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 * Copyright (c) 2013 Steven Hartland. All rights reserved.
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 five I/O classes
45 * prioritized in the following order: sync read, sync write, async read,
46 * async write, and scrub/resilver. 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 */
121 uint32_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 */
139 uint32_t zfs_vdev_sync_read_min_active = 10;
140 uint32_t zfs_vdev_sync_read_max_active = 10;
141 uint32_t zfs_vdev_sync_write_min_active = 10;
142 uint32_t zfs_vdev_sync_write_max_active = 10;
143 uint32_t zfs_vdev_async_read_min_active = 1;
144 uint32_t zfs_vdev_async_read_max_active = 3;
145 uint32_t zfs_vdev_async_write_min_active = 1;
146 uint32_t zfs_vdev_async_write_max_active = 10;
147 uint32_t zfs_vdev_scrub_min_active = 1;
148 uint32_t zfs_vdev_scrub_max_active = 2;
149
150 /*
151 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
152 * dirty data, use zfs_vdev_async_write_min_active. When it has more than
153 * zfs_vdev_async_write_active_max_dirty_percent, use
154 * zfs_vdev_async_write_max_active. The value is linearly interpolated
155 * between min and max.
156 */
157 int zfs_vdev_async_write_active_min_dirty_percent = 30;
158 int zfs_vdev_async_write_active_max_dirty_percent = 60;
159
160 /*
161 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
162 * For read I/Os, we also aggregate across small adjacency gaps; for writes
163 * we include spans of optional I/Os to aid aggregation at the disk even when
164 * they aren't able to help us aggregate at this level.
165 */
166 int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
167 int zfs_vdev_read_gap_limit = 32 << 10;
168 int zfs_vdev_write_gap_limit = 4 << 10;
169
170 int
171 vdev_queue_offset_compare(const void *x1, const void *x2)
172 {
173 const zio_t *z1 = x1;
174 const zio_t *z2 = x2;
175
176 if (z1->io_offset < z2->io_offset)
177 return (-1);
178 if (z1->io_offset > z2->io_offset)
179 return (1);
180
181 if (z1 < z2)
182 return (-1);
183 if (z1 > z2)
184 return (1);
185
186 return (0);
187 }
188
189 int
190 vdev_queue_timestamp_compare(const void *x1, const void *x2)
191 {
192 const zio_t *z1 = x1;
193 const zio_t *z2 = x2;
194
195 if (z1->io_timestamp < z2->io_timestamp)
196 return (-1);
197 if (z1->io_timestamp > z2->io_timestamp)
198 return (1);
199
200 if (z1 < z2)
201 return (-1);
202 if (z1 > z2)
203 return (1);
204
205 return (0);
206 }
207
208 void
209 vdev_queue_init(vdev_t *vd)
210 {
211 vdev_queue_t *vq = &vd->vdev_queue;
212
213 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
214 vq->vq_vdev = vd;
215
216 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
217 sizeof (zio_t), offsetof(struct zio, io_queue_node));
218
219 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
220 /*
221 * The synchronous i/o queues are FIFO rather than LBA ordered.
222 * This provides more consistent latency for these i/os, and
223 * they tend to not be tightly clustered anyway so there is
224 * little to no throughput loss.
225 */
226 boolean_t fifo = (p == ZIO_PRIORITY_SYNC_READ ||
227 p == ZIO_PRIORITY_SYNC_WRITE);
228 avl_create(&vq->vq_class[p].vqc_queued_tree,
229 fifo ? vdev_queue_timestamp_compare :
230 vdev_queue_offset_compare,
231 sizeof (zio_t), offsetof(struct zio, io_queue_node));
232 }
233
234 vq->vq_last_queued_offset = 0;
235 }
236
237 void
238 vdev_queue_fini(vdev_t *vd)
239 {
240 vdev_queue_t *vq = &vd->vdev_queue;
241
242 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
243 avl_destroy(&vq->vq_class[p].vqc_queued_tree);
244 avl_destroy(&vq->vq_active_tree);
245
246 mutex_destroy(&vq->vq_lock);
247 }
248
249 static void
250 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
251 {
252 spa_t *spa = zio->io_spa;
253 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
254 avl_add(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
255
256 mutex_enter(&spa->spa_iokstat_lock);
257 spa->spa_queue_stats[zio->io_priority].spa_queued++;
258 if (spa->spa_iokstat != NULL)
259 kstat_waitq_enter(spa->spa_iokstat->ks_data);
260 mutex_exit(&spa->spa_iokstat_lock);
261 }
262
263 static void
264 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
265 {
266 spa_t *spa = zio->io_spa;
267 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
268 avl_remove(&vq->vq_class[zio->io_priority].vqc_queued_tree, zio);
269
270 mutex_enter(&spa->spa_iokstat_lock);
271 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
272 spa->spa_queue_stats[zio->io_priority].spa_queued--;
273 if (spa->spa_iokstat != NULL)
274 kstat_waitq_exit(spa->spa_iokstat->ks_data);
275 mutex_exit(&spa->spa_iokstat_lock);
276 }
277
278 static void
279 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
280 {
281 spa_t *spa = zio->io_spa;
282 ASSERT(MUTEX_HELD(&vq->vq_lock));
283 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
284 vq->vq_class[zio->io_priority].vqc_active++;
285 avl_add(&vq->vq_active_tree, zio);
286
287 mutex_enter(&spa->spa_iokstat_lock);
288 spa->spa_queue_stats[zio->io_priority].spa_active++;
289 if (spa->spa_iokstat != NULL)
290 kstat_runq_enter(spa->spa_iokstat->ks_data);
291 mutex_exit(&spa->spa_iokstat_lock);
292 }
293
294 static void
295 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
296 {
297 spa_t *spa = zio->io_spa;
298 ASSERT(MUTEX_HELD(&vq->vq_lock));
299 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
300 vq->vq_class[zio->io_priority].vqc_active--;
301 avl_remove(&vq->vq_active_tree, zio);
302
303 mutex_enter(&spa->spa_iokstat_lock);
304 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
305 spa->spa_queue_stats[zio->io_priority].spa_active--;
306 if (spa->spa_iokstat != NULL) {
307 kstat_io_t *ksio = spa->spa_iokstat->ks_data;
308
309 kstat_runq_exit(spa->spa_iokstat->ks_data);
310 if (zio->io_type == ZIO_TYPE_READ) {
311 ksio->reads++;
312 ksio->nread += zio->io_size;
313 } else if (zio->io_type == ZIO_TYPE_WRITE) {
314 ksio->writes++;
315 ksio->nwritten += zio->io_size;
316 }
317 }
318 mutex_exit(&spa->spa_iokstat_lock);
319 }
320
321 static void
322 vdev_queue_agg_io_done(zio_t *aio)
323 {
324 if (aio->io_type == ZIO_TYPE_READ) {
325 zio_t *pio;
326 while ((pio = zio_walk_parents(aio)) != NULL) {
327 bcopy((char *)aio->io_data + (pio->io_offset -
328 aio->io_offset), pio->io_data, pio->io_size);
329 }
330 }
331
332 zio_buf_free(aio->io_data, aio->io_size);
333 }
334
335 static int
336 vdev_queue_class_min_active(zio_priority_t p)
337 {
338 switch (p) {
339 case ZIO_PRIORITY_SYNC_READ:
340 return (zfs_vdev_sync_read_min_active);
341 case ZIO_PRIORITY_SYNC_WRITE:
342 return (zfs_vdev_sync_write_min_active);
343 case ZIO_PRIORITY_ASYNC_READ:
344 return (zfs_vdev_async_read_min_active);
345 case ZIO_PRIORITY_ASYNC_WRITE:
346 return (zfs_vdev_async_write_min_active);
347 case ZIO_PRIORITY_SCRUB:
348 return (zfs_vdev_scrub_min_active);
349 default:
350 panic("invalid priority %u", p);
351 return (0);
352 }
353 }
354
355 static int
356 vdev_queue_max_async_writes(uint64_t dirty)
357 {
358 int writes;
359 uint64_t min_bytes = zfs_dirty_data_max *
360 zfs_vdev_async_write_active_min_dirty_percent / 100;
361 uint64_t max_bytes = zfs_dirty_data_max *
362 zfs_vdev_async_write_active_max_dirty_percent / 100;
363
364 if (dirty < min_bytes)
365 return (zfs_vdev_async_write_min_active);
366 if (dirty > max_bytes)
367 return (zfs_vdev_async_write_max_active);
368
369 /*
370 * linear interpolation:
371 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
372 * move right by min_bytes
373 * move up by min_writes
374 */
375 writes = (dirty - min_bytes) *
376 (zfs_vdev_async_write_max_active -
377 zfs_vdev_async_write_min_active) /
378 (max_bytes - min_bytes) +
379 zfs_vdev_async_write_min_active;
380 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
381 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
382 return (writes);
383 }
384
385 static int
386 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
387 {
388 switch (p) {
389 case ZIO_PRIORITY_SYNC_READ:
390 return (zfs_vdev_sync_read_max_active);
391 case ZIO_PRIORITY_SYNC_WRITE:
392 return (zfs_vdev_sync_write_max_active);
393 case ZIO_PRIORITY_ASYNC_READ:
394 return (zfs_vdev_async_read_max_active);
395 case ZIO_PRIORITY_ASYNC_WRITE:
396 return (vdev_queue_max_async_writes(
397 spa->spa_dsl_pool->dp_dirty_total));
398 case ZIO_PRIORITY_SCRUB:
399 return (zfs_vdev_scrub_max_active);
400 default:
401 panic("invalid priority %u", p);
402 return (0);
403 }
404 }
405
406 /*
407 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
408 * there is no eligible class.
409 */
410 static zio_priority_t
411 vdev_queue_class_to_issue(vdev_queue_t *vq)
412 {
413 spa_t *spa = vq->vq_vdev->vdev_spa;
414 zio_priority_t p;
415
416 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
417 return (ZIO_PRIORITY_NUM_QUEUEABLE);
418
419 /* find a queue that has not reached its minimum # outstanding i/os */
420 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
421 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
422 vq->vq_class[p].vqc_active <
423 vdev_queue_class_min_active(p))
424 return (p);
425 }
426
427 /*
428 * If we haven't found a queue, look for one that hasn't reached its
429 * maximum # outstanding i/os.
430 */
431 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
432 if (avl_numnodes(&vq->vq_class[p].vqc_queued_tree) > 0 &&
433 vq->vq_class[p].vqc_active <
434 vdev_queue_class_max_active(spa, p))
435 return (p);
436 }
437
438 /* No eligible queued i/os */
439 return (ZIO_PRIORITY_NUM_QUEUEABLE);
440 }
441
442 /*
443 * Compute the range spanned by two i/os, which is the endpoint of the last
444 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
445 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
446 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
447 */
448 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
449 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
450
451 static zio_t *
452 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
453 {
454 zio_t *first, *last, *aio, *dio, *mandatory, *nio;
455 uint64_t maxgap = 0;
456 uint64_t size;
457 boolean_t stretch = B_FALSE;
458 vdev_queue_class_t *vqc = &vq->vq_class[zio->io_priority];
459 avl_tree_t *t = &vqc->vqc_queued_tree;
460 enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
461
462 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
463 return (NULL);
464
465 /*
466 * The synchronous i/o queues are not sorted by LBA, so we can't
467 * find adjacent i/os. These i/os tend to not be tightly clustered,
468 * or too large to aggregate, so this has little impact on performance.
469 */
470 if (zio->io_priority == ZIO_PRIORITY_SYNC_READ ||
471 zio->io_priority == ZIO_PRIORITY_SYNC_WRITE)
472 return (NULL);
473
474 first = last = zio;
475
476 if (zio->io_type == ZIO_TYPE_READ)
477 maxgap = zfs_vdev_read_gap_limit;
478
479 /*
480 * We can aggregate I/Os that are sufficiently adjacent and of
481 * the same flavor, as expressed by the AGG_INHERIT flags.
482 * The latter requirement is necessary so that certain
483 * attributes of the I/O, such as whether it's a normal I/O
484 * or a scrub/resilver, can be preserved in the aggregate.
485 * We can include optional I/Os, but don't allow them
486 * to begin a range as they add no benefit in that situation.
487 */
488
489 /*
490 * We keep track of the last non-optional I/O.
491 */
492 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
493
494 /*
495 * Walk backwards through sufficiently contiguous I/Os
496 * recording the last non-option I/O.
497 */
498 while ((dio = AVL_PREV(t, first)) != NULL &&
499 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
500 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
501 IO_GAP(dio, first) <= maxgap) {
502 first = dio;
503 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
504 mandatory = first;
505 }
506
507 /*
508 * Skip any initial optional I/Os.
509 */
510 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
511 first = AVL_NEXT(t, first);
512 ASSERT(first != NULL);
513 }
514
515 /*
516 * Walk forward through sufficiently contiguous I/Os.
517 */
518 while ((dio = AVL_NEXT(t, last)) != NULL &&
519 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
520 IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit &&
521 IO_GAP(last, dio) <= maxgap) {
522 last = dio;
523 if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
524 mandatory = last;
525 }
526
527 /*
528 * Now that we've established the range of the I/O aggregation
529 * we must decide what to do with trailing optional I/Os.
530 * For reads, there's nothing to do. While we are unable to
531 * aggregate further, it's possible that a trailing optional
532 * I/O would allow the underlying device to aggregate with
533 * subsequent I/Os. We must therefore determine if the next
534 * non-optional I/O is close enough to make aggregation
535 * worthwhile.
536 */
537 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
538 zio_t *nio = last;
539 while ((dio = AVL_NEXT(t, nio)) != NULL &&
540 IO_GAP(nio, dio) == 0 &&
541 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
542 nio = dio;
543 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
544 stretch = B_TRUE;
545 break;
546 }
547 }
548 }
549
550 if (stretch) {
551 /* This may be a no-op. */
552 dio = AVL_NEXT(t, last);
553 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
554 } else {
555 while (last != mandatory && last != first) {
556 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
557 last = AVL_PREV(t, last);
558 ASSERT(last != NULL);
559 }
560 }
561
562 if (first == last)
563 return (NULL);
564
565 size = IO_SPAN(first, last);
566 ASSERT3U(size, <=, zfs_vdev_aggregation_limit);
567
568 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
569 zio_buf_alloc(size), size, first->io_type, zio->io_priority,
570 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
571 vdev_queue_agg_io_done, NULL);
572 aio->io_timestamp = first->io_timestamp;
573
574 nio = first;
575 do {
576 dio = nio;
577 nio = AVL_NEXT(t, dio);
578 ASSERT3U(dio->io_type, ==, aio->io_type);
579
580 if (dio->io_flags & ZIO_FLAG_NODATA) {
581 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
582 bzero((char *)aio->io_data + (dio->io_offset -
583 aio->io_offset), dio->io_size);
584 } else if (dio->io_type == ZIO_TYPE_WRITE) {
585 bcopy(dio->io_data, (char *)aio->io_data +
586 (dio->io_offset - aio->io_offset),
587 dio->io_size);
588 }
589
590 zio_add_child(dio, aio);
591 vdev_queue_io_remove(vq, dio);
592 zio_vdev_io_bypass(dio);
593 zio_execute(dio);
594 } while (dio != last);
595
596 return (aio);
597 }
598
599 static zio_t *
600 vdev_queue_io_to_issue(vdev_queue_t *vq)
601 {
602 zio_t *zio, *aio;
603 zio_priority_t p;
604 avl_index_t idx;
605 vdev_queue_class_t *vqc;
606 zio_t search;
607
608 again:
609 ASSERT(MUTEX_HELD(&vq->vq_lock));
610
611 p = vdev_queue_class_to_issue(vq);
612
613 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
614 /* No eligible queued i/os */
615 return (NULL);
616 }
617
618 /*
619 * For LBA-ordered queues (async / scrub), issue the i/o which follows
620 * the most recently issued i/o in LBA (offset) order.
621 *
622 * For FIFO queues (sync), issue the i/o with the lowest timestamp.
623 */
624 vqc = &vq->vq_class[p];
625 search.io_timestamp = 0;
626 search.io_offset = vq->vq_last_offset + 1;
627 VERIFY3P(avl_find(&vqc->vqc_queued_tree, &search, &idx), ==, NULL);
628 zio = avl_nearest(&vqc->vqc_queued_tree, idx, AVL_AFTER);
629 if (zio == NULL)
630 zio = avl_first(&vqc->vqc_queued_tree);
631 ASSERT3U(zio->io_priority, ==, p);
632
633 aio = vdev_queue_aggregate(vq, zio);
634 if (aio != NULL)
635 zio = aio;
636 else
637 vdev_queue_io_remove(vq, zio);
638
639 /*
640 * If the I/O is or was optional and therefore has no data, we need to
641 * simply discard it. We need to drop the vdev queue's lock to avoid a
642 * deadlock that we could encounter since this I/O will complete
643 * immediately.
644 */
645 if (zio->io_flags & ZIO_FLAG_NODATA) {
646 mutex_exit(&vq->vq_lock);
647 zio_vdev_io_bypass(zio);
648 zio_execute(zio);
649 mutex_enter(&vq->vq_lock);
650 goto again;
651 }
652
653 vdev_queue_pending_add(vq, zio);
654 vq->vq_last_offset = zio->io_offset;
655
656 return (zio);
657 }
658
659 zio_t *
660 vdev_queue_io(zio_t *zio)
661 {
662 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
663 zio_t *nio;
664
665 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
666 return (zio);
667
668 /*
669 * Children i/os inherent their parent's priority, which might
670 * not match the child's i/o type. Fix it up here.
671 */
672 if (zio->io_type == ZIO_TYPE_READ) {
673 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
674 zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
675 zio->io_priority != ZIO_PRIORITY_SCRUB)
676 zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
677 } else {
678 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
679 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
680 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE)
681 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
682 }
683
684 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
685
686 mutex_enter(&vq->vq_lock);
687 zio->io_timestamp = gethrtime();
688 vdev_queue_io_add(vq, zio);
689 nio = vdev_queue_io_to_issue(vq);
690 mutex_exit(&vq->vq_lock);
691
692 if (nio == NULL)
693 return (NULL);
694
695 if (nio->io_done == vdev_queue_agg_io_done) {
696 zio_nowait(nio);
697 return (NULL);
698 }
699
700 return (nio);
701 }
702
703 void
704 vdev_queue_io_done(zio_t *zio)
705 {
706 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
707 zio_t *nio;
708
709 if (zio_injection_enabled)
710 delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
711
712 mutex_enter(&vq->vq_lock);
713
714 vdev_queue_pending_remove(vq, zio);
715
716 vq->vq_io_complete_ts = gethrtime();
717
718 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
719 mutex_exit(&vq->vq_lock);
720 if (nio->io_done == vdev_queue_agg_io_done) {
721 zio_nowait(nio);
722 } else {
723 zio_vdev_io_reissue(nio);
724 zio_execute(nio);
725 }
726 mutex_enter(&vq->vq_lock);
727 }
728
729 mutex_exit(&vq->vq_lock);
730 }
731
732 /*
733 * As these three methods are only used for load calculations we're not
734 * concerned if we get an incorrect value on 32bit platforms due to lack of
735 * vq_lock mutex use here, instead we prefer to keep it lock free for
736 * performance.
737 */
738 int
739 vdev_queue_length(vdev_t *vd)
740 {
741 vdev_queue_t *vq = &vd->vdev_queue;
742 int len = 0;
743
744 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
745 len += avl_numnodes(&vq->vq_class[p].vqc_queued_tree);
746
747 return (len);
748 }
749
750 uint64_t
751 vdev_queue_last_queued_offset(vdev_t *vd)
752 {
753 return (vd->vdev_queue.vq_last_queued_offset);
754 }
755
756 void
757 vdev_queue_register_last_queued_offset(vdev_t *vd, zio_t *zio)
758 {
759 vd->vdev_queue.vq_last_queued_offset = zio->io_offset + zio->io_size;
760 }