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) 2013 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 five I/O classes
44 * prioritized in the following order: sync read, sync write, async read,
45 * async write, and scrub/resilver. 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 */
120 uint32_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 */
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
149 /*
150 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
151 * dirty data, use zfs_vdev_async_write_min_active. When it has more than
152 * zfs_vdev_async_write_active_max_dirty_percent, use
153 * zfs_vdev_async_write_max_active. The value is linearly interpolated
154 * between min and max.
155 */
156 int zfs_vdev_async_write_active_min_dirty_percent = 30;
157 int zfs_vdev_async_write_active_max_dirty_percent = 60;
158
159 /*
160 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
161 * For read I/Os, we also aggregate across small adjacency gaps; for writes
162 * we include spans of optional I/Os to aid aggregation at the disk even when
163 * they aren't able to help us aggregate at this level.
164 */
165 int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
166 int zfs_vdev_read_gap_limit = 32 << 10;
167 int zfs_vdev_write_gap_limit = 4 << 10;
168
169 int
170 vdev_queue_offset_compare(const void *x1, const void *x2)
171 {
172 const zio_t *z1 = x1;
173 const zio_t *z2 = x2;
174
175 if (z1->io_offset < z2->io_offset)
176 return (-1);
177 if (z1->io_offset > z2->io_offset)
178 return (1);
179
180 if (z1 < z2)
181 return (-1);
182 if (z1 > z2)
183 return (1);
184
185 return (0);
186 }
187
188 int
189 vdev_queue_timestamp_compare(const void *x1, const void *x2)
190 {
191 const zio_t *z1 = x1;
192 const zio_t *z2 = x2;
193
194 if (z1->io_timestamp < z2->io_timestamp)
195 return (-1);
196 if (z1->io_timestamp > z2->io_timestamp)
197 return (1);
198
199 if (z1 < z2)
200 return (-1);
201 if (z1 > z2)
202 return (1);
203
204 return (0);
205 }
206
207 void
208 vdev_queue_init(vdev_t *vd)
209 {
210 vdev_queue_t *vq = &vd->vdev_queue;
211
212 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
213 vq->vq_vdev = vd;
214
215 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
216 sizeof (zio_t), offsetof(struct zio, io_queue_node));
217
218 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
219 /*
220 * The synchronous i/o queues are FIFO rather than LBA ordered.
221 * This provides more consistent latency for these i/os, and
222 * they tend to not be tightly clustered anyway so there is
223 * little to no throughput loss.
224 */
225 boolean_t fifo = (p == ZIO_PRIORITY_SYNC_READ ||
226 p == ZIO_PRIORITY_SYNC_WRITE);
227 avl_create(&vq->vq_class[p].vqc_queued_tree,
228 fifo ? vdev_queue_timestamp_compare :
229 vdev_queue_offset_compare,
230 sizeof (zio_t), offsetof(struct zio, io_queue_node));
231 }
232 }
233
234 void
235 vdev_queue_fini(vdev_t *vd)
236 {
237 vdev_queue_t *vq = &vd->vdev_queue;
238
239 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
240 avl_destroy(&vq->vq_class[p].vqc_queued_tree);
241 avl_destroy(&vq->vq_active_tree);
242
243 mutex_destroy(&vq->vq_lock);
244 }
245
246 static void
247 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
248 {
249 spa_t *spa = zio->io_spa;
250 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
251 avl_add(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
252
253 mutex_enter(&spa->spa_iokstat_lock);
254 spa->spa_queue_stats[zio->io_priority].spa_queued++;
255 if (spa->spa_iokstat != NULL)
256 kstat_waitq_enter(spa->spa_iokstat->ks_data);
257 mutex_exit(&spa->spa_iokstat_lock);
258 }
259
260 static void
261 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
262 {
263 spa_t *spa = zio->io_spa;
264 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
265 avl_remove(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
266
267 mutex_enter(&spa->spa_iokstat_lock);
268 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
269 spa->spa_queue_stats[zio->io_priority].spa_queued--;
270 if (spa->spa_iokstat != NULL)
271 kstat_waitq_exit(spa->spa_iokstat->ks_data);
272 mutex_exit(&spa->spa_iokstat_lock);
273 }
274
275 static void
276 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
277 {
278 spa_t *spa = zio->io_spa;
279 ASSERT(MUTEX_HELD(&vq->vq_lock));
280 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
281 vq->vq_class[zio->io_priority].vqc_active++;
282 avl_add(&vq->vq_active_tree, zio);
283
284 mutex_enter(&spa->spa_iokstat_lock);
285 spa->spa_queue_stats[zio->io_priority].spa_active++;
286 if (spa->spa_iokstat != NULL)
287 kstat_runq_enter(spa->spa_iokstat->ks_data);
288 mutex_exit(&spa->spa_iokstat_lock);
289 }
290
291 static void
292 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
293 {
294 spa_t *spa = zio->io_spa;
295 ASSERT(MUTEX_HELD(&vq->vq_lock));
296 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
297 vq->vq_class[zio->io_priority].vqc_active--;
298 avl_remove(&vq->vq_active_tree, zio);
299
300 mutex_enter(&spa->spa_iokstat_lock);
301 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
302 spa->spa_queue_stats[zio->io_priority].spa_active--;
303 if (spa->spa_iokstat != NULL) {
304 kstat_io_t *ksio = spa->spa_iokstat->ks_data;
305
306 kstat_runq_exit(spa->spa_iokstat->ks_data);
307 if (zio->io_type == ZIO_TYPE_READ) {
308 ksio->reads++;
309 ksio->nread += zio->io_size;
310 } else if (zio->io_type == ZIO_TYPE_WRITE) {
311 ksio->writes++;
312 ksio->nwritten += zio->io_size;
313 }
314 }
315 mutex_exit(&spa->spa_iokstat_lock);
316 }
317
318 static void
319 vdev_queue_agg_io_done(zio_t *aio)
320 {
321 if (aio->io_type == ZIO_TYPE_READ) {
322 zio_t *pio;
323 while ((pio = zio_walk_parents(aio)) != NULL) {
324 bcopy((char *)aio->io_data + (pio->io_offset -
325 aio->io_offset), pio->io_data, pio->io_size);
326 }
327 }
328
329 zio_buf_free(aio->io_data, aio->io_size);
330 }
331
332 static int
333 vdev_queue_class_min_active(zio_priority_t p)
334 {
335 switch (p) {
336 case ZIO_PRIORITY_SYNC_READ:
337 return (zfs_vdev_sync_read_min_active);
338 case ZIO_PRIORITY_SYNC_WRITE:
339 return (zfs_vdev_sync_write_min_active);
340 case ZIO_PRIORITY_ASYNC_READ:
341 return (zfs_vdev_async_read_min_active);
342 case ZIO_PRIORITY_ASYNC_WRITE:
343 return (zfs_vdev_async_write_min_active);
344 case ZIO_PRIORITY_SCRUB:
345 return (zfs_vdev_scrub_min_active);
346 default:
347 panic("invalid priority %u", p);
348 return (0);
349 }
350 }
351
352 static int
353 vdev_queue_max_async_writes(uint64_t dirty)
354 {
355 int writes;
356 uint64_t min_bytes = zfs_dirty_data_max *
357 zfs_vdev_async_write_active_min_dirty_percent / 100;
358 uint64_t max_bytes = zfs_dirty_data_max *
359 zfs_vdev_async_write_active_max_dirty_percent / 100;
360
361 if (dirty < min_bytes)
362 return (zfs_vdev_async_write_min_active);
363 if (dirty > max_bytes)
364 return (zfs_vdev_async_write_max_active);
365
366 /*
367 * linear interpolation:
368 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
369 * move right by min_bytes
370 * move up by min_writes
371 */
372 writes = (dirty - min_bytes) *
373 (zfs_vdev_async_write_max_active -
374 zfs_vdev_async_write_min_active) /
375 (max_bytes - min_bytes) +
376 zfs_vdev_async_write_min_active;
377 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
378 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
379 return (writes);
380 }
381
382 static int
383 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
384 {
385 switch (p) {
386 case ZIO_PRIORITY_SYNC_READ:
387 return (zfs_vdev_sync_read_max_active);
388 case ZIO_PRIORITY_SYNC_WRITE:
389 return (zfs_vdev_sync_write_max_active);
390 case ZIO_PRIORITY_ASYNC_READ:
391 return (zfs_vdev_async_read_max_active);
392 case ZIO_PRIORITY_ASYNC_WRITE:
393 return (vdev_queue_max_async_writes(
394 spa->spa_dsl_pool->dp_dirty_total));
395 case ZIO_PRIORITY_SCRUB:
396 return (zfs_vdev_scrub_max_active);
397 default:
398 panic("invalid priority %u", p);
399 return (0);
400 }
401 }
402
403 /*
404 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
405 * there is no eligible class.
406 */
407 static zio_priority_t
408 vdev_queue_class_to_issue(vdev_queue_t *vq)
409 {
410 spa_t *spa = vq->vq_vdev->vdev_spa;
411 zio_priority_t p;
412
413 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
414 return (ZIO_PRIORITY_NUM_QUEUEABLE);
415
416 /* find a queue that has not reached its minimum # outstanding i/os */
417 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
418 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
419 vq->vq_class[p].vqc_active <
420 vdev_queue_class_min_active(p))
421 return (p);
422 }
423
424 /*
425 * If we haven't found a queue, look for one that hasn't reached its
426 * maximum # outstanding i/os.
427 */
428 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
429 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
430 vq->vq_class[p].vqc_active <
431 vdev_queue_class_max_active(spa, p))
432 return (p);
433 }
434
435 /* No eligible queued i/os */
436 return (ZIO_PRIORITY_NUM_QUEUEABLE);
437 }
438
439 /*
440 * Compute the range spanned by two i/os, which is the endpoint of the last
441 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
442 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
443 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
444 */
445 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
446 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
447
448 static zio_t *
449 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
450 {
451 zio_t *first, *last, *aio, *dio, *mandatory, *nio;
452 uint64_t maxgap = 0;
453 uint64_t size;
454 boolean_t stretch = B_FALSE;
455 vdev_queue_class_t *vqc = &vq->vq_class[zio->io_priority];
456 avl_tree_t *t = &vqc->vqc_queued_tree;
457 enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
458
459 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
460 return (NULL);
461
462 /*
463 * The synchronous i/o queues are not sorted by LBA, so we can't
464 * find adjacent i/os. These i/os tend to not be tightly clustered,
465 * or too large to aggregate, so this has little impact on performance.
466 */
467 if (zio->io_priority == ZIO_PRIORITY_SYNC_READ ||
468 zio->io_priority == ZIO_PRIORITY_SYNC_WRITE)
469 return (NULL);
470
471 first = last = zio;
472
473 if (zio->io_type == ZIO_TYPE_READ)
474 maxgap = zfs_vdev_read_gap_limit;
475
476 /*
477 * We can aggregate I/Os that are sufficiently adjacent and of
478 * the same flavor, as expressed by the AGG_INHERIT flags.
479 * The latter requirement is necessary so that certain
480 * attributes of the I/O, such as whether it's a normal I/O
481 * or a scrub/resilver, can be preserved in the aggregate.
482 * We can include optional I/Os, but don't allow them
483 * to begin a range as they add no benefit in that situation.
484 */
485
486 /*
487 * We keep track of the last non-optional I/O.
488 */
489 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
490
491 /*
492 * Walk backwards through sufficiently contiguous I/Os
493 * recording the last non-option I/O.
494 */
495 while ((dio = AVL_PREV(t, first)) != NULL &&
496 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
497 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
498 IO_GAP(dio, first) <= maxgap) {
499 first = dio;
500 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
501 mandatory = first;
502 }
503
504 /*
505 * Skip any initial optional I/Os.
506 */
507 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
508 first = AVL_NEXT(t, first);
509 ASSERT(first != NULL);
510 }
511
512 /*
513 * Walk forward through sufficiently contiguous I/Os.
514 */
515 while ((dio = AVL_NEXT(t, last)) != NULL &&
516 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
517 IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit &&
518 IO_GAP(last, dio) <= maxgap) {
519 last = dio;
520 if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
521 mandatory = last;
522 }
523
524 /*
525 * Now that we've established the range of the I/O aggregation
526 * we must decide what to do with trailing optional I/Os.
527 * For reads, there's nothing to do. While we are unable to
528 * aggregate further, it's possible that a trailing optional
529 * I/O would allow the underlying device to aggregate with
530 * subsequent I/Os. We must therefore determine if the next
531 * non-optional I/O is close enough to make aggregation
532 * worthwhile.
533 */
534 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
535 zio_t *nio = last;
536 while ((dio = AVL_NEXT(t, nio)) != NULL &&
537 IO_GAP(nio, dio) == 0 &&
538 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
539 nio = dio;
540 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
541 stretch = B_TRUE;
542 break;
543 }
544 }
545 }
546
547 if (stretch) {
548 /* This may be a no-op. */
549 dio = AVL_NEXT(t, last);
550 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
551 } else {
552 while (last != mandatory && last != first) {
553 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
554 last = AVL_PREV(t, last);
555 ASSERT(last != NULL);
556 }
557 }
558
559 if (first == last)
560 return (NULL);
561
562 size = IO_SPAN(first, last);
563 ASSERT3U(size, <=, zfs_vdev_aggregation_limit);
564
565 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
566 zio_buf_alloc(size), size, first->io_type, zio->io_priority,
567 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
568 vdev_queue_agg_io_done, NULL);
569 aio->io_timestamp = first->io_timestamp;
570
571 nio = first;
572 do {
573 dio = nio;
574 nio = AVL_NEXT(t, dio);
575 ASSERT3U(dio->io_type, ==, aio->io_type);
576
577 if (dio->io_flags & ZIO_FLAG_NODATA) {
578 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
579 bzero((char *)aio->io_data + (dio->io_offset -
580 aio->io_offset), dio->io_size);
581 } else if (dio->io_type == ZIO_TYPE_WRITE) {
582 bcopy(dio->io_data, (char *)aio->io_data +
583 (dio->io_offset - aio->io_offset),
584 dio->io_size);
585 }
586
587 zio_add_child(dio, aio);
588 vdev_queue_io_remove(vq, dio);
589 zio_vdev_io_bypass(dio);
590 zio_execute(dio);
591 } while (dio != last);
592
593 return (aio);
594 }
595
596 static zio_t *
597 vdev_queue_io_to_issue(vdev_queue_t *vq)
598 {
599 zio_t *zio, *aio;
600 zio_priority_t p;
601 avl_index_t idx;
602 vdev_queue_class_t *vqc;
603 zio_t search;
604
605 again:
606 ASSERT(MUTEX_HELD(&vq->vq_lock));
607
608 p = vdev_queue_class_to_issue(vq);
609
610 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
611 /* No eligible queued i/os */
612 return (NULL);
613 }
614
615 /*
616 * For LBA-ordered queues (async / scrub), issue the i/o which follows
617 * the most recently issued i/o in LBA (offset) order.
618 *
619 * For FIFO queues (sync), issue the i/o with the lowest timestamp.
620 */
621 vqc = &vq->vq_class[p];
622 search.io_timestamp = 0;
623 search.io_offset = vq->vq_last_offset + 1;
624 VERIFY3P(avl_find(&vqc->vqc_queued_tree, &search, &idx), ==, NULL);
625 zio = avl_nearest(&vqc->vqc_queued_tree, idx, AVL_AFTER);
626 if (zio == NULL)
627 zio = avl_first(&vqc->vqc_queued_tree);
628 ASSERT3U(zio->io_priority, ==, p);
629
630 aio = vdev_queue_aggregate(vq, zio);
631 if (aio != NULL)
632 zio = aio;
633 else
634 vdev_queue_io_remove(vq, zio);
635
636 /*
637 * If the I/O is or was optional and therefore has no data, we need to
638 * simply discard it. We need to drop the vdev queue's lock to avoid a
639 * deadlock that we could encounter since this I/O will complete
640 * immediately.
641 */
642 if (zio->io_flags & ZIO_FLAG_NODATA) {
643 mutex_exit(&vq->vq_lock);
644 zio_vdev_io_bypass(zio);
645 zio_execute(zio);
646 mutex_enter(&vq->vq_lock);
647 goto again;
648 }
649
650 vdev_queue_pending_add(vq, zio);
651 vq->vq_last_offset = zio->io_offset;
652
653 return (zio);
654 }
655
656 zio_t *
657 vdev_queue_io(zio_t *zio)
658 {
659 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
660 zio_t *nio;
661
662 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
663 return (zio);
664
665 /*
666 * Children i/os inherent their parent's priority, which might
667 * not match the child's i/o type. Fix it up here.
668 */
669 if (zio->io_type == ZIO_TYPE_READ) {
670 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
671 zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
672 zio->io_priority != ZIO_PRIORITY_SCRUB)
673 zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
674 } else {
675 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
676 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
677 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE)
678 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
679 }
680
681 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
682
683 mutex_enter(&vq->vq_lock);
684 zio->io_timestamp = gethrtime();
685 vdev_queue_io_add(vq, zio);
686 nio = vdev_queue_io_to_issue(vq);
687 mutex_exit(&vq->vq_lock);
688
689 if (nio == NULL)
690 return (NULL);
691
692 if (nio->io_done == vdev_queue_agg_io_done) {
693 zio_nowait(nio);
694 return (NULL);
695 }
696
697 return (nio);
698 }
699
700 void
701 vdev_queue_io_done(zio_t *zio)
702 {
703 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
704 zio_t *nio;
705
706 if (zio_injection_enabled)
707 delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
708
709 mutex_enter(&vq->vq_lock);
710
711 vdev_queue_pending_remove(vq, zio);
712
713 vq->vq_io_complete_ts = gethrtime();
714
715 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
716 mutex_exit(&vq->vq_lock);
717 if (nio->io_done == vdev_queue_agg_io_done) {
718 zio_nowait(nio);
719 } else {
720 zio_vdev_io_reissue(nio);
721 zio_execute(nio);
722 }
723 mutex_enter(&vq->vq_lock);
724 }
725
726 mutex_exit(&vq->vq_lock);
727 }