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3741 zfs needs better comments
Submitted by: Will Andrews <willa@spectralogic.com>
Submitted by: Justin Gibbs <justing@spectralogic.com>
Submitted by: Alan Somers <alans@spectralogic.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
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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 *
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 23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 24 * Copyright (c) 2013 by Delphix. All rights reserved.
25 25 */
26 26
27 27 /*
28 28 * DVA-based Adjustable Replacement Cache
29 29 *
30 30 * While much of the theory of operation used here is
31 31 * based on the self-tuning, low overhead replacement cache
32 32 * presented by Megiddo and Modha at FAST 2003, there are some
33 33 * significant differences:
34 34 *
35 35 * 1. The Megiddo and Modha model assumes any page is evictable.
36 36 * Pages in its cache cannot be "locked" into memory. This makes
37 37 * the eviction algorithm simple: evict the last page in the list.
38 38 * This also make the performance characteristics easy to reason
39 39 * about. Our cache is not so simple. At any given moment, some
40 40 * subset of the blocks in the cache are un-evictable because we
41 41 * have handed out a reference to them. Blocks are only evictable
42 42 * when there are no external references active. This makes
43 43 * eviction far more problematic: we choose to evict the evictable
44 44 * blocks that are the "lowest" in the list.
45 45 *
46 46 * There are times when it is not possible to evict the requested
47 47 * space. In these circumstances we are unable to adjust the cache
48 48 * size. To prevent the cache growing unbounded at these times we
49 49 * implement a "cache throttle" that slows the flow of new data
50 50 * into the cache until we can make space available.
51 51 *
52 52 * 2. The Megiddo and Modha model assumes a fixed cache size.
53 53 * Pages are evicted when the cache is full and there is a cache
54 54 * miss. Our model has a variable sized cache. It grows with
55 55 * high use, but also tries to react to memory pressure from the
56 56 * operating system: decreasing its size when system memory is
57 57 * tight.
58 58 *
59 59 * 3. The Megiddo and Modha model assumes a fixed page size. All
60 60 * elements of the cache are therefor exactly the same size. So
61 61 * when adjusting the cache size following a cache miss, its simply
62 62 * a matter of choosing a single page to evict. In our model, we
63 63 * have variable sized cache blocks (rangeing from 512 bytes to
64 64 * 128K bytes). We therefor choose a set of blocks to evict to make
65 65 * space for a cache miss that approximates as closely as possible
66 66 * the space used by the new block.
67 67 *
68 68 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
69 69 * by N. Megiddo & D. Modha, FAST 2003
70 70 */
71 71
72 72 /*
73 73 * The locking model:
74 74 *
75 75 * A new reference to a cache buffer can be obtained in two
76 76 * ways: 1) via a hash table lookup using the DVA as a key,
77 77 * or 2) via one of the ARC lists. The arc_read() interface
78 78 * uses method 1, while the internal arc algorithms for
79 79 * adjusting the cache use method 2. We therefor provide two
80 80 * types of locks: 1) the hash table lock array, and 2) the
81 81 * arc list locks.
82 82 *
83 83 * Buffers do not have their own mutexes, rather they rely on the
84 84 * hash table mutexes for the bulk of their protection (i.e. most
85 85 * fields in the arc_buf_hdr_t are protected by these mutexes).
86 86 *
87 87 * buf_hash_find() returns the appropriate mutex (held) when it
88 88 * locates the requested buffer in the hash table. It returns
89 89 * NULL for the mutex if the buffer was not in the table.
90 90 *
91 91 * buf_hash_remove() expects the appropriate hash mutex to be
92 92 * already held before it is invoked.
93 93 *
94 94 * Each arc state also has a mutex which is used to protect the
95 95 * buffer list associated with the state. When attempting to
96 96 * obtain a hash table lock while holding an arc list lock you
97 97 * must use: mutex_tryenter() to avoid deadlock. Also note that
98 98 * the active state mutex must be held before the ghost state mutex.
99 99 *
100 100 * Arc buffers may have an associated eviction callback function.
101 101 * This function will be invoked prior to removing the buffer (e.g.
102 102 * in arc_do_user_evicts()). Note however that the data associated
103 103 * with the buffer may be evicted prior to the callback. The callback
104 104 * must be made with *no locks held* (to prevent deadlock). Additionally,
105 105 * the users of callbacks must ensure that their private data is
106 106 * protected from simultaneous callbacks from arc_buf_evict()
107 107 * and arc_do_user_evicts().
108 108 *
109 109 * Note that the majority of the performance stats are manipulated
110 110 * with atomic operations.
111 111 *
112 112 * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
113 113 *
114 114 * - L2ARC buflist creation
115 115 * - L2ARC buflist eviction
116 116 * - L2ARC write completion, which walks L2ARC buflists
117 117 * - ARC header destruction, as it removes from L2ARC buflists
118 118 * - ARC header release, as it removes from L2ARC buflists
119 119 */
120 120
121 121 #include <sys/spa.h>
122 122 #include <sys/zio.h>
123 123 #include <sys/zfs_context.h>
124 124 #include <sys/arc.h>
125 125 #include <sys/refcount.h>
126 126 #include <sys/vdev.h>
127 127 #include <sys/vdev_impl.h>
128 128 #ifdef _KERNEL
129 129 #include <sys/vmsystm.h>
130 130 #include <vm/anon.h>
131 131 #include <sys/fs/swapnode.h>
132 132 #include <sys/dnlc.h>
133 133 #endif
134 134 #include <sys/callb.h>
135 135 #include <sys/kstat.h>
136 136 #include <zfs_fletcher.h>
137 137
138 138 #ifndef _KERNEL
139 139 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
140 140 boolean_t arc_watch = B_FALSE;
141 141 int arc_procfd;
142 142 #endif
143 143
144 144 static kmutex_t arc_reclaim_thr_lock;
145 145 static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
146 146 static uint8_t arc_thread_exit;
147 147
148 148 extern int zfs_write_limit_shift;
149 149 extern uint64_t zfs_write_limit_max;
150 150 extern kmutex_t zfs_write_limit_lock;
151 151
152 152 #define ARC_REDUCE_DNLC_PERCENT 3
153 153 uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
154 154
155 155 typedef enum arc_reclaim_strategy {
156 156 ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
157 157 ARC_RECLAIM_CONS /* Conservative reclaim strategy */
158 158 } arc_reclaim_strategy_t;
159 159
160 160 /* number of seconds before growing cache again */
161 161 static int arc_grow_retry = 60;
162 162
163 163 /* shift of arc_c for calculating both min and max arc_p */
164 164 static int arc_p_min_shift = 4;
165 165
166 166 /* log2(fraction of arc to reclaim) */
167 167 static int arc_shrink_shift = 5;
168 168
169 169 /*
170 170 * minimum lifespan of a prefetch block in clock ticks
171 171 * (initialized in arc_init())
172 172 */
173 173 static int arc_min_prefetch_lifespan;
174 174
175 175 static int arc_dead;
176 176
177 177 /*
178 178 * The arc has filled available memory and has now warmed up.
179 179 */
180 180 static boolean_t arc_warm;
181 181
182 182 /*
183 183 * These tunables are for performance analysis.
184 184 */
185 185 uint64_t zfs_arc_max;
186 186 uint64_t zfs_arc_min;
187 187 uint64_t zfs_arc_meta_limit = 0;
188 188 int zfs_arc_grow_retry = 0;
189 189 int zfs_arc_shrink_shift = 0;
190 190 int zfs_arc_p_min_shift = 0;
191 191 int zfs_disable_dup_eviction = 0;
192 192
193 193 /*
194 194 * Note that buffers can be in one of 6 states:
195 195 * ARC_anon - anonymous (discussed below)
196 196 * ARC_mru - recently used, currently cached
197 197 * ARC_mru_ghost - recentely used, no longer in cache
198 198 * ARC_mfu - frequently used, currently cached
199 199 * ARC_mfu_ghost - frequently used, no longer in cache
200 200 * ARC_l2c_only - exists in L2ARC but not other states
201 201 * When there are no active references to the buffer, they are
202 202 * are linked onto a list in one of these arc states. These are
203 203 * the only buffers that can be evicted or deleted. Within each
204 204 * state there are multiple lists, one for meta-data and one for
205 205 * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
206 206 * etc.) is tracked separately so that it can be managed more
207 207 * explicitly: favored over data, limited explicitly.
208 208 *
209 209 * Anonymous buffers are buffers that are not associated with
210 210 * a DVA. These are buffers that hold dirty block copies
211 211 * before they are written to stable storage. By definition,
212 212 * they are "ref'd" and are considered part of arc_mru
213 213 * that cannot be freed. Generally, they will aquire a DVA
214 214 * as they are written and migrate onto the arc_mru list.
215 215 *
216 216 * The ARC_l2c_only state is for buffers that are in the second
217 217 * level ARC but no longer in any of the ARC_m* lists. The second
218 218 * level ARC itself may also contain buffers that are in any of
219 219 * the ARC_m* states - meaning that a buffer can exist in two
220 220 * places. The reason for the ARC_l2c_only state is to keep the
221 221 * buffer header in the hash table, so that reads that hit the
222 222 * second level ARC benefit from these fast lookups.
223 223 */
224 224
225 225 typedef struct arc_state {
226 226 list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
227 227 uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
228 228 uint64_t arcs_size; /* total amount of data in this state */
229 229 kmutex_t arcs_mtx;
230 230 } arc_state_t;
231 231
232 232 /* The 6 states: */
233 233 static arc_state_t ARC_anon;
234 234 static arc_state_t ARC_mru;
235 235 static arc_state_t ARC_mru_ghost;
236 236 static arc_state_t ARC_mfu;
237 237 static arc_state_t ARC_mfu_ghost;
238 238 static arc_state_t ARC_l2c_only;
239 239
240 240 typedef struct arc_stats {
241 241 kstat_named_t arcstat_hits;
242 242 kstat_named_t arcstat_misses;
243 243 kstat_named_t arcstat_demand_data_hits;
244 244 kstat_named_t arcstat_demand_data_misses;
245 245 kstat_named_t arcstat_demand_metadata_hits;
246 246 kstat_named_t arcstat_demand_metadata_misses;
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247 247 kstat_named_t arcstat_prefetch_data_hits;
248 248 kstat_named_t arcstat_prefetch_data_misses;
249 249 kstat_named_t arcstat_prefetch_metadata_hits;
250 250 kstat_named_t arcstat_prefetch_metadata_misses;
251 251 kstat_named_t arcstat_mru_hits;
252 252 kstat_named_t arcstat_mru_ghost_hits;
253 253 kstat_named_t arcstat_mfu_hits;
254 254 kstat_named_t arcstat_mfu_ghost_hits;
255 255 kstat_named_t arcstat_deleted;
256 256 kstat_named_t arcstat_recycle_miss;
257 + /*
258 + * Number of buffers that could not be evicted because the hash lock
259 + * was held by another thread. The lock may not necessarily be held
260 + * by something using the same buffer, since hash locks are shared
261 + * by multiple buffers.
262 + */
257 263 kstat_named_t arcstat_mutex_miss;
264 + /*
265 + * Number of buffers skipped because they have I/O in progress, are
266 + * indrect prefetch buffers that have not lived long enough, or are
267 + * not from the spa we're trying to evict from.
268 + */
258 269 kstat_named_t arcstat_evict_skip;
259 270 kstat_named_t arcstat_evict_l2_cached;
260 271 kstat_named_t arcstat_evict_l2_eligible;
261 272 kstat_named_t arcstat_evict_l2_ineligible;
262 273 kstat_named_t arcstat_hash_elements;
263 274 kstat_named_t arcstat_hash_elements_max;
264 275 kstat_named_t arcstat_hash_collisions;
265 276 kstat_named_t arcstat_hash_chains;
266 277 kstat_named_t arcstat_hash_chain_max;
267 278 kstat_named_t arcstat_p;
268 279 kstat_named_t arcstat_c;
269 280 kstat_named_t arcstat_c_min;
270 281 kstat_named_t arcstat_c_max;
271 282 kstat_named_t arcstat_size;
272 283 kstat_named_t arcstat_hdr_size;
273 284 kstat_named_t arcstat_data_size;
274 285 kstat_named_t arcstat_other_size;
275 286 kstat_named_t arcstat_l2_hits;
276 287 kstat_named_t arcstat_l2_misses;
277 288 kstat_named_t arcstat_l2_feeds;
278 289 kstat_named_t arcstat_l2_rw_clash;
279 290 kstat_named_t arcstat_l2_read_bytes;
280 291 kstat_named_t arcstat_l2_write_bytes;
281 292 kstat_named_t arcstat_l2_writes_sent;
282 293 kstat_named_t arcstat_l2_writes_done;
283 294 kstat_named_t arcstat_l2_writes_error;
284 295 kstat_named_t arcstat_l2_writes_hdr_miss;
285 296 kstat_named_t arcstat_l2_evict_lock_retry;
286 297 kstat_named_t arcstat_l2_evict_reading;
287 298 kstat_named_t arcstat_l2_free_on_write;
288 299 kstat_named_t arcstat_l2_abort_lowmem;
289 300 kstat_named_t arcstat_l2_cksum_bad;
290 301 kstat_named_t arcstat_l2_io_error;
291 302 kstat_named_t arcstat_l2_size;
292 303 kstat_named_t arcstat_l2_hdr_size;
293 304 kstat_named_t arcstat_memory_throttle_count;
294 305 kstat_named_t arcstat_duplicate_buffers;
295 306 kstat_named_t arcstat_duplicate_buffers_size;
296 307 kstat_named_t arcstat_duplicate_reads;
297 308 kstat_named_t arcstat_meta_used;
298 309 kstat_named_t arcstat_meta_limit;
299 310 kstat_named_t arcstat_meta_max;
300 311 } arc_stats_t;
301 312
302 313 static arc_stats_t arc_stats = {
303 314 { "hits", KSTAT_DATA_UINT64 },
304 315 { "misses", KSTAT_DATA_UINT64 },
305 316 { "demand_data_hits", KSTAT_DATA_UINT64 },
306 317 { "demand_data_misses", KSTAT_DATA_UINT64 },
307 318 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
308 319 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
309 320 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
310 321 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
311 322 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
312 323 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
313 324 { "mru_hits", KSTAT_DATA_UINT64 },
314 325 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
315 326 { "mfu_hits", KSTAT_DATA_UINT64 },
316 327 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
317 328 { "deleted", KSTAT_DATA_UINT64 },
318 329 { "recycle_miss", KSTAT_DATA_UINT64 },
319 330 { "mutex_miss", KSTAT_DATA_UINT64 },
320 331 { "evict_skip", KSTAT_DATA_UINT64 },
321 332 { "evict_l2_cached", KSTAT_DATA_UINT64 },
322 333 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
323 334 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
324 335 { "hash_elements", KSTAT_DATA_UINT64 },
325 336 { "hash_elements_max", KSTAT_DATA_UINT64 },
326 337 { "hash_collisions", KSTAT_DATA_UINT64 },
327 338 { "hash_chains", KSTAT_DATA_UINT64 },
328 339 { "hash_chain_max", KSTAT_DATA_UINT64 },
329 340 { "p", KSTAT_DATA_UINT64 },
330 341 { "c", KSTAT_DATA_UINT64 },
331 342 { "c_min", KSTAT_DATA_UINT64 },
332 343 { "c_max", KSTAT_DATA_UINT64 },
333 344 { "size", KSTAT_DATA_UINT64 },
334 345 { "hdr_size", KSTAT_DATA_UINT64 },
335 346 { "data_size", KSTAT_DATA_UINT64 },
336 347 { "other_size", KSTAT_DATA_UINT64 },
337 348 { "l2_hits", KSTAT_DATA_UINT64 },
338 349 { "l2_misses", KSTAT_DATA_UINT64 },
339 350 { "l2_feeds", KSTAT_DATA_UINT64 },
340 351 { "l2_rw_clash", KSTAT_DATA_UINT64 },
341 352 { "l2_read_bytes", KSTAT_DATA_UINT64 },
342 353 { "l2_write_bytes", KSTAT_DATA_UINT64 },
343 354 { "l2_writes_sent", KSTAT_DATA_UINT64 },
344 355 { "l2_writes_done", KSTAT_DATA_UINT64 },
345 356 { "l2_writes_error", KSTAT_DATA_UINT64 },
346 357 { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
347 358 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
348 359 { "l2_evict_reading", KSTAT_DATA_UINT64 },
349 360 { "l2_free_on_write", KSTAT_DATA_UINT64 },
350 361 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
351 362 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
352 363 { "l2_io_error", KSTAT_DATA_UINT64 },
353 364 { "l2_size", KSTAT_DATA_UINT64 },
354 365 { "l2_hdr_size", KSTAT_DATA_UINT64 },
355 366 { "memory_throttle_count", KSTAT_DATA_UINT64 },
356 367 { "duplicate_buffers", KSTAT_DATA_UINT64 },
357 368 { "duplicate_buffers_size", KSTAT_DATA_UINT64 },
358 369 { "duplicate_reads", KSTAT_DATA_UINT64 },
359 370 { "arc_meta_used", KSTAT_DATA_UINT64 },
360 371 { "arc_meta_limit", KSTAT_DATA_UINT64 },
361 372 { "arc_meta_max", KSTAT_DATA_UINT64 }
362 373 };
363 374
364 375 #define ARCSTAT(stat) (arc_stats.stat.value.ui64)
365 376
366 377 #define ARCSTAT_INCR(stat, val) \
367 378 atomic_add_64(&arc_stats.stat.value.ui64, (val));
368 379
369 380 #define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
370 381 #define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
371 382
372 383 #define ARCSTAT_MAX(stat, val) { \
373 384 uint64_t m; \
374 385 while ((val) > (m = arc_stats.stat.value.ui64) && \
375 386 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
376 387 continue; \
377 388 }
378 389
379 390 #define ARCSTAT_MAXSTAT(stat) \
380 391 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
381 392
382 393 /*
383 394 * We define a macro to allow ARC hits/misses to be easily broken down by
384 395 * two separate conditions, giving a total of four different subtypes for
385 396 * each of hits and misses (so eight statistics total).
386 397 */
387 398 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
388 399 if (cond1) { \
389 400 if (cond2) { \
390 401 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
391 402 } else { \
392 403 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
393 404 } \
394 405 } else { \
395 406 if (cond2) { \
396 407 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
397 408 } else { \
398 409 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
399 410 } \
400 411 }
401 412
402 413 kstat_t *arc_ksp;
403 414 static arc_state_t *arc_anon;
404 415 static arc_state_t *arc_mru;
405 416 static arc_state_t *arc_mru_ghost;
406 417 static arc_state_t *arc_mfu;
407 418 static arc_state_t *arc_mfu_ghost;
408 419 static arc_state_t *arc_l2c_only;
409 420
410 421 /*
411 422 * There are several ARC variables that are critical to export as kstats --
412 423 * but we don't want to have to grovel around in the kstat whenever we wish to
413 424 * manipulate them. For these variables, we therefore define them to be in
414 425 * terms of the statistic variable. This assures that we are not introducing
415 426 * the possibility of inconsistency by having shadow copies of the variables,
416 427 * while still allowing the code to be readable.
417 428 */
418 429 #define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
419 430 #define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
420 431 #define arc_c ARCSTAT(arcstat_c) /* target size of cache */
421 432 #define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
422 433 #define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
423 434 #define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
424 435 #define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
425 436 #define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
426 437
427 438 static int arc_no_grow; /* Don't try to grow cache size */
428 439 static uint64_t arc_tempreserve;
429 440 static uint64_t arc_loaned_bytes;
430 441
431 442 typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
432 443
433 444 typedef struct arc_callback arc_callback_t;
434 445
435 446 struct arc_callback {
436 447 void *acb_private;
437 448 arc_done_func_t *acb_done;
438 449 arc_buf_t *acb_buf;
439 450 zio_t *acb_zio_dummy;
440 451 arc_callback_t *acb_next;
441 452 };
442 453
443 454 typedef struct arc_write_callback arc_write_callback_t;
444 455
445 456 struct arc_write_callback {
446 457 void *awcb_private;
447 458 arc_done_func_t *awcb_ready;
448 459 arc_done_func_t *awcb_done;
449 460 arc_buf_t *awcb_buf;
450 461 };
451 462
452 463 struct arc_buf_hdr {
453 464 /* protected by hash lock */
454 465 dva_t b_dva;
455 466 uint64_t b_birth;
456 467 uint64_t b_cksum0;
457 468
458 469 kmutex_t b_freeze_lock;
459 470 zio_cksum_t *b_freeze_cksum;
460 471 void *b_thawed;
461 472
462 473 arc_buf_hdr_t *b_hash_next;
463 474 arc_buf_t *b_buf;
464 475 uint32_t b_flags;
465 476 uint32_t b_datacnt;
466 477
467 478 arc_callback_t *b_acb;
468 479 kcondvar_t b_cv;
469 480
470 481 /* immutable */
471 482 arc_buf_contents_t b_type;
472 483 uint64_t b_size;
473 484 uint64_t b_spa;
474 485
475 486 /* protected by arc state mutex */
476 487 arc_state_t *b_state;
477 488 list_node_t b_arc_node;
478 489
479 490 /* updated atomically */
480 491 clock_t b_arc_access;
481 492
482 493 /* self protecting */
483 494 refcount_t b_refcnt;
484 495
485 496 l2arc_buf_hdr_t *b_l2hdr;
486 497 list_node_t b_l2node;
487 498 };
488 499
489 500 static arc_buf_t *arc_eviction_list;
490 501 static kmutex_t arc_eviction_mtx;
491 502 static arc_buf_hdr_t arc_eviction_hdr;
492 503 static void arc_get_data_buf(arc_buf_t *buf);
493 504 static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
494 505 static int arc_evict_needed(arc_buf_contents_t type);
495 506 static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
496 507 static void arc_buf_watch(arc_buf_t *buf);
497 508
498 509 static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
499 510
500 511 #define GHOST_STATE(state) \
501 512 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
502 513 (state) == arc_l2c_only)
503 514
504 515 /*
505 516 * Private ARC flags. These flags are private ARC only flags that will show up
506 517 * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
507 518 * be passed in as arc_flags in things like arc_read. However, these flags
508 519 * should never be passed and should only be set by ARC code. When adding new
509 520 * public flags, make sure not to smash the private ones.
510 521 */
511 522
512 523 #define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
513 524 #define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
514 525 #define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
515 526 #define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
516 527 #define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
517 528 #define ARC_INDIRECT (1 << 14) /* this is an indirect block */
518 529 #define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
519 530 #define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
520 531 #define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
521 532 #define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
522 533
523 534 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
524 535 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
525 536 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
526 537 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
527 538 #define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
528 539 #define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
529 540 #define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
530 541 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
531 542 #define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
532 543 (hdr)->b_l2hdr != NULL)
533 544 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
534 545 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
535 546 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
536 547
537 548 /*
538 549 * Other sizes
539 550 */
540 551
541 552 #define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
542 553 #define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
543 554
544 555 /*
545 556 * Hash table routines
546 557 */
547 558
548 559 #define HT_LOCK_PAD 64
549 560
550 561 struct ht_lock {
551 562 kmutex_t ht_lock;
552 563 #ifdef _KERNEL
553 564 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
554 565 #endif
555 566 };
556 567
557 568 #define BUF_LOCKS 256
558 569 typedef struct buf_hash_table {
559 570 uint64_t ht_mask;
560 571 arc_buf_hdr_t **ht_table;
561 572 struct ht_lock ht_locks[BUF_LOCKS];
562 573 } buf_hash_table_t;
563 574
564 575 static buf_hash_table_t buf_hash_table;
565 576
566 577 #define BUF_HASH_INDEX(spa, dva, birth) \
567 578 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
568 579 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
569 580 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
570 581 #define HDR_LOCK(hdr) \
571 582 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
572 583
573 584 uint64_t zfs_crc64_table[256];
574 585
575 586 /*
576 587 * Level 2 ARC
577 588 */
578 589
579 590 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
580 591 #define L2ARC_HEADROOM 2 /* num of writes */
581 592 #define L2ARC_FEED_SECS 1 /* caching interval secs */
582 593 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
583 594
584 595 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
585 596 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
586 597
587 598 /*
588 599 * L2ARC Performance Tunables
589 600 */
590 601 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
591 602 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
592 603 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
593 604 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
594 605 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
595 606 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
596 607 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
597 608 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
598 609
599 610 /*
600 611 * L2ARC Internals
601 612 */
602 613 typedef struct l2arc_dev {
603 614 vdev_t *l2ad_vdev; /* vdev */
604 615 spa_t *l2ad_spa; /* spa */
605 616 uint64_t l2ad_hand; /* next write location */
606 617 uint64_t l2ad_write; /* desired write size, bytes */
607 618 uint64_t l2ad_boost; /* warmup write boost, bytes */
608 619 uint64_t l2ad_start; /* first addr on device */
609 620 uint64_t l2ad_end; /* last addr on device */
610 621 uint64_t l2ad_evict; /* last addr eviction reached */
611 622 boolean_t l2ad_first; /* first sweep through */
612 623 boolean_t l2ad_writing; /* currently writing */
613 624 list_t *l2ad_buflist; /* buffer list */
614 625 list_node_t l2ad_node; /* device list node */
615 626 } l2arc_dev_t;
616 627
617 628 static list_t L2ARC_dev_list; /* device list */
618 629 static list_t *l2arc_dev_list; /* device list pointer */
619 630 static kmutex_t l2arc_dev_mtx; /* device list mutex */
620 631 static l2arc_dev_t *l2arc_dev_last; /* last device used */
621 632 static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
622 633 static list_t L2ARC_free_on_write; /* free after write buf list */
623 634 static list_t *l2arc_free_on_write; /* free after write list ptr */
624 635 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
625 636 static uint64_t l2arc_ndev; /* number of devices */
626 637
627 638 typedef struct l2arc_read_callback {
628 639 arc_buf_t *l2rcb_buf; /* read buffer */
629 640 spa_t *l2rcb_spa; /* spa */
630 641 blkptr_t l2rcb_bp; /* original blkptr */
631 642 zbookmark_t l2rcb_zb; /* original bookmark */
632 643 int l2rcb_flags; /* original flags */
633 644 } l2arc_read_callback_t;
634 645
635 646 typedef struct l2arc_write_callback {
636 647 l2arc_dev_t *l2wcb_dev; /* device info */
637 648 arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
638 649 } l2arc_write_callback_t;
639 650
640 651 struct l2arc_buf_hdr {
641 652 /* protected by arc_buf_hdr mutex */
642 653 l2arc_dev_t *b_dev; /* L2ARC device */
643 654 uint64_t b_daddr; /* disk address, offset byte */
644 655 };
645 656
646 657 typedef struct l2arc_data_free {
647 658 /* protected by l2arc_free_on_write_mtx */
648 659 void *l2df_data;
649 660 size_t l2df_size;
650 661 void (*l2df_func)(void *, size_t);
651 662 list_node_t l2df_list_node;
652 663 } l2arc_data_free_t;
653 664
654 665 static kmutex_t l2arc_feed_thr_lock;
655 666 static kcondvar_t l2arc_feed_thr_cv;
656 667 static uint8_t l2arc_thread_exit;
657 668
658 669 static void l2arc_read_done(zio_t *zio);
659 670 static void l2arc_hdr_stat_add(void);
660 671 static void l2arc_hdr_stat_remove(void);
661 672
662 673 static uint64_t
663 674 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
664 675 {
665 676 uint8_t *vdva = (uint8_t *)dva;
666 677 uint64_t crc = -1ULL;
667 678 int i;
668 679
669 680 ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
670 681
671 682 for (i = 0; i < sizeof (dva_t); i++)
672 683 crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
673 684
674 685 crc ^= (spa>>8) ^ birth;
675 686
676 687 return (crc);
677 688 }
678 689
679 690 #define BUF_EMPTY(buf) \
680 691 ((buf)->b_dva.dva_word[0] == 0 && \
681 692 (buf)->b_dva.dva_word[1] == 0 && \
682 693 (buf)->b_birth == 0)
683 694
684 695 #define BUF_EQUAL(spa, dva, birth, buf) \
685 696 ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
686 697 ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
687 698 ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
688 699
689 700 static void
690 701 buf_discard_identity(arc_buf_hdr_t *hdr)
691 702 {
692 703 hdr->b_dva.dva_word[0] = 0;
693 704 hdr->b_dva.dva_word[1] = 0;
694 705 hdr->b_birth = 0;
695 706 hdr->b_cksum0 = 0;
696 707 }
697 708
698 709 static arc_buf_hdr_t *
699 710 buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
700 711 {
701 712 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
702 713 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
703 714 arc_buf_hdr_t *buf;
704 715
705 716 mutex_enter(hash_lock);
706 717 for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
707 718 buf = buf->b_hash_next) {
708 719 if (BUF_EQUAL(spa, dva, birth, buf)) {
709 720 *lockp = hash_lock;
710 721 return (buf);
711 722 }
712 723 }
713 724 mutex_exit(hash_lock);
714 725 *lockp = NULL;
715 726 return (NULL);
716 727 }
717 728
718 729 /*
719 730 * Insert an entry into the hash table. If there is already an element
720 731 * equal to elem in the hash table, then the already existing element
721 732 * will be returned and the new element will not be inserted.
722 733 * Otherwise returns NULL.
723 734 */
724 735 static arc_buf_hdr_t *
725 736 buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
726 737 {
727 738 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
728 739 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
729 740 arc_buf_hdr_t *fbuf;
730 741 uint32_t i;
731 742
732 743 ASSERT(!HDR_IN_HASH_TABLE(buf));
733 744 *lockp = hash_lock;
734 745 mutex_enter(hash_lock);
735 746 for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
736 747 fbuf = fbuf->b_hash_next, i++) {
737 748 if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
738 749 return (fbuf);
739 750 }
740 751
741 752 buf->b_hash_next = buf_hash_table.ht_table[idx];
742 753 buf_hash_table.ht_table[idx] = buf;
743 754 buf->b_flags |= ARC_IN_HASH_TABLE;
744 755
745 756 /* collect some hash table performance data */
746 757 if (i > 0) {
747 758 ARCSTAT_BUMP(arcstat_hash_collisions);
748 759 if (i == 1)
749 760 ARCSTAT_BUMP(arcstat_hash_chains);
750 761
751 762 ARCSTAT_MAX(arcstat_hash_chain_max, i);
752 763 }
753 764
754 765 ARCSTAT_BUMP(arcstat_hash_elements);
755 766 ARCSTAT_MAXSTAT(arcstat_hash_elements);
756 767
757 768 return (NULL);
758 769 }
759 770
760 771 static void
761 772 buf_hash_remove(arc_buf_hdr_t *buf)
762 773 {
763 774 arc_buf_hdr_t *fbuf, **bufp;
764 775 uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
765 776
766 777 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
767 778 ASSERT(HDR_IN_HASH_TABLE(buf));
768 779
769 780 bufp = &buf_hash_table.ht_table[idx];
770 781 while ((fbuf = *bufp) != buf) {
771 782 ASSERT(fbuf != NULL);
772 783 bufp = &fbuf->b_hash_next;
773 784 }
774 785 *bufp = buf->b_hash_next;
775 786 buf->b_hash_next = NULL;
776 787 buf->b_flags &= ~ARC_IN_HASH_TABLE;
777 788
778 789 /* collect some hash table performance data */
779 790 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
780 791
781 792 if (buf_hash_table.ht_table[idx] &&
782 793 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
783 794 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
784 795 }
785 796
786 797 /*
787 798 * Global data structures and functions for the buf kmem cache.
788 799 */
789 800 static kmem_cache_t *hdr_cache;
790 801 static kmem_cache_t *buf_cache;
791 802
792 803 static void
793 804 buf_fini(void)
794 805 {
795 806 int i;
796 807
797 808 kmem_free(buf_hash_table.ht_table,
798 809 (buf_hash_table.ht_mask + 1) * sizeof (void *));
799 810 for (i = 0; i < BUF_LOCKS; i++)
800 811 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
801 812 kmem_cache_destroy(hdr_cache);
802 813 kmem_cache_destroy(buf_cache);
803 814 }
804 815
805 816 /*
806 817 * Constructor callback - called when the cache is empty
807 818 * and a new buf is requested.
808 819 */
809 820 /* ARGSUSED */
810 821 static int
811 822 hdr_cons(void *vbuf, void *unused, int kmflag)
812 823 {
813 824 arc_buf_hdr_t *buf = vbuf;
814 825
815 826 bzero(buf, sizeof (arc_buf_hdr_t));
816 827 refcount_create(&buf->b_refcnt);
817 828 cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
818 829 mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
819 830 arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
820 831
821 832 return (0);
822 833 }
823 834
824 835 /* ARGSUSED */
825 836 static int
826 837 buf_cons(void *vbuf, void *unused, int kmflag)
827 838 {
828 839 arc_buf_t *buf = vbuf;
829 840
830 841 bzero(buf, sizeof (arc_buf_t));
831 842 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
832 843 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
833 844
834 845 return (0);
835 846 }
836 847
837 848 /*
838 849 * Destructor callback - called when a cached buf is
839 850 * no longer required.
840 851 */
841 852 /* ARGSUSED */
842 853 static void
843 854 hdr_dest(void *vbuf, void *unused)
844 855 {
845 856 arc_buf_hdr_t *buf = vbuf;
846 857
847 858 ASSERT(BUF_EMPTY(buf));
848 859 refcount_destroy(&buf->b_refcnt);
849 860 cv_destroy(&buf->b_cv);
850 861 mutex_destroy(&buf->b_freeze_lock);
851 862 arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
852 863 }
853 864
854 865 /* ARGSUSED */
855 866 static void
856 867 buf_dest(void *vbuf, void *unused)
857 868 {
858 869 arc_buf_t *buf = vbuf;
859 870
860 871 mutex_destroy(&buf->b_evict_lock);
861 872 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
862 873 }
863 874
864 875 /*
865 876 * Reclaim callback -- invoked when memory is low.
866 877 */
867 878 /* ARGSUSED */
868 879 static void
869 880 hdr_recl(void *unused)
870 881 {
871 882 dprintf("hdr_recl called\n");
872 883 /*
873 884 * umem calls the reclaim func when we destroy the buf cache,
874 885 * which is after we do arc_fini().
875 886 */
876 887 if (!arc_dead)
877 888 cv_signal(&arc_reclaim_thr_cv);
878 889 }
879 890
880 891 static void
881 892 buf_init(void)
882 893 {
883 894 uint64_t *ct;
884 895 uint64_t hsize = 1ULL << 12;
885 896 int i, j;
886 897
887 898 /*
888 899 * The hash table is big enough to fill all of physical memory
889 900 * with an average 64K block size. The table will take up
890 901 * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
891 902 */
892 903 while (hsize * 65536 < physmem * PAGESIZE)
893 904 hsize <<= 1;
894 905 retry:
895 906 buf_hash_table.ht_mask = hsize - 1;
896 907 buf_hash_table.ht_table =
897 908 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
898 909 if (buf_hash_table.ht_table == NULL) {
899 910 ASSERT(hsize > (1ULL << 8));
900 911 hsize >>= 1;
901 912 goto retry;
902 913 }
903 914
904 915 hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
905 916 0, hdr_cons, hdr_dest, hdr_recl, NULL, NULL, 0);
906 917 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
907 918 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
908 919
909 920 for (i = 0; i < 256; i++)
910 921 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
911 922 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
912 923
913 924 for (i = 0; i < BUF_LOCKS; i++) {
914 925 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
915 926 NULL, MUTEX_DEFAULT, NULL);
916 927 }
917 928 }
918 929
919 930 #define ARC_MINTIME (hz>>4) /* 62 ms */
920 931
921 932 static void
922 933 arc_cksum_verify(arc_buf_t *buf)
923 934 {
924 935 zio_cksum_t zc;
925 936
926 937 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
927 938 return;
928 939
929 940 mutex_enter(&buf->b_hdr->b_freeze_lock);
930 941 if (buf->b_hdr->b_freeze_cksum == NULL ||
931 942 (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
932 943 mutex_exit(&buf->b_hdr->b_freeze_lock);
933 944 return;
934 945 }
935 946 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
936 947 if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
937 948 panic("buffer modified while frozen!");
938 949 mutex_exit(&buf->b_hdr->b_freeze_lock);
939 950 }
940 951
941 952 static int
942 953 arc_cksum_equal(arc_buf_t *buf)
943 954 {
944 955 zio_cksum_t zc;
945 956 int equal;
946 957
947 958 mutex_enter(&buf->b_hdr->b_freeze_lock);
948 959 fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
949 960 equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
950 961 mutex_exit(&buf->b_hdr->b_freeze_lock);
951 962
952 963 return (equal);
953 964 }
954 965
955 966 static void
956 967 arc_cksum_compute(arc_buf_t *buf, boolean_t force)
957 968 {
958 969 if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
959 970 return;
960 971
961 972 mutex_enter(&buf->b_hdr->b_freeze_lock);
962 973 if (buf->b_hdr->b_freeze_cksum != NULL) {
963 974 mutex_exit(&buf->b_hdr->b_freeze_lock);
964 975 return;
965 976 }
966 977 buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
967 978 fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
968 979 buf->b_hdr->b_freeze_cksum);
969 980 mutex_exit(&buf->b_hdr->b_freeze_lock);
970 981 arc_buf_watch(buf);
971 982 }
972 983
973 984 #ifndef _KERNEL
974 985 typedef struct procctl {
975 986 long cmd;
976 987 prwatch_t prwatch;
977 988 } procctl_t;
978 989 #endif
979 990
980 991 /* ARGSUSED */
981 992 static void
982 993 arc_buf_unwatch(arc_buf_t *buf)
983 994 {
984 995 #ifndef _KERNEL
985 996 if (arc_watch) {
986 997 int result;
987 998 procctl_t ctl;
988 999 ctl.cmd = PCWATCH;
989 1000 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
990 1001 ctl.prwatch.pr_size = 0;
991 1002 ctl.prwatch.pr_wflags = 0;
992 1003 result = write(arc_procfd, &ctl, sizeof (ctl));
993 1004 ASSERT3U(result, ==, sizeof (ctl));
994 1005 }
995 1006 #endif
996 1007 }
997 1008
998 1009 /* ARGSUSED */
999 1010 static void
1000 1011 arc_buf_watch(arc_buf_t *buf)
1001 1012 {
1002 1013 #ifndef _KERNEL
1003 1014 if (arc_watch) {
1004 1015 int result;
1005 1016 procctl_t ctl;
1006 1017 ctl.cmd = PCWATCH;
1007 1018 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1008 1019 ctl.prwatch.pr_size = buf->b_hdr->b_size;
1009 1020 ctl.prwatch.pr_wflags = WA_WRITE;
1010 1021 result = write(arc_procfd, &ctl, sizeof (ctl));
1011 1022 ASSERT3U(result, ==, sizeof (ctl));
1012 1023 }
1013 1024 #endif
1014 1025 }
1015 1026
1016 1027 void
1017 1028 arc_buf_thaw(arc_buf_t *buf)
1018 1029 {
1019 1030 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1020 1031 if (buf->b_hdr->b_state != arc_anon)
1021 1032 panic("modifying non-anon buffer!");
1022 1033 if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
1023 1034 panic("modifying buffer while i/o in progress!");
1024 1035 arc_cksum_verify(buf);
1025 1036 }
1026 1037
1027 1038 mutex_enter(&buf->b_hdr->b_freeze_lock);
1028 1039 if (buf->b_hdr->b_freeze_cksum != NULL) {
1029 1040 kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1030 1041 buf->b_hdr->b_freeze_cksum = NULL;
1031 1042 }
1032 1043
1033 1044 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1034 1045 if (buf->b_hdr->b_thawed)
1035 1046 kmem_free(buf->b_hdr->b_thawed, 1);
1036 1047 buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
1037 1048 }
1038 1049
1039 1050 mutex_exit(&buf->b_hdr->b_freeze_lock);
1040 1051
1041 1052 arc_buf_unwatch(buf);
1042 1053 }
1043 1054
1044 1055 void
1045 1056 arc_buf_freeze(arc_buf_t *buf)
1046 1057 {
1047 1058 kmutex_t *hash_lock;
1048 1059
1049 1060 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1050 1061 return;
1051 1062
1052 1063 hash_lock = HDR_LOCK(buf->b_hdr);
1053 1064 mutex_enter(hash_lock);
1054 1065
1055 1066 ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
1056 1067 buf->b_hdr->b_state == arc_anon);
1057 1068 arc_cksum_compute(buf, B_FALSE);
1058 1069 mutex_exit(hash_lock);
1059 1070
1060 1071 }
1061 1072
1062 1073 static void
1063 1074 add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1064 1075 {
1065 1076 ASSERT(MUTEX_HELD(hash_lock));
1066 1077
1067 1078 if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
1068 1079 (ab->b_state != arc_anon)) {
1069 1080 uint64_t delta = ab->b_size * ab->b_datacnt;
1070 1081 list_t *list = &ab->b_state->arcs_list[ab->b_type];
1071 1082 uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
1072 1083
1073 1084 ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
1074 1085 mutex_enter(&ab->b_state->arcs_mtx);
1075 1086 ASSERT(list_link_active(&ab->b_arc_node));
1076 1087 list_remove(list, ab);
1077 1088 if (GHOST_STATE(ab->b_state)) {
1078 1089 ASSERT0(ab->b_datacnt);
1079 1090 ASSERT3P(ab->b_buf, ==, NULL);
1080 1091 delta = ab->b_size;
1081 1092 }
1082 1093 ASSERT(delta > 0);
1083 1094 ASSERT3U(*size, >=, delta);
1084 1095 atomic_add_64(size, -delta);
1085 1096 mutex_exit(&ab->b_state->arcs_mtx);
1086 1097 /* remove the prefetch flag if we get a reference */
1087 1098 if (ab->b_flags & ARC_PREFETCH)
1088 1099 ab->b_flags &= ~ARC_PREFETCH;
1089 1100 }
1090 1101 }
1091 1102
1092 1103 static int
1093 1104 remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
1094 1105 {
1095 1106 int cnt;
1096 1107 arc_state_t *state = ab->b_state;
1097 1108
1098 1109 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
1099 1110 ASSERT(!GHOST_STATE(state));
1100 1111
1101 1112 if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
1102 1113 (state != arc_anon)) {
1103 1114 uint64_t *size = &state->arcs_lsize[ab->b_type];
1104 1115
1105 1116 ASSERT(!MUTEX_HELD(&state->arcs_mtx));
1106 1117 mutex_enter(&state->arcs_mtx);
1107 1118 ASSERT(!list_link_active(&ab->b_arc_node));
1108 1119 list_insert_head(&state->arcs_list[ab->b_type], ab);
1109 1120 ASSERT(ab->b_datacnt > 0);
1110 1121 atomic_add_64(size, ab->b_size * ab->b_datacnt);
1111 1122 mutex_exit(&state->arcs_mtx);
1112 1123 }
1113 1124 return (cnt);
1114 1125 }
1115 1126
1116 1127 /*
1117 1128 * Move the supplied buffer to the indicated state. The mutex
1118 1129 * for the buffer must be held by the caller.
1119 1130 */
1120 1131 static void
1121 1132 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
1122 1133 {
1123 1134 arc_state_t *old_state = ab->b_state;
1124 1135 int64_t refcnt = refcount_count(&ab->b_refcnt);
1125 1136 uint64_t from_delta, to_delta;
1126 1137
1127 1138 ASSERT(MUTEX_HELD(hash_lock));
1128 1139 ASSERT(new_state != old_state);
1129 1140 ASSERT(refcnt == 0 || ab->b_datacnt > 0);
1130 1141 ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
1131 1142 ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
1132 1143
1133 1144 from_delta = to_delta = ab->b_datacnt * ab->b_size;
1134 1145
1135 1146 /*
1136 1147 * If this buffer is evictable, transfer it from the
1137 1148 * old state list to the new state list.
1138 1149 */
1139 1150 if (refcnt == 0) {
1140 1151 if (old_state != arc_anon) {
1141 1152 int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
1142 1153 uint64_t *size = &old_state->arcs_lsize[ab->b_type];
1143 1154
1144 1155 if (use_mutex)
1145 1156 mutex_enter(&old_state->arcs_mtx);
1146 1157
1147 1158 ASSERT(list_link_active(&ab->b_arc_node));
1148 1159 list_remove(&old_state->arcs_list[ab->b_type], ab);
1149 1160
1150 1161 /*
1151 1162 * If prefetching out of the ghost cache,
1152 1163 * we will have a non-zero datacnt.
1153 1164 */
1154 1165 if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
1155 1166 /* ghost elements have a ghost size */
1156 1167 ASSERT(ab->b_buf == NULL);
1157 1168 from_delta = ab->b_size;
1158 1169 }
1159 1170 ASSERT3U(*size, >=, from_delta);
1160 1171 atomic_add_64(size, -from_delta);
1161 1172
1162 1173 if (use_mutex)
1163 1174 mutex_exit(&old_state->arcs_mtx);
1164 1175 }
1165 1176 if (new_state != arc_anon) {
1166 1177 int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
1167 1178 uint64_t *size = &new_state->arcs_lsize[ab->b_type];
1168 1179
1169 1180 if (use_mutex)
1170 1181 mutex_enter(&new_state->arcs_mtx);
1171 1182
1172 1183 list_insert_head(&new_state->arcs_list[ab->b_type], ab);
1173 1184
1174 1185 /* ghost elements have a ghost size */
1175 1186 if (GHOST_STATE(new_state)) {
1176 1187 ASSERT(ab->b_datacnt == 0);
1177 1188 ASSERT(ab->b_buf == NULL);
1178 1189 to_delta = ab->b_size;
1179 1190 }
1180 1191 atomic_add_64(size, to_delta);
1181 1192
1182 1193 if (use_mutex)
1183 1194 mutex_exit(&new_state->arcs_mtx);
1184 1195 }
1185 1196 }
1186 1197
1187 1198 ASSERT(!BUF_EMPTY(ab));
1188 1199 if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
1189 1200 buf_hash_remove(ab);
1190 1201
1191 1202 /* adjust state sizes */
1192 1203 if (to_delta)
1193 1204 atomic_add_64(&new_state->arcs_size, to_delta);
1194 1205 if (from_delta) {
1195 1206 ASSERT3U(old_state->arcs_size, >=, from_delta);
1196 1207 atomic_add_64(&old_state->arcs_size, -from_delta);
1197 1208 }
1198 1209 ab->b_state = new_state;
1199 1210
1200 1211 /* adjust l2arc hdr stats */
1201 1212 if (new_state == arc_l2c_only)
1202 1213 l2arc_hdr_stat_add();
1203 1214 else if (old_state == arc_l2c_only)
1204 1215 l2arc_hdr_stat_remove();
1205 1216 }
1206 1217
1207 1218 void
1208 1219 arc_space_consume(uint64_t space, arc_space_type_t type)
1209 1220 {
1210 1221 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1211 1222
1212 1223 switch (type) {
1213 1224 case ARC_SPACE_DATA:
1214 1225 ARCSTAT_INCR(arcstat_data_size, space);
1215 1226 break;
1216 1227 case ARC_SPACE_OTHER:
1217 1228 ARCSTAT_INCR(arcstat_other_size, space);
1218 1229 break;
1219 1230 case ARC_SPACE_HDRS:
1220 1231 ARCSTAT_INCR(arcstat_hdr_size, space);
1221 1232 break;
1222 1233 case ARC_SPACE_L2HDRS:
1223 1234 ARCSTAT_INCR(arcstat_l2_hdr_size, space);
1224 1235 break;
1225 1236 }
1226 1237
1227 1238 ARCSTAT_INCR(arcstat_meta_used, space);
1228 1239 atomic_add_64(&arc_size, space);
1229 1240 }
1230 1241
1231 1242 void
1232 1243 arc_space_return(uint64_t space, arc_space_type_t type)
1233 1244 {
1234 1245 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
1235 1246
1236 1247 switch (type) {
1237 1248 case ARC_SPACE_DATA:
1238 1249 ARCSTAT_INCR(arcstat_data_size, -space);
1239 1250 break;
1240 1251 case ARC_SPACE_OTHER:
1241 1252 ARCSTAT_INCR(arcstat_other_size, -space);
1242 1253 break;
1243 1254 case ARC_SPACE_HDRS:
1244 1255 ARCSTAT_INCR(arcstat_hdr_size, -space);
1245 1256 break;
1246 1257 case ARC_SPACE_L2HDRS:
1247 1258 ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
1248 1259 break;
1249 1260 }
1250 1261
1251 1262 ASSERT(arc_meta_used >= space);
1252 1263 if (arc_meta_max < arc_meta_used)
1253 1264 arc_meta_max = arc_meta_used;
1254 1265 ARCSTAT_INCR(arcstat_meta_used, -space);
1255 1266 ASSERT(arc_size >= space);
1256 1267 atomic_add_64(&arc_size, -space);
1257 1268 }
1258 1269
1259 1270 void *
1260 1271 arc_data_buf_alloc(uint64_t size)
1261 1272 {
1262 1273 if (arc_evict_needed(ARC_BUFC_DATA))
1263 1274 cv_signal(&arc_reclaim_thr_cv);
1264 1275 atomic_add_64(&arc_size, size);
1265 1276 return (zio_data_buf_alloc(size));
1266 1277 }
1267 1278
1268 1279 void
1269 1280 arc_data_buf_free(void *buf, uint64_t size)
1270 1281 {
1271 1282 zio_data_buf_free(buf, size);
1272 1283 ASSERT(arc_size >= size);
1273 1284 atomic_add_64(&arc_size, -size);
1274 1285 }
1275 1286
1276 1287 arc_buf_t *
1277 1288 arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
1278 1289 {
1279 1290 arc_buf_hdr_t *hdr;
1280 1291 arc_buf_t *buf;
1281 1292
1282 1293 ASSERT3U(size, >, 0);
1283 1294 hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
1284 1295 ASSERT(BUF_EMPTY(hdr));
1285 1296 hdr->b_size = size;
1286 1297 hdr->b_type = type;
1287 1298 hdr->b_spa = spa_load_guid(spa);
1288 1299 hdr->b_state = arc_anon;
1289 1300 hdr->b_arc_access = 0;
1290 1301 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1291 1302 buf->b_hdr = hdr;
1292 1303 buf->b_data = NULL;
1293 1304 buf->b_efunc = NULL;
1294 1305 buf->b_private = NULL;
1295 1306 buf->b_next = NULL;
1296 1307 hdr->b_buf = buf;
1297 1308 arc_get_data_buf(buf);
1298 1309 hdr->b_datacnt = 1;
1299 1310 hdr->b_flags = 0;
1300 1311 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1301 1312 (void) refcount_add(&hdr->b_refcnt, tag);
1302 1313
1303 1314 return (buf);
1304 1315 }
1305 1316
1306 1317 static char *arc_onloan_tag = "onloan";
1307 1318
1308 1319 /*
1309 1320 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
1310 1321 * flight data by arc_tempreserve_space() until they are "returned". Loaned
1311 1322 * buffers must be returned to the arc before they can be used by the DMU or
1312 1323 * freed.
1313 1324 */
1314 1325 arc_buf_t *
1315 1326 arc_loan_buf(spa_t *spa, int size)
1316 1327 {
1317 1328 arc_buf_t *buf;
1318 1329
1319 1330 buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
1320 1331
1321 1332 atomic_add_64(&arc_loaned_bytes, size);
1322 1333 return (buf);
1323 1334 }
1324 1335
1325 1336 /*
1326 1337 * Return a loaned arc buffer to the arc.
1327 1338 */
1328 1339 void
1329 1340 arc_return_buf(arc_buf_t *buf, void *tag)
1330 1341 {
1331 1342 arc_buf_hdr_t *hdr = buf->b_hdr;
1332 1343
1333 1344 ASSERT(buf->b_data != NULL);
1334 1345 (void) refcount_add(&hdr->b_refcnt, tag);
1335 1346 (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
1336 1347
1337 1348 atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
1338 1349 }
1339 1350
1340 1351 /* Detach an arc_buf from a dbuf (tag) */
1341 1352 void
1342 1353 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
1343 1354 {
1344 1355 arc_buf_hdr_t *hdr;
1345 1356
1346 1357 ASSERT(buf->b_data != NULL);
1347 1358 hdr = buf->b_hdr;
1348 1359 (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
1349 1360 (void) refcount_remove(&hdr->b_refcnt, tag);
1350 1361 buf->b_efunc = NULL;
1351 1362 buf->b_private = NULL;
1352 1363
1353 1364 atomic_add_64(&arc_loaned_bytes, hdr->b_size);
1354 1365 }
1355 1366
1356 1367 static arc_buf_t *
1357 1368 arc_buf_clone(arc_buf_t *from)
1358 1369 {
1359 1370 arc_buf_t *buf;
1360 1371 arc_buf_hdr_t *hdr = from->b_hdr;
1361 1372 uint64_t size = hdr->b_size;
1362 1373
1363 1374 ASSERT(hdr->b_state != arc_anon);
1364 1375
1365 1376 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
1366 1377 buf->b_hdr = hdr;
1367 1378 buf->b_data = NULL;
1368 1379 buf->b_efunc = NULL;
1369 1380 buf->b_private = NULL;
1370 1381 buf->b_next = hdr->b_buf;
1371 1382 hdr->b_buf = buf;
1372 1383 arc_get_data_buf(buf);
1373 1384 bcopy(from->b_data, buf->b_data, size);
1374 1385
1375 1386 /*
1376 1387 * This buffer already exists in the arc so create a duplicate
1377 1388 * copy for the caller. If the buffer is associated with user data
1378 1389 * then track the size and number of duplicates. These stats will be
1379 1390 * updated as duplicate buffers are created and destroyed.
1380 1391 */
1381 1392 if (hdr->b_type == ARC_BUFC_DATA) {
1382 1393 ARCSTAT_BUMP(arcstat_duplicate_buffers);
1383 1394 ARCSTAT_INCR(arcstat_duplicate_buffers_size, size);
1384 1395 }
1385 1396 hdr->b_datacnt += 1;
1386 1397 return (buf);
1387 1398 }
1388 1399
1389 1400 void
1390 1401 arc_buf_add_ref(arc_buf_t *buf, void* tag)
1391 1402 {
1392 1403 arc_buf_hdr_t *hdr;
1393 1404 kmutex_t *hash_lock;
1394 1405
1395 1406 /*
1396 1407 * Check to see if this buffer is evicted. Callers
1397 1408 * must verify b_data != NULL to know if the add_ref
1398 1409 * was successful.
1399 1410 */
1400 1411 mutex_enter(&buf->b_evict_lock);
1401 1412 if (buf->b_data == NULL) {
1402 1413 mutex_exit(&buf->b_evict_lock);
1403 1414 return;
1404 1415 }
1405 1416 hash_lock = HDR_LOCK(buf->b_hdr);
1406 1417 mutex_enter(hash_lock);
1407 1418 hdr = buf->b_hdr;
1408 1419 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1409 1420 mutex_exit(&buf->b_evict_lock);
1410 1421
1411 1422 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
1412 1423 add_reference(hdr, hash_lock, tag);
1413 1424 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
1414 1425 arc_access(hdr, hash_lock);
1415 1426 mutex_exit(hash_lock);
1416 1427 ARCSTAT_BUMP(arcstat_hits);
1417 1428 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
1418 1429 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
1419 1430 data, metadata, hits);
1420 1431 }
1421 1432
1422 1433 /*
1423 1434 * Free the arc data buffer. If it is an l2arc write in progress,
1424 1435 * the buffer is placed on l2arc_free_on_write to be freed later.
1425 1436 */
1426 1437 static void
1427 1438 arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
1428 1439 {
1429 1440 arc_buf_hdr_t *hdr = buf->b_hdr;
1430 1441
1431 1442 if (HDR_L2_WRITING(hdr)) {
1432 1443 l2arc_data_free_t *df;
1433 1444 df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
1434 1445 df->l2df_data = buf->b_data;
1435 1446 df->l2df_size = hdr->b_size;
1436 1447 df->l2df_func = free_func;
1437 1448 mutex_enter(&l2arc_free_on_write_mtx);
1438 1449 list_insert_head(l2arc_free_on_write, df);
1439 1450 mutex_exit(&l2arc_free_on_write_mtx);
1440 1451 ARCSTAT_BUMP(arcstat_l2_free_on_write);
1441 1452 } else {
1442 1453 free_func(buf->b_data, hdr->b_size);
1443 1454 }
1444 1455 }
1445 1456
1446 1457 static void
1447 1458 arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
1448 1459 {
1449 1460 arc_buf_t **bufp;
1450 1461
1451 1462 /* free up data associated with the buf */
1452 1463 if (buf->b_data) {
1453 1464 arc_state_t *state = buf->b_hdr->b_state;
1454 1465 uint64_t size = buf->b_hdr->b_size;
1455 1466 arc_buf_contents_t type = buf->b_hdr->b_type;
1456 1467
1457 1468 arc_cksum_verify(buf);
1458 1469 arc_buf_unwatch(buf);
1459 1470
1460 1471 if (!recycle) {
1461 1472 if (type == ARC_BUFC_METADATA) {
1462 1473 arc_buf_data_free(buf, zio_buf_free);
1463 1474 arc_space_return(size, ARC_SPACE_DATA);
1464 1475 } else {
1465 1476 ASSERT(type == ARC_BUFC_DATA);
1466 1477 arc_buf_data_free(buf, zio_data_buf_free);
1467 1478 ARCSTAT_INCR(arcstat_data_size, -size);
1468 1479 atomic_add_64(&arc_size, -size);
1469 1480 }
1470 1481 }
1471 1482 if (list_link_active(&buf->b_hdr->b_arc_node)) {
1472 1483 uint64_t *cnt = &state->arcs_lsize[type];
1473 1484
1474 1485 ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
1475 1486 ASSERT(state != arc_anon);
1476 1487
1477 1488 ASSERT3U(*cnt, >=, size);
1478 1489 atomic_add_64(cnt, -size);
1479 1490 }
1480 1491 ASSERT3U(state->arcs_size, >=, size);
1481 1492 atomic_add_64(&state->arcs_size, -size);
1482 1493 buf->b_data = NULL;
1483 1494
1484 1495 /*
1485 1496 * If we're destroying a duplicate buffer make sure
1486 1497 * that the appropriate statistics are updated.
1487 1498 */
1488 1499 if (buf->b_hdr->b_datacnt > 1 &&
1489 1500 buf->b_hdr->b_type == ARC_BUFC_DATA) {
1490 1501 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
1491 1502 ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
1492 1503 }
1493 1504 ASSERT(buf->b_hdr->b_datacnt > 0);
1494 1505 buf->b_hdr->b_datacnt -= 1;
1495 1506 }
1496 1507
1497 1508 /* only remove the buf if requested */
1498 1509 if (!all)
1499 1510 return;
1500 1511
1501 1512 /* remove the buf from the hdr list */
1502 1513 for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
1503 1514 continue;
1504 1515 *bufp = buf->b_next;
1505 1516 buf->b_next = NULL;
1506 1517
1507 1518 ASSERT(buf->b_efunc == NULL);
1508 1519
1509 1520 /* clean up the buf */
1510 1521 buf->b_hdr = NULL;
1511 1522 kmem_cache_free(buf_cache, buf);
1512 1523 }
1513 1524
1514 1525 static void
1515 1526 arc_hdr_destroy(arc_buf_hdr_t *hdr)
1516 1527 {
1517 1528 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1518 1529 ASSERT3P(hdr->b_state, ==, arc_anon);
1519 1530 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1520 1531 l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
1521 1532
1522 1533 if (l2hdr != NULL) {
1523 1534 boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
1524 1535 /*
1525 1536 * To prevent arc_free() and l2arc_evict() from
1526 1537 * attempting to free the same buffer at the same time,
1527 1538 * a FREE_IN_PROGRESS flag is given to arc_free() to
1528 1539 * give it priority. l2arc_evict() can't destroy this
1529 1540 * header while we are waiting on l2arc_buflist_mtx.
1530 1541 *
1531 1542 * The hdr may be removed from l2ad_buflist before we
1532 1543 * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
1533 1544 */
1534 1545 if (!buflist_held) {
1535 1546 mutex_enter(&l2arc_buflist_mtx);
1536 1547 l2hdr = hdr->b_l2hdr;
1537 1548 }
1538 1549
1539 1550 if (l2hdr != NULL) {
1540 1551 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
1541 1552 ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
1542 1553 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
1543 1554 if (hdr->b_state == arc_l2c_only)
1544 1555 l2arc_hdr_stat_remove();
1545 1556 hdr->b_l2hdr = NULL;
1546 1557 }
1547 1558
1548 1559 if (!buflist_held)
1549 1560 mutex_exit(&l2arc_buflist_mtx);
1550 1561 }
1551 1562
1552 1563 if (!BUF_EMPTY(hdr)) {
1553 1564 ASSERT(!HDR_IN_HASH_TABLE(hdr));
1554 1565 buf_discard_identity(hdr);
1555 1566 }
1556 1567 while (hdr->b_buf) {
1557 1568 arc_buf_t *buf = hdr->b_buf;
1558 1569
1559 1570 if (buf->b_efunc) {
1560 1571 mutex_enter(&arc_eviction_mtx);
1561 1572 mutex_enter(&buf->b_evict_lock);
1562 1573 ASSERT(buf->b_hdr != NULL);
1563 1574 arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
1564 1575 hdr->b_buf = buf->b_next;
1565 1576 buf->b_hdr = &arc_eviction_hdr;
1566 1577 buf->b_next = arc_eviction_list;
1567 1578 arc_eviction_list = buf;
1568 1579 mutex_exit(&buf->b_evict_lock);
1569 1580 mutex_exit(&arc_eviction_mtx);
1570 1581 } else {
1571 1582 arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
1572 1583 }
1573 1584 }
1574 1585 if (hdr->b_freeze_cksum != NULL) {
1575 1586 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
1576 1587 hdr->b_freeze_cksum = NULL;
1577 1588 }
1578 1589 if (hdr->b_thawed) {
1579 1590 kmem_free(hdr->b_thawed, 1);
1580 1591 hdr->b_thawed = NULL;
1581 1592 }
1582 1593
1583 1594 ASSERT(!list_link_active(&hdr->b_arc_node));
1584 1595 ASSERT3P(hdr->b_hash_next, ==, NULL);
1585 1596 ASSERT3P(hdr->b_acb, ==, NULL);
1586 1597 kmem_cache_free(hdr_cache, hdr);
1587 1598 }
1588 1599
1589 1600 void
1590 1601 arc_buf_free(arc_buf_t *buf, void *tag)
1591 1602 {
1592 1603 arc_buf_hdr_t *hdr = buf->b_hdr;
1593 1604 int hashed = hdr->b_state != arc_anon;
1594 1605
1595 1606 ASSERT(buf->b_efunc == NULL);
1596 1607 ASSERT(buf->b_data != NULL);
1597 1608
1598 1609 if (hashed) {
1599 1610 kmutex_t *hash_lock = HDR_LOCK(hdr);
1600 1611
1601 1612 mutex_enter(hash_lock);
1602 1613 hdr = buf->b_hdr;
1603 1614 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1604 1615
1605 1616 (void) remove_reference(hdr, hash_lock, tag);
1606 1617 if (hdr->b_datacnt > 1) {
1607 1618 arc_buf_destroy(buf, FALSE, TRUE);
1608 1619 } else {
1609 1620 ASSERT(buf == hdr->b_buf);
1610 1621 ASSERT(buf->b_efunc == NULL);
1611 1622 hdr->b_flags |= ARC_BUF_AVAILABLE;
1612 1623 }
1613 1624 mutex_exit(hash_lock);
1614 1625 } else if (HDR_IO_IN_PROGRESS(hdr)) {
1615 1626 int destroy_hdr;
1616 1627 /*
1617 1628 * We are in the middle of an async write. Don't destroy
1618 1629 * this buffer unless the write completes before we finish
1619 1630 * decrementing the reference count.
1620 1631 */
1621 1632 mutex_enter(&arc_eviction_mtx);
1622 1633 (void) remove_reference(hdr, NULL, tag);
1623 1634 ASSERT(refcount_is_zero(&hdr->b_refcnt));
1624 1635 destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
1625 1636 mutex_exit(&arc_eviction_mtx);
1626 1637 if (destroy_hdr)
1627 1638 arc_hdr_destroy(hdr);
1628 1639 } else {
1629 1640 if (remove_reference(hdr, NULL, tag) > 0)
1630 1641 arc_buf_destroy(buf, FALSE, TRUE);
1631 1642 else
1632 1643 arc_hdr_destroy(hdr);
1633 1644 }
1634 1645 }
1635 1646
1636 1647 boolean_t
1637 1648 arc_buf_remove_ref(arc_buf_t *buf, void* tag)
1638 1649 {
1639 1650 arc_buf_hdr_t *hdr = buf->b_hdr;
1640 1651 kmutex_t *hash_lock = HDR_LOCK(hdr);
1641 1652 boolean_t no_callback = (buf->b_efunc == NULL);
1642 1653
1643 1654 if (hdr->b_state == arc_anon) {
1644 1655 ASSERT(hdr->b_datacnt == 1);
1645 1656 arc_buf_free(buf, tag);
1646 1657 return (no_callback);
1647 1658 }
1648 1659
1649 1660 mutex_enter(hash_lock);
1650 1661 hdr = buf->b_hdr;
1651 1662 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
1652 1663 ASSERT(hdr->b_state != arc_anon);
1653 1664 ASSERT(buf->b_data != NULL);
1654 1665
1655 1666 (void) remove_reference(hdr, hash_lock, tag);
1656 1667 if (hdr->b_datacnt > 1) {
1657 1668 if (no_callback)
1658 1669 arc_buf_destroy(buf, FALSE, TRUE);
1659 1670 } else if (no_callback) {
1660 1671 ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
1661 1672 ASSERT(buf->b_efunc == NULL);
1662 1673 hdr->b_flags |= ARC_BUF_AVAILABLE;
1663 1674 }
1664 1675 ASSERT(no_callback || hdr->b_datacnt > 1 ||
1665 1676 refcount_is_zero(&hdr->b_refcnt));
1666 1677 mutex_exit(hash_lock);
1667 1678 return (no_callback);
1668 1679 }
1669 1680
1670 1681 int
1671 1682 arc_buf_size(arc_buf_t *buf)
1672 1683 {
1673 1684 return (buf->b_hdr->b_size);
1674 1685 }
1675 1686
1676 1687 /*
1677 1688 * Called from the DMU to determine if the current buffer should be
1678 1689 * evicted. In order to ensure proper locking, the eviction must be initiated
1679 1690 * from the DMU. Return true if the buffer is associated with user data and
1680 1691 * duplicate buffers still exist.
1681 1692 */
1682 1693 boolean_t
1683 1694 arc_buf_eviction_needed(arc_buf_t *buf)
1684 1695 {
1685 1696 arc_buf_hdr_t *hdr;
1686 1697 boolean_t evict_needed = B_FALSE;
1687 1698
1688 1699 if (zfs_disable_dup_eviction)
1689 1700 return (B_FALSE);
1690 1701
1691 1702 mutex_enter(&buf->b_evict_lock);
1692 1703 hdr = buf->b_hdr;
1693 1704 if (hdr == NULL) {
1694 1705 /*
1695 1706 * We are in arc_do_user_evicts(); let that function
1696 1707 * perform the eviction.
1697 1708 */
1698 1709 ASSERT(buf->b_data == NULL);
1699 1710 mutex_exit(&buf->b_evict_lock);
1700 1711 return (B_FALSE);
1701 1712 } else if (buf->b_data == NULL) {
1702 1713 /*
1703 1714 * We have already been added to the arc eviction list;
1704 1715 * recommend eviction.
1705 1716 */
1706 1717 ASSERT3P(hdr, ==, &arc_eviction_hdr);
1707 1718 mutex_exit(&buf->b_evict_lock);
1708 1719 return (B_TRUE);
1709 1720 }
1710 1721
1711 1722 if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
1712 1723 evict_needed = B_TRUE;
1713 1724
1714 1725 mutex_exit(&buf->b_evict_lock);
1715 1726 return (evict_needed);
1716 1727 }
1717 1728
1718 1729 /*
1719 1730 * Evict buffers from list until we've removed the specified number of
1720 1731 * bytes. Move the removed buffers to the appropriate evict state.
1721 1732 * If the recycle flag is set, then attempt to "recycle" a buffer:
1722 1733 * - look for a buffer to evict that is `bytes' long.
1723 1734 * - return the data block from this buffer rather than freeing it.
1724 1735 * This flag is used by callers that are trying to make space for a
1725 1736 * new buffer in a full arc cache.
1726 1737 *
1727 1738 * This function makes a "best effort". It skips over any buffers
1728 1739 * it can't get a hash_lock on, and so may not catch all candidates.
1729 1740 * It may also return without evicting as much space as requested.
1730 1741 */
1731 1742 static void *
1732 1743 arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
1733 1744 arc_buf_contents_t type)
1734 1745 {
1735 1746 arc_state_t *evicted_state;
1736 1747 uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
1737 1748 arc_buf_hdr_t *ab, *ab_prev = NULL;
1738 1749 list_t *list = &state->arcs_list[type];
1739 1750 kmutex_t *hash_lock;
1740 1751 boolean_t have_lock;
1741 1752 void *stolen = NULL;
1742 1753
1743 1754 ASSERT(state == arc_mru || state == arc_mfu);
1744 1755
1745 1756 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
1746 1757
1747 1758 mutex_enter(&state->arcs_mtx);
1748 1759 mutex_enter(&evicted_state->arcs_mtx);
1749 1760
1750 1761 for (ab = list_tail(list); ab; ab = ab_prev) {
1751 1762 ab_prev = list_prev(list, ab);
1752 1763 /* prefetch buffers have a minimum lifespan */
1753 1764 if (HDR_IO_IN_PROGRESS(ab) ||
1754 1765 (spa && ab->b_spa != spa) ||
1755 1766 (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
1756 1767 ddi_get_lbolt() - ab->b_arc_access <
1757 1768 arc_min_prefetch_lifespan)) {
1758 1769 skipped++;
1759 1770 continue;
1760 1771 }
1761 1772 /* "lookahead" for better eviction candidate */
1762 1773 if (recycle && ab->b_size != bytes &&
1763 1774 ab_prev && ab_prev->b_size == bytes)
1764 1775 continue;
1765 1776 hash_lock = HDR_LOCK(ab);
1766 1777 have_lock = MUTEX_HELD(hash_lock);
1767 1778 if (have_lock || mutex_tryenter(hash_lock)) {
1768 1779 ASSERT0(refcount_count(&ab->b_refcnt));
1769 1780 ASSERT(ab->b_datacnt > 0);
1770 1781 while (ab->b_buf) {
1771 1782 arc_buf_t *buf = ab->b_buf;
1772 1783 if (!mutex_tryenter(&buf->b_evict_lock)) {
1773 1784 missed += 1;
1774 1785 break;
1775 1786 }
1776 1787 if (buf->b_data) {
1777 1788 bytes_evicted += ab->b_size;
1778 1789 if (recycle && ab->b_type == type &&
1779 1790 ab->b_size == bytes &&
1780 1791 !HDR_L2_WRITING(ab)) {
1781 1792 stolen = buf->b_data;
1782 1793 recycle = FALSE;
1783 1794 }
1784 1795 }
1785 1796 if (buf->b_efunc) {
1786 1797 mutex_enter(&arc_eviction_mtx);
1787 1798 arc_buf_destroy(buf,
1788 1799 buf->b_data == stolen, FALSE);
1789 1800 ab->b_buf = buf->b_next;
1790 1801 buf->b_hdr = &arc_eviction_hdr;
1791 1802 buf->b_next = arc_eviction_list;
1792 1803 arc_eviction_list = buf;
1793 1804 mutex_exit(&arc_eviction_mtx);
1794 1805 mutex_exit(&buf->b_evict_lock);
1795 1806 } else {
1796 1807 mutex_exit(&buf->b_evict_lock);
1797 1808 arc_buf_destroy(buf,
1798 1809 buf->b_data == stolen, TRUE);
1799 1810 }
1800 1811 }
1801 1812
1802 1813 if (ab->b_l2hdr) {
1803 1814 ARCSTAT_INCR(arcstat_evict_l2_cached,
1804 1815 ab->b_size);
1805 1816 } else {
1806 1817 if (l2arc_write_eligible(ab->b_spa, ab)) {
1807 1818 ARCSTAT_INCR(arcstat_evict_l2_eligible,
1808 1819 ab->b_size);
1809 1820 } else {
1810 1821 ARCSTAT_INCR(
1811 1822 arcstat_evict_l2_ineligible,
1812 1823 ab->b_size);
1813 1824 }
1814 1825 }
1815 1826
1816 1827 if (ab->b_datacnt == 0) {
1817 1828 arc_change_state(evicted_state, ab, hash_lock);
1818 1829 ASSERT(HDR_IN_HASH_TABLE(ab));
1819 1830 ab->b_flags |= ARC_IN_HASH_TABLE;
1820 1831 ab->b_flags &= ~ARC_BUF_AVAILABLE;
1821 1832 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
1822 1833 }
1823 1834 if (!have_lock)
1824 1835 mutex_exit(hash_lock);
1825 1836 if (bytes >= 0 && bytes_evicted >= bytes)
1826 1837 break;
1827 1838 } else {
1828 1839 missed += 1;
1829 1840 }
1830 1841 }
1831 1842
1832 1843 mutex_exit(&evicted_state->arcs_mtx);
1833 1844 mutex_exit(&state->arcs_mtx);
1834 1845
1835 1846 if (bytes_evicted < bytes)
1836 1847 dprintf("only evicted %lld bytes from %x",
1837 1848 (longlong_t)bytes_evicted, state);
1838 1849
1839 1850 if (skipped)
1840 1851 ARCSTAT_INCR(arcstat_evict_skip, skipped);
1841 1852
1842 1853 if (missed)
1843 1854 ARCSTAT_INCR(arcstat_mutex_miss, missed);
1844 1855
1845 1856 /*
1846 1857 * We have just evicted some data into the ghost state, make
1847 1858 * sure we also adjust the ghost state size if necessary.
1848 1859 */
1849 1860 if (arc_no_grow &&
1850 1861 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
1851 1862 int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
1852 1863 arc_mru_ghost->arcs_size - arc_c;
1853 1864
1854 1865 if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
1855 1866 int64_t todelete =
1856 1867 MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
1857 1868 arc_evict_ghost(arc_mru_ghost, NULL, todelete);
1858 1869 } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
1859 1870 int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
1860 1871 arc_mru_ghost->arcs_size +
1861 1872 arc_mfu_ghost->arcs_size - arc_c);
1862 1873 arc_evict_ghost(arc_mfu_ghost, NULL, todelete);
1863 1874 }
1864 1875 }
1865 1876
1866 1877 return (stolen);
1867 1878 }
1868 1879
1869 1880 /*
1870 1881 * Remove buffers from list until we've removed the specified number of
1871 1882 * bytes. Destroy the buffers that are removed.
1872 1883 */
1873 1884 static void
1874 1885 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
1875 1886 {
1876 1887 arc_buf_hdr_t *ab, *ab_prev;
1877 1888 arc_buf_hdr_t marker = { 0 };
1878 1889 list_t *list = &state->arcs_list[ARC_BUFC_DATA];
1879 1890 kmutex_t *hash_lock;
1880 1891 uint64_t bytes_deleted = 0;
1881 1892 uint64_t bufs_skipped = 0;
1882 1893
1883 1894 ASSERT(GHOST_STATE(state));
1884 1895 top:
1885 1896 mutex_enter(&state->arcs_mtx);
1886 1897 for (ab = list_tail(list); ab; ab = ab_prev) {
1887 1898 ab_prev = list_prev(list, ab);
1888 1899 if (spa && ab->b_spa != spa)
1889 1900 continue;
1890 1901
1891 1902 /* ignore markers */
1892 1903 if (ab->b_spa == 0)
1893 1904 continue;
1894 1905
1895 1906 hash_lock = HDR_LOCK(ab);
1896 1907 /* caller may be trying to modify this buffer, skip it */
1897 1908 if (MUTEX_HELD(hash_lock))
1898 1909 continue;
1899 1910 if (mutex_tryenter(hash_lock)) {
1900 1911 ASSERT(!HDR_IO_IN_PROGRESS(ab));
1901 1912 ASSERT(ab->b_buf == NULL);
1902 1913 ARCSTAT_BUMP(arcstat_deleted);
1903 1914 bytes_deleted += ab->b_size;
1904 1915
1905 1916 if (ab->b_l2hdr != NULL) {
1906 1917 /*
1907 1918 * This buffer is cached on the 2nd Level ARC;
1908 1919 * don't destroy the header.
1909 1920 */
1910 1921 arc_change_state(arc_l2c_only, ab, hash_lock);
1911 1922 mutex_exit(hash_lock);
1912 1923 } else {
1913 1924 arc_change_state(arc_anon, ab, hash_lock);
1914 1925 mutex_exit(hash_lock);
1915 1926 arc_hdr_destroy(ab);
1916 1927 }
1917 1928
1918 1929 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
1919 1930 if (bytes >= 0 && bytes_deleted >= bytes)
1920 1931 break;
1921 1932 } else if (bytes < 0) {
1922 1933 /*
1923 1934 * Insert a list marker and then wait for the
1924 1935 * hash lock to become available. Once its
1925 1936 * available, restart from where we left off.
1926 1937 */
1927 1938 list_insert_after(list, ab, &marker);
1928 1939 mutex_exit(&state->arcs_mtx);
1929 1940 mutex_enter(hash_lock);
1930 1941 mutex_exit(hash_lock);
1931 1942 mutex_enter(&state->arcs_mtx);
1932 1943 ab_prev = list_prev(list, &marker);
1933 1944 list_remove(list, &marker);
1934 1945 } else
1935 1946 bufs_skipped += 1;
1936 1947 }
1937 1948 mutex_exit(&state->arcs_mtx);
1938 1949
1939 1950 if (list == &state->arcs_list[ARC_BUFC_DATA] &&
1940 1951 (bytes < 0 || bytes_deleted < bytes)) {
1941 1952 list = &state->arcs_list[ARC_BUFC_METADATA];
1942 1953 goto top;
1943 1954 }
1944 1955
1945 1956 if (bufs_skipped) {
1946 1957 ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
1947 1958 ASSERT(bytes >= 0);
1948 1959 }
1949 1960
1950 1961 if (bytes_deleted < bytes)
1951 1962 dprintf("only deleted %lld bytes from %p",
1952 1963 (longlong_t)bytes_deleted, state);
1953 1964 }
1954 1965
1955 1966 static void
1956 1967 arc_adjust(void)
1957 1968 {
1958 1969 int64_t adjustment, delta;
1959 1970
1960 1971 /*
1961 1972 * Adjust MRU size
1962 1973 */
1963 1974
1964 1975 adjustment = MIN((int64_t)(arc_size - arc_c),
1965 1976 (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
1966 1977 arc_p));
1967 1978
1968 1979 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
1969 1980 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
1970 1981 (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
1971 1982 adjustment -= delta;
1972 1983 }
1973 1984
1974 1985 if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1975 1986 delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
1976 1987 (void) arc_evict(arc_mru, NULL, delta, FALSE,
1977 1988 ARC_BUFC_METADATA);
1978 1989 }
1979 1990
1980 1991 /*
1981 1992 * Adjust MFU size
1982 1993 */
1983 1994
1984 1995 adjustment = arc_size - arc_c;
1985 1996
1986 1997 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
1987 1998 delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
1988 1999 (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
1989 2000 adjustment -= delta;
1990 2001 }
1991 2002
1992 2003 if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
1993 2004 int64_t delta = MIN(adjustment,
1994 2005 arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
1995 2006 (void) arc_evict(arc_mfu, NULL, delta, FALSE,
1996 2007 ARC_BUFC_METADATA);
1997 2008 }
1998 2009
1999 2010 /*
2000 2011 * Adjust ghost lists
2001 2012 */
2002 2013
2003 2014 adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
2004 2015
2005 2016 if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
2006 2017 delta = MIN(arc_mru_ghost->arcs_size, adjustment);
2007 2018 arc_evict_ghost(arc_mru_ghost, NULL, delta);
2008 2019 }
2009 2020
2010 2021 adjustment =
2011 2022 arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
2012 2023
2013 2024 if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
2014 2025 delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
2015 2026 arc_evict_ghost(arc_mfu_ghost, NULL, delta);
2016 2027 }
2017 2028 }
2018 2029
2019 2030 static void
2020 2031 arc_do_user_evicts(void)
2021 2032 {
2022 2033 mutex_enter(&arc_eviction_mtx);
2023 2034 while (arc_eviction_list != NULL) {
2024 2035 arc_buf_t *buf = arc_eviction_list;
2025 2036 arc_eviction_list = buf->b_next;
2026 2037 mutex_enter(&buf->b_evict_lock);
2027 2038 buf->b_hdr = NULL;
2028 2039 mutex_exit(&buf->b_evict_lock);
2029 2040 mutex_exit(&arc_eviction_mtx);
2030 2041
2031 2042 if (buf->b_efunc != NULL)
2032 2043 VERIFY(buf->b_efunc(buf) == 0);
2033 2044
2034 2045 buf->b_efunc = NULL;
2035 2046 buf->b_private = NULL;
2036 2047 kmem_cache_free(buf_cache, buf);
2037 2048 mutex_enter(&arc_eviction_mtx);
2038 2049 }
2039 2050 mutex_exit(&arc_eviction_mtx);
2040 2051 }
2041 2052
2042 2053 /*
2043 2054 * Flush all *evictable* data from the cache for the given spa.
2044 2055 * NOTE: this will not touch "active" (i.e. referenced) data.
2045 2056 */
2046 2057 void
2047 2058 arc_flush(spa_t *spa)
2048 2059 {
2049 2060 uint64_t guid = 0;
2050 2061
2051 2062 if (spa)
2052 2063 guid = spa_load_guid(spa);
2053 2064
2054 2065 while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
2055 2066 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
2056 2067 if (spa)
2057 2068 break;
2058 2069 }
2059 2070 while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
2060 2071 (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
2061 2072 if (spa)
2062 2073 break;
2063 2074 }
2064 2075 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
2065 2076 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
2066 2077 if (spa)
2067 2078 break;
2068 2079 }
2069 2080 while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
2070 2081 (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
2071 2082 if (spa)
2072 2083 break;
2073 2084 }
2074 2085
2075 2086 arc_evict_ghost(arc_mru_ghost, guid, -1);
2076 2087 arc_evict_ghost(arc_mfu_ghost, guid, -1);
2077 2088
2078 2089 mutex_enter(&arc_reclaim_thr_lock);
2079 2090 arc_do_user_evicts();
2080 2091 mutex_exit(&arc_reclaim_thr_lock);
2081 2092 ASSERT(spa || arc_eviction_list == NULL);
2082 2093 }
2083 2094
2084 2095 void
2085 2096 arc_shrink(void)
2086 2097 {
2087 2098 if (arc_c > arc_c_min) {
2088 2099 uint64_t to_free;
2089 2100
2090 2101 #ifdef _KERNEL
2091 2102 to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
2092 2103 #else
2093 2104 to_free = arc_c >> arc_shrink_shift;
2094 2105 #endif
2095 2106 if (arc_c > arc_c_min + to_free)
2096 2107 atomic_add_64(&arc_c, -to_free);
2097 2108 else
2098 2109 arc_c = arc_c_min;
2099 2110
2100 2111 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
2101 2112 if (arc_c > arc_size)
2102 2113 arc_c = MAX(arc_size, arc_c_min);
2103 2114 if (arc_p > arc_c)
2104 2115 arc_p = (arc_c >> 1);
2105 2116 ASSERT(arc_c >= arc_c_min);
2106 2117 ASSERT((int64_t)arc_p >= 0);
2107 2118 }
2108 2119
2109 2120 if (arc_size > arc_c)
2110 2121 arc_adjust();
2111 2122 }
2112 2123
2113 2124 /*
2114 2125 * Determine if the system is under memory pressure and is asking
2115 2126 * to reclaim memory. A return value of 1 indicates that the system
2116 2127 * is under memory pressure and that the arc should adjust accordingly.
2117 2128 */
2118 2129 static int
2119 2130 arc_reclaim_needed(void)
2120 2131 {
2121 2132 uint64_t extra;
2122 2133
2123 2134 #ifdef _KERNEL
2124 2135
2125 2136 if (needfree)
2126 2137 return (1);
2127 2138
2128 2139 /*
2129 2140 * take 'desfree' extra pages, so we reclaim sooner, rather than later
2130 2141 */
2131 2142 extra = desfree;
2132 2143
2133 2144 /*
2134 2145 * check that we're out of range of the pageout scanner. It starts to
2135 2146 * schedule paging if freemem is less than lotsfree and needfree.
2136 2147 * lotsfree is the high-water mark for pageout, and needfree is the
2137 2148 * number of needed free pages. We add extra pages here to make sure
2138 2149 * the scanner doesn't start up while we're freeing memory.
2139 2150 */
2140 2151 if (freemem < lotsfree + needfree + extra)
2141 2152 return (1);
2142 2153
2143 2154 /*
2144 2155 * check to make sure that swapfs has enough space so that anon
2145 2156 * reservations can still succeed. anon_resvmem() checks that the
2146 2157 * availrmem is greater than swapfs_minfree, and the number of reserved
2147 2158 * swap pages. We also add a bit of extra here just to prevent
2148 2159 * circumstances from getting really dire.
2149 2160 */
2150 2161 if (availrmem < swapfs_minfree + swapfs_reserve + extra)
2151 2162 return (1);
2152 2163
2153 2164 #if defined(__i386)
2154 2165 /*
2155 2166 * If we're on an i386 platform, it's possible that we'll exhaust the
2156 2167 * kernel heap space before we ever run out of available physical
2157 2168 * memory. Most checks of the size of the heap_area compare against
2158 2169 * tune.t_minarmem, which is the minimum available real memory that we
2159 2170 * can have in the system. However, this is generally fixed at 25 pages
2160 2171 * which is so low that it's useless. In this comparison, we seek to
2161 2172 * calculate the total heap-size, and reclaim if more than 3/4ths of the
2162 2173 * heap is allocated. (Or, in the calculation, if less than 1/4th is
2163 2174 * free)
2164 2175 */
2165 2176 if (vmem_size(heap_arena, VMEM_FREE) <
2166 2177 (vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2))
2167 2178 return (1);
2168 2179 #endif
2169 2180
2170 2181 /*
2171 2182 * If zio data pages are being allocated out of a separate heap segment,
2172 2183 * then enforce that the size of available vmem for this arena remains
2173 2184 * above about 1/16th free.
2174 2185 *
2175 2186 * Note: The 1/16th arena free requirement was put in place
2176 2187 * to aggressively evict memory from the arc in order to avoid
2177 2188 * memory fragmentation issues.
2178 2189 */
2179 2190 if (zio_arena != NULL &&
2180 2191 vmem_size(zio_arena, VMEM_FREE) <
2181 2192 (vmem_size(zio_arena, VMEM_ALLOC) >> 4))
2182 2193 return (1);
2183 2194 #else
2184 2195 if (spa_get_random(100) == 0)
2185 2196 return (1);
2186 2197 #endif
2187 2198 return (0);
2188 2199 }
2189 2200
2190 2201 static void
2191 2202 arc_kmem_reap_now(arc_reclaim_strategy_t strat)
2192 2203 {
2193 2204 size_t i;
2194 2205 kmem_cache_t *prev_cache = NULL;
2195 2206 kmem_cache_t *prev_data_cache = NULL;
2196 2207 extern kmem_cache_t *zio_buf_cache[];
2197 2208 extern kmem_cache_t *zio_data_buf_cache[];
2198 2209
2199 2210 #ifdef _KERNEL
2200 2211 if (arc_meta_used >= arc_meta_limit) {
2201 2212 /*
2202 2213 * We are exceeding our meta-data cache limit.
2203 2214 * Purge some DNLC entries to release holds on meta-data.
2204 2215 */
2205 2216 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
2206 2217 }
2207 2218 #if defined(__i386)
2208 2219 /*
2209 2220 * Reclaim unused memory from all kmem caches.
2210 2221 */
2211 2222 kmem_reap();
2212 2223 #endif
2213 2224 #endif
2214 2225
2215 2226 /*
2216 2227 * An aggressive reclamation will shrink the cache size as well as
2217 2228 * reap free buffers from the arc kmem caches.
2218 2229 */
2219 2230 if (strat == ARC_RECLAIM_AGGR)
2220 2231 arc_shrink();
2221 2232
2222 2233 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
2223 2234 if (zio_buf_cache[i] != prev_cache) {
2224 2235 prev_cache = zio_buf_cache[i];
2225 2236 kmem_cache_reap_now(zio_buf_cache[i]);
2226 2237 }
2227 2238 if (zio_data_buf_cache[i] != prev_data_cache) {
2228 2239 prev_data_cache = zio_data_buf_cache[i];
2229 2240 kmem_cache_reap_now(zio_data_buf_cache[i]);
2230 2241 }
2231 2242 }
2232 2243 kmem_cache_reap_now(buf_cache);
2233 2244 kmem_cache_reap_now(hdr_cache);
2234 2245
2235 2246 /*
2236 2247 * Ask the vmem areana to reclaim unused memory from its
2237 2248 * quantum caches.
2238 2249 */
2239 2250 if (zio_arena != NULL && strat == ARC_RECLAIM_AGGR)
2240 2251 vmem_qcache_reap(zio_arena);
2241 2252 }
2242 2253
2243 2254 static void
2244 2255 arc_reclaim_thread(void)
2245 2256 {
2246 2257 clock_t growtime = 0;
2247 2258 arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
2248 2259 callb_cpr_t cpr;
2249 2260
2250 2261 CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
2251 2262
2252 2263 mutex_enter(&arc_reclaim_thr_lock);
2253 2264 while (arc_thread_exit == 0) {
2254 2265 if (arc_reclaim_needed()) {
2255 2266
2256 2267 if (arc_no_grow) {
2257 2268 if (last_reclaim == ARC_RECLAIM_CONS) {
2258 2269 last_reclaim = ARC_RECLAIM_AGGR;
2259 2270 } else {
2260 2271 last_reclaim = ARC_RECLAIM_CONS;
2261 2272 }
2262 2273 } else {
2263 2274 arc_no_grow = TRUE;
2264 2275 last_reclaim = ARC_RECLAIM_AGGR;
2265 2276 membar_producer();
2266 2277 }
2267 2278
2268 2279 /* reset the growth delay for every reclaim */
2269 2280 growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
2270 2281
2271 2282 arc_kmem_reap_now(last_reclaim);
2272 2283 arc_warm = B_TRUE;
2273 2284
2274 2285 } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
2275 2286 arc_no_grow = FALSE;
2276 2287 }
2277 2288
2278 2289 arc_adjust();
2279 2290
2280 2291 if (arc_eviction_list != NULL)
2281 2292 arc_do_user_evicts();
2282 2293
2283 2294 /* block until needed, or one second, whichever is shorter */
2284 2295 CALLB_CPR_SAFE_BEGIN(&cpr);
2285 2296 (void) cv_timedwait(&arc_reclaim_thr_cv,
2286 2297 &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
2287 2298 CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
2288 2299 }
2289 2300
2290 2301 arc_thread_exit = 0;
2291 2302 cv_broadcast(&arc_reclaim_thr_cv);
2292 2303 CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
2293 2304 thread_exit();
2294 2305 }
2295 2306
2296 2307 /*
2297 2308 * Adapt arc info given the number of bytes we are trying to add and
2298 2309 * the state that we are comming from. This function is only called
2299 2310 * when we are adding new content to the cache.
2300 2311 */
2301 2312 static void
2302 2313 arc_adapt(int bytes, arc_state_t *state)
2303 2314 {
2304 2315 int mult;
2305 2316 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
2306 2317
2307 2318 if (state == arc_l2c_only)
2308 2319 return;
2309 2320
2310 2321 ASSERT(bytes > 0);
2311 2322 /*
2312 2323 * Adapt the target size of the MRU list:
2313 2324 * - if we just hit in the MRU ghost list, then increase
2314 2325 * the target size of the MRU list.
2315 2326 * - if we just hit in the MFU ghost list, then increase
2316 2327 * the target size of the MFU list by decreasing the
2317 2328 * target size of the MRU list.
2318 2329 */
2319 2330 if (state == arc_mru_ghost) {
2320 2331 mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
2321 2332 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
2322 2333 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
2323 2334
2324 2335 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
2325 2336 } else if (state == arc_mfu_ghost) {
2326 2337 uint64_t delta;
2327 2338
2328 2339 mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
2329 2340 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
2330 2341 mult = MIN(mult, 10);
2331 2342
2332 2343 delta = MIN(bytes * mult, arc_p);
2333 2344 arc_p = MAX(arc_p_min, arc_p - delta);
2334 2345 }
2335 2346 ASSERT((int64_t)arc_p >= 0);
2336 2347
2337 2348 if (arc_reclaim_needed()) {
2338 2349 cv_signal(&arc_reclaim_thr_cv);
2339 2350 return;
2340 2351 }
2341 2352
2342 2353 if (arc_no_grow)
2343 2354 return;
2344 2355
2345 2356 if (arc_c >= arc_c_max)
2346 2357 return;
2347 2358
2348 2359 /*
2349 2360 * If we're within (2 * maxblocksize) bytes of the target
2350 2361 * cache size, increment the target cache size
2351 2362 */
2352 2363 if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
2353 2364 atomic_add_64(&arc_c, (int64_t)bytes);
2354 2365 if (arc_c > arc_c_max)
2355 2366 arc_c = arc_c_max;
2356 2367 else if (state == arc_anon)
2357 2368 atomic_add_64(&arc_p, (int64_t)bytes);
2358 2369 if (arc_p > arc_c)
2359 2370 arc_p = arc_c;
2360 2371 }
2361 2372 ASSERT((int64_t)arc_p >= 0);
2362 2373 }
2363 2374
2364 2375 /*
2365 2376 * Check if the cache has reached its limits and eviction is required
2366 2377 * prior to insert.
2367 2378 */
2368 2379 static int
2369 2380 arc_evict_needed(arc_buf_contents_t type)
2370 2381 {
2371 2382 if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
2372 2383 return (1);
2373 2384
2374 2385 if (arc_reclaim_needed())
2375 2386 return (1);
2376 2387
2377 2388 return (arc_size > arc_c);
2378 2389 }
2379 2390
2380 2391 /*
2381 2392 * The buffer, supplied as the first argument, needs a data block.
2382 2393 * So, if we are at cache max, determine which cache should be victimized.
2383 2394 * We have the following cases:
2384 2395 *
2385 2396 * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
2386 2397 * In this situation if we're out of space, but the resident size of the MFU is
2387 2398 * under the limit, victimize the MFU cache to satisfy this insertion request.
2388 2399 *
2389 2400 * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
2390 2401 * Here, we've used up all of the available space for the MRU, so we need to
2391 2402 * evict from our own cache instead. Evict from the set of resident MRU
2392 2403 * entries.
2393 2404 *
2394 2405 * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
2395 2406 * c minus p represents the MFU space in the cache, since p is the size of the
2396 2407 * cache that is dedicated to the MRU. In this situation there's still space on
2397 2408 * the MFU side, so the MRU side needs to be victimized.
2398 2409 *
2399 2410 * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
2400 2411 * MFU's resident set is consuming more space than it has been allotted. In
2401 2412 * this situation, we must victimize our own cache, the MFU, for this insertion.
2402 2413 */
2403 2414 static void
2404 2415 arc_get_data_buf(arc_buf_t *buf)
2405 2416 {
2406 2417 arc_state_t *state = buf->b_hdr->b_state;
2407 2418 uint64_t size = buf->b_hdr->b_size;
2408 2419 arc_buf_contents_t type = buf->b_hdr->b_type;
2409 2420
2410 2421 arc_adapt(size, state);
2411 2422
2412 2423 /*
2413 2424 * We have not yet reached cache maximum size,
2414 2425 * just allocate a new buffer.
2415 2426 */
2416 2427 if (!arc_evict_needed(type)) {
2417 2428 if (type == ARC_BUFC_METADATA) {
2418 2429 buf->b_data = zio_buf_alloc(size);
2419 2430 arc_space_consume(size, ARC_SPACE_DATA);
2420 2431 } else {
2421 2432 ASSERT(type == ARC_BUFC_DATA);
2422 2433 buf->b_data = zio_data_buf_alloc(size);
2423 2434 ARCSTAT_INCR(arcstat_data_size, size);
2424 2435 atomic_add_64(&arc_size, size);
2425 2436 }
2426 2437 goto out;
2427 2438 }
2428 2439
2429 2440 /*
2430 2441 * If we are prefetching from the mfu ghost list, this buffer
2431 2442 * will end up on the mru list; so steal space from there.
2432 2443 */
2433 2444 if (state == arc_mfu_ghost)
2434 2445 state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
2435 2446 else if (state == arc_mru_ghost)
2436 2447 state = arc_mru;
2437 2448
2438 2449 if (state == arc_mru || state == arc_anon) {
2439 2450 uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
2440 2451 state = (arc_mfu->arcs_lsize[type] >= size &&
2441 2452 arc_p > mru_used) ? arc_mfu : arc_mru;
2442 2453 } else {
2443 2454 /* MFU cases */
2444 2455 uint64_t mfu_space = arc_c - arc_p;
2445 2456 state = (arc_mru->arcs_lsize[type] >= size &&
2446 2457 mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
2447 2458 }
2448 2459 if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
2449 2460 if (type == ARC_BUFC_METADATA) {
2450 2461 buf->b_data = zio_buf_alloc(size);
2451 2462 arc_space_consume(size, ARC_SPACE_DATA);
2452 2463 } else {
2453 2464 ASSERT(type == ARC_BUFC_DATA);
2454 2465 buf->b_data = zio_data_buf_alloc(size);
2455 2466 ARCSTAT_INCR(arcstat_data_size, size);
2456 2467 atomic_add_64(&arc_size, size);
2457 2468 }
2458 2469 ARCSTAT_BUMP(arcstat_recycle_miss);
2459 2470 }
2460 2471 ASSERT(buf->b_data != NULL);
2461 2472 out:
2462 2473 /*
2463 2474 * Update the state size. Note that ghost states have a
2464 2475 * "ghost size" and so don't need to be updated.
2465 2476 */
2466 2477 if (!GHOST_STATE(buf->b_hdr->b_state)) {
2467 2478 arc_buf_hdr_t *hdr = buf->b_hdr;
2468 2479
2469 2480 atomic_add_64(&hdr->b_state->arcs_size, size);
2470 2481 if (list_link_active(&hdr->b_arc_node)) {
2471 2482 ASSERT(refcount_is_zero(&hdr->b_refcnt));
2472 2483 atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
2473 2484 }
2474 2485 /*
2475 2486 * If we are growing the cache, and we are adding anonymous
2476 2487 * data, and we have outgrown arc_p, update arc_p
2477 2488 */
2478 2489 if (arc_size < arc_c && hdr->b_state == arc_anon &&
2479 2490 arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
2480 2491 arc_p = MIN(arc_c, arc_p + size);
2481 2492 }
2482 2493 }
2483 2494
2484 2495 /*
2485 2496 * This routine is called whenever a buffer is accessed.
2486 2497 * NOTE: the hash lock is dropped in this function.
2487 2498 */
2488 2499 static void
2489 2500 arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
2490 2501 {
2491 2502 clock_t now;
2492 2503
2493 2504 ASSERT(MUTEX_HELD(hash_lock));
2494 2505
2495 2506 if (buf->b_state == arc_anon) {
2496 2507 /*
2497 2508 * This buffer is not in the cache, and does not
2498 2509 * appear in our "ghost" list. Add the new buffer
2499 2510 * to the MRU state.
2500 2511 */
2501 2512
2502 2513 ASSERT(buf->b_arc_access == 0);
2503 2514 buf->b_arc_access = ddi_get_lbolt();
2504 2515 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2505 2516 arc_change_state(arc_mru, buf, hash_lock);
2506 2517
2507 2518 } else if (buf->b_state == arc_mru) {
2508 2519 now = ddi_get_lbolt();
2509 2520
2510 2521 /*
2511 2522 * If this buffer is here because of a prefetch, then either:
2512 2523 * - clear the flag if this is a "referencing" read
2513 2524 * (any subsequent access will bump this into the MFU state).
2514 2525 * or
2515 2526 * - move the buffer to the head of the list if this is
2516 2527 * another prefetch (to make it less likely to be evicted).
2517 2528 */
2518 2529 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2519 2530 if (refcount_count(&buf->b_refcnt) == 0) {
2520 2531 ASSERT(list_link_active(&buf->b_arc_node));
2521 2532 } else {
2522 2533 buf->b_flags &= ~ARC_PREFETCH;
2523 2534 ARCSTAT_BUMP(arcstat_mru_hits);
2524 2535 }
2525 2536 buf->b_arc_access = now;
2526 2537 return;
2527 2538 }
2528 2539
2529 2540 /*
2530 2541 * This buffer has been "accessed" only once so far,
2531 2542 * but it is still in the cache. Move it to the MFU
2532 2543 * state.
2533 2544 */
2534 2545 if (now > buf->b_arc_access + ARC_MINTIME) {
2535 2546 /*
2536 2547 * More than 125ms have passed since we
2537 2548 * instantiated this buffer. Move it to the
2538 2549 * most frequently used state.
2539 2550 */
2540 2551 buf->b_arc_access = now;
2541 2552 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2542 2553 arc_change_state(arc_mfu, buf, hash_lock);
2543 2554 }
2544 2555 ARCSTAT_BUMP(arcstat_mru_hits);
2545 2556 } else if (buf->b_state == arc_mru_ghost) {
2546 2557 arc_state_t *new_state;
2547 2558 /*
2548 2559 * This buffer has been "accessed" recently, but
2549 2560 * was evicted from the cache. Move it to the
2550 2561 * MFU state.
2551 2562 */
2552 2563
2553 2564 if (buf->b_flags & ARC_PREFETCH) {
2554 2565 new_state = arc_mru;
2555 2566 if (refcount_count(&buf->b_refcnt) > 0)
2556 2567 buf->b_flags &= ~ARC_PREFETCH;
2557 2568 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
2558 2569 } else {
2559 2570 new_state = arc_mfu;
2560 2571 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2561 2572 }
2562 2573
2563 2574 buf->b_arc_access = ddi_get_lbolt();
2564 2575 arc_change_state(new_state, buf, hash_lock);
2565 2576
2566 2577 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
2567 2578 } else if (buf->b_state == arc_mfu) {
2568 2579 /*
2569 2580 * This buffer has been accessed more than once and is
2570 2581 * still in the cache. Keep it in the MFU state.
2571 2582 *
2572 2583 * NOTE: an add_reference() that occurred when we did
2573 2584 * the arc_read() will have kicked this off the list.
2574 2585 * If it was a prefetch, we will explicitly move it to
2575 2586 * the head of the list now.
2576 2587 */
2577 2588 if ((buf->b_flags & ARC_PREFETCH) != 0) {
2578 2589 ASSERT(refcount_count(&buf->b_refcnt) == 0);
2579 2590 ASSERT(list_link_active(&buf->b_arc_node));
2580 2591 }
2581 2592 ARCSTAT_BUMP(arcstat_mfu_hits);
2582 2593 buf->b_arc_access = ddi_get_lbolt();
2583 2594 } else if (buf->b_state == arc_mfu_ghost) {
2584 2595 arc_state_t *new_state = arc_mfu;
2585 2596 /*
2586 2597 * This buffer has been accessed more than once but has
2587 2598 * been evicted from the cache. Move it back to the
2588 2599 * MFU state.
2589 2600 */
2590 2601
2591 2602 if (buf->b_flags & ARC_PREFETCH) {
2592 2603 /*
2593 2604 * This is a prefetch access...
2594 2605 * move this block back to the MRU state.
2595 2606 */
2596 2607 ASSERT0(refcount_count(&buf->b_refcnt));
2597 2608 new_state = arc_mru;
2598 2609 }
2599 2610
2600 2611 buf->b_arc_access = ddi_get_lbolt();
2601 2612 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2602 2613 arc_change_state(new_state, buf, hash_lock);
2603 2614
2604 2615 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
2605 2616 } else if (buf->b_state == arc_l2c_only) {
2606 2617 /*
2607 2618 * This buffer is on the 2nd Level ARC.
2608 2619 */
2609 2620
2610 2621 buf->b_arc_access = ddi_get_lbolt();
2611 2622 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
2612 2623 arc_change_state(arc_mfu, buf, hash_lock);
2613 2624 } else {
2614 2625 ASSERT(!"invalid arc state");
2615 2626 }
2616 2627 }
2617 2628
2618 2629 /* a generic arc_done_func_t which you can use */
2619 2630 /* ARGSUSED */
2620 2631 void
2621 2632 arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
2622 2633 {
2623 2634 if (zio == NULL || zio->io_error == 0)
2624 2635 bcopy(buf->b_data, arg, buf->b_hdr->b_size);
2625 2636 VERIFY(arc_buf_remove_ref(buf, arg));
2626 2637 }
2627 2638
2628 2639 /* a generic arc_done_func_t */
2629 2640 void
2630 2641 arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
2631 2642 {
2632 2643 arc_buf_t **bufp = arg;
2633 2644 if (zio && zio->io_error) {
2634 2645 VERIFY(arc_buf_remove_ref(buf, arg));
2635 2646 *bufp = NULL;
2636 2647 } else {
2637 2648 *bufp = buf;
2638 2649 ASSERT(buf->b_data);
2639 2650 }
2640 2651 }
2641 2652
2642 2653 static void
2643 2654 arc_read_done(zio_t *zio)
2644 2655 {
2645 2656 arc_buf_hdr_t *hdr, *found;
2646 2657 arc_buf_t *buf;
2647 2658 arc_buf_t *abuf; /* buffer we're assigning to callback */
2648 2659 kmutex_t *hash_lock;
2649 2660 arc_callback_t *callback_list, *acb;
2650 2661 int freeable = FALSE;
2651 2662
2652 2663 buf = zio->io_private;
2653 2664 hdr = buf->b_hdr;
2654 2665
2655 2666 /*
2656 2667 * The hdr was inserted into hash-table and removed from lists
2657 2668 * prior to starting I/O. We should find this header, since
2658 2669 * it's in the hash table, and it should be legit since it's
2659 2670 * not possible to evict it during the I/O. The only possible
2660 2671 * reason for it not to be found is if we were freed during the
2661 2672 * read.
2662 2673 */
2663 2674 found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
2664 2675 &hash_lock);
2665 2676
2666 2677 ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
2667 2678 (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
2668 2679 (found == hdr && HDR_L2_READING(hdr)));
2669 2680
2670 2681 hdr->b_flags &= ~ARC_L2_EVICTED;
2671 2682 if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
2672 2683 hdr->b_flags &= ~ARC_L2CACHE;
2673 2684
2674 2685 /* byteswap if necessary */
2675 2686 callback_list = hdr->b_acb;
2676 2687 ASSERT(callback_list != NULL);
2677 2688 if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
2678 2689 dmu_object_byteswap_t bswap =
2679 2690 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
2680 2691 arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
2681 2692 byteswap_uint64_array :
2682 2693 dmu_ot_byteswap[bswap].ob_func;
2683 2694 func(buf->b_data, hdr->b_size);
2684 2695 }
2685 2696
2686 2697 arc_cksum_compute(buf, B_FALSE);
2687 2698 arc_buf_watch(buf);
2688 2699
2689 2700 if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
2690 2701 /*
2691 2702 * Only call arc_access on anonymous buffers. This is because
2692 2703 * if we've issued an I/O for an evicted buffer, we've already
2693 2704 * called arc_access (to prevent any simultaneous readers from
2694 2705 * getting confused).
2695 2706 */
2696 2707 arc_access(hdr, hash_lock);
2697 2708 }
2698 2709
2699 2710 /* create copies of the data buffer for the callers */
2700 2711 abuf = buf;
2701 2712 for (acb = callback_list; acb; acb = acb->acb_next) {
2702 2713 if (acb->acb_done) {
2703 2714 if (abuf == NULL) {
2704 2715 ARCSTAT_BUMP(arcstat_duplicate_reads);
2705 2716 abuf = arc_buf_clone(buf);
2706 2717 }
2707 2718 acb->acb_buf = abuf;
2708 2719 abuf = NULL;
2709 2720 }
2710 2721 }
2711 2722 hdr->b_acb = NULL;
2712 2723 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
2713 2724 ASSERT(!HDR_BUF_AVAILABLE(hdr));
2714 2725 if (abuf == buf) {
2715 2726 ASSERT(buf->b_efunc == NULL);
2716 2727 ASSERT(hdr->b_datacnt == 1);
2717 2728 hdr->b_flags |= ARC_BUF_AVAILABLE;
2718 2729 }
2719 2730
2720 2731 ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
2721 2732
2722 2733 if (zio->io_error != 0) {
2723 2734 hdr->b_flags |= ARC_IO_ERROR;
2724 2735 if (hdr->b_state != arc_anon)
2725 2736 arc_change_state(arc_anon, hdr, hash_lock);
2726 2737 if (HDR_IN_HASH_TABLE(hdr))
2727 2738 buf_hash_remove(hdr);
2728 2739 freeable = refcount_is_zero(&hdr->b_refcnt);
2729 2740 }
2730 2741
2731 2742 /*
2732 2743 * Broadcast before we drop the hash_lock to avoid the possibility
2733 2744 * that the hdr (and hence the cv) might be freed before we get to
2734 2745 * the cv_broadcast().
2735 2746 */
2736 2747 cv_broadcast(&hdr->b_cv);
2737 2748
2738 2749 if (hash_lock) {
2739 2750 mutex_exit(hash_lock);
2740 2751 } else {
2741 2752 /*
2742 2753 * This block was freed while we waited for the read to
2743 2754 * complete. It has been removed from the hash table and
2744 2755 * moved to the anonymous state (so that it won't show up
2745 2756 * in the cache).
2746 2757 */
2747 2758 ASSERT3P(hdr->b_state, ==, arc_anon);
2748 2759 freeable = refcount_is_zero(&hdr->b_refcnt);
2749 2760 }
2750 2761
2751 2762 /* execute each callback and free its structure */
2752 2763 while ((acb = callback_list) != NULL) {
2753 2764 if (acb->acb_done)
2754 2765 acb->acb_done(zio, acb->acb_buf, acb->acb_private);
2755 2766
2756 2767 if (acb->acb_zio_dummy != NULL) {
2757 2768 acb->acb_zio_dummy->io_error = zio->io_error;
2758 2769 zio_nowait(acb->acb_zio_dummy);
2759 2770 }
2760 2771
2761 2772 callback_list = acb->acb_next;
2762 2773 kmem_free(acb, sizeof (arc_callback_t));
2763 2774 }
2764 2775
2765 2776 if (freeable)
2766 2777 arc_hdr_destroy(hdr);
2767 2778 }
2768 2779
2769 2780 /*
2770 2781 * "Read" the block at the specified DVA (in bp) via the
2771 2782 * cache. If the block is found in the cache, invoke the provided
2772 2783 * callback immediately and return. Note that the `zio' parameter
2773 2784 * in the callback will be NULL in this case, since no IO was
2774 2785 * required. If the block is not in the cache pass the read request
2775 2786 * on to the spa with a substitute callback function, so that the
2776 2787 * requested block will be added to the cache.
2777 2788 *
2778 2789 * If a read request arrives for a block that has a read in-progress,
2779 2790 * either wait for the in-progress read to complete (and return the
2780 2791 * results); or, if this is a read with a "done" func, add a record
2781 2792 * to the read to invoke the "done" func when the read completes,
2782 2793 * and return; or just return.
2783 2794 *
2784 2795 * arc_read_done() will invoke all the requested "done" functions
2785 2796 * for readers of this block.
2786 2797 */
2787 2798 int
2788 2799 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
2789 2800 void *private, int priority, int zio_flags, uint32_t *arc_flags,
2790 2801 const zbookmark_t *zb)
2791 2802 {
2792 2803 arc_buf_hdr_t *hdr;
2793 2804 arc_buf_t *buf = NULL;
2794 2805 kmutex_t *hash_lock;
2795 2806 zio_t *rzio;
2796 2807 uint64_t guid = spa_load_guid(spa);
2797 2808
2798 2809 top:
2799 2810 hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
2800 2811 &hash_lock);
2801 2812 if (hdr && hdr->b_datacnt > 0) {
2802 2813
2803 2814 *arc_flags |= ARC_CACHED;
2804 2815
2805 2816 if (HDR_IO_IN_PROGRESS(hdr)) {
2806 2817
2807 2818 if (*arc_flags & ARC_WAIT) {
2808 2819 cv_wait(&hdr->b_cv, hash_lock);
2809 2820 mutex_exit(hash_lock);
2810 2821 goto top;
2811 2822 }
2812 2823 ASSERT(*arc_flags & ARC_NOWAIT);
2813 2824
2814 2825 if (done) {
2815 2826 arc_callback_t *acb = NULL;
2816 2827
2817 2828 acb = kmem_zalloc(sizeof (arc_callback_t),
2818 2829 KM_SLEEP);
2819 2830 acb->acb_done = done;
2820 2831 acb->acb_private = private;
2821 2832 if (pio != NULL)
2822 2833 acb->acb_zio_dummy = zio_null(pio,
2823 2834 spa, NULL, NULL, NULL, zio_flags);
2824 2835
2825 2836 ASSERT(acb->acb_done != NULL);
2826 2837 acb->acb_next = hdr->b_acb;
2827 2838 hdr->b_acb = acb;
2828 2839 add_reference(hdr, hash_lock, private);
2829 2840 mutex_exit(hash_lock);
2830 2841 return (0);
2831 2842 }
2832 2843 mutex_exit(hash_lock);
2833 2844 return (0);
2834 2845 }
2835 2846
2836 2847 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
2837 2848
2838 2849 if (done) {
2839 2850 add_reference(hdr, hash_lock, private);
2840 2851 /*
2841 2852 * If this block is already in use, create a new
2842 2853 * copy of the data so that we will be guaranteed
2843 2854 * that arc_release() will always succeed.
2844 2855 */
2845 2856 buf = hdr->b_buf;
2846 2857 ASSERT(buf);
2847 2858 ASSERT(buf->b_data);
2848 2859 if (HDR_BUF_AVAILABLE(hdr)) {
2849 2860 ASSERT(buf->b_efunc == NULL);
2850 2861 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
2851 2862 } else {
2852 2863 buf = arc_buf_clone(buf);
2853 2864 }
2854 2865
2855 2866 } else if (*arc_flags & ARC_PREFETCH &&
2856 2867 refcount_count(&hdr->b_refcnt) == 0) {
2857 2868 hdr->b_flags |= ARC_PREFETCH;
2858 2869 }
2859 2870 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
2860 2871 arc_access(hdr, hash_lock);
2861 2872 if (*arc_flags & ARC_L2CACHE)
2862 2873 hdr->b_flags |= ARC_L2CACHE;
2863 2874 mutex_exit(hash_lock);
2864 2875 ARCSTAT_BUMP(arcstat_hits);
2865 2876 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2866 2877 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2867 2878 data, metadata, hits);
2868 2879
2869 2880 if (done)
2870 2881 done(NULL, buf, private);
2871 2882 } else {
2872 2883 uint64_t size = BP_GET_LSIZE(bp);
2873 2884 arc_callback_t *acb;
2874 2885 vdev_t *vd = NULL;
2875 2886 uint64_t addr = 0;
2876 2887 boolean_t devw = B_FALSE;
2877 2888
2878 2889 if (hdr == NULL) {
2879 2890 /* this block is not in the cache */
2880 2891 arc_buf_hdr_t *exists;
2881 2892 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
2882 2893 buf = arc_buf_alloc(spa, size, private, type);
2883 2894 hdr = buf->b_hdr;
2884 2895 hdr->b_dva = *BP_IDENTITY(bp);
2885 2896 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
2886 2897 hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
2887 2898 exists = buf_hash_insert(hdr, &hash_lock);
2888 2899 if (exists) {
2889 2900 /* somebody beat us to the hash insert */
2890 2901 mutex_exit(hash_lock);
2891 2902 buf_discard_identity(hdr);
2892 2903 (void) arc_buf_remove_ref(buf, private);
2893 2904 goto top; /* restart the IO request */
2894 2905 }
2895 2906 /* if this is a prefetch, we don't have a reference */
2896 2907 if (*arc_flags & ARC_PREFETCH) {
2897 2908 (void) remove_reference(hdr, hash_lock,
2898 2909 private);
2899 2910 hdr->b_flags |= ARC_PREFETCH;
2900 2911 }
2901 2912 if (*arc_flags & ARC_L2CACHE)
2902 2913 hdr->b_flags |= ARC_L2CACHE;
2903 2914 if (BP_GET_LEVEL(bp) > 0)
2904 2915 hdr->b_flags |= ARC_INDIRECT;
2905 2916 } else {
2906 2917 /* this block is in the ghost cache */
2907 2918 ASSERT(GHOST_STATE(hdr->b_state));
2908 2919 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
2909 2920 ASSERT0(refcount_count(&hdr->b_refcnt));
2910 2921 ASSERT(hdr->b_buf == NULL);
2911 2922
2912 2923 /* if this is a prefetch, we don't have a reference */
2913 2924 if (*arc_flags & ARC_PREFETCH)
2914 2925 hdr->b_flags |= ARC_PREFETCH;
2915 2926 else
2916 2927 add_reference(hdr, hash_lock, private);
2917 2928 if (*arc_flags & ARC_L2CACHE)
2918 2929 hdr->b_flags |= ARC_L2CACHE;
2919 2930 buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2920 2931 buf->b_hdr = hdr;
2921 2932 buf->b_data = NULL;
2922 2933 buf->b_efunc = NULL;
2923 2934 buf->b_private = NULL;
2924 2935 buf->b_next = NULL;
2925 2936 hdr->b_buf = buf;
2926 2937 ASSERT(hdr->b_datacnt == 0);
2927 2938 hdr->b_datacnt = 1;
2928 2939 arc_get_data_buf(buf);
2929 2940 arc_access(hdr, hash_lock);
2930 2941 }
2931 2942
2932 2943 ASSERT(!GHOST_STATE(hdr->b_state));
2933 2944
2934 2945 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
2935 2946 acb->acb_done = done;
2936 2947 acb->acb_private = private;
2937 2948
2938 2949 ASSERT(hdr->b_acb == NULL);
2939 2950 hdr->b_acb = acb;
2940 2951 hdr->b_flags |= ARC_IO_IN_PROGRESS;
2941 2952
2942 2953 if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
2943 2954 (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
2944 2955 devw = hdr->b_l2hdr->b_dev->l2ad_writing;
2945 2956 addr = hdr->b_l2hdr->b_daddr;
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2946 2957 /*
2947 2958 * Lock out device removal.
2948 2959 */
2949 2960 if (vdev_is_dead(vd) ||
2950 2961 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
2951 2962 vd = NULL;
2952 2963 }
2953 2964
2954 2965 mutex_exit(hash_lock);
2955 2966
2967 + /*
2968 + * At this point, we have a level 1 cache miss. Try again in
2969 + * L2ARC if possible.
2970 + */
2956 2971 ASSERT3U(hdr->b_size, ==, size);
2957 2972 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
2958 2973 uint64_t, size, zbookmark_t *, zb);
2959 2974 ARCSTAT_BUMP(arcstat_misses);
2960 2975 ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
2961 2976 demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
2962 2977 data, metadata, misses);
2963 2978
2964 2979 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
2965 2980 /*
2966 2981 * Read from the L2ARC if the following are true:
2967 2982 * 1. The L2ARC vdev was previously cached.
2968 2983 * 2. This buffer still has L2ARC metadata.
2969 2984 * 3. This buffer isn't currently writing to the L2ARC.
2970 2985 * 4. The L2ARC entry wasn't evicted, which may
2971 2986 * also have invalidated the vdev.
2972 2987 * 5. This isn't prefetch and l2arc_noprefetch is set.
2973 2988 */
2974 2989 if (hdr->b_l2hdr != NULL &&
2975 2990 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
2976 2991 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
2977 2992 l2arc_read_callback_t *cb;
2978 2993
2979 2994 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
2980 2995 ARCSTAT_BUMP(arcstat_l2_hits);
2981 2996
2982 2997 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
2983 2998 KM_SLEEP);
2984 2999 cb->l2rcb_buf = buf;
2985 3000 cb->l2rcb_spa = spa;
2986 3001 cb->l2rcb_bp = *bp;
2987 3002 cb->l2rcb_zb = *zb;
2988 3003 cb->l2rcb_flags = zio_flags;
2989 3004
2990 3005 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
2991 3006 addr + size < vd->vdev_psize -
2992 3007 VDEV_LABEL_END_SIZE);
2993 3008
2994 3009 /*
2995 3010 * l2arc read. The SCL_L2ARC lock will be
2996 3011 * released by l2arc_read_done().
2997 3012 */
2998 3013 rzio = zio_read_phys(pio, vd, addr, size,
2999 3014 buf->b_data, ZIO_CHECKSUM_OFF,
3000 3015 l2arc_read_done, cb, priority, zio_flags |
3001 3016 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
3002 3017 ZIO_FLAG_DONT_PROPAGATE |
3003 3018 ZIO_FLAG_DONT_RETRY, B_FALSE);
3004 3019 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
3005 3020 zio_t *, rzio);
3006 3021 ARCSTAT_INCR(arcstat_l2_read_bytes, size);
3007 3022
3008 3023 if (*arc_flags & ARC_NOWAIT) {
3009 3024 zio_nowait(rzio);
3010 3025 return (0);
3011 3026 }
3012 3027
3013 3028 ASSERT(*arc_flags & ARC_WAIT);
3014 3029 if (zio_wait(rzio) == 0)
3015 3030 return (0);
3016 3031
3017 3032 /* l2arc read error; goto zio_read() */
3018 3033 } else {
3019 3034 DTRACE_PROBE1(l2arc__miss,
3020 3035 arc_buf_hdr_t *, hdr);
3021 3036 ARCSTAT_BUMP(arcstat_l2_misses);
3022 3037 if (HDR_L2_WRITING(hdr))
3023 3038 ARCSTAT_BUMP(arcstat_l2_rw_clash);
3024 3039 spa_config_exit(spa, SCL_L2ARC, vd);
3025 3040 }
3026 3041 } else {
3027 3042 if (vd != NULL)
3028 3043 spa_config_exit(spa, SCL_L2ARC, vd);
3029 3044 if (l2arc_ndev != 0) {
3030 3045 DTRACE_PROBE1(l2arc__miss,
3031 3046 arc_buf_hdr_t *, hdr);
3032 3047 ARCSTAT_BUMP(arcstat_l2_misses);
3033 3048 }
3034 3049 }
3035 3050
3036 3051 rzio = zio_read(pio, spa, bp, buf->b_data, size,
3037 3052 arc_read_done, buf, priority, zio_flags, zb);
3038 3053
3039 3054 if (*arc_flags & ARC_WAIT)
3040 3055 return (zio_wait(rzio));
3041 3056
3042 3057 ASSERT(*arc_flags & ARC_NOWAIT);
3043 3058 zio_nowait(rzio);
3044 3059 }
3045 3060 return (0);
3046 3061 }
3047 3062
3048 3063 void
3049 3064 arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
3050 3065 {
3051 3066 ASSERT(buf->b_hdr != NULL);
3052 3067 ASSERT(buf->b_hdr->b_state != arc_anon);
3053 3068 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
3054 3069 ASSERT(buf->b_efunc == NULL);
3055 3070 ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
3056 3071
3057 3072 buf->b_efunc = func;
3058 3073 buf->b_private = private;
3059 3074 }
3060 3075
3061 3076 /*
3062 3077 * This is used by the DMU to let the ARC know that a buffer is
3063 3078 * being evicted, so the ARC should clean up. If this arc buf
3064 3079 * is not yet in the evicted state, it will be put there.
3065 3080 */
3066 3081 int
3067 3082 arc_buf_evict(arc_buf_t *buf)
3068 3083 {
3069 3084 arc_buf_hdr_t *hdr;
3070 3085 kmutex_t *hash_lock;
3071 3086 arc_buf_t **bufp;
3072 3087
3073 3088 mutex_enter(&buf->b_evict_lock);
3074 3089 hdr = buf->b_hdr;
3075 3090 if (hdr == NULL) {
3076 3091 /*
3077 3092 * We are in arc_do_user_evicts().
3078 3093 */
3079 3094 ASSERT(buf->b_data == NULL);
3080 3095 mutex_exit(&buf->b_evict_lock);
3081 3096 return (0);
3082 3097 } else if (buf->b_data == NULL) {
3083 3098 arc_buf_t copy = *buf; /* structure assignment */
3084 3099 /*
3085 3100 * We are on the eviction list; process this buffer now
3086 3101 * but let arc_do_user_evicts() do the reaping.
3087 3102 */
3088 3103 buf->b_efunc = NULL;
3089 3104 mutex_exit(&buf->b_evict_lock);
3090 3105 VERIFY(copy.b_efunc(©) == 0);
3091 3106 return (1);
3092 3107 }
3093 3108 hash_lock = HDR_LOCK(hdr);
3094 3109 mutex_enter(hash_lock);
3095 3110 hdr = buf->b_hdr;
3096 3111 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3097 3112
3098 3113 ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
3099 3114 ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
3100 3115
3101 3116 /*
3102 3117 * Pull this buffer off of the hdr
3103 3118 */
3104 3119 bufp = &hdr->b_buf;
3105 3120 while (*bufp != buf)
3106 3121 bufp = &(*bufp)->b_next;
3107 3122 *bufp = buf->b_next;
3108 3123
3109 3124 ASSERT(buf->b_data != NULL);
3110 3125 arc_buf_destroy(buf, FALSE, FALSE);
3111 3126
3112 3127 if (hdr->b_datacnt == 0) {
3113 3128 arc_state_t *old_state = hdr->b_state;
3114 3129 arc_state_t *evicted_state;
3115 3130
3116 3131 ASSERT(hdr->b_buf == NULL);
3117 3132 ASSERT(refcount_is_zero(&hdr->b_refcnt));
3118 3133
3119 3134 evicted_state =
3120 3135 (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3121 3136
3122 3137 mutex_enter(&old_state->arcs_mtx);
3123 3138 mutex_enter(&evicted_state->arcs_mtx);
3124 3139
3125 3140 arc_change_state(evicted_state, hdr, hash_lock);
3126 3141 ASSERT(HDR_IN_HASH_TABLE(hdr));
3127 3142 hdr->b_flags |= ARC_IN_HASH_TABLE;
3128 3143 hdr->b_flags &= ~ARC_BUF_AVAILABLE;
3129 3144
3130 3145 mutex_exit(&evicted_state->arcs_mtx);
3131 3146 mutex_exit(&old_state->arcs_mtx);
3132 3147 }
3133 3148 mutex_exit(hash_lock);
3134 3149 mutex_exit(&buf->b_evict_lock);
3135 3150
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3136 3151 VERIFY(buf->b_efunc(buf) == 0);
3137 3152 buf->b_efunc = NULL;
3138 3153 buf->b_private = NULL;
3139 3154 buf->b_hdr = NULL;
3140 3155 buf->b_next = NULL;
3141 3156 kmem_cache_free(buf_cache, buf);
3142 3157 return (1);
3143 3158 }
3144 3159
3145 3160 /*
3146 - * Release this buffer from the cache. This must be done
3147 - * after a read and prior to modifying the buffer contents.
3161 + * Release this buffer from the cache, making it an anonymous buffer. This
3162 + * must be done after a read and prior to modifying the buffer contents.
3148 3163 * If the buffer has more than one reference, we must make
3149 3164 * a new hdr for the buffer.
3150 3165 */
3151 3166 void
3152 3167 arc_release(arc_buf_t *buf, void *tag)
3153 3168 {
3154 3169 arc_buf_hdr_t *hdr;
3155 3170 kmutex_t *hash_lock = NULL;
3156 3171 l2arc_buf_hdr_t *l2hdr;
3157 3172 uint64_t buf_size;
3158 3173
3159 3174 /*
3160 3175 * It would be nice to assert that if it's DMU metadata (level >
3161 3176 * 0 || it's the dnode file), then it must be syncing context.
3162 3177 * But we don't know that information at this level.
3163 3178 */
3164 3179
3165 3180 mutex_enter(&buf->b_evict_lock);
3166 3181 hdr = buf->b_hdr;
3167 3182
3168 3183 /* this buffer is not on any list */
3169 3184 ASSERT(refcount_count(&hdr->b_refcnt) > 0);
3170 3185
3171 3186 if (hdr->b_state == arc_anon) {
3172 3187 /* this buffer is already released */
3173 3188 ASSERT(buf->b_efunc == NULL);
3174 3189 } else {
3175 3190 hash_lock = HDR_LOCK(hdr);
3176 3191 mutex_enter(hash_lock);
3177 3192 hdr = buf->b_hdr;
3178 3193 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3179 3194 }
3180 3195
3181 3196 l2hdr = hdr->b_l2hdr;
3182 3197 if (l2hdr) {
3183 3198 mutex_enter(&l2arc_buflist_mtx);
3184 3199 hdr->b_l2hdr = NULL;
3185 3200 }
3186 3201 buf_size = hdr->b_size;
3187 3202
3188 3203 /*
3189 3204 * Do we have more than one buf?
3190 3205 */
3191 3206 if (hdr->b_datacnt > 1) {
3192 3207 arc_buf_hdr_t *nhdr;
3193 3208 arc_buf_t **bufp;
3194 3209 uint64_t blksz = hdr->b_size;
3195 3210 uint64_t spa = hdr->b_spa;
3196 3211 arc_buf_contents_t type = hdr->b_type;
3197 3212 uint32_t flags = hdr->b_flags;
3198 3213
3199 3214 ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
3200 3215 /*
3201 3216 * Pull the data off of this hdr and attach it to
3202 3217 * a new anonymous hdr.
3203 3218 */
3204 3219 (void) remove_reference(hdr, hash_lock, tag);
3205 3220 bufp = &hdr->b_buf;
3206 3221 while (*bufp != buf)
3207 3222 bufp = &(*bufp)->b_next;
3208 3223 *bufp = buf->b_next;
3209 3224 buf->b_next = NULL;
3210 3225
3211 3226 ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
3212 3227 atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
3213 3228 if (refcount_is_zero(&hdr->b_refcnt)) {
3214 3229 uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
3215 3230 ASSERT3U(*size, >=, hdr->b_size);
3216 3231 atomic_add_64(size, -hdr->b_size);
3217 3232 }
3218 3233
3219 3234 /*
3220 3235 * We're releasing a duplicate user data buffer, update
3221 3236 * our statistics accordingly.
3222 3237 */
3223 3238 if (hdr->b_type == ARC_BUFC_DATA) {
3224 3239 ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
3225 3240 ARCSTAT_INCR(arcstat_duplicate_buffers_size,
3226 3241 -hdr->b_size);
3227 3242 }
3228 3243 hdr->b_datacnt -= 1;
3229 3244 arc_cksum_verify(buf);
3230 3245 arc_buf_unwatch(buf);
3231 3246
3232 3247 mutex_exit(hash_lock);
3233 3248
3234 3249 nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
3235 3250 nhdr->b_size = blksz;
3236 3251 nhdr->b_spa = spa;
3237 3252 nhdr->b_type = type;
3238 3253 nhdr->b_buf = buf;
3239 3254 nhdr->b_state = arc_anon;
3240 3255 nhdr->b_arc_access = 0;
3241 3256 nhdr->b_flags = flags & ARC_L2_WRITING;
3242 3257 nhdr->b_l2hdr = NULL;
3243 3258 nhdr->b_datacnt = 1;
3244 3259 nhdr->b_freeze_cksum = NULL;
3245 3260 (void) refcount_add(&nhdr->b_refcnt, tag);
3246 3261 buf->b_hdr = nhdr;
3247 3262 mutex_exit(&buf->b_evict_lock);
3248 3263 atomic_add_64(&arc_anon->arcs_size, blksz);
3249 3264 } else {
3250 3265 mutex_exit(&buf->b_evict_lock);
3251 3266 ASSERT(refcount_count(&hdr->b_refcnt) == 1);
3252 3267 ASSERT(!list_link_active(&hdr->b_arc_node));
3253 3268 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3254 3269 if (hdr->b_state != arc_anon)
3255 3270 arc_change_state(arc_anon, hdr, hash_lock);
3256 3271 hdr->b_arc_access = 0;
3257 3272 if (hash_lock)
3258 3273 mutex_exit(hash_lock);
3259 3274
3260 3275 buf_discard_identity(hdr);
3261 3276 arc_buf_thaw(buf);
3262 3277 }
3263 3278 buf->b_efunc = NULL;
3264 3279 buf->b_private = NULL;
3265 3280
3266 3281 if (l2hdr) {
3267 3282 list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
3268 3283 kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
3269 3284 ARCSTAT_INCR(arcstat_l2_size, -buf_size);
3270 3285 mutex_exit(&l2arc_buflist_mtx);
3271 3286 }
3272 3287 }
3273 3288
3274 3289 int
3275 3290 arc_released(arc_buf_t *buf)
3276 3291 {
3277 3292 int released;
3278 3293
3279 3294 mutex_enter(&buf->b_evict_lock);
3280 3295 released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
3281 3296 mutex_exit(&buf->b_evict_lock);
3282 3297 return (released);
3283 3298 }
3284 3299
3285 3300 int
3286 3301 arc_has_callback(arc_buf_t *buf)
3287 3302 {
3288 3303 int callback;
3289 3304
3290 3305 mutex_enter(&buf->b_evict_lock);
3291 3306 callback = (buf->b_efunc != NULL);
3292 3307 mutex_exit(&buf->b_evict_lock);
3293 3308 return (callback);
3294 3309 }
3295 3310
3296 3311 #ifdef ZFS_DEBUG
3297 3312 int
3298 3313 arc_referenced(arc_buf_t *buf)
3299 3314 {
3300 3315 int referenced;
3301 3316
3302 3317 mutex_enter(&buf->b_evict_lock);
3303 3318 referenced = (refcount_count(&buf->b_hdr->b_refcnt));
3304 3319 mutex_exit(&buf->b_evict_lock);
3305 3320 return (referenced);
3306 3321 }
3307 3322 #endif
3308 3323
3309 3324 static void
3310 3325 arc_write_ready(zio_t *zio)
3311 3326 {
3312 3327 arc_write_callback_t *callback = zio->io_private;
3313 3328 arc_buf_t *buf = callback->awcb_buf;
3314 3329 arc_buf_hdr_t *hdr = buf->b_hdr;
3315 3330
3316 3331 ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
3317 3332 callback->awcb_ready(zio, buf, callback->awcb_private);
3318 3333
3319 3334 /*
3320 3335 * If the IO is already in progress, then this is a re-write
3321 3336 * attempt, so we need to thaw and re-compute the cksum.
3322 3337 * It is the responsibility of the callback to handle the
3323 3338 * accounting for any re-write attempt.
3324 3339 */
3325 3340 if (HDR_IO_IN_PROGRESS(hdr)) {
3326 3341 mutex_enter(&hdr->b_freeze_lock);
3327 3342 if (hdr->b_freeze_cksum != NULL) {
3328 3343 kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
3329 3344 hdr->b_freeze_cksum = NULL;
3330 3345 }
3331 3346 mutex_exit(&hdr->b_freeze_lock);
3332 3347 }
3333 3348 arc_cksum_compute(buf, B_FALSE);
3334 3349 hdr->b_flags |= ARC_IO_IN_PROGRESS;
3335 3350 }
3336 3351
3337 3352 static void
3338 3353 arc_write_done(zio_t *zio)
3339 3354 {
3340 3355 arc_write_callback_t *callback = zio->io_private;
3341 3356 arc_buf_t *buf = callback->awcb_buf;
3342 3357 arc_buf_hdr_t *hdr = buf->b_hdr;
3343 3358
3344 3359 ASSERT(hdr->b_acb == NULL);
3345 3360
3346 3361 if (zio->io_error == 0) {
3347 3362 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
3348 3363 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
3349 3364 hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
3350 3365 } else {
3351 3366 ASSERT(BUF_EMPTY(hdr));
3352 3367 }
3353 3368
3354 3369 /*
3355 3370 * If the block to be written was all-zero, we may have
3356 3371 * compressed it away. In this case no write was performed
3357 3372 * so there will be no dva/birth/checksum. The buffer must
3358 3373 * therefore remain anonymous (and uncached).
3359 3374 */
3360 3375 if (!BUF_EMPTY(hdr)) {
3361 3376 arc_buf_hdr_t *exists;
3362 3377 kmutex_t *hash_lock;
3363 3378
3364 3379 ASSERT(zio->io_error == 0);
3365 3380
3366 3381 arc_cksum_verify(buf);
3367 3382
3368 3383 exists = buf_hash_insert(hdr, &hash_lock);
3369 3384 if (exists) {
3370 3385 /*
3371 3386 * This can only happen if we overwrite for
3372 3387 * sync-to-convergence, because we remove
3373 3388 * buffers from the hash table when we arc_free().
3374 3389 */
3375 3390 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
3376 3391 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3377 3392 panic("bad overwrite, hdr=%p exists=%p",
3378 3393 (void *)hdr, (void *)exists);
3379 3394 ASSERT(refcount_is_zero(&exists->b_refcnt));
3380 3395 arc_change_state(arc_anon, exists, hash_lock);
3381 3396 mutex_exit(hash_lock);
3382 3397 arc_hdr_destroy(exists);
3383 3398 exists = buf_hash_insert(hdr, &hash_lock);
3384 3399 ASSERT3P(exists, ==, NULL);
3385 3400 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
3386 3401 /* nopwrite */
3387 3402 ASSERT(zio->io_prop.zp_nopwrite);
3388 3403 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
3389 3404 panic("bad nopwrite, hdr=%p exists=%p",
3390 3405 (void *)hdr, (void *)exists);
3391 3406 } else {
3392 3407 /* Dedup */
3393 3408 ASSERT(hdr->b_datacnt == 1);
3394 3409 ASSERT(hdr->b_state == arc_anon);
3395 3410 ASSERT(BP_GET_DEDUP(zio->io_bp));
3396 3411 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
3397 3412 }
3398 3413 }
3399 3414 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3400 3415 /* if it's not anon, we are doing a scrub */
3401 3416 if (!exists && hdr->b_state == arc_anon)
3402 3417 arc_access(hdr, hash_lock);
3403 3418 mutex_exit(hash_lock);
3404 3419 } else {
3405 3420 hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
3406 3421 }
3407 3422
3408 3423 ASSERT(!refcount_is_zero(&hdr->b_refcnt));
3409 3424 callback->awcb_done(zio, buf, callback->awcb_private);
3410 3425
3411 3426 kmem_free(callback, sizeof (arc_write_callback_t));
3412 3427 }
3413 3428
3414 3429 zio_t *
3415 3430 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
3416 3431 blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
3417 3432 arc_done_func_t *ready, arc_done_func_t *done, void *private,
3418 3433 int priority, int zio_flags, const zbookmark_t *zb)
3419 3434 {
3420 3435 arc_buf_hdr_t *hdr = buf->b_hdr;
3421 3436 arc_write_callback_t *callback;
3422 3437 zio_t *zio;
3423 3438
3424 3439 ASSERT(ready != NULL);
3425 3440 ASSERT(done != NULL);
3426 3441 ASSERT(!HDR_IO_ERROR(hdr));
3427 3442 ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
3428 3443 ASSERT(hdr->b_acb == NULL);
3429 3444 if (l2arc)
3430 3445 hdr->b_flags |= ARC_L2CACHE;
3431 3446 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
3432 3447 callback->awcb_ready = ready;
3433 3448 callback->awcb_done = done;
3434 3449 callback->awcb_private = private;
3435 3450 callback->awcb_buf = buf;
3436 3451
3437 3452 zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
3438 3453 arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
3439 3454
3440 3455 return (zio);
3441 3456 }
3442 3457
3443 3458 static int
3444 3459 arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
3445 3460 {
3446 3461 #ifdef _KERNEL
3447 3462 uint64_t available_memory = ptob(freemem);
3448 3463 static uint64_t page_load = 0;
3449 3464 static uint64_t last_txg = 0;
3450 3465
3451 3466 #if defined(__i386)
3452 3467 available_memory =
3453 3468 MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
3454 3469 #endif
3455 3470 if (available_memory >= zfs_write_limit_max)
3456 3471 return (0);
3457 3472
3458 3473 if (txg > last_txg) {
3459 3474 last_txg = txg;
3460 3475 page_load = 0;
3461 3476 }
3462 3477 /*
3463 3478 * If we are in pageout, we know that memory is already tight,
3464 3479 * the arc is already going to be evicting, so we just want to
3465 3480 * continue to let page writes occur as quickly as possible.
3466 3481 */
3467 3482 if (curproc == proc_pageout) {
3468 3483 if (page_load > MAX(ptob(minfree), available_memory) / 4)
3469 3484 return (SET_ERROR(ERESTART));
3470 3485 /* Note: reserve is inflated, so we deflate */
3471 3486 page_load += reserve / 8;
3472 3487 return (0);
3473 3488 } else if (page_load > 0 && arc_reclaim_needed()) {
3474 3489 /* memory is low, delay before restarting */
3475 3490 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3476 3491 return (SET_ERROR(EAGAIN));
3477 3492 }
3478 3493 page_load = 0;
3479 3494
3480 3495 if (arc_size > arc_c_min) {
3481 3496 uint64_t evictable_memory =
3482 3497 arc_mru->arcs_lsize[ARC_BUFC_DATA] +
3483 3498 arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
3484 3499 arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
3485 3500 arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
3486 3501 available_memory += MIN(evictable_memory, arc_size - arc_c_min);
3487 3502 }
3488 3503
3489 3504 if (inflight_data > available_memory / 4) {
3490 3505 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
3491 3506 return (SET_ERROR(ERESTART));
3492 3507 }
3493 3508 #endif
3494 3509 return (0);
3495 3510 }
3496 3511
3497 3512 void
3498 3513 arc_tempreserve_clear(uint64_t reserve)
3499 3514 {
3500 3515 atomic_add_64(&arc_tempreserve, -reserve);
3501 3516 ASSERT((int64_t)arc_tempreserve >= 0);
3502 3517 }
3503 3518
3504 3519 int
3505 3520 arc_tempreserve_space(uint64_t reserve, uint64_t txg)
3506 3521 {
3507 3522 int error;
3508 3523 uint64_t anon_size;
3509 3524
3510 3525 #ifdef ZFS_DEBUG
3511 3526 /*
3512 3527 * Once in a while, fail for no reason. Everything should cope.
3513 3528 */
3514 3529 if (spa_get_random(10000) == 0) {
3515 3530 dprintf("forcing random failure\n");
3516 3531 return (SET_ERROR(ERESTART));
3517 3532 }
3518 3533 #endif
3519 3534 if (reserve > arc_c/4 && !arc_no_grow)
3520 3535 arc_c = MIN(arc_c_max, reserve * 4);
3521 3536 if (reserve > arc_c)
3522 3537 return (SET_ERROR(ENOMEM));
3523 3538
3524 3539 /*
3525 3540 * Don't count loaned bufs as in flight dirty data to prevent long
3526 3541 * network delays from blocking transactions that are ready to be
3527 3542 * assigned to a txg.
3528 3543 */
3529 3544 anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
3530 3545
3531 3546 /*
3532 3547 * Writes will, almost always, require additional memory allocations
3533 3548 * in order to compress/encrypt/etc the data. We therefor need to
3534 3549 * make sure that there is sufficient available memory for this.
3535 3550 */
3536 3551 if (error = arc_memory_throttle(reserve, anon_size, txg))
3537 3552 return (error);
3538 3553
3539 3554 /*
3540 3555 * Throttle writes when the amount of dirty data in the cache
3541 3556 * gets too large. We try to keep the cache less than half full
3542 3557 * of dirty blocks so that our sync times don't grow too large.
3543 3558 * Note: if two requests come in concurrently, we might let them
3544 3559 * both succeed, when one of them should fail. Not a huge deal.
3545 3560 */
3546 3561
3547 3562 if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
3548 3563 anon_size > arc_c / 4) {
3549 3564 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
3550 3565 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
3551 3566 arc_tempreserve>>10,
3552 3567 arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
3553 3568 arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
3554 3569 reserve>>10, arc_c>>10);
3555 3570 return (SET_ERROR(ERESTART));
3556 3571 }
3557 3572 atomic_add_64(&arc_tempreserve, reserve);
3558 3573 return (0);
3559 3574 }
3560 3575
3561 3576 void
3562 3577 arc_init(void)
3563 3578 {
3564 3579 mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
3565 3580 cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
3566 3581
3567 3582 /* Convert seconds to clock ticks */
3568 3583 arc_min_prefetch_lifespan = 1 * hz;
3569 3584
3570 3585 /* Start out with 1/8 of all memory */
3571 3586 arc_c = physmem * PAGESIZE / 8;
3572 3587
3573 3588 #ifdef _KERNEL
3574 3589 /*
3575 3590 * On architectures where the physical memory can be larger
3576 3591 * than the addressable space (intel in 32-bit mode), we may
3577 3592 * need to limit the cache to 1/8 of VM size.
3578 3593 */
3579 3594 arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
3580 3595 #endif
3581 3596
3582 3597 /* set min cache to 1/32 of all memory, or 64MB, whichever is more */
3583 3598 arc_c_min = MAX(arc_c / 4, 64<<20);
3584 3599 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
3585 3600 if (arc_c * 8 >= 1<<30)
3586 3601 arc_c_max = (arc_c * 8) - (1<<30);
3587 3602 else
3588 3603 arc_c_max = arc_c_min;
3589 3604 arc_c_max = MAX(arc_c * 6, arc_c_max);
3590 3605
3591 3606 /*
3592 3607 * Allow the tunables to override our calculations if they are
3593 3608 * reasonable (ie. over 64MB)
3594 3609 */
3595 3610 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
3596 3611 arc_c_max = zfs_arc_max;
3597 3612 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
3598 3613 arc_c_min = zfs_arc_min;
3599 3614
3600 3615 arc_c = arc_c_max;
3601 3616 arc_p = (arc_c >> 1);
3602 3617
3603 3618 /* limit meta-data to 1/4 of the arc capacity */
3604 3619 arc_meta_limit = arc_c_max / 4;
3605 3620
3606 3621 /* Allow the tunable to override if it is reasonable */
3607 3622 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
3608 3623 arc_meta_limit = zfs_arc_meta_limit;
3609 3624
3610 3625 if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
3611 3626 arc_c_min = arc_meta_limit / 2;
3612 3627
3613 3628 if (zfs_arc_grow_retry > 0)
3614 3629 arc_grow_retry = zfs_arc_grow_retry;
3615 3630
3616 3631 if (zfs_arc_shrink_shift > 0)
3617 3632 arc_shrink_shift = zfs_arc_shrink_shift;
3618 3633
3619 3634 if (zfs_arc_p_min_shift > 0)
3620 3635 arc_p_min_shift = zfs_arc_p_min_shift;
3621 3636
3622 3637 /* if kmem_flags are set, lets try to use less memory */
3623 3638 if (kmem_debugging())
3624 3639 arc_c = arc_c / 2;
3625 3640 if (arc_c < arc_c_min)
3626 3641 arc_c = arc_c_min;
3627 3642
3628 3643 arc_anon = &ARC_anon;
3629 3644 arc_mru = &ARC_mru;
3630 3645 arc_mru_ghost = &ARC_mru_ghost;
3631 3646 arc_mfu = &ARC_mfu;
3632 3647 arc_mfu_ghost = &ARC_mfu_ghost;
3633 3648 arc_l2c_only = &ARC_l2c_only;
3634 3649 arc_size = 0;
3635 3650
3636 3651 mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3637 3652 mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3638 3653 mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3639 3654 mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3640 3655 mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3641 3656 mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
3642 3657
3643 3658 list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
3644 3659 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3645 3660 list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
3646 3661 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3647 3662 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
3648 3663 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3649 3664 list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
3650 3665 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3651 3666 list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
3652 3667 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3653 3668 list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
3654 3669 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3655 3670 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
3656 3671 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3657 3672 list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
3658 3673 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3659 3674 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
3660 3675 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3661 3676 list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
3662 3677 sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
3663 3678
3664 3679 buf_init();
3665 3680
3666 3681 arc_thread_exit = 0;
3667 3682 arc_eviction_list = NULL;
3668 3683 mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
3669 3684 bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
3670 3685
3671 3686 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
3672 3687 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
3673 3688
3674 3689 if (arc_ksp != NULL) {
3675 3690 arc_ksp->ks_data = &arc_stats;
3676 3691 kstat_install(arc_ksp);
3677 3692 }
3678 3693
3679 3694 (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
3680 3695 TS_RUN, minclsyspri);
3681 3696
3682 3697 arc_dead = FALSE;
3683 3698 arc_warm = B_FALSE;
3684 3699
3685 3700 if (zfs_write_limit_max == 0)
3686 3701 zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
3687 3702 else
3688 3703 zfs_write_limit_shift = 0;
3689 3704 mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
3690 3705 }
3691 3706
3692 3707 void
3693 3708 arc_fini(void)
3694 3709 {
3695 3710 mutex_enter(&arc_reclaim_thr_lock);
3696 3711 arc_thread_exit = 1;
3697 3712 while (arc_thread_exit != 0)
3698 3713 cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
3699 3714 mutex_exit(&arc_reclaim_thr_lock);
3700 3715
3701 3716 arc_flush(NULL);
3702 3717
3703 3718 arc_dead = TRUE;
3704 3719
3705 3720 if (arc_ksp != NULL) {
3706 3721 kstat_delete(arc_ksp);
3707 3722 arc_ksp = NULL;
3708 3723 }
3709 3724
3710 3725 mutex_destroy(&arc_eviction_mtx);
3711 3726 mutex_destroy(&arc_reclaim_thr_lock);
3712 3727 cv_destroy(&arc_reclaim_thr_cv);
3713 3728
3714 3729 list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
3715 3730 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
3716 3731 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
3717 3732 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
3718 3733 list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
3719 3734 list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
3720 3735 list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
3721 3736 list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
3722 3737
3723 3738 mutex_destroy(&arc_anon->arcs_mtx);
3724 3739 mutex_destroy(&arc_mru->arcs_mtx);
3725 3740 mutex_destroy(&arc_mru_ghost->arcs_mtx);
3726 3741 mutex_destroy(&arc_mfu->arcs_mtx);
3727 3742 mutex_destroy(&arc_mfu_ghost->arcs_mtx);
3728 3743 mutex_destroy(&arc_l2c_only->arcs_mtx);
3729 3744
3730 3745 mutex_destroy(&zfs_write_limit_lock);
3731 3746
3732 3747 buf_fini();
3733 3748
3734 3749 ASSERT(arc_loaned_bytes == 0);
3735 3750 }
3736 3751
3737 3752 /*
3738 3753 * Level 2 ARC
3739 3754 *
3740 3755 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
3741 3756 * It uses dedicated storage devices to hold cached data, which are populated
3742 3757 * using large infrequent writes. The main role of this cache is to boost
3743 3758 * the performance of random read workloads. The intended L2ARC devices
3744 3759 * include short-stroked disks, solid state disks, and other media with
3745 3760 * substantially faster read latency than disk.
3746 3761 *
3747 3762 * +-----------------------+
3748 3763 * | ARC |
3749 3764 * +-----------------------+
3750 3765 * | ^ ^
3751 3766 * | | |
3752 3767 * l2arc_feed_thread() arc_read()
3753 3768 * | | |
3754 3769 * | l2arc read |
3755 3770 * V | |
3756 3771 * +---------------+ |
3757 3772 * | L2ARC | |
3758 3773 * +---------------+ |
3759 3774 * | ^ |
3760 3775 * l2arc_write() | |
3761 3776 * | | |
3762 3777 * V | |
3763 3778 * +-------+ +-------+
3764 3779 * | vdev | | vdev |
3765 3780 * | cache | | cache |
3766 3781 * +-------+ +-------+
3767 3782 * +=========+ .-----.
3768 3783 * : L2ARC : |-_____-|
3769 3784 * : devices : | Disks |
3770 3785 * +=========+ `-_____-'
3771 3786 *
3772 3787 * Read requests are satisfied from the following sources, in order:
3773 3788 *
3774 3789 * 1) ARC
3775 3790 * 2) vdev cache of L2ARC devices
3776 3791 * 3) L2ARC devices
3777 3792 * 4) vdev cache of disks
3778 3793 * 5) disks
3779 3794 *
3780 3795 * Some L2ARC device types exhibit extremely slow write performance.
3781 3796 * To accommodate for this there are some significant differences between
3782 3797 * the L2ARC and traditional cache design:
3783 3798 *
3784 3799 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
3785 3800 * the ARC behave as usual, freeing buffers and placing headers on ghost
3786 3801 * lists. The ARC does not send buffers to the L2ARC during eviction as
3787 3802 * this would add inflated write latencies for all ARC memory pressure.
3788 3803 *
3789 3804 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
3790 3805 * It does this by periodically scanning buffers from the eviction-end of
3791 3806 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
3792 3807 * not already there. It scans until a headroom of buffers is satisfied,
3793 3808 * which itself is a buffer for ARC eviction. The thread that does this is
3794 3809 * l2arc_feed_thread(), illustrated below; example sizes are included to
3795 3810 * provide a better sense of ratio than this diagram:
3796 3811 *
3797 3812 * head --> tail
3798 3813 * +---------------------+----------+
3799 3814 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
3800 3815 * +---------------------+----------+ | o L2ARC eligible
3801 3816 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
3802 3817 * +---------------------+----------+ |
3803 3818 * 15.9 Gbytes ^ 32 Mbytes |
3804 3819 * headroom |
3805 3820 * l2arc_feed_thread()
3806 3821 * |
3807 3822 * l2arc write hand <--[oooo]--'
3808 3823 * | 8 Mbyte
3809 3824 * | write max
3810 3825 * V
3811 3826 * +==============================+
3812 3827 * L2ARC dev |####|#|###|###| |####| ... |
3813 3828 * +==============================+
3814 3829 * 32 Gbytes
3815 3830 *
3816 3831 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
3817 3832 * evicted, then the L2ARC has cached a buffer much sooner than it probably
3818 3833 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
3819 3834 * safe to say that this is an uncommon case, since buffers at the end of
3820 3835 * the ARC lists have moved there due to inactivity.
3821 3836 *
3822 3837 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
3823 3838 * then the L2ARC simply misses copying some buffers. This serves as a
3824 3839 * pressure valve to prevent heavy read workloads from both stalling the ARC
3825 3840 * with waits and clogging the L2ARC with writes. This also helps prevent
3826 3841 * the potential for the L2ARC to churn if it attempts to cache content too
3827 3842 * quickly, such as during backups of the entire pool.
3828 3843 *
3829 3844 * 5. After system boot and before the ARC has filled main memory, there are
3830 3845 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
3831 3846 * lists can remain mostly static. Instead of searching from tail of these
3832 3847 * lists as pictured, the l2arc_feed_thread() will search from the list heads
3833 3848 * for eligible buffers, greatly increasing its chance of finding them.
3834 3849 *
3835 3850 * The L2ARC device write speed is also boosted during this time so that
3836 3851 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
3837 3852 * there are no L2ARC reads, and no fear of degrading read performance
3838 3853 * through increased writes.
3839 3854 *
3840 3855 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
3841 3856 * the vdev queue can aggregate them into larger and fewer writes. Each
3842 3857 * device is written to in a rotor fashion, sweeping writes through
3843 3858 * available space then repeating.
3844 3859 *
3845 3860 * 7. The L2ARC does not store dirty content. It never needs to flush
3846 3861 * write buffers back to disk based storage.
3847 3862 *
3848 3863 * 8. If an ARC buffer is written (and dirtied) which also exists in the
3849 3864 * L2ARC, the now stale L2ARC buffer is immediately dropped.
3850 3865 *
3851 3866 * The performance of the L2ARC can be tweaked by a number of tunables, which
3852 3867 * may be necessary for different workloads:
3853 3868 *
3854 3869 * l2arc_write_max max write bytes per interval
3855 3870 * l2arc_write_boost extra write bytes during device warmup
3856 3871 * l2arc_noprefetch skip caching prefetched buffers
3857 3872 * l2arc_headroom number of max device writes to precache
3858 3873 * l2arc_feed_secs seconds between L2ARC writing
3859 3874 *
3860 3875 * Tunables may be removed or added as future performance improvements are
3861 3876 * integrated, and also may become zpool properties.
3862 3877 *
3863 3878 * There are three key functions that control how the L2ARC warms up:
3864 3879 *
3865 3880 * l2arc_write_eligible() check if a buffer is eligible to cache
3866 3881 * l2arc_write_size() calculate how much to write
3867 3882 * l2arc_write_interval() calculate sleep delay between writes
3868 3883 *
3869 3884 * These three functions determine what to write, how much, and how quickly
3870 3885 * to send writes.
3871 3886 */
3872 3887
3873 3888 static boolean_t
3874 3889 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
3875 3890 {
3876 3891 /*
3877 3892 * A buffer is *not* eligible for the L2ARC if it:
3878 3893 * 1. belongs to a different spa.
3879 3894 * 2. is already cached on the L2ARC.
3880 3895 * 3. has an I/O in progress (it may be an incomplete read).
3881 3896 * 4. is flagged not eligible (zfs property).
3882 3897 */
3883 3898 if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
3884 3899 HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
3885 3900 return (B_FALSE);
3886 3901
3887 3902 return (B_TRUE);
3888 3903 }
3889 3904
3890 3905 static uint64_t
3891 3906 l2arc_write_size(l2arc_dev_t *dev)
3892 3907 {
3893 3908 uint64_t size;
3894 3909
3895 3910 size = dev->l2ad_write;
3896 3911
3897 3912 if (arc_warm == B_FALSE)
3898 3913 size += dev->l2ad_boost;
3899 3914
3900 3915 return (size);
3901 3916
3902 3917 }
3903 3918
3904 3919 static clock_t
3905 3920 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
3906 3921 {
3907 3922 clock_t interval, next, now;
3908 3923
3909 3924 /*
3910 3925 * If the ARC lists are busy, increase our write rate; if the
3911 3926 * lists are stale, idle back. This is achieved by checking
3912 3927 * how much we previously wrote - if it was more than half of
3913 3928 * what we wanted, schedule the next write much sooner.
3914 3929 */
3915 3930 if (l2arc_feed_again && wrote > (wanted / 2))
3916 3931 interval = (hz * l2arc_feed_min_ms) / 1000;
3917 3932 else
3918 3933 interval = hz * l2arc_feed_secs;
3919 3934
3920 3935 now = ddi_get_lbolt();
3921 3936 next = MAX(now, MIN(now + interval, began + interval));
3922 3937
3923 3938 return (next);
3924 3939 }
3925 3940
3926 3941 static void
3927 3942 l2arc_hdr_stat_add(void)
3928 3943 {
3929 3944 ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
3930 3945 ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
3931 3946 }
3932 3947
3933 3948 static void
3934 3949 l2arc_hdr_stat_remove(void)
3935 3950 {
3936 3951 ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
3937 3952 ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
3938 3953 }
3939 3954
3940 3955 /*
3941 3956 * Cycle through L2ARC devices. This is how L2ARC load balances.
3942 3957 * If a device is returned, this also returns holding the spa config lock.
3943 3958 */
3944 3959 static l2arc_dev_t *
3945 3960 l2arc_dev_get_next(void)
3946 3961 {
3947 3962 l2arc_dev_t *first, *next = NULL;
3948 3963
3949 3964 /*
3950 3965 * Lock out the removal of spas (spa_namespace_lock), then removal
3951 3966 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
3952 3967 * both locks will be dropped and a spa config lock held instead.
3953 3968 */
3954 3969 mutex_enter(&spa_namespace_lock);
3955 3970 mutex_enter(&l2arc_dev_mtx);
3956 3971
3957 3972 /* if there are no vdevs, there is nothing to do */
3958 3973 if (l2arc_ndev == 0)
3959 3974 goto out;
3960 3975
3961 3976 first = NULL;
3962 3977 next = l2arc_dev_last;
3963 3978 do {
3964 3979 /* loop around the list looking for a non-faulted vdev */
3965 3980 if (next == NULL) {
3966 3981 next = list_head(l2arc_dev_list);
3967 3982 } else {
3968 3983 next = list_next(l2arc_dev_list, next);
3969 3984 if (next == NULL)
3970 3985 next = list_head(l2arc_dev_list);
3971 3986 }
3972 3987
3973 3988 /* if we have come back to the start, bail out */
3974 3989 if (first == NULL)
3975 3990 first = next;
3976 3991 else if (next == first)
3977 3992 break;
3978 3993
3979 3994 } while (vdev_is_dead(next->l2ad_vdev));
3980 3995
3981 3996 /* if we were unable to find any usable vdevs, return NULL */
3982 3997 if (vdev_is_dead(next->l2ad_vdev))
3983 3998 next = NULL;
3984 3999
3985 4000 l2arc_dev_last = next;
3986 4001
3987 4002 out:
3988 4003 mutex_exit(&l2arc_dev_mtx);
3989 4004
3990 4005 /*
3991 4006 * Grab the config lock to prevent the 'next' device from being
3992 4007 * removed while we are writing to it.
3993 4008 */
3994 4009 if (next != NULL)
3995 4010 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
3996 4011 mutex_exit(&spa_namespace_lock);
3997 4012
3998 4013 return (next);
3999 4014 }
4000 4015
4001 4016 /*
4002 4017 * Free buffers that were tagged for destruction.
4003 4018 */
4004 4019 static void
4005 4020 l2arc_do_free_on_write()
4006 4021 {
4007 4022 list_t *buflist;
4008 4023 l2arc_data_free_t *df, *df_prev;
4009 4024
4010 4025 mutex_enter(&l2arc_free_on_write_mtx);
4011 4026 buflist = l2arc_free_on_write;
4012 4027
4013 4028 for (df = list_tail(buflist); df; df = df_prev) {
4014 4029 df_prev = list_prev(buflist, df);
4015 4030 ASSERT(df->l2df_data != NULL);
4016 4031 ASSERT(df->l2df_func != NULL);
4017 4032 df->l2df_func(df->l2df_data, df->l2df_size);
4018 4033 list_remove(buflist, df);
4019 4034 kmem_free(df, sizeof (l2arc_data_free_t));
4020 4035 }
4021 4036
4022 4037 mutex_exit(&l2arc_free_on_write_mtx);
4023 4038 }
4024 4039
4025 4040 /*
4026 4041 * A write to a cache device has completed. Update all headers to allow
4027 4042 * reads from these buffers to begin.
4028 4043 */
4029 4044 static void
4030 4045 l2arc_write_done(zio_t *zio)
4031 4046 {
4032 4047 l2arc_write_callback_t *cb;
4033 4048 l2arc_dev_t *dev;
4034 4049 list_t *buflist;
4035 4050 arc_buf_hdr_t *head, *ab, *ab_prev;
4036 4051 l2arc_buf_hdr_t *abl2;
4037 4052 kmutex_t *hash_lock;
4038 4053
4039 4054 cb = zio->io_private;
4040 4055 ASSERT(cb != NULL);
4041 4056 dev = cb->l2wcb_dev;
4042 4057 ASSERT(dev != NULL);
4043 4058 head = cb->l2wcb_head;
4044 4059 ASSERT(head != NULL);
4045 4060 buflist = dev->l2ad_buflist;
4046 4061 ASSERT(buflist != NULL);
4047 4062 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
4048 4063 l2arc_write_callback_t *, cb);
4049 4064
4050 4065 if (zio->io_error != 0)
4051 4066 ARCSTAT_BUMP(arcstat_l2_writes_error);
4052 4067
4053 4068 mutex_enter(&l2arc_buflist_mtx);
4054 4069
4055 4070 /*
4056 4071 * All writes completed, or an error was hit.
4057 4072 */
4058 4073 for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
4059 4074 ab_prev = list_prev(buflist, ab);
4060 4075
4061 4076 hash_lock = HDR_LOCK(ab);
4062 4077 if (!mutex_tryenter(hash_lock)) {
4063 4078 /*
4064 4079 * This buffer misses out. It may be in a stage
4065 4080 * of eviction. Its ARC_L2_WRITING flag will be
4066 4081 * left set, denying reads to this buffer.
4067 4082 */
4068 4083 ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
4069 4084 continue;
4070 4085 }
4071 4086
4072 4087 if (zio->io_error != 0) {
4073 4088 /*
4074 4089 * Error - drop L2ARC entry.
4075 4090 */
4076 4091 list_remove(buflist, ab);
4077 4092 abl2 = ab->b_l2hdr;
4078 4093 ab->b_l2hdr = NULL;
4079 4094 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4080 4095 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4081 4096 }
4082 4097
4083 4098 /*
4084 4099 * Allow ARC to begin reads to this L2ARC entry.
4085 4100 */
4086 4101 ab->b_flags &= ~ARC_L2_WRITING;
4087 4102
4088 4103 mutex_exit(hash_lock);
4089 4104 }
4090 4105
4091 4106 atomic_inc_64(&l2arc_writes_done);
4092 4107 list_remove(buflist, head);
4093 4108 kmem_cache_free(hdr_cache, head);
4094 4109 mutex_exit(&l2arc_buflist_mtx);
4095 4110
4096 4111 l2arc_do_free_on_write();
4097 4112
4098 4113 kmem_free(cb, sizeof (l2arc_write_callback_t));
4099 4114 }
4100 4115
4101 4116 /*
4102 4117 * A read to a cache device completed. Validate buffer contents before
4103 4118 * handing over to the regular ARC routines.
4104 4119 */
4105 4120 static void
4106 4121 l2arc_read_done(zio_t *zio)
4107 4122 {
4108 4123 l2arc_read_callback_t *cb;
4109 4124 arc_buf_hdr_t *hdr;
4110 4125 arc_buf_t *buf;
4111 4126 kmutex_t *hash_lock;
4112 4127 int equal;
4113 4128
4114 4129 ASSERT(zio->io_vd != NULL);
4115 4130 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
4116 4131
4117 4132 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
4118 4133
4119 4134 cb = zio->io_private;
4120 4135 ASSERT(cb != NULL);
4121 4136 buf = cb->l2rcb_buf;
4122 4137 ASSERT(buf != NULL);
4123 4138
4124 4139 hash_lock = HDR_LOCK(buf->b_hdr);
4125 4140 mutex_enter(hash_lock);
4126 4141 hdr = buf->b_hdr;
4127 4142 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
4128 4143
4129 4144 /*
4130 4145 * Check this survived the L2ARC journey.
4131 4146 */
4132 4147 equal = arc_cksum_equal(buf);
4133 4148 if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
4134 4149 mutex_exit(hash_lock);
4135 4150 zio->io_private = buf;
4136 4151 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
4137 4152 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
4138 4153 arc_read_done(zio);
4139 4154 } else {
4140 4155 mutex_exit(hash_lock);
4141 4156 /*
4142 4157 * Buffer didn't survive caching. Increment stats and
4143 4158 * reissue to the original storage device.
4144 4159 */
4145 4160 if (zio->io_error != 0) {
4146 4161 ARCSTAT_BUMP(arcstat_l2_io_error);
4147 4162 } else {
4148 4163 zio->io_error = SET_ERROR(EIO);
4149 4164 }
4150 4165 if (!equal)
4151 4166 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
4152 4167
4153 4168 /*
4154 4169 * If there's no waiter, issue an async i/o to the primary
4155 4170 * storage now. If there *is* a waiter, the caller must
4156 4171 * issue the i/o in a context where it's OK to block.
4157 4172 */
4158 4173 if (zio->io_waiter == NULL) {
4159 4174 zio_t *pio = zio_unique_parent(zio);
4160 4175
4161 4176 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
4162 4177
4163 4178 zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
4164 4179 buf->b_data, zio->io_size, arc_read_done, buf,
4165 4180 zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
4166 4181 }
4167 4182 }
4168 4183
4169 4184 kmem_free(cb, sizeof (l2arc_read_callback_t));
4170 4185 }
4171 4186
4172 4187 /*
4173 4188 * This is the list priority from which the L2ARC will search for pages to
4174 4189 * cache. This is used within loops (0..3) to cycle through lists in the
4175 4190 * desired order. This order can have a significant effect on cache
4176 4191 * performance.
4177 4192 *
4178 4193 * Currently the metadata lists are hit first, MFU then MRU, followed by
4179 4194 * the data lists. This function returns a locked list, and also returns
4180 4195 * the lock pointer.
4181 4196 */
4182 4197 static list_t *
4183 4198 l2arc_list_locked(int list_num, kmutex_t **lock)
4184 4199 {
4185 4200 list_t *list = NULL;
4186 4201
4187 4202 ASSERT(list_num >= 0 && list_num <= 3);
4188 4203
4189 4204 switch (list_num) {
4190 4205 case 0:
4191 4206 list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
4192 4207 *lock = &arc_mfu->arcs_mtx;
4193 4208 break;
4194 4209 case 1:
4195 4210 list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
4196 4211 *lock = &arc_mru->arcs_mtx;
4197 4212 break;
4198 4213 case 2:
4199 4214 list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
4200 4215 *lock = &arc_mfu->arcs_mtx;
4201 4216 break;
4202 4217 case 3:
4203 4218 list = &arc_mru->arcs_list[ARC_BUFC_DATA];
4204 4219 *lock = &arc_mru->arcs_mtx;
4205 4220 break;
4206 4221 }
4207 4222
4208 4223 ASSERT(!(MUTEX_HELD(*lock)));
4209 4224 mutex_enter(*lock);
4210 4225 return (list);
4211 4226 }
4212 4227
4213 4228 /*
4214 4229 * Evict buffers from the device write hand to the distance specified in
4215 4230 * bytes. This distance may span populated buffers, it may span nothing.
4216 4231 * This is clearing a region on the L2ARC device ready for writing.
4217 4232 * If the 'all' boolean is set, every buffer is evicted.
4218 4233 */
4219 4234 static void
4220 4235 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
4221 4236 {
4222 4237 list_t *buflist;
4223 4238 l2arc_buf_hdr_t *abl2;
4224 4239 arc_buf_hdr_t *ab, *ab_prev;
4225 4240 kmutex_t *hash_lock;
4226 4241 uint64_t taddr;
4227 4242
4228 4243 buflist = dev->l2ad_buflist;
4229 4244
4230 4245 if (buflist == NULL)
4231 4246 return;
4232 4247
4233 4248 if (!all && dev->l2ad_first) {
4234 4249 /*
4235 4250 * This is the first sweep through the device. There is
4236 4251 * nothing to evict.
4237 4252 */
4238 4253 return;
4239 4254 }
4240 4255
4241 4256 if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
4242 4257 /*
4243 4258 * When nearing the end of the device, evict to the end
4244 4259 * before the device write hand jumps to the start.
4245 4260 */
4246 4261 taddr = dev->l2ad_end;
4247 4262 } else {
4248 4263 taddr = dev->l2ad_hand + distance;
4249 4264 }
4250 4265 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
4251 4266 uint64_t, taddr, boolean_t, all);
4252 4267
4253 4268 top:
4254 4269 mutex_enter(&l2arc_buflist_mtx);
4255 4270 for (ab = list_tail(buflist); ab; ab = ab_prev) {
4256 4271 ab_prev = list_prev(buflist, ab);
4257 4272
4258 4273 hash_lock = HDR_LOCK(ab);
4259 4274 if (!mutex_tryenter(hash_lock)) {
4260 4275 /*
4261 4276 * Missed the hash lock. Retry.
4262 4277 */
4263 4278 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
4264 4279 mutex_exit(&l2arc_buflist_mtx);
4265 4280 mutex_enter(hash_lock);
4266 4281 mutex_exit(hash_lock);
4267 4282 goto top;
4268 4283 }
4269 4284
4270 4285 if (HDR_L2_WRITE_HEAD(ab)) {
4271 4286 /*
4272 4287 * We hit a write head node. Leave it for
4273 4288 * l2arc_write_done().
4274 4289 */
4275 4290 list_remove(buflist, ab);
4276 4291 mutex_exit(hash_lock);
4277 4292 continue;
4278 4293 }
4279 4294
4280 4295 if (!all && ab->b_l2hdr != NULL &&
4281 4296 (ab->b_l2hdr->b_daddr > taddr ||
4282 4297 ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
4283 4298 /*
4284 4299 * We've evicted to the target address,
4285 4300 * or the end of the device.
4286 4301 */
4287 4302 mutex_exit(hash_lock);
4288 4303 break;
4289 4304 }
4290 4305
4291 4306 if (HDR_FREE_IN_PROGRESS(ab)) {
4292 4307 /*
4293 4308 * Already on the path to destruction.
4294 4309 */
4295 4310 mutex_exit(hash_lock);
4296 4311 continue;
4297 4312 }
4298 4313
4299 4314 if (ab->b_state == arc_l2c_only) {
4300 4315 ASSERT(!HDR_L2_READING(ab));
4301 4316 /*
4302 4317 * This doesn't exist in the ARC. Destroy.
4303 4318 * arc_hdr_destroy() will call list_remove()
4304 4319 * and decrement arcstat_l2_size.
4305 4320 */
4306 4321 arc_change_state(arc_anon, ab, hash_lock);
4307 4322 arc_hdr_destroy(ab);
4308 4323 } else {
4309 4324 /*
4310 4325 * Invalidate issued or about to be issued
4311 4326 * reads, since we may be about to write
4312 4327 * over this location.
4313 4328 */
4314 4329 if (HDR_L2_READING(ab)) {
4315 4330 ARCSTAT_BUMP(arcstat_l2_evict_reading);
4316 4331 ab->b_flags |= ARC_L2_EVICTED;
4317 4332 }
4318 4333
4319 4334 /*
4320 4335 * Tell ARC this no longer exists in L2ARC.
4321 4336 */
4322 4337 if (ab->b_l2hdr != NULL) {
4323 4338 abl2 = ab->b_l2hdr;
4324 4339 ab->b_l2hdr = NULL;
4325 4340 kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
4326 4341 ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
4327 4342 }
4328 4343 list_remove(buflist, ab);
4329 4344
4330 4345 /*
4331 4346 * This may have been leftover after a
4332 4347 * failed write.
4333 4348 */
4334 4349 ab->b_flags &= ~ARC_L2_WRITING;
4335 4350 }
4336 4351 mutex_exit(hash_lock);
4337 4352 }
4338 4353 mutex_exit(&l2arc_buflist_mtx);
4339 4354
4340 4355 vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
4341 4356 dev->l2ad_evict = taddr;
4342 4357 }
4343 4358
4344 4359 /*
4345 4360 * Find and write ARC buffers to the L2ARC device.
4346 4361 *
4347 4362 * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
4348 4363 * for reading until they have completed writing.
4349 4364 */
4350 4365 static uint64_t
4351 4366 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
4352 4367 {
4353 4368 arc_buf_hdr_t *ab, *ab_prev, *head;
4354 4369 l2arc_buf_hdr_t *hdrl2;
4355 4370 list_t *list;
4356 4371 uint64_t passed_sz, write_sz, buf_sz, headroom;
4357 4372 void *buf_data;
4358 4373 kmutex_t *hash_lock, *list_lock;
4359 4374 boolean_t have_lock, full;
4360 4375 l2arc_write_callback_t *cb;
4361 4376 zio_t *pio, *wzio;
4362 4377 uint64_t guid = spa_load_guid(spa);
4363 4378
4364 4379 ASSERT(dev->l2ad_vdev != NULL);
4365 4380
4366 4381 pio = NULL;
4367 4382 write_sz = 0;
4368 4383 full = B_FALSE;
4369 4384 head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
4370 4385 head->b_flags |= ARC_L2_WRITE_HEAD;
4371 4386
4372 4387 /*
4373 4388 * Copy buffers for L2ARC writing.
4374 4389 */
4375 4390 mutex_enter(&l2arc_buflist_mtx);
4376 4391 for (int try = 0; try <= 3; try++) {
4377 4392 list = l2arc_list_locked(try, &list_lock);
4378 4393 passed_sz = 0;
4379 4394
4380 4395 /*
4381 4396 * L2ARC fast warmup.
4382 4397 *
4383 4398 * Until the ARC is warm and starts to evict, read from the
4384 4399 * head of the ARC lists rather than the tail.
4385 4400 */
4386 4401 headroom = target_sz * l2arc_headroom;
4387 4402 if (arc_warm == B_FALSE)
4388 4403 ab = list_head(list);
4389 4404 else
4390 4405 ab = list_tail(list);
4391 4406
4392 4407 for (; ab; ab = ab_prev) {
4393 4408 if (arc_warm == B_FALSE)
4394 4409 ab_prev = list_next(list, ab);
4395 4410 else
4396 4411 ab_prev = list_prev(list, ab);
4397 4412
4398 4413 hash_lock = HDR_LOCK(ab);
4399 4414 have_lock = MUTEX_HELD(hash_lock);
4400 4415 if (!have_lock && !mutex_tryenter(hash_lock)) {
4401 4416 /*
4402 4417 * Skip this buffer rather than waiting.
4403 4418 */
4404 4419 continue;
4405 4420 }
4406 4421
4407 4422 passed_sz += ab->b_size;
4408 4423 if (passed_sz > headroom) {
4409 4424 /*
4410 4425 * Searched too far.
4411 4426 */
4412 4427 mutex_exit(hash_lock);
4413 4428 break;
4414 4429 }
4415 4430
4416 4431 if (!l2arc_write_eligible(guid, ab)) {
4417 4432 mutex_exit(hash_lock);
4418 4433 continue;
4419 4434 }
4420 4435
4421 4436 if ((write_sz + ab->b_size) > target_sz) {
4422 4437 full = B_TRUE;
4423 4438 mutex_exit(hash_lock);
4424 4439 break;
4425 4440 }
4426 4441
4427 4442 if (pio == NULL) {
4428 4443 /*
4429 4444 * Insert a dummy header on the buflist so
4430 4445 * l2arc_write_done() can find where the
4431 4446 * write buffers begin without searching.
4432 4447 */
4433 4448 list_insert_head(dev->l2ad_buflist, head);
4434 4449
4435 4450 cb = kmem_alloc(
4436 4451 sizeof (l2arc_write_callback_t), KM_SLEEP);
4437 4452 cb->l2wcb_dev = dev;
4438 4453 cb->l2wcb_head = head;
4439 4454 pio = zio_root(spa, l2arc_write_done, cb,
4440 4455 ZIO_FLAG_CANFAIL);
4441 4456 }
4442 4457
4443 4458 /*
4444 4459 * Create and add a new L2ARC header.
4445 4460 */
4446 4461 hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
4447 4462 hdrl2->b_dev = dev;
4448 4463 hdrl2->b_daddr = dev->l2ad_hand;
4449 4464
4450 4465 ab->b_flags |= ARC_L2_WRITING;
4451 4466 ab->b_l2hdr = hdrl2;
4452 4467 list_insert_head(dev->l2ad_buflist, ab);
4453 4468 buf_data = ab->b_buf->b_data;
4454 4469 buf_sz = ab->b_size;
4455 4470
4456 4471 /*
4457 4472 * Compute and store the buffer cksum before
4458 4473 * writing. On debug the cksum is verified first.
4459 4474 */
4460 4475 arc_cksum_verify(ab->b_buf);
4461 4476 arc_cksum_compute(ab->b_buf, B_TRUE);
4462 4477
4463 4478 mutex_exit(hash_lock);
4464 4479
4465 4480 wzio = zio_write_phys(pio, dev->l2ad_vdev,
4466 4481 dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
4467 4482 NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
4468 4483 ZIO_FLAG_CANFAIL, B_FALSE);
4469 4484
4470 4485 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
4471 4486 zio_t *, wzio);
4472 4487 (void) zio_nowait(wzio);
4473 4488
4474 4489 /*
4475 4490 * Keep the clock hand suitably device-aligned.
4476 4491 */
4477 4492 buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
4478 4493
4479 4494 write_sz += buf_sz;
4480 4495 dev->l2ad_hand += buf_sz;
4481 4496 }
4482 4497
4483 4498 mutex_exit(list_lock);
4484 4499
4485 4500 if (full == B_TRUE)
4486 4501 break;
4487 4502 }
4488 4503 mutex_exit(&l2arc_buflist_mtx);
4489 4504
4490 4505 if (pio == NULL) {
4491 4506 ASSERT0(write_sz);
4492 4507 kmem_cache_free(hdr_cache, head);
4493 4508 return (0);
4494 4509 }
4495 4510
4496 4511 ASSERT3U(write_sz, <=, target_sz);
4497 4512 ARCSTAT_BUMP(arcstat_l2_writes_sent);
4498 4513 ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
4499 4514 ARCSTAT_INCR(arcstat_l2_size, write_sz);
4500 4515 vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
4501 4516
4502 4517 /*
4503 4518 * Bump device hand to the device start if it is approaching the end.
4504 4519 * l2arc_evict() will already have evicted ahead for this case.
4505 4520 */
4506 4521 if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
4507 4522 vdev_space_update(dev->l2ad_vdev,
4508 4523 dev->l2ad_end - dev->l2ad_hand, 0, 0);
4509 4524 dev->l2ad_hand = dev->l2ad_start;
4510 4525 dev->l2ad_evict = dev->l2ad_start;
4511 4526 dev->l2ad_first = B_FALSE;
4512 4527 }
4513 4528
4514 4529 dev->l2ad_writing = B_TRUE;
4515 4530 (void) zio_wait(pio);
4516 4531 dev->l2ad_writing = B_FALSE;
4517 4532
4518 4533 return (write_sz);
4519 4534 }
4520 4535
4521 4536 /*
4522 4537 * This thread feeds the L2ARC at regular intervals. This is the beating
4523 4538 * heart of the L2ARC.
4524 4539 */
4525 4540 static void
4526 4541 l2arc_feed_thread(void)
4527 4542 {
4528 4543 callb_cpr_t cpr;
4529 4544 l2arc_dev_t *dev;
4530 4545 spa_t *spa;
4531 4546 uint64_t size, wrote;
4532 4547 clock_t begin, next = ddi_get_lbolt();
4533 4548
4534 4549 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
4535 4550
4536 4551 mutex_enter(&l2arc_feed_thr_lock);
4537 4552
4538 4553 while (l2arc_thread_exit == 0) {
4539 4554 CALLB_CPR_SAFE_BEGIN(&cpr);
4540 4555 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
4541 4556 next);
4542 4557 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
4543 4558 next = ddi_get_lbolt() + hz;
4544 4559
4545 4560 /*
4546 4561 * Quick check for L2ARC devices.
4547 4562 */
4548 4563 mutex_enter(&l2arc_dev_mtx);
4549 4564 if (l2arc_ndev == 0) {
4550 4565 mutex_exit(&l2arc_dev_mtx);
4551 4566 continue;
4552 4567 }
4553 4568 mutex_exit(&l2arc_dev_mtx);
4554 4569 begin = ddi_get_lbolt();
4555 4570
4556 4571 /*
4557 4572 * This selects the next l2arc device to write to, and in
4558 4573 * doing so the next spa to feed from: dev->l2ad_spa. This
4559 4574 * will return NULL if there are now no l2arc devices or if
4560 4575 * they are all faulted.
4561 4576 *
4562 4577 * If a device is returned, its spa's config lock is also
4563 4578 * held to prevent device removal. l2arc_dev_get_next()
4564 4579 * will grab and release l2arc_dev_mtx.
4565 4580 */
4566 4581 if ((dev = l2arc_dev_get_next()) == NULL)
4567 4582 continue;
4568 4583
4569 4584 spa = dev->l2ad_spa;
4570 4585 ASSERT(spa != NULL);
4571 4586
4572 4587 /*
4573 4588 * If the pool is read-only then force the feed thread to
4574 4589 * sleep a little longer.
4575 4590 */
4576 4591 if (!spa_writeable(spa)) {
4577 4592 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
4578 4593 spa_config_exit(spa, SCL_L2ARC, dev);
4579 4594 continue;
4580 4595 }
4581 4596
4582 4597 /*
4583 4598 * Avoid contributing to memory pressure.
4584 4599 */
4585 4600 if (arc_reclaim_needed()) {
4586 4601 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
4587 4602 spa_config_exit(spa, SCL_L2ARC, dev);
4588 4603 continue;
4589 4604 }
4590 4605
4591 4606 ARCSTAT_BUMP(arcstat_l2_feeds);
4592 4607
4593 4608 size = l2arc_write_size(dev);
4594 4609
4595 4610 /*
4596 4611 * Evict L2ARC buffers that will be overwritten.
4597 4612 */
4598 4613 l2arc_evict(dev, size, B_FALSE);
4599 4614
4600 4615 /*
4601 4616 * Write ARC buffers.
4602 4617 */
4603 4618 wrote = l2arc_write_buffers(spa, dev, size);
4604 4619
4605 4620 /*
4606 4621 * Calculate interval between writes.
4607 4622 */
4608 4623 next = l2arc_write_interval(begin, size, wrote);
4609 4624 spa_config_exit(spa, SCL_L2ARC, dev);
4610 4625 }
4611 4626
4612 4627 l2arc_thread_exit = 0;
4613 4628 cv_broadcast(&l2arc_feed_thr_cv);
4614 4629 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
4615 4630 thread_exit();
4616 4631 }
4617 4632
4618 4633 boolean_t
4619 4634 l2arc_vdev_present(vdev_t *vd)
4620 4635 {
4621 4636 l2arc_dev_t *dev;
4622 4637
4623 4638 mutex_enter(&l2arc_dev_mtx);
4624 4639 for (dev = list_head(l2arc_dev_list); dev != NULL;
4625 4640 dev = list_next(l2arc_dev_list, dev)) {
4626 4641 if (dev->l2ad_vdev == vd)
4627 4642 break;
4628 4643 }
4629 4644 mutex_exit(&l2arc_dev_mtx);
4630 4645
4631 4646 return (dev != NULL);
4632 4647 }
4633 4648
4634 4649 /*
4635 4650 * Add a vdev for use by the L2ARC. By this point the spa has already
4636 4651 * validated the vdev and opened it.
4637 4652 */
4638 4653 void
4639 4654 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
4640 4655 {
4641 4656 l2arc_dev_t *adddev;
4642 4657
4643 4658 ASSERT(!l2arc_vdev_present(vd));
4644 4659
4645 4660 /*
4646 4661 * Create a new l2arc device entry.
4647 4662 */
4648 4663 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
4649 4664 adddev->l2ad_spa = spa;
4650 4665 adddev->l2ad_vdev = vd;
4651 4666 adddev->l2ad_write = l2arc_write_max;
4652 4667 adddev->l2ad_boost = l2arc_write_boost;
4653 4668 adddev->l2ad_start = VDEV_LABEL_START_SIZE;
4654 4669 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
4655 4670 adddev->l2ad_hand = adddev->l2ad_start;
4656 4671 adddev->l2ad_evict = adddev->l2ad_start;
4657 4672 adddev->l2ad_first = B_TRUE;
4658 4673 adddev->l2ad_writing = B_FALSE;
4659 4674 ASSERT3U(adddev->l2ad_write, >, 0);
4660 4675
4661 4676 /*
4662 4677 * This is a list of all ARC buffers that are still valid on the
4663 4678 * device.
4664 4679 */
4665 4680 adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
4666 4681 list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
4667 4682 offsetof(arc_buf_hdr_t, b_l2node));
4668 4683
4669 4684 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
4670 4685
4671 4686 /*
4672 4687 * Add device to global list
4673 4688 */
4674 4689 mutex_enter(&l2arc_dev_mtx);
4675 4690 list_insert_head(l2arc_dev_list, adddev);
4676 4691 atomic_inc_64(&l2arc_ndev);
4677 4692 mutex_exit(&l2arc_dev_mtx);
4678 4693 }
4679 4694
4680 4695 /*
4681 4696 * Remove a vdev from the L2ARC.
4682 4697 */
4683 4698 void
4684 4699 l2arc_remove_vdev(vdev_t *vd)
4685 4700 {
4686 4701 l2arc_dev_t *dev, *nextdev, *remdev = NULL;
4687 4702
4688 4703 /*
4689 4704 * Find the device by vdev
4690 4705 */
4691 4706 mutex_enter(&l2arc_dev_mtx);
4692 4707 for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
4693 4708 nextdev = list_next(l2arc_dev_list, dev);
4694 4709 if (vd == dev->l2ad_vdev) {
4695 4710 remdev = dev;
4696 4711 break;
4697 4712 }
4698 4713 }
4699 4714 ASSERT(remdev != NULL);
4700 4715
4701 4716 /*
4702 4717 * Remove device from global list
4703 4718 */
4704 4719 list_remove(l2arc_dev_list, remdev);
4705 4720 l2arc_dev_last = NULL; /* may have been invalidated */
4706 4721 atomic_dec_64(&l2arc_ndev);
4707 4722 mutex_exit(&l2arc_dev_mtx);
4708 4723
4709 4724 /*
4710 4725 * Clear all buflists and ARC references. L2ARC device flush.
4711 4726 */
4712 4727 l2arc_evict(remdev, 0, B_TRUE);
4713 4728 list_destroy(remdev->l2ad_buflist);
4714 4729 kmem_free(remdev->l2ad_buflist, sizeof (list_t));
4715 4730 kmem_free(remdev, sizeof (l2arc_dev_t));
4716 4731 }
4717 4732
4718 4733 void
4719 4734 l2arc_init(void)
4720 4735 {
4721 4736 l2arc_thread_exit = 0;
4722 4737 l2arc_ndev = 0;
4723 4738 l2arc_writes_sent = 0;
4724 4739 l2arc_writes_done = 0;
4725 4740
4726 4741 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
4727 4742 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
4728 4743 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
4729 4744 mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
4730 4745 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
4731 4746
4732 4747 l2arc_dev_list = &L2ARC_dev_list;
4733 4748 l2arc_free_on_write = &L2ARC_free_on_write;
4734 4749 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
4735 4750 offsetof(l2arc_dev_t, l2ad_node));
4736 4751 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
4737 4752 offsetof(l2arc_data_free_t, l2df_list_node));
4738 4753 }
4739 4754
4740 4755 void
4741 4756 l2arc_fini(void)
4742 4757 {
4743 4758 /*
4744 4759 * This is called from dmu_fini(), which is called from spa_fini();
4745 4760 * Because of this, we can assume that all l2arc devices have
4746 4761 * already been removed when the pools themselves were removed.
4747 4762 */
4748 4763
4749 4764 l2arc_do_free_on_write();
4750 4765
4751 4766 mutex_destroy(&l2arc_feed_thr_lock);
4752 4767 cv_destroy(&l2arc_feed_thr_cv);
4753 4768 mutex_destroy(&l2arc_dev_mtx);
4754 4769 mutex_destroy(&l2arc_buflist_mtx);
4755 4770 mutex_destroy(&l2arc_free_on_write_mtx);
4756 4771
4757 4772 list_destroy(l2arc_dev_list);
4758 4773 list_destroy(l2arc_free_on_write);
4759 4774 }
4760 4775
4761 4776 void
4762 4777 l2arc_start(void)
4763 4778 {
4764 4779 if (!(spa_mode_global & FWRITE))
4765 4780 return;
4766 4781
4767 4782 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
4768 4783 TS_RUN, minclsyspri);
4769 4784 }
4770 4785
4771 4786 void
4772 4787 l2arc_stop(void)
4773 4788 {
4774 4789 if (!(spa_mode_global & FWRITE))
4775 4790 return;
4776 4791
4777 4792 mutex_enter(&l2arc_feed_thr_lock);
4778 4793 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
4779 4794 l2arc_thread_exit = 1;
4780 4795 while (l2arc_thread_exit != 0)
4781 4796 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
4782 4797 mutex_exit(&l2arc_feed_thr_lock);
4783 4798 }
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