1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2012, Joyent, Inc. All rights reserved.
24 * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
27 */
28
29 /*
30 * DVA-based Adjustable Replacement Cache
31 *
32 * While much of the theory of operation used here is
33 * based on the self-tuning, low overhead replacement cache
34 * presented by Megiddo and Modha at FAST 2003, there are some
35 * significant differences:
36 *
37 * 1. The Megiddo and Modha model assumes any page is evictable.
38 * Pages in its cache cannot be "locked" into memory. This makes
39 * the eviction algorithm simple: evict the last page in the list.
40 * This also make the performance characteristics easy to reason
41 * about. Our cache is not so simple. At any given moment, some
42 * subset of the blocks in the cache are un-evictable because we
43 * have handed out a reference to them. Blocks are only evictable
44 * when there are no external references active. This makes
45 * eviction far more problematic: we choose to evict the evictable
46 * blocks that are the "lowest" in the list.
47 *
48 * There are times when it is not possible to evict the requested
49 * space. In these circumstances we are unable to adjust the cache
50 * size. To prevent the cache growing unbounded at these times we
51 * implement a "cache throttle" that slows the flow of new data
52 * into the cache until we can make space available.
53 *
54 * 2. The Megiddo and Modha model assumes a fixed cache size.
55 * Pages are evicted when the cache is full and there is a cache
56 * miss. Our model has a variable sized cache. It grows with
57 * high use, but also tries to react to memory pressure from the
58 * operating system: decreasing its size when system memory is
59 * tight.
60 *
61 * 3. The Megiddo and Modha model assumes a fixed page size. All
62 * elements of the cache are therefore exactly the same size. So
63 * when adjusting the cache size following a cache miss, its simply
64 * a matter of choosing a single page to evict. In our model, we
65 * have variable sized cache blocks (rangeing from 512 bytes to
66 * 128K bytes). We therefore choose a set of blocks to evict to make
67 * space for a cache miss that approximates as closely as possible
68 * the space used by the new block.
69 *
70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 * by N. Megiddo & D. Modha, FAST 2003
72 */
73
74 /*
75 * The locking model:
76 *
77 * A new reference to a cache buffer can be obtained in two
78 * ways: 1) via a hash table lookup using the DVA as a key,
79 * or 2) via one of the ARC lists. The arc_read() interface
80 * uses method 1, while the internal arc algorithms for
81 * adjusting the cache use method 2. We therefore provide two
82 * types of locks: 1) the hash table lock array, and 2) the
83 * arc list locks.
84 *
85 * Buffers do not have their own mutexes, rather they rely on the
86 * hash table mutexes for the bulk of their protection (i.e. most
87 * fields in the arc_buf_hdr_t are protected by these mutexes).
88 *
89 * buf_hash_find() returns the appropriate mutex (held) when it
90 * locates the requested buffer in the hash table. It returns
91 * NULL for the mutex if the buffer was not in the table.
92 *
93 * buf_hash_remove() expects the appropriate hash mutex to be
94 * already held before it is invoked.
95 *
96 * Each arc state also has a mutex which is used to protect the
97 * buffer list associated with the state. When attempting to
98 * obtain a hash table lock while holding an arc list lock you
99 * must use: mutex_tryenter() to avoid deadlock. Also note that
100 * the active state mutex must be held before the ghost state mutex.
101 *
102 * Arc buffers may have an associated eviction callback function.
103 * This function will be invoked prior to removing the buffer (e.g.
104 * in arc_do_user_evicts()). Note however that the data associated
105 * with the buffer may be evicted prior to the callback. The callback
106 * must be made with *no locks held* (to prevent deadlock). Additionally,
107 * the users of callbacks must ensure that their private data is
108 * protected from simultaneous callbacks from arc_clear_callback()
109 * and arc_do_user_evicts().
110 *
111 * Note that the majority of the performance stats are manipulated
112 * with atomic operations.
113 *
114 * The L2ARC uses the l2ad_mtx on each vdev for the following:
115 *
116 * - L2ARC buflist creation
117 * - L2ARC buflist eviction
118 * - L2ARC write completion, which walks L2ARC buflists
119 * - ARC header destruction, as it removes from L2ARC buflists
120 * - ARC header release, as it removes from L2ARC buflists
121 */
122
123 #include <sys/spa.h>
124 #include <sys/zio.h>
125 #include <sys/zio_compress.h>
126 #include <sys/zfs_context.h>
127 #include <sys/arc.h>
128 #include <sys/refcount.h>
129 #include <sys/vdev.h>
130 #include <sys/vdev_impl.h>
131 #include <sys/dsl_pool.h>
132 #include <sys/multilist.h>
133 #ifdef _KERNEL
134 #include <sys/vmsystm.h>
135 #include <vm/anon.h>
136 #include <sys/fs/swapnode.h>
137 #include <sys/dnlc.h>
138 #endif
139 #include <sys/callb.h>
140 #include <sys/kstat.h>
141 #include <zfs_fletcher.h>
142
143 #ifndef _KERNEL
144 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
145 boolean_t arc_watch = B_FALSE;
146 int arc_procfd;
147 #endif
148
149 static kmutex_t arc_reclaim_lock;
150 static kcondvar_t arc_reclaim_thread_cv;
151 static boolean_t arc_reclaim_thread_exit;
152 static kcondvar_t arc_reclaim_waiters_cv;
153
154 static kmutex_t arc_user_evicts_lock;
155 static kcondvar_t arc_user_evicts_cv;
156 static boolean_t arc_user_evicts_thread_exit;
157
158 uint_t arc_reduce_dnlc_percent = 3;
159
160 /*
161 * The number of headers to evict in arc_evict_state_impl() before
162 * dropping the sublist lock and evicting from another sublist. A lower
163 * value means we're more likely to evict the "correct" header (i.e. the
164 * oldest header in the arc state), but comes with higher overhead
165 * (i.e. more invocations of arc_evict_state_impl()).
166 */
167 int zfs_arc_evict_batch_limit = 10;
168
169 /*
170 * The number of sublists used for each of the arc state lists. If this
171 * is not set to a suitable value by the user, it will be configured to
172 * the number of CPUs on the system in arc_init().
173 */
174 int zfs_arc_num_sublists_per_state = 0;
175
176 /* number of seconds before growing cache again */
177 static int arc_grow_retry = 60;
178
179 /* shift of arc_c for calculating overflow limit in arc_get_data_buf */
180 int zfs_arc_overflow_shift = 8;
181
182 /* shift of arc_c for calculating both min and max arc_p */
183 static int arc_p_min_shift = 4;
184
185 /* log2(fraction of arc to reclaim) */
186 static int arc_shrink_shift = 7;
187
188 /*
189 * log2(fraction of ARC which must be free to allow growing).
190 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
191 * when reading a new block into the ARC, we will evict an equal-sized block
192 * from the ARC.
193 *
194 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
195 * we will still not allow it to grow.
196 */
197 int arc_no_grow_shift = 5;
198
199
200 /*
201 * minimum lifespan of a prefetch block in clock ticks
202 * (initialized in arc_init())
203 */
204 static int arc_min_prefetch_lifespan;
205
206 /*
207 * If this percent of memory is free, don't throttle.
208 */
209 int arc_lotsfree_percent = 10;
210
211 static int arc_dead;
212
213 /*
214 * The arc has filled available memory and has now warmed up.
215 */
216 static boolean_t arc_warm;
217
218 /*
219 * These tunables are for performance analysis.
220 */
221 uint64_t zfs_arc_max;
222 uint64_t zfs_arc_min;
223 uint64_t zfs_arc_meta_limit = 0;
224 uint64_t zfs_arc_meta_min = 0;
225 int zfs_arc_grow_retry = 0;
226 int zfs_arc_shrink_shift = 0;
227 int zfs_arc_p_min_shift = 0;
228 int zfs_disable_dup_eviction = 0;
229 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
230
231 /*
232 * Note that buffers can be in one of 6 states:
233 * ARC_anon - anonymous (discussed below)
234 * ARC_mru - recently used, currently cached
235 * ARC_mru_ghost - recentely used, no longer in cache
236 * ARC_mfu - frequently used, currently cached
237 * ARC_mfu_ghost - frequently used, no longer in cache
238 * ARC_l2c_only - exists in L2ARC but not other states
239 * When there are no active references to the buffer, they are
240 * are linked onto a list in one of these arc states. These are
241 * the only buffers that can be evicted or deleted. Within each
242 * state there are multiple lists, one for meta-data and one for
243 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
244 * etc.) is tracked separately so that it can be managed more
245 * explicitly: favored over data, limited explicitly.
246 *
247 * Anonymous buffers are buffers that are not associated with
248 * a DVA. These are buffers that hold dirty block copies
249 * before they are written to stable storage. By definition,
250 * they are "ref'd" and are considered part of arc_mru
251 * that cannot be freed. Generally, they will aquire a DVA
252 * as they are written and migrate onto the arc_mru list.
253 *
254 * The ARC_l2c_only state is for buffers that are in the second
255 * level ARC but no longer in any of the ARC_m* lists. The second
256 * level ARC itself may also contain buffers that are in any of
257 * the ARC_m* states - meaning that a buffer can exist in two
258 * places. The reason for the ARC_l2c_only state is to keep the
259 * buffer header in the hash table, so that reads that hit the
260 * second level ARC benefit from these fast lookups.
261 */
262
263 typedef struct arc_state {
264 /*
265 * list of evictable buffers
266 */
267 multilist_t arcs_list[ARC_BUFC_NUMTYPES];
268 /*
269 * total amount of evictable data in this state
270 */
271 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES];
272 /*
273 * total amount of data in this state; this includes: evictable,
274 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
275 */
276 refcount_t arcs_size;
277 } arc_state_t;
278
279 /* The 6 states: */
280 static arc_state_t ARC_anon;
281 static arc_state_t ARC_mru;
282 static arc_state_t ARC_mru_ghost;
283 static arc_state_t ARC_mfu;
284 static arc_state_t ARC_mfu_ghost;
285 static arc_state_t ARC_l2c_only;
286
287 typedef struct arc_stats {
288 kstat_named_t arcstat_hits;
289 kstat_named_t arcstat_misses;
290 kstat_named_t arcstat_demand_data_hits;
291 kstat_named_t arcstat_demand_data_misses;
292 kstat_named_t arcstat_demand_metadata_hits;
293 kstat_named_t arcstat_demand_metadata_misses;
294 kstat_named_t arcstat_prefetch_data_hits;
295 kstat_named_t arcstat_prefetch_data_misses;
296 kstat_named_t arcstat_prefetch_metadata_hits;
297 kstat_named_t arcstat_prefetch_metadata_misses;
298 kstat_named_t arcstat_mru_hits;
299 kstat_named_t arcstat_mru_ghost_hits;
300 kstat_named_t arcstat_mfu_hits;
301 kstat_named_t arcstat_mfu_ghost_hits;
302 kstat_named_t arcstat_deleted;
303 /*
304 * Number of buffers that could not be evicted because the hash lock
305 * was held by another thread. The lock may not necessarily be held
306 * by something using the same buffer, since hash locks are shared
307 * by multiple buffers.
308 */
309 kstat_named_t arcstat_mutex_miss;
310 /*
311 * Number of buffers skipped because they have I/O in progress, are
312 * indrect prefetch buffers that have not lived long enough, or are
313 * not from the spa we're trying to evict from.
314 */
315 kstat_named_t arcstat_evict_skip;
316 /*
317 * Number of times arc_evict_state() was unable to evict enough
318 * buffers to reach it's target amount.
319 */
320 kstat_named_t arcstat_evict_not_enough;
321 kstat_named_t arcstat_evict_l2_cached;
322 kstat_named_t arcstat_evict_l2_eligible;
323 kstat_named_t arcstat_evict_l2_ineligible;
324 kstat_named_t arcstat_evict_l2_skip;
325 kstat_named_t arcstat_hash_elements;
326 kstat_named_t arcstat_hash_elements_max;
327 kstat_named_t arcstat_hash_collisions;
328 kstat_named_t arcstat_hash_chains;
329 kstat_named_t arcstat_hash_chain_max;
330 kstat_named_t arcstat_p;
331 kstat_named_t arcstat_c;
332 kstat_named_t arcstat_c_min;
333 kstat_named_t arcstat_c_max;
334 kstat_named_t arcstat_size;
335 /*
336 * Number of bytes consumed by internal ARC structures necessary
337 * for tracking purposes; these structures are not actually
338 * backed by ARC buffers. This includes arc_buf_hdr_t structures
339 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
340 * caches), and arc_buf_t structures (allocated via arc_buf_t
341 * cache).
342 */
343 kstat_named_t arcstat_hdr_size;
344 /*
345 * Number of bytes consumed by ARC buffers of type equal to
346 * ARC_BUFC_DATA. This is generally consumed by buffers backing
347 * on disk user data (e.g. plain file contents).
348 */
349 kstat_named_t arcstat_data_size;
350 /*
351 * Number of bytes consumed by ARC buffers of type equal to
352 * ARC_BUFC_METADATA. This is generally consumed by buffers
353 * backing on disk data that is used for internal ZFS
354 * structures (e.g. ZAP, dnode, indirect blocks, etc).
355 */
356 kstat_named_t arcstat_metadata_size;
357 /*
358 * Number of bytes consumed by various buffers and structures
359 * not actually backed with ARC buffers. This includes bonus
360 * buffers (allocated directly via zio_buf_* functions),
361 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
362 * cache), and dnode_t structures (allocated via dnode_t cache).
363 */
364 kstat_named_t arcstat_other_size;
365 /*
366 * Total number of bytes consumed by ARC buffers residing in the
367 * arc_anon state. This includes *all* buffers in the arc_anon
368 * state; e.g. data, metadata, evictable, and unevictable buffers
369 * are all included in this value.
370 */
371 kstat_named_t arcstat_anon_size;
372 /*
373 * Number of bytes consumed by ARC buffers that meet the
374 * following criteria: backing buffers of type ARC_BUFC_DATA,
375 * residing in the arc_anon state, and are eligible for eviction
376 * (e.g. have no outstanding holds on the buffer).
377 */
378 kstat_named_t arcstat_anon_evictable_data;
379 /*
380 * Number of bytes consumed by ARC buffers that meet the
381 * following criteria: backing buffers of type ARC_BUFC_METADATA,
382 * residing in the arc_anon state, and are eligible for eviction
383 * (e.g. have no outstanding holds on the buffer).
384 */
385 kstat_named_t arcstat_anon_evictable_metadata;
386 /*
387 * Total number of bytes consumed by ARC buffers residing in the
388 * arc_mru state. This includes *all* buffers in the arc_mru
389 * state; e.g. data, metadata, evictable, and unevictable buffers
390 * are all included in this value.
391 */
392 kstat_named_t arcstat_mru_size;
393 /*
394 * Number of bytes consumed by ARC buffers that meet the
395 * following criteria: backing buffers of type ARC_BUFC_DATA,
396 * residing in the arc_mru state, and are eligible for eviction
397 * (e.g. have no outstanding holds on the buffer).
398 */
399 kstat_named_t arcstat_mru_evictable_data;
400 /*
401 * Number of bytes consumed by ARC buffers that meet the
402 * following criteria: backing buffers of type ARC_BUFC_METADATA,
403 * residing in the arc_mru state, and are eligible for eviction
404 * (e.g. have no outstanding holds on the buffer).
405 */
406 kstat_named_t arcstat_mru_evictable_metadata;
407 /*
408 * Total number of bytes that *would have been* consumed by ARC
409 * buffers in the arc_mru_ghost state. The key thing to note
410 * here, is the fact that this size doesn't actually indicate
411 * RAM consumption. The ghost lists only consist of headers and
412 * don't actually have ARC buffers linked off of these headers.
413 * Thus, *if* the headers had associated ARC buffers, these
414 * buffers *would have* consumed this number of bytes.
415 */
416 kstat_named_t arcstat_mru_ghost_size;
417 /*
418 * Number of bytes that *would have been* consumed by ARC
419 * buffers that are eligible for eviction, of type
420 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
421 */
422 kstat_named_t arcstat_mru_ghost_evictable_data;
423 /*
424 * Number of bytes that *would have been* consumed by ARC
425 * buffers that are eligible for eviction, of type
426 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
427 */
428 kstat_named_t arcstat_mru_ghost_evictable_metadata;
429 /*
430 * Total number of bytes consumed by ARC buffers residing in the
431 * arc_mfu state. This includes *all* buffers in the arc_mfu
432 * state; e.g. data, metadata, evictable, and unevictable buffers
433 * are all included in this value.
434 */
435 kstat_named_t arcstat_mfu_size;
436 /*
437 * Number of bytes consumed by ARC buffers that are eligible for
438 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
439 * state.
440 */
441 kstat_named_t arcstat_mfu_evictable_data;
442 /*
443 * Number of bytes consumed by ARC buffers that are eligible for
444 * eviction, of type ARC_BUFC_METADATA, and reside in the
445 * arc_mfu state.
446 */
447 kstat_named_t arcstat_mfu_evictable_metadata;
448 /*
449 * Total number of bytes that *would have been* consumed by ARC
450 * buffers in the arc_mfu_ghost state. See the comment above
451 * arcstat_mru_ghost_size for more details.
452 */
453 kstat_named_t arcstat_mfu_ghost_size;
454 /*
455 * Number of bytes that *would have been* consumed by ARC
456 * buffers that are eligible for eviction, of type
457 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
458 */
459 kstat_named_t arcstat_mfu_ghost_evictable_data;
460 /*
461 * Number of bytes that *would have been* consumed by ARC
462 * buffers that are eligible for eviction, of type
463 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
464 */
465 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
466 kstat_named_t arcstat_l2_hits;
467 kstat_named_t arcstat_l2_misses;
468 kstat_named_t arcstat_l2_feeds;
469 kstat_named_t arcstat_l2_rw_clash;
470 kstat_named_t arcstat_l2_read_bytes;
471 kstat_named_t arcstat_l2_write_bytes;
472 kstat_named_t arcstat_l2_writes_sent;
473 kstat_named_t arcstat_l2_writes_done;
474 kstat_named_t arcstat_l2_writes_error;
475 kstat_named_t arcstat_l2_writes_lock_retry;
476 kstat_named_t arcstat_l2_evict_lock_retry;
477 kstat_named_t arcstat_l2_evict_reading;
478 kstat_named_t arcstat_l2_evict_l1cached;
479 kstat_named_t arcstat_l2_free_on_write;
480 kstat_named_t arcstat_l2_cdata_free_on_write;
481 kstat_named_t arcstat_l2_abort_lowmem;
482 kstat_named_t arcstat_l2_cksum_bad;
483 kstat_named_t arcstat_l2_io_error;
484 kstat_named_t arcstat_l2_size;
485 kstat_named_t arcstat_l2_asize;
486 kstat_named_t arcstat_l2_hdr_size;
487 kstat_named_t arcstat_l2_compress_successes;
488 kstat_named_t arcstat_l2_compress_zeros;
489 kstat_named_t arcstat_l2_compress_failures;
490 kstat_named_t arcstat_memory_throttle_count;
491 kstat_named_t arcstat_duplicate_buffers;
492 kstat_named_t arcstat_duplicate_buffers_size;
493 kstat_named_t arcstat_duplicate_reads;
494 kstat_named_t arcstat_meta_used;
495 kstat_named_t arcstat_meta_limit;
496 kstat_named_t arcstat_meta_max;
497 kstat_named_t arcstat_meta_min;
498 } arc_stats_t;
499
500 static arc_stats_t arc_stats = {
501 { "hits", KSTAT_DATA_UINT64 },
502 { "misses", KSTAT_DATA_UINT64 },
503 { "demand_data_hits", KSTAT_DATA_UINT64 },
504 { "demand_data_misses", KSTAT_DATA_UINT64 },
505 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
506 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
507 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
508 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
509 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
510 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
511 { "mru_hits", KSTAT_DATA_UINT64 },
512 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
513 { "mfu_hits", KSTAT_DATA_UINT64 },
514 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
515 { "deleted", KSTAT_DATA_UINT64 },
516 { "mutex_miss", KSTAT_DATA_UINT64 },
517 { "evict_skip", KSTAT_DATA_UINT64 },
518 { "evict_not_enough", KSTAT_DATA_UINT64 },
519 { "evict_l2_cached", KSTAT_DATA_UINT64 },
520 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
521 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
522 { "evict_l2_skip", KSTAT_DATA_UINT64 },
523 { "hash_elements", KSTAT_DATA_UINT64 },
524 { "hash_elements_max", KSTAT_DATA_UINT64 },
525 { "hash_collisions", KSTAT_DATA_UINT64 },
526 { "hash_chains", KSTAT_DATA_UINT64 },
527 { "hash_chain_max", KSTAT_DATA_UINT64 },
528 { "p", KSTAT_DATA_UINT64 },
529 { "c", KSTAT_DATA_UINT64 },
530 { "c_min", KSTAT_DATA_UINT64 },
531 { "c_max", KSTAT_DATA_UINT64 },
532 { "size", KSTAT_DATA_UINT64 },
533 { "hdr_size", KSTAT_DATA_UINT64 },
534 { "data_size", KSTAT_DATA_UINT64 },
535 { "metadata_size", KSTAT_DATA_UINT64 },
536 { "other_size", KSTAT_DATA_UINT64 },
537 { "anon_size", KSTAT_DATA_UINT64 },
538 { "anon_evictable_data", KSTAT_DATA_UINT64 },
539 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
540 { "mru_size", KSTAT_DATA_UINT64 },
541 { "mru_evictable_data", KSTAT_DATA_UINT64 },
542 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
543 { "mru_ghost_size", KSTAT_DATA_UINT64 },
544 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
545 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
546 { "mfu_size", KSTAT_DATA_UINT64 },
547 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
548 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
549 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
550 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
551 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
552 { "l2_hits", KSTAT_DATA_UINT64 },
553 { "l2_misses", KSTAT_DATA_UINT64 },
554 { "l2_feeds", KSTAT_DATA_UINT64 },
555 { "l2_rw_clash", KSTAT_DATA_UINT64 },
556 { "l2_read_bytes", KSTAT_DATA_UINT64 },
557 { "l2_write_bytes", KSTAT_DATA_UINT64 },
558 { "l2_writes_sent", KSTAT_DATA_UINT64 },
559 { "l2_writes_done", KSTAT_DATA_UINT64 },
560 { "l2_writes_error", KSTAT_DATA_UINT64 },
561 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
562 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
563 { "l2_evict_reading", KSTAT_DATA_UINT64 },
564 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
565 { "l2_free_on_write", KSTAT_DATA_UINT64 },
566 { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 },
567 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
568 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
569 { "l2_io_error", KSTAT_DATA_UINT64 },
570 { "l2_size", KSTAT_DATA_UINT64 },
571 { "l2_asize", KSTAT_DATA_UINT64 },
572 { "l2_hdr_size", KSTAT_DATA_UINT64 },
573 { "l2_compress_successes", KSTAT_DATA_UINT64 },
574 { "l2_compress_zeros", KSTAT_DATA_UINT64 },
575 { "l2_compress_failures", KSTAT_DATA_UINT64 },
576 { "memory_throttle_count", KSTAT_DATA_UINT64 },
577 { "duplicate_buffers", KSTAT_DATA_UINT64 },
578 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
579 { "duplicate_reads", KSTAT_DATA_UINT64 },
580 { "arc_meta_used", KSTAT_DATA_UINT64 },
581 { "arc_meta_limit", KSTAT_DATA_UINT64 },
582 { "arc_meta_max", KSTAT_DATA_UINT64 },
583 { "arc_meta_min", KSTAT_DATA_UINT64 }
584 };
585
586 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
587
588 #define ARCSTAT_INCR(stat, val) \
589 atomic_add_64(&arc_stats.stat.value.ui64, (val))
590
591 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
592 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
593
594 #define ARCSTAT_MAX(stat, val) { \
595 uint64_t m; \
596 while ((val) > (m = arc_stats.stat.value.ui64) && \
597 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
598 continue; \
599 }
600
601 #define ARCSTAT_MAXSTAT(stat) \
602 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
603
604 /*
605 * We define a macro to allow ARC hits/misses to be easily broken down by
606 * two separate conditions, giving a total of four different subtypes for
607 * each of hits and misses (so eight statistics total).
608 */
609 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
610 if (cond1) { \
611 if (cond2) { \
612 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
613 } else { \
614 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
615 } \
616 } else { \
617 if (cond2) { \
618 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
619 } else { \
620 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
621 } \
622 }
623
624 kstat_t *arc_ksp;
625 static arc_state_t *arc_anon;
626 static arc_state_t *arc_mru;
627 static arc_state_t *arc_mru_ghost;
628 static arc_state_t *arc_mfu;
629 static arc_state_t *arc_mfu_ghost;
630 static arc_state_t *arc_l2c_only;
631
632 /*
633 * There are several ARC variables that are critical to export as kstats --
634 * but we don't want to have to grovel around in the kstat whenever we wish to
635 * manipulate them. For these variables, we therefore define them to be in
636 * terms of the statistic variable. This assures that we are not introducing
637 * the possibility of inconsistency by having shadow copies of the variables,
638 * while still allowing the code to be readable.
639 */
640 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
641 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
642 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
643 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
644 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
645 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
646 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
647 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
648 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
649
650 #define L2ARC_IS_VALID_COMPRESS(_c_) \
651 ((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
652
653 static int arc_no_grow; /* Don't try to grow cache size */
654 static uint64_t arc_tempreserve;
655 static uint64_t arc_loaned_bytes;
656
657 typedef struct arc_callback arc_callback_t;
658
659 struct arc_callback {
660 void *acb_private;
661 arc_done_func_t *acb_done;
662 arc_buf_t *acb_buf;
663 zio_t *acb_zio_dummy;
664 arc_callback_t *acb_next;
665 };
666
667 typedef struct arc_write_callback arc_write_callback_t;
668
669 struct arc_write_callback {
670 void *awcb_private;
671 arc_done_func_t *awcb_ready;
672 arc_done_func_t *awcb_physdone;
673 arc_done_func_t *awcb_done;
674 arc_buf_t *awcb_buf;
675 };
676
677 /*
678 * ARC buffers are separated into multiple structs as a memory saving measure:
679 * - Common fields struct, always defined, and embedded within it:
680 * - L2-only fields, always allocated but undefined when not in L2ARC
681 * - L1-only fields, only allocated when in L1ARC
682 *
683 * Buffer in L1 Buffer only in L2
684 * +------------------------+ +------------------------+
685 * | arc_buf_hdr_t | | arc_buf_hdr_t |
686 * | | | |
687 * | | | |
688 * | | | |
689 * +------------------------+ +------------------------+
690 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
691 * | (undefined if L1-only) | | |
692 * +------------------------+ +------------------------+
693 * | l1arc_buf_hdr_t |
694 * | |
695 * | |
696 * | |
697 * | |
698 * +------------------------+
699 *
700 * Because it's possible for the L2ARC to become extremely large, we can wind
701 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
702 * is minimized by only allocating the fields necessary for an L1-cached buffer
703 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
704 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
705 * words in pointers. arc_hdr_realloc() is used to switch a header between
706 * these two allocation states.
707 */
708 typedef struct l1arc_buf_hdr {
709 kmutex_t b_freeze_lock;
710 #ifdef ZFS_DEBUG
711 /*
712 * used for debugging wtih kmem_flags - by allocating and freeing
713 * b_thawed when the buffer is thawed, we get a record of the stack
714 * trace that thawed it.
715 */
716 void *b_thawed;
717 #endif
718
719 arc_buf_t *b_buf;
720 uint32_t b_datacnt;
721 /* for waiting on writes to complete */
722 kcondvar_t b_cv;
723
724 /* protected by arc state mutex */
725 arc_state_t *b_state;
726 multilist_node_t b_arc_node;
727
728 /* updated atomically */
729 clock_t b_arc_access;
730
731 /* self protecting */
732 refcount_t b_refcnt;
733
734 arc_callback_t *b_acb;
735 /* temporary buffer holder for in-flight compressed data */
736 void *b_tmp_cdata;
737 } l1arc_buf_hdr_t;
738
739 typedef struct l2arc_dev l2arc_dev_t;
740
741 typedef struct l2arc_buf_hdr {
742 /* protected by arc_buf_hdr mutex */
743 l2arc_dev_t *b_dev; /* L2ARC device */
744 uint64_t b_daddr; /* disk address, offset byte */
745 /* real alloc'd buffer size depending on b_compress applied */
746 int32_t b_asize;
747
748 list_node_t b_l2node;
749 } l2arc_buf_hdr_t;
750
751 struct arc_buf_hdr {
752 /* protected by hash lock */
753 dva_t b_dva;
754 uint64_t b_birth;
755 /*
756 * Even though this checksum is only set/verified when a buffer is in
757 * the L1 cache, it needs to be in the set of common fields because it
758 * must be preserved from the time before a buffer is written out to
759 * L2ARC until after it is read back in.
760 */
761 zio_cksum_t *b_freeze_cksum;
762
763 arc_buf_hdr_t *b_hash_next;
764 arc_flags_t b_flags;
765
766 /* immutable */
767 int32_t b_size;
768 uint64_t b_spa;
769
770 /* L2ARC fields. Undefined when not in L2ARC. */
771 l2arc_buf_hdr_t b_l2hdr;
772 /* L1ARC fields. Undefined when in l2arc_only state */
773 l1arc_buf_hdr_t b_l1hdr;
774 };
775
776 static arc_buf_t *arc_eviction_list;
777 static arc_buf_hdr_t arc_eviction_hdr;
778
779 #define GHOST_STATE(state) \
780 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
781 (state) == arc_l2c_only)
782
783 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
784 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
785 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
786 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
787 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ)
788 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE)
789
790 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
791 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS)
792 #define HDR_L2_READING(hdr) \
793 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
794 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
795 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
796 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
797 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
798
799 #define HDR_ISTYPE_METADATA(hdr) \
800 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
801 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
802
803 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
804 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
805
806 /* For storing compression mode in b_flags */
807 #define HDR_COMPRESS_OFFSET 24
808 #define HDR_COMPRESS_NBITS 7
809
810 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \
811 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS))
812 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \
813 HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp))
814
815 /*
816 * Other sizes
817 */
818
819 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
820 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
821
822 /*
823 * Hash table routines
824 */
825
826 #define HT_LOCK_PAD 64
827
828 struct ht_lock {
829 kmutex_t ht_lock;
830 #ifdef _KERNEL
831 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
832 #endif
833 };
834
835 #define BUF_LOCKS 256
836 typedef struct buf_hash_table {
837 uint64_t ht_mask;
838 arc_buf_hdr_t **ht_table;
839 struct ht_lock ht_locks[BUF_LOCKS];
840 } buf_hash_table_t;
841
842 static buf_hash_table_t buf_hash_table;
843
844 #define BUF_HASH_INDEX(spa, dva, birth) \
845 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
846 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
847 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
848 #define HDR_LOCK(hdr) \
849 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
850
851 uint64_t zfs_crc64_table[256];
852
853 /*
854 * Level 2 ARC
855 */
856
857 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
858 #define L2ARC_HEADROOM 2 /* num of writes */
859 /*
860 * If we discover during ARC scan any buffers to be compressed, we boost
861 * our headroom for the next scanning cycle by this percentage multiple.
862 */
863 #define L2ARC_HEADROOM_BOOST 200
864 #define L2ARC_FEED_SECS 1 /* caching interval secs */
865 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
866
867 /*
868 * Used to distinguish headers that are being process by
869 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk
870 * address. This can happen when the header is added to the l2arc's list
871 * of buffers to write in the first stage of l2arc_write_buffers(), but
872 * has not yet been written out which happens in the second stage of
873 * l2arc_write_buffers().
874 */
875 #define L2ARC_ADDR_UNSET ((uint64_t)(-1))
876
877 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
878 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
879
880 /* L2ARC Performance Tunables */
881 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
882 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
883 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
884 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
885 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
886 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
887 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
888 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
889 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
890
891 /*
892 * L2ARC Internals
893 */
894 struct l2arc_dev {
895 vdev_t *l2ad_vdev; /* vdev */
896 spa_t *l2ad_spa; /* spa */
897 uint64_t l2ad_hand; /* next write location */
898 uint64_t l2ad_start; /* first addr on device */
899 uint64_t l2ad_end; /* last addr on device */
900 boolean_t l2ad_first; /* first sweep through */
901 boolean_t l2ad_writing; /* currently writing */
902 kmutex_t l2ad_mtx; /* lock for buffer list */
903 list_t l2ad_buflist; /* buffer list */
904 list_node_t l2ad_node; /* device list node */
905 refcount_t l2ad_alloc; /* allocated bytes */
906 };
907
908 static list_t L2ARC_dev_list; /* device list */
909 static list_t *l2arc_dev_list; /* device list pointer */
910 static kmutex_t l2arc_dev_mtx; /* device list mutex */
911 static l2arc_dev_t *l2arc_dev_last; /* last device used */
912 static list_t L2ARC_free_on_write; /* free after write buf list */
913 static list_t *l2arc_free_on_write; /* free after write list ptr */
914 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
915 static uint64_t l2arc_ndev; /* number of devices */
916
917 typedef struct l2arc_read_callback {
918 arc_buf_t *l2rcb_buf; /* read buffer */
919 spa_t *l2rcb_spa; /* spa */
920 blkptr_t l2rcb_bp; /* original blkptr */
921 zbookmark_phys_t l2rcb_zb; /* original bookmark */
922 int l2rcb_flags; /* original flags */
923 enum zio_compress l2rcb_compress; /* applied compress */
924 } l2arc_read_callback_t;
925
926 typedef struct l2arc_write_callback {
927 l2arc_dev_t *l2wcb_dev; /* device info */
928 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
929 } l2arc_write_callback_t;
930
931 typedef struct l2arc_data_free {
932 /* protected by l2arc_free_on_write_mtx */
933 void *l2df_data;
934 size_t l2df_size;
935 void (*l2df_func)(void *, size_t);
936 list_node_t l2df_list_node;
937 } l2arc_data_free_t;
938
939 static kmutex_t l2arc_feed_thr_lock;
940 static kcondvar_t l2arc_feed_thr_cv;
941 static uint8_t l2arc_thread_exit;
942
943 static void arc_get_data_buf(arc_buf_t *);
944 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
945 static boolean_t arc_is_overflowing();
946 static void arc_buf_watch(arc_buf_t *);
947
948 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
949 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
950
951 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
952 static void l2arc_read_done(zio_t *);
953
954 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *);
955 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress);
956 static void l2arc_release_cdata_buf(arc_buf_hdr_t *);
957
958 static uint64_t
959 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
960 {
961 uint8_t *vdva = (uint8_t *)dva;
962 uint64_t crc = -1ULL;
963 int i;
964
965 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
966
967 for (i = 0; i < sizeof (dva_t); i++)
968 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
969
970 crc ^= (spa>>8) ^ birth;
971
972 return (crc);
973 }
974
975 #define BUF_EMPTY(buf) \
976 ((buf)->b_dva.dva_word[0] == 0 && \
977 (buf)->b_dva.dva_word[1] == 0)
978
979 #define BUF_EQUAL(spa, dva, birth, buf) \
980 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
981 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
982 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
983
984 static void
985 buf_discard_identity(arc_buf_hdr_t *hdr)
986 {
987 hdr->b_dva.dva_word[0] = 0;
988 hdr->b_dva.dva_word[1] = 0;
989 hdr->b_birth = 0;
990 }
991
992 static arc_buf_hdr_t *
993 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
994 {
995 const dva_t *dva = BP_IDENTITY(bp);
996 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
997 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
998 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
999 arc_buf_hdr_t *hdr;
1000
1001 mutex_enter(hash_lock);
1002 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1003 hdr = hdr->b_hash_next) {
1004 if (BUF_EQUAL(spa, dva, birth, hdr)) {
1005 *lockp = hash_lock;
1006 return (hdr);
1007 }
1008 }
1009 mutex_exit(hash_lock);
1010 *lockp = NULL;
1011 return (NULL);
1012 }
1013
1014 /*
1015 * Insert an entry into the hash table. If there is already an element
1016 * equal to elem in the hash table, then the already existing element
1017 * will be returned and the new element will not be inserted.
1018 * Otherwise returns NULL.
1019 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1020 */
1021 static arc_buf_hdr_t *
1022 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1023 {
1024 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1025 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1026 arc_buf_hdr_t *fhdr;
1027 uint32_t i;
1028
1029 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1030 ASSERT(hdr->b_birth != 0);
1031 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1032
1033 if (lockp != NULL) {
1034 *lockp = hash_lock;
1035 mutex_enter(hash_lock);
1036 } else {
1037 ASSERT(MUTEX_HELD(hash_lock));
1038 }
1039
1040 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1041 fhdr = fhdr->b_hash_next, i++) {
1042 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1043 return (fhdr);
1044 }
1045
1046 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1047 buf_hash_table.ht_table[idx] = hdr;
1048 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
1049
1050 /* collect some hash table performance data */
1051 if (i > 0) {
1052 ARCSTAT_BUMP(arcstat_hash_collisions);
1053 if (i == 1)
1054 ARCSTAT_BUMP(arcstat_hash_chains);
1055
1056 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1057 }
1058
1059 ARCSTAT_BUMP(arcstat_hash_elements);
1060 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1061
1062 return (NULL);
1063 }
1064
1065 static void
1066 buf_hash_remove(arc_buf_hdr_t *hdr)
1067 {
1068 arc_buf_hdr_t *fhdr, **hdrp;
1069 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1070
1071 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1072 ASSERT(HDR_IN_HASH_TABLE(hdr));
1073
1074 hdrp = &buf_hash_table.ht_table[idx];
1075 while ((fhdr = *hdrp) != hdr) {
1076 ASSERT(fhdr != NULL);
1077 hdrp = &fhdr->b_hash_next;
1078 }
1079 *hdrp = hdr->b_hash_next;
1080 hdr->b_hash_next = NULL;
1081 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE;
1082
1083 /* collect some hash table performance data */
1084 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1085
1086 if (buf_hash_table.ht_table[idx] &&
1087 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1088 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1089 }
1090
1091 /*
1092 * Global data structures and functions for the buf kmem cache.
1093 */
1094 static kmem_cache_t *hdr_full_cache;
1095 static kmem_cache_t *hdr_l2only_cache;
1096 static kmem_cache_t *buf_cache;
1097
1098 static void
1099 buf_fini(void)
1100 {
1101 int i;
1102
1103 kmem_free(buf_hash_table.ht_table,
1104 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1105 for (i = 0; i < BUF_LOCKS; i++)
1106 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1107 kmem_cache_destroy(hdr_full_cache);
1108 kmem_cache_destroy(hdr_l2only_cache);
1109 kmem_cache_destroy(buf_cache);
1110 }
1111
1112 /*
1113 * Constructor callback - called when the cache is empty
1114 * and a new buf is requested.
1115 */
1116 /* ARGSUSED */
1117 static int
1118 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1119 {
1120 arc_buf_hdr_t *hdr = vbuf;
1121
1122 bzero(hdr, HDR_FULL_SIZE);
1123 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1124 refcount_create(&hdr->b_l1hdr.b_refcnt);
1125 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1126 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1127 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1128
1129 return (0);
1130 }
1131
1132 /* ARGSUSED */
1133 static int
1134 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1135 {
1136 arc_buf_hdr_t *hdr = vbuf;
1137
1138 bzero(hdr, HDR_L2ONLY_SIZE);
1139 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1140
1141 return (0);
1142 }
1143
1144 /* ARGSUSED */
1145 static int
1146 buf_cons(void *vbuf, void *unused, int kmflag)
1147 {
1148 arc_buf_t *buf = vbuf;
1149
1150 bzero(buf, sizeof (arc_buf_t));
1151 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1152 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1153
1154 return (0);
1155 }
1156
1157 /*
1158 * Destructor callback - called when a cached buf is
1159 * no longer required.
1160 */
1161 /* ARGSUSED */
1162 static void
1163 hdr_full_dest(void *vbuf, void *unused)
1164 {
1165 arc_buf_hdr_t *hdr = vbuf;
1166
1167 ASSERT(BUF_EMPTY(hdr));
1168 cv_destroy(&hdr->b_l1hdr.b_cv);
1169 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1170 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1171 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1172 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1173 }
1174
1175 /* ARGSUSED */
1176 static void
1177 hdr_l2only_dest(void *vbuf, void *unused)
1178 {
1179 arc_buf_hdr_t *hdr = vbuf;
1180
1181 ASSERT(BUF_EMPTY(hdr));
1182 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1183 }
1184
1185 /* ARGSUSED */
1186 static void
1187 buf_dest(void *vbuf, void *unused)
1188 {
1189 arc_buf_t *buf = vbuf;
1190
1191 mutex_destroy(&buf->b_evict_lock);
1192 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1193 }
1194
1195 /*
1196 * Reclaim callback -- invoked when memory is low.
1197 */
1198 /* ARGSUSED */
1199 static void
1200 hdr_recl(void *unused)
1201 {
1202 dprintf("hdr_recl called\n");
1203 /*
1204 * umem calls the reclaim func when we destroy the buf cache,
1205 * which is after we do arc_fini().
1206 */
1207 if (!arc_dead)
1208 cv_signal(&arc_reclaim_thread_cv);
1209 }
1210
1211 static void
1212 buf_init(void)
1213 {
1214 uint64_t *ct;
1215 uint64_t hsize = 1ULL << 12;
1216 int i, j;
1217
1218 /*
1219 * The hash table is big enough to fill all of physical memory
1220 * with an average block size of zfs_arc_average_blocksize (default 8K).
1221 * By default, the table will take up
1222 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1223 */
1224 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1225 hsize <<= 1;
1226 retry:
1227 buf_hash_table.ht_mask = hsize - 1;
1228 buf_hash_table.ht_table =
1229 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1230 if (buf_hash_table.ht_table == NULL) {
1231 ASSERT(hsize > (1ULL << 8));
1232 hsize >>= 1;
1233 goto retry;
1234 }
1235
1236 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1237 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1238 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1239 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1240 NULL, NULL, 0);
1241 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1242 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1243
1244 for (i = 0; i < 256; i++)
1245 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1246 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1247
1248 for (i = 0; i < BUF_LOCKS; i++) {
1249 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1250 NULL, MUTEX_DEFAULT, NULL);
1251 }
1252 }
1253
1254 /*
1255 * Transition between the two allocation states for the arc_buf_hdr struct.
1256 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
1257 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
1258 * version is used when a cache buffer is only in the L2ARC in order to reduce
1259 * memory usage.
1260 */
1261 static arc_buf_hdr_t *
1262 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
1263 {
1264 ASSERT(HDR_HAS_L2HDR(hdr));
1265
1266 arc_buf_hdr_t *nhdr;
1267 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
1268
1269 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
1270 (old == hdr_l2only_cache && new == hdr_full_cache));
1271
1272 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
1273
1274 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
1275 buf_hash_remove(hdr);
1276
1277 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
1278
1279 if (new == hdr_full_cache) {
1280 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
1281 /*
1282 * arc_access and arc_change_state need to be aware that a
1283 * header has just come out of L2ARC, so we set its state to
1284 * l2c_only even though it's about to change.
1285 */
1286 nhdr->b_l1hdr.b_state = arc_l2c_only;
1287
1288 /* Verify previous threads set to NULL before freeing */
1289 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL);
1290 } else {
1291 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1292 ASSERT0(hdr->b_l1hdr.b_datacnt);
1293
1294 /*
1295 * If we've reached here, We must have been called from
1296 * arc_evict_hdr(), as such we should have already been
1297 * removed from any ghost list we were previously on
1298 * (which protects us from racing with arc_evict_state),
1299 * thus no locking is needed during this check.
1300 */
1301 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1302
1303 /*
1304 * A buffer must not be moved into the arc_l2c_only
1305 * state if it's not finished being written out to the
1306 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field
1307 * might try to be accessed, even though it was removed.
1308 */
1309 VERIFY(!HDR_L2_WRITING(hdr));
1310 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
1311
1312 #ifdef ZFS_DEBUG
1313 if (hdr->b_l1hdr.b_thawed != NULL)
1314 kmem_free(hdr->b_l1hdr.b_thawed, 1);
1315 hdr->b_l1hdr.b_thawed = NULL;
1316 #endif
1317
1318 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR;
1319 }
1320 /*
1321 * The header has been reallocated so we need to re-insert it into any
1322 * lists it was on.
1323 */
1324 (void) buf_hash_insert(nhdr, NULL);
1325
1326 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
1327
1328 mutex_enter(&dev->l2ad_mtx);
1329
1330 /*
1331 * We must place the realloc'ed header back into the list at
1332 * the same spot. Otherwise, if it's placed earlier in the list,
1333 * l2arc_write_buffers() could find it during the function's
1334 * write phase, and try to write it out to the l2arc.
1335 */
1336 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
1337 list_remove(&dev->l2ad_buflist, hdr);
1338
1339 mutex_exit(&dev->l2ad_mtx);
1340
1341 /*
1342 * Since we're using the pointer address as the tag when
1343 * incrementing and decrementing the l2ad_alloc refcount, we
1344 * must remove the old pointer (that we're about to destroy) and
1345 * add the new pointer to the refcount. Otherwise we'd remove
1346 * the wrong pointer address when calling arc_hdr_destroy() later.
1347 */
1348
1349 (void) refcount_remove_many(&dev->l2ad_alloc,
1350 hdr->b_l2hdr.b_asize, hdr);
1351
1352 (void) refcount_add_many(&dev->l2ad_alloc,
1353 nhdr->b_l2hdr.b_asize, nhdr);
1354
1355 buf_discard_identity(hdr);
1356 hdr->b_freeze_cksum = NULL;
1357 kmem_cache_free(old, hdr);
1358
1359 return (nhdr);
1360 }
1361
1362
1363 #define ARC_MINTIME (hz>>4) /* 62 ms */
1364
1365 static void
1366 arc_cksum_verify(arc_buf_t *buf)
1367 {
1368 zio_cksum_t zc;
1369
1370 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1371 return;
1372
1373 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1374 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) {
1375 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1376 return;
1377 }
1378 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1379 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1380 panic("buffer modified while frozen!");
1381 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1382 }
1383
1384 static int
1385 arc_cksum_equal(arc_buf_t *buf)
1386 {
1387 zio_cksum_t zc;
1388 int equal;
1389
1390 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1391 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1392 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1393 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1394
1395 return (equal);
1396 }
1397
1398 static void
1399 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1400 {
1401 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1402 return;
1403
1404 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1405 if (buf->b_hdr->b_freeze_cksum != NULL) {
1406 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1407 return;
1408 }
1409 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1410 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1411 buf->b_hdr->b_freeze_cksum);
1412 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1413 arc_buf_watch(buf);
1414 }
1415
1416 #ifndef _KERNEL
1417 typedef struct procctl {
1418 long cmd;
1419 prwatch_t prwatch;
1420 } procctl_t;
1421 #endif
1422
1423 /* ARGSUSED */
1424 static void
1425 arc_buf_unwatch(arc_buf_t *buf)
1426 {
1427 #ifndef _KERNEL
1428 if (arc_watch) {
1429 int result;
1430 procctl_t ctl;
1431 ctl.cmd = PCWATCH;
1432 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1433 ctl.prwatch.pr_size = 0;
1434 ctl.prwatch.pr_wflags = 0;
1435 result = write(arc_procfd, &ctl, sizeof (ctl));
1436 ASSERT3U(result, ==, sizeof (ctl));
1437 }
1438 #endif
1439 }
1440
1441 /* ARGSUSED */
1442 static void
1443 arc_buf_watch(arc_buf_t *buf)
1444 {
1445 #ifndef _KERNEL
1446 if (arc_watch) {
1447 int result;
1448 procctl_t ctl;
1449 ctl.cmd = PCWATCH;
1450 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1451 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1452 ctl.prwatch.pr_wflags = WA_WRITE;
1453 result = write(arc_procfd, &ctl, sizeof (ctl));
1454 ASSERT3U(result, ==, sizeof (ctl));
1455 }
1456 #endif
1457 }
1458
1459 static arc_buf_contents_t
1460 arc_buf_type(arc_buf_hdr_t *hdr)
1461 {
1462 if (HDR_ISTYPE_METADATA(hdr)) {
1463 return (ARC_BUFC_METADATA);
1464 } else {
1465 return (ARC_BUFC_DATA);
1466 }
1467 }
1468
1469 static uint32_t
1470 arc_bufc_to_flags(arc_buf_contents_t type)
1471 {
1472 switch (type) {
1473 case ARC_BUFC_DATA:
1474 /* metadata field is 0 if buffer contains normal data */
1475 return (0);
1476 case ARC_BUFC_METADATA:
1477 return (ARC_FLAG_BUFC_METADATA);
1478 default:
1479 break;
1480 }
1481 panic("undefined ARC buffer type!");
1482 return ((uint32_t)-1);
1483 }
1484
1485 void
1486 arc_buf_thaw(arc_buf_t *buf)
1487 {
1488 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1489 if (buf->b_hdr->b_l1hdr.b_state != arc_anon)
1490 panic("modifying non-anon buffer!");
1491 if (HDR_IO_IN_PROGRESS(buf->b_hdr))
1492 panic("modifying buffer while i/o in progress!");
1493 arc_cksum_verify(buf);
1494 }
1495
1496 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1497 if (buf->b_hdr->b_freeze_cksum != NULL) {
1498 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1499 buf->b_hdr->b_freeze_cksum = NULL;
1500 }
1501
1502 #ifdef ZFS_DEBUG
1503 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1504 if (buf->b_hdr->b_l1hdr.b_thawed != NULL)
1505 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1);
1506 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
1507 }
1508 #endif
1509
1510 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1511
1512 arc_buf_unwatch(buf);
1513 }
1514
1515 void
1516 arc_buf_freeze(arc_buf_t *buf)
1517 {
1518 kmutex_t *hash_lock;
1519
1520 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1521 return;
1522
1523 hash_lock = HDR_LOCK(buf->b_hdr);
1524 mutex_enter(hash_lock);
1525
1526 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1527 buf->b_hdr->b_l1hdr.b_state == arc_anon);
1528 arc_cksum_compute(buf, B_FALSE);
1529 mutex_exit(hash_lock);
1530
1531 }
1532
1533 static void
1534 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
1535 {
1536 ASSERT(HDR_HAS_L1HDR(hdr));
1537 ASSERT(MUTEX_HELD(hash_lock));
1538 arc_state_t *state = hdr->b_l1hdr.b_state;
1539
1540 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
1541 (state != arc_anon)) {
1542 /* We don't use the L2-only state list. */
1543 if (state != arc_l2c_only) {
1544 arc_buf_contents_t type = arc_buf_type(hdr);
1545 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt;
1546 multilist_t *list = &state->arcs_list[type];
1547 uint64_t *size = &state->arcs_lsize[type];
1548
1549 multilist_remove(list, hdr);
1550
1551 if (GHOST_STATE(state)) {
1552 ASSERT0(hdr->b_l1hdr.b_datacnt);
1553 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
1554 delta = hdr->b_size;
1555 }
1556 ASSERT(delta > 0);
1557 ASSERT3U(*size, >=, delta);
1558 atomic_add_64(size, -delta);
1559 }
1560 /* remove the prefetch flag if we get a reference */
1561 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
1562 }
1563 }
1564
1565 static int
1566 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
1567 {
1568 int cnt;
1569 arc_state_t *state = hdr->b_l1hdr.b_state;
1570
1571 ASSERT(HDR_HAS_L1HDR(hdr));
1572 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1573 ASSERT(!GHOST_STATE(state));
1574
1575 /*
1576 * arc_l2c_only counts as a ghost state so we don't need to explicitly
1577 * check to prevent usage of the arc_l2c_only list.
1578 */
1579 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
1580 (state != arc_anon)) {
1581 arc_buf_contents_t type = arc_buf_type(hdr);
1582 multilist_t *list = &state->arcs_list[type];
1583 uint64_t *size = &state->arcs_lsize[type];
1584
1585 multilist_insert(list, hdr);
1586
1587 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
1588 atomic_add_64(size, hdr->b_size *
1589 hdr->b_l1hdr.b_datacnt);
1590 }
1591 return (cnt);
1592 }
1593
1594 /*
1595 * Move the supplied buffer to the indicated state. The hash lock
1596 * for the buffer must be held by the caller.
1597 */
1598 static void
1599 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
1600 kmutex_t *hash_lock)
1601 {
1602 arc_state_t *old_state;
1603 int64_t refcnt;
1604 uint32_t datacnt;
1605 uint64_t from_delta, to_delta;
1606 arc_buf_contents_t buftype = arc_buf_type(hdr);
1607
1608 /*
1609 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
1610 * in arc_read() when bringing a buffer out of the L2ARC. However, the
1611 * L1 hdr doesn't always exist when we change state to arc_anon before
1612 * destroying a header, in which case reallocating to add the L1 hdr is
1613 * pointless.
1614 */
1615 if (HDR_HAS_L1HDR(hdr)) {
1616 old_state = hdr->b_l1hdr.b_state;
1617 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
1618 datacnt = hdr->b_l1hdr.b_datacnt;
1619 } else {
1620 old_state = arc_l2c_only;
1621 refcnt = 0;
1622 datacnt = 0;
1623 }
1624
1625 ASSERT(MUTEX_HELD(hash_lock));
1626 ASSERT3P(new_state, !=, old_state);
1627 ASSERT(refcnt == 0 || datacnt > 0);
1628 ASSERT(!GHOST_STATE(new_state) || datacnt == 0);
1629 ASSERT(old_state != arc_anon || datacnt <= 1);
1630
1631 from_delta = to_delta = datacnt * hdr->b_size;
1632
1633 /*
1634 * If this buffer is evictable, transfer it from the
1635 * old state list to the new state list.
1636 */
1637 if (refcnt == 0) {
1638 if (old_state != arc_anon && old_state != arc_l2c_only) {
1639 uint64_t *size = &old_state->arcs_lsize[buftype];
1640
1641 ASSERT(HDR_HAS_L1HDR(hdr));
1642 multilist_remove(&old_state->arcs_list[buftype], hdr);
1643
1644 /*
1645 * If prefetching out of the ghost cache,
1646 * we will have a non-zero datacnt.
1647 */
1648 if (GHOST_STATE(old_state) && datacnt == 0) {
1649 /* ghost elements have a ghost size */
1650 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1651 from_delta = hdr->b_size;
1652 }
1653 ASSERT3U(*size, >=, from_delta);
1654 atomic_add_64(size, -from_delta);
1655 }
1656 if (new_state != arc_anon && new_state != arc_l2c_only) {
1657 uint64_t *size = &new_state->arcs_lsize[buftype];
1658
1659 /*
1660 * An L1 header always exists here, since if we're
1661 * moving to some L1-cached state (i.e. not l2c_only or
1662 * anonymous), we realloc the header to add an L1hdr
1663 * beforehand.
1664 */
1665 ASSERT(HDR_HAS_L1HDR(hdr));
1666 multilist_insert(&new_state->arcs_list[buftype], hdr);
1667
1668 /* ghost elements have a ghost size */
1669 if (GHOST_STATE(new_state)) {
1670 ASSERT0(datacnt);
1671 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1672 to_delta = hdr->b_size;
1673 }
1674 atomic_add_64(size, to_delta);
1675 }
1676 }
1677
1678 ASSERT(!BUF_EMPTY(hdr));
1679 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
1680 buf_hash_remove(hdr);
1681
1682 /* adjust state sizes (ignore arc_l2c_only) */
1683
1684 if (to_delta && new_state != arc_l2c_only) {
1685 ASSERT(HDR_HAS_L1HDR(hdr));
1686 if (GHOST_STATE(new_state)) {
1687 ASSERT0(datacnt);
1688
1689 /*
1690 * We moving a header to a ghost state, we first
1691 * remove all arc buffers. Thus, we'll have a
1692 * datacnt of zero, and no arc buffer to use for
1693 * the reference. As a result, we use the arc
1694 * header pointer for the reference.
1695 */
1696 (void) refcount_add_many(&new_state->arcs_size,
1697 hdr->b_size, hdr);
1698 } else {
1699 ASSERT3U(datacnt, !=, 0);
1700
1701 /*
1702 * Each individual buffer holds a unique reference,
1703 * thus we must remove each of these references one
1704 * at a time.
1705 */
1706 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
1707 buf = buf->b_next) {
1708 (void) refcount_add_many(&new_state->arcs_size,
1709 hdr->b_size, buf);
1710 }
1711 }
1712 }
1713
1714 if (from_delta && old_state != arc_l2c_only) {
1715 ASSERT(HDR_HAS_L1HDR(hdr));
1716 if (GHOST_STATE(old_state)) {
1717 /*
1718 * When moving a header off of a ghost state,
1719 * there's the possibility for datacnt to be
1720 * non-zero. This is because we first add the
1721 * arc buffer to the header prior to changing
1722 * the header's state. Since we used the header
1723 * for the reference when putting the header on
1724 * the ghost state, we must balance that and use
1725 * the header when removing off the ghost state
1726 * (even though datacnt is non zero).
1727 */
1728
1729 IMPLY(datacnt == 0, new_state == arc_anon ||
1730 new_state == arc_l2c_only);
1731
1732 (void) refcount_remove_many(&old_state->arcs_size,
1733 hdr->b_size, hdr);
1734 } else {
1735 ASSERT3P(datacnt, !=, 0);
1736
1737 /*
1738 * Each individual buffer holds a unique reference,
1739 * thus we must remove each of these references one
1740 * at a time.
1741 */
1742 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
1743 buf = buf->b_next) {
1744 (void) refcount_remove_many(
1745 &old_state->arcs_size, hdr->b_size, buf);
1746 }
1747 }
1748 }
1749
1750 if (HDR_HAS_L1HDR(hdr))
1751 hdr->b_l1hdr.b_state = new_state;
1752
1753 /*
1754 * L2 headers should never be on the L2 state list since they don't
1755 * have L1 headers allocated.
1756 */
1757 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
1758 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
1759 }
1760
1761 void
1762 arc_space_consume(uint64_t space, arc_space_type_t type)
1763 {
1764 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1765
1766 switch (type) {
1767 case ARC_SPACE_DATA:
1768 ARCSTAT_INCR(arcstat_data_size, space);
1769 break;
1770 case ARC_SPACE_META:
1771 ARCSTAT_INCR(arcstat_metadata_size, space);
1772 break;
1773 case ARC_SPACE_OTHER:
1774 ARCSTAT_INCR(arcstat_other_size, space);
1775 break;
1776 case ARC_SPACE_HDRS:
1777 ARCSTAT_INCR(arcstat_hdr_size, space);
1778 break;
1779 case ARC_SPACE_L2HDRS:
1780 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1781 break;
1782 }
1783
1784 if (type != ARC_SPACE_DATA)
1785 ARCSTAT_INCR(arcstat_meta_used, space);
1786
1787 atomic_add_64(&arc_size, space);
1788 }
1789
1790 void
1791 arc_space_return(uint64_t space, arc_space_type_t type)
1792 {
1793 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1794
1795 switch (type) {
1796 case ARC_SPACE_DATA:
1797 ARCSTAT_INCR(arcstat_data_size, -space);
1798 break;
1799 case ARC_SPACE_META:
1800 ARCSTAT_INCR(arcstat_metadata_size, -space);
1801 break;
1802 case ARC_SPACE_OTHER:
1803 ARCSTAT_INCR(arcstat_other_size, -space);
1804 break;
1805 case ARC_SPACE_HDRS:
1806 ARCSTAT_INCR(arcstat_hdr_size, -space);
1807 break;
1808 case ARC_SPACE_L2HDRS:
1809 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1810 break;
1811 }
1812
1813 if (type != ARC_SPACE_DATA) {
1814 ASSERT(arc_meta_used >= space);
1815 if (arc_meta_max < arc_meta_used)
1816 arc_meta_max = arc_meta_used;
1817 ARCSTAT_INCR(arcstat_meta_used, -space);
1818 }
1819
1820 ASSERT(arc_size >= space);
1821 atomic_add_64(&arc_size, -space);
1822 }
1823
1824 arc_buf_t *
1825 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type)
1826 {
1827 arc_buf_hdr_t *hdr;
1828 arc_buf_t *buf;
1829
1830 ASSERT3U(size, >, 0);
1831 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
1832 ASSERT(BUF_EMPTY(hdr));
1833 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
1834 hdr->b_size = size;
1835 hdr->b_spa = spa_load_guid(spa);
1836
1837 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1838 buf->b_hdr = hdr;
1839 buf->b_data = NULL;
1840 buf->b_efunc = NULL;
1841 buf->b_private = NULL;
1842 buf->b_next = NULL;
1843
1844 hdr->b_flags = arc_bufc_to_flags(type);
1845 hdr->b_flags |= ARC_FLAG_HAS_L1HDR;
1846
1847 hdr->b_l1hdr.b_buf = buf;
1848 hdr->b_l1hdr.b_state = arc_anon;
1849 hdr->b_l1hdr.b_arc_access = 0;
1850 hdr->b_l1hdr.b_datacnt = 1;
1851 hdr->b_l1hdr.b_tmp_cdata = NULL;
1852
1853 arc_get_data_buf(buf);
1854 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
1855 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
1856
1857 return (buf);
1858 }
1859
1860 static char *arc_onloan_tag = "onloan";
1861
1862 /*
1863 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1864 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1865 * buffers must be returned to the arc before they can be used by the DMU or
1866 * freed.
1867 */
1868 arc_buf_t *
1869 arc_loan_buf(spa_t *spa, int size)
1870 {
1871 arc_buf_t *buf;
1872
1873 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1874
1875 atomic_add_64(&arc_loaned_bytes, size);
1876 return (buf);
1877 }
1878
1879 /*
1880 * Return a loaned arc buffer to the arc.
1881 */
1882 void
1883 arc_return_buf(arc_buf_t *buf, void *tag)
1884 {
1885 arc_buf_hdr_t *hdr = buf->b_hdr;
1886
1887 ASSERT(buf->b_data != NULL);
1888 ASSERT(HDR_HAS_L1HDR(hdr));
1889 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
1890 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
1891
1892 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1893 }
1894
1895 /* Detach an arc_buf from a dbuf (tag) */
1896 void
1897 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1898 {
1899 arc_buf_hdr_t *hdr = buf->b_hdr;
1900
1901 ASSERT(buf->b_data != NULL);
1902 ASSERT(HDR_HAS_L1HDR(hdr));
1903 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
1904 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
1905 buf->b_efunc = NULL;
1906 buf->b_private = NULL;
1907
1908 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1909 }
1910
1911 static arc_buf_t *
1912 arc_buf_clone(arc_buf_t *from)
1913 {
1914 arc_buf_t *buf;
1915 arc_buf_hdr_t *hdr = from->b_hdr;
1916 uint64_t size = hdr->b_size;
1917
1918 ASSERT(HDR_HAS_L1HDR(hdr));
1919 ASSERT(hdr->b_l1hdr.b_state != arc_anon);
1920
1921 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1922 buf->b_hdr = hdr;
1923 buf->b_data = NULL;
1924 buf->b_efunc = NULL;
1925 buf->b_private = NULL;
1926 buf->b_next = hdr->b_l1hdr.b_buf;
1927 hdr->b_l1hdr.b_buf = buf;
1928 arc_get_data_buf(buf);
1929 bcopy(from->b_data, buf->b_data, size);
1930
1931 /*
1932 * This buffer already exists in the arc so create a duplicate
1933 * copy for the caller. If the buffer is associated with user data
1934 * then track the size and number of duplicates. These stats will be
1935 * updated as duplicate buffers are created and destroyed.
1936 */
1937 if (HDR_ISTYPE_DATA(hdr)) {
1938 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1939 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1940 }
1941 hdr->b_l1hdr.b_datacnt += 1;
1942 return (buf);
1943 }
1944
1945 void
1946 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1947 {
1948 arc_buf_hdr_t *hdr;
1949 kmutex_t *hash_lock;
1950
1951 /*
1952 * Check to see if this buffer is evicted. Callers
1953 * must verify b_data != NULL to know if the add_ref
1954 * was successful.
1955 */
1956 mutex_enter(&buf->b_evict_lock);
1957 if (buf->b_data == NULL) {
1958 mutex_exit(&buf->b_evict_lock);
1959 return;
1960 }
1961 hash_lock = HDR_LOCK(buf->b_hdr);
1962 mutex_enter(hash_lock);
1963 hdr = buf->b_hdr;
1964 ASSERT(HDR_HAS_L1HDR(hdr));
1965 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1966 mutex_exit(&buf->b_evict_lock);
1967
1968 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
1969 hdr->b_l1hdr.b_state == arc_mfu);
1970
1971 add_reference(hdr, hash_lock, tag);
1972 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1973 arc_access(hdr, hash_lock);
1974 mutex_exit(hash_lock);
1975 ARCSTAT_BUMP(arcstat_hits);
1976 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
1977 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
1978 data, metadata, hits);
1979 }
1980
1981 static void
1982 arc_buf_free_on_write(void *data, size_t size,
1983 void (*free_func)(void *, size_t))
1984 {
1985 l2arc_data_free_t *df;
1986
1987 df = kmem_alloc(sizeof (*df), KM_SLEEP);
1988 df->l2df_data = data;
1989 df->l2df_size = size;
1990 df->l2df_func = free_func;
1991 mutex_enter(&l2arc_free_on_write_mtx);
1992 list_insert_head(l2arc_free_on_write, df);
1993 mutex_exit(&l2arc_free_on_write_mtx);
1994 }
1995
1996 /*
1997 * Free the arc data buffer. If it is an l2arc write in progress,
1998 * the buffer is placed on l2arc_free_on_write to be freed later.
1999 */
2000 static void
2001 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
2002 {
2003 arc_buf_hdr_t *hdr = buf->b_hdr;
2004
2005 if (HDR_L2_WRITING(hdr)) {
2006 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
2007 ARCSTAT_BUMP(arcstat_l2_free_on_write);
2008 } else {
2009 free_func(buf->b_data, hdr->b_size);
2010 }
2011 }
2012
2013 static void
2014 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
2015 {
2016 ASSERT(HDR_HAS_L2HDR(hdr));
2017 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx));
2018
2019 /*
2020 * The b_tmp_cdata field is linked off of the b_l1hdr, so if
2021 * that doesn't exist, the header is in the arc_l2c_only state,
2022 * and there isn't anything to free (it's already been freed).
2023 */
2024 if (!HDR_HAS_L1HDR(hdr))
2025 return;
2026
2027 /*
2028 * The header isn't being written to the l2arc device, thus it
2029 * shouldn't have a b_tmp_cdata to free.
2030 */
2031 if (!HDR_L2_WRITING(hdr)) {
2032 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
2033 return;
2034 }
2035
2036 /*
2037 * The header does not have compression enabled. This can be due
2038 * to the buffer not being compressible, or because we're
2039 * freeing the buffer before the second phase of
2040 * l2arc_write_buffer() has started (which does the compression
2041 * step). In either case, b_tmp_cdata does not point to a
2042 * separately compressed buffer, so there's nothing to free (it
2043 * points to the same buffer as the arc_buf_t's b_data field).
2044 */
2045 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) {
2046 hdr->b_l1hdr.b_tmp_cdata = NULL;
2047 return;
2048 }
2049
2050 /*
2051 * There's nothing to free since the buffer was all zero's and
2052 * compressed to a zero length buffer.
2053 */
2054 if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) {
2055 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
2056 return;
2057 }
2058
2059 ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr)));
2060
2061 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata,
2062 hdr->b_size, zio_data_buf_free);
2063
2064 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
2065 hdr->b_l1hdr.b_tmp_cdata = NULL;
2066 }
2067
2068 /*
2069 * Free up buf->b_data and if 'remove' is set, then pull the
2070 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
2071 */
2072 static void
2073 arc_buf_destroy(arc_buf_t *buf, boolean_t remove)
2074 {
2075 arc_buf_t **bufp;
2076
2077 /* free up data associated with the buf */
2078 if (buf->b_data != NULL) {
2079 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
2080 uint64_t size = buf->b_hdr->b_size;
2081 arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
2082
2083 arc_cksum_verify(buf);
2084 arc_buf_unwatch(buf);
2085
2086 if (type == ARC_BUFC_METADATA) {
2087 arc_buf_data_free(buf, zio_buf_free);
2088 arc_space_return(size, ARC_SPACE_META);
2089 } else {
2090 ASSERT(type == ARC_BUFC_DATA);
2091 arc_buf_data_free(buf, zio_data_buf_free);
2092 arc_space_return(size, ARC_SPACE_DATA);
2093 }
2094
2095 /* protected by hash lock, if in the hash table */
2096 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) {
2097 uint64_t *cnt = &state->arcs_lsize[type];
2098
2099 ASSERT(refcount_is_zero(
2100 &buf->b_hdr->b_l1hdr.b_refcnt));
2101 ASSERT(state != arc_anon && state != arc_l2c_only);
2102
2103 ASSERT3U(*cnt, >=, size);
2104 atomic_add_64(cnt, -size);
2105 }
2106
2107 (void) refcount_remove_many(&state->arcs_size, size, buf);
2108 buf->b_data = NULL;
2109
2110 /*
2111 * If we're destroying a duplicate buffer make sure
2112 * that the appropriate statistics are updated.
2113 */
2114 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 &&
2115 HDR_ISTYPE_DATA(buf->b_hdr)) {
2116 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
2117 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
2118 }
2119 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0);
2120 buf->b_hdr->b_l1hdr.b_datacnt -= 1;
2121 }
2122
2123 /* only remove the buf if requested */
2124 if (!remove)
2125 return;
2126
2127 /* remove the buf from the hdr list */
2128 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf;
2129 bufp = &(*bufp)->b_next)
2130 continue;
2131 *bufp = buf->b_next;
2132 buf->b_next = NULL;
2133
2134 ASSERT(buf->b_efunc == NULL);
2135
2136 /* clean up the buf */
2137 buf->b_hdr = NULL;
2138 kmem_cache_free(buf_cache, buf);
2139 }
2140
2141 static void
2142 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
2143 {
2144 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
2145 l2arc_dev_t *dev = l2hdr->b_dev;
2146
2147 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
2148 ASSERT(HDR_HAS_L2HDR(hdr));
2149
2150 list_remove(&dev->l2ad_buflist, hdr);
2151
2152 /*
2153 * We don't want to leak the b_tmp_cdata buffer that was
2154 * allocated in l2arc_write_buffers()
2155 */
2156 arc_buf_l2_cdata_free(hdr);
2157
2158 /*
2159 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then
2160 * this header is being processed by l2arc_write_buffers() (i.e.
2161 * it's in the first stage of l2arc_write_buffers()).
2162 * Re-affirming that truth here, just to serve as a reminder. If
2163 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or
2164 * may not have its HDR_L2_WRITING flag set. (the write may have
2165 * completed, in which case HDR_L2_WRITING will be false and the
2166 * b_daddr field will point to the address of the buffer on disk).
2167 */
2168 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr));
2169
2170 /*
2171 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with
2172 * l2arc_write_buffers(). Since we've just removed this header
2173 * from the l2arc buffer list, this header will never reach the
2174 * second stage of l2arc_write_buffers(), which increments the
2175 * accounting stats for this header. Thus, we must be careful
2176 * not to decrement them for this header either.
2177 */
2178 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) {
2179 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
2180 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
2181
2182 vdev_space_update(dev->l2ad_vdev,
2183 -l2hdr->b_asize, 0, 0);
2184
2185 (void) refcount_remove_many(&dev->l2ad_alloc,
2186 l2hdr->b_asize, hdr);
2187 }
2188
2189 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
2190 }
2191
2192 static void
2193 arc_hdr_destroy(arc_buf_hdr_t *hdr)
2194 {
2195 if (HDR_HAS_L1HDR(hdr)) {
2196 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
2197 hdr->b_l1hdr.b_datacnt > 0);
2198 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2199 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
2200 }
2201 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2202 ASSERT(!HDR_IN_HASH_TABLE(hdr));
2203
2204 if (HDR_HAS_L2HDR(hdr)) {
2205 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
2206 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
2207
2208 if (!buflist_held)
2209 mutex_enter(&dev->l2ad_mtx);
2210
2211 /*
2212 * Even though we checked this conditional above, we
2213 * need to check this again now that we have the
2214 * l2ad_mtx. This is because we could be racing with
2215 * another thread calling l2arc_evict() which might have
2216 * destroyed this header's L2 portion as we were waiting
2217 * to acquire the l2ad_mtx. If that happens, we don't
2218 * want to re-destroy the header's L2 portion.
2219 */
2220 if (HDR_HAS_L2HDR(hdr))
2221 arc_hdr_l2hdr_destroy(hdr);
2222
2223 if (!buflist_held)
2224 mutex_exit(&dev->l2ad_mtx);
2225 }
2226
2227 if (!BUF_EMPTY(hdr))
2228 buf_discard_identity(hdr);
2229
2230 if (hdr->b_freeze_cksum != NULL) {
2231 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
2232 hdr->b_freeze_cksum = NULL;
2233 }
2234
2235 if (HDR_HAS_L1HDR(hdr)) {
2236 while (hdr->b_l1hdr.b_buf) {
2237 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
2238
2239 if (buf->b_efunc != NULL) {
2240 mutex_enter(&arc_user_evicts_lock);
2241 mutex_enter(&buf->b_evict_lock);
2242 ASSERT(buf->b_hdr != NULL);
2243 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE);
2244 hdr->b_l1hdr.b_buf = buf->b_next;
2245 buf->b_hdr = &arc_eviction_hdr;
2246 buf->b_next = arc_eviction_list;
2247 arc_eviction_list = buf;
2248 mutex_exit(&buf->b_evict_lock);
2249 cv_signal(&arc_user_evicts_cv);
2250 mutex_exit(&arc_user_evicts_lock);
2251 } else {
2252 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE);
2253 }
2254 }
2255 #ifdef ZFS_DEBUG
2256 if (hdr->b_l1hdr.b_thawed != NULL) {
2257 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2258 hdr->b_l1hdr.b_thawed = NULL;
2259 }
2260 #endif
2261 }
2262
2263 ASSERT3P(hdr->b_hash_next, ==, NULL);
2264 if (HDR_HAS_L1HDR(hdr)) {
2265 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
2266 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
2267 kmem_cache_free(hdr_full_cache, hdr);
2268 } else {
2269 kmem_cache_free(hdr_l2only_cache, hdr);
2270 }
2271 }
2272
2273 void
2274 arc_buf_free(arc_buf_t *buf, void *tag)
2275 {
2276 arc_buf_hdr_t *hdr = buf->b_hdr;
2277 int hashed = hdr->b_l1hdr.b_state != arc_anon;
2278
2279 ASSERT(buf->b_efunc == NULL);
2280 ASSERT(buf->b_data != NULL);
2281
2282 if (hashed) {
2283 kmutex_t *hash_lock = HDR_LOCK(hdr);
2284
2285 mutex_enter(hash_lock);
2286 hdr = buf->b_hdr;
2287 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
2288
2289 (void) remove_reference(hdr, hash_lock, tag);
2290 if (hdr->b_l1hdr.b_datacnt > 1) {
2291 arc_buf_destroy(buf, TRUE);
2292 } else {
2293 ASSERT(buf == hdr->b_l1hdr.b_buf);
2294 ASSERT(buf->b_efunc == NULL);
2295 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
2296 }
2297 mutex_exit(hash_lock);
2298 } else if (HDR_IO_IN_PROGRESS(hdr)) {
2299 int destroy_hdr;
2300 /*
2301 * We are in the middle of an async write. Don't destroy
2302 * this buffer unless the write completes before we finish
2303 * decrementing the reference count.
2304 */
2305 mutex_enter(&arc_user_evicts_lock);
2306 (void) remove_reference(hdr, NULL, tag);
2307 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2308 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
2309 mutex_exit(&arc_user_evicts_lock);
2310 if (destroy_hdr)
2311 arc_hdr_destroy(hdr);
2312 } else {
2313 if (remove_reference(hdr, NULL, tag) > 0)
2314 arc_buf_destroy(buf, TRUE);
2315 else
2316 arc_hdr_destroy(hdr);
2317 }
2318 }
2319
2320 boolean_t
2321 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
2322 {
2323 arc_buf_hdr_t *hdr = buf->b_hdr;
2324 kmutex_t *hash_lock = HDR_LOCK(hdr);
2325 boolean_t no_callback = (buf->b_efunc == NULL);
2326
2327 if (hdr->b_l1hdr.b_state == arc_anon) {
2328 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
2329 arc_buf_free(buf, tag);
2330 return (no_callback);
2331 }
2332
2333 mutex_enter(hash_lock);
2334 hdr = buf->b_hdr;
2335 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
2336 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
2337 ASSERT(hdr->b_l1hdr.b_state != arc_anon);
2338 ASSERT(buf->b_data != NULL);
2339
2340 (void) remove_reference(hdr, hash_lock, tag);
2341 if (hdr->b_l1hdr.b_datacnt > 1) {
2342 if (no_callback)
2343 arc_buf_destroy(buf, TRUE);
2344 } else if (no_callback) {
2345 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL);
2346 ASSERT(buf->b_efunc == NULL);
2347 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
2348 }
2349 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 ||
2350 refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2351 mutex_exit(hash_lock);
2352 return (no_callback);
2353 }
2354
2355 int32_t
2356 arc_buf_size(arc_buf_t *buf)
2357 {
2358 return (buf->b_hdr->b_size);
2359 }
2360
2361 /*
2362 * Called from the DMU to determine if the current buffer should be
2363 * evicted. In order to ensure proper locking, the eviction must be initiated
2364 * from the DMU. Return true if the buffer is associated with user data and
2365 * duplicate buffers still exist.
2366 */
2367 boolean_t
2368 arc_buf_eviction_needed(arc_buf_t *buf)
2369 {
2370 arc_buf_hdr_t *hdr;
2371 boolean_t evict_needed = B_FALSE;
2372
2373 if (zfs_disable_dup_eviction)
2374 return (B_FALSE);
2375
2376 mutex_enter(&buf->b_evict_lock);
2377 hdr = buf->b_hdr;
2378 if (hdr == NULL) {
2379 /*
2380 * We are in arc_do_user_evicts(); let that function
2381 * perform the eviction.
2382 */
2383 ASSERT(buf->b_data == NULL);
2384 mutex_exit(&buf->b_evict_lock);
2385 return (B_FALSE);
2386 } else if (buf->b_data == NULL) {
2387 /*
2388 * We have already been added to the arc eviction list;
2389 * recommend eviction.
2390 */
2391 ASSERT3P(hdr, ==, &arc_eviction_hdr);
2392 mutex_exit(&buf->b_evict_lock);
2393 return (B_TRUE);
2394 }
2395
2396 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr))
2397 evict_needed = B_TRUE;
2398
2399 mutex_exit(&buf->b_evict_lock);
2400 return (evict_needed);
2401 }
2402
2403 /*
2404 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
2405 * state of the header is dependent on it's state prior to entering this
2406 * function. The following transitions are possible:
2407 *
2408 * - arc_mru -> arc_mru_ghost
2409 * - arc_mfu -> arc_mfu_ghost
2410 * - arc_mru_ghost -> arc_l2c_only
2411 * - arc_mru_ghost -> deleted
2412 * - arc_mfu_ghost -> arc_l2c_only
2413 * - arc_mfu_ghost -> deleted
2414 */
2415 static int64_t
2416 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
2417 {
2418 arc_state_t *evicted_state, *state;
2419 int64_t bytes_evicted = 0;
2420
2421 ASSERT(MUTEX_HELD(hash_lock));
2422 ASSERT(HDR_HAS_L1HDR(hdr));
2423
2424 state = hdr->b_l1hdr.b_state;
2425 if (GHOST_STATE(state)) {
2426 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2427 ASSERT(hdr->b_l1hdr.b_buf == NULL);
2428
2429 /*
2430 * l2arc_write_buffers() relies on a header's L1 portion
2431 * (i.e. it's b_tmp_cdata field) during it's write phase.
2432 * Thus, we cannot push a header onto the arc_l2c_only
2433 * state (removing it's L1 piece) until the header is
2434 * done being written to the l2arc.
2435 */
2436 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
2437 ARCSTAT_BUMP(arcstat_evict_l2_skip);
2438 return (bytes_evicted);
2439 }
2440
2441 ARCSTAT_BUMP(arcstat_deleted);
2442 bytes_evicted += hdr->b_size;
2443
2444 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
2445
2446 if (HDR_HAS_L2HDR(hdr)) {
2447 /*
2448 * This buffer is cached on the 2nd Level ARC;
2449 * don't destroy the header.
2450 */
2451 arc_change_state(arc_l2c_only, hdr, hash_lock);
2452 /*
2453 * dropping from L1+L2 cached to L2-only,
2454 * realloc to remove the L1 header.
2455 */
2456 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
2457 hdr_l2only_cache);
2458 } else {
2459 arc_change_state(arc_anon, hdr, hash_lock);
2460 arc_hdr_destroy(hdr);
2461 }
2462 return (bytes_evicted);
2463 }
2464
2465 ASSERT(state == arc_mru || state == arc_mfu);
2466 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2467
2468 /* prefetch buffers have a minimum lifespan */
2469 if (HDR_IO_IN_PROGRESS(hdr) ||
2470 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
2471 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
2472 arc_min_prefetch_lifespan)) {
2473 ARCSTAT_BUMP(arcstat_evict_skip);
2474 return (bytes_evicted);
2475 }
2476
2477 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
2478 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0);
2479 while (hdr->b_l1hdr.b_buf) {
2480 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
2481 if (!mutex_tryenter(&buf->b_evict_lock)) {
2482 ARCSTAT_BUMP(arcstat_mutex_miss);
2483 break;
2484 }
2485 if (buf->b_data != NULL)
2486 bytes_evicted += hdr->b_size;
2487 if (buf->b_efunc != NULL) {
2488 mutex_enter(&arc_user_evicts_lock);
2489 arc_buf_destroy(buf, FALSE);
2490 hdr->b_l1hdr.b_buf = buf->b_next;
2491 buf->b_hdr = &arc_eviction_hdr;
2492 buf->b_next = arc_eviction_list;
2493 arc_eviction_list = buf;
2494 cv_signal(&arc_user_evicts_cv);
2495 mutex_exit(&arc_user_evicts_lock);
2496 mutex_exit(&buf->b_evict_lock);
2497 } else {
2498 mutex_exit(&buf->b_evict_lock);
2499 arc_buf_destroy(buf, TRUE);
2500 }
2501 }
2502
2503 if (HDR_HAS_L2HDR(hdr)) {
2504 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size);
2505 } else {
2506 if (l2arc_write_eligible(hdr->b_spa, hdr))
2507 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size);
2508 else
2509 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size);
2510 }
2511
2512 if (hdr->b_l1hdr.b_datacnt == 0) {
2513 arc_change_state(evicted_state, hdr, hash_lock);
2514 ASSERT(HDR_IN_HASH_TABLE(hdr));
2515 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
2516 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
2517 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
2518 }
2519
2520 return (bytes_evicted);
2521 }
2522
2523 static uint64_t
2524 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
2525 uint64_t spa, int64_t bytes)
2526 {
2527 multilist_sublist_t *mls;
2528 uint64_t bytes_evicted = 0;
2529 arc_buf_hdr_t *hdr;
2530 kmutex_t *hash_lock;
2531 int evict_count = 0;
2532
2533 ASSERT3P(marker, !=, NULL);
2534 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
2535
2536 mls = multilist_sublist_lock(ml, idx);
2537
2538 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
2539 hdr = multilist_sublist_prev(mls, marker)) {
2540 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
2541 (evict_count >= zfs_arc_evict_batch_limit))
2542 break;
2543
2544 /*
2545 * To keep our iteration location, move the marker
2546 * forward. Since we're not holding hdr's hash lock, we
2547 * must be very careful and not remove 'hdr' from the
2548 * sublist. Otherwise, other consumers might mistake the
2549 * 'hdr' as not being on a sublist when they call the
2550 * multilist_link_active() function (they all rely on
2551 * the hash lock protecting concurrent insertions and
2552 * removals). multilist_sublist_move_forward() was
2553 * specifically implemented to ensure this is the case
2554 * (only 'marker' will be removed and re-inserted).
2555 */
2556 multilist_sublist_move_forward(mls, marker);
2557
2558 /*
2559 * The only case where the b_spa field should ever be
2560 * zero, is the marker headers inserted by
2561 * arc_evict_state(). It's possible for multiple threads
2562 * to be calling arc_evict_state() concurrently (e.g.
2563 * dsl_pool_close() and zio_inject_fault()), so we must
2564 * skip any markers we see from these other threads.
2565 */
2566 if (hdr->b_spa == 0)
2567 continue;
2568
2569 /* we're only interested in evicting buffers of a certain spa */
2570 if (spa != 0 && hdr->b_spa != spa) {
2571 ARCSTAT_BUMP(arcstat_evict_skip);
2572 continue;
2573 }
2574
2575 hash_lock = HDR_LOCK(hdr);
2576
2577 /*
2578 * We aren't calling this function from any code path
2579 * that would already be holding a hash lock, so we're
2580 * asserting on this assumption to be defensive in case
2581 * this ever changes. Without this check, it would be
2582 * possible to incorrectly increment arcstat_mutex_miss
2583 * below (e.g. if the code changed such that we called
2584 * this function with a hash lock held).
2585 */
2586 ASSERT(!MUTEX_HELD(hash_lock));
2587
2588 if (mutex_tryenter(hash_lock)) {
2589 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
2590 mutex_exit(hash_lock);
2591
2592 bytes_evicted += evicted;
2593
2594 /*
2595 * If evicted is zero, arc_evict_hdr() must have
2596 * decided to skip this header, don't increment
2597 * evict_count in this case.
2598 */
2599 if (evicted != 0)
2600 evict_count++;
2601
2602 /*
2603 * If arc_size isn't overflowing, signal any
2604 * threads that might happen to be waiting.
2605 *
2606 * For each header evicted, we wake up a single
2607 * thread. If we used cv_broadcast, we could
2608 * wake up "too many" threads causing arc_size
2609 * to significantly overflow arc_c; since
2610 * arc_get_data_buf() doesn't check for overflow
2611 * when it's woken up (it doesn't because it's
2612 * possible for the ARC to be overflowing while
2613 * full of un-evictable buffers, and the
2614 * function should proceed in this case).
2615 *
2616 * If threads are left sleeping, due to not
2617 * using cv_broadcast, they will be woken up
2618 * just before arc_reclaim_thread() sleeps.
2619 */
2620 mutex_enter(&arc_reclaim_lock);
2621 if (!arc_is_overflowing())
2622 cv_signal(&arc_reclaim_waiters_cv);
2623 mutex_exit(&arc_reclaim_lock);
2624 } else {
2625 ARCSTAT_BUMP(arcstat_mutex_miss);
2626 }
2627 }
2628
2629 multilist_sublist_unlock(mls);
2630
2631 return (bytes_evicted);
2632 }
2633
2634 /*
2635 * Evict buffers from the given arc state, until we've removed the
2636 * specified number of bytes. Move the removed buffers to the
2637 * appropriate evict state.
2638 *
2639 * This function makes a "best effort". It skips over any buffers
2640 * it can't get a hash_lock on, and so, may not catch all candidates.
2641 * It may also return without evicting as much space as requested.
2642 *
2643 * If bytes is specified using the special value ARC_EVICT_ALL, this
2644 * will evict all available (i.e. unlocked and evictable) buffers from
2645 * the given arc state; which is used by arc_flush().
2646 */
2647 static uint64_t
2648 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
2649 arc_buf_contents_t type)
2650 {
2651 uint64_t total_evicted = 0;
2652 multilist_t *ml = &state->arcs_list[type];
2653 int num_sublists;
2654 arc_buf_hdr_t **markers;
2655
2656 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
2657
2658 num_sublists = multilist_get_num_sublists(ml);
2659
2660 /*
2661 * If we've tried to evict from each sublist, made some
2662 * progress, but still have not hit the target number of bytes
2663 * to evict, we want to keep trying. The markers allow us to
2664 * pick up where we left off for each individual sublist, rather
2665 * than starting from the tail each time.
2666 */
2667 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
2668 for (int i = 0; i < num_sublists; i++) {
2669 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
2670
2671 /*
2672 * A b_spa of 0 is used to indicate that this header is
2673 * a marker. This fact is used in arc_adjust_type() and
2674 * arc_evict_state_impl().
2675 */
2676 markers[i]->b_spa = 0;
2677
2678 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
2679 multilist_sublist_insert_tail(mls, markers[i]);
2680 multilist_sublist_unlock(mls);
2681 }
2682
2683 /*
2684 * While we haven't hit our target number of bytes to evict, or
2685 * we're evicting all available buffers.
2686 */
2687 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
2688 /*
2689 * Start eviction using a randomly selected sublist,
2690 * this is to try and evenly balance eviction across all
2691 * sublists. Always starting at the same sublist
2692 * (e.g. index 0) would cause evictions to favor certain
2693 * sublists over others.
2694 */
2695 int sublist_idx = multilist_get_random_index(ml);
2696 uint64_t scan_evicted = 0;
2697
2698 for (int i = 0; i < num_sublists; i++) {
2699 uint64_t bytes_remaining;
2700 uint64_t bytes_evicted;
2701
2702 if (bytes == ARC_EVICT_ALL)
2703 bytes_remaining = ARC_EVICT_ALL;
2704 else if (total_evicted < bytes)
2705 bytes_remaining = bytes - total_evicted;
2706 else
2707 break;
2708
2709 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
2710 markers[sublist_idx], spa, bytes_remaining);
2711
2712 scan_evicted += bytes_evicted;
2713 total_evicted += bytes_evicted;
2714
2715 /* we've reached the end, wrap to the beginning */
2716 if (++sublist_idx >= num_sublists)
2717 sublist_idx = 0;
2718 }
2719
2720 /*
2721 * If we didn't evict anything during this scan, we have
2722 * no reason to believe we'll evict more during another
2723 * scan, so break the loop.
2724 */
2725 if (scan_evicted == 0) {
2726 /* This isn't possible, let's make that obvious */
2727 ASSERT3S(bytes, !=, 0);
2728
2729 /*
2730 * When bytes is ARC_EVICT_ALL, the only way to
2731 * break the loop is when scan_evicted is zero.
2732 * In that case, we actually have evicted enough,
2733 * so we don't want to increment the kstat.
2734 */
2735 if (bytes != ARC_EVICT_ALL) {
2736 ASSERT3S(total_evicted, <, bytes);
2737 ARCSTAT_BUMP(arcstat_evict_not_enough);
2738 }
2739
2740 break;
2741 }
2742 }
2743
2744 for (int i = 0; i < num_sublists; i++) {
2745 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
2746 multilist_sublist_remove(mls, markers[i]);
2747 multilist_sublist_unlock(mls);
2748
2749 kmem_cache_free(hdr_full_cache, markers[i]);
2750 }
2751 kmem_free(markers, sizeof (*markers) * num_sublists);
2752
2753 return (total_evicted);
2754 }
2755
2756 /*
2757 * Flush all "evictable" data of the given type from the arc state
2758 * specified. This will not evict any "active" buffers (i.e. referenced).
2759 *
2760 * When 'retry' is set to FALSE, the function will make a single pass
2761 * over the state and evict any buffers that it can. Since it doesn't
2762 * continually retry the eviction, it might end up leaving some buffers
2763 * in the ARC due to lock misses.
2764 *
2765 * When 'retry' is set to TRUE, the function will continually retry the
2766 * eviction until *all* evictable buffers have been removed from the
2767 * state. As a result, if concurrent insertions into the state are
2768 * allowed (e.g. if the ARC isn't shutting down), this function might
2769 * wind up in an infinite loop, continually trying to evict buffers.
2770 */
2771 static uint64_t
2772 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
2773 boolean_t retry)
2774 {
2775 uint64_t evicted = 0;
2776
2777 while (state->arcs_lsize[type] != 0) {
2778 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
2779
2780 if (!retry)
2781 break;
2782 }
2783
2784 return (evicted);
2785 }
2786
2787 /*
2788 * Evict the specified number of bytes from the state specified,
2789 * restricting eviction to the spa and type given. This function
2790 * prevents us from trying to evict more from a state's list than
2791 * is "evictable", and to skip evicting altogether when passed a
2792 * negative value for "bytes". In contrast, arc_evict_state() will
2793 * evict everything it can, when passed a negative value for "bytes".
2794 */
2795 static uint64_t
2796 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
2797 arc_buf_contents_t type)
2798 {
2799 int64_t delta;
2800
2801 if (bytes > 0 && state->arcs_lsize[type] > 0) {
2802 delta = MIN(state->arcs_lsize[type], bytes);
2803 return (arc_evict_state(state, spa, delta, type));
2804 }
2805
2806 return (0);
2807 }
2808
2809 /*
2810 * Evict metadata buffers from the cache, such that arc_meta_used is
2811 * capped by the arc_meta_limit tunable.
2812 */
2813 static uint64_t
2814 arc_adjust_meta(void)
2815 {
2816 uint64_t total_evicted = 0;
2817 int64_t target;
2818
2819 /*
2820 * If we're over the meta limit, we want to evict enough
2821 * metadata to get back under the meta limit. We don't want to
2822 * evict so much that we drop the MRU below arc_p, though. If
2823 * we're over the meta limit more than we're over arc_p, we
2824 * evict some from the MRU here, and some from the MFU below.
2825 */
2826 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
2827 (int64_t)(refcount_count(&arc_anon->arcs_size) +
2828 refcount_count(&arc_mru->arcs_size) - arc_p));
2829
2830 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2831
2832 /*
2833 * Similar to the above, we want to evict enough bytes to get us
2834 * below the meta limit, but not so much as to drop us below the
2835 * space alloted to the MFU (which is defined as arc_c - arc_p).
2836 */
2837 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
2838 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
2839
2840 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
2841
2842 return (total_evicted);
2843 }
2844
2845 /*
2846 * Return the type of the oldest buffer in the given arc state
2847 *
2848 * This function will select a random sublist of type ARC_BUFC_DATA and
2849 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
2850 * is compared, and the type which contains the "older" buffer will be
2851 * returned.
2852 */
2853 static arc_buf_contents_t
2854 arc_adjust_type(arc_state_t *state)
2855 {
2856 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA];
2857 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA];
2858 int data_idx = multilist_get_random_index(data_ml);
2859 int meta_idx = multilist_get_random_index(meta_ml);
2860 multilist_sublist_t *data_mls;
2861 multilist_sublist_t *meta_mls;
2862 arc_buf_contents_t type;
2863 arc_buf_hdr_t *data_hdr;
2864 arc_buf_hdr_t *meta_hdr;
2865
2866 /*
2867 * We keep the sublist lock until we're finished, to prevent
2868 * the headers from being destroyed via arc_evict_state().
2869 */
2870 data_mls = multilist_sublist_lock(data_ml, data_idx);
2871 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
2872
2873 /*
2874 * These two loops are to ensure we skip any markers that
2875 * might be at the tail of the lists due to arc_evict_state().
2876 */
2877
2878 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
2879 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
2880 if (data_hdr->b_spa != 0)
2881 break;
2882 }
2883
2884 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
2885 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
2886 if (meta_hdr->b_spa != 0)
2887 break;
2888 }
2889
2890 if (data_hdr == NULL && meta_hdr == NULL) {
2891 type = ARC_BUFC_DATA;
2892 } else if (data_hdr == NULL) {
2893 ASSERT3P(meta_hdr, !=, NULL);
2894 type = ARC_BUFC_METADATA;
2895 } else if (meta_hdr == NULL) {
2896 ASSERT3P(data_hdr, !=, NULL);
2897 type = ARC_BUFC_DATA;
2898 } else {
2899 ASSERT3P(data_hdr, !=, NULL);
2900 ASSERT3P(meta_hdr, !=, NULL);
2901
2902 /* The headers can't be on the sublist without an L1 header */
2903 ASSERT(HDR_HAS_L1HDR(data_hdr));
2904 ASSERT(HDR_HAS_L1HDR(meta_hdr));
2905
2906 if (data_hdr->b_l1hdr.b_arc_access <
2907 meta_hdr->b_l1hdr.b_arc_access) {
2908 type = ARC_BUFC_DATA;
2909 } else {
2910 type = ARC_BUFC_METADATA;
2911 }
2912 }
2913
2914 multilist_sublist_unlock(meta_mls);
2915 multilist_sublist_unlock(data_mls);
2916
2917 return (type);
2918 }
2919
2920 /*
2921 * Evict buffers from the cache, such that arc_size is capped by arc_c.
2922 */
2923 static uint64_t
2924 arc_adjust(void)
2925 {
2926 uint64_t total_evicted = 0;
2927 uint64_t bytes;
2928 int64_t target;
2929
2930 /*
2931 * If we're over arc_meta_limit, we want to correct that before
2932 * potentially evicting data buffers below.
2933 */
2934 total_evicted += arc_adjust_meta();
2935
2936 /*
2937 * Adjust MRU size
2938 *
2939 * If we're over the target cache size, we want to evict enough
2940 * from the list to get back to our target size. We don't want
2941 * to evict too much from the MRU, such that it drops below
2942 * arc_p. So, if we're over our target cache size more than
2943 * the MRU is over arc_p, we'll evict enough to get back to
2944 * arc_p here, and then evict more from the MFU below.
2945 */
2946 target = MIN((int64_t)(arc_size - arc_c),
2947 (int64_t)(refcount_count(&arc_anon->arcs_size) +
2948 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
2949
2950 /*
2951 * If we're below arc_meta_min, always prefer to evict data.
2952 * Otherwise, try to satisfy the requested number of bytes to
2953 * evict from the type which contains older buffers; in an
2954 * effort to keep newer buffers in the cache regardless of their
2955 * type. If we cannot satisfy the number of bytes from this
2956 * type, spill over into the next type.
2957 */
2958 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
2959 arc_meta_used > arc_meta_min) {
2960 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2961 total_evicted += bytes;
2962
2963 /*
2964 * If we couldn't evict our target number of bytes from
2965 * metadata, we try to get the rest from data.
2966 */
2967 target -= bytes;
2968
2969 total_evicted +=
2970 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
2971 } else {
2972 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
2973 total_evicted += bytes;
2974
2975 /*
2976 * If we couldn't evict our target number of bytes from
2977 * data, we try to get the rest from metadata.
2978 */
2979 target -= bytes;
2980
2981 total_evicted +=
2982 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2983 }
2984
2985 /*
2986 * Adjust MFU size
2987 *
2988 * Now that we've tried to evict enough from the MRU to get its
2989 * size back to arc_p, if we're still above the target cache
2990 * size, we evict the rest from the MFU.
2991 */
2992 target = arc_size - arc_c;
2993
2994 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
2995 arc_meta_used > arc_meta_min) {
2996 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
2997 total_evicted += bytes;
2998
2999 /*
3000 * If we couldn't evict our target number of bytes from
3001 * metadata, we try to get the rest from data.
3002 */
3003 target -= bytes;
3004
3005 total_evicted +=
3006 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
3007 } else {
3008 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
3009 total_evicted += bytes;
3010
3011 /*
3012 * If we couldn't evict our target number of bytes from
3013 * data, we try to get the rest from data.
3014 */
3015 target -= bytes;
3016
3017 total_evicted +=
3018 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3019 }
3020
3021 /*
3022 * Adjust ghost lists
3023 *
3024 * In addition to the above, the ARC also defines target values
3025 * for the ghost lists. The sum of the mru list and mru ghost
3026 * list should never exceed the target size of the cache, and
3027 * the sum of the mru list, mfu list, mru ghost list, and mfu
3028 * ghost list should never exceed twice the target size of the
3029 * cache. The following logic enforces these limits on the ghost
3030 * caches, and evicts from them as needed.
3031 */
3032 target = refcount_count(&arc_mru->arcs_size) +
3033 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
3034
3035 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
3036 total_evicted += bytes;
3037
3038 target -= bytes;
3039
3040 total_evicted +=
3041 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
3042
3043 /*
3044 * We assume the sum of the mru list and mfu list is less than
3045 * or equal to arc_c (we enforced this above), which means we
3046 * can use the simpler of the two equations below:
3047 *
3048 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
3049 * mru ghost + mfu ghost <= arc_c
3050 */
3051 target = refcount_count(&arc_mru_ghost->arcs_size) +
3052 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
3053
3054 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
3055 total_evicted += bytes;
3056
3057 target -= bytes;
3058
3059 total_evicted +=
3060 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
3061
3062 return (total_evicted);
3063 }
3064
3065 static void
3066 arc_do_user_evicts(void)
3067 {
3068 mutex_enter(&arc_user_evicts_lock);
3069 while (arc_eviction_list != NULL) {
3070 arc_buf_t *buf = arc_eviction_list;
3071 arc_eviction_list = buf->b_next;
3072 mutex_enter(&buf->b_evict_lock);
3073 buf->b_hdr = NULL;
3074 mutex_exit(&buf->b_evict_lock);
3075 mutex_exit(&arc_user_evicts_lock);
3076
3077 if (buf->b_efunc != NULL)
3078 VERIFY0(buf->b_efunc(buf->b_private));
3079
3080 buf->b_efunc = NULL;
3081 buf->b_private = NULL;
3082 kmem_cache_free(buf_cache, buf);
3083 mutex_enter(&arc_user_evicts_lock);
3084 }
3085 mutex_exit(&arc_user_evicts_lock);
3086 }
3087
3088 void
3089 arc_flush(spa_t *spa, boolean_t retry)
3090 {
3091 uint64_t guid = 0;
3092
3093 /*
3094 * If retry is TRUE, a spa must not be specified since we have
3095 * no good way to determine if all of a spa's buffers have been
3096 * evicted from an arc state.
3097 */
3098 ASSERT(!retry || spa == 0);
3099
3100 if (spa != NULL)
3101 guid = spa_load_guid(spa);
3102
3103 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
3104 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
3105
3106 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
3107 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
3108
3109 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
3110 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
3111
3112 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
3113 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
3114
3115 arc_do_user_evicts();
3116 ASSERT(spa || arc_eviction_list == NULL);
3117 }
3118
3119 void
3120 arc_shrink(int64_t to_free)
3121 {
3122 if (arc_c > arc_c_min) {
3123
3124 if (arc_c > arc_c_min + to_free)
3125 atomic_add_64(&arc_c, -to_free);
3126 else
3127 arc_c = arc_c_min;
3128
3129 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
3130 if (arc_c > arc_size)
3131 arc_c = MAX(arc_size, arc_c_min);
3132 if (arc_p > arc_c)
3133 arc_p = (arc_c >> 1);
3134 ASSERT(arc_c >= arc_c_min);
3135 ASSERT((int64_t)arc_p >= 0);
3136 }
3137
3138 if (arc_size > arc_c)
3139 (void) arc_adjust();
3140 }
3141
3142 typedef enum free_memory_reason_t {
3143 FMR_UNKNOWN,
3144 FMR_NEEDFREE,
3145 FMR_LOTSFREE,
3146 FMR_SWAPFS_MINFREE,
3147 FMR_PAGES_PP_MAXIMUM,
3148 FMR_HEAP_ARENA,
3149 FMR_ZIO_ARENA,
3150 } free_memory_reason_t;
3151
3152 int64_t last_free_memory;
3153 free_memory_reason_t last_free_reason;
3154
3155 /*
3156 * Additional reserve of pages for pp_reserve.
3157 */
3158 int64_t arc_pages_pp_reserve = 64;
3159
3160 /*
3161 * Additional reserve of pages for swapfs.
3162 */
3163 int64_t arc_swapfs_reserve = 64;
3164
3165 /*
3166 * Return the amount of memory that can be consumed before reclaim will be
3167 * needed. Positive if there is sufficient free memory, negative indicates
3168 * the amount of memory that needs to be freed up.
3169 */
3170 static int64_t
3171 arc_available_memory(void)
3172 {
3173 int64_t lowest = INT64_MAX;
3174 int64_t n;
3175 free_memory_reason_t r = FMR_UNKNOWN;
3176
3177 #ifdef _KERNEL
3178 if (needfree > 0) {
3179 n = PAGESIZE * (-needfree);
3180 if (n < lowest) {
3181 lowest = n;
3182 r = FMR_NEEDFREE;
3183 }
3184 }
3185
3186 /*
3187 * check that we're out of range of the pageout scanner. It starts to
3188 * schedule paging if freemem is less than lotsfree and needfree.
3189 * lotsfree is the high-water mark for pageout, and needfree is the
3190 * number of needed free pages. We add extra pages here to make sure
3191 * the scanner doesn't start up while we're freeing memory.
3192 */
3193 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
3194 if (n < lowest) {
3195 lowest = n;
3196 r = FMR_LOTSFREE;
3197 }
3198
3199 /*
3200 * check to make sure that swapfs has enough space so that anon
3201 * reservations can still succeed. anon_resvmem() checks that the
3202 * availrmem is greater than swapfs_minfree, and the number of reserved
3203 * swap pages. We also add a bit of extra here just to prevent
3204 * circumstances from getting really dire.
3205 */
3206 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
3207 desfree - arc_swapfs_reserve);
3208 if (n < lowest) {
3209 lowest = n;
3210 r = FMR_SWAPFS_MINFREE;
3211 }
3212
3213
3214 /*
3215 * Check that we have enough availrmem that memory locking (e.g., via
3216 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
3217 * stores the number of pages that cannot be locked; when availrmem
3218 * drops below pages_pp_maximum, page locking mechanisms such as
3219 * page_pp_lock() will fail.)
3220 */
3221 n = PAGESIZE * (availrmem - pages_pp_maximum -
3222 arc_pages_pp_reserve);
3223 if (n < lowest) {
3224 lowest = n;
3225 r = FMR_PAGES_PP_MAXIMUM;
3226 }
3227
3228 #if defined(__i386)
3229 /*
3230 * If we're on an i386 platform, it's possible that we'll exhaust the
3231 * kernel heap space before we ever run out of available physical
3232 * memory. Most checks of the size of the heap_area compare against
3233 * tune.t_minarmem, which is the minimum available real memory that we
3234 * can have in the system. However, this is generally fixed at 25 pages
3235 * which is so low that it's useless. In this comparison, we seek to
3236 * calculate the total heap-size, and reclaim if more than 3/4ths of the
3237 * heap is allocated. (Or, in the calculation, if less than 1/4th is
3238 * free)
3239 */
3240 n = vmem_size(heap_arena, VMEM_FREE) -
3241 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
3242 if (n < lowest) {
3243 lowest = n;
3244 r = FMR_HEAP_ARENA;
3245 }
3246 #endif
3247
3248 /*
3249 * If zio data pages are being allocated out of a separate heap segment,
3250 * then enforce that the size of available vmem for this arena remains
3251 * above about 1/16th free.
3252 *
3253 * Note: The 1/16th arena free requirement was put in place
3254 * to aggressively evict memory from the arc in order to avoid
3255 * memory fragmentation issues.
3256 */
3257 if (zio_arena != NULL) {
3258 n = vmem_size(zio_arena, VMEM_FREE) -
3259 (vmem_size(zio_arena, VMEM_ALLOC) >> 4);
3260 if (n < lowest) {
3261 lowest = n;
3262 r = FMR_ZIO_ARENA;
3263 }
3264 }
3265 #else
3266 /* Every 100 calls, free a small amount */
3267 if (spa_get_random(100) == 0)
3268 lowest = -1024;
3269 #endif
3270
3271 last_free_memory = lowest;
3272 last_free_reason = r;
3273
3274 return (lowest);
3275 }
3276
3277
3278 /*
3279 * Determine if the system is under memory pressure and is asking
3280 * to reclaim memory. A return value of TRUE indicates that the system
3281 * is under memory pressure and that the arc should adjust accordingly.
3282 */
3283 static boolean_t
3284 arc_reclaim_needed(void)
3285 {
3286 return (arc_available_memory() < 0);
3287 }
3288
3289 static void
3290 arc_kmem_reap_now(void)
3291 {
3292 size_t i;
3293 kmem_cache_t *prev_cache = NULL;
3294 kmem_cache_t *prev_data_cache = NULL;
3295 extern kmem_cache_t *zio_buf_cache[];
3296 extern kmem_cache_t *zio_data_buf_cache[];
3297 extern kmem_cache_t *range_seg_cache;
3298
3299 #ifdef _KERNEL
3300 if (arc_meta_used >= arc_meta_limit) {
3301 /*
3302 * We are exceeding our meta-data cache limit.
3303 * Purge some DNLC entries to release holds on meta-data.
3304 */
3305 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
3306 }
3307 #if defined(__i386)
3308 /*
3309 * Reclaim unused memory from all kmem caches.
3310 */
3311 kmem_reap();
3312 #endif
3313 #endif
3314
3315 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
3316 if (zio_buf_cache[i] != prev_cache) {
3317 prev_cache = zio_buf_cache[i];
3318 kmem_cache_reap_now(zio_buf_cache[i]);
3319 }
3320 if (zio_data_buf_cache[i] != prev_data_cache) {
3321 prev_data_cache = zio_data_buf_cache[i];
3322 kmem_cache_reap_now(zio_data_buf_cache[i]);
3323 }
3324 }
3325 kmem_cache_reap_now(buf_cache);
3326 kmem_cache_reap_now(hdr_full_cache);
3327 kmem_cache_reap_now(hdr_l2only_cache);
3328 kmem_cache_reap_now(range_seg_cache);
3329
3330 if (zio_arena != NULL) {
3331 /*
3332 * Ask the vmem arena to reclaim unused memory from its
3333 * quantum caches.
3334 */
3335 vmem_qcache_reap(zio_arena);
3336 }
3337 }
3338
3339 /*
3340 * Threads can block in arc_get_data_buf() waiting for this thread to evict
3341 * enough data and signal them to proceed. When this happens, the threads in
3342 * arc_get_data_buf() are sleeping while holding the hash lock for their
3343 * particular arc header. Thus, we must be careful to never sleep on a
3344 * hash lock in this thread. This is to prevent the following deadlock:
3345 *
3346 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L",
3347 * waiting for the reclaim thread to signal it.
3348 *
3349 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
3350 * fails, and goes to sleep forever.
3351 *
3352 * This possible deadlock is avoided by always acquiring a hash lock
3353 * using mutex_tryenter() from arc_reclaim_thread().
3354 */
3355 static void
3356 arc_reclaim_thread(void)
3357 {
3358 clock_t growtime = 0;
3359 callb_cpr_t cpr;
3360
3361 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
3362
3363 mutex_enter(&arc_reclaim_lock);
3364 while (!arc_reclaim_thread_exit) {
3365 int64_t free_memory = arc_available_memory();
3366 uint64_t evicted = 0;
3367
3368 mutex_exit(&arc_reclaim_lock);
3369
3370 if (free_memory < 0) {
3371
3372 arc_no_grow = B_TRUE;
3373 arc_warm = B_TRUE;
3374
3375 /*
3376 * Wait at least zfs_grow_retry (default 60) seconds
3377 * before considering growing.
3378 */
3379 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
3380
3381 arc_kmem_reap_now();
3382
3383 /*
3384 * If we are still low on memory, shrink the ARC
3385 * so that we have arc_shrink_min free space.
3386 */
3387 free_memory = arc_available_memory();
3388
3389 int64_t to_free =
3390 (arc_c >> arc_shrink_shift) - free_memory;
3391 if (to_free > 0) {
3392 #ifdef _KERNEL
3393 to_free = MAX(to_free, ptob(needfree));
3394 #endif
3395 arc_shrink(to_free);
3396 }
3397 } else if (free_memory < arc_c >> arc_no_grow_shift) {
3398 arc_no_grow = B_TRUE;
3399 } else if (ddi_get_lbolt() >= growtime) {
3400 arc_no_grow = B_FALSE;
3401 }
3402
3403 evicted = arc_adjust();
3404
3405 mutex_enter(&arc_reclaim_lock);
3406
3407 /*
3408 * If evicted is zero, we couldn't evict anything via
3409 * arc_adjust(). This could be due to hash lock
3410 * collisions, but more likely due to the majority of
3411 * arc buffers being unevictable. Therefore, even if
3412 * arc_size is above arc_c, another pass is unlikely to
3413 * be helpful and could potentially cause us to enter an
3414 * infinite loop.
3415 */
3416 if (arc_size <= arc_c || evicted == 0) {
3417 /*
3418 * We're either no longer overflowing, or we
3419 * can't evict anything more, so we should wake
3420 * up any threads before we go to sleep.
3421 */
3422 cv_broadcast(&arc_reclaim_waiters_cv);
3423
3424 /*
3425 * Block until signaled, or after one second (we
3426 * might need to perform arc_kmem_reap_now()
3427 * even if we aren't being signalled)
3428 */
3429 CALLB_CPR_SAFE_BEGIN(&cpr);
3430 (void) cv_timedwait(&arc_reclaim_thread_cv,
3431 &arc_reclaim_lock, ddi_get_lbolt() + hz);
3432 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
3433 }
3434 }
3435
3436 arc_reclaim_thread_exit = FALSE;
3437 cv_broadcast(&arc_reclaim_thread_cv);
3438 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
3439 thread_exit();
3440 }
3441
3442 static void
3443 arc_user_evicts_thread(void)
3444 {
3445 callb_cpr_t cpr;
3446
3447 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG);
3448
3449 mutex_enter(&arc_user_evicts_lock);
3450 while (!arc_user_evicts_thread_exit) {
3451 mutex_exit(&arc_user_evicts_lock);
3452
3453 arc_do_user_evicts();
3454
3455 /*
3456 * This is necessary in order for the mdb ::arc dcmd to
3457 * show up to date information. Since the ::arc command
3458 * does not call the kstat's update function, without
3459 * this call, the command may show stale stats for the
3460 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
3461 * with this change, the data might be up to 1 second
3462 * out of date; but that should suffice. The arc_state_t
3463 * structures can be queried directly if more accurate
3464 * information is needed.
3465 */
3466 if (arc_ksp != NULL)
3467 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
3468
3469 mutex_enter(&arc_user_evicts_lock);
3470
3471 /*
3472 * Block until signaled, or after one second (we need to
3473 * call the arc's kstat update function regularly).
3474 */
3475 CALLB_CPR_SAFE_BEGIN(&cpr);
3476 (void) cv_timedwait(&arc_user_evicts_cv,
3477 &arc_user_evicts_lock, ddi_get_lbolt() + hz);
3478 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock);
3479 }
3480
3481 arc_user_evicts_thread_exit = FALSE;
3482 cv_broadcast(&arc_user_evicts_cv);
3483 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */
3484 thread_exit();
3485 }
3486
3487 /*
3488 * Adapt arc info given the number of bytes we are trying to add and
3489 * the state that we are comming from. This function is only called
3490 * when we are adding new content to the cache.
3491 */
3492 static void
3493 arc_adapt(int bytes, arc_state_t *state)
3494 {
3495 int mult;
3496 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
3497 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
3498 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
3499
3500 if (state == arc_l2c_only)
3501 return;
3502
3503 ASSERT(bytes > 0);
3504 /*
3505 * Adapt the target size of the MRU list:
3506 * - if we just hit in the MRU ghost list, then increase
3507 * the target size of the MRU list.
3508 * - if we just hit in the MFU ghost list, then increase
3509 * the target size of the MFU list by decreasing the
3510 * target size of the MRU list.
3511 */
3512 if (state == arc_mru_ghost) {
3513 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
3514 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
3515
3516 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
3517 } else if (state == arc_mfu_ghost) {
3518 uint64_t delta;
3519
3520 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
3521 mult = MIN(mult, 10);
3522
3523 delta = MIN(bytes * mult, arc_p);
3524 arc_p = MAX(arc_p_min, arc_p - delta);
3525 }
3526 ASSERT((int64_t)arc_p >= 0);
3527
3528 if (arc_reclaim_needed()) {
3529 cv_signal(&arc_reclaim_thread_cv);
3530 return;
3531 }
3532
3533 if (arc_no_grow)
3534 return;
3535
3536 if (arc_c >= arc_c_max)
3537 return;
3538
3539 /*
3540 * If we're within (2 * maxblocksize) bytes of the target
3541 * cache size, increment the target cache size
3542 */
3543 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
3544 atomic_add_64(&arc_c, (int64_t)bytes);
3545 if (arc_c > arc_c_max)
3546 arc_c = arc_c_max;
3547 else if (state == arc_anon)
3548 atomic_add_64(&arc_p, (int64_t)bytes);
3549 if (arc_p > arc_c)
3550 arc_p = arc_c;
3551 }
3552 ASSERT((int64_t)arc_p >= 0);
3553 }
3554
3555 /*
3556 * Check if arc_size has grown past our upper threshold, determined by
3557 * zfs_arc_overflow_shift.
3558 */
3559 static boolean_t
3560 arc_is_overflowing(void)
3561 {
3562 /* Always allow at least one block of overflow */
3563 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
3564 arc_c >> zfs_arc_overflow_shift);
3565
3566 return (arc_size >= arc_c + overflow);
3567 }
3568
3569 /*
3570 * The buffer, supplied as the first argument, needs a data block. If we
3571 * are hitting the hard limit for the cache size, we must sleep, waiting
3572 * for the eviction thread to catch up. If we're past the target size
3573 * but below the hard limit, we'll only signal the reclaim thread and
3574 * continue on.
3575 */
3576 static void
3577 arc_get_data_buf(arc_buf_t *buf)
3578 {
3579 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
3580 uint64_t size = buf->b_hdr->b_size;
3581 arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
3582
3583 arc_adapt(size, state);
3584
3585 /*
3586 * If arc_size is currently overflowing, and has grown past our
3587 * upper limit, we must be adding data faster than the evict
3588 * thread can evict. Thus, to ensure we don't compound the
3589 * problem by adding more data and forcing arc_size to grow even
3590 * further past it's target size, we halt and wait for the
3591 * eviction thread to catch up.
3592 *
3593 * It's also possible that the reclaim thread is unable to evict
3594 * enough buffers to get arc_size below the overflow limit (e.g.
3595 * due to buffers being un-evictable, or hash lock collisions).
3596 * In this case, we want to proceed regardless if we're
3597 * overflowing; thus we don't use a while loop here.
3598 */
3599 if (arc_is_overflowing()) {
3600 mutex_enter(&arc_reclaim_lock);
3601
3602 /*
3603 * Now that we've acquired the lock, we may no longer be
3604 * over the overflow limit, lets check.
3605 *
3606 * We're ignoring the case of spurious wake ups. If that
3607 * were to happen, it'd let this thread consume an ARC
3608 * buffer before it should have (i.e. before we're under
3609 * the overflow limit and were signalled by the reclaim
3610 * thread). As long as that is a rare occurrence, it
3611 * shouldn't cause any harm.
3612 */
3613 if (arc_is_overflowing()) {
3614 cv_signal(&arc_reclaim_thread_cv);
3615 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
3616 }
3617
3618 mutex_exit(&arc_reclaim_lock);
3619 }
3620
3621 if (type == ARC_BUFC_METADATA) {
3622 buf->b_data = zio_buf_alloc(size);
3623 arc_space_consume(size, ARC_SPACE_META);
3624 } else {
3625 ASSERT(type == ARC_BUFC_DATA);
3626 buf->b_data = zio_data_buf_alloc(size);
3627 arc_space_consume(size, ARC_SPACE_DATA);
3628 }
3629
3630 /*
3631 * Update the state size. Note that ghost states have a
3632 * "ghost size" and so don't need to be updated.
3633 */
3634 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) {
3635 arc_buf_hdr_t *hdr = buf->b_hdr;
3636 arc_state_t *state = hdr->b_l1hdr.b_state;
3637
3638 (void) refcount_add_many(&state->arcs_size, size, buf);
3639
3640 /*
3641 * If this is reached via arc_read, the link is
3642 * protected by the hash lock. If reached via
3643 * arc_buf_alloc, the header should not be accessed by
3644 * any other thread. And, if reached via arc_read_done,
3645 * the hash lock will protect it if it's found in the
3646 * hash table; otherwise no other thread should be
3647 * trying to [add|remove]_reference it.
3648 */
3649 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
3650 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3651 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type],
3652 size);
3653 }
3654 /*
3655 * If we are growing the cache, and we are adding anonymous
3656 * data, and we have outgrown arc_p, update arc_p
3657 */
3658 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
3659 (refcount_count(&arc_anon->arcs_size) +
3660 refcount_count(&arc_mru->arcs_size) > arc_p))
3661 arc_p = MIN(arc_c, arc_p + size);
3662 }
3663 }
3664
3665 /*
3666 * This routine is called whenever a buffer is accessed.
3667 * NOTE: the hash lock is dropped in this function.
3668 */
3669 static void
3670 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3671 {
3672 clock_t now;
3673
3674 ASSERT(MUTEX_HELD(hash_lock));
3675 ASSERT(HDR_HAS_L1HDR(hdr));
3676
3677 if (hdr->b_l1hdr.b_state == arc_anon) {
3678 /*
3679 * This buffer is not in the cache, and does not
3680 * appear in our "ghost" list. Add the new buffer
3681 * to the MRU state.
3682 */
3683
3684 ASSERT0(hdr->b_l1hdr.b_arc_access);
3685 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3686 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
3687 arc_change_state(arc_mru, hdr, hash_lock);
3688
3689 } else if (hdr->b_l1hdr.b_state == arc_mru) {
3690 now = ddi_get_lbolt();
3691
3692 /*
3693 * If this buffer is here because of a prefetch, then either:
3694 * - clear the flag if this is a "referencing" read
3695 * (any subsequent access will bump this into the MFU state).
3696 * or
3697 * - move the buffer to the head of the list if this is
3698 * another prefetch (to make it less likely to be evicted).
3699 */
3700 if (HDR_PREFETCH(hdr)) {
3701 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
3702 /* link protected by hash lock */
3703 ASSERT(multilist_link_active(
3704 &hdr->b_l1hdr.b_arc_node));
3705 } else {
3706 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
3707 ARCSTAT_BUMP(arcstat_mru_hits);
3708 }
3709 hdr->b_l1hdr.b_arc_access = now;
3710 return;
3711 }
3712
3713 /*
3714 * This buffer has been "accessed" only once so far,
3715 * but it is still in the cache. Move it to the MFU
3716 * state.
3717 */
3718 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
3719 /*
3720 * More than 125ms have passed since we
3721 * instantiated this buffer. Move it to the
3722 * most frequently used state.
3723 */
3724 hdr->b_l1hdr.b_arc_access = now;
3725 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3726 arc_change_state(arc_mfu, hdr, hash_lock);
3727 }
3728 ARCSTAT_BUMP(arcstat_mru_hits);
3729 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
3730 arc_state_t *new_state;
3731 /*
3732 * This buffer has been "accessed" recently, but
3733 * was evicted from the cache. Move it to the
3734 * MFU state.
3735 */
3736
3737 if (HDR_PREFETCH(hdr)) {
3738 new_state = arc_mru;
3739 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
3740 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
3741 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
3742 } else {
3743 new_state = arc_mfu;
3744 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3745 }
3746
3747 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3748 arc_change_state(new_state, hdr, hash_lock);
3749
3750 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
3751 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
3752 /*
3753 * This buffer has been accessed more than once and is
3754 * still in the cache. Keep it in the MFU state.
3755 *
3756 * NOTE: an add_reference() that occurred when we did
3757 * the arc_read() will have kicked this off the list.
3758 * If it was a prefetch, we will explicitly move it to
3759 * the head of the list now.
3760 */
3761 if ((HDR_PREFETCH(hdr)) != 0) {
3762 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3763 /* link protected by hash_lock */
3764 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3765 }
3766 ARCSTAT_BUMP(arcstat_mfu_hits);
3767 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3768 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
3769 arc_state_t *new_state = arc_mfu;
3770 /*
3771 * This buffer has been accessed more than once but has
3772 * been evicted from the cache. Move it back to the
3773 * MFU state.
3774 */
3775
3776 if (HDR_PREFETCH(hdr)) {
3777 /*
3778 * This is a prefetch access...
3779 * move this block back to the MRU state.
3780 */
3781 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3782 new_state = arc_mru;
3783 }
3784
3785 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3786 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3787 arc_change_state(new_state, hdr, hash_lock);
3788
3789 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
3790 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
3791 /*
3792 * This buffer is on the 2nd Level ARC.
3793 */
3794
3795 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3796 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3797 arc_change_state(arc_mfu, hdr, hash_lock);
3798 } else {
3799 ASSERT(!"invalid arc state");
3800 }
3801 }
3802
3803 /* a generic arc_done_func_t which you can use */
3804 /* ARGSUSED */
3805 void
3806 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
3807 {
3808 if (zio == NULL || zio->io_error == 0)
3809 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
3810 VERIFY(arc_buf_remove_ref(buf, arg));
3811 }
3812
3813 /* a generic arc_done_func_t */
3814 void
3815 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
3816 {
3817 arc_buf_t **bufp = arg;
3818 if (zio && zio->io_error) {
3819 VERIFY(arc_buf_remove_ref(buf, arg));
3820 *bufp = NULL;
3821 } else {
3822 *bufp = buf;
3823 ASSERT(buf->b_data);
3824 }
3825 }
3826
3827 static void
3828 arc_read_done(zio_t *zio)
3829 {
3830 arc_buf_hdr_t *hdr;
3831 arc_buf_t *buf;
3832 arc_buf_t *abuf; /* buffer we're assigning to callback */
3833 kmutex_t *hash_lock = NULL;
3834 arc_callback_t *callback_list, *acb;
3835 int freeable = FALSE;
3836
3837 buf = zio->io_private;
3838 hdr = buf->b_hdr;
3839
3840 /*
3841 * The hdr was inserted into hash-table and removed from lists
3842 * prior to starting I/O. We should find this header, since
3843 * it's in the hash table, and it should be legit since it's
3844 * not possible to evict it during the I/O. The only possible
3845 * reason for it not to be found is if we were freed during the
3846 * read.
3847 */
3848 if (HDR_IN_HASH_TABLE(hdr)) {
3849 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
3850 ASSERT3U(hdr->b_dva.dva_word[0], ==,
3851 BP_IDENTITY(zio->io_bp)->dva_word[0]);
3852 ASSERT3U(hdr->b_dva.dva_word[1], ==,
3853 BP_IDENTITY(zio->io_bp)->dva_word[1]);
3854
3855 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
3856 &hash_lock);
3857
3858 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
3859 hash_lock == NULL) ||
3860 (found == hdr &&
3861 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
3862 (found == hdr && HDR_L2_READING(hdr)));
3863 }
3864
3865 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED;
3866 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
3867 hdr->b_flags &= ~ARC_FLAG_L2CACHE;
3868
3869 /* byteswap if necessary */
3870 callback_list = hdr->b_l1hdr.b_acb;
3871 ASSERT(callback_list != NULL);
3872 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3873 dmu_object_byteswap_t bswap =
3874 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3875 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3876 byteswap_uint64_array :
3877 dmu_ot_byteswap[bswap].ob_func;
3878 func(buf->b_data, hdr->b_size);
3879 }
3880
3881 arc_cksum_compute(buf, B_FALSE);
3882 arc_buf_watch(buf);
3883
3884 if (hash_lock && zio->io_error == 0 &&
3885 hdr->b_l1hdr.b_state == arc_anon) {
3886 /*
3887 * Only call arc_access on anonymous buffers. This is because
3888 * if we've issued an I/O for an evicted buffer, we've already
3889 * called arc_access (to prevent any simultaneous readers from
3890 * getting confused).
3891 */
3892 arc_access(hdr, hash_lock);
3893 }
3894
3895 /* create copies of the data buffer for the callers */
3896 abuf = buf;
3897 for (acb = callback_list; acb; acb = acb->acb_next) {
3898 if (acb->acb_done) {
3899 if (abuf == NULL) {
3900 ARCSTAT_BUMP(arcstat_duplicate_reads);
3901 abuf = arc_buf_clone(buf);
3902 }
3903 acb->acb_buf = abuf;
3904 abuf = NULL;
3905 }
3906 }
3907 hdr->b_l1hdr.b_acb = NULL;
3908 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
3909 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3910 if (abuf == buf) {
3911 ASSERT(buf->b_efunc == NULL);
3912 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
3913 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
3914 }
3915
3916 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
3917 callback_list != NULL);
3918
3919 if (zio->io_error != 0) {
3920 hdr->b_flags |= ARC_FLAG_IO_ERROR;
3921 if (hdr->b_l1hdr.b_state != arc_anon)
3922 arc_change_state(arc_anon, hdr, hash_lock);
3923 if (HDR_IN_HASH_TABLE(hdr))
3924 buf_hash_remove(hdr);
3925 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
3926 }
3927
3928 /*
3929 * Broadcast before we drop the hash_lock to avoid the possibility
3930 * that the hdr (and hence the cv) might be freed before we get to
3931 * the cv_broadcast().
3932 */
3933 cv_broadcast(&hdr->b_l1hdr.b_cv);
3934
3935 if (hash_lock != NULL) {
3936 mutex_exit(hash_lock);
3937 } else {
3938 /*
3939 * This block was freed while we waited for the read to
3940 * complete. It has been removed from the hash table and
3941 * moved to the anonymous state (so that it won't show up
3942 * in the cache).
3943 */
3944 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3945 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
3946 }
3947
3948 /* execute each callback and free its structure */
3949 while ((acb = callback_list) != NULL) {
3950 if (acb->acb_done)
3951 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3952
3953 if (acb->acb_zio_dummy != NULL) {
3954 acb->acb_zio_dummy->io_error = zio->io_error;
3955 zio_nowait(acb->acb_zio_dummy);
3956 }
3957
3958 callback_list = acb->acb_next;
3959 kmem_free(acb, sizeof (arc_callback_t));
3960 }
3961
3962 if (freeable)
3963 arc_hdr_destroy(hdr);
3964 }
3965
3966 /*
3967 * "Read" the block at the specified DVA (in bp) via the
3968 * cache. If the block is found in the cache, invoke the provided
3969 * callback immediately and return. Note that the `zio' parameter
3970 * in the callback will be NULL in this case, since no IO was
3971 * required. If the block is not in the cache pass the read request
3972 * on to the spa with a substitute callback function, so that the
3973 * requested block will be added to the cache.
3974 *
3975 * If a read request arrives for a block that has a read in-progress,
3976 * either wait for the in-progress read to complete (and return the
3977 * results); or, if this is a read with a "done" func, add a record
3978 * to the read to invoke the "done" func when the read completes,
3979 * and return; or just return.
3980 *
3981 * arc_read_done() will invoke all the requested "done" functions
3982 * for readers of this block.
3983 */
3984 int
3985 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3986 void *private, zio_priority_t priority, int zio_flags,
3987 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
3988 {
3989 arc_buf_hdr_t *hdr = NULL;
3990 arc_buf_t *buf = NULL;
3991 kmutex_t *hash_lock = NULL;
3992 zio_t *rzio;
3993 uint64_t guid = spa_load_guid(spa);
3994
3995 ASSERT(!BP_IS_EMBEDDED(bp) ||
3996 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3997
3998 top:
3999 if (!BP_IS_EMBEDDED(bp)) {
4000 /*
4001 * Embedded BP's have no DVA and require no I/O to "read".
4002 * Create an anonymous arc buf to back it.
4003 */
4004 hdr = buf_hash_find(guid, bp, &hash_lock);
4005 }
4006
4007 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) {
4008
4009 *arc_flags |= ARC_FLAG_CACHED;
4010
4011 if (HDR_IO_IN_PROGRESS(hdr)) {
4012
4013 if (*arc_flags & ARC_FLAG_WAIT) {
4014 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
4015 mutex_exit(hash_lock);
4016 goto top;
4017 }
4018 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
4019
4020 if (done) {
4021 arc_callback_t *acb = NULL;
4022
4023 acb = kmem_zalloc(sizeof (arc_callback_t),
4024 KM_SLEEP);
4025 acb->acb_done = done;
4026 acb->acb_private = private;
4027 if (pio != NULL)
4028 acb->acb_zio_dummy = zio_null(pio,
4029 spa, NULL, NULL, NULL, zio_flags);
4030
4031 ASSERT(acb->acb_done != NULL);
4032 acb->acb_next = hdr->b_l1hdr.b_acb;
4033 hdr->b_l1hdr.b_acb = acb;
4034 add_reference(hdr, hash_lock, private);
4035 mutex_exit(hash_lock);
4036 return (0);
4037 }
4038 mutex_exit(hash_lock);
4039 return (0);
4040 }
4041
4042 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
4043 hdr->b_l1hdr.b_state == arc_mfu);
4044
4045 if (done) {
4046 add_reference(hdr, hash_lock, private);
4047 /*
4048 * If this block is already in use, create a new
4049 * copy of the data so that we will be guaranteed
4050 * that arc_release() will always succeed.
4051 */
4052 buf = hdr->b_l1hdr.b_buf;
4053 ASSERT(buf);
4054 ASSERT(buf->b_data);
4055 if (HDR_BUF_AVAILABLE(hdr)) {
4056 ASSERT(buf->b_efunc == NULL);
4057 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
4058 } else {
4059 buf = arc_buf_clone(buf);
4060 }
4061
4062 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
4063 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4064 hdr->b_flags |= ARC_FLAG_PREFETCH;
4065 }
4066 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
4067 arc_access(hdr, hash_lock);
4068 if (*arc_flags & ARC_FLAG_L2CACHE)
4069 hdr->b_flags |= ARC_FLAG_L2CACHE;
4070 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4071 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4072 mutex_exit(hash_lock);
4073 ARCSTAT_BUMP(arcstat_hits);
4074 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
4075 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
4076 data, metadata, hits);
4077
4078 if (done)
4079 done(NULL, buf, private);
4080 } else {
4081 uint64_t size = BP_GET_LSIZE(bp);
4082 arc_callback_t *acb;
4083 vdev_t *vd = NULL;
4084 uint64_t addr = 0;
4085 boolean_t devw = B_FALSE;
4086 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
4087 int32_t b_asize = 0;
4088
4089 if (hdr == NULL) {
4090 /* this block is not in the cache */
4091 arc_buf_hdr_t *exists = NULL;
4092 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
4093 buf = arc_buf_alloc(spa, size, private, type);
4094 hdr = buf->b_hdr;
4095 if (!BP_IS_EMBEDDED(bp)) {
4096 hdr->b_dva = *BP_IDENTITY(bp);
4097 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
4098 exists = buf_hash_insert(hdr, &hash_lock);
4099 }
4100 if (exists != NULL) {
4101 /* somebody beat us to the hash insert */
4102 mutex_exit(hash_lock);
4103 buf_discard_identity(hdr);
4104 (void) arc_buf_remove_ref(buf, private);
4105 goto top; /* restart the IO request */
4106 }
4107
4108 /* if this is a prefetch, we don't have a reference */
4109 if (*arc_flags & ARC_FLAG_PREFETCH) {
4110 (void) remove_reference(hdr, hash_lock,
4111 private);
4112 hdr->b_flags |= ARC_FLAG_PREFETCH;
4113 }
4114 if (*arc_flags & ARC_FLAG_L2CACHE)
4115 hdr->b_flags |= ARC_FLAG_L2CACHE;
4116 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4117 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4118 if (BP_GET_LEVEL(bp) > 0)
4119 hdr->b_flags |= ARC_FLAG_INDIRECT;
4120 } else {
4121 /*
4122 * This block is in the ghost cache. If it was L2-only
4123 * (and thus didn't have an L1 hdr), we realloc the
4124 * header to add an L1 hdr.
4125 */
4126 if (!HDR_HAS_L1HDR(hdr)) {
4127 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
4128 hdr_full_cache);
4129 }
4130
4131 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
4132 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4133 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4134 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
4135
4136 /* if this is a prefetch, we don't have a reference */
4137 if (*arc_flags & ARC_FLAG_PREFETCH)
4138 hdr->b_flags |= ARC_FLAG_PREFETCH;
4139 else
4140 add_reference(hdr, hash_lock, private);
4141 if (*arc_flags & ARC_FLAG_L2CACHE)
4142 hdr->b_flags |= ARC_FLAG_L2CACHE;
4143 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4144 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4145 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
4146 buf->b_hdr = hdr;
4147 buf->b_data = NULL;
4148 buf->b_efunc = NULL;
4149 buf->b_private = NULL;
4150 buf->b_next = NULL;
4151 hdr->b_l1hdr.b_buf = buf;
4152 ASSERT0(hdr->b_l1hdr.b_datacnt);
4153 hdr->b_l1hdr.b_datacnt = 1;
4154 arc_get_data_buf(buf);
4155 arc_access(hdr, hash_lock);
4156 }
4157
4158 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
4159
4160 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
4161 acb->acb_done = done;
4162 acb->acb_private = private;
4163
4164 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4165 hdr->b_l1hdr.b_acb = acb;
4166 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
4167
4168 if (HDR_HAS_L2HDR(hdr) &&
4169 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
4170 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
4171 addr = hdr->b_l2hdr.b_daddr;
4172 b_compress = HDR_GET_COMPRESS(hdr);
4173 b_asize = hdr->b_l2hdr.b_asize;
4174 /*
4175 * Lock out device removal.
4176 */
4177 if (vdev_is_dead(vd) ||
4178 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
4179 vd = NULL;
4180 }
4181
4182 if (hash_lock != NULL)
4183 mutex_exit(hash_lock);
4184
4185 /*
4186 * At this point, we have a level 1 cache miss. Try again in
4187 * L2ARC if possible.
4188 */
4189 ASSERT3U(hdr->b_size, ==, size);
4190 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
4191 uint64_t, size, zbookmark_phys_t *, zb);
4192 ARCSTAT_BUMP(arcstat_misses);
4193 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
4194 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
4195 data, metadata, misses);
4196
4197 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
4198 /*
4199 * Read from the L2ARC if the following are true:
4200 * 1. The L2ARC vdev was previously cached.
4201 * 2. This buffer still has L2ARC metadata.
4202 * 3. This buffer isn't currently writing to the L2ARC.
4203 * 4. The L2ARC entry wasn't evicted, which may
4204 * also have invalidated the vdev.
4205 * 5. This isn't prefetch and l2arc_noprefetch is set.
4206 */
4207 if (HDR_HAS_L2HDR(hdr) &&
4208 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
4209 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
4210 l2arc_read_callback_t *cb;
4211
4212 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
4213 ARCSTAT_BUMP(arcstat_l2_hits);
4214
4215 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
4216 KM_SLEEP);
4217 cb->l2rcb_buf = buf;
4218 cb->l2rcb_spa = spa;
4219 cb->l2rcb_bp = *bp;
4220 cb->l2rcb_zb = *zb;
4221 cb->l2rcb_flags = zio_flags;
4222 cb->l2rcb_compress = b_compress;
4223
4224 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
4225 addr + size < vd->vdev_psize -
4226 VDEV_LABEL_END_SIZE);
4227
4228 /*
4229 * l2arc read. The SCL_L2ARC lock will be
4230 * released by l2arc_read_done().
4231 * Issue a null zio if the underlying buffer
4232 * was squashed to zero size by compression.
4233 */
4234 if (b_compress == ZIO_COMPRESS_EMPTY) {
4235 rzio = zio_null(pio, spa, vd,
4236 l2arc_read_done, cb,
4237 zio_flags | ZIO_FLAG_DONT_CACHE |
4238 ZIO_FLAG_CANFAIL |
4239 ZIO_FLAG_DONT_PROPAGATE |
4240 ZIO_FLAG_DONT_RETRY);
4241 } else {
4242 rzio = zio_read_phys(pio, vd, addr,
4243 b_asize, buf->b_data,
4244 ZIO_CHECKSUM_OFF,
4245 l2arc_read_done, cb, priority,
4246 zio_flags | ZIO_FLAG_DONT_CACHE |
4247 ZIO_FLAG_CANFAIL |
4248 ZIO_FLAG_DONT_PROPAGATE |
4249 ZIO_FLAG_DONT_RETRY, B_FALSE);
4250 }
4251 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
4252 zio_t *, rzio);
4253 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
4254
4255 if (*arc_flags & ARC_FLAG_NOWAIT) {
4256 zio_nowait(rzio);
4257 return (0);
4258 }
4259
4260 ASSERT(*arc_flags & ARC_FLAG_WAIT);
4261 if (zio_wait(rzio) == 0)
4262 return (0);
4263
4264 /* l2arc read error; goto zio_read() */
4265 } else {
4266 DTRACE_PROBE1(l2arc__miss,
4267 arc_buf_hdr_t *, hdr);
4268 ARCSTAT_BUMP(arcstat_l2_misses);
4269 if (HDR_L2_WRITING(hdr))
4270 ARCSTAT_BUMP(arcstat_l2_rw_clash);
4271 spa_config_exit(spa, SCL_L2ARC, vd);
4272 }
4273 } else {
4274 if (vd != NULL)
4275 spa_config_exit(spa, SCL_L2ARC, vd);
4276 if (l2arc_ndev != 0) {
4277 DTRACE_PROBE1(l2arc__miss,
4278 arc_buf_hdr_t *, hdr);
4279 ARCSTAT_BUMP(arcstat_l2_misses);
4280 }
4281 }
4282
4283 rzio = zio_read(pio, spa, bp, buf->b_data, size,
4284 arc_read_done, buf, priority, zio_flags, zb);
4285
4286 if (*arc_flags & ARC_FLAG_WAIT)
4287 return (zio_wait(rzio));
4288
4289 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
4290 zio_nowait(rzio);
4291 }
4292 return (0);
4293 }
4294
4295 void
4296 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
4297 {
4298 ASSERT(buf->b_hdr != NULL);
4299 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon);
4300 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) ||
4301 func == NULL);
4302 ASSERT(buf->b_efunc == NULL);
4303 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
4304
4305 buf->b_efunc = func;
4306 buf->b_private = private;
4307 }
4308
4309 /*
4310 * Notify the arc that a block was freed, and thus will never be used again.
4311 */
4312 void
4313 arc_freed(spa_t *spa, const blkptr_t *bp)
4314 {
4315 arc_buf_hdr_t *hdr;
4316 kmutex_t *hash_lock;
4317 uint64_t guid = spa_load_guid(spa);
4318
4319 ASSERT(!BP_IS_EMBEDDED(bp));
4320
4321 hdr = buf_hash_find(guid, bp, &hash_lock);
4322 if (hdr == NULL)
4323 return;
4324 if (HDR_BUF_AVAILABLE(hdr)) {
4325 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
4326 add_reference(hdr, hash_lock, FTAG);
4327 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
4328 mutex_exit(hash_lock);
4329
4330 arc_release(buf, FTAG);
4331 (void) arc_buf_remove_ref(buf, FTAG);
4332 } else {
4333 mutex_exit(hash_lock);
4334 }
4335
4336 }
4337
4338 /*
4339 * Clear the user eviction callback set by arc_set_callback(), first calling
4340 * it if it exists. Because the presence of a callback keeps an arc_buf cached
4341 * clearing the callback may result in the arc_buf being destroyed. However,
4342 * it will not result in the *last* arc_buf being destroyed, hence the data
4343 * will remain cached in the ARC. We make a copy of the arc buffer here so
4344 * that we can process the callback without holding any locks.
4345 *
4346 * It's possible that the callback is already in the process of being cleared
4347 * by another thread. In this case we can not clear the callback.
4348 *
4349 * Returns B_TRUE if the callback was successfully called and cleared.
4350 */
4351 boolean_t
4352 arc_clear_callback(arc_buf_t *buf)
4353 {
4354 arc_buf_hdr_t *hdr;
4355 kmutex_t *hash_lock;
4356 arc_evict_func_t *efunc = buf->b_efunc;
4357 void *private = buf->b_private;
4358
4359 mutex_enter(&buf->b_evict_lock);
4360 hdr = buf->b_hdr;
4361 if (hdr == NULL) {
4362 /*
4363 * We are in arc_do_user_evicts().
4364 */
4365 ASSERT(buf->b_data == NULL);
4366 mutex_exit(&buf->b_evict_lock);
4367 return (B_FALSE);
4368 } else if (buf->b_data == NULL) {
4369 /*
4370 * We are on the eviction list; process this buffer now
4371 * but let arc_do_user_evicts() do the reaping.
4372 */
4373 buf->b_efunc = NULL;
4374 mutex_exit(&buf->b_evict_lock);
4375 VERIFY0(efunc(private));
4376 return (B_TRUE);
4377 }
4378 hash_lock = HDR_LOCK(hdr);
4379 mutex_enter(hash_lock);
4380 hdr = buf->b_hdr;
4381 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4382
4383 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <,
4384 hdr->b_l1hdr.b_datacnt);
4385 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
4386 hdr->b_l1hdr.b_state == arc_mfu);
4387
4388 buf->b_efunc = NULL;
4389 buf->b_private = NULL;
4390
4391 if (hdr->b_l1hdr.b_datacnt > 1) {
4392 mutex_exit(&buf->b_evict_lock);
4393 arc_buf_destroy(buf, TRUE);
4394 } else {
4395 ASSERT(buf == hdr->b_l1hdr.b_buf);
4396 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
4397 mutex_exit(&buf->b_evict_lock);
4398 }
4399
4400 mutex_exit(hash_lock);
4401 VERIFY0(efunc(private));
4402 return (B_TRUE);
4403 }
4404
4405 /*
4406 * Release this buffer from the cache, making it an anonymous buffer. This
4407 * must be done after a read and prior to modifying the buffer contents.
4408 * If the buffer has more than one reference, we must make
4409 * a new hdr for the buffer.
4410 */
4411 void
4412 arc_release(arc_buf_t *buf, void *tag)
4413 {
4414 arc_buf_hdr_t *hdr = buf->b_hdr;
4415
4416 /*
4417 * It would be nice to assert that if it's DMU metadata (level >
4418 * 0 || it's the dnode file), then it must be syncing context.
4419 * But we don't know that information at this level.
4420 */
4421
4422 mutex_enter(&buf->b_evict_lock);
4423
4424 ASSERT(HDR_HAS_L1HDR(hdr));
4425
4426 /*
4427 * We don't grab the hash lock prior to this check, because if
4428 * the buffer's header is in the arc_anon state, it won't be
4429 * linked into the hash table.
4430 */
4431 if (hdr->b_l1hdr.b_state == arc_anon) {
4432 mutex_exit(&buf->b_evict_lock);
4433 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4434 ASSERT(!HDR_IN_HASH_TABLE(hdr));
4435 ASSERT(!HDR_HAS_L2HDR(hdr));
4436 ASSERT(BUF_EMPTY(hdr));
4437
4438 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1);
4439 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
4440 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
4441
4442 ASSERT3P(buf->b_efunc, ==, NULL);
4443 ASSERT3P(buf->b_private, ==, NULL);
4444
4445 hdr->b_l1hdr.b_arc_access = 0;
4446 arc_buf_thaw(buf);
4447
4448 return;
4449 }
4450
4451 kmutex_t *hash_lock = HDR_LOCK(hdr);
4452 mutex_enter(hash_lock);
4453
4454 /*
4455 * This assignment is only valid as long as the hash_lock is
4456 * held, we must be careful not to reference state or the
4457 * b_state field after dropping the lock.
4458 */
4459 arc_state_t *state = hdr->b_l1hdr.b_state;
4460 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4461 ASSERT3P(state, !=, arc_anon);
4462
4463 /* this buffer is not on any list */
4464 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0);
4465
4466 if (HDR_HAS_L2HDR(hdr)) {
4467 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
4468
4469 /*
4470 * We have to recheck this conditional again now that
4471 * we're holding the l2ad_mtx to prevent a race with
4472 * another thread which might be concurrently calling
4473 * l2arc_evict(). In that case, l2arc_evict() might have
4474 * destroyed the header's L2 portion as we were waiting
4475 * to acquire the l2ad_mtx.
4476 */
4477 if (HDR_HAS_L2HDR(hdr))
4478 arc_hdr_l2hdr_destroy(hdr);
4479
4480 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
4481 }
4482
4483 /*
4484 * Do we have more than one buf?
4485 */
4486 if (hdr->b_l1hdr.b_datacnt > 1) {
4487 arc_buf_hdr_t *nhdr;
4488 arc_buf_t **bufp;
4489 uint64_t blksz = hdr->b_size;
4490 uint64_t spa = hdr->b_spa;
4491 arc_buf_contents_t type = arc_buf_type(hdr);
4492 uint32_t flags = hdr->b_flags;
4493
4494 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
4495 /*
4496 * Pull the data off of this hdr and attach it to
4497 * a new anonymous hdr.
4498 */
4499 (void) remove_reference(hdr, hash_lock, tag);
4500 bufp = &hdr->b_l1hdr.b_buf;
4501 while (*bufp != buf)
4502 bufp = &(*bufp)->b_next;
4503 *bufp = buf->b_next;
4504 buf->b_next = NULL;
4505
4506 ASSERT3P(state, !=, arc_l2c_only);
4507
4508 (void) refcount_remove_many(
4509 &state->arcs_size, hdr->b_size, buf);
4510
4511 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
4512 ASSERT3P(state, !=, arc_l2c_only);
4513 uint64_t *size = &state->arcs_lsize[type];
4514 ASSERT3U(*size, >=, hdr->b_size);
4515 atomic_add_64(size, -hdr->b_size);
4516 }
4517
4518 /*
4519 * We're releasing a duplicate user data buffer, update
4520 * our statistics accordingly.
4521 */
4522 if (HDR_ISTYPE_DATA(hdr)) {
4523 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
4524 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
4525 -hdr->b_size);
4526 }
4527 hdr->b_l1hdr.b_datacnt -= 1;
4528 arc_cksum_verify(buf);
4529 arc_buf_unwatch(buf);
4530
4531 mutex_exit(hash_lock);
4532
4533 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
4534 nhdr->b_size = blksz;
4535 nhdr->b_spa = spa;
4536
4537 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING;
4538 nhdr->b_flags |= arc_bufc_to_flags(type);
4539 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
4540
4541 nhdr->b_l1hdr.b_buf = buf;
4542 nhdr->b_l1hdr.b_datacnt = 1;
4543 nhdr->b_l1hdr.b_state = arc_anon;
4544 nhdr->b_l1hdr.b_arc_access = 0;
4545 nhdr->b_l1hdr.b_tmp_cdata = NULL;
4546 nhdr->b_freeze_cksum = NULL;
4547
4548 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
4549 buf->b_hdr = nhdr;
4550 mutex_exit(&buf->b_evict_lock);
4551 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf);
4552 } else {
4553 mutex_exit(&buf->b_evict_lock);
4554 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
4555 /* protected by hash lock, or hdr is on arc_anon */
4556 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
4557 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4558 arc_change_state(arc_anon, hdr, hash_lock);
4559 hdr->b_l1hdr.b_arc_access = 0;
4560 mutex_exit(hash_lock);
4561
4562 buf_discard_identity(hdr);
4563 arc_buf_thaw(buf);
4564 }
4565 buf->b_efunc = NULL;
4566 buf->b_private = NULL;
4567 }
4568
4569 int
4570 arc_released(arc_buf_t *buf)
4571 {
4572 int released;
4573
4574 mutex_enter(&buf->b_evict_lock);
4575 released = (buf->b_data != NULL &&
4576 buf->b_hdr->b_l1hdr.b_state == arc_anon);
4577 mutex_exit(&buf->b_evict_lock);
4578 return (released);
4579 }
4580
4581 #ifdef ZFS_DEBUG
4582 int
4583 arc_referenced(arc_buf_t *buf)
4584 {
4585 int referenced;
4586
4587 mutex_enter(&buf->b_evict_lock);
4588 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
4589 mutex_exit(&buf->b_evict_lock);
4590 return (referenced);
4591 }
4592 #endif
4593
4594 static void
4595 arc_write_ready(zio_t *zio)
4596 {
4597 arc_write_callback_t *callback = zio->io_private;
4598 arc_buf_t *buf = callback->awcb_buf;
4599 arc_buf_hdr_t *hdr = buf->b_hdr;
4600
4601 ASSERT(HDR_HAS_L1HDR(hdr));
4602 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
4603 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
4604 callback->awcb_ready(zio, buf, callback->awcb_private);
4605
4606 /*
4607 * If the IO is already in progress, then this is a re-write
4608 * attempt, so we need to thaw and re-compute the cksum.
4609 * It is the responsibility of the callback to handle the
4610 * accounting for any re-write attempt.
4611 */
4612 if (HDR_IO_IN_PROGRESS(hdr)) {
4613 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
4614 if (hdr->b_freeze_cksum != NULL) {
4615 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
4616 hdr->b_freeze_cksum = NULL;
4617 }
4618 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
4619 }
4620 arc_cksum_compute(buf, B_FALSE);
4621 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
4622 }
4623
4624 /*
4625 * The SPA calls this callback for each physical write that happens on behalf
4626 * of a logical write. See the comment in dbuf_write_physdone() for details.
4627 */
4628 static void
4629 arc_write_physdone(zio_t *zio)
4630 {
4631 arc_write_callback_t *cb = zio->io_private;
4632 if (cb->awcb_physdone != NULL)
4633 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
4634 }
4635
4636 static void
4637 arc_write_done(zio_t *zio)
4638 {
4639 arc_write_callback_t *callback = zio->io_private;
4640 arc_buf_t *buf = callback->awcb_buf;
4641 arc_buf_hdr_t *hdr = buf->b_hdr;
4642
4643 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4644
4645 if (zio->io_error == 0) {
4646 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
4647 buf_discard_identity(hdr);
4648 } else {
4649 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
4650 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
4651 }
4652 } else {
4653 ASSERT(BUF_EMPTY(hdr));
4654 }
4655
4656 /*
4657 * If the block to be written was all-zero or compressed enough to be
4658 * embedded in the BP, no write was performed so there will be no
4659 * dva/birth/checksum. The buffer must therefore remain anonymous
4660 * (and uncached).
4661 */
4662 if (!BUF_EMPTY(hdr)) {
4663 arc_buf_hdr_t *exists;
4664 kmutex_t *hash_lock;
4665
4666 ASSERT(zio->io_error == 0);
4667
4668 arc_cksum_verify(buf);
4669
4670 exists = buf_hash_insert(hdr, &hash_lock);
4671 if (exists != NULL) {
4672 /*
4673 * This can only happen if we overwrite for
4674 * sync-to-convergence, because we remove
4675 * buffers from the hash table when we arc_free().
4676 */
4677 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
4678 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
4679 panic("bad overwrite, hdr=%p exists=%p",
4680 (void *)hdr, (void *)exists);
4681 ASSERT(refcount_is_zero(
4682 &exists->b_l1hdr.b_refcnt));
4683 arc_change_state(arc_anon, exists, hash_lock);
4684 mutex_exit(hash_lock);
4685 arc_hdr_destroy(exists);
4686 exists = buf_hash_insert(hdr, &hash_lock);
4687 ASSERT3P(exists, ==, NULL);
4688 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
4689 /* nopwrite */
4690 ASSERT(zio->io_prop.zp_nopwrite);
4691 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
4692 panic("bad nopwrite, hdr=%p exists=%p",
4693 (void *)hdr, (void *)exists);
4694 } else {
4695 /* Dedup */
4696 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
4697 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
4698 ASSERT(BP_GET_DEDUP(zio->io_bp));
4699 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
4700 }
4701 }
4702 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
4703 /* if it's not anon, we are doing a scrub */
4704 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
4705 arc_access(hdr, hash_lock);
4706 mutex_exit(hash_lock);
4707 } else {
4708 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
4709 }
4710
4711 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4712 callback->awcb_done(zio, buf, callback->awcb_private);
4713
4714 kmem_free(callback, sizeof (arc_write_callback_t));
4715 }
4716
4717 zio_t *
4718 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
4719 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
4720 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
4721 arc_done_func_t *done, void *private, zio_priority_t priority,
4722 int zio_flags, const zbookmark_phys_t *zb)
4723 {
4724 arc_buf_hdr_t *hdr = buf->b_hdr;
4725 arc_write_callback_t *callback;
4726 zio_t *zio;
4727
4728 ASSERT(ready != NULL);
4729 ASSERT(done != NULL);
4730 ASSERT(!HDR_IO_ERROR(hdr));
4731 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4732 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4733 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
4734 if (l2arc)
4735 hdr->b_flags |= ARC_FLAG_L2CACHE;
4736 if (l2arc_compress)
4737 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4738 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
4739 callback->awcb_ready = ready;
4740 callback->awcb_physdone = physdone;
4741 callback->awcb_done = done;
4742 callback->awcb_private = private;
4743 callback->awcb_buf = buf;
4744
4745 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
4746 arc_write_ready, arc_write_physdone, arc_write_done, callback,
4747 priority, zio_flags, zb);
4748
4749 return (zio);
4750 }
4751
4752 static int
4753 arc_memory_throttle(uint64_t reserve, uint64_t txg)
4754 {
4755 #ifdef _KERNEL
4756 uint64_t available_memory = ptob(freemem);
4757 static uint64_t page_load = 0;
4758 static uint64_t last_txg = 0;
4759
4760 #if defined(__i386)
4761 available_memory =
4762 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
4763 #endif
4764
4765 if (freemem > physmem * arc_lotsfree_percent / 100)
4766 return (0);
4767
4768 if (txg > last_txg) {
4769 last_txg = txg;
4770 page_load = 0;
4771 }
4772 /*
4773 * If we are in pageout, we know that memory is already tight,
4774 * the arc is already going to be evicting, so we just want to
4775 * continue to let page writes occur as quickly as possible.
4776 */
4777 if (curproc == proc_pageout) {
4778 if (page_load > MAX(ptob(minfree), available_memory) / 4)
4779 return (SET_ERROR(ERESTART));
4780 /* Note: reserve is inflated, so we deflate */
4781 page_load += reserve / 8;
4782 return (0);
4783 } else if (page_load > 0 && arc_reclaim_needed()) {
4784 /* memory is low, delay before restarting */
4785 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
4786 return (SET_ERROR(EAGAIN));
4787 }
4788 page_load = 0;
4789 #endif
4790 return (0);
4791 }
4792
4793 void
4794 arc_tempreserve_clear(uint64_t reserve)
4795 {
4796 atomic_add_64(&arc_tempreserve, -reserve);
4797 ASSERT((int64_t)arc_tempreserve >= 0);
4798 }
4799
4800 int
4801 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
4802 {
4803 int error;
4804 uint64_t anon_size;
4805
4806 if (reserve > arc_c/4 && !arc_no_grow)
4807 arc_c = MIN(arc_c_max, reserve * 4);
4808 if (reserve > arc_c)
4809 return (SET_ERROR(ENOMEM));
4810
4811 /*
4812 * Don't count loaned bufs as in flight dirty data to prevent long
4813 * network delays from blocking transactions that are ready to be
4814 * assigned to a txg.
4815 */
4816 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
4817 arc_loaned_bytes), 0);
4818
4819 /*
4820 * Writes will, almost always, require additional memory allocations
4821 * in order to compress/encrypt/etc the data. We therefore need to
4822 * make sure that there is sufficient available memory for this.
4823 */
4824 error = arc_memory_throttle(reserve, txg);
4825 if (error != 0)
4826 return (error);
4827
4828 /*
4829 * Throttle writes when the amount of dirty data in the cache
4830 * gets too large. We try to keep the cache less than half full
4831 * of dirty blocks so that our sync times don't grow too large.
4832 * Note: if two requests come in concurrently, we might let them
4833 * both succeed, when one of them should fail. Not a huge deal.
4834 */
4835
4836 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
4837 anon_size > arc_c / 4) {
4838 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
4839 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
4840 arc_tempreserve>>10,
4841 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
4842 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
4843 reserve>>10, arc_c>>10);
4844 return (SET_ERROR(ERESTART));
4845 }
4846 atomic_add_64(&arc_tempreserve, reserve);
4847 return (0);
4848 }
4849
4850 static void
4851 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
4852 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
4853 {
4854 size->value.ui64 = refcount_count(&state->arcs_size);
4855 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA];
4856 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA];
4857 }
4858
4859 static int
4860 arc_kstat_update(kstat_t *ksp, int rw)
4861 {
4862 arc_stats_t *as = ksp->ks_data;
4863
4864 if (rw == KSTAT_WRITE) {
4865 return (EACCES);
4866 } else {
4867 arc_kstat_update_state(arc_anon,
4868 &as->arcstat_anon_size,
4869 &as->arcstat_anon_evictable_data,
4870 &as->arcstat_anon_evictable_metadata);
4871 arc_kstat_update_state(arc_mru,
4872 &as->arcstat_mru_size,
4873 &as->arcstat_mru_evictable_data,
4874 &as->arcstat_mru_evictable_metadata);
4875 arc_kstat_update_state(arc_mru_ghost,
4876 &as->arcstat_mru_ghost_size,
4877 &as->arcstat_mru_ghost_evictable_data,
4878 &as->arcstat_mru_ghost_evictable_metadata);
4879 arc_kstat_update_state(arc_mfu,
4880 &as->arcstat_mfu_size,
4881 &as->arcstat_mfu_evictable_data,
4882 &as->arcstat_mfu_evictable_metadata);
4883 arc_kstat_update_state(arc_mfu_ghost,
4884 &as->arcstat_mfu_ghost_size,
4885 &as->arcstat_mfu_ghost_evictable_data,
4886 &as->arcstat_mfu_ghost_evictable_metadata);
4887 }
4888
4889 return (0);
4890 }
4891
4892 /*
4893 * This function *must* return indices evenly distributed between all
4894 * sublists of the multilist. This is needed due to how the ARC eviction
4895 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
4896 * distributed between all sublists and uses this assumption when
4897 * deciding which sublist to evict from and how much to evict from it.
4898 */
4899 unsigned int
4900 arc_state_multilist_index_func(multilist_t *ml, void *obj)
4901 {
4902 arc_buf_hdr_t *hdr = obj;
4903
4904 /*
4905 * We rely on b_dva to generate evenly distributed index
4906 * numbers using buf_hash below. So, as an added precaution,
4907 * let's make sure we never add empty buffers to the arc lists.
4908 */
4909 ASSERT(!BUF_EMPTY(hdr));
4910
4911 /*
4912 * The assumption here, is the hash value for a given
4913 * arc_buf_hdr_t will remain constant throughout it's lifetime
4914 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
4915 * Thus, we don't need to store the header's sublist index
4916 * on insertion, as this index can be recalculated on removal.
4917 *
4918 * Also, the low order bits of the hash value are thought to be
4919 * distributed evenly. Otherwise, in the case that the multilist
4920 * has a power of two number of sublists, each sublists' usage
4921 * would not be evenly distributed.
4922 */
4923 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
4924 multilist_get_num_sublists(ml));
4925 }
4926
4927 void
4928 arc_init(void)
4929 {
4930 /*
4931 * allmem is "all memory that we could possibly use".
4932 */
4933 #ifdef _KERNEL
4934 uint64_t allmem = ptob(physmem - swapfs_minfree);
4935 #else
4936 uint64_t allmem = (physmem * PAGESIZE) / 2;
4937 #endif
4938
4939 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
4940 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
4941 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
4942
4943 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
4944 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL);
4945
4946 /* Convert seconds to clock ticks */
4947 arc_min_prefetch_lifespan = 1 * hz;
4948
4949 /* Start out with 1/8 of all memory */
4950 arc_c = allmem / 8;
4951
4952 #ifdef _KERNEL
4953 /*
4954 * On architectures where the physical memory can be larger
4955 * than the addressable space (intel in 32-bit mode), we may
4956 * need to limit the cache to 1/8 of VM size.
4957 */
4958 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
4959 #endif
4960
4961 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
4962 arc_c_min = MAX(allmem / 32, 64 << 20);
4963 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
4964 if (allmem >= 1 << 30)
4965 arc_c_max = allmem - (1 << 30);
4966 else
4967 arc_c_max = arc_c_min;
4968 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
4969
4970 /*
4971 * Allow the tunables to override our calculations if they are
4972 * reasonable (ie. over 64MB)
4973 */
4974 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem)
4975 arc_c_max = zfs_arc_max;
4976 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
4977 arc_c_min = zfs_arc_min;
4978
4979 arc_c = arc_c_max;
4980 arc_p = (arc_c >> 1);
4981
4982 /* limit meta-data to 1/4 of the arc capacity */
4983 arc_meta_limit = arc_c_max / 4;
4984
4985 /* Allow the tunable to override if it is reasonable */
4986 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
4987 arc_meta_limit = zfs_arc_meta_limit;
4988
4989 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
4990 arc_c_min = arc_meta_limit / 2;
4991
4992 if (zfs_arc_meta_min > 0) {
4993 arc_meta_min = zfs_arc_meta_min;
4994 } else {
4995 arc_meta_min = arc_c_min / 2;
4996 }
4997
4998 if (zfs_arc_grow_retry > 0)
4999 arc_grow_retry = zfs_arc_grow_retry;
5000
5001 if (zfs_arc_shrink_shift > 0)
5002 arc_shrink_shift = zfs_arc_shrink_shift;
5003
5004 /*
5005 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
5006 */
5007 if (arc_no_grow_shift >= arc_shrink_shift)
5008 arc_no_grow_shift = arc_shrink_shift - 1;
5009
5010 if (zfs_arc_p_min_shift > 0)
5011 arc_p_min_shift = zfs_arc_p_min_shift;
5012
5013 if (zfs_arc_num_sublists_per_state < 1)
5014 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1);
5015
5016 /* if kmem_flags are set, lets try to use less memory */
5017 if (kmem_debugging())
5018 arc_c = arc_c / 2;
5019 if (arc_c < arc_c_min)
5020 arc_c = arc_c_min;
5021
5022 arc_anon = &ARC_anon;
5023 arc_mru = &ARC_mru;
5024 arc_mru_ghost = &ARC_mru_ghost;
5025 arc_mfu = &ARC_mfu;
5026 arc_mfu_ghost = &ARC_mfu_ghost;
5027 arc_l2c_only = &ARC_l2c_only;
5028 arc_size = 0;
5029
5030 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
5031 sizeof (arc_buf_hdr_t),
5032 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5033 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5034 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
5035 sizeof (arc_buf_hdr_t),
5036 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5037 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5038 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
5039 sizeof (arc_buf_hdr_t),
5040 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5041 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5042 multilist_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
5043 sizeof (arc_buf_hdr_t),
5044 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5045 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5046 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
5047 sizeof (arc_buf_hdr_t),
5048 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5049 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5050 multilist_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
5051 sizeof (arc_buf_hdr_t),
5052 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5053 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5054 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
5055 sizeof (arc_buf_hdr_t),
5056 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5057 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5058 multilist_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
5059 sizeof (arc_buf_hdr_t),
5060 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5061 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5062 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
5063 sizeof (arc_buf_hdr_t),
5064 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5065 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5066 multilist_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
5067 sizeof (arc_buf_hdr_t),
5068 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5069 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5070
5071 refcount_create(&arc_anon->arcs_size);
5072 refcount_create(&arc_mru->arcs_size);
5073 refcount_create(&arc_mru_ghost->arcs_size);
5074 refcount_create(&arc_mfu->arcs_size);
5075 refcount_create(&arc_mfu_ghost->arcs_size);
5076 refcount_create(&arc_l2c_only->arcs_size);
5077
5078 buf_init();
5079
5080 arc_reclaim_thread_exit = FALSE;
5081 arc_user_evicts_thread_exit = FALSE;
5082 arc_eviction_list = NULL;
5083 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
5084
5085 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
5086 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
5087
5088 if (arc_ksp != NULL) {
5089 arc_ksp->ks_data = &arc_stats;
5090 arc_ksp->ks_update = arc_kstat_update;
5091 kstat_install(arc_ksp);
5092 }
5093
5094 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
5095 TS_RUN, minclsyspri);
5096
5097 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0,
5098 TS_RUN, minclsyspri);
5099
5100 arc_dead = FALSE;
5101 arc_warm = B_FALSE;
5102
5103 /*
5104 * Calculate maximum amount of dirty data per pool.
5105 *
5106 * If it has been set by /etc/system, take that.
5107 * Otherwise, use a percentage of physical memory defined by
5108 * zfs_dirty_data_max_percent (default 10%) with a cap at
5109 * zfs_dirty_data_max_max (default 4GB).
5110 */
5111 if (zfs_dirty_data_max == 0) {
5112 zfs_dirty_data_max = physmem * PAGESIZE *
5113 zfs_dirty_data_max_percent / 100;
5114 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
5115 zfs_dirty_data_max_max);
5116 }
5117 }
5118
5119 void
5120 arc_fini(void)
5121 {
5122 mutex_enter(&arc_reclaim_lock);
5123 arc_reclaim_thread_exit = TRUE;
5124 /*
5125 * The reclaim thread will set arc_reclaim_thread_exit back to
5126 * FALSE when it is finished exiting; we're waiting for that.
5127 */
5128 while (arc_reclaim_thread_exit) {
5129 cv_signal(&arc_reclaim_thread_cv);
5130 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
5131 }
5132 mutex_exit(&arc_reclaim_lock);
5133
5134 mutex_enter(&arc_user_evicts_lock);
5135 arc_user_evicts_thread_exit = TRUE;
5136 /*
5137 * The user evicts thread will set arc_user_evicts_thread_exit
5138 * to FALSE when it is finished exiting; we're waiting for that.
5139 */
5140 while (arc_user_evicts_thread_exit) {
5141 cv_signal(&arc_user_evicts_cv);
5142 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock);
5143 }
5144 mutex_exit(&arc_user_evicts_lock);
5145
5146 /* Use TRUE to ensure *all* buffers are evicted */
5147 arc_flush(NULL, TRUE);
5148
5149 arc_dead = TRUE;
5150
5151 if (arc_ksp != NULL) {
5152 kstat_delete(arc_ksp);
5153 arc_ksp = NULL;
5154 }
5155
5156 mutex_destroy(&arc_reclaim_lock);
5157 cv_destroy(&arc_reclaim_thread_cv);
5158 cv_destroy(&arc_reclaim_waiters_cv);
5159
5160 mutex_destroy(&arc_user_evicts_lock);
5161 cv_destroy(&arc_user_evicts_cv);
5162
5163 refcount_destroy(&arc_anon->arcs_size);
5164 refcount_destroy(&arc_mru->arcs_size);
5165 refcount_destroy(&arc_mru_ghost->arcs_size);
5166 refcount_destroy(&arc_mfu->arcs_size);
5167 refcount_destroy(&arc_mfu_ghost->arcs_size);
5168 refcount_destroy(&arc_l2c_only->arcs_size);
5169
5170 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
5171 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
5172 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
5173 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
5174 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
5175 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
5176 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
5177 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
5178
5179 buf_fini();
5180
5181 ASSERT0(arc_loaned_bytes);
5182 }
5183
5184 /*
5185 * Level 2 ARC
5186 *
5187 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
5188 * It uses dedicated storage devices to hold cached data, which are populated
5189 * using large infrequent writes. The main role of this cache is to boost
5190 * the performance of random read workloads. The intended L2ARC devices
5191 * include short-stroked disks, solid state disks, and other media with
5192 * substantially faster read latency than disk.
5193 *
5194 * +-----------------------+
5195 * | ARC |
5196 * +-----------------------+
5197 * | ^ ^
5198 * | | |
5199 * l2arc_feed_thread() arc_read()
5200 * | | |
5201 * | l2arc read |
5202 * V | |
5203 * +---------------+ |
5204 * | L2ARC | |
5205 * +---------------+ |
5206 * | ^ |
5207 * l2arc_write() | |
5208 * | | |
5209 * V | |
5210 * +-------+ +-------+
5211 * | vdev | | vdev |
5212 * | cache | | cache |
5213 * +-------+ +-------+
5214 * +=========+ .-----.
5215 * : L2ARC : |-_____-|
5216 * : devices : | Disks |
5217 * +=========+ `-_____-'
5218 *
5219 * Read requests are satisfied from the following sources, in order:
5220 *
5221 * 1) ARC
5222 * 2) vdev cache of L2ARC devices
5223 * 3) L2ARC devices
5224 * 4) vdev cache of disks
5225 * 5) disks
5226 *
5227 * Some L2ARC device types exhibit extremely slow write performance.
5228 * To accommodate for this there are some significant differences between
5229 * the L2ARC and traditional cache design:
5230 *
5231 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
5232 * the ARC behave as usual, freeing buffers and placing headers on ghost
5233 * lists. The ARC does not send buffers to the L2ARC during eviction as
5234 * this would add inflated write latencies for all ARC memory pressure.
5235 *
5236 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
5237 * It does this by periodically scanning buffers from the eviction-end of
5238 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
5239 * not already there. It scans until a headroom of buffers is satisfied,
5240 * which itself is a buffer for ARC eviction. If a compressible buffer is
5241 * found during scanning and selected for writing to an L2ARC device, we
5242 * temporarily boost scanning headroom during the next scan cycle to make
5243 * sure we adapt to compression effects (which might significantly reduce
5244 * the data volume we write to L2ARC). The thread that does this is
5245 * l2arc_feed_thread(), illustrated below; example sizes are included to
5246 * provide a better sense of ratio than this diagram:
5247 *
5248 * head --> tail
5249 * +---------------------+----------+
5250 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
5251 * +---------------------+----------+ | o L2ARC eligible
5252 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
5253 * +---------------------+----------+ |
5254 * 15.9 Gbytes ^ 32 Mbytes |
5255 * headroom |
5256 * l2arc_feed_thread()
5257 * |
5258 * l2arc write hand <--[oooo]--'
5259 * | 8 Mbyte
5260 * | write max
5261 * V
5262 * +==============================+
5263 * L2ARC dev |####|#|###|###| |####| ... |
5264 * +==============================+
5265 * 32 Gbytes
5266 *
5267 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
5268 * evicted, then the L2ARC has cached a buffer much sooner than it probably
5269 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
5270 * safe to say that this is an uncommon case, since buffers at the end of
5271 * the ARC lists have moved there due to inactivity.
5272 *
5273 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
5274 * then the L2ARC simply misses copying some buffers. This serves as a
5275 * pressure valve to prevent heavy read workloads from both stalling the ARC
5276 * with waits and clogging the L2ARC with writes. This also helps prevent
5277 * the potential for the L2ARC to churn if it attempts to cache content too
5278 * quickly, such as during backups of the entire pool.
5279 *
5280 * 5. After system boot and before the ARC has filled main memory, there are
5281 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
5282 * lists can remain mostly static. Instead of searching from tail of these
5283 * lists as pictured, the l2arc_feed_thread() will search from the list heads
5284 * for eligible buffers, greatly increasing its chance of finding them.
5285 *
5286 * The L2ARC device write speed is also boosted during this time so that
5287 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
5288 * there are no L2ARC reads, and no fear of degrading read performance
5289 * through increased writes.
5290 *
5291 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
5292 * the vdev queue can aggregate them into larger and fewer writes. Each
5293 * device is written to in a rotor fashion, sweeping writes through
5294 * available space then repeating.
5295 *
5296 * 7. The L2ARC does not store dirty content. It never needs to flush
5297 * write buffers back to disk based storage.
5298 *
5299 * 8. If an ARC buffer is written (and dirtied) which also exists in the
5300 * L2ARC, the now stale L2ARC buffer is immediately dropped.
5301 *
5302 * The performance of the L2ARC can be tweaked by a number of tunables, which
5303 * may be necessary for different workloads:
5304 *
5305 * l2arc_write_max max write bytes per interval
5306 * l2arc_write_boost extra write bytes during device warmup
5307 * l2arc_noprefetch skip caching prefetched buffers
5308 * l2arc_headroom number of max device writes to precache
5309 * l2arc_headroom_boost when we find compressed buffers during ARC
5310 * scanning, we multiply headroom by this
5311 * percentage factor for the next scan cycle,
5312 * since more compressed buffers are likely to
5313 * be present
5314 * l2arc_feed_secs seconds between L2ARC writing
5315 *
5316 * Tunables may be removed or added as future performance improvements are
5317 * integrated, and also may become zpool properties.
5318 *
5319 * There are three key functions that control how the L2ARC warms up:
5320 *
5321 * l2arc_write_eligible() check if a buffer is eligible to cache
5322 * l2arc_write_size() calculate how much to write
5323 * l2arc_write_interval() calculate sleep delay between writes
5324 *
5325 * These three functions determine what to write, how much, and how quickly
5326 * to send writes.
5327 */
5328
5329 static boolean_t
5330 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
5331 {
5332 /*
5333 * A buffer is *not* eligible for the L2ARC if it:
5334 * 1. belongs to a different spa.
5335 * 2. is already cached on the L2ARC.
5336 * 3. has an I/O in progress (it may be an incomplete read).
5337 * 4. is flagged not eligible (zfs property).
5338 */
5339 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
5340 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
5341 return (B_FALSE);
5342
5343 return (B_TRUE);
5344 }
5345
5346 static uint64_t
5347 l2arc_write_size(void)
5348 {
5349 uint64_t size;
5350
5351 /*
5352 * Make sure our globals have meaningful values in case the user
5353 * altered them.
5354 */
5355 size = l2arc_write_max;
5356 if (size == 0) {
5357 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
5358 "be greater than zero, resetting it to the default (%d)",
5359 L2ARC_WRITE_SIZE);
5360 size = l2arc_write_max = L2ARC_WRITE_SIZE;
5361 }
5362
5363 if (arc_warm == B_FALSE)
5364 size += l2arc_write_boost;
5365
5366 return (size);
5367
5368 }
5369
5370 static clock_t
5371 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
5372 {
5373 clock_t interval, next, now;
5374
5375 /*
5376 * If the ARC lists are busy, increase our write rate; if the
5377 * lists are stale, idle back. This is achieved by checking
5378 * how much we previously wrote - if it was more than half of
5379 * what we wanted, schedule the next write much sooner.
5380 */
5381 if (l2arc_feed_again && wrote > (wanted / 2))
5382 interval = (hz * l2arc_feed_min_ms) / 1000;
5383 else
5384 interval = hz * l2arc_feed_secs;
5385
5386 now = ddi_get_lbolt();
5387 next = MAX(now, MIN(now + interval, began + interval));
5388
5389 return (next);
5390 }
5391
5392 /*
5393 * Cycle through L2ARC devices. This is how L2ARC load balances.
5394 * If a device is returned, this also returns holding the spa config lock.
5395 */
5396 static l2arc_dev_t *
5397 l2arc_dev_get_next(void)
5398 {
5399 l2arc_dev_t *first, *next = NULL;
5400
5401 /*
5402 * Lock out the removal of spas (spa_namespace_lock), then removal
5403 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
5404 * both locks will be dropped and a spa config lock held instead.
5405 */
5406 mutex_enter(&spa_namespace_lock);
5407 mutex_enter(&l2arc_dev_mtx);
5408
5409 /* if there are no vdevs, there is nothing to do */
5410 if (l2arc_ndev == 0)
5411 goto out;
5412
5413 first = NULL;
5414 next = l2arc_dev_last;
5415 do {
5416 /* loop around the list looking for a non-faulted vdev */
5417 if (next == NULL) {
5418 next = list_head(l2arc_dev_list);
5419 } else {
5420 next = list_next(l2arc_dev_list, next);
5421 if (next == NULL)
5422 next = list_head(l2arc_dev_list);
5423 }
5424
5425 /* if we have come back to the start, bail out */
5426 if (first == NULL)
5427 first = next;
5428 else if (next == first)
5429 break;
5430
5431 } while (vdev_is_dead(next->l2ad_vdev));
5432
5433 /* if we were unable to find any usable vdevs, return NULL */
5434 if (vdev_is_dead(next->l2ad_vdev))
5435 next = NULL;
5436
5437 l2arc_dev_last = next;
5438
5439 out:
5440 mutex_exit(&l2arc_dev_mtx);
5441
5442 /*
5443 * Grab the config lock to prevent the 'next' device from being
5444 * removed while we are writing to it.
5445 */
5446 if (next != NULL)
5447 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
5448 mutex_exit(&spa_namespace_lock);
5449
5450 return (next);
5451 }
5452
5453 /*
5454 * Free buffers that were tagged for destruction.
5455 */
5456 static void
5457 l2arc_do_free_on_write()
5458 {
5459 list_t *buflist;
5460 l2arc_data_free_t *df, *df_prev;
5461
5462 mutex_enter(&l2arc_free_on_write_mtx);
5463 buflist = l2arc_free_on_write;
5464
5465 for (df = list_tail(buflist); df; df = df_prev) {
5466 df_prev = list_prev(buflist, df);
5467 ASSERT(df->l2df_data != NULL);
5468 ASSERT(df->l2df_func != NULL);
5469 df->l2df_func(df->l2df_data, df->l2df_size);
5470 list_remove(buflist, df);
5471 kmem_free(df, sizeof (l2arc_data_free_t));
5472 }
5473
5474 mutex_exit(&l2arc_free_on_write_mtx);
5475 }
5476
5477 /*
5478 * A write to a cache device has completed. Update all headers to allow
5479 * reads from these buffers to begin.
5480 */
5481 static void
5482 l2arc_write_done(zio_t *zio)
5483 {
5484 l2arc_write_callback_t *cb;
5485 l2arc_dev_t *dev;
5486 list_t *buflist;
5487 arc_buf_hdr_t *head, *hdr, *hdr_prev;
5488 kmutex_t *hash_lock;
5489 int64_t bytes_dropped = 0;
5490
5491 cb = zio->io_private;
5492 ASSERT(cb != NULL);
5493 dev = cb->l2wcb_dev;
5494 ASSERT(dev != NULL);
5495 head = cb->l2wcb_head;
5496 ASSERT(head != NULL);
5497 buflist = &dev->l2ad_buflist;
5498 ASSERT(buflist != NULL);
5499 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
5500 l2arc_write_callback_t *, cb);
5501
5502 if (zio->io_error != 0)
5503 ARCSTAT_BUMP(arcstat_l2_writes_error);
5504
5505 /*
5506 * All writes completed, or an error was hit.
5507 */
5508 top:
5509 mutex_enter(&dev->l2ad_mtx);
5510 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
5511 hdr_prev = list_prev(buflist, hdr);
5512
5513 hash_lock = HDR_LOCK(hdr);
5514
5515 /*
5516 * We cannot use mutex_enter or else we can deadlock
5517 * with l2arc_write_buffers (due to swapping the order
5518 * the hash lock and l2ad_mtx are taken).
5519 */
5520 if (!mutex_tryenter(hash_lock)) {
5521 /*
5522 * Missed the hash lock. We must retry so we
5523 * don't leave the ARC_FLAG_L2_WRITING bit set.
5524 */
5525 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
5526
5527 /*
5528 * We don't want to rescan the headers we've
5529 * already marked as having been written out, so
5530 * we reinsert the head node so we can pick up
5531 * where we left off.
5532 */
5533 list_remove(buflist, head);
5534 list_insert_after(buflist, hdr, head);
5535
5536 mutex_exit(&dev->l2ad_mtx);
5537
5538 /*
5539 * We wait for the hash lock to become available
5540 * to try and prevent busy waiting, and increase
5541 * the chance we'll be able to acquire the lock
5542 * the next time around.
5543 */
5544 mutex_enter(hash_lock);
5545 mutex_exit(hash_lock);
5546 goto top;
5547 }
5548
5549 /*
5550 * We could not have been moved into the arc_l2c_only
5551 * state while in-flight due to our ARC_FLAG_L2_WRITING
5552 * bit being set. Let's just ensure that's being enforced.
5553 */
5554 ASSERT(HDR_HAS_L1HDR(hdr));
5555
5556 /*
5557 * We may have allocated a buffer for L2ARC compression,
5558 * we must release it to avoid leaking this data.
5559 */
5560 l2arc_release_cdata_buf(hdr);
5561
5562 if (zio->io_error != 0) {
5563 /*
5564 * Error - drop L2ARC entry.
5565 */
5566 list_remove(buflist, hdr);
5567 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
5568
5569 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize);
5570 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
5571
5572 bytes_dropped += hdr->b_l2hdr.b_asize;
5573 (void) refcount_remove_many(&dev->l2ad_alloc,
5574 hdr->b_l2hdr.b_asize, hdr);
5575 }
5576
5577 /*
5578 * Allow ARC to begin reads and ghost list evictions to
5579 * this L2ARC entry.
5580 */
5581 hdr->b_flags &= ~ARC_FLAG_L2_WRITING;
5582
5583 mutex_exit(hash_lock);
5584 }
5585
5586 atomic_inc_64(&l2arc_writes_done);
5587 list_remove(buflist, head);
5588 ASSERT(!HDR_HAS_L1HDR(head));
5589 kmem_cache_free(hdr_l2only_cache, head);
5590 mutex_exit(&dev->l2ad_mtx);
5591
5592 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
5593
5594 l2arc_do_free_on_write();
5595
5596 kmem_free(cb, sizeof (l2arc_write_callback_t));
5597 }
5598
5599 /*
5600 * A read to a cache device completed. Validate buffer contents before
5601 * handing over to the regular ARC routines.
5602 */
5603 static void
5604 l2arc_read_done(zio_t *zio)
5605 {
5606 l2arc_read_callback_t *cb;
5607 arc_buf_hdr_t *hdr;
5608 arc_buf_t *buf;
5609 kmutex_t *hash_lock;
5610 int equal;
5611
5612 ASSERT(zio->io_vd != NULL);
5613 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
5614
5615 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
5616
5617 cb = zio->io_private;
5618 ASSERT(cb != NULL);
5619 buf = cb->l2rcb_buf;
5620 ASSERT(buf != NULL);
5621
5622 hash_lock = HDR_LOCK(buf->b_hdr);
5623 mutex_enter(hash_lock);
5624 hdr = buf->b_hdr;
5625 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5626
5627 /*
5628 * If the buffer was compressed, decompress it first.
5629 */
5630 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
5631 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
5632 ASSERT(zio->io_data != NULL);
5633
5634 /*
5635 * Check this survived the L2ARC journey.
5636 */
5637 equal = arc_cksum_equal(buf);
5638 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
5639 mutex_exit(hash_lock);
5640 zio->io_private = buf;
5641 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
5642 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
5643 arc_read_done(zio);
5644 } else {
5645 mutex_exit(hash_lock);
5646 /*
5647 * Buffer didn't survive caching. Increment stats and
5648 * reissue to the original storage device.
5649 */
5650 if (zio->io_error != 0) {
5651 ARCSTAT_BUMP(arcstat_l2_io_error);
5652 } else {
5653 zio->io_error = SET_ERROR(EIO);
5654 }
5655 if (!equal)
5656 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
5657
5658 /*
5659 * If there's no waiter, issue an async i/o to the primary
5660 * storage now. If there *is* a waiter, the caller must
5661 * issue the i/o in a context where it's OK to block.
5662 */
5663 if (zio->io_waiter == NULL) {
5664 zio_t *pio = zio_unique_parent(zio);
5665
5666 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
5667
5668 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
5669 buf->b_data, zio->io_size, arc_read_done, buf,
5670 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
5671 }
5672 }
5673
5674 kmem_free(cb, sizeof (l2arc_read_callback_t));
5675 }
5676
5677 /*
5678 * This is the list priority from which the L2ARC will search for pages to
5679 * cache. This is used within loops (0..3) to cycle through lists in the
5680 * desired order. This order can have a significant effect on cache
5681 * performance.
5682 *
5683 * Currently the metadata lists are hit first, MFU then MRU, followed by
5684 * the data lists. This function returns a locked list, and also returns
5685 * the lock pointer.
5686 */
5687 static multilist_sublist_t *
5688 l2arc_sublist_lock(int list_num)
5689 {
5690 multilist_t *ml = NULL;
5691 unsigned int idx;
5692
5693 ASSERT(list_num >= 0 && list_num <= 3);
5694
5695 switch (list_num) {
5696 case 0:
5697 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
5698 break;
5699 case 1:
5700 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA];
5701 break;
5702 case 2:
5703 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA];
5704 break;
5705 case 3:
5706 ml = &arc_mru->arcs_list[ARC_BUFC_DATA];
5707 break;
5708 }
5709
5710 /*
5711 * Return a randomly-selected sublist. This is acceptable
5712 * because the caller feeds only a little bit of data for each
5713 * call (8MB). Subsequent calls will result in different
5714 * sublists being selected.
5715 */
5716 idx = multilist_get_random_index(ml);
5717 return (multilist_sublist_lock(ml, idx));
5718 }
5719
5720 /*
5721 * Evict buffers from the device write hand to the distance specified in
5722 * bytes. This distance may span populated buffers, it may span nothing.
5723 * This is clearing a region on the L2ARC device ready for writing.
5724 * If the 'all' boolean is set, every buffer is evicted.
5725 */
5726 static void
5727 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
5728 {
5729 list_t *buflist;
5730 arc_buf_hdr_t *hdr, *hdr_prev;
5731 kmutex_t *hash_lock;
5732 uint64_t taddr;
5733
5734 buflist = &dev->l2ad_buflist;
5735
5736 if (!all && dev->l2ad_first) {
5737 /*
5738 * This is the first sweep through the device. There is
5739 * nothing to evict.
5740 */
5741 return;
5742 }
5743
5744 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
5745 /*
5746 * When nearing the end of the device, evict to the end
5747 * before the device write hand jumps to the start.
5748 */
5749 taddr = dev->l2ad_end;
5750 } else {
5751 taddr = dev->l2ad_hand + distance;
5752 }
5753 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
5754 uint64_t, taddr, boolean_t, all);
5755
5756 top:
5757 mutex_enter(&dev->l2ad_mtx);
5758 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
5759 hdr_prev = list_prev(buflist, hdr);
5760
5761 hash_lock = HDR_LOCK(hdr);
5762
5763 /*
5764 * We cannot use mutex_enter or else we can deadlock
5765 * with l2arc_write_buffers (due to swapping the order
5766 * the hash lock and l2ad_mtx are taken).
5767 */
5768 if (!mutex_tryenter(hash_lock)) {
5769 /*
5770 * Missed the hash lock. Retry.
5771 */
5772 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
5773 mutex_exit(&dev->l2ad_mtx);
5774 mutex_enter(hash_lock);
5775 mutex_exit(hash_lock);
5776 goto top;
5777 }
5778
5779 if (HDR_L2_WRITE_HEAD(hdr)) {
5780 /*
5781 * We hit a write head node. Leave it for
5782 * l2arc_write_done().
5783 */
5784 list_remove(buflist, hdr);
5785 mutex_exit(hash_lock);
5786 continue;
5787 }
5788
5789 if (!all && HDR_HAS_L2HDR(hdr) &&
5790 (hdr->b_l2hdr.b_daddr > taddr ||
5791 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
5792 /*
5793 * We've evicted to the target address,
5794 * or the end of the device.
5795 */
5796 mutex_exit(hash_lock);
5797 break;
5798 }
5799
5800 ASSERT(HDR_HAS_L2HDR(hdr));
5801 if (!HDR_HAS_L1HDR(hdr)) {
5802 ASSERT(!HDR_L2_READING(hdr));
5803 /*
5804 * This doesn't exist in the ARC. Destroy.
5805 * arc_hdr_destroy() will call list_remove()
5806 * and decrement arcstat_l2_size.
5807 */
5808 arc_change_state(arc_anon, hdr, hash_lock);
5809 arc_hdr_destroy(hdr);
5810 } else {
5811 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
5812 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
5813 /*
5814 * Invalidate issued or about to be issued
5815 * reads, since we may be about to write
5816 * over this location.
5817 */
5818 if (HDR_L2_READING(hdr)) {
5819 ARCSTAT_BUMP(arcstat_l2_evict_reading);
5820 hdr->b_flags |= ARC_FLAG_L2_EVICTED;
5821 }
5822
5823 /* Ensure this header has finished being written */
5824 ASSERT(!HDR_L2_WRITING(hdr));
5825 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
5826
5827 arc_hdr_l2hdr_destroy(hdr);
5828 }
5829 mutex_exit(hash_lock);
5830 }
5831 mutex_exit(&dev->l2ad_mtx);
5832 }
5833
5834 /*
5835 * Find and write ARC buffers to the L2ARC device.
5836 *
5837 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
5838 * for reading until they have completed writing.
5839 * The headroom_boost is an in-out parameter used to maintain headroom boost
5840 * state between calls to this function.
5841 *
5842 * Returns the number of bytes actually written (which may be smaller than
5843 * the delta by which the device hand has changed due to alignment).
5844 */
5845 static uint64_t
5846 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
5847 boolean_t *headroom_boost)
5848 {
5849 arc_buf_hdr_t *hdr, *hdr_prev, *head;
5850 uint64_t write_asize, write_psize, write_sz, headroom,
5851 buf_compress_minsz;
5852 void *buf_data;
5853 boolean_t full;
5854 l2arc_write_callback_t *cb;
5855 zio_t *pio, *wzio;
5856 uint64_t guid = spa_load_guid(spa);
5857 const boolean_t do_headroom_boost = *headroom_boost;
5858
5859 ASSERT(dev->l2ad_vdev != NULL);
5860
5861 /* Lower the flag now, we might want to raise it again later. */
5862 *headroom_boost = B_FALSE;
5863
5864 pio = NULL;
5865 write_sz = write_asize = write_psize = 0;
5866 full = B_FALSE;
5867 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
5868 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD;
5869 head->b_flags |= ARC_FLAG_HAS_L2HDR;
5870
5871 /*
5872 * We will want to try to compress buffers that are at least 2x the
5873 * device sector size.
5874 */
5875 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
5876
5877 /*
5878 * Copy buffers for L2ARC writing.
5879 */
5880 for (int try = 0; try <= 3; try++) {
5881 multilist_sublist_t *mls = l2arc_sublist_lock(try);
5882 uint64_t passed_sz = 0;
5883
5884 /*
5885 * L2ARC fast warmup.
5886 *
5887 * Until the ARC is warm and starts to evict, read from the
5888 * head of the ARC lists rather than the tail.
5889 */
5890 if (arc_warm == B_FALSE)
5891 hdr = multilist_sublist_head(mls);
5892 else
5893 hdr = multilist_sublist_tail(mls);
5894
5895 headroom = target_sz * l2arc_headroom;
5896 if (do_headroom_boost)
5897 headroom = (headroom * l2arc_headroom_boost) / 100;
5898
5899 for (; hdr; hdr = hdr_prev) {
5900 kmutex_t *hash_lock;
5901 uint64_t buf_sz;
5902
5903 if (arc_warm == B_FALSE)
5904 hdr_prev = multilist_sublist_next(mls, hdr);
5905 else
5906 hdr_prev = multilist_sublist_prev(mls, hdr);
5907
5908 hash_lock = HDR_LOCK(hdr);
5909 if (!mutex_tryenter(hash_lock)) {
5910 /*
5911 * Skip this buffer rather than waiting.
5912 */
5913 continue;
5914 }
5915
5916 passed_sz += hdr->b_size;
5917 if (passed_sz > headroom) {
5918 /*
5919 * Searched too far.
5920 */
5921 mutex_exit(hash_lock);
5922 break;
5923 }
5924
5925 if (!l2arc_write_eligible(guid, hdr)) {
5926 mutex_exit(hash_lock);
5927 continue;
5928 }
5929
5930 if ((write_sz + hdr->b_size) > target_sz) {
5931 full = B_TRUE;
5932 mutex_exit(hash_lock);
5933 break;
5934 }
5935
5936 if (pio == NULL) {
5937 /*
5938 * Insert a dummy header on the buflist so
5939 * l2arc_write_done() can find where the
5940 * write buffers begin without searching.
5941 */
5942 mutex_enter(&dev->l2ad_mtx);
5943 list_insert_head(&dev->l2ad_buflist, head);
5944 mutex_exit(&dev->l2ad_mtx);
5945
5946 cb = kmem_alloc(
5947 sizeof (l2arc_write_callback_t), KM_SLEEP);
5948 cb->l2wcb_dev = dev;
5949 cb->l2wcb_head = head;
5950 pio = zio_root(spa, l2arc_write_done, cb,
5951 ZIO_FLAG_CANFAIL);
5952 }
5953
5954 /*
5955 * Create and add a new L2ARC header.
5956 */
5957 hdr->b_l2hdr.b_dev = dev;
5958 hdr->b_flags |= ARC_FLAG_L2_WRITING;
5959 /*
5960 * Temporarily stash the data buffer in b_tmp_cdata.
5961 * The subsequent write step will pick it up from
5962 * there. This is because can't access b_l1hdr.b_buf
5963 * without holding the hash_lock, which we in turn
5964 * can't access without holding the ARC list locks
5965 * (which we want to avoid during compression/writing).
5966 */
5967 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
5968 hdr->b_l2hdr.b_asize = hdr->b_size;
5969 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data;
5970
5971 /*
5972 * Explicitly set the b_daddr field to a known
5973 * value which means "invalid address". This
5974 * enables us to differentiate which stage of
5975 * l2arc_write_buffers() the particular header
5976 * is in (e.g. this loop, or the one below).
5977 * ARC_FLAG_L2_WRITING is not enough to make
5978 * this distinction, and we need to know in
5979 * order to do proper l2arc vdev accounting in
5980 * arc_release() and arc_hdr_destroy().
5981 *
5982 * Note, we can't use a new flag to distinguish
5983 * the two stages because we don't hold the
5984 * header's hash_lock below, in the second stage
5985 * of this function. Thus, we can't simply
5986 * change the b_flags field to denote that the
5987 * IO has been sent. We can change the b_daddr
5988 * field of the L2 portion, though, since we'll
5989 * be holding the l2ad_mtx; which is why we're
5990 * using it to denote the header's state change.
5991 */
5992 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET;
5993
5994 buf_sz = hdr->b_size;
5995 hdr->b_flags |= ARC_FLAG_HAS_L2HDR;
5996
5997 mutex_enter(&dev->l2ad_mtx);
5998 list_insert_head(&dev->l2ad_buflist, hdr);
5999 mutex_exit(&dev->l2ad_mtx);
6000
6001 /*
6002 * Compute and store the buffer cksum before
6003 * writing. On debug the cksum is verified first.
6004 */
6005 arc_cksum_verify(hdr->b_l1hdr.b_buf);
6006 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE);
6007
6008 mutex_exit(hash_lock);
6009
6010 write_sz += buf_sz;
6011 }
6012
6013 multilist_sublist_unlock(mls);
6014
6015 if (full == B_TRUE)
6016 break;
6017 }
6018
6019 /* No buffers selected for writing? */
6020 if (pio == NULL) {
6021 ASSERT0(write_sz);
6022 ASSERT(!HDR_HAS_L1HDR(head));
6023 kmem_cache_free(hdr_l2only_cache, head);
6024 return (0);
6025 }
6026
6027 mutex_enter(&dev->l2ad_mtx);
6028
6029 /*
6030 * Now start writing the buffers. We're starting at the write head
6031 * and work backwards, retracing the course of the buffer selector
6032 * loop above.
6033 */
6034 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr;
6035 hdr = list_prev(&dev->l2ad_buflist, hdr)) {
6036 uint64_t buf_sz;
6037
6038 /*
6039 * We rely on the L1 portion of the header below, so
6040 * it's invalid for this header to have been evicted out
6041 * of the ghost cache, prior to being written out. The
6042 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
6043 */
6044 ASSERT(HDR_HAS_L1HDR(hdr));
6045
6046 /*
6047 * We shouldn't need to lock the buffer here, since we flagged
6048 * it as ARC_FLAG_L2_WRITING in the previous step, but we must
6049 * take care to only access its L2 cache parameters. In
6050 * particular, hdr->l1hdr.b_buf may be invalid by now due to
6051 * ARC eviction.
6052 */
6053 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
6054
6055 if ((HDR_L2COMPRESS(hdr)) &&
6056 hdr->b_l2hdr.b_asize >= buf_compress_minsz) {
6057 if (l2arc_compress_buf(hdr)) {
6058 /*
6059 * If compression succeeded, enable headroom
6060 * boost on the next scan cycle.
6061 */
6062 *headroom_boost = B_TRUE;
6063 }
6064 }
6065
6066 /*
6067 * Pick up the buffer data we had previously stashed away
6068 * (and now potentially also compressed).
6069 */
6070 buf_data = hdr->b_l1hdr.b_tmp_cdata;
6071 buf_sz = hdr->b_l2hdr.b_asize;
6072
6073 /*
6074 * We need to do this regardless if buf_sz is zero or
6075 * not, otherwise, when this l2hdr is evicted we'll
6076 * remove a reference that was never added.
6077 */
6078 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr);
6079
6080 /* Compression may have squashed the buffer to zero length. */
6081 if (buf_sz != 0) {
6082 uint64_t buf_p_sz;
6083
6084 wzio = zio_write_phys(pio, dev->l2ad_vdev,
6085 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
6086 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
6087 ZIO_FLAG_CANFAIL, B_FALSE);
6088
6089 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
6090 zio_t *, wzio);
6091 (void) zio_nowait(wzio);
6092
6093 write_asize += buf_sz;
6094
6095 /*
6096 * Keep the clock hand suitably device-aligned.
6097 */
6098 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
6099 write_psize += buf_p_sz;
6100 dev->l2ad_hand += buf_p_sz;
6101 }
6102 }
6103
6104 mutex_exit(&dev->l2ad_mtx);
6105
6106 ASSERT3U(write_asize, <=, target_sz);
6107 ARCSTAT_BUMP(arcstat_l2_writes_sent);
6108 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
6109 ARCSTAT_INCR(arcstat_l2_size, write_sz);
6110 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
6111 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0);
6112
6113 /*
6114 * Bump device hand to the device start if it is approaching the end.
6115 * l2arc_evict() will already have evicted ahead for this case.
6116 */
6117 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
6118 dev->l2ad_hand = dev->l2ad_start;
6119 dev->l2ad_first = B_FALSE;
6120 }
6121
6122 dev->l2ad_writing = B_TRUE;
6123 (void) zio_wait(pio);
6124 dev->l2ad_writing = B_FALSE;
6125
6126 return (write_asize);
6127 }
6128
6129 /*
6130 * Compresses an L2ARC buffer.
6131 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its
6132 * size in l2hdr->b_asize. This routine tries to compress the data and
6133 * depending on the compression result there are three possible outcomes:
6134 * *) The buffer was incompressible. The original l2hdr contents were left
6135 * untouched and are ready for writing to an L2 device.
6136 * *) The buffer was all-zeros, so there is no need to write it to an L2
6137 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
6138 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
6139 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
6140 * data buffer which holds the compressed data to be written, and b_asize
6141 * tells us how much data there is. b_compress is set to the appropriate
6142 * compression algorithm. Once writing is done, invoke
6143 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
6144 *
6145 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
6146 * buffer was incompressible).
6147 */
6148 static boolean_t
6149 l2arc_compress_buf(arc_buf_hdr_t *hdr)
6150 {
6151 void *cdata;
6152 size_t csize, len, rounded;
6153 ASSERT(HDR_HAS_L2HDR(hdr));
6154 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
6155
6156 ASSERT(HDR_HAS_L1HDR(hdr));
6157 ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF);
6158 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
6159
6160 len = l2hdr->b_asize;
6161 cdata = zio_data_buf_alloc(len);
6162 ASSERT3P(cdata, !=, NULL);
6163 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata,
6164 cdata, l2hdr->b_asize);
6165
6166 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
6167 if (rounded > csize) {
6168 bzero((char *)cdata + csize, rounded - csize);
6169 csize = rounded;
6170 }
6171
6172 if (csize == 0) {
6173 /* zero block, indicate that there's nothing to write */
6174 zio_data_buf_free(cdata, len);
6175 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY);
6176 l2hdr->b_asize = 0;
6177 hdr->b_l1hdr.b_tmp_cdata = NULL;
6178 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
6179 return (B_TRUE);
6180 } else if (csize > 0 && csize < len) {
6181 /*
6182 * Compression succeeded, we'll keep the cdata around for
6183 * writing and release it afterwards.
6184 */
6185 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4);
6186 l2hdr->b_asize = csize;
6187 hdr->b_l1hdr.b_tmp_cdata = cdata;
6188 ARCSTAT_BUMP(arcstat_l2_compress_successes);
6189 return (B_TRUE);
6190 } else {
6191 /*
6192 * Compression failed, release the compressed buffer.
6193 * l2hdr will be left unmodified.
6194 */
6195 zio_data_buf_free(cdata, len);
6196 ARCSTAT_BUMP(arcstat_l2_compress_failures);
6197 return (B_FALSE);
6198 }
6199 }
6200
6201 /*
6202 * Decompresses a zio read back from an l2arc device. On success, the
6203 * underlying zio's io_data buffer is overwritten by the uncompressed
6204 * version. On decompression error (corrupt compressed stream), the
6205 * zio->io_error value is set to signal an I/O error.
6206 *
6207 * Please note that the compressed data stream is not checksummed, so
6208 * if the underlying device is experiencing data corruption, we may feed
6209 * corrupt data to the decompressor, so the decompressor needs to be
6210 * able to handle this situation (LZ4 does).
6211 */
6212 static void
6213 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
6214 {
6215 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
6216
6217 if (zio->io_error != 0) {
6218 /*
6219 * An io error has occured, just restore the original io
6220 * size in preparation for a main pool read.
6221 */
6222 zio->io_orig_size = zio->io_size = hdr->b_size;
6223 return;
6224 }
6225
6226 if (c == ZIO_COMPRESS_EMPTY) {
6227 /*
6228 * An empty buffer results in a null zio, which means we
6229 * need to fill its io_data after we're done restoring the
6230 * buffer's contents.
6231 */
6232 ASSERT(hdr->b_l1hdr.b_buf != NULL);
6233 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size);
6234 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data;
6235 } else {
6236 ASSERT(zio->io_data != NULL);
6237 /*
6238 * We copy the compressed data from the start of the arc buffer
6239 * (the zio_read will have pulled in only what we need, the
6240 * rest is garbage which we will overwrite at decompression)
6241 * and then decompress back to the ARC data buffer. This way we
6242 * can minimize copying by simply decompressing back over the
6243 * original compressed data (rather than decompressing to an
6244 * aux buffer and then copying back the uncompressed buffer,
6245 * which is likely to be much larger).
6246 */
6247 uint64_t csize;
6248 void *cdata;
6249
6250 csize = zio->io_size;
6251 cdata = zio_data_buf_alloc(csize);
6252 bcopy(zio->io_data, cdata, csize);
6253 if (zio_decompress_data(c, cdata, zio->io_data, csize,
6254 hdr->b_size) != 0)
6255 zio->io_error = EIO;
6256 zio_data_buf_free(cdata, csize);
6257 }
6258
6259 /* Restore the expected uncompressed IO size. */
6260 zio->io_orig_size = zio->io_size = hdr->b_size;
6261 }
6262
6263 /*
6264 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
6265 * This buffer serves as a temporary holder of compressed data while
6266 * the buffer entry is being written to an l2arc device. Once that is
6267 * done, we can dispose of it.
6268 */
6269 static void
6270 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr)
6271 {
6272 enum zio_compress comp = HDR_GET_COMPRESS(hdr);
6273
6274 ASSERT(HDR_HAS_L1HDR(hdr));
6275 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp));
6276
6277 if (comp == ZIO_COMPRESS_OFF) {
6278 /*
6279 * In this case, b_tmp_cdata points to the same buffer
6280 * as the arc_buf_t's b_data field. We don't want to
6281 * free it, since the arc_buf_t will handle that.
6282 */
6283 hdr->b_l1hdr.b_tmp_cdata = NULL;
6284 } else if (comp == ZIO_COMPRESS_EMPTY) {
6285 /*
6286 * In this case, b_tmp_cdata was compressed to an empty
6287 * buffer, thus there's nothing to free and b_tmp_cdata
6288 * should have been set to NULL in l2arc_write_buffers().
6289 */
6290 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
6291 } else {
6292 /*
6293 * If the data was compressed, then we've allocated a
6294 * temporary buffer for it, so now we need to release it.
6295 */
6296 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
6297 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata,
6298 hdr->b_size);
6299 hdr->b_l1hdr.b_tmp_cdata = NULL;
6300 }
6301
6302 }
6303
6304 /*
6305 * This thread feeds the L2ARC at regular intervals. This is the beating
6306 * heart of the L2ARC.
6307 */
6308 static void
6309 l2arc_feed_thread(void)
6310 {
6311 callb_cpr_t cpr;
6312 l2arc_dev_t *dev;
6313 spa_t *spa;
6314 uint64_t size, wrote;
6315 clock_t begin, next = ddi_get_lbolt();
6316 boolean_t headroom_boost = B_FALSE;
6317
6318 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
6319
6320 mutex_enter(&l2arc_feed_thr_lock);
6321
6322 while (l2arc_thread_exit == 0) {
6323 CALLB_CPR_SAFE_BEGIN(&cpr);
6324 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
6325 next);
6326 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
6327 next = ddi_get_lbolt() + hz;
6328
6329 /*
6330 * Quick check for L2ARC devices.
6331 */
6332 mutex_enter(&l2arc_dev_mtx);
6333 if (l2arc_ndev == 0) {
6334 mutex_exit(&l2arc_dev_mtx);
6335 continue;
6336 }
6337 mutex_exit(&l2arc_dev_mtx);
6338 begin = ddi_get_lbolt();
6339
6340 /*
6341 * This selects the next l2arc device to write to, and in
6342 * doing so the next spa to feed from: dev->l2ad_spa. This
6343 * will return NULL if there are now no l2arc devices or if
6344 * they are all faulted.
6345 *
6346 * If a device is returned, its spa's config lock is also
6347 * held to prevent device removal. l2arc_dev_get_next()
6348 * will grab and release l2arc_dev_mtx.
6349 */
6350 if ((dev = l2arc_dev_get_next()) == NULL)
6351 continue;
6352
6353 spa = dev->l2ad_spa;
6354 ASSERT(spa != NULL);
6355
6356 /*
6357 * If the pool is read-only then force the feed thread to
6358 * sleep a little longer.
6359 */
6360 if (!spa_writeable(spa)) {
6361 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
6362 spa_config_exit(spa, SCL_L2ARC, dev);
6363 continue;
6364 }
6365
6366 /*
6367 * Avoid contributing to memory pressure.
6368 */
6369 if (arc_reclaim_needed()) {
6370 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
6371 spa_config_exit(spa, SCL_L2ARC, dev);
6372 continue;
6373 }
6374
6375 ARCSTAT_BUMP(arcstat_l2_feeds);
6376
6377 size = l2arc_write_size();
6378
6379 /*
6380 * Evict L2ARC buffers that will be overwritten.
6381 */
6382 l2arc_evict(dev, size, B_FALSE);
6383
6384 /*
6385 * Write ARC buffers.
6386 */
6387 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
6388
6389 /*
6390 * Calculate interval between writes.
6391 */
6392 next = l2arc_write_interval(begin, size, wrote);
6393 spa_config_exit(spa, SCL_L2ARC, dev);
6394 }
6395
6396 l2arc_thread_exit = 0;
6397 cv_broadcast(&l2arc_feed_thr_cv);
6398 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
6399 thread_exit();
6400 }
6401
6402 boolean_t
6403 l2arc_vdev_present(vdev_t *vd)
6404 {
6405 l2arc_dev_t *dev;
6406
6407 mutex_enter(&l2arc_dev_mtx);
6408 for (dev = list_head(l2arc_dev_list); dev != NULL;
6409 dev = list_next(l2arc_dev_list, dev)) {
6410 if (dev->l2ad_vdev == vd)
6411 break;
6412 }
6413 mutex_exit(&l2arc_dev_mtx);
6414
6415 return (dev != NULL);
6416 }
6417
6418 /*
6419 * Add a vdev for use by the L2ARC. By this point the spa has already
6420 * validated the vdev and opened it.
6421 */
6422 void
6423 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
6424 {
6425 l2arc_dev_t *adddev;
6426
6427 ASSERT(!l2arc_vdev_present(vd));
6428
6429 /*
6430 * Create a new l2arc device entry.
6431 */
6432 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
6433 adddev->l2ad_spa = spa;
6434 adddev->l2ad_vdev = vd;
6435 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
6436 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
6437 adddev->l2ad_hand = adddev->l2ad_start;
6438 adddev->l2ad_first = B_TRUE;
6439 adddev->l2ad_writing = B_FALSE;
6440
6441 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
6442 /*
6443 * This is a list of all ARC buffers that are still valid on the
6444 * device.
6445 */
6446 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
6447 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
6448
6449 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
6450 refcount_create(&adddev->l2ad_alloc);
6451
6452 /*
6453 * Add device to global list
6454 */
6455 mutex_enter(&l2arc_dev_mtx);
6456 list_insert_head(l2arc_dev_list, adddev);
6457 atomic_inc_64(&l2arc_ndev);
6458 mutex_exit(&l2arc_dev_mtx);
6459 }
6460
6461 /*
6462 * Remove a vdev from the L2ARC.
6463 */
6464 void
6465 l2arc_remove_vdev(vdev_t *vd)
6466 {
6467 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
6468
6469 /*
6470 * Find the device by vdev
6471 */
6472 mutex_enter(&l2arc_dev_mtx);
6473 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
6474 nextdev = list_next(l2arc_dev_list, dev);
6475 if (vd == dev->l2ad_vdev) {
6476 remdev = dev;
6477 break;
6478 }
6479 }
6480 ASSERT(remdev != NULL);
6481
6482 /*
6483 * Remove device from global list
6484 */
6485 list_remove(l2arc_dev_list, remdev);
6486 l2arc_dev_last = NULL; /* may have been invalidated */
6487 atomic_dec_64(&l2arc_ndev);
6488 mutex_exit(&l2arc_dev_mtx);
6489
6490 /*
6491 * Clear all buflists and ARC references. L2ARC device flush.
6492 */
6493 l2arc_evict(remdev, 0, B_TRUE);
6494 list_destroy(&remdev->l2ad_buflist);
6495 mutex_destroy(&remdev->l2ad_mtx);
6496 refcount_destroy(&remdev->l2ad_alloc);
6497 kmem_free(remdev, sizeof (l2arc_dev_t));
6498 }
6499
6500 void
6501 l2arc_init(void)
6502 {
6503 l2arc_thread_exit = 0;
6504 l2arc_ndev = 0;
6505 l2arc_writes_sent = 0;
6506 l2arc_writes_done = 0;
6507
6508 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
6509 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
6510 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
6511 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
6512
6513 l2arc_dev_list = &L2ARC_dev_list;
6514 l2arc_free_on_write = &L2ARC_free_on_write;
6515 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
6516 offsetof(l2arc_dev_t, l2ad_node));
6517 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
6518 offsetof(l2arc_data_free_t, l2df_list_node));
6519 }
6520
6521 void
6522 l2arc_fini(void)
6523 {
6524 /*
6525 * This is called from dmu_fini(), which is called from spa_fini();
6526 * Because of this, we can assume that all l2arc devices have
6527 * already been removed when the pools themselves were removed.
6528 */
6529
6530 l2arc_do_free_on_write();
6531
6532 mutex_destroy(&l2arc_feed_thr_lock);
6533 cv_destroy(&l2arc_feed_thr_cv);
6534 mutex_destroy(&l2arc_dev_mtx);
6535 mutex_destroy(&l2arc_free_on_write_mtx);
6536
6537 list_destroy(l2arc_dev_list);
6538 list_destroy(l2arc_free_on_write);
6539 }
6540
6541 void
6542 l2arc_start(void)
6543 {
6544 if (!(spa_mode_global & FWRITE))
6545 return;
6546
6547 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
6548 TS_RUN, minclsyspri);
6549 }
6550
6551 void
6552 l2arc_stop(void)
6553 {
6554 if (!(spa_mode_global & FWRITE))
6555 return;
6556
6557 mutex_enter(&l2arc_feed_thr_lock);
6558 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
6559 l2arc_thread_exit = 1;
6560 while (l2arc_thread_exit != 0)
6561 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
6562 mutex_exit(&l2arc_feed_thr_lock);
6563 }