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 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
27 * DVA-based Adjustable Replacement Cache
29 * While much of the theory of operation used here is
30 * based on the self-tuning, low overhead replacement cache
31 * presented by Megiddo and Modha at FAST 2003, there are some
32 * significant differences:
34 * 1. The Megiddo and Modha model assumes any page is evictable.
35 * Pages in its cache cannot be "locked" into memory. This makes
36 * the eviction algorithm simple: evict the last page in the list.
37 * This also make the performance characteristics easy to reason
38 * about. Our cache is not so simple. At any given moment, some
39 * subset of the blocks in the cache are un-evictable because we
40 * have handed out a reference to them. Blocks are only evictable
41 * when there are no external references active. This makes
42 * eviction far more problematic: we choose to evict the evictable
43 * blocks that are the "lowest" in the list.
45 * There are times when it is not possible to evict the requested
46 * space. In these circumstances we are unable to adjust the cache
47 * size. To prevent the cache growing unbounded at these times we
48 * implement a "cache throttle" that slows the flow of new data
49 * into the cache until we can make space available.
51 * 2. The Megiddo and Modha model assumes a fixed cache size.
52 * Pages are evicted when the cache is full and there is a cache
53 * miss. Our model has a variable sized cache. It grows with
54 * high use, but also tries to react to memory pressure from the
55 * operating system: decreasing its size when system memory is
58 * 3. The Megiddo and Modha model assumes a fixed page size. All
59 * elements of the cache are therefor exactly the same size. So
60 * when adjusting the cache size following a cache miss, its simply
61 * a matter of choosing a single page to evict. In our model, we
62 * have variable sized cache blocks (rangeing from 512 bytes to
63 * 128K bytes). We therefor choose a set of blocks to evict to make
64 * space for a cache miss that approximates as closely as possible
65 * the space used by the new block.
67 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
68 * by N. Megiddo & D. Modha, FAST 2003
74 * A new reference to a cache buffer can be obtained in two
75 * ways: 1) via a hash table lookup using the DVA as a key,
76 * or 2) via one of the ARC lists. The arc_read() interface
77 * uses method 1, while the internal arc algorithms for
78 * adjusting the cache use method 2. We therefor provide two
79 * types of locks: 1) the hash table lock array, and 2) the
82 * Buffers do not have their own mutexs, rather they rely on the
83 * hash table mutexs for the bulk of their protection (i.e. most
84 * fields in the arc_buf_hdr_t are protected by these mutexs).
86 * buf_hash_find() returns the appropriate mutex (held) when it
87 * locates the requested buffer in the hash table. It returns
88 * NULL for the mutex if the buffer was not in the table.
90 * buf_hash_remove() expects the appropriate hash mutex to be
91 * already held before it is invoked.
93 * Each arc state also has a mutex which is used to protect the
94 * buffer list associated with the state. When attempting to
95 * obtain a hash table lock while holding an arc list lock you
96 * must use: mutex_tryenter() to avoid deadlock. Also note that
97 * the active state mutex must be held before the ghost state mutex.
99 * Arc buffers may have an associated eviction callback function.
100 * This function will be invoked prior to removing the buffer (e.g.
101 * in arc_do_user_evicts()). Note however that the data associated
102 * with the buffer may be evicted prior to the callback. The callback
103 * must be made with *no locks held* (to prevent deadlock). Additionally,
104 * the users of callbacks must ensure that their private data is
105 * protected from simultaneous callbacks from arc_buf_evict()
106 * and arc_do_user_evicts().
108 * Note that the majority of the performance stats are manipulated
109 * with atomic operations.
111 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
113 * - L2ARC buflist creation
114 * - L2ARC buflist eviction
115 * - L2ARC write completion, which walks L2ARC buflists
116 * - ARC header destruction, as it removes from L2ARC buflists
117 * - ARC header release, as it removes from L2ARC buflists
122 #include <sys/zio_checksum.h>
123 #include <sys/zfs_context.h>
125 #include <sys/refcount.h>
126 #include <sys/vdev.h>
128 #include <sys/dnlc.h>
130 #include <sys/callb.h>
131 #include <sys/kstat.h>
134 #include <vm/vm_pageout.h>
136 static kmutex_t arc_reclaim_thr_lock;
137 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
138 static uint8_t arc_thread_exit;
140 extern int zfs_write_limit_shift;
141 extern uint64_t zfs_write_limit_max;
142 extern kmutex_t zfs_write_limit_lock;
144 #define ARC_REDUCE_DNLC_PERCENT 3
145 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
147 typedef enum arc_reclaim_strategy {
148 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
149 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
150 } arc_reclaim_strategy_t;
152 /* number of seconds before growing cache again */
153 static int arc_grow_retry = 60;
155 /* shift of arc_c for calculating both min and max arc_p */
156 static int arc_p_min_shift = 4;
158 /* log2(fraction of arc to reclaim) */
159 static int arc_shrink_shift = 5;
162 * minimum lifespan of a prefetch block in clock ticks
163 * (initialized in arc_init())
165 static int arc_min_prefetch_lifespan;
168 extern int zfs_prefetch_disable;
171 * The arc has filled available memory and has now warmed up.
173 static boolean_t arc_warm;
176 * These tunables are for performance analysis.
178 uint64_t zfs_arc_max;
179 uint64_t zfs_arc_min;
180 uint64_t zfs_arc_meta_limit = 0;
181 int zfs_mdcomp_disable = 0;
182 int zfs_arc_grow_retry = 0;
183 int zfs_arc_shrink_shift = 0;
184 int zfs_arc_p_min_shift = 0;
186 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
187 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
188 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
189 TUNABLE_INT("vfs.zfs.mdcomp_disable", &zfs_mdcomp_disable);
190 SYSCTL_DECL(_vfs_zfs);
191 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
193 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
195 SYSCTL_INT(_vfs_zfs, OID_AUTO, mdcomp_disable, CTLFLAG_RDTUN,
196 &zfs_mdcomp_disable, 0, "Disable metadata compression");
199 * Note that buffers can be in one of 6 states:
200 * ARC_anon - anonymous (discussed below)
201 * ARC_mru - recently used, currently cached
202 * ARC_mru_ghost - recentely used, no longer in cache
203 * ARC_mfu - frequently used, currently cached
204 * ARC_mfu_ghost - frequently used, no longer in cache
205 * ARC_l2c_only - exists in L2ARC but not other states
206 * When there are no active references to the buffer, they are
207 * are linked onto a list in one of these arc states. These are
208 * the only buffers that can be evicted or deleted. Within each
209 * state there are multiple lists, one for meta-data and one for
210 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
211 * etc.) is tracked separately so that it can be managed more
212 * explicitly: favored over data, limited explicitly.
214 * Anonymous buffers are buffers that are not associated with
215 * a DVA. These are buffers that hold dirty block copies
216 * before they are written to stable storage. By definition,
217 * they are "ref'd" and are considered part of arc_mru
218 * that cannot be freed. Generally, they will aquire a DVA
219 * as they are written and migrate onto the arc_mru list.
221 * The ARC_l2c_only state is for buffers that are in the second
222 * level ARC but no longer in any of the ARC_m* lists. The second
223 * level ARC itself may also contain buffers that are in any of
224 * the ARC_m* states - meaning that a buffer can exist in two
225 * places. The reason for the ARC_l2c_only state is to keep the
226 * buffer header in the hash table, so that reads that hit the
227 * second level ARC benefit from these fast lookups.
230 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
234 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
239 * must be power of two for mask use to work
242 #define ARC_BUFC_NUMDATALISTS 16
243 #define ARC_BUFC_NUMMETADATALISTS 16
244 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
246 typedef struct arc_state {
247 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
248 uint64_t arcs_size; /* total amount of data in this state */
249 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
250 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
253 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
256 static arc_state_t ARC_anon;
257 static arc_state_t ARC_mru;
258 static arc_state_t ARC_mru_ghost;
259 static arc_state_t ARC_mfu;
260 static arc_state_t ARC_mfu_ghost;
261 static arc_state_t ARC_l2c_only;
263 typedef struct arc_stats {
264 kstat_named_t arcstat_hits;
265 kstat_named_t arcstat_misses;
266 kstat_named_t arcstat_demand_data_hits;
267 kstat_named_t arcstat_demand_data_misses;
268 kstat_named_t arcstat_demand_metadata_hits;
269 kstat_named_t arcstat_demand_metadata_misses;
270 kstat_named_t arcstat_prefetch_data_hits;
271 kstat_named_t arcstat_prefetch_data_misses;
272 kstat_named_t arcstat_prefetch_metadata_hits;
273 kstat_named_t arcstat_prefetch_metadata_misses;
274 kstat_named_t arcstat_mru_hits;
275 kstat_named_t arcstat_mru_ghost_hits;
276 kstat_named_t arcstat_mfu_hits;
277 kstat_named_t arcstat_mfu_ghost_hits;
278 kstat_named_t arcstat_allocated;
279 kstat_named_t arcstat_deleted;
280 kstat_named_t arcstat_stolen;
281 kstat_named_t arcstat_recycle_miss;
282 kstat_named_t arcstat_mutex_miss;
283 kstat_named_t arcstat_evict_skip;
284 kstat_named_t arcstat_evict_l2_cached;
285 kstat_named_t arcstat_evict_l2_eligible;
286 kstat_named_t arcstat_evict_l2_ineligible;
287 kstat_named_t arcstat_hash_elements;
288 kstat_named_t arcstat_hash_elements_max;
289 kstat_named_t arcstat_hash_collisions;
290 kstat_named_t arcstat_hash_chains;
291 kstat_named_t arcstat_hash_chain_max;
292 kstat_named_t arcstat_p;
293 kstat_named_t arcstat_c;
294 kstat_named_t arcstat_c_min;
295 kstat_named_t arcstat_c_max;
296 kstat_named_t arcstat_size;
297 kstat_named_t arcstat_hdr_size;
298 kstat_named_t arcstat_data_size;
299 kstat_named_t arcstat_other_size;
300 kstat_named_t arcstat_l2_hits;
301 kstat_named_t arcstat_l2_misses;
302 kstat_named_t arcstat_l2_feeds;
303 kstat_named_t arcstat_l2_rw_clash;
304 kstat_named_t arcstat_l2_read_bytes;
305 kstat_named_t arcstat_l2_write_bytes;
306 kstat_named_t arcstat_l2_writes_sent;
307 kstat_named_t arcstat_l2_writes_done;
308 kstat_named_t arcstat_l2_writes_error;
309 kstat_named_t arcstat_l2_writes_hdr_miss;
310 kstat_named_t arcstat_l2_evict_lock_retry;
311 kstat_named_t arcstat_l2_evict_reading;
312 kstat_named_t arcstat_l2_free_on_write;
313 kstat_named_t arcstat_l2_abort_lowmem;
314 kstat_named_t arcstat_l2_cksum_bad;
315 kstat_named_t arcstat_l2_io_error;
316 kstat_named_t arcstat_l2_size;
317 kstat_named_t arcstat_l2_hdr_size;
318 kstat_named_t arcstat_memory_throttle_count;
319 kstat_named_t arcstat_l2_write_trylock_fail;
320 kstat_named_t arcstat_l2_write_passed_headroom;
321 kstat_named_t arcstat_l2_write_spa_mismatch;
322 kstat_named_t arcstat_l2_write_in_l2;
323 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
324 kstat_named_t arcstat_l2_write_not_cacheable;
325 kstat_named_t arcstat_l2_write_full;
326 kstat_named_t arcstat_l2_write_buffer_iter;
327 kstat_named_t arcstat_l2_write_pios;
328 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
329 kstat_named_t arcstat_l2_write_buffer_list_iter;
330 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
333 static arc_stats_t arc_stats = {
334 { "hits", KSTAT_DATA_UINT64 },
335 { "misses", KSTAT_DATA_UINT64 },
336 { "demand_data_hits", KSTAT_DATA_UINT64 },
337 { "demand_data_misses", KSTAT_DATA_UINT64 },
338 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
339 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
340 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
341 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
342 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
343 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
344 { "mru_hits", KSTAT_DATA_UINT64 },
345 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
346 { "mfu_hits", KSTAT_DATA_UINT64 },
347 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
348 { "allocated", KSTAT_DATA_UINT64 },
349 { "deleted", KSTAT_DATA_UINT64 },
350 { "stolen", KSTAT_DATA_UINT64 },
351 { "recycle_miss", KSTAT_DATA_UINT64 },
352 { "mutex_miss", KSTAT_DATA_UINT64 },
353 { "evict_skip", KSTAT_DATA_UINT64 },
354 { "evict_l2_cached", KSTAT_DATA_UINT64 },
355 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
356 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
357 { "hash_elements", KSTAT_DATA_UINT64 },
358 { "hash_elements_max", KSTAT_DATA_UINT64 },
359 { "hash_collisions", KSTAT_DATA_UINT64 },
360 { "hash_chains", KSTAT_DATA_UINT64 },
361 { "hash_chain_max", KSTAT_DATA_UINT64 },
362 { "p", KSTAT_DATA_UINT64 },
363 { "c", KSTAT_DATA_UINT64 },
364 { "c_min", KSTAT_DATA_UINT64 },
365 { "c_max", KSTAT_DATA_UINT64 },
366 { "size", KSTAT_DATA_UINT64 },
367 { "hdr_size", KSTAT_DATA_UINT64 },
368 { "data_size", KSTAT_DATA_UINT64 },
369 { "other_size", KSTAT_DATA_UINT64 },
370 { "l2_hits", KSTAT_DATA_UINT64 },
371 { "l2_misses", KSTAT_DATA_UINT64 },
372 { "l2_feeds", KSTAT_DATA_UINT64 },
373 { "l2_rw_clash", KSTAT_DATA_UINT64 },
374 { "l2_read_bytes", KSTAT_DATA_UINT64 },
375 { "l2_write_bytes", KSTAT_DATA_UINT64 },
376 { "l2_writes_sent", KSTAT_DATA_UINT64 },
377 { "l2_writes_done", KSTAT_DATA_UINT64 },
378 { "l2_writes_error", KSTAT_DATA_UINT64 },
379 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
380 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
381 { "l2_evict_reading", KSTAT_DATA_UINT64 },
382 { "l2_free_on_write", KSTAT_DATA_UINT64 },
383 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
384 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
385 { "l2_io_error", KSTAT_DATA_UINT64 },
386 { "l2_size", KSTAT_DATA_UINT64 },
387 { "l2_hdr_size", KSTAT_DATA_UINT64 },
388 { "memory_throttle_count", KSTAT_DATA_UINT64 },
389 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
390 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
391 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
392 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
393 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
394 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
395 { "l2_write_full", KSTAT_DATA_UINT64 },
396 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
397 { "l2_write_pios", KSTAT_DATA_UINT64 },
398 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
399 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
400 { "l2_write_buffer_list_null_iter", 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 */
463 static int arc_no_grow; /* Don't try to grow cache size */
464 static uint64_t arc_tempreserve;
465 static uint64_t arc_meta_used;
466 static uint64_t arc_meta_limit;
467 static uint64_t arc_meta_max = 0;
468 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RDTUN,
469 &arc_meta_used, 0, "ARC metadata used");
470 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RDTUN,
471 &arc_meta_limit, 0, "ARC metadata limit");
473 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
475 typedef struct arc_callback arc_callback_t;
477 struct arc_callback {
479 arc_done_func_t *acb_done;
481 zio_t *acb_zio_dummy;
482 arc_callback_t *acb_next;
485 typedef struct arc_write_callback arc_write_callback_t;
487 struct arc_write_callback {
489 arc_done_func_t *awcb_ready;
490 arc_done_func_t *awcb_done;
495 /* protected by hash lock */
500 kmutex_t b_freeze_lock;
501 zio_cksum_t *b_freeze_cksum;
503 arc_buf_hdr_t *b_hash_next;
508 arc_callback_t *b_acb;
512 arc_buf_contents_t b_type;
516 /* protected by arc state mutex */
517 arc_state_t *b_state;
518 list_node_t b_arc_node;
520 /* updated atomically */
521 clock_t b_arc_access;
523 /* self protecting */
526 l2arc_buf_hdr_t *b_l2hdr;
527 list_node_t b_l2node;
530 static arc_buf_t *arc_eviction_list;
531 static kmutex_t arc_eviction_mtx;
532 static arc_buf_hdr_t arc_eviction_hdr;
533 static void arc_get_data_buf(arc_buf_t *buf);
534 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
535 static int arc_evict_needed(arc_buf_contents_t type);
536 static void arc_evict_ghost(arc_state_t *state, spa_t *spa, int64_t bytes);
538 static boolean_t l2arc_write_eligible(spa_t *spa, arc_buf_hdr_t *ab);
540 #define GHOST_STATE(state) \
541 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
542 (state) == arc_l2c_only)
545 * Private ARC flags. These flags are private ARC only flags that will show up
546 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
547 * be passed in as arc_flags in things like arc_read. However, these flags
548 * should never be passed and should only be set by ARC code. When adding new
549 * public flags, make sure not to smash the private ones.
552 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
553 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
554 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
555 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
556 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
557 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
558 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
559 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
560 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
561 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
562 #define ARC_STORED (1 << 19) /* has been store()d to */
564 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
565 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
566 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
567 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
568 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
569 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
570 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
571 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
572 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
573 (hdr)->b_l2hdr != NULL)
574 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
575 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
576 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
582 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
583 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
586 * Hash table routines
589 #define HT_LOCK_PAD CACHE_LINE_SIZE
594 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
598 #define BUF_LOCKS 256
599 typedef struct buf_hash_table {
601 arc_buf_hdr_t **ht_table;
602 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
605 static buf_hash_table_t buf_hash_table;
607 #define BUF_HASH_INDEX(spa, dva, birth) \
608 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
609 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
610 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
611 #define HDR_LOCK(buf) \
612 (BUF_HASH_LOCK(BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth)))
614 uint64_t zfs_crc64_table[256];
620 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
621 #define L2ARC_HEADROOM 2 /* num of writes */
622 #define L2ARC_FEED_SECS 1 /* caching interval secs */
623 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
625 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
626 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
629 * L2ARC Performance Tunables
631 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
632 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
633 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
634 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
635 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
636 boolean_t l2arc_noprefetch = B_FALSE; /* don't cache prefetch bufs */
637 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
638 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
640 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
641 &l2arc_write_max, 0, "max write size");
642 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
643 &l2arc_write_boost, 0, "extra write during warmup");
644 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
645 &l2arc_headroom, 0, "number of dev writes");
646 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
647 &l2arc_feed_secs, 0, "interval seconds");
648 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
649 &l2arc_feed_min_ms, 0, "min interval milliseconds");
651 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
652 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
653 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
654 &l2arc_feed_again, 0, "turbo warmup");
655 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
656 &l2arc_norw, 0, "no reads during writes");
658 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
659 &ARC_anon.arcs_size, 0, "size of anonymous state");
660 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
661 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
662 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
663 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
665 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
666 &ARC_mru.arcs_size, 0, "size of mru state");
667 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
668 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
669 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
670 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
672 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
673 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
674 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
675 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
676 "size of metadata in mru ghost state");
677 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
678 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
679 "size of data in mru ghost state");
681 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
682 &ARC_mfu.arcs_size, 0, "size of mfu state");
683 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
684 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
685 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
686 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
688 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
689 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
690 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
691 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
692 "size of metadata in mfu ghost state");
693 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
694 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
695 "size of data in mfu ghost state");
697 SYSCTL_QUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
698 &ARC_l2c_only.arcs_size, 0, "size of mru state");
703 typedef struct l2arc_dev {
704 vdev_t *l2ad_vdev; /* vdev */
705 spa_t *l2ad_spa; /* spa */
706 uint64_t l2ad_hand; /* next write location */
707 uint64_t l2ad_write; /* desired write size, bytes */
708 uint64_t l2ad_boost; /* warmup write boost, bytes */
709 uint64_t l2ad_start; /* first addr on device */
710 uint64_t l2ad_end; /* last addr on device */
711 uint64_t l2ad_evict; /* last addr eviction reached */
712 boolean_t l2ad_first; /* first sweep through */
713 boolean_t l2ad_writing; /* currently writing */
714 list_t *l2ad_buflist; /* buffer list */
715 list_node_t l2ad_node; /* device list node */
718 static list_t L2ARC_dev_list; /* device list */
719 static list_t *l2arc_dev_list; /* device list pointer */
720 static kmutex_t l2arc_dev_mtx; /* device list mutex */
721 static l2arc_dev_t *l2arc_dev_last; /* last device used */
722 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
723 static list_t L2ARC_free_on_write; /* free after write buf list */
724 static list_t *l2arc_free_on_write; /* free after write list ptr */
725 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
726 static uint64_t l2arc_ndev; /* number of devices */
728 typedef struct l2arc_read_callback {
729 arc_buf_t *l2rcb_buf; /* read buffer */
730 spa_t *l2rcb_spa; /* spa */
731 blkptr_t l2rcb_bp; /* original blkptr */
732 zbookmark_t l2rcb_zb; /* original bookmark */
733 int l2rcb_flags; /* original flags */
734 } l2arc_read_callback_t;
736 typedef struct l2arc_write_callback {
737 l2arc_dev_t *l2wcb_dev; /* device info */
738 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
739 } l2arc_write_callback_t;
741 struct l2arc_buf_hdr {
742 /* protected by arc_buf_hdr mutex */
743 l2arc_dev_t *b_dev; /* L2ARC device */
744 uint64_t b_daddr; /* disk address, offset byte */
747 typedef struct l2arc_data_free {
748 /* protected by l2arc_free_on_write_mtx */
751 void (*l2df_func)(void *, size_t);
752 list_node_t l2df_list_node;
755 static kmutex_t l2arc_feed_thr_lock;
756 static kcondvar_t l2arc_feed_thr_cv;
757 static uint8_t l2arc_thread_exit;
759 static void l2arc_read_done(zio_t *zio);
760 static void l2arc_hdr_stat_add(void);
761 static void l2arc_hdr_stat_remove(void);
764 buf_hash(spa_t *spa, const dva_t *dva, uint64_t birth)
766 uintptr_t spav = (uintptr_t)spa;
767 uint8_t *vdva = (uint8_t *)dva;
768 uint64_t crc = -1ULL;
771 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
773 for (i = 0; i < sizeof (dva_t); i++)
774 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
776 crc ^= (spav>>8) ^ birth;
781 #define BUF_EMPTY(buf) \
782 ((buf)->b_dva.dva_word[0] == 0 && \
783 (buf)->b_dva.dva_word[1] == 0 && \
786 #define BUF_EQUAL(spa, dva, birth, buf) \
787 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
788 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
789 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
791 static arc_buf_hdr_t *
792 buf_hash_find(spa_t *spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
794 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
795 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
798 mutex_enter(hash_lock);
799 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
800 buf = buf->b_hash_next) {
801 if (BUF_EQUAL(spa, dva, birth, buf)) {
806 mutex_exit(hash_lock);
812 * Insert an entry into the hash table. If there is already an element
813 * equal to elem in the hash table, then the already existing element
814 * will be returned and the new element will not be inserted.
815 * Otherwise returns NULL.
817 static arc_buf_hdr_t *
818 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
820 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
821 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
825 ASSERT(!HDR_IN_HASH_TABLE(buf));
827 mutex_enter(hash_lock);
828 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
829 fbuf = fbuf->b_hash_next, i++) {
830 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
834 buf->b_hash_next = buf_hash_table.ht_table[idx];
835 buf_hash_table.ht_table[idx] = buf;
836 buf->b_flags |= ARC_IN_HASH_TABLE;
838 /* collect some hash table performance data */
840 ARCSTAT_BUMP(arcstat_hash_collisions);
842 ARCSTAT_BUMP(arcstat_hash_chains);
844 ARCSTAT_MAX(arcstat_hash_chain_max, i);
847 ARCSTAT_BUMP(arcstat_hash_elements);
848 ARCSTAT_MAXSTAT(arcstat_hash_elements);
854 buf_hash_remove(arc_buf_hdr_t *buf)
856 arc_buf_hdr_t *fbuf, **bufp;
857 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
859 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
860 ASSERT(HDR_IN_HASH_TABLE(buf));
862 bufp = &buf_hash_table.ht_table[idx];
863 while ((fbuf = *bufp) != buf) {
864 ASSERT(fbuf != NULL);
865 bufp = &fbuf->b_hash_next;
867 *bufp = buf->b_hash_next;
868 buf->b_hash_next = NULL;
869 buf->b_flags &= ~ARC_IN_HASH_TABLE;
871 /* collect some hash table performance data */
872 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
874 if (buf_hash_table.ht_table[idx] &&
875 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
876 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
880 * Global data structures and functions for the buf kmem cache.
882 static kmem_cache_t *hdr_cache;
883 static kmem_cache_t *buf_cache;
890 kmem_free(buf_hash_table.ht_table,
891 (buf_hash_table.ht_mask + 1) * sizeof (void *));
892 for (i = 0; i < BUF_LOCKS; i++)
893 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
894 kmem_cache_destroy(hdr_cache);
895 kmem_cache_destroy(buf_cache);
899 * Constructor callback - called when the cache is empty
900 * and a new buf is requested.
904 hdr_cons(void *vbuf, void *unused, int kmflag)
906 arc_buf_hdr_t *buf = vbuf;
908 bzero(buf, sizeof (arc_buf_hdr_t));
909 refcount_create(&buf->b_refcnt);
910 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
911 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
912 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
919 buf_cons(void *vbuf, void *unused, int kmflag)
921 arc_buf_t *buf = vbuf;
923 bzero(buf, sizeof (arc_buf_t));
924 rw_init(&buf->b_lock, NULL, RW_DEFAULT, NULL);
925 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
931 * Destructor callback - called when a cached buf is
932 * no longer required.
936 hdr_dest(void *vbuf, void *unused)
938 arc_buf_hdr_t *buf = vbuf;
940 refcount_destroy(&buf->b_refcnt);
941 cv_destroy(&buf->b_cv);
942 mutex_destroy(&buf->b_freeze_lock);
943 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
948 buf_dest(void *vbuf, void *unused)
950 arc_buf_t *buf = vbuf;
952 rw_destroy(&buf->b_lock);
953 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
957 * Reclaim callback -- invoked when memory is low.
961 hdr_recl(void *unused)
963 dprintf("hdr_recl called\n");
965 * umem calls the reclaim func when we destroy the buf cache,
966 * which is after we do arc_fini().
969 cv_signal(&arc_reclaim_thr_cv);
976 uint64_t hsize = 1ULL << 12;
980 * The hash table is big enough to fill all of physical memory
981 * with an average 64K block size. The table will take up
982 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
984 while (hsize * 65536 < (uint64_t)physmem * PAGESIZE)
987 buf_hash_table.ht_mask = hsize - 1;
988 buf_hash_table.ht_table =
989 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
990 if (buf_hash_table.ht_table == NULL) {
991 ASSERT(hsize > (1ULL << 8));
996 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
997 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
998 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
999 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1001 for (i = 0; i < 256; i++)
1002 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1003 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1005 for (i = 0; i < BUF_LOCKS; i++) {
1006 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1007 NULL, MUTEX_DEFAULT, NULL);
1011 #define ARC_MINTIME (hz>>4) /* 62 ms */
1014 arc_cksum_verify(arc_buf_t *buf)
1018 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1021 mutex_enter(&buf->b_hdr->b_freeze_lock);
1022 if (buf->b_hdr->b_freeze_cksum == NULL ||
1023 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1024 mutex_exit(&buf->b_hdr->b_freeze_lock);
1027 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1028 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1029 panic("buffer modified while frozen!");
1030 mutex_exit(&buf->b_hdr->b_freeze_lock);
1034 arc_cksum_equal(arc_buf_t *buf)
1039 mutex_enter(&buf->b_hdr->b_freeze_lock);
1040 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1041 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1042 mutex_exit(&buf->b_hdr->b_freeze_lock);
1048 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1050 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1053 mutex_enter(&buf->b_hdr->b_freeze_lock);
1054 if (buf->b_hdr->b_freeze_cksum != NULL) {
1055 mutex_exit(&buf->b_hdr->b_freeze_lock);
1058 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1059 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1060 buf->b_hdr->b_freeze_cksum);
1061 mutex_exit(&buf->b_hdr->b_freeze_lock);
1065 arc_buf_thaw(arc_buf_t *buf)
1067 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1068 if (buf->b_hdr->b_state != arc_anon)
1069 panic("modifying non-anon buffer!");
1070 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1071 panic("modifying buffer while i/o in progress!");
1072 arc_cksum_verify(buf);
1075 mutex_enter(&buf->b_hdr->b_freeze_lock);
1076 if (buf->b_hdr->b_freeze_cksum != NULL) {
1077 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1078 buf->b_hdr->b_freeze_cksum = NULL;
1080 mutex_exit(&buf->b_hdr->b_freeze_lock);
1084 arc_buf_freeze(arc_buf_t *buf)
1086 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1089 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1090 buf->b_hdr->b_state == arc_anon);
1091 arc_cksum_compute(buf, B_FALSE);
1095 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1097 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1099 if (ab->b_type == ARC_BUFC_METADATA)
1100 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1102 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1103 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1106 *list = &state->arcs_lists[buf_hashid];
1107 *lock = ARCS_LOCK(state, buf_hashid);
1112 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1115 ASSERT(MUTEX_HELD(hash_lock));
1117 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1118 (ab->b_state != arc_anon)) {
1119 uint64_t delta = ab->b_size * ab->b_datacnt;
1120 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1124 get_buf_info(ab, ab->b_state, &list, &lock);
1125 ASSERT(!MUTEX_HELD(lock));
1127 ASSERT(list_link_active(&ab->b_arc_node));
1128 list_remove(list, ab);
1129 if (GHOST_STATE(ab->b_state)) {
1130 ASSERT3U(ab->b_datacnt, ==, 0);
1131 ASSERT3P(ab->b_buf, ==, NULL);
1135 ASSERT3U(*size, >=, delta);
1136 atomic_add_64(size, -delta);
1138 /* remove the prefetch flag if we get a reference */
1139 if (ab->b_flags & ARC_PREFETCH)
1140 ab->b_flags &= ~ARC_PREFETCH;
1145 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1148 arc_state_t *state = ab->b_state;
1150 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1151 ASSERT(!GHOST_STATE(state));
1153 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1154 (state != arc_anon)) {
1155 uint64_t *size = &state->arcs_lsize[ab->b_type];
1159 get_buf_info(ab, state, &list, &lock);
1160 ASSERT(!MUTEX_HELD(lock));
1162 ASSERT(!list_link_active(&ab->b_arc_node));
1163 list_insert_head(list, ab);
1164 ASSERT(ab->b_datacnt > 0);
1165 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1172 * Move the supplied buffer to the indicated state. The mutex
1173 * for the buffer must be held by the caller.
1176 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1178 arc_state_t *old_state = ab->b_state;
1179 int64_t refcnt = refcount_count(&ab->b_refcnt);
1180 uint64_t from_delta, to_delta;
1184 ASSERT(MUTEX_HELD(hash_lock));
1185 ASSERT(new_state != old_state);
1186 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1187 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1189 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1192 * If this buffer is evictable, transfer it from the
1193 * old state list to the new state list.
1196 if (old_state != arc_anon) {
1198 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1200 get_buf_info(ab, old_state, &list, &lock);
1201 use_mutex = !MUTEX_HELD(lock);
1205 ASSERT(list_link_active(&ab->b_arc_node));
1206 list_remove(list, ab);
1209 * If prefetching out of the ghost cache,
1210 * we will have a non-null datacnt.
1212 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1213 /* ghost elements have a ghost size */
1214 ASSERT(ab->b_buf == NULL);
1215 from_delta = ab->b_size;
1217 ASSERT3U(*size, >=, from_delta);
1218 atomic_add_64(size, -from_delta);
1223 if (new_state != arc_anon) {
1225 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1227 get_buf_info(ab, new_state, &list, &lock);
1228 use_mutex = !MUTEX_HELD(lock);
1232 list_insert_head(list, ab);
1234 /* ghost elements have a ghost size */
1235 if (GHOST_STATE(new_state)) {
1236 ASSERT(ab->b_datacnt == 0);
1237 ASSERT(ab->b_buf == NULL);
1238 to_delta = ab->b_size;
1240 atomic_add_64(size, to_delta);
1247 ASSERT(!BUF_EMPTY(ab));
1248 if (new_state == arc_anon) {
1249 buf_hash_remove(ab);
1252 /* adjust state sizes */
1254 atomic_add_64(&new_state->arcs_size, to_delta);
1256 ASSERT3U(old_state->arcs_size, >=, from_delta);
1257 atomic_add_64(&old_state->arcs_size, -from_delta);
1259 ab->b_state = new_state;
1261 /* adjust l2arc hdr stats */
1262 if (new_state == arc_l2c_only)
1263 l2arc_hdr_stat_add();
1264 else if (old_state == arc_l2c_only)
1265 l2arc_hdr_stat_remove();
1269 arc_space_consume(uint64_t space, arc_space_type_t type)
1271 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1274 case ARC_SPACE_DATA:
1275 ARCSTAT_INCR(arcstat_data_size, space);
1277 case ARC_SPACE_OTHER:
1278 ARCSTAT_INCR(arcstat_other_size, space);
1280 case ARC_SPACE_HDRS:
1281 ARCSTAT_INCR(arcstat_hdr_size, space);
1283 case ARC_SPACE_L2HDRS:
1284 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1288 atomic_add_64(&arc_meta_used, space);
1289 atomic_add_64(&arc_size, space);
1293 arc_space_return(uint64_t space, arc_space_type_t type)
1295 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1298 case ARC_SPACE_DATA:
1299 ARCSTAT_INCR(arcstat_data_size, -space);
1301 case ARC_SPACE_OTHER:
1302 ARCSTAT_INCR(arcstat_other_size, -space);
1304 case ARC_SPACE_HDRS:
1305 ARCSTAT_INCR(arcstat_hdr_size, -space);
1307 case ARC_SPACE_L2HDRS:
1308 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1312 ASSERT(arc_meta_used >= space);
1313 if (arc_meta_max < arc_meta_used)
1314 arc_meta_max = arc_meta_used;
1315 atomic_add_64(&arc_meta_used, -space);
1316 ASSERT(arc_size >= space);
1317 atomic_add_64(&arc_size, -space);
1321 arc_data_buf_alloc(uint64_t size)
1323 if (arc_evict_needed(ARC_BUFC_DATA))
1324 cv_signal(&arc_reclaim_thr_cv);
1325 atomic_add_64(&arc_size, size);
1326 return (zio_data_buf_alloc(size));
1330 arc_data_buf_free(void *buf, uint64_t size)
1332 zio_data_buf_free(buf, size);
1333 ASSERT(arc_size >= size);
1334 atomic_add_64(&arc_size, -size);
1338 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1343 ASSERT3U(size, >, 0);
1344 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1345 ASSERT(BUF_EMPTY(hdr));
1349 hdr->b_state = arc_anon;
1350 hdr->b_arc_access = 0;
1351 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1354 buf->b_efunc = NULL;
1355 buf->b_private = NULL;
1358 arc_get_data_buf(buf);
1361 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1362 (void) refcount_add(&hdr->b_refcnt, tag);
1368 arc_buf_clone(arc_buf_t *from)
1371 arc_buf_hdr_t *hdr = from->b_hdr;
1372 uint64_t size = hdr->b_size;
1374 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1377 buf->b_efunc = NULL;
1378 buf->b_private = NULL;
1379 buf->b_next = hdr->b_buf;
1381 arc_get_data_buf(buf);
1382 bcopy(from->b_data, buf->b_data, size);
1383 hdr->b_datacnt += 1;
1388 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1391 kmutex_t *hash_lock;
1394 * Check to see if this buffer is evicted. Callers
1395 * must verify b_data != NULL to know if the add_ref
1398 rw_enter(&buf->b_lock, RW_READER);
1399 if (buf->b_data == NULL) {
1400 rw_exit(&buf->b_lock);
1404 ASSERT(hdr != NULL);
1405 hash_lock = HDR_LOCK(hdr);
1406 mutex_enter(hash_lock);
1407 rw_exit(&buf->b_lock);
1409 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1410 add_reference(hdr, hash_lock, tag);
1411 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1412 arc_access(hdr, hash_lock);
1413 mutex_exit(hash_lock);
1414 ARCSTAT_BUMP(arcstat_hits);
1415 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1416 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1417 data, metadata, hits);
1421 * Free the arc data buffer. If it is an l2arc write in progress,
1422 * the buffer is placed on l2arc_free_on_write to be freed later.
1425 arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
1426 void *data, size_t size)
1428 if (HDR_L2_WRITING(hdr)) {
1429 l2arc_data_free_t *df;
1430 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1431 df->l2df_data = data;
1432 df->l2df_size = size;
1433 df->l2df_func = free_func;
1434 mutex_enter(&l2arc_free_on_write_mtx);
1435 list_insert_head(l2arc_free_on_write, df);
1436 mutex_exit(&l2arc_free_on_write_mtx);
1437 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1439 free_func(data, size);
1444 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1448 /* free up data associated with the buf */
1450 arc_state_t *state = buf->b_hdr->b_state;
1451 uint64_t size = buf->b_hdr->b_size;
1452 arc_buf_contents_t type = buf->b_hdr->b_type;
1454 arc_cksum_verify(buf);
1456 if (type == ARC_BUFC_METADATA) {
1457 arc_buf_data_free(buf->b_hdr, zio_buf_free,
1459 arc_space_return(size, ARC_SPACE_DATA);
1461 ASSERT(type == ARC_BUFC_DATA);
1462 arc_buf_data_free(buf->b_hdr,
1463 zio_data_buf_free, buf->b_data, size);
1464 ARCSTAT_INCR(arcstat_data_size, -size);
1465 atomic_add_64(&arc_size, -size);
1468 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1469 uint64_t *cnt = &state->arcs_lsize[type];
1471 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1472 ASSERT(state != arc_anon);
1474 ASSERT3U(*cnt, >=, size);
1475 atomic_add_64(cnt, -size);
1477 ASSERT3U(state->arcs_size, >=, size);
1478 atomic_add_64(&state->arcs_size, -size);
1480 ASSERT(buf->b_hdr->b_datacnt > 0);
1481 buf->b_hdr->b_datacnt -= 1;
1484 /* only remove the buf if requested */
1488 /* remove the buf from the hdr list */
1489 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1491 *bufp = buf->b_next;
1493 ASSERT(buf->b_efunc == NULL);
1495 /* clean up the buf */
1497 kmem_cache_free(buf_cache, buf);
1501 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1503 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1504 ASSERT3P(hdr->b_state, ==, arc_anon);
1505 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1506 ASSERT(!(hdr->b_flags & ARC_STORED));
1508 if (hdr->b_l2hdr != NULL) {
1509 if (!MUTEX_HELD(&l2arc_buflist_mtx)) {
1511 * To prevent arc_free() and l2arc_evict() from
1512 * attempting to free the same buffer at the same time,
1513 * a FREE_IN_PROGRESS flag is given to arc_free() to
1514 * give it priority. l2arc_evict() can't destroy this
1515 * header while we are waiting on l2arc_buflist_mtx.
1517 * The hdr may be removed from l2ad_buflist before we
1518 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1520 mutex_enter(&l2arc_buflist_mtx);
1521 if (hdr->b_l2hdr != NULL) {
1522 list_remove(hdr->b_l2hdr->b_dev->l2ad_buflist,
1525 mutex_exit(&l2arc_buflist_mtx);
1527 list_remove(hdr->b_l2hdr->b_dev->l2ad_buflist, hdr);
1529 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1530 kmem_free(hdr->b_l2hdr, sizeof (l2arc_buf_hdr_t));
1531 if (hdr->b_state == arc_l2c_only)
1532 l2arc_hdr_stat_remove();
1533 hdr->b_l2hdr = NULL;
1536 if (!BUF_EMPTY(hdr)) {
1537 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1538 bzero(&hdr->b_dva, sizeof (dva_t));
1542 while (hdr->b_buf) {
1543 arc_buf_t *buf = hdr->b_buf;
1546 mutex_enter(&arc_eviction_mtx);
1547 rw_enter(&buf->b_lock, RW_WRITER);
1548 ASSERT(buf->b_hdr != NULL);
1549 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1550 hdr->b_buf = buf->b_next;
1551 buf->b_hdr = &arc_eviction_hdr;
1552 buf->b_next = arc_eviction_list;
1553 arc_eviction_list = buf;
1554 rw_exit(&buf->b_lock);
1555 mutex_exit(&arc_eviction_mtx);
1557 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1560 if (hdr->b_freeze_cksum != NULL) {
1561 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1562 hdr->b_freeze_cksum = NULL;
1565 ASSERT(!list_link_active(&hdr->b_arc_node));
1566 ASSERT3P(hdr->b_hash_next, ==, NULL);
1567 ASSERT3P(hdr->b_acb, ==, NULL);
1568 kmem_cache_free(hdr_cache, hdr);
1572 arc_buf_free(arc_buf_t *buf, void *tag)
1574 arc_buf_hdr_t *hdr = buf->b_hdr;
1575 int hashed = hdr->b_state != arc_anon;
1577 ASSERT(buf->b_efunc == NULL);
1578 ASSERT(buf->b_data != NULL);
1581 kmutex_t *hash_lock = HDR_LOCK(hdr);
1583 mutex_enter(hash_lock);
1584 (void) remove_reference(hdr, hash_lock, tag);
1585 if (hdr->b_datacnt > 1)
1586 arc_buf_destroy(buf, FALSE, TRUE);
1588 hdr->b_flags |= ARC_BUF_AVAILABLE;
1589 mutex_exit(hash_lock);
1590 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1593 * We are in the middle of an async write. Don't destroy
1594 * this buffer unless the write completes before we finish
1595 * decrementing the reference count.
1597 mutex_enter(&arc_eviction_mtx);
1598 (void) remove_reference(hdr, NULL, tag);
1599 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1600 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1601 mutex_exit(&arc_eviction_mtx);
1603 arc_hdr_destroy(hdr);
1605 if (remove_reference(hdr, NULL, tag) > 0) {
1606 ASSERT(HDR_IO_ERROR(hdr));
1607 arc_buf_destroy(buf, FALSE, TRUE);
1609 arc_hdr_destroy(hdr);
1615 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1617 arc_buf_hdr_t *hdr = buf->b_hdr;
1618 kmutex_t *hash_lock = HDR_LOCK(hdr);
1619 int no_callback = (buf->b_efunc == NULL);
1621 if (hdr->b_state == arc_anon) {
1622 arc_buf_free(buf, tag);
1623 return (no_callback);
1626 mutex_enter(hash_lock);
1627 ASSERT(hdr->b_state != arc_anon);
1628 ASSERT(buf->b_data != NULL);
1630 (void) remove_reference(hdr, hash_lock, tag);
1631 if (hdr->b_datacnt > 1) {
1633 arc_buf_destroy(buf, FALSE, TRUE);
1634 } else if (no_callback) {
1635 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1636 hdr->b_flags |= ARC_BUF_AVAILABLE;
1638 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1639 refcount_is_zero(&hdr->b_refcnt));
1640 mutex_exit(hash_lock);
1641 return (no_callback);
1645 arc_buf_size(arc_buf_t *buf)
1647 return (buf->b_hdr->b_size);
1651 * Evict buffers from list until we've removed the specified number of
1652 * bytes. Move the removed buffers to the appropriate evict state.
1653 * If the recycle flag is set, then attempt to "recycle" a buffer:
1654 * - look for a buffer to evict that is `bytes' long.
1655 * - return the data block from this buffer rather than freeing it.
1656 * This flag is used by callers that are trying to make space for a
1657 * new buffer in a full arc cache.
1659 * This function makes a "best effort". It skips over any buffers
1660 * it can't get a hash_lock on, and so may not catch all candidates.
1661 * It may also return without evicting as much space as requested.
1664 arc_evict(arc_state_t *state, spa_t *spa, int64_t bytes, boolean_t recycle,
1665 arc_buf_contents_t type)
1667 arc_state_t *evicted_state;
1668 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1669 int64_t bytes_remaining;
1670 arc_buf_hdr_t *ab, *ab_prev = NULL;
1671 list_t *evicted_list, *list, *evicted_list_start, *list_start;
1672 kmutex_t *lock, *evicted_lock;
1673 kmutex_t *hash_lock;
1674 boolean_t have_lock;
1675 void *stolen = NULL;
1676 static int evict_metadata_offset, evict_data_offset;
1677 int i, idx, offset, list_count, count;
1679 ASSERT(state == arc_mru || state == arc_mfu);
1681 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1683 if (type == ARC_BUFC_METADATA) {
1685 list_count = ARC_BUFC_NUMMETADATALISTS;
1686 list_start = &state->arcs_lists[0];
1687 evicted_list_start = &evicted_state->arcs_lists[0];
1688 idx = evict_metadata_offset;
1690 offset = ARC_BUFC_NUMMETADATALISTS;
1691 list_start = &state->arcs_lists[offset];
1692 evicted_list_start = &evicted_state->arcs_lists[offset];
1693 list_count = ARC_BUFC_NUMDATALISTS;
1694 idx = evict_data_offset;
1696 bytes_remaining = evicted_state->arcs_lsize[type];
1700 list = &list_start[idx];
1701 evicted_list = &evicted_list_start[idx];
1702 lock = ARCS_LOCK(state, (offset + idx));
1703 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
1706 mutex_enter(evicted_lock);
1708 for (ab = list_tail(list); ab; ab = ab_prev) {
1709 ab_prev = list_prev(list, ab);
1710 bytes_remaining -= (ab->b_size * ab->b_datacnt);
1711 /* prefetch buffers have a minimum lifespan */
1712 if (HDR_IO_IN_PROGRESS(ab) ||
1713 (spa && ab->b_spa != spa) ||
1714 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1715 LBOLT - ab->b_arc_access < arc_min_prefetch_lifespan)) {
1719 /* "lookahead" for better eviction candidate */
1720 if (recycle && ab->b_size != bytes &&
1721 ab_prev && ab_prev->b_size == bytes)
1723 hash_lock = HDR_LOCK(ab);
1724 have_lock = MUTEX_HELD(hash_lock);
1725 if (have_lock || mutex_tryenter(hash_lock)) {
1726 ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
1727 ASSERT(ab->b_datacnt > 0);
1729 arc_buf_t *buf = ab->b_buf;
1730 if (!rw_tryenter(&buf->b_lock, RW_WRITER)) {
1735 bytes_evicted += ab->b_size;
1736 if (recycle && ab->b_type == type &&
1737 ab->b_size == bytes &&
1738 !HDR_L2_WRITING(ab)) {
1739 stolen = buf->b_data;
1744 mutex_enter(&arc_eviction_mtx);
1745 arc_buf_destroy(buf,
1746 buf->b_data == stolen, FALSE);
1747 ab->b_buf = buf->b_next;
1748 buf->b_hdr = &arc_eviction_hdr;
1749 buf->b_next = arc_eviction_list;
1750 arc_eviction_list = buf;
1751 mutex_exit(&arc_eviction_mtx);
1752 rw_exit(&buf->b_lock);
1754 rw_exit(&buf->b_lock);
1755 arc_buf_destroy(buf,
1756 buf->b_data == stolen, TRUE);
1761 ARCSTAT_INCR(arcstat_evict_l2_cached,
1764 if (l2arc_write_eligible(ab->b_spa, ab)) {
1765 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1769 arcstat_evict_l2_ineligible,
1774 if (ab->b_datacnt == 0) {
1775 arc_change_state(evicted_state, ab, hash_lock);
1776 ASSERT(HDR_IN_HASH_TABLE(ab));
1777 ab->b_flags |= ARC_IN_HASH_TABLE;
1778 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1779 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1782 mutex_exit(hash_lock);
1783 if (bytes >= 0 && bytes_evicted >= bytes)
1785 if (bytes_remaining > 0) {
1786 mutex_exit(evicted_lock);
1788 idx = ((idx + 1) & (list_count - 1));
1797 mutex_exit(evicted_lock);
1800 idx = ((idx + 1) & (list_count - 1));
1803 if (bytes_evicted < bytes) {
1804 if (count < list_count)
1807 dprintf("only evicted %lld bytes from %x",
1808 (longlong_t)bytes_evicted, state);
1810 if (type == ARC_BUFC_METADATA)
1811 evict_metadata_offset = idx;
1813 evict_data_offset = idx;
1816 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1819 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1822 * We have just evicted some date into the ghost state, make
1823 * sure we also adjust the ghost state size if necessary.
1826 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1827 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1828 arc_mru_ghost->arcs_size - arc_c;
1830 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1832 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1833 arc_evict_ghost(arc_mru_ghost, NULL, todelete);
1834 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1835 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1836 arc_mru_ghost->arcs_size +
1837 arc_mfu_ghost->arcs_size - arc_c);
1838 arc_evict_ghost(arc_mfu_ghost, NULL, todelete);
1842 ARCSTAT_BUMP(arcstat_stolen);
1848 * Remove buffers from list until we've removed the specified number of
1849 * bytes. Destroy the buffers that are removed.
1852 arc_evict_ghost(arc_state_t *state, spa_t *spa, int64_t bytes)
1854 arc_buf_hdr_t *ab, *ab_prev;
1855 list_t *list, *list_start;
1856 kmutex_t *hash_lock, *lock;
1857 uint64_t bytes_deleted = 0;
1858 uint64_t bufs_skipped = 0;
1859 static int evict_offset;
1860 int list_count, idx = evict_offset;
1861 int offset, count = 0;
1863 ASSERT(GHOST_STATE(state));
1866 * data lists come after metadata lists
1868 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
1869 list_count = ARC_BUFC_NUMDATALISTS;
1870 offset = ARC_BUFC_NUMMETADATALISTS;
1873 list = &list_start[idx];
1874 lock = ARCS_LOCK(state, idx + offset);
1877 for (ab = list_tail(list); ab; ab = ab_prev) {
1878 ab_prev = list_prev(list, ab);
1879 if (spa && ab->b_spa != spa)
1881 hash_lock = HDR_LOCK(ab);
1882 if (mutex_tryenter(hash_lock)) {
1883 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1884 ASSERT(ab->b_buf == NULL);
1885 ARCSTAT_BUMP(arcstat_deleted);
1886 bytes_deleted += ab->b_size;
1888 if (ab->b_l2hdr != NULL) {
1890 * This buffer is cached on the 2nd Level ARC;
1891 * don't destroy the header.
1893 arc_change_state(arc_l2c_only, ab, hash_lock);
1894 mutex_exit(hash_lock);
1896 arc_change_state(arc_anon, ab, hash_lock);
1897 mutex_exit(hash_lock);
1898 arc_hdr_destroy(ab);
1901 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1902 if (bytes >= 0 && bytes_deleted >= bytes)
1907 * we're draining the ARC, retry
1910 mutex_enter(hash_lock);
1911 mutex_exit(hash_lock);
1918 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
1921 if (count < list_count)
1925 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
1926 (bytes < 0 || bytes_deleted < bytes)) {
1927 list_start = &state->arcs_lists[0];
1928 list_count = ARC_BUFC_NUMMETADATALISTS;
1934 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
1938 if (bytes_deleted < bytes)
1939 dprintf("only deleted %lld bytes from %p",
1940 (longlong_t)bytes_deleted, state);
1946 int64_t adjustment, delta;
1952 adjustment = MIN(arc_size - arc_c,
1953 arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - arc_p);
1955 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
1956 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
1957 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
1958 adjustment -= delta;
1961 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1962 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
1963 (void) arc_evict(arc_mru, NULL, delta, FALSE,
1971 adjustment = arc_size - arc_c;
1973 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
1974 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
1975 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
1976 adjustment -= delta;
1979 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1980 int64_t delta = MIN(adjustment,
1981 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
1982 (void) arc_evict(arc_mfu, NULL, delta, FALSE,
1987 * Adjust ghost lists
1990 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
1992 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
1993 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
1994 arc_evict_ghost(arc_mru_ghost, NULL, delta);
1998 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2000 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2001 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2002 arc_evict_ghost(arc_mfu_ghost, NULL, delta);
2007 arc_do_user_evicts(void)
2009 static arc_buf_t *tmp_arc_eviction_list;
2012 * Move list over to avoid LOR
2015 mutex_enter(&arc_eviction_mtx);
2016 tmp_arc_eviction_list = arc_eviction_list;
2017 arc_eviction_list = NULL;
2018 mutex_exit(&arc_eviction_mtx);
2020 while (tmp_arc_eviction_list != NULL) {
2021 arc_buf_t *buf = tmp_arc_eviction_list;
2022 tmp_arc_eviction_list = buf->b_next;
2023 rw_enter(&buf->b_lock, RW_WRITER);
2025 rw_exit(&buf->b_lock);
2027 if (buf->b_efunc != NULL)
2028 VERIFY(buf->b_efunc(buf) == 0);
2030 buf->b_efunc = NULL;
2031 buf->b_private = NULL;
2032 kmem_cache_free(buf_cache, buf);
2035 if (arc_eviction_list != NULL)
2040 * Flush all *evictable* data from the cache for the given spa.
2041 * NOTE: this will not touch "active" (i.e. referenced) data.
2044 arc_flush(spa_t *spa)
2046 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2047 (void) arc_evict(arc_mru, spa, -1, FALSE, ARC_BUFC_DATA);
2051 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2052 (void) arc_evict(arc_mru, spa, -1, FALSE, ARC_BUFC_METADATA);
2056 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2057 (void) arc_evict(arc_mfu, spa, -1, FALSE, ARC_BUFC_DATA);
2061 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2062 (void) arc_evict(arc_mfu, spa, -1, FALSE, ARC_BUFC_METADATA);
2067 arc_evict_ghost(arc_mru_ghost, spa, -1);
2068 arc_evict_ghost(arc_mfu_ghost, spa, -1);
2070 mutex_enter(&arc_reclaim_thr_lock);
2071 arc_do_user_evicts();
2072 mutex_exit(&arc_reclaim_thr_lock);
2073 ASSERT(spa || arc_eviction_list == NULL);
2079 if (arc_c > arc_c_min) {
2083 to_free = arc_c >> arc_shrink_shift;
2085 to_free = arc_c >> arc_shrink_shift;
2087 if (arc_c > arc_c_min + to_free)
2088 atomic_add_64(&arc_c, -to_free);
2092 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2093 if (arc_c > arc_size)
2094 arc_c = MAX(arc_size, arc_c_min);
2096 arc_p = (arc_c >> 1);
2097 ASSERT(arc_c >= arc_c_min);
2098 ASSERT((int64_t)arc_p >= 0);
2101 if (arc_size > arc_c)
2105 static int needfree = 0;
2108 arc_reclaim_needed(void)
2117 if (arc_size > arc_c_max)
2119 if (arc_size <= arc_c_min)
2123 * If pages are needed or we're within 2048 pages
2124 * of needing to page need to reclaim
2126 if (vm_pages_needed || (vm_paging_target() > -2048))
2131 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2136 * check that we're out of range of the pageout scanner. It starts to
2137 * schedule paging if freemem is less than lotsfree and needfree.
2138 * lotsfree is the high-water mark for pageout, and needfree is the
2139 * number of needed free pages. We add extra pages here to make sure
2140 * the scanner doesn't start up while we're freeing memory.
2142 if (freemem < lotsfree + needfree + extra)
2146 * check to make sure that swapfs has enough space so that anon
2147 * reservations can still succeed. anon_resvmem() checks that the
2148 * availrmem is greater than swapfs_minfree, and the number of reserved
2149 * swap pages. We also add a bit of extra here just to prevent
2150 * circumstances from getting really dire.
2152 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2157 * If we're on an i386 platform, it's possible that we'll exhaust the
2158 * kernel heap space before we ever run out of available physical
2159 * memory. Most checks of the size of the heap_area compare against
2160 * tune.t_minarmem, which is the minimum available real memory that we
2161 * can have in the system. However, this is generally fixed at 25 pages
2162 * which is so low that it's useless. In this comparison, we seek to
2163 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2164 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2167 if (btop(vmem_size(heap_arena, VMEM_FREE)) <
2168 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
2172 if (kmem_used() > (kmem_size() * 3) / 4)
2177 if (spa_get_random(100) == 0)
2183 extern kmem_cache_t *zio_buf_cache[];
2184 extern kmem_cache_t *zio_data_buf_cache[];
2187 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2190 kmem_cache_t *prev_cache = NULL;
2191 kmem_cache_t *prev_data_cache = NULL;
2194 if (arc_meta_used >= arc_meta_limit) {
2196 * We are exceeding our meta-data cache limit.
2197 * Purge some DNLC entries to release holds on meta-data.
2199 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2203 * Reclaim unused memory from all kmem caches.
2210 * An aggressive reclamation will shrink the cache size as well as
2211 * reap free buffers from the arc kmem caches.
2213 if (strat == ARC_RECLAIM_AGGR)
2216 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2217 if (zio_buf_cache[i] != prev_cache) {
2218 prev_cache = zio_buf_cache[i];
2219 kmem_cache_reap_now(zio_buf_cache[i]);
2221 if (zio_data_buf_cache[i] != prev_data_cache) {
2222 prev_data_cache = zio_data_buf_cache[i];
2223 kmem_cache_reap_now(zio_data_buf_cache[i]);
2226 kmem_cache_reap_now(buf_cache);
2227 kmem_cache_reap_now(hdr_cache);
2231 arc_reclaim_thread(void *dummy __unused)
2233 clock_t growtime = 0;
2234 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2237 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2239 mutex_enter(&arc_reclaim_thr_lock);
2240 while (arc_thread_exit == 0) {
2241 if (arc_reclaim_needed()) {
2244 if (last_reclaim == ARC_RECLAIM_CONS) {
2245 last_reclaim = ARC_RECLAIM_AGGR;
2247 last_reclaim = ARC_RECLAIM_CONS;
2251 last_reclaim = ARC_RECLAIM_AGGR;
2255 /* reset the growth delay for every reclaim */
2256 growtime = LBOLT + (arc_grow_retry * hz);
2258 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2260 * If needfree is TRUE our vm_lowmem hook
2261 * was called and in that case we must free some
2262 * memory, so switch to aggressive mode.
2265 last_reclaim = ARC_RECLAIM_AGGR;
2267 arc_kmem_reap_now(last_reclaim);
2270 } else if (arc_no_grow && LBOLT >= growtime) {
2271 arc_no_grow = FALSE;
2275 (2 * arc_c < arc_size +
2276 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size))
2279 if (arc_eviction_list != NULL)
2280 arc_do_user_evicts();
2282 if (arc_reclaim_needed()) {
2289 /* block until needed, or one second, whichever is shorter */
2290 CALLB_CPR_SAFE_BEGIN(&cpr);
2291 (void) cv_timedwait(&arc_reclaim_thr_cv,
2292 &arc_reclaim_thr_lock, hz);
2293 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2296 arc_thread_exit = 0;
2297 cv_broadcast(&arc_reclaim_thr_cv);
2298 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2303 * Adapt arc info given the number of bytes we are trying to add and
2304 * the state that we are comming from. This function is only called
2305 * when we are adding new content to the cache.
2308 arc_adapt(int bytes, arc_state_t *state)
2311 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2313 if (state == arc_l2c_only)
2318 * Adapt the target size of the MRU list:
2319 * - if we just hit in the MRU ghost list, then increase
2320 * the target size of the MRU list.
2321 * - if we just hit in the MFU ghost list, then increase
2322 * the target size of the MFU list by decreasing the
2323 * target size of the MRU list.
2325 if (state == arc_mru_ghost) {
2326 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2327 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2329 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2330 } else if (state == arc_mfu_ghost) {
2333 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2334 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2336 delta = MIN(bytes * mult, arc_p);
2337 arc_p = MAX(arc_p_min, arc_p - delta);
2339 ASSERT((int64_t)arc_p >= 0);
2341 if (arc_reclaim_needed()) {
2342 cv_signal(&arc_reclaim_thr_cv);
2349 if (arc_c >= arc_c_max)
2353 * If we're within (2 * maxblocksize) bytes of the target
2354 * cache size, increment the target cache size
2356 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2357 atomic_add_64(&arc_c, (int64_t)bytes);
2358 if (arc_c > arc_c_max)
2360 else if (state == arc_anon)
2361 atomic_add_64(&arc_p, (int64_t)bytes);
2365 ASSERT((int64_t)arc_p >= 0);
2369 * Check if the cache has reached its limits and eviction is required
2373 arc_evict_needed(arc_buf_contents_t type)
2375 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2381 * If zio data pages are being allocated out of a separate heap segment,
2382 * then enforce that the size of available vmem for this area remains
2383 * above about 1/32nd free.
2385 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2386 vmem_size(zio_arena, VMEM_FREE) <
2387 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2392 if (arc_reclaim_needed())
2395 return (arc_size > arc_c);
2399 * The buffer, supplied as the first argument, needs a data block.
2400 * So, if we are at cache max, determine which cache should be victimized.
2401 * We have the following cases:
2403 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2404 * In this situation if we're out of space, but the resident size of the MFU is
2405 * under the limit, victimize the MFU cache to satisfy this insertion request.
2407 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2408 * Here, we've used up all of the available space for the MRU, so we need to
2409 * evict from our own cache instead. Evict from the set of resident MRU
2412 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2413 * c minus p represents the MFU space in the cache, since p is the size of the
2414 * cache that is dedicated to the MRU. In this situation there's still space on
2415 * the MFU side, so the MRU side needs to be victimized.
2417 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2418 * MFU's resident set is consuming more space than it has been allotted. In
2419 * this situation, we must victimize our own cache, the MFU, for this insertion.
2422 arc_get_data_buf(arc_buf_t *buf)
2424 arc_state_t *state = buf->b_hdr->b_state;
2425 uint64_t size = buf->b_hdr->b_size;
2426 arc_buf_contents_t type = buf->b_hdr->b_type;
2428 arc_adapt(size, state);
2431 * We have not yet reached cache maximum size,
2432 * just allocate a new buffer.
2434 if (!arc_evict_needed(type)) {
2435 if (type == ARC_BUFC_METADATA) {
2436 buf->b_data = zio_buf_alloc(size);
2437 arc_space_consume(size, ARC_SPACE_DATA);
2439 ASSERT(type == ARC_BUFC_DATA);
2440 buf->b_data = zio_data_buf_alloc(size);
2441 ARCSTAT_INCR(arcstat_data_size, size);
2442 atomic_add_64(&arc_size, size);
2448 * If we are prefetching from the mfu ghost list, this buffer
2449 * will end up on the mru list; so steal space from there.
2451 if (state == arc_mfu_ghost)
2452 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2453 else if (state == arc_mru_ghost)
2456 if (state == arc_mru || state == arc_anon) {
2457 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2458 state = (arc_mfu->arcs_lsize[type] >= size &&
2459 arc_p > mru_used) ? arc_mfu : arc_mru;
2462 uint64_t mfu_space = arc_c - arc_p;
2463 state = (arc_mru->arcs_lsize[type] >= size &&
2464 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2466 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
2467 if (type == ARC_BUFC_METADATA) {
2468 buf->b_data = zio_buf_alloc(size);
2469 arc_space_consume(size, ARC_SPACE_DATA);
2471 ASSERT(type == ARC_BUFC_DATA);
2472 buf->b_data = zio_data_buf_alloc(size);
2473 ARCSTAT_INCR(arcstat_data_size, size);
2474 atomic_add_64(&arc_size, size);
2476 ARCSTAT_BUMP(arcstat_recycle_miss);
2478 ASSERT(buf->b_data != NULL);
2481 * Update the state size. Note that ghost states have a
2482 * "ghost size" and so don't need to be updated.
2484 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2485 arc_buf_hdr_t *hdr = buf->b_hdr;
2487 atomic_add_64(&hdr->b_state->arcs_size, size);
2488 if (list_link_active(&hdr->b_arc_node)) {
2489 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2490 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2493 * If we are growing the cache, and we are adding anonymous
2494 * data, and we have outgrown arc_p, update arc_p
2496 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2497 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2498 arc_p = MIN(arc_c, arc_p + size);
2500 ARCSTAT_BUMP(arcstat_allocated);
2504 * This routine is called whenever a buffer is accessed.
2505 * NOTE: the hash lock is dropped in this function.
2508 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2510 ASSERT(MUTEX_HELD(hash_lock));
2512 if (buf->b_state == arc_anon) {
2514 * This buffer is not in the cache, and does not
2515 * appear in our "ghost" list. Add the new buffer
2519 ASSERT(buf->b_arc_access == 0);
2520 buf->b_arc_access = LBOLT;
2521 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2522 arc_change_state(arc_mru, buf, hash_lock);
2524 } else if (buf->b_state == arc_mru) {
2526 * If this buffer is here because of a prefetch, then either:
2527 * - clear the flag if this is a "referencing" read
2528 * (any subsequent access will bump this into the MFU state).
2530 * - move the buffer to the head of the list if this is
2531 * another prefetch (to make it less likely to be evicted).
2533 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2534 if (refcount_count(&buf->b_refcnt) == 0) {
2535 ASSERT(list_link_active(&buf->b_arc_node));
2537 buf->b_flags &= ~ARC_PREFETCH;
2538 ARCSTAT_BUMP(arcstat_mru_hits);
2540 buf->b_arc_access = LBOLT;
2545 * This buffer has been "accessed" only once so far,
2546 * but it is still in the cache. Move it to the MFU
2549 if (LBOLT > buf->b_arc_access + ARC_MINTIME) {
2551 * More than 125ms have passed since we
2552 * instantiated this buffer. Move it to the
2553 * most frequently used state.
2555 buf->b_arc_access = LBOLT;
2556 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2557 arc_change_state(arc_mfu, buf, hash_lock);
2559 ARCSTAT_BUMP(arcstat_mru_hits);
2560 } else if (buf->b_state == arc_mru_ghost) {
2561 arc_state_t *new_state;
2563 * This buffer has been "accessed" recently, but
2564 * was evicted from the cache. Move it to the
2568 if (buf->b_flags & ARC_PREFETCH) {
2569 new_state = arc_mru;
2570 if (refcount_count(&buf->b_refcnt) > 0)
2571 buf->b_flags &= ~ARC_PREFETCH;
2572 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2574 new_state = arc_mfu;
2575 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2578 buf->b_arc_access = LBOLT;
2579 arc_change_state(new_state, buf, hash_lock);
2581 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2582 } else if (buf->b_state == arc_mfu) {
2584 * This buffer has been accessed more than once and is
2585 * still in the cache. Keep it in the MFU state.
2587 * NOTE: an add_reference() that occurred when we did
2588 * the arc_read() will have kicked this off the list.
2589 * If it was a prefetch, we will explicitly move it to
2590 * the head of the list now.
2592 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2593 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2594 ASSERT(list_link_active(&buf->b_arc_node));
2596 ARCSTAT_BUMP(arcstat_mfu_hits);
2597 buf->b_arc_access = LBOLT;
2598 } else if (buf->b_state == arc_mfu_ghost) {
2599 arc_state_t *new_state = arc_mfu;
2601 * This buffer has been accessed more than once but has
2602 * been evicted from the cache. Move it back to the
2606 if (buf->b_flags & ARC_PREFETCH) {
2608 * This is a prefetch access...
2609 * move this block back to the MRU state.
2611 ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
2612 new_state = arc_mru;
2615 buf->b_arc_access = LBOLT;
2616 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2617 arc_change_state(new_state, buf, hash_lock);
2619 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2620 } else if (buf->b_state == arc_l2c_only) {
2622 * This buffer is on the 2nd Level ARC.
2625 buf->b_arc_access = LBOLT;
2626 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2627 arc_change_state(arc_mfu, buf, hash_lock);
2629 ASSERT(!"invalid arc state");
2633 /* a generic arc_done_func_t which you can use */
2636 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2638 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2639 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2642 /* a generic arc_done_func_t */
2644 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2646 arc_buf_t **bufp = arg;
2647 if (zio && zio->io_error) {
2648 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2656 arc_read_done(zio_t *zio)
2658 arc_buf_hdr_t *hdr, *found;
2660 arc_buf_t *abuf; /* buffer we're assigning to callback */
2661 kmutex_t *hash_lock;
2662 arc_callback_t *callback_list, *acb;
2663 int freeable = FALSE;
2665 buf = zio->io_private;
2669 * The hdr was inserted into hash-table and removed from lists
2670 * prior to starting I/O. We should find this header, since
2671 * it's in the hash table, and it should be legit since it's
2672 * not possible to evict it during the I/O. The only possible
2673 * reason for it not to be found is if we were freed during the
2676 found = buf_hash_find(zio->io_spa, &hdr->b_dva, hdr->b_birth,
2679 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2680 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2681 (found == hdr && HDR_L2_READING(hdr)));
2683 hdr->b_flags &= ~ARC_L2_EVICTED;
2684 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2685 hdr->b_flags &= ~ARC_L2CACHE;
2687 /* byteswap if necessary */
2688 callback_list = hdr->b_acb;
2689 ASSERT(callback_list != NULL);
2690 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
2691 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2692 byteswap_uint64_array :
2693 dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
2694 func(buf->b_data, hdr->b_size);
2697 arc_cksum_compute(buf, B_FALSE);
2699 /* create copies of the data buffer for the callers */
2701 for (acb = callback_list; acb; acb = acb->acb_next) {
2702 if (acb->acb_done) {
2704 abuf = arc_buf_clone(buf);
2705 acb->acb_buf = abuf;
2710 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2711 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2713 hdr->b_flags |= ARC_BUF_AVAILABLE;
2715 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2717 if (zio->io_error != 0) {
2718 hdr->b_flags |= ARC_IO_ERROR;
2719 if (hdr->b_state != arc_anon)
2720 arc_change_state(arc_anon, hdr, hash_lock);
2721 if (HDR_IN_HASH_TABLE(hdr))
2722 buf_hash_remove(hdr);
2723 freeable = refcount_is_zero(&hdr->b_refcnt);
2727 * Broadcast before we drop the hash_lock to avoid the possibility
2728 * that the hdr (and hence the cv) might be freed before we get to
2729 * the cv_broadcast().
2731 cv_broadcast(&hdr->b_cv);
2735 * Only call arc_access on anonymous buffers. This is because
2736 * if we've issued an I/O for an evicted buffer, we've already
2737 * called arc_access (to prevent any simultaneous readers from
2738 * getting confused).
2740 if (zio->io_error == 0 && hdr->b_state == arc_anon)
2741 arc_access(hdr, hash_lock);
2742 mutex_exit(hash_lock);
2745 * This block was freed while we waited for the read to
2746 * complete. It has been removed from the hash table and
2747 * moved to the anonymous state (so that it won't show up
2750 ASSERT3P(hdr->b_state, ==, arc_anon);
2751 freeable = refcount_is_zero(&hdr->b_refcnt);
2754 /* execute each callback and free its structure */
2755 while ((acb = callback_list) != NULL) {
2757 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2759 if (acb->acb_zio_dummy != NULL) {
2760 acb->acb_zio_dummy->io_error = zio->io_error;
2761 zio_nowait(acb->acb_zio_dummy);
2764 callback_list = acb->acb_next;
2765 kmem_free(acb, sizeof (arc_callback_t));
2769 arc_hdr_destroy(hdr);
2773 * "Read" the block block at the specified DVA (in bp) via the
2774 * cache. If the block is found in the cache, invoke the provided
2775 * callback immediately and return. Note that the `zio' parameter
2776 * in the callback will be NULL in this case, since no IO was
2777 * required. If the block is not in the cache pass the read request
2778 * on to the spa with a substitute callback function, so that the
2779 * requested block will be added to the cache.
2781 * If a read request arrives for a block that has a read in-progress,
2782 * either wait for the in-progress read to complete (and return the
2783 * results); or, if this is a read with a "done" func, add a record
2784 * to the read to invoke the "done" func when the read completes,
2785 * and return; or just return.
2787 * arc_read_done() will invoke all the requested "done" functions
2788 * for readers of this block.
2790 * Normal callers should use arc_read and pass the arc buffer and offset
2791 * for the bp. But if you know you don't need locking, you can use
2795 arc_read(zio_t *pio, spa_t *spa, blkptr_t *bp, arc_buf_t *pbuf,
2796 arc_done_func_t *done, void *private, int priority, int zio_flags,
2797 uint32_t *arc_flags, const zbookmark_t *zb)
2801 ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
2802 ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
2803 rw_enter(&pbuf->b_lock, RW_READER);
2805 err = arc_read_nolock(pio, spa, bp, done, private, priority,
2806 zio_flags, arc_flags, zb);
2807 rw_exit(&pbuf->b_lock);
2812 arc_read_nolock(zio_t *pio, spa_t *spa, blkptr_t *bp,
2813 arc_done_func_t *done, void *private, int priority, int zio_flags,
2814 uint32_t *arc_flags, const zbookmark_t *zb)
2818 kmutex_t *hash_lock;
2822 hdr = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
2823 if (hdr && hdr->b_datacnt > 0) {
2825 *arc_flags |= ARC_CACHED;
2827 if (HDR_IO_IN_PROGRESS(hdr)) {
2829 if (*arc_flags & ARC_WAIT) {
2830 cv_wait(&hdr->b_cv, hash_lock);
2831 mutex_exit(hash_lock);
2834 ASSERT(*arc_flags & ARC_NOWAIT);
2837 arc_callback_t *acb = NULL;
2839 acb = kmem_zalloc(sizeof (arc_callback_t),
2841 acb->acb_done = done;
2842 acb->acb_private = private;
2844 acb->acb_zio_dummy = zio_null(pio,
2845 spa, NULL, NULL, zio_flags);
2847 ASSERT(acb->acb_done != NULL);
2848 acb->acb_next = hdr->b_acb;
2850 add_reference(hdr, hash_lock, private);
2851 mutex_exit(hash_lock);
2854 mutex_exit(hash_lock);
2858 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2861 add_reference(hdr, hash_lock, private);
2863 * If this block is already in use, create a new
2864 * copy of the data so that we will be guaranteed
2865 * that arc_release() will always succeed.
2869 ASSERT(buf->b_data);
2870 if (HDR_BUF_AVAILABLE(hdr)) {
2871 ASSERT(buf->b_efunc == NULL);
2872 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2874 buf = arc_buf_clone(buf);
2876 } else if (*arc_flags & ARC_PREFETCH &&
2877 refcount_count(&hdr->b_refcnt) == 0) {
2878 hdr->b_flags |= ARC_PREFETCH;
2880 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
2881 arc_access(hdr, hash_lock);
2882 if (*arc_flags & ARC_L2CACHE)
2883 hdr->b_flags |= ARC_L2CACHE;
2884 mutex_exit(hash_lock);
2885 ARCSTAT_BUMP(arcstat_hits);
2886 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2887 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2888 data, metadata, hits);
2891 done(NULL, buf, private);
2893 uint64_t size = BP_GET_LSIZE(bp);
2894 arc_callback_t *acb;
2897 boolean_t devw = B_FALSE;
2900 /* this block is not in the cache */
2901 arc_buf_hdr_t *exists;
2902 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
2903 buf = arc_buf_alloc(spa, size, private, type);
2905 hdr->b_dva = *BP_IDENTITY(bp);
2906 hdr->b_birth = bp->blk_birth;
2907 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
2908 exists = buf_hash_insert(hdr, &hash_lock);
2910 /* somebody beat us to the hash insert */
2911 mutex_exit(hash_lock);
2912 bzero(&hdr->b_dva, sizeof (dva_t));
2915 (void) arc_buf_remove_ref(buf, private);
2916 goto top; /* restart the IO request */
2918 /* if this is a prefetch, we don't have a reference */
2919 if (*arc_flags & ARC_PREFETCH) {
2920 (void) remove_reference(hdr, hash_lock,
2922 hdr->b_flags |= ARC_PREFETCH;
2924 if (*arc_flags & ARC_L2CACHE)
2925 hdr->b_flags |= ARC_L2CACHE;
2926 if (BP_GET_LEVEL(bp) > 0)
2927 hdr->b_flags |= ARC_INDIRECT;
2929 /* this block is in the ghost cache */
2930 ASSERT(GHOST_STATE(hdr->b_state));
2931 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2932 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
2933 ASSERT(hdr->b_buf == NULL);
2935 /* if this is a prefetch, we don't have a reference */
2936 if (*arc_flags & ARC_PREFETCH)
2937 hdr->b_flags |= ARC_PREFETCH;
2939 add_reference(hdr, hash_lock, private);
2940 if (*arc_flags & ARC_L2CACHE)
2941 hdr->b_flags |= ARC_L2CACHE;
2942 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2945 buf->b_efunc = NULL;
2946 buf->b_private = NULL;
2949 arc_get_data_buf(buf);
2950 ASSERT(hdr->b_datacnt == 0);
2955 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
2956 acb->acb_done = done;
2957 acb->acb_private = private;
2959 ASSERT(hdr->b_acb == NULL);
2961 hdr->b_flags |= ARC_IO_IN_PROGRESS;
2964 * If the buffer has been evicted, migrate it to a present state
2965 * before issuing the I/O. Once we drop the hash-table lock,
2966 * the header will be marked as I/O in progress and have an
2967 * attached buffer. At this point, anybody who finds this
2968 * buffer ought to notice that it's legit but has a pending I/O.
2971 if (GHOST_STATE(hdr->b_state))
2972 arc_access(hdr, hash_lock);
2974 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
2975 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
2976 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
2977 addr = hdr->b_l2hdr->b_daddr;
2979 * Lock out device removal.
2981 if (vdev_is_dead(vd) ||
2982 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
2986 mutex_exit(hash_lock);
2988 ASSERT3U(hdr->b_size, ==, size);
2989 DTRACE_PROBE3(arc__miss, blkptr_t *, bp, uint64_t, size,
2991 ARCSTAT_BUMP(arcstat_misses);
2992 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2993 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2994 data, metadata, misses);
2996 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
2998 * Read from the L2ARC if the following are true:
2999 * 1. The L2ARC vdev was previously cached.
3000 * 2. This buffer still has L2ARC metadata.
3001 * 3. This buffer isn't currently writing to the L2ARC.
3002 * 4. The L2ARC entry wasn't evicted, which may
3003 * also have invalidated the vdev.
3004 * 5. This isn't prefetch and l2arc_noprefetch is set.
3006 if (hdr->b_l2hdr != NULL &&
3007 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3008 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3009 l2arc_read_callback_t *cb;
3011 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3012 ARCSTAT_BUMP(arcstat_l2_hits);
3014 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3016 cb->l2rcb_buf = buf;
3017 cb->l2rcb_spa = spa;
3020 cb->l2rcb_flags = zio_flags;
3023 * l2arc read. The SCL_L2ARC lock will be
3024 * released by l2arc_read_done().
3026 rzio = zio_read_phys(pio, vd, addr, size,
3027 buf->b_data, ZIO_CHECKSUM_OFF,
3028 l2arc_read_done, cb, priority, zio_flags |
3029 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3030 ZIO_FLAG_DONT_PROPAGATE |
3031 ZIO_FLAG_DONT_RETRY, B_FALSE);
3032 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3034 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3036 if (*arc_flags & ARC_NOWAIT) {
3041 ASSERT(*arc_flags & ARC_WAIT);
3042 if (zio_wait(rzio) == 0)
3045 /* l2arc read error; goto zio_read() */
3047 DTRACE_PROBE1(l2arc__miss,
3048 arc_buf_hdr_t *, hdr);
3049 ARCSTAT_BUMP(arcstat_l2_misses);
3050 if (HDR_L2_WRITING(hdr))
3051 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3052 spa_config_exit(spa, SCL_L2ARC, vd);
3056 spa_config_exit(spa, SCL_L2ARC, vd);
3057 if (l2arc_ndev != 0) {
3058 DTRACE_PROBE1(l2arc__miss,
3059 arc_buf_hdr_t *, hdr);
3060 ARCSTAT_BUMP(arcstat_l2_misses);
3064 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3065 arc_read_done, buf, priority, zio_flags, zb);
3067 if (*arc_flags & ARC_WAIT)
3068 return (zio_wait(rzio));
3070 ASSERT(*arc_flags & ARC_NOWAIT);
3077 * arc_read() variant to support pool traversal. If the block is already
3078 * in the ARC, make a copy of it; otherwise, the caller will do the I/O.
3079 * The idea is that we don't want pool traversal filling up memory, but
3080 * if the ARC already has the data anyway, we shouldn't pay for the I/O.
3083 arc_tryread(spa_t *spa, blkptr_t *bp, void *data)
3089 hdr = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_mtx);
3091 if (hdr && hdr->b_datacnt > 0 && !HDR_IO_IN_PROGRESS(hdr)) {
3092 arc_buf_t *buf = hdr->b_buf;
3095 while (buf->b_data == NULL) {
3099 bcopy(buf->b_data, data, hdr->b_size);
3105 mutex_exit(hash_mtx);
3111 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3113 ASSERT(buf->b_hdr != NULL);
3114 ASSERT(buf->b_hdr->b_state != arc_anon);
3115 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3116 buf->b_efunc = func;
3117 buf->b_private = private;
3121 * This is used by the DMU to let the ARC know that a buffer is
3122 * being evicted, so the ARC should clean up. If this arc buf
3123 * is not yet in the evicted state, it will be put there.
3126 arc_buf_evict(arc_buf_t *buf)
3129 kmutex_t *hash_lock;
3131 list_t *list, *evicted_list;
3132 kmutex_t *lock, *evicted_lock;
3134 rw_enter(&buf->b_lock, RW_WRITER);
3138 * We are in arc_do_user_evicts().
3140 ASSERT(buf->b_data == NULL);
3141 rw_exit(&buf->b_lock);
3143 } else if (buf->b_data == NULL) {
3144 arc_buf_t copy = *buf; /* structure assignment */
3146 * We are on the eviction list; process this buffer now
3147 * but let arc_do_user_evicts() do the reaping.
3149 buf->b_efunc = NULL;
3150 rw_exit(&buf->b_lock);
3151 VERIFY(copy.b_efunc(©) == 0);
3154 hash_lock = HDR_LOCK(hdr);
3155 mutex_enter(hash_lock);
3157 ASSERT(buf->b_hdr == hdr);
3158 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3159 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3162 * Pull this buffer off of the hdr
3165 while (*bufp != buf)
3166 bufp = &(*bufp)->b_next;
3167 *bufp = buf->b_next;
3169 ASSERT(buf->b_data != NULL);
3170 arc_buf_destroy(buf, FALSE, FALSE);
3172 if (hdr->b_datacnt == 0) {
3173 arc_state_t *old_state = hdr->b_state;
3174 arc_state_t *evicted_state;
3176 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3179 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3181 get_buf_info(hdr, old_state, &list, &lock);
3182 get_buf_info(hdr, evicted_state, &evicted_list, &evicted_lock);
3184 mutex_enter(evicted_lock);
3186 arc_change_state(evicted_state, hdr, hash_lock);
3187 ASSERT(HDR_IN_HASH_TABLE(hdr));
3188 hdr->b_flags |= ARC_IN_HASH_TABLE;
3189 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3191 mutex_exit(evicted_lock);
3194 mutex_exit(hash_lock);
3195 rw_exit(&buf->b_lock);
3197 VERIFY(buf->b_efunc(buf) == 0);
3198 buf->b_efunc = NULL;
3199 buf->b_private = NULL;
3201 kmem_cache_free(buf_cache, buf);
3206 * Release this buffer from the cache. This must be done
3207 * after a read and prior to modifying the buffer contents.
3208 * If the buffer has more than one reference, we must make
3209 * a new hdr for the buffer.
3212 arc_release(arc_buf_t *buf, void *tag)
3215 kmutex_t *hash_lock;
3216 l2arc_buf_hdr_t *l2hdr;
3218 boolean_t released = B_FALSE;
3220 rw_enter(&buf->b_lock, RW_WRITER);
3223 /* this buffer is not on any list */
3224 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3225 ASSERT(!(hdr->b_flags & ARC_STORED));
3227 if (hdr->b_state == arc_anon) {
3228 /* this buffer is already released */
3229 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 1);
3230 ASSERT(BUF_EMPTY(hdr));
3231 ASSERT(buf->b_efunc == NULL);
3233 rw_exit(&buf->b_lock);
3236 hash_lock = HDR_LOCK(hdr);
3237 mutex_enter(hash_lock);
3240 l2hdr = hdr->b_l2hdr;
3242 mutex_enter(&l2arc_buflist_mtx);
3243 hdr->b_l2hdr = NULL;
3244 buf_size = hdr->b_size;
3251 * Do we have more than one buf?
3253 if (hdr->b_datacnt > 1) {
3254 arc_buf_hdr_t *nhdr;
3256 uint64_t blksz = hdr->b_size;
3257 spa_t *spa = hdr->b_spa;
3258 arc_buf_contents_t type = hdr->b_type;
3259 uint32_t flags = hdr->b_flags;
3261 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3263 * Pull the data off of this buf and attach it to
3264 * a new anonymous buf.
3266 (void) remove_reference(hdr, hash_lock, tag);
3268 while (*bufp != buf)
3269 bufp = &(*bufp)->b_next;
3270 *bufp = (*bufp)->b_next;
3273 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3274 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3275 if (refcount_is_zero(&hdr->b_refcnt)) {
3276 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3277 ASSERT3U(*size, >=, hdr->b_size);
3278 atomic_add_64(size, -hdr->b_size);
3280 hdr->b_datacnt -= 1;
3281 arc_cksum_verify(buf);
3283 mutex_exit(hash_lock);
3285 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3286 nhdr->b_size = blksz;
3288 nhdr->b_type = type;
3290 nhdr->b_state = arc_anon;
3291 nhdr->b_arc_access = 0;
3292 nhdr->b_flags = flags & ARC_L2_WRITING;
3293 nhdr->b_l2hdr = NULL;
3294 nhdr->b_datacnt = 1;
3295 nhdr->b_freeze_cksum = NULL;
3296 (void) refcount_add(&nhdr->b_refcnt, tag);
3298 rw_exit(&buf->b_lock);
3299 atomic_add_64(&arc_anon->arcs_size, blksz);
3301 rw_exit(&buf->b_lock);
3302 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3303 ASSERT(!list_link_active(&hdr->b_arc_node));
3304 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3305 arc_change_state(arc_anon, hdr, hash_lock);
3306 hdr->b_arc_access = 0;
3307 mutex_exit(hash_lock);
3309 bzero(&hdr->b_dva, sizeof (dva_t));
3314 buf->b_efunc = NULL;
3315 buf->b_private = NULL;
3319 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3320 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3321 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3322 mutex_exit(&l2arc_buflist_mtx);
3327 arc_released(arc_buf_t *buf)
3331 rw_enter(&buf->b_lock, RW_READER);
3332 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3333 rw_exit(&buf->b_lock);
3338 arc_has_callback(arc_buf_t *buf)
3342 rw_enter(&buf->b_lock, RW_READER);
3343 callback = (buf->b_efunc != NULL);
3344 rw_exit(&buf->b_lock);
3350 arc_referenced(arc_buf_t *buf)
3354 rw_enter(&buf->b_lock, RW_READER);
3355 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3356 rw_exit(&buf->b_lock);
3357 return (referenced);
3362 arc_write_ready(zio_t *zio)
3364 arc_write_callback_t *callback = zio->io_private;
3365 arc_buf_t *buf = callback->awcb_buf;
3366 arc_buf_hdr_t *hdr = buf->b_hdr;
3368 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3369 callback->awcb_ready(zio, buf, callback->awcb_private);
3372 * If the IO is already in progress, then this is a re-write
3373 * attempt, so we need to thaw and re-compute the cksum.
3374 * It is the responsibility of the callback to handle the
3375 * accounting for any re-write attempt.
3377 if (HDR_IO_IN_PROGRESS(hdr)) {
3378 mutex_enter(&hdr->b_freeze_lock);
3379 if (hdr->b_freeze_cksum != NULL) {
3380 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3381 hdr->b_freeze_cksum = NULL;
3383 mutex_exit(&hdr->b_freeze_lock);
3385 arc_cksum_compute(buf, B_FALSE);
3386 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3390 arc_write_done(zio_t *zio)
3392 arc_write_callback_t *callback = zio->io_private;
3393 arc_buf_t *buf = callback->awcb_buf;
3394 arc_buf_hdr_t *hdr = buf->b_hdr;
3398 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3399 hdr->b_birth = zio->io_bp->blk_birth;
3400 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3402 * If the block to be written was all-zero, we may have
3403 * compressed it away. In this case no write was performed
3404 * so there will be no dva/birth-date/checksum. The buffer
3405 * must therefor remain anonymous (and uncached).
3407 if (!BUF_EMPTY(hdr)) {
3408 arc_buf_hdr_t *exists;
3409 kmutex_t *hash_lock;
3411 arc_cksum_verify(buf);
3413 exists = buf_hash_insert(hdr, &hash_lock);
3416 * This can only happen if we overwrite for
3417 * sync-to-convergence, because we remove
3418 * buffers from the hash table when we arc_free().
3420 ASSERT(zio->io_flags & ZIO_FLAG_IO_REWRITE);
3421 ASSERT(DVA_EQUAL(BP_IDENTITY(&zio->io_bp_orig),
3422 BP_IDENTITY(zio->io_bp)));
3423 ASSERT3U(zio->io_bp_orig.blk_birth, ==,
3424 zio->io_bp->blk_birth);
3426 ASSERT(refcount_is_zero(&exists->b_refcnt));
3427 arc_change_state(arc_anon, exists, hash_lock);
3428 mutex_exit(hash_lock);
3429 arc_hdr_destroy(exists);
3430 exists = buf_hash_insert(hdr, &hash_lock);
3431 ASSERT3P(exists, ==, NULL);
3433 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3434 /* if it's not anon, we are doing a scrub */
3435 if (hdr->b_state == arc_anon)
3436 arc_access(hdr, hash_lock);
3437 mutex_exit(hash_lock);
3438 } else if (callback->awcb_done == NULL) {
3441 * This is an anonymous buffer with no user callback,
3442 * destroy it if there are no active references.
3444 mutex_enter(&arc_eviction_mtx);
3445 destroy_hdr = refcount_is_zero(&hdr->b_refcnt);
3446 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3447 mutex_exit(&arc_eviction_mtx);
3449 arc_hdr_destroy(hdr);
3451 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3453 hdr->b_flags &= ~ARC_STORED;
3455 if (callback->awcb_done) {
3456 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3457 callback->awcb_done(zio, buf, callback->awcb_private);
3460 kmem_free(callback, sizeof (arc_write_callback_t));
3464 write_policy(spa_t *spa, const writeprops_t *wp, zio_prop_t *zp)
3466 boolean_t ismd = (wp->wp_level > 0 || dmu_ot[wp->wp_type].ot_metadata);
3468 /* Determine checksum setting */
3471 * Metadata always gets checksummed. If the data
3472 * checksum is multi-bit correctable, and it's not a
3473 * ZBT-style checksum, then it's suitable for metadata
3474 * as well. Otherwise, the metadata checksum defaults
3477 if (zio_checksum_table[wp->wp_oschecksum].ci_correctable &&
3478 !zio_checksum_table[wp->wp_oschecksum].ci_zbt)
3479 zp->zp_checksum = wp->wp_oschecksum;
3481 zp->zp_checksum = ZIO_CHECKSUM_FLETCHER_4;
3483 zp->zp_checksum = zio_checksum_select(wp->wp_dnchecksum,
3487 /* Determine compression setting */
3490 * XXX -- we should design a compression algorithm
3491 * that specializes in arrays of bps.
3493 zp->zp_compress = zfs_mdcomp_disable ? ZIO_COMPRESS_EMPTY :
3496 zp->zp_compress = zio_compress_select(wp->wp_dncompress,
3500 zp->zp_type = wp->wp_type;
3501 zp->zp_level = wp->wp_level;
3502 zp->zp_ndvas = MIN(wp->wp_copies + ismd, spa_max_replication(spa));
3506 arc_write(zio_t *pio, spa_t *spa, const writeprops_t *wp,
3507 boolean_t l2arc, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
3508 arc_done_func_t *ready, arc_done_func_t *done, void *private, int priority,
3509 int zio_flags, const zbookmark_t *zb)
3511 arc_buf_hdr_t *hdr = buf->b_hdr;
3512 arc_write_callback_t *callback;
3516 ASSERT(ready != NULL);
3517 ASSERT(!HDR_IO_ERROR(hdr));
3518 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3519 ASSERT(hdr->b_acb == 0);
3521 hdr->b_flags |= ARC_L2CACHE;
3522 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3523 callback->awcb_ready = ready;
3524 callback->awcb_done = done;
3525 callback->awcb_private = private;
3526 callback->awcb_buf = buf;
3528 write_policy(spa, wp, &zp);
3529 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, &zp,
3530 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3536 arc_free(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
3537 zio_done_func_t *done, void *private, uint32_t arc_flags)
3540 kmutex_t *hash_lock;
3544 * If this buffer is in the cache, release it, so it
3547 ab = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
3550 * The checksum of blocks to free is not always
3551 * preserved (eg. on the deadlist). However, if it is
3552 * nonzero, it should match what we have in the cache.
3554 ASSERT(bp->blk_cksum.zc_word[0] == 0 ||
3555 bp->blk_cksum.zc_word[0] == ab->b_cksum0 ||
3556 bp->blk_fill == BLK_FILL_ALREADY_FREED);
3558 if (ab->b_state != arc_anon)
3559 arc_change_state(arc_anon, ab, hash_lock);
3560 if (HDR_IO_IN_PROGRESS(ab)) {
3562 * This should only happen when we prefetch.
3564 ASSERT(ab->b_flags & ARC_PREFETCH);
3565 ASSERT3U(ab->b_datacnt, ==, 1);
3566 ab->b_flags |= ARC_FREED_IN_READ;
3567 if (HDR_IN_HASH_TABLE(ab))
3568 buf_hash_remove(ab);
3569 ab->b_arc_access = 0;
3570 bzero(&ab->b_dva, sizeof (dva_t));
3573 ab->b_buf->b_efunc = NULL;
3574 ab->b_buf->b_private = NULL;
3575 mutex_exit(hash_lock);
3576 } else if (refcount_is_zero(&ab->b_refcnt)) {
3577 ab->b_flags |= ARC_FREE_IN_PROGRESS;
3578 mutex_exit(hash_lock);
3579 arc_hdr_destroy(ab);
3580 ARCSTAT_BUMP(arcstat_deleted);
3583 * We still have an active reference on this
3584 * buffer. This can happen, e.g., from
3585 * dbuf_unoverride().
3587 ASSERT(!HDR_IN_HASH_TABLE(ab));
3588 ab->b_arc_access = 0;
3589 bzero(&ab->b_dva, sizeof (dva_t));
3592 ab->b_buf->b_efunc = NULL;
3593 ab->b_buf->b_private = NULL;
3594 mutex_exit(hash_lock);
3598 zio = zio_free(pio, spa, txg, bp, done, private, ZIO_FLAG_MUSTSUCCEED);
3600 if (arc_flags & ARC_WAIT)
3601 return (zio_wait(zio));
3603 ASSERT(arc_flags & ARC_NOWAIT);
3610 arc_memory_throttle(uint64_t reserve, uint64_t txg)
3613 uint64_t inflight_data = arc_anon->arcs_size;
3614 uint64_t available_memory = ptoa((uintmax_t)cnt.v_free_count);
3615 static uint64_t page_load = 0;
3616 static uint64_t last_txg = 0;
3621 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3624 if (available_memory >= zfs_write_limit_max)
3627 if (txg > last_txg) {
3632 * If we are in pageout, we know that memory is already tight,
3633 * the arc is already going to be evicting, so we just want to
3634 * continue to let page writes occur as quickly as possible.
3636 if (curproc == pageproc) {
3637 if (page_load > available_memory / 4)
3639 /* Note: reserve is inflated, so we deflate */
3640 page_load += reserve / 8;
3642 } else if (page_load > 0 && arc_reclaim_needed()) {
3643 /* memory is low, delay before restarting */
3644 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3649 if (arc_size > arc_c_min) {
3650 uint64_t evictable_memory =
3651 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3652 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3653 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3654 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3655 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3658 if (inflight_data > available_memory / 4) {
3659 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3667 arc_tempreserve_clear(uint64_t reserve)
3669 atomic_add_64(&arc_tempreserve, -reserve);
3670 ASSERT((int64_t)arc_tempreserve >= 0);
3674 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3680 * Once in a while, fail for no reason. Everything should cope.
3682 if (spa_get_random(10000) == 0) {
3683 dprintf("forcing random failure\n");
3687 if (reserve > arc_c/4 && !arc_no_grow)
3688 arc_c = MIN(arc_c_max, reserve * 4);
3689 if (reserve > arc_c)
3693 * Writes will, almost always, require additional memory allocations
3694 * in order to compress/encrypt/etc the data. We therefor need to
3695 * make sure that there is sufficient available memory for this.
3697 if (error = arc_memory_throttle(reserve, txg))
3701 * Throttle writes when the amount of dirty data in the cache
3702 * gets too large. We try to keep the cache less than half full
3703 * of dirty blocks so that our sync times don't grow too large.
3704 * Note: if two requests come in concurrently, we might let them
3705 * both succeed, when one of them should fail. Not a huge deal.
3707 if (reserve + arc_tempreserve + arc_anon->arcs_size > arc_c / 2 &&
3708 arc_anon->arcs_size > arc_c / 4) {
3709 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3710 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3711 arc_tempreserve>>10,
3712 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3713 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3714 reserve>>10, arc_c>>10);
3717 atomic_add_64(&arc_tempreserve, reserve);
3721 static kmutex_t arc_lowmem_lock;
3723 static eventhandler_tag arc_event_lowmem = NULL;
3726 arc_lowmem(void *arg __unused, int howto __unused)
3729 /* Serialize access via arc_lowmem_lock. */
3730 mutex_enter(&arc_lowmem_lock);
3732 cv_signal(&arc_reclaim_thr_cv);
3734 tsleep(&needfree, 0, "zfs:lowmem", hz / 5);
3735 mutex_exit(&arc_lowmem_lock);
3742 int prefetch_tunable_set = 0;
3745 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3746 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3747 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
3749 /* Convert seconds to clock ticks */
3750 arc_min_prefetch_lifespan = 1 * hz;
3752 /* Start out with 1/8 of all memory */
3753 arc_c = kmem_size() / 8;
3757 * On architectures where the physical memory can be larger
3758 * than the addressable space (intel in 32-bit mode), we may
3759 * need to limit the cache to 1/8 of VM size.
3761 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3764 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
3765 arc_c_min = MAX(arc_c / 4, 64<<18);
3766 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
3767 if (arc_c * 8 >= 1<<30)
3768 arc_c_max = (arc_c * 8) - (1<<30);
3770 arc_c_max = arc_c_min;
3771 arc_c_max = MAX(arc_c * 5, arc_c_max);
3774 * Allow the tunables to override our calculations if they are
3775 * reasonable (ie. over 16MB)
3777 if (zfs_arc_max >= 64<<18 && zfs_arc_max < kmem_size())
3778 arc_c_max = zfs_arc_max;
3779 if (zfs_arc_min >= 64<<18 && zfs_arc_min <= arc_c_max)
3780 arc_c_min = zfs_arc_min;
3783 arc_p = (arc_c >> 1);
3785 /* limit meta-data to 1/4 of the arc capacity */
3786 arc_meta_limit = arc_c_max / 4;
3788 /* Allow the tunable to override if it is reasonable */
3789 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3790 arc_meta_limit = zfs_arc_meta_limit;
3792 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3793 arc_c_min = arc_meta_limit / 2;
3795 if (zfs_arc_grow_retry > 0)
3796 arc_grow_retry = zfs_arc_grow_retry;
3798 if (zfs_arc_shrink_shift > 0)
3799 arc_shrink_shift = zfs_arc_shrink_shift;
3801 if (zfs_arc_p_min_shift > 0)
3802 arc_p_min_shift = zfs_arc_p_min_shift;
3804 /* if kmem_flags are set, lets try to use less memory */
3805 if (kmem_debugging())
3807 if (arc_c < arc_c_min)
3810 zfs_arc_min = arc_c_min;
3811 zfs_arc_max = arc_c_max;
3813 arc_anon = &ARC_anon;
3815 arc_mru_ghost = &ARC_mru_ghost;
3817 arc_mfu_ghost = &ARC_mfu_ghost;
3818 arc_l2c_only = &ARC_l2c_only;
3821 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
3822 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
3823 NULL, MUTEX_DEFAULT, NULL);
3824 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
3825 NULL, MUTEX_DEFAULT, NULL);
3826 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
3827 NULL, MUTEX_DEFAULT, NULL);
3828 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
3829 NULL, MUTEX_DEFAULT, NULL);
3830 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
3831 NULL, MUTEX_DEFAULT, NULL);
3832 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
3833 NULL, MUTEX_DEFAULT, NULL);
3835 list_create(&arc_mru->arcs_lists[i],
3836 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3837 list_create(&arc_mru_ghost->arcs_lists[i],
3838 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3839 list_create(&arc_mfu->arcs_lists[i],
3840 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3841 list_create(&arc_mfu_ghost->arcs_lists[i],
3842 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3843 list_create(&arc_mfu_ghost->arcs_lists[i],
3844 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3845 list_create(&arc_l2c_only->arcs_lists[i],
3846 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3851 arc_thread_exit = 0;
3852 arc_eviction_list = NULL;
3853 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3854 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3856 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3857 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3859 if (arc_ksp != NULL) {
3860 arc_ksp->ks_data = &arc_stats;
3861 kstat_install(arc_ksp);
3864 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3865 TS_RUN, minclsyspri);
3868 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
3869 EVENTHANDLER_PRI_FIRST);
3875 if (zfs_write_limit_max == 0)
3876 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3878 zfs_write_limit_shift = 0;
3879 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3882 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
3883 prefetch_tunable_set = 1;
3886 if (prefetch_tunable_set == 0) {
3887 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
3889 printf(" add \"vfs.zfs.prefetch_disable=0\" "
3890 "to /boot/loader.conf.\n");
3891 zfs_prefetch_disable=1;
3894 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
3895 prefetch_tunable_set == 0) {
3896 printf("ZFS NOTICE: Prefetch is disabled by default if less "
3897 "than 4GB of RAM is present;\n"
3898 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
3899 "to /boot/loader.conf.\n");
3900 zfs_prefetch_disable=1;
3903 /* Warn about ZFS memory and address space requirements. */
3904 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
3905 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
3906 "expect unstable behavior.\n");
3908 if (kmem_size() < 512 * (1 << 20)) {
3909 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
3910 "expect unstable behavior.\n");
3911 printf(" Consider tuning vm.kmem_size and "
3912 "vm.kmem_size_max\n");
3913 printf(" in /boot/loader.conf.\n");
3923 mutex_enter(&arc_reclaim_thr_lock);
3924 arc_thread_exit = 1;
3925 cv_signal(&arc_reclaim_thr_cv);
3926 while (arc_thread_exit != 0)
3927 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3928 mutex_exit(&arc_reclaim_thr_lock);
3934 if (arc_ksp != NULL) {
3935 kstat_delete(arc_ksp);
3939 mutex_destroy(&arc_eviction_mtx);
3940 mutex_destroy(&arc_reclaim_thr_lock);
3941 cv_destroy(&arc_reclaim_thr_cv);
3943 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
3944 list_destroy(&arc_mru->arcs_lists[i]);
3945 list_destroy(&arc_mru_ghost->arcs_lists[i]);
3946 list_destroy(&arc_mfu->arcs_lists[i]);
3947 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
3948 list_destroy(&arc_l2c_only->arcs_lists[i]);
3950 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
3951 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
3952 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
3953 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
3954 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
3955 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
3958 mutex_destroy(&zfs_write_limit_lock);
3962 mutex_destroy(&arc_lowmem_lock);
3964 if (arc_event_lowmem != NULL)
3965 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
3972 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3973 * It uses dedicated storage devices to hold cached data, which are populated
3974 * using large infrequent writes. The main role of this cache is to boost
3975 * the performance of random read workloads. The intended L2ARC devices
3976 * include short-stroked disks, solid state disks, and other media with
3977 * substantially faster read latency than disk.
3979 * +-----------------------+
3981 * +-----------------------+
3984 * l2arc_feed_thread() arc_read()
3988 * +---------------+ |
3990 * +---------------+ |
3995 * +-------+ +-------+
3997 * | cache | | cache |
3998 * +-------+ +-------+
3999 * +=========+ .-----.
4000 * : L2ARC : |-_____-|
4001 * : devices : | Disks |
4002 * +=========+ `-_____-'
4004 * Read requests are satisfied from the following sources, in order:
4007 * 2) vdev cache of L2ARC devices
4009 * 4) vdev cache of disks
4012 * Some L2ARC device types exhibit extremely slow write performance.
4013 * To accommodate for this there are some significant differences between
4014 * the L2ARC and traditional cache design:
4016 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4017 * the ARC behave as usual, freeing buffers and placing headers on ghost
4018 * lists. The ARC does not send buffers to the L2ARC during eviction as
4019 * this would add inflated write latencies for all ARC memory pressure.
4021 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4022 * It does this by periodically scanning buffers from the eviction-end of
4023 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4024 * not already there. It scans until a headroom of buffers is satisfied,
4025 * which itself is a buffer for ARC eviction. The thread that does this is
4026 * l2arc_feed_thread(), illustrated below; example sizes are included to
4027 * provide a better sense of ratio than this diagram:
4030 * +---------------------+----------+
4031 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4032 * +---------------------+----------+ | o L2ARC eligible
4033 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4034 * +---------------------+----------+ |
4035 * 15.9 Gbytes ^ 32 Mbytes |
4037 * l2arc_feed_thread()
4039 * l2arc write hand <--[oooo]--'
4043 * +==============================+
4044 * L2ARC dev |####|#|###|###| |####| ... |
4045 * +==============================+
4048 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4049 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4050 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4051 * safe to say that this is an uncommon case, since buffers at the end of
4052 * the ARC lists have moved there due to inactivity.
4054 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4055 * then the L2ARC simply misses copying some buffers. This serves as a
4056 * pressure valve to prevent heavy read workloads from both stalling the ARC
4057 * with waits and clogging the L2ARC with writes. This also helps prevent
4058 * the potential for the L2ARC to churn if it attempts to cache content too
4059 * quickly, such as during backups of the entire pool.
4061 * 5. After system boot and before the ARC has filled main memory, there are
4062 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4063 * lists can remain mostly static. Instead of searching from tail of these
4064 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4065 * for eligible buffers, greatly increasing its chance of finding them.
4067 * The L2ARC device write speed is also boosted during this time so that
4068 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4069 * there are no L2ARC reads, and no fear of degrading read performance
4070 * through increased writes.
4072 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4073 * the vdev queue can aggregate them into larger and fewer writes. Each
4074 * device is written to in a rotor fashion, sweeping writes through
4075 * available space then repeating.
4077 * 7. The L2ARC does not store dirty content. It never needs to flush
4078 * write buffers back to disk based storage.
4080 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4081 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4083 * The performance of the L2ARC can be tweaked by a number of tunables, which
4084 * may be necessary for different workloads:
4086 * l2arc_write_max max write bytes per interval
4087 * l2arc_write_boost extra write bytes during device warmup
4088 * l2arc_noprefetch skip caching prefetched buffers
4089 * l2arc_headroom number of max device writes to precache
4090 * l2arc_feed_secs seconds between L2ARC writing
4092 * Tunables may be removed or added as future performance improvements are
4093 * integrated, and also may become zpool properties.
4095 * There are three key functions that control how the L2ARC warms up:
4097 * l2arc_write_eligible() check if a buffer is eligible to cache
4098 * l2arc_write_size() calculate how much to write
4099 * l2arc_write_interval() calculate sleep delay between writes
4101 * These three functions determine what to write, how much, and how quickly
4106 l2arc_write_eligible(spa_t *spa, arc_buf_hdr_t *ab)
4109 * A buffer is *not* eligible for the L2ARC if it:
4110 * 1. belongs to a different spa.
4111 * 2. is already cached on the L2ARC.
4112 * 3. has an I/O in progress (it may be an incomplete read).
4113 * 4. is flagged not eligible (zfs property).
4115 if (ab->b_spa != spa) {
4116 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4119 if (ab->b_l2hdr != NULL) {
4120 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4123 if (HDR_IO_IN_PROGRESS(ab)) {
4124 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4127 if (!HDR_L2CACHE(ab)) {
4128 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4136 l2arc_write_size(l2arc_dev_t *dev)
4140 size = dev->l2ad_write;
4142 if (arc_warm == B_FALSE)
4143 size += dev->l2ad_boost;
4150 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4152 clock_t interval, next;
4155 * If the ARC lists are busy, increase our write rate; if the
4156 * lists are stale, idle back. This is achieved by checking
4157 * how much we previously wrote - if it was more than half of
4158 * what we wanted, schedule the next write much sooner.
4160 if (l2arc_feed_again && wrote > (wanted / 2))
4161 interval = (hz * l2arc_feed_min_ms) / 1000;
4163 interval = hz * l2arc_feed_secs;
4165 next = MAX(LBOLT, MIN(LBOLT + interval, began + interval));
4171 l2arc_hdr_stat_add(void)
4173 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4174 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4178 l2arc_hdr_stat_remove(void)
4180 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4181 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4185 * Cycle through L2ARC devices. This is how L2ARC load balances.
4186 * If a device is returned, this also returns holding the spa config lock.
4188 static l2arc_dev_t *
4189 l2arc_dev_get_next(void)
4191 l2arc_dev_t *first, *next = NULL;
4194 * Lock out the removal of spas (spa_namespace_lock), then removal
4195 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4196 * both locks will be dropped and a spa config lock held instead.
4198 mutex_enter(&spa_namespace_lock);
4199 mutex_enter(&l2arc_dev_mtx);
4201 /* if there are no vdevs, there is nothing to do */
4202 if (l2arc_ndev == 0)
4206 next = l2arc_dev_last;
4208 /* loop around the list looking for a non-faulted vdev */
4210 next = list_head(l2arc_dev_list);
4212 next = list_next(l2arc_dev_list, next);
4214 next = list_head(l2arc_dev_list);
4217 /* if we have come back to the start, bail out */
4220 else if (next == first)
4223 } while (vdev_is_dead(next->l2ad_vdev));
4225 /* if we were unable to find any usable vdevs, return NULL */
4226 if (vdev_is_dead(next->l2ad_vdev))
4229 l2arc_dev_last = next;
4232 mutex_exit(&l2arc_dev_mtx);
4235 * Grab the config lock to prevent the 'next' device from being
4236 * removed while we are writing to it.
4239 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4240 mutex_exit(&spa_namespace_lock);
4246 * Free buffers that were tagged for destruction.
4249 l2arc_do_free_on_write()
4252 l2arc_data_free_t *df, *df_prev;
4254 mutex_enter(&l2arc_free_on_write_mtx);
4255 buflist = l2arc_free_on_write;
4257 for (df = list_tail(buflist); df; df = df_prev) {
4258 df_prev = list_prev(buflist, df);
4259 ASSERT(df->l2df_data != NULL);
4260 ASSERT(df->l2df_func != NULL);
4261 df->l2df_func(df->l2df_data, df->l2df_size);
4262 list_remove(buflist, df);
4263 kmem_free(df, sizeof (l2arc_data_free_t));
4266 mutex_exit(&l2arc_free_on_write_mtx);
4270 * A write to a cache device has completed. Update all headers to allow
4271 * reads from these buffers to begin.
4274 l2arc_write_done(zio_t *zio)
4276 l2arc_write_callback_t *cb;
4279 arc_buf_hdr_t *head, *ab, *ab_prev;
4280 l2arc_buf_hdr_t *abl2;
4281 kmutex_t *hash_lock;
4283 cb = zio->io_private;
4285 dev = cb->l2wcb_dev;
4286 ASSERT(dev != NULL);
4287 head = cb->l2wcb_head;
4288 ASSERT(head != NULL);
4289 buflist = dev->l2ad_buflist;
4290 ASSERT(buflist != NULL);
4291 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4292 l2arc_write_callback_t *, cb);
4294 if (zio->io_error != 0)
4295 ARCSTAT_BUMP(arcstat_l2_writes_error);
4297 mutex_enter(&l2arc_buflist_mtx);
4300 * All writes completed, or an error was hit.
4302 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4303 ab_prev = list_prev(buflist, ab);
4305 hash_lock = HDR_LOCK(ab);
4306 if (!mutex_tryenter(hash_lock)) {
4308 * This buffer misses out. It may be in a stage
4309 * of eviction. Its ARC_L2_WRITING flag will be
4310 * left set, denying reads to this buffer.
4312 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4316 if (zio->io_error != 0) {
4318 * Error - drop L2ARC entry.
4320 list_remove(buflist, ab);
4323 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4324 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4328 * Allow ARC to begin reads to this L2ARC entry.
4330 ab->b_flags &= ~ARC_L2_WRITING;
4332 mutex_exit(hash_lock);
4335 atomic_inc_64(&l2arc_writes_done);
4336 list_remove(buflist, head);
4337 kmem_cache_free(hdr_cache, head);
4338 mutex_exit(&l2arc_buflist_mtx);
4340 l2arc_do_free_on_write();
4342 kmem_free(cb, sizeof (l2arc_write_callback_t));
4346 * A read to a cache device completed. Validate buffer contents before
4347 * handing over to the regular ARC routines.
4350 l2arc_read_done(zio_t *zio)
4352 l2arc_read_callback_t *cb;
4355 kmutex_t *hash_lock;
4358 ASSERT(zio->io_vd != NULL);
4359 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4361 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4363 cb = zio->io_private;
4365 buf = cb->l2rcb_buf;
4366 ASSERT(buf != NULL);
4368 ASSERT(hdr != NULL);
4370 hash_lock = HDR_LOCK(hdr);
4371 mutex_enter(hash_lock);
4374 * Check this survived the L2ARC journey.
4376 equal = arc_cksum_equal(buf);
4377 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4378 mutex_exit(hash_lock);
4379 zio->io_private = buf;
4380 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4381 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4384 mutex_exit(hash_lock);
4386 * Buffer didn't survive caching. Increment stats and
4387 * reissue to the original storage device.
4389 if (zio->io_error != 0) {
4390 ARCSTAT_BUMP(arcstat_l2_io_error);
4392 zio->io_error = EIO;
4395 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4398 * If there's no waiter, issue an async i/o to the primary
4399 * storage now. If there *is* a waiter, the caller must
4400 * issue the i/o in a context where it's OK to block.
4402 if (zio->io_waiter == NULL)
4403 zio_nowait(zio_read(zio->io_parent,
4404 cb->l2rcb_spa, &cb->l2rcb_bp,
4405 buf->b_data, zio->io_size, arc_read_done, buf,
4406 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4409 kmem_free(cb, sizeof (l2arc_read_callback_t));
4413 * This is the list priority from which the L2ARC will search for pages to
4414 * cache. This is used within loops (0..3) to cycle through lists in the
4415 * desired order. This order can have a significant effect on cache
4418 * Currently the metadata lists are hit first, MFU then MRU, followed by
4419 * the data lists. This function returns a locked list, and also returns
4423 l2arc_list_locked(int list_num, kmutex_t **lock)
4428 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4430 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4432 list = &arc_mfu->arcs_lists[idx];
4433 *lock = ARCS_LOCK(arc_mfu, idx);
4434 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4435 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4436 list = &arc_mru->arcs_lists[idx];
4437 *lock = ARCS_LOCK(arc_mru, idx);
4438 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4439 ARC_BUFC_NUMDATALISTS)) {
4440 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4441 list = &arc_mfu->arcs_lists[idx];
4442 *lock = ARCS_LOCK(arc_mfu, idx);
4444 idx = list_num - ARC_BUFC_NUMLISTS;
4445 list = &arc_mru->arcs_lists[idx];
4446 *lock = ARCS_LOCK(arc_mru, idx);
4449 ASSERT(!(MUTEX_HELD(*lock)));
4455 * Evict buffers from the device write hand to the distance specified in
4456 * bytes. This distance may span populated buffers, it may span nothing.
4457 * This is clearing a region on the L2ARC device ready for writing.
4458 * If the 'all' boolean is set, every buffer is evicted.
4461 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4464 l2arc_buf_hdr_t *abl2;
4465 arc_buf_hdr_t *ab, *ab_prev;
4466 kmutex_t *hash_lock;
4469 buflist = dev->l2ad_buflist;
4471 if (buflist == NULL)
4474 if (!all && dev->l2ad_first) {
4476 * This is the first sweep through the device. There is
4482 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4484 * When nearing the end of the device, evict to the end
4485 * before the device write hand jumps to the start.
4487 taddr = dev->l2ad_end;
4489 taddr = dev->l2ad_hand + distance;
4491 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4492 uint64_t, taddr, boolean_t, all);
4495 mutex_enter(&l2arc_buflist_mtx);
4496 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4497 ab_prev = list_prev(buflist, ab);
4499 hash_lock = HDR_LOCK(ab);
4500 if (!mutex_tryenter(hash_lock)) {
4502 * Missed the hash lock. Retry.
4504 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4505 mutex_exit(&l2arc_buflist_mtx);
4506 mutex_enter(hash_lock);
4507 mutex_exit(hash_lock);
4511 if (HDR_L2_WRITE_HEAD(ab)) {
4513 * We hit a write head node. Leave it for
4514 * l2arc_write_done().
4516 list_remove(buflist, ab);
4517 mutex_exit(hash_lock);
4521 if (!all && ab->b_l2hdr != NULL &&
4522 (ab->b_l2hdr->b_daddr > taddr ||
4523 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4525 * We've evicted to the target address,
4526 * or the end of the device.
4528 mutex_exit(hash_lock);
4532 if (HDR_FREE_IN_PROGRESS(ab)) {
4534 * Already on the path to destruction.
4536 mutex_exit(hash_lock);
4540 if (ab->b_state == arc_l2c_only) {
4541 ASSERT(!HDR_L2_READING(ab));
4543 * This doesn't exist in the ARC. Destroy.
4544 * arc_hdr_destroy() will call list_remove()
4545 * and decrement arcstat_l2_size.
4547 arc_change_state(arc_anon, ab, hash_lock);
4548 arc_hdr_destroy(ab);
4551 * Invalidate issued or about to be issued
4552 * reads, since we may be about to write
4553 * over this location.
4555 if (HDR_L2_READING(ab)) {
4556 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4557 ab->b_flags |= ARC_L2_EVICTED;
4561 * Tell ARC this no longer exists in L2ARC.
4563 if (ab->b_l2hdr != NULL) {
4566 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4567 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4569 list_remove(buflist, ab);
4572 * This may have been leftover after a
4575 ab->b_flags &= ~ARC_L2_WRITING;
4577 mutex_exit(hash_lock);
4579 mutex_exit(&l2arc_buflist_mtx);
4581 spa_l2cache_space_update(dev->l2ad_vdev, 0, -(taddr - dev->l2ad_evict));
4582 dev->l2ad_evict = taddr;
4586 * Find and write ARC buffers to the L2ARC device.
4588 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4589 * for reading until they have completed writing.
4592 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4594 arc_buf_hdr_t *ab, *ab_prev, *head;
4595 l2arc_buf_hdr_t *hdrl2;
4597 uint64_t passed_sz, write_sz, buf_sz, headroom;
4599 kmutex_t *hash_lock, *list_lock;
4600 boolean_t have_lock, full;
4601 l2arc_write_callback_t *cb;
4605 ASSERT(dev->l2ad_vdev != NULL);
4610 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4611 head->b_flags |= ARC_L2_WRITE_HEAD;
4613 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
4615 * Copy buffers for L2ARC writing.
4617 mutex_enter(&l2arc_buflist_mtx);
4618 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
4619 list = l2arc_list_locked(try, &list_lock);
4621 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
4624 * L2ARC fast warmup.
4626 * Until the ARC is warm and starts to evict, read from the
4627 * head of the ARC lists rather than the tail.
4629 headroom = target_sz * l2arc_headroom;
4630 if (arc_warm == B_FALSE)
4631 ab = list_head(list);
4633 ab = list_tail(list);
4635 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
4637 for (; ab; ab = ab_prev) {
4638 if (arc_warm == B_FALSE)
4639 ab_prev = list_next(list, ab);
4641 ab_prev = list_prev(list, ab);
4642 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
4644 hash_lock = HDR_LOCK(ab);
4645 have_lock = MUTEX_HELD(hash_lock);
4646 if (!have_lock && !mutex_tryenter(hash_lock)) {
4647 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
4649 * Skip this buffer rather than waiting.
4654 passed_sz += ab->b_size;
4655 if (passed_sz > headroom) {
4659 mutex_exit(hash_lock);
4660 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
4664 if (!l2arc_write_eligible(spa, ab)) {
4665 mutex_exit(hash_lock);
4669 if ((write_sz + ab->b_size) > target_sz) {
4671 mutex_exit(hash_lock);
4672 ARCSTAT_BUMP(arcstat_l2_write_full);
4678 * Insert a dummy header on the buflist so
4679 * l2arc_write_done() can find where the
4680 * write buffers begin without searching.
4682 list_insert_head(dev->l2ad_buflist, head);
4685 sizeof (l2arc_write_callback_t), KM_SLEEP);
4686 cb->l2wcb_dev = dev;
4687 cb->l2wcb_head = head;
4688 pio = zio_root(spa, l2arc_write_done, cb,
4690 ARCSTAT_BUMP(arcstat_l2_write_pios);
4694 * Create and add a new L2ARC header.
4696 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4698 hdrl2->b_daddr = dev->l2ad_hand;
4700 ab->b_flags |= ARC_L2_WRITING;
4701 ab->b_l2hdr = hdrl2;
4702 list_insert_head(dev->l2ad_buflist, ab);
4703 buf_data = ab->b_buf->b_data;
4704 buf_sz = ab->b_size;
4707 * Compute and store the buffer cksum before
4708 * writing. On debug the cksum is verified first.
4710 arc_cksum_verify(ab->b_buf);
4711 arc_cksum_compute(ab->b_buf, B_TRUE);
4713 mutex_exit(hash_lock);
4715 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4716 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4717 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4718 ZIO_FLAG_CANFAIL, B_FALSE);
4720 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4722 (void) zio_nowait(wzio);
4725 * Keep the clock hand suitably device-aligned.
4727 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4730 dev->l2ad_hand += buf_sz;
4733 mutex_exit(list_lock);
4738 mutex_exit(&l2arc_buflist_mtx);
4741 ASSERT3U(write_sz, ==, 0);
4742 kmem_cache_free(hdr_cache, head);
4746 ASSERT3U(write_sz, <=, target_sz);
4747 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4748 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4749 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4750 spa_l2cache_space_update(dev->l2ad_vdev, 0, write_sz);
4753 * Bump device hand to the device start if it is approaching the end.
4754 * l2arc_evict() will already have evicted ahead for this case.
4756 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4757 spa_l2cache_space_update(dev->l2ad_vdev, 0,
4758 dev->l2ad_end - dev->l2ad_hand);
4759 dev->l2ad_hand = dev->l2ad_start;
4760 dev->l2ad_evict = dev->l2ad_start;
4761 dev->l2ad_first = B_FALSE;
4764 dev->l2ad_writing = B_TRUE;
4765 (void) zio_wait(pio);
4766 dev->l2ad_writing = B_FALSE;
4772 * This thread feeds the L2ARC at regular intervals. This is the beating
4773 * heart of the L2ARC.
4776 l2arc_feed_thread(void *dummy __unused)
4781 uint64_t size, wrote;
4782 clock_t begin, next = LBOLT;
4784 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4786 mutex_enter(&l2arc_feed_thr_lock);
4788 while (l2arc_thread_exit == 0) {
4789 CALLB_CPR_SAFE_BEGIN(&cpr);
4790 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4792 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4796 * Quick check for L2ARC devices.
4798 mutex_enter(&l2arc_dev_mtx);
4799 if (l2arc_ndev == 0) {
4800 mutex_exit(&l2arc_dev_mtx);
4803 mutex_exit(&l2arc_dev_mtx);
4807 * This selects the next l2arc device to write to, and in
4808 * doing so the next spa to feed from: dev->l2ad_spa. This
4809 * will return NULL if there are now no l2arc devices or if
4810 * they are all faulted.
4812 * If a device is returned, its spa's config lock is also
4813 * held to prevent device removal. l2arc_dev_get_next()
4814 * will grab and release l2arc_dev_mtx.
4816 if ((dev = l2arc_dev_get_next()) == NULL)
4819 spa = dev->l2ad_spa;
4820 ASSERT(spa != NULL);
4823 * Avoid contributing to memory pressure.
4825 if (arc_reclaim_needed()) {
4826 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4827 spa_config_exit(spa, SCL_L2ARC, dev);
4831 ARCSTAT_BUMP(arcstat_l2_feeds);
4833 size = l2arc_write_size(dev);
4836 * Evict L2ARC buffers that will be overwritten.
4838 l2arc_evict(dev, size, B_FALSE);
4841 * Write ARC buffers.
4843 wrote = l2arc_write_buffers(spa, dev, size);
4846 * Calculate interval between writes.
4848 next = l2arc_write_interval(begin, size, wrote);
4849 spa_config_exit(spa, SCL_L2ARC, dev);
4852 l2arc_thread_exit = 0;
4853 cv_broadcast(&l2arc_feed_thr_cv);
4854 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4859 l2arc_vdev_present(vdev_t *vd)
4863 mutex_enter(&l2arc_dev_mtx);
4864 for (dev = list_head(l2arc_dev_list); dev != NULL;
4865 dev = list_next(l2arc_dev_list, dev)) {
4866 if (dev->l2ad_vdev == vd)
4869 mutex_exit(&l2arc_dev_mtx);
4871 return (dev != NULL);
4875 * Add a vdev for use by the L2ARC. By this point the spa has already
4876 * validated the vdev and opened it.
4879 l2arc_add_vdev(spa_t *spa, vdev_t *vd, uint64_t start, uint64_t end)
4881 l2arc_dev_t *adddev;
4883 ASSERT(!l2arc_vdev_present(vd));
4886 * Create a new l2arc device entry.
4888 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4889 adddev->l2ad_spa = spa;
4890 adddev->l2ad_vdev = vd;
4891 adddev->l2ad_write = l2arc_write_max;
4892 adddev->l2ad_boost = l2arc_write_boost;
4893 adddev->l2ad_start = start;
4894 adddev->l2ad_end = end;
4895 adddev->l2ad_hand = adddev->l2ad_start;
4896 adddev->l2ad_evict = adddev->l2ad_start;
4897 adddev->l2ad_first = B_TRUE;
4898 adddev->l2ad_writing = B_FALSE;
4899 ASSERT3U(adddev->l2ad_write, >, 0);
4902 * This is a list of all ARC buffers that are still valid on the
4905 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4906 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4907 offsetof(arc_buf_hdr_t, b_l2node));
4909 spa_l2cache_space_update(vd, adddev->l2ad_end - adddev->l2ad_hand, 0);
4912 * Add device to global list
4914 mutex_enter(&l2arc_dev_mtx);
4915 list_insert_head(l2arc_dev_list, adddev);
4916 atomic_inc_64(&l2arc_ndev);
4917 mutex_exit(&l2arc_dev_mtx);
4921 * Remove a vdev from the L2ARC.
4924 l2arc_remove_vdev(vdev_t *vd)
4926 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4929 * Find the device by vdev
4931 mutex_enter(&l2arc_dev_mtx);
4932 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4933 nextdev = list_next(l2arc_dev_list, dev);
4934 if (vd == dev->l2ad_vdev) {
4939 ASSERT(remdev != NULL);
4942 * Remove device from global list
4944 list_remove(l2arc_dev_list, remdev);
4945 l2arc_dev_last = NULL; /* may have been invalidated */
4946 atomic_dec_64(&l2arc_ndev);
4947 mutex_exit(&l2arc_dev_mtx);
4950 * Clear all buflists and ARC references. L2ARC device flush.
4952 l2arc_evict(remdev, 0, B_TRUE);
4953 list_destroy(remdev->l2ad_buflist);
4954 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4955 kmem_free(remdev, sizeof (l2arc_dev_t));
4961 l2arc_thread_exit = 0;
4963 l2arc_writes_sent = 0;
4964 l2arc_writes_done = 0;
4966 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4967 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4968 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4969 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4970 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4972 l2arc_dev_list = &L2ARC_dev_list;
4973 l2arc_free_on_write = &L2ARC_free_on_write;
4974 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4975 offsetof(l2arc_dev_t, l2ad_node));
4976 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4977 offsetof(l2arc_data_free_t, l2df_list_node));
4984 * This is called from dmu_fini(), which is called from spa_fini();
4985 * Because of this, we can assume that all l2arc devices have
4986 * already been removed when the pools themselves were removed.
4989 l2arc_do_free_on_write();
4991 mutex_destroy(&l2arc_feed_thr_lock);
4992 cv_destroy(&l2arc_feed_thr_cv);
4993 mutex_destroy(&l2arc_dev_mtx);
4994 mutex_destroy(&l2arc_buflist_mtx);
4995 mutex_destroy(&l2arc_free_on_write_mtx);
4997 list_destroy(l2arc_dev_list);
4998 list_destroy(l2arc_free_on_write);
5004 if (!(spa_mode & FWRITE))
5007 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5008 TS_RUN, minclsyspri);
5014 if (!(spa_mode & FWRITE))
5017 mutex_enter(&l2arc_feed_thr_lock);
5018 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5019 l2arc_thread_exit = 1;
5020 while (l2arc_thread_exit != 0)
5021 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5022 mutex_exit(&l2arc_feed_thr_lock);
projects / FreeBSD / releng / 8.1.git / blob