dmu_zfetch.c revision 260763
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 2009 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26/* 27 * Copyright (c) 2013 by Delphix. All rights reserved. 28 */ 29 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> 36#include <sys/kstat.h> 37 38/* 39 * I'm against tune-ables, but these should probably exist as tweakable globals 40 * until we can get this working the way we want it to. 41 */ 42 43int zfs_prefetch_disable = 0; 44 45/* max # of streams per zfetch */ 46uint32_t zfetch_max_streams = 8; 47/* min time before stream reclaim */ 48uint32_t zfetch_min_sec_reap = 2; 49/* max number of blocks to fetch at a time */ 50uint32_t zfetch_block_cap = 256; 51/* number of bytes in a array_read at which we stop prefetching (1Mb) */ 52uint64_t zfetch_array_rd_sz = 1024 * 1024; 53 54SYSCTL_DECL(_vfs_zfs); 55SYSCTL_INT(_vfs_zfs, OID_AUTO, prefetch_disable, CTLFLAG_RW, 56 &zfs_prefetch_disable, 0, "Disable prefetch"); 57SYSCTL_NODE(_vfs_zfs, OID_AUTO, zfetch, CTLFLAG_RW, 0, "ZFS ZFETCH"); 58TUNABLE_INT("vfs.zfs.zfetch.max_streams", &zfetch_max_streams); 59SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_streams, CTLFLAG_RW, 60 &zfetch_max_streams, 0, "Max # of streams per zfetch"); 61TUNABLE_INT("vfs.zfs.zfetch.min_sec_reap", &zfetch_min_sec_reap); 62SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, min_sec_reap, CTLFLAG_RDTUN, 63 &zfetch_min_sec_reap, 0, "Min time before stream reclaim"); 64TUNABLE_INT("vfs.zfs.zfetch.block_cap", &zfetch_block_cap); 65SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, block_cap, CTLFLAG_RDTUN, 66 &zfetch_block_cap, 0, "Max number of blocks to fetch at a time"); 67TUNABLE_QUAD("vfs.zfs.zfetch.array_rd_sz", &zfetch_array_rd_sz); 68SYSCTL_UQUAD(_vfs_zfs_zfetch, OID_AUTO, array_rd_sz, CTLFLAG_RDTUN, 69 &zfetch_array_rd_sz, 0, 70 "Number of bytes in a array_read at which we stop prefetching"); 71 72/* forward decls for static routines */ 73static boolean_t dmu_zfetch_colinear(zfetch_t *, zstream_t *); 74static void dmu_zfetch_dofetch(zfetch_t *, zstream_t *); 75static uint64_t dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t); 76static uint64_t dmu_zfetch_fetchsz(dnode_t *, uint64_t, uint64_t); 77static boolean_t dmu_zfetch_find(zfetch_t *, zstream_t *, int); 78static int dmu_zfetch_stream_insert(zfetch_t *, zstream_t *); 79static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *); 80static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *); 81static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *); 82 83typedef struct zfetch_stats { 84 kstat_named_t zfetchstat_hits; 85 kstat_named_t zfetchstat_misses; 86 kstat_named_t zfetchstat_colinear_hits; 87 kstat_named_t zfetchstat_colinear_misses; 88 kstat_named_t zfetchstat_stride_hits; 89 kstat_named_t zfetchstat_stride_misses; 90 kstat_named_t zfetchstat_reclaim_successes; 91 kstat_named_t zfetchstat_reclaim_failures; 92 kstat_named_t zfetchstat_stream_resets; 93 kstat_named_t zfetchstat_stream_noresets; 94 kstat_named_t zfetchstat_bogus_streams; 95} zfetch_stats_t; 96 97static zfetch_stats_t zfetch_stats = { 98 { "hits", KSTAT_DATA_UINT64 }, 99 { "misses", KSTAT_DATA_UINT64 }, 100 { "colinear_hits", KSTAT_DATA_UINT64 }, 101 { "colinear_misses", KSTAT_DATA_UINT64 }, 102 { "stride_hits", KSTAT_DATA_UINT64 }, 103 { "stride_misses", KSTAT_DATA_UINT64 }, 104 { "reclaim_successes", KSTAT_DATA_UINT64 }, 105 { "reclaim_failures", KSTAT_DATA_UINT64 }, 106 { "streams_resets", KSTAT_DATA_UINT64 }, 107 { "streams_noresets", KSTAT_DATA_UINT64 }, 108 { "bogus_streams", KSTAT_DATA_UINT64 }, 109}; 110 111#define ZFETCHSTAT_INCR(stat, val) \ 112 atomic_add_64(&zfetch_stats.stat.value.ui64, (val)); 113 114#define ZFETCHSTAT_BUMP(stat) ZFETCHSTAT_INCR(stat, 1); 115 116kstat_t *zfetch_ksp; 117 118/* 119 * Given a zfetch structure and a zstream structure, determine whether the 120 * blocks to be read are part of a co-linear pair of existing prefetch 121 * streams. If a set is found, coalesce the streams, removing one, and 122 * configure the prefetch so it looks for a strided access pattern. 123 * 124 * In other words: if we find two sequential access streams that are 125 * the same length and distance N appart, and this read is N from the 126 * last stream, then we are probably in a strided access pattern. So 127 * combine the two sequential streams into a single strided stream. 128 * 129 * Returns whether co-linear streams were found. 130 */ 131static boolean_t 132dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh) 133{ 134 zstream_t *z_walk; 135 zstream_t *z_comp; 136 137 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 138 return (0); 139 140 if (zh == NULL) { 141 rw_exit(&zf->zf_rwlock); 142 return (0); 143 } 144 145 for (z_walk = list_head(&zf->zf_stream); z_walk; 146 z_walk = list_next(&zf->zf_stream, z_walk)) { 147 for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp; 148 z_comp = list_next(&zf->zf_stream, z_comp)) { 149 int64_t diff; 150 151 if (z_walk->zst_len != z_walk->zst_stride || 152 z_comp->zst_len != z_comp->zst_stride) { 153 continue; 154 } 155 156 diff = z_comp->zst_offset - z_walk->zst_offset; 157 if (z_comp->zst_offset + diff == zh->zst_offset) { 158 z_walk->zst_offset = zh->zst_offset; 159 z_walk->zst_direction = diff < 0 ? -1 : 1; 160 z_walk->zst_stride = 161 diff * z_walk->zst_direction; 162 z_walk->zst_ph_offset = 163 zh->zst_offset + z_walk->zst_stride; 164 dmu_zfetch_stream_remove(zf, z_comp); 165 mutex_destroy(&z_comp->zst_lock); 166 kmem_free(z_comp, sizeof (zstream_t)); 167 168 dmu_zfetch_dofetch(zf, z_walk); 169 170 rw_exit(&zf->zf_rwlock); 171 return (1); 172 } 173 174 diff = z_walk->zst_offset - z_comp->zst_offset; 175 if (z_walk->zst_offset + diff == zh->zst_offset) { 176 z_walk->zst_offset = zh->zst_offset; 177 z_walk->zst_direction = diff < 0 ? -1 : 1; 178 z_walk->zst_stride = 179 diff * z_walk->zst_direction; 180 z_walk->zst_ph_offset = 181 zh->zst_offset + z_walk->zst_stride; 182 dmu_zfetch_stream_remove(zf, z_comp); 183 mutex_destroy(&z_comp->zst_lock); 184 kmem_free(z_comp, sizeof (zstream_t)); 185 186 dmu_zfetch_dofetch(zf, z_walk); 187 188 rw_exit(&zf->zf_rwlock); 189 return (1); 190 } 191 } 192 } 193 194 rw_exit(&zf->zf_rwlock); 195 return (0); 196} 197 198/* 199 * Given a zstream_t, determine the bounds of the prefetch. Then call the 200 * routine that actually prefetches the individual blocks. 201 */ 202static void 203dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs) 204{ 205 uint64_t prefetch_tail; 206 uint64_t prefetch_limit; 207 uint64_t prefetch_ofst; 208 uint64_t prefetch_len; 209 uint64_t blocks_fetched; 210 211 zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len); 212 zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap); 213 214 prefetch_tail = MAX((int64_t)zs->zst_ph_offset, 215 (int64_t)(zs->zst_offset + zs->zst_stride)); 216 /* 217 * XXX: use a faster division method? 218 */ 219 prefetch_limit = zs->zst_offset + zs->zst_len + 220 (zs->zst_cap * zs->zst_stride) / zs->zst_len; 221 222 while (prefetch_tail < prefetch_limit) { 223 prefetch_ofst = zs->zst_offset + zs->zst_direction * 224 (prefetch_tail - zs->zst_offset); 225 226 prefetch_len = zs->zst_len; 227 228 /* 229 * Don't prefetch beyond the end of the file, if working 230 * backwards. 231 */ 232 if ((zs->zst_direction == ZFETCH_BACKWARD) && 233 (prefetch_ofst > prefetch_tail)) { 234 prefetch_len += prefetch_ofst; 235 prefetch_ofst = 0; 236 } 237 238 /* don't prefetch more than we're supposed to */ 239 if (prefetch_len > zs->zst_len) 240 break; 241 242 blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode, 243 prefetch_ofst, zs->zst_len); 244 245 prefetch_tail += zs->zst_stride; 246 /* stop if we've run out of stuff to prefetch */ 247 if (blocks_fetched < zs->zst_len) 248 break; 249 } 250 zs->zst_ph_offset = prefetch_tail; 251 zs->zst_last = ddi_get_lbolt(); 252} 253 254void 255zfetch_init(void) 256{ 257 258 zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc", 259 KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t), 260 KSTAT_FLAG_VIRTUAL); 261 262 if (zfetch_ksp != NULL) { 263 zfetch_ksp->ks_data = &zfetch_stats; 264 kstat_install(zfetch_ksp); 265 } 266} 267 268void 269zfetch_fini(void) 270{ 271 if (zfetch_ksp != NULL) { 272 kstat_delete(zfetch_ksp); 273 zfetch_ksp = NULL; 274 } 275} 276 277/* 278 * This takes a pointer to a zfetch structure and a dnode. It performs the 279 * necessary setup for the zfetch structure, grokking data from the 280 * associated dnode. 281 */ 282void 283dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) 284{ 285 if (zf == NULL) { 286 return; 287 } 288 289 zf->zf_dnode = dno; 290 zf->zf_stream_cnt = 0; 291 zf->zf_alloc_fail = 0; 292 293 list_create(&zf->zf_stream, sizeof (zstream_t), 294 offsetof(zstream_t, zst_node)); 295 296 rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); 297} 298 299/* 300 * This function computes the actual size, in blocks, that can be prefetched, 301 * and fetches it. 302 */ 303static uint64_t 304dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks) 305{ 306 uint64_t fetchsz; 307 uint64_t i; 308 309 fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks); 310 311 for (i = 0; i < fetchsz; i++) { 312 dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_ASYNC_READ); 313 } 314 315 return (fetchsz); 316} 317 318/* 319 * this function returns the number of blocks that would be prefetched, based 320 * upon the supplied dnode, blockid, and nblks. This is used so that we can 321 * update streams in place, and then prefetch with their old value after the 322 * fact. This way, we can delay the prefetch, but subsequent accesses to the 323 * stream won't result in the same data being prefetched multiple times. 324 */ 325static uint64_t 326dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks) 327{ 328 uint64_t fetchsz; 329 330 if (blkid > dn->dn_maxblkid) { 331 return (0); 332 } 333 334 /* compute fetch size */ 335 if (blkid + nblks + 1 > dn->dn_maxblkid) { 336 fetchsz = (dn->dn_maxblkid - blkid) + 1; 337 ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid); 338 } else { 339 fetchsz = nblks; 340 } 341 342 343 return (fetchsz); 344} 345 346/* 347 * given a zfetch and a zstream structure, see if there is an associated zstream 348 * for this block read. If so, it starts a prefetch for the stream it 349 * located and returns true, otherwise it returns false 350 */ 351static boolean_t 352dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched) 353{ 354 zstream_t *zs; 355 int64_t diff; 356 int reset = !prefetched; 357 int rc = 0; 358 359 if (zh == NULL) 360 return (0); 361 362 /* 363 * XXX: This locking strategy is a bit coarse; however, it's impact has 364 * yet to be tested. If this turns out to be an issue, it can be 365 * modified in a number of different ways. 366 */ 367 368 rw_enter(&zf->zf_rwlock, RW_READER); 369top: 370 371 for (zs = list_head(&zf->zf_stream); zs; 372 zs = list_next(&zf->zf_stream, zs)) { 373 374 /* 375 * XXX - should this be an assert? 376 */ 377 if (zs->zst_len == 0) { 378 /* bogus stream */ 379 ZFETCHSTAT_BUMP(zfetchstat_bogus_streams); 380 continue; 381 } 382 383 /* 384 * We hit this case when we are in a strided prefetch stream: 385 * we will read "len" blocks before "striding". 386 */ 387 if (zh->zst_offset >= zs->zst_offset && 388 zh->zst_offset < zs->zst_offset + zs->zst_len) { 389 if (prefetched) { 390 /* already fetched */ 391 ZFETCHSTAT_BUMP(zfetchstat_stride_hits); 392 rc = 1; 393 goto out; 394 } else { 395 ZFETCHSTAT_BUMP(zfetchstat_stride_misses); 396 } 397 } 398 399 /* 400 * This is the forward sequential read case: we increment 401 * len by one each time we hit here, so we will enter this 402 * case on every read. 403 */ 404 if (zh->zst_offset == zs->zst_offset + zs->zst_len) { 405 406 reset = !prefetched && zs->zst_len > 1; 407 408 if (mutex_tryenter(&zs->zst_lock) == 0) { 409 rc = 1; 410 goto out; 411 } 412 413 if (zh->zst_offset != zs->zst_offset + zs->zst_len) { 414 mutex_exit(&zs->zst_lock); 415 goto top; 416 } 417 zs->zst_len += zh->zst_len; 418 diff = zs->zst_len - zfetch_block_cap; 419 if (diff > 0) { 420 zs->zst_offset += diff; 421 zs->zst_len = zs->zst_len > diff ? 422 zs->zst_len - diff : 0; 423 } 424 zs->zst_direction = ZFETCH_FORWARD; 425 426 break; 427 428 /* 429 * Same as above, but reading backwards through the file. 430 */ 431 } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) { 432 /* backwards sequential access */ 433 434 reset = !prefetched && zs->zst_len > 1; 435 436 if (mutex_tryenter(&zs->zst_lock) == 0) { 437 rc = 1; 438 goto out; 439 } 440 441 if (zh->zst_offset != zs->zst_offset - zh->zst_len) { 442 mutex_exit(&zs->zst_lock); 443 goto top; 444 } 445 446 zs->zst_offset = zs->zst_offset > zh->zst_len ? 447 zs->zst_offset - zh->zst_len : 0; 448 zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ? 449 zs->zst_ph_offset - zh->zst_len : 0; 450 zs->zst_len += zh->zst_len; 451 452 diff = zs->zst_len - zfetch_block_cap; 453 if (diff > 0) { 454 zs->zst_ph_offset = zs->zst_ph_offset > diff ? 455 zs->zst_ph_offset - diff : 0; 456 zs->zst_len = zs->zst_len > diff ? 457 zs->zst_len - diff : zs->zst_len; 458 } 459 zs->zst_direction = ZFETCH_BACKWARD; 460 461 break; 462 463 } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride < 464 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 465 /* strided forward access */ 466 467 if (mutex_tryenter(&zs->zst_lock) == 0) { 468 rc = 1; 469 goto out; 470 } 471 472 if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >= 473 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 474 mutex_exit(&zs->zst_lock); 475 goto top; 476 } 477 478 zs->zst_offset += zs->zst_stride; 479 zs->zst_direction = ZFETCH_FORWARD; 480 481 break; 482 483 } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride < 484 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 485 /* strided reverse access */ 486 487 if (mutex_tryenter(&zs->zst_lock) == 0) { 488 rc = 1; 489 goto out; 490 } 491 492 if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >= 493 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 494 mutex_exit(&zs->zst_lock); 495 goto top; 496 } 497 498 zs->zst_offset = zs->zst_offset > zs->zst_stride ? 499 zs->zst_offset - zs->zst_stride : 0; 500 zs->zst_ph_offset = (zs->zst_ph_offset > 501 (2 * zs->zst_stride)) ? 502 (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0; 503 zs->zst_direction = ZFETCH_BACKWARD; 504 505 break; 506 } 507 } 508 509 if (zs) { 510 if (reset) { 511 zstream_t *remove = zs; 512 513 ZFETCHSTAT_BUMP(zfetchstat_stream_resets); 514 rc = 0; 515 mutex_exit(&zs->zst_lock); 516 rw_exit(&zf->zf_rwlock); 517 rw_enter(&zf->zf_rwlock, RW_WRITER); 518 /* 519 * Relocate the stream, in case someone removes 520 * it while we were acquiring the WRITER lock. 521 */ 522 for (zs = list_head(&zf->zf_stream); zs; 523 zs = list_next(&zf->zf_stream, zs)) { 524 if (zs == remove) { 525 dmu_zfetch_stream_remove(zf, zs); 526 mutex_destroy(&zs->zst_lock); 527 kmem_free(zs, sizeof (zstream_t)); 528 break; 529 } 530 } 531 } else { 532 ZFETCHSTAT_BUMP(zfetchstat_stream_noresets); 533 rc = 1; 534 dmu_zfetch_dofetch(zf, zs); 535 mutex_exit(&zs->zst_lock); 536 } 537 } 538out: 539 rw_exit(&zf->zf_rwlock); 540 return (rc); 541} 542 543/* 544 * Clean-up state associated with a zfetch structure. This frees allocated 545 * structure members, empties the zf_stream tree, and generally makes things 546 * nice. This doesn't free the zfetch_t itself, that's left to the caller. 547 */ 548void 549dmu_zfetch_rele(zfetch_t *zf) 550{ 551 zstream_t *zs; 552 zstream_t *zs_next; 553 554 ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock)); 555 556 for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) { 557 zs_next = list_next(&zf->zf_stream, zs); 558 559 list_remove(&zf->zf_stream, zs); 560 mutex_destroy(&zs->zst_lock); 561 kmem_free(zs, sizeof (zstream_t)); 562 } 563 list_destroy(&zf->zf_stream); 564 rw_destroy(&zf->zf_rwlock); 565 566 zf->zf_dnode = NULL; 567} 568 569/* 570 * Given a zfetch and zstream structure, insert the zstream structure into the 571 * AVL tree contained within the zfetch structure. Peform the appropriate 572 * book-keeping. It is possible that another thread has inserted a stream which 573 * matches one that we are about to insert, so we must be sure to check for this 574 * case. If one is found, return failure, and let the caller cleanup the 575 * duplicates. 576 */ 577static int 578dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs) 579{ 580 zstream_t *zs_walk; 581 zstream_t *zs_next; 582 583 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 584 585 for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) { 586 zs_next = list_next(&zf->zf_stream, zs_walk); 587 588 if (dmu_zfetch_streams_equal(zs_walk, zs)) { 589 return (0); 590 } 591 } 592 593 list_insert_head(&zf->zf_stream, zs); 594 zf->zf_stream_cnt++; 595 return (1); 596} 597 598 599/* 600 * Walk the list of zstreams in the given zfetch, find an old one (by time), and 601 * reclaim it for use by the caller. 602 */ 603static zstream_t * 604dmu_zfetch_stream_reclaim(zfetch_t *zf) 605{ 606 zstream_t *zs; 607 608 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 609 return (0); 610 611 for (zs = list_head(&zf->zf_stream); zs; 612 zs = list_next(&zf->zf_stream, zs)) { 613 614 if (((ddi_get_lbolt() - zs->zst_last)/hz) > zfetch_min_sec_reap) 615 break; 616 } 617 618 if (zs) { 619 dmu_zfetch_stream_remove(zf, zs); 620 mutex_destroy(&zs->zst_lock); 621 bzero(zs, sizeof (zstream_t)); 622 } else { 623 zf->zf_alloc_fail++; 624 } 625 rw_exit(&zf->zf_rwlock); 626 627 return (zs); 628} 629 630/* 631 * Given a zfetch and zstream structure, remove the zstream structure from its 632 * container in the zfetch structure. Perform the appropriate book-keeping. 633 */ 634static void 635dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) 636{ 637 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 638 639 list_remove(&zf->zf_stream, zs); 640 zf->zf_stream_cnt--; 641} 642 643static int 644dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2) 645{ 646 if (zs1->zst_offset != zs2->zst_offset) 647 return (0); 648 649 if (zs1->zst_len != zs2->zst_len) 650 return (0); 651 652 if (zs1->zst_stride != zs2->zst_stride) 653 return (0); 654 655 if (zs1->zst_ph_offset != zs2->zst_ph_offset) 656 return (0); 657 658 if (zs1->zst_cap != zs2->zst_cap) 659 return (0); 660 661 if (zs1->zst_direction != zs2->zst_direction) 662 return (0); 663 664 return (1); 665} 666 667/* 668 * This is the prefetch entry point. It calls all of the other dmu_zfetch 669 * routines to create, delete, find, or operate upon prefetch streams. 670 */ 671void 672dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched) 673{ 674 zstream_t zst; 675 zstream_t *newstream; 676 boolean_t fetched; 677 int inserted; 678 unsigned int blkshft; 679 uint64_t blksz; 680 681 if (zfs_prefetch_disable) 682 return; 683 684 /* files that aren't ln2 blocksz are only one block -- nothing to do */ 685 if (!zf->zf_dnode->dn_datablkshift) 686 return; 687 688 /* convert offset and size, into blockid and nblocks */ 689 blkshft = zf->zf_dnode->dn_datablkshift; 690 blksz = (1 << blkshft); 691 692 bzero(&zst, sizeof (zstream_t)); 693 zst.zst_offset = offset >> blkshft; 694 zst.zst_len = (P2ROUNDUP(offset + size, blksz) - 695 P2ALIGN(offset, blksz)) >> blkshft; 696 697 fetched = dmu_zfetch_find(zf, &zst, prefetched); 698 if (fetched) { 699 ZFETCHSTAT_BUMP(zfetchstat_hits); 700 } else { 701 ZFETCHSTAT_BUMP(zfetchstat_misses); 702 fetched = dmu_zfetch_colinear(zf, &zst); 703 if (fetched) { 704 ZFETCHSTAT_BUMP(zfetchstat_colinear_hits); 705 } else { 706 ZFETCHSTAT_BUMP(zfetchstat_colinear_misses); 707 } 708 } 709 710 if (!fetched) { 711 newstream = dmu_zfetch_stream_reclaim(zf); 712 713 /* 714 * we still couldn't find a stream, drop the lock, and allocate 715 * one if possible. Otherwise, give up and go home. 716 */ 717 if (newstream) { 718 ZFETCHSTAT_BUMP(zfetchstat_reclaim_successes); 719 } else { 720 uint64_t maxblocks; 721 uint32_t max_streams; 722 uint32_t cur_streams; 723 724 ZFETCHSTAT_BUMP(zfetchstat_reclaim_failures); 725 cur_streams = zf->zf_stream_cnt; 726 maxblocks = zf->zf_dnode->dn_maxblkid; 727 728 max_streams = MIN(zfetch_max_streams, 729 (maxblocks / zfetch_block_cap)); 730 if (max_streams == 0) { 731 max_streams++; 732 } 733 734 if (cur_streams >= max_streams) { 735 return; 736 } 737 newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP); 738 } 739 740 newstream->zst_offset = zst.zst_offset; 741 newstream->zst_len = zst.zst_len; 742 newstream->zst_stride = zst.zst_len; 743 newstream->zst_ph_offset = zst.zst_len + zst.zst_offset; 744 newstream->zst_cap = zst.zst_len; 745 newstream->zst_direction = ZFETCH_FORWARD; 746 newstream->zst_last = ddi_get_lbolt(); 747 748 mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL); 749 750 rw_enter(&zf->zf_rwlock, RW_WRITER); 751 inserted = dmu_zfetch_stream_insert(zf, newstream); 752 rw_exit(&zf->zf_rwlock); 753 754 if (!inserted) { 755 mutex_destroy(&newstream->zst_lock); 756 kmem_free(newstream, sizeof (zstream_t)); 757 } 758 } 759} 760