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, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 #include <sys/zfs_context.h> 30 #include <sys/dnode.h> 31 #include <sys/dmu_objset.h> 32 #include <sys/dmu_zfetch.h> 33 #include <sys/dmu.h> 34 #include <sys/dbuf.h> 35 36 /* 37 * I'm against tune-ables, but these should probably exist as tweakable globals 38 * until we can get this working the way we want it to. 39 */ 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 = 32; 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 *); 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 void dmu_zfetch_stream_update(zfetch_t *, zstream_t *); 60 static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *); 61 62 63 /* 64 * Given a zfetch structure and a zstream structure, determine whether the 65 * blocks to be read are part of a co-linear to a pair of existing prefetch 66 * streams. If a set is found, coalesce the streams, removing one, and 67 * configure the prefetch so it looks for a strided access pattern. 68 * 69 * If no co-linear streams are found, return NULL. 70 */ 71 static int 72 dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh) 73 { 74 zstream_t *z_walk; 75 zstream_t *z_comp; 76 77 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 78 return (0); 79 80 if (zh == NULL) { 81 rw_exit(&zf->zf_rwlock); 82 return (0); 83 } 84 85 for (z_walk = list_head(&zf->zf_stream); z_walk; 86 z_walk = list_next(&zf->zf_stream, z_walk)) { 87 for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp; 88 z_comp = list_next(&zf->zf_stream, z_comp)) { 89 int64_t diff; 90 91 if (z_walk->zst_len != z_walk->zst_stride || 92 z_comp->zst_len != z_comp->zst_stride) { 93 continue; 94 } 95 96 diff = z_comp->zst_offset - z_walk->zst_offset; 97 if (z_comp->zst_offset + diff == zh->zst_offset) { 98 z_walk->zst_offset = zh->zst_offset; 99 z_walk->zst_direction = diff < 0 ? -1 : 1; 100 z_walk->zst_stride = 101 diff * z_walk->zst_direction; 102 z_walk->zst_ph_offset = 103 zh->zst_offset + z_walk->zst_stride; 104 dmu_zfetch_stream_remove(zf, z_comp); 105 mutex_destroy(&z_comp->zst_lock); 106 kmem_free(z_comp, sizeof (zstream_t)); 107 108 dmu_zfetch_dofetch(zf, z_walk); 109 110 rw_exit(&zf->zf_rwlock); 111 return (1); 112 } 113 114 diff = z_walk->zst_offset - z_comp->zst_offset; 115 if (z_walk->zst_offset + diff == zh->zst_offset) { 116 z_walk->zst_offset = zh->zst_offset; 117 z_walk->zst_direction = diff < 0 ? -1 : 1; 118 z_walk->zst_stride = 119 diff * z_walk->zst_direction; 120 z_walk->zst_ph_offset = 121 zh->zst_offset + z_walk->zst_stride; 122 dmu_zfetch_stream_remove(zf, z_comp); 123 mutex_destroy(&z_comp->zst_lock); 124 kmem_free(z_comp, sizeof (zstream_t)); 125 126 dmu_zfetch_dofetch(zf, z_walk); 127 128 rw_exit(&zf->zf_rwlock); 129 return (1); 130 } 131 } 132 } 133 134 rw_exit(&zf->zf_rwlock); 135 return (0); 136 } 137 138 /* 139 * Given a zstream_t, determine the bounds of the prefetch. Then call the 140 * routine that actually prefetches the individual blocks. 141 */ 142 static void 143 dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs) 144 { 145 uint64_t prefetch_tail; 146 uint64_t prefetch_limit; 147 uint64_t prefetch_ofst; 148 uint64_t prefetch_len; 149 uint64_t blocks_fetched; 150 151 zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len); 152 zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap); 153 154 prefetch_tail = MAX((int64_t)zs->zst_ph_offset, 155 (int64_t)(zs->zst_offset + zs->zst_stride)); 156 /* 157 * XXX: use a faster division method? 158 */ 159 prefetch_limit = zs->zst_offset + zs->zst_len + 160 (zs->zst_cap * zs->zst_stride) / zs->zst_len; 161 162 while (prefetch_tail < prefetch_limit) { 163 prefetch_ofst = zs->zst_offset + zs->zst_direction * 164 (prefetch_tail - zs->zst_offset); 165 166 prefetch_len = zs->zst_len; 167 168 /* 169 * Don't prefetch beyond the end of the file, if working 170 * backwards. 171 */ 172 if ((zs->zst_direction == ZFETCH_BACKWARD) && 173 (prefetch_ofst > prefetch_tail)) { 174 prefetch_len += prefetch_ofst; 175 prefetch_ofst = 0; 176 } 177 178 /* don't prefetch more than we're supposed to */ 179 if (prefetch_len > zs->zst_len) 180 break; 181 182 blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode, 183 prefetch_ofst, zs->zst_len); 184 185 prefetch_tail += zs->zst_stride; 186 /* stop if we've run out of stuff to prefetch */ 187 if (blocks_fetched < zs->zst_len) 188 break; 189 } 190 zs->zst_ph_offset = prefetch_tail; 191 zs->zst_last = lbolt; 192 } 193 194 /* 195 * This takes a pointer to a zfetch structure and a dnode. It performs the 196 * necessary setup for the zfetch structure, grokking data from the 197 * associated dnode. 198 */ 199 void 200 dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) 201 { 202 if (zf == NULL) { 203 return; 204 } 205 206 zf->zf_dnode = dno; 207 zf->zf_stream_cnt = 0; 208 zf->zf_alloc_fail = 0; 209 210 list_create(&zf->zf_stream, sizeof (zstream_t), 211 offsetof(zstream_t, zst_node)); 212 213 rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL); 214 } 215 216 /* 217 * This function computes the actual size, in blocks, that can be prefetched, 218 * and fetches it. 219 */ 220 static uint64_t 221 dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks) 222 { 223 uint64_t fetchsz; 224 uint64_t i; 225 226 fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks); 227 228 for (i = 0; i < fetchsz; i++) { 229 dbuf_prefetch(dn, blkid + i); 230 } 231 232 return (fetchsz); 233 } 234 235 /* 236 * this function returns the number of blocks that would be prefetched, based 237 * upon the supplied dnode, blockid, and nblks. This is used so that we can 238 * update streams in place, and then prefetch with their old value after the 239 * fact. This way, we can delay the prefetch, but subsequent accesses to the 240 * stream won't result in the same data being prefetched multiple times. 241 */ 242 static uint64_t 243 dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks) 244 { 245 uint64_t fetchsz; 246 247 if (blkid > dn->dn_maxblkid) { 248 return (0); 249 } 250 251 /* compute fetch size */ 252 if (blkid + nblks > dn->dn_maxblkid) { 253 fetchsz = dn->dn_maxblkid - blkid; 254 ASSERT(blkid + fetchsz <= dn->dn_maxblkid); 255 } else { 256 fetchsz = nblks; 257 } 258 259 260 return (fetchsz); 261 } 262 263 /* 264 * given a zfetch and a zsearch structure, see if there is an associated zstream 265 * for this block read. If so, it starts a prefetch for the stream it 266 * located and returns true, otherwise it returns false 267 */ 268 static int 269 dmu_zfetch_find(zfetch_t *zf, zstream_t *zh) 270 { 271 zstream_t *zs; 272 int64_t diff; 273 int rc = 0; 274 275 if (zh == NULL) 276 return (0); 277 278 /* 279 * XXX: This locking strategy is a bit coarse; however, it's impact has 280 * yet to be tested. If this turns out to be an issue, it can be 281 * modified in a number of different ways. 282 */ 283 284 rw_enter(&zf->zf_rwlock, RW_READER); 285 top: 286 287 for (zs = list_head(&zf->zf_stream); zs; 288 zs = list_next(&zf->zf_stream, zs)) { 289 290 291 if (zs->zst_len == 0) { 292 /* bogus stream */ 293 continue; 294 } 295 296 if (zh->zst_offset - zs->zst_offset < zs->zst_len) { 297 /* already fetched */ 298 rw_exit(&zf->zf_rwlock); 299 return (1); 300 } 301 302 if (zh->zst_offset == zs->zst_offset + zs->zst_len) { 303 /* forward sequential access */ 304 305 mutex_enter(&zs->zst_lock); 306 307 if (zh->zst_offset != zs->zst_offset + zs->zst_len) { 308 mutex_exit(&zs->zst_lock); 309 goto top; 310 } 311 312 zs->zst_len += zh->zst_len; 313 diff = zs->zst_len - zfetch_block_cap; 314 if (diff > 0) { 315 zs->zst_offset += diff; 316 zs->zst_len = zs->zst_len > diff ? 317 zs->zst_len - diff : 0; 318 } 319 zs->zst_direction = ZFETCH_FORWARD; 320 321 break; 322 323 } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) { 324 /* backwards sequential access */ 325 326 mutex_enter(&zs->zst_lock); 327 328 if (zh->zst_offset != zs->zst_offset - zh->zst_len) { 329 mutex_exit(&zs->zst_lock); 330 goto top; 331 } 332 333 zs->zst_offset = zs->zst_offset > zh->zst_len ? 334 zs->zst_offset - zh->zst_len : 0; 335 zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ? 336 zs->zst_ph_offset - zh->zst_len : 0; 337 zs->zst_len += zh->zst_len; 338 339 diff = zs->zst_len - zfetch_block_cap; 340 if (diff > 0) { 341 zs->zst_ph_offset = zs->zst_ph_offset > diff ? 342 zs->zst_ph_offset - diff : 0; 343 zs->zst_len = zs->zst_len > diff ? 344 zs->zst_len - diff : zs->zst_len; 345 } 346 zs->zst_direction = ZFETCH_BACKWARD; 347 348 break; 349 350 } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride < 351 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 352 /* strided forward access */ 353 354 mutex_enter(&zs->zst_lock); 355 356 if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >= 357 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 358 mutex_exit(&zs->zst_lock); 359 goto top; 360 } 361 362 zs->zst_offset += zs->zst_stride; 363 zs->zst_direction = ZFETCH_FORWARD; 364 365 break; 366 367 } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride < 368 zs->zst_len) && (zs->zst_len != zs->zst_stride)) { 369 /* strided reverse access */ 370 371 mutex_enter(&zs->zst_lock); 372 373 if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >= 374 zs->zst_len) || (zs->zst_len == zs->zst_stride)) { 375 mutex_exit(&zs->zst_lock); 376 goto top; 377 } 378 379 zs->zst_offset = zs->zst_offset > zs->zst_stride ? 380 zs->zst_offset - zs->zst_stride : 0; 381 zs->zst_ph_offset = (zs->zst_ph_offset > 382 (2 * zs->zst_stride)) ? 383 (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0; 384 zs->zst_direction = ZFETCH_BACKWARD; 385 386 break; 387 } 388 } 389 390 if (zs) { 391 rc = 1; 392 dmu_zfetch_dofetch(zf, zs); 393 mutex_exit(&zs->zst_lock); 394 } 395 396 rw_exit(&zf->zf_rwlock); 397 return (rc); 398 } 399 400 /* 401 * Clean-up state associated with a zfetch structure. This frees allocated 402 * structure members, empties the zf_stream tree, and generally makes things 403 * nice. This doesn't free the zfetch_t itself, that's left to the caller. 404 */ 405 void 406 dmu_zfetch_rele(zfetch_t *zf) 407 { 408 zstream_t *zs; 409 zstream_t *zs_next; 410 411 ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock)); 412 413 for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) { 414 zs_next = list_next(&zf->zf_stream, zs); 415 416 list_remove(&zf->zf_stream, zs); 417 mutex_destroy(&zs->zst_lock); 418 kmem_free(zs, sizeof (zstream_t)); 419 } 420 list_destroy(&zf->zf_stream); 421 rw_destroy(&zf->zf_rwlock); 422 423 zf->zf_dnode = NULL; 424 } 425 426 /* 427 * Given a zfetch and zstream structure, insert the zstream structure into the 428 * AVL tree contained within the zfetch structure. Peform the appropriate 429 * book-keeping. It is possible that another thread has inserted a stream which 430 * matches one that we are about to insert, so we must be sure to check for this 431 * case. If one is found, return failure, and let the caller cleanup the 432 * duplicates. 433 */ 434 static int 435 dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs) 436 { 437 zstream_t *zs_walk; 438 zstream_t *zs_next; 439 440 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 441 442 for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) { 443 zs_next = list_next(&zf->zf_stream, zs_walk); 444 445 if (dmu_zfetch_streams_equal(zs_walk, zs)) { 446 return (0); 447 } 448 } 449 450 list_insert_head(&zf->zf_stream, zs); 451 zf->zf_stream_cnt++; 452 453 return (1); 454 } 455 456 457 /* 458 * Walk the list of zstreams in the given zfetch, find an old one (by time), and 459 * reclaim it for use by the caller. 460 */ 461 static zstream_t * 462 dmu_zfetch_stream_reclaim(zfetch_t *zf) 463 { 464 zstream_t *zs; 465 466 if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER)) 467 return (0); 468 469 for (zs = list_head(&zf->zf_stream); zs; 470 zs = list_next(&zf->zf_stream, zs)) { 471 472 if (((lbolt - zs->zst_last) / hz) > zfetch_min_sec_reap) 473 break; 474 } 475 476 if (zs) { 477 dmu_zfetch_stream_remove(zf, zs); 478 mutex_destroy(&zs->zst_lock); 479 bzero(zs, sizeof (zstream_t)); 480 } else { 481 zf->zf_alloc_fail++; 482 } 483 rw_exit(&zf->zf_rwlock); 484 485 return (zs); 486 } 487 488 /* 489 * Given a zfetch and zstream structure, remove the zstream structure from its 490 * container in the zfetch structure. Perform the appropriate book-keeping. 491 */ 492 static void 493 dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) 494 { 495 ASSERT(RW_WRITE_HELD(&zf->zf_rwlock)); 496 497 list_remove(&zf->zf_stream, zs); 498 zf->zf_stream_cnt--; 499 } 500 501 static int 502 dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2) 503 { 504 if (zs1->zst_offset != zs2->zst_offset) 505 return (0); 506 507 if (zs1->zst_len != zs2->zst_len) 508 return (0); 509 510 if (zs1->zst_stride != zs2->zst_stride) 511 return (0); 512 513 if (zs1->zst_ph_offset != zs2->zst_ph_offset) 514 return (0); 515 516 if (zs1->zst_cap != zs2->zst_cap) 517 return (0); 518 519 if (zs1->zst_direction != zs2->zst_direction) 520 return (0); 521 522 return (1); 523 } 524 525 /* 526 * This is the prefetch entry point. It calls all of the other dmu_zfetch 527 * routines to create, delete, find, or operate upon prefetch streams. 528 */ 529 void 530 dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size) 531 { 532 zstream_t zst; 533 zstream_t *newstream; 534 int fetched; 535 int inserted; 536 unsigned int blkshft; 537 uint64_t blksz; 538 539 /* files that aren't ln2 blocksz are only one block -- nothing to do */ 540 if (!zf->zf_dnode->dn_datablkshift) { 541 return; 542 } 543 544 /* convert offset and size, into blockid and nblocks */ 545 blkshft = zf->zf_dnode->dn_datablkshift; 546 blksz = (1 << blkshft); 547 548 bzero(&zst, sizeof (zstream_t)); 549 zst.zst_offset = offset >> blkshft; 550 zst.zst_len = (P2ROUNDUP(offset + size, blksz) - 551 P2ALIGN(offset, blksz)) >> blkshft; 552 553 fetched = dmu_zfetch_find(zf, &zst); 554 if (!fetched) { 555 fetched = dmu_zfetch_colinear(zf, &zst); 556 } 557 558 if (!fetched) { 559 newstream = dmu_zfetch_stream_reclaim(zf); 560 561 /* 562 * we still couldn't find a stream, drop the lock, and allocate 563 * one if possible. Otherwise, give up and go home. 564 */ 565 if (newstream == NULL) { 566 uint64_t maxblocks; 567 uint32_t max_streams; 568 uint32_t cur_streams; 569 570 cur_streams = zf->zf_stream_cnt; 571 maxblocks = zf->zf_dnode->dn_maxblkid; 572 573 max_streams = MIN(zfetch_max_streams, 574 (maxblocks / zfetch_block_cap)); 575 if (max_streams == 0) { 576 max_streams++; 577 } 578 579 if (cur_streams >= max_streams) { 580 return; 581 } 582 583 newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP); 584 } 585 586 newstream->zst_offset = zst.zst_offset; 587 newstream->zst_len = zst.zst_len; 588 newstream->zst_stride = zst.zst_len; 589 newstream->zst_ph_offset = zst.zst_len + zst.zst_offset; 590 newstream->zst_cap = zst.zst_len; 591 newstream->zst_direction = ZFETCH_FORWARD; 592 newstream->zst_last = lbolt; 593 594 mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL); 595 596 rw_enter(&zf->zf_rwlock, RW_WRITER); 597 inserted = dmu_zfetch_stream_insert(zf, newstream); 598 rw_exit(&zf->zf_rwlock); 599 600 if (!inserted) { 601 mutex_destroy(&newstream->zst_lock); 602 kmem_free(newstream, sizeof (zstream_t)); 603 } 604 } 605 } 606