vdev_queue.c revision 277700
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 */ 29 30#include <sys/zfs_context.h> 31#include <sys/vdev_impl.h> 32#include <sys/spa_impl.h> 33#include <sys/zio.h> 34#include <sys/avl.h> 35#include <sys/dsl_pool.h> 36 37/* 38 * ZFS I/O Scheduler 39 * --------------- 40 * 41 * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios. The 42 * I/O scheduler determines when and in what order those operations are 43 * issued. The I/O scheduler divides operations into six I/O classes 44 * prioritized in the following order: sync read, sync write, async read, 45 * async write, scrub/resilver and trim. Each queue defines the minimum and 46 * maximum number of concurrent operations that may be issued to the device. 47 * In addition, the device has an aggregate maximum. Note that the sum of the 48 * per-queue minimums must not exceed the aggregate maximum, and if the 49 * aggregate maximum is equal to or greater than the sum of the per-queue 50 * maximums, the per-queue minimum has no effect. 51 * 52 * For many physical devices, throughput increases with the number of 53 * concurrent operations, but latency typically suffers. Further, physical 54 * devices typically have a limit at which more concurrent operations have no 55 * effect on throughput or can actually cause it to decrease. 56 * 57 * The scheduler selects the next operation to issue by first looking for an 58 * I/O class whose minimum has not been satisfied. Once all are satisfied and 59 * the aggregate maximum has not been hit, the scheduler looks for classes 60 * whose maximum has not been satisfied. Iteration through the I/O classes is 61 * done in the order specified above. No further operations are issued if the 62 * aggregate maximum number of concurrent operations has been hit or if there 63 * are no operations queued for an I/O class that has not hit its maximum. 64 * Every time an I/O is queued or an operation completes, the I/O scheduler 65 * looks for new operations to issue. 66 * 67 * All I/O classes have a fixed maximum number of outstanding operations 68 * except for the async write class. Asynchronous writes represent the data 69 * that is committed to stable storage during the syncing stage for 70 * transaction groups (see txg.c). Transaction groups enter the syncing state 71 * periodically so the number of queued async writes will quickly burst up and 72 * then bleed down to zero. Rather than servicing them as quickly as possible, 73 * the I/O scheduler changes the maximum number of active async write I/Os 74 * according to the amount of dirty data in the pool (see dsl_pool.c). Since 75 * both throughput and latency typically increase with the number of 76 * concurrent operations issued to physical devices, reducing the burstiness 77 * in the number of concurrent operations also stabilizes the response time of 78 * operations from other -- and in particular synchronous -- queues. In broad 79 * strokes, the I/O scheduler will issue more concurrent operations from the 80 * async write queue as there's more dirty data in the pool. 81 * 82 * Async Writes 83 * 84 * The number of concurrent operations issued for the async write I/O class 85 * follows a piece-wise linear function defined by a few adjustable points. 86 * 87 * | o---------| <-- zfs_vdev_async_write_max_active 88 * ^ | /^ | 89 * | | / | | 90 * active | / | | 91 * I/O | / | | 92 * count | / | | 93 * | / | | 94 * |------------o | | <-- zfs_vdev_async_write_min_active 95 * 0|____________^______|_________| 96 * 0% | | 100% of zfs_dirty_data_max 97 * | | 98 * | `-- zfs_vdev_async_write_active_max_dirty_percent 99 * `--------- zfs_vdev_async_write_active_min_dirty_percent 100 * 101 * Until the amount of dirty data exceeds a minimum percentage of the dirty 102 * data allowed in the pool, the I/O scheduler will limit the number of 103 * concurrent operations to the minimum. As that threshold is crossed, the 104 * number of concurrent operations issued increases linearly to the maximum at 105 * the specified maximum percentage of the dirty data allowed in the pool. 106 * 107 * Ideally, the amount of dirty data on a busy pool will stay in the sloped 108 * part of the function between zfs_vdev_async_write_active_min_dirty_percent 109 * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the 110 * maximum percentage, this indicates that the rate of incoming data is 111 * greater than the rate that the backend storage can handle. In this case, we 112 * must further throttle incoming writes (see dmu_tx_delay() for details). 113 */ 114 115/* 116 * The maximum number of I/Os active to each device. Ideally, this will be >= 117 * the sum of each queue's max_active. It must be at least the sum of each 118 * queue's min_active. 119 */ 120uint32_t zfs_vdev_max_active = 1000; 121 122/* 123 * Per-queue limits on the number of I/Os active to each device. If the 124 * sum of the queue's max_active is < zfs_vdev_max_active, then the 125 * min_active comes into play. We will send min_active from each queue, 126 * and then select from queues in the order defined by zio_priority_t. 127 * 128 * In general, smaller max_active's will lead to lower latency of synchronous 129 * operations. Larger max_active's may lead to higher overall throughput, 130 * depending on underlying storage. 131 * 132 * The ratio of the queues' max_actives determines the balance of performance 133 * between reads, writes, and scrubs. E.g., increasing 134 * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete 135 * more quickly, but reads and writes to have higher latency and lower 136 * throughput. 137 */ 138uint32_t zfs_vdev_sync_read_min_active = 10; 139uint32_t zfs_vdev_sync_read_max_active = 10; 140uint32_t zfs_vdev_sync_write_min_active = 10; 141uint32_t zfs_vdev_sync_write_max_active = 10; 142uint32_t zfs_vdev_async_read_min_active = 1; 143uint32_t zfs_vdev_async_read_max_active = 3; 144uint32_t zfs_vdev_async_write_min_active = 1; 145uint32_t zfs_vdev_async_write_max_active = 10; 146uint32_t zfs_vdev_scrub_min_active = 1; 147uint32_t zfs_vdev_scrub_max_active = 2; 148uint32_t zfs_vdev_trim_min_active = 1; 149/* 150 * TRIM max active is large in comparison to the other values due to the fact 151 * that TRIM IOs are coalesced at the device layer. This value is set such 152 * that a typical SSD can process the queued IOs in a single request. 153 */ 154uint32_t zfs_vdev_trim_max_active = 64; 155 156 157/* 158 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent 159 * dirty data, use zfs_vdev_async_write_min_active. When it has more than 160 * zfs_vdev_async_write_active_max_dirty_percent, use 161 * zfs_vdev_async_write_max_active. The value is linearly interpolated 162 * between min and max. 163 */ 164int zfs_vdev_async_write_active_min_dirty_percent = 30; 165int zfs_vdev_async_write_active_max_dirty_percent = 60; 166 167/* 168 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O. 169 * For read I/Os, we also aggregate across small adjacency gaps; for writes 170 * we include spans of optional I/Os to aid aggregation at the disk even when 171 * they aren't able to help us aggregate at this level. 172 */ 173int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE; 174int zfs_vdev_read_gap_limit = 32 << 10; 175int zfs_vdev_write_gap_limit = 4 << 10; 176 177#ifdef __FreeBSD__ 178SYSCTL_DECL(_vfs_zfs_vdev); 179 180TUNABLE_INT("vfs.zfs.vdev.async_write_active_min_dirty_percent", 181 &zfs_vdev_async_write_active_min_dirty_percent); 182static int sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS); 183SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_min_dirty_percent, 184 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int), 185 sysctl_zfs_async_write_active_min_dirty_percent, "I", 186 "Percentage of async write dirty data below which " 187 "async_write_min_active is used."); 188 189TUNABLE_INT("vfs.zfs.vdev.async_write_active_max_dirty_percent", 190 &zfs_vdev_async_write_active_max_dirty_percent); 191static int sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS); 192SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_max_dirty_percent, 193 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int), 194 sysctl_zfs_async_write_active_max_dirty_percent, "I", 195 "Percentage of async write dirty data above which " 196 "async_write_max_active is used."); 197 198TUNABLE_INT("vfs.zfs.vdev.max_active", &zfs_vdev_max_active); 199SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, max_active, CTLFLAG_RWTUN, 200 &zfs_vdev_max_active, 0, 201 "The maximum number of I/Os of all types active for each device."); 202 203#define ZFS_VDEV_QUEUE_KNOB_MIN(name) \ 204TUNABLE_INT("vfs.zfs.vdev." #name "_min_active", \ 205 &zfs_vdev_ ## name ## _min_active); \ 206SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _min_active, \ 207 CTLFLAG_RWTUN, &zfs_vdev_ ## name ## _min_active, 0, \ 208 "Initial number of I/O requests of type " #name \ 209 " active for each device"); 210 211#define ZFS_VDEV_QUEUE_KNOB_MAX(name) \ 212TUNABLE_INT("vfs.zfs.vdev." #name "_max_active", \ 213 &zfs_vdev_ ## name ## _max_active); \ 214SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _max_active, \ 215 CTLFLAG_RWTUN, &zfs_vdev_ ## name ## _max_active, 0, \ 216 "Maximum number of I/O requests of type " #name \ 217 " active for each device"); 218 219ZFS_VDEV_QUEUE_KNOB_MIN(sync_read); 220ZFS_VDEV_QUEUE_KNOB_MAX(sync_read); 221ZFS_VDEV_QUEUE_KNOB_MIN(sync_write); 222ZFS_VDEV_QUEUE_KNOB_MAX(sync_write); 223ZFS_VDEV_QUEUE_KNOB_MIN(async_read); 224ZFS_VDEV_QUEUE_KNOB_MAX(async_read); 225ZFS_VDEV_QUEUE_KNOB_MIN(async_write); 226ZFS_VDEV_QUEUE_KNOB_MAX(async_write); 227ZFS_VDEV_QUEUE_KNOB_MIN(scrub); 228ZFS_VDEV_QUEUE_KNOB_MAX(scrub); 229ZFS_VDEV_QUEUE_KNOB_MIN(trim); 230ZFS_VDEV_QUEUE_KNOB_MAX(trim); 231 232#undef ZFS_VDEV_QUEUE_KNOB 233 234TUNABLE_INT("vfs.zfs.vdev.aggregation_limit", &zfs_vdev_aggregation_limit); 235SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, aggregation_limit, CTLFLAG_RWTUN, 236 &zfs_vdev_aggregation_limit, 0, 237 "I/O requests are aggregated up to this size"); 238TUNABLE_INT("vfs.zfs.vdev.read_gap_limit", &zfs_vdev_read_gap_limit); 239SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, read_gap_limit, CTLFLAG_RWTUN, 240 &zfs_vdev_read_gap_limit, 0, 241 "Acceptable gap between two reads being aggregated"); 242TUNABLE_INT("vfs.zfs.vdev.write_gap_limit", &zfs_vdev_write_gap_limit); 243SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, write_gap_limit, CTLFLAG_RWTUN, 244 &zfs_vdev_write_gap_limit, 0, 245 "Acceptable gap between two writes being aggregated"); 246 247static int 248sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS) 249{ 250 int val, err; 251 252 val = zfs_vdev_async_write_active_min_dirty_percent; 253 err = sysctl_handle_int(oidp, &val, 0, req); 254 if (err != 0 || req->newptr == NULL) 255 return (err); 256 257 if (val < 0 || val > 100 || 258 val >= zfs_vdev_async_write_active_max_dirty_percent) 259 return (EINVAL); 260 261 zfs_vdev_async_write_active_min_dirty_percent = val; 262 263 return (0); 264} 265 266static int 267sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS) 268{ 269 int val, err; 270 271 val = zfs_vdev_async_write_active_max_dirty_percent; 272 err = sysctl_handle_int(oidp, &val, 0, req); 273 if (err != 0 || req->newptr == NULL) 274 return (err); 275 276 if (val < 0 || val > 100 || 277 val <= zfs_vdev_async_write_active_min_dirty_percent) 278 return (EINVAL); 279 280 zfs_vdev_async_write_active_max_dirty_percent = val; 281 282 return (0); 283} 284#endif 285 286int 287vdev_queue_offset_compare(const void *x1, const void *x2) 288{ 289 const zio_t *z1 = x1; 290 const zio_t *z2 = x2; 291 292 if (z1->io_offset < z2->io_offset) 293 return (-1); 294 if (z1->io_offset > z2->io_offset) 295 return (1); 296 297 if (z1 < z2) 298 return (-1); 299 if (z1 > z2) 300 return (1); 301 302 return (0); 303} 304 305int 306vdev_queue_timestamp_compare(const void *x1, const void *x2) 307{ 308 const zio_t *z1 = x1; 309 const zio_t *z2 = x2; 310 311 if (z1->io_timestamp < z2->io_timestamp) 312 return (-1); 313 if (z1->io_timestamp > z2->io_timestamp) 314 return (1); 315 316 if (z1->io_offset < z2->io_offset) 317 return (-1); 318 if (z1->io_offset > z2->io_offset) 319 return (1); 320 321 if (z1 < z2) 322 return (-1); 323 if (z1 > z2) 324 return (1); 325 326 return (0); 327} 328 329void 330vdev_queue_init(vdev_t *vd) 331{ 332 vdev_queue_t *vq = &vd->vdev_queue; 333 334 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL); 335 vq->vq_vdev = vd; 336 337 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare, 338 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 339 340 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 341 /* 342 * The synchronous i/o queues are FIFO rather than LBA ordered. 343 * This provides more consistent latency for these i/os, and 344 * they tend to not be tightly clustered anyway so there is 345 * little to no throughput loss. 346 */ 347 boolean_t fifo = (p == ZIO_PRIORITY_SYNC_READ || 348 p == ZIO_PRIORITY_SYNC_WRITE); 349 avl_create(&vq->vq_class[p].vqc_queued_tree, 350 fifo ? vdev_queue_timestamp_compare : 351 vdev_queue_offset_compare, 352 sizeof (zio_t), offsetof(struct zio, io_queue_node)); 353 } 354 355 vq->vq_lastoffset = 0; 356} 357 358void 359vdev_queue_fini(vdev_t *vd) 360{ 361 vdev_queue_t *vq = &vd->vdev_queue; 362 363 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) 364 avl_destroy(&vq->vq_class[p].vqc_queued_tree); 365 avl_destroy(&vq->vq_active_tree); 366 367 mutex_destroy(&vq->vq_lock); 368} 369 370static void 371vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio) 372{ 373 spa_t *spa = zio->io_spa; 374 ASSERT(MUTEX_HELD(&vq->vq_lock)); 375 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 376 avl_add(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio); 377 378#ifdef illumos 379 mutex_enter(&spa->spa_iokstat_lock); 380 spa->spa_queue_stats[zio->io_priority].spa_queued++; 381 if (spa->spa_iokstat != NULL) 382 kstat_waitq_enter(spa->spa_iokstat->ks_data); 383 mutex_exit(&spa->spa_iokstat_lock); 384#endif 385} 386 387static void 388vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio) 389{ 390 spa_t *spa = zio->io_spa; 391 ASSERT(MUTEX_HELD(&vq->vq_lock)); 392 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 393 avl_remove(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio); 394 395#ifdef illumos 396 mutex_enter(&spa->spa_iokstat_lock); 397 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0); 398 spa->spa_queue_stats[zio->io_priority].spa_queued--; 399 if (spa->spa_iokstat != NULL) 400 kstat_waitq_exit(spa->spa_iokstat->ks_data); 401 mutex_exit(&spa->spa_iokstat_lock); 402#endif 403} 404 405static void 406vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio) 407{ 408 spa_t *spa = zio->io_spa; 409 ASSERT(MUTEX_HELD(&vq->vq_lock)); 410 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 411 vq->vq_class[zio->io_priority].vqc_active++; 412 avl_add(&vq->vq_active_tree, zio); 413 414#ifdef illumos 415 mutex_enter(&spa->spa_iokstat_lock); 416 spa->spa_queue_stats[zio->io_priority].spa_active++; 417 if (spa->spa_iokstat != NULL) 418 kstat_runq_enter(spa->spa_iokstat->ks_data); 419 mutex_exit(&spa->spa_iokstat_lock); 420#endif 421} 422 423static void 424vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio) 425{ 426 spa_t *spa = zio->io_spa; 427 ASSERT(MUTEX_HELD(&vq->vq_lock)); 428 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE); 429 vq->vq_class[zio->io_priority].vqc_active--; 430 avl_remove(&vq->vq_active_tree, zio); 431 432#ifdef illumos 433 mutex_enter(&spa->spa_iokstat_lock); 434 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0); 435 spa->spa_queue_stats[zio->io_priority].spa_active--; 436 if (spa->spa_iokstat != NULL) { 437 kstat_io_t *ksio = spa->spa_iokstat->ks_data; 438 439 kstat_runq_exit(spa->spa_iokstat->ks_data); 440 if (zio->io_type == ZIO_TYPE_READ) { 441 ksio->reads++; 442 ksio->nread += zio->io_size; 443 } else if (zio->io_type == ZIO_TYPE_WRITE) { 444 ksio->writes++; 445 ksio->nwritten += zio->io_size; 446 } 447 } 448 mutex_exit(&spa->spa_iokstat_lock); 449#endif 450} 451 452static void 453vdev_queue_agg_io_done(zio_t *aio) 454{ 455 if (aio->io_type == ZIO_TYPE_READ) { 456 zio_t *pio; 457 while ((pio = zio_walk_parents(aio)) != NULL) { 458 bcopy((char *)aio->io_data + (pio->io_offset - 459 aio->io_offset), pio->io_data, pio->io_size); 460 } 461 } 462 463 zio_buf_free(aio->io_data, aio->io_size); 464} 465 466static int 467vdev_queue_class_min_active(zio_priority_t p) 468{ 469 switch (p) { 470 case ZIO_PRIORITY_SYNC_READ: 471 return (zfs_vdev_sync_read_min_active); 472 case ZIO_PRIORITY_SYNC_WRITE: 473 return (zfs_vdev_sync_write_min_active); 474 case ZIO_PRIORITY_ASYNC_READ: 475 return (zfs_vdev_async_read_min_active); 476 case ZIO_PRIORITY_ASYNC_WRITE: 477 return (zfs_vdev_async_write_min_active); 478 case ZIO_PRIORITY_SCRUB: 479 return (zfs_vdev_scrub_min_active); 480 case ZIO_PRIORITY_TRIM: 481 return (zfs_vdev_trim_min_active); 482 default: 483 panic("invalid priority %u", p); 484 return (0); 485 } 486} 487 488static int 489vdev_queue_max_async_writes(spa_t *spa) 490{ 491 int writes; 492 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total; 493 uint64_t min_bytes = zfs_dirty_data_max * 494 zfs_vdev_async_write_active_min_dirty_percent / 100; 495 uint64_t max_bytes = zfs_dirty_data_max * 496 zfs_vdev_async_write_active_max_dirty_percent / 100; 497 498 /* 499 * Sync tasks correspond to interactive user actions. To reduce the 500 * execution time of those actions we push data out as fast as possible. 501 */ 502 if (spa_has_pending_synctask(spa)) { 503 return (zfs_vdev_async_write_max_active); 504 } 505 506 if (dirty < min_bytes) 507 return (zfs_vdev_async_write_min_active); 508 if (dirty > max_bytes) 509 return (zfs_vdev_async_write_max_active); 510 511 /* 512 * linear interpolation: 513 * slope = (max_writes - min_writes) / (max_bytes - min_bytes) 514 * move right by min_bytes 515 * move up by min_writes 516 */ 517 writes = (dirty - min_bytes) * 518 (zfs_vdev_async_write_max_active - 519 zfs_vdev_async_write_min_active) / 520 (max_bytes - min_bytes) + 521 zfs_vdev_async_write_min_active; 522 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active); 523 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active); 524 return (writes); 525} 526 527static int 528vdev_queue_class_max_active(spa_t *spa, zio_priority_t p) 529{ 530 switch (p) { 531 case ZIO_PRIORITY_SYNC_READ: 532 return (zfs_vdev_sync_read_max_active); 533 case ZIO_PRIORITY_SYNC_WRITE: 534 return (zfs_vdev_sync_write_max_active); 535 case ZIO_PRIORITY_ASYNC_READ: 536 return (zfs_vdev_async_read_max_active); 537 case ZIO_PRIORITY_ASYNC_WRITE: 538 return (vdev_queue_max_async_writes(spa)); 539 case ZIO_PRIORITY_SCRUB: 540 return (zfs_vdev_scrub_max_active); 541 case ZIO_PRIORITY_TRIM: 542 return (zfs_vdev_trim_max_active); 543 default: 544 panic("invalid priority %u", p); 545 return (0); 546 } 547} 548 549/* 550 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if 551 * there is no eligible class. 552 */ 553static zio_priority_t 554vdev_queue_class_to_issue(vdev_queue_t *vq) 555{ 556 spa_t *spa = vq->vq_vdev->vdev_spa; 557 zio_priority_t p; 558 559 ASSERT(MUTEX_HELD(&vq->vq_lock)); 560 561 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active) 562 return (ZIO_PRIORITY_NUM_QUEUEABLE); 563 564 /* find a queue that has not reached its minimum # outstanding i/os */ 565 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 566 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 && 567 vq->vq_class[p].vqc_active < 568 vdev_queue_class_min_active(p)) 569 return (p); 570 } 571 572 /* 573 * If we haven't found a queue, look for one that hasn't reached its 574 * maximum # outstanding i/os. 575 */ 576 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) { 577 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 && 578 vq->vq_class[p].vqc_active < 579 vdev_queue_class_max_active(spa, p)) 580 return (p); 581 } 582 583 /* No eligible queued i/os */ 584 return (ZIO_PRIORITY_NUM_QUEUEABLE); 585} 586 587/* 588 * Compute the range spanned by two i/os, which is the endpoint of the last 589 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset). 590 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio); 591 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0. 592 */ 593#define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset) 594#define IO_GAP(fio, lio) (-IO_SPAN(lio, fio)) 595 596static zio_t * 597vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio) 598{ 599 zio_t *first, *last, *aio, *dio, *mandatory, *nio; 600 uint64_t maxgap = 0; 601 uint64_t size; 602 boolean_t stretch; 603 avl_tree_t *t; 604 enum zio_flag flags; 605 606 ASSERT(MUTEX_HELD(&vq->vq_lock)); 607 608 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE) 609 return (NULL); 610 611 /* 612 * The synchronous i/o queues are not sorted by LBA, so we can't 613 * find adjacent i/os. These i/os tend to not be tightly clustered, 614 * or too large to aggregate, so this has little impact on performance. 615 */ 616 if (zio->io_priority == ZIO_PRIORITY_SYNC_READ || 617 zio->io_priority == ZIO_PRIORITY_SYNC_WRITE) 618 return (NULL); 619 620 first = last = zio; 621 622 if (zio->io_type == ZIO_TYPE_READ) 623 maxgap = zfs_vdev_read_gap_limit; 624 625 /* 626 * We can aggregate I/Os that are sufficiently adjacent and of 627 * the same flavor, as expressed by the AGG_INHERIT flags. 628 * The latter requirement is necessary so that certain 629 * attributes of the I/O, such as whether it's a normal I/O 630 * or a scrub/resilver, can be preserved in the aggregate. 631 * We can include optional I/Os, but don't allow them 632 * to begin a range as they add no benefit in that situation. 633 */ 634 635 /* 636 * We keep track of the last non-optional I/O. 637 */ 638 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first; 639 640 /* 641 * Walk backwards through sufficiently contiguous I/Os 642 * recording the last non-option I/O. 643 */ 644 flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT; 645 t = &vq->vq_class[zio->io_priority].vqc_queued_tree; 646 while ((dio = AVL_PREV(t, first)) != NULL && 647 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 648 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit && 649 IO_GAP(dio, first) <= maxgap) { 650 first = dio; 651 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL)) 652 mandatory = first; 653 } 654 655 /* 656 * Skip any initial optional I/Os. 657 */ 658 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) { 659 first = AVL_NEXT(t, first); 660 ASSERT(first != NULL); 661 } 662 663 /* 664 * Walk forward through sufficiently contiguous I/Os. 665 */ 666 while ((dio = AVL_NEXT(t, last)) != NULL && 667 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 668 IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit && 669 IO_GAP(last, dio) <= maxgap) { 670 last = dio; 671 if (!(last->io_flags & ZIO_FLAG_OPTIONAL)) 672 mandatory = last; 673 } 674 675 /* 676 * Now that we've established the range of the I/O aggregation 677 * we must decide what to do with trailing optional I/Os. 678 * For reads, there's nothing to do. While we are unable to 679 * aggregate further, it's possible that a trailing optional 680 * I/O would allow the underlying device to aggregate with 681 * subsequent I/Os. We must therefore determine if the next 682 * non-optional I/O is close enough to make aggregation 683 * worthwhile. 684 */ 685 stretch = B_FALSE; 686 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) { 687 zio_t *nio = last; 688 while ((dio = AVL_NEXT(t, nio)) != NULL && 689 IO_GAP(nio, dio) == 0 && 690 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) { 691 nio = dio; 692 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) { 693 stretch = B_TRUE; 694 break; 695 } 696 } 697 } 698 699 if (stretch) { 700 /* This may be a no-op. */ 701 dio = AVL_NEXT(t, last); 702 dio->io_flags &= ~ZIO_FLAG_OPTIONAL; 703 } else { 704 while (last != mandatory && last != first) { 705 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL); 706 last = AVL_PREV(t, last); 707 ASSERT(last != NULL); 708 } 709 } 710 711 if (first == last) 712 return (NULL); 713 714 size = IO_SPAN(first, last); 715 ASSERT3U(size, <=, zfs_vdev_aggregation_limit); 716 717 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset, 718 zio_buf_alloc(size), size, first->io_type, zio->io_priority, 719 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE, 720 vdev_queue_agg_io_done, NULL); 721 aio->io_timestamp = first->io_timestamp; 722 723 nio = first; 724 do { 725 dio = nio; 726 nio = AVL_NEXT(t, dio); 727 ASSERT3U(dio->io_type, ==, aio->io_type); 728 729 if (dio->io_flags & ZIO_FLAG_NODATA) { 730 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE); 731 bzero((char *)aio->io_data + (dio->io_offset - 732 aio->io_offset), dio->io_size); 733 } else if (dio->io_type == ZIO_TYPE_WRITE) { 734 bcopy(dio->io_data, (char *)aio->io_data + 735 (dio->io_offset - aio->io_offset), 736 dio->io_size); 737 } 738 739 zio_add_child(dio, aio); 740 vdev_queue_io_remove(vq, dio); 741 zio_vdev_io_bypass(dio); 742 zio_execute(dio); 743 } while (dio != last); 744 745 return (aio); 746} 747 748static zio_t * 749vdev_queue_io_to_issue(vdev_queue_t *vq) 750{ 751 zio_t *zio, *aio; 752 zio_priority_t p; 753 avl_index_t idx; 754 vdev_queue_class_t *vqc; 755 zio_t search; 756 757again: 758 ASSERT(MUTEX_HELD(&vq->vq_lock)); 759 760 p = vdev_queue_class_to_issue(vq); 761 762 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) { 763 /* No eligible queued i/os */ 764 return (NULL); 765 } 766 767 /* 768 * For LBA-ordered queues (async / scrub), issue the i/o which follows 769 * the most recently issued i/o in LBA (offset) order. 770 * 771 * For FIFO queues (sync), issue the i/o with the lowest timestamp. 772 */ 773 vqc = &vq->vq_class[p]; 774 search.io_timestamp = 0; 775 search.io_offset = vq->vq_last_offset + 1; 776 VERIFY3P(avl_find(&vqc->vqc_queued_tree, &search, &idx), ==, NULL); 777 zio = avl_nearest(&vqc->vqc_queued_tree, idx, AVL_AFTER); 778 if (zio == NULL) 779 zio = avl_first(&vqc->vqc_queued_tree); 780 ASSERT3U(zio->io_priority, ==, p); 781 782 aio = vdev_queue_aggregate(vq, zio); 783 if (aio != NULL) 784 zio = aio; 785 else 786 vdev_queue_io_remove(vq, zio); 787 788 /* 789 * If the I/O is or was optional and therefore has no data, we need to 790 * simply discard it. We need to drop the vdev queue's lock to avoid a 791 * deadlock that we could encounter since this I/O will complete 792 * immediately. 793 */ 794 if (zio->io_flags & ZIO_FLAG_NODATA) { 795 mutex_exit(&vq->vq_lock); 796 zio_vdev_io_bypass(zio); 797 zio_execute(zio); 798 mutex_enter(&vq->vq_lock); 799 goto again; 800 } 801 802 vdev_queue_pending_add(vq, zio); 803 vq->vq_last_offset = zio->io_offset; 804 805 return (zio); 806} 807 808zio_t * 809vdev_queue_io(zio_t *zio) 810{ 811 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 812 zio_t *nio; 813 814 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE) 815 return (zio); 816 817 /* 818 * Children i/os inherent their parent's priority, which might 819 * not match the child's i/o type. Fix it up here. 820 */ 821 if (zio->io_type == ZIO_TYPE_READ) { 822 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ && 823 zio->io_priority != ZIO_PRIORITY_ASYNC_READ && 824 zio->io_priority != ZIO_PRIORITY_SCRUB) 825 zio->io_priority = ZIO_PRIORITY_ASYNC_READ; 826 } else if (zio->io_type == ZIO_TYPE_WRITE) { 827 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE && 828 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE) 829 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE; 830 } else { 831 ASSERT(zio->io_type == ZIO_TYPE_FREE); 832 zio->io_priority = ZIO_PRIORITY_TRIM; 833 } 834 835 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE; 836 837 mutex_enter(&vq->vq_lock); 838 zio->io_timestamp = gethrtime(); 839 vdev_queue_io_add(vq, zio); 840 nio = vdev_queue_io_to_issue(vq); 841 mutex_exit(&vq->vq_lock); 842 843 if (nio == NULL) 844 return (NULL); 845 846 if (nio->io_done == vdev_queue_agg_io_done) { 847 zio_nowait(nio); 848 return (NULL); 849 } 850 851 return (nio); 852} 853 854void 855vdev_queue_io_done(zio_t *zio) 856{ 857 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 858 zio_t *nio; 859 860 if (zio_injection_enabled) 861 delay(SEC_TO_TICK(zio_handle_io_delay(zio))); 862 863 mutex_enter(&vq->vq_lock); 864 865 vdev_queue_pending_remove(vq, zio); 866 867 vq->vq_io_complete_ts = gethrtime(); 868 869 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) { 870 mutex_exit(&vq->vq_lock); 871 if (nio->io_done == vdev_queue_agg_io_done) { 872 zio_nowait(nio); 873 } else { 874 zio_vdev_io_reissue(nio); 875 zio_execute(nio); 876 } 877 mutex_enter(&vq->vq_lock); 878 } 879 880 mutex_exit(&vq->vq_lock); 881} 882 883/* 884 * As these three methods are only used for load calculations we're not concerned 885 * if we get an incorrect value on 32bit platforms due to lack of vq_lock mutex 886 * use here, instead we prefer to keep it lock free for performance. 887 */ 888int 889vdev_queue_length(vdev_t *vd) 890{ 891 return (avl_numnodes(&vd->vdev_queue.vq_active_tree)); 892} 893 894uint64_t 895vdev_queue_lastoffset(vdev_t *vd) 896{ 897 return (vd->vdev_queue.vq_lastoffset); 898} 899 900void 901vdev_queue_register_lastoffset(vdev_t *vd, zio_t *zio) 902{ 903 vd->vdev_queue.vq_lastoffset = zio->io_offset + zio->io_size; 904} 905