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9018 Replace kmem_cache_reap_now() with kmem_cache_reap_soon()
Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Yuri Pankov <yuripv@yuripv.net>
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--- old/usr/src/uts/common/fs/zfs/arc.c
+++ new/usr/src/uts/common/fs/zfs/arc.c
1 1 /*
2 2 * CDDL HEADER START
3 3 *
4 4 * The contents of this file are subject to the terms of the
5 5 * Common Development and Distribution License (the "License").
6 6 * You may not use this file except in compliance with the License.
7 7 *
8 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 9 * or http://www.opensolaris.org/os/licensing.
10 10 * See the License for the specific language governing permissions
11 11 * and limitations under the License.
12 12 *
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13 13 * When distributing Covered Code, include this CDDL HEADER in each
14 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 15 * If applicable, add the following below this CDDL HEADER, with the
16 16 * fields enclosed by brackets "[]" replaced with your own identifying
17 17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 18 *
19 19 * CDDL HEADER END
20 20 */
21 21 /*
22 22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 - * Copyright (c) 2012, Joyent, Inc. All rights reserved.
23 + * Copyright (c) 2018, Joyent, Inc.
24 24 * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
25 25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved.
27 27 */
28 28
29 29 /*
30 30 * DVA-based Adjustable Replacement Cache
31 31 *
32 32 * While much of the theory of operation used here is
33 33 * based on the self-tuning, low overhead replacement cache
34 34 * presented by Megiddo and Modha at FAST 2003, there are some
35 35 * significant differences:
36 36 *
37 37 * 1. The Megiddo and Modha model assumes any page is evictable.
38 38 * Pages in its cache cannot be "locked" into memory. This makes
39 39 * the eviction algorithm simple: evict the last page in the list.
40 40 * This also make the performance characteristics easy to reason
41 41 * about. Our cache is not so simple. At any given moment, some
42 42 * subset of the blocks in the cache are un-evictable because we
43 43 * have handed out a reference to them. Blocks are only evictable
44 44 * when there are no external references active. This makes
45 45 * eviction far more problematic: we choose to evict the evictable
46 46 * blocks that are the "lowest" in the list.
47 47 *
48 48 * There are times when it is not possible to evict the requested
49 49 * space. In these circumstances we are unable to adjust the cache
50 50 * size. To prevent the cache growing unbounded at these times we
51 51 * implement a "cache throttle" that slows the flow of new data
52 52 * into the cache until we can make space available.
53 53 *
54 54 * 2. The Megiddo and Modha model assumes a fixed cache size.
55 55 * Pages are evicted when the cache is full and there is a cache
56 56 * miss. Our model has a variable sized cache. It grows with
57 57 * high use, but also tries to react to memory pressure from the
58 58 * operating system: decreasing its size when system memory is
59 59 * tight.
60 60 *
61 61 * 3. The Megiddo and Modha model assumes a fixed page size. All
62 62 * elements of the cache are therefore exactly the same size. So
63 63 * when adjusting the cache size following a cache miss, its simply
64 64 * a matter of choosing a single page to evict. In our model, we
65 65 * have variable sized cache blocks (rangeing from 512 bytes to
66 66 * 128K bytes). We therefore choose a set of blocks to evict to make
67 67 * space for a cache miss that approximates as closely as possible
68 68 * the space used by the new block.
69 69 *
70 70 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
71 71 * by N. Megiddo & D. Modha, FAST 2003
72 72 */
73 73
74 74 /*
75 75 * The locking model:
76 76 *
77 77 * A new reference to a cache buffer can be obtained in two
78 78 * ways: 1) via a hash table lookup using the DVA as a key,
79 79 * or 2) via one of the ARC lists. The arc_read() interface
80 80 * uses method 1, while the internal ARC algorithms for
81 81 * adjusting the cache use method 2. We therefore provide two
82 82 * types of locks: 1) the hash table lock array, and 2) the
83 83 * ARC list locks.
84 84 *
85 85 * Buffers do not have their own mutexes, rather they rely on the
86 86 * hash table mutexes for the bulk of their protection (i.e. most
87 87 * fields in the arc_buf_hdr_t are protected by these mutexes).
88 88 *
89 89 * buf_hash_find() returns the appropriate mutex (held) when it
90 90 * locates the requested buffer in the hash table. It returns
91 91 * NULL for the mutex if the buffer was not in the table.
92 92 *
93 93 * buf_hash_remove() expects the appropriate hash mutex to be
94 94 * already held before it is invoked.
95 95 *
96 96 * Each ARC state also has a mutex which is used to protect the
97 97 * buffer list associated with the state. When attempting to
98 98 * obtain a hash table lock while holding an ARC list lock you
99 99 * must use: mutex_tryenter() to avoid deadlock. Also note that
100 100 * the active state mutex must be held before the ghost state mutex.
101 101 *
102 102 * Note that the majority of the performance stats are manipulated
103 103 * with atomic operations.
104 104 *
105 105 * The L2ARC uses the l2ad_mtx on each vdev for the following:
106 106 *
107 107 * - L2ARC buflist creation
108 108 * - L2ARC buflist eviction
109 109 * - L2ARC write completion, which walks L2ARC buflists
110 110 * - ARC header destruction, as it removes from L2ARC buflists
111 111 * - ARC header release, as it removes from L2ARC buflists
112 112 */
113 113
114 114 /*
115 115 * ARC operation:
116 116 *
117 117 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
118 118 * This structure can point either to a block that is still in the cache or to
119 119 * one that is only accessible in an L2 ARC device, or it can provide
120 120 * information about a block that was recently evicted. If a block is
121 121 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
122 122 * information to retrieve it from the L2ARC device. This information is
123 123 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
124 124 * that is in this state cannot access the data directly.
125 125 *
126 126 * Blocks that are actively being referenced or have not been evicted
127 127 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
128 128 * the arc_buf_hdr_t that will point to the data block in memory. A block can
129 129 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
130 130 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
131 131 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
132 132 *
133 133 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
134 134 * ability to store the physical data (b_pabd) associated with the DVA of the
135 135 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
136 136 * it will match its on-disk compression characteristics. This behavior can be
137 137 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
138 138 * compressed ARC functionality is disabled, the b_pabd will point to an
139 139 * uncompressed version of the on-disk data.
140 140 *
141 141 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
142 142 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
143 143 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
144 144 * consumer. The ARC will provide references to this data and will keep it
145 145 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
146 146 * data block and will evict any arc_buf_t that is no longer referenced. The
147 147 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
148 148 * "overhead_size" kstat.
149 149 *
150 150 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
151 151 * compressed form. The typical case is that consumers will want uncompressed
152 152 * data, and when that happens a new data buffer is allocated where the data is
153 153 * decompressed for them to use. Currently the only consumer who wants
154 154 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
155 155 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
156 156 * with the arc_buf_hdr_t.
157 157 *
158 158 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
159 159 * first one is owned by a compressed send consumer (and therefore references
160 160 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
161 161 * used by any other consumer (and has its own uncompressed copy of the data
162 162 * buffer).
163 163 *
164 164 * arc_buf_hdr_t
165 165 * +-----------+
166 166 * | fields |
167 167 * | common to |
168 168 * | L1- and |
169 169 * | L2ARC |
170 170 * +-----------+
171 171 * | l2arc_buf_hdr_t
172 172 * | |
173 173 * +-----------+
174 174 * | l1arc_buf_hdr_t
175 175 * | | arc_buf_t
176 176 * | b_buf +------------>+-----------+ arc_buf_t
177 177 * | b_pabd +-+ |b_next +---->+-----------+
178 178 * +-----------+ | |-----------| |b_next +-->NULL
179 179 * | |b_comp = T | +-----------+
180 180 * | |b_data +-+ |b_comp = F |
181 181 * | +-----------+ | |b_data +-+
182 182 * +->+------+ | +-----------+ |
183 183 * compressed | | | |
184 184 * data | |<--------------+ | uncompressed
185 185 * +------+ compressed, | data
186 186 * shared +-->+------+
187 187 * data | |
188 188 * | |
189 189 * +------+
190 190 *
191 191 * When a consumer reads a block, the ARC must first look to see if the
192 192 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
193 193 * arc_buf_t and either copies uncompressed data into a new data buffer from an
194 194 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
195 195 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
196 196 * hdr is compressed and the desired compression characteristics of the
197 197 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
198 198 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
199 199 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
200 200 * be anywhere in the hdr's list.
201 201 *
202 202 * The diagram below shows an example of an uncompressed ARC hdr that is
203 203 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
204 204 * the last element in the buf list):
205 205 *
206 206 * arc_buf_hdr_t
207 207 * +-----------+
208 208 * | |
209 209 * | |
210 210 * | |
211 211 * +-----------+
212 212 * l2arc_buf_hdr_t| |
213 213 * | |
214 214 * +-----------+
215 215 * l1arc_buf_hdr_t| |
216 216 * | | arc_buf_t (shared)
217 217 * | b_buf +------------>+---------+ arc_buf_t
218 218 * | | |b_next +---->+---------+
219 219 * | b_pabd +-+ |---------| |b_next +-->NULL
220 220 * +-----------+ | | | +---------+
221 221 * | |b_data +-+ | |
222 222 * | +---------+ | |b_data +-+
223 223 * +->+------+ | +---------+ |
224 224 * | | | |
225 225 * uncompressed | | | |
226 226 * data +------+ | |
227 227 * ^ +->+------+ |
228 228 * | uncompressed | | |
229 229 * | data | | |
230 230 * | +------+ |
231 231 * +---------------------------------+
232 232 *
233 233 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
234 234 * since the physical block is about to be rewritten. The new data contents
235 235 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
236 236 * it may compress the data before writing it to disk. The ARC will be called
237 237 * with the transformed data and will bcopy the transformed on-disk block into
238 238 * a newly allocated b_pabd. Writes are always done into buffers which have
239 239 * either been loaned (and hence are new and don't have other readers) or
240 240 * buffers which have been released (and hence have their own hdr, if there
241 241 * were originally other readers of the buf's original hdr). This ensures that
242 242 * the ARC only needs to update a single buf and its hdr after a write occurs.
243 243 *
244 244 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
245 245 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
246 246 * that when compressed ARC is enabled that the L2ARC blocks are identical
247 247 * to the on-disk block in the main data pool. This provides a significant
248 248 * advantage since the ARC can leverage the bp's checksum when reading from the
249 249 * L2ARC to determine if the contents are valid. However, if the compressed
250 250 * ARC is disabled, then the L2ARC's block must be transformed to look
251 251 * like the physical block in the main data pool before comparing the
252 252 * checksum and determining its validity.
253 253 */
254 254
255 255 #include <sys/spa.h>
256 256 #include <sys/zio.h>
257 257 #include <sys/spa_impl.h>
258 258 #include <sys/zio_compress.h>
259 259 #include <sys/zio_checksum.h>
260 260 #include <sys/zfs_context.h>
261 261 #include <sys/arc.h>
262 262 #include <sys/refcount.h>
263 263 #include <sys/vdev.h>
264 264 #include <sys/vdev_impl.h>
265 265 #include <sys/dsl_pool.h>
266 266 #include <sys/zio_checksum.h>
267 267 #include <sys/multilist.h>
268 268 #include <sys/abd.h>
269 269 #ifdef _KERNEL
270 270 #include <sys/vmsystm.h>
271 271 #include <vm/anon.h>
272 272 #include <sys/fs/swapnode.h>
273 273 #include <sys/dnlc.h>
274 274 #endif
275 275 #include <sys/callb.h>
276 276 #include <sys/kstat.h>
277 277 #include <zfs_fletcher.h>
278 278
279 279 #ifndef _KERNEL
280 280 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
281 281 boolean_t arc_watch = B_FALSE;
282 282 int arc_procfd;
283 283 #endif
284 284
285 285 static kmutex_t arc_reclaim_lock;
286 286 static kcondvar_t arc_reclaim_thread_cv;
287 287 static boolean_t arc_reclaim_thread_exit;
288 288 static kcondvar_t arc_reclaim_waiters_cv;
289 289
290 290 uint_t arc_reduce_dnlc_percent = 3;
291 291
292 292 /*
293 293 * The number of headers to evict in arc_evict_state_impl() before
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294 294 * dropping the sublist lock and evicting from another sublist. A lower
295 295 * value means we're more likely to evict the "correct" header (i.e. the
296 296 * oldest header in the arc state), but comes with higher overhead
297 297 * (i.e. more invocations of arc_evict_state_impl()).
298 298 */
299 299 int zfs_arc_evict_batch_limit = 10;
300 300
301 301 /* number of seconds before growing cache again */
302 302 static int arc_grow_retry = 60;
303 303
304 +/* number of milliseconds before attempting a kmem-cache-reap */
305 +static int arc_kmem_cache_reap_retry_ms = 1000;
306 +
304 307 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
305 308 int zfs_arc_overflow_shift = 8;
306 309
307 310 /* shift of arc_c for calculating both min and max arc_p */
308 311 static int arc_p_min_shift = 4;
309 312
310 313 /* log2(fraction of arc to reclaim) */
311 314 static int arc_shrink_shift = 7;
312 315
313 316 /*
314 317 * log2(fraction of ARC which must be free to allow growing).
315 318 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
316 319 * when reading a new block into the ARC, we will evict an equal-sized block
317 320 * from the ARC.
318 321 *
319 322 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
320 323 * we will still not allow it to grow.
321 324 */
322 325 int arc_no_grow_shift = 5;
323 326
324 327
325 328 /*
326 329 * minimum lifespan of a prefetch block in clock ticks
327 330 * (initialized in arc_init())
328 331 */
329 332 static int arc_min_prefetch_lifespan;
330 333
331 334 /*
332 335 * If this percent of memory is free, don't throttle.
333 336 */
334 337 int arc_lotsfree_percent = 10;
335 338
336 339 static int arc_dead;
337 340
338 341 /*
339 342 * The arc has filled available memory and has now warmed up.
340 343 */
341 344 static boolean_t arc_warm;
342 345
343 346 /*
344 347 * log2 fraction of the zio arena to keep free.
345 348 */
346 349 int arc_zio_arena_free_shift = 2;
347 350
348 351 /*
349 352 * These tunables are for performance analysis.
350 353 */
351 354 uint64_t zfs_arc_max;
352 355 uint64_t zfs_arc_min;
353 356 uint64_t zfs_arc_meta_limit = 0;
354 357 uint64_t zfs_arc_meta_min = 0;
355 358 int zfs_arc_grow_retry = 0;
356 359 int zfs_arc_shrink_shift = 0;
357 360 int zfs_arc_p_min_shift = 0;
358 361 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
359 362
360 363 boolean_t zfs_compressed_arc_enabled = B_TRUE;
361 364
362 365 /*
363 366 * Note that buffers can be in one of 6 states:
364 367 * ARC_anon - anonymous (discussed below)
365 368 * ARC_mru - recently used, currently cached
366 369 * ARC_mru_ghost - recentely used, no longer in cache
367 370 * ARC_mfu - frequently used, currently cached
368 371 * ARC_mfu_ghost - frequently used, no longer in cache
369 372 * ARC_l2c_only - exists in L2ARC but not other states
370 373 * When there are no active references to the buffer, they are
371 374 * are linked onto a list in one of these arc states. These are
372 375 * the only buffers that can be evicted or deleted. Within each
373 376 * state there are multiple lists, one for meta-data and one for
374 377 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
375 378 * etc.) is tracked separately so that it can be managed more
376 379 * explicitly: favored over data, limited explicitly.
377 380 *
378 381 * Anonymous buffers are buffers that are not associated with
379 382 * a DVA. These are buffers that hold dirty block copies
380 383 * before they are written to stable storage. By definition,
381 384 * they are "ref'd" and are considered part of arc_mru
382 385 * that cannot be freed. Generally, they will aquire a DVA
383 386 * as they are written and migrate onto the arc_mru list.
384 387 *
385 388 * The ARC_l2c_only state is for buffers that are in the second
386 389 * level ARC but no longer in any of the ARC_m* lists. The second
387 390 * level ARC itself may also contain buffers that are in any of
388 391 * the ARC_m* states - meaning that a buffer can exist in two
389 392 * places. The reason for the ARC_l2c_only state is to keep the
390 393 * buffer header in the hash table, so that reads that hit the
391 394 * second level ARC benefit from these fast lookups.
392 395 */
393 396
394 397 typedef struct arc_state {
395 398 /*
396 399 * list of evictable buffers
397 400 */
398 401 multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
399 402 /*
400 403 * total amount of evictable data in this state
401 404 */
402 405 refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
403 406 /*
404 407 * total amount of data in this state; this includes: evictable,
405 408 * non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
406 409 */
407 410 refcount_t arcs_size;
408 411 } arc_state_t;
409 412
410 413 /* The 6 states: */
411 414 static arc_state_t ARC_anon;
412 415 static arc_state_t ARC_mru;
413 416 static arc_state_t ARC_mru_ghost;
414 417 static arc_state_t ARC_mfu;
415 418 static arc_state_t ARC_mfu_ghost;
416 419 static arc_state_t ARC_l2c_only;
417 420
418 421 typedef struct arc_stats {
419 422 kstat_named_t arcstat_hits;
420 423 kstat_named_t arcstat_misses;
421 424 kstat_named_t arcstat_demand_data_hits;
422 425 kstat_named_t arcstat_demand_data_misses;
423 426 kstat_named_t arcstat_demand_metadata_hits;
424 427 kstat_named_t arcstat_demand_metadata_misses;
425 428 kstat_named_t arcstat_prefetch_data_hits;
426 429 kstat_named_t arcstat_prefetch_data_misses;
427 430 kstat_named_t arcstat_prefetch_metadata_hits;
428 431 kstat_named_t arcstat_prefetch_metadata_misses;
429 432 kstat_named_t arcstat_mru_hits;
430 433 kstat_named_t arcstat_mru_ghost_hits;
431 434 kstat_named_t arcstat_mfu_hits;
432 435 kstat_named_t arcstat_mfu_ghost_hits;
433 436 kstat_named_t arcstat_deleted;
434 437 /*
435 438 * Number of buffers that could not be evicted because the hash lock
436 439 * was held by another thread. The lock may not necessarily be held
437 440 * by something using the same buffer, since hash locks are shared
438 441 * by multiple buffers.
439 442 */
440 443 kstat_named_t arcstat_mutex_miss;
441 444 /*
442 445 * Number of buffers skipped because they have I/O in progress, are
443 446 * indrect prefetch buffers that have not lived long enough, or are
444 447 * not from the spa we're trying to evict from.
445 448 */
446 449 kstat_named_t arcstat_evict_skip;
447 450 /*
448 451 * Number of times arc_evict_state() was unable to evict enough
449 452 * buffers to reach it's target amount.
450 453 */
451 454 kstat_named_t arcstat_evict_not_enough;
452 455 kstat_named_t arcstat_evict_l2_cached;
453 456 kstat_named_t arcstat_evict_l2_eligible;
454 457 kstat_named_t arcstat_evict_l2_ineligible;
455 458 kstat_named_t arcstat_evict_l2_skip;
456 459 kstat_named_t arcstat_hash_elements;
457 460 kstat_named_t arcstat_hash_elements_max;
458 461 kstat_named_t arcstat_hash_collisions;
459 462 kstat_named_t arcstat_hash_chains;
460 463 kstat_named_t arcstat_hash_chain_max;
461 464 kstat_named_t arcstat_p;
462 465 kstat_named_t arcstat_c;
463 466 kstat_named_t arcstat_c_min;
464 467 kstat_named_t arcstat_c_max;
465 468 kstat_named_t arcstat_size;
466 469 /*
467 470 * Number of compressed bytes stored in the arc_buf_hdr_t's b_pabd.
468 471 * Note that the compressed bytes may match the uncompressed bytes
469 472 * if the block is either not compressed or compressed arc is disabled.
470 473 */
471 474 kstat_named_t arcstat_compressed_size;
472 475 /*
473 476 * Uncompressed size of the data stored in b_pabd. If compressed
474 477 * arc is disabled then this value will be identical to the stat
475 478 * above.
476 479 */
477 480 kstat_named_t arcstat_uncompressed_size;
478 481 /*
479 482 * Number of bytes stored in all the arc_buf_t's. This is classified
480 483 * as "overhead" since this data is typically short-lived and will
481 484 * be evicted from the arc when it becomes unreferenced unless the
482 485 * zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
483 486 * values have been set (see comment in dbuf.c for more information).
484 487 */
485 488 kstat_named_t arcstat_overhead_size;
486 489 /*
487 490 * Number of bytes consumed by internal ARC structures necessary
488 491 * for tracking purposes; these structures are not actually
489 492 * backed by ARC buffers. This includes arc_buf_hdr_t structures
490 493 * (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
491 494 * caches), and arc_buf_t structures (allocated via arc_buf_t
492 495 * cache).
493 496 */
494 497 kstat_named_t arcstat_hdr_size;
495 498 /*
496 499 * Number of bytes consumed by ARC buffers of type equal to
497 500 * ARC_BUFC_DATA. This is generally consumed by buffers backing
498 501 * on disk user data (e.g. plain file contents).
499 502 */
500 503 kstat_named_t arcstat_data_size;
501 504 /*
502 505 * Number of bytes consumed by ARC buffers of type equal to
503 506 * ARC_BUFC_METADATA. This is generally consumed by buffers
504 507 * backing on disk data that is used for internal ZFS
505 508 * structures (e.g. ZAP, dnode, indirect blocks, etc).
506 509 */
507 510 kstat_named_t arcstat_metadata_size;
508 511 /*
509 512 * Number of bytes consumed by various buffers and structures
510 513 * not actually backed with ARC buffers. This includes bonus
511 514 * buffers (allocated directly via zio_buf_* functions),
512 515 * dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
513 516 * cache), and dnode_t structures (allocated via dnode_t cache).
514 517 */
515 518 kstat_named_t arcstat_other_size;
516 519 /*
517 520 * Total number of bytes consumed by ARC buffers residing in the
518 521 * arc_anon state. This includes *all* buffers in the arc_anon
519 522 * state; e.g. data, metadata, evictable, and unevictable buffers
520 523 * are all included in this value.
521 524 */
522 525 kstat_named_t arcstat_anon_size;
523 526 /*
524 527 * Number of bytes consumed by ARC buffers that meet the
525 528 * following criteria: backing buffers of type ARC_BUFC_DATA,
526 529 * residing in the arc_anon state, and are eligible for eviction
527 530 * (e.g. have no outstanding holds on the buffer).
528 531 */
529 532 kstat_named_t arcstat_anon_evictable_data;
530 533 /*
531 534 * Number of bytes consumed by ARC buffers that meet the
532 535 * following criteria: backing buffers of type ARC_BUFC_METADATA,
533 536 * residing in the arc_anon state, and are eligible for eviction
534 537 * (e.g. have no outstanding holds on the buffer).
535 538 */
536 539 kstat_named_t arcstat_anon_evictable_metadata;
537 540 /*
538 541 * Total number of bytes consumed by ARC buffers residing in the
539 542 * arc_mru state. This includes *all* buffers in the arc_mru
540 543 * state; e.g. data, metadata, evictable, and unevictable buffers
541 544 * are all included in this value.
542 545 */
543 546 kstat_named_t arcstat_mru_size;
544 547 /*
545 548 * Number of bytes consumed by ARC buffers that meet the
546 549 * following criteria: backing buffers of type ARC_BUFC_DATA,
547 550 * residing in the arc_mru state, and are eligible for eviction
548 551 * (e.g. have no outstanding holds on the buffer).
549 552 */
550 553 kstat_named_t arcstat_mru_evictable_data;
551 554 /*
552 555 * Number of bytes consumed by ARC buffers that meet the
553 556 * following criteria: backing buffers of type ARC_BUFC_METADATA,
554 557 * residing in the arc_mru state, and are eligible for eviction
555 558 * (e.g. have no outstanding holds on the buffer).
556 559 */
557 560 kstat_named_t arcstat_mru_evictable_metadata;
558 561 /*
559 562 * Total number of bytes that *would have been* consumed by ARC
560 563 * buffers in the arc_mru_ghost state. The key thing to note
561 564 * here, is the fact that this size doesn't actually indicate
562 565 * RAM consumption. The ghost lists only consist of headers and
563 566 * don't actually have ARC buffers linked off of these headers.
564 567 * Thus, *if* the headers had associated ARC buffers, these
565 568 * buffers *would have* consumed this number of bytes.
566 569 */
567 570 kstat_named_t arcstat_mru_ghost_size;
568 571 /*
569 572 * Number of bytes that *would have been* consumed by ARC
570 573 * buffers that are eligible for eviction, of type
571 574 * ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
572 575 */
573 576 kstat_named_t arcstat_mru_ghost_evictable_data;
574 577 /*
575 578 * Number of bytes that *would have been* consumed by ARC
576 579 * buffers that are eligible for eviction, of type
577 580 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
578 581 */
579 582 kstat_named_t arcstat_mru_ghost_evictable_metadata;
580 583 /*
581 584 * Total number of bytes consumed by ARC buffers residing in the
582 585 * arc_mfu state. This includes *all* buffers in the arc_mfu
583 586 * state; e.g. data, metadata, evictable, and unevictable buffers
584 587 * are all included in this value.
585 588 */
586 589 kstat_named_t arcstat_mfu_size;
587 590 /*
588 591 * Number of bytes consumed by ARC buffers that are eligible for
589 592 * eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
590 593 * state.
591 594 */
592 595 kstat_named_t arcstat_mfu_evictable_data;
593 596 /*
594 597 * Number of bytes consumed by ARC buffers that are eligible for
595 598 * eviction, of type ARC_BUFC_METADATA, and reside in the
596 599 * arc_mfu state.
597 600 */
598 601 kstat_named_t arcstat_mfu_evictable_metadata;
599 602 /*
600 603 * Total number of bytes that *would have been* consumed by ARC
601 604 * buffers in the arc_mfu_ghost state. See the comment above
602 605 * arcstat_mru_ghost_size for more details.
603 606 */
604 607 kstat_named_t arcstat_mfu_ghost_size;
605 608 /*
606 609 * Number of bytes that *would have been* consumed by ARC
607 610 * buffers that are eligible for eviction, of type
608 611 * ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
609 612 */
610 613 kstat_named_t arcstat_mfu_ghost_evictable_data;
611 614 /*
612 615 * Number of bytes that *would have been* consumed by ARC
613 616 * buffers that are eligible for eviction, of type
614 617 * ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
615 618 */
616 619 kstat_named_t arcstat_mfu_ghost_evictable_metadata;
617 620 kstat_named_t arcstat_l2_hits;
618 621 kstat_named_t arcstat_l2_misses;
619 622 kstat_named_t arcstat_l2_feeds;
620 623 kstat_named_t arcstat_l2_rw_clash;
621 624 kstat_named_t arcstat_l2_read_bytes;
622 625 kstat_named_t arcstat_l2_write_bytes;
623 626 kstat_named_t arcstat_l2_writes_sent;
624 627 kstat_named_t arcstat_l2_writes_done;
625 628 kstat_named_t arcstat_l2_writes_error;
626 629 kstat_named_t arcstat_l2_writes_lock_retry;
627 630 kstat_named_t arcstat_l2_evict_lock_retry;
628 631 kstat_named_t arcstat_l2_evict_reading;
629 632 kstat_named_t arcstat_l2_evict_l1cached;
630 633 kstat_named_t arcstat_l2_free_on_write;
631 634 kstat_named_t arcstat_l2_abort_lowmem;
632 635 kstat_named_t arcstat_l2_cksum_bad;
633 636 kstat_named_t arcstat_l2_io_error;
634 637 kstat_named_t arcstat_l2_lsize;
635 638 kstat_named_t arcstat_l2_psize;
636 639 kstat_named_t arcstat_l2_hdr_size;
637 640 kstat_named_t arcstat_memory_throttle_count;
638 641 kstat_named_t arcstat_meta_used;
639 642 kstat_named_t arcstat_meta_limit;
640 643 kstat_named_t arcstat_meta_max;
641 644 kstat_named_t arcstat_meta_min;
642 645 kstat_named_t arcstat_sync_wait_for_async;
643 646 kstat_named_t arcstat_demand_hit_predictive_prefetch;
644 647 } arc_stats_t;
645 648
646 649 static arc_stats_t arc_stats = {
647 650 { "hits", KSTAT_DATA_UINT64 },
648 651 { "misses", KSTAT_DATA_UINT64 },
649 652 { "demand_data_hits", KSTAT_DATA_UINT64 },
650 653 { "demand_data_misses", KSTAT_DATA_UINT64 },
651 654 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
652 655 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
653 656 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
654 657 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
655 658 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
656 659 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
657 660 { "mru_hits", KSTAT_DATA_UINT64 },
658 661 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
659 662 { "mfu_hits", KSTAT_DATA_UINT64 },
660 663 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
661 664 { "deleted", KSTAT_DATA_UINT64 },
662 665 { "mutex_miss", KSTAT_DATA_UINT64 },
663 666 { "evict_skip", KSTAT_DATA_UINT64 },
664 667 { "evict_not_enough", KSTAT_DATA_UINT64 },
665 668 { "evict_l2_cached", KSTAT_DATA_UINT64 },
666 669 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
667 670 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
668 671 { "evict_l2_skip", KSTAT_DATA_UINT64 },
669 672 { "hash_elements", KSTAT_DATA_UINT64 },
670 673 { "hash_elements_max", KSTAT_DATA_UINT64 },
671 674 { "hash_collisions", KSTAT_DATA_UINT64 },
672 675 { "hash_chains", KSTAT_DATA_UINT64 },
673 676 { "hash_chain_max", KSTAT_DATA_UINT64 },
674 677 { "p", KSTAT_DATA_UINT64 },
675 678 { "c", KSTAT_DATA_UINT64 },
676 679 { "c_min", KSTAT_DATA_UINT64 },
677 680 { "c_max", KSTAT_DATA_UINT64 },
678 681 { "size", KSTAT_DATA_UINT64 },
679 682 { "compressed_size", KSTAT_DATA_UINT64 },
680 683 { "uncompressed_size", KSTAT_DATA_UINT64 },
681 684 { "overhead_size", KSTAT_DATA_UINT64 },
682 685 { "hdr_size", KSTAT_DATA_UINT64 },
683 686 { "data_size", KSTAT_DATA_UINT64 },
684 687 { "metadata_size", KSTAT_DATA_UINT64 },
685 688 { "other_size", KSTAT_DATA_UINT64 },
686 689 { "anon_size", KSTAT_DATA_UINT64 },
687 690 { "anon_evictable_data", KSTAT_DATA_UINT64 },
688 691 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
689 692 { "mru_size", KSTAT_DATA_UINT64 },
690 693 { "mru_evictable_data", KSTAT_DATA_UINT64 },
691 694 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
692 695 { "mru_ghost_size", KSTAT_DATA_UINT64 },
693 696 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
694 697 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
695 698 { "mfu_size", KSTAT_DATA_UINT64 },
696 699 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
697 700 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
698 701 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
699 702 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
700 703 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
701 704 { "l2_hits", KSTAT_DATA_UINT64 },
702 705 { "l2_misses", KSTAT_DATA_UINT64 },
703 706 { "l2_feeds", KSTAT_DATA_UINT64 },
704 707 { "l2_rw_clash", KSTAT_DATA_UINT64 },
705 708 { "l2_read_bytes", KSTAT_DATA_UINT64 },
706 709 { "l2_write_bytes", KSTAT_DATA_UINT64 },
707 710 { "l2_writes_sent", KSTAT_DATA_UINT64 },
708 711 { "l2_writes_done", KSTAT_DATA_UINT64 },
709 712 { "l2_writes_error", KSTAT_DATA_UINT64 },
710 713 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
711 714 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
712 715 { "l2_evict_reading", KSTAT_DATA_UINT64 },
713 716 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
714 717 { "l2_free_on_write", KSTAT_DATA_UINT64 },
715 718 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
716 719 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
717 720 { "l2_io_error", KSTAT_DATA_UINT64 },
718 721 { "l2_size", KSTAT_DATA_UINT64 },
719 722 { "l2_asize", KSTAT_DATA_UINT64 },
720 723 { "l2_hdr_size", KSTAT_DATA_UINT64 },
721 724 { "memory_throttle_count", KSTAT_DATA_UINT64 },
722 725 { "arc_meta_used", KSTAT_DATA_UINT64 },
723 726 { "arc_meta_limit", KSTAT_DATA_UINT64 },
724 727 { "arc_meta_max", KSTAT_DATA_UINT64 },
725 728 { "arc_meta_min", KSTAT_DATA_UINT64 },
726 729 { "sync_wait_for_async", KSTAT_DATA_UINT64 },
727 730 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
728 731 };
729 732
730 733 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
731 734
732 735 #define ARCSTAT_INCR(stat, val) \
733 736 atomic_add_64(&arc_stats.stat.value.ui64, (val))
734 737
735 738 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
736 739 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
737 740
738 741 #define ARCSTAT_MAX(stat, val) { \
739 742 uint64_t m; \
740 743 while ((val) > (m = arc_stats.stat.value.ui64) && \
741 744 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
742 745 continue; \
743 746 }
744 747
745 748 #define ARCSTAT_MAXSTAT(stat) \
746 749 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
747 750
748 751 /*
749 752 * We define a macro to allow ARC hits/misses to be easily broken down by
750 753 * two separate conditions, giving a total of four different subtypes for
751 754 * each of hits and misses (so eight statistics total).
752 755 */
753 756 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
754 757 if (cond1) { \
755 758 if (cond2) { \
756 759 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
757 760 } else { \
758 761 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
759 762 } \
760 763 } else { \
761 764 if (cond2) { \
762 765 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
763 766 } else { \
764 767 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
765 768 } \
766 769 }
767 770
768 771 kstat_t *arc_ksp;
769 772 static arc_state_t *arc_anon;
770 773 static arc_state_t *arc_mru;
771 774 static arc_state_t *arc_mru_ghost;
772 775 static arc_state_t *arc_mfu;
773 776 static arc_state_t *arc_mfu_ghost;
774 777 static arc_state_t *arc_l2c_only;
775 778
776 779 /*
777 780 * There are several ARC variables that are critical to export as kstats --
778 781 * but we don't want to have to grovel around in the kstat whenever we wish to
779 782 * manipulate them. For these variables, we therefore define them to be in
780 783 * terms of the statistic variable. This assures that we are not introducing
781 784 * the possibility of inconsistency by having shadow copies of the variables,
782 785 * while still allowing the code to be readable.
783 786 */
784 787 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
785 788 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
786 789 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
787 790 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
788 791 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
789 792 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
790 793 #define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
791 794 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
792 795 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
793 796
794 797 /* compressed size of entire arc */
795 798 #define arc_compressed_size ARCSTAT(arcstat_compressed_size)
796 799 /* uncompressed size of entire arc */
797 800 #define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
798 801 /* number of bytes in the arc from arc_buf_t's */
799 802 #define arc_overhead_size ARCSTAT(arcstat_overhead_size)
800 803
801 804 static int arc_no_grow; /* Don't try to grow cache size */
802 805 static uint64_t arc_tempreserve;
803 806 static uint64_t arc_loaned_bytes;
804 807
805 808 typedef struct arc_callback arc_callback_t;
806 809
807 810 struct arc_callback {
808 811 void *acb_private;
809 812 arc_done_func_t *acb_done;
810 813 arc_buf_t *acb_buf;
811 814 boolean_t acb_compressed;
812 815 zio_t *acb_zio_dummy;
813 816 arc_callback_t *acb_next;
814 817 };
815 818
816 819 typedef struct arc_write_callback arc_write_callback_t;
817 820
818 821 struct arc_write_callback {
819 822 void *awcb_private;
820 823 arc_done_func_t *awcb_ready;
821 824 arc_done_func_t *awcb_children_ready;
822 825 arc_done_func_t *awcb_physdone;
823 826 arc_done_func_t *awcb_done;
824 827 arc_buf_t *awcb_buf;
825 828 };
826 829
827 830 /*
828 831 * ARC buffers are separated into multiple structs as a memory saving measure:
829 832 * - Common fields struct, always defined, and embedded within it:
830 833 * - L2-only fields, always allocated but undefined when not in L2ARC
831 834 * - L1-only fields, only allocated when in L1ARC
832 835 *
833 836 * Buffer in L1 Buffer only in L2
834 837 * +------------------------+ +------------------------+
835 838 * | arc_buf_hdr_t | | arc_buf_hdr_t |
836 839 * | | | |
837 840 * | | | |
838 841 * | | | |
839 842 * +------------------------+ +------------------------+
840 843 * | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
841 844 * | (undefined if L1-only) | | |
842 845 * +------------------------+ +------------------------+
843 846 * | l1arc_buf_hdr_t |
844 847 * | |
845 848 * | |
846 849 * | |
847 850 * | |
848 851 * +------------------------+
849 852 *
850 853 * Because it's possible for the L2ARC to become extremely large, we can wind
851 854 * up eating a lot of memory in L2ARC buffer headers, so the size of a header
852 855 * is minimized by only allocating the fields necessary for an L1-cached buffer
853 856 * when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
854 857 * l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
855 858 * words in pointers. arc_hdr_realloc() is used to switch a header between
856 859 * these two allocation states.
857 860 */
858 861 typedef struct l1arc_buf_hdr {
859 862 kmutex_t b_freeze_lock;
860 863 zio_cksum_t *b_freeze_cksum;
861 864 #ifdef ZFS_DEBUG
862 865 /*
863 866 * Used for debugging with kmem_flags - by allocating and freeing
864 867 * b_thawed when the buffer is thawed, we get a record of the stack
865 868 * trace that thawed it.
866 869 */
867 870 void *b_thawed;
868 871 #endif
869 872
870 873 arc_buf_t *b_buf;
871 874 uint32_t b_bufcnt;
872 875 /* for waiting on writes to complete */
873 876 kcondvar_t b_cv;
874 877 uint8_t b_byteswap;
875 878
876 879 /* protected by arc state mutex */
877 880 arc_state_t *b_state;
878 881 multilist_node_t b_arc_node;
879 882
880 883 /* updated atomically */
881 884 clock_t b_arc_access;
882 885
883 886 /* self protecting */
884 887 refcount_t b_refcnt;
885 888
886 889 arc_callback_t *b_acb;
887 890 abd_t *b_pabd;
888 891 } l1arc_buf_hdr_t;
889 892
890 893 typedef struct l2arc_dev l2arc_dev_t;
891 894
892 895 typedef struct l2arc_buf_hdr {
893 896 /* protected by arc_buf_hdr mutex */
894 897 l2arc_dev_t *b_dev; /* L2ARC device */
895 898 uint64_t b_daddr; /* disk address, offset byte */
896 899
897 900 list_node_t b_l2node;
898 901 } l2arc_buf_hdr_t;
899 902
900 903 struct arc_buf_hdr {
901 904 /* protected by hash lock */
902 905 dva_t b_dva;
903 906 uint64_t b_birth;
904 907
905 908 arc_buf_contents_t b_type;
906 909 arc_buf_hdr_t *b_hash_next;
907 910 arc_flags_t b_flags;
908 911
909 912 /*
910 913 * This field stores the size of the data buffer after
911 914 * compression, and is set in the arc's zio completion handlers.
912 915 * It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
913 916 *
914 917 * While the block pointers can store up to 32MB in their psize
915 918 * field, we can only store up to 32MB minus 512B. This is due
916 919 * to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
917 920 * a field of zeros represents 512B in the bp). We can't use a
918 921 * bias of 1 since we need to reserve a psize of zero, here, to
919 922 * represent holes and embedded blocks.
920 923 *
921 924 * This isn't a problem in practice, since the maximum size of a
922 925 * buffer is limited to 16MB, so we never need to store 32MB in
923 926 * this field. Even in the upstream illumos code base, the
924 927 * maximum size of a buffer is limited to 16MB.
925 928 */
926 929 uint16_t b_psize;
927 930
928 931 /*
929 932 * This field stores the size of the data buffer before
930 933 * compression, and cannot change once set. It is in units
931 934 * of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
932 935 */
933 936 uint16_t b_lsize; /* immutable */
934 937 uint64_t b_spa; /* immutable */
935 938
936 939 /* L2ARC fields. Undefined when not in L2ARC. */
937 940 l2arc_buf_hdr_t b_l2hdr;
938 941 /* L1ARC fields. Undefined when in l2arc_only state */
939 942 l1arc_buf_hdr_t b_l1hdr;
940 943 };
941 944
942 945 #define GHOST_STATE(state) \
943 946 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
944 947 (state) == arc_l2c_only)
945 948
946 949 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
947 950 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
948 951 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
949 952 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
950 953 #define HDR_COMPRESSION_ENABLED(hdr) \
951 954 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
952 955
953 956 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
954 957 #define HDR_L2_READING(hdr) \
955 958 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
956 959 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
957 960 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
958 961 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
959 962 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
960 963 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
961 964
962 965 #define HDR_ISTYPE_METADATA(hdr) \
963 966 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
964 967 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
965 968
966 969 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
967 970 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
968 971
969 972 /* For storing compression mode in b_flags */
970 973 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
971 974
972 975 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
973 976 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
974 977 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
975 978 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
976 979
977 980 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
978 981 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
979 982 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
980 983
981 984 /*
982 985 * Other sizes
983 986 */
984 987
985 988 #define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
986 989 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
987 990
988 991 /*
989 992 * Hash table routines
990 993 */
991 994
992 995 #define HT_LOCK_PAD 64
993 996
994 997 struct ht_lock {
995 998 kmutex_t ht_lock;
996 999 #ifdef _KERNEL
997 1000 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
998 1001 #endif
999 1002 };
1000 1003
1001 1004 #define BUF_LOCKS 256
1002 1005 typedef struct buf_hash_table {
1003 1006 uint64_t ht_mask;
1004 1007 arc_buf_hdr_t **ht_table;
1005 1008 struct ht_lock ht_locks[BUF_LOCKS];
1006 1009 } buf_hash_table_t;
1007 1010
1008 1011 static buf_hash_table_t buf_hash_table;
1009 1012
1010 1013 #define BUF_HASH_INDEX(spa, dva, birth) \
1011 1014 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
1012 1015 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
1013 1016 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
1014 1017 #define HDR_LOCK(hdr) \
1015 1018 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
1016 1019
1017 1020 uint64_t zfs_crc64_table[256];
1018 1021
1019 1022 /*
1020 1023 * Level 2 ARC
1021 1024 */
1022 1025
1023 1026 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
1024 1027 #define L2ARC_HEADROOM 2 /* num of writes */
1025 1028 /*
1026 1029 * If we discover during ARC scan any buffers to be compressed, we boost
1027 1030 * our headroom for the next scanning cycle by this percentage multiple.
1028 1031 */
1029 1032 #define L2ARC_HEADROOM_BOOST 200
1030 1033 #define L2ARC_FEED_SECS 1 /* caching interval secs */
1031 1034 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
1032 1035
1033 1036 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
1034 1037 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
1035 1038
1036 1039 /* L2ARC Performance Tunables */
1037 1040 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
1038 1041 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
1039 1042 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
1040 1043 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
1041 1044 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
1042 1045 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
1043 1046 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
1044 1047 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
1045 1048 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
1046 1049
1047 1050 /*
1048 1051 * L2ARC Internals
1049 1052 */
1050 1053 struct l2arc_dev {
1051 1054 vdev_t *l2ad_vdev; /* vdev */
1052 1055 spa_t *l2ad_spa; /* spa */
1053 1056 uint64_t l2ad_hand; /* next write location */
1054 1057 uint64_t l2ad_start; /* first addr on device */
1055 1058 uint64_t l2ad_end; /* last addr on device */
1056 1059 boolean_t l2ad_first; /* first sweep through */
1057 1060 boolean_t l2ad_writing; /* currently writing */
1058 1061 kmutex_t l2ad_mtx; /* lock for buffer list */
1059 1062 list_t l2ad_buflist; /* buffer list */
1060 1063 list_node_t l2ad_node; /* device list node */
1061 1064 refcount_t l2ad_alloc; /* allocated bytes */
1062 1065 };
1063 1066
1064 1067 static list_t L2ARC_dev_list; /* device list */
1065 1068 static list_t *l2arc_dev_list; /* device list pointer */
1066 1069 static kmutex_t l2arc_dev_mtx; /* device list mutex */
1067 1070 static l2arc_dev_t *l2arc_dev_last; /* last device used */
1068 1071 static list_t L2ARC_free_on_write; /* free after write buf list */
1069 1072 static list_t *l2arc_free_on_write; /* free after write list ptr */
1070 1073 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
1071 1074 static uint64_t l2arc_ndev; /* number of devices */
1072 1075
1073 1076 typedef struct l2arc_read_callback {
1074 1077 arc_buf_hdr_t *l2rcb_hdr; /* read header */
1075 1078 blkptr_t l2rcb_bp; /* original blkptr */
1076 1079 zbookmark_phys_t l2rcb_zb; /* original bookmark */
1077 1080 int l2rcb_flags; /* original flags */
1078 1081 abd_t *l2rcb_abd; /* temporary buffer */
1079 1082 } l2arc_read_callback_t;
1080 1083
1081 1084 typedef struct l2arc_write_callback {
1082 1085 l2arc_dev_t *l2wcb_dev; /* device info */
1083 1086 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
1084 1087 } l2arc_write_callback_t;
1085 1088
1086 1089 typedef struct l2arc_data_free {
1087 1090 /* protected by l2arc_free_on_write_mtx */
1088 1091 abd_t *l2df_abd;
1089 1092 size_t l2df_size;
1090 1093 arc_buf_contents_t l2df_type;
1091 1094 list_node_t l2df_list_node;
1092 1095 } l2arc_data_free_t;
1093 1096
1094 1097 static kmutex_t l2arc_feed_thr_lock;
1095 1098 static kcondvar_t l2arc_feed_thr_cv;
1096 1099 static uint8_t l2arc_thread_exit;
1097 1100
1098 1101 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *);
1099 1102 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
1100 1103 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *);
1101 1104 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
1102 1105 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
1103 1106 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
1104 1107 static void arc_hdr_free_pabd(arc_buf_hdr_t *);
1105 1108 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *);
1106 1109 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
1107 1110 static boolean_t arc_is_overflowing();
1108 1111 static void arc_buf_watch(arc_buf_t *);
1109 1112
1110 1113 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
1111 1114 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
1112 1115 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1113 1116 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
1114 1117
1115 1118 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
1116 1119 static void l2arc_read_done(zio_t *);
1117 1120
1118 1121 static uint64_t
1119 1122 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
1120 1123 {
1121 1124 uint8_t *vdva = (uint8_t *)dva;
1122 1125 uint64_t crc = -1ULL;
1123 1126 int i;
1124 1127
1125 1128 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
1126 1129
1127 1130 for (i = 0; i < sizeof (dva_t); i++)
1128 1131 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
1129 1132
1130 1133 crc ^= (spa>>8) ^ birth;
1131 1134
1132 1135 return (crc);
1133 1136 }
1134 1137
1135 1138 #define HDR_EMPTY(hdr) \
1136 1139 ((hdr)->b_dva.dva_word[0] == 0 && \
1137 1140 (hdr)->b_dva.dva_word[1] == 0)
1138 1141
1139 1142 #define HDR_EQUAL(spa, dva, birth, hdr) \
1140 1143 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
1141 1144 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
1142 1145 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
1143 1146
1144 1147 static void
1145 1148 buf_discard_identity(arc_buf_hdr_t *hdr)
1146 1149 {
1147 1150 hdr->b_dva.dva_word[0] = 0;
1148 1151 hdr->b_dva.dva_word[1] = 0;
1149 1152 hdr->b_birth = 0;
1150 1153 }
1151 1154
1152 1155 static arc_buf_hdr_t *
1153 1156 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
1154 1157 {
1155 1158 const dva_t *dva = BP_IDENTITY(bp);
1156 1159 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
1157 1160 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
1158 1161 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1159 1162 arc_buf_hdr_t *hdr;
1160 1163
1161 1164 mutex_enter(hash_lock);
1162 1165 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
1163 1166 hdr = hdr->b_hash_next) {
1164 1167 if (HDR_EQUAL(spa, dva, birth, hdr)) {
1165 1168 *lockp = hash_lock;
1166 1169 return (hdr);
1167 1170 }
1168 1171 }
1169 1172 mutex_exit(hash_lock);
1170 1173 *lockp = NULL;
1171 1174 return (NULL);
1172 1175 }
1173 1176
1174 1177 /*
1175 1178 * Insert an entry into the hash table. If there is already an element
1176 1179 * equal to elem in the hash table, then the already existing element
1177 1180 * will be returned and the new element will not be inserted.
1178 1181 * Otherwise returns NULL.
1179 1182 * If lockp == NULL, the caller is assumed to already hold the hash lock.
1180 1183 */
1181 1184 static arc_buf_hdr_t *
1182 1185 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
1183 1186 {
1184 1187 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1185 1188 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
1186 1189 arc_buf_hdr_t *fhdr;
1187 1190 uint32_t i;
1188 1191
1189 1192 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
1190 1193 ASSERT(hdr->b_birth != 0);
1191 1194 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1192 1195
1193 1196 if (lockp != NULL) {
1194 1197 *lockp = hash_lock;
1195 1198 mutex_enter(hash_lock);
1196 1199 } else {
1197 1200 ASSERT(MUTEX_HELD(hash_lock));
1198 1201 }
1199 1202
1200 1203 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
1201 1204 fhdr = fhdr->b_hash_next, i++) {
1202 1205 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
1203 1206 return (fhdr);
1204 1207 }
1205 1208
1206 1209 hdr->b_hash_next = buf_hash_table.ht_table[idx];
1207 1210 buf_hash_table.ht_table[idx] = hdr;
1208 1211 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1209 1212
1210 1213 /* collect some hash table performance data */
1211 1214 if (i > 0) {
1212 1215 ARCSTAT_BUMP(arcstat_hash_collisions);
1213 1216 if (i == 1)
1214 1217 ARCSTAT_BUMP(arcstat_hash_chains);
1215 1218
1216 1219 ARCSTAT_MAX(arcstat_hash_chain_max, i);
1217 1220 }
1218 1221
1219 1222 ARCSTAT_BUMP(arcstat_hash_elements);
1220 1223 ARCSTAT_MAXSTAT(arcstat_hash_elements);
1221 1224
1222 1225 return (NULL);
1223 1226 }
1224 1227
1225 1228 static void
1226 1229 buf_hash_remove(arc_buf_hdr_t *hdr)
1227 1230 {
1228 1231 arc_buf_hdr_t *fhdr, **hdrp;
1229 1232 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
1230 1233
1231 1234 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
1232 1235 ASSERT(HDR_IN_HASH_TABLE(hdr));
1233 1236
1234 1237 hdrp = &buf_hash_table.ht_table[idx];
1235 1238 while ((fhdr = *hdrp) != hdr) {
1236 1239 ASSERT3P(fhdr, !=, NULL);
1237 1240 hdrp = &fhdr->b_hash_next;
1238 1241 }
1239 1242 *hdrp = hdr->b_hash_next;
1240 1243 hdr->b_hash_next = NULL;
1241 1244 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
1242 1245
1243 1246 /* collect some hash table performance data */
1244 1247 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
1245 1248
1246 1249 if (buf_hash_table.ht_table[idx] &&
1247 1250 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
1248 1251 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
1249 1252 }
1250 1253
1251 1254 /*
1252 1255 * Global data structures and functions for the buf kmem cache.
1253 1256 */
1254 1257 static kmem_cache_t *hdr_full_cache;
1255 1258 static kmem_cache_t *hdr_l2only_cache;
1256 1259 static kmem_cache_t *buf_cache;
1257 1260
1258 1261 static void
1259 1262 buf_fini(void)
1260 1263 {
1261 1264 int i;
1262 1265
1263 1266 kmem_free(buf_hash_table.ht_table,
1264 1267 (buf_hash_table.ht_mask + 1) * sizeof (void *));
1265 1268 for (i = 0; i < BUF_LOCKS; i++)
1266 1269 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
1267 1270 kmem_cache_destroy(hdr_full_cache);
1268 1271 kmem_cache_destroy(hdr_l2only_cache);
1269 1272 kmem_cache_destroy(buf_cache);
1270 1273 }
1271 1274
1272 1275 /*
1273 1276 * Constructor callback - called when the cache is empty
1274 1277 * and a new buf is requested.
1275 1278 */
1276 1279 /* ARGSUSED */
1277 1280 static int
1278 1281 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1279 1282 {
1280 1283 arc_buf_hdr_t *hdr = vbuf;
1281 1284
1282 1285 bzero(hdr, HDR_FULL_SIZE);
1283 1286 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1284 1287 refcount_create(&hdr->b_l1hdr.b_refcnt);
1285 1288 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1286 1289 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1287 1290 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1288 1291
1289 1292 return (0);
1290 1293 }
1291 1294
1292 1295 /* ARGSUSED */
1293 1296 static int
1294 1297 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1295 1298 {
1296 1299 arc_buf_hdr_t *hdr = vbuf;
1297 1300
1298 1301 bzero(hdr, HDR_L2ONLY_SIZE);
1299 1302 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1300 1303
1301 1304 return (0);
1302 1305 }
1303 1306
1304 1307 /* ARGSUSED */
1305 1308 static int
1306 1309 buf_cons(void *vbuf, void *unused, int kmflag)
1307 1310 {
1308 1311 arc_buf_t *buf = vbuf;
1309 1312
1310 1313 bzero(buf, sizeof (arc_buf_t));
1311 1314 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1312 1315 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1313 1316
1314 1317 return (0);
1315 1318 }
1316 1319
1317 1320 /*
1318 1321 * Destructor callback - called when a cached buf is
1319 1322 * no longer required.
1320 1323 */
1321 1324 /* ARGSUSED */
1322 1325 static void
1323 1326 hdr_full_dest(void *vbuf, void *unused)
1324 1327 {
1325 1328 arc_buf_hdr_t *hdr = vbuf;
1326 1329
1327 1330 ASSERT(HDR_EMPTY(hdr));
1328 1331 cv_destroy(&hdr->b_l1hdr.b_cv);
1329 1332 refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1330 1333 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1331 1334 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1332 1335 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1333 1336 }
1334 1337
1335 1338 /* ARGSUSED */
1336 1339 static void
1337 1340 hdr_l2only_dest(void *vbuf, void *unused)
1338 1341 {
1339 1342 arc_buf_hdr_t *hdr = vbuf;
1340 1343
1341 1344 ASSERT(HDR_EMPTY(hdr));
1342 1345 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1343 1346 }
1344 1347
1345 1348 /* ARGSUSED */
1346 1349 static void
1347 1350 buf_dest(void *vbuf, void *unused)
1348 1351 {
1349 1352 arc_buf_t *buf = vbuf;
1350 1353
1351 1354 mutex_destroy(&buf->b_evict_lock);
1352 1355 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1353 1356 }
1354 1357
1355 1358 /*
1356 1359 * Reclaim callback -- invoked when memory is low.
1357 1360 */
1358 1361 /* ARGSUSED */
1359 1362 static void
1360 1363 hdr_recl(void *unused)
1361 1364 {
1362 1365 dprintf("hdr_recl called\n");
1363 1366 /*
1364 1367 * umem calls the reclaim func when we destroy the buf cache,
1365 1368 * which is after we do arc_fini().
1366 1369 */
1367 1370 if (!arc_dead)
1368 1371 cv_signal(&arc_reclaim_thread_cv);
1369 1372 }
1370 1373
1371 1374 static void
1372 1375 buf_init(void)
1373 1376 {
1374 1377 uint64_t *ct;
1375 1378 uint64_t hsize = 1ULL << 12;
1376 1379 int i, j;
1377 1380
1378 1381 /*
1379 1382 * The hash table is big enough to fill all of physical memory
1380 1383 * with an average block size of zfs_arc_average_blocksize (default 8K).
1381 1384 * By default, the table will take up
1382 1385 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1383 1386 */
1384 1387 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1385 1388 hsize <<= 1;
1386 1389 retry:
1387 1390 buf_hash_table.ht_mask = hsize - 1;
1388 1391 buf_hash_table.ht_table =
1389 1392 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1390 1393 if (buf_hash_table.ht_table == NULL) {
1391 1394 ASSERT(hsize > (1ULL << 8));
1392 1395 hsize >>= 1;
1393 1396 goto retry;
1394 1397 }
1395 1398
1396 1399 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1397 1400 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1398 1401 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1399 1402 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1400 1403 NULL, NULL, 0);
1401 1404 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1402 1405 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1403 1406
1404 1407 for (i = 0; i < 256; i++)
1405 1408 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1406 1409 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1407 1410
1408 1411 for (i = 0; i < BUF_LOCKS; i++) {
1409 1412 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1410 1413 NULL, MUTEX_DEFAULT, NULL);
1411 1414 }
1412 1415 }
1413 1416
1414 1417 /*
1415 1418 * This is the size that the buf occupies in memory. If the buf is compressed,
1416 1419 * it will correspond to the compressed size. You should use this method of
1417 1420 * getting the buf size unless you explicitly need the logical size.
1418 1421 */
1419 1422 int32_t
1420 1423 arc_buf_size(arc_buf_t *buf)
1421 1424 {
1422 1425 return (ARC_BUF_COMPRESSED(buf) ?
1423 1426 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1424 1427 }
1425 1428
1426 1429 int32_t
1427 1430 arc_buf_lsize(arc_buf_t *buf)
1428 1431 {
1429 1432 return (HDR_GET_LSIZE(buf->b_hdr));
1430 1433 }
1431 1434
1432 1435 enum zio_compress
1433 1436 arc_get_compression(arc_buf_t *buf)
1434 1437 {
1435 1438 return (ARC_BUF_COMPRESSED(buf) ?
1436 1439 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1437 1440 }
1438 1441
1439 1442 #define ARC_MINTIME (hz>>4) /* 62 ms */
1440 1443
1441 1444 static inline boolean_t
1442 1445 arc_buf_is_shared(arc_buf_t *buf)
1443 1446 {
1444 1447 boolean_t shared = (buf->b_data != NULL &&
1445 1448 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1446 1449 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1447 1450 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1448 1451 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1449 1452 IMPLY(shared, ARC_BUF_SHARED(buf));
1450 1453 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1451 1454
1452 1455 /*
1453 1456 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1454 1457 * already being shared" requirement prevents us from doing that.
1455 1458 */
1456 1459
1457 1460 return (shared);
1458 1461 }
1459 1462
1460 1463 /*
1461 1464 * Free the checksum associated with this header. If there is no checksum, this
1462 1465 * is a no-op.
1463 1466 */
1464 1467 static inline void
1465 1468 arc_cksum_free(arc_buf_hdr_t *hdr)
1466 1469 {
1467 1470 ASSERT(HDR_HAS_L1HDR(hdr));
1468 1471 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1469 1472 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1470 1473 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1471 1474 hdr->b_l1hdr.b_freeze_cksum = NULL;
1472 1475 }
1473 1476 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1474 1477 }
1475 1478
1476 1479 /*
1477 1480 * Return true iff at least one of the bufs on hdr is not compressed.
1478 1481 */
1479 1482 static boolean_t
1480 1483 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1481 1484 {
1482 1485 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1483 1486 if (!ARC_BUF_COMPRESSED(b)) {
1484 1487 return (B_TRUE);
1485 1488 }
1486 1489 }
1487 1490 return (B_FALSE);
1488 1491 }
1489 1492
1490 1493 /*
1491 1494 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1492 1495 * matches the checksum that is stored in the hdr. If there is no checksum,
1493 1496 * or if the buf is compressed, this is a no-op.
1494 1497 */
1495 1498 static void
1496 1499 arc_cksum_verify(arc_buf_t *buf)
1497 1500 {
1498 1501 arc_buf_hdr_t *hdr = buf->b_hdr;
1499 1502 zio_cksum_t zc;
1500 1503
1501 1504 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1502 1505 return;
1503 1506
1504 1507 if (ARC_BUF_COMPRESSED(buf)) {
1505 1508 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1506 1509 arc_hdr_has_uncompressed_buf(hdr));
1507 1510 return;
1508 1511 }
1509 1512
1510 1513 ASSERT(HDR_HAS_L1HDR(hdr));
1511 1514
1512 1515 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1513 1516 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1514 1517 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1515 1518 return;
1516 1519 }
1517 1520
1518 1521 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1519 1522 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1520 1523 panic("buffer modified while frozen!");
1521 1524 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1522 1525 }
1523 1526
1524 1527 static boolean_t
1525 1528 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1526 1529 {
1527 1530 enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
1528 1531 boolean_t valid_cksum;
1529 1532
1530 1533 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1531 1534 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1532 1535
1533 1536 /*
1534 1537 * We rely on the blkptr's checksum to determine if the block
1535 1538 * is valid or not. When compressed arc is enabled, the l2arc
1536 1539 * writes the block to the l2arc just as it appears in the pool.
1537 1540 * This allows us to use the blkptr's checksum to validate the
1538 1541 * data that we just read off of the l2arc without having to store
1539 1542 * a separate checksum in the arc_buf_hdr_t. However, if compressed
1540 1543 * arc is disabled, then the data written to the l2arc is always
1541 1544 * uncompressed and won't match the block as it exists in the main
1542 1545 * pool. When this is the case, we must first compress it if it is
1543 1546 * compressed on the main pool before we can validate the checksum.
1544 1547 */
1545 1548 if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
1546 1549 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1547 1550 uint64_t lsize = HDR_GET_LSIZE(hdr);
1548 1551 uint64_t csize;
1549 1552
1550 1553 abd_t *cdata = abd_alloc_linear(HDR_GET_PSIZE(hdr), B_TRUE);
1551 1554 csize = zio_compress_data(compress, zio->io_abd,
1552 1555 abd_to_buf(cdata), lsize);
1553 1556
1554 1557 ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
1555 1558 if (csize < HDR_GET_PSIZE(hdr)) {
1556 1559 /*
1557 1560 * Compressed blocks are always a multiple of the
1558 1561 * smallest ashift in the pool. Ideally, we would
1559 1562 * like to round up the csize to the next
1560 1563 * spa_min_ashift but that value may have changed
1561 1564 * since the block was last written. Instead,
1562 1565 * we rely on the fact that the hdr's psize
1563 1566 * was set to the psize of the block when it was
1564 1567 * last written. We set the csize to that value
1565 1568 * and zero out any part that should not contain
1566 1569 * data.
1567 1570 */
1568 1571 abd_zero_off(cdata, csize, HDR_GET_PSIZE(hdr) - csize);
1569 1572 csize = HDR_GET_PSIZE(hdr);
1570 1573 }
1571 1574 zio_push_transform(zio, cdata, csize, HDR_GET_PSIZE(hdr), NULL);
1572 1575 }
1573 1576
1574 1577 /*
1575 1578 * Block pointers always store the checksum for the logical data.
1576 1579 * If the block pointer has the gang bit set, then the checksum
1577 1580 * it represents is for the reconstituted data and not for an
1578 1581 * individual gang member. The zio pipeline, however, must be able to
1579 1582 * determine the checksum of each of the gang constituents so it
1580 1583 * treats the checksum comparison differently than what we need
1581 1584 * for l2arc blocks. This prevents us from using the
1582 1585 * zio_checksum_error() interface directly. Instead we must call the
1583 1586 * zio_checksum_error_impl() so that we can ensure the checksum is
1584 1587 * generated using the correct checksum algorithm and accounts for the
1585 1588 * logical I/O size and not just a gang fragment.
1586 1589 */
1587 1590 valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1588 1591 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1589 1592 zio->io_offset, NULL) == 0);
1590 1593 zio_pop_transforms(zio);
1591 1594 return (valid_cksum);
1592 1595 }
1593 1596
1594 1597 /*
1595 1598 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1596 1599 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1597 1600 * isn't modified later on. If buf is compressed or there is already a checksum
1598 1601 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1599 1602 */
1600 1603 static void
1601 1604 arc_cksum_compute(arc_buf_t *buf)
1602 1605 {
1603 1606 arc_buf_hdr_t *hdr = buf->b_hdr;
1604 1607
1605 1608 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1606 1609 return;
1607 1610
1608 1611 ASSERT(HDR_HAS_L1HDR(hdr));
1609 1612
1610 1613 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1611 1614 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1612 1615 ASSERT(arc_hdr_has_uncompressed_buf(hdr));
1613 1616 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1614 1617 return;
1615 1618 } else if (ARC_BUF_COMPRESSED(buf)) {
1616 1619 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1617 1620 return;
1618 1621 }
1619 1622
1620 1623 ASSERT(!ARC_BUF_COMPRESSED(buf));
1621 1624 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1622 1625 KM_SLEEP);
1623 1626 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1624 1627 hdr->b_l1hdr.b_freeze_cksum);
1625 1628 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1626 1629 arc_buf_watch(buf);
1627 1630 }
1628 1631
1629 1632 #ifndef _KERNEL
1630 1633 typedef struct procctl {
1631 1634 long cmd;
1632 1635 prwatch_t prwatch;
1633 1636 } procctl_t;
1634 1637 #endif
1635 1638
1636 1639 /* ARGSUSED */
1637 1640 static void
1638 1641 arc_buf_unwatch(arc_buf_t *buf)
1639 1642 {
1640 1643 #ifndef _KERNEL
1641 1644 if (arc_watch) {
1642 1645 int result;
1643 1646 procctl_t ctl;
1644 1647 ctl.cmd = PCWATCH;
1645 1648 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1646 1649 ctl.prwatch.pr_size = 0;
1647 1650 ctl.prwatch.pr_wflags = 0;
1648 1651 result = write(arc_procfd, &ctl, sizeof (ctl));
1649 1652 ASSERT3U(result, ==, sizeof (ctl));
1650 1653 }
1651 1654 #endif
1652 1655 }
1653 1656
1654 1657 /* ARGSUSED */
1655 1658 static void
1656 1659 arc_buf_watch(arc_buf_t *buf)
1657 1660 {
1658 1661 #ifndef _KERNEL
1659 1662 if (arc_watch) {
1660 1663 int result;
1661 1664 procctl_t ctl;
1662 1665 ctl.cmd = PCWATCH;
1663 1666 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1664 1667 ctl.prwatch.pr_size = arc_buf_size(buf);
1665 1668 ctl.prwatch.pr_wflags = WA_WRITE;
1666 1669 result = write(arc_procfd, &ctl, sizeof (ctl));
1667 1670 ASSERT3U(result, ==, sizeof (ctl));
1668 1671 }
1669 1672 #endif
1670 1673 }
1671 1674
1672 1675 static arc_buf_contents_t
1673 1676 arc_buf_type(arc_buf_hdr_t *hdr)
1674 1677 {
1675 1678 arc_buf_contents_t type;
1676 1679 if (HDR_ISTYPE_METADATA(hdr)) {
1677 1680 type = ARC_BUFC_METADATA;
1678 1681 } else {
1679 1682 type = ARC_BUFC_DATA;
1680 1683 }
1681 1684 VERIFY3U(hdr->b_type, ==, type);
1682 1685 return (type);
1683 1686 }
1684 1687
1685 1688 boolean_t
1686 1689 arc_is_metadata(arc_buf_t *buf)
1687 1690 {
1688 1691 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
1689 1692 }
1690 1693
1691 1694 static uint32_t
1692 1695 arc_bufc_to_flags(arc_buf_contents_t type)
1693 1696 {
1694 1697 switch (type) {
1695 1698 case ARC_BUFC_DATA:
1696 1699 /* metadata field is 0 if buffer contains normal data */
1697 1700 return (0);
1698 1701 case ARC_BUFC_METADATA:
1699 1702 return (ARC_FLAG_BUFC_METADATA);
1700 1703 default:
1701 1704 break;
1702 1705 }
1703 1706 panic("undefined ARC buffer type!");
1704 1707 return ((uint32_t)-1);
1705 1708 }
1706 1709
1707 1710 void
1708 1711 arc_buf_thaw(arc_buf_t *buf)
1709 1712 {
1710 1713 arc_buf_hdr_t *hdr = buf->b_hdr;
1711 1714
1712 1715 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
1713 1716 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1714 1717
1715 1718 arc_cksum_verify(buf);
1716 1719
1717 1720 /*
1718 1721 * Compressed buffers do not manipulate the b_freeze_cksum or
1719 1722 * allocate b_thawed.
1720 1723 */
1721 1724 if (ARC_BUF_COMPRESSED(buf)) {
1722 1725 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1723 1726 arc_hdr_has_uncompressed_buf(hdr));
1724 1727 return;
1725 1728 }
1726 1729
1727 1730 ASSERT(HDR_HAS_L1HDR(hdr));
1728 1731 arc_cksum_free(hdr);
1729 1732
1730 1733 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1731 1734 #ifdef ZFS_DEBUG
1732 1735 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1733 1736 if (hdr->b_l1hdr.b_thawed != NULL)
1734 1737 kmem_free(hdr->b_l1hdr.b_thawed, 1);
1735 1738 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
1736 1739 }
1737 1740 #endif
1738 1741
1739 1742 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1740 1743
1741 1744 arc_buf_unwatch(buf);
1742 1745 }
1743 1746
1744 1747 void
1745 1748 arc_buf_freeze(arc_buf_t *buf)
1746 1749 {
1747 1750 arc_buf_hdr_t *hdr = buf->b_hdr;
1748 1751 kmutex_t *hash_lock;
1749 1752
1750 1753 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1751 1754 return;
1752 1755
1753 1756 if (ARC_BUF_COMPRESSED(buf)) {
1754 1757 ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
1755 1758 arc_hdr_has_uncompressed_buf(hdr));
1756 1759 return;
1757 1760 }
1758 1761
1759 1762 hash_lock = HDR_LOCK(hdr);
1760 1763 mutex_enter(hash_lock);
1761 1764
1762 1765 ASSERT(HDR_HAS_L1HDR(hdr));
1763 1766 ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL ||
1764 1767 hdr->b_l1hdr.b_state == arc_anon);
1765 1768 arc_cksum_compute(buf);
1766 1769 mutex_exit(hash_lock);
1767 1770 }
1768 1771
1769 1772 /*
1770 1773 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
1771 1774 * the following functions should be used to ensure that the flags are
1772 1775 * updated in a thread-safe way. When manipulating the flags either
1773 1776 * the hash_lock must be held or the hdr must be undiscoverable. This
1774 1777 * ensures that we're not racing with any other threads when updating
1775 1778 * the flags.
1776 1779 */
1777 1780 static inline void
1778 1781 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1779 1782 {
1780 1783 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1781 1784 hdr->b_flags |= flags;
1782 1785 }
1783 1786
1784 1787 static inline void
1785 1788 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1786 1789 {
1787 1790 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1788 1791 hdr->b_flags &= ~flags;
1789 1792 }
1790 1793
1791 1794 /*
1792 1795 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
1793 1796 * done in a special way since we have to clear and set bits
1794 1797 * at the same time. Consumers that wish to set the compression bits
1795 1798 * must use this function to ensure that the flags are updated in
1796 1799 * thread-safe manner.
1797 1800 */
1798 1801 static void
1799 1802 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
1800 1803 {
1801 1804 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
1802 1805
1803 1806 /*
1804 1807 * Holes and embedded blocks will always have a psize = 0 so
1805 1808 * we ignore the compression of the blkptr and set the
1806 1809 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
1807 1810 * Holes and embedded blocks remain anonymous so we don't
1808 1811 * want to uncompress them. Mark them as uncompressed.
1809 1812 */
1810 1813 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
1811 1814 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1812 1815 HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
1813 1816 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
1814 1817 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1815 1818 } else {
1816 1819 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1817 1820 HDR_SET_COMPRESS(hdr, cmp);
1818 1821 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
1819 1822 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
1820 1823 }
1821 1824 }
1822 1825
1823 1826 /*
1824 1827 * Looks for another buf on the same hdr which has the data decompressed, copies
1825 1828 * from it, and returns true. If no such buf exists, returns false.
1826 1829 */
1827 1830 static boolean_t
1828 1831 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
1829 1832 {
1830 1833 arc_buf_hdr_t *hdr = buf->b_hdr;
1831 1834 boolean_t copied = B_FALSE;
1832 1835
1833 1836 ASSERT(HDR_HAS_L1HDR(hdr));
1834 1837 ASSERT3P(buf->b_data, !=, NULL);
1835 1838 ASSERT(!ARC_BUF_COMPRESSED(buf));
1836 1839
1837 1840 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
1838 1841 from = from->b_next) {
1839 1842 /* can't use our own data buffer */
1840 1843 if (from == buf) {
1841 1844 continue;
1842 1845 }
1843 1846
1844 1847 if (!ARC_BUF_COMPRESSED(from)) {
1845 1848 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
1846 1849 copied = B_TRUE;
1847 1850 break;
1848 1851 }
1849 1852 }
1850 1853
1851 1854 /*
1852 1855 * There were no decompressed bufs, so there should not be a
1853 1856 * checksum on the hdr either.
1854 1857 */
1855 1858 EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
1856 1859
1857 1860 return (copied);
1858 1861 }
1859 1862
1860 1863 /*
1861 1864 * Given a buf that has a data buffer attached to it, this function will
1862 1865 * efficiently fill the buf with data of the specified compression setting from
1863 1866 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
1864 1867 * are already sharing a data buf, no copy is performed.
1865 1868 *
1866 1869 * If the buf is marked as compressed but uncompressed data was requested, this
1867 1870 * will allocate a new data buffer for the buf, remove that flag, and fill the
1868 1871 * buf with uncompressed data. You can't request a compressed buf on a hdr with
1869 1872 * uncompressed data, and (since we haven't added support for it yet) if you
1870 1873 * want compressed data your buf must already be marked as compressed and have
1871 1874 * the correct-sized data buffer.
1872 1875 */
1873 1876 static int
1874 1877 arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
1875 1878 {
1876 1879 arc_buf_hdr_t *hdr = buf->b_hdr;
1877 1880 boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
1878 1881 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
1879 1882
1880 1883 ASSERT3P(buf->b_data, !=, NULL);
1881 1884 IMPLY(compressed, hdr_compressed);
1882 1885 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
1883 1886
1884 1887 if (hdr_compressed == compressed) {
1885 1888 if (!arc_buf_is_shared(buf)) {
1886 1889 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
1887 1890 arc_buf_size(buf));
1888 1891 }
1889 1892 } else {
1890 1893 ASSERT(hdr_compressed);
1891 1894 ASSERT(!compressed);
1892 1895 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
1893 1896
1894 1897 /*
1895 1898 * If the buf is sharing its data with the hdr, unlink it and
1896 1899 * allocate a new data buffer for the buf.
1897 1900 */
1898 1901 if (arc_buf_is_shared(buf)) {
1899 1902 ASSERT(ARC_BUF_COMPRESSED(buf));
1900 1903
1901 1904 /* We need to give the buf it's own b_data */
1902 1905 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
1903 1906 buf->b_data =
1904 1907 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
1905 1908 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
1906 1909
1907 1910 /* Previously overhead was 0; just add new overhead */
1908 1911 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
1909 1912 } else if (ARC_BUF_COMPRESSED(buf)) {
1910 1913 /* We need to reallocate the buf's b_data */
1911 1914 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
1912 1915 buf);
1913 1916 buf->b_data =
1914 1917 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
1915 1918
1916 1919 /* We increased the size of b_data; update overhead */
1917 1920 ARCSTAT_INCR(arcstat_overhead_size,
1918 1921 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
1919 1922 }
1920 1923
1921 1924 /*
1922 1925 * Regardless of the buf's previous compression settings, it
1923 1926 * should not be compressed at the end of this function.
1924 1927 */
1925 1928 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
1926 1929
1927 1930 /*
1928 1931 * Try copying the data from another buf which already has a
1929 1932 * decompressed version. If that's not possible, it's time to
1930 1933 * bite the bullet and decompress the data from the hdr.
1931 1934 */
1932 1935 if (arc_buf_try_copy_decompressed_data(buf)) {
1933 1936 /* Skip byteswapping and checksumming (already done) */
1934 1937 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
1935 1938 return (0);
1936 1939 } else {
1937 1940 int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
1938 1941 hdr->b_l1hdr.b_pabd, buf->b_data,
1939 1942 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
1940 1943
1941 1944 /*
1942 1945 * Absent hardware errors or software bugs, this should
1943 1946 * be impossible, but log it anyway so we can debug it.
1944 1947 */
1945 1948 if (error != 0) {
1946 1949 zfs_dbgmsg(
1947 1950 "hdr %p, compress %d, psize %d, lsize %d",
1948 1951 hdr, HDR_GET_COMPRESS(hdr),
1949 1952 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
1950 1953 return (SET_ERROR(EIO));
1951 1954 }
1952 1955 }
1953 1956 }
1954 1957
1955 1958 /* Byteswap the buf's data if necessary */
1956 1959 if (bswap != DMU_BSWAP_NUMFUNCS) {
1957 1960 ASSERT(!HDR_SHARED_DATA(hdr));
1958 1961 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
1959 1962 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
1960 1963 }
1961 1964
1962 1965 /* Compute the hdr's checksum if necessary */
1963 1966 arc_cksum_compute(buf);
1964 1967
1965 1968 return (0);
1966 1969 }
1967 1970
1968 1971 int
1969 1972 arc_decompress(arc_buf_t *buf)
1970 1973 {
1971 1974 return (arc_buf_fill(buf, B_FALSE));
1972 1975 }
1973 1976
1974 1977 /*
1975 1978 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
1976 1979 */
1977 1980 static uint64_t
1978 1981 arc_hdr_size(arc_buf_hdr_t *hdr)
1979 1982 {
1980 1983 uint64_t size;
1981 1984
1982 1985 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1983 1986 HDR_GET_PSIZE(hdr) > 0) {
1984 1987 size = HDR_GET_PSIZE(hdr);
1985 1988 } else {
1986 1989 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
1987 1990 size = HDR_GET_LSIZE(hdr);
1988 1991 }
1989 1992 return (size);
1990 1993 }
1991 1994
1992 1995 /*
1993 1996 * Increment the amount of evictable space in the arc_state_t's refcount.
1994 1997 * We account for the space used by the hdr and the arc buf individually
1995 1998 * so that we can add and remove them from the refcount individually.
1996 1999 */
1997 2000 static void
1998 2001 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
1999 2002 {
2000 2003 arc_buf_contents_t type = arc_buf_type(hdr);
2001 2004
2002 2005 ASSERT(HDR_HAS_L1HDR(hdr));
2003 2006
2004 2007 if (GHOST_STATE(state)) {
2005 2008 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2006 2009 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2007 2010 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2008 2011 (void) refcount_add_many(&state->arcs_esize[type],
2009 2012 HDR_GET_LSIZE(hdr), hdr);
2010 2013 return;
2011 2014 }
2012 2015
2013 2016 ASSERT(!GHOST_STATE(state));
2014 2017 if (hdr->b_l1hdr.b_pabd != NULL) {
2015 2018 (void) refcount_add_many(&state->arcs_esize[type],
2016 2019 arc_hdr_size(hdr), hdr);
2017 2020 }
2018 2021 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2019 2022 buf = buf->b_next) {
2020 2023 if (arc_buf_is_shared(buf))
2021 2024 continue;
2022 2025 (void) refcount_add_many(&state->arcs_esize[type],
2023 2026 arc_buf_size(buf), buf);
2024 2027 }
2025 2028 }
2026 2029
2027 2030 /*
2028 2031 * Decrement the amount of evictable space in the arc_state_t's refcount.
2029 2032 * We account for the space used by the hdr and the arc buf individually
2030 2033 * so that we can add and remove them from the refcount individually.
2031 2034 */
2032 2035 static void
2033 2036 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2034 2037 {
2035 2038 arc_buf_contents_t type = arc_buf_type(hdr);
2036 2039
2037 2040 ASSERT(HDR_HAS_L1HDR(hdr));
2038 2041
2039 2042 if (GHOST_STATE(state)) {
2040 2043 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2041 2044 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2042 2045 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2043 2046 (void) refcount_remove_many(&state->arcs_esize[type],
2044 2047 HDR_GET_LSIZE(hdr), hdr);
2045 2048 return;
2046 2049 }
2047 2050
2048 2051 ASSERT(!GHOST_STATE(state));
2049 2052 if (hdr->b_l1hdr.b_pabd != NULL) {
2050 2053 (void) refcount_remove_many(&state->arcs_esize[type],
2051 2054 arc_hdr_size(hdr), hdr);
2052 2055 }
2053 2056 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2054 2057 buf = buf->b_next) {
2055 2058 if (arc_buf_is_shared(buf))
2056 2059 continue;
2057 2060 (void) refcount_remove_many(&state->arcs_esize[type],
2058 2061 arc_buf_size(buf), buf);
2059 2062 }
2060 2063 }
2061 2064
2062 2065 /*
2063 2066 * Add a reference to this hdr indicating that someone is actively
2064 2067 * referencing that memory. When the refcount transitions from 0 to 1,
2065 2068 * we remove it from the respective arc_state_t list to indicate that
2066 2069 * it is not evictable.
2067 2070 */
2068 2071 static void
2069 2072 add_reference(arc_buf_hdr_t *hdr, void *tag)
2070 2073 {
2071 2074 ASSERT(HDR_HAS_L1HDR(hdr));
2072 2075 if (!MUTEX_HELD(HDR_LOCK(hdr))) {
2073 2076 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2074 2077 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2075 2078 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2076 2079 }
2077 2080
2078 2081 arc_state_t *state = hdr->b_l1hdr.b_state;
2079 2082
2080 2083 if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2081 2084 (state != arc_anon)) {
2082 2085 /* We don't use the L2-only state list. */
2083 2086 if (state != arc_l2c_only) {
2084 2087 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2085 2088 hdr);
2086 2089 arc_evictable_space_decrement(hdr, state);
2087 2090 }
2088 2091 /* remove the prefetch flag if we get a reference */
2089 2092 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2090 2093 }
2091 2094 }
2092 2095
2093 2096 /*
2094 2097 * Remove a reference from this hdr. When the reference transitions from
2095 2098 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2096 2099 * list making it eligible for eviction.
2097 2100 */
2098 2101 static int
2099 2102 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2100 2103 {
2101 2104 int cnt;
2102 2105 arc_state_t *state = hdr->b_l1hdr.b_state;
2103 2106
2104 2107 ASSERT(HDR_HAS_L1HDR(hdr));
2105 2108 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2106 2109 ASSERT(!GHOST_STATE(state));
2107 2110
2108 2111 /*
2109 2112 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2110 2113 * check to prevent usage of the arc_l2c_only list.
2111 2114 */
2112 2115 if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2113 2116 (state != arc_anon)) {
2114 2117 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2115 2118 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2116 2119 arc_evictable_space_increment(hdr, state);
2117 2120 }
2118 2121 return (cnt);
2119 2122 }
2120 2123
2121 2124 /*
2122 2125 * Move the supplied buffer to the indicated state. The hash lock
2123 2126 * for the buffer must be held by the caller.
2124 2127 */
2125 2128 static void
2126 2129 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2127 2130 kmutex_t *hash_lock)
2128 2131 {
2129 2132 arc_state_t *old_state;
2130 2133 int64_t refcnt;
2131 2134 uint32_t bufcnt;
2132 2135 boolean_t update_old, update_new;
2133 2136 arc_buf_contents_t buftype = arc_buf_type(hdr);
2134 2137
2135 2138 /*
2136 2139 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2137 2140 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2138 2141 * L1 hdr doesn't always exist when we change state to arc_anon before
2139 2142 * destroying a header, in which case reallocating to add the L1 hdr is
2140 2143 * pointless.
2141 2144 */
2142 2145 if (HDR_HAS_L1HDR(hdr)) {
2143 2146 old_state = hdr->b_l1hdr.b_state;
2144 2147 refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
2145 2148 bufcnt = hdr->b_l1hdr.b_bufcnt;
2146 2149 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL);
2147 2150 } else {
2148 2151 old_state = arc_l2c_only;
2149 2152 refcnt = 0;
2150 2153 bufcnt = 0;
2151 2154 update_old = B_FALSE;
2152 2155 }
2153 2156 update_new = update_old;
2154 2157
2155 2158 ASSERT(MUTEX_HELD(hash_lock));
2156 2159 ASSERT3P(new_state, !=, old_state);
2157 2160 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2158 2161 ASSERT(old_state != arc_anon || bufcnt <= 1);
2159 2162
2160 2163 /*
2161 2164 * If this buffer is evictable, transfer it from the
2162 2165 * old state list to the new state list.
2163 2166 */
2164 2167 if (refcnt == 0) {
2165 2168 if (old_state != arc_anon && old_state != arc_l2c_only) {
2166 2169 ASSERT(HDR_HAS_L1HDR(hdr));
2167 2170 multilist_remove(old_state->arcs_list[buftype], hdr);
2168 2171
2169 2172 if (GHOST_STATE(old_state)) {
2170 2173 ASSERT0(bufcnt);
2171 2174 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2172 2175 update_old = B_TRUE;
2173 2176 }
2174 2177 arc_evictable_space_decrement(hdr, old_state);
2175 2178 }
2176 2179 if (new_state != arc_anon && new_state != arc_l2c_only) {
2177 2180
2178 2181 /*
2179 2182 * An L1 header always exists here, since if we're
2180 2183 * moving to some L1-cached state (i.e. not l2c_only or
2181 2184 * anonymous), we realloc the header to add an L1hdr
2182 2185 * beforehand.
2183 2186 */
2184 2187 ASSERT(HDR_HAS_L1HDR(hdr));
2185 2188 multilist_insert(new_state->arcs_list[buftype], hdr);
2186 2189
2187 2190 if (GHOST_STATE(new_state)) {
2188 2191 ASSERT0(bufcnt);
2189 2192 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2190 2193 update_new = B_TRUE;
2191 2194 }
2192 2195 arc_evictable_space_increment(hdr, new_state);
2193 2196 }
2194 2197 }
2195 2198
2196 2199 ASSERT(!HDR_EMPTY(hdr));
2197 2200 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2198 2201 buf_hash_remove(hdr);
2199 2202
2200 2203 /* adjust state sizes (ignore arc_l2c_only) */
2201 2204
2202 2205 if (update_new && new_state != arc_l2c_only) {
2203 2206 ASSERT(HDR_HAS_L1HDR(hdr));
2204 2207 if (GHOST_STATE(new_state)) {
2205 2208 ASSERT0(bufcnt);
2206 2209
2207 2210 /*
2208 2211 * When moving a header to a ghost state, we first
2209 2212 * remove all arc buffers. Thus, we'll have a
2210 2213 * bufcnt of zero, and no arc buffer to use for
2211 2214 * the reference. As a result, we use the arc
2212 2215 * header pointer for the reference.
2213 2216 */
2214 2217 (void) refcount_add_many(&new_state->arcs_size,
2215 2218 HDR_GET_LSIZE(hdr), hdr);
2216 2219 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2217 2220 } else {
2218 2221 uint32_t buffers = 0;
2219 2222
2220 2223 /*
2221 2224 * Each individual buffer holds a unique reference,
2222 2225 * thus we must remove each of these references one
2223 2226 * at a time.
2224 2227 */
2225 2228 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2226 2229 buf = buf->b_next) {
2227 2230 ASSERT3U(bufcnt, !=, 0);
2228 2231 buffers++;
2229 2232
2230 2233 /*
2231 2234 * When the arc_buf_t is sharing the data
2232 2235 * block with the hdr, the owner of the
2233 2236 * reference belongs to the hdr. Only
2234 2237 * add to the refcount if the arc_buf_t is
2235 2238 * not shared.
2236 2239 */
2237 2240 if (arc_buf_is_shared(buf))
2238 2241 continue;
2239 2242
2240 2243 (void) refcount_add_many(&new_state->arcs_size,
2241 2244 arc_buf_size(buf), buf);
2242 2245 }
2243 2246 ASSERT3U(bufcnt, ==, buffers);
2244 2247
2245 2248 if (hdr->b_l1hdr.b_pabd != NULL) {
2246 2249 (void) refcount_add_many(&new_state->arcs_size,
2247 2250 arc_hdr_size(hdr), hdr);
2248 2251 } else {
2249 2252 ASSERT(GHOST_STATE(old_state));
2250 2253 }
2251 2254 }
2252 2255 }
2253 2256
2254 2257 if (update_old && old_state != arc_l2c_only) {
2255 2258 ASSERT(HDR_HAS_L1HDR(hdr));
2256 2259 if (GHOST_STATE(old_state)) {
2257 2260 ASSERT0(bufcnt);
2258 2261 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2259 2262
2260 2263 /*
2261 2264 * When moving a header off of a ghost state,
2262 2265 * the header will not contain any arc buffers.
2263 2266 * We use the arc header pointer for the reference
2264 2267 * which is exactly what we did when we put the
2265 2268 * header on the ghost state.
2266 2269 */
2267 2270
2268 2271 (void) refcount_remove_many(&old_state->arcs_size,
2269 2272 HDR_GET_LSIZE(hdr), hdr);
2270 2273 } else {
2271 2274 uint32_t buffers = 0;
2272 2275
2273 2276 /*
2274 2277 * Each individual buffer holds a unique reference,
2275 2278 * thus we must remove each of these references one
2276 2279 * at a time.
2277 2280 */
2278 2281 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2279 2282 buf = buf->b_next) {
2280 2283 ASSERT3U(bufcnt, !=, 0);
2281 2284 buffers++;
2282 2285
2283 2286 /*
2284 2287 * When the arc_buf_t is sharing the data
2285 2288 * block with the hdr, the owner of the
2286 2289 * reference belongs to the hdr. Only
2287 2290 * add to the refcount if the arc_buf_t is
2288 2291 * not shared.
2289 2292 */
2290 2293 if (arc_buf_is_shared(buf))
2291 2294 continue;
2292 2295
2293 2296 (void) refcount_remove_many(
2294 2297 &old_state->arcs_size, arc_buf_size(buf),
2295 2298 buf);
2296 2299 }
2297 2300 ASSERT3U(bufcnt, ==, buffers);
2298 2301 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2299 2302 (void) refcount_remove_many(
2300 2303 &old_state->arcs_size, arc_hdr_size(hdr), hdr);
2301 2304 }
2302 2305 }
2303 2306
2304 2307 if (HDR_HAS_L1HDR(hdr))
2305 2308 hdr->b_l1hdr.b_state = new_state;
2306 2309
2307 2310 /*
2308 2311 * L2 headers should never be on the L2 state list since they don't
2309 2312 * have L1 headers allocated.
2310 2313 */
2311 2314 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2312 2315 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2313 2316 }
2314 2317
2315 2318 void
2316 2319 arc_space_consume(uint64_t space, arc_space_type_t type)
2317 2320 {
2318 2321 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2319 2322
2320 2323 switch (type) {
2321 2324 case ARC_SPACE_DATA:
2322 2325 ARCSTAT_INCR(arcstat_data_size, space);
2323 2326 break;
2324 2327 case ARC_SPACE_META:
2325 2328 ARCSTAT_INCR(arcstat_metadata_size, space);
2326 2329 break;
2327 2330 case ARC_SPACE_OTHER:
2328 2331 ARCSTAT_INCR(arcstat_other_size, space);
2329 2332 break;
2330 2333 case ARC_SPACE_HDRS:
2331 2334 ARCSTAT_INCR(arcstat_hdr_size, space);
2332 2335 break;
2333 2336 case ARC_SPACE_L2HDRS:
2334 2337 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
2335 2338 break;
2336 2339 }
2337 2340
2338 2341 if (type != ARC_SPACE_DATA)
2339 2342 ARCSTAT_INCR(arcstat_meta_used, space);
2340 2343
2341 2344 atomic_add_64(&arc_size, space);
2342 2345 }
2343 2346
2344 2347 void
2345 2348 arc_space_return(uint64_t space, arc_space_type_t type)
2346 2349 {
2347 2350 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2348 2351
2349 2352 switch (type) {
2350 2353 case ARC_SPACE_DATA:
2351 2354 ARCSTAT_INCR(arcstat_data_size, -space);
2352 2355 break;
2353 2356 case ARC_SPACE_META:
2354 2357 ARCSTAT_INCR(arcstat_metadata_size, -space);
2355 2358 break;
2356 2359 case ARC_SPACE_OTHER:
2357 2360 ARCSTAT_INCR(arcstat_other_size, -space);
2358 2361 break;
2359 2362 case ARC_SPACE_HDRS:
2360 2363 ARCSTAT_INCR(arcstat_hdr_size, -space);
2361 2364 break;
2362 2365 case ARC_SPACE_L2HDRS:
2363 2366 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
2364 2367 break;
2365 2368 }
2366 2369
2367 2370 if (type != ARC_SPACE_DATA) {
2368 2371 ASSERT(arc_meta_used >= space);
2369 2372 if (arc_meta_max < arc_meta_used)
2370 2373 arc_meta_max = arc_meta_used;
2371 2374 ARCSTAT_INCR(arcstat_meta_used, -space);
2372 2375 }
2373 2376
2374 2377 ASSERT(arc_size >= space);
2375 2378 atomic_add_64(&arc_size, -space);
2376 2379 }
2377 2380
2378 2381 /*
2379 2382 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2380 2383 * with the hdr's b_pabd.
2381 2384 */
2382 2385 static boolean_t
2383 2386 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2384 2387 {
2385 2388 /*
2386 2389 * The criteria for sharing a hdr's data are:
2387 2390 * 1. the hdr's compression matches the buf's compression
2388 2391 * 2. the hdr doesn't need to be byteswapped
2389 2392 * 3. the hdr isn't already being shared
2390 2393 * 4. the buf is either compressed or it is the last buf in the hdr list
2391 2394 *
2392 2395 * Criterion #4 maintains the invariant that shared uncompressed
2393 2396 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2394 2397 * might ask, "if a compressed buf is allocated first, won't that be the
2395 2398 * last thing in the list?", but in that case it's impossible to create
2396 2399 * a shared uncompressed buf anyway (because the hdr must be compressed
2397 2400 * to have the compressed buf). You might also think that #3 is
2398 2401 * sufficient to make this guarantee, however it's possible
2399 2402 * (specifically in the rare L2ARC write race mentioned in
2400 2403 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2401 2404 * is sharable, but wasn't at the time of its allocation. Rather than
2402 2405 * allow a new shared uncompressed buf to be created and then shuffle
2403 2406 * the list around to make it the last element, this simply disallows
2404 2407 * sharing if the new buf isn't the first to be added.
2405 2408 */
2406 2409 ASSERT3P(buf->b_hdr, ==, hdr);
2407 2410 boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
2408 2411 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2409 2412 return (buf_compressed == hdr_compressed &&
2410 2413 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2411 2414 !HDR_SHARED_DATA(hdr) &&
2412 2415 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2413 2416 }
2414 2417
2415 2418 /*
2416 2419 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2417 2420 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2418 2421 * copy was made successfully, or an error code otherwise.
2419 2422 */
2420 2423 static int
2421 2424 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
2422 2425 boolean_t fill, arc_buf_t **ret)
2423 2426 {
2424 2427 arc_buf_t *buf;
2425 2428
2426 2429 ASSERT(HDR_HAS_L1HDR(hdr));
2427 2430 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2428 2431 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2429 2432 hdr->b_type == ARC_BUFC_METADATA);
2430 2433 ASSERT3P(ret, !=, NULL);
2431 2434 ASSERT3P(*ret, ==, NULL);
2432 2435
2433 2436 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2434 2437 buf->b_hdr = hdr;
2435 2438 buf->b_data = NULL;
2436 2439 buf->b_next = hdr->b_l1hdr.b_buf;
2437 2440 buf->b_flags = 0;
2438 2441
2439 2442 add_reference(hdr, tag);
2440 2443
2441 2444 /*
2442 2445 * We're about to change the hdr's b_flags. We must either
2443 2446 * hold the hash_lock or be undiscoverable.
2444 2447 */
2445 2448 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2446 2449
2447 2450 /*
2448 2451 * Only honor requests for compressed bufs if the hdr is actually
2449 2452 * compressed.
2450 2453 */
2451 2454 if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
2452 2455 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2453 2456
2454 2457 /*
2455 2458 * If the hdr's data can be shared then we share the data buffer and
2456 2459 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2457 2460 * sharing it's b_pabd with the arc_buf_t. Otherwise, we allocate a new
2458 2461 * buffer to store the buf's data.
2459 2462 *
2460 2463 * There are two additional restrictions here because we're sharing
2461 2464 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2462 2465 * actively involved in an L2ARC write, because if this buf is used by
2463 2466 * an arc_write() then the hdr's data buffer will be released when the
2464 2467 * write completes, even though the L2ARC write might still be using it.
2465 2468 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2466 2469 * need to be ABD-aware.
2467 2470 */
2468 2471 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2469 2472 abd_is_linear(hdr->b_l1hdr.b_pabd);
2470 2473
2471 2474 /* Set up b_data and sharing */
2472 2475 if (can_share) {
2473 2476 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2474 2477 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2475 2478 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2476 2479 } else {
2477 2480 buf->b_data =
2478 2481 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2479 2482 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2480 2483 }
2481 2484 VERIFY3P(buf->b_data, !=, NULL);
2482 2485
2483 2486 hdr->b_l1hdr.b_buf = buf;
2484 2487 hdr->b_l1hdr.b_bufcnt += 1;
2485 2488
2486 2489 /*
2487 2490 * If the user wants the data from the hdr, we need to either copy or
2488 2491 * decompress the data.
2489 2492 */
2490 2493 if (fill) {
2491 2494 return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
2492 2495 }
2493 2496
2494 2497 return (0);
2495 2498 }
2496 2499
2497 2500 static char *arc_onloan_tag = "onloan";
2498 2501
2499 2502 static inline void
2500 2503 arc_loaned_bytes_update(int64_t delta)
2501 2504 {
2502 2505 atomic_add_64(&arc_loaned_bytes, delta);
2503 2506
2504 2507 /* assert that it did not wrap around */
2505 2508 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2506 2509 }
2507 2510
2508 2511 /*
2509 2512 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2510 2513 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2511 2514 * buffers must be returned to the arc before they can be used by the DMU or
2512 2515 * freed.
2513 2516 */
2514 2517 arc_buf_t *
2515 2518 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2516 2519 {
2517 2520 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2518 2521 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2519 2522
2520 2523 arc_loaned_bytes_update(size);
2521 2524
2522 2525 return (buf);
2523 2526 }
2524 2527
2525 2528 arc_buf_t *
2526 2529 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2527 2530 enum zio_compress compression_type)
2528 2531 {
2529 2532 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2530 2533 psize, lsize, compression_type);
2531 2534
2532 2535 arc_loaned_bytes_update(psize);
2533 2536
2534 2537 return (buf);
2535 2538 }
2536 2539
2537 2540
2538 2541 /*
2539 2542 * Return a loaned arc buffer to the arc.
2540 2543 */
2541 2544 void
2542 2545 arc_return_buf(arc_buf_t *buf, void *tag)
2543 2546 {
2544 2547 arc_buf_hdr_t *hdr = buf->b_hdr;
2545 2548
2546 2549 ASSERT3P(buf->b_data, !=, NULL);
2547 2550 ASSERT(HDR_HAS_L1HDR(hdr));
2548 2551 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2549 2552 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2550 2553
2551 2554 arc_loaned_bytes_update(-arc_buf_size(buf));
2552 2555 }
2553 2556
2554 2557 /* Detach an arc_buf from a dbuf (tag) */
2555 2558 void
2556 2559 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2557 2560 {
2558 2561 arc_buf_hdr_t *hdr = buf->b_hdr;
2559 2562
2560 2563 ASSERT3P(buf->b_data, !=, NULL);
2561 2564 ASSERT(HDR_HAS_L1HDR(hdr));
2562 2565 (void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2563 2566 (void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2564 2567
2565 2568 arc_loaned_bytes_update(arc_buf_size(buf));
2566 2569 }
2567 2570
2568 2571 static void
2569 2572 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2570 2573 {
2571 2574 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2572 2575
2573 2576 df->l2df_abd = abd;
2574 2577 df->l2df_size = size;
2575 2578 df->l2df_type = type;
2576 2579 mutex_enter(&l2arc_free_on_write_mtx);
2577 2580 list_insert_head(l2arc_free_on_write, df);
2578 2581 mutex_exit(&l2arc_free_on_write_mtx);
2579 2582 }
2580 2583
2581 2584 static void
2582 2585 arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
2583 2586 {
2584 2587 arc_state_t *state = hdr->b_l1hdr.b_state;
2585 2588 arc_buf_contents_t type = arc_buf_type(hdr);
2586 2589 uint64_t size = arc_hdr_size(hdr);
2587 2590
2588 2591 /* protected by hash lock, if in the hash table */
2589 2592 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2590 2593 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2591 2594 ASSERT(state != arc_anon && state != arc_l2c_only);
2592 2595
2593 2596 (void) refcount_remove_many(&state->arcs_esize[type],
2594 2597 size, hdr);
2595 2598 }
2596 2599 (void) refcount_remove_many(&state->arcs_size, size, hdr);
2597 2600 if (type == ARC_BUFC_METADATA) {
2598 2601 arc_space_return(size, ARC_SPACE_META);
2599 2602 } else {
2600 2603 ASSERT(type == ARC_BUFC_DATA);
2601 2604 arc_space_return(size, ARC_SPACE_DATA);
2602 2605 }
2603 2606
2604 2607 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2605 2608 }
2606 2609
2607 2610 /*
2608 2611 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2609 2612 * data buffer, we transfer the refcount ownership to the hdr and update
2610 2613 * the appropriate kstats.
2611 2614 */
2612 2615 static void
2613 2616 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2614 2617 {
2615 2618 arc_state_t *state = hdr->b_l1hdr.b_state;
2616 2619
2617 2620 ASSERT(arc_can_share(hdr, buf));
2618 2621 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2619 2622 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2620 2623
2621 2624 /*
2622 2625 * Start sharing the data buffer. We transfer the
2623 2626 * refcount ownership to the hdr since it always owns
2624 2627 * the refcount whenever an arc_buf_t is shared.
2625 2628 */
2626 2629 refcount_transfer_ownership(&state->arcs_size, buf, hdr);
2627 2630 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
2628 2631 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
2629 2632 HDR_ISTYPE_METADATA(hdr));
2630 2633 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2631 2634 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2632 2635
2633 2636 /*
2634 2637 * Since we've transferred ownership to the hdr we need
2635 2638 * to increment its compressed and uncompressed kstats and
2636 2639 * decrement the overhead size.
2637 2640 */
2638 2641 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2639 2642 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2640 2643 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
2641 2644 }
2642 2645
2643 2646 static void
2644 2647 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2645 2648 {
2646 2649 arc_state_t *state = hdr->b_l1hdr.b_state;
2647 2650
2648 2651 ASSERT(arc_buf_is_shared(buf));
2649 2652 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2650 2653 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2651 2654
2652 2655 /*
2653 2656 * We are no longer sharing this buffer so we need
2654 2657 * to transfer its ownership to the rightful owner.
2655 2658 */
2656 2659 refcount_transfer_ownership(&state->arcs_size, hdr, buf);
2657 2660 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2658 2661 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
2659 2662 abd_put(hdr->b_l1hdr.b_pabd);
2660 2663 hdr->b_l1hdr.b_pabd = NULL;
2661 2664 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2662 2665
2663 2666 /*
2664 2667 * Since the buffer is no longer shared between
2665 2668 * the arc buf and the hdr, count it as overhead.
2666 2669 */
2667 2670 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2668 2671 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2669 2672 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2670 2673 }
2671 2674
2672 2675 /*
2673 2676 * Remove an arc_buf_t from the hdr's buf list and return the last
2674 2677 * arc_buf_t on the list. If no buffers remain on the list then return
2675 2678 * NULL.
2676 2679 */
2677 2680 static arc_buf_t *
2678 2681 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2679 2682 {
2680 2683 ASSERT(HDR_HAS_L1HDR(hdr));
2681 2684 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2682 2685
2683 2686 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
2684 2687 arc_buf_t *lastbuf = NULL;
2685 2688
2686 2689 /*
2687 2690 * Remove the buf from the hdr list and locate the last
2688 2691 * remaining buffer on the list.
2689 2692 */
2690 2693 while (*bufp != NULL) {
2691 2694 if (*bufp == buf)
2692 2695 *bufp = buf->b_next;
2693 2696
2694 2697 /*
2695 2698 * If we've removed a buffer in the middle of
2696 2699 * the list then update the lastbuf and update
2697 2700 * bufp.
2698 2701 */
2699 2702 if (*bufp != NULL) {
2700 2703 lastbuf = *bufp;
2701 2704 bufp = &(*bufp)->b_next;
2702 2705 }
2703 2706 }
2704 2707 buf->b_next = NULL;
2705 2708 ASSERT3P(lastbuf, !=, buf);
2706 2709 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
2707 2710 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
2708 2711 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
2709 2712
2710 2713 return (lastbuf);
2711 2714 }
2712 2715
2713 2716 /*
2714 2717 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
2715 2718 * list and free it.
2716 2719 */
2717 2720 static void
2718 2721 arc_buf_destroy_impl(arc_buf_t *buf)
2719 2722 {
2720 2723 arc_buf_hdr_t *hdr = buf->b_hdr;
2721 2724
2722 2725 /*
2723 2726 * Free up the data associated with the buf but only if we're not
2724 2727 * sharing this with the hdr. If we are sharing it with the hdr, the
2725 2728 * hdr is responsible for doing the free.
2726 2729 */
2727 2730 if (buf->b_data != NULL) {
2728 2731 /*
2729 2732 * We're about to change the hdr's b_flags. We must either
2730 2733 * hold the hash_lock or be undiscoverable.
2731 2734 */
2732 2735 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
2733 2736
2734 2737 arc_cksum_verify(buf);
2735 2738 arc_buf_unwatch(buf);
2736 2739
2737 2740 if (arc_buf_is_shared(buf)) {
2738 2741 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2739 2742 } else {
2740 2743 uint64_t size = arc_buf_size(buf);
2741 2744 arc_free_data_buf(hdr, buf->b_data, size, buf);
2742 2745 ARCSTAT_INCR(arcstat_overhead_size, -size);
2743 2746 }
2744 2747 buf->b_data = NULL;
2745 2748
2746 2749 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
2747 2750 hdr->b_l1hdr.b_bufcnt -= 1;
2748 2751 }
2749 2752
2750 2753 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
2751 2754
2752 2755 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
2753 2756 /*
2754 2757 * If the current arc_buf_t is sharing its data buffer with the
2755 2758 * hdr, then reassign the hdr's b_pabd to share it with the new
2756 2759 * buffer at the end of the list. The shared buffer is always
2757 2760 * the last one on the hdr's buffer list.
2758 2761 *
2759 2762 * There is an equivalent case for compressed bufs, but since
2760 2763 * they aren't guaranteed to be the last buf in the list and
2761 2764 * that is an exceedingly rare case, we just allow that space be
2762 2765 * wasted temporarily.
2763 2766 */
2764 2767 if (lastbuf != NULL) {
2765 2768 /* Only one buf can be shared at once */
2766 2769 VERIFY(!arc_buf_is_shared(lastbuf));
2767 2770 /* hdr is uncompressed so can't have compressed buf */
2768 2771 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
2769 2772
2770 2773 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2771 2774 arc_hdr_free_pabd(hdr);
2772 2775
2773 2776 /*
2774 2777 * We must setup a new shared block between the
2775 2778 * last buffer and the hdr. The data would have
2776 2779 * been allocated by the arc buf so we need to transfer
2777 2780 * ownership to the hdr since it's now being shared.
2778 2781 */
2779 2782 arc_share_buf(hdr, lastbuf);
2780 2783 }
2781 2784 } else if (HDR_SHARED_DATA(hdr)) {
2782 2785 /*
2783 2786 * Uncompressed shared buffers are always at the end
2784 2787 * of the list. Compressed buffers don't have the
2785 2788 * same requirements. This makes it hard to
2786 2789 * simply assert that the lastbuf is shared so
2787 2790 * we rely on the hdr's compression flags to determine
2788 2791 * if we have a compressed, shared buffer.
2789 2792 */
2790 2793 ASSERT3P(lastbuf, !=, NULL);
2791 2794 ASSERT(arc_buf_is_shared(lastbuf) ||
2792 2795 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
2793 2796 }
2794 2797
2795 2798 /*
2796 2799 * Free the checksum if we're removing the last uncompressed buf from
2797 2800 * this hdr.
2798 2801 */
2799 2802 if (!arc_hdr_has_uncompressed_buf(hdr)) {
2800 2803 arc_cksum_free(hdr);
2801 2804 }
2802 2805
2803 2806 /* clean up the buf */
2804 2807 buf->b_hdr = NULL;
2805 2808 kmem_cache_free(buf_cache, buf);
2806 2809 }
2807 2810
2808 2811 static void
2809 2812 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr)
2810 2813 {
2811 2814 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2812 2815 ASSERT(HDR_HAS_L1HDR(hdr));
2813 2816 ASSERT(!HDR_SHARED_DATA(hdr));
2814 2817
2815 2818 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2816 2819 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr);
2817 2820 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
2818 2821 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2819 2822
2820 2823 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2821 2824 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2822 2825 }
2823 2826
2824 2827 static void
2825 2828 arc_hdr_free_pabd(arc_buf_hdr_t *hdr)
2826 2829 {
2827 2830 ASSERT(HDR_HAS_L1HDR(hdr));
2828 2831 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2829 2832
2830 2833 /*
2831 2834 * If the hdr is currently being written to the l2arc then
2832 2835 * we defer freeing the data by adding it to the l2arc_free_on_write
2833 2836 * list. The l2arc will free the data once it's finished
2834 2837 * writing it to the l2arc device.
2835 2838 */
2836 2839 if (HDR_L2_WRITING(hdr)) {
2837 2840 arc_hdr_free_on_write(hdr);
2838 2841 ARCSTAT_BUMP(arcstat_l2_free_on_write);
2839 2842 } else {
2840 2843 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
2841 2844 arc_hdr_size(hdr), hdr);
2842 2845 }
2843 2846 hdr->b_l1hdr.b_pabd = NULL;
2844 2847 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
2845 2848
2846 2849 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2847 2850 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2848 2851 }
2849 2852
2850 2853 static arc_buf_hdr_t *
2851 2854 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
2852 2855 enum zio_compress compression_type, arc_buf_contents_t type)
2853 2856 {
2854 2857 arc_buf_hdr_t *hdr;
2855 2858
2856 2859 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
2857 2860
2858 2861 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
2859 2862 ASSERT(HDR_EMPTY(hdr));
2860 2863 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
2861 2864 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
2862 2865 HDR_SET_PSIZE(hdr, psize);
2863 2866 HDR_SET_LSIZE(hdr, lsize);
2864 2867 hdr->b_spa = spa;
2865 2868 hdr->b_type = type;
2866 2869 hdr->b_flags = 0;
2867 2870 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
2868 2871 arc_hdr_set_compress(hdr, compression_type);
2869 2872
2870 2873 hdr->b_l1hdr.b_state = arc_anon;
2871 2874 hdr->b_l1hdr.b_arc_access = 0;
2872 2875 hdr->b_l1hdr.b_bufcnt = 0;
2873 2876 hdr->b_l1hdr.b_buf = NULL;
2874 2877
2875 2878 /*
2876 2879 * Allocate the hdr's buffer. This will contain either
2877 2880 * the compressed or uncompressed data depending on the block
2878 2881 * it references and compressed arc enablement.
2879 2882 */
2880 2883 arc_hdr_alloc_pabd(hdr);
2881 2884 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2882 2885
2883 2886 return (hdr);
2884 2887 }
2885 2888
2886 2889 /*
2887 2890 * Transition between the two allocation states for the arc_buf_hdr struct.
2888 2891 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
2889 2892 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
2890 2893 * version is used when a cache buffer is only in the L2ARC in order to reduce
2891 2894 * memory usage.
2892 2895 */
2893 2896 static arc_buf_hdr_t *
2894 2897 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
2895 2898 {
2896 2899 ASSERT(HDR_HAS_L2HDR(hdr));
2897 2900
2898 2901 arc_buf_hdr_t *nhdr;
2899 2902 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
2900 2903
2901 2904 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
2902 2905 (old == hdr_l2only_cache && new == hdr_full_cache));
2903 2906
2904 2907 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
2905 2908
2906 2909 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
2907 2910 buf_hash_remove(hdr);
2908 2911
2909 2912 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
2910 2913
2911 2914 if (new == hdr_full_cache) {
2912 2915 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
2913 2916 /*
2914 2917 * arc_access and arc_change_state need to be aware that a
2915 2918 * header has just come out of L2ARC, so we set its state to
2916 2919 * l2c_only even though it's about to change.
2917 2920 */
2918 2921 nhdr->b_l1hdr.b_state = arc_l2c_only;
2919 2922
2920 2923 /* Verify previous threads set to NULL before freeing */
2921 2924 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
2922 2925 } else {
2923 2926 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2924 2927 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2925 2928 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
2926 2929
2927 2930 /*
2928 2931 * If we've reached here, We must have been called from
2929 2932 * arc_evict_hdr(), as such we should have already been
2930 2933 * removed from any ghost list we were previously on
2931 2934 * (which protects us from racing with arc_evict_state),
2932 2935 * thus no locking is needed during this check.
2933 2936 */
2934 2937 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
2935 2938
2936 2939 /*
2937 2940 * A buffer must not be moved into the arc_l2c_only
2938 2941 * state if it's not finished being written out to the
2939 2942 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
2940 2943 * might try to be accessed, even though it was removed.
2941 2944 */
2942 2945 VERIFY(!HDR_L2_WRITING(hdr));
2943 2946 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2944 2947
2945 2948 #ifdef ZFS_DEBUG
2946 2949 if (hdr->b_l1hdr.b_thawed != NULL) {
2947 2950 kmem_free(hdr->b_l1hdr.b_thawed, 1);
2948 2951 hdr->b_l1hdr.b_thawed = NULL;
2949 2952 }
2950 2953 #endif
2951 2954
2952 2955 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
2953 2956 }
2954 2957 /*
2955 2958 * The header has been reallocated so we need to re-insert it into any
2956 2959 * lists it was on.
2957 2960 */
2958 2961 (void) buf_hash_insert(nhdr, NULL);
2959 2962
2960 2963 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
2961 2964
2962 2965 mutex_enter(&dev->l2ad_mtx);
2963 2966
2964 2967 /*
2965 2968 * We must place the realloc'ed header back into the list at
2966 2969 * the same spot. Otherwise, if it's placed earlier in the list,
2967 2970 * l2arc_write_buffers() could find it during the function's
2968 2971 * write phase, and try to write it out to the l2arc.
2969 2972 */
2970 2973 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
2971 2974 list_remove(&dev->l2ad_buflist, hdr);
2972 2975
2973 2976 mutex_exit(&dev->l2ad_mtx);
2974 2977
2975 2978 /*
2976 2979 * Since we're using the pointer address as the tag when
2977 2980 * incrementing and decrementing the l2ad_alloc refcount, we
2978 2981 * must remove the old pointer (that we're about to destroy) and
2979 2982 * add the new pointer to the refcount. Otherwise we'd remove
2980 2983 * the wrong pointer address when calling arc_hdr_destroy() later.
2981 2984 */
2982 2985
2983 2986 (void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
2984 2987 (void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
2985 2988
2986 2989 buf_discard_identity(hdr);
2987 2990 kmem_cache_free(old, hdr);
2988 2991
2989 2992 return (nhdr);
2990 2993 }
2991 2994
2992 2995 /*
2993 2996 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
2994 2997 * The buf is returned thawed since we expect the consumer to modify it.
2995 2998 */
2996 2999 arc_buf_t *
2997 3000 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
2998 3001 {
2999 3002 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3000 3003 ZIO_COMPRESS_OFF, type);
3001 3004 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3002 3005
3003 3006 arc_buf_t *buf = NULL;
3004 3007 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
3005 3008 arc_buf_thaw(buf);
3006 3009
3007 3010 return (buf);
3008 3011 }
3009 3012
3010 3013 /*
3011 3014 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3012 3015 * for bufs containing metadata.
3013 3016 */
3014 3017 arc_buf_t *
3015 3018 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3016 3019 enum zio_compress compression_type)
3017 3020 {
3018 3021 ASSERT3U(lsize, >, 0);
3019 3022 ASSERT3U(lsize, >=, psize);
3020 3023 ASSERT(compression_type > ZIO_COMPRESS_OFF);
3021 3024 ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
3022 3025
3023 3026 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3024 3027 compression_type, ARC_BUFC_DATA);
3025 3028 ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
3026 3029
3027 3030 arc_buf_t *buf = NULL;
3028 3031 VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
3029 3032 arc_buf_thaw(buf);
3030 3033 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3031 3034
3032 3035 if (!arc_buf_is_shared(buf)) {
3033 3036 /*
3034 3037 * To ensure that the hdr has the correct data in it if we call
3035 3038 * arc_decompress() on this buf before it's been written to
3036 3039 * disk, it's easiest if we just set up sharing between the
3037 3040 * buf and the hdr.
3038 3041 */
3039 3042 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3040 3043 arc_hdr_free_pabd(hdr);
3041 3044 arc_share_buf(hdr, buf);
3042 3045 }
3043 3046
3044 3047 return (buf);
3045 3048 }
3046 3049
3047 3050 static void
3048 3051 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3049 3052 {
3050 3053 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3051 3054 l2arc_dev_t *dev = l2hdr->b_dev;
3052 3055 uint64_t psize = arc_hdr_size(hdr);
3053 3056
3054 3057 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3055 3058 ASSERT(HDR_HAS_L2HDR(hdr));
3056 3059
3057 3060 list_remove(&dev->l2ad_buflist, hdr);
3058 3061
3059 3062 ARCSTAT_INCR(arcstat_l2_psize, -psize);
3060 3063 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
3061 3064
3062 3065 vdev_space_update(dev->l2ad_vdev, -psize, 0, 0);
3063 3066
3064 3067 (void) refcount_remove_many(&dev->l2ad_alloc, psize, hdr);
3065 3068 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3066 3069 }
3067 3070
3068 3071 static void
3069 3072 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3070 3073 {
3071 3074 if (HDR_HAS_L1HDR(hdr)) {
3072 3075 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3073 3076 hdr->b_l1hdr.b_bufcnt > 0);
3074 3077 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3075 3078 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3076 3079 }
3077 3080 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3078 3081 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3079 3082
3080 3083 if (!HDR_EMPTY(hdr))
3081 3084 buf_discard_identity(hdr);
3082 3085
3083 3086 if (HDR_HAS_L2HDR(hdr)) {
3084 3087 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3085 3088 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3086 3089
3087 3090 if (!buflist_held)
3088 3091 mutex_enter(&dev->l2ad_mtx);
3089 3092
3090 3093 /*
3091 3094 * Even though we checked this conditional above, we
3092 3095 * need to check this again now that we have the
3093 3096 * l2ad_mtx. This is because we could be racing with
3094 3097 * another thread calling l2arc_evict() which might have
3095 3098 * destroyed this header's L2 portion as we were waiting
3096 3099 * to acquire the l2ad_mtx. If that happens, we don't
3097 3100 * want to re-destroy the header's L2 portion.
3098 3101 */
3099 3102 if (HDR_HAS_L2HDR(hdr))
3100 3103 arc_hdr_l2hdr_destroy(hdr);
3101 3104
3102 3105 if (!buflist_held)
3103 3106 mutex_exit(&dev->l2ad_mtx);
3104 3107 }
3105 3108
3106 3109 if (HDR_HAS_L1HDR(hdr)) {
3107 3110 arc_cksum_free(hdr);
3108 3111
3109 3112 while (hdr->b_l1hdr.b_buf != NULL)
3110 3113 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3111 3114
3112 3115 #ifdef ZFS_DEBUG
3113 3116 if (hdr->b_l1hdr.b_thawed != NULL) {
3114 3117 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3115 3118 hdr->b_l1hdr.b_thawed = NULL;
3116 3119 }
3117 3120 #endif
3118 3121
3119 3122 if (hdr->b_l1hdr.b_pabd != NULL) {
3120 3123 arc_hdr_free_pabd(hdr);
3121 3124 }
3122 3125 }
3123 3126
3124 3127 ASSERT3P(hdr->b_hash_next, ==, NULL);
3125 3128 if (HDR_HAS_L1HDR(hdr)) {
3126 3129 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3127 3130 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3128 3131 kmem_cache_free(hdr_full_cache, hdr);
3129 3132 } else {
3130 3133 kmem_cache_free(hdr_l2only_cache, hdr);
3131 3134 }
3132 3135 }
3133 3136
3134 3137 void
3135 3138 arc_buf_destroy(arc_buf_t *buf, void* tag)
3136 3139 {
3137 3140 arc_buf_hdr_t *hdr = buf->b_hdr;
3138 3141 kmutex_t *hash_lock = HDR_LOCK(hdr);
3139 3142
3140 3143 if (hdr->b_l1hdr.b_state == arc_anon) {
3141 3144 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3142 3145 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3143 3146 VERIFY0(remove_reference(hdr, NULL, tag));
3144 3147 arc_hdr_destroy(hdr);
3145 3148 return;
3146 3149 }
3147 3150
3148 3151 mutex_enter(hash_lock);
3149 3152 ASSERT3P(hdr, ==, buf->b_hdr);
3150 3153 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3151 3154 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3152 3155 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3153 3156 ASSERT3P(buf->b_data, !=, NULL);
3154 3157
3155 3158 (void) remove_reference(hdr, hash_lock, tag);
3156 3159 arc_buf_destroy_impl(buf);
3157 3160 mutex_exit(hash_lock);
3158 3161 }
3159 3162
3160 3163 /*
3161 3164 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3162 3165 * state of the header is dependent on it's state prior to entering this
3163 3166 * function. The following transitions are possible:
3164 3167 *
3165 3168 * - arc_mru -> arc_mru_ghost
3166 3169 * - arc_mfu -> arc_mfu_ghost
3167 3170 * - arc_mru_ghost -> arc_l2c_only
3168 3171 * - arc_mru_ghost -> deleted
3169 3172 * - arc_mfu_ghost -> arc_l2c_only
3170 3173 * - arc_mfu_ghost -> deleted
3171 3174 */
3172 3175 static int64_t
3173 3176 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3174 3177 {
3175 3178 arc_state_t *evicted_state, *state;
3176 3179 int64_t bytes_evicted = 0;
3177 3180
3178 3181 ASSERT(MUTEX_HELD(hash_lock));
3179 3182 ASSERT(HDR_HAS_L1HDR(hdr));
3180 3183
3181 3184 state = hdr->b_l1hdr.b_state;
3182 3185 if (GHOST_STATE(state)) {
3183 3186 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3184 3187 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3185 3188
3186 3189 /*
3187 3190 * l2arc_write_buffers() relies on a header's L1 portion
3188 3191 * (i.e. its b_pabd field) during it's write phase.
3189 3192 * Thus, we cannot push a header onto the arc_l2c_only
3190 3193 * state (removing it's L1 piece) until the header is
3191 3194 * done being written to the l2arc.
3192 3195 */
3193 3196 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3194 3197 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3195 3198 return (bytes_evicted);
3196 3199 }
3197 3200
3198 3201 ARCSTAT_BUMP(arcstat_deleted);
3199 3202 bytes_evicted += HDR_GET_LSIZE(hdr);
3200 3203
3201 3204 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3202 3205
3203 3206 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3204 3207 if (HDR_HAS_L2HDR(hdr)) {
3205 3208 /*
3206 3209 * This buffer is cached on the 2nd Level ARC;
3207 3210 * don't destroy the header.
3208 3211 */
3209 3212 arc_change_state(arc_l2c_only, hdr, hash_lock);
3210 3213 /*
3211 3214 * dropping from L1+L2 cached to L2-only,
3212 3215 * realloc to remove the L1 header.
3213 3216 */
3214 3217 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3215 3218 hdr_l2only_cache);
3216 3219 } else {
3217 3220 arc_change_state(arc_anon, hdr, hash_lock);
3218 3221 arc_hdr_destroy(hdr);
3219 3222 }
3220 3223 return (bytes_evicted);
3221 3224 }
3222 3225
3223 3226 ASSERT(state == arc_mru || state == arc_mfu);
3224 3227 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3225 3228
3226 3229 /* prefetch buffers have a minimum lifespan */
3227 3230 if (HDR_IO_IN_PROGRESS(hdr) ||
3228 3231 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3229 3232 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
3230 3233 arc_min_prefetch_lifespan)) {
3231 3234 ARCSTAT_BUMP(arcstat_evict_skip);
3232 3235 return (bytes_evicted);
3233 3236 }
3234 3237
3235 3238 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
3236 3239 while (hdr->b_l1hdr.b_buf) {
3237 3240 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3238 3241 if (!mutex_tryenter(&buf->b_evict_lock)) {
3239 3242 ARCSTAT_BUMP(arcstat_mutex_miss);
3240 3243 break;
3241 3244 }
3242 3245 if (buf->b_data != NULL)
3243 3246 bytes_evicted += HDR_GET_LSIZE(hdr);
3244 3247 mutex_exit(&buf->b_evict_lock);
3245 3248 arc_buf_destroy_impl(buf);
3246 3249 }
3247 3250
3248 3251 if (HDR_HAS_L2HDR(hdr)) {
3249 3252 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3250 3253 } else {
3251 3254 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3252 3255 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3253 3256 HDR_GET_LSIZE(hdr));
3254 3257 } else {
3255 3258 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3256 3259 HDR_GET_LSIZE(hdr));
3257 3260 }
3258 3261 }
3259 3262
3260 3263 if (hdr->b_l1hdr.b_bufcnt == 0) {
3261 3264 arc_cksum_free(hdr);
3262 3265
3263 3266 bytes_evicted += arc_hdr_size(hdr);
3264 3267
3265 3268 /*
3266 3269 * If this hdr is being evicted and has a compressed
3267 3270 * buffer then we discard it here before we change states.
3268 3271 * This ensures that the accounting is updated correctly
3269 3272 * in arc_free_data_impl().
3270 3273 */
3271 3274 arc_hdr_free_pabd(hdr);
3272 3275
3273 3276 arc_change_state(evicted_state, hdr, hash_lock);
3274 3277 ASSERT(HDR_IN_HASH_TABLE(hdr));
3275 3278 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3276 3279 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3277 3280 }
3278 3281
3279 3282 return (bytes_evicted);
3280 3283 }
3281 3284
3282 3285 static uint64_t
3283 3286 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3284 3287 uint64_t spa, int64_t bytes)
3285 3288 {
3286 3289 multilist_sublist_t *mls;
3287 3290 uint64_t bytes_evicted = 0;
3288 3291 arc_buf_hdr_t *hdr;
3289 3292 kmutex_t *hash_lock;
3290 3293 int evict_count = 0;
3291 3294
3292 3295 ASSERT3P(marker, !=, NULL);
3293 3296 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3294 3297
3295 3298 mls = multilist_sublist_lock(ml, idx);
3296 3299
3297 3300 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3298 3301 hdr = multilist_sublist_prev(mls, marker)) {
3299 3302 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3300 3303 (evict_count >= zfs_arc_evict_batch_limit))
3301 3304 break;
3302 3305
3303 3306 /*
3304 3307 * To keep our iteration location, move the marker
3305 3308 * forward. Since we're not holding hdr's hash lock, we
3306 3309 * must be very careful and not remove 'hdr' from the
3307 3310 * sublist. Otherwise, other consumers might mistake the
3308 3311 * 'hdr' as not being on a sublist when they call the
3309 3312 * multilist_link_active() function (they all rely on
3310 3313 * the hash lock protecting concurrent insertions and
3311 3314 * removals). multilist_sublist_move_forward() was
3312 3315 * specifically implemented to ensure this is the case
3313 3316 * (only 'marker' will be removed and re-inserted).
3314 3317 */
3315 3318 multilist_sublist_move_forward(mls, marker);
3316 3319
3317 3320 /*
3318 3321 * The only case where the b_spa field should ever be
3319 3322 * zero, is the marker headers inserted by
3320 3323 * arc_evict_state(). It's possible for multiple threads
3321 3324 * to be calling arc_evict_state() concurrently (e.g.
3322 3325 * dsl_pool_close() and zio_inject_fault()), so we must
3323 3326 * skip any markers we see from these other threads.
3324 3327 */
3325 3328 if (hdr->b_spa == 0)
3326 3329 continue;
3327 3330
3328 3331 /* we're only interested in evicting buffers of a certain spa */
3329 3332 if (spa != 0 && hdr->b_spa != spa) {
3330 3333 ARCSTAT_BUMP(arcstat_evict_skip);
3331 3334 continue;
3332 3335 }
3333 3336
3334 3337 hash_lock = HDR_LOCK(hdr);
3335 3338
3336 3339 /*
3337 3340 * We aren't calling this function from any code path
3338 3341 * that would already be holding a hash lock, so we're
3339 3342 * asserting on this assumption to be defensive in case
3340 3343 * this ever changes. Without this check, it would be
3341 3344 * possible to incorrectly increment arcstat_mutex_miss
3342 3345 * below (e.g. if the code changed such that we called
3343 3346 * this function with a hash lock held).
3344 3347 */
3345 3348 ASSERT(!MUTEX_HELD(hash_lock));
3346 3349
3347 3350 if (mutex_tryenter(hash_lock)) {
3348 3351 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3349 3352 mutex_exit(hash_lock);
3350 3353
3351 3354 bytes_evicted += evicted;
3352 3355
3353 3356 /*
3354 3357 * If evicted is zero, arc_evict_hdr() must have
3355 3358 * decided to skip this header, don't increment
3356 3359 * evict_count in this case.
3357 3360 */
3358 3361 if (evicted != 0)
3359 3362 evict_count++;
3360 3363
3361 3364 /*
3362 3365 * If arc_size isn't overflowing, signal any
3363 3366 * threads that might happen to be waiting.
3364 3367 *
3365 3368 * For each header evicted, we wake up a single
3366 3369 * thread. If we used cv_broadcast, we could
3367 3370 * wake up "too many" threads causing arc_size
3368 3371 * to significantly overflow arc_c; since
3369 3372 * arc_get_data_impl() doesn't check for overflow
3370 3373 * when it's woken up (it doesn't because it's
3371 3374 * possible for the ARC to be overflowing while
3372 3375 * full of un-evictable buffers, and the
3373 3376 * function should proceed in this case).
3374 3377 *
3375 3378 * If threads are left sleeping, due to not
3376 3379 * using cv_broadcast, they will be woken up
3377 3380 * just before arc_reclaim_thread() sleeps.
3378 3381 */
3379 3382 mutex_enter(&arc_reclaim_lock);
3380 3383 if (!arc_is_overflowing())
3381 3384 cv_signal(&arc_reclaim_waiters_cv);
3382 3385 mutex_exit(&arc_reclaim_lock);
3383 3386 } else {
3384 3387 ARCSTAT_BUMP(arcstat_mutex_miss);
3385 3388 }
3386 3389 }
3387 3390
3388 3391 multilist_sublist_unlock(mls);
3389 3392
3390 3393 return (bytes_evicted);
3391 3394 }
3392 3395
3393 3396 /*
3394 3397 * Evict buffers from the given arc state, until we've removed the
3395 3398 * specified number of bytes. Move the removed buffers to the
3396 3399 * appropriate evict state.
3397 3400 *
3398 3401 * This function makes a "best effort". It skips over any buffers
3399 3402 * it can't get a hash_lock on, and so, may not catch all candidates.
3400 3403 * It may also return without evicting as much space as requested.
3401 3404 *
3402 3405 * If bytes is specified using the special value ARC_EVICT_ALL, this
3403 3406 * will evict all available (i.e. unlocked and evictable) buffers from
3404 3407 * the given arc state; which is used by arc_flush().
3405 3408 */
3406 3409 static uint64_t
3407 3410 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
3408 3411 arc_buf_contents_t type)
3409 3412 {
3410 3413 uint64_t total_evicted = 0;
3411 3414 multilist_t *ml = state->arcs_list[type];
3412 3415 int num_sublists;
3413 3416 arc_buf_hdr_t **markers;
3414 3417
3415 3418 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3416 3419
3417 3420 num_sublists = multilist_get_num_sublists(ml);
3418 3421
3419 3422 /*
3420 3423 * If we've tried to evict from each sublist, made some
3421 3424 * progress, but still have not hit the target number of bytes
3422 3425 * to evict, we want to keep trying. The markers allow us to
3423 3426 * pick up where we left off for each individual sublist, rather
3424 3427 * than starting from the tail each time.
3425 3428 */
3426 3429 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
3427 3430 for (int i = 0; i < num_sublists; i++) {
3428 3431 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
3429 3432
3430 3433 /*
3431 3434 * A b_spa of 0 is used to indicate that this header is
3432 3435 * a marker. This fact is used in arc_adjust_type() and
3433 3436 * arc_evict_state_impl().
3434 3437 */
3435 3438 markers[i]->b_spa = 0;
3436 3439
3437 3440 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3438 3441 multilist_sublist_insert_tail(mls, markers[i]);
3439 3442 multilist_sublist_unlock(mls);
3440 3443 }
3441 3444
3442 3445 /*
3443 3446 * While we haven't hit our target number of bytes to evict, or
3444 3447 * we're evicting all available buffers.
3445 3448 */
3446 3449 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
3447 3450 /*
3448 3451 * Start eviction using a randomly selected sublist,
3449 3452 * this is to try and evenly balance eviction across all
3450 3453 * sublists. Always starting at the same sublist
3451 3454 * (e.g. index 0) would cause evictions to favor certain
3452 3455 * sublists over others.
3453 3456 */
3454 3457 int sublist_idx = multilist_get_random_index(ml);
3455 3458 uint64_t scan_evicted = 0;
3456 3459
3457 3460 for (int i = 0; i < num_sublists; i++) {
3458 3461 uint64_t bytes_remaining;
3459 3462 uint64_t bytes_evicted;
3460 3463
3461 3464 if (bytes == ARC_EVICT_ALL)
3462 3465 bytes_remaining = ARC_EVICT_ALL;
3463 3466 else if (total_evicted < bytes)
3464 3467 bytes_remaining = bytes - total_evicted;
3465 3468 else
3466 3469 break;
3467 3470
3468 3471 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
3469 3472 markers[sublist_idx], spa, bytes_remaining);
3470 3473
3471 3474 scan_evicted += bytes_evicted;
3472 3475 total_evicted += bytes_evicted;
3473 3476
3474 3477 /* we've reached the end, wrap to the beginning */
3475 3478 if (++sublist_idx >= num_sublists)
3476 3479 sublist_idx = 0;
3477 3480 }
3478 3481
3479 3482 /*
3480 3483 * If we didn't evict anything during this scan, we have
3481 3484 * no reason to believe we'll evict more during another
3482 3485 * scan, so break the loop.
3483 3486 */
3484 3487 if (scan_evicted == 0) {
3485 3488 /* This isn't possible, let's make that obvious */
3486 3489 ASSERT3S(bytes, !=, 0);
3487 3490
3488 3491 /*
3489 3492 * When bytes is ARC_EVICT_ALL, the only way to
3490 3493 * break the loop is when scan_evicted is zero.
3491 3494 * In that case, we actually have evicted enough,
3492 3495 * so we don't want to increment the kstat.
3493 3496 */
3494 3497 if (bytes != ARC_EVICT_ALL) {
3495 3498 ASSERT3S(total_evicted, <, bytes);
3496 3499 ARCSTAT_BUMP(arcstat_evict_not_enough);
3497 3500 }
3498 3501
3499 3502 break;
3500 3503 }
3501 3504 }
3502 3505
3503 3506 for (int i = 0; i < num_sublists; i++) {
3504 3507 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
3505 3508 multilist_sublist_remove(mls, markers[i]);
3506 3509 multilist_sublist_unlock(mls);
3507 3510
3508 3511 kmem_cache_free(hdr_full_cache, markers[i]);
3509 3512 }
3510 3513 kmem_free(markers, sizeof (*markers) * num_sublists);
3511 3514
3512 3515 return (total_evicted);
3513 3516 }
3514 3517
3515 3518 /*
3516 3519 * Flush all "evictable" data of the given type from the arc state
3517 3520 * specified. This will not evict any "active" buffers (i.e. referenced).
3518 3521 *
3519 3522 * When 'retry' is set to B_FALSE, the function will make a single pass
3520 3523 * over the state and evict any buffers that it can. Since it doesn't
3521 3524 * continually retry the eviction, it might end up leaving some buffers
3522 3525 * in the ARC due to lock misses.
3523 3526 *
3524 3527 * When 'retry' is set to B_TRUE, the function will continually retry the
3525 3528 * eviction until *all* evictable buffers have been removed from the
3526 3529 * state. As a result, if concurrent insertions into the state are
3527 3530 * allowed (e.g. if the ARC isn't shutting down), this function might
3528 3531 * wind up in an infinite loop, continually trying to evict buffers.
3529 3532 */
3530 3533 static uint64_t
3531 3534 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
3532 3535 boolean_t retry)
3533 3536 {
3534 3537 uint64_t evicted = 0;
3535 3538
3536 3539 while (refcount_count(&state->arcs_esize[type]) != 0) {
3537 3540 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
3538 3541
3539 3542 if (!retry)
3540 3543 break;
3541 3544 }
3542 3545
3543 3546 return (evicted);
3544 3547 }
3545 3548
3546 3549 /*
3547 3550 * Evict the specified number of bytes from the state specified,
3548 3551 * restricting eviction to the spa and type given. This function
3549 3552 * prevents us from trying to evict more from a state's list than
3550 3553 * is "evictable", and to skip evicting altogether when passed a
3551 3554 * negative value for "bytes". In contrast, arc_evict_state() will
3552 3555 * evict everything it can, when passed a negative value for "bytes".
3553 3556 */
3554 3557 static uint64_t
3555 3558 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
3556 3559 arc_buf_contents_t type)
3557 3560 {
3558 3561 int64_t delta;
3559 3562
3560 3563 if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
3561 3564 delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
3562 3565 return (arc_evict_state(state, spa, delta, type));
3563 3566 }
3564 3567
3565 3568 return (0);
3566 3569 }
3567 3570
3568 3571 /*
3569 3572 * Evict metadata buffers from the cache, such that arc_meta_used is
3570 3573 * capped by the arc_meta_limit tunable.
3571 3574 */
3572 3575 static uint64_t
3573 3576 arc_adjust_meta(void)
3574 3577 {
3575 3578 uint64_t total_evicted = 0;
3576 3579 int64_t target;
3577 3580
3578 3581 /*
3579 3582 * If we're over the meta limit, we want to evict enough
3580 3583 * metadata to get back under the meta limit. We don't want to
3581 3584 * evict so much that we drop the MRU below arc_p, though. If
3582 3585 * we're over the meta limit more than we're over arc_p, we
3583 3586 * evict some from the MRU here, and some from the MFU below.
3584 3587 */
3585 3588 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3586 3589 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3587 3590 refcount_count(&arc_mru->arcs_size) - arc_p));
3588 3591
3589 3592 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3590 3593
3591 3594 /*
3592 3595 * Similar to the above, we want to evict enough bytes to get us
3593 3596 * below the meta limit, but not so much as to drop us below the
3594 3597 * space allotted to the MFU (which is defined as arc_c - arc_p).
3595 3598 */
3596 3599 target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
3597 3600 (int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
3598 3601
3599 3602 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3600 3603
3601 3604 return (total_evicted);
3602 3605 }
3603 3606
3604 3607 /*
3605 3608 * Return the type of the oldest buffer in the given arc state
3606 3609 *
3607 3610 * This function will select a random sublist of type ARC_BUFC_DATA and
3608 3611 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
3609 3612 * is compared, and the type which contains the "older" buffer will be
3610 3613 * returned.
3611 3614 */
3612 3615 static arc_buf_contents_t
3613 3616 arc_adjust_type(arc_state_t *state)
3614 3617 {
3615 3618 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
3616 3619 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
3617 3620 int data_idx = multilist_get_random_index(data_ml);
3618 3621 int meta_idx = multilist_get_random_index(meta_ml);
3619 3622 multilist_sublist_t *data_mls;
3620 3623 multilist_sublist_t *meta_mls;
3621 3624 arc_buf_contents_t type;
3622 3625 arc_buf_hdr_t *data_hdr;
3623 3626 arc_buf_hdr_t *meta_hdr;
3624 3627
3625 3628 /*
3626 3629 * We keep the sublist lock until we're finished, to prevent
3627 3630 * the headers from being destroyed via arc_evict_state().
3628 3631 */
3629 3632 data_mls = multilist_sublist_lock(data_ml, data_idx);
3630 3633 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
3631 3634
3632 3635 /*
3633 3636 * These two loops are to ensure we skip any markers that
3634 3637 * might be at the tail of the lists due to arc_evict_state().
3635 3638 */
3636 3639
3637 3640 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
3638 3641 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
3639 3642 if (data_hdr->b_spa != 0)
3640 3643 break;
3641 3644 }
3642 3645
3643 3646 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
3644 3647 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
3645 3648 if (meta_hdr->b_spa != 0)
3646 3649 break;
3647 3650 }
3648 3651
3649 3652 if (data_hdr == NULL && meta_hdr == NULL) {
3650 3653 type = ARC_BUFC_DATA;
3651 3654 } else if (data_hdr == NULL) {
3652 3655 ASSERT3P(meta_hdr, !=, NULL);
3653 3656 type = ARC_BUFC_METADATA;
3654 3657 } else if (meta_hdr == NULL) {
3655 3658 ASSERT3P(data_hdr, !=, NULL);
3656 3659 type = ARC_BUFC_DATA;
3657 3660 } else {
3658 3661 ASSERT3P(data_hdr, !=, NULL);
3659 3662 ASSERT3P(meta_hdr, !=, NULL);
3660 3663
3661 3664 /* The headers can't be on the sublist without an L1 header */
3662 3665 ASSERT(HDR_HAS_L1HDR(data_hdr));
3663 3666 ASSERT(HDR_HAS_L1HDR(meta_hdr));
3664 3667
3665 3668 if (data_hdr->b_l1hdr.b_arc_access <
3666 3669 meta_hdr->b_l1hdr.b_arc_access) {
3667 3670 type = ARC_BUFC_DATA;
3668 3671 } else {
3669 3672 type = ARC_BUFC_METADATA;
3670 3673 }
3671 3674 }
3672 3675
3673 3676 multilist_sublist_unlock(meta_mls);
3674 3677 multilist_sublist_unlock(data_mls);
3675 3678
3676 3679 return (type);
3677 3680 }
3678 3681
3679 3682 /*
3680 3683 * Evict buffers from the cache, such that arc_size is capped by arc_c.
3681 3684 */
3682 3685 static uint64_t
3683 3686 arc_adjust(void)
3684 3687 {
3685 3688 uint64_t total_evicted = 0;
3686 3689 uint64_t bytes;
3687 3690 int64_t target;
3688 3691
3689 3692 /*
3690 3693 * If we're over arc_meta_limit, we want to correct that before
3691 3694 * potentially evicting data buffers below.
3692 3695 */
3693 3696 total_evicted += arc_adjust_meta();
3694 3697
3695 3698 /*
3696 3699 * Adjust MRU size
3697 3700 *
3698 3701 * If we're over the target cache size, we want to evict enough
3699 3702 * from the list to get back to our target size. We don't want
3700 3703 * to evict too much from the MRU, such that it drops below
3701 3704 * arc_p. So, if we're over our target cache size more than
3702 3705 * the MRU is over arc_p, we'll evict enough to get back to
3703 3706 * arc_p here, and then evict more from the MFU below.
3704 3707 */
3705 3708 target = MIN((int64_t)(arc_size - arc_c),
3706 3709 (int64_t)(refcount_count(&arc_anon->arcs_size) +
3707 3710 refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
3708 3711
3709 3712 /*
3710 3713 * If we're below arc_meta_min, always prefer to evict data.
3711 3714 * Otherwise, try to satisfy the requested number of bytes to
3712 3715 * evict from the type which contains older buffers; in an
3713 3716 * effort to keep newer buffers in the cache regardless of their
3714 3717 * type. If we cannot satisfy the number of bytes from this
3715 3718 * type, spill over into the next type.
3716 3719 */
3717 3720 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
3718 3721 arc_meta_used > arc_meta_min) {
3719 3722 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3720 3723 total_evicted += bytes;
3721 3724
3722 3725 /*
3723 3726 * If we couldn't evict our target number of bytes from
3724 3727 * metadata, we try to get the rest from data.
3725 3728 */
3726 3729 target -= bytes;
3727 3730
3728 3731 total_evicted +=
3729 3732 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
3730 3733 } else {
3731 3734 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
3732 3735 total_evicted += bytes;
3733 3736
3734 3737 /*
3735 3738 * If we couldn't evict our target number of bytes from
3736 3739 * data, we try to get the rest from metadata.
3737 3740 */
3738 3741 target -= bytes;
3739 3742
3740 3743 total_evicted +=
3741 3744 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
3742 3745 }
3743 3746
3744 3747 /*
3745 3748 * Adjust MFU size
3746 3749 *
3747 3750 * Now that we've tried to evict enough from the MRU to get its
3748 3751 * size back to arc_p, if we're still above the target cache
3749 3752 * size, we evict the rest from the MFU.
3750 3753 */
3751 3754 target = arc_size - arc_c;
3752 3755
3753 3756 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
3754 3757 arc_meta_used > arc_meta_min) {
3755 3758 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3756 3759 total_evicted += bytes;
3757 3760
3758 3761 /*
3759 3762 * If we couldn't evict our target number of bytes from
3760 3763 * metadata, we try to get the rest from data.
3761 3764 */
3762 3765 target -= bytes;
3763 3766
3764 3767 total_evicted +=
3765 3768 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
3766 3769 } else {
3767 3770 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
3768 3771 total_evicted += bytes;
3769 3772
3770 3773 /*
3771 3774 * If we couldn't evict our target number of bytes from
3772 3775 * data, we try to get the rest from data.
3773 3776 */
3774 3777 target -= bytes;
3775 3778
3776 3779 total_evicted +=
3777 3780 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
3778 3781 }
3779 3782
3780 3783 /*
3781 3784 * Adjust ghost lists
3782 3785 *
3783 3786 * In addition to the above, the ARC also defines target values
3784 3787 * for the ghost lists. The sum of the mru list and mru ghost
3785 3788 * list should never exceed the target size of the cache, and
3786 3789 * the sum of the mru list, mfu list, mru ghost list, and mfu
3787 3790 * ghost list should never exceed twice the target size of the
3788 3791 * cache. The following logic enforces these limits on the ghost
3789 3792 * caches, and evicts from them as needed.
3790 3793 */
3791 3794 target = refcount_count(&arc_mru->arcs_size) +
3792 3795 refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
3793 3796
3794 3797 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
3795 3798 total_evicted += bytes;
3796 3799
3797 3800 target -= bytes;
3798 3801
3799 3802 total_evicted +=
3800 3803 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
3801 3804
3802 3805 /*
3803 3806 * We assume the sum of the mru list and mfu list is less than
3804 3807 * or equal to arc_c (we enforced this above), which means we
3805 3808 * can use the simpler of the two equations below:
3806 3809 *
3807 3810 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
3808 3811 * mru ghost + mfu ghost <= arc_c
3809 3812 */
3810 3813 target = refcount_count(&arc_mru_ghost->arcs_size) +
3811 3814 refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
3812 3815
3813 3816 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
3814 3817 total_evicted += bytes;
3815 3818
3816 3819 target -= bytes;
3817 3820
3818 3821 total_evicted +=
3819 3822 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
3820 3823
3821 3824 return (total_evicted);
3822 3825 }
3823 3826
3824 3827 void
3825 3828 arc_flush(spa_t *spa, boolean_t retry)
3826 3829 {
3827 3830 uint64_t guid = 0;
3828 3831
3829 3832 /*
3830 3833 * If retry is B_TRUE, a spa must not be specified since we have
3831 3834 * no good way to determine if all of a spa's buffers have been
3832 3835 * evicted from an arc state.
3833 3836 */
3834 3837 ASSERT(!retry || spa == 0);
3835 3838
3836 3839 if (spa != NULL)
3837 3840 guid = spa_load_guid(spa);
3838 3841
3839 3842 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
3840 3843 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
3841 3844
3842 3845 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
3843 3846 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
3844 3847
3845 3848 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
3846 3849 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
3847 3850
3848 3851 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
3849 3852 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
3850 3853 }
3851 3854
3852 3855 void
3853 3856 arc_shrink(int64_t to_free)
3854 3857 {
3855 3858 if (arc_c > arc_c_min) {
3856 3859
3857 3860 if (arc_c > arc_c_min + to_free)
3858 3861 atomic_add_64(&arc_c, -to_free);
3859 3862 else
3860 3863 arc_c = arc_c_min;
3861 3864
3862 3865 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
3863 3866 if (arc_c > arc_size)
3864 3867 arc_c = MAX(arc_size, arc_c_min);
3865 3868 if (arc_p > arc_c)
3866 3869 arc_p = (arc_c >> 1);
3867 3870 ASSERT(arc_c >= arc_c_min);
3868 3871 ASSERT((int64_t)arc_p >= 0);
3869 3872 }
3870 3873
3871 3874 if (arc_size > arc_c)
3872 3875 (void) arc_adjust();
3873 3876 }
3874 3877
3875 3878 typedef enum free_memory_reason_t {
3876 3879 FMR_UNKNOWN,
3877 3880 FMR_NEEDFREE,
3878 3881 FMR_LOTSFREE,
3879 3882 FMR_SWAPFS_MINFREE,
3880 3883 FMR_PAGES_PP_MAXIMUM,
3881 3884 FMR_HEAP_ARENA,
3882 3885 FMR_ZIO_ARENA,
3883 3886 } free_memory_reason_t;
3884 3887
3885 3888 int64_t last_free_memory;
3886 3889 free_memory_reason_t last_free_reason;
3887 3890
3888 3891 /*
3889 3892 * Additional reserve of pages for pp_reserve.
3890 3893 */
3891 3894 int64_t arc_pages_pp_reserve = 64;
3892 3895
3893 3896 /*
3894 3897 * Additional reserve of pages for swapfs.
3895 3898 */
3896 3899 int64_t arc_swapfs_reserve = 64;
3897 3900
3898 3901 /*
3899 3902 * Return the amount of memory that can be consumed before reclaim will be
3900 3903 * needed. Positive if there is sufficient free memory, negative indicates
3901 3904 * the amount of memory that needs to be freed up.
3902 3905 */
3903 3906 static int64_t
3904 3907 arc_available_memory(void)
3905 3908 {
3906 3909 int64_t lowest = INT64_MAX;
3907 3910 int64_t n;
3908 3911 free_memory_reason_t r = FMR_UNKNOWN;
3909 3912
3910 3913 #ifdef _KERNEL
3911 3914 if (needfree > 0) {
3912 3915 n = PAGESIZE * (-needfree);
3913 3916 if (n < lowest) {
3914 3917 lowest = n;
3915 3918 r = FMR_NEEDFREE;
3916 3919 }
3917 3920 }
3918 3921
3919 3922 /*
3920 3923 * check that we're out of range of the pageout scanner. It starts to
3921 3924 * schedule paging if freemem is less than lotsfree and needfree.
3922 3925 * lotsfree is the high-water mark for pageout, and needfree is the
3923 3926 * number of needed free pages. We add extra pages here to make sure
3924 3927 * the scanner doesn't start up while we're freeing memory.
3925 3928 */
3926 3929 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
3927 3930 if (n < lowest) {
3928 3931 lowest = n;
3929 3932 r = FMR_LOTSFREE;
3930 3933 }
3931 3934
3932 3935 /*
3933 3936 * check to make sure that swapfs has enough space so that anon
3934 3937 * reservations can still succeed. anon_resvmem() checks that the
3935 3938 * availrmem is greater than swapfs_minfree, and the number of reserved
3936 3939 * swap pages. We also add a bit of extra here just to prevent
3937 3940 * circumstances from getting really dire.
3938 3941 */
3939 3942 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
3940 3943 desfree - arc_swapfs_reserve);
3941 3944 if (n < lowest) {
3942 3945 lowest = n;
3943 3946 r = FMR_SWAPFS_MINFREE;
3944 3947 }
3945 3948
3946 3949
3947 3950 /*
3948 3951 * Check that we have enough availrmem that memory locking (e.g., via
3949 3952 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
3950 3953 * stores the number of pages that cannot be locked; when availrmem
3951 3954 * drops below pages_pp_maximum, page locking mechanisms such as
3952 3955 * page_pp_lock() will fail.)
3953 3956 */
3954 3957 n = PAGESIZE * (availrmem - pages_pp_maximum -
3955 3958 arc_pages_pp_reserve);
3956 3959 if (n < lowest) {
3957 3960 lowest = n;
3958 3961 r = FMR_PAGES_PP_MAXIMUM;
3959 3962 }
3960 3963
3961 3964 #if defined(__i386)
3962 3965 /*
3963 3966 * If we're on an i386 platform, it's possible that we'll exhaust the
3964 3967 * kernel heap space before we ever run out of available physical
3965 3968 * memory. Most checks of the size of the heap_area compare against
3966 3969 * tune.t_minarmem, which is the minimum available real memory that we
3967 3970 * can have in the system. However, this is generally fixed at 25 pages
3968 3971 * which is so low that it's useless. In this comparison, we seek to
3969 3972 * calculate the total heap-size, and reclaim if more than 3/4ths of the
3970 3973 * heap is allocated. (Or, in the calculation, if less than 1/4th is
3971 3974 * free)
3972 3975 */
3973 3976 n = (int64_t)vmem_size(heap_arena, VMEM_FREE) -
3974 3977 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
3975 3978 if (n < lowest) {
3976 3979 lowest = n;
3977 3980 r = FMR_HEAP_ARENA;
3978 3981 }
3979 3982 #endif
3980 3983
3981 3984 /*
3982 3985 * If zio data pages are being allocated out of a separate heap segment,
3983 3986 * then enforce that the size of available vmem for this arena remains
3984 3987 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
3985 3988 *
3986 3989 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
3987 3990 * memory (in the zio_arena) free, which can avoid memory
3988 3991 * fragmentation issues.
3989 3992 */
3990 3993 if (zio_arena != NULL) {
3991 3994 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
3992 3995 (vmem_size(zio_arena, VMEM_ALLOC) >>
3993 3996 arc_zio_arena_free_shift);
3994 3997 if (n < lowest) {
3995 3998 lowest = n;
3996 3999 r = FMR_ZIO_ARENA;
3997 4000 }
3998 4001 }
3999 4002 #else
4000 4003 /* Every 100 calls, free a small amount */
4001 4004 if (spa_get_random(100) == 0)
4002 4005 lowest = -1024;
4003 4006 #endif
4004 4007
4005 4008 last_free_memory = lowest;
4006 4009 last_free_reason = r;
4007 4010
4008 4011 return (lowest);
4009 4012 }
4010 4013
4011 4014
4012 4015 /*
4013 4016 * Determine if the system is under memory pressure and is asking
4014 4017 * to reclaim memory. A return value of B_TRUE indicates that the system
4015 4018 * is under memory pressure and that the arc should adjust accordingly.
4016 4019 */
4017 4020 static boolean_t
4018 4021 arc_reclaim_needed(void)
4019 4022 {
4020 4023 return (arc_available_memory() < 0);
4021 4024 }
4022 4025
4023 4026 static void
4024 4027 arc_kmem_reap_now(void)
4025 4028 {
4026 4029 size_t i;
4027 4030 kmem_cache_t *prev_cache = NULL;
4028 4031 kmem_cache_t *prev_data_cache = NULL;
4029 4032 extern kmem_cache_t *zio_buf_cache[];
4030 4033 extern kmem_cache_t *zio_data_buf_cache[];
4031 4034 extern kmem_cache_t *range_seg_cache;
4032 4035 extern kmem_cache_t *abd_chunk_cache;
4033 4036
4034 4037 #ifdef _KERNEL
4035 4038 if (arc_meta_used >= arc_meta_limit) {
4036 4039 /*
4037 4040 * We are exceeding our meta-data cache limit.
4038 4041 * Purge some DNLC entries to release holds on meta-data.
4039 4042 */
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4040 4043 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4041 4044 }
4042 4045 #if defined(__i386)
4043 4046 /*
4044 4047 * Reclaim unused memory from all kmem caches.
4045 4048 */
4046 4049 kmem_reap();
4047 4050 #endif
4048 4051 #endif
4049 4052
4053 + /*
4054 + * If a kmem reap is already active, don't schedule more. We must
4055 + * check for this because kmem_cache_reap_soon() won't actually
4056 + * block on the cache being reaped (this is to prevent callers from
4057 + * becoming implicitly blocked by a system-wide kmem reap -- which,
4058 + * on a system with many, many full magazines, can take minutes).
4059 + */
4060 + if (kmem_cache_reap_active())
4061 + return;
4062 +
4050 4063 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4051 4064 if (zio_buf_cache[i] != prev_cache) {
4052 4065 prev_cache = zio_buf_cache[i];
4053 - kmem_cache_reap_now(zio_buf_cache[i]);
4066 + kmem_cache_reap_soon(zio_buf_cache[i]);
4054 4067 }
4055 4068 if (zio_data_buf_cache[i] != prev_data_cache) {
4056 4069 prev_data_cache = zio_data_buf_cache[i];
4057 - kmem_cache_reap_now(zio_data_buf_cache[i]);
4070 + kmem_cache_reap_soon(zio_data_buf_cache[i]);
4058 4071 }
4059 4072 }
4060 - kmem_cache_reap_now(abd_chunk_cache);
4061 - kmem_cache_reap_now(buf_cache);
4062 - kmem_cache_reap_now(hdr_full_cache);
4063 - kmem_cache_reap_now(hdr_l2only_cache);
4064 - kmem_cache_reap_now(range_seg_cache);
4073 + kmem_cache_reap_soon(abd_chunk_cache);
4074 + kmem_cache_reap_soon(buf_cache);
4075 + kmem_cache_reap_soon(hdr_full_cache);
4076 + kmem_cache_reap_soon(hdr_l2only_cache);
4077 + kmem_cache_reap_soon(range_seg_cache);
4065 4078
4066 4079 if (zio_arena != NULL) {
4067 4080 /*
4068 4081 * Ask the vmem arena to reclaim unused memory from its
4069 4082 * quantum caches.
4070 4083 */
4071 4084 vmem_qcache_reap(zio_arena);
4072 4085 }
4073 4086 }
4074 4087
4075 4088 /*
4076 4089 * Threads can block in arc_get_data_impl() waiting for this thread to evict
4077 4090 * enough data and signal them to proceed. When this happens, the threads in
4078 4091 * arc_get_data_impl() are sleeping while holding the hash lock for their
4079 4092 * particular arc header. Thus, we must be careful to never sleep on a
4080 4093 * hash lock in this thread. This is to prevent the following deadlock:
4081 4094 *
4082 4095 * - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
4083 4096 * waiting for the reclaim thread to signal it.
4084 4097 *
4085 4098 * - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
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4086 4099 * fails, and goes to sleep forever.
4087 4100 *
4088 4101 * This possible deadlock is avoided by always acquiring a hash lock
4089 4102 * using mutex_tryenter() from arc_reclaim_thread().
4090 4103 */
4091 4104 /* ARGSUSED */
4092 4105 static void
4093 4106 arc_reclaim_thread(void *unused)
4094 4107 {
4095 4108 hrtime_t growtime = 0;
4109 + hrtime_t kmem_reap_time = 0;
4096 4110 callb_cpr_t cpr;
4097 4111
4098 4112 CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
4099 4113
4100 4114 mutex_enter(&arc_reclaim_lock);
4101 4115 while (!arc_reclaim_thread_exit) {
4102 4116 uint64_t evicted = 0;
4103 4117
4104 4118 /*
4105 4119 * This is necessary in order for the mdb ::arc dcmd to
4106 4120 * show up to date information. Since the ::arc command
4107 4121 * does not call the kstat's update function, without
4108 4122 * this call, the command may show stale stats for the
4109 4123 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4110 4124 * with this change, the data might be up to 1 second
4111 4125 * out of date; but that should suffice. The arc_state_t
4112 4126 * structures can be queried directly if more accurate
4113 4127 * information is needed.
4114 4128 */
4115 4129 if (arc_ksp != NULL)
4116 4130 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4117 4131
4118 4132 mutex_exit(&arc_reclaim_lock);
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4119 4133
4120 4134 /*
4121 4135 * We call arc_adjust() before (possibly) calling
4122 4136 * arc_kmem_reap_now(), so that we can wake up
4123 4137 * arc_get_data_impl() sooner.
4124 4138 */
4125 4139 evicted = arc_adjust();
4126 4140
4127 4141 int64_t free_memory = arc_available_memory();
4128 4142 if (free_memory < 0) {
4129 -
4143 + hrtime_t curtime = gethrtime();
4130 4144 arc_no_grow = B_TRUE;
4131 4145 arc_warm = B_TRUE;
4132 4146
4133 4147 /*
4134 4148 * Wait at least zfs_grow_retry (default 60) seconds
4135 4149 * before considering growing.
4136 4150 */
4137 - growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
4151 + growtime = curtime + SEC2NSEC(arc_grow_retry);
4138 4152
4139 - arc_kmem_reap_now();
4153 + /*
4154 + * Wait at least arc_kmem_cache_reap_retry_ms
4155 + * between arc_kmem_reap_now() calls. Without
4156 + * this check it is possible to end up in a
4157 + * situation where we spend lots of time
4158 + * reaping caches, while we're near arc_c_min.
4159 + */
4160 + if (curtime >= kmem_reap_time) {
4161 + arc_kmem_reap_now();
4162 + kmem_reap_time = gethrtime() +
4163 + MSEC2NSEC(arc_kmem_cache_reap_retry_ms);
4164 + }
4140 4165
4141 4166 /*
4142 4167 * If we are still low on memory, shrink the ARC
4143 4168 * so that we have arc_shrink_min free space.
4144 4169 */
4145 4170 free_memory = arc_available_memory();
4146 4171
4147 4172 int64_t to_free =
4148 4173 (arc_c >> arc_shrink_shift) - free_memory;
4149 4174 if (to_free > 0) {
4150 4175 #ifdef _KERNEL
4151 4176 to_free = MAX(to_free, ptob(needfree));
4152 4177 #endif
4153 4178 arc_shrink(to_free);
4154 4179 }
4155 4180 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4156 4181 arc_no_grow = B_TRUE;
4157 4182 } else if (gethrtime() >= growtime) {
4158 4183 arc_no_grow = B_FALSE;
4159 4184 }
4160 4185
4161 4186 mutex_enter(&arc_reclaim_lock);
4162 4187
4163 4188 /*
4164 4189 * If evicted is zero, we couldn't evict anything via
4165 4190 * arc_adjust(). This could be due to hash lock
4166 4191 * collisions, but more likely due to the majority of
4167 4192 * arc buffers being unevictable. Therefore, even if
4168 4193 * arc_size is above arc_c, another pass is unlikely to
4169 4194 * be helpful and could potentially cause us to enter an
4170 4195 * infinite loop.
4171 4196 */
4172 4197 if (arc_size <= arc_c || evicted == 0) {
4173 4198 /*
4174 4199 * We're either no longer overflowing, or we
4175 4200 * can't evict anything more, so we should wake
4176 4201 * up any threads before we go to sleep.
4177 4202 */
4178 4203 cv_broadcast(&arc_reclaim_waiters_cv);
4179 4204
4180 4205 /*
4181 4206 * Block until signaled, or after one second (we
4182 4207 * might need to perform arc_kmem_reap_now()
4183 4208 * even if we aren't being signalled)
4184 4209 */
4185 4210 CALLB_CPR_SAFE_BEGIN(&cpr);
4186 4211 (void) cv_timedwait_hires(&arc_reclaim_thread_cv,
4187 4212 &arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
4188 4213 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
4189 4214 }
4190 4215 }
4191 4216
4192 4217 arc_reclaim_thread_exit = B_FALSE;
4193 4218 cv_broadcast(&arc_reclaim_thread_cv);
4194 4219 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
4195 4220 thread_exit();
4196 4221 }
4197 4222
4198 4223 /*
4199 4224 * Adapt arc info given the number of bytes we are trying to add and
4200 4225 * the state that we are comming from. This function is only called
4201 4226 * when we are adding new content to the cache.
4202 4227 */
4203 4228 static void
4204 4229 arc_adapt(int bytes, arc_state_t *state)
4205 4230 {
4206 4231 int mult;
4207 4232 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4208 4233 int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
4209 4234 int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
4210 4235
4211 4236 if (state == arc_l2c_only)
4212 4237 return;
4213 4238
4214 4239 ASSERT(bytes > 0);
4215 4240 /*
4216 4241 * Adapt the target size of the MRU list:
4217 4242 * - if we just hit in the MRU ghost list, then increase
4218 4243 * the target size of the MRU list.
4219 4244 * - if we just hit in the MFU ghost list, then increase
4220 4245 * the target size of the MFU list by decreasing the
4221 4246 * target size of the MRU list.
4222 4247 */
4223 4248 if (state == arc_mru_ghost) {
4224 4249 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4225 4250 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4226 4251
4227 4252 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4228 4253 } else if (state == arc_mfu_ghost) {
4229 4254 uint64_t delta;
4230 4255
4231 4256 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4232 4257 mult = MIN(mult, 10);
4233 4258
4234 4259 delta = MIN(bytes * mult, arc_p);
4235 4260 arc_p = MAX(arc_p_min, arc_p - delta);
4236 4261 }
4237 4262 ASSERT((int64_t)arc_p >= 0);
4238 4263
4239 4264 if (arc_reclaim_needed()) {
4240 4265 cv_signal(&arc_reclaim_thread_cv);
4241 4266 return;
4242 4267 }
4243 4268
4244 4269 if (arc_no_grow)
4245 4270 return;
4246 4271
4247 4272 if (arc_c >= arc_c_max)
4248 4273 return;
4249 4274
4250 4275 /*
4251 4276 * If we're within (2 * maxblocksize) bytes of the target
4252 4277 * cache size, increment the target cache size
4253 4278 */
4254 4279 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
4255 4280 atomic_add_64(&arc_c, (int64_t)bytes);
4256 4281 if (arc_c > arc_c_max)
4257 4282 arc_c = arc_c_max;
4258 4283 else if (state == arc_anon)
4259 4284 atomic_add_64(&arc_p, (int64_t)bytes);
4260 4285 if (arc_p > arc_c)
4261 4286 arc_p = arc_c;
4262 4287 }
4263 4288 ASSERT((int64_t)arc_p >= 0);
4264 4289 }
4265 4290
4266 4291 /*
4267 4292 * Check if arc_size has grown past our upper threshold, determined by
4268 4293 * zfs_arc_overflow_shift.
4269 4294 */
4270 4295 static boolean_t
4271 4296 arc_is_overflowing(void)
4272 4297 {
4273 4298 /* Always allow at least one block of overflow */
4274 4299 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4275 4300 arc_c >> zfs_arc_overflow_shift);
4276 4301
4277 4302 return (arc_size >= arc_c + overflow);
4278 4303 }
4279 4304
4280 4305 static abd_t *
4281 4306 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4282 4307 {
4283 4308 arc_buf_contents_t type = arc_buf_type(hdr);
4284 4309
4285 4310 arc_get_data_impl(hdr, size, tag);
4286 4311 if (type == ARC_BUFC_METADATA) {
4287 4312 return (abd_alloc(size, B_TRUE));
4288 4313 } else {
4289 4314 ASSERT(type == ARC_BUFC_DATA);
4290 4315 return (abd_alloc(size, B_FALSE));
4291 4316 }
4292 4317 }
4293 4318
4294 4319 static void *
4295 4320 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4296 4321 {
4297 4322 arc_buf_contents_t type = arc_buf_type(hdr);
4298 4323
4299 4324 arc_get_data_impl(hdr, size, tag);
4300 4325 if (type == ARC_BUFC_METADATA) {
4301 4326 return (zio_buf_alloc(size));
4302 4327 } else {
4303 4328 ASSERT(type == ARC_BUFC_DATA);
4304 4329 return (zio_data_buf_alloc(size));
4305 4330 }
4306 4331 }
4307 4332
4308 4333 /*
4309 4334 * Allocate a block and return it to the caller. If we are hitting the
4310 4335 * hard limit for the cache size, we must sleep, waiting for the eviction
4311 4336 * thread to catch up. If we're past the target size but below the hard
4312 4337 * limit, we'll only signal the reclaim thread and continue on.
4313 4338 */
4314 4339 static void
4315 4340 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4316 4341 {
4317 4342 arc_state_t *state = hdr->b_l1hdr.b_state;
4318 4343 arc_buf_contents_t type = arc_buf_type(hdr);
4319 4344
4320 4345 arc_adapt(size, state);
4321 4346
4322 4347 /*
4323 4348 * If arc_size is currently overflowing, and has grown past our
4324 4349 * upper limit, we must be adding data faster than the evict
4325 4350 * thread can evict. Thus, to ensure we don't compound the
4326 4351 * problem by adding more data and forcing arc_size to grow even
4327 4352 * further past it's target size, we halt and wait for the
4328 4353 * eviction thread to catch up.
4329 4354 *
4330 4355 * It's also possible that the reclaim thread is unable to evict
4331 4356 * enough buffers to get arc_size below the overflow limit (e.g.
4332 4357 * due to buffers being un-evictable, or hash lock collisions).
4333 4358 * In this case, we want to proceed regardless if we're
4334 4359 * overflowing; thus we don't use a while loop here.
4335 4360 */
4336 4361 if (arc_is_overflowing()) {
4337 4362 mutex_enter(&arc_reclaim_lock);
4338 4363
4339 4364 /*
4340 4365 * Now that we've acquired the lock, we may no longer be
4341 4366 * over the overflow limit, lets check.
4342 4367 *
4343 4368 * We're ignoring the case of spurious wake ups. If that
4344 4369 * were to happen, it'd let this thread consume an ARC
4345 4370 * buffer before it should have (i.e. before we're under
4346 4371 * the overflow limit and were signalled by the reclaim
4347 4372 * thread). As long as that is a rare occurrence, it
4348 4373 * shouldn't cause any harm.
4349 4374 */
4350 4375 if (arc_is_overflowing()) {
4351 4376 cv_signal(&arc_reclaim_thread_cv);
4352 4377 cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
4353 4378 }
4354 4379
4355 4380 mutex_exit(&arc_reclaim_lock);
4356 4381 }
4357 4382
4358 4383 VERIFY3U(hdr->b_type, ==, type);
4359 4384 if (type == ARC_BUFC_METADATA) {
4360 4385 arc_space_consume(size, ARC_SPACE_META);
4361 4386 } else {
4362 4387 arc_space_consume(size, ARC_SPACE_DATA);
4363 4388 }
4364 4389
4365 4390 /*
4366 4391 * Update the state size. Note that ghost states have a
4367 4392 * "ghost size" and so don't need to be updated.
4368 4393 */
4369 4394 if (!GHOST_STATE(state)) {
4370 4395
4371 4396 (void) refcount_add_many(&state->arcs_size, size, tag);
4372 4397
4373 4398 /*
4374 4399 * If this is reached via arc_read, the link is
4375 4400 * protected by the hash lock. If reached via
4376 4401 * arc_buf_alloc, the header should not be accessed by
4377 4402 * any other thread. And, if reached via arc_read_done,
4378 4403 * the hash lock will protect it if it's found in the
4379 4404 * hash table; otherwise no other thread should be
4380 4405 * trying to [add|remove]_reference it.
4381 4406 */
4382 4407 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4383 4408 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4384 4409 (void) refcount_add_many(&state->arcs_esize[type],
4385 4410 size, tag);
4386 4411 }
4387 4412
4388 4413 /*
4389 4414 * If we are growing the cache, and we are adding anonymous
4390 4415 * data, and we have outgrown arc_p, update arc_p
4391 4416 */
4392 4417 if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
4393 4418 (refcount_count(&arc_anon->arcs_size) +
4394 4419 refcount_count(&arc_mru->arcs_size) > arc_p))
4395 4420 arc_p = MIN(arc_c, arc_p + size);
4396 4421 }
4397 4422 }
4398 4423
4399 4424 static void
4400 4425 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
4401 4426 {
4402 4427 arc_free_data_impl(hdr, size, tag);
4403 4428 abd_free(abd);
4404 4429 }
4405 4430
4406 4431 static void
4407 4432 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
4408 4433 {
4409 4434 arc_buf_contents_t type = arc_buf_type(hdr);
4410 4435
4411 4436 arc_free_data_impl(hdr, size, tag);
4412 4437 if (type == ARC_BUFC_METADATA) {
4413 4438 zio_buf_free(buf, size);
4414 4439 } else {
4415 4440 ASSERT(type == ARC_BUFC_DATA);
4416 4441 zio_data_buf_free(buf, size);
4417 4442 }
4418 4443 }
4419 4444
4420 4445 /*
4421 4446 * Free the arc data buffer.
4422 4447 */
4423 4448 static void
4424 4449 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4425 4450 {
4426 4451 arc_state_t *state = hdr->b_l1hdr.b_state;
4427 4452 arc_buf_contents_t type = arc_buf_type(hdr);
4428 4453
4429 4454 /* protected by hash lock, if in the hash table */
4430 4455 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
4431 4456 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4432 4457 ASSERT(state != arc_anon && state != arc_l2c_only);
4433 4458
4434 4459 (void) refcount_remove_many(&state->arcs_esize[type],
4435 4460 size, tag);
4436 4461 }
4437 4462 (void) refcount_remove_many(&state->arcs_size, size, tag);
4438 4463
4439 4464 VERIFY3U(hdr->b_type, ==, type);
4440 4465 if (type == ARC_BUFC_METADATA) {
4441 4466 arc_space_return(size, ARC_SPACE_META);
4442 4467 } else {
4443 4468 ASSERT(type == ARC_BUFC_DATA);
4444 4469 arc_space_return(size, ARC_SPACE_DATA);
4445 4470 }
4446 4471 }
4447 4472
4448 4473 /*
4449 4474 * This routine is called whenever a buffer is accessed.
4450 4475 * NOTE: the hash lock is dropped in this function.
4451 4476 */
4452 4477 static void
4453 4478 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
4454 4479 {
4455 4480 clock_t now;
4456 4481
4457 4482 ASSERT(MUTEX_HELD(hash_lock));
4458 4483 ASSERT(HDR_HAS_L1HDR(hdr));
4459 4484
4460 4485 if (hdr->b_l1hdr.b_state == arc_anon) {
4461 4486 /*
4462 4487 * This buffer is not in the cache, and does not
4463 4488 * appear in our "ghost" list. Add the new buffer
4464 4489 * to the MRU state.
4465 4490 */
4466 4491
4467 4492 ASSERT0(hdr->b_l1hdr.b_arc_access);
4468 4493 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4469 4494 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4470 4495 arc_change_state(arc_mru, hdr, hash_lock);
4471 4496
4472 4497 } else if (hdr->b_l1hdr.b_state == arc_mru) {
4473 4498 now = ddi_get_lbolt();
4474 4499
4475 4500 /*
4476 4501 * If this buffer is here because of a prefetch, then either:
4477 4502 * - clear the flag if this is a "referencing" read
4478 4503 * (any subsequent access will bump this into the MFU state).
4479 4504 * or
4480 4505 * - move the buffer to the head of the list if this is
4481 4506 * another prefetch (to make it less likely to be evicted).
4482 4507 */
4483 4508 if (HDR_PREFETCH(hdr)) {
4484 4509 if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4485 4510 /* link protected by hash lock */
4486 4511 ASSERT(multilist_link_active(
4487 4512 &hdr->b_l1hdr.b_arc_node));
4488 4513 } else {
4489 4514 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4490 4515 ARCSTAT_BUMP(arcstat_mru_hits);
4491 4516 }
4492 4517 hdr->b_l1hdr.b_arc_access = now;
4493 4518 return;
4494 4519 }
4495 4520
4496 4521 /*
4497 4522 * This buffer has been "accessed" only once so far,
4498 4523 * but it is still in the cache. Move it to the MFU
4499 4524 * state.
4500 4525 */
4501 4526 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
4502 4527 /*
4503 4528 * More than 125ms have passed since we
4504 4529 * instantiated this buffer. Move it to the
4505 4530 * most frequently used state.
4506 4531 */
4507 4532 hdr->b_l1hdr.b_arc_access = now;
4508 4533 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4509 4534 arc_change_state(arc_mfu, hdr, hash_lock);
4510 4535 }
4511 4536 ARCSTAT_BUMP(arcstat_mru_hits);
4512 4537 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
4513 4538 arc_state_t *new_state;
4514 4539 /*
4515 4540 * This buffer has been "accessed" recently, but
4516 4541 * was evicted from the cache. Move it to the
4517 4542 * MFU state.
4518 4543 */
4519 4544
4520 4545 if (HDR_PREFETCH(hdr)) {
4521 4546 new_state = arc_mru;
4522 4547 if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
4523 4548 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
4524 4549 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
4525 4550 } else {
4526 4551 new_state = arc_mfu;
4527 4552 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4528 4553 }
4529 4554
4530 4555 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4531 4556 arc_change_state(new_state, hdr, hash_lock);
4532 4557
4533 4558 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
4534 4559 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
4535 4560 /*
4536 4561 * This buffer has been accessed more than once and is
4537 4562 * still in the cache. Keep it in the MFU state.
4538 4563 *
4539 4564 * NOTE: an add_reference() that occurred when we did
4540 4565 * the arc_read() will have kicked this off the list.
4541 4566 * If it was a prefetch, we will explicitly move it to
4542 4567 * the head of the list now.
4543 4568 */
4544 4569 if ((HDR_PREFETCH(hdr)) != 0) {
4545 4570 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4546 4571 /* link protected by hash_lock */
4547 4572 ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
4548 4573 }
4549 4574 ARCSTAT_BUMP(arcstat_mfu_hits);
4550 4575 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4551 4576 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
4552 4577 arc_state_t *new_state = arc_mfu;
4553 4578 /*
4554 4579 * This buffer has been accessed more than once but has
4555 4580 * been evicted from the cache. Move it back to the
4556 4581 * MFU state.
4557 4582 */
4558 4583
4559 4584 if (HDR_PREFETCH(hdr)) {
4560 4585 /*
4561 4586 * This is a prefetch access...
4562 4587 * move this block back to the MRU state.
4563 4588 */
4564 4589 ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
4565 4590 new_state = arc_mru;
4566 4591 }
4567 4592
4568 4593 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4569 4594 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4570 4595 arc_change_state(new_state, hdr, hash_lock);
4571 4596
4572 4597 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
4573 4598 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
4574 4599 /*
4575 4600 * This buffer is on the 2nd Level ARC.
4576 4601 */
4577 4602
4578 4603 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
4579 4604 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
4580 4605 arc_change_state(arc_mfu, hdr, hash_lock);
4581 4606 } else {
4582 4607 ASSERT(!"invalid arc state");
4583 4608 }
4584 4609 }
4585 4610
4586 4611 /* a generic arc_done_func_t which you can use */
4587 4612 /* ARGSUSED */
4588 4613 void
4589 4614 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
4590 4615 {
4591 4616 if (zio == NULL || zio->io_error == 0)
4592 4617 bcopy(buf->b_data, arg, arc_buf_size(buf));
4593 4618 arc_buf_destroy(buf, arg);
4594 4619 }
4595 4620
4596 4621 /* a generic arc_done_func_t */
4597 4622 void
4598 4623 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
4599 4624 {
4600 4625 arc_buf_t **bufp = arg;
4601 4626 if (zio && zio->io_error) {
4602 4627 arc_buf_destroy(buf, arg);
4603 4628 *bufp = NULL;
4604 4629 } else {
4605 4630 *bufp = buf;
4606 4631 ASSERT(buf->b_data);
4607 4632 }
4608 4633 }
4609 4634
4610 4635 static void
4611 4636 arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
4612 4637 {
4613 4638 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
4614 4639 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
4615 4640 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
4616 4641 } else {
4617 4642 if (HDR_COMPRESSION_ENABLED(hdr)) {
4618 4643 ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
4619 4644 BP_GET_COMPRESS(bp));
4620 4645 }
4621 4646 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
4622 4647 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
4623 4648 }
4624 4649 }
4625 4650
4626 4651 static void
4627 4652 arc_read_done(zio_t *zio)
4628 4653 {
4629 4654 arc_buf_hdr_t *hdr = zio->io_private;
4630 4655 kmutex_t *hash_lock = NULL;
4631 4656 arc_callback_t *callback_list;
4632 4657 arc_callback_t *acb;
4633 4658 boolean_t freeable = B_FALSE;
4634 4659 boolean_t no_zio_error = (zio->io_error == 0);
4635 4660
4636 4661 /*
4637 4662 * The hdr was inserted into hash-table and removed from lists
4638 4663 * prior to starting I/O. We should find this header, since
4639 4664 * it's in the hash table, and it should be legit since it's
4640 4665 * not possible to evict it during the I/O. The only possible
4641 4666 * reason for it not to be found is if we were freed during the
4642 4667 * read.
4643 4668 */
4644 4669 if (HDR_IN_HASH_TABLE(hdr)) {
4645 4670 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
4646 4671 ASSERT3U(hdr->b_dva.dva_word[0], ==,
4647 4672 BP_IDENTITY(zio->io_bp)->dva_word[0]);
4648 4673 ASSERT3U(hdr->b_dva.dva_word[1], ==,
4649 4674 BP_IDENTITY(zio->io_bp)->dva_word[1]);
4650 4675
4651 4676 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
4652 4677 &hash_lock);
4653 4678
4654 4679 ASSERT((found == hdr &&
4655 4680 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
4656 4681 (found == hdr && HDR_L2_READING(hdr)));
4657 4682 ASSERT3P(hash_lock, !=, NULL);
4658 4683 }
4659 4684
4660 4685 if (no_zio_error) {
4661 4686 /* byteswap if necessary */
4662 4687 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
4663 4688 if (BP_GET_LEVEL(zio->io_bp) > 0) {
4664 4689 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
4665 4690 } else {
4666 4691 hdr->b_l1hdr.b_byteswap =
4667 4692 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
4668 4693 }
4669 4694 } else {
4670 4695 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
4671 4696 }
4672 4697 }
4673 4698
4674 4699 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
4675 4700 if (l2arc_noprefetch && HDR_PREFETCH(hdr))
4676 4701 arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
4677 4702
4678 4703 callback_list = hdr->b_l1hdr.b_acb;
4679 4704 ASSERT3P(callback_list, !=, NULL);
4680 4705
4681 4706 if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) {
4682 4707 /*
4683 4708 * Only call arc_access on anonymous buffers. This is because
4684 4709 * if we've issued an I/O for an evicted buffer, we've already
4685 4710 * called arc_access (to prevent any simultaneous readers from
4686 4711 * getting confused).
4687 4712 */
4688 4713 arc_access(hdr, hash_lock);
4689 4714 }
4690 4715
4691 4716 /*
4692 4717 * If a read request has a callback (i.e. acb_done is not NULL), then we
4693 4718 * make a buf containing the data according to the parameters which were
4694 4719 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
4695 4720 * aren't needlessly decompressing the data multiple times.
4696 4721 */
4697 4722 int callback_cnt = 0;
4698 4723 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
4699 4724 if (!acb->acb_done)
4700 4725 continue;
4701 4726
4702 4727 /* This is a demand read since prefetches don't use callbacks */
4703 4728 callback_cnt++;
4704 4729
4705 4730 int error = arc_buf_alloc_impl(hdr, acb->acb_private,
4706 4731 acb->acb_compressed, no_zio_error, &acb->acb_buf);
4707 4732 if (no_zio_error) {
4708 4733 zio->io_error = error;
4709 4734 }
4710 4735 }
4711 4736 hdr->b_l1hdr.b_acb = NULL;
4712 4737 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
4713 4738 if (callback_cnt == 0) {
4714 4739 ASSERT(HDR_PREFETCH(hdr));
4715 4740 ASSERT0(hdr->b_l1hdr.b_bufcnt);
4716 4741 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
4717 4742 }
4718 4743
4719 4744 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
4720 4745 callback_list != NULL);
4721 4746
4722 4747 if (no_zio_error) {
4723 4748 arc_hdr_verify(hdr, zio->io_bp);
4724 4749 } else {
4725 4750 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
4726 4751 if (hdr->b_l1hdr.b_state != arc_anon)
4727 4752 arc_change_state(arc_anon, hdr, hash_lock);
4728 4753 if (HDR_IN_HASH_TABLE(hdr))
4729 4754 buf_hash_remove(hdr);
4730 4755 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
4731 4756 }
4732 4757
4733 4758 /*
4734 4759 * Broadcast before we drop the hash_lock to avoid the possibility
4735 4760 * that the hdr (and hence the cv) might be freed before we get to
4736 4761 * the cv_broadcast().
4737 4762 */
4738 4763 cv_broadcast(&hdr->b_l1hdr.b_cv);
4739 4764
4740 4765 if (hash_lock != NULL) {
4741 4766 mutex_exit(hash_lock);
4742 4767 } else {
4743 4768 /*
4744 4769 * This block was freed while we waited for the read to
4745 4770 * complete. It has been removed from the hash table and
4746 4771 * moved to the anonymous state (so that it won't show up
4747 4772 * in the cache).
4748 4773 */
4749 4774 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
4750 4775 freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
4751 4776 }
4752 4777
4753 4778 /* execute each callback and free its structure */
4754 4779 while ((acb = callback_list) != NULL) {
4755 4780 if (acb->acb_done)
4756 4781 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
4757 4782
4758 4783 if (acb->acb_zio_dummy != NULL) {
4759 4784 acb->acb_zio_dummy->io_error = zio->io_error;
4760 4785 zio_nowait(acb->acb_zio_dummy);
4761 4786 }
4762 4787
4763 4788 callback_list = acb->acb_next;
4764 4789 kmem_free(acb, sizeof (arc_callback_t));
4765 4790 }
4766 4791
4767 4792 if (freeable)
4768 4793 arc_hdr_destroy(hdr);
4769 4794 }
4770 4795
4771 4796 /*
4772 4797 * "Read" the block at the specified DVA (in bp) via the
4773 4798 * cache. If the block is found in the cache, invoke the provided
4774 4799 * callback immediately and return. Note that the `zio' parameter
4775 4800 * in the callback will be NULL in this case, since no IO was
4776 4801 * required. If the block is not in the cache pass the read request
4777 4802 * on to the spa with a substitute callback function, so that the
4778 4803 * requested block will be added to the cache.
4779 4804 *
4780 4805 * If a read request arrives for a block that has a read in-progress,
4781 4806 * either wait for the in-progress read to complete (and return the
4782 4807 * results); or, if this is a read with a "done" func, add a record
4783 4808 * to the read to invoke the "done" func when the read completes,
4784 4809 * and return; or just return.
4785 4810 *
4786 4811 * arc_read_done() will invoke all the requested "done" functions
4787 4812 * for readers of this block.
4788 4813 */
4789 4814 int
4790 4815 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
4791 4816 void *private, zio_priority_t priority, int zio_flags,
4792 4817 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
4793 4818 {
4794 4819 arc_buf_hdr_t *hdr = NULL;
4795 4820 kmutex_t *hash_lock = NULL;
4796 4821 zio_t *rzio;
4797 4822 uint64_t guid = spa_load_guid(spa);
4798 4823 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
4799 4824
4800 4825 ASSERT(!BP_IS_EMBEDDED(bp) ||
4801 4826 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
4802 4827
4803 4828 top:
4804 4829 if (!BP_IS_EMBEDDED(bp)) {
4805 4830 /*
4806 4831 * Embedded BP's have no DVA and require no I/O to "read".
4807 4832 * Create an anonymous arc buf to back it.
4808 4833 */
4809 4834 hdr = buf_hash_find(guid, bp, &hash_lock);
4810 4835 }
4811 4836
4812 4837 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pabd != NULL) {
4813 4838 arc_buf_t *buf = NULL;
4814 4839 *arc_flags |= ARC_FLAG_CACHED;
4815 4840
4816 4841 if (HDR_IO_IN_PROGRESS(hdr)) {
4817 4842
4818 4843 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
4819 4844 priority == ZIO_PRIORITY_SYNC_READ) {
4820 4845 /*
4821 4846 * This sync read must wait for an
4822 4847 * in-progress async read (e.g. a predictive
4823 4848 * prefetch). Async reads are queued
4824 4849 * separately at the vdev_queue layer, so
4825 4850 * this is a form of priority inversion.
4826 4851 * Ideally, we would "inherit" the demand
4827 4852 * i/o's priority by moving the i/o from
4828 4853 * the async queue to the synchronous queue,
4829 4854 * but there is currently no mechanism to do
4830 4855 * so. Track this so that we can evaluate
4831 4856 * the magnitude of this potential performance
4832 4857 * problem.
4833 4858 *
4834 4859 * Note that if the prefetch i/o is already
4835 4860 * active (has been issued to the device),
4836 4861 * the prefetch improved performance, because
4837 4862 * we issued it sooner than we would have
4838 4863 * without the prefetch.
4839 4864 */
4840 4865 DTRACE_PROBE1(arc__sync__wait__for__async,
4841 4866 arc_buf_hdr_t *, hdr);
4842 4867 ARCSTAT_BUMP(arcstat_sync_wait_for_async);
4843 4868 }
4844 4869 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
4845 4870 arc_hdr_clear_flags(hdr,
4846 4871 ARC_FLAG_PREDICTIVE_PREFETCH);
4847 4872 }
4848 4873
4849 4874 if (*arc_flags & ARC_FLAG_WAIT) {
4850 4875 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
4851 4876 mutex_exit(hash_lock);
4852 4877 goto top;
4853 4878 }
4854 4879 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
4855 4880
4856 4881 if (done) {
4857 4882 arc_callback_t *acb = NULL;
4858 4883
4859 4884 acb = kmem_zalloc(sizeof (arc_callback_t),
4860 4885 KM_SLEEP);
4861 4886 acb->acb_done = done;
4862 4887 acb->acb_private = private;
4863 4888 acb->acb_compressed = compressed_read;
4864 4889 if (pio != NULL)
4865 4890 acb->acb_zio_dummy = zio_null(pio,
4866 4891 spa, NULL, NULL, NULL, zio_flags);
4867 4892
4868 4893 ASSERT3P(acb->acb_done, !=, NULL);
4869 4894 acb->acb_next = hdr->b_l1hdr.b_acb;
4870 4895 hdr->b_l1hdr.b_acb = acb;
4871 4896 mutex_exit(hash_lock);
4872 4897 return (0);
4873 4898 }
4874 4899 mutex_exit(hash_lock);
4875 4900 return (0);
4876 4901 }
4877 4902
4878 4903 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
4879 4904 hdr->b_l1hdr.b_state == arc_mfu);
4880 4905
4881 4906 if (done) {
4882 4907 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
4883 4908 /*
4884 4909 * This is a demand read which does not have to
4885 4910 * wait for i/o because we did a predictive
4886 4911 * prefetch i/o for it, which has completed.
4887 4912 */
4888 4913 DTRACE_PROBE1(
4889 4914 arc__demand__hit__predictive__prefetch,
4890 4915 arc_buf_hdr_t *, hdr);
4891 4916 ARCSTAT_BUMP(
4892 4917 arcstat_demand_hit_predictive_prefetch);
4893 4918 arc_hdr_clear_flags(hdr,
4894 4919 ARC_FLAG_PREDICTIVE_PREFETCH);
4895 4920 }
4896 4921 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
4897 4922
4898 4923 /* Get a buf with the desired data in it. */
4899 4924 VERIFY0(arc_buf_alloc_impl(hdr, private,
4900 4925 compressed_read, B_TRUE, &buf));
4901 4926 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
4902 4927 refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
4903 4928 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
4904 4929 }
4905 4930 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
4906 4931 arc_access(hdr, hash_lock);
4907 4932 if (*arc_flags & ARC_FLAG_L2CACHE)
4908 4933 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
4909 4934 mutex_exit(hash_lock);
4910 4935 ARCSTAT_BUMP(arcstat_hits);
4911 4936 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
4912 4937 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
4913 4938 data, metadata, hits);
4914 4939
4915 4940 if (done)
4916 4941 done(NULL, buf, private);
4917 4942 } else {
4918 4943 uint64_t lsize = BP_GET_LSIZE(bp);
4919 4944 uint64_t psize = BP_GET_PSIZE(bp);
4920 4945 arc_callback_t *acb;
4921 4946 vdev_t *vd = NULL;
4922 4947 uint64_t addr = 0;
4923 4948 boolean_t devw = B_FALSE;
4924 4949 uint64_t size;
4925 4950
4926 4951 if (hdr == NULL) {
4927 4952 /* this block is not in the cache */
4928 4953 arc_buf_hdr_t *exists = NULL;
4929 4954 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
4930 4955 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
4931 4956 BP_GET_COMPRESS(bp), type);
4932 4957
4933 4958 if (!BP_IS_EMBEDDED(bp)) {
4934 4959 hdr->b_dva = *BP_IDENTITY(bp);
4935 4960 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
4936 4961 exists = buf_hash_insert(hdr, &hash_lock);
4937 4962 }
4938 4963 if (exists != NULL) {
4939 4964 /* somebody beat us to the hash insert */
4940 4965 mutex_exit(hash_lock);
4941 4966 buf_discard_identity(hdr);
4942 4967 arc_hdr_destroy(hdr);
4943 4968 goto top; /* restart the IO request */
4944 4969 }
4945 4970 } else {
4946 4971 /*
4947 4972 * This block is in the ghost cache. If it was L2-only
4948 4973 * (and thus didn't have an L1 hdr), we realloc the
4949 4974 * header to add an L1 hdr.
4950 4975 */
4951 4976 if (!HDR_HAS_L1HDR(hdr)) {
4952 4977 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
4953 4978 hdr_full_cache);
4954 4979 }
4955 4980 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
4956 4981 ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
4957 4982 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
4958 4983 ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
4959 4984 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
4960 4985 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
4961 4986
4962 4987 /*
4963 4988 * This is a delicate dance that we play here.
4964 4989 * This hdr is in the ghost list so we access it
4965 4990 * to move it out of the ghost list before we
4966 4991 * initiate the read. If it's a prefetch then
4967 4992 * it won't have a callback so we'll remove the
4968 4993 * reference that arc_buf_alloc_impl() created. We
4969 4994 * do this after we've called arc_access() to
4970 4995 * avoid hitting an assert in remove_reference().
4971 4996 */
4972 4997 arc_access(hdr, hash_lock);
4973 4998 arc_hdr_alloc_pabd(hdr);
4974 4999 }
4975 5000 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
4976 5001 size = arc_hdr_size(hdr);
4977 5002
4978 5003 /*
4979 5004 * If compression is enabled on the hdr, then will do
4980 5005 * RAW I/O and will store the compressed data in the hdr's
4981 5006 * data block. Otherwise, the hdr's data block will contain
4982 5007 * the uncompressed data.
4983 5008 */
4984 5009 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
4985 5010 zio_flags |= ZIO_FLAG_RAW;
4986 5011 }
4987 5012
4988 5013 if (*arc_flags & ARC_FLAG_PREFETCH)
4989 5014 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
4990 5015 if (*arc_flags & ARC_FLAG_L2CACHE)
4991 5016 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
4992 5017 if (BP_GET_LEVEL(bp) > 0)
4993 5018 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
4994 5019 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
4995 5020 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
4996 5021 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
4997 5022
4998 5023 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
4999 5024 acb->acb_done = done;
5000 5025 acb->acb_private = private;
5001 5026 acb->acb_compressed = compressed_read;
5002 5027
5003 5028 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5004 5029 hdr->b_l1hdr.b_acb = acb;
5005 5030 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5006 5031
5007 5032 if (HDR_HAS_L2HDR(hdr) &&
5008 5033 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5009 5034 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5010 5035 addr = hdr->b_l2hdr.b_daddr;
5011 5036 /*
5012 5037 * Lock out L2ARC device removal.
5013 5038 */
5014 5039 if (vdev_is_dead(vd) ||
5015 5040 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5016 5041 vd = NULL;
5017 5042 }
5018 5043
5019 5044 if (priority == ZIO_PRIORITY_ASYNC_READ)
5020 5045 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5021 5046 else
5022 5047 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5023 5048
5024 5049 if (hash_lock != NULL)
5025 5050 mutex_exit(hash_lock);
5026 5051
5027 5052 /*
5028 5053 * At this point, we have a level 1 cache miss. Try again in
5029 5054 * L2ARC if possible.
5030 5055 */
5031 5056 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5032 5057
5033 5058 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5034 5059 uint64_t, lsize, zbookmark_phys_t *, zb);
5035 5060 ARCSTAT_BUMP(arcstat_misses);
5036 5061 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5037 5062 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5038 5063 data, metadata, misses);
5039 5064
5040 5065 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5041 5066 /*
5042 5067 * Read from the L2ARC if the following are true:
5043 5068 * 1. The L2ARC vdev was previously cached.
5044 5069 * 2. This buffer still has L2ARC metadata.
5045 5070 * 3. This buffer isn't currently writing to the L2ARC.
5046 5071 * 4. The L2ARC entry wasn't evicted, which may
5047 5072 * also have invalidated the vdev.
5048 5073 * 5. This isn't prefetch and l2arc_noprefetch is set.
5049 5074 */
5050 5075 if (HDR_HAS_L2HDR(hdr) &&
5051 5076 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5052 5077 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5053 5078 l2arc_read_callback_t *cb;
5054 5079 abd_t *abd;
5055 5080 uint64_t asize;
5056 5081
5057 5082 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5058 5083 ARCSTAT_BUMP(arcstat_l2_hits);
5059 5084
5060 5085 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5061 5086 KM_SLEEP);
5062 5087 cb->l2rcb_hdr = hdr;
5063 5088 cb->l2rcb_bp = *bp;
5064 5089 cb->l2rcb_zb = *zb;
5065 5090 cb->l2rcb_flags = zio_flags;
5066 5091
5067 5092 asize = vdev_psize_to_asize(vd, size);
5068 5093 if (asize != size) {
5069 5094 abd = abd_alloc_for_io(asize,
5070 5095 HDR_ISTYPE_METADATA(hdr));
5071 5096 cb->l2rcb_abd = abd;
5072 5097 } else {
5073 5098 abd = hdr->b_l1hdr.b_pabd;
5074 5099 }
5075 5100
5076 5101 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
5077 5102 addr + asize <= vd->vdev_psize -
5078 5103 VDEV_LABEL_END_SIZE);
5079 5104
5080 5105 /*
5081 5106 * l2arc read. The SCL_L2ARC lock will be
5082 5107 * released by l2arc_read_done().
5083 5108 * Issue a null zio if the underlying buffer
5084 5109 * was squashed to zero size by compression.
5085 5110 */
5086 5111 ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
5087 5112 ZIO_COMPRESS_EMPTY);
5088 5113 rzio = zio_read_phys(pio, vd, addr,
5089 5114 asize, abd,
5090 5115 ZIO_CHECKSUM_OFF,
5091 5116 l2arc_read_done, cb, priority,
5092 5117 zio_flags | ZIO_FLAG_DONT_CACHE |
5093 5118 ZIO_FLAG_CANFAIL |
5094 5119 ZIO_FLAG_DONT_PROPAGATE |
5095 5120 ZIO_FLAG_DONT_RETRY, B_FALSE);
5096 5121 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
5097 5122 zio_t *, rzio);
5098 5123 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
5099 5124
5100 5125 if (*arc_flags & ARC_FLAG_NOWAIT) {
5101 5126 zio_nowait(rzio);
5102 5127 return (0);
5103 5128 }
5104 5129
5105 5130 ASSERT(*arc_flags & ARC_FLAG_WAIT);
5106 5131 if (zio_wait(rzio) == 0)
5107 5132 return (0);
5108 5133
5109 5134 /* l2arc read error; goto zio_read() */
5110 5135 } else {
5111 5136 DTRACE_PROBE1(l2arc__miss,
5112 5137 arc_buf_hdr_t *, hdr);
5113 5138 ARCSTAT_BUMP(arcstat_l2_misses);
5114 5139 if (HDR_L2_WRITING(hdr))
5115 5140 ARCSTAT_BUMP(arcstat_l2_rw_clash);
5116 5141 spa_config_exit(spa, SCL_L2ARC, vd);
5117 5142 }
5118 5143 } else {
5119 5144 if (vd != NULL)
5120 5145 spa_config_exit(spa, SCL_L2ARC, vd);
5121 5146 if (l2arc_ndev != 0) {
5122 5147 DTRACE_PROBE1(l2arc__miss,
5123 5148 arc_buf_hdr_t *, hdr);
5124 5149 ARCSTAT_BUMP(arcstat_l2_misses);
5125 5150 }
5126 5151 }
5127 5152
5128 5153 rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pabd, size,
5129 5154 arc_read_done, hdr, priority, zio_flags, zb);
5130 5155
5131 5156 if (*arc_flags & ARC_FLAG_WAIT)
5132 5157 return (zio_wait(rzio));
5133 5158
5134 5159 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5135 5160 zio_nowait(rzio);
5136 5161 }
5137 5162 return (0);
5138 5163 }
5139 5164
5140 5165 /*
5141 5166 * Notify the arc that a block was freed, and thus will never be used again.
5142 5167 */
5143 5168 void
5144 5169 arc_freed(spa_t *spa, const blkptr_t *bp)
5145 5170 {
5146 5171 arc_buf_hdr_t *hdr;
5147 5172 kmutex_t *hash_lock;
5148 5173 uint64_t guid = spa_load_guid(spa);
5149 5174
5150 5175 ASSERT(!BP_IS_EMBEDDED(bp));
5151 5176
5152 5177 hdr = buf_hash_find(guid, bp, &hash_lock);
5153 5178 if (hdr == NULL)
5154 5179 return;
5155 5180
5156 5181 /*
5157 5182 * We might be trying to free a block that is still doing I/O
5158 5183 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
5159 5184 * dmu_sync-ed block). If this block is being prefetched, then it
5160 5185 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
5161 5186 * until the I/O completes. A block may also have a reference if it is
5162 5187 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
5163 5188 * have written the new block to its final resting place on disk but
5164 5189 * without the dedup flag set. This would have left the hdr in the MRU
5165 5190 * state and discoverable. When the txg finally syncs it detects that
5166 5191 * the block was overridden in open context and issues an override I/O.
5167 5192 * Since this is a dedup block, the override I/O will determine if the
5168 5193 * block is already in the DDT. If so, then it will replace the io_bp
5169 5194 * with the bp from the DDT and allow the I/O to finish. When the I/O
5170 5195 * reaches the done callback, dbuf_write_override_done, it will
5171 5196 * check to see if the io_bp and io_bp_override are identical.
5172 5197 * If they are not, then it indicates that the bp was replaced with
5173 5198 * the bp in the DDT and the override bp is freed. This allows
5174 5199 * us to arrive here with a reference on a block that is being
5175 5200 * freed. So if we have an I/O in progress, or a reference to
5176 5201 * this hdr, then we don't destroy the hdr.
5177 5202 */
5178 5203 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
5179 5204 refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
5180 5205 arc_change_state(arc_anon, hdr, hash_lock);
5181 5206 arc_hdr_destroy(hdr);
5182 5207 mutex_exit(hash_lock);
5183 5208 } else {
5184 5209 mutex_exit(hash_lock);
5185 5210 }
5186 5211
5187 5212 }
5188 5213
5189 5214 /*
5190 5215 * Release this buffer from the cache, making it an anonymous buffer. This
5191 5216 * must be done after a read and prior to modifying the buffer contents.
5192 5217 * If the buffer has more than one reference, we must make
5193 5218 * a new hdr for the buffer.
5194 5219 */
5195 5220 void
5196 5221 arc_release(arc_buf_t *buf, void *tag)
5197 5222 {
5198 5223 arc_buf_hdr_t *hdr = buf->b_hdr;
5199 5224
5200 5225 /*
5201 5226 * It would be nice to assert that if it's DMU metadata (level >
5202 5227 * 0 || it's the dnode file), then it must be syncing context.
5203 5228 * But we don't know that information at this level.
5204 5229 */
5205 5230
5206 5231 mutex_enter(&buf->b_evict_lock);
5207 5232
5208 5233 ASSERT(HDR_HAS_L1HDR(hdr));
5209 5234
5210 5235 /*
5211 5236 * We don't grab the hash lock prior to this check, because if
5212 5237 * the buffer's header is in the arc_anon state, it won't be
5213 5238 * linked into the hash table.
5214 5239 */
5215 5240 if (hdr->b_l1hdr.b_state == arc_anon) {
5216 5241 mutex_exit(&buf->b_evict_lock);
5217 5242 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5218 5243 ASSERT(!HDR_IN_HASH_TABLE(hdr));
5219 5244 ASSERT(!HDR_HAS_L2HDR(hdr));
5220 5245 ASSERT(HDR_EMPTY(hdr));
5221 5246
5222 5247 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5223 5248 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
5224 5249 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
5225 5250
5226 5251 hdr->b_l1hdr.b_arc_access = 0;
5227 5252
5228 5253 /*
5229 5254 * If the buf is being overridden then it may already
5230 5255 * have a hdr that is not empty.
5231 5256 */
5232 5257 buf_discard_identity(hdr);
5233 5258 arc_buf_thaw(buf);
5234 5259
5235 5260 return;
5236 5261 }
5237 5262
5238 5263 kmutex_t *hash_lock = HDR_LOCK(hdr);
5239 5264 mutex_enter(hash_lock);
5240 5265
5241 5266 /*
5242 5267 * This assignment is only valid as long as the hash_lock is
5243 5268 * held, we must be careful not to reference state or the
5244 5269 * b_state field after dropping the lock.
5245 5270 */
5246 5271 arc_state_t *state = hdr->b_l1hdr.b_state;
5247 5272 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
5248 5273 ASSERT3P(state, !=, arc_anon);
5249 5274
5250 5275 /* this buffer is not on any list */
5251 5276 ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
5252 5277
5253 5278 if (HDR_HAS_L2HDR(hdr)) {
5254 5279 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5255 5280
5256 5281 /*
5257 5282 * We have to recheck this conditional again now that
5258 5283 * we're holding the l2ad_mtx to prevent a race with
5259 5284 * another thread which might be concurrently calling
5260 5285 * l2arc_evict(). In that case, l2arc_evict() might have
5261 5286 * destroyed the header's L2 portion as we were waiting
5262 5287 * to acquire the l2ad_mtx.
5263 5288 */
5264 5289 if (HDR_HAS_L2HDR(hdr))
5265 5290 arc_hdr_l2hdr_destroy(hdr);
5266 5291
5267 5292 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
5268 5293 }
5269 5294
5270 5295 /*
5271 5296 * Do we have more than one buf?
5272 5297 */
5273 5298 if (hdr->b_l1hdr.b_bufcnt > 1) {
5274 5299 arc_buf_hdr_t *nhdr;
5275 5300 uint64_t spa = hdr->b_spa;
5276 5301 uint64_t psize = HDR_GET_PSIZE(hdr);
5277 5302 uint64_t lsize = HDR_GET_LSIZE(hdr);
5278 5303 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
5279 5304 arc_buf_contents_t type = arc_buf_type(hdr);
5280 5305 VERIFY3U(hdr->b_type, ==, type);
5281 5306
5282 5307 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
5283 5308 (void) remove_reference(hdr, hash_lock, tag);
5284 5309
5285 5310 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
5286 5311 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
5287 5312 ASSERT(ARC_BUF_LAST(buf));
5288 5313 }
5289 5314
5290 5315 /*
5291 5316 * Pull the data off of this hdr and attach it to
5292 5317 * a new anonymous hdr. Also find the last buffer
5293 5318 * in the hdr's buffer list.
5294 5319 */
5295 5320 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
5296 5321 ASSERT3P(lastbuf, !=, NULL);
5297 5322
5298 5323 /*
5299 5324 * If the current arc_buf_t and the hdr are sharing their data
5300 5325 * buffer, then we must stop sharing that block.
5301 5326 */
5302 5327 if (arc_buf_is_shared(buf)) {
5303 5328 VERIFY(!arc_buf_is_shared(lastbuf));
5304 5329
5305 5330 /*
5306 5331 * First, sever the block sharing relationship between
5307 5332 * buf and the arc_buf_hdr_t.
5308 5333 */
5309 5334 arc_unshare_buf(hdr, buf);
5310 5335
5311 5336 /*
5312 5337 * Now we need to recreate the hdr's b_pabd. Since we
5313 5338 * have lastbuf handy, we try to share with it, but if
5314 5339 * we can't then we allocate a new b_pabd and copy the
5315 5340 * data from buf into it.
5316 5341 */
5317 5342 if (arc_can_share(hdr, lastbuf)) {
5318 5343 arc_share_buf(hdr, lastbuf);
5319 5344 } else {
5320 5345 arc_hdr_alloc_pabd(hdr);
5321 5346 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
5322 5347 buf->b_data, psize);
5323 5348 }
5324 5349 VERIFY3P(lastbuf->b_data, !=, NULL);
5325 5350 } else if (HDR_SHARED_DATA(hdr)) {
5326 5351 /*
5327 5352 * Uncompressed shared buffers are always at the end
5328 5353 * of the list. Compressed buffers don't have the
5329 5354 * same requirements. This makes it hard to
5330 5355 * simply assert that the lastbuf is shared so
5331 5356 * we rely on the hdr's compression flags to determine
5332 5357 * if we have a compressed, shared buffer.
5333 5358 */
5334 5359 ASSERT(arc_buf_is_shared(lastbuf) ||
5335 5360 HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
5336 5361 ASSERT(!ARC_BUF_SHARED(buf));
5337 5362 }
5338 5363 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5339 5364 ASSERT3P(state, !=, arc_l2c_only);
5340 5365
5341 5366 (void) refcount_remove_many(&state->arcs_size,
5342 5367 arc_buf_size(buf), buf);
5343 5368
5344 5369 if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5345 5370 ASSERT3P(state, !=, arc_l2c_only);
5346 5371 (void) refcount_remove_many(&state->arcs_esize[type],
5347 5372 arc_buf_size(buf), buf);
5348 5373 }
5349 5374
5350 5375 hdr->b_l1hdr.b_bufcnt -= 1;
5351 5376 arc_cksum_verify(buf);
5352 5377 arc_buf_unwatch(buf);
5353 5378
5354 5379 mutex_exit(hash_lock);
5355 5380
5356 5381 /*
5357 5382 * Allocate a new hdr. The new hdr will contain a b_pabd
5358 5383 * buffer which will be freed in arc_write().
5359 5384 */
5360 5385 nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
5361 5386 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
5362 5387 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
5363 5388 ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
5364 5389 VERIFY3U(nhdr->b_type, ==, type);
5365 5390 ASSERT(!HDR_SHARED_DATA(nhdr));
5366 5391
5367 5392 nhdr->b_l1hdr.b_buf = buf;
5368 5393 nhdr->b_l1hdr.b_bufcnt = 1;
5369 5394 (void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
5370 5395 buf->b_hdr = nhdr;
5371 5396
5372 5397 mutex_exit(&buf->b_evict_lock);
5373 5398 (void) refcount_add_many(&arc_anon->arcs_size,
5374 5399 arc_buf_size(buf), buf);
5375 5400 } else {
5376 5401 mutex_exit(&buf->b_evict_lock);
5377 5402 ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
5378 5403 /* protected by hash lock, or hdr is on arc_anon */
5379 5404 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
5380 5405 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5381 5406 arc_change_state(arc_anon, hdr, hash_lock);
5382 5407 hdr->b_l1hdr.b_arc_access = 0;
5383 5408 mutex_exit(hash_lock);
5384 5409
5385 5410 buf_discard_identity(hdr);
5386 5411 arc_buf_thaw(buf);
5387 5412 }
5388 5413 }
5389 5414
5390 5415 int
5391 5416 arc_released(arc_buf_t *buf)
5392 5417 {
5393 5418 int released;
5394 5419
5395 5420 mutex_enter(&buf->b_evict_lock);
5396 5421 released = (buf->b_data != NULL &&
5397 5422 buf->b_hdr->b_l1hdr.b_state == arc_anon);
5398 5423 mutex_exit(&buf->b_evict_lock);
5399 5424 return (released);
5400 5425 }
5401 5426
5402 5427 #ifdef ZFS_DEBUG
5403 5428 int
5404 5429 arc_referenced(arc_buf_t *buf)
5405 5430 {
5406 5431 int referenced;
5407 5432
5408 5433 mutex_enter(&buf->b_evict_lock);
5409 5434 referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
5410 5435 mutex_exit(&buf->b_evict_lock);
5411 5436 return (referenced);
5412 5437 }
5413 5438 #endif
5414 5439
5415 5440 static void
5416 5441 arc_write_ready(zio_t *zio)
5417 5442 {
5418 5443 arc_write_callback_t *callback = zio->io_private;
5419 5444 arc_buf_t *buf = callback->awcb_buf;
5420 5445 arc_buf_hdr_t *hdr = buf->b_hdr;
5421 5446 uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
5422 5447
5423 5448 ASSERT(HDR_HAS_L1HDR(hdr));
5424 5449 ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
5425 5450 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
5426 5451
5427 5452 /*
5428 5453 * If we're reexecuting this zio because the pool suspended, then
5429 5454 * cleanup any state that was previously set the first time the
5430 5455 * callback was invoked.
5431 5456 */
5432 5457 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
5433 5458 arc_cksum_free(hdr);
5434 5459 arc_buf_unwatch(buf);
5435 5460 if (hdr->b_l1hdr.b_pabd != NULL) {
5436 5461 if (arc_buf_is_shared(buf)) {
5437 5462 arc_unshare_buf(hdr, buf);
5438 5463 } else {
5439 5464 arc_hdr_free_pabd(hdr);
5440 5465 }
5441 5466 }
5442 5467 }
5443 5468 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5444 5469 ASSERT(!HDR_SHARED_DATA(hdr));
5445 5470 ASSERT(!arc_buf_is_shared(buf));
5446 5471
5447 5472 callback->awcb_ready(zio, buf, callback->awcb_private);
5448 5473
5449 5474 if (HDR_IO_IN_PROGRESS(hdr))
5450 5475 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
5451 5476
5452 5477 arc_cksum_compute(buf);
5453 5478 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5454 5479
5455 5480 enum zio_compress compress;
5456 5481 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5457 5482 compress = ZIO_COMPRESS_OFF;
5458 5483 } else {
5459 5484 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
5460 5485 compress = BP_GET_COMPRESS(zio->io_bp);
5461 5486 }
5462 5487 HDR_SET_PSIZE(hdr, psize);
5463 5488 arc_hdr_set_compress(hdr, compress);
5464 5489
5465 5490
5466 5491 /*
5467 5492 * Fill the hdr with data. If the hdr is compressed, the data we want
5468 5493 * is available from the zio, otherwise we can take it from the buf.
5469 5494 *
5470 5495 * We might be able to share the buf's data with the hdr here. However,
5471 5496 * doing so would cause the ARC to be full of linear ABDs if we write a
5472 5497 * lot of shareable data. As a compromise, we check whether scattered
5473 5498 * ABDs are allowed, and assume that if they are then the user wants
5474 5499 * the ARC to be primarily filled with them regardless of the data being
5475 5500 * written. Therefore, if they're allowed then we allocate one and copy
5476 5501 * the data into it; otherwise, we share the data directly if we can.
5477 5502 */
5478 5503 if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
5479 5504 arc_hdr_alloc_pabd(hdr);
5480 5505
5481 5506 /*
5482 5507 * Ideally, we would always copy the io_abd into b_pabd, but the
5483 5508 * user may have disabled compressed ARC, thus we must check the
5484 5509 * hdr's compression setting rather than the io_bp's.
5485 5510 */
5486 5511 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
5487 5512 ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=,
5488 5513 ZIO_COMPRESS_OFF);
5489 5514 ASSERT3U(psize, >, 0);
5490 5515
5491 5516 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
5492 5517 } else {
5493 5518 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
5494 5519
5495 5520 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
5496 5521 arc_buf_size(buf));
5497 5522 }
5498 5523 } else {
5499 5524 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
5500 5525 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
5501 5526 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
5502 5527
5503 5528 arc_share_buf(hdr, buf);
5504 5529 }
5505 5530
5506 5531 arc_hdr_verify(hdr, zio->io_bp);
5507 5532 }
5508 5533
5509 5534 static void
5510 5535 arc_write_children_ready(zio_t *zio)
5511 5536 {
5512 5537 arc_write_callback_t *callback = zio->io_private;
5513 5538 arc_buf_t *buf = callback->awcb_buf;
5514 5539
5515 5540 callback->awcb_children_ready(zio, buf, callback->awcb_private);
5516 5541 }
5517 5542
5518 5543 /*
5519 5544 * The SPA calls this callback for each physical write that happens on behalf
5520 5545 * of a logical write. See the comment in dbuf_write_physdone() for details.
5521 5546 */
5522 5547 static void
5523 5548 arc_write_physdone(zio_t *zio)
5524 5549 {
5525 5550 arc_write_callback_t *cb = zio->io_private;
5526 5551 if (cb->awcb_physdone != NULL)
5527 5552 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
5528 5553 }
5529 5554
5530 5555 static void
5531 5556 arc_write_done(zio_t *zio)
5532 5557 {
5533 5558 arc_write_callback_t *callback = zio->io_private;
5534 5559 arc_buf_t *buf = callback->awcb_buf;
5535 5560 arc_buf_hdr_t *hdr = buf->b_hdr;
5536 5561
5537 5562 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5538 5563
5539 5564 if (zio->io_error == 0) {
5540 5565 arc_hdr_verify(hdr, zio->io_bp);
5541 5566
5542 5567 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
5543 5568 buf_discard_identity(hdr);
5544 5569 } else {
5545 5570 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
5546 5571 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
5547 5572 }
5548 5573 } else {
5549 5574 ASSERT(HDR_EMPTY(hdr));
5550 5575 }
5551 5576
5552 5577 /*
5553 5578 * If the block to be written was all-zero or compressed enough to be
5554 5579 * embedded in the BP, no write was performed so there will be no
5555 5580 * dva/birth/checksum. The buffer must therefore remain anonymous
5556 5581 * (and uncached).
5557 5582 */
5558 5583 if (!HDR_EMPTY(hdr)) {
5559 5584 arc_buf_hdr_t *exists;
5560 5585 kmutex_t *hash_lock;
5561 5586
5562 5587 ASSERT3U(zio->io_error, ==, 0);
5563 5588
5564 5589 arc_cksum_verify(buf);
5565 5590
5566 5591 exists = buf_hash_insert(hdr, &hash_lock);
5567 5592 if (exists != NULL) {
5568 5593 /*
5569 5594 * This can only happen if we overwrite for
5570 5595 * sync-to-convergence, because we remove
5571 5596 * buffers from the hash table when we arc_free().
5572 5597 */
5573 5598 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
5574 5599 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
5575 5600 panic("bad overwrite, hdr=%p exists=%p",
5576 5601 (void *)hdr, (void *)exists);
5577 5602 ASSERT(refcount_is_zero(
5578 5603 &exists->b_l1hdr.b_refcnt));
5579 5604 arc_change_state(arc_anon, exists, hash_lock);
5580 5605 mutex_exit(hash_lock);
5581 5606 arc_hdr_destroy(exists);
5582 5607 exists = buf_hash_insert(hdr, &hash_lock);
5583 5608 ASSERT3P(exists, ==, NULL);
5584 5609 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
5585 5610 /* nopwrite */
5586 5611 ASSERT(zio->io_prop.zp_nopwrite);
5587 5612 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
5588 5613 panic("bad nopwrite, hdr=%p exists=%p",
5589 5614 (void *)hdr, (void *)exists);
5590 5615 } else {
5591 5616 /* Dedup */
5592 5617 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
5593 5618 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
5594 5619 ASSERT(BP_GET_DEDUP(zio->io_bp));
5595 5620 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
5596 5621 }
5597 5622 }
5598 5623 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5599 5624 /* if it's not anon, we are doing a scrub */
5600 5625 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
5601 5626 arc_access(hdr, hash_lock);
5602 5627 mutex_exit(hash_lock);
5603 5628 } else {
5604 5629 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5605 5630 }
5606 5631
5607 5632 ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5608 5633 callback->awcb_done(zio, buf, callback->awcb_private);
5609 5634
5610 5635 abd_put(zio->io_abd);
5611 5636 kmem_free(callback, sizeof (arc_write_callback_t));
5612 5637 }
5613 5638
5614 5639 zio_t *
5615 5640 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
5616 5641 boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready,
5617 5642 arc_done_func_t *children_ready, arc_done_func_t *physdone,
5618 5643 arc_done_func_t *done, void *private, zio_priority_t priority,
5619 5644 int zio_flags, const zbookmark_phys_t *zb)
5620 5645 {
5621 5646 arc_buf_hdr_t *hdr = buf->b_hdr;
5622 5647 arc_write_callback_t *callback;
5623 5648 zio_t *zio;
5624 5649 zio_prop_t localprop = *zp;
5625 5650
5626 5651 ASSERT3P(ready, !=, NULL);
5627 5652 ASSERT3P(done, !=, NULL);
5628 5653 ASSERT(!HDR_IO_ERROR(hdr));
5629 5654 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5630 5655 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5631 5656 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
5632 5657 if (l2arc)
5633 5658 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5634 5659 if (ARC_BUF_COMPRESSED(buf)) {
5635 5660 /*
5636 5661 * We're writing a pre-compressed buffer. Make the
5637 5662 * compression algorithm requested by the zio_prop_t match
5638 5663 * the pre-compressed buffer's compression algorithm.
5639 5664 */
5640 5665 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
5641 5666
5642 5667 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
5643 5668 zio_flags |= ZIO_FLAG_RAW;
5644 5669 }
5645 5670 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
5646 5671 callback->awcb_ready = ready;
5647 5672 callback->awcb_children_ready = children_ready;
5648 5673 callback->awcb_physdone = physdone;
5649 5674 callback->awcb_done = done;
5650 5675 callback->awcb_private = private;
5651 5676 callback->awcb_buf = buf;
5652 5677
5653 5678 /*
5654 5679 * The hdr's b_pabd is now stale, free it now. A new data block
5655 5680 * will be allocated when the zio pipeline calls arc_write_ready().
5656 5681 */
5657 5682 if (hdr->b_l1hdr.b_pabd != NULL) {
5658 5683 /*
5659 5684 * If the buf is currently sharing the data block with
5660 5685 * the hdr then we need to break that relationship here.
5661 5686 * The hdr will remain with a NULL data pointer and the
5662 5687 * buf will take sole ownership of the block.
5663 5688 */
5664 5689 if (arc_buf_is_shared(buf)) {
5665 5690 arc_unshare_buf(hdr, buf);
5666 5691 } else {
5667 5692 arc_hdr_free_pabd(hdr);
5668 5693 }
5669 5694 VERIFY3P(buf->b_data, !=, NULL);
5670 5695 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
5671 5696 }
5672 5697 ASSERT(!arc_buf_is_shared(buf));
5673 5698 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5674 5699
5675 5700 zio = zio_write(pio, spa, txg, bp,
5676 5701 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
5677 5702 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
5678 5703 (children_ready != NULL) ? arc_write_children_ready : NULL,
5679 5704 arc_write_physdone, arc_write_done, callback,
5680 5705 priority, zio_flags, zb);
5681 5706
5682 5707 return (zio);
5683 5708 }
5684 5709
5685 5710 static int
5686 5711 arc_memory_throttle(uint64_t reserve, uint64_t txg)
5687 5712 {
5688 5713 #ifdef _KERNEL
5689 5714 uint64_t available_memory = ptob(freemem);
5690 5715 static uint64_t page_load = 0;
5691 5716 static uint64_t last_txg = 0;
5692 5717
5693 5718 #if defined(__i386)
5694 5719 available_memory =
5695 5720 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
5696 5721 #endif
5697 5722
5698 5723 if (freemem > physmem * arc_lotsfree_percent / 100)
5699 5724 return (0);
5700 5725
5701 5726 if (txg > last_txg) {
5702 5727 last_txg = txg;
5703 5728 page_load = 0;
5704 5729 }
5705 5730 /*
5706 5731 * If we are in pageout, we know that memory is already tight,
5707 5732 * the arc is already going to be evicting, so we just want to
5708 5733 * continue to let page writes occur as quickly as possible.
5709 5734 */
5710 5735 if (curproc == proc_pageout) {
5711 5736 if (page_load > MAX(ptob(minfree), available_memory) / 4)
5712 5737 return (SET_ERROR(ERESTART));
5713 5738 /* Note: reserve is inflated, so we deflate */
5714 5739 page_load += reserve / 8;
5715 5740 return (0);
5716 5741 } else if (page_load > 0 && arc_reclaim_needed()) {
5717 5742 /* memory is low, delay before restarting */
5718 5743 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
5719 5744 return (SET_ERROR(EAGAIN));
5720 5745 }
5721 5746 page_load = 0;
5722 5747 #endif
5723 5748 return (0);
5724 5749 }
5725 5750
5726 5751 void
5727 5752 arc_tempreserve_clear(uint64_t reserve)
5728 5753 {
5729 5754 atomic_add_64(&arc_tempreserve, -reserve);
5730 5755 ASSERT((int64_t)arc_tempreserve >= 0);
5731 5756 }
5732 5757
5733 5758 int
5734 5759 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
5735 5760 {
5736 5761 int error;
5737 5762 uint64_t anon_size;
5738 5763
5739 5764 if (reserve > arc_c/4 && !arc_no_grow)
5740 5765 arc_c = MIN(arc_c_max, reserve * 4);
5741 5766 if (reserve > arc_c)
5742 5767 return (SET_ERROR(ENOMEM));
5743 5768
5744 5769 /*
5745 5770 * Don't count loaned bufs as in flight dirty data to prevent long
5746 5771 * network delays from blocking transactions that are ready to be
5747 5772 * assigned to a txg.
5748 5773 */
5749 5774
5750 5775 /* assert that it has not wrapped around */
5751 5776 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
5752 5777
5753 5778 anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
5754 5779 arc_loaned_bytes), 0);
5755 5780
5756 5781 /*
5757 5782 * Writes will, almost always, require additional memory allocations
5758 5783 * in order to compress/encrypt/etc the data. We therefore need to
5759 5784 * make sure that there is sufficient available memory for this.
5760 5785 */
5761 5786 error = arc_memory_throttle(reserve, txg);
5762 5787 if (error != 0)
5763 5788 return (error);
5764 5789
5765 5790 /*
5766 5791 * Throttle writes when the amount of dirty data in the cache
5767 5792 * gets too large. We try to keep the cache less than half full
5768 5793 * of dirty blocks so that our sync times don't grow too large.
5769 5794 * Note: if two requests come in concurrently, we might let them
5770 5795 * both succeed, when one of them should fail. Not a huge deal.
5771 5796 */
5772 5797
5773 5798 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
5774 5799 anon_size > arc_c / 4) {
5775 5800 uint64_t meta_esize =
5776 5801 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
5777 5802 uint64_t data_esize =
5778 5803 refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
5779 5804 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
5780 5805 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
5781 5806 arc_tempreserve >> 10, meta_esize >> 10,
5782 5807 data_esize >> 10, reserve >> 10, arc_c >> 10);
5783 5808 return (SET_ERROR(ERESTART));
5784 5809 }
5785 5810 atomic_add_64(&arc_tempreserve, reserve);
5786 5811 return (0);
5787 5812 }
5788 5813
5789 5814 static void
5790 5815 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
5791 5816 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
5792 5817 {
5793 5818 size->value.ui64 = refcount_count(&state->arcs_size);
5794 5819 evict_data->value.ui64 =
5795 5820 refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
5796 5821 evict_metadata->value.ui64 =
5797 5822 refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
5798 5823 }
5799 5824
5800 5825 static int
5801 5826 arc_kstat_update(kstat_t *ksp, int rw)
5802 5827 {
5803 5828 arc_stats_t *as = ksp->ks_data;
5804 5829
5805 5830 if (rw == KSTAT_WRITE) {
5806 5831 return (EACCES);
5807 5832 } else {
5808 5833 arc_kstat_update_state(arc_anon,
5809 5834 &as->arcstat_anon_size,
5810 5835 &as->arcstat_anon_evictable_data,
5811 5836 &as->arcstat_anon_evictable_metadata);
5812 5837 arc_kstat_update_state(arc_mru,
5813 5838 &as->arcstat_mru_size,
5814 5839 &as->arcstat_mru_evictable_data,
5815 5840 &as->arcstat_mru_evictable_metadata);
5816 5841 arc_kstat_update_state(arc_mru_ghost,
5817 5842 &as->arcstat_mru_ghost_size,
5818 5843 &as->arcstat_mru_ghost_evictable_data,
5819 5844 &as->arcstat_mru_ghost_evictable_metadata);
5820 5845 arc_kstat_update_state(arc_mfu,
5821 5846 &as->arcstat_mfu_size,
5822 5847 &as->arcstat_mfu_evictable_data,
5823 5848 &as->arcstat_mfu_evictable_metadata);
5824 5849 arc_kstat_update_state(arc_mfu_ghost,
5825 5850 &as->arcstat_mfu_ghost_size,
5826 5851 &as->arcstat_mfu_ghost_evictable_data,
5827 5852 &as->arcstat_mfu_ghost_evictable_metadata);
5828 5853 }
5829 5854
5830 5855 return (0);
5831 5856 }
5832 5857
5833 5858 /*
5834 5859 * This function *must* return indices evenly distributed between all
5835 5860 * sublists of the multilist. This is needed due to how the ARC eviction
5836 5861 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
5837 5862 * distributed between all sublists and uses this assumption when
5838 5863 * deciding which sublist to evict from and how much to evict from it.
5839 5864 */
5840 5865 unsigned int
5841 5866 arc_state_multilist_index_func(multilist_t *ml, void *obj)
5842 5867 {
5843 5868 arc_buf_hdr_t *hdr = obj;
5844 5869
5845 5870 /*
5846 5871 * We rely on b_dva to generate evenly distributed index
5847 5872 * numbers using buf_hash below. So, as an added precaution,
5848 5873 * let's make sure we never add empty buffers to the arc lists.
5849 5874 */
5850 5875 ASSERT(!HDR_EMPTY(hdr));
5851 5876
5852 5877 /*
5853 5878 * The assumption here, is the hash value for a given
5854 5879 * arc_buf_hdr_t will remain constant throughout it's lifetime
5855 5880 * (i.e. it's b_spa, b_dva, and b_birth fields don't change).
5856 5881 * Thus, we don't need to store the header's sublist index
5857 5882 * on insertion, as this index can be recalculated on removal.
5858 5883 *
5859 5884 * Also, the low order bits of the hash value are thought to be
5860 5885 * distributed evenly. Otherwise, in the case that the multilist
5861 5886 * has a power of two number of sublists, each sublists' usage
5862 5887 * would not be evenly distributed.
5863 5888 */
5864 5889 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
5865 5890 multilist_get_num_sublists(ml));
5866 5891 }
5867 5892
5868 5893 static void
5869 5894 arc_state_init(void)
5870 5895 {
5871 5896 arc_anon = &ARC_anon;
5872 5897 arc_mru = &ARC_mru;
5873 5898 arc_mru_ghost = &ARC_mru_ghost;
5874 5899 arc_mfu = &ARC_mfu;
5875 5900 arc_mfu_ghost = &ARC_mfu_ghost;
5876 5901 arc_l2c_only = &ARC_l2c_only;
5877 5902
5878 5903 arc_mru->arcs_list[ARC_BUFC_METADATA] =
5879 5904 multilist_create(sizeof (arc_buf_hdr_t),
5880 5905 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5881 5906 arc_state_multilist_index_func);
5882 5907 arc_mru->arcs_list[ARC_BUFC_DATA] =
5883 5908 multilist_create(sizeof (arc_buf_hdr_t),
5884 5909 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5885 5910 arc_state_multilist_index_func);
5886 5911 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
5887 5912 multilist_create(sizeof (arc_buf_hdr_t),
5888 5913 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5889 5914 arc_state_multilist_index_func);
5890 5915 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
5891 5916 multilist_create(sizeof (arc_buf_hdr_t),
5892 5917 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5893 5918 arc_state_multilist_index_func);
5894 5919 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
5895 5920 multilist_create(sizeof (arc_buf_hdr_t),
5896 5921 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5897 5922 arc_state_multilist_index_func);
5898 5923 arc_mfu->arcs_list[ARC_BUFC_DATA] =
5899 5924 multilist_create(sizeof (arc_buf_hdr_t),
5900 5925 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5901 5926 arc_state_multilist_index_func);
5902 5927 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
5903 5928 multilist_create(sizeof (arc_buf_hdr_t),
5904 5929 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5905 5930 arc_state_multilist_index_func);
5906 5931 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
5907 5932 multilist_create(sizeof (arc_buf_hdr_t),
5908 5933 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5909 5934 arc_state_multilist_index_func);
5910 5935 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
5911 5936 multilist_create(sizeof (arc_buf_hdr_t),
5912 5937 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5913 5938 arc_state_multilist_index_func);
5914 5939 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
5915 5940 multilist_create(sizeof (arc_buf_hdr_t),
5916 5941 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
5917 5942 arc_state_multilist_index_func);
5918 5943
5919 5944 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
5920 5945 refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
5921 5946 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
5922 5947 refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
5923 5948 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
5924 5949 refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
5925 5950 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
5926 5951 refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
5927 5952 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
5928 5953 refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
5929 5954 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
5930 5955 refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
5931 5956
5932 5957 refcount_create(&arc_anon->arcs_size);
5933 5958 refcount_create(&arc_mru->arcs_size);
5934 5959 refcount_create(&arc_mru_ghost->arcs_size);
5935 5960 refcount_create(&arc_mfu->arcs_size);
5936 5961 refcount_create(&arc_mfu_ghost->arcs_size);
5937 5962 refcount_create(&arc_l2c_only->arcs_size);
5938 5963 }
5939 5964
5940 5965 static void
5941 5966 arc_state_fini(void)
5942 5967 {
5943 5968 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
5944 5969 refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
5945 5970 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
5946 5971 refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
5947 5972 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
5948 5973 refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
5949 5974 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
5950 5975 refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
5951 5976 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
5952 5977 refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
5953 5978 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
5954 5979 refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
5955 5980
5956 5981 refcount_destroy(&arc_anon->arcs_size);
5957 5982 refcount_destroy(&arc_mru->arcs_size);
5958 5983 refcount_destroy(&arc_mru_ghost->arcs_size);
5959 5984 refcount_destroy(&arc_mfu->arcs_size);
5960 5985 refcount_destroy(&arc_mfu_ghost->arcs_size);
5961 5986 refcount_destroy(&arc_l2c_only->arcs_size);
5962 5987
5963 5988 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
5964 5989 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
5965 5990 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
5966 5991 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
5967 5992 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
5968 5993 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
5969 5994 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
5970 5995 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
5971 5996 }
5972 5997
5973 5998 uint64_t
5974 5999 arc_max_bytes(void)
5975 6000 {
5976 6001 return (arc_c_max);
5977 6002 }
5978 6003
5979 6004 void
5980 6005 arc_init(void)
5981 6006 {
5982 6007 /*
5983 6008 * allmem is "all memory that we could possibly use".
5984 6009 */
5985 6010 #ifdef _KERNEL
5986 6011 uint64_t allmem = ptob(physmem - swapfs_minfree);
5987 6012 #else
5988 6013 uint64_t allmem = (physmem * PAGESIZE) / 2;
5989 6014 #endif
5990 6015
5991 6016 mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
5992 6017 cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
5993 6018 cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
5994 6019
5995 6020 /* Convert seconds to clock ticks */
5996 6021 arc_min_prefetch_lifespan = 1 * hz;
5997 6022
5998 6023 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
5999 6024 arc_c_min = MAX(allmem / 32, 64 << 20);
6000 6025 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
6001 6026 if (allmem >= 1 << 30)
6002 6027 arc_c_max = allmem - (1 << 30);
6003 6028 else
6004 6029 arc_c_max = arc_c_min;
6005 6030 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
6006 6031
6007 6032 /*
6008 6033 * In userland, there's only the memory pressure that we artificially
6009 6034 * create (see arc_available_memory()). Don't let arc_c get too
6010 6035 * small, because it can cause transactions to be larger than
6011 6036 * arc_c, causing arc_tempreserve_space() to fail.
6012 6037 */
6013 6038 #ifndef _KERNEL
6014 6039 arc_c_min = arc_c_max / 2;
6015 6040 #endif
6016 6041
6017 6042 /*
6018 6043 * Allow the tunables to override our calculations if they are
6019 6044 * reasonable (ie. over 64MB)
6020 6045 */
6021 6046 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) {
6022 6047 arc_c_max = zfs_arc_max;
6023 6048 arc_c_min = MIN(arc_c_min, arc_c_max);
6024 6049 }
6025 6050 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
6026 6051 arc_c_min = zfs_arc_min;
6027 6052
6028 6053 arc_c = arc_c_max;
6029 6054 arc_p = (arc_c >> 1);
6030 6055 arc_size = 0;
6031 6056
6032 6057 /* limit meta-data to 1/4 of the arc capacity */
6033 6058 arc_meta_limit = arc_c_max / 4;
6034 6059
6035 6060 #ifdef _KERNEL
6036 6061 /*
6037 6062 * Metadata is stored in the kernel's heap. Don't let us
6038 6063 * use more than half the heap for the ARC.
6039 6064 */
6040 6065 arc_meta_limit = MIN(arc_meta_limit,
6041 6066 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
6042 6067 #endif
6043 6068
6044 6069 /* Allow the tunable to override if it is reasonable */
6045 6070 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
6046 6071 arc_meta_limit = zfs_arc_meta_limit;
6047 6072
6048 6073 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
6049 6074 arc_c_min = arc_meta_limit / 2;
6050 6075
6051 6076 if (zfs_arc_meta_min > 0) {
6052 6077 arc_meta_min = zfs_arc_meta_min;
6053 6078 } else {
6054 6079 arc_meta_min = arc_c_min / 2;
6055 6080 }
6056 6081
6057 6082 if (zfs_arc_grow_retry > 0)
6058 6083 arc_grow_retry = zfs_arc_grow_retry;
6059 6084
6060 6085 if (zfs_arc_shrink_shift > 0)
6061 6086 arc_shrink_shift = zfs_arc_shrink_shift;
6062 6087
6063 6088 /*
6064 6089 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
6065 6090 */
6066 6091 if (arc_no_grow_shift >= arc_shrink_shift)
6067 6092 arc_no_grow_shift = arc_shrink_shift - 1;
6068 6093
6069 6094 if (zfs_arc_p_min_shift > 0)
6070 6095 arc_p_min_shift = zfs_arc_p_min_shift;
6071 6096
6072 6097 /* if kmem_flags are set, lets try to use less memory */
6073 6098 if (kmem_debugging())
6074 6099 arc_c = arc_c / 2;
6075 6100 if (arc_c < arc_c_min)
6076 6101 arc_c = arc_c_min;
6077 6102
6078 6103 arc_state_init();
6079 6104 buf_init();
6080 6105
6081 6106 arc_reclaim_thread_exit = B_FALSE;
6082 6107
6083 6108 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
6084 6109 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
6085 6110
6086 6111 if (arc_ksp != NULL) {
6087 6112 arc_ksp->ks_data = &arc_stats;
6088 6113 arc_ksp->ks_update = arc_kstat_update;
6089 6114 kstat_install(arc_ksp);
6090 6115 }
6091 6116
6092 6117 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
6093 6118 TS_RUN, minclsyspri);
6094 6119
6095 6120 arc_dead = B_FALSE;
6096 6121 arc_warm = B_FALSE;
6097 6122
6098 6123 /*
6099 6124 * Calculate maximum amount of dirty data per pool.
6100 6125 *
6101 6126 * If it has been set by /etc/system, take that.
6102 6127 * Otherwise, use a percentage of physical memory defined by
6103 6128 * zfs_dirty_data_max_percent (default 10%) with a cap at
6104 6129 * zfs_dirty_data_max_max (default 4GB).
6105 6130 */
6106 6131 if (zfs_dirty_data_max == 0) {
6107 6132 zfs_dirty_data_max = physmem * PAGESIZE *
6108 6133 zfs_dirty_data_max_percent / 100;
6109 6134 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
6110 6135 zfs_dirty_data_max_max);
6111 6136 }
6112 6137 }
6113 6138
6114 6139 void
6115 6140 arc_fini(void)
6116 6141 {
6117 6142 mutex_enter(&arc_reclaim_lock);
6118 6143 arc_reclaim_thread_exit = B_TRUE;
6119 6144 /*
6120 6145 * The reclaim thread will set arc_reclaim_thread_exit back to
6121 6146 * B_FALSE when it is finished exiting; we're waiting for that.
6122 6147 */
6123 6148 while (arc_reclaim_thread_exit) {
6124 6149 cv_signal(&arc_reclaim_thread_cv);
6125 6150 cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
6126 6151 }
6127 6152 mutex_exit(&arc_reclaim_lock);
6128 6153
6129 6154 /* Use B_TRUE to ensure *all* buffers are evicted */
6130 6155 arc_flush(NULL, B_TRUE);
6131 6156
6132 6157 arc_dead = B_TRUE;
6133 6158
6134 6159 if (arc_ksp != NULL) {
6135 6160 kstat_delete(arc_ksp);
6136 6161 arc_ksp = NULL;
6137 6162 }
6138 6163
6139 6164 mutex_destroy(&arc_reclaim_lock);
6140 6165 cv_destroy(&arc_reclaim_thread_cv);
6141 6166 cv_destroy(&arc_reclaim_waiters_cv);
6142 6167
6143 6168 arc_state_fini();
6144 6169 buf_fini();
6145 6170
6146 6171 ASSERT0(arc_loaned_bytes);
6147 6172 }
6148 6173
6149 6174 /*
6150 6175 * Level 2 ARC
6151 6176 *
6152 6177 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
6153 6178 * It uses dedicated storage devices to hold cached data, which are populated
6154 6179 * using large infrequent writes. The main role of this cache is to boost
6155 6180 * the performance of random read workloads. The intended L2ARC devices
6156 6181 * include short-stroked disks, solid state disks, and other media with
6157 6182 * substantially faster read latency than disk.
6158 6183 *
6159 6184 * +-----------------------+
6160 6185 * | ARC |
6161 6186 * +-----------------------+
6162 6187 * | ^ ^
6163 6188 * | | |
6164 6189 * l2arc_feed_thread() arc_read()
6165 6190 * | | |
6166 6191 * | l2arc read |
6167 6192 * V | |
6168 6193 * +---------------+ |
6169 6194 * | L2ARC | |
6170 6195 * +---------------+ |
6171 6196 * | ^ |
6172 6197 * l2arc_write() | |
6173 6198 * | | |
6174 6199 * V | |
6175 6200 * +-------+ +-------+
6176 6201 * | vdev | | vdev |
6177 6202 * | cache | | cache |
6178 6203 * +-------+ +-------+
6179 6204 * +=========+ .-----.
6180 6205 * : L2ARC : |-_____-|
6181 6206 * : devices : | Disks |
6182 6207 * +=========+ `-_____-'
6183 6208 *
6184 6209 * Read requests are satisfied from the following sources, in order:
6185 6210 *
6186 6211 * 1) ARC
6187 6212 * 2) vdev cache of L2ARC devices
6188 6213 * 3) L2ARC devices
6189 6214 * 4) vdev cache of disks
6190 6215 * 5) disks
6191 6216 *
6192 6217 * Some L2ARC device types exhibit extremely slow write performance.
6193 6218 * To accommodate for this there are some significant differences between
6194 6219 * the L2ARC and traditional cache design:
6195 6220 *
6196 6221 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
6197 6222 * the ARC behave as usual, freeing buffers and placing headers on ghost
6198 6223 * lists. The ARC does not send buffers to the L2ARC during eviction as
6199 6224 * this would add inflated write latencies for all ARC memory pressure.
6200 6225 *
6201 6226 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
6202 6227 * It does this by periodically scanning buffers from the eviction-end of
6203 6228 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
6204 6229 * not already there. It scans until a headroom of buffers is satisfied,
6205 6230 * which itself is a buffer for ARC eviction. If a compressible buffer is
6206 6231 * found during scanning and selected for writing to an L2ARC device, we
6207 6232 * temporarily boost scanning headroom during the next scan cycle to make
6208 6233 * sure we adapt to compression effects (which might significantly reduce
6209 6234 * the data volume we write to L2ARC). The thread that does this is
6210 6235 * l2arc_feed_thread(), illustrated below; example sizes are included to
6211 6236 * provide a better sense of ratio than this diagram:
6212 6237 *
6213 6238 * head --> tail
6214 6239 * +---------------------+----------+
6215 6240 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
6216 6241 * +---------------------+----------+ | o L2ARC eligible
6217 6242 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
6218 6243 * +---------------------+----------+ |
6219 6244 * 15.9 Gbytes ^ 32 Mbytes |
6220 6245 * headroom |
6221 6246 * l2arc_feed_thread()
6222 6247 * |
6223 6248 * l2arc write hand <--[oooo]--'
6224 6249 * | 8 Mbyte
6225 6250 * | write max
6226 6251 * V
6227 6252 * +==============================+
6228 6253 * L2ARC dev |####|#|###|###| |####| ... |
6229 6254 * +==============================+
6230 6255 * 32 Gbytes
6231 6256 *
6232 6257 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
6233 6258 * evicted, then the L2ARC has cached a buffer much sooner than it probably
6234 6259 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
6235 6260 * safe to say that this is an uncommon case, since buffers at the end of
6236 6261 * the ARC lists have moved there due to inactivity.
6237 6262 *
6238 6263 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
6239 6264 * then the L2ARC simply misses copying some buffers. This serves as a
6240 6265 * pressure valve to prevent heavy read workloads from both stalling the ARC
6241 6266 * with waits and clogging the L2ARC with writes. This also helps prevent
6242 6267 * the potential for the L2ARC to churn if it attempts to cache content too
6243 6268 * quickly, such as during backups of the entire pool.
6244 6269 *
6245 6270 * 5. After system boot and before the ARC has filled main memory, there are
6246 6271 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
6247 6272 * lists can remain mostly static. Instead of searching from tail of these
6248 6273 * lists as pictured, the l2arc_feed_thread() will search from the list heads
6249 6274 * for eligible buffers, greatly increasing its chance of finding them.
6250 6275 *
6251 6276 * The L2ARC device write speed is also boosted during this time so that
6252 6277 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
6253 6278 * there are no L2ARC reads, and no fear of degrading read performance
6254 6279 * through increased writes.
6255 6280 *
6256 6281 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
6257 6282 * the vdev queue can aggregate them into larger and fewer writes. Each
6258 6283 * device is written to in a rotor fashion, sweeping writes through
6259 6284 * available space then repeating.
6260 6285 *
6261 6286 * 7. The L2ARC does not store dirty content. It never needs to flush
6262 6287 * write buffers back to disk based storage.
6263 6288 *
6264 6289 * 8. If an ARC buffer is written (and dirtied) which also exists in the
6265 6290 * L2ARC, the now stale L2ARC buffer is immediately dropped.
6266 6291 *
6267 6292 * The performance of the L2ARC can be tweaked by a number of tunables, which
6268 6293 * may be necessary for different workloads:
6269 6294 *
6270 6295 * l2arc_write_max max write bytes per interval
6271 6296 * l2arc_write_boost extra write bytes during device warmup
6272 6297 * l2arc_noprefetch skip caching prefetched buffers
6273 6298 * l2arc_headroom number of max device writes to precache
6274 6299 * l2arc_headroom_boost when we find compressed buffers during ARC
6275 6300 * scanning, we multiply headroom by this
6276 6301 * percentage factor for the next scan cycle,
6277 6302 * since more compressed buffers are likely to
6278 6303 * be present
6279 6304 * l2arc_feed_secs seconds between L2ARC writing
6280 6305 *
6281 6306 * Tunables may be removed or added as future performance improvements are
6282 6307 * integrated, and also may become zpool properties.
6283 6308 *
6284 6309 * There are three key functions that control how the L2ARC warms up:
6285 6310 *
6286 6311 * l2arc_write_eligible() check if a buffer is eligible to cache
6287 6312 * l2arc_write_size() calculate how much to write
6288 6313 * l2arc_write_interval() calculate sleep delay between writes
6289 6314 *
6290 6315 * These three functions determine what to write, how much, and how quickly
6291 6316 * to send writes.
6292 6317 */
6293 6318
6294 6319 static boolean_t
6295 6320 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
6296 6321 {
6297 6322 /*
6298 6323 * A buffer is *not* eligible for the L2ARC if it:
6299 6324 * 1. belongs to a different spa.
6300 6325 * 2. is already cached on the L2ARC.
6301 6326 * 3. has an I/O in progress (it may be an incomplete read).
6302 6327 * 4. is flagged not eligible (zfs property).
6303 6328 */
6304 6329 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
6305 6330 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
6306 6331 return (B_FALSE);
6307 6332
6308 6333 return (B_TRUE);
6309 6334 }
6310 6335
6311 6336 static uint64_t
6312 6337 l2arc_write_size(void)
6313 6338 {
6314 6339 uint64_t size;
6315 6340
6316 6341 /*
6317 6342 * Make sure our globals have meaningful values in case the user
6318 6343 * altered them.
6319 6344 */
6320 6345 size = l2arc_write_max;
6321 6346 if (size == 0) {
6322 6347 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
6323 6348 "be greater than zero, resetting it to the default (%d)",
6324 6349 L2ARC_WRITE_SIZE);
6325 6350 size = l2arc_write_max = L2ARC_WRITE_SIZE;
6326 6351 }
6327 6352
6328 6353 if (arc_warm == B_FALSE)
6329 6354 size += l2arc_write_boost;
6330 6355
6331 6356 return (size);
6332 6357
6333 6358 }
6334 6359
6335 6360 static clock_t
6336 6361 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
6337 6362 {
6338 6363 clock_t interval, next, now;
6339 6364
6340 6365 /*
6341 6366 * If the ARC lists are busy, increase our write rate; if the
6342 6367 * lists are stale, idle back. This is achieved by checking
6343 6368 * how much we previously wrote - if it was more than half of
6344 6369 * what we wanted, schedule the next write much sooner.
6345 6370 */
6346 6371 if (l2arc_feed_again && wrote > (wanted / 2))
6347 6372 interval = (hz * l2arc_feed_min_ms) / 1000;
6348 6373 else
6349 6374 interval = hz * l2arc_feed_secs;
6350 6375
6351 6376 now = ddi_get_lbolt();
6352 6377 next = MAX(now, MIN(now + interval, began + interval));
6353 6378
6354 6379 return (next);
6355 6380 }
6356 6381
6357 6382 /*
6358 6383 * Cycle through L2ARC devices. This is how L2ARC load balances.
6359 6384 * If a device is returned, this also returns holding the spa config lock.
6360 6385 */
6361 6386 static l2arc_dev_t *
6362 6387 l2arc_dev_get_next(void)
6363 6388 {
6364 6389 l2arc_dev_t *first, *next = NULL;
6365 6390
6366 6391 /*
6367 6392 * Lock out the removal of spas (spa_namespace_lock), then removal
6368 6393 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
6369 6394 * both locks will be dropped and a spa config lock held instead.
6370 6395 */
6371 6396 mutex_enter(&spa_namespace_lock);
6372 6397 mutex_enter(&l2arc_dev_mtx);
6373 6398
6374 6399 /* if there are no vdevs, there is nothing to do */
6375 6400 if (l2arc_ndev == 0)
6376 6401 goto out;
6377 6402
6378 6403 first = NULL;
6379 6404 next = l2arc_dev_last;
6380 6405 do {
6381 6406 /* loop around the list looking for a non-faulted vdev */
6382 6407 if (next == NULL) {
6383 6408 next = list_head(l2arc_dev_list);
6384 6409 } else {
6385 6410 next = list_next(l2arc_dev_list, next);
6386 6411 if (next == NULL)
6387 6412 next = list_head(l2arc_dev_list);
6388 6413 }
6389 6414
6390 6415 /* if we have come back to the start, bail out */
6391 6416 if (first == NULL)
6392 6417 first = next;
6393 6418 else if (next == first)
6394 6419 break;
6395 6420
6396 6421 } while (vdev_is_dead(next->l2ad_vdev));
6397 6422
6398 6423 /* if we were unable to find any usable vdevs, return NULL */
6399 6424 if (vdev_is_dead(next->l2ad_vdev))
6400 6425 next = NULL;
6401 6426
6402 6427 l2arc_dev_last = next;
6403 6428
6404 6429 out:
6405 6430 mutex_exit(&l2arc_dev_mtx);
6406 6431
6407 6432 /*
6408 6433 * Grab the config lock to prevent the 'next' device from being
6409 6434 * removed while we are writing to it.
6410 6435 */
6411 6436 if (next != NULL)
6412 6437 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
6413 6438 mutex_exit(&spa_namespace_lock);
6414 6439
6415 6440 return (next);
6416 6441 }
6417 6442
6418 6443 /*
6419 6444 * Free buffers that were tagged for destruction.
6420 6445 */
6421 6446 static void
6422 6447 l2arc_do_free_on_write()
6423 6448 {
6424 6449 list_t *buflist;
6425 6450 l2arc_data_free_t *df, *df_prev;
6426 6451
6427 6452 mutex_enter(&l2arc_free_on_write_mtx);
6428 6453 buflist = l2arc_free_on_write;
6429 6454
6430 6455 for (df = list_tail(buflist); df; df = df_prev) {
6431 6456 df_prev = list_prev(buflist, df);
6432 6457 ASSERT3P(df->l2df_abd, !=, NULL);
6433 6458 abd_free(df->l2df_abd);
6434 6459 list_remove(buflist, df);
6435 6460 kmem_free(df, sizeof (l2arc_data_free_t));
6436 6461 }
6437 6462
6438 6463 mutex_exit(&l2arc_free_on_write_mtx);
6439 6464 }
6440 6465
6441 6466 /*
6442 6467 * A write to a cache device has completed. Update all headers to allow
6443 6468 * reads from these buffers to begin.
6444 6469 */
6445 6470 static void
6446 6471 l2arc_write_done(zio_t *zio)
6447 6472 {
6448 6473 l2arc_write_callback_t *cb;
6449 6474 l2arc_dev_t *dev;
6450 6475 list_t *buflist;
6451 6476 arc_buf_hdr_t *head, *hdr, *hdr_prev;
6452 6477 kmutex_t *hash_lock;
6453 6478 int64_t bytes_dropped = 0;
6454 6479
6455 6480 cb = zio->io_private;
6456 6481 ASSERT3P(cb, !=, NULL);
6457 6482 dev = cb->l2wcb_dev;
6458 6483 ASSERT3P(dev, !=, NULL);
6459 6484 head = cb->l2wcb_head;
6460 6485 ASSERT3P(head, !=, NULL);
6461 6486 buflist = &dev->l2ad_buflist;
6462 6487 ASSERT3P(buflist, !=, NULL);
6463 6488 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
6464 6489 l2arc_write_callback_t *, cb);
6465 6490
6466 6491 if (zio->io_error != 0)
6467 6492 ARCSTAT_BUMP(arcstat_l2_writes_error);
6468 6493
6469 6494 /*
6470 6495 * All writes completed, or an error was hit.
6471 6496 */
6472 6497 top:
6473 6498 mutex_enter(&dev->l2ad_mtx);
6474 6499 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
6475 6500 hdr_prev = list_prev(buflist, hdr);
6476 6501
6477 6502 hash_lock = HDR_LOCK(hdr);
6478 6503
6479 6504 /*
6480 6505 * We cannot use mutex_enter or else we can deadlock
6481 6506 * with l2arc_write_buffers (due to swapping the order
6482 6507 * the hash lock and l2ad_mtx are taken).
6483 6508 */
6484 6509 if (!mutex_tryenter(hash_lock)) {
6485 6510 /*
6486 6511 * Missed the hash lock. We must retry so we
6487 6512 * don't leave the ARC_FLAG_L2_WRITING bit set.
6488 6513 */
6489 6514 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
6490 6515
6491 6516 /*
6492 6517 * We don't want to rescan the headers we've
6493 6518 * already marked as having been written out, so
6494 6519 * we reinsert the head node so we can pick up
6495 6520 * where we left off.
6496 6521 */
6497 6522 list_remove(buflist, head);
6498 6523 list_insert_after(buflist, hdr, head);
6499 6524
6500 6525 mutex_exit(&dev->l2ad_mtx);
6501 6526
6502 6527 /*
6503 6528 * We wait for the hash lock to become available
6504 6529 * to try and prevent busy waiting, and increase
6505 6530 * the chance we'll be able to acquire the lock
6506 6531 * the next time around.
6507 6532 */
6508 6533 mutex_enter(hash_lock);
6509 6534 mutex_exit(hash_lock);
6510 6535 goto top;
6511 6536 }
6512 6537
6513 6538 /*
6514 6539 * We could not have been moved into the arc_l2c_only
6515 6540 * state while in-flight due to our ARC_FLAG_L2_WRITING
6516 6541 * bit being set. Let's just ensure that's being enforced.
6517 6542 */
6518 6543 ASSERT(HDR_HAS_L1HDR(hdr));
6519 6544
6520 6545 if (zio->io_error != 0) {
6521 6546 /*
6522 6547 * Error - drop L2ARC entry.
6523 6548 */
6524 6549 list_remove(buflist, hdr);
6525 6550 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
6526 6551
6527 6552 ARCSTAT_INCR(arcstat_l2_psize, -arc_hdr_size(hdr));
6528 6553 ARCSTAT_INCR(arcstat_l2_lsize, -HDR_GET_LSIZE(hdr));
6529 6554
6530 6555 bytes_dropped += arc_hdr_size(hdr);
6531 6556 (void) refcount_remove_many(&dev->l2ad_alloc,
6532 6557 arc_hdr_size(hdr), hdr);
6533 6558 }
6534 6559
6535 6560 /*
6536 6561 * Allow ARC to begin reads and ghost list evictions to
6537 6562 * this L2ARC entry.
6538 6563 */
6539 6564 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
6540 6565
6541 6566 mutex_exit(hash_lock);
6542 6567 }
6543 6568
6544 6569 atomic_inc_64(&l2arc_writes_done);
6545 6570 list_remove(buflist, head);
6546 6571 ASSERT(!HDR_HAS_L1HDR(head));
6547 6572 kmem_cache_free(hdr_l2only_cache, head);
6548 6573 mutex_exit(&dev->l2ad_mtx);
6549 6574
6550 6575 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
6551 6576
6552 6577 l2arc_do_free_on_write();
6553 6578
6554 6579 kmem_free(cb, sizeof (l2arc_write_callback_t));
6555 6580 }
6556 6581
6557 6582 /*
6558 6583 * A read to a cache device completed. Validate buffer contents before
6559 6584 * handing over to the regular ARC routines.
6560 6585 */
6561 6586 static void
6562 6587 l2arc_read_done(zio_t *zio)
6563 6588 {
6564 6589 l2arc_read_callback_t *cb;
6565 6590 arc_buf_hdr_t *hdr;
6566 6591 kmutex_t *hash_lock;
6567 6592 boolean_t valid_cksum;
6568 6593
6569 6594 ASSERT3P(zio->io_vd, !=, NULL);
6570 6595 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
6571 6596
6572 6597 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
6573 6598
6574 6599 cb = zio->io_private;
6575 6600 ASSERT3P(cb, !=, NULL);
6576 6601 hdr = cb->l2rcb_hdr;
6577 6602 ASSERT3P(hdr, !=, NULL);
6578 6603
6579 6604 hash_lock = HDR_LOCK(hdr);
6580 6605 mutex_enter(hash_lock);
6581 6606 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
6582 6607
6583 6608 /*
6584 6609 * If the data was read into a temporary buffer,
6585 6610 * move it and free the buffer.
6586 6611 */
6587 6612 if (cb->l2rcb_abd != NULL) {
6588 6613 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
6589 6614 if (zio->io_error == 0) {
6590 6615 abd_copy(hdr->b_l1hdr.b_pabd, cb->l2rcb_abd,
6591 6616 arc_hdr_size(hdr));
6592 6617 }
6593 6618
6594 6619 /*
6595 6620 * The following must be done regardless of whether
6596 6621 * there was an error:
6597 6622 * - free the temporary buffer
6598 6623 * - point zio to the real ARC buffer
6599 6624 * - set zio size accordingly
6600 6625 * These are required because zio is either re-used for
6601 6626 * an I/O of the block in the case of the error
6602 6627 * or the zio is passed to arc_read_done() and it
6603 6628 * needs real data.
6604 6629 */
6605 6630 abd_free(cb->l2rcb_abd);
6606 6631 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
6607 6632 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
6608 6633 }
6609 6634
6610 6635 ASSERT3P(zio->io_abd, !=, NULL);
6611 6636
6612 6637 /*
6613 6638 * Check this survived the L2ARC journey.
6614 6639 */
6615 6640 ASSERT3P(zio->io_abd, ==, hdr->b_l1hdr.b_pabd);
6616 6641 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
6617 6642 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
6618 6643
6619 6644 valid_cksum = arc_cksum_is_equal(hdr, zio);
6620 6645 if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
6621 6646 mutex_exit(hash_lock);
6622 6647 zio->io_private = hdr;
6623 6648 arc_read_done(zio);
6624 6649 } else {
6625 6650 mutex_exit(hash_lock);
6626 6651 /*
6627 6652 * Buffer didn't survive caching. Increment stats and
6628 6653 * reissue to the original storage device.
6629 6654 */
6630 6655 if (zio->io_error != 0) {
6631 6656 ARCSTAT_BUMP(arcstat_l2_io_error);
6632 6657 } else {
6633 6658 zio->io_error = SET_ERROR(EIO);
6634 6659 }
6635 6660 if (!valid_cksum)
6636 6661 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
6637 6662
6638 6663 /*
6639 6664 * If there's no waiter, issue an async i/o to the primary
6640 6665 * storage now. If there *is* a waiter, the caller must
6641 6666 * issue the i/o in a context where it's OK to block.
6642 6667 */
6643 6668 if (zio->io_waiter == NULL) {
6644 6669 zio_t *pio = zio_unique_parent(zio);
6645 6670
6646 6671 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
6647 6672
6648 6673 zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
6649 6674 hdr->b_l1hdr.b_pabd, zio->io_size, arc_read_done,
6650 6675 hdr, zio->io_priority, cb->l2rcb_flags,
6651 6676 &cb->l2rcb_zb));
6652 6677 }
6653 6678 }
6654 6679
6655 6680 kmem_free(cb, sizeof (l2arc_read_callback_t));
6656 6681 }
6657 6682
6658 6683 /*
6659 6684 * This is the list priority from which the L2ARC will search for pages to
6660 6685 * cache. This is used within loops (0..3) to cycle through lists in the
6661 6686 * desired order. This order can have a significant effect on cache
6662 6687 * performance.
6663 6688 *
6664 6689 * Currently the metadata lists are hit first, MFU then MRU, followed by
6665 6690 * the data lists. This function returns a locked list, and also returns
6666 6691 * the lock pointer.
6667 6692 */
6668 6693 static multilist_sublist_t *
6669 6694 l2arc_sublist_lock(int list_num)
6670 6695 {
6671 6696 multilist_t *ml = NULL;
6672 6697 unsigned int idx;
6673 6698
6674 6699 ASSERT(list_num >= 0 && list_num <= 3);
6675 6700
6676 6701 switch (list_num) {
6677 6702 case 0:
6678 6703 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
6679 6704 break;
6680 6705 case 1:
6681 6706 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
6682 6707 break;
6683 6708 case 2:
6684 6709 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
6685 6710 break;
6686 6711 case 3:
6687 6712 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
6688 6713 break;
6689 6714 }
6690 6715
6691 6716 /*
6692 6717 * Return a randomly-selected sublist. This is acceptable
6693 6718 * because the caller feeds only a little bit of data for each
6694 6719 * call (8MB). Subsequent calls will result in different
6695 6720 * sublists being selected.
6696 6721 */
6697 6722 idx = multilist_get_random_index(ml);
6698 6723 return (multilist_sublist_lock(ml, idx));
6699 6724 }
6700 6725
6701 6726 /*
6702 6727 * Evict buffers from the device write hand to the distance specified in
6703 6728 * bytes. This distance may span populated buffers, it may span nothing.
6704 6729 * This is clearing a region on the L2ARC device ready for writing.
6705 6730 * If the 'all' boolean is set, every buffer is evicted.
6706 6731 */
6707 6732 static void
6708 6733 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
6709 6734 {
6710 6735 list_t *buflist;
6711 6736 arc_buf_hdr_t *hdr, *hdr_prev;
6712 6737 kmutex_t *hash_lock;
6713 6738 uint64_t taddr;
6714 6739
6715 6740 buflist = &dev->l2ad_buflist;
6716 6741
6717 6742 if (!all && dev->l2ad_first) {
6718 6743 /*
6719 6744 * This is the first sweep through the device. There is
6720 6745 * nothing to evict.
6721 6746 */
6722 6747 return;
6723 6748 }
6724 6749
6725 6750 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
6726 6751 /*
6727 6752 * When nearing the end of the device, evict to the end
6728 6753 * before the device write hand jumps to the start.
6729 6754 */
6730 6755 taddr = dev->l2ad_end;
6731 6756 } else {
6732 6757 taddr = dev->l2ad_hand + distance;
6733 6758 }
6734 6759 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
6735 6760 uint64_t, taddr, boolean_t, all);
6736 6761
6737 6762 top:
6738 6763 mutex_enter(&dev->l2ad_mtx);
6739 6764 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
6740 6765 hdr_prev = list_prev(buflist, hdr);
6741 6766
6742 6767 hash_lock = HDR_LOCK(hdr);
6743 6768
6744 6769 /*
6745 6770 * We cannot use mutex_enter or else we can deadlock
6746 6771 * with l2arc_write_buffers (due to swapping the order
6747 6772 * the hash lock and l2ad_mtx are taken).
6748 6773 */
6749 6774 if (!mutex_tryenter(hash_lock)) {
6750 6775 /*
6751 6776 * Missed the hash lock. Retry.
6752 6777 */
6753 6778 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
6754 6779 mutex_exit(&dev->l2ad_mtx);
6755 6780 mutex_enter(hash_lock);
6756 6781 mutex_exit(hash_lock);
6757 6782 goto top;
6758 6783 }
6759 6784
6760 6785 /*
6761 6786 * A header can't be on this list if it doesn't have L2 header.
6762 6787 */
6763 6788 ASSERT(HDR_HAS_L2HDR(hdr));
6764 6789
6765 6790 /* Ensure this header has finished being written. */
6766 6791 ASSERT(!HDR_L2_WRITING(hdr));
6767 6792 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
6768 6793
6769 6794 if (!all && (hdr->b_l2hdr.b_daddr >= taddr ||
6770 6795 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
6771 6796 /*
6772 6797 * We've evicted to the target address,
6773 6798 * or the end of the device.
6774 6799 */
6775 6800 mutex_exit(hash_lock);
6776 6801 break;
6777 6802 }
6778 6803
6779 6804 if (!HDR_HAS_L1HDR(hdr)) {
6780 6805 ASSERT(!HDR_L2_READING(hdr));
6781 6806 /*
6782 6807 * This doesn't exist in the ARC. Destroy.
6783 6808 * arc_hdr_destroy() will call list_remove()
6784 6809 * and decrement arcstat_l2_lsize.
6785 6810 */
6786 6811 arc_change_state(arc_anon, hdr, hash_lock);
6787 6812 arc_hdr_destroy(hdr);
6788 6813 } else {
6789 6814 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
6790 6815 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
6791 6816 /*
6792 6817 * Invalidate issued or about to be issued
6793 6818 * reads, since we may be about to write
6794 6819 * over this location.
6795 6820 */
6796 6821 if (HDR_L2_READING(hdr)) {
6797 6822 ARCSTAT_BUMP(arcstat_l2_evict_reading);
6798 6823 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
6799 6824 }
6800 6825
6801 6826 arc_hdr_l2hdr_destroy(hdr);
6802 6827 }
6803 6828 mutex_exit(hash_lock);
6804 6829 }
6805 6830 mutex_exit(&dev->l2ad_mtx);
6806 6831 }
6807 6832
6808 6833 /*
6809 6834 * Find and write ARC buffers to the L2ARC device.
6810 6835 *
6811 6836 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
6812 6837 * for reading until they have completed writing.
6813 6838 * The headroom_boost is an in-out parameter used to maintain headroom boost
6814 6839 * state between calls to this function.
6815 6840 *
6816 6841 * Returns the number of bytes actually written (which may be smaller than
6817 6842 * the delta by which the device hand has changed due to alignment).
6818 6843 */
6819 6844 static uint64_t
6820 6845 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
6821 6846 {
6822 6847 arc_buf_hdr_t *hdr, *hdr_prev, *head;
6823 6848 uint64_t write_asize, write_psize, write_lsize, headroom;
6824 6849 boolean_t full;
6825 6850 l2arc_write_callback_t *cb;
6826 6851 zio_t *pio, *wzio;
6827 6852 uint64_t guid = spa_load_guid(spa);
6828 6853
6829 6854 ASSERT3P(dev->l2ad_vdev, !=, NULL);
6830 6855
6831 6856 pio = NULL;
6832 6857 write_lsize = write_asize = write_psize = 0;
6833 6858 full = B_FALSE;
6834 6859 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
6835 6860 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
6836 6861
6837 6862 /*
6838 6863 * Copy buffers for L2ARC writing.
6839 6864 */
6840 6865 for (int try = 0; try <= 3; try++) {
6841 6866 multilist_sublist_t *mls = l2arc_sublist_lock(try);
6842 6867 uint64_t passed_sz = 0;
6843 6868
6844 6869 /*
6845 6870 * L2ARC fast warmup.
6846 6871 *
6847 6872 * Until the ARC is warm and starts to evict, read from the
6848 6873 * head of the ARC lists rather than the tail.
6849 6874 */
6850 6875 if (arc_warm == B_FALSE)
6851 6876 hdr = multilist_sublist_head(mls);
6852 6877 else
6853 6878 hdr = multilist_sublist_tail(mls);
6854 6879
6855 6880 headroom = target_sz * l2arc_headroom;
6856 6881 if (zfs_compressed_arc_enabled)
6857 6882 headroom = (headroom * l2arc_headroom_boost) / 100;
6858 6883
6859 6884 for (; hdr; hdr = hdr_prev) {
6860 6885 kmutex_t *hash_lock;
6861 6886
6862 6887 if (arc_warm == B_FALSE)
6863 6888 hdr_prev = multilist_sublist_next(mls, hdr);
6864 6889 else
6865 6890 hdr_prev = multilist_sublist_prev(mls, hdr);
6866 6891
6867 6892 hash_lock = HDR_LOCK(hdr);
6868 6893 if (!mutex_tryenter(hash_lock)) {
6869 6894 /*
6870 6895 * Skip this buffer rather than waiting.
6871 6896 */
6872 6897 continue;
6873 6898 }
6874 6899
6875 6900 passed_sz += HDR_GET_LSIZE(hdr);
6876 6901 if (passed_sz > headroom) {
6877 6902 /*
6878 6903 * Searched too far.
6879 6904 */
6880 6905 mutex_exit(hash_lock);
6881 6906 break;
6882 6907 }
6883 6908
6884 6909 if (!l2arc_write_eligible(guid, hdr)) {
6885 6910 mutex_exit(hash_lock);
6886 6911 continue;
6887 6912 }
6888 6913
6889 6914 /*
6890 6915 * We rely on the L1 portion of the header below, so
6891 6916 * it's invalid for this header to have been evicted out
6892 6917 * of the ghost cache, prior to being written out. The
6893 6918 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
6894 6919 */
6895 6920 ASSERT(HDR_HAS_L1HDR(hdr));
6896 6921
6897 6922 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
6898 6923 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
6899 6924 ASSERT3U(arc_hdr_size(hdr), >, 0);
6900 6925 uint64_t psize = arc_hdr_size(hdr);
6901 6926 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
6902 6927 psize);
6903 6928
6904 6929 if ((write_asize + asize) > target_sz) {
6905 6930 full = B_TRUE;
6906 6931 mutex_exit(hash_lock);
6907 6932 break;
6908 6933 }
6909 6934
6910 6935 if (pio == NULL) {
6911 6936 /*
6912 6937 * Insert a dummy header on the buflist so
6913 6938 * l2arc_write_done() can find where the
6914 6939 * write buffers begin without searching.
6915 6940 */
6916 6941 mutex_enter(&dev->l2ad_mtx);
6917 6942 list_insert_head(&dev->l2ad_buflist, head);
6918 6943 mutex_exit(&dev->l2ad_mtx);
6919 6944
6920 6945 cb = kmem_alloc(
6921 6946 sizeof (l2arc_write_callback_t), KM_SLEEP);
6922 6947 cb->l2wcb_dev = dev;
6923 6948 cb->l2wcb_head = head;
6924 6949 pio = zio_root(spa, l2arc_write_done, cb,
6925 6950 ZIO_FLAG_CANFAIL);
6926 6951 }
6927 6952
6928 6953 hdr->b_l2hdr.b_dev = dev;
6929 6954 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
6930 6955 arc_hdr_set_flags(hdr,
6931 6956 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
6932 6957
6933 6958 mutex_enter(&dev->l2ad_mtx);
6934 6959 list_insert_head(&dev->l2ad_buflist, hdr);
6935 6960 mutex_exit(&dev->l2ad_mtx);
6936 6961
6937 6962 (void) refcount_add_many(&dev->l2ad_alloc, psize, hdr);
6938 6963
6939 6964 /*
6940 6965 * Normally the L2ARC can use the hdr's data, but if
6941 6966 * we're sharing data between the hdr and one of its
6942 6967 * bufs, L2ARC needs its own copy of the data so that
6943 6968 * the ZIO below can't race with the buf consumer.
6944 6969 * Another case where we need to create a copy of the
6945 6970 * data is when the buffer size is not device-aligned
6946 6971 * and we need to pad the block to make it such.
6947 6972 * That also keeps the clock hand suitably aligned.
6948 6973 *
6949 6974 * To ensure that the copy will be available for the
6950 6975 * lifetime of the ZIO and be cleaned up afterwards, we
6951 6976 * add it to the l2arc_free_on_write queue.
6952 6977 */
6953 6978 abd_t *to_write;
6954 6979 if (!HDR_SHARED_DATA(hdr) && psize == asize) {
6955 6980 to_write = hdr->b_l1hdr.b_pabd;
6956 6981 } else {
6957 6982 to_write = abd_alloc_for_io(asize,
6958 6983 HDR_ISTYPE_METADATA(hdr));
6959 6984 abd_copy(to_write, hdr->b_l1hdr.b_pabd, psize);
6960 6985 if (asize != psize) {
6961 6986 abd_zero_off(to_write, psize,
6962 6987 asize - psize);
6963 6988 }
6964 6989 l2arc_free_abd_on_write(to_write, asize,
6965 6990 arc_buf_type(hdr));
6966 6991 }
6967 6992 wzio = zio_write_phys(pio, dev->l2ad_vdev,
6968 6993 hdr->b_l2hdr.b_daddr, asize, to_write,
6969 6994 ZIO_CHECKSUM_OFF, NULL, hdr,
6970 6995 ZIO_PRIORITY_ASYNC_WRITE,
6971 6996 ZIO_FLAG_CANFAIL, B_FALSE);
6972 6997
6973 6998 write_lsize += HDR_GET_LSIZE(hdr);
6974 6999 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
6975 7000 zio_t *, wzio);
6976 7001
6977 7002 write_psize += psize;
6978 7003 write_asize += asize;
6979 7004 dev->l2ad_hand += asize;
6980 7005
6981 7006 mutex_exit(hash_lock);
6982 7007
6983 7008 (void) zio_nowait(wzio);
6984 7009 }
6985 7010
6986 7011 multilist_sublist_unlock(mls);
6987 7012
6988 7013 if (full == B_TRUE)
6989 7014 break;
6990 7015 }
6991 7016
6992 7017 /* No buffers selected for writing? */
6993 7018 if (pio == NULL) {
6994 7019 ASSERT0(write_lsize);
6995 7020 ASSERT(!HDR_HAS_L1HDR(head));
6996 7021 kmem_cache_free(hdr_l2only_cache, head);
6997 7022 return (0);
6998 7023 }
6999 7024
7000 7025 ASSERT3U(write_asize, <=, target_sz);
7001 7026 ARCSTAT_BUMP(arcstat_l2_writes_sent);
7002 7027 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
7003 7028 ARCSTAT_INCR(arcstat_l2_lsize, write_lsize);
7004 7029 ARCSTAT_INCR(arcstat_l2_psize, write_psize);
7005 7030 vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
7006 7031
7007 7032 /*
7008 7033 * Bump device hand to the device start if it is approaching the end.
7009 7034 * l2arc_evict() will already have evicted ahead for this case.
7010 7035 */
7011 7036 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
7012 7037 dev->l2ad_hand = dev->l2ad_start;
7013 7038 dev->l2ad_first = B_FALSE;
7014 7039 }
7015 7040
7016 7041 dev->l2ad_writing = B_TRUE;
7017 7042 (void) zio_wait(pio);
7018 7043 dev->l2ad_writing = B_FALSE;
7019 7044
7020 7045 return (write_asize);
7021 7046 }
7022 7047
7023 7048 /*
7024 7049 * This thread feeds the L2ARC at regular intervals. This is the beating
7025 7050 * heart of the L2ARC.
7026 7051 */
7027 7052 /* ARGSUSED */
7028 7053 static void
7029 7054 l2arc_feed_thread(void *unused)
7030 7055 {
7031 7056 callb_cpr_t cpr;
7032 7057 l2arc_dev_t *dev;
7033 7058 spa_t *spa;
7034 7059 uint64_t size, wrote;
7035 7060 clock_t begin, next = ddi_get_lbolt();
7036 7061
7037 7062 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
7038 7063
7039 7064 mutex_enter(&l2arc_feed_thr_lock);
7040 7065
7041 7066 while (l2arc_thread_exit == 0) {
7042 7067 CALLB_CPR_SAFE_BEGIN(&cpr);
7043 7068 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
7044 7069 next);
7045 7070 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
7046 7071 next = ddi_get_lbolt() + hz;
7047 7072
7048 7073 /*
7049 7074 * Quick check for L2ARC devices.
7050 7075 */
7051 7076 mutex_enter(&l2arc_dev_mtx);
7052 7077 if (l2arc_ndev == 0) {
7053 7078 mutex_exit(&l2arc_dev_mtx);
7054 7079 continue;
7055 7080 }
7056 7081 mutex_exit(&l2arc_dev_mtx);
7057 7082 begin = ddi_get_lbolt();
7058 7083
7059 7084 /*
7060 7085 * This selects the next l2arc device to write to, and in
7061 7086 * doing so the next spa to feed from: dev->l2ad_spa. This
7062 7087 * will return NULL if there are now no l2arc devices or if
7063 7088 * they are all faulted.
7064 7089 *
7065 7090 * If a device is returned, its spa's config lock is also
7066 7091 * held to prevent device removal. l2arc_dev_get_next()
7067 7092 * will grab and release l2arc_dev_mtx.
7068 7093 */
7069 7094 if ((dev = l2arc_dev_get_next()) == NULL)
7070 7095 continue;
7071 7096
7072 7097 spa = dev->l2ad_spa;
7073 7098 ASSERT3P(spa, !=, NULL);
7074 7099
7075 7100 /*
7076 7101 * If the pool is read-only then force the feed thread to
7077 7102 * sleep a little longer.
7078 7103 */
7079 7104 if (!spa_writeable(spa)) {
7080 7105 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
7081 7106 spa_config_exit(spa, SCL_L2ARC, dev);
7082 7107 continue;
7083 7108 }
7084 7109
7085 7110 /*
7086 7111 * Avoid contributing to memory pressure.
7087 7112 */
7088 7113 if (arc_reclaim_needed()) {
7089 7114 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
7090 7115 spa_config_exit(spa, SCL_L2ARC, dev);
7091 7116 continue;
7092 7117 }
7093 7118
7094 7119 ARCSTAT_BUMP(arcstat_l2_feeds);
7095 7120
7096 7121 size = l2arc_write_size();
7097 7122
7098 7123 /*
7099 7124 * Evict L2ARC buffers that will be overwritten.
7100 7125 */
7101 7126 l2arc_evict(dev, size, B_FALSE);
7102 7127
7103 7128 /*
7104 7129 * Write ARC buffers.
7105 7130 */
7106 7131 wrote = l2arc_write_buffers(spa, dev, size);
7107 7132
7108 7133 /*
7109 7134 * Calculate interval between writes.
7110 7135 */
7111 7136 next = l2arc_write_interval(begin, size, wrote);
7112 7137 spa_config_exit(spa, SCL_L2ARC, dev);
7113 7138 }
7114 7139
7115 7140 l2arc_thread_exit = 0;
7116 7141 cv_broadcast(&l2arc_feed_thr_cv);
7117 7142 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
7118 7143 thread_exit();
7119 7144 }
7120 7145
7121 7146 boolean_t
7122 7147 l2arc_vdev_present(vdev_t *vd)
7123 7148 {
7124 7149 l2arc_dev_t *dev;
7125 7150
7126 7151 mutex_enter(&l2arc_dev_mtx);
7127 7152 for (dev = list_head(l2arc_dev_list); dev != NULL;
7128 7153 dev = list_next(l2arc_dev_list, dev)) {
7129 7154 if (dev->l2ad_vdev == vd)
7130 7155 break;
7131 7156 }
7132 7157 mutex_exit(&l2arc_dev_mtx);
7133 7158
7134 7159 return (dev != NULL);
7135 7160 }
7136 7161
7137 7162 /*
7138 7163 * Add a vdev for use by the L2ARC. By this point the spa has already
7139 7164 * validated the vdev and opened it.
7140 7165 */
7141 7166 void
7142 7167 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
7143 7168 {
7144 7169 l2arc_dev_t *adddev;
7145 7170
7146 7171 ASSERT(!l2arc_vdev_present(vd));
7147 7172
7148 7173 /*
7149 7174 * Create a new l2arc device entry.
7150 7175 */
7151 7176 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
7152 7177 adddev->l2ad_spa = spa;
7153 7178 adddev->l2ad_vdev = vd;
7154 7179 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
7155 7180 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
7156 7181 adddev->l2ad_hand = adddev->l2ad_start;
7157 7182 adddev->l2ad_first = B_TRUE;
7158 7183 adddev->l2ad_writing = B_FALSE;
7159 7184
7160 7185 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
7161 7186 /*
7162 7187 * This is a list of all ARC buffers that are still valid on the
7163 7188 * device.
7164 7189 */
7165 7190 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
7166 7191 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
7167 7192
7168 7193 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
7169 7194 refcount_create(&adddev->l2ad_alloc);
7170 7195
7171 7196 /*
7172 7197 * Add device to global list
7173 7198 */
7174 7199 mutex_enter(&l2arc_dev_mtx);
7175 7200 list_insert_head(l2arc_dev_list, adddev);
7176 7201 atomic_inc_64(&l2arc_ndev);
7177 7202 mutex_exit(&l2arc_dev_mtx);
7178 7203 }
7179 7204
7180 7205 /*
7181 7206 * Remove a vdev from the L2ARC.
7182 7207 */
7183 7208 void
7184 7209 l2arc_remove_vdev(vdev_t *vd)
7185 7210 {
7186 7211 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
7187 7212
7188 7213 /*
7189 7214 * Find the device by vdev
7190 7215 */
7191 7216 mutex_enter(&l2arc_dev_mtx);
7192 7217 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
7193 7218 nextdev = list_next(l2arc_dev_list, dev);
7194 7219 if (vd == dev->l2ad_vdev) {
7195 7220 remdev = dev;
7196 7221 break;
7197 7222 }
7198 7223 }
7199 7224 ASSERT3P(remdev, !=, NULL);
7200 7225
7201 7226 /*
7202 7227 * Remove device from global list
7203 7228 */
7204 7229 list_remove(l2arc_dev_list, remdev);
7205 7230 l2arc_dev_last = NULL; /* may have been invalidated */
7206 7231 atomic_dec_64(&l2arc_ndev);
7207 7232 mutex_exit(&l2arc_dev_mtx);
7208 7233
7209 7234 /*
7210 7235 * Clear all buflists and ARC references. L2ARC device flush.
7211 7236 */
7212 7237 l2arc_evict(remdev, 0, B_TRUE);
7213 7238 list_destroy(&remdev->l2ad_buflist);
7214 7239 mutex_destroy(&remdev->l2ad_mtx);
7215 7240 refcount_destroy(&remdev->l2ad_alloc);
7216 7241 kmem_free(remdev, sizeof (l2arc_dev_t));
7217 7242 }
7218 7243
7219 7244 void
7220 7245 l2arc_init(void)
7221 7246 {
7222 7247 l2arc_thread_exit = 0;
7223 7248 l2arc_ndev = 0;
7224 7249 l2arc_writes_sent = 0;
7225 7250 l2arc_writes_done = 0;
7226 7251
7227 7252 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
7228 7253 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
7229 7254 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
7230 7255 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
7231 7256
7232 7257 l2arc_dev_list = &L2ARC_dev_list;
7233 7258 l2arc_free_on_write = &L2ARC_free_on_write;
7234 7259 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
7235 7260 offsetof(l2arc_dev_t, l2ad_node));
7236 7261 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
7237 7262 offsetof(l2arc_data_free_t, l2df_list_node));
7238 7263 }
7239 7264
7240 7265 void
7241 7266 l2arc_fini(void)
7242 7267 {
7243 7268 /*
7244 7269 * This is called from dmu_fini(), which is called from spa_fini();
7245 7270 * Because of this, we can assume that all l2arc devices have
7246 7271 * already been removed when the pools themselves were removed.
7247 7272 */
7248 7273
7249 7274 l2arc_do_free_on_write();
7250 7275
7251 7276 mutex_destroy(&l2arc_feed_thr_lock);
7252 7277 cv_destroy(&l2arc_feed_thr_cv);
7253 7278 mutex_destroy(&l2arc_dev_mtx);
7254 7279 mutex_destroy(&l2arc_free_on_write_mtx);
7255 7280
7256 7281 list_destroy(l2arc_dev_list);
7257 7282 list_destroy(l2arc_free_on_write);
7258 7283 }
7259 7284
7260 7285 void
7261 7286 l2arc_start(void)
7262 7287 {
7263 7288 if (!(spa_mode_global & FWRITE))
7264 7289 return;
7265 7290
7266 7291 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
7267 7292 TS_RUN, minclsyspri);
7268 7293 }
7269 7294
7270 7295 void
7271 7296 l2arc_stop(void)
7272 7297 {
7273 7298 if (!(spa_mode_global & FWRITE))
7274 7299 return;
7275 7300
7276 7301 mutex_enter(&l2arc_feed_thr_lock);
7277 7302 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
7278 7303 l2arc_thread_exit = 1;
7279 7304 while (l2arc_thread_exit != 0)
7280 7305 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
7281 7306 mutex_exit(&l2arc_feed_thr_lock);
7282 7307 }
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