4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
26 * DVA-based Adjustable Replacement Cache
28 * While much of the theory of operation used here is
29 * based on the self-tuning, low overhead replacement cache
30 * presented by Megiddo and Modha at FAST 2003, there are some
31 * significant differences:
33 * 1. The Megiddo and Modha model assumes any page is evictable.
34 * Pages in its cache cannot be "locked" into memory. This makes
35 * the eviction algorithm simple: evict the last page in the list.
36 * This also make the performance characteristics easy to reason
37 * about. Our cache is not so simple. At any given moment, some
38 * subset of the blocks in the cache are un-evictable because we
39 * have handed out a reference to them. Blocks are only evictable
40 * when there are no external references active. This makes
41 * eviction far more problematic: we choose to evict the evictable
42 * blocks that are the "lowest" in the list.
44 * There are times when it is not possible to evict the requested
45 * space. In these circumstances we are unable to adjust the cache
46 * size. To prevent the cache growing unbounded at these times we
47 * implement a "cache throttle" that slows the flow of new data
48 * into the cache until we can make space available.
50 * 2. The Megiddo and Modha model assumes a fixed cache size.
51 * Pages are evicted when the cache is full and there is a cache
52 * miss. Our model has a variable sized cache. It grows with
53 * high use, but also tries to react to memory pressure from the
54 * operating system: decreasing its size when system memory is
57 * 3. The Megiddo and Modha model assumes a fixed page size. All
58 * elements of the cache are therefor exactly the same size. So
59 * when adjusting the cache size following a cache miss, its simply
60 * a matter of choosing a single page to evict. In our model, we
61 * have variable sized cache blocks (rangeing from 512 bytes to
62 * 128K bytes). We therefor choose a set of blocks to evict to make
63 * space for a cache miss that approximates as closely as possible
64 * the space used by the new block.
66 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
67 * by N. Megiddo & D. Modha, FAST 2003
73 * A new reference to a cache buffer can be obtained in two
74 * ways: 1) via a hash table lookup using the DVA as a key,
75 * or 2) via one of the ARC lists. The arc_read() interface
76 * uses method 1, while the internal arc algorithms for
77 * adjusting the cache use method 2. We therefor provide two
78 * types of locks: 1) the hash table lock array, and 2) the
81 * Buffers do not have their own mutexs, rather they rely on the
82 * hash table mutexs for the bulk of their protection (i.e. most
83 * fields in the arc_buf_hdr_t are protected by these mutexs).
85 * buf_hash_find() returns the appropriate mutex (held) when it
86 * locates the requested buffer in the hash table. It returns
87 * NULL for the mutex if the buffer was not in the table.
89 * buf_hash_remove() expects the appropriate hash mutex to be
90 * already held before it is invoked.
92 * Each arc state also has a mutex which is used to protect the
93 * buffer list associated with the state. When attempting to
94 * obtain a hash table lock while holding an arc list lock you
95 * must use: mutex_tryenter() to avoid deadlock. Also note that
96 * the active state mutex must be held before the ghost state mutex.
98 * Arc buffers may have an associated eviction callback function.
99 * This function will be invoked prior to removing the buffer (e.g.
100 * in arc_do_user_evicts()). Note however that the data associated
101 * with the buffer may be evicted prior to the callback. The callback
102 * must be made with *no locks held* (to prevent deadlock). Additionally,
103 * the users of callbacks must ensure that their private data is
104 * protected from simultaneous callbacks from arc_buf_evict()
105 * and arc_do_user_evicts().
107 * Note that the majority of the performance stats are manipulated
108 * with atomic operations.
110 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
112 * - L2ARC buflist creation
113 * - L2ARC buflist eviction
114 * - L2ARC write completion, which walks L2ARC buflists
115 * - ARC header destruction, as it removes from L2ARC buflists
116 * - ARC header release, as it removes from L2ARC buflists
121 #include <sys/zfs_context.h>
123 #include <sys/refcount.h>
124 #include <sys/vdev.h>
125 #include <sys/vdev_impl.h>
127 #include <sys/dnlc.h>
129 #include <sys/callb.h>
130 #include <sys/kstat.h>
131 #include <zfs_fletcher.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_arc_grow_retry = 0;
182 int zfs_arc_shrink_shift = 0;
183 int zfs_arc_p_min_shift = 0;
185 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
186 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
187 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
188 SYSCTL_DECL(_vfs_zfs);
189 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
191 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
195 * Note that buffers can be in one of 6 states:
196 * ARC_anon - anonymous (discussed below)
197 * ARC_mru - recently used, currently cached
198 * ARC_mru_ghost - recentely used, no longer in cache
199 * ARC_mfu - frequently used, currently cached
200 * ARC_mfu_ghost - frequently used, no longer in cache
201 * ARC_l2c_only - exists in L2ARC but not other states
202 * When there are no active references to the buffer, they are
203 * are linked onto a list in one of these arc states. These are
204 * the only buffers that can be evicted or deleted. Within each
205 * state there are multiple lists, one for meta-data and one for
206 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
207 * etc.) is tracked separately so that it can be managed more
208 * explicitly: favored over data, limited explicitly.
210 * Anonymous buffers are buffers that are not associated with
211 * a DVA. These are buffers that hold dirty block copies
212 * before they are written to stable storage. By definition,
213 * they are "ref'd" and are considered part of arc_mru
214 * that cannot be freed. Generally, they will aquire a DVA
215 * as they are written and migrate onto the arc_mru list.
217 * The ARC_l2c_only state is for buffers that are in the second
218 * level ARC but no longer in any of the ARC_m* lists. The second
219 * level ARC itself may also contain buffers that are in any of
220 * the ARC_m* states - meaning that a buffer can exist in two
221 * places. The reason for the ARC_l2c_only state is to keep the
222 * buffer header in the hash table, so that reads that hit the
223 * second level ARC benefit from these fast lookups.
226 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
230 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
235 * must be power of two for mask use to work
238 #define ARC_BUFC_NUMDATALISTS 16
239 #define ARC_BUFC_NUMMETADATALISTS 16
240 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
242 typedef struct arc_state {
243 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
244 uint64_t arcs_size; /* total amount of data in this state */
245 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
246 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
249 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
252 static arc_state_t ARC_anon;
253 static arc_state_t ARC_mru;
254 static arc_state_t ARC_mru_ghost;
255 static arc_state_t ARC_mfu;
256 static arc_state_t ARC_mfu_ghost;
257 static arc_state_t ARC_l2c_only;
259 typedef struct arc_stats {
260 kstat_named_t arcstat_hits;
261 kstat_named_t arcstat_misses;
262 kstat_named_t arcstat_demand_data_hits;
263 kstat_named_t arcstat_demand_data_misses;
264 kstat_named_t arcstat_demand_metadata_hits;
265 kstat_named_t arcstat_demand_metadata_misses;
266 kstat_named_t arcstat_prefetch_data_hits;
267 kstat_named_t arcstat_prefetch_data_misses;
268 kstat_named_t arcstat_prefetch_metadata_hits;
269 kstat_named_t arcstat_prefetch_metadata_misses;
270 kstat_named_t arcstat_mru_hits;
271 kstat_named_t arcstat_mru_ghost_hits;
272 kstat_named_t arcstat_mfu_hits;
273 kstat_named_t arcstat_mfu_ghost_hits;
274 kstat_named_t arcstat_allocated;
275 kstat_named_t arcstat_deleted;
276 kstat_named_t arcstat_stolen;
277 kstat_named_t arcstat_recycle_miss;
278 kstat_named_t arcstat_mutex_miss;
279 kstat_named_t arcstat_evict_skip;
280 kstat_named_t arcstat_evict_l2_cached;
281 kstat_named_t arcstat_evict_l2_eligible;
282 kstat_named_t arcstat_evict_l2_ineligible;
283 kstat_named_t arcstat_hash_elements;
284 kstat_named_t arcstat_hash_elements_max;
285 kstat_named_t arcstat_hash_collisions;
286 kstat_named_t arcstat_hash_chains;
287 kstat_named_t arcstat_hash_chain_max;
288 kstat_named_t arcstat_p;
289 kstat_named_t arcstat_c;
290 kstat_named_t arcstat_c_min;
291 kstat_named_t arcstat_c_max;
292 kstat_named_t arcstat_size;
293 kstat_named_t arcstat_hdr_size;
294 kstat_named_t arcstat_data_size;
295 kstat_named_t arcstat_other_size;
296 kstat_named_t arcstat_l2_hits;
297 kstat_named_t arcstat_l2_misses;
298 kstat_named_t arcstat_l2_feeds;
299 kstat_named_t arcstat_l2_rw_clash;
300 kstat_named_t arcstat_l2_read_bytes;
301 kstat_named_t arcstat_l2_write_bytes;
302 kstat_named_t arcstat_l2_writes_sent;
303 kstat_named_t arcstat_l2_writes_done;
304 kstat_named_t arcstat_l2_writes_error;
305 kstat_named_t arcstat_l2_writes_hdr_miss;
306 kstat_named_t arcstat_l2_evict_lock_retry;
307 kstat_named_t arcstat_l2_evict_reading;
308 kstat_named_t arcstat_l2_free_on_write;
309 kstat_named_t arcstat_l2_abort_lowmem;
310 kstat_named_t arcstat_l2_cksum_bad;
311 kstat_named_t arcstat_l2_io_error;
312 kstat_named_t arcstat_l2_size;
313 kstat_named_t arcstat_l2_hdr_size;
314 kstat_named_t arcstat_memory_throttle_count;
315 kstat_named_t arcstat_l2_write_trylock_fail;
316 kstat_named_t arcstat_l2_write_passed_headroom;
317 kstat_named_t arcstat_l2_write_spa_mismatch;
318 kstat_named_t arcstat_l2_write_in_l2;
319 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
320 kstat_named_t arcstat_l2_write_not_cacheable;
321 kstat_named_t arcstat_l2_write_full;
322 kstat_named_t arcstat_l2_write_buffer_iter;
323 kstat_named_t arcstat_l2_write_pios;
324 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
325 kstat_named_t arcstat_l2_write_buffer_list_iter;
326 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
329 static arc_stats_t arc_stats = {
330 { "hits", KSTAT_DATA_UINT64 },
331 { "misses", KSTAT_DATA_UINT64 },
332 { "demand_data_hits", KSTAT_DATA_UINT64 },
333 { "demand_data_misses", KSTAT_DATA_UINT64 },
334 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
335 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
336 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
337 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
338 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
339 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
340 { "mru_hits", KSTAT_DATA_UINT64 },
341 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
342 { "mfu_hits", KSTAT_DATA_UINT64 },
343 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
344 { "allocated", KSTAT_DATA_UINT64 },
345 { "deleted", KSTAT_DATA_UINT64 },
346 { "stolen", KSTAT_DATA_UINT64 },
347 { "recycle_miss", KSTAT_DATA_UINT64 },
348 { "mutex_miss", KSTAT_DATA_UINT64 },
349 { "evict_skip", KSTAT_DATA_UINT64 },
350 { "evict_l2_cached", KSTAT_DATA_UINT64 },
351 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
352 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
353 { "hash_elements", KSTAT_DATA_UINT64 },
354 { "hash_elements_max", KSTAT_DATA_UINT64 },
355 { "hash_collisions", KSTAT_DATA_UINT64 },
356 { "hash_chains", KSTAT_DATA_UINT64 },
357 { "hash_chain_max", KSTAT_DATA_UINT64 },
358 { "p", KSTAT_DATA_UINT64 },
359 { "c", KSTAT_DATA_UINT64 },
360 { "c_min", KSTAT_DATA_UINT64 },
361 { "c_max", KSTAT_DATA_UINT64 },
362 { "size", KSTAT_DATA_UINT64 },
363 { "hdr_size", KSTAT_DATA_UINT64 },
364 { "data_size", KSTAT_DATA_UINT64 },
365 { "other_size", KSTAT_DATA_UINT64 },
366 { "l2_hits", KSTAT_DATA_UINT64 },
367 { "l2_misses", KSTAT_DATA_UINT64 },
368 { "l2_feeds", KSTAT_DATA_UINT64 },
369 { "l2_rw_clash", KSTAT_DATA_UINT64 },
370 { "l2_read_bytes", KSTAT_DATA_UINT64 },
371 { "l2_write_bytes", KSTAT_DATA_UINT64 },
372 { "l2_writes_sent", KSTAT_DATA_UINT64 },
373 { "l2_writes_done", KSTAT_DATA_UINT64 },
374 { "l2_writes_error", KSTAT_DATA_UINT64 },
375 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
376 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
377 { "l2_evict_reading", KSTAT_DATA_UINT64 },
378 { "l2_free_on_write", KSTAT_DATA_UINT64 },
379 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
380 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
381 { "l2_io_error", KSTAT_DATA_UINT64 },
382 { "l2_size", KSTAT_DATA_UINT64 },
383 { "l2_hdr_size", KSTAT_DATA_UINT64 },
384 { "memory_throttle_count", KSTAT_DATA_UINT64 },
385 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
386 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
387 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
388 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
389 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
390 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
391 { "l2_write_full", KSTAT_DATA_UINT64 },
392 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
393 { "l2_write_pios", KSTAT_DATA_UINT64 },
394 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
395 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
396 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 }
399 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
401 #define ARCSTAT_INCR(stat, val) \
402 atomic_add_64(&arc_stats.stat.value.ui64, (val));
404 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
405 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
407 #define ARCSTAT_MAX(stat, val) { \
409 while ((val) > (m = arc_stats.stat.value.ui64) && \
410 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
414 #define ARCSTAT_MAXSTAT(stat) \
415 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
418 * We define a macro to allow ARC hits/misses to be easily broken down by
419 * two separate conditions, giving a total of four different subtypes for
420 * each of hits and misses (so eight statistics total).
422 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
425 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
427 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
431 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
433 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
438 static arc_state_t *arc_anon;
439 static arc_state_t *arc_mru;
440 static arc_state_t *arc_mru_ghost;
441 static arc_state_t *arc_mfu;
442 static arc_state_t *arc_mfu_ghost;
443 static arc_state_t *arc_l2c_only;
446 * There are several ARC variables that are critical to export as kstats --
447 * but we don't want to have to grovel around in the kstat whenever we wish to
448 * manipulate them. For these variables, we therefore define them to be in
449 * terms of the statistic variable. This assures that we are not introducing
450 * the possibility of inconsistency by having shadow copies of the variables,
451 * while still allowing the code to be readable.
453 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
454 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
455 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
456 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
457 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
459 static int arc_no_grow; /* Don't try to grow cache size */
460 static uint64_t arc_tempreserve;
461 static uint64_t arc_loaned_bytes;
462 static uint64_t arc_meta_used;
463 static uint64_t arc_meta_limit;
464 static uint64_t arc_meta_max = 0;
465 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RDTUN,
466 &arc_meta_used, 0, "ARC metadata used");
467 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RDTUN,
468 &arc_meta_limit, 0, "ARC metadata limit");
470 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
472 typedef struct arc_callback arc_callback_t;
474 struct arc_callback {
476 arc_done_func_t *acb_done;
478 zio_t *acb_zio_dummy;
479 arc_callback_t *acb_next;
482 typedef struct arc_write_callback arc_write_callback_t;
484 struct arc_write_callback {
486 arc_done_func_t *awcb_ready;
487 arc_done_func_t *awcb_done;
492 /* protected by hash lock */
497 kmutex_t b_freeze_lock;
498 zio_cksum_t *b_freeze_cksum;
501 arc_buf_hdr_t *b_hash_next;
506 arc_callback_t *b_acb;
510 arc_buf_contents_t b_type;
514 /* protected by arc state mutex */
515 arc_state_t *b_state;
516 list_node_t b_arc_node;
518 /* updated atomically */
519 clock_t b_arc_access;
521 /* self protecting */
524 l2arc_buf_hdr_t *b_l2hdr;
525 list_node_t b_l2node;
528 static arc_buf_t *arc_eviction_list;
529 static kmutex_t arc_eviction_mtx;
530 static arc_buf_hdr_t arc_eviction_hdr;
531 static void arc_get_data_buf(arc_buf_t *buf);
532 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
533 static int arc_evict_needed(arc_buf_contents_t type);
534 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
536 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
538 #define GHOST_STATE(state) \
539 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
540 (state) == arc_l2c_only)
543 * Private ARC flags. These flags are private ARC only flags that will show up
544 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
545 * be passed in as arc_flags in things like arc_read. However, these flags
546 * should never be passed and should only be set by ARC code. When adding new
547 * public flags, make sure not to smash the private ones.
550 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
551 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
552 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
553 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
554 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
555 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
556 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
557 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
558 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
559 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
561 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
562 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
563 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
564 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
565 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
566 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
567 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
568 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
569 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
570 (hdr)->b_l2hdr != NULL)
571 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
572 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
573 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
579 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
580 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
583 * Hash table routines
586 #define HT_LOCK_PAD CACHE_LINE_SIZE
591 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
595 #define BUF_LOCKS 256
596 typedef struct buf_hash_table {
598 arc_buf_hdr_t **ht_table;
599 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
602 static buf_hash_table_t buf_hash_table;
604 #define BUF_HASH_INDEX(spa, dva, birth) \
605 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
606 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
607 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
608 #define HDR_LOCK(hdr) \
609 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
611 uint64_t zfs_crc64_table[256];
617 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
618 #define L2ARC_HEADROOM 2 /* num of writes */
619 #define L2ARC_FEED_SECS 1 /* caching interval secs */
620 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
622 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
623 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
626 * L2ARC Performance Tunables
628 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
629 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
630 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
631 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
632 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
633 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
634 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
635 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
637 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
638 &l2arc_write_max, 0, "max write size");
639 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
640 &l2arc_write_boost, 0, "extra write during warmup");
641 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
642 &l2arc_headroom, 0, "number of dev writes");
643 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
644 &l2arc_feed_secs, 0, "interval seconds");
645 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
646 &l2arc_feed_min_ms, 0, "min interval milliseconds");
648 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
649 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
650 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
651 &l2arc_feed_again, 0, "turbo warmup");
652 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
653 &l2arc_norw, 0, "no reads during writes");
655 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
656 &ARC_anon.arcs_size, 0, "size of anonymous state");
657 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
658 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
659 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
660 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
662 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
663 &ARC_mru.arcs_size, 0, "size of mru state");
664 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
665 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
666 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
667 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
669 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
670 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
671 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
672 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
673 "size of metadata in mru ghost state");
674 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
675 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
676 "size of data in mru ghost state");
678 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
679 &ARC_mfu.arcs_size, 0, "size of mfu state");
680 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
681 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
682 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
683 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
685 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
686 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
687 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
688 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
689 "size of metadata in mfu ghost state");
690 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
691 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
692 "size of data in mfu ghost state");
694 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
695 &ARC_l2c_only.arcs_size, 0, "size of mru state");
700 typedef struct l2arc_dev {
701 vdev_t *l2ad_vdev; /* vdev */
702 spa_t *l2ad_spa; /* spa */
703 uint64_t l2ad_hand; /* next write location */
704 uint64_t l2ad_write; /* desired write size, bytes */
705 uint64_t l2ad_boost; /* warmup write boost, bytes */
706 uint64_t l2ad_start; /* first addr on device */
707 uint64_t l2ad_end; /* last addr on device */
708 uint64_t l2ad_evict; /* last addr eviction reached */
709 boolean_t l2ad_first; /* first sweep through */
710 boolean_t l2ad_writing; /* currently writing */
711 list_t *l2ad_buflist; /* buffer list */
712 list_node_t l2ad_node; /* device list node */
715 static list_t L2ARC_dev_list; /* device list */
716 static list_t *l2arc_dev_list; /* device list pointer */
717 static kmutex_t l2arc_dev_mtx; /* device list mutex */
718 static l2arc_dev_t *l2arc_dev_last; /* last device used */
719 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
720 static list_t L2ARC_free_on_write; /* free after write buf list */
721 static list_t *l2arc_free_on_write; /* free after write list ptr */
722 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
723 static uint64_t l2arc_ndev; /* number of devices */
725 typedef struct l2arc_read_callback {
726 arc_buf_t *l2rcb_buf; /* read buffer */
727 spa_t *l2rcb_spa; /* spa */
728 blkptr_t l2rcb_bp; /* original blkptr */
729 zbookmark_t l2rcb_zb; /* original bookmark */
730 int l2rcb_flags; /* original flags */
731 } l2arc_read_callback_t;
733 typedef struct l2arc_write_callback {
734 l2arc_dev_t *l2wcb_dev; /* device info */
735 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
736 } l2arc_write_callback_t;
738 struct l2arc_buf_hdr {
739 /* protected by arc_buf_hdr mutex */
740 l2arc_dev_t *b_dev; /* L2ARC device */
741 uint64_t b_daddr; /* disk address, offset byte */
744 typedef struct l2arc_data_free {
745 /* protected by l2arc_free_on_write_mtx */
748 void (*l2df_func)(void *, size_t);
749 list_node_t l2df_list_node;
752 static kmutex_t l2arc_feed_thr_lock;
753 static kcondvar_t l2arc_feed_thr_cv;
754 static uint8_t l2arc_thread_exit;
756 static void l2arc_read_done(zio_t *zio);
757 static void l2arc_hdr_stat_add(void);
758 static void l2arc_hdr_stat_remove(void);
761 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
763 uint8_t *vdva = (uint8_t *)dva;
764 uint64_t crc = -1ULL;
767 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
769 for (i = 0; i < sizeof (dva_t); i++)
770 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
772 crc ^= (spa>>8) ^ birth;
777 #define BUF_EMPTY(buf) \
778 ((buf)->b_dva.dva_word[0] == 0 && \
779 (buf)->b_dva.dva_word[1] == 0 && \
782 #define BUF_EQUAL(spa, dva, birth, buf) \
783 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
784 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
785 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
788 buf_discard_identity(arc_buf_hdr_t *hdr)
790 hdr->b_dva.dva_word[0] = 0;
791 hdr->b_dva.dva_word[1] = 0;
796 static arc_buf_hdr_t *
797 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
799 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
800 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
803 mutex_enter(hash_lock);
804 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
805 buf = buf->b_hash_next) {
806 if (BUF_EQUAL(spa, dva, birth, buf)) {
811 mutex_exit(hash_lock);
817 * Insert an entry into the hash table. If there is already an element
818 * equal to elem in the hash table, then the already existing element
819 * will be returned and the new element will not be inserted.
820 * Otherwise returns NULL.
822 static arc_buf_hdr_t *
823 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
825 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
826 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
830 ASSERT(!HDR_IN_HASH_TABLE(buf));
832 mutex_enter(hash_lock);
833 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
834 fbuf = fbuf->b_hash_next, i++) {
835 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
839 buf->b_hash_next = buf_hash_table.ht_table[idx];
840 buf_hash_table.ht_table[idx] = buf;
841 buf->b_flags |= ARC_IN_HASH_TABLE;
843 /* collect some hash table performance data */
845 ARCSTAT_BUMP(arcstat_hash_collisions);
847 ARCSTAT_BUMP(arcstat_hash_chains);
849 ARCSTAT_MAX(arcstat_hash_chain_max, i);
852 ARCSTAT_BUMP(arcstat_hash_elements);
853 ARCSTAT_MAXSTAT(arcstat_hash_elements);
859 buf_hash_remove(arc_buf_hdr_t *buf)
861 arc_buf_hdr_t *fbuf, **bufp;
862 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
864 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
865 ASSERT(HDR_IN_HASH_TABLE(buf));
867 bufp = &buf_hash_table.ht_table[idx];
868 while ((fbuf = *bufp) != buf) {
869 ASSERT(fbuf != NULL);
870 bufp = &fbuf->b_hash_next;
872 *bufp = buf->b_hash_next;
873 buf->b_hash_next = NULL;
874 buf->b_flags &= ~ARC_IN_HASH_TABLE;
876 /* collect some hash table performance data */
877 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
879 if (buf_hash_table.ht_table[idx] &&
880 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
881 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
885 * Global data structures and functions for the buf kmem cache.
887 static kmem_cache_t *hdr_cache;
888 static kmem_cache_t *buf_cache;
895 kmem_free(buf_hash_table.ht_table,
896 (buf_hash_table.ht_mask + 1) * sizeof (void *));
897 for (i = 0; i < BUF_LOCKS; i++)
898 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
899 kmem_cache_destroy(hdr_cache);
900 kmem_cache_destroy(buf_cache);
904 * Constructor callback - called when the cache is empty
905 * and a new buf is requested.
909 hdr_cons(void *vbuf, void *unused, int kmflag)
911 arc_buf_hdr_t *buf = vbuf;
913 bzero(buf, sizeof (arc_buf_hdr_t));
914 refcount_create(&buf->b_refcnt);
915 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
916 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
917 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
924 buf_cons(void *vbuf, void *unused, int kmflag)
926 arc_buf_t *buf = vbuf;
928 bzero(buf, sizeof (arc_buf_t));
929 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
930 rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL);
931 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
937 * Destructor callback - called when a cached buf is
938 * no longer required.
942 hdr_dest(void *vbuf, void *unused)
944 arc_buf_hdr_t *buf = vbuf;
946 ASSERT(BUF_EMPTY(buf));
947 refcount_destroy(&buf->b_refcnt);
948 cv_destroy(&buf->b_cv);
949 mutex_destroy(&buf->b_freeze_lock);
950 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
955 buf_dest(void *vbuf, void *unused)
957 arc_buf_t *buf = vbuf;
959 mutex_destroy(&buf->b_evict_lock);
960 rw_destroy(&buf->b_data_lock);
961 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
965 * Reclaim callback -- invoked when memory is low.
969 hdr_recl(void *unused)
971 dprintf("hdr_recl called\n");
973 * umem calls the reclaim func when we destroy the buf cache,
974 * which is after we do arc_fini().
977 cv_signal(&arc_reclaim_thr_cv);
984 uint64_t hsize = 1ULL << 12;
988 * The hash table is big enough to fill all of physical memory
989 * with an average 64K block size. The table will take up
990 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
992 while (hsize * 65536 < (uint64_t)physmem * PAGESIZE)
995 buf_hash_table.ht_mask = hsize - 1;
996 buf_hash_table.ht_table =
997 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
998 if (buf_hash_table.ht_table == NULL) {
999 ASSERT(hsize > (1ULL << 8));
1004 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
1005 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
1006 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1007 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1009 for (i = 0; i < 256; i++)
1010 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1011 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1013 for (i = 0; i < BUF_LOCKS; i++) {
1014 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1015 NULL, MUTEX_DEFAULT, NULL);
1019 #define ARC_MINTIME (hz>>4) /* 62 ms */
1022 arc_cksum_verify(arc_buf_t *buf)
1026 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1029 mutex_enter(&buf->b_hdr->b_freeze_lock);
1030 if (buf->b_hdr->b_freeze_cksum == NULL ||
1031 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1032 mutex_exit(&buf->b_hdr->b_freeze_lock);
1035 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1036 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1037 panic("buffer modified while frozen!");
1038 mutex_exit(&buf->b_hdr->b_freeze_lock);
1042 arc_cksum_equal(arc_buf_t *buf)
1047 mutex_enter(&buf->b_hdr->b_freeze_lock);
1048 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1049 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1050 mutex_exit(&buf->b_hdr->b_freeze_lock);
1056 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1058 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1061 mutex_enter(&buf->b_hdr->b_freeze_lock);
1062 if (buf->b_hdr->b_freeze_cksum != NULL) {
1063 mutex_exit(&buf->b_hdr->b_freeze_lock);
1066 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1067 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1068 buf->b_hdr->b_freeze_cksum);
1069 mutex_exit(&buf->b_hdr->b_freeze_lock);
1073 arc_buf_thaw(arc_buf_t *buf)
1075 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1076 if (buf->b_hdr->b_state != arc_anon)
1077 panic("modifying non-anon buffer!");
1078 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1079 panic("modifying buffer while i/o in progress!");
1080 arc_cksum_verify(buf);
1083 mutex_enter(&buf->b_hdr->b_freeze_lock);
1084 if (buf->b_hdr->b_freeze_cksum != NULL) {
1085 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1086 buf->b_hdr->b_freeze_cksum = NULL;
1089 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1090 if (buf->b_hdr->b_thawed)
1091 kmem_free(buf->b_hdr->b_thawed, 1);
1092 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1095 mutex_exit(&buf->b_hdr->b_freeze_lock);
1099 arc_buf_freeze(arc_buf_t *buf)
1101 kmutex_t *hash_lock;
1103 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1106 hash_lock = HDR_LOCK(buf->b_hdr);
1107 mutex_enter(hash_lock);
1109 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1110 buf->b_hdr->b_state == arc_anon);
1111 arc_cksum_compute(buf, B_FALSE);
1112 mutex_exit(hash_lock);
1116 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1118 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1120 if (ab->b_type == ARC_BUFC_METADATA)
1121 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1123 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1124 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1127 *list = &state->arcs_lists[buf_hashid];
1128 *lock = ARCS_LOCK(state, buf_hashid);
1133 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1135 ASSERT(MUTEX_HELD(hash_lock));
1137 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1138 (ab->b_state != arc_anon)) {
1139 uint64_t delta = ab->b_size * ab->b_datacnt;
1140 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1144 get_buf_info(ab, ab->b_state, &list, &lock);
1145 ASSERT(!MUTEX_HELD(lock));
1147 ASSERT(list_link_active(&ab->b_arc_node));
1148 list_remove(list, ab);
1149 if (GHOST_STATE(ab->b_state)) {
1150 ASSERT3U(ab->b_datacnt, ==, 0);
1151 ASSERT3P(ab->b_buf, ==, NULL);
1155 ASSERT3U(*size, >=, delta);
1156 atomic_add_64(size, -delta);
1158 /* remove the prefetch flag if we get a reference */
1159 if (ab->b_flags & ARC_PREFETCH)
1160 ab->b_flags &= ~ARC_PREFETCH;
1165 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1168 arc_state_t *state = ab->b_state;
1170 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1171 ASSERT(!GHOST_STATE(state));
1173 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1174 (state != arc_anon)) {
1175 uint64_t *size = &state->arcs_lsize[ab->b_type];
1179 get_buf_info(ab, state, &list, &lock);
1180 ASSERT(!MUTEX_HELD(lock));
1182 ASSERT(!list_link_active(&ab->b_arc_node));
1183 list_insert_head(list, ab);
1184 ASSERT(ab->b_datacnt > 0);
1185 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1192 * Move the supplied buffer to the indicated state. The mutex
1193 * for the buffer must be held by the caller.
1196 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1198 arc_state_t *old_state = ab->b_state;
1199 int64_t refcnt = refcount_count(&ab->b_refcnt);
1200 uint64_t from_delta, to_delta;
1204 ASSERT(MUTEX_HELD(hash_lock));
1205 ASSERT(new_state != old_state);
1206 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1207 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1208 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1210 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1213 * If this buffer is evictable, transfer it from the
1214 * old state list to the new state list.
1217 if (old_state != arc_anon) {
1219 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1221 get_buf_info(ab, old_state, &list, &lock);
1222 use_mutex = !MUTEX_HELD(lock);
1226 ASSERT(list_link_active(&ab->b_arc_node));
1227 list_remove(list, ab);
1230 * If prefetching out of the ghost cache,
1231 * we will have a non-zero datacnt.
1233 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1234 /* ghost elements have a ghost size */
1235 ASSERT(ab->b_buf == NULL);
1236 from_delta = ab->b_size;
1238 ASSERT3U(*size, >=, from_delta);
1239 atomic_add_64(size, -from_delta);
1244 if (new_state != arc_anon) {
1246 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1248 get_buf_info(ab, new_state, &list, &lock);
1249 use_mutex = !MUTEX_HELD(lock);
1253 list_insert_head(list, ab);
1255 /* ghost elements have a ghost size */
1256 if (GHOST_STATE(new_state)) {
1257 ASSERT(ab->b_datacnt == 0);
1258 ASSERT(ab->b_buf == NULL);
1259 to_delta = ab->b_size;
1261 atomic_add_64(size, to_delta);
1268 ASSERT(!BUF_EMPTY(ab));
1269 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1270 buf_hash_remove(ab);
1272 /* adjust state sizes */
1274 atomic_add_64(&new_state->arcs_size, to_delta);
1276 ASSERT3U(old_state->arcs_size, >=, from_delta);
1277 atomic_add_64(&old_state->arcs_size, -from_delta);
1279 ab->b_state = new_state;
1281 /* adjust l2arc hdr stats */
1282 if (new_state == arc_l2c_only)
1283 l2arc_hdr_stat_add();
1284 else if (old_state == arc_l2c_only)
1285 l2arc_hdr_stat_remove();
1289 arc_space_consume(uint64_t space, arc_space_type_t type)
1291 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1294 case ARC_SPACE_DATA:
1295 ARCSTAT_INCR(arcstat_data_size, space);
1297 case ARC_SPACE_OTHER:
1298 ARCSTAT_INCR(arcstat_other_size, space);
1300 case ARC_SPACE_HDRS:
1301 ARCSTAT_INCR(arcstat_hdr_size, space);
1303 case ARC_SPACE_L2HDRS:
1304 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1308 atomic_add_64(&arc_meta_used, space);
1309 atomic_add_64(&arc_size, space);
1313 arc_space_return(uint64_t space, arc_space_type_t type)
1315 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1318 case ARC_SPACE_DATA:
1319 ARCSTAT_INCR(arcstat_data_size, -space);
1321 case ARC_SPACE_OTHER:
1322 ARCSTAT_INCR(arcstat_other_size, -space);
1324 case ARC_SPACE_HDRS:
1325 ARCSTAT_INCR(arcstat_hdr_size, -space);
1327 case ARC_SPACE_L2HDRS:
1328 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1332 ASSERT(arc_meta_used >= space);
1333 if (arc_meta_max < arc_meta_used)
1334 arc_meta_max = arc_meta_used;
1335 atomic_add_64(&arc_meta_used, -space);
1336 ASSERT(arc_size >= space);
1337 atomic_add_64(&arc_size, -space);
1341 arc_data_buf_alloc(uint64_t size)
1343 if (arc_evict_needed(ARC_BUFC_DATA))
1344 cv_signal(&arc_reclaim_thr_cv);
1345 atomic_add_64(&arc_size, size);
1346 return (zio_data_buf_alloc(size));
1350 arc_data_buf_free(void *buf, uint64_t size)
1352 zio_data_buf_free(buf, size);
1353 ASSERT(arc_size >= size);
1354 atomic_add_64(&arc_size, -size);
1358 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1363 ASSERT3U(size, >, 0);
1364 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1365 ASSERT(BUF_EMPTY(hdr));
1368 hdr->b_spa = spa_guid(spa);
1369 hdr->b_state = arc_anon;
1370 hdr->b_arc_access = 0;
1371 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1374 buf->b_efunc = NULL;
1375 buf->b_private = NULL;
1378 arc_get_data_buf(buf);
1381 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1382 (void) refcount_add(&hdr->b_refcnt, tag);
1387 static char *arc_onloan_tag = "onloan";
1390 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1391 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1392 * buffers must be returned to the arc before they can be used by the DMU or
1396 arc_loan_buf(spa_t *spa, int size)
1400 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1402 atomic_add_64(&arc_loaned_bytes, size);
1407 * Return a loaned arc buffer to the arc.
1410 arc_return_buf(arc_buf_t *buf, void *tag)
1412 arc_buf_hdr_t *hdr = buf->b_hdr;
1414 ASSERT(buf->b_data != NULL);
1415 (void) refcount_add(&hdr->b_refcnt, tag);
1416 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1418 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1421 /* Detach an arc_buf from a dbuf (tag) */
1423 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1427 ASSERT(buf->b_data != NULL);
1429 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1430 (void) refcount_remove(&hdr->b_refcnt, tag);
1431 buf->b_efunc = NULL;
1432 buf->b_private = NULL;
1434 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1438 arc_buf_clone(arc_buf_t *from)
1441 arc_buf_hdr_t *hdr = from->b_hdr;
1442 uint64_t size = hdr->b_size;
1444 ASSERT(hdr->b_state != arc_anon);
1446 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1449 buf->b_efunc = NULL;
1450 buf->b_private = NULL;
1451 buf->b_next = hdr->b_buf;
1453 arc_get_data_buf(buf);
1454 bcopy(from->b_data, buf->b_data, size);
1455 hdr->b_datacnt += 1;
1460 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1463 kmutex_t *hash_lock;
1466 * Check to see if this buffer is evicted. Callers
1467 * must verify b_data != NULL to know if the add_ref
1470 mutex_enter(&buf->b_evict_lock);
1471 if (buf->b_data == NULL) {
1472 mutex_exit(&buf->b_evict_lock);
1475 hash_lock = HDR_LOCK(buf->b_hdr);
1476 mutex_enter(hash_lock);
1478 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1479 mutex_exit(&buf->b_evict_lock);
1481 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1482 add_reference(hdr, hash_lock, tag);
1483 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1484 arc_access(hdr, hash_lock);
1485 mutex_exit(hash_lock);
1486 ARCSTAT_BUMP(arcstat_hits);
1487 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1488 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1489 data, metadata, hits);
1493 * Free the arc data buffer. If it is an l2arc write in progress,
1494 * the buffer is placed on l2arc_free_on_write to be freed later.
1497 arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
1498 void *data, size_t size)
1500 if (HDR_L2_WRITING(hdr)) {
1501 l2arc_data_free_t *df;
1502 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1503 df->l2df_data = data;
1504 df->l2df_size = size;
1505 df->l2df_func = free_func;
1506 mutex_enter(&l2arc_free_on_write_mtx);
1507 list_insert_head(l2arc_free_on_write, df);
1508 mutex_exit(&l2arc_free_on_write_mtx);
1509 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1511 free_func(data, size);
1516 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1520 /* free up data associated with the buf */
1522 arc_state_t *state = buf->b_hdr->b_state;
1523 uint64_t size = buf->b_hdr->b_size;
1524 arc_buf_contents_t type = buf->b_hdr->b_type;
1526 arc_cksum_verify(buf);
1529 if (type == ARC_BUFC_METADATA) {
1530 arc_buf_data_free(buf->b_hdr, zio_buf_free,
1532 arc_space_return(size, ARC_SPACE_DATA);
1534 ASSERT(type == ARC_BUFC_DATA);
1535 arc_buf_data_free(buf->b_hdr,
1536 zio_data_buf_free, buf->b_data, size);
1537 ARCSTAT_INCR(arcstat_data_size, -size);
1538 atomic_add_64(&arc_size, -size);
1541 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1542 uint64_t *cnt = &state->arcs_lsize[type];
1544 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1545 ASSERT(state != arc_anon);
1547 ASSERT3U(*cnt, >=, size);
1548 atomic_add_64(cnt, -size);
1550 ASSERT3U(state->arcs_size, >=, size);
1551 atomic_add_64(&state->arcs_size, -size);
1553 ASSERT(buf->b_hdr->b_datacnt > 0);
1554 buf->b_hdr->b_datacnt -= 1;
1557 /* only remove the buf if requested */
1561 /* remove the buf from the hdr list */
1562 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1564 *bufp = buf->b_next;
1567 ASSERT(buf->b_efunc == NULL);
1569 /* clean up the buf */
1571 kmem_cache_free(buf_cache, buf);
1575 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1577 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1578 ASSERT3P(hdr->b_state, ==, arc_anon);
1579 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1580 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1582 if (l2hdr != NULL) {
1583 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1585 * To prevent arc_free() and l2arc_evict() from
1586 * attempting to free the same buffer at the same time,
1587 * a FREE_IN_PROGRESS flag is given to arc_free() to
1588 * give it priority. l2arc_evict() can't destroy this
1589 * header while we are waiting on l2arc_buflist_mtx.
1591 * The hdr may be removed from l2ad_buflist before we
1592 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1594 if (!buflist_held) {
1595 mutex_enter(&l2arc_buflist_mtx);
1596 l2hdr = hdr->b_l2hdr;
1599 if (l2hdr != NULL) {
1600 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1601 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1602 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1603 if (hdr->b_state == arc_l2c_only)
1604 l2arc_hdr_stat_remove();
1605 hdr->b_l2hdr = NULL;
1609 mutex_exit(&l2arc_buflist_mtx);
1612 if (!BUF_EMPTY(hdr)) {
1613 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1614 buf_discard_identity(hdr);
1616 while (hdr->b_buf) {
1617 arc_buf_t *buf = hdr->b_buf;
1620 mutex_enter(&arc_eviction_mtx);
1621 mutex_enter(&buf->b_evict_lock);
1622 ASSERT(buf->b_hdr != NULL);
1623 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1624 hdr->b_buf = buf->b_next;
1625 buf->b_hdr = &arc_eviction_hdr;
1626 buf->b_next = arc_eviction_list;
1627 arc_eviction_list = buf;
1628 mutex_exit(&buf->b_evict_lock);
1629 mutex_exit(&arc_eviction_mtx);
1631 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1634 if (hdr->b_freeze_cksum != NULL) {
1635 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1636 hdr->b_freeze_cksum = NULL;
1638 if (hdr->b_thawed) {
1639 kmem_free(hdr->b_thawed, 1);
1640 hdr->b_thawed = NULL;
1643 ASSERT(!list_link_active(&hdr->b_arc_node));
1644 ASSERT3P(hdr->b_hash_next, ==, NULL);
1645 ASSERT3P(hdr->b_acb, ==, NULL);
1646 kmem_cache_free(hdr_cache, hdr);
1650 arc_buf_free(arc_buf_t *buf, void *tag)
1652 arc_buf_hdr_t *hdr = buf->b_hdr;
1653 int hashed = hdr->b_state != arc_anon;
1655 ASSERT(buf->b_efunc == NULL);
1656 ASSERT(buf->b_data != NULL);
1659 kmutex_t *hash_lock = HDR_LOCK(hdr);
1661 mutex_enter(hash_lock);
1663 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1665 (void) remove_reference(hdr, hash_lock, tag);
1666 if (hdr->b_datacnt > 1) {
1667 arc_buf_destroy(buf, FALSE, TRUE);
1669 ASSERT(buf == hdr->b_buf);
1670 ASSERT(buf->b_efunc == NULL);
1671 hdr->b_flags |= ARC_BUF_AVAILABLE;
1673 mutex_exit(hash_lock);
1674 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1677 * We are in the middle of an async write. Don't destroy
1678 * this buffer unless the write completes before we finish
1679 * decrementing the reference count.
1681 mutex_enter(&arc_eviction_mtx);
1682 (void) remove_reference(hdr, NULL, tag);
1683 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1684 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1685 mutex_exit(&arc_eviction_mtx);
1687 arc_hdr_destroy(hdr);
1689 if (remove_reference(hdr, NULL, tag) > 0)
1690 arc_buf_destroy(buf, FALSE, TRUE);
1692 arc_hdr_destroy(hdr);
1697 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1699 arc_buf_hdr_t *hdr = buf->b_hdr;
1700 kmutex_t *hash_lock = HDR_LOCK(hdr);
1701 int no_callback = (buf->b_efunc == NULL);
1703 if (hdr->b_state == arc_anon) {
1704 ASSERT(hdr->b_datacnt == 1);
1705 arc_buf_free(buf, tag);
1706 return (no_callback);
1709 mutex_enter(hash_lock);
1711 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1712 ASSERT(hdr->b_state != arc_anon);
1713 ASSERT(buf->b_data != NULL);
1715 (void) remove_reference(hdr, hash_lock, tag);
1716 if (hdr->b_datacnt > 1) {
1718 arc_buf_destroy(buf, FALSE, TRUE);
1719 } else if (no_callback) {
1720 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1721 ASSERT(buf->b_efunc == NULL);
1722 hdr->b_flags |= ARC_BUF_AVAILABLE;
1724 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1725 refcount_is_zero(&hdr->b_refcnt));
1726 mutex_exit(hash_lock);
1727 return (no_callback);
1731 arc_buf_size(arc_buf_t *buf)
1733 return (buf->b_hdr->b_size);
1737 * Evict buffers from list until we've removed the specified number of
1738 * bytes. Move the removed buffers to the appropriate evict state.
1739 * If the recycle flag is set, then attempt to "recycle" a buffer:
1740 * - look for a buffer to evict that is `bytes' long.
1741 * - return the data block from this buffer rather than freeing it.
1742 * This flag is used by callers that are trying to make space for a
1743 * new buffer in a full arc cache.
1745 * This function makes a "best effort". It skips over any buffers
1746 * it can't get a hash_lock on, and so may not catch all candidates.
1747 * It may also return without evicting as much space as requested.
1750 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1751 arc_buf_contents_t type)
1753 arc_state_t *evicted_state;
1754 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1755 int64_t bytes_remaining;
1756 arc_buf_hdr_t *ab, *ab_prev = NULL;
1757 list_t *evicted_list, *list, *evicted_list_start, *list_start;
1758 kmutex_t *lock, *evicted_lock;
1759 kmutex_t *hash_lock;
1760 boolean_t have_lock;
1761 void *stolen = NULL;
1762 static int evict_metadata_offset, evict_data_offset;
1763 int i, idx, offset, list_count, count;
1765 ASSERT(state == arc_mru || state == arc_mfu);
1767 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1769 if (type == ARC_BUFC_METADATA) {
1771 list_count = ARC_BUFC_NUMMETADATALISTS;
1772 list_start = &state->arcs_lists[0];
1773 evicted_list_start = &evicted_state->arcs_lists[0];
1774 idx = evict_metadata_offset;
1776 offset = ARC_BUFC_NUMMETADATALISTS;
1777 list_start = &state->arcs_lists[offset];
1778 evicted_list_start = &evicted_state->arcs_lists[offset];
1779 list_count = ARC_BUFC_NUMDATALISTS;
1780 idx = evict_data_offset;
1782 bytes_remaining = evicted_state->arcs_lsize[type];
1786 list = &list_start[idx];
1787 evicted_list = &evicted_list_start[idx];
1788 lock = ARCS_LOCK(state, (offset + idx));
1789 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
1792 mutex_enter(evicted_lock);
1794 for (ab = list_tail(list); ab; ab = ab_prev) {
1795 ab_prev = list_prev(list, ab);
1796 bytes_remaining -= (ab->b_size * ab->b_datacnt);
1797 /* prefetch buffers have a minimum lifespan */
1798 if (HDR_IO_IN_PROGRESS(ab) ||
1799 (spa && ab->b_spa != spa) ||
1800 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1801 ddi_get_lbolt() - ab->b_arc_access <
1802 arc_min_prefetch_lifespan)) {
1806 /* "lookahead" for better eviction candidate */
1807 if (recycle && ab->b_size != bytes &&
1808 ab_prev && ab_prev->b_size == bytes)
1810 hash_lock = HDR_LOCK(ab);
1811 have_lock = MUTEX_HELD(hash_lock);
1812 if (have_lock || mutex_tryenter(hash_lock)) {
1813 ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
1814 ASSERT(ab->b_datacnt > 0);
1816 arc_buf_t *buf = ab->b_buf;
1817 if (!mutex_tryenter(&buf->b_evict_lock)) {
1822 bytes_evicted += ab->b_size;
1823 if (recycle && ab->b_type == type &&
1824 ab->b_size == bytes &&
1825 !HDR_L2_WRITING(ab)) {
1826 stolen = buf->b_data;
1831 mutex_enter(&arc_eviction_mtx);
1832 arc_buf_destroy(buf,
1833 buf->b_data == stolen, FALSE);
1834 ab->b_buf = buf->b_next;
1835 buf->b_hdr = &arc_eviction_hdr;
1836 buf->b_next = arc_eviction_list;
1837 arc_eviction_list = buf;
1838 mutex_exit(&arc_eviction_mtx);
1839 mutex_exit(&buf->b_evict_lock);
1841 mutex_exit(&buf->b_evict_lock);
1842 arc_buf_destroy(buf,
1843 buf->b_data == stolen, TRUE);
1848 ARCSTAT_INCR(arcstat_evict_l2_cached,
1851 if (l2arc_write_eligible(ab->b_spa, ab)) {
1852 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1856 arcstat_evict_l2_ineligible,
1861 if (ab->b_datacnt == 0) {
1862 arc_change_state(evicted_state, ab, hash_lock);
1863 ASSERT(HDR_IN_HASH_TABLE(ab));
1864 ab->b_flags |= ARC_IN_HASH_TABLE;
1865 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1866 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1869 mutex_exit(hash_lock);
1870 if (bytes >= 0 && bytes_evicted >= bytes)
1872 if (bytes_remaining > 0) {
1873 mutex_exit(evicted_lock);
1875 idx = ((idx + 1) & (list_count - 1));
1884 mutex_exit(evicted_lock);
1887 idx = ((idx + 1) & (list_count - 1));
1890 if (bytes_evicted < bytes) {
1891 if (count < list_count)
1894 dprintf("only evicted %lld bytes from %x",
1895 (longlong_t)bytes_evicted, state);
1897 if (type == ARC_BUFC_METADATA)
1898 evict_metadata_offset = idx;
1900 evict_data_offset = idx;
1903 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1906 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1909 * We have just evicted some date into the ghost state, make
1910 * sure we also adjust the ghost state size if necessary.
1913 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1914 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1915 arc_mru_ghost->arcs_size - arc_c;
1917 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1919 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1920 arc_evict_ghost(arc_mru_ghost, 0, todelete);
1921 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1922 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1923 arc_mru_ghost->arcs_size +
1924 arc_mfu_ghost->arcs_size - arc_c);
1925 arc_evict_ghost(arc_mfu_ghost, 0, todelete);
1929 ARCSTAT_BUMP(arcstat_stolen);
1935 * Remove buffers from list until we've removed the specified number of
1936 * bytes. Destroy the buffers that are removed.
1939 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1941 arc_buf_hdr_t *ab, *ab_prev;
1942 arc_buf_hdr_t marker = { 0 };
1943 list_t *list, *list_start;
1944 kmutex_t *hash_lock, *lock;
1945 uint64_t bytes_deleted = 0;
1946 uint64_t bufs_skipped = 0;
1947 static int evict_offset;
1948 int list_count, idx = evict_offset;
1949 int offset, count = 0;
1951 ASSERT(GHOST_STATE(state));
1954 * data lists come after metadata lists
1956 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
1957 list_count = ARC_BUFC_NUMDATALISTS;
1958 offset = ARC_BUFC_NUMMETADATALISTS;
1961 list = &list_start[idx];
1962 lock = ARCS_LOCK(state, idx + offset);
1965 for (ab = list_tail(list); ab; ab = ab_prev) {
1966 ab_prev = list_prev(list, ab);
1967 if (spa && ab->b_spa != spa)
1970 /* ignore markers */
1974 hash_lock = HDR_LOCK(ab);
1975 /* caller may be trying to modify this buffer, skip it */
1976 if (MUTEX_HELD(hash_lock))
1978 if (mutex_tryenter(hash_lock)) {
1979 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1980 ASSERT(ab->b_buf == NULL);
1981 ARCSTAT_BUMP(arcstat_deleted);
1982 bytes_deleted += ab->b_size;
1984 if (ab->b_l2hdr != NULL) {
1986 * This buffer is cached on the 2nd Level ARC;
1987 * don't destroy the header.
1989 arc_change_state(arc_l2c_only, ab, hash_lock);
1990 mutex_exit(hash_lock);
1992 arc_change_state(arc_anon, ab, hash_lock);
1993 mutex_exit(hash_lock);
1994 arc_hdr_destroy(ab);
1997 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1998 if (bytes >= 0 && bytes_deleted >= bytes)
2000 } else if (bytes < 0) {
2002 * Insert a list marker and then wait for the
2003 * hash lock to become available. Once its
2004 * available, restart from where we left off.
2006 list_insert_after(list, ab, &marker);
2008 mutex_enter(hash_lock);
2009 mutex_exit(hash_lock);
2011 ab_prev = list_prev(list, &marker);
2012 list_remove(list, &marker);
2017 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
2020 if (count < list_count)
2024 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
2025 (bytes < 0 || bytes_deleted < bytes)) {
2026 list_start = &state->arcs_lists[0];
2027 list_count = ARC_BUFC_NUMMETADATALISTS;
2033 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2037 if (bytes_deleted < bytes)
2038 dprintf("only deleted %lld bytes from %p",
2039 (longlong_t)bytes_deleted, state);
2045 int64_t adjustment, delta;
2051 adjustment = MIN((int64_t)(arc_size - arc_c),
2052 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2055 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2056 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2057 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
2058 adjustment -= delta;
2061 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2062 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2063 (void) arc_evict(arc_mru, 0, delta, FALSE,
2071 adjustment = arc_size - arc_c;
2073 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2074 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2075 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
2076 adjustment -= delta;
2079 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2080 int64_t delta = MIN(adjustment,
2081 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2082 (void) arc_evict(arc_mfu, 0, delta, FALSE,
2087 * Adjust ghost lists
2090 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2092 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2093 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2094 arc_evict_ghost(arc_mru_ghost, 0, delta);
2098 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2100 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2101 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2102 arc_evict_ghost(arc_mfu_ghost, 0, delta);
2107 arc_do_user_evicts(void)
2109 static arc_buf_t *tmp_arc_eviction_list;
2112 * Move list over to avoid LOR
2115 mutex_enter(&arc_eviction_mtx);
2116 tmp_arc_eviction_list = arc_eviction_list;
2117 arc_eviction_list = NULL;
2118 mutex_exit(&arc_eviction_mtx);
2120 while (tmp_arc_eviction_list != NULL) {
2121 arc_buf_t *buf = tmp_arc_eviction_list;
2122 tmp_arc_eviction_list = buf->b_next;
2123 mutex_enter(&buf->b_evict_lock);
2125 mutex_exit(&buf->b_evict_lock);
2127 if (buf->b_efunc != NULL)
2128 VERIFY(buf->b_efunc(buf) == 0);
2130 buf->b_efunc = NULL;
2131 buf->b_private = NULL;
2132 kmem_cache_free(buf_cache, buf);
2135 if (arc_eviction_list != NULL)
2140 * Flush all *evictable* data from the cache for the given spa.
2141 * NOTE: this will not touch "active" (i.e. referenced) data.
2144 arc_flush(spa_t *spa)
2149 guid = spa_guid(spa);
2151 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2152 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2156 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2157 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2161 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2162 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2166 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2167 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2172 arc_evict_ghost(arc_mru_ghost, guid, -1);
2173 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2175 mutex_enter(&arc_reclaim_thr_lock);
2176 arc_do_user_evicts();
2177 mutex_exit(&arc_reclaim_thr_lock);
2178 ASSERT(spa || arc_eviction_list == NULL);
2184 if (arc_c > arc_c_min) {
2188 to_free = arc_c >> arc_shrink_shift;
2190 to_free = arc_c >> arc_shrink_shift;
2192 if (arc_c > arc_c_min + to_free)
2193 atomic_add_64(&arc_c, -to_free);
2197 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2198 if (arc_c > arc_size)
2199 arc_c = MAX(arc_size, arc_c_min);
2201 arc_p = (arc_c >> 1);
2202 ASSERT(arc_c >= arc_c_min);
2203 ASSERT((int64_t)arc_p >= 0);
2206 if (arc_size > arc_c)
2210 static int needfree = 0;
2213 arc_reclaim_needed(void)
2222 * Cooperate with pagedaemon when it's time for it to scan
2223 * and reclaim some pages.
2225 if (vm_paging_needed())
2230 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2235 * check that we're out of range of the pageout scanner. It starts to
2236 * schedule paging if freemem is less than lotsfree and needfree.
2237 * lotsfree is the high-water mark for pageout, and needfree is the
2238 * number of needed free pages. We add extra pages here to make sure
2239 * the scanner doesn't start up while we're freeing memory.
2241 if (freemem < lotsfree + needfree + extra)
2245 * check to make sure that swapfs has enough space so that anon
2246 * reservations can still succeed. anon_resvmem() checks that the
2247 * availrmem is greater than swapfs_minfree, and the number of reserved
2248 * swap pages. We also add a bit of extra here just to prevent
2249 * circumstances from getting really dire.
2251 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2256 * If we're on an i386 platform, it's possible that we'll exhaust the
2257 * kernel heap space before we ever run out of available physical
2258 * memory. Most checks of the size of the heap_area compare against
2259 * tune.t_minarmem, which is the minimum available real memory that we
2260 * can have in the system. However, this is generally fixed at 25 pages
2261 * which is so low that it's useless. In this comparison, we seek to
2262 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2263 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2266 if (btop(vmem_size(heap_arena, VMEM_FREE)) <
2267 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
2271 if (kmem_used() > (kmem_size() * 3) / 4)
2276 if (spa_get_random(100) == 0)
2282 extern kmem_cache_t *zio_buf_cache[];
2283 extern kmem_cache_t *zio_data_buf_cache[];
2286 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2289 kmem_cache_t *prev_cache = NULL;
2290 kmem_cache_t *prev_data_cache = NULL;
2293 if (arc_meta_used >= arc_meta_limit) {
2295 * We are exceeding our meta-data cache limit.
2296 * Purge some DNLC entries to release holds on meta-data.
2298 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2302 * Reclaim unused memory from all kmem caches.
2309 * An aggressive reclamation will shrink the cache size as well as
2310 * reap free buffers from the arc kmem caches.
2312 if (strat == ARC_RECLAIM_AGGR)
2315 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2316 if (zio_buf_cache[i] != prev_cache) {
2317 prev_cache = zio_buf_cache[i];
2318 kmem_cache_reap_now(zio_buf_cache[i]);
2320 if (zio_data_buf_cache[i] != prev_data_cache) {
2321 prev_data_cache = zio_data_buf_cache[i];
2322 kmem_cache_reap_now(zio_data_buf_cache[i]);
2325 kmem_cache_reap_now(buf_cache);
2326 kmem_cache_reap_now(hdr_cache);
2330 arc_reclaim_thread(void *dummy __unused)
2332 clock_t growtime = 0;
2333 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2336 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2338 mutex_enter(&arc_reclaim_thr_lock);
2339 while (arc_thread_exit == 0) {
2340 if (arc_reclaim_needed()) {
2343 if (last_reclaim == ARC_RECLAIM_CONS) {
2344 last_reclaim = ARC_RECLAIM_AGGR;
2346 last_reclaim = ARC_RECLAIM_CONS;
2350 last_reclaim = ARC_RECLAIM_AGGR;
2354 /* reset the growth delay for every reclaim */
2355 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2357 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2359 * If needfree is TRUE our vm_lowmem hook
2360 * was called and in that case we must free some
2361 * memory, so switch to aggressive mode.
2364 last_reclaim = ARC_RECLAIM_AGGR;
2366 arc_kmem_reap_now(last_reclaim);
2369 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2370 arc_no_grow = FALSE;
2375 if (arc_eviction_list != NULL)
2376 arc_do_user_evicts();
2385 /* block until needed, or one second, whichever is shorter */
2386 CALLB_CPR_SAFE_BEGIN(&cpr);
2387 (void) cv_timedwait(&arc_reclaim_thr_cv,
2388 &arc_reclaim_thr_lock, hz);
2389 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2392 arc_thread_exit = 0;
2393 cv_broadcast(&arc_reclaim_thr_cv);
2394 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2399 * Adapt arc info given the number of bytes we are trying to add and
2400 * the state that we are comming from. This function is only called
2401 * when we are adding new content to the cache.
2404 arc_adapt(int bytes, arc_state_t *state)
2407 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2409 if (state == arc_l2c_only)
2414 * Adapt the target size of the MRU list:
2415 * - if we just hit in the MRU ghost list, then increase
2416 * the target size of the MRU list.
2417 * - if we just hit in the MFU ghost list, then increase
2418 * the target size of the MFU list by decreasing the
2419 * target size of the MRU list.
2421 if (state == arc_mru_ghost) {
2422 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2423 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2424 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2426 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2427 } else if (state == arc_mfu_ghost) {
2430 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2431 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2432 mult = MIN(mult, 10);
2434 delta = MIN(bytes * mult, arc_p);
2435 arc_p = MAX(arc_p_min, arc_p - delta);
2437 ASSERT((int64_t)arc_p >= 0);
2439 if (arc_reclaim_needed()) {
2440 cv_signal(&arc_reclaim_thr_cv);
2447 if (arc_c >= arc_c_max)
2451 * If we're within (2 * maxblocksize) bytes of the target
2452 * cache size, increment the target cache size
2454 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2455 atomic_add_64(&arc_c, (int64_t)bytes);
2456 if (arc_c > arc_c_max)
2458 else if (state == arc_anon)
2459 atomic_add_64(&arc_p, (int64_t)bytes);
2463 ASSERT((int64_t)arc_p >= 0);
2467 * Check if the cache has reached its limits and eviction is required
2471 arc_evict_needed(arc_buf_contents_t type)
2473 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2479 * If zio data pages are being allocated out of a separate heap segment,
2480 * then enforce that the size of available vmem for this area remains
2481 * above about 1/32nd free.
2483 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2484 vmem_size(zio_arena, VMEM_FREE) <
2485 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2490 if (arc_reclaim_needed())
2493 return (arc_size > arc_c);
2497 * The buffer, supplied as the first argument, needs a data block.
2498 * So, if we are at cache max, determine which cache should be victimized.
2499 * We have the following cases:
2501 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2502 * In this situation if we're out of space, but the resident size of the MFU is
2503 * under the limit, victimize the MFU cache to satisfy this insertion request.
2505 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2506 * Here, we've used up all of the available space for the MRU, so we need to
2507 * evict from our own cache instead. Evict from the set of resident MRU
2510 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2511 * c minus p represents the MFU space in the cache, since p is the size of the
2512 * cache that is dedicated to the MRU. In this situation there's still space on
2513 * the MFU side, so the MRU side needs to be victimized.
2515 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2516 * MFU's resident set is consuming more space than it has been allotted. In
2517 * this situation, we must victimize our own cache, the MFU, for this insertion.
2520 arc_get_data_buf(arc_buf_t *buf)
2522 arc_state_t *state = buf->b_hdr->b_state;
2523 uint64_t size = buf->b_hdr->b_size;
2524 arc_buf_contents_t type = buf->b_hdr->b_type;
2526 arc_adapt(size, state);
2529 * We have not yet reached cache maximum size,
2530 * just allocate a new buffer.
2532 if (!arc_evict_needed(type)) {
2533 if (type == ARC_BUFC_METADATA) {
2534 buf->b_data = zio_buf_alloc(size);
2535 arc_space_consume(size, ARC_SPACE_DATA);
2537 ASSERT(type == ARC_BUFC_DATA);
2538 buf->b_data = zio_data_buf_alloc(size);
2539 ARCSTAT_INCR(arcstat_data_size, size);
2540 atomic_add_64(&arc_size, size);
2546 * If we are prefetching from the mfu ghost list, this buffer
2547 * will end up on the mru list; so steal space from there.
2549 if (state == arc_mfu_ghost)
2550 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2551 else if (state == arc_mru_ghost)
2554 if (state == arc_mru || state == arc_anon) {
2555 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2556 state = (arc_mfu->arcs_lsize[type] >= size &&
2557 arc_p > mru_used) ? arc_mfu : arc_mru;
2560 uint64_t mfu_space = arc_c - arc_p;
2561 state = (arc_mru->arcs_lsize[type] >= size &&
2562 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2564 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2565 if (type == ARC_BUFC_METADATA) {
2566 buf->b_data = zio_buf_alloc(size);
2567 arc_space_consume(size, ARC_SPACE_DATA);
2569 ASSERT(type == ARC_BUFC_DATA);
2570 buf->b_data = zio_data_buf_alloc(size);
2571 ARCSTAT_INCR(arcstat_data_size, size);
2572 atomic_add_64(&arc_size, size);
2574 ARCSTAT_BUMP(arcstat_recycle_miss);
2576 ASSERT(buf->b_data != NULL);
2579 * Update the state size. Note that ghost states have a
2580 * "ghost size" and so don't need to be updated.
2582 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2583 arc_buf_hdr_t *hdr = buf->b_hdr;
2585 atomic_add_64(&hdr->b_state->arcs_size, size);
2586 if (list_link_active(&hdr->b_arc_node)) {
2587 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2588 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2591 * If we are growing the cache, and we are adding anonymous
2592 * data, and we have outgrown arc_p, update arc_p
2594 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2595 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2596 arc_p = MIN(arc_c, arc_p + size);
2598 ARCSTAT_BUMP(arcstat_allocated);
2602 * This routine is called whenever a buffer is accessed.
2603 * NOTE: the hash lock is dropped in this function.
2606 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2610 ASSERT(MUTEX_HELD(hash_lock));
2612 if (buf->b_state == arc_anon) {
2614 * This buffer is not in the cache, and does not
2615 * appear in our "ghost" list. Add the new buffer
2619 ASSERT(buf->b_arc_access == 0);
2620 buf->b_arc_access = ddi_get_lbolt();
2621 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2622 arc_change_state(arc_mru, buf, hash_lock);
2624 } else if (buf->b_state == arc_mru) {
2625 now = ddi_get_lbolt();
2628 * If this buffer is here because of a prefetch, then either:
2629 * - clear the flag if this is a "referencing" read
2630 * (any subsequent access will bump this into the MFU state).
2632 * - move the buffer to the head of the list if this is
2633 * another prefetch (to make it less likely to be evicted).
2635 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2636 if (refcount_count(&buf->b_refcnt) == 0) {
2637 ASSERT(list_link_active(&buf->b_arc_node));
2639 buf->b_flags &= ~ARC_PREFETCH;
2640 ARCSTAT_BUMP(arcstat_mru_hits);
2642 buf->b_arc_access = now;
2647 * This buffer has been "accessed" only once so far,
2648 * but it is still in the cache. Move it to the MFU
2651 if (now > buf->b_arc_access + ARC_MINTIME) {
2653 * More than 125ms have passed since we
2654 * instantiated this buffer. Move it to the
2655 * most frequently used state.
2657 buf->b_arc_access = now;
2658 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2659 arc_change_state(arc_mfu, buf, hash_lock);
2661 ARCSTAT_BUMP(arcstat_mru_hits);
2662 } else if (buf->b_state == arc_mru_ghost) {
2663 arc_state_t *new_state;
2665 * This buffer has been "accessed" recently, but
2666 * was evicted from the cache. Move it to the
2670 if (buf->b_flags & ARC_PREFETCH) {
2671 new_state = arc_mru;
2672 if (refcount_count(&buf->b_refcnt) > 0)
2673 buf->b_flags &= ~ARC_PREFETCH;
2674 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2676 new_state = arc_mfu;
2677 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2680 buf->b_arc_access = ddi_get_lbolt();
2681 arc_change_state(new_state, buf, hash_lock);
2683 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2684 } else if (buf->b_state == arc_mfu) {
2686 * This buffer has been accessed more than once and is
2687 * still in the cache. Keep it in the MFU state.
2689 * NOTE: an add_reference() that occurred when we did
2690 * the arc_read() will have kicked this off the list.
2691 * If it was a prefetch, we will explicitly move it to
2692 * the head of the list now.
2694 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2695 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2696 ASSERT(list_link_active(&buf->b_arc_node));
2698 ARCSTAT_BUMP(arcstat_mfu_hits);
2699 buf->b_arc_access = ddi_get_lbolt();
2700 } else if (buf->b_state == arc_mfu_ghost) {
2701 arc_state_t *new_state = arc_mfu;
2703 * This buffer has been accessed more than once but has
2704 * been evicted from the cache. Move it back to the
2708 if (buf->b_flags & ARC_PREFETCH) {
2710 * This is a prefetch access...
2711 * move this block back to the MRU state.
2713 ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
2714 new_state = arc_mru;
2717 buf->b_arc_access = ddi_get_lbolt();
2718 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2719 arc_change_state(new_state, buf, hash_lock);
2721 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2722 } else if (buf->b_state == arc_l2c_only) {
2724 * This buffer is on the 2nd Level ARC.
2727 buf->b_arc_access = ddi_get_lbolt();
2728 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2729 arc_change_state(arc_mfu, buf, hash_lock);
2731 ASSERT(!"invalid arc state");
2735 /* a generic arc_done_func_t which you can use */
2738 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2740 if (zio == NULL || zio->io_error == 0)
2741 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2742 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2745 /* a generic arc_done_func_t */
2747 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2749 arc_buf_t **bufp = arg;
2750 if (zio && zio->io_error) {
2751 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2755 ASSERT(buf->b_data);
2760 arc_read_done(zio_t *zio)
2762 arc_buf_hdr_t *hdr, *found;
2764 arc_buf_t *abuf; /* buffer we're assigning to callback */
2765 kmutex_t *hash_lock;
2766 arc_callback_t *callback_list, *acb;
2767 int freeable = FALSE;
2769 buf = zio->io_private;
2773 * The hdr was inserted into hash-table and removed from lists
2774 * prior to starting I/O. We should find this header, since
2775 * it's in the hash table, and it should be legit since it's
2776 * not possible to evict it during the I/O. The only possible
2777 * reason for it not to be found is if we were freed during the
2780 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2783 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2784 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2785 (found == hdr && HDR_L2_READING(hdr)));
2787 hdr->b_flags &= ~ARC_L2_EVICTED;
2788 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2789 hdr->b_flags &= ~ARC_L2CACHE;
2791 /* byteswap if necessary */
2792 callback_list = hdr->b_acb;
2793 ASSERT(callback_list != NULL);
2794 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
2795 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2796 byteswap_uint64_array :
2797 dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
2798 func(buf->b_data, hdr->b_size);
2801 arc_cksum_compute(buf, B_FALSE);
2803 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
2805 * Only call arc_access on anonymous buffers. This is because
2806 * if we've issued an I/O for an evicted buffer, we've already
2807 * called arc_access (to prevent any simultaneous readers from
2808 * getting confused).
2810 arc_access(hdr, hash_lock);
2813 /* create copies of the data buffer for the callers */
2815 for (acb = callback_list; acb; acb = acb->acb_next) {
2816 if (acb->acb_done) {
2818 abuf = arc_buf_clone(buf);
2819 acb->acb_buf = abuf;
2824 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2825 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2827 ASSERT(buf->b_efunc == NULL);
2828 ASSERT(hdr->b_datacnt == 1);
2829 hdr->b_flags |= ARC_BUF_AVAILABLE;
2832 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2834 if (zio->io_error != 0) {
2835 hdr->b_flags |= ARC_IO_ERROR;
2836 if (hdr->b_state != arc_anon)
2837 arc_change_state(arc_anon, hdr, hash_lock);
2838 if (HDR_IN_HASH_TABLE(hdr))
2839 buf_hash_remove(hdr);
2840 freeable = refcount_is_zero(&hdr->b_refcnt);
2844 * Broadcast before we drop the hash_lock to avoid the possibility
2845 * that the hdr (and hence the cv) might be freed before we get to
2846 * the cv_broadcast().
2848 cv_broadcast(&hdr->b_cv);
2851 mutex_exit(hash_lock);
2854 * This block was freed while we waited for the read to
2855 * complete. It has been removed from the hash table and
2856 * moved to the anonymous state (so that it won't show up
2859 ASSERT3P(hdr->b_state, ==, arc_anon);
2860 freeable = refcount_is_zero(&hdr->b_refcnt);
2863 /* execute each callback and free its structure */
2864 while ((acb = callback_list) != NULL) {
2866 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2868 if (acb->acb_zio_dummy != NULL) {
2869 acb->acb_zio_dummy->io_error = zio->io_error;
2870 zio_nowait(acb->acb_zio_dummy);
2873 callback_list = acb->acb_next;
2874 kmem_free(acb, sizeof (arc_callback_t));
2878 arc_hdr_destroy(hdr);
2882 * "Read" the block block at the specified DVA (in bp) via the
2883 * cache. If the block is found in the cache, invoke the provided
2884 * callback immediately and return. Note that the `zio' parameter
2885 * in the callback will be NULL in this case, since no IO was
2886 * required. If the block is not in the cache pass the read request
2887 * on to the spa with a substitute callback function, so that the
2888 * requested block will be added to the cache.
2890 * If a read request arrives for a block that has a read in-progress,
2891 * either wait for the in-progress read to complete (and return the
2892 * results); or, if this is a read with a "done" func, add a record
2893 * to the read to invoke the "done" func when the read completes,
2894 * and return; or just return.
2896 * arc_read_done() will invoke all the requested "done" functions
2897 * for readers of this block.
2899 * Normal callers should use arc_read and pass the arc buffer and offset
2900 * for the bp. But if you know you don't need locking, you can use
2904 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf,
2905 arc_done_func_t *done, void *private, int priority, int zio_flags,
2906 uint32_t *arc_flags, const zbookmark_t *zb)
2912 * XXX This happens from traverse callback funcs, for
2913 * the objset_phys_t block.
2915 return (arc_read_nolock(pio, spa, bp, done, private, priority,
2916 zio_flags, arc_flags, zb));
2919 ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
2920 ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
2921 rw_enter(&pbuf->b_data_lock, RW_READER);
2923 err = arc_read_nolock(pio, spa, bp, done, private, priority,
2924 zio_flags, arc_flags, zb);
2925 rw_exit(&pbuf->b_data_lock);
2931 arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
2932 arc_done_func_t *done, void *private, int priority, int zio_flags,
2933 uint32_t *arc_flags, const zbookmark_t *zb)
2937 kmutex_t *hash_lock;
2939 uint64_t guid = spa_guid(spa);
2942 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
2944 if (hdr && hdr->b_datacnt > 0) {
2946 *arc_flags |= ARC_CACHED;
2948 if (HDR_IO_IN_PROGRESS(hdr)) {
2950 if (*arc_flags & ARC_WAIT) {
2951 cv_wait(&hdr->b_cv, hash_lock);
2952 mutex_exit(hash_lock);
2955 ASSERT(*arc_flags & ARC_NOWAIT);
2958 arc_callback_t *acb = NULL;
2960 acb = kmem_zalloc(sizeof (arc_callback_t),
2962 acb->acb_done = done;
2963 acb->acb_private = private;
2965 acb->acb_zio_dummy = zio_null(pio,
2966 spa, NULL, NULL, NULL, zio_flags);
2968 ASSERT(acb->acb_done != NULL);
2969 acb->acb_next = hdr->b_acb;
2971 add_reference(hdr, hash_lock, private);
2972 mutex_exit(hash_lock);
2975 mutex_exit(hash_lock);
2979 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2982 add_reference(hdr, hash_lock, private);
2984 * If this block is already in use, create a new
2985 * copy of the data so that we will be guaranteed
2986 * that arc_release() will always succeed.
2990 ASSERT(buf->b_data);
2991 if (HDR_BUF_AVAILABLE(hdr)) {
2992 ASSERT(buf->b_efunc == NULL);
2993 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2995 buf = arc_buf_clone(buf);
2998 } else if (*arc_flags & ARC_PREFETCH &&
2999 refcount_count(&hdr->b_refcnt) == 0) {
3000 hdr->b_flags |= ARC_PREFETCH;
3002 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3003 arc_access(hdr, hash_lock);
3004 if (*arc_flags & ARC_L2CACHE)
3005 hdr->b_flags |= ARC_L2CACHE;
3006 mutex_exit(hash_lock);
3007 ARCSTAT_BUMP(arcstat_hits);
3008 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3009 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3010 data, metadata, hits);
3013 done(NULL, buf, private);
3015 uint64_t size = BP_GET_LSIZE(bp);
3016 arc_callback_t *acb;
3019 boolean_t devw = B_FALSE;
3022 /* this block is not in the cache */
3023 arc_buf_hdr_t *exists;
3024 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3025 buf = arc_buf_alloc(spa, size, private, type);
3027 hdr->b_dva = *BP_IDENTITY(bp);
3028 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3029 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3030 exists = buf_hash_insert(hdr, &hash_lock);
3032 /* somebody beat us to the hash insert */
3033 mutex_exit(hash_lock);
3034 buf_discard_identity(hdr);
3035 (void) arc_buf_remove_ref(buf, private);
3036 goto top; /* restart the IO request */
3038 /* if this is a prefetch, we don't have a reference */
3039 if (*arc_flags & ARC_PREFETCH) {
3040 (void) remove_reference(hdr, hash_lock,
3042 hdr->b_flags |= ARC_PREFETCH;
3044 if (*arc_flags & ARC_L2CACHE)
3045 hdr->b_flags |= ARC_L2CACHE;
3046 if (BP_GET_LEVEL(bp) > 0)
3047 hdr->b_flags |= ARC_INDIRECT;
3049 /* this block is in the ghost cache */
3050 ASSERT(GHOST_STATE(hdr->b_state));
3051 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3052 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
3053 ASSERT(hdr->b_buf == NULL);
3055 /* if this is a prefetch, we don't have a reference */
3056 if (*arc_flags & ARC_PREFETCH)
3057 hdr->b_flags |= ARC_PREFETCH;
3059 add_reference(hdr, hash_lock, private);
3060 if (*arc_flags & ARC_L2CACHE)
3061 hdr->b_flags |= ARC_L2CACHE;
3062 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3065 buf->b_efunc = NULL;
3066 buf->b_private = NULL;
3069 ASSERT(hdr->b_datacnt == 0);
3071 arc_get_data_buf(buf);
3072 arc_access(hdr, hash_lock);
3075 ASSERT(!GHOST_STATE(hdr->b_state));
3077 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3078 acb->acb_done = done;
3079 acb->acb_private = private;
3081 ASSERT(hdr->b_acb == NULL);
3083 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3085 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
3086 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3087 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3088 addr = hdr->b_l2hdr->b_daddr;
3090 * Lock out device removal.
3092 if (vdev_is_dead(vd) ||
3093 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3097 mutex_exit(hash_lock);
3099 ASSERT3U(hdr->b_size, ==, size);
3100 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3101 uint64_t, size, zbookmark_t *, zb);
3102 ARCSTAT_BUMP(arcstat_misses);
3103 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3104 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3105 data, metadata, misses);
3107 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3109 * Read from the L2ARC if the following are true:
3110 * 1. The L2ARC vdev was previously cached.
3111 * 2. This buffer still has L2ARC metadata.
3112 * 3. This buffer isn't currently writing to the L2ARC.
3113 * 4. The L2ARC entry wasn't evicted, which may
3114 * also have invalidated the vdev.
3115 * 5. This isn't prefetch and l2arc_noprefetch is set.
3117 if (hdr->b_l2hdr != NULL &&
3118 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3119 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3120 l2arc_read_callback_t *cb;
3122 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3123 ARCSTAT_BUMP(arcstat_l2_hits);
3125 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3127 cb->l2rcb_buf = buf;
3128 cb->l2rcb_spa = spa;
3131 cb->l2rcb_flags = zio_flags;
3134 * l2arc read. The SCL_L2ARC lock will be
3135 * released by l2arc_read_done().
3137 rzio = zio_read_phys(pio, vd, addr, size,
3138 buf->b_data, ZIO_CHECKSUM_OFF,
3139 l2arc_read_done, cb, priority, zio_flags |
3140 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3141 ZIO_FLAG_DONT_PROPAGATE |
3142 ZIO_FLAG_DONT_RETRY, B_FALSE);
3143 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3145 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3147 if (*arc_flags & ARC_NOWAIT) {
3152 ASSERT(*arc_flags & ARC_WAIT);
3153 if (zio_wait(rzio) == 0)
3156 /* l2arc read error; goto zio_read() */
3158 DTRACE_PROBE1(l2arc__miss,
3159 arc_buf_hdr_t *, hdr);
3160 ARCSTAT_BUMP(arcstat_l2_misses);
3161 if (HDR_L2_WRITING(hdr))
3162 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3163 spa_config_exit(spa, SCL_L2ARC, vd);
3167 spa_config_exit(spa, SCL_L2ARC, vd);
3168 if (l2arc_ndev != 0) {
3169 DTRACE_PROBE1(l2arc__miss,
3170 arc_buf_hdr_t *, hdr);
3171 ARCSTAT_BUMP(arcstat_l2_misses);
3175 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3176 arc_read_done, buf, priority, zio_flags, zb);
3178 if (*arc_flags & ARC_WAIT)
3179 return (zio_wait(rzio));
3181 ASSERT(*arc_flags & ARC_NOWAIT);
3188 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3190 ASSERT(buf->b_hdr != NULL);
3191 ASSERT(buf->b_hdr->b_state != arc_anon);
3192 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3193 ASSERT(buf->b_efunc == NULL);
3194 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3196 buf->b_efunc = func;
3197 buf->b_private = private;
3201 * This is used by the DMU to let the ARC know that a buffer is
3202 * being evicted, so the ARC should clean up. If this arc buf
3203 * is not yet in the evicted state, it will be put there.
3206 arc_buf_evict(arc_buf_t *buf)
3209 kmutex_t *hash_lock;
3211 list_t *list, *evicted_list;
3212 kmutex_t *lock, *evicted_lock;
3214 mutex_enter(&buf->b_evict_lock);
3218 * We are in arc_do_user_evicts().
3220 ASSERT(buf->b_data == NULL);
3221 mutex_exit(&buf->b_evict_lock);
3223 } else if (buf->b_data == NULL) {
3224 arc_buf_t copy = *buf; /* structure assignment */
3226 * We are on the eviction list; process this buffer now
3227 * but let arc_do_user_evicts() do the reaping.
3229 buf->b_efunc = NULL;
3230 mutex_exit(&buf->b_evict_lock);
3231 VERIFY(copy.b_efunc(©) == 0);
3234 hash_lock = HDR_LOCK(hdr);
3235 mutex_enter(hash_lock);
3237 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3239 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3240 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3243 * Pull this buffer off of the hdr
3246 while (*bufp != buf)
3247 bufp = &(*bufp)->b_next;
3248 *bufp = buf->b_next;
3250 ASSERT(buf->b_data != NULL);
3251 arc_buf_destroy(buf, FALSE, FALSE);
3253 if (hdr->b_datacnt == 0) {
3254 arc_state_t *old_state = hdr->b_state;
3255 arc_state_t *evicted_state;
3257 ASSERT(hdr->b_buf == NULL);
3258 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3261 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3263 get_buf_info(hdr, old_state, &list, &lock);
3264 get_buf_info(hdr, evicted_state, &evicted_list, &evicted_lock);
3266 mutex_enter(evicted_lock);
3268 arc_change_state(evicted_state, hdr, hash_lock);
3269 ASSERT(HDR_IN_HASH_TABLE(hdr));
3270 hdr->b_flags |= ARC_IN_HASH_TABLE;
3271 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3273 mutex_exit(evicted_lock);
3276 mutex_exit(hash_lock);
3277 mutex_exit(&buf->b_evict_lock);
3279 VERIFY(buf->b_efunc(buf) == 0);
3280 buf->b_efunc = NULL;
3281 buf->b_private = NULL;
3284 kmem_cache_free(buf_cache, buf);
3289 * Release this buffer from the cache. This must be done
3290 * after a read and prior to modifying the buffer contents.
3291 * If the buffer has more than one reference, we must make
3292 * a new hdr for the buffer.
3295 arc_release(arc_buf_t *buf, void *tag)
3298 kmutex_t *hash_lock = NULL;
3299 l2arc_buf_hdr_t *l2hdr;
3303 * It would be nice to assert that if it's DMU metadata (level >
3304 * 0 || it's the dnode file), then it must be syncing context.
3305 * But we don't know that information at this level.
3308 mutex_enter(&buf->b_evict_lock);
3311 /* this buffer is not on any list */
3312 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3314 if (hdr->b_state == arc_anon) {
3315 /* this buffer is already released */
3316 ASSERT(buf->b_efunc == NULL);
3318 hash_lock = HDR_LOCK(hdr);
3319 mutex_enter(hash_lock);
3321 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3324 l2hdr = hdr->b_l2hdr;
3326 mutex_enter(&l2arc_buflist_mtx);
3327 hdr->b_l2hdr = NULL;
3328 buf_size = hdr->b_size;
3332 * Do we have more than one buf?
3334 if (hdr->b_datacnt > 1) {
3335 arc_buf_hdr_t *nhdr;
3337 uint64_t blksz = hdr->b_size;
3338 uint64_t spa = hdr->b_spa;
3339 arc_buf_contents_t type = hdr->b_type;
3340 uint32_t flags = hdr->b_flags;
3342 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3344 * Pull the data off of this hdr and attach it to
3345 * a new anonymous hdr.
3347 (void) remove_reference(hdr, hash_lock, tag);
3349 while (*bufp != buf)
3350 bufp = &(*bufp)->b_next;
3351 *bufp = buf->b_next;
3354 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3355 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3356 if (refcount_is_zero(&hdr->b_refcnt)) {
3357 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3358 ASSERT3U(*size, >=, hdr->b_size);
3359 atomic_add_64(size, -hdr->b_size);
3361 hdr->b_datacnt -= 1;
3362 arc_cksum_verify(buf);
3364 mutex_exit(hash_lock);
3366 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3367 nhdr->b_size = blksz;
3369 nhdr->b_type = type;
3371 nhdr->b_state = arc_anon;
3372 nhdr->b_arc_access = 0;
3373 nhdr->b_flags = flags & ARC_L2_WRITING;
3374 nhdr->b_l2hdr = NULL;
3375 nhdr->b_datacnt = 1;
3376 nhdr->b_freeze_cksum = NULL;
3377 (void) refcount_add(&nhdr->b_refcnt, tag);
3379 mutex_exit(&buf->b_evict_lock);
3380 atomic_add_64(&arc_anon->arcs_size, blksz);
3382 mutex_exit(&buf->b_evict_lock);
3383 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3384 ASSERT(!list_link_active(&hdr->b_arc_node));
3385 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3386 if (hdr->b_state != arc_anon)
3387 arc_change_state(arc_anon, hdr, hash_lock);
3388 hdr->b_arc_access = 0;
3390 mutex_exit(hash_lock);
3392 buf_discard_identity(hdr);
3395 buf->b_efunc = NULL;
3396 buf->b_private = NULL;
3399 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3400 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3401 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3402 mutex_exit(&l2arc_buflist_mtx);
3407 * Release this buffer. If it does not match the provided BP, fill it
3408 * with that block's contents.
3412 arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa,
3415 arc_release(buf, tag);
3420 arc_released(arc_buf_t *buf)
3424 mutex_enter(&buf->b_evict_lock);
3425 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3426 mutex_exit(&buf->b_evict_lock);
3431 arc_has_callback(arc_buf_t *buf)
3435 mutex_enter(&buf->b_evict_lock);
3436 callback = (buf->b_efunc != NULL);
3437 mutex_exit(&buf->b_evict_lock);
3443 arc_referenced(arc_buf_t *buf)
3447 mutex_enter(&buf->b_evict_lock);
3448 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3449 mutex_exit(&buf->b_evict_lock);
3450 return (referenced);
3455 arc_write_ready(zio_t *zio)
3457 arc_write_callback_t *callback = zio->io_private;
3458 arc_buf_t *buf = callback->awcb_buf;
3459 arc_buf_hdr_t *hdr = buf->b_hdr;
3461 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3462 callback->awcb_ready(zio, buf, callback->awcb_private);
3465 * If the IO is already in progress, then this is a re-write
3466 * attempt, so we need to thaw and re-compute the cksum.
3467 * It is the responsibility of the callback to handle the
3468 * accounting for any re-write attempt.
3470 if (HDR_IO_IN_PROGRESS(hdr)) {
3471 mutex_enter(&hdr->b_freeze_lock);
3472 if (hdr->b_freeze_cksum != NULL) {
3473 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3474 hdr->b_freeze_cksum = NULL;
3476 mutex_exit(&hdr->b_freeze_lock);
3478 arc_cksum_compute(buf, B_FALSE);
3479 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3483 arc_write_done(zio_t *zio)
3485 arc_write_callback_t *callback = zio->io_private;
3486 arc_buf_t *buf = callback->awcb_buf;
3487 arc_buf_hdr_t *hdr = buf->b_hdr;
3489 ASSERT(hdr->b_acb == NULL);
3491 if (zio->io_error == 0) {
3492 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3493 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3494 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3496 ASSERT(BUF_EMPTY(hdr));
3500 * If the block to be written was all-zero, we may have
3501 * compressed it away. In this case no write was performed
3502 * so there will be no dva/birth/checksum. The buffer must
3503 * therefore remain anonymous (and uncached).
3505 if (!BUF_EMPTY(hdr)) {
3506 arc_buf_hdr_t *exists;
3507 kmutex_t *hash_lock;
3509 ASSERT(zio->io_error == 0);
3511 arc_cksum_verify(buf);
3513 exists = buf_hash_insert(hdr, &hash_lock);
3516 * This can only happen if we overwrite for
3517 * sync-to-convergence, because we remove
3518 * buffers from the hash table when we arc_free().
3520 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3521 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3522 panic("bad overwrite, hdr=%p exists=%p",
3523 (void *)hdr, (void *)exists);
3524 ASSERT(refcount_is_zero(&exists->b_refcnt));
3525 arc_change_state(arc_anon, exists, hash_lock);
3526 mutex_exit(hash_lock);
3527 arc_hdr_destroy(exists);
3528 exists = buf_hash_insert(hdr, &hash_lock);
3529 ASSERT3P(exists, ==, NULL);
3532 ASSERT(hdr->b_datacnt == 1);
3533 ASSERT(hdr->b_state == arc_anon);
3534 ASSERT(BP_GET_DEDUP(zio->io_bp));
3535 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3538 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3539 /* if it's not anon, we are doing a scrub */
3540 if (!exists && hdr->b_state == arc_anon)
3541 arc_access(hdr, hash_lock);
3542 mutex_exit(hash_lock);
3544 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3547 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3548 callback->awcb_done(zio, buf, callback->awcb_private);
3550 kmem_free(callback, sizeof (arc_write_callback_t));
3554 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3555 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
3556 arc_done_func_t *ready, arc_done_func_t *done, void *private,
3557 int priority, int zio_flags, const zbookmark_t *zb)
3559 arc_buf_hdr_t *hdr = buf->b_hdr;
3560 arc_write_callback_t *callback;
3563 ASSERT(ready != NULL);
3564 ASSERT(done != NULL);
3565 ASSERT(!HDR_IO_ERROR(hdr));
3566 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3567 ASSERT(hdr->b_acb == NULL);
3569 hdr->b_flags |= ARC_L2CACHE;
3570 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3571 callback->awcb_ready = ready;
3572 callback->awcb_done = done;
3573 callback->awcb_private = private;
3574 callback->awcb_buf = buf;
3576 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3577 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3583 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3586 uint64_t available_memory =
3587 ptoa((uintmax_t)cnt.v_free_count + cnt.v_cache_count);
3588 static uint64_t page_load = 0;
3589 static uint64_t last_txg = 0;
3594 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3597 if (available_memory >= zfs_write_limit_max)
3600 if (txg > last_txg) {
3605 * If we are in pageout, we know that memory is already tight,
3606 * the arc is already going to be evicting, so we just want to
3607 * continue to let page writes occur as quickly as possible.
3609 if (curproc == pageproc) {
3610 if (page_load > available_memory / 4)
3612 /* Note: reserve is inflated, so we deflate */
3613 page_load += reserve / 8;
3615 } else if (page_load > 0 && arc_reclaim_needed()) {
3616 /* memory is low, delay before restarting */
3617 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3622 if (arc_size > arc_c_min) {
3623 uint64_t evictable_memory =
3624 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3625 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3626 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3627 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3628 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3631 if (inflight_data > available_memory / 4) {
3632 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3640 arc_tempreserve_clear(uint64_t reserve)
3642 atomic_add_64(&arc_tempreserve, -reserve);
3643 ASSERT((int64_t)arc_tempreserve >= 0);
3647 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3654 * Once in a while, fail for no reason. Everything should cope.
3656 if (spa_get_random(10000) == 0) {
3657 dprintf("forcing random failure\n");
3661 if (reserve > arc_c/4 && !arc_no_grow)
3662 arc_c = MIN(arc_c_max, reserve * 4);
3663 if (reserve > arc_c)
3667 * Don't count loaned bufs as in flight dirty data to prevent long
3668 * network delays from blocking transactions that are ready to be
3669 * assigned to a txg.
3671 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3674 * Writes will, almost always, require additional memory allocations
3675 * in order to compress/encrypt/etc the data. We therefor need to
3676 * make sure that there is sufficient available memory for this.
3678 if (error = arc_memory_throttle(reserve, anon_size, txg))
3682 * Throttle writes when the amount of dirty data in the cache
3683 * gets too large. We try to keep the cache less than half full
3684 * of dirty blocks so that our sync times don't grow too large.
3685 * Note: if two requests come in concurrently, we might let them
3686 * both succeed, when one of them should fail. Not a huge deal.
3689 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3690 anon_size > arc_c / 4) {
3691 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3692 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3693 arc_tempreserve>>10,
3694 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3695 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3696 reserve>>10, arc_c>>10);
3699 atomic_add_64(&arc_tempreserve, reserve);
3703 static kmutex_t arc_lowmem_lock;
3705 static eventhandler_tag arc_event_lowmem = NULL;
3708 arc_lowmem(void *arg __unused, int howto __unused)
3711 /* Serialize access via arc_lowmem_lock. */
3712 mutex_enter(&arc_lowmem_lock);
3713 mutex_enter(&arc_reclaim_thr_lock);
3715 cv_signal(&arc_reclaim_thr_cv);
3717 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
3718 mutex_exit(&arc_reclaim_thr_lock);
3719 mutex_exit(&arc_lowmem_lock);
3726 int i, prefetch_tunable_set = 0;
3728 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3729 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3730 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
3732 /* Convert seconds to clock ticks */
3733 arc_min_prefetch_lifespan = 1 * hz;
3735 /* Start out with 1/8 of all memory */
3736 arc_c = kmem_size() / 8;
3741 * On architectures where the physical memory can be larger
3742 * than the addressable space (intel in 32-bit mode), we may
3743 * need to limit the cache to 1/8 of VM size.
3745 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3748 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
3749 arc_c_min = MAX(arc_c / 4, 64<<18);
3750 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
3751 if (arc_c * 8 >= 1<<30)
3752 arc_c_max = (arc_c * 8) - (1<<30);
3754 arc_c_max = arc_c_min;
3755 arc_c_max = MAX(arc_c * 5, arc_c_max);
3759 * Allow the tunables to override our calculations if they are
3760 * reasonable (ie. over 16MB)
3762 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size())
3763 arc_c_max = zfs_arc_max;
3764 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max)
3765 arc_c_min = zfs_arc_min;
3769 arc_p = (arc_c >> 1);
3771 /* limit meta-data to 1/4 of the arc capacity */
3772 arc_meta_limit = arc_c_max / 4;
3774 /* Allow the tunable to override if it is reasonable */
3775 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3776 arc_meta_limit = zfs_arc_meta_limit;
3778 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3779 arc_c_min = arc_meta_limit / 2;
3781 if (zfs_arc_grow_retry > 0)
3782 arc_grow_retry = zfs_arc_grow_retry;
3784 if (zfs_arc_shrink_shift > 0)
3785 arc_shrink_shift = zfs_arc_shrink_shift;
3787 if (zfs_arc_p_min_shift > 0)
3788 arc_p_min_shift = zfs_arc_p_min_shift;
3790 /* if kmem_flags are set, lets try to use less memory */
3791 if (kmem_debugging())
3793 if (arc_c < arc_c_min)
3796 zfs_arc_min = arc_c_min;
3797 zfs_arc_max = arc_c_max;
3799 arc_anon = &ARC_anon;
3801 arc_mru_ghost = &ARC_mru_ghost;
3803 arc_mfu_ghost = &ARC_mfu_ghost;
3804 arc_l2c_only = &ARC_l2c_only;
3807 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
3808 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
3809 NULL, MUTEX_DEFAULT, NULL);
3810 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
3811 NULL, MUTEX_DEFAULT, NULL);
3812 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
3813 NULL, MUTEX_DEFAULT, NULL);
3814 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
3815 NULL, MUTEX_DEFAULT, NULL);
3816 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
3817 NULL, MUTEX_DEFAULT, NULL);
3818 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
3819 NULL, MUTEX_DEFAULT, NULL);
3821 list_create(&arc_mru->arcs_lists[i],
3822 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3823 list_create(&arc_mru_ghost->arcs_lists[i],
3824 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3825 list_create(&arc_mfu->arcs_lists[i],
3826 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3827 list_create(&arc_mfu_ghost->arcs_lists[i],
3828 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3829 list_create(&arc_mfu_ghost->arcs_lists[i],
3830 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3831 list_create(&arc_l2c_only->arcs_lists[i],
3832 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3837 arc_thread_exit = 0;
3838 arc_eviction_list = NULL;
3839 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3840 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3842 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3843 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3845 if (arc_ksp != NULL) {
3846 arc_ksp->ks_data = &arc_stats;
3847 kstat_install(arc_ksp);
3850 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3851 TS_RUN, minclsyspri);
3854 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
3855 EVENTHANDLER_PRI_FIRST);
3861 if (zfs_write_limit_max == 0)
3862 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3864 zfs_write_limit_shift = 0;
3865 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3868 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
3869 prefetch_tunable_set = 1;
3872 if (prefetch_tunable_set == 0) {
3873 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
3875 printf(" add \"vfs.zfs.prefetch_disable=0\" "
3876 "to /boot/loader.conf.\n");
3877 zfs_prefetch_disable = 1;
3880 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
3881 prefetch_tunable_set == 0) {
3882 printf("ZFS NOTICE: Prefetch is disabled by default if less "
3883 "than 4GB of RAM is present;\n"
3884 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
3885 "to /boot/loader.conf.\n");
3886 zfs_prefetch_disable = 1;
3889 /* Warn about ZFS memory and address space requirements. */
3890 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
3891 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
3892 "expect unstable behavior.\n");
3894 if (kmem_size() < 512 * (1 << 20)) {
3895 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
3896 "expect unstable behavior.\n");
3897 printf(" Consider tuning vm.kmem_size and "
3898 "vm.kmem_size_max\n");
3899 printf(" in /boot/loader.conf.\n");
3909 mutex_enter(&arc_reclaim_thr_lock);
3910 arc_thread_exit = 1;
3911 cv_signal(&arc_reclaim_thr_cv);
3912 while (arc_thread_exit != 0)
3913 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3914 mutex_exit(&arc_reclaim_thr_lock);
3920 if (arc_ksp != NULL) {
3921 kstat_delete(arc_ksp);
3925 mutex_destroy(&arc_eviction_mtx);
3926 mutex_destroy(&arc_reclaim_thr_lock);
3927 cv_destroy(&arc_reclaim_thr_cv);
3929 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
3930 list_destroy(&arc_mru->arcs_lists[i]);
3931 list_destroy(&arc_mru_ghost->arcs_lists[i]);
3932 list_destroy(&arc_mfu->arcs_lists[i]);
3933 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
3934 list_destroy(&arc_l2c_only->arcs_lists[i]);
3936 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
3937 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
3938 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
3939 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
3940 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
3941 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
3944 mutex_destroy(&zfs_write_limit_lock);
3948 ASSERT(arc_loaned_bytes == 0);
3950 mutex_destroy(&arc_lowmem_lock);
3952 if (arc_event_lowmem != NULL)
3953 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
3960 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3961 * It uses dedicated storage devices to hold cached data, which are populated
3962 * using large infrequent writes. The main role of this cache is to boost
3963 * the performance of random read workloads. The intended L2ARC devices
3964 * include short-stroked disks, solid state disks, and other media with
3965 * substantially faster read latency than disk.
3967 * +-----------------------+
3969 * +-----------------------+
3972 * l2arc_feed_thread() arc_read()
3976 * +---------------+ |
3978 * +---------------+ |
3983 * +-------+ +-------+
3985 * | cache | | cache |
3986 * +-------+ +-------+
3987 * +=========+ .-----.
3988 * : L2ARC : |-_____-|
3989 * : devices : | Disks |
3990 * +=========+ `-_____-'
3992 * Read requests are satisfied from the following sources, in order:
3995 * 2) vdev cache of L2ARC devices
3997 * 4) vdev cache of disks
4000 * Some L2ARC device types exhibit extremely slow write performance.
4001 * To accommodate for this there are some significant differences between
4002 * the L2ARC and traditional cache design:
4004 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4005 * the ARC behave as usual, freeing buffers and placing headers on ghost
4006 * lists. The ARC does not send buffers to the L2ARC during eviction as
4007 * this would add inflated write latencies for all ARC memory pressure.
4009 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4010 * It does this by periodically scanning buffers from the eviction-end of
4011 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4012 * not already there. It scans until a headroom of buffers is satisfied,
4013 * which itself is a buffer for ARC eviction. The thread that does this is
4014 * l2arc_feed_thread(), illustrated below; example sizes are included to
4015 * provide a better sense of ratio than this diagram:
4018 * +---------------------+----------+
4019 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4020 * +---------------------+----------+ | o L2ARC eligible
4021 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4022 * +---------------------+----------+ |
4023 * 15.9 Gbytes ^ 32 Mbytes |
4025 * l2arc_feed_thread()
4027 * l2arc write hand <--[oooo]--'
4031 * +==============================+
4032 * L2ARC dev |####|#|###|###| |####| ... |
4033 * +==============================+
4036 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4037 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4038 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4039 * safe to say that this is an uncommon case, since buffers at the end of
4040 * the ARC lists have moved there due to inactivity.
4042 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4043 * then the L2ARC simply misses copying some buffers. This serves as a
4044 * pressure valve to prevent heavy read workloads from both stalling the ARC
4045 * with waits and clogging the L2ARC with writes. This also helps prevent
4046 * the potential for the L2ARC to churn if it attempts to cache content too
4047 * quickly, such as during backups of the entire pool.
4049 * 5. After system boot and before the ARC has filled main memory, there are
4050 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4051 * lists can remain mostly static. Instead of searching from tail of these
4052 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4053 * for eligible buffers, greatly increasing its chance of finding them.
4055 * The L2ARC device write speed is also boosted during this time so that
4056 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4057 * there are no L2ARC reads, and no fear of degrading read performance
4058 * through increased writes.
4060 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4061 * the vdev queue can aggregate them into larger and fewer writes. Each
4062 * device is written to in a rotor fashion, sweeping writes through
4063 * available space then repeating.
4065 * 7. The L2ARC does not store dirty content. It never needs to flush
4066 * write buffers back to disk based storage.
4068 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4069 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4071 * The performance of the L2ARC can be tweaked by a number of tunables, which
4072 * may be necessary for different workloads:
4074 * l2arc_write_max max write bytes per interval
4075 * l2arc_write_boost extra write bytes during device warmup
4076 * l2arc_noprefetch skip caching prefetched buffers
4077 * l2arc_headroom number of max device writes to precache
4078 * l2arc_feed_secs seconds between L2ARC writing
4080 * Tunables may be removed or added as future performance improvements are
4081 * integrated, and also may become zpool properties.
4083 * There are three key functions that control how the L2ARC warms up:
4085 * l2arc_write_eligible() check if a buffer is eligible to cache
4086 * l2arc_write_size() calculate how much to write
4087 * l2arc_write_interval() calculate sleep delay between writes
4089 * These three functions determine what to write, how much, and how quickly
4094 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4097 * A buffer is *not* eligible for the L2ARC if it:
4098 * 1. belongs to a different spa.
4099 * 2. is already cached on the L2ARC.
4100 * 3. has an I/O in progress (it may be an incomplete read).
4101 * 4. is flagged not eligible (zfs property).
4103 if (ab->b_spa != spa_guid) {
4104 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4107 if (ab->b_l2hdr != NULL) {
4108 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4111 if (HDR_IO_IN_PROGRESS(ab)) {
4112 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4115 if (!HDR_L2CACHE(ab)) {
4116 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4124 l2arc_write_size(l2arc_dev_t *dev)
4128 size = dev->l2ad_write;
4130 if (arc_warm == B_FALSE)
4131 size += dev->l2ad_boost;
4138 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4140 clock_t interval, next, now;
4143 * If the ARC lists are busy, increase our write rate; if the
4144 * lists are stale, idle back. This is achieved by checking
4145 * how much we previously wrote - if it was more than half of
4146 * what we wanted, schedule the next write much sooner.
4148 if (l2arc_feed_again && wrote > (wanted / 2))
4149 interval = (hz * l2arc_feed_min_ms) / 1000;
4151 interval = hz * l2arc_feed_secs;
4153 now = ddi_get_lbolt();
4154 next = MAX(now, MIN(now + interval, began + interval));
4160 l2arc_hdr_stat_add(void)
4162 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4163 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4167 l2arc_hdr_stat_remove(void)
4169 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4170 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4174 * Cycle through L2ARC devices. This is how L2ARC load balances.
4175 * If a device is returned, this also returns holding the spa config lock.
4177 static l2arc_dev_t *
4178 l2arc_dev_get_next(void)
4180 l2arc_dev_t *first, *next = NULL;
4183 * Lock out the removal of spas (spa_namespace_lock), then removal
4184 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4185 * both locks will be dropped and a spa config lock held instead.
4187 mutex_enter(&spa_namespace_lock);
4188 mutex_enter(&l2arc_dev_mtx);
4190 /* if there are no vdevs, there is nothing to do */
4191 if (l2arc_ndev == 0)
4195 next = l2arc_dev_last;
4197 /* loop around the list looking for a non-faulted vdev */
4199 next = list_head(l2arc_dev_list);
4201 next = list_next(l2arc_dev_list, next);
4203 next = list_head(l2arc_dev_list);
4206 /* if we have come back to the start, bail out */
4209 else if (next == first)
4212 } while (vdev_is_dead(next->l2ad_vdev));
4214 /* if we were unable to find any usable vdevs, return NULL */
4215 if (vdev_is_dead(next->l2ad_vdev))
4218 l2arc_dev_last = next;
4221 mutex_exit(&l2arc_dev_mtx);
4224 * Grab the config lock to prevent the 'next' device from being
4225 * removed while we are writing to it.
4228 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4229 mutex_exit(&spa_namespace_lock);
4235 * Free buffers that were tagged for destruction.
4238 l2arc_do_free_on_write()
4241 l2arc_data_free_t *df, *df_prev;
4243 mutex_enter(&l2arc_free_on_write_mtx);
4244 buflist = l2arc_free_on_write;
4246 for (df = list_tail(buflist); df; df = df_prev) {
4247 df_prev = list_prev(buflist, df);
4248 ASSERT(df->l2df_data != NULL);
4249 ASSERT(df->l2df_func != NULL);
4250 df->l2df_func(df->l2df_data, df->l2df_size);
4251 list_remove(buflist, df);
4252 kmem_free(df, sizeof (l2arc_data_free_t));
4255 mutex_exit(&l2arc_free_on_write_mtx);
4259 * A write to a cache device has completed. Update all headers to allow
4260 * reads from these buffers to begin.
4263 l2arc_write_done(zio_t *zio)
4265 l2arc_write_callback_t *cb;
4268 arc_buf_hdr_t *head, *ab, *ab_prev;
4269 l2arc_buf_hdr_t *abl2;
4270 kmutex_t *hash_lock;
4272 cb = zio->io_private;
4274 dev = cb->l2wcb_dev;
4275 ASSERT(dev != NULL);
4276 head = cb->l2wcb_head;
4277 ASSERT(head != NULL);
4278 buflist = dev->l2ad_buflist;
4279 ASSERT(buflist != NULL);
4280 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4281 l2arc_write_callback_t *, cb);
4283 if (zio->io_error != 0)
4284 ARCSTAT_BUMP(arcstat_l2_writes_error);
4286 mutex_enter(&l2arc_buflist_mtx);
4289 * All writes completed, or an error was hit.
4291 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4292 ab_prev = list_prev(buflist, ab);
4294 hash_lock = HDR_LOCK(ab);
4295 if (!mutex_tryenter(hash_lock)) {
4297 * This buffer misses out. It may be in a stage
4298 * of eviction. Its ARC_L2_WRITING flag will be
4299 * left set, denying reads to this buffer.
4301 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4305 if (zio->io_error != 0) {
4307 * Error - drop L2ARC entry.
4309 list_remove(buflist, ab);
4312 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4313 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4317 * Allow ARC to begin reads to this L2ARC entry.
4319 ab->b_flags &= ~ARC_L2_WRITING;
4321 mutex_exit(hash_lock);
4324 atomic_inc_64(&l2arc_writes_done);
4325 list_remove(buflist, head);
4326 kmem_cache_free(hdr_cache, head);
4327 mutex_exit(&l2arc_buflist_mtx);
4329 l2arc_do_free_on_write();
4331 kmem_free(cb, sizeof (l2arc_write_callback_t));
4335 * A read to a cache device completed. Validate buffer contents before
4336 * handing over to the regular ARC routines.
4339 l2arc_read_done(zio_t *zio)
4341 l2arc_read_callback_t *cb;
4344 kmutex_t *hash_lock;
4347 ASSERT(zio->io_vd != NULL);
4348 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4350 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4352 cb = zio->io_private;
4354 buf = cb->l2rcb_buf;
4355 ASSERT(buf != NULL);
4357 hash_lock = HDR_LOCK(buf->b_hdr);
4358 mutex_enter(hash_lock);
4360 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4363 * Check this survived the L2ARC journey.
4365 equal = arc_cksum_equal(buf);
4366 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4367 mutex_exit(hash_lock);
4368 zio->io_private = buf;
4369 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4370 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4373 mutex_exit(hash_lock);
4375 * Buffer didn't survive caching. Increment stats and
4376 * reissue to the original storage device.
4378 if (zio->io_error != 0) {
4379 ARCSTAT_BUMP(arcstat_l2_io_error);
4381 zio->io_error = EIO;
4384 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4387 * If there's no waiter, issue an async i/o to the primary
4388 * storage now. If there *is* a waiter, the caller must
4389 * issue the i/o in a context where it's OK to block.
4391 if (zio->io_waiter == NULL) {
4392 zio_t *pio = zio_unique_parent(zio);
4394 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4396 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4397 buf->b_data, zio->io_size, arc_read_done, buf,
4398 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4402 kmem_free(cb, sizeof (l2arc_read_callback_t));
4406 * This is the list priority from which the L2ARC will search for pages to
4407 * cache. This is used within loops (0..3) to cycle through lists in the
4408 * desired order. This order can have a significant effect on cache
4411 * Currently the metadata lists are hit first, MFU then MRU, followed by
4412 * the data lists. This function returns a locked list, and also returns
4416 l2arc_list_locked(int list_num, kmutex_t **lock)
4421 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4423 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4425 list = &arc_mfu->arcs_lists[idx];
4426 *lock = ARCS_LOCK(arc_mfu, idx);
4427 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4428 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4429 list = &arc_mru->arcs_lists[idx];
4430 *lock = ARCS_LOCK(arc_mru, idx);
4431 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4432 ARC_BUFC_NUMDATALISTS)) {
4433 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4434 list = &arc_mfu->arcs_lists[idx];
4435 *lock = ARCS_LOCK(arc_mfu, idx);
4437 idx = list_num - ARC_BUFC_NUMLISTS;
4438 list = &arc_mru->arcs_lists[idx];
4439 *lock = ARCS_LOCK(arc_mru, idx);
4442 ASSERT(!(MUTEX_HELD(*lock)));
4448 * Evict buffers from the device write hand to the distance specified in
4449 * bytes. This distance may span populated buffers, it may span nothing.
4450 * This is clearing a region on the L2ARC device ready for writing.
4451 * If the 'all' boolean is set, every buffer is evicted.
4454 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4457 l2arc_buf_hdr_t *abl2;
4458 arc_buf_hdr_t *ab, *ab_prev;
4459 kmutex_t *hash_lock;
4462 buflist = dev->l2ad_buflist;
4464 if (buflist == NULL)
4467 if (!all && dev->l2ad_first) {
4469 * This is the first sweep through the device. There is
4475 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4477 * When nearing the end of the device, evict to the end
4478 * before the device write hand jumps to the start.
4480 taddr = dev->l2ad_end;
4482 taddr = dev->l2ad_hand + distance;
4484 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4485 uint64_t, taddr, boolean_t, all);
4488 mutex_enter(&l2arc_buflist_mtx);
4489 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4490 ab_prev = list_prev(buflist, ab);
4492 hash_lock = HDR_LOCK(ab);
4493 if (!mutex_tryenter(hash_lock)) {
4495 * Missed the hash lock. Retry.
4497 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4498 mutex_exit(&l2arc_buflist_mtx);
4499 mutex_enter(hash_lock);
4500 mutex_exit(hash_lock);
4504 if (HDR_L2_WRITE_HEAD(ab)) {
4506 * We hit a write head node. Leave it for
4507 * l2arc_write_done().
4509 list_remove(buflist, ab);
4510 mutex_exit(hash_lock);
4514 if (!all && ab->b_l2hdr != NULL &&
4515 (ab->b_l2hdr->b_daddr > taddr ||
4516 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4518 * We've evicted to the target address,
4519 * or the end of the device.
4521 mutex_exit(hash_lock);
4525 if (HDR_FREE_IN_PROGRESS(ab)) {
4527 * Already on the path to destruction.
4529 mutex_exit(hash_lock);
4533 if (ab->b_state == arc_l2c_only) {
4534 ASSERT(!HDR_L2_READING(ab));
4536 * This doesn't exist in the ARC. Destroy.
4537 * arc_hdr_destroy() will call list_remove()
4538 * and decrement arcstat_l2_size.
4540 arc_change_state(arc_anon, ab, hash_lock);
4541 arc_hdr_destroy(ab);
4544 * Invalidate issued or about to be issued
4545 * reads, since we may be about to write
4546 * over this location.
4548 if (HDR_L2_READING(ab)) {
4549 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4550 ab->b_flags |= ARC_L2_EVICTED;
4554 * Tell ARC this no longer exists in L2ARC.
4556 if (ab->b_l2hdr != NULL) {
4559 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4560 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4562 list_remove(buflist, ab);
4565 * This may have been leftover after a
4568 ab->b_flags &= ~ARC_L2_WRITING;
4570 mutex_exit(hash_lock);
4572 mutex_exit(&l2arc_buflist_mtx);
4574 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
4575 dev->l2ad_evict = taddr;
4579 * Find and write ARC buffers to the L2ARC device.
4581 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4582 * for reading until they have completed writing.
4585 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4587 arc_buf_hdr_t *ab, *ab_prev, *head;
4588 l2arc_buf_hdr_t *hdrl2;
4590 uint64_t passed_sz, write_sz, buf_sz, headroom;
4592 kmutex_t *hash_lock, *list_lock;
4593 boolean_t have_lock, full;
4594 l2arc_write_callback_t *cb;
4596 uint64_t guid = spa_guid(spa);
4599 ASSERT(dev->l2ad_vdev != NULL);
4604 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4605 head->b_flags |= ARC_L2_WRITE_HEAD;
4607 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
4609 * Copy buffers for L2ARC writing.
4611 mutex_enter(&l2arc_buflist_mtx);
4612 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
4613 list = l2arc_list_locked(try, &list_lock);
4615 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
4618 * L2ARC fast warmup.
4620 * Until the ARC is warm and starts to evict, read from the
4621 * head of the ARC lists rather than the tail.
4623 headroom = target_sz * l2arc_headroom;
4624 if (arc_warm == B_FALSE)
4625 ab = list_head(list);
4627 ab = list_tail(list);
4629 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
4631 for (; ab; ab = ab_prev) {
4632 if (arc_warm == B_FALSE)
4633 ab_prev = list_next(list, ab);
4635 ab_prev = list_prev(list, ab);
4636 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
4638 hash_lock = HDR_LOCK(ab);
4639 have_lock = MUTEX_HELD(hash_lock);
4640 if (!have_lock && !mutex_tryenter(hash_lock)) {
4641 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
4643 * Skip this buffer rather than waiting.
4648 passed_sz += ab->b_size;
4649 if (passed_sz > headroom) {
4653 mutex_exit(hash_lock);
4654 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
4658 if (!l2arc_write_eligible(guid, ab)) {
4659 mutex_exit(hash_lock);
4663 if ((write_sz + ab->b_size) > target_sz) {
4665 mutex_exit(hash_lock);
4666 ARCSTAT_BUMP(arcstat_l2_write_full);
4672 * Insert a dummy header on the buflist so
4673 * l2arc_write_done() can find where the
4674 * write buffers begin without searching.
4676 list_insert_head(dev->l2ad_buflist, head);
4679 sizeof (l2arc_write_callback_t), KM_SLEEP);
4680 cb->l2wcb_dev = dev;
4681 cb->l2wcb_head = head;
4682 pio = zio_root(spa, l2arc_write_done, cb,
4684 ARCSTAT_BUMP(arcstat_l2_write_pios);
4688 * Create and add a new L2ARC header.
4690 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4692 hdrl2->b_daddr = dev->l2ad_hand;
4694 ab->b_flags |= ARC_L2_WRITING;
4695 ab->b_l2hdr = hdrl2;
4696 list_insert_head(dev->l2ad_buflist, ab);
4697 buf_data = ab->b_buf->b_data;
4698 buf_sz = ab->b_size;
4701 * Compute and store the buffer cksum before
4702 * writing. On debug the cksum is verified first.
4704 arc_cksum_verify(ab->b_buf);
4705 arc_cksum_compute(ab->b_buf, B_TRUE);
4707 mutex_exit(hash_lock);
4709 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4710 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4711 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4712 ZIO_FLAG_CANFAIL, B_FALSE);
4714 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4716 (void) zio_nowait(wzio);
4719 * Keep the clock hand suitably device-aligned.
4721 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4724 dev->l2ad_hand += buf_sz;
4727 mutex_exit(list_lock);
4732 mutex_exit(&l2arc_buflist_mtx);
4735 ASSERT3U(write_sz, ==, 0);
4736 kmem_cache_free(hdr_cache, head);
4740 ASSERT3U(write_sz, <=, target_sz);
4741 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4742 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4743 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4744 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
4747 * Bump device hand to the device start if it is approaching the end.
4748 * l2arc_evict() will already have evicted ahead for this case.
4750 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4751 vdev_space_update(dev->l2ad_vdev,
4752 dev->l2ad_end - dev->l2ad_hand, 0, 0);
4753 dev->l2ad_hand = dev->l2ad_start;
4754 dev->l2ad_evict = dev->l2ad_start;
4755 dev->l2ad_first = B_FALSE;
4758 dev->l2ad_writing = B_TRUE;
4759 (void) zio_wait(pio);
4760 dev->l2ad_writing = B_FALSE;
4766 * This thread feeds the L2ARC at regular intervals. This is the beating
4767 * heart of the L2ARC.
4770 l2arc_feed_thread(void *dummy __unused)
4775 uint64_t size, wrote;
4776 clock_t begin, next = ddi_get_lbolt();
4778 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4780 mutex_enter(&l2arc_feed_thr_lock);
4782 while (l2arc_thread_exit == 0) {
4783 CALLB_CPR_SAFE_BEGIN(&cpr);
4784 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4785 next - ddi_get_lbolt());
4786 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4787 next = ddi_get_lbolt() + hz;
4790 * Quick check for L2ARC devices.
4792 mutex_enter(&l2arc_dev_mtx);
4793 if (l2arc_ndev == 0) {
4794 mutex_exit(&l2arc_dev_mtx);
4797 mutex_exit(&l2arc_dev_mtx);
4798 begin = ddi_get_lbolt();
4801 * This selects the next l2arc device to write to, and in
4802 * doing so the next spa to feed from: dev->l2ad_spa. This
4803 * will return NULL if there are now no l2arc devices or if
4804 * they are all faulted.
4806 * If a device is returned, its spa's config lock is also
4807 * held to prevent device removal. l2arc_dev_get_next()
4808 * will grab and release l2arc_dev_mtx.
4810 if ((dev = l2arc_dev_get_next()) == NULL)
4813 spa = dev->l2ad_spa;
4814 ASSERT(spa != NULL);
4817 * If the pool is read-only then force the feed thread to
4818 * sleep a little longer.
4820 if (!spa_writeable(spa)) {
4821 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
4822 spa_config_exit(spa, SCL_L2ARC, dev);
4827 * Avoid contributing to memory pressure.
4829 if (arc_reclaim_needed()) {
4830 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4831 spa_config_exit(spa, SCL_L2ARC, dev);
4835 ARCSTAT_BUMP(arcstat_l2_feeds);
4837 size = l2arc_write_size(dev);
4840 * Evict L2ARC buffers that will be overwritten.
4842 l2arc_evict(dev, size, B_FALSE);
4845 * Write ARC buffers.
4847 wrote = l2arc_write_buffers(spa, dev, size);
4850 * Calculate interval between writes.
4852 next = l2arc_write_interval(begin, size, wrote);
4853 spa_config_exit(spa, SCL_L2ARC, dev);
4856 l2arc_thread_exit = 0;
4857 cv_broadcast(&l2arc_feed_thr_cv);
4858 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4863 l2arc_vdev_present(vdev_t *vd)
4867 mutex_enter(&l2arc_dev_mtx);
4868 for (dev = list_head(l2arc_dev_list); dev != NULL;
4869 dev = list_next(l2arc_dev_list, dev)) {
4870 if (dev->l2ad_vdev == vd)
4873 mutex_exit(&l2arc_dev_mtx);
4875 return (dev != NULL);
4879 * Add a vdev for use by the L2ARC. By this point the spa has already
4880 * validated the vdev and opened it.
4883 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
4885 l2arc_dev_t *adddev;
4887 ASSERT(!l2arc_vdev_present(vd));
4890 * Create a new l2arc device entry.
4892 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4893 adddev->l2ad_spa = spa;
4894 adddev->l2ad_vdev = vd;
4895 adddev->l2ad_write = l2arc_write_max;
4896 adddev->l2ad_boost = l2arc_write_boost;
4897 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
4898 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
4899 adddev->l2ad_hand = adddev->l2ad_start;
4900 adddev->l2ad_evict = adddev->l2ad_start;
4901 adddev->l2ad_first = B_TRUE;
4902 adddev->l2ad_writing = B_FALSE;
4903 ASSERT3U(adddev->l2ad_write, >, 0);
4906 * This is a list of all ARC buffers that are still valid on the
4909 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4910 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4911 offsetof(arc_buf_hdr_t, b_l2node));
4913 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
4916 * Add device to global list
4918 mutex_enter(&l2arc_dev_mtx);
4919 list_insert_head(l2arc_dev_list, adddev);
4920 atomic_inc_64(&l2arc_ndev);
4921 mutex_exit(&l2arc_dev_mtx);
4925 * Remove a vdev from the L2ARC.
4928 l2arc_remove_vdev(vdev_t *vd)
4930 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4933 * Find the device by vdev
4935 mutex_enter(&l2arc_dev_mtx);
4936 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4937 nextdev = list_next(l2arc_dev_list, dev);
4938 if (vd == dev->l2ad_vdev) {
4943 ASSERT(remdev != NULL);
4946 * Remove device from global list
4948 list_remove(l2arc_dev_list, remdev);
4949 l2arc_dev_last = NULL; /* may have been invalidated */
4950 atomic_dec_64(&l2arc_ndev);
4951 mutex_exit(&l2arc_dev_mtx);
4954 * Clear all buflists and ARC references. L2ARC device flush.
4956 l2arc_evict(remdev, 0, B_TRUE);
4957 list_destroy(remdev->l2ad_buflist);
4958 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4959 kmem_free(remdev, sizeof (l2arc_dev_t));
4965 l2arc_thread_exit = 0;
4967 l2arc_writes_sent = 0;
4968 l2arc_writes_done = 0;
4970 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4971 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4972 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4973 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4974 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4976 l2arc_dev_list = &L2ARC_dev_list;
4977 l2arc_free_on_write = &L2ARC_free_on_write;
4978 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4979 offsetof(l2arc_dev_t, l2ad_node));
4980 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4981 offsetof(l2arc_data_free_t, l2df_list_node));
4988 * This is called from dmu_fini(), which is called from spa_fini();
4989 * Because of this, we can assume that all l2arc devices have
4990 * already been removed when the pools themselves were removed.
4993 l2arc_do_free_on_write();
4995 mutex_destroy(&l2arc_feed_thr_lock);
4996 cv_destroy(&l2arc_feed_thr_cv);
4997 mutex_destroy(&l2arc_dev_mtx);
4998 mutex_destroy(&l2arc_buflist_mtx);
4999 mutex_destroy(&l2arc_free_on_write_mtx);
5001 list_destroy(l2arc_dev_list);
5002 list_destroy(l2arc_free_on_write);
5008 if (!(spa_mode_global & FWRITE))
5011 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5012 TS_RUN, minclsyspri);
5018 if (!(spa_mode_global & FWRITE))
5021 mutex_enter(&l2arc_feed_thr_lock);
5022 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5023 l2arc_thread_exit = 1;
5024 while (l2arc_thread_exit != 0)
5025 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5026 mutex_exit(&l2arc_feed_thr_lock);
projects / FreeBSD / releng / 9.0.git / blob