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