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, 2017 by Delphix. All rights reserved.
28 * Copyright (c) 2014 Integros [integros.com]
29 */
30
31 #include <sys/zfs_context.h>
32 #include <sys/vdev_impl.h>
33 #include <sys/spa_impl.h>
34 #include <sys/zio.h>
35 #include <sys/avl.h>
36 #include <sys/dsl_pool.h>
37 #include <sys/metaslab_impl.h>
38 #include <sys/abd.h>
39
40 /*
41 * ZFS I/O Scheduler
42 * ---------------
43 *
44 * ZFS issues I/O operations to leaf vdevs to satisfy and complete zios. The
45 * I/O scheduler determines when and in what order those operations are
46 * issued. The I/O scheduler divides operations into five I/O classes
47 * prioritized in the following order: sync read, sync write, async read,
48 * async write, and scrub/resilver. Each queue defines the minimum and
49 * maximum number of concurrent operations that may be issued to the device.
50 * In addition, the device has an aggregate maximum. Note that the sum of the
51 * per-queue minimums must not exceed the aggregate maximum, and if the
52 * aggregate maximum is equal to or greater than the sum of the per-queue
53 * maximums, the per-queue minimum has no effect.
54 *
55 * For many physical devices, throughput increases with the number of
56 * concurrent operations, but latency typically suffers. Further, physical
57 * devices typically have a limit at which more concurrent operations have no
58 * effect on throughput or can actually cause it to decrease.
59 *
60 * The scheduler selects the next operation to issue by first looking for an
61 * I/O class whose minimum has not been satisfied. Once all are satisfied and
62 * the aggregate maximum has not been hit, the scheduler looks for classes
63 * whose maximum has not been satisfied. Iteration through the I/O classes is
64 * done in the order specified above. No further operations are issued if the
65 * aggregate maximum number of concurrent operations has been hit or if there
66 * are no operations queued for an I/O class that has not hit its maximum.
67 * Every time an i/o is queued or an operation completes, the I/O scheduler
68 * looks for new operations to issue.
69 *
70 * All I/O classes have a fixed maximum number of outstanding operations
71 * except for the async write class. Asynchronous writes represent the data
72 * that is committed to stable storage during the syncing stage for
73 * transaction groups (see txg.c). Transaction groups enter the syncing state
74 * periodically so the number of queued async writes will quickly burst up and
75 * then bleed down to zero. Rather than servicing them as quickly as possible,
76 * the I/O scheduler changes the maximum number of active async write i/os
77 * according to the amount of dirty data in the pool (see dsl_pool.c). Since
78 * both throughput and latency typically increase with the number of
79 * concurrent operations issued to physical devices, reducing the burstiness
80 * in the number of concurrent operations also stabilizes the response time of
81 * operations from other -- and in particular synchronous -- queues. In broad
82 * strokes, the I/O scheduler will issue more concurrent operations from the
83 * async write queue as there's more dirty data in the pool.
84 *
85 * Async Writes
86 *
87 * The number of concurrent operations issued for the async write I/O class
88 * follows a piece-wise linear function defined by a few adjustable points.
89 *
90 * | o---------| <-- zfs_vdev_async_write_max_active
91 * ^ | /^ |
92 * | | / | |
93 * active | / | |
94 * I/O | / | |
95 * count | / | |
96 * | / | |
97 * |------------o | | <-- zfs_vdev_async_write_min_active
98 * 0|____________^______|_________|
99 * 0% | | 100% of zfs_dirty_data_max
100 * | |
101 * | `-- zfs_vdev_async_write_active_max_dirty_percent
102 * `--------- zfs_vdev_async_write_active_min_dirty_percent
103 *
104 * Until the amount of dirty data exceeds a minimum percentage of the dirty
105 * data allowed in the pool, the I/O scheduler will limit the number of
106 * concurrent operations to the minimum. As that threshold is crossed, the
107 * number of concurrent operations issued increases linearly to the maximum at
108 * the specified maximum percentage of the dirty data allowed in the pool.
109 *
110 * Ideally, the amount of dirty data on a busy pool will stay in the sloped
111 * part of the function between zfs_vdev_async_write_active_min_dirty_percent
112 * and zfs_vdev_async_write_active_max_dirty_percent. If it exceeds the
113 * maximum percentage, this indicates that the rate of incoming data is
114 * greater than the rate that the backend storage can handle. In this case, we
115 * must further throttle incoming writes (see dmu_tx_delay() for details).
116 */
117
118 /*
119 * The maximum number of i/os active to each device. Ideally, this will be >=
120 * the sum of each queue's max_active. It must be at least the sum of each
121 * queue's min_active.
122 */
123 uint32_t zfs_vdev_max_active = 1000;
124
125 /*
126 * Per-queue limits on the number of i/os active to each device. If the
127 * sum of the queue's max_active is < zfs_vdev_max_active, then the
128 * min_active comes into play. We will send min_active from each queue,
129 * and then select from queues in the order defined by zio_priority_t.
130 *
131 * In general, smaller max_active's will lead to lower latency of synchronous
132 * operations. Larger max_active's may lead to higher overall throughput,
133 * depending on underlying storage.
134 *
135 * The ratio of the queues' max_actives determines the balance of performance
136 * between reads, writes, and scrubs. E.g., increasing
137 * zfs_vdev_scrub_max_active will cause the scrub or resilver to complete
138 * more quickly, but reads and writes to have higher latency and lower
139 * throughput.
140 */
141 uint32_t zfs_vdev_sync_read_min_active = 10;
142 uint32_t zfs_vdev_sync_read_max_active = 10;
143 uint32_t zfs_vdev_sync_write_min_active = 10;
144 uint32_t zfs_vdev_sync_write_max_active = 10;
145 uint32_t zfs_vdev_async_read_min_active = 1;
146 uint32_t zfs_vdev_async_read_max_active = 3;
147 uint32_t zfs_vdev_async_write_min_active = 1;
148 uint32_t zfs_vdev_async_write_max_active = 10;
149 uint32_t zfs_vdev_scrub_min_active = 1;
150 uint32_t zfs_vdev_scrub_max_active = 2;
151 uint32_t zfs_vdev_removal_min_active = 1;
152 uint32_t zfs_vdev_removal_max_active = 2;
153
154 /*
155 * When the pool has less than zfs_vdev_async_write_active_min_dirty_percent
156 * dirty data, use zfs_vdev_async_write_min_active. When it has more than
157 * zfs_vdev_async_write_active_max_dirty_percent, use
158 * zfs_vdev_async_write_max_active. The value is linearly interpolated
159 * between min and max.
160 */
161 int zfs_vdev_async_write_active_min_dirty_percent = 30;
162 int zfs_vdev_async_write_active_max_dirty_percent = 60;
163
164 /*
165 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
166 * For read I/Os, we also aggregate across small adjacency gaps; for writes
167 * we include spans of optional I/Os to aid aggregation at the disk even when
168 * they aren't able to help us aggregate at this level.
169 */
170 int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE;
171 int zfs_vdev_read_gap_limit = 32 << 10;
172 int zfs_vdev_write_gap_limit = 4 << 10;
173
174 /*
175 * Define the queue depth percentage for each top-level. This percentage is
176 * used in conjunction with zfs_vdev_async_max_active to determine how many
177 * allocations a specific top-level vdev should handle. Once the queue depth
178 * reaches zfs_vdev_queue_depth_pct * zfs_vdev_async_write_max_active / 100
179 * then allocator will stop allocating blocks on that top-level device.
180 * The default kernel setting is 1000% which will yield 100 allocations per
181 * device. For userland testing, the default setting is 300% which equates
182 * to 30 allocations per device.
183 */
184 #ifdef _KERNEL
185 int zfs_vdev_queue_depth_pct = 1000;
186 #else
187 int zfs_vdev_queue_depth_pct = 300;
188 #endif
189
190
191 int
192 vdev_queue_offset_compare(const void *x1, const void *x2)
193 {
194 const zio_t *z1 = x1;
195 const zio_t *z2 = x2;
196
197 if (z1->io_offset < z2->io_offset)
198 return (-1);
199 if (z1->io_offset > z2->io_offset)
200 return (1);
201
202 if (z1 < z2)
203 return (-1);
204 if (z1 > z2)
205 return (1);
206
207 return (0);
208 }
209
210 static inline avl_tree_t *
211 vdev_queue_class_tree(vdev_queue_t *vq, zio_priority_t p)
212 {
213 return (&vq->vq_class[p].vqc_queued_tree);
214 }
215
216 static inline avl_tree_t *
217 vdev_queue_type_tree(vdev_queue_t *vq, zio_type_t t)
218 {
219 ASSERT(t == ZIO_TYPE_READ || t == ZIO_TYPE_WRITE);
220 if (t == ZIO_TYPE_READ)
221 return (&vq->vq_read_offset_tree);
222 else
223 return (&vq->vq_write_offset_tree);
224 }
225
226 int
227 vdev_queue_timestamp_compare(const void *x1, const void *x2)
228 {
229 const zio_t *z1 = x1;
230 const zio_t *z2 = x2;
231
232 if (z1->io_timestamp < z2->io_timestamp)
233 return (-1);
234 if (z1->io_timestamp > z2->io_timestamp)
235 return (1);
236
237 if (z1 < z2)
238 return (-1);
239 if (z1 > z2)
240 return (1);
241
242 return (0);
243 }
244
245 void
246 vdev_queue_init(vdev_t *vd)
247 {
248 vdev_queue_t *vq = &vd->vdev_queue;
249
250 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
251 vq->vq_vdev = vd;
252
253 avl_create(&vq->vq_active_tree, vdev_queue_offset_compare,
254 sizeof (zio_t), offsetof(struct zio, io_queue_node));
255 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_READ),
256 vdev_queue_offset_compare, sizeof (zio_t),
257 offsetof(struct zio, io_offset_node));
258 avl_create(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE),
259 vdev_queue_offset_compare, sizeof (zio_t),
260 offsetof(struct zio, io_offset_node));
261
262 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
263 int (*compfn) (const void *, const void *);
264
265 /*
266 * The synchronous i/o queues are dispatched in FIFO rather
267 * than LBA order. This provides more consistent latency for
268 * these i/os.
269 */
270 if (p == ZIO_PRIORITY_SYNC_READ || p == ZIO_PRIORITY_SYNC_WRITE)
271 compfn = vdev_queue_timestamp_compare;
272 else
273 compfn = vdev_queue_offset_compare;
274
275 avl_create(vdev_queue_class_tree(vq, p), compfn,
276 sizeof (zio_t), offsetof(struct zio, io_queue_node));
277 }
278 }
279
280 void
281 vdev_queue_fini(vdev_t *vd)
282 {
283 vdev_queue_t *vq = &vd->vdev_queue;
284
285 for (zio_priority_t p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++)
286 avl_destroy(vdev_queue_class_tree(vq, p));
287 avl_destroy(&vq->vq_active_tree);
288 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_READ));
289 avl_destroy(vdev_queue_type_tree(vq, ZIO_TYPE_WRITE));
290
291 mutex_destroy(&vq->vq_lock);
292 }
293
294 static void
295 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
296 {
297 spa_t *spa = zio->io_spa;
298
299 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
300 avl_add(vdev_queue_class_tree(vq, zio->io_priority), zio);
301 avl_add(vdev_queue_type_tree(vq, zio->io_type), zio);
302
303 mutex_enter(&spa->spa_iokstat_lock);
304 spa->spa_queue_stats[zio->io_priority].spa_queued++;
305 if (spa->spa_iokstat != NULL)
306 kstat_waitq_enter(spa->spa_iokstat->ks_data);
307 mutex_exit(&spa->spa_iokstat_lock);
308 }
309
310 static void
311 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
312 {
313 spa_t *spa = zio->io_spa;
314
315 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
316 avl_remove(vdev_queue_class_tree(vq, zio->io_priority), zio);
317 avl_remove(vdev_queue_type_tree(vq, zio->io_type), zio);
318
319 mutex_enter(&spa->spa_iokstat_lock);
320 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_queued, >, 0);
321 spa->spa_queue_stats[zio->io_priority].spa_queued--;
322 if (spa->spa_iokstat != NULL)
323 kstat_waitq_exit(spa->spa_iokstat->ks_data);
324 mutex_exit(&spa->spa_iokstat_lock);
325 }
326
327 static void
328 vdev_queue_pending_add(vdev_queue_t *vq, zio_t *zio)
329 {
330 spa_t *spa = zio->io_spa;
331 ASSERT(MUTEX_HELD(&vq->vq_lock));
332 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
333 vq->vq_class[zio->io_priority].vqc_active++;
334 avl_add(&vq->vq_active_tree, zio);
335
336 mutex_enter(&spa->spa_iokstat_lock);
337 spa->spa_queue_stats[zio->io_priority].spa_active++;
338 if (spa->spa_iokstat != NULL)
339 kstat_runq_enter(spa->spa_iokstat->ks_data);
340 mutex_exit(&spa->spa_iokstat_lock);
341 }
342
343 static void
344 vdev_queue_pending_remove(vdev_queue_t *vq, zio_t *zio)
345 {
346 spa_t *spa = zio->io_spa;
347 ASSERT(MUTEX_HELD(&vq->vq_lock));
348 ASSERT3U(zio->io_priority, <, ZIO_PRIORITY_NUM_QUEUEABLE);
349 vq->vq_class[zio->io_priority].vqc_active--;
350 avl_remove(&vq->vq_active_tree, zio);
351
352 mutex_enter(&spa->spa_iokstat_lock);
353 ASSERT3U(spa->spa_queue_stats[zio->io_priority].spa_active, >, 0);
354 spa->spa_queue_stats[zio->io_priority].spa_active--;
355 if (spa->spa_iokstat != NULL) {
356 kstat_io_t *ksio = spa->spa_iokstat->ks_data;
357
358 kstat_runq_exit(spa->spa_iokstat->ks_data);
359 if (zio->io_type == ZIO_TYPE_READ) {
360 ksio->reads++;
361 ksio->nread += zio->io_size;
362 } else if (zio->io_type == ZIO_TYPE_WRITE) {
363 ksio->writes++;
364 ksio->nwritten += zio->io_size;
365 }
366 }
367 mutex_exit(&spa->spa_iokstat_lock);
368 }
369
370 static void
371 vdev_queue_agg_io_done(zio_t *aio)
372 {
373 if (aio->io_type == ZIO_TYPE_READ) {
374 zio_t *pio;
375 zio_link_t *zl = NULL;
376 while ((pio = zio_walk_parents(aio, &zl)) != NULL) {
377 abd_copy_off(pio->io_abd, aio->io_abd,
378 0, pio->io_offset - aio->io_offset, pio->io_size);
379 }
380 }
381
382 abd_free(aio->io_abd);
383 }
384
385 static int
386 vdev_queue_class_min_active(zio_priority_t p)
387 {
388 switch (p) {
389 case ZIO_PRIORITY_SYNC_READ:
390 return (zfs_vdev_sync_read_min_active);
391 case ZIO_PRIORITY_SYNC_WRITE:
392 return (zfs_vdev_sync_write_min_active);
393 case ZIO_PRIORITY_ASYNC_READ:
394 return (zfs_vdev_async_read_min_active);
395 case ZIO_PRIORITY_ASYNC_WRITE:
396 return (zfs_vdev_async_write_min_active);
397 case ZIO_PRIORITY_SCRUB:
398 return (zfs_vdev_scrub_min_active);
399 case ZIO_PRIORITY_REMOVAL:
400 return (zfs_vdev_removal_min_active);
401 default:
402 panic("invalid priority %u", p);
403 return (0);
404 }
405 }
406
407 static int
408 vdev_queue_max_async_writes(spa_t *spa)
409 {
410 int writes;
411 uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
412 uint64_t min_bytes = zfs_dirty_data_max *
413 zfs_vdev_async_write_active_min_dirty_percent / 100;
414 uint64_t max_bytes = zfs_dirty_data_max *
415 zfs_vdev_async_write_active_max_dirty_percent / 100;
416
417 /*
418 * Sync tasks correspond to interactive user actions. To reduce the
419 * execution time of those actions we push data out as fast as possible.
420 */
421 if (spa_has_pending_synctask(spa)) {
422 return (zfs_vdev_async_write_max_active);
423 }
424
425 if (dirty < min_bytes)
426 return (zfs_vdev_async_write_min_active);
427 if (dirty > max_bytes)
428 return (zfs_vdev_async_write_max_active);
429
430 /*
431 * linear interpolation:
432 * slope = (max_writes - min_writes) / (max_bytes - min_bytes)
433 * move right by min_bytes
434 * move up by min_writes
435 */
436 writes = (dirty - min_bytes) *
437 (zfs_vdev_async_write_max_active -
438 zfs_vdev_async_write_min_active) /
439 (max_bytes - min_bytes) +
440 zfs_vdev_async_write_min_active;
441 ASSERT3U(writes, >=, zfs_vdev_async_write_min_active);
442 ASSERT3U(writes, <=, zfs_vdev_async_write_max_active);
443 return (writes);
444 }
445
446 static int
447 vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
448 {
449 switch (p) {
450 case ZIO_PRIORITY_SYNC_READ:
451 return (zfs_vdev_sync_read_max_active);
452 case ZIO_PRIORITY_SYNC_WRITE:
453 return (zfs_vdev_sync_write_max_active);
454 case ZIO_PRIORITY_ASYNC_READ:
455 return (zfs_vdev_async_read_max_active);
456 case ZIO_PRIORITY_ASYNC_WRITE:
457 return (vdev_queue_max_async_writes(spa));
458 case ZIO_PRIORITY_SCRUB:
459 return (zfs_vdev_scrub_max_active);
460 case ZIO_PRIORITY_REMOVAL:
461 return (zfs_vdev_removal_max_active);
462 default:
463 panic("invalid priority %u", p);
464 return (0);
465 }
466 }
467
468 /*
469 * Return the i/o class to issue from, or ZIO_PRIORITY_MAX_QUEUEABLE if
470 * there is no eligible class.
471 */
472 static zio_priority_t
473 vdev_queue_class_to_issue(vdev_queue_t *vq)
474 {
475 spa_t *spa = vq->vq_vdev->vdev_spa;
476 zio_priority_t p;
477
478 if (avl_numnodes(&vq->vq_active_tree) >= zfs_vdev_max_active)
479 return (ZIO_PRIORITY_NUM_QUEUEABLE);
480
481 /* find a queue that has not reached its minimum # outstanding i/os */
482 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
483 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
484 vq->vq_class[p].vqc_active <
485 vdev_queue_class_min_active(p))
486 return (p);
487 }
488
489 /*
490 * If we haven't found a queue, look for one that hasn't reached its
491 * maximum # outstanding i/os.
492 */
493 for (p = 0; p < ZIO_PRIORITY_NUM_QUEUEABLE; p++) {
494 if (avl_numnodes(vdev_queue_class_tree(vq, p)) > 0 &&
495 vq->vq_class[p].vqc_active <
496 vdev_queue_class_max_active(spa, p))
497 return (p);
498 }
499
500 /* No eligible queued i/os */
501 return (ZIO_PRIORITY_NUM_QUEUEABLE);
502 }
503
504 /*
505 * Compute the range spanned by two i/os, which is the endpoint of the last
506 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
507 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
508 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
509 */
510 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
511 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
512
513 static zio_t *
514 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
515 {
516 zio_t *first, *last, *aio, *dio, *mandatory, *nio;
517 uint64_t maxgap = 0;
518 uint64_t size;
519 boolean_t stretch = B_FALSE;
520 avl_tree_t *t = vdev_queue_type_tree(vq, zio->io_type);
521 enum zio_flag flags = zio->io_flags & ZIO_FLAG_AGG_INHERIT;
522
523 if (zio->io_flags & ZIO_FLAG_DONT_AGGREGATE)
524 return (NULL);
525
526 first = last = zio;
527
528 if (zio->io_type == ZIO_TYPE_READ)
529 maxgap = zfs_vdev_read_gap_limit;
530
531 /*
532 * We can aggregate I/Os that are sufficiently adjacent and of
533 * the same flavor, as expressed by the AGG_INHERIT flags.
534 * The latter requirement is necessary so that certain
535 * attributes of the I/O, such as whether it's a normal I/O
536 * or a scrub/resilver, can be preserved in the aggregate.
537 * We can include optional I/Os, but don't allow them
538 * to begin a range as they add no benefit in that situation.
539 */
540
541 /*
542 * We keep track of the last non-optional I/O.
543 */
544 mandatory = (first->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : first;
545
546 /*
547 * Walk backwards through sufficiently contiguous I/Os
548 * recording the last non-optional I/O.
549 */
550 while ((dio = AVL_PREV(t, first)) != NULL &&
551 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
552 IO_SPAN(dio, last) <= zfs_vdev_aggregation_limit &&
553 IO_GAP(dio, first) <= maxgap &&
554 dio->io_type == zio->io_type) {
555 first = dio;
556 if (mandatory == NULL && !(first->io_flags & ZIO_FLAG_OPTIONAL))
557 mandatory = first;
558 }
559
560 /*
561 * Skip any initial optional I/Os.
562 */
563 while ((first->io_flags & ZIO_FLAG_OPTIONAL) && first != last) {
564 first = AVL_NEXT(t, first);
565 ASSERT(first != NULL);
566 }
567
568 /*
569 * Walk forward through sufficiently contiguous I/Os.
570 * The aggregation limit does not apply to optional i/os, so that
571 * we can issue contiguous writes even if they are larger than the
572 * aggregation limit.
573 */
574 while ((dio = AVL_NEXT(t, last)) != NULL &&
575 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
576 (IO_SPAN(first, dio) <= zfs_vdev_aggregation_limit ||
577 (dio->io_flags & ZIO_FLAG_OPTIONAL)) &&
578 IO_GAP(last, dio) <= maxgap &&
579 dio->io_type == zio->io_type) {
580 last = dio;
581 if (!(last->io_flags & ZIO_FLAG_OPTIONAL))
582 mandatory = last;
583 }
584
585 /*
586 * Now that we've established the range of the I/O aggregation
587 * we must decide what to do with trailing optional I/Os.
588 * For reads, there's nothing to do. While we are unable to
589 * aggregate further, it's possible that a trailing optional
590 * I/O would allow the underlying device to aggregate with
591 * subsequent I/Os. We must therefore determine if the next
592 * non-optional I/O is close enough to make aggregation
593 * worthwhile.
594 */
595 if (zio->io_type == ZIO_TYPE_WRITE && mandatory != NULL) {
596 zio_t *nio = last;
597 while ((dio = AVL_NEXT(t, nio)) != NULL &&
598 IO_GAP(nio, dio) == 0 &&
599 IO_GAP(mandatory, dio) <= zfs_vdev_write_gap_limit) {
600 nio = dio;
601 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
602 stretch = B_TRUE;
603 break;
604 }
605 }
606 }
607
608 if (stretch) {
609 /*
610 * We are going to include an optional io in our aggregated
611 * span, thus closing the write gap. Only mandatory i/os can
612 * start aggregated spans, so make sure that the next i/o
613 * after our span is mandatory.
614 */
615 dio = AVL_NEXT(t, last);
616 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
617 } else {
618 /* do not include the optional i/o */
619 while (last != mandatory && last != first) {
620 ASSERT(last->io_flags & ZIO_FLAG_OPTIONAL);
621 last = AVL_PREV(t, last);
622 ASSERT(last != NULL);
623 }
624 }
625
626 if (first == last)
627 return (NULL);
628
629 size = IO_SPAN(first, last);
630 ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
631
632 aio = zio_vdev_delegated_io(first->io_vd, first->io_offset,
633 abd_alloc_for_io(size, B_TRUE), size, first->io_type,
634 zio->io_priority, flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
635 vdev_queue_agg_io_done, NULL);
636 aio->io_timestamp = first->io_timestamp;
637
638 nio = first;
639 do {
640 dio = nio;
641 nio = AVL_NEXT(t, dio);
642 ASSERT3U(dio->io_type, ==, aio->io_type);
643
644 if (dio->io_flags & ZIO_FLAG_NODATA) {
645 ASSERT3U(dio->io_type, ==, ZIO_TYPE_WRITE);
646 abd_zero_off(aio->io_abd,
647 dio->io_offset - aio->io_offset, dio->io_size);
648 } else if (dio->io_type == ZIO_TYPE_WRITE) {
649 abd_copy_off(aio->io_abd, dio->io_abd,
650 dio->io_offset - aio->io_offset, 0, dio->io_size);
651 }
652
653 zio_add_child(dio, aio);
654 vdev_queue_io_remove(vq, dio);
655 zio_vdev_io_bypass(dio);
656 zio_execute(dio);
657 } while (dio != last);
658
659 return (aio);
660 }
661
662 static zio_t *
663 vdev_queue_io_to_issue(vdev_queue_t *vq)
664 {
665 zio_t *zio, *aio;
666 zio_priority_t p;
667 avl_index_t idx;
668 avl_tree_t *tree;
669 zio_t search;
670
671 again:
672 ASSERT(MUTEX_HELD(&vq->vq_lock));
673
674 p = vdev_queue_class_to_issue(vq);
675
676 if (p == ZIO_PRIORITY_NUM_QUEUEABLE) {
677 /* No eligible queued i/os */
678 return (NULL);
679 }
680
681 /*
682 * For LBA-ordered queues (async / scrub), issue the i/o which follows
683 * the most recently issued i/o in LBA (offset) order.
684 *
685 * For FIFO queues (sync), issue the i/o with the lowest timestamp.
686 */
687 tree = vdev_queue_class_tree(vq, p);
688 search.io_timestamp = 0;
689 search.io_offset = vq->vq_last_offset + 1;
690 VERIFY3P(avl_find(tree, &search, &idx), ==, NULL);
691 zio = avl_nearest(tree, idx, AVL_AFTER);
692 if (zio == NULL)
693 zio = avl_first(tree);
694 ASSERT3U(zio->io_priority, ==, p);
695
696 aio = vdev_queue_aggregate(vq, zio);
697 if (aio != NULL)
698 zio = aio;
699 else
700 vdev_queue_io_remove(vq, zio);
701
702 /*
703 * If the I/O is or was optional and therefore has no data, we need to
704 * simply discard it. We need to drop the vdev queue's lock to avoid a
705 * deadlock that we could encounter since this I/O will complete
706 * immediately.
707 */
708 if (zio->io_flags & ZIO_FLAG_NODATA) {
709 mutex_exit(&vq->vq_lock);
710 zio_vdev_io_bypass(zio);
711 zio_execute(zio);
712 mutex_enter(&vq->vq_lock);
713 goto again;
714 }
715
716 vdev_queue_pending_add(vq, zio);
717 vq->vq_last_offset = zio->io_offset;
718
719 return (zio);
720 }
721
722 zio_t *
723 vdev_queue_io(zio_t *zio)
724 {
725 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
726 zio_t *nio;
727
728 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
729 return (zio);
730
731 /*
732 * Children i/os inherent their parent's priority, which might
733 * not match the child's i/o type. Fix it up here.
734 */
735 if (zio->io_type == ZIO_TYPE_READ) {
736 if (zio->io_priority != ZIO_PRIORITY_SYNC_READ &&
737 zio->io_priority != ZIO_PRIORITY_ASYNC_READ &&
738 zio->io_priority != ZIO_PRIORITY_SCRUB &&
739 zio->io_priority != ZIO_PRIORITY_REMOVAL)
740 zio->io_priority = ZIO_PRIORITY_ASYNC_READ;
741 } else {
742 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
743 if (zio->io_priority != ZIO_PRIORITY_SYNC_WRITE &&
744 zio->io_priority != ZIO_PRIORITY_ASYNC_WRITE &&
745 zio->io_priority != ZIO_PRIORITY_REMOVAL)
746 zio->io_priority = ZIO_PRIORITY_ASYNC_WRITE;
747 }
748
749 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
750
751 mutex_enter(&vq->vq_lock);
752 zio->io_timestamp = gethrtime();
753 vdev_queue_io_add(vq, zio);
754 nio = vdev_queue_io_to_issue(vq);
755 mutex_exit(&vq->vq_lock);
756
757 if (nio == NULL)
758 return (NULL);
759
760 if (nio->io_done == vdev_queue_agg_io_done) {
761 zio_nowait(nio);
762 return (NULL);
763 }
764
765 return (nio);
766 }
767
768 void
769 vdev_queue_io_done(zio_t *zio)
770 {
771 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
772 zio_t *nio;
773
774 mutex_enter(&vq->vq_lock);
775
776 vdev_queue_pending_remove(vq, zio);
777
778 vq->vq_io_complete_ts = gethrtime();
779
780 while ((nio = vdev_queue_io_to_issue(vq)) != NULL) {
781 mutex_exit(&vq->vq_lock);
782 if (nio->io_done == vdev_queue_agg_io_done) {
783 zio_nowait(nio);
784 } else {
785 zio_vdev_io_reissue(nio);
786 zio_execute(nio);
787 }
788 mutex_enter(&vq->vq_lock);
789 }
790
791 mutex_exit(&vq->vq_lock);
792 }