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) 2012, 2018 by Delphix. All rights reserved. 28 * Copyright (c) 2014 Integros [integros.com] 29 */ 30 31 #include <sys/zfs_context.h> 32 #include <sys/vdev_impl.h> 33 #include <sys/spa_impl.h> 34 #include <sys/zio.h> 35 #include <sys/avl.h> 36 #include <sys/dsl_pool.h> 37 #include <sys/metaslab_impl.h> 38 #include <sys/abd.h> 39 40 /* 41 * ZFS I/O Scheduler 42 * --------------- 43 * 44 * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios. The 45 * I/O scheduler determines when and in what order those operations are 46 * issued. The I/O scheduler divides operations into five I/O classes 47 * prioritized in the following order: sync read, sync write, async read, 48 * async write, and scrub/resilver. Each queue defines the minimum and 49 * maximum number of concurrent operations that may be issued to the device. 50 * In addition, the device has an aggregate maximum. Note that the sum of the 51 * per-queue minimums must not exceed the aggregate maximum, and if the 52 * aggregate maximum is equal to or greater than the sum of the per-queue 53 * maximums, the per-queue minimum has no effect. 54 * 55 * For many physical devices, throughput increases with the number of 56 * concurrent operations, but latency typically suffers. Further, physical 57 * devices typically have a limit at which more concurrent operations have no 58 * effect on throughput or can actually cause it to decrease. 59 * 60 * The scheduler selects the next operation to issue by first looking for an 61 * I/O class whose minimum has not been satisfied. Once all are satisfied and 62 * the aggregate maximum has not been hit, the scheduler looks for classes 63 * whose maximum has not been satisfied. Iteration through the I/O classes is 64 * done in the order specified above. No further operations are issued if the 65 * aggregate maximum number of concurrent operations has been hit or if there 66 * are no operations queued for an I/O class that has not hit its maximum. 67 * Every time an i/o is queued or an operation completes, the I/O scheduler 68 * looks for new operations to issue. 69 * 70 * All I/O classes have a fixed maximum number of outstanding operations 71 * except for the async write class. Asynchronous writes represent the data 72 * that is committed to stable storage during the syncing stage for 73 * transaction groups (see txg.c). Transaction groups enter the syncing state 74 * periodically so the number of queued async writes will quickly burst up and 75 * then bleed down to zero. Rather than servicing them as quickly as possible, 76 * the I/O scheduler changes the maximum number of active async write i/os 77 * according to the amount of dirty data in the pool (see dsl_pool.c). Since 78 * both throughput and latency typically increase with the number of 79 * concurrent operations issued to physical devices, reducing the burstiness 80 * in the number of concurrent operations also stabilizes the response time of 81 * operations from other -- and in particular synchronous -- queues. In broad 82 * strokes, the I/O scheduler will issue more concurrent operations from the 83 * async write queue as there's more dirty data in the pool. 84 * 85 * Async Writes 86 * 87 * The number of concurrent operations issued for the async write I/O class 88 * follows a piece-wise linear function defined by a few adjustable points. 89 * 90 * | o---------| <-- zfs_vdev_async_write_max_active 91 * ^ | /^ | 92 * | | / | | 93 * active | / | | 94 * I/O | / | | 95 * count | / | | 96 * | / | | 97 * |------------o | | <-- zfs_vdev_async_write_min_active 98 * 0|____________^______|_________| 99 * 0% | | 100% of zfs_dirty_data_max 100 * | | 101 * | `-- zfs_vdev_async_write_active_max_dirty_percent 102 * `--------- zfs_vdev_async_write_active_min_dirty_percent 103 * 104 * Until the amount of dirty data exceeds a minimum percentage of the dirty 105 * data allowed in the pool, the I/O scheduler will limit the number of 106 * concurrent operations to the minimum. As that threshold is crossed, the 107 * number of concurrent operations issued increases linearly to the maximum at 108 * the specified maximum percentage of the dirty data allowed in the pool. 109 * 110 * Ideally, the amount of dirty data on a busy pool will stay in the sloped 111 * part of the function between zfs_vdev_async_write_active_min_dirty_percent 112 * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the 113 * maximum percentage, this indicates that the rate of incoming data is 114 * greater than the rate that the backend storage can handle. In this case, we 115 * must further throttle incoming writes (see dmu_tx_delay() for details). 116 */ 117 118 /* 119 * The maximum number of i/os active to each device. Ideally, this will be >= 120 * the sum of each queue's max_active. It must be at least the sum of each 121 * queue's min_active. 122 */ 123 uint32_t zfs_vdev_max_active = 1000; 124 125 /* 126 * Per-queue limits on the number of i/os active to each device. If the 127 * sum of the queue's max_active is < zfs_vdev_max_active, then the 128 * min_active comes into play. We will send min_active from each queue, 129 * and then select from queues in the order defined by zio_priority_t. 130 * 131 * In general, smaller max_active's will lead to lower latency of synchronous 132 * operations. Larger max_active's may lead to higher overall throughput, 133 * depending on underlying storage. 134 * 135 * The ratio of the queues' max_actives determines the balance of performance 136 * between reads, writes, and scrubs. E.g., increasing 137 * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete 138 * more quickly, but reads and writes to have higher latency and lower 139 * throughput. 140 */ 141 uint32_t zfs_vdev_sync_read_min_active = 10; 142 uint32_t zfs_vdev_sync_read_max_active = 10; 143 uint32_t zfs_vdev_sync_write_min_active = 10; 144 uint32_t zfs_vdev_sync_write_max_active = 10; 145 uint32_t zfs_vdev_async_read_min_active = 1; 146 uint32_t zfs_vdev_async_read_max_active = 3; 147 uint32_t zfs_vdev_async_write_min_active = 1; 148 uint32_t zfs_vdev_async_write_max_active = 10; 149 uint32_t zfs_vdev_scrub_min_active = 1; 150 uint32_t zfs_vdev_scrub_max_active = 2; 151 uint32_t zfs_vdev_removal_min_active = 1; 152 uint32_t zfs_vdev_removal_max_active = 2; 153 154 /* 155 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent 156 * dirty data, use zfs_vdev_async_write_min_active. When it has more than 157 * zfs_vdev_async_write_active_max_dirty_percent, use 158 * zfs_vdev_async_write_max_active. The value is linearly interpolated 159 * between min and max. 160 */ 161 int zfs_vdev_async_write_active_min_dirty_percent = 30; 162 int zfs_vdev_async_write_active_max_dirty_percent = 60; 163 164 /* 165 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O. 166 * For read I/Os, we also aggregate across small adjacency gaps; for writes 167 * we include spans of optional I/Os to aid aggregation at the disk even when 168 * they aren't able to help us aggregate at this level. 169 */ 170 int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE; 171 int zfs_vdev_read_gap_limit = 32 << 10; 172 int zfs_vdev_write_gap_limit = 4 << 10; 173 174 /* 175 * Define the queue depth percentage for each top-level. This percentage is 176 * used in conjunction with zfs_vdev_async_max_active to determine how many 177 * allocations a specific top-level vdev should handle. Once the queue depth 178 * reaches zfs_vdev_queue_depth_pct * zfs_vdev_async_write_max_active / 100 179 * then allocator will stop allocating blocks on that top-level device. 180 * The default kernel setting is 1000% which will yield 100 allocations per 181 * device. For userland testing, the default setting is 300% which equates 182 * to 30 allocations per device. 183 */ 184 #ifdef _KERNEL 185 int zfs_vdev_queue_depth_pct = 1000; 186 #else 187 int zfs_vdev_queue_depth_pct = 300; 188 #endif 189 190 /* 191 * When performing allocations for a given metaslab, we want to make sure that 192 * there are enough IOs to aggregate together to improve throughput. We want to 193 * ensure that there are at least 128k worth of IOs that can be aggregated, and 194 * we assume that the average allocation size is 4k, so we need the queue depth 195 * to be 32 per allocator to get good aggregation of sequential writes. 196 */ 197 int zfs_vdev_def_queue_depth = 32; 198 199 200 int 201 vdev_queue_offset_compare(const void *x1, const void *x2) 202 { 203 const zio_t *z1 = x1; 204 const zio_t *z2 = x2; 205 206 if (z1->io_offset < z2->io_offset) 207 return (-1); 208 if (z1->io_offset > z2->io_offset) 209 return (1); 210 211 if (z1 < z2) 212 return (-1); 213 if (z1 > z2) 214 return (1); 215 216 return (0); 217 } 218 219 static inline avl_tree_t * 220 vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p) 221 { 222 return (&vq->vq_class[p].vqc_queued_tree); 223 } 224 225 static inline avl_tree_t * 226 vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t) 227 { 228 ASSERT(t == ZIO_TYPE_READ || t == ZIO_TYPE_WRITE); 229 if (t == ZIO_TYPE_READ) 230 return (&vq->vq_read_offset_tree); 231 else 232 return (&vq->vq_write_offset_tree); 233 } 234 235 int 236 vdev_queue_timestamp_compare(const void *x1, const void *x2) 237 { 238 const zio_t *z1 = x1; 239 const zio_t *z2 = x2; 240 241 if (z1->io_timestamp < z2->io_timestamp) 242 return (-1); 243 if (z1->io_timestamp > z2->io_timestamp) 244 return (1); 245 246 if (z1 < z2) 247 return (-1); 248 if (z1 > z2) 249 return (1); 250 251 return (0); 252 } 253 254 void 255 vdev_queue_init(vdev_t *vd) 256 { 257 vdev_queue_t *vq = &vd->vdev_queue; 258 259 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL); 260 vq->vq_vdev = vd; 261 262 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare, 263 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 264 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ), 265 vdev_queue_offset_compare, sizeof (zio_t), 266 offsetof(struct zio, io_offset_node)); 267 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE), 268 vdev_queue_offset_compare, sizeof (zio_t), 269 offsetof(struct zio, io_offset_node)); 270 271 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 272 int (*compfn) (const void *, const void *); 273 274 /* 275 * The synchronous i/o queues are dispatched in FIFO rather 276 * than LBA order. This provides more consistent latency for 277 * these i/os. 278 */ 279 if (p == ZIO_PRIORITY_SYNC_READ || p == ZIO_PRIORITY_SYNC_WRITE) 280 compfn = vdev_queue_timestamp_compare; 281 else 282 compfn = vdev_queue_offset_compare; 283 284 avl_create(vdev_queue_class_tree(vq, p), compfn, 285 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 286 } 287 } 288 289 void 290 vdev_queue_fini(vdev_t *vd) 291 { 292 vdev_queue_t *vq = &vd->vdev_queue; 293 294 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) 295 avl_destroy(vdev_queue_class_tree(vq, p)); 296 avl_destroy(&vq->vq_active_tree); 297 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ)); 298 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE)); 299 300 mutex_destroy(&vq->vq_lock); 301 } 302 303 static void 304 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio) 305 { 306 spa_t *spa = zio->io_spa; 307 308 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 309 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio); 310 avl_add(vdev_queue_type_tree(vq, zio->io_type), zio); 311 312 mutex_enter(&spa->spa_iokstat_lock); 313 spa->spa_queue_stats[zio->io_priority].spa_queued++; 314 if (spa->spa_iokstat != NULL) 315 kstat_waitq_enter(spa->spa_iokstat->ks_data); 316 mutex_exit(&spa->spa_iokstat_lock); 317 } 318 319 static void 320 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio) 321 { 322 spa_t *spa = zio->io_spa; 323 324 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 325 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio); 326 avl_remove(vdev_queue_type_tree(vq, zio->io_type), zio); 327 328 mutex_enter(&spa->spa_iokstat_lock); 329 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0); 330 spa->spa_queue_stats[zio->io_priority].spa_queued--; 331 if (spa->spa_iokstat != NULL) 332 kstat_waitq_exit(spa->spa_iokstat->ks_data); 333 mutex_exit(&spa->spa_iokstat_lock); 334 } 335 336 static void 337 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio) 338 { 339 spa_t *spa = zio->io_spa; 340 ASSERT(MUTEX_HELD(&vq->vq_lock)); 341 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 342 vq->vq_class[zio->io_priority].vqc_active++; 343 avl_add(&vq->vq_active_tree, zio); 344 345 mutex_enter(&spa->spa_iokstat_lock); 346 spa->spa_queue_stats[zio->io_priority].spa_active++; 347 if (spa->spa_iokstat != NULL) 348 kstat_runq_enter(spa->spa_iokstat->ks_data); 349 mutex_exit(&spa->spa_iokstat_lock); 350 } 351 352 static void 353 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio) 354 { 355 spa_t *spa = zio->io_spa; 356 ASSERT(MUTEX_HELD(&vq->vq_lock)); 357 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 358 vq->vq_class[zio->io_priority].vqc_active--; 359 avl_remove(&vq->vq_active_tree, zio); 360 361 mutex_enter(&spa->spa_iokstat_lock); 362 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0); 363 spa->spa_queue_stats[zio->io_priority].spa_active--; 364 if (spa->spa_iokstat != NULL) { 365 kstat_io_t *ksio = spa->spa_iokstat->ks_data; 366 367 kstat_runq_exit(spa->spa_iokstat->ks_data); 368 if (zio->io_type == ZIO_TYPE_READ) { 369 ksio->reads++; 370 ksio->nread += zio->io_size; 371 } else if (zio->io_type == ZIO_TYPE_WRITE) { 372 ksio->writes++; 373 ksio->nwritten += zio->io_size; 374 } 375 } 376 mutex_exit(&spa->spa_iokstat_lock); 377 } 378 379 static void 380 vdev_queue_agg_io_done(zio_t *aio) 381 { 382 if (aio->io_type == ZIO_TYPE_READ) { 383 zio_t *pio; 384 zio_link_t *zl = NULL; 385 while ((pio = zio_walk_parents(aio, &zl)) != NULL) { 386 abd_copy_off(pio->io_abd, aio->io_abd, 387 0, pio->io_offset - aio->io_offset, pio->io_size); 388 } 389 } 390 391 abd_free(aio->io_abd); 392 } 393 394 static int 395 vdev_queue_class_min_active(zio_priority_t p) 396 { 397 switch (p) { 398 case ZIO_PRIORITY_SYNC_READ: 399 return (zfs_vdev_sync_read_min_active); 400 case ZIO_PRIORITY_SYNC_WRITE: 401 return (zfs_vdev_sync_write_min_active); 402 case ZIO_PRIORITY_ASYNC_READ: 403 return (zfs_vdev_async_read_min_active); 404 case ZIO_PRIORITY_ASYNC_WRITE: 405 return (zfs_vdev_async_write_min_active); 406 case ZIO_PRIORITY_SCRUB: 407 return (zfs_vdev_scrub_min_active); 408 case ZIO_PRIORITY_REMOVAL: 409 return (zfs_vdev_removal_min_active); 410 default: 411 panic("invalid priority %u", p); 412 return (0); 413 } 414 } 415 416 static int 417 vdev_queue_max_async_writes(spa_t *spa) 418 { 419 int writes; 420 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total; 421 uint64_t min_bytes = zfs_dirty_data_max * 422 zfs_vdev_async_write_active_min_dirty_percent / 100; 423 uint64_t max_bytes = zfs_dirty_data_max * 424 zfs_vdev_async_write_active_max_dirty_percent / 100; 425 426 /* 427 * Sync tasks correspond to interactive user actions. To reduce the 428 * execution time of those actions we push data out as fast as possible. 429 */ 430 if (spa_has_pending_synctask(spa)) { 431 return (zfs_vdev_async_write_max_active); 432 } 433 434 if (dirty < min_bytes) 435 return (zfs_vdev_async_write_min_active); 436 if (dirty > max_bytes) 437 return (zfs_vdev_async_write_max_active); 438 439 /* 440 * linear interpolation: 441 * slope = (max_writes - min_writes) / (max_bytes - min_bytes) 442 * move right by min_bytes 443 * move up by min_writes 444 */ 445 writes = (dirty - min_bytes) * 446 (zfs_vdev_async_write_max_active - 447 zfs_vdev_async_write_min_active) / 448 (max_bytes - min_bytes) + 449 zfs_vdev_async_write_min_active; 450 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active); 451 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active); 452 return (writes); 453 } 454 455 static int 456 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p) 457 { 458 switch (p) { 459 case ZIO_PRIORITY_SYNC_READ: 460 return (zfs_vdev_sync_read_max_active); 461 case ZIO_PRIORITY_SYNC_WRITE: 462 return (zfs_vdev_sync_write_max_active); 463 case ZIO_PRIORITY_ASYNC_READ: 464 return (zfs_vdev_async_read_max_active); 465 case ZIO_PRIORITY_ASYNC_WRITE: 466 return (vdev_queue_max_async_writes(spa)); 467 case ZIO_PRIORITY_SCRUB: 468 return (zfs_vdev_scrub_max_active); 469 case ZIO_PRIORITY_REMOVAL: 470 return (zfs_vdev_removal_max_active); 471 default: 472 panic("invalid priority %u", p); 473 return (0); 474 } 475 } 476 477 /* 478 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if 479 * there is no eligible class. 480 */ 481 static zio_priority_t 482 vdev_queue_class_to_issue(vdev_queue_t *vq) 483 { 484 spa_t *spa = vq->vq_vdev->vdev_spa; 485 zio_priority_t p; 486 487 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active) 488 return (ZIO_PRIORITY_NUM_QUEUEABLE); 489 490 /* find a queue that has not reached its minimum # outstanding i/os */ 491 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 492 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 && 493 vq->vq_class[p].vqc_active < 494 vdev_queue_class_min_active(p)) 495 return (p); 496 } 497 498 /* 499 * If we haven't found a queue, look for one that hasn't reached its 500 * maximum # outstanding i/os. 501 */ 502 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 503 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 && 504 vq->vq_class[p].vqc_active < 505 vdev_queue_class_max_active(spa, p)) 506 return (p); 507 } 508 509 /* No eligible queued i/os */ 510 return (ZIO_PRIORITY_NUM_QUEUEABLE); 511 } 512 513 /* 514 * Compute the range spanned by two i/os, which is the endpoint of the last 515 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset). 516 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio); 517 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0. 518 */ 519 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset) 520 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio)) 521 522 static zio_t * 523 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio) 524 { 525 zio_t *first, *last, *aio, *dio, *mandatory, *nio; 526 uint64_t maxgap = 0; 527 uint64_t size; 528 boolean_t stretch = B_FALSE; 529 avl_tree_t *t = vdev_queue_type_tree(vq, zio->io_type); 530 enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT; 531 532 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE) 533 return (NULL); 534 535 first = last = zio; 536 537 if (zio->io_type == ZIO_TYPE_READ) 538 maxgap = zfs_vdev_read_gap_limit; 539 540 /* 541 * We can aggregate I/Os that are sufficiently adjacent and of 542 * the same flavor, as expressed by the AGG_INHERIT flags. 543 * The latter requirement is necessary so that certain 544 * attributes of the I/O, such as whether it's a normal I/O 545 * or a scrub/resilver, can be preserved in the aggregate. 546 * We can include optional I/Os, but don't allow them 547 * to begin a range as they add no benefit in that situation. 548 */ 549 550 /* 551 * We keep track of the last non-optional I/O. 552 */ 553 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first; 554 555 /* 556 * Walk backwards through sufficiently contiguous I/Os 557 * recording the last non-optional I/O. 558 */ 559 while ((dio = AVL_PREV(t, first)) != NULL && 560 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 561 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit && 562 IO_GAP(dio, first) <= maxgap && 563 dio->io_type == zio->io_type) { 564 first = dio; 565 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL)) 566 mandatory = first; 567 } 568 569 /* 570 * Skip any initial optional I/Os. 571 */ 572 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) { 573 first = AVL_NEXT(t, first); 574 ASSERT(first != NULL); 575 } 576 577 /* 578 * Walk forward through sufficiently contiguous I/Os. 579 * The aggregation limit does not apply to optional i/os, so that 580 * we can issue contiguous writes even if they are larger than the 581 * aggregation limit. 582 */ 583 while ((dio = AVL_NEXT(t, last)) != NULL && 584 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 585 (IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit || 586 (dio->io_flags & ZIO_FLAG_OPTIONAL)) && 587 IO_GAP(last, dio) <= maxgap && 588 dio->io_type == zio->io_type) { 589 last = dio; 590 if (!(last->io_flags & ZIO_FLAG_OPTIONAL)) 591 mandatory = last; 592 } 593 594 /* 595 * Now that we've established the range of the I/O aggregation 596 * we must decide what to do with trailing optional I/Os. 597 * For reads, there's nothing to do. While we are unable to 598 * aggregate further, it's possible that a trailing optional 599 * I/O would allow the underlying device to aggregate with 600 * subsequent I/Os. We must therefore determine if the next 601 * non-optional I/O is close enough to make aggregation 602 * worthwhile. 603 */ 604 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) { 605 zio_t *nio = last; 606 while ((dio = AVL_NEXT(t, nio)) != NULL && 607 IO_GAP(nio, dio) == 0 && 608 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) { 609 nio = dio; 610 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) { 611 stretch = B_TRUE; 612 break; 613 } 614 } 615 } 616 617 if (stretch) { 618 /* 619 * We are going to include an optional io in our aggregated 620 * span, thus closing the write gap. Only mandatory i/os can 621 * start aggregated spans, so make sure that the next i/o 622 * after our span is mandatory. 623 */ 624 dio = AVL_NEXT(t, last); 625 dio->io_flags &= ~ZIO_FLAG_OPTIONAL; 626 } else { 627 /* do not include the optional i/o */ 628 while (last != mandatory && last != first) { 629 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL); 630 last = AVL_PREV(t, last); 631 ASSERT(last != NULL); 632 } 633 } 634 635 if (first == last) 636 return (NULL); 637 638 size = IO_SPAN(first, last); 639 ASSERT3U(size, <=, SPA_MAXBLOCKSIZE); 640 641 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset, 642 abd_alloc_for_io(size, B_TRUE), size, first->io_type, 643 zio->io_priority, flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE, 644 vdev_queue_agg_io_done, NULL); 645 aio->io_timestamp = first->io_timestamp; 646 647 nio = first; 648 do { 649 dio = nio; 650 nio = AVL_NEXT(t, dio); 651 ASSERT3U(dio->io_type, ==, aio->io_type); 652 653 if (dio->io_flags & ZIO_FLAG_NODATA) { 654 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE); 655 abd_zero_off(aio->io_abd, 656 dio->io_offset - aio->io_offset, dio->io_size); 657 } else if (dio->io_type == ZIO_TYPE_WRITE) { 658 abd_copy_off(aio->io_abd, dio->io_abd, 659 dio->io_offset - aio->io_offset, 0, dio->io_size); 660 } 661 662 zio_add_child(dio, aio); 663 vdev_queue_io_remove(vq, dio); 664 zio_vdev_io_bypass(dio); 665 zio_execute(dio); 666 } while (dio != last); 667 668 return (aio); 669 } 670 671 static zio_t * 672 vdev_queue_io_to_issue(vdev_queue_t *vq) 673 { 674 zio_t *zio, *aio; 675 zio_priority_t p; 676 avl_index_t idx; 677 avl_tree_t *tree; 678 zio_t search; 679 680 again: 681 ASSERT(MUTEX_HELD(&vq->vq_lock)); 682 683 p = vdev_queue_class_to_issue(vq); 684 685 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) { 686 /* No eligible queued i/os */ 687 return (NULL); 688 } 689 690 /* 691 * For LBA-ordered queues (async / scrub), issue the i/o which follows 692 * the most recently issued i/o in LBA (offset) order. 693 * 694 * For FIFO queues (sync), issue the i/o with the lowest timestamp. 695 */ 696 tree = vdev_queue_class_tree(vq, p); 697 search.io_timestamp = 0; 698 search.io_offset = vq->vq_last_offset + 1; 699 VERIFY3P(avl_find(tree, &search, &idx), ==, NULL); 700 zio = avl_nearest(tree, idx, AVL_AFTER); 701 if (zio == NULL) 702 zio = avl_first(tree); 703 ASSERT3U(zio->io_priority, ==, p); 704 705 aio = vdev_queue_aggregate(vq, zio); 706 if (aio != NULL) 707 zio = aio; 708 else 709 vdev_queue_io_remove(vq, zio); 710 711 /* 712 * If the I/O is or was optional and therefore has no data, we need to 713 * simply discard it. We need to drop the vdev queue's lock to avoid a 714 * deadlock that we could encounter since this I/O will complete 715 * immediately. 716 */ 717 if (zio->io_flags & ZIO_FLAG_NODATA) { 718 mutex_exit(&vq->vq_lock); 719 zio_vdev_io_bypass(zio); 720 zio_execute(zio); 721 mutex_enter(&vq->vq_lock); 722 goto again; 723 } 724 725 vdev_queue_pending_add(vq, zio); 726 vq->vq_last_offset = zio->io_offset; 727 728 return (zio); 729 } 730 731 zio_t * 732 vdev_queue_io(zio_t *zio) 733 { 734 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 735 zio_t *nio; 736 737 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE) 738 return (zio); 739 740 /* 741 * Children i/os inherent their parent's priority, which might 742 * not match the child's i/o type. Fix it up here. 743 */ 744 if (zio->io_type == ZIO_TYPE_READ) { 745 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ && 746 zio->io_priority != ZIO_PRIORITY_ASYNC_READ && 747 zio->io_priority != ZIO_PRIORITY_SCRUB && 748 zio->io_priority != ZIO_PRIORITY_REMOVAL) 749 zio->io_priority = ZIO_PRIORITY_ASYNC_READ; 750 } else { 751 ASSERT(zio->io_type == ZIO_TYPE_WRITE); 752 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE && 753 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE && 754 zio->io_priority != ZIO_PRIORITY_REMOVAL) 755 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE; 756 } 757 758 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE; 759 760 mutex_enter(&vq->vq_lock); 761 zio->io_timestamp = gethrtime(); 762 vdev_queue_io_add(vq, zio); 763 nio = vdev_queue_io_to_issue(vq); 764 mutex_exit(&vq->vq_lock); 765 766 if (nio == NULL) 767 return (NULL); 768 769 if (nio->io_done == vdev_queue_agg_io_done) { 770 zio_nowait(nio); 771 return (NULL); 772 } 773 774 return (nio); 775 } 776 777 void 778 vdev_queue_io_done(zio_t *zio) 779 { 780 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 781 zio_t *nio; 782 783 mutex_enter(&vq->vq_lock); 784 785 vdev_queue_pending_remove(vq, zio); 786 787 vq->vq_io_complete_ts = gethrtime(); 788 789 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) { 790 mutex_exit(&vq->vq_lock); 791 if (nio->io_done == vdev_queue_agg_io_done) { 792 zio_nowait(nio); 793 } else { 794 zio_vdev_io_reissue(nio); 795 zio_execute(nio); 796 } 797 mutex_enter(&vq->vq_lock); 798 } 799 800 mutex_exit(&vq->vq_lock); 801 } 802