vdev_queue.c revision 297112
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, 2014 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 38/* 39 * ZFS I/O Scheduler 40 * --------------- 41 * 42 * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios. The 43 * I/O scheduler determines when and in what order those operations are 44 * issued. The I/O scheduler divides operations into six I/O classes 45 * prioritized in the following order: sync read, sync write, async read, 46 * async write, scrub/resilver and trim. Each queue defines the minimum and 47 * maximum number of concurrent operations that may be issued to the device. 48 * In addition, the device has an aggregate maximum. Note that the sum of the 49 * per-queue minimums must not exceed the aggregate maximum, and if the 50 * aggregate maximum is equal to or greater than the sum of the per-queue 51 * maximums, the per-queue minimum has no effect. 52 * 53 * For many physical devices, throughput increases with the number of 54 * concurrent operations, but latency typically suffers. Further, physical 55 * devices typically have a limit at which more concurrent operations have no 56 * effect on throughput or can actually cause it to decrease. 57 * 58 * The scheduler selects the next operation to issue by first looking for an 59 * I/O class whose minimum has not been satisfied. Once all are satisfied and 60 * the aggregate maximum has not been hit, the scheduler looks for classes 61 * whose maximum has not been satisfied. Iteration through the I/O classes is 62 * done in the order specified above. No further operations are issued if the 63 * aggregate maximum number of concurrent operations has been hit or if there 64 * are no operations queued for an I/O class that has not hit its maximum. 65 * Every time an I/O is queued or an operation completes, the I/O scheduler 66 * looks for new operations to issue. 67 * 68 * All I/O classes have a fixed maximum number of outstanding operations 69 * except for the async write class. Asynchronous writes represent the data 70 * that is committed to stable storage during the syncing stage for 71 * transaction groups (see txg.c). Transaction groups enter the syncing state 72 * periodically so the number of queued async writes will quickly burst up and 73 * then bleed down to zero. Rather than servicing them as quickly as possible, 74 * the I/O scheduler changes the maximum number of active async write I/Os 75 * according to the amount of dirty data in the pool (see dsl_pool.c). Since 76 * both throughput and latency typically increase with the number of 77 * concurrent operations issued to physical devices, reducing the burstiness 78 * in the number of concurrent operations also stabilizes the response time of 79 * operations from other -- and in particular synchronous -- queues. In broad 80 * strokes, the I/O scheduler will issue more concurrent operations from the 81 * async write queue as there's more dirty data in the pool. 82 * 83 * Async Writes 84 * 85 * The number of concurrent operations issued for the async write I/O class 86 * follows a piece-wise linear function defined by a few adjustable points. 87 * 88 * | o---------| <-- zfs_vdev_async_write_max_active 89 * ^ | /^ | 90 * | | / | | 91 * active | / | | 92 * I/O | / | | 93 * count | / | | 94 * | / | | 95 * |------------o | | <-- zfs_vdev_async_write_min_active 96 * 0|____________^______|_________| 97 * 0% | | 100% of zfs_dirty_data_max 98 * | | 99 * | `-- zfs_vdev_async_write_active_max_dirty_percent 100 * `--------- zfs_vdev_async_write_active_min_dirty_percent 101 * 102 * Until the amount of dirty data exceeds a minimum percentage of the dirty 103 * data allowed in the pool, the I/O scheduler will limit the number of 104 * concurrent operations to the minimum. As that threshold is crossed, the 105 * number of concurrent operations issued increases linearly to the maximum at 106 * the specified maximum percentage of the dirty data allowed in the pool. 107 * 108 * Ideally, the amount of dirty data on a busy pool will stay in the sloped 109 * part of the function between zfs_vdev_async_write_active_min_dirty_percent 110 * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the 111 * maximum percentage, this indicates that the rate of incoming data is 112 * greater than the rate that the backend storage can handle. In this case, we 113 * must further throttle incoming writes (see dmu_tx_delay() for details). 114 */ 115 116/* 117 * The maximum number of I/Os active to each device. Ideally, this will be >= 118 * the sum of each queue's max_active. It must be at least the sum of each 119 * queue's min_active. 120 */ 121uint32_t zfs_vdev_max_active = 1000; 122 123/* 124 * Per-queue limits on the number of I/Os active to each device. If the 125 * sum of the queue's max_active is < zfs_vdev_max_active, then the 126 * min_active comes into play. We will send min_active from each queue, 127 * and then select from queues in the order defined by zio_priority_t. 128 * 129 * In general, smaller max_active's will lead to lower latency of synchronous 130 * operations. Larger max_active's may lead to higher overall throughput, 131 * depending on underlying storage. 132 * 133 * The ratio of the queues' max_actives determines the balance of performance 134 * between reads, writes, and scrubs. E.g., increasing 135 * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete 136 * more quickly, but reads and writes to have higher latency and lower 137 * throughput. 138 */ 139uint32_t zfs_vdev_sync_read_min_active = 10; 140uint32_t zfs_vdev_sync_read_max_active = 10; 141uint32_t zfs_vdev_sync_write_min_active = 10; 142uint32_t zfs_vdev_sync_write_max_active = 10; 143uint32_t zfs_vdev_async_read_min_active = 1; 144uint32_t zfs_vdev_async_read_max_active = 3; 145uint32_t zfs_vdev_async_write_min_active = 1; 146uint32_t zfs_vdev_async_write_max_active = 10; 147uint32_t zfs_vdev_scrub_min_active = 1; 148uint32_t zfs_vdev_scrub_max_active = 2; 149uint32_t zfs_vdev_trim_min_active = 1; 150/* 151 * TRIM max active is large in comparison to the other values due to the fact 152 * that TRIM IOs are coalesced at the device layer. This value is set such 153 * that a typical SSD can process the queued IOs in a single request. 154 */ 155uint32_t zfs_vdev_trim_max_active = 64; 156 157 158/* 159 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent 160 * dirty data, use zfs_vdev_async_write_min_active. When it has more than 161 * zfs_vdev_async_write_active_max_dirty_percent, use 162 * zfs_vdev_async_write_max_active. The value is linearly interpolated 163 * between min and max. 164 */ 165int zfs_vdev_async_write_active_min_dirty_percent = 30; 166int zfs_vdev_async_write_active_max_dirty_percent = 60; 167 168/* 169 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O. 170 * For read I/Os, we also aggregate across small adjacency gaps; for writes 171 * we include spans of optional I/Os to aid aggregation at the disk even when 172 * they aren't able to help us aggregate at this level. 173 */ 174int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE; 175int zfs_vdev_read_gap_limit = 32 << 10; 176int zfs_vdev_write_gap_limit = 4 << 10; 177 178#ifdef __FreeBSD__ 179SYSCTL_DECL(_vfs_zfs_vdev); 180 181TUNABLE_INT("vfs.zfs.vdev.async_write_active_min_dirty_percent", 182 &zfs_vdev_async_write_active_min_dirty_percent); 183static int sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS); 184SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_min_dirty_percent, 185 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int), 186 sysctl_zfs_async_write_active_min_dirty_percent, "I", 187 "Percentage of async write dirty data below which " 188 "async_write_min_active is used."); 189 190TUNABLE_INT("vfs.zfs.vdev.async_write_active_max_dirty_percent", 191 &zfs_vdev_async_write_active_max_dirty_percent); 192static int sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS); 193SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_max_dirty_percent, 194 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int), 195 sysctl_zfs_async_write_active_max_dirty_percent, "I", 196 "Percentage of async write dirty data above which " 197 "async_write_max_active is used."); 198 199TUNABLE_INT("vfs.zfs.vdev.max_active", &zfs_vdev_max_active); 200SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, max_active, CTLFLAG_RWTUN, 201 &zfs_vdev_max_active, 0, 202 "The maximum number of I/Os of all types active for each device."); 203 204#define ZFS_VDEV_QUEUE_KNOB_MIN(name) \ 205TUNABLE_INT("vfs.zfs.vdev." #name "_min_active", \ 206 &zfs_vdev_ ## name ## _min_active); \ 207SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _min_active, \ 208 CTLFLAG_RWTUN, &zfs_vdev_ ## name ## _min_active, 0, \ 209 "Initial number of I/O requests of type " #name \ 210 " active for each device"); 211 212#define ZFS_VDEV_QUEUE_KNOB_MAX(name) \ 213TUNABLE_INT("vfs.zfs.vdev." #name "_max_active", \ 214 &zfs_vdev_ ## name ## _max_active); \ 215SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _max_active, \ 216 CTLFLAG_RWTUN, &zfs_vdev_ ## name ## _max_active, 0, \ 217 "Maximum number of I/O requests of type " #name \ 218 " active for each device"); 219 220ZFS_VDEV_QUEUE_KNOB_MIN(sync_read); 221ZFS_VDEV_QUEUE_KNOB_MAX(sync_read); 222ZFS_VDEV_QUEUE_KNOB_MIN(sync_write); 223ZFS_VDEV_QUEUE_KNOB_MAX(sync_write); 224ZFS_VDEV_QUEUE_KNOB_MIN(async_read); 225ZFS_VDEV_QUEUE_KNOB_MAX(async_read); 226ZFS_VDEV_QUEUE_KNOB_MIN(async_write); 227ZFS_VDEV_QUEUE_KNOB_MAX(async_write); 228ZFS_VDEV_QUEUE_KNOB_MIN(scrub); 229ZFS_VDEV_QUEUE_KNOB_MAX(scrub); 230ZFS_VDEV_QUEUE_KNOB_MIN(trim); 231ZFS_VDEV_QUEUE_KNOB_MAX(trim); 232 233#undef ZFS_VDEV_QUEUE_KNOB 234 235TUNABLE_INT("vfs.zfs.vdev.aggregation_limit", &zfs_vdev_aggregation_limit); 236SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, aggregation_limit, CTLFLAG_RWTUN, 237 &zfs_vdev_aggregation_limit, 0, 238 "I/O requests are aggregated up to this size"); 239TUNABLE_INT("vfs.zfs.vdev.read_gap_limit", &zfs_vdev_read_gap_limit); 240SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, read_gap_limit, CTLFLAG_RWTUN, 241 &zfs_vdev_read_gap_limit, 0, 242 "Acceptable gap between two reads being aggregated"); 243TUNABLE_INT("vfs.zfs.vdev.write_gap_limit", &zfs_vdev_write_gap_limit); 244SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, write_gap_limit, CTLFLAG_RWTUN, 245 &zfs_vdev_write_gap_limit, 0, 246 "Acceptable gap between two writes being aggregated"); 247 248static int 249sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS) 250{ 251 int val, err; 252 253 val = zfs_vdev_async_write_active_min_dirty_percent; 254 err = sysctl_handle_int(oidp, &val, 0, req); 255 if (err != 0 || req->newptr == NULL) 256 return (err); 257 258 if (val < 0 || val > 100 || 259 val >= zfs_vdev_async_write_active_max_dirty_percent) 260 return (EINVAL); 261 262 zfs_vdev_async_write_active_min_dirty_percent = val; 263 264 return (0); 265} 266 267static int 268sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS) 269{ 270 int val, err; 271 272 val = zfs_vdev_async_write_active_max_dirty_percent; 273 err = sysctl_handle_int(oidp, &val, 0, req); 274 if (err != 0 || req->newptr == NULL) 275 return (err); 276 277 if (val < 0 || val > 100 || 278 val <= zfs_vdev_async_write_active_min_dirty_percent) 279 return (EINVAL); 280 281 zfs_vdev_async_write_active_max_dirty_percent = val; 282 283 return (0); 284} 285#endif 286 287int 288vdev_queue_offset_compare(const void *x1, const void *x2) 289{ 290 const zio_t *z1 = x1; 291 const zio_t *z2 = x2; 292 293 if (z1->io_offset < z2->io_offset) 294 return (-1); 295 if (z1->io_offset > z2->io_offset) 296 return (1); 297 298 if (z1 < z2) 299 return (-1); 300 if (z1 > z2) 301 return (1); 302 303 return (0); 304} 305 306static inline avl_tree_t * 307vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p) 308{ 309 return (&vq->vq_class[p].vqc_queued_tree); 310} 311 312static inline avl_tree_t * 313vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t) 314{ 315 if (t == ZIO_TYPE_READ) 316 return (&vq->vq_read_offset_tree); 317 else if (t == ZIO_TYPE_WRITE) 318 return (&vq->vq_write_offset_tree); 319 else 320 return (NULL); 321} 322 323int 324vdev_queue_timestamp_compare(const void *x1, const void *x2) 325{ 326 const zio_t *z1 = x1; 327 const zio_t *z2 = x2; 328 329 if (z1->io_timestamp < z2->io_timestamp) 330 return (-1); 331 if (z1->io_timestamp > z2->io_timestamp) 332 return (1); 333 334 if (z1->io_offset < z2->io_offset) 335 return (-1); 336 if (z1->io_offset > z2->io_offset) 337 return (1); 338 339 if (z1 < z2) 340 return (-1); 341 if (z1 > z2) 342 return (1); 343 344 return (0); 345} 346 347void 348vdev_queue_init(vdev_t *vd) 349{ 350 vdev_queue_t *vq = &vd->vdev_queue; 351 352 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL); 353 vq->vq_vdev = vd; 354 355 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare, 356 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 357 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ), 358 vdev_queue_offset_compare, sizeof (zio_t), 359 offsetof(struct zio, io_offset_node)); 360 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE), 361 vdev_queue_offset_compare, sizeof (zio_t), 362 offsetof(struct zio, io_offset_node)); 363 364 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 365 int (*compfn) (const void *, const void *); 366 367 /* 368 * The synchronous i/o queues are dispatched in FIFO rather 369 * than LBA order. This provides more consistent latency for 370 * these i/os. 371 */ 372 if (p == ZIO_PRIORITY_SYNC_READ || p == ZIO_PRIORITY_SYNC_WRITE) 373 compfn = vdev_queue_timestamp_compare; 374 else 375 compfn = vdev_queue_offset_compare; 376 377 avl_create(vdev_queue_class_tree(vq, p), compfn, 378 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 379 } 380 381 vq->vq_lastoffset = 0; 382} 383 384void 385vdev_queue_fini(vdev_t *vd) 386{ 387 vdev_queue_t *vq = &vd->vdev_queue; 388 389 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) 390 avl_destroy(vdev_queue_class_tree(vq, p)); 391 avl_destroy(&vq->vq_active_tree); 392 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ)); 393 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE)); 394 395 mutex_destroy(&vq->vq_lock); 396} 397 398static void 399vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio) 400{ 401 spa_t *spa = zio->io_spa; 402 avl_tree_t *qtt; 403 ASSERT(MUTEX_HELD(&vq->vq_lock)); 404 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 405 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio); 406 qtt = vdev_queue_type_tree(vq, zio->io_type); 407 if (qtt) 408 avl_add(qtt, zio); 409 410#ifdef illumos 411 mutex_enter(&spa->spa_iokstat_lock); 412 spa->spa_queue_stats[zio->io_priority].spa_queued++; 413 if (spa->spa_iokstat != NULL) 414 kstat_waitq_enter(spa->spa_iokstat->ks_data); 415 mutex_exit(&spa->spa_iokstat_lock); 416#endif 417} 418 419static void 420vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio) 421{ 422 spa_t *spa = zio->io_spa; 423 avl_tree_t *qtt; 424 ASSERT(MUTEX_HELD(&vq->vq_lock)); 425 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 426 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio); 427 qtt = vdev_queue_type_tree(vq, zio->io_type); 428 if (qtt) 429 avl_remove(qtt, zio); 430 431#ifdef illumos 432 mutex_enter(&spa->spa_iokstat_lock); 433 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0); 434 spa->spa_queue_stats[zio->io_priority].spa_queued--; 435 if (spa->spa_iokstat != NULL) 436 kstat_waitq_exit(spa->spa_iokstat->ks_data); 437 mutex_exit(&spa->spa_iokstat_lock); 438#endif 439} 440 441static void 442vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio) 443{ 444 spa_t *spa = zio->io_spa; 445 ASSERT(MUTEX_HELD(&vq->vq_lock)); 446 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 447 vq->vq_class[zio->io_priority].vqc_active++; 448 avl_add(&vq->vq_active_tree, zio); 449 450#ifdef illumos 451 mutex_enter(&spa->spa_iokstat_lock); 452 spa->spa_queue_stats[zio->io_priority].spa_active++; 453 if (spa->spa_iokstat != NULL) 454 kstat_runq_enter(spa->spa_iokstat->ks_data); 455 mutex_exit(&spa->spa_iokstat_lock); 456#endif 457} 458 459static void 460vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio) 461{ 462 spa_t *spa = zio->io_spa; 463 ASSERT(MUTEX_HELD(&vq->vq_lock)); 464 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 465 vq->vq_class[zio->io_priority].vqc_active--; 466 avl_remove(&vq->vq_active_tree, zio); 467 468#ifdef illumos 469 mutex_enter(&spa->spa_iokstat_lock); 470 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0); 471 spa->spa_queue_stats[zio->io_priority].spa_active--; 472 if (spa->spa_iokstat != NULL) { 473 kstat_io_t *ksio = spa->spa_iokstat->ks_data; 474 475 kstat_runq_exit(spa->spa_iokstat->ks_data); 476 if (zio->io_type == ZIO_TYPE_READ) { 477 ksio->reads++; 478 ksio->nread += zio->io_size; 479 } else if (zio->io_type == ZIO_TYPE_WRITE) { 480 ksio->writes++; 481 ksio->nwritten += zio->io_size; 482 } 483 } 484 mutex_exit(&spa->spa_iokstat_lock); 485#endif 486} 487 488static void 489vdev_queue_agg_io_done(zio_t *aio) 490{ 491 if (aio->io_type == ZIO_TYPE_READ) { 492 zio_t *pio; 493 while ((pio = zio_walk_parents(aio)) != NULL) { 494 bcopy((char *)aio->io_data + (pio->io_offset - 495 aio->io_offset), pio->io_data, pio->io_size); 496 } 497 } 498 499 zio_buf_free(aio->io_data, aio->io_size); 500} 501 502static int 503vdev_queue_class_min_active(zio_priority_t p) 504{ 505 switch (p) { 506 case ZIO_PRIORITY_SYNC_READ: 507 return (zfs_vdev_sync_read_min_active); 508 case ZIO_PRIORITY_SYNC_WRITE: 509 return (zfs_vdev_sync_write_min_active); 510 case ZIO_PRIORITY_ASYNC_READ: 511 return (zfs_vdev_async_read_min_active); 512 case ZIO_PRIORITY_ASYNC_WRITE: 513 return (zfs_vdev_async_write_min_active); 514 case ZIO_PRIORITY_SCRUB: 515 return (zfs_vdev_scrub_min_active); 516 case ZIO_PRIORITY_TRIM: 517 return (zfs_vdev_trim_min_active); 518 default: 519 panic("invalid priority %u", p); 520 return (0); 521 } 522} 523 524static __noinline int 525vdev_queue_max_async_writes(spa_t *spa) 526{ 527 int writes; 528 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total; 529 uint64_t min_bytes = zfs_dirty_data_max * 530 zfs_vdev_async_write_active_min_dirty_percent / 100; 531 uint64_t max_bytes = zfs_dirty_data_max * 532 zfs_vdev_async_write_active_max_dirty_percent / 100; 533 534 /* 535 * Sync tasks correspond to interactive user actions. To reduce the 536 * execution time of those actions we push data out as fast as possible. 537 */ 538 if (spa_has_pending_synctask(spa)) { 539 return (zfs_vdev_async_write_max_active); 540 } 541 542 if (dirty < min_bytes) 543 return (zfs_vdev_async_write_min_active); 544 if (dirty > max_bytes) 545 return (zfs_vdev_async_write_max_active); 546 547 /* 548 * linear interpolation: 549 * slope = (max_writes - min_writes) / (max_bytes - min_bytes) 550 * move right by min_bytes 551 * move up by min_writes 552 */ 553 writes = (dirty - min_bytes) * 554 (zfs_vdev_async_write_max_active - 555 zfs_vdev_async_write_min_active) / 556 (max_bytes - min_bytes) + 557 zfs_vdev_async_write_min_active; 558 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active); 559 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active); 560 return (writes); 561} 562 563static int 564vdev_queue_class_max_active(spa_t *spa, zio_priority_t p) 565{ 566 switch (p) { 567 case ZIO_PRIORITY_SYNC_READ: 568 return (zfs_vdev_sync_read_max_active); 569 case ZIO_PRIORITY_SYNC_WRITE: 570 return (zfs_vdev_sync_write_max_active); 571 case ZIO_PRIORITY_ASYNC_READ: 572 return (zfs_vdev_async_read_max_active); 573 case ZIO_PRIORITY_ASYNC_WRITE: 574 return (vdev_queue_max_async_writes(spa)); 575 case ZIO_PRIORITY_SCRUB: 576 return (zfs_vdev_scrub_max_active); 577 case ZIO_PRIORITY_TRIM: 578 return (zfs_vdev_trim_max_active); 579 default: 580 panic("invalid priority %u", p); 581 return (0); 582 } 583} 584 585/* 586 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if 587 * there is no eligible class. 588 */ 589static zio_priority_t 590vdev_queue_class_to_issue(vdev_queue_t *vq) 591{ 592 spa_t *spa = vq->vq_vdev->vdev_spa; 593 zio_priority_t p; 594 595 ASSERT(MUTEX_HELD(&vq->vq_lock)); 596 597 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active) 598 return (ZIO_PRIORITY_NUM_QUEUEABLE); 599 600 /* find a queue that has not reached its minimum # outstanding i/os */ 601 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 602 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 && 603 vq->vq_class[p].vqc_active < 604 vdev_queue_class_min_active(p)) 605 return (p); 606 } 607 608 /* 609 * If we haven't found a queue, look for one that hasn't reached its 610 * maximum # outstanding i/os. 611 */ 612 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 613 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 && 614 vq->vq_class[p].vqc_active < 615 vdev_queue_class_max_active(spa, p)) 616 return (p); 617 } 618 619 /* No eligible queued i/os */ 620 return (ZIO_PRIORITY_NUM_QUEUEABLE); 621} 622 623/* 624 * Compute the range spanned by two i/os, which is the endpoint of the last 625 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset). 626 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio); 627 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0. 628 */ 629#define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset) 630#define IO_GAP(fio, lio) (-IO_SPAN(lio, fio)) 631 632static zio_t * 633vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio) 634{ 635 zio_t *first, *last, *aio, *dio, *mandatory, *nio; 636 uint64_t maxgap = 0; 637 uint64_t size; 638 boolean_t stretch; 639 avl_tree_t *t; 640 enum zio_flag flags; 641 642 ASSERT(MUTEX_HELD(&vq->vq_lock)); 643 644 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE) 645 return (NULL); 646 647 first = last = zio; 648 649 if (zio->io_type == ZIO_TYPE_READ) 650 maxgap = zfs_vdev_read_gap_limit; 651 652 /* 653 * We can aggregate I/Os that are sufficiently adjacent and of 654 * the same flavor, as expressed by the AGG_INHERIT flags. 655 * The latter requirement is necessary so that certain 656 * attributes of the I/O, such as whether it's a normal I/O 657 * or a scrub/resilver, can be preserved in the aggregate. 658 * We can include optional I/Os, but don't allow them 659 * to begin a range as they add no benefit in that situation. 660 */ 661 662 /* 663 * We keep track of the last non-optional I/O. 664 */ 665 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first; 666 667 /* 668 * Walk backwards through sufficiently contiguous I/Os 669 * recording the last non-option I/O. 670 */ 671 flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT; 672 t = vdev_queue_type_tree(vq, zio->io_type); 673 while (t != NULL && (dio = AVL_PREV(t, first)) != NULL && 674 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 675 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit && 676 IO_GAP(dio, first) <= maxgap) { 677 first = dio; 678 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL)) 679 mandatory = first; 680 } 681 682 /* 683 * Skip any initial optional I/Os. 684 */ 685 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) { 686 first = AVL_NEXT(t, first); 687 ASSERT(first != NULL); 688 } 689 690 /* 691 * Walk forward through sufficiently contiguous I/Os. 692 */ 693 while ((dio = AVL_NEXT(t, last)) != NULL && 694 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 695 IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit && 696 IO_GAP(last, dio) <= maxgap) { 697 last = dio; 698 if (!(last->io_flags & ZIO_FLAG_OPTIONAL)) 699 mandatory = last; 700 } 701 702 /* 703 * Now that we've established the range of the I/O aggregation 704 * we must decide what to do with trailing optional I/Os. 705 * For reads, there's nothing to do. While we are unable to 706 * aggregate further, it's possible that a trailing optional 707 * I/O would allow the underlying device to aggregate with 708 * subsequent I/Os. We must therefore determine if the next 709 * non-optional I/O is close enough to make aggregation 710 * worthwhile. 711 */ 712 stretch = B_FALSE; 713 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) { 714 zio_t *nio = last; 715 while ((dio = AVL_NEXT(t, nio)) != NULL && 716 IO_GAP(nio, dio) == 0 && 717 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) { 718 nio = dio; 719 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) { 720 stretch = B_TRUE; 721 break; 722 } 723 } 724 } 725 726 if (stretch) { 727 /* This may be a no-op. */ 728 dio = AVL_NEXT(t, last); 729 dio->io_flags &= ~ZIO_FLAG_OPTIONAL; 730 } else { 731 while (last != mandatory && last != first) { 732 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL); 733 last = AVL_PREV(t, last); 734 ASSERT(last != NULL); 735 } 736 } 737 738 if (first == last) 739 return (NULL); 740 741 size = IO_SPAN(first, last); 742 ASSERT3U(size, <=, zfs_vdev_aggregation_limit); 743 744 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset, 745 zio_buf_alloc(size), size, first->io_type, zio->io_priority, 746 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE, 747 vdev_queue_agg_io_done, NULL); 748 aio->io_timestamp = first->io_timestamp; 749 750 nio = first; 751 do { 752 dio = nio; 753 nio = AVL_NEXT(t, dio); 754 ASSERT3U(dio->io_type, ==, aio->io_type); 755 756 if (dio->io_flags & ZIO_FLAG_NODATA) { 757 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE); 758 bzero((char *)aio->io_data + (dio->io_offset - 759 aio->io_offset), dio->io_size); 760 } else if (dio->io_type == ZIO_TYPE_WRITE) { 761 bcopy(dio->io_data, (char *)aio->io_data + 762 (dio->io_offset - aio->io_offset), 763 dio->io_size); 764 } 765 766 zio_add_child(dio, aio); 767 vdev_queue_io_remove(vq, dio); 768 zio_vdev_io_bypass(dio); 769 zio_execute(dio); 770 } while (dio != last); 771 772 return (aio); 773} 774 775static zio_t * 776vdev_queue_io_to_issue(vdev_queue_t *vq) 777{ 778 zio_t *zio, *aio; 779 zio_priority_t p; 780 avl_index_t idx; 781 avl_tree_t *tree; 782 zio_t search; 783 784again: 785 ASSERT(MUTEX_HELD(&vq->vq_lock)); 786 787 p = vdev_queue_class_to_issue(vq); 788 789 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) { 790 /* No eligible queued i/os */ 791 return (NULL); 792 } 793 794 /* 795 * For LBA-ordered queues (async / scrub), issue the i/o which follows 796 * the most recently issued i/o in LBA (offset) order. 797 * 798 * For FIFO queues (sync), issue the i/o with the lowest timestamp. 799 */ 800 tree = vdev_queue_class_tree(vq, p); 801 search.io_timestamp = 0; 802 search.io_offset = vq->vq_last_offset + 1; 803 VERIFY3P(avl_find(tree, &search, &idx), ==, NULL); 804 zio = avl_nearest(tree, idx, AVL_AFTER); 805 if (zio == NULL) 806 zio = avl_first(tree); 807 ASSERT3U(zio->io_priority, ==, p); 808 809 aio = vdev_queue_aggregate(vq, zio); 810 if (aio != NULL) 811 zio = aio; 812 else 813 vdev_queue_io_remove(vq, zio); 814 815 /* 816 * If the I/O is or was optional and therefore has no data, we need to 817 * simply discard it. We need to drop the vdev queue's lock to avoid a 818 * deadlock that we could encounter since this I/O will complete 819 * immediately. 820 */ 821 if (zio->io_flags & ZIO_FLAG_NODATA) { 822 mutex_exit(&vq->vq_lock); 823 zio_vdev_io_bypass(zio); 824 zio_execute(zio); 825 mutex_enter(&vq->vq_lock); 826 goto again; 827 } 828 829 vdev_queue_pending_add(vq, zio); 830 vq->vq_last_offset = zio->io_offset; 831 832 return (zio); 833} 834 835zio_t * 836vdev_queue_io(zio_t *zio) 837{ 838 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 839 zio_t *nio; 840 841 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE) 842 return (zio); 843 844 /* 845 * Children i/os inherent their parent's priority, which might 846 * not match the child's i/o type. Fix it up here. 847 */ 848 if (zio->io_type == ZIO_TYPE_READ) { 849 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ && 850 zio->io_priority != ZIO_PRIORITY_ASYNC_READ && 851 zio->io_priority != ZIO_PRIORITY_SCRUB) 852 zio->io_priority = ZIO_PRIORITY_ASYNC_READ; 853 } else if (zio->io_type == ZIO_TYPE_WRITE) { 854 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE && 855 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE) 856 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE; 857 } else { 858 ASSERT(zio->io_type == ZIO_TYPE_FREE); 859 zio->io_priority = ZIO_PRIORITY_TRIM; 860 } 861 862 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE; 863 864 mutex_enter(&vq->vq_lock); 865 zio->io_timestamp = gethrtime(); 866 vdev_queue_io_add(vq, zio); 867 nio = vdev_queue_io_to_issue(vq); 868 mutex_exit(&vq->vq_lock); 869 870 if (nio == NULL) 871 return (NULL); 872 873 if (nio->io_done == vdev_queue_agg_io_done) { 874 zio_nowait(nio); 875 return (NULL); 876 } 877 878 return (nio); 879} 880 881void 882vdev_queue_io_done(zio_t *zio) 883{ 884 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 885 zio_t *nio; 886 887 mutex_enter(&vq->vq_lock); 888 889 vdev_queue_pending_remove(vq, zio); 890 891 vq->vq_io_complete_ts = gethrtime(); 892 893 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) { 894 mutex_exit(&vq->vq_lock); 895 if (nio->io_done == vdev_queue_agg_io_done) { 896 zio_nowait(nio); 897 } else { 898 zio_vdev_io_reissue(nio); 899 zio_execute(nio); 900 } 901 mutex_enter(&vq->vq_lock); 902 } 903 904 mutex_exit(&vq->vq_lock); 905} 906 907/* 908 * As these three methods are only used for load calculations we're not concerned 909 * if we get an incorrect value on 32bit platforms due to lack of vq_lock mutex 910 * use here, instead we prefer to keep it lock free for performance. 911 */ 912int 913vdev_queue_length(vdev_t *vd) 914{ 915 return (avl_numnodes(&vd->vdev_queue.vq_active_tree)); 916} 917 918uint64_t 919vdev_queue_lastoffset(vdev_t *vd) 920{ 921 return (vd->vdev_queue.vq_lastoffset); 922} 923 924void 925vdev_queue_register_lastoffset(vdev_t *vd, zio_t *zio) 926{ 927 vd->vdev_queue.vq_lastoffset = zio->io_offset + zio->io_size; 928} 929