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 (c) 2012, Joyent, Inc. All rights reserved.
24 * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2014 Nexenta Systems, Inc. All rights reserved.
27 */
28
29 /*
30 * DVA-based Adjustable Replacement Cache
31 *
32 * While much of the theory of operation used here is
33 * based on the self-tuning, low overhead replacement cache
34 * presented by Megiddo and Modha at FAST 2003, there are some
35 * significant differences:
36 *
37 * 1. The Megiddo and Modha model assumes any page is evictable.
38 * Pages in its cache cannot be "locked" into memory. This makes
39 * the eviction algorithm simple: evict the last page in the list.
40 * This also make the performance characteristics easy to reason
41 * about. Our cache is not so simple. At any given moment, some
42 * subset of the blocks in the cache are un-evictable because we
43 * have handed out a reference to them. Blocks are only evictable
44 * when there are no external references active. This makes
45 * eviction far more problematic: we choose to evict the evictable
46 * blocks that are the "lowest" in the list.
47 *
48 * There are times when it is not possible to evict the requested
49 * space. In these circumstances we are unable to adjust the cache
50 * size. To prevent the cache growing unbounded at these times we
51 * implement a "cache throttle" that slows the flow of new data
52 * into the cache until we can make space available.
53 *
54 * 2. The Megiddo and Modha model assumes a fixed cache size.
55 * Pages are evicted when the cache is full and there is a cache
56 * miss. Our model has a variable sized cache. It grows with
57 * high use, but also tries to react to memory pressure from the
58 * operating system: decreasing its size when system memory is
59 * tight.
60 *
61 * 3. The Megiddo and Modha model assumes a fixed page size. All
62 * elements of the cache are therefore exactly the same size. So
63 * when adjusting the cache size following a cache miss, its simply
64 * a matter of choosing a single page to evict. In our model, we
65 * have variable sized cache blocks (rangeing from 512 bytes to
66 * 128K bytes). We therefore choose a set of blocks to evict to make
67 * space for a cache miss that approximates as closely as possible
68 * the space used by the new block.
69 *
70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 * by N. Megiddo & D. Modha, FAST 2003
72 */
73
74 /*
75 * The locking model:
76 *
77 * A new reference to a cache buffer can be obtained in two
78 * ways: 1) via a hash table lookup using the DVA as a key,
79 * or 2) via one of the ARC lists. The arc_read() interface
80 * uses method 1, while the internal arc algorithms for
81 * adjusting the cache use method 2. We therefore provide two
82 * types of locks: 1) the hash table lock array, and 2) the
83 * arc list locks.
84 *
85 * Buffers do not have their own mutexes, rather they rely on the
86 * hash table mutexes for the bulk of their protection (i.e. most
87 * fields in the arc_buf_hdr_t are protected by these mutexes).
88 *
89 * buf_hash_find() returns the appropriate mutex (held) when it
90 * locates the requested buffer in the hash table. It returns
91 * NULL for the mutex if the buffer was not in the table.
92 *
93 * buf_hash_remove() expects the appropriate hash mutex to be
94 * already held before it is invoked.
95 *
96 * Each arc state also has a mutex which is used to protect the
97 * buffer list associated with the state. When attempting to
98 * obtain a hash table lock while holding an arc list lock you
99 * must use: mutex_tryenter() to avoid deadlock. Also note that
100 * the active state mutex must be held before the ghost state mutex.
101 *
102 * Arc buffers may have an associated eviction callback function.
103 * This function will be invoked prior to removing the buffer (e.g.
104 * in arc_do_user_evicts()). Note however that the data associated
105 * with the buffer may be evicted prior to the callback. The callback
106 * must be made with *no locks held* (to prevent deadlock). Additionally,
107 * the users of callbacks must ensure that their private data is
108 * protected from simultaneous callbacks from arc_clear_callback()
109 * and arc_do_user_evicts().
110 *
111 * Note that the majority of the performance stats are manipulated
112 * with atomic operations.
113 *
114 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
115 *
116 * - L2ARC buflist creation
117 * - L2ARC buflist eviction
118 * - L2ARC write completion, which walks L2ARC buflists
119 * - ARC header destruction, as it removes from L2ARC buflists
120 * - ARC header release, as it removes from L2ARC buflists
121 */
122
123 #include <sys/spa.h>
124 #include <sys/zio.h>
125 #include <sys/zio_compress.h>
126 #include <sys/zfs_context.h>
127 #include <sys/arc.h>
128 #include <sys/refcount.h>
129 #include <sys/vdev.h>
130 #include <sys/vdev_impl.h>
131 #include <sys/dsl_pool.h>
132 #ifdef _KERNEL
133 #include <sys/vmsystm.h>
134 #include <vm/anon.h>
135 #include <sys/fs/swapnode.h>
136 #include <sys/dnlc.h>
137 #endif
138 #include <sys/callb.h>
139 #include <sys/kstat.h>
140 #include <zfs_fletcher.h>
141
142 #ifndef _KERNEL
143 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
144 boolean_t arc_watch = B_FALSE;
145 int arc_procfd;
146 #endif
147
148 static kmutex_t arc_reclaim_thr_lock;
149 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
150 static uint8_t arc_thread_exit;
151
152 static kmutex_t arc_pressure_thr_lock;
153 static kcondvar_t arc_pressure_thr_cv;
154 static uint8_t arc_pressure_thread_exit;
155 static uint64_t arc_pressure_threshold;
156
157 #define ARC_REDUCE_DNLC_PERCENT 3
158 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
159
160 typedef enum arc_reclaim_strategy {
161 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
162 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
163 } arc_reclaim_strategy_t;
164
165 /*
166 * The number of iterations through arc_evict_*() before we
167 * drop & reacquire the lock.
168 */
169 int arc_evict_iterations = 100;
170
171 /* number of seconds before growing cache again */
172 static int arc_grow_retry = 60;
173
174 /* shift of arc_c for calculating both min and max arc_p */
175 static int arc_p_min_shift = 4;
176
177 /* log2(fraction of arc to reclaim) */
178 static int arc_shrink_shift = 5;
179
180 /*
181 * minimum lifespan of a prefetch block in clock ticks
182 * (initialized in arc_init())
183 */
184 static int arc_min_prefetch_lifespan;
185
186 /*
187 * If this percent of memory is free, don't throttle.
188 */
189 int arc_lotsfree_percent = 10;
190
191 static int arc_dead;
192
193 /*
194 * The arc has filled available memory and has now warmed up.
195 */
196 static boolean_t arc_warm;
197
198 /*
199 * These tunables are for performance analysis.
200 */
201 uint64_t zfs_arc_max;
202 uint64_t zfs_arc_min;
203 uint64_t zfs_arc_meta_limit = 0;
204 int zfs_arc_grow_retry = 0;
205 int zfs_arc_shrink_shift = 0;
206 int zfs_arc_p_min_shift = 0;
207 int zfs_disable_dup_eviction = 0;
208 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
209
210 /*
211 * Note that buffers can be in one of 6 states:
212 * ARC_anon - anonymous (discussed below)
213 * ARC_mru - recently used, currently cached
214 * ARC_mru_ghost - recentely used, no longer in cache
215 * ARC_mfu - frequently used, currently cached
216 * ARC_mfu_ghost - frequently used, no longer in cache
217 * ARC_l2c_only - exists in L2ARC but not other states
218 * When there are no active references to the buffer, they are
219 * are linked onto a list in one of these arc states. These are
220 * the only buffers that can be evicted or deleted. Within each
221 * state there are multiple lists, one for meta-data and one for
222 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
223 * etc.) is tracked separately so that it can be managed more
224 * explicitly: favored over data, limited explicitly.
225 *
226 * Anonymous buffers are buffers that are not associated with
227 * a DVA. These are buffers that hold dirty block copies
228 * before they are written to stable storage. By definition,
229 * they are "ref'd" and are considered part of arc_mru
230 * that cannot be freed. Generally, they will aquire a DVA
231 * as they are written and migrate onto the arc_mru list.
232 *
233 * The ARC_l2c_only state is for buffers that are in the second
234 * level ARC but no longer in any of the ARC_m* lists. The second
235 * level ARC itself may also contain buffers that are in any of
236 * the ARC_m* states - meaning that a buffer can exist in two
237 * places. The reason for the ARC_l2c_only state is to keep the
238 * buffer header in the hash table, so that reads that hit the
239 * second level ARC benefit from these fast lookups.
240 */
241
242 typedef struct arc_state {
243 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
244 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
245 uint64_t arcs_size; /* total amount of data in this state */
246 kmutex_t arcs_mtx;
247 } arc_state_t;
248
249 /* The 6 states: */
250 static arc_state_t ARC_anon;
251 static arc_state_t ARC_mru;
252 static arc_state_t ARC_mru_ghost;
253 static arc_state_t ARC_mfu;
254 static arc_state_t ARC_mfu_ghost;
255 static arc_state_t ARC_l2c_only;
256
257 typedef struct arc_stats {
258 kstat_named_t arcstat_hits;
259 kstat_named_t arcstat_misses;
260 kstat_named_t arcstat_demand_data_hits;
261 kstat_named_t arcstat_demand_data_misses;
262 kstat_named_t arcstat_demand_metadata_hits;
263 kstat_named_t arcstat_demand_metadata_misses;
264 kstat_named_t arcstat_prefetch_data_hits;
265 kstat_named_t arcstat_prefetch_data_misses;
266 kstat_named_t arcstat_prefetch_metadata_hits;
267 kstat_named_t arcstat_prefetch_metadata_misses;
268 kstat_named_t arcstat_mru_hits;
269 kstat_named_t arcstat_mru_ghost_hits;
270 kstat_named_t arcstat_mfu_hits;
271 kstat_named_t arcstat_mfu_ghost_hits;
272 kstat_named_t arcstat_deleted;
273 kstat_named_t arcstat_recycle_miss;
274 /*
275 * Number of buffers that could not be evicted because the hash lock
276 * was held by another thread. The lock may not necessarily be held
277 * by something using the same buffer, since hash locks are shared
278 * by multiple buffers.
279 */
280 kstat_named_t arcstat_mutex_miss;
281 /*
282 * Number of buffers skipped because they have I/O in progress, are
283 * indrect prefetch buffers that have not lived long enough, or are
284 * not from the spa we're trying to evict from.
285 */
286 kstat_named_t arcstat_evict_skip;
287 kstat_named_t arcstat_evict_l2_cached;
288 kstat_named_t arcstat_evict_l2_eligible;
289 kstat_named_t arcstat_evict_l2_ineligible;
290 kstat_named_t arcstat_hash_elements;
291 kstat_named_t arcstat_hash_elements_max;
292 kstat_named_t arcstat_hash_collisions;
293 kstat_named_t arcstat_hash_chains;
294 kstat_named_t arcstat_hash_chain_max;
295 kstat_named_t arcstat_p;
296 kstat_named_t arcstat_c;
297 kstat_named_t arcstat_c_min;
298 kstat_named_t arcstat_c_max;
299 kstat_named_t arcstat_size;
300 kstat_named_t arcstat_hdr_size;
301 kstat_named_t arcstat_data_size;
302 kstat_named_t arcstat_other_size;
303 kstat_named_t arcstat_growth_rate;
304 kstat_named_t arcstat_l2_hits;
305 kstat_named_t arcstat_l2_misses;
306 kstat_named_t arcstat_l2_feeds;
307 kstat_named_t arcstat_l2_rw_clash;
308 kstat_named_t arcstat_l2_read_bytes;
309 kstat_named_t arcstat_l2_write_bytes;
310 kstat_named_t arcstat_l2_writes_sent;
311 kstat_named_t arcstat_l2_writes_done;
312 kstat_named_t arcstat_l2_writes_error;
313 kstat_named_t arcstat_l2_writes_hdr_miss;
314 kstat_named_t arcstat_l2_evict_lock_retry;
315 kstat_named_t arcstat_l2_evict_reading;
316 kstat_named_t arcstat_l2_free_on_write;
317 kstat_named_t arcstat_l2_abort_lowmem;
318 kstat_named_t arcstat_l2_cksum_bad;
319 kstat_named_t arcstat_l2_io_error;
320 kstat_named_t arcstat_l2_size;
321 kstat_named_t arcstat_l2_asize;
322 kstat_named_t arcstat_l2_hdr_size;
323 kstat_named_t arcstat_l2_compress_successes;
324 kstat_named_t arcstat_l2_compress_zeros;
325 kstat_named_t arcstat_l2_compress_failures;
326 kstat_named_t arcstat_memory_throttle_count;
327 kstat_named_t arcstat_duplicate_buffers;
328 kstat_named_t arcstat_duplicate_buffers_size;
329 kstat_named_t arcstat_duplicate_reads;
330 kstat_named_t arcstat_meta_used;
331 kstat_named_t arcstat_meta_limit;
332 kstat_named_t arcstat_meta_max;
333 } arc_stats_t;
334
335 static arc_stats_t arc_stats = {
336 { "hits", KSTAT_DATA_UINT64 },
337 { "misses", KSTAT_DATA_UINT64 },
338 { "demand_data_hits", KSTAT_DATA_UINT64 },
339 { "demand_data_misses", KSTAT_DATA_UINT64 },
340 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
341 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
342 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
343 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
344 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
345 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
346 { "mru_hits", KSTAT_DATA_UINT64 },
347 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
348 { "mfu_hits", KSTAT_DATA_UINT64 },
349 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
350 { "deleted", KSTAT_DATA_UINT64 },
351 { "recycle_miss", KSTAT_DATA_UINT64 },
352 { "mutex_miss", KSTAT_DATA_UINT64 },
353 { "evict_skip", KSTAT_DATA_UINT64 },
354 { "evict_l2_cached", KSTAT_DATA_UINT64 },
355 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
356 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
357 { "hash_elements", KSTAT_DATA_UINT64 },
358 { "hash_elements_max", KSTAT_DATA_UINT64 },
359 { "hash_collisions", KSTAT_DATA_UINT64 },
360 { "hash_chains", KSTAT_DATA_UINT64 },
361 { "hash_chain_max", KSTAT_DATA_UINT64 },
362 { "p", KSTAT_DATA_UINT64 },
363 { "c", KSTAT_DATA_UINT64 },
364 { "c_min", KSTAT_DATA_UINT64 },
365 { "c_max", KSTAT_DATA_UINT64 },
366 { "size", KSTAT_DATA_UINT64 },
367 { "hdr_size", KSTAT_DATA_UINT64 },
368 { "data_size", KSTAT_DATA_UINT64 },
369 { "other_size", KSTAT_DATA_UINT64 },
370 { "growth_rate", KSTAT_DATA_UINT64 },
371 { "l2_hits", KSTAT_DATA_UINT64 },
372 { "l2_misses", KSTAT_DATA_UINT64 },
373 { "l2_feeds", KSTAT_DATA_UINT64 },
374 { "l2_rw_clash", KSTAT_DATA_UINT64 },
375 { "l2_read_bytes", KSTAT_DATA_UINT64 },
376 { "l2_write_bytes", KSTAT_DATA_UINT64 },
377 { "l2_writes_sent", KSTAT_DATA_UINT64 },
378 { "l2_writes_done", KSTAT_DATA_UINT64 },
379 { "l2_writes_error", KSTAT_DATA_UINT64 },
380 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
381 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
382 { "l2_evict_reading", KSTAT_DATA_UINT64 },
383 { "l2_free_on_write", KSTAT_DATA_UINT64 },
384 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
385 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
386 { "l2_io_error", KSTAT_DATA_UINT64 },
387 { "l2_size", KSTAT_DATA_UINT64 },
388 { "l2_asize", KSTAT_DATA_UINT64 },
389 { "l2_hdr_size", KSTAT_DATA_UINT64 },
390 { "l2_compress_successes", KSTAT_DATA_UINT64 },
391 { "l2_compress_zeros", KSTAT_DATA_UINT64 },
392 { "l2_compress_failures", KSTAT_DATA_UINT64 },
393 { "memory_throttle_count", KSTAT_DATA_UINT64 },
394 { "duplicate_buffers", KSTAT_DATA_UINT64 },
395 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
396 { "duplicate_reads", KSTAT_DATA_UINT64 },
397 { "arc_meta_used", KSTAT_DATA_UINT64 },
398 { "arc_meta_limit", KSTAT_DATA_UINT64 },
399 { "arc_meta_max", KSTAT_DATA_UINT64 }
400 };
401
402 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
403
404 #define ARCSTAT_INCR(stat, val) \
405 atomic_add_64(&arc_stats.stat.value.ui64, (val))
406
407 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
408 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
409
410 #define ARCSTAT_MAX(stat, val) { \
411 uint64_t m; \
412 while ((val) > (m = arc_stats.stat.value.ui64) && \
413 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
414 continue; \
415 }
416
417 #define ARCSTAT_MAXSTAT(stat) \
418 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
419
420 /*
421 * We define a macro to allow ARC hits/misses to be easily broken down by
422 * two separate conditions, giving a total of four different subtypes for
423 * each of hits and misses (so eight statistics total).
424 */
425 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
426 if (cond1) { \
427 if (cond2) { \
428 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
429 } else { \
430 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
431 } \
432 } else { \
433 if (cond2) { \
434 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
435 } else { \
436 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
437 } \
438 }
439
440 /*
441 * This macro allows us to use kstats as floating averages. Each time we
442 * update this kstat, we first factor it and the update value by `factor'
443 * to shrink the new value's contribution to the overall average. This
444 * macro assumes that integer loads and stores are atomic, but is not
445 * safe for multiple writers updating the kstat in parallel (only the
446 * last writer's update will remain).
447 */
448 #define ARCSTAT_F_AVG(stat, value, factor) \
449 do { \
450 uint64_t x = ARCSTAT(stat); \
451 x = x - x / factor + (value) / factor; \
452 ARCSTAT(stat) = x; \
453 _NOTE(NOTREACHED) \
454 _NOTE(CONSTCOND) \
455 } while (0)
456
457 kstat_t *arc_ksp;
458 static arc_state_t *arc_anon;
459 static arc_state_t *arc_mru;
460 static arc_state_t *arc_mru_ghost;
461 static arc_state_t *arc_mfu;
462 static arc_state_t *arc_mfu_ghost;
463 static arc_state_t *arc_l2c_only;
464
465 /*
466 * There are several ARC variables that are critical to export as kstats --
467 * but we don't want to have to grovel around in the kstat whenever we wish to
468 * manipulate them. For these variables, we therefore define them to be in
469 * terms of the statistic variable. This assures that we are not introducing
470 * the possibility of inconsistency by having shadow copies of the variables,
471 * while still allowing the code to be readable.
472 */
473 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
474 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
475 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
476 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
477 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
478 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
479 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
480 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
481
482 #define L2ARC_IS_VALID_COMPRESS(_c_) \
483 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
484
485 static int arc_no_grow; /* Don't try to grow cache size */
486 static uint64_t arc_tempreserve;
487 static uint64_t arc_loaned_bytes;
488 static uint64_t arc_bytes_allocd = 0;
489
490 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
491
492 typedef struct arc_callback arc_callback_t;
493
494 struct arc_callback {
495 void *acb_private;
496 arc_done_func_t *acb_done;
497 arc_buf_t *acb_buf;
498 zio_t *acb_zio_dummy;
499 arc_callback_t *acb_next;
500 };
501
502 typedef struct arc_write_callback arc_write_callback_t;
503
504 struct arc_write_callback {
505 void *awcb_private;
506 arc_done_func_t *awcb_ready;
507 arc_done_func_t *awcb_physdone;
508 arc_done_func_t *awcb_done;
509 arc_buf_t *awcb_buf;
510 };
511
512 struct arc_buf_hdr {
513 /* protected by hash lock */
514 dva_t b_dva;
515 uint64_t b_birth;
516 uint64_t b_cksum0;
517
518 kmutex_t b_freeze_lock;
519 zio_cksum_t *b_freeze_cksum;
520 void *b_thawed;
521
522 arc_buf_hdr_t *b_hash_next;
523 arc_buf_t *b_buf;
524 uint32_t b_flags;
525 uint32_t b_datacnt;
526
527 arc_callback_t *b_acb;
528 kcondvar_t b_cv;
529
530 /* immutable */
531 arc_buf_contents_t b_type;
532 uint64_t b_size;
533 uint64_t b_spa;
534
535 /* protected by arc state mutex */
536 arc_state_t *b_state;
537 list_node_t b_arc_node;
538
539 /* updated atomically */
540 clock_t b_arc_access;
541
542 /* self protecting */
543 refcount_t b_refcnt;
544
545 l2arc_buf_hdr_t *b_l2hdr;
546 list_node_t b_l2node;
547 };
548
549 static arc_buf_t *arc_eviction_list;
550 static kmutex_t arc_eviction_mtx;
551 static arc_buf_hdr_t arc_eviction_hdr;
552 static void arc_get_data_buf(arc_buf_t *buf);
553 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
554 static int arc_evict_needed(arc_buf_contents_t type);
555 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
556 static void arc_buf_watch(arc_buf_t *buf);
557
558 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
559
560 #define GHOST_STATE(state) \
561 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
562 (state) == arc_l2c_only)
563
564 /*
565 * Private ARC flags. These flags are private ARC only flags that will show up
566 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
567 * be passed in as arc_flags in things like arc_read. However, these flags
568 * should never be passed and should only be set by ARC code. When adding new
569 * public flags, make sure not to smash the private ones.
570 */
571
572 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
573 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
574 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
575 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
576 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
577 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
578 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
579 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
580 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
581 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
582
583 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
584 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
585 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
586 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
587 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
588 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
589 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
590 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
591 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
592 (hdr)->b_l2hdr != NULL)
593 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
594 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
595 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
596
597 /*
598 * Other sizes
599 */
600
601 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
602 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
603
604 /*
605 * Hash table routines
606 */
607
608 struct ht_table {
609 arc_buf_hdr_t *hdr;
610 kmutex_t lock;
611 };
612
613 typedef struct buf_hash_table {
614 uint64_t ht_mask;
615 struct ht_table *ht_table;
616 } buf_hash_table_t;
617
618 #pragma align 64(buf_hash_table)
619 static buf_hash_table_t buf_hash_table;
620
621 #define BUF_HASH_INDEX(spa, dva, birth) \
622 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
623 #define BUF_HASH_LOCK(idx) (&buf_hash_table.ht_table[idx].lock)
624 #define HDR_LOCK(hdr) \
625 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
626
627 uint64_t zfs_crc64_table[256];
628
629 /*
630 * Level 2 ARC
631 */
632
633 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
634 #define L2ARC_HEADROOM 2 /* num of writes */
635 /*
636 * If we discover during ARC scan any buffers to be compressed, we boost
637 * our headroom for the next scanning cycle by this percentage multiple.
638 */
639 #define L2ARC_HEADROOM_BOOST 200
640 #define L2ARC_FEED_SECS 1 /* caching interval secs */
641 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
642
643 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
644 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
645
646 /* L2ARC Performance Tunables */
647 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
648 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
649 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
650 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
651 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
652 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
653 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
654 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
655 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
656
657 /*
658 * L2ARC Internals
659 */
660 typedef struct l2arc_dev {
661 vdev_t *l2ad_vdev; /* vdev */
662 spa_t *l2ad_spa; /* spa */
663 uint64_t l2ad_hand; /* next write location */
664 uint64_t l2ad_start; /* first addr on device */
665 uint64_t l2ad_end; /* last addr on device */
666 uint64_t l2ad_evict; /* last addr eviction reached */
667 boolean_t l2ad_first; /* first sweep through */
668 boolean_t l2ad_writing; /* currently writing */
669 list_t *l2ad_buflist; /* buffer list */
670 list_node_t l2ad_node; /* device list node */
671 } l2arc_dev_t;
672
673 static list_t L2ARC_dev_list; /* device list */
674 static list_t *l2arc_dev_list; /* device list pointer */
675 static kmutex_t l2arc_dev_mtx; /* device list mutex */
676 static l2arc_dev_t *l2arc_dev_last; /* last device used */
677 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
678 static list_t L2ARC_free_on_write; /* free after write buf list */
679 static list_t *l2arc_free_on_write; /* free after write list ptr */
680 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
681 static uint64_t l2arc_ndev; /* number of devices */
682
683 typedef struct l2arc_read_callback {
684 arc_buf_t *l2rcb_buf; /* read buffer */
685 spa_t *l2rcb_spa; /* spa */
686 blkptr_t l2rcb_bp; /* original blkptr */
687 zbookmark_phys_t l2rcb_zb; /* original bookmark */
688 int l2rcb_flags; /* original flags */
689 enum zio_compress l2rcb_compress; /* applied compress */
690 } l2arc_read_callback_t;
691
692 typedef struct l2arc_write_callback {
693 l2arc_dev_t *l2wcb_dev; /* device info */
694 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
695 } l2arc_write_callback_t;
696
697 struct l2arc_buf_hdr {
698 /* protected by arc_buf_hdr mutex */
699 l2arc_dev_t *b_dev; /* L2ARC device */
700 uint64_t b_daddr; /* disk address, offset byte */
701 /* compression applied to buffer data */
702 enum zio_compress b_compress;
703 /* real alloc'd buffer size depending on b_compress applied */
704 int b_asize;
705 /* temporary buffer holder for in-flight compressed data */
706 void *b_tmp_cdata;
707 };
708
709 typedef struct l2arc_data_free {
710 /* protected by l2arc_free_on_write_mtx */
711 void *l2df_data;
712 size_t l2df_size;
713 void (*l2df_func)(void *, size_t);
714 list_node_t l2df_list_node;
715 } l2arc_data_free_t;
716
717 static kmutex_t l2arc_feed_thr_lock;
718 static kcondvar_t l2arc_feed_thr_cv;
719 static uint8_t l2arc_thread_exit;
720
721 static void l2arc_read_done(zio_t *zio);
722 static void l2arc_hdr_stat_add(void);
723 static void l2arc_hdr_stat_remove(void);
724
725 static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
726 static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
727 enum zio_compress c);
728 static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
729
730 static uint64_t
731 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
732 {
733 uint8_t *vdva = (uint8_t *)dva;
734 uint64_t crc = -1ULL;
735 int i;
736
737 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
738
739 for (i = 0; i < sizeof (dva_t); i++)
740 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
741
742 crc ^= (spa>>8) ^ birth;
743
744 return (crc);
745 }
746
747 #define BUF_EMPTY(buf) \
748 ((buf)->b_dva.dva_word[0] == 0 && \
749 (buf)->b_dva.dva_word[1] == 0 && \
750 (buf)->b_cksum0 == 0)
751
752 #define BUF_EQUAL(spa, dva, birth, buf) \
753 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
754 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
755 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
756
757 static void
758 buf_discard_identity(arc_buf_hdr_t *hdr)
759 {
760 hdr->b_dva.dva_word[0] = 0;
761 hdr->b_dva.dva_word[1] = 0;
762 hdr->b_birth = 0;
763 hdr->b_cksum0 = 0;
764 }
765
766 static arc_buf_hdr_t *
767 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
768 {
769 const dva_t *dva = BP_IDENTITY(bp);
770 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
771 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
772 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
773 arc_buf_hdr_t *buf;
774
775 mutex_enter(hash_lock);
776 for (buf = buf_hash_table.ht_table[idx].hdr; buf != NULL;
777 buf = buf->b_hash_next) {
778 if (BUF_EQUAL(spa, dva, birth, buf)) {
779 *lockp = hash_lock;
780 return (buf);
781 }
782 }
783 mutex_exit(hash_lock);
784 *lockp = NULL;
785 return (NULL);
786 }
787
788 /*
789 * Insert an entry into the hash table. If there is already an element
790 * equal to elem in the hash table, then the already existing element
791 * will be returned and the new element will not be inserted.
792 * Otherwise returns NULL.
793 */
794 static arc_buf_hdr_t *
795 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
796 {
797 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
798 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
799 arc_buf_hdr_t *fbuf;
800 uint32_t i;
801
802 ASSERT(!DVA_IS_EMPTY(&buf->b_dva));
803 ASSERT(buf->b_birth != 0);
804 ASSERT(!HDR_IN_HASH_TABLE(buf));
805 *lockp = hash_lock;
806 mutex_enter(hash_lock);
807 for (fbuf = buf_hash_table.ht_table[idx].hdr, i = 0; fbuf != NULL;
808 fbuf = fbuf->b_hash_next, i++) {
809 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
810 return (fbuf);
811 }
812
813 buf->b_hash_next = buf_hash_table.ht_table[idx].hdr;
814 buf_hash_table.ht_table[idx].hdr = buf;
815 buf->b_flags |= ARC_IN_HASH_TABLE;
816
817 /* collect some hash table performance data */
818 if (i > 0) {
819 ARCSTAT_BUMP(arcstat_hash_collisions);
820 if (i == 1)
821 ARCSTAT_BUMP(arcstat_hash_chains);
822
823 ARCSTAT_MAX(arcstat_hash_chain_max, i);
824 }
825
826 ARCSTAT_BUMP(arcstat_hash_elements);
827 ARCSTAT_MAXSTAT(arcstat_hash_elements);
828
829 return (NULL);
830 }
831
832 static void
833 buf_hash_remove(arc_buf_hdr_t *buf)
834 {
835 arc_buf_hdr_t *fbuf, **bufp;
836 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
837
838 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
839 ASSERT(HDR_IN_HASH_TABLE(buf));
840
841 bufp = &buf_hash_table.ht_table[idx].hdr;
842 while ((fbuf = *bufp) != buf) {
843 ASSERT(fbuf != NULL);
844 bufp = &fbuf->b_hash_next;
845 }
846 *bufp = buf->b_hash_next;
847 buf->b_hash_next = NULL;
848 buf->b_flags &= ~ARC_IN_HASH_TABLE;
849
850 /* collect some hash table performance data */
851 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
852
853 if (buf_hash_table.ht_table[idx].hdr &&
854 buf_hash_table.ht_table[idx].hdr->b_hash_next == NULL)
855 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
856 }
857
858 /*
859 * Global data structures and functions for the buf kmem cache.
860 */
861 static kmem_cache_t *hdr_cache;
862 static kmem_cache_t *buf_cache;
863
864 static void
865 buf_fini(void)
866 {
867 int i;
868
869 for (i = 0; i < buf_hash_table.ht_mask + 1; i++)
870 mutex_destroy(&buf_hash_table.ht_table[i].lock);
871 kmem_free(buf_hash_table.ht_table,
872 (buf_hash_table.ht_mask + 1) * sizeof (struct ht_table));
873 kmem_cache_destroy(hdr_cache);
874 kmem_cache_destroy(buf_cache);
875 }
876
877 /*
878 * Constructor callback - called when the cache is empty
879 * and a new buf is requested.
880 */
881 /* ARGSUSED */
882 static int
883 hdr_cons(void *vbuf, void *unused, int kmflag)
884 {
885 arc_buf_hdr_t *buf = vbuf;
886
887 bzero(buf, sizeof (arc_buf_hdr_t));
888 refcount_create(&buf->b_refcnt);
889 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
890 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
891 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
892
893 return (0);
894 }
895
896 /* ARGSUSED */
897 static int
898 buf_cons(void *vbuf, void *unused, int kmflag)
899 {
900 arc_buf_t *buf = vbuf;
901
902 bzero(buf, sizeof (arc_buf_t));
903 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
904 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
905
906 return (0);
907 }
908
909 /*
910 * Destructor callback - called when a cached buf is
911 * no longer required.
912 */
913 /* ARGSUSED */
914 static void
915 hdr_dest(void *vbuf, void *unused)
916 {
917 arc_buf_hdr_t *buf = vbuf;
918
919 ASSERT(BUF_EMPTY(buf));
920 refcount_destroy(&buf->b_refcnt);
921 cv_destroy(&buf->b_cv);
922 mutex_destroy(&buf->b_freeze_lock);
923 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
924 }
925
926 /* ARGSUSED */
927 static void
928 buf_dest(void *vbuf, void *unused)
929 {
930 arc_buf_t *buf = vbuf;
931
932 mutex_destroy(&buf->b_evict_lock);
933 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
934 }
935
936 /*
937 * Reclaim callback -- invoked when memory is low.
938 */
939 /* ARGSUSED */
940 static void
941 hdr_recl(void *unused)
942 {
943 dprintf("hdr_recl called\n");
944 /*
945 * umem calls the reclaim func when we destroy the buf cache,
946 * which is after we do arc_fini().
947 */
948 if (!arc_dead)
949 cv_signal(&arc_reclaim_thr_cv);
950 }
951
952 static void
953 buf_init(void)
954 {
955 uint64_t *ct;
956 uint64_t hsize = 1ULL << 12;
957 int i, j;
958
959 /*
960 * The hash table is big enough to fill all of physical memory
961 * with an average block size of zfs_arc_average_blocksize (default 8K).
962 * By default, the table will take up
963 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
964 */
965 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
966 hsize <<= 1;
967 retry:
968 buf_hash_table.ht_mask = hsize - 1;
969 buf_hash_table.ht_table =
970 kmem_zalloc(hsize * sizeof (struct ht_table), KM_NOSLEEP);
971 if (buf_hash_table.ht_table == NULL) {
972 ASSERT(hsize > (1ULL << 8));
973 hsize >>= 1;
974 goto retry;
975 }
976
977 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
978 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
979 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
980 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
981
982 for (i = 0; i < 256; i++)
983 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
984 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
985
986 for (i = 0; i < hsize; i++) {
987 mutex_init(&buf_hash_table.ht_table[i].lock,
988 NULL, MUTEX_DEFAULT, NULL);
989 }
990 }
991
992 #define ARC_MINTIME (hz>>4) /* 62 ms */
993
994 static void
995 arc_cksum_verify(arc_buf_t *buf)
996 {
997 zio_cksum_t zc;
998
999 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1000 return;
1001
1002 mutex_enter(&buf->b_hdr->b_freeze_lock);
1003 if (buf->b_hdr->b_freeze_cksum == NULL ||
1004 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
1005 mutex_exit(&buf->b_hdr->b_freeze_lock);
1006 return;
1007 }
1008 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1009 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1010 panic("buffer modified while frozen!");
1011 mutex_exit(&buf->b_hdr->b_freeze_lock);
1012 }
1013
1014 static int
1015 arc_cksum_equal(arc_buf_t *buf)
1016 {
1017 zio_cksum_t zc;
1018 int equal;
1019
1020 mutex_enter(&buf->b_hdr->b_freeze_lock);
1021 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1022 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1023 mutex_exit(&buf->b_hdr->b_freeze_lock);
1024
1025 return (equal);
1026 }
1027
1028 static void
1029 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1030 {
1031 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1032 return;
1033
1034 mutex_enter(&buf->b_hdr->b_freeze_lock);
1035 if (buf->b_hdr->b_freeze_cksum != NULL) {
1036 mutex_exit(&buf->b_hdr->b_freeze_lock);
1037 return;
1038 }
1039 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1040 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1041 buf->b_hdr->b_freeze_cksum);
1042 mutex_exit(&buf->b_hdr->b_freeze_lock);
1043 arc_buf_watch(buf);
1044 }
1045
1046 #ifndef _KERNEL
1047 typedef struct procctl {
1048 long cmd;
1049 prwatch_t prwatch;
1050 } procctl_t;
1051 #endif
1052
1053 /* ARGSUSED */
1054 static void
1055 arc_buf_unwatch(arc_buf_t *buf)
1056 {
1057 #ifndef _KERNEL
1058 if (arc_watch) {
1059 int result;
1060 procctl_t ctl;
1061 ctl.cmd = PCWATCH;
1062 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1063 ctl.prwatch.pr_size = 0;
1064 ctl.prwatch.pr_wflags = 0;
1065 result = write(arc_procfd, &ctl, sizeof (ctl));
1066 ASSERT3U(result, ==, sizeof (ctl));
1067 }
1068 #endif
1069 }
1070
1071 /* ARGSUSED */
1072 static void
1073 arc_buf_watch(arc_buf_t *buf)
1074 {
1075 #ifndef _KERNEL
1076 if (arc_watch) {
1077 int result;
1078 procctl_t ctl;
1079 ctl.cmd = PCWATCH;
1080 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1081 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1082 ctl.prwatch.pr_wflags = WA_WRITE;
1083 result = write(arc_procfd, &ctl, sizeof (ctl));
1084 ASSERT3U(result, ==, sizeof (ctl));
1085 }
1086 #endif
1087 }
1088
1089 void
1090 arc_buf_thaw(arc_buf_t *buf)
1091 {
1092 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1093 if (buf->b_hdr->b_state != arc_anon)
1094 panic("modifying non-anon buffer!");
1095 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1096 panic("modifying buffer while i/o in progress!");
1097 arc_cksum_verify(buf);
1098 }
1099
1100 mutex_enter(&buf->b_hdr->b_freeze_lock);
1101 if (buf->b_hdr->b_freeze_cksum != NULL) {
1102 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1103 buf->b_hdr->b_freeze_cksum = NULL;
1104 }
1105
1106 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1107 if (buf->b_hdr->b_thawed)
1108 kmem_free(buf->b_hdr->b_thawed, 1);
1109 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1110 }
1111
1112 mutex_exit(&buf->b_hdr->b_freeze_lock);
1113
1114 arc_buf_unwatch(buf);
1115 }
1116
1117 void
1118 arc_buf_freeze(arc_buf_t *buf)
1119 {
1120 kmutex_t *hash_lock;
1121
1122 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1123 return;
1124
1125 hash_lock = HDR_LOCK(buf->b_hdr);
1126 mutex_enter(hash_lock);
1127
1128 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1129 buf->b_hdr->b_state == arc_anon);
1130 arc_cksum_compute(buf, B_FALSE);
1131 mutex_exit(hash_lock);
1132
1133 }
1134
1135 static void
1136 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1137 {
1138 ASSERT(MUTEX_HELD(hash_lock));
1139
1140 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1141 (ab->b_state != arc_anon)) {
1142 uint64_t delta = ab->b_size * ab->b_datacnt;
1143 list_t *list = &ab->b_state->arcs_list[ab->b_type];
1144 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1145
1146 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
1147 mutex_enter(&ab->b_state->arcs_mtx);
1148 ASSERT(list_link_active(&ab->b_arc_node));
1149 list_remove(list, ab);
1150 if (GHOST_STATE(ab->b_state)) {
1151 ASSERT0(ab->b_datacnt);
1152 ASSERT3P(ab->b_buf, ==, NULL);
1153 delta = ab->b_size;
1154 }
1155 ASSERT(delta > 0);
1156 ASSERT3U(*size, >=, delta);
1157 atomic_add_64(size, -delta);
1158 mutex_exit(&ab->b_state->arcs_mtx);
1159 /* remove the prefetch flag if we get a reference */
1160 if (ab->b_flags & ARC_PREFETCH)
1161 ab->b_flags &= ~ARC_PREFETCH;
1162 }
1163 }
1164
1165 static int
1166 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1167 {
1168 int cnt;
1169 arc_state_t *state = ab->b_state;
1170
1171 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1172 ASSERT(!GHOST_STATE(state));
1173
1174 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1175 (state != arc_anon)) {
1176 uint64_t *size = &state->arcs_lsize[ab->b_type];
1177
1178 ASSERT(!MUTEX_HELD(&state->arcs_mtx));
1179 mutex_enter(&state->arcs_mtx);
1180 ASSERT(!list_link_active(&ab->b_arc_node));
1181 list_insert_head(&state->arcs_list[ab->b_type], ab);
1182 ASSERT(ab->b_datacnt > 0);
1183 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1184 mutex_exit(&state->arcs_mtx);
1185 }
1186 return (cnt);
1187 }
1188
1189 /*
1190 * Move the supplied buffer to the indicated state. The mutex
1191 * for the buffer must be held by the caller.
1192 */
1193 static void
1194 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1195 {
1196 arc_state_t *old_state = ab->b_state;
1197 int64_t refcnt = refcount_count(&ab->b_refcnt);
1198 uint64_t from_delta, to_delta;
1199
1200 ASSERT(MUTEX_HELD(hash_lock));
1201 ASSERT3P(new_state, !=, old_state);
1202 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1203 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1204 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1205
1206 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1207
1208 /*
1209 * If this buffer is evictable, transfer it from the
1210 * old state list to the new state list.
1211 */
1212 if (refcnt == 0) {
1213 if (old_state != arc_anon) {
1214 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
1215 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1216
1217 if (use_mutex)
1218 mutex_enter(&old_state->arcs_mtx);
1219
1220 ASSERT(list_link_active(&ab->b_arc_node));
1221 list_remove(&old_state->arcs_list[ab->b_type], ab);
1222
1223 /*
1224 * If prefetching out of the ghost cache,
1225 * we will have a non-zero datacnt.
1226 */
1227 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1228 /* ghost elements have a ghost size */
1229 ASSERT(ab->b_buf == NULL);
1230 from_delta = ab->b_size;
1231 }
1232 ASSERT3U(*size, >=, from_delta);
1233 atomic_add_64(size, -from_delta);
1234
1235 if (use_mutex)
1236 mutex_exit(&old_state->arcs_mtx);
1237 }
1238 if (new_state != arc_anon) {
1239 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
1240 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1241
1242 if (use_mutex)
1243 mutex_enter(&new_state->arcs_mtx);
1244
1245 list_insert_head(&new_state->arcs_list[ab->b_type], ab);
1246
1247 /* ghost elements have a ghost size */
1248 if (GHOST_STATE(new_state)) {
1249 ASSERT(ab->b_datacnt == 0);
1250 ASSERT(ab->b_buf == NULL);
1251 to_delta = ab->b_size;
1252 }
1253 atomic_add_64(size, to_delta);
1254
1255 if (use_mutex)
1256 mutex_exit(&new_state->arcs_mtx);
1257 }
1258 }
1259
1260 ASSERT(!BUF_EMPTY(ab));
1261 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1262 buf_hash_remove(ab);
1263
1264 /* adjust state sizes */
1265 if (to_delta)
1266 atomic_add_64(&new_state->arcs_size, to_delta);
1267 if (from_delta) {
1268 ASSERT3U(old_state->arcs_size, >=, from_delta);
1269 atomic_add_64(&old_state->arcs_size, -from_delta);
1270 }
1271 ab->b_state = new_state;
1272
1273 /* adjust l2arc hdr stats */
1274 if (new_state == arc_l2c_only)
1275 l2arc_hdr_stat_add();
1276 else if (old_state == arc_l2c_only)
1277 l2arc_hdr_stat_remove();
1278 }
1279
1280 void
1281 arc_space_consume(uint64_t space, arc_space_type_t type)
1282 {
1283 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1284
1285 switch (type) {
1286 case ARC_SPACE_DATA:
1287 ARCSTAT_INCR(arcstat_data_size, space);
1288 break;
1289 case ARC_SPACE_OTHER:
1290 ARCSTAT_INCR(arcstat_other_size, space);
1291 break;
1292 case ARC_SPACE_HDRS:
1293 ARCSTAT_INCR(arcstat_hdr_size, space);
1294 break;
1295 case ARC_SPACE_L2HDRS:
1296 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1297 break;
1298 }
1299
1300 ARCSTAT_INCR(arcstat_meta_used, space);
1301 atomic_add_64(&arc_size, space);
1302 atomic_add_64(&arc_bytes_allocd, space);
1303 }
1304
1305 void
1306 arc_space_return(uint64_t space, arc_space_type_t type)
1307 {
1308 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1309
1310 switch (type) {
1311 case ARC_SPACE_DATA:
1312 ARCSTAT_INCR(arcstat_data_size, -space);
1313 break;
1314 case ARC_SPACE_OTHER:
1315 ARCSTAT_INCR(arcstat_other_size, -space);
1316 break;
1317 case ARC_SPACE_HDRS:
1318 ARCSTAT_INCR(arcstat_hdr_size, -space);
1319 break;
1320 case ARC_SPACE_L2HDRS:
1321 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1322 break;
1323 }
1324
1325 ASSERT(arc_meta_used >= space);
1326 if (arc_meta_max < arc_meta_used)
1327 arc_meta_max = arc_meta_used;
1328 ARCSTAT_INCR(arcstat_meta_used, -space);
1329 ASSERT(arc_size >= space);
1330 atomic_add_64(&arc_size, -space);
1331 }
1332
1333 void *
1334 arc_data_buf_alloc(uint64_t size)
1335 {
1336 if (arc_evict_needed(ARC_BUFC_DATA))
1337 cv_signal(&arc_reclaim_thr_cv);
1338 atomic_add_64(&arc_size, size);
1339 atomic_add_64(&arc_bytes_allocd, size);
1340 return (zio_data_buf_alloc(size));
1341 }
1342
1343 void
1344 arc_data_buf_free(void *buf, uint64_t size)
1345 {
1346 zio_data_buf_free(buf, size);
1347 ASSERT(arc_size >= size);
1348 atomic_add_64(&arc_size, -size);
1349 }
1350
1351 arc_buf_t *
1352 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1353 {
1354 arc_buf_hdr_t *hdr;
1355 arc_buf_t *buf;
1356
1357 ASSERT3U(size, >, 0);
1358 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1359 ASSERT(BUF_EMPTY(hdr));
1360 hdr->b_size = size;
1361 hdr->b_type = type;
1362 hdr->b_spa = spa_load_guid(spa);
1363 hdr->b_state = arc_anon;
1364 hdr->b_arc_access = 0;
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 = NULL;
1371 hdr->b_buf = buf;
1372 arc_get_data_buf(buf);
1373 hdr->b_datacnt = 1;
1374 hdr->b_flags = 0;
1375 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1376 (void) refcount_add(&hdr->b_refcnt, tag);
1377
1378 return (buf);
1379 }
1380
1381 static char *arc_onloan_tag = "onloan";
1382
1383 /*
1384 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1385 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1386 * buffers must be returned to the arc before they can be used by the DMU or
1387 * freed.
1388 */
1389 arc_buf_t *
1390 arc_loan_buf(spa_t *spa, int size)
1391 {
1392 arc_buf_t *buf;
1393
1394 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1395
1396 atomic_add_64(&arc_loaned_bytes, size);
1397 return (buf);
1398 }
1399
1400 /*
1401 * Return a loaned arc buffer to the arc.
1402 */
1403 void
1404 arc_return_buf(arc_buf_t *buf, void *tag)
1405 {
1406 arc_buf_hdr_t *hdr = buf->b_hdr;
1407
1408 ASSERT(buf->b_data != NULL);
1409 (void) refcount_add(&hdr->b_refcnt, tag);
1410 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1411
1412 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1413 }
1414
1415 /* Detach an arc_buf from a dbuf (tag) */
1416 void
1417 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1418 {
1419 arc_buf_hdr_t *hdr;
1420
1421 ASSERT(buf->b_data != NULL);
1422 hdr = buf->b_hdr;
1423 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1424 (void) refcount_remove(&hdr->b_refcnt, tag);
1425 buf->b_efunc = NULL;
1426 buf->b_private = NULL;
1427
1428 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1429 }
1430
1431 static arc_buf_t *
1432 arc_buf_clone(arc_buf_t *from)
1433 {
1434 arc_buf_t *buf;
1435 arc_buf_hdr_t *hdr = from->b_hdr;
1436 uint64_t size = hdr->b_size;
1437
1438 ASSERT(hdr->b_state != arc_anon);
1439
1440 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1441 buf->b_hdr = hdr;
1442 buf->b_data = NULL;
1443 buf->b_efunc = NULL;
1444 buf->b_private = NULL;
1445 buf->b_next = hdr->b_buf;
1446 hdr->b_buf = buf;
1447 arc_get_data_buf(buf);
1448 bcopy(from->b_data, buf->b_data, size);
1449
1450 /*
1451 * This buffer already exists in the arc so create a duplicate
1452 * copy for the caller. If the buffer is associated with user data
1453 * then track the size and number of duplicates. These stats will be
1454 * updated as duplicate buffers are created and destroyed.
1455 */
1456 if (hdr->b_type == ARC_BUFC_DATA) {
1457 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1458 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1459 }
1460 hdr->b_datacnt += 1;
1461 return (buf);
1462 }
1463
1464 void
1465 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1466 {
1467 arc_buf_hdr_t *hdr;
1468 kmutex_t *hash_lock;
1469
1470 /*
1471 * Check to see if this buffer is evicted. Callers
1472 * must verify b_data != NULL to know if the add_ref
1473 * was successful.
1474 */
1475 mutex_enter(&buf->b_evict_lock);
1476 if (buf->b_data == NULL) {
1477 mutex_exit(&buf->b_evict_lock);
1478 return;
1479 }
1480 hash_lock = HDR_LOCK(buf->b_hdr);
1481 mutex_enter(hash_lock);
1482 hdr = buf->b_hdr;
1483 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1484 mutex_exit(&buf->b_evict_lock);
1485
1486 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1487 add_reference(hdr, hash_lock, tag);
1488 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1489 arc_access(hdr, hash_lock);
1490 mutex_exit(hash_lock);
1491 ARCSTAT_BUMP(arcstat_hits);
1492 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1493 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1494 data, metadata, hits);
1495 }
1496
1497 /*
1498 * Free the arc data buffer. If it is an l2arc write in progress,
1499 * the buffer is placed on l2arc_free_on_write to be freed later.
1500 */
1501 static void
1502 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1503 {
1504 arc_buf_hdr_t *hdr = buf->b_hdr;
1505
1506 if (HDR_L2_WRITING(hdr)) {
1507 l2arc_data_free_t *df;
1508 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1509 df->l2df_data = buf->b_data;
1510 df->l2df_size = hdr->b_size;
1511 df->l2df_func = free_func;
1512 mutex_enter(&l2arc_free_on_write_mtx);
1513 list_insert_head(l2arc_free_on_write, df);
1514 mutex_exit(&l2arc_free_on_write_mtx);
1515 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1516 } else {
1517 free_func(buf->b_data, hdr->b_size);
1518 }
1519 }
1520
1521 /*
1522 * Free up buf->b_data and if 'remove' is set, then pull the
1523 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
1524 */
1525 static void
1526 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
1527 {
1528 arc_buf_t **bufp;
1529
1530 /* free up data associated with the buf */
1531 if (buf->b_data) {
1532 arc_state_t *state = buf->b_hdr->b_state;
1533 uint64_t size = buf->b_hdr->b_size;
1534 arc_buf_contents_t type = buf->b_hdr->b_type;
1535
1536 arc_cksum_verify(buf);
1537 arc_buf_unwatch(buf);
1538
1539 if (!recycle) {
1540 if (type == ARC_BUFC_METADATA) {
1541 arc_buf_data_free(buf, zio_buf_free);
1542 arc_space_return(size, ARC_SPACE_DATA);
1543 } else {
1544 ASSERT(type == ARC_BUFC_DATA);
1545 arc_buf_data_free(buf, zio_data_buf_free);
1546 ARCSTAT_INCR(arcstat_data_size, -size);
1547 atomic_add_64(&arc_size, -size);
1548 }
1549 }
1550 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1551 uint64_t *cnt = &state->arcs_lsize[type];
1552
1553 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1554 ASSERT(state != arc_anon);
1555
1556 ASSERT3U(*cnt, >=, size);
1557 atomic_add_64(cnt, -size);
1558 }
1559 ASSERT3U(state->arcs_size, >=, size);
1560 atomic_add_64(&state->arcs_size, -size);
1561 buf->b_data = NULL;
1562
1563 /*
1564 * If we're destroying a duplicate buffer make sure
1565 * that the appropriate statistics are updated.
1566 */
1567 if (buf->b_hdr->b_datacnt > 1 &&
1568 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1569 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1570 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1571 }
1572 ASSERT(buf->b_hdr->b_datacnt > 0);
1573 buf->b_hdr->b_datacnt -= 1;
1574 }
1575
1576 /* only remove the buf if requested */
1577 if (!remove)
1578 return;
1579
1580 /* remove the buf from the hdr list */
1581 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1582 continue;
1583 *bufp = buf->b_next;
1584 buf->b_next = NULL;
1585
1586 ASSERT(buf->b_efunc == NULL);
1587
1588 /* clean up the buf */
1589 buf->b_hdr = NULL;
1590 kmem_cache_free(buf_cache, buf);
1591 }
1592
1593 static void
1594 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1595 {
1596 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1597 ASSERT3P(hdr->b_state, ==, arc_anon);
1598 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1599 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1600
1601 if (l2hdr != NULL) {
1602 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1603 /*
1604 * To prevent arc_free() and l2arc_evict() from
1605 * attempting to free the same buffer at the same time,
1606 * a FREE_IN_PROGRESS flag is given to arc_free() to
1607 * give it priority. l2arc_evict() can't destroy this
1608 * header while we are waiting on l2arc_buflist_mtx.
1609 *
1610 * The hdr may be removed from l2ad_buflist before we
1611 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1612 */
1613 if (!buflist_held) {
1614 mutex_enter(&l2arc_buflist_mtx);
1615 l2hdr = hdr->b_l2hdr;
1616 }
1617
1618 if (l2hdr != NULL) {
1619 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1620 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1621 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
1622 if (l2hdr->b_dev->l2ad_vdev)
1623 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
1624 -l2hdr->b_asize, 0, 0);
1625 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1626 if (hdr->b_state == arc_l2c_only)
1627 l2arc_hdr_stat_remove();
1628 hdr->b_l2hdr = NULL;
1629 }
1630
1631 if (!buflist_held)
1632 mutex_exit(&l2arc_buflist_mtx);
1633 }
1634
1635 if (!BUF_EMPTY(hdr)) {
1636 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1637 buf_discard_identity(hdr);
1638 }
1639 while (hdr->b_buf) {
1640 arc_buf_t *buf = hdr->b_buf;
1641
1642 if (buf->b_efunc) {
1643 mutex_enter(&arc_eviction_mtx);
1644 mutex_enter(&buf->b_evict_lock);
1645 ASSERT(buf->b_hdr != NULL);
1646 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1647 hdr->b_buf = buf->b_next;
1648 buf->b_hdr = &arc_eviction_hdr;
1649 buf->b_next = arc_eviction_list;
1650 arc_eviction_list = buf;
1651 mutex_exit(&buf->b_evict_lock);
1652 mutex_exit(&arc_eviction_mtx);
1653 } else {
1654 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1655 }
1656 }
1657 if (hdr->b_freeze_cksum != NULL) {
1658 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1659 hdr->b_freeze_cksum = NULL;
1660 }
1661 if (hdr->b_thawed) {
1662 kmem_free(hdr->b_thawed, 1);
1663 hdr->b_thawed = NULL;
1664 }
1665
1666 ASSERT(!list_link_active(&hdr->b_arc_node));
1667 ASSERT3P(hdr->b_hash_next, ==, NULL);
1668 ASSERT3P(hdr->b_acb, ==, NULL);
1669 kmem_cache_free(hdr_cache, hdr);
1670 }
1671
1672 void
1673 arc_buf_free(arc_buf_t *buf, void *tag)
1674 {
1675 arc_buf_hdr_t *hdr = buf->b_hdr;
1676 int hashed = hdr->b_state != arc_anon;
1677
1678 ASSERT(buf->b_efunc == NULL);
1679 ASSERT(buf->b_data != NULL);
1680
1681 if (hashed) {
1682 kmutex_t *hash_lock = HDR_LOCK(hdr);
1683
1684 mutex_enter(hash_lock);
1685 hdr = buf->b_hdr;
1686 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1687
1688 (void) remove_reference(hdr, hash_lock, tag);
1689 if (hdr->b_datacnt > 1) {
1690 arc_buf_destroy(buf, FALSE, TRUE);
1691 } else {
1692 ASSERT(buf == hdr->b_buf);
1693 ASSERT(buf->b_efunc == NULL);
1694 hdr->b_flags |= ARC_BUF_AVAILABLE;
1695 }
1696 mutex_exit(hash_lock);
1697 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1698 int destroy_hdr;
1699 /*
1700 * We are in the middle of an async write. Don't destroy
1701 * this buffer unless the write completes before we finish
1702 * decrementing the reference count.
1703 */
1704 mutex_enter(&arc_eviction_mtx);
1705 (void) remove_reference(hdr, NULL, tag);
1706 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1707 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1708 mutex_exit(&arc_eviction_mtx);
1709 if (destroy_hdr)
1710 arc_hdr_destroy(hdr);
1711 } else {
1712 if (remove_reference(hdr, NULL, tag) > 0)
1713 arc_buf_destroy(buf, FALSE, TRUE);
1714 else
1715 arc_hdr_destroy(hdr);
1716 }
1717 }
1718
1719 boolean_t
1720 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1721 {
1722 arc_buf_hdr_t *hdr = buf->b_hdr;
1723 kmutex_t *hash_lock = HDR_LOCK(hdr);
1724 boolean_t no_callback = (buf->b_efunc == NULL);
1725
1726 if (hdr->b_state == arc_anon) {
1727 ASSERT(hdr->b_datacnt == 1);
1728 arc_buf_free(buf, tag);
1729 return (no_callback);
1730 }
1731
1732 mutex_enter(hash_lock);
1733 hdr = buf->b_hdr;
1734 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1735 ASSERT(hdr->b_state != arc_anon);
1736 ASSERT(buf->b_data != NULL);
1737
1738 (void) remove_reference(hdr, hash_lock, tag);
1739 if (hdr->b_datacnt > 1) {
1740 if (no_callback)
1741 arc_buf_destroy(buf, FALSE, TRUE);
1742 } else if (no_callback) {
1743 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1744 ASSERT(buf->b_efunc == NULL);
1745 hdr->b_flags |= ARC_BUF_AVAILABLE;
1746 }
1747 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1748 refcount_is_zero(&hdr->b_refcnt));
1749 mutex_exit(hash_lock);
1750 return (no_callback);
1751 }
1752
1753 int
1754 arc_buf_size(arc_buf_t *buf)
1755 {
1756 return (buf->b_hdr->b_size);
1757 }
1758
1759 /*
1760 * Called from the DMU to determine if the current buffer should be
1761 * evicted. In order to ensure proper locking, the eviction must be initiated
1762 * from the DMU. Return true if the buffer is associated with user data and
1763 * duplicate buffers still exist.
1764 */
1765 boolean_t
1766 arc_buf_eviction_needed(arc_buf_t *buf)
1767 {
1768 arc_buf_hdr_t *hdr;
1769 boolean_t evict_needed = B_FALSE;
1770
1771 if (zfs_disable_dup_eviction)
1772 return (B_FALSE);
1773
1774 mutex_enter(&buf->b_evict_lock);
1775 hdr = buf->b_hdr;
1776 if (hdr == NULL) {
1777 /*
1778 * We are in arc_do_user_evicts(); let that function
1779 * perform the eviction.
1780 */
1781 ASSERT(buf->b_data == NULL);
1782 mutex_exit(&buf->b_evict_lock);
1783 return (B_FALSE);
1784 } else if (buf->b_data == NULL) {
1785 /*
1786 * We have already been added to the arc eviction list;
1787 * recommend eviction.
1788 */
1789 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1790 mutex_exit(&buf->b_evict_lock);
1791 return (B_TRUE);
1792 }
1793
1794 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1795 evict_needed = B_TRUE;
1796
1797 mutex_exit(&buf->b_evict_lock);
1798 return (evict_needed);
1799 }
1800
1801 int zfs_fastflush = 1;
1802
1803 /*
1804 * Evict buffers from list until we've removed the specified number of
1805 * bytes. Move the removed buffers to the appropriate evict state.
1806 * If the recycle flag is set, then attempt to "recycle" a buffer:
1807 * - look for a buffer to evict that is `bytes' long.
1808 * - return the data block from this buffer rather than freeing it.
1809 * This flag is used by callers that are trying to make space for a
1810 * new buffer in a full arc cache.
1811 *
1812 * This function makes a "best effort". It skips over any buffers
1813 * it can't get a hash_lock on, and so may not catch all candidates.
1814 * It may also return without evicting as much space as requested.
1815 */
1816 static void *
1817 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1818 arc_buf_contents_t type)
1819 {
1820 arc_state_t *evicted_state;
1821 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1822 arc_buf_hdr_t *ab, *ab_prev = NULL;
1823 list_t *list = &state->arcs_list[type];
1824 kmutex_t *hash_lock;
1825 boolean_t have_lock;
1826 void *stolen = NULL;
1827 arc_buf_hdr_t marker = { 0 };
1828 int count = 0;
1829
1830 ASSERT(state == arc_mru || state == arc_mfu);
1831
1832 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1833
1834 mutex_enter(&state->arcs_mtx);
1835 mutex_enter(&evicted_state->arcs_mtx);
1836
1837 for (ab = list_tail(list); ab; ab = ab_prev) {
1838 ab_prev = list_prev(list, ab);
1839 /* prefetch buffers have a minimum lifespan */
1840 if (HDR_IO_IN_PROGRESS(ab) ||
1841 (spa && ab->b_spa != spa) ||
1842 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1843 ddi_get_lbolt() - ab->b_arc_access <
1844 arc_min_prefetch_lifespan)) {
1845 skipped++;
1846 continue;
1847 }
1848 /* "lookahead" for better eviction candidate */
1849 if (recycle && ab->b_size != bytes &&
1850 ab_prev && ab_prev->b_size == bytes)
1851 continue;
1852
1853 /* ignore markers */
1854 if (ab->b_spa == 0)
1855 continue;
1856
1857 /*
1858 * It may take a long time to evict all the bufs requested.
1859 * To avoid blocking all arc activity, periodically drop
1860 * the arcs_mtx and give other threads a chance to run
1861 * before reacquiring the lock.
1862 *
1863 * If we are looking for a buffer to recycle, we are in
1864 * the hot code path, so don't sleep.
1865 */
1866 if (!recycle && count++ > arc_evict_iterations) {
1867 list_insert_after(list, ab, &marker);
1868 mutex_exit(&evicted_state->arcs_mtx);
1869 mutex_exit(&state->arcs_mtx);
1870 kpreempt(KPREEMPT_SYNC);
1871 mutex_enter(&state->arcs_mtx);
1872 mutex_enter(&evicted_state->arcs_mtx);
1873 ab_prev = list_prev(list, &marker);
1874 list_remove(list, &marker);
1875 count = 0;
1876 continue;
1877 }
1878
1879 hash_lock = HDR_LOCK(ab);
1880 have_lock = MUTEX_HELD(hash_lock);
1881 if (have_lock || mutex_tryenter(hash_lock)) {
1882 ASSERT0(refcount_count(&ab->b_refcnt));
1883 ASSERT(ab->b_datacnt > 0);
1884 while (ab->b_buf) {
1885 arc_buf_t *buf = ab->b_buf;
1886 if (!mutex_tryenter(&buf->b_evict_lock)) {
1887 missed += 1;
1888 break;
1889 }
1890 if (buf->b_data) {
1891 bytes_evicted += ab->b_size;
1892 if (recycle && ab->b_type == type &&
1893 ab->b_size == bytes &&
1894 !HDR_L2_WRITING(ab)) {
1895 stolen = buf->b_data;
1896 recycle = FALSE;
1897 }
1898 }
1899 if (buf->b_efunc) {
1900 mutex_enter(&arc_eviction_mtx);
1901 arc_buf_destroy(buf,
1902 buf->b_data == stolen, FALSE);
1903 ab->b_buf = buf->b_next;
1904 buf->b_hdr = &arc_eviction_hdr;
1905 buf->b_next = arc_eviction_list;
1906 arc_eviction_list = buf;
1907 mutex_exit(&arc_eviction_mtx);
1908 mutex_exit(&buf->b_evict_lock);
1909 } else {
1910 mutex_exit(&buf->b_evict_lock);
1911 arc_buf_destroy(buf,
1912 buf->b_data == stolen, TRUE);
1913 }
1914 }
1915
1916 if (ab->b_l2hdr) {
1917 ARCSTAT_INCR(arcstat_evict_l2_cached,
1918 ab->b_size);
1919 } else {
1920 if (l2arc_write_eligible(ab->b_spa, ab)) {
1921 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1922 ab->b_size);
1923 } else {
1924 ARCSTAT_INCR(
1925 arcstat_evict_l2_ineligible,
1926 ab->b_size);
1927 }
1928 }
1929
1930 if (ab->b_datacnt == 0) {
1931 arc_change_state(evicted_state, ab, hash_lock);
1932 ASSERT(HDR_IN_HASH_TABLE(ab));
1933 ab->b_flags |= ARC_IN_HASH_TABLE;
1934 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1935 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1936 }
1937 if (!have_lock)
1938 mutex_exit(hash_lock);
1939 if (bytes >= 0 && bytes_evicted >= bytes)
1940 break;
1941 } else {
1942 missed += 1;
1943 }
1944 }
1945
1946 mutex_exit(&evicted_state->arcs_mtx);
1947 mutex_exit(&state->arcs_mtx);
1948
1949 if (bytes_evicted < bytes)
1950 dprintf("only evicted %lld bytes from %x",
1951 (longlong_t)bytes_evicted, state);
1952
1953 if (skipped)
1954 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1955
1956 if (missed)
1957 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1958
1959 /*
1960 * Note: we have just evicted some data into the ghost state,
1961 * potentially putting the ghost size over the desired size. Rather
1962 * that evicting from the ghost list in this hot code path, leave
1963 * this chore to the arc_reclaim_thread().
1964 */
1965
1966 return (stolen);
1967 }
1968
1969 /*
1970 * Remove buffers from list until we've removed the specified number of
1971 * bytes. Destroy the buffers that are removed.
1972 */
1973 static void
1974 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1975 {
1976 arc_buf_hdr_t *ab, *ab_prev;
1977 arc_buf_hdr_t marker = { 0 };
1978 list_t *list = &state->arcs_list[ARC_BUFC_DATA];
1979 kmutex_t *hash_lock;
1980 uint64_t bytes_deleted = 0;
1981 uint64_t bufs_skipped = 0;
1982 int count = 0;
1983
1984 ASSERT(GHOST_STATE(state));
1985 top:
1986 mutex_enter(&state->arcs_mtx);
1987 for (ab = list_tail(list); ab; ab = ab_prev) {
1988 ab_prev = list_prev(list, ab);
1989 if (ab->b_type > ARC_BUFC_NUMTYPES)
1990 panic("invalid ab=%p", (void *)ab);
1991 if (spa && ab->b_spa != spa)
1992 continue;
1993
1994 /* ignore markers */
1995 if (ab->b_spa == 0)
1996 continue;
1997
1998 hash_lock = HDR_LOCK(ab);
1999 /* caller may be trying to modify this buffer, skip it */
2000 if (MUTEX_HELD(hash_lock))
2001 continue;
2002
2003 /*
2004 * It may take a long time to evict all the bufs requested.
2005 * To avoid blocking all arc activity, periodically drop
2006 * the arcs_mtx and give other threads a chance to run
2007 * before reacquiring the lock.
2008 */
2009 if (count++ > arc_evict_iterations) {
2010 list_insert_after(list, ab, &marker);
2011 mutex_exit(&state->arcs_mtx);
2012 kpreempt(KPREEMPT_SYNC);
2013 mutex_enter(&state->arcs_mtx);
2014 ab_prev = list_prev(list, &marker);
2015 list_remove(list, &marker);
2016 count = 0;
2017 continue;
2018 }
2019 if (mutex_tryenter(hash_lock)) {
2020 ASSERT(!HDR_IO_IN_PROGRESS(ab));
2021 ASSERT(ab->b_buf == NULL);
2022 ARCSTAT_BUMP(arcstat_deleted);
2023 bytes_deleted += ab->b_size;
2024
2025 if (ab->b_l2hdr != NULL) {
2026 /*
2027 * This buffer is cached on the 2nd Level ARC;
2028 * don't destroy the header.
2029 */
2030 arc_change_state(arc_l2c_only, ab, hash_lock);
2031 mutex_exit(hash_lock);
2032 } else {
2033 arc_change_state(arc_anon, ab, hash_lock);
2034 mutex_exit(hash_lock);
2035 arc_hdr_destroy(ab);
2036 }
2037
2038 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
2039 if (bytes >= 0 && bytes_deleted >= bytes)
2040 break;
2041 } else if (bytes < 0) {
2042 /*
2043 * Insert a list marker and then wait for the
2044 * hash lock to become available. Once its
2045 * available, restart from where we left off.
2046 */
2047 list_insert_after(list, ab, &marker);
2048 mutex_exit(&state->arcs_mtx);
2049 mutex_enter(hash_lock);
2050 mutex_exit(hash_lock);
2051 mutex_enter(&state->arcs_mtx);
2052 ab_prev = list_prev(list, &marker);
2053 list_remove(list, &marker);
2054 } else {
2055 bufs_skipped += 1;
2056 }
2057
2058 }
2059 mutex_exit(&state->arcs_mtx);
2060
2061 if (list == &state->arcs_list[ARC_BUFC_DATA] &&
2062 (bytes < 0 || bytes_deleted < bytes)) {
2063 list = &state->arcs_list[ARC_BUFC_METADATA];
2064 goto top;
2065 }
2066
2067 if (bufs_skipped) {
2068 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
2069 ASSERT(bytes >= 0);
2070 }
2071
2072 if (bytes_deleted < bytes)
2073 dprintf("only deleted %lld bytes from %p",
2074 (longlong_t)bytes_deleted, state);
2075 }
2076
2077 static void
2078 arc_adjust(void)
2079 {
2080 int64_t adjustment, delta;
2081
2082 /*
2083 * Adjust MRU size
2084 */
2085
2086 adjustment = MIN((int64_t)(arc_size - arc_c),
2087 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
2088 arc_p));
2089
2090 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
2091 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
2092 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
2093 adjustment -= delta;
2094 }
2095
2096 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2097 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
2098 (void) arc_evict(arc_mru, NULL, delta, FALSE,
2099 ARC_BUFC_METADATA);
2100 }
2101
2102 /*
2103 * Adjust MFU size
2104 */
2105
2106 adjustment = arc_size - arc_c;
2107
2108 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
2109 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
2110 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
2111 adjustment -= delta;
2112 }
2113
2114 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
2115 int64_t delta = MIN(adjustment,
2116 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
2117 (void) arc_evict(arc_mfu, NULL, delta, FALSE,
2118 ARC_BUFC_METADATA);
2119 }
2120
2121 /*
2122 * Adjust ghost lists
2123 */
2124
2125 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2126
2127 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2128 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2129 arc_evict_ghost(arc_mru_ghost, NULL, delta);
2130 }
2131
2132 adjustment =
2133 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2134
2135 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2136 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2137 arc_evict_ghost(arc_mfu_ghost, NULL, delta);
2138 }
2139 }
2140
2141 #define ACCURACY 1000
2142
2143 static void
2144 arc_reclaim_bytes(uint64_t to_evict)
2145 {
2146 uint64_t to_evict_data_mru, to_evict_data_mfu;
2147 uint64_t to_evict_meta_mru, to_evict_meta_mfu;
2148
2149 to_evict_meta_mru = (((arc_mru->arcs_lsize[ARC_BUFC_METADATA] *
2150 ACCURACY) / (arc_mru->arcs_size + arc_mfu->arcs_size)) *
2151 to_evict) / ACCURACY;
2152 to_evict_data_mru = (((arc_mru->arcs_lsize[ARC_BUFC_DATA] *
2153 ACCURACY) / (arc_mru->arcs_size + arc_mfu->arcs_size)) *
2154 to_evict) / ACCURACY;
2155 to_evict_meta_mfu = (((arc_mfu->arcs_lsize[ARC_BUFC_METADATA] *
2156 ACCURACY) / (arc_mru->arcs_size + arc_mfu->arcs_size)) *
2157 to_evict) / ACCURACY;
2158 to_evict_data_mfu = (((arc_mfu->arcs_lsize[ARC_BUFC_DATA] *
2159 ACCURACY) / (arc_mru->arcs_size + arc_mfu->arcs_size)) *
2160 to_evict) / ACCURACY;
2161
2162 if (to_evict_meta_mru > 0)
2163 (void) arc_evict(arc_mru, NULL, to_evict_meta_mru, FALSE,
2164 ARC_BUFC_METADATA);
2165 if (to_evict_data_mru > 0)
2166 (void) arc_evict(arc_mru, NULL, to_evict_data_mru, FALSE,
2167 ARC_BUFC_DATA);
2168 if (to_evict_meta_mfu > 0)
2169 (void) arc_evict(arc_mfu, NULL, to_evict_meta_mfu, FALSE,
2170 ARC_BUFC_METADATA);
2171 if (to_evict_data_mfu > 0)
2172 (void) arc_evict(arc_mfu, NULL, to_evict_data_mfu, FALSE,
2173 ARC_BUFC_DATA);
2174 }
2175
2176 static void
2177 arc_do_user_evicts(void)
2178 {
2179 mutex_enter(&arc_eviction_mtx);
2180 while (arc_eviction_list != NULL) {
2181 arc_buf_t *buf = arc_eviction_list;
2182 arc_eviction_list = buf->b_next;
2183 mutex_enter(&buf->b_evict_lock);
2184 buf->b_hdr = NULL;
2185 mutex_exit(&buf->b_evict_lock);
2186 mutex_exit(&arc_eviction_mtx);
2187
2188 if (buf->b_efunc != NULL)
2189 VERIFY0(buf->b_efunc(buf->b_private));
2190
2191 buf->b_efunc = NULL;
2192 buf->b_private = NULL;
2193 kmem_cache_free(buf_cache, buf);
2194 mutex_enter(&arc_eviction_mtx);
2195 }
2196 mutex_exit(&arc_eviction_mtx);
2197 }
2198
2199 typedef struct arc_async_flush_data {
2200 uint64_t aaf_guid;
2201 } arc_async_flush_data_t;
2202
2203 static taskq_t *arc_flush_taskq;
2204
2205 static void
2206 _arc_flush(uint64_t guid)
2207 {
2208 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
2209 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2210 if (guid)
2211 break;
2212 }
2213 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
2214 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2215 if (guid)
2216 break;
2217 }
2218 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
2219 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2220 if (guid)
2221 break;
2222 }
2223 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
2224 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2225 if (guid)
2226 break;
2227 }
2228
2229 arc_evict_ghost(arc_mru_ghost, guid, -1);
2230 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2231
2232 mutex_enter(&arc_reclaim_thr_lock);
2233 arc_do_user_evicts();
2234 mutex_exit(&arc_reclaim_thr_lock);
2235 }
2236
2237 static void
2238 arc_flush_task(void *arg)
2239 {
2240 arc_async_flush_data_t *aaf = (arc_async_flush_data_t *)arg;
2241 _arc_flush(aaf->aaf_guid);
2242 kmem_free(aaf, sizeof (arc_async_flush_data_t));
2243 }
2244
2245 /*
2246 * Flush all *evictable* data from the cache for the given spa.
2247 * NOTE: this will not touch "active" (i.e. referenced) data.
2248 */
2249 void
2250 arc_flush(spa_t *spa)
2251 {
2252 uint64_t guid = 0;
2253 boolean_t async_flush = (spa ? zfs_fastflush : FALSE);
2254 arc_async_flush_data_t *aaf = NULL;
2255
2256 if (spa) {
2257 guid = spa_load_guid(spa);
2258 if (async_flush) {
2259 aaf = kmem_alloc(sizeof (arc_async_flush_data_t),
2260 KM_SLEEP);
2261 aaf->aaf_guid = guid;
2262 }
2263 }
2264
2265 /*
2266 * Try to flush per-spa remaining ARC ghost buffers and buffers in
2267 * arc_eviction_list asynchronously while a pool is being closed.
2268 * An ARC buffer is bound to spa only by guid, so buffer can
2269 * exist even when pool has already gone. If asynchronous flushing
2270 * fails we fall back to regular (synchronous) one.
2271 * NOTE: If asynchronous flushing had not yet finished when the pool
2272 * was imported again it wouldn't be a problem, even when guids before
2273 * and after export/import are the same. We can evict only unreferenced
2274 * buffers, other are skipped.
2275 */
2276 if (!async_flush || (taskq_dispatch(arc_flush_taskq, arc_flush_task,
2277 aaf, TQ_NOSLEEP) == NULL)) {
2278 _arc_flush(guid);
2279 ASSERT(spa || arc_eviction_list == NULL);
2280 if (async_flush)
2281 kmem_free(aaf, sizeof (arc_async_flush_data_t));
2282 }
2283 }
2284
2285 void
2286 arc_shrink(void)
2287 {
2288 if (arc_c > arc_c_min) {
2289 uint64_t to_free;
2290
2291 #ifdef _KERNEL
2292 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
2293 #else
2294 to_free = arc_c >> arc_shrink_shift;
2295 #endif
2296 if (arc_c > arc_c_min + to_free)
2297 atomic_add_64(&arc_c, -to_free);
2298 else
2299 arc_c = arc_c_min;
2300
2301 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2302 if (arc_c > arc_size)
2303 arc_c = MAX(arc_size, arc_c_min);
2304 if (arc_p > arc_c)
2305 arc_p = (arc_c >> 1);
2306 ASSERT(arc_c >= arc_c_min);
2307 ASSERT((int64_t)arc_p >= 0);
2308 }
2309
2310 if (arc_size > arc_c)
2311 arc_adjust();
2312 }
2313
2314 #define PHYSMEM_PRESSURE_FRACTION 100
2315
2316 static boolean_t
2317 arc_mem_pressure(void)
2318 {
2319 #ifdef _KERNEL
2320 uint64_t extra = desfree + physmem / PHYSMEM_PRESSURE_FRACTION;
2321
2322 if ((freemem < lotsfree + needfree + extra) ||
2323 (needfree || availrmem < swapfs_minfree + swapfs_reserve + extra) ||
2324 (zio_arena != NULL && vmem_size(zio_arena, VMEM_FREE) <
2325 (vmem_size(zio_arena, VMEM_ALLOC) >> 4) +
2326 physmem / PHYSMEM_PRESSURE_FRACTION))
2327 return (B_TRUE);
2328
2329 return (freemem < physmem / PHYSMEM_PRESSURE_FRACTION);
2330 #else
2331 return (0);
2332 #endif
2333 }
2334
2335 /*
2336 * Determine if the system is under memory pressure and is asking
2337 * to reclaim memory. A return value of 1 indicates that the system
2338 * is under memory pressure and that the arc should adjust accordingly.
2339 */
2340 static int
2341 arc_reclaim_needed(void)
2342 {
2343 uint64_t extra;
2344
2345 #ifdef _KERNEL
2346
2347 if (needfree)
2348 return (1);
2349
2350 /*
2351 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2352 */
2353 extra = desfree;
2354
2355 /*
2356 * check that we're out of range of the pageout scanner. It starts to
2357 * schedule paging if freemem is less than lotsfree and needfree.
2358 * lotsfree is the high-water mark for pageout, and needfree is the
2359 * number of needed free pages. We add extra pages here to make sure
2360 * the scanner doesn't start up while we're freeing memory.
2361 */
2362 if (freemem < lotsfree + needfree + extra)
2363 return (1);
2364
2365 /*
2366 * check to make sure that swapfs has enough space so that anon
2367 * reservations can still succeed. anon_resvmem() checks that the
2368 * availrmem is greater than swapfs_minfree, and the number of reserved
2369 * swap pages. We also add a bit of extra here just to prevent
2370 * circumstances from getting really dire.
2371 */
2372 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2373 return (1);
2374
2375 /*
2376 * Check that we have enough availrmem that memory locking (e.g., via
2377 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
2378 * stores the number of pages that cannot be locked; when availrmem
2379 * drops below pages_pp_maximum, page locking mechanisms such as
2380 * page_pp_lock() will fail.)
2381 */
2382 if (availrmem <= pages_pp_maximum)
2383 return (1);
2384
2385 #if defined(__i386)
2386 /*
2387 * If we're on an i386 platform, it's possible that we'll exhaust the
2388 * kernel heap space before we ever run out of available physical
2389 * memory. Most checks of the size of the heap_area compare against
2390 * tune.t_minarmem, which is the minimum available real memory that we
2391 * can have in the system. However, this is generally fixed at 25 pages
2392 * which is so low that it's useless. In this comparison, we seek to
2393 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2394 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2395 * free)
2396 */
2397 if (vmem_size(heap_arena, VMEM_FREE) <
2398 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2))
2399 return (1);
2400 #endif
2401
2402 /*
2403 * If zio data pages are being allocated out of a separate heap segment,
2404 * then enforce that the size of available vmem for this arena remains
2405 * above about 1/16th free.
2406 *
2407 * Note: The 1/16th arena free requirement was put in place
2408 * to aggressively evict memory from the arc in order to avoid
2409 * memory fragmentation issues.
2410 */
2411 if (zio_arena != NULL &&
2412 vmem_size(zio_arena, VMEM_FREE) <
2413 (vmem_size(zio_arena, VMEM_ALLOC) >> 4))
2414 return (1);
2415 #else
2416 if (spa_get_random(100) == 0)
2417 return (1);
2418 #endif
2419 return (0);
2420 }
2421
2422 static void
2423 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2424 {
2425 size_t i;
2426 kmem_cache_t *prev_cache = NULL;
2427 kmem_cache_t *prev_data_cache = NULL;
2428 extern kmem_cache_t *zio_buf_cache[];
2429 extern kmem_cache_t *zio_data_buf_cache[];
2430 extern kmem_cache_t *range_seg_cache;
2431
2432 #ifdef _KERNEL
2433 if (arc_meta_used >= arc_meta_limit) {
2434 /*
2435 * We are exceeding our meta-data cache limit.
2436 * Purge some DNLC entries to release holds on meta-data.
2437 */
2438 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2439 }
2440 #if defined(__i386)
2441 /*
2442 * Reclaim unused memory from all kmem caches.
2443 */
2444 kmem_reap();
2445 #endif
2446 #endif
2447
2448 /*
2449 * An aggressive reclamation will shrink the cache size as well as
2450 * reap free buffers from the arc kmem caches.
2451 */
2452 if (strat == ARC_RECLAIM_AGGR)
2453 arc_shrink();
2454
2455 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2456 if (zio_buf_cache[i] != prev_cache) {
2457 prev_cache = zio_buf_cache[i];
2458 kmem_cache_reap_now(zio_buf_cache[i]);
2459 }
2460 if (zio_data_buf_cache[i] != prev_data_cache) {
2461 prev_data_cache = zio_data_buf_cache[i];
2462 kmem_cache_reap_now(zio_data_buf_cache[i]);
2463 }
2464 }
2465 kmem_cache_reap_now(buf_cache);
2466 kmem_cache_reap_now(hdr_cache);
2467 kmem_cache_reap_now(range_seg_cache);
2468
2469 /*
2470 * Ask the vmem areana to reclaim unused memory from its
2471 * quantum caches.
2472 */
2473 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
2474 vmem_qcache_reap(zio_arena);
2475 }
2476
2477 #define RECLAIMS_PER_SEC 20
2478 #define STAT_UPDATES_PER_SEC 5
2479
2480 /*
2481 * During heavy use, the ARC naturally wants to oscilate its arc_c around
2482 * a maximum memory pressure point which corresponds to the arc_reclaim_needed
2483 * function evaluating to 1. This results in the arc_size slowly growing
2484 * towards this reclaim_needed threshold and exceeding it periodically. Once
2485 * this happens, both arc_c and arc_size are down-adjusted by the
2486 * arc_reclaim_thread and kmem_reap is initiated. This is problematic on
2487 * bigmem systems with a small recordsize (4k or 8k), because reaping a kmem
2488 * cache which contains very large numbers of objects is extremely expensive
2489 * from an xcall perspective (several seconds of heavy CPU use):
2490 *
2491 * (mem)
2492 * ^ arc_reclaim_thread reacts
2493 * | | |
2494 * | V V
2495 * |
2496 * | + +
2497 * | /| /|
2498 * | ......./..|................/..|.............. arc_reclaim_needed threshold
2499 * | / \_____________/ \___________/(etc)
2500 * | / kmem reap kmem reap
2501 * | /
2502 * |/
2503 * +----------------------------------------------------------------->
2504 * (time)
2505 *
2506 * To help address this stairstep pattern, the arc_pressure_thread periodically
2507 * gauges the distance of the current arc_size to the arc_reclaim_needed
2508 * threshold by way of an estimation algorithm (in arc_mem_pressure).
2509 */
2510 static void
2511 arc_pressure_thread(void)
2512 {
2513 clock_t last_update = ddi_get_lbolt();
2514 callb_cpr_t cpr;
2515
2516 CALLB_CPR_INIT(&cpr, &arc_pressure_thr_lock, callb_generic_cpr, FTAG);
2517
2518 mutex_enter(&arc_pressure_thr_lock);
2519 while (arc_pressure_thread_exit == 0) {
2520 clock_t now;
2521
2522 now = ddi_get_lbolt();
2523 if (now - last_update >= hz / STAT_UPDATES_PER_SEC) {
2524 uint64_t new_rate;
2525
2526 new_rate = (atomic_swap_64(&arc_bytes_allocd, 0) *
2527 hz) / (now - last_update);
2528
2529 if (ARCSTAT(arcstat_growth_rate) < new_rate)
2530 ARCSTAT(arcstat_growth_rate) = new_rate;
2531 else
2532 ARCSTAT_F_AVG(arcstat_growth_rate, new_rate, 4);
2533 last_update = now;
2534 }
2535
2536 arc_pressure_threshold = arc_c - ARCSTAT(arcstat_growth_rate);
2537 if (arc_size > arc_pressure_threshold) {
2538 arc_reclaim_bytes(arc_size - arc_pressure_threshold);
2539 }
2540
2541 CALLB_CPR_SAFE_BEGIN(&cpr);
2542 (void) cv_timedwait(&arc_pressure_thr_cv,
2543 &arc_pressure_thr_lock,
2544 ddi_get_lbolt() + hz / RECLAIMS_PER_SEC);
2545 CALLB_CPR_SAFE_END(&cpr, &arc_pressure_thr_lock);
2546 }
2547
2548 arc_pressure_thread_exit = 0;
2549 cv_broadcast(&arc_pressure_thr_cv);
2550 CALLB_CPR_EXIT(&cpr); /* drops arc_pressure_thr_lock */
2551 thread_exit();
2552 }
2553
2554 static void
2555 arc_reclaim_thread(void)
2556 {
2557 clock_t growtime = 0;
2558 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2559 callb_cpr_t cpr;
2560
2561 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2562
2563 mutex_enter(&arc_reclaim_thr_lock);
2564 while (arc_thread_exit == 0) {
2565 if (arc_reclaim_needed()) {
2566
2567 if (arc_no_grow) {
2568 if (last_reclaim == ARC_RECLAIM_CONS) {
2569 last_reclaim = ARC_RECLAIM_AGGR;
2570 } else {
2571 last_reclaim = ARC_RECLAIM_CONS;
2572 }
2573 } else {
2574 arc_no_grow = TRUE;
2575 last_reclaim = ARC_RECLAIM_AGGR;
2576 membar_producer();
2577 }
2578
2579 /* reset the growth delay for every reclaim */
2580 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2581
2582 arc_kmem_reap_now(last_reclaim);
2583 arc_warm = B_TRUE;
2584
2585 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2586 arc_no_grow = FALSE;
2587 }
2588
2589 arc_adjust();
2590
2591 if (arc_eviction_list != NULL)
2592 arc_do_user_evicts();
2593
2594 /* block until needed, or one second, whichever is shorter */
2595 CALLB_CPR_SAFE_BEGIN(&cpr);
2596 (void) cv_timedwait(&arc_reclaim_thr_cv,
2597 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
2598 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2599 }
2600
2601 arc_thread_exit = 0;
2602 cv_broadcast(&arc_reclaim_thr_cv);
2603 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2604 thread_exit();
2605 }
2606
2607 /*
2608 * Adapt arc info given the number of bytes we are trying to add and
2609 * the state that we are comming from. This function is only called
2610 * when we are adding new content to the cache.
2611 */
2612 static void
2613 arc_adapt(int bytes, arc_state_t *state)
2614 {
2615 int mult;
2616 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2617
2618 if (state == arc_l2c_only)
2619 return;
2620
2621 ASSERT(bytes > 0);
2622 /*
2623 * Adapt the target size of the MRU list:
2624 * - if we just hit in the MRU ghost list, then increase
2625 * the target size of the MRU list.
2626 * - if we just hit in the MFU ghost list, then increase
2627 * the target size of the MFU list by decreasing the
2628 * target size of the MRU list.
2629 */
2630 if (state == arc_mru_ghost) {
2631 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2632 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2633 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2634
2635 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2636 } else if (state == arc_mfu_ghost) {
2637 uint64_t delta;
2638
2639 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2640 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2641 mult = MIN(mult, 10);
2642
2643 delta = MIN(bytes * mult, arc_p);
2644 arc_p = MAX(arc_p_min, arc_p - delta);
2645 }
2646 ASSERT((int64_t)arc_p >= 0);
2647
2648 if (arc_reclaim_needed()) {
2649 cv_signal(&arc_reclaim_thr_cv);
2650 return;
2651 }
2652
2653 if (arc_no_grow)
2654 return;
2655
2656 if (arc_c >= arc_c_max)
2657 return;
2658
2659 /*
2660 * If we're within (2 * maxblocksize) bytes of the target
2661 * cache size, increment the target cache size
2662 */
2663 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT) ||
2664 (arc_size >= arc_pressure_threshold && arc_mem_pressure() == 0)) {
2665 atomic_add_64(&arc_c, (int64_t)bytes);
2666 if (arc_c > arc_c_max)
2667 arc_c = arc_c_max;
2668 else if (state == arc_anon)
2669 atomic_add_64(&arc_p, (int64_t)bytes);
2670 if (arc_p > arc_c)
2671 arc_p = arc_c;
2672 }
2673 ASSERT((int64_t)arc_p >= 0);
2674 }
2675
2676 /*
2677 * Check if the cache has reached its limits and eviction is required
2678 * prior to insert.
2679 */
2680 static int
2681 arc_evict_needed(arc_buf_contents_t type)
2682 {
2683 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2684 return (1);
2685
2686 if (arc_reclaim_needed())
2687 return (1);
2688
2689 return (arc_size > arc_c);
2690 }
2691
2692 /*
2693 * The buffer, supplied as the first argument, needs a data block.
2694 * So, if we are at cache max, determine which cache should be victimized.
2695 * We have the following cases:
2696 *
2697 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2698 * In this situation if we're out of space, but the resident size of the MFU is
2699 * under the limit, victimize the MFU cache to satisfy this insertion request.
2700 *
2701 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2702 * Here, we've used up all of the available space for the MRU, so we need to
2703 * evict from our own cache instead. Evict from the set of resident MRU
2704 * entries.
2705 *
2706 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2707 * c minus p represents the MFU space in the cache, since p is the size of the
2708 * cache that is dedicated to the MRU. In this situation there's still space on
2709 * the MFU side, so the MRU side needs to be victimized.
2710 *
2711 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2712 * MFU's resident set is consuming more space than it has been allotted. In
2713 * this situation, we must victimize our own cache, the MFU, for this insertion.
2714 */
2715 static void
2716 arc_get_data_buf(arc_buf_t *buf)
2717 {
2718 arc_state_t *state = buf->b_hdr->b_state;
2719 uint64_t size = buf->b_hdr->b_size;
2720 arc_buf_contents_t type = buf->b_hdr->b_type;
2721
2722 arc_adapt(size, state);
2723
2724 /*
2725 * We have not yet reached cache maximum size,
2726 * just allocate a new buffer.
2727 */
2728 if (!arc_evict_needed(type)) {
2729 if (type == ARC_BUFC_METADATA) {
2730 buf->b_data = zio_buf_alloc(size);
2731 arc_space_consume(size, ARC_SPACE_DATA);
2732 } else {
2733 ASSERT(type == ARC_BUFC_DATA);
2734 buf->b_data = zio_data_buf_alloc(size);
2735 ARCSTAT_INCR(arcstat_data_size, size);
2736 atomic_add_64(&arc_size, size);
2737 atomic_add_64(&arc_bytes_allocd, size);
2738 }
2739 goto out;
2740 }
2741
2742 /*
2743 * If we are prefetching from the mfu ghost list, this buffer
2744 * will end up on the mru list; so steal space from there.
2745 */
2746 if (state == arc_mfu_ghost)
2747 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2748 else if (state == arc_mru_ghost)
2749 state = arc_mru;
2750
2751 if (state == arc_mru || state == arc_anon) {
2752 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2753 state = (arc_mfu->arcs_lsize[type] >= size &&
2754 arc_p > mru_used) ? arc_mfu : arc_mru;
2755 } else {
2756 /* MFU cases */
2757 uint64_t mfu_space = arc_c - arc_p;
2758 state = (arc_mru->arcs_lsize[type] >= size &&
2759 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2760 }
2761 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
2762 if (type == ARC_BUFC_METADATA) {
2763 buf->b_data = zio_buf_alloc(size);
2764 arc_space_consume(size, ARC_SPACE_DATA);
2765 } else {
2766 ASSERT(type == ARC_BUFC_DATA);
2767 buf->b_data = zio_data_buf_alloc(size);
2768 ARCSTAT_INCR(arcstat_data_size, size);
2769 atomic_add_64(&arc_size, size);
2770 atomic_add_64(&arc_bytes_allocd, size);
2771 }
2772 ARCSTAT_BUMP(arcstat_recycle_miss);
2773 }
2774 ASSERT(buf->b_data != NULL);
2775 out:
2776 /*
2777 * Update the state size. Note that ghost states have a
2778 * "ghost size" and so don't need to be updated.
2779 */
2780 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2781 arc_buf_hdr_t *hdr = buf->b_hdr;
2782
2783 atomic_add_64(&hdr->b_state->arcs_size, size);
2784 if (list_link_active(&hdr->b_arc_node)) {
2785 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2786 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2787 }
2788 /*
2789 * If we are growing the cache, and we are adding anonymous
2790 * data, and we have outgrown arc_p, update arc_p
2791 */
2792 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2793 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2794 arc_p = MIN(arc_c, arc_p + size);
2795 }
2796 }
2797
2798 /*
2799 * This routine is called whenever a buffer is accessed.
2800 * NOTE: the hash lock is dropped in this function.
2801 */
2802 static void
2803 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2804 {
2805 clock_t now;
2806
2807 ASSERT(MUTEX_HELD(hash_lock));
2808
2809 if (buf->b_state == arc_anon) {
2810 /*
2811 * This buffer is not in the cache, and does not
2812 * appear in our "ghost" list. Add the new buffer
2813 * to the MRU state.
2814 */
2815
2816 ASSERT(buf->b_arc_access == 0);
2817 buf->b_arc_access = ddi_get_lbolt();
2818 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2819 arc_change_state(arc_mru, buf, hash_lock);
2820
2821 } else if (buf->b_state == arc_mru) {
2822 now = ddi_get_lbolt();
2823
2824 /*
2825 * If this buffer is here because of a prefetch, then either:
2826 * - clear the flag if this is a "referencing" read
2827 * (any subsequent access will bump this into the MFU state).
2828 * or
2829 * - move the buffer to the head of the list if this is
2830 * another prefetch (to make it less likely to be evicted).
2831 */
2832 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2833 if (refcount_count(&buf->b_refcnt) == 0) {
2834 ASSERT(list_link_active(&buf->b_arc_node));
2835 } else {
2836 buf->b_flags &= ~ARC_PREFETCH;
2837 ARCSTAT_BUMP(arcstat_mru_hits);
2838 }
2839 buf->b_arc_access = now;
2840 return;
2841 }
2842
2843 /*
2844 * This buffer has been "accessed" only once so far,
2845 * but it is still in the cache. Move it to the MFU
2846 * state.
2847 */
2848 if (now > buf->b_arc_access + ARC_MINTIME) {
2849 /*
2850 * More than 125ms have passed since we
2851 * instantiated this buffer. Move it to the
2852 * most frequently used state.
2853 */
2854 buf->b_arc_access = now;
2855 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2856 arc_change_state(arc_mfu, buf, hash_lock);
2857 }
2858 ARCSTAT_BUMP(arcstat_mru_hits);
2859 } else if (buf->b_state == arc_mru_ghost) {
2860 arc_state_t *new_state;
2861 /*
2862 * This buffer has been "accessed" recently, but
2863 * was evicted from the cache. Move it to the
2864 * MFU state.
2865 */
2866
2867 if (buf->b_flags & ARC_PREFETCH) {
2868 new_state = arc_mru;
2869 if (refcount_count(&buf->b_refcnt) > 0)
2870 buf->b_flags &= ~ARC_PREFETCH;
2871 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2872 } else {
2873 new_state = arc_mfu;
2874 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2875 }
2876
2877 buf->b_arc_access = ddi_get_lbolt();
2878 arc_change_state(new_state, buf, hash_lock);
2879
2880 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2881 } else if (buf->b_state == arc_mfu) {
2882 /*
2883 * This buffer has been accessed more than once and is
2884 * still in the cache. Keep it in the MFU state.
2885 *
2886 * NOTE: an add_reference() that occurred when we did
2887 * the arc_read() will have kicked this off the list.
2888 * If it was a prefetch, we will explicitly move it to
2889 * the head of the list now.
2890 */
2891 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2892 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2893 ASSERT(list_link_active(&buf->b_arc_node));
2894 }
2895 ARCSTAT_BUMP(arcstat_mfu_hits);
2896 buf->b_arc_access = ddi_get_lbolt();
2897 } else if (buf->b_state == arc_mfu_ghost) {
2898 arc_state_t *new_state = arc_mfu;
2899 /*
2900 * This buffer has been accessed more than once but has
2901 * been evicted from the cache. Move it back to the
2902 * MFU state.
2903 */
2904
2905 if (buf->b_flags & ARC_PREFETCH) {
2906 /*
2907 * This is a prefetch access...
2908 * move this block back to the MRU state.
2909 */
2910 ASSERT0(refcount_count(&buf->b_refcnt));
2911 new_state = arc_mru;
2912 }
2913
2914 buf->b_arc_access = ddi_get_lbolt();
2915 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2916 arc_change_state(new_state, buf, hash_lock);
2917
2918 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2919 } else if (buf->b_state == arc_l2c_only) {
2920 /*
2921 * This buffer is on the 2nd Level ARC.
2922 */
2923
2924 buf->b_arc_access = ddi_get_lbolt();
2925 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2926 arc_change_state(arc_mfu, buf, hash_lock);
2927 } else {
2928 ASSERT(!"invalid arc state");
2929 }
2930 }
2931
2932 /* a generic arc_done_func_t which you can use */
2933 /* ARGSUSED */
2934 void
2935 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2936 {
2937 if (zio == NULL || zio->io_error == 0)
2938 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2939 VERIFY(arc_buf_remove_ref(buf, arg));
2940 }
2941
2942 /* a generic arc_done_func_t */
2943 void
2944 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2945 {
2946 arc_buf_t **bufp = arg;
2947 if (zio && zio->io_error) {
2948 VERIFY(arc_buf_remove_ref(buf, arg));
2949 *bufp = NULL;
2950 } else {
2951 *bufp = buf;
2952 ASSERT(buf->b_data);
2953 }
2954 }
2955
2956 static void
2957 arc_read_done(zio_t *zio)
2958 {
2959 arc_buf_hdr_t *hdr;
2960 arc_buf_t *buf;
2961 arc_buf_t *abuf; /* buffer we're assigning to callback */
2962 kmutex_t *hash_lock = NULL;
2963 arc_callback_t *callback_list, *acb;
2964 int freeable = FALSE;
2965
2966 buf = zio->io_private;
2967 hdr = buf->b_hdr;
2968
2969 /*
2970 * The hdr was inserted into hash-table and removed from lists
2971 * prior to starting I/O. We should find this header, since
2972 * it's in the hash table, and it should be legit since it's
2973 * not possible to evict it during the I/O. The only possible
2974 * reason for it not to be found is if we were freed during the
2975 * read.
2976 */
2977 if (HDR_IN_HASH_TABLE(hdr)) {
2978 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
2979 ASSERT3U(hdr->b_dva.dva_word[0], ==,
2980 BP_IDENTITY(zio->io_bp)->dva_word[0]);
2981 ASSERT3U(hdr->b_dva.dva_word[1], ==,
2982 BP_IDENTITY(zio->io_bp)->dva_word[1]);
2983
2984 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
2985 &hash_lock);
2986
2987 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
2988 hash_lock == NULL) ||
2989 (found == hdr &&
2990 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2991 (found == hdr && HDR_L2_READING(hdr)));
2992 }
2993
2994 hdr->b_flags &= ~ARC_L2_EVICTED;
2995 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2996 hdr->b_flags &= ~ARC_L2CACHE;
2997
2998 /* byteswap if necessary */
2999 callback_list = hdr->b_acb;
3000 ASSERT(callback_list != NULL);
3001 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3002 dmu_object_byteswap_t bswap =
3003 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3004 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3005 byteswap_uint64_array :
3006 dmu_ot_byteswap[bswap].ob_func;
3007 func(buf->b_data, hdr->b_size);
3008 }
3009
3010 arc_cksum_compute(buf, B_FALSE);
3011 arc_buf_watch(buf);
3012
3013 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
3014 /*
3015 * Only call arc_access on anonymous buffers. This is because
3016 * if we've issued an I/O for an evicted buffer, we've already
3017 * called arc_access (to prevent any simultaneous readers from
3018 * getting confused).
3019 */
3020 arc_access(hdr, hash_lock);
3021 }
3022
3023 /* create copies of the data buffer for the callers */
3024 abuf = buf;
3025 for (acb = callback_list; acb; acb = acb->acb_next) {
3026 if (acb->acb_done) {
3027 if (abuf == NULL) {
3028 ARCSTAT_BUMP(arcstat_duplicate_reads);
3029 abuf = arc_buf_clone(buf);
3030 }
3031 acb->acb_buf = abuf;
3032 abuf = NULL;
3033 }
3034 }
3035 hdr->b_acb = NULL;
3036 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3037 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3038 if (abuf == buf) {
3039 ASSERT(buf->b_efunc == NULL);
3040 ASSERT(hdr->b_datacnt == 1);
3041 hdr->b_flags |= ARC_BUF_AVAILABLE;
3042 }
3043
3044 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
3045
3046 if (zio->io_error != 0) {
3047 hdr->b_flags |= ARC_IO_ERROR;
3048 if (hdr->b_state != arc_anon)
3049 arc_change_state(arc_anon, hdr, hash_lock);
3050 if (HDR_IN_HASH_TABLE(hdr))
3051 buf_hash_remove(hdr);
3052 freeable = refcount_is_zero(&hdr->b_refcnt);
3053 }
3054
3055 /*
3056 * Broadcast before we drop the hash_lock to avoid the possibility
3057 * that the hdr (and hence the cv) might be freed before we get to
3058 * the cv_broadcast().
3059 */
3060 cv_broadcast(&hdr->b_cv);
3061
3062 if (hash_lock) {
3063 mutex_exit(hash_lock);
3064 } else {
3065 /*
3066 * This block was freed while we waited for the read to
3067 * complete. It has been removed from the hash table and
3068 * moved to the anonymous state (so that it won't show up
3069 * in the cache).
3070 */
3071 ASSERT3P(hdr->b_state, ==, arc_anon);
3072 freeable = refcount_is_zero(&hdr->b_refcnt);
3073 }
3074
3075 /* execute each callback and free its structure */
3076 while ((acb = callback_list) != NULL) {
3077 if (acb->acb_done)
3078 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3079
3080 if (acb->acb_zio_dummy != NULL) {
3081 acb->acb_zio_dummy->io_error = zio->io_error;
3082 zio_nowait(acb->acb_zio_dummy);
3083 }
3084
3085 callback_list = acb->acb_next;
3086 kmem_free(acb, sizeof (arc_callback_t));
3087 }
3088
3089 if (freeable)
3090 arc_hdr_destroy(hdr);
3091 }
3092
3093 /*
3094 * "Read" the block at the specified DVA (in bp) via the
3095 * cache. If the block is found in the cache, invoke the provided
3096 * callback immediately and return. Note that the `zio' parameter
3097 * in the callback will be NULL in this case, since no IO was
3098 * required. If the block is not in the cache pass the read request
3099 * on to the spa with a substitute callback function, so that the
3100 * requested block will be added to the cache.
3101 *
3102 * If a read request arrives for a block that has a read in-progress,
3103 * either wait for the in-progress read to complete (and return the
3104 * results); or, if this is a read with a "done" func, add a record
3105 * to the read to invoke the "done" func when the read completes,
3106 * and return; or just return.
3107 *
3108 * arc_read_done() will invoke all the requested "done" functions
3109 * for readers of this block.
3110 */
3111 int
3112 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3113 void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
3114 const zbookmark_phys_t *zb)
3115 {
3116 arc_buf_hdr_t *hdr = NULL;
3117 arc_buf_t *buf = NULL;
3118 kmutex_t *hash_lock = NULL;
3119 zio_t *rzio;
3120 uint64_t guid = spa_load_guid(spa);
3121
3122 ASSERT(!BP_IS_EMBEDDED(bp) ||
3123 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3124
3125 top:
3126 if (!BP_IS_EMBEDDED(bp)) {
3127 /*
3128 * Embedded BP's have no DVA and require no I/O to "read".
3129 * Create an anonymous arc buf to back it.
3130 */
3131 hdr = buf_hash_find(guid, bp, &hash_lock);
3132 }
3133
3134 if (hdr != NULL && hdr->b_datacnt > 0) {
3135
3136 *arc_flags |= ARC_CACHED;
3137
3138 if (HDR_IO_IN_PROGRESS(hdr)) {
3139
3140 if (*arc_flags & ARC_WAIT) {
3141 cv_wait(&hdr->b_cv, hash_lock);
3142 mutex_exit(hash_lock);
3143 goto top;
3144 }
3145 ASSERT(*arc_flags & ARC_NOWAIT);
3146
3147 if (done) {
3148 arc_callback_t *acb = NULL;
3149
3150 acb = kmem_zalloc(sizeof (arc_callback_t),
3151 KM_SLEEP);
3152 acb->acb_done = done;
3153 acb->acb_private = private;
3154 if (pio != NULL)
3155 acb->acb_zio_dummy = zio_null(pio,
3156 spa, NULL, NULL, NULL, zio_flags);
3157
3158 ASSERT(acb->acb_done != NULL);
3159 acb->acb_next = hdr->b_acb;
3160 hdr->b_acb = acb;
3161 add_reference(hdr, hash_lock, private);
3162 mutex_exit(hash_lock);
3163 return (0);
3164 }
3165 mutex_exit(hash_lock);
3166 return (0);
3167 }
3168
3169 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3170
3171 if (done) {
3172 add_reference(hdr, hash_lock, private);
3173 /*
3174 * If this block is already in use, create a new
3175 * copy of the data so that we will be guaranteed
3176 * that arc_release() will always succeed.
3177 */
3178 buf = hdr->b_buf;
3179 ASSERT(buf);
3180 ASSERT(buf->b_data);
3181 if (HDR_BUF_AVAILABLE(hdr)) {
3182 ASSERT(buf->b_efunc == NULL);
3183 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3184 } else {
3185 buf = arc_buf_clone(buf);
3186 }
3187
3188 } else if (*arc_flags & ARC_PREFETCH &&
3189 refcount_count(&hdr->b_refcnt) == 0) {
3190 hdr->b_flags |= ARC_PREFETCH;
3191 }
3192 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
3193 arc_access(hdr, hash_lock);
3194 if (*arc_flags & ARC_L2CACHE)
3195 hdr->b_flags |= ARC_L2CACHE;
3196 if (*arc_flags & ARC_L2COMPRESS)
3197 hdr->b_flags |= ARC_L2COMPRESS;
3198 mutex_exit(hash_lock);
3199 ARCSTAT_BUMP(arcstat_hits);
3200 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3201 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3202 data, metadata, hits);
3203
3204 if (done)
3205 done(NULL, buf, private);
3206 } else {
3207 uint64_t size = BP_GET_LSIZE(bp);
3208 arc_callback_t *acb;
3209 vdev_t *vd = NULL;
3210 uint64_t addr = 0;
3211 boolean_t devw = B_FALSE;
3212 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
3213 uint64_t b_asize = 0;
3214
3215 if (hdr == NULL) {
3216 /* this block is not in the cache */
3217 arc_buf_hdr_t *exists = NULL;
3218 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
3219 buf = arc_buf_alloc(spa, size, private, type);
3220 hdr = buf->b_hdr;
3221 if (!BP_IS_EMBEDDED(bp)) {
3222 hdr->b_dva = *BP_IDENTITY(bp);
3223 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
3224 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
3225 exists = buf_hash_insert(hdr, &hash_lock);
3226 }
3227 if (exists != NULL) {
3228 /* somebody beat us to the hash insert */
3229 mutex_exit(hash_lock);
3230 buf_discard_identity(hdr);
3231 (void) arc_buf_remove_ref(buf, private);
3232 goto top; /* restart the IO request */
3233 }
3234 /* if this is a prefetch, we don't have a reference */
3235 if (*arc_flags & ARC_PREFETCH) {
3236 (void) remove_reference(hdr, hash_lock,
3237 private);
3238 hdr->b_flags |= ARC_PREFETCH;
3239 }
3240 if (*arc_flags & ARC_L2CACHE)
3241 hdr->b_flags |= ARC_L2CACHE;
3242 if (*arc_flags & ARC_L2COMPRESS)
3243 hdr->b_flags |= ARC_L2COMPRESS;
3244 if (BP_GET_LEVEL(bp) > 0)
3245 hdr->b_flags |= ARC_INDIRECT;
3246 } else {
3247 /* this block is in the ghost cache */
3248 ASSERT(GHOST_STATE(hdr->b_state));
3249 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3250 ASSERT0(refcount_count(&hdr->b_refcnt));
3251 ASSERT(hdr->b_buf == NULL);
3252
3253 /* if this is a prefetch, we don't have a reference */
3254 if (*arc_flags & ARC_PREFETCH)
3255 hdr->b_flags |= ARC_PREFETCH;
3256 else
3257 add_reference(hdr, hash_lock, private);
3258 if (*arc_flags & ARC_L2CACHE)
3259 hdr->b_flags |= ARC_L2CACHE;
3260 if (*arc_flags & ARC_L2COMPRESS)
3261 hdr->b_flags |= ARC_L2COMPRESS;
3262 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
3263 buf->b_hdr = hdr;
3264 buf->b_data = NULL;
3265 buf->b_efunc = NULL;
3266 buf->b_private = NULL;
3267 buf->b_next = NULL;
3268 hdr->b_buf = buf;
3269 ASSERT(hdr->b_datacnt == 0);
3270 hdr->b_datacnt = 1;
3271 arc_get_data_buf(buf);
3272 arc_access(hdr, hash_lock);
3273 }
3274
3275 ASSERT(!GHOST_STATE(hdr->b_state));
3276
3277 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
3278 acb->acb_done = done;
3279 acb->acb_private = private;
3280
3281 ASSERT(hdr->b_acb == NULL);
3282 hdr->b_acb = acb;
3283 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3284
3285 if (hdr->b_l2hdr != NULL &&
3286 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
3287 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
3288 addr = hdr->b_l2hdr->b_daddr;
3289 b_compress = hdr->b_l2hdr->b_compress;
3290 b_asize = hdr->b_l2hdr->b_asize;
3291 /*
3292 * Lock out device removal.
3293 */
3294 if (vdev_is_dead(vd) ||
3295 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
3296 vd = NULL;
3297 }
3298
3299 if (hash_lock != NULL)
3300 mutex_exit(hash_lock);
3301
3302 /*
3303 * At this point, we have a level 1 cache miss. Try again in
3304 * L2ARC if possible.
3305 */
3306 ASSERT3U(hdr->b_size, ==, size);
3307 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
3308 uint64_t, size, zbookmark_phys_t *, zb);
3309 ARCSTAT_BUMP(arcstat_misses);
3310 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
3311 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
3312 data, metadata, misses);
3313
3314 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
3315 /*
3316 * Read from the L2ARC if the following are true:
3317 * 1. The L2ARC vdev was previously cached.
3318 * 2. This buffer still has L2ARC metadata.
3319 * 3. This buffer isn't currently writing to the L2ARC.
3320 * 4. The L2ARC entry wasn't evicted, which may
3321 * also have invalidated the vdev.
3322 * 5. This isn't prefetch and l2arc_noprefetch is set.
3323 */
3324 if (hdr->b_l2hdr != NULL &&
3325 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
3326 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
3327 l2arc_read_callback_t *cb;
3328
3329 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
3330 ARCSTAT_BUMP(arcstat_l2_hits);
3331
3332 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
3333 KM_SLEEP);
3334 cb->l2rcb_buf = buf;
3335 cb->l2rcb_spa = spa;
3336 cb->l2rcb_bp = *bp;
3337 cb->l2rcb_zb = *zb;
3338 cb->l2rcb_flags = zio_flags;
3339 cb->l2rcb_compress = b_compress;
3340
3341 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
3342 addr + size < vd->vdev_psize -
3343 VDEV_LABEL_END_SIZE);
3344
3345 /*
3346 * l2arc read. The SCL_L2ARC lock will be
3347 * released by l2arc_read_done().
3348 * Issue a null zio if the underlying buffer
3349 * was squashed to zero size by compression.
3350 */
3351 if (b_compress == ZIO_COMPRESS_EMPTY) {
3352 rzio = zio_null(pio, spa, vd,
3353 l2arc_read_done, cb,
3354 zio_flags | ZIO_FLAG_DONT_CACHE |
3355 ZIO_FLAG_CANFAIL |
3356 ZIO_FLAG_DONT_PROPAGATE |
3357 ZIO_FLAG_DONT_RETRY);
3358 } else {
3359 rzio = zio_read_phys(pio, vd, addr,
3360 b_asize, buf->b_data,
3361 ZIO_CHECKSUM_OFF,
3362 l2arc_read_done, cb, priority,
3363 zio_flags | ZIO_FLAG_DONT_CACHE |
3364 ZIO_FLAG_CANFAIL |
3365 ZIO_FLAG_DONT_PROPAGATE |
3366 ZIO_FLAG_DONT_RETRY, B_FALSE);
3367 }
3368 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3369 zio_t *, rzio);
3370 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
3371
3372 if (*arc_flags & ARC_NOWAIT) {
3373 zio_nowait(rzio);
3374 return (0);
3375 }
3376
3377 ASSERT(*arc_flags & ARC_WAIT);
3378 if (zio_wait(rzio) == 0)
3379 return (0);
3380
3381 /* l2arc read error; goto zio_read() */
3382 } else {
3383 DTRACE_PROBE1(l2arc__miss,
3384 arc_buf_hdr_t *, hdr);
3385 ARCSTAT_BUMP(arcstat_l2_misses);
3386 if (HDR_L2_WRITING(hdr))
3387 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3388 spa_config_exit(spa, SCL_L2ARC, vd);
3389 }
3390 } else {
3391 if (vd != NULL)
3392 spa_config_exit(spa, SCL_L2ARC, vd);
3393 if (l2arc_ndev != 0) {
3394 DTRACE_PROBE1(l2arc__miss,
3395 arc_buf_hdr_t *, hdr);
3396 ARCSTAT_BUMP(arcstat_l2_misses);
3397 }
3398 }
3399
3400 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3401 arc_read_done, buf, priority, zio_flags, zb);
3402
3403 if (*arc_flags & ARC_WAIT)
3404 return (zio_wait(rzio));
3405
3406 ASSERT(*arc_flags & ARC_NOWAIT);
3407 zio_nowait(rzio);
3408 }
3409 return (0);
3410 }
3411
3412 void
3413 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3414 {
3415 ASSERT(buf->b_hdr != NULL);
3416 ASSERT(buf->b_hdr->b_state != arc_anon);
3417 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3418 ASSERT(buf->b_efunc == NULL);
3419 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3420
3421 buf->b_efunc = func;
3422 buf->b_private = private;
3423 }
3424
3425 /*
3426 * Notify the arc that a block was freed, and thus will never be used again.
3427 */
3428 void
3429 arc_freed(spa_t *spa, const blkptr_t *bp)
3430 {
3431 arc_buf_hdr_t *hdr;
3432 kmutex_t *hash_lock;
3433 uint64_t guid = spa_load_guid(spa);
3434
3435 ASSERT(!BP_IS_EMBEDDED(bp));
3436
3437 hdr = buf_hash_find(guid, bp, &hash_lock);
3438 if (hdr == NULL)
3439 return;
3440 if (HDR_BUF_AVAILABLE(hdr)) {
3441 arc_buf_t *buf = hdr->b_buf;
3442 add_reference(hdr, hash_lock, FTAG);
3443 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3444 mutex_exit(hash_lock);
3445
3446 arc_release(buf, FTAG);
3447 (void) arc_buf_remove_ref(buf, FTAG);
3448 } else {
3449 mutex_exit(hash_lock);
3450 }
3451
3452 }
3453
3454 /*
3455 * Clear the user eviction callback set by arc_set_callback(), first calling
3456 * it if it exists. Because the presence of a callback keeps an arc_buf cached
3457 * clearing the callback may result in the arc_buf being destroyed. However,
3458 * it will not result in the *last* arc_buf being destroyed, hence the data
3459 * will remain cached in the ARC. We make a copy of the arc buffer here so
3460 * that we can process the callback without holding any locks.
3461 *
3462 * It's possible that the callback is already in the process of being cleared
3463 * by another thread. In this case we can not clear the callback.
3464 *
3465 * Returns B_TRUE if the callback was successfully called and cleared.
3466 */
3467 boolean_t
3468 arc_clear_callback(arc_buf_t *buf)
3469 {
3470 arc_buf_hdr_t *hdr;
3471 kmutex_t *hash_lock;
3472 arc_evict_func_t *efunc = buf->b_efunc;
3473 void *private = buf->b_private;
3474
3475 mutex_enter(&buf->b_evict_lock);
3476 hdr = buf->b_hdr;
3477 if (hdr == NULL) {
3478 /*
3479 * We are in arc_do_user_evicts().
3480 */
3481 ASSERT(buf->b_data == NULL);
3482 mutex_exit(&buf->b_evict_lock);
3483 return (B_FALSE);
3484 } else if (buf->b_data == NULL) {
3485 /*
3486 * We are on the eviction list; process this buffer now
3487 * but let arc_do_user_evicts() do the reaping.
3488 */
3489 buf->b_efunc = NULL;
3490 mutex_exit(&buf->b_evict_lock);
3491 VERIFY0(efunc(private));
3492 return (B_TRUE);
3493 }
3494 hash_lock = HDR_LOCK(hdr);
3495 mutex_enter(hash_lock);
3496 hdr = buf->b_hdr;
3497 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3498
3499 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3500 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3501
3502 buf->b_efunc = NULL;
3503 buf->b_private = NULL;
3504
3505 if (hdr->b_datacnt > 1) {
3506 mutex_exit(&buf->b_evict_lock);
3507 arc_buf_destroy(buf, FALSE, TRUE);
3508 } else {
3509 ASSERT(buf == hdr->b_buf);
3510 hdr->b_flags |= ARC_BUF_AVAILABLE;
3511 mutex_exit(&buf->b_evict_lock);
3512 }
3513
3514 mutex_exit(hash_lock);
3515 VERIFY0(efunc(private));
3516 return (B_TRUE);
3517 }
3518
3519 /*
3520 * Release this buffer from the cache, making it an anonymous buffer. This
3521 * must be done after a read and prior to modifying the buffer contents.
3522 * If the buffer has more than one reference, we must make
3523 * a new hdr for the buffer.
3524 */
3525 void
3526 arc_release(arc_buf_t *buf, void *tag)
3527 {
3528 arc_buf_hdr_t *hdr;
3529 kmutex_t *hash_lock = NULL;
3530 l2arc_buf_hdr_t *l2hdr;
3531 uint64_t buf_size;
3532
3533 /*
3534 * It would be nice to assert that if it's DMU metadata (level >
3535 * 0 || it's the dnode file), then it must be syncing context.
3536 * But we don't know that information at this level.
3537 */
3538
3539 mutex_enter(&buf->b_evict_lock);
3540 hdr = buf->b_hdr;
3541
3542 /* this buffer is not on any list */
3543 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3544
3545 if (hdr->b_state == arc_anon) {
3546 /* this buffer is already released */
3547 ASSERT(buf->b_efunc == NULL);
3548 } else {
3549 hash_lock = HDR_LOCK(hdr);
3550 mutex_enter(hash_lock);
3551 hdr = buf->b_hdr;
3552 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3553 }
3554
3555 l2hdr = hdr->b_l2hdr;
3556 if (l2hdr) {
3557 mutex_enter(&l2arc_buflist_mtx);
3558 hdr->b_l2hdr = NULL;
3559 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3560 }
3561 buf_size = hdr->b_size;
3562
3563 /*
3564 * Do we have more than one buf?
3565 */
3566 if (hdr->b_datacnt > 1) {
3567 arc_buf_hdr_t *nhdr;
3568 arc_buf_t **bufp;
3569 uint64_t blksz = hdr->b_size;
3570 uint64_t spa = hdr->b_spa;
3571 arc_buf_contents_t type = hdr->b_type;
3572 uint32_t flags = hdr->b_flags;
3573
3574 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3575 /*
3576 * Pull the data off of this hdr and attach it to
3577 * a new anonymous hdr.
3578 */
3579 (void) remove_reference(hdr, hash_lock, tag);
3580 bufp = &hdr->b_buf;
3581 while (*bufp != buf)
3582 bufp = &(*bufp)->b_next;
3583 *bufp = buf->b_next;
3584 buf->b_next = NULL;
3585
3586 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3587 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3588 if (refcount_is_zero(&hdr->b_refcnt)) {
3589 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3590 ASSERT3U(*size, >=, hdr->b_size);
3591 atomic_add_64(size, -hdr->b_size);
3592 }
3593
3594 /*
3595 * We're releasing a duplicate user data buffer, update
3596 * our statistics accordingly.
3597 */
3598 if (hdr->b_type == ARC_BUFC_DATA) {
3599 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3600 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3601 -hdr->b_size);
3602 }
3603 hdr->b_datacnt -= 1;
3604 arc_cksum_verify(buf);
3605 arc_buf_unwatch(buf);
3606
3607 mutex_exit(hash_lock);
3608
3609 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3610 nhdr->b_size = blksz;
3611 nhdr->b_spa = spa;
3612 nhdr->b_type = type;
3613 nhdr->b_buf = buf;
3614 nhdr->b_state = arc_anon;
3615 nhdr->b_arc_access = 0;
3616 nhdr->b_flags = flags & ARC_L2_WRITING;
3617 nhdr->b_l2hdr = NULL;
3618 nhdr->b_datacnt = 1;
3619 nhdr->b_freeze_cksum = NULL;
3620 (void) refcount_add(&nhdr->b_refcnt, tag);
3621 buf->b_hdr = nhdr;
3622 mutex_exit(&buf->b_evict_lock);
3623 atomic_add_64(&arc_anon->arcs_size, blksz);
3624 } else {
3625 mutex_exit(&buf->b_evict_lock);
3626 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3627 ASSERT(!list_link_active(&hdr->b_arc_node));
3628 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3629 if (hdr->b_state != arc_anon)
3630 arc_change_state(arc_anon, hdr, hash_lock);
3631 hdr->b_arc_access = 0;
3632 if (hash_lock)
3633 mutex_exit(hash_lock);
3634
3635 buf_discard_identity(hdr);
3636 arc_buf_thaw(buf);
3637 }
3638 buf->b_efunc = NULL;
3639 buf->b_private = NULL;
3640
3641 if (l2hdr) {
3642 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
3643 if (l2hdr->b_dev->l2ad_vdev)
3644 vdev_space_update(l2hdr->b_dev->l2ad_vdev,
3645 -l2hdr->b_asize, 0, 0);
3646 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3647 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3648 mutex_exit(&l2arc_buflist_mtx);
3649 }
3650 }
3651
3652 int
3653 arc_released(arc_buf_t *buf)
3654 {
3655 int released;
3656
3657 mutex_enter(&buf->b_evict_lock);
3658 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3659 mutex_exit(&buf->b_evict_lock);
3660 return (released);
3661 }
3662
3663 #ifdef ZFS_DEBUG
3664 int
3665 arc_referenced(arc_buf_t *buf)
3666 {
3667 int referenced;
3668
3669 mutex_enter(&buf->b_evict_lock);
3670 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3671 mutex_exit(&buf->b_evict_lock);
3672 return (referenced);
3673 }
3674 #endif
3675
3676 static void
3677 arc_write_ready(zio_t *zio)
3678 {
3679 arc_write_callback_t *callback = zio->io_private;
3680 arc_buf_t *buf = callback->awcb_buf;
3681 arc_buf_hdr_t *hdr = buf->b_hdr;
3682
3683 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3684 callback->awcb_ready(zio, buf, callback->awcb_private);
3685
3686 /*
3687 * If the IO is already in progress, then this is a re-write
3688 * attempt, so we need to thaw and re-compute the cksum.
3689 * It is the responsibility of the callback to handle the
3690 * accounting for any re-write attempt.
3691 */
3692 if (HDR_IO_IN_PROGRESS(hdr)) {
3693 mutex_enter(&hdr->b_freeze_lock);
3694 if (hdr->b_freeze_cksum != NULL) {
3695 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3696 hdr->b_freeze_cksum = NULL;
3697 }
3698 mutex_exit(&hdr->b_freeze_lock);
3699 }
3700 arc_cksum_compute(buf, B_FALSE);
3701 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3702 }
3703
3704 /*
3705 * The SPA calls this callback for each physical write that happens on behalf
3706 * of a logical write. See the comment in dbuf_write_physdone() for details.
3707 */
3708 static void
3709 arc_write_physdone(zio_t *zio)
3710 {
3711 arc_write_callback_t *cb = zio->io_private;
3712 if (cb->awcb_physdone != NULL)
3713 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
3714 }
3715
3716 static void
3717 arc_write_done(zio_t *zio)
3718 {
3719 arc_write_callback_t *callback = zio->io_private;
3720 arc_buf_t *buf = callback->awcb_buf;
3721 arc_buf_hdr_t *hdr = buf->b_hdr;
3722
3723 ASSERT(hdr->b_acb == NULL);
3724
3725 if (zio->io_error == 0) {
3726 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
3727 buf_discard_identity(hdr);
3728 } else {
3729 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3730 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3731 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3732 }
3733 } else {
3734 ASSERT(BUF_EMPTY(hdr));
3735 }
3736
3737 /*
3738 * If the block to be written was all-zero or compressed enough to be
3739 * embedded in the BP, no write was performed so there will be no
3740 * dva/birth/checksum. The buffer must therefore remain anonymous
3741 * (and uncached).
3742 */
3743 if (!BUF_EMPTY(hdr)) {
3744 arc_buf_hdr_t *exists;
3745 kmutex_t *hash_lock;
3746
3747 ASSERT(zio->io_error == 0);
3748
3749 arc_cksum_verify(buf);
3750
3751 exists = buf_hash_insert(hdr, &hash_lock);
3752 if (exists) {
3753 /*
3754 * This can only happen if we overwrite for
3755 * sync-to-convergence, because we remove
3756 * buffers from the hash table when we arc_free().
3757 */
3758 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3759 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3760 panic("bad overwrite, hdr=%p exists=%p",
3761 (void *)hdr, (void *)exists);
3762 ASSERT(refcount_is_zero(&exists->b_refcnt));
3763 arc_change_state(arc_anon, exists, hash_lock);
3764 mutex_exit(hash_lock);
3765 arc_hdr_destroy(exists);
3766 exists = buf_hash_insert(hdr, &hash_lock);
3767 ASSERT3P(exists, ==, NULL);
3768 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3769 /* nopwrite */
3770 ASSERT(zio->io_prop.zp_nopwrite);
3771 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3772 panic("bad nopwrite, hdr=%p exists=%p",
3773 (void *)hdr, (void *)exists);
3774 } else {
3775 /* Dedup */
3776 ASSERT(hdr->b_datacnt == 1);
3777 ASSERT(hdr->b_state == arc_anon);
3778 ASSERT(BP_GET_DEDUP(zio->io_bp));
3779 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3780 }
3781 }
3782 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3783 /* if it's not anon, we are doing a scrub */
3784 if (!exists && hdr->b_state == arc_anon)
3785 arc_access(hdr, hash_lock);
3786 mutex_exit(hash_lock);
3787 } else {
3788 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3789 }
3790
3791 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3792 callback->awcb_done(zio, buf, callback->awcb_private);
3793
3794 kmem_free(callback, sizeof (arc_write_callback_t));
3795 }
3796
3797 zio_t *
3798 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3799 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
3800 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
3801 arc_done_func_t *done, void *private, zio_priority_t priority,
3802 int zio_flags, const zbookmark_phys_t *zb)
3803 {
3804 arc_buf_hdr_t *hdr = buf->b_hdr;
3805 arc_write_callback_t *callback;
3806 zio_t *zio;
3807
3808 ASSERT(ready != NULL);
3809 ASSERT(done != NULL);
3810 ASSERT(!HDR_IO_ERROR(hdr));
3811 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3812 ASSERT(hdr->b_acb == NULL);
3813 if (l2arc)
3814 hdr->b_flags |= ARC_L2CACHE;
3815 if (l2arc_compress)
3816 hdr->b_flags |= ARC_L2COMPRESS;
3817 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3818 callback->awcb_ready = ready;
3819 callback->awcb_physdone = physdone;
3820 callback->awcb_done = done;
3821 callback->awcb_private = private;
3822 callback->awcb_buf = buf;
3823
3824 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3825 arc_write_ready, arc_write_physdone, arc_write_done, callback,
3826 priority, zio_flags, zb);
3827
3828 return (zio);
3829 }
3830
3831 static int
3832 arc_memory_throttle(uint64_t reserve, uint64_t txg)
3833 {
3834 #ifdef _KERNEL
3835 uint64_t available_memory = ptob(freemem);
3836 static uint64_t page_load = 0;
3837 static uint64_t last_txg = 0;
3838
3839 #if defined(__i386)
3840 available_memory =
3841 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3842 #endif
3843
3844 if (freemem > physmem * arc_lotsfree_percent / 100)
3845 return (0);
3846
3847 if (txg > last_txg) {
3848 last_txg = txg;
3849 page_load = 0;
3850 }
3851 /*
3852 * If we are in pageout, we know that memory is already tight,
3853 * the arc is already going to be evicting, so we just want to
3854 * continue to let page writes occur as quickly as possible.
3855 */
3856 if (curproc == proc_pageout) {
3857 if (page_load > MAX(ptob(minfree), available_memory) / 4)
3858 return (SET_ERROR(ERESTART));
3859 /* Note: reserve is inflated, so we deflate */
3860 page_load += reserve / 8;
3861 return (0);
3862 } else if (page_load > 0 && arc_reclaim_needed()) {
3863 /* memory is low, delay before restarting */
3864 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3865 return (SET_ERROR(EAGAIN));
3866 }
3867 page_load = 0;
3868 #endif
3869 return (0);
3870 }
3871
3872 void
3873 arc_tempreserve_clear(uint64_t reserve)
3874 {
3875 atomic_add_64(&arc_tempreserve, -reserve);
3876 ASSERT((int64_t)arc_tempreserve >= 0);
3877 }
3878
3879 int
3880 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3881 {
3882 int error;
3883 uint64_t anon_size;
3884
3885 if (reserve > arc_c/4 && !arc_no_grow)
3886 arc_c = MIN(arc_c_max, reserve * 4);
3887 if (reserve > arc_c)
3888 return (SET_ERROR(ENOMEM));
3889
3890 /*
3891 * Don't count loaned bufs as in flight dirty data to prevent long
3892 * network delays from blocking transactions that are ready to be
3893 * assigned to a txg.
3894 */
3895 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3896
3897 /*
3898 * Writes will, almost always, require additional memory allocations
3899 * in order to compress/encrypt/etc the data. We therefore need to
3900 * make sure that there is sufficient available memory for this.
3901 */
3902 error = arc_memory_throttle(reserve, txg);
3903 if (error != 0)
3904 return (error);
3905
3906 /*
3907 * Throttle writes when the amount of dirty data in the cache
3908 * gets too large. We try to keep the cache less than half full
3909 * of dirty blocks so that our sync times don't grow too large.
3910 * Note: if two requests come in concurrently, we might let them
3911 * both succeed, when one of them should fail. Not a huge deal.
3912 */
3913
3914 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3915 anon_size > arc_c / 4) {
3916 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3917 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3918 arc_tempreserve>>10,
3919 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3920 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3921 reserve>>10, arc_c>>10);
3922 return (SET_ERROR(ERESTART));
3923 }
3924 atomic_add_64(&arc_tempreserve, reserve);
3925 return (0);
3926 }
3927
3928 /* Tuneable, default is 64, which is essentially arbitrary */
3929 int zfs_flush_ntasks = 64;
3930
3931 void
3932 arc_init(void)
3933 {
3934 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3935 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3936
3937 mutex_init(&arc_pressure_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3938 cv_init(&arc_pressure_thr_cv, NULL, CV_DEFAULT, NULL);
3939
3940 /* Convert seconds to clock ticks */
3941 arc_min_prefetch_lifespan = 1 * hz;
3942
3943 /* Start out with 1/8 of all memory */
3944 arc_c = physmem * PAGESIZE / 8;
3945
3946 #ifdef _KERNEL
3947 /*
3948 * On architectures where the physical memory can be larger
3949 * than the addressable space (intel in 32-bit mode), we may
3950 * need to limit the cache to 1/8 of VM size.
3951 */
3952 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3953 #endif
3954
3955 /* initial sensible value */
3956 arc_pressure_threshold = arc_c;
3957 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3958 arc_c_min = MAX(arc_c / 4, 64<<20);
3959 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3960 if (arc_c * 8 >= 1<<30)
3961 arc_c_max = (arc_c * 8) - (1<<30);
3962 else
3963 arc_c_max = arc_c_min;
3964 arc_c_max = MAX(arc_c * 6, arc_c_max);
3965
3966 /*
3967 * Allow the tunables to override our calculations if they are
3968 * reasonable (ie. over 64MB)
3969 */
3970 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
3971 arc_c_max = zfs_arc_max;
3972 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
3973 arc_c_min = zfs_arc_min;
3974
3975 arc_c = arc_c_max;
3976 arc_p = (arc_c >> 1);
3977
3978 /* limit meta-data to 1/4 of the arc capacity */
3979 arc_meta_limit = arc_c_max / 4;
3980
3981 /* Allow the tunable to override if it is reasonable */
3982 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3983 arc_meta_limit = zfs_arc_meta_limit;
3984
3985 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3986 arc_c_min = arc_meta_limit / 2;
3987
3988 if (zfs_arc_grow_retry > 0)
3989 arc_grow_retry = zfs_arc_grow_retry;
3990
3991 if (zfs_arc_shrink_shift > 0)
3992 arc_shrink_shift = zfs_arc_shrink_shift;
3993
3994 if (zfs_arc_p_min_shift > 0)
3995 arc_p_min_shift = zfs_arc_p_min_shift;
3996
3997 /* if kmem_flags are set, lets try to use less memory */
3998 if (kmem_debugging())
3999 arc_c = arc_c / 2;
4000 if (arc_c < arc_c_min)
4001 arc_c = arc_c_min;
4002
4003 arc_anon = &ARC_anon;
4004 arc_mru = &ARC_mru;
4005 arc_mru_ghost = &ARC_mru_ghost;
4006 arc_mfu = &ARC_mfu;
4007 arc_mfu_ghost = &ARC_mfu_ghost;
4008 arc_l2c_only = &ARC_l2c_only;
4009 arc_size = 0;
4010
4011 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4012 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4013 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4014 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4015 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4016 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
4017
4018 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
4019 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4020 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
4021 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4022 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
4023 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4024 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
4025 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4026 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
4027 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4028 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
4029 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4030 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
4031 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4032 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
4033 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4034 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
4035 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4036 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
4037 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
4038
4039 arc_flush_taskq = taskq_create("arc_flush_tq",
4040 max_ncpus, minclsyspri, 1, zfs_flush_ntasks, TASKQ_DYNAMIC);
4041 buf_init();
4042
4043 arc_thread_exit = 0;
4044 arc_eviction_list = NULL;
4045 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
4046 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
4047
4048 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
4049 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
4050
4051 if (arc_ksp != NULL) {
4052 arc_ksp->ks_data = &arc_stats;
4053 kstat_install(arc_ksp);
4054 }
4055
4056 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
4057 TS_RUN, minclsyspri);
4058 (void) thread_create(NULL, 0, arc_pressure_thread, NULL, 0, &p0,
4059 TS_RUN, minclsyspri);
4060
4061 arc_dead = FALSE;
4062 arc_warm = B_FALSE;
4063
4064 /*
4065 * Calculate maximum amount of dirty data per pool.
4066 *
4067 * If it has been set by /etc/system, take that.
4068 * Otherwise, use a percentage of physical memory defined by
4069 * zfs_dirty_data_max_percent (default 10%) with a cap at
4070 * zfs_dirty_data_max_max (default 4GB).
4071 */
4072 if (zfs_dirty_data_max == 0) {
4073 zfs_dirty_data_max = physmem * PAGESIZE *
4074 zfs_dirty_data_max_percent / 100;
4075 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
4076 zfs_dirty_data_max_max);
4077 }
4078 }
4079
4080 void
4081 arc_fini(void)
4082 {
4083 mutex_enter(&arc_reclaim_thr_lock);
4084 arc_thread_exit = 1;
4085 while (arc_thread_exit != 0)
4086 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
4087 mutex_exit(&arc_reclaim_thr_lock);
4088
4089 mutex_enter(&arc_pressure_thr_lock);
4090 arc_pressure_thread_exit = 1;
4091 while (arc_pressure_thread_exit != 0)
4092 cv_wait(&arc_pressure_thr_cv, &arc_pressure_thr_lock);
4093 mutex_exit(&arc_pressure_thr_lock);
4094
4095 arc_flush(NULL);
4096
4097 arc_dead = TRUE;
4098
4099 if (arc_ksp != NULL) {
4100 kstat_delete(arc_ksp);
4101 arc_ksp = NULL;
4102 }
4103
4104 mutex_destroy(&arc_eviction_mtx);
4105 mutex_destroy(&arc_reclaim_thr_lock);
4106 cv_destroy(&arc_reclaim_thr_cv);
4107 mutex_destroy(&arc_pressure_thr_lock);
4108 cv_destroy(&arc_pressure_thr_cv);
4109
4110 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
4111 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
4112 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
4113 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
4114 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
4115 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
4116 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
4117 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
4118
4119 mutex_destroy(&arc_anon->arcs_mtx);
4120 mutex_destroy(&arc_mru->arcs_mtx);
4121 mutex_destroy(&arc_mru_ghost->arcs_mtx);
4122 mutex_destroy(&arc_mfu->arcs_mtx);
4123 mutex_destroy(&arc_mfu_ghost->arcs_mtx);
4124 mutex_destroy(&arc_l2c_only->arcs_mtx);
4125
4126 taskq_destroy(arc_flush_taskq);
4127 buf_fini();
4128
4129 ASSERT(arc_loaned_bytes == 0);
4130 }
4131
4132 /*
4133 * Level 2 ARC
4134 *
4135 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
4136 * It uses dedicated storage devices to hold cached data, which are populated
4137 * using large infrequent writes. The main role of this cache is to boost
4138 * the performance of random read workloads. The intended L2ARC devices
4139 * include short-stroked disks, solid state disks, and other media with
4140 * substantially faster read latency than disk.
4141 *
4142 * +-----------------------+
4143 * | ARC |
4144 * +-----------------------+
4145 * | ^ ^
4146 * | | |
4147 * l2arc_feed_thread() arc_read()
4148 * | | |
4149 * | l2arc read |
4150 * V | |
4151 * +---------------+ |
4152 * | L2ARC | |
4153 * +---------------+ |
4154 * | ^ |
4155 * l2arc_write() | |
4156 * | | |
4157 * V | |
4158 * +-------+ +-------+
4159 * | vdev | | vdev |
4160 * | cache | | cache |
4161 * +-------+ +-------+
4162 * +=========+ .-----.
4163 * : L2ARC : |-_____-|
4164 * : devices : | Disks |
4165 * +=========+ `-_____-'
4166 *
4167 * Read requests are satisfied from the following sources, in order:
4168 *
4169 * 1) ARC
4170 * 2) vdev cache of L2ARC devices
4171 * 3) L2ARC devices
4172 * 4) vdev cache of disks
4173 * 5) disks
4174 *
4175 * Some L2ARC device types exhibit extremely slow write performance.
4176 * To accommodate for this there are some significant differences between
4177 * the L2ARC and traditional cache design:
4178 *
4179 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
4180 * the ARC behave as usual, freeing buffers and placing headers on ghost
4181 * lists. The ARC does not send buffers to the L2ARC during eviction as
4182 * this would add inflated write latencies for all ARC memory pressure.
4183 *
4184 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
4185 * It does this by periodically scanning buffers from the eviction-end of
4186 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
4187 * not already there. It scans until a headroom of buffers is satisfied,
4188 * which itself is a buffer for ARC eviction. If a compressible buffer is
4189 * found during scanning and selected for writing to an L2ARC device, we
4190 * temporarily boost scanning headroom during the next scan cycle to make
4191 * sure we adapt to compression effects (which might significantly reduce
4192 * the data volume we write to L2ARC). The thread that does this is
4193 * l2arc_feed_thread(), illustrated below; example sizes are included to
4194 * provide a better sense of ratio than this diagram:
4195 *
4196 * head --> tail
4197 * +---------------------+----------+
4198 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
4199 * +---------------------+----------+ | o L2ARC eligible
4200 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
4201 * +---------------------+----------+ |
4202 * 15.9 Gbytes ^ 32 Mbytes |
4203 * headroom |
4204 * l2arc_feed_thread()
4205 * |
4206 * l2arc write hand <--[oooo]--'
4207 * | 8 Mbyte
4208 * | write max
4209 * V
4210 * +==============================+
4211 * L2ARC dev |####|#|###|###| |####| ... |
4212 * +==============================+
4213 * 32 Gbytes
4214 *
4215 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
4216 * evicted, then the L2ARC has cached a buffer much sooner than it probably
4217 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
4218 * safe to say that this is an uncommon case, since buffers at the end of
4219 * the ARC lists have moved there due to inactivity.
4220 *
4221 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
4222 * then the L2ARC simply misses copying some buffers. This serves as a
4223 * pressure valve to prevent heavy read workloads from both stalling the ARC
4224 * with waits and clogging the L2ARC with writes. This also helps prevent
4225 * the potential for the L2ARC to churn if it attempts to cache content too
4226 * quickly, such as during backups of the entire pool.
4227 *
4228 * 5. After system boot and before the ARC has filled main memory, there are
4229 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
4230 * lists can remain mostly static. Instead of searching from tail of these
4231 * lists as pictured, the l2arc_feed_thread() will search from the list heads
4232 * for eligible buffers, greatly increasing its chance of finding them.
4233 *
4234 * The L2ARC device write speed is also boosted during this time so that
4235 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
4236 * there are no L2ARC reads, and no fear of degrading read performance
4237 * through increased writes.
4238 *
4239 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
4240 * the vdev queue can aggregate them into larger and fewer writes. Each
4241 * device is written to in a rotor fashion, sweeping writes through
4242 * available space then repeating.
4243 *
4244 * 7. The L2ARC does not store dirty content. It never needs to flush
4245 * write buffers back to disk based storage.
4246 *
4247 * 8. If an ARC buffer is written (and dirtied) which also exists in the
4248 * L2ARC, the now stale L2ARC buffer is immediately dropped.
4249 *
4250 * The performance of the L2ARC can be tweaked by a number of tunables, which
4251 * may be necessary for different workloads:
4252 *
4253 * l2arc_write_max max write bytes per interval
4254 * l2arc_write_boost extra write bytes during device warmup
4255 * l2arc_noprefetch skip caching prefetched buffers
4256 * l2arc_headroom number of max device writes to precache
4257 * l2arc_headroom_boost when we find compressed buffers during ARC
4258 * scanning, we multiply headroom by this
4259 * percentage factor for the next scan cycle,
4260 * since more compressed buffers are likely to
4261 * be present
4262 * l2arc_feed_secs seconds between L2ARC writing
4263 *
4264 * Tunables may be removed or added as future performance improvements are
4265 * integrated, and also may become zpool properties.
4266 *
4267 * There are three key functions that control how the L2ARC warms up:
4268 *
4269 * l2arc_write_eligible() check if a buffer is eligible to cache
4270 * l2arc_write_size() calculate how much to write
4271 * l2arc_write_interval() calculate sleep delay between writes
4272 *
4273 * These three functions determine what to write, how much, and how quickly
4274 * to send writes.
4275 */
4276
4277 static boolean_t
4278 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
4279 {
4280 /*
4281 * A buffer is *not* eligible for the L2ARC if it:
4282 * 1. belongs to a different spa.
4283 * 2. is already cached on the L2ARC.
4284 * 3. has an I/O in progress (it may be an incomplete read).
4285 * 4. is flagged not eligible (zfs property).
4286 */
4287 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
4288 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
4289 return (B_FALSE);
4290
4291 return (B_TRUE);
4292 }
4293
4294 static uint64_t
4295 l2arc_write_size(void)
4296 {
4297 uint64_t size;
4298
4299 /*
4300 * Make sure our globals have meaningful values in case the user
4301 * altered them.
4302 */
4303 size = l2arc_write_max;
4304 if (size == 0) {
4305 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
4306 "be greater than zero, resetting it to the default (%d)",
4307 L2ARC_WRITE_SIZE);
4308 size = l2arc_write_max = L2ARC_WRITE_SIZE;
4309 }
4310
4311 if (arc_warm == B_FALSE)
4312 size += l2arc_write_boost;
4313
4314 return (size);
4315
4316 }
4317
4318 static clock_t
4319 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
4320 {
4321 clock_t interval, next, now;
4322
4323 /*
4324 * If the ARC lists are busy, increase our write rate; if the
4325 * lists are stale, idle back. This is achieved by checking
4326 * how much we previously wrote - if it was more than half of
4327 * what we wanted, schedule the next write much sooner.
4328 */
4329 if (l2arc_feed_again && wrote > (wanted / 2))
4330 interval = (hz * l2arc_feed_min_ms) / 1000;
4331 else
4332 interval = hz * l2arc_feed_secs;
4333
4334 now = ddi_get_lbolt();
4335 next = MAX(now, MIN(now + interval, began + interval));
4336
4337 return (next);
4338 }
4339
4340 static void
4341 l2arc_hdr_stat_add(void)
4342 {
4343 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
4344 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
4345 }
4346
4347 static void
4348 l2arc_hdr_stat_remove(void)
4349 {
4350 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
4351 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
4352 }
4353
4354 /*
4355 * Cycle through L2ARC devices. This is how L2ARC load balances.
4356 * If a device is returned, this also returns holding the spa config lock.
4357 */
4358 static l2arc_dev_t *
4359 l2arc_dev_get_next(void)
4360 {
4361 l2arc_dev_t *first, *next = NULL;
4362
4363 /*
4364 * Lock out the removal of spas (spa_namespace_lock), then removal
4365 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
4366 * both locks will be dropped and a spa config lock held instead.
4367 */
4368 mutex_enter(&spa_namespace_lock);
4369 mutex_enter(&l2arc_dev_mtx);
4370
4371 /* if there are no vdevs, there is nothing to do */
4372 if (l2arc_ndev == 0)
4373 goto out;
4374
4375 first = NULL;
4376 next = l2arc_dev_last;
4377 do {
4378 /* loop around the list looking for a non-faulted vdev */
4379 if (next == NULL) {
4380 next = list_head(l2arc_dev_list);
4381 } else {
4382 next = list_next(l2arc_dev_list, next);
4383 if (next == NULL)
4384 next = list_head(l2arc_dev_list);
4385 }
4386
4387 /* if we have come back to the start, bail out */
4388 if (first == NULL)
4389 first = next;
4390 else if (next == first)
4391 break;
4392
4393 } while (vdev_is_dead(next->l2ad_vdev));
4394
4395 /* if we were unable to find any usable vdevs, return NULL */
4396 if (vdev_is_dead(next->l2ad_vdev))
4397 next = NULL;
4398
4399 l2arc_dev_last = next;
4400
4401 out:
4402 mutex_exit(&l2arc_dev_mtx);
4403
4404 /*
4405 * Grab the config lock to prevent the 'next' device from being
4406 * removed while we are writing to it.
4407 */
4408 if (next != NULL)
4409 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
4410 mutex_exit(&spa_namespace_lock);
4411
4412 return (next);
4413 }
4414
4415 /*
4416 * Free buffers that were tagged for destruction.
4417 */
4418 static void
4419 l2arc_do_free_on_write()
4420 {
4421 list_t *buflist;
4422 l2arc_data_free_t *df, *df_prev;
4423
4424 mutex_enter(&l2arc_free_on_write_mtx);
4425 buflist = l2arc_free_on_write;
4426
4427 for (df = list_tail(buflist); df; df = df_prev) {
4428 df_prev = list_prev(buflist, df);
4429 ASSERT(df->l2df_data != NULL);
4430 ASSERT(df->l2df_func != NULL);
4431 df->l2df_func(df->l2df_data, df->l2df_size);
4432 list_remove(buflist, df);
4433 kmem_free(df, sizeof (l2arc_data_free_t));
4434 }
4435
4436 mutex_exit(&l2arc_free_on_write_mtx);
4437 }
4438
4439 /*
4440 * A write to a cache device has completed. Update all headers to allow
4441 * reads from these buffers to begin.
4442 */
4443 static void
4444 l2arc_write_done(zio_t *zio)
4445 {
4446 l2arc_write_callback_t *cb;
4447 l2arc_dev_t *dev;
4448 list_t *buflist;
4449 arc_buf_hdr_t *head, *ab, *ab_prev;
4450 l2arc_buf_hdr_t *abl2;
4451 kmutex_t *hash_lock;
4452 int64_t bytes_dropped = 0;
4453
4454 cb = zio->io_private;
4455 ASSERT(cb != NULL);
4456 dev = cb->l2wcb_dev;
4457 ASSERT(dev != NULL);
4458 head = cb->l2wcb_head;
4459 ASSERT(head != NULL);
4460 buflist = dev->l2ad_buflist;
4461 ASSERT(buflist != NULL);
4462 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4463 l2arc_write_callback_t *, cb);
4464
4465 if (zio->io_error != 0)
4466 ARCSTAT_BUMP(arcstat_l2_writes_error);
4467
4468 mutex_enter(&l2arc_buflist_mtx);
4469
4470 /*
4471 * All writes completed, or an error was hit.
4472 */
4473 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4474 ab_prev = list_prev(buflist, ab);
4475 abl2 = ab->b_l2hdr;
4476
4477 /*
4478 * Release the temporary compressed buffer as soon as possible.
4479 */
4480 if (abl2->b_compress != ZIO_COMPRESS_OFF)
4481 l2arc_release_cdata_buf(ab);
4482
4483 hash_lock = HDR_LOCK(ab);
4484 if (!mutex_tryenter(hash_lock)) {
4485 /*
4486 * This buffer misses out. It may be in a stage
4487 * of eviction. Its ARC_L2_WRITING flag will be
4488 * left set, denying reads to this buffer.
4489 */
4490 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4491 continue;
4492 }
4493
4494 if (zio->io_error != 0) {
4495 /*
4496 * Error - drop L2ARC entry.
4497 */
4498 list_remove(buflist, ab);
4499 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4500 bytes_dropped += abl2->b_asize;
4501 ab->b_l2hdr = NULL;
4502 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4503 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4504 }
4505
4506 /*
4507 * Allow ARC to begin reads to this L2ARC entry.
4508 */
4509 ab->b_flags &= ~ARC_L2_WRITING;
4510
4511 mutex_exit(hash_lock);
4512 }
4513
4514 atomic_inc_64(&l2arc_writes_done);
4515 list_remove(buflist, head);
4516 kmem_cache_free(hdr_cache, head);
4517 mutex_exit(&l2arc_buflist_mtx);
4518
4519 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
4520
4521 l2arc_do_free_on_write();
4522
4523 kmem_free(cb, sizeof (l2arc_write_callback_t));
4524 }
4525
4526 /*
4527 * A read to a cache device completed. Validate buffer contents before
4528 * handing over to the regular ARC routines.
4529 */
4530 static void
4531 l2arc_read_done(zio_t *zio)
4532 {
4533 l2arc_read_callback_t *cb;
4534 arc_buf_hdr_t *hdr;
4535 arc_buf_t *buf;
4536 kmutex_t *hash_lock;
4537 int equal;
4538
4539 ASSERT(zio->io_vd != NULL);
4540 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4541
4542 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4543
4544 cb = zio->io_private;
4545 ASSERT(cb != NULL);
4546 buf = cb->l2rcb_buf;
4547 ASSERT(buf != NULL);
4548
4549 hash_lock = HDR_LOCK(buf->b_hdr);
4550 mutex_enter(hash_lock);
4551 hdr = buf->b_hdr;
4552 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4553
4554 /*
4555 * If the buffer was compressed, decompress it first.
4556 */
4557 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
4558 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
4559 ASSERT(zio->io_data != NULL);
4560
4561 /*
4562 * Check this survived the L2ARC journey.
4563 */
4564 equal = arc_cksum_equal(buf);
4565 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4566 mutex_exit(hash_lock);
4567 zio->io_private = buf;
4568 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4569 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4570 arc_read_done(zio);
4571 } else {
4572 mutex_exit(hash_lock);
4573 /*
4574 * Buffer didn't survive caching. Increment stats and
4575 * reissue to the original storage device.
4576 */
4577 if (zio->io_error != 0) {
4578 ARCSTAT_BUMP(arcstat_l2_io_error);
4579 } else {
4580 zio->io_error = SET_ERROR(EIO);
4581 }
4582 if (!equal)
4583 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4584
4585 /*
4586 * If there's no waiter, issue an async i/o to the primary
4587 * storage now. If there *is* a waiter, the caller must
4588 * issue the i/o in a context where it's OK to block.
4589 */
4590 if (zio->io_waiter == NULL) {
4591 zio_t *pio = zio_unique_parent(zio);
4592
4593 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4594
4595 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4596 buf->b_data, zio->io_size, arc_read_done, buf,
4597 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4598 }
4599 }
4600
4601 kmem_free(cb, sizeof (l2arc_read_callback_t));
4602 }
4603
4604 /*
4605 * This is the list priority from which the L2ARC will search for pages to
4606 * cache. This is used within loops (0..3) to cycle through lists in the
4607 * desired order. This order can have a significant effect on cache
4608 * performance.
4609 *
4610 * Currently the metadata lists are hit first, MFU then MRU, followed by
4611 * the data lists. This function returns a locked list, and also returns
4612 * the lock pointer.
4613 */
4614 static list_t *
4615 l2arc_list_locked(int list_num, kmutex_t **lock)
4616 {
4617 list_t *list = NULL;
4618
4619 ASSERT(list_num >= 0 && list_num <= 3);
4620
4621 switch (list_num) {
4622 case 0:
4623 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
4624 *lock = &arc_mfu->arcs_mtx;
4625 break;
4626 case 1:
4627 list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
4628 *lock = &arc_mru->arcs_mtx;
4629 break;
4630 case 2:
4631 list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
4632 *lock = &arc_mfu->arcs_mtx;
4633 break;
4634 case 3:
4635 list = &arc_mru->arcs_list[ARC_BUFC_DATA];
4636 *lock = &arc_mru->arcs_mtx;
4637 break;
4638 }
4639
4640 ASSERT(!(MUTEX_HELD(*lock)));
4641 mutex_enter(*lock);
4642 return (list);
4643 }
4644
4645 /*
4646 * Evict buffers from the device write hand to the distance specified in
4647 * bytes. This distance may span populated buffers, it may span nothing.
4648 * This is clearing a region on the L2ARC device ready for writing.
4649 * If the 'all' boolean is set, every buffer is evicted.
4650 */
4651 static void
4652 _l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all,
4653 boolean_t space_update)
4654 {
4655 list_t *buflist;
4656 l2arc_buf_hdr_t *abl2;
4657 arc_buf_hdr_t *ab, *ab_prev;
4658 kmutex_t *hash_lock;
4659 uint64_t taddr;
4660 int64_t bytes_evicted = 0;
4661
4662 buflist = dev->l2ad_buflist;
4663
4664 if (buflist == NULL)
4665 return;
4666
4667 if (!all && dev->l2ad_first) {
4668 /*
4669 * This is the first sweep through the device. There is
4670 * nothing to evict.
4671 */
4672 return;
4673 }
4674
4675 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4676 /*
4677 * When nearing the end of the device, evict to the end
4678 * before the device write hand jumps to the start.
4679 */
4680 taddr = dev->l2ad_end;
4681 } else {
4682 taddr = dev->l2ad_hand + distance;
4683 }
4684 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4685 uint64_t, taddr, boolean_t, all);
4686
4687 top:
4688 mutex_enter(&l2arc_buflist_mtx);
4689 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4690 ab_prev = list_prev(buflist, ab);
4691
4692 hash_lock = HDR_LOCK(ab);
4693 if (!mutex_tryenter(hash_lock)) {
4694 /*
4695 * Missed the hash lock. Retry.
4696 */
4697 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4698 mutex_exit(&l2arc_buflist_mtx);
4699 mutex_enter(hash_lock);
4700 mutex_exit(hash_lock);
4701 goto top;
4702 }
4703
4704 if (HDR_L2_WRITE_HEAD(ab)) {
4705 /*
4706 * We hit a write head node. Leave it for
4707 * l2arc_write_done().
4708 */
4709 list_remove(buflist, ab);
4710 mutex_exit(hash_lock);
4711 continue;
4712 }
4713
4714 if (!all && ab->b_l2hdr != NULL &&
4715 (ab->b_l2hdr->b_daddr > taddr ||
4716 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4717 /*
4718 * We've evicted to the target address,
4719 * or the end of the device.
4720 */
4721 mutex_exit(hash_lock);
4722 break;
4723 }
4724
4725 if (HDR_FREE_IN_PROGRESS(ab)) {
4726 /*
4727 * Already on the path to destruction.
4728 */
4729 mutex_exit(hash_lock);
4730 continue;
4731 }
4732
4733 if (ab->b_state == arc_l2c_only) {
4734 ASSERT(!HDR_L2_READING(ab));
4735 /*
4736 * This doesn't exist in the ARC. Destroy.
4737 * arc_hdr_destroy() will call list_remove()
4738 * and decrement arcstat_l2_size.
4739 */
4740 arc_change_state(arc_anon, ab, hash_lock);
4741 arc_hdr_destroy(ab);
4742 } else {
4743 /*
4744 * Invalidate issued or about to be issued
4745 * reads, since we may be about to write
4746 * over this location.
4747 */
4748 if (HDR_L2_READING(ab)) {
4749 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4750 ab->b_flags |= ARC_L2_EVICTED;
4751 }
4752
4753 /*
4754 * Tell ARC this no longer exists in L2ARC.
4755 */
4756 if (ab->b_l2hdr != NULL) {
4757 abl2 = ab->b_l2hdr;
4758 ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
4759 bytes_evicted += abl2->b_asize;
4760 ab->b_l2hdr = NULL;
4761 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4762 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4763 }
4764 list_remove(buflist, ab);
4765
4766 /*
4767 * This may have been leftover after a
4768 * failed write.
4769 */
4770 ab->b_flags &= ~ARC_L2_WRITING;
4771 }
4772 mutex_exit(hash_lock);
4773 }
4774 mutex_exit(&l2arc_buflist_mtx);
4775
4776 /*
4777 * Note: l2ad_vdev can only be touched if space_update is set,
4778 * otherwise the vdev might have been removed by an async
4779 * spa_unload.
4780 */
4781 if (space_update) {
4782 vdev_space_update(dev->l2ad_vdev, -bytes_evicted, 0, 0);
4783 dev->l2ad_evict = taddr;
4784 }
4785 }
4786
4787 /*
4788 * Asynchronous task for eviction of all the buffers for this L2ARC device
4789 * The task is dispatched in l2arc_evict()
4790 */
4791 typedef struct {
4792 l2arc_dev_t *dev;
4793 } l2arc_evict_data_t;
4794
4795 static void
4796 l2arc_evict_task(void *arg)
4797 {
4798 l2arc_evict_data_t *d = (l2arc_evict_data_t *)arg;
4799 ASSERT(d && d->dev);
4800
4801 /*
4802 * Evict l2arc buffers asynchronously; we need to keep the device
4803 * around until we are sure there aren't any buffers referencing it.
4804 * We do not need to hold any config locks, etc. because at this point,
4805 * we are the only ones who knows about this device (the in-core
4806 * structure), so no new buffers can be created (e.g. if the pool is
4807 * re-imported while the asynchronous eviction is in progress) that
4808 * reference this same in-core structure. Also remove the vdev link
4809 * since further use of it as l2arc device is prohibited.
4810 */
4811 d->dev->l2ad_vdev = NULL;
4812 _l2arc_evict(d->dev, 0LL, B_TRUE, B_FALSE);
4813
4814 /* Same cleanup as in the synchronous path */
4815 list_destroy(d->dev->l2ad_buflist);
4816 kmem_free(d->dev->l2ad_buflist, sizeof (list_t));
4817 kmem_free(d->dev, sizeof (l2arc_dev_t));
4818 /* Task argument cleanup */
4819 kmem_free(arg, sizeof (l2arc_evict_data_t));
4820 }
4821
4822 boolean_t zfs_l2arc_async_evict = B_TRUE;
4823
4824 /*
4825 * Perform l2arc eviction for buffers associated with this device
4826 * If evicting all buffers (done at pool export time), try to evict
4827 * asynchronously, and fall back to synchronous eviction in case of error
4828 * Tell the caller whether to cleanup the device:
4829 * - B_TRUE means "asynchronous eviction, do not cleanup"
4830 * - B_FALSE means "synchronous eviction, done, please cleanup"
4831 */
4832 static boolean_t
4833 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4834 {
4835 /*
4836 * If we are evicting all the buffers for this device, which happens
4837 * at pool export time, schedule asynchronous task
4838 */
4839 if (all && zfs_l2arc_async_evict) {
4840 l2arc_evict_data_t *arg =
4841 kmem_alloc(sizeof (l2arc_evict_data_t), KM_SLEEP);
4842 arg->dev = dev;
4843
4844 dev->l2ad_evict = dev->l2ad_end;
4845
4846 if ((taskq_dispatch(arc_flush_taskq, l2arc_evict_task,
4847 arg, TQ_NOSLEEP) == NULL)) {
4848 /*
4849 * Failed to dispatch asynchronous task
4850 * cleanup, evict synchronously, avoid adjusting
4851 * vdev space second time
4852 */
4853 kmem_free(arg, sizeof (l2arc_evict_data_t));
4854 _l2arc_evict(dev, distance, all, B_FALSE);
4855 } else {
4856 /*
4857 * Successfull dispatch, vdev space updated
4858 */
4859 return (B_TRUE);
4860 }
4861 } else {
4862 /* Evict synchronously */
4863 _l2arc_evict(dev, distance, all, B_TRUE);
4864 }
4865
4866 return (B_FALSE);
4867 }
4868
4869 /*
4870 * Find and write ARC buffers to the L2ARC device.
4871 *
4872 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4873 * for reading until they have completed writing.
4874 * The headroom_boost is an in-out parameter used to maintain headroom boost
4875 * state between calls to this function.
4876 *
4877 * Returns the number of bytes actually written (which may be smaller than
4878 * the delta by which the device hand has changed due to alignment).
4879 */
4880 static uint64_t
4881 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
4882 boolean_t *headroom_boost)
4883 {
4884 arc_buf_hdr_t *ab, *ab_prev, *head;
4885 list_t *list;
4886 uint64_t write_asize, write_psize, write_sz, headroom,
4887 buf_compress_minsz;
4888 void *buf_data;
4889 kmutex_t *list_lock;
4890 boolean_t full;
4891 l2arc_write_callback_t *cb;
4892 zio_t *pio, *wzio;
4893 uint64_t guid = spa_load_guid(spa);
4894 const boolean_t do_headroom_boost = *headroom_boost;
4895
4896 ASSERT(dev->l2ad_vdev != NULL);
4897
4898 /* Lower the flag now, we might want to raise it again later. */
4899 *headroom_boost = B_FALSE;
4900
4901 pio = NULL;
4902 write_sz = write_asize = write_psize = 0;
4903 full = B_FALSE;
4904 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4905 head->b_flags |= ARC_L2_WRITE_HEAD;
4906
4907 /*
4908 * We will want to try to compress buffers that are at least 2x the
4909 * device sector size.
4910 */
4911 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
4912
4913 /*
4914 * Copy buffers for L2ARC writing.
4915 */
4916 mutex_enter(&l2arc_buflist_mtx);
4917 for (int try = 0; try <= 3; try++) {
4918 uint64_t passed_sz = 0;
4919
4920 list = l2arc_list_locked(try, &list_lock);
4921
4922 /*
4923 * L2ARC fast warmup.
4924 *
4925 * Until the ARC is warm and starts to evict, read from the
4926 * head of the ARC lists rather than the tail.
4927 */
4928 if (arc_warm == B_FALSE)
4929 ab = list_head(list);
4930 else
4931 ab = list_tail(list);
4932
4933 headroom = target_sz * l2arc_headroom;
4934 if (do_headroom_boost)
4935 headroom = (headroom * l2arc_headroom_boost) / 100;
4936
4937 for (; ab; ab = ab_prev) {
4938 l2arc_buf_hdr_t *l2hdr;
4939 kmutex_t *hash_lock;
4940 uint64_t buf_sz;
4941
4942 if (arc_warm == B_FALSE)
4943 ab_prev = list_next(list, ab);
4944 else
4945 ab_prev = list_prev(list, ab);
4946
4947 hash_lock = HDR_LOCK(ab);
4948 if (!mutex_tryenter(hash_lock)) {
4949 /*
4950 * Skip this buffer rather than waiting.
4951 */
4952 continue;
4953 }
4954
4955 passed_sz += ab->b_size;
4956 if (passed_sz > headroom) {
4957 /*
4958 * Searched too far.
4959 */
4960 mutex_exit(hash_lock);
4961 break;
4962 }
4963
4964 if (!l2arc_write_eligible(guid, ab)) {
4965 mutex_exit(hash_lock);
4966 continue;
4967 }
4968
4969 if ((write_sz + ab->b_size) > target_sz) {
4970 full = B_TRUE;
4971 mutex_exit(hash_lock);
4972 break;
4973 }
4974
4975 if (pio == NULL) {
4976 /*
4977 * Insert a dummy header on the buflist so
4978 * l2arc_write_done() can find where the
4979 * write buffers begin without searching.
4980 */
4981 list_insert_head(dev->l2ad_buflist, head);
4982
4983 cb = kmem_alloc(
4984 sizeof (l2arc_write_callback_t), KM_SLEEP);
4985 cb->l2wcb_dev = dev;
4986 cb->l2wcb_head = head;
4987 pio = zio_root(spa, l2arc_write_done, cb,
4988 ZIO_FLAG_CANFAIL);
4989 }
4990
4991 /*
4992 * Create and add a new L2ARC header.
4993 */
4994 l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4995 l2hdr->b_dev = dev;
4996 ab->b_flags |= ARC_L2_WRITING;
4997
4998 /*
4999 * Temporarily stash the data buffer in b_tmp_cdata.
5000 * The subsequent write step will pick it up from
5001 * there. This is because can't access ab->b_buf
5002 * without holding the hash_lock, which we in turn
5003 * can't access without holding the ARC list locks
5004 * (which we want to avoid during compression/writing).
5005 */
5006 l2hdr->b_compress = ZIO_COMPRESS_OFF;
5007 l2hdr->b_asize = ab->b_size;
5008 l2hdr->b_tmp_cdata = ab->b_buf->b_data;
5009
5010 buf_sz = ab->b_size;
5011 ab->b_l2hdr = l2hdr;
5012
5013 list_insert_head(dev->l2ad_buflist, ab);
5014
5015 /*
5016 * Compute and store the buffer cksum before
5017 * writing. On debug the cksum is verified first.
5018 */
5019 arc_cksum_verify(ab->b_buf);
5020 arc_cksum_compute(ab->b_buf, B_TRUE);
5021
5022 mutex_exit(hash_lock);
5023
5024 write_sz += buf_sz;
5025 }
5026
5027 mutex_exit(list_lock);
5028
5029 if (full == B_TRUE)
5030 break;
5031 }
5032
5033 /* No buffers selected for writing? */
5034 if (pio == NULL) {
5035 ASSERT0(write_sz);
5036 mutex_exit(&l2arc_buflist_mtx);
5037 kmem_cache_free(hdr_cache, head);
5038 return (0);
5039 }
5040
5041 /*
5042 * Now start writing the buffers. We're starting at the write head
5043 * and work backwards, retracing the course of the buffer selector
5044 * loop above.
5045 */
5046 for (ab = list_prev(dev->l2ad_buflist, head); ab;
5047 ab = list_prev(dev->l2ad_buflist, ab)) {
5048 l2arc_buf_hdr_t *l2hdr;
5049 uint64_t buf_sz;
5050
5051 /*
5052 * We shouldn't need to lock the buffer here, since we flagged
5053 * it as ARC_L2_WRITING in the previous step, but we must take
5054 * care to only access its L2 cache parameters. In particular,
5055 * ab->b_buf may be invalid by now due to ARC eviction.
5056 */
5057 l2hdr = ab->b_l2hdr;
5058 l2hdr->b_daddr = dev->l2ad_hand;
5059
5060 if ((ab->b_flags & ARC_L2COMPRESS) &&
5061 l2hdr->b_asize >= buf_compress_minsz) {
5062 if (l2arc_compress_buf(l2hdr)) {
5063 /*
5064 * If compression succeeded, enable headroom
5065 * boost on the next scan cycle.
5066 */
5067 *headroom_boost = B_TRUE;
5068 }
5069 }
5070
5071 /*
5072 * Pick up the buffer data we had previously stashed away
5073 * (and now potentially also compressed).
5074 */
5075 buf_data = l2hdr->b_tmp_cdata;
5076 buf_sz = l2hdr->b_asize;
5077
5078 /* Compression may have squashed the buffer to zero length. */
5079 if (buf_sz != 0) {
5080 uint64_t buf_p_sz;
5081
5082 wzio = zio_write_phys(pio, dev->l2ad_vdev,
5083 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
5084 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
5085 ZIO_FLAG_CANFAIL, B_FALSE);
5086
5087 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
5088 zio_t *, wzio);
5089 (void) zio_nowait(wzio);
5090
5091 write_asize += buf_sz;
5092 /*
5093 * Keep the clock hand suitably device-aligned.
5094 */
5095 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
5096 write_psize += buf_p_sz;
5097 dev->l2ad_hand += buf_p_sz;
5098 }
5099 }
5100
5101 mutex_exit(&l2arc_buflist_mtx);
5102
5103 ASSERT3U(write_asize, <=, target_sz);
5104 ARCSTAT_BUMP(arcstat_l2_writes_sent);
5105 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
5106 ARCSTAT_INCR(arcstat_l2_size, write_sz);
5107 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
5108 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0);
5109
5110 /*
5111 * Bump device hand to the device start if it is approaching the end.
5112 * l2arc_evict() will already have evicted ahead for this case.
5113 */
5114 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
5115 dev->l2ad_hand = dev->l2ad_start;
5116 dev->l2ad_evict = dev->l2ad_start;
5117 dev->l2ad_first = B_FALSE;
5118 }
5119
5120 dev->l2ad_writing = B_TRUE;
5121 (void) zio_wait(pio);
5122 dev->l2ad_writing = B_FALSE;
5123
5124 return (write_asize);
5125 }
5126
5127 /*
5128 * Compresses an L2ARC buffer.
5129 * The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
5130 * size in l2hdr->b_asize. This routine tries to compress the data and
5131 * depending on the compression result there are three possible outcomes:
5132 * *) The buffer was incompressible. The original l2hdr contents were left
5133 * untouched and are ready for writing to an L2 device.
5134 * *) The buffer was all-zeros, so there is no need to write it to an L2
5135 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
5136 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
5137 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
5138 * data buffer which holds the compressed data to be written, and b_asize
5139 * tells us how much data there is. b_compress is set to the appropriate
5140 * compression algorithm. Once writing is done, invoke
5141 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
5142 *
5143 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
5144 * buffer was incompressible).
5145 */
5146 static boolean_t
5147 l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
5148 {
5149 void *cdata;
5150 size_t csize, len, rounded;
5151
5152 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
5153 ASSERT(l2hdr->b_tmp_cdata != NULL);
5154
5155 len = l2hdr->b_asize;
5156 cdata = zio_data_buf_alloc(len);
5157 csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
5158 cdata, l2hdr->b_asize);
5159
5160 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
5161 if (rounded > csize) {
5162 bzero((char *)cdata + csize, rounded - csize);
5163 csize = rounded;
5164 }
5165
5166 if (csize == 0) {
5167 /* zero block, indicate that there's nothing to write */
5168 zio_data_buf_free(cdata, len);
5169 l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
5170 l2hdr->b_asize = 0;
5171 l2hdr->b_tmp_cdata = NULL;
5172 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
5173 return (B_TRUE);
5174 } else if (csize > 0 && csize < len) {
5175 /*
5176 * Compression succeeded, we'll keep the cdata around for
5177 * writing and release it afterwards.
5178 */
5179 l2hdr->b_compress = ZIO_COMPRESS_LZ4;
5180 l2hdr->b_asize = csize;
5181 l2hdr->b_tmp_cdata = cdata;
5182 ARCSTAT_BUMP(arcstat_l2_compress_successes);
5183 return (B_TRUE);
5184 } else {
5185 /*
5186 * Compression failed, release the compressed buffer.
5187 * l2hdr will be left unmodified.
5188 */
5189 zio_data_buf_free(cdata, len);
5190 ARCSTAT_BUMP(arcstat_l2_compress_failures);
5191 return (B_FALSE);
5192 }
5193 }
5194
5195 /*
5196 * Decompresses a zio read back from an l2arc device. On success, the
5197 * underlying zio's io_data buffer is overwritten by the uncompressed
5198 * version. On decompression error (corrupt compressed stream), the
5199 * zio->io_error value is set to signal an I/O error.
5200 *
5201 * Please note that the compressed data stream is not checksummed, so
5202 * if the underlying device is experiencing data corruption, we may feed
5203 * corrupt data to the decompressor, so the decompressor needs to be
5204 * able to handle this situation (LZ4 does).
5205 */
5206 static void
5207 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
5208 {
5209 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
5210
5211 if (zio->io_error != 0) {
5212 /*
5213 * An io error has occured, just restore the original io
5214 * size in preparation for a main pool read.
5215 */
5216 zio->io_orig_size = zio->io_size = hdr->b_size;
5217 return;
5218 }
5219
5220 if (c == ZIO_COMPRESS_EMPTY) {
5221 /*
5222 * An empty buffer results in a null zio, which means we
5223 * need to fill its io_data after we're done restoring the
5224 * buffer's contents.
5225 */
5226 ASSERT(hdr->b_buf != NULL);
5227 bzero(hdr->b_buf->b_data, hdr->b_size);
5228 zio->io_data = zio->io_orig_data = hdr->b_buf->b_data;
5229 } else {
5230 ASSERT(zio->io_data != NULL);
5231 /*
5232 * We copy the compressed data from the start of the arc buffer
5233 * (the zio_read will have pulled in only what we need, the
5234 * rest is garbage which we will overwrite at decompression)
5235 * and then decompress back to the ARC data buffer. This way we
5236 * can minimize copying by simply decompressing back over the
5237 * original compressed data (rather than decompressing to an
5238 * aux buffer and then copying back the uncompressed buffer,
5239 * which is likely to be much larger).
5240 */
5241 uint64_t csize;
5242 void *cdata;
5243
5244 csize = zio->io_size;
5245 cdata = zio_data_buf_alloc(csize);
5246 bcopy(zio->io_data, cdata, csize);
5247 if (zio_decompress_data(c, cdata, zio->io_data, csize,
5248 hdr->b_size) != 0)
5249 zio->io_error = EIO;
5250 zio_data_buf_free(cdata, csize);
5251 }
5252
5253 /* Restore the expected uncompressed IO size. */
5254 zio->io_orig_size = zio->io_size = hdr->b_size;
5255 }
5256
5257 /*
5258 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
5259 * This buffer serves as a temporary holder of compressed data while
5260 * the buffer entry is being written to an l2arc device. Once that is
5261 * done, we can dispose of it.
5262 */
5263 static void
5264 l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
5265 {
5266 l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
5267
5268 if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) {
5269 /*
5270 * If the data was compressed, then we've allocated a
5271 * temporary buffer for it, so now we need to release it.
5272 */
5273 ASSERT(l2hdr->b_tmp_cdata != NULL);
5274 zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
5275 }
5276 l2hdr->b_tmp_cdata = NULL;
5277 }
5278
5279 /*
5280 * This thread feeds the L2ARC at regular intervals. This is the beating
5281 * heart of the L2ARC.
5282 */
5283 static void
5284 l2arc_feed_thread(void)
5285 {
5286 callb_cpr_t cpr;
5287 l2arc_dev_t *dev;
5288 spa_t *spa;
5289 uint64_t size, wrote;
5290 clock_t begin, next = ddi_get_lbolt();
5291 boolean_t headroom_boost = B_FALSE;
5292
5293 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
5294
5295 mutex_enter(&l2arc_feed_thr_lock);
5296
5297 while (l2arc_thread_exit == 0) {
5298 CALLB_CPR_SAFE_BEGIN(&cpr);
5299 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
5300 next);
5301 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
5302 next = ddi_get_lbolt() + hz;
5303
5304 /*
5305 * Quick check for L2ARC devices.
5306 */
5307 mutex_enter(&l2arc_dev_mtx);
5308 if (l2arc_ndev == 0) {
5309 mutex_exit(&l2arc_dev_mtx);
5310 continue;
5311 }
5312 mutex_exit(&l2arc_dev_mtx);
5313 begin = ddi_get_lbolt();
5314
5315 /*
5316 * This selects the next l2arc device to write to, and in
5317 * doing so the next spa to feed from: dev->l2ad_spa. This
5318 * will return NULL if there are now no l2arc devices or if
5319 * they are all faulted.
5320 *
5321 * If a device is returned, its spa's config lock is also
5322 * held to prevent device removal. l2arc_dev_get_next()
5323 * will grab and release l2arc_dev_mtx.
5324 */
5325 if ((dev = l2arc_dev_get_next()) == NULL)
5326 continue;
5327
5328 spa = dev->l2ad_spa;
5329 ASSERT(spa != NULL);
5330
5331 /*
5332 * If the pool is read-only then force the feed thread to
5333 * sleep a little longer.
5334 */
5335 if (!spa_writeable(spa)) {
5336 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
5337 spa_config_exit(spa, SCL_L2ARC, dev);
5338 continue;
5339 }
5340
5341 /*
5342 * Avoid contributing to memory pressure.
5343 */
5344 if (arc_reclaim_needed()) {
5345 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
5346 spa_config_exit(spa, SCL_L2ARC, dev);
5347 continue;
5348 }
5349
5350 ARCSTAT_BUMP(arcstat_l2_feeds);
5351
5352 size = l2arc_write_size();
5353
5354 /*
5355 * Evict L2ARC buffers that will be overwritten.
5356 * B_FALSE guarantees synchronous eviction.
5357 */
5358 (void) l2arc_evict(dev, size, B_FALSE);
5359
5360 /*
5361 * Write ARC buffers.
5362 */
5363 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
5364
5365 /*
5366 * Calculate interval between writes.
5367 */
5368 next = l2arc_write_interval(begin, size, wrote);
5369 spa_config_exit(spa, SCL_L2ARC, dev);
5370 }
5371
5372 l2arc_thread_exit = 0;
5373 cv_broadcast(&l2arc_feed_thr_cv);
5374 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
5375 thread_exit();
5376 }
5377
5378 boolean_t
5379 l2arc_vdev_present(vdev_t *vd)
5380 {
5381 l2arc_dev_t *dev;
5382
5383 mutex_enter(&l2arc_dev_mtx);
5384 for (dev = list_head(l2arc_dev_list); dev != NULL;
5385 dev = list_next(l2arc_dev_list, dev)) {
5386 if (dev->l2ad_vdev == vd)
5387 break;
5388 }
5389 mutex_exit(&l2arc_dev_mtx);
5390
5391 return (dev != NULL);
5392 }
5393
5394 /*
5395 * Add a vdev for use by the L2ARC. By this point the spa has already
5396 * validated the vdev and opened it.
5397 */
5398 void
5399 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
5400 {
5401 l2arc_dev_t *adddev;
5402
5403 ASSERT(!l2arc_vdev_present(vd));
5404
5405 /*
5406 * Create a new l2arc device entry.
5407 */
5408 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
5409 adddev->l2ad_spa = spa;
5410 adddev->l2ad_vdev = vd;
5411 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
5412 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
5413 adddev->l2ad_hand = adddev->l2ad_start;
5414 adddev->l2ad_evict = adddev->l2ad_start;
5415 adddev->l2ad_first = B_TRUE;
5416 adddev->l2ad_writing = B_FALSE;
5417
5418 /*
5419 * This is a list of all ARC buffers that are still valid on the
5420 * device.
5421 */
5422 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
5423 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
5424 offsetof(arc_buf_hdr_t, b_l2node));
5425
5426 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
5427
5428 /*
5429 * Add device to global list
5430 */
5431 mutex_enter(&l2arc_dev_mtx);
5432 list_insert_head(l2arc_dev_list, adddev);
5433 atomic_inc_64(&l2arc_ndev);
5434 mutex_exit(&l2arc_dev_mtx);
5435 }
5436
5437 /*
5438 * Remove a vdev from the L2ARC.
5439 */
5440 void
5441 l2arc_remove_vdev(vdev_t *vd)
5442 {
5443 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
5444
5445 /*
5446 * Find the device by vdev
5447 */
5448 mutex_enter(&l2arc_dev_mtx);
5449 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
5450 nextdev = list_next(l2arc_dev_list, dev);
5451 if (vd == dev->l2ad_vdev) {
5452 remdev = dev;
5453 break;
5454 }
5455 }
5456 ASSERT(remdev != NULL);
5457
5458 /*
5459 * Remove device from global list
5460 */
5461 list_remove(l2arc_dev_list, remdev);
5462 l2arc_dev_last = NULL; /* may have been invalidated */
5463 atomic_dec_64(&l2arc_ndev);
5464 mutex_exit(&l2arc_dev_mtx);
5465
5466 /*
5467 * Clear all buflists and ARC references. L2ARC device flush.
5468 */
5469 if (l2arc_evict(remdev, 0, B_TRUE) == B_FALSE) {
5470 /*
5471 * The eviction was done synchronously, cleanup here
5472 * Otherwise, the asynchronous task will cleanup
5473 */
5474 list_destroy(remdev->l2ad_buflist);
5475 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
5476 kmem_free(remdev, sizeof (l2arc_dev_t));
5477 }
5478 }
5479
5480 void
5481 l2arc_init(void)
5482 {
5483 l2arc_thread_exit = 0;
5484 l2arc_ndev = 0;
5485 l2arc_writes_sent = 0;
5486 l2arc_writes_done = 0;
5487
5488 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
5489 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
5490 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
5491 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
5492 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
5493
5494 l2arc_dev_list = &L2ARC_dev_list;
5495 l2arc_free_on_write = &L2ARC_free_on_write;
5496 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
5497 offsetof(l2arc_dev_t, l2ad_node));
5498 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
5499 offsetof(l2arc_data_free_t, l2df_list_node));
5500 }
5501
5502 void
5503 l2arc_fini(void)
5504 {
5505 /*
5506 * This is called from dmu_fini(), which is called from spa_fini();
5507 * Because of this, we can assume that all l2arc devices have
5508 * already been removed when the pools themselves were removed.
5509 */
5510
5511 l2arc_do_free_on_write();
5512
5513 mutex_destroy(&l2arc_feed_thr_lock);
5514 cv_destroy(&l2arc_feed_thr_cv);
5515 mutex_destroy(&l2arc_dev_mtx);
5516 mutex_destroy(&l2arc_buflist_mtx);
5517 mutex_destroy(&l2arc_free_on_write_mtx);
5518
5519 list_destroy(l2arc_dev_list);
5520 list_destroy(l2arc_free_on_write);
5521 }
5522
5523 void
5524 l2arc_start(void)
5525 {
5526 if (!(spa_mode_global & FWRITE))
5527 return;
5528
5529 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
5530 TS_RUN, minclsyspri);
5531 }
5532
5533 void
5534 l2arc_stop(void)
5535 {
5536 if (!(spa_mode_global & FWRITE))
5537 return;
5538
5539 mutex_enter(&l2arc_feed_thr_lock);
5540 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
5541 l2arc_thread_exit = 1;
5542 while (l2arc_thread_exit != 0)
5543 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
5544 mutex_exit(&l2arc_feed_thr_lock);
5545 }