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34dc7c2f BB |
1 | /* |
2 | * CDDL HEADER START | |
3 | * | |
4 | * The contents of this file are subject to the terms of the | |
5 | * Common Development and Distribution License (the "License"). | |
6 | * You may not use this file except in compliance with the License. | |
7 | * | |
8 | * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE | |
9 | * or http://www.opensolaris.org/os/licensing. | |
10 | * See the License for the specific language governing permissions | |
11 | * and limitations under the License. | |
12 | * | |
13 | * When distributing Covered Code, include this CDDL HEADER in each | |
14 | * file and include the License file at usr/src/OPENSOLARIS.LICENSE. | |
15 | * If applicable, add the following below this CDDL HEADER, with the | |
16 | * fields enclosed by brackets "[]" replaced with your own identifying | |
17 | * information: Portions Copyright [yyyy] [name of copyright owner] | |
18 | * | |
19 | * CDDL HEADER END | |
20 | */ | |
21 | /* | |
428870ff | 22 | * Copyright 2009 Sun Microsystems, Inc. All rights reserved. |
34dc7c2f BB |
23 | * Use is subject to license terms. |
24 | */ | |
25 | ||
e8b96c60 | 26 | /* |
a6fb32b8 | 27 | * Copyright (c) 2013, 2015 by Delphix. All rights reserved. |
e8b96c60 MA |
28 | */ |
29 | ||
34dc7c2f BB |
30 | #include <sys/zfs_context.h> |
31 | #include <sys/dnode.h> | |
32 | #include <sys/dmu_objset.h> | |
33 | #include <sys/dmu_zfetch.h> | |
34 | #include <sys/dmu.h> | |
35 | #include <sys/dbuf.h> | |
428870ff | 36 | #include <sys/kstat.h> |
34dc7c2f BB |
37 | |
38 | /* | |
7f60329a MA |
39 | * This tunable disables predictive prefetch. Note that it leaves "prescient" |
40 | * prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch, | |
41 | * prescient prefetch never issues i/os that end up not being needed, | |
42 | * so it can't hurt performance. | |
34dc7c2f BB |
43 | */ |
44 | ||
7f60329a | 45 | int zfs_prefetch_disable = B_FALSE; |
34dc7c2f BB |
46 | |
47 | /* max # of streams per zfetch */ | |
c409e464 | 48 | unsigned int zfetch_max_streams = 8; |
34dc7c2f | 49 | /* min time before stream reclaim */ |
c409e464 | 50 | unsigned int zfetch_min_sec_reap = 2; |
7f60329a MA |
51 | /* max bytes to prefetch per stream (default 8MB) */ |
52 | unsigned int zfetch_max_distance = 8 * 1024 * 1024; | |
755065f3 AM |
53 | /* max bytes to prefetch indirects for per stream (default 64MB) */ |
54 | unsigned int zfetch_max_idistance = 64 * 1024 * 1024; | |
a6fb32b8 | 55 | /* max number of bytes in an array_read in which we allow prefetching (1MB) */ |
c409e464 | 56 | unsigned long zfetch_array_rd_sz = 1024 * 1024; |
34dc7c2f | 57 | |
428870ff BB |
58 | typedef struct zfetch_stats { |
59 | kstat_named_t zfetchstat_hits; | |
60 | kstat_named_t zfetchstat_misses; | |
7f60329a | 61 | kstat_named_t zfetchstat_max_streams; |
428870ff BB |
62 | } zfetch_stats_t; |
63 | ||
64 | static zfetch_stats_t zfetch_stats = { | |
65 | { "hits", KSTAT_DATA_UINT64 }, | |
66 | { "misses", KSTAT_DATA_UINT64 }, | |
7f60329a | 67 | { "max_streams", KSTAT_DATA_UINT64 }, |
428870ff BB |
68 | }; |
69 | ||
7f60329a MA |
70 | #define ZFETCHSTAT_BUMP(stat) \ |
71 | atomic_inc_64(&zfetch_stats.stat.value.ui64); | |
428870ff BB |
72 | |
73 | kstat_t *zfetch_ksp; | |
74 | ||
428870ff BB |
75 | void |
76 | zfetch_init(void) | |
77 | { | |
428870ff BB |
78 | zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc", |
79 | KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t), | |
80 | KSTAT_FLAG_VIRTUAL); | |
81 | ||
82 | if (zfetch_ksp != NULL) { | |
83 | zfetch_ksp->ks_data = &zfetch_stats; | |
84 | kstat_install(zfetch_ksp); | |
85 | } | |
86 | } | |
87 | ||
88 | void | |
89 | zfetch_fini(void) | |
90 | { | |
91 | if (zfetch_ksp != NULL) { | |
92 | kstat_delete(zfetch_ksp); | |
93 | zfetch_ksp = NULL; | |
94 | } | |
34dc7c2f BB |
95 | } |
96 | ||
97 | /* | |
98 | * This takes a pointer to a zfetch structure and a dnode. It performs the | |
99 | * necessary setup for the zfetch structure, grokking data from the | |
100 | * associated dnode. | |
101 | */ | |
102 | void | |
103 | dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) | |
104 | { | |
7f60329a | 105 | if (zf == NULL) |
34dc7c2f | 106 | return; |
34dc7c2f BB |
107 | |
108 | zf->zf_dnode = dno; | |
34dc7c2f BB |
109 | |
110 | list_create(&zf->zf_stream, sizeof (zstream_t), | |
7f60329a | 111 | offsetof(zstream_t, zs_node)); |
34dc7c2f BB |
112 | |
113 | rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); | |
114 | } | |
115 | ||
7f60329a MA |
116 | static void |
117 | dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) | |
34dc7c2f | 118 | { |
7f60329a MA |
119 | ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); |
120 | list_remove(&zf->zf_stream, zs); | |
121 | mutex_destroy(&zs->zs_lock); | |
122 | kmem_free(zs, sizeof (*zs)); | |
34dc7c2f BB |
123 | } |
124 | ||
125 | /* | |
7f60329a MA |
126 | * Clean-up state associated with a zfetch structure (e.g. destroy the |
127 | * streams). This doesn't free the zfetch_t itself, that's left to the caller. | |
34dc7c2f BB |
128 | */ |
129 | void | |
7f60329a | 130 | dmu_zfetch_fini(zfetch_t *zf) |
34dc7c2f | 131 | { |
7f60329a | 132 | zstream_t *zs; |
34dc7c2f BB |
133 | |
134 | ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock)); | |
135 | ||
7f60329a MA |
136 | rw_enter(&zf->zf_rwlock, RW_WRITER); |
137 | while ((zs = list_head(&zf->zf_stream)) != NULL) | |
138 | dmu_zfetch_stream_remove(zf, zs); | |
139 | rw_exit(&zf->zf_rwlock); | |
34dc7c2f BB |
140 | list_destroy(&zf->zf_stream); |
141 | rw_destroy(&zf->zf_rwlock); | |
142 | ||
143 | zf->zf_dnode = NULL; | |
144 | } | |
145 | ||
146 | /* | |
7f60329a MA |
147 | * If there aren't too many streams already, create a new stream. |
148 | * The "blkid" argument is the next block that we expect this stream to access. | |
149 | * While we're here, clean up old streams (which haven't been | |
150 | * accessed for at least zfetch_min_sec_reap seconds). | |
34dc7c2f | 151 | */ |
7f60329a MA |
152 | static void |
153 | dmu_zfetch_stream_create(zfetch_t *zf, uint64_t blkid) | |
34dc7c2f | 154 | { |
7f60329a MA |
155 | zstream_t *zs; |
156 | zstream_t *zs_next; | |
157 | int numstreams = 0; | |
158 | uint32_t max_streams; | |
34dc7c2f BB |
159 | |
160 | ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); | |
161 | ||
7f60329a MA |
162 | /* |
163 | * Clean up old streams. | |
164 | */ | |
165 | for (zs = list_head(&zf->zf_stream); | |
166 | zs != NULL; zs = zs_next) { | |
167 | zs_next = list_next(&zf->zf_stream, zs); | |
168 | if (((gethrtime() - zs->zs_atime) / NANOSEC) > | |
169 | zfetch_min_sec_reap) | |
170 | dmu_zfetch_stream_remove(zf, zs); | |
171 | else | |
172 | numstreams++; | |
34dc7c2f BB |
173 | } |
174 | ||
7f60329a MA |
175 | /* |
176 | * The maximum number of streams is normally zfetch_max_streams, | |
177 | * but for small files we lower it such that it's at least possible | |
178 | * for all the streams to be non-overlapping. | |
179 | * | |
180 | * If we are already at the maximum number of streams for this file, | |
181 | * even after removing old streams, then don't create this stream. | |
182 | */ | |
183 | max_streams = MAX(1, MIN(zfetch_max_streams, | |
184 | zf->zf_dnode->dn_maxblkid * zf->zf_dnode->dn_datablksz / | |
185 | zfetch_max_distance)); | |
186 | if (numstreams >= max_streams) { | |
187 | ZFETCHSTAT_BUMP(zfetchstat_max_streams); | |
188 | return; | |
34dc7c2f | 189 | } |
34dc7c2f | 190 | |
7f60329a MA |
191 | zs = kmem_zalloc(sizeof (*zs), KM_SLEEP); |
192 | zs->zs_blkid = blkid; | |
193 | zs->zs_pf_blkid = blkid; | |
755065f3 | 194 | zs->zs_ipf_blkid = blkid; |
7f60329a MA |
195 | zs->zs_atime = gethrtime(); |
196 | mutex_init(&zs->zs_lock, NULL, MUTEX_DEFAULT, NULL); | |
34dc7c2f | 197 | |
7f60329a | 198 | list_insert_head(&zf->zf_stream, zs); |
34dc7c2f BB |
199 | } |
200 | ||
201 | /* | |
755065f3 AM |
202 | * This is the predictive prefetch entry point. It associates dnode access |
203 | * specified with blkid and nblks arguments with prefetch stream, predicts | |
204 | * further accesses based on that stats and initiates speculative prefetch. | |
205 | * fetch_data argument specifies whether actual data blocks should be fetched: | |
206 | * FALSE -- prefetch only indirect blocks for predicted data blocks; | |
207 | * TRUE -- prefetch predicted data blocks plus following indirect blocks. | |
34dc7c2f BB |
208 | */ |
209 | void | |
755065f3 | 210 | dmu_zfetch(zfetch_t *zf, uint64_t blkid, uint64_t nblks, boolean_t fetch_data) |
34dc7c2f | 211 | { |
7f60329a | 212 | zstream_t *zs; |
755065f3 AM |
213 | int64_t pf_start, ipf_start, ipf_istart, ipf_iend; |
214 | int64_t pf_ahead_blks, max_blks, iblk; | |
215 | int epbs, max_dist_blks, pf_nblks, ipf_nblks, i; | |
216 | uint64_t end_of_access_blkid; | |
217 | end_of_access_blkid = blkid + nblks; | |
34dc7c2f BB |
218 | |
219 | if (zfs_prefetch_disable) | |
220 | return; | |
221 | ||
7f60329a MA |
222 | /* |
223 | * As a fast path for small (single-block) files, ignore access | |
224 | * to the first block. | |
225 | */ | |
226 | if (blkid == 0) | |
34dc7c2f BB |
227 | return; |
228 | ||
7f60329a | 229 | rw_enter(&zf->zf_rwlock, RW_READER); |
34dc7c2f | 230 | |
7f60329a MA |
231 | for (zs = list_head(&zf->zf_stream); zs != NULL; |
232 | zs = list_next(&zf->zf_stream, zs)) { | |
233 | if (blkid == zs->zs_blkid) { | |
234 | mutex_enter(&zs->zs_lock); | |
235 | /* | |
236 | * zs_blkid could have changed before we | |
237 | * acquired zs_lock; re-check them here. | |
238 | */ | |
239 | if (blkid != zs->zs_blkid) { | |
240 | mutex_exit(&zs->zs_lock); | |
241 | continue; | |
242 | } | |
243 | break; | |
428870ff | 244 | } |
34dc7c2f BB |
245 | } |
246 | ||
7f60329a | 247 | if (zs == NULL) { |
34dc7c2f | 248 | /* |
7f60329a MA |
249 | * This access is not part of any existing stream. Create |
250 | * a new stream for it. | |
34dc7c2f | 251 | */ |
7f60329a MA |
252 | ZFETCHSTAT_BUMP(zfetchstat_misses); |
253 | if (rw_tryupgrade(&zf->zf_rwlock)) | |
755065f3 | 254 | dmu_zfetch_stream_create(zf, end_of_access_blkid); |
7f60329a MA |
255 | rw_exit(&zf->zf_rwlock); |
256 | return; | |
257 | } | |
34dc7c2f | 258 | |
7f60329a MA |
259 | /* |
260 | * This access was to a block that we issued a prefetch for on | |
261 | * behalf of this stream. Issue further prefetches for this stream. | |
262 | * | |
263 | * Normally, we start prefetching where we stopped | |
264 | * prefetching last (zs_pf_blkid). But when we get our first | |
265 | * hit on this stream, zs_pf_blkid == zs_blkid, we don't | |
755065f3 | 266 | * want to prefetch the block we just accessed. In this case, |
7f60329a MA |
267 | * start just after the block we just accessed. |
268 | */ | |
755065f3 | 269 | pf_start = MAX(zs->zs_pf_blkid, end_of_access_blkid); |
34dc7c2f | 270 | |
7f60329a MA |
271 | /* |
272 | * Double our amount of prefetched data, but don't let the | |
273 | * prefetch get further ahead than zfetch_max_distance. | |
274 | */ | |
755065f3 AM |
275 | if (fetch_data) { |
276 | max_dist_blks = | |
277 | zfetch_max_distance >> zf->zf_dnode->dn_datablkshift; | |
278 | /* | |
279 | * Previously, we were (zs_pf_blkid - blkid) ahead. We | |
280 | * want to now be double that, so read that amount again, | |
281 | * plus the amount we are catching up by (i.e. the amount | |
282 | * read just now). | |
283 | */ | |
284 | pf_ahead_blks = zs->zs_pf_blkid - blkid + nblks; | |
285 | max_blks = max_dist_blks - (pf_start - end_of_access_blkid); | |
286 | pf_nblks = MIN(pf_ahead_blks, max_blks); | |
287 | } else { | |
288 | pf_nblks = 0; | |
289 | } | |
34dc7c2f | 290 | |
7f60329a | 291 | zs->zs_pf_blkid = pf_start + pf_nblks; |
34dc7c2f | 292 | |
7f60329a | 293 | /* |
755065f3 AM |
294 | * Do the same for indirects, starting from where we stopped last, |
295 | * or where we will stop reading data blocks (and the indirects | |
296 | * that point to them). | |
7f60329a | 297 | */ |
755065f3 AM |
298 | ipf_start = MAX(zs->zs_ipf_blkid, zs->zs_pf_blkid); |
299 | max_dist_blks = zfetch_max_idistance >> zf->zf_dnode->dn_datablkshift; | |
300 | /* | |
301 | * We want to double our distance ahead of the data prefetch | |
302 | * (or reader, if we are not prefetching data). Previously, we | |
303 | * were (zs_ipf_blkid - blkid) ahead. To double that, we read | |
304 | * that amount again, plus the amount we are catching up by | |
305 | * (i.e. the amount read now + the amount of data prefetched now). | |
306 | */ | |
307 | pf_ahead_blks = zs->zs_ipf_blkid - blkid + nblks + pf_nblks; | |
308 | max_blks = max_dist_blks - (ipf_start - end_of_access_blkid); | |
309 | ipf_nblks = MIN(pf_ahead_blks, max_blks); | |
310 | zs->zs_ipf_blkid = ipf_start + ipf_nblks; | |
311 | ||
312 | epbs = zf->zf_dnode->dn_indblkshift - SPA_BLKPTRSHIFT; | |
313 | ipf_istart = P2ROUNDUP(ipf_start, 1 << epbs) >> epbs; | |
314 | ipf_iend = P2ROUNDUP(zs->zs_ipf_blkid, 1 << epbs) >> epbs; | |
315 | ||
316 | zs->zs_atime = gethrtime(); | |
317 | zs->zs_blkid = end_of_access_blkid; | |
7f60329a MA |
318 | mutex_exit(&zs->zs_lock); |
319 | rw_exit(&zf->zf_rwlock); | |
755065f3 AM |
320 | |
321 | /* | |
322 | * dbuf_prefetch() is asynchronous (even when it needs to read | |
323 | * indirect blocks), but we still prefer to drop our locks before | |
324 | * calling it to reduce the time we hold them. | |
325 | */ | |
326 | ||
7f60329a MA |
327 | for (i = 0; i < pf_nblks; i++) { |
328 | dbuf_prefetch(zf->zf_dnode, 0, pf_start + i, | |
329 | ZIO_PRIORITY_ASYNC_READ, ARC_FLAG_PREDICTIVE_PREFETCH); | |
34dc7c2f | 330 | } |
755065f3 AM |
331 | for (iblk = ipf_istart; iblk < ipf_iend; iblk++) { |
332 | dbuf_prefetch(zf->zf_dnode, 1, iblk, | |
333 | ZIO_PRIORITY_ASYNC_READ, ARC_FLAG_PREDICTIVE_PREFETCH); | |
334 | } | |
7f60329a | 335 | ZFETCHSTAT_BUMP(zfetchstat_hits); |
34dc7c2f | 336 | } |
c28b2279 BB |
337 | |
338 | #if defined(_KERNEL) && defined(HAVE_SPL) | |
02730c33 | 339 | /* BEGIN CSTYLED */ |
c28b2279 BB |
340 | module_param(zfs_prefetch_disable, int, 0644); |
341 | MODULE_PARM_DESC(zfs_prefetch_disable, "Disable all ZFS prefetching"); | |
c409e464 BB |
342 | |
343 | module_param(zfetch_max_streams, uint, 0644); | |
344 | MODULE_PARM_DESC(zfetch_max_streams, "Max number of streams per zfetch"); | |
345 | ||
346 | module_param(zfetch_min_sec_reap, uint, 0644); | |
347 | MODULE_PARM_DESC(zfetch_min_sec_reap, "Min time before stream reclaim"); | |
348 | ||
7f60329a MA |
349 | module_param(zfetch_max_distance, uint, 0644); |
350 | MODULE_PARM_DESC(zfetch_max_distance, | |
351 | "Max bytes to prefetch per stream (default 8MB)"); | |
c409e464 BB |
352 | |
353 | module_param(zfetch_array_rd_sz, ulong, 0644); | |
354 | MODULE_PARM_DESC(zfetch_array_rd_sz, "Number of bytes in a array_read"); | |
02730c33 | 355 | /* END CSTYLED */ |
c28b2279 | 356 | #endif |