1 /*
2 * CDDL HEADER START
3 *
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.
7 *
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.
12 *
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]
18 *
19 * CDDL HEADER END
20 */
21 /*
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.
25 */
26
27 /*
28 * DVA-based Adjustable Replacement Cache
29 *
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:
34 *
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.
45 *
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.
51 *
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
57 * tight.
58 *
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.
67 *
68 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
69 * by N. Megiddo & D. Modha, FAST 2003
70 */
71
72 /*
73 * The locking model:
74 *
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
81 * arc list locks.
82 *
83 * Buffers do not have their own mutexes, rather they rely on the
84 * hash table mutexes for the bulk of their protection (i.e. most
85 * fields in the arc_buf_hdr_t are protected by these mutexes).
86 *
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.
90 *
91 * buf_hash_remove() expects the appropriate hash mutex to be
92 * already held before it is invoked.
93 *
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.
99 *
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().
108 *
109 * Note that the majority of the performance stats are manipulated
110 * with atomic operations.
111 *
112 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
113 *
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
119 */
120
121 #include <sys/spa.h>
122 #include <sys/zio.h>
123 #include <sys/zfs_context.h>
124 #include <sys/arc.h>
125 #include <sys/refcount.h>
126 #include <sys/vdev.h>
127 #include <sys/vdev_impl.h>
128 #ifdef _KERNEL
129 #include <sys/vmsystm.h>
130 #include <vm/anon.h>
131 #include <sys/fs/swapnode.h>
132 #include <sys/dnlc.h>
133 #endif
134 #include <sys/callb.h>
135 #include <sys/kstat.h>
136 #include <zfs_fletcher.h>
137
138 #ifndef _KERNEL
139 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
140 boolean_t arc_watch = B_FALSE;
141 int arc_procfd;
142 #endif
143
144 static kmutex_t arc_reclaim_thr_lock;
145 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
146 static uint8_t arc_thread_exit;
147
148 extern int zfs_write_limit_shift;
149 extern uint64_t zfs_write_limit_max;
150 extern kmutex_t zfs_write_limit_lock;
151
152 #define ARC_REDUCE_DNLC_PERCENT 3
153 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
154
155 typedef enum arc_reclaim_strategy {
156 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
157 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
158 } arc_reclaim_strategy_t;
159
160 /* number of seconds before growing cache again */
161 static int arc_grow_retry = 60;
162
163 /* shift of arc_c for calculating both min and max arc_p */
164 static int arc_p_min_shift = 4;
165
166 /* log2(fraction of arc to reclaim) */
167 static int arc_shrink_shift = 5;
168
169 /*
170 * minimum lifespan of a prefetch block in clock ticks
171 * (initialized in arc_init())
172 */
173 static int arc_min_prefetch_lifespan;
174
175 static int arc_dead;
176
177 /*
178 * The arc has filled available memory and has now warmed up.
179 */
180 static boolean_t arc_warm;
181
182 /*
183 * These tunables are for performance analysis.
184 */
185 uint64_t zfs_arc_max;
186 uint64_t zfs_arc_min;
187 uint64_t zfs_arc_meta_limit = 0;
188 int zfs_arc_grow_retry = 0;
189 int zfs_arc_shrink_shift = 0;
190 int zfs_arc_p_min_shift = 0;
191 int zfs_disable_dup_eviction = 0;
192
193 /*
194 * Note that buffers can be in one of 6 states:
195 * ARC_anon - anonymous (discussed below)
196 * ARC_mru - recently used, currently cached
197 * ARC_mru_ghost - recentely used, no longer in cache
198 * ARC_mfu - frequently used, currently cached
199 * ARC_mfu_ghost - frequently used, no longer in cache
200 * ARC_l2c_only - exists in L2ARC but not other states
201 * When there are no active references to the buffer, they are
202 * are linked onto a list in one of these arc states. These are
203 * the only buffers that can be evicted or deleted. Within each
204 * state there are multiple lists, one for meta-data and one for
205 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
206 * etc.) is tracked separately so that it can be managed more
207 * explicitly: favored over data, limited explicitly.
208 *
209 * Anonymous buffers are buffers that are not associated with
210 * a DVA. These are buffers that hold dirty block copies
211 * before they are written to stable storage. By definition,
212 * they are "ref'd" and are considered part of arc_mru
213 * that cannot be freed. Generally, they will aquire a DVA
214 * as they are written and migrate onto the arc_mru list.
215 *
216 * The ARC_l2c_only state is for buffers that are in the second
217 * level ARC but no longer in any of the ARC_m* lists. The second
218 * level ARC itself may also contain buffers that are in any of
219 * the ARC_m* states - meaning that a buffer can exist in two
220 * places. The reason for the ARC_l2c_only state is to keep the
221 * buffer header in the hash table, so that reads that hit the
222 * second level ARC benefit from these fast lookups.
223 */
224
225 typedef struct arc_state {
226 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
227 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
228 uint64_t arcs_size; /* total amount of data in this state */
229 kmutex_t arcs_mtx;
230 } arc_state_t;
231
232 /* The 6 states: */
233 static arc_state_t ARC_anon;
234 static arc_state_t ARC_mru;
235 static arc_state_t ARC_mru_ghost;
236 static arc_state_t ARC_mfu;
237 static arc_state_t ARC_mfu_ghost;
238 static arc_state_t ARC_l2c_only;
239
240 typedef struct arc_stats {
241 kstat_named_t arcstat_hits;
242 kstat_named_t arcstat_misses;
243 kstat_named_t arcstat_demand_data_hits;
244 kstat_named_t arcstat_demand_data_misses;
245 kstat_named_t arcstat_demand_metadata_hits;
246 kstat_named_t arcstat_demand_metadata_misses;
247 kstat_named_t arcstat_prefetch_data_hits;
248 kstat_named_t arcstat_prefetch_data_misses;
249 kstat_named_t arcstat_prefetch_metadata_hits;
250 kstat_named_t arcstat_prefetch_metadata_misses;
251 kstat_named_t arcstat_mru_hits;
252 kstat_named_t arcstat_mru_ghost_hits;
253 kstat_named_t arcstat_mfu_hits;
254 kstat_named_t arcstat_mfu_ghost_hits;
255 kstat_named_t arcstat_deleted;
256 kstat_named_t arcstat_recycle_miss;
257 /*
258 * Number of buffers that could not be evicted because the hash lock
259 * was held by another thread. The lock may not necessarily be held
260 * by something using the same buffer, since hash locks are shared
261 * by multiple buffers.
262 */
263 kstat_named_t arcstat_mutex_miss;
264 /*
265 * Number of buffers skipped because they have I/O in progress, are
266 * indrect prefetch buffers that have not lived long enough, or are
267 * not from the spa we're trying to evict from.
268 */
269 kstat_named_t arcstat_evict_skip;
270 kstat_named_t arcstat_evict_l2_cached;
271 kstat_named_t arcstat_evict_l2_eligible;
272 kstat_named_t arcstat_evict_l2_ineligible;
273 kstat_named_t arcstat_hash_elements;
274 kstat_named_t arcstat_hash_elements_max;
275 kstat_named_t arcstat_hash_collisions;
276 kstat_named_t arcstat_hash_chains;
277 kstat_named_t arcstat_hash_chain_max;
278 kstat_named_t arcstat_p;
279 kstat_named_t arcstat_c;
280 kstat_named_t arcstat_c_min;
281 kstat_named_t arcstat_c_max;
282 kstat_named_t arcstat_size;
283 kstat_named_t arcstat_hdr_size;
284 kstat_named_t arcstat_data_size;
285 kstat_named_t arcstat_other_size;
286 kstat_named_t arcstat_l2_hits;
287 kstat_named_t arcstat_l2_misses;
288 kstat_named_t arcstat_l2_feeds;
289 kstat_named_t arcstat_l2_rw_clash;
290 kstat_named_t arcstat_l2_read_bytes;
291 kstat_named_t arcstat_l2_write_bytes;
292 kstat_named_t arcstat_l2_writes_sent;
293 kstat_named_t arcstat_l2_writes_done;
294 kstat_named_t arcstat_l2_writes_error;
295 kstat_named_t arcstat_l2_writes_hdr_miss;
296 kstat_named_t arcstat_l2_evict_lock_retry;
297 kstat_named_t arcstat_l2_evict_reading;
298 kstat_named_t arcstat_l2_free_on_write;
299 kstat_named_t arcstat_l2_abort_lowmem;
300 kstat_named_t arcstat_l2_cksum_bad;
301 kstat_named_t arcstat_l2_io_error;
302 kstat_named_t arcstat_l2_size;
303 kstat_named_t arcstat_l2_hdr_size;
304 kstat_named_t arcstat_memory_throttle_count;
305 kstat_named_t arcstat_duplicate_buffers;
306 kstat_named_t arcstat_duplicate_buffers_size;
307 kstat_named_t arcstat_duplicate_reads;
308 kstat_named_t arcstat_meta_used;
309 kstat_named_t arcstat_meta_limit;
310 kstat_named_t arcstat_meta_max;
311 } arc_stats_t;
312
313 static arc_stats_t arc_stats = {
314 { "hits", KSTAT_DATA_UINT64 },
315 { "misses", KSTAT_DATA_UINT64 },
316 { "demand_data_hits", KSTAT_DATA_UINT64 },
317 { "demand_data_misses", KSTAT_DATA_UINT64 },
318 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
319 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
320 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
321 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
322 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
323 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
324 { "mru_hits", KSTAT_DATA_UINT64 },
325 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
326 { "mfu_hits", KSTAT_DATA_UINT64 },
327 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
328 { "deleted", KSTAT_DATA_UINT64 },
329 { "recycle_miss", KSTAT_DATA_UINT64 },
330 { "mutex_miss", KSTAT_DATA_UINT64 },
331 { "evict_skip", KSTAT_DATA_UINT64 },
332 { "evict_l2_cached", KSTAT_DATA_UINT64 },
333 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
334 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
335 { "hash_elements", KSTAT_DATA_UINT64 },
336 { "hash_elements_max", KSTAT_DATA_UINT64 },
337 { "hash_collisions", KSTAT_DATA_UINT64 },
338 { "hash_chains", KSTAT_DATA_UINT64 },
339 { "hash_chain_max", KSTAT_DATA_UINT64 },
340 { "p", KSTAT_DATA_UINT64 },
341 { "c", KSTAT_DATA_UINT64 },
342 { "c_min", KSTAT_DATA_UINT64 },
343 { "c_max", KSTAT_DATA_UINT64 },
344 { "size", KSTAT_DATA_UINT64 },
345 { "hdr_size", KSTAT_DATA_UINT64 },
346 { "data_size", KSTAT_DATA_UINT64 },
347 { "other_size", KSTAT_DATA_UINT64 },
348 { "l2_hits", KSTAT_DATA_UINT64 },
349 { "l2_misses", KSTAT_DATA_UINT64 },
350 { "l2_feeds", KSTAT_DATA_UINT64 },
351 { "l2_rw_clash", KSTAT_DATA_UINT64 },
352 { "l2_read_bytes", KSTAT_DATA_UINT64 },
353 { "l2_write_bytes", KSTAT_DATA_UINT64 },
354 { "l2_writes_sent", KSTAT_DATA_UINT64 },
355 { "l2_writes_done", KSTAT_DATA_UINT64 },
356 { "l2_writes_error", KSTAT_DATA_UINT64 },
357 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
358 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
359 { "l2_evict_reading", KSTAT_DATA_UINT64 },
360 { "l2_free_on_write", KSTAT_DATA_UINT64 },
361 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
362 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
363 { "l2_io_error", KSTAT_DATA_UINT64 },
364 { "l2_size", KSTAT_DATA_UINT64 },
365 { "l2_hdr_size", KSTAT_DATA_UINT64 },
366 { "memory_throttle_count", KSTAT_DATA_UINT64 },
367 { "duplicate_buffers", KSTAT_DATA_UINT64 },
368 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
369 { "duplicate_reads", KSTAT_DATA_UINT64 },
370 { "arc_meta_used", KSTAT_DATA_UINT64 },
371 { "arc_meta_limit", KSTAT_DATA_UINT64 },
372 { "arc_meta_max", KSTAT_DATA_UINT64 }
373 };
374
375 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
376
377 #define ARCSTAT_INCR(stat, val) \
378 atomic_add_64(&arc_stats.stat.value.ui64, (val));
379
380 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
381 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
382
383 #define ARCSTAT_MAX(stat, val) { \
384 uint64_t m; \
385 while ((val) > (m = arc_stats.stat.value.ui64) && \
386 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
387 continue; \
388 }
389
390 #define ARCSTAT_MAXSTAT(stat) \
391 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
392
393 /*
394 * We define a macro to allow ARC hits/misses to be easily broken down by
395 * two separate conditions, giving a total of four different subtypes for
396 * each of hits and misses (so eight statistics total).
397 */
398 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
399 if (cond1) { \
400 if (cond2) { \
401 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
402 } else { \
403 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
404 } \
405 } else { \
406 if (cond2) { \
407 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
408 } else { \
409 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
410 } \
411 }
412
413 kstat_t *arc_ksp;
414 static arc_state_t *arc_anon;
415 static arc_state_t *arc_mru;
416 static arc_state_t *arc_mru_ghost;
417 static arc_state_t *arc_mfu;
418 static arc_state_t *arc_mfu_ghost;
419 static arc_state_t *arc_l2c_only;
420
421 /*
422 * There are several ARC variables that are critical to export as kstats --
423 * but we don't want to have to grovel around in the kstat whenever we wish to
424 * manipulate them. For these variables, we therefore define them to be in
425 * terms of the statistic variable. This assures that we are not introducing
426 * the possibility of inconsistency by having shadow copies of the variables,
427 * while still allowing the code to be readable.
428 */
429 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
430 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
431 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
432 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
433 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
434 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
435 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
436 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
437
438 static int arc_no_grow; /* Don't try to grow cache size */
439 static uint64_t arc_tempreserve;
440 static uint64_t arc_loaned_bytes;
441
442 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
443
444 typedef struct arc_callback arc_callback_t;
445
446 struct arc_callback {
447 void *acb_private;
448 arc_done_func_t *acb_done;
449 arc_buf_t *acb_buf;
450 zio_t *acb_zio_dummy;
451 arc_callback_t *acb_next;
452 };
453
454 typedef struct arc_write_callback arc_write_callback_t;
455
456 struct arc_write_callback {
457 void *awcb_private;
458 arc_done_func_t *awcb_ready;
459 arc_done_func_t *awcb_done;
460 arc_buf_t *awcb_buf;
461 };
462
463 struct arc_buf_hdr {
464 /* protected by hash lock */
465 dva_t b_dva;
466 uint64_t b_birth;
467 uint64_t b_cksum0;
468
469 kmutex_t b_freeze_lock;
470 zio_cksum_t *b_freeze_cksum;
471 void *b_thawed;
472
473 arc_buf_hdr_t *b_hash_next;
474 arc_buf_t *b_buf;
475 uint32_t b_flags;
476 uint32_t b_datacnt;
477
478 arc_callback_t *b_acb;
479 kcondvar_t b_cv;
480
481 /* immutable */
482 arc_buf_contents_t b_type;
483 uint64_t b_size;
484 uint64_t b_spa;
485
486 /* protected by arc state mutex */
487 arc_state_t *b_state;
488 list_node_t b_arc_node;
489
490 /* updated atomically */
491 clock_t b_arc_access;
492
493 /* self protecting */
494 refcount_t b_refcnt;
495
496 l2arc_buf_hdr_t *b_l2hdr;
497 list_node_t b_l2node;
498 };
499
500 static arc_buf_t *arc_eviction_list;
501 static kmutex_t arc_eviction_mtx;
502 static arc_buf_hdr_t arc_eviction_hdr;
503 static void arc_get_data_buf(arc_buf_t *buf);
504 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
505 static int arc_evict_needed(arc_buf_contents_t type);
506 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
507 static void arc_buf_watch(arc_buf_t *buf);
508
509 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
510
511 #define GHOST_STATE(state) \
512 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
513 (state) == arc_l2c_only)
514
515 /*
516 * Private ARC flags. These flags are private ARC only flags that will show up
517 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
518 * be passed in as arc_flags in things like arc_read. However, these flags
519 * should never be passed and should only be set by ARC code. When adding new
520 * public flags, make sure not to smash the private ones.
521 */
522
523 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
524 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
525 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
526 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
527 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
528 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
529 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
530 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
531 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
532 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
533
534 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
535 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
536 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
537 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
538 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
539 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
540 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
541 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
542 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
543 (hdr)->b_l2hdr != NULL)
544 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
545 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
546 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
547
548 /*
549 * Other sizes
550 */
551
552 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
553 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
554
555 /*
556 * Hash table routines
557 */
558
559 #define HT_LOCK_PAD 64
560
561 struct ht_lock {
562 kmutex_t ht_lock;
563 #ifdef _KERNEL
564 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
565 #endif
566 };
567
568 #define BUF_LOCKS 256
569 typedef struct buf_hash_table {
570 uint64_t ht_mask;
571 arc_buf_hdr_t **ht_table;
572 struct ht_lock ht_locks[BUF_LOCKS];
573 } buf_hash_table_t;
574
575 static buf_hash_table_t buf_hash_table;
576
577 #define BUF_HASH_INDEX(spa, dva, birth) \
578 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
579 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
580 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
581 #define HDR_LOCK(hdr) \
582 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
583
584 uint64_t zfs_crc64_table[256];
585
586 /*
587 * Level 2 ARC
588 */
589
590 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
591 #define L2ARC_HEADROOM 2 /* num of writes */
592 #define L2ARC_FEED_SECS 1 /* caching interval secs */
593 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
594
595 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
596 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
597
598 /*
599 * L2ARC Performance Tunables
600 */
601 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
602 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
603 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
604 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
605 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
606 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
607 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
608 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
609
610 /*
611 * L2ARC Internals
612 */
613 typedef struct l2arc_dev {
614 vdev_t *l2ad_vdev; /* vdev */
615 spa_t *l2ad_spa; /* spa */
616 uint64_t l2ad_hand; /* next write location */
617 uint64_t l2ad_write; /* desired write size, bytes */
618 uint64_t l2ad_boost; /* warmup write boost, bytes */
619 uint64_t l2ad_start; /* first addr on device */
620 uint64_t l2ad_end; /* last addr on device */
621 uint64_t l2ad_evict; /* last addr eviction reached */
622 boolean_t l2ad_first; /* first sweep through */
623 boolean_t l2ad_writing; /* currently writing */
624 list_t *l2ad_buflist; /* buffer list */
625 list_node_t l2ad_node; /* device list node */
626 } l2arc_dev_t;
627
628 static list_t L2ARC_dev_list; /* device list */
629 static list_t *l2arc_dev_list; /* device list pointer */
630 static kmutex_t l2arc_dev_mtx; /* device list mutex */
631 static l2arc_dev_t *l2arc_dev_last; /* last device used */
632 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
633 static list_t L2ARC_free_on_write; /* free after write buf list */
634 static list_t *l2arc_free_on_write; /* free after write list ptr */
635 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
636 static uint64_t l2arc_ndev; /* number of devices */
637
638 typedef struct l2arc_read_callback {
639 arc_buf_t *l2rcb_buf; /* read buffer */
640 spa_t *l2rcb_spa; /* spa */
641 blkptr_t l2rcb_bp; /* original blkptr */
642 zbookmark_t l2rcb_zb; /* original bookmark */
643 int l2rcb_flags; /* original flags */
644 } l2arc_read_callback_t;
645
646 typedef struct l2arc_write_callback {
647 l2arc_dev_t *l2wcb_dev; /* device info */
648 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
649 } l2arc_write_callback_t;
650
651 struct l2arc_buf_hdr {
652 /* protected by arc_buf_hdr mutex */
653 l2arc_dev_t *b_dev; /* L2ARC device */
654 uint64_t b_daddr; /* disk address, offset byte */
655 };
656
657 typedef struct l2arc_data_free {
658 /* protected by l2arc_free_on_write_mtx */
659 void *l2df_data;
660 size_t l2df_size;
661 void (*l2df_func)(void *, size_t);
662 list_node_t l2df_list_node;
663 } l2arc_data_free_t;
664
665 static kmutex_t l2arc_feed_thr_lock;
666 static kcondvar_t l2arc_feed_thr_cv;
667 static uint8_t l2arc_thread_exit;
668
669 static void l2arc_read_done(zio_t *zio);
670 static void l2arc_hdr_stat_add(void);
671 static void l2arc_hdr_stat_remove(void);
672
673 static uint64_t
674 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
675 {
676 uint8_t *vdva = (uint8_t *)dva;
677 uint64_t crc = -1ULL;
678 int i;
679
680 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
681
682 for (i = 0; i < sizeof (dva_t); i++)
683 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
684
685 crc ^= (spa>>8) ^ birth;
686
687 return (crc);
688 }
689
690 #define BUF_EMPTY(buf) \
691 ((buf)->b_dva.dva_word[0] == 0 && \
692 (buf)->b_dva.dva_word[1] == 0 && \
693 (buf)->b_birth == 0)
694
695 #define BUF_EQUAL(spa, dva, birth, buf) \
696 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
697 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
698 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
699
700 static void
701 buf_discard_identity(arc_buf_hdr_t *hdr)
702 {
703 hdr->b_dva.dva_word[0] = 0;
704 hdr->b_dva.dva_word[1] = 0;
705 hdr->b_birth = 0;
706 hdr->b_cksum0 = 0;
707 }
708
709 static arc_buf_hdr_t *
710 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
711 {
712 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
713 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
714 arc_buf_hdr_t *buf;
715
716 mutex_enter(hash_lock);
717 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
718 buf = buf->b_hash_next) {
719 if (BUF_EQUAL(spa, dva, birth, buf)) {
720 *lockp = hash_lock;
721 return (buf);
722 }
723 }
724 mutex_exit(hash_lock);
725 *lockp = NULL;
726 return (NULL);
727 }
728
729 /*
730 * Insert an entry into the hash table. If there is already an element
731 * equal to elem in the hash table, then the already existing element
732 * will be returned and the new element will not be inserted.
733 * Otherwise returns NULL.
734 */
735 static arc_buf_hdr_t *
736 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
737 {
738 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
739 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
740 arc_buf_hdr_t *fbuf;
741 uint32_t i;
742
743 ASSERT(!HDR_IN_HASH_TABLE(buf));
744 *lockp = hash_lock;
745 mutex_enter(hash_lock);
746 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
747 fbuf = fbuf->b_hash_next, i++) {
748 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
749 return (fbuf);
750 }
751
752 buf->b_hash_next = buf_hash_table.ht_table[idx];
753 buf_hash_table.ht_table[idx] = buf;
754 buf->b_flags |= ARC_IN_HASH_TABLE;
755
756 /* collect some hash table performance data */
757 if (i > 0) {
758 ARCSTAT_BUMP(arcstat_hash_collisions);
759 if (i == 1)
760 ARCSTAT_BUMP(arcstat_hash_chains);
761
762 ARCSTAT_MAX(arcstat_hash_chain_max, i);
763 }
764
765 ARCSTAT_BUMP(arcstat_hash_elements);
766 ARCSTAT_MAXSTAT(arcstat_hash_elements);
767
768 return (NULL);
769 }
770
771 static void
772 buf_hash_remove(arc_buf_hdr_t *buf)
773 {
774 arc_buf_hdr_t *fbuf, **bufp;
775 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
776
777 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
778 ASSERT(HDR_IN_HASH_TABLE(buf));
779
780 bufp = &buf_hash_table.ht_table[idx];
781 while ((fbuf = *bufp) != buf) {
782 ASSERT(fbuf != NULL);
783 bufp = &fbuf->b_hash_next;
784 }
785 *bufp = buf->b_hash_next;
786 buf->b_hash_next = NULL;
787 buf->b_flags &= ~ARC_IN_HASH_TABLE;
788
789 /* collect some hash table performance data */
790 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
791
792 if (buf_hash_table.ht_table[idx] &&
793 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
794 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
795 }
796
797 /*
798 * Global data structures and functions for the buf kmem cache.
799 */
800 static kmem_cache_t *hdr_cache;
801 static kmem_cache_t *buf_cache;
802
803 static void
804 buf_fini(void)
805 {
806 int i;
807
808 kmem_free(buf_hash_table.ht_table,
809 (buf_hash_table.ht_mask + 1) * sizeof (void *));
810 for (i = 0; i < BUF_LOCKS; i++)
811 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
812 kmem_cache_destroy(hdr_cache);
813 kmem_cache_destroy(buf_cache);
814 }
815
816 /*
817 * Constructor callback - called when the cache is empty
818 * and a new buf is requested.
819 */
820 /* ARGSUSED */
821 static int
822 hdr_cons(void *vbuf, void *unused, int kmflag)
823 {
824 arc_buf_hdr_t *buf = vbuf;
825
826 bzero(buf, sizeof (arc_buf_hdr_t));
827 refcount_create(&buf->b_refcnt);
828 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
829 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
830 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
831
832 return (0);
833 }
834
835 /* ARGSUSED */
836 static int
837 buf_cons(void *vbuf, void *unused, int kmflag)
838 {
839 arc_buf_t *buf = vbuf;
840
841 bzero(buf, sizeof (arc_buf_t));
842 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
843 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
844
845 return (0);
846 }
847
848 /*
849 * Destructor callback - called when a cached buf is
850 * no longer required.
851 */
852 /* ARGSUSED */
853 static void
854 hdr_dest(void *vbuf, void *unused)
855 {
856 arc_buf_hdr_t *buf = vbuf;
857
858 ASSERT(BUF_EMPTY(buf));
859 refcount_destroy(&buf->b_refcnt);
860 cv_destroy(&buf->b_cv);
861 mutex_destroy(&buf->b_freeze_lock);
862 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
863 }
864
865 /* ARGSUSED */
866 static void
867 buf_dest(void *vbuf, void *unused)
868 {
869 arc_buf_t *buf = vbuf;
870
871 mutex_destroy(&buf->b_evict_lock);
872 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
873 }
874
875 /*
876 * Reclaim callback -- invoked when memory is low.
877 */
878 /* ARGSUSED */
879 static void
880 hdr_recl(void *unused)
881 {
882 dprintf("hdr_recl called\n");
883 /*
884 * umem calls the reclaim func when we destroy the buf cache,
885 * which is after we do arc_fini().
886 */
887 if (!arc_dead)
888 cv_signal(&arc_reclaim_thr_cv);
889 }
890
891 static void
892 buf_init(void)
893 {
894 uint64_t *ct;
895 uint64_t hsize = 1ULL << 12;
896 int i, j;
897
898 /*
899 * The hash table is big enough to fill all of physical memory
900 * with an average 64K block size. The table will take up
901 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
902 */
903 while (hsize * 65536 < physmem * PAGESIZE)
904 hsize <<= 1;
905 retry:
906 buf_hash_table.ht_mask = hsize - 1;
907 buf_hash_table.ht_table =
908 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
909 if (buf_hash_table.ht_table == NULL) {
910 ASSERT(hsize > (1ULL << 8));
911 hsize >>= 1;
912 goto retry;
913 }
914
915 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
916 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
917 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
918 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
919
920 for (i = 0; i < 256; i++)
921 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
922 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
923
924 for (i = 0; i < BUF_LOCKS; i++) {
925 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
926 NULL, MUTEX_DEFAULT, NULL);
927 }
928 }
929
930 #define ARC_MINTIME (hz>>4) /* 62 ms */
931
932 static void
933 arc_cksum_verify(arc_buf_t *buf)
934 {
935 zio_cksum_t zc;
936
937 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
938 return;
939
940 mutex_enter(&buf->b_hdr->b_freeze_lock);
941 if (buf->b_hdr->b_freeze_cksum == NULL ||
942 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
943 mutex_exit(&buf->b_hdr->b_freeze_lock);
944 return;
945 }
946 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
947 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
948 panic("buffer modified while frozen!");
949 mutex_exit(&buf->b_hdr->b_freeze_lock);
950 }
951
952 static int
953 arc_cksum_equal(arc_buf_t *buf)
954 {
955 zio_cksum_t zc;
956 int equal;
957
958 mutex_enter(&buf->b_hdr->b_freeze_lock);
959 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
960 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
961 mutex_exit(&buf->b_hdr->b_freeze_lock);
962
963 return (equal);
964 }
965
966 static void
967 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
968 {
969 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
970 return;
971
972 mutex_enter(&buf->b_hdr->b_freeze_lock);
973 if (buf->b_hdr->b_freeze_cksum != NULL) {
974 mutex_exit(&buf->b_hdr->b_freeze_lock);
975 return;
976 }
977 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
978 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
979 buf->b_hdr->b_freeze_cksum);
980 mutex_exit(&buf->b_hdr->b_freeze_lock);
981 arc_buf_watch(buf);
982 }
983
984 #ifndef _KERNEL
985 typedef struct procctl {
986 long cmd;
987 prwatch_t prwatch;
988 } procctl_t;
989 #endif
990
991 /* ARGSUSED */
992 static void
993 arc_buf_unwatch(arc_buf_t *buf)
994 {
995 #ifndef _KERNEL
996 if (arc_watch) {
997 int result;
998 procctl_t ctl;
999 ctl.cmd = PCWATCH;
1000 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1001 ctl.prwatch.pr_size = 0;
1002 ctl.prwatch.pr_wflags = 0;
1003 result = write(arc_procfd, &ctl, sizeof (ctl));
1004 ASSERT3U(result, ==, sizeof (ctl));
1005 }
1006 #endif
1007 }
1008
1009 /* ARGSUSED */
1010 static void
1011 arc_buf_watch(arc_buf_t *buf)
1012 {
1013 #ifndef _KERNEL
1014 if (arc_watch) {
1015 int result;
1016 procctl_t ctl;
1017 ctl.cmd = PCWATCH;
1018 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1019 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1020 ctl.prwatch.pr_wflags = WA_WRITE;
1021 result = write(arc_procfd, &ctl, sizeof (ctl));
1022 ASSERT3U(result, ==, sizeof (ctl));
1023 }
1024 #endif
1025 }
1026
1027 void
1028 arc_buf_thaw(arc_buf_t *buf)
1029 {
1030 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1031 if (buf->b_hdr->b_state != arc_anon)
1032 panic("modifying non-anon buffer!");
1033 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1034 panic("modifying buffer while i/o in progress!");
1035 arc_cksum_verify(buf);
1036 }
1037
1038 mutex_enter(&buf->b_hdr->b_freeze_lock);
1039 if (buf->b_hdr->b_freeze_cksum != NULL) {
1040 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1041 buf->b_hdr->b_freeze_cksum = NULL;
1042 }
1043
1044 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1045 if (buf->b_hdr->b_thawed)
1046 kmem_free(buf->b_hdr->b_thawed, 1);
1047 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1048 }
1049
1050 mutex_exit(&buf->b_hdr->b_freeze_lock);
1051
1052 arc_buf_unwatch(buf);
1053 }
1054
1055 void
1056 arc_buf_freeze(arc_buf_t *buf)
1057 {
1058 kmutex_t *hash_lock;
1059
1060 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1061 return;
1062
1063 hash_lock = HDR_LOCK(buf->b_hdr);
1064 mutex_enter(hash_lock);
1065
1066 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1067 buf->b_hdr->b_state == arc_anon);
1068 arc_cksum_compute(buf, B_FALSE);
1069 mutex_exit(hash_lock);
1070
1071 }
1072
1073 static void
1074 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1075 {
1076 ASSERT(MUTEX_HELD(hash_lock));
1077
1078 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1079 (ab->b_state != arc_anon)) {
1080 uint64_t delta = ab->b_size * ab->b_datacnt;
1081 list_t *list = &ab->b_state->arcs_list[ab->b_type];
1082 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1083
1084 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
1085 mutex_enter(&ab->b_state->arcs_mtx);
1086 ASSERT(list_link_active(&ab->b_arc_node));
1087 list_remove(list, ab);
1088 if (GHOST_STATE(ab->b_state)) {
1089 ASSERT0(ab->b_datacnt);
1090 ASSERT3P(ab->b_buf, ==, NULL);
1091 delta = ab->b_size;
1092 }
1093 ASSERT(delta > 0);
1094 ASSERT3U(*size, >=, delta);
1095 atomic_add_64(size, -delta);
1096 mutex_exit(&ab->b_state->arcs_mtx);
1097 /* remove the prefetch flag if we get a reference */
1098 if (ab->b_flags & ARC_PREFETCH)
1099 ab->b_flags &= ~ARC_PREFETCH;
1100 }
1101 }
1102
1103 static int
1104 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1105 {
1106 int cnt;
1107 arc_state_t *state = ab->b_state;
1108
1109 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1110 ASSERT(!GHOST_STATE(state));
1111
1112 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1113 (state != arc_anon)) {
1114 uint64_t *size = &state->arcs_lsize[ab->b_type];
1115
1116 ASSERT(!MUTEX_HELD(&state->arcs_mtx));
1117 mutex_enter(&state->arcs_mtx);
1118 ASSERT(!list_link_active(&ab->b_arc_node));
1119 list_insert_head(&state->arcs_list[ab->b_type], ab);
1120 ASSERT(ab->b_datacnt > 0);
1121 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1122 mutex_exit(&state->arcs_mtx);
1123 }
1124 return (cnt);
1125 }
1126
1127 /*
1128 * Move the supplied buffer to the indicated state. The mutex
1129 * for the buffer must be held by the caller.
1130 */
1131 static void
1132 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1133 {
1134 arc_state_t *old_state = ab->b_state;
1135 int64_t refcnt = refcount_count(&ab->b_refcnt);
1136 uint64_t from_delta, to_delta;
1137
1138 ASSERT(MUTEX_HELD(hash_lock));
1139 ASSERT(new_state != old_state);
1140 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1141 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1142 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1143
1144 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1145
1146 /*
1147 * If this buffer is evictable, transfer it from the
1148 * old state list to the new state list.
1149 */
1150 if (refcnt == 0) {
1151 if (old_state != arc_anon) {
1152 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
1153 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1154
1155 if (use_mutex)
1156 mutex_enter(&old_state->arcs_mtx);
1157
1158 ASSERT(list_link_active(&ab->b_arc_node));
1159 list_remove(&old_state->arcs_list[ab->b_type], ab);
1160
1161 /*
1162 * If prefetching out of the ghost cache,
1163 * we will have a non-zero datacnt.
1164 */
1165 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1166 /* ghost elements have a ghost size */
1167 ASSERT(ab->b_buf == NULL);
1168 from_delta = ab->b_size;
1169 }
1170 ASSERT3U(*size, >=, from_delta);
1171 atomic_add_64(size, -from_delta);
1172
1173 if (use_mutex)
1174 mutex_exit(&old_state->arcs_mtx);
1175 }
1176 if (new_state != arc_anon) {
1177 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
1178 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1179
1180 if (use_mutex)
1181 mutex_enter(&new_state->arcs_mtx);
1182
1183 list_insert_head(&new_state->arcs_list[ab->b_type], ab);
1184
1185 /* ghost elements have a ghost size */
1186 if (GHOST_STATE(new_state)) {
1187 ASSERT(ab->b_datacnt == 0);
1188 ASSERT(ab->b_buf == NULL);
1189 to_delta = ab->b_size;
1190 }
1191 atomic_add_64(size, to_delta);
1192
1193 if (use_mutex)
1194 mutex_exit(&new_state->arcs_mtx);
1195 }
1196 }
1197
1198 ASSERT(!BUF_EMPTY(ab));
1199 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1200 buf_hash_remove(ab);
1201
1202 /* adjust state sizes */
1203 if (to_delta)
1204 atomic_add_64(&new_state->arcs_size, to_delta);
1205 if (from_delta) {
1206 ASSERT3U(old_state->arcs_size, >=, from_delta);
1207 atomic_add_64(&old_state->arcs_size, -from_delta);
1208 }
1209 ab->b_state = new_state;
1210
1211 /* adjust l2arc hdr stats */
1212 if (new_state == arc_l2c_only)
1213 l2arc_hdr_stat_add();
1214 else if (old_state == arc_l2c_only)
1215 l2arc_hdr_stat_remove();
1216 }
1217
1218 void
1219 arc_space_consume(uint64_t space, arc_space_type_t type)
1220 {
1221 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1222
1223 switch (type) {
1224 case ARC_SPACE_DATA:
1225 ARCSTAT_INCR(arcstat_data_size, space);
1226 break;
1227 case ARC_SPACE_OTHER:
1228 ARCSTAT_INCR(arcstat_other_size, space);
1229 break;
1230 case ARC_SPACE_HDRS:
1231 ARCSTAT_INCR(arcstat_hdr_size, space);
1232 break;
1233 case ARC_SPACE_L2HDRS:
1234 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1235 break;
1236 }
1237
1238 ARCSTAT_INCR(arcstat_meta_used, space);
1239 atomic_add_64(&arc_size, space);
1240 }
1241
1242 void
1243 arc_space_return(uint64_t space, arc_space_type_t type)
1244 {
1245 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1246
1247 switch (type) {
1248 case ARC_SPACE_DATA:
1249 ARCSTAT_INCR(arcstat_data_size, -space);
1250 break;
1251 case ARC_SPACE_OTHER:
1252 ARCSTAT_INCR(arcstat_other_size, -space);
1253 break;
1254 case ARC_SPACE_HDRS:
1255 ARCSTAT_INCR(arcstat_hdr_size, -space);
1256 break;
1257 case ARC_SPACE_L2HDRS:
1258 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1259 break;
1260 }
1261
1262 ASSERT(arc_meta_used >= space);
1263 if (arc_meta_max < arc_meta_used)
1264 arc_meta_max = arc_meta_used;
1265 ARCSTAT_INCR(arcstat_meta_used, -space);
1266 ASSERT(arc_size >= space);
1267 atomic_add_64(&arc_size, -space);
1268 }
1269
1270 void *
1271 arc_data_buf_alloc(uint64_t size)
1272 {
1273 if (arc_evict_needed(ARC_BUFC_DATA))
1274 cv_signal(&arc_reclaim_thr_cv);
1275 atomic_add_64(&arc_size, size);
1276 return (zio_data_buf_alloc(size));
1277 }
1278
1279 void
1280 arc_data_buf_free(void *buf, uint64_t size)
1281 {
1282 zio_data_buf_free(buf, size);
1283 ASSERT(arc_size >= size);
1284 atomic_add_64(&arc_size, -size);
1285 }
1286
1287 arc_buf_t *
1288 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1289 {
1290 arc_buf_hdr_t *hdr;
1291 arc_buf_t *buf;
1292
1293 ASSERT3U(size, >, 0);
1294 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1295 ASSERT(BUF_EMPTY(hdr));
1296 hdr->b_size = size;
1297 hdr->b_type = type;
1298 hdr->b_spa = spa_load_guid(spa);
1299 hdr->b_state = arc_anon;
1300 hdr->b_arc_access = 0;
1301 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1302 buf->b_hdr = hdr;
1303 buf->b_data = NULL;
1304 buf->b_efunc = NULL;
1305 buf->b_private = NULL;
1306 buf->b_next = NULL;
1307 hdr->b_buf = buf;
1308 arc_get_data_buf(buf);
1309 hdr->b_datacnt = 1;
1310 hdr->b_flags = 0;
1311 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1312 (void) refcount_add(&hdr->b_refcnt, tag);
1313
1314 return (buf);
1315 }
1316
1317 static char *arc_onloan_tag = "onloan";
1318
1319 /*
1320 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1321 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1322 * buffers must be returned to the arc before they can be used by the DMU or
1323 * freed.
1324 */
1325 arc_buf_t *
1326 arc_loan_buf(spa_t *spa, int size)
1327 {
1328 arc_buf_t *buf;
1329
1330 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1331
1332 atomic_add_64(&arc_loaned_bytes, size);
1333 return (buf);
1334 }
1335
1336 /*
1337 * Return a loaned arc buffer to the arc.
1338 */
1339 void
1340 arc_return_buf(arc_buf_t *buf, void *tag)
1341 {
1342 arc_buf_hdr_t *hdr = buf->b_hdr;
1343
1344 ASSERT(buf->b_data != NULL);
1345 (void) refcount_add(&hdr->b_refcnt, tag);
1346 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1347
1348 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1349 }
1350
1351 /* Detach an arc_buf from a dbuf (tag) */
1352 void
1353 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1354 {
1355 arc_buf_hdr_t *hdr;
1356
1357 ASSERT(buf->b_data != NULL);
1358 hdr = buf->b_hdr;
1359 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1360 (void) refcount_remove(&hdr->b_refcnt, tag);
1361 buf->b_efunc = NULL;
1362 buf->b_private = NULL;
1363
1364 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1365 }
1366
1367 static arc_buf_t *
1368 arc_buf_clone(arc_buf_t *from)
1369 {
1370 arc_buf_t *buf;
1371 arc_buf_hdr_t *hdr = from->b_hdr;
1372 uint64_t size = hdr->b_size;
1373
1374 ASSERT(hdr->b_state != arc_anon);
1375
1376 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1377 buf->b_hdr = hdr;
1378 buf->b_data = NULL;
1379 buf->b_efunc = NULL;
1380 buf->b_private = NULL;
1381 buf->b_next = hdr->b_buf;
1382 hdr->b_buf = buf;
1383 arc_get_data_buf(buf);
1384 bcopy(from->b_data, buf->b_data, size);
1385
1386 /*
1387 * This buffer already exists in the arc so create a duplicate
1388 * copy for the caller. If the buffer is associated with user data
1389 * then track the size and number of duplicates. These stats will be
1390 * updated as duplicate buffers are created and destroyed.
1391 */
1392 if (hdr->b_type == ARC_BUFC_DATA) {
1393 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1394 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1395 }
1396 hdr->b_datacnt += 1;
1397 return (buf);
1398 }
1399
1400 void
1401 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1402 {
1403 arc_buf_hdr_t *hdr;
1404 kmutex_t *hash_lock;
1405
1406 /*
1407 * Check to see if this buffer is evicted. Callers
1408 * must verify b_data != NULL to know if the add_ref
1409 * was successful.
1410 */
1411 mutex_enter(&buf->b_evict_lock);
1412 if (buf->b_data == NULL) {
1413 mutex_exit(&buf->b_evict_lock);
1414 return;
1415 }
1416 hash_lock = HDR_LOCK(buf->b_hdr);
1417 mutex_enter(hash_lock);
1418 hdr = buf->b_hdr;
1419 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1420 mutex_exit(&buf->b_evict_lock);
1421
1422 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1423 add_reference(hdr, hash_lock, tag);
1424 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1425 arc_access(hdr, hash_lock);
1426 mutex_exit(hash_lock);
1427 ARCSTAT_BUMP(arcstat_hits);
1428 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1429 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1430 data, metadata, hits);
1431 }
1432
1433 /*
1434 * Free the arc data buffer. If it is an l2arc write in progress,
1435 * the buffer is placed on l2arc_free_on_write to be freed later.
1436 */
1437 static void
1438 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1439 {
1440 arc_buf_hdr_t *hdr = buf->b_hdr;
1441
1442 if (HDR_L2_WRITING(hdr)) {
1443 l2arc_data_free_t *df;
1444 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1445 df->l2df_data = buf->b_data;
1446 df->l2df_size = hdr->b_size;
1447 df->l2df_func = free_func;
1448 mutex_enter(&l2arc_free_on_write_mtx);
1449 list_insert_head(l2arc_free_on_write, df);
1450 mutex_exit(&l2arc_free_on_write_mtx);
1451 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1452 } else {
1453 free_func(buf->b_data, hdr->b_size);
1454 }
1455 }
1456
1457 static void
1458 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1459 {
1460 arc_buf_t **bufp;
1461
1462 /* free up data associated with the buf */
1463 if (buf->b_data) {
1464 arc_state_t *state = buf->b_hdr->b_state;
1465 uint64_t size = buf->b_hdr->b_size;
1466 arc_buf_contents_t type = buf->b_hdr->b_type;
1467
1468 arc_cksum_verify(buf);
1469 arc_buf_unwatch(buf);
1470
1471 if (!recycle) {
1472 if (type == ARC_BUFC_METADATA) {
1473 arc_buf_data_free(buf, zio_buf_free);
1474 arc_space_return(size, ARC_SPACE_DATA);
1475 } else {
1476 ASSERT(type == ARC_BUFC_DATA);
1477 arc_buf_data_free(buf, zio_data_buf_free);
1478 ARCSTAT_INCR(arcstat_data_size, -size);
1479 atomic_add_64(&arc_size, -size);
1480 }
1481 }
1482 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1483 uint64_t *cnt = &state->arcs_lsize[type];
1484
1485 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1486 ASSERT(state != arc_anon);
1487
1488 ASSERT3U(*cnt, >=, size);
1489 atomic_add_64(cnt, -size);
1490 }
1491 ASSERT3U(state->arcs_size, >=, size);
1492 atomic_add_64(&state->arcs_size, -size);
1493 buf->b_data = NULL;
1494
1495 /*
1496 * If we're destroying a duplicate buffer make sure
1497 * that the appropriate statistics are updated.
1498 */
1499 if (buf->b_hdr->b_datacnt > 1 &&
1500 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1501 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1502 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1503 }
1504 ASSERT(buf->b_hdr->b_datacnt > 0);
1505 buf->b_hdr->b_datacnt -= 1;
1506 }
1507
1508 /* only remove the buf if requested */
1509 if (!all)
1510 return;
1511
1512 /* remove the buf from the hdr list */
1513 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1514 continue;
1515 *bufp = buf->b_next;
1516 buf->b_next = NULL;
1517
1518 ASSERT(buf->b_efunc == NULL);
1519
1520 /* clean up the buf */
1521 buf->b_hdr = NULL;
1522 kmem_cache_free(buf_cache, buf);
1523 }
1524
1525 static void
1526 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1527 {
1528 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1529 ASSERT3P(hdr->b_state, ==, arc_anon);
1530 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1531 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1532
1533 if (l2hdr != NULL) {
1534 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1535 /*
1536 * To prevent arc_free() and l2arc_evict() from
1537 * attempting to free the same buffer at the same time,
1538 * a FREE_IN_PROGRESS flag is given to arc_free() to
1539 * give it priority. l2arc_evict() can't destroy this
1540 * header while we are waiting on l2arc_buflist_mtx.
1541 *
1542 * The hdr may be removed from l2ad_buflist before we
1543 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1544 */
1545 if (!buflist_held) {
1546 mutex_enter(&l2arc_buflist_mtx);
1547 l2hdr = hdr->b_l2hdr;
1548 }
1549
1550 if (l2hdr != NULL) {
1551 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1552 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1553 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1554 if (hdr->b_state == arc_l2c_only)
1555 l2arc_hdr_stat_remove();
1556 hdr->b_l2hdr = NULL;
1557 }
1558
1559 if (!buflist_held)
1560 mutex_exit(&l2arc_buflist_mtx);
1561 }
1562
1563 if (!BUF_EMPTY(hdr)) {
1564 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1565 buf_discard_identity(hdr);
1566 }
1567 while (hdr->b_buf) {
1568 arc_buf_t *buf = hdr->b_buf;
1569
1570 if (buf->b_efunc) {
1571 mutex_enter(&arc_eviction_mtx);
1572 mutex_enter(&buf->b_evict_lock);
1573 ASSERT(buf->b_hdr != NULL);
1574 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1575 hdr->b_buf = buf->b_next;
1576 buf->b_hdr = &arc_eviction_hdr;
1577 buf->b_next = arc_eviction_list;
1578 arc_eviction_list = buf;
1579 mutex_exit(&buf->b_evict_lock);
1580 mutex_exit(&arc_eviction_mtx);
1581 } else {
1582 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1583 }
1584 }
1585 if (hdr->b_freeze_cksum != NULL) {
1586 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1587 hdr->b_freeze_cksum = NULL;
1588 }
1589 if (hdr->b_thawed) {
1590 kmem_free(hdr->b_thawed, 1);
1591 hdr->b_thawed = NULL;
1592 }
1593
1594 ASSERT(!list_link_active(&hdr->b_arc_node));
1595 ASSERT3P(hdr->b_hash_next, ==, NULL);
1596 ASSERT3P(hdr->b_acb, ==, NULL);
1597 kmem_cache_free(hdr_cache, hdr);
1598 }
1599
1600 void
1601 arc_buf_free(arc_buf_t *buf, void *tag)
1602 {
1603 arc_buf_hdr_t *hdr = buf->b_hdr;
1604 int hashed = hdr->b_state != arc_anon;
1605
1606 ASSERT(buf->b_efunc == NULL);
1607 ASSERT(buf->b_data != NULL);
1608
1609 if (hashed) {
1610 kmutex_t *hash_lock = HDR_LOCK(hdr);
1611
1612 mutex_enter(hash_lock);
1613 hdr = buf->b_hdr;
1614 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1615
1616 (void) remove_reference(hdr, hash_lock, tag);
1617 if (hdr->b_datacnt > 1) {
1618 arc_buf_destroy(buf, FALSE, TRUE);
1619 } else {
1620 ASSERT(buf == hdr->b_buf);
1621 ASSERT(buf->b_efunc == NULL);
1622 hdr->b_flags |= ARC_BUF_AVAILABLE;
1623 }
1624 mutex_exit(hash_lock);
1625 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1626 int destroy_hdr;
1627 /*
1628 * We are in the middle of an async write. Don't destroy
1629 * this buffer unless the write completes before we finish
1630 * decrementing the reference count.
1631 */
1632 mutex_enter(&arc_eviction_mtx);
1633 (void) remove_reference(hdr, NULL, tag);
1634 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1635 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1636 mutex_exit(&arc_eviction_mtx);
1637 if (destroy_hdr)
1638 arc_hdr_destroy(hdr);
1639 } else {
1640 if (remove_reference(hdr, NULL, tag) > 0)
1641 arc_buf_destroy(buf, FALSE, TRUE);
1642 else
1643 arc_hdr_destroy(hdr);
1644 }
1645 }
1646
1647 boolean_t
1648 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1649 {
1650 arc_buf_hdr_t *hdr = buf->b_hdr;
1651 kmutex_t *hash_lock = HDR_LOCK(hdr);
1652 boolean_t no_callback = (buf->b_efunc == NULL);
1653
1654 if (hdr->b_state == arc_anon) {
1655 ASSERT(hdr->b_datacnt == 1);
1656 arc_buf_free(buf, tag);
1657 return (no_callback);
1658 }
1659
1660 mutex_enter(hash_lock);
1661 hdr = buf->b_hdr;
1662 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1663 ASSERT(hdr->b_state != arc_anon);
1664 ASSERT(buf->b_data != NULL);
1665
1666 (void) remove_reference(hdr, hash_lock, tag);
1667 if (hdr->b_datacnt > 1) {
1668 if (no_callback)
1669 arc_buf_destroy(buf, FALSE, TRUE);
1670 } else if (no_callback) {
1671 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1672 ASSERT(buf->b_efunc == NULL);
1673 hdr->b_flags |= ARC_BUF_AVAILABLE;
1674 }
1675 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1676 refcount_is_zero(&hdr->b_refcnt));
1677 mutex_exit(hash_lock);
1678 return (no_callback);
1679 }
1680
1681 int
1682 arc_buf_size(arc_buf_t *buf)
1683 {
1684 return (buf->b_hdr->b_size);
1685 }
1686
1687 /*
1688 * Called from the DMU to determine if the current buffer should be
1689 * evicted. In order to ensure proper locking, the eviction must be initiated
1690 * from the DMU. Return true if the buffer is associated with user data and
1691 * duplicate buffers still exist.
1692 */
1693 boolean_t
1694 arc_buf_eviction_needed(arc_buf_t *buf)
1695 {
1696 arc_buf_hdr_t *hdr;
1697 boolean_t evict_needed = B_FALSE;
1698
1699 if (zfs_disable_dup_eviction)
1700 return (B_FALSE);
1701
1702 mutex_enter(&buf->b_evict_lock);
1703 hdr = buf->b_hdr;
1704 if (hdr == NULL) {
1705 /*
1706 * We are in arc_do_user_evicts(); let that function
1707 * perform the eviction.
1708 */
1709 ASSERT(buf->b_data == NULL);
1710 mutex_exit(&buf->b_evict_lock);
1711 return (B_FALSE);
1712 } else if (buf->b_data == NULL) {
1713 /*
1714 * We have already been added to the arc eviction list;
1715 * recommend eviction.
1716 */
1717 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1718 mutex_exit(&buf->b_evict_lock);
1719 return (B_TRUE);
1720 }
1721
1722 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1723 evict_needed = B_TRUE;
1724
1725 mutex_exit(&buf->b_evict_lock);
1726 return (evict_needed);
1727 }
1728
1729 /*
1730 * Evict buffers from list until we've removed the specified number of
1731 * bytes. Move the removed buffers to the appropriate evict state.
1732 * If the recycle flag is set, then attempt to "recycle" a buffer:
1733 * - look for a buffer to evict that is `bytes' long.
1734 * - return the data block from this buffer rather than freeing it.
1735 * This flag is used by callers that are trying to make space for a
1736 * new buffer in a full arc cache.
1737 *
1738 * This function makes a "best effort". It skips over any buffers
1739 * it can't get a hash_lock on, and so may not catch all candidates.
1740 * It may also return without evicting as much space as requested.
1741 */
1742 static void *
1743 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1744 arc_buf_contents_t type)
1745 {
1746 arc_state_t *evicted_state;
1747 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1748 arc_buf_hdr_t *ab, *ab_prev = NULL;
1749 list_t *list = &state->arcs_list[type];
1750 kmutex_t *hash_lock;
1751 boolean_t have_lock;
1752 void *stolen = NULL;
1753
1754 ASSERT(state == arc_mru || state == arc_mfu);
1755
1756 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1757
1758 mutex_enter(&state->arcs_mtx);
1759 mutex_enter(&evicted_state->arcs_mtx);
1760
1761 for (ab = list_tail(list); ab; ab = ab_prev) {
1762 ab_prev = list_prev(list, ab);
1763 /* prefetch buffers have a minimum lifespan */
1764 if (HDR_IO_IN_PROGRESS(ab) ||
1765 (spa && ab->b_spa != spa) ||
1766 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1767 ddi_get_lbolt() - ab->b_arc_access <
1768 arc_min_prefetch_lifespan)) {
1769 skipped++;
1770 continue;
1771 }
1772 /* "lookahead" for better eviction candidate */
1773 if (recycle && ab->b_size != bytes &&
1774 ab_prev && ab_prev->b_size == bytes)
1775 continue;
1776 hash_lock = HDR_LOCK(ab);
1777 have_lock = MUTEX_HELD(hash_lock);
1778 if (have_lock || mutex_tryenter(hash_lock)) {
1779 ASSERT0(refcount_count(&ab->b_refcnt));
1780 ASSERT(ab->b_datacnt > 0);
1781 while (ab->b_buf) {
1782 arc_buf_t *buf = ab->b_buf;
1783 if (!mutex_tryenter(&buf->b_evict_lock)) {
1784 missed += 1;
1785 break;
1786 }
1787 if (buf->b_data) {
1788 bytes_evicted += ab->b_size;
1789 if (recycle && ab->b_type == type &&
1790 ab->b_size == bytes &&
1791 !HDR_L2_WRITING(ab)) {
1792 stolen = buf->b_data;
1793 recycle = FALSE;
1794 }
1795 }
1796 if (buf->b_efunc) {
1797 mutex_enter(&arc_eviction_mtx);
1798 arc_buf_destroy(buf,
1799 buf->b_data == stolen, FALSE);
1800 ab->b_buf = buf->b_next;
1801 buf->b_hdr = &arc_eviction_hdr;
1802 buf->b_next = arc_eviction_list;
1803 arc_eviction_list = buf;
1804 mutex_exit(&arc_eviction_mtx);
1805 mutex_exit(&buf->b_evict_lock);
1806 } else {
1807 mutex_exit(&buf->b_evict_lock);
1808 arc_buf_destroy(buf,
1809 buf->b_data == stolen, TRUE);
1810 }
1811 }
1812
1813 if (ab->b_l2hdr) {
1814 ARCSTAT_INCR(arcstat_evict_l2_cached,
1815 ab->b_size);
1816 } else {
1817 if (l2arc_write_eligible(ab->b_spa, ab)) {
1818 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1819 ab->b_size);
1820 } else {
1821 ARCSTAT_INCR(
1822 arcstat_evict_l2_ineligible,
1823 ab->b_size);
1824 }
1825 }
1826
1827 if (ab->b_datacnt == 0) {
1828 arc_change_state(evicted_state, ab, hash_lock);
1829 ASSERT(HDR_IN_HASH_TABLE(ab));
1830 ab->b_flags |= ARC_IN_HASH_TABLE;
1831 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1832 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1833 }
1834 if (!have_lock)
1835 mutex_exit(hash_lock);
1836 if (bytes >= 0 && bytes_evicted >= bytes)
1837 break;
1838 } else {
1839 missed += 1;
1840 }
1841 }
1842
1843 mutex_exit(&evicted_state->arcs_mtx);
1844 mutex_exit(&state->arcs_mtx);
1845
1846 if (bytes_evicted < bytes)
1847 dprintf("only evicted %lld bytes from %x",
1848 (longlong_t)bytes_evicted, state);
1849
1850 if (skipped)
1851 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1852
1853 if (missed)
1854 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1855
1856 /*
1857 * We have just evicted some data into the ghost state, make
1858 * sure we also adjust the ghost state size if necessary.
1859 */
1860 if (arc_no_grow &&
1861 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1862 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1863 arc_mru_ghost->arcs_size - arc_c;
1864
1865 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1866 int64_t todelete =
1867 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1868 arc_evict_ghost(arc_mru_ghost, NULL, todelete);
1869 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1870 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1871 arc_mru_ghost->arcs_size +
1872 arc_mfu_ghost->arcs_size - arc_c);
1873 arc_evict_ghost(arc_mfu_ghost, NULL, todelete);
1874 }
1875 }
1876
1877 return (stolen);
1878 }
1879
1880 /*
1881 * Remove buffers from list until we've removed the specified number of
1882 * bytes. Destroy the buffers that are removed.
1883 */
1884 static void
1885 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1886 {
1887 arc_buf_hdr_t *ab, *ab_prev;
1888 arc_buf_hdr_t marker = { 0 };
1889 list_t *list = &state->arcs_list[ARC_BUFC_DATA];
1890 kmutex_t *hash_lock;
1891 uint64_t bytes_deleted = 0;
1892 uint64_t bufs_skipped = 0;
1893
1894 ASSERT(GHOST_STATE(state));
1895 top:
1896 mutex_enter(&state->arcs_mtx);
1897 for (ab = list_tail(list); ab; ab = ab_prev) {
1898 ab_prev = list_prev(list, ab);
1899 if (spa && ab->b_spa != spa)
1900 continue;
1901
1902 /* ignore markers */
1903 if (ab->b_spa == 0)
1904 continue;
1905
1906 hash_lock = HDR_LOCK(ab);
1907 /* caller may be trying to modify this buffer, skip it */
1908 if (MUTEX_HELD(hash_lock))
1909 continue;
1910 if (mutex_tryenter(hash_lock)) {
1911 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1912 ASSERT(ab->b_buf == NULL);
1913 ARCSTAT_BUMP(arcstat_deleted);
1914 bytes_deleted += ab->b_size;
1915
1916 if (ab->b_l2hdr != NULL) {
1917 /*
1918 * This buffer is cached on the 2nd Level ARC;
1919 * don't destroy the header.
1920 */
1921 arc_change_state(arc_l2c_only, ab, hash_lock);
1922 mutex_exit(hash_lock);
1923 } else {
1924 arc_change_state(arc_anon, ab, hash_lock);
1925 mutex_exit(hash_lock);
1926 arc_hdr_destroy(ab);
1927 }
1928
1929 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1930 if (bytes >= 0 && bytes_deleted >= bytes)
1931 break;
1932 } else if (bytes < 0) {
1933 /*
1934 * Insert a list marker and then wait for the
1935 * hash lock to become available. Once its
1936 * available, restart from where we left off.
1937 */
1938 list_insert_after(list, ab, &marker);
1939 mutex_exit(&state->arcs_mtx);
1940 mutex_enter(hash_lock);
1941 mutex_exit(hash_lock);
1942 mutex_enter(&state->arcs_mtx);
1943 ab_prev = list_prev(list, &marker);
1944 list_remove(list, &marker);
1945 } else
1946 bufs_skipped += 1;
1947 }
1948 mutex_exit(&state->arcs_mtx);
1949
1950 if (list == &state->arcs_list[ARC_BUFC_DATA] &&
1951 (bytes < 0 || bytes_deleted < bytes)) {
1952 list = &state->arcs_list[ARC_BUFC_METADATA];
1953 goto top;
1954 }
1955
1956 if (bufs_skipped) {
1957 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
1958 ASSERT(bytes >= 0);
1959 }
1960
1961 if (bytes_deleted < bytes)
1962 dprintf("only deleted %lld bytes from %p",
1963 (longlong_t)bytes_deleted, state);
1964 }
1965
1966 static void
1967 arc_adjust(void)
1968 {
1969 int64_t adjustment, delta;
1970
1971 /*
1972 * Adjust MRU size
1973 */
1974
1975 adjustment = MIN((int64_t)(arc_size - arc_c),
1976 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
1977 arc_p));
1978
1979 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
1980 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
1981 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
1982 adjustment -= delta;
1983 }
1984
1985 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1986 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
1987 (void) arc_evict(arc_mru, NULL, delta, FALSE,
1988 ARC_BUFC_METADATA);
1989 }
1990
1991 /*
1992 * Adjust MFU size
1993 */
1994
1995 adjustment = arc_size - arc_c;
1996
1997 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
1998 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
1999 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
2000 adjustment -= delta;
2001 }
2002
2003 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2004 int64_t delta = MIN(adjustment,
2005 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2006 (void) arc_evict(arc_mfu, NULL, delta, FALSE,
2007 ARC_BUFC_METADATA);
2008 }
2009
2010 /*
2011 * Adjust ghost lists
2012 */
2013
2014 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2015
2016 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2017 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2018 arc_evict_ghost(arc_mru_ghost, NULL, delta);
2019 }
2020
2021 adjustment =
2022 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2023
2024 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2025 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2026 arc_evict_ghost(arc_mfu_ghost, NULL, delta);
2027 }
2028 }
2029
2030 static void
2031 arc_do_user_evicts(void)
2032 {
2033 mutex_enter(&arc_eviction_mtx);
2034 while (arc_eviction_list != NULL) {
2035 arc_buf_t *buf = arc_eviction_list;
2036 arc_eviction_list = buf->b_next;
2037 mutex_enter(&buf->b_evict_lock);
2038 buf->b_hdr = NULL;
2039 mutex_exit(&buf->b_evict_lock);
2040 mutex_exit(&arc_eviction_mtx);
2041
2042 if (buf->b_efunc != NULL)
2043 VERIFY(buf->b_efunc(buf) == 0);
2044
2045 buf->b_efunc = NULL;
2046 buf->b_private = NULL;
2047 kmem_cache_free(buf_cache, buf);
2048 mutex_enter(&arc_eviction_mtx);
2049 }
2050 mutex_exit(&arc_eviction_mtx);
2051 }
2052
2053 /*
2054 * Flush all *evictable* data from the cache for the given spa.
2055 * NOTE: this will not touch "active" (i.e. referenced) data.
2056 */
2057 void
2058 arc_flush(spa_t *spa)
2059 {
2060 uint64_t guid = 0;
2061
2062 if (spa)
2063 guid = spa_load_guid(spa);
2064
2065 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
2066 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2067 if (spa)
2068 break;
2069 }
2070 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
2071 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2072 if (spa)
2073 break;
2074 }
2075 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
2076 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2077 if (spa)
2078 break;
2079 }
2080 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
2081 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2082 if (spa)
2083 break;
2084 }
2085
2086 arc_evict_ghost(arc_mru_ghost, guid, -1);
2087 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2088
2089 mutex_enter(&arc_reclaim_thr_lock);
2090 arc_do_user_evicts();
2091 mutex_exit(&arc_reclaim_thr_lock);
2092 ASSERT(spa || arc_eviction_list == NULL);
2093 }
2094
2095 void
2096 arc_shrink(void)
2097 {
2098 if (arc_c > arc_c_min) {
2099 uint64_t to_free;
2100
2101 #ifdef _KERNEL
2102 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
2103 #else
2104 to_free = arc_c >> arc_shrink_shift;
2105 #endif
2106 if (arc_c > arc_c_min + to_free)
2107 atomic_add_64(&arc_c, -to_free);
2108 else
2109 arc_c = arc_c_min;
2110
2111 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2112 if (arc_c > arc_size)
2113 arc_c = MAX(arc_size, arc_c_min);
2114 if (arc_p > arc_c)
2115 arc_p = (arc_c >> 1);
2116 ASSERT(arc_c >= arc_c_min);
2117 ASSERT((int64_t)arc_p >= 0);
2118 }
2119
2120 if (arc_size > arc_c)
2121 arc_adjust();
2122 }
2123
2124 /*
2125 * Determine if the system is under memory pressure and is asking
2126 * to reclaim memory. A return value of 1 indicates that the system
2127 * is under memory pressure and that the arc should adjust accordingly.
2128 */
2129 static int
2130 arc_reclaim_needed(void)
2131 {
2132 uint64_t extra;
2133
2134 #ifdef _KERNEL
2135
2136 if (needfree)
2137 return (1);
2138
2139 /*
2140 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2141 */
2142 extra = desfree;
2143
2144 /*
2145 * check that we're out of range of the pageout scanner. It starts to
2146 * schedule paging if freemem is less than lotsfree and needfree.
2147 * lotsfree is the high-water mark for pageout, and needfree is the
2148 * number of needed free pages. We add extra pages here to make sure
2149 * the scanner doesn't start up while we're freeing memory.
2150 */
2151 if (freemem < lotsfree + needfree + extra)
2152 return (1);
2153
2154 /*
2155 * check to make sure that swapfs has enough space so that anon
2156 * reservations can still succeed. anon_resvmem() checks that the
2157 * availrmem is greater than swapfs_minfree, and the number of reserved
2158 * swap pages. We also add a bit of extra here just to prevent
2159 * circumstances from getting really dire.
2160 */
2161 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2162 return (1);
2163
2164 #if defined(__i386)
2165 /*
2166 * If we're on an i386 platform, it's possible that we'll exhaust the
2167 * kernel heap space before we ever run out of available physical
2168 * memory. Most checks of the size of the heap_area compare against
2169 * tune.t_minarmem, which is the minimum available real memory that we
2170 * can have in the system. However, this is generally fixed at 25 pages
2171 * which is so low that it's useless. In this comparison, we seek to
2172 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2173 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2174 * free)
2175 */
2176 if (vmem_size(heap_arena, VMEM_FREE) <
2177 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2))
2178 return (1);
2179 #endif
2180
2181 /*
2182 * If zio data pages are being allocated out of a separate heap segment,
2183 * then enforce that the size of available vmem for this arena remains
2184 * above about 1/16th free.
2185 *
2186 * Note: The 1/16th arena free requirement was put in place
2187 * to aggressively evict memory from the arc in order to avoid
2188 * memory fragmentation issues.
2189 */
2190 if (zio_arena != NULL &&
2191 vmem_size(zio_arena, VMEM_FREE) <
2192 (vmem_size(zio_arena, VMEM_ALLOC) >> 4))
2193 return (1);
2194 #else
2195 if (spa_get_random(100) == 0)
2196 return (1);
2197 #endif
2198 return (0);
2199 }
2200
2201 static void
2202 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2203 {
2204 size_t i;
2205 kmem_cache_t *prev_cache = NULL;
2206 kmem_cache_t *prev_data_cache = NULL;
2207 extern kmem_cache_t *zio_buf_cache[];
2208 extern kmem_cache_t *zio_data_buf_cache[];
2209
2210 #ifdef _KERNEL
2211 if (arc_meta_used >= arc_meta_limit) {
2212 /*
2213 * We are exceeding our meta-data cache limit.
2214 * Purge some DNLC entries to release holds on meta-data.
2215 */
2216 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2217 }
2218 #if defined(__i386)
2219 /*
2220 * Reclaim unused memory from all kmem caches.
2221 */
2222 kmem_reap();
2223 #endif
2224 #endif
2225
2226 /*
2227 * An aggressive reclamation will shrink the cache size as well as
2228 * reap free buffers from the arc kmem caches.
2229 */
2230 if (strat == ARC_RECLAIM_AGGR)
2231 arc_shrink();
2232
2233 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2234 if (zio_buf_cache[i] != prev_cache) {
2235 prev_cache = zio_buf_cache[i];
2236 kmem_cache_reap_now(zio_buf_cache[i]);
2237 }
2238 if (zio_data_buf_cache[i] != prev_data_cache) {
2239 prev_data_cache = zio_data_buf_cache[i];
2240 kmem_cache_reap_now(zio_data_buf_cache[i]);
2241 }
2242 }
2243 kmem_cache_reap_now(buf_cache);
2244 kmem_cache_reap_now(hdr_cache);
2245
2246 /*
2247 * Ask the vmem areana to reclaim unused memory from its
2248 * quantum caches.
2249 */
2250 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
2251 vmem_qcache_reap(zio_arena);
2252 }
2253
2254 static void
2255 arc_reclaim_thread(void)
2256 {
2257 clock_t growtime = 0;
2258 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2259 callb_cpr_t cpr;
2260
2261 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2262
2263 mutex_enter(&arc_reclaim_thr_lock);
2264 while (arc_thread_exit == 0) {
2265 if (arc_reclaim_needed()) {
2266
2267 if (arc_no_grow) {
2268 if (last_reclaim == ARC_RECLAIM_CONS) {
2269 last_reclaim = ARC_RECLAIM_AGGR;
2270 } else {
2271 last_reclaim = ARC_RECLAIM_CONS;
2272 }
2273 } else {
2274 arc_no_grow = TRUE;
2275 last_reclaim = ARC_RECLAIM_AGGR;
2276 membar_producer();
2277 }
2278
2279 /* reset the growth delay for every reclaim */
2280 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2281
2282 arc_kmem_reap_now(last_reclaim);
2283 arc_warm = B_TRUE;
2284
2285 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2286 arc_no_grow = FALSE;
2287 }
2288
2289 arc_adjust();
2290
2291 if (arc_eviction_list != NULL)
2292 arc_do_user_evicts();
2293
2294 /* block until needed, or one second, whichever is shorter */
2295 CALLB_CPR_SAFE_BEGIN(&cpr);
2296 (void) cv_timedwait(&arc_reclaim_thr_cv,
2297 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
2298 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2299 }
2300
2301 arc_thread_exit = 0;
2302 cv_broadcast(&arc_reclaim_thr_cv);
2303 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2304 thread_exit();
2305 }
2306
2307 /*
2308 * Adapt arc info given the number of bytes we are trying to add and
2309 * the state that we are comming from. This function is only called
2310 * when we are adding new content to the cache.
2311 */
2312 static void
2313 arc_adapt(int bytes, arc_state_t *state)
2314 {
2315 int mult;
2316 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2317
2318 if (state == arc_l2c_only)
2319 return;
2320
2321 ASSERT(bytes > 0);
2322 /*
2323 * Adapt the target size of the MRU list:
2324 * - if we just hit in the MRU ghost list, then increase
2325 * the target size of the MRU list.
2326 * - if we just hit in the MFU ghost list, then increase
2327 * the target size of the MFU list by decreasing the
2328 * target size of the MRU list.
2329 */
2330 if (state == arc_mru_ghost) {
2331 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2332 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2333 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2334
2335 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2336 } else if (state == arc_mfu_ghost) {
2337 uint64_t delta;
2338
2339 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2340 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2341 mult = MIN(mult, 10);
2342
2343 delta = MIN(bytes * mult, arc_p);
2344 arc_p = MAX(arc_p_min, arc_p - delta);
2345 }
2346 ASSERT((int64_t)arc_p >= 0);
2347
2348 if (arc_reclaim_needed()) {
2349 cv_signal(&arc_reclaim_thr_cv);
2350 return;
2351 }
2352
2353 if (arc_no_grow)
2354 return;
2355
2356 if (arc_c >= arc_c_max)
2357 return;
2358
2359 /*
2360 * If we're within (2 * maxblocksize) bytes of the target
2361 * cache size, increment the target cache size
2362 */
2363 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2364 atomic_add_64(&arc_c, (int64_t)bytes);
2365 if (arc_c > arc_c_max)
2366 arc_c = arc_c_max;
2367 else if (state == arc_anon)
2368 atomic_add_64(&arc_p, (int64_t)bytes);
2369 if (arc_p > arc_c)
2370 arc_p = arc_c;
2371 }
2372 ASSERT((int64_t)arc_p >= 0);
2373 }
2374
2375 /*
2376 * Check if the cache has reached its limits and eviction is required
2377 * prior to insert.
2378 */
2379 static int
2380 arc_evict_needed(arc_buf_contents_t type)
2381 {
2382 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2383 return (1);
2384
2385 if (arc_reclaim_needed())
2386 return (1);
2387
2388 return (arc_size > arc_c);
2389 }
2390
2391 /*
2392 * The buffer, supplied as the first argument, needs a data block.
2393 * So, if we are at cache max, determine which cache should be victimized.
2394 * We have the following cases:
2395 *
2396 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2397 * In this situation if we're out of space, but the resident size of the MFU is
2398 * under the limit, victimize the MFU cache to satisfy this insertion request.
2399 *
2400 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2401 * Here, we've used up all of the available space for the MRU, so we need to
2402 * evict from our own cache instead. Evict from the set of resident MRU
2403 * entries.
2404 *
2405 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2406 * c minus p represents the MFU space in the cache, since p is the size of the
2407 * cache that is dedicated to the MRU. In this situation there's still space on
2408 * the MFU side, so the MRU side needs to be victimized.
2409 *
2410 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2411 * MFU's resident set is consuming more space than it has been allotted. In
2412 * this situation, we must victimize our own cache, the MFU, for this insertion.
2413 */
2414 static void
2415 arc_get_data_buf(arc_buf_t *buf)
2416 {
2417 arc_state_t *state = buf->b_hdr->b_state;
2418 uint64_t size = buf->b_hdr->b_size;
2419 arc_buf_contents_t type = buf->b_hdr->b_type;
2420
2421 arc_adapt(size, state);
2422
2423 /*
2424 * We have not yet reached cache maximum size,
2425 * just allocate a new buffer.
2426 */
2427 if (!arc_evict_needed(type)) {
2428 if (type == ARC_BUFC_METADATA) {
2429 buf->b_data = zio_buf_alloc(size);
2430 arc_space_consume(size, ARC_SPACE_DATA);
2431 } else {
2432 ASSERT(type == ARC_BUFC_DATA);
2433 buf->b_data = zio_data_buf_alloc(size);
2434 ARCSTAT_INCR(arcstat_data_size, size);
2435 atomic_add_64(&arc_size, size);
2436 }
2437 goto out;
2438 }
2439
2440 /*
2441 * If we are prefetching from the mfu ghost list, this buffer
2442 * will end up on the mru list; so steal space from there.
2443 */
2444 if (state == arc_mfu_ghost)
2445 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2446 else if (state == arc_mru_ghost)
2447 state = arc_mru;
2448
2449 if (state == arc_mru || state == arc_anon) {
2450 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2451 state = (arc_mfu->arcs_lsize[type] >= size &&
2452 arc_p > mru_used) ? arc_mfu : arc_mru;
2453 } else {
2454 /* MFU cases */
2455 uint64_t mfu_space = arc_c - arc_p;
2456 state = (arc_mru->arcs_lsize[type] >= size &&
2457 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2458 }
2459 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
2460 if (type == ARC_BUFC_METADATA) {
2461 buf->b_data = zio_buf_alloc(size);
2462 arc_space_consume(size, ARC_SPACE_DATA);
2463 } else {
2464 ASSERT(type == ARC_BUFC_DATA);
2465 buf->b_data = zio_data_buf_alloc(size);
2466 ARCSTAT_INCR(arcstat_data_size, size);
2467 atomic_add_64(&arc_size, size);
2468 }
2469 ARCSTAT_BUMP(arcstat_recycle_miss);
2470 }
2471 ASSERT(buf->b_data != NULL);
2472 out:
2473 /*
2474 * Update the state size. Note that ghost states have a
2475 * "ghost size" and so don't need to be updated.
2476 */
2477 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2478 arc_buf_hdr_t *hdr = buf->b_hdr;
2479
2480 atomic_add_64(&hdr->b_state->arcs_size, size);
2481 if (list_link_active(&hdr->b_arc_node)) {
2482 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2483 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2484 }
2485 /*
2486 * If we are growing the cache, and we are adding anonymous
2487 * data, and we have outgrown arc_p, update arc_p
2488 */
2489 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2490 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2491 arc_p = MIN(arc_c, arc_p + size);
2492 }
2493 }
2494
2495 /*
2496 * This routine is called whenever a buffer is accessed.
2497 * NOTE: the hash lock is dropped in this function.
2498 */
2499 static void
2500 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2501 {
2502 clock_t now;
2503
2504 ASSERT(MUTEX_HELD(hash_lock));
2505
2506 if (buf->b_state == arc_anon) {
2507 /*
2508 * This buffer is not in the cache, and does not
2509 * appear in our "ghost" list. Add the new buffer
2510 * to the MRU state.
2511 */
2512
2513 ASSERT(buf->b_arc_access == 0);
2514 buf->b_arc_access = ddi_get_lbolt();
2515 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2516 arc_change_state(arc_mru, buf, hash_lock);
2517
2518 } else if (buf->b_state == arc_mru) {
2519 now = ddi_get_lbolt();
2520
2521 /*
2522 * If this buffer is here because of a prefetch, then either:
2523 * - clear the flag if this is a "referencing" read
2524 * (any subsequent access will bump this into the MFU state).
2525 * or
2526 * - move the buffer to the head of the list if this is
2527 * another prefetch (to make it less likely to be evicted).
2528 */
2529 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2530 if (refcount_count(&buf->b_refcnt) == 0) {
2531 ASSERT(list_link_active(&buf->b_arc_node));
2532 } else {
2533 buf->b_flags &= ~ARC_PREFETCH;
2534 ARCSTAT_BUMP(arcstat_mru_hits);
2535 }
2536 buf->b_arc_access = now;
2537 return;
2538 }
2539
2540 /*
2541 * This buffer has been "accessed" only once so far,
2542 * but it is still in the cache. Move it to the MFU
2543 * state.
2544 */
2545 if (now > buf->b_arc_access + ARC_MINTIME) {
2546 /*
2547 * More than 125ms have passed since we
2548 * instantiated this buffer. Move it to the
2549 * most frequently used state.
2550 */
2551 buf->b_arc_access = now;
2552 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2553 arc_change_state(arc_mfu, buf, hash_lock);
2554 }
2555 ARCSTAT_BUMP(arcstat_mru_hits);
2556 } else if (buf->b_state == arc_mru_ghost) {
2557 arc_state_t *new_state;
2558 /*
2559 * This buffer has been "accessed" recently, but
2560 * was evicted from the cache. Move it to the
2561 * MFU state.
2562 */
2563
2564 if (buf->b_flags & ARC_PREFETCH) {
2565 new_state = arc_mru;
2566 if (refcount_count(&buf->b_refcnt) > 0)
2567 buf->b_flags &= ~ARC_PREFETCH;
2568 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2569 } else {
2570 new_state = arc_mfu;
2571 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2572 }
2573
2574 buf->b_arc_access = ddi_get_lbolt();
2575 arc_change_state(new_state, buf, hash_lock);
2576
2577 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2578 } else if (buf->b_state == arc_mfu) {
2579 /*
2580 * This buffer has been accessed more than once and is
2581 * still in the cache. Keep it in the MFU state.
2582 *
2583 * NOTE: an add_reference() that occurred when we did
2584 * the arc_read() will have kicked this off the list.
2585 * If it was a prefetch, we will explicitly move it to
2586 * the head of the list now.
2587 */
2588 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2589 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2590 ASSERT(list_link_active(&buf->b_arc_node));
2591 }
2592 ARCSTAT_BUMP(arcstat_mfu_hits);
2593 buf->b_arc_access = ddi_get_lbolt();
2594 } else if (buf->b_state == arc_mfu_ghost) {
2595 arc_state_t *new_state = arc_mfu;
2596 /*
2597 * This buffer has been accessed more than once but has
2598 * been evicted from the cache. Move it back to the
2599 * MFU state.
2600 */
2601
2602 if (buf->b_flags & ARC_PREFETCH) {
2603 /*
2604 * This is a prefetch access...
2605 * move this block back to the MRU state.
2606 */
2607 ASSERT0(refcount_count(&buf->b_refcnt));
2608 new_state = arc_mru;
2609 }
2610
2611 buf->b_arc_access = ddi_get_lbolt();
2612 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2613 arc_change_state(new_state, buf, hash_lock);
2614
2615 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2616 } else if (buf->b_state == arc_l2c_only) {
2617 /*
2618 * This buffer is on the 2nd Level ARC.
2619 */
2620
2621 buf->b_arc_access = ddi_get_lbolt();
2622 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2623 arc_change_state(arc_mfu, buf, hash_lock);
2624 } else {
2625 ASSERT(!"invalid arc state");
2626 }
2627 }
2628
2629 /* a generic arc_done_func_t which you can use */
2630 /* ARGSUSED */
2631 void
2632 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2633 {
2634 if (zio == NULL || zio->io_error == 0)
2635 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2636 VERIFY(arc_buf_remove_ref(buf, arg));
2637 }
2638
2639 /* a generic arc_done_func_t */
2640 void
2641 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2642 {
2643 arc_buf_t **bufp = arg;
2644 if (zio && zio->io_error) {
2645 VERIFY(arc_buf_remove_ref(buf, arg));
2646 *bufp = NULL;
2647 } else {
2648 *bufp = buf;
2649 ASSERT(buf->b_data);
2650 }
2651 }
2652
2653 static void
2654 arc_read_done(zio_t *zio)
2655 {
2656 arc_buf_hdr_t *hdr, *found;
2657 arc_buf_t *buf;
2658 arc_buf_t *abuf; /* buffer we're assigning to callback */
2659 kmutex_t *hash_lock;
2660 arc_callback_t *callback_list, *acb;
2661 int freeable = FALSE;
2662
2663 buf = zio->io_private;
2664 hdr = buf->b_hdr;
2665
2666 /*
2667 * The hdr was inserted into hash-table and removed from lists
2668 * prior to starting I/O. We should find this header, since
2669 * it's in the hash table, and it should be legit since it's
2670 * not possible to evict it during the I/O. The only possible
2671 * reason for it not to be found is if we were freed during the
2672 * read.
2673 */
2674 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2675 &hash_lock);
2676
2677 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2678 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2679 (found == hdr && HDR_L2_READING(hdr)));
2680
2681 hdr->b_flags &= ~ARC_L2_EVICTED;
2682 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2683 hdr->b_flags &= ~ARC_L2CACHE;
2684
2685 /* byteswap if necessary */
2686 callback_list = hdr->b_acb;
2687 ASSERT(callback_list != NULL);
2688 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
2689 dmu_object_byteswap_t bswap =
2690 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
2691 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2692 byteswap_uint64_array :
2693 dmu_ot_byteswap[bswap].ob_func;
2694 func(buf->b_data, hdr->b_size);
2695 }
2696
2697 arc_cksum_compute(buf, B_FALSE);
2698 arc_buf_watch(buf);
2699
2700 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
2701 /*
2702 * Only call arc_access on anonymous buffers. This is because
2703 * if we've issued an I/O for an evicted buffer, we've already
2704 * called arc_access (to prevent any simultaneous readers from
2705 * getting confused).
2706 */
2707 arc_access(hdr, hash_lock);
2708 }
2709
2710 /* create copies of the data buffer for the callers */
2711 abuf = buf;
2712 for (acb = callback_list; acb; acb = acb->acb_next) {
2713 if (acb->acb_done) {
2714 if (abuf == NULL) {
2715 ARCSTAT_BUMP(arcstat_duplicate_reads);
2716 abuf = arc_buf_clone(buf);
2717 }
2718 acb->acb_buf = abuf;
2719 abuf = NULL;
2720 }
2721 }
2722 hdr->b_acb = NULL;
2723 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2724 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2725 if (abuf == buf) {
2726 ASSERT(buf->b_efunc == NULL);
2727 ASSERT(hdr->b_datacnt == 1);
2728 hdr->b_flags |= ARC_BUF_AVAILABLE;
2729 }
2730
2731 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2732
2733 if (zio->io_error != 0) {
2734 hdr->b_flags |= ARC_IO_ERROR;
2735 if (hdr->b_state != arc_anon)
2736 arc_change_state(arc_anon, hdr, hash_lock);
2737 if (HDR_IN_HASH_TABLE(hdr))
2738 buf_hash_remove(hdr);
2739 freeable = refcount_is_zero(&hdr->b_refcnt);
2740 }
2741
2742 /*
2743 * Broadcast before we drop the hash_lock to avoid the possibility
2744 * that the hdr (and hence the cv) might be freed before we get to
2745 * the cv_broadcast().
2746 */
2747 cv_broadcast(&hdr->b_cv);
2748
2749 if (hash_lock) {
2750 mutex_exit(hash_lock);
2751 } else {
2752 /*
2753 * This block was freed while we waited for the read to
2754 * complete. It has been removed from the hash table and
2755 * moved to the anonymous state (so that it won't show up
2756 * in the cache).
2757 */
2758 ASSERT3P(hdr->b_state, ==, arc_anon);
2759 freeable = refcount_is_zero(&hdr->b_refcnt);
2760 }
2761
2762 /* execute each callback and free its structure */
2763 while ((acb = callback_list) != NULL) {
2764 if (acb->acb_done)
2765 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2766
2767 if (acb->acb_zio_dummy != NULL) {
2768 acb->acb_zio_dummy->io_error = zio->io_error;
2769 zio_nowait(acb->acb_zio_dummy);
2770 }
2771
2772 callback_list = acb->acb_next;
2773 kmem_free(acb, sizeof (arc_callback_t));
2774 }
2775
2776 if (freeable)
2777 arc_hdr_destroy(hdr);
2778 }
2779
2780 /*
2781 * "Read" the block at the specified DVA (in bp) via the
2782 * cache. If the block is found in the cache, invoke the provided
2783 * callback immediately and return. Note that the `zio' parameter
2784 * in the callback will be NULL in this case, since no IO was
2785 * required. If the block is not in the cache pass the read request
2786 * on to the spa with a substitute callback function, so that the
2787 * requested block will be added to the cache.
2788 *
2789 * If a read request arrives for a block that has a read in-progress,
2790 * either wait for the in-progress read to complete (and return the
2791 * results); or, if this is a read with a "done" func, add a record
2792 * to the read to invoke the "done" func when the read completes,
2793 * and return; or just return.
2794 *
2795 * arc_read_done() will invoke all the requested "done" functions
2796 * for readers of this block.
2797 */
2798 int
2799 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
2800 void *private, int priority, int zio_flags, uint32_t *arc_flags,
2801 const zbookmark_t *zb)
2802 {
2803 arc_buf_hdr_t *hdr;
2804 arc_buf_t *buf = NULL;
2805 kmutex_t *hash_lock;
2806 zio_t *rzio;
2807 uint64_t guid = spa_load_guid(spa);
2808
2809 top:
2810 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
2811 &hash_lock);
2812 if (hdr && hdr->b_datacnt > 0) {
2813
2814 *arc_flags |= ARC_CACHED;
2815
2816 if (HDR_IO_IN_PROGRESS(hdr)) {
2817
2818 if (*arc_flags & ARC_WAIT) {
2819 cv_wait(&hdr->b_cv, hash_lock);
2820 mutex_exit(hash_lock);
2821 goto top;
2822 }
2823 ASSERT(*arc_flags & ARC_NOWAIT);
2824
2825 if (done) {
2826 arc_callback_t *acb = NULL;
2827
2828 acb = kmem_zalloc(sizeof (arc_callback_t),
2829 KM_SLEEP);
2830 acb->acb_done = done;
2831 acb->acb_private = private;
2832 if (pio != NULL)
2833 acb->acb_zio_dummy = zio_null(pio,
2834 spa, NULL, NULL, NULL, zio_flags);
2835
2836 ASSERT(acb->acb_done != NULL);
2837 acb->acb_next = hdr->b_acb;
2838 hdr->b_acb = acb;
2839 add_reference(hdr, hash_lock, private);
2840 mutex_exit(hash_lock);
2841 return (0);
2842 }
2843 mutex_exit(hash_lock);
2844 return (0);
2845 }
2846
2847 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2848
2849 if (done) {
2850 add_reference(hdr, hash_lock, private);
2851 /*
2852 * If this block is already in use, create a new
2853 * copy of the data so that we will be guaranteed
2854 * that arc_release() will always succeed.
2855 */
2856 buf = hdr->b_buf;
2857 ASSERT(buf);
2858 ASSERT(buf->b_data);
2859 if (HDR_BUF_AVAILABLE(hdr)) {
2860 ASSERT(buf->b_efunc == NULL);
2861 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2862 } else {
2863 buf = arc_buf_clone(buf);
2864 }
2865
2866 } else if (*arc_flags & ARC_PREFETCH &&
2867 refcount_count(&hdr->b_refcnt) == 0) {
2868 hdr->b_flags |= ARC_PREFETCH;
2869 }
2870 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
2871 arc_access(hdr, hash_lock);
2872 if (*arc_flags & ARC_L2CACHE)
2873 hdr->b_flags |= ARC_L2CACHE;
2874 mutex_exit(hash_lock);
2875 ARCSTAT_BUMP(arcstat_hits);
2876 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2877 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2878 data, metadata, hits);
2879
2880 if (done)
2881 done(NULL, buf, private);
2882 } else {
2883 uint64_t size = BP_GET_LSIZE(bp);
2884 arc_callback_t *acb;
2885 vdev_t *vd = NULL;
2886 uint64_t addr = 0;
2887 boolean_t devw = B_FALSE;
2888
2889 if (hdr == NULL) {
2890 /* this block is not in the cache */
2891 arc_buf_hdr_t *exists;
2892 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
2893 buf = arc_buf_alloc(spa, size, private, type);
2894 hdr = buf->b_hdr;
2895 hdr->b_dva = *BP_IDENTITY(bp);
2896 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
2897 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
2898 exists = buf_hash_insert(hdr, &hash_lock);
2899 if (exists) {
2900 /* somebody beat us to the hash insert */
2901 mutex_exit(hash_lock);
2902 buf_discard_identity(hdr);
2903 (void) arc_buf_remove_ref(buf, private);
2904 goto top; /* restart the IO request */
2905 }
2906 /* if this is a prefetch, we don't have a reference */
2907 if (*arc_flags & ARC_PREFETCH) {
2908 (void) remove_reference(hdr, hash_lock,
2909 private);
2910 hdr->b_flags |= ARC_PREFETCH;
2911 }
2912 if (*arc_flags & ARC_L2CACHE)
2913 hdr->b_flags |= ARC_L2CACHE;
2914 if (BP_GET_LEVEL(bp) > 0)
2915 hdr->b_flags |= ARC_INDIRECT;
2916 } else {
2917 /* this block is in the ghost cache */
2918 ASSERT(GHOST_STATE(hdr->b_state));
2919 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2920 ASSERT0(refcount_count(&hdr->b_refcnt));
2921 ASSERT(hdr->b_buf == NULL);
2922
2923 /* if this is a prefetch, we don't have a reference */
2924 if (*arc_flags & ARC_PREFETCH)
2925 hdr->b_flags |= ARC_PREFETCH;
2926 else
2927 add_reference(hdr, hash_lock, private);
2928 if (*arc_flags & ARC_L2CACHE)
2929 hdr->b_flags |= ARC_L2CACHE;
2930 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2931 buf->b_hdr = hdr;
2932 buf->b_data = NULL;
2933 buf->b_efunc = NULL;
2934 buf->b_private = NULL;
2935 buf->b_next = NULL;
2936 hdr->b_buf = buf;
2937 ASSERT(hdr->b_datacnt == 0);
2938 hdr->b_datacnt = 1;
2939 arc_get_data_buf(buf);
2940 arc_access(hdr, hash_lock);
2941 }
2942
2943 ASSERT(!GHOST_STATE(hdr->b_state));
2944
2945 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
2946 acb->acb_done = done;
2947 acb->acb_private = private;
2948
2949 ASSERT(hdr->b_acb == NULL);
2950 hdr->b_acb = acb;
2951 hdr->b_flags |= ARC_IO_IN_PROGRESS;
2952
2953 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
2954 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
2955 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
2956 addr = hdr->b_l2hdr->b_daddr;
2957 /*
2958 * Lock out device removal.
2959 */
2960 if (vdev_is_dead(vd) ||
2961 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
2962 vd = NULL;
2963 }
2964
2965 mutex_exit(hash_lock);
2966
2967 /*
2968 * At this point, we have a level 1 cache miss. Try again in
2969 * L2ARC if possible.
2970 */
2971 ASSERT3U(hdr->b_size, ==, size);
2972 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
2973 uint64_t, size, zbookmark_t *, zb);
2974 ARCSTAT_BUMP(arcstat_misses);
2975 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2976 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2977 data, metadata, misses);
2978
2979 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
2980 /*
2981 * Read from the L2ARC if the following are true:
2982 * 1. The L2ARC vdev was previously cached.
2983 * 2. This buffer still has L2ARC metadata.
2984 * 3. This buffer isn't currently writing to the L2ARC.
2985 * 4. The L2ARC entry wasn't evicted, which may
2986 * also have invalidated the vdev.
2987 * 5. This isn't prefetch and l2arc_noprefetch is set.
2988 */
2989 if (hdr->b_l2hdr != NULL &&
2990 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
2991 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
2992 l2arc_read_callback_t *cb;
2993
2994 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
2995 ARCSTAT_BUMP(arcstat_l2_hits);
2996
2997 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
2998 KM_SLEEP);
2999 cb->l2rcb_buf = buf;
3000 cb->l2rcb_spa = spa;
3001 cb->l2rcb_bp = *bp;
3002 cb->l2rcb_zb = *zb;
3003 cb->l2rcb_flags = zio_flags;
3004
3005 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3006 addr + size < vd->vdev_psize -
3007 VDEV_LABEL_END_SIZE);
3008
3009 /*
3010 * l2arc read. The SCL_L2ARC lock will be
3011 * released by l2arc_read_done().
3012 */
3013 rzio = zio_read_phys(pio, vd, addr, size,
3014 buf->b_data, ZIO_CHECKSUM_OFF,
3015 l2arc_read_done, cb, priority, zio_flags |
3016 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3017 ZIO_FLAG_DONT_PROPAGATE |
3018 ZIO_FLAG_DONT_RETRY, B_FALSE);
3019 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3020 zio_t *, rzio);
3021 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3022
3023 if (*arc_flags & ARC_NOWAIT) {
3024 zio_nowait(rzio);
3025 return (0);
3026 }
3027
3028 ASSERT(*arc_flags & ARC_WAIT);
3029 if (zio_wait(rzio) == 0)
3030 return (0);
3031
3032 /* l2arc read error; goto zio_read() */
3033 } else {
3034 DTRACE_PROBE1(l2arc__miss,
3035 arc_buf_hdr_t *, hdr);
3036 ARCSTAT_BUMP(arcstat_l2_misses);
3037 if (HDR_L2_WRITING(hdr))
3038 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3039 spa_config_exit(spa, SCL_L2ARC, vd);
3040 }
3041 } else {
3042 if (vd != NULL)
3043 spa_config_exit(spa, SCL_L2ARC, vd);
3044 if (l2arc_ndev != 0) {
3045 DTRACE_PROBE1(l2arc__miss,
3046 arc_buf_hdr_t *, hdr);
3047 ARCSTAT_BUMP(arcstat_l2_misses);
3048 }
3049 }
3050
3051 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3052 arc_read_done, buf, priority, zio_flags, zb);
3053
3054 if (*arc_flags & ARC_WAIT)
3055 return (zio_wait(rzio));
3056
3057 ASSERT(*arc_flags & ARC_NOWAIT);
3058 zio_nowait(rzio);
3059 }
3060 return (0);
3061 }
3062
3063 void
3064 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3065 {
3066 ASSERT(buf->b_hdr != NULL);
3067 ASSERT(buf->b_hdr->b_state != arc_anon);
3068 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3069 ASSERT(buf->b_efunc == NULL);
3070 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3071
3072 buf->b_efunc = func;
3073 buf->b_private = private;
3074 }
3075
3076 /*
3077 * This is used by the DMU to let the ARC know that a buffer is
3078 * being evicted, so the ARC should clean up. If this arc buf
3079 * is not yet in the evicted state, it will be put there.
3080 */
3081 int
3082 arc_buf_evict(arc_buf_t *buf)
3083 {
3084 arc_buf_hdr_t *hdr;
3085 kmutex_t *hash_lock;
3086 arc_buf_t **bufp;
3087
3088 mutex_enter(&buf->b_evict_lock);
3089 hdr = buf->b_hdr;
3090 if (hdr == NULL) {
3091 /*
3092 * We are in arc_do_user_evicts().
3093 */
3094 ASSERT(buf->b_data == NULL);
3095 mutex_exit(&buf->b_evict_lock);
3096 return (0);
3097 } else if (buf->b_data == NULL) {
3098 arc_buf_t copy = *buf; /* structure assignment */
3099 /*
3100 * We are on the eviction list; process this buffer now
3101 * but let arc_do_user_evicts() do the reaping.
3102 */
3103 buf->b_efunc = NULL;
3104 mutex_exit(&buf->b_evict_lock);
3105 VERIFY(copy.b_efunc(©) == 0);
3106 return (1);
3107 }
3108 hash_lock = HDR_LOCK(hdr);
3109 mutex_enter(hash_lock);
3110 hdr = buf->b_hdr;
3111 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3112
3113 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3114 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3115
3116 /*
3117 * Pull this buffer off of the hdr
3118 */
3119 bufp = &hdr->b_buf;
3120 while (*bufp != buf)
3121 bufp = &(*bufp)->b_next;
3122 *bufp = buf->b_next;
3123
3124 ASSERT(buf->b_data != NULL);
3125 arc_buf_destroy(buf, FALSE, FALSE);
3126
3127 if (hdr->b_datacnt == 0) {
3128 arc_state_t *old_state = hdr->b_state;
3129 arc_state_t *evicted_state;
3130
3131 ASSERT(hdr->b_buf == NULL);
3132 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3133
3134 evicted_state =
3135 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3136
3137 mutex_enter(&old_state->arcs_mtx);
3138 mutex_enter(&evicted_state->arcs_mtx);
3139
3140 arc_change_state(evicted_state, hdr, hash_lock);
3141 ASSERT(HDR_IN_HASH_TABLE(hdr));
3142 hdr->b_flags |= ARC_IN_HASH_TABLE;
3143 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3144
3145 mutex_exit(&evicted_state->arcs_mtx);
3146 mutex_exit(&old_state->arcs_mtx);
3147 }
3148 mutex_exit(hash_lock);
3149 mutex_exit(&buf->b_evict_lock);
3150
3151 VERIFY(buf->b_efunc(buf) == 0);
3152 buf->b_efunc = NULL;
3153 buf->b_private = NULL;
3154 buf->b_hdr = NULL;
3155 buf->b_next = NULL;
3156 kmem_cache_free(buf_cache, buf);
3157 return (1);
3158 }
3159
3160 /*
3161 * Release this buffer from the cache, making it an anonymous buffer. This
3162 * must be done after a read and prior to modifying the buffer contents.
3163 * If the buffer has more than one reference, we must make
3164 * a new hdr for the buffer.
3165 */
3166 void
3167 arc_release(arc_buf_t *buf, void *tag)
3168 {
3169 arc_buf_hdr_t *hdr;
3170 kmutex_t *hash_lock = NULL;
3171 l2arc_buf_hdr_t *l2hdr;
3172 uint64_t buf_size;
3173
3174 /*
3175 * It would be nice to assert that if it's DMU metadata (level >
3176 * 0 || it's the dnode file), then it must be syncing context.
3177 * But we don't know that information at this level.
3178 */
3179
3180 mutex_enter(&buf->b_evict_lock);
3181 hdr = buf->b_hdr;
3182
3183 /* this buffer is not on any list */
3184 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3185
3186 if (hdr->b_state == arc_anon) {
3187 /* this buffer is already released */
3188 ASSERT(buf->b_efunc == NULL);
3189 } else {
3190 hash_lock = HDR_LOCK(hdr);
3191 mutex_enter(hash_lock);
3192 hdr = buf->b_hdr;
3193 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3194 }
3195
3196 l2hdr = hdr->b_l2hdr;
3197 if (l2hdr) {
3198 mutex_enter(&l2arc_buflist_mtx);
3199 hdr->b_l2hdr = NULL;
3200 }
3201 buf_size = hdr->b_size;
3202
3203 /*
3204 * Do we have more than one buf?
3205 */
3206 if (hdr->b_datacnt > 1) {
3207 arc_buf_hdr_t *nhdr;
3208 arc_buf_t **bufp;
3209 uint64_t blksz = hdr->b_size;
3210 uint64_t spa = hdr->b_spa;
3211 arc_buf_contents_t type = hdr->b_type;
3212 uint32_t flags = hdr->b_flags;
3213
3214 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3215 /*
3216 * Pull the data off of this hdr and attach it to
3217 * a new anonymous hdr.
3218 */
3219 (void) remove_reference(hdr, hash_lock, tag);
3220 bufp = &hdr->b_buf;
3221 while (*bufp != buf)
3222 bufp = &(*bufp)->b_next;
3223 *bufp = buf->b_next;
3224 buf->b_next = NULL;
3225
3226 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3227 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3228 if (refcount_is_zero(&hdr->b_refcnt)) {
3229 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3230 ASSERT3U(*size, >=, hdr->b_size);
3231 atomic_add_64(size, -hdr->b_size);
3232 }
3233
3234 /*
3235 * We're releasing a duplicate user data buffer, update
3236 * our statistics accordingly.
3237 */
3238 if (hdr->b_type == ARC_BUFC_DATA) {
3239 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3240 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3241 -hdr->b_size);
3242 }
3243 hdr->b_datacnt -= 1;
3244 arc_cksum_verify(buf);
3245 arc_buf_unwatch(buf);
3246
3247 mutex_exit(hash_lock);
3248
3249 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3250 nhdr->b_size = blksz;
3251 nhdr->b_spa = spa;
3252 nhdr->b_type = type;
3253 nhdr->b_buf = buf;
3254 nhdr->b_state = arc_anon;
3255 nhdr->b_arc_access = 0;
3256 nhdr->b_flags = flags & ARC_L2_WRITING;
3257 nhdr->b_l2hdr = NULL;
3258 nhdr->b_datacnt = 1;
3259 nhdr->b_freeze_cksum = NULL;
3260 (void) refcount_add(&nhdr->b_refcnt, tag);
3261 buf->b_hdr = nhdr;
3262 mutex_exit(&buf->b_evict_lock);
3263 atomic_add_64(&arc_anon->arcs_size, blksz);
3264 } else {
3265 mutex_exit(&buf->b_evict_lock);
3266 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3267 ASSERT(!list_link_active(&hdr->b_arc_node));
3268 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3269 if (hdr->b_state != arc_anon)
3270 arc_change_state(arc_anon, hdr, hash_lock);
3271 hdr->b_arc_access = 0;
3272 if (hash_lock)
3273 mutex_exit(hash_lock);
3274
3275 buf_discard_identity(hdr);
3276 arc_buf_thaw(buf);
3277 }
3278 buf->b_efunc = NULL;
3279 buf->b_private = NULL;
3280
3281 if (l2hdr) {
3282 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3283 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3284 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3285 mutex_exit(&l2arc_buflist_mtx);
3286 }
3287 }
3288
3289 int
3290 arc_released(arc_buf_t *buf)
3291 {
3292 int released;
3293
3294 mutex_enter(&buf->b_evict_lock);
3295 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3296 mutex_exit(&buf->b_evict_lock);
3297 return (released);
3298 }
3299
3300 int
3301 arc_has_callback(arc_buf_t *buf)
3302 {
3303 int callback;
3304
3305 mutex_enter(&buf->b_evict_lock);
3306 callback = (buf->b_efunc != NULL);
3307 mutex_exit(&buf->b_evict_lock);
3308 return (callback);
3309 }
3310
3311 #ifdef ZFS_DEBUG
3312 int
3313 arc_referenced(arc_buf_t *buf)
3314 {
3315 int referenced;
3316
3317 mutex_enter(&buf->b_evict_lock);
3318 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3319 mutex_exit(&buf->b_evict_lock);
3320 return (referenced);
3321 }
3322 #endif
3323
3324 static void
3325 arc_write_ready(zio_t *zio)
3326 {
3327 arc_write_callback_t *callback = zio->io_private;
3328 arc_buf_t *buf = callback->awcb_buf;
3329 arc_buf_hdr_t *hdr = buf->b_hdr;
3330
3331 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3332 callback->awcb_ready(zio, buf, callback->awcb_private);
3333
3334 /*
3335 * If the IO is already in progress, then this is a re-write
3336 * attempt, so we need to thaw and re-compute the cksum.
3337 * It is the responsibility of the callback to handle the
3338 * accounting for any re-write attempt.
3339 */
3340 if (HDR_IO_IN_PROGRESS(hdr)) {
3341 mutex_enter(&hdr->b_freeze_lock);
3342 if (hdr->b_freeze_cksum != NULL) {
3343 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3344 hdr->b_freeze_cksum = NULL;
3345 }
3346 mutex_exit(&hdr->b_freeze_lock);
3347 }
3348 arc_cksum_compute(buf, B_FALSE);
3349 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3350 }
3351
3352 static void
3353 arc_write_done(zio_t *zio)
3354 {
3355 arc_write_callback_t *callback = zio->io_private;
3356 arc_buf_t *buf = callback->awcb_buf;
3357 arc_buf_hdr_t *hdr = buf->b_hdr;
3358
3359 ASSERT(hdr->b_acb == NULL);
3360
3361 if (zio->io_error == 0) {
3362 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3363 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3364 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3365 } else {
3366 ASSERT(BUF_EMPTY(hdr));
3367 }
3368
3369 /*
3370 * If the block to be written was all-zero, we may have
3371 * compressed it away. In this case no write was performed
3372 * so there will be no dva/birth/checksum. The buffer must
3373 * therefore remain anonymous (and uncached).
3374 */
3375 if (!BUF_EMPTY(hdr)) {
3376 arc_buf_hdr_t *exists;
3377 kmutex_t *hash_lock;
3378
3379 ASSERT(zio->io_error == 0);
3380
3381 arc_cksum_verify(buf);
3382
3383 exists = buf_hash_insert(hdr, &hash_lock);
3384 if (exists) {
3385 /*
3386 * This can only happen if we overwrite for
3387 * sync-to-convergence, because we remove
3388 * buffers from the hash table when we arc_free().
3389 */
3390 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3391 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3392 panic("bad overwrite, hdr=%p exists=%p",
3393 (void *)hdr, (void *)exists);
3394 ASSERT(refcount_is_zero(&exists->b_refcnt));
3395 arc_change_state(arc_anon, exists, hash_lock);
3396 mutex_exit(hash_lock);
3397 arc_hdr_destroy(exists);
3398 exists = buf_hash_insert(hdr, &hash_lock);
3399 ASSERT3P(exists, ==, NULL);
3400 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3401 /* nopwrite */
3402 ASSERT(zio->io_prop.zp_nopwrite);
3403 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3404 panic("bad nopwrite, hdr=%p exists=%p",
3405 (void *)hdr, (void *)exists);
3406 } else {
3407 /* Dedup */
3408 ASSERT(hdr->b_datacnt == 1);
3409 ASSERT(hdr->b_state == arc_anon);
3410 ASSERT(BP_GET_DEDUP(zio->io_bp));
3411 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3412 }
3413 }
3414 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3415 /* if it's not anon, we are doing a scrub */
3416 if (!exists && hdr->b_state == arc_anon)
3417 arc_access(hdr, hash_lock);
3418 mutex_exit(hash_lock);
3419 } else {
3420 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3421 }
3422
3423 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3424 callback->awcb_done(zio, buf, callback->awcb_private);
3425
3426 kmem_free(callback, sizeof (arc_write_callback_t));
3427 }
3428
3429 zio_t *
3430 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3431 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
3432 arc_done_func_t *ready, arc_done_func_t *done, void *private,
3433 int priority, int zio_flags, const zbookmark_t *zb)
3434 {
3435 arc_buf_hdr_t *hdr = buf->b_hdr;
3436 arc_write_callback_t *callback;
3437 zio_t *zio;
3438
3439 ASSERT(ready != NULL);
3440 ASSERT(done != NULL);
3441 ASSERT(!HDR_IO_ERROR(hdr));
3442 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3443 ASSERT(hdr->b_acb == NULL);
3444 if (l2arc)
3445 hdr->b_flags |= ARC_L2CACHE;
3446 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3447 callback->awcb_ready = ready;
3448 callback->awcb_done = done;
3449 callback->awcb_private = private;
3450 callback->awcb_buf = buf;
3451
3452 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3453 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3454
3455 return (zio);
3456 }
3457
3458 static int
3459 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3460 {
3461 #ifdef _KERNEL
3462 uint64_t available_memory = ptob(freemem);
3463 static uint64_t page_load = 0;
3464 static uint64_t last_txg = 0;
3465
3466 #if defined(__i386)
3467 available_memory =
3468 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3469 #endif
3470 if (available_memory >= zfs_write_limit_max)
3471 return (0);
3472
3473 if (txg > last_txg) {
3474 last_txg = txg;
3475 page_load = 0;
3476 }
3477 /*
3478 * If we are in pageout, we know that memory is already tight,
3479 * the arc is already going to be evicting, so we just want to
3480 * continue to let page writes occur as quickly as possible.
3481 */
3482 if (curproc == proc_pageout) {
3483 if (page_load > MAX(ptob(minfree), available_memory) / 4)
3484 return (SET_ERROR(ERESTART));
3485 /* Note: reserve is inflated, so we deflate */
3486 page_load += reserve / 8;
3487 return (0);
3488 } else if (page_load > 0 && arc_reclaim_needed()) {
3489 /* memory is low, delay before restarting */
3490 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3491 return (SET_ERROR(EAGAIN));
3492 }
3493 page_load = 0;
3494
3495 if (arc_size > arc_c_min) {
3496 uint64_t evictable_memory =
3497 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3498 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3499 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3500 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3501 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3502 }
3503
3504 if (inflight_data > available_memory / 4) {
3505 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3506 return (SET_ERROR(ERESTART));
3507 }
3508 #endif
3509 return (0);
3510 }
3511
3512 void
3513 arc_tempreserve_clear(uint64_t reserve)
3514 {
3515 atomic_add_64(&arc_tempreserve, -reserve);
3516 ASSERT((int64_t)arc_tempreserve >= 0);
3517 }
3518
3519 int
3520 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3521 {
3522 int error;
3523 uint64_t anon_size;
3524
3525 #ifdef ZFS_DEBUG
3526 /*
3527 * Once in a while, fail for no reason. Everything should cope.
3528 */
3529 if (spa_get_random(10000) == 0) {
3530 dprintf("forcing random failure\n");
3531 return (SET_ERROR(ERESTART));
3532 }
3533 #endif
3534 if (reserve > arc_c/4 && !arc_no_grow)
3535 arc_c = MIN(arc_c_max, reserve * 4);
3536 if (reserve > arc_c)
3537 return (SET_ERROR(ENOMEM));
3538
3539 /*
3540 * Don't count loaned bufs as in flight dirty data to prevent long
3541 * network delays from blocking transactions that are ready to be
3542 * assigned to a txg.
3543 */
3544 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3545
3546 /*
3547 * Writes will, almost always, require additional memory allocations
3548 * in order to compress/encrypt/etc the data. We therefor need to
3549 * make sure that there is sufficient available memory for this.
3550 */
3551 if (error = arc_memory_throttle(reserve, anon_size, txg))
3552 return (error);
3553
3554 /*
3555 * Throttle writes when the amount of dirty data in the cache
3556 * gets too large. We try to keep the cache less than half full
3557 * of dirty blocks so that our sync times don't grow too large.
3558 * Note: if two requests come in concurrently, we might let them
3559 * both succeed, when one of them should fail. Not a huge deal.
3560 */
3561
3562 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3563 anon_size > arc_c / 4) {
3564 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3565 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3566 arc_tempreserve>>10,
3567 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3568 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3569 reserve>>10, arc_c>>10);
3570 return (SET_ERROR(ERESTART));
3571 }
3572 atomic_add_64(&arc_tempreserve, reserve);
3573 return (0);
3574 }
3575
3576 void
3577 arc_init(void)
3578 {
3579 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3580 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3581
3582 /* Convert seconds to clock ticks */
3583 arc_min_prefetch_lifespan = 1 * hz;
3584
3585 /* Start out with 1/8 of all memory */
3586 arc_c = physmem * PAGESIZE / 8;
3587
3588 #ifdef _KERNEL
3589 /*
3590 * On architectures where the physical memory can be larger
3591 * than the addressable space (intel in 32-bit mode), we may
3592 * need to limit the cache to 1/8 of VM size.
3593 */
3594 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3595 #endif
3596
3597 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3598 arc_c_min = MAX(arc_c / 4, 64<<20);
3599 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3600 if (arc_c * 8 >= 1<<30)
3601 arc_c_max = (arc_c * 8) - (1<<30);
3602 else
3603 arc_c_max = arc_c_min;
3604 arc_c_max = MAX(arc_c * 6, arc_c_max);
3605
3606 /*
3607 * Allow the tunables to override our calculations if they are
3608 * reasonable (ie. over 64MB)
3609 */
3610 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
3611 arc_c_max = zfs_arc_max;
3612 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
3613 arc_c_min = zfs_arc_min;
3614
3615 arc_c = arc_c_max;
3616 arc_p = (arc_c >> 1);
3617
3618 /* limit meta-data to 1/4 of the arc capacity */
3619 arc_meta_limit = arc_c_max / 4;
3620
3621 /* Allow the tunable to override if it is reasonable */
3622 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3623 arc_meta_limit = zfs_arc_meta_limit;
3624
3625 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3626 arc_c_min = arc_meta_limit / 2;
3627
3628 if (zfs_arc_grow_retry > 0)
3629 arc_grow_retry = zfs_arc_grow_retry;
3630
3631 if (zfs_arc_shrink_shift > 0)
3632 arc_shrink_shift = zfs_arc_shrink_shift;
3633
3634 if (zfs_arc_p_min_shift > 0)
3635 arc_p_min_shift = zfs_arc_p_min_shift;
3636
3637 /* if kmem_flags are set, lets try to use less memory */
3638 if (kmem_debugging())
3639 arc_c = arc_c / 2;
3640 if (arc_c < arc_c_min)
3641 arc_c = arc_c_min;
3642
3643 arc_anon = &ARC_anon;
3644 arc_mru = &ARC_mru;
3645 arc_mru_ghost = &ARC_mru_ghost;
3646 arc_mfu = &ARC_mfu;
3647 arc_mfu_ghost = &ARC_mfu_ghost;
3648 arc_l2c_only = &ARC_l2c_only;
3649 arc_size = 0;
3650
3651 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3652 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3653 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3654 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3655 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3656 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3657
3658 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
3659 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3660 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
3661 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3662 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
3663 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3664 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
3665 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3666 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
3667 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3668 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
3669 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3670 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
3671 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3672 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
3673 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3674 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
3675 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3676 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
3677 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3678
3679 buf_init();
3680
3681 arc_thread_exit = 0;
3682 arc_eviction_list = NULL;
3683 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3684 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3685
3686 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3687 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3688
3689 if (arc_ksp != NULL) {
3690 arc_ksp->ks_data = &arc_stats;
3691 kstat_install(arc_ksp);
3692 }
3693
3694 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3695 TS_RUN, minclsyspri);
3696
3697 arc_dead = FALSE;
3698 arc_warm = B_FALSE;
3699
3700 if (zfs_write_limit_max == 0)
3701 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3702 else
3703 zfs_write_limit_shift = 0;
3704 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3705 }
3706
3707 void
3708 arc_fini(void)
3709 {
3710 mutex_enter(&arc_reclaim_thr_lock);
3711 arc_thread_exit = 1;
3712 while (arc_thread_exit != 0)
3713 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3714 mutex_exit(&arc_reclaim_thr_lock);
3715
3716 arc_flush(NULL);
3717
3718 arc_dead = TRUE;
3719
3720 if (arc_ksp != NULL) {
3721 kstat_delete(arc_ksp);
3722 arc_ksp = NULL;
3723 }
3724
3725 mutex_destroy(&arc_eviction_mtx);
3726 mutex_destroy(&arc_reclaim_thr_lock);
3727 cv_destroy(&arc_reclaim_thr_cv);
3728
3729 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
3730 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
3731 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
3732 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
3733 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
3734 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
3735 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
3736 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
3737
3738 mutex_destroy(&arc_anon->arcs_mtx);
3739 mutex_destroy(&arc_mru->arcs_mtx);
3740 mutex_destroy(&arc_mru_ghost->arcs_mtx);
3741 mutex_destroy(&arc_mfu->arcs_mtx);
3742 mutex_destroy(&arc_mfu_ghost->arcs_mtx);
3743 mutex_destroy(&arc_l2c_only->arcs_mtx);
3744
3745 mutex_destroy(&zfs_write_limit_lock);
3746
3747 buf_fini();
3748
3749 ASSERT(arc_loaned_bytes == 0);
3750 }
3751
3752 /*
3753 * Level 2 ARC
3754 *
3755 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3756 * It uses dedicated storage devices to hold cached data, which are populated
3757 * using large infrequent writes. The main role of this cache is to boost
3758 * the performance of random read workloads. The intended L2ARC devices
3759 * include short-stroked disks, solid state disks, and other media with
3760 * substantially faster read latency than disk.
3761 *
3762 * +-----------------------+
3763 * | ARC |
3764 * +-----------------------+
3765 * | ^ ^
3766 * | | |
3767 * l2arc_feed_thread() arc_read()
3768 * | | |
3769 * | l2arc read |
3770 * V | |
3771 * +---------------+ |
3772 * | L2ARC | |
3773 * +---------------+ |
3774 * | ^ |
3775 * l2arc_write() | |
3776 * | | |
3777 * V | |
3778 * +-------+ +-------+
3779 * | vdev | | vdev |
3780 * | cache | | cache |
3781 * +-------+ +-------+
3782 * +=========+ .-----.
3783 * : L2ARC : |-_____-|
3784 * : devices : | Disks |
3785 * +=========+ `-_____-'
3786 *
3787 * Read requests are satisfied from the following sources, in order:
3788 *
3789 * 1) ARC
3790 * 2) vdev cache of L2ARC devices
3791 * 3) L2ARC devices
3792 * 4) vdev cache of disks
3793 * 5) disks
3794 *
3795 * Some L2ARC device types exhibit extremely slow write performance.
3796 * To accommodate for this there are some significant differences between
3797 * the L2ARC and traditional cache design:
3798 *
3799 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3800 * the ARC behave as usual, freeing buffers and placing headers on ghost
3801 * lists. The ARC does not send buffers to the L2ARC during eviction as
3802 * this would add inflated write latencies for all ARC memory pressure.
3803 *
3804 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3805 * It does this by periodically scanning buffers from the eviction-end of
3806 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3807 * not already there. It scans until a headroom of buffers is satisfied,
3808 * which itself is a buffer for ARC eviction. The thread that does this is
3809 * l2arc_feed_thread(), illustrated below; example sizes are included to
3810 * provide a better sense of ratio than this diagram:
3811 *
3812 * head --> tail
3813 * +---------------------+----------+
3814 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3815 * +---------------------+----------+ | o L2ARC eligible
3816 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3817 * +---------------------+----------+ |
3818 * 15.9 Gbytes ^ 32 Mbytes |
3819 * headroom |
3820 * l2arc_feed_thread()
3821 * |
3822 * l2arc write hand <--[oooo]--'
3823 * | 8 Mbyte
3824 * | write max
3825 * V
3826 * +==============================+
3827 * L2ARC dev |####|#|###|###| |####| ... |
3828 * +==============================+
3829 * 32 Gbytes
3830 *
3831 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3832 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3833 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3834 * safe to say that this is an uncommon case, since buffers at the end of
3835 * the ARC lists have moved there due to inactivity.
3836 *
3837 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3838 * then the L2ARC simply misses copying some buffers. This serves as a
3839 * pressure valve to prevent heavy read workloads from both stalling the ARC
3840 * with waits and clogging the L2ARC with writes. This also helps prevent
3841 * the potential for the L2ARC to churn if it attempts to cache content too
3842 * quickly, such as during backups of the entire pool.
3843 *
3844 * 5. After system boot and before the ARC has filled main memory, there are
3845 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3846 * lists can remain mostly static. Instead of searching from tail of these
3847 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3848 * for eligible buffers, greatly increasing its chance of finding them.
3849 *
3850 * The L2ARC device write speed is also boosted during this time so that
3851 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
3852 * there are no L2ARC reads, and no fear of degrading read performance
3853 * through increased writes.
3854 *
3855 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
3856 * the vdev queue can aggregate them into larger and fewer writes. Each
3857 * device is written to in a rotor fashion, sweeping writes through
3858 * available space then repeating.
3859 *
3860 * 7. The L2ARC does not store dirty content. It never needs to flush
3861 * write buffers back to disk based storage.
3862 *
3863 * 8. If an ARC buffer is written (and dirtied) which also exists in the
3864 * L2ARC, the now stale L2ARC buffer is immediately dropped.
3865 *
3866 * The performance of the L2ARC can be tweaked by a number of tunables, which
3867 * may be necessary for different workloads:
3868 *
3869 * l2arc_write_max max write bytes per interval
3870 * l2arc_write_boost extra write bytes during device warmup
3871 * l2arc_noprefetch skip caching prefetched buffers
3872 * l2arc_headroom number of max device writes to precache
3873 * l2arc_feed_secs seconds between L2ARC writing
3874 *
3875 * Tunables may be removed or added as future performance improvements are
3876 * integrated, and also may become zpool properties.
3877 *
3878 * There are three key functions that control how the L2ARC warms up:
3879 *
3880 * l2arc_write_eligible() check if a buffer is eligible to cache
3881 * l2arc_write_size() calculate how much to write
3882 * l2arc_write_interval() calculate sleep delay between writes
3883 *
3884 * These three functions determine what to write, how much, and how quickly
3885 * to send writes.
3886 */
3887
3888 static boolean_t
3889 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
3890 {
3891 /*
3892 * A buffer is *not* eligible for the L2ARC if it:
3893 * 1. belongs to a different spa.
3894 * 2. is already cached on the L2ARC.
3895 * 3. has an I/O in progress (it may be an incomplete read).
3896 * 4. is flagged not eligible (zfs property).
3897 */
3898 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
3899 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
3900 return (B_FALSE);
3901
3902 return (B_TRUE);
3903 }
3904
3905 static uint64_t
3906 l2arc_write_size(l2arc_dev_t *dev)
3907 {
3908 uint64_t size;
3909
3910 size = dev->l2ad_write;
3911
3912 if (arc_warm == B_FALSE)
3913 size += dev->l2ad_boost;
3914
3915 return (size);
3916
3917 }
3918
3919 static clock_t
3920 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
3921 {
3922 clock_t interval, next, now;
3923
3924 /*
3925 * If the ARC lists are busy, increase our write rate; if the
3926 * lists are stale, idle back. This is achieved by checking
3927 * how much we previously wrote - if it was more than half of
3928 * what we wanted, schedule the next write much sooner.
3929 */
3930 if (l2arc_feed_again && wrote > (wanted / 2))
3931 interval = (hz * l2arc_feed_min_ms) / 1000;
3932 else
3933 interval = hz * l2arc_feed_secs;
3934
3935 now = ddi_get_lbolt();
3936 next = MAX(now, MIN(now + interval, began + interval));
3937
3938 return (next);
3939 }
3940
3941 static void
3942 l2arc_hdr_stat_add(void)
3943 {
3944 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
3945 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
3946 }
3947
3948 static void
3949 l2arc_hdr_stat_remove(void)
3950 {
3951 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
3952 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
3953 }
3954
3955 /*
3956 * Cycle through L2ARC devices. This is how L2ARC load balances.
3957 * If a device is returned, this also returns holding the spa config lock.
3958 */
3959 static l2arc_dev_t *
3960 l2arc_dev_get_next(void)
3961 {
3962 l2arc_dev_t *first, *next = NULL;
3963
3964 /*
3965 * Lock out the removal of spas (spa_namespace_lock), then removal
3966 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
3967 * both locks will be dropped and a spa config lock held instead.
3968 */
3969 mutex_enter(&spa_namespace_lock);
3970 mutex_enter(&l2arc_dev_mtx);
3971
3972 /* if there are no vdevs, there is nothing to do */
3973 if (l2arc_ndev == 0)
3974 goto out;
3975
3976 first = NULL;
3977 next = l2arc_dev_last;
3978 do {
3979 /* loop around the list looking for a non-faulted vdev */
3980 if (next == NULL) {
3981 next = list_head(l2arc_dev_list);
3982 } else {
3983 next = list_next(l2arc_dev_list, next);
3984 if (next == NULL)
3985 next = list_head(l2arc_dev_list);
3986 }
3987
3988 /* if we have come back to the start, bail out */
3989 if (first == NULL)
3990 first = next;
3991 else if (next == first)
3992 break;
3993
3994 } while (vdev_is_dead(next->l2ad_vdev));
3995
3996 /* if we were unable to find any usable vdevs, return NULL */
3997 if (vdev_is_dead(next->l2ad_vdev))
3998 next = NULL;
3999
4000 l2arc_dev_last = next;
4001
4002 out:
4003 mutex_exit(&l2arc_dev_mtx);
4004
4005 /*
4006 * Grab the config lock to prevent the 'next' device from being
4007 * removed while we are writing to it.
4008 */
4009 if (next != NULL)
4010 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4011 mutex_exit(&spa_namespace_lock);
4012
4013 return (next);
4014 }
4015
4016 /*
4017 * Free buffers that were tagged for destruction.
4018 */
4019 static void
4020 l2arc_do_free_on_write()
4021 {
4022 list_t *buflist;
4023 l2arc_data_free_t *df, *df_prev;
4024
4025 mutex_enter(&l2arc_free_on_write_mtx);
4026 buflist = l2arc_free_on_write;
4027
4028 for (df = list_tail(buflist); df; df = df_prev) {
4029 df_prev = list_prev(buflist, df);
4030 ASSERT(df->l2df_data != NULL);
4031 ASSERT(df->l2df_func != NULL);
4032 df->l2df_func(df->l2df_data, df->l2df_size);
4033 list_remove(buflist, df);
4034 kmem_free(df, sizeof (l2arc_data_free_t));
4035 }
4036
4037 mutex_exit(&l2arc_free_on_write_mtx);
4038 }
4039
4040 /*
4041 * A write to a cache device has completed. Update all headers to allow
4042 * reads from these buffers to begin.
4043 */
4044 static void
4045 l2arc_write_done(zio_t *zio)
4046 {
4047 l2arc_write_callback_t *cb;
4048 l2arc_dev_t *dev;
4049 list_t *buflist;
4050 arc_buf_hdr_t *head, *ab, *ab_prev;
4051 l2arc_buf_hdr_t *abl2;
4052 kmutex_t *hash_lock;
4053
4054 cb = zio->io_private;
4055 ASSERT(cb != NULL);
4056 dev = cb->l2wcb_dev;
4057 ASSERT(dev != NULL);
4058 head = cb->l2wcb_head;
4059 ASSERT(head != NULL);
4060 buflist = dev->l2ad_buflist;
4061 ASSERT(buflist != NULL);
4062 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4063 l2arc_write_callback_t *, cb);
4064
4065 if (zio->io_error != 0)
4066 ARCSTAT_BUMP(arcstat_l2_writes_error);
4067
4068 mutex_enter(&l2arc_buflist_mtx);
4069
4070 /*
4071 * All writes completed, or an error was hit.
4072 */
4073 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4074 ab_prev = list_prev(buflist, ab);
4075
4076 hash_lock = HDR_LOCK(ab);
4077 if (!mutex_tryenter(hash_lock)) {
4078 /*
4079 * This buffer misses out. It may be in a stage
4080 * of eviction. Its ARC_L2_WRITING flag will be
4081 * left set, denying reads to this buffer.
4082 */
4083 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4084 continue;
4085 }
4086
4087 if (zio->io_error != 0) {
4088 /*
4089 * Error - drop L2ARC entry.
4090 */
4091 list_remove(buflist, ab);
4092 abl2 = ab->b_l2hdr;
4093 ab->b_l2hdr = NULL;
4094 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4095 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4096 }
4097
4098 /*
4099 * Allow ARC to begin reads to this L2ARC entry.
4100 */
4101 ab->b_flags &= ~ARC_L2_WRITING;
4102
4103 mutex_exit(hash_lock);
4104 }
4105
4106 atomic_inc_64(&l2arc_writes_done);
4107 list_remove(buflist, head);
4108 kmem_cache_free(hdr_cache, head);
4109 mutex_exit(&l2arc_buflist_mtx);
4110
4111 l2arc_do_free_on_write();
4112
4113 kmem_free(cb, sizeof (l2arc_write_callback_t));
4114 }
4115
4116 /*
4117 * A read to a cache device completed. Validate buffer contents before
4118 * handing over to the regular ARC routines.
4119 */
4120 static void
4121 l2arc_read_done(zio_t *zio)
4122 {
4123 l2arc_read_callback_t *cb;
4124 arc_buf_hdr_t *hdr;
4125 arc_buf_t *buf;
4126 kmutex_t *hash_lock;
4127 int equal;
4128
4129 ASSERT(zio->io_vd != NULL);
4130 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4131
4132 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4133
4134 cb = zio->io_private;
4135 ASSERT(cb != NULL);
4136 buf = cb->l2rcb_buf;
4137 ASSERT(buf != NULL);
4138
4139 hash_lock = HDR_LOCK(buf->b_hdr);
4140 mutex_enter(hash_lock);
4141 hdr = buf->b_hdr;
4142 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4143
4144 /*
4145 * Check this survived the L2ARC journey.
4146 */
4147 equal = arc_cksum_equal(buf);
4148 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4149 mutex_exit(hash_lock);
4150 zio->io_private = buf;
4151 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4152 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4153 arc_read_done(zio);
4154 } else {
4155 mutex_exit(hash_lock);
4156 /*
4157 * Buffer didn't survive caching. Increment stats and
4158 * reissue to the original storage device.
4159 */
4160 if (zio->io_error != 0) {
4161 ARCSTAT_BUMP(arcstat_l2_io_error);
4162 } else {
4163 zio->io_error = SET_ERROR(EIO);
4164 }
4165 if (!equal)
4166 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4167
4168 /*
4169 * If there's no waiter, issue an async i/o to the primary
4170 * storage now. If there *is* a waiter, the caller must
4171 * issue the i/o in a context where it's OK to block.
4172 */
4173 if (zio->io_waiter == NULL) {
4174 zio_t *pio = zio_unique_parent(zio);
4175
4176 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4177
4178 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4179 buf->b_data, zio->io_size, arc_read_done, buf,
4180 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4181 }
4182 }
4183
4184 kmem_free(cb, sizeof (l2arc_read_callback_t));
4185 }
4186
4187 /*
4188 * This is the list priority from which the L2ARC will search for pages to
4189 * cache. This is used within loops (0..3) to cycle through lists in the
4190 * desired order. This order can have a significant effect on cache
4191 * performance.
4192 *
4193 * Currently the metadata lists are hit first, MFU then MRU, followed by
4194 * the data lists. This function returns a locked list, and also returns
4195 * the lock pointer.
4196 */
4197 static list_t *
4198 l2arc_list_locked(int list_num, kmutex_t **lock)
4199 {
4200 list_t *list = NULL;
4201
4202 ASSERT(list_num >= 0 && list_num <= 3);
4203
4204 switch (list_num) {
4205 case 0:
4206 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
4207 *lock = &arc_mfu->arcs_mtx;
4208 break;
4209 case 1:
4210 list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
4211 *lock = &arc_mru->arcs_mtx;
4212 break;
4213 case 2:
4214 list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
4215 *lock = &arc_mfu->arcs_mtx;
4216 break;
4217 case 3:
4218 list = &arc_mru->arcs_list[ARC_BUFC_DATA];
4219 *lock = &arc_mru->arcs_mtx;
4220 break;
4221 }
4222
4223 ASSERT(!(MUTEX_HELD(*lock)));
4224 mutex_enter(*lock);
4225 return (list);
4226 }
4227
4228 /*
4229 * Evict buffers from the device write hand to the distance specified in
4230 * bytes. This distance may span populated buffers, it may span nothing.
4231 * This is clearing a region on the L2ARC device ready for writing.
4232 * If the 'all' boolean is set, every buffer is evicted.
4233 */
4234 static void
4235 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4236 {
4237 list_t *buflist;
4238 l2arc_buf_hdr_t *abl2;
4239 arc_buf_hdr_t *ab, *ab_prev;
4240 kmutex_t *hash_lock;
4241 uint64_t taddr;
4242
4243 buflist = dev->l2ad_buflist;
4244
4245 if (buflist == NULL)
4246 return;
4247
4248 if (!all && dev->l2ad_first) {
4249 /*
4250 * This is the first sweep through the device. There is
4251 * nothing to evict.
4252 */
4253 return;
4254 }
4255
4256 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4257 /*
4258 * When nearing the end of the device, evict to the end
4259 * before the device write hand jumps to the start.
4260 */
4261 taddr = dev->l2ad_end;
4262 } else {
4263 taddr = dev->l2ad_hand + distance;
4264 }
4265 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4266 uint64_t, taddr, boolean_t, all);
4267
4268 top:
4269 mutex_enter(&l2arc_buflist_mtx);
4270 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4271 ab_prev = list_prev(buflist, ab);
4272
4273 hash_lock = HDR_LOCK(ab);
4274 if (!mutex_tryenter(hash_lock)) {
4275 /*
4276 * Missed the hash lock. Retry.
4277 */
4278 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4279 mutex_exit(&l2arc_buflist_mtx);
4280 mutex_enter(hash_lock);
4281 mutex_exit(hash_lock);
4282 goto top;
4283 }
4284
4285 if (HDR_L2_WRITE_HEAD(ab)) {
4286 /*
4287 * We hit a write head node. Leave it for
4288 * l2arc_write_done().
4289 */
4290 list_remove(buflist, ab);
4291 mutex_exit(hash_lock);
4292 continue;
4293 }
4294
4295 if (!all && ab->b_l2hdr != NULL &&
4296 (ab->b_l2hdr->b_daddr > taddr ||
4297 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4298 /*
4299 * We've evicted to the target address,
4300 * or the end of the device.
4301 */
4302 mutex_exit(hash_lock);
4303 break;
4304 }
4305
4306 if (HDR_FREE_IN_PROGRESS(ab)) {
4307 /*
4308 * Already on the path to destruction.
4309 */
4310 mutex_exit(hash_lock);
4311 continue;
4312 }
4313
4314 if (ab->b_state == arc_l2c_only) {
4315 ASSERT(!HDR_L2_READING(ab));
4316 /*
4317 * This doesn't exist in the ARC. Destroy.
4318 * arc_hdr_destroy() will call list_remove()
4319 * and decrement arcstat_l2_size.
4320 */
4321 arc_change_state(arc_anon, ab, hash_lock);
4322 arc_hdr_destroy(ab);
4323 } else {
4324 /*
4325 * Invalidate issued or about to be issued
4326 * reads, since we may be about to write
4327 * over this location.
4328 */
4329 if (HDR_L2_READING(ab)) {
4330 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4331 ab->b_flags |= ARC_L2_EVICTED;
4332 }
4333
4334 /*
4335 * Tell ARC this no longer exists in L2ARC.
4336 */
4337 if (ab->b_l2hdr != NULL) {
4338 abl2 = ab->b_l2hdr;
4339 ab->b_l2hdr = NULL;
4340 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4341 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4342 }
4343 list_remove(buflist, ab);
4344
4345 /*
4346 * This may have been leftover after a
4347 * failed write.
4348 */
4349 ab->b_flags &= ~ARC_L2_WRITING;
4350 }
4351 mutex_exit(hash_lock);
4352 }
4353 mutex_exit(&l2arc_buflist_mtx);
4354
4355 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
4356 dev->l2ad_evict = taddr;
4357 }
4358
4359 /*
4360 * Find and write ARC buffers to the L2ARC device.
4361 *
4362 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4363 * for reading until they have completed writing.
4364 */
4365 static uint64_t
4366 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4367 {
4368 arc_buf_hdr_t *ab, *ab_prev, *head;
4369 l2arc_buf_hdr_t *hdrl2;
4370 list_t *list;
4371 uint64_t passed_sz, write_sz, buf_sz, headroom;
4372 void *buf_data;
4373 kmutex_t *hash_lock, *list_lock;
4374 boolean_t have_lock, full;
4375 l2arc_write_callback_t *cb;
4376 zio_t *pio, *wzio;
4377 uint64_t guid = spa_load_guid(spa);
4378
4379 ASSERT(dev->l2ad_vdev != NULL);
4380
4381 pio = NULL;
4382 write_sz = 0;
4383 full = B_FALSE;
4384 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4385 head->b_flags |= ARC_L2_WRITE_HEAD;
4386
4387 /*
4388 * Copy buffers for L2ARC writing.
4389 */
4390 mutex_enter(&l2arc_buflist_mtx);
4391 for (int try = 0; try <= 3; try++) {
4392 list = l2arc_list_locked(try, &list_lock);
4393 passed_sz = 0;
4394
4395 /*
4396 * L2ARC fast warmup.
4397 *
4398 * Until the ARC is warm and starts to evict, read from the
4399 * head of the ARC lists rather than the tail.
4400 */
4401 headroom = target_sz * l2arc_headroom;
4402 if (arc_warm == B_FALSE)
4403 ab = list_head(list);
4404 else
4405 ab = list_tail(list);
4406
4407 for (; ab; ab = ab_prev) {
4408 if (arc_warm == B_FALSE)
4409 ab_prev = list_next(list, ab);
4410 else
4411 ab_prev = list_prev(list, ab);
4412
4413 hash_lock = HDR_LOCK(ab);
4414 have_lock = MUTEX_HELD(hash_lock);
4415 if (!have_lock && !mutex_tryenter(hash_lock)) {
4416 /*
4417 * Skip this buffer rather than waiting.
4418 */
4419 continue;
4420 }
4421
4422 passed_sz += ab->b_size;
4423 if (passed_sz > headroom) {
4424 /*
4425 * Searched too far.
4426 */
4427 mutex_exit(hash_lock);
4428 break;
4429 }
4430
4431 if (!l2arc_write_eligible(guid, ab)) {
4432 mutex_exit(hash_lock);
4433 continue;
4434 }
4435
4436 if ((write_sz + ab->b_size) > target_sz) {
4437 full = B_TRUE;
4438 mutex_exit(hash_lock);
4439 break;
4440 }
4441
4442 if (pio == NULL) {
4443 /*
4444 * Insert a dummy header on the buflist so
4445 * l2arc_write_done() can find where the
4446 * write buffers begin without searching.
4447 */
4448 list_insert_head(dev->l2ad_buflist, head);
4449
4450 cb = kmem_alloc(
4451 sizeof (l2arc_write_callback_t), KM_SLEEP);
4452 cb->l2wcb_dev = dev;
4453 cb->l2wcb_head = head;
4454 pio = zio_root(spa, l2arc_write_done, cb,
4455 ZIO_FLAG_CANFAIL);
4456 }
4457
4458 /*
4459 * Create and add a new L2ARC header.
4460 */
4461 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4462 hdrl2->b_dev = dev;
4463 hdrl2->b_daddr = dev->l2ad_hand;
4464
4465 ab->b_flags |= ARC_L2_WRITING;
4466 ab->b_l2hdr = hdrl2;
4467 list_insert_head(dev->l2ad_buflist, ab);
4468 buf_data = ab->b_buf->b_data;
4469 buf_sz = ab->b_size;
4470
4471 /*
4472 * Compute and store the buffer cksum before
4473 * writing. On debug the cksum is verified first.
4474 */
4475 arc_cksum_verify(ab->b_buf);
4476 arc_cksum_compute(ab->b_buf, B_TRUE);
4477
4478 mutex_exit(hash_lock);
4479
4480 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4481 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4482 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4483 ZIO_FLAG_CANFAIL, B_FALSE);
4484
4485 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4486 zio_t *, wzio);
4487 (void) zio_nowait(wzio);
4488
4489 /*
4490 * Keep the clock hand suitably device-aligned.
4491 */
4492 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4493
4494 write_sz += buf_sz;
4495 dev->l2ad_hand += buf_sz;
4496 }
4497
4498 mutex_exit(list_lock);
4499
4500 if (full == B_TRUE)
4501 break;
4502 }
4503 mutex_exit(&l2arc_buflist_mtx);
4504
4505 if (pio == NULL) {
4506 ASSERT0(write_sz);
4507 kmem_cache_free(hdr_cache, head);
4508 return (0);
4509 }
4510
4511 ASSERT3U(write_sz, <=, target_sz);
4512 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4513 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4514 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4515 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
4516
4517 /*
4518 * Bump device hand to the device start if it is approaching the end.
4519 * l2arc_evict() will already have evicted ahead for this case.
4520 */
4521 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4522 vdev_space_update(dev->l2ad_vdev,
4523 dev->l2ad_end - dev->l2ad_hand, 0, 0);
4524 dev->l2ad_hand = dev->l2ad_start;
4525 dev->l2ad_evict = dev->l2ad_start;
4526 dev->l2ad_first = B_FALSE;
4527 }
4528
4529 dev->l2ad_writing = B_TRUE;
4530 (void) zio_wait(pio);
4531 dev->l2ad_writing = B_FALSE;
4532
4533 return (write_sz);
4534 }
4535
4536 /*
4537 * This thread feeds the L2ARC at regular intervals. This is the beating
4538 * heart of the L2ARC.
4539 */
4540 static void
4541 l2arc_feed_thread(void)
4542 {
4543 callb_cpr_t cpr;
4544 l2arc_dev_t *dev;
4545 spa_t *spa;
4546 uint64_t size, wrote;
4547 clock_t begin, next = ddi_get_lbolt();
4548
4549 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4550
4551 mutex_enter(&l2arc_feed_thr_lock);
4552
4553 while (l2arc_thread_exit == 0) {
4554 CALLB_CPR_SAFE_BEGIN(&cpr);
4555 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4556 next);
4557 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4558 next = ddi_get_lbolt() + hz;
4559
4560 /*
4561 * Quick check for L2ARC devices.
4562 */
4563 mutex_enter(&l2arc_dev_mtx);
4564 if (l2arc_ndev == 0) {
4565 mutex_exit(&l2arc_dev_mtx);
4566 continue;
4567 }
4568 mutex_exit(&l2arc_dev_mtx);
4569 begin = ddi_get_lbolt();
4570
4571 /*
4572 * This selects the next l2arc device to write to, and in
4573 * doing so the next spa to feed from: dev->l2ad_spa. This
4574 * will return NULL if there are now no l2arc devices or if
4575 * they are all faulted.
4576 *
4577 * If a device is returned, its spa's config lock is also
4578 * held to prevent device removal. l2arc_dev_get_next()
4579 * will grab and release l2arc_dev_mtx.
4580 */
4581 if ((dev = l2arc_dev_get_next()) == NULL)
4582 continue;
4583
4584 spa = dev->l2ad_spa;
4585 ASSERT(spa != NULL);
4586
4587 /*
4588 * If the pool is read-only then force the feed thread to
4589 * sleep a little longer.
4590 */
4591 if (!spa_writeable(spa)) {
4592 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
4593 spa_config_exit(spa, SCL_L2ARC, dev);
4594 continue;
4595 }
4596
4597 /*
4598 * Avoid contributing to memory pressure.
4599 */
4600 if (arc_reclaim_needed()) {
4601 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4602 spa_config_exit(spa, SCL_L2ARC, dev);
4603 continue;
4604 }
4605
4606 ARCSTAT_BUMP(arcstat_l2_feeds);
4607
4608 size = l2arc_write_size(dev);
4609
4610 /*
4611 * Evict L2ARC buffers that will be overwritten.
4612 */
4613 l2arc_evict(dev, size, B_FALSE);
4614
4615 /*
4616 * Write ARC buffers.
4617 */
4618 wrote = l2arc_write_buffers(spa, dev, size);
4619
4620 /*
4621 * Calculate interval between writes.
4622 */
4623 next = l2arc_write_interval(begin, size, wrote);
4624 spa_config_exit(spa, SCL_L2ARC, dev);
4625 }
4626
4627 l2arc_thread_exit = 0;
4628 cv_broadcast(&l2arc_feed_thr_cv);
4629 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4630 thread_exit();
4631 }
4632
4633 boolean_t
4634 l2arc_vdev_present(vdev_t *vd)
4635 {
4636 l2arc_dev_t *dev;
4637
4638 mutex_enter(&l2arc_dev_mtx);
4639 for (dev = list_head(l2arc_dev_list); dev != NULL;
4640 dev = list_next(l2arc_dev_list, dev)) {
4641 if (dev->l2ad_vdev == vd)
4642 break;
4643 }
4644 mutex_exit(&l2arc_dev_mtx);
4645
4646 return (dev != NULL);
4647 }
4648
4649 /*
4650 * Add a vdev for use by the L2ARC. By this point the spa has already
4651 * validated the vdev and opened it.
4652 */
4653 void
4654 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
4655 {
4656 l2arc_dev_t *adddev;
4657
4658 ASSERT(!l2arc_vdev_present(vd));
4659
4660 /*
4661 * Create a new l2arc device entry.
4662 */
4663 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4664 adddev->l2ad_spa = spa;
4665 adddev->l2ad_vdev = vd;
4666 adddev->l2ad_write = l2arc_write_max;
4667 adddev->l2ad_boost = l2arc_write_boost;
4668 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
4669 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
4670 adddev->l2ad_hand = adddev->l2ad_start;
4671 adddev->l2ad_evict = adddev->l2ad_start;
4672 adddev->l2ad_first = B_TRUE;
4673 adddev->l2ad_writing = B_FALSE;
4674 ASSERT3U(adddev->l2ad_write, >, 0);
4675
4676 /*
4677 * This is a list of all ARC buffers that are still valid on the
4678 * device.
4679 */
4680 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4681 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4682 offsetof(arc_buf_hdr_t, b_l2node));
4683
4684 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
4685
4686 /*
4687 * Add device to global list
4688 */
4689 mutex_enter(&l2arc_dev_mtx);
4690 list_insert_head(l2arc_dev_list, adddev);
4691 atomic_inc_64(&l2arc_ndev);
4692 mutex_exit(&l2arc_dev_mtx);
4693 }
4694
4695 /*
4696 * Remove a vdev from the L2ARC.
4697 */
4698 void
4699 l2arc_remove_vdev(vdev_t *vd)
4700 {
4701 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4702
4703 /*
4704 * Find the device by vdev
4705 */
4706 mutex_enter(&l2arc_dev_mtx);
4707 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4708 nextdev = list_next(l2arc_dev_list, dev);
4709 if (vd == dev->l2ad_vdev) {
4710 remdev = dev;
4711 break;
4712 }
4713 }
4714 ASSERT(remdev != NULL);
4715
4716 /*
4717 * Remove device from global list
4718 */
4719 list_remove(l2arc_dev_list, remdev);
4720 l2arc_dev_last = NULL; /* may have been invalidated */
4721 atomic_dec_64(&l2arc_ndev);
4722 mutex_exit(&l2arc_dev_mtx);
4723
4724 /*
4725 * Clear all buflists and ARC references. L2ARC device flush.
4726 */
4727 l2arc_evict(remdev, 0, B_TRUE);
4728 list_destroy(remdev->l2ad_buflist);
4729 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4730 kmem_free(remdev, sizeof (l2arc_dev_t));
4731 }
4732
4733 void
4734 l2arc_init(void)
4735 {
4736 l2arc_thread_exit = 0;
4737 l2arc_ndev = 0;
4738 l2arc_writes_sent = 0;
4739 l2arc_writes_done = 0;
4740
4741 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4742 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4743 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4744 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4745 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4746
4747 l2arc_dev_list = &L2ARC_dev_list;
4748 l2arc_free_on_write = &L2ARC_free_on_write;
4749 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4750 offsetof(l2arc_dev_t, l2ad_node));
4751 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4752 offsetof(l2arc_data_free_t, l2df_list_node));
4753 }
4754
4755 void
4756 l2arc_fini(void)
4757 {
4758 /*
4759 * This is called from dmu_fini(), which is called from spa_fini();
4760 * Because of this, we can assume that all l2arc devices have
4761 * already been removed when the pools themselves were removed.
4762 */
4763
4764 l2arc_do_free_on_write();
4765
4766 mutex_destroy(&l2arc_feed_thr_lock);
4767 cv_destroy(&l2arc_feed_thr_cv);
4768 mutex_destroy(&l2arc_dev_mtx);
4769 mutex_destroy(&l2arc_buflist_mtx);
4770 mutex_destroy(&l2arc_free_on_write_mtx);
4771
4772 list_destroy(l2arc_dev_list);
4773 list_destroy(l2arc_free_on_write);
4774 }
4775
4776 void
4777 l2arc_start(void)
4778 {
4779 if (!(spa_mode_global & FWRITE))
4780 return;
4781
4782 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
4783 TS_RUN, minclsyspri);
4784 }
4785
4786 void
4787 l2arc_stop(void)
4788 {
4789 if (!(spa_mode_global & FWRITE))
4790 return;
4791
4792 mutex_enter(&l2arc_feed_thr_lock);
4793 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
4794 l2arc_thread_exit = 1;
4795 while (l2arc_thread_exit != 0)
4796 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
4797 mutex_exit(&l2arc_feed_thr_lock);
4798 }