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