4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 * Copyright (c) 2013 by Delphix. All rights reserved.
28 * DVA-based Adjustable Replacement Cache
30 * While much of the theory of operation used here is
31 * based on the self-tuning, low overhead replacement cache
32 * presented by Megiddo and Modha at FAST 2003, there are some
33 * significant differences:
35 * 1. The Megiddo and Modha model assumes any page is evictable.
36 * Pages in its cache cannot be "locked" into memory. This makes
37 * the eviction algorithm simple: evict the last page in the list.
38 * This also make the performance characteristics easy to reason
39 * about. Our cache is not so simple. At any given moment, some
40 * subset of the blocks in the cache are un-evictable because we
41 * have handed out a reference to them. Blocks are only evictable
42 * when there are no external references active. This makes
43 * eviction far more problematic: we choose to evict the evictable
44 * blocks that are the "lowest" in the list.
46 * There are times when it is not possible to evict the requested
47 * space. In these circumstances we are unable to adjust the cache
48 * size. To prevent the cache growing unbounded at these times we
49 * implement a "cache throttle" that slows the flow of new data
50 * into the cache until we can make space available.
52 * 2. The Megiddo and Modha model assumes a fixed cache size.
53 * Pages are evicted when the cache is full and there is a cache
54 * miss. Our model has a variable sized cache. It grows with
55 * high use, but also tries to react to memory pressure from the
56 * operating system: decreasing its size when system memory is
59 * 3. The Megiddo and Modha model assumes a fixed page size. All
60 * elements of the cache are therefor exactly the same size. So
61 * when adjusting the cache size following a cache miss, its simply
62 * a matter of choosing a single page to evict. In our model, we
63 * have variable sized cache blocks (rangeing from 512 bytes to
64 * 128K bytes). We therefor choose a set of blocks to evict to make
65 * space for a cache miss that approximates as closely as possible
66 * the space used by the new block.
68 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
69 * by N. Megiddo & D. Modha, FAST 2003
75 * A new reference to a cache buffer can be obtained in two
76 * ways: 1) via a hash table lookup using the DVA as a key,
77 * or 2) via one of the ARC lists. The arc_read() interface
78 * uses method 1, while the internal arc algorithms for
79 * adjusting the cache use method 2. We therefor provide two
80 * types of locks: 1) the hash table lock array, and 2) the
83 * Buffers do not have their own mutexs, rather they rely on the
84 * hash table mutexs for the bulk of their protection (i.e. most
85 * fields in the arc_buf_hdr_t are protected by these mutexs).
87 * buf_hash_find() returns the appropriate mutex (held) when it
88 * locates the requested buffer in the hash table. It returns
89 * NULL for the mutex if the buffer was not in the table.
91 * buf_hash_remove() expects the appropriate hash mutex to be
92 * already held before it is invoked.
94 * Each arc state also has a mutex which is used to protect the
95 * buffer list associated with the state. When attempting to
96 * obtain a hash table lock while holding an arc list lock you
97 * must use: mutex_tryenter() to avoid deadlock. Also note that
98 * the active state mutex must be held before the ghost state mutex.
100 * Arc buffers may have an associated eviction callback function.
101 * This function will be invoked prior to removing the buffer (e.g.
102 * in arc_do_user_evicts()). Note however that the data associated
103 * with the buffer may be evicted prior to the callback. The callback
104 * must be made with *no locks held* (to prevent deadlock). Additionally,
105 * the users of callbacks must ensure that their private data is
106 * protected from simultaneous callbacks from arc_buf_evict()
107 * and arc_do_user_evicts().
109 * Note that the majority of the performance stats are manipulated
110 * with atomic operations.
112 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
114 * - L2ARC buflist creation
115 * - L2ARC buflist eviction
116 * - L2ARC write completion, which walks L2ARC buflists
117 * - ARC header destruction, as it removes from L2ARC buflists
118 * - ARC header release, as it removes from L2ARC buflists
123 #include <sys/zfs_context.h>
125 #include <sys/refcount.h>
126 #include <sys/vdev.h>
127 #include <sys/vdev_impl.h>
129 #include <sys/dnlc.h>
131 #include <sys/callb.h>
132 #include <sys/kstat.h>
133 #include <sys/trim_map.h>
134 #include <zfs_fletcher.h>
137 #include <vm/vm_pageout.h>
141 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
142 boolean_t arc_watch = B_FALSE;
147 static kmutex_t arc_reclaim_thr_lock;
148 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
149 static uint8_t arc_thread_exit;
151 extern int zfs_write_limit_shift;
152 extern uint64_t zfs_write_limit_max;
153 extern kmutex_t zfs_write_limit_lock;
155 #define ARC_REDUCE_DNLC_PERCENT 3
156 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
158 typedef enum arc_reclaim_strategy {
159 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
160 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
161 } arc_reclaim_strategy_t;
163 /* number of seconds before growing cache again */
164 static int arc_grow_retry = 60;
166 /* shift of arc_c for calculating both min and max arc_p */
167 static int arc_p_min_shift = 4;
169 /* log2(fraction of arc to reclaim) */
170 static int arc_shrink_shift = 5;
173 * minimum lifespan of a prefetch block in clock ticks
174 * (initialized in arc_init())
176 static int arc_min_prefetch_lifespan;
179 extern int zfs_prefetch_disable;
182 * The arc has filled available memory and has now warmed up.
184 static boolean_t arc_warm;
187 * These tunables are for performance analysis.
189 uint64_t zfs_arc_max;
190 uint64_t zfs_arc_min;
191 uint64_t zfs_arc_meta_limit = 0;
192 int zfs_arc_grow_retry = 0;
193 int zfs_arc_shrink_shift = 0;
194 int zfs_arc_p_min_shift = 0;
195 int zfs_disable_dup_eviction = 0;
197 TUNABLE_QUAD("vfs.zfs.arc_max", &zfs_arc_max);
198 TUNABLE_QUAD("vfs.zfs.arc_min", &zfs_arc_min);
199 TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
200 SYSCTL_DECL(_vfs_zfs);
201 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_max, CTLFLAG_RDTUN, &zfs_arc_max, 0,
203 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_min, CTLFLAG_RDTUN, &zfs_arc_min, 0,
207 * Note that buffers can be in one of 6 states:
208 * ARC_anon - anonymous (discussed below)
209 * ARC_mru - recently used, currently cached
210 * ARC_mru_ghost - recentely used, no longer in cache
211 * ARC_mfu - frequently used, currently cached
212 * ARC_mfu_ghost - frequently used, no longer in cache
213 * ARC_l2c_only - exists in L2ARC but not other states
214 * When there are no active references to the buffer, they are
215 * are linked onto a list in one of these arc states. These are
216 * the only buffers that can be evicted or deleted. Within each
217 * state there are multiple lists, one for meta-data and one for
218 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
219 * etc.) is tracked separately so that it can be managed more
220 * explicitly: favored over data, limited explicitly.
222 * Anonymous buffers are buffers that are not associated with
223 * a DVA. These are buffers that hold dirty block copies
224 * before they are written to stable storage. By definition,
225 * they are "ref'd" and are considered part of arc_mru
226 * that cannot be freed. Generally, they will aquire a DVA
227 * as they are written and migrate onto the arc_mru list.
229 * The ARC_l2c_only state is for buffers that are in the second
230 * level ARC but no longer in any of the ARC_m* lists. The second
231 * level ARC itself may also contain buffers that are in any of
232 * the ARC_m* states - meaning that a buffer can exist in two
233 * places. The reason for the ARC_l2c_only state is to keep the
234 * buffer header in the hash table, so that reads that hit the
235 * second level ARC benefit from these fast lookups.
238 #define ARCS_LOCK_PAD CACHE_LINE_SIZE
242 unsigned char pad[(ARCS_LOCK_PAD - sizeof (kmutex_t))];
247 * must be power of two for mask use to work
250 #define ARC_BUFC_NUMDATALISTS 16
251 #define ARC_BUFC_NUMMETADATALISTS 16
252 #define ARC_BUFC_NUMLISTS (ARC_BUFC_NUMMETADATALISTS + ARC_BUFC_NUMDATALISTS)
254 typedef struct arc_state {
255 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
256 uint64_t arcs_size; /* total amount of data in this state */
257 list_t arcs_lists[ARC_BUFC_NUMLISTS]; /* list of evictable buffers */
258 struct arcs_lock arcs_locks[ARC_BUFC_NUMLISTS] __aligned(CACHE_LINE_SIZE);
261 #define ARCS_LOCK(s, i) (&((s)->arcs_locks[(i)].arcs_lock))
264 static arc_state_t ARC_anon;
265 static arc_state_t ARC_mru;
266 static arc_state_t ARC_mru_ghost;
267 static arc_state_t ARC_mfu;
268 static arc_state_t ARC_mfu_ghost;
269 static arc_state_t ARC_l2c_only;
271 typedef struct arc_stats {
272 kstat_named_t arcstat_hits;
273 kstat_named_t arcstat_misses;
274 kstat_named_t arcstat_demand_data_hits;
275 kstat_named_t arcstat_demand_data_misses;
276 kstat_named_t arcstat_demand_metadata_hits;
277 kstat_named_t arcstat_demand_metadata_misses;
278 kstat_named_t arcstat_prefetch_data_hits;
279 kstat_named_t arcstat_prefetch_data_misses;
280 kstat_named_t arcstat_prefetch_metadata_hits;
281 kstat_named_t arcstat_prefetch_metadata_misses;
282 kstat_named_t arcstat_mru_hits;
283 kstat_named_t arcstat_mru_ghost_hits;
284 kstat_named_t arcstat_mfu_hits;
285 kstat_named_t arcstat_mfu_ghost_hits;
286 kstat_named_t arcstat_allocated;
287 kstat_named_t arcstat_deleted;
288 kstat_named_t arcstat_stolen;
289 kstat_named_t arcstat_recycle_miss;
290 kstat_named_t arcstat_mutex_miss;
291 kstat_named_t arcstat_evict_skip;
292 kstat_named_t arcstat_evict_l2_cached;
293 kstat_named_t arcstat_evict_l2_eligible;
294 kstat_named_t arcstat_evict_l2_ineligible;
295 kstat_named_t arcstat_hash_elements;
296 kstat_named_t arcstat_hash_elements_max;
297 kstat_named_t arcstat_hash_collisions;
298 kstat_named_t arcstat_hash_chains;
299 kstat_named_t arcstat_hash_chain_max;
300 kstat_named_t arcstat_p;
301 kstat_named_t arcstat_c;
302 kstat_named_t arcstat_c_min;
303 kstat_named_t arcstat_c_max;
304 kstat_named_t arcstat_size;
305 kstat_named_t arcstat_hdr_size;
306 kstat_named_t arcstat_data_size;
307 kstat_named_t arcstat_other_size;
308 kstat_named_t arcstat_l2_hits;
309 kstat_named_t arcstat_l2_misses;
310 kstat_named_t arcstat_l2_feeds;
311 kstat_named_t arcstat_l2_rw_clash;
312 kstat_named_t arcstat_l2_read_bytes;
313 kstat_named_t arcstat_l2_write_bytes;
314 kstat_named_t arcstat_l2_writes_sent;
315 kstat_named_t arcstat_l2_writes_done;
316 kstat_named_t arcstat_l2_writes_error;
317 kstat_named_t arcstat_l2_writes_hdr_miss;
318 kstat_named_t arcstat_l2_evict_lock_retry;
319 kstat_named_t arcstat_l2_evict_reading;
320 kstat_named_t arcstat_l2_free_on_write;
321 kstat_named_t arcstat_l2_abort_lowmem;
322 kstat_named_t arcstat_l2_cksum_bad;
323 kstat_named_t arcstat_l2_io_error;
324 kstat_named_t arcstat_l2_size;
325 kstat_named_t arcstat_l2_hdr_size;
326 kstat_named_t arcstat_l2_write_trylock_fail;
327 kstat_named_t arcstat_l2_write_passed_headroom;
328 kstat_named_t arcstat_l2_write_spa_mismatch;
329 kstat_named_t arcstat_l2_write_in_l2;
330 kstat_named_t arcstat_l2_write_hdr_io_in_progress;
331 kstat_named_t arcstat_l2_write_not_cacheable;
332 kstat_named_t arcstat_l2_write_full;
333 kstat_named_t arcstat_l2_write_buffer_iter;
334 kstat_named_t arcstat_l2_write_pios;
335 kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
336 kstat_named_t arcstat_l2_write_buffer_list_iter;
337 kstat_named_t arcstat_l2_write_buffer_list_null_iter;
338 kstat_named_t arcstat_memory_throttle_count;
339 kstat_named_t arcstat_duplicate_buffers;
340 kstat_named_t arcstat_duplicate_buffers_size;
341 kstat_named_t arcstat_duplicate_reads;
344 static arc_stats_t arc_stats = {
345 { "hits", KSTAT_DATA_UINT64 },
346 { "misses", KSTAT_DATA_UINT64 },
347 { "demand_data_hits", KSTAT_DATA_UINT64 },
348 { "demand_data_misses", KSTAT_DATA_UINT64 },
349 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
350 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
351 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
352 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
353 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
354 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
355 { "mru_hits", KSTAT_DATA_UINT64 },
356 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
357 { "mfu_hits", KSTAT_DATA_UINT64 },
358 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
359 { "allocated", KSTAT_DATA_UINT64 },
360 { "deleted", KSTAT_DATA_UINT64 },
361 { "stolen", KSTAT_DATA_UINT64 },
362 { "recycle_miss", KSTAT_DATA_UINT64 },
363 { "mutex_miss", KSTAT_DATA_UINT64 },
364 { "evict_skip", KSTAT_DATA_UINT64 },
365 { "evict_l2_cached", KSTAT_DATA_UINT64 },
366 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
367 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
368 { "hash_elements", KSTAT_DATA_UINT64 },
369 { "hash_elements_max", KSTAT_DATA_UINT64 },
370 { "hash_collisions", KSTAT_DATA_UINT64 },
371 { "hash_chains", KSTAT_DATA_UINT64 },
372 { "hash_chain_max", KSTAT_DATA_UINT64 },
373 { "p", KSTAT_DATA_UINT64 },
374 { "c", KSTAT_DATA_UINT64 },
375 { "c_min", KSTAT_DATA_UINT64 },
376 { "c_max", KSTAT_DATA_UINT64 },
377 { "size", KSTAT_DATA_UINT64 },
378 { "hdr_size", KSTAT_DATA_UINT64 },
379 { "data_size", KSTAT_DATA_UINT64 },
380 { "other_size", KSTAT_DATA_UINT64 },
381 { "l2_hits", KSTAT_DATA_UINT64 },
382 { "l2_misses", KSTAT_DATA_UINT64 },
383 { "l2_feeds", KSTAT_DATA_UINT64 },
384 { "l2_rw_clash", KSTAT_DATA_UINT64 },
385 { "l2_read_bytes", KSTAT_DATA_UINT64 },
386 { "l2_write_bytes", KSTAT_DATA_UINT64 },
387 { "l2_writes_sent", KSTAT_DATA_UINT64 },
388 { "l2_writes_done", KSTAT_DATA_UINT64 },
389 { "l2_writes_error", KSTAT_DATA_UINT64 },
390 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
391 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
392 { "l2_evict_reading", KSTAT_DATA_UINT64 },
393 { "l2_free_on_write", KSTAT_DATA_UINT64 },
394 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
395 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
396 { "l2_io_error", KSTAT_DATA_UINT64 },
397 { "l2_size", KSTAT_DATA_UINT64 },
398 { "l2_hdr_size", KSTAT_DATA_UINT64 },
399 { "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
400 { "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
401 { "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
402 { "l2_write_in_l2", KSTAT_DATA_UINT64 },
403 { "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
404 { "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
405 { "l2_write_full", KSTAT_DATA_UINT64 },
406 { "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
407 { "l2_write_pios", KSTAT_DATA_UINT64 },
408 { "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
409 { "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
410 { "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
411 { "memory_throttle_count", KSTAT_DATA_UINT64 },
412 { "duplicate_buffers", KSTAT_DATA_UINT64 },
413 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
414 { "duplicate_reads", KSTAT_DATA_UINT64 }
417 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
419 #define ARCSTAT_INCR(stat, val) \
420 atomic_add_64(&arc_stats.stat.value.ui64, (val));
422 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
423 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
425 #define ARCSTAT_MAX(stat, val) { \
427 while ((val) > (m = arc_stats.stat.value.ui64) && \
428 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
432 #define ARCSTAT_MAXSTAT(stat) \
433 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
436 * We define a macro to allow ARC hits/misses to be easily broken down by
437 * two separate conditions, giving a total of four different subtypes for
438 * each of hits and misses (so eight statistics total).
440 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
443 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
445 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
449 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
451 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
456 static arc_state_t *arc_anon;
457 static arc_state_t *arc_mru;
458 static arc_state_t *arc_mru_ghost;
459 static arc_state_t *arc_mfu;
460 static arc_state_t *arc_mfu_ghost;
461 static arc_state_t *arc_l2c_only;
464 * There are several ARC variables that are critical to export as kstats --
465 * but we don't want to have to grovel around in the kstat whenever we wish to
466 * manipulate them. For these variables, we therefore define them to be in
467 * terms of the statistic variable. This assures that we are not introducing
468 * the possibility of inconsistency by having shadow copies of the variables,
469 * while still allowing the code to be readable.
471 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
472 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
473 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
474 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
475 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
477 static int arc_no_grow; /* Don't try to grow cache size */
478 static uint64_t arc_tempreserve;
479 static uint64_t arc_loaned_bytes;
480 static uint64_t arc_meta_used;
481 static uint64_t arc_meta_limit;
482 static uint64_t arc_meta_max = 0;
483 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_used, CTLFLAG_RDTUN,
484 &arc_meta_used, 0, "ARC metadata used");
485 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_meta_limit, CTLFLAG_RDTUN,
486 &arc_meta_limit, 0, "ARC metadata limit");
488 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
490 typedef struct arc_callback arc_callback_t;
492 struct arc_callback {
494 arc_done_func_t *acb_done;
496 zio_t *acb_zio_dummy;
497 arc_callback_t *acb_next;
500 typedef struct arc_write_callback arc_write_callback_t;
502 struct arc_write_callback {
504 arc_done_func_t *awcb_ready;
505 arc_done_func_t *awcb_done;
510 /* protected by hash lock */
515 kmutex_t b_freeze_lock;
516 zio_cksum_t *b_freeze_cksum;
519 arc_buf_hdr_t *b_hash_next;
524 arc_callback_t *b_acb;
528 arc_buf_contents_t b_type;
532 /* protected by arc state mutex */
533 arc_state_t *b_state;
534 list_node_t b_arc_node;
536 /* updated atomically */
537 clock_t b_arc_access;
539 /* self protecting */
542 l2arc_buf_hdr_t *b_l2hdr;
543 list_node_t b_l2node;
546 static arc_buf_t *arc_eviction_list;
547 static kmutex_t arc_eviction_mtx;
548 static arc_buf_hdr_t arc_eviction_hdr;
549 static void arc_get_data_buf(arc_buf_t *buf);
550 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
551 static int arc_evict_needed(arc_buf_contents_t type);
552 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
554 static void arc_buf_watch(arc_buf_t *buf);
557 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
559 #define GHOST_STATE(state) \
560 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
561 (state) == arc_l2c_only)
564 * Private ARC flags. These flags are private ARC only flags that will show up
565 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
566 * be passed in as arc_flags in things like arc_read. However, these flags
567 * should never be passed and should only be set by ARC code. When adding new
568 * public flags, make sure not to smash the private ones.
571 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
572 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
573 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
574 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
575 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
576 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
577 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
578 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
579 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
580 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
582 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
583 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
584 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
585 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
586 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
587 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
588 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
589 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
590 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
591 (hdr)->b_l2hdr != NULL)
592 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
593 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
594 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
600 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
601 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
604 * Hash table routines
607 #define HT_LOCK_PAD CACHE_LINE_SIZE
612 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
616 #define BUF_LOCKS 256
617 typedef struct buf_hash_table {
619 arc_buf_hdr_t **ht_table;
620 struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
623 static buf_hash_table_t buf_hash_table;
625 #define BUF_HASH_INDEX(spa, dva, birth) \
626 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
627 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
628 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
629 #define HDR_LOCK(hdr) \
630 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
632 uint64_t zfs_crc64_table[256];
638 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
639 #define L2ARC_HEADROOM 2 /* num of writes */
640 #define L2ARC_FEED_SECS 1 /* caching interval secs */
641 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
643 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
644 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
647 * L2ARC Performance Tunables
649 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
650 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
651 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
652 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
653 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
654 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
655 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
656 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
658 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
659 &l2arc_write_max, 0, "max write size");
660 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
661 &l2arc_write_boost, 0, "extra write during warmup");
662 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
663 &l2arc_headroom, 0, "number of dev writes");
664 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
665 &l2arc_feed_secs, 0, "interval seconds");
666 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
667 &l2arc_feed_min_ms, 0, "min interval milliseconds");
669 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
670 &l2arc_noprefetch, 0, "don't cache prefetch bufs");
671 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
672 &l2arc_feed_again, 0, "turbo warmup");
673 SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
674 &l2arc_norw, 0, "no reads during writes");
676 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
677 &ARC_anon.arcs_size, 0, "size of anonymous state");
678 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_lsize, CTLFLAG_RD,
679 &ARC_anon.arcs_lsize[ARC_BUFC_METADATA], 0, "size of anonymous state");
680 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_lsize, CTLFLAG_RD,
681 &ARC_anon.arcs_lsize[ARC_BUFC_DATA], 0, "size of anonymous state");
683 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
684 &ARC_mru.arcs_size, 0, "size of mru state");
685 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_lsize, CTLFLAG_RD,
686 &ARC_mru.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mru state");
687 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_lsize, CTLFLAG_RD,
688 &ARC_mru.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mru state");
690 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
691 &ARC_mru_ghost.arcs_size, 0, "size of mru ghost state");
692 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_lsize, CTLFLAG_RD,
693 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
694 "size of metadata in mru ghost state");
695 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_lsize, CTLFLAG_RD,
696 &ARC_mru_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
697 "size of data in mru ghost state");
699 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
700 &ARC_mfu.arcs_size, 0, "size of mfu state");
701 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_lsize, CTLFLAG_RD,
702 &ARC_mfu.arcs_lsize[ARC_BUFC_METADATA], 0, "size of metadata in mfu state");
703 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_lsize, CTLFLAG_RD,
704 &ARC_mfu.arcs_lsize[ARC_BUFC_DATA], 0, "size of data in mfu state");
706 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
707 &ARC_mfu_ghost.arcs_size, 0, "size of mfu ghost state");
708 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_lsize, CTLFLAG_RD,
709 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_METADATA], 0,
710 "size of metadata in mfu ghost state");
711 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_lsize, CTLFLAG_RD,
712 &ARC_mfu_ghost.arcs_lsize[ARC_BUFC_DATA], 0,
713 "size of data in mfu ghost state");
715 SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
716 &ARC_l2c_only.arcs_size, 0, "size of mru state");
721 typedef struct l2arc_dev {
722 vdev_t *l2ad_vdev; /* vdev */
723 spa_t *l2ad_spa; /* spa */
724 uint64_t l2ad_hand; /* next write location */
725 uint64_t l2ad_write; /* desired write size, bytes */
726 uint64_t l2ad_boost; /* warmup write boost, bytes */
727 uint64_t l2ad_start; /* first addr on device */
728 uint64_t l2ad_end; /* last addr on device */
729 uint64_t l2ad_evict; /* last addr eviction reached */
730 boolean_t l2ad_first; /* first sweep through */
731 boolean_t l2ad_writing; /* currently writing */
732 list_t *l2ad_buflist; /* buffer list */
733 list_node_t l2ad_node; /* device list node */
736 static list_t L2ARC_dev_list; /* device list */
737 static list_t *l2arc_dev_list; /* device list pointer */
738 static kmutex_t l2arc_dev_mtx; /* device list mutex */
739 static l2arc_dev_t *l2arc_dev_last; /* last device used */
740 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
741 static list_t L2ARC_free_on_write; /* free after write buf list */
742 static list_t *l2arc_free_on_write; /* free after write list ptr */
743 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
744 static uint64_t l2arc_ndev; /* number of devices */
746 typedef struct l2arc_read_callback {
747 arc_buf_t *l2rcb_buf; /* read buffer */
748 spa_t *l2rcb_spa; /* spa */
749 blkptr_t l2rcb_bp; /* original blkptr */
750 zbookmark_t l2rcb_zb; /* original bookmark */
751 int l2rcb_flags; /* original flags */
752 } l2arc_read_callback_t;
754 typedef struct l2arc_write_callback {
755 l2arc_dev_t *l2wcb_dev; /* device info */
756 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
757 } l2arc_write_callback_t;
759 struct l2arc_buf_hdr {
760 /* protected by arc_buf_hdr mutex */
761 l2arc_dev_t *b_dev; /* L2ARC device */
762 uint64_t b_daddr; /* disk address, offset byte */
765 typedef struct l2arc_data_free {
766 /* protected by l2arc_free_on_write_mtx */
769 void (*l2df_func)(void *, size_t);
770 list_node_t l2df_list_node;
773 static kmutex_t l2arc_feed_thr_lock;
774 static kcondvar_t l2arc_feed_thr_cv;
775 static uint8_t l2arc_thread_exit;
777 static void l2arc_read_done(zio_t *zio);
778 static void l2arc_hdr_stat_add(void);
779 static void l2arc_hdr_stat_remove(void);
782 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
784 uint8_t *vdva = (uint8_t *)dva;
785 uint64_t crc = -1ULL;
788 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
790 for (i = 0; i < sizeof (dva_t); i++)
791 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
793 crc ^= (spa>>8) ^ birth;
798 #define BUF_EMPTY(buf) \
799 ((buf)->b_dva.dva_word[0] == 0 && \
800 (buf)->b_dva.dva_word[1] == 0 && \
803 #define BUF_EQUAL(spa, dva, birth, buf) \
804 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
805 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
806 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
809 buf_discard_identity(arc_buf_hdr_t *hdr)
811 hdr->b_dva.dva_word[0] = 0;
812 hdr->b_dva.dva_word[1] = 0;
817 static arc_buf_hdr_t *
818 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
820 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
821 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
824 mutex_enter(hash_lock);
825 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
826 buf = buf->b_hash_next) {
827 if (BUF_EQUAL(spa, dva, birth, buf)) {
832 mutex_exit(hash_lock);
838 * Insert an entry into the hash table. If there is already an element
839 * equal to elem in the hash table, then the already existing element
840 * will be returned and the new element will not be inserted.
841 * Otherwise returns NULL.
843 static arc_buf_hdr_t *
844 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
846 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
847 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
851 ASSERT(!HDR_IN_HASH_TABLE(buf));
853 mutex_enter(hash_lock);
854 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
855 fbuf = fbuf->b_hash_next, i++) {
856 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
860 buf->b_hash_next = buf_hash_table.ht_table[idx];
861 buf_hash_table.ht_table[idx] = buf;
862 buf->b_flags |= ARC_IN_HASH_TABLE;
864 /* collect some hash table performance data */
866 ARCSTAT_BUMP(arcstat_hash_collisions);
868 ARCSTAT_BUMP(arcstat_hash_chains);
870 ARCSTAT_MAX(arcstat_hash_chain_max, i);
873 ARCSTAT_BUMP(arcstat_hash_elements);
874 ARCSTAT_MAXSTAT(arcstat_hash_elements);
880 buf_hash_remove(arc_buf_hdr_t *buf)
882 arc_buf_hdr_t *fbuf, **bufp;
883 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
885 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
886 ASSERT(HDR_IN_HASH_TABLE(buf));
888 bufp = &buf_hash_table.ht_table[idx];
889 while ((fbuf = *bufp) != buf) {
890 ASSERT(fbuf != NULL);
891 bufp = &fbuf->b_hash_next;
893 *bufp = buf->b_hash_next;
894 buf->b_hash_next = NULL;
895 buf->b_flags &= ~ARC_IN_HASH_TABLE;
897 /* collect some hash table performance data */
898 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
900 if (buf_hash_table.ht_table[idx] &&
901 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
902 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
906 * Global data structures and functions for the buf kmem cache.
908 static kmem_cache_t *hdr_cache;
909 static kmem_cache_t *buf_cache;
916 kmem_free(buf_hash_table.ht_table,
917 (buf_hash_table.ht_mask + 1) * sizeof (void *));
918 for (i = 0; i < BUF_LOCKS; i++)
919 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
920 kmem_cache_destroy(hdr_cache);
921 kmem_cache_destroy(buf_cache);
925 * Constructor callback - called when the cache is empty
926 * and a new buf is requested.
930 hdr_cons(void *vbuf, void *unused, int kmflag)
932 arc_buf_hdr_t *buf = vbuf;
934 bzero(buf, sizeof (arc_buf_hdr_t));
935 refcount_create(&buf->b_refcnt);
936 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
937 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
938 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
945 buf_cons(void *vbuf, void *unused, int kmflag)
947 arc_buf_t *buf = vbuf;
949 bzero(buf, sizeof (arc_buf_t));
950 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
951 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
957 * Destructor callback - called when a cached buf is
958 * no longer required.
962 hdr_dest(void *vbuf, void *unused)
964 arc_buf_hdr_t *buf = vbuf;
966 ASSERT(BUF_EMPTY(buf));
967 refcount_destroy(&buf->b_refcnt);
968 cv_destroy(&buf->b_cv);
969 mutex_destroy(&buf->b_freeze_lock);
970 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
975 buf_dest(void *vbuf, void *unused)
977 arc_buf_t *buf = vbuf;
979 mutex_destroy(&buf->b_evict_lock);
980 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
984 * Reclaim callback -- invoked when memory is low.
988 hdr_recl(void *unused)
990 dprintf("hdr_recl called\n");
992 * umem calls the reclaim func when we destroy the buf cache,
993 * which is after we do arc_fini().
996 cv_signal(&arc_reclaim_thr_cv);
1003 uint64_t hsize = 1ULL << 12;
1007 * The hash table is big enough to fill all of physical memory
1008 * with an average 64K block size. The table will take up
1009 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
1011 while (hsize * 65536 < (uint64_t)physmem * PAGESIZE)
1014 buf_hash_table.ht_mask = hsize - 1;
1015 buf_hash_table.ht_table =
1016 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1017 if (buf_hash_table.ht_table == NULL) {
1018 ASSERT(hsize > (1ULL << 8));
1023 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
1024 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
1025 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1026 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1028 for (i = 0; i < 256; i++)
1029 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1030 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1032 for (i = 0; i < BUF_LOCKS; i++) {
1033 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1034 NULL, MUTEX_DEFAULT, NULL);
1038 #define ARC_MINTIME (hz>>4) /* 62 ms */
1041 arc_cksum_verify(arc_buf_t *buf)
1045 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1048 mutex_enter(&buf->b_hdr->b_freeze_lock);
1049 if (buf->b_hdr->b_freeze_cksum == NULL ||
1050 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1051 mutex_exit(&buf->b_hdr->b_freeze_lock);
1054 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1055 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1056 panic("buffer modified while frozen!");
1057 mutex_exit(&buf->b_hdr->b_freeze_lock);
1061 arc_cksum_equal(arc_buf_t *buf)
1066 mutex_enter(&buf->b_hdr->b_freeze_lock);
1067 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1068 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1069 mutex_exit(&buf->b_hdr->b_freeze_lock);
1075 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1077 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1080 mutex_enter(&buf->b_hdr->b_freeze_lock);
1081 if (buf->b_hdr->b_freeze_cksum != NULL) {
1082 mutex_exit(&buf->b_hdr->b_freeze_lock);
1085 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1086 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1087 buf->b_hdr->b_freeze_cksum);
1088 mutex_exit(&buf->b_hdr->b_freeze_lock);
1091 #endif /* illumos */
1096 typedef struct procctl {
1104 arc_buf_unwatch(arc_buf_t *buf)
1111 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1112 ctl.prwatch.pr_size = 0;
1113 ctl.prwatch.pr_wflags = 0;
1114 result = write(arc_procfd, &ctl, sizeof (ctl));
1115 ASSERT3U(result, ==, sizeof (ctl));
1122 arc_buf_watch(arc_buf_t *buf)
1129 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1130 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1131 ctl.prwatch.pr_wflags = WA_WRITE;
1132 result = write(arc_procfd, &ctl, sizeof (ctl));
1133 ASSERT3U(result, ==, sizeof (ctl));
1137 #endif /* illumos */
1140 arc_buf_thaw(arc_buf_t *buf)
1142 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1143 if (buf->b_hdr->b_state != arc_anon)
1144 panic("modifying non-anon buffer!");
1145 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1146 panic("modifying buffer while i/o in progress!");
1147 arc_cksum_verify(buf);
1150 mutex_enter(&buf->b_hdr->b_freeze_lock);
1151 if (buf->b_hdr->b_freeze_cksum != NULL) {
1152 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1153 buf->b_hdr->b_freeze_cksum = NULL;
1156 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1157 if (buf->b_hdr->b_thawed)
1158 kmem_free(buf->b_hdr->b_thawed, 1);
1159 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1162 mutex_exit(&buf->b_hdr->b_freeze_lock);
1165 arc_buf_unwatch(buf);
1166 #endif /* illumos */
1170 arc_buf_freeze(arc_buf_t *buf)
1172 kmutex_t *hash_lock;
1174 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1177 hash_lock = HDR_LOCK(buf->b_hdr);
1178 mutex_enter(hash_lock);
1180 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1181 buf->b_hdr->b_state == arc_anon);
1182 arc_cksum_compute(buf, B_FALSE);
1183 mutex_exit(hash_lock);
1188 get_buf_info(arc_buf_hdr_t *ab, arc_state_t *state, list_t **list, kmutex_t **lock)
1190 uint64_t buf_hashid = buf_hash(ab->b_spa, &ab->b_dva, ab->b_birth);
1192 if (ab->b_type == ARC_BUFC_METADATA)
1193 buf_hashid &= (ARC_BUFC_NUMMETADATALISTS - 1);
1195 buf_hashid &= (ARC_BUFC_NUMDATALISTS - 1);
1196 buf_hashid += ARC_BUFC_NUMMETADATALISTS;
1199 *list = &state->arcs_lists[buf_hashid];
1200 *lock = ARCS_LOCK(state, buf_hashid);
1205 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1207 ASSERT(MUTEX_HELD(hash_lock));
1209 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1210 (ab->b_state != arc_anon)) {
1211 uint64_t delta = ab->b_size * ab->b_datacnt;
1212 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1216 get_buf_info(ab, ab->b_state, &list, &lock);
1217 ASSERT(!MUTEX_HELD(lock));
1219 ASSERT(list_link_active(&ab->b_arc_node));
1220 list_remove(list, ab);
1221 if (GHOST_STATE(ab->b_state)) {
1222 ASSERT0(ab->b_datacnt);
1223 ASSERT3P(ab->b_buf, ==, NULL);
1227 ASSERT3U(*size, >=, delta);
1228 atomic_add_64(size, -delta);
1230 /* remove the prefetch flag if we get a reference */
1231 if (ab->b_flags & ARC_PREFETCH)
1232 ab->b_flags &= ~ARC_PREFETCH;
1237 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1240 arc_state_t *state = ab->b_state;
1242 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1243 ASSERT(!GHOST_STATE(state));
1245 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1246 (state != arc_anon)) {
1247 uint64_t *size = &state->arcs_lsize[ab->b_type];
1251 get_buf_info(ab, state, &list, &lock);
1252 ASSERT(!MUTEX_HELD(lock));
1254 ASSERT(!list_link_active(&ab->b_arc_node));
1255 list_insert_head(list, ab);
1256 ASSERT(ab->b_datacnt > 0);
1257 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1264 * Move the supplied buffer to the indicated state. The mutex
1265 * for the buffer must be held by the caller.
1268 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1270 arc_state_t *old_state = ab->b_state;
1271 int64_t refcnt = refcount_count(&ab->b_refcnt);
1272 uint64_t from_delta, to_delta;
1276 ASSERT(MUTEX_HELD(hash_lock));
1277 ASSERT(new_state != old_state);
1278 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1279 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1280 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1282 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1285 * If this buffer is evictable, transfer it from the
1286 * old state list to the new state list.
1289 if (old_state != arc_anon) {
1291 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1293 get_buf_info(ab, old_state, &list, &lock);
1294 use_mutex = !MUTEX_HELD(lock);
1298 ASSERT(list_link_active(&ab->b_arc_node));
1299 list_remove(list, ab);
1302 * If prefetching out of the ghost cache,
1303 * we will have a non-zero datacnt.
1305 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1306 /* ghost elements have a ghost size */
1307 ASSERT(ab->b_buf == NULL);
1308 from_delta = ab->b_size;
1310 ASSERT3U(*size, >=, from_delta);
1311 atomic_add_64(size, -from_delta);
1316 if (new_state != arc_anon) {
1318 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1320 get_buf_info(ab, new_state, &list, &lock);
1321 use_mutex = !MUTEX_HELD(lock);
1325 list_insert_head(list, ab);
1327 /* ghost elements have a ghost size */
1328 if (GHOST_STATE(new_state)) {
1329 ASSERT(ab->b_datacnt == 0);
1330 ASSERT(ab->b_buf == NULL);
1331 to_delta = ab->b_size;
1333 atomic_add_64(size, to_delta);
1340 ASSERT(!BUF_EMPTY(ab));
1341 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1342 buf_hash_remove(ab);
1344 /* adjust state sizes */
1346 atomic_add_64(&new_state->arcs_size, to_delta);
1348 ASSERT3U(old_state->arcs_size, >=, from_delta);
1349 atomic_add_64(&old_state->arcs_size, -from_delta);
1351 ab->b_state = new_state;
1353 /* adjust l2arc hdr stats */
1354 if (new_state == arc_l2c_only)
1355 l2arc_hdr_stat_add();
1356 else if (old_state == arc_l2c_only)
1357 l2arc_hdr_stat_remove();
1361 arc_space_consume(uint64_t space, arc_space_type_t type)
1363 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1366 case ARC_SPACE_DATA:
1367 ARCSTAT_INCR(arcstat_data_size, space);
1369 case ARC_SPACE_OTHER:
1370 ARCSTAT_INCR(arcstat_other_size, space);
1372 case ARC_SPACE_HDRS:
1373 ARCSTAT_INCR(arcstat_hdr_size, space);
1375 case ARC_SPACE_L2HDRS:
1376 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1380 atomic_add_64(&arc_meta_used, space);
1381 atomic_add_64(&arc_size, space);
1385 arc_space_return(uint64_t space, arc_space_type_t type)
1387 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1390 case ARC_SPACE_DATA:
1391 ARCSTAT_INCR(arcstat_data_size, -space);
1393 case ARC_SPACE_OTHER:
1394 ARCSTAT_INCR(arcstat_other_size, -space);
1396 case ARC_SPACE_HDRS:
1397 ARCSTAT_INCR(arcstat_hdr_size, -space);
1399 case ARC_SPACE_L2HDRS:
1400 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1404 ASSERT(arc_meta_used >= space);
1405 if (arc_meta_max < arc_meta_used)
1406 arc_meta_max = arc_meta_used;
1407 atomic_add_64(&arc_meta_used, -space);
1408 ASSERT(arc_size >= space);
1409 atomic_add_64(&arc_size, -space);
1413 arc_data_buf_alloc(uint64_t size)
1415 if (arc_evict_needed(ARC_BUFC_DATA))
1416 cv_signal(&arc_reclaim_thr_cv);
1417 atomic_add_64(&arc_size, size);
1418 return (zio_data_buf_alloc(size));
1422 arc_data_buf_free(void *buf, uint64_t size)
1424 zio_data_buf_free(buf, size);
1425 ASSERT(arc_size >= size);
1426 atomic_add_64(&arc_size, -size);
1430 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1435 ASSERT3U(size, >, 0);
1436 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1437 ASSERT(BUF_EMPTY(hdr));
1440 hdr->b_spa = spa_load_guid(spa);
1441 hdr->b_state = arc_anon;
1442 hdr->b_arc_access = 0;
1443 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1446 buf->b_efunc = NULL;
1447 buf->b_private = NULL;
1450 arc_get_data_buf(buf);
1453 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1454 (void) refcount_add(&hdr->b_refcnt, tag);
1459 static char *arc_onloan_tag = "onloan";
1462 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1463 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1464 * buffers must be returned to the arc before they can be used by the DMU or
1468 arc_loan_buf(spa_t *spa, int size)
1472 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1474 atomic_add_64(&arc_loaned_bytes, size);
1479 * Return a loaned arc buffer to the arc.
1482 arc_return_buf(arc_buf_t *buf, void *tag)
1484 arc_buf_hdr_t *hdr = buf->b_hdr;
1486 ASSERT(buf->b_data != NULL);
1487 (void) refcount_add(&hdr->b_refcnt, tag);
1488 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1490 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1493 /* Detach an arc_buf from a dbuf (tag) */
1495 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1499 ASSERT(buf->b_data != NULL);
1501 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1502 (void) refcount_remove(&hdr->b_refcnt, tag);
1503 buf->b_efunc = NULL;
1504 buf->b_private = NULL;
1506 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1510 arc_buf_clone(arc_buf_t *from)
1513 arc_buf_hdr_t *hdr = from->b_hdr;
1514 uint64_t size = hdr->b_size;
1516 ASSERT(hdr->b_state != arc_anon);
1518 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1521 buf->b_efunc = NULL;
1522 buf->b_private = NULL;
1523 buf->b_next = hdr->b_buf;
1525 arc_get_data_buf(buf);
1526 bcopy(from->b_data, buf->b_data, size);
1529 * This buffer already exists in the arc so create a duplicate
1530 * copy for the caller. If the buffer is associated with user data
1531 * then track the size and number of duplicates. These stats will be
1532 * updated as duplicate buffers are created and destroyed.
1534 if (hdr->b_type == ARC_BUFC_DATA) {
1535 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1536 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1538 hdr->b_datacnt += 1;
1543 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1546 kmutex_t *hash_lock;
1549 * Check to see if this buffer is evicted. Callers
1550 * must verify b_data != NULL to know if the add_ref
1553 mutex_enter(&buf->b_evict_lock);
1554 if (buf->b_data == NULL) {
1555 mutex_exit(&buf->b_evict_lock);
1558 hash_lock = HDR_LOCK(buf->b_hdr);
1559 mutex_enter(hash_lock);
1561 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1562 mutex_exit(&buf->b_evict_lock);
1564 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1565 add_reference(hdr, hash_lock, tag);
1566 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1567 arc_access(hdr, hash_lock);
1568 mutex_exit(hash_lock);
1569 ARCSTAT_BUMP(arcstat_hits);
1570 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1571 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1572 data, metadata, hits);
1576 * Free the arc data buffer. If it is an l2arc write in progress,
1577 * the buffer is placed on l2arc_free_on_write to be freed later.
1580 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1582 arc_buf_hdr_t *hdr = buf->b_hdr;
1584 if (HDR_L2_WRITING(hdr)) {
1585 l2arc_data_free_t *df;
1586 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1587 df->l2df_data = buf->b_data;
1588 df->l2df_size = hdr->b_size;
1589 df->l2df_func = free_func;
1590 mutex_enter(&l2arc_free_on_write_mtx);
1591 list_insert_head(l2arc_free_on_write, df);
1592 mutex_exit(&l2arc_free_on_write_mtx);
1593 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1595 free_func(buf->b_data, hdr->b_size);
1600 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1604 /* free up data associated with the buf */
1606 arc_state_t *state = buf->b_hdr->b_state;
1607 uint64_t size = buf->b_hdr->b_size;
1608 arc_buf_contents_t type = buf->b_hdr->b_type;
1610 arc_cksum_verify(buf);
1612 arc_buf_unwatch(buf);
1613 #endif /* illumos */
1616 if (type == ARC_BUFC_METADATA) {
1617 arc_buf_data_free(buf, zio_buf_free);
1618 arc_space_return(size, ARC_SPACE_DATA);
1620 ASSERT(type == ARC_BUFC_DATA);
1621 arc_buf_data_free(buf, zio_data_buf_free);
1622 ARCSTAT_INCR(arcstat_data_size, -size);
1623 atomic_add_64(&arc_size, -size);
1626 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1627 uint64_t *cnt = &state->arcs_lsize[type];
1629 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1630 ASSERT(state != arc_anon);
1632 ASSERT3U(*cnt, >=, size);
1633 atomic_add_64(cnt, -size);
1635 ASSERT3U(state->arcs_size, >=, size);
1636 atomic_add_64(&state->arcs_size, -size);
1640 * If we're destroying a duplicate buffer make sure
1641 * that the appropriate statistics are updated.
1643 if (buf->b_hdr->b_datacnt > 1 &&
1644 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1645 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1646 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1648 ASSERT(buf->b_hdr->b_datacnt > 0);
1649 buf->b_hdr->b_datacnt -= 1;
1652 /* only remove the buf if requested */
1656 /* remove the buf from the hdr list */
1657 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1659 *bufp = buf->b_next;
1662 ASSERT(buf->b_efunc == NULL);
1664 /* clean up the buf */
1666 kmem_cache_free(buf_cache, buf);
1670 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1672 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1673 ASSERT3P(hdr->b_state, ==, arc_anon);
1674 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1675 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1677 if (l2hdr != NULL) {
1678 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1680 * To prevent arc_free() and l2arc_evict() from
1681 * attempting to free the same buffer at the same time,
1682 * a FREE_IN_PROGRESS flag is given to arc_free() to
1683 * give it priority. l2arc_evict() can't destroy this
1684 * header while we are waiting on l2arc_buflist_mtx.
1686 * The hdr may be removed from l2ad_buflist before we
1687 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1689 if (!buflist_held) {
1690 mutex_enter(&l2arc_buflist_mtx);
1691 l2hdr = hdr->b_l2hdr;
1694 if (l2hdr != NULL) {
1695 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
1697 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1698 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1699 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1700 if (hdr->b_state == arc_l2c_only)
1701 l2arc_hdr_stat_remove();
1702 hdr->b_l2hdr = NULL;
1706 mutex_exit(&l2arc_buflist_mtx);
1709 if (!BUF_EMPTY(hdr)) {
1710 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1711 buf_discard_identity(hdr);
1713 while (hdr->b_buf) {
1714 arc_buf_t *buf = hdr->b_buf;
1717 mutex_enter(&arc_eviction_mtx);
1718 mutex_enter(&buf->b_evict_lock);
1719 ASSERT(buf->b_hdr != NULL);
1720 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1721 hdr->b_buf = buf->b_next;
1722 buf->b_hdr = &arc_eviction_hdr;
1723 buf->b_next = arc_eviction_list;
1724 arc_eviction_list = buf;
1725 mutex_exit(&buf->b_evict_lock);
1726 mutex_exit(&arc_eviction_mtx);
1728 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1731 if (hdr->b_freeze_cksum != NULL) {
1732 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1733 hdr->b_freeze_cksum = NULL;
1735 if (hdr->b_thawed) {
1736 kmem_free(hdr->b_thawed, 1);
1737 hdr->b_thawed = NULL;
1740 ASSERT(!list_link_active(&hdr->b_arc_node));
1741 ASSERT3P(hdr->b_hash_next, ==, NULL);
1742 ASSERT3P(hdr->b_acb, ==, NULL);
1743 kmem_cache_free(hdr_cache, hdr);
1747 arc_buf_free(arc_buf_t *buf, void *tag)
1749 arc_buf_hdr_t *hdr = buf->b_hdr;
1750 int hashed = hdr->b_state != arc_anon;
1752 ASSERT(buf->b_efunc == NULL);
1753 ASSERT(buf->b_data != NULL);
1756 kmutex_t *hash_lock = HDR_LOCK(hdr);
1758 mutex_enter(hash_lock);
1760 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1762 (void) remove_reference(hdr, hash_lock, tag);
1763 if (hdr->b_datacnt > 1) {
1764 arc_buf_destroy(buf, FALSE, TRUE);
1766 ASSERT(buf == hdr->b_buf);
1767 ASSERT(buf->b_efunc == NULL);
1768 hdr->b_flags |= ARC_BUF_AVAILABLE;
1770 mutex_exit(hash_lock);
1771 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1774 * We are in the middle of an async write. Don't destroy
1775 * this buffer unless the write completes before we finish
1776 * decrementing the reference count.
1778 mutex_enter(&arc_eviction_mtx);
1779 (void) remove_reference(hdr, NULL, tag);
1780 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1781 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1782 mutex_exit(&arc_eviction_mtx);
1784 arc_hdr_destroy(hdr);
1786 if (remove_reference(hdr, NULL, tag) > 0)
1787 arc_buf_destroy(buf, FALSE, TRUE);
1789 arc_hdr_destroy(hdr);
1794 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1796 arc_buf_hdr_t *hdr = buf->b_hdr;
1797 kmutex_t *hash_lock = HDR_LOCK(hdr);
1798 boolean_t no_callback = (buf->b_efunc == NULL);
1800 if (hdr->b_state == arc_anon) {
1801 ASSERT(hdr->b_datacnt == 1);
1802 arc_buf_free(buf, tag);
1803 return (no_callback);
1806 mutex_enter(hash_lock);
1808 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1809 ASSERT(hdr->b_state != arc_anon);
1810 ASSERT(buf->b_data != NULL);
1812 (void) remove_reference(hdr, hash_lock, tag);
1813 if (hdr->b_datacnt > 1) {
1815 arc_buf_destroy(buf, FALSE, TRUE);
1816 } else if (no_callback) {
1817 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1818 ASSERT(buf->b_efunc == NULL);
1819 hdr->b_flags |= ARC_BUF_AVAILABLE;
1821 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1822 refcount_is_zero(&hdr->b_refcnt));
1823 mutex_exit(hash_lock);
1824 return (no_callback);
1828 arc_buf_size(arc_buf_t *buf)
1830 return (buf->b_hdr->b_size);
1834 * Called from the DMU to determine if the current buffer should be
1835 * evicted. In order to ensure proper locking, the eviction must be initiated
1836 * from the DMU. Return true if the buffer is associated with user data and
1837 * duplicate buffers still exist.
1840 arc_buf_eviction_needed(arc_buf_t *buf)
1843 boolean_t evict_needed = B_FALSE;
1845 if (zfs_disable_dup_eviction)
1848 mutex_enter(&buf->b_evict_lock);
1852 * We are in arc_do_user_evicts(); let that function
1853 * perform the eviction.
1855 ASSERT(buf->b_data == NULL);
1856 mutex_exit(&buf->b_evict_lock);
1858 } else if (buf->b_data == NULL) {
1860 * We have already been added to the arc eviction list;
1861 * recommend eviction.
1863 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1864 mutex_exit(&buf->b_evict_lock);
1868 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1869 evict_needed = B_TRUE;
1871 mutex_exit(&buf->b_evict_lock);
1872 return (evict_needed);
1876 * Evict buffers from list until we've removed the specified number of
1877 * bytes. Move the removed buffers to the appropriate evict state.
1878 * If the recycle flag is set, then attempt to "recycle" a buffer:
1879 * - look for a buffer to evict that is `bytes' long.
1880 * - return the data block from this buffer rather than freeing it.
1881 * This flag is used by callers that are trying to make space for a
1882 * new buffer in a full arc cache.
1884 * This function makes a "best effort". It skips over any buffers
1885 * it can't get a hash_lock on, and so may not catch all candidates.
1886 * It may also return without evicting as much space as requested.
1889 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1890 arc_buf_contents_t type)
1892 arc_state_t *evicted_state;
1893 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1894 int64_t bytes_remaining;
1895 arc_buf_hdr_t *ab, *ab_prev = NULL;
1896 list_t *evicted_list, *list, *evicted_list_start, *list_start;
1897 kmutex_t *lock, *evicted_lock;
1898 kmutex_t *hash_lock;
1899 boolean_t have_lock;
1900 void *stolen = NULL;
1901 static int evict_metadata_offset, evict_data_offset;
1902 int i, idx, offset, list_count, count;
1904 ASSERT(state == arc_mru || state == arc_mfu);
1906 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1908 if (type == ARC_BUFC_METADATA) {
1910 list_count = ARC_BUFC_NUMMETADATALISTS;
1911 list_start = &state->arcs_lists[0];
1912 evicted_list_start = &evicted_state->arcs_lists[0];
1913 idx = evict_metadata_offset;
1915 offset = ARC_BUFC_NUMMETADATALISTS;
1916 list_start = &state->arcs_lists[offset];
1917 evicted_list_start = &evicted_state->arcs_lists[offset];
1918 list_count = ARC_BUFC_NUMDATALISTS;
1919 idx = evict_data_offset;
1921 bytes_remaining = evicted_state->arcs_lsize[type];
1925 list = &list_start[idx];
1926 evicted_list = &evicted_list_start[idx];
1927 lock = ARCS_LOCK(state, (offset + idx));
1928 evicted_lock = ARCS_LOCK(evicted_state, (offset + idx));
1931 mutex_enter(evicted_lock);
1933 for (ab = list_tail(list); ab; ab = ab_prev) {
1934 ab_prev = list_prev(list, ab);
1935 bytes_remaining -= (ab->b_size * ab->b_datacnt);
1936 /* prefetch buffers have a minimum lifespan */
1937 if (HDR_IO_IN_PROGRESS(ab) ||
1938 (spa && ab->b_spa != spa) ||
1939 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1940 ddi_get_lbolt() - ab->b_arc_access <
1941 arc_min_prefetch_lifespan)) {
1945 /* "lookahead" for better eviction candidate */
1946 if (recycle && ab->b_size != bytes &&
1947 ab_prev && ab_prev->b_size == bytes)
1949 hash_lock = HDR_LOCK(ab);
1950 have_lock = MUTEX_HELD(hash_lock);
1951 if (have_lock || mutex_tryenter(hash_lock)) {
1952 ASSERT0(refcount_count(&ab->b_refcnt));
1953 ASSERT(ab->b_datacnt > 0);
1955 arc_buf_t *buf = ab->b_buf;
1956 if (!mutex_tryenter(&buf->b_evict_lock)) {
1961 bytes_evicted += ab->b_size;
1962 if (recycle && ab->b_type == type &&
1963 ab->b_size == bytes &&
1964 !HDR_L2_WRITING(ab)) {
1965 stolen = buf->b_data;
1970 mutex_enter(&arc_eviction_mtx);
1971 arc_buf_destroy(buf,
1972 buf->b_data == stolen, FALSE);
1973 ab->b_buf = buf->b_next;
1974 buf->b_hdr = &arc_eviction_hdr;
1975 buf->b_next = arc_eviction_list;
1976 arc_eviction_list = buf;
1977 mutex_exit(&arc_eviction_mtx);
1978 mutex_exit(&buf->b_evict_lock);
1980 mutex_exit(&buf->b_evict_lock);
1981 arc_buf_destroy(buf,
1982 buf->b_data == stolen, TRUE);
1987 ARCSTAT_INCR(arcstat_evict_l2_cached,
1990 if (l2arc_write_eligible(ab->b_spa, ab)) {
1991 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1995 arcstat_evict_l2_ineligible,
2000 if (ab->b_datacnt == 0) {
2001 arc_change_state(evicted_state, ab, hash_lock);
2002 ASSERT(HDR_IN_HASH_TABLE(ab));
2003 ab->b_flags |= ARC_IN_HASH_TABLE;
2004 ab->b_flags &= ~ARC_BUF_AVAILABLE;
2005 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
2008 mutex_exit(hash_lock);
2009 if (bytes >= 0 && bytes_evicted >= bytes)
2011 if (bytes_remaining > 0) {
2012 mutex_exit(evicted_lock);
2014 idx = ((idx + 1) & (list_count - 1));
2023 mutex_exit(evicted_lock);
2026 idx = ((idx + 1) & (list_count - 1));
2029 if (bytes_evicted < bytes) {
2030 if (count < list_count)
2033 dprintf("only evicted %lld bytes from %x",
2034 (longlong_t)bytes_evicted, state);
2036 if (type == ARC_BUFC_METADATA)
2037 evict_metadata_offset = idx;
2039 evict_data_offset = idx;
2042 ARCSTAT_INCR(arcstat_evict_skip, skipped);
2045 ARCSTAT_INCR(arcstat_mutex_miss, missed);
2048 * We have just evicted some data into the ghost state, make
2049 * sure we also adjust the ghost state size if necessary.
2052 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
2053 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
2054 arc_mru_ghost->arcs_size - arc_c;
2056 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
2058 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
2059 arc_evict_ghost(arc_mru_ghost, 0, todelete);
2060 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
2061 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
2062 arc_mru_ghost->arcs_size +
2063 arc_mfu_ghost->arcs_size - arc_c);
2064 arc_evict_ghost(arc_mfu_ghost, 0, todelete);
2068 ARCSTAT_BUMP(arcstat_stolen);
2074 * Remove buffers from list until we've removed the specified number of
2075 * bytes. Destroy the buffers that are removed.
2078 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
2080 arc_buf_hdr_t *ab, *ab_prev;
2081 arc_buf_hdr_t marker = { 0 };
2082 list_t *list, *list_start;
2083 kmutex_t *hash_lock, *lock;
2084 uint64_t bytes_deleted = 0;
2085 uint64_t bufs_skipped = 0;
2086 static int evict_offset;
2087 int list_count, idx = evict_offset;
2088 int offset, count = 0;
2090 ASSERT(GHOST_STATE(state));
2093 * data lists come after metadata lists
2095 list_start = &state->arcs_lists[ARC_BUFC_NUMMETADATALISTS];
2096 list_count = ARC_BUFC_NUMDATALISTS;
2097 offset = ARC_BUFC_NUMMETADATALISTS;
2100 list = &list_start[idx];
2101 lock = ARCS_LOCK(state, idx + offset);
2104 for (ab = list_tail(list); ab; ab = ab_prev) {
2105 ab_prev = list_prev(list, ab);
2106 if (spa && ab->b_spa != spa)
2109 /* ignore markers */
2113 hash_lock = HDR_LOCK(ab);
2114 /* caller may be trying to modify this buffer, skip it */
2115 if (MUTEX_HELD(hash_lock))
2117 if (mutex_tryenter(hash_lock)) {
2118 ASSERT(!HDR_IO_IN_PROGRESS(ab));
2119 ASSERT(ab->b_buf == NULL);
2120 ARCSTAT_BUMP(arcstat_deleted);
2121 bytes_deleted += ab->b_size;
2123 if (ab->b_l2hdr != NULL) {
2125 * This buffer is cached on the 2nd Level ARC;
2126 * don't destroy the header.
2128 arc_change_state(arc_l2c_only, ab, hash_lock);
2129 mutex_exit(hash_lock);
2131 arc_change_state(arc_anon, ab, hash_lock);
2132 mutex_exit(hash_lock);
2133 arc_hdr_destroy(ab);
2136 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
2137 if (bytes >= 0 && bytes_deleted >= bytes)
2139 } else if (bytes < 0) {
2141 * Insert a list marker and then wait for the
2142 * hash lock to become available. Once its
2143 * available, restart from where we left off.
2145 list_insert_after(list, ab, &marker);
2147 mutex_enter(hash_lock);
2148 mutex_exit(hash_lock);
2150 ab_prev = list_prev(list, &marker);
2151 list_remove(list, &marker);
2156 idx = ((idx + 1) & (ARC_BUFC_NUMDATALISTS - 1));
2159 if (count < list_count)
2163 if ((uintptr_t)list > (uintptr_t)&state->arcs_lists[ARC_BUFC_NUMMETADATALISTS] &&
2164 (bytes < 0 || bytes_deleted < bytes)) {
2165 list_start = &state->arcs_lists[0];
2166 list_count = ARC_BUFC_NUMMETADATALISTS;
2172 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2176 if (bytes_deleted < bytes)
2177 dprintf("only deleted %lld bytes from %p",
2178 (longlong_t)bytes_deleted, state);
2184 int64_t adjustment, delta;
2190 adjustment = MIN((int64_t)(arc_size - arc_c),
2191 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2194 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2195 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2196 (void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
2197 adjustment -= delta;
2200 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2201 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2202 (void) arc_evict(arc_mru, 0, delta, FALSE,
2210 adjustment = arc_size - arc_c;
2212 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2213 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2214 (void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
2215 adjustment -= delta;
2218 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2219 int64_t delta = MIN(adjustment,
2220 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2221 (void) arc_evict(arc_mfu, 0, delta, FALSE,
2226 * Adjust ghost lists
2229 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2231 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2232 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2233 arc_evict_ghost(arc_mru_ghost, 0, delta);
2237 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2239 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2240 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2241 arc_evict_ghost(arc_mfu_ghost, 0, delta);
2246 arc_do_user_evicts(void)
2248 static arc_buf_t *tmp_arc_eviction_list;
2251 * Move list over to avoid LOR
2254 mutex_enter(&arc_eviction_mtx);
2255 tmp_arc_eviction_list = arc_eviction_list;
2256 arc_eviction_list = NULL;
2257 mutex_exit(&arc_eviction_mtx);
2259 while (tmp_arc_eviction_list != NULL) {
2260 arc_buf_t *buf = tmp_arc_eviction_list;
2261 tmp_arc_eviction_list = buf->b_next;
2262 mutex_enter(&buf->b_evict_lock);
2264 mutex_exit(&buf->b_evict_lock);
2266 if (buf->b_efunc != NULL)
2267 VERIFY(buf->b_efunc(buf) == 0);
2269 buf->b_efunc = NULL;
2270 buf->b_private = NULL;
2271 kmem_cache_free(buf_cache, buf);
2274 if (arc_eviction_list != NULL)
2279 * Flush all *evictable* data from the cache for the given spa.
2280 * NOTE: this will not touch "active" (i.e. referenced) data.
2283 arc_flush(spa_t *spa)
2288 guid = spa_load_guid(spa);
2290 while (arc_mru->arcs_lsize[ARC_BUFC_DATA]) {
2291 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2295 while (arc_mru->arcs_lsize[ARC_BUFC_METADATA]) {
2296 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2300 while (arc_mfu->arcs_lsize[ARC_BUFC_DATA]) {
2301 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2305 while (arc_mfu->arcs_lsize[ARC_BUFC_METADATA]) {
2306 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2311 arc_evict_ghost(arc_mru_ghost, guid, -1);
2312 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2314 mutex_enter(&arc_reclaim_thr_lock);
2315 arc_do_user_evicts();
2316 mutex_exit(&arc_reclaim_thr_lock);
2317 ASSERT(spa || arc_eviction_list == NULL);
2323 if (arc_c > arc_c_min) {
2327 to_free = arc_c >> arc_shrink_shift;
2329 to_free = arc_c >> arc_shrink_shift;
2331 if (arc_c > arc_c_min + to_free)
2332 atomic_add_64(&arc_c, -to_free);
2336 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2337 if (arc_c > arc_size)
2338 arc_c = MAX(arc_size, arc_c_min);
2340 arc_p = (arc_c >> 1);
2341 ASSERT(arc_c >= arc_c_min);
2342 ASSERT((int64_t)arc_p >= 0);
2345 if (arc_size > arc_c)
2349 static int needfree = 0;
2352 arc_reclaim_needed(void)
2361 * Cooperate with pagedaemon when it's time for it to scan
2362 * and reclaim some pages.
2364 if (vm_paging_needed())
2369 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2374 * check that we're out of range of the pageout scanner. It starts to
2375 * schedule paging if freemem is less than lotsfree and needfree.
2376 * lotsfree is the high-water mark for pageout, and needfree is the
2377 * number of needed free pages. We add extra pages here to make sure
2378 * the scanner doesn't start up while we're freeing memory.
2380 if (freemem < lotsfree + needfree + extra)
2384 * check to make sure that swapfs has enough space so that anon
2385 * reservations can still succeed. anon_resvmem() checks that the
2386 * availrmem is greater than swapfs_minfree, and the number of reserved
2387 * swap pages. We also add a bit of extra here just to prevent
2388 * circumstances from getting really dire.
2390 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2395 * If we're on an i386 platform, it's possible that we'll exhaust the
2396 * kernel heap space before we ever run out of available physical
2397 * memory. Most checks of the size of the heap_area compare against
2398 * tune.t_minarmem, which is the minimum available real memory that we
2399 * can have in the system. However, this is generally fixed at 25 pages
2400 * which is so low that it's useless. In this comparison, we seek to
2401 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2402 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2405 if (btop(vmem_size(heap_arena, VMEM_FREE)) <
2406 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
2410 if (kmem_used() > (kmem_size() * 3) / 4)
2415 if (spa_get_random(100) == 0)
2421 extern kmem_cache_t *zio_buf_cache[];
2422 extern kmem_cache_t *zio_data_buf_cache[];
2425 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2428 kmem_cache_t *prev_cache = NULL;
2429 kmem_cache_t *prev_data_cache = NULL;
2432 if (arc_meta_used >= arc_meta_limit) {
2434 * We are exceeding our meta-data cache limit.
2435 * Purge some DNLC entries to release holds on meta-data.
2437 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2441 * Reclaim unused memory from all kmem caches.
2448 * An aggressive reclamation will shrink the cache size as well as
2449 * reap free buffers from the arc kmem caches.
2451 if (strat == ARC_RECLAIM_AGGR)
2454 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2455 if (zio_buf_cache[i] != prev_cache) {
2456 prev_cache = zio_buf_cache[i];
2457 kmem_cache_reap_now(zio_buf_cache[i]);
2459 if (zio_data_buf_cache[i] != prev_data_cache) {
2460 prev_data_cache = zio_data_buf_cache[i];
2461 kmem_cache_reap_now(zio_data_buf_cache[i]);
2464 kmem_cache_reap_now(buf_cache);
2465 kmem_cache_reap_now(hdr_cache);
2469 arc_reclaim_thread(void *dummy __unused)
2471 clock_t growtime = 0;
2472 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2475 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2477 mutex_enter(&arc_reclaim_thr_lock);
2478 while (arc_thread_exit == 0) {
2479 if (arc_reclaim_needed()) {
2482 if (last_reclaim == ARC_RECLAIM_CONS) {
2483 last_reclaim = ARC_RECLAIM_AGGR;
2485 last_reclaim = ARC_RECLAIM_CONS;
2489 last_reclaim = ARC_RECLAIM_AGGR;
2493 /* reset the growth delay for every reclaim */
2494 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2496 if (needfree && last_reclaim == ARC_RECLAIM_CONS) {
2498 * If needfree is TRUE our vm_lowmem hook
2499 * was called and in that case we must free some
2500 * memory, so switch to aggressive mode.
2503 last_reclaim = ARC_RECLAIM_AGGR;
2505 arc_kmem_reap_now(last_reclaim);
2508 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2509 arc_no_grow = FALSE;
2514 if (arc_eviction_list != NULL)
2515 arc_do_user_evicts();
2524 /* block until needed, or one second, whichever is shorter */
2525 CALLB_CPR_SAFE_BEGIN(&cpr);
2526 (void) cv_timedwait(&arc_reclaim_thr_cv,
2527 &arc_reclaim_thr_lock, hz);
2528 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2531 arc_thread_exit = 0;
2532 cv_broadcast(&arc_reclaim_thr_cv);
2533 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2538 * Adapt arc info given the number of bytes we are trying to add and
2539 * the state that we are comming from. This function is only called
2540 * when we are adding new content to the cache.
2543 arc_adapt(int bytes, arc_state_t *state)
2546 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2548 if (state == arc_l2c_only)
2553 * Adapt the target size of the MRU list:
2554 * - if we just hit in the MRU ghost list, then increase
2555 * the target size of the MRU list.
2556 * - if we just hit in the MFU ghost list, then increase
2557 * the target size of the MFU list by decreasing the
2558 * target size of the MRU list.
2560 if (state == arc_mru_ghost) {
2561 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2562 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2563 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2565 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2566 } else if (state == arc_mfu_ghost) {
2569 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2570 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2571 mult = MIN(mult, 10);
2573 delta = MIN(bytes * mult, arc_p);
2574 arc_p = MAX(arc_p_min, arc_p - delta);
2576 ASSERT((int64_t)arc_p >= 0);
2578 if (arc_reclaim_needed()) {
2579 cv_signal(&arc_reclaim_thr_cv);
2586 if (arc_c >= arc_c_max)
2590 * If we're within (2 * maxblocksize) bytes of the target
2591 * cache size, increment the target cache size
2593 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2594 atomic_add_64(&arc_c, (int64_t)bytes);
2595 if (arc_c > arc_c_max)
2597 else if (state == arc_anon)
2598 atomic_add_64(&arc_p, (int64_t)bytes);
2602 ASSERT((int64_t)arc_p >= 0);
2606 * Check if the cache has reached its limits and eviction is required
2610 arc_evict_needed(arc_buf_contents_t type)
2612 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2618 * If zio data pages are being allocated out of a separate heap segment,
2619 * then enforce that the size of available vmem for this area remains
2620 * above about 1/32nd free.
2622 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2623 vmem_size(zio_arena, VMEM_FREE) <
2624 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2629 if (arc_reclaim_needed())
2632 return (arc_size > arc_c);
2636 * The buffer, supplied as the first argument, needs a data block.
2637 * So, if we are at cache max, determine which cache should be victimized.
2638 * We have the following cases:
2640 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2641 * In this situation if we're out of space, but the resident size of the MFU is
2642 * under the limit, victimize the MFU cache to satisfy this insertion request.
2644 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2645 * Here, we've used up all of the available space for the MRU, so we need to
2646 * evict from our own cache instead. Evict from the set of resident MRU
2649 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2650 * c minus p represents the MFU space in the cache, since p is the size of the
2651 * cache that is dedicated to the MRU. In this situation there's still space on
2652 * the MFU side, so the MRU side needs to be victimized.
2654 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2655 * MFU's resident set is consuming more space than it has been allotted. In
2656 * this situation, we must victimize our own cache, the MFU, for this insertion.
2659 arc_get_data_buf(arc_buf_t *buf)
2661 arc_state_t *state = buf->b_hdr->b_state;
2662 uint64_t size = buf->b_hdr->b_size;
2663 arc_buf_contents_t type = buf->b_hdr->b_type;
2665 arc_adapt(size, state);
2668 * We have not yet reached cache maximum size,
2669 * just allocate a new buffer.
2671 if (!arc_evict_needed(type)) {
2672 if (type == ARC_BUFC_METADATA) {
2673 buf->b_data = zio_buf_alloc(size);
2674 arc_space_consume(size, ARC_SPACE_DATA);
2676 ASSERT(type == ARC_BUFC_DATA);
2677 buf->b_data = zio_data_buf_alloc(size);
2678 ARCSTAT_INCR(arcstat_data_size, size);
2679 atomic_add_64(&arc_size, size);
2685 * If we are prefetching from the mfu ghost list, this buffer
2686 * will end up on the mru list; so steal space from there.
2688 if (state == arc_mfu_ghost)
2689 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2690 else if (state == arc_mru_ghost)
2693 if (state == arc_mru || state == arc_anon) {
2694 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2695 state = (arc_mfu->arcs_lsize[type] >= size &&
2696 arc_p > mru_used) ? arc_mfu : arc_mru;
2699 uint64_t mfu_space = arc_c - arc_p;
2700 state = (arc_mru->arcs_lsize[type] >= size &&
2701 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2703 if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
2704 if (type == ARC_BUFC_METADATA) {
2705 buf->b_data = zio_buf_alloc(size);
2706 arc_space_consume(size, ARC_SPACE_DATA);
2708 ASSERT(type == ARC_BUFC_DATA);
2709 buf->b_data = zio_data_buf_alloc(size);
2710 ARCSTAT_INCR(arcstat_data_size, size);
2711 atomic_add_64(&arc_size, size);
2713 ARCSTAT_BUMP(arcstat_recycle_miss);
2715 ASSERT(buf->b_data != NULL);
2718 * Update the state size. Note that ghost states have a
2719 * "ghost size" and so don't need to be updated.
2721 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2722 arc_buf_hdr_t *hdr = buf->b_hdr;
2724 atomic_add_64(&hdr->b_state->arcs_size, size);
2725 if (list_link_active(&hdr->b_arc_node)) {
2726 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2727 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2730 * If we are growing the cache, and we are adding anonymous
2731 * data, and we have outgrown arc_p, update arc_p
2733 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2734 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2735 arc_p = MIN(arc_c, arc_p + size);
2737 ARCSTAT_BUMP(arcstat_allocated);
2741 * This routine is called whenever a buffer is accessed.
2742 * NOTE: the hash lock is dropped in this function.
2745 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2749 ASSERT(MUTEX_HELD(hash_lock));
2751 if (buf->b_state == arc_anon) {
2753 * This buffer is not in the cache, and does not
2754 * appear in our "ghost" list. Add the new buffer
2758 ASSERT(buf->b_arc_access == 0);
2759 buf->b_arc_access = ddi_get_lbolt();
2760 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2761 arc_change_state(arc_mru, buf, hash_lock);
2763 } else if (buf->b_state == arc_mru) {
2764 now = ddi_get_lbolt();
2767 * If this buffer is here because of a prefetch, then either:
2768 * - clear the flag if this is a "referencing" read
2769 * (any subsequent access will bump this into the MFU state).
2771 * - move the buffer to the head of the list if this is
2772 * another prefetch (to make it less likely to be evicted).
2774 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2775 if (refcount_count(&buf->b_refcnt) == 0) {
2776 ASSERT(list_link_active(&buf->b_arc_node));
2778 buf->b_flags &= ~ARC_PREFETCH;
2779 ARCSTAT_BUMP(arcstat_mru_hits);
2781 buf->b_arc_access = now;
2786 * This buffer has been "accessed" only once so far,
2787 * but it is still in the cache. Move it to the MFU
2790 if (now > buf->b_arc_access + ARC_MINTIME) {
2792 * More than 125ms have passed since we
2793 * instantiated this buffer. Move it to the
2794 * most frequently used state.
2796 buf->b_arc_access = now;
2797 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2798 arc_change_state(arc_mfu, buf, hash_lock);
2800 ARCSTAT_BUMP(arcstat_mru_hits);
2801 } else if (buf->b_state == arc_mru_ghost) {
2802 arc_state_t *new_state;
2804 * This buffer has been "accessed" recently, but
2805 * was evicted from the cache. Move it to the
2809 if (buf->b_flags & ARC_PREFETCH) {
2810 new_state = arc_mru;
2811 if (refcount_count(&buf->b_refcnt) > 0)
2812 buf->b_flags &= ~ARC_PREFETCH;
2813 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2815 new_state = arc_mfu;
2816 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2819 buf->b_arc_access = ddi_get_lbolt();
2820 arc_change_state(new_state, buf, hash_lock);
2822 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2823 } else if (buf->b_state == arc_mfu) {
2825 * This buffer has been accessed more than once and is
2826 * still in the cache. Keep it in the MFU state.
2828 * NOTE: an add_reference() that occurred when we did
2829 * the arc_read() will have kicked this off the list.
2830 * If it was a prefetch, we will explicitly move it to
2831 * the head of the list now.
2833 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2834 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2835 ASSERT(list_link_active(&buf->b_arc_node));
2837 ARCSTAT_BUMP(arcstat_mfu_hits);
2838 buf->b_arc_access = ddi_get_lbolt();
2839 } else if (buf->b_state == arc_mfu_ghost) {
2840 arc_state_t *new_state = arc_mfu;
2842 * This buffer has been accessed more than once but has
2843 * been evicted from the cache. Move it back to the
2847 if (buf->b_flags & ARC_PREFETCH) {
2849 * This is a prefetch access...
2850 * move this block back to the MRU state.
2852 ASSERT0(refcount_count(&buf->b_refcnt));
2853 new_state = arc_mru;
2856 buf->b_arc_access = ddi_get_lbolt();
2857 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2858 arc_change_state(new_state, buf, hash_lock);
2860 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2861 } else if (buf->b_state == arc_l2c_only) {
2863 * This buffer is on the 2nd Level ARC.
2866 buf->b_arc_access = ddi_get_lbolt();
2867 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2868 arc_change_state(arc_mfu, buf, hash_lock);
2870 ASSERT(!"invalid arc state");
2874 /* a generic arc_done_func_t which you can use */
2877 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2879 if (zio == NULL || zio->io_error == 0)
2880 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2881 VERIFY(arc_buf_remove_ref(buf, arg));
2884 /* a generic arc_done_func_t */
2886 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2888 arc_buf_t **bufp = arg;
2889 if (zio && zio->io_error) {
2890 VERIFY(arc_buf_remove_ref(buf, arg));
2894 ASSERT(buf->b_data);
2899 arc_read_done(zio_t *zio)
2901 arc_buf_hdr_t *hdr, *found;
2903 arc_buf_t *abuf; /* buffer we're assigning to callback */
2904 kmutex_t *hash_lock;
2905 arc_callback_t *callback_list, *acb;
2906 int freeable = FALSE;
2908 buf = zio->io_private;
2912 * The hdr was inserted into hash-table and removed from lists
2913 * prior to starting I/O. We should find this header, since
2914 * it's in the hash table, and it should be legit since it's
2915 * not possible to evict it during the I/O. The only possible
2916 * reason for it not to be found is if we were freed during the
2919 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2922 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2923 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2924 (found == hdr && HDR_L2_READING(hdr)));
2926 hdr->b_flags &= ~ARC_L2_EVICTED;
2927 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2928 hdr->b_flags &= ~ARC_L2CACHE;
2930 /* byteswap if necessary */
2931 callback_list = hdr->b_acb;
2932 ASSERT(callback_list != NULL);
2933 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
2934 dmu_object_byteswap_t bswap =
2935 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
2936 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2937 byteswap_uint64_array :
2938 dmu_ot_byteswap[bswap].ob_func;
2939 func(buf->b_data, hdr->b_size);
2942 arc_cksum_compute(buf, B_FALSE);
2945 #endif /* illumos */
2947 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
2949 * Only call arc_access on anonymous buffers. This is because
2950 * if we've issued an I/O for an evicted buffer, we've already
2951 * called arc_access (to prevent any simultaneous readers from
2952 * getting confused).
2954 arc_access(hdr, hash_lock);
2957 /* create copies of the data buffer for the callers */
2959 for (acb = callback_list; acb; acb = acb->acb_next) {
2960 if (acb->acb_done) {
2962 ARCSTAT_BUMP(arcstat_duplicate_reads);
2963 abuf = arc_buf_clone(buf);
2965 acb->acb_buf = abuf;
2970 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2971 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2973 ASSERT(buf->b_efunc == NULL);
2974 ASSERT(hdr->b_datacnt == 1);
2975 hdr->b_flags |= ARC_BUF_AVAILABLE;
2978 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2980 if (zio->io_error != 0) {
2981 hdr->b_flags |= ARC_IO_ERROR;
2982 if (hdr->b_state != arc_anon)
2983 arc_change_state(arc_anon, hdr, hash_lock);
2984 if (HDR_IN_HASH_TABLE(hdr))
2985 buf_hash_remove(hdr);
2986 freeable = refcount_is_zero(&hdr->b_refcnt);
2990 * Broadcast before we drop the hash_lock to avoid the possibility
2991 * that the hdr (and hence the cv) might be freed before we get to
2992 * the cv_broadcast().
2994 cv_broadcast(&hdr->b_cv);
2997 mutex_exit(hash_lock);
3000 * This block was freed while we waited for the read to
3001 * complete. It has been removed from the hash table and
3002 * moved to the anonymous state (so that it won't show up
3005 ASSERT3P(hdr->b_state, ==, arc_anon);
3006 freeable = refcount_is_zero(&hdr->b_refcnt);
3009 /* execute each callback and free its structure */
3010 while ((acb = callback_list) != NULL) {
3012 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3014 if (acb->acb_zio_dummy != NULL) {
3015 acb->acb_zio_dummy->io_error = zio->io_error;
3016 zio_nowait(acb->acb_zio_dummy);
3019 callback_list = acb->acb_next;
3020 kmem_free(acb, sizeof (arc_callback_t));
3024 arc_hdr_destroy(hdr);
3028 * "Read" the block block at the specified DVA (in bp) via the
3029 * cache. If the block is found in the cache, invoke the provided
3030 * callback immediately and return. Note that the `zio' parameter
3031 * in the callback will be NULL in this case, since no IO was
3032 * required. If the block is not in the cache pass the read request
3033 * on to the spa with a substitute callback function, so that the
3034 * requested block will be added to the cache.
3036 * If a read request arrives for a block that has a read in-progress,
3037 * either wait for the in-progress read to complete (and return the
3038 * results); or, if this is a read with a "done" func, add a record
3039 * to the read to invoke the "done" func when the read completes,
3040 * and return; or just return.
3042 * arc_read_done() will invoke all the requested "done" functions
3043 * for readers of this block.
3046 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3047 void *private, int priority, int zio_flags, uint32_t *arc_flags,
3048 const zbookmark_t *zb)
3051 arc_buf_t *buf = NULL;
3052 kmutex_t *hash_lock;
3054 uint64_t guid = spa_load_guid(spa);
3057 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
3059 if (hdr && hdr->b_datacnt > 0) {
3061 *arc_flags |= ARC_CACHED;
3063 if (HDR_IO_IN_PROGRESS(hdr)) {
3065 if (*arc_flags & ARC_WAIT) {
3066 cv_wait(&hdr->b_cv, hash_lock);
3067 mutex_exit(hash_lock);
3070 ASSERT(*arc_flags & ARC_NOWAIT);
3073 arc_callback_t *acb = NULL;
3075 acb = kmem_zalloc(sizeof (arc_callback_t),
3077 acb->acb_done = done;
3078 acb->acb_private = private;
3080 acb->acb_zio_dummy = zio_null(pio,
3081 spa, NULL, NULL, NULL, zio_flags);
3083 ASSERT(acb->acb_done != NULL);
3084 acb->acb_next = hdr->b_acb;
3086 add_reference(hdr, hash_lock, private);
3087 mutex_exit(hash_lock);
3090 mutex_exit(hash_lock);
3094 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3097 add_reference(hdr, hash_lock, private);
3099 * If this block is already in use, create a new
3100 * copy of the data so that we will be guaranteed
3101 * that arc_release() will always succeed.
3105 ASSERT(buf->b_data);
3106 if (HDR_BUF_AVAILABLE(hdr)) {
3107 ASSERT(buf->b_efunc == NULL);
3108 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3110 buf = arc_buf_clone(buf);
3113 } else if (*arc_flags & ARC_PREFETCH &&
3114 refcount_count(&hdr->b_refcnt) == 0) {
3115 hdr->b_flags |= ARC_PREFETCH;
3117 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3118 arc_access(hdr, hash_lock);
3119 if (*arc_flags & ARC_L2CACHE)
3120 hdr->b_flags |= ARC_L2CACHE;
3121 mutex_exit(hash_lock);
3122 ARCSTAT_BUMP(arcstat_hits);
3123 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3124 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3125 data, metadata, hits);
3128 done(NULL, buf, private);
3130 uint64_t size = BP_GET_LSIZE(bp);
3131 arc_callback_t *acb;
3134 boolean_t devw = B_FALSE;
3137 /* this block is not in the cache */
3138 arc_buf_hdr_t *exists;
3139 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3140 buf = arc_buf_alloc(spa, size, private, type);
3142 hdr->b_dva = *BP_IDENTITY(bp);
3143 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3144 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3145 exists = buf_hash_insert(hdr, &hash_lock);
3147 /* somebody beat us to the hash insert */
3148 mutex_exit(hash_lock);
3149 buf_discard_identity(hdr);
3150 (void) arc_buf_remove_ref(buf, private);
3151 goto top; /* restart the IO request */
3153 /* if this is a prefetch, we don't have a reference */
3154 if (*arc_flags & ARC_PREFETCH) {
3155 (void) remove_reference(hdr, hash_lock,
3157 hdr->b_flags |= ARC_PREFETCH;
3159 if (*arc_flags & ARC_L2CACHE)
3160 hdr->b_flags |= ARC_L2CACHE;
3161 if (BP_GET_LEVEL(bp) > 0)
3162 hdr->b_flags |= ARC_INDIRECT;
3164 /* this block is in the ghost cache */
3165 ASSERT(GHOST_STATE(hdr->b_state));
3166 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3167 ASSERT0(refcount_count(&hdr->b_refcnt));
3168 ASSERT(hdr->b_buf == NULL);
3170 /* if this is a prefetch, we don't have a reference */
3171 if (*arc_flags & ARC_PREFETCH)
3172 hdr->b_flags |= ARC_PREFETCH;
3174 add_reference(hdr, hash_lock, private);
3175 if (*arc_flags & ARC_L2CACHE)
3176 hdr->b_flags |= ARC_L2CACHE;
3177 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3180 buf->b_efunc = NULL;
3181 buf->b_private = NULL;
3184 ASSERT(hdr->b_datacnt == 0);
3186 arc_get_data_buf(buf);
3187 arc_access(hdr, hash_lock);
3190 ASSERT(!GHOST_STATE(hdr->b_state));
3192 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3193 acb->acb_done = done;
3194 acb->acb_private = private;
3196 ASSERT(hdr->b_acb == NULL);
3198 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3200 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
3201 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3202 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3203 addr = hdr->b_l2hdr->b_daddr;
3205 * Lock out device removal.
3207 if (vdev_is_dead(vd) ||
3208 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3212 mutex_exit(hash_lock);
3214 ASSERT3U(hdr->b_size, ==, size);
3215 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3216 uint64_t, size, zbookmark_t *, zb);
3217 ARCSTAT_BUMP(arcstat_misses);
3218 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3219 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3220 data, metadata, misses);
3222 curthread->td_ru.ru_inblock++;
3225 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3227 * Read from the L2ARC if the following are true:
3228 * 1. The L2ARC vdev was previously cached.
3229 * 2. This buffer still has L2ARC metadata.
3230 * 3. This buffer isn't currently writing to the L2ARC.
3231 * 4. The L2ARC entry wasn't evicted, which may
3232 * also have invalidated the vdev.
3233 * 5. This isn't prefetch and l2arc_noprefetch is set.
3235 if (hdr->b_l2hdr != NULL &&
3236 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3237 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3238 l2arc_read_callback_t *cb;
3240 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3241 ARCSTAT_BUMP(arcstat_l2_hits);
3243 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3245 cb->l2rcb_buf = buf;
3246 cb->l2rcb_spa = spa;
3249 cb->l2rcb_flags = zio_flags;
3251 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3252 addr + size < vd->vdev_psize -
3253 VDEV_LABEL_END_SIZE);
3256 * l2arc read. The SCL_L2ARC lock will be
3257 * released by l2arc_read_done().
3259 rzio = zio_read_phys(pio, vd, addr, size,
3260 buf->b_data, ZIO_CHECKSUM_OFF,
3261 l2arc_read_done, cb, priority, zio_flags |
3262 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3263 ZIO_FLAG_DONT_PROPAGATE |
3264 ZIO_FLAG_DONT_RETRY, B_FALSE);
3265 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3267 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3269 if (*arc_flags & ARC_NOWAIT) {
3274 ASSERT(*arc_flags & ARC_WAIT);
3275 if (zio_wait(rzio) == 0)
3278 /* l2arc read error; goto zio_read() */
3280 DTRACE_PROBE1(l2arc__miss,
3281 arc_buf_hdr_t *, hdr);
3282 ARCSTAT_BUMP(arcstat_l2_misses);
3283 if (HDR_L2_WRITING(hdr))
3284 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3285 spa_config_exit(spa, SCL_L2ARC, vd);
3289 spa_config_exit(spa, SCL_L2ARC, vd);
3290 if (l2arc_ndev != 0) {
3291 DTRACE_PROBE1(l2arc__miss,
3292 arc_buf_hdr_t *, hdr);
3293 ARCSTAT_BUMP(arcstat_l2_misses);
3297 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3298 arc_read_done, buf, priority, zio_flags, zb);
3300 if (*arc_flags & ARC_WAIT)
3301 return (zio_wait(rzio));
3303 ASSERT(*arc_flags & ARC_NOWAIT);
3310 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3312 ASSERT(buf->b_hdr != NULL);
3313 ASSERT(buf->b_hdr->b_state != arc_anon);
3314 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3315 ASSERT(buf->b_efunc == NULL);
3316 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3318 buf->b_efunc = func;
3319 buf->b_private = private;
3323 * This is used by the DMU to let the ARC know that a buffer is
3324 * being evicted, so the ARC should clean up. If this arc buf
3325 * is not yet in the evicted state, it will be put there.
3328 arc_buf_evict(arc_buf_t *buf)
3331 kmutex_t *hash_lock;
3333 list_t *list, *evicted_list;
3334 kmutex_t *lock, *evicted_lock;
3336 mutex_enter(&buf->b_evict_lock);
3340 * We are in arc_do_user_evicts().
3342 ASSERT(buf->b_data == NULL);
3343 mutex_exit(&buf->b_evict_lock);
3345 } else if (buf->b_data == NULL) {
3346 arc_buf_t copy = *buf; /* structure assignment */
3348 * We are on the eviction list; process this buffer now
3349 * but let arc_do_user_evicts() do the reaping.
3351 buf->b_efunc = NULL;
3352 mutex_exit(&buf->b_evict_lock);
3353 VERIFY(copy.b_efunc(©) == 0);
3356 hash_lock = HDR_LOCK(hdr);
3357 mutex_enter(hash_lock);
3359 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3361 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3362 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3365 * Pull this buffer off of the hdr
3368 while (*bufp != buf)
3369 bufp = &(*bufp)->b_next;
3370 *bufp = buf->b_next;
3372 ASSERT(buf->b_data != NULL);
3373 arc_buf_destroy(buf, FALSE, FALSE);
3375 if (hdr->b_datacnt == 0) {
3376 arc_state_t *old_state = hdr->b_state;
3377 arc_state_t *evicted_state;
3379 ASSERT(hdr->b_buf == NULL);
3380 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3383 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3385 get_buf_info(hdr, old_state, &list, &lock);
3386 get_buf_info(hdr, evicted_state, &evicted_list, &evicted_lock);
3388 mutex_enter(evicted_lock);
3390 arc_change_state(evicted_state, hdr, hash_lock);
3391 ASSERT(HDR_IN_HASH_TABLE(hdr));
3392 hdr->b_flags |= ARC_IN_HASH_TABLE;
3393 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3395 mutex_exit(evicted_lock);
3398 mutex_exit(hash_lock);
3399 mutex_exit(&buf->b_evict_lock);
3401 VERIFY(buf->b_efunc(buf) == 0);
3402 buf->b_efunc = NULL;
3403 buf->b_private = NULL;
3406 kmem_cache_free(buf_cache, buf);
3411 * Release this buffer from the cache. This must be done
3412 * after a read and prior to modifying the buffer contents.
3413 * If the buffer has more than one reference, we must make
3414 * a new hdr for the buffer.
3417 arc_release(arc_buf_t *buf, void *tag)
3420 kmutex_t *hash_lock = NULL;
3421 l2arc_buf_hdr_t *l2hdr;
3425 * It would be nice to assert that if it's DMU metadata (level >
3426 * 0 || it's the dnode file), then it must be syncing context.
3427 * But we don't know that information at this level.
3430 mutex_enter(&buf->b_evict_lock);
3433 /* this buffer is not on any list */
3434 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3436 if (hdr->b_state == arc_anon) {
3437 /* this buffer is already released */
3438 ASSERT(buf->b_efunc == NULL);
3440 hash_lock = HDR_LOCK(hdr);
3441 mutex_enter(hash_lock);
3443 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3446 l2hdr = hdr->b_l2hdr;
3448 mutex_enter(&l2arc_buflist_mtx);
3449 hdr->b_l2hdr = NULL;
3451 buf_size = hdr->b_size;
3454 * Do we have more than one buf?
3456 if (hdr->b_datacnt > 1) {
3457 arc_buf_hdr_t *nhdr;
3459 uint64_t blksz = hdr->b_size;
3460 uint64_t spa = hdr->b_spa;
3461 arc_buf_contents_t type = hdr->b_type;
3462 uint32_t flags = hdr->b_flags;
3464 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3466 * Pull the data off of this hdr and attach it to
3467 * a new anonymous hdr.
3469 (void) remove_reference(hdr, hash_lock, tag);
3471 while (*bufp != buf)
3472 bufp = &(*bufp)->b_next;
3473 *bufp = buf->b_next;
3476 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3477 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3478 if (refcount_is_zero(&hdr->b_refcnt)) {
3479 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3480 ASSERT3U(*size, >=, hdr->b_size);
3481 atomic_add_64(size, -hdr->b_size);
3485 * We're releasing a duplicate user data buffer, update
3486 * our statistics accordingly.
3488 if (hdr->b_type == ARC_BUFC_DATA) {
3489 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3490 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3493 hdr->b_datacnt -= 1;
3494 arc_cksum_verify(buf);
3496 arc_buf_unwatch(buf);
3497 #endif /* illumos */
3499 mutex_exit(hash_lock);
3501 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3502 nhdr->b_size = blksz;
3504 nhdr->b_type = type;
3506 nhdr->b_state = arc_anon;
3507 nhdr->b_arc_access = 0;
3508 nhdr->b_flags = flags & ARC_L2_WRITING;
3509 nhdr->b_l2hdr = NULL;
3510 nhdr->b_datacnt = 1;
3511 nhdr->b_freeze_cksum = NULL;
3512 (void) refcount_add(&nhdr->b_refcnt, tag);
3514 mutex_exit(&buf->b_evict_lock);
3515 atomic_add_64(&arc_anon->arcs_size, blksz);
3517 mutex_exit(&buf->b_evict_lock);
3518 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3519 ASSERT(!list_link_active(&hdr->b_arc_node));
3520 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3521 if (hdr->b_state != arc_anon)
3522 arc_change_state(arc_anon, hdr, hash_lock);
3523 hdr->b_arc_access = 0;
3525 mutex_exit(hash_lock);
3527 buf_discard_identity(hdr);
3530 buf->b_efunc = NULL;
3531 buf->b_private = NULL;
3534 trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
3536 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3537 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3538 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3539 mutex_exit(&l2arc_buflist_mtx);
3544 arc_released(arc_buf_t *buf)
3548 mutex_enter(&buf->b_evict_lock);
3549 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3550 mutex_exit(&buf->b_evict_lock);
3555 arc_has_callback(arc_buf_t *buf)
3559 mutex_enter(&buf->b_evict_lock);
3560 callback = (buf->b_efunc != NULL);
3561 mutex_exit(&buf->b_evict_lock);
3567 arc_referenced(arc_buf_t *buf)
3571 mutex_enter(&buf->b_evict_lock);
3572 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3573 mutex_exit(&buf->b_evict_lock);
3574 return (referenced);
3579 arc_write_ready(zio_t *zio)
3581 arc_write_callback_t *callback = zio->io_private;
3582 arc_buf_t *buf = callback->awcb_buf;
3583 arc_buf_hdr_t *hdr = buf->b_hdr;
3585 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3586 callback->awcb_ready(zio, buf, callback->awcb_private);
3589 * If the IO is already in progress, then this is a re-write
3590 * attempt, so we need to thaw and re-compute the cksum.
3591 * It is the responsibility of the callback to handle the
3592 * accounting for any re-write attempt.
3594 if (HDR_IO_IN_PROGRESS(hdr)) {
3595 mutex_enter(&hdr->b_freeze_lock);
3596 if (hdr->b_freeze_cksum != NULL) {
3597 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3598 hdr->b_freeze_cksum = NULL;
3600 mutex_exit(&hdr->b_freeze_lock);
3602 arc_cksum_compute(buf, B_FALSE);
3603 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3607 arc_write_done(zio_t *zio)
3609 arc_write_callback_t *callback = zio->io_private;
3610 arc_buf_t *buf = callback->awcb_buf;
3611 arc_buf_hdr_t *hdr = buf->b_hdr;
3613 ASSERT(hdr->b_acb == NULL);
3615 if (zio->io_error == 0) {
3616 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3617 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3618 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3620 ASSERT(BUF_EMPTY(hdr));
3624 * If the block to be written was all-zero, we may have
3625 * compressed it away. In this case no write was performed
3626 * so there will be no dva/birth/checksum. The buffer must
3627 * therefore remain anonymous (and uncached).
3629 if (!BUF_EMPTY(hdr)) {
3630 arc_buf_hdr_t *exists;
3631 kmutex_t *hash_lock;
3633 ASSERT(zio->io_error == 0);
3635 arc_cksum_verify(buf);
3637 exists = buf_hash_insert(hdr, &hash_lock);
3640 * This can only happen if we overwrite for
3641 * sync-to-convergence, because we remove
3642 * buffers from the hash table when we arc_free().
3644 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3645 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3646 panic("bad overwrite, hdr=%p exists=%p",
3647 (void *)hdr, (void *)exists);
3648 ASSERT(refcount_is_zero(&exists->b_refcnt));
3649 arc_change_state(arc_anon, exists, hash_lock);
3650 mutex_exit(hash_lock);
3651 arc_hdr_destroy(exists);
3652 exists = buf_hash_insert(hdr, &hash_lock);
3653 ASSERT3P(exists, ==, NULL);
3654 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3656 ASSERT(zio->io_prop.zp_nopwrite);
3657 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3658 panic("bad nopwrite, hdr=%p exists=%p",
3659 (void *)hdr, (void *)exists);
3662 ASSERT(hdr->b_datacnt == 1);
3663 ASSERT(hdr->b_state == arc_anon);
3664 ASSERT(BP_GET_DEDUP(zio->io_bp));
3665 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3668 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3669 /* if it's not anon, we are doing a scrub */
3670 if (!exists && hdr->b_state == arc_anon)
3671 arc_access(hdr, hash_lock);
3672 mutex_exit(hash_lock);
3674 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3677 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3678 callback->awcb_done(zio, buf, callback->awcb_private);
3680 kmem_free(callback, sizeof (arc_write_callback_t));
3684 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3685 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
3686 arc_done_func_t *ready, arc_done_func_t *done, void *private,
3687 int priority, int zio_flags, const zbookmark_t *zb)
3689 arc_buf_hdr_t *hdr = buf->b_hdr;
3690 arc_write_callback_t *callback;
3693 ASSERT(ready != NULL);
3694 ASSERT(done != NULL);
3695 ASSERT(!HDR_IO_ERROR(hdr));
3696 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3697 ASSERT(hdr->b_acb == NULL);
3699 hdr->b_flags |= ARC_L2CACHE;
3700 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3701 callback->awcb_ready = ready;
3702 callback->awcb_done = done;
3703 callback->awcb_private = private;
3704 callback->awcb_buf = buf;
3706 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3707 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3713 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3716 uint64_t available_memory =
3717 ptoa((uintmax_t)cnt.v_free_count + cnt.v_cache_count);
3718 static uint64_t page_load = 0;
3719 static uint64_t last_txg = 0;
3724 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3727 if (available_memory >= zfs_write_limit_max)
3730 if (txg > last_txg) {
3735 * If we are in pageout, we know that memory is already tight,
3736 * the arc is already going to be evicting, so we just want to
3737 * continue to let page writes occur as quickly as possible.
3739 if (curproc == pageproc) {
3740 if (page_load > available_memory / 4)
3741 return (SET_ERROR(ERESTART));
3742 /* Note: reserve is inflated, so we deflate */
3743 page_load += reserve / 8;
3745 } else if (page_load > 0 && arc_reclaim_needed()) {
3746 /* memory is low, delay before restarting */
3747 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3748 return (SET_ERROR(EAGAIN));
3752 if (arc_size > arc_c_min) {
3753 uint64_t evictable_memory =
3754 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3755 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3756 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3757 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3758 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3761 if (inflight_data > available_memory / 4) {
3762 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3763 return (SET_ERROR(ERESTART));
3770 arc_tempreserve_clear(uint64_t reserve)
3772 atomic_add_64(&arc_tempreserve, -reserve);
3773 ASSERT((int64_t)arc_tempreserve >= 0);
3777 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3784 * Once in a while, fail for no reason. Everything should cope.
3786 if (spa_get_random(10000) == 0) {
3787 dprintf("forcing random failure\n");
3788 return (SET_ERROR(ERESTART));
3791 if (reserve > arc_c/4 && !arc_no_grow)
3792 arc_c = MIN(arc_c_max, reserve * 4);
3793 if (reserve > arc_c)
3794 return (SET_ERROR(ENOMEM));
3797 * Don't count loaned bufs as in flight dirty data to prevent long
3798 * network delays from blocking transactions that are ready to be
3799 * assigned to a txg.
3801 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3804 * Writes will, almost always, require additional memory allocations
3805 * in order to compress/encrypt/etc the data. We therefor need to
3806 * make sure that there is sufficient available memory for this.
3808 if (error = arc_memory_throttle(reserve, anon_size, txg))
3812 * Throttle writes when the amount of dirty data in the cache
3813 * gets too large. We try to keep the cache less than half full
3814 * of dirty blocks so that our sync times don't grow too large.
3815 * Note: if two requests come in concurrently, we might let them
3816 * both succeed, when one of them should fail. Not a huge deal.
3819 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3820 anon_size > arc_c / 4) {
3821 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3822 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3823 arc_tempreserve>>10,
3824 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3825 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3826 reserve>>10, arc_c>>10);
3827 return (SET_ERROR(ERESTART));
3829 atomic_add_64(&arc_tempreserve, reserve);
3833 static kmutex_t arc_lowmem_lock;
3835 static eventhandler_tag arc_event_lowmem = NULL;
3838 arc_lowmem(void *arg __unused, int howto __unused)
3841 /* Serialize access via arc_lowmem_lock. */
3842 mutex_enter(&arc_lowmem_lock);
3843 mutex_enter(&arc_reclaim_thr_lock);
3845 cv_signal(&arc_reclaim_thr_cv);
3848 * It is unsafe to block here in arbitrary threads, because we can come
3849 * here from ARC itself and may hold ARC locks and thus risk a deadlock
3850 * with ARC reclaim thread.
3852 if (curproc == pageproc) {
3854 msleep(&needfree, &arc_reclaim_thr_lock, 0, "zfs:lowmem", 0);
3856 mutex_exit(&arc_reclaim_thr_lock);
3857 mutex_exit(&arc_lowmem_lock);
3864 int i, prefetch_tunable_set = 0;
3866 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3867 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3868 mutex_init(&arc_lowmem_lock, NULL, MUTEX_DEFAULT, NULL);
3870 /* Convert seconds to clock ticks */
3871 arc_min_prefetch_lifespan = 1 * hz;
3873 /* Start out with 1/8 of all memory */
3874 arc_c = kmem_size() / 8;
3879 * On architectures where the physical memory can be larger
3880 * than the addressable space (intel in 32-bit mode), we may
3881 * need to limit the cache to 1/8 of VM size.
3883 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3886 /* set min cache to 1/32 of all memory, or 16MB, whichever is more */
3887 arc_c_min = MAX(arc_c / 4, 64<<18);
3888 /* set max to 1/2 of all memory, or all but 1GB, whichever is more */
3889 if (arc_c * 8 >= 1<<30)
3890 arc_c_max = (arc_c * 8) - (1<<30);
3892 arc_c_max = arc_c_min;
3893 arc_c_max = MAX(arc_c * 5, arc_c_max);
3897 * Allow the tunables to override our calculations if they are
3898 * reasonable (ie. over 16MB)
3900 if (zfs_arc_max > 64<<18 && zfs_arc_max < kmem_size())
3901 arc_c_max = zfs_arc_max;
3902 if (zfs_arc_min > 64<<18 && zfs_arc_min <= arc_c_max)
3903 arc_c_min = zfs_arc_min;
3907 arc_p = (arc_c >> 1);
3909 /* limit meta-data to 1/4 of the arc capacity */
3910 arc_meta_limit = arc_c_max / 4;
3912 /* Allow the tunable to override if it is reasonable */
3913 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3914 arc_meta_limit = zfs_arc_meta_limit;
3916 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3917 arc_c_min = arc_meta_limit / 2;
3919 if (zfs_arc_grow_retry > 0)
3920 arc_grow_retry = zfs_arc_grow_retry;
3922 if (zfs_arc_shrink_shift > 0)
3923 arc_shrink_shift = zfs_arc_shrink_shift;
3925 if (zfs_arc_p_min_shift > 0)
3926 arc_p_min_shift = zfs_arc_p_min_shift;
3928 /* if kmem_flags are set, lets try to use less memory */
3929 if (kmem_debugging())
3931 if (arc_c < arc_c_min)
3934 zfs_arc_min = arc_c_min;
3935 zfs_arc_max = arc_c_max;
3937 arc_anon = &ARC_anon;
3939 arc_mru_ghost = &ARC_mru_ghost;
3941 arc_mfu_ghost = &ARC_mfu_ghost;
3942 arc_l2c_only = &ARC_l2c_only;
3945 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
3946 mutex_init(&arc_anon->arcs_locks[i].arcs_lock,
3947 NULL, MUTEX_DEFAULT, NULL);
3948 mutex_init(&arc_mru->arcs_locks[i].arcs_lock,
3949 NULL, MUTEX_DEFAULT, NULL);
3950 mutex_init(&arc_mru_ghost->arcs_locks[i].arcs_lock,
3951 NULL, MUTEX_DEFAULT, NULL);
3952 mutex_init(&arc_mfu->arcs_locks[i].arcs_lock,
3953 NULL, MUTEX_DEFAULT, NULL);
3954 mutex_init(&arc_mfu_ghost->arcs_locks[i].arcs_lock,
3955 NULL, MUTEX_DEFAULT, NULL);
3956 mutex_init(&arc_l2c_only->arcs_locks[i].arcs_lock,
3957 NULL, MUTEX_DEFAULT, NULL);
3959 list_create(&arc_mru->arcs_lists[i],
3960 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3961 list_create(&arc_mru_ghost->arcs_lists[i],
3962 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3963 list_create(&arc_mfu->arcs_lists[i],
3964 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3965 list_create(&arc_mfu_ghost->arcs_lists[i],
3966 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3967 list_create(&arc_mfu_ghost->arcs_lists[i],
3968 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3969 list_create(&arc_l2c_only->arcs_lists[i],
3970 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3975 arc_thread_exit = 0;
3976 arc_eviction_list = NULL;
3977 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3978 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3980 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3981 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3983 if (arc_ksp != NULL) {
3984 arc_ksp->ks_data = &arc_stats;
3985 kstat_install(arc_ksp);
3988 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3989 TS_RUN, minclsyspri);
3992 arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
3993 EVENTHANDLER_PRI_FIRST);
3999 if (zfs_write_limit_max == 0)
4000 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
4002 zfs_write_limit_shift = 0;
4003 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
4006 if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
4007 prefetch_tunable_set = 1;
4010 if (prefetch_tunable_set == 0) {
4011 printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
4013 printf(" add \"vfs.zfs.prefetch_disable=0\" "
4014 "to /boot/loader.conf.\n");
4015 zfs_prefetch_disable = 1;
4018 if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
4019 prefetch_tunable_set == 0) {
4020 printf("ZFS NOTICE: Prefetch is disabled by default if less "
4021 "than 4GB of RAM is present;\n"
4022 " to enable, add \"vfs.zfs.prefetch_disable=0\" "
4023 "to /boot/loader.conf.\n");
4024 zfs_prefetch_disable = 1;
4027 /* Warn about ZFS memory and address space requirements. */
4028 if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
4029 printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
4030 "expect unstable behavior.\n");
4032 if (kmem_size() < 512 * (1 << 20)) {
4033 printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
4034 "expect unstable behavior.\n");
4035 printf(" Consider tuning vm.kmem_size and "
4036 "vm.kmem_size_max\n");
4037 printf(" in /boot/loader.conf.\n");
4047 mutex_enter(&arc_reclaim_thr_lock);
4048 arc_thread_exit = 1;
4049 cv_signal(&arc_reclaim_thr_cv);
4050 while (arc_thread_exit != 0)
4051 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
4052 mutex_exit(&arc_reclaim_thr_lock);
4058 if (arc_ksp != NULL) {
4059 kstat_delete(arc_ksp);
4063 mutex_destroy(&arc_eviction_mtx);
4064 mutex_destroy(&arc_reclaim_thr_lock);
4065 cv_destroy(&arc_reclaim_thr_cv);
4067 for (i = 0; i < ARC_BUFC_NUMLISTS; i++) {
4068 list_destroy(&arc_mru->arcs_lists[i]);
4069 list_destroy(&arc_mru_ghost->arcs_lists[i]);
4070 list_destroy(&arc_mfu->arcs_lists[i]);
4071 list_destroy(&arc_mfu_ghost->arcs_lists[i]);
4072 list_destroy(&arc_l2c_only->arcs_lists[i]);
4074 mutex_destroy(&arc_anon->arcs_locks[i].arcs_lock);
4075 mutex_destroy(&arc_mru->arcs_locks[i].arcs_lock);
4076 mutex_destroy(&arc_mru_ghost->arcs_locks[i].arcs_lock);
4077 mutex_destroy(&arc_mfu->arcs_locks[i].arcs_lock);
4078 mutex_destroy(&arc_mfu_ghost->arcs_locks[i].arcs_lock);
4079 mutex_destroy(&arc_l2c_only->arcs_locks[i].arcs_lock);
4082 mutex_destroy(&zfs_write_limit_lock);
4086 ASSERT(arc_loaned_bytes == 0);
4088 mutex_destroy(&arc_lowmem_lock);
4090 if (arc_event_lowmem != NULL)
4091 EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
4098 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
4099 * It uses dedicated storage devices to hold cached data, which are populated
4100 * using large infrequent writes. The main role of this cache is to boost
4101 * the performance of random read workloads. The intended L2ARC devices
4102 * include short-stroked disks, solid state disks, and other media with
4103 * substantially faster read latency than disk.
4105 * +-----------------------+
4107 * +-----------------------+
4110 * l2arc_feed_thread() arc_read()
4114 * +---------------+ |
4116 * +---------------+ |
4121 * +-------+ +-------+
4123 * | cache | | cache |
4124 * +-------+ +-------+
4125 * +=========+ .-----.
4126 * : L2ARC : |-_____-|
4127 * : devices : | Disks |
4128 * +=========+ `-_____-'
4130 * Read requests are satisfied from the following sources, in order:
4133 * 2) vdev cache of L2ARC devices
4135 * 4) vdev cache of disks
4138 * Some L2ARC device types exhibit extremely slow write performance.
4139 * To accommodate for this there are some significant differences between
4140 * the L2ARC and traditional cache design:
4142 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4143 * the ARC behave as usual, freeing buffers and placing headers on ghost
4144 * lists. The ARC does not send buffers to the L2ARC during eviction as
4145 * this would add inflated write latencies for all ARC memory pressure.
4147 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4148 * It does this by periodically scanning buffers from the eviction-end of
4149 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4150 * not already there. It scans until a headroom of buffers is satisfied,
4151 * which itself is a buffer for ARC eviction. The thread that does this is
4152 * l2arc_feed_thread(), illustrated below; example sizes are included to
4153 * provide a better sense of ratio than this diagram:
4156 * +---------------------+----------+
4157 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4158 * +---------------------+----------+ | o L2ARC eligible
4159 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4160 * +---------------------+----------+ |
4161 * 15.9 Gbytes ^ 32 Mbytes |
4163 * l2arc_feed_thread()
4165 * l2arc write hand <--[oooo]--'
4169 * +==============================+
4170 * L2ARC dev |####|#|###|###| |####| ... |
4171 * +==============================+
4174 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4175 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4176 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4177 * safe to say that this is an uncommon case, since buffers at the end of
4178 * the ARC lists have moved there due to inactivity.
4180 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4181 * then the L2ARC simply misses copying some buffers. This serves as a
4182 * pressure valve to prevent heavy read workloads from both stalling the ARC
4183 * with waits and clogging the L2ARC with writes. This also helps prevent
4184 * the potential for the L2ARC to churn if it attempts to cache content too
4185 * quickly, such as during backups of the entire pool.
4187 * 5. After system boot and before the ARC has filled main memory, there are
4188 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4189 * lists can remain mostly static. Instead of searching from tail of these
4190 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4191 * for eligible buffers, greatly increasing its chance of finding them.
4193 * The L2ARC device write speed is also boosted during this time so that
4194 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4195 * there are no L2ARC reads, and no fear of degrading read performance
4196 * through increased writes.
4198 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4199 * the vdev queue can aggregate them into larger and fewer writes. Each
4200 * device is written to in a rotor fashion, sweeping writes through
4201 * available space then repeating.
4203 * 7. The L2ARC does not store dirty content. It never needs to flush
4204 * write buffers back to disk based storage.
4206 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4207 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4209 * The performance of the L2ARC can be tweaked by a number of tunables, which
4210 * may be necessary for different workloads:
4212 * l2arc_write_max max write bytes per interval
4213 * l2arc_write_boost extra write bytes during device warmup
4214 * l2arc_noprefetch skip caching prefetched buffers
4215 * l2arc_headroom number of max device writes to precache
4216 * l2arc_feed_secs seconds between L2ARC writing
4218 * Tunables may be removed or added as future performance improvements are
4219 * integrated, and also may become zpool properties.
4221 * There are three key functions that control how the L2ARC warms up:
4223 * l2arc_write_eligible() check if a buffer is eligible to cache
4224 * l2arc_write_size() calculate how much to write
4225 * l2arc_write_interval() calculate sleep delay between writes
4227 * These three functions determine what to write, how much, and how quickly
4232 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4235 * A buffer is *not* eligible for the L2ARC if it:
4236 * 1. belongs to a different spa.
4237 * 2. is already cached on the L2ARC.
4238 * 3. has an I/O in progress (it may be an incomplete read).
4239 * 4. is flagged not eligible (zfs property).
4241 if (ab->b_spa != spa_guid) {
4242 ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
4245 if (ab->b_l2hdr != NULL) {
4246 ARCSTAT_BUMP(arcstat_l2_write_in_l2);
4249 if (HDR_IO_IN_PROGRESS(ab)) {
4250 ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
4253 if (!HDR_L2CACHE(ab)) {
4254 ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
4262 l2arc_write_size(l2arc_dev_t *dev)
4266 size = dev->l2ad_write;
4268 if (arc_warm == B_FALSE)
4269 size += dev->l2ad_boost;
4276 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4278 clock_t interval, next, now;
4281 * If the ARC lists are busy, increase our write rate; if the
4282 * lists are stale, idle back. This is achieved by checking
4283 * how much we previously wrote - if it was more than half of
4284 * what we wanted, schedule the next write much sooner.
4286 if (l2arc_feed_again && wrote > (wanted / 2))
4287 interval = (hz * l2arc_feed_min_ms) / 1000;
4289 interval = hz * l2arc_feed_secs;
4291 now = ddi_get_lbolt();
4292 next = MAX(now, MIN(now + interval, began + interval));
4298 l2arc_hdr_stat_add(void)
4300 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4301 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4305 l2arc_hdr_stat_remove(void)
4307 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4308 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4312 * Cycle through L2ARC devices. This is how L2ARC load balances.
4313 * If a device is returned, this also returns holding the spa config lock.
4315 static l2arc_dev_t *
4316 l2arc_dev_get_next(void)
4318 l2arc_dev_t *first, *next = NULL;
4321 * Lock out the removal of spas (spa_namespace_lock), then removal
4322 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4323 * both locks will be dropped and a spa config lock held instead.
4325 mutex_enter(&spa_namespace_lock);
4326 mutex_enter(&l2arc_dev_mtx);
4328 /* if there are no vdevs, there is nothing to do */
4329 if (l2arc_ndev == 0)
4333 next = l2arc_dev_last;
4335 /* loop around the list looking for a non-faulted vdev */
4337 next = list_head(l2arc_dev_list);
4339 next = list_next(l2arc_dev_list, next);
4341 next = list_head(l2arc_dev_list);
4344 /* if we have come back to the start, bail out */
4347 else if (next == first)
4350 } while (vdev_is_dead(next->l2ad_vdev));
4352 /* if we were unable to find any usable vdevs, return NULL */
4353 if (vdev_is_dead(next->l2ad_vdev))
4356 l2arc_dev_last = next;
4359 mutex_exit(&l2arc_dev_mtx);
4362 * Grab the config lock to prevent the 'next' device from being
4363 * removed while we are writing to it.
4366 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4367 mutex_exit(&spa_namespace_lock);
4373 * Free buffers that were tagged for destruction.
4376 l2arc_do_free_on_write()
4379 l2arc_data_free_t *df, *df_prev;
4381 mutex_enter(&l2arc_free_on_write_mtx);
4382 buflist = l2arc_free_on_write;
4384 for (df = list_tail(buflist); df; df = df_prev) {
4385 df_prev = list_prev(buflist, df);
4386 ASSERT(df->l2df_data != NULL);
4387 ASSERT(df->l2df_func != NULL);
4388 df->l2df_func(df->l2df_data, df->l2df_size);
4389 list_remove(buflist, df);
4390 kmem_free(df, sizeof (l2arc_data_free_t));
4393 mutex_exit(&l2arc_free_on_write_mtx);
4397 * A write to a cache device has completed. Update all headers to allow
4398 * reads from these buffers to begin.
4401 l2arc_write_done(zio_t *zio)
4403 l2arc_write_callback_t *cb;
4406 arc_buf_hdr_t *head, *ab, *ab_prev;
4407 l2arc_buf_hdr_t *abl2;
4408 kmutex_t *hash_lock;
4410 cb = zio->io_private;
4412 dev = cb->l2wcb_dev;
4413 ASSERT(dev != NULL);
4414 head = cb->l2wcb_head;
4415 ASSERT(head != NULL);
4416 buflist = dev->l2ad_buflist;
4417 ASSERT(buflist != NULL);
4418 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4419 l2arc_write_callback_t *, cb);
4421 if (zio->io_error != 0)
4422 ARCSTAT_BUMP(arcstat_l2_writes_error);
4424 mutex_enter(&l2arc_buflist_mtx);
4427 * All writes completed, or an error was hit.
4429 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4430 ab_prev = list_prev(buflist, ab);
4432 hash_lock = HDR_LOCK(ab);
4433 if (!mutex_tryenter(hash_lock)) {
4435 * This buffer misses out. It may be in a stage
4436 * of eviction. Its ARC_L2_WRITING flag will be
4437 * left set, denying reads to this buffer.
4439 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4443 if (zio->io_error != 0) {
4445 * Error - drop L2ARC entry.
4447 list_remove(buflist, ab);
4450 trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr,
4452 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4453 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4457 * Allow ARC to begin reads to this L2ARC entry.
4459 ab->b_flags &= ~ARC_L2_WRITING;
4461 mutex_exit(hash_lock);
4464 atomic_inc_64(&l2arc_writes_done);
4465 list_remove(buflist, head);
4466 kmem_cache_free(hdr_cache, head);
4467 mutex_exit(&l2arc_buflist_mtx);
4469 l2arc_do_free_on_write();
4471 kmem_free(cb, sizeof (l2arc_write_callback_t));
4475 * A read to a cache device completed. Validate buffer contents before
4476 * handing over to the regular ARC routines.
4479 l2arc_read_done(zio_t *zio)
4481 l2arc_read_callback_t *cb;
4484 kmutex_t *hash_lock;
4487 ASSERT(zio->io_vd != NULL);
4488 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4490 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4492 cb = zio->io_private;
4494 buf = cb->l2rcb_buf;
4495 ASSERT(buf != NULL);
4497 hash_lock = HDR_LOCK(buf->b_hdr);
4498 mutex_enter(hash_lock);
4500 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4503 * Check this survived the L2ARC journey.
4505 equal = arc_cksum_equal(buf);
4506 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4507 mutex_exit(hash_lock);
4508 zio->io_private = buf;
4509 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4510 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4513 mutex_exit(hash_lock);
4515 * Buffer didn't survive caching. Increment stats and
4516 * reissue to the original storage device.
4518 if (zio->io_error != 0) {
4519 ARCSTAT_BUMP(arcstat_l2_io_error);
4521 zio->io_error = SET_ERROR(EIO);
4524 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4527 * If there's no waiter, issue an async i/o to the primary
4528 * storage now. If there *is* a waiter, the caller must
4529 * issue the i/o in a context where it's OK to block.
4531 if (zio->io_waiter == NULL) {
4532 zio_t *pio = zio_unique_parent(zio);
4534 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4536 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4537 buf->b_data, zio->io_size, arc_read_done, buf,
4538 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4542 kmem_free(cb, sizeof (l2arc_read_callback_t));
4546 * This is the list priority from which the L2ARC will search for pages to
4547 * cache. This is used within loops (0..3) to cycle through lists in the
4548 * desired order. This order can have a significant effect on cache
4551 * Currently the metadata lists are hit first, MFU then MRU, followed by
4552 * the data lists. This function returns a locked list, and also returns
4556 l2arc_list_locked(int list_num, kmutex_t **lock)
4558 list_t *list = NULL;
4561 ASSERT(list_num >= 0 && list_num < 2 * ARC_BUFC_NUMLISTS);
4563 if (list_num < ARC_BUFC_NUMMETADATALISTS) {
4565 list = &arc_mfu->arcs_lists[idx];
4566 *lock = ARCS_LOCK(arc_mfu, idx);
4567 } else if (list_num < ARC_BUFC_NUMMETADATALISTS * 2) {
4568 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4569 list = &arc_mru->arcs_lists[idx];
4570 *lock = ARCS_LOCK(arc_mru, idx);
4571 } else if (list_num < (ARC_BUFC_NUMMETADATALISTS * 2 +
4572 ARC_BUFC_NUMDATALISTS)) {
4573 idx = list_num - ARC_BUFC_NUMMETADATALISTS;
4574 list = &arc_mfu->arcs_lists[idx];
4575 *lock = ARCS_LOCK(arc_mfu, idx);
4577 idx = list_num - ARC_BUFC_NUMLISTS;
4578 list = &arc_mru->arcs_lists[idx];
4579 *lock = ARCS_LOCK(arc_mru, idx);
4582 ASSERT(!(MUTEX_HELD(*lock)));
4588 * Evict buffers from the device write hand to the distance specified in
4589 * bytes. This distance may span populated buffers, it may span nothing.
4590 * This is clearing a region on the L2ARC device ready for writing.
4591 * If the 'all' boolean is set, every buffer is evicted.
4594 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4597 l2arc_buf_hdr_t *abl2;
4598 arc_buf_hdr_t *ab, *ab_prev;
4599 kmutex_t *hash_lock;
4602 buflist = dev->l2ad_buflist;
4604 if (buflist == NULL)
4607 if (!all && dev->l2ad_first) {
4609 * This is the first sweep through the device. There is
4615 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4617 * When nearing the end of the device, evict to the end
4618 * before the device write hand jumps to the start.
4620 taddr = dev->l2ad_end;
4622 taddr = dev->l2ad_hand + distance;
4624 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4625 uint64_t, taddr, boolean_t, all);
4628 mutex_enter(&l2arc_buflist_mtx);
4629 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4630 ab_prev = list_prev(buflist, ab);
4632 hash_lock = HDR_LOCK(ab);
4633 if (!mutex_tryenter(hash_lock)) {
4635 * Missed the hash lock. Retry.
4637 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4638 mutex_exit(&l2arc_buflist_mtx);
4639 mutex_enter(hash_lock);
4640 mutex_exit(hash_lock);
4644 if (HDR_L2_WRITE_HEAD(ab)) {
4646 * We hit a write head node. Leave it for
4647 * l2arc_write_done().
4649 list_remove(buflist, ab);
4650 mutex_exit(hash_lock);
4654 if (!all && ab->b_l2hdr != NULL &&
4655 (ab->b_l2hdr->b_daddr > taddr ||
4656 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4658 * We've evicted to the target address,
4659 * or the end of the device.
4661 mutex_exit(hash_lock);
4665 if (HDR_FREE_IN_PROGRESS(ab)) {
4667 * Already on the path to destruction.
4669 mutex_exit(hash_lock);
4673 if (ab->b_state == arc_l2c_only) {
4674 ASSERT(!HDR_L2_READING(ab));
4676 * This doesn't exist in the ARC. Destroy.
4677 * arc_hdr_destroy() will call list_remove()
4678 * and decrement arcstat_l2_size.
4680 arc_change_state(arc_anon, ab, hash_lock);
4681 arc_hdr_destroy(ab);
4684 * Invalidate issued or about to be issued
4685 * reads, since we may be about to write
4686 * over this location.
4688 if (HDR_L2_READING(ab)) {
4689 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4690 ab->b_flags |= ARC_L2_EVICTED;
4694 * Tell ARC this no longer exists in L2ARC.
4696 if (ab->b_l2hdr != NULL) {
4699 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4700 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4702 list_remove(buflist, ab);
4705 * This may have been leftover after a
4708 ab->b_flags &= ~ARC_L2_WRITING;
4710 mutex_exit(hash_lock);
4712 mutex_exit(&l2arc_buflist_mtx);
4714 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
4715 dev->l2ad_evict = taddr;
4719 * Find and write ARC buffers to the L2ARC device.
4721 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4722 * for reading until they have completed writing.
4725 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4727 arc_buf_hdr_t *ab, *ab_prev, *head;
4728 l2arc_buf_hdr_t *hdrl2;
4730 uint64_t passed_sz, write_sz, buf_sz, headroom;
4732 kmutex_t *hash_lock, *list_lock;
4733 boolean_t have_lock, full;
4734 l2arc_write_callback_t *cb;
4736 uint64_t guid = spa_load_guid(spa);
4739 ASSERT(dev->l2ad_vdev != NULL);
4744 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4745 head->b_flags |= ARC_L2_WRITE_HEAD;
4747 ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
4749 * Copy buffers for L2ARC writing.
4751 mutex_enter(&l2arc_buflist_mtx);
4752 for (try = 0; try < 2 * ARC_BUFC_NUMLISTS; try++) {
4753 list = l2arc_list_locked(try, &list_lock);
4755 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
4758 * L2ARC fast warmup.
4760 * Until the ARC is warm and starts to evict, read from the
4761 * head of the ARC lists rather than the tail.
4763 headroom = target_sz * l2arc_headroom;
4764 if (arc_warm == B_FALSE)
4765 ab = list_head(list);
4767 ab = list_tail(list);
4769 ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
4771 for (; ab; ab = ab_prev) {
4772 if (arc_warm == B_FALSE)
4773 ab_prev = list_next(list, ab);
4775 ab_prev = list_prev(list, ab);
4776 ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned, ab->b_size);
4778 hash_lock = HDR_LOCK(ab);
4779 have_lock = MUTEX_HELD(hash_lock);
4780 if (!have_lock && !mutex_tryenter(hash_lock)) {
4781 ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
4783 * Skip this buffer rather than waiting.
4788 passed_sz += ab->b_size;
4789 if (passed_sz > headroom) {
4793 mutex_exit(hash_lock);
4794 ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
4798 if (!l2arc_write_eligible(guid, ab)) {
4799 mutex_exit(hash_lock);
4803 if ((write_sz + ab->b_size) > target_sz) {
4805 mutex_exit(hash_lock);
4806 ARCSTAT_BUMP(arcstat_l2_write_full);
4812 * Insert a dummy header on the buflist so
4813 * l2arc_write_done() can find where the
4814 * write buffers begin without searching.
4816 list_insert_head(dev->l2ad_buflist, head);
4819 sizeof (l2arc_write_callback_t), KM_SLEEP);
4820 cb->l2wcb_dev = dev;
4821 cb->l2wcb_head = head;
4822 pio = zio_root(spa, l2arc_write_done, cb,
4824 ARCSTAT_BUMP(arcstat_l2_write_pios);
4828 * Create and add a new L2ARC header.
4830 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4832 hdrl2->b_daddr = dev->l2ad_hand;
4834 ab->b_flags |= ARC_L2_WRITING;
4835 ab->b_l2hdr = hdrl2;
4836 list_insert_head(dev->l2ad_buflist, ab);
4837 buf_data = ab->b_buf->b_data;
4838 buf_sz = ab->b_size;
4841 * Compute and store the buffer cksum before
4842 * writing. On debug the cksum is verified first.
4844 arc_cksum_verify(ab->b_buf);
4845 arc_cksum_compute(ab->b_buf, B_TRUE);
4847 mutex_exit(hash_lock);
4849 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4850 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4851 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4852 ZIO_FLAG_CANFAIL, B_FALSE);
4854 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4856 (void) zio_nowait(wzio);
4859 * Keep the clock hand suitably device-aligned.
4861 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4864 dev->l2ad_hand += buf_sz;
4867 mutex_exit(list_lock);
4872 mutex_exit(&l2arc_buflist_mtx);
4876 kmem_cache_free(hdr_cache, head);
4880 ASSERT3U(write_sz, <=, target_sz);
4881 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4882 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4883 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4884 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
4887 * Bump device hand to the device start if it is approaching the end.
4888 * l2arc_evict() will already have evicted ahead for this case.
4890 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4891 vdev_space_update(dev->l2ad_vdev,
4892 dev->l2ad_end - dev->l2ad_hand, 0, 0);
4893 dev->l2ad_hand = dev->l2ad_start;
4894 dev->l2ad_evict = dev->l2ad_start;
4895 dev->l2ad_first = B_FALSE;
4898 dev->l2ad_writing = B_TRUE;
4899 (void) zio_wait(pio);
4900 dev->l2ad_writing = B_FALSE;
4906 * This thread feeds the L2ARC at regular intervals. This is the beating
4907 * heart of the L2ARC.
4910 l2arc_feed_thread(void *dummy __unused)
4915 uint64_t size, wrote;
4916 clock_t begin, next = ddi_get_lbolt();
4918 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4920 mutex_enter(&l2arc_feed_thr_lock);
4922 while (l2arc_thread_exit == 0) {
4923 CALLB_CPR_SAFE_BEGIN(&cpr);
4924 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4925 next - ddi_get_lbolt());
4926 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4927 next = ddi_get_lbolt() + hz;
4930 * Quick check for L2ARC devices.
4932 mutex_enter(&l2arc_dev_mtx);
4933 if (l2arc_ndev == 0) {
4934 mutex_exit(&l2arc_dev_mtx);
4937 mutex_exit(&l2arc_dev_mtx);
4938 begin = ddi_get_lbolt();
4941 * This selects the next l2arc device to write to, and in
4942 * doing so the next spa to feed from: dev->l2ad_spa. This
4943 * will return NULL if there are now no l2arc devices or if
4944 * they are all faulted.
4946 * If a device is returned, its spa's config lock is also
4947 * held to prevent device removal. l2arc_dev_get_next()
4948 * will grab and release l2arc_dev_mtx.
4950 if ((dev = l2arc_dev_get_next()) == NULL)
4953 spa = dev->l2ad_spa;
4954 ASSERT(spa != NULL);
4957 * If the pool is read-only then force the feed thread to
4958 * sleep a little longer.
4960 if (!spa_writeable(spa)) {
4961 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
4962 spa_config_exit(spa, SCL_L2ARC, dev);
4967 * Avoid contributing to memory pressure.
4969 if (arc_reclaim_needed()) {
4970 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4971 spa_config_exit(spa, SCL_L2ARC, dev);
4975 ARCSTAT_BUMP(arcstat_l2_feeds);
4977 size = l2arc_write_size(dev);
4980 * Evict L2ARC buffers that will be overwritten.
4982 l2arc_evict(dev, size, B_FALSE);
4985 * Write ARC buffers.
4987 wrote = l2arc_write_buffers(spa, dev, size);
4990 * Calculate interval between writes.
4992 next = l2arc_write_interval(begin, size, wrote);
4993 spa_config_exit(spa, SCL_L2ARC, dev);
4996 l2arc_thread_exit = 0;
4997 cv_broadcast(&l2arc_feed_thr_cv);
4998 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
5003 l2arc_vdev_present(vdev_t *vd)
5007 mutex_enter(&l2arc_dev_mtx);
5008 for (dev = list_head(l2arc_dev_list); dev != NULL;
5009 dev = list_next(l2arc_dev_list, dev)) {
5010 if (dev->l2ad_vdev == vd)
5013 mutex_exit(&l2arc_dev_mtx);
5015 return (dev != NULL);
5019 * Add a vdev for use by the L2ARC. By this point the spa has already
5020 * validated the vdev and opened it.
5023 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
5025 l2arc_dev_t *adddev;
5027 ASSERT(!l2arc_vdev_present(vd));
5030 * Create a new l2arc device entry.
5032 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
5033 adddev->l2ad_spa = spa;
5034 adddev->l2ad_vdev = vd;
5035 adddev->l2ad_write = l2arc_write_max;
5036 adddev->l2ad_boost = l2arc_write_boost;
5037 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
5038 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
5039 adddev->l2ad_hand = adddev->l2ad_start;
5040 adddev->l2ad_evict = adddev->l2ad_start;
5041 adddev->l2ad_first = B_TRUE;
5042 adddev->l2ad_writing = B_FALSE;
5043 ASSERT3U(adddev->l2ad_write, >, 0);
5046 * This is a list of all ARC buffers that are still valid on the
5049 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
5050 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
5051 offsetof(arc_buf_hdr_t, b_l2node));
5053 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
5056 * Add device to global list
5058 mutex_enter(&l2arc_dev_mtx);
5059 list_insert_head(l2arc_dev_list, adddev);
5060 atomic_inc_64(&l2arc_ndev);
5061 mutex_exit(&l2arc_dev_mtx);
5065 * Remove a vdev from the L2ARC.
5068 l2arc_remove_vdev(vdev_t *vd)
5070 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
5073 * Find the device by vdev
5075 mutex_enter(&l2arc_dev_mtx);
5076 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
5077 nextdev = list_next(l2arc_dev_list, dev);
5078 if (vd == dev->l2ad_vdev) {
5083 ASSERT(remdev != NULL);
5086 * Remove device from global list
5088 list_remove(l2arc_dev_list, remdev);
5089 l2arc_dev_last = NULL; /* may have been invalidated */
5090 atomic_dec_64(&l2arc_ndev);
5091 mutex_exit(&l2arc_dev_mtx);
5094 * Clear all buflists and ARC references. L2ARC device flush.
5096 l2arc_evict(remdev, 0, B_TRUE);
5097 list_destroy(remdev->l2ad_buflist);
5098 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
5099 kmem_free(remdev, sizeof (l2arc_dev_t));
5105 l2arc_thread_exit = 0;
5107 l2arc_writes_sent = 0;
5108 l2arc_writes_done = 0;
5110 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
5111 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
5112 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
5113 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
5114 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
5116 l2arc_dev_list = &L2ARC_dev_list;
5117 l2arc_free_on_write = &L2ARC_free_on_write;
5118 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
5119 offsetof(l2arc_dev_t, l2ad_node));
5120 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
5121 offsetof(l2arc_data_free_t, l2df_list_node));
5128 * This is called from dmu_fini(), which is called from spa_fini();
5129 * Because of this, we can assume that all l2arc devices have
5130 * already been removed when the pools themselves were removed.
5133 l2arc_do_free_on_write();
5135 mutex_destroy(&l2arc_feed_thr_lock);
5136 cv_destroy(&l2arc_feed_thr_cv);
5137 mutex_destroy(&l2arc_dev_mtx);
5138 mutex_destroy(&l2arc_buflist_mtx);
5139 mutex_destroy(&l2arc_free_on_write_mtx);
5141 list_destroy(l2arc_dev_list);
5142 list_destroy(l2arc_free_on_write);
5148 if (!(spa_mode_global & FWRITE))
5151 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5152 TS_RUN, minclsyspri);
5158 if (!(spa_mode_global & FWRITE))
5161 mutex_enter(&l2arc_feed_thr_lock);
5162 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5163 l2arc_thread_exit = 1;
5164 while (l2arc_thread_exit != 0)
5165 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5166 mutex_exit(&l2arc_feed_thr_lock);
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