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 uint8_t b_compress;
748
749 list_node_t b_l2node;
750 } l2arc_buf_hdr_t;
751
752 struct arc_buf_hdr {
753 /* protected by hash lock */
754 dva_t b_dva;
755 uint64_t b_birth;
756 /*
757 * Even though this checksum is only set/verified when a buffer is in
758 * the L1 cache, it needs to be in the set of common fields because it
759 * must be preserved from the time before a buffer is written out to
760 * L2ARC until after it is read back in.
761 */
762 zio_cksum_t *b_freeze_cksum;
763
764 arc_buf_hdr_t *b_hash_next;
765 arc_flags_t b_flags;
766
767 /* immutable */
768 int32_t b_size;
769 uint64_t b_spa;
770
771 /* L2ARC fields. Undefined when not in L2ARC. */
772 l2arc_buf_hdr_t b_l2hdr;
773 /* L1ARC fields. Undefined when in l2arc_only state */
774 l1arc_buf_hdr_t b_l1hdr;
775 };
776
777 static arc_buf_t *arc_eviction_list;
778 static arc_buf_hdr_t arc_eviction_hdr;
779
780 #define GHOST_STATE(state) \
781 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
782 (state) == arc_l2c_only)
783
784 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
785 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
786 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
787 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
788 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FLAG_FREED_IN_READ)
789 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE)
790
791 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
792 #define HDR_L2COMPRESS(hdr) ((hdr)->b_flags & ARC_FLAG_L2COMPRESS)
793 #define HDR_L2_READING(hdr) \
794 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
795 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
796 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
797 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
798 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
799
800 #define HDR_ISTYPE_METADATA(hdr) \
801 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
802 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
803
804 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
805 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
806
807 /*
808 * Other sizes
809 */
810
811 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
812 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
813
814 /*
815 * Hash table routines
816 */
817
818 #define HT_LOCK_PAD 64
819
820 struct ht_lock {
821 kmutex_t ht_lock;
822 #ifdef _KERNEL
823 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
824 #endif
825 };
826
827 #define BUF_LOCKS 256
828 typedef struct buf_hash_table {
829 uint64_t ht_mask;
830 arc_buf_hdr_t **ht_table;
831 struct ht_lock ht_locks[BUF_LOCKS];
832 } buf_hash_table_t;
833
834 static buf_hash_table_t buf_hash_table;
835
836 #define BUF_HASH_INDEX(spa, dva, birth) \
837 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
838 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
839 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
840 #define HDR_LOCK(hdr) \
841 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
842
843 uint64_t zfs_crc64_table[256];
844
845 /*
846 * Level 2 ARC
847 */
848
849 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
850 #define L2ARC_HEADROOM 2 /* num of writes */
851 /*
852 * If we discover during ARC scan any buffers to be compressed, we boost
853 * our headroom for the next scanning cycle by this percentage multiple.
854 */
855 #define L2ARC_HEADROOM_BOOST 200
856 #define L2ARC_FEED_SECS 1 /* caching interval secs */
857 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
858
859 /*
860 * Used to distinguish headers that are being process by
861 * l2arc_write_buffers(), but have yet to be assigned to a l2arc disk
862 * address. This can happen when the header is added to the l2arc's list
863 * of buffers to write in the first stage of l2arc_write_buffers(), but
864 * has not yet been written out which happens in the second stage of
865 * l2arc_write_buffers().
866 */
867 #define L2ARC_ADDR_UNSET ((uint64_t)(-1))
868
869 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
870 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
871
872 /* L2ARC Performance Tunables */
873 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
874 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
875 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
876 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
877 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
878 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
879 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
880 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
881 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
882
883 /*
884 * L2ARC Internals
885 */
886 struct l2arc_dev {
887 vdev_t *l2ad_vdev; /* vdev */
888 spa_t *l2ad_spa; /* spa */
889 uint64_t l2ad_hand; /* next write location */
890 uint64_t l2ad_start; /* first addr on device */
891 uint64_t l2ad_end; /* last addr on device */
892 boolean_t l2ad_first; /* first sweep through */
893 boolean_t l2ad_writing; /* currently writing */
894 kmutex_t l2ad_mtx; /* lock for buffer list */
895 list_t l2ad_buflist; /* buffer list */
896 list_node_t l2ad_node; /* device list node */
897 refcount_t l2ad_alloc; /* allocated bytes */
898 };
899
900 static list_t L2ARC_dev_list; /* device list */
901 static list_t *l2arc_dev_list; /* device list pointer */
902 static kmutex_t l2arc_dev_mtx; /* device list mutex */
903 static l2arc_dev_t *l2arc_dev_last; /* last device used */
904 static list_t L2ARC_free_on_write; /* free after write buf list */
905 static list_t *l2arc_free_on_write; /* free after write list ptr */
906 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
907 static uint64_t l2arc_ndev; /* number of devices */
908
909 typedef struct l2arc_read_callback {
910 arc_buf_t *l2rcb_buf; /* read buffer */
911 spa_t *l2rcb_spa; /* spa */
912 blkptr_t l2rcb_bp; /* original blkptr */
913 zbookmark_phys_t l2rcb_zb; /* original bookmark */
914 int l2rcb_flags; /* original flags */
915 enum zio_compress l2rcb_compress; /* applied compress */
916 } l2arc_read_callback_t;
917
918 typedef struct l2arc_write_callback {
919 l2arc_dev_t *l2wcb_dev; /* device info */
920 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
921 } l2arc_write_callback_t;
922
923 typedef struct l2arc_data_free {
924 /* protected by l2arc_free_on_write_mtx */
925 void *l2df_data;
926 size_t l2df_size;
927 void (*l2df_func)(void *, size_t);
928 list_node_t l2df_list_node;
929 } l2arc_data_free_t;
930
931 static kmutex_t l2arc_feed_thr_lock;
932 static kcondvar_t l2arc_feed_thr_cv;
933 static uint8_t l2arc_thread_exit;
934
935 static void arc_get_data_buf(arc_buf_t *);
936 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
937 static boolean_t arc_is_overflowing();
938 static void arc_buf_watch(arc_buf_t *);
939
940 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
941 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
942
943 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
944 static void l2arc_read_done(zio_t *);
945
946 static boolean_t l2arc_compress_buf(arc_buf_hdr_t *);
947 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress);
948 static void l2arc_release_cdata_buf(arc_buf_hdr_t *);
949
950 static uint64_t
951 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
952 {
953 uint8_t *vdva = (uint8_t *)dva;
954 uint64_t crc = -1ULL;
955 int i;
956
957 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
958
959 for (i = 0; i < sizeof (dva_t); i++)
960 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
961
962 crc ^= (spa>>8) ^ birth;
963
964 return (crc);
965 }
966
967 #define BUF_EMPTY(buf) \
968 ((buf)->b_dva.dva_word[0] == 0 && \
969 (buf)->b_dva.dva_word[1] == 0)
970
971 #define BUF_EQUAL(spa, dva, birth, buf) \
972 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
973 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
974 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
975
976 static void
977 buf_discard_identity(arc_buf_hdr_t *hdr)
978 {
979 hdr->b_dva.dva_word[0] = 0;
980 hdr->b_dva.dva_word[1] = 0;
981 hdr->b_birth = 0;
982 }
983
984 static arc_buf_hdr_t *
985 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
986 {
987 const dva_t *dva = BP_IDENTITY(bp);
988 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
989 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
990 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
991 arc_buf_hdr_t *hdr;
992
993 mutex_enter(hash_lock);
994 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
995 hdr = hdr->b_hash_next) {
996 if (BUF_EQUAL(spa, dva, birth, hdr)) {
997 *lockp = hash_lock;
998 return (hdr);
999 }
1000 }
1001 mutex_exit(hash_lock);
1002 *lockp = NULL;
1003 return (NULL);
1004 }
1005
1006 /*
1007 * Insert an entry into the hash table. If there is already an element
1008 * equal to elem in the hash table, then the already existing element
1009 * will be returned and the new element will not be inserted.
1010 * Otherwise returns NULL.
1011 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1012 */
1013 static arc_buf_hdr_t *
1014 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1015 {
1016 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1017 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1018 arc_buf_hdr_t *fhdr;
1019 uint32_t i;
1020
1021 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1022 ASSERT(hdr->b_birth != 0);
1023 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1024
1025 if (lockp != NULL) {
1026 *lockp = hash_lock;
1027 mutex_enter(hash_lock);
1028 } else {
1029 ASSERT(MUTEX_HELD(hash_lock));
1030 }
1031
1032 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1033 fhdr = fhdr->b_hash_next, i++) {
1034 if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1035 return (fhdr);
1036 }
1037
1038 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1039 buf_hash_table.ht_table[idx] = hdr;
1040 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
1041
1042 /* collect some hash table performance data */
1043 if (i > 0) {
1044 ARCSTAT_BUMP(arcstat_hash_collisions);
1045 if (i == 1)
1046 ARCSTAT_BUMP(arcstat_hash_chains);
1047
1048 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1049 }
1050
1051 ARCSTAT_BUMP(arcstat_hash_elements);
1052 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1053
1054 return (NULL);
1055 }
1056
1057 static void
1058 buf_hash_remove(arc_buf_hdr_t *hdr)
1059 {
1060 arc_buf_hdr_t *fhdr, **hdrp;
1061 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1062
1063 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1064 ASSERT(HDR_IN_HASH_TABLE(hdr));
1065
1066 hdrp = &buf_hash_table.ht_table[idx];
1067 while ((fhdr = *hdrp) != hdr) {
1068 ASSERT(fhdr != NULL);
1069 hdrp = &fhdr->b_hash_next;
1070 }
1071 *hdrp = hdr->b_hash_next;
1072 hdr->b_hash_next = NULL;
1073 hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE;
1074
1075 /* collect some hash table performance data */
1076 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1077
1078 if (buf_hash_table.ht_table[idx] &&
1079 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1080 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1081 }
1082
1083 /*
1084 * Global data structures and functions for the buf kmem cache.
1085 */
1086 static kmem_cache_t *hdr_full_cache;
1087 static kmem_cache_t *hdr_l2only_cache;
1088 static kmem_cache_t *buf_cache;
1089
1090 static void
1091 buf_fini(void)
1092 {
1093 int i;
1094
1095 kmem_free(buf_hash_table.ht_table,
1096 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1097 for (i = 0; i < BUF_LOCKS; i++)
1098 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1099 kmem_cache_destroy(hdr_full_cache);
1100 kmem_cache_destroy(hdr_l2only_cache);
1101 kmem_cache_destroy(buf_cache);
1102 }
1103
1104 /*
1105 * Constructor callback - called when the cache is empty
1106 * and a new buf is requested.
1107 */
1108 /* ARGSUSED */
1109 static int
1110 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1111 {
1112 arc_buf_hdr_t *hdr = vbuf;
1113
1114 bzero(hdr, HDR_FULL_SIZE);
1115 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1116 refcount_create(&hdr->b_l1hdr.b_refcnt);
1117 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1118 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1119 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1120
1121 return (0);
1122 }
1123
1124 /* ARGSUSED */
1125 static int
1126 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1127 {
1128 arc_buf_hdr_t *hdr = vbuf;
1129
1130 bzero(hdr, HDR_L2ONLY_SIZE);
1131 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1132
1133 return (0);
1134 }
1135
1136 /* ARGSUSED */
1137 static int
1138 buf_cons(void *vbuf, void *unused, int kmflag)
1139 {
1140 arc_buf_t *buf = vbuf;
1141
1142 bzero(buf, sizeof (arc_buf_t));
1143 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1144 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1145
1146 return (0);
1147 }
1148
1149 /*
1150 * Destructor callback - called when a cached buf is
1151 * no longer required.
1152 */
1153 /* ARGSUSED */
1154 static void
1155 hdr_full_dest(void *vbuf, void *unused)
1156 {
1157 arc_buf_hdr_t *hdr = vbuf;
1158
1159 ASSERT(BUF_EMPTY(hdr));
1160 cv_destroy(&hdr->b_l1hdr.b_cv);
1161 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1162 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1163 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1164 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1165 }
1166
1167 /* ARGSUSED */
1168 static void
1169 hdr_l2only_dest(void *vbuf, void *unused)
1170 {
1171 arc_buf_hdr_t *hdr = vbuf;
1172
1173 ASSERT(BUF_EMPTY(hdr));
1174 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1175 }
1176
1177 /* ARGSUSED */
1178 static void
1179 buf_dest(void *vbuf, void *unused)
1180 {
1181 arc_buf_t *buf = vbuf;
1182
1183 mutex_destroy(&buf->b_evict_lock);
1184 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1185 }
1186
1187 /*
1188 * Reclaim callback -- invoked when memory is low.
1189 */
1190 /* ARGSUSED */
1191 static void
1192 hdr_recl(void *unused)
1193 {
1194 dprintf("hdr_recl called\n");
1195 /*
1196 * umem calls the reclaim func when we destroy the buf cache,
1197 * which is after we do arc_fini().
1198 */
1199 if (!arc_dead)
1200 cv_signal(&arc_reclaim_thread_cv);
1201 }
1202
1203 static void
1204 buf_init(void)
1205 {
1206 uint64_t *ct;
1207 uint64_t hsize = 1ULL << 12;
1208 int i, j;
1209
1210 /*
1211 * The hash table is big enough to fill all of physical memory
1212 * with an average block size of zfs_arc_average_blocksize (default 8K).
1213 * By default, the table will take up
1214 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1215 */
1216 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1217 hsize <<= 1;
1218 retry:
1219 buf_hash_table.ht_mask = hsize - 1;
1220 buf_hash_table.ht_table =
1221 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1222 if (buf_hash_table.ht_table == NULL) {
1223 ASSERT(hsize > (1ULL << 8));
1224 hsize >>= 1;
1225 goto retry;
1226 }
1227
1228 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1229 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1230 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1231 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1232 NULL, NULL, 0);
1233 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1234 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1235
1236 for (i = 0; i < 256; i++)
1237 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1238 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1239
1240 for (i = 0; i < BUF_LOCKS; i++) {
1241 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1242 NULL, MUTEX_DEFAULT, NULL);
1243 }
1244 }
1245
1246 /*
1247 * Transition between the two allocation states for the arc_buf_hdr struct.
1248 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
1249 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
1250 * version is used when a cache buffer is only in the L2ARC in order to reduce
1251 * memory usage.
1252 */
1253 static arc_buf_hdr_t *
1254 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
1255 {
1256 ASSERT(HDR_HAS_L2HDR(hdr));
1257
1258 arc_buf_hdr_t *nhdr;
1259 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
1260
1261 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
1262 (old == hdr_l2only_cache && new == hdr_full_cache));
1263
1264 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
1265
1266 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
1267 buf_hash_remove(hdr);
1268
1269 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
1270
1271 if (new == hdr_full_cache) {
1272 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
1273 /*
1274 * arc_access and arc_change_state need to be aware that a
1275 * header has just come out of L2ARC, so we set its state to
1276 * l2c_only even though it's about to change.
1277 */
1278 nhdr->b_l1hdr.b_state = arc_l2c_only;
1279
1280 /* Verify previous threads set to NULL before freeing */
1281 ASSERT3P(nhdr->b_l1hdr.b_tmp_cdata, ==, NULL);
1282 } else {
1283 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1284 ASSERT0(hdr->b_l1hdr.b_datacnt);
1285
1286 /*
1287 * If we've reached here, We must have been called from
1288 * arc_evict_hdr(), as such we should have already been
1289 * removed from any ghost list we were previously on
1290 * (which protects us from racing with arc_evict_state),
1291 * thus no locking is needed during this check.
1292 */
1293 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1294
1295 /*
1296 * A buffer must not be moved into the arc_l2c_only
1297 * state if it's not finished being written out to the
1298 * l2arc device. Otherwise, the b_l1hdr.b_tmp_cdata field
1299 * might try to be accessed, even though it was removed.
1300 */
1301 VERIFY(!HDR_L2_WRITING(hdr));
1302 VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
1303
1304 #ifdef ZFS_DEBUG
1305 if (hdr->b_l1hdr.b_thawed != NULL)
1306 kmem_free(hdr->b_l1hdr.b_thawed, 1);
1307 hdr->b_l1hdr.b_thawed = NULL;
1308 #endif
1309
1310 nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR;
1311 }
1312 /*
1313 * The header has been reallocated so we need to re-insert it into any
1314 * lists it was on.
1315 */
1316 (void) buf_hash_insert(nhdr, NULL);
1317
1318 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
1319
1320 mutex_enter(&dev->l2ad_mtx);
1321
1322 /*
1323 * We must place the realloc'ed header back into the list at
1324 * the same spot. Otherwise, if it's placed earlier in the list,
1325 * l2arc_write_buffers() could find it during the function's
1326 * write phase, and try to write it out to the l2arc.
1327 */
1328 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
1329 list_remove(&dev->l2ad_buflist, hdr);
1330
1331 mutex_exit(&dev->l2ad_mtx);
1332
1333 /*
1334 * Since we're using the pointer address as the tag when
1335 * incrementing and decrementing the l2ad_alloc refcount, we
1336 * must remove the old pointer (that we're about to destroy) and
1337 * add the new pointer to the refcount. Otherwise we'd remove
1338 * the wrong pointer address when calling arc_hdr_destroy() later.
1339 */
1340
1341 (void) refcount_remove_many(&dev->l2ad_alloc,
1342 hdr->b_l2hdr.b_asize, hdr);
1343
1344 (void) refcount_add_many(&dev->l2ad_alloc,
1345 nhdr->b_l2hdr.b_asize, nhdr);
1346
1347 buf_discard_identity(hdr);
1348 hdr->b_freeze_cksum = NULL;
1349 kmem_cache_free(old, hdr);
1350
1351 return (nhdr);
1352 }
1353
1354
1355 #define ARC_MINTIME (hz>>4) /* 62 ms */
1356
1357 static void
1358 arc_cksum_verify(arc_buf_t *buf)
1359 {
1360 zio_cksum_t zc;
1361
1362 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1363 return;
1364
1365 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1366 if (buf->b_hdr->b_freeze_cksum == NULL || HDR_IO_ERROR(buf->b_hdr)) {
1367 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1368 return;
1369 }
1370 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1371 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
1372 panic("buffer modified while frozen!");
1373 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1374 }
1375
1376 static int
1377 arc_cksum_equal(arc_buf_t *buf)
1378 {
1379 zio_cksum_t zc;
1380 int equal;
1381
1382 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1383 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
1384 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
1385 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1386
1387 return (equal);
1388 }
1389
1390 static void
1391 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
1392 {
1393 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
1394 return;
1395
1396 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1397 if (buf->b_hdr->b_freeze_cksum != NULL) {
1398 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1399 return;
1400 }
1401 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
1402 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
1403 buf->b_hdr->b_freeze_cksum);
1404 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1405 arc_buf_watch(buf);
1406 }
1407
1408 #ifndef _KERNEL
1409 typedef struct procctl {
1410 long cmd;
1411 prwatch_t prwatch;
1412 } procctl_t;
1413 #endif
1414
1415 /* ARGSUSED */
1416 static void
1417 arc_buf_unwatch(arc_buf_t *buf)
1418 {
1419 #ifndef _KERNEL
1420 if (arc_watch) {
1421 int result;
1422 procctl_t ctl;
1423 ctl.cmd = PCWATCH;
1424 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1425 ctl.prwatch.pr_size = 0;
1426 ctl.prwatch.pr_wflags = 0;
1427 result = write(arc_procfd, &ctl, sizeof (ctl));
1428 ASSERT3U(result, ==, sizeof (ctl));
1429 }
1430 #endif
1431 }
1432
1433 /* ARGSUSED */
1434 static void
1435 arc_buf_watch(arc_buf_t *buf)
1436 {
1437 #ifndef _KERNEL
1438 if (arc_watch) {
1439 int result;
1440 procctl_t ctl;
1441 ctl.cmd = PCWATCH;
1442 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1443 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1444 ctl.prwatch.pr_wflags = WA_WRITE;
1445 result = write(arc_procfd, &ctl, sizeof (ctl));
1446 ASSERT3U(result, ==, sizeof (ctl));
1447 }
1448 #endif
1449 }
1450
1451 static arc_buf_contents_t
1452 arc_buf_type(arc_buf_hdr_t *hdr)
1453 {
1454 if (HDR_ISTYPE_METADATA(hdr)) {
1455 return (ARC_BUFC_METADATA);
1456 } else {
1457 return (ARC_BUFC_DATA);
1458 }
1459 }
1460
1461 static uint32_t
1462 arc_bufc_to_flags(arc_buf_contents_t type)
1463 {
1464 switch (type) {
1465 case ARC_BUFC_DATA:
1466 /* metadata field is 0 if buffer contains normal data */
1467 return (0);
1468 case ARC_BUFC_METADATA:
1469 return (ARC_FLAG_BUFC_METADATA);
1470 default:
1471 break;
1472 }
1473 panic("undefined ARC buffer type!");
1474 return ((uint32_t)-1);
1475 }
1476
1477 void
1478 arc_buf_thaw(arc_buf_t *buf)
1479 {
1480 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1481 if (buf->b_hdr->b_l1hdr.b_state != arc_anon)
1482 panic("modifying non-anon buffer!");
1483 if (HDR_IO_IN_PROGRESS(buf->b_hdr))
1484 panic("modifying buffer while i/o in progress!");
1485 arc_cksum_verify(buf);
1486 }
1487
1488 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1489 if (buf->b_hdr->b_freeze_cksum != NULL) {
1490 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1491 buf->b_hdr->b_freeze_cksum = NULL;
1492 }
1493
1494 #ifdef ZFS_DEBUG
1495 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1496 if (buf->b_hdr->b_l1hdr.b_thawed != NULL)
1497 kmem_free(buf->b_hdr->b_l1hdr.b_thawed, 1);
1498 buf->b_hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
1499 }
1500 #endif
1501
1502 mutex_exit(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1503
1504 arc_buf_unwatch(buf);
1505 }
1506
1507 void
1508 arc_buf_freeze(arc_buf_t *buf)
1509 {
1510 kmutex_t *hash_lock;
1511
1512 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1513 return;
1514
1515 hash_lock = HDR_LOCK(buf->b_hdr);
1516 mutex_enter(hash_lock);
1517
1518 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1519 buf->b_hdr->b_l1hdr.b_state == arc_anon);
1520 arc_cksum_compute(buf, B_FALSE);
1521 mutex_exit(hash_lock);
1522
1523 }
1524
1525 static void
1526 add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
1527 {
1528 ASSERT(HDR_HAS_L1HDR(hdr));
1529 ASSERT(MUTEX_HELD(hash_lock));
1530 arc_state_t *state = hdr->b_l1hdr.b_state;
1531
1532 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
1533 (state != arc_anon)) {
1534 /* We don't use the L2-only state list. */
1535 if (state != arc_l2c_only) {
1536 arc_buf_contents_t type = arc_buf_type(hdr);
1537 uint64_t delta = hdr->b_size * hdr->b_l1hdr.b_datacnt;
1538 multilist_t *list = &state->arcs_list[type];
1539 uint64_t *size = &state->arcs_lsize[type];
1540
1541 multilist_remove(list, hdr);
1542
1543 if (GHOST_STATE(state)) {
1544 ASSERT0(hdr->b_l1hdr.b_datacnt);
1545 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
1546 delta = hdr->b_size;
1547 }
1548 ASSERT(delta > 0);
1549 ASSERT3U(*size, >=, delta);
1550 atomic_add_64(size, -delta);
1551 }
1552 /* remove the prefetch flag if we get a reference */
1553 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
1554 }
1555 }
1556
1557 static int
1558 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
1559 {
1560 int cnt;
1561 arc_state_t *state = hdr->b_l1hdr.b_state;
1562
1563 ASSERT(HDR_HAS_L1HDR(hdr));
1564 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1565 ASSERT(!GHOST_STATE(state));
1566
1567 /*
1568 * arc_l2c_only counts as a ghost state so we don't need to explicitly
1569 * check to prevent usage of the arc_l2c_only list.
1570 */
1571 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
1572 (state != arc_anon)) {
1573 arc_buf_contents_t type = arc_buf_type(hdr);
1574 multilist_t *list = &state->arcs_list[type];
1575 uint64_t *size = &state->arcs_lsize[type];
1576
1577 multilist_insert(list, hdr);
1578
1579 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
1580 atomic_add_64(size, hdr->b_size *
1581 hdr->b_l1hdr.b_datacnt);
1582 }
1583 return (cnt);
1584 }
1585
1586 /*
1587 * Move the supplied buffer to the indicated state. The hash lock
1588 * for the buffer must be held by the caller.
1589 */
1590 static void
1591 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
1592 kmutex_t *hash_lock)
1593 {
1594 arc_state_t *old_state;
1595 int64_t refcnt;
1596 uint32_t datacnt;
1597 uint64_t from_delta, to_delta;
1598 arc_buf_contents_t buftype = arc_buf_type(hdr);
1599
1600 /*
1601 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
1602 * in arc_read() when bringing a buffer out of the L2ARC. However, the
1603 * L1 hdr doesn't always exist when we change state to arc_anon before
1604 * destroying a header, in which case reallocating to add the L1 hdr is
1605 * pointless.
1606 */
1607 if (HDR_HAS_L1HDR(hdr)) {
1608 old_state = hdr->b_l1hdr.b_state;
1609 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
1610 datacnt = hdr->b_l1hdr.b_datacnt;
1611 } else {
1612 old_state = arc_l2c_only;
1613 refcnt = 0;
1614 datacnt = 0;
1615 }
1616
1617 ASSERT(MUTEX_HELD(hash_lock));
1618 ASSERT3P(new_state, !=, old_state);
1619 ASSERT(refcnt == 0 || datacnt > 0);
1620 ASSERT(!GHOST_STATE(new_state) || datacnt == 0);
1621 ASSERT(old_state != arc_anon || datacnt <= 1);
1622
1623 from_delta = to_delta = datacnt * hdr->b_size;
1624
1625 /*
1626 * If this buffer is evictable, transfer it from the
1627 * old state list to the new state list.
1628 */
1629 if (refcnt == 0) {
1630 if (old_state != arc_anon && old_state != arc_l2c_only) {
1631 uint64_t *size = &old_state->arcs_lsize[buftype];
1632
1633 ASSERT(HDR_HAS_L1HDR(hdr));
1634 multilist_remove(&old_state->arcs_list[buftype], hdr);
1635
1636 /*
1637 * If prefetching out of the ghost cache,
1638 * we will have a non-zero datacnt.
1639 */
1640 if (GHOST_STATE(old_state) && datacnt == 0) {
1641 /* ghost elements have a ghost size */
1642 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1643 from_delta = hdr->b_size;
1644 }
1645 ASSERT3U(*size, >=, from_delta);
1646 atomic_add_64(size, -from_delta);
1647 }
1648 if (new_state != arc_anon && new_state != arc_l2c_only) {
1649 uint64_t *size = &new_state->arcs_lsize[buftype];
1650
1651 /*
1652 * An L1 header always exists here, since if we're
1653 * moving to some L1-cached state (i.e. not l2c_only or
1654 * anonymous), we realloc the header to add an L1hdr
1655 * beforehand.
1656 */
1657 ASSERT(HDR_HAS_L1HDR(hdr));
1658 multilist_insert(&new_state->arcs_list[buftype], hdr);
1659
1660 /* ghost elements have a ghost size */
1661 if (GHOST_STATE(new_state)) {
1662 ASSERT0(datacnt);
1663 ASSERT(hdr->b_l1hdr.b_buf == NULL);
1664 to_delta = hdr->b_size;
1665 }
1666 atomic_add_64(size, to_delta);
1667 }
1668 }
1669
1670 ASSERT(!BUF_EMPTY(hdr));
1671 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
1672 buf_hash_remove(hdr);
1673
1674 /* adjust state sizes (ignore arc_l2c_only) */
1675
1676 if (to_delta && new_state != arc_l2c_only) {
1677 ASSERT(HDR_HAS_L1HDR(hdr));
1678 if (GHOST_STATE(new_state)) {
1679 ASSERT0(datacnt);
1680
1681 /*
1682 * We moving a header to a ghost state, we first
1683 * remove all arc buffers. Thus, we'll have a
1684 * datacnt of zero, and no arc buffer to use for
1685 * the reference. As a result, we use the arc
1686 * header pointer for the reference.
1687 */
1688 (void) refcount_add_many(&new_state->arcs_size,
1689 hdr->b_size, hdr);
1690 } else {
1691 ASSERT3U(datacnt, !=, 0);
1692
1693 /*
1694 * Each individual buffer holds a unique reference,
1695 * thus we must remove each of these references one
1696 * at a time.
1697 */
1698 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
1699 buf = buf->b_next) {
1700 (void) refcount_add_many(&new_state->arcs_size,
1701 hdr->b_size, buf);
1702 }
1703 }
1704 }
1705
1706 if (from_delta && old_state != arc_l2c_only) {
1707 ASSERT(HDR_HAS_L1HDR(hdr));
1708 if (GHOST_STATE(old_state)) {
1709 /*
1710 * When moving a header off of a ghost state,
1711 * there's the possibility for datacnt to be
1712 * non-zero. This is because we first add the
1713 * arc buffer to the header prior to changing
1714 * the header's state. Since we used the header
1715 * for the reference when putting the header on
1716 * the ghost state, we must balance that and use
1717 * the header when removing off the ghost state
1718 * (even though datacnt is non zero).
1719 */
1720
1721 IMPLY(datacnt == 0, new_state == arc_anon ||
1722 new_state == arc_l2c_only);
1723
1724 (void) refcount_remove_many(&old_state->arcs_size,
1725 hdr->b_size, hdr);
1726 } else {
1727 ASSERT3P(datacnt, !=, 0);
1728
1729 /*
1730 * Each individual buffer holds a unique reference,
1731 * thus we must remove each of these references one
1732 * at a time.
1733 */
1734 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
1735 buf = buf->b_next) {
1736 (void) refcount_remove_many(
1737 &old_state->arcs_size, hdr->b_size, buf);
1738 }
1739 }
1740 }
1741
1742 if (HDR_HAS_L1HDR(hdr))
1743 hdr->b_l1hdr.b_state = new_state;
1744
1745 /*
1746 * L2 headers should never be on the L2 state list since they don't
1747 * have L1 headers allocated.
1748 */
1749 ASSERT(multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
1750 multilist_is_empty(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
1751 }
1752
1753 void
1754 arc_space_consume(uint64_t space, arc_space_type_t type)
1755 {
1756 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1757
1758 switch (type) {
1759 case ARC_SPACE_DATA:
1760 ARCSTAT_INCR(arcstat_data_size, space);
1761 break;
1762 case ARC_SPACE_META:
1763 ARCSTAT_INCR(arcstat_metadata_size, space);
1764 break;
1765 case ARC_SPACE_OTHER:
1766 ARCSTAT_INCR(arcstat_other_size, space);
1767 break;
1768 case ARC_SPACE_HDRS:
1769 ARCSTAT_INCR(arcstat_hdr_size, space);
1770 break;
1771 case ARC_SPACE_L2HDRS:
1772 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1773 break;
1774 }
1775
1776 if (type != ARC_SPACE_DATA)
1777 ARCSTAT_INCR(arcstat_meta_used, space);
1778
1779 atomic_add_64(&arc_size, space);
1780 }
1781
1782 void
1783 arc_space_return(uint64_t space, arc_space_type_t type)
1784 {
1785 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1786
1787 switch (type) {
1788 case ARC_SPACE_DATA:
1789 ARCSTAT_INCR(arcstat_data_size, -space);
1790 break;
1791 case ARC_SPACE_META:
1792 ARCSTAT_INCR(arcstat_metadata_size, -space);
1793 break;
1794 case ARC_SPACE_OTHER:
1795 ARCSTAT_INCR(arcstat_other_size, -space);
1796 break;
1797 case ARC_SPACE_HDRS:
1798 ARCSTAT_INCR(arcstat_hdr_size, -space);
1799 break;
1800 case ARC_SPACE_L2HDRS:
1801 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1802 break;
1803 }
1804
1805 if (type != ARC_SPACE_DATA) {
1806 ASSERT(arc_meta_used >= space);
1807 if (arc_meta_max < arc_meta_used)
1808 arc_meta_max = arc_meta_used;
1809 ARCSTAT_INCR(arcstat_meta_used, -space);
1810 }
1811
1812 ASSERT(arc_size >= space);
1813 atomic_add_64(&arc_size, -space);
1814 }
1815
1816 arc_buf_t *
1817 arc_buf_alloc(spa_t *spa, int32_t size, void *tag, arc_buf_contents_t type)
1818 {
1819 arc_buf_hdr_t *hdr;
1820 arc_buf_t *buf;
1821
1822 ASSERT3U(size, >, 0);
1823 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
1824 ASSERT(BUF_EMPTY(hdr));
1825 ASSERT3P(hdr->b_freeze_cksum, ==, NULL);
1826 hdr->b_size = size;
1827 hdr->b_spa = spa_load_guid(spa);
1828
1829 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1830 buf->b_hdr = hdr;
1831 buf->b_data = NULL;
1832 buf->b_efunc = NULL;
1833 buf->b_private = NULL;
1834 buf->b_next = NULL;
1835
1836 hdr->b_flags = arc_bufc_to_flags(type);
1837 hdr->b_flags |= ARC_FLAG_HAS_L1HDR;
1838
1839 hdr->b_l1hdr.b_buf = buf;
1840 hdr->b_l1hdr.b_state = arc_anon;
1841 hdr->b_l1hdr.b_arc_access = 0;
1842 hdr->b_l1hdr.b_datacnt = 1;
1843 hdr->b_l1hdr.b_tmp_cdata = NULL;
1844
1845 arc_get_data_buf(buf);
1846 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
1847 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
1848
1849 return (buf);
1850 }
1851
1852 static char *arc_onloan_tag = "onloan";
1853
1854 /*
1855 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1856 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1857 * buffers must be returned to the arc before they can be used by the DMU or
1858 * freed.
1859 */
1860 arc_buf_t *
1861 arc_loan_buf(spa_t *spa, int size)
1862 {
1863 arc_buf_t *buf;
1864
1865 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1866
1867 atomic_add_64(&arc_loaned_bytes, size);
1868 return (buf);
1869 }
1870
1871 /*
1872 * Return a loaned arc buffer to the arc.
1873 */
1874 void
1875 arc_return_buf(arc_buf_t *buf, void *tag)
1876 {
1877 arc_buf_hdr_t *hdr = buf->b_hdr;
1878
1879 ASSERT(buf->b_data != NULL);
1880 ASSERT(HDR_HAS_L1HDR(hdr));
1881 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
1882 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
1883
1884 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1885 }
1886
1887 /* Detach an arc_buf from a dbuf (tag) */
1888 void
1889 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1890 {
1891 arc_buf_hdr_t *hdr = buf->b_hdr;
1892
1893 ASSERT(buf->b_data != NULL);
1894 ASSERT(HDR_HAS_L1HDR(hdr));
1895 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
1896 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
1897 buf->b_efunc = NULL;
1898 buf->b_private = NULL;
1899
1900 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1901 }
1902
1903 static arc_buf_t *
1904 arc_buf_clone(arc_buf_t *from)
1905 {
1906 arc_buf_t *buf;
1907 arc_buf_hdr_t *hdr = from->b_hdr;
1908 uint64_t size = hdr->b_size;
1909
1910 ASSERT(HDR_HAS_L1HDR(hdr));
1911 ASSERT(hdr->b_l1hdr.b_state != arc_anon);
1912
1913 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1914 buf->b_hdr = hdr;
1915 buf->b_data = NULL;
1916 buf->b_efunc = NULL;
1917 buf->b_private = NULL;
1918 buf->b_next = hdr->b_l1hdr.b_buf;
1919 hdr->b_l1hdr.b_buf = buf;
1920 arc_get_data_buf(buf);
1921 bcopy(from->b_data, buf->b_data, size);
1922
1923 /*
1924 * This buffer already exists in the arc so create a duplicate
1925 * copy for the caller. If the buffer is associated with user data
1926 * then track the size and number of duplicates. These stats will be
1927 * updated as duplicate buffers are created and destroyed.
1928 */
1929 if (HDR_ISTYPE_DATA(hdr)) {
1930 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1931 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1932 }
1933 hdr->b_l1hdr.b_datacnt += 1;
1934 return (buf);
1935 }
1936
1937 void
1938 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1939 {
1940 arc_buf_hdr_t *hdr;
1941 kmutex_t *hash_lock;
1942
1943 /*
1944 * Check to see if this buffer is evicted. Callers
1945 * must verify b_data != NULL to know if the add_ref
1946 * was successful.
1947 */
1948 mutex_enter(&buf->b_evict_lock);
1949 if (buf->b_data == NULL) {
1950 mutex_exit(&buf->b_evict_lock);
1951 return;
1952 }
1953 hash_lock = HDR_LOCK(buf->b_hdr);
1954 mutex_enter(hash_lock);
1955 hdr = buf->b_hdr;
1956 ASSERT(HDR_HAS_L1HDR(hdr));
1957 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1958 mutex_exit(&buf->b_evict_lock);
1959
1960 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
1961 hdr->b_l1hdr.b_state == arc_mfu);
1962
1963 add_reference(hdr, hash_lock, tag);
1964 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1965 arc_access(hdr, hash_lock);
1966 mutex_exit(hash_lock);
1967 ARCSTAT_BUMP(arcstat_hits);
1968 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
1969 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
1970 data, metadata, hits);
1971 }
1972
1973 static void
1974 arc_buf_free_on_write(void *data, size_t size,
1975 void (*free_func)(void *, size_t))
1976 {
1977 l2arc_data_free_t *df;
1978
1979 df = kmem_alloc(sizeof (*df), KM_SLEEP);
1980 df->l2df_data = data;
1981 df->l2df_size = size;
1982 df->l2df_func = free_func;
1983 mutex_enter(&l2arc_free_on_write_mtx);
1984 list_insert_head(l2arc_free_on_write, df);
1985 mutex_exit(&l2arc_free_on_write_mtx);
1986 }
1987
1988 /*
1989 * Free the arc data buffer. If it is an l2arc write in progress,
1990 * the buffer is placed on l2arc_free_on_write to be freed later.
1991 */
1992 static void
1993 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1994 {
1995 arc_buf_hdr_t *hdr = buf->b_hdr;
1996
1997 if (HDR_L2_WRITING(hdr)) {
1998 arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
1999 ARCSTAT_BUMP(arcstat_l2_free_on_write);
2000 } else {
2001 free_func(buf->b_data, hdr->b_size);
2002 }
2003 }
2004
2005 static void
2006 arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
2007 {
2008 ASSERT(HDR_HAS_L2HDR(hdr));
2009 ASSERT(MUTEX_HELD(&hdr->b_l2hdr.b_dev->l2ad_mtx));
2010
2011 /*
2012 * The b_tmp_cdata field is linked off of the b_l1hdr, so if
2013 * that doesn't exist, the header is in the arc_l2c_only state,
2014 * and there isn't anything to free (it's already been freed).
2015 */
2016 if (!HDR_HAS_L1HDR(hdr))
2017 return;
2018
2019 /*
2020 * The header isn't being written to the l2arc device, thus it
2021 * shouldn't have a b_tmp_cdata to free.
2022 */
2023 if (!HDR_L2_WRITING(hdr)) {
2024 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
2025 return;
2026 }
2027
2028 /*
2029 * The header does not have compression enabled. This can be due
2030 * to the buffer not being compressible, or because we're
2031 * freeing the buffer before the second phase of
2032 * l2arc_write_buffer() has started (which does the compression
2033 * step). In either case, b_tmp_cdata does not point to a
2034 * separately compressed buffer, so there's nothing to free (it
2035 * points to the same buffer as the arc_buf_t's b_data field).
2036 */
2037 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) {
2038 hdr->b_l1hdr.b_tmp_cdata = NULL;
2039 return;
2040 }
2041
2042 /*
2043 * There's nothing to free since the buffer was all zero's and
2044 * compressed to a zero length buffer.
2045 */
2046 if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) {
2047 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
2048 return;
2049 }
2050
2051 ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress));
2052
2053 arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata,
2054 hdr->b_size, zio_data_buf_free);
2055
2056 ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
2057 hdr->b_l1hdr.b_tmp_cdata = NULL;
2058 }
2059
2060 /*
2061 * Free up buf->b_data and if 'remove' is set, then pull the
2062 * arc_buf_t off of the the arc_buf_hdr_t's list and free it.
2063 */
2064 static void
2065 arc_buf_destroy(arc_buf_t *buf, boolean_t remove)
2066 {
2067 arc_buf_t **bufp;
2068
2069 /* free up data associated with the buf */
2070 if (buf->b_data != NULL) {
2071 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
2072 uint64_t size = buf->b_hdr->b_size;
2073 arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
2074
2075 arc_cksum_verify(buf);
2076 arc_buf_unwatch(buf);
2077
2078 if (type == ARC_BUFC_METADATA) {
2079 arc_buf_data_free(buf, zio_buf_free);
2080 arc_space_return(size, ARC_SPACE_META);
2081 } else {
2082 ASSERT(type == ARC_BUFC_DATA);
2083 arc_buf_data_free(buf, zio_data_buf_free);
2084 arc_space_return(size, ARC_SPACE_DATA);
2085 }
2086
2087 /* protected by hash lock, if in the hash table */
2088 if (multilist_link_active(&buf->b_hdr->b_l1hdr.b_arc_node)) {
2089 uint64_t *cnt = &state->arcs_lsize[type];
2090
2091 ASSERT(refcount_is_zero(
2092 &buf->b_hdr->b_l1hdr.b_refcnt));
2093 ASSERT(state != arc_anon && state != arc_l2c_only);
2094
2095 ASSERT3U(*cnt, >=, size);
2096 atomic_add_64(cnt, -size);
2097 }
2098
2099 (void) refcount_remove_many(&state->arcs_size, size, buf);
2100 buf->b_data = NULL;
2101
2102 /*
2103 * If we're destroying a duplicate buffer make sure
2104 * that the appropriate statistics are updated.
2105 */
2106 if (buf->b_hdr->b_l1hdr.b_datacnt > 1 &&
2107 HDR_ISTYPE_DATA(buf->b_hdr)) {
2108 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
2109 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
2110 }
2111 ASSERT(buf->b_hdr->b_l1hdr.b_datacnt > 0);
2112 buf->b_hdr->b_l1hdr.b_datacnt -= 1;
2113 }
2114
2115 /* only remove the buf if requested */
2116 if (!remove)
2117 return;
2118
2119 /* remove the buf from the hdr list */
2120 for (bufp = &buf->b_hdr->b_l1hdr.b_buf; *bufp != buf;
2121 bufp = &(*bufp)->b_next)
2122 continue;
2123 *bufp = buf->b_next;
2124 buf->b_next = NULL;
2125
2126 ASSERT(buf->b_efunc == NULL);
2127
2128 /* clean up the buf */
2129 buf->b_hdr = NULL;
2130 kmem_cache_free(buf_cache, buf);
2131 }
2132
2133 static void
2134 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
2135 {
2136 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
2137 l2arc_dev_t *dev = l2hdr->b_dev;
2138
2139 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
2140 ASSERT(HDR_HAS_L2HDR(hdr));
2141
2142 list_remove(&dev->l2ad_buflist, hdr);
2143
2144 /*
2145 * We don't want to leak the b_tmp_cdata buffer that was
2146 * allocated in l2arc_write_buffers()
2147 */
2148 arc_buf_l2_cdata_free(hdr);
2149
2150 /*
2151 * If the l2hdr's b_daddr is equal to L2ARC_ADDR_UNSET, then
2152 * this header is being processed by l2arc_write_buffers() (i.e.
2153 * it's in the first stage of l2arc_write_buffers()).
2154 * Re-affirming that truth here, just to serve as a reminder. If
2155 * b_daddr does not equal L2ARC_ADDR_UNSET, then the header may or
2156 * may not have its HDR_L2_WRITING flag set. (the write may have
2157 * completed, in which case HDR_L2_WRITING will be false and the
2158 * b_daddr field will point to the address of the buffer on disk).
2159 */
2160 IMPLY(l2hdr->b_daddr == L2ARC_ADDR_UNSET, HDR_L2_WRITING(hdr));
2161
2162 /*
2163 * If b_daddr is equal to L2ARC_ADDR_UNSET, we're racing with
2164 * l2arc_write_buffers(). Since we've just removed this header
2165 * from the l2arc buffer list, this header will never reach the
2166 * second stage of l2arc_write_buffers(), which increments the
2167 * accounting stats for this header. Thus, we must be careful
2168 * not to decrement them for this header either.
2169 */
2170 if (l2hdr->b_daddr != L2ARC_ADDR_UNSET) {
2171 ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
2172 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
2173
2174 vdev_space_update(dev->l2ad_vdev,
2175 -l2hdr->b_asize, 0, 0);
2176
2177 (void) refcount_remove_many(&dev->l2ad_alloc,
2178 l2hdr->b_asize, hdr);
2179 }
2180
2181 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
2182 }
2183
2184 static void
2185 arc_hdr_destroy(arc_buf_hdr_t *hdr)
2186 {
2187 if (HDR_HAS_L1HDR(hdr)) {
2188 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
2189 hdr->b_l1hdr.b_datacnt > 0);
2190 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2191 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
2192 }
2193 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2194 ASSERT(!HDR_IN_HASH_TABLE(hdr));
2195
2196 if (HDR_HAS_L2HDR(hdr)) {
2197 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
2198 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
2199
2200 if (!buflist_held)
2201 mutex_enter(&dev->l2ad_mtx);
2202
2203 /*
2204 * Even though we checked this conditional above, we
2205 * need to check this again now that we have the
2206 * l2ad_mtx. This is because we could be racing with
2207 * another thread calling l2arc_evict() which might have
2208 * destroyed this header's L2 portion as we were waiting
2209 * to acquire the l2ad_mtx. If that happens, we don't
2210 * want to re-destroy the header's L2 portion.
2211 */
2212 if (HDR_HAS_L2HDR(hdr))
2213 arc_hdr_l2hdr_destroy(hdr);
2214
2215 if (!buflist_held)
2216 mutex_exit(&dev->l2ad_mtx);
2217 }
2218
2219 if (!BUF_EMPTY(hdr))
2220 buf_discard_identity(hdr);
2221
2222 if (hdr->b_freeze_cksum != NULL) {
2223 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
2224 hdr->b_freeze_cksum = NULL;
2225 }
2226
2227 if (HDR_HAS_L1HDR(hdr)) {
2228 while (hdr->b_l1hdr.b_buf) {
2229 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
2230
2231 if (buf->b_efunc != NULL) {
2232 mutex_enter(&arc_user_evicts_lock);
2233 mutex_enter(&buf->b_evict_lock);
2234 ASSERT(buf->b_hdr != NULL);
2235 arc_buf_destroy(hdr->b_l1hdr.b_buf, FALSE);
2236 hdr->b_l1hdr.b_buf = buf->b_next;
2237 buf->b_hdr = &arc_eviction_hdr;
2238 buf->b_next = arc_eviction_list;
2239 arc_eviction_list = buf;
2240 mutex_exit(&buf->b_evict_lock);
2241 cv_signal(&arc_user_evicts_cv);
2242 mutex_exit(&arc_user_evicts_lock);
2243 } else {
2244 arc_buf_destroy(hdr->b_l1hdr.b_buf, TRUE);
2245 }
2246 }
2247 #ifdef ZFS_DEBUG
2248 if (hdr->b_l1hdr.b_thawed != NULL) {
2249 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2250 hdr->b_l1hdr.b_thawed = NULL;
2251 }
2252 #endif
2253 }
2254
2255 ASSERT3P(hdr->b_hash_next, ==, NULL);
2256 if (HDR_HAS_L1HDR(hdr)) {
2257 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
2258 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
2259 kmem_cache_free(hdr_full_cache, hdr);
2260 } else {
2261 kmem_cache_free(hdr_l2only_cache, hdr);
2262 }
2263 }
2264
2265 void
2266 arc_buf_free(arc_buf_t *buf, void *tag)
2267 {
2268 arc_buf_hdr_t *hdr = buf->b_hdr;
2269 int hashed = hdr->b_l1hdr.b_state != arc_anon;
2270
2271 ASSERT(buf->b_efunc == NULL);
2272 ASSERT(buf->b_data != NULL);
2273
2274 if (hashed) {
2275 kmutex_t *hash_lock = HDR_LOCK(hdr);
2276
2277 mutex_enter(hash_lock);
2278 hdr = buf->b_hdr;
2279 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
2280
2281 (void) remove_reference(hdr, hash_lock, tag);
2282 if (hdr->b_l1hdr.b_datacnt > 1) {
2283 arc_buf_destroy(buf, TRUE);
2284 } else {
2285 ASSERT(buf == hdr->b_l1hdr.b_buf);
2286 ASSERT(buf->b_efunc == NULL);
2287 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
2288 }
2289 mutex_exit(hash_lock);
2290 } else if (HDR_IO_IN_PROGRESS(hdr)) {
2291 int destroy_hdr;
2292 /*
2293 * We are in the middle of an async write. Don't destroy
2294 * this buffer unless the write completes before we finish
2295 * decrementing the reference count.
2296 */
2297 mutex_enter(&arc_user_evicts_lock);
2298 (void) remove_reference(hdr, NULL, tag);
2299 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2300 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
2301 mutex_exit(&arc_user_evicts_lock);
2302 if (destroy_hdr)
2303 arc_hdr_destroy(hdr);
2304 } else {
2305 if (remove_reference(hdr, NULL, tag) > 0)
2306 arc_buf_destroy(buf, TRUE);
2307 else
2308 arc_hdr_destroy(hdr);
2309 }
2310 }
2311
2312 boolean_t
2313 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
2314 {
2315 arc_buf_hdr_t *hdr = buf->b_hdr;
2316 kmutex_t *hash_lock = HDR_LOCK(hdr);
2317 boolean_t no_callback = (buf->b_efunc == NULL);
2318
2319 if (hdr->b_l1hdr.b_state == arc_anon) {
2320 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
2321 arc_buf_free(buf, tag);
2322 return (no_callback);
2323 }
2324
2325 mutex_enter(hash_lock);
2326 hdr = buf->b_hdr;
2327 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
2328 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
2329 ASSERT(hdr->b_l1hdr.b_state != arc_anon);
2330 ASSERT(buf->b_data != NULL);
2331
2332 (void) remove_reference(hdr, hash_lock, tag);
2333 if (hdr->b_l1hdr.b_datacnt > 1) {
2334 if (no_callback)
2335 arc_buf_destroy(buf, TRUE);
2336 } else if (no_callback) {
2337 ASSERT(hdr->b_l1hdr.b_buf == buf && buf->b_next == NULL);
2338 ASSERT(buf->b_efunc == NULL);
2339 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
2340 }
2341 ASSERT(no_callback || hdr->b_l1hdr.b_datacnt > 1 ||
2342 refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2343 mutex_exit(hash_lock);
2344 return (no_callback);
2345 }
2346
2347 int32_t
2348 arc_buf_size(arc_buf_t *buf)
2349 {
2350 return (buf->b_hdr->b_size);
2351 }
2352
2353 /*
2354 * Called from the DMU to determine if the current buffer should be
2355 * evicted. In order to ensure proper locking, the eviction must be initiated
2356 * from the DMU. Return true if the buffer is associated with user data and
2357 * duplicate buffers still exist.
2358 */
2359 boolean_t
2360 arc_buf_eviction_needed(arc_buf_t *buf)
2361 {
2362 arc_buf_hdr_t *hdr;
2363 boolean_t evict_needed = B_FALSE;
2364
2365 if (zfs_disable_dup_eviction)
2366 return (B_FALSE);
2367
2368 mutex_enter(&buf->b_evict_lock);
2369 hdr = buf->b_hdr;
2370 if (hdr == NULL) {
2371 /*
2372 * We are in arc_do_user_evicts(); let that function
2373 * perform the eviction.
2374 */
2375 ASSERT(buf->b_data == NULL);
2376 mutex_exit(&buf->b_evict_lock);
2377 return (B_FALSE);
2378 } else if (buf->b_data == NULL) {
2379 /*
2380 * We have already been added to the arc eviction list;
2381 * recommend eviction.
2382 */
2383 ASSERT3P(hdr, ==, &arc_eviction_hdr);
2384 mutex_exit(&buf->b_evict_lock);
2385 return (B_TRUE);
2386 }
2387
2388 if (hdr->b_l1hdr.b_datacnt > 1 && HDR_ISTYPE_DATA(hdr))
2389 evict_needed = B_TRUE;
2390
2391 mutex_exit(&buf->b_evict_lock);
2392 return (evict_needed);
2393 }
2394
2395 /*
2396 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
2397 * state of the header is dependent on it's state prior to entering this
2398 * function. The following transitions are possible:
2399 *
2400 * - arc_mru -> arc_mru_ghost
2401 * - arc_mfu -> arc_mfu_ghost
2402 * - arc_mru_ghost -> arc_l2c_only
2403 * - arc_mru_ghost -> deleted
2404 * - arc_mfu_ghost -> arc_l2c_only
2405 * - arc_mfu_ghost -> deleted
2406 */
2407 static int64_t
2408 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
2409 {
2410 arc_state_t *evicted_state, *state;
2411 int64_t bytes_evicted = 0;
2412
2413 ASSERT(MUTEX_HELD(hash_lock));
2414 ASSERT(HDR_HAS_L1HDR(hdr));
2415
2416 state = hdr->b_l1hdr.b_state;
2417 if (GHOST_STATE(state)) {
2418 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2419 ASSERT(hdr->b_l1hdr.b_buf == NULL);
2420
2421 /*
2422 * l2arc_write_buffers() relies on a header's L1 portion
2423 * (i.e. it's b_tmp_cdata field) during it's write phase.
2424 * Thus, we cannot push a header onto the arc_l2c_only
2425 * state (removing it's L1 piece) until the header is
2426 * done being written to the l2arc.
2427 */
2428 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
2429 ARCSTAT_BUMP(arcstat_evict_l2_skip);
2430 return (bytes_evicted);
2431 }
2432
2433 ARCSTAT_BUMP(arcstat_deleted);
2434 bytes_evicted += hdr->b_size;
2435
2436 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
2437
2438 if (HDR_HAS_L2HDR(hdr)) {
2439 /*
2440 * This buffer is cached on the 2nd Level ARC;
2441 * don't destroy the header.
2442 */
2443 arc_change_state(arc_l2c_only, hdr, hash_lock);
2444 /*
2445 * dropping from L1+L2 cached to L2-only,
2446 * realloc to remove the L1 header.
2447 */
2448 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
2449 hdr_l2only_cache);
2450 } else {
2451 arc_change_state(arc_anon, hdr, hash_lock);
2452 arc_hdr_destroy(hdr);
2453 }
2454 return (bytes_evicted);
2455 }
2456
2457 ASSERT(state == arc_mru || state == arc_mfu);
2458 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
2459
2460 /* prefetch buffers have a minimum lifespan */
2461 if (HDR_IO_IN_PROGRESS(hdr) ||
2462 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
2463 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
2464 arc_min_prefetch_lifespan)) {
2465 ARCSTAT_BUMP(arcstat_evict_skip);
2466 return (bytes_evicted);
2467 }
2468
2469 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
2470 ASSERT3U(hdr->b_l1hdr.b_datacnt, >, 0);
2471 while (hdr->b_l1hdr.b_buf) {
2472 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
2473 if (!mutex_tryenter(&buf->b_evict_lock)) {
2474 ARCSTAT_BUMP(arcstat_mutex_miss);
2475 break;
2476 }
2477 if (buf->b_data != NULL)
2478 bytes_evicted += hdr->b_size;
2479 if (buf->b_efunc != NULL) {
2480 mutex_enter(&arc_user_evicts_lock);
2481 arc_buf_destroy(buf, FALSE);
2482 hdr->b_l1hdr.b_buf = buf->b_next;
2483 buf->b_hdr = &arc_eviction_hdr;
2484 buf->b_next = arc_eviction_list;
2485 arc_eviction_list = buf;
2486 cv_signal(&arc_user_evicts_cv);
2487 mutex_exit(&arc_user_evicts_lock);
2488 mutex_exit(&buf->b_evict_lock);
2489 } else {
2490 mutex_exit(&buf->b_evict_lock);
2491 arc_buf_destroy(buf, TRUE);
2492 }
2493 }
2494
2495 if (HDR_HAS_L2HDR(hdr)) {
2496 ARCSTAT_INCR(arcstat_evict_l2_cached, hdr->b_size);
2497 } else {
2498 if (l2arc_write_eligible(hdr->b_spa, hdr))
2499 ARCSTAT_INCR(arcstat_evict_l2_eligible, hdr->b_size);
2500 else
2501 ARCSTAT_INCR(arcstat_evict_l2_ineligible, hdr->b_size);
2502 }
2503
2504 if (hdr->b_l1hdr.b_datacnt == 0) {
2505 arc_change_state(evicted_state, hdr, hash_lock);
2506 ASSERT(HDR_IN_HASH_TABLE(hdr));
2507 hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
2508 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
2509 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
2510 }
2511
2512 return (bytes_evicted);
2513 }
2514
2515 static uint64_t
2516 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
2517 uint64_t spa, int64_t bytes)
2518 {
2519 multilist_sublist_t *mls;
2520 uint64_t bytes_evicted = 0;
2521 arc_buf_hdr_t *hdr;
2522 kmutex_t *hash_lock;
2523 int evict_count = 0;
2524
2525 ASSERT3P(marker, !=, NULL);
2526 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
2527
2528 mls = multilist_sublist_lock(ml, idx);
2529
2530 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
2531 hdr = multilist_sublist_prev(mls, marker)) {
2532 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
2533 (evict_count >= zfs_arc_evict_batch_limit))
2534 break;
2535
2536 /*
2537 * To keep our iteration location, move the marker
2538 * forward. Since we're not holding hdr's hash lock, we
2539 * must be very careful and not remove 'hdr' from the
2540 * sublist. Otherwise, other consumers might mistake the
2541 * 'hdr' as not being on a sublist when they call the
2542 * multilist_link_active() function (they all rely on
2543 * the hash lock protecting concurrent insertions and
2544 * removals). multilist_sublist_move_forward() was
2545 * specifically implemented to ensure this is the case
2546 * (only 'marker' will be removed and re-inserted).
2547 */
2548 multilist_sublist_move_forward(mls, marker);
2549
2550 /*
2551 * The only case where the b_spa field should ever be
2552 * zero, is the marker headers inserted by
2553 * arc_evict_state(). It's possible for multiple threads
2554 * to be calling arc_evict_state() concurrently (e.g.
2555 * dsl_pool_close() and zio_inject_fault()), so we must
2556 * skip any markers we see from these other threads.
2557 */
2558 if (hdr->b_spa == 0)
2559 continue;
2560
2561 /* we're only interested in evicting buffers of a certain spa */
2562 if (spa != 0 && hdr->b_spa != spa) {
2563 ARCSTAT_BUMP(arcstat_evict_skip);
2564 continue;
2565 }
2566
2567 hash_lock = HDR_LOCK(hdr);
2568
2569 /*
2570 * We aren't calling this function from any code path
2571 * that would already be holding a hash lock, so we're
2572 * asserting on this assumption to be defensive in case
2573 * this ever changes. Without this check, it would be
2574 * possible to incorrectly increment arcstat_mutex_miss
2575 * below (e.g. if the code changed such that we called
2576 * this function with a hash lock held).
2577 */
2578 ASSERT(!MUTEX_HELD(hash_lock));
2579
2580 if (mutex_tryenter(hash_lock)) {
2581 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
2582 mutex_exit(hash_lock);
2583
2584 bytes_evicted += evicted;
2585
2586 /*
2587 * If evicted is zero, arc_evict_hdr() must have
2588 * decided to skip this header, don't increment
2589 * evict_count in this case.
2590 */
2591 if (evicted != 0)
2592 evict_count++;
2593
2594 /*
2595 * If arc_size isn't overflowing, signal any
2596 * threads that might happen to be waiting.
2597 *
2598 * For each header evicted, we wake up a single
2599 * thread. If we used cv_broadcast, we could
2600 * wake up "too many" threads causing arc_size
2601 * to significantly overflow arc_c; since
2602 * arc_get_data_buf() doesn't check for overflow
2603 * when it's woken up (it doesn't because it's
2604 * possible for the ARC to be overflowing while
2605 * full of un-evictable buffers, and the
2606 * function should proceed in this case).
2607 *
2608 * If threads are left sleeping, due to not
2609 * using cv_broadcast, they will be woken up
2610 * just before arc_reclaim_thread() sleeps.
2611 */
2612 mutex_enter(&arc_reclaim_lock);
2613 if (!arc_is_overflowing())
2614 cv_signal(&arc_reclaim_waiters_cv);
2615 mutex_exit(&arc_reclaim_lock);
2616 } else {
2617 ARCSTAT_BUMP(arcstat_mutex_miss);
2618 }
2619 }
2620
2621 multilist_sublist_unlock(mls);
2622
2623 return (bytes_evicted);
2624 }
2625
2626 /*
2627 * Evict buffers from the given arc state, until we've removed the
2628 * specified number of bytes. Move the removed buffers to the
2629 * appropriate evict state.
2630 *
2631 * This function makes a "best effort". It skips over any buffers
2632 * it can't get a hash_lock on, and so, may not catch all candidates.
2633 * It may also return without evicting as much space as requested.
2634 *
2635 * If bytes is specified using the special value ARC_EVICT_ALL, this
2636 * will evict all available (i.e. unlocked and evictable) buffers from
2637 * the given arc state; which is used by arc_flush().
2638 */
2639 static uint64_t
2640 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
2641 arc_buf_contents_t type)
2642 {
2643 uint64_t total_evicted = 0;
2644 multilist_t *ml = &state->arcs_list[type];
2645 int num_sublists;
2646 arc_buf_hdr_t **markers;
2647
2648 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
2649
2650 num_sublists = multilist_get_num_sublists(ml);
2651
2652 /*
2653 * If we've tried to evict from each sublist, made some
2654 * progress, but still have not hit the target number of bytes
2655 * to evict, we want to keep trying. The markers allow us to
2656 * pick up where we left off for each individual sublist, rather
2657 * than starting from the tail each time.
2658 */
2659 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
2660 for (int i = 0; i < num_sublists; i++) {
2661 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
2662
2663 /*
2664 * A b_spa of 0 is used to indicate that this header is
2665 * a marker. This fact is used in arc_adjust_type() and
2666 * arc_evict_state_impl().
2667 */
2668 markers[i]->b_spa = 0;
2669
2670 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
2671 multilist_sublist_insert_tail(mls, markers[i]);
2672 multilist_sublist_unlock(mls);
2673 }
2674
2675 /*
2676 * While we haven't hit our target number of bytes to evict, or
2677 * we're evicting all available buffers.
2678 */
2679 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
2680 /*
2681 * Start eviction using a randomly selected sublist,
2682 * this is to try and evenly balance eviction across all
2683 * sublists. Always starting at the same sublist
2684 * (e.g. index 0) would cause evictions to favor certain
2685 * sublists over others.
2686 */
2687 int sublist_idx = multilist_get_random_index(ml);
2688 uint64_t scan_evicted = 0;
2689
2690 for (int i = 0; i < num_sublists; i++) {
2691 uint64_t bytes_remaining;
2692 uint64_t bytes_evicted;
2693
2694 if (bytes == ARC_EVICT_ALL)
2695 bytes_remaining = ARC_EVICT_ALL;
2696 else if (total_evicted < bytes)
2697 bytes_remaining = bytes - total_evicted;
2698 else
2699 break;
2700
2701 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
2702 markers[sublist_idx], spa, bytes_remaining);
2703
2704 scan_evicted += bytes_evicted;
2705 total_evicted += bytes_evicted;
2706
2707 /* we've reached the end, wrap to the beginning */
2708 if (++sublist_idx >= num_sublists)
2709 sublist_idx = 0;
2710 }
2711
2712 /*
2713 * If we didn't evict anything during this scan, we have
2714 * no reason to believe we'll evict more during another
2715 * scan, so break the loop.
2716 */
2717 if (scan_evicted == 0) {
2718 /* This isn't possible, let's make that obvious */
2719 ASSERT3S(bytes, !=, 0);
2720
2721 /*
2722 * When bytes is ARC_EVICT_ALL, the only way to
2723 * break the loop is when scan_evicted is zero.
2724 * In that case, we actually have evicted enough,
2725 * so we don't want to increment the kstat.
2726 */
2727 if (bytes != ARC_EVICT_ALL) {
2728 ASSERT3S(total_evicted, <, bytes);
2729 ARCSTAT_BUMP(arcstat_evict_not_enough);
2730 }
2731
2732 break;
2733 }
2734 }
2735
2736 for (int i = 0; i < num_sublists; i++) {
2737 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
2738 multilist_sublist_remove(mls, markers[i]);
2739 multilist_sublist_unlock(mls);
2740
2741 kmem_cache_free(hdr_full_cache, markers[i]);
2742 }
2743 kmem_free(markers, sizeof (*markers) * num_sublists);
2744
2745 return (total_evicted);
2746 }
2747
2748 /*
2749 * Flush all "evictable" data of the given type from the arc state
2750 * specified. This will not evict any "active" buffers (i.e. referenced).
2751 *
2752 * When 'retry' is set to FALSE, the function will make a single pass
2753 * over the state and evict any buffers that it can. Since it doesn't
2754 * continually retry the eviction, it might end up leaving some buffers
2755 * in the ARC due to lock misses.
2756 *
2757 * When 'retry' is set to TRUE, the function will continually retry the
2758 * eviction until *all* evictable buffers have been removed from the
2759 * state. As a result, if concurrent insertions into the state are
2760 * allowed (e.g. if the ARC isn't shutting down), this function might
2761 * wind up in an infinite loop, continually trying to evict buffers.
2762 */
2763 static uint64_t
2764 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
2765 boolean_t retry)
2766 {
2767 uint64_t evicted = 0;
2768
2769 while (state->arcs_lsize[type] != 0) {
2770 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
2771
2772 if (!retry)
2773 break;
2774 }
2775
2776 return (evicted);
2777 }
2778
2779 /*
2780 * Evict the specified number of bytes from the state specified,
2781 * restricting eviction to the spa and type given. This function
2782 * prevents us from trying to evict more from a state's list than
2783 * is "evictable", and to skip evicting altogether when passed a
2784 * negative value for "bytes". In contrast, arc_evict_state() will
2785 * evict everything it can, when passed a negative value for "bytes".
2786 */
2787 static uint64_t
2788 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
2789 arc_buf_contents_t type)
2790 {
2791 int64_t delta;
2792
2793 if (bytes > 0 && state->arcs_lsize[type] > 0) {
2794 delta = MIN(state->arcs_lsize[type], bytes);
2795 return (arc_evict_state(state, spa, delta, type));
2796 }
2797
2798 return (0);
2799 }
2800
2801 /*
2802 * Evict metadata buffers from the cache, such that arc_meta_used is
2803 * capped by the arc_meta_limit tunable.
2804 */
2805 static uint64_t
2806 arc_adjust_meta(void)
2807 {
2808 uint64_t total_evicted = 0;
2809 int64_t target;
2810
2811 /*
2812 * If we're over the meta limit, we want to evict enough
2813 * metadata to get back under the meta limit. We don't want to
2814 * evict so much that we drop the MRU below arc_p, though. If
2815 * we're over the meta limit more than we're over arc_p, we
2816 * evict some from the MRU here, and some from the MFU below.
2817 */
2818 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
2819 (int64_t)(refcount_count(&arc_anon->arcs_size) +
2820 refcount_count(&arc_mru->arcs_size) - arc_p));
2821
2822 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2823
2824 /*
2825 * Similar to the above, we want to evict enough bytes to get us
2826 * below the meta limit, but not so much as to drop us below the
2827 * space alloted to the MFU (which is defined as arc_c - arc_p).
2828 */
2829 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
2830 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
2831
2832 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
2833
2834 return (total_evicted);
2835 }
2836
2837 /*
2838 * Return the type of the oldest buffer in the given arc state
2839 *
2840 * This function will select a random sublist of type ARC_BUFC_DATA and
2841 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
2842 * is compared, and the type which contains the "older" buffer will be
2843 * returned.
2844 */
2845 static arc_buf_contents_t
2846 arc_adjust_type(arc_state_t *state)
2847 {
2848 multilist_t *data_ml = &state->arcs_list[ARC_BUFC_DATA];
2849 multilist_t *meta_ml = &state->arcs_list[ARC_BUFC_METADATA];
2850 int data_idx = multilist_get_random_index(data_ml);
2851 int meta_idx = multilist_get_random_index(meta_ml);
2852 multilist_sublist_t *data_mls;
2853 multilist_sublist_t *meta_mls;
2854 arc_buf_contents_t type;
2855 arc_buf_hdr_t *data_hdr;
2856 arc_buf_hdr_t *meta_hdr;
2857
2858 /*
2859 * We keep the sublist lock until we're finished, to prevent
2860 * the headers from being destroyed via arc_evict_state().
2861 */
2862 data_mls = multilist_sublist_lock(data_ml, data_idx);
2863 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
2864
2865 /*
2866 * These two loops are to ensure we skip any markers that
2867 * might be at the tail of the lists due to arc_evict_state().
2868 */
2869
2870 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
2871 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
2872 if (data_hdr->b_spa != 0)
2873 break;
2874 }
2875
2876 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
2877 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
2878 if (meta_hdr->b_spa != 0)
2879 break;
2880 }
2881
2882 if (data_hdr == NULL && meta_hdr == NULL) {
2883 type = ARC_BUFC_DATA;
2884 } else if (data_hdr == NULL) {
2885 ASSERT3P(meta_hdr, !=, NULL);
2886 type = ARC_BUFC_METADATA;
2887 } else if (meta_hdr == NULL) {
2888 ASSERT3P(data_hdr, !=, NULL);
2889 type = ARC_BUFC_DATA;
2890 } else {
2891 ASSERT3P(data_hdr, !=, NULL);
2892 ASSERT3P(meta_hdr, !=, NULL);
2893
2894 /* The headers can't be on the sublist without an L1 header */
2895 ASSERT(HDR_HAS_L1HDR(data_hdr));
2896 ASSERT(HDR_HAS_L1HDR(meta_hdr));
2897
2898 if (data_hdr->b_l1hdr.b_arc_access <
2899 meta_hdr->b_l1hdr.b_arc_access) {
2900 type = ARC_BUFC_DATA;
2901 } else {
2902 type = ARC_BUFC_METADATA;
2903 }
2904 }
2905
2906 multilist_sublist_unlock(meta_mls);
2907 multilist_sublist_unlock(data_mls);
2908
2909 return (type);
2910 }
2911
2912 /*
2913 * Evict buffers from the cache, such that arc_size is capped by arc_c.
2914 */
2915 static uint64_t
2916 arc_adjust(void)
2917 {
2918 uint64_t total_evicted = 0;
2919 uint64_t bytes;
2920 int64_t target;
2921
2922 /*
2923 * If we're over arc_meta_limit, we want to correct that before
2924 * potentially evicting data buffers below.
2925 */
2926 total_evicted += arc_adjust_meta();
2927
2928 /*
2929 * Adjust MRU size
2930 *
2931 * If we're over the target cache size, we want to evict enough
2932 * from the list to get back to our target size. We don't want
2933 * to evict too much from the MRU, such that it drops below
2934 * arc_p. So, if we're over our target cache size more than
2935 * the MRU is over arc_p, we'll evict enough to get back to
2936 * arc_p here, and then evict more from the MFU below.
2937 */
2938 target = MIN((int64_t)(arc_size - arc_c),
2939 (int64_t)(refcount_count(&arc_anon->arcs_size) +
2940 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
2941
2942 /*
2943 * If we're below arc_meta_min, always prefer to evict data.
2944 * Otherwise, try to satisfy the requested number of bytes to
2945 * evict from the type which contains older buffers; in an
2946 * effort to keep newer buffers in the cache regardless of their
2947 * type. If we cannot satisfy the number of bytes from this
2948 * type, spill over into the next type.
2949 */
2950 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
2951 arc_meta_used > arc_meta_min) {
2952 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2953 total_evicted += bytes;
2954
2955 /*
2956 * If we couldn't evict our target number of bytes from
2957 * metadata, we try to get the rest from data.
2958 */
2959 target -= bytes;
2960
2961 total_evicted +=
2962 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
2963 } else {
2964 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
2965 total_evicted += bytes;
2966
2967 /*
2968 * If we couldn't evict our target number of bytes from
2969 * data, we try to get the rest from metadata.
2970 */
2971 target -= bytes;
2972
2973 total_evicted +=
2974 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
2975 }
2976
2977 /*
2978 * Adjust MFU size
2979 *
2980 * Now that we've tried to evict enough from the MRU to get its
2981 * size back to arc_p, if we're still above the target cache
2982 * size, we evict the rest from the MFU.
2983 */
2984 target = arc_size - arc_c;
2985
2986 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
2987 arc_meta_used > arc_meta_min) {
2988 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
2989 total_evicted += bytes;
2990
2991 /*
2992 * If we couldn't evict our target number of bytes from
2993 * metadata, we try to get the rest from data.
2994 */
2995 target -= bytes;
2996
2997 total_evicted +=
2998 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
2999 } else {
3000 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
3001 total_evicted += bytes;
3002
3003 /*
3004 * If we couldn't evict our target number of bytes from
3005 * data, we try to get the rest from data.
3006 */
3007 target -= bytes;
3008
3009 total_evicted +=
3010 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3011 }
3012
3013 /*
3014 * Adjust ghost lists
3015 *
3016 * In addition to the above, the ARC also defines target values
3017 * for the ghost lists. The sum of the mru list and mru ghost
3018 * list should never exceed the target size of the cache, and
3019 * the sum of the mru list, mfu list, mru ghost list, and mfu
3020 * ghost list should never exceed twice the target size of the
3021 * cache. The following logic enforces these limits on the ghost
3022 * caches, and evicts from them as needed.
3023 */
3024 target = refcount_count(&arc_mru->arcs_size) +
3025 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
3026
3027 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
3028 total_evicted += bytes;
3029
3030 target -= bytes;
3031
3032 total_evicted +=
3033 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
3034
3035 /*
3036 * We assume the sum of the mru list and mfu list is less than
3037 * or equal to arc_c (we enforced this above), which means we
3038 * can use the simpler of the two equations below:
3039 *
3040 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
3041 * mru ghost + mfu ghost <= arc_c
3042 */
3043 target = refcount_count(&arc_mru_ghost->arcs_size) +
3044 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
3045
3046 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
3047 total_evicted += bytes;
3048
3049 target -= bytes;
3050
3051 total_evicted +=
3052 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
3053
3054 return (total_evicted);
3055 }
3056
3057 static void
3058 arc_do_user_evicts(void)
3059 {
3060 mutex_enter(&arc_user_evicts_lock);
3061 while (arc_eviction_list != NULL) {
3062 arc_buf_t *buf = arc_eviction_list;
3063 arc_eviction_list = buf->b_next;
3064 mutex_enter(&buf->b_evict_lock);
3065 buf->b_hdr = NULL;
3066 mutex_exit(&buf->b_evict_lock);
3067 mutex_exit(&arc_user_evicts_lock);
3068
3069 if (buf->b_efunc != NULL)
3070 VERIFY0(buf->b_efunc(buf->b_private));
3071
3072 buf->b_efunc = NULL;
3073 buf->b_private = NULL;
3074 kmem_cache_free(buf_cache, buf);
3075 mutex_enter(&arc_user_evicts_lock);
3076 }
3077 mutex_exit(&arc_user_evicts_lock);
3078 }
3079
3080 void
3081 arc_flush(spa_t *spa, boolean_t retry)
3082 {
3083 uint64_t guid = 0;
3084
3085 /*
3086 * If retry is TRUE, a spa must not be specified since we have
3087 * no good way to determine if all of a spa's buffers have been
3088 * evicted from an arc state.
3089 */
3090 ASSERT(!retry || spa == 0);
3091
3092 if (spa != NULL)
3093 guid = spa_load_guid(spa);
3094
3095 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
3096 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
3097
3098 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
3099 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
3100
3101 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
3102 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
3103
3104 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
3105 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
3106
3107 arc_do_user_evicts();
3108 ASSERT(spa || arc_eviction_list == NULL);
3109 }
3110
3111 void
3112 arc_shrink(int64_t to_free)
3113 {
3114 if (arc_c > arc_c_min) {
3115
3116 if (arc_c > arc_c_min + to_free)
3117 atomic_add_64(&arc_c, -to_free);
3118 else
3119 arc_c = arc_c_min;
3120
3121 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
3122 if (arc_c > arc_size)
3123 arc_c = MAX(arc_size, arc_c_min);
3124 if (arc_p > arc_c)
3125 arc_p = (arc_c >> 1);
3126 ASSERT(arc_c >= arc_c_min);
3127 ASSERT((int64_t)arc_p >= 0);
3128 }
3129
3130 if (arc_size > arc_c)
3131 (void) arc_adjust();
3132 }
3133
3134 typedef enum free_memory_reason_t {
3135 FMR_UNKNOWN,
3136 FMR_NEEDFREE,
3137 FMR_LOTSFREE,
3138 FMR_SWAPFS_MINFREE,
3139 FMR_PAGES_PP_MAXIMUM,
3140 FMR_HEAP_ARENA,
3141 FMR_ZIO_ARENA,
3142 } free_memory_reason_t;
3143
3144 int64_t last_free_memory;
3145 free_memory_reason_t last_free_reason;
3146
3147 /*
3148 * Additional reserve of pages for pp_reserve.
3149 */
3150 int64_t arc_pages_pp_reserve = 64;
3151
3152 /*
3153 * Additional reserve of pages for swapfs.
3154 */
3155 int64_t arc_swapfs_reserve = 64;
3156
3157 /*
3158 * Return the amount of memory that can be consumed before reclaim will be
3159 * needed. Positive if there is sufficient free memory, negative indicates
3160 * the amount of memory that needs to be freed up.
3161 */
3162 static int64_t
3163 arc_available_memory(void)
3164 {
3165 int64_t lowest = INT64_MAX;
3166 int64_t n;
3167 free_memory_reason_t r = FMR_UNKNOWN;
3168
3169 #ifdef _KERNEL
3170 if (needfree > 0) {
3171 n = PAGESIZE * (-needfree);
3172 if (n < lowest) {
3173 lowest = n;
3174 r = FMR_NEEDFREE;
3175 }
3176 }
3177
3178 /*
3179 * check that we're out of range of the pageout scanner. It starts to
3180 * schedule paging if freemem is less than lotsfree and needfree.
3181 * lotsfree is the high-water mark for pageout, and needfree is the
3182 * number of needed free pages. We add extra pages here to make sure
3183 * the scanner doesn't start up while we're freeing memory.
3184 */
3185 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
3186 if (n < lowest) {
3187 lowest = n;
3188 r = FMR_LOTSFREE;
3189 }
3190
3191 /*
3192 * check to make sure that swapfs has enough space so that anon
3193 * reservations can still succeed. anon_resvmem() checks that the
3194 * availrmem is greater than swapfs_minfree, and the number of reserved
3195 * swap pages. We also add a bit of extra here just to prevent
3196 * circumstances from getting really dire.
3197 */
3198 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
3199 desfree - arc_swapfs_reserve);
3200 if (n < lowest) {
3201 lowest = n;
3202 r = FMR_SWAPFS_MINFREE;
3203 }
3204
3205
3206 /*
3207 * Check that we have enough availrmem that memory locking (e.g., via
3208 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
3209 * stores the number of pages that cannot be locked; when availrmem
3210 * drops below pages_pp_maximum, page locking mechanisms such as
3211 * page_pp_lock() will fail.)
3212 */
3213 n = PAGESIZE * (availrmem - pages_pp_maximum -
3214 arc_pages_pp_reserve);
3215 if (n < lowest) {
3216 lowest = n;
3217 r = FMR_PAGES_PP_MAXIMUM;
3218 }
3219
3220 #if defined(__i386)
3221 /*
3222 * If we're on an i386 platform, it's possible that we'll exhaust the
3223 * kernel heap space before we ever run out of available physical
3224 * memory. Most checks of the size of the heap_area compare against
3225 * tune.t_minarmem, which is the minimum available real memory that we
3226 * can have in the system. However, this is generally fixed at 25 pages
3227 * which is so low that it's useless. In this comparison, we seek to
3228 * calculate the total heap-size, and reclaim if more than 3/4ths of the
3229 * heap is allocated. (Or, in the calculation, if less than 1/4th is
3230 * free)
3231 */
3232 n = vmem_size(heap_arena, VMEM_FREE) -
3233 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
3234 if (n < lowest) {
3235 lowest = n;
3236 r = FMR_HEAP_ARENA;
3237 }
3238 #endif
3239
3240 /*
3241 * If zio data pages are being allocated out of a separate heap segment,
3242 * then enforce that the size of available vmem for this arena remains
3243 * above about 1/16th free.
3244 *
3245 * Note: The 1/16th arena free requirement was put in place
3246 * to aggressively evict memory from the arc in order to avoid
3247 * memory fragmentation issues.
3248 */
3249 if (zio_arena != NULL) {
3250 n = vmem_size(zio_arena, VMEM_FREE) -
3251 (vmem_size(zio_arena, VMEM_ALLOC) >> 4);
3252 if (n < lowest) {
3253 lowest = n;
3254 r = FMR_ZIO_ARENA;
3255 }
3256 }
3257 #else
3258 /* Every 100 calls, free a small amount */
3259 if (spa_get_random(100) == 0)
3260 lowest = -1024;
3261 #endif
3262
3263 last_free_memory = lowest;
3264 last_free_reason = r;
3265
3266 return (lowest);
3267 }
3268
3269
3270 /*
3271 * Determine if the system is under memory pressure and is asking
3272 * to reclaim memory. A return value of TRUE indicates that the system
3273 * is under memory pressure and that the arc should adjust accordingly.
3274 */
3275 static boolean_t
3276 arc_reclaim_needed(void)
3277 {
3278 return (arc_available_memory() < 0);
3279 }
3280
3281 static void
3282 arc_kmem_reap_now(void)
3283 {
3284 size_t i;
3285 kmem_cache_t *prev_cache = NULL;
3286 kmem_cache_t *prev_data_cache = NULL;
3287 extern kmem_cache_t *zio_buf_cache[];
3288 extern kmem_cache_t *zio_data_buf_cache[];
3289 extern kmem_cache_t *range_seg_cache;
3290
3291 #ifdef _KERNEL
3292 if (arc_meta_used >= arc_meta_limit) {
3293 /*
3294 * We are exceeding our meta-data cache limit.
3295 * Purge some DNLC entries to release holds on meta-data.
3296 */
3297 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
3298 }
3299 #if defined(__i386)
3300 /*
3301 * Reclaim unused memory from all kmem caches.
3302 */
3303 kmem_reap();
3304 #endif
3305 #endif
3306
3307 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
3308 if (zio_buf_cache[i] != prev_cache) {
3309 prev_cache = zio_buf_cache[i];
3310 kmem_cache_reap_now(zio_buf_cache[i]);
3311 }
3312 if (zio_data_buf_cache[i] != prev_data_cache) {
3313 prev_data_cache = zio_data_buf_cache[i];
3314 kmem_cache_reap_now(zio_data_buf_cache[i]);
3315 }
3316 }
3317 kmem_cache_reap_now(buf_cache);
3318 kmem_cache_reap_now(hdr_full_cache);
3319 kmem_cache_reap_now(hdr_l2only_cache);
3320 kmem_cache_reap_now(range_seg_cache);
3321
3322 if (zio_arena != NULL) {
3323 /*
3324 * Ask the vmem arena to reclaim unused memory from its
3325 * quantum caches.
3326 */
3327 vmem_qcache_reap(zio_arena);
3328 }
3329 }
3330
3331 /*
3332 * Threads can block in arc_get_data_buf() waiting for this thread to evict
3333 * enough data and signal them to proceed. When this happens, the threads in
3334 * arc_get_data_buf() are sleeping while holding the hash lock for their
3335 * particular arc header. Thus, we must be careful to never sleep on a
3336 * hash lock in this thread. This is to prevent the following deadlock:
3337 *
3338 * - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L",
3339 * waiting for the reclaim thread to signal it.
3340 *
3341 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
3342 * fails, and goes to sleep forever.
3343 *
3344 * This possible deadlock is avoided by always acquiring a hash lock
3345 * using mutex_tryenter() from arc_reclaim_thread().
3346 */
3347 static void
3348 arc_reclaim_thread(void)
3349 {
3350 clock_t growtime = 0;
3351 callb_cpr_t cpr;
3352
3353 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
3354
3355 mutex_enter(&arc_reclaim_lock);
3356 while (!arc_reclaim_thread_exit) {
3357 int64_t free_memory = arc_available_memory();
3358 uint64_t evicted = 0;
3359
3360 mutex_exit(&arc_reclaim_lock);
3361
3362 if (free_memory < 0) {
3363
3364 arc_no_grow = B_TRUE;
3365 arc_warm = B_TRUE;
3366
3367 /*
3368 * Wait at least zfs_grow_retry (default 60) seconds
3369 * before considering growing.
3370 */
3371 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
3372
3373 arc_kmem_reap_now();
3374
3375 /*
3376 * If we are still low on memory, shrink the ARC
3377 * so that we have arc_shrink_min free space.
3378 */
3379 free_memory = arc_available_memory();
3380
3381 int64_t to_free =
3382 (arc_c >> arc_shrink_shift) - free_memory;
3383 if (to_free > 0) {
3384 #ifdef _KERNEL
3385 to_free = MAX(to_free, ptob(needfree));
3386 #endif
3387 arc_shrink(to_free);
3388 }
3389 } else if (free_memory < arc_c >> arc_no_grow_shift) {
3390 arc_no_grow = B_TRUE;
3391 } else if (ddi_get_lbolt() >= growtime) {
3392 arc_no_grow = B_FALSE;
3393 }
3394
3395 evicted = arc_adjust();
3396
3397 mutex_enter(&arc_reclaim_lock);
3398
3399 /*
3400 * If evicted is zero, we couldn't evict anything via
3401 * arc_adjust(). This could be due to hash lock
3402 * collisions, but more likely due to the majority of
3403 * arc buffers being unevictable. Therefore, even if
3404 * arc_size is above arc_c, another pass is unlikely to
3405 * be helpful and could potentially cause us to enter an
3406 * infinite loop.
3407 */
3408 if (arc_size <= arc_c || evicted == 0) {
3409 /*
3410 * We're either no longer overflowing, or we
3411 * can't evict anything more, so we should wake
3412 * up any threads before we go to sleep.
3413 */
3414 cv_broadcast(&arc_reclaim_waiters_cv);
3415
3416 /*
3417 * Block until signaled, or after one second (we
3418 * might need to perform arc_kmem_reap_now()
3419 * even if we aren't being signalled)
3420 */
3421 CALLB_CPR_SAFE_BEGIN(&cpr);
3422 (void) cv_timedwait(&arc_reclaim_thread_cv,
3423 &arc_reclaim_lock, ddi_get_lbolt() + hz);
3424 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
3425 }
3426 }
3427
3428 arc_reclaim_thread_exit = FALSE;
3429 cv_broadcast(&arc_reclaim_thread_cv);
3430 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
3431 thread_exit();
3432 }
3433
3434 static void
3435 arc_user_evicts_thread(void)
3436 {
3437 callb_cpr_t cpr;
3438
3439 CALLB_CPR_INIT(&cpr, &arc_user_evicts_lock, callb_generic_cpr, FTAG);
3440
3441 mutex_enter(&arc_user_evicts_lock);
3442 while (!arc_user_evicts_thread_exit) {
3443 mutex_exit(&arc_user_evicts_lock);
3444
3445 arc_do_user_evicts();
3446
3447 /*
3448 * This is necessary in order for the mdb ::arc dcmd to
3449 * show up to date information. Since the ::arc command
3450 * does not call the kstat's update function, without
3451 * this call, the command may show stale stats for the
3452 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
3453 * with this change, the data might be up to 1 second
3454 * out of date; but that should suffice. The arc_state_t
3455 * structures can be queried directly if more accurate
3456 * information is needed.
3457 */
3458 if (arc_ksp != NULL)
3459 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
3460
3461 mutex_enter(&arc_user_evicts_lock);
3462
3463 /*
3464 * Block until signaled, or after one second (we need to
3465 * call the arc's kstat update function regularly).
3466 */
3467 CALLB_CPR_SAFE_BEGIN(&cpr);
3468 (void) cv_timedwait(&arc_user_evicts_cv,
3469 &arc_user_evicts_lock, ddi_get_lbolt() + hz);
3470 CALLB_CPR_SAFE_END(&cpr, &arc_user_evicts_lock);
3471 }
3472
3473 arc_user_evicts_thread_exit = FALSE;
3474 cv_broadcast(&arc_user_evicts_cv);
3475 CALLB_CPR_EXIT(&cpr); /* drops arc_user_evicts_lock */
3476 thread_exit();
3477 }
3478
3479 /*
3480 * Adapt arc info given the number of bytes we are trying to add and
3481 * the state that we are comming from. This function is only called
3482 * when we are adding new content to the cache.
3483 */
3484 static void
3485 arc_adapt(int bytes, arc_state_t *state)
3486 {
3487 int mult;
3488 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
3489 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
3490 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
3491
3492 if (state == arc_l2c_only)
3493 return;
3494
3495 ASSERT(bytes > 0);
3496 /*
3497 * Adapt the target size of the MRU list:
3498 * - if we just hit in the MRU ghost list, then increase
3499 * the target size of the MRU list.
3500 * - if we just hit in the MFU ghost list, then increase
3501 * the target size of the MFU list by decreasing the
3502 * target size of the MRU list.
3503 */
3504 if (state == arc_mru_ghost) {
3505 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
3506 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
3507
3508 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
3509 } else if (state == arc_mfu_ghost) {
3510 uint64_t delta;
3511
3512 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
3513 mult = MIN(mult, 10);
3514
3515 delta = MIN(bytes * mult, arc_p);
3516 arc_p = MAX(arc_p_min, arc_p - delta);
3517 }
3518 ASSERT((int64_t)arc_p >= 0);
3519
3520 if (arc_reclaim_needed()) {
3521 cv_signal(&arc_reclaim_thread_cv);
3522 return;
3523 }
3524
3525 if (arc_no_grow)
3526 return;
3527
3528 if (arc_c >= arc_c_max)
3529 return;
3530
3531 /*
3532 * If we're within (2 * maxblocksize) bytes of the target
3533 * cache size, increment the target cache size
3534 */
3535 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
3536 atomic_add_64(&arc_c, (int64_t)bytes);
3537 if (arc_c > arc_c_max)
3538 arc_c = arc_c_max;
3539 else if (state == arc_anon)
3540 atomic_add_64(&arc_p, (int64_t)bytes);
3541 if (arc_p > arc_c)
3542 arc_p = arc_c;
3543 }
3544 ASSERT((int64_t)arc_p >= 0);
3545 }
3546
3547 /*
3548 * Check if arc_size has grown past our upper threshold, determined by
3549 * zfs_arc_overflow_shift.
3550 */
3551 static boolean_t
3552 arc_is_overflowing(void)
3553 {
3554 /* Always allow at least one block of overflow */
3555 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
3556 arc_c >> zfs_arc_overflow_shift);
3557
3558 return (arc_size >= arc_c + overflow);
3559 }
3560
3561 /*
3562 * The buffer, supplied as the first argument, needs a data block. If we
3563 * are hitting the hard limit for the cache size, we must sleep, waiting
3564 * for the eviction thread to catch up. If we're past the target size
3565 * but below the hard limit, we'll only signal the reclaim thread and
3566 * continue on.
3567 */
3568 static void
3569 arc_get_data_buf(arc_buf_t *buf)
3570 {
3571 arc_state_t *state = buf->b_hdr->b_l1hdr.b_state;
3572 uint64_t size = buf->b_hdr->b_size;
3573 arc_buf_contents_t type = arc_buf_type(buf->b_hdr);
3574
3575 arc_adapt(size, state);
3576
3577 /*
3578 * If arc_size is currently overflowing, and has grown past our
3579 * upper limit, we must be adding data faster than the evict
3580 * thread can evict. Thus, to ensure we don't compound the
3581 * problem by adding more data and forcing arc_size to grow even
3582 * further past it's target size, we halt and wait for the
3583 * eviction thread to catch up.
3584 *
3585 * It's also possible that the reclaim thread is unable to evict
3586 * enough buffers to get arc_size below the overflow limit (e.g.
3587 * due to buffers being un-evictable, or hash lock collisions).
3588 * In this case, we want to proceed regardless if we're
3589 * overflowing; thus we don't use a while loop here.
3590 */
3591 if (arc_is_overflowing()) {
3592 mutex_enter(&arc_reclaim_lock);
3593
3594 /*
3595 * Now that we've acquired the lock, we may no longer be
3596 * over the overflow limit, lets check.
3597 *
3598 * We're ignoring the case of spurious wake ups. If that
3599 * were to happen, it'd let this thread consume an ARC
3600 * buffer before it should have (i.e. before we're under
3601 * the overflow limit and were signalled by the reclaim
3602 * thread). As long as that is a rare occurrence, it
3603 * shouldn't cause any harm.
3604 */
3605 if (arc_is_overflowing()) {
3606 cv_signal(&arc_reclaim_thread_cv);
3607 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
3608 }
3609
3610 mutex_exit(&arc_reclaim_lock);
3611 }
3612
3613 if (type == ARC_BUFC_METADATA) {
3614 buf->b_data = zio_buf_alloc(size);
3615 arc_space_consume(size, ARC_SPACE_META);
3616 } else {
3617 ASSERT(type == ARC_BUFC_DATA);
3618 buf->b_data = zio_data_buf_alloc(size);
3619 arc_space_consume(size, ARC_SPACE_DATA);
3620 }
3621
3622 /*
3623 * Update the state size. Note that ghost states have a
3624 * "ghost size" and so don't need to be updated.
3625 */
3626 if (!GHOST_STATE(buf->b_hdr->b_l1hdr.b_state)) {
3627 arc_buf_hdr_t *hdr = buf->b_hdr;
3628 arc_state_t *state = hdr->b_l1hdr.b_state;
3629
3630 (void) refcount_add_many(&state->arcs_size, size, buf);
3631
3632 /*
3633 * If this is reached via arc_read, the link is
3634 * protected by the hash lock. If reached via
3635 * arc_buf_alloc, the header should not be accessed by
3636 * any other thread. And, if reached via arc_read_done,
3637 * the hash lock will protect it if it's found in the
3638 * hash table; otherwise no other thread should be
3639 * trying to [add|remove]_reference it.
3640 */
3641 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
3642 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3643 atomic_add_64(&hdr->b_l1hdr.b_state->arcs_lsize[type],
3644 size);
3645 }
3646 /*
3647 * If we are growing the cache, and we are adding anonymous
3648 * data, and we have outgrown arc_p, update arc_p
3649 */
3650 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
3651 (refcount_count(&arc_anon->arcs_size) +
3652 refcount_count(&arc_mru->arcs_size) > arc_p))
3653 arc_p = MIN(arc_c, arc_p + size);
3654 }
3655 }
3656
3657 /*
3658 * This routine is called whenever a buffer is accessed.
3659 * NOTE: the hash lock is dropped in this function.
3660 */
3661 static void
3662 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3663 {
3664 clock_t now;
3665
3666 ASSERT(MUTEX_HELD(hash_lock));
3667 ASSERT(HDR_HAS_L1HDR(hdr));
3668
3669 if (hdr->b_l1hdr.b_state == arc_anon) {
3670 /*
3671 * This buffer is not in the cache, and does not
3672 * appear in our "ghost" list. Add the new buffer
3673 * to the MRU state.
3674 */
3675
3676 ASSERT0(hdr->b_l1hdr.b_arc_access);
3677 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3678 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
3679 arc_change_state(arc_mru, hdr, hash_lock);
3680
3681 } else if (hdr->b_l1hdr.b_state == arc_mru) {
3682 now = ddi_get_lbolt();
3683
3684 /*
3685 * If this buffer is here because of a prefetch, then either:
3686 * - clear the flag if this is a "referencing" read
3687 * (any subsequent access will bump this into the MFU state).
3688 * or
3689 * - move the buffer to the head of the list if this is
3690 * another prefetch (to make it less likely to be evicted).
3691 */
3692 if (HDR_PREFETCH(hdr)) {
3693 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
3694 /* link protected by hash lock */
3695 ASSERT(multilist_link_active(
3696 &hdr->b_l1hdr.b_arc_node));
3697 } else {
3698 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
3699 ARCSTAT_BUMP(arcstat_mru_hits);
3700 }
3701 hdr->b_l1hdr.b_arc_access = now;
3702 return;
3703 }
3704
3705 /*
3706 * This buffer has been "accessed" only once so far,
3707 * but it is still in the cache. Move it to the MFU
3708 * state.
3709 */
3710 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
3711 /*
3712 * More than 125ms have passed since we
3713 * instantiated this buffer. Move it to the
3714 * most frequently used state.
3715 */
3716 hdr->b_l1hdr.b_arc_access = now;
3717 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3718 arc_change_state(arc_mfu, hdr, hash_lock);
3719 }
3720 ARCSTAT_BUMP(arcstat_mru_hits);
3721 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
3722 arc_state_t *new_state;
3723 /*
3724 * This buffer has been "accessed" recently, but
3725 * was evicted from the cache. Move it to the
3726 * MFU state.
3727 */
3728
3729 if (HDR_PREFETCH(hdr)) {
3730 new_state = arc_mru;
3731 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
3732 hdr->b_flags &= ~ARC_FLAG_PREFETCH;
3733 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
3734 } else {
3735 new_state = arc_mfu;
3736 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3737 }
3738
3739 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3740 arc_change_state(new_state, hdr, hash_lock);
3741
3742 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
3743 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
3744 /*
3745 * This buffer has been accessed more than once and is
3746 * still in the cache. Keep it in the MFU state.
3747 *
3748 * NOTE: an add_reference() that occurred when we did
3749 * the arc_read() will have kicked this off the list.
3750 * If it was a prefetch, we will explicitly move it to
3751 * the head of the list now.
3752 */
3753 if ((HDR_PREFETCH(hdr)) != 0) {
3754 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3755 /* link protected by hash_lock */
3756 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3757 }
3758 ARCSTAT_BUMP(arcstat_mfu_hits);
3759 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3760 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
3761 arc_state_t *new_state = arc_mfu;
3762 /*
3763 * This buffer has been accessed more than once but has
3764 * been evicted from the cache. Move it back to the
3765 * MFU state.
3766 */
3767
3768 if (HDR_PREFETCH(hdr)) {
3769 /*
3770 * This is a prefetch access...
3771 * move this block back to the MRU state.
3772 */
3773 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3774 new_state = arc_mru;
3775 }
3776
3777 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3778 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3779 arc_change_state(new_state, hdr, hash_lock);
3780
3781 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
3782 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
3783 /*
3784 * This buffer is on the 2nd Level ARC.
3785 */
3786
3787 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
3788 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
3789 arc_change_state(arc_mfu, hdr, hash_lock);
3790 } else {
3791 ASSERT(!"invalid arc state");
3792 }
3793 }
3794
3795 /* a generic arc_done_func_t which you can use */
3796 /* ARGSUSED */
3797 void
3798 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
3799 {
3800 if (zio == NULL || zio->io_error == 0)
3801 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
3802 VERIFY(arc_buf_remove_ref(buf, arg));
3803 }
3804
3805 /* a generic arc_done_func_t */
3806 void
3807 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
3808 {
3809 arc_buf_t **bufp = arg;
3810 if (zio && zio->io_error) {
3811 VERIFY(arc_buf_remove_ref(buf, arg));
3812 *bufp = NULL;
3813 } else {
3814 *bufp = buf;
3815 ASSERT(buf->b_data);
3816 }
3817 }
3818
3819 static void
3820 arc_read_done(zio_t *zio)
3821 {
3822 arc_buf_hdr_t *hdr;
3823 arc_buf_t *buf;
3824 arc_buf_t *abuf; /* buffer we're assigning to callback */
3825 kmutex_t *hash_lock = NULL;
3826 arc_callback_t *callback_list, *acb;
3827 int freeable = FALSE;
3828
3829 buf = zio->io_private;
3830 hdr = buf->b_hdr;
3831
3832 /*
3833 * The hdr was inserted into hash-table and removed from lists
3834 * prior to starting I/O. We should find this header, since
3835 * it's in the hash table, and it should be legit since it's
3836 * not possible to evict it during the I/O. The only possible
3837 * reason for it not to be found is if we were freed during the
3838 * read.
3839 */
3840 if (HDR_IN_HASH_TABLE(hdr)) {
3841 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
3842 ASSERT3U(hdr->b_dva.dva_word[0], ==,
3843 BP_IDENTITY(zio->io_bp)->dva_word[0]);
3844 ASSERT3U(hdr->b_dva.dva_word[1], ==,
3845 BP_IDENTITY(zio->io_bp)->dva_word[1]);
3846
3847 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
3848 &hash_lock);
3849
3850 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) &&
3851 hash_lock == NULL) ||
3852 (found == hdr &&
3853 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
3854 (found == hdr && HDR_L2_READING(hdr)));
3855 }
3856
3857 hdr->b_flags &= ~ARC_FLAG_L2_EVICTED;
3858 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
3859 hdr->b_flags &= ~ARC_FLAG_L2CACHE;
3860
3861 /* byteswap if necessary */
3862 callback_list = hdr->b_l1hdr.b_acb;
3863 ASSERT(callback_list != NULL);
3864 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
3865 dmu_object_byteswap_t bswap =
3866 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
3867 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
3868 byteswap_uint64_array :
3869 dmu_ot_byteswap[bswap].ob_func;
3870 func(buf->b_data, hdr->b_size);
3871 }
3872
3873 arc_cksum_compute(buf, B_FALSE);
3874 arc_buf_watch(buf);
3875
3876 if (hash_lock && zio->io_error == 0 &&
3877 hdr->b_l1hdr.b_state == arc_anon) {
3878 /*
3879 * Only call arc_access on anonymous buffers. This is because
3880 * if we've issued an I/O for an evicted buffer, we've already
3881 * called arc_access (to prevent any simultaneous readers from
3882 * getting confused).
3883 */
3884 arc_access(hdr, hash_lock);
3885 }
3886
3887 /* create copies of the data buffer for the callers */
3888 abuf = buf;
3889 for (acb = callback_list; acb; acb = acb->acb_next) {
3890 if (acb->acb_done) {
3891 if (abuf == NULL) {
3892 ARCSTAT_BUMP(arcstat_duplicate_reads);
3893 abuf = arc_buf_clone(buf);
3894 }
3895 acb->acb_buf = abuf;
3896 abuf = NULL;
3897 }
3898 }
3899 hdr->b_l1hdr.b_acb = NULL;
3900 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
3901 ASSERT(!HDR_BUF_AVAILABLE(hdr));
3902 if (abuf == buf) {
3903 ASSERT(buf->b_efunc == NULL);
3904 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
3905 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
3906 }
3907
3908 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
3909 callback_list != NULL);
3910
3911 if (zio->io_error != 0) {
3912 hdr->b_flags |= ARC_FLAG_IO_ERROR;
3913 if (hdr->b_l1hdr.b_state != arc_anon)
3914 arc_change_state(arc_anon, hdr, hash_lock);
3915 if (HDR_IN_HASH_TABLE(hdr))
3916 buf_hash_remove(hdr);
3917 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
3918 }
3919
3920 /*
3921 * Broadcast before we drop the hash_lock to avoid the possibility
3922 * that the hdr (and hence the cv) might be freed before we get to
3923 * the cv_broadcast().
3924 */
3925 cv_broadcast(&hdr->b_l1hdr.b_cv);
3926
3927 if (hash_lock != NULL) {
3928 mutex_exit(hash_lock);
3929 } else {
3930 /*
3931 * This block was freed while we waited for the read to
3932 * complete. It has been removed from the hash table and
3933 * moved to the anonymous state (so that it won't show up
3934 * in the cache).
3935 */
3936 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3937 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
3938 }
3939
3940 /* execute each callback and free its structure */
3941 while ((acb = callback_list) != NULL) {
3942 if (acb->acb_done)
3943 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
3944
3945 if (acb->acb_zio_dummy != NULL) {
3946 acb->acb_zio_dummy->io_error = zio->io_error;
3947 zio_nowait(acb->acb_zio_dummy);
3948 }
3949
3950 callback_list = acb->acb_next;
3951 kmem_free(acb, sizeof (arc_callback_t));
3952 }
3953
3954 if (freeable)
3955 arc_hdr_destroy(hdr);
3956 }
3957
3958 /*
3959 * "Read" the block at the specified DVA (in bp) via the
3960 * cache. If the block is found in the cache, invoke the provided
3961 * callback immediately and return. Note that the `zio' parameter
3962 * in the callback will be NULL in this case, since no IO was
3963 * required. If the block is not in the cache pass the read request
3964 * on to the spa with a substitute callback function, so that the
3965 * requested block will be added to the cache.
3966 *
3967 * If a read request arrives for a block that has a read in-progress,
3968 * either wait for the in-progress read to complete (and return the
3969 * results); or, if this is a read with a "done" func, add a record
3970 * to the read to invoke the "done" func when the read completes,
3971 * and return; or just return.
3972 *
3973 * arc_read_done() will invoke all the requested "done" functions
3974 * for readers of this block.
3975 */
3976 int
3977 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
3978 void *private, zio_priority_t priority, int zio_flags,
3979 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
3980 {
3981 arc_buf_hdr_t *hdr = NULL;
3982 arc_buf_t *buf = NULL;
3983 kmutex_t *hash_lock = NULL;
3984 zio_t *rzio;
3985 uint64_t guid = spa_load_guid(spa);
3986
3987 ASSERT(!BP_IS_EMBEDDED(bp) ||
3988 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
3989
3990 top:
3991 if (!BP_IS_EMBEDDED(bp)) {
3992 /*
3993 * Embedded BP's have no DVA and require no I/O to "read".
3994 * Create an anonymous arc buf to back it.
3995 */
3996 hdr = buf_hash_find(guid, bp, &hash_lock);
3997 }
3998
3999 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_datacnt > 0) {
4000
4001 *arc_flags |= ARC_FLAG_CACHED;
4002
4003 if (HDR_IO_IN_PROGRESS(hdr)) {
4004
4005 if (*arc_flags & ARC_FLAG_WAIT) {
4006 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
4007 mutex_exit(hash_lock);
4008 goto top;
4009 }
4010 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
4011
4012 if (done) {
4013 arc_callback_t *acb = NULL;
4014
4015 acb = kmem_zalloc(sizeof (arc_callback_t),
4016 KM_SLEEP);
4017 acb->acb_done = done;
4018 acb->acb_private = private;
4019 if (pio != NULL)
4020 acb->acb_zio_dummy = zio_null(pio,
4021 spa, NULL, NULL, NULL, zio_flags);
4022
4023 ASSERT(acb->acb_done != NULL);
4024 acb->acb_next = hdr->b_l1hdr.b_acb;
4025 hdr->b_l1hdr.b_acb = acb;
4026 add_reference(hdr, hash_lock, private);
4027 mutex_exit(hash_lock);
4028 return (0);
4029 }
4030 mutex_exit(hash_lock);
4031 return (0);
4032 }
4033
4034 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
4035 hdr->b_l1hdr.b_state == arc_mfu);
4036
4037 if (done) {
4038 add_reference(hdr, hash_lock, private);
4039 /*
4040 * If this block is already in use, create a new
4041 * copy of the data so that we will be guaranteed
4042 * that arc_release() will always succeed.
4043 */
4044 buf = hdr->b_l1hdr.b_buf;
4045 ASSERT(buf);
4046 ASSERT(buf->b_data);
4047 if (HDR_BUF_AVAILABLE(hdr)) {
4048 ASSERT(buf->b_efunc == NULL);
4049 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
4050 } else {
4051 buf = arc_buf_clone(buf);
4052 }
4053
4054 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
4055 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4056 hdr->b_flags |= ARC_FLAG_PREFETCH;
4057 }
4058 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
4059 arc_access(hdr, hash_lock);
4060 if (*arc_flags & ARC_FLAG_L2CACHE)
4061 hdr->b_flags |= ARC_FLAG_L2CACHE;
4062 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4063 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4064 mutex_exit(hash_lock);
4065 ARCSTAT_BUMP(arcstat_hits);
4066 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
4067 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
4068 data, metadata, hits);
4069
4070 if (done)
4071 done(NULL, buf, private);
4072 } else {
4073 uint64_t size = BP_GET_LSIZE(bp);
4074 arc_callback_t *acb;
4075 vdev_t *vd = NULL;
4076 uint64_t addr = 0;
4077 boolean_t devw = B_FALSE;
4078 enum zio_compress b_compress = ZIO_COMPRESS_OFF;
4079 int32_t b_asize = 0;
4080
4081 if (hdr == NULL) {
4082 /* this block is not in the cache */
4083 arc_buf_hdr_t *exists = NULL;
4084 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
4085 buf = arc_buf_alloc(spa, size, private, type);
4086 hdr = buf->b_hdr;
4087 if (!BP_IS_EMBEDDED(bp)) {
4088 hdr->b_dva = *BP_IDENTITY(bp);
4089 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
4090 exists = buf_hash_insert(hdr, &hash_lock);
4091 }
4092 if (exists != NULL) {
4093 /* somebody beat us to the hash insert */
4094 mutex_exit(hash_lock);
4095 buf_discard_identity(hdr);
4096 (void) arc_buf_remove_ref(buf, private);
4097 goto top; /* restart the IO request */
4098 }
4099
4100 /* if this is a prefetch, we don't have a reference */
4101 if (*arc_flags & ARC_FLAG_PREFETCH) {
4102 (void) remove_reference(hdr, hash_lock,
4103 private);
4104 hdr->b_flags |= ARC_FLAG_PREFETCH;
4105 }
4106 if (*arc_flags & ARC_FLAG_L2CACHE)
4107 hdr->b_flags |= ARC_FLAG_L2CACHE;
4108 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4109 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4110 if (BP_GET_LEVEL(bp) > 0)
4111 hdr->b_flags |= ARC_FLAG_INDIRECT;
4112 } else {
4113 /*
4114 * This block is in the ghost cache. If it was L2-only
4115 * (and thus didn't have an L1 hdr), we realloc the
4116 * header to add an L1 hdr.
4117 */
4118 if (!HDR_HAS_L1HDR(hdr)) {
4119 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
4120 hdr_full_cache);
4121 }
4122
4123 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
4124 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4125 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4126 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
4127
4128 /* if this is a prefetch, we don't have a reference */
4129 if (*arc_flags & ARC_FLAG_PREFETCH)
4130 hdr->b_flags |= ARC_FLAG_PREFETCH;
4131 else
4132 add_reference(hdr, hash_lock, private);
4133 if (*arc_flags & ARC_FLAG_L2CACHE)
4134 hdr->b_flags |= ARC_FLAG_L2CACHE;
4135 if (*arc_flags & ARC_FLAG_L2COMPRESS)
4136 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4137 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
4138 buf->b_hdr = hdr;
4139 buf->b_data = NULL;
4140 buf->b_efunc = NULL;
4141 buf->b_private = NULL;
4142 buf->b_next = NULL;
4143 hdr->b_l1hdr.b_buf = buf;
4144 ASSERT0(hdr->b_l1hdr.b_datacnt);
4145 hdr->b_l1hdr.b_datacnt = 1;
4146 arc_get_data_buf(buf);
4147 arc_access(hdr, hash_lock);
4148 }
4149
4150 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
4151
4152 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
4153 acb->acb_done = done;
4154 acb->acb_private = private;
4155
4156 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4157 hdr->b_l1hdr.b_acb = acb;
4158 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
4159
4160 if (HDR_HAS_L2HDR(hdr) &&
4161 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
4162 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
4163 addr = hdr->b_l2hdr.b_daddr;
4164 b_compress = hdr->b_l2hdr.b_compress;
4165 b_asize = hdr->b_l2hdr.b_asize;
4166 /*
4167 * Lock out device removal.
4168 */
4169 if (vdev_is_dead(vd) ||
4170 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
4171 vd = NULL;
4172 }
4173
4174 if (hash_lock != NULL)
4175 mutex_exit(hash_lock);
4176
4177 /*
4178 * At this point, we have a level 1 cache miss. Try again in
4179 * L2ARC if possible.
4180 */
4181 ASSERT3U(hdr->b_size, ==, size);
4182 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
4183 uint64_t, size, zbookmark_phys_t *, zb);
4184 ARCSTAT_BUMP(arcstat_misses);
4185 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
4186 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
4187 data, metadata, misses);
4188
4189 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
4190 /*
4191 * Read from the L2ARC if the following are true:
4192 * 1. The L2ARC vdev was previously cached.
4193 * 2. This buffer still has L2ARC metadata.
4194 * 3. This buffer isn't currently writing to the L2ARC.
4195 * 4. The L2ARC entry wasn't evicted, which may
4196 * also have invalidated the vdev.
4197 * 5. This isn't prefetch and l2arc_noprefetch is set.
4198 */
4199 if (HDR_HAS_L2HDR(hdr) &&
4200 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
4201 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
4202 l2arc_read_callback_t *cb;
4203
4204 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
4205 ARCSTAT_BUMP(arcstat_l2_hits);
4206
4207 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
4208 KM_SLEEP);
4209 cb->l2rcb_buf = buf;
4210 cb->l2rcb_spa = spa;
4211 cb->l2rcb_bp = *bp;
4212 cb->l2rcb_zb = *zb;
4213 cb->l2rcb_flags = zio_flags;
4214 cb->l2rcb_compress = b_compress;
4215
4216 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
4217 addr + size < vd->vdev_psize -
4218 VDEV_LABEL_END_SIZE);
4219
4220 /*
4221 * l2arc read. The SCL_L2ARC lock will be
4222 * released by l2arc_read_done().
4223 * Issue a null zio if the underlying buffer
4224 * was squashed to zero size by compression.
4225 */
4226 if (b_compress == ZIO_COMPRESS_EMPTY) {
4227 rzio = zio_null(pio, spa, vd,
4228 l2arc_read_done, cb,
4229 zio_flags | ZIO_FLAG_DONT_CACHE |
4230 ZIO_FLAG_CANFAIL |
4231 ZIO_FLAG_DONT_PROPAGATE |
4232 ZIO_FLAG_DONT_RETRY);
4233 } else {
4234 rzio = zio_read_phys(pio, vd, addr,
4235 b_asize, buf->b_data,
4236 ZIO_CHECKSUM_OFF,
4237 l2arc_read_done, cb, priority,
4238 zio_flags | ZIO_FLAG_DONT_CACHE |
4239 ZIO_FLAG_CANFAIL |
4240 ZIO_FLAG_DONT_PROPAGATE |
4241 ZIO_FLAG_DONT_RETRY, B_FALSE);
4242 }
4243 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
4244 zio_t *, rzio);
4245 ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
4246
4247 if (*arc_flags & ARC_FLAG_NOWAIT) {
4248 zio_nowait(rzio);
4249 return (0);
4250 }
4251
4252 ASSERT(*arc_flags & ARC_FLAG_WAIT);
4253 if (zio_wait(rzio) == 0)
4254 return (0);
4255
4256 /* l2arc read error; goto zio_read() */
4257 } else {
4258 DTRACE_PROBE1(l2arc__miss,
4259 arc_buf_hdr_t *, hdr);
4260 ARCSTAT_BUMP(arcstat_l2_misses);
4261 if (HDR_L2_WRITING(hdr))
4262 ARCSTAT_BUMP(arcstat_l2_rw_clash);
4263 spa_config_exit(spa, SCL_L2ARC, vd);
4264 }
4265 } else {
4266 if (vd != NULL)
4267 spa_config_exit(spa, SCL_L2ARC, vd);
4268 if (l2arc_ndev != 0) {
4269 DTRACE_PROBE1(l2arc__miss,
4270 arc_buf_hdr_t *, hdr);
4271 ARCSTAT_BUMP(arcstat_l2_misses);
4272 }
4273 }
4274
4275 rzio = zio_read(pio, spa, bp, buf->b_data, size,
4276 arc_read_done, buf, priority, zio_flags, zb);
4277
4278 if (*arc_flags & ARC_FLAG_WAIT)
4279 return (zio_wait(rzio));
4280
4281 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
4282 zio_nowait(rzio);
4283 }
4284 return (0);
4285 }
4286
4287 void
4288 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
4289 {
4290 ASSERT(buf->b_hdr != NULL);
4291 ASSERT(buf->b_hdr->b_l1hdr.b_state != arc_anon);
4292 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt) ||
4293 func == NULL);
4294 ASSERT(buf->b_efunc == NULL);
4295 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
4296
4297 buf->b_efunc = func;
4298 buf->b_private = private;
4299 }
4300
4301 /*
4302 * Notify the arc that a block was freed, and thus will never be used again.
4303 */
4304 void
4305 arc_freed(spa_t *spa, const blkptr_t *bp)
4306 {
4307 arc_buf_hdr_t *hdr;
4308 kmutex_t *hash_lock;
4309 uint64_t guid = spa_load_guid(spa);
4310
4311 ASSERT(!BP_IS_EMBEDDED(bp));
4312
4313 hdr = buf_hash_find(guid, bp, &hash_lock);
4314 if (hdr == NULL)
4315 return;
4316 if (HDR_BUF_AVAILABLE(hdr)) {
4317 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
4318 add_reference(hdr, hash_lock, FTAG);
4319 hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
4320 mutex_exit(hash_lock);
4321
4322 arc_release(buf, FTAG);
4323 (void) arc_buf_remove_ref(buf, FTAG);
4324 } else {
4325 mutex_exit(hash_lock);
4326 }
4327
4328 }
4329
4330 /*
4331 * Clear the user eviction callback set by arc_set_callback(), first calling
4332 * it if it exists. Because the presence of a callback keeps an arc_buf cached
4333 * clearing the callback may result in the arc_buf being destroyed. However,
4334 * it will not result in the *last* arc_buf being destroyed, hence the data
4335 * will remain cached in the ARC. We make a copy of the arc buffer here so
4336 * that we can process the callback without holding any locks.
4337 *
4338 * It's possible that the callback is already in the process of being cleared
4339 * by another thread. In this case we can not clear the callback.
4340 *
4341 * Returns B_TRUE if the callback was successfully called and cleared.
4342 */
4343 boolean_t
4344 arc_clear_callback(arc_buf_t *buf)
4345 {
4346 arc_buf_hdr_t *hdr;
4347 kmutex_t *hash_lock;
4348 arc_evict_func_t *efunc = buf->b_efunc;
4349 void *private = buf->b_private;
4350
4351 mutex_enter(&buf->b_evict_lock);
4352 hdr = buf->b_hdr;
4353 if (hdr == NULL) {
4354 /*
4355 * We are in arc_do_user_evicts().
4356 */
4357 ASSERT(buf->b_data == NULL);
4358 mutex_exit(&buf->b_evict_lock);
4359 return (B_FALSE);
4360 } else if (buf->b_data == NULL) {
4361 /*
4362 * We are on the eviction list; process this buffer now
4363 * but let arc_do_user_evicts() do the reaping.
4364 */
4365 buf->b_efunc = NULL;
4366 mutex_exit(&buf->b_evict_lock);
4367 VERIFY0(efunc(private));
4368 return (B_TRUE);
4369 }
4370 hash_lock = HDR_LOCK(hdr);
4371 mutex_enter(hash_lock);
4372 hdr = buf->b_hdr;
4373 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4374
4375 ASSERT3U(refcount_count(&hdr->b_l1hdr.b_refcnt), <,
4376 hdr->b_l1hdr.b_datacnt);
4377 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
4378 hdr->b_l1hdr.b_state == arc_mfu);
4379
4380 buf->b_efunc = NULL;
4381 buf->b_private = NULL;
4382
4383 if (hdr->b_l1hdr.b_datacnt > 1) {
4384 mutex_exit(&buf->b_evict_lock);
4385 arc_buf_destroy(buf, TRUE);
4386 } else {
4387 ASSERT(buf == hdr->b_l1hdr.b_buf);
4388 hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
4389 mutex_exit(&buf->b_evict_lock);
4390 }
4391
4392 mutex_exit(hash_lock);
4393 VERIFY0(efunc(private));
4394 return (B_TRUE);
4395 }
4396
4397 /*
4398 * Release this buffer from the cache, making it an anonymous buffer. This
4399 * must be done after a read and prior to modifying the buffer contents.
4400 * If the buffer has more than one reference, we must make
4401 * a new hdr for the buffer.
4402 */
4403 void
4404 arc_release(arc_buf_t *buf, void *tag)
4405 {
4406 arc_buf_hdr_t *hdr = buf->b_hdr;
4407
4408 /*
4409 * It would be nice to assert that if it's DMU metadata (level >
4410 * 0 || it's the dnode file), then it must be syncing context.
4411 * But we don't know that information at this level.
4412 */
4413
4414 mutex_enter(&buf->b_evict_lock);
4415
4416 ASSERT(HDR_HAS_L1HDR(hdr));
4417
4418 /*
4419 * We don't grab the hash lock prior to this check, because if
4420 * the buffer's header is in the arc_anon state, it won't be
4421 * linked into the hash table.
4422 */
4423 if (hdr->b_l1hdr.b_state == arc_anon) {
4424 mutex_exit(&buf->b_evict_lock);
4425 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4426 ASSERT(!HDR_IN_HASH_TABLE(hdr));
4427 ASSERT(!HDR_HAS_L2HDR(hdr));
4428 ASSERT(BUF_EMPTY(hdr));
4429
4430 ASSERT3U(hdr->b_l1hdr.b_datacnt, ==, 1);
4431 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
4432 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
4433
4434 ASSERT3P(buf->b_efunc, ==, NULL);
4435 ASSERT3P(buf->b_private, ==, NULL);
4436
4437 hdr->b_l1hdr.b_arc_access = 0;
4438 arc_buf_thaw(buf);
4439
4440 return;
4441 }
4442
4443 kmutex_t *hash_lock = HDR_LOCK(hdr);
4444 mutex_enter(hash_lock);
4445
4446 /*
4447 * This assignment is only valid as long as the hash_lock is
4448 * held, we must be careful not to reference state or the
4449 * b_state field after dropping the lock.
4450 */
4451 arc_state_t *state = hdr->b_l1hdr.b_state;
4452 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4453 ASSERT3P(state, !=, arc_anon);
4454
4455 /* this buffer is not on any list */
4456 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) > 0);
4457
4458 if (HDR_HAS_L2HDR(hdr)) {
4459 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
4460
4461 /*
4462 * We have to recheck this conditional again now that
4463 * we're holding the l2ad_mtx to prevent a race with
4464 * another thread which might be concurrently calling
4465 * l2arc_evict(). In that case, l2arc_evict() might have
4466 * destroyed the header's L2 portion as we were waiting
4467 * to acquire the l2ad_mtx.
4468 */
4469 if (HDR_HAS_L2HDR(hdr))
4470 arc_hdr_l2hdr_destroy(hdr);
4471
4472 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
4473 }
4474
4475 /*
4476 * Do we have more than one buf?
4477 */
4478 if (hdr->b_l1hdr.b_datacnt > 1) {
4479 arc_buf_hdr_t *nhdr;
4480 arc_buf_t **bufp;
4481 uint64_t blksz = hdr->b_size;
4482 uint64_t spa = hdr->b_spa;
4483 arc_buf_contents_t type = arc_buf_type(hdr);
4484 uint32_t flags = hdr->b_flags;
4485
4486 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
4487 /*
4488 * Pull the data off of this hdr and attach it to
4489 * a new anonymous hdr.
4490 */
4491 (void) remove_reference(hdr, hash_lock, tag);
4492 bufp = &hdr->b_l1hdr.b_buf;
4493 while (*bufp != buf)
4494 bufp = &(*bufp)->b_next;
4495 *bufp = buf->b_next;
4496 buf->b_next = NULL;
4497
4498 ASSERT3P(state, !=, arc_l2c_only);
4499
4500 (void) refcount_remove_many(
4501 &state->arcs_size, hdr->b_size, buf);
4502
4503 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
4504 ASSERT3P(state, !=, arc_l2c_only);
4505 uint64_t *size = &state->arcs_lsize[type];
4506 ASSERT3U(*size, >=, hdr->b_size);
4507 atomic_add_64(size, -hdr->b_size);
4508 }
4509
4510 /*
4511 * We're releasing a duplicate user data buffer, update
4512 * our statistics accordingly.
4513 */
4514 if (HDR_ISTYPE_DATA(hdr)) {
4515 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
4516 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
4517 -hdr->b_size);
4518 }
4519 hdr->b_l1hdr.b_datacnt -= 1;
4520 arc_cksum_verify(buf);
4521 arc_buf_unwatch(buf);
4522
4523 mutex_exit(hash_lock);
4524
4525 nhdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
4526 nhdr->b_size = blksz;
4527 nhdr->b_spa = spa;
4528
4529 nhdr->b_flags = flags & ARC_FLAG_L2_WRITING;
4530 nhdr->b_flags |= arc_bufc_to_flags(type);
4531 nhdr->b_flags |= ARC_FLAG_HAS_L1HDR;
4532
4533 nhdr->b_l1hdr.b_buf = buf;
4534 nhdr->b_l1hdr.b_datacnt = 1;
4535 nhdr->b_l1hdr.b_state = arc_anon;
4536 nhdr->b_l1hdr.b_arc_access = 0;
4537 nhdr->b_l1hdr.b_tmp_cdata = NULL;
4538 nhdr->b_freeze_cksum = NULL;
4539
4540 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
4541 buf->b_hdr = nhdr;
4542 mutex_exit(&buf->b_evict_lock);
4543 (void) refcount_add_many(&arc_anon->arcs_size, blksz, buf);
4544 } else {
4545 mutex_exit(&buf->b_evict_lock);
4546 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
4547 /* protected by hash lock, or hdr is on arc_anon */
4548 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
4549 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4550 arc_change_state(arc_anon, hdr, hash_lock);
4551 hdr->b_l1hdr.b_arc_access = 0;
4552 mutex_exit(hash_lock);
4553
4554 buf_discard_identity(hdr);
4555 arc_buf_thaw(buf);
4556 }
4557 buf->b_efunc = NULL;
4558 buf->b_private = NULL;
4559 }
4560
4561 int
4562 arc_released(arc_buf_t *buf)
4563 {
4564 int released;
4565
4566 mutex_enter(&buf->b_evict_lock);
4567 released = (buf->b_data != NULL &&
4568 buf->b_hdr->b_l1hdr.b_state == arc_anon);
4569 mutex_exit(&buf->b_evict_lock);
4570 return (released);
4571 }
4572
4573 #ifdef ZFS_DEBUG
4574 int
4575 arc_referenced(arc_buf_t *buf)
4576 {
4577 int referenced;
4578
4579 mutex_enter(&buf->b_evict_lock);
4580 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
4581 mutex_exit(&buf->b_evict_lock);
4582 return (referenced);
4583 }
4584 #endif
4585
4586 static void
4587 arc_write_ready(zio_t *zio)
4588 {
4589 arc_write_callback_t *callback = zio->io_private;
4590 arc_buf_t *buf = callback->awcb_buf;
4591 arc_buf_hdr_t *hdr = buf->b_hdr;
4592
4593 ASSERT(HDR_HAS_L1HDR(hdr));
4594 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
4595 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
4596 callback->awcb_ready(zio, buf, callback->awcb_private);
4597
4598 /*
4599 * If the IO is already in progress, then this is a re-write
4600 * attempt, so we need to thaw and re-compute the cksum.
4601 * It is the responsibility of the callback to handle the
4602 * accounting for any re-write attempt.
4603 */
4604 if (HDR_IO_IN_PROGRESS(hdr)) {
4605 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
4606 if (hdr->b_freeze_cksum != NULL) {
4607 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
4608 hdr->b_freeze_cksum = NULL;
4609 }
4610 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
4611 }
4612 arc_cksum_compute(buf, B_FALSE);
4613 hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
4614 }
4615
4616 /*
4617 * The SPA calls this callback for each physical write that happens on behalf
4618 * of a logical write. See the comment in dbuf_write_physdone() for details.
4619 */
4620 static void
4621 arc_write_physdone(zio_t *zio)
4622 {
4623 arc_write_callback_t *cb = zio->io_private;
4624 if (cb->awcb_physdone != NULL)
4625 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
4626 }
4627
4628 static void
4629 arc_write_done(zio_t *zio)
4630 {
4631 arc_write_callback_t *callback = zio->io_private;
4632 arc_buf_t *buf = callback->awcb_buf;
4633 arc_buf_hdr_t *hdr = buf->b_hdr;
4634
4635 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4636
4637 if (zio->io_error == 0) {
4638 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
4639 buf_discard_identity(hdr);
4640 } else {
4641 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
4642 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
4643 }
4644 } else {
4645 ASSERT(BUF_EMPTY(hdr));
4646 }
4647
4648 /*
4649 * If the block to be written was all-zero or compressed enough to be
4650 * embedded in the BP, no write was performed so there will be no
4651 * dva/birth/checksum. The buffer must therefore remain anonymous
4652 * (and uncached).
4653 */
4654 if (!BUF_EMPTY(hdr)) {
4655 arc_buf_hdr_t *exists;
4656 kmutex_t *hash_lock;
4657
4658 ASSERT(zio->io_error == 0);
4659
4660 arc_cksum_verify(buf);
4661
4662 exists = buf_hash_insert(hdr, &hash_lock);
4663 if (exists != NULL) {
4664 /*
4665 * This can only happen if we overwrite for
4666 * sync-to-convergence, because we remove
4667 * buffers from the hash table when we arc_free().
4668 */
4669 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
4670 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
4671 panic("bad overwrite, hdr=%p exists=%p",
4672 (void *)hdr, (void *)exists);
4673 ASSERT(refcount_is_zero(
4674 &exists->b_l1hdr.b_refcnt));
4675 arc_change_state(arc_anon, exists, hash_lock);
4676 mutex_exit(hash_lock);
4677 arc_hdr_destroy(exists);
4678 exists = buf_hash_insert(hdr, &hash_lock);
4679 ASSERT3P(exists, ==, NULL);
4680 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
4681 /* nopwrite */
4682 ASSERT(zio->io_prop.zp_nopwrite);
4683 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
4684 panic("bad nopwrite, hdr=%p exists=%p",
4685 (void *)hdr, (void *)exists);
4686 } else {
4687 /* Dedup */
4688 ASSERT(hdr->b_l1hdr.b_datacnt == 1);
4689 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
4690 ASSERT(BP_GET_DEDUP(zio->io_bp));
4691 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
4692 }
4693 }
4694 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
4695 /* if it's not anon, we are doing a scrub */
4696 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
4697 arc_access(hdr, hash_lock);
4698 mutex_exit(hash_lock);
4699 } else {
4700 hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
4701 }
4702
4703 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4704 callback->awcb_done(zio, buf, callback->awcb_private);
4705
4706 kmem_free(callback, sizeof (arc_write_callback_t));
4707 }
4708
4709 zio_t *
4710 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
4711 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
4712 const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
4713 arc_done_func_t *done, void *private, zio_priority_t priority,
4714 int zio_flags, const zbookmark_phys_t *zb)
4715 {
4716 arc_buf_hdr_t *hdr = buf->b_hdr;
4717 arc_write_callback_t *callback;
4718 zio_t *zio;
4719
4720 ASSERT(ready != NULL);
4721 ASSERT(done != NULL);
4722 ASSERT(!HDR_IO_ERROR(hdr));
4723 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4724 ASSERT(hdr->b_l1hdr.b_acb == NULL);
4725 ASSERT(hdr->b_l1hdr.b_datacnt > 0);
4726 if (l2arc)
4727 hdr->b_flags |= ARC_FLAG_L2CACHE;
4728 if (l2arc_compress)
4729 hdr->b_flags |= ARC_FLAG_L2COMPRESS;
4730 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
4731 callback->awcb_ready = ready;
4732 callback->awcb_physdone = physdone;
4733 callback->awcb_done = done;
4734 callback->awcb_private = private;
4735 callback->awcb_buf = buf;
4736
4737 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
4738 arc_write_ready, arc_write_physdone, arc_write_done, callback,
4739 priority, zio_flags, zb);
4740
4741 return (zio);
4742 }
4743
4744 static int
4745 arc_memory_throttle(uint64_t reserve, uint64_t txg)
4746 {
4747 #ifdef _KERNEL
4748 uint64_t available_memory = ptob(freemem);
4749 static uint64_t page_load = 0;
4750 static uint64_t last_txg = 0;
4751
4752 #if defined(__i386)
4753 available_memory =
4754 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
4755 #endif
4756
4757 if (freemem > physmem * arc_lotsfree_percent / 100)
4758 return (0);
4759
4760 if (txg > last_txg) {
4761 last_txg = txg;
4762 page_load = 0;
4763 }
4764 /*
4765 * If we are in pageout, we know that memory is already tight,
4766 * the arc is already going to be evicting, so we just want to
4767 * continue to let page writes occur as quickly as possible.
4768 */
4769 if (curproc == proc_pageout) {
4770 if (page_load > MAX(ptob(minfree), available_memory) / 4)
4771 return (SET_ERROR(ERESTART));
4772 /* Note: reserve is inflated, so we deflate */
4773 page_load += reserve / 8;
4774 return (0);
4775 } else if (page_load > 0 && arc_reclaim_needed()) {
4776 /* memory is low, delay before restarting */
4777 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
4778 return (SET_ERROR(EAGAIN));
4779 }
4780 page_load = 0;
4781 #endif
4782 return (0);
4783 }
4784
4785 void
4786 arc_tempreserve_clear(uint64_t reserve)
4787 {
4788 atomic_add_64(&arc_tempreserve, -reserve);
4789 ASSERT((int64_t)arc_tempreserve >= 0);
4790 }
4791
4792 int
4793 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
4794 {
4795 int error;
4796 uint64_t anon_size;
4797
4798 if (reserve > arc_c/4 && !arc_no_grow)
4799 arc_c = MIN(arc_c_max, reserve * 4);
4800 if (reserve > arc_c)
4801 return (SET_ERROR(ENOMEM));
4802
4803 /*
4804 * Don't count loaned bufs as in flight dirty data to prevent long
4805 * network delays from blocking transactions that are ready to be
4806 * assigned to a txg.
4807 */
4808 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
4809 arc_loaned_bytes), 0);
4810
4811 /*
4812 * Writes will, almost always, require additional memory allocations
4813 * in order to compress/encrypt/etc the data. We therefore need to
4814 * make sure that there is sufficient available memory for this.
4815 */
4816 error = arc_memory_throttle(reserve, txg);
4817 if (error != 0)
4818 return (error);
4819
4820 /*
4821 * Throttle writes when the amount of dirty data in the cache
4822 * gets too large. We try to keep the cache less than half full
4823 * of dirty blocks so that our sync times don't grow too large.
4824 * Note: if two requests come in concurrently, we might let them
4825 * both succeed, when one of them should fail. Not a huge deal.
4826 */
4827
4828 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
4829 anon_size > arc_c / 4) {
4830 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
4831 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
4832 arc_tempreserve>>10,
4833 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
4834 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
4835 reserve>>10, arc_c>>10);
4836 return (SET_ERROR(ERESTART));
4837 }
4838 atomic_add_64(&arc_tempreserve, reserve);
4839 return (0);
4840 }
4841
4842 static void
4843 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
4844 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
4845 {
4846 size->value.ui64 = refcount_count(&state->arcs_size);
4847 evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA];
4848 evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA];
4849 }
4850
4851 static int
4852 arc_kstat_update(kstat_t *ksp, int rw)
4853 {
4854 arc_stats_t *as = ksp->ks_data;
4855
4856 if (rw == KSTAT_WRITE) {
4857 return (EACCES);
4858 } else {
4859 arc_kstat_update_state(arc_anon,
4860 &as->arcstat_anon_size,
4861 &as->arcstat_anon_evictable_data,
4862 &as->arcstat_anon_evictable_metadata);
4863 arc_kstat_update_state(arc_mru,
4864 &as->arcstat_mru_size,
4865 &as->arcstat_mru_evictable_data,
4866 &as->arcstat_mru_evictable_metadata);
4867 arc_kstat_update_state(arc_mru_ghost,
4868 &as->arcstat_mru_ghost_size,
4869 &as->arcstat_mru_ghost_evictable_data,
4870 &as->arcstat_mru_ghost_evictable_metadata);
4871 arc_kstat_update_state(arc_mfu,
4872 &as->arcstat_mfu_size,
4873 &as->arcstat_mfu_evictable_data,
4874 &as->arcstat_mfu_evictable_metadata);
4875 arc_kstat_update_state(arc_mfu_ghost,
4876 &as->arcstat_mfu_ghost_size,
4877 &as->arcstat_mfu_ghost_evictable_data,
4878 &as->arcstat_mfu_ghost_evictable_metadata);
4879 }
4880
4881 return (0);
4882 }
4883
4884 /*
4885 * This function *must* return indices evenly distributed between all
4886 * sublists of the multilist. This is needed due to how the ARC eviction
4887 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
4888 * distributed between all sublists and uses this assumption when
4889 * deciding which sublist to evict from and how much to evict from it.
4890 */
4891 unsigned int
4892 arc_state_multilist_index_func(multilist_t *ml, void *obj)
4893 {
4894 arc_buf_hdr_t *hdr = obj;
4895
4896 /*
4897 * We rely on b_dva to generate evenly distributed index
4898 * numbers using buf_hash below. So, as an added precaution,
4899 * let's make sure we never add empty buffers to the arc lists.
4900 */
4901 ASSERT(!BUF_EMPTY(hdr));
4902
4903 /*
4904 * The assumption here, is the hash value for a given
4905 * arc_buf_hdr_t will remain constant throughout it's lifetime
4906 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
4907 * Thus, we don't need to store the header's sublist index
4908 * on insertion, as this index can be recalculated on removal.
4909 *
4910 * Also, the low order bits of the hash value are thought to be
4911 * distributed evenly. Otherwise, in the case that the multilist
4912 * has a power of two number of sublists, each sublists' usage
4913 * would not be evenly distributed.
4914 */
4915 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
4916 multilist_get_num_sublists(ml));
4917 }
4918
4919 void
4920 arc_init(void)
4921 {
4922 /*
4923 * allmem is "all memory that we could possibly use".
4924 */
4925 #ifdef _KERNEL
4926 uint64_t allmem = ptob(physmem - swapfs_minfree);
4927 #else
4928 uint64_t allmem = (physmem * PAGESIZE) / 2;
4929 #endif
4930
4931 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
4932 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
4933 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
4934
4935 mutex_init(&arc_user_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
4936 cv_init(&arc_user_evicts_cv, NULL, CV_DEFAULT, NULL);
4937
4938 /* Convert seconds to clock ticks */
4939 arc_min_prefetch_lifespan = 1 * hz;
4940
4941 /* Start out with 1/8 of all memory */
4942 arc_c = allmem / 8;
4943
4944 #ifdef _KERNEL
4945 /*
4946 * On architectures where the physical memory can be larger
4947 * than the addressable space (intel in 32-bit mode), we may
4948 * need to limit the cache to 1/8 of VM size.
4949 */
4950 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
4951 #endif
4952
4953 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
4954 arc_c_min = MAX(allmem / 32, 64 << 20);
4955 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
4956 if (allmem >= 1 << 30)
4957 arc_c_max = allmem - (1 << 30);
4958 else
4959 arc_c_max = arc_c_min;
4960 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
4961
4962 /*
4963 * Allow the tunables to override our calculations if they are
4964 * reasonable (ie. over 64MB)
4965 */
4966 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem)
4967 arc_c_max = zfs_arc_max;
4968 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
4969 arc_c_min = zfs_arc_min;
4970
4971 arc_c = arc_c_max;
4972 arc_p = (arc_c >> 1);
4973
4974 /* limit meta-data to 1/4 of the arc capacity */
4975 arc_meta_limit = arc_c_max / 4;
4976
4977 /* Allow the tunable to override if it is reasonable */
4978 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
4979 arc_meta_limit = zfs_arc_meta_limit;
4980
4981 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
4982 arc_c_min = arc_meta_limit / 2;
4983
4984 if (zfs_arc_meta_min > 0) {
4985 arc_meta_min = zfs_arc_meta_min;
4986 } else {
4987 arc_meta_min = arc_c_min / 2;
4988 }
4989
4990 if (zfs_arc_grow_retry > 0)
4991 arc_grow_retry = zfs_arc_grow_retry;
4992
4993 if (zfs_arc_shrink_shift > 0)
4994 arc_shrink_shift = zfs_arc_shrink_shift;
4995
4996 /*
4997 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
4998 */
4999 if (arc_no_grow_shift >= arc_shrink_shift)
5000 arc_no_grow_shift = arc_shrink_shift - 1;
5001
5002 if (zfs_arc_p_min_shift > 0)
5003 arc_p_min_shift = zfs_arc_p_min_shift;
5004
5005 if (zfs_arc_num_sublists_per_state < 1)
5006 zfs_arc_num_sublists_per_state = MAX(boot_ncpus, 1);
5007
5008 /* if kmem_flags are set, lets try to use less memory */
5009 if (kmem_debugging())
5010 arc_c = arc_c / 2;
5011 if (arc_c < arc_c_min)
5012 arc_c = arc_c_min;
5013
5014 arc_anon = &ARC_anon;
5015 arc_mru = &ARC_mru;
5016 arc_mru_ghost = &ARC_mru_ghost;
5017 arc_mfu = &ARC_mfu;
5018 arc_mfu_ghost = &ARC_mfu_ghost;
5019 arc_l2c_only = &ARC_l2c_only;
5020 arc_size = 0;
5021
5022 multilist_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
5023 sizeof (arc_buf_hdr_t),
5024 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5025 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5026 multilist_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
5027 sizeof (arc_buf_hdr_t),
5028 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5029 zfs_arc_num_sublists_per_state, arc_state_multilist_index_func);
5030 multilist_create(&arc_mru_ghost->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_ghost->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_mfu->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_mfu->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_ghost->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_ghost->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_l2c_only->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_l2c_only->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
5063 refcount_create(&arc_anon->arcs_size);
5064 refcount_create(&arc_mru->arcs_size);
5065 refcount_create(&arc_mru_ghost->arcs_size);
5066 refcount_create(&arc_mfu->arcs_size);
5067 refcount_create(&arc_mfu_ghost->arcs_size);
5068 refcount_create(&arc_l2c_only->arcs_size);
5069
5070 buf_init();
5071
5072 arc_reclaim_thread_exit = FALSE;
5073 arc_user_evicts_thread_exit = FALSE;
5074 arc_eviction_list = NULL;
5075 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
5076
5077 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
5078 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
5079
5080 if (arc_ksp != NULL) {
5081 arc_ksp->ks_data = &arc_stats;
5082 arc_ksp->ks_update = arc_kstat_update;
5083 kstat_install(arc_ksp);
5084 }
5085
5086 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
5087 TS_RUN, minclsyspri);
5088
5089 (void) thread_create(NULL, 0, arc_user_evicts_thread, NULL, 0, &p0,
5090 TS_RUN, minclsyspri);
5091
5092 arc_dead = FALSE;
5093 arc_warm = B_FALSE;
5094
5095 /*
5096 * Calculate maximum amount of dirty data per pool.
5097 *
5098 * If it has been set by /etc/system, take that.
5099 * Otherwise, use a percentage of physical memory defined by
5100 * zfs_dirty_data_max_percent (default 10%) with a cap at
5101 * zfs_dirty_data_max_max (default 4GB).
5102 */
5103 if (zfs_dirty_data_max == 0) {
5104 zfs_dirty_data_max = physmem * PAGESIZE *
5105 zfs_dirty_data_max_percent / 100;
5106 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
5107 zfs_dirty_data_max_max);
5108 }
5109 }
5110
5111 void
5112 arc_fini(void)
5113 {
5114 mutex_enter(&arc_reclaim_lock);
5115 arc_reclaim_thread_exit = TRUE;
5116 /*
5117 * The reclaim thread will set arc_reclaim_thread_exit back to
5118 * FALSE when it is finished exiting; we're waiting for that.
5119 */
5120 while (arc_reclaim_thread_exit) {
5121 cv_signal(&arc_reclaim_thread_cv);
5122 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
5123 }
5124 mutex_exit(&arc_reclaim_lock);
5125
5126 mutex_enter(&arc_user_evicts_lock);
5127 arc_user_evicts_thread_exit = TRUE;
5128 /*
5129 * The user evicts thread will set arc_user_evicts_thread_exit
5130 * to FALSE when it is finished exiting; we're waiting for that.
5131 */
5132 while (arc_user_evicts_thread_exit) {
5133 cv_signal(&arc_user_evicts_cv);
5134 cv_wait(&arc_user_evicts_cv, &arc_user_evicts_lock);
5135 }
5136 mutex_exit(&arc_user_evicts_lock);
5137
5138 /* Use TRUE to ensure *all* buffers are evicted */
5139 arc_flush(NULL, TRUE);
5140
5141 arc_dead = TRUE;
5142
5143 if (arc_ksp != NULL) {
5144 kstat_delete(arc_ksp);
5145 arc_ksp = NULL;
5146 }
5147
5148 mutex_destroy(&arc_reclaim_lock);
5149 cv_destroy(&arc_reclaim_thread_cv);
5150 cv_destroy(&arc_reclaim_waiters_cv);
5151
5152 mutex_destroy(&arc_user_evicts_lock);
5153 cv_destroy(&arc_user_evicts_cv);
5154
5155 refcount_destroy(&arc_anon->arcs_size);
5156 refcount_destroy(&arc_mru->arcs_size);
5157 refcount_destroy(&arc_mru_ghost->arcs_size);
5158 refcount_destroy(&arc_mfu->arcs_size);
5159 refcount_destroy(&arc_mfu_ghost->arcs_size);
5160 refcount_destroy(&arc_l2c_only->arcs_size);
5161
5162 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
5163 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
5164 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
5165 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
5166 multilist_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
5167 multilist_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
5168 multilist_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
5169 multilist_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
5170
5171 buf_fini();
5172
5173 ASSERT0(arc_loaned_bytes);
5174 }
5175
5176 /*
5177 * Level 2 ARC
5178 *
5179 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
5180 * It uses dedicated storage devices to hold cached data, which are populated
5181 * using large infrequent writes. The main role of this cache is to boost
5182 * the performance of random read workloads. The intended L2ARC devices
5183 * include short-stroked disks, solid state disks, and other media with
5184 * substantially faster read latency than disk.
5185 *
5186 * +-----------------------+
5187 * | ARC |
5188 * +-----------------------+
5189 * | ^ ^
5190 * | | |
5191 * l2arc_feed_thread() arc_read()
5192 * | | |
5193 * | l2arc read |
5194 * V | |
5195 * +---------------+ |
5196 * | L2ARC | |
5197 * +---------------+ |
5198 * | ^ |
5199 * l2arc_write() | |
5200 * | | |
5201 * V | |
5202 * +-------+ +-------+
5203 * | vdev | | vdev |
5204 * | cache | | cache |
5205 * +-------+ +-------+
5206 * +=========+ .-----.
5207 * : L2ARC : |-_____-|
5208 * : devices : | Disks |
5209 * +=========+ `-_____-'
5210 *
5211 * Read requests are satisfied from the following sources, in order:
5212 *
5213 * 1) ARC
5214 * 2) vdev cache of L2ARC devices
5215 * 3) L2ARC devices
5216 * 4) vdev cache of disks
5217 * 5) disks
5218 *
5219 * Some L2ARC device types exhibit extremely slow write performance.
5220 * To accommodate for this there are some significant differences between
5221 * the L2ARC and traditional cache design:
5222 *
5223 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
5224 * the ARC behave as usual, freeing buffers and placing headers on ghost
5225 * lists. The ARC does not send buffers to the L2ARC during eviction as
5226 * this would add inflated write latencies for all ARC memory pressure.
5227 *
5228 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
5229 * It does this by periodically scanning buffers from the eviction-end of
5230 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
5231 * not already there. It scans until a headroom of buffers is satisfied,
5232 * which itself is a buffer for ARC eviction. If a compressible buffer is
5233 * found during scanning and selected for writing to an L2ARC device, we
5234 * temporarily boost scanning headroom during the next scan cycle to make
5235 * sure we adapt to compression effects (which might significantly reduce
5236 * the data volume we write to L2ARC). The thread that does this is
5237 * l2arc_feed_thread(), illustrated below; example sizes are included to
5238 * provide a better sense of ratio than this diagram:
5239 *
5240 * head --> tail
5241 * +---------------------+----------+
5242 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
5243 * +---------------------+----------+ | o L2ARC eligible
5244 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
5245 * +---------------------+----------+ |
5246 * 15.9 Gbytes ^ 32 Mbytes |
5247 * headroom |
5248 * l2arc_feed_thread()
5249 * |
5250 * l2arc write hand <--[oooo]--'
5251 * | 8 Mbyte
5252 * | write max
5253 * V
5254 * +==============================+
5255 * L2ARC dev |####|#|###|###| |####| ... |
5256 * +==============================+
5257 * 32 Gbytes
5258 *
5259 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
5260 * evicted, then the L2ARC has cached a buffer much sooner than it probably
5261 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
5262 * safe to say that this is an uncommon case, since buffers at the end of
5263 * the ARC lists have moved there due to inactivity.
5264 *
5265 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
5266 * then the L2ARC simply misses copying some buffers. This serves as a
5267 * pressure valve to prevent heavy read workloads from both stalling the ARC
5268 * with waits and clogging the L2ARC with writes. This also helps prevent
5269 * the potential for the L2ARC to churn if it attempts to cache content too
5270 * quickly, such as during backups of the entire pool.
5271 *
5272 * 5. After system boot and before the ARC has filled main memory, there are
5273 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
5274 * lists can remain mostly static. Instead of searching from tail of these
5275 * lists as pictured, the l2arc_feed_thread() will search from the list heads
5276 * for eligible buffers, greatly increasing its chance of finding them.
5277 *
5278 * The L2ARC device write speed is also boosted during this time so that
5279 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
5280 * there are no L2ARC reads, and no fear of degrading read performance
5281 * through increased writes.
5282 *
5283 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
5284 * the vdev queue can aggregate them into larger and fewer writes. Each
5285 * device is written to in a rotor fashion, sweeping writes through
5286 * available space then repeating.
5287 *
5288 * 7. The L2ARC does not store dirty content. It never needs to flush
5289 * write buffers back to disk based storage.
5290 *
5291 * 8. If an ARC buffer is written (and dirtied) which also exists in the
5292 * L2ARC, the now stale L2ARC buffer is immediately dropped.
5293 *
5294 * The performance of the L2ARC can be tweaked by a number of tunables, which
5295 * may be necessary for different workloads:
5296 *
5297 * l2arc_write_max max write bytes per interval
5298 * l2arc_write_boost extra write bytes during device warmup
5299 * l2arc_noprefetch skip caching prefetched buffers
5300 * l2arc_headroom number of max device writes to precache
5301 * l2arc_headroom_boost when we find compressed buffers during ARC
5302 * scanning, we multiply headroom by this
5303 * percentage factor for the next scan cycle,
5304 * since more compressed buffers are likely to
5305 * be present
5306 * l2arc_feed_secs seconds between L2ARC writing
5307 *
5308 * Tunables may be removed or added as future performance improvements are
5309 * integrated, and also may become zpool properties.
5310 *
5311 * There are three key functions that control how the L2ARC warms up:
5312 *
5313 * l2arc_write_eligible() check if a buffer is eligible to cache
5314 * l2arc_write_size() calculate how much to write
5315 * l2arc_write_interval() calculate sleep delay between writes
5316 *
5317 * These three functions determine what to write, how much, and how quickly
5318 * to send writes.
5319 */
5320
5321 static boolean_t
5322 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
5323 {
5324 /*
5325 * A buffer is *not* eligible for the L2ARC if it:
5326 * 1. belongs to a different spa.
5327 * 2. is already cached on the L2ARC.
5328 * 3. has an I/O in progress (it may be an incomplete read).
5329 * 4. is flagged not eligible (zfs property).
5330 */
5331 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
5332 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
5333 return (B_FALSE);
5334
5335 return (B_TRUE);
5336 }
5337
5338 static uint64_t
5339 l2arc_write_size(void)
5340 {
5341 uint64_t size;
5342
5343 /*
5344 * Make sure our globals have meaningful values in case the user
5345 * altered them.
5346 */
5347 size = l2arc_write_max;
5348 if (size == 0) {
5349 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
5350 "be greater than zero, resetting it to the default (%d)",
5351 L2ARC_WRITE_SIZE);
5352 size = l2arc_write_max = L2ARC_WRITE_SIZE;
5353 }
5354
5355 if (arc_warm == B_FALSE)
5356 size += l2arc_write_boost;
5357
5358 return (size);
5359
5360 }
5361
5362 static clock_t
5363 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
5364 {
5365 clock_t interval, next, now;
5366
5367 /*
5368 * If the ARC lists are busy, increase our write rate; if the
5369 * lists are stale, idle back. This is achieved by checking
5370 * how much we previously wrote - if it was more than half of
5371 * what we wanted, schedule the next write much sooner.
5372 */
5373 if (l2arc_feed_again && wrote > (wanted / 2))
5374 interval = (hz * l2arc_feed_min_ms) / 1000;
5375 else
5376 interval = hz * l2arc_feed_secs;
5377
5378 now = ddi_get_lbolt();
5379 next = MAX(now, MIN(now + interval, began + interval));
5380
5381 return (next);
5382 }
5383
5384 /*
5385 * Cycle through L2ARC devices. This is how L2ARC load balances.
5386 * If a device is returned, this also returns holding the spa config lock.
5387 */
5388 static l2arc_dev_t *
5389 l2arc_dev_get_next(void)
5390 {
5391 l2arc_dev_t *first, *next = NULL;
5392
5393 /*
5394 * Lock out the removal of spas (spa_namespace_lock), then removal
5395 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
5396 * both locks will be dropped and a spa config lock held instead.
5397 */
5398 mutex_enter(&spa_namespace_lock);
5399 mutex_enter(&l2arc_dev_mtx);
5400
5401 /* if there are no vdevs, there is nothing to do */
5402 if (l2arc_ndev == 0)
5403 goto out;
5404
5405 first = NULL;
5406 next = l2arc_dev_last;
5407 do {
5408 /* loop around the list looking for a non-faulted vdev */
5409 if (next == NULL) {
5410 next = list_head(l2arc_dev_list);
5411 } else {
5412 next = list_next(l2arc_dev_list, next);
5413 if (next == NULL)
5414 next = list_head(l2arc_dev_list);
5415 }
5416
5417 /* if we have come back to the start, bail out */
5418 if (first == NULL)
5419 first = next;
5420 else if (next == first)
5421 break;
5422
5423 } while (vdev_is_dead(next->l2ad_vdev));
5424
5425 /* if we were unable to find any usable vdevs, return NULL */
5426 if (vdev_is_dead(next->l2ad_vdev))
5427 next = NULL;
5428
5429 l2arc_dev_last = next;
5430
5431 out:
5432 mutex_exit(&l2arc_dev_mtx);
5433
5434 /*
5435 * Grab the config lock to prevent the 'next' device from being
5436 * removed while we are writing to it.
5437 */
5438 if (next != NULL)
5439 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
5440 mutex_exit(&spa_namespace_lock);
5441
5442 return (next);
5443 }
5444
5445 /*
5446 * Free buffers that were tagged for destruction.
5447 */
5448 static void
5449 l2arc_do_free_on_write()
5450 {
5451 list_t *buflist;
5452 l2arc_data_free_t *df, *df_prev;
5453
5454 mutex_enter(&l2arc_free_on_write_mtx);
5455 buflist = l2arc_free_on_write;
5456
5457 for (df = list_tail(buflist); df; df = df_prev) {
5458 df_prev = list_prev(buflist, df);
5459 ASSERT(df->l2df_data != NULL);
5460 ASSERT(df->l2df_func != NULL);
5461 df->l2df_func(df->l2df_data, df->l2df_size);
5462 list_remove(buflist, df);
5463 kmem_free(df, sizeof (l2arc_data_free_t));
5464 }
5465
5466 mutex_exit(&l2arc_free_on_write_mtx);
5467 }
5468
5469 /*
5470 * A write to a cache device has completed. Update all headers to allow
5471 * reads from these buffers to begin.
5472 */
5473 static void
5474 l2arc_write_done(zio_t *zio)
5475 {
5476 l2arc_write_callback_t *cb;
5477 l2arc_dev_t *dev;
5478 list_t *buflist;
5479 arc_buf_hdr_t *head, *hdr, *hdr_prev;
5480 kmutex_t *hash_lock;
5481 int64_t bytes_dropped = 0;
5482
5483 cb = zio->io_private;
5484 ASSERT(cb != NULL);
5485 dev = cb->l2wcb_dev;
5486 ASSERT(dev != NULL);
5487 head = cb->l2wcb_head;
5488 ASSERT(head != NULL);
5489 buflist = &dev->l2ad_buflist;
5490 ASSERT(buflist != NULL);
5491 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
5492 l2arc_write_callback_t *, cb);
5493
5494 if (zio->io_error != 0)
5495 ARCSTAT_BUMP(arcstat_l2_writes_error);
5496
5497 /*
5498 * All writes completed, or an error was hit.
5499 */
5500 top:
5501 mutex_enter(&dev->l2ad_mtx);
5502 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
5503 hdr_prev = list_prev(buflist, hdr);
5504
5505 hash_lock = HDR_LOCK(hdr);
5506
5507 /*
5508 * We cannot use mutex_enter or else we can deadlock
5509 * with l2arc_write_buffers (due to swapping the order
5510 * the hash lock and l2ad_mtx are taken).
5511 */
5512 if (!mutex_tryenter(hash_lock)) {
5513 /*
5514 * Missed the hash lock. We must retry so we
5515 * don't leave the ARC_FLAG_L2_WRITING bit set.
5516 */
5517 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
5518
5519 /*
5520 * We don't want to rescan the headers we've
5521 * already marked as having been written out, so
5522 * we reinsert the head node so we can pick up
5523 * where we left off.
5524 */
5525 list_remove(buflist, head);
5526 list_insert_after(buflist, hdr, head);
5527
5528 mutex_exit(&dev->l2ad_mtx);
5529
5530 /*
5531 * We wait for the hash lock to become available
5532 * to try and prevent busy waiting, and increase
5533 * the chance we'll be able to acquire the lock
5534 * the next time around.
5535 */
5536 mutex_enter(hash_lock);
5537 mutex_exit(hash_lock);
5538 goto top;
5539 }
5540
5541 /*
5542 * We could not have been moved into the arc_l2c_only
5543 * state while in-flight due to our ARC_FLAG_L2_WRITING
5544 * bit being set. Let's just ensure that's being enforced.
5545 */
5546 ASSERT(HDR_HAS_L1HDR(hdr));
5547
5548 /*
5549 * We may have allocated a buffer for L2ARC compression,
5550 * we must release it to avoid leaking this data.
5551 */
5552 l2arc_release_cdata_buf(hdr);
5553
5554 if (zio->io_error != 0) {
5555 /*
5556 * Error - drop L2ARC entry.
5557 */
5558 list_remove(buflist, hdr);
5559 hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
5560
5561 ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize);
5562 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
5563
5564 bytes_dropped += hdr->b_l2hdr.b_asize;
5565 (void) refcount_remove_many(&dev->l2ad_alloc,
5566 hdr->b_l2hdr.b_asize, hdr);
5567 }
5568
5569 /*
5570 * Allow ARC to begin reads and ghost list evictions to
5571 * this L2ARC entry.
5572 */
5573 hdr->b_flags &= ~ARC_FLAG_L2_WRITING;
5574
5575 mutex_exit(hash_lock);
5576 }
5577
5578 atomic_inc_64(&l2arc_writes_done);
5579 list_remove(buflist, head);
5580 ASSERT(!HDR_HAS_L1HDR(head));
5581 kmem_cache_free(hdr_l2only_cache, head);
5582 mutex_exit(&dev->l2ad_mtx);
5583
5584 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
5585
5586 l2arc_do_free_on_write();
5587
5588 kmem_free(cb, sizeof (l2arc_write_callback_t));
5589 }
5590
5591 /*
5592 * A read to a cache device completed. Validate buffer contents before
5593 * handing over to the regular ARC routines.
5594 */
5595 static void
5596 l2arc_read_done(zio_t *zio)
5597 {
5598 l2arc_read_callback_t *cb;
5599 arc_buf_hdr_t *hdr;
5600 arc_buf_t *buf;
5601 kmutex_t *hash_lock;
5602 int equal;
5603
5604 ASSERT(zio->io_vd != NULL);
5605 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
5606
5607 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
5608
5609 cb = zio->io_private;
5610 ASSERT(cb != NULL);
5611 buf = cb->l2rcb_buf;
5612 ASSERT(buf != NULL);
5613
5614 hash_lock = HDR_LOCK(buf->b_hdr);
5615 mutex_enter(hash_lock);
5616 hdr = buf->b_hdr;
5617 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5618
5619 /*
5620 * If the buffer was compressed, decompress it first.
5621 */
5622 if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
5623 l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
5624 ASSERT(zio->io_data != NULL);
5625 ASSERT3U(zio->io_size, ==, hdr->b_size);
5626 ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size);
5627
5628 /*
5629 * Check this survived the L2ARC journey.
5630 */
5631 equal = arc_cksum_equal(buf);
5632 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
5633 mutex_exit(hash_lock);
5634 zio->io_private = buf;
5635 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
5636 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
5637 arc_read_done(zio);
5638 } else {
5639 mutex_exit(hash_lock);
5640 /*
5641 * Buffer didn't survive caching. Increment stats and
5642 * reissue to the original storage device.
5643 */
5644 if (zio->io_error != 0) {
5645 ARCSTAT_BUMP(arcstat_l2_io_error);
5646 } else {
5647 zio->io_error = SET_ERROR(EIO);
5648 }
5649 if (!equal)
5650 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
5651
5652 /*
5653 * If there's no waiter, issue an async i/o to the primary
5654 * storage now. If there *is* a waiter, the caller must
5655 * issue the i/o in a context where it's OK to block.
5656 */
5657 if (zio->io_waiter == NULL) {
5658 zio_t *pio = zio_unique_parent(zio);
5659
5660 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
5661
5662 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
5663 buf->b_data, hdr->b_size, arc_read_done, buf,
5664 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
5665 }
5666 }
5667
5668 kmem_free(cb, sizeof (l2arc_read_callback_t));
5669 }
5670
5671 /*
5672 * This is the list priority from which the L2ARC will search for pages to
5673 * cache. This is used within loops (0..3) to cycle through lists in the
5674 * desired order. This order can have a significant effect on cache
5675 * performance.
5676 *
5677 * Currently the metadata lists are hit first, MFU then MRU, followed by
5678 * the data lists. This function returns a locked list, and also returns
5679 * the lock pointer.
5680 */
5681 static multilist_sublist_t *
5682 l2arc_sublist_lock(int list_num)
5683 {
5684 multilist_t *ml = NULL;
5685 unsigned int idx;
5686
5687 ASSERT(list_num >= 0 && list_num <= 3);
5688
5689 switch (list_num) {
5690 case 0:
5691 ml = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
5692 break;
5693 case 1:
5694 ml = &arc_mru->arcs_list[ARC_BUFC_METADATA];
5695 break;
5696 case 2:
5697 ml = &arc_mfu->arcs_list[ARC_BUFC_DATA];
5698 break;
5699 case 3:
5700 ml = &arc_mru->arcs_list[ARC_BUFC_DATA];
5701 break;
5702 }
5703
5704 /*
5705 * Return a randomly-selected sublist. This is acceptable
5706 * because the caller feeds only a little bit of data for each
5707 * call (8MB). Subsequent calls will result in different
5708 * sublists being selected.
5709 */
5710 idx = multilist_get_random_index(ml);
5711 return (multilist_sublist_lock(ml, idx));
5712 }
5713
5714 /*
5715 * Evict buffers from the device write hand to the distance specified in
5716 * bytes. This distance may span populated buffers, it may span nothing.
5717 * This is clearing a region on the L2ARC device ready for writing.
5718 * If the 'all' boolean is set, every buffer is evicted.
5719 */
5720 static void
5721 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
5722 {
5723 list_t *buflist;
5724 arc_buf_hdr_t *hdr, *hdr_prev;
5725 kmutex_t *hash_lock;
5726 uint64_t taddr;
5727
5728 buflist = &dev->l2ad_buflist;
5729
5730 if (!all && dev->l2ad_first) {
5731 /*
5732 * This is the first sweep through the device. There is
5733 * nothing to evict.
5734 */
5735 return;
5736 }
5737
5738 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
5739 /*
5740 * When nearing the end of the device, evict to the end
5741 * before the device write hand jumps to the start.
5742 */
5743 taddr = dev->l2ad_end;
5744 } else {
5745 taddr = dev->l2ad_hand + distance;
5746 }
5747 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
5748 uint64_t, taddr, boolean_t, all);
5749
5750 top:
5751 mutex_enter(&dev->l2ad_mtx);
5752 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
5753 hdr_prev = list_prev(buflist, hdr);
5754
5755 hash_lock = HDR_LOCK(hdr);
5756
5757 /*
5758 * We cannot use mutex_enter or else we can deadlock
5759 * with l2arc_write_buffers (due to swapping the order
5760 * the hash lock and l2ad_mtx are taken).
5761 */
5762 if (!mutex_tryenter(hash_lock)) {
5763 /*
5764 * Missed the hash lock. Retry.
5765 */
5766 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
5767 mutex_exit(&dev->l2ad_mtx);
5768 mutex_enter(hash_lock);
5769 mutex_exit(hash_lock);
5770 goto top;
5771 }
5772
5773 if (HDR_L2_WRITE_HEAD(hdr)) {
5774 /*
5775 * We hit a write head node. Leave it for
5776 * l2arc_write_done().
5777 */
5778 list_remove(buflist, hdr);
5779 mutex_exit(hash_lock);
5780 continue;
5781 }
5782
5783 if (!all && HDR_HAS_L2HDR(hdr) &&
5784 (hdr->b_l2hdr.b_daddr > taddr ||
5785 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
5786 /*
5787 * We've evicted to the target address,
5788 * or the end of the device.
5789 */
5790 mutex_exit(hash_lock);
5791 break;
5792 }
5793
5794 ASSERT(HDR_HAS_L2HDR(hdr));
5795 if (!HDR_HAS_L1HDR(hdr)) {
5796 ASSERT(!HDR_L2_READING(hdr));
5797 /*
5798 * This doesn't exist in the ARC. Destroy.
5799 * arc_hdr_destroy() will call list_remove()
5800 * and decrement arcstat_l2_size.
5801 */
5802 arc_change_state(arc_anon, hdr, hash_lock);
5803 arc_hdr_destroy(hdr);
5804 } else {
5805 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
5806 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
5807 /*
5808 * Invalidate issued or about to be issued
5809 * reads, since we may be about to write
5810 * over this location.
5811 */
5812 if (HDR_L2_READING(hdr)) {
5813 ARCSTAT_BUMP(arcstat_l2_evict_reading);
5814 hdr->b_flags |= ARC_FLAG_L2_EVICTED;
5815 }
5816
5817 /* Ensure this header has finished being written */
5818 ASSERT(!HDR_L2_WRITING(hdr));
5819 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
5820
5821 arc_hdr_l2hdr_destroy(hdr);
5822 }
5823 mutex_exit(hash_lock);
5824 }
5825 mutex_exit(&dev->l2ad_mtx);
5826 }
5827
5828 /*
5829 * Find and write ARC buffers to the L2ARC device.
5830 *
5831 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
5832 * for reading until they have completed writing.
5833 * The headroom_boost is an in-out parameter used to maintain headroom boost
5834 * state between calls to this function.
5835 *
5836 * Returns the number of bytes actually written (which may be smaller than
5837 * the delta by which the device hand has changed due to alignment).
5838 */
5839 static uint64_t
5840 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
5841 boolean_t *headroom_boost)
5842 {
5843 arc_buf_hdr_t *hdr, *hdr_prev, *head;
5844 uint64_t write_asize, write_psize, write_sz, headroom,
5845 buf_compress_minsz;
5846 void *buf_data;
5847 boolean_t full;
5848 l2arc_write_callback_t *cb;
5849 zio_t *pio, *wzio;
5850 uint64_t guid = spa_load_guid(spa);
5851 const boolean_t do_headroom_boost = *headroom_boost;
5852
5853 ASSERT(dev->l2ad_vdev != NULL);
5854
5855 /* Lower the flag now, we might want to raise it again later. */
5856 *headroom_boost = B_FALSE;
5857
5858 pio = NULL;
5859 write_sz = write_asize = write_psize = 0;
5860 full = B_FALSE;
5861 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
5862 head->b_flags |= ARC_FLAG_L2_WRITE_HEAD;
5863 head->b_flags |= ARC_FLAG_HAS_L2HDR;
5864
5865 /*
5866 * We will want to try to compress buffers that are at least 2x the
5867 * device sector size.
5868 */
5869 buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
5870
5871 /*
5872 * Copy buffers for L2ARC writing.
5873 */
5874 for (int try = 0; try <= 3; try++) {
5875 multilist_sublist_t *mls = l2arc_sublist_lock(try);
5876 uint64_t passed_sz = 0;
5877
5878 /*
5879 * L2ARC fast warmup.
5880 *
5881 * Until the ARC is warm and starts to evict, read from the
5882 * head of the ARC lists rather than the tail.
5883 */
5884 if (arc_warm == B_FALSE)
5885 hdr = multilist_sublist_head(mls);
5886 else
5887 hdr = multilist_sublist_tail(mls);
5888
5889 headroom = target_sz * l2arc_headroom;
5890 if (do_headroom_boost)
5891 headroom = (headroom * l2arc_headroom_boost) / 100;
5892
5893 for (; hdr; hdr = hdr_prev) {
5894 kmutex_t *hash_lock;
5895 uint64_t buf_sz;
5896
5897 if (arc_warm == B_FALSE)
5898 hdr_prev = multilist_sublist_next(mls, hdr);
5899 else
5900 hdr_prev = multilist_sublist_prev(mls, hdr);
5901
5902 hash_lock = HDR_LOCK(hdr);
5903 if (!mutex_tryenter(hash_lock)) {
5904 /*
5905 * Skip this buffer rather than waiting.
5906 */
5907 continue;
5908 }
5909
5910 passed_sz += hdr->b_size;
5911 if (passed_sz > headroom) {
5912 /*
5913 * Searched too far.
5914 */
5915 mutex_exit(hash_lock);
5916 break;
5917 }
5918
5919 if (!l2arc_write_eligible(guid, hdr)) {
5920 mutex_exit(hash_lock);
5921 continue;
5922 }
5923
5924 if ((write_sz + hdr->b_size) > target_sz) {
5925 full = B_TRUE;
5926 mutex_exit(hash_lock);
5927 break;
5928 }
5929
5930 if (pio == NULL) {
5931 /*
5932 * Insert a dummy header on the buflist so
5933 * l2arc_write_done() can find where the
5934 * write buffers begin without searching.
5935 */
5936 mutex_enter(&dev->l2ad_mtx);
5937 list_insert_head(&dev->l2ad_buflist, head);
5938 mutex_exit(&dev->l2ad_mtx);
5939
5940 cb = kmem_alloc(
5941 sizeof (l2arc_write_callback_t), KM_SLEEP);
5942 cb->l2wcb_dev = dev;
5943 cb->l2wcb_head = head;
5944 pio = zio_root(spa, l2arc_write_done, cb,
5945 ZIO_FLAG_CANFAIL);
5946 }
5947
5948 /*
5949 * Create and add a new L2ARC header.
5950 */
5951 hdr->b_l2hdr.b_dev = dev;
5952 hdr->b_flags |= ARC_FLAG_L2_WRITING;
5953 /*
5954 * Temporarily stash the data buffer in b_tmp_cdata.
5955 * The subsequent write step will pick it up from
5956 * there. This is because can't access b_l1hdr.b_buf
5957 * without holding the hash_lock, which we in turn
5958 * can't access without holding the ARC list locks
5959 * (which we want to avoid during compression/writing).
5960 */
5961 hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF;
5962 hdr->b_l2hdr.b_asize = hdr->b_size;
5963 hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data;
5964
5965 /*
5966 * Explicitly set the b_daddr field to a known
5967 * value which means "invalid address". This
5968 * enables us to differentiate which stage of
5969 * l2arc_write_buffers() the particular header
5970 * is in (e.g. this loop, or the one below).
5971 * ARC_FLAG_L2_WRITING is not enough to make
5972 * this distinction, and we need to know in
5973 * order to do proper l2arc vdev accounting in
5974 * arc_release() and arc_hdr_destroy().
5975 *
5976 * Note, we can't use a new flag to distinguish
5977 * the two stages because we don't hold the
5978 * header's hash_lock below, in the second stage
5979 * of this function. Thus, we can't simply
5980 * change the b_flags field to denote that the
5981 * IO has been sent. We can change the b_daddr
5982 * field of the L2 portion, though, since we'll
5983 * be holding the l2ad_mtx; which is why we're
5984 * using it to denote the header's state change.
5985 */
5986 hdr->b_l2hdr.b_daddr = L2ARC_ADDR_UNSET;
5987
5988 buf_sz = hdr->b_size;
5989 hdr->b_flags |= ARC_FLAG_HAS_L2HDR;
5990
5991 mutex_enter(&dev->l2ad_mtx);
5992 list_insert_head(&dev->l2ad_buflist, hdr);
5993 mutex_exit(&dev->l2ad_mtx);
5994
5995 /*
5996 * Compute and store the buffer cksum before
5997 * writing. On debug the cksum is verified first.
5998 */
5999 arc_cksum_verify(hdr->b_l1hdr.b_buf);
6000 arc_cksum_compute(hdr->b_l1hdr.b_buf, B_TRUE);
6001
6002 mutex_exit(hash_lock);
6003
6004 write_sz += buf_sz;
6005 }
6006
6007 multilist_sublist_unlock(mls);
6008
6009 if (full == B_TRUE)
6010 break;
6011 }
6012
6013 /* No buffers selected for writing? */
6014 if (pio == NULL) {
6015 ASSERT0(write_sz);
6016 ASSERT(!HDR_HAS_L1HDR(head));
6017 kmem_cache_free(hdr_l2only_cache, head);
6018 return (0);
6019 }
6020
6021 mutex_enter(&dev->l2ad_mtx);
6022
6023 /*
6024 * Now start writing the buffers. We're starting at the write head
6025 * and work backwards, retracing the course of the buffer selector
6026 * loop above.
6027 */
6028 for (hdr = list_prev(&dev->l2ad_buflist, head); hdr;
6029 hdr = list_prev(&dev->l2ad_buflist, hdr)) {
6030 uint64_t buf_sz;
6031
6032 /*
6033 * We rely on the L1 portion of the header below, so
6034 * it's invalid for this header to have been evicted out
6035 * of the ghost cache, prior to being written out. The
6036 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
6037 */
6038 ASSERT(HDR_HAS_L1HDR(hdr));
6039
6040 /*
6041 * We shouldn't need to lock the buffer here, since we flagged
6042 * it as ARC_FLAG_L2_WRITING in the previous step, but we must
6043 * take care to only access its L2 cache parameters. In
6044 * particular, hdr->l1hdr.b_buf may be invalid by now due to
6045 * ARC eviction.
6046 */
6047 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
6048
6049 if ((HDR_L2COMPRESS(hdr)) &&
6050 hdr->b_l2hdr.b_asize >= buf_compress_minsz) {
6051 if (l2arc_compress_buf(hdr)) {
6052 /*
6053 * If compression succeeded, enable headroom
6054 * boost on the next scan cycle.
6055 */
6056 *headroom_boost = B_TRUE;
6057 }
6058 }
6059
6060 /*
6061 * Pick up the buffer data we had previously stashed away
6062 * (and now potentially also compressed).
6063 */
6064 buf_data = hdr->b_l1hdr.b_tmp_cdata;
6065 buf_sz = hdr->b_l2hdr.b_asize;
6066
6067 /*
6068 * We need to do this regardless if buf_sz is zero or
6069 * not, otherwise, when this l2hdr is evicted we'll
6070 * remove a reference that was never added.
6071 */
6072 (void) refcount_add_many(&dev->l2ad_alloc, buf_sz, hdr);
6073
6074 /* Compression may have squashed the buffer to zero length. */
6075 if (buf_sz != 0) {
6076 uint64_t buf_p_sz;
6077
6078 wzio = zio_write_phys(pio, dev->l2ad_vdev,
6079 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
6080 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
6081 ZIO_FLAG_CANFAIL, B_FALSE);
6082
6083 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
6084 zio_t *, wzio);
6085 (void) zio_nowait(wzio);
6086
6087 write_asize += buf_sz;
6088
6089 /*
6090 * Keep the clock hand suitably device-aligned.
6091 */
6092 buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
6093 write_psize += buf_p_sz;
6094 dev->l2ad_hand += buf_p_sz;
6095 }
6096 }
6097
6098 mutex_exit(&dev->l2ad_mtx);
6099
6100 ASSERT3U(write_asize, <=, target_sz);
6101 ARCSTAT_BUMP(arcstat_l2_writes_sent);
6102 ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
6103 ARCSTAT_INCR(arcstat_l2_size, write_sz);
6104 ARCSTAT_INCR(arcstat_l2_asize, write_asize);
6105 vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0);
6106
6107 /*
6108 * Bump device hand to the device start if it is approaching the end.
6109 * l2arc_evict() will already have evicted ahead for this case.
6110 */
6111 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
6112 dev->l2ad_hand = dev->l2ad_start;
6113 dev->l2ad_first = B_FALSE;
6114 }
6115
6116 dev->l2ad_writing = B_TRUE;
6117 (void) zio_wait(pio);
6118 dev->l2ad_writing = B_FALSE;
6119
6120 return (write_asize);
6121 }
6122
6123 /*
6124 * Compresses an L2ARC buffer.
6125 * The data to be compressed must be prefilled in l1hdr.b_tmp_cdata and its
6126 * size in l2hdr->b_asize. This routine tries to compress the data and
6127 * depending on the compression result there are three possible outcomes:
6128 * *) The buffer was incompressible. The original l2hdr contents were left
6129 * untouched and are ready for writing to an L2 device.
6130 * *) The buffer was all-zeros, so there is no need to write it to an L2
6131 * device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
6132 * set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
6133 * *) Compression succeeded and b_tmp_cdata was replaced with a temporary
6134 * data buffer which holds the compressed data to be written, and b_asize
6135 * tells us how much data there is. b_compress is set to the appropriate
6136 * compression algorithm. Once writing is done, invoke
6137 * l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
6138 *
6139 * Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
6140 * buffer was incompressible).
6141 */
6142 static boolean_t
6143 l2arc_compress_buf(arc_buf_hdr_t *hdr)
6144 {
6145 void *cdata;
6146 size_t csize, len, rounded;
6147 ASSERT(HDR_HAS_L2HDR(hdr));
6148 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
6149
6150 ASSERT(HDR_HAS_L1HDR(hdr));
6151 ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
6152 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
6153
6154 len = l2hdr->b_asize;
6155 cdata = zio_data_buf_alloc(len);
6156 ASSERT3P(cdata, !=, NULL);
6157 csize = zio_compress_data(ZIO_COMPRESS_LZ4, hdr->b_l1hdr.b_tmp_cdata,
6158 cdata, l2hdr->b_asize);
6159
6160 rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
6161 if (rounded > csize) {
6162 bzero((char *)cdata + csize, rounded - csize);
6163 csize = rounded;
6164 }
6165
6166 if (csize == 0) {
6167 /* zero block, indicate that there's nothing to write */
6168 zio_data_buf_free(cdata, len);
6169 l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
6170 l2hdr->b_asize = 0;
6171 hdr->b_l1hdr.b_tmp_cdata = NULL;
6172 ARCSTAT_BUMP(arcstat_l2_compress_zeros);
6173 return (B_TRUE);
6174 } else if (csize > 0 && csize < len) {
6175 /*
6176 * Compression succeeded, we'll keep the cdata around for
6177 * writing and release it afterwards.
6178 */
6179 l2hdr->b_compress = ZIO_COMPRESS_LZ4;
6180 l2hdr->b_asize = csize;
6181 hdr->b_l1hdr.b_tmp_cdata = cdata;
6182 ARCSTAT_BUMP(arcstat_l2_compress_successes);
6183 return (B_TRUE);
6184 } else {
6185 /*
6186 * Compression failed, release the compressed buffer.
6187 * l2hdr will be left unmodified.
6188 */
6189 zio_data_buf_free(cdata, len);
6190 ARCSTAT_BUMP(arcstat_l2_compress_failures);
6191 return (B_FALSE);
6192 }
6193 }
6194
6195 /*
6196 * Decompresses a zio read back from an l2arc device. On success, the
6197 * underlying zio's io_data buffer is overwritten by the uncompressed
6198 * version. On decompression error (corrupt compressed stream), the
6199 * zio->io_error value is set to signal an I/O error.
6200 *
6201 * Please note that the compressed data stream is not checksummed, so
6202 * if the underlying device is experiencing data corruption, we may feed
6203 * corrupt data to the decompressor, so the decompressor needs to be
6204 * able to handle this situation (LZ4 does).
6205 */
6206 static void
6207 l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
6208 {
6209 ASSERT(L2ARC_IS_VALID_COMPRESS(c));
6210
6211 if (zio->io_error != 0) {
6212 /*
6213 * An io error has occured, just restore the original io
6214 * size in preparation for a main pool read.
6215 */
6216 zio->io_orig_size = zio->io_size = hdr->b_size;
6217 return;
6218 }
6219
6220 if (c == ZIO_COMPRESS_EMPTY) {
6221 /*
6222 * An empty buffer results in a null zio, which means we
6223 * need to fill its io_data after we're done restoring the
6224 * buffer's contents.
6225 */
6226 ASSERT(hdr->b_l1hdr.b_buf != NULL);
6227 bzero(hdr->b_l1hdr.b_buf->b_data, hdr->b_size);
6228 zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_buf->b_data;
6229 } else {
6230 ASSERT(zio->io_data != NULL);
6231 /*
6232 * We copy the compressed data from the start of the arc buffer
6233 * (the zio_read will have pulled in only what we need, the
6234 * rest is garbage which we will overwrite at decompression)
6235 * and then decompress back to the ARC data buffer. This way we
6236 * can minimize copying by simply decompressing back over the
6237 * original compressed data (rather than decompressing to an
6238 * aux buffer and then copying back the uncompressed buffer,
6239 * which is likely to be much larger).
6240 */
6241 uint64_t csize;
6242 void *cdata;
6243
6244 csize = zio->io_size;
6245 cdata = zio_data_buf_alloc(csize);
6246 bcopy(zio->io_data, cdata, csize);
6247 if (zio_decompress_data(c, cdata, zio->io_data, csize,
6248 hdr->b_size) != 0)
6249 zio->io_error = EIO;
6250 zio_data_buf_free(cdata, csize);
6251 }
6252
6253 /* Restore the expected uncompressed IO size. */
6254 zio->io_orig_size = zio->io_size = hdr->b_size;
6255 }
6256
6257 /*
6258 * Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
6259 * This buffer serves as a temporary holder of compressed data while
6260 * the buffer entry is being written to an l2arc device. Once that is
6261 * done, we can dispose of it.
6262 */
6263 static void
6264 l2arc_release_cdata_buf(arc_buf_hdr_t *hdr)
6265 {
6266 ASSERT(HDR_HAS_L2HDR(hdr));
6267 enum zio_compress comp = hdr->b_l2hdr.b_compress;
6268
6269 ASSERT(HDR_HAS_L1HDR(hdr));
6270 ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp));
6271
6272 if (comp == ZIO_COMPRESS_OFF) {
6273 /*
6274 * In this case, b_tmp_cdata points to the same buffer
6275 * as the arc_buf_t's b_data field. We don't want to
6276 * free it, since the arc_buf_t will handle that.
6277 */
6278 hdr->b_l1hdr.b_tmp_cdata = NULL;
6279 } else if (comp == ZIO_COMPRESS_EMPTY) {
6280 /*
6281 * In this case, b_tmp_cdata was compressed to an empty
6282 * buffer, thus there's nothing to free and b_tmp_cdata
6283 * should have been set to NULL in l2arc_write_buffers().
6284 */
6285 ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
6286 } else {
6287 /*
6288 * If the data was compressed, then we've allocated a
6289 * temporary buffer for it, so now we need to release it.
6290 */
6291 ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);
6292 zio_data_buf_free(hdr->b_l1hdr.b_tmp_cdata,
6293 hdr->b_size);
6294 hdr->b_l1hdr.b_tmp_cdata = NULL;
6295 }
6296
6297 }
6298
6299 /*
6300 * This thread feeds the L2ARC at regular intervals. This is the beating
6301 * heart of the L2ARC.
6302 */
6303 static void
6304 l2arc_feed_thread(void)
6305 {
6306 callb_cpr_t cpr;
6307 l2arc_dev_t *dev;
6308 spa_t *spa;
6309 uint64_t size, wrote;
6310 clock_t begin, next = ddi_get_lbolt();
6311 boolean_t headroom_boost = B_FALSE;
6312
6313 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
6314
6315 mutex_enter(&l2arc_feed_thr_lock);
6316
6317 while (l2arc_thread_exit == 0) {
6318 CALLB_CPR_SAFE_BEGIN(&cpr);
6319 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
6320 next);
6321 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
6322 next = ddi_get_lbolt() + hz;
6323
6324 /*
6325 * Quick check for L2ARC devices.
6326 */
6327 mutex_enter(&l2arc_dev_mtx);
6328 if (l2arc_ndev == 0) {
6329 mutex_exit(&l2arc_dev_mtx);
6330 continue;
6331 }
6332 mutex_exit(&l2arc_dev_mtx);
6333 begin = ddi_get_lbolt();
6334
6335 /*
6336 * This selects the next l2arc device to write to, and in
6337 * doing so the next spa to feed from: dev->l2ad_spa. This
6338 * will return NULL if there are now no l2arc devices or if
6339 * they are all faulted.
6340 *
6341 * If a device is returned, its spa's config lock is also
6342 * held to prevent device removal. l2arc_dev_get_next()
6343 * will grab and release l2arc_dev_mtx.
6344 */
6345 if ((dev = l2arc_dev_get_next()) == NULL)
6346 continue;
6347
6348 spa = dev->l2ad_spa;
6349 ASSERT(spa != NULL);
6350
6351 /*
6352 * If the pool is read-only then force the feed thread to
6353 * sleep a little longer.
6354 */
6355 if (!spa_writeable(spa)) {
6356 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
6357 spa_config_exit(spa, SCL_L2ARC, dev);
6358 continue;
6359 }
6360
6361 /*
6362 * Avoid contributing to memory pressure.
6363 */
6364 if (arc_reclaim_needed()) {
6365 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
6366 spa_config_exit(spa, SCL_L2ARC, dev);
6367 continue;
6368 }
6369
6370 ARCSTAT_BUMP(arcstat_l2_feeds);
6371
6372 size = l2arc_write_size();
6373
6374 /*
6375 * Evict L2ARC buffers that will be overwritten.
6376 */
6377 l2arc_evict(dev, size, B_FALSE);
6378
6379 /*
6380 * Write ARC buffers.
6381 */
6382 wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
6383
6384 /*
6385 * Calculate interval between writes.
6386 */
6387 next = l2arc_write_interval(begin, size, wrote);
6388 spa_config_exit(spa, SCL_L2ARC, dev);
6389 }
6390
6391 l2arc_thread_exit = 0;
6392 cv_broadcast(&l2arc_feed_thr_cv);
6393 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
6394 thread_exit();
6395 }
6396
6397 boolean_t
6398 l2arc_vdev_present(vdev_t *vd)
6399 {
6400 l2arc_dev_t *dev;
6401
6402 mutex_enter(&l2arc_dev_mtx);
6403 for (dev = list_head(l2arc_dev_list); dev != NULL;
6404 dev = list_next(l2arc_dev_list, dev)) {
6405 if (dev->l2ad_vdev == vd)
6406 break;
6407 }
6408 mutex_exit(&l2arc_dev_mtx);
6409
6410 return (dev != NULL);
6411 }
6412
6413 /*
6414 * Add a vdev for use by the L2ARC. By this point the spa has already
6415 * validated the vdev and opened it.
6416 */
6417 void
6418 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
6419 {
6420 l2arc_dev_t *adddev;
6421
6422 ASSERT(!l2arc_vdev_present(vd));
6423
6424 /*
6425 * Create a new l2arc device entry.
6426 */
6427 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
6428 adddev->l2ad_spa = spa;
6429 adddev->l2ad_vdev = vd;
6430 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
6431 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
6432 adddev->l2ad_hand = adddev->l2ad_start;
6433 adddev->l2ad_first = B_TRUE;
6434 adddev->l2ad_writing = B_FALSE;
6435
6436 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
6437 /*
6438 * This is a list of all ARC buffers that are still valid on the
6439 * device.
6440 */
6441 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
6442 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
6443
6444 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
6445 refcount_create(&adddev->l2ad_alloc);
6446
6447 /*
6448 * Add device to global list
6449 */
6450 mutex_enter(&l2arc_dev_mtx);
6451 list_insert_head(l2arc_dev_list, adddev);
6452 atomic_inc_64(&l2arc_ndev);
6453 mutex_exit(&l2arc_dev_mtx);
6454 }
6455
6456 /*
6457 * Remove a vdev from the L2ARC.
6458 */
6459 void
6460 l2arc_remove_vdev(vdev_t *vd)
6461 {
6462 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
6463
6464 /*
6465 * Find the device by vdev
6466 */
6467 mutex_enter(&l2arc_dev_mtx);
6468 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
6469 nextdev = list_next(l2arc_dev_list, dev);
6470 if (vd == dev->l2ad_vdev) {
6471 remdev = dev;
6472 break;
6473 }
6474 }
6475 ASSERT(remdev != NULL);
6476
6477 /*
6478 * Remove device from global list
6479 */
6480 list_remove(l2arc_dev_list, remdev);
6481 l2arc_dev_last = NULL; /* may have been invalidated */
6482 atomic_dec_64(&l2arc_ndev);
6483 mutex_exit(&l2arc_dev_mtx);
6484
6485 /*
6486 * Clear all buflists and ARC references. L2ARC device flush.
6487 */
6488 l2arc_evict(remdev, 0, B_TRUE);
6489 list_destroy(&remdev->l2ad_buflist);
6490 mutex_destroy(&remdev->l2ad_mtx);
6491 refcount_destroy(&remdev->l2ad_alloc);
6492 kmem_free(remdev, sizeof (l2arc_dev_t));
6493 }
6494
6495 void
6496 l2arc_init(void)
6497 {
6498 l2arc_thread_exit = 0;
6499 l2arc_ndev = 0;
6500 l2arc_writes_sent = 0;
6501 l2arc_writes_done = 0;
6502
6503 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
6504 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
6505 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
6506 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
6507
6508 l2arc_dev_list = &L2ARC_dev_list;
6509 l2arc_free_on_write = &L2ARC_free_on_write;
6510 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
6511 offsetof(l2arc_dev_t, l2ad_node));
6512 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
6513 offsetof(l2arc_data_free_t, l2df_list_node));
6514 }
6515
6516 void
6517 l2arc_fini(void)
6518 {
6519 /*
6520 * This is called from dmu_fini(), which is called from spa_fini();
6521 * Because of this, we can assume that all l2arc devices have
6522 * already been removed when the pools themselves were removed.
6523 */
6524
6525 l2arc_do_free_on_write();
6526
6527 mutex_destroy(&l2arc_feed_thr_lock);
6528 cv_destroy(&l2arc_feed_thr_cv);
6529 mutex_destroy(&l2arc_dev_mtx);
6530 mutex_destroy(&l2arc_free_on_write_mtx);
6531
6532 list_destroy(l2arc_dev_list);
6533 list_destroy(l2arc_free_on_write);
6534 }
6535
6536 void
6537 l2arc_start(void)
6538 {
6539 if (!(spa_mode_global & FWRITE))
6540 return;
6541
6542 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
6543 TS_RUN, minclsyspri);
6544 }
6545
6546 void
6547 l2arc_stop(void)
6548 {
6549 if (!(spa_mode_global & FWRITE))
6550 return;
6551
6552 mutex_enter(&l2arc_feed_thr_lock);
6553 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
6554 l2arc_thread_exit = 1;
6555 while (l2arc_thread_exit != 0)
6556 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
6557 mutex_exit(&l2arc_feed_thr_lock);
6558 }