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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 | /* | |
22 | * Copyright 2006 Sun Microsystems, Inc. All rights reserved. | |
23 | * Use is subject to license terms. | |
24 | */ | |
25 | ||
b128c09f | 26 | #pragma ident "%Z%%M% %I% %E% SMI" |
34dc7c2f BB |
27 | |
28 | #include <sys/zfs_context.h> | |
29 | #include <sys/dnode.h> | |
30 | #include <sys/dmu_objset.h> | |
31 | #include <sys/dmu_zfetch.h> | |
32 | #include <sys/dmu.h> | |
33 | #include <sys/dbuf.h> | |
34 | ||
35 | /* | |
36 | * I'm against tune-ables, but these should probably exist as tweakable globals | |
37 | * until we can get this working the way we want it to. | |
38 | */ | |
39 | ||
40 | int zfs_prefetch_disable = 0; | |
41 | ||
42 | /* max # of streams per zfetch */ | |
43 | uint32_t zfetch_max_streams = 8; | |
44 | /* min time before stream reclaim */ | |
45 | uint32_t zfetch_min_sec_reap = 2; | |
46 | /* max number of blocks to fetch at a time */ | |
47 | uint32_t zfetch_block_cap = 256; | |
48 | /* number of bytes in a array_read at which we stop prefetching (1Mb) */ | |
49 | uint64_t zfetch_array_rd_sz = 1024 * 1024; | |
50 | ||
51 | /* forward decls for static routines */ | |
52 | static int dmu_zfetch_colinear(zfetch_t *, zstream_t *); | |
53 | static void dmu_zfetch_dofetch(zfetch_t *, zstream_t *); | |
54 | static uint64_t dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t); | |
55 | static uint64_t dmu_zfetch_fetchsz(dnode_t *, uint64_t, uint64_t); | |
56 | static int dmu_zfetch_find(zfetch_t *, zstream_t *, int); | |
57 | static int dmu_zfetch_stream_insert(zfetch_t *, zstream_t *); | |
58 | static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *); | |
59 | static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *); | |
60 | static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *); | |
61 | ||
62 | /* | |
63 | * Given a zfetch structure and a zstream structure, determine whether the | |
64 | * blocks to be read are part of a co-linear pair of existing prefetch | |
65 | * streams. If a set is found, coalesce the streams, removing one, and | |
66 | * configure the prefetch so it looks for a strided access pattern. | |
67 | * | |
68 | * In other words: if we find two sequential access streams that are | |
69 | * the same length and distance N appart, and this read is N from the | |
70 | * last stream, then we are probably in a strided access pattern. So | |
71 | * combine the two sequential streams into a single strided stream. | |
72 | * | |
73 | * If no co-linear streams are found, return NULL. | |
74 | */ | |
75 | static int | |
76 | dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh) | |
77 | { | |
78 | zstream_t *z_walk; | |
79 | zstream_t *z_comp; | |
80 | ||
81 | if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) | |
82 | return (0); | |
83 | ||
84 | if (zh == NULL) { | |
85 | rw_exit(&zf->zf_rwlock); | |
86 | return (0); | |
87 | } | |
88 | ||
89 | for (z_walk = list_head(&zf->zf_stream); z_walk; | |
90 | z_walk = list_next(&zf->zf_stream, z_walk)) { | |
91 | for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp; | |
92 | z_comp = list_next(&zf->zf_stream, z_comp)) { | |
93 | int64_t diff; | |
94 | ||
95 | if (z_walk->zst_len != z_walk->zst_stride || | |
96 | z_comp->zst_len != z_comp->zst_stride) { | |
97 | continue; | |
98 | } | |
99 | ||
100 | diff = z_comp->zst_offset - z_walk->zst_offset; | |
101 | if (z_comp->zst_offset + diff == zh->zst_offset) { | |
102 | z_walk->zst_offset = zh->zst_offset; | |
103 | z_walk->zst_direction = diff < 0 ? -1 : 1; | |
104 | z_walk->zst_stride = | |
105 | diff * z_walk->zst_direction; | |
106 | z_walk->zst_ph_offset = | |
107 | zh->zst_offset + z_walk->zst_stride; | |
108 | dmu_zfetch_stream_remove(zf, z_comp); | |
109 | mutex_destroy(&z_comp->zst_lock); | |
110 | kmem_free(z_comp, sizeof (zstream_t)); | |
111 | ||
112 | dmu_zfetch_dofetch(zf, z_walk); | |
113 | ||
114 | rw_exit(&zf->zf_rwlock); | |
115 | return (1); | |
116 | } | |
117 | ||
118 | diff = z_walk->zst_offset - z_comp->zst_offset; | |
119 | if (z_walk->zst_offset + diff == zh->zst_offset) { | |
120 | z_walk->zst_offset = zh->zst_offset; | |
121 | z_walk->zst_direction = diff < 0 ? -1 : 1; | |
122 | z_walk->zst_stride = | |
123 | diff * z_walk->zst_direction; | |
124 | z_walk->zst_ph_offset = | |
125 | zh->zst_offset + z_walk->zst_stride; | |
126 | dmu_zfetch_stream_remove(zf, z_comp); | |
127 | mutex_destroy(&z_comp->zst_lock); | |
128 | kmem_free(z_comp, sizeof (zstream_t)); | |
129 | ||
130 | dmu_zfetch_dofetch(zf, z_walk); | |
131 | ||
132 | rw_exit(&zf->zf_rwlock); | |
133 | return (1); | |
134 | } | |
135 | } | |
136 | } | |
137 | ||
138 | rw_exit(&zf->zf_rwlock); | |
139 | return (0); | |
140 | } | |
141 | ||
142 | /* | |
143 | * Given a zstream_t, determine the bounds of the prefetch. Then call the | |
144 | * routine that actually prefetches the individual blocks. | |
145 | */ | |
146 | static void | |
147 | dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs) | |
148 | { | |
149 | uint64_t prefetch_tail; | |
150 | uint64_t prefetch_limit; | |
151 | uint64_t prefetch_ofst; | |
152 | uint64_t prefetch_len; | |
153 | uint64_t blocks_fetched; | |
154 | ||
155 | zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len); | |
156 | zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap); | |
157 | ||
158 | prefetch_tail = MAX((int64_t)zs->zst_ph_offset, | |
159 | (int64_t)(zs->zst_offset + zs->zst_stride)); | |
160 | /* | |
161 | * XXX: use a faster division method? | |
162 | */ | |
163 | prefetch_limit = zs->zst_offset + zs->zst_len + | |
164 | (zs->zst_cap * zs->zst_stride) / zs->zst_len; | |
165 | ||
166 | while (prefetch_tail < prefetch_limit) { | |
167 | prefetch_ofst = zs->zst_offset + zs->zst_direction * | |
168 | (prefetch_tail - zs->zst_offset); | |
169 | ||
170 | prefetch_len = zs->zst_len; | |
171 | ||
172 | /* | |
173 | * Don't prefetch beyond the end of the file, if working | |
174 | * backwards. | |
175 | */ | |
176 | if ((zs->zst_direction == ZFETCH_BACKWARD) && | |
177 | (prefetch_ofst > prefetch_tail)) { | |
178 | prefetch_len += prefetch_ofst; | |
179 | prefetch_ofst = 0; | |
180 | } | |
181 | ||
182 | /* don't prefetch more than we're supposed to */ | |
183 | if (prefetch_len > zs->zst_len) | |
184 | break; | |
185 | ||
186 | blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode, | |
187 | prefetch_ofst, zs->zst_len); | |
188 | ||
189 | prefetch_tail += zs->zst_stride; | |
190 | /* stop if we've run out of stuff to prefetch */ | |
191 | if (blocks_fetched < zs->zst_len) | |
192 | break; | |
193 | } | |
194 | zs->zst_ph_offset = prefetch_tail; | |
195 | zs->zst_last = lbolt; | |
196 | } | |
197 | ||
198 | /* | |
199 | * This takes a pointer to a zfetch structure and a dnode. It performs the | |
200 | * necessary setup for the zfetch structure, grokking data from the | |
201 | * associated dnode. | |
202 | */ | |
203 | void | |
204 | dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) | |
205 | { | |
206 | if (zf == NULL) { | |
207 | return; | |
208 | } | |
209 | ||
210 | zf->zf_dnode = dno; | |
211 | zf->zf_stream_cnt = 0; | |
212 | zf->zf_alloc_fail = 0; | |
213 | ||
214 | list_create(&zf->zf_stream, sizeof (zstream_t), | |
215 | offsetof(zstream_t, zst_node)); | |
216 | ||
217 | rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); | |
218 | } | |
219 | ||
220 | /* | |
221 | * This function computes the actual size, in blocks, that can be prefetched, | |
222 | * and fetches it. | |
223 | */ | |
224 | static uint64_t | |
225 | dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks) | |
226 | { | |
227 | uint64_t fetchsz; | |
228 | uint64_t i; | |
229 | ||
230 | fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks); | |
231 | ||
232 | for (i = 0; i < fetchsz; i++) { | |
233 | dbuf_prefetch(dn, blkid + i); | |
234 | } | |
235 | ||
236 | return (fetchsz); | |
237 | } | |
238 | ||
239 | /* | |
240 | * this function returns the number of blocks that would be prefetched, based | |
241 | * upon the supplied dnode, blockid, and nblks. This is used so that we can | |
242 | * update streams in place, and then prefetch with their old value after the | |
243 | * fact. This way, we can delay the prefetch, but subsequent accesses to the | |
244 | * stream won't result in the same data being prefetched multiple times. | |
245 | */ | |
246 | static uint64_t | |
247 | dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks) | |
248 | { | |
249 | uint64_t fetchsz; | |
250 | ||
251 | if (blkid > dn->dn_maxblkid) { | |
252 | return (0); | |
253 | } | |
254 | ||
255 | /* compute fetch size */ | |
256 | if (blkid + nblks + 1 > dn->dn_maxblkid) { | |
257 | fetchsz = (dn->dn_maxblkid - blkid) + 1; | |
258 | ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid); | |
259 | } else { | |
260 | fetchsz = nblks; | |
261 | } | |
262 | ||
263 | ||
264 | return (fetchsz); | |
265 | } | |
266 | ||
267 | /* | |
268 | * given a zfetch and a zsearch structure, see if there is an associated zstream | |
269 | * for this block read. If so, it starts a prefetch for the stream it | |
270 | * located and returns true, otherwise it returns false | |
271 | */ | |
272 | static int | |
273 | dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched) | |
274 | { | |
275 | zstream_t *zs; | |
276 | int64_t diff; | |
277 | int reset = !prefetched; | |
278 | int rc = 0; | |
279 | ||
280 | if (zh == NULL) | |
281 | return (0); | |
282 | ||
283 | /* | |
284 | * XXX: This locking strategy is a bit coarse; however, it's impact has | |
285 | * yet to be tested. If this turns out to be an issue, it can be | |
286 | * modified in a number of different ways. | |
287 | */ | |
288 | ||
289 | rw_enter(&zf->zf_rwlock, RW_READER); | |
290 | top: | |
291 | ||
292 | for (zs = list_head(&zf->zf_stream); zs; | |
293 | zs = list_next(&zf->zf_stream, zs)) { | |
294 | ||
295 | /* | |
296 | * XXX - should this be an assert? | |
297 | */ | |
298 | if (zs->zst_len == 0) { | |
299 | /* bogus stream */ | |
300 | continue; | |
301 | } | |
302 | ||
303 | /* | |
304 | * We hit this case when we are in a strided prefetch stream: | |
305 | * we will read "len" blocks before "striding". | |
306 | */ | |
307 | if (zh->zst_offset >= zs->zst_offset && | |
308 | zh->zst_offset < zs->zst_offset + zs->zst_len) { | |
309 | /* already fetched */ | |
310 | rc = 1; | |
311 | goto out; | |
312 | } | |
313 | ||
314 | /* | |
315 | * This is the forward sequential read case: we increment | |
316 | * len by one each time we hit here, so we will enter this | |
317 | * case on every read. | |
318 | */ | |
319 | if (zh->zst_offset == zs->zst_offset + zs->zst_len) { | |
320 | ||
321 | reset = !prefetched && zs->zst_len > 1; | |
322 | ||
323 | mutex_enter(&zs->zst_lock); | |
324 | ||
325 | if (zh->zst_offset != zs->zst_offset + zs->zst_len) { | |
326 | mutex_exit(&zs->zst_lock); | |
327 | goto top; | |
328 | } | |
329 | zs->zst_len += zh->zst_len; | |
330 | diff = zs->zst_len - zfetch_block_cap; | |
331 | if (diff > 0) { | |
332 | zs->zst_offset += diff; | |
333 | zs->zst_len = zs->zst_len > diff ? | |
334 | zs->zst_len - diff : 0; | |
335 | } | |
336 | zs->zst_direction = ZFETCH_FORWARD; | |
337 | ||
338 | break; | |
339 | ||
340 | /* | |
341 | * Same as above, but reading backwards through the file. | |
342 | */ | |
343 | } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) { | |
344 | /* backwards sequential access */ | |
345 | ||
346 | reset = !prefetched && zs->zst_len > 1; | |
347 | ||
348 | mutex_enter(&zs->zst_lock); | |
349 | ||
350 | if (zh->zst_offset != zs->zst_offset - zh->zst_len) { | |
351 | mutex_exit(&zs->zst_lock); | |
352 | goto top; | |
353 | } | |
354 | ||
355 | zs->zst_offset = zs->zst_offset > zh->zst_len ? | |
356 | zs->zst_offset - zh->zst_len : 0; | |
357 | zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ? | |
358 | zs->zst_ph_offset - zh->zst_len : 0; | |
359 | zs->zst_len += zh->zst_len; | |
360 | ||
361 | diff = zs->zst_len - zfetch_block_cap; | |
362 | if (diff > 0) { | |
363 | zs->zst_ph_offset = zs->zst_ph_offset > diff ? | |
364 | zs->zst_ph_offset - diff : 0; | |
365 | zs->zst_len = zs->zst_len > diff ? | |
366 | zs->zst_len - diff : zs->zst_len; | |
367 | } | |
368 | zs->zst_direction = ZFETCH_BACKWARD; | |
369 | ||
370 | break; | |
371 | ||
372 | } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride < | |
373 | zs->zst_len) && (zs->zst_len != zs->zst_stride)) { | |
374 | /* strided forward access */ | |
375 | ||
376 | mutex_enter(&zs->zst_lock); | |
377 | ||
378 | if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >= | |
379 | zs->zst_len) || (zs->zst_len == zs->zst_stride)) { | |
380 | mutex_exit(&zs->zst_lock); | |
381 | goto top; | |
382 | } | |
383 | ||
384 | zs->zst_offset += zs->zst_stride; | |
385 | zs->zst_direction = ZFETCH_FORWARD; | |
386 | ||
387 | break; | |
388 | ||
389 | } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride < | |
390 | zs->zst_len) && (zs->zst_len != zs->zst_stride)) { | |
391 | /* strided reverse access */ | |
392 | ||
393 | mutex_enter(&zs->zst_lock); | |
394 | ||
395 | if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >= | |
396 | zs->zst_len) || (zs->zst_len == zs->zst_stride)) { | |
397 | mutex_exit(&zs->zst_lock); | |
398 | goto top; | |
399 | } | |
400 | ||
401 | zs->zst_offset = zs->zst_offset > zs->zst_stride ? | |
402 | zs->zst_offset - zs->zst_stride : 0; | |
403 | zs->zst_ph_offset = (zs->zst_ph_offset > | |
404 | (2 * zs->zst_stride)) ? | |
405 | (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0; | |
406 | zs->zst_direction = ZFETCH_BACKWARD; | |
407 | ||
408 | break; | |
409 | } | |
410 | } | |
411 | ||
412 | if (zs) { | |
413 | if (reset) { | |
414 | zstream_t *remove = zs; | |
415 | ||
416 | rc = 0; | |
417 | mutex_exit(&zs->zst_lock); | |
418 | rw_exit(&zf->zf_rwlock); | |
419 | rw_enter(&zf->zf_rwlock, RW_WRITER); | |
420 | /* | |
421 | * Relocate the stream, in case someone removes | |
422 | * it while we were acquiring the WRITER lock. | |
423 | */ | |
424 | for (zs = list_head(&zf->zf_stream); zs; | |
425 | zs = list_next(&zf->zf_stream, zs)) { | |
426 | if (zs == remove) { | |
427 | dmu_zfetch_stream_remove(zf, zs); | |
428 | mutex_destroy(&zs->zst_lock); | |
429 | kmem_free(zs, sizeof (zstream_t)); | |
430 | break; | |
431 | } | |
432 | } | |
433 | } else { | |
434 | rc = 1; | |
435 | dmu_zfetch_dofetch(zf, zs); | |
436 | mutex_exit(&zs->zst_lock); | |
437 | } | |
438 | } | |
439 | out: | |
440 | rw_exit(&zf->zf_rwlock); | |
441 | return (rc); | |
442 | } | |
443 | ||
444 | /* | |
445 | * Clean-up state associated with a zfetch structure. This frees allocated | |
446 | * structure members, empties the zf_stream tree, and generally makes things | |
447 | * nice. This doesn't free the zfetch_t itself, that's left to the caller. | |
448 | */ | |
449 | void | |
450 | dmu_zfetch_rele(zfetch_t *zf) | |
451 | { | |
452 | zstream_t *zs; | |
453 | zstream_t *zs_next; | |
454 | ||
455 | ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock)); | |
456 | ||
457 | for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) { | |
458 | zs_next = list_next(&zf->zf_stream, zs); | |
459 | ||
460 | list_remove(&zf->zf_stream, zs); | |
461 | mutex_destroy(&zs->zst_lock); | |
462 | kmem_free(zs, sizeof (zstream_t)); | |
463 | } | |
464 | list_destroy(&zf->zf_stream); | |
465 | rw_destroy(&zf->zf_rwlock); | |
466 | ||
467 | zf->zf_dnode = NULL; | |
468 | } | |
469 | ||
470 | /* | |
471 | * Given a zfetch and zstream structure, insert the zstream structure into the | |
472 | * AVL tree contained within the zfetch structure. Peform the appropriate | |
473 | * book-keeping. It is possible that another thread has inserted a stream which | |
474 | * matches one that we are about to insert, so we must be sure to check for this | |
475 | * case. If one is found, return failure, and let the caller cleanup the | |
476 | * duplicates. | |
477 | */ | |
478 | static int | |
479 | dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs) | |
480 | { | |
481 | zstream_t *zs_walk; | |
482 | zstream_t *zs_next; | |
483 | ||
484 | ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); | |
485 | ||
486 | for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) { | |
487 | zs_next = list_next(&zf->zf_stream, zs_walk); | |
488 | ||
489 | if (dmu_zfetch_streams_equal(zs_walk, zs)) { | |
490 | return (0); | |
491 | } | |
492 | } | |
493 | ||
494 | list_insert_head(&zf->zf_stream, zs); | |
495 | zf->zf_stream_cnt++; | |
496 | ||
497 | return (1); | |
498 | } | |
499 | ||
500 | ||
501 | /* | |
502 | * Walk the list of zstreams in the given zfetch, find an old one (by time), and | |
503 | * reclaim it for use by the caller. | |
504 | */ | |
505 | static zstream_t * | |
506 | dmu_zfetch_stream_reclaim(zfetch_t *zf) | |
507 | { | |
508 | zstream_t *zs; | |
509 | ||
510 | if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) | |
511 | return (0); | |
512 | ||
513 | for (zs = list_head(&zf->zf_stream); zs; | |
514 | zs = list_next(&zf->zf_stream, zs)) { | |
515 | ||
516 | if (((lbolt - zs->zst_last) / hz) > zfetch_min_sec_reap) | |
517 | break; | |
518 | } | |
519 | ||
520 | if (zs) { | |
521 | dmu_zfetch_stream_remove(zf, zs); | |
522 | mutex_destroy(&zs->zst_lock); | |
523 | bzero(zs, sizeof (zstream_t)); | |
524 | } else { | |
525 | zf->zf_alloc_fail++; | |
526 | } | |
527 | rw_exit(&zf->zf_rwlock); | |
528 | ||
529 | return (zs); | |
530 | } | |
531 | ||
532 | /* | |
533 | * Given a zfetch and zstream structure, remove the zstream structure from its | |
534 | * container in the zfetch structure. Perform the appropriate book-keeping. | |
535 | */ | |
536 | static void | |
537 | dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) | |
538 | { | |
539 | ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); | |
540 | ||
541 | list_remove(&zf->zf_stream, zs); | |
542 | zf->zf_stream_cnt--; | |
543 | } | |
544 | ||
545 | static int | |
546 | dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2) | |
547 | { | |
548 | if (zs1->zst_offset != zs2->zst_offset) | |
549 | return (0); | |
550 | ||
551 | if (zs1->zst_len != zs2->zst_len) | |
552 | return (0); | |
553 | ||
554 | if (zs1->zst_stride != zs2->zst_stride) | |
555 | return (0); | |
556 | ||
557 | if (zs1->zst_ph_offset != zs2->zst_ph_offset) | |
558 | return (0); | |
559 | ||
560 | if (zs1->zst_cap != zs2->zst_cap) | |
561 | return (0); | |
562 | ||
563 | if (zs1->zst_direction != zs2->zst_direction) | |
564 | return (0); | |
565 | ||
566 | return (1); | |
567 | } | |
568 | ||
569 | /* | |
570 | * This is the prefetch entry point. It calls all of the other dmu_zfetch | |
571 | * routines to create, delete, find, or operate upon prefetch streams. | |
572 | */ | |
573 | void | |
574 | dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched) | |
575 | { | |
576 | zstream_t zst; | |
577 | zstream_t *newstream; | |
578 | int fetched; | |
579 | int inserted; | |
580 | unsigned int blkshft; | |
581 | uint64_t blksz; | |
582 | ||
583 | if (zfs_prefetch_disable) | |
584 | return; | |
585 | ||
586 | /* files that aren't ln2 blocksz are only one block -- nothing to do */ | |
587 | if (!zf->zf_dnode->dn_datablkshift) | |
588 | return; | |
589 | ||
590 | /* convert offset and size, into blockid and nblocks */ | |
591 | blkshft = zf->zf_dnode->dn_datablkshift; | |
592 | blksz = (1 << blkshft); | |
593 | ||
594 | bzero(&zst, sizeof (zstream_t)); | |
595 | zst.zst_offset = offset >> blkshft; | |
596 | zst.zst_len = (P2ROUNDUP(offset + size, blksz) - | |
597 | P2ALIGN(offset, blksz)) >> blkshft; | |
598 | ||
599 | fetched = dmu_zfetch_find(zf, &zst, prefetched); | |
600 | if (!fetched) { | |
601 | fetched = dmu_zfetch_colinear(zf, &zst); | |
602 | } | |
603 | ||
604 | if (!fetched) { | |
605 | newstream = dmu_zfetch_stream_reclaim(zf); | |
606 | ||
607 | /* | |
608 | * we still couldn't find a stream, drop the lock, and allocate | |
609 | * one if possible. Otherwise, give up and go home. | |
610 | */ | |
611 | if (newstream == NULL) { | |
612 | uint64_t maxblocks; | |
613 | uint32_t max_streams; | |
614 | uint32_t cur_streams; | |
615 | ||
616 | cur_streams = zf->zf_stream_cnt; | |
617 | maxblocks = zf->zf_dnode->dn_maxblkid; | |
618 | ||
619 | max_streams = MIN(zfetch_max_streams, | |
620 | (maxblocks / zfetch_block_cap)); | |
621 | if (max_streams == 0) { | |
622 | max_streams++; | |
623 | } | |
624 | ||
625 | if (cur_streams >= max_streams) { | |
626 | return; | |
627 | } | |
628 | ||
629 | newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP); | |
630 | } | |
631 | ||
632 | newstream->zst_offset = zst.zst_offset; | |
633 | newstream->zst_len = zst.zst_len; | |
634 | newstream->zst_stride = zst.zst_len; | |
635 | newstream->zst_ph_offset = zst.zst_len + zst.zst_offset; | |
636 | newstream->zst_cap = zst.zst_len; | |
637 | newstream->zst_direction = ZFETCH_FORWARD; | |
638 | newstream->zst_last = lbolt; | |
639 | ||
640 | mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL); | |
641 | ||
642 | rw_enter(&zf->zf_rwlock, RW_WRITER); | |
643 | inserted = dmu_zfetch_stream_insert(zf, newstream); | |
644 | rw_exit(&zf->zf_rwlock); | |
645 | ||
646 | if (!inserted) { | |
647 | mutex_destroy(&newstream->zst_lock); | |
648 | kmem_free(newstream, sizeof (zstream_t)); | |
649 | } | |
650 | } | |
651 | } |