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