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