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