FreeBSD/Linux Kernel Cross Reference
sys/common/fs/zfs/arc.c
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 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25
26 /*
27 * DVA-based Adjustable Replacement Cache
28 *
29 * While much of the theory of operation used here is
30 * based on the self-tuning, low overhead replacement cache
31 * presented by Megiddo and Modha at FAST 2003, there are some
32 * significant differences:
33 *
34 * 1. The Megiddo and Modha model assumes any page is evictable.
35 * Pages in its cache cannot be "locked" into memory. This makes
36 * the eviction algorithm simple: evict the last page in the list.
37 * This also make the performance characteristics easy to reason
38 * about. Our cache is not so simple. At any given moment, some
39 * subset of the blocks in the cache are un-evictable because we
40 * have handed out a reference to them. Blocks are only evictable
41 * when there are no external references active. This makes
42 * eviction far more problematic: we choose to evict the evictable
43 * blocks that are the "lowest" in the list.
44 *
45 * There are times when it is not possible to evict the requested
46 * space. In these circumstances we are unable to adjust the cache
47 * size. To prevent the cache growing unbounded at these times we
48 * implement a "cache throttle" that slows the flow of new data
49 * into the cache until we can make space available.
50 *
51 * 2. The Megiddo and Modha model assumes a fixed cache size.
52 * Pages are evicted when the cache is full and there is a cache
53 * miss. Our model has a variable sized cache. It grows with
54 * high use, but also tries to react to memory pressure from the
55 * operating system: decreasing its size when system memory is
56 * tight.
57 *
58 * 3. The Megiddo and Modha model assumes a fixed page size. All
59 * elements of the cache are therefor exactly the same size. So
60 * when adjusting the cache size following a cache miss, its simply
61 * a matter of choosing a single page to evict. In our model, we
62 * have variable sized cache blocks (rangeing from 512 bytes to
63 * 128K bytes). We therefor choose a set of blocks to evict to make
64 * space for a cache miss that approximates as closely as possible
65 * the space used by the new block.
66 *
67 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
68 * by N. Megiddo & D. Modha, FAST 2003
69 */
70
71 /*
72 * The locking model:
73 *
74 * A new reference to a cache buffer can be obtained in two
75 * ways: 1) via a hash table lookup using the DVA as a key,
76 * or 2) via one of the ARC lists. The arc_read() interface
77 * uses method 1, while the internal arc algorithms for
78 * adjusting the cache use method 2. We therefor provide two
79 * types of locks: 1) the hash table lock array, and 2) the
80 * arc list locks.
81 *
82 * Buffers do not have their own mutexs, rather they rely on the
83 * hash table mutexs for the bulk of their protection (i.e. most
84 * fields in the arc_buf_hdr_t are protected by these mutexs).
85 *
86 * buf_hash_find() returns the appropriate mutex (held) when it
87 * locates the requested buffer in the hash table. It returns
88 * NULL for the mutex if the buffer was not in the table.
89 *
90 * buf_hash_remove() expects the appropriate hash mutex to be
91 * already held before it is invoked.
92 *
93 * Each arc state also has a mutex which is used to protect the
94 * buffer list associated with the state. When attempting to
95 * obtain a hash table lock while holding an arc list lock you
96 * must use: mutex_tryenter() to avoid deadlock. Also note that
97 * the active state mutex must be held before the ghost state mutex.
98 *
99 * Arc buffers may have an associated eviction callback function.
100 * This function will be invoked prior to removing the buffer (e.g.
101 * in arc_do_user_evicts()). Note however that the data associated
102 * with the buffer may be evicted prior to the callback. The callback
103 * must be made with *no locks held* (to prevent deadlock). Additionally,
104 * the users of callbacks must ensure that their private data is
105 * protected from simultaneous callbacks from arc_buf_evict()
106 * and arc_do_user_evicts().
107 *
108 * Note that the majority of the performance stats are manipulated
109 * with atomic operations.
110 *
111 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
112 *
113 * - L2ARC buflist creation
114 * - L2ARC buflist eviction
115 * - L2ARC write completion, which walks L2ARC buflists
116 * - ARC header destruction, as it removes from L2ARC buflists
117 * - ARC header release, as it removes from L2ARC buflists
118 */
119
120 #include <sys/spa.h>
121 #include <sys/zio.h>
122 #include <sys/zio_checksum.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
137 static kmutex_t arc_reclaim_thr_lock;
138 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
139 static uint8_t arc_thread_exit;
140
141 extern int zfs_write_limit_shift;
142 extern uint64_t zfs_write_limit_max;
143 extern kmutex_t zfs_write_limit_lock;
144
145 #define ARC_REDUCE_DNLC_PERCENT 3
146 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
147
148 typedef enum arc_reclaim_strategy {
149 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
150 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
151 } arc_reclaim_strategy_t;
152
153 /* number of seconds before growing cache again */
154 static int arc_grow_retry = 60;
155
156 /* shift of arc_c for calculating both min and max arc_p */
157 static int arc_p_min_shift = 4;
158
159 /* log2(fraction of arc to reclaim) */
160 static int arc_shrink_shift = 5;
161
162 /*
163 * minimum lifespan of a prefetch block in clock ticks
164 * (initialized in arc_init())
165 */
166 static int arc_min_prefetch_lifespan;
167
168 static int arc_dead;
169
170 /*
171 * The arc has filled available memory and has now warmed up.
172 */
173 static boolean_t arc_warm;
174
175 /*
176 * These tunables are for performance analysis.
177 */
178 uint64_t zfs_arc_max;
179 uint64_t zfs_arc_min;
180 uint64_t zfs_arc_meta_limit = 0;
181 int zfs_mdcomp_disable = 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
442 arc_buf_hdr_t *b_hash_next;
443 arc_buf_t *b_buf;
444 uint32_t b_flags;
445 uint32_t b_datacnt;
446
447 arc_callback_t *b_acb;
448 kcondvar_t b_cv;
449
450 /* immutable */
451 arc_buf_contents_t b_type;
452 uint64_t b_size;
453 uint64_t b_spa;
454
455 /* protected by arc state mutex */
456 arc_state_t *b_state;
457 list_node_t b_arc_node;
458
459 /* updated atomically */
460 clock_t b_arc_access;
461
462 /* self protecting */
463 refcount_t b_refcnt;
464
465 l2arc_buf_hdr_t *b_l2hdr;
466 list_node_t b_l2node;
467 };
468
469 static arc_buf_t *arc_eviction_list;
470 static kmutex_t arc_eviction_mtx;
471 static arc_buf_hdr_t arc_eviction_hdr;
472 static void arc_get_data_buf(arc_buf_t *buf);
473 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
474 static int arc_evict_needed(arc_buf_contents_t type);
475 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
476
477 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
478
479 #define GHOST_STATE(state) \
480 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
481 (state) == arc_l2c_only)
482
483 /*
484 * Private ARC flags. These flags are private ARC only flags that will show up
485 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
486 * be passed in as arc_flags in things like arc_read. However, these flags
487 * should never be passed and should only be set by ARC code. When adding new
488 * public flags, make sure not to smash the private ones.
489 */
490
491 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
492 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
493 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
494 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
495 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
496 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
497 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
498 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
499 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
500 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
501 #define ARC_STORED (1 << 19) /* has been store()d to */
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(buf) \
551 (BUF_HASH_LOCK(BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->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 arc_buf_hdr_t *
670 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
671 {
672 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
673 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
674 arc_buf_hdr_t *buf;
675
676 mutex_enter(hash_lock);
677 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
678 buf = buf->b_hash_next) {
679 if (BUF_EQUAL(spa, dva, birth, buf)) {
680 *lockp = hash_lock;
681 return (buf);
682 }
683 }
684 mutex_exit(hash_lock);
685 *lockp = NULL;
686 return (NULL);
687 }
688
689 /*
690 * Insert an entry into the hash table. If there is already an element
691 * equal to elem in the hash table, then the already existing element
692 * will be returned and the new element will not be inserted.
693 * Otherwise returns NULL.
694 */
695 static arc_buf_hdr_t *
696 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
697 {
698 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
699 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
700 arc_buf_hdr_t *fbuf;
701 uint32_t i;
702
703 ASSERT(!HDR_IN_HASH_TABLE(buf));
704 *lockp = hash_lock;
705 mutex_enter(hash_lock);
706 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
707 fbuf = fbuf->b_hash_next, i++) {
708 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
709 return (fbuf);
710 }
711
712 buf->b_hash_next = buf_hash_table.ht_table[idx];
713 buf_hash_table.ht_table[idx] = buf;
714 buf->b_flags |= ARC_IN_HASH_TABLE;
715
716 /* collect some hash table performance data */
717 if (i > 0) {
718 ARCSTAT_BUMP(arcstat_hash_collisions);
719 if (i == 1)
720 ARCSTAT_BUMP(arcstat_hash_chains);
721
722 ARCSTAT_MAX(arcstat_hash_chain_max, i);
723 }
724
725 ARCSTAT_BUMP(arcstat_hash_elements);
726 ARCSTAT_MAXSTAT(arcstat_hash_elements);
727
728 return (NULL);
729 }
730
731 static void
732 buf_hash_remove(arc_buf_hdr_t *buf)
733 {
734 arc_buf_hdr_t *fbuf, **bufp;
735 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
736
737 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
738 ASSERT(HDR_IN_HASH_TABLE(buf));
739
740 bufp = &buf_hash_table.ht_table[idx];
741 while ((fbuf = *bufp) != buf) {
742 ASSERT(fbuf != NULL);
743 bufp = &fbuf->b_hash_next;
744 }
745 *bufp = buf->b_hash_next;
746 buf->b_hash_next = NULL;
747 buf->b_flags &= ~ARC_IN_HASH_TABLE;
748
749 /* collect some hash table performance data */
750 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
751
752 if (buf_hash_table.ht_table[idx] &&
753 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
754 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
755 }
756
757 /*
758 * Global data structures and functions for the buf kmem cache.
759 */
760 static kmem_cache_t *hdr_cache;
761 static kmem_cache_t *buf_cache;
762
763 static void
764 buf_fini(void)
765 {
766 int i;
767
768 kmem_free(buf_hash_table.ht_table,
769 (buf_hash_table.ht_mask + 1) * sizeof (void *));
770 for (i = 0; i < BUF_LOCKS; i++)
771 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
772 kmem_cache_destroy(hdr_cache);
773 kmem_cache_destroy(buf_cache);
774 }
775
776 /*
777 * Constructor callback - called when the cache is empty
778 * and a new buf is requested.
779 */
780 /* ARGSUSED */
781 static int
782 hdr_cons(void *vbuf, void *unused, int kmflag)
783 {
784 arc_buf_hdr_t *buf = vbuf;
785
786 bzero(buf, sizeof (arc_buf_hdr_t));
787 refcount_create(&buf->b_refcnt);
788 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
789 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
790 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
791
792 return (0);
793 }
794
795 /* ARGSUSED */
796 static int
797 buf_cons(void *vbuf, void *unused, int kmflag)
798 {
799 arc_buf_t *buf = vbuf;
800
801 bzero(buf, sizeof (arc_buf_t));
802 rw_init(&buf->b_lock, NULL, RW_DEFAULT, NULL);
803 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
804
805 return (0);
806 }
807
808 /*
809 * Destructor callback - called when a cached buf is
810 * no longer required.
811 */
812 /* ARGSUSED */
813 static void
814 hdr_dest(void *vbuf, void *unused)
815 {
816 arc_buf_hdr_t *buf = vbuf;
817
818 refcount_destroy(&buf->b_refcnt);
819 cv_destroy(&buf->b_cv);
820 mutex_destroy(&buf->b_freeze_lock);
821 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
822 }
823
824 /* ARGSUSED */
825 static void
826 buf_dest(void *vbuf, void *unused)
827 {
828 arc_buf_t *buf = vbuf;
829
830 rw_destroy(&buf->b_lock);
831 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
832 }
833
834 /*
835 * Reclaim callback -- invoked when memory is low.
836 */
837 /* ARGSUSED */
838 static void
839 hdr_recl(void *unused)
840 {
841 dprintf("hdr_recl called\n");
842 /*
843 * umem calls the reclaim func when we destroy the buf cache,
844 * which is after we do arc_fini().
845 */
846 if (!arc_dead)
847 cv_signal(&arc_reclaim_thr_cv);
848 }
849
850 static void
851 buf_init(void)
852 {
853 uint64_t *ct;
854 uint64_t hsize = 1ULL << 12;
855 int i, j;
856
857 /*
858 * The hash table is big enough to fill all of physical memory
859 * with an average 64K block size. The table will take up
860 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
861 */
862 while (hsize * 65536 < physmem * PAGESIZE)
863 hsize <<= 1;
864 retry:
865 buf_hash_table.ht_mask = hsize - 1;
866 buf_hash_table.ht_table =
867 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
868 if (buf_hash_table.ht_table == NULL) {
869 ASSERT(hsize > (1ULL << 8));
870 hsize >>= 1;
871 goto retry;
872 }
873
874 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
875 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
876 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
877 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
878
879 for (i = 0; i < 256; i++)
880 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
881 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
882
883 for (i = 0; i < BUF_LOCKS; i++) {
884 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
885 NULL, MUTEX_DEFAULT, NULL);
886 }
887 }
888
889 #define ARC_MINTIME (hz>>4) /* 62 ms */
890
891 static void
892 arc_cksum_verify(arc_buf_t *buf)
893 {
894 zio_cksum_t zc;
895
896 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
897 return;
898
899 mutex_enter(&buf->b_hdr->b_freeze_lock);
900 if (buf->b_hdr->b_freeze_cksum == NULL ||
901 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
902 mutex_exit(&buf->b_hdr->b_freeze_lock);
903 return;
904 }
905 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
906 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
907 panic("buffer modified while frozen!");
908 mutex_exit(&buf->b_hdr->b_freeze_lock);
909 }
910
911 static int
912 arc_cksum_equal(arc_buf_t *buf)
913 {
914 zio_cksum_t zc;
915 int equal;
916
917 mutex_enter(&buf->b_hdr->b_freeze_lock);
918 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
919 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
920 mutex_exit(&buf->b_hdr->b_freeze_lock);
921
922 return (equal);
923 }
924
925 static void
926 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
927 {
928 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
929 return;
930
931 mutex_enter(&buf->b_hdr->b_freeze_lock);
932 if (buf->b_hdr->b_freeze_cksum != NULL) {
933 mutex_exit(&buf->b_hdr->b_freeze_lock);
934 return;
935 }
936 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
937 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
938 buf->b_hdr->b_freeze_cksum);
939 mutex_exit(&buf->b_hdr->b_freeze_lock);
940 }
941
942 void
943 arc_buf_thaw(arc_buf_t *buf)
944 {
945 if (zfs_flags & ZFS_DEBUG_MODIFY) {
946 if (buf->b_hdr->b_state != arc_anon)
947 panic("modifying non-anon buffer!");
948 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
949 panic("modifying buffer while i/o in progress!");
950 arc_cksum_verify(buf);
951 }
952
953 mutex_enter(&buf->b_hdr->b_freeze_lock);
954 if (buf->b_hdr->b_freeze_cksum != NULL) {
955 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
956 buf->b_hdr->b_freeze_cksum = NULL;
957 }
958 mutex_exit(&buf->b_hdr->b_freeze_lock);
959 }
960
961 void
962 arc_buf_freeze(arc_buf_t *buf)
963 {
964 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
965 return;
966
967 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
968 buf->b_hdr->b_state == arc_anon);
969 arc_cksum_compute(buf, B_FALSE);
970 }
971
972 static void
973 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
974 {
975 ASSERT(MUTEX_HELD(hash_lock));
976
977 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
978 (ab->b_state != arc_anon)) {
979 uint64_t delta = ab->b_size * ab->b_datacnt;
980 list_t *list = &ab->b_state->arcs_list[ab->b_type];
981 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
982
983 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
984 mutex_enter(&ab->b_state->arcs_mtx);
985 ASSERT(list_link_active(&ab->b_arc_node));
986 list_remove(list, ab);
987 if (GHOST_STATE(ab->b_state)) {
988 ASSERT3U(ab->b_datacnt, ==, 0);
989 ASSERT3P(ab->b_buf, ==, NULL);
990 delta = ab->b_size;
991 }
992 ASSERT(delta > 0);
993 ASSERT3U(*size, >=, delta);
994 atomic_add_64(size, -delta);
995 mutex_exit(&ab->b_state->arcs_mtx);
996 /* remove the prefetch flag if we get a reference */
997 if (ab->b_flags & ARC_PREFETCH)
998 ab->b_flags &= ~ARC_PREFETCH;
999 }
1000 }
1001
1002 static int
1003 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1004 {
1005 int cnt;
1006 arc_state_t *state = ab->b_state;
1007
1008 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1009 ASSERT(!GHOST_STATE(state));
1010
1011 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1012 (state != arc_anon)) {
1013 uint64_t *size = &state->arcs_lsize[ab->b_type];
1014
1015 ASSERT(!MUTEX_HELD(&state->arcs_mtx));
1016 mutex_enter(&state->arcs_mtx);
1017 ASSERT(!list_link_active(&ab->b_arc_node));
1018 list_insert_head(&state->arcs_list[ab->b_type], ab);
1019 ASSERT(ab->b_datacnt > 0);
1020 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1021 mutex_exit(&state->arcs_mtx);
1022 }
1023 return (cnt);
1024 }
1025
1026 /*
1027 * Move the supplied buffer to the indicated state. The mutex
1028 * for the buffer must be held by the caller.
1029 */
1030 static void
1031 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1032 {
1033 arc_state_t *old_state = ab->b_state;
1034 int64_t refcnt = refcount_count(&ab->b_refcnt);
1035 uint64_t from_delta, to_delta;
1036
1037 ASSERT(MUTEX_HELD(hash_lock));
1038 ASSERT(new_state != old_state);
1039 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1040 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1041
1042 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1043
1044 /*
1045 * If this buffer is evictable, transfer it from the
1046 * old state list to the new state list.
1047 */
1048 if (refcnt == 0) {
1049 if (old_state != arc_anon) {
1050 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
1051 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1052
1053 if (use_mutex)
1054 mutex_enter(&old_state->arcs_mtx);
1055
1056 ASSERT(list_link_active(&ab->b_arc_node));
1057 list_remove(&old_state->arcs_list[ab->b_type], ab);
1058
1059 /*
1060 * If prefetching out of the ghost cache,
1061 * we will have a non-null datacnt.
1062 */
1063 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1064 /* ghost elements have a ghost size */
1065 ASSERT(ab->b_buf == NULL);
1066 from_delta = ab->b_size;
1067 }
1068 ASSERT3U(*size, >=, from_delta);
1069 atomic_add_64(size, -from_delta);
1070
1071 if (use_mutex)
1072 mutex_exit(&old_state->arcs_mtx);
1073 }
1074 if (new_state != arc_anon) {
1075 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
1076 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1077
1078 if (use_mutex)
1079 mutex_enter(&new_state->arcs_mtx);
1080
1081 list_insert_head(&new_state->arcs_list[ab->b_type], ab);
1082
1083 /* ghost elements have a ghost size */
1084 if (GHOST_STATE(new_state)) {
1085 ASSERT(ab->b_datacnt == 0);
1086 ASSERT(ab->b_buf == NULL);
1087 to_delta = ab->b_size;
1088 }
1089 atomic_add_64(size, to_delta);
1090
1091 if (use_mutex)
1092 mutex_exit(&new_state->arcs_mtx);
1093 }
1094 }
1095
1096 ASSERT(!BUF_EMPTY(ab));
1097 if (new_state == arc_anon) {
1098 buf_hash_remove(ab);
1099 }
1100
1101 /* adjust state sizes */
1102 if (to_delta)
1103 atomic_add_64(&new_state->arcs_size, to_delta);
1104 if (from_delta) {
1105 ASSERT3U(old_state->arcs_size, >=, from_delta);
1106 atomic_add_64(&old_state->arcs_size, -from_delta);
1107 }
1108 ab->b_state = new_state;
1109
1110 /* adjust l2arc hdr stats */
1111 if (new_state == arc_l2c_only)
1112 l2arc_hdr_stat_add();
1113 else if (old_state == arc_l2c_only)
1114 l2arc_hdr_stat_remove();
1115 }
1116
1117 void
1118 arc_space_consume(uint64_t space, arc_space_type_t type)
1119 {
1120 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1121
1122 switch (type) {
1123 case ARC_SPACE_DATA:
1124 ARCSTAT_INCR(arcstat_data_size, space);
1125 break;
1126 case ARC_SPACE_OTHER:
1127 ARCSTAT_INCR(arcstat_other_size, space);
1128 break;
1129 case ARC_SPACE_HDRS:
1130 ARCSTAT_INCR(arcstat_hdr_size, space);
1131 break;
1132 case ARC_SPACE_L2HDRS:
1133 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1134 break;
1135 }
1136
1137 atomic_add_64(&arc_meta_used, space);
1138 atomic_add_64(&arc_size, space);
1139 }
1140
1141 void
1142 arc_space_return(uint64_t space, arc_space_type_t type)
1143 {
1144 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1145
1146 switch (type) {
1147 case ARC_SPACE_DATA:
1148 ARCSTAT_INCR(arcstat_data_size, -space);
1149 break;
1150 case ARC_SPACE_OTHER:
1151 ARCSTAT_INCR(arcstat_other_size, -space);
1152 break;
1153 case ARC_SPACE_HDRS:
1154 ARCSTAT_INCR(arcstat_hdr_size, -space);
1155 break;
1156 case ARC_SPACE_L2HDRS:
1157 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1158 break;
1159 }
1160
1161 ASSERT(arc_meta_used >= space);
1162 if (arc_meta_max < arc_meta_used)
1163 arc_meta_max = arc_meta_used;
1164 atomic_add_64(&arc_meta_used, -space);
1165 ASSERT(arc_size >= space);
1166 atomic_add_64(&arc_size, -space);
1167 }
1168
1169 void *
1170 arc_data_buf_alloc(uint64_t size)
1171 {
1172 if (arc_evict_needed(ARC_BUFC_DATA))
1173 cv_signal(&arc_reclaim_thr_cv);
1174 atomic_add_64(&arc_size, size);
1175 return (zio_data_buf_alloc(size));
1176 }
1177
1178 void
1179 arc_data_buf_free(void *buf, uint64_t size)
1180 {
1181 zio_data_buf_free(buf, size);
1182 ASSERT(arc_size >= size);
1183 atomic_add_64(&arc_size, -size);
1184 }
1185
1186 arc_buf_t *
1187 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1188 {
1189 arc_buf_hdr_t *hdr;
1190 arc_buf_t *buf;
1191
1192 ASSERT3U(size, >, 0);
1193 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1194 ASSERT(BUF_EMPTY(hdr));
1195 hdr->b_size = size;
1196 hdr->b_type = type;
1197 hdr->b_spa = spa_guid(spa);
1198 hdr->b_state = arc_anon;
1199 hdr->b_arc_access = 0;
1200 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1201 buf->b_hdr = hdr;
1202 buf->b_data = NULL;
1203 buf->b_efunc = NULL;
1204 buf->b_private = NULL;
1205 buf->b_next = NULL;
1206 hdr->b_buf = buf;
1207 arc_get_data_buf(buf);
1208 hdr->b_datacnt = 1;
1209 hdr->b_flags = 0;
1210 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1211 (void) refcount_add(&hdr->b_refcnt, tag);
1212
1213 return (buf);
1214 }
1215
1216 static char *arc_onloan_tag = "onloan";
1217
1218 /*
1219 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1220 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1221 * buffers must be returned to the arc before they can be used by the DMU or
1222 * freed.
1223 */
1224 arc_buf_t *
1225 arc_loan_buf(spa_t *spa, int size)
1226 {
1227 arc_buf_t *buf;
1228
1229 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1230
1231 atomic_add_64(&arc_loaned_bytes, size);
1232 return (buf);
1233 }
1234
1235 /*
1236 * Return a loaned arc buffer to the arc.
1237 */
1238 void
1239 arc_return_buf(arc_buf_t *buf, void *tag)
1240 {
1241 arc_buf_hdr_t *hdr = buf->b_hdr;
1242
1243 ASSERT(hdr->b_state == arc_anon);
1244 ASSERT(buf->b_data != NULL);
1245 VERIFY(refcount_remove(&hdr->b_refcnt, arc_onloan_tag) == 0);
1246 VERIFY(refcount_add(&hdr->b_refcnt, tag) == 1);
1247
1248 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1249 }
1250
1251 static arc_buf_t *
1252 arc_buf_clone(arc_buf_t *from)
1253 {
1254 arc_buf_t *buf;
1255 arc_buf_hdr_t *hdr = from->b_hdr;
1256 uint64_t size = hdr->b_size;
1257
1258 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1259 buf->b_hdr = hdr;
1260 buf->b_data = NULL;
1261 buf->b_efunc = NULL;
1262 buf->b_private = NULL;
1263 buf->b_next = hdr->b_buf;
1264 hdr->b_buf = buf;
1265 arc_get_data_buf(buf);
1266 bcopy(from->b_data, buf->b_data, size);
1267 hdr->b_datacnt += 1;
1268 return (buf);
1269 }
1270
1271 void
1272 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1273 {
1274 arc_buf_hdr_t *hdr;
1275 kmutex_t *hash_lock;
1276
1277 /*
1278 * Check to see if this buffer is evicted. Callers
1279 * must verify b_data != NULL to know if the add_ref
1280 * was successful.
1281 */
1282 rw_enter(&buf->b_lock, RW_READER);
1283 if (buf->b_data == NULL) {
1284 rw_exit(&buf->b_lock);
1285 return;
1286 }
1287 hdr = buf->b_hdr;
1288 ASSERT(hdr != NULL);
1289 hash_lock = HDR_LOCK(hdr);
1290 mutex_enter(hash_lock);
1291 rw_exit(&buf->b_lock);
1292
1293 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1294 add_reference(hdr, hash_lock, tag);
1295 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1296 arc_access(hdr, hash_lock);
1297 mutex_exit(hash_lock);
1298 ARCSTAT_BUMP(arcstat_hits);
1299 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1300 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1301 data, metadata, hits);
1302 }
1303
1304 /*
1305 * Free the arc data buffer. If it is an l2arc write in progress,
1306 * the buffer is placed on l2arc_free_on_write to be freed later.
1307 */
1308 static void
1309 arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
1310 void *data, size_t size)
1311 {
1312 if (HDR_L2_WRITING(hdr)) {
1313 l2arc_data_free_t *df;
1314 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1315 df->l2df_data = data;
1316 df->l2df_size = size;
1317 df->l2df_func = free_func;
1318 mutex_enter(&l2arc_free_on_write_mtx);
1319 list_insert_head(l2arc_free_on_write, df);
1320 mutex_exit(&l2arc_free_on_write_mtx);
1321 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1322 } else {
1323 free_func(data, size);
1324 }
1325 }
1326
1327 static void
1328 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1329 {
1330 arc_buf_t **bufp;
1331
1332 /* free up data associated with the buf */
1333 if (buf->b_data) {
1334 arc_state_t *state = buf->b_hdr->b_state;
1335 uint64_t size = buf->b_hdr->b_size;
1336 arc_buf_contents_t type = buf->b_hdr->b_type;
1337
1338 arc_cksum_verify(buf);
1339 if (!recycle) {
1340 if (type == ARC_BUFC_METADATA) {
1341 arc_buf_data_free(buf->b_hdr, zio_buf_free,
1342 buf->b_data, size);
1343 arc_space_return(size, ARC_SPACE_DATA);
1344 } else {
1345 ASSERT(type == ARC_BUFC_DATA);
1346 arc_buf_data_free(buf->b_hdr,
1347 zio_data_buf_free, buf->b_data, size);
1348 ARCSTAT_INCR(arcstat_data_size, -size);
1349 atomic_add_64(&arc_size, -size);
1350 }
1351 }
1352 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1353 uint64_t *cnt = &state->arcs_lsize[type];
1354
1355 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1356 ASSERT(state != arc_anon);
1357
1358 ASSERT3U(*cnt, >=, size);
1359 atomic_add_64(cnt, -size);
1360 }
1361 ASSERT3U(state->arcs_size, >=, size);
1362 atomic_add_64(&state->arcs_size, -size);
1363 buf->b_data = NULL;
1364 ASSERT(buf->b_hdr->b_datacnt > 0);
1365 buf->b_hdr->b_datacnt -= 1;
1366 }
1367
1368 /* only remove the buf if requested */
1369 if (!all)
1370 return;
1371
1372 /* remove the buf from the hdr list */
1373 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1374 continue;
1375 *bufp = buf->b_next;
1376
1377 ASSERT(buf->b_efunc == NULL);
1378
1379 /* clean up the buf */
1380 buf->b_hdr = NULL;
1381 kmem_cache_free(buf_cache, buf);
1382 }
1383
1384 static void
1385 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1386 {
1387 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1388 ASSERT3P(hdr->b_state, ==, arc_anon);
1389 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1390 ASSERT(!(hdr->b_flags & ARC_STORED));
1391
1392 if (hdr->b_l2hdr != NULL) {
1393 if (!MUTEX_HELD(&l2arc_buflist_mtx)) {
1394 /*
1395 * To prevent arc_free() and l2arc_evict() from
1396 * attempting to free the same buffer at the same time,
1397 * a FREE_IN_PROGRESS flag is given to arc_free() to
1398 * give it priority. l2arc_evict() can't destroy this
1399 * header while we are waiting on l2arc_buflist_mtx.
1400 *
1401 * The hdr may be removed from l2ad_buflist before we
1402 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1403 */
1404 mutex_enter(&l2arc_buflist_mtx);
1405 if (hdr->b_l2hdr != NULL) {
1406 list_remove(hdr->b_l2hdr->b_dev->l2ad_buflist,
1407 hdr);
1408 }
1409 mutex_exit(&l2arc_buflist_mtx);
1410 } else {
1411 list_remove(hdr->b_l2hdr->b_dev->l2ad_buflist, hdr);
1412 }
1413 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1414 kmem_free(hdr->b_l2hdr, sizeof (l2arc_buf_hdr_t));
1415 if (hdr->b_state == arc_l2c_only)
1416 l2arc_hdr_stat_remove();
1417 hdr->b_l2hdr = NULL;
1418 }
1419
1420 if (!BUF_EMPTY(hdr)) {
1421 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1422 bzero(&hdr->b_dva, sizeof (dva_t));
1423 hdr->b_birth = 0;
1424 hdr->b_cksum0 = 0;
1425 }
1426 while (hdr->b_buf) {
1427 arc_buf_t *buf = hdr->b_buf;
1428
1429 if (buf->b_efunc) {
1430 mutex_enter(&arc_eviction_mtx);
1431 rw_enter(&buf->b_lock, RW_WRITER);
1432 ASSERT(buf->b_hdr != NULL);
1433 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1434 hdr->b_buf = buf->b_next;
1435 buf->b_hdr = &arc_eviction_hdr;
1436 buf->b_next = arc_eviction_list;
1437 arc_eviction_list = buf;
1438 rw_exit(&buf->b_lock);
1439 mutex_exit(&arc_eviction_mtx);
1440 } else {
1441 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1442 }
1443 }
1444 if (hdr->b_freeze_cksum != NULL) {
1445 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1446 hdr->b_freeze_cksum = NULL;
1447 }
1448
1449 ASSERT(!list_link_active(&hdr->b_arc_node));
1450 ASSERT3P(hdr->b_hash_next, ==, NULL);
1451 ASSERT3P(hdr->b_acb, ==, NULL);
1452 kmem_cache_free(hdr_cache, hdr);
1453 }
1454
1455 void
1456 arc_buf_free(arc_buf_t *buf, void *tag)
1457 {
1458 arc_buf_hdr_t *hdr = buf->b_hdr;
1459 int hashed = hdr->b_state != arc_anon;
1460
1461 ASSERT(buf->b_efunc == NULL);
1462 ASSERT(buf->b_data != NULL);
1463
1464 if (hashed) {
1465 kmutex_t *hash_lock = HDR_LOCK(hdr);
1466
1467 mutex_enter(hash_lock);
1468 (void) remove_reference(hdr, hash_lock, tag);
1469 if (hdr->b_datacnt > 1)
1470 arc_buf_destroy(buf, FALSE, TRUE);
1471 else
1472 hdr->b_flags |= ARC_BUF_AVAILABLE;
1473 mutex_exit(hash_lock);
1474 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1475 int destroy_hdr;
1476 /*
1477 * We are in the middle of an async write. Don't destroy
1478 * this buffer unless the write completes before we finish
1479 * decrementing the reference count.
1480 */
1481 mutex_enter(&arc_eviction_mtx);
1482 (void) remove_reference(hdr, NULL, tag);
1483 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1484 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1485 mutex_exit(&arc_eviction_mtx);
1486 if (destroy_hdr)
1487 arc_hdr_destroy(hdr);
1488 } else {
1489 if (remove_reference(hdr, NULL, tag) > 0) {
1490 ASSERT(HDR_IO_ERROR(hdr));
1491 arc_buf_destroy(buf, FALSE, TRUE);
1492 } else {
1493 arc_hdr_destroy(hdr);
1494 }
1495 }
1496 }
1497
1498 int
1499 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1500 {
1501 arc_buf_hdr_t *hdr = buf->b_hdr;
1502 kmutex_t *hash_lock = HDR_LOCK(hdr);
1503 int no_callback = (buf->b_efunc == NULL);
1504
1505 if (hdr->b_state == arc_anon) {
1506 arc_buf_free(buf, tag);
1507 return (no_callback);
1508 }
1509
1510 mutex_enter(hash_lock);
1511 ASSERT(hdr->b_state != arc_anon);
1512 ASSERT(buf->b_data != NULL);
1513
1514 (void) remove_reference(hdr, hash_lock, tag);
1515 if (hdr->b_datacnt > 1) {
1516 if (no_callback)
1517 arc_buf_destroy(buf, FALSE, TRUE);
1518 } else if (no_callback) {
1519 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1520 hdr->b_flags |= ARC_BUF_AVAILABLE;
1521 }
1522 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1523 refcount_is_zero(&hdr->b_refcnt));
1524 mutex_exit(hash_lock);
1525 return (no_callback);
1526 }
1527
1528 int
1529 arc_buf_size(arc_buf_t *buf)
1530 {
1531 return (buf->b_hdr->b_size);
1532 }
1533
1534 /*
1535 * Evict buffers from list until we've removed the specified number of
1536 * bytes. Move the removed buffers to the appropriate evict state.
1537 * If the recycle flag is set, then attempt to "recycle" a buffer:
1538 * - look for a buffer to evict that is `bytes' long.
1539 * - return the data block from this buffer rather than freeing it.
1540 * This flag is used by callers that are trying to make space for a
1541 * new buffer in a full arc cache.
1542 *
1543 * This function makes a "best effort". It skips over any buffers
1544 * it can't get a hash_lock on, and so may not catch all candidates.
1545 * It may also return without evicting as much space as requested.
1546 */
1547 static void *
1548 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1549 arc_buf_contents_t type)
1550 {
1551 arc_state_t *evicted_state;
1552 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1553 arc_buf_hdr_t *ab, *ab_prev = NULL;
1554 list_t *list = &state->arcs_list[type];
1555 kmutex_t *hash_lock;
1556 boolean_t have_lock;
1557 void *stolen = NULL;
1558
1559 ASSERT(state == arc_mru || state == arc_mfu);
1560
1561 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1562
1563 mutex_enter(&state->arcs_mtx);
1564 mutex_enter(&evicted_state->arcs_mtx);
1565
1566 for (ab = list_tail(list); ab; ab = ab_prev) {
1567 ab_prev = list_prev(list, ab);
1568 /* prefetch buffers have a minimum lifespan */
1569 if (HDR_IO_IN_PROGRESS(ab) ||
1570 (spa && ab->b_spa != spa) ||
1571 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1572 lbolt - ab->b_arc_access < arc_min_prefetch_lifespan)) {
1573 skipped++;
1574 continue;
1575 }
1576 /* "lookahead" for better eviction candidate */
1577 if (recycle && ab->b_size != bytes &&
1578 ab_prev && ab_prev->b_size == bytes)
1579 continue;
1580 hash_lock = HDR_LOCK(ab);
1581 have_lock = MUTEX_HELD(hash_lock);
1582 if (have_lock || mutex_tryenter(hash_lock)) {
1583 ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
1584 ASSERT(ab->b_datacnt > 0);
1585 while (ab->b_buf) {
1586 arc_buf_t *buf = ab->b_buf;
1587 if (!rw_tryenter(&buf->b_lock, RW_WRITER)) {
1588 missed += 1;
1589 break;
1590 }
1591 if (buf->b_data) {
1592 bytes_evicted += ab->b_size;
1593 if (recycle && ab->b_type == type &&
1594 ab->b_size == bytes &&
1595 !HDR_L2_WRITING(ab)) {
1596 stolen = buf->b_data;
1597 recycle = FALSE;
1598 }
1599 }
1600 if (buf->b_efunc) {
1601 mutex_enter(&arc_eviction_mtx);
1602 arc_buf_destroy(buf,
1603 buf->b_data == stolen, FALSE);
1604 ab->b_buf = buf->b_next;
1605 buf->b_hdr = &arc_eviction_hdr;
1606 buf->b_next = arc_eviction_list;
1607 arc_eviction_list = buf;
1608 mutex_exit(&arc_eviction_mtx);
1609 rw_exit(&buf->b_lock);
1610 } else {
1611 rw_exit(&buf->b_lock);
1612 arc_buf_destroy(buf,
1613 buf->b_data == stolen, TRUE);
1614 }
1615 }
1616
1617 if (ab->b_l2hdr) {
1618 ARCSTAT_INCR(arcstat_evict_l2_cached,
1619 ab->b_size);
1620 } else {
1621 if (l2arc_write_eligible(ab->b_spa, ab)) {
1622 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1623 ab->b_size);
1624 } else {
1625 ARCSTAT_INCR(
1626 arcstat_evict_l2_ineligible,
1627 ab->b_size);
1628 }
1629 }
1630
1631 if (ab->b_datacnt == 0) {
1632 arc_change_state(evicted_state, ab, hash_lock);
1633 ASSERT(HDR_IN_HASH_TABLE(ab));
1634 ab->b_flags |= ARC_IN_HASH_TABLE;
1635 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1636 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1637 }
1638 if (!have_lock)
1639 mutex_exit(hash_lock);
1640 if (bytes >= 0 && bytes_evicted >= bytes)
1641 break;
1642 } else {
1643 missed += 1;
1644 }
1645 }
1646
1647 mutex_exit(&evicted_state->arcs_mtx);
1648 mutex_exit(&state->arcs_mtx);
1649
1650 if (bytes_evicted < bytes)
1651 dprintf("only evicted %lld bytes from %x",
1652 (longlong_t)bytes_evicted, state);
1653
1654 if (skipped)
1655 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1656
1657 if (missed)
1658 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1659
1660 /*
1661 * We have just evicted some date into the ghost state, make
1662 * sure we also adjust the ghost state size if necessary.
1663 */
1664 if (arc_no_grow &&
1665 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1666 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1667 arc_mru_ghost->arcs_size - arc_c;
1668
1669 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1670 int64_t todelete =
1671 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1672 arc_evict_ghost(arc_mru_ghost, NULL, todelete);
1673 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1674 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1675 arc_mru_ghost->arcs_size +
1676 arc_mfu_ghost->arcs_size - arc_c);
1677 arc_evict_ghost(arc_mfu_ghost, NULL, todelete);
1678 }
1679 }
1680
1681 return (stolen);
1682 }
1683
1684 /*
1685 * Remove buffers from list until we've removed the specified number of
1686 * bytes. Destroy the buffers that are removed.
1687 */
1688 static void
1689 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1690 {
1691 arc_buf_hdr_t *ab, *ab_prev;
1692 list_t *list = &state->arcs_list[ARC_BUFC_DATA];
1693 kmutex_t *hash_lock;
1694 uint64_t bytes_deleted = 0;
1695 uint64_t bufs_skipped = 0;
1696
1697 ASSERT(GHOST_STATE(state));
1698 top:
1699 mutex_enter(&state->arcs_mtx);
1700 for (ab = list_tail(list); ab; ab = ab_prev) {
1701 ab_prev = list_prev(list, ab);
1702 if (spa && ab->b_spa != spa)
1703 continue;
1704 hash_lock = HDR_LOCK(ab);
1705 if (mutex_tryenter(hash_lock)) {
1706 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1707 ASSERT(ab->b_buf == NULL);
1708 ARCSTAT_BUMP(arcstat_deleted);
1709 bytes_deleted += ab->b_size;
1710
1711 if (ab->b_l2hdr != NULL) {
1712 /*
1713 * This buffer is cached on the 2nd Level ARC;
1714 * don't destroy the header.
1715 */
1716 arc_change_state(arc_l2c_only, ab, hash_lock);
1717 mutex_exit(hash_lock);
1718 } else {
1719 arc_change_state(arc_anon, ab, hash_lock);
1720 mutex_exit(hash_lock);
1721 arc_hdr_destroy(ab);
1722 }
1723
1724 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1725 if (bytes >= 0 && bytes_deleted >= bytes)
1726 break;
1727 } else {
1728 if (bytes < 0) {
1729 mutex_exit(&state->arcs_mtx);
1730 mutex_enter(hash_lock);
1731 mutex_exit(hash_lock);
1732 goto top;
1733 }
1734 bufs_skipped += 1;
1735 }
1736 }
1737 mutex_exit(&state->arcs_mtx);
1738
1739 if (list == &state->arcs_list[ARC_BUFC_DATA] &&
1740 (bytes < 0 || bytes_deleted < bytes)) {
1741 list = &state->arcs_list[ARC_BUFC_METADATA];
1742 goto top;
1743 }
1744
1745 if (bufs_skipped) {
1746 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
1747 ASSERT(bytes >= 0);
1748 }
1749
1750 if (bytes_deleted < bytes)
1751 dprintf("only deleted %lld bytes from %p",
1752 (longlong_t)bytes_deleted, state);
1753 }
1754
1755 static void
1756 arc_adjust(void)
1757 {
1758 int64_t adjustment, delta;
1759
1760 /*
1761 * Adjust MRU size
1762 */
1763
1764 adjustment = MIN(arc_size - arc_c,
1765 arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used - arc_p);
1766
1767 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
1768 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
1769 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
1770 adjustment -= delta;
1771 }
1772
1773 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1774 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
1775 (void) arc_evict(arc_mru, NULL, delta, FALSE,
1776 ARC_BUFC_METADATA);
1777 }
1778
1779 /*
1780 * Adjust MFU size
1781 */
1782
1783 adjustment = arc_size - arc_c;
1784
1785 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
1786 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
1787 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
1788 adjustment -= delta;
1789 }
1790
1791 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1792 int64_t delta = MIN(adjustment,
1793 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
1794 (void) arc_evict(arc_mfu, NULL, delta, FALSE,
1795 ARC_BUFC_METADATA);
1796 }
1797
1798 /*
1799 * Adjust ghost lists
1800 */
1801
1802 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
1803
1804 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
1805 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
1806 arc_evict_ghost(arc_mru_ghost, NULL, delta);
1807 }
1808
1809 adjustment =
1810 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
1811
1812 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
1813 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
1814 arc_evict_ghost(arc_mfu_ghost, NULL, delta);
1815 }
1816 }
1817
1818 static void
1819 arc_do_user_evicts(void)
1820 {
1821 mutex_enter(&arc_eviction_mtx);
1822 while (arc_eviction_list != NULL) {
1823 arc_buf_t *buf = arc_eviction_list;
1824 arc_eviction_list = buf->b_next;
1825 rw_enter(&buf->b_lock, RW_WRITER);
1826 buf->b_hdr = NULL;
1827 rw_exit(&buf->b_lock);
1828 mutex_exit(&arc_eviction_mtx);
1829
1830 if (buf->b_efunc != NULL)
1831 VERIFY(buf->b_efunc(buf) == 0);
1832
1833 buf->b_efunc = NULL;
1834 buf->b_private = NULL;
1835 kmem_cache_free(buf_cache, buf);
1836 mutex_enter(&arc_eviction_mtx);
1837 }
1838 mutex_exit(&arc_eviction_mtx);
1839 }
1840
1841 /*
1842 * Flush all *evictable* data from the cache for the given spa.
1843 * NOTE: this will not touch "active" (i.e. referenced) data.
1844 */
1845 void
1846 arc_flush(spa_t *spa)
1847 {
1848 uint64_t guid = 0;
1849
1850 if (spa)
1851 guid = spa_guid(spa);
1852
1853 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
1854 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
1855 if (spa)
1856 break;
1857 }
1858 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
1859 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
1860 if (spa)
1861 break;
1862 }
1863 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
1864 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
1865 if (spa)
1866 break;
1867 }
1868 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
1869 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
1870 if (spa)
1871 break;
1872 }
1873
1874 arc_evict_ghost(arc_mru_ghost, guid, -1);
1875 arc_evict_ghost(arc_mfu_ghost, guid, -1);
1876
1877 mutex_enter(&arc_reclaim_thr_lock);
1878 arc_do_user_evicts();
1879 mutex_exit(&arc_reclaim_thr_lock);
1880 ASSERT(spa || arc_eviction_list == NULL);
1881 }
1882
1883 void
1884 arc_shrink(void)
1885 {
1886 if (arc_c > arc_c_min) {
1887 uint64_t to_free;
1888
1889 #ifdef _KERNEL
1890 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
1891 #else
1892 to_free = arc_c >> arc_shrink_shift;
1893 #endif
1894 if (arc_c > arc_c_min + to_free)
1895 atomic_add_64(&arc_c, -to_free);
1896 else
1897 arc_c = arc_c_min;
1898
1899 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
1900 if (arc_c > arc_size)
1901 arc_c = MAX(arc_size, arc_c_min);
1902 if (arc_p > arc_c)
1903 arc_p = (arc_c >> 1);
1904 ASSERT(arc_c >= arc_c_min);
1905 ASSERT((int64_t)arc_p >= 0);
1906 }
1907
1908 if (arc_size > arc_c)
1909 arc_adjust();
1910 }
1911
1912 static int
1913 arc_reclaim_needed(void)
1914 {
1915 uint64_t extra;
1916
1917 #ifdef _KERNEL
1918
1919 if (needfree)
1920 return (1);
1921
1922 /*
1923 * take 'desfree' extra pages, so we reclaim sooner, rather than later
1924 */
1925 extra = desfree;
1926
1927 /*
1928 * check that we're out of range of the pageout scanner. It starts to
1929 * schedule paging if freemem is less than lotsfree and needfree.
1930 * lotsfree is the high-water mark for pageout, and needfree is the
1931 * number of needed free pages. We add extra pages here to make sure
1932 * the scanner doesn't start up while we're freeing memory.
1933 */
1934 if (freemem < lotsfree + needfree + extra)
1935 return (1);
1936
1937 /*
1938 * check to make sure that swapfs has enough space so that anon
1939 * reservations can still succeed. anon_resvmem() checks that the
1940 * availrmem is greater than swapfs_minfree, and the number of reserved
1941 * swap pages. We also add a bit of extra here just to prevent
1942 * circumstances from getting really dire.
1943 */
1944 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
1945 return (1);
1946
1947 #if defined(__i386)
1948 /*
1949 * If we're on an i386 platform, it's possible that we'll exhaust the
1950 * kernel heap space before we ever run out of available physical
1951 * memory. Most checks of the size of the heap_area compare against
1952 * tune.t_minarmem, which is the minimum available real memory that we
1953 * can have in the system. However, this is generally fixed at 25 pages
1954 * which is so low that it's useless. In this comparison, we seek to
1955 * calculate the total heap-size, and reclaim if more than 3/4ths of the
1956 * heap is allocated. (Or, in the calculation, if less than 1/4th is
1957 * free)
1958 */
1959 if (btop(vmem_size(heap_arena, VMEM_FREE)) <
1960 (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
1961 return (1);
1962 #endif
1963
1964 #else
1965 if (spa_get_random(100) == 0)
1966 return (1);
1967 #endif
1968 return (0);
1969 }
1970
1971 static void
1972 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
1973 {
1974 size_t i;
1975 kmem_cache_t *prev_cache = NULL;
1976 kmem_cache_t *prev_data_cache = NULL;
1977 extern kmem_cache_t *zio_buf_cache[];
1978 extern kmem_cache_t *zio_data_buf_cache[];
1979
1980 #ifdef _KERNEL
1981 if (arc_meta_used >= arc_meta_limit) {
1982 /*
1983 * We are exceeding our meta-data cache limit.
1984 * Purge some DNLC entries to release holds on meta-data.
1985 */
1986 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
1987 }
1988 #if defined(__i386)
1989 /*
1990 * Reclaim unused memory from all kmem caches.
1991 */
1992 kmem_reap();
1993 #endif
1994 #endif
1995
1996 /*
1997 * An aggressive reclamation will shrink the cache size as well as
1998 * reap free buffers from the arc kmem caches.
1999 */
2000 if (strat == ARC_RECLAIM_AGGR)
2001 arc_shrink();
2002
2003 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2004 if (zio_buf_cache[i] != prev_cache) {
2005 prev_cache = zio_buf_cache[i];
2006 kmem_cache_reap_now(zio_buf_cache[i]);
2007 }
2008 if (zio_data_buf_cache[i] != prev_data_cache) {
2009 prev_data_cache = zio_data_buf_cache[i];
2010 kmem_cache_reap_now(zio_data_buf_cache[i]);
2011 }
2012 }
2013 kmem_cache_reap_now(buf_cache);
2014 kmem_cache_reap_now(hdr_cache);
2015 }
2016
2017 static void
2018 arc_reclaim_thread(void)
2019 {
2020 clock_t growtime = 0;
2021 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2022 callb_cpr_t cpr;
2023
2024 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2025
2026 mutex_enter(&arc_reclaim_thr_lock);
2027 while (arc_thread_exit == 0) {
2028 if (arc_reclaim_needed()) {
2029
2030 if (arc_no_grow) {
2031 if (last_reclaim == ARC_RECLAIM_CONS) {
2032 last_reclaim = ARC_RECLAIM_AGGR;
2033 } else {
2034 last_reclaim = ARC_RECLAIM_CONS;
2035 }
2036 } else {
2037 arc_no_grow = TRUE;
2038 last_reclaim = ARC_RECLAIM_AGGR;
2039 membar_producer();
2040 }
2041
2042 /* reset the growth delay for every reclaim */
2043 growtime = lbolt + (arc_grow_retry * hz);
2044
2045 arc_kmem_reap_now(last_reclaim);
2046 arc_warm = B_TRUE;
2047
2048 } else if (arc_no_grow && lbolt >= growtime) {
2049 arc_no_grow = FALSE;
2050 }
2051
2052 if (2 * arc_c < arc_size +
2053 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size)
2054 arc_adjust();
2055
2056 if (arc_eviction_list != NULL)
2057 arc_do_user_evicts();
2058
2059 /* block until needed, or one second, whichever is shorter */
2060 CALLB_CPR_SAFE_BEGIN(&cpr);
2061 (void) cv_timedwait(&arc_reclaim_thr_cv,
2062 &arc_reclaim_thr_lock, (lbolt + hz));
2063 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2064 }
2065
2066 arc_thread_exit = 0;
2067 cv_broadcast(&arc_reclaim_thr_cv);
2068 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2069 thread_exit();
2070 }
2071
2072 /*
2073 * Adapt arc info given the number of bytes we are trying to add and
2074 * the state that we are comming from. This function is only called
2075 * when we are adding new content to the cache.
2076 */
2077 static void
2078 arc_adapt(int bytes, arc_state_t *state)
2079 {
2080 int mult;
2081 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2082
2083 if (state == arc_l2c_only)
2084 return;
2085
2086 ASSERT(bytes > 0);
2087 /*
2088 * Adapt the target size of the MRU list:
2089 * - if we just hit in the MRU ghost list, then increase
2090 * the target size of the MRU list.
2091 * - if we just hit in the MFU ghost list, then increase
2092 * the target size of the MFU list by decreasing the
2093 * target size of the MRU list.
2094 */
2095 if (state == arc_mru_ghost) {
2096 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2097 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2098
2099 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2100 } else if (state == arc_mfu_ghost) {
2101 uint64_t delta;
2102
2103 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2104 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2105
2106 delta = MIN(bytes * mult, arc_p);
2107 arc_p = MAX(arc_p_min, arc_p - delta);
2108 }
2109 ASSERT((int64_t)arc_p >= 0);
2110
2111 if (arc_reclaim_needed()) {
2112 cv_signal(&arc_reclaim_thr_cv);
2113 return;
2114 }
2115
2116 if (arc_no_grow)
2117 return;
2118
2119 if (arc_c >= arc_c_max)
2120 return;
2121
2122 /*
2123 * If we're within (2 * maxblocksize) bytes of the target
2124 * cache size, increment the target cache size
2125 */
2126 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2127 atomic_add_64(&arc_c, (int64_t)bytes);
2128 if (arc_c > arc_c_max)
2129 arc_c = arc_c_max;
2130 else if (state == arc_anon)
2131 atomic_add_64(&arc_p, (int64_t)bytes);
2132 if (arc_p > arc_c)
2133 arc_p = arc_c;
2134 }
2135 ASSERT((int64_t)arc_p >= 0);
2136 }
2137
2138 /*
2139 * Check if the cache has reached its limits and eviction is required
2140 * prior to insert.
2141 */
2142 static int
2143 arc_evict_needed(arc_buf_contents_t type)
2144 {
2145 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2146 return (1);
2147
2148 #ifdef _KERNEL
2149 /*
2150 * If zio data pages are being allocated out of a separate heap segment,
2151 * then enforce that the size of available vmem for this area remains
2152 * above about 1/32nd free.
2153 */
2154 if (type == ARC_BUFC_DATA && zio_arena != NULL &&
2155 vmem_size(zio_arena, VMEM_FREE) <
2156 (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
2157 return (1);
2158 #endif
2159
2160 if (arc_reclaim_needed())
2161 return (1);
2162
2163 return (arc_size > arc_c);
2164 }
2165
2166 /*
2167 * The buffer, supplied as the first argument, needs a data block.
2168 * So, if we are at cache max, determine which cache should be victimized.
2169 * We have the following cases:
2170 *
2171 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2172 * In this situation if we're out of space, but the resident size of the MFU is
2173 * under the limit, victimize the MFU cache to satisfy this insertion request.
2174 *
2175 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2176 * Here, we've used up all of the available space for the MRU, so we need to
2177 * evict from our own cache instead. Evict from the set of resident MRU
2178 * entries.
2179 *
2180 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2181 * c minus p represents the MFU space in the cache, since p is the size of the
2182 * cache that is dedicated to the MRU. In this situation there's still space on
2183 * the MFU side, so the MRU side needs to be victimized.
2184 *
2185 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2186 * MFU's resident set is consuming more space than it has been allotted. In
2187 * this situation, we must victimize our own cache, the MFU, for this insertion.
2188 */
2189 static void
2190 arc_get_data_buf(arc_buf_t *buf)
2191 {
2192 arc_state_t *state = buf->b_hdr->b_state;
2193 uint64_t size = buf->b_hdr->b_size;
2194 arc_buf_contents_t type = buf->b_hdr->b_type;
2195
2196 arc_adapt(size, state);
2197
2198 /*
2199 * We have not yet reached cache maximum size,
2200 * just allocate a new buffer.
2201 */
2202 if (!arc_evict_needed(type)) {
2203 if (type == ARC_BUFC_METADATA) {
2204 buf->b_data = zio_buf_alloc(size);
2205 arc_space_consume(size, ARC_SPACE_DATA);
2206 } else {
2207 ASSERT(type == ARC_BUFC_DATA);
2208 buf->b_data = zio_data_buf_alloc(size);
2209 ARCSTAT_INCR(arcstat_data_size, size);
2210 atomic_add_64(&arc_size, size);
2211 }
2212 goto out;
2213 }
2214
2215 /*
2216 * If we are prefetching from the mfu ghost list, this buffer
2217 * will end up on the mru list; so steal space from there.
2218 */
2219 if (state == arc_mfu_ghost)
2220 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2221 else if (state == arc_mru_ghost)
2222 state = arc_mru;
2223
2224 if (state == arc_mru || state == arc_anon) {
2225 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2226 state = (arc_mfu->arcs_lsize[type] >= size &&
2227 arc_p > mru_used) ? arc_mfu : arc_mru;
2228 } else {
2229 /* MFU cases */
2230 uint64_t mfu_space = arc_c - arc_p;
2231 state = (arc_mru->arcs_lsize[type] >= size &&
2232 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2233 }
2234 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
2235 if (type == ARC_BUFC_METADATA) {
2236 buf->b_data = zio_buf_alloc(size);
2237 arc_space_consume(size, ARC_SPACE_DATA);
2238 } else {
2239 ASSERT(type == ARC_BUFC_DATA);
2240 buf->b_data = zio_data_buf_alloc(size);
2241 ARCSTAT_INCR(arcstat_data_size, size);
2242 atomic_add_64(&arc_size, size);
2243 }
2244 ARCSTAT_BUMP(arcstat_recycle_miss);
2245 }
2246 ASSERT(buf->b_data != NULL);
2247 out:
2248 /*
2249 * Update the state size. Note that ghost states have a
2250 * "ghost size" and so don't need to be updated.
2251 */
2252 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2253 arc_buf_hdr_t *hdr = buf->b_hdr;
2254
2255 atomic_add_64(&hdr->b_state->arcs_size, size);
2256 if (list_link_active(&hdr->b_arc_node)) {
2257 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2258 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2259 }
2260 /*
2261 * If we are growing the cache, and we are adding anonymous
2262 * data, and we have outgrown arc_p, update arc_p
2263 */
2264 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2265 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2266 arc_p = MIN(arc_c, arc_p + size);
2267 }
2268 }
2269
2270 /*
2271 * This routine is called whenever a buffer is accessed.
2272 * NOTE: the hash lock is dropped in this function.
2273 */
2274 static void
2275 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2276 {
2277 ASSERT(MUTEX_HELD(hash_lock));
2278
2279 if (buf->b_state == arc_anon) {
2280 /*
2281 * This buffer is not in the cache, and does not
2282 * appear in our "ghost" list. Add the new buffer
2283 * to the MRU state.
2284 */
2285
2286 ASSERT(buf->b_arc_access == 0);
2287 buf->b_arc_access = lbolt;
2288 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2289 arc_change_state(arc_mru, buf, hash_lock);
2290
2291 } else if (buf->b_state == arc_mru) {
2292 /*
2293 * If this buffer is here because of a prefetch, then either:
2294 * - clear the flag if this is a "referencing" read
2295 * (any subsequent access will bump this into the MFU state).
2296 * or
2297 * - move the buffer to the head of the list if this is
2298 * another prefetch (to make it less likely to be evicted).
2299 */
2300 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2301 if (refcount_count(&buf->b_refcnt) == 0) {
2302 ASSERT(list_link_active(&buf->b_arc_node));
2303 } else {
2304 buf->b_flags &= ~ARC_PREFETCH;
2305 ARCSTAT_BUMP(arcstat_mru_hits);
2306 }
2307 buf->b_arc_access = lbolt;
2308 return;
2309 }
2310
2311 /*
2312 * This buffer has been "accessed" only once so far,
2313 * but it is still in the cache. Move it to the MFU
2314 * state.
2315 */
2316 if (lbolt > buf->b_arc_access + ARC_MINTIME) {
2317 /*
2318 * More than 125ms have passed since we
2319 * instantiated this buffer. Move it to the
2320 * most frequently used state.
2321 */
2322 buf->b_arc_access = lbolt;
2323 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2324 arc_change_state(arc_mfu, buf, hash_lock);
2325 }
2326 ARCSTAT_BUMP(arcstat_mru_hits);
2327 } else if (buf->b_state == arc_mru_ghost) {
2328 arc_state_t *new_state;
2329 /*
2330 * This buffer has been "accessed" recently, but
2331 * was evicted from the cache. Move it to the
2332 * MFU state.
2333 */
2334
2335 if (buf->b_flags & ARC_PREFETCH) {
2336 new_state = arc_mru;
2337 if (refcount_count(&buf->b_refcnt) > 0)
2338 buf->b_flags &= ~ARC_PREFETCH;
2339 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2340 } else {
2341 new_state = arc_mfu;
2342 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2343 }
2344
2345 buf->b_arc_access = lbolt;
2346 arc_change_state(new_state, buf, hash_lock);
2347
2348 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2349 } else if (buf->b_state == arc_mfu) {
2350 /*
2351 * This buffer has been accessed more than once and is
2352 * still in the cache. Keep it in the MFU state.
2353 *
2354 * NOTE: an add_reference() that occurred when we did
2355 * the arc_read() will have kicked this off the list.
2356 * If it was a prefetch, we will explicitly move it to
2357 * the head of the list now.
2358 */
2359 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2360 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2361 ASSERT(list_link_active(&buf->b_arc_node));
2362 }
2363 ARCSTAT_BUMP(arcstat_mfu_hits);
2364 buf->b_arc_access = lbolt;
2365 } else if (buf->b_state == arc_mfu_ghost) {
2366 arc_state_t *new_state = arc_mfu;
2367 /*
2368 * This buffer has been accessed more than once but has
2369 * been evicted from the cache. Move it back to the
2370 * MFU state.
2371 */
2372
2373 if (buf->b_flags & ARC_PREFETCH) {
2374 /*
2375 * This is a prefetch access...
2376 * move this block back to the MRU state.
2377 */
2378 ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
2379 new_state = arc_mru;
2380 }
2381
2382 buf->b_arc_access = lbolt;
2383 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2384 arc_change_state(new_state, buf, hash_lock);
2385
2386 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2387 } else if (buf->b_state == arc_l2c_only) {
2388 /*
2389 * This buffer is on the 2nd Level ARC.
2390 */
2391
2392 buf->b_arc_access = lbolt;
2393 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2394 arc_change_state(arc_mfu, buf, hash_lock);
2395 } else {
2396 ASSERT(!"invalid arc state");
2397 }
2398 }
2399
2400 /* a generic arc_done_func_t which you can use */
2401 /* ARGSUSED */
2402 void
2403 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2404 {
2405 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2406 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2407 }
2408
2409 /* a generic arc_done_func_t */
2410 void
2411 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2412 {
2413 arc_buf_t **bufp = arg;
2414 if (zio && zio->io_error) {
2415 VERIFY(arc_buf_remove_ref(buf, arg) == 1);
2416 *bufp = NULL;
2417 } else {
2418 *bufp = buf;
2419 }
2420 }
2421
2422 static void
2423 arc_read_done(zio_t *zio)
2424 {
2425 arc_buf_hdr_t *hdr, *found;
2426 arc_buf_t *buf;
2427 arc_buf_t *abuf; /* buffer we're assigning to callback */
2428 kmutex_t *hash_lock;
2429 arc_callback_t *callback_list, *acb;
2430 int freeable = FALSE;
2431
2432 buf = zio->io_private;
2433 hdr = buf->b_hdr;
2434
2435 /*
2436 * The hdr was inserted into hash-table and removed from lists
2437 * prior to starting I/O. We should find this header, since
2438 * it's in the hash table, and it should be legit since it's
2439 * not possible to evict it during the I/O. The only possible
2440 * reason for it not to be found is if we were freed during the
2441 * read.
2442 */
2443 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2444 &hash_lock);
2445
2446 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2447 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2448 (found == hdr && HDR_L2_READING(hdr)));
2449
2450 hdr->b_flags &= ~ARC_L2_EVICTED;
2451 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2452 hdr->b_flags &= ~ARC_L2CACHE;
2453
2454 /* byteswap if necessary */
2455 callback_list = hdr->b_acb;
2456 ASSERT(callback_list != NULL);
2457 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
2458 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2459 byteswap_uint64_array :
2460 dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
2461 func(buf->b_data, hdr->b_size);
2462 }
2463
2464 arc_cksum_compute(buf, B_FALSE);
2465
2466 /* create copies of the data buffer for the callers */
2467 abuf = buf;
2468 for (acb = callback_list; acb; acb = acb->acb_next) {
2469 if (acb->acb_done) {
2470 if (abuf == NULL)
2471 abuf = arc_buf_clone(buf);
2472 acb->acb_buf = abuf;
2473 abuf = NULL;
2474 }
2475 }
2476 hdr->b_acb = NULL;
2477 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2478 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2479 if (abuf == buf)
2480 hdr->b_flags |= ARC_BUF_AVAILABLE;
2481
2482 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2483
2484 if (zio->io_error != 0) {
2485 hdr->b_flags |= ARC_IO_ERROR;
2486 if (hdr->b_state != arc_anon)
2487 arc_change_state(arc_anon, hdr, hash_lock);
2488 if (HDR_IN_HASH_TABLE(hdr))
2489 buf_hash_remove(hdr);
2490 freeable = refcount_is_zero(&hdr->b_refcnt);
2491 }
2492
2493 /*
2494 * Broadcast before we drop the hash_lock to avoid the possibility
2495 * that the hdr (and hence the cv) might be freed before we get to
2496 * the cv_broadcast().
2497 */
2498 cv_broadcast(&hdr->b_cv);
2499
2500 if (hash_lock) {
2501 /*
2502 * Only call arc_access on anonymous buffers. This is because
2503 * if we've issued an I/O for an evicted buffer, we've already
2504 * called arc_access (to prevent any simultaneous readers from
2505 * getting confused).
2506 */
2507 if (zio->io_error == 0 && hdr->b_state == arc_anon)
2508 arc_access(hdr, hash_lock);
2509 mutex_exit(hash_lock);
2510 } else {
2511 /*
2512 * This block was freed while we waited for the read to
2513 * complete. It has been removed from the hash table and
2514 * moved to the anonymous state (so that it won't show up
2515 * in the cache).
2516 */
2517 ASSERT3P(hdr->b_state, ==, arc_anon);
2518 freeable = refcount_is_zero(&hdr->b_refcnt);
2519 }
2520
2521 /* execute each callback and free its structure */
2522 while ((acb = callback_list) != NULL) {
2523 if (acb->acb_done)
2524 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2525
2526 if (acb->acb_zio_dummy != NULL) {
2527 acb->acb_zio_dummy->io_error = zio->io_error;
2528 zio_nowait(acb->acb_zio_dummy);
2529 }
2530
2531 callback_list = acb->acb_next;
2532 kmem_free(acb, sizeof (arc_callback_t));
2533 }
2534
2535 if (freeable)
2536 arc_hdr_destroy(hdr);
2537 }
2538
2539 /*
2540 * "Read" the block block at the specified DVA (in bp) via the
2541 * cache. If the block is found in the cache, invoke the provided
2542 * callback immediately and return. Note that the `zio' parameter
2543 * in the callback will be NULL in this case, since no IO was
2544 * required. If the block is not in the cache pass the read request
2545 * on to the spa with a substitute callback function, so that the
2546 * requested block will be added to the cache.
2547 *
2548 * If a read request arrives for a block that has a read in-progress,
2549 * either wait for the in-progress read to complete (and return the
2550 * results); or, if this is a read with a "done" func, add a record
2551 * to the read to invoke the "done" func when the read completes,
2552 * and return; or just return.
2553 *
2554 * arc_read_done() will invoke all the requested "done" functions
2555 * for readers of this block.
2556 *
2557 * Normal callers should use arc_read and pass the arc buffer and offset
2558 * for the bp. But if you know you don't need locking, you can use
2559 * arc_read_bp.
2560 */
2561 int
2562 arc_read(zio_t *pio, spa_t *spa, blkptr_t *bp, arc_buf_t *pbuf,
2563 arc_done_func_t *done, void *private, int priority, int zio_flags,
2564 uint32_t *arc_flags, const zbookmark_t *zb)
2565 {
2566 int err;
2567
2568 ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
2569 ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
2570 rw_enter(&pbuf->b_lock, RW_READER);
2571
2572 err = arc_read_nolock(pio, spa, bp, done, private, priority,
2573 zio_flags, arc_flags, zb);
2574 rw_exit(&pbuf->b_lock);
2575
2576 return (err);
2577 }
2578
2579 int
2580 arc_read_nolock(zio_t *pio, spa_t *spa, blkptr_t *bp,
2581 arc_done_func_t *done, void *private, int priority, int zio_flags,
2582 uint32_t *arc_flags, const zbookmark_t *zb)
2583 {
2584 arc_buf_hdr_t *hdr;
2585 arc_buf_t *buf;
2586 kmutex_t *hash_lock;
2587 zio_t *rzio;
2588 uint64_t guid = spa_guid(spa);
2589
2590 top:
2591 hdr = buf_hash_find(guid, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
2592 if (hdr && hdr->b_datacnt > 0) {
2593
2594 *arc_flags |= ARC_CACHED;
2595
2596 if (HDR_IO_IN_PROGRESS(hdr)) {
2597
2598 if (*arc_flags & ARC_WAIT) {
2599 cv_wait(&hdr->b_cv, hash_lock);
2600 mutex_exit(hash_lock);
2601 goto top;
2602 }
2603 ASSERT(*arc_flags & ARC_NOWAIT);
2604
2605 if (done) {
2606 arc_callback_t *acb = NULL;
2607
2608 acb = kmem_zalloc(sizeof (arc_callback_t),
2609 KM_SLEEP);
2610 acb->acb_done = done;
2611 acb->acb_private = private;
2612 if (pio != NULL)
2613 acb->acb_zio_dummy = zio_null(pio,
2614 spa, NULL, NULL, NULL, zio_flags);
2615
2616 ASSERT(acb->acb_done != NULL);
2617 acb->acb_next = hdr->b_acb;
2618 hdr->b_acb = acb;
2619 add_reference(hdr, hash_lock, private);
2620 mutex_exit(hash_lock);
2621 return (0);
2622 }
2623 mutex_exit(hash_lock);
2624 return (0);
2625 }
2626
2627 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2628
2629 if (done) {
2630 add_reference(hdr, hash_lock, private);
2631 /*
2632 * If this block is already in use, create a new
2633 * copy of the data so that we will be guaranteed
2634 * that arc_release() will always succeed.
2635 */
2636 buf = hdr->b_buf;
2637 ASSERT(buf);
2638 ASSERT(buf->b_data);
2639 if (HDR_BUF_AVAILABLE(hdr)) {
2640 ASSERT(buf->b_efunc == NULL);
2641 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2642 } else {
2643 buf = arc_buf_clone(buf);
2644 }
2645 } else if (*arc_flags & ARC_PREFETCH &&
2646 refcount_count(&hdr->b_refcnt) == 0) {
2647 hdr->b_flags |= ARC_PREFETCH;
2648 }
2649 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
2650 arc_access(hdr, hash_lock);
2651 if (*arc_flags & ARC_L2CACHE)
2652 hdr->b_flags |= ARC_L2CACHE;
2653 mutex_exit(hash_lock);
2654 ARCSTAT_BUMP(arcstat_hits);
2655 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2656 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2657 data, metadata, hits);
2658
2659 if (done)
2660 done(NULL, buf, private);
2661 } else {
2662 uint64_t size = BP_GET_LSIZE(bp);
2663 arc_callback_t *acb;
2664 vdev_t *vd = NULL;
2665 uint64_t addr;
2666 boolean_t devw = B_FALSE;
2667
2668 if (hdr == NULL) {
2669 /* this block is not in the cache */
2670 arc_buf_hdr_t *exists;
2671 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
2672 buf = arc_buf_alloc(spa, size, private, type);
2673 hdr = buf->b_hdr;
2674 hdr->b_dva = *BP_IDENTITY(bp);
2675 hdr->b_birth = bp->blk_birth;
2676 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
2677 exists = buf_hash_insert(hdr, &hash_lock);
2678 if (exists) {
2679 /* somebody beat us to the hash insert */
2680 mutex_exit(hash_lock);
2681 bzero(&hdr->b_dva, sizeof (dva_t));
2682 hdr->b_birth = 0;
2683 hdr->b_cksum0 = 0;
2684 (void) arc_buf_remove_ref(buf, private);
2685 goto top; /* restart the IO request */
2686 }
2687 /* if this is a prefetch, we don't have a reference */
2688 if (*arc_flags & ARC_PREFETCH) {
2689 (void) remove_reference(hdr, hash_lock,
2690 private);
2691 hdr->b_flags |= ARC_PREFETCH;
2692 }
2693 if (*arc_flags & ARC_L2CACHE)
2694 hdr->b_flags |= ARC_L2CACHE;
2695 if (BP_GET_LEVEL(bp) > 0)
2696 hdr->b_flags |= ARC_INDIRECT;
2697 } else {
2698 /* this block is in the ghost cache */
2699 ASSERT(GHOST_STATE(hdr->b_state));
2700 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2701 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
2702 ASSERT(hdr->b_buf == NULL);
2703
2704 /* if this is a prefetch, we don't have a reference */
2705 if (*arc_flags & ARC_PREFETCH)
2706 hdr->b_flags |= ARC_PREFETCH;
2707 else
2708 add_reference(hdr, hash_lock, private);
2709 if (*arc_flags & ARC_L2CACHE)
2710 hdr->b_flags |= ARC_L2CACHE;
2711 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2712 buf->b_hdr = hdr;
2713 buf->b_data = NULL;
2714 buf->b_efunc = NULL;
2715 buf->b_private = NULL;
2716 buf->b_next = NULL;
2717 hdr->b_buf = buf;
2718 arc_get_data_buf(buf);
2719 ASSERT(hdr->b_datacnt == 0);
2720 hdr->b_datacnt = 1;
2721
2722 }
2723
2724 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
2725 acb->acb_done = done;
2726 acb->acb_private = private;
2727
2728 ASSERT(hdr->b_acb == NULL);
2729 hdr->b_acb = acb;
2730 hdr->b_flags |= ARC_IO_IN_PROGRESS;
2731
2732 /*
2733 * If the buffer has been evicted, migrate it to a present state
2734 * before issuing the I/O. Once we drop the hash-table lock,
2735 * the header will be marked as I/O in progress and have an
2736 * attached buffer. At this point, anybody who finds this
2737 * buffer ought to notice that it's legit but has a pending I/O.
2738 */
2739
2740 if (GHOST_STATE(hdr->b_state))
2741 arc_access(hdr, hash_lock);
2742
2743 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
2744 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
2745 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
2746 addr = hdr->b_l2hdr->b_daddr;
2747 /*
2748 * Lock out device removal.
2749 */
2750 if (vdev_is_dead(vd) ||
2751 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
2752 vd = NULL;
2753 }
2754
2755 mutex_exit(hash_lock);
2756
2757 ASSERT3U(hdr->b_size, ==, size);
2758 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
2759 uint64_t, size, zbookmark_t *, zb);
2760 ARCSTAT_BUMP(arcstat_misses);
2761 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2762 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2763 data, metadata, misses);
2764
2765 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
2766 /*
2767 * Read from the L2ARC if the following are true:
2768 * 1. The L2ARC vdev was previously cached.
2769 * 2. This buffer still has L2ARC metadata.
2770 * 3. This buffer isn't currently writing to the L2ARC.
2771 * 4. The L2ARC entry wasn't evicted, which may
2772 * also have invalidated the vdev.
2773 * 5. This isn't prefetch and l2arc_noprefetch is set.
2774 */
2775 if (hdr->b_l2hdr != NULL &&
2776 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
2777 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
2778 l2arc_read_callback_t *cb;
2779
2780 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
2781 ARCSTAT_BUMP(arcstat_l2_hits);
2782
2783 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
2784 KM_SLEEP);
2785 cb->l2rcb_buf = buf;
2786 cb->l2rcb_spa = spa;
2787 cb->l2rcb_bp = *bp;
2788 cb->l2rcb_zb = *zb;
2789 cb->l2rcb_flags = zio_flags;
2790
2791 /*
2792 * l2arc read. The SCL_L2ARC lock will be
2793 * released by l2arc_read_done().
2794 */
2795 rzio = zio_read_phys(pio, vd, addr, size,
2796 buf->b_data, ZIO_CHECKSUM_OFF,
2797 l2arc_read_done, cb, priority, zio_flags |
2798 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
2799 ZIO_FLAG_DONT_PROPAGATE |
2800 ZIO_FLAG_DONT_RETRY, B_FALSE);
2801 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
2802 zio_t *, rzio);
2803 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
2804
2805 if (*arc_flags & ARC_NOWAIT) {
2806 zio_nowait(rzio);
2807 return (0);
2808 }
2809
2810 ASSERT(*arc_flags & ARC_WAIT);
2811 if (zio_wait(rzio) == 0)
2812 return (0);
2813
2814 /* l2arc read error; goto zio_read() */
2815 } else {
2816 DTRACE_PROBE1(l2arc__miss,
2817 arc_buf_hdr_t *, hdr);
2818 ARCSTAT_BUMP(arcstat_l2_misses);
2819 if (HDR_L2_WRITING(hdr))
2820 ARCSTAT_BUMP(arcstat_l2_rw_clash);
2821 spa_config_exit(spa, SCL_L2ARC, vd);
2822 }
2823 } else {
2824 if (vd != NULL)
2825 spa_config_exit(spa, SCL_L2ARC, vd);
2826 if (l2arc_ndev != 0) {
2827 DTRACE_PROBE1(l2arc__miss,
2828 arc_buf_hdr_t *, hdr);
2829 ARCSTAT_BUMP(arcstat_l2_misses);
2830 }
2831 }
2832
2833 rzio = zio_read(pio, spa, bp, buf->b_data, size,
2834 arc_read_done, buf, priority, zio_flags, zb);
2835
2836 if (*arc_flags & ARC_WAIT)
2837 return (zio_wait(rzio));
2838
2839 ASSERT(*arc_flags & ARC_NOWAIT);
2840 zio_nowait(rzio);
2841 }
2842 return (0);
2843 }
2844
2845 void
2846 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
2847 {
2848 ASSERT(buf->b_hdr != NULL);
2849 ASSERT(buf->b_hdr->b_state != arc_anon);
2850 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
2851 buf->b_efunc = func;
2852 buf->b_private = private;
2853 }
2854
2855 /*
2856 * This is used by the DMU to let the ARC know that a buffer is
2857 * being evicted, so the ARC should clean up. If this arc buf
2858 * is not yet in the evicted state, it will be put there.
2859 */
2860 int
2861 arc_buf_evict(arc_buf_t *buf)
2862 {
2863 arc_buf_hdr_t *hdr;
2864 kmutex_t *hash_lock;
2865 arc_buf_t **bufp;
2866
2867 rw_enter(&buf->b_lock, RW_WRITER);
2868 hdr = buf->b_hdr;
2869 if (hdr == NULL) {
2870 /*
2871 * We are in arc_do_user_evicts().
2872 */
2873 ASSERT(buf->b_data == NULL);
2874 rw_exit(&buf->b_lock);
2875 return (0);
2876 } else if (buf->b_data == NULL) {
2877 arc_buf_t copy = *buf; /* structure assignment */
2878 /*
2879 * We are on the eviction list; process this buffer now
2880 * but let arc_do_user_evicts() do the reaping.
2881 */
2882 buf->b_efunc = NULL;
2883 rw_exit(&buf->b_lock);
2884 VERIFY(copy.b_efunc(©) == 0);
2885 return (1);
2886 }
2887 hash_lock = HDR_LOCK(hdr);
2888 mutex_enter(hash_lock);
2889
2890 ASSERT(buf->b_hdr == hdr);
2891 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
2892 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2893
2894 /*
2895 * Pull this buffer off of the hdr
2896 */
2897 bufp = &hdr->b_buf;
2898 while (*bufp != buf)
2899 bufp = &(*bufp)->b_next;
2900 *bufp = buf->b_next;
2901
2902 ASSERT(buf->b_data != NULL);
2903 arc_buf_destroy(buf, FALSE, FALSE);
2904
2905 if (hdr->b_datacnt == 0) {
2906 arc_state_t *old_state = hdr->b_state;
2907 arc_state_t *evicted_state;
2908
2909 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2910
2911 evicted_state =
2912 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2913
2914 mutex_enter(&old_state->arcs_mtx);
2915 mutex_enter(&evicted_state->arcs_mtx);
2916
2917 arc_change_state(evicted_state, hdr, hash_lock);
2918 ASSERT(HDR_IN_HASH_TABLE(hdr));
2919 hdr->b_flags |= ARC_IN_HASH_TABLE;
2920 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2921
2922 mutex_exit(&evicted_state->arcs_mtx);
2923 mutex_exit(&old_state->arcs_mtx);
2924 }
2925 mutex_exit(hash_lock);
2926 rw_exit(&buf->b_lock);
2927
2928 VERIFY(buf->b_efunc(buf) == 0);
2929 buf->b_efunc = NULL;
2930 buf->b_private = NULL;
2931 buf->b_hdr = NULL;
2932 kmem_cache_free(buf_cache, buf);
2933 return (1);
2934 }
2935
2936 /*
2937 * Release this buffer from the cache. This must be done
2938 * after a read and prior to modifying the buffer contents.
2939 * If the buffer has more than one reference, we must make
2940 * a new hdr for the buffer.
2941 */
2942 void
2943 arc_release(arc_buf_t *buf, void *tag)
2944 {
2945 arc_buf_hdr_t *hdr;
2946 kmutex_t *hash_lock;
2947 l2arc_buf_hdr_t *l2hdr;
2948 uint64_t buf_size;
2949 boolean_t released = B_FALSE;
2950
2951 rw_enter(&buf->b_lock, RW_WRITER);
2952 hdr = buf->b_hdr;
2953
2954 /* this buffer is not on any list */
2955 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
2956 ASSERT(!(hdr->b_flags & ARC_STORED));
2957
2958 if (hdr->b_state == arc_anon) {
2959 /* this buffer is already released */
2960 ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 1);
2961 ASSERT(BUF_EMPTY(hdr));
2962 ASSERT(buf->b_efunc == NULL);
2963 arc_buf_thaw(buf);
2964 rw_exit(&buf->b_lock);
2965 released = B_TRUE;
2966 } else {
2967 hash_lock = HDR_LOCK(hdr);
2968 mutex_enter(hash_lock);
2969 }
2970
2971 l2hdr = hdr->b_l2hdr;
2972 if (l2hdr) {
2973 mutex_enter(&l2arc_buflist_mtx);
2974 hdr->b_l2hdr = NULL;
2975 buf_size = hdr->b_size;
2976 }
2977
2978 if (released)
2979 goto out;
2980
2981 /*
2982 * Do we have more than one buf?
2983 */
2984 if (hdr->b_datacnt > 1) {
2985 arc_buf_hdr_t *nhdr;
2986 arc_buf_t **bufp;
2987 uint64_t blksz = hdr->b_size;
2988 uint64_t spa = hdr->b_spa;
2989 arc_buf_contents_t type = hdr->b_type;
2990 uint32_t flags = hdr->b_flags;
2991
2992 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
2993 /*
2994 * Pull the data off of this buf and attach it to
2995 * a new anonymous buf.
2996 */
2997 (void) remove_reference(hdr, hash_lock, tag);
2998 bufp = &hdr->b_buf;
2999 while (*bufp != buf)
3000 bufp = &(*bufp)->b_next;
3001 *bufp = (*bufp)->b_next;
3002 buf->b_next = NULL;
3003
3004 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3005 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3006 if (refcount_is_zero(&hdr->b_refcnt)) {
3007 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3008 ASSERT3U(*size, >=, hdr->b_size);
3009 atomic_add_64(size, -hdr->b_size);
3010 }
3011 hdr->b_datacnt -= 1;
3012 arc_cksum_verify(buf);
3013
3014 mutex_exit(hash_lock);
3015
3016 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3017 nhdr->b_size = blksz;
3018 nhdr->b_spa = spa;
3019 nhdr->b_type = type;
3020 nhdr->b_buf = buf;
3021 nhdr->b_state = arc_anon;
3022 nhdr->b_arc_access = 0;
3023 nhdr->b_flags = flags & ARC_L2_WRITING;
3024 nhdr->b_l2hdr = NULL;
3025 nhdr->b_datacnt = 1;
3026 nhdr->b_freeze_cksum = NULL;
3027 (void) refcount_add(&nhdr->b_refcnt, tag);
3028 buf->b_hdr = nhdr;
3029 rw_exit(&buf->b_lock);
3030 atomic_add_64(&arc_anon->arcs_size, blksz);
3031 } else {
3032 rw_exit(&buf->b_lock);
3033 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3034 ASSERT(!list_link_active(&hdr->b_arc_node));
3035 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3036 arc_change_state(arc_anon, hdr, hash_lock);
3037 hdr->b_arc_access = 0;
3038 mutex_exit(hash_lock);
3039
3040 bzero(&hdr->b_dva, sizeof (dva_t));
3041 hdr->b_birth = 0;
3042 hdr->b_cksum0 = 0;
3043 arc_buf_thaw(buf);
3044 }
3045 buf->b_efunc = NULL;
3046 buf->b_private = NULL;
3047
3048 out:
3049 if (l2hdr) {
3050 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3051 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3052 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3053 mutex_exit(&l2arc_buflist_mtx);
3054 }
3055 }
3056
3057 int
3058 arc_released(arc_buf_t *buf)
3059 {
3060 int released;
3061
3062 rw_enter(&buf->b_lock, RW_READER);
3063 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3064 rw_exit(&buf->b_lock);
3065 return (released);
3066 }
3067
3068 int
3069 arc_has_callback(arc_buf_t *buf)
3070 {
3071 int callback;
3072
3073 rw_enter(&buf->b_lock, RW_READER);
3074 callback = (buf->b_efunc != NULL);
3075 rw_exit(&buf->b_lock);
3076 return (callback);
3077 }
3078
3079 #ifdef ZFS_DEBUG
3080 int
3081 arc_referenced(arc_buf_t *buf)
3082 {
3083 int referenced;
3084
3085 rw_enter(&buf->b_lock, RW_READER);
3086 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3087 rw_exit(&buf->b_lock);
3088 return (referenced);
3089 }
3090 #endif
3091
3092 static void
3093 arc_write_ready(zio_t *zio)
3094 {
3095 arc_write_callback_t *callback = zio->io_private;
3096 arc_buf_t *buf = callback->awcb_buf;
3097 arc_buf_hdr_t *hdr = buf->b_hdr;
3098
3099 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3100 callback->awcb_ready(zio, buf, callback->awcb_private);
3101
3102 /*
3103 * If the IO is already in progress, then this is a re-write
3104 * attempt, so we need to thaw and re-compute the cksum.
3105 * It is the responsibility of the callback to handle the
3106 * accounting for any re-write attempt.
3107 */
3108 if (HDR_IO_IN_PROGRESS(hdr)) {
3109 mutex_enter(&hdr->b_freeze_lock);
3110 if (hdr->b_freeze_cksum != NULL) {
3111 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3112 hdr->b_freeze_cksum = NULL;
3113 }
3114 mutex_exit(&hdr->b_freeze_lock);
3115 }
3116 arc_cksum_compute(buf, B_FALSE);
3117 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3118 }
3119
3120 static void
3121 arc_write_done(zio_t *zio)
3122 {
3123 arc_write_callback_t *callback = zio->io_private;
3124 arc_buf_t *buf = callback->awcb_buf;
3125 arc_buf_hdr_t *hdr = buf->b_hdr;
3126
3127 hdr->b_acb = NULL;
3128
3129 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3130 hdr->b_birth = zio->io_bp->blk_birth;
3131 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3132 /*
3133 * If the block to be written was all-zero, we may have
3134 * compressed it away. In this case no write was performed
3135 * so there will be no dva/birth-date/checksum. The buffer
3136 * must therefor remain anonymous (and uncached).
3137 */
3138 if (!BUF_EMPTY(hdr)) {
3139 arc_buf_hdr_t *exists;
3140 kmutex_t *hash_lock;
3141
3142 arc_cksum_verify(buf);
3143
3144 exists = buf_hash_insert(hdr, &hash_lock);
3145 if (exists) {
3146 /*
3147 * This can only happen if we overwrite for
3148 * sync-to-convergence, because we remove
3149 * buffers from the hash table when we arc_free().
3150 */
3151 if (!(zio->io_flags & ZIO_FLAG_IO_REWRITE) ||
3152 !DVA_EQUAL(BP_IDENTITY(&zio->io_bp_orig),
3153 BP_IDENTITY(zio->io_bp)) ||
3154 zio->io_bp_orig.blk_birth !=
3155 zio->io_bp->blk_birth) {
3156 panic("bad overwrite, hdr=%p exists=%p",
3157 (void *)hdr, (void *)exists);
3158 }
3159
3160 ASSERT(refcount_is_zero(&exists->b_refcnt));
3161 arc_change_state(arc_anon, exists, hash_lock);
3162 mutex_exit(hash_lock);
3163 arc_hdr_destroy(exists);
3164 exists = buf_hash_insert(hdr, &hash_lock);
3165 ASSERT3P(exists, ==, NULL);
3166 }
3167 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3168 /* if it's not anon, we are doing a scrub */
3169 if (hdr->b_state == arc_anon)
3170 arc_access(hdr, hash_lock);
3171 mutex_exit(hash_lock);
3172 } else if (callback->awcb_done == NULL) {
3173 int destroy_hdr;
3174 /*
3175 * This is an anonymous buffer with no user callback,
3176 * destroy it if there are no active references.
3177 */
3178 mutex_enter(&arc_eviction_mtx);
3179 destroy_hdr = refcount_is_zero(&hdr->b_refcnt);
3180 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3181 mutex_exit(&arc_eviction_mtx);
3182 if (destroy_hdr)
3183 arc_hdr_destroy(hdr);
3184 } else {
3185 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3186 }
3187 hdr->b_flags &= ~ARC_STORED;
3188
3189 if (callback->awcb_done) {
3190 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3191 callback->awcb_done(zio, buf, callback->awcb_private);
3192 }
3193
3194 kmem_free(callback, sizeof (arc_write_callback_t));
3195 }
3196
3197 void
3198 write_policy(spa_t *spa, const writeprops_t *wp, zio_prop_t *zp)
3199 {
3200 boolean_t ismd = (wp->wp_level > 0 || dmu_ot[wp->wp_type].ot_metadata);
3201
3202 /* Determine checksum setting */
3203 if (ismd) {
3204 /*
3205 * Metadata always gets checksummed. If the data
3206 * checksum is multi-bit correctable, and it's not a
3207 * ZBT-style checksum, then it's suitable for metadata
3208 * as well. Otherwise, the metadata checksum defaults
3209 * to fletcher4.
3210 */
3211 if (zio_checksum_table[wp->wp_oschecksum].ci_correctable &&
3212 !zio_checksum_table[wp->wp_oschecksum].ci_zbt)
3213 zp->zp_checksum = wp->wp_oschecksum;
3214 else
3215 zp->zp_checksum = ZIO_CHECKSUM_FLETCHER_4;
3216 } else {
3217 zp->zp_checksum = zio_checksum_select(wp->wp_dnchecksum,
3218 wp->wp_oschecksum);
3219 }
3220
3221 /* Determine compression setting */
3222 if (ismd) {
3223 /*
3224 * XXX -- we should design a compression algorithm
3225 * that specializes in arrays of bps.
3226 */
3227 zp->zp_compress = zfs_mdcomp_disable ? ZIO_COMPRESS_EMPTY :
3228 ZIO_COMPRESS_LZJB;
3229 } else {
3230 zp->zp_compress = zio_compress_select(wp->wp_dncompress,
3231 wp->wp_oscompress);
3232 }
3233
3234 zp->zp_type = wp->wp_type;
3235 zp->zp_level = wp->wp_level;
3236 zp->zp_ndvas = MIN(wp->wp_copies + ismd, spa_max_replication(spa));
3237 }
3238
3239 zio_t *
3240 arc_write(zio_t *pio, spa_t *spa, const writeprops_t *wp,
3241 boolean_t l2arc, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
3242 arc_done_func_t *ready, arc_done_func_t *done, void *private, int priority,
3243 int zio_flags, const zbookmark_t *zb)
3244 {
3245 arc_buf_hdr_t *hdr = buf->b_hdr;
3246 arc_write_callback_t *callback;
3247 zio_t *zio;
3248 zio_prop_t zp;
3249
3250 ASSERT(ready != NULL);
3251 ASSERT(!HDR_IO_ERROR(hdr));
3252 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3253 ASSERT(hdr->b_acb == 0);
3254 if (l2arc)
3255 hdr->b_flags |= ARC_L2CACHE;
3256 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3257 callback->awcb_ready = ready;
3258 callback->awcb_done = done;
3259 callback->awcb_private = private;
3260 callback->awcb_buf = buf;
3261
3262 write_policy(spa, wp, &zp);
3263 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, &zp,
3264 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3265
3266 return (zio);
3267 }
3268
3269 int
3270 arc_free(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
3271 zio_done_func_t *done, void *private, uint32_t arc_flags)
3272 {
3273 arc_buf_hdr_t *ab;
3274 kmutex_t *hash_lock;
3275 zio_t *zio;
3276 uint64_t guid = spa_guid(spa);
3277
3278 /*
3279 * If this buffer is in the cache, release it, so it
3280 * can be re-used.
3281 */
3282 ab = buf_hash_find(guid, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
3283 if (ab != NULL) {
3284 /*
3285 * The checksum of blocks to free is not always
3286 * preserved (eg. on the deadlist). However, if it is
3287 * nonzero, it should match what we have in the cache.
3288 */
3289 ASSERT(bp->blk_cksum.zc_word[0] == 0 ||
3290 bp->blk_cksum.zc_word[0] == ab->b_cksum0 ||
3291 bp->blk_fill == BLK_FILL_ALREADY_FREED);
3292
3293 if (ab->b_state != arc_anon)
3294 arc_change_state(arc_anon, ab, hash_lock);
3295 if (HDR_IO_IN_PROGRESS(ab)) {
3296 /*
3297 * This should only happen when we prefetch.
3298 */
3299 ASSERT(ab->b_flags & ARC_PREFETCH);
3300 ASSERT3U(ab->b_datacnt, ==, 1);
3301 ab->b_flags |= ARC_FREED_IN_READ;
3302 if (HDR_IN_HASH_TABLE(ab))
3303 buf_hash_remove(ab);
3304 ab->b_arc_access = 0;
3305 bzero(&ab->b_dva, sizeof (dva_t));
3306 ab->b_birth = 0;
3307 ab->b_cksum0 = 0;
3308 ab->b_buf->b_efunc = NULL;
3309 ab->b_buf->b_private = NULL;
3310 mutex_exit(hash_lock);
3311 } else if (refcount_is_zero(&ab->b_refcnt)) {
3312 ab->b_flags |= ARC_FREE_IN_PROGRESS;
3313 mutex_exit(hash_lock);
3314 arc_hdr_destroy(ab);
3315 ARCSTAT_BUMP(arcstat_deleted);
3316 } else {
3317 /*
3318 * We still have an active reference on this
3319 * buffer. This can happen, e.g., from
3320 * dbuf_unoverride().
3321 */
3322 ASSERT(!HDR_IN_HASH_TABLE(ab));
3323 ab->b_arc_access = 0;
3324 bzero(&ab->b_dva, sizeof (dva_t));
3325 ab->b_birth = 0;
3326 ab->b_cksum0 = 0;
3327 ab->b_buf->b_efunc = NULL;
3328 ab->b_buf->b_private = NULL;
3329 mutex_exit(hash_lock);
3330 }
3331 }
3332
3333 zio = zio_free(pio, spa, txg, bp, done, private, ZIO_FLAG_MUSTSUCCEED);
3334
3335 if (arc_flags & ARC_WAIT)
3336 return (zio_wait(zio));
3337
3338 ASSERT(arc_flags & ARC_NOWAIT);
3339 zio_nowait(zio);
3340
3341 return (0);
3342 }
3343
3344 static int
3345 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3346 {
3347 #ifdef _KERNEL
3348 uint64_t available_memory = ptob(freemem);
3349 static uint64_t page_load = 0;
3350 static uint64_t last_txg = 0;
3351
3352 #if defined(__i386)
3353 available_memory =
3354 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3355 #endif
3356 if (available_memory >= zfs_write_limit_max)
3357 return (0);
3358
3359 if (txg > last_txg) {
3360 last_txg = txg;
3361 page_load = 0;
3362 }
3363 /*
3364 * If we are in pageout, we know that memory is already tight,
3365 * the arc is already going to be evicting, so we just want to
3366 * continue to let page writes occur as quickly as possible.
3367 */
3368 if (curproc == proc_pageout) {
3369 if (page_load > MAX(ptob(minfree), available_memory) / 4)
3370 return (ERESTART);
3371 /* Note: reserve is inflated, so we deflate */
3372 page_load += reserve / 8;
3373 return (0);
3374 } else if (page_load > 0 && arc_reclaim_needed()) {
3375 /* memory is low, delay before restarting */
3376 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3377 return (EAGAIN);
3378 }
3379 page_load = 0;
3380
3381 if (arc_size > arc_c_min) {
3382 uint64_t evictable_memory =
3383 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3384 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3385 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3386 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3387 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3388 }
3389
3390 if (inflight_data > available_memory / 4) {
3391 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3392 return (ERESTART);
3393 }
3394 #endif
3395 return (0);
3396 }
3397
3398 void
3399 arc_tempreserve_clear(uint64_t reserve)
3400 {
3401 atomic_add_64(&arc_tempreserve, -reserve);
3402 ASSERT((int64_t)arc_tempreserve >= 0);
3403 }
3404
3405 int
3406 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3407 {
3408 int error;
3409 uint64_t anon_size;
3410
3411 #ifdef ZFS_DEBUG
3412 /*
3413 * Once in a while, fail for no reason. Everything should cope.
3414 */
3415 if (spa_get_random(10000) == 0) {
3416 dprintf("forcing random failure\n");
3417 return (ERESTART);
3418 }
3419 #endif
3420 if (reserve > arc_c/4 && !arc_no_grow)
3421 arc_c = MIN(arc_c_max, reserve * 4);
3422 if (reserve > arc_c)
3423 return (ENOMEM);
3424
3425 /*
3426 * Don't count loaned bufs as in flight dirty data to prevent long
3427 * network delays from blocking transactions that are ready to be
3428 * assigned to a txg.
3429 */
3430 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3431
3432 /*
3433 * Writes will, almost always, require additional memory allocations
3434 * in order to compress/encrypt/etc the data. We therefor need to
3435 * make sure that there is sufficient available memory for this.
3436 */
3437 if (error = arc_memory_throttle(reserve, anon_size, txg))
3438 return (error);
3439
3440 /*
3441 * Throttle writes when the amount of dirty data in the cache
3442 * gets too large. We try to keep the cache less than half full
3443 * of dirty blocks so that our sync times don't grow too large.
3444 * Note: if two requests come in concurrently, we might let them
3445 * both succeed, when one of them should fail. Not a huge deal.
3446 */
3447
3448 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3449 anon_size > arc_c / 4) {
3450 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3451 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3452 arc_tempreserve>>10,
3453 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3454 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3455 reserve>>10, arc_c>>10);
3456 return (ERESTART);
3457 }
3458 atomic_add_64(&arc_tempreserve, reserve);
3459 return (0);
3460 }
3461
3462 void
3463 arc_init(void)
3464 {
3465 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3466 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3467
3468 /* Convert seconds to clock ticks */
3469 arc_min_prefetch_lifespan = 1 * hz;
3470
3471 /* Start out with 1/8 of all memory */
3472 arc_c = physmem * PAGESIZE / 8;
3473
3474 #ifdef _KERNEL
3475 /*
3476 * On architectures where the physical memory can be larger
3477 * than the addressable space (intel in 32-bit mode), we may
3478 * need to limit the cache to 1/8 of VM size.
3479 */
3480 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3481 #endif
3482
3483 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3484 arc_c_min = MAX(arc_c / 4, 64<<20);
3485 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3486 if (arc_c * 8 >= 1<<30)
3487 arc_c_max = (arc_c * 8) - (1<<30);
3488 else
3489 arc_c_max = arc_c_min;
3490 arc_c_max = MAX(arc_c * 6, arc_c_max);
3491
3492 /*
3493 * Allow the tunables to override our calculations if they are
3494 * reasonable (ie. over 64MB)
3495 */
3496 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
3497 arc_c_max = zfs_arc_max;
3498 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
3499 arc_c_min = zfs_arc_min;
3500
3501 arc_c = arc_c_max;
3502 arc_p = (arc_c >> 1);
3503
3504 /* limit meta-data to 1/4 of the arc capacity */
3505 arc_meta_limit = arc_c_max / 4;
3506
3507 /* Allow the tunable to override if it is reasonable */
3508 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3509 arc_meta_limit = zfs_arc_meta_limit;
3510
3511 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3512 arc_c_min = arc_meta_limit / 2;
3513
3514 if (zfs_arc_grow_retry > 0)
3515 arc_grow_retry = zfs_arc_grow_retry;
3516
3517 if (zfs_arc_shrink_shift > 0)
3518 arc_shrink_shift = zfs_arc_shrink_shift;
3519
3520 if (zfs_arc_p_min_shift > 0)
3521 arc_p_min_shift = zfs_arc_p_min_shift;
3522
3523 /* if kmem_flags are set, lets try to use less memory */
3524 if (kmem_debugging())
3525 arc_c = arc_c / 2;
3526 if (arc_c < arc_c_min)
3527 arc_c = arc_c_min;
3528
3529 arc_anon = &ARC_anon;
3530 arc_mru = &ARC_mru;
3531 arc_mru_ghost = &ARC_mru_ghost;
3532 arc_mfu = &ARC_mfu;
3533 arc_mfu_ghost = &ARC_mfu_ghost;
3534 arc_l2c_only = &ARC_l2c_only;
3535 arc_size = 0;
3536
3537 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3538 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3539 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3540 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3541 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3542 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3543
3544 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
3545 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3546 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
3547 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3548 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
3549 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3550 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
3551 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3552 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
3553 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3554 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
3555 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3556 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
3557 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3558 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
3559 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3560 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
3561 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3562 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
3563 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3564
3565 buf_init();
3566
3567 arc_thread_exit = 0;
3568 arc_eviction_list = NULL;
3569 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3570 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3571
3572 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3573 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3574
3575 if (arc_ksp != NULL) {
3576 arc_ksp->ks_data = &arc_stats;
3577 kstat_install(arc_ksp);
3578 }
3579
3580 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3581 TS_RUN, minclsyspri);
3582
3583 arc_dead = FALSE;
3584 arc_warm = B_FALSE;
3585
3586 if (zfs_write_limit_max == 0)
3587 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3588 else
3589 zfs_write_limit_shift = 0;
3590 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3591 }
3592
3593 void
3594 arc_fini(void)
3595 {
3596 mutex_enter(&arc_reclaim_thr_lock);
3597 arc_thread_exit = 1;
3598 while (arc_thread_exit != 0)
3599 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3600 mutex_exit(&arc_reclaim_thr_lock);
3601
3602 arc_flush(NULL);
3603
3604 arc_dead = TRUE;
3605
3606 if (arc_ksp != NULL) {
3607 kstat_delete(arc_ksp);
3608 arc_ksp = NULL;
3609 }
3610
3611 mutex_destroy(&arc_eviction_mtx);
3612 mutex_destroy(&arc_reclaim_thr_lock);
3613 cv_destroy(&arc_reclaim_thr_cv);
3614
3615 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
3616 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
3617 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
3618 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
3619 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
3620 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
3621 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
3622 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
3623
3624 mutex_destroy(&arc_anon->arcs_mtx);
3625 mutex_destroy(&arc_mru->arcs_mtx);
3626 mutex_destroy(&arc_mru_ghost->arcs_mtx);
3627 mutex_destroy(&arc_mfu->arcs_mtx);
3628 mutex_destroy(&arc_mfu_ghost->arcs_mtx);
3629 mutex_destroy(&arc_l2c_only->arcs_mtx);
3630
3631 mutex_destroy(&zfs_write_limit_lock);
3632
3633 buf_fini();
3634
3635 ASSERT(arc_loaned_bytes == 0);
3636 }
3637
3638 /*
3639 * Level 2 ARC
3640 *
3641 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3642 * It uses dedicated storage devices to hold cached data, which are populated
3643 * using large infrequent writes. The main role of this cache is to boost
3644 * the performance of random read workloads. The intended L2ARC devices
3645 * include short-stroked disks, solid state disks, and other media with
3646 * substantially faster read latency than disk.
3647 *
3648 * +-----------------------+
3649 * | ARC |
3650 * +-----------------------+
3651 * | ^ ^
3652 * | | |
3653 * l2arc_feed_thread() arc_read()
3654 * | | |
3655 * | l2arc read |
3656 * V | |
3657 * +---------------+ |
3658 * | L2ARC | |
3659 * +---------------+ |
3660 * | ^ |
3661 * l2arc_write() | |
3662 * | | |
3663 * V | |
3664 * +-------+ +-------+
3665 * | vdev | | vdev |
3666 * | cache | | cache |
3667 * +-------+ +-------+
3668 * +=========+ .-----.
3669 * : L2ARC : |-_____-|
3670 * : devices : | Disks |
3671 * +=========+ `-_____-'
3672 *
3673 * Read requests are satisfied from the following sources, in order:
3674 *
3675 * 1) ARC
3676 * 2) vdev cache of L2ARC devices
3677 * 3) L2ARC devices
3678 * 4) vdev cache of disks
3679 * 5) disks
3680 *
3681 * Some L2ARC device types exhibit extremely slow write performance.
3682 * To accommodate for this there are some significant differences between
3683 * the L2ARC and traditional cache design:
3684 *
3685 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3686 * the ARC behave as usual, freeing buffers and placing headers on ghost
3687 * lists. The ARC does not send buffers to the L2ARC during eviction as
3688 * this would add inflated write latencies for all ARC memory pressure.
3689 *
3690 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3691 * It does this by periodically scanning buffers from the eviction-end of
3692 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3693 * not already there. It scans until a headroom of buffers is satisfied,
3694 * which itself is a buffer for ARC eviction. The thread that does this is
3695 * l2arc_feed_thread(), illustrated below; example sizes are included to
3696 * provide a better sense of ratio than this diagram:
3697 *
3698 * head --> tail
3699 * +---------------------+----------+
3700 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3701 * +---------------------+----------+ | o L2ARC eligible
3702 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3703 * +---------------------+----------+ |
3704 * 15.9 Gbytes ^ 32 Mbytes |
3705 * headroom |
3706 * l2arc_feed_thread()
3707 * |
3708 * l2arc write hand <--[oooo]--'
3709 * | 8 Mbyte
3710 * | write max
3711 * V
3712 * +==============================+
3713 * L2ARC dev |####|#|###|###| |####| ... |
3714 * +==============================+
3715 * 32 Gbytes
3716 *
3717 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3718 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3719 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3720 * safe to say that this is an uncommon case, since buffers at the end of
3721 * the ARC lists have moved there due to inactivity.
3722 *
3723 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3724 * then the L2ARC simply misses copying some buffers. This serves as a
3725 * pressure valve to prevent heavy read workloads from both stalling the ARC
3726 * with waits and clogging the L2ARC with writes. This also helps prevent
3727 * the potential for the L2ARC to churn if it attempts to cache content too
3728 * quickly, such as during backups of the entire pool.
3729 *
3730 * 5. After system boot and before the ARC has filled main memory, there are
3731 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3732 * lists can remain mostly static. Instead of searching from tail of these
3733 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3734 * for eligible buffers, greatly increasing its chance of finding them.
3735 *
3736 * The L2ARC device write speed is also boosted during this time so that
3737 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
3738 * there are no L2ARC reads, and no fear of degrading read performance
3739 * through increased writes.
3740 *
3741 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
3742 * the vdev queue can aggregate them into larger and fewer writes. Each
3743 * device is written to in a rotor fashion, sweeping writes through
3744 * available space then repeating.
3745 *
3746 * 7. The L2ARC does not store dirty content. It never needs to flush
3747 * write buffers back to disk based storage.
3748 *
3749 * 8. If an ARC buffer is written (and dirtied) which also exists in the
3750 * L2ARC, the now stale L2ARC buffer is immediately dropped.
3751 *
3752 * The performance of the L2ARC can be tweaked by a number of tunables, which
3753 * may be necessary for different workloads:
3754 *
3755 * l2arc_write_max max write bytes per interval
3756 * l2arc_write_boost extra write bytes during device warmup
3757 * l2arc_noprefetch skip caching prefetched buffers
3758 * l2arc_headroom number of max device writes to precache
3759 * l2arc_feed_secs seconds between L2ARC writing
3760 *
3761 * Tunables may be removed or added as future performance improvements are
3762 * integrated, and also may become zpool properties.
3763 *
3764 * There are three key functions that control how the L2ARC warms up:
3765 *
3766 * l2arc_write_eligible() check if a buffer is eligible to cache
3767 * l2arc_write_size() calculate how much to write
3768 * l2arc_write_interval() calculate sleep delay between writes
3769 *
3770 * These three functions determine what to write, how much, and how quickly
3771 * to send writes.
3772 */
3773
3774 static boolean_t
3775 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
3776 {
3777 /*
3778 * A buffer is *not* eligible for the L2ARC if it:
3779 * 1. belongs to a different spa.
3780 * 2. is already cached on the L2ARC.
3781 * 3. has an I/O in progress (it may be an incomplete read).
3782 * 4. is flagged not eligible (zfs property).
3783 */
3784 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
3785 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
3786 return (B_FALSE);
3787
3788 return (B_TRUE);
3789 }
3790
3791 static uint64_t
3792 l2arc_write_size(l2arc_dev_t *dev)
3793 {
3794 uint64_t size;
3795
3796 size = dev->l2ad_write;
3797
3798 if (arc_warm == B_FALSE)
3799 size += dev->l2ad_boost;
3800
3801 return (size);
3802
3803 }
3804
3805 static clock_t
3806 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
3807 {
3808 clock_t interval, next;
3809
3810 /*
3811 * If the ARC lists are busy, increase our write rate; if the
3812 * lists are stale, idle back. This is achieved by checking
3813 * how much we previously wrote - if it was more than half of
3814 * what we wanted, schedule the next write much sooner.
3815 */
3816 if (l2arc_feed_again && wrote > (wanted / 2))
3817 interval = (hz * l2arc_feed_min_ms) / 1000;
3818 else
3819 interval = hz * l2arc_feed_secs;
3820
3821 next = MAX(lbolt, MIN(lbolt + interval, began + interval));
3822
3823 return (next);
3824 }
3825
3826 static void
3827 l2arc_hdr_stat_add(void)
3828 {
3829 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
3830 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
3831 }
3832
3833 static void
3834 l2arc_hdr_stat_remove(void)
3835 {
3836 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
3837 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
3838 }
3839
3840 /*
3841 * Cycle through L2ARC devices. This is how L2ARC load balances.
3842 * If a device is returned, this also returns holding the spa config lock.
3843 */
3844 static l2arc_dev_t *
3845 l2arc_dev_get_next(void)
3846 {
3847 l2arc_dev_t *first, *next = NULL;
3848
3849 /*
3850 * Lock out the removal of spas (spa_namespace_lock), then removal
3851 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
3852 * both locks will be dropped and a spa config lock held instead.
3853 */
3854 mutex_enter(&spa_namespace_lock);
3855 mutex_enter(&l2arc_dev_mtx);
3856
3857 /* if there are no vdevs, there is nothing to do */
3858 if (l2arc_ndev == 0)
3859 goto out;
3860
3861 first = NULL;
3862 next = l2arc_dev_last;
3863 do {
3864 /* loop around the list looking for a non-faulted vdev */
3865 if (next == NULL) {
3866 next = list_head(l2arc_dev_list);
3867 } else {
3868 next = list_next(l2arc_dev_list, next);
3869 if (next == NULL)
3870 next = list_head(l2arc_dev_list);
3871 }
3872
3873 /* if we have come back to the start, bail out */
3874 if (first == NULL)
3875 first = next;
3876 else if (next == first)
3877 break;
3878
3879 } while (vdev_is_dead(next->l2ad_vdev));
3880
3881 /* if we were unable to find any usable vdevs, return NULL */
3882 if (vdev_is_dead(next->l2ad_vdev))
3883 next = NULL;
3884
3885 l2arc_dev_last = next;
3886
3887 out:
3888 mutex_exit(&l2arc_dev_mtx);
3889
3890 /*
3891 * Grab the config lock to prevent the 'next' device from being
3892 * removed while we are writing to it.
3893 */
3894 if (next != NULL)
3895 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
3896 mutex_exit(&spa_namespace_lock);
3897
3898 return (next);
3899 }
3900
3901 /*
3902 * Free buffers that were tagged for destruction.
3903 */
3904 static void
3905 l2arc_do_free_on_write()
3906 {
3907 list_t *buflist;
3908 l2arc_data_free_t *df, *df_prev;
3909
3910 mutex_enter(&l2arc_free_on_write_mtx);
3911 buflist = l2arc_free_on_write;
3912
3913 for (df = list_tail(buflist); df; df = df_prev) {
3914 df_prev = list_prev(buflist, df);
3915 ASSERT(df->l2df_data != NULL);
3916 ASSERT(df->l2df_func != NULL);
3917 df->l2df_func(df->l2df_data, df->l2df_size);
3918 list_remove(buflist, df);
3919 kmem_free(df, sizeof (l2arc_data_free_t));
3920 }
3921
3922 mutex_exit(&l2arc_free_on_write_mtx);
3923 }
3924
3925 /*
3926 * A write to a cache device has completed. Update all headers to allow
3927 * reads from these buffers to begin.
3928 */
3929 static void
3930 l2arc_write_done(zio_t *zio)
3931 {
3932 l2arc_write_callback_t *cb;
3933 l2arc_dev_t *dev;
3934 list_t *buflist;
3935 arc_buf_hdr_t *head, *ab, *ab_prev;
3936 l2arc_buf_hdr_t *abl2;
3937 kmutex_t *hash_lock;
3938
3939 cb = zio->io_private;
3940 ASSERT(cb != NULL);
3941 dev = cb->l2wcb_dev;
3942 ASSERT(dev != NULL);
3943 head = cb->l2wcb_head;
3944 ASSERT(head != NULL);
3945 buflist = dev->l2ad_buflist;
3946 ASSERT(buflist != NULL);
3947 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
3948 l2arc_write_callback_t *, cb);
3949
3950 if (zio->io_error != 0)
3951 ARCSTAT_BUMP(arcstat_l2_writes_error);
3952
3953 mutex_enter(&l2arc_buflist_mtx);
3954
3955 /*
3956 * All writes completed, or an error was hit.
3957 */
3958 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
3959 ab_prev = list_prev(buflist, ab);
3960
3961 hash_lock = HDR_LOCK(ab);
3962 if (!mutex_tryenter(hash_lock)) {
3963 /*
3964 * This buffer misses out. It may be in a stage
3965 * of eviction. Its ARC_L2_WRITING flag will be
3966 * left set, denying reads to this buffer.
3967 */
3968 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
3969 continue;
3970 }
3971
3972 if (zio->io_error != 0) {
3973 /*
3974 * Error - drop L2ARC entry.
3975 */
3976 list_remove(buflist, ab);
3977 abl2 = ab->b_l2hdr;
3978 ab->b_l2hdr = NULL;
3979 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
3980 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
3981 }
3982
3983 /*
3984 * Allow ARC to begin reads to this L2ARC entry.
3985 */
3986 ab->b_flags &= ~ARC_L2_WRITING;
3987
3988 mutex_exit(hash_lock);
3989 }
3990
3991 atomic_inc_64(&l2arc_writes_done);
3992 list_remove(buflist, head);
3993 kmem_cache_free(hdr_cache, head);
3994 mutex_exit(&l2arc_buflist_mtx);
3995
3996 l2arc_do_free_on_write();
3997
3998 kmem_free(cb, sizeof (l2arc_write_callback_t));
3999 }
4000
4001 /*
4002 * A read to a cache device completed. Validate buffer contents before
4003 * handing over to the regular ARC routines.
4004 */
4005 static void
4006 l2arc_read_done(zio_t *zio)
4007 {
4008 l2arc_read_callback_t *cb;
4009 arc_buf_hdr_t *hdr;
4010 arc_buf_t *buf;
4011 kmutex_t *hash_lock;
4012 int equal;
4013
4014 ASSERT(zio->io_vd != NULL);
4015 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4016
4017 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4018
4019 cb = zio->io_private;
4020 ASSERT(cb != NULL);
4021 buf = cb->l2rcb_buf;
4022 ASSERT(buf != NULL);
4023 hdr = buf->b_hdr;
4024 ASSERT(hdr != NULL);
4025
4026 hash_lock = HDR_LOCK(hdr);
4027 mutex_enter(hash_lock);
4028
4029 /*
4030 * Check this survived the L2ARC journey.
4031 */
4032 equal = arc_cksum_equal(buf);
4033 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4034 mutex_exit(hash_lock);
4035 zio->io_private = buf;
4036 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4037 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4038 arc_read_done(zio);
4039 } else {
4040 mutex_exit(hash_lock);
4041 /*
4042 * Buffer didn't survive caching. Increment stats and
4043 * reissue to the original storage device.
4044 */
4045 if (zio->io_error != 0) {
4046 ARCSTAT_BUMP(arcstat_l2_io_error);
4047 } else {
4048 zio->io_error = EIO;
4049 }
4050 if (!equal)
4051 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4052
4053 /*
4054 * If there's no waiter, issue an async i/o to the primary
4055 * storage now. If there *is* a waiter, the caller must
4056 * issue the i/o in a context where it's OK to block.
4057 */
4058 if (zio->io_waiter == NULL) {
4059 zio_t *pio = zio_unique_parent(zio);
4060
4061 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4062
4063 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4064 buf->b_data, zio->io_size, arc_read_done, buf,
4065 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4066 }
4067 }
4068
4069 kmem_free(cb, sizeof (l2arc_read_callback_t));
4070 }
4071
4072 /*
4073 * This is the list priority from which the L2ARC will search for pages to
4074 * cache. This is used within loops (0..3) to cycle through lists in the
4075 * desired order. This order can have a significant effect on cache
4076 * performance.
4077 *
4078 * Currently the metadata lists are hit first, MFU then MRU, followed by
4079 * the data lists. This function returns a locked list, and also returns
4080 * the lock pointer.
4081 */
4082 static list_t *
4083 l2arc_list_locked(int list_num, kmutex_t **lock)
4084 {
4085 list_t *list;
4086
4087 ASSERT(list_num >= 0 && list_num <= 3);
4088
4089 switch (list_num) {
4090 case 0:
4091 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
4092 *lock = &arc_mfu->arcs_mtx;
4093 break;
4094 case 1:
4095 list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
4096 *lock = &arc_mru->arcs_mtx;
4097 break;
4098 case 2:
4099 list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
4100 *lock = &arc_mfu->arcs_mtx;
4101 break;
4102 case 3:
4103 list = &arc_mru->arcs_list[ARC_BUFC_DATA];
4104 *lock = &arc_mru->arcs_mtx;
4105 break;
4106 }
4107
4108 ASSERT(!(MUTEX_HELD(*lock)));
4109 mutex_enter(*lock);
4110 return (list);
4111 }
4112
4113 /*
4114 * Evict buffers from the device write hand to the distance specified in
4115 * bytes. This distance may span populated buffers, it may span nothing.
4116 * This is clearing a region on the L2ARC device ready for writing.
4117 * If the 'all' boolean is set, every buffer is evicted.
4118 */
4119 static void
4120 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4121 {
4122 list_t *buflist;
4123 l2arc_buf_hdr_t *abl2;
4124 arc_buf_hdr_t *ab, *ab_prev;
4125 kmutex_t *hash_lock;
4126 uint64_t taddr;
4127
4128 buflist = dev->l2ad_buflist;
4129
4130 if (buflist == NULL)
4131 return;
4132
4133 if (!all && dev->l2ad_first) {
4134 /*
4135 * This is the first sweep through the device. There is
4136 * nothing to evict.
4137 */
4138 return;
4139 }
4140
4141 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4142 /*
4143 * When nearing the end of the device, evict to the end
4144 * before the device write hand jumps to the start.
4145 */
4146 taddr = dev->l2ad_end;
4147 } else {
4148 taddr = dev->l2ad_hand + distance;
4149 }
4150 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4151 uint64_t, taddr, boolean_t, all);
4152
4153 top:
4154 mutex_enter(&l2arc_buflist_mtx);
4155 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4156 ab_prev = list_prev(buflist, ab);
4157
4158 hash_lock = HDR_LOCK(ab);
4159 if (!mutex_tryenter(hash_lock)) {
4160 /*
4161 * Missed the hash lock. Retry.
4162 */
4163 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4164 mutex_exit(&l2arc_buflist_mtx);
4165 mutex_enter(hash_lock);
4166 mutex_exit(hash_lock);
4167 goto top;
4168 }
4169
4170 if (HDR_L2_WRITE_HEAD(ab)) {
4171 /*
4172 * We hit a write head node. Leave it for
4173 * l2arc_write_done().
4174 */
4175 list_remove(buflist, ab);
4176 mutex_exit(hash_lock);
4177 continue;
4178 }
4179
4180 if (!all && ab->b_l2hdr != NULL &&
4181 (ab->b_l2hdr->b_daddr > taddr ||
4182 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4183 /*
4184 * We've evicted to the target address,
4185 * or the end of the device.
4186 */
4187 mutex_exit(hash_lock);
4188 break;
4189 }
4190
4191 if (HDR_FREE_IN_PROGRESS(ab)) {
4192 /*
4193 * Already on the path to destruction.
4194 */
4195 mutex_exit(hash_lock);
4196 continue;
4197 }
4198
4199 if (ab->b_state == arc_l2c_only) {
4200 ASSERT(!HDR_L2_READING(ab));
4201 /*
4202 * This doesn't exist in the ARC. Destroy.
4203 * arc_hdr_destroy() will call list_remove()
4204 * and decrement arcstat_l2_size.
4205 */
4206 arc_change_state(arc_anon, ab, hash_lock);
4207 arc_hdr_destroy(ab);
4208 } else {
4209 /*
4210 * Invalidate issued or about to be issued
4211 * reads, since we may be about to write
4212 * over this location.
4213 */
4214 if (HDR_L2_READING(ab)) {
4215 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4216 ab->b_flags |= ARC_L2_EVICTED;
4217 }
4218
4219 /*
4220 * Tell ARC this no longer exists in L2ARC.
4221 */
4222 if (ab->b_l2hdr != NULL) {
4223 abl2 = ab->b_l2hdr;
4224 ab->b_l2hdr = NULL;
4225 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4226 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4227 }
4228 list_remove(buflist, ab);
4229
4230 /*
4231 * This may have been leftover after a
4232 * failed write.
4233 */
4234 ab->b_flags &= ~ARC_L2_WRITING;
4235 }
4236 mutex_exit(hash_lock);
4237 }
4238 mutex_exit(&l2arc_buflist_mtx);
4239
4240 spa_l2cache_space_update(dev->l2ad_vdev, 0, -(taddr - dev->l2ad_evict));
4241 dev->l2ad_evict = taddr;
4242 }
4243
4244 /*
4245 * Find and write ARC buffers to the L2ARC device.
4246 *
4247 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4248 * for reading until they have completed writing.
4249 */
4250 static uint64_t
4251 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4252 {
4253 arc_buf_hdr_t *ab, *ab_prev, *head;
4254 l2arc_buf_hdr_t *hdrl2;
4255 list_t *list;
4256 uint64_t passed_sz, write_sz, buf_sz, headroom;
4257 void *buf_data;
4258 kmutex_t *hash_lock, *list_lock;
4259 boolean_t have_lock, full;
4260 l2arc_write_callback_t *cb;
4261 zio_t *pio, *wzio;
4262 uint64_t guid = spa_guid(spa);
4263
4264 ASSERT(dev->l2ad_vdev != NULL);
4265
4266 pio = NULL;
4267 write_sz = 0;
4268 full = B_FALSE;
4269 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4270 head->b_flags |= ARC_L2_WRITE_HEAD;
4271
4272 /*
4273 * Copy buffers for L2ARC writing.
4274 */
4275 mutex_enter(&l2arc_buflist_mtx);
4276 for (int try = 0; try <= 3; try++) {
4277 list = l2arc_list_locked(try, &list_lock);
4278 passed_sz = 0;
4279
4280 /*
4281 * L2ARC fast warmup.
4282 *
4283 * Until the ARC is warm and starts to evict, read from the
4284 * head of the ARC lists rather than the tail.
4285 */
4286 headroom = target_sz * l2arc_headroom;
4287 if (arc_warm == B_FALSE)
4288 ab = list_head(list);
4289 else
4290 ab = list_tail(list);
4291
4292 for (; ab; ab = ab_prev) {
4293 if (arc_warm == B_FALSE)
4294 ab_prev = list_next(list, ab);
4295 else
4296 ab_prev = list_prev(list, ab);
4297
4298 hash_lock = HDR_LOCK(ab);
4299 have_lock = MUTEX_HELD(hash_lock);
4300 if (!have_lock && !mutex_tryenter(hash_lock)) {
4301 /*
4302 * Skip this buffer rather than waiting.
4303 */
4304 continue;
4305 }
4306
4307 passed_sz += ab->b_size;
4308 if (passed_sz > headroom) {
4309 /*
4310 * Searched too far.
4311 */
4312 mutex_exit(hash_lock);
4313 break;
4314 }
4315
4316 if (!l2arc_write_eligible(guid, ab)) {
4317 mutex_exit(hash_lock);
4318 continue;
4319 }
4320
4321 if ((write_sz + ab->b_size) > target_sz) {
4322 full = B_TRUE;
4323 mutex_exit(hash_lock);
4324 break;
4325 }
4326
4327 if (pio == NULL) {
4328 /*
4329 * Insert a dummy header on the buflist so
4330 * l2arc_write_done() can find where the
4331 * write buffers begin without searching.
4332 */
4333 list_insert_head(dev->l2ad_buflist, head);
4334
4335 cb = kmem_alloc(
4336 sizeof (l2arc_write_callback_t), KM_SLEEP);
4337 cb->l2wcb_dev = dev;
4338 cb->l2wcb_head = head;
4339 pio = zio_root(spa, l2arc_write_done, cb,
4340 ZIO_FLAG_CANFAIL);
4341 }
4342
4343 /*
4344 * Create and add a new L2ARC header.
4345 */
4346 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4347 hdrl2->b_dev = dev;
4348 hdrl2->b_daddr = dev->l2ad_hand;
4349
4350 ab->b_flags |= ARC_L2_WRITING;
4351 ab->b_l2hdr = hdrl2;
4352 list_insert_head(dev->l2ad_buflist, ab);
4353 buf_data = ab->b_buf->b_data;
4354 buf_sz = ab->b_size;
4355
4356 /*
4357 * Compute and store the buffer cksum before
4358 * writing. On debug the cksum is verified first.
4359 */
4360 arc_cksum_verify(ab->b_buf);
4361 arc_cksum_compute(ab->b_buf, B_TRUE);
4362
4363 mutex_exit(hash_lock);
4364
4365 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4366 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4367 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4368 ZIO_FLAG_CANFAIL, B_FALSE);
4369
4370 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4371 zio_t *, wzio);
4372 (void) zio_nowait(wzio);
4373
4374 /*
4375 * Keep the clock hand suitably device-aligned.
4376 */
4377 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4378
4379 write_sz += buf_sz;
4380 dev->l2ad_hand += buf_sz;
4381 }
4382
4383 mutex_exit(list_lock);
4384
4385 if (full == B_TRUE)
4386 break;
4387 }
4388 mutex_exit(&l2arc_buflist_mtx);
4389
4390 if (pio == NULL) {
4391 ASSERT3U(write_sz, ==, 0);
4392 kmem_cache_free(hdr_cache, head);
4393 return (0);
4394 }
4395
4396 ASSERT3U(write_sz, <=, target_sz);
4397 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4398 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4399 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4400 spa_l2cache_space_update(dev->l2ad_vdev, 0, write_sz);
4401
4402 /*
4403 * Bump device hand to the device start if it is approaching the end.
4404 * l2arc_evict() will already have evicted ahead for this case.
4405 */
4406 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4407 spa_l2cache_space_update(dev->l2ad_vdev, 0,
4408 dev->l2ad_end - dev->l2ad_hand);
4409 dev->l2ad_hand = dev->l2ad_start;
4410 dev->l2ad_evict = dev->l2ad_start;
4411 dev->l2ad_first = B_FALSE;
4412 }
4413
4414 dev->l2ad_writing = B_TRUE;
4415 (void) zio_wait(pio);
4416 dev->l2ad_writing = B_FALSE;
4417
4418 return (write_sz);
4419 }
4420
4421 /*
4422 * This thread feeds the L2ARC at regular intervals. This is the beating
4423 * heart of the L2ARC.
4424 */
4425 static void
4426 l2arc_feed_thread(void)
4427 {
4428 callb_cpr_t cpr;
4429 l2arc_dev_t *dev;
4430 spa_t *spa;
4431 uint64_t size, wrote;
4432 clock_t begin, next = lbolt;
4433
4434 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4435
4436 mutex_enter(&l2arc_feed_thr_lock);
4437
4438 while (l2arc_thread_exit == 0) {
4439 CALLB_CPR_SAFE_BEGIN(&cpr);
4440 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4441 next);
4442 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4443 next = lbolt + hz;
4444
4445 /*
4446 * Quick check for L2ARC devices.
4447 */
4448 mutex_enter(&l2arc_dev_mtx);
4449 if (l2arc_ndev == 0) {
4450 mutex_exit(&l2arc_dev_mtx);
4451 continue;
4452 }
4453 mutex_exit(&l2arc_dev_mtx);
4454 begin = lbolt;
4455
4456 /*
4457 * This selects the next l2arc device to write to, and in
4458 * doing so the next spa to feed from: dev->l2ad_spa. This
4459 * will return NULL if there are now no l2arc devices or if
4460 * they are all faulted.
4461 *
4462 * If a device is returned, its spa's config lock is also
4463 * held to prevent device removal. l2arc_dev_get_next()
4464 * will grab and release l2arc_dev_mtx.
4465 */
4466 if ((dev = l2arc_dev_get_next()) == NULL)
4467 continue;
4468
4469 spa = dev->l2ad_spa;
4470 ASSERT(spa != NULL);
4471
4472 /*
4473 * Avoid contributing to memory pressure.
4474 */
4475 if (arc_reclaim_needed()) {
4476 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4477 spa_config_exit(spa, SCL_L2ARC, dev);
4478 continue;
4479 }
4480
4481 ARCSTAT_BUMP(arcstat_l2_feeds);
4482
4483 size = l2arc_write_size(dev);
4484
4485 /*
4486 * Evict L2ARC buffers that will be overwritten.
4487 */
4488 l2arc_evict(dev, size, B_FALSE);
4489
4490 /*
4491 * Write ARC buffers.
4492 */
4493 wrote = l2arc_write_buffers(spa, dev, size);
4494
4495 /*
4496 * Calculate interval between writes.
4497 */
4498 next = l2arc_write_interval(begin, size, wrote);
4499 spa_config_exit(spa, SCL_L2ARC, dev);
4500 }
4501
4502 l2arc_thread_exit = 0;
4503 cv_broadcast(&l2arc_feed_thr_cv);
4504 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4505 thread_exit();
4506 }
4507
4508 boolean_t
4509 l2arc_vdev_present(vdev_t *vd)
4510 {
4511 l2arc_dev_t *dev;
4512
4513 mutex_enter(&l2arc_dev_mtx);
4514 for (dev = list_head(l2arc_dev_list); dev != NULL;
4515 dev = list_next(l2arc_dev_list, dev)) {
4516 if (dev->l2ad_vdev == vd)
4517 break;
4518 }
4519 mutex_exit(&l2arc_dev_mtx);
4520
4521 return (dev != NULL);
4522 }
4523
4524 /*
4525 * Add a vdev for use by the L2ARC. By this point the spa has already
4526 * validated the vdev and opened it.
4527 */
4528 void
4529 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
4530 {
4531 l2arc_dev_t *adddev;
4532
4533 ASSERT(!l2arc_vdev_present(vd));
4534
4535 /*
4536 * Create a new l2arc device entry.
4537 */
4538 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4539 adddev->l2ad_spa = spa;
4540 adddev->l2ad_vdev = vd;
4541 adddev->l2ad_write = l2arc_write_max;
4542 adddev->l2ad_boost = l2arc_write_boost;
4543 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
4544 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
4545 adddev->l2ad_hand = adddev->l2ad_start;
4546 adddev->l2ad_evict = adddev->l2ad_start;
4547 adddev->l2ad_first = B_TRUE;
4548 adddev->l2ad_writing = B_FALSE;
4549 ASSERT3U(adddev->l2ad_write, >, 0);
4550
4551 /*
4552 * This is a list of all ARC buffers that are still valid on the
4553 * device.
4554 */
4555 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4556 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4557 offsetof(arc_buf_hdr_t, b_l2node));
4558
4559 spa_l2cache_space_update(vd, adddev->l2ad_end - adddev->l2ad_hand, 0);
4560
4561 /*
4562 * Add device to global list
4563 */
4564 mutex_enter(&l2arc_dev_mtx);
4565 list_insert_head(l2arc_dev_list, adddev);
4566 atomic_inc_64(&l2arc_ndev);
4567 mutex_exit(&l2arc_dev_mtx);
4568 }
4569
4570 /*
4571 * Remove a vdev from the L2ARC.
4572 */
4573 void
4574 l2arc_remove_vdev(vdev_t *vd)
4575 {
4576 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4577
4578 /*
4579 * Find the device by vdev
4580 */
4581 mutex_enter(&l2arc_dev_mtx);
4582 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4583 nextdev = list_next(l2arc_dev_list, dev);
4584 if (vd == dev->l2ad_vdev) {
4585 remdev = dev;
4586 break;
4587 }
4588 }
4589 ASSERT(remdev != NULL);
4590
4591 /*
4592 * Remove device from global list
4593 */
4594 list_remove(l2arc_dev_list, remdev);
4595 l2arc_dev_last = NULL; /* may have been invalidated */
4596 atomic_dec_64(&l2arc_ndev);
4597 mutex_exit(&l2arc_dev_mtx);
4598
4599 /*
4600 * Clear all buflists and ARC references. L2ARC device flush.
4601 */
4602 l2arc_evict(remdev, 0, B_TRUE);
4603 list_destroy(remdev->l2ad_buflist);
4604 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4605 kmem_free(remdev, sizeof (l2arc_dev_t));
4606 }
4607
4608 void
4609 l2arc_init(void)
4610 {
4611 l2arc_thread_exit = 0;
4612 l2arc_ndev = 0;
4613 l2arc_writes_sent = 0;
4614 l2arc_writes_done = 0;
4615
4616 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4617 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4618 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4619 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4620 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4621
4622 l2arc_dev_list = &L2ARC_dev_list;
4623 l2arc_free_on_write = &L2ARC_free_on_write;
4624 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4625 offsetof(l2arc_dev_t, l2ad_node));
4626 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4627 offsetof(l2arc_data_free_t, l2df_list_node));
4628 }
4629
4630 void
4631 l2arc_fini(void)
4632 {
4633 /*
4634 * This is called from dmu_fini(), which is called from spa_fini();
4635 * Because of this, we can assume that all l2arc devices have
4636 * already been removed when the pools themselves were removed.
4637 */
4638
4639 l2arc_do_free_on_write();
4640
4641 mutex_destroy(&l2arc_feed_thr_lock);
4642 cv_destroy(&l2arc_feed_thr_cv);
4643 mutex_destroy(&l2arc_dev_mtx);
4644 mutex_destroy(&l2arc_buflist_mtx);
4645 mutex_destroy(&l2arc_free_on_write_mtx);
4646
4647 list_destroy(l2arc_dev_list);
4648 list_destroy(l2arc_free_on_write);
4649 }
4650
4651 void
4652 l2arc_start(void)
4653 {
4654 if (!(spa_mode_global & FWRITE))
4655 return;
4656
4657 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
4658 TS_RUN, minclsyspri);
4659 }
4660
4661 void
4662 l2arc_stop(void)
4663 {
4664 if (!(spa_mode_global & FWRITE))
4665 return;
4666
4667 mutex_enter(&l2arc_feed_thr_lock);
4668 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
4669 l2arc_thread_exit = 1;
4670 while (l2arc_thread_exit != 0)
4671 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
4672 mutex_exit(&l2arc_feed_thr_lock);
4673 }
Cache object: ba5be096798130e0a1ee23ee4227a90e
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