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.
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.
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]
22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
27 * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
30 #include <sys/zfs_context.h>
31 #include <sys/vdev_impl.h>
32 #include <sys/spa_impl.h>
35 #include <sys/dsl_pool.h>
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.
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.
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.
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.
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.
87 * | o---------| <-- zfs_vdev_async_write_max_active
94 * |------------o | | <-- zfs_vdev_async_write_min_active
95 * 0|____________^______|_________|
96 * 0% | | 100% of zfs_dirty_data_max
98 * | `-- zfs_vdev_async_write_active_max_dirty_percent
99 * `--------- zfs_vdev_async_write_active_min_dirty_percent
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.
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).
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.
120 uint32_t zfs_vdev_max_active = 1000;
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.
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.
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
138 uint32_t zfs_vdev_sync_read_min_active = 10;
139 uint32_t zfs_vdev_sync_read_max_active = 10;
140 uint32_t zfs_vdev_sync_write_min_active = 10;
141 uint32_t zfs_vdev_sync_write_max_active = 10;
142 uint32_t zfs_vdev_async_read_min_active = 1;
143 uint32_t zfs_vdev_async_read_max_active = 3;
144 uint32_t zfs_vdev_async_write_min_active = 1;
145 uint32_t zfs_vdev_async_write_max_active = 10;
146 uint32_t zfs_vdev_scrub_min_active = 1;
147 uint32_t zfs_vdev_scrub_max_active = 2;
148 uint32_t zfs_vdev_trim_min_active = 1;
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.
154 uint32_t zfs_vdev_trim_max_active = 64;
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.
164 int zfs_vdev_async_write_active_min_dirty_percent = 30;
165 int zfs_vdev_async_write_active_max_dirty_percent = 60;
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.
173 int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE;
174 int zfs_vdev_read_gap_limit = 32 << 10;
175 int zfs_vdev_write_gap_limit = 4 << 10;
178 SYSCTL_DECL(_vfs_zfs_vdev);
180 static int sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS);
181 SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_min_dirty_percent,
182 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int),
183 sysctl_zfs_async_write_active_min_dirty_percent, "I",
184 "Percentage of async write dirty data below which "
185 "async_write_min_active is used.");
187 static int sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS);
188 SYSCTL_PROC(_vfs_zfs_vdev, OID_AUTO, async_write_active_max_dirty_percent,
189 CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RWTUN, 0, sizeof(int),
190 sysctl_zfs_async_write_active_max_dirty_percent, "I",
191 "Percentage of async write dirty data above which "
192 "async_write_max_active is used.");
194 SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, max_active, CTLFLAG_RWTUN,
195 &zfs_vdev_max_active, 0,
196 "The maximum number of I/Os of all types active for each device.");
198 #define ZFS_VDEV_QUEUE_KNOB_MIN(name) \
199 SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _min_active, CTLFLAG_RWTUN,\
200 &zfs_vdev_ ## name ## _min_active, 0, \
201 "Initial number of I/O requests of type " #name \
202 " active for each device");
204 #define ZFS_VDEV_QUEUE_KNOB_MAX(name) \
205 SYSCTL_UINT(_vfs_zfs_vdev, OID_AUTO, name ## _max_active, CTLFLAG_RWTUN,\
206 &zfs_vdev_ ## name ## _max_active, 0, \
207 "Maximum number of I/O requests of type " #name \
208 " active for each device");
210 ZFS_VDEV_QUEUE_KNOB_MIN(sync_read);
211 ZFS_VDEV_QUEUE_KNOB_MAX(sync_read);
212 ZFS_VDEV_QUEUE_KNOB_MIN(sync_write);
213 ZFS_VDEV_QUEUE_KNOB_MAX(sync_write);
214 ZFS_VDEV_QUEUE_KNOB_MIN(async_read);
215 ZFS_VDEV_QUEUE_KNOB_MAX(async_read);
216 ZFS_VDEV_QUEUE_KNOB_MIN(async_write);
217 ZFS_VDEV_QUEUE_KNOB_MAX(async_write);
218 ZFS_VDEV_QUEUE_KNOB_MIN(scrub);
219 ZFS_VDEV_QUEUE_KNOB_MAX(scrub);
220 ZFS_VDEV_QUEUE_KNOB_MIN(trim);
221 ZFS_VDEV_QUEUE_KNOB_MAX(trim);
223 #undef ZFS_VDEV_QUEUE_KNOB
225 SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, aggregation_limit, CTLFLAG_RWTUN,
226 &zfs_vdev_aggregation_limit, 0,
227 "I/O requests are aggregated up to this size");
228 SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, read_gap_limit, CTLFLAG_RWTUN,
229 &zfs_vdev_read_gap_limit, 0,
230 "Acceptable gap between two reads being aggregated");
231 SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, write_gap_limit, CTLFLAG_RWTUN,
232 &zfs_vdev_write_gap_limit, 0,
233 "Acceptable gap between two writes being aggregated");
236 sysctl_zfs_async_write_active_min_dirty_percent(SYSCTL_HANDLER_ARGS)
240 val = zfs_vdev_async_write_active_min_dirty_percent;
241 err = sysctl_handle_int(oidp, &val, 0, req);
242 if (err != 0 || req->newptr == NULL)
245 if (val < 0 || val > 100 ||
246 val >= zfs_vdev_async_write_active_max_dirty_percent)
249 zfs_vdev_async_write_active_min_dirty_percent = val;
255 sysctl_zfs_async_write_active_max_dirty_percent(SYSCTL_HANDLER_ARGS)
259 val = zfs_vdev_async_write_active_max_dirty_percent;
260 err = sysctl_handle_int(oidp, &val, 0, req);
261 if (err != 0 || req->newptr == NULL)
264 if (val < 0 || val > 100 ||
265 val <= zfs_vdev_async_write_active_min_dirty_percent)
268 zfs_vdev_async_write_active_max_dirty_percent = val;
275 vdev_queue_offset_compare(const void *x1, const void *x2)
277 const zio_t *z1 = x1;
278 const zio_t *z2 = x2;
280 if (z1->io_offset < z2->io_offset)
282 if (z1->io_offset > z2->io_offset)
293 static inline avl_tree_t *
294 vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p)
296 return (&vq->vq_class[p].vqc_queued_tree);
299 static inline avl_tree_t *
300 vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t)
302 if (t == ZIO_TYPE_READ)
303 return (&vq->vq_read_offset_tree);
304 else if (t == ZIO_TYPE_WRITE)
305 return (&vq->vq_write_offset_tree);
311 vdev_queue_timestamp_compare(const void *x1, const void *x2)
313 const zio_t *z1 = x1;
314 const zio_t *z2 = x2;
316 if (z1->io_timestamp < z2->io_timestamp)
318 if (z1->io_timestamp > z2->io_timestamp)
321 if (z1->io_offset < z2->io_offset)
323 if (z1->io_offset > z2->io_offset)
335 vdev_queue_init(vdev_t *vd)
337 vdev_queue_t *vq = &vd->vdev_queue;
339 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
342 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
343 sizeof (zio_t), offsetof(struct zio, io_queue_node));
344 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ),
345 vdev_queue_offset_compare, sizeof (zio_t),
346 offsetof(struct zio, io_offset_node));
347 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE),
348 vdev_queue_offset_compare, sizeof (zio_t),
349 offsetof(struct zio, io_offset_node));
351 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
352 int (*compfn) (const void *, const void *);
355 * The synchronous i/o queues are dispatched in FIFO rather
356 * than LBA order. This provides more consistent latency for
359 if (p == ZIO_PRIORITY_SYNC_READ || p == ZIO_PRIORITY_SYNC_WRITE)
360 compfn = vdev_queue_timestamp_compare;
362 compfn = vdev_queue_offset_compare;
364 avl_create(vdev_queue_class_tree(vq, p), compfn,
365 sizeof (zio_t), offsetof(struct zio, io_queue_node));
368 vq->vq_lastoffset = 0;
372 vdev_queue_fini(vdev_t *vd)
374 vdev_queue_t *vq = &vd->vdev_queue;
376 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
377 avl_destroy(vdev_queue_class_tree(vq, p));
378 avl_destroy(&vq->vq_active_tree);
379 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ));
380 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE));
382 mutex_destroy(&vq->vq_lock);
386 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
388 spa_t *spa = zio->io_spa;
390 ASSERT(MUTEX_HELD(&vq->vq_lock));
391 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
392 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
393 qtt = vdev_queue_type_tree(vq, zio->io_type);
398 mutex_enter(&spa->spa_iokstat_lock);
399 spa->spa_queue_stats[zio->io_priority].spa_queued++;
400 if (spa->spa_iokstat != NULL)
401 kstat_waitq_enter(spa->spa_iokstat->ks_data);
402 mutex_exit(&spa->spa_iokstat_lock);
407 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
409 spa_t *spa = zio->io_spa;
411 ASSERT(MUTEX_HELD(&vq->vq_lock));
412 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
413 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
414 qtt = vdev_queue_type_tree(vq, zio->io_type);
416 avl_remove(qtt, zio);
419 mutex_enter(&spa->spa_iokstat_lock);
420 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
421 spa->spa_queue_stats[zio->io_priority].spa_queued--;
422 if (spa->spa_iokstat != NULL)
423 kstat_waitq_exit(spa->spa_iokstat->ks_data);
424 mutex_exit(&spa->spa_iokstat_lock);
429 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
431 spa_t *spa = zio->io_spa;
432 ASSERT(MUTEX_HELD(&vq->vq_lock));
433 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
434 vq->vq_class[zio->io_priority].vqc_active++;
435 avl_add(&vq->vq_active_tree, zio);
438 mutex_enter(&spa->spa_iokstat_lock);
439 spa->spa_queue_stats[zio->io_priority].spa_active++;
440 if (spa->spa_iokstat != NULL)
441 kstat_runq_enter(spa->spa_iokstat->ks_data);
442 mutex_exit(&spa->spa_iokstat_lock);
447 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
449 spa_t *spa = zio->io_spa;
450 ASSERT(MUTEX_HELD(&vq->vq_lock));
451 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
452 vq->vq_class[zio->io_priority].vqc_active--;
453 avl_remove(&vq->vq_active_tree, zio);
456 mutex_enter(&spa->spa_iokstat_lock);
457 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
458 spa->spa_queue_stats[zio->io_priority].spa_active--;
459 if (spa->spa_iokstat != NULL) {
460 kstat_io_t *ksio = spa->spa_iokstat->ks_data;
462 kstat_runq_exit(spa->spa_iokstat->ks_data);
463 if (zio->io_type == ZIO_TYPE_READ) {
465 ksio->nread += zio->io_size;
466 } else if (zio->io_type == ZIO_TYPE_WRITE) {
468 ksio->nwritten += zio->io_size;
471 mutex_exit(&spa->spa_iokstat_lock);
476 vdev_queue_agg_io_done(zio_t *aio)
478 if (aio->io_type == ZIO_TYPE_READ) {
480 while ((pio = zio_walk_parents(aio)) != NULL) {
481 bcopy((char *)aio->io_data + (pio->io_offset -
482 aio->io_offset), pio->io_data, pio->io_size);
486 zio_buf_free(aio->io_data, aio->io_size);
490 vdev_queue_class_min_active(zio_priority_t p)
493 case ZIO_PRIORITY_SYNC_READ:
494 return (zfs_vdev_sync_read_min_active);
495 case ZIO_PRIORITY_SYNC_WRITE:
496 return (zfs_vdev_sync_write_min_active);
497 case ZIO_PRIORITY_ASYNC_READ:
498 return (zfs_vdev_async_read_min_active);
499 case ZIO_PRIORITY_ASYNC_WRITE:
500 return (zfs_vdev_async_write_min_active);
501 case ZIO_PRIORITY_SCRUB:
502 return (zfs_vdev_scrub_min_active);
503 case ZIO_PRIORITY_TRIM:
504 return (zfs_vdev_trim_min_active);
506 panic("invalid priority %u", p);
511 static __noinline int
512 vdev_queue_max_async_writes(spa_t *spa)
515 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
516 uint64_t min_bytes = zfs_dirty_data_max *
517 zfs_vdev_async_write_active_min_dirty_percent / 100;
518 uint64_t max_bytes = zfs_dirty_data_max *
519 zfs_vdev_async_write_active_max_dirty_percent / 100;
522 * Sync tasks correspond to interactive user actions. To reduce the
523 * execution time of those actions we push data out as fast as possible.
525 if (spa_has_pending_synctask(spa)) {
526 return (zfs_vdev_async_write_max_active);
529 if (dirty < min_bytes)
530 return (zfs_vdev_async_write_min_active);
531 if (dirty > max_bytes)
532 return (zfs_vdev_async_write_max_active);
535 * linear interpolation:
536 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
537 * move right by min_bytes
538 * move up by min_writes
540 writes = (dirty - min_bytes) *
541 (zfs_vdev_async_write_max_active -
542 zfs_vdev_async_write_min_active) /
543 (max_bytes - min_bytes) +
544 zfs_vdev_async_write_min_active;
545 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
546 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
551 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
554 case ZIO_PRIORITY_SYNC_READ:
555 return (zfs_vdev_sync_read_max_active);
556 case ZIO_PRIORITY_SYNC_WRITE:
557 return (zfs_vdev_sync_write_max_active);
558 case ZIO_PRIORITY_ASYNC_READ:
559 return (zfs_vdev_async_read_max_active);
560 case ZIO_PRIORITY_ASYNC_WRITE:
561 return (vdev_queue_max_async_writes(spa));
562 case ZIO_PRIORITY_SCRUB:
563 return (zfs_vdev_scrub_max_active);
564 case ZIO_PRIORITY_TRIM:
565 return (zfs_vdev_trim_max_active);
567 panic("invalid priority %u", p);
573 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
574 * there is no eligible class.
576 static zio_priority_t
577 vdev_queue_class_to_issue(vdev_queue_t *vq)
579 spa_t *spa = vq->vq_vdev->vdev_spa;
582 ASSERT(MUTEX_HELD(&vq->vq_lock));
584 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
585 return (ZIO_PRIORITY_NUM_QUEUEABLE);
587 /* find a queue that has not reached its minimum # outstanding i/os */
588 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
589 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
590 vq->vq_class[p].vqc_active <
591 vdev_queue_class_min_active(p))
596 * If we haven't found a queue, look for one that hasn't reached its
597 * maximum # outstanding i/os.
599 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
600 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
601 vq->vq_class[p].vqc_active <
602 vdev_queue_class_max_active(spa, p))
606 /* No eligible queued i/os */
607 return (ZIO_PRIORITY_NUM_QUEUEABLE);
611 * Compute the range spanned by two i/os, which is the endpoint of the last
612 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
613 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
614 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
616 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
617 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
620 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
622 zio_t *first, *last, *aio, *dio, *mandatory, *nio;
629 ASSERT(MUTEX_HELD(&vq->vq_lock));
631 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
636 if (zio->io_type == ZIO_TYPE_READ)
637 maxgap = zfs_vdev_read_gap_limit;
640 * We can aggregate I/Os that are sufficiently adjacent and of
641 * the same flavor, as expressed by the AGG_INHERIT flags.
642 * The latter requirement is necessary so that certain
643 * attributes of the I/O, such as whether it's a normal I/O
644 * or a scrub/resilver, can be preserved in the aggregate.
645 * We can include optional I/Os, but don't allow them
646 * to begin a range as they add no benefit in that situation.
650 * We keep track of the last non-optional I/O.
652 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
655 * Walk backwards through sufficiently contiguous I/Os
656 * recording the last non-option I/O.
658 flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
659 t = vdev_queue_type_tree(vq, zio->io_type);
660 while (t != NULL && (dio = AVL_PREV(t, first)) != NULL &&
661 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
662 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
663 IO_GAP(dio, first) <= maxgap) {
665 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
670 * Skip any initial optional I/Os.
672 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
673 first = AVL_NEXT(t, first);
674 ASSERT(first != NULL);
678 * Walk forward through sufficiently contiguous I/Os.
680 while ((dio = AVL_NEXT(t, last)) != NULL &&
681 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
682 IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit &&
683 IO_GAP(last, dio) <= maxgap) {
685 if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
690 * Now that we've established the range of the I/O aggregation
691 * we must decide what to do with trailing optional I/Os.
692 * For reads, there's nothing to do. While we are unable to
693 * aggregate further, it's possible that a trailing optional
694 * I/O would allow the underlying device to aggregate with
695 * subsequent I/Os. We must therefore determine if the next
696 * non-optional I/O is close enough to make aggregation
700 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
702 while ((dio = AVL_NEXT(t, nio)) != NULL &&
703 IO_GAP(nio, dio) == 0 &&
704 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
706 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
714 /* This may be a no-op. */
715 dio = AVL_NEXT(t, last);
716 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
718 while (last != mandatory && last != first) {
719 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
720 last = AVL_PREV(t, last);
721 ASSERT(last != NULL);
728 size = IO_SPAN(first, last);
729 ASSERT3U(size, <=, zfs_vdev_aggregation_limit);
731 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
732 zio_buf_alloc(size), size, first->io_type, zio->io_priority,
733 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
734 vdev_queue_agg_io_done, NULL);
735 aio->io_timestamp = first->io_timestamp;
740 nio = AVL_NEXT(t, dio);
741 ASSERT3U(dio->io_type, ==, aio->io_type);
743 if (dio->io_flags & ZIO_FLAG_NODATA) {
744 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
745 bzero((char *)aio->io_data + (dio->io_offset -
746 aio->io_offset), dio->io_size);
747 } else if (dio->io_type == ZIO_TYPE_WRITE) {
748 bcopy(dio->io_data, (char *)aio->io_data +
749 (dio->io_offset - aio->io_offset),
753 zio_add_child(dio, aio);
754 vdev_queue_io_remove(vq, dio);
755 zio_vdev_io_bypass(dio);
757 } while (dio != last);
763 vdev_queue_io_to_issue(vdev_queue_t *vq)
772 ASSERT(MUTEX_HELD(&vq->vq_lock));
774 p = vdev_queue_class_to_issue(vq);
776 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
777 /* No eligible queued i/os */
782 * For LBA-ordered queues (async / scrub), issue the i/o which follows
783 * the most recently issued i/o in LBA (offset) order.
785 * For FIFO queues (sync), issue the i/o with the lowest timestamp.
787 tree = vdev_queue_class_tree(vq, p);
788 search.io_timestamp = 0;
789 search.io_offset = vq->vq_last_offset + 1;
790 VERIFY3P(avl_find(tree, &search, &idx), ==, NULL);
791 zio = avl_nearest(tree, idx, AVL_AFTER);
793 zio = avl_first(tree);
794 ASSERT3U(zio->io_priority, ==, p);
796 aio = vdev_queue_aggregate(vq, zio);
800 vdev_queue_io_remove(vq, zio);
803 * If the I/O is or was optional and therefore has no data, we need to
804 * simply discard it. We need to drop the vdev queue's lock to avoid a
805 * deadlock that we could encounter since this I/O will complete
808 if (zio->io_flags & ZIO_FLAG_NODATA) {
809 mutex_exit(&vq->vq_lock);
810 zio_vdev_io_bypass(zio);
812 mutex_enter(&vq->vq_lock);
816 vdev_queue_pending_add(vq, zio);
817 vq->vq_last_offset = zio->io_offset;
823 vdev_queue_io(zio_t *zio)
825 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
828 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
832 * Children i/os inherent their parent's priority, which might
833 * not match the child's i/o type. Fix it up here.
835 if (zio->io_type == ZIO_TYPE_READ) {
836 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
837 zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
838 zio->io_priority != ZIO_PRIORITY_SCRUB)
839 zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
840 } else if (zio->io_type == ZIO_TYPE_WRITE) {
841 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
842 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE)
843 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
845 ASSERT(zio->io_type == ZIO_TYPE_FREE);
846 zio->io_priority = ZIO_PRIORITY_TRIM;
849 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
851 mutex_enter(&vq->vq_lock);
852 zio->io_timestamp = gethrtime();
853 vdev_queue_io_add(vq, zio);
854 nio = vdev_queue_io_to_issue(vq);
855 mutex_exit(&vq->vq_lock);
860 if (nio->io_done == vdev_queue_agg_io_done) {
869 vdev_queue_io_done(zio_t *zio)
871 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
874 if (zio_injection_enabled)
875 delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
877 mutex_enter(&vq->vq_lock);
879 vdev_queue_pending_remove(vq, zio);
881 vq->vq_io_complete_ts = gethrtime();
883 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
884 mutex_exit(&vq->vq_lock);
885 if (nio->io_done == vdev_queue_agg_io_done) {
888 zio_vdev_io_reissue(nio);
891 mutex_enter(&vq->vq_lock);
894 mutex_exit(&vq->vq_lock);
898 * As these three methods are only used for load calculations we're not concerned
899 * if we get an incorrect value on 32bit platforms due to lack of vq_lock mutex
900 * use here, instead we prefer to keep it lock free for performance.
903 vdev_queue_length(vdev_t *vd)
905 return (avl_numnodes(&vd->vdev_queue.vq_active_tree));
909 vdev_queue_lastoffset(vdev_t *vd)
911 return (vd->vdev_queue.vq_lastoffset);
915 vdev_queue_register_lastoffset(vdev_t *vd, zio_t *zio)
917 vd->vdev_queue.vq_lastoffset = zio->io_offset + zio->io_size;