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3817 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3819 if (arc_ksp != NULL) {
3820 arc_ksp->ks_data = &arc_stats;
3821 arc_ksp->ks_update = arc_kstat_update;
3822 kstat_install(arc_ksp);
3825 (void) thread_create(NULL, 0, arc_adapt_thread, NULL, 0, &p0,
3826 TS_RUN, minclsyspri);
3831 if (zfs_write_limit_max == 0)
3832 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3834 zfs_write_limit_shift = 0;
3835 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3843 mutex_enter(&arc_reclaim_thr_lock);
3845 spl_unregister_shrinker(&arc_shrinker);
3846 #endif /* _KERNEL */
3848 arc_thread_exit = 1;
3849 while (arc_thread_exit != 0)
3850 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3851 mutex_exit(&arc_reclaim_thr_lock);
3857 if (arc_ksp != NULL) {
3858 kstat_delete(arc_ksp);
3862 mutex_enter(&arc_prune_mtx);
3863 while ((p = list_head(&arc_prune_list)) != NULL) {
3864 list_remove(&arc_prune_list, p);
3865 refcount_remove(&p->p_refcnt, &arc_prune_list);
3866 refcount_destroy(&p->p_refcnt);
3867 kmem_free(p, sizeof (*p));
3869 mutex_exit(&arc_prune_mtx);
3871 list_destroy(&arc_prune_list);
3872 mutex_destroy(&arc_prune_mtx);
3873 mutex_destroy(&arc_eviction_mtx);
3874 mutex_destroy(&arc_reclaim_thr_lock);
3875 cv_destroy(&arc_reclaim_thr_cv);
3877 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
3878 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
3879 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
3880 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
3881 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
3882 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
3883 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
3884 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
3886 mutex_destroy(&arc_anon->arcs_mtx);
3887 mutex_destroy(&arc_mru->arcs_mtx);
3888 mutex_destroy(&arc_mru_ghost->arcs_mtx);
3889 mutex_destroy(&arc_mfu->arcs_mtx);
3890 mutex_destroy(&arc_mfu_ghost->arcs_mtx);
3891 mutex_destroy(&arc_l2c_only->arcs_mtx);
3893 mutex_destroy(&zfs_write_limit_lock);
3897 ASSERT(arc_loaned_bytes == 0);
3903 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3904 * It uses dedicated storage devices to hold cached data, which are populated
3905 * using large infrequent writes. The main role of this cache is to boost
3906 * the performance of random read workloads. The intended L2ARC devices
3907 * include short-stroked disks, solid state disks, and other media with
3908 * substantially faster read latency than disk.
3910 * +-----------------------+
3912 * +-----------------------+
3915 * l2arc_feed_thread() arc_read()
3919 * +---------------+ |
3921 * +---------------+ |
3926 * +-------+ +-------+
3928 * | cache | | cache |
3929 * +-------+ +-------+
3930 * +=========+ .-----.
3931 * : L2ARC : |-_____-|
3932 * : devices : | Disks |
3933 * +=========+ `-_____-'
3935 * Read requests are satisfied from the following sources, in order:
3938 * 2) vdev cache of L2ARC devices
3940 * 4) vdev cache of disks
3943 * Some L2ARC device types exhibit extremely slow write performance.
3944 * To accommodate for this there are some significant differences between
3945 * the L2ARC and traditional cache design:
3947 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3948 * the ARC behave as usual, freeing buffers and placing headers on ghost
3949 * lists. The ARC does not send buffers to the L2ARC during eviction as
3950 * this would add inflated write latencies for all ARC memory pressure.
3952 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3953 * It does this by periodically scanning buffers from the eviction-end of
3954 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3955 * not already there. It scans until a headroom of buffers is satisfied,
3956 * which itself is a buffer for ARC eviction. The thread that does this is
3957 * l2arc_feed_thread(), illustrated below; example sizes are included to
3958 * provide a better sense of ratio than this diagram:
3961 * +---------------------+----------+
3962 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3963 * +---------------------+----------+ | o L2ARC eligible
3964 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3965 * +---------------------+----------+ |
3966 * 15.9 Gbytes ^ 32 Mbytes |
3968 * l2arc_feed_thread()
3970 * l2arc write hand <--[oooo]--'
3974 * +==============================+
3975 * L2ARC dev |####|#|###|###| |####| ... |
3976 * +==============================+
3979 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3980 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3981 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3982 * safe to say that this is an uncommon case, since buffers at the end of
3983 * the ARC lists have moved there due to inactivity.
3985 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3986 * then the L2ARC simply misses copying some buffers. This serves as a
3987 * pressure valve to prevent heavy read workloads from both stalling the ARC
3988 * with waits and clogging the L2ARC with writes. This also helps prevent
3989 * the potential for the L2ARC to churn if it attempts to cache content too
3990 * quickly, such as during backups of the entire pool.
3992 * 5. After system boot and before the ARC has filled main memory, there are
3993 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3994 * lists can remain mostly static. Instead of searching from tail of these
3995 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3996 * for eligible buffers, greatly increasing its chance of finding them.
3998 * The L2ARC device write speed is also boosted during this time so that
3999 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4000 * there are no L2ARC reads, and no fear of degrading read performance
4001 * through increased writes.
4003 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4004 * the vdev queue can aggregate them into larger and fewer writes. Each
4005 * device is written to in a rotor fashion, sweeping writes through
4006 * available space then repeating.
4008 * 7. The L2ARC does not store dirty content. It never needs to flush
4009 * write buffers back to disk based storage.
4011 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4012 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4014 * The performance of the L2ARC can be tweaked by a number of tunables, which
4015 * may be necessary for different workloads:
4017 * l2arc_write_max max write bytes per interval
4018 * l2arc_write_boost extra write bytes during device warmup
4019 * l2arc_noprefetch skip caching prefetched buffers
4020 * l2arc_headroom number of max device writes to precache
4021 * l2arc_feed_secs seconds between L2ARC writing
4023 * Tunables may be removed or added as future performance improvements are
4024 * integrated, and also may become zpool properties.
4026 * There are three key functions that control how the L2ARC warms up:
4028 * l2arc_write_eligible() check if a buffer is eligible to cache
4029 * l2arc_write_size() calculate how much to write
4030 * l2arc_write_interval() calculate sleep delay between writes
4032 * These three functions determine what to write, how much, and how quickly
4037 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4040 * A buffer is *not* eligible for the L2ARC if it:
4041 * 1. belongs to a different spa.
4042 * 2. is already cached on the L2ARC.
4043 * 3. has an I/O in progress (it may be an incomplete read).
4044 * 4. is flagged not eligible (zfs property).
4046 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
4047 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
4054 l2arc_write_size(l2arc_dev_t *dev)
4058 size = dev->l2ad_write;
4060 if (arc_warm == B_FALSE)
4061 size += dev->l2ad_boost;
4068 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4070 clock_t interval, next, now;
4073 * If the ARC lists are busy, increase our write rate; if the
4074 * lists are stale, idle back. This is achieved by checking
4075 * how much we previously wrote - if it was more than half of
4076 * what we wanted, schedule the next write much sooner.
4078 if (l2arc_feed_again && wrote > (wanted / 2))
4079 interval = (hz * l2arc_feed_min_ms) / 1000;
4081 interval = hz * l2arc_feed_secs;
4083 now = ddi_get_lbolt();
4084 next = MAX(now, MIN(now + interval, began + interval));
4090 l2arc_hdr_stat_add(void)
4092 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4093 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4097 l2arc_hdr_stat_remove(void)
4099 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4100 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4104 * Cycle through L2ARC devices. This is how L2ARC load balances.
4105 * If a device is returned, this also returns holding the spa config lock.
4107 static l2arc_dev_t *
4108 l2arc_dev_get_next(void)
4110 l2arc_dev_t *first, *next = NULL;
4113 * Lock out the removal of spas (spa_namespace_lock), then removal
4114 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4115 * both locks will be dropped and a spa config lock held instead.
4117 mutex_enter(&spa_namespace_lock);
4118 mutex_enter(&l2arc_dev_mtx);
4120 /* if there are no vdevs, there is nothing to do */
4121 if (l2arc_ndev == 0)
4125 next = l2arc_dev_last;
4127 /* loop around the list looking for a non-faulted vdev */
4129 next = list_head(l2arc_dev_list);
4131 next = list_next(l2arc_dev_list, next);
4133 next = list_head(l2arc_dev_list);
4136 /* if we have come back to the start, bail out */
4139 else if (next == first)
4142 } while (vdev_is_dead(next->l2ad_vdev));
4144 /* if we were unable to find any usable vdevs, return NULL */
4145 if (vdev_is_dead(next->l2ad_vdev))
4148 l2arc_dev_last = next;
4151 mutex_exit(&l2arc_dev_mtx);
4154 * Grab the config lock to prevent the 'next' device from being
4155 * removed while we are writing to it.
4158 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4159 mutex_exit(&spa_namespace_lock);
4165 * Free buffers that were tagged for destruction.
4168 l2arc_do_free_on_write(void)
4171 l2arc_data_free_t *df, *df_prev;
4173 mutex_enter(&l2arc_free_on_write_mtx);
4174 buflist = l2arc_free_on_write;
4176 for (df = list_tail(buflist); df; df = df_prev) {
4177 df_prev = list_prev(buflist, df);
4178 ASSERT(df->l2df_data != NULL);
4179 ASSERT(df->l2df_func != NULL);
4180 df->l2df_func(df->l2df_data, df->l2df_size);
4181 list_remove(buflist, df);
4182 kmem_free(df, sizeof (l2arc_data_free_t));
4185 mutex_exit(&l2arc_free_on_write_mtx);
4189 * A write to a cache device has completed. Update all headers to allow
4190 * reads from these buffers to begin.
4193 l2arc_write_done(zio_t *zio)
4195 l2arc_write_callback_t *cb;
4198 arc_buf_hdr_t *head, *ab, *ab_prev;
4199 l2arc_buf_hdr_t *abl2;
4200 kmutex_t *hash_lock;
4202 cb = zio->io_private;
4204 dev = cb->l2wcb_dev;
4205 ASSERT(dev != NULL);
4206 head = cb->l2wcb_head;
4207 ASSERT(head != NULL);
4208 buflist = dev->l2ad_buflist;
4209 ASSERT(buflist != NULL);
4210 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4211 l2arc_write_callback_t *, cb);
4213 if (zio->io_error != 0)
4214 ARCSTAT_BUMP(arcstat_l2_writes_error);
4216 mutex_enter(&l2arc_buflist_mtx);
4219 * All writes completed, or an error was hit.
4221 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4222 ab_prev = list_prev(buflist, ab);
4224 hash_lock = HDR_LOCK(ab);
4225 if (!mutex_tryenter(hash_lock)) {
4227 * This buffer misses out. It may be in a stage
4228 * of eviction. Its ARC_L2_WRITING flag will be
4229 * left set, denying reads to this buffer.
4231 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4235 if (zio->io_error != 0) {
4237 * Error - drop L2ARC entry.
4239 list_remove(buflist, ab);
4242 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4243 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4247 * Allow ARC to begin reads to this L2ARC entry.
4249 ab->b_flags &= ~ARC_L2_WRITING;
4251 mutex_exit(hash_lock);
4254 atomic_inc_64(&l2arc_writes_done);
4255 list_remove(buflist, head);
4256 kmem_cache_free(hdr_cache, head);
4257 mutex_exit(&l2arc_buflist_mtx);
4259 l2arc_do_free_on_write();
4261 kmem_free(cb, sizeof (l2arc_write_callback_t));
4265 * A read to a cache device completed. Validate buffer contents before
4266 * handing over to the regular ARC routines.
4269 l2arc_read_done(zio_t *zio)
4271 l2arc_read_callback_t *cb;
4274 kmutex_t *hash_lock;
4277 ASSERT(zio->io_vd != NULL);
4278 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4280 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4282 cb = zio->io_private;
4284 buf = cb->l2rcb_buf;
4285 ASSERT(buf != NULL);
4287 hash_lock = HDR_LOCK(buf->b_hdr);
4288 mutex_enter(hash_lock);
4290 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4293 * Check this survived the L2ARC journey.
4295 equal = arc_cksum_equal(buf);
4296 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4297 mutex_exit(hash_lock);
4298 zio->io_private = buf;
4299 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4300 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4303 mutex_exit(hash_lock);
4305 * Buffer didn't survive caching. Increment stats and
4306 * reissue to the original storage device.
4308 if (zio->io_error != 0) {
4309 ARCSTAT_BUMP(arcstat_l2_io_error);
4311 zio->io_error = EIO;
4314 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4317 * If there's no waiter, issue an async i/o to the primary
4318 * storage now. If there *is* a waiter, the caller must
4319 * issue the i/o in a context where it's OK to block.
4321 if (zio->io_waiter == NULL) {
4322 zio_t *pio = zio_unique_parent(zio);
4324 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4326 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4327 buf->b_data, zio->io_size, arc_read_done, buf,
4328 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4332 kmem_free(cb, sizeof (l2arc_read_callback_t));
4336 * This is the list priority from which the L2ARC will search for pages to
4337 * cache. This is used within loops (0..3) to cycle through lists in the
4338 * desired order. This order can have a significant effect on cache
4341 * Currently the metadata lists are hit first, MFU then MRU, followed by
4342 * the data lists. This function returns a locked list, and also returns
4346 l2arc_list_locked(int list_num, kmutex_t **lock)
4348 list_t *list = NULL;
4350 ASSERT(list_num >= 0 && list_num <= 3);
4354 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
4355 *lock = &arc_mfu->arcs_mtx;
4358 list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
4359 *lock = &arc_mru->arcs_mtx;
4362 list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
4363 *lock = &arc_mfu->arcs_mtx;
4366 list = &arc_mru->arcs_list[ARC_BUFC_DATA];
4367 *lock = &arc_mru->arcs_mtx;
4371 ASSERT(!(MUTEX_HELD(*lock)));
4377 * Evict buffers from the device write hand to the distance specified in
4378 * bytes. This distance may span populated buffers, it may span nothing.
4379 * This is clearing a region on the L2ARC device ready for writing.
4380 * If the 'all' boolean is set, every buffer is evicted.
4383 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4386 l2arc_buf_hdr_t *abl2;
4387 arc_buf_hdr_t *ab, *ab_prev;
4388 kmutex_t *hash_lock;
4391 buflist = dev->l2ad_buflist;
4393 if (buflist == NULL)
4396 if (!all && dev->l2ad_first) {
4398 * This is the first sweep through the device. There is
4404 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4406 * When nearing the end of the device, evict to the end
4407 * before the device write hand jumps to the start.
4409 taddr = dev->l2ad_end;
4411 taddr = dev->l2ad_hand + distance;
4413 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4414 uint64_t, taddr, boolean_t, all);
4417 mutex_enter(&l2arc_buflist_mtx);
4418 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4419 ab_prev = list_prev(buflist, ab);
4421 hash_lock = HDR_LOCK(ab);
4422 if (!mutex_tryenter(hash_lock)) {
4424 * Missed the hash lock. Retry.
4426 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4427 mutex_exit(&l2arc_buflist_mtx);
4428 mutex_enter(hash_lock);
4429 mutex_exit(hash_lock);
4433 if (HDR_L2_WRITE_HEAD(ab)) {
4435 * We hit a write head node. Leave it for
4436 * l2arc_write_done().
4438 list_remove(buflist, ab);
4439 mutex_exit(hash_lock);
4443 if (!all && ab->b_l2hdr != NULL &&
4444 (ab->b_l2hdr->b_daddr > taddr ||
4445 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4447 * We've evicted to the target address,
4448 * or the end of the device.
4450 mutex_exit(hash_lock);
4454 if (HDR_FREE_IN_PROGRESS(ab)) {
4456 * Already on the path to destruction.
4458 mutex_exit(hash_lock);
4462 if (ab->b_state == arc_l2c_only) {
4463 ASSERT(!HDR_L2_READING(ab));
4465 * This doesn't exist in the ARC. Destroy.
4466 * arc_hdr_destroy() will call list_remove()
4467 * and decrement arcstat_l2_size.
4469 arc_change_state(arc_anon, ab, hash_lock);
4470 arc_hdr_destroy(ab);
4473 * Invalidate issued or about to be issued
4474 * reads, since we may be about to write
4475 * over this location.
4477 if (HDR_L2_READING(ab)) {
4478 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4479 ab->b_flags |= ARC_L2_EVICTED;
4483 * Tell ARC this no longer exists in L2ARC.
4485 if (ab->b_l2hdr != NULL) {
4488 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4489 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4491 list_remove(buflist, ab);
4494 * This may have been leftover after a
4497 ab->b_flags &= ~ARC_L2_WRITING;
4499 mutex_exit(hash_lock);
4501 mutex_exit(&l2arc_buflist_mtx);
4503 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
4504 dev->l2ad_evict = taddr;
4508 * Find and write ARC buffers to the L2ARC device.
4510 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4511 * for reading until they have completed writing.
4514 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4516 arc_buf_hdr_t *ab, *ab_prev, *head;
4517 l2arc_buf_hdr_t *hdrl2;
4519 uint64_t passed_sz, write_sz, buf_sz, headroom;
4521 kmutex_t *hash_lock, *list_lock = NULL;
4522 boolean_t have_lock, full;
4523 l2arc_write_callback_t *cb;
4525 uint64_t guid = spa_guid(spa);
4528 ASSERT(dev->l2ad_vdev != NULL);
4533 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4534 head->b_flags |= ARC_L2_WRITE_HEAD;
4537 * Copy buffers for L2ARC writing.
4539 mutex_enter(&l2arc_buflist_mtx);
4540 for (try = 0; try <= 3; try++) {
4541 list = l2arc_list_locked(try, &list_lock);
4545 * L2ARC fast warmup.
4547 * Until the ARC is warm and starts to evict, read from the
4548 * head of the ARC lists rather than the tail.
4550 headroom = target_sz * l2arc_headroom;
4551 if (arc_warm == B_FALSE)
4552 ab = list_head(list);
4554 ab = list_tail(list);
4556 for (; ab; ab = ab_prev) {
4557 if (arc_warm == B_FALSE)
4558 ab_prev = list_next(list, ab);
4560 ab_prev = list_prev(list, ab);
4562 hash_lock = HDR_LOCK(ab);
4563 have_lock = MUTEX_HELD(hash_lock);
4564 if (!have_lock && !mutex_tryenter(hash_lock)) {
4566 * Skip this buffer rather than waiting.
4571 passed_sz += ab->b_size;
4572 if (passed_sz > headroom) {
4576 mutex_exit(hash_lock);
4580 if (!l2arc_write_eligible(guid, ab)) {
4581 mutex_exit(hash_lock);
4585 if ((write_sz + ab->b_size) > target_sz) {
4587 mutex_exit(hash_lock);
4593 * Insert a dummy header on the buflist so
4594 * l2arc_write_done() can find where the
4595 * write buffers begin without searching.
4597 list_insert_head(dev->l2ad_buflist, head);
4599 cb = kmem_alloc(sizeof (l2arc_write_callback_t),
4601 cb->l2wcb_dev = dev;
4602 cb->l2wcb_head = head;
4603 pio = zio_root(spa, l2arc_write_done, cb,
4608 * Create and add a new L2ARC header.
4610 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t),
4613 hdrl2->b_daddr = dev->l2ad_hand;
4615 ab->b_flags |= ARC_L2_WRITING;
4616 ab->b_l2hdr = hdrl2;
4617 list_insert_head(dev->l2ad_buflist, ab);
4618 buf_data = ab->b_buf->b_data;
4619 buf_sz = ab->b_size;
4622 * Compute and store the buffer cksum before
4623 * writing. On debug the cksum is verified first.
4625 arc_cksum_verify(ab->b_buf);
4626 arc_cksum_compute(ab->b_buf, B_TRUE);
4628 mutex_exit(hash_lock);
4630 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4631 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4632 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4633 ZIO_FLAG_CANFAIL, B_FALSE);
4635 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4637 (void) zio_nowait(wzio);
4640 * Keep the clock hand suitably device-aligned.
4642 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4645 dev->l2ad_hand += buf_sz;
4648 mutex_exit(list_lock);
4653 mutex_exit(&l2arc_buflist_mtx);
4656 ASSERT3U(write_sz, ==, 0);
4657 kmem_cache_free(hdr_cache, head);
4661 ASSERT3U(write_sz, <=, target_sz);
4662 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4663 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4664 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4665 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
4668 * Bump device hand to the device start if it is approaching the end.
4669 * l2arc_evict() will already have evicted ahead for this case.
4671 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4672 vdev_space_update(dev->l2ad_vdev,
4673 dev->l2ad_end - dev->l2ad_hand, 0, 0);
4674 dev->l2ad_hand = dev->l2ad_start;
4675 dev->l2ad_evict = dev->l2ad_start;
4676 dev->l2ad_first = B_FALSE;
4679 dev->l2ad_writing = B_TRUE;
4680 (void) zio_wait(pio);
4681 dev->l2ad_writing = B_FALSE;
4687 * This thread feeds the L2ARC at regular intervals. This is the beating
4688 * heart of the L2ARC.
4691 l2arc_feed_thread(void)
4696 uint64_t size, wrote;
4697 clock_t begin, next = ddi_get_lbolt();
4699 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4701 mutex_enter(&l2arc_feed_thr_lock);
4703 while (l2arc_thread_exit == 0) {
4704 CALLB_CPR_SAFE_BEGIN(&cpr);
4705 (void) cv_timedwait_interruptible(&l2arc_feed_thr_cv,
4706 &l2arc_feed_thr_lock, next);
4707 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4708 next = ddi_get_lbolt() + hz;
4711 * Quick check for L2ARC devices.
4713 mutex_enter(&l2arc_dev_mtx);
4714 if (l2arc_ndev == 0) {
4715 mutex_exit(&l2arc_dev_mtx);
4718 mutex_exit(&l2arc_dev_mtx);
4719 begin = ddi_get_lbolt();
4722 * This selects the next l2arc device to write to, and in
4723 * doing so the next spa to feed from: dev->l2ad_spa. This
4724 * will return NULL if there are now no l2arc devices or if
4725 * they are all faulted.
4727 * If a device is returned, its spa's config lock is also
4728 * held to prevent device removal. l2arc_dev_get_next()
4729 * will grab and release l2arc_dev_mtx.
4731 if ((dev = l2arc_dev_get_next()) == NULL)
4734 spa = dev->l2ad_spa;
4735 ASSERT(spa != NULL);
4738 * If the pool is read-only then force the feed thread to
4739 * sleep a little longer.
4741 if (!spa_writeable(spa)) {
4742 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
4743 spa_config_exit(spa, SCL_L2ARC, dev);
4748 * Avoid contributing to memory pressure.
4751 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4752 spa_config_exit(spa, SCL_L2ARC, dev);
4756 ARCSTAT_BUMP(arcstat_l2_feeds);
4758 size = l2arc_write_size(dev);
4761 * Evict L2ARC buffers that will be overwritten.
4763 l2arc_evict(dev, size, B_FALSE);
4766 * Write ARC buffers.
4768 wrote = l2arc_write_buffers(spa, dev, size);
4771 * Calculate interval between writes.
4773 next = l2arc_write_interval(begin, size, wrote);
4774 spa_config_exit(spa, SCL_L2ARC, dev);
4777 l2arc_thread_exit = 0;
4778 cv_broadcast(&l2arc_feed_thr_cv);
4779 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4784 l2arc_vdev_present(vdev_t *vd)
4788 mutex_enter(&l2arc_dev_mtx);
4789 for (dev = list_head(l2arc_dev_list); dev != NULL;
4790 dev = list_next(l2arc_dev_list, dev)) {
4791 if (dev->l2ad_vdev == vd)
4794 mutex_exit(&l2arc_dev_mtx);
4796 return (dev != NULL);
4800 * Add a vdev for use by the L2ARC. By this point the spa has already
4801 * validated the vdev and opened it.
4804 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
4806 l2arc_dev_t *adddev;
4808 ASSERT(!l2arc_vdev_present(vd));
4811 * Create a new l2arc device entry.
4813 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4814 adddev->l2ad_spa = spa;
4815 adddev->l2ad_vdev = vd;
4816 adddev->l2ad_write = l2arc_write_max;
4817 adddev->l2ad_boost = l2arc_write_boost;
4818 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
4819 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
4820 adddev->l2ad_hand = adddev->l2ad_start;
4821 adddev->l2ad_evict = adddev->l2ad_start;
4822 adddev->l2ad_first = B_TRUE;
4823 adddev->l2ad_writing = B_FALSE;
4824 list_link_init(&adddev->l2ad_node);
4825 ASSERT3U(adddev->l2ad_write, >, 0);
4828 * This is a list of all ARC buffers that are still valid on the
4831 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4832 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4833 offsetof(arc_buf_hdr_t, b_l2node));
4835 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
4838 * Add device to global list
4840 mutex_enter(&l2arc_dev_mtx);
4841 list_insert_head(l2arc_dev_list, adddev);
4842 atomic_inc_64(&l2arc_ndev);
4843 mutex_exit(&l2arc_dev_mtx);
4847 * Remove a vdev from the L2ARC.
4850 l2arc_remove_vdev(vdev_t *vd)
4852 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4855 * Find the device by vdev
4857 mutex_enter(&l2arc_dev_mtx);
4858 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4859 nextdev = list_next(l2arc_dev_list, dev);
4860 if (vd == dev->l2ad_vdev) {
4865 ASSERT(remdev != NULL);
4868 * Remove device from global list
4870 list_remove(l2arc_dev_list, remdev);
4871 l2arc_dev_last = NULL; /* may have been invalidated */
4872 atomic_dec_64(&l2arc_ndev);
4873 mutex_exit(&l2arc_dev_mtx);
4876 * Clear all buflists and ARC references. L2ARC device flush.
4878 l2arc_evict(remdev, 0, B_TRUE);
4879 list_destroy(remdev->l2ad_buflist);
4880 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4881 kmem_free(remdev, sizeof (l2arc_dev_t));
4887 l2arc_thread_exit = 0;
4889 l2arc_writes_sent = 0;
4890 l2arc_writes_done = 0;
4892 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4893 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4894 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4895 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4896 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4898 l2arc_dev_list = &L2ARC_dev_list;
4899 l2arc_free_on_write = &L2ARC_free_on_write;
4900 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4901 offsetof(l2arc_dev_t, l2ad_node));
4902 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4903 offsetof(l2arc_data_free_t, l2df_list_node));
4910 * This is called from dmu_fini(), which is called from spa_fini();
4911 * Because of this, we can assume that all l2arc devices have
4912 * already been removed when the pools themselves were removed.
4915 l2arc_do_free_on_write();
4917 mutex_destroy(&l2arc_feed_thr_lock);
4918 cv_destroy(&l2arc_feed_thr_cv);
4919 mutex_destroy(&l2arc_dev_mtx);
4920 mutex_destroy(&l2arc_buflist_mtx);
4921 mutex_destroy(&l2arc_free_on_write_mtx);
4923 list_destroy(l2arc_dev_list);
4924 list_destroy(l2arc_free_on_write);
4930 if (!(spa_mode_global & FWRITE))
4933 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
4934 TS_RUN, minclsyspri);
4940 if (!(spa_mode_global & FWRITE))
4943 mutex_enter(&l2arc_feed_thr_lock);
4944 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
4945 l2arc_thread_exit = 1;
4946 while (l2arc_thread_exit != 0)
4947 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
4948 mutex_exit(&l2arc_feed_thr_lock);
4951 #if defined(_KERNEL) && defined(HAVE_SPL)
4952 EXPORT_SYMBOL(arc_read);
4953 EXPORT_SYMBOL(arc_buf_remove_ref);
4954 EXPORT_SYMBOL(arc_getbuf_func);
4955 EXPORT_SYMBOL(arc_add_prune_callback);
4956 EXPORT_SYMBOL(arc_remove_prune_callback);
4958 module_param(zfs_arc_min, ulong, 0444);
4959 MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
4961 module_param(zfs_arc_max, ulong, 0444);
4962 MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
4964 module_param(zfs_arc_meta_limit, ulong, 0444);
4965 MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
4967 module_param(zfs_arc_meta_prune, int, 0444);
4968 MODULE_PARM_DESC(zfs_arc_meta_prune, "Bytes of meta data to prune");
4970 module_param(zfs_arc_grow_retry, int, 0444);
4971 MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
4973 module_param(zfs_arc_shrink_shift, int, 0444);
4974 MODULE_PARM_DESC(zfs_arc_shrink_shift, "log2(fraction of arc to reclaim)");
4976 module_param(zfs_arc_p_min_shift, int, 0444);
4977 MODULE_PARM_DESC(zfs_arc_p_min_shift, "arc_c shift to calc min/max arc_p");
4979 module_param(l2arc_write_max, ulong, 0444);
4980 MODULE_PARM_DESC(l2arc_write_max, "Max write bytes per interval");
4982 module_param(l2arc_write_boost, ulong, 0444);
4983 MODULE_PARM_DESC(l2arc_write_boost, "Extra write bytes during device warmup");
4985 module_param(l2arc_headroom, ulong, 0444);
4986 MODULE_PARM_DESC(l2arc_headroom, "Number of max device writes to precache");
4988 module_param(l2arc_feed_secs, ulong, 0444);
4989 MODULE_PARM_DESC(l2arc_feed_secs, "Seconds between L2ARC writing");
4991 module_param(l2arc_feed_min_ms, ulong, 0444);
4992 MODULE_PARM_DESC(l2arc_feed_min_ms, "Min feed interval in milliseconds");
4994 module_param(l2arc_noprefetch, int, 0444);
4995 MODULE_PARM_DESC(l2arc_noprefetch, "Skip caching prefetched buffers");
4997 module_param(l2arc_feed_again, int, 0444);
4998 MODULE_PARM_DESC(l2arc_feed_again, "Turbo L2ARC warmup");
5000 module_param(l2arc_norw, int, 0444);
5001 MODULE_PARM_DESC(l2arc_norw, "No reads during writes");