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 #include <sys/zfs_context.h> 27 #include <sys/dnode.h> 28 #include <sys/dmu_objset.h> 29 #include <sys/dmu_zfetch.h> 30 #include <sys/dmu.h> 31 #include <sys/dbuf.h> 32 #include <sys/kstat.h> 33 34 /* 35 * I'm against tune-ables, but these should probably exist as tweakable globals 36 * until we can get this working the way we want it to. 37 */ 38 39 int zfs_prefetch_disable = 0; 40 41 /* max # of streams per zfetch */ 42 uint32_t zfetch_max_streams = 8; 43 /* min time before stream reclaim */ 44 uint32_t zfetch_min_sec_reap = 2; 45 /* max number of blocks to fetch at a time */ 46 uint32_t zfetch_block_cap = 256; 47 /* number of bytes in a array_read at which we stop prefetching (1Mb) */ 48 uint64_t zfetch_array_rd_sz = 1024 * 1024; 49 50 /* forward decls for static routines */ 51 static int dmu_zfetch_colinear(zfetch_t *, zstream_t *); 52 static void dmu_zfetch_dofetch(zfetch_t *, zstream_t *); 53 static uint64_t dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t); 54 static uint64_t dmu_zfetch_fetchsz(dnode_t *, uint64_t, uint64_t); 55 static int dmu_zfetch_find(zfetch_t *, zstream_t *, int); 56 static int dmu_zfetch_stream_insert(zfetch_t *, zstream_t *); 57 static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *); 58 static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *); 59 static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *); 60 61 typedef struct zfetch_stats { 62 kstat_named_t zfetchstat_hits; 63 kstat_named_t zfetchstat_misses; 64 kstat_named_t zfetchstat_colinear_hits; 65 kstat_named_t zfetchstat_colinear_misses; 66 kstat_named_t zfetchstat_stride_hits; 67 kstat_named_t zfetchstat_stride_misses; 68 kstat_named_t zfetchstat_reclaim_successes; 69 kstat_named_t zfetchstat_reclaim_failures; 70 kstat_named_t zfetchstat_stream_resets; 71 kstat_named_t zfetchstat_stream_noresets; 72 kstat_named_t zfetchstat_bogus_streams; 73 } zfetch_stats_t; 74 75 static zfetch_stats_t zfetch_stats = { 76 { "hits", KSTAT_DATA_UINT64 }, 77 { "misses", KSTAT_DATA_UINT64 }, 78 { "colinear_hits", KSTAT_DATA_UINT64 }, 79 { "colinear_misses", KSTAT_DATA_UINT64 }, 80 { "stride_hits", KSTAT_DATA_UINT64 }, 81 { "stride_misses", KSTAT_DATA_UINT64 }, 82 { "reclaim_successes", KSTAT_DATA_UINT64 }, 83 { "reclaim_failures", KSTAT_DATA_UINT64 }, 84 { "streams_resets", KSTAT_DATA_UINT64 }, 85 { "streams_noresets", KSTAT_DATA_UINT64 }, 86 { "bogus_streams", KSTAT_DATA_UINT64 }, 87 }; 88 89 #define ZFETCHSTAT_INCR(stat, val) \ 90 atomic_add_64(&zfetch_stats.stat.value.ui64, (val)); 91 92 #define ZFETCHSTAT_BUMP(stat) ZFETCHSTAT_INCR(stat, 1); 93 94 kstat_t *zfetch_ksp; 95 96 /* 97 * Given a zfetch structure and a zstream structure, determine whether the 98 * blocks to be read are part of a co-linear pair of existing prefetch 99 * streams. If a set is found, coalesce the streams, removing one, and 100 * configure the prefetch so it looks for a strided access pattern. 101 * 102 * In other words: if we find two sequential access streams that are 103 * the same length and distance N appart, and this read is N from the 104 * last stream, then we are probably in a strided access pattern. So 105 * combine the two sequential streams into a single strided stream. 106 * 107 * If no co-linear streams are found, return NULL. 108 */ 109 static int 110 dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh) 111 { 112 zstream_t *z_walk; 113 zstream_t *z_comp; 114 115 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 116 return (0); 117 118 if (zh == NULL) { 119 rw_exit(&zf->zf_rwlock); 120 return (0); 121 } 122 123 for (z_walk = list_head(&zf->zf_stream); z_walk; 124 z_walk = list_next(&zf->zf_stream, z_walk)) { 125 for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp; 126 z_comp = list_next(&zf->zf_stream, z_comp)) { 127 int64_t diff; 128 129 if (z_walk->zst_len != z_walk->zst_stride || 130 z_comp->zst_len != z_comp->zst_stride) { 131 continue; 132 } 133 134 diff = z_comp->zst_offset - z_walk->zst_offset; 135 if (z_comp->zst_offset + diff == zh->zst_offset) { 136 z_walk->zst_offset = zh->zst_offset; 137 z_walk->zst_direction = diff < 0 ? -1 : 1; 138 z_walk->zst_stride = 139 diff * z_walk->zst_direction; 140 z_walk->zst_ph_offset = 141 zh->zst_offset + z_walk->zst_stride; 142 dmu_zfetch_stream_remove(zf, z_comp); 143 mutex_destroy(&z_comp->zst_lock); 144 kmem_free(z_comp, sizeof (zstream_t)); 145 146 dmu_zfetch_dofetch(zf, z_walk); 147 148 rw_exit(&zf->zf_rwlock); 149 return (1); 150 } 151 152 diff = z_walk->zst_offset - z_comp->zst_offset; 153 if (z_walk->zst_offset + diff == zh->zst_offset) { 154 z_walk->zst_offset = zh->zst_offset; 155 z_walk->zst_direction = diff < 0 ? -1 : 1; 156 z_walk->zst_stride = 157 diff * z_walk->zst_direction; 158 z_walk->zst_ph_offset = 159 zh->zst_offset + z_walk->zst_stride; 160 dmu_zfetch_stream_remove(zf, z_comp); 161 mutex_destroy(&z_comp->zst_lock); 162 kmem_free(z_comp, sizeof (zstream_t)); 163 164 dmu_zfetch_dofetch(zf, z_walk); 165 166 rw_exit(&zf->zf_rwlock); 167 return (1); 168 } 169 } 170 } 171 172 rw_exit(&zf->zf_rwlock); 173 return (0); 174 } 175 176 /* 177 * Given a zstream_t, determine the bounds of the prefetch. Then call the 178 * routine that actually prefetches the individual blocks. 179 */ 180 static void 181 dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs) 182 { 183 uint64_t prefetch_tail; 184 uint64_t prefetch_limit; 185 uint64_t prefetch_ofst; 186 uint64_t prefetch_len; 187 uint64_t blocks_fetched; 188 189 zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len); 190 zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap); 191 192 prefetch_tail = MAX((int64_t)zs->zst_ph_offset, 193 (int64_t)(zs->zst_offset + zs->zst_stride)); 194 /* 195 * XXX: use a faster division method? 196 */ 197 prefetch_limit = zs->zst_offset + zs->zst_len + 198 (zs->zst_cap * zs->zst_stride) / zs->zst_len; 199 200 while (prefetch_tail < prefetch_limit) { 201 prefetch_ofst = zs->zst_offset + zs->zst_direction * 202 (prefetch_tail - zs->zst_offset); 203 204 prefetch_len = zs->zst_len; 205 206 /* 207 * Don't prefetch beyond the end of the file, if working 208 * backwards. 209 */ 210 if ((zs->zst_direction == ZFETCH_BACKWARD) && 211 (prefetch_ofst > prefetch_tail)) { 212 prefetch_len += prefetch_ofst; 213 prefetch_ofst = 0; 214 } 215 216 /* don't prefetch more than we're supposed to */ 217 if (prefetch_len > zs->zst_len) 218 break; 219 220 blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode, 221 prefetch_ofst, zs->zst_len); 222 223 prefetch_tail += zs->zst_stride; 224 /* stop if we've run out of stuff to prefetch */ 225 if (blocks_fetched < zs->zst_len) 226 break; 227 } 228 zs->zst_ph_offset = prefetch_tail; 229 zs->zst_last = ddi_get_lbolt(); 230 } 231 232 void 233 zfetch_init(void) 234 { 235 236 zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc", 237 KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t), 238 KSTAT_FLAG_VIRTUAL); 239 240 if (zfetch_ksp != NULL) { 241 zfetch_ksp->ks_data = &zfetch_stats; 242 kstat_install(zfetch_ksp); 243 } 244 } 245 246 void 247 zfetch_fini(void) 248 { 249 if (zfetch_ksp != NULL) { 250 kstat_delete(zfetch_ksp); 251 zfetch_ksp = NULL; 252 } 253 } 254 255 /* 256 * This takes a pointer to a zfetch structure and a dnode. It performs the 257 * necessary setup for the zfetch structure, grokking data from the 258 * associated dnode. 259 */ 260 void 261 dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) 262 { 263 if (zf == NULL) { 264 return; 265 } 266 267 zf->zf_dnode = dno; 268 zf->zf_stream_cnt = 0; 269 zf->zf_alloc_fail = 0; 270 271 list_create(&zf->zf_stream, sizeof (zstream_t), 272 offsetof(zstream_t, zst_node)); 273 274 rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); 275 } 276 277 /* 278 * This function computes the actual size, in blocks, that can be prefetched, 279 * and fetches it. 280 */ 281 static uint64_t 282 dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks) 283 { 284 uint64_t fetchsz; 285 uint64_t i; 286 287 fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks); 288 289 for (i = 0; i < fetchsz; i++) { 290 dbuf_prefetch(dn, blkid + i); 291 } 292 293 return (fetchsz); 294 } 295 296 /* 297 * this function returns the number of blocks that would be prefetched, based 298 * upon the supplied dnode, blockid, and nblks. This is used so that we can 299 * update streams in place, and then prefetch with their old value after the 300 * fact. This way, we can delay the prefetch, but subsequent accesses to the 301 * stream won't result in the same data being prefetched multiple times. 302 */ 303 static uint64_t 304 dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks) 305 { 306 uint64_t fetchsz; 307 308 if (blkid > dn->dn_maxblkid) { 309 return (0); 310 } 311 312 /* compute fetch size */ 313 if (blkid + nblks + 1 > dn->dn_maxblkid) { 314 fetchsz = (dn->dn_maxblkid - blkid) + 1; 315 ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid); 316 } else { 317 fetchsz = nblks; 318 } 319 320 321 return (fetchsz); 322 } 323 324 /* 325 * given a zfetch and a zstream structure, see if there is an associated zstream 326 * for this block read. If so, it starts a prefetch for the stream it 327 * located and returns true, otherwise it returns false 328 */ 329 static int 330 dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched) 331 { 332 zstream_t *zs; 333 int64_t diff; 334 int reset = !prefetched; 335 int rc = 0; 336 337 if (zh == NULL) 338 return (0); 339 340 /* 341 * XXX: This locking strategy is a bit coarse; however, it's impact has 342 * yet to be tested. If this turns out to be an issue, it can be 343 * modified in a number of different ways. 344 */ 345 346 rw_enter(&zf->zf_rwlock, RW_READER); 347 top: 348 349 for (zs = list_head(&zf->zf_stream); zs; 350 zs = list_next(&zf->zf_stream, zs)) { 351 352 /* 353 * XXX - should this be an assert? 354 */ 355 if (zs->zst_len == 0) { 356 /* bogus stream */ 357 ZFETCHSTAT_BUMP(zfetchstat_bogus_streams); 358 continue; 359 } 360 361 /* 362 * We hit this case when we are in a strided prefetch stream: 363 * we will read "len" blocks before "striding". 364 */ 365 if (zh->zst_offset >= zs->zst_offset && 366 zh->zst_offset < zs->zst_offset + zs->zst_len) { 367 if (prefetched) { 368 /* already fetched */ 369 ZFETCHSTAT_BUMP(zfetchstat_stride_hits); 370 rc = 1; 371 goto out; 372 } else { 373 ZFETCHSTAT_BUMP(zfetchstat_stride_misses); 374 } 375 } 376 377 /* 378 * This is the forward sequential read case: we increment 379 * len by one each time we hit here, so we will enter this 380 * case on every read. 381 */ 382 if (zh->zst_offset == zs->zst_offset + zs->zst_len) { 383 384 reset = !prefetched && zs->zst_len > 1; 385 386 mutex_enter(&zs->zst_lock); 387 388 if (zh->zst_offset != zs->zst_offset + zs->zst_len) { 389 mutex_exit(&zs->zst_lock); 390 goto top; 391 } 392 zs->zst_len += zh->zst_len; 393 diff = zs->zst_len - zfetch_block_cap; 394 if (diff > 0) { 395 zs->zst_offset += diff; 396 zs->zst_len = zs->zst_len > diff ? 397 zs->zst_len - diff : 0; 398 } 399 zs->zst_direction = ZFETCH_FORWARD; 400 401 break; 402 403 /* 404 * Same as above, but reading backwards through the file. 405 */ 406 } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) { 407 /* backwards sequential access */ 408 409 reset = !prefetched && zs->zst_len > 1; 410 411 mutex_enter(&zs->zst_lock); 412 413 if (zh->zst_offset != zs->zst_offset - zh->zst_len) { 414 mutex_exit(&zs->zst_lock); 415 goto top; 416 } 417 418 zs->zst_offset = zs->zst_offset > zh->zst_len ? 419 zs->zst_offset - zh->zst_len : 0; 420 zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ? 421 zs->zst_ph_offset - zh->zst_len : 0; 422 zs->zst_len += zh->zst_len; 423 424 diff = zs->zst_len - zfetch_block_cap; 425 if (diff > 0) { 426 zs->zst_ph_offset = zs->zst_ph_offset > diff ? 427 zs->zst_ph_offset - diff : 0; 428 zs->zst_len = zs->zst_len > diff ? 429 zs->zst_len - diff : zs->zst_len; 430 } 431 zs->zst_direction = ZFETCH_BACKWARD; 432 433 break; 434 435 } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride < 436 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 437 /* strided forward access */ 438 439 mutex_enter(&zs->zst_lock); 440 441 if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >= 442 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 443 mutex_exit(&zs->zst_lock); 444 goto top; 445 } 446 447 zs->zst_offset += zs->zst_stride; 448 zs->zst_direction = ZFETCH_FORWARD; 449 450 break; 451 452 } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride < 453 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 454 /* strided reverse access */ 455 456 mutex_enter(&zs->zst_lock); 457 458 if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >= 459 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 460 mutex_exit(&zs->zst_lock); 461 goto top; 462 } 463 464 zs->zst_offset = zs->zst_offset > zs->zst_stride ? 465 zs->zst_offset - zs->zst_stride : 0; 466 zs->zst_ph_offset = (zs->zst_ph_offset > 467 (2 * zs->zst_stride)) ? 468 (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0; 469 zs->zst_direction = ZFETCH_BACKWARD; 470 471 break; 472 } 473 } 474 475 if (zs) { 476 if (reset) { 477 zstream_t *remove = zs; 478 479 ZFETCHSTAT_BUMP(zfetchstat_stream_resets); 480 rc = 0; 481 mutex_exit(&zs->zst_lock); 482 rw_exit(&zf->zf_rwlock); 483 rw_enter(&zf->zf_rwlock, RW_WRITER); 484 /* 485 * Relocate the stream, in case someone removes 486 * it while we were acquiring the WRITER lock. 487 */ 488 for (zs = list_head(&zf->zf_stream); zs; 489 zs = list_next(&zf->zf_stream, zs)) { 490 if (zs == remove) { 491 dmu_zfetch_stream_remove(zf, zs); 492 mutex_destroy(&zs->zst_lock); 493 kmem_free(zs, sizeof (zstream_t)); 494 break; 495 } 496 } 497 } else { 498 ZFETCHSTAT_BUMP(zfetchstat_stream_noresets); 499 rc = 1; 500 dmu_zfetch_dofetch(zf, zs); 501 mutex_exit(&zs->zst_lock); 502 } 503 } 504 out: 505 rw_exit(&zf->zf_rwlock); 506 return (rc); 507 } 508 509 /* 510 * Clean-up state associated with a zfetch structure. This frees allocated 511 * structure members, empties the zf_stream tree, and generally makes things 512 * nice. This doesn't free the zfetch_t itself, that's left to the caller. 513 */ 514 void 515 dmu_zfetch_rele(zfetch_t *zf) 516 { 517 zstream_t *zs; 518 zstream_t *zs_next; 519 520 ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock)); 521 522 for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) { 523 zs_next = list_next(&zf->zf_stream, zs); 524 525 list_remove(&zf->zf_stream, zs); 526 mutex_destroy(&zs->zst_lock); 527 kmem_free(zs, sizeof (zstream_t)); 528 } 529 list_destroy(&zf->zf_stream); 530 rw_destroy(&zf->zf_rwlock); 531 532 zf->zf_dnode = NULL; 533 } 534 535 /* 536 * Given a zfetch and zstream structure, insert the zstream structure into the 537 * AVL tree contained within the zfetch structure. Peform the appropriate 538 * book-keeping. It is possible that another thread has inserted a stream which 539 * matches one that we are about to insert, so we must be sure to check for this 540 * case. If one is found, return failure, and let the caller cleanup the 541 * duplicates. 542 */ 543 static int 544 dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs) 545 { 546 zstream_t *zs_walk; 547 zstream_t *zs_next; 548 549 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 550 551 for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) { 552 zs_next = list_next(&zf->zf_stream, zs_walk); 553 554 if (dmu_zfetch_streams_equal(zs_walk, zs)) { 555 return (0); 556 } 557 } 558 559 list_insert_head(&zf->zf_stream, zs); 560 zf->zf_stream_cnt++; 561 return (1); 562 } 563 564 565 /* 566 * Walk the list of zstreams in the given zfetch, find an old one (by time), and 567 * reclaim it for use by the caller. 568 */ 569 static zstream_t * 570 dmu_zfetch_stream_reclaim(zfetch_t *zf) 571 { 572 zstream_t *zs; 573 574 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 575 return (0); 576 577 for (zs = list_head(&zf->zf_stream); zs; 578 zs = list_next(&zf->zf_stream, zs)) { 579 580 if (((ddi_get_lbolt() - zs->zst_last)/hz) > zfetch_min_sec_reap) 581 break; 582 } 583 584 if (zs) { 585 dmu_zfetch_stream_remove(zf, zs); 586 mutex_destroy(&zs->zst_lock); 587 bzero(zs, sizeof (zstream_t)); 588 } else { 589 zf->zf_alloc_fail++; 590 } 591 rw_exit(&zf->zf_rwlock); 592 593 return (zs); 594 } 595 596 /* 597 * Given a zfetch and zstream structure, remove the zstream structure from its 598 * container in the zfetch structure. Perform the appropriate book-keeping. 599 */ 600 static void 601 dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) 602 { 603 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 604 605 list_remove(&zf->zf_stream, zs); 606 zf->zf_stream_cnt--; 607 } 608 609 static int 610 dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2) 611 { 612 if (zs1->zst_offset != zs2->zst_offset) 613 return (0); 614 615 if (zs1->zst_len != zs2->zst_len) 616 return (0); 617 618 if (zs1->zst_stride != zs2->zst_stride) 619 return (0); 620 621 if (zs1->zst_ph_offset != zs2->zst_ph_offset) 622 return (0); 623 624 if (zs1->zst_cap != zs2->zst_cap) 625 return (0); 626 627 if (zs1->zst_direction != zs2->zst_direction) 628 return (0); 629 630 return (1); 631 } 632 633 /* 634 * This is the prefetch entry point. It calls all of the other dmu_zfetch 635 * routines to create, delete, find, or operate upon prefetch streams. 636 */ 637 void 638 dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched) 639 { 640 zstream_t zst; 641 zstream_t *newstream; 642 int fetched; 643 int inserted; 644 unsigned int blkshft; 645 uint64_t blksz; 646 647 if (zfs_prefetch_disable) 648 return; 649 650 /* files that aren't ln2 blocksz are only one block -- nothing to do */ 651 if (!zf->zf_dnode->dn_datablkshift) 652 return; 653 654 /* convert offset and size, into blockid and nblocks */ 655 blkshft = zf->zf_dnode->dn_datablkshift; 656 blksz = (1 << blkshft); 657 658 bzero(&zst, sizeof (zstream_t)); 659 zst.zst_offset = offset >> blkshft; 660 zst.zst_len = (P2ROUNDUP(offset + size, blksz) - 661 P2ALIGN(offset, blksz)) >> blkshft; 662 663 fetched = dmu_zfetch_find(zf, &zst, prefetched); 664 if (fetched) { 665 ZFETCHSTAT_BUMP(zfetchstat_hits); 666 } else { 667 ZFETCHSTAT_BUMP(zfetchstat_misses); 668 if (fetched = dmu_zfetch_colinear(zf, &zst)) { 669 ZFETCHSTAT_BUMP(zfetchstat_colinear_hits); 670 } else { 671 ZFETCHSTAT_BUMP(zfetchstat_colinear_misses); 672 } 673 } 674 675 if (!fetched) { 676 newstream = dmu_zfetch_stream_reclaim(zf); 677 678 /* 679 * we still couldn't find a stream, drop the lock, and allocate 680 * one if possible. Otherwise, give up and go home. 681 */ 682 if (newstream) { 683 ZFETCHSTAT_BUMP(zfetchstat_reclaim_successes); 684 } else { 685 uint64_t maxblocks; 686 uint32_t max_streams; 687 uint32_t cur_streams; 688 689 ZFETCHSTAT_BUMP(zfetchstat_reclaim_failures); 690 cur_streams = zf->zf_stream_cnt; 691 maxblocks = zf->zf_dnode->dn_maxblkid; 692 693 max_streams = MIN(zfetch_max_streams, 694 (maxblocks / zfetch_block_cap)); 695 if (max_streams == 0) { 696 max_streams++; 697 } 698 699 if (cur_streams >= max_streams) { 700 return; 701 } 702 newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP); 703 } 704 705 newstream->zst_offset = zst.zst_offset; 706 newstream->zst_len = zst.zst_len; 707 newstream->zst_stride = zst.zst_len; 708 newstream->zst_ph_offset = zst.zst_len + zst.zst_offset; 709 newstream->zst_cap = zst.zst_len; 710 newstream->zst_direction = ZFETCH_FORWARD; 711 newstream->zst_last = ddi_get_lbolt(); 712 713 mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL); 714 715 rw_enter(&zf->zf_rwlock, RW_WRITER); 716 inserted = dmu_zfetch_stream_insert(zf, newstream); 717 rw_exit(&zf->zf_rwlock); 718 719 if (!inserted) { 720 mutex_destroy(&newstream->zst_lock); 721 kmem_free(newstream, sizeof (zstream_t)); 722 } 723 } 724 } 725